WO2012160762A1 - リチウムイオン二次電池用電極及びその製造方法、並びにその電極を用いたリチウムイオン二次電池 - Google Patents
リチウムイオン二次電池用電極及びその製造方法、並びにその電極を用いたリチウムイオン二次電池 Download PDFInfo
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- WO2012160762A1 WO2012160762A1 PCT/JP2012/002976 JP2012002976W WO2012160762A1 WO 2012160762 A1 WO2012160762 A1 WO 2012160762A1 JP 2012002976 W JP2012002976 W JP 2012002976W WO 2012160762 A1 WO2012160762 A1 WO 2012160762A1
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- active material
- electrode
- lithium ion
- ion secondary
- secondary battery
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- 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
- H01M4/628—Inhibitors, e.g. gassing inhibitors, corrosion inhibitors
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- 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
- H01M4/04—Processes of manufacture in general
- H01M4/0402—Methods of deposition of the material
- H01M4/0404—Methods of deposition of the material by coating on electrode collectors
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- 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
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- 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
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- 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
- H01M4/139—Processes of manufacture
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- 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
- H01M4/621—Binders
- H01M4/622—Binders being polymers
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- 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
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- 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
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
- Y02P70/50—Manufacturing or production processes characterised by the final manufactured product
Definitions
- the present invention relates to an electrode for a lithium ion secondary battery, a method for producing the same, and a lithium ion secondary battery using the electrode.
- the lithium ion secondary battery is a secondary battery that has a high charge / discharge capacity and can achieve high output. Currently, it is mainly used as a power source for portable electronic devices, and is further expected as a power source for electric vehicles expected to be widely used in the future.
- a lithium ion secondary battery has an active material capable of inserting and removing lithium (Li) on a positive electrode and a negative electrode, respectively. The lithium ion secondary battery operates by moving lithium ions in the electrolyte provided between the two electrodes.
- the lithium ion secondary battery is required to maintain the discharge capacity even after repeated charge and discharge.
- the charge and discharge cycle life of the lithium ion secondary battery is shortened by the gradual reaction of the electrode active material and the electrolytic solution to decompose the electrolytic solution.
- Patent Document 1 discloses that a compound containing polysiloxane, perfluoropolyether, perfluoroalkane and derivatives thereof is mixed in an electrolytic solution to form a film of the above compound on a positive electrode or a negative electrode. There is. Since these compounds have lower surface tension than the electrolyte and are insoluble in the electrolyte, it is disclosed that when the battery is assembled, a film is formed on the electrode in the battery.
- Patent Document 2 discloses that a lithium ion conductive polymer compound having a polyethylene glycol unit is coated on an active material composed of tin oxide or complex tin oxide.
- the present inventor has intensively studied to achieve the above-mentioned purpose. As a result, it has been found that the cycle characteristics of the lithium ion secondary battery can be improved by forming a film made of a cured silicone-acrylic graft copolymer on at least a part of the surface of the active material layer.
- the electrode for a lithium ion secondary battery of the present invention comprises a current collector, an active material layer containing a binder formed on the surface of the current collector, and a film formed on at least a part of the surface of the active material layer
- the film is composed of a cured silicone-acrylic graft copolymer comprising an acrylic main chain having a functional group and a side chain having a silicone grafted onto the acrylic main chain, and the film is It is characterized in that it is chemically bonded to a binder.
- the film is preferably formed on the surface of the active material layer by chemically bonding with the binder via the functional group of the acrylic main chain.
- the lithium ion secondary battery can be mounted on a vehicle.
