WO2011145177A1 - 負極活物質の評価方法および負極活物質 - Google Patents
負極活物質の評価方法および負極活物質 Download PDFInfo
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- WO2011145177A1 WO2011145177A1 PCT/JP2010/058387 JP2010058387W WO2011145177A1 WO 2011145177 A1 WO2011145177 A1 WO 2011145177A1 JP 2010058387 W JP2010058387 W JP 2010058387W WO 2011145177 A1 WO2011145177 A1 WO 2011145177A1
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- active material
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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
- H01M4/133—Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
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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
- H01M10/05—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
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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
- H01M4/36—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
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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
- H01M2004/021—Physical characteristics, e.g. porosity, surface area
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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
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T10/00—Road transport of goods or passengers
- Y02T10/60—Other road transportation technologies with climate change mitigation effect
- Y02T10/70—Energy storage systems for electromobility, e.g. batteries
Definitions
- the present invention relates to a negative electrode active material for lithium ion secondary batteries and other batteries.
- the lithium ion secondary battery includes a positive electrode and a negative electrode, and an electrolyte interposed between the two electrodes, and performs charging / discharging as lithium ions in the electrolyte move between the two electrodes.
- the negative electrode includes a negative electrode active material capable of reversibly occluding and releasing lithium ions.
- As the negative electrode active material various carbon materials prepared in a particulate form are mainly used.
- Patent document 1 is mentioned as a technical document regarding the negative electrode material for lithium ion secondary batteries.
- Lithium ion secondary batteries are increasingly used in various fields, and their performance (charging / discharging characteristics, durability, etc.) is significantly affected by negative electrode performance. Therefore, improvement and stabilization of negative electrode performance is required. It has been.
- a negative electrode active material that can form a high-performance negative electrode for example, a composite carbon body in which a low crystalline carbon material adheres to the surface of highly crystalline carbonaceous particles has been studied.
- the target upper limit charging current density maximum charging current density that can be allowed to flow without causing a significant decrease in capacity
- high-temperature storage stability in a charged state
- batteries typically, between batteries using negative electrode active materials of different lots.
- the present inventor has found an index that can grasp a difference in surface activity that cannot be distinguished by a conventional index for a composite carbon body as a negative electrode active material, and has completed the present invention.
- a method for evaluating, as a negative electrode active material, a composite carbon body having at least partially a low crystalline carbon material on the surface of highly crystalline carbonaceous particles includes (A) performing a micro-Raman analysis n times at a wavelength of 532 nm on the sample of the negative electrode active material (where n is 20 or more). The method also determines the (B) Raman spectrum obtained by each round of Raman analysis, the value of the ratio of the intensity I G of the intensity I D D to G band R (I D / I G) Including that.
- the D band is a Raman peak that appears in the vicinity of 1360 cm ⁇ 1 due to vibration of sp 2 C—sp 2 C bonds with low conjugation (continuity).
- the G band is a Raman peak that appears in the vicinity of 1580 cm ⁇ 1 due to vibration of sp 2 C—sp 2 C bonds having high conjugation.
- the intensity of each band the value of each peak top corrected with the base line as zero is adopted.
- This negative electrode active material evaluation method applies to highly crystalline carbonaceous particles (composite carbon bodies) having a low crystalline carbon material attached to the surface.
- the low crystalline carbon material hereinafter also referred to as amorphous carbon
- the highly crystalline carbonaceous material hereinafter also referred to as graphite
- Typical graphitic R values can be less than 0.2.
- Lithium ion secondary batteries especially when charging at low temperatures (eg, about 0 ° C.), if the charging current density is too high for the battery performance, lithium is deposited on the negative electrode surface, and the performance deteriorates significantly. May occur. In order to avoid such a problem, it is required to improve the upper limit charging current density (mA / cm 2 ).
- the upper limit charging current density tends to increase as the electrochemical reaction rate at the negative electrode increases, and the rate of this electrochemical reaction increases as the effective area for lithium ion insertion increases as long as the crystal structure is approximately the same. .
- lithium ion insertion occurs in the surface of the surface covered with amorphous carbon and the exposed portion of the graphite edge surface and the damaged portion (that is, the low crystalline portion), and the graphite basal surface. It does not occur in the exposed part (that is, the high crystal part).
- the activity against side reactions also tends to be high at the low crystal part and low at the high crystal part. Therefore, the activity against lithium ion insertion and side reaction does not necessarily correspond to a mere specific surface area.
- variation may occur in at least one of the upper limit charging current density and the high temperature storage stability.
- the low crystal part (covered part of amorphous carbon, the edge face of the graphite (crystal edge part), the damaged part, etc.) and the high crystal part (the basal face of the graphite (sp 2 C is hexagonal)
- the mesh surface of the graphene sheet conjugated in a net shape) can be detected as the D band and G band.
- microscopic Raman analysis of 20 times or more per sample is performed on a part of different complex carbon bodies selected at random each time, so that statistical data including deviation between particles is obtained. It is done. Therefore, according to the above evaluation method, the negative electrode active material as an aggregate of composite carbon particles can be evaluated in consideration of the difference in crystallinity on the surface.
- Such an evaluation method can be used, for example, for grasping the covering condition (uniformity, etc.) of each composite carbon particle surface with amorphous carbon. Or, for multiple carbon lots of different lots, detect the difference in activity that could not be detected by conventional indicators, and select the ones with higher activity or those that are less likely to achieve the target activity. Can be used. From these things, the said evaluation method is useful in order to form stably the lithium ion secondary battery provided with the predetermined performance.
- the composite carbon body is characterized in that a distribution ratio ( DR ⁇ 0.2 ) having an R value determined by the above evaluation method of 0.2 or more ( DR ⁇ 0.2 ) is 20% or more.
- a negative electrode active material is provided. According to such a negative electrode active material, it is possible to more stably form a lithium ion secondary battery having predetermined performance (in particular, an upper limit charging current density at low temperature and high temperature storage stability).
- the nitrogen adsorption specific surface area is in the range of 4 to 9 m 2 / g. According to such a negative electrode active material, an excellent lithium ion secondary battery can be stably formed due to the balance between the upper limit charging current density at low temperature and the high temperature storage stability.
- a lithium ion secondary battery comprising a negative electrode having any of the negative electrode active materials disclosed herein, a positive electrode having a positive electrode active material, and a non-aqueous electrolyte. Is done.
