Electrode for non-aqueous electrolyte secondary battery and non-aqueous electrolyte secondary battery

Abstract

The electrode for a non-aqueous electrolyte secondary battery includes a current collector, an active material layer formed on the current collector, and an aggregate of filler particles present in an island shape on the surface of the active material layer. The filler particles are compound particles containing at least one of phosphorus, silicon, boron, nitrogen, potassium, sodium, and bromine, and the phase change point from a solid phase to a liquid phase or thermal decomposition is in the range of 180°C to 1000°C.

Description

Technical Field

[0001] The present disclosure relates to an electrode for a non-aqueous electrolyte secondary battery and a non-aqueous electrolyte secondary battery. Background Art

[0002] In recent years, as a secondary battery with high output and high energy density, a non-aqueous electrolyte secondary battery in which lithium ions move between a positive electrode and a negative electrode for charge and discharge has been widely used.

[0003] However, as a safety evaluation test for confirming the internal short-circuit resistance of a battery, there is a nail penetration test. The nail penetration test is a test in which, for example, a nail is driven into the battery to simulate an internal short circuit and the degree of heat generation is studied to confirm the safety of the battery. Suppressing the heat generation of the battery during such nail penetration is important for ensuring the safety of the battery.

[0004] For example, Patent Document 1 discloses a technique for suppressing heat generation of a battery in a nail penetration test by disposing a coating containing a functional material selected from a phosphorus-containing compound, a nitrogen-containing compound, and an inorganic silicon compound on the plate surfaces of a positive electrode and a negative electrode.

[0005] For example, Patent Document 2 discloses a technique for suppressing a temperature rise during abnormal heat generation of a battery by disposing an intermediate layer containing polyphosphate between a positive electrode and a negative electrode.

[0006] Prior Art Documents

[0007] Patent Documents

[0008] Patent Document 1: Japanese Patent Application Laid-Open No. 2017-534138

[0009] Patent Document 2: Japanese Patent No. 6249399 Summary of the Invention

[0010] When, as in Patent Document 1 and Patent Document 2, an intermediate layer of polyphosphate having a coating of a functional material disposed on the plate surface is provided, these layers become resistances and there is a problem of an increase in battery resistance.

[0011] An electrode for a non-aqueous electrolyte secondary battery according to one aspect of the present disclosure includes a current collector, an active material layer formed on the current collector, and an aggregate of filler particles present in an island shape on the surface of the active material layer. The filler particles are compound particles containing at least any one of phosphorus, silicon, boron, nitrogen, potassium, sodium, and bromine, and the phase change point from a solid phase to a liquid phase or thermal decomposition is in the range of 180°C to 1000°C.

[0012] A non-aqueous electrolyte secondary battery according to one aspect of the present disclosure has a positive electrode and a negative electrode, and at least one of the positive electrode and the negative electrode is the electrode for a non-aqueous electrolyte secondary battery.

[0013] According to the present disclosure, it is possible to suppress an increase in battery resistance and suppress heat generation of the battery in a nail penetration test. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 FIG. is a schematic cross-sectional view showing an example of the configuration of the electrode of the present embodiment.

[0015] Figure 2 FIG. is a schematic cross-sectional view of a non-aqueous electrolyte secondary battery as an example of the embodiment. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0016] Hereinafter, embodiments of the present disclosure will be described based on the drawings.

[0017] Figure 1 FIG. is a schematic cross-sectional view showing an example of the configuration of the electrode of the present embodiment. Figure 1 The shown electrode 60 is an electrode for a non-aqueous electrolyte secondary battery and is applied to at least one of a positive electrode and a negative electrode of the non-aqueous electrolyte secondary battery.

[0018] Figure 1 The shown electrode 60 includes a current collector 62, an active material layer 64 formed on the current collector 62, and an aggregate 66 of filler particles existing in an island shape on the surface of the active material layer 64. That is, the surface structure of the electrode 60 forms a sea-island structure having a sea region on the surface of the active material layer and an island region of the aggregate 66 of filler particles. The aggregate 66 is a monomer or is formed by aggregating a plurality of filler particles.

[0019] The filler particles constituting the aggregate 66 are compound particles containing at least any one of phosphorus, silicon, boron, nitrogen, potassium, sodium, and bromine, and the phase change point from a solid phase to a liquid phase or thermal decomposition is in the range of 180°C to 1000°C.

