JP6872149B2 - Non-aqueous electrolyte secondary battery - Google Patents

Description

The present invention relates to a non-aqueous electrolyte secondary battery.

Non-aqueous electrolyte secondary batteries such as lithium ion secondary batteries (lithium secondary batteries) are lighter and have higher energy density than existing batteries. Therefore, in recent years, so-called portable power supplies and vehicles such as personal computers and mobile terminals have been used. It is used as a 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 (see, for example, Patent Document 1). When the battery is overcharged, such an inorganic phosphoric acid compound adsorbs an acid (for example, hydrogen fluoride (HF)) generated by decomposition of a non-aqueous electrolyte solution on the particle surface to cause overcharging. It is possible to suppress heat generation and the like.

Japanese Unexamined Patent Publication No. 2014-103098

In the technique described in Patent Document 1 described above, the content of the inorganic phosphoric acid compound with respect to the positive electrode active material in the positive electrode mixture layer is defined in order to appropriately exert the effect of the inorganic phosphoric acid compound such as trilithium phosphate. ing. However, when trilithium phosphate is actually contained in the positive electrode mixture layer, the function of trilithium phosphate is enhanced even though the content of trilithium phosphate is specified as in the conventional technique described above. In some cases, variation occurred and a suitable effect could not be obtained. Therefore, a technique capable of more appropriately exerting the function of trilithium phosphate is desired.

In particular, a lithium ion secondary battery (so-called 4V class battery) using a positive electrode active material having an operating potential of ^{less than 4.3V (vs. Li /} Li +) generates a large amount of heat when it is in a high voltage state, especially in an overcharged state. Therefore, in the field of such a 4V class battery, it is desired to develop a technique capable of appropriately exerting the function of trilithium phosphate and suppressing heat generation at the time of overcharging.

The present invention has been made in view of this point, and an object of the present invention is a non-aqueous electrolyte secondary battery in which trilithium phosphate is added to a positive electrode mixture layer, and when overcharged by trilithium phosphate. It is an object of the present invention to provide a non-aqueous electrolyte secondary battery in which heat generation is appropriately suppressed.

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 includes a separator interposed between the positive electrode and the negative electrode, and a non-aqueous electrolyte solution containing a lithium compound containing fluorine as a supporting salt. The positive electrode mixture layer contains at least a positive electrode active material and trilithium phosphate particles. The non-aqueous electrolyte secondary battery satisfies at least one of the following conditions (A) and (B).
(A) The specific surface area (m ² / g) of the trilithium phosphate particles, the median diameter d50 (μm) of the trilithium phosphate particles, and the content ratio of the trilithium phosphate particles in the positive electrode mixture layer. When the product with (mass%) is used as the denominator and the air permeability (sec / 100 mL ) of the separator is used as the numerator, the ratio represented by the numerator / denominator is 0.8 or more and 64.1 or less.
(B) The specific surface area (m ² / g) of the trilithium phosphate particles, the median diameter d50 (μm) of the trilithium phosphate particles, and the content ratio of the trilithium phosphate particles in the positive electrode mixture layer. When the product with (mass%) is used as the denominator and the volume ratio of the non-aqueous electrolyte solution to the electrode space is used as the particle, the ratio expressed by the particle / denominator is 0.008 or more and 0.321 or less.

When the numerator / denominator ratio of the above condition (A) is 6.41 or less, heat generation during overcharging can be suppressed. Further, when the numerator / denominator ratio of the above condition (A) is 0.8 or more, the increase in resistance can be suppressed even under the condition that metallic lithium is precipitated. Therefore, when the numerator / denominator ratio of the above condition (A) is 0.8 or more and 6.41 or less, the function of trilithium phosphate can be appropriately exerted and heat generation during overcharging can be suppressed. it can.
Further, when the numerator / denominator ratio of the above condition (B) is 0.008 or more, heat generation at the time of overcharging can be suppressed. Further, since the numerator / denominator ratio of the condition (B) is 0.321 or less, the increase in resistance can be suppressed even after repeated charging and discharging at a high rate. Therefore, when the numerator / denominator ratio of the above condition (B) is 0.008 or more and 0.321 or less, the function of trilithium phosphate can be appropriately exerted and heat generation during overcharging can be suppressed. it can.
That is, according to such a configuration, the non-aqueous electrolytic solution secondary battery in which trilithium phosphate is added to the positive electrode mixture layer, and the heat generation at the time of overcharging is appropriately suppressed by the trilithium phosphate. A non-aqueous electrolyte secondary battery can be provided.