- negative electrode performance is highly controlled, and predetermined performance (low temperature upper limit charging current density, high temperature storage stability) can be stably realized.
- the non-aqueous electrolyte contains vinylene carbonate (VC).
- VC vinylene carbonate
- the lithium ion secondary battery disclosed herein has an upper limit charge current density at low temperature that is important for dealing with rapid charge and discharge, and durability against high temperature storage or use (high temperature storage stability). Can be balanced and highly balanced.
- a battery is suitable, for example, as a power source used in a vehicle that can be used or stored (leaved) under a wide range of temperatures. Therefore, according to this invention, the vehicle provided with one of the lithium ion secondary batteries disclosed here is provided.
- a vehicle for example, an automobile
- a lithium ion secondary battery as a power source typically, a power source of a hybrid vehicle or an electric vehicle
- FIG. 1 is a perspective view schematically showing an outer shape of a lithium ion secondary battery according to an embodiment.
- 2 is a cross-sectional view taken along line II-II in FIG.
- FIG. 3 is a graph plotting the upper limit charging current density against the specific surface area for the lithium ion secondary batteries according to Examples 1 to 7.
- FIG. 4 is a side view schematically showing a vehicle (automobile) provided with the lithium ion secondary battery of the present invention.
- FIG. 5 is a perspective view schematically showing the shape of a 18650 type lithium ion battery.
- the negative electrode active material evaluation method disclosed herein can be applied to a negative electrode active material composed of a composite carbon body in which amorphous carbon is at least partially adhered to the surface of graphite particles as a core material.
- This evaluation method includes the following steps (A) to (D): (A) The sample of the negative electrode active material is subjected to micro Raman analysis n times at a wavelength of 532 nm (where n is 20 or more); (B) Raman spectrum obtained by each round of Raman analysis, determining the value of the ratio of the intensity I G of the intensity I D D to G band R (I D / I G); (C) obtaining the number m of analyzes in which the value of R was 0.2 or more; and (D) obtaining a ratio (m / n) of m to the total number of analyzes n as a distribution ratio (D R ⁇ 0.2 ) having an R value of 0.2 or more; Is included.
- the micro Raman analysis may be performed n times on the same sample using a micro laser Raman spectrometer having high spatial resolution (for example, 2 ⁇ m or less). Typically, the next analysis is performed by tapping the sample or slightly shifting the arrangement after the end of each analysis so that the analysis location is different each time.
- the spectroscope for example, model “Nicolet Almega XR” manufactured by Thermo Fisher Scientific Co., Ltd. or an equivalent thereof can be used. If the spatial resolution is too low (that is, if the minimum distance is too large), the variation between particles is difficult to be reflected in the R value, and the accuracy of the evaluation result may be reduced.
- the number of micro Raman analysis (n) is 20 times or more.
- the number of analyzes is preferably 50 times or more, and more preferably 75 times or more.
- the upper limit of the number of analyzes is not particularly limited, but can be about 125 times. If the number of analyzes is too small, the accuracy of the evaluation results of the negative electrode active material may not be sufficient, and it may be difficult to obtain desired negative electrode performance (upper limit charging current density, high temperature storage stability, etc.).
- This negative electrode active material evaluation method can be applied to a negative electrode active material made of a composite carbon body.
- a negative electrode active material is typically formed by adhering and carbonizing a coating raw material (coat type) capable of forming an amorphous carbon film on the surface of graphite particles (core material).
- the core material it is possible to use various graphites such as natural graphite and artificial graphite processed into particles (spherical) (pulverization, spherical molding, etc.).
- the average particle size of the core material is preferably about 6 to 20 ⁇ m.
- the specific surface area (before coating) is preferably about 5 to 15 m 2 / g.
- a method of processing various graphites into particles a conventionally known method can be employed without any particular limitation.
- a material capable of forming a carbon film can be appropriately selected and used depending on the amorphous carbon coating forming method employed.
- the coating formation method include a vapor phase method such as a CVD (Chemical Vapor Deposition) method in which a vapor phase coating material is deposited on the surface of the core material (graphite particles) in an inert gas atmosphere; A liquid phase method in which a solution diluted with a solvent is mixed with a core material, and then the coating material is fired and carbonized in an inert gas atmosphere; after the core material and the coating material are kneaded without using a solvent A conventionally known method such as a solid phase method of baking and carbonizing in an inert gas atmosphere can be appropriately employed.
- a compound (gas) that can be decomposed by heat, plasma, or the like to form a carbon film on the surface of the core material can be used.
- examples of such compounds include unsaturated aliphatic hydrocarbons such as ethylene, acetylene and propylene; saturated aliphatic hydrocarbons such as methane, ethane and propane; aromatic hydrocarbons such as benzene, toluene and naphthalene; Is mentioned. These compounds may be used alone or as a mixed gas of two or more. What is necessary is just to select suitably the temperature, pressure, time, etc. which perform a CVD process according to the kind of coating raw material to be used, and the desired coating amount.
- a compound that is soluble in various solvents and that can be thermally decomposed to form a carbon film on the surface of the core material can be used.
- Preferable examples include pitches such as coal tar pitch, petroleum pitch, and wood tar pitch. These can be used alone or in combination of two or more.
- the firing temperature and time may be appropriately selected according to the type of coating raw material so that an amorphous carbon film is formed. Typically, the baking may be performed at a temperature of about 800 to 1600 ° C. for about 2 to 3 hours.
- the solid phase coating material one or more of the same materials as in the liquid phase method can be used. What is necessary is just to select suitably about the temperature and time of baking according to the kind etc. of a coating raw material, For example, it can be set as the range comparable as a liquid phase method.
- various additives for example, an additive effective for amorphous carbonization of the coating raw material
- the coating amount of amorphous carbon in the composite carbon body can be about 0.5 to 8% by mass (preferably 2 to 6% by mass). If the coating amount is too small, the characteristics of amorphous carbon (such as low self-discharge) may not be sufficiently reflected in the negative electrode performance. If the coating amount is too large, amorphous carbon has a complicated Li ion movement path inside, so that the diffusion of Li ions becomes slow, and the electrochemical reaction rate at the negative electrode may decrease.
