A lithium ion secondary battery

Abstract

The present application belongs to the technical field of lithium ion secondary battery, especially a kind of lithium ion secondary battery, in the negative electrode of active material with silicon as main component, even in the volume expansion of negative electrode active material when charging, electrode structure body keeps electrolyte in negative electrode, provide a kind of high capacity and long life lithium ion secondary battery;In the secondary battery (lithium ion secondary battery) of the present application can absorb and release lithium ions, because containing the porous ceramic particles of keeping electrolyte in the negative electrode of silicon material, so there is no situation that the electrolyte kept in the fine hole part of porous ceramic particles is excluded by the volume expansion of silicon-containing particles by absorbing lithium ions and alloying with lithium when charging, so even in the repeated charge and discharge, lithium ion conduction in the negative electrode can be maintained, the decrease of secondary battery performance can be inhibited.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of lithium ion secondary batteries, and particularly relates to a lithium ion secondary battery. BACKGROUND

[0002] In recent years, it has been pointed out that the increase in the amount of carbon dioxide gas in the atmosphere can be the main cause of the greenhouse effect-induced global climate change. The atmospheric pollution containing carbon dioxide, nitrogen oxides, hydrocarbons, etc. emitted from the automobile used as a moving means is also pointed out to have an impact on health. From the viewpoint of environmental protection, recently, a smart grid, which is a hybrid vehicle, an electric vehicle, a solar power generation and a wind power generation device using a combination of an electric motor and an engine working with high energy efficiency using the power stored in a power storage device, is expected to optimize the power demand balance by performing the network management of the power storage of the electric power. In addition, in the information communication field, information terminals such as smartphones also easily perform the reception and transmission of information, and thus are rapidly penetrating into society. Under such circumstances, in order to improve the performance of smartphones, hybrid vehicles, electric vehicles, smart grids, etc., and to suppress the production cost, the development of a power storage device such as a secondary battery having high output density, high energy density, and long life is expected;

[0003] As the above-described power storage device, among currently productized devices, the highest energy density device is a lithium ion secondary battery (broadly referred to as a lithium secondary battery) in which a carbon such as graphite is used for the negative electrode and a compound of lithium and a transition metal is used for the positive electrode. However, in this lithium ion secondary battery, since the negative electrode is composed of a carbon material, theoretically, at most 1 / 6 of lithium atoms can be inserted per carbon atom. Therefore, it is difficult to further increase the capacity, and a new electrode material for high capacity is required. In addition, the above-described lithium ion secondary battery is expected as a power source for an electric vehicle due to the high energy density, but in order to increase the travel distance per charge, it is necessary to load more lithium ion secondary batteries on the vehicle body. Although the manufacturing cost of lithium ion batteries has decreased a lot compared to the beginning, it is desirable to develop a lithium ion battery that accounts for a large portion of the price of the vehicle body, has a higher energy density, and is cheaper. In order to meet these requirements, the application of a silicon material (for example, silicon and their alloys) that can store and release more lithium ions than graphite is being studied. Silicon materials can store more lithium ions electrochemically, but due to lithium absorption during charging, the silicon material particles expand in volume to about 4 times, and the electrolyte in the void portion remaining in the electrode is discharged to the void portion inside the battery case. In addition, due to the volume expansion of the silicon material particles, sites where the conductive path between the silicon material particles or between the silicon material particles and the current collector is interrupted are generated. Therefore, a region where isolated silicon material particles that have extremely little electrolyte and are difficult to electrochemically react exist is generated on the surface of the silicon material particles, and as a result, the charge and discharge performance of the battery is reduced. For the above reasons, a lithium ion secondary battery in which a negative electrode formed of silicon material particles as the main active material has not been put into practical use due to the long cycle life of charging and discharging.

[0004] In order to improve the cycle life of a silicon electrode using a silicon material, in Patent Literature 1 (Japanese Patent Application Publication No. 2016225207), a method of obtaining a negative electrode active material composition by gelating a mixture containing a silica sol formed by hydrolysis of a silicate, a carbon in fine particles, and the above-described silicon-containing particles, performing hydrothermal treatment, drying and firing, and then pulverizing is proposed. However, in the above-described Patent Literature 1, the negative electrode active material composition obtained is a particle in which the silica sol, the carbon fine particles, and the silicon-containing particles are complexed, and due to the cost increase caused by the complexing process, the relatively large particle diameter of the silicon-containing particles, and the high content of silicon dioxide, the volume expansion during charging easily causes disintegration of the negative electrode active material composition.

[0005] In addition, in Patent Literature 2 (Japanese Patent Application Laid-Open No. 2015-503185), a nanosilicon-carbon composite material including silicon oxide SiOx (0 < x < 2) covering the surface of nanosilicon other than the interface at which nanosilicon is connected to carbon, carbon serving as a base, nanosilicon dispersed on the carbon serving as a base, and nanosilicon carbide SiC dispersed at the interface between the carbon serving as a base and the nanosilicon has been proposed, which is manufactured by a molten salt electrolysis method using a porous electrode composed of silicon dioxide and carbon as a raw material and electrochemically reducing the silicon dioxide. However, high-temperature processing is required in the manufacturing, and since SiC, which does not participate in charge and discharge, and SiOx, which reduces the charge and discharge efficiency through an irreversible reaction, are contained in the product, there are problems in that the cost becomes high and the capacity density is also lower than that of Si.

[0006] Silicon is a material that can electrochemically store and release a large amount of lithium, but has a large volume expansion when storing lithium ions. In addition, by storing lithium ions, it expands to about 4 times the volume at the maximum, and shrinks by releasing lithium ions, but in the case where the particle size of a silicon-containing particle (hereinafter collectively referred to as a silicon-containing particle, and also a silicon-based particle including a silicon alloy particle) is large, it collapses until it is micronized by repeated expansion and shrinkage. In the case where the silicon-containing particle is micronized from the beginning, even in the case where micronization does not occur at the time of lithium ion occlusion, in an electrode formed of at least a silicon-containing particle and a binder, due to the expansion and shrinkage of the silicon-containing particle, the electrolyte present in the voids of the electrode layer is squeezed out, and the amount of electrolyte around the silicon-containing particle is deficient, a dead zone is generated in the electrode reaction at the time of charging, the electrochemical reaction is localized to the silicon-containing particle where the electrolyte exists, a non-uniform volume expansion occurs as a whole electrode, and the silicon-containing particle is disintegrated by secondary particle formation. In the case where the electrolyte is solidified by a polymer gel, at the time of volume expansion of the silicon-containing particle at the time of charging, the electrolyte is trapped between the molecules of the polymer gel, and thus it is difficult to squeeze out the electrolyte that is more liquid, but under the pressure accompanying the volume expansion of the silicon-containing particle, the electrolyte is squeezed out from the polymer gel. As a result, the electronic conductivity and the lithium ion conductivity of the electrode are reduced, leading to a decrease in the performance of the battery.