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 graph which shows the evaluation result of the heat generation at the time of overcharging in Experiment A. It is a graph which shows the evaluation result of the resistance increase ratio in Experiment A. It is a graph which shows the evaluation result of the heat generation at the time of overcharging in Experiment B. It is a graph which shows the evaluation result of the resistance increase ratio in Experiment B.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the following drawings, members and parts that perform 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, general techniques for constructing a non-aqueous electrolyte secondary battery) are in the art. It can be grasped as a design matter of a person skilled in the art based on the prior art.

Hereinafter, a lithium ion secondary battery will be described as an example of the non-aqueous electrolyte secondary battery disclosed here. 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. The battery case 50 is made of, for example, aluminum.

(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, positive electrode mixture layers 14 are formed on 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 contains a positive electrode active material as a main component and trilithium phosphate (Li ₃ PO ₄ ) particles.
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). In the present embodiment, the type of the positive electrode active material is not particularly limited, and the same positive electrode active material as that of a general lithium ion secondary battery can be used. Specific examples of such a positive electrode active material include lithium nickel composite oxide, lithium nickel cobalt composite oxide, and lithium nickel cobalt manganese composite oxide. As the positive electrode active material, since the effect of the present invention is particularly high, those having an operating potential of ^{less than 4.3 V (vs. Li /} Li +) are preferable, and 4.25 V (vs. Li ^/ Li +) or less. ^{Those of 4.2 V (vs. Li /} Li +) or less are more preferable, and those of 4.2 V (vs. Li / Li +) or less are further preferable.
The content of trilithium phosphate in the positive electrode mixture layer 14 is, for example, 0.5% by mass or more and 10% by mass or less, preferably 1% by mass or more and 8% by mass or less, and more preferably 1.5% by mass. % Or more and 6% by mass or less.
Further, the positive electrode mixture layer 14 may contain additives such as a conductive agent and a binder, as in the case of a general lithium ion secondary battery. As the conductive agent, for example, a carbon material such as carbon black can be used. As the binder, for example, polyvinylidene fluoride (PVDF), polyvinylidene chloride (PVDC), polyethylene oxide (PEO) and the like can be preferably used.
Further, the positive electrode mixture layer 14 may contain metal elements such as Si, Na, K, Cl, Fe, Cu, Zn, Pb, Ni, Co and Cr. These metal elements are contained in the powder of trilithium phosphate when preparing the paste-like positive electrode mixture, and these metal elements are contained in the positive electrode mixture layer 14. However, it is possible to suitably suppress heat generation and elution of metal elements during overcharging, and prevent problems that may occur due to the addition of trilithium phosphate, such as a decrease in productivity and an increase in reaction resistance. be able to.

(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.

The negative electrode mixture layer 24 contains a negative electrode active material.
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 can be used. .. From the viewpoint of energy density, it is preferable to use graphite-based materials (natural graphite (stone ink), artificial graphite, etc.) among these carbon materials. The content of the negative electrode active material in the negative electrode mixture layer 24 is, for example, 85% by mass or more, preferably 90% by mass or more, and more preferably 95% by mass or more.
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. 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. The thickness of the separator 40 is, for example, 10 μm or more and 50 μm or less, preferably 15 μm or more and 35 μm or less.

(3) Non-aqueous electrolytic solution In the battery case 50 of the lithium ion secondary battery 100 according to the present embodiment, the non-aqueous electrolytic solution is stored (filled) together with the wound electrode body 80 described above. As such a non-aqueous electrolyte solution, a non-aqueous solvent such as carbonates containing a supporting salt is typically used, and for example, ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate ( A solvent containing EMC) and a mixed solvent (for example, a volume ratio of 3: 4: 3) containing a supporting salt at a predetermined concentration (for example, about 1 mol / L) can be used. As the supporting salt, a lithium compound containing fluorine is used, and examples thereof include LiPF ₆ , LiBF ₄ , LiCF ₃ SO _{3, and the} like.

