Classifications

• • 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
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
  • C01G53/00—Compounds of nickel
  • C01G53/40—Nickelates
  • C01G53/42—Nickelates containing alkali metals, e.g. LiNiO2
  • C01G53/44—Nickelates containing alkali metals, e.g. LiNiO2 containing manganese
  • C01G53/50—Nickelates containing alkali metals, e.g. LiNiO2 containing manganese of the type [MnO2]n-, e.g. Li(NixMn1-x)O2, Li(MyNixMn1-x-y)O2
• • H—ELECTRICITY
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  • 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
  • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
  • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
  • H01M10/0566—Liquid materials
  • H01M10/0568—Liquid materials characterised by the solutes
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  • H01M10/05—Accumulators with non-aqueous electrolyte
  • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
  • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
  • H01M10/0566—Liquid materials
  • H01M10/0569—Liquid materials characterised by the solvents
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  • H01M10/058—Construction or manufacture
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  • 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
  • H01M10/44—Methods for charging or discharging
  • H01M10/446—Initial charging measures
• • 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
• • 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
  • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
• • H—ELECTRICITY
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  • 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
  • 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
  • H01M4/1391—Processes of manufacture of electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
• • H—ELECTRICITY
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  • 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
  • H01M4/1393—Processes of manufacture of electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
• • H—ELECTRICITY
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  • 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
  • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
  • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
  • H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
• • H—ELECTRICITY
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  • 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
  • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
  • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
  • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
• • 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
• • 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
• • 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
  • H01M4/623—Binders being polymers fluorinated polymers
• • 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
  • H01M4/624—Electric conductive fillers
  • H01M4/625—Carbon or graphite
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2004/00—Particle morphology
  • C01P2004/01—Particle morphology depicted by an image
  • C01P2004/03—Particle morphology depicted by an image obtained by SEM
• • H—ELECTRICITY
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  • 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
  • H01M2010/4292—Aspects relating to capacity ratio of electrodes/electrolyte or anode/cathode
• • 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
• • 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 invention relates to the general field of lithium-ion rechargeable batteries.
• the invention relates to rechargeable lithium - ion batteries comprising a lithium rich positive electrode material and a graphite - based negative electrode material.
• the invention also relates to a method for preparing lithium-ion batteries comprising such electrodes.
• the invention relates to a method for cycling lithium-ion batteries comprising such electrodes, with moderate capacities making it possible to improve the life of a lithium-ion battery cell.
• the Li-ion batteries comprise one or more positive electrode (s), one or more negative electrode (s), an electrolyte and a separator composed of a porous polymer or any other suitable material so to avoid any direct contact between the electrodes.
• Li-ion batteries are increasingly being used as an autonomous power source, particularly in applications related to electric mobility. This trend can be explained in particular by densities of mass and volumetric energy which are much higher than those of conventional nickel cadmium (Ni-Cd) and nickel-metal hydride (Ni-MH) accumulators, an absence of memory effect, a self-discharge low compared to other accumulators and also by a drop in costs per kilowatt hour related to this technology.
• Ni-Cd nickel cadmium
• Ni-MH nickel-metal hydride
• Carbon based materials in particular graphite, have been successfully developed and widely marketed as electrochemically active negative electrode materials for Li-ion batteries. These materials are particularly effective because of their structure conducive to intercalation and deintercalation lithium and their stability during different charging and discharging cycles.
• Li-ion batteries comprising negative electrode graphite materials are generally designed so that the reversible capacitance (N) of the negative electrode is greater than the reversible capacitance (P) of the positive electrode (P. Arora, RE White, Capacity fade mechanism and side reactions in lithium-ion batteries, J. Electrochem Soc, Vol 145 (1998) 3647-3667, B. Son, M.-H. Ryou, J. Choi, S. Kim, JM Ko, YM Lee, Effect of cathode / anode area on the electrochemical performance of lithium-ion batteries, J. Power Sources, Vol 243 (2013) 641-647, Y. Li, M. Bettge, B. Polzin, Y. Zhu, M. Balasubramanian, DP Abraham Understanding Long-Term Cycling Performance of
• the batteries thus designed have a N / P ratio> 1 (1.05 - 1.3).
• excess graphite is placed in the cell to prevent lithium plating to the negative electrode during charging and discharging cycles which results in degradation of the battery.
• this excess graphite leads to a decrease in the specific energy density of the cell.
• batteries having N / P ratios ⁇ 1 have been designed comprising a lithium titanate (Li 4 TisOi 2, LTO) negative electrode material as described in US2009 / 0035662, US2011 / 0281148 and US2013 / 164584.
• Li 4 TisOi 2, LTO lithium titanate
• the LTO-based material is a negative electrode material well known to those skilled in the art which has several specific characteristics. When it is of spinel structure, it has a high operating voltage of about 1.5 V and a theoretical low specific capacitance of 175 mAh / g. With respect to the graphite which has an operating voltage of approximately 0.15 V and a theoretical specific capacity of 372 mAh / g, the LTO-based material therefore has a reduced energy density. Thanks to the tension Because of the high operating efficiency and because of the absence of SEI layer on the surface of this electrode, there is no risk of lithium plating on the surface of the LTO material. On the other hand, the lithiation of graphite can lead to a deposition of metallic lithium during the formation of the "SEI" layer. Thus, it is not possible to design batteries having a N / P ratio ⁇ 1 when the material of the negative electrode is based on graphite.