[0007] To solve the above problems, a lithium ion secondary battery is proposed in the present application. SUMMARY

[0008] To solve the problems presented in the above background art, the present application provides a lithium ion secondary battery, by disposing hydrophobic porous ceramic (inorganic compound material as a combination of metal elements and non-metal elements) particles having a small bulk density in a negative electrode layer composed of a lithium ion secondary battery (also containing silicon alloy particles) containing silicon particles, electrolyte is held between the ceramic particles or in the fine pores of the ceramic particles, it is found that even if the silicon-containing particles alloy with lithium and expand in volume when charged, electrolyte can be ensured around the silicon-containing particles, the decrease in ion conductivity in the electrode during charging and discharging can be inhibited, and the decrease in battery performance can be reduced. The ceramic particles have a strength that does not deform even under the pressure generated by the volume expansion of silicon, so electrolyte can be held in the fine pores of the ceramic particles, and the decrease in lithium ion conductivity within the electrode can be prevented. In the case of using ceramic particles that have not been subjected to hydrophobic treatment instead of ceramic particles that are hydrophobic in the hydrophobic treatment, since the surface of the ceramic particles is hydrophilic, more moisture is adsorbed on the surface of the fine pores, reducing the performance of the lithium ion secondary battery.

[0009] Furthermore, it has also been found that by containing in the electrolyte a polymer solution electrolyte formed by a polymer generated by polymerization and cross-linking reaction of a vinyl monomer such as a monovinyl monomer, divinyl monomer or trivinyl monomer, tetra vinyl monomer, etc. within a plurality of molecules, the performance of the battery of the negative electrode composed of silicon-containing particles can be inhibited, and the performance decrease can be further inhibited.

[0010] To achieve the above object, the present application provides the following technical solution: a lithium ion secondary battery, which is a secondary battery capable of occluding and releasing lithium ions, composed of a negative electrode, an electrolyte as a lithium ion conductor, and a positive electrode;

[0011] The negative electrode is composed of at least a negative electrode active material containing an inorganic material that stores lithium by charging and releases lithium by discharging, a hydrophobic porous ceramic particle that holds electrolyte, a carbon material, and an organic polymer that constitutes a binder.

[0012] As a lithium ion secondary battery of the present application, preferably, the average particle size of the porous ceramic particles is in the range of 0.1 to 4 μm, and the bulk density is in the range of 0.05 to 0.2 g / cm 3 .

[0013] As a lithium ion secondary battery of the present application, preferably, the material of the porous ceramic particles is an oxide containing at least one or more elements selected from silicon, aluminum, magnesium, zirconium, and titanium.

[0014] As a lithium ion secondary battery of the present application, preferably, the mass % of the porous ceramic particles in the negative electrode is in the range of 0.5 to 20%.

[0015] As a lithium ion secondary battery of the present application, preferably, the specific surface area of the porous ceramic particles in the negative electrode is 35 m 2 / g or more.

[0016] As a lithium ion secondary battery of the present application, preferably, the porous ceramic particles in the negative electrode have lithium element. By containing lithium element, the lithium ion conductivity in the vicinity of the surface of the ceramic particles is improved.

[0017] As a lithium ion secondary battery of the present application, preferably, in the electrolyte, the electrolyte containing both a monovinyl monomer and a monomer having multiple vinyl groups in the molecule, which undergo polymerization and cross-linking reaction at the time of charging, is contained at the time of assembly of the battery.

[0018] As a lithium ion secondary battery of the present application, preferably, the electrolyte is held in the fine pore portion of the porous ceramic particles by cross-linking polymer gel.

[0019] The negative electrode of the lithium ion secondary battery of the present application, which is composed of a negative electrode active material of an inorganic material containing silicon element (referred to as silicon-containing particles), is formed by coating a metal foil collector such as a copper foil. The silicon-containing particles and the conductive material are characterized by a structure of an electrode layer containing a carbon material as an auxiliary agent, hydrophobic porous ceramic particles, and a polymer as a binder. As the silicon-containing particles, silicon oxide, silicon, silicon alloy, and a composite containing these silicon-based materials are preferable. In order to make the volume expansion at the time of lithium insertion reaction more uniform and suppress local volume expansion, the average particle diameter should be in the range of 10 nm to 10 μm, and in order to facilitate handling and extend the charge-discharge cycle life, a range of 200 nm to 2 μm is more preferable. In addition, the silicon alloy can be manufactured using an ingot as a raw material, has the advantages of being able to be manufactured at low cost, being able to reduce the crystallite size, being excellent in electronic conductivity, and being able to control the volume expansion coefficient by changing the content of silicon element, and is more preferable. In order to maintain a high capacity density and extend the charge-discharge cycle life, the content of the silicon-containing particles in the electrode layer is preferably 10 to 60 mass%. If the content of the silicon-containing particles is less than 10 mass%, a capacity density much higher than that of graphite cannot be obtained. In addition, when the content of the silicon-containing particles exceeds 60 mass%, although a higher capacity density can be obtained, the repeated charge-discharge cycle life becomes shorter. In order to maintain a high capacity density and reduce the volume expansion rate, the content of the silicon-containing particles is more preferably 20 to 50 mass%. Furthermore, the silicon-containing particles are compounded with silicon or silicon alloy and an inorganic lithium ion conductor, and amorphous or nanocrystalline silicon is dispersed in the silicon-containing composite particles, which is more preferable for reducing the decomposition side reaction of the liquid.

[0020] The aforementioned lithium ion conductor of inorganic material is a compound that can be expressed as LixMyAz = Lix(M1aM2bM3cM4dM5eM6fM7g)(A1hA2iA3j), and preferable conditions in the compound are as follows, wherein M is a metal element, and is one or more elements selected from the group consisting of Group 1 elements (M1), Group 2 elements (M2), Group 3 elements (M3), Group 4 elements (M4), Group 5 elements (M5), Group 13 elements (M6), and Group 14 elements (M7), A is a non-metal element, and is one or more elements selected from the group consisting of Group 15 elements (A1), Group 16 elements (A2), and Group 17 elements (A3), x > 0, y > 0, z > 0, a ≥ 0, b ≥ 0, c ≥ 0, d ≥ 0, e ≥ 0, f ≥ 0, g ≥ 0, h ≥ 0, i ≥ 0, j ≥ 0, (a + b + c + d + e + f + g) > 0, and (h + i + j) > 0. In addition, preferably, in the lithium ion conductor Lix(M1aM2bM3cM4dM5eM6fM7g)(A1hA2iA3j), the Group 1 elements (M1) are one or more elements selected from the group consisting of Na and K, the Group 2 elements (M2) are one or more elements selected from the group consisting of Mg, Ca, Sr, and Ba, the Group 3 elements (M3) are one or more elements selected from the group consisting of Sc, Y, and La, the Group 4 elements (M4) are one or more elements selected from the group consisting of Ti, Zr, and Hf, the Group 5 elements (M5) are one or more elements selected from the group consisting of V, Nb, and Ta, the Group 13 elements (M6) are one or more elements selected from the group consisting of B, Al, Ga, and In, the Group 14 elements (M7) are one or more elements selected from the group consisting of Si, Ge, and Sn, the Group 15 elements (A1) are one or more elements selected from the group consisting of N, P, and Bi, the Group 16 elements (A2) are one or more elements selected from the group consisting of O and S, and the Group 17 elements (A3) are one or more elements selected from the group consisting of F, Cl, Br, and I. In order to obtain a high ion conductivity of the ion conductor, more preferably, the combination of the metal elements and the non-metal elements consists of three or more elements. In order to obtain a higher ion conductivity of the ion conductor, it is preferable to include a P element as the Group 15 element (A1). More preferably, the Group 16 element (A2) is an O element. The oxide in which the Group 16 element (A2) is an O element is harder than the sulfide in which the Group 16 element (A2) is an S element, the active material for the negative electrode of the lithium ion secondary battery can promote the amorphization of silicon or a silicon alloy during high-speed mechanical milling and mechanical alloying during the manufacturing process of the composite particles as the material, and the charge and discharge cycle life of the negative electrode can be extended.

