JP6948562B2 - Non-aqueous electrolyte secondary battery - Google Patents

Description

The present invention relates to a non-aqueous electrolyte secondary battery. More specifically, the present invention relates to a non-aqueous electrolyte secondary battery in which _{trilithium phosphate (Li 3} PO ₄ ) is added to the positive electrode mixture layer.

Non-aqueous electrolyte secondary batteries such as lithium-ion secondary batteries (hereinafter, also simply referred to as "secondary batteries") are lighter in weight and have a higher energy density than existing batteries. Therefore, in recent years, personal computers, mobile terminals, etc. It is used as a so-called portable power source and a vehicle drive power source. The positive electrode of such a non-aqueous electrolyte secondary battery is formed by, for example, applying a positive electrode mixture layer to the surface of a positive electrode current collector which is a conductive foil body.

In the non-aqueous electrolyte secondary battery described above, in order to suppress various problems that occur when the battery is overcharged (high voltage state), trilithium phosphate (Li ₃ PO) has been conventionally applied to the positive electrode mixture layer. _{A technique for adding an inorganic phosphoric acid compound such as 4} ) has been proposed (for example, Patent Document 1). When the battery is overcharged, the inorganic phosphoric acid compound adsorbs an acid (for example, hydrogen fluoride (HF)) generated by the decomposition of the non-aqueous electrolyte solution on the particle surface to cause the battery to be overcharged. It is possible to suppress heat generation and elution of metal elements.

Japanese Unexamined Patent Publication No. 2014-103098

As described above, in Patent Document 1, Li ₃ PO _{4 and the} like are added to the positive electrode mixture layer in order to suppress various problems in the overcharged state, but there is still room for improvement in such a technique. Therefore, a technique capable of efficiently obtaining a secondary battery having more suitable performance has been desired.
In particular, Patent Document 1 is a technique for a high potential battery having an operating potential (opening voltage) of 4.3 V (vs. Li ^/ Li +) or more, and a secondary battery having an operating potential of 4.25 V or less ( Since it was difficult to say that the technology can be preferably applied to a 4V class battery), the development of a technology suitable for a 4V class battery has been desired.

The present invention has been made in view of the above points, and a main object thereof is to provide a non-aqueous electrolyte secondary battery having suitable battery performance in a technique of adding _{Li 3} PO _{4 to a positive electrode mixture layer.} It is to provide a technology that can be obtained efficiently.

In order to realize the above object, the present invention provides a non-aqueous electrolyte secondary battery having the following configuration.

The non-aqueous electrolyte secondary battery disclosed here includes a positive electrode having a positive electrode mixture layer formed on a positive electrode current collector, and a negative electrode having a negative electrode mixture layer formed on a negative electrode current collector. It is provided with a non-aqueous electrolytic solution having a lithium compound containing fluorine as a supporting salt, and the positive electrode mixture layer contains a positive electrode active material, Li ₃ PO _4, and a binder.
Further, in the non-aqueous electrolyte secondary battery disclosed herein, the positive-electrode mixture layer, and the active material for a lithium compound which is a precursor of the positive electrode active material, Li ₃ PO _4, which is a precursor of Li ₃ PO ₄ Contains at least one of the lithium compounds for use. Then, the weight ratio of _Li 3 PO _Li 3 PO ₄ for a lithium compound in ₄ and _{L A,} the weight ratio of _Li 3 PO ₄ and _{W A} for the positive-electrode mixture layer, the active material for a lithium compound in the positive electrode active material the weight ratio of the L _B, when the weight ratio of the cathode active material for the positive-electrode mixture layer was W _B, the positive-electrode mixture layer is formed to satisfy equation (1) below.
_{0.44 ≦ (L A × W A} ) + (L B × W B) ≦ 30.6 (1)

As a result of various experiments and studies to solve the above-mentioned problems, the present inventor contains a large amount of "surplus lithium" in the positive electrode mixture layer, and the content of such "surplus lithium" is high. It was found that it has a great influence on the battery performance.