[0020] By using the electrode for a non-aqueous electrolyte secondary battery of the present embodiment, the rise in the battery temperature during the nail penetration test is suppressed. The mechanism is not fully clear, but it can be speculated as follows. The heat released by the battery during the nail penetration test and the heat released by the battery when internal short circuit is simulated by nailing into the battery cause the filler particles constituting the aggregate 66 to change from the solid phase to the liquid phase and flow on the surface of the active material layer 64, or to stretch on the surface of the active material layer 64 by thermal decomposition, forming a coating film covering the surface of the active material layer 64. This coating film functions as a resistance component, so the amount of short-circuit current flowing between the positive and negative electrodes by the nail is suppressed. As a result, the rise in the battery temperature during the nail penetration test is also suppressed. It should be noted that the formation of the coating film after the filler particles change to the liquid phase depends on the type of filler particles, but also on, for example, the temperature rise above the melting point of the filler material, hot welding reaction, dehydration condensation reaction, thermal polymerization reaction, etc.

[0021] In addition, by using the electrode for a non-aqueous electrolyte secondary battery of the present embodiment, the rise in the battery resistance is suppressed. In the case of normal use where no abnormal heat release of the battery occurs, the aggregate 66 of the filler particles is a material with low lithium ion conductivity. Therefore, if it exists in a layered form, it will hinder the movement of lithium ions and cause an increase in the battery resistance. However, since it is in an island shape in the present embodiment, there are gaps between the aggregates 66, and lithium ions and the like can easily pass through these gaps. Therefore, during the charge and discharge of the battery, compared with the case where the entire surface of the active material layer 64 is covered without gaps by the covering layer of the filler particles, lithium ions move smoothly between the positive and negative electrodes, so it is considered that the rise in the battery resistance is suppressed.

[0022] Hereinafter, the constituent materials of the electrode 60 will be described in further detail.

[0023] The filler particles are not particularly limited as long as they are compound particles containing at least any one of phosphorus, silicon, boron, nitrogen, potassium, sodium, and bromine, and the phase change point from solid phase to liquid phase or thermal decomposition is in the range of 180°C to 1000°C. Examples of the filler particles include phosphoric acid compounds, silicic acid compounds, boric acid compounds, melamine compounds, potassium salt compounds, sodium salt compounds, etc. Examples of the phosphoric acid compounds include phosphoric acid-metal salts such as lithium phosphate, sodium phosphate, potassium phosphate, calcium phosphate, magnesium phosphate, and aluminum phosphate, condensed phosphates such as ammonium polyphosphate, sodium tripolyphosphate, and melamine polyphosphate, and phosphate esters such as trimethyl phosphate and triphenyl phosphate. Examples of the boric acid compounds include boric acid-metal salts such as sodium borate, potassium borate, calcium borate, magnesium borate, aluminum borate, and melamine borate, borate esters such as trimethyl borate, boron oxides, and condensed borates. Examples of the silicic acid compounds include silicic acid-metal salts such as sodium silicate, potassium silicate, calcium silicate, magnesium silicate, barium silicate, and manganese silicate. Examples of the melamine compounds include melamine cyanurate, melamine pyrophosphate, ethylidene bis(melamine), trimethylene bis(melamine), tetramethylene bis(melamine), hexamethylene bis(melamine), and 1,3-hexylene bis(melamine). Examples of the potassium salt compounds include potassium pyrosulfate (K2S2O7), potassium citrate monohydrate (C6H5K3O7·H2O), and potassium carbonate. Examples of the sodium salt compounds include sodium carbonate. Among these, melamine polyphosphate, ammonium polyphosphate, sodium tripolyphosphate, sodium silicate, sodium borate, potassium citrate monohydrate, lithium metaphosphate, potassium dihydrogen phosphate, melamine cyanurate, potassium pyrosulfate, boron oxide, ethylidene-1,2-bis(pentabromobenzene), ethylene bis(tetrabromophthalimide), potassium carbonate, and sodium carbonate are preferred.

[0024] The phase change point of the filler particles can be in the range of 180°C to 1000°C, preferably in the range of 250°C to 600°C, so that the heat release of the battery passing the nail penetration test and appropriately changing from solid phase to liquid phase or undergoing thermal decomposition.

[0025] From the aspect of suppressing the increase in battery resistance, the coverage rate of the aggregate 66 relative to the surface of the active material layer 64 is preferably 90% or less, more preferably 65% or less. In addition, from the aspect of suppressing the increase in battery temperature during the nail penetration test, the coverage rate of the aggregate 66 relative to the surface of the active material layer 64 is preferably 5% or more. If the coverage rate increases, the formation time of the covering layer covering the surface of the active material layer 64 during battery heat release becomes shorter, but there will be an increase in battery resistance. Therefore, it is necessary to adopt an optimal configuration according to the purpose. The coverage rate of the aggregate 66 can be calculated as follows.

