WO2014181447A1 - Lithium-ion secondary battery - Google Patents

Lithium-ion secondary battery Download PDF

Info

Publication number
WO2014181447A1
WO2014181447A1 PCT/JP2013/063099 JP2013063099W WO2014181447A1 WO 2014181447 A1 WO2014181447 A1 WO 2014181447A1 JP 2013063099 W JP2013063099 W JP 2013063099W WO 2014181447 A1 WO2014181447 A1 WO 2014181447A1
Authority
WO
WIPO (PCT)
Prior art keywords
negative electrode
battery
secondary battery
overcharge
active material
Prior art date
Application number
PCT/JP2013/063099
Other languages
French (fr)
Japanese (ja)
Inventor
斉景 田中
宏文 ▲高▼橋
山本　恒典
Original Assignee
株式会社 日立製作所
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by 株式会社 日立製作所 filed Critical 株式会社 日立製作所
Priority to PCT/JP2013/063099 priority Critical patent/WO2014181447A1/en
Publication of WO2014181447A1 publication Critical patent/WO2014181447A1/en

Links

Images

Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/133—Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/4235—Safety or regulating additives or arrangements in electrodes, separators or electrolyte
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/027—Negative electrodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/364—Composites as mixtures
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H01M4/386—Silicon or alloys based on silicon
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H01M4/387—Tin or alloys based on tin
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present invention relates to a non-aqueous secondary battery, and in particular, a high energy density lithium ion secondary battery excellent in safety during overcharge and suitable for use in portable equipment, electric vehicles, power storage, and the like, and a battery module thereof. About.
  • Lithium ion secondary batteries (hereinafter referred to as lithium ion batteries) that use the insertion and release of lithium ions for charge / discharge reactions have higher energy density and output density than conventional lead batteries and nickel cadmium batteries. Application to portable devices, electric vehicles, and power storage is in progress.
  • One of the most important battery abnormalities is overcharge.
  • the battery When the battery is charged beyond an appropriate charge / discharge range, the battery may be heated, ruptured, or ignited due to decomposition of the positive electrode active material, deposition of metallic lithium on the negative electrode, decomposition of the electrolyte, or the like. Therefore, a safe battery is expected even if the control system falls into an abnormal state.
  • Patent Document 1 discloses, as a conventional technique for solving this problem, a negative electrode made of a carbon material and an additive made of a material containing Si or Sn, or a material containing these elements, which is known as a high capacity alloy negative electrode material. Is added to suppress the generation of Li dendrite and to selectively deposit the metal eluted from the positive electrode active material on the surface of the additive.
  • the alloy-based negative electrode material described in Patent Document 1 has problems such as a large volume change and a large irreversible capacity. If it is added in a large amount, it may cause a decrease in battery characteristics. On the other hand, when there is too little addition amount, there exists a subject by which the safety improvement effect at the time of overcharge is limited.
  • the purpose of the present invention is to solve such problems and problems.
  • an object of the present invention is to provide a secondary battery capable of suppressing deterioration of battery characteristics due to the alloy-based negative electrode material while suppressing generation of Li dendrite by adding the alloy-based negative electrode material as an overcharge preventing material. It is to provide.
  • the secondary battery according to the present invention is a secondary battery having a positive electrode having a Li-containing transition metal oxide as a main active material and a negative electrode having graphite as a main active material.
  • the negative electrode includes Si, Sn, Or an overcharge preventive material having a particle composed of either Al as a nucleus and a coating composed of SiO 2 or SiC provided on the outer periphery of the nucleus, and the thickness of the coating is 2 nm to 100 nm It is characterized by that.
  • the high-resistance barrier layer on which the surface of the alloy-based negative electrode material is formed can prevent charging and discharging of the alloy-based negative electrode material at normal times. It is possible to suppress deterioration in battery characteristics due to volume change and high irreversible capacity. Once overcharge occurs, lithium ions move through the barrier layer to prevent Li dendrite precipitation. Furthermore, since the alloy-based negative electrode material contributes to charging / discharging, the charging / discharging curve of the battery changes. From this change, it becomes possible to grasp the history of overcharging and the progress of overcharging.
  • the present invention detects battery overcharge and improves safety. Problems, configurations, and effects other than those described above will be clarified by the following description of embodiments.
  • FIG. 2A is a diagram illustrating a schematic diagram of a Li ion battery according to the present embodiment, and FIG. It is a figure which shows the AA sectional drawing of Fig.1 (a).
  • A The figure which shows the overcharge prevention material 100
  • (b) The figure which shows the preparation method of the overcharge prevention material 100. It is a figure which shows the change (change of the reaction form with Li) of the charge curve by high resistance film provision. It is a figure which shows the change (change of the reaction form with Li) of the discharge curve by high resistance film provision.
  • 2 is a detailed view of a negative electrode 200.
  • FIG. It is a figure which shows the battery internal (positive / negative state) analysis result by battery measurement information. It is an experimental data of each Example and a comparative example.
  • FIG. 1A is a diagram showing a cylindrical Li ion battery 1 of the present embodiment.
  • the cylindrical Li-ion battery 1 is a wound battery in which an electrode group 3 wound with a positive electrode 200 and a negative electrode 300 facing each other through a separator 350 and an electrolyte solution are housed inside a battery can 4. It is.
  • the electrode group 3 has a shaft core 2 at the start of the electrode group 3, and the electrode group 3 is configured to be wound around the shaft core 2, and the electrode group 3 and the shaft core 2 are accommodated inside the battery can 4. It has become.
  • the upper and lower ends of the electrode group 3 are provided with electrical insulating plates 5 so that the electrode group 3 does not come into contact with the battery can 4 due to vibration or the like and is not short-circuited.
  • a positive conductive lead 7 is provided at the upper end of the electrode group 3, one end of the conductive lead 7 is electrically connected to the positive electrode 200 of the electrode group 3, and the other end of the conductive lead 7 is the battery lid 6. It is the structure electrically connected to.
  • a negative electrode conductive lead 8 is provided at the lower end of the electrode group 3, one end of the conductive lead 8 is electrically connected to the negative electrode 300 of the electrode group 3, and the other end of the conductive lead 8 is a battery can. 4 is joined to the bottom.
  • the electrolytic solution is injected into the battery can 4 when the dehumidifying atmosphere or the inert atmosphere is controlled.
  • a gasket 9 serving both as an electric insulator and a gas seal is disposed between the battery can 4 and the battery lid 6, and the battery can 4 and the battery lid 6 are integrated by caulking the battery can 4. 4 It is the structure which keeps the inside sealed.
  • FIG. 2 is a cross-sectional view of the Li ion battery of FIG. As described above, the shaft core 2 and the electrode group 3 are accommodated in the battery can 4.
  • the electrode group 3 has a structure in which the positive electrode 200 and the negative electrode 300 are wound through the separator 350 as described above.
  • the positive electrode 200 has a structure in which a positive electrode material 202 is provided on both surfaces of the positive electrode foil 201.
  • the negative electrode 300 has a structure in which the negative electrode material 302 is provided on both surfaces of the negative electrode foil 301.
  • the shaft core 2 may be any known one as long as it can carry the positive electrode, the separator, and the negative electrode. It is desirable to use an aluminum foil for the positive foil 202 and a copper foil for the negative foil 302, but any material may be used as long as it is chemically stable in the charge / discharge reaction of the lithium ion battery.
  • the battery which can be applied is not restricted to a cylindrical battery, It is possible to apply this invention also to a square battery and a laminate cell battery.
  • the electrode group 3 can have various shapes obtained by winding the positive electrode 200 and the negative electrode 300 into an arbitrary shape such as a flat shape.
  • the electrode group 3 may be produced by winding without using the shaft core 2, or a laminate in which a positive electrode and a negative electrode are laminated via a separator like a laminated cell battery may be used.
  • the shape of the battery can 4 may be selected from shapes such as a cylindrical shape, a flat oval shape, a flat oval shape, and a square shape according to the shape of the electrode group 3.
  • the material of the battery can 4 is selected from materials that are corrosion resistant to the nonaqueous electrolyte, such as aluminum, stainless steel, and nickel-plated steel. Further, when the battery can 4 is electrically connected to the positive electrode 200 or the negative electrode 300, the material is not deteriorated due to corrosion of the battery can 4 or alloying with lithium ions in the portion in contact with the nonaqueous electrolyte. Thus, the material of the battery can 4 is selected.
  • the electrolytic solution 3 may be injected directly into the electrode group with the battery lid 6 open, or from the injection port installed in the battery lid 20.
  • the positive electrode 200 includes a positive electrode active material, a conductive agent, a binder, and a positive electrode foil 201.
  • the positive electrode active material include LiCoO 2 , LiNiO 2 , and LiMn 2 O 4 .
  • the particle size of the positive electrode active material is usually specified so as to be equal to or less than the thickness of the mixture layer formed of the positive electrode active material, the conductive agent, and the binder.
  • the coarse particles can be removed in advance by sieving classification, wind classification, etc. preferable.
  • the positive electrode active material is generally oxide-based and has high electric resistance
  • a conductive agent made of carbon powder for supplementing electric conductivity is used. Since both the positive electrode active material and the conductive agent are usually powders, a binder can be mixed with the powders, and the powders can be bonded together and simultaneously bonded to the positive electrode foil 201.
  • the positive electrode foil 201 an aluminum foil having a thickness of 10 to 100 ⁇ m, an aluminum perforated foil having a thickness of 10 to 100 ⁇ m and a pore diameter of 0.1 to 10 mm, an expanded metal, a foam metal plate, or the like is used.
  • materials such as stainless steel and titanium are also applicable.
  • any positive foil 201 can be used without being limited by the material, shape, manufacturing method and the like.
  • a positive electrode slurry in which a positive electrode active material, a conductive agent, a binder, and an organic solvent are mixed is attached to the positive electrode foil 201 by a doctor blade method, a dipping method, or a spray method, and then the organic solvent is dried and applied by a roll press.
  • a positive electrode can be produced by pressure forming.
  • a plurality of mixture layers can be laminated on the positive electrode foil 201 by performing a plurality of times from application to drying.
  • the negative electrode 300 includes a negative electrode active material, a binder, and a negative electrode foil 301.
  • a conductive agent may be added.
  • the negative electrode active material that can be used in the present invention include graphite, non-graphite carbon, metals such as aluminum, silicon, and tin, and alloys thereof, lithium-containing transition metal nitrides Li (3-X) M X N, silicon
  • the lower oxide Li x SiO y (0 ⁇ x, 0 ⁇ y ⁇ 2) and the tin lower oxide Li x SnO y are selected from materials that form an alloy with lithium or materials that form an intermetallic compound. be able to.
  • the material of the negative electrode active material is not particularly limited and can be used other than the above materials. However, when a part of the material such as a material having a large expansion and contraction is selected, if the range used by the negative electrode is too large, Resistance rise may be large. In this case, it is preferable to confirm whether or not the negative electrode potential is below a certain level as a condition for changing the battery voltage.
  • the graphite is included, and the graphite has a graphite interlayer distance (d002) of 0.335 nm or more and 0.338 nm or less.
  • d002 graphite interlayer distance
  • the potential curve of graphite has a stage structure, so that the cycle characteristics of the lithium ion secondary battery can be further improved.
  • the graphite used for the negative electrode is natural graphite that can occlude and release lithium ions, artificial graphite, mesophase carbon, expanded graphite, carbon fiber, vapor grown carbon fiber, pitch-based carbonaceous material, needle coke, Manufactured using petroleum coke and polyacrylonitrile-based carbon fiber as raw materials.
  • the graphite interlayer distance (d002) can be measured using XRD (X-Ray Diffraction Method) or the like.
  • the non-graphitic carbon used for the negative electrode 300 is a carbon material excluding the above-mentioned graphite, and can occlude or release lithium ions.
  • Amorphous carbon materials synthesized by pyrolysis of organic compounds are included.
  • a material that forms an alloy with lithium or a material that forms an intermetallic compound may be added as a third negative electrode active material to the negative electrode 300 having a voltage change rate different from that of the positive electrode 200.
  • the third negative electrode active material include metals such as aluminum, silicon, and tin and alloys thereof, lithium-containing transition metal nitrides Li (3-X) M X N, and lower oxides of silicon Li X SiO y ( 0 ⁇ x, 0 ⁇ y ⁇ 2), and the lower oxide of tin Li x SnO y .
  • the negative electrode active material generally used is a powder
  • a binder is mixed with the negative electrode active material, and the powders are bonded together and simultaneously bonded to the negative electrode foil 301.
  • the particle size of the negative electrode active material be equal to or less than the thickness of the mixture layer formed from the negative electrode active material and the binder.
  • the coarse particles may be removed in advance by sieving classification or wind classification, and particles having a thickness of the mixture layer thickness or less may be used. preferable.
  • a copper foil having a thickness of 10 to 100 ⁇ m, a copper perforated foil having a thickness of 10 to 100 ⁇ m and a hole diameter of 0.1 to 10 mm, an expanded metal, a foam metal plate, or the like is used.
  • materials such as stainless steel, titanium, or nickel are also applicable.
  • any negative electrode foil 301 can be used without being limited by the material, shape, manufacturing method and the like.
  • a negative electrode slurry in which a negative electrode active material, a binder, and an organic solvent are mixed is attached to the negative electrode foil 301 by a doctor blade method, a dipping method, a spray method, or the like, and then the organic solvent is dried and pressure-molded by a roll press. Thereby, a negative electrode can be produced. Moreover, it is also possible to form a multilayer mixture layer on the negative electrode foil 301 by performing from application to drying a plurality of times.
  • a separator 350 is inserted between the positive electrode 200 and the negative electrode 300 manufactured by the above method to prevent a short circuit between the positive electrode and the negative electrode.
  • the separator 350 can be a polyolefin polymer sheet made of polyethylene, polypropylene, or the like, or a two-layer structure in which a polyolefin polymer and a fluorine polymer sheet typified by tetrafluoropolyethylene are welded. It is.
  • a mixture of ceramics and a binder may be formed in a thin layer on the surface of the separator 350 so that the separator does not shrink when the battery temperature increases. Since these separators need to allow lithium ions to permeate during charge and discharge of the battery, they can be used for lithium ion batteries as long as the pore diameter is generally 0.01 to 10 ⁇ m and the porosity is 20 to 90%.
  • Electrolyte As a representative example of the electrolyte that can be used in an embodiment of the present invention, lithium hexafluorophosphate (LiPF 6 ) as an electrolyte, a solvent obtained by mixing dimethyl carbonate, diethyl carbonate, or ethyl methyl carbonate with ethylene carbonate, Alternatively, there is a solution in which lithium borofluoride (LiBF 4 ) is dissolved.
  • the present invention is not limited to the type of solvent and electrolyte, and the mixing ratio of solvents, and other electrolytes can be used.
  • non-aqueous solvents examples include propylene carbonate, ethylene carbonate, butylene carbonate, vinylene carbonate, ⁇ -butyrolactone, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, 1,2-dimethoxyethane, -Methyltetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolane, formamide, dimethylformamide, methyl propionate, ethyl propionate, phosphate triester, trimethoxymethane, dioxolane, diethyl ether, sulfolane, 3-methyl-2-
  • non-aqueous solvents such as oxazolidinone, tetrahydrofuran, 1,2-diethoxyethane, chloroethylene carbonate, or chloropropylene carbonate.
  • Other solvents may be used as long as they do not decompose on the positive electrode or the negative electrode
  • examples of the electrolyte LiPF 6, LiBF 4, LiClO 4, LiCF 3 SO 3, LiCF 3 CO 2, LiAsF 6, LiSbF 6, or imide salts such as lithium represented by lithium trifluoromethane sulfonimide, multi
  • lithium salts A nonaqueous electrolytic solution obtained by dissolving these salts in the above-mentioned solvent can be used as a battery electrolytic solution.
  • An electrolyte other than this may be used as long as it does not decompose on the positive electrode and the negative electrode of the battery according to this embodiment.
  • ion conductive polymers such as polyethylene oxide, polyacrylonitrile, polyvinylidene fluoride, polymethyl methacrylate, polyhexafluoropropylene, and polyethylene oxide can be used for the electrolyte.
  • polyethylene oxide polyacrylonitrile
  • polyvinylidene fluoride polymethyl methacrylate
  • polyhexafluoropropylene polyethylene oxide
  • an ionic liquid can be used.
  • EMI-BF4 1-ethyl-3-methylimidazole tetrafluoroborate
  • LiTFSI lithium salt LiN (SO 2 CF 3 ) 2
  • triglyme and tetraglyme a mixed salt of lithium salt LiN (SO 2 CF 3 ) 2
  • LiTFSI lithium salt LiN (SO 2 CF 3 ) 2
  • triglyme and tetraglyme LiN (SO 2 CF 3 ) 2
  • a cyclic quaternary ammonium cation N-methyl) -N-propylpyrrolidinium
  • an imide-based anion example is bis (fluorosulfonyl) imide
  • the overcharge prevention material 100 is a characteristic part of the present invention.
  • the overcharge prevention material 100 in the present invention is a high-capacity Li storage material 10 provided with a high resistance film.
  • the high-capacity Li storage material 10 is specifically Si, Sn, and Al particles. Since these materials have a Li storage capacity as high as 2 to 7 times that of graphite, the Li storage capacity of the negative electrode can be enhanced only by mixing a small amount.
  • the high resistance film 11 is specifically made of SiO 2 or SiC.
  • the volume resistivity of SiO 2 is about 10 6 to 10 10 ⁇ cm, and SiC is 10 6 ⁇ cm. Therefore, a value higher than the volume resistivity of Si or the like is shown, and it becomes possible to function as a high resistance film.
  • the thickness of the SiO 2 or SiC coating 11 is preferably 2 nm to 100 nm.
  • the reason why the thickness of the coating 11 is required to be 2 nm or more is that when the thickness of the coating 11 is less than 2 nm, dielectric breakdown occurs even at a low potential, and even when no overvoltage actually occurs, an overcharge prevention material This is because there is a risk that the performance of the Li-ion battery may deteriorate. Moreover, when it becomes a thin film, the influence of the resistance value resulting from crystallinity will become large, and it will operate
  • the reason why the thickness of the coating film 11 must be 100 nm or less is that when the thickness of the coating film 11 exceeds 100 nm, the electronic conductivity of the overvoltage prevention material 100 becomes too low, and a considerable overvoltage is not applied. This is because the overvoltage prevention material 100 does not work.
  • the resistance value of the film is 10 ⁇ 1 to 10 3 ⁇ . In this case, charging starts near 0 V at the Li / Li + potential, and the high-capacity Li storage material 10 can absorb Li ions.
  • the overvoltage prevention material 100 Inside the battery, at a potential at which Li does not precipitate, the resistance of the negative electrode active material is lower than that of the overcharge preventing material 100, so that a current flows into the negative electrode active material and a charging reaction is performed. However, in the vicinity of 0 V at which Li is deposited, the amount of Li ions that can be occluded in the negative electrode active material is almost in a limit state (a state in which charging is impossible any more), and the mobility of Li ions becomes small. As a result, the resistance of the negative electrode active material itself increases, and the overcharge preventing material 100 is also put in a voltage state. In this state, Li ions are inserted into the overcharge prevention material 100 and function as an overcharge prevention material.
  • the overvoltage prevention material 100 is used by being added to the negative electrode material 302.
  • the overvoltage prevention material 100 has an increased electrical resistance due to the formation of the coating 11, and the high-capacity Li storage material 10 (for example, Si) and Li at the time of overvoltage generation. It becomes possible to reduce the initial reaction potential.
  • Li ions are inserted into the high-capacity Li storage material 10 having a higher reaction potential with Li than the negative electrode active material such as graphite (that is, the high-capacity Li storage material 10 is present before the graphite or the like). To react).
  • the overvoltage prevention material 100 When the overvoltage prevention material 100 is used for the above reason, it has the effect of suppressing the occurrence of overvoltage in addition to the overcharge prevention effect.
  • the electric resistance and the Li diffusion resistance can be further increased, and the high-capacity Li storage material 10
  • the overvoltage required for the initial reaction between (for example, Si) and Li can be increased, and the overvoltage prevention material can be reliably operated.
  • the Li reaction potential can be lowered to the vicinity of the Li deposition potential.
  • the negative electrode active material such as graphite
  • Si is not included in the SiO 2 matrix, but the volume of the high-capacity Li absorbing material 10 (for example, Si) is larger than that of the coating film 11 (for example, SiO 2 ). Is a point. This is because the structure in which Si is included in the SiO 2 matrix does not sufficiently function as an overvoltage prevention material because the resistance is too high and the amount of Si is small.
  • the coating 11 provided on the high-capacity Li absorbent material 10 must cover the entire surface of the high-capacity Li absorbent material 10. If the high-capacity Li-occlusion material 10 (for example, Si) is exposed, the resistance of the exposed surface is low, so that a conduction path to Si can be made directly. Therefore, conduction to Si through the SiO 2 coating 11 is performed. This is because there is no phenomenon that a pass can be made, that is, an insulation pass is made due to dielectric breakdown at the time of overvoltage, and the function as an overvoltage prevention material is not exhibited unless a very large overvoltage prevention occurs.
  • the high-capacity Li-occlusion material 10 for example, Si
  • all the overvoltage preventions 100 in all the negative electrode materials 301 have a structure in which the entire surface of the high-capacity Li storage material 10 is covered with the coating 11.
  • the film 11 is formed on the entire surface of most particles (50% or more) in the overvoltage prevention material 100.
  • the overvoltage prevention material 100 of the present invention has the high voltage Li storage material 10 larger than the volume of the coating 11, so that the dielectric breakdown of the coating 11 occurs at an appropriate voltage. It is possible to function as.
  • the coating 11 is formed on the entire surface of the majority (50% or more) of the particles in the overvoltage prevention material 100, it can function as an overvoltage prevention material.
  • the film 11 is formed on the entire surface of 95% or more of the particles in the overvoltage preventing material 100.
  • FIG. 3A is a diagram illustrating the overcharge preventing material 100 according to the present embodiment. It has a core-shell structure in which particles of a high-capacity Li-absorbing material 10 (Si, Al, Sn) capable of storing Li are used as a core layer and a coating 11 (shell layer) having a high resistivity is formed on the surface thereof.
  • a high-capacity Li-absorbing material 10 Si, Al, Sn
  • a coating 11 shell layer having a high resistivity
  • the overvoltage prevention material 100 has an arbitrary thickness by placing Si particles in a high-temperature firing furnace and firing in an Ar / O 2 mixed gas at a temperature of 900 to 1200 ° C. for a predetermined time.
  • SiO 2 layer can be applied (range 5-100 nm). Also, these oxide films can be produced by high-pressure steam oxidation.
  • the overvoltage prevention material 100 When a SiC layer is formed as a coating, it is possible to prepare the overvoltage prevention material 100 by mixing Si particles with tar pitch and a carbon-containing organic substance and firing in an inert atmosphere at 1300 ° C. or higher.
  • FIG. 4 shows characteristics at the time of charging of the overvoltage prevention material 100 in which Si is used as the high-capacity Li storage material 10 and a high-resistance coating (SiO 2) is applied around the Si.
  • the solid line shown in FIG. 4 is a charge curve of Si using Si with no surface coating applied as an active material. As shown by the solid line, it can be seen that the capacity increases from 0.4 V (at Li / Li + potential) when Si with no surface coating is used as the active material. This means that Si reacts with Li from 0.4 V at the Li / Li + potential.
  • the broken line in FIG. 4 is a charging curve of the Si surface provided with the SiO 2 coating 11. From this data, it can be seen that Si to which the SiO 2 coating 11 is applied does not start the reaction with Li unless an overvoltage is applied until it reaches around 0V.
  • the reaction start potential can be lowered.
  • This overvoltage decrease in reaction initiation potential
  • the electrical resistance of the coating on the surface is higher. More specifically, for example, increasing the thickness of the coating 11 can be mentioned.
  • the electric resistance of the coating layer is too large, the overvoltage for initiating the reaction is too large, and it may not operate even at the Li deposition potential.
  • FIG. 5 shows a discharge curve curve of Si coated with a SiO 2 layer (shown by a dotted line), a discharge curve of Si not coated (shown by a broken line), and a discharge curve of graphite (shown by a solid line). Indicated).
  • the mixing ratio of the overcharge prevention material is desirably 5 to 15 wt% or less with respect to the main active material.
  • the mixing ratio of the overcharge prevention material is lower than 5 wt%, the amount of Li absorption is small and the effect becomes minute.
  • the mixing ratio is higher than 15 wt%, the overcharge prevention material 100 dispersed in the main active material is connected. This is because the electric conduction path of the main active material is obstructed and the electric resistance of the negative electrode mixture layer is increased.
  • FIG. 6 shows a cross-sectional view of the negative electrode 300 in the present embodiment.
  • the graphite 110 and the overvoltage preventing material 100 are applied.
  • the overcharge prevention material may be mixed with the main active material so as to be uniform, or a concentration gradient may be provided so that the abundance ratio is increased in a portion where Li is likely to precipitate, for example, in the vicinity of the surface.
  • the overcharge prevention material 100 mixed with the main active material is not limited to a single form, and may have a plurality of forms.
  • the thickness and material of the high resistance film or the material of the Li storage material may be different.
  • Si particles having different SiO 2 layer thicknesses, SiO 2 and SiC Si particles on the surface, SiO 2 on the surface layer, and Si and Sn particles mixed therein may be used.
  • FIG. 7 shows a charge / discharge curve when the above-described overvoltage prevention material 100 is used.
  • the reaction potential between the core material of the overcharge prevention material 100 (inside the coating) and Li takes a value specific to the substance.
  • the lower diagram in FIG. 7 shows data when the reaction amount of the overcharge prevention material 100 is larger than that in the upper diagram in FIG.
  • LiFePO4 as positive electrode active material 88 parts by mass (active material and mixing ratio may be changed), artificial graphite as conductive aid: 1 part by mass, Ketjen black: 1 part by mass, and PVDF as binder: 10 parts by mass
  • NMP as a solvent
  • the positive electrode mixture-containing paste is intermittently applied to both surfaces of an aluminum foil (thickness: 15 ⁇ m) by adjusting the thickness, dried, and then subjected to a calendering process, so that the total thickness of the positive electrode mixture layer is 183 ⁇ m. Was adjusted to produce a positive electrode.
  • the Si particles coated with SiO 2 are placed in a high-temperature firing furnace with Si particles having an average particle diameter D50 of 1 ⁇ m, fired in an Ar / O 2 mixed gas at a temperature of 900 to 1200 ° C. for a predetermined time, and then crushed and coated.
  • the thickness was made in the range of 2 to 100 nm.
  • ⁇ Production of negative electrode> Mixture of SiO2 coated Si particles and graphite having an average particle diameter D50 of 20 ⁇ m mixed at a mass ratio of 15:85: 98 parts by mass, CMC aqueous solution adjusted to have a viscosity of 1500 to 5000 mPa ⁇ s (concentration: 1 mass%): 1 mass part and SBR: 1 mass part were mixed, and the aqueous negative mix containing paste was prepared.
  • the negative electrode mixture-containing paste is intermittently applied on both sides of a current collector made of copper foil with a thickness of 8 ⁇ m while adjusting the thickness, dried, and then calendered to give a total thickness of 108 ⁇ m.
  • a negative electrode was prepared by adjusting the thickness of the mixture layer.
  • LiPF 6 as a lithium salt was dissolved at a concentration of 1 mol / l in a mixture of ethylene carbonate, ethyl methyl carbonate and dimethyl carbonate in a volume ratio of 1: 1: 1 to prepare a non-aqueous electrolyte.
  • ⁇ Battery assembly> The positive electrode and the negative electrode were cut into a predetermined size, and a wound electrode body was produced through a separator made of a microporous polyethylene film having a thickness of 30 ⁇ m and a porosity of 50%. This wound electrode body was inserted into a cylindrical battery can, and then the non-aqueous electrolyte was poured into the can and sealed to produce a cylindrical non-aqueous secondary battery.
  • Example 2 A cylindrical non-aqueous secondary battery was fabricated in the same manner as in Experimental Example 1 except that the overcharge prevention material was changed to 5 parts by mass (Experimental Example 3). A cylindrical non-aqueous secondary battery was produced in the same manner as in Experimental Example 1 except that the overcharge prevention material was changed to 15 parts by mass (Comparative Example 1). A cylindrical non-aqueous secondary battery was produced in the same manner as in Example 1 except that the overcharge prevention material was changed to 0 part by mass (Comparative Example 2). A cylindrical non-aqueous secondary battery was produced in the same manner as in Example 1 except that the overcharge prevention material was changed to 20 parts by mass.
  • ⁇ Overcharge detection test> The amount of current discharged in 1 hour is 1 C with respect to the initial discharge capacity of the manufactured battery, and the capacity change width is centered on a voltage at which the capacity is exactly half of the discharge capacity at a discharge current of 0.2 C.
  • the constant current charge / discharge cycle test was carried out in a thermostatic bath maintained at 25 ° C. with a charge / discharge current of 2C within a range of 80%.
  • the lower limit value of the discharge termination condition was that the battery voltage reached 1.5V.
  • constant current / constant voltage charging was performed at a predetermined voltage (3.8 V in the process) every 200 cycles, and constant current discharging was performed at a current amount of 0.1C.
  • the first signal is detected at the stage where the reaction between Si and Li, which are overcharge prevention materials, is detected, and the capacity of the overcharge prevention material (the peak derived from Si and the rising peak at the end of discharge in the differential curve)
  • the second signal is different from the first signal when the charged overcharge prevention material has completely reacted, and the overcharge prevention material capacity is 3/4 or more. In some cases, the test was terminated after 5 cycles after emitting a signal different from the first and second signals.
  • the first signal was emitted in 2200 cycles
  • the second signal was emitted in 2600
  • the third signal was emitted in 2800 cycles.
  • the first signal is 2000 cycles
  • the second signal is 2200
  • the third signal is 2400.
  • the number of cycles at the time of signal generation is faster, and the interval between each signal Also became shorter.
  • Comparative Example 1 the test was terminated when the discharge termination condition of 1.5 V was reached without observing a signal, and Li deposition was observed on the negative electrode in the decomposition observation.