Specifically, the positive electrode active material, which is the main component of the positive electrode mixture layer, uses _{a precursor (lithium compound for active material) such as lithium hydroxide (LiOH) or lithium carbonate (Li 2} CO ₃ ) as another material (lithium compound for active material). It is produced by reacting with a transition metal compound, etc.). At the time of producing such a positive electrode active material, a surplus of lithium compound for active material is added in order to appropriately react the lithium compound for active material with another material, and the positive electrode active material after production is not charged. Lithium compounds for the active material of the reaction may be included.
Further, in _{the production of the powder material of Li 3} PO _{4 , the precursor (lithium compound for Li 3} PO ₄ ) such as lithium hydroxide (LiOH) and other materials are used in the same manner as in the production of the positive electrode active material described above. It has reacted with (phosphoric acid (H ₂ PO ₃ ), etc.) and has not reacted with _{the powder material of Li 3} PO ₄ after formation (hereinafter, such powder material is simply referred to as "Li ₃ PO ₄ "). Lithium compounds for Li ₃ PO ₄ may be included.
As described above, the positive electrode _{mixture layer containing the positive electrode active material and Li 3} PO ₄ may contain a lithium compound which is a precursor of each in an unreacted state. In the present specification, the _{lithium compound for Li 3} PO ₄ and the lithium compound for active material are collectively referred to as "surplus lithium".

As a result of various studies, the present inventor has found that the above-mentioned excess lithium content has a great influence on the performance of the secondary battery. Specifically, if the content of excess lithium becomes too small, the resistance value of the positive electrode mixture layer drops significantly, and the reaction tends to proceed rapidly at the initial stage of the charge / discharge reaction, so that the capacity retention rate and high temperature durability There is a risk that the sex will deteriorate.
The present inventor has also found that the above-mentioned content of excess lithium can have a great influence on the production efficiency of the secondary battery. Specifically, if the positive electrode mixture contains a large amount of excess lithium, the binder and the excess lithium may react with each other to gel the positive electrode mixture. When such gelation occurs, it becomes difficult to form a positive electrode mixture layer having a desired thickness on the surface of the positive electrode current collector, which causes a significant decrease in the production efficiency of the secondary battery.

The non-aqueous electrolyte secondary battery disclosed here is the result of various experiments and studies based on the above findings, and the "surplus lithium content" in the positive electrode mixture layer is predetermined. It is adjusted within the range of. Incidentally, "the content of the excess lithium" This is, _Li 3 PO ₄ in a weight ratio of _Li 3 PO ₄ for lithium compounds (powder materials) in the _{L A,} the weight ratio of _Li 3 PO ₄ with respect to the positive-electrode mixture layer when was the W _a, the weight ratio of the active material for a lithium compound in the positive electrode active material and L _B, the weight ratio of the cathode active material for the positive-electrode mixture layer was W _B, "(L _a × W _a) + _{(L B} × _{W B)} "that can be represented by the formula.
And here the non-aqueous electrolyte secondary battery disclosed, the content of the excess lithium of the formula described above _{((L A × W A)} + (L B × W B)) is 0.44 or more It is adjusted within the range of 30.6 or less. As a result, it is possible to prevent gelation of the positive electrode mixture layer due to an excessively high content of excess lithium, and it is preferable to reduce the capacity retention rate and high temperature durability due to an excessively low content of excess lithium. Can be prevented.
Therefore, according to the non-aqueous electrolyte secondary battery disclosed here, a secondary battery having suitable battery performance can be efficiently obtained.

It is a perspective view which shows typically the outer shape of the lithium ion secondary battery which concerns on one Embodiment of this invention. It is a perspective view which shows typically the electrode body of the lithium ion secondary battery which concerns on one Embodiment of this invention. It is a figure explaining the neutralization titration method used for the measurement of surplus lithium. It is a graph which shows the relationship between the total amount of surplus lithium and the resistance increase rate. It is a graph which shows the relationship between the total amount of surplus lithium, and the thickening rate of a positive electrode mixture layer.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the following drawings, members / parts having the same action are described with the same reference numerals. Further, the dimensional relations (length, width, thickness, etc.) in each drawing do not reflect the actual dimensional relations. In addition, matters other than those specifically mentioned in the present specification and necessary for carrying out the present invention (for example, the composition of the negative electrode, general techniques for constructing a non-aqueous electrolyte secondary battery, etc.) , Can be grasped as a design matter of a person skilled in the art based on the prior art in the field.