- the mixing ratio of the core material and the coating material can be appropriately selected so that the coating amount after performing an appropriate post-treatment (such as removal of impurities and unreacted substances) is within the above range depending on the coating method to be applied. Good.
- Such a composite carbon body can be evaluated by the above evaluation method.
- the negative electrode active material disclosed herein is composed of a composite carbon body, and DR ⁇ 0.2 is 20% or more. When DR ⁇ 0.2 is too smaller than this, at least one of the upper limit charging current density and the high temperature storage stability may be lowered, or the balance may be deteriorated.
- the upper limit of DR ⁇ 0.2 is not particularly limited, but can usually be about 95% or less.
- the specific surface area of the negative electrode active material (after coating) can be, for example, about 1 to 10 m 2 / g. Usually, it is preferably in the range of about 4 to 9 m 2 / g.
- DR ⁇ 0.2 is 20% or more and the specific surface area is within the above preferred range, an excellent lithium ion secondary battery can be formed due to a balance between the upper limit charging current density and high temperature storage stability. . If the specific surface area is too small, a sufficient current density may not be obtained during charging and discharging. If the specific surface area is too large, the battery capacity may be significantly reduced due to an increase in irreversible capacity.
- a value measured by a nitrogen adsorption method is adopted.
- a lithium ion secondary battery comprising a negative electrode having any of the negative electrode active materials disclosed herein.
- An embodiment of such a lithium ion secondary battery will be described in detail by taking as an example a lithium ion secondary battery 100 (FIG. 1) having a configuration in which an electrode body and a non-aqueous electrolyte are accommodated in a rectangular battery case.
- the technology disclosed herein is not limited to such an embodiment. That is, the shape of the lithium ion secondary battery disclosed herein is not particularly limited, and the battery case, electrode body, and the like can be appropriately selected in material, shape, size, and the like according to the application and capacity. .
- the battery case may have a rectangular parallelepiped shape, a flat shape, a cylindrical shape, or the like.
- symbol is attached
- the dimensional relationships (length, width, thickness, etc.) in each drawing do not reflect actual dimensional relationships.
- the lithium ion secondary battery 100 includes a wound electrode body 20 and a flat box-shaped battery case 10 corresponding to the shape of the electrode body 20 together with an electrolyte (not shown). It can be constructed by being housed inside the opening 12 and closing the opening 12 of the case 10 with a lid 14.
- the lid body 14 is provided with a positive terminal 38 and a negative terminal 48 for external connection so that a part of the terminals protrudes to the surface side of the lid body 14.
- the electrode body 20 includes a positive electrode sheet 30 in which a positive electrode active material layer 34 is formed on the surface of a long sheet-like positive electrode current collector 32, and a negative electrode active material layer on the surface of a long sheet-like negative electrode current collector 42.
- the negative electrode sheet 40 on which the electrode 44 is formed is rolled up with two long sheet-like separators 50, and the obtained wound body is crushed from the side surface and ablated to form a flat shape. ing.
- the positive electrode sheet 30 is formed such that the positive electrode active material layer 34 is not provided (or removed) at one end along the longitudinal direction, and the positive electrode current collector 32 is exposed.
- the negative electrode sheet 40 to be wound is not provided with (or removed from) the negative electrode active material layer 44 at one end along the longitudinal direction so that the negative electrode current collector 42 is exposed. Is formed.
- the positive electrode terminal 38 is joined to the exposed end portion of the positive electrode current collector 32, and the negative electrode terminal 48 is joined to the exposed end portion of the negative electrode current collector 42, respectively.
- the positive electrode sheet 30 or the negative electrode sheet 40 is electrically connected.
- the positive and negative terminals 38 and 48 and the positive and negative current collectors 32 and 42 can be joined by, for example, ultrasonic welding, resistance welding, or the like.
- the negative electrode active material layer 44 is, for example, a paste or slurry composition (negative electrode mixture) in which any of the negative electrode active materials disclosed herein is dispersed in a suitable solvent together with a binder or the like. Is preferably applied to the negative electrode current collector 42, and the composition is dried.
- the amount of the negative electrode active material contained in the negative electrode mixture is not particularly limited, but is preferably about 90 to 99% by mass, more preferably about 95 to 99% by mass.
- a binder it can select from various polymers suitably and can be used. Only one kind may be used alone, or two or more kinds may be used in combination.
- water-soluble polymers such as carboxymethylcellulose (CMC), methylcellulose (MC), cellulose acetate phthalate (CAP), hydroxypropylmethylcellulose (HPMC), hydroxypropylmethylcellulose phthalate (HPMCP), polyvinyl alcohol (PVA); Fluorine such as fluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), ethylene-tetrafluoroethylene copolymer (ETFE), etc.
- CMC carboxymethylcellulose
- MC methylcellulose
- CAP cellulose acetate phthalate
- HPMC hydroxypropylmethylcellulose
- HPMCP hydroxypropylmethylcellulose phthalate
- PVA polyvinyl alcohol
- Resin vinyl acetate copolymer, styrene butadiene block copolymer (SBR), acrylic acid-modified SBR resin (SBR latex), rubbers (such as gum arabic), Dispersible polymers; oil-soluble polymers such as polyvinylidene fluoride (PVDF), polyvinylidene chloride (PVDC), polyethylene oxide (PEO), polypropylene oxide (PPO), polyethylene oxide-propylene oxide copolymer (PEO-PPO); Etc.
- the addition amount of the binder may be appropriately selected according to the type and amount of the negative electrode active material, and can be, for example, about 1 to 5% by mass of the negative electrode mixture.
- a conductive member made of a highly conductive metal is preferably used.
- copper or an alloy containing copper as a main component can be used.
- the shape of the negative electrode current collector 42 may vary depending on the shape of the lithium ion secondary battery and the like, so there is no particular limitation, and various shapes such as a rod shape, a plate shape, a sheet shape, a foil shape, and a mesh shape possible.
- a sheet-like copper negative electrode current collector 42 is used, and can be preferably used for the lithium ion secondary battery 100 including the wound electrode body 20.
- a copper sheet having a thickness of about 6 to 30 ⁇ m can be preferably used.
- the positive electrode active material layer 34 includes, for example, a paste or slurry composition (positive electrode mixture) in which a positive electrode active material is dispersed in an appropriate solvent together with a conductive material, a binder (binder), and the like as necessary. It can preferably be produced by applying to the positive electrode current collector 32 and drying the composition.
