JP6774632B2 - 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 configured by, for example, applying a positive electrode mixture layer to the surface of a positive electrode current collector which is a foil body having conductivity.

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. Techniques for adding inorganic phosphoric acid compounds such as ₄ ) have been proposed (see, for example, Patent Documents 1 and 2). 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 when the battery is overcharged, thereby causing overcharging. It is possible to suppress heat generation and the like.

Japanese Unexamined Patent Publication No. 2014-103098 JP-A-2015-103332

In the techniques described in Patent Documents 1 and 2 described above, in order to appropriately exert the effect of the inorganic phosphoric acid compound such as trilithium phosphate, the content of the inorganic phosphoric acid compound with respect to the positive electrode active material in the positive electrode mixture layer is determined. It stipulates. 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. Since there are cases where a suitable effect cannot be obtained due to variations, 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 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. On the other hand, in a lithium ion secondary battery, it is desired that the battery resistance in the low SOC (State of Charge) region is small.

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 heat generation during overcharging is suppressed. At the same time, it is an object of the present invention to provide a non-aqueous electrolyte secondary battery having a low battery resistance in a low SOC region.

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. A non-aqueous electrolytic solution containing a lithium compound containing fluorine as a supporting salt is provided. The positive electrode mixture layer contains at least a positive electrode active material and trilithium phosphate particles. The negative electrode mixture layer contains at least a negative electrode active material. The amount of the negative electrode mixture layer (mg / cm ² ), the specific surface area of the negative electrode active material (m ² / g), and the content ratio (mass%) of the negative electrode active material in the negative electrode mixture layer. 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 with respect to the product. The percentage of the product with (mass%) is 0.05% or more and 6.55% or less. That is, [{(specific surface area of trilithium phosphate particles (m ² / g)) × (median diameter d50 (μm) of trilithium phosphate particles) × (containing trilithium phosphate particles in the positive electrode mixture layer). Ratio (mass%))} / {(Amount of grain of negative electrode mixture layer (mg / cm ² )) × (Specific surface area of negative electrode active material (m ² / g)) × (Negative electrode active material in negative electrode mixture layer) Content ratio (mass%))}] The value of the percentage (%) represented by × 100 is 0.05 or more and 6.55 or less.

When the above percentage is 6.55% or less, the resistance of the non-aqueous electrolyte secondary battery in the low SOC region can be sufficiently reduced. Further, when the percentage is 0.05% or more, heat generation at the time of overcharging of the non-aqueous electrolyte secondary battery can be suppressed. Therefore, according to such a configuration, it is a non-aqueous electrolyte secondary battery in which trilithium phosphate is added to the positive electrode mixture layer, and heat generation during overcharging is suppressed and in a low SOC region. It is possible to provide a non-aqueous electrolyte secondary battery having a low battery resistance.

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 resistance in Experiment A. 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 resistance in Experiment B. It is a graph which shows the evaluation result of the heat generation at the time of overcharging 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. Moreover, the dimensional relationship (length, width, thickness, etc.) in each drawing does not reflect the actual dimensional relationship. 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 rectangular 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 electrolyte 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 a lithium nickel composite oxide, a lithium nickel cobalt composite oxide, and a lithium nickel cobalt manganese composite oxide. As the positive electrode active material, a material having an operating potential of less than 4.3 V (vs. Li ^/ Li ⁺ ) is preferable because the effect of the present invention is particularly high.
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 an additive such as a conductive agent or 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 may be contained in the positive electrode mixture layer 14. However, heat generation during overcharging, elution of metal elements, etc. can be suitably suppressed, and problems that may occur due to the addition of trilithium phosphate, such as a decrease in productivity and an increase in reaction resistance, are prevented. 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.