(4) Specific Conditions The lithium ion secondary battery 100 according to the present embodiment satisfies at least one of the following conditions (A) and (B).
Condition (A): The specific surface area (m ² / g) of the trilithium phosphate particles, the median diameter d50 (μm) of the trilithium phosphate particles, and the content ratio of the trilithium phosphate particles in the positive mixture layer 14. When the product with (mass%) is the denominator and the air permeability (sec / 100 mL ) of the separator 40 is the particle, the ratio represented by the particle / denominator (hereinafter, also referred to as "ratio of condition (A)"). ) Is 0.8 or more and 64.1 or less.
Condition (B): The specific surface area (m ² / g) of the trilithium phosphate particles, the median diameter d50 (μm) of the trilithium phosphate particles, and the content ratio of the trilithium phosphate particles in the positive electrode mixture layer 14. When the product with (mass%) is used as the denominator and the volume ratio of the non-aqueous electrolyte solution to the electrode space is used as the molecule, the ratio represented by the particle / denominator (hereinafter, also referred to as “condition (B) ratio”) However, it is 0.008 or more and 0.321 or less.

(A) Condition (A)
The condition (A) is, in other words, the air permeability of the separator 40 (sec / 100 mL ) / {specific surface area ^{of the trilithium phosphate particles (m 2} / g) × median diameter d50 (μm) of the trilithium phosphate particles × The ratio represented by the content ratio (mass%) of the trilithium phosphate particles in the positive electrode mixture layer 14 is 0.8 or more and 64.1 or less.
According to the study by the present inventors, it was found that the heat generated by the lithium ion secondary battery 100 during overcharging occurs not only in the positive electrode 10 but also in the negative electrode 20. The mechanism for suppressing heat generation at the negative electrode 20 is that when the electrode is overcharged, trilithium phosphate reacts with an acid (for example, hydrogen fluoride (HF)) generated by the decomposition of the non-aqueous electrolyte solution, which is a separator. It is considered that this is due to the movement to the negative electrode 20 side via the 40 and forming a film on the particle surface of the substance (particularly the negative electrode active material) constituting the negative electrode 20. Therefore, since the suppression of heat generation involves the passage of the reaction product of trilithium phosphate and the acid through the separator 40, the ease with which this reaction product moves from the positive electrode 10 to the negative electrode 20 is determined by the separator 40. Affected by nature.
Therefore, when the ratio of the condition (A) using the air permeability of the separator 40 is 0.8 or more and 64.1 or less, the function of trilithium phosphate is appropriately exhibited and heat is generated during overcharging. Can be suppressed.
If the ratio of condition (A) is less than 0.8, the resistance increases when metallic lithium is deposited. That is, the function of trilithium phosphate cannot be properly exerted. This is because if the ratio of the condition (A) is less than 0.8, the substance easily passes through the separator 40, and when metallic lithium is deposited on the surface of the negative electrode, it is likely to be deposited toward the inside of the separator 40. Is considered to be. In this case, if the deposition of metallic lithium further progresses, an internal short circuit may occur. On the other hand, if the ratio of the condition (A) exceeds 64.1, it becomes impossible to suppress heat generation at the time of overcharging. It is considered that this is because when the ratio of the condition (A) exceeds 64.1, it becomes difficult for the reaction product of trilithium phosphate and the acid to pass through the separator 40, and as a result, it becomes difficult to form a film. Be done.
The air permeability of the separator 40 can be determined by measuring it by a known method. For example, it can be measured by the method described in JIS P 8117.
The specific surface area of the trilithium phosphate particles can be determined by measuring according to a known method. For example, it can be obtained by a physical gas adsorption method.
The median diameter d50 of the trilithium phosphate particles can be determined by measuring according to a known method. For example, it can be obtained by a laser diffraction / scattering method.