Abstract

The purpose of the present invention is to provide a secondary battery wherein, while suppressing the formation of lithium dendrites via the addition of an alloy negative-electrode material as an overcharge-preventing material, decreases in battery characteristics due to said alloy negative-electrode material can be minimized. This secondary battery has the following: a positive electrode, the primary active material of which is a lithium-containing transition-metal oxide; and a negative electrode, the primary active material of which is graphite. Said secondary battery is characterized in that: the negative electrode thereof contains an overcharge-preventing material in which core particles comprising silicon, tin, or aluminum are each coated with a film comprising SiO2 or SiC; and said films are between 2 and 100 nm thick, inclusive.

Description

リチウムイオン二次電池Lithium ion secondary battery
　本発明は、非水系二次電池に係り、特に、ポータブル機器、電気自動車、電力貯蔵等に用いるに好適な、過充電時の安全性に優れた高エネルギー密度リチウムイオン二次電池及びその電池モジュールに関する。 The present invention relates to a non-aqueous secondary battery, and in particular, a high energy density lithium ion secondary battery excellent in safety during overcharge and suitable for use in portable equipment, electric vehicles, power storage, and the like, and a battery module thereof. About.
　充放電反応にリチウムイオンの吸蔵・放出を利用するリチウムイオン二次電池（以下、リチウムイオン電池）は、従来の鉛電池やニッケルカドミウム電池と比較して高いエネルギー密度、出力密度が得られることから、ポータブル機器、電気自動車、電力貯蔵への適用が進められている。 Lithium ion secondary batteries (hereinafter referred to as lithium ion batteries) that use the insertion and release of lithium ions for charge / discharge reactions have higher energy density and output density than conventional lead batteries and nickel cadmium batteries. Application to portable devices, electric vehicles, and power storage is in progress.
　一方で、制御系の異常により、電池が異常な環境にさらされると、大きな破壊が起こることがあるため、安全性の向上がますます期待されている。 On the other hand, if the battery is exposed to an abnormal environment due to an abnormality in the control system, a large destruction may occur.
　最も重要視されている電池の異常状態の一つが、過充電である。電池が適切な充放電範囲を超えて充電されると、正極活物質の分解、負極への金属リチウムの析出、電解液の分解などにより、電池の発熱や破裂、発火に至る場合がある。そのため、制御系が異常状態に陥っても安全な電池が期待されている。 One of the most important battery abnormalities is overcharge. When the battery is charged beyond an appropriate charge / discharge range, the battery may be heated, ruptured, or ignited due to decomposition of the positive electrode active material, deposition of metallic lithium on the negative electrode, decomposition of the electrolyte, or the like. Therefore, a safe battery is expected even if the control system falls into an abnormal state.
　特許文献１には、この課題を解決する従来技術として、炭素材料からなる負極に、高容量な合金系負極材料として知られている「ＳｉもしくはＳｎ、またはこれらの元素を含む材料からなる添加剤」を添加することで、Ｌｉデンドライトの発生抑制や、正極活物質から溶出した金属を添加材表面に選択的に析出させる技術が開示されている。 Patent Document 1 discloses, as a conventional technique for solving this problem, a negative electrode made of a carbon material and an additive made of a material containing Si or Sn, or a material containing these elements, which is known as a high capacity alloy negative electrode material. Is added to suppress the generation of Li dendrite and to selectively deposit the metal eluted from the positive electrode active material on the surface of the additive.
特開２０１２－８４４２６号公報JP 2012-84426 A
　しかしながら、特許文献１に記載の合金系負極材料は、体積変化が大きく、また不可逆容量が大きいなどの課題があり、多量に添加すると電池の特性低下を招く要因となることがある。一方で、添加量が少なすぎると過充電時の安全性の向上効果が限定される課題がある。 However, the alloy-based negative electrode material described in Patent Document 1 has problems such as a large volume change and a large irreversible capacity. If it is added in a large amount, it may cause a decrease in battery characteristics. On the other hand, when there is too little addition amount, there exists a subject by which the safety improvement effect at the time of overcharge is limited.
　本発明の目的は、このような問題や課題を解決することである。 The purpose of the present invention is to solve such problems and problems.
　すなわち、本発明の目的は、前記合金系負極材料を過充電防止材として添加することでＬｉデンドライトの発生を抑制しつつ、前記合金系負極材料による電池の特性低下を抑制可能な二次電池を提供することにある。 That is, an object of the present invention is to provide a secondary battery capable of suppressing deterioration of battery characteristics due to the alloy-based negative electrode material while suppressing generation of Li dendrite by adding the alloy-based negative electrode material as an overcharge preventing material. It is to provide.
　本発明にかかる二次電池は、Ｌｉ含有遷移金属酸化物を主活物質とする正極と、黒鉛を主活物質とする負極と、を有する二次電池において、前記負極には、Ｓｉ、Ｓｎ、又はＡｌのいずれかで構成される粒子を核とし、当該核の外周にＳｉＯ2又はＳｉＣで構成される被膜を設けた過充電防止材が含有され、前記被膜の厚さは２ｎｍ～１００ｎｍであることを特徴とする。 The secondary battery according to the present invention is a secondary battery having a positive electrode having a Li-containing transition metal oxide as a main active material and a negative electrode having graphite as a main active material. The negative electrode includes Si, Sn, Or an overcharge preventive material having a particle composed of either Al as a nucleus and a coating composed of SiO 2 or SiC provided on the outer periphery of the nucleus, and the thickness of the coating is 2 nm to 100 nm It is characterized by that.
　本発明によれば、前記合金系負極材料の表面を形成された高抵抗のバリア層が通常時の前記合金系負極材料の充放電を防止することができるため、前記合金系負極材料に起因した体積変化や高い不可逆容量による電池の特性低下を抑制することができる。ひとたび過充電に至った場合には、前記バリア層を貫いてリチウムイオンが移動し、Ｌｉデンドライトの析出を防止する。さらに、前記合金系負極材料が充放電に寄与することで、電池の充放電カーブが変化するため、この変化から過充電の履歴および過充電の進行度を把握することが可能になる。 According to the present invention, the high-resistance barrier layer on which the surface of the alloy-based negative electrode material is formed can prevent charging and discharging of the alloy-based negative electrode material at normal times. It is possible to suppress deterioration in battery characteristics due to volume change and high irreversible capacity. Once overcharge occurs, lithium ions move through the barrier layer to prevent Li dendrite precipitation. Furthermore, since the alloy-based negative electrode material contributes to charging / discharging, the charging / discharging curve of the battery changes. From this change, it becomes possible to grasp the history of overcharging and the progress of overcharging.
　本発明により、電池の過充電を検知し、安全性を向上させる。上記した以外の課題、構成および効果は以下の実施形態の説明により明らかにされる。 The present invention detects battery overcharge and improves safety. Problems, configurations, and effects other than those described above will be clarified by the following description of embodiments.
本実施形態のＬｉイオン電池の（ａ）概略図を示す図、（ｂ）電極群３を示す図である。FIG. 2A is a diagram illustrating a schematic diagram of a Li ion battery according to the present embodiment, and FIG. 図１（ａ）のＡ－Ａ断面図を示す図である。It is a figure which shows the AA sectional drawing of Fig.1 (a). （ａ）過充電防止材１００を示す図、および（ｂ）過充電防止材１００の作成方法を示す図である。(A) The figure which shows the overcharge prevention material 100, and (b) The figure which shows the preparation method of the overcharge prevention material 100. 高抵抗被膜付与による充電カーブの変化（Ｌｉとの反応形態の変化）を示す図である。It is a figure which shows the change (change of the reaction form with Li) of the charge curve by high resistance film provision. 高抵抗被膜付与による放電カーブの変化（Ｌｉとの反応形態の変化）を示す図である。It is a figure which shows the change (change of the reaction form with Li) of the discharge curve by high resistance film provision. 負極２００の詳細図である。2 is a detailed view of a negative electrode 200. FIG. 電池測定情報による電池内部（正負極の状態）解析結果を示す図である。It is a figure which shows the battery internal (positive / negative state) analysis result by battery measurement information. 各実施例及び比較例の実験データである。It is an experimental data of each Example and a comparative example.
　Ｌｉデンドライトの発生を抑制する手法の一つは、負極材料の量を増やして、過充電時にも全てのリチウムイオンを吸蔵可能な負極を用いることである。しかし、この手法は、負極材料の量に比例した不可逆容量の増大による、電池の特性低下を免れることができない。本発明者は、鋭意検討の結果、上述した課題を解決する手法に想到した。 One method of suppressing the generation of Li dendrite is to increase the amount of negative electrode material and use a negative electrode that can occlude all lithium ions even during overcharge. However, this technique cannot avoid the deterioration of battery characteristics due to an increase in irreversible capacity proportional to the amount of negative electrode material. As a result of intensive studies, the present inventor has come up with a technique for solving the above-described problems.
　以下、本発明を実施するための最良の形態を具体的な実施例によって説明するが、本発明はこれに限定されるものではない。また、実施例における図は、略図であり、図中の位置関係系や寸法等に正確さを保証するものではない。本明細書に開示される技術的思想の範囲内において当業者による様々な変更および修正が可能である。また、本発明を説明するための全図において、同一の機能を有するものは、同一の符号を付け、その繰り返しの説明は省略する場合がある。 Hereinafter, the best mode for carrying out the present invention will be described by way of specific examples, but the present invention is not limited thereto. Further, the drawings in the embodiments are schematic diagrams and do not guarantee the accuracy of the positional relationship system, dimensions, and the like in the drawings. Various changes and modifications can be made by those skilled in the art within the scope of the technical idea disclosed in this specification. In all the drawings for explaining the present invention, components having the same function are denoted by the same reference numerals, and repeated description thereof may be omitted.
　〈第一の実施形態〉
　まず、図１を用いて本発明のＬｉイオン電池の概要について説明する。 <First embodiment>
First, the outline | summary of the Li ion battery of this invention is demonstrated using FIG.
　図１（ａ）は本実施形態の円筒型Ｌｉイオン電池１を示す図である。当該円筒型Ｌｉイオン電池１は、正極２００と負極３００とがセパレータ３５０を介して対向するように捲回された電極群３と電解液が電池缶４の内部に収納された捲回式の電池である。 FIG. 1A is a diagram showing a cylindrical Li ion battery 1 of the present embodiment. The cylindrical Li-ion battery 1 is a wound battery in which an electrode group 3 wound with a positive electrode 200 and a negative electrode 300 facing each other through a separator 350 and an electrolyte solution are housed inside a battery can 4. It is.
　電極群３の捲始め部には軸芯２があり、電極群３は当該軸芯２に捲きつけられる形で構成され当該電極群３および軸芯２は電池缶４の内部に収納される形となっている。 The electrode group 3 has a shaft core 2 at the start of the electrode group 3, and the electrode group 3 is configured to be wound around the shaft core 2, and the electrode group 3 and the shaft core 2 are accommodated inside the battery can 4. It has become.
　電極群３の上端と下端には電気絶縁板５が備えられており、振動等によって電極群３が電池缶４に接触して短絡しないような構造になっている。 The upper and lower ends of the electrode group 3 are provided with electrical insulating plates 5 so that the electrode group 3 does not come into contact with the battery can 4 due to vibration or the like and is not short-circuited.
　電極群３の上部端には正極の導電リード７が設けられており、導電リード７の一端は電極群３の正極２００と電気的に接続されており、導電リード７の他端は電池蓋６に電気的に接続される構成となっている。 A positive conductive lead 7 is provided at the upper end of the electrode group 3, one end of the conductive lead 7 is electrically connected to the positive electrode 200 of the electrode group 3, and the other end of the conductive lead 7 is the battery lid 6. It is the structure electrically connected to.
　一方、電極群３の下端には負極の導電リード８が設けられており、導電リード８の一端は電極群３の負極３００と電気的に接続されており、導電リード８の他端は電池缶４の底部に接合されている。 On the other hand, a negative electrode conductive lead 8 is provided at the lower end of the electrode group 3, one end of the conductive lead 8 is electrically connected to the negative electrode 300 of the electrode group 3, and the other end of the conductive lead 8 is a battery can. 4 is joined to the bottom.
　電池缶４内には除湿雰囲気あるいは不活性雰囲気に制御されたところで電解液が注入される。そして、その後電池缶４と電池蓋６の間に電気絶縁とガスシールを兼ねたガスケット９を配置し、電池缶４をかしめることによって当該電池缶４と電池蓋６を一体にし、画電池缶４内部を密閉に保つ構成となっている。 The electrolytic solution is injected into the battery can 4 when the dehumidifying atmosphere or the inert atmosphere is controlled. After that, a gasket 9 serving both as an electric insulator and a gas seal is disposed between the battery can 4 and the battery lid 6, and the battery can 4 and the battery lid 6 are integrated by caulking the battery can 4. 4 It is the structure which keeps the inside sealed.
　図２は、図１（ａ）のＬｉイオン電池をＡ－Ａ断面から見た断面図となっている。このように軸芯２および電極群３は電池缶４内部に収納されている。 FIG. 2 is a cross-sectional view of the Li ion battery of FIG. As described above, the shaft core 2 and the electrode group 3 are accommodated in the battery can 4.