[0021] Further, in the secondary battery of the present application, the silicon-containing composite particles are compounded with one or more carbon materials selected from the group consisting of graphite, amorphous carbon, carbon nanofiber, carbon nanotube, and graphene. It is also preferable that the silicon-containing composite particles compounded with an inorganic lithium ion conductor be compounded with a carbon material. The compounding with a carbon material improves the electron conductivity of the silicon-containing composite particles.

[0022] The present application has the advantage that, in the secondary battery (lithium ion secondary battery) of the present application capable of occluding and releasing lithium ions, since the negative electrode is composed of a silicon material containing porous ceramic particles that hold electrolyte, there is no case where the electrolyte held in the fine pore portions of the porous ceramic particles is expelled due to the volume expansion of the silicon-containing particles caused by occluding lithium ions and alloying with lithium at the time of charging, so the lithium ion conduction within the negative electrode can be maintained even in repeated charging and discharging, and the decrease in the performance of the secondary battery can be suppressed. DETAILED DESCRIPTION

[0023] The technical solutions in the embodiments of the present application will be described below clearly and completely. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application.

[0024] A lithium ion secondary battery, the secondary battery of the present application capable of occluding and releasing lithium ions is composed of a negative electrode, a lithium ion conductor, and a positive electrode. As the ion conductor, a liquid electrolyte is used at the time of assembling the battery.

[0025] The negative electrode of the lithium ion secondary battery of the present application includes a silicon-containing particle containing silicon element that stores lithium by charging and releases lithium by discharging as a negative electrode active material, a hydrophobic porous ceramic (an inorganic compound material as a combination of metal element and nonmetal element) particle that holds electrolyte, a carbon material, and a binder composed of an organic polymer. In the secondary battery of the present application, when the silicon-containing particle as the active material in the negative electrode alloyed with lithium and expands in volume at the time of charging, the liquid electrolyte present in the negative electrode has fluidity and thus can be squeezed out of the negative electrode, but is not squeezed out of the negative electrode due to the porous ceramic particle that holds electrolyte, thereby maintaining the ion conduction in the negative electrode.

[0026] The negative electrode of the battery of the present application described above is manufactured by the following method. First, a negative electrode active material composed of a silicon-based inorganic material (silicon-containing particle), a hydrophobic porous ceramic particle that holds electrolyte, a carbon material, a binder composed of an organic polymer, and a solvent thereof are mixed and kneaded, and a slurry having a viscosity suitable for coating is prepared. Next, the slurry is coated on a current collector, and after drying, pressing is performed to adjust the density and thickness of the electrode layer, thereby manufacturing an electrode structure for a negative electrode.

[0027] [Anode active material for lithium ion secondary battery]

[0028] The active material for the anode of the lithium ion secondary battery of the present application contains silicon-containing particles containing silicon element, and as the anode active material, one or more materials selected from the group consisting of silicon, silicon alloy, a composite of silicon and graphite, a composite of silicon alloy and graphite, a composite of silicon and lithium ion conductor, and a composite of silicon alloy and lithium ion conductor, and a mixture of these materials and graphite can be cited. As the silicon alloy, an alloy composed of at least silicon and a transition metal element is preferred. As the composite of silicon and lithium ion conductor, and the composite of silicon alloy and lithium ion conductor, it is characterized in that amorphous or nanocrystalline silicon is dispersed in the lithium ion conductor of inorganic material, and the silicon in the particles is preferably 20 to 60 mass% amorphous or nanocrystalline silicon. In addition, the composite of silicon and lithium ion conductor, and the composite of silicon alloy and lithium ion conductor can be further complexed with a carbon material;

[0029] The composite of the above-mentioned silicon or silicon alloy fine particles and graphite can be formed by mixing graphite powder, a resin as a binder, and silicon or silicon alloy fine particles above the melting point of the resin, and performing firing at a temperature above the carbonization temperature of the resin in an inert gas atmosphere. In addition, the above-mentioned composite can be formed by adding a solvent of the resin to the graphite powder, the resin as a binder, and the silicon or silicon alloy fine particles, mixing, drying, and then firing at a temperature above the carbonization temperature of the resin as a binder in an inert gas atmosphere.

[0030] The crystal size of silicon in the above-mentioned active material for the anode is preferably 50 nm or less, and more preferably 20 nm or less. The smaller the crystal size of silicon, the more uniform the Li insertion, and the volume expansion is also reduced. In addition, the crystal size is calculated from the half-value width of the peak of X-ray diffraction and the Scherrer equation. In addition, the size of the crystal can also be observed from the transmission electron microscope image.

[0031] The inorganic material of the above-mentioned lithium ion conductor of the composite of silicon and lithium ion conductor, or the composite of silicon alloy and lithium ion conductor is a material that can be denoted as Li x M y A z = Li x (M1 a M2 b M3 c M4 d M5 e M6 f M7 g )(A1 h A2 i A3 jThe compound is defined as follows: M is a metallic element selected from one or more elements chosen from Group 1 (M1), Group 2 (M2), Group 3 (M3), Group 4 (M4), Group 5 (M5), Group 13 (M6), and Group 14 (M7) of the periodic table; A is a nonmetallic element selected from one or more elements chosen from Group 15 (A1), Group 16 (A2), and Group 17 (A3); x>0, y>0, z>0, a≥0, b≥0, c≥0, d≥0, d≥0, f≥0, g≥0, h≥0, i≥0, j≥0, (a+b+c+d+e+f+g)>0, (h+i+j)>0. To obtain high ionic conductivity, the combination of metallic and nonmetallic elements is more preferably composed of three or more elements. To improve the ionic conductivity of the ionic conductor, it is preferable to contain phosphorus (P) as a Group 15 element (A1). The Group 16 element (A2) is more preferably oxygen (O). Oxides of Group 16 element (A2) containing oxygen have higher hardness than sulfides of Group 16 element (A2) containing sulfur (S), making it easier to amorphize silicon.

[0032] As a representative example of the lithium-ion conductor in the inorganic material, Li7La3Zr2O can be used. 12 System, Li 10 GeP2O 12 Various inorganic solid electrolytes, including those based on the following systems: Li3BO3Li2SO4, aluminate (Li6PS5Cl), and glass-ceramic Li2S-P2S5. Examples of these inorganic solid electrolytes include Li0.34La0.51TiO2.94, Li1.07Ti1.46Al0.69P3O12, Li1.5Ti1.5Al0.5P3O12, Li1.5Ti1.7Al0.3Si0.2P2.8O12, Li1.5Al0.5Ge1.5P3O12, Li7La3Zr2O12, Li3YCl6, Li3YBr6, Li9.54Si1.74P1.44S11.7Cl0.3, Li10GeP2S12, LiS57-SiS57SiO4, and 75Li2S-25P2S5.