1. 1. Lithium-ion secondary battery Hereinafter, a lithium-ion secondary battery will be described as an example of the non-aqueous electrolyte secondary battery disclosed herein. FIG. 1 is a perspective view schematically showing the outer shape of the lithium ion secondary battery according to the present embodiment, and FIG. 2 is a perspective view schematically showing an electrode body of the lithium ion secondary battery according to the present embodiment. .. The lithium ion secondary battery 100 is configured by accommodating the electrode body 80 shown in FIG. 2 inside the square battery case 50 shown in FIG.

(1) Battery Case The battery case 50 is composed of a flat case body 52 having an open upper end and a lid 54 that closes an opening at the upper end thereof. The lid 54 is provided with a positive electrode terminal 70 and a negative electrode terminal 72. Although not shown, the positive electrode terminal 70 is electrically connected to the positive electrode 10 of the electrode body 80 housed in the battery case 50, and the negative electrode terminal 72 is electrically connected to the negative electrode 20.

(2) Electrode body Next, the electrode body 80 housed inside the battery case 50 described above will be described. As shown in FIG. 2, the electrode body 80 in the present embodiment is a wound electrode body produced by laminating and winding a long sheet-shaped positive electrode 10 and a negative electrode 20 together with a long sheet-shaped separator 40. Is. The electrode body used in the non-aqueous electrolytic solution secondary battery disclosed here is not limited to the wound electrode body as shown in FIG. 2, and for example, a plurality of positive electrodes and negative electrodes are separated by a separator. It may be a laminated electrode body which is laminated alternately.

(A) Positive electrode In the positive electrode 10 in FIG. 2, a positive electrode mixture layer 14 containing a positive electrode active material as a main component is formed on the surface (both sides) of a long sheet-shaped positive electrode current collector 12. A positive electrode mixture layer non-forming portion 16 in which the positive electrode mixture layer 14 is not coated is formed on one side edge portion in the width direction of the positive electrode 10, and the positive electrode mixture layer non-forming portion 16 is formed. Is electrically connected to the positive electrode terminal 70 (see FIG. 1) described above.
The positive electrode mixture layer 14 in the present embodiment contains at least a positive electrode active material, trilithium phosphate (Li ₃ PO ₄ ), and a binder. Further, in such a positive-electrode mixture layer 14, the lithium compound which is a precursor of positive electrode active material (active material for a lithium compound), a lithium compound which is a precursor of _{Li 3 PO 4 (Li 3 PO} 4 for lithium compound) At least one of and is included. As used herein, the term "excess lithium" is a general term for _{"lithium compounds for active materials" and "lithium compounds for Li 3} PO ₄ " that are present in the positive electrode mixture layer 14 in an unreacted state. The detailed composition of the positive electrode mixture layer 14 containing the surplus lithium will be described in detail later.

(B) Negative electrode As for the negative electrode 20, similarly to the positive electrode 10, negative electrode mixture layers 24 containing a negative electrode active material as a main component are formed on both sides of a long sheet-shaped negative electrode current collector 22. A negative electrode mixture layer non-forming portion 26 is formed on one side edge portion in the width direction of the negative electrode 20, and the negative electrode mixture layer non-forming portion 26 is electrically connected to the negative electrode terminal 72 (see FIG. 1). Be connected.

In the present embodiment, the composition of the negative electrode mixture layer 24 is not particularly limited, and can be the same composition as the negative electrode mixture layer of a general lithium ion secondary battery. For example, as the negative electrode active material, a carbon material such as graphite (graphite), non-graphitized carbon (hard carbon), easily graphitized carbon (soft carbon), carbon nanotubes, or a material having a structure combining these is used. Can be done. From the viewpoint of energy density, it is preferable to use a graphite-based material (natural graphite (stone ink), artificial graphite, etc.) among these carbon materials. Further, the negative electrode mixture layer 24 may contain other additives (for example, a binder, a thickener, etc.). Examples of the binder include styrene-butadiene rubber (SBR) and the like, and examples of the thickener include carboxymethyl cellulose (CMC) and the like.

