JP6071243B2 - Method for producing electrode for non-aqueous electrolyte secondary battery - Google Patents

Description

  The present invention provides an electrode for a nonaqueous electrolyte secondary battery having a high electrode capacity per unit volume and an electrode capacity per unit mass of an active material and good charge / discharge cycle characteristics, and a nonaqueous electrolyte secondary battery using the same The present invention relates to a battery and a method for producing the electrode for the nonaqueous electrolyte secondary battery.

  In recent years, non-aqueous electrolyte secondary batteries have become widespread for reasons such as having a high energy density. Such a nonaqueous electrolyte secondary battery utilizes the principle of charging and discharging by moving lithium ions between the positive electrode and the negative electrode. In nonaqueous electrolyte secondary batteries, lithium metal oxides such as lithium cobalt oxide, lithium manganate, lithium nickelate, and lithium iron phosphate are being put into practical use or commercialized as positive electrode active materials. As the negative electrode active material, a carbon material such as graphite is used. Then, a positive electrode or a negative electrode is configured by supporting an electrode mixture obtained by adding a conductive agent or a binder to the positive electrode active material and the negative electrode active material on a current collector of a metal foil such as an aluminum foil or a copper foil. The

  Such an electrode is formed by applying a slurry-like electrode mixture on an aluminum foil and dispersing the solvent by drying. Therefore, although the active materials are in a state of being bound together by the binder, it is not sufficient as a measure for preventing the active material from dropping off due to repeated expansion and contraction of the active material during charge and discharge, When it is thick, there is a problem in that the electrode capacity is reduced.

  In addition to the electrode as described above, only a positive electrode active material made of a lithium composite oxide, or a pressure-molded body made of a mixture obtained by adding a small amount of a binder to this, and carbonizing the binder A positive electrode having a high packing density of the active material by sintering is proposed (Patent Document 1). However, this positive electrode has a problem that the active material is gradually powdered and dropped from the electrode due to repeated expansion and contraction associated with the charge / discharge cycle, leading to a significant decrease in battery capacity in the charge / discharge cycle.

Japanese Patent No. 3427570

  The present invention has been made in view of the above circumstances, and has a high electrode capacity per unit volume and an electrode capacity per unit mass of an active material, and an electrode for a nonaqueous electrolyte secondary battery excellent in charge / discharge cycle characteristics. An object of the present invention is to provide a non-aqueous electrolyte secondary battery using the same and a method for producing the non-aqueous electrolyte secondary battery electrode.

  As a result of intensive studies to solve the problems of the prior art, the present inventors have sintered a mixture of aluminum powder and electrode active material, so that a small structure in which the aluminum powders are continuously connected to each other. It was found that the arrangement of the active material is firmly fixed with high density by forming this small structure. Due to the high density of the active material, a large amount of the active material can be used for the electrode reaction, and the active material is firmly fixed, so that dropping from the electrode is suppressed.

That is, the present invention according to claim 1, wherein a mixture of an electrode mixture containing an active material capable of occluding and releasing lithium and an aluminum powder is used as a pressure molded body, and the pressure molded body is heat-treated at a temperature equal to or higher than the melting point of the aluminum powder. Forming a sintered body of a pressure-formed body in which aluminum powders are bonded to each other, and in the mixture before sintering, the electrode mixture is added to the active material and at least one of a conductive additive and a binder. And the ratio of the total amount of the conductive additive and the binder to the total mass of the mixture is 1 to 20% by mass, which is a method for producing a non-aqueous electrolyte secondary battery electrode.

In the present invention, the mixing ratio of the active material to the total mass of the mixture is 45 to 95 % by mass, and the mixing ratio of the aluminum powder is 4 to 54 % by mass. .

According to the third aspect of the present invention, in the first or second aspect, the sintered body has a density of 1.8 to 3.6 g / cm ³ .

