JP5708610B2 - Lithium ion battery - Google Patents

Description

  The present invention relates to a lithium ion battery and a vehicle equipped with the lithium ion battery. In particular, according to the present invention, the electric capacity and energy density of the lithium ion battery can be further improved.

  The spread of various electric vehicles is expected to solve environmental and energy problems. Development of motor drive batteries, which hold the key to the spread of these electric vehicles, has been actively conducted. As a battery for driving a motor, a lithium ion battery having the highest theoretical energy among all the batteries is attracting attention, and is currently being developed rapidly.

  In general, a lithium ion battery has an electrolyte solution in which a positive electrode in which a positive electrode active material or the like is applied to both surfaces of a positive electrode current collector using a binder and a negative electrode in which a negative electrode active material or the like is applied to both surfaces of a negative electrode current collector using a binder. It is connected through a separator layer impregnated with and is housed in a battery case.

  However, in order for such electric vehicles to become widespread, it is necessary to make lithium ion batteries high performance and cheaper. In addition, for electric vehicles, it is necessary to bring the distance for one charge closer to a gasoline engine vehicle, and a battery with higher energy is desired. In order to make the battery have a high energy density, it is necessary to increase the amount of electricity stored per unit mass of the positive electrode and the negative electrode.

A so-called solid solution positive electrode has been studied as a positive electrode material that may meet this demand. Among them, the solid solution of the electrochemically inactive layered Li ₂ MnO ₃ and the electrochemically active layered LiMO ₂ (where M is a transition metal such as Co or Ni) is 200 mAh / g. It is expected as a high-capacity positive electrode candidate material capable of exhibiting a large electric capacity exceeding (see Patent Document 1).

JP-A-9-55211

  However, the solid solution positive electrode material described in Patent Document 1 has a problem that the initial charge / discharge efficiency is very poor. Therefore, when a lithium ion battery is configured using this type of solid solution positive electrode material, a large amount of negative electrode material that cannot contribute to the charge / discharge capacity of the battery is required, and the electric capacity and energy density of the battery cannot be increased. there were.

  Accordingly, an object of the present invention is to provide a lithium ion battery that improves the initial charge / discharge efficiency of a high-capacity positive electrode material and improves the electric capacity and energy density.

  The present inventors have intensively studied to solve the above problems. As a result, as a positive electrode material of a lithium ion battery, the above problem can be solved by adopting a battery configuration in which a positive electrode active material that is in a charged state at the stage of configuring the battery is used as the second positive electrode active material. The headline and the present invention have been completed.

That is, the present invention uses a positive electrode active material comprising two types of a first positive electrode active material that is in a discharged state at the stage of constituting a battery and a second positive electrode active material that is in a charged state at the stage of constituting a battery. The first positive electrode active material is a lithium ion battery represented by a general formula: xLiMO ₂ · (1-x) Li ₂ M ¹ O ₃ . In the above formula, x is 0 <x <1, M is one or more transition metals having an average oxidation state of 3 ⁺ , and M ¹ is one or more transition metals having an average oxidation state of 4 ⁺ .

  According to the present invention, even if the initial charge / discharge efficiency of the first positive electrode active material is low, the amount of the negative electrode active material contributing to the battery capacity can be increased, so that the electric capacity and energy density of the battery can be improved. I can plan.

1 is a schematic cross-sectional view schematically showing an outline of a laminated flat non-bipolar lithium ion secondary battery which is a typical embodiment of a lithium ion battery of the present invention. It is a schematic diagram for demonstrating the charging / discharging mechanism in the existing lithium ion secondary battery at the time of using the solid solution type | system | group positive electrode in a discharge state as a positive electrode active material as a high capacity | capacitance positive electrode material. As the positive electrode active material, the lithium ion battery of the present invention using two kinds of a first positive electrode active material in a solid solution system that is in a discharge state at the battery construction stage and a second positive electrode active material in a discharge state at the battery construction stage. It is a schematic diagram for demonstrating the charging / discharging mechanism. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view schematically showing an appearance of a stacked flat lithium ion secondary battery that is a typical embodiment of a lithium ion battery according to the present invention. 4A and 4B are external views schematically showing typical embodiments of the assembled battery according to the present invention, in which FIG. 4A is a plan view of the assembled battery, FIG. 4B is a front view of the assembled battery, and FIG. It is a side view of a battery. It is a conceptual diagram of the vehicle carrying the assembled battery of this invention. 6 is a graph showing a second discharge curve of the batteries of Example 1, Example 5, and Comparative Example 1. FIG.

  The lithium ion battery of the present invention has two main positive electrode active materials, and the first main positive electrode active material is in a discharged state at the stage of constituting the battery (hereinafter also referred to as the battery constituent stage). The positive electrode active material is in a charged state at the stage of constituting the battery.

  Hereinafter, typical embodiments of the lithium ion battery of the present invention will be described with reference to the drawings, but the technical scope of the present invention should be determined based on the description of the claims, and the following embodiments It is not limited to only. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted. In addition, the dimensional ratios in the drawings are exaggerated for convenience of explanation, and may be different from the actual ratios.

  First, since the lithium ion battery according to the present invention can have a high capacity and a high energy density, it can be suitably used as a drive power source for vehicles. In addition, it can be sufficiently applied to lithium ion batteries for portable devices such as mobile phones. In particular, when the battery of the present invention is used as a power source for mounting on a vehicle, the battery energy density is high, so the cruising range of the electric vehicle can be extended, the amount of battery load of the plug-in hybrid electric vehicle can be reduced, and the hybrid electric vehicle can be further updated. It is excellent in that high performance can be achieved.

  That is, the lithium ion battery that is the subject of the present invention only needs to use two kinds of main positive electrode active materials, that is, a discharged state and a charged state in the above-described battery configuration stage. It should not be restricted.

  For example, when the lithium ion battery is distinguished by its form / structure, it can be applied to any conventionally known form / structure, such as a stacked (flat) battery or a wound (cylindrical) battery. is there. By adopting a laminated (flat) battery structure, long-term reliability can be secured by a sealing technique such as simple thermocompression bonding, which is advantageous in terms of cost and workability.

  In terms of electrical connection (electrode structure) in lithium-ion batteries, both non-bipolar (internal parallel connection type) lithium-ion batteries and bipolar (internal series connection type) lithium-ion batteries Is also applicable. In the present invention, a non-bipolar (internal series connection type) lithium ion battery is desirable. This is because the battery configuration (internal parallel connection type) suitable for use as a high-capacity positive electrode by increasing the charge / discharge potential as described above.

  Conventionally known, such as a solution electrolyte type battery using a solution electrolyte such as a non-aqueous electrolyte for the electrolyte layer, a polymer battery using a polymer electrolyte for the electrolyte layer when distinguished by the type of electrolyte layer in the lithium ion battery It can be applied to any electrolyte layer type. The polymer battery is further divided into a gel electrolyte type battery using a polymer gel electrolyte (also simply referred to as a gel electrolyte) and a solid polymer (all solid) type battery using a polymer solid electrolyte (also simply referred to as a polymer electrolyte). It is done.

  Therefore, in the following description, a non-bipolar type (internal parallel connection type) lithium ion secondary battery using the two main cathode active materials of the present invention will be briefly described with reference to the drawings. It should not be restricted.

  FIG. 1 schematically shows the overall structure of a flat (stacked) non-bipolar lithium ion secondary battery (hereinafter also simply referred to as a lithium ion battery), which is a typical embodiment of the lithium ion battery of the present invention. FIG.