• the LTO material is generally used as a nanoscale material to achieve high lithium intercalation / deintercalation kinetics. High power applications are thus appropriate but the associated cost is high.
• graphite is used as a micron or submicron size material and is generally less expensive than the LTO material.
• Li-ion batteries Another problem with Li-ion batteries is the ability of said batteries to withstand the repetition of charging and discharging cycles that involve deep discharge, ie, close to 0 volt (V). These charge and deep discharge cycles can decrease the full accessible capacity of said batteries. For example, a battery that has an initial charge of 3 V can, after 150 cycles of charge and deep discharge, have a full accessible capacity significantly lower than the initial capacity.
• SEI Solid Electrolyte Interphase
• Li-ion battery cell comprising electrode materials that both avoids the problems of lithium plating and increases the resistance to capacitance loss.
• the term "lithium-rich positive electrode material" is intended to mean any lamellar oxide of general formula:
• the invention also relates to a method for preparing Li-ion batteries according to the invention.
• the subject of the invention is a particular cycling method for the batteries according to the invention.
• FIG. 1 compares the specific discharge capacities of Li-ion battery cells having different N / P ratios as a function of the number of charge and discharge cycles
• FIG. 2 represents a scanning electron microscope micrograph of a lithium-rich material for a positive electrode
• FIG. 3 also shows a scanning electron microscope micrograph of a lithium-rich material for a positive electrode
• FIG. 4 shows a scanning electron micrograph of a graphite-based material for negative electrode.
• Li-ion batteries generally include a positive electrode, a negative electrode, a separator between the electrodes and an electrolyte comprising lithium ions.
• the lithium ions move towards the negative electrode by passing through a separator.
• the same ions move from the negative electrode to the positive electrode again through a separator.
• the Li-ion battery according to the invention comprises a lithium-rich positive electrode material.
• Said electrode material A lithium-rich positive comprises an active material which is generally a lithiated metal oxide selected from nickel, cobalt and / or manganese and optionally another doping metal.
• the lithium-rich positive electrode material may also include carbon fibers.
• these are vapor phase growth carbon fibers (VGCF for "Vapor Grown Carbon Fibers") marketed by the company Showa Denko.
• VGCF vapor phase growth carbon fibers
• Other types of suitable carbon fibers may be carbon nanotubes, doped nanotubes (possibly graphite), carbon nanofibers, doped nano fibers (possibly graphite), carbon nanotubes single sheets or nanotubes multi-walled carbon. Synthetic methods for these materials may include arc discharge, laser ablation, plasma torch, and chemical vapor phase decomposition.
• the lithium-rich positive electrode material may further comprise one or more binders.
• the binder (s) may be chosen from polybutadiene-styrene latices and organic polymers, and preferably from polybutadiene-styrene latices, polyesters, polyethers, methylmethacrylate polymer derivatives, polymeric derivatives and the like. acrylonitrile, methylcellulose carboxyl and its derivatives, polyvinyl acetates or polyacrylate acetate, polyvinylidene fluorides, and mixtures thereof.
• the Li-ion battery according to the invention comprises a negative electrode material based on graphite.
• the graphite carbon may be chosen from synthetic graphite carbons, and natural from natural precursors followed by a purification and / or a post treatment.
• Other active carbon materials may be used such as pyrolytic carbon, amorphous carbon, activated carbon, coke, coal tar pitch and graphene. Mixtures of graphite with one or more of these materials are possible.
• Materials having a core - shell structure may be used when the core comprises high capacity graphite and when the shell comprises a carbon - based material protecting the core from degradation due to the repeated phenomenon of intercalation / deintercalation of lithium ions. .
• the graphite negative electrode material may further comprise one or more binders as for the positive electrode.
• the binders described above for the positive electrode can be used for the negative electrode.
• the Li-ion battery according to the invention also comprises a separator located between the electrodes. It plays the role of electrical insulator. Several materials can be used as separators.
• the separators are generally composed of porous polymers, preferably polyethylene and / or polypropylene.
• the Li-ion battery according to the invention also comprises an electrolyte, preferably a liquid.
• This electrolyte generally comprises one or more lithium salts and one or more solvents.
• the lithium salt or salts generally comprise inert anions.
• Suitable lithium salts may be selected from lithium bis [(trifluoromethyl) sulfonyl] imide (LiN (CF 3 S 0 2 ) 2 ), lithium trifluoromethanesulfonate (LiCF 3 SO 3 ), bis (oxalato) borate lithium (LiBOB), lithium difluoro (oxolato) borate (LiDFOB), lithium bis (perfluoroethylsulfonyl) imide (LiN (CF 3 CF 2 SiO 2 ) 2 ), LiClO 4 , LiAsF 6 , LiPF 6 , LiBF 4, Lil, LiCH 3 S0 3, LiB (C 2 0 4) 2, LiR F SOSR F, LiN (R F S 0 2) 2, liC (R F S0 2) 3, R F is a group selected from fluorine atom and a perfluoroalkyl group having between one and
• the lithium salt or salts are preferably dissolved in one or more solvents chosen from aprotic polar solvents, for example ethylene carbonate (denoted “EC”), propylene carbonate, dimethyl carbonate, diethyl carbonate (denoted “DEC”) and methyl and ethyl carbonate.