  In the electrode for a non-aqueous electrolyte secondary battery according to the present invention, a small structure that is continuously connected is formed in the electrode by bonding aluminum powders together, and the arrangement of active materials in the small structure is high density. And firmly fixed. As a result, a large amount of active material can be used for the electrode reaction, so that an electrode having a high electrode capacity can be obtained, and dropout of the active material due to repeated charge / discharge can be suppressed, so that a decrease in electrode capacity can be prevented. Furthermore, by using such a nonaqueous electrolyte secondary battery electrode for at least one of the positive electrode and the negative electrode, a high energy density nonaqueous electrolyte secondary battery can be obtained. By the manufacturing method according to the present invention, an electrode for a nonaqueous electrolyte secondary battery can be manufactured easily and with good reproducibility.

  The electrode for a nonaqueous electrolyte secondary battery according to the present invention will be described in detail below.

(A) Sintered body The electrode for a nonaqueous electrolyte secondary battery according to the present invention is formed by press-molding a mixture of an aluminum powder and an electrode mixture mixed at a predetermined mass ratio, and then inactivating the pressure-formed body. It consists of a sintered body that is heat-treated in an atmosphere and hardened. Moreover, it is good also as a sintered compact which compounded this mixture with the metal plate. Such a sintered body can be applied to both the positive electrode and the negative electrode.

(B) Aluminum powder Pure aluminum powder, aluminum alloy powder, or a mixture thereof is used for the aluminum powder used in the present invention. In the case where the alloy components cause corrosion resistance deterioration under the usage environment, it is preferable to use pure aluminum powder. Pure aluminum is aluminum having a purity of 99.0 mass% or more.

  On the other hand, when it is desired to obtain higher strength, it is preferable to use aluminum alloy powder or a mixture of this and pure aluminum powder. As the aluminum alloy, 1000 series, 2000 series, 3000 series, 4000 series, 5000 series, 6000 series, and 7000 series aluminum alloys are used.

  The particle size of the aluminum powder is preferably 1 to 50 μm. In order to form a small structure that is continuously and firmly connected by bonding aluminum powders, the particle size of the aluminum powder is preferably smaller, and more preferably 1 to 10 μm. The particle size of the aluminum powder is defined by the median diameter measured by the laser diffraction scattering method (microtrack method).

(C) Additive element powder You may use the mixture which added the additive element powder to the pure aluminum powder. As such an additive element, a plurality of elements consisting of a single element selected from magnesium, silicon, titanium, iron, nickel, copper, zinc and the like or any combination of two or more are preferably used. Such a mixture forms an alloy of aluminum and an additive element by heat treatment. Depending on the type of additive element, an intermetallic compound of aluminum and the additive element is further formed. Various effects can be obtained by including such an aluminum alloy or an intermetallic compound. For example, in an aluminum alloy of aluminum and an additive element such as silicon or copper, the melting point of the aluminum powder is lowered and the temperature required for the heat treatment can be lowered, so that the energy required for production can be reduced and the strength by alloying can be reduced. Will improve. Further, when an intermetallic compound of aluminum and an additive element such as nickel is formed, heat is generated and sintering is promoted, and a structure in which the intermetallic compound is dispersed is formed, so that high strength can be achieved.

  The additive element powder may be added to the aluminum alloy powder, or the additive element powder may be added to a mixture of the aluminum alloy powder and the pure aluminum powder. In these cases, new alloy systems and intermetallic compounds are formed. Furthermore, an additive element alloy powder obtained by alloying a plurality of additive element powders may be used as the additive element powder.

The addition amount of the additive element powder or additive element alloy powder to the aluminum alloy powder or pure aluminum powder is appropriately determined based on the chemical formula amount of the alloy or intermetallic compound to be formed.
The particle size of the additive element powder is preferably 1 to 50 μm. The particle diameter of the additive element powder is defined by the median diameter measured by the laser diffraction scattering method (microtrack method) in the same manner as the aluminum powder.

(D) Electrode mixture As the electrode for a nonaqueous electrolyte secondary battery according to the present invention, either a positive electrode or a negative electrode can be applied. Such an electrode contains an electrode mixture containing an active material capable of occluding and releasing lithium. The arrangement of the active material contained in the electrode mixture is fixed in a small structure in which the above-described aluminum powders are continuously connected to each other. The electrode mixture may contain a conductive additive and a binder in addition to the active material.