　続いて、図１（ｂ）を用いて、電極群３の詳細な構造を説明する。電極群３は、上述したように正極２００と負極３００がセパレータ３５０を介して捲回された構造となっている。正極２００は正極箔２０１の両面に正極材２０２が設けられた構造になっている。一方、負極３００は負極箔３０１の両面に負極材３０２が設けられた構造になっている。正極２００と負極３００の間にセパレータを挿入し、軸芯２に捲回すれば電極群３が完成する。なお、軸芯２は、正極、セパレータ及び負極を担持できるものであれば、公知の任意のものを用いることができる。正極箔２０２はアルミ箔、負極箔３０２は銅箔を用いるのが望ましいが、リチウムイオン電池の充放電反応において、化学的に安定であればどの材料を用いても良い。 Subsequently, the detailed structure of the electrode group 3 will be described with reference to FIG. The electrode group 3 has a structure in which the positive electrode 200 and the negative electrode 300 are wound through the separator 350 as described above. The positive electrode 200 has a structure in which a positive electrode material 202 is provided on both surfaces of the positive electrode foil 201. On the other hand, the negative electrode 300 has a structure in which the negative electrode material 302 is provided on both surfaces of the negative electrode foil 301. When a separator is inserted between the positive electrode 200 and the negative electrode 300 and wound around the shaft core 2, the electrode group 3 is completed. The shaft core 2 may be any known one as long as it can carry the positive electrode, the separator, and the negative electrode. It is desirable to use an aluminum foil for the positive foil 202 and a copper foil for the negative foil 302, but any material may be used as long as it is chemically stable in the charge / discharge reaction of the lithium ion battery.
　なお、本実施形態では具体例として円筒型電池を用いて説明するが、適用できる電池は円筒型電池に限らず、角型電池、ラミネートセル電池でも本発明を適用することが可能である。例えば、電極群３は、図２に示した円筒形状の他に、正極２００と負極３００を扁平状等の任意の形状に捲回したもの種々の形状にすることができる。また、軸芯２を用いずに捲回し電極群３を作製してもよいし、ラミネートセル電池のようにセパレータを介し、正極と負極を積層したものを用いても良い。 In addition, although this embodiment demonstrates using a cylindrical battery as a specific example, the battery which can be applied is not restricted to a cylindrical battery, It is possible to apply this invention also to a square battery and a laminate cell battery. For example, in addition to the cylindrical shape shown in FIG. 2, the electrode group 3 can have various shapes obtained by winding the positive electrode 200 and the negative electrode 300 into an arbitrary shape such as a flat shape. Moreover, the electrode group 3 may be produced by winding without using the shaft core 2, or a laminate in which a positive electrode and a negative electrode are laminated via a separator like a laminated cell battery may be used.
　また、電池缶４の形状は、電極群３の形状に合わせ、円筒形、偏平長円形状、扁平楕円形状、角形等の形状を選択してもよい。電池缶４の材質は、アルミニウム、ステンレス鋼、ニッケルメッキ鋼製等、非水電解質に対し耐食性のある材料から選択される。また、電池缶４を正極２００又は負極３００に電気的に接続する場合は、非水電解質と接触している部分において、電池缶４の腐食やリチウムイオンとの合金化による材料の変質が起こらないように、電池缶４の材料の選定を行う。 Also, the shape of the battery can 4 may be selected from shapes such as a cylindrical shape, a flat oval shape, a flat oval shape, and a square shape according to the shape of the electrode group 3. The material of the battery can 4 is selected from materials that are corrosion resistant to the nonaqueous electrolyte, such as aluminum, stainless steel, and nickel-plated steel. Further, when the battery can 4 is electrically connected to the positive electrode 200 or the negative electrode 300, the material is not deteriorated due to corrosion of the battery can 4 or alloying with lithium ions in the portion in contact with the nonaqueous electrolyte. Thus, the material of the battery can 4 is selected.
　また、電解液３の注入方法は、上述した方法の他に電池蓋６を解放した状態にて電極群に直接添加する方法、又は電池蓋２０に設置した注入口から添加する方法がある。 In addition to the method described above, the electrolytic solution 3 may be injected directly into the electrode group with the battery lid 6 open, or from the injection port installed in the battery lid 20.
　また、電池缶４を密閉する方法としては、具体例として電池缶４をかしめて電池蓋６と密閉する方法で説明したが、その他の方法として溶接等の方法がある。 Further, as a method of sealing the battery can 4, as a specific example, the method of caulking the battery can 4 and sealing it with the battery lid 6 has been described, but other methods include a method such as welding.
　続いて本発明の一実施形態に係るリチウムイオン二次電池の正極２００、負極３００のより詳細な構成について説明する。 Subsequently, more detailed configurations of the positive electrode 200 and the negative electrode 300 of the lithium ion secondary battery according to the embodiment of the present invention will be described.
　＜正極２００＞
　正極２００は、正極活物質、導電剤、バインダ、及び正極箔２０１から構成される。正極活物質を例示すると、ＬｉＣｏＯ2、ＬｉＮｉＯ2、及びＬｉＭｎ2Ｏ4が代表例である。他に、ＬｉＭｎＯ3、ＬｉＭｎ2Ｏ3、ＬｉＭｎＯ2、Ｌｉ4Ｍｎ5Ｏ12、ＬｉＭｎ2-xＭｘＯ2（ただし、Ｍ＝Ｃｏ、Ｎｉ、Ｆｅ、Ｃｒ、Ｚｎ、Ｔｉからなる群から選ばれる少なくとも１種、ｘ＝０．０１～０．２）、Ｌｉ2Ｍｎ3ＭＯ8（ただし、Ｍ＝Ｆｅ、Ｃｏ、Ｎｉ、Ｃｕ、Ｚｎからなる群から選ばれる少なくとも１種）、Ｌｉ1-xＡxＭｎ2Ｏ4（ただし、Ａ＝Ｍｇ、Ｂ、Ａｌ、Ｆｅ、Ｃｏ、Ｎｉ、Ｃｒ、Ｚｎ、Ｃａからなる群から選ばれる少なくとも１種、ｘ＝０．０１～０．１）、ＬｉＮｉ1-xＭxＯ2（ただし、Ｍ＝Ｃｏ、Ｆｅ、Ｇａからなる群から選ばれる少なくとも１種、ｘ＝０．０１～０．２）、ＬｉＦｅＯ2、Ｆｅ2（ＳＯ4）3、ＬｉＣｏ1-xＭxＯ2（ただし、Ｍ＝Ｎｉ、Ｆｅ、Ｍｎからなる群から選ばれる少なくとも１種、ｘ＝０．０１～０．２）、ＬｉＮｉ1-xＭxＯ2（ただし、Ｍ＝Ｍｎ、Ｆｅ、Ｃｏ、Ａｌ、Ｇａ、Ｃａ、Ｍｇからなる群から選ばれる少なくとも１種、ｘ＝０．０１～０．２）、Ｆｅ（ＭｏＯ4）3、ＦｅＦ3、ＬｉＦｅＰＯ4、及びＬｉＭｎＰＯ4等を列挙することができる。 <Positive electrode 200>
The positive electrode 200 includes a positive electrode active material, a conductive agent, a binder, and a positive electrode foil 201. Illustrative examples of the positive electrode active material include LiCoO 2 , LiNiO 2 , and LiMn 2 O 4 . In addition, LiMnO 3 , LiMn 2 O 3 , LiMnO 2 , Li 4 Mn 5 O 12 , LiMn 2−x MxO 2 (however, at least selected from the group consisting of M = Co, Ni, Fe, Cr, Zn, Ti) 1 type, x = 0.01 to 0.2), Li 2 Mn 3 MO 8 (however, M = at least one selected from the group consisting of Fe, Co, Ni, Cu, Zn), Li 1-x A x Mn 2 O 4 (where A = Mg, B, Al, Fe, Co, Ni, Cr, Zn, Ca, at least one selected from the group consisting of x = 0.01 to 0.1), LiNi 1 -x M x O 2 (however, at least one selected from the group consisting of M = Co, Fe, and Ga, x = 0.01 to 0.2), LiFeO 2 , Fe 2 (SO 4 ) 3 , LiCo 1 -x M x O 2 (where little is selected from the group consisting of M = Ni, Fe, Mn Both one, x = 0.01 ~ 0.2), LiNi 1-x M x O 2 ( however, M = Mn, Fe, Co , Al, Ga, Ca, at least one selected from the group consisting of Mg X = 0.01 to 0.2), Fe (MoO 4 ) 3 , FeF 3 , LiFePO 4 , LiMnPO 4 and the like.
　正極活物質の粒径は、正極活物質、導電剤、及びバインダから形成される合剤層の厚さ以下になるように通常は規定される。正極活物質の粉末中に合剤層厚さ以上のサイズを有する粗粒がある場合、予めふるい分級や風流分級等により粗粒を除去し、合剤層厚さ以下の粒子を作製することが好ましい。 The particle size of the positive electrode active material is usually specified so as to be equal to or less than the thickness of the mixture layer formed of the positive electrode active material, the conductive agent, and the binder. When there are coarse particles having a size equal to or greater than the thickness of the mixture layer in the positive electrode active material powder, the coarse particles can be removed in advance by sieving classification, wind classification, etc. preferable.
　また、正極活物質は、一般に酸化物系であるために電気抵抗が高いので、電気伝導性を補うための炭素粉末からなる導電剤を利用する。正極活物質及び導電剤はともに通常は粉末であるので、粉末にバインダを混合して、粉末同士を結合させると同時に正極箔２０１へ接着させることができる。 In addition, since the positive electrode active material is generally oxide-based and has high electric resistance, a conductive agent made of carbon powder for supplementing electric conductivity is used. Since both the positive electrode active material and the conductive agent are usually powders, a binder can be mixed with the powders, and the powders can be bonded together and simultaneously bonded to the positive electrode foil 201.
　正極箔２０１には、厚さが１０～１００μｍのアルミニウム箔、厚さが１０～１００μｍで孔径が０．１～１０ｍｍのアルミニウム製穿孔箔、エキスパンドメタル、又は発泡金属板等が用いられる。アルミニウムの他に、ステンレスやチタン等の材質も適用可能である。本発明では、材質、形状、製造方法等に制限されることなく、任意の正極箔２０１を使用することができる。 As the positive electrode foil 201, an aluminum foil having a thickness of 10 to 100 μm, an aluminum perforated foil having a thickness of 10 to 100 μm and a pore diameter of 0.1 to 10 mm, an expanded metal, a foam metal plate, or the like is used. In addition to aluminum, materials such as stainless steel and titanium are also applicable. In the present invention, any positive foil 201 can be used without being limited by the material, shape, manufacturing method and the like.
　正極活物質、導電剤、バインダ、及び有機溶媒を混合した正極スラリーを、ドクターブレード法、ディッピング法、又はスプレー法等によって正極箔２０１へ付着させた後、有機溶媒を乾燥させ、ロールプレスによって加圧成形することにより、正極を作製することができる。また、塗布から乾燥までを複数回行うことにより、複数の合剤層を正極箔２０１に積層化させることも可能である。 A positive electrode slurry in which a positive electrode active material, a conductive agent, a binder, and an organic solvent are mixed is attached to the positive electrode foil 201 by a doctor blade method, a dipping method, or a spray method, and then the organic solvent is dried and applied by a roll press. A positive electrode can be produced by pressure forming. In addition, a plurality of mixture layers can be laminated on the positive electrode foil 201 by performing a plurality of times from application to drying.
　＜負極３００＞
　負極３００は、負極活物質、バインダ、及び負極箔３０１からなる。高レート充放電が必要な場合に、導電剤を添加することもある。本発明で使用可能な負極活物質としては、黒鉛と非黒鉛炭素や例えばアルミニウム、シリコン、スズ等の金属及びこれらの合金、リチウム含有の遷移金属窒化物Ｌｉ(3-X)ＭXＮ、ケイ素の低級酸化物ＬｉXＳｉＯy（０≦ｘ、０＜ｙ＜２）、及びスズの低級酸化物ＬｉXＳｎＯyのリチウムと合金を形成する材料又は金属間化合物を形成する材料等を選択することができる。 <Negative electrode 300>
The negative electrode 300 includes a negative electrode active material, a binder, and a negative electrode foil 301. When high rate charge / discharge is required, a conductive agent may be added. Examples of the negative electrode active material that can be used in the present invention include graphite, non-graphite carbon, metals such as aluminum, silicon, and tin, and alloys thereof, lithium-containing transition metal nitrides Li (3-X) M X N, silicon The lower oxide Li x SiO y (0 ≦ x, 0 <y <2) and the tin lower oxide Li x SnO y are selected from materials that form an alloy with lithium or materials that form an intermetallic compound. be able to.
　負極活物質の材料には特に制限がなく、上記の材料以外でも利用可能であるが、膨張収縮が大きい材料等の一部材料を選択した場合には、負極の利用する範囲を大きくし過ぎると抵抗上昇が大きくなることがある。この場合、電池電圧を変更する場合の条件に負極電位が一定以下であるかどうかを確認するのが好ましい。 The material of the negative electrode active material is not particularly limited and can be used other than the above materials. However, when a part of the material such as a material having a large expansion and contraction is selected, if the range used by the negative electrode is too large, Resistance rise may be large. In this case, it is preferable to confirm whether or not the negative electrode potential is below a certain level as a condition for changing the battery voltage.
　ただし、黒鉛を含むことが好ましく、当該黒鉛は黒鉛層間距離（ｄ００２）が０．３３５ｎｍ以上０．３３８ｎｍ以下であることが好ましい。このような黒鉛を負極が含むことにより、黒鉛の電位曲線にはステージ構造を有するため、リチウムイオン二次電池のサイクル特性の向上をより大きなものにすることができる。 However, it is preferable that graphite is included, and the graphite has a graphite interlayer distance (d002) of 0.335 nm or more and 0.338 nm or less. By including such graphite in the negative electrode, the potential curve of graphite has a stage structure, so that the cycle characteristics of the lithium ion secondary battery can be further improved.
　負極に用いる黒鉛は、リチウムイオンを化学的に吸蔵・放出可能な天然黒鉛、人造黒鉛、メソフェ－ズ炭素、膨張黒鉛、炭素繊維、気相成長法炭素繊維、ピッチ系炭素質材料、ニードルコークス、石油コークス、及びポリアクリロニトリル系炭素繊維等を原料として製造される。なお、上記の黒鉛層間距離（ｄ００２）は、ＸＲＤ（Ｘ線粉末回折法）（Ｘ－Ｒａｙ　Ｄｉｆｆｒａｃｔｉｏｎ　Ｍｅｔｈｏｄ）等を用いて測定することができる。 The graphite used for the negative electrode is natural graphite that can occlude and release lithium ions, artificial graphite, mesophase carbon, expanded graphite, carbon fiber, vapor grown carbon fiber, pitch-based carbonaceous material, needle coke, Manufactured using petroleum coke and polyacrylonitrile-based carbon fiber as raw materials. The graphite interlayer distance (d002) can be measured using XRD (X-Ray Diffraction Method) or the like.
　また、負極３００に用いる非黒鉛炭素は、上記の黒鉛を除く炭素材料であって、リチウムイオンを吸蔵又は放出することができるものである。これには、黒鉛層の間隔が０．３４ｎｍ以上であって、２０００℃以上の高温熱処理により黒鉛に変化する炭素材料や、５員環又は６員環の環式炭化水素や、環式含酸素有機化合物を熱分解によって合成した非晶質炭素材料等が含まれる。 The non-graphitic carbon used for the negative electrode 300 is a carbon material excluding the above-mentioned graphite, and can occlude or release lithium ions. This includes a carbon material that has a graphite layer spacing of 0.34 nm or more and changes to graphite by high-temperature heat treatment at 2000 ° C. or more, a 5-membered or 6-membered cyclic hydrocarbon, or a cyclic oxygen-containing material. Amorphous carbon materials synthesized by pyrolysis of organic compounds are included.
　このように正極２００と異なる電圧変化率を有する負極３００に、リチウムと合金を形成する材料又は金属間化合物を形成する材料を、第３の負極活物質として添加してもよい。第３の負極活物質としては、例えばアルミニウム、シリコン、スズ等の金属及びこれらの合金、リチウム含有の遷移金属窒化物Ｌｉ(3-X)ＭXＮ、ケイ素の低級酸化物ＬｉXＳｉＯy（０≦ｘ、０＜ｙ＜２）、及びスズの低級酸化物ＬｉXＳｎＯyが挙げられる。第３の負極活物質の材料には特に制限がなく、上記の材料以外でも利用可能である。 As described above, a material that forms an alloy with lithium or a material that forms an intermetallic compound may be added as a third negative electrode active material to the negative electrode 300 having a voltage change rate different from that of the positive electrode 200. Examples of the third negative electrode active material include metals such as aluminum, silicon, and tin and alloys thereof, lithium-containing transition metal nitrides Li (3-X) M X N, and lower oxides of silicon Li X SiO y ( 0 ≦ x, 0 <y <2), and the lower oxide of tin Li x SnO y . There is no restriction | limiting in particular in the material of a 3rd negative electrode active material, It can utilize also other than said material.