- the method for producing an electrode for a lithium ion secondary battery according to the present invention comprises a slurry forming step of mixing an active material, a binder resin, and a silicone-acrylic graft copolymer to form a slurry, and collecting the slurry
- the binder resin and the silicone-acrylic graft copolymer are cured by heating the slurry applied to the surface of the slurry and the slurry applied to the surface of the current collector, and the silicone-acrylic graft copolymer and the binder And a heat treatment step of chemically bonding with a resin, and the silicone-acrylic graft copolymer is composed of an acrylic main chain having a functional group and a side chain having silicone grafted onto the acrylic main chain. It is characterized by
- a film made of a cured product of a silicone-acrylic graft copolymer chemically bonded to a binder is formed on the surface of at least a part of the active material layer.
- the lithium ion secondary battery including the electrode for a lithium ion secondary battery has excellent cycle characteristics.
- the method of the present invention for producing a lithium ion secondary battery electrode it is possible to produce an electrode capable of making a lithium ion secondary battery excellent in cycle characteristics.
- the lithium ion secondary battery is excellent in cycle characteristics, when the lithium ion secondary battery is mounted on a vehicle, the vehicle becomes a high performance vehicle.
- FIG. 1 is a schematic view illustrating an electrode for a lithium ion secondary battery according to the present embodiment.
- FIG. 1 shows a current collector 1 and an active material layer 5 formed on the current collector 1.
- the active material 2 and the conductive auxiliary agent 4 are held on the current collector 1 via the binder 3.
- a film 6 chemically bonded to the binder 3 at a location 6a.
- FIG. 1 is a schematic view, and the size and shape are not accurate. For example, although the film 6 is shown in a plate shape in FIG. 1, the actual film 6 is indeterminate and formed in a thin film along the surface of the active material layer 5.
- the film 6 also covers at least a part of the surface of the active material layer 5. Therefore, the film 6 also covers the active material 2 on the surface of the active material layer 5. Although the surface of the active material layer 5 may be partially not covered by the film 6, it is desirable that the entire surface of the active material layer 5 be covered by the film 6.
- a film 6 is formed on the surface of at least a part of the active material layer 5, and the film 6 is bonded to the binder 3. Therefore, the film 6 can suppress decomposition of the electrolytic solution by the active material 2 or the like contained in the active material layer 5 for a long time.
- the electrode for a lithium ion secondary battery of the present invention comprises a current collector, an active material layer containing a binder formed on the surface of the current collector, and a film formed on at least a part of the surface of the active material layer; And the coating comprises a cured silicone-acrylic graft copolymer comprising an acrylic main chain having a functional group and a side chain having a silicone grafted onto the acrylic main chain, and the coating is a binder And a chemical bond.
- the current collector is a chemically inert electron conductor for keeping current flowing to the electrode during discharge or charge.
- the current collector may be in the form of a foil, a plate or the like, but is not particularly limited as long as it has a shape according to the purpose.
- metal foils such as copper foil, nickel foil, aluminum foil, stainless steel foil, can be used suitably, for example.
- the active material layer contains an active material and a binder. You may add a conductive support agent as needed.
- Active materials are substances that directly contribute to electrode reactions such as charge reactions and discharge reactions.
- a lithium containing compound is suitable.
- the positive electrode active material for example, lithium-containing metal complex oxides such as lithium cobalt complex oxide, lithium nickel complex oxide, lithium manganese complex oxide and the like can be used.
- the carbon-based material examples include non-graphitizable carbon, artificial graphite, cokes, graphites, glassy carbons, organic polymer compound fired bodies, carbon fibers, activated carbon or carbon blacks.
- the organic polymer compound fired body refers to a material obtained by firing and carbonizing a polymer material such as phenol or furan at an appropriate temperature.
- elemental compounds having an element capable of alloying with lithium, ZnLiAl, AlSb, SiB 4 , SiB 6 , Mg 2 Si, Mg 2 Sn, Ni 2 Si, TiSi 2 , MoSi 2 , CoSi 2 , NiSi 2 , CaSi 2 , CrSi 2, Cu 5 Si, FeSi 2, MnSi 2, NbSi 2, TaSi 2, VSi 2, WSi 2, ZnSi 2, SiC, Si 3 N 4, Si 2 N 2 O, SiO v (0 ⁇ v ⁇ 2 And SnO w (0 ⁇ w ⁇ 2), SnSiO 3 , LiSiO or LiSnO.