  As shown in FIG. 1, in the lithium ion battery 10 of the present embodiment, by using a laminate film that is a composite of polymer and metal for the battery exterior material 22, the entire periphery thereof is joined by thermal fusion. The power generation element (battery element) 17 is housed and sealed. The power generation element 17 includes a positive electrode plate having a positive electrode (positive electrode active material layer) 12 formed on both surfaces of the positive electrode current collector 11, an electrolyte layer (or separator layer) 13, and both surfaces of the negative electrode current collector 14 (most of the power generation element). It has a configuration in which a negative electrode plate on which a negative electrode (negative electrode active material layer) 15 is formed is laminated on one side for the lower layer and the uppermost layer. At this time, the positive electrode (positive electrode active material layer) 12 on one surface of one positive electrode plate and the negative electrode (negative electrode active material layer) 15 on one surface of one negative electrode plate adjacent to the one positive electrode plate face each other through the electrolyte layer 13. Thus, a plurality of layers of the positive electrode plate, the electrolyte layer 13, and the negative electrode plate are laminated in this order. Hereinafter, a set (battery minimum unit) in which the positive electrode plate, the electrolyte layer 13 and the negative electrode plate are stacked in this order is also referred to as a single battery layer (single cell) 16.

  As a result, the adjacent positive electrode (positive electrode active material layer) 12, electrolyte layer 13, and negative electrode (negative electrode active material layer) 15 constitute one unit cell layer 16. Therefore, it can be said that the lithium ion battery 10 of the present embodiment has a configuration in which a plurality of single battery layers 16 are stacked and electrically connected in parallel. Note that the negative electrode (negative electrode active material layer) 15 is formed on only one side of the outermost layer negative electrode current collector 14 a located in both outermost layers of the power generation element (battery element; laminate) 17. In addition, by changing the arrangement of the positive electrode plate and the negative electrode plate in FIG. 1, the outermost positive electrode current collector (not shown) is positioned in both outermost layers of the power generation element (battery element) 17, and the outermost positive electrode Also in the case of the current collector, the positive electrode (positive electrode active material layer) 12 may be formed only on one side.

  Further, the positive electrode tab 18 and the negative electrode tab 19 that are electrically connected to the respective electrode plates (positive electrode plate and negative electrode plate) are connected to the positive electrode current collector 11 and the negative electrode of each electrode plate via the positive electrode terminal lead 20 and the negative electrode terminal lead 21. It is attached to the current collector 14 by ultrasonic welding or resistance welding. Thus, the positive electrode tab 18 and the negative electrode tab 19 have a structure that is sandwiched between the heat-sealed portions and exposed to the outside of the battery outer packaging material 22 (see also FIG. 4).

  The following description will be focused on the above-described constituent elements of the lithium ion battery.

  First, in the present invention, as a characteristic configuration, the main positive electrode active material of the positive electrode (positive electrode active material layer) 12 includes a first positive electrode active material in a discharged state at the battery configuration stage, and a charged state at the battery configuration stage. The second positive electrode active material is used.

This characteristic configuration is based on the following findings. That is, the Li ₂ MnO ₃ and LiMO ₂ solid solution, which is expected to have a large electric capacity as described above, has a high charge / discharge potential and is used as a high capacity positive electrode material. There is a capacity that cannot be used (this is called initial loss capacity). Therefore, the electric capacity that can be discharged is considerably smaller than the amount of electricity required for the initial charging. The cause of this is not well understood. However, according to the published papers, it is considered that when charging at a high potential exceeding 4.5 V on the lithium metal basis, Li ₂ O is released from the material as a result of the progress of charging, and at least A part of oxygen is detected as oxygen gas. When a lithium ion battery is configured using this type of positive electrode material, the opposing negative electrode needs to have a capacity equal to or greater than the amount of electricity corresponding to this initial charge amount. The reason for using a larger negative electrode capacity than the positive electrode charge capacity is to prevent lithium metal from being deposited on the negative electrode during charging. Anyway, due to such circumstances, a large amount of negative electrode active material that cannot contribute to the battery capacity is required at the stage where the battery is actually charged and discharged many times. This situation is schematically shown in FIG. In the present invention, in order to solve this problem, the capacity of the negative electrode used only in the initial charge can be utilized by using the second active material in a charged state together with the positive electrode. . This situation is schematically shown in FIG.

That is, FIG. 2 shows an existing lithium ion secondary in the case of using a solid solution system positive electrode (for example, a solid solution of Li ₂ MnO ₃ and LiMO ₂ ) as a positive electrode active material in a discharge state at the battery construction stage as a high capacity positive electrode material. It is a schematic diagram for demonstrating the charging / discharging mechanism in a battery. FIG. 3 is a schematic diagram for explaining the charge / discharge mechanism in the lithium ion battery of the present invention. Specifically, the main positive electrode active material is composed of two types, and as one of the first positive electrode active materials, a solid solution type positive electrode similar to that shown in FIG. It is the schematic diagram demonstrated taking the case where the positive electrode active material is a charge condition in a battery structure stage.

  2 and 3, the negative electrode active material is not particularly limited, and may be generally used as a negative electrode active material for a lithium ion battery. 2 and 3 are diagrams showing states of the lithium ion battery at each time point of charging and discharging. The vertical axis indicates the capacity density (dQ / dE) of each active material, and the horizontal axis indicates the potential (V). Further, the straight line P indicates the potential of the positive electrode, and the straight line N indicates the potential of the negative electrode. Therefore, the distance between the straight line P and the straight line N indicates the battery voltage. The shaded portion indicates the chargeable capacity (reversible capacity), and the shaded area indicates the non-dischargeable charge capacity (irreversible capacity).

  FIG. 2A is a diagram showing a state immediately after battery production (that is, a battery configuration stage) in an existing lithium ion secondary battery. Immediately after manufacturing the battery and before initial charging, the battery voltage is about 1V. The reason why a potential is generated in the electrode immediately before charging immediately after the battery is produced and a constant battery voltage is generated is not completely clear, but it is considered that a very small amount of impurities are involved. The block of the code | symbol 31 in a figure shows the magnitude | size of the theoretical capacity | capacitance of the solid solution system positive electrode material which is a positive electrode active material material. The block of the code | symbol 33 shows the magnitude | size of the theoretical capacity | capacitance of a negative electrode active material material.

  FIG.2 (b) is a figure which shows the intermediate charge state of the initial stage charge in the existing lithium ion secondary battery. When initial charging is started, charging of the positive electrode and the negative electrode active material proceeds.

FIG.2 (c) is a figure which shows the state (full charge state) in which the initial charge in the existing lithium ion secondary battery was completed. When the initial charging is further continued from the state of FIG. 2B, charging of the existing positive electrode active material having a high charge / discharge potential further proceeds. On the other hand, charging proceeds similarly in the negative electrode. In practice, the reversible capacity of the negative electrode is slightly increased, but for the sake of clarity, the reversible capacity is schematically shown as balanced. The same applies to other cases (FIG. 3C). When both the positive and negative active materials are fully charged, the initial charging is completed. As described above, when charging at a high potential exceeding 4.5 V on the basis of lithium metal, Li ₂ O is released from the positive electrode active material as a result of the progress of charging, and the irreversible capacity (= initial loss capacity 31a ) Part is formed. Incidentally, while the initial charge electricity amount (first charge amount) of the solid solution used in Example 1 described later is as high as 340 mAh / g, the initial discharge electricity amount is about 256 mAh / g. It can be said that the irreversible capacity (= initial loss capacity) portion released as ₂ O is considerably large as shown.

  FIG. 2D is a diagram illustrating a state where the initial discharge in the existing lithium ion secondary battery is completed. Next, when the initial discharge of the battery that has been initially charged is started, in the positive electrode, only the portion 31b corresponding to the reversible capacity of the theoretical capacity 31 proceeds, and corresponds to the initial loss capacity 31a of the positive electrode active material. The discharge of the capacity 33a corresponding to the initial loss capacity on the negative electrode side is not performed.

  As described above, when a high capacity positive electrode material of a solid solution system is used, a large amount of negative electrode material that cannot contribute to the charge / discharge capacity of the battery is required, and the electric capacity that can be discharged is considerably larger than the amount of electricity required for the initial charge. It becomes small and initial charge / discharge efficiency becomes low. In addition, since the initial loss capacity 31a of the positive electrode active material and the corresponding capacity portion 33a corresponding to the initial loss capacity on the negative electrode side cannot contribute to charge and discharge after the second cycle, the electric capacity and energy density of the battery are increased. There was a problem that could not be done.