[0033] The composite of the inorganic lithium-ion conductor with silicon or silicon alloy is achieved using a high-acceleration mechanical pulverization device, such as a vibratory mill, atomic mill, planetary ball mill, or other similar technology, to mechanically mill, alloy, and composite the powdered lithium-ion conductor with silicon or silicon alloy. Alternatively, the composite can be achieved by mechanically alloying the raw materials and silicon materials instead of using inorganic lithium-ion conductors.

[0034] (Ceramic material powder)

[0035] As the hydrophobic ceramic material powder constituting the negative electrode of the present application, an oxide composed of at least one or more elements selected from the group consisting of silicon, aluminum, magnesium, titanium, and zirconium is preferable, and an oxide composed of elements selected from the group consisting of silicon, aluminum, and titanium is more preferable. The content of the ceramic material powder in the above-mentioned negative electrode layer (electrode mixture layer) is preferably in the range of 0.5 to 20%, and more preferably in the range of 0.5 to 15%. Thus, the battery can maintain a high charge capacity, and a long charge-discharge cycle life is obtained.

[0036] The average particle diameter of the above-mentioned ceramic material powder is preferably in the range of 0.1 to 4 μm. The specific surface area of the above-mentioned ceramic material powder is preferably in the range of 35 m 2 / g to 350 m 2 / g. Further, the bulk density of the above-mentioned ceramic material powder is more preferably in the range of 0.05 to 0.2 g / cm 3 . A large specific surface area and a small bulk density mean that the volume of the space of the concave-convex portions of the particle surface or the volume of the gap between the particles is large, and by including this in the electrode, the electrolyte can be held in the gap space in the power storage device using an electrolyte.

[0037] Note that the oxide particles of the above-mentioned ceramic particles have lithium elements that contribute to lithium ion conduction.

[0038] Further, the ceramic particles are preferably subjected to hydrophobic treatment in order to suppress the adsorption of moisture, and in order to improve the electronic conductivity in the negative electrode, a carbon coating is preferably applied to the surface of the ceramic particles, or the ceramic particles are complexed with a carbon material. The hydrophobic treatment of the ceramic particles is obtained by treating the ceramic particles with a hydrophobic ceramic particle with an organosilane compound having an aliphatic hydrocarbon group or a fluorinated hydrocarbon group. As examples of the organosilane compound, polydimethylsiloxane, methylchlorosilane, hexamethyldisilazane, alkyltrimethoxysilane, and the like can be given.

[0039] By dispersing the ceramic particles in the negative electrode of the present application, the flame retardancy of the negative electrode is improved, and the safety is also improved. Similarly, by containing the above-mentioned ceramic particles in the positive electrode, the flame retardancy of the positive electrode can also be improved.

[0040] (Carbon material)

[0041] As the carbon material constituting the negative electrode electrode structure of the lithium ion secondary battery of the present application, one or more carbon materials selected from the group consisting of graphite powder, amorphous carbon powder, carbon nanofiber, carbon nanotube, and graphene are used, and the electronic conduction of the electrode is improved. By adjusting the content of the silicon-containing particles and graphite as the negative electrode active material in the above-mentioned electrode structure, in the case of assembling the negative electrode into a lithium ion secondary battery, the capacity of the battery and the volume expansion rate of the negative electrode can be adjusted.

[0042] (Binder)

[0043] As a specific binder used in the formation of the electrode layer of the negative electrode structure of the above-described battery of the present application, sodium alginate, sodium carboxymethyl cellulose, carboxymethyl cellulose, sodium polyacrylate, polyacrylic acid, polyvinyl alcohol, polyvinyl alcohol copolymer, chitin, chitosan, polyamide acid (polyimide precursor), polyimide, polyamide-imide, epoxy resin, and the like can be given.

[0044] (collector)

[0045] As the material of the collector of the electrode structure used in the negative electrode of the secondary battery of the present application, in the charge-discharge reaction of the power storage device, it is required to be stable without dissolving, and specifically, copper, stainless steel, titanium, nickel can be given. In addition, the collector is in the form of a plate, but the thickness of this "plate" is not specified in the practical range, and the form called "foil" having a thickness of about 5 μm to 100 μm or so. In addition, as the plate, for example, a mesh, a sponge, a member formed in a fiber shape, a punched metal, a metal foil having a three-dimensional concave-convex pattern formed on both surfaces, a steel plate mesh, and the like can be used.

[0046] [Method for manufacturing negative electrode for lithium ion secondary battery]

[0047] The negative electrode for lithium ion secondary battery of the present application mixes silicon-containing particles, graphite powder, a conductive aid such as a carbon material, a hydrophobic porous ceramic powder, a polymer as a binder, and appropriately adds a solvent of the binder to perform kneading, and prepares a slurry. Next, the prepared slurry is coated on a collector and dried, and the density of the electrode layer is adjusted with a roll press, and an electrode structure is produced by removing moisture under reduced pressure.

[0048] [lithium ion secondary battery]

[0049] The lithium ion secondary battery of the present application is a power storage device utilizing the reduction-oxidation reaction of lithium ions, and is configured by at least sequentially stacking a positive electrode composed of the above-described negative electrode of the present application, a lithium ion conductor, and a lithium transition metal compound. As a specific battery shape of the battery, for example, a flat shape, a cylindrical shape, a cuboid shape, a sheet shape, and the like can be given. In addition, as the structure of the battery, for example, a single layer type, a multi-layer type, a spiral type, and the like can be given.

[0050] (positive electrode)

[0051] The above-described positive electrode is formed with a positive electrode active material layer composed of a lithium-transition metal compound as a positive electrode active material, a binder, and a conductive auxiliary material such as carbon black on a positive electrode collector.

[0052] As the above lithium-transition metal compound, a lithium-transition metal oxide, a lithium-transition metal phosphoric acid compound is used. As the above positive electrode active material containing a transition metal element, Ni, Co, Mn, Fe, Cr, V, etc. are more preferably used as a main element. In addition, the above positive electrode active material surface is preferably composed of at least a lithium-transition metal compound microparticle of a composite metal oxide covering the surface layer composed of one or more metal elements selected from Al, Zr, Mg, Ca, La and Li. The surface of the above positive electrode material covered with the composite metal oxide is preferably further compounded with amorphous carbon.

[0053] As the above binder, a fluorine resin such as polyvinylidene fluoride, a polyacrylate, a polyamide acid (polyimide precursor), a polyimide, a polyamide-imide, an epoxy resin, a styrene butadiene copolymer-carboxymethyl cellulose can be used.

[0054] As the material of the above current collector, a material having high conductivity and being inert to the battery reaction is preferable. The preferable material includes one or more metal materials selected from aluminum, nickel, iron, stainless steel and titanium. As a more preferable material, aluminum which is inexpensive and has low resistance is used. In addition, the current collector has a plate shape, but the thickness of the "plate shape" is not specified in the practical range, and a form called "foil" having a thickness of about 5 μm to 100 μm or so. In addition, as the plate shape, for example, a mesh shape, a sponge shape, a member formed in a fiber shape, a punched metal, a metal foil having a three-dimensional concave-convex pattern formed on both surfaces, an expanded metal, etc. can be adopted.