　一般に使用される負極活物質は粉末であるため、それにバインダを混合して、粉末同士を結合させると同時に負極箔３０１へ接着させている。本実施形態に係る電池が有する負極では、負極活物質の粒径を、負極活物質及びバインダから形成される合剤層の厚さ以下にすることが望ましい。負極活物質の粉末中に合剤層厚さ以上のサイズを有する粗粒がある場合、予めふるい分級や風流分級等により粗粒を除去し、合剤層厚さ以下の粒子を使用することが好ましい。 Since the negative electrode active material generally used is a powder, a binder is mixed with the negative electrode active material, and the powders are bonded together and simultaneously bonded to the negative electrode foil 301. In the negative electrode included in the battery according to this embodiment, it is desirable that the particle size of the negative electrode active material be equal to or less than the thickness of the mixture layer formed from the negative electrode active material and the binder. When there are coarse particles having a size equal to or greater than the thickness of the mixture layer in the negative electrode active material powder, the coarse particles may be removed in advance by sieving classification or wind classification, and particles having a thickness of the mixture layer thickness or less may be used. preferable.
　負極の負極箔３０１には、厚さが１０～１００μｍの銅箔、厚さが１０～１００μｍで孔径０．１～１０ｍｍの銅製穿孔箔、エキスパンドメタル、又は発泡金属板等が用いられる。銅の他に、ステンレス、チタン、又はニッケル等の材質も適用可能である。本発明では、材質、形状、製造方法等に制限されることなく、任意の負極箔３０１を使用することができる。 For the negative electrode foil 301 of the negative electrode, a copper foil having a thickness of 10 to 100 μm, a copper perforated foil having a thickness of 10 to 100 μm and a hole diameter of 0.1 to 10 mm, an expanded metal, a foam metal plate, or the like is used. In addition to copper, materials such as stainless steel, titanium, or nickel are also applicable. In the present invention, any negative electrode foil 301 can be used without being limited by the material, shape, manufacturing method and the like.
　負極活物質、バインダ、及び有機溶媒を混合した負極スラリーを、ドクターブレード法、ディッピング法、又はスプレー法等によって負極箔３０１へ付着させた後、有機溶媒を乾燥させ、ロールプレスによって加圧成形することにより、負極を作製することができる。また、塗布から乾燥までを複数回行うことにより、多層合剤層を負極箔３０１に形成させることも可能である。 A negative electrode slurry in which a negative electrode active material, a binder, and an organic solvent are mixed is attached to the negative electrode foil 301 by a doctor blade method, a dipping method, a spray method, or the like, and then the organic solvent is dried and pressure-molded by a roll press. Thereby, a negative electrode can be produced. Moreover, it is also possible to form a multilayer mixture layer on the negative electrode foil 301 by performing from application to drying a plurality of times.
　＜セパレータ＞
　上記の方法で作製した正極２００及び負極３００の間にセパレータ３５０を挿入し、正極及び負極の短絡を防止する。セパレータ３５０には、ポリエチレン、ポリプロピレン等からなるポリオレフィン系高分子シート、又はポリオレフィン系高分子と４フッ化ポリエチレンを代表とするフッ素系高分子シートを溶着させた２層構造等を使用することが可能である。電池温度が高くなったときにセパレータが収縮しないように、セパレータ３５０の表面にセラミックス及びバインダの混合物を薄層状に形成してもよい。これらのセパレータは、電池の充放電時にリチウムイオンを透過させる必要があるため、一般に細孔径が０．０１～１０μｍ、気孔率が２０～９０％であれば、リチウムイオン電池に使用可能である。 <Separator>
A separator 350 is inserted between the positive electrode 200 and the negative electrode 300 manufactured by the above method to prevent a short circuit between the positive electrode and the negative electrode. The separator 350 can be a polyolefin polymer sheet made of polyethylene, polypropylene, or the like, or a two-layer structure in which a polyolefin polymer and a fluorine polymer sheet typified by tetrafluoropolyethylene are welded. It is. A mixture of ceramics and a binder may be formed in a thin layer on the surface of the separator 350 so that the separator does not shrink when the battery temperature increases. Since these separators need to allow lithium ions to permeate during charge and discharge of the battery, they can be used for lithium ion batteries as long as the pore diameter is generally 0.01 to 10 μm and the porosity is 20 to 90%.
　＜電解液＞
　本発明の一実施形態で使用可能な電解液の代表例として、エチレンカーボネートにジメチルカーボネート、ジエチルカーボネート、又はエチルメチルカーボネート等を混合した溶媒に、電解質として６フッ化リン酸リチウム（ＬｉＰＦ6）、又はホウフッ化リチウム（ＬｉＢＦ4）を溶解させた溶液がある。本発明は、溶媒や電解質の種類、溶媒の混合比に制限されることなく、他の電解液も利用可能である。 <Electrolyte>
As a representative example of the electrolyte that can be used in an embodiment of the present invention, lithium hexafluorophosphate (LiPF 6 ) as an electrolyte, a solvent obtained by mixing dimethyl carbonate, diethyl carbonate, or ethyl methyl carbonate with ethylene carbonate, Alternatively, there is a solution in which lithium borofluoride (LiBF 4 ) is dissolved. The present invention is not limited to the type of solvent and electrolyte, and the mixing ratio of solvents, and other electrolytes can be used.
　なお、電解液に使用可能な非水溶媒の例としては、プロピレンカーボネート、エチレンカーボネート、ブチレンカーボネート、ビニレンカーボネート、γ－ブチロラクトン、ジメチルカーボネート、ジエチルカーボネート、メチルエチルカーボネート、１、２－ジメトキシエタン、２－メチルテトラヒドロフラン、ジメチルスルフォキシド、１、３－ジオキソラン、ホルムアミド、ジメチルホルムアミド、プロピオン酸メチル、プロピオン酸エチル、リン酸トリエステル、トリメトキシメタン、ジオキソラン、ジエチルエーテル、スルホラン、３－メチル－２－オキサゾリジノン、テトラヒドロフラン、１、２－ジエトキシエタン、クロルエチレンカーボネート、又はクロルプロピレンカーボネート等の非水溶媒がある。本発明の電池に内蔵される正極又は負極上で分解しなければ、これ以外の溶媒を用いてもよい。 Examples of non-aqueous solvents that can be used for the electrolyte include propylene carbonate, ethylene carbonate, butylene carbonate, vinylene carbonate, γ-butyrolactone, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, 1,2-dimethoxyethane, -Methyltetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolane, formamide, dimethylformamide, methyl propionate, ethyl propionate, phosphate triester, trimethoxymethane, dioxolane, diethyl ether, sulfolane, 3-methyl-2- There are non-aqueous solvents such as oxazolidinone, tetrahydrofuran, 1,2-diethoxyethane, chloroethylene carbonate, or chloropropylene carbonate. Other solvents may be used as long as they do not decompose on the positive electrode or the negative electrode incorporated in the battery of the present invention.
　また、電解質の例としては、ＬｉＰＦ6、ＬｉＢＦ4、ＬｉＣｌＯ4、ＬｉＣＦ3ＳＯ3、ＬｉＣＦ3ＣＯ2、ＬｉＡｓＦ6、ＬｉＳｂＦ6、又はリチウムトリフルオロメタンスルホンイミドで代表されるリチウムのイミド塩等、多種類のリチウム塩がある。これらの塩を、上記の溶媒に溶解してできた非水電解液を電池用電解液として使用することができる。本実施形態に係る電池が有する正極及び負極上で分解しなければ、これ以外の電解質を用いてもよい。 In addition, examples of the electrolyte, LiPF 6, LiBF 4, LiClO 4, LiCF 3 SO 3, LiCF 3 CO 2, LiAsF 6, LiSbF 6, or imide salts such as lithium represented by lithium trifluoromethane sulfonimide, multi There are different types of lithium salts. A nonaqueous electrolytic solution obtained by dissolving these salts in the above-mentioned solvent can be used as a battery electrolytic solution. An electrolyte other than this may be used as long as it does not decompose on the positive electrode and the negative electrode of the battery according to this embodiment.
　固体高分子電解質（ポリマー電解質）を用いる場合には、ポリエチレンオキシド、ポリアクリロニトリル、ポリフッ化ビニリデン、ポリメタクリル酸メチル、ポリヘキサフルオロプロピレン、ポリエチレンオキサイド等のイオン伝導性ポリマーを電解質に用いることができる。これらの固体高分子電解質を用いた場合、セパレータ１１を省略することができる利点がある。 In the case of using a solid polymer electrolyte (polymer electrolyte), ion conductive polymers such as polyethylene oxide, polyacrylonitrile, polyvinylidene fluoride, polymethyl methacrylate, polyhexafluoropropylene, and polyethylene oxide can be used for the electrolyte. When these solid polymer electrolytes are used, there is an advantage that the separator 11 can be omitted.
　さらに、イオン性液体を用いることができる。例えば、１－ｅｔｈｙｌ－３－ｍｅｔｈｙｌｉｍｉｄａｚｏｌｉｕｍ　ｔｅｔｒａｆｌｕｏｒｏｂｏｒａｔｅ（ＥＭＩ－ＢＦ４）、リチウム塩ＬｉＮ（ＳＯ2ＣＦ3）2（ＬｉＴＦＳＩ）とトリグライムとテトラグライムとの混合錯体、環状四級アンモニウム系陽イオン（Ｎ－ｍｅｔｈｙｌ－Ｎ－ｐｒｏｐｙｌｐｙｒｒｏｌｉｄｉｎｉｕｍが例示される。）、及びイミド系陰イオン（ｂｉｓ（ｆｌｕｏｒｏｓｕｌｆｏｎｙｌ）ｉｍｉｄｅが例示される。）より、正極及び負極にて分解しない組み合わせを選択して、本実施形態に係る電池に用いることができる。 Furthermore, an ionic liquid can be used. For example, 1-ethyl-3-methylimidazole tetrafluoroborate (EMI-BF4), a mixed salt of lithium salt LiN (SO 2 CF 3 ) 2 (LiTFSI), triglyme and tetraglyme, a cyclic quaternary ammonium cation (N-methyl) -N-propylpyrrolidinium is exemplified) and an imide-based anion (example is bis (fluorosulfonyl) imide), and a combination that does not decompose at the positive electrode and the negative electrode is selected. Can be used.
　＜過充電防止材１００＞
　当該過充電防止材１００は本発明の特徴部分となる。本発明における過充電防止材１００は高容量Ｌｉ吸蔵材料１０に高抵抗被膜を設けたものとなる。高容量Ｌｉ吸蔵材料１０は、具体的にはＳｉ、Ｓｎ、Ａｌ粒子である。これらの材料は黒鉛に比して、Ｌｉ吸蔵能力が２～７倍と高いため、少量混合するだけで負極のＬｉ吸蔵能力を強化することができる。また、高抵抗被膜１１は、具体的にはＳｉＯ2又はＳｉＣである。ＳｉＯ2の体積抵抗率は１０6から１０10Ωｃｍ程度であり、ＳｉＣは１０6Ωｃｍである。そのため、Ｓｉ等の体積抵抗率より高い値を示し、高抵抗皮膜として機能することが可能となる。 <Overcharge prevention material 100>
The overcharge prevention material 100 is a characteristic part of the present invention. The overcharge prevention material 100 in the present invention is a high-capacity Li storage material 10 provided with a high resistance film. The high-capacity Li storage material 10 is specifically Si, Sn, and Al particles. Since these materials have a Li storage capacity as high as 2 to 7 times that of graphite, the Li storage capacity of the negative electrode can be enhanced only by mixing a small amount. The high resistance film 11 is specifically made of SiO 2 or SiC. The volume resistivity of SiO 2 is about 10 6 to 10 10 Ωcm, and SiC is 10 6 Ωcm. Therefore, a value higher than the volume resistivity of Si or the like is shown, and it becomes possible to function as a high resistance film.
　当該ＳｉＯ2又はＳｉＣの被膜１１の厚さは２ｎｍ～１００ｎｍが好ましい。被膜１１の厚さが２ｎｍ以上必要な理由としては、被膜１１の厚さが２ｎｍより小さくなると低い電位でも絶縁破壊が発生してしまい、実際に過電圧が発生していない場合にも過充電防止材として作動し、Ｌｉイオン電池の性能低下を招く恐れがあるためである。また、厚さが薄い被膜になると、結晶性に起因する抵抗値の影響が大きくなり、０．２Ｖ程度で過充電防止材１００として作動してしまう。そのため、厚さは２ｎｍ以上必要となる。 The thickness of the SiO 2 or SiC coating 11 is preferably 2 nm to 100 nm. The reason why the thickness of the coating 11 is required to be 2 nm or more is that when the thickness of the coating 11 is less than 2 nm, dielectric breakdown occurs even at a low potential, and even when no overvoltage actually occurs, an overcharge prevention material This is because there is a risk that the performance of the Li-ion battery may deteriorate. Moreover, when it becomes a thin film, the influence of the resistance value resulting from crystallinity will become large, and it will operate | move as the overcharge prevention material 100 at about 0.2V. Therefore, the thickness needs to be 2 nm or more.
　一方、被膜１１の厚さが１００ｎｍ以下でなければならない理由としては、被膜１１の厚さが１００ｎｍより多くなると当該過電圧防止材１００の電子伝導性が低くなりすぎ、かなりの大きさの過電圧がかからないと過電圧防止材１００として働かなくなってしまうためである。 On the other hand, the reason why the thickness of the coating film 11 must be 100 nm or less is that when the thickness of the coating film 11 exceeds 100 nm, the electronic conductivity of the overvoltage prevention material 100 becomes too low, and a considerable overvoltage is not applied. This is because the overvoltage prevention material 100 does not work.
　なお、被膜１１の厚さは２ｎｍ～１００ｎｍとした場合には、被膜の抵抗値は１０-1～１０3Ωになる。この場合にはＬｉ／Ｌｉ＋電位において０Ｖ付近で充電が開始され、高容量Ｌｉ吸蔵材料１０がＬｉイオンを吸収することができる。 When the thickness of the film 11 is 2 nm to 100 nm, the resistance value of the film is 10 −1 to 10 3 Ω. In this case, charging starts near 0 V at the Li / Li + potential, and the high-capacity Li storage material 10 can absorb Li ions.
　ここで、過電圧防止材１００が動作する原理について説明する。電池内部では、Ｌｉが析出しない電位においては、過充電防止材１００よりも負極活物質の抵抗が低いため、電流が負極活物質に流れ込み、充電反応が行なわれる。しかし、Ｌｉが析出してくる０Ｖ付近では負極活物質に吸蔵できるＬｉイオンの量がほぼ限界な状態（それ以上充電不可能な状態）になり、Ｌｉイオンの移動度が小さくなる。その結果、負極活物質自体の抵抗が上昇し、過充電防止材１００にも電圧がかかる状態となる。当該状態では過充電防止材１００にＬｉイオンが挿入されるようになり、過充電防止材として機能する。 Here, the principle of operation of the overvoltage prevention material 100 will be described. Inside the battery, at a potential at which Li does not precipitate, the resistance of the negative electrode active material is lower than that of the overcharge preventing material 100, so that a current flows into the negative electrode active material and a charging reaction is performed. However, in the vicinity of 0 V at which Li is deposited, the amount of Li ions that can be occluded in the negative electrode active material is almost in a limit state (a state in which charging is impossible any more), and the mobility of Li ions becomes small. As a result, the resistance of the negative electrode active material itself increases, and the overcharge preventing material 100 is also put in a voltage state. In this state, Li ions are inserted into the overcharge prevention material 100 and function as an overcharge prevention material.