  On the other hand, Fig.3 (a) is a figure which shows the state immediately after battery production (namely, battery structure stage) in the lithium ion secondary battery of this invention. In the present invention, in order to solve the problem shown in FIG. 2, the capacity of the negative electrode used only in the initial charge can be utilized by using the second active material in the charged state together with the positive electrode. Is. As described with reference to FIG. 2, it is considered that a very small amount of impurities are involved in the battery voltage. That is, the block denoted by reference numeral 41 in the drawing indicates the theoretical capacity of the first positive electrode active material using the same solid solution positive electrode active material as the positive electrode active material of FIG. A block denoted by reference numeral 42 represents the theoretical capacity of the second positive electrode active material. A block denoted by reference numeral 43 indicates the theoretical capacity of the negative electrode active material similar to that shown in FIG.

  FIG.3 (b) is a figure which shows the intermediate charge state of the initial stage charge in the lithium ion secondary battery of this invention. When initial charging is started, charging of the positive electrode and the negative electrode active material proceeds. In particular, in the positive electrode, since the second positive electrode active material has already been fully charged (full charge state), charging of the first positive electrode active material proceeds.

FIG.3 (c) is a figure which shows the state (full charge state) in which the initial charge in the lithium ion secondary battery of this invention was completed. When the initial charging is further continued from the state of FIG. 3B, charging of the first positive electrode active material having a high charge / discharge potential further proceeds. On the other hand, charging proceeds similarly in the negative electrode. When both the positive and negative active materials are fully charged, the initial charging is completed. As described above, when charging is performed at a high potential exceeding 4.5 V on the basis of lithium metal, Li ₂ O is released from the positive electrode active material as a result of the progress of charging, and the irreversible capacity (= initial loss capacity 41a ) Part is formed.

  FIG.3 (d) is a figure which shows the intermediate discharge state of the initial stage discharge in the lithium ion secondary battery of this invention. Next, when the initial discharge of the battery that has been initially charged is started, in the positive electrode, the discharge of the portion 41b corresponding to the reversible capacity out of the theoretical capacity 41 of the first positive electrode active material proceeds, and the first positive electrode active A negative-side initial loss capacity corresponding capacity 43a corresponding to the initial loss capacity 41a of the substance remains. In the present invention, in addition to the reversible capacity of the first positive electrode active material, the capacity 42 of the second positive electrode active material is present in a charged state (reversible capacity). Therefore, the negative electrode side initial loss capacity correspondence capacity 43a corresponding to the initial loss capacity 41a of the first positive electrode active material is accepted by the second positive electrode active material added in the charged state at the battery configuration stage and continues to discharge. can do.

  FIG. 3 (e) is a diagram showing a state in which initial discharge in the lithium ion secondary battery of the present invention has been completed. When the initial charge is further continued from the state of FIG. 3D, the discharge of the second positive electrode active material capacity 42 proceeds in the positive electrode, and the negative electrode corresponds to the initial loss capacity 41a of the positive electrode active material. Discharge of the capacity 43a corresponding to the initial loss capacity on the negative electrode side proceeds. When the reversible capacity of both the positive and negative active materials is completely discharged, the initial discharge is completed. As described above, in the present invention, even when a high capacity positive electrode material of a solid solution system having a low initial charge / discharge efficiency is used, it can be utilized without generating a large amount of negative electrode material that cannot contribute to the charge / discharge capacity of the battery. Can be increased. In addition, during the second charge and discharge, the capacity 42 of the second positive electrode active material can be effectively utilized instead of the initial loss capacity 41a. It was also found that the second and subsequent charging / discharging did not form a large irreversible capacity such as the initial loss capacity 41a (the second discharging in Examples 1 and 5 and Comparative Example 1 in FIG. 7). (See contrast curve.) Therefore, high charge / discharge efficiency can be maintained even after the second time, and an improvement in the electric capacity and energy density of the battery can be achieved over a long period of time.

  In FIG. 3, for the sake of convenience, the first positive electrode active material and the second positive electrode active material are sequentially charged and discharged in the positive electrode, but in the actual charge and discharge, the first positive electrode active material is shown. The active material and the second positive electrode active material may be charged and discharged in parallel.

  FIG. 3 shows that the first positive electrode active material, the second positive electrode active material, and further the initial discharge of the negative electrode active material are completely performed. However, the technical scope of the present invention is limited to these. It is not done. In some cases, the capacity (theoretical capacity) of the negative electrode (active material layer) and the capacity (theoretical capacity) of the positive electrode (active material layer) are intentionally different. On the side, it may be partially uncharged.

  In the present invention, as in the case of the conventional lithium ion battery, the stage of configuring the battery = the state at the product stage is defined as the product of the invention, and it is necessary to bother the requirement to construct the battery. It can be said that there is no. However, for example, when a battery that has been initially charged and discharged as described with reference to FIGS. 2 and 3 is a product (= invention product), that is, the initial charge / discharge is performed as a constituent requirement of the invention (product manufacturing). In order to clarify that it is included in the technical scope (right range) of the present invention, the requirements for the stage of configuring the battery are defined. Therefore, as described above, the technical scope of the present invention also applies to the requirement of performing initial charge / discharge in the battery manufacturing stage or the electrode manufacturing stage having the same main positive electrode active material configuration of the present invention. Needless to say, it is included in the scope of rights. The electrode manufacturing stage is included in the battery configuration shown in FIG. 3, for example, by performing initial charge and discharge by using the negative electrode side as an appropriate target electrode and only the positive electrode as the constituent electrode of the present invention. This is because the same mechanism as described in 3 is performed on the positive electrode side. Therefore, what constituted the battery using such a positive electrode shall also be included in this invention. Needless to say, the “stage of constituting the battery” in this case refers to the positive electrode manufacturing stage before the initial charge / discharge. That is, in the positive electrode manufacturing stage before initial charge / discharge, the first positive electrode active material may be in a discharged state and the second positive electrode active material may be in a charged state. Therefore, in the battery assembled using the positive electrode after the initial charge / discharge (the state before the second charge), both the first positive electrode active material and the second positive electrode active material are in a discharged state. It can be said that. Such a battery is also included in the technical scope of the present invention.

  In the present invention, the main positive electrode active material is composed of two types, the first positive electrode active material may be in a discharged state at the battery configuration stage, and the second positive electrode active material may be in a charged state at the battery configuration stage. Preferably, the first positive electrode active material is a solid solution positive electrode material that is expected as a high-capacity material having a large electric capacity exceeding 200 mAh / g so that the electric capacity and energy density of the battery can be increased. It is desirable to use it. On the other hand, the second positive electrode active material is not particularly limited as long as it is of a different type from the first positive electrode active material and is in a charged state at the battery construction stage. A wide range of substances can be used. Preferably, the first positive electrode active material, particularly a material having a low initial charge / discharge efficiency, such as a high capacity solid solution positive electrode material, is desirable. Hereinafter, the main positive electrode active material which is a characteristic constituent feature of the present invention will be described in detail.

(First positive electrode active material)
The first positive electrode active material that can be used in the present invention is one of the main positive electrode active materials, and is in a discharged state at the battery construction stage. Preferably, it is desirable to use a solid solution positive electrode material that is expected as a high-capacity material having a large electric capacity exceeding 200 mAh / g so that the electric capacity and energy density of the battery can be increased as described above. Specifically, the following general formula

(Where x is 0 <x <1, M is one or more transition metals with an average oxidation state of 3 ⁺ , and M ¹ is one or more transition metals with an average oxidation state of 4 ⁺ The so-called solid-solution high-capacity positive electrode material represented by. In a lithium ion battery using a positive electrode material of the so-called solid solution system represented by the general formula: xLiMO ₂ · (1-x) Li ₂ M ¹ O ₃ , the battery is already charged at the battery construction stage (at the time of battery preparation). This is because the negative electrode capacity can be effectively utilized by using the positive electrode materials together as a positive electrode active material, and a lithium ion battery having a large capacity and excellent energy density can be configured.

