JP2019087510A - Nonaqueous electrolyte secondary battery - Google Patents

Abstract

To provide a technique, in a technique of adding LiPOto a positive electrode mixture layer, by which a nonaqueous electrolyte secondary battery having a suitable battery performance can be obtained efficiently.SOLUTION: In a nonaqueous electrolyte secondary battery herein disclosed, a positive electrode mixture layer includes a positive electrode active material, LiPOand a binder. In the nonaqueous electrolyte secondary battery, the positive electrode mixture layer includes at least one of a lithium compound for an active material, which is a precursor of the positive electrode active material, and a lithium compound for LiPO, which is a precursor of LiPO. The positive electrode mixture layer is formed so as to satisfy the following expression (1): 0.44≤(L×W)+(L×W)≤30.6 (1), where Lis a weight proportion of the lithium compound for LiPOin LiPO, Wis a weight proportion of LiPOto the positive electrode mixture layer, Lis a weight proportion of the lithium compound for the active material in the positive electrode active material, and Wis a weight proportion of the positive electrode active material to the positive electrode mixture layer.SELECTED DRAWING: None

Description

The present invention relates to a non-aqueous electrolyte secondary battery. Specifically, the present invention relates to a non-aqueous electrolyte secondary battery in which trilithium phosphate (Li ₃ PO ₄ ) is added to a 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 and have higher energy density than existing batteries. Is used as a so-called portable power source for vehicles and a power source for driving a vehicle. The positive electrode of the non-aqueous electrolyte secondary battery is configured by, for example, applying a positive electrode mixture layer to the surface of a positive electrode current collector that is a conductive foil.

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

JP 2014-103098 A

As described above, in Patent Document 1, Li ₃ PO ₄ or the like is added to the positive electrode mixture layer in order to suppress various problems in the overcharged state, but there is room for improvement in such technology. There is a need for a technology that can efficiently obtain a secondary battery having more preferable performance.
In particular, Patent Document 1 is a technology directed to a high potential battery having an operating potential (open circuit voltage) of 4.3 V (vs. Li ^/ Li ⁺ ) or more, and a secondary battery having an operating potential of 4.25 V or less It has been difficult to say that the technology is preferably applicable to 4V class batteries), and therefore, development of technology suitable for 4V class batteries has been desired.

This invention is made in view of this point, The main objective is the technology which adds Li ₃ PO ₄ to the positive electrode mixture layer, and the non-aqueous electrolyte secondary battery having suitable battery performance. It is providing a technology that can be obtained efficiently.

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

The non-aqueous electrolyte secondary battery disclosed herein comprises 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 the negative electrode current collector. A non-aqueous electrolytic solution having a lithium compound containing fluorine as a support salt is provided, 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 And / or at least one of the lithium compounds. 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 Assuming that the weight ratio of L is L _B and the weight ratio of the positive electrode active material to the positive electrode mixture layer is W _B , the positive electrode mixture layer is formed so as to satisfy the following formula (1).
0.44 ≦ (L _A × W _A ) + (L _B × W _B ) ≦ 30.6 (1)

  As a result of conducting various experiments and studies in order 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 the "surplus lithium" is It has been found that the battery performance is greatly affected.

Specifically, the positive electrode active material which is the main component of the positive electrode mixture layer is made of 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.). In order to cause the lithium compound for the active material and the other material to react appropriately when generating the positive electrode active material, an excess of the lithium compound for the active material is added, and the positive electrode active material after generation is not yet The reaction may contain a lithium compound for active material.
Further, also in the production of a powder material of Li ₃ PO ₄ , a precursor (lithium compound for Li ₃ PO ₄ ) such as lithium hydroxide (LiOH) and other materials as in the production of the positive electrode active material described above (Phosphoric acid (H ₂ PO ₃ ), etc.) is reacted, and unreacted Li ₃ PO ₄ powder material (hereinafter, such powder material is also simply referred to as “Li ₃ PO ₄ ”) after generation. Lithium compounds for Li ₃ PO ₄ may be included.
This way the positive-electrode mixture layer containing a positive electrode active material and Li ₃ PO _4, may be a lithium compound are each precursor is contained in an unreacted state. In the present specification, the lithium compound for Li ₃ PO ₄ and the lithium compound for the active material are generally referred to as “excess lithium”.