[0055] (Lithium ion conductor)

[0056] In the above ion conductor, a separator holding an electrolyte (an electrolyte solution prepared by dissolving an electrolyte in a solvent), a solid electrolyte, a solidified electrolyte obtained by gelating an electrolyte with a polymer gel or the like, a composite of a polymer gel and a solid electrolyte, an ionic liquid, etc. of a lithium ion conductor can be used.

[0057] As the above separator for preventing electrical short-circuit between the negative electrode and the positive electrode, a resin film having a microporous structure or a nonwoven fabric structure is used, and as the resin material, a polyolefin such as polyethylene, polypropylene, a polyimide, a polyamide-imide, cellulose is preferable. The above microporous resin film can have a layer containing metal oxide particles such as aluminum oxide, zirconium oxide, titanium dioxide, etc. on the surface for the purpose of improving heat resistance.

[0058] Examples of the above electrolyte include a lithium ion (Li+) and a Lewis acid ion (BF4 - , PF6 -, AsF6, ClO4", CF3SO3", BPh4"(Ph: phenyl), lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethylsulfonyl)imide, and mixed salts and ionic liquids thereof.

[0059] The above salt is preferably dehydrated and deoxidized by heating under reduced pressure. In addition, an electrolyte prepared by dissolving the above lithium salt in an ionic liquid can also be used. As the above electrolyte solvent, acetonitrile, benzonitrile, propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, dimethylformamide, tetrahydrofuran, nitrobenzene, dichloroethane diethoxyethane, 1,2-dimethoxyethane, chlorobenzene, γ-butyrolactone, dioxolane, sulfolane, nitromethane, dimethyl sulfide, dimethyl sulfide, 3-methyl-2-oxazolidinone, 2-methyltetrahydrofuran, 3-propylsultone, sulfur dioxide, or a mixture thereof can be used, for example. A solvent in which a hydrogen element of the above solvent is replaced with a fluorine element can also be used.

[0060] The above solvent can be dehydrated with activated alumina, molecular sieves, phosphorus pentoxide, calcium chloride, or the like, or can be distilled in the presence of an alkali metal in an inert gas depending on the solvent, to remove impurities and dehydrate.

[0061] In addition, in order to suppress the reaction of the electrode with the electrolyte, it is preferable to add an organic fluorine compound such as fluorine ethylene carbonate or difluoro ethylene carbonate, which forms a stable SEI layer on the surface of the electrode, a compound such as vinylene carbonate.

[0062] As the above solid electrolyte, Li7La3Zr2O 12 , Li 10 GeP2O 12 , Li3BO3-Li2SO4, Li6PS5Cl, Li2S-P2S5, and the like can be used. As examples of the above inorganic solid electrolyte, Li 0.34 La 0.51 TiO 2.94 , Li 1.07 Ti 1.46 Al 0.69 P3O 12 , Li 1.5 Ti 1.5 Al 0.5 P3O 12 , Li 1.5 Ti 1.7 Al 0.3 Si 0.2 P 2.8 O 12 , Li1.5 Al 0.5 Ge 1.5 P3O 12 , Li7La3Zr2O 12 , Li3YCl6, Li3YBr6, Li 9.54 Si 1.74 P 1.44 S 11.7 Cl 0.3 , Li 10 GeP2S 12 , 57Li2S-38SiS2-5Li4SiO4, 75Li2S-25P2S5, etc., and further, an amorphous solid electrolyte in which the above stoichiometric ratio is deviated.

[0063] As the above solidified electrolyte, it is preferable to gelate the above electrolyte with a gelling agent and solidify. As the gelling agent, it is preferable to use a polymer, silica gel, or the like porous material having a large liquid absorption amount which swells by absorbing the electrolyte. As the above polymer, polyethylene oxide, polyacrylonitrile, polymethyl methacrylate, a vinylidene fluoride-hexafluoropropylene copolymer, polyethylene glycol, 2, 4, 6, 8-tetramethyl-2, 4, 6, 8-tetravinylcyclotetrasiloxane, or the like can be used. Further, the above polymer is more preferable to have a crosslinked structure.

[0064] Example

[0065] The present application is further explained in detail based on the examples below.

[0066] Preparation of silicon alloy composite as negative active material for lithium ion secondary battery

[0067] Preparation of silicon alloy / C (carbon) composite

[0068] First, metallic silicon, metallic tin, and metallic copper were mixed and melted at a mass ratio of 65:30:5, and a Si-Sn-Cu alloy powder was formed using a water atomization device. Next, the obtained Si-Sn-Cu alloy and graphite powder were mixed at a mass ratio of 95:5, a small amount of lithium citrate, aluminum nitrate, and ethanol were added, and a vibration mill with a zirconia pot was used for pulverization treatment for 10 hours to prepare an amorphous Si-Sn-Cu alloy / C (carbon) composite powder formed of an amorphous lithium aluminum oxide and carbon composite coating. Next, the powder was pulverized using a jet mill, and classified using a classification device to have a particle size of about 1 μm or less to obtain a silicon alloy powder complexed with graphite.

[0069] Preparation of silicon alloy / oxide composite

[0070] A Si-Ni alloy powder in a flake shape was formed by mixing metallic silicon and metallic nickel at a mass ratio of 65:35 using a single-roller liquid quenching solidification device. Next, the obtained Si-Ni alloy, tri-lithium phosphate, aluminum hydroxide, germanium oxide, and silicon dioxide were mixed at a mass ratio of 60:21.2:2.4:9.6:6.9, respectively, and were subjected to a pulverization treatment for 8 hours using a planetary ball mill with a silicon nitride pot. After heat treatment at 350°C, an amorphous Si-Ni alloy and oxide composite powder was prepared. Then, the silicon alloy / oxide composite powder was classified by a classifier to obtain a particle size of about 1 μm or less using a jet mill. In addition, the above composite has lithium ion conductivity because it contains lithium.

[0071] [Manufacture of electrode structure as negative electrode of lithium ion secondary battery]

[0072] In the following examples, an electrode structure was formed from various silicon material particles (silicon-containing particles), carbon material particles containing graphite, hydrophobic porous ceramic particles, and a binder.

[0073] (Example 1)

[0074] A silicon powder having an average particle size of 3 μm, a graphite powder having an average particle size of 5 μm, acetylene black, hydrophobically treated silicon dioxide powder having an average particle size of 3.9 μm and a bulk density of 0.15 g / cm 3 having a specific surface area of 180 m 2 / g, polyvinyl alcohol (PVA), and carboxymethyl cellulose sodium salt (CMC) were mixed at a mass ratio of 54:18:17.5:0.5:7.5:2.5, and ion exchange water was added, and the mixture was kneaded using a bead mill device to prepare a slurry. Next, the prepared slurry was coated on a copper foil using a coater, and was dried at 110°C, and the electrode layer density was adjusted using a roll press machine, and moisture was removed at 150°C under reduced pressure to manufacture an electrode structure. Next, the electrode structure was cut to a predetermined size, and a nickel lead wire was welded to the joint of the copper foil of the current collector using a spot welding machine, and the lead terminal was extracted to manufacture an electrode structure. In the preparation of the slurry, a 10 mass% aqueous solution of PVA and a 2 mass% aqueous solution of CMC were used.