  When the electrode is a positive electrode, the positive electrode active material used is not particularly limited as long as it can be used for a non-aqueous electrolyte secondary battery. For example, lithium cobaltate, lithium manganate, lithium nickelate, phosphoric acid Lithium metal oxides such as iron lithium are used. When an electrode is a negative electrode, the negative electrode active material used will not be restrict | limited especially if it can be used for a nonaqueous electrolyte secondary battery. For example, lithium titanium composite oxide, lithium tungsten composite oxide, lithium niobium composite oxide, lithium molybdenum composite oxide, and the like can be given. Among these lithium-containing composite oxides, it is preferable to use a lithium titanium composite oxide from the viewpoint of the rate characteristics, cycle characteristics, and safety of the nonaqueous electrolyte secondary battery.

  The mixing ratio of the active material to the total mass of the mixture is preferably 50 to 99% by mass, and similarly the mixing ratio of the aluminum powder is preferably 1 to 50% by mass. When the mixing ratio of the active material is less than 50% by mass or when the mixing ratio of the aluminum powder exceeds 50%, the ratio of the active material to the electrode may be low and sufficient electrode capacity may not be obtained. On the other hand, when the mixing ratio of the active material exceeds 99% by mass or when the mixing ratio of the aluminum powder is less than 1% by mass, the ratio of the aluminum powder occupying the electrode is reduced, and the aluminum powders are bonded to each other. In some cases, the distribution density of the continuously connected small structures is lowered, and the arrangement of a large amount of active materials cannot be fixed. As a result, the capacity is reduced when the cycle is repeated due to dropping of the active material from the electrode.

  In both the positive electrode and the negative electrode, adding a conductive additive to the electrode mixture improves the conductivity of the entire electrode, so it is preferable to add it. It does not specifically limit as a conductive support agent, A well-known or commercially available thing can be used. Examples thereof include carbon black such as acetylene black and ketjen black, activated carbon, graphitic carbon fiber, and conductive metal oxide.

  Furthermore, a material that carbonizes through heat treatment during aluminum powder sintering can also be used as a conductive aid. Examples of such materials include thermosetting resins such as phenol resin, polyester resin, epoxy resin, urea resin, and melamine resin; polyethylene resin, polypropylene resin, vinyl chloride resin, polyvinyl acetate resin, polyvinyl pyrrolidone, and acrylic resin. Resin, styrene resin, polycarbonate resin, nylon resin, acrylonitrile, methacrylonitrile, vinyl fluoride, chloroprene, vinyl pyridine and derivatives thereof, vinylidene chloride, ethylene, propylene, celluloses, cyclic dienes (for example, cyclopentadiene, 1,3- Cyclohexadiene, etc.), thermoplastic resins such as polymers and copolymers such as styrene-butadiene rubber; carbohydrates such as sugars and starches; hydrocarbons such as paraffin, tar, pitch, coke, and the like.

  By adding a binder to the electrode mixture in both the positive electrode and the negative electrode, the binding of the components via the binder, that is, the bonding between the active materials, between the conductive assistants, and between the active material and the conductive auxiliary agent is strengthened. Thus, the active material from the electrode is less likely to fall off. Therefore, it is preferable to add a binder. It does not specifically limit as a binder to be used, A well-known or commercially available thing can be used. For example, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyvinylpyrrolidone (PVP), polyvinyl chloride (PVC), polyethylene (PE), polypropylene (PP), ethylene-propylene copolymer, styrene butadiene rubber (SBR), polyvinyl alcohol (PVA), carboxymethyl cellulose (CMC) and the like.

  As described above, it is preferable to add at least one of a conductive additive and a binder to the electrode mixture. When added, the ratio of the conductive additive and the binder to the total mass of the mixture in both the positive electrode and the negative electrode is preferably 20% by mass or less. This mass ratio is the ratio when either one of the conductive additive and the binder is added, and is the total ratio when both are added. When this ratio exceeds 20% by mass, the mass ratio of the active material is relatively reduced, and it is not possible to achieve high electrode capacity, and the mass ratio of the aluminum powder is also relatively decreased, so that the aluminum powders are bonded to each other. By doing this, there may be a case where a small structure connected continuously cannot be sufficiently formed. In the present invention, it is needless to say that the conductive additive and the binder need not be contained in the electrode mixture when the conductivity of the entire electrode and the bonding strength of the electrode mixture component are not a problem.