As a result of conducting various studies, the present inventor has found that the content of the above-mentioned excess lithium significantly affects the performance of the secondary battery. Specifically, if the content of the excess lithium is too small, the resistance value of the positive electrode mixture layer is significantly reduced, and the reaction is likely to progress rapidly in the early stage of the charge / discharge reaction. There is a risk that the sex etc. will decrease.
In addition, the inventor has found that the content of the above-mentioned excess lithium can greatly affect the production efficiency of the secondary battery. Specifically, when the positive electrode mixture contains a large amount of excess lithium, the binder and the excess lithium may react to gelate the positive electrode mixture. When such gelation occurs, it becomes difficult to form a positive electrode mixture layer of a desired thickness on the surface of the positive electrode current collector, which causes the production efficiency of the secondary battery to be significantly reduced.

The non-aqueous electrolyte secondary battery disclosed herein is made as a result of conducting various experiments and studies based on the above-described findings, and the "content of excess lithium" in the positive electrode mixture layer is predetermined. It is adjusted in 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 Where W _A is the weight ratio of the lithium compound for the active material in the positive electrode active material to L _B and the weight ratio of the positive electrode active material to the positive electrode mixture layer is W _B , “(L _A × W _A ) + It can be represented by the formula (L _B × W _B ).
And, in the non-aqueous electrolyte secondary battery disclosed herein, the content ((L _A × W _A ) + (L _B × W _B )) of the excess lithium represented by the above-mentioned formula 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 the content of excess lithium being too large, and to preferably lower the capacity retention ratio and the high temperature durability due to the content of excess lithium being too small. It can be prevented.
Therefore, according to the non-aqueous electrolyte secondary battery disclosed herein, it is possible to efficiently obtain a secondary battery having suitable battery performance.

It is a perspective view which shows typically the external 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 excess lithium. It is a graph which shows the relationship between the total amount of excess lithium, and a resistance increase rate. 5 is a graph showing the relationship between the total amount of excess lithium and the thickening rate of the positive electrode mixture layer.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the following drawings, the same reference numerals are given to members and portions that exhibit the same action. Also, the dimensional relationships (length, width, thickness, etc.) in the drawings do not reflect the actual dimensional relationships. Further, matters other than the matters particularly mentioned in the present specification and matters necessary for the practice of the present invention (for example, the general technology concerning the composition of the negative electrode and the construction of the non-aqueous electrolyte secondary battery) are This can be understood as a design matter of a person skilled in the art based on prior art in the field.

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 housing the electrode body 80 shown in FIG. 2 inside the rectangular battery case 50 shown in FIG.

(1) Battery Case The battery case 50 is composed of a flat case main body 52 whose upper end is opened and a lid 54 for closing the opening of the upper end. 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 above-described battery case 50 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-like positive electrode 10 and a negative electrode 20 together with a long sheet-like separator 40. It is. In addition, the electrode body used for the non-aqueous-electrolyte secondary battery disclosed here is not limited to a wound electrode body as shown in FIG. 2, For example, the positive electrode of several sheets and a negative electrode are interposed via a separator. It may be a laminated electrode body laminated alternately.

(A) Positive Electrode In the positive electrode 10 in FIG. 2, the positive electrode mixture layer 14 mainly composed of a positive electrode active material is formed on the surface (both sides) of the long sheet-like positive electrode current collector 12. A positive electrode mixture layer non-formed portion 16 not coated with the positive electrode mixture layer 14 is formed at one side edge portion in the width direction of the positive electrode 10. This positive electrode mixture layer non-formed portion 16 Are electrically connected to the above-mentioned positive electrode terminal 70 (see FIG. 1).
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) And at least one side is included. The “excess lithium” in the present specification is a generic term for “lithium compound for active material” and “lithium compound for Li ₃ PO ₄ ” existing in the positive electrode mixture layer 14 in an unreacted state. The detailed composition of the positive electrode mixture layer 14 containing such excess lithium will be described in detail later.