(3) Non-aqueous electrolyte solution The battery case 50 of the lithium ion secondary battery 100 according to the present embodiment contains (fills) the non-aqueous electrolyte solution together with the wound electrode body 80 described above. As such a non-aqueous electrolytic 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 Percentage Value for Trilithium Phosphate Particles and Negative Electrode In the lithium ion secondary battery 100 according to the present embodiment, the amount of the negative electrode mixture layer 24 (mg / cm ² ) and the negative electrode active material The specific surface area (m ² / g) of the trilithium phosphate particles and the phosphoric acid with respect to the product of the specific surface area (m ² / g) and the content ratio (mass%) of the negative electrode active material in the negative electrode mixture layer 24. The percentage of the product of the median diameter d50 (μm) of the trilithium particles and the content ratio (mass%) of the trilithium phosphate particles in the positive electrode mixture layer 14 is 0.05% or more and 6.55% or less. .. That is, [{(specific surface area of trilithium phosphate particles (m ² / g)) × (median diameter d50 (μm) of trilithium phosphate particles) × (trilithium phosphate particles in the positive electrode mixture layer 14). Content ratio (mass%))} / {(grain size of negative electrode mixture layer 24 (mg / cm ² )) × (specific surface area of negative electrode active material (m ² / g)) × (in negative electrode mixture layer 24) The value of the percentage (%) represented by the content ratio (mass%) of the negative electrode active material)}] × 100 is 0.05 or more and 6.55 or less.
When the percentage is 6.55% or less, the resistance of the lithium ion secondary battery 100 in the low SOC region can be sufficiently reduced. Further, when the percentage is 0.05% or more, heat generation at the time of overcharging of the lithium ion secondary battery 100 can be suppressed.
Therefore, in the lithium ion secondary battery 100, when the percentage is 0.05% or more and 6.55% or less, it is possible to achieve both suppression of heat generation during overcharging and low resistance in a low SOC region. The reason is unknown, but it is presumed as follows. Trilithium phosphate forms a film on the surface of the negative electrode active material. When overcharged, heat is generated not only from the positive electrode but also from the negative electrode. Therefore, in order to obtain the heat generation suppressing effect at the time of overcharging without variation, in addition to appropriately suppressing heat generation by the action of trilithium phosphate on the positive electrode side, a coating derived from trilithium phosphate is applied on the negative electrode side. It is also considered important to optimize the amount of formation and suppress heat generation. Further, in order to suppress the resistance in the low SOC region to a small value, it is considered important that the reaction resistance of the positive electrode and the increase in the resistance of the negative electrode due to the formation of the trilithium phosphate-derived film are appropriately suppressed. In order to optimize the amount of film formed and suppress the increase in resistance, the specific surface area of the trilithium phosphate particles, the median diameter d50 of the trilithium phosphate particles, the content ratio of the trilithium phosphate particles, and the texture of the negative electrode mixture layer The amount, the specific surface area of the negative electrode active material, and the content ratio of the negative electrode active material may be involved, and the formation of a film is formed by setting the above-mentioned specific percentage range to 0.05% or more and 6.55% or less. It is considered that the appropriate amount and the suppression of the increase in resistance can be preferably achieved.

The specific surface area of the trilithium phosphate particles and the specific surface area of the negative electrode active material can be measured and determined 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.

(4) Half-value width of the positive electrode active material and a specific percentage value for trilithium phosphate particles The half-value width of the diffraction peak on the (003) plane in the X-ray diffraction measurement of the positive electrode active material can affect the battery characteristics. Therefore, in the present embodiment, 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 The percentage of the half-value width value of the diffraction peak of the (003) plane in the X-ray diffraction measurement of the positive electrode active material with respect to the product of (mass%) is preferably 0.05% or more and 3.21% or less. That is, the half-value width of the diffraction peak on the (003) plane in the X-ray diffraction measurement of the positive electrode active material / {(specific surface area of trilithium phosphate particles (m ² / g)) × (median diameter of trilithium phosphate particles) The value of the percentage (%) represented by d50 (μm)) × (content ratio (mass%) of trilithium phosphate particles in the positive electrode mixture layer) × 100 is 0.05 or more and 3.21 or less. Is preferable. When the percentage is 0.05% or more, the battery resistance of the lithium ion secondary battery 100 in the low SOC region can be particularly lowered. Further, when the percentage is 3.21% or less, heat generation during overcharging of the lithium ion secondary battery 100 can be particularly suppressed. It is considered that this is because the trilithium phosphate particles are more likely to adsorb the acid generated by the decomposition of the non-aqueous electrolytic solution. Therefore, when the percentage is 0.05% or more and 3.21% or less, it is possible to achieve both suppression of heat generation during charging and low resistance in the low SOC region at a high level.