  Here, x in the above formula may be a number satisfying 0 <x <1.

In addition, as the M of LiMO ₂ which is electrochemically active in the solid solution represented by the above general formula: xLiMO ₂ · (1-x) Li ₂ M ¹ O ₃ , the average oxidation state is 3 ⁺ There is no particular limitation as long as it is one or more transition metals. M in the above formula may be one or more elements selected from Mn, Ni, Co, Fe, V, and Cr, but preferably selected from Mn, Ni, Co, and Fe. One or more elements are desirable. This is because when these transition metals are used, a lithium ion battery having a higher capacity and a higher energy density can be produced.

The general _{formula: xLiMO 2 · (1-x} ) Li 2 M 1 O 3 in an electrochemically inert of solid solution represented _as the M ¹ of Li ² M 1 _{O 3,} average oxidation state It may be one or more transition metals that are 4 ⁺ and is not particularly limited. M ¹ in the above formula may be one or more elements selected from Mn, Zr, and Ti. This is because when these transition metals are used, a lithium ion battery having a higher capacity and a higher energy density can be produced.

Further, the method for producing the solid solution represented by the general formula: xLiMO ₂ · (1-x) Li ₂ M ¹ O ₃ is not particularly limited, and a conventionally known production method is appropriately used. be able to. For example, as shown in the Examples, the composite carbonate method can be used as follows. That is, a predetermined amount of, for example, nickel sulfate, cobalt sulfate, and manganese sulfate, each of which is a metal element corresponding to M and M ¹ in the above formula, such as nickel sulfate, cobalt sulfate, and manganese sulfate, is prepared to prepare a mixed solution thereof. Then, ammonia water was added dropwise to this until pH 7 was reached, and then a Na ₂ CO ₃ solution was further added dropwise to form a complex carbonate of Ni—Co—Mn (however, the M and M ¹ in the above formulas indicate the M - type of the metal complex carbonate of M ¹ is precipitated different), after suction filtration, washed with water, a predetermined temperature, a time (e.g., 5 hours at 120 ° C.) and dried. This is calcined at a predetermined temperature and time (for example, at 500 ° C. for 5 hours). A small excess of LiOH.H ₂ O was added thereto and mixed for a predetermined time (for example, 30 minutes) in an automatic mortar. Thereafter, the main calcination is performed at a predetermined temperature and time (for example, at 900 ° C. for 12 hours) and then rapidly cooled using liquid nitrogen, whereby the above general formula: xLiMO ₂ · (1-x) Li ₂ M A solid solution represented by ¹ O ₃ can be produced. The last rapid cooling using liquid nitrogen is not particularly necessary, but can be said to be a useful processing operation in that a solid solution can be produced with a very beautiful state by performing such processing. .

The solid solution represented by the above general formula: xLiMO ₂ · (1-x) Li ₂ M ¹ O ₃ is identified by X-ray diffraction (XRD), inductively coupled plasma (as in the examples described later). ICP) can be analyzed using elemental analysis.

(Second positive electrode active material)
The second positive electrode active material that can be used in the present invention is one of the main positive electrode active materials and is different from the first positive electrode active material, and is charged at the battery configuration stage (at the time of battery manufacture). If it is in. Accordingly, various types of conventionally known positive electrode active materials can be widely used, and although there is no particular limitation, initial charge and discharge like the first positive electrode active material, particularly a high capacity solid solution system positive electrode material. Materials that are not less efficient are desirable.

  Specifically, the second positive electrode active material is charged with respect to the total amount of lithium that can be occluded in the active material by discharging in a potential range of 5 V to 2 V with respect to lithium metal. It is desirable that the battery is in a charged state capable of taking in 70% or more of lithium. This is because the positive electrode active material releases lithium ions during charging, occludes lithium ions during discharge, and takes them into the positive electrode active material. Therefore, substantially 100% of the lithium in the positive electrode active material is released in the fully charged state, and the lithium occlusion site is in an empty state (= a charged state in which 100% of lithium can be taken up). On the other hand, in a state where the battery is almost completely discharged to a predetermined potential (2 V), lithium is occluded (taken in) in the lithium occlusion site in the positive electrode active material, and there is no room for lithium to be taken up (= more than that) (Discharged state). Therefore, in other words, the second positive electrode active material has a charge state of 70% or more with respect to a discharge capacity in a potential range of 2 V to 5 V with respect to lithium metal in the second positive electrode active material. Is preferable. This is because the effect of the present invention is small if the state of charge at the battery construction stage (battery manufacturing) is too low.

  Accordingly, it is more preferable to use a charged state in which lithium is taken in by 85% or more, and particularly preferably substantially 100% lithium, that is, a material that does not substantially contain lithium as described later. In other words, it can be said that it is more preferably 85% or more, particularly preferably substantially 100% charged state with respect to the discharge capacity in the potential range of 2V to 5V with respect to lithium metal.

  In addition, as the second positive electrode active material, a material having a large charge / discharge capacity can increase the energy density of a lithium ion battery to be produced, and therefore, a material that does not substantially contain lithium and has a large charge / discharge capacity is particularly desirable. is there. The combined use of the second positive electrode active material in a charged state with a large charge / discharge capacity is superior in that a lithium ion battery having a higher capacity and a higher energy density can be produced.

  From such a viewpoint, it is desirable that the second positive electrode active material that is in a charged state in the battery configuration stage substantially does not contain lithium. Here, “substantially” means that 5% by mass or less of lithium is allowed to be mixed with respect to the total amount of the second positive electrode active material. However, it goes without saying that an active material material substantially containing lithium may be used as the second positive electrode active material beyond the range specified above as long as the effects of the present invention are not impaired. Nor.

  The second positive electrode active material which does not substantially contain lithium is not particularly limited, but is preferably an oxide of a transition metal, a phosphoric acid compound, a sulfuric acid compound, a tungstic acid compound, a molybdic acid compound and What consists of one or more types chosen from a vanadic acid compound is desirable. This is because it can be an effective second positive electrode active material substantially free of lithium. By using this second positive electrode active material together, a lithium ion battery having a high capacity and a high energy density can be produced.

  The transition metal oxide is not particularly limited, and for example, vanadium oxides such as manganese dioxide and vanadium pentoxide can be used. Among these, manganese dioxide having a large charge / discharge capacity and appropriate oxidation-reduction potential can be used as a preferred second positive electrode active material. The use of manganese dioxide as the second positive electrode active material is excellent in that a lithium ion battery having a higher capacity and a higher energy density can be produced.

The phosphoric acid compound is not particularly limited, and for example, FePO ₄ can be used. Fe ₂ (SO ₄ ) ₃ having an appropriate redox potential can be used as a preferred second positive electrode active material.

  Content of a 2nd positive electrode active material is 5-50 mass% with respect to positive electrode active material whole quantity, Preferably it is 10-40 mass%. When the content of the second positive electrode active material is 5% by mass or more, the blending balance with the first positive electrode active material is excellent, and the second charged state corresponding to the initial loss capacity of the first positive electrode active material is obtained. The charge capacity by the positive electrode active material can be ensured. As a result, the amount of the negative electrode active material that does not contribute to the battery capacity can be further reduced, and the electric capacity and energy density of the lithium ion battery can be increased. In addition, when the content of the second positive electrode active material is 50% by mass or less, the mass of the positive electrode active material is not significantly increased, and a predetermined amount of the high-capacity first positive electrode active material can be secured, Provides a high-energy battery that has an excellent blending balance with the first positive electrode active material and can increase the amount of electricity stored per unit mass of the positive electrode even if the initial charge / discharge efficiency of the first positive electrode active material is low. It is excellent in that it can be done.

  In the present invention, the positive electrode active material is classified (classified) into one of the two main positive electrode active materials, that is, the above-described charged state and discharged state. However, other positive electrode active materials may be included as necessary.