(E) Metal plate In the present invention, a mixture of an aluminum powder and an electrode mixture may be used in a composite state with a metal plate. The metal plate is a non-porous plate or foil, and a net-like body such as a perforated wire mesh, expanded metal, or punching metal. The metal plate becomes a support and the strength of the sintered body is improved, and the conductivity is further improved. As the metal plate, a material that does not evaporate or decompose during heat treatment, specifically, a metal such as aluminum, titanium, iron, nickel, copper, or an alloy thereof is preferably used.

  The compounding of the mixture and the metal plate refers to an integrated state in which, for example, when a metal mesh is used for the metal plate, the entire net is covered with the mixture while filling the mesh in the mesh. When filling the mixture on both sides of the metal plate, if the metal plate is a perforated network, even if it is filling from one side of the region divided by the metal plate, it can be filled to the other region The metal plate is preferably a net-like body. Here, the perforated means a mesh part of a metal mesh, a punch part of a punching metal, a mesh part of an expanded metal, and a gap part between fibers of metal fibers. The pore diameter of the perforated body of the network is appropriately selected according to the particle diameter of the aluminum powder or electrode mixture.

(F) Mixing method As a mixing means for mixing the aluminum powder and the electrode mixture, a vibration stirrer, a container rotating mixer, or the like is used, but it is not particularly limited as long as a sufficient mixing state is obtained. .
When the mixture and the metal plate are combined, the metal plate may be sandwiched between the mixtures or the mixture may be sandwiched between the metal plates. Further, the mixture of the mixture and the metal plate can be repeated to make a multi-stage. In the case of compounding, it is possible to combine a mixture of different particle sizes and mixing ratios of aluminum powder and electrode mixture, and a plurality of different types of metal plates.

(G) Pressure molding method Next, the said mixture is made into a pressure-molded body by pressure molding. The pressure during the pressure molding is preferably 200 MPa or more. By forming by applying sufficient pressure, the aluminum powders rub against each other, and the strong oxide film on the surface of the aluminum powder that inhibits the bonding between the aluminum powders is destroyed. This oxide film confines molten aluminum and prevents it from coming into contact with each other, and is inferior in wettability with molten aluminum and has the effect of rejecting liquid aluminum. Therefore, when the pressure of pressure molding is less than 200 MPa, the destruction of the oxide film on the surface of the aluminum powder is insufficient, and the aluminum melted during heating oozes out of the molded body to form a ball-shaped aluminum lump. There is a case. The shape collapses due to the formation of such an aluminum lump, which must be removed. It is preferable that the molding pressure is as large as the apparatus and mold used allow, since the sintered body becomes stronger. However, if it exceeds 400 MPa, the effect tends to be saturated. In addition, it is preferable to use lubricants such as fatty acids such as stearic acid, metal soaps such as zinc stearate, various waxes, synthetic resins, and olefinic synthetic hydrocarbons for the purpose of enhancing the mold release properties of the pressure-molded body.

(H) Heat treatment method By heat-treating the pressure-formed body, a sintered body in which a mixture of the electrode mixture and aluminum powder is baked and hardened is obtained. The heat treatment is performed at a temperature equal to or higher than the melting point of the aluminum powder to be used. Thereby, the small structure body connected continuously is formed when at least some aluminum powder couple | bond together. In the composite of the mixture and the metal plate, when the melting point of the metal plate is lower than that of the aluminum powder, the metal plate is also melted to form a continuous small structure together with the aluminum powder. When the melting point of the metal plate is higher than that of the aluminum powder, when the heating temperature is equal to or higher than the melting point of the metal plate, the metal plate is also melted to form a continuous small structure together with the aluminum powder. On the other hand, when the heating temperature is lower than the melting point of the metal plate, the metal plate does not melt, and a continuous small structure is formed only by the aluminum powder. Here, the melting point of the aluminum powder is a temperature at which a liquid phase of pure aluminum or an aluminum alloy is generated, and the melting point of the metal plate is a temperature at which a liquid phase is similarly generated. By heating to a temperature at which a liquid phase is generated, the liquid phase exudes from the aluminum powder or this and the metal plate, and when the liquid phase comes in contact, the aluminum powder or this and the metal plate are bonded metallically. To do.