- a paste or slurry composition positive electrode mixture
- a positive electrode active material is dispersed in an appropriate solvent together with a conductive material, a binder (binder), and the like as necessary. It can preferably be produced by applying to the positive electrode current collector 32 and drying the composition.
- the positive electrode active material a positive electrode material capable of occluding and releasing lithium is used, and one or more of materials conventionally used in lithium ion secondary batteries (for example, oxides having a layered structure or oxides having a spinel structure) are used.
- materials conventionally used in lithium ion secondary batteries for example, oxides having a layered structure or oxides having a spinel structure
- examples thereof include lithium-containing composite oxides such as lithium nickel composite oxides, lithium cobalt composite oxides, lithium manganese composite oxides, and lithium magnesium composite oxides.
- the lithium nickel-based composite oxide is an oxide having lithium (Li) and nickel (Ni) as constituent metal elements, and at least one other metal element (that is, Li and nickel) in addition to lithium and nickel.
- the metal element other than Li and Ni include, for example, cobalt (Co), aluminum (Al), manganese (Mn), chromium (Cr), iron (Fe), vanadium (V), magnesium (Mg), and titanium (Ti ), Zirconium (Zr), niobium (Nb), molybdenum (Mo), tungsten (W), copper (Cu), zinc (Zn), gallium (Ga), indium (In), tin (Sn), lanthanum (La) And one or more metal elements selected from the group consisting of cerium (Ce).
- an olivine type lithium phosphate represented by the general formula LiMPO 4 (M is at least one element of Co, Ni, Mn, and Fe; for example, LiFePO 4 , LiMnPO 4 ) is used as the positive electrode active material. Also good.
- the amount of the positive electrode active material contained in the positive electrode mixture can be, for example, about 80 to 95% by mass.
- a conductive powder material such as carbon powder or carbon fiber is preferably used.
- carbon powder various carbon blacks such as acetylene black, furnace black, ketjen black, and graphite powder are preferable.
- a conductive material can be used alone or in combination of two or more.
- the amount of the conductive material contained in the positive electrode mixture may be appropriately selected according to the type and amount of the positive electrode active material, and may be, for example, about 4 to 15% by mass.
- the same negative electrode as described above can be used alone or in combination of two or more.
- the addition amount of the binder may be appropriately selected according to the type and amount of the positive electrode active material, and can be, for example, about 1 to 5% by mass of the positive electrode mixture.
- a conductive member made of a metal having good conductivity is preferably used.
- aluminum or an alloy containing aluminum as a main component can be used.
- the shape of the positive electrode current collector 32 may vary depending on the shape of the lithium ion secondary battery, and is not particularly limited, and may be various forms such as a rod shape, a plate shape, a sheet shape, a foil shape, and a mesh shape.
- a sheet-like aluminum positive electrode current collector 32 is used, and can be preferably used for the lithium ion secondary battery 100 including the wound electrode body 20.
- an aluminum sheet having a thickness of about 10 ⁇ m to 30 ⁇ m can be preferably used.
- the nonaqueous electrolytic solution contains a supporting salt in a nonaqueous solvent (organic solvent).
- a lithium salt used as a supporting salt in a general lithium ion secondary battery can be appropriately selected and used.
- the lithium salt include LiPF 6 , LiBF 4 , LiClO 4 , LiAsF 6 , Li (CF 3 SO 2 ) 2 N, LiCF 3 SO 3 and the like.
- These supporting salts can be used alone or in combination of two or more.
- a particularly preferred example is LiPF 6 .
- the nonaqueous electrolytic solution is preferably prepared so that the concentration of the supporting salt is within a range of 0.7 to 1.3 mol / L, for example.
- an organic solvent used for a general lithium ion secondary battery can be appropriately selected and used.
- Particularly preferred non-aqueous solvents include carbonates such as ethylene carbonate (EC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), vinylene carbonate (VC), propylene carbonate (PC) and the like.
- EC ethylene carbonate
- DMC dimethyl carbonate
- EMC ethyl methyl carbonate
- DEC diethyl carbonate
- VC vinylene carbonate
- PC propylene carbonate
- the These organic solvents can be used alone or in combination of two or more.
- a mixed solvent of EC, DMC, and EMC or a solution obtained by adding VC to this can be preferably used.
- the nonaqueous electrolytic solution contains VC.
- the amount of VC added is preferably about 0.1 to 3% by mass (more preferably 0.3 to 1% by mass) of the nonaqueous solvent. According to such a configuration, it is possible to improve the high temperature storage stability while maintaining the upper limit charging current density at a high level.
- the VC has a function of stabilizing a SEI (Solid Electrolyte Interface) film on the negative electrode surface.
- the formation state (uniformity, etc.) of the SEI film is also the crystal on the active material particle surface as described above. Can be affected by the difference in degrees. Therefore, using DR ⁇ 0.2 as an index is also useful for the purpose of stably realizing the high temperature storage stability improvement effect by adding VC. If the amount of VC added is too small, the high temperature storage stability improving effect may not be sufficient. If the amount of VC added is too large, the amount of VC decomposed during high-temperature storage may increase, and the high-temperature storage stability may decrease.
- the separator 50 is a sheet interposed between the positive electrode sheet 30 and the negative electrode sheet 40, and is disposed so as to be in contact with the positive electrode active material layer 34 of the positive electrode sheet 30 and the negative electrode active material layer 44 of the negative electrode sheet 40. . Then, prevention of short circuit due to the contact between the electrode active material layers 34 and 44 in the positive electrode sheet 30 and the negative electrode sheet 40, and the conduction path between the electrodes (conductive path) by impregnating the electrolyte in the pores of the separator 50. ).
- this separator 50 a conventionally well-known thing can be especially used without a restriction
- a porous polyolefin resin sheet such as polyethylene (PE), polypropylene (PP), and polystyrene is preferred.
- PE polyethylene
- PP polypropylene
- polystyrene polystyrene
- a PE sheet, a PP sheet, a multilayer structure sheet in which a PE layer and a PP layer are laminated, and the like can be suitably used.
- the thickness of the separator is preferably set within a range of about 10 ⁇ m to 40 ⁇ m, for example.
- a negative electrode active material composed of a composite carbon body can be selected using DR ⁇ 0.2 as an index.