[0026] The coverage rate can be determined by performing elemental mapping of the electrode surface using, for example, SEM-EDX (Energy Dispersive X-ray Spectroscopy). For example, by using elemental mapping, the island regions of the aggregate 66 and the sea regions on the surface of the active material layer are distinguished, and the ratio of the area of the island regions to the total area of the island regions and the sea regions is calculated to determine the coverage rate. As the accuracy of elemental mapping, if there is a non-covered region of about 2 μm square, the sea regions and the island regions can be distinguished.

[0027] The number of aggregates 66 having an area of 1000 μm 2 or less relative to the total number of aggregates 66 is preferably 80% or more, more preferably 90% or more. If the number of aggregates 66 having an area of 1000 μm 2 or less is larger, the gaps between the aggregates 66, which are paths through which lithium ion plasmas easily pass, will increase in a large range, in large quantities, and in a more uniform form, so that an increase in battery resistance can be suppressed.

[0028] Preferably, there are 100 or more aggregates 66 per 1 mm 2 and more preferably 200 or more. If there are more filler particles constituting the aggregate 66, the coverage of the surface of the active material layer 64 by the exotherm of the battery during the nail penetration test and the phase change of the filler particles from the solid phase to the liquid phase or the thermal decomposition proceeds more rapidly, so that the rise in the battery temperature during the nail penetration test can be effectively suppressed.

[0029] The average particle size of the filler particles constituting the aggregate 66 is preferably in the range of 0.1 μm to 20 μm, more preferably 0.5 μm to 3 μm. The average particle size of the filler particles is determined as follows. First, 20 filler particles are randomly selected from the SEM image of the electrode surface. Then, the grain boundaries of the selected 20 filler particles are observed, and based on determining the outer shape of the filler particles, the area of each of the 20 filler particles is determined, and the average particle size of the filler particles is calculated from their average value.

[0030] In the aggregate 66, in addition to the aforementioned filler particles, a binder material may also be included. By including the binder material, the adhesiveness between the filler particles and the adhesiveness between the filler particles and the current collector 62 can be improved. The binder material is not particularly limited, and examples thereof include polyvinylidene fluoride (PVdF), ethylene glycol dimethacrylate, allyl methacrylate, tert-dodecyl mercaptan, α-methylstyrene dimer, and methacrylic acid. It should be noted that polyvinylidene fluoride (PVdF), ethylene glycol dimethacrylate, allyl methacrylate, tert-dodecyl mercaptan, α-methylstyrene dimer, and methacrylic acid can bond the electrode 60 and the separator 13 by applying pressure and / or heat to the aggregate 66. In addition, the aggregate 66 may also include compound particles other than the aforementioned filler particles. Examples of the compound particles other than the aforementioned filler particles include inorganic particles such as alumina, boehmite, and titanium dioxide.

[0031] When the electrode 60 is used as the positive electrode, as the current collector 62 of the positive electrode current collector, for example, a foil of a metal such as aluminum that is stable within the potential range of the positive electrode, a thin film having the metal disposed on the surface layer, or the like can be used. In addition, the active material layer 64 as the positive electrode active material layer contains a positive electrode active material, and it is desirable to include a conductive material and a binder material.

[0032] Examples of the positive electrode active material include lithium transition metal composite oxides. Specifically, lithium cobalt oxide, lithium manganese oxide, lithium nickel oxide, lithium nickel manganese composite oxide, lithium nickel cobalt composite oxide, etc. can be used. Al, Ti, Zr, Nb, B, W, Mg, Mo, etc. can also be added to these lithium transition metal composite oxides.

[0033] As the conductive material, carbon powders such as carbon black, acetylene black, Ketjen black, and graphite can be used alone or in combination of two or more.

[0034] Examples of the binder material include fluorine-based resins such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), polyimide-based resins, acrylic resins, polyolefin-based resins, etc. These can be used alone or in combination of two or more.

[0035] An example of the method for manufacturing the positive electrode will be described. First, a positive electrode composite material slurry containing a positive electrode active material, a binder material, a conductive material, a solvent, etc. is coated on the positive electrode current collector, and after the coating film is dried, it is rolled to form a positive electrode active material layer on the positive electrode current collector. Next, a filler slurry containing filler particles, a binder material, a solvent, etc. is prepared. Then, the prepared filler slurry is sprayed, dropped, transferred, or coated on the positive electrode active material layer, and then dried to form an aggregate of filler particles present in an island shape on the surface of the positive electrode active material layer. Examples of the solvent contained in the slurry include water, N-methyl-2-pyrrolidone (NMP), ethanol, etc.