(B) Negative Electrode In the same manner as the positive electrode 10, the negative electrode mixture layer 24 mainly composed of a negative electrode active material is formed on both sides of the long sheet-like negative electrode current collector 22. Then, a negative electrode mixture layer non-formed portion 26 is formed at one side edge portion in the width direction of the negative electrode 20, and this negative electrode mixture layer non-formed portion 26 electrically connects with the negative electrode terminal 72 (see FIG. 1). 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, carbon materials such as graphite (graphite), non-graphitizable carbon (hard carbon), graphitizable carbon (soft carbon), carbon nanotubes, or materials having a combination thereof are used. Can. Among these carbon materials, it is preferable to use a graphite-based material (natural graphite (graphite), artificial graphite or the like) from the viewpoint of energy density. The negative electrode mixture layer 24 may also contain other additives (for example, a binder, a thickener, and the like). Examples of the binder include styrene butadiene rubber (SBR), and examples of the thickener include carboxymethyl cellulose (CMC).

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

(3) Nonaqueous Electrolyte Further, in the battery case 50 of the lithium ion secondary battery 100 according to this embodiment, the nonaqueous electrolyte is housed (filled) together with the above-mentioned electrode body 80. As the non-aqueous electrolytic solution, for example, a mixed solvent of ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) (for example, volume ratio 3: 4: 3) What is contained by (for example, about 1 mol / L) is mentioned. As such a supporting salt, lithium compounds containing fluorine, for example, LiPF ₆ , LiBF ₄ , LiCF ₃ SO _{3 and the} like are 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 includes a positive electrode active material, Li ₃ PO ₄ , a binder, and excess 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 absorbing and desorbing 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% (eg, 88 wt%), where the solid content of the entire positive electrode mixture layer 14 is 100 wt%.
Moreover, the kind in particular of the positive electrode active material in this embodiment is not restrict | limited, The thing similar to the positive electrode active material of a general lithium ion secondary battery can be used. Specific examples of the lithium composite oxide used for the positive electrode active material include lithium nickel composite oxide (for example, LiNiO ₂ ), lithium cobalt composite oxide (for example, LiCoO ₂ ), lithium manganese composite oxide (for example, LiMn) ₂ O ₄ ), lithium-nickel-cobalt-manganese composite oxide (eg, LiNi _1/3 Co _1/3 Mn _1/3 O ₂ ), and the like.
These lithium composite oxides are produced by mixing a precursor lithium compound for an active material and a source of another metal element and then calcining. Specific examples of such an active material for a lithium compound, lithium hydroxide (LiOH) and lithium carbonate _(Li 2 CO _3), and the like.

(2) Trilithium Phosphate As described above, the positive electrode mixture layer 14 in the present embodiment contains trilithium phosphate (Li ₃ PO ₄ ). When the lithium ion secondary battery 100 is overcharged, the Li ₃ PO ₄ can adsorb an acid (for example, hydrogen fluoride (HF)) generated by the decomposition of the non-aqueous electrolytic solution on the surface. . By this, it is possible to suppress heat generation at the time of overcharge, elution of the metal element, and the like. The solid content of the Li ₃ PO ₄ is preferably 1 wt% to 4 wt% (for example, 3 wt%), where the solid content of the entire positive electrode mixture layer 14 is 100 wt%.
The powder material of this Li ₃ PO ₄ is produced by reacting a lithium compound for Li ₃ PO ₄ , which is a precursor, with phosphoric acid (H ₂ PO ₃ ). Concrete examples of the _Li 3 PO ₄ for lithium compound include lithium hydroxide (LiOH).

(3) Binder Further, in order to adhere the positive electrode mixture layer 14 to the surface of the positive electrode current collector 12, a binder is added to the positive electrode mixture layer 14. 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.
In addition, additives other than the binder may be added to the positive electrode mixture layer 14. As an example of an additive other than a binder, the electrically conductive agent which consists of carbon materials, such as carbon black, is mentioned. When the solid content of the entire positive electrode mixture layer 14 is 100 wt%, the total solid content of the additive including the binder is preferably 6 wt% to 12 wt% (e.g. 9 wt%).