- the negative electrode active material preferably contains silicon (Si), and further preferably has SiO x (0.5 ⁇ x ⁇ 1.5). Since silicon has a large theoretical capacity but a large volume change during charge and discharge, the volume change can be reduced by using SiO x .
- polymer material examples include polyacetylene and polypyrrole.
- a binder is used as a binder for fixing an active material and a conductive support agent to a collector.
- the binder is required to bind the active material and the like in an amount as small as possible, and the amount thereof is 0.5 mass% to 100 mass% of the total of the active material, the conductive additive and the binder as the mass of the binder It is desirable to be 50% by mass.
- a binder for example, a cured product of polyvinylidene fluoride (PVDF), a cured product of a fluorine-based polymer such as polytetrafluoroethylene (PTFE), a cured product of a rubber such as styrene butadiene rubber (SBR), polyimide, polyamide imide, etc.
- PVDF polyvinylidene fluoride
- PTFE polytetrafluoroethylene
- SBR styrene butadiene rubber
- a cured product of an imide type polymer and a cured product of an alkoxylsilyl group-containing resin can be used.
- the conductive aid is added to enhance the conductivity of the electrode layer.
- carbon black fine particles such as carbon black, graphite, acetylene black (AB), ketjen black (KB), vapor grown carbon fiber (VGCF), etc. may be used alone or in combination. Can be added.
- the amount of the conductive aid used is not particularly limited, but can be, for example, about 20 to 100 parts by mass with respect to 100 parts by mass of the active material.
- the film is made of a cured silicone-acrylic graft copolymer, and the main skeleton of the film is acrylic.
- the silicone-acrylic graft copolymer whose main skeleton is acrylic is added to the slurry formed by mixing the active material and the binder resin, the surface tension of the slurry can be lowered. Since the film is formed on the surface of the slurry, the film can be made a uniform film without extreme unevenness in film thickness by lowering the surface tension of the slurry. Therefore, if the film has extreme unevenness in film thickness, in the case of a battery, the film locally has high resistance at a thick film thickness, and lithium may be deposited in the high resistance portion of the film to cause internal short circuit. There is, but it can be prevented.
- the film may be formed on at least a part of the surface of the active material layer, but preferably covers the entire surface of the active material layer. By covering the entire surface of the active material layer, the film can prevent the entire active group such as the active material which is considered to decompose the electrolyte from coming into contact with the electrolyte, thereby reliably suppressing the decomposition of the electrolyte. I can do it.
- the film in the present invention comprises a cured silicone-acrylic graft copolymer comprising an acrylic main chain having a functional group and a side chain having silicone grafted onto the acrylic main chain.
- the silicone-acrylic graft copolymer can be obtained by graft copolymerization of a dimethylpolysiloxane having a polymerizable reactive group at one end and an acrylic monomer such as methyl acrylate or methyl methacrylate.
- a functional group can be introduced into the acrylic monomer.
- a functional group a hydroxyl group, an aldehyde group, a ketone group, a carboxyl group, a nitro group, an amino group, a sulfo group etc. are mentioned, for example.
- the coating is chemically bonded to the binder.
- Chemical bonding refers to a state of chemical bonding, and generally includes types such as ionic bonding, covalent bonding, metal bonding, and hydrogen bonding.
- the chemical bond between the film and the binder is a chemical bond between the main chain acrylic (organic matter) and the binder (organic matter), so this chemical bond is mainly a covalent bond.
- the functional group of the acrylic, which is the main chain of the silicone-acrylic graft copolymer, and the binder react with each other to form a chemical bond. Since the film is chemically bonded to the binder, even when the active material expands and contracts due to charge and discharge of the electrode, the film is less likely to peel off from the active material layer. Therefore, the effect of suppressing the decomposition of the electrolyte continues for a long time.