  The above is the description regarding the characteristic structural requirements of the lithium ion battery of the present invention, and the other structural requirements are not particularly limited. Therefore, in the following, the configuration requirements other than the characteristic configuration requirements of the lithium ion battery of the present invention will be described focusing on the configuration requirements of the typical lithium ion battery described with reference to FIG. However, the present invention is not limited to these.

[Current collector (positive electrode current collector and negative electrode current collector)]
The positive electrode current collector 11 and the negative electrode current collector 14 are not particularly limited, and conventionally known ones can be appropriately used. Specifically, it is composed of at least one current collector material selected from the group consisting of iron, chromium, nickel, manganese, titanium, molybdenum, vanadium, niobium, aluminum, copper, silver, gold, platinum, and carbon. Current collectors can be used.

  The thicknesses of the positive electrode current collector 11 and the negative electrode current collector 14 are not particularly limited, but each current collector is usually about 1 to 100 μm, preferably about 5 to 20 μm. However, even if it is outside the above range, it is included in the technical scope of the present invention as long as it does not impair the effects of the present invention.

[Electrodes (positive electrode and negative electrode)]
The configuration of the positive electrode (positive electrode active material layer) 12 and the negative electrode (negative electrode active material layer) 15 may be any as long as it uses the main positive electrode active material which is the characteristic configuration of the present invention described above. There is no particular limitation, and a known negative electrode can be applied.

  As the positive electrode active material, it is only necessary to use the main positive electrode active material which is a characteristic configuration of the present invention. Since the main positive electrode active material has already been described, the description thereof is omitted here.

The negative electrode active material is not particularly limited, and may be appropriately selected according to the type of battery and usage. Any negative electrode active material usually used in lithium ion secondary batteries may be used. Specifically, carbon or lithium-transition metal composite oxide can be preferably used. Carbon or lithium-transition metal composite oxide as the negative electrode active material is not particularly limited, and is a crystalline carbon such as natural graphite, artificial graphite, soft carbon or hard carbon (non-graphitizable carbon material). Carbon such as raw material and amorphous carbon material; lithium-tin alloy, lithium-silicon alloy, and lithium alloy obtained by adding other elements to these; lithium-titanium composite oxide (lithium titanate: Li ₄ Ti ₅ O ₁₂ ), And the like. However, the present invention is not limited to these. These may be used alone or in combination of two or more.

  When the optimum particle size is different for expressing the unique effect of each substance, the optimum particle size for expressing each unique effect may be blended and used. It is not always necessary to make the diameter uniform.

  The thickness of the positive electrode (positive electrode active material layer: one side) 12 may be appropriately determined in consideration of the intended use of the battery (evaluation of output, importance of energy, etc.) and ion conductivity, and is usually 1 to 500 μm, preferably 20 to It is about 300 μm.

  The thickness of the negative electrode (negative electrode active material layer: one side) 15 may be appropriately determined in consideration of the intended use of the battery (output-oriented, energy-oriented, etc.) and ion conductivity, and is usually 1 to 500 μm, preferably 30 to 30 μm. It is about 200 μm.

  The positive electrode (positive electrode active material layer: one side) 12 and the negative electrode (negative electrode active material layer) 15 are all made by sputtering, vapor deposition, CVD, PVD, ion plating, and thermal spraying, in addition to the usual method of applying (coating) slurry. It can be formed by any method.

  The electrodes (the positive electrode 12 and the negative electrode 15) may include an electrolyte (all solid polymer, gel, electrolyte solution, etc.) containing a conductive additive for enhancing electronic conductivity, a binder, and a lithium salt.

  Examples of the conductive aid include acetylene black, carbon black, graphite, and carbon fiber. By including a conductive additive, the conductivity of electrons generated at the electrode can be increased, and the battery performance can be improved.

  Examples of the binder include polyvinylidene fluoride (PVdF), styrene butadiene rubber, and polyimide. However, it is not necessarily limited to these.

  Examples of the all solid polymer electrolyte include ion conductive polymers (solid polymer electrolytes) including lithium salts such as polyethylene oxide (PEO), polypropylene oxide (PPO), and copolymers thereof.

  As the solvent for the electrolytic solution, a nonaqueous solvent selected from propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, and the like is used, but is not limited thereto. Various additives may be used.

  As the gel electrolyte, a matrix polymer such as PEO or PVdF containing the above-described electrolyte solution can be used, but is not limited thereto.

What is necessary is just to select the lithium salt used according to the kind of battery. The electrolyte supporting salt (lithium _{salt), LiPF 6, LiBF 4,} LiClO 4, LiAsF 6, LiTaF 6, LiAlCl 4, Li 2 B 10 Cl 10 inorganic acid anion salts such _{as, LiCF 3 SO 3, Li (} CF Organic acid anion salts such as ₃ SO ₂ ) ₂ N and Li (C ₂ F ₅ SO ₂ ) ₂ N, or a mixture thereof can be used. However, it is not necessarily limited to these.

  The amount of electrode components such as active materials, conductive additives, binders, electrolytes (polymer matrix, ion conductive polymers, electrolytes, etc.), electrolyte support salts (lithium salts), etc. It is preferable to determine in consideration of ionic conductivity.

[Electrolyte layer]
Specifically, as the electrolyte layer, conventionally known materials include (a) polymer gel electrolyte (gel polymer electrolyte), (b) all solid polymer electrolyte (polymer solid electrolyte, inorganic solid electrolyte), ( c) Liquid electrolytes (electrolytic solutions) or (d) Separators impregnated with these electrolytes (including nonwoven fabric separators and polyethylene or polypropylene microporous membrane separators) can be used.

(A) Gel polymer electrolyte (polymer gel electrolyte)
The gel polymer electrolyte (polymer gel electrolyte) refers to an electrolyte solution held in a polymer matrix. By using a gel polymer electrolyte as the electrolyte, the fluidity of the electrolyte is lost, and it is easy to cut off the ionic conductivity between each layer by suppressing the outflow of the electrolyte to the current collector layer such as a conductive polymer film. Is excellent.

Examples of the polymer matrix (polymer) used as the polymer gel electrolyte or the host polymer of the gel electrolyte include polymers having polyethylene oxide in the main chain or side chain (PEO), polymers having polypropylene oxide in the main chain or side chain ( PPO), polyethylene glycol (PEG), polyacrylonitrile (PAN), polymethacrylic acid ester, polyvinylidene fluoride (PVdF), a copolymer of polyvinylidene fluoride and hexafluoropropylene (PVdF-HFP), poly (methyl methacrylate) ( PMMA) and copolymers thereof are desirable, and among them, PEO, PPO and copolymers thereof, or PVdF-HFP is desirably used. Moreover, as a plasticizer, it is possible to use the electrolyte solution normally used for a lithium ion battery. And such electrolyte, which electrolyte salt dissolved in a solvent, as the _{electrolyte, LiPF 6, LiBF 4, LiClO} 4, LiAsF 6, LiTaF 6, LiAlCl 4, Li 2 B 10 Cl 10 inorganic acid anions such as As a solvent, at least one selected from organic acid anion salts such as ionic salt, LiCF ₃ SO ₃ , Li (CF ₃ SO ₂ ) ₂ N, Li (C ₂ F ₅ SO ₂ ) ₂ N, etc. Ethylene carbonate (EC), propylene carbonate (PC), γ-butyrolactone (GBL), dimethyl carbonate (DMC), diethyl carbonate (DEC) and mixtures thereof are preferred.

  The ratio of the electrolytic solution in the gel electrolyte in the present invention is not particularly limited, but is preferably about several mass% to 98 mass% from the viewpoint of ionic conductivity. The present invention is particularly effective for a gel electrolyte having a large amount of electrolytic solution in which the proportion of the electrolytic solution is 70% by mass or more.

(B) All solid electrolyte (all solid polymer electrolyte, polymer solid electrolyte, inorganic solid electrolyte)
The use of an all solid electrolyte as the electrolyte is superior in that the fluidity of the electrolyte is lost, the electrolyte does not flow out to the current collector layer, and the ion conductivity between the layers can be blocked.