　動作原理を簡単に纏めると、Ｌｉが析出する０Ｖ付近まで電位が下がると、負極活物質の抵抗値と活物質の抵抗値の差が小さくなり、その大小が逆転し、その結果、絶縁被膜が破壊され、高容量Ｌｉ吸蔵材料１０にＬｉが挿入されるようになるということである。 To summarize the principle of operation, when the potential drops to around 0V where Li is deposited, the difference between the resistance value of the negative electrode active material and the resistance value of the active material becomes smaller, and the magnitude is reversed. It is destroyed and Li is inserted into the high-capacity Li storage material 10.
　当該過電圧防止材１００は、負極材３０２に添加されて使用される。この過電圧防止材１００は、上述した過充電防止の効果のほかに、被膜１１が形成されていることによって電気抵抗が大きくなり、過電圧発生時の高容量Ｌｉ吸蔵材料１０（例えばＳｉ）とＬｉの初回反応電位を低下させることが可能となる。 The overvoltage prevention material 100 is used by being added to the negative electrode material 302. In addition to the above-described effect of preventing overcharge, the overvoltage prevention material 100 has an increased electrical resistance due to the formation of the coating 11, and the high-capacity Li storage material 10 (for example, Si) and Li at the time of overvoltage generation. It becomes possible to reduce the initial reaction potential.
　より具体的に原理を説明すると、初回反応時に一部被膜を破壊するように作用する。その結果、黒鉛等の負極活物質よりもＬｉとの反応電位が高い高容量Ｌｉ吸蔵材料１０にＬｉイオンが挿入されるようになる（つまり、黒鉛等よりも先に高容量Ｌｉ吸蔵材料１０が反応する）ためである。 Describing the principle more specifically, it acts to partially destroy the coating during the initial reaction. As a result, Li ions are inserted into the high-capacity Li storage material 10 having a higher reaction potential with Li than the negative electrode active material such as graphite (that is, the high-capacity Li storage material 10 is present before the graphite or the like). To react).
　上記理由によって当該過電圧防止材１００を用いた場合には、過充電防止効果のほかに過電圧発生を抑制する効果もある。 When the overvoltage prevention material 100 is used for the above reason, it has the effect of suppressing the occurrence of overvoltage in addition to the overcharge prevention effect.
　また、上述した範囲内で被膜１１の厚さを厚くする、或いはＳｉＯ2またはＳｉＣ中の欠損を少なくすることによって、電気抵抗およびＬｉ拡散抵抗をより上昇させることが出来、高容量Ｌｉ吸蔵材料１０（例えばＳｉ）とＬｉとの初回反応に要する過電圧を大きくすることができ、確実に過電圧防止材を作動させることが可能となる。 Further, by increasing the thickness of the coating film 11 within the above-mentioned range or reducing defects in SiO 2 or SiC, the electric resistance and the Li diffusion resistance can be further increased, and the high-capacity Li storage material 10 The overvoltage required for the initial reaction between (for example, Si) and Li can be increased, and the overvoltage prevention material can be reliably operated.
　このように、高容量Ｌｉ吸蔵材料１０の表面に高抵抗被膜１１を設けることによって、Ｌｉ反応電位をＬｉ析出電位付近まで下げることが可能となる。その結果として、黒鉛等の負極活物質にＬｉイオンが入らなくなる直前に、高抵抗被膜１１の絶縁を破壊して高容量Ｌｉ吸蔵材料１０でＬｉイオンを吸蔵することが可能となり、過充電を防止する効果が得られる。 Thus, by providing the high-resistance coating 11 on the surface of the high-capacity Li storage material 10, the Li reaction potential can be lowered to the vicinity of the Li deposition potential. As a result, immediately before Li ions do not enter the negative electrode active material such as graphite, it becomes possible to break the insulation of the high-resistance coating 11 and occlude Li ions with the high-capacity Li storage material 10 to prevent overcharge. Effect is obtained.
　また、本発明の特徴としては、ＳｉＯ2のマトリクスにＳｉが包含されているのではなく、あくまで高容量Ｌｉ吸収材料１０（例えばＳｉ）の方が被膜１１（例えばＳｉＯ2）よりも体積が大きい点である。ＳｉＯ2のマトリクスの中にＳｉが包含されるような構成では、抵抗が高すぎること、およびＳｉの量が少ないことから過電圧防止材として十分に機能しないからである。 Further, as a feature of the present invention, Si is not included in the SiO 2 matrix, but the volume of the high-capacity Li absorbing material 10 (for example, Si) is larger than that of the coating film 11 (for example, SiO 2 ). Is a point. This is because the structure in which Si is included in the SiO 2 matrix does not sufficiently function as an overvoltage prevention material because the resistance is too high and the amount of Si is small.
　また、本発明のもう一つの特徴としては、高容量Ｌｉ吸収材料１０に設けられた被膜１１が、当該高容量Ｌｉ吸収材料１０の全面を覆っていなければならない点が挙げられる。もし高容量Ｌｉ吸蔵材料１０（例えばＳｉ）が露出している場合には、当該露出面の抵抗が低いので直接Ｓｉへの伝導パスが出来るため、ＳｉＯ2の被膜１１を介してＳｉへの伝導パスが出来る、つまり過電圧時に絶縁破壊して絶縁パスが出来るという現象が発生しないため、よほど大きな過電圧防止が発生しない限り過電圧防止材としての機能が発揮しないからである。 Another feature of the present invention is that the coating 11 provided on the high-capacity Li absorbent material 10 must cover the entire surface of the high-capacity Li absorbent material 10. If the high-capacity Li-occlusion material 10 (for example, Si) is exposed, the resistance of the exposed surface is low, so that a conduction path to Si can be made directly. Therefore, conduction to Si through the SiO 2 coating 11 is performed. This is because there is no phenomenon that a pass can be made, that is, an insulation pass is made due to dielectric breakdown at the time of overvoltage, and the function as an overvoltage prevention material is not exhibited unless a very large overvoltage prevention occurs.
　また、好ましくは全ての負極材３０１内にある全ての過電圧防止１００が、高容量Ｌｉ吸蔵材料１０の全面が被膜１１により覆われた構造であることが好ましい。 In addition, it is preferable that all the overvoltage preventions 100 in all the negative electrode materials 301 have a structure in which the entire surface of the high-capacity Li storage material 10 is covered with the coating 11.
　しかし、実際には過電圧防止材１００を作成した後の力学的作用等により、全ての粒子の全面に被膜１１が形成されるのは難しい。そこで、現実には過電圧防止材１００中の大半（５０％以上）の粒子において、全面に被膜１１が形成されていることが好ましい。 However, in reality, it is difficult to form the coating 11 on the entire surface of all the particles due to the mechanical action after the overvoltage prevention material 100 is formed. Therefore, in reality, it is preferable that the film 11 is formed on the entire surface of most particles (50% or more) in the overvoltage prevention material 100.
　以上、上述したように本発明の過電圧防止材１００は、高容量Ｌｉ吸蔵材料１０の方が被膜１１の体積よりも大きいことによって、適切な電圧で被膜１１の絶縁破壊が発生するため過電圧防止材として機能させることが可能である。 As described above, the overvoltage prevention material 100 of the present invention has the high voltage Li storage material 10 larger than the volume of the coating 11, so that the dielectric breakdown of the coating 11 occurs at an appropriate voltage. It is possible to function as.
　また、過電圧防止材１００中の大半（５０％以上）の粒子において、全面に被膜１１が形成されていれば、過電圧防止材として機能することが出来る。 Further, if the coating 11 is formed on the entire surface of the majority (50% or more) of the particles in the overvoltage prevention material 100, it can function as an overvoltage prevention material.
　また、過電圧防止材１００中の９５％以上の粒子において、全面に被膜１１が形成されていることが、反応効率の面から好ましい。 Further, it is preferable from the viewpoint of reaction efficiency that the film 11 is formed on the entire surface of 95% or more of the particles in the overvoltage preventing material 100.
　＜高抵抗被膜付与方法＞
　続いて、高容量Ｌｉ吸蔵材料１０に被膜１１を設けた過電圧防止材１００を作成する方法について説明する。図３（ａ）は本実施形態における過充電防止材１００を説明する図である。Ｌｉ吸蔵可能な高容量Ｌｉ吸収材料１０（Ｓｉ、Ａｌ、Ｓｎ）の粒子をコア層とし、その表面に高抵抗率を有する被膜１１（シェル層）をもつコア－シェル構造となっている。より具体的な例として、Ｓｉ粒子をコア層とした場合を説明する。 <High resistance coating method>
Next, a method for creating the overvoltage prevention material 100 in which the coating 11 is provided on the high-capacity Li storage material 10 will be described. FIG. 3A is a diagram illustrating the overcharge preventing material 100 according to the present embodiment. It has a core-shell structure in which particles of a high-capacity Li-absorbing material 10 (Si, Al, Sn) capable of storing Li are used as a core layer and a coating 11 (shell layer) having a high resistivity is formed on the surface thereof. As a more specific example, a case where Si particles are used as a core layer will be described.
　図３（ｂ）に示すように、過電圧防止材１００は、Ｓｉ粒子を高温焼成炉に入れ、Ａｒ/Ｏ２混合ガス中で９００～１２００℃の温度で所定時間焼成することで、任意の厚さのＳｉＯ2層を付与することができる（５～１００ｎｍの範囲）。また、高圧水蒸気酸化によってもこれらの酸化被膜を作製可能である。 As shown in FIG. 3B, the overvoltage prevention material 100 has an arbitrary thickness by placing Si particles in a high-temperature firing furnace and firing in an Ar / O 2 mixed gas at a temperature of 900 to 1200 ° C. for a predetermined time. SiO 2 layer can be applied (range 5-100 nm). Also, these oxide films can be produced by high-pressure steam oxidation.
　また、Ｌｉ吸蔵可能な活物質（Ｓｉ、Ｓｎ、Ａｌ）に対し、表面被膜層をスパッタリング、ＣＶＤ、ゾルゲル法によって付与することも可能である。 It is also possible to apply a surface coating layer to the active material (Si, Sn, Al) capable of occluding Li by sputtering, CVD, or sol-gel method.
　続いて、Ｓｉの表面にＳｉＣ層を作成する方法について説明する。被膜としてＳｉＣ層を作成する場合には、Ｓｉ粒子をタールピッチ、炭素含有有機物と混合し、１３００℃以上の不活性雰囲気化で焼成することによって過電圧防止材１００を作成することが可能である。 Next, a method for creating a SiC layer on the surface of Si will be described. When a SiC layer is formed as a coating, it is possible to prepare the overvoltage prevention material 100 by mixing Si particles with tar pitch and a carbon-containing organic substance and firing in an inert atmosphere at 1300 ° C. or higher.
　このようにして、上述したコア－シェル構造の過電圧防止材１００を作成することが可能である。 In this way, the above-described core-shell structure overvoltage prevention material 100 can be produced.
　（実験例１）
　図４は高容量Ｌｉ吸蔵材料１０としてＳｉを用い、当該Ｓｉの周りに高抵抗被膜（ＳｉＯ２）を施した過電圧防止材１００の充電時の特性を示す。図４中に示した実線は、表面被膜を付与していないＳｉを活物質とするＳｉの充電カーブである。当該実線で示すように、表面被膜を付与していないＳｉを活物質とした場合には、０．４Ｖ（Ｌｉ／Ｌｉ＋電位において）から容量が増加していくことがわかる。これはＬｉ／Ｌｉ＋電位において０．４Ｖから、ＳｉがＬｉと反応するということを意味する。 (Experimental example 1)
FIG. 4 shows characteristics at the time of charging of the overvoltage prevention material 100 in which Si is used as the high-capacity Li storage material 10 and a high-resistance coating (SiO 2) is applied around the Si. The solid line shown in FIG. 4 is a charge curve of Si using Si with no surface coating applied as an active material. As shown by the solid line, it can be seen that the capacity increases from 0.4 V (at Li / Li + potential) when Si with no surface coating is used as the active material. This means that Si reacts with Li from 0.4 V at the Li / Li + potential.
　一方で、図４中の破線はＳｉの表面にＳｉＯ2の被膜１１を付与したものの充電カーブである。このデータよりＳｉＯ2の被膜１１を付与したＳｉは、０Ｖ付近になるまで過電圧がかからないとＬｉとの反応が開始しないことがわかる。 On the other hand, the broken line in FIG. 4 is a charging curve of the Si surface provided with the SiO 2 coating 11. From this data, it can be seen that Si to which the SiO 2 coating 11 is applied does not start the reaction with Li unless an overvoltage is applied until it reaches around 0V.
　また、反応が開始される段階で当該過充電防止材を用いた場合には、反応開始電位を下げることができる。この過電圧（反応開始電位の低下）は表面の被膜の電気抵抗が高いほど、低くすることができる。より具体的には、例えば被膜１１を厚くすることが挙げられる。 In addition, when the overcharge prevention material is used at the stage where the reaction starts, the reaction start potential can be lowered. This overvoltage (decrease in reaction initiation potential) can be made lower as the electrical resistance of the coating on the surface is higher. More specifically, for example, increasing the thickness of the coating 11 can be mentioned.
　しかし、被膜層の電気抵抗が大きすぎると、反応を開始させるための過電圧が大きすぎるため、Ｌｉ析出電位においても作動しなくなることがある。 However, if the electric resistance of the coating layer is too large, the overvoltage for initiating the reaction is too large, and it may not operate even at the Li deposition potential.
　図５には、表面にＳｉＯ2層で被覆したＳｉの放電曲線カーブ（点線で示したもの）、被覆していないＳｉの放電カーブ（破線で示したもの）、及び黒鉛の放電カーブ（実線で示したもの）を示す。 FIG. 5 shows a discharge curve curve of Si coated with a SiO 2 layer (shown by a dotted line), a discharge curve of Si not coated (shown by a broken line), and a discharge curve of graphite (shown by a solid line). Indicated).
　表面被覆層の状態により、被覆処理をしていないＳｉの放電カーブと比較すると、形状の変化はみられるものの、Ｌｉを脱離する電位に大きな変化はなく、Ｓｉ固有の値をもつことがわかる。また、この電位は黒鉛のＬｉ脱離が脱離する電位に比べ明らかに高い事がわかる。 Compared with the discharge curve of Si that has not been coated, depending on the state of the surface coating layer, although there is a change in shape, there is no significant change in the potential for desorbing Li, and it can be seen that it has a value unique to Si. . It can also be seen that this potential is clearly higher than the potential at which Li desorption of graphite is eliminated.
　＜混合の仕方＞
　過充電防止材の混合比率は主活物質に対し、５～１５ｗｔ％以下が望ましい。過充電防止材の混合比率５ｗｔ％よりも低いと、Ｌｉの吸収量が少なく効果が微小になり、混合比率が１５ｗｔ％よりも多いと主活物質中に分散した過充電防止材１００が繋がるようになり、主活物質の電気伝導経路が阻害され、負極合材層の電気抵抗が大きくなってしまうためである。 <How to mix>
The mixing ratio of the overcharge prevention material is desirably 5 to 15 wt% or less with respect to the main active material. When the mixing ratio of the overcharge prevention material is lower than 5 wt%, the amount of Li absorption is small and the effect becomes minute. When the mixing ratio is higher than 15 wt%, the overcharge prevention material 100 dispersed in the main active material is connected. This is because the electric conduction path of the main active material is obstructed and the electric resistance of the negative electrode mixture layer is increased.