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.

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, [{(specific surface area of trilithium phosphate particles (m ² / g)) × (median diameter d50 (μm) of trilithium phosphate particles) × (trilithium phosphate particles in the positive electrode mixture layer) Content ratio (mass%))} / {(grain of negative electrode mixture layer (mg / cm ² )) × (specific surface area of negative electrode active material (m ² / g)) × (negative electrode in negative electrode mixture layer) The percentage of active material content (% by mass)}]] × 100 (hereinafter, also referred to as “specific percentage of trilithium phosphate particles and negative electrode”) was examined.

(1) Preparation of Lithium Ion Secondary Battery of Test Examples 1 to 14 As a positive electrode active material, a lithium nickel cobalt manganese composite having a half-value width of the diffraction peak on the (003) plane in X-ray diffraction measurement of 0.2. Oxides were prepared. A dispersion medium (NMP:) of lithium nickel-cobalt-manganese composite oxide as the positive electrode active material, particles of trilithium phosphate (Li ₃ PO ₄ ), a conductive material (AB: acetylene black), and a binder (PVDF). N-methylpyrrolidone) was dispersed 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 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 rubber), and a thickener (CMC) were mixed with a dispersion medium (water) to prepare a paste-like negative electrode mixture. A negative electrode active material having a specific surface area (m ² / g) shown in Table 1 is used, and the blending amount (mass%) of the negative electrode active material is the value shown in Table 1 with respect to the total solid content of the negative electrode mixture. (Note that this blending amount corresponds to the content in the negative electrode mixture). Then, the prepared negative electrode mixture was applied to both sides of the sheet-shaped negative electrode current collector (copper foil), dried, and then pressed to prepare a sheet-shaped negative electrode. At this time, the coating amount of the negative electrode mixture and the pressing conditions were adjusted so that the basis weight (mg / cm ² ) of the negative electrode mixture layer was as shown in Table 1.

Then, after laminating the positive electrode and the negative electrode via the separator, the wound electrode body is produced by winding the laminated body, and the wound electrode body is housed in the battery case together with the non-aqueous electrolytic solution and sealed. By doing so, the lithium ion secondary batteries of Test Examples 1 to 14 were produced. These lithium ion secondary batteries are 4V class lithium ion secondary batteries. In addition, the non-aqueous electrolytic 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 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) Battery resistance evaluation 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 IV resistance was calculated by dividing the amount of such voltage drop by the discharge current value. The ratio of the IV resistance obtained for each battery when the predetermined reference value was set to 100 was calculated. 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 specific percentage of the trilithium phosphate particles and the negative electrode is 6.55% or less, the battery resistance is kept low. Understand. On the other hand, as shown by the results in Table 1 and FIG. 4, when the specific percentage of the trilithium phosphate particles and the negative electrode is 0.05% or more, the heat generation during overcharging is suppressed. Understand. Therefore, when the specific percentage of the trilithium phosphate particles and the negative electrode is 0.05% or more and 6.55% or less, suppression of heat generation during overcharging and low battery resistance in the low SOC region are simultaneously achieved. You can see that you can.

2. Experiment B
In Experiment B, [half-value width of the diffraction peak on the (003) plane in the X-ray diffraction measurement of the positive electrode active material / {(specific surface area of trilithium phosphate particles (m ² / g)) × (trilithium phosphate particles). The median diameter d50 (μm)) × (content ratio of trilithium phosphate particles in the positive electrode mixture layer (mass%))}] × 100 (hereinafter, “half-value range of positive electrode active material and We also examined "a specific percentage of trilithium phosphate particles") and investigated the optimum value of the percentage.