Examples of the all solid polymer electrolyte include known solid polymer electrolytes such as PEO, PPO, and copolymers thereof, and inorganic solid electrolytes having ion conductivity such as ceramics. The solid polymer electrolyte contains a lithium salt in order to ensure ionic conductivity. As the lithium salt, LiBF ₄ , LiPF ₆ , LiN (SO ₂ CF ₃ ) ₂ , LiN (SO ₂ C ₂ F ₅ ) ₂ , or a mixture thereof can be used.

(C) Liquid electrolyte (electrolyte)
Examples of the electrolytic solution include those obtained by dissolving an electrolyte salt in a solvent. Here, as the _{electrolyte, LiPF 6, LiBF 4, LiClO} 4, LiAsF 6, LiTaF 6, LiAlCl 4, Li 2 B 10 Cl 10 inorganic acid anion salts such _{as, LiCF 3 SO 3, Li (} CF 3 SO 2 ) At least one selected from organic acid anion salts such as ₂ N, Li (C ₂ F ₅ SO ₂ ) ₂ N, and the solvent is EC, PC, GBL, DMC, DEC and mixtures thereof Is desirable.

(D) Separator impregnated with the above electrolyte (including non-woven separator, polyethylene or polypropylene microporous membrane separator)
As the electrolyte that can be impregnated in the separator, the same electrolytes as those already described (a) to (c) can be used.

  Examples of the separator include a porous sheet and a nonwoven fabric made of a polymer that absorbs and holds the electrolyte.

  As the porous sheet, for example, a microporous separator can be used. Examples of the polymer include polyolefins such as polyethylene (PE) and polypropylene (PP); laminates having a three-layer structure of PP / PE / PP, polyimide, and aramid. The thickness of the separator cannot be unambiguously defined because it varies depending on the intended use, but a secondary battery for driving a motor such as an electric vehicle (EV), a hybrid electric vehicle (HEV), a fuel cell vehicle (FCV), etc. In other applications, it is desirable that the thickness is 4 to 60 μm in a single layer or multiple layers. The separator preferably has a fine pore size of 1 μm or less (usually a pore size of about several tens of nm) and a porosity of 20 to 80%.

  As the nonwoven fabric, cotton, rayon, acetate, nylon, polyester; polyolefins such as PP and PE; conventionally known materials such as polyimide and aramid are used alone or in combination. The bulk density of the nonwoven fabric is not particularly limited as long as sufficient battery characteristics can be obtained by the impregnated polymer gel electrolyte. The porosity of the nonwoven fabric separator is preferably 50 to 90%. Furthermore, the thickness of the nonwoven fabric separator may be the same as that of the electrolyte layer, preferably 5 to 200 μm, particularly preferably 10 to 100 μm. When the thickness is less than 5 μm, the electrolyte retention deteriorates, and when it exceeds 200 μm, the resistance increases.

[Seal part]
The seal (also referred to as the peripheral insulating layer) is used to prevent the adjacent current collectors in the battery from contacting each other and short-circuiting due to slight unevenness at the end of the laminated electrode. It arrange | positions in the peripheral part of the cell layer (it is not shown in FIG. 1). As the seal portion, for example, polyolefin resin such as PE and PP, epoxy resin, rubber, polyimide and the like can be used, and polyolefin resin is preferable from the viewpoint of corrosion resistance, chemical resistance, film forming property, economy and the like. However, it is not limited to these.

[Tab (positive tab and negative tab)]
Tabs (positive electrode tab 18 and negative electrode tab 19) that are electrically connected to each current collector are taken out of the battery exterior material for the purpose of taking out the current outside the battery. Specifically, as shown in FIG. 1, a positive electrode tab 18 electrically connected to each positive electrode current collector 11 and a negative electrode tab 19 electrically connected to each negative electrode current collector 14 are battery exterior materials. 22 is taken out of the laminate sheet.

  The material which comprises a tab (the positive electrode tab 18 and the negative electrode tab 19) is not restrict | limited in particular, The well-known highly electroconductive material conventionally used as a tab for lithium ion batteries can be used. As a constituent material of the tab, for example, metal materials such as aluminum, copper, titanium, nickel, stainless steel (SUS), and alloys thereof are preferable, and aluminum, nickel, and the like are more preferable from the viewpoint of light weight, corrosion resistance, and high conductivity. Is preferred.

[Positive electrode and negative electrode lead]
The positive terminal lead 20 and the negative terminal lead 21 are also used as necessary. For example, when the positive electrode tab 18 and the negative electrode tab 19 serving as output electrode terminals are directly taken out from the current collectors 11 and 14, the positive electrode terminal lead 20 and the negative electrode terminal lead 21 may not be used.

  As the material of the positive terminal lead 20 and the negative terminal lead 21, a terminal lead used in a known lithium ion battery can be used. In addition, the part taken out from the battery outer packaging material 22 has a heat insulating property so as not to affect a product (for example, an automobile part, particularly an electronic device, etc.) by touching a peripheral device or wiring and causing a leakage. It is preferable to coat with a heat shrinkable tube or the like.

[Battery exterior materials]
As the battery exterior member 22, a conventionally known metal can case can be used, and a bag-like case that can cover a power generation element (battery element) using a laminate film containing aluminum can be used. For example, a laminate film having a three-layer structure in which PP, aluminum, and nylon are laminated in this order can be used as the laminate film, but the laminate film is not limited thereto.

[External structure of lithium-ion battery]
FIG. 4 is a perspective view showing the appearance of a laminated flat (non-bipolar) lithium ion secondary battery which is a typical embodiment of the lithium ion battery according to the present invention.

  As shown in FIG. 4, the stacked flat lithium ion secondary battery 50 has a rectangular flat shape, and a positive electrode tab 58 and a negative electrode tab 59 for taking out electric power from both sides thereof. Has been pulled out. The power generation element (battery element) 57 is wrapped by the battery outer packaging material 52 of the lithium ion secondary battery 50, and the periphery thereof is heat-sealed. The power generation element (battery element) 57 includes a positive electrode tab 58 and a negative electrode tab 59. It is sealed in a state where it is pulled out to the outside. Here, the power generation element (battery element) 57 corresponds to the power generation element (battery element) 17 of the non-bipolar lithium ion secondary battery 10 shown in FIG. Layer) 12, electrolyte layer 13, and negative electrode (negative electrode active material layer) 15, a plurality of single battery layers (single cells) 16 are laminated.

  The lithium ion battery of the present invention is not limited to the stacked flat shape as shown in FIG. 1, and the wound lithium ion battery may be of a cylindrical shape. The cylindrical shape may be deformed into a rectangular flat shape, and is not particularly limited.

  The tabs 58 and 59 shown in FIG. 4 are not particularly limited, and the positive electrode tab 58 and the negative electrode tab 59 may be pulled out from the same side, or the positive electrode tab 58 and the negative electrode tab 59 may be pulled out. However, the present invention is not limited to the one shown in FIG. 4, for example. Further, in a wound type lithium ion battery, instead of a tab, for example, a terminal may be formed using a cylindrical can (metal can).

  The lithium ion battery of the present invention is suitably used as a power source for driving a vehicle or an auxiliary power source that requires a high volume energy density and a high volume output density as a large capacity power source for an electric vehicle, a hybrid electric vehicle, a fuel cell vehicle, etc. Can do.

[Battery]
The assembled battery of the present invention is constituted by connecting a plurality of lithium ion batteries of the present invention. Specifically, at least two or more are used, and are configured by serialization, parallelization, or both. Capacitance and voltage can be freely adjusted by paralleling in series. In the assembled battery of the present invention, the non-bipolar lithium ion battery and the bipolar lithium ion battery of the present invention are used, and a plurality of these are combined in series, in parallel, or in series and in parallel. Can also be configured.

  5 is an external view of a typical embodiment of the assembled battery according to the present invention, FIG. 5A is a plan view of the assembled battery, FIG. 5B is a front view of the assembled battery, and FIG. It is a side view of an assembled battery.