　図６には本実施形態のおける負極３００の断面図を示す。負極箔３０１の中には、黒鉛１１０と、過電圧防止材１００が塗布されている。過充電防止材は主活物質に均一になるように混合しても良いし、Ｌｉが析出し易い部位、例えば表面近傍に存在比率が大きくなるように濃度の勾配を設けても良い。 FIG. 6 shows a cross-sectional view of the negative electrode 300 in the present embodiment. In the negative electrode foil 301, the graphite 110 and the overvoltage preventing material 100 are applied. The overcharge prevention material may be mixed with the main active material so as to be uniform, or a concentration gradient may be provided so that the abundance ratio is increased in a portion where Li is likely to precipitate, for example, in the vicinity of the surface.
　主活物質に混合する過充電防止材１００は、単一な形態に限らず、複数の形態を有していてもよい。例えば、高抵抗被膜の厚さや材質、あるいはＬｉ吸蔵材料の材質が異なっていても良い。例えばＳｉＯ2層の厚みが異なるＳｉ粒子、表面がＳｉＯ2、ＳｉＣのＳｉ粒子、表面層がＳｉＯ2で中の材質はＳｉやＳｎの粒子の混在したものであっても良い。 The overcharge prevention material 100 mixed with the main active material is not limited to a single form, and may have a plurality of forms. For example, the thickness and material of the high resistance film or the material of the Li storage material may be different. For example, Si particles having different SiO 2 layer thicknesses, SiO 2 and SiC Si particles on the surface, SiO 2 on the surface layer, and Si and Sn particles mixed therein may be used.
　＜充放電挙動＞
　図７には上述した過電圧防止材１００を用いた場合の充放電曲線を示すものである。過充電防止材１００のコア材（被膜の内部）とＬｉとの反応電位は物質固有の値をとる。 <Charge / discharge behavior>
FIG. 7 shows a charge / discharge curve when the above-described overvoltage prevention material 100 is used. The reaction potential between the core material of the overcharge prevention material 100 (inside the coating) and Li takes a value specific to the substance.
　図７の下段の図は、図７の上段の図よりも過充電防止材１００の反応量が多くした場合のデータである。 The lower diagram in FIG. 7 shows data when the reaction amount of the overcharge prevention material 100 is larger than that in the upper diagram in FIG.
　主活物質と過充電防止材との混合電極において、過充電状態となり前記過充電防止材１００とＬｉが反応すると、図７に示すように充放電カーブ（実線）、あるいはその微分曲線（点線）において、主活物質の放電カーブとは異なる固有の波形が検出される。 In the mixed electrode of the main active material and the overcharge prevention material, when the overcharge state is entered and the overcharge prevention material 100 reacts with Li, a charge / discharge curve (solid line) or its differential curve (dotted line) is shown in FIG. , A unique waveform different from the discharge curve of the main active material is detected.
　図７の下段に示すように、過充電防止材１００の反応量が増加すると過充電防止材１００に起因するピークが高容量側にシフトすることがわかる。そのため、過電圧防止材１００が十分に作用していることがわかる。
（実験例１）
　以下、実施例に基づいて本発明を詳細に述べる。ただし、下記実施例は、本発明を制限するものではない。 As shown in the lower part of FIG. 7, it can be seen that when the reaction amount of the overcharge prevention material 100 increases, the peak due to the overcharge prevention material 100 shifts to the high capacity side. Therefore, it can be seen that the overvoltage prevention material 100 is sufficiently acting.
(Experimental example 1)
Hereinafter, the present invention will be described in detail based on examples. However, the following examples do not limit the present invention.
　＜正極の作製＞
　正極活物質であるＬｉＦｅＰＯ４：８８質量部（活物質や混合比を変えるかも）、導電助剤である人造黒鉛：１質量部、ケッチェンブラック：１質量部、およびバインダであるＰＶＤＦ：１０質量部を、ＮＭＰを溶剤として均一になるように混合して、正極合剤含有ペーストを調製した。前記正極合剤含有ペーストを、アルミニウム箔（厚み１５μｍ）の両面に厚みを調節して間欠塗布し、乾燥した後、カレンダー処理を行って、全厚が１８３μｍになるように正極合剤層の厚みを調整して正極を作製した。 <Preparation of positive electrode>
LiFePO4 as positive electrode active material: 88 parts by mass (active material and mixing ratio may be changed), artificial graphite as conductive aid: 1 part by mass, Ketjen black: 1 part by mass, and PVDF as binder: 10 parts by mass Were mixed so as to be uniform using NMP as a solvent to prepare a positive electrode mixture-containing paste. The positive electrode mixture-containing paste is intermittently applied to both surfaces of an aluminum foil (thickness: 15 μm) by adjusting the thickness, dried, and then subjected to a calendering process, so that the total thickness of the positive electrode mixture layer is 183 μm. Was adjusted to produce a positive electrode.
　＜過充電防止材の作製＞
　ＳｉＯ２に被覆されたＳｉ粒子は、平均粒子径Ｄ５０が１μｍのＳｉ粒子を高温焼成炉に入れ、Ａｒ/Ｏ2混合ガス中で９００～１２００℃の温度で所定時間焼成後、解砕して被膜の厚さが２～１００ｎｍの範囲になるよう作製した。 <Preparation of overcharge prevention material>
The Si particles coated with SiO 2 are placed in a high-temperature firing furnace with Si particles having an average particle diameter D50 of 1 μm, fired in an Ar / O 2 mixed gas at a temperature of 900 to 1200 ° C. for a predetermined time, and then crushed and coated. The thickness was made in the range of 2 to 100 nm.
　＜負極の作製＞
　ＳｉＯ２被覆Ｓｉ粒子と平均粒子径Ｄ５０が２０μｍである黒鉛とを、１５：８５の質量比で混合した混合物：９８質量部、粘度が１５００～５０００ｍＰａ・ｓの範囲に調整されたＣＭＣ水溶液（濃度：１質量％）：１質量部、およびＳＢＲ：１質量部を混合して、水系の負極合剤含有ペーストを調製した。　前記の負極合剤含有ペーストを、銅箔からなる厚みが８μｍの集電体の両面に厚みを調節して間欠塗布し、乾燥した後、カレンダー処理を行って全厚が１０８μｍになるように負極合剤層の厚みを調整して負極を作製した。 <Production of negative electrode>
Mixture of SiO2 coated Si particles and graphite having an average particle diameter D50 of 20 μm mixed at a mass ratio of 15:85: 98 parts by mass, CMC aqueous solution adjusted to have a viscosity of 1500 to 5000 mPa · s (concentration: 1 mass%): 1 mass part and SBR: 1 mass part were mixed, and the aqueous negative mix containing paste was prepared. The negative electrode mixture-containing paste is intermittently applied on both sides of a current collector made of copper foil with a thickness of 8 μm while adjusting the thickness, dried, and then calendered to give a total thickness of 108 μm. A negative electrode was prepared by adjusting the thickness of the mixture layer.
　　＜非水電解液の調整＞
　　エチレンカーボネート、エチルメチルカーボネートおよびジメチルカーボネートを体積比で１：１：１に混合したものに、リチウム塩としてＬｉＰＦ6を濃度１ｍｏｌ／ｌで溶解させて非水電解液を調製した。 <Adjustment of non-aqueous electrolyte>
LiPF 6 as a lithium salt was dissolved at a concentration of 1 mol / l in a mixture of ethylene carbonate, ethyl methyl carbonate and dimethyl carbonate in a volume ratio of 1: 1: 1 to prepare a non-aqueous electrolyte.
　　＜電池の組み立て＞
　　前記正極と前記負極とを所定のサイズに切断し、厚さ３０μｍ開孔率５０％の微多孔性ポリエチレンフィルム製セパレータを介して巻回電極体を作製した。この巻回電極体を円筒形電池缶に挿入し、次に前記非水電解液を缶内に注入し、封口して円筒形非水二次電池を作製した。 <Battery assembly>
The positive electrode and the negative electrode were cut into a predetermined size, and a wound electrode body was produced through a separator made of a microporous polyethylene film having a thickness of 30 μm and a porosity of 50%. This wound electrode body was inserted into a cylindrical battery can, and then the non-aqueous electrolyte was poured into the can and sealed to produce a cylindrical non-aqueous secondary battery.
　（実験例２）
　過充電防止材を５質量部と変更した以外、実験例１と同様にして円筒形非水二次電池を作製した
　（実験例３）
　過充電防止材を１５質量部と変更した以外、実験例１と同様にして円筒形非水二次電池を作製した
　（比較例１）
　過充電防止材を０質量部と変更した以外、実施例１と同様にして円筒形非水二次電池を作製した
　（比較例２）
　過充電防止材を２０質量部と変更した以外、実施例１と同様にして円筒形非水二次電池を作製した。 (Experimental example 2)
A cylindrical non-aqueous secondary battery was fabricated in the same manner as in Experimental Example 1 except that the overcharge prevention material was changed to 5 parts by mass (Experimental Example 3).
A cylindrical non-aqueous secondary battery was produced in the same manner as in Experimental Example 1 except that the overcharge prevention material was changed to 15 parts by mass (Comparative Example 1).
A cylindrical non-aqueous secondary battery was produced in the same manner as in Example 1 except that the overcharge prevention material was changed to 0 part by mass (Comparative Example 2).
A cylindrical non-aqueous secondary battery was produced in the same manner as in Example 1 except that the overcharge prevention material was changed to 20 parts by mass.
　＜過充電検知試験＞
　作製した電池の初回の放電容量に対して１時間で放電する電流量を１Ｃとし、放電電流０．２Ｃ時の放電容量に対し、容量がちょうど半分になる電圧を中心にして、容量変化幅が８０％となる範囲で、充放電電流を２Ｃとし、２５℃に保たれた恒温槽中で定電流充放電サイクル試験を実施した。放電終止条件の下限値は電池電圧が１.５Ｖに到達とした。 <Overcharge detection test>
The amount of current discharged in 1 hour is 1 C with respect to the initial discharge capacity of the manufactured battery, and the capacity change width is centered on a voltage at which the capacity is exactly half of the discharge capacity at a discharge current of 0.2 C. The constant current charge / discharge cycle test was carried out in a thermostatic bath maintained at 25 ° C. with a charge / discharge current of 2C within a range of 80%. The lower limit value of the discharge termination condition was that the battery voltage reached 1.5V.
　電池内部情報の取得条件として２００サイクル毎に所定電圧（３．８Ｖを過程）で定電流・定電圧充電をし、電流量０．１Ｃで定電流放電を行った。 As a condition for acquiring battery internal information, constant current / constant voltage charging was performed at a predetermined voltage (3.8 V in the process) every 200 cycles, and constant current discharging was performed at a current amount of 0.1C.
　過充電判定機能として、過充電防止材であるＳｉとＬｉの反応を検出した段階で第一のシグナルを、過充電防止材の容量（微分曲線においてＳｉに由来するピークと放電末期の立ち上がりピークとの距離）が、仕込んだ過充電防止材が完全に反応した時の容量の半分なった際に第一シグナルとは異なる第二シグナルを、過充電防止材の容量が３/４以上になった場合に第一および第二シグナルとは異なる信号を発した後に５サイクル後に試験を終了するようにした。 As an overcharge determination function, the first signal is detected at the stage where the reaction between Si and Li, which are overcharge prevention materials, is detected, and the capacity of the overcharge prevention material (the peak derived from Si and the rising peak at the end of discharge in the differential curve) The second signal is different from the first signal when the charged overcharge prevention material has completely reacted, and the overcharge prevention material capacity is 3/4 or more. In some cases, the test was terminated after 5 cycles after emitting a signal different from the first and second signals.
　＜電池の解体＞
　試験が終了後した電池において、Ａｒガスで満たされたグローブボックス中で試験電池を解体し、Ｌｉ析出の有無を目視で観察した。 <Disassembly of batteries>
In the battery after the test was completed, the test battery was disassembled in a glove box filled with Ar gas, and the presence or absence of Li precipitation was visually observed.
　これらの結果を図８の表にまとめる。 These results are summarized in the table of FIG.
　実験例１、実験例２では第一シグナルは２２００サイクル、第二シグナルは２６００、第三シグナルは２８００サイクルに発せられた。実験例３において、第一シグナルは２０００サイクル、第二シグナルは２２００、第三シグナルは２４００となり、実験例１および実験例２と比べ、シグナル発生時のサイクル数が早くなり、各シグナル間の間隔も短くなった。 In Experimental Examples 1 and 2, the first signal was emitted in 2200 cycles, the second signal was emitted in 2600, and the third signal was emitted in 2800 cycles. In Experimental Example 3, the first signal is 2000 cycles, the second signal is 2200, and the third signal is 2400. Compared with Experimental Example 1 and Experimental Example 2, the number of cycles at the time of signal generation is faster, and the interval between each signal Also became shorter.
　一方、比較例１では、シグナルを観測することなく放電の終止条件である１．５Ｖに到達して試験が終了し、分解観察では負極上にＬｉ析出が観察された。 On the other hand, in Comparative Example 1, the test was terminated when the discharge termination condition of 1.5 V was reached without observing a signal, and Li deposition was observed on the negative electrode in the decomposition observation.
　比較例２では第一シグナル発信時のサイクルは実験例１から３に比べて大幅に早く発生した。また第２シグナルは観察されず第３シグナルが観察された。これは過充電防止材の含有量が高いために、負極全体の抵抗が増加し、過電圧がかかりやすくなり、過充電防止材が作動したものと推察される
　以上説明したように、本発明によって高抵抗被膜を有する活物質を負極に含有し、その充放電カーブの変化を検出する実験により、過充電によるＬｉの析出を抑制することができていることがわかった。 In Comparative Example 2, the cycle for transmitting the first signal occurred significantly earlier than in Experimental Examples 1 to 3. The second signal was not observed and the third signal was observed. This is because the overcharge prevention material content is high, the resistance of the entire negative electrode increases, it is likely that overvoltage is applied, and it is assumed that the overcharge prevention material was activated. An experiment in which an active material having a resistance film is contained in the negative electrode and a change in its charge / discharge curve is detected has been found to suppress precipitation of Li due to overcharge.
　以上、本発明の実施形態について詳述したが、本発明は、前記の実施形態に限定されるものではなく、特許請求の範囲に記載された本発明の精神を逸脱しない範囲で、種々の設計変更を行うことができるものである。例えば、前記した実施の形態は本発明を分かりやすく説明するために詳細に説明したものであり、必ずしも説明した全ての構成を備えるものに限定されるものではない。 Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above-described embodiments, and various designs can be made without departing from the spirit of the present invention described in the claims. It can be changed. For example, the above-described embodiment has been described in detail for easy understanding of the present invention, and is not necessarily limited to one having all the configurations described.
１００　過電圧防止材
１１０　黒鉛
３０１　負極箔 100 Overvoltage prevention material 110 Graphite 301 Negative electrode foil