(C) Separator As the separator 40, a strip-shaped sheet material having a plurality of minute holes and having a predetermined width is used. As the separator 40, the same one as that used for a general lithium ion secondary battery can be used, and for example, a sheet material made of a porous polyolefin resin or the like can be used.

(3) Non-aqueous electrolytic solution Further, the non-aqueous electrolytic solution is stored (filled) together with the above-mentioned electrode body 80 in the battery case 50 of the lithium ion secondary battery 100 according to the present embodiment. As such a non-aqueous electrolytic solution, for example, a supporting salt is added to a mixed solvent (for example, volume ratio 3: 4: 3) of ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) at a predetermined concentration. Examples thereof include those contained at (for example, about 1 mol / L). As the supporting salt, a lithium compound containing fluorine, for example, LiPF ₆ , LiBF ₄ , LiCF ₃ SO _3, or the like is used.

2. Detailed Composition of Positive Electrode Mixture Layer As described above, the positive electrode mixture layer 14 of the lithium ion secondary battery 100 according to the present embodiment contains a positive electrode active material, Li ₃ PO ₄ , a binder, and surplus lithium. It is included. The detailed composition of the positive electrode mixture layer 14 including these will be described below.

(1) Positive Electrode Active Material The positive electrode active material is a compound capable of reversibly occluding and releasing lithium ions, and is composed of an oxide containing at least lithium (lithium composite oxide). The solid content of the positive electrode active material is preferably 87 wt% to 90 wt% (for example, 88 wt%) when the solid content of the entire positive electrode mixture layer 14 is 100 wt%.
Further, the type of the positive electrode active material in the present embodiment is not particularly limited, and the same type as the positive electrode active material of a general lithium ion secondary battery can be used. Specific examples of the lithium composite oxide used in such a positive electrode active material include a lithium nickel composite oxide (for example, LiNiO ₂ ), a lithium cobalt composite oxide (for example, LiCoO ₂ ), and a lithium manganese composite oxide (for example, LiMn). ₂ O ₄ ), lithium nickel cobalt manganese composite oxide (for example, LiNi _1/3 Co _1/3 Mn _1/3 O ₂ ) and the like can be mentioned.
These lithium composite oxides are produced by mixing a lithium compound for an active material, which is a precursor, with a source of other metal elements, and then firing the mixture. Specific examples of such lithium compounds for active materials include lithium hydroxide (LiOH) and lithium carbonate (Li ₂ CO ₃ ).

(2) Trilithium Phosphate As described above, the positive electrode mixture layer 14 in the present embodiment contains trilithium phosphate (Li ₃ PO ₄ ). The Li ₃ PO ₄ can adsorb an acid (for example, hydrogen fluoride (HF)) generated by decomposition of a non-aqueous electrolytic solution on the surface when the lithium ion secondary battery 100 is in an overcharged state. .. This makes it possible to suppress heat generation during overcharging, elution of metal elements, and the like. The solid content of Li ₃ PO ₄ is preferably 1 wt% to 4 wt% (for example, 3 wt%) when the solid content of the entire positive electrode mixture layer 14 is 100 wt%.
This Li ₃ PO ₄ powder material is produced by reacting a _{lithium compound for Li 3} PO ₄ , which is a precursor, with phosphoric acid (H ₂ PO _3). Specific examples of the lithium compound for Li ₃ PO _{4 include lithium hydroxide (LiOH).}

(3) Binder A binder is added to the positive electrode mixture layer 14 in order to suitably adhere the positive electrode mixture layer 14 to the surface of the positive electrode current collector 12. As the binder, a resin material used in a general lithium ion secondary battery can be used. Examples of such a binder include polyvinylidene fluoride (PVdF), polyvinylidene chloride (PVdC), polyethylene oxide (PEO) and the like.
Further, an additive other than the binder may be added to the positive electrode mixture layer 14. An example of an additive other than a binder is a conductive agent made of a carbon material such as carbon black. When the solid content of the entire positive electrode mixture layer 14 is 100 wt%, the total solid content of the additive containing the binder is preferably 6 wt% to 12 wt% (for example, 9 wt%).