  As shown in FIG. 5, an assembled battery 300 according to the present invention forms a small assembled battery 250 in which a plurality of lithium ion batteries of the present invention are connected in series or in parallel, and can be attached and detached. A plurality of small battery packs 250 connected in series or in parallel to provide a large capacity and large output suitable for vehicle drive power supplies and auxiliary power supplies that require high volume energy density and high volume output density 300 can also be formed. 5A is a plan view of the assembled battery, FIG. 5A is a front view, and FIG. 5C is a side view. The small assembled battery 250 that can be attached and detached is provided with an electrical connection means such as a bus bar. The assembled battery 250 is stacked in a plurality of stages using the connection jig 310. How many non-bipolar or bipolar lithium-ion batteries are connected to create the assembled battery 250, and how many assembled batteries 250 are stacked to produce the assembled battery 300 depends on the vehicle mounted. What is necessary is just to determine according to the battery capacity and output of (electric vehicle).

[vehicle]
The vehicle of the present invention is characterized in that the lithium ion battery of the present invention or an assembled battery formed by combining a plurality of these is mounted. In the present invention, since a battery having a high capacity and a high energy density can be configured, a plug-in hybrid electric vehicle having a long EV travel distance or an electric vehicle having a long charge travel distance can be configured by mounting such a battery. In other words, the lithium ion battery of the present invention or an assembled battery formed by combining a plurality of these can be used as a power source for driving a vehicle. The lithium ion battery of the present invention or an assembled battery obtained by combining a plurality of these batteries is a vehicle, for example, a hybrid vehicle, a fuel cell vehicle, an electric vehicle (all automobiles such as automobiles, commercial vehicles such as passenger cars, trucks, and buses, This is because it can be used for motorcycles (including motorcycles) and tricycles (in addition to mini vehicles, etc.)) to provide a long-life and highly reliable vehicle. However, the application is not limited to automobiles, and it can be applied to various power sources for other vehicles, for example, moving bodies such as trains, and can be used as a power source for mounting such as an uninterruptible power supply. It is also possible to do.

  FIG. 6 is a conceptual diagram of a vehicle equipped with the assembled battery of the present invention.

  As shown in FIG. 6, in order to mount the assembled battery 300 on a vehicle such as the electric vehicle 400, the battery pack 300 is mounted under the seat at the center of the vehicle body of the electric vehicle 400. This is because if it is installed under the seat, the interior space and the trunk room can be widened. The place where the assembled battery 300 is mounted is not limited to the position under the seat, but may be a lower part of the rear trunk room or an engine room in front of the vehicle. The electric vehicle 400 using the assembled battery 300 as described above has high durability and can provide sufficient output even when used for a long period of time. Furthermore, it is possible to provide electric vehicles and hybrid vehicles that are excellent in fuel efficiency and running performance. A vehicle equipped with the assembled battery of the present invention can be widely applied to a hybrid vehicle, a fuel cell vehicle and the like in addition to an electric vehicle as shown in FIG.

[Method of manufacturing lithium ion battery]
Next, the method for producing the lithium ion battery of the present invention is not particularly limited except for the method for producing a solid solution system positive electrode material suitable as the first positive electrode active material described above. The method can be applied.

  Therefore, below, it demonstrates about the manufacturing method of the lithium ion battery of this invention other than the manufacturing method of the solid solution system positive electrode material demonstrated above. However, the production method of the present invention is not limited to these.

  To make a battery with an electrolyte as an electrolyte, the negative electrode is slightly enlarged and cut out from the positive electrode and negative electrode prepared by applying (coating) an electrode slurry containing an electrode material such as an active material or a conductive additive to both sides of the current collector. Each was dried for one day in a vacuum dryer at 90 ° C. and used. Between the positive electrode and the negative electrode, the positive electrode and the negative electrode are alternately laminated so that the outermost electrode becomes a negative electrode through a porous film such as polypropylene having an appropriate thickness (for example, about 25 μm). Bundled and welded with lead, and this laminate was placed in an aluminum laminate film back with a structure in which the positive and negative lead were taken out, and the electrolyte was injected with a liquid injector, and sealed under reduced pressure. Battery.

  In addition to electrolyte batteries, electrolyte batteries, gel batteries, all-solid polymer batteries, and bipolar batteries using the electrolytes listed here can be produced by our well-known technology, so they are omitted here. To do.

  The effects of the present invention will be described using the following examples and comparative examples. However, the technical scope of the present invention is not limited only to the following examples.

1. Electrode Material First, the solid solution positive electrode material of the first positive electrode active material in a discharged state at the battery construction stage was synthesized as follows using a composite carbonate method. A predetermined amount of nickel sulfate, cobalt sulfate, and manganese sulfate was weighed to prepare a mixed solution thereof. Aqueous ammonia was added dropwise to the mixed solution until pH 7, and a Na ₂ CO ₃ solution was further added dropwise to precipitate Ni—Co—Mn complex carbonate. After suction filtration, washed with water, and at 120 ° C. Dried for 5 hours. This was calcined at 500 ° C. for 5 hours. A small excess of LiOH.H ₂ O was added thereto and mixed for 30 minutes in an automatic mortar. Thereafter, the main calcination was performed at 900 ° C. for 12 hours, followed by rapid cooling using liquid nitrogen. Thereby, the solid solution positive electrode materials used in Examples 1 to 4 and Comparative Example 1 shown in Table 1 below and the solid solution positive electrode materials used in Example 5 and Comparative Example 2 were respectively synthesized.

As the γ-manganese dioxide as the second positive electrode active material in a charged state at the battery construction stage, electrolytic manganese dioxide obtained by heating and drying at 400 ° C. for 6 hours in the atmosphere was used in Examples 1 to 3 and 5. In addition, another ferric sulfate anhydrous (Fe ₂ (SO ₄ ) ₃ ), which is another second positive electrode active material charged in the battery construction stage, was synthesized in accordance with literature methods and used in Example 4 (J. Power Sources, 26 (1987) 403.).

As the negative electrode active material, graphite having an average particle size of 20 μm was used. PVdF was used for the binder, and acetylene black was used as the conductive additive. An aluminum foil with a thickness of 20 μm was used for the positive electrode current collector, and a copper foil with a thickness of 15 μm was used for the negative electrode current collector. As the electrolytic solution, 1M LiPF ₆ EC: DEC (3: 7 (volume ratio)) (where EC is ethylene carbonate and DEC is diethyl carbonate) was used.

2. Production of Electrode The production of the positive electrode was carried out by mixing the first positive electrode active material and the second positive electrode active material according to the composition ratio shown in Table 1 for each Example and Comparative Example. Electrode composition ratio is positive electrode active material (Example is first positive electrode active material + total amount of second positive electrode active material, comparative example is only first positive electrode active material): Acetylene black: PVdF = 86: 7: 7 ( (Mass ratio), an appropriate amount of NMP (N-methyl-2-pyrrolidone) was added thereto, and the mixture was well stirred and mixed with a homogenizer. Thereafter, a certain amount of this slurry was applied to an aluminum foil using a die coater and dried. In this way, the positive electrode (positive electrode active material layer) is formed on both surfaces of the aluminum foil, and is pressed by a roll press so that the positive electrode active material layer portion is 50 mm × 100 mm, and the positive electrode active material layer is Cut out leaving no lead part. The amount of the active material per unit area was adjusted by repeating the coating so that the ratio of the active material density of the graphite negative electrode was as shown in Table 1.

  In the production of the negative electrode, the mass ratio of graphite (negative electrode active material), acetylene black, and PVdF was 88: 4: 8. A negative electrode active material, PVdF, and an appropriate amount of NMP were added to a homogenizer container and well stirred and mixed to prepare a slurry. This slurry was applied onto a copper foil using a die coater and dried. As with the positive electrode, a negative electrode (negative electrode active material layer) is formed on both sides of the copper foil, and pressed so that the negative electrode active material layer portion becomes 55 mm × 105 mm and the lead portion without the negative electrode active material layer is formed. Cut out. The thickness of the negative electrode active material layer (the negative electrode active material layer on one side of the copper foil current collector) was 80 μm at the time of completion.