Claims (5)

  1. 　Ｌｉ含有遷移金属酸化物を主活物質とする正極と、
    　黒鉛を主活物質とする負極と、を有する二次電池において、
    　前記負極には、Ｓｉ、Ｓｎ、又はＡｌのいずれかで構成される粒子を核とし、当該核の外周にＳｉＯ2又はＳｉＣで構成される被膜を設けた過充電防止材が含有され、
    　前記被膜の厚さは２ｎｍ～１００ｎｍであることを特徴とする二次電池。     A positive electrode having a Li-containing transition metal oxide as a main active material;
    In a secondary battery having a negative electrode mainly composed of graphite,
    The negative electrode contains an overcharge preventing material having particles composed of any one of Si, Sn, or Al as nuclei and provided with a coating composed of SiO 2 or SiC on the outer periphery of the nuclei,
    A secondary battery, wherein the thickness of the coating is 2 nm to 100 nm.
  2. 　請求項１に記載の二次電池において、
    　前記過充電防止材の量は、前記黒鉛の量に対して５～１５ｗｔ％であることを特徴とする二次電池。     The secondary battery according to claim 1,
    The secondary battery according to claim 1, wherein an amount of the overcharge preventing material is 5 to 15 wt% with respect to an amount of the graphite.
  3. 　請求項２に記載の二次電池において、
    　前記負極に含有される過充電防止材のうち、５０％以上の粒子において前記核の全周にわたって前記被膜が形成されていることを特徴とする二次電池。     The secondary battery according to claim 2,
    A secondary battery in which the coating film is formed over the entire circumference of the nucleus in 50% or more of the overcharge prevention material contained in the negative electrode.
  4. 　請求項３に記載の二次電池において、
    　前記負極に含有される過充電防止材のうち、９５％以上の粒子において前記核の全周にわたって前記被膜が形成されていることを特徴とする二次電池。     The secondary battery according to claim 3,
    The secondary battery, wherein the film is formed over the entire circumference of the core in 95% or more of the overcharge prevention material contained in the negative electrode.
  5. 　請求項４に記載の二次電池において、
    　前記被膜の抵抗は、１０-1～１０3Ωであることを特徴とする二次電池。     The secondary battery according to claim 4,
    The secondary battery is characterized in that the resistance of the coating is 10 -1 to 10 3 Ω.
PCT/JP2013/063099 2013-05-10 2013-05-10 Lithium-ion secondary battery WO2014181447A1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
PCT/JP2013/063099 WO2014181447A1 (en) 2013-05-10 2013-05-10 Lithium-ion secondary battery