(4) Surplus Lithium In the positive electrode mixture layer 14 of the present embodiment, surplus lithium such as the above-mentioned lithium compound for active material and lithium compound for Li ₃ PO ₄ (that is, lithium hydroxide (LiOH) and lithium carbonate) (Li ₂ CO ₃ ) etc.) are included.
If the content of the excess lithium is too small, the resistance value of the positive electrode mixture layer 14 is significantly reduced, so that the reaction proceeds rapidly at the initial stage of the charge / discharge reaction, and the capacity retention rate and high temperature durability are significantly improved. May drop to. Further, if the content of the surplus lithium is too large, there is a possibility that the binder and the surplus lithium react with each other to gel the positive electrode mixture layer 14, resulting in a problem that the production efficiency is lowered.
On the other hand, in the lithium ion secondary battery 100 according to the present embodiment, the content of excess lithium in the positive electrode mixture layer 14 is adjusted. The total amount of excess lithium contained in such mixture layer 14, _Li 3 PO ₄ in a weight ratio of _Li 3 PO ₄ for lithium compounds (powder materials) in the _{L A, Li} 3 PO for the positive-electrode mixture layer 14 ₄ weight ratio of the W _a, when the weight ratio of the active material for a lithium compound in the positive electrode active material and L _B, the weight ratio of the cathode active material for the positive-electrode mixture layer 14 was set to W _B (L _a × W represented by the expression _{A) + (L B × W} B). In the lithium ion secondary battery 100 according to the present embodiment, the total amount of the surplus lithium is adjusted so as to satisfy the following formula (1).
_{0.44 ≦ (L A × W A} ) + (L B × W B) ≦ 30.6 (1)

By adjusting the total amount of surplus lithium so as to satisfy the above formula (1), the resistance value of the positive electrode mixture layer 14 can be maintained at an appropriate value, so that the capacity retention rate due to a significant decrease in the resistance value can be maintained. And deterioration of high temperature durability can be appropriately prevented. Further, it is possible to prevent gelation of the positive electrode mixture layer 14 due to the reaction between the binder and the excess lithium. Therefore, according to the present embodiment, a lithium ion secondary battery having suitable battery performance can be efficiently obtained.

The total amount of excess lithium in the positive electrode mixture layer 14 can be measured by the neutralization titration method. For example, a test solution is prepared by peeling off the positive electrode mixture layer from the positive electrode current collector, collecting the positive electrode mixture layer, and mixing the positive electrode mixture layer with a predetermined solvent (for example, NMP). Next, a phenolphthalein solution is added to the prepared test solution, and a 1 mol / L HCl aqueous solution is added dropwise to the first neutralization point (see FIG. 3) at pH ≈8 where the test solution discolors. Then, based on the dropping amount of aqueous HCl in this case, the total amount of excess lithium contained in the positive-electrode mixture layer _{((L A × W A)} + (L B × W B)) can be measured.

Then, when producing the lithium ion secondary battery 100 according to the present embodiment, before forming the positive electrode mixture layer 14, the lithium compound for _{Li 3} PO _{4 in Li 3} PO ₄ (powder material) is used. the weight ratio L _a, when measuring the weight ratio L _B of the active material for a lithium compound in the positive electrode active material preferably. By adjusting the weight ratio _{W B} weight ratio _{W A} and the positive electrode active material of _Li 3 PO ₄ based on the measurement result, the total amount of excess lithium in the positive-electrode mixture layer _{14 ((L A × W A} ) + _{(L B} × _{W B))} it is possible to easily adjust the range of from 0.44 to 30.6.
The weight ratio _{L B} of the general cathode active material active material for a lithium compound in about 0wt% ~0.3wt% (e.g., 0.12 wt%) was, _Li 3 PO ₄ (powder materials) the weight ratio _{L a} of _Li 3 PO ₄ for a lithium compound in an about 0wt% ~0.9wt% (e.g., 0.36 wt%).