- a lithium ion secondary battery having certain performance for example, low temperature upper limit charging current density and high temperature storage stability
- Such a negative electrode active material evaluation method can be incorporated, for example, as a part of the quality inspection process in the final stage of the production process of the negative electrode active material made of composite carbon. In the inspection step, other indices (specific surface area, particle size, etc.) may be used in addition to DR ⁇ 0.2 .
- the method further includes an inspection step including at least selecting a negative electrode active material having DR ⁇ 0.2 calculated by the evaluation method of 20% or more.
- a negative electrode active material manufacturing method comprising a composite carbon body is provided.
- a method for producing a lithium ion secondary battery characterized by using a negative electrode including any of the negative electrode active materials disclosed herein. For example, the following steps: (W) grasping DR ⁇ 0.2 ; (X) determining pass / fail; (Y) producing a negative electrode using an acceptable product; and (Z) constructing a battery using the negative electrode; A method for producing a lithium ion secondary battery is provided. In the step (W), DR ⁇ 0.2 may be measured every time, or past measurement results may be applied.
- Example 1 The graphite particles (core material) were subjected to CVD treatment to obtain a negative electrode active material composed of a composite carbon body having a coating amount of 2% and a specific surface area of 1.9 m 2 / g.
- Example 2 Graphite particles (core material) and coating raw material) were kneaded and fired to obtain a negative electrode active material composed of a composite carbon body having a coating amount of 2% and a specific surface area of 2 m 2 / g.
- Example 3 Graphite particles (core material) and coating raw material) were kneaded and fired to obtain a negative electrode active material composed of a composite carbon body having a coating amount of 2% and a specific surface area of 3.6 m 2 / g.
- Example 4 The graphite particles (core material) were subjected to a CVD treatment to obtain a negative electrode active material composed of a composite carbon body having a coating amount of 2% and a specific surface area of 3.6 m 2 / g.
- Example 5 Graphite particles (core material) and coating raw material) were kneaded and fired to obtain a negative electrode active material composed of a composite carbon body having a coating amount of 2% and a specific surface area of 3.7 m 2 / g.
- Example 6 The graphite particles (core material) were subjected to CVD treatment to obtain a negative electrode active material composed of a composite carbon body having a coating amount of 2% and a specific surface area of 4.2 m 2 / g.
- Example 7 A negative electrode active material composed of a composite carbon body having a coating amount of 2% and a specific surface area of 4.3 m 2 / g was obtained.
- Example 8 A negative electrode active material composed of a composite carbon body having a coating amount of 2% and a specific surface area of 4.5 m 2 / g was obtained.
- Example 9 A negative electrode active material composed of a composite carbon body having a coating amount of 2% and a specific surface area of 5.3 m 2 / g was obtained.
- Example 10 A negative electrode active material composed of a composite carbon body having a coating amount of 2% and a specific surface area of 6.2 m 2 / g was obtained.
- Example 11 A negative electrode active material composed of a composite carbon body having a coating amount of 2% and a specific surface area of 6.3 m 2 / g was obtained.
- Example 12 A negative electrode active material composed of a composite carbon body having a coating amount of 2% and a specific surface area of 6.3 m 2 / g was obtained.
- Example 13 A negative electrode active material composed of a composite carbon body having a coating amount of 2% and a specific surface area of 8.1 m 2 / g was obtained.
- Example 14 A negative electrode active material composed of a composite carbon body having a coating amount of 2% and a specific surface area of 8.9 m 2 / g was obtained.
- Example 15 A negative electrode active material composed of a composite carbon body having a coating amount of 2% and a specific surface area of 9.9 m 2 / g was obtained.
- Example 16 The same negative electrode active material as in Example 7 was prepared.
- Example 17 The same negative electrode active material as in Example 8 was prepared.
- Example 18 The same negative electrode active material as in Example 12 was prepared.
- Example 19 The same negative electrode active material as in Example 13 was prepared.
- the specific surface area of each of the negative electrode active materials was measured by a nitrogen adsorption method using a specific surface area measuring device (manufactured by Mounttech, model “Macsorb HM model-1200”).
- a laminate cell type battery and an 18650 type battery (cylindrical type having a diameter of 18 mm and a height of 65 mm) were prepared according to the following procedure.
- a negative electrode active material As a negative electrode mixture, a negative electrode active material, SBR, and CMC are mixed with ion-exchanged water so that the mass ratio thereof is 98: 1: 1 and NV is 45% to prepare a slurry composition. did.
- This negative electrode mixture was applied to both sides of a copper foil having a thickness of 10 ⁇ m so that the total coating amount on both sides was 8 mg / cm 2 . This was dried and then pressed to prepare a negative electrode sheet.
- This negative electrode sheet was cut into a 5 cm ⁇ 5 cm square shape with a 10 mm wide strip-like portion attached to one corner. The coated material was removed from both sides of the belt-like portion, the copper foil was exposed to form a terminal portion, and a negative electrode sheet with a terminal portion was obtained.
- LiNi 1/3 Co 1/3 Mn 1/3 O 2 , acetylene black (AB), and polyvinylidene fluoride (PVDF) have a mass ratio of 85: 10: 5 and A slurry composition was prepared by mixing with N-methyl-2-pyrrolidone (NMP) so that NV was 50%. This composition was applied to both surfaces of an aluminum foil having a thickness of 15 ⁇ m so that the total coating amount on both surfaces was 16.7 mg / cm 2 (based on solid content). This was dried and pressed to produce a positive electrode sheet. This positive electrode sheet was processed into the same size and shape as the negative electrode sheet to obtain a positive electrode sheet with terminal portions.
- NMP N-methyl-2-pyrrolidone
- non-aqueous electrolytes of Examples 1 to 15 a LiPF 6 solution having a concentration of 1 mol / L (1M) prepared using a mixed solvent of EC, DMC and EMC in a volume ratio of 1: 1: 1 was used.
- 1M LiPF 6 solution using 100 parts of the above mixed solvent with 0.5 part of VC added as a solvent was used.
- the positive electrode sheet and the negative electrode sheet are laminated so that a porous polyethylene sheet having a thickness of 2.5 ⁇ m is interposed, and both terminal portions are arranged symmetrically at both ends of one side, and a part of both terminal portions is Covered with laminate film to expose.
- the above non-aqueous electrolyte was poured into this, and the film was sealed to construct a laminated cell type battery having a capacity of 45 mAh.