- the manufacturing method of the electrode for lithium ion secondary batteries of the present invention has a slurry preparation process, a slurry application process, and a heat treatment process.
- the slurry preparation step the active material, the binder resin, and the silicone-acrylic graft copolymer are mixed to prepare a slurry. If necessary, a solvent and a conductive additive may be added to the slurry.
- the slurry application step the slurry is applied to the surface of the current collector.
- the binder resin and the silicone-acrylic graft copolymer are cured and the silicone-acrylic graft copolymer is chemically bonded to the binder resin by heating the slurry applied to the surface of the current collector.
- the active material, the binder resin, the silicone-acrylic graft copolymer and the conductive aid are the same as those described above.
- the solvent is not particularly limited.
- NMP N-methyl pyrrolidone
- methanol methyl isobutyl ketone (MIBK) and the like can be used.
- a general mixing apparatus such as a planetary mixer, a defoaming kneader, a ball mill, a paint shaker, a vibration mill, a lice mill, and an agitator mill can be used.
- the mixing ratio of the silicone-acrylic graft copolymer to the slurry is preferably 0.1% by mass to 1% by mass of the silicone-acrylic graft copolymer, based on 100% by mass of the entire slurry. By using this mixing ratio, it is possible to coat almost the entire active material layer with a coating made of a very thin cured silicone-acrylic graft copolymer.
- a coating method generally used for producing an electrode for a secondary battery such as a roll coating method, a dip coating method, a doctor blade method, a spray coating method, and a curtain coating method can be used.
- the coating thickness of the slurry applied to the surface of the current collector is preferably 10 ⁇ m to 20 ⁇ m.
- heating is performed in accordance with the curing temperature of the binder resin and silicone-acrylic graft copolymer to be used, and at a temperature at which the silicone-acrylic graft copolymer and the binder resin can be chemically bonded.
- a functional group is introduced into the acrylic main chain. for that reason.
- the silicone-acrylic graft copolymer can be chemically bonded to the binder resin at the acrylic main chain portion oriented on the slurry side.
- an active material layer is formed on the current collector, and a film is formed on the surface of the active material layer.
- the coating is chemically bonded to the binder.
- At least one of the positive electrode and the negative electrode is the electrode for a lithium ion secondary battery. If at least one of the positive electrode and the negative electrode is the electrode for a lithium ion secondary battery, decomposition of the electrolytic solution by the positive electrode active material or the negative electrode active material can be suppressed, and the lithium ion secondary battery is excellent It can have cycle characteristics.
- a lithium ion secondary battery using the above-described lithium ion secondary battery electrode can use known battery components except using the above lithium ion secondary battery electrode, and can be manufactured by a known method. Can do.
- the lithium ion secondary battery of the present invention has a positive electrode, a negative electrode, a separator and an electrolytic solution.
- the lithium ion secondary battery of the present invention at least one of the positive electrode and the negative electrode is the electrode for a lithium ion secondary battery.
- the positive electrode active material not containing Li is not particularly limited, but preferably contains at least one selected from elemental sulfur, a complex of sulfur and carbon, manganese dioxide and vanadium oxide. By using the positive electrode containing these positive electrode active materials, a lithium ion secondary battery with high battery capacity can be obtained.
- a method of doping Li into the negative electrode active material a method of inserting Li in advance into the negative electrode active material (pre-doping) may be used, or when used as a battery, Li is inserted into the negative electrode active material A method may be used.
- a method of pre-doping Li into a negative electrode active material a method of forming a half cell using metallic lithium as a counter electrode and inserting Li by an electrolytic doping method in which Li is electrochemically doped; After that, there is a method of inserting Li by a bonding pre-doping method of leaving in an electrolytic solution and doping using diffusion of lithium to the electrode.
- the battery may be configured in combination with the counter electrode.