[0075] (Comparative Example 1)

[0076] In the preparation of the slurry of Example 1, the ceramic powder was not mixed, and a silicon powder having an average particle size of 3 μm, a graphite powder having an average particle size of 5 μm, acetylene black, polyvinyl alcohol (PVA), and carboxymethyl cellulose sodium salt (CMC) were mixed at a mass ratio of 54:18:18:7.5:2.5 to manufacture an electrode structure.

[0077] (Example 2)

[0078] In the preparation of the slurry of Example 1, silicon powder having an average particle diameter of 3 μm, graphite powder having an average particle diameter of 5 μm, acetylene black, hydrophobically treated silica powder having a particle diameter of 3.9 μm, a bulk density of 0.15 g / cm3, and a specific surface area of 180 m2 / g as a porous ceramic, polyvinyl alcohol (PVA), and sodium carboxymethyl cellulose (CMC) were mixed in a mass ratio of 54:18:17:1:7.5:2.5 to produce an electrode structure.

[0079] (Example 3)

[0080] In the preparation of the slurry of Example 1, silicon powder having an average particle diameter of 3 μm, graphite powder having an average particle diameter of 5 μm, acetylene black, hydrophobically treated silica powder having a particle diameter of 3.9 μm, a bulk density of 0.15 g / cm3, and a specific surface area of 180 m2 / g as a porous ceramic, polyvinyl alcohol (PVA), and sodium carboxymethyl cellulose (CMC) were mixed in a mass ratio of 54:18:13:5:7.5:2.5 to produce an electrode structure.

[0081] (Example 4)

[0082] In the preparation of the slurry of Example 1, silicon powder having an average particle diameter of 3 μm, graphite powder having an average particle diameter of 5 μm, acetylene black, hydrophobically treated silica powder having a particle diameter of 3.9 μm, a bulk density of 0.15 g / cm3, and a specific surface area of 180 m2 / g as a porous ceramic, polyvinyl alcohol (PVA), and sodium carboxymethyl cellulose (CMC) were mixed in a mass ratio of 54:18:10:7.5:2.5 to produce an electrode structure.

[0083] (Example 5)

[0084] In the preparation of the slurry of Example 1, silicon powder having an average particle diameter of 3 μm, graphite powder having an average particle diameter of 5 μm, acetylene black, hydrophobically treated silica powder having a particle diameter of 3.9 μm, a bulk density of 0.15 g / cm3, and a specific surface area of 180 m2 / g as a porous ceramic, polyvinyl alcohol (PVA), and sodium carboxymethyl cellulose (CMC) were mixed in a mass ratio of 54:18:3:15:7.5:2.5 to produce an electrode structure.

[0085] (Example 6)

[0086] In the preparation of the slurry of Example 1, silicon powder having an average particle diameter of 3 μm, graphite powder having an average particle diameter of 5 μm, acetylene black, hydrophobically treated silica powder having a particle diameter of 3.9 μm, a bulk density of 0.15 g / cm3, and a specific surface area of 180 m2 / g as a porous ceramic, polyvinyl alcohol (PVA), and sodium carboxymethyl cellulose (CMC) were mixed in a mass ratio of 54:16:20:7.5:2.5 to produce an electrode structure.

[0087] (Example 7)

[0088] In the preparation of the slurry of Example 1, silicon powder having an average particle diameter of 3 μm, graphite powder having an average particle diameter of 5 μm, acetylene black, carbon-coated conductive silica powder having a particle diameter of 3.0 μm, a bulk density of 0.13 g / cm3, and a specific surface area of 160 m2 / g as a porous ceramic, polyvinyl alcohol (PVA), and sodium salt of carboxymethyl cellulose (CMC) were mixed at a mass ratio of 54:18:3:15:7.5:2.5 to produce an electrode structure.

[0089] (Example 8)

[0090] In the preparation of the slurry of Example 1, silicon powder having an average particle diameter of 3 μm, graphite powder having an average particle diameter of 5 μm, acetylene black, alumina powder having a particle diameter of 0.1 μm, a bulk density of 0.05 g / cm3, and a specific surface area of 90 m2 / g as a porous ceramic, polyvinyl alcohol (PVA), and sodium salt of carboxymethyl cellulose (CMC) were mixed at a mass ratio of 54:18:17.5:0.5:7.5:2.5 to produce an electrode structure. 3 2 In the preparation of the slurry of Example 1, silicon powder having an average particle diameter of 3 μm, graphite powder having an average particle diameter of 5 μm, acetylene black, alumina powder having a particle diameter of 0.1 μm, a bulk density of 0.05 g / cm3, and a specific surface area of 90 m2 / g as a porous ceramic, polyvinyl alcohol (PVA), and sodium salt of carboxymethyl cellulose (CMC) were mixed at a mass ratio of 54:18:17.5:0.5:7.5:2.5 to produce an electrode structure.

[0091] (Example 9)

[0092] In the preparation of the slurry of Example 1, silicon powder having an average particle diameter of 3 μm, graphite powder having an average particle diameter of 5 μm, acetylene black, alumina powder having a particle diameter of 0.1 μm, a bulk density of 0.05 g / cm3, and a specific surface area of 90 m2 / g as a porous ceramic, polyvinyl alcohol (PVA), and sodium salt of carboxymethyl cellulose (CMC) were mixed at a mass ratio of 54:18:17.5:0.5:7.5:2.5 to produce an electrode structure. 3 2 In the preparation of the slurry of Example 1, silicon powder having an average particle diameter of 3 μm, graphite powder having an average particle diameter of 5 μm, acetylene black, alumina powder having a particle diameter of 0.1 μm, a bulk density of 0.05 g / cm3, and a specific surface area of 90 m2 / g as a porous ceramic, polyvinyl alcohol (PVA), and sodium salt of carboxymethyl cellulose (CMC) were mixed at a mass ratio of 54:18:17.5:0.5:7.5:2.5 to produce an electrode structure.

[0093] (Example 10)

[0094] In the preparation of the slurry of Example 1, silicon powder having an average particle diameter of 3 μm, graphite powder having an average particle diameter of 5 μm, acetylene black, alumina powder having a particle diameter of 0.1 μm, a bulk density of 0.05 g / cm3, and a specific surface area of 90 m2 / g as a porous ceramic, polyvinyl alcohol (PVA), and sodium salt of carboxymethyl cellulose (CMC) were mixed at a mass ratio of 54:18:17.5:0.5:7.5:2.5 to produce an electrode structure. 3 2 In the preparation of the slurry of Example 1, silicon powder having an average particle diameter of 3 μm, graphite powder having an average particle diameter of 5 μm, acetylene black, alumina powder having a particle diameter of 0.1 μm, a bulk density of 0.05 g / cm3, and a specific surface area of 90 m2 / g as a porous ceramic, polyvinyl alcohol (PVA), and sodium salt of carboxymethyl cellulose (CMC) were mixed at a mass ratio of 54:18:17.5:0.5:7.5:2.5 to produce an electrode structure.