[0036] For island-shaped aggregates, for example, island-shaped aggregates are obtained by adjusting the filler particles and the solvent amount contained in the slurry for the filler, and controlling the spraying amount, dropping amount, or coating amount of the slurry for the filler. In addition, for example, island-shaped aggregates can also be obtained by disposing a masking sheet or the like provided with a plurality of through holes of a specified size on the positive electrode active material layer, and spraying, dropping, or coating the slurry for the filler from the disposed masking sheet.

[0037] When using the electrode 60 as the negative electrode, as the current collector 62 of the negative electrode current collector, for example, a foil of a metal stable within the potential range of the negative electrode such as copper, a thin film of this metal disposed on the surface layer, or the like can be used. In addition, the active material layer 64 as the negative electrode active material layer contains a negative electrode active material, and it is desirable to contain a binder material or the like.

[0038] As the negative electrode active material, a carbon material capable of storing / releasing lithium ions can be used. In addition to graphite, non-graphitizable carbon, graphitizable carbon, fibrous carbon, coke, carbon black, etc. can be used. Further, as non-carbon-based materials, silicon, tin, and alloys and oxides mainly composed of them can be used.

[0039] Examples of the binder material include fluororesin, PAN, polyimide resin, acrylic resin, polyolefin resin, styrene-butadiene rubber (SBR), nitrile rubber (NBR), carboxymethyl cellulose (CMC) or its salt, polyacrylic acid (PAA) or its salt (PAA-Na, PAA-K, etc., and a partially neutralized salt can also be used), polyvinyl alcohol (PVA), etc. These can be used alone or in combination of two or more.

[0040] An example of the method for manufacturing the negative electrode will be described below. First, a negative electrode composite slurry containing a negative electrode active material, a binder material, a solvent, etc. is coated on the negative electrode current collector, and after drying the coating film, it is rolled to form a negative electrode active material layer on the negative electrode current collector. Next, a slurry for the filler containing filler particles, a binder material, a solvent, etc. is sprayed, dropped, or coated on the negative electrode active material layer, and then dried to form an aggregate of filler particles existing in an island shape on the surface of the negative electrode active material layer. The method for obtaining the island-shaped aggregate is as described above.

[0041] An example of the non-aqueous electrolyte secondary battery of the present embodiment will be described below.

[0042] Figure 2 It is a schematic cross-sectional view of a non-aqueous electrolyte secondary battery as an example of the embodiment. Figure 2The non-aqueous electrolyte secondary battery 10 shown includes: a wound electrode body 14 formed by winding a positive electrode 11 and a negative electrode 12 with a separator 13 interposed therebetween, a non-aqueous electrolyte, insulating plates 18 and 19 respectively disposed above and below the electrode body 14, and a battery case 15 for housing the above components. The battery case 15 is composed of a bottomed cylindrical case main body 16 and a sealing body 17 that seals the opening of the case main body 16. It should be noted that instead of the wound electrode body 14, an electrode body of other types such as a stacked electrode body formed by alternately stacking a positive electrode and a negative electrode with a separator interposed therebetween can also be applied. In addition, as the battery case 15, examples include metal cases such as cylindrical, square, coin-shaped, and button-shaped cases, and resin cases (so-called laminated types) formed by laminating resin sheets, etc.

[0043] The case main body 16 is, for example, a bottomed cylindrical metal container. A gasket 28 is provided between the case main body 16 and the sealing body 17 to ensure the airtightness inside the battery. The case main body 16, for example, has a protruding portion 22 that protrudes inward from a part of the side surface and is used to support the sealing body 17. The protruding portion 22 is preferably formed in a ring shape along the circumferential direction of the case main body 16, and the sealing body 17 is supported by its upper surface.

[0044] The sealing body 17 has a structure in which a metal plate 23 with an opening, a lower valve body 24, an insulating member 25, an upper valve body 26, and a lid 27 are laminated in sequence from the side of the electrode body 14. Each component constituting the sealing body 17, for example, has a circular plate shape or a ring shape, and the components other than the insulating member 25 are electrically connected to each other. The lower valve body 24 and the upper valve body 26 are connected to each other at their central portions, and the insulating member 25 is sandwiched between their peripheral portions. When the internal pressure of the secondary battery 10 rises due to heat generation caused by internal short circuit or the like, for example, the lower valve body 24 deforms and breaks in a manner of pushing the upper valve body 26 toward the lid 27 side, and the current path between the lower valve body 24 and the upper valve body 26 is blocked. When the internal pressure further rises, the upper valve body 26 breaks, and gas is discharged from the opening of the lid 27.