Further, in the above-described embodiment, the lithium ion secondary battery has been described as an example of the non-aqueous electrolyte secondary battery disclosed here, but the description is intended to limit the application of the present invention. Rather, the present invention can also be applied to non-aqueous electrolyte secondary batteries other than lithium ion secondary batteries.
However, in a lithium ion secondary battery (4V class battery) having an operating potential of 4.25V (vs. ^{Li / Li +} ) or less, the total amount of excess lithium in the positive electrode mixture layer has a large effect on the battery performance. It has the property that high temperature durability and the like are likely to decrease. Therefore, such a 4V class battery is particularly preferable as an application target of the present invention because the effect of the present invention can be exhibited more remarkably.

[Test example]
Hereinafter, test examples relating to the present invention will be described, but the description of the test examples is not intended to limit the present invention.

1. 1. Preparation of each test example In this test example, seven types of positive electrode mixture with different total excess lithium are prepared, and 4V class lithium ion secondary batteries (samples 1 to 7) are prepared using each positive electrode mixture. Made.

Specifically, for each of Samples 1 to 7, a positive electrode active material (lithium nickel cobalt manganese composite oxide), Li ₃ PO ₄ , a conductive material (AB: acetylene black), and a binder (PVdF) are used. A paste-like positive electrode mixture was prepared by mixing and dispersing the mixture in a dispersion medium (water). Then, the prepared positive electrode mixture was applied to both sides of the positive electrode current collector (aluminum foil), dried, and then pressed at a predetermined pressure to prepare a sheet-shaped positive electrode.
Further, a negative electrode active material (graphite), a binder (SBR: styrene-butadiene copolymer), and a thickener (CMC: carboxymethyl cellulose) are mixed with a dispersion medium (water) to form a paste-like negative electrode mixture. A sheet-shaped negative electrode was prepared by applying the negative electrode mixture to both sides of a sheet-shaped negative electrode current collector (copper foil), drying the mixture, and then pressing the sheet-shaped negative electrode mixture.
Next, after laminating the above-mentioned positive electrode and negative electrode via a separator, the wound electrode body was produced by winding the laminated body. Then, after the wound electrode body was housed in the battery case together with the non-aqueous electrolytic solution, the battery case was sealed to prepare a 4V class lithium ion secondary battery for evaluation test. _{The non-aqueous electrolyte solution is a non-aqueous electrolyte solution in which a supporting salt (LiPF 6} ) is contained at a concentration of about 1 mol / liter in a mixed solvent containing EC, DMC, and EMC in a volume ratio of 3: 4: 3. It was used.

2. In the preparation of the measurement described above battery excess lithium, pasty collected positive electrode active material before preparing the positive electrode, the positive electrode active neutralizing weight ratio L _B of the active material for a lithium compound in the substance titration Measured by. Specifically, 2.01 g to 2.04 g of the positive electrode active material was mixed with 100 ml of a solvent (ion-exchanged water) to prepare a test solution. Next, a 10% barium chloride aqueous solution (2 ml) and a phenolphthalein solution were added to the test solution, and then a 1 mol / L HCl aqueous solution was added dropwise. Then, based on the dropping amount of aqueous HCl at which the test solution was discolored (pH ≒ 8), to calculate the weight ratio L _B of the active material for a lithium compound in the positive electrode active material.
Furthermore, in the present test example, according to the procedure similar to the positive electrode active material described above, it was weighed ratio _{L A} of _Li 3 PO _{4 Li} 3 PO ₄ for lithium compounds (powder materials) in. The results of each measurement are shown in Table 1.
In the present test example, based on the weight ratio L _B weight ratio L _A and the active material for a lithium compound Li ₃ PO ₄ for a lithium compound described above, the total amount of excess lithium positive electrode layer ((L _{a × W a) + (L} B × W B)) was calculated. The calculation results are shown in Table 1.

3. 3. Evaluation test In this test example, the viscosity increase rate (%) of the above samples 1 to 7 was measured and a high temperature durability test was performed. Specific conditions will be described below.

(1) Viscosity increase rate A paste-like positive electrode mixture was collected during the preparation of the secondary batteries of Samples 1 to 7, and the viscosity was measured using a B-type viscometer (No. 5 rotor, 2 rpm). Then, using the viscosity of sample 1 as a reference (100%), the viscosity of the positive electrode mixture of each sample with respect to the viscosity of sample 1 was calculated as the viscosity increase rate. The calculation results are shown in Table 1 and FIG.