[0095] (Example 11)

[0096] ​​​In the preparation of the slurry of Example 1, the silicon alloy / C (carbon) composite powder having an average particle diameter of 1.6 μm obtained by the above production method, the graphite powder having an average particle diameter of 5 μm, acetylene black, the hydrophobic-treated silica powder having a particle diameter of 3.9 μm, a bulk density of 0.15 g / cm3, and a specific surface area of 180 m2 / g as the porous ceramic, polyvinyl alcohol (PVA), and sodium carboxymethyl cellulose (CMC) were mixed at a mass ratio of 54:18:13:5:7.5:2.5, and an electrode structure was produced. 2 / g of the porous ceramic, polyvinyl alcohol (PVA), and sodium carboxymethyl cellulose (CMC) were mixed at a mass ratio of 54:18:18:7.5:2.5, and an electrode structure was produced.

[0097] (Comparative Example 2)

[0098] In the preparation of the slurry of Example 1, the silicon alloy / C (carbon) composite powder having an average particle diameter of 1.6 μm obtained by the above production method, the graphite powder having an average particle diameter of 5 μm, acetylene black, the hydrophobic-treated silica powder having a particle diameter of 3.9 μm, a bulk density of 0.15 g / cm3, and a specific surface area of 180 m2 / g as the porous ceramic, polyvinyl alcohol (PVA), and sodium carboxymethyl cellulose (CMC) were mixed at a mass ratio of 54:18:13:5:7.5:2.5, and an electrode structure was produced.

[0099] (Example 12)

[0100] In the preparation of the slurry of Example 1, the silicon alloy / C (carbon) composite powder having an average particle diameter of 1.6 μm obtained by the above production method, the graphite powder having an average particle diameter of 5 μm, acetylene black, the hydrophobic-treated silica powder having a particle diameter of 3.9 μm, a bulk density of 0.15 g / cm3, and a specific surface area of 180 m2 / g as the porous ceramic, polyvinyl alcohol (PVA), and sodium carboxymethyl cellulose (CMC) were mixed at a mass ratio of 54:18:13:5:7.5:2.5, and an electrode structure was produced. 3 / g of the porous ceramic, polyvinyl alcohol (PVA), and sodium carboxymethyl cellulose (CMC) were mixed at a mass ratio of 54:18:18:7.5:2.5, and an electrode structure was produced. 2 / g of the porous ceramic, polyvinyl alcohol (PVA), and sodium carboxymethyl cellulose (CMC) were mixed at a mass ratio of 54:18:18:7.5:2.5, and an electrode structure was produced.

[0101] (Comparative Example 3)

[0102] In the preparation of the slurry of Example 1, the silicon alloy / C (carbon) composite powder having an average particle diameter of 1.6 μm obtained by the above production method, the graphite powder having an average particle diameter of 5 μm, acetylene black, the hydrophobic-treated silica powder having a particle diameter of 3.9 μm, a bulk density of 0.15 g / cm3, and a specific surface area of 180 m2 / g as the porous ceramic, polyvinyl alcohol (PVA), and sodium carboxymethyl cellulose (CMC) were mixed at a mass ratio of 54:18:13:5:7.5:2.5, and an electrode structure was produced.

[0103] [Assessment of electrochemical lithium intercalation amount of electrode structure]

[0104] The assessment of the electrochemical lithium intercalation amount of the single electrode of the electrode structure as the negative electrode of the above power storage device was performed in the following order.

[0105] Each electrode of the above Examples 1 to 12 and Comparative Examples 1 to 3 was used as a working electrode, and a battery (half cell) combined with metallic lithium as its counter electrode was produced, and the electrochemical lithium intercalation amount and release amount were assessed.

[0106] The lithium pole was made by pressure bonding a metal lithium foil on a nickel foil, and punching to a predetermined size. As the evaluation battery, a pouch cell was used. The evaluation battery of the pouch cell was made in the following order. The making of the pouch cell (laminated cell) was performed in a dry atmosphere in which the dew point was managed to be -60°C or less. An electrode group of working electrode / separator / lithium pole was inserted into an electrode tank in which a polyethylene / aluminum foil / nylon structured aluminum laminated film was formed into a bag shape, electrolyte solution was injected, the electrode lead was taken out, heat sealing was performed, and the battery for evaluation was made. The outer side of the aluminum laminated film was a nylon film, and the inner side was a polyethylene film. As the separator, a polyethylene film of a microporous structure was used.

[0107] In addition, the electrolyte solution was prepared by dissolving 1.2 M (mole / liter) of lithium hexafluorophosphate (LiPF6) in a solvent in which ethylene carbonate and diethyl carbonate, from which moisture was sufficiently removed, were mixed at a volume ratio of 3:7, and adding 3 mass% of vinylene carbonate (VC).

[0108] The charge and discharge was performed at a constant current of about 0.2 C (1 C: current for charging and discharging the battery capacity in 1 hour), and the discharge was performed to a voltage of 0.01 V of the battery, and the charge was performed to 1.50 V, whereby the evaluation was performed. The amount of electricity of the discharge was set as the amount of electricity for inserting lithium, and the amount of electricity of the charge was set as the amount of electricity for releasing lithium.

[0109] In the performance evaluation, the charge and discharge was repeatedly performed, and the evaluation of the amount of Li release at the 50th time with respect to the amount of Li release (amount of electricity) at the 1st time was performed. The evaluation results were as follows.

[0110] (Performance comparison evaluation results of the electrodes of Example 1 to 10 and Comparative Example 1, Example 11 and Comparative Example 2, and Example 12 and Comparative Example 3)

[0111] The ratio of the amount of Li release at the 50th time with respect to the amount of Li release (amount of electricity) at the 1st time of the electrodes of Example 1 to 10 was a value larger than that of the electrode of Comparative Example 1. The ratio of the amount of Li release at the 50th time with respect to the amount of Li release (amount of electricity) at the 1st time of the electrode of Example 11 and Comparative Example 2 and the electrode of Example 12 and Comparative Example 3 was a value larger than that of the electrode of Example.

[0112] In addition, the electrode capacitance at the 1st time of the electrodes of Example 1 to 5 and 7 to 10 and Comparative Example 1 was about 1700 mAh / g. The electrode capacitance at the 1st time of the electrode of Example 6, the electrode of Example 11 and Comparative Example 2, and the electrode of Example 12 and Comparative Example 3 was about 1500 mAh / g and about 1000 mAh / g, respectively. When the content of the ceramic powder in the electrode is increased, the content of the conductive material must be reduced, and further the content of the mixed graphite must be reduced, the electrode capacitance of the electrode must be reduced, and the electron conductivity of the electrode is also reduced.

[0113] [Manufacture of lithium ion secondary battery]

[0114] A lithium ion secondary battery full cell in which the positive electrode was combined as a counter electrode on the manufactured electrode was manufactured, and the charge-discharge performance was evaluated. The charge-discharge characteristics of the battery were evaluated under the charge-discharge conditions of charging to an upper limit voltage of 4.2 V at constant current-constant voltage and discharging to 2.5 V at constant current.

[0115] (Example F1)

[0116] [Manufacture of positive electrode]

[0117] The positive electrode material LiNi 0.8 Co 0.1 Mn 0.1 O2was dispersed in a liquid in an ethanol solution of trilithium citrate tetrahydrate and aluminum nitrate nonahydrate (mass ratio of trilithium citrate tetrahydrate: aluminum nitrate nonahydrate: ethanol = 1.25:5.0:100), which was spray dried at ambient temperature of about 200°C and heat-treated at 350°C in a nitrogen atmosphere to manufacture Li x Al y O2and amorphous carbon surface-coated LiNi 0.8 Co 0.1 Mn 0.1 O2powder.