- a method of inserting Li into the negative electrode active material when used as a battery there is a method of forming a negative electrode by integrating a Li source (for example, metallic Li) on the surface and / or inside of the negative electrode beforehand. It can be used.
- a Li source for example, metallic Li
- the amount of Li to be pre-doped into the negative electrode active material or the amount of Li integrated into the negative electrode varies depending on the type of the positive electrode active material, the negative electrode active material, the electrolyte, etc. . Therefore, the amount of Li may be determined by actual measurement or calculation as appropriate depending on the configuration of the battery to be manufactured.
- the separator separates the positive electrode and the negative electrode, and allows lithium ions to pass while preventing the short circuit of the current due to the contact of the both electrodes.
- the separator may be, for example, a porous film made of synthetic resin such as polytetrafluoroethylene, polypropylene or polyethylene, or a porous film made of ceramic.
- the electrolytic solution contains a solvent and an electrolyte dissolved in the solvent.
- ethers for example, tetrahydrofuran, 2-methyltetrahydrofuran, 1,4-dioxane, 1,2-dimethoxyethane, 1,2-diethoxyethane, 1,2-dibutoxyethane and the like can be used.
- lithium salts such as LiClO 4 , LiAsF 6 , LiPF 6 , LiBF 4 , LiCF 3 SO 3 , LiN (CF 3 SO 2 ) 2 can be used.
- lithium salt such as LiClO 4 , LiPF 6 , LiBF 4 , LiCF 3 SO 3 or the like in a solvent such as ethylene carbonate, dimethyl carbonate, propylene carbonate, dimethyl carbonate It is possible to use solutions dissolved at a certain concentration.
- the lithium ion secondary battery can be mounted on a vehicle. Since the lithium ion secondary battery has excellent cycle characteristics, when the lithium ion secondary battery is mounted on a vehicle, the vehicle has high performance.
- the vehicle may be any vehicle that uses electric energy from batteries for all or part of the power source, for example, electric vehicles, hybrid vehicles, plug-in hybrid vehicles, hybrid railway vehicles, forklifts, electric wheelchairs, electric assists There are bicycles and electric motorcycles.
- the present invention is not limited to the above embodiments. . In the range which does not deviate from the summary of the present invention, it can carry out with various forms which gave change, improvement, etc. which a person skilled in the art can make.
- the mixture was adjusted by adding an appropriate amount of NMP as a solvent, and then a silicone-acrylic graft copolymer was added to form a slurry.
- the addition amount of the silicone-acrylic graft copolymer at this time was 0.6 mass%, with the entire slurry as 100 mass%.
- the above slurry was placed on an electrolytic copper foil of 20 ⁇ m thickness, and the slurry was applied in a film form on the electrolytic copper foil using a doctor blade.
- the obtained sheet was dried at 80 ° C. for 20 minutes to volatilize and remove NMP, and then the current collector and the coated product on the current collector were firmly and closely bonded by a roll press.
- the bonded product was heated at 200 ° C. for 2 hours in a vacuum dryer, cut into a predetermined shape (26 mm ⁇ 31 mm rectangular shape), and used as an electrode having a thickness of about 35 ⁇ m. This electrode was used as the electrode of Example 1.
- the thickness of the coating is estimated to be about 200 nm from the compounding amount of the silicone-acrylic graft copolymer.
- Example 1 ⁇ Production of laminate type lithium ion secondary battery>
- the electrode of Example 1 was used as a negative electrode.
- the following electrodes were produced as a positive electrode.
- Polyvinylidene fluoride (PVDF) as a binder resin using a 20 ⁇ m aluminum foil as a current collector, using LiNi 1/3 Co 1/3 Mn 1/3 O 2 as a positive electrode active material, using acetylene black as a conductive additive was used.