  By setting the heat treatment temperature to be equal to or higher than the melting point of the aluminum powder, aluminum powders, or in the case of a composite, a metal plate is joined together with the aluminum powder to form a continuously connected small structure. An active material is arrange | positioned and the arrangement | positioning state is fixed firmly. On the other hand, when the heat treatment temperature is lower than the melting point of the aluminum powder, the bonding between the aluminum powders becomes insufficient, and the formation density of the small structures connected by the bonding between the aluminum powders is lowered. As a result, the arrangement of the active material in the electrode is not sufficiently fixed. Further, in the composite, bonding between the aluminum powder and the metal plate is insufficient.

  The heating temperature is preferably 800 ° C. or lower, and more preferably 700 ° C. or lower. When heated at a temperature exceeding 800 ° C., the viscosity of the melted aluminum decreases, the melted aluminum oozes out to the outside of the pressure-formed body, and a convex aluminum lump is formed. The shape collapses due to the formation of such an aluminum lump, which must be removed. The heat holding time in the heat treatment is preferably 1 minute to 24 hours. If it is less than 1 minute, the melting of the aluminum powder is not sufficient, and the formation density of the small structures connected by bonding of the aluminum powders may be low. On the other hand, even if it exceeds 24 hours, there is no further change, so that it is preferably within 24 hours from the viewpoint of productivity. Further, a load may be applied to the pressure-formed body during the heat treatment to compress the pressure-formed body, or heating and cooling may be repeated a plurality of times.

The heat treatment is preferably performed in an inert atmosphere. The inert atmosphere is an atmosphere that suppresses oxidation of aluminum, and an atmosphere of vacuum; nitrogen, argon, hydrogen, decomposed ammonia, and a mixed gas thereof is preferably used, and a vacuum atmosphere is preferable. The vacuum atmosphere is preferably 2 × 10 ⁻² Pa or less, more preferably 1 × 10 ⁻² Pa or less. When it exceeds 2 × 10 ⁻² Pa, removal of moisture adsorbed on the surface of the aluminum powder becomes insufficient, and oxidation of the aluminum surface proceeds during heat treatment. As described above, the oxide film on the aluminum surface is inferior in wettability with liquid aluminum, and as a result, molten aluminum oozes out to form a ball-like lump. In the case of an inert gas atmosphere such as nitrogen, it is preferable that the oxygen concentration is 1000 ppm or less and the dew point is −30 ° C. or less.

(I) Density of sintered body The sintered body obtained by the heat treatment as described above preferably has a density of 1.8 to 4.3 g / cm ³ . When the density is less than 1.8 g / cm ³ , sufficient electrode capacity per unit volume cannot be obtained when the electrode is used. In addition, the active materials are not sufficiently in contact with each other in the sintered body, and the active materials that fall off from the electrode increase. As a result, battery characteristics such as a decrease in cycle capacity maintenance rate are deteriorated. On the other hand, when the density exceeds 4.3 g / cm ³ , the active materials are consolidated, and the electrolytic solution cannot sufficiently penetrate into the inside of the electrode in the thickness direction. As a result, the utilization factor of the active materials present in the thickness direction is lowered, and the electrode capacity per unit mass of the active materials is reduced.

(J) Non-aqueous electrolyte secondary battery A non-aqueous electrolyte secondary battery according to the present invention includes an electrode made of a sintered body produced as described above, a separator disposed between electrical conductors, a non-aqueous electrolyte, Is assembled into a non-aqueous electrolyte secondary battery. In addition, although it is preferable to comprise both a positive electrode and a negative electrode, or only a positive electrode with the said sintered compact, you may comprise only a negative electrode with the said sintered compact.

As the separator, generally used polymer films such as polyethylene (PE) and polypropylene (PP) are used. As the non-aqueous electrolyte, lithium hexafluorophosphate (LiPF ₆ ) or lithium perchlorate (LiClO ₄ ) dissolved in an organic solvent such as ethylene carbonate (EC) or diethyl carbonate (DEC) can be used.