[0045] Figure 2 In the non-aqueous electrolyte secondary battery 10 shown, the positive electrode lead 20 attached to the positive electrode 11 extends toward the sealing body 17 side through the through hole of the insulating plate 18, and the negative electrode lead 21 attached to the negative electrode 12 extends toward the bottom side of the case main body 16 through the outside of the insulating plate 19. The positive electrode lead 20 is connected to the lower surface of the metal plate 23 with an opening, which is the bottom plate of the sealing body 17, by welding or the like, and the lid 27, which is the top plate of the sealing body 17 and is electrically connected to the metal plate 23 with an opening, becomes the positive electrode terminal. The negative electrode lead 21 is connected to the inner surface of the bottom of the case main body 16 by welding or the like, and the case main body 16 becomes the negative electrode terminal.

[0046] The aforementioned electrode 60 is applied to at least one of the positive electrode 11 and the negative electrode 12. The separator 13 can be a porous sheet or the like having ion permeability and insulation. Specific examples of the porous sheet include microporous films, woven fabrics, non-woven fabrics, etc. As the material of the separator 13, olefin-based resins such as polyethylene and polypropylene, cellulose, etc. are preferable. The separator 13 can also be a laminate having a cellulose fiber layer and a thermoplastic resin fiber layer such as an olefin-based resin. In addition, it can also be a multi-layer separator including a polyethylene layer and a polypropylene layer, and a material in which an aramid-based resin, ceramics, etc. are coated on the surface of the separator 13 can also be used.

[0047] The non-aqueous electrolyte contains a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent. As the non-aqueous solvent, for example, esters, ethers, nitriles, amides, and mixed solvents of two or more of these can be used. The non-aqueous solvent can also contain a halogen substitute obtained by substituting at least a part of the hydrogen of these solvents with a halogen atom such as fluorine. As the electrolyte salt, for example, lithium salts such as LiPF6 can be used.

[0048] Next, examples will be described.

[0049] <Example>

[0050] <Example 1>

[0051] [Fabrication of positive electrode]

[0052] 100 parts by weight of the positive electrode active material represented by LiNi 0.82 Co 0.15 Al 0.03 O2, 1 part by weight of acetylene black (AB), and 1 part by weight of polyvinylidene fluoride (PVdF) were mixed, and further an appropriate amount of N-methyl-2-pyrrolidone (NMP) was added to prepare a positive electrode composite material slurry. Next, the positive electrode composite material slurry was coated on both sides of the positive electrode current collector formed of aluminum foil and dried. It was cut into a specified electrode size and rolled using a roller to form a positive electrode active material layer on both sides of the positive electrode current collector. Next, 5 parts by weight of melamine polyphosphate particles and 1 part by weight of polyvinylidene fluoride (PVdF) were mixed, and further 100 mL of N-methyl-2-pyrrolidone (NMP) was added to prepare a slurry for the filler. 100 mL of the slurry for the filler was coated on the positive electrode active material layer to a Wet (wet) film thickness equivalent to 4 μm and dried. This was used as the positive electrode of Example 1.

[0053] The surface of the positive electrode of Example 1 was observed by SEM-EDX, and as a result, it was confirmed that the aggregate of melamine polyphosphate particles was in an island shape, and the coverage rate of the aggregate of melamine polyphosphate particles was 5%.

[0054] [Fabrication of negative electrode]

[0055] Mix 100 parts by weight of graphite powder, 1 part by weight of carboxymethyl cellulose (CMC), and 1 part by weight of styrene-butadiene rubber (SBR), and then appropriately add water to prepare a negative electrode composite material slurry. Next, coat both sides of the negative electrode current collector formed of copper foil with the negative electrode composite material slurry and dry it. Cut it into a specified electrode size and roll it using a roller to form a negative electrode active material layer on both sides of the negative electrode current collector.

[0056] [Preparation of Non-aqueous Electrolyte]

[0057] For a mixed solvent in which ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) are mixed in a volume ratio of 3:3:4, dissolve lithium hexafluorophosphate (LiPF6) to a concentration of 1 mol / L to prepare a non-aqueous electrolyte.

[0058] [Fabrication of Non-aqueous Electrolyte Secondary Battery]

[0059] (1) After installing a positive electrode lead on the positive electrode current collector and a negative electrode lead on the negative electrode current collector, wind it with a polyethylene separator between the positive electrode and the negative electrode to fabricate a wound electrode body.