[0118] The Li x Al y O2and amorphous carbon surface-coated LiNi 0.8 Co 0.1 Mn 0.1 O2powder, acetylene black, and a 12 mass% N-methyl-2-pyrrolidone (NMP) solution of a solid component of polyvinylidene fluoride (PVdF) were mixed in a mass ratio of 97:1:2, NMP was added as appropriate, and kneading was performed to prepare a slurry for forming an electrode active material layer. Next, the obtained slurry was coated on an aluminum foil using a coater, dried at 110°C for 1 hour, and then subjected to flattening of the electrode surface and thickness adjustment using a roll press, and dried at 150°C under reduced pressure to obtain an electrode structure body in which an electrode active material layer was formed. The obtained electrode structure body was punched to a prescribed size, an aluminum lead was welded to an aluminum current collector tab by ultrasonic welding, and a positive electrode was manufactured.

[0119] [Preparation of electrolyte]

[0120] In a solvent in which ethylene carbonate and diethyl carbonate, which were sufficiently removed of moisture, were mixed at a volume ratio of 3:7, 1.2 M (moles / liter) of lithium hexafluorophosphate (LiPF6) was dissolved, and 3 mass% of vinylene carbonate (VC) was added to prepare an electrolyte.

[0121] <Manufacture and performance evaluation of lithium ion secondary battery>

[0122] A soft-pack battery was manufactured using the electrode structure of Example 1 as the negative electrode in the following order. The manufacture of the soft-pack battery (laminated battery) was performed entirely under a dry atmosphere in which the dew point was managed to be -60°C or less. An electrode group of negative electrode / separator / positive electrode was inserted into an electrode tank in which an aluminum laminated film of polyethylene / aluminum foil / nylon structure was formed into a pouch shape, electrolyte solution was injected, the electrode lead was taken out, heat sealing was performed, and an evaluation battery as a lithium ion secondary battery was manufactured.

[0123] In addition, the weight per unit area of the active material layer of the positive electrode was adjusted to a negative electrode capacity / positive electrode capacity ratio of 1.05 with respect to the charge capacity of each negative electrode calculated from the results of the half-cell according to the above.

[0124] The manufactured soft-pack battery was first charged to 4.2 V at a constant current of 0.1 C, then charged at a constant voltage of 4.2 V, and then discharged to 2.5 V at a constant current of 0.1 C, and the generated gas was discharged and then sealed again.

[0125] (Examples F2 to F12)

[0126] In Example F1, an evaluation battery was manufactured in the same manner as in Example F1, except that each electrode structure of Examples 2 to 12 was used as the negative electrode.

[0127] (Comparative Examples F1 to F3)

[0128] In Example F1, an evaluation battery was manufactured in the same manner as in Example F1, except that each electrode structure of Comparative Examples 1 to 3 was used as the negative electrode.

[0129] (Example F13)

[0130] In Example F3, an evaluation battery was manufactured using an electrolyte solution instead of the following electrolyte solution. As the used electrolyte solution, an electrolyte solution prepared by dissolving 1.2 M (moles / liter) of lithium hexafluorophosphate (LiPF6) in a solvent in which ethylene carbonate and diethyl carbonate, from which moisture was sufficiently removed, were mixed at a volume ratio of 3:7, and adding 6 mass% of vinyl carbonate and 1 mass% of diethylene glycol divinyl ether was used.

[0131] [Performance evaluation of power storage device]

[0132] The above full cells were evaluated for rate performance by measuring the ratio of the 1.0C discharge capacity to the 0.2C discharge capacity after charging at 0.2C constant current - 4.2V constant voltage and then discharging at 1.0C to 2.5V after the same charging condition. Further, the ratio of the discharge capacity at the 100th cycle to the initial discharge capacity (capacity retention rate) was evaluated after 100 cycles of discharging at 0.5C to 2.5V after charging at 0.5C constant current - 4.2V constant voltage.

[0133] The ratio of the 1.0C discharge capacity to the 0.2C discharge capacity in Example F5, Example F6 and Example F7 was in the order of Example F7 > Example F5 > Example F6. In the batteries of the examples, if the amount of the ceramic contained in the electrode was more than 20%, the rate performance decreased, and it was found that the ceramic containing additional conductivity could improve the rate performance.

[0134] Further, with respect to the capacity retention rate, as with the evaluation results of the half cells described above, the batteries composed of the negative electrodes containing the ceramics of the examples had higher capacity retention rates during repeated charge and discharge than the batteries of the comparative examples.

[0135] In the comparison of the batteries of Example F3 and Example F13, the capacity retention rate of Example F13 was higher at the 100th cycle, and when the battery of Example F13 was disassembled after charge and discharge, it was observed that the electrolyte gelled.

[0136] When the rate characteristics of the 1.0C discharge capacity to the 0.2C discharge capacity of Comparative Examples F1 to F6 were compared, the rate characteristics of Example F1, F2, F3 and F4 were approximately the same and high, and in Example F5, the rate characteristics slightly decreased, and in Example F6, the rate characteristics further decreased, and it was found that if the content of the ceramic powder was more, there was a tendency that the rate characteristics decreased, and it was also found that the electrode design needed to be made according to the use.

[0137] As described above, according to the present application, it is possible to provide a lithium ion secondary battery which is a power storage device having high energy density and long repeated life.

[0138] Finally, it should be noted that the above-mentioned only constitutes the preferred embodiments of the present application, and is not intended to limit the present application, and although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments, or make equivalent replacements to some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A lithium-ion secondary battery, characterized in that: It is a secondary battery consisting of a negative electrode, an electrolyte that acts as a lithium-ion conductor, and a positive electrode, capable of absorbing and releasing lithium ions. The negative electrode is composed of at least a silicon-containing inorganic material that stores lithium by charging and releases lithium by discharging, hydrophobic porous ceramic particles that retain the electrolyte, carbon materials, and an organic polymer binder; the porous ceramic particles in the negative electrode contain lithium; and the electrolyte is retained by gelling the fine pores of the porous ceramic particles with a cross-linked polymer.

2. The lithium-ion secondary battery according to claim 1, characterized in that: The porous ceramic particles have an average particle size ranging from 0.1 to 4 μm and a bulk density ranging from 0.05 to 0.2 g / cm³. 3 The range.

3. The lithium-ion secondary battery according to claim 1, characterized in that: The porous ceramic particles are made of oxides containing at least one element selected from silicon, aluminum, magnesium, zirconium, and titanium.

4. The lithium-ion secondary battery according to claim 1, characterized in that: The mass percentage of porous ceramic particles in the negative electrode is in the range of 0.5% to 20%.

5. The lithium-ion secondary battery according to claim 1, characterized in that: The specific surface area of ​​the porous ceramic particles in the negative electrode is 35m². 2 / g or more.

6. The lithium-ion secondary battery according to claim 1, characterized in that: The electrolyte, which is included during battery assembly, contains both monovinyl monomers that undergo polymerization and cross-linking reactions during charging and monomers having multiple vinyl groups within their molecules.