(1) Preparation of Lithium Ion Secondary Batteries of Test Examples 15 to 26 Various lithium nickel-cobalt-manganese composite oxides having different half-value widths of diffraction peaks on the (003) plane in X-ray diffraction measurement as positive electrode active materials. Prepared. A dispersion medium (NMP:) of lithium nickel-cobalt-manganese composite oxide as the positive electrode active material, particles of trilithium phosphate (Li ₃ PO ₄ ), a conductive material (AB: acetylene black), and a binder (PVDF). N-methylpyrrolidone) was dispersed to prepare a paste-like positive electrode mixture. At this time, a positive electrode active material having a value of the half specific surface area of the diffraction peak on the (003) plane in the X-ray diffraction measurement shown in Table 2 was used, and trilithium phosphate was used as the median diameter d50 shown in Table 2. The particles having (μm) and specific surface area (m ² / g) were used, and the blending amount of the trilithium phosphate particles was set to the values shown in Table 2 with respect to the total solid content of the positive electrode mixture (note that the values shown in Table 2 were obtained). 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) were mixed with a dispersion medium (water) to prepare a paste-like negative electrode mixture. .. As the negative electrode active material, a material having a specific surface area of 4.3 m ² / g was used, and the blending amount of the negative electrode active material was set to 98.8% by mass with respect to the total solid content of the negative electrode mixture (). In addition, this compounding amount corresponds to the content in the negative electrode mixture layer). Then, the prepared negative electrode mixture was applied to both sides of the sheet-shaped negative electrode current collector (copper foil), dried, and then pressed to prepare a sheet-shaped negative electrode. At this time, the basis weight of the negative electrode mixture layer was set to 10.5 mg / cm ² .

Then, after laminating the positive electrode and the negative electrode via the separator, the wound electrode body is produced by winding the laminated body, and the wound electrode body is housed in the battery case together with the non-aqueous electrolytic solution and sealed. By doing so, the lithium ion secondary batteries of Test Examples 15 to 26 were produced. These lithium ion secondary batteries are 4V class lithium ion secondary batteries. In addition, the non-aqueous electrolytic 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 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 2 and FIG.

(B) Battery resistance evaluation 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 IV resistance was calculated by dividing the amount of such voltage drop by the discharge current value. The ratio of the IV resistance obtained for each battery when the predetermined reference value was set to 100 was calculated. The results are shown in Table 2 and FIG.

(3) Evaluation Results As shown in the results of Table 2 and FIG. 5, the battery resistance is low when the half-value width of the positive electrode active material and the specific percentage of the trilithium phosphate particles are 0.05% or more. You can see that it is suppressed. On the other hand, as shown in the results of Table 2 and FIG. 6, when the half-value width of the positive electrode active material and the specific percentage of the trilithium phosphate particles are 3.21% or less, heat generation during overcharging is suppressed. You can see that it is done. Therefore, when the half-value range of the positive electrode active material and the specific percentage value for the trilithium phosphate particles are 0.05% or more and 3.21% or less, the heat generation during overcharging is suppressed and low at a high level. It can be seen that low battery resistance in the SOC region can be achieved at the same time.

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 with a positive electrode mixture layer formed on the positive electrode current collector,
Negative electrode with a negative electrode mixture layer formed on the negative electrode current collector
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.
The negative electrode mixture layer contains at least the negative electrode active material and contains.
The amount of the negative electrode mixture layer (mg / cm ² ), the specific surface area of the negative electrode active material (m ² / g), and the content ratio (mass%) of the negative electrode active material in the negative electrode mixture layer. 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 with respect to the product. The percentage of the product with (mass%) is 0.05% or more and 6.55% or less.
Non-aqueous electrolyte secondary battery.

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