- a laminate type battery was manufactured using the above positive electrode and negative electrode. Specifically, a rectangular sheet (27 ⁇ 32 mm, 25 ⁇ m thick) made of polypropylene resin as a separator is sandwiched between the positive electrode and the negative electrode to form an electrode plate group. The electrode plate group was covered with a pair of laminate films, and the three sides were sealed, and then the above electrolytic solution was injected into the bag-like laminate film. Thereafter, by sealing the other side, the four sides were airtightly sealed to obtain a laminate type battery in which the electrode plate group and the electrolytic solution were sealed. The positive electrode and the negative electrode are provided with a tab electrically connectable to the outside, and a part of the tab extends to the outside of the laminate type battery. Through the above steps, a laminate-type lithium ion secondary battery using the electrode of Example 1 was obtained. The resulting battery is referred to as the lithium ion secondary battery of Example 1.
- Example 2 Using the electrode of Example 1 as the negative electrode, first, a half cell is assembled using the negative electrode of Example 1 and metal lithium foil, and Li is inserted at a temperature: 25 ° C., rate: 1/100 C, cutoff: 0 CV to 0.01 V
- the lithium ion secondary battery of Example 2 was produced in combination with the positive electrode prepared in the same manner as the positive electrode of Example 1 except that the prepared negative electrode was used and vanadium oxide (V 2 O 5 ) was used as the positive electrode active material. .
- Comparative Example 1 An electrode of Comparative Example 1 is prepared in the same manner as the electrode of Example 1 except that the silicone-acrylic graft copolymer is not added to the slurry, and in the same manner as the lithium ion secondary battery of Example 1 A laminate type lithium ion secondary battery using an electrode was produced. This is referred to as a lithium ion secondary battery of Comparative Example 1.
- the load test was conducted twice, from the first cycle to the sixth cycle and from the 107th cycle to the sixth cycle.
- charging is performed by CCCV charging (constant current constant voltage charging) with a charging rate of 0.2C and voltage 4.2V, discharge is at a voltage of 2.5V, and the charging rate is 0.2C, 1C CC discharge (constant current discharge) of 2C, 3C, 4C, 5C was performed.
- the current for discharging the electric capacity in one hour is represented as 1 C
- the current for discharging in 5 hours is represented as 0.2 C. Therefore, the 1C current value is five times the 0.2C current value.
- the cycle test was performed from 7 cycles to 106 cycles after the first load test and continuously to 200 cycles after the second load test.
- the charge was performed at a voltage of 4.2 V and CCCV charge at a charge rate of 1 C
- the discharge was performed at a voltage of 2.5 V and CC discharge of a discharge rate of 1 C.
- Each discharge capacity retention rate was calculated based on the discharge capacity of the charge and discharge performed at the discharge rate 1C at the seventh cycle. This cycle test was conducted at 45 ° C. as an accelerated test.
- the discharge capacity retention rate (%) was determined by the following equation.
- FIG. 2 A graph showing the relationship between the number of cycles and the discharge capacity retention ratio (%) for the lithium ion secondary batteries of Example 1 and Comparative Example 1 is shown in FIG. As apparent from FIG. 2, first, in the lithium ion secondary battery of Example 1, compared with the lithium ion secondary battery of Comparative Example 1, the decreasing rate of the discharge capacity was smaller in each cycle. Further, in the lithium ion secondary battery of Comparative Example 1, the discharge capacity retention ratio after 200 cycles is about 83%, while in the lithium ion secondary battery of Example 1, the discharge capacity retention ratio after 200 cycles is 84% It was found that the degree was maintained.
- the lithium ion secondary battery of Example 1 had a higher discharge capacity retention rate than the lithium ion secondary battery of Comparative Example 1 up to a discharge rate of 2C. From this, it was found that the above-mentioned film exhibited the effect of suppressing the decomposition of the electrolytic solution even during rapid charge and discharge at a discharge rate of 2C, and the discharge capacity retention rate of the battery was improved.