(2) High-temperature durability test In this test, after initial charging and discharging of the secondary batteries of each sample, a high-temperature durability test is conducted in which each secondary battery is stored in a high-temperature environment, and resistance increases before and after the test. The rate was measured.
Specifically, the secondary battery of each sample was charged to 4.1 V and then initially charged and discharged to discharge to 3.0 V. Then, the secondary battery of each sample is adjusted to a state of SOC 60%, CC discharge is performed at a rate of 10 C for 10 seconds in a temperature environment of 25 ° C., and a plot of current (I) -voltage (V) at this time is performed. The initial resistance value was obtained from the slope of the linear approximation line of the value.
Next, after conducting a high-temperature durability test in which the secondary batteries of each sample are stored in a high-temperature environment of 60 ° C. for 24 hours, the resistance value (resistance value after the test) is measured under the same conditions as the above initial resistance value. Then, based on the resistance value after the test and the initial resistance value, the resistance increase rate (%) by the high temperature durability test was determined. The results are shown in Table 1 and FIG.

As shown in Table 1 and FIG. 4, in Sample 7 in which the total amount of excess lithium exceeded 30.6, an increase in the viscosity of the positive electrode mixture was confirmed. It is understood that this is because the excess lithium contained in the positive electrode mixture layer reacts with the binder and the positive electrode mixture gels.
Further, as shown in Table 1 and FIG. 5, it was confirmed that the resistance of Sample 1 in which the total amount of surplus lithium was less than 0.44 increased after the high temperature durability test. It is understood that this is because the excess lithium in the positive electrode mixture layer is too small and the resistance value of the positive electrode mixture layer is significantly reduced, so that the reaction tends to proceed rapidly and the high temperature durability is lowered.
Then, in Samples 2 to 6, gelation of the positive electrode mixture and deterioration of high temperature durability were suitably suppressed. From this, it was confirmed that a high-performance secondary battery can be efficiently manufactured by adjusting the total amount of surplus lithium within the range of 0.44 to 30.6.

Although the present invention has been described in detail above, the above-described embodiment is merely an example, and the invention disclosed here includes various modifications and modifications of the above-mentioned specific examples.

10 Positive electrode 12 Positive electrode current collector 14 Positive electrode mixture layer 16 Positive electrode mixture layer non-formed part 20 Negative electrode 22 Negative electrode current collector 24 Negative electrode mixture layer 26 Negative electrode mixture layer non-formed part 40 Separator 50 Battery case 52 Case body 54 Lid Body 70 Positive electrode terminal 72 Negative electrode terminal 80 Winding electrode body 100 Lithium ion secondary battery

Claims (1)

Non-aqueous electrolysis having a positive electrode having a positive electrode mixture layer formed on a positive electrode current collector, a negative electrode having a negative electrode mixture layer formed on a negative electrode current collector, and a lithium compound containing fluorine as a supporting salt. A non-aqueous electrolytic solution secondary battery comprising a liquid and containing a positive electrode active material, Li ₃ PO _{4 and a binder in the positive electrode mixture layer.}
Here, in the positive-electrode mixture layer, at least one of the positive electrode active excess lithium compound in the material and the excess lithium compound in the Li ₃ PO ₄ as measured by the neutralization titration method which is measured by the neutralization titration method Is included,
The weight ratio of the excess lithium compound in the _Li 3 PO ₄ in the _Li 3 PO ₄ and (wt%) and _{L A,} the weight ratio of the _Li 3 PO ₄ with respect to the positive-electrode mixture layer of (wt%) and _{W A} , when the weight ratio of the positive electrode active excess lithium compound in the material in the positive electrode active material (wt%) and L _B, the weight ratio of the positive active material for the positive electrode composite layer (wt%) was W _B , The positive electrode mixture layer is formed so as to satisfy the following formula (1) .
A non-aqueous electrolyte secondary battery in which the solid content of the _{Li 3} PO ₄ is 1 wt% to 4 wt% when the solid content of the entire positive electrode mixture layer is 100 wt%.
_{0.44 ≦ (L A × W A} ) + (L B × W B) ≦ 30.6 (1)

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