  Hereinafter, the present invention will be described in detail by way of examples of the present invention and comparative examples. The present invention is not limited to the following examples of the present invention and comparative examples.

(Invention Examples 2, 4, 7 to 10, 13 and Comparative Examples 1 to 6)
First, the positive electrode for a nonaqueous electrolyte secondary battery according to the present invention was produced as follows.

(Preparation of positive electrode)
The following aluminum powder (A1, A2) was used as the aluminum powder. As the positive electrode active material, lithium metal oxides shown in Table 1 were used. Further, the following conductive assistants (B1, B2, B3) and the following binder (C1) were used. As shown in Table 1, each material was mixed at a predetermined mass ratio to prepare a mixture. In addition, the mass ratio of at least one of the positive electrode active material, the aluminum powder, and the conductive auxiliary agent and the binder shown in Table 1 was set to 100 mass%, and the mass ratio with respect to it.

  A mold having a hole of φ13 mm was filled with a predetermined mass of the above mixture, and pressure-molded at a pressure of 200 MPa. This press-molded body was heat-treated at a temperature shown in Table 1 for 1 hour in an argon atmosphere to produce a sintered body. In this manner, a sintered body having a diameter of 13 mm and a thickness of 0.5 mm was produced and used as a positive electrode sample for a nonaqueous electrolyte secondary battery. The thickness of the positive electrode sample was measured with a micrometer.

A1: Pure aluminum powder having an aluminum purity of 99.9 mass%, median diameter: 3 μm (melting point: 660 ° C.)
A2: Al-7.5% Si-1% Mg aluminum alloy powder, median diameter: 27 μm (melting point: 555 ° C.)
B1: Acetylene black B2: Sugar B3: Polyvinyl acetate resin C1: CMC

(Positive electrode density)
The mass of the positive electrode sample made of the sintered body was measured and divided by the volume to obtain the positive electrode density.

(Production of evaluation cell)
A bipolar evaluation cell using the positive electrode sample as a working electrode was produced. Lithium metal was used for the counter electrode. As the electrolytic solution, a non-aqueous electrolytic solution in which 1.3 mol / L of LiPF ₆ was dissolved in a mixed solvent of ethylene carbonate and ethyl methyl carbonate (3: 7 by volume) was used, and a microporous polyethylene membrane was used as the separator. Using. For the exterior body, a resin container in which a polypropylene block was processed was used, and the electrode group was housed and sealed so that the open ends of the terminals provided on the working electrode and the counter electrode were exposed to the outside.

(Battery test)
A performance test was performed using the evaluation cell produced as described above, and the electrode capacity per unit volume and the electrode capacity per unit mass of the positive electrode active material were determined as follows.

In the case of a positive electrode sample using LiFePO ₄ as the positive electrode active material, the fabricated evaluation cell was charged to 0.2 V at 4 C, and then discharged at 0.2 C until the voltage fell below 2 V. When other positive electrode active materials were used, the fabricated evaluation cell was charged to 4.2 V at 0.2 C and then discharged until the voltage dropped below 2.75 V at 0.2 C. The product of the current flowing during discharge and the time required for discharge was defined as the electrode capacity.

(Electrode capacity per unit volume)
A value obtained by dividing the electrode capacity by the volume of the positive electrode sample was defined as an electrode capacity per unit volume. The electrode capacity per unit volume is 140 mAh / cm ³ or more, ◯, 130 mAh / cm ³ or more and less than 140 mAh / cm ³ is Δ, and less than 130 mAh / cm ³ is x. ○ was accepted, and Δ and x were rejected.

(Electrode capacity per unit mass of positive electrode active material)
A value obtained by dividing the electrode capacity by the mass of the active material filled in the positive electrode sample was defined as the electrode capacity per unit mass of the positive electrode active material. The electrode capacity per unit mass (1 g) of the positive electrode active material was 120 mAh / g or more, ◯, 100 mAh / g or more and less than 120 mAh / g was Δ, and less than 100 Ah / g was x. ○ and Δ were accepted, and x was rejected.

  Table 1 shows the results of the electrode capacity per unit volume and the electrode capacity per unit mass of the positive electrode active material.