- Example 2 Although the case where the film was formed in the negative electrode was shown in the Example, the same effect is acquired even when the film is formed in the positive electrode. In addition, it is considered that the same effect as in Example 1 can be obtained in Example 2.
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Abstract
Description
ここで図1を用いて本発明のリチウムイオン二次電池用電極を説明する。図1は本実施形態のリチウムイオン二次電池用電極を説明する模式図である。
本発明のリチウムイオン二次電池用電極の製造方法は、スラリー作成工程と、スラリー塗布工程と、熱処理工程と、を有する。スラリー作成工程では、活物質と、バインダー樹脂と、シリコーンーアクリルグラフト共重合体と、を混合してスラリーを作成する。必要に応じて溶媒、導電助剤をスラリーに添加しても良い。
本発明のリチウムイオン二次電池は、正極及び負極のうちの少なくとも一方が上記リチウムイオン二次電池用電極である。正極及び負極のうちの少なくとも一方が上記リチウムイオン二次電池用電極であれば、正極活物質または負極活物質などによる電解液の分解を抑制することが出来、リチウムイオン二次電池は、優れたサイクル特性を有することが出来る。
<評価用電極作製>
活物質として、SiO(アルドリッチ社製)を準備した。バインダー樹脂としてアルコキシ基含有シラン変性ポリアミドイミド樹脂(荒川化学工業株式会社製、商品名コンポセラン、品番H901-2、溶剤組成:N-メチルピロリドン(NMP)/キシレン(Xyl)、硬化残分30%、粘度8000mPa・s、硬化残分中のシリカ、2質量%、硬化残分とは樹脂硬化させ揮発性成分を除いた固形分を意味する)を準備した。緩衝材として、塊状人造黒鉛“MAG(Massive Artifical Graphite)”(日立化成工業株式会社製)を準備した。導電助剤としてケッチェンブラックインターナショナル社製のKB(ケッチェンブラック)を準備した。シリコーンーアクリルグラフト共重合体としてビックケミージャパン株式会社製、品名BYK-3550(硬化残分52%、硬化残分とは揮発性成分を除いた固形分を意味する)を準備した。
実施例1の電極を負極とした。正極として以下の電極を作製した。集電体として20μmのアルミニウム箔を用い、正極活物質としてLiNi1/3Co1/3Mn1/3O2を用い、導電助剤としてアセチレンブラックを用い、バインダー樹脂としてポリフッ化ビニリデン(PVDF)を用いた。上記活物質、導電助剤及びバインダー樹脂を、LiNi1/3Co1/3Mn1/3O2:アセチレンブラック:ポリフッ化ビニリデン(PVDF)=88:6:6(質量%)の割合で混合した。この混合物に、溶媒としてNMPを適量入れて調整してスラリーとした。厚さ20μmのアルミニウム箔に上記スラリ-を乗せて、ドクターブレードを用いてアルミニウム箔にスラリーを膜状に塗布した。得られたシートを80℃で30分間乾燥してNMPを揮発させて除去した後、ロ-ルプレス機により、集電体と集電体上の塗布物を、塗膜の厚さが50μmになるように、つまり電極の合計厚さが70μmとなるようにプレスした。これを負極と同様の所定形状に打ち抜き、抜き取ったものを120℃で6時間、真空で加熱し、正極を得た。この正極の容量は3.0mAh/cm2であり、電極密度は2.3g/cm2であった。電解液としてエチレンカ-ボネ-ト(EC)とジエチルカ-ボネ-ト(DEC)をEC:DEC=3:7(体積比)で混合した溶媒に1モルのLiPF6を溶解した溶液を用いた。
実施例1の電極を負極とし、まず実施例1の負極と金属リチウム箔を用いて半電池を組み、温度:25℃、レート:1/100C、カットオフ:0CV~0.01V でLiを挿入した負極を用意し、正極活物質として酸化バナジウム(V2O5)を用いたこと以外は実施例1の正極と同様にした正極と組み合わせて、実施例2のリチウムイオン二次電池を作製した。
シリコーンーアクリルグラフト共重合体をスラリーに添加しないこと以外は実施例1の電極と同様にして比較例1の電極を作製し、実施例1のリチウムイオン二次電池と同様にして比較例1の電極を用いたラミネート型リチウムイオン二次電池を作製した。これを比較例1のリチウムイオン二次電池とする。