- the negative electrode mixture was applied to both sides of a long copper foil having a thickness of 10 ⁇ m so that the total coating amount on both sides was 8 mg / cm 2 (NV standard). After drying this, it was pressed so that the total thickness was about 65 ⁇ m to obtain a negative electrode sheet.
- the positive electrode mixture was applied to both surfaces of a 15 ⁇ m thick long aluminum foil so that the total coating amount on both surfaces was 24 mg / cm 2 (NV standard). This was dried and then pressed so as to have a total thickness of about 84 ⁇ m to obtain a positive electrode sheet.
- These negative electrode sheet and positive electrode sheet were laminated together with two long porous polyethylene sheets, and the laminate was wound in the longitudinal direction.
- the obtained wound electrode body is housed in a cylindrical container together with the above non-aqueous electrolyte (Examples 16 to 19 only contain VC), the container is sealed, and the 18650 battery 200 having a capacity of 800 mAh (FIG. 7). ) was built.
- Each battery is charged with a constant current (CC) for 3 hours at a rate of 1/10 C, then charged to 4.1 V at a rate of 1/3 C, and 3.0 V at a rate of 1/3 C. The operation of discharging until 3 times was repeated.
- 1C points out the electric current value which can be fully charged / discharged in 1 hour.
- Each battery is CC charged at a temperature of 25 ° C. at a rate of 1 C until the voltage between the terminals reaches 4.1 V, followed by constant voltage (CV) charging until the total charging time reaches 2.5 hours. It was. After 10 minutes from the completion of charging, CC discharge was performed at a rate of 0.33 C from 4.1 V to 3.0 V at the same temperature, and then CV discharge was performed until the total discharge time was 4 hours. The discharge capacity at this time was measured as the initial capacity of each battery.
- Each battery whose initial capacity was measured was CC charged at a rate of 1 C until the terminal voltage reached 4.1 V, and then CV charged until the SOC reached 60%.
- the battery was sandwiched between two plates and restrained to a state where a 350 kgf load was applied.
- CC charge was performed at 0 ° C. for 10 seconds at a current density of 14.0 mA / cm 2 (obtained by dividing the applied current value by the electrode area).
- CC discharge was performed for 10 seconds at a current density of 14.0 mA / cm 2 and rested for 10 minutes.
- the discharge capacity was measured in the same manner as the initial capacity measurement.
- the current density was increased by 1.2 mA / cm 2 every 250 cycles, and the discharge capacity after 250 cycles at each current density was measured.
- the capacity retention rate %, the percentage of the discharge capacity after each cycle with respect to the initial capacity was determined. The measurement was terminated when the capacity retention rate decreased by 3% or more compared to the value after the previous cycle, and the current density in the cycle immediately before the cycle where the final measurement was performed was defined as the upper limit charging current density. .
- Table 2 shows the measurement results of the negative electrode active materials and batteries of Examples 1 to 19.
- Example 1 in which DR ⁇ 0.2 was 20% or more was compared with Example 2 in which DR ⁇ 0.2 was less than 20%.
- the upper limit charging current density and high temperature storage were both high.
- Example 1 was 23% higher than Example 2.
- Example 4 in which DR ⁇ 0.2 is 20% or more is higher than Examples 3 and 5 in which DR ⁇ 0.2 is less than 20%.
- Both high temperature storage stability and high temperature storage were high.