[0060] (2) Dispose insulating plates above and below the electrode body, weld the negative electrode lead to the outer shell body, weld the positive electrode lead to the sealing body, and accommodate the electrode body in the outer shell body.

[0061] (3) After injecting the non-aqueous electrolyte into the outer shell body by a vacuum method, seal the open end of the outer shell body with the sealing body through a gasket. Use it as a non-aqueous electrolyte secondary battery.

[0062] <Example 2>

[0063] In the preparation of the filler slurry, set the addition amount of melamine polyphosphate particles to 30 parts by weight, and coat 100 mL of the prepared filler slurry on the positive electrode active material layer with a Wet film thickness equivalent to 6 μm. Except for this, fabricate a non-aqueous electrolyte secondary battery in the same manner as in Example 1. Observe the surface of the positive electrode of Example 2 by SEM-EDX. As a result, it was confirmed that the aggregates of melamine polyphosphate particles were island-shaped, and in addition, the coverage rate of the aggregates of melamine polyphosphate particles was 65%.

[0064] <Example 3>

[0065] In the preparation of the slurry for the filler, the addition amount of melamine polyphosphate particles was set to 30 parts by weight, and 100 mL of the prepared slurry for the filler was coated on the positive electrode active material layer to be equivalent to 10 μm in terms of Wet film thickness. Except for this, a non-aqueous electrolyte secondary battery was produced in the same manner as in Example 1. The surface of the positive electrode of Example 3 was observed by SEM-EDX, and as a result, it was confirmed that the aggregates of melamine polyphosphate particles were island-shaped. In addition, the coverage rate of the aggregates of melamine polyphosphate particles was 90%.

[0066] <Examples 4 to 6>

[0067] In the preparation of the slurry for the filler, the melamine polyphosphate particles were replaced with ammonium polyphosphate particles. Except for this, Example 4 was produced in the same manner as Example 1, Example 5 was produced in the same manner as Example 2, and Example 6 was produced in the same manner as Example 3 for the non-aqueous electrolyte secondary battery. The surfaces of the positive electrodes of Examples 4 to 6 were observed by SEM-EDX, and as a result, it was confirmed that the aggregates of ammonium polyphosphate particles were island-shaped. In addition, the coverage rates of the aggregates of ammonium polyphosphate particles were 5%, 65%, and 90% respectively.

[0068] <Examples 7 to 9>

[0069] In the preparation of the slurry for the filler, the melamine polyphosphate particles were replaced with lithium metaphosphate ((LiPO3) n ) particles. Except for this, Example 7 was produced in the same manner as Example 1, Example 8 was produced in the same manner as Example 2, and Example 9 was produced in the same manner as Example 3 for the non-aqueous electrolyte secondary battery. The surfaces of the positive electrodes of Examples 7 to 9 were observed by SEM-EDX, and as a result, it was confirmed that the aggregates of lithium metaphosphate particles were island-shaped. In addition, the coverage rates of the aggregates of lithium metaphosphate particles were 5%, 65%, and 90% respectively.

[0070] <Examples 10 to 12>

[0071] In the preparation of the slurry for the filler, the melamine polyphosphate particles were replaced with sodium silicate (Na2SiO3) particles. Except for this, Example 10 was produced in the same manner as Example 1, Example 11 was produced in the same manner as Example 2, and Example 12 was produced in the same manner as Example 3 for the non-aqueous electrolyte secondary battery. The surfaces of the positive electrodes of Examples 10 to 12 were observed by SEM-EDX, and as a result, it was confirmed that the aggregates of sodium silicate particles were island-shaped. In addition, the coverage rates of the aggregates of sodium silicate particles were 5%, 65%, and 90% respectively.

[0072] <Examples 13 to 15>

[0073] In the preparation of the slurry for the filler, the melamine polyphosphate particles were replaced with sodium borate (Na2B4O7) particles. Except for this, non-aqueous electrolyte secondary batteries were fabricated in the same manner as in Example 1 for Example 13, in the same manner as in Example 2 for Example 14, and in the same manner as in Example 3 for Example 15. The surfaces of the positive electrodes of Examples 13 to 15 were observed by SEM-EDX. As a result, it was confirmed that the aggregates of sodium borate particles were in the shape of islands. In addition, the coverage rates of the aggregates of sodium borate particles were 5%, 65%, and 90%, respectively.

[0074] <Comparative Example 1>

[0075] A non-aqueous electrolyte secondary battery was fabricated in the same manner as in Example 1, except that the slurry for the filler was not used.