(充放電試験)
上記実施例1のリチウムイオン二次電池及び比較例1のリチウムイオン二次電池の充放電試験を行った。充放電試験では、負荷試験(6サイクル)とサイクル試験(100サイクル)とを組み合わせた。
Claims (6)
- 集電体と、
該集電体の表面に形成されたバインダーを含む活物質層と、
該活物質層の少なくとも一部の表面に形成された被膜と、
を有し、
該被膜は、官能基を有するアクリル系主鎖と、該アクリル系主鎖にグラフト重合されたシリコーンを有する側鎖と、からなるシリコーンーアクリルグラフト共重合体硬化物からなり、該被膜は該バインダーと化学結合していることを特徴とするリチウムイオン二次電池用電極。 - 前記被膜は、該官能基を介して該バインダーと化学結合することによって、前記活物質層の表面に形成されている請求項1に記載のリチウムイオン二次電池用電極。
- 正極及び負極のうちの少なくとも一方が請求項1または2に記載のリチウムイオン二次電池用電極であるリチウムイオン二次電池。
- 前記正極はLiを含まない正極活物質を有する請求項3に記載のリチウムイオン二次電池。
- 前記正極活物質は、硫黄単体、硫黄とカーボンとの複合体、二酸化マンガンおよび酸化バナジウムから選ばれる少なくとも1つを含む請求項4に記載のリチウムイオン二次電池。
- 活物質と、バインダー樹脂と、シリコーンーアクリルグラフト共重合体と、を混合してスラリーを作成するスラリー作成工程と、
該スラリーを集電体の表面に塗布するスラリー塗布工程と、
該集電体の表面に塗布された該スラリーを加熱することにより、該バインダー樹脂及び該シリコーンーアクリルグラフト共重合体を硬化させ、かつ該シリコーンーアクリルグラフト共重合体と該バインダー樹脂とを化学結合させる熱処理工程と、
を有し、該シリコーンーアクリルグラフト共重合体は、官能基を有するアクリル系主鎖と該アクリル系主鎖にグラフト重合されたシリコーンを有する側鎖とからなることを特徴とするリチウムイオン二次電池用電極の製造方法。
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US14/119,235 US9306220B2 (en) | 2011-05-23 | 2012-05-02 | Lithium ion secondary battery electrode, manufacturing process for the same, and lithium ion secondary battery using the electrode |
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US20170229703A1 (en) * | 2014-08-07 | 2017-08-10 | Academia Sinica | Method of preparation a battery electrode by spray coating, an electrode and a battery made by method thereof |
WO2019203739A1 (en) * | 2018-04-18 | 2019-10-24 | Enwair Enerji̇ Teknoloji̇leri̇ A.Ş. | Modification of silicon with acrylic or methacrylic derivatives used as an anode active material in the lithium ion battery technology |
KR102420593B1 (ko) * | 2018-05-24 | 2022-07-13 | 주식회사 엘지에너지솔루션 | 리튬-황 전지용 분리막 및 이를 포함하는 리튬-황 전지 |
CN111261874B (zh) * | 2020-02-12 | 2021-08-13 | 西安交通大学 | 一种锂离子电池负极及其制备方法和应用 |
CN113939927B (zh) * | 2020-12-31 | 2022-12-06 | 东莞新能源科技有限公司 | 一种电化学装置、电子装置及电化学装置制备方法 |
CN116169428B (zh) * | 2023-04-06 | 2023-06-20 | 宁德新能源科技有限公司 | 一种隔膜及包含该隔膜的电化学装置和电子装置 |
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