(Maintenance rate of electrode capacity after cycle test)
In the case of a positive electrode sample using LiFePO ₄ as the positive electrode active material, the process of charging to 0.2V at 4C and then discharging until the voltage drops below 2V at 0.2C is one cycle, and other positive electrode active materials are used. When used, the process of discharging to 4.2 V at 0.2 C and then discharging until the voltage fell below 2.75 V at 0.2 C was defined as one cycle. The electrode capacity after 10 cycles of the test was measured and compared with the electrode capacity before the cycle test. Table 1 shows the ratio of the electrode capacity after the cycle test to the electrode capacity before the test as the electrode capacity retention rate. The electrode capacity maintenance ratio was evaluated as “◯” when 90% or more, “Δ” when 80% or more and less than 90%, and “X” when less than 80%. ○ and Δ were accepted, and x was rejected.

(Comprehensive evaluation)
It is composed of the electrode capacity ○ per unit volume as a comprehensive evaluation, and, if the evaluation of the electrode capacity per unit mass of the positive electrode active material and the capacity retention after cycle test is constituted by the ○ △ Was determined to be acceptable (O), and the other cases were regarded as unacceptable (X).

In Invention Examples 2, 4, 7 to 10, and 13, the mass ratio of the aluminum powder and the positive electrode active material was within the range defined by the present invention, and the heating temperature was equal to or higher than the melting point of the aluminum powder. As a result, the electrode capacity per unit volume, the electrode capacity per unit mass of the positive electrode active material, and the capacity retention rate after the cycle test passed, and the overall evaluation also passed.

  On the other hand, in Comparative Example 1, since the sintered body did not contain aluminum powder, the electrode capacity per unit volume, the electrode capacity per unit mass of the positive electrode active material, and the capacity maintenance ratio after the cycle test were It was rejected and the overall evaluation was also rejected.

  In Comparative Example 2, since the conductive additive was included in the sintered body but the aluminum powder was not included, the capacity retention rate after the cycle test was rejected, and the overall evaluation was also rejected.

  In Comparative Example 3, since the heat treatment temperature of the mixture was too low, the capacity retention rate after the cycle test was rejected, and the overall evaluation was also rejected.

  In Comparative Example 4, since the heat treatment temperature of the mixture was too low, the electrode capacity per unit mass of the positive electrode active material and the capacity retention rate after the cycle test were rejected, and the overall evaluation was also rejected.

In Comparative Examples 5 and 6 , since the ratio of the conductive auxiliary agent was large, the ratio of the electrode active material in the electrode decreased, the electrode capacity per unit volume was rejected, and the overall evaluation was also rejected.

  The electrode for a nonaqueous electrolyte secondary battery according to the present invention has a high electrode capacity per unit volume and an electrode capacity per unit mass of the active material, and there is almost no decrease in the electrode capacity even after repeated charge and discharge. And the nonaqueous electrolyte secondary battery using this has a high energy density, and is excellent also in the cycling characteristics by charging / discharging. Furthermore, the electrode for a nonaqueous electrolyte secondary battery can be manufactured easily and with good reproducibility by the manufacturing method according to the present invention.

Claims (3)

A mixture of an electrode mixture containing an active material capable of occluding and releasing lithium and an aluminum powder is used as a pressure molded body, and the aluminum powder is bonded by heat-treating the pressure molded body at a temperature equal to or higher than the melting point of the aluminum powder. In the mixture before forming the sintered body of the pressure-molded body and sintering, the electrode mixture contains at least one of a conductive additive and a binder in addition to the active material, and the total mass of the mixture A method for producing an electrode for a non-aqueous electrolyte secondary battery, wherein a total ratio of the conductive additive and the binder is 1 to 20% by mass. The electrode for a nonaqueous electrolyte secondary battery according to claim 1, wherein the mixing ratio of the active material to the total mass of the mixture is 45 to 95 mass%, and the mixing ratio of the aluminum powder is 4 to 54 mass%. Manufacturing method . Method for producing the sintered body has a density of 1.8~ 3.6 g / cm ^3, a non-aqueous electrolyte secondary battery according to claim 1 or 2.