(B) Condition (B)
In other words, the condition (B) is the volume ratio of the non-aqueous electrolyte solution to the electrode space / {specific surface area ^{of trilithium phosphate particles (m 2} / g) × median diameter d50 (μm) of trilithium phosphate particles × positive electrode. The ratio represented by the content ratio (mass%) of trilithium phosphate particles in the mixture layer 14 is 0.008 or more and 0.321 or less.
According to the studies by the present inventors, it was found that the ratio of the volume of the non-aqueous electrolyte solution to the amount of space in the electrode is not a little related to the suppression of heat generation during overcharging.
Therefore, the ratio of the condition (B) using the volume ratio of the non-aqueous electrolyte solution to the electrode space (hereinafter, also referred to as “void ratio”) is 0.008 or more and 0.321 or less, so that trilithium phosphate is trilithium phosphate. It is possible to properly exert the function of the above and suppress heat generation at the time of overcharging.
If the ratio of the condition (B) is less than 0.008, it becomes impossible to suppress heat generation at the time of overcharging. It is considered that this is because the amount of the non-aqueous electrolytic solution that reacts with trilithium phosphate becomes too small. On the other hand, when the ratio of the condition (B) exceeds 0.321, the resistance increases when charging / discharging is performed at a high rate. That is, the function of trilithium phosphate cannot be properly exerted. It is considered that this is because a large amount of non-aqueous electrolytic solution flows through the electrode body 80 when charging / discharging is performed at a high rate, and so-called salt concentration unevenness occurs.
The volume of the electrode space used for the void ratio refers to the total volume of the voids existing in each of the positive electrode 10 and the negative electrode 20.
The volume of the non-aqueous electrolytic solution used for the void ratio is the total volume of the non-aqueous electrolytic solution contained in the lithium ion secondary battery 100.

The lithium ion secondary battery 100 configured as described above can be used for various purposes. Suitable applications include drive power supplies mounted on vehicles such as electric vehicles (EVs), hybrid vehicles (HVs), and plug-in hybrid vehicles (PHVs). The lithium ion secondary battery 100 may also be used in the form of an assembled battery, which typically consists of a plurality of batteries connected in series and / or in parallel. When used in the form of an assembled battery, the lithium ion secondary battery 100 is preferably constrained at an appropriate confining pressure (for example, 9 kN ± 1 kN).

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, as described above, a lithium ion secondary battery (4V class battery) using a positive electrode active material (for example, lithium nickel cobalt manganese composite oxide) having ^{an operating potential of less than 4.3V (vs. Li / Li +).} Is particularly preferable as an application target of the present invention because it has a property that a large amount of heat is generated when it is in an overcharged state and the effect of the present invention can be exerted 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. Experiment A
In Experiment A, the specific surface area (m ² / g) of the trilithium phosphate particles, the median diameter d50 (μm) of the trilithium phosphate particles, and the content ratio (mass) of the trilithium phosphate particles in the positive mixture layer. %) As the denominator, and the air permeability (sec / 100 mL ) of the separator 40 as the particle, the ratio expressed by the particle / denominator (that is, the ratio of condition (A)) is examined. It was.

(1) Preparation of Lithium Ion Secondary Battery of Test Examples 1 to 11 A positive electrode active material (lithium nickel cobalt manganese composite oxide), particles of trilithium _{phosphate (Li 3 PO 4} ), and a conductive material (AB). : Acetylene black) and binder (PVDF) were dispersed in a dispersion medium (NMP: N-methylpyrrolidone) to prepare a paste-like positive electrode mixture. At this time, as the trilithium phosphate particles, those having a median diameter d50 (μm) and a specific surface area (m ² / g) shown in Table 1 were used, and the blending amount (mass%) of the trilithium phosphate particles was a positive electrode. The values shown in Table 1 were set for the total solid content of the mixture (this blending amount corresponds to the content in the positive electrode mixture layer). 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.

Next, a negative electrode active material (graphite), a binder (SBR: styrene-butadiene copolymer), and a thickener (CMC) are mixed with a dispersion medium (water) to prepare a paste-like negative electrode mixture. , The negative electrode mixture was applied to both sides of a sheet-shaped negative electrode current collector (copper foil), dried, and then pressed to prepare a sheet-shaped negative electrode.
Then, after laminating the positive electrode and the negative electrode through a separator having a thickness of 20 ± 2 μm, a wound electrode body is produced by winding the laminated body, and the wound electrode body is combined with a non-aqueous electrolyte solution to make a battery. A 4V class lithium ion secondary battery for evaluation test was produced by housing it in a case and sealing it. At this time, a separator having the air permeability shown in Table 1 was used. _{The non-aqueous electrolyte solution contains a supporting salt (LiPF 6} ) at a concentration of about 1 mol / liter in a mixed solvent containing EC, DMC, and EMC in a volume ratio of about 3: 4: 3. Liquid was used.