[0076] <Comparative Example 2>

[0077] In the preparation of the slurry for the filler, the addition amount of the melamine polyphosphate particles was set to 30 parts by weight, and 100 mL of the prepared slurry for the filler was coated on the positive electrode active material layer to be equivalent to 15 μm in terms of wet film thickness. Except for this, a non-aqueous electrolyte secondary battery was fabricated in the same manner as in Example 1.

[0078] <Comparative Examples 3 to 6>

[0079] In the preparation of the slurry for the filler, the melamine polyphosphate particles were replaced with ammonium polyphosphate particles in Comparative Example 3, with lithium metaphosphate particles in Comparative Example 4, with sodium silicate particles in Comparative Example 5, and with sodium borate particles in Comparative Example 6. Except for this, non-aqueous electrolyte secondary batteries were fabricated in the same manner as in Comparative Example 2.

[0080] The surfaces of the positive electrodes of Comparative Examples 2 to 6 were observed by SEM-EDX. As a result, aggregates of island-shaped filler particles were not confirmed. In addition, the coverage rate of the aggregates of filler particles was 100%.

[0081] [Stab Test]

[0082] The non-aqueous electrolyte secondary batteries of Examples 1 to 15 and Comparative Examples 1 to 6 were subjected to the stab test according to the following steps.

[0083] (1) In an environment at 25°C, charging was performed at a constant current of 600 mA until the battery voltage reached 4.2 V, and then charging was continued at a constant voltage until the current value reached 90 mA.

[0084] (2) In an environment at 25°C, the center of the side surface of the battery charged in (1) was brought into contact with the tip of a round nail with a diameter of 2.7 mm, and the round nail was inserted into the battery in the stacking direction of the electrode body at a speed of 1 mm / second. After detecting a decrease in the battery voltage caused by an internal short circuit, the insertion of the round nail was immediately stopped.

[0085] (3) Measure the surface temperature of the battery 1 minute after the battery starts to short-circuit through a round nail. Take the measured temperature as the temperature after the nail penetration test and summarize it in Table 1.

[0086] [Battery Resistance]

[0087] Measure the battery resistance of the non-aqueous electrolyte secondary batteries of Examples 1 to 15 and Comparative Examples 1 to 6 as follows. In a temperature environment of 25 °C, charge the non-aqueous electrolyte secondary battery with a constant current of 0.3C until the battery voltage reaches 4.2V, then charge with a constant voltage until the current value becomes 0.05C, and then discharge with a constant current of 0.3C to make the SOC 50%. Next, obtain the voltage values when discharging currents of 0A, 0.1A, 0.5A, and 1.0A are applied for 10 seconds. Calculate the DC-IR based on the absolute value of the slope when linearly approximating the voltage values 10 seconds after each discharge current value by the least squares method, and take this value as the battery resistance and summarize it in Table 1.

[0088] [Table 1]

[0089]

[0090] As shown in Table 1, in Examples 1 to 15 where the aggregates of filler particles exist in an island shape on the surface of the positive electrode active material layer, the battery temperature after the nail penetration test is lower than that of Comparative Example 1 where there are no filler particles on the surface of the positive electrode active material layer. Here, as in Comparative Examples 2 to 6, when the coverage rate of the aggregates of filler particles is set to 100%, the battery resistance increases significantly compared to Comparative Example 1. However, in Examples 1 to 15, the increase in battery resistance is suppressed compared to Comparative Examples 2 to 6. That is, Examples 1 to 15 can suppress the increase in battery resistance and suppress the heat release of the battery during the nail penetration test.

[0091] <Examples 16 to 30>

[0092] Replace the operation of coating the filler on the positive electrode active material layer with the operation of coating it on the negative electrode active material layer. Except for this, non-aqueous electrolyte secondary batteries of Examples 16 to 30 are produced in the same manner as Examples 1 to 15 respectively.

[0093] <Comparative Examples 7 to 10>

[0094] Replace the operation of coating the filler on the positive electrode active material layer with the operation of coating it on the negative electrode active material layer. Except for this, non-aqueous electrolyte secondary batteries of Comparative Examples 7 to 10 are produced in the same manner as Comparative Examples 2 to 6 respectively.

[0095] The coverage rates of the aggregates of the filler particles in Examples 16 to 30 and Comparative Examples 7 to 10 are summarized in Table 2. In addition, in the non-aqueous electrolyte secondary batteries of Examples 16 to 30 and Comparative Examples 7 to 10, the above-mentioned nail penetration test and battery resistance measurement were carried out, and the results are summarized in Table 2.