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/JP2013/063099 WO2014181447A1 (en) 2013-05-10 2013-05-10 Lithium-ion secondary battery

Publications (1)

Publication Number Publication Date
WO2014181447A1 true WO2014181447A1 (en) 2014-11-13

Family

ID=51866948

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/JP2013/063099 WO2014181447A1 (en) 2013-05-10 2013-05-10 Lithium-ion secondary battery

Country Status (1)

Country Link
WO (1) WO2014181447A1 (en)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2019188757A1 (en) * 2018-03-29 2019-10-03 パナソニックＩｐマネジメント株式会社 Electrochemical device
CN111244410A (en) * 2020-01-16 2020-06-05 兰溪致德新能源材料有限公司 Lithium battery negative electrode material and preparation method thereof
US20210143411A1 (en) * 2019-11-07 2021-05-13 Samsung Sdi Co., Ltd. Negative active material for rechargeable lithium battery and rechargeable lithium battery including the same

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2005294078A (en) * 2004-03-31 2005-10-20 Nec Corp Negative electrode for secondary battery, and secondary battery
JP2007172858A (en) * 2005-12-19 2007-07-05 Matsushita Electric Ind Co Ltd Negative electrode material for nonaqueous electrolyte secondary battery and its manufacturing method
JP2011076822A (en) * 2009-09-30 2011-04-14 Hitachi Vehicle Energy Ltd Lithium ion secondary battery
JP2012084426A (en) * 2010-10-13 2012-04-26 Hitachi Maxell Energy Ltd Nonaqueous electrolyte secondary battery

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2005294078A (en) * 2004-03-31 2005-10-20 Nec Corp Negative electrode for secondary battery, and secondary battery
JP2007172858A (en) * 2005-12-19 2007-07-05 Matsushita Electric Ind Co Ltd Negative electrode material for nonaqueous electrolyte secondary battery and its manufacturing method
JP2011076822A (en) * 2009-09-30 2011-04-14 Hitachi Vehicle Energy Ltd Lithium ion secondary battery
JP2012084426A (en) * 2010-10-13 2012-04-26 Hitachi Maxell Energy Ltd Nonaqueous electrolyte secondary battery

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2019188757A1 (en) * 2018-03-29 2019-10-03 パナソニックＩｐマネジメント株式会社 Electrochemical device
US20210143411A1 (en) * 2019-11-07 2021-05-13 Samsung Sdi Co., Ltd. Negative active material for rechargeable lithium battery and rechargeable lithium battery including the same
CN111244410A (en) * 2020-01-16 2020-06-05 兰溪致德新能源材料有限公司 Lithium battery negative electrode material and preparation method thereof
CN111244410B (en) * 2020-01-16 2022-05-27 兰溪致德新能源材料有限公司 Lithium battery negative electrode material and preparation method thereof

Similar Documents

Publication Publication Date Title
JP5177361B2 (en) Negative electrode for secondary battery and secondary battery
JP5070753B2 (en) battery
JP5103945B2 (en) Nonaqueous electrolyte secondary battery
JP5514394B2 (en) Non-aqueous electrolyte for secondary battery and non-aqueous electrolyte secondary battery using the same
JP2009048981A (en) Nonaqueous electrolyte secondary battery
KR102183164B1 (en) Lithium secondary cell pack, as well as electronic device, charging system, and charging method using said pack
JP2007141831A (en) Nonaqueous electrolyte solution for secondary battery and nonaqueous electrolyte secondary battery using same
JP2009193744A (en) Positive electrode and nonaqueous electrolyte battery
JP6107926B2 (en) Non-aqueous electrolyte for secondary battery and non-aqueous electrolyte secondary battery using the same
EP2238643A2 (en) Pouch-type lithium secondary battery
JP5402974B2 (en) Non-aqueous electrolyte for secondary battery and secondary battery using the same
JP2007173222A (en) Lithium ion secondary battery
WO2016157735A1 (en) Non-aqueous electrolyte secondary battery
JP2019114323A (en) Lithium secondary battery
JP2011159506A (en) Nonaqueous secondary battery
US10637048B2 (en) Silicon anode materials
JP4715848B2 (en) battery
JP2016062810A (en) Negative electrode for nonaqueous electrolyte secondary battery, and nonaqueous electrolyte secondary battery including the same
JP2009238387A (en) Nonaqueous electrolyte secondary battery
JP6484995B2 (en) Lithium ion secondary battery
JP2007165299A (en) Lithium secondary battery
JPWO2015177830A1 (en) Negative electrode material, negative electrode for lithium ion secondary battery, lithium ion secondary battery, and production method thereof
JP2010186689A (en) Nonaqueous electrolyte secondary battery
JP5205863B2 (en) Non-aqueous electrolyte secondary battery
JP2009054469A (en) Nonaqueous secondary battery

Legal Events

Date Code Title Description
121 Ep: the epo has been informed by wipo that ep was designated in this application

Ref document number: 13884112

Country of ref document: EP

Kind code of ref document: A1

NENP Non-entry into the national phase

Ref country code: DE

122 Ep: pct application non-entry in european phase

Ref document number: 13884112

Country of ref document: EP

Kind code of ref document: A1

NENP Non-entry into the national phase

Ref country code: JP