- the specific surface areas of Examples 6 and 7 were substantially the same, but the upper limit charging current density was higher in Example 6 in which DR ⁇ 0.2 was 20% or more than in Example 7 in which DR ⁇ 0.2 was less than 20%.
- the high temperature storage stability was high.
- the upper limit charging current density of Example 6 was 22% higher than Example 7.
- Examples 1 to 19 Examples 6, 8 to 14, and 17 to 19 having a specific surface area in the range of 4 to 9 m 2 / g and DR ⁇ 0.2 of 20% or more are the upper limit charging current.
- the density was 20 mA / cm 2 (44% of the battery capacity) or more, and the capacity retention rate after storage was 80% or more. Both characteristics were realized in a highly balanced manner. Further, when Examples 16 to 19 with VC addition and Examples 7, 8, 12, and 13 without VC addition corresponding thereto were compared, DR ⁇ 0.2 was less than 20% (Example 7). 16), the addition of VC improved the high-temperature storage stability, but resulted in a decrease in the upper limit charging current density.
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Abstract
Description
この評価方法は、下記工程(A)~(D):
(A)かかる負極活物質のサンプルに対し、波長532nmにて顕微ラマン分析をn回行うこと(ここで、nは20以上である);
(B)各回の顕微ラマン分析によって得られたラマンスペクトルについて、Dバンドの強度IDとGバンドの強度IGとの比の値R(ID/IG)を求めること;
(C)Rの値が0.2以上であった分析回数mを求めること;および、
(D)R値0.2以上の分布割合(DR≧0.2)として、総分析回数nに対するmの割合(m/n)を求めること;
を包含する。
核材とコート原料との混合割合は、適用するコーティング法に応じ、適当な後処理(不純物や未反応物の除去等)を行った後のコート量が上記範囲となるように適宜選択すればよい。
例えば、カルボキシメチルセルロース(CMC)、メチルセルロース(MC)、酢酸フタル酸セルロース(CAP)、ヒドロキシプロピルメチルセルロース(HPMC)、ヒドロキシプロピルメチルセルロースフタレート(HPMCP)、ポリビニルアルコール(PVA)等の、水溶性ポリマー;ポリテトラフルオロエチレン(PTFE)、テトラフルオロエチレン-パーフルオロアルキルビニルエーテル共重含体(PFA)、テトラフルオロエチレン-ヘキサフルオロプロピレン共重合体(FEP)、エチレン-テトラフルオロエチレン共重合体(ETFE)等のフッ素系樹脂、酢酸ビニル共重合体、スチレンブタジエンブロック共重合体(SBR)、アクリル酸変性SBR樹脂(SBR系ラテックス)、ゴム類(アラビアゴム等)等の、水分散性ポリマー;ポリフッ化ビニリデン(PVDF)、ポリ塩化ビニリデン(PVDC)、ポリエチレンオキサイド(PEO)、ポリプロピレンオキサイド(PPO)、ポリエチレンオキサイド-プロピレンオキサイド共重合体(PEO-PPO)等の、油溶性ポリマー;等が挙げられる。
結着剤の添加量は、負極活物質の種類や量に応じて適宜選択すればよく、例えば、上記負極合材の1~5質量%程度とすることができる。
ここで、リチウムニッケル系複合酸化物とは、リチウム(Li)とニッケル(Ni)とを構成金属元素とする酸化物のほか、リチウムおよびニッケル以外に他の少なくとも一種の金属元素(すなわち、LiとNi以外の遷移金属元素および/または典型金属元素)を、原子数換算でニッケルと同程度またはニッケルよりも少ない割合(典型的にはニッケルよりも少ない割合)で構成金属元素として含む酸化物をも包含する意味である。上記LiおよびNi以外の金属元素は、例えば、コバルト(Co)、アルミニウム(Al)、マンガン(Mn)、クロム(Cr)、鉄(Fe)、バナジウム(V)、マグネシウム(Mg)、チタン(Ti)、ジルコニウム(Zr)、ニオブ(Nb)、モリブデン(Mo)、タングステン(W)、銅(Cu)、亜鉛(Zn)、ガリウム(Ga)、インジウム(In)、スズ(Sn)、ランタン(La)およびセリウム(Ce)からなる群から選択される一種または二種以上の金属元素であり得る。なお、リチウムコバルト系複合酸化物、リチウムマンガン系複合酸化物およびリチウムマグネシウム系複合酸化物についても同様の意味である。
また、一般式がLiMPO4(MはCo、Ni、Mn、Feのうちの少なくとも一種以上の元素;例えばLiFePO4、LiMnPO4)で表記されるオリビン型リン酸リチウムを上記正極活物質として用いてもよい。
正極合材に含まれる正極活物質の量は、例えば、80~95質量%程度とすることができる。
正極合材に含まれる導電材の量は、正極活物質の種類や量に応じて適宜選択すればよく、例えば、4~15質量%程度とすることができる。
(W)DR≧0.2を把握すること;
(X)合否を判定すること;
(Y)合格品を用いて負極を作製すること;および、
(Z)その負極を用いて電池を構築すること;
を包含するリチウムイオン二次電池製造方法が提供される。なお、上記(W)工程では、DR≧0.2を毎回測定してもよく、過去の測定結果を適用してもよい。
黒鉛粒子(核材)にCVD処理を施して、コート量2%、比表面積1.9m2/gの複合炭素体からなる負極活物質を得た。
黒鉛粒子(核材)とコート原料)とを混練・焼成して、コート量2%、比表面積2m2/gの複合炭素体からなる負極活物質を得た。
黒鉛粒子(核材)とコート原料)とを混練・焼成して、コート量2%、比表面積3.6m2/gの複合炭素体からなる負極活物質を得た。
黒鉛粒子(核材)にCVD処理を施して、コート量2%、比表面積3.6m2/gの複合炭素体からなる負極活物質を得た。
黒鉛粒子(核材)とコート原料)とを混練・焼成して、コート量2%、比表面積3.7m2/gの複合炭素体からなる負極活物質を得た。
黒鉛粒子(核材)にCVD処理を施して、コート量2%、比表面積4.2m2/gの複合炭素体からなる負極活物質を得た。
コート量2%、比表面積4.3m2/gの複合炭素体からなる負極活物質を得た。
コート量2%、比表面積4.5m2/gの複合炭素体からなる負極活物質を得た。
コート量2%、比表面積5.3m2/gの複合炭素体からなる負極活物質を得た。
コート量2%、比表面積6.2m2/gの複合炭素体からなる負極活物質を得た。
コート量2%、比表面積6.3m2/gの複合炭素体からなる負極活物質を得た。
コート量2%、比表面積6.3m2/gの複合炭素体からなる負極活物質を得た。
コート量2%、比表面積8.1m2/gの複合炭素体からなる負極活物質を得た。
コート量2%、比表面積8.9m2/gの複合炭素体からなる負極活物質を得た。
コート量2%、比表面積9.9m2/gの複合炭素体からなる負極活物質を得た。
例7と同じ負極活物質を用意した。
例8と同じ負極活物質を用意した。
例12と同じ負極活物質を用意した。
例13と同じ負極活物質を用意した。
[顕微ラマン分析]
各例の負極活物質サンプル0.1mgに対し、顕微レーザーラマンシステム(サーモフィッシャーサイエンティフィック株式会社製、型式「Nicolet Almega XR」)を用い、波長532nm、測定時間30秒、分解能2μm、レーザー出力レベル100%にて、顕微ラマン分析を125回行い、各回におけるR値を求めた。DR≧0.2として、総分析回数に対するR値0.2以上の回数の百分率を算出した。例12に係る顕微ラマン分析結果について、100回までのR値分布およびDR≧0.2を表1に示す。