(4) Excess Lithium And, in the positive electrode mixture layer 14 in the present embodiment, excess lithium such as the above-mentioned lithium compound for active material or lithium compound for Li ₃ PO ₄ (ie, lithium hydroxide (LiOH) or lithium carbonate (Such as Li ₂ CO ₃ ).
If the content of the excess lithium is too small, the resistance value of the positive electrode mixture layer 14 is significantly reduced, so the reaction proceeds rapidly at the beginning of the charge / discharge reaction, and the capacity retention rate, high temperature durability, etc. are significantly reduced. There is a risk of In addition, when the content of the excess lithium is too large, there is a possibility that the binder and the excess lithium react to gelate the positive electrode mixture layer 14 to cause 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 the 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 Assuming that the weight ratio of ₄ is W _A , the weight ratio of the lithium compound for the active material in the positive electrode active material is L _B, and the weight ratio of the positive electrode active material to the positive electrode mixture layer 14 is W _B (L _A × W _A ) It is represented by the formula called (L _B × W _B ). In the lithium ion secondary battery 100 according to the present embodiment, the total amount of surplus lithium is adjusted 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 excess lithium so as to satisfy the above-mentioned equation (1), the resistance value of the positive electrode mixture layer 14 can be maintained at an appropriate value, so the capacity retention ratio due to the significant reduction of the resistance value And high temperature durability can be properly prevented. Moreover, gelation of the positive electrode mixture layer 14 due to the reaction between the binder and the excess lithium can be prevented. Therefore, according to this 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, the positive electrode mixture layer is peeled off and collected from the positive electrode current collector, and the positive electrode mixture layer is mixed with a predetermined solvent (for example, NMP) to prepare a test solution. Next, a phenolphthalein solution is added to the prepared test solution, and a 1 mol / L aqueous HCl solution is dropped to a first neutralization point (see FIG. 3) of pH ≒ 8 at which the test solution is discolored. And based on the dripping amount of the HCl aqueous solution at this time, the total amount ((L _A × W _A ) + (L _B × W _B )) of the excess lithium contained in the positive electrode mixture layer can be measured.

Then, in making a lithium ion secondary battery 100 according to this embodiment, before forming the positive-electrode mixture layer 14, the _Li 3 PO _{4 Li} 3 PO ₄ for lithium compounds (powder materials) in 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 )) can be easily adjusted within the range of 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 embodiment, the lithium ion secondary battery has been described as an example of the non-aqueous electrolyte secondary battery disclosed herein, but such description is intended to limit the application object of the present invention Instead, the present invention can also be applied to non-aqueous electrolyte secondary batteries other than lithium ion secondary batteries.
However, a lithium ion secondary battery (4 V class battery) whose working potential is 4.25 V (vs. Li / Li ⁺ ) or less has a large effect on the battery performance due to the total amount of excess lithium in the positive electrode mixture layer. It has the property that high temperature durability and the like are easily reduced. Accordingly, such a 4V class battery is particularly preferable as an application target of the present invention, since the effect of the present invention can be exhibited more remarkably.

[Test example]
Hereinafter, although the test example regarding this invention is demonstrated, description of a test example is not intending limiting this invention.

1. Preparation of Each Test Example In this test example, 7 types of positive electrode mixtures having different total amounts of surplus lithium are prepared, and 4 V class lithium ion secondary batteries (samples 1 to 7) are prepared using each positive electrode mixture. Made.

Specifically, for each of the samples 1 to 7, the positive electrode active material (lithium-nickel-cobalt-manganese composite oxide), Li ₃ PO ₄ , the conductive material (AB: acetylene black), and the binder (PVdF) The mixture was mixed, and the mixture was dispersed in a dispersion medium (water) to prepare a paste-like positive electrode mixture. Then, the prepared positive electrode mixture was applied to both surfaces of a positive electrode current collector (aluminum foil) and dried, and then pressed at a predetermined pressure to produce a sheet-like positive electrode.
In addition, a negative electrode active material (graphite), a binder (SBR: styrene-butadiene copolymer), and a thickener (CMC: carboxymethyl cellulose) are mixed in a dispersion medium (water) to form a paste-like negative electrode mixture. After preparing and apply | coating and drying the said negative electrode compound material on both surfaces of a sheet-like negative electrode collector (copper foil), the sheet-like negative electrode was produced by pressing.
Next, the positive electrode and the negative electrode described above were laminated via a separator, and then the laminated body was wound to produce a wound electrode body. Then, after the wound electrode body was housed in the battery case together with the non-aqueous electrolyte, the battery case was sealed to prepare a 4V class lithium ion secondary battery for evaluation test. In addition, the non-aqueous electrolyte is a non-aqueous electrolyte in which a mixed solvent containing EC, DMC and EMC in a volume ratio of 3: 4: 3 contains a supporting salt (LiPF ₆ ) at a concentration of about 1 mol / liter. 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, a test solution was prepared by mixing 2.01 g to 2.04 g of the positive electrode active material in 100 ml of a solvent (ion-exchanged water). Next, a 10% aqueous solution of barium chloride (2 ml) and a phenolphthalein solution were added to the test solution, and then a 1 mol / L aqueous solution of HCl was dropped 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 respective measurement results 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 x W _A ) + (L _B x W _B )) was calculated. The calculation results are shown in Table 1.