3. Production of Battery Each of the positive electrode and the negative electrode cut out above was dried for one day in a 90 ° C. vacuum dryer and used. Between the positive electrode and the negative electrode, five positive electrodes and seven negative electrodes are alternately laminated with a 25 μm thick polypropylene porous film interposed between the positive electrode and the negative electrode, and each positive electrode and negative electrode are bundled. The lead was welded, and the laminate was taken out of the positive and negative lead leads, placed in an aluminum laminate film back, injected with an electrolyte with a liquid injector, sealed under reduced pressure, and sealed. It was. In addition, the seal | sticker at this time is a temporary seal | sticker, and it has the structure which can be opened again after charge / discharge and can be sealed again.

Thus, in the batteries of Examples 1 to 3, the solid solution 0.3Li ₂ MnO ₃ .0.7LiMn _0.5 Ni _0.5 O ₂ was used as the first positive electrode active material, and manganese dioxide was used as the second positive electrode active material. Made as a material. The battery of Comparative Example 1 was fabricated using the same first positive electrode active material as in Examples 1 to 3 without using the second positive electrode active material. The battery of Example 4 was manufactured by using the same first positive electrode active material as in Examples 1 to 3 and using the second positive electrode active material as anhydrous ferric sulfate. Moreover, the battery of Example 5 uses the solid solution 0.3Li ₂ MnO ₃ .0.7LiMn _0.33 Ni _0.33 Co _0.33 O ₂ as the first positive electrode active material, and the second positive electrode active material. A battery was prepared using manganese dioxide. In the battery of Comparative Example 2, the first positive electrode active material was the same as that of Example 5, and a battery was produced without using the second positive electrode active material. Table 1 shows an outline of the electrode configuration of the batteries of the examples and comparative examples.

4). Electrode evaluation The battery was evaluated in a high-temperature bath at a temperature of 45 ° C. At 0.125 A, the voltage range was 2 V to 4.6 V, and constant current was used. In order to explain the effect of the present invention, a second discharge curve is shown in FIG. In FIG. 7, the discharge curves of the battery of Comparative Example 1 and the batteries of Example 1 and Example 5 are compared. It can be seen that the discharge capacity of the battery of Example 1 using manganese dioxide as the second positive electrode active material is increased compared to Comparative Example 1. In addition, it can be seen that the discharge capacity is similarly increased in Example 5 using anhydrous ferric sulfate (Fe ₂ (SO ₄ ) ₃ ) as the second positive electrode active material.

  The evaluation results of the fabricated battery are summarized in Table 1. Table 1 shows not only the discharge capacity of the battery but also the ratio of the energy density of the battery calculated based on the discharge curve. The battery capacity ratio in Table 1 indicates the ratio of the second discharge capacity of each battery of Examples 1 to 4 when the second discharge capacity of the battery of Comparative Example 1 is 1. Similarly, the ratio of the second discharge capacity of the battery of Example 5 when the second discharge capacity of the battery of Comparative Example 2 is 1 is shown. As for the energy density ratio of the batteries in Table 1, the second discharge of each battery of Examples 1 to 4 when the energy density of the battery calculated from the second discharge curve of the battery of Comparative Example 1 is 1. The battery energy density ratio calculated from the curve is shown. Similarly, when the battery energy density calculated from the second discharge curve of the battery of Comparative Example 2 is 1, the ratio of the battery energy density calculated from the second discharge curve of the battery of Example 5 is Show.

The solid solution 1 in Table 1 represents the solid solution 0.3Li ₂ MnO ₃ .0.7LiMn _0.5 Ni _0.5 O ₂ .

The solid solution 2 in Table 1 is solid solution 0.3Li ₂ MnO ₃ .0.7LiMn _0.33 Ni _0.33 Co _0.33 O ₂ (= 0.3Li ₂ MnO ₃ .0.7LiMn _1/3 Ni _{1 / 3} Co
_1/3 O ₂ ).

  As can be seen from Table 1 above, by using the second positive electrode active material in the charged state at the battery preparation stage, even if a high capacity solid solution positive electrode active material having a considerably poor initial charge / discharge efficiency is used, the negative electrode (active material capacity) It can be seen that a battery excellent in the amount of electricity and energy density of the battery can be constructed without wasting.

  Furthermore, when an electric vehicle is configured using the lithium ion battery of the present invention, the battery energy density is high, so the cruising range of the electric vehicle can be extended, the amount of battery load of the plug-in hybrid electric vehicle can be reduced, and the hybrid electric vehicle can be reduced. It is possible to further improve the performance of automobiles. As a result, it is expected that the spread of electric vehicles can be promoted, which contributes greatly to environmental and energy problems.

10 Lithium ion battery,
11 positive electrode current collector,
12 positive electrode (positive electrode active material layer),
13 electrolyte layer,
14 negative electrode current collector,
14a outermost layer negative electrode current collector,
15 negative electrode (negative electrode active material layer),
16 single cell layer (= battery unit or single cell),
17, 57 Power generation element (battery element; laminate),
18, 58 positive electrode tab,
19, 59 negative electrode tab,
20 positive terminal lead,
21 negative terminal lead,
22, 52 Battery exterior material (for example, laminate film),
31 A block representing the theoretical capacity of a solid solution positive electrode active material,
31a Initial loss capacity of positive electrode active material,
31b The initial reversible capacity of the positive electrode active material,
33, 43 Blocks representing the theoretical capacity of the negative electrode active material,
33a The amount corresponding to the initial loss capacity corresponding to the negative electrode side corresponding to the initial loss capacity of the positive electrode active material,
41 A block representing the size of the theoretical capacity of the first positive electrode active material,
41a Initial loss capacity of the first positive electrode active material,
41b the initial reversible capacity of the first positive electrode active material,
42 a block representing the theoretical capacity of the second positive electrode active material,
43a Initial loss capacity corresponding capacity on the negative electrode side corresponding to the initial loss capacity of the first positive electrode active material,
50 lithium ion battery,
250 small battery pack,
300 battery packs,
310 connection jig,
400 electric car,
P A straight line representing the potential of the positive electrode,
N A straight line representing the potential of the negative electrode.

Claims (5)

In a lithium ion battery, there are two main cathode active materials,
The first positive electrode active material, which is one of the main positive electrode active materials, is a stage that constitutes a battery, and is in a discharged state before the initial charge and discharge .
The second positive electrode active material, which is one of the main positive electrode active materials, is in a stage of constituting a battery, and is in a charged state before performing initial charge / discharge ,
The first positive electrode active material has the following general formula
(Where, x is 0 <x <1, M is Mn average oxidation state is ^{3 +, Ni, Co, Fe} , V, one or more transition metal composed is selected from Cr, ^{M 1} a solid solution represented by a one or more transition metals selected from the average oxidation state is 4 ⁺ Mn, Zr and Ti.),
The lithium ion battery, wherein the second positive electrode active material is made of at least one selected from a phosphoric acid compound and a sulfuric acid compound .   The content of the first positive electrode active material is 50 to 95% by mass with respect to the total amount of the positive electrode active material, and the content of the second positive electrode active material is 5 to 50% by mass with respect to the total amount of the positive electrode active material. The lithium ion battery according to claim 1, wherein the battery is a lithium ion battery.   The content of the first positive electrode active material is 60 to 90% by mass with respect to the total amount of the positive electrode active material, and the content of the second positive electrode active material is 10 to 40% by mass with respect to the total amount of the positive electrode active material. The lithium ion battery according to claim 1, wherein the lithium ion battery is provided.   4. The lithium ion battery according to claim 1, wherein M is one or more elements selected from Mn, Ni, Co, and Fe. The sulfuric acid _compound, a lithium ion battery according to any one of claims 1 to 4, wherein the Fe 2 _{(SO 4) 3.}