上記各負極活物質の比表面積は、比表面積測定装置(Mountech社製、型式「Macsorb HM model-1200」)を用いて、窒素吸着法により測定した。
負極合材として、負極活物質とSBRとCMCとを、これらの質量比が98:1:1であり且つNVが45%となるようにイオン交換水と混合して、スラリー状組成物を調製した。この負極合材を、厚さ10μmの銅箔の両面に、それら両面の合計塗布量が8mg/cm2となるように塗布した。これを乾燥後プレスして負極シートを作製した。この負極シートを、一角に幅10mmの帯状部が付いた5cm×5cmの正方形状に切り出した。この帯状部の両面から上記塗布物を除去し、銅箔を露出させて端子部を形成し、端子部付負極シートを得た。
上記正極シートと負極シートとを、厚さ2.5μmの多孔質ポリエチレンシートを介在させ、両端子部が一辺の両端に対称的に配置されるように積層し、これら両端子部の一部が露出するようにラミネートフィルムで覆った。これに上述の非水電解液を注入し、該フィルムを封止して容量が45mAhのラミネートセル型電池を構築した。
上記負極合材を、厚さ10μmの長尺状銅箔の両面に、それら両面の合計塗布量が8mg/cm2(NV基準)となるように塗布した。これを乾燥後、全体の厚さが約65μmとなるようにプレスして負極シートを得た。
上記正極合材を、厚さ15μmの長尺状アルミニウム箔の両面に、それら両面の合計塗布量が24mg/cm2(NV基準)となるように塗布した。これを乾燥後、全体の厚さが約84μmとなるようにプレスして正極シートを得た。
これら負極シートおよび正極シートを2枚の長尺状多孔質ポリエチレンシートとともに積層し、その積層体を長手方向に捲回した。得られた捲回電極体を、上述の非水電解液(例16~19のみVC入り)とともに円筒型容器に収容し、該容器を封止して容量が800mAhの18650型電池200(図7)を構築した。
各電池に対して、1/10Cのレートで3時間の定電流(CC)充電を行い、次いで、1/3Cのレートで4.1Vまで充電する操作と、1/3Cのレートで3.0Vまで放電させる操作とを3回繰り返した。なお、1Cは、1時間で満充放電できる電流値を指す。
各電池を、温度25℃にて、1Cのレートで端子間電圧が4.1VになるまでCC充電を行い、続いて合計充電時間が2.5時間になるまで定電圧(CV)充電を行った。充電完了から10分休止した後、同温度にて、4.1Vから3.0Vまで0.33CのレートでCC放電を行い、続いて合計放電時間が4時間となるまでCV放電を行った。このときの放電容量を各電池の初期容量として測定した。
初期容量を測定した各電池に対して、1Cのレートで端子間電圧が4.1VとなるまでCC充電し、次いでSOC60%となるまでCV充電をおこなった。該電池を、二枚の板で挟み、350kgfの負荷がかかる状態に拘束した。これに対し、1回目の充放電サイクルとして、0℃にて、14.0mA/cm2の電流密度(適用した電流値を電極面積で除して求められる。)で10秒間CC充電し、10分間休止した後、14.0mA/cm2の電流密度で10秒間CC放電し、10分間休止した。このサイクルを250サイクル繰り返した後、上記初期容量の測定と同様にして放電容量を測定した。
250サイクルごとに、電流密度を1.2mA/cm2ずつ増加させ、各電流密度における250サイクル後の放電容量を測定した。
容量維持率(%)として、初期容量に対する各サイクル後の放電容量の百分率を求めた。この容量維持率が一つ前のサイクル後の値と比べて3%以上低下した時点で測定を終了し、最終測定を行ったサイクルの一つ前のサイクルにおける電流密度を上限充電電流密度とした。
コンディショニング後SOC80%に調整した各例の18650型電池を、室温(23℃)にて、SOCが0%となるまで1/3CのレートでCC放電させ、このときの放電容量を初期容量として測定した。次いで、1/3CのレートでSOC80%に再調整し、60℃で30日間保存した後、初期容量の測定と同様にして保存後の放電容量を測定した。容量維持率(%)として、初期容量に対する保存後の放電容量の百分率を求めた。
例1~19のうち、比表面積が4~9m2/gの範囲にあり、且つDR≧0.2が20%以上であった例6,8~14,17~19は、上限充電電流密度が20mA/cm2(電池容量の44%)以上、且つ保存後の容量維持率が80%以上と、両特性をより高度にバランスよく実現するものであった。
また、VC添加ありの例16~19と、これらに対応するVC添加なしの例7,8,12,13とを比べると、DR≧0.2が20%未満であった場合(例7,16)では、VC添加により、高温保存性は向上したものの、上限充電電流密度が低下してしまう結果となった。これに対し、DR≧0.2が20%以上の場合(例8,17;例12,18;例13,19)では、VC添加により、上限充電電流密度を低下させることなく、高温保存性を向上させることができた。
20 捲回電極体
30 正極シート
32 正極集電体
34 正極活物質層
38 正極端子
40 負極シート
42 負極集電体
44 負極活物質層
48 負極端子
50 セパレータ
100,200 リチウムイオン二次電池
Claims (6)
- 高結晶性炭素質粒子の表面に低結晶性炭素材料を少なくとも部分的に有する複合炭素体を、負極活物質として評価する方法であって、
前記負極活物質のサンプルに対し、波長532nmにて顕微ラマン分析をn回行うこと(ここで、nは20以上である)、
各回の顕微ラマン分析によって得られたラマンスペクトルについて、Dバンドの強度IDとGバンドの強度IGとの比の値R(ID/IG)を求めること、
Rの値が0.2以上であった分析回数mを求めること、および、
R値0.2以上の分布割合(DR≧0.2)として、nに対するmの割合(m/n)を求めること、
を包含する、負極活物質評価方法。 - 高結晶性炭素粒子表面に低結晶性炭素被膜を有する複合炭素体からなる負極活物質であって、請求項1記載の方法により求められるR値0.2以上の分布割合が20%以上であることを特徴とする、負極活物質。
- さらに、窒素吸着比表面積が4~9m2/gの範囲にあることを特徴とする、請求項2に記載の負極活物質。
- 請求項2または3に記載の負極活物質を有する負極と、正極活物質を有する正極と、非水電解液と、を備えるリチウムイオン二次電池。
- 前記非水電解液が、ビニレンカーボネートを含むことを特徴とする、請求項4に記載のリチウムイオン二次電池。
- 請求項4または5に記載のリチウムイオン二次電池を備える、車両。
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WO2014083870A1 (ja) * | 2012-11-29 | 2014-06-05 | 日本電気株式会社 | リチウムイオン二次電池の負極活材の品質管理方法、リチウムイオン二次電池の負極の製造方法、リチウムイオン二次電池の製造方法、リチウムイオン二次電池の負極及びリチウムイオン二次電池 |
KR101816400B1 (ko) | 2016-05-12 | 2018-01-09 | 에스케이이노베이션 주식회사 | 이차전지용 활물질의 평가방법 |
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KR101640937B1 (ko) * | 2009-11-13 | 2016-07-20 | 삼성에스디아이 주식회사 | 리튬 이차 전지 |
WO2011145178A1 (ja) * | 2010-05-18 | 2011-11-24 | トヨタ自動車株式会社 | 負極活物質 |
JP5517007B2 (ja) * | 2010-08-05 | 2014-06-11 | トヨタ自動車株式会社 | リチウムイオン二次電池 |
JPWO2015011937A1 (ja) * | 2013-07-25 | 2017-03-02 | 三井金属鉱業株式会社 | リチウムイオン電池用硫化物系固体電解質 |
EP3285316B1 (en) * | 2015-04-16 | 2019-12-11 | Kureha Corporation | Electrode structure and method for manufacturing same |
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