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

(1) Viscosity increase rate During preparation of the secondary batteries of Samples 1 to 7, the paste-like positive electrode mixture was collected, and the viscosity was measured using a B-type viscometer (No. 5 rotor, 2 rpm). And the viscosity of the sample 1 was made into the reference | standard (100%), and the viscosity of the positive electrode compound material of each sample with respect to the viscosity of the said sample 1 was computed as a viscosity increase rate. The calculation results are shown in Table 1 and FIG.

(2) High-Temperature Durability Test In this test, the secondary battery of each sample is subjected to initial charge and discharge, and then the high-temperature durability test for storing each secondary battery in a high temperature environment is performed. The rate was measured.
Specifically, an initial charge and discharge was performed in which the secondary battery of each sample was charged to 4.1 V and then discharged to 3.0 V. Then, the secondary battery of each sample is adjusted to a state of SOC 60%, CC discharge is performed for 10 seconds at a rate of 10 C in a temperature environment of 25 ° C., and a plot of current (I) -voltage (V) at this time. The initial resistance value was determined from the slope of the linear approximation of the value.
Next, after performing a high temperature endurance test for storing the secondary battery of each sample 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 initial resistance value described above. Then, based on the resistance value and the initial resistance value after the test, the resistance increase rate (%) in the high temperature endurance 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 considered that this is because excess lithium contained in the positive electrode mixture layer reacts with the binder to gel the positive electrode mixture.
In addition, as shown in Table 1 and FIG. 5, it was confirmed that, in sample 1 in which the total amount of excess lithium was less than 0.44, the resistance increased after the high temperature durability test. This is considered to be due to the fact that the reaction easily progresses rapidly and the high temperature durability is lowered as the excess lithium in the positive electrode mixture layer becomes too small and the resistance value of the positive electrode mixture layer is significantly reduced.
And in Samples 2 to 6, the gelation of the positive electrode mixture and the lowering of the high temperature durability were suitably suppressed. From this, it was confirmed that a high-performance secondary battery can be efficiently produced by adjusting the total amount of excess lithium in the range of 0.44 to 30.6.

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

10 positive electrode 12 positive electrode current collector 14 positive electrode mixture layer 16 positive electrode mixture layer non-formed portion 20 negative electrode 22 negative electrode current collector 24 negative electrode mixture layer 26 negative electrode mixture layer non-formed portion 40 separator 50 battery case 52 case main body 54 lid 70 positive electrode terminal 72 negative electrode terminal 80 wound electrode body 100 lithium ion secondary battery

Claims (1)

Nonaqueous electrolysis comprising 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 support salt A non-aqueous electrolyte secondary battery comprising: a solution; and the positive electrode mixture layer containing a positive electrode active material, Li ₃ PO ₄ and a binder,
Here, the positive electrode mixture layer contains at least one of a lithium compound for an active material which is a precursor of the positive electrode active material and a lithium compound for Li ₃ PO ₄ which is a precursor of the Li ₃ PO ₄ . Yes,
Wherein the weight ratio of _Li 3 PO the _Li 3 PO ₄ for a lithium compound in ₄ and _{L A,} the weight ratio of the _Li 3 PO ₄ with respect to the positive-electrode mixture layer and _{W A,} the utilization of the positive electrode active material in the weight ratio of the material for a lithium compound and L _B, when the weight ratio of the positive active material for the positive-electrode mixture layer was W _B, the positive-electrode mixture layer is formed to satisfy equation (1) below The non-aqueous electrolyte secondary battery.
0.44 ≦ (L _A × W _A ) + (L _B × W _B ) ≦ 30.6 (1)

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