[0096] [Table 2]

[0097]

[0098] From Table 2, it can be seen that the results on the negative electrode side are the same as those on the positive electrode side. That is, Examples 16 to 30 can suppress the increase in battery resistance and suppress the heat release of the battery in the nail penetration test.

[0099] <Examples 31 to 40>

[0100] In the preparation of the slurry for the filler, the melamine polyphosphate particles were replaced with sodium tripolyphosphate particles in Example 31, with potassium phosphate (KH2PO4) particles in Example 32, with melamine cyanurate in Example 33, with potassium pyrosulfate (K2S2O7) particles in Example 34, with boron oxide (B2O3) particles in Example 35, with ethylidene-1,2-bis(pentabromobenzene) particles in Example 36, with ethylene bis(tetrabromophthalimide) particles in Example 37, with potassium citrate (C6H5K3O7) particles in Example 38, with potassium carbonate (K2CO3) particles in Example 39, and with sodium carbonate (Na2CO3) particles in Example 40. Except for this, the non-aqueous electrolyte secondary battery was produced in the same manner as in Example 1.

[0101] The coverage rates of the aggregates of the filler particles in Examples 31 to 40 are summarized in Table 3. In addition, in the non-aqueous electrolyte secondary batteries of Examples 31 to 40, the above-mentioned nail penetration test and battery resistance measurement were carried out, and the results are summarized in Table 3.

[0102] [Table 3]

[0103]

[0104] Compared with Comparative Example 1 in which there are no filler particles on the surface of the positive electrode active material layer, the battery temperatures after the nail penetration test in Examples 31 to 40 are all lower. In addition, although the battery resistance increases compared with Comparative Example 1, it is at the same level as that in Example 1. That is, it can also be considered that Examples 31 to 40 can also suppress the increase in battery resistance and suppress the heat release of the battery in the nail penetration test.

[0105] Description of the reference numerals

[0106] 10 Non-aqueous electrolyte secondary battery

[0107] 11 Positive electrode

[0108] 12 Negative electrode

[0109] 13 Separator

[0110] 14 Electrode body

[0111] 15 Battery case

[0112] 16 Case main body

[0113] 17 Sealing body

[0114] 18, 19 Insulating plate

[0115] 20 Positive electrode lead

[0116] 21 Negative electrode lead

[0117] 22 Protrusion

[0118] 23 Metal plate with opening

[0119] 24 Lower valve body

[0120] 25 Insulating member

[0121] 26 Upper valve body

[0122] 27 Cover

[0123] 28 Gasket

[0124] 60 Electrode

[0125] 62 Current collector

[0126] 64 Active material layer

[0127] 66 Aggregate

Claims

1. A positive electrode for a non-aqueous electrolyte secondary battery, comprising: a current collector, a positive electrode active material layer formed on the current collector, and an aggregate of filler particles present in an island shape on the surface of the positive electrode active material layer, wherein the filler particles are compound particles containing at least one of phosphorus, silicon, boron, nitrogen, potassium, sodium, and bromine, and the phase change point from solid phase to liquid phase or thermal decomposition is in the range of 180°C to 1000°C, the filler particles contain at least one of melamine polyphosphate, ammonium polyphosphate, lithium metaphosphate, sodium silicate, sodium borate, sodium tripolyphosphate, potassium phosphate, melamine cyanurate, potassium pyrosulfate, boron oxide, ethylene-1,2-bis(pentabromobenzene), ethylene bis(tetrabromophthalimide), potassium citrate, potassium carbonate, and sodium carbonate, the average particle diameter of the filler particles is 0.1 μm to 20 μm, the coverage rate of the aggregate with respect to the surface of the positive electrode active material layer is 5% or more and 65% or less.

2. The positive electrode for a non-aqueous electrolyte secondary battery according to claim 1, wherein, Having an area of 1000 μm or less 2 The number of the aggregates having an area of 1000 μm or less is 80% or more relative to the total number of the aggregates.

3. The positive electrode for a non-aqueous electrolyte secondary battery according to claim 1 or 2, wherein, Per 1 mm 2 There are more than 100 of the said aggregates therein.

4. The positive electrode for a non-aqueous electrolyte secondary battery according to claim 1 or 2, wherein, The aggregate contains a binder material, and the binder material contains at least one of polyvinylidene fluoride (PVdF), ethylene glycol dimethacrylate, allyl methacrylate, tert-dodecyl mercaptan, α-methylstyrene dimer, and methacrylic acid.

5. A non-aqueous electrolyte secondary battery having a positive electrode and a negative electrode, wherein the positive electrode is the positive electrode for a non-aqueous electrolyte secondary battery according to any one of claims 1 to 4.

Images