(2) Evaluation test (a) Evaluation of heat generation during overcharging Each battery is overcharged by charging the 4V class lithium-ion secondary battery of each test example to 5.1V with a constant current of 20C. By measuring the temperature at the center of the outside of the battery case of each battery, the battery temperature at the time of overcharging was measured. Then, the difference between the battery temperature at the time of overcharging and the battery temperature before charging was calculated. The ratio of the temperature difference obtained for each battery when the predetermined reference value was set to 100 was calculated. The results are shown in Table 1 and FIG.

(B) Evaluation of resistance increase after Li precipitation test Under a temperature environment of 25 ° C., the 4V class lithium ion secondary battery of each test example was adjusted to a state of SOC 20%. Next, in a temperature environment of 25 ° C., the battery was subjected to constant current discharge at a rate of 125 A for 10 seconds, and the amount of voltage drop was measured. Next, the amount of voltage drop was divided by the discharge current value to calculate the IV resistance, which was used as the initial resistance.
Next, a low-temperature pulse charge / discharge cycle test (Li precipitation test) was performed on the lithium ion secondary batteries of each test example under the condition that metallic lithium (Li) was deposited. Specifically, the lithium ion secondary battery of each test example is adjusted to SOC 80%, pulse charged at a constant current of 80 A for 10 seconds under a temperature condition of -10 ° C, paused for 5 seconds, and then 80 A. The pulse discharge was performed for 10 seconds at the constant current of the above, and the pulse charge / discharge pattern resting for 5 seconds was repeated for 1000 cycles.
Then, the IV resistance was determined in the same manner as the method for measuring the initial resistance. The ratio of the resistance after the Li precipitation test when the initial resistance was 100 was determined as the resistance increase ratio. The results are shown in Table 1 and FIG.

(3) Test Results As shown in the results of Table 1 and FIG. 3, when the ratio of the condition (A) is 6.41 or less, it can be seen that the heat generation during overcharging is suppressed. On the other hand, as shown by the results of Table 1 and FIG. 4, when the ratio of the condition (A) is 0.8 or more, it can be seen that the resistance increase is suppressed even after the Li precipitation test. Therefore, it can be seen that when the ratio of the condition (A) is 0.8 or more and 6.41 or less, the function of trilithium phosphate can be appropriately exerted and heat generation at the time of overcharging can be suppressed.

2. Experiment B
In Experiment B, the specific surface area (m ² / g) of the trilithium phosphate particles, the median diameter d50 (μm) of the trilithium phosphate particles, and the content ratio of the trilithium phosphate particles in the positive electrode mixture layer 14 ( When the product with (% by mass) is used as the denominator and the volume ratio (void ratio) of the non-aqueous electrolyte solution to the electrode space is used as the particle, the ratio expressed by the particle / denominator (that is, the “ratio of condition (B)”” ) Was investigated.

(1) Preparation of Lithium Ion Secondary Battery of Test Examples 12 to 21 A positive electrode active material (lithium nickel cobalt manganese composite oxide), particles of trilithium _{phosphate (Li 3 PO 4} ), and a conductive material (AB). : Acetylene black) and binder (PVDF) were dispersed in a dispersion medium (NMP: N-methylpyrrolidone) to prepare a paste-like positive electrode mixture. At this time, as the trilithium phosphate particles, those having a median diameter d50 (μm) and a specific surface area (m ² / g) shown in Table 2 were used, and the blending amount (mass%) of the trilithium phosphate particles was a positive electrode. The values shown in Table 2 were set with respect to the total solid content of the mixture (this blending amount corresponds to the content in the positive electrode mixture layer). 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.

Next, a negative electrode active material (graphite), a binder (SBR: styrene-butadiene copolymer), and a thickener (CMC) are mixed with a dispersion medium (water) to prepare a paste-like negative electrode mixture. , The negative electrode mixture was applied to both sides of a sheet-shaped negative electrode current collector (copper foil), dried, and then pressed to prepare a sheet-shaped negative electrode.
Then, after laminating the positive electrode and the negative electrode through a separator having a thickness of 20 ± 2 μm, a wound electrode body is produced by winding the laminated body, and the wound electrode body is combined with a non-aqueous electrolyte solution to make a battery. A 4V class lithium ion secondary battery for evaluation test was produced by housing it in a case and sealing it. _{The non-aqueous electrolyte solution contains a supporting salt (LiPF 6} ) at a concentration of about 1 mol / liter in a mixed solvent containing EC, DMC, and EMC in a volume ratio of about 3: 4: 3. Liquid was used.
The void ratio was set to the value shown in Table 2 by changing the press conditions at the time of producing the positive electrode and the negative electrode and the amount of the non-aqueous electrolytic solution used.

(2) Evaluation test (a) Evaluation of heat generation during overcharging Each battery is overcharged by charging the 4V class lithium-ion secondary battery of each test example to 5.1V with a constant current of 20C. By measuring the temperature at the center of the outside of the battery case of each battery, the battery temperature at the time of overcharging was measured. Then, the difference between the battery temperature at the time of overcharging and the battery temperature before charging was calculated. The ratio of the temperature difference obtained for each battery when the predetermined reference value was set to 100 was calculated. The results are shown in Table 2 and FIG.

(B) Evaluation of resistance increase after high-rate test Under a temperature environment of 25 ° C., the 4V class lithium ion secondary battery of each test example was adjusted to a state of SOC 20%. Next, in a temperature environment of 25 ° C., the battery was subjected to constant current discharge at a rate of 125 A for 10 seconds, and the amount of voltage drop was measured. Next, the amount of voltage drop was divided by the discharge current value to calculate the IV resistance, which was used as the initial resistance.
Next, a high-rate charge / discharge cycle test (high-rate test) was performed on the lithium-ion secondary batteries of each test example. Specifically, the lithium ion secondary batteries of each test example are charged with a constant current at a rate of 30 C for 10 seconds, paused for 10 minutes, discharged at a rate of 5 C for 1 minute, and then discharged at a constant current for 10 minutes. The charge / discharge cycle of resting for 1 minute was repeated for 10,000 cycles.
Then, the IV resistance was determined in the same manner as the method for measuring the initial resistance. The ratio of the resistance after the high rate test when the initial resistance was 100 was determined as the resistance increase ratio. The results are shown in Table 2 and FIG.

(3) Evaluation Results As shown in the results of Table 2 and FIG. 5, when the ratio of the condition (B) is 0.008 or more, it can be seen that the heat generation at the time of overcharging is suppressed. On the other hand, as shown by the results of Table 2 and FIG. 6, when the ratio of the condition (A) is 0.321 or less, it can be seen that the resistance increase is suppressed even after the high rate test. Therefore, it can be seen that when the ratio of the condition (B) is 0.008 or more and 0.321 or less, the function of trilithium phosphate can be appropriately exerted and heat generation at the time of overcharging can be suppressed.

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)

A positive electrode having a positive electrode mixture layer formed on the positive electrode current collector, and a positive electrode
A negative electrode with a negative electrode mixture layer formed on the negative electrode current collector, and a negative electrode
A separator interposed between the positive electrode and the negative electrode,
A non-aqueous electrolyte solution containing a lithium compound containing fluorine as a supporting salt,
A non-aqueous electrolyte secondary battery equipped with
The positive electrode mixture layer contains at least a positive electrode active material and trilithium phosphate particles.
A non-aqueous electrolyte secondary battery that satisfies at least one of the following conditions (A) and (B).
(A) The specific surface area (m ² / g) of the trilithium phosphate particles, the median diameter d50 (μm) of the trilithium phosphate particles, and the content ratio of the trilithium phosphate particles in the positive electrode mixture layer. When the product with (mass%) is used as the denominator and the air permeability (sec / 100 mL ) of the separator is used as the numerator, the ratio represented by the numerator / denominator is 0.8 or more and 64.1 or less.
(B) The specific surface area (m ² / g) of the trilithium phosphate particles, the median diameter d50 (μm) of the trilithium phosphate particles, and the content ratio of the trilithium phosphate particles in the positive electrode mixture layer. When the product with (mass%) is used as the denominator and the volume ratio of the non-aqueous electrolyte solution to the electrode space is used as the particle, the ratio expressed by the particle / denominator is 0.008 or more and 0.321 or less.

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