• aprotic polar solvents for example ethylene carbonate (denoted “EC”), propylene carbonate, dimethyl carbonate, diethyl carbonate (denoted “DEC”) and methyl and ethyl carbonate.
• the invention also relates to a method for preparing Li-ion batteries according to the invention, comprising the following steps:
• Q + rev is the reversible surface capacity of the positive electrode (mAh / cm 2 );
• L denotes the density of active material for the negative electrode (mg / cm);
• L denotes the density of active material for the positive electrode (mg / cm 2 );
• Q ' rev.spe refers to the specific reversible capacity of the negative electrode (mAh / mg);
• Q rev.spe designates the specific reversible capacitance of the positive electrode (mAh / mg),
• N / P 1, a material for positive electrode rich in lithium as defined above, on a current collector;
• a method for preparing Li-ion batteries according to the invention comprises the following steps:
• the invention also relates to a particular cycling method of a Li-ion battery according to the invention comprising the following steps:
• the cycles being carried out at a capacity of between C / 20 and C, C denoting the capacity of the Li-ion battery.
• the first activation cycle is at a capacity of C / 10.
• the following charging and discharging cycles occur at a capacitance of C / 2.
• a high voltage is used during the activation cycle.
• This "overvoltage” can be likened to an additional capacity of the lithium-rich positive electrode material.
• Said material is used as a “sacrificed lithium” material in this step to form SEI ("Solid Electrolyte Interphase") on the graphite-based negative electrode active material.
• An active material for lithium rich positive electrode is provided by Umicore and has the formula Lii i2 Mno, 5Nio, 2Coo, i 0 2.
• the positive electrode is prepared by mixing 86% by weight of active material, 3% by weight of Super P® carbon additive, 3% by weight of carbon fiber (VGCF) and 8% by weight of dissolved polyvinylidene fluoride. in N-methyl-2-pyrrolidone (NMP).
• Two types of electrode are prepared, one for comparison and one according to the invention.
• the two electrodes are manufactured by depositing the mixture respectively on an aluminum sheet 20 ⁇ thick.
• the electrodes are dried and calendered at 80 ° C so that they each have a porosity of 35%.
• Figures 2 and 3 show snapshots with a scanning electron microscope of the positive electrode thus manufactured. Preparation of the negative electrode
• Active graphite material is provided by Hitachi (SMGHE2). Two types of electrode are prepared, one for comparison and one according to the invention, by mixing 96% by weight of graphite, 2% by weight of carboxyl methyl cellulose (CMC) and 2% by weight of Styrofan latex, c. that is, a carboxylated styrene-butadiene copolymer.
• CMC carboxyl methyl cellulose
• Styrofan latex c. that is, a carboxylated styrene-butadiene copolymer.
• the resulting mixture is respectively deposited on a copper sheet 15 ⁇ thick and then dried and compressed by calendering at 80 ° C.
• the negative electrodes thus manufactured each have a porosity of 43%.
• the density of electrode material is 4.46 mg / cm 2
• FIG. 4 represents a scanning electron microscope photograph of the positive electrode thus produced.
• Table 1 shows that the positive electrode is designed such that a specific reversible surface capacitance of 1.25 mAh / cm 2 is measured. A specific reversible surface capacitance of 1.58 mAh / cm 2 is measured for the negative electrode.
• Table 1 shows that the positive electrode is designed such that a specific reversible surface capacitance of 1.77 mAh / cm 2 is measured. A specific reversible surface capacity of 1.77 mAh / cm 2 is measured for the negative electrode.
• the Celgard® 2500 separator is used to prevent short circuits between the positive electrode and the negative electrode during charging and discharging cycles.
• the area of this separator is 16 cm 2 .
• the electrolyte used is a mixture of ethylene carbonate, methyl ethyl carbonate and dimethyl carbonate (EC / EMC / DMC) in a ratio 1/1/1 by volume with the lithium salt LiPF 6 at 1M.
• the Celgard® 2500 separator is a microporous single-layer membrane with a thickness of 25 ⁇ made of polypropylene.
• FIG. 1 shows a graph comparing the specific discharge capacities of three Li-ion battery cells each comprising a lithium-rich positive electrode material and a graphite-based negative electrode material. with different N / P ratios depending on the number of charge and discharge cycles.
• FIG. 1 clearly shows that the electrochemical behavior (curve A) is very unstable with respect to the cell of the battery A. A drop in electrochemical performance is observed and a specific discharge capacity of about 100 mAh / g is measured after about 150 cycles.
• Figure 1 shows on the other hand that the electrochemical performances (curves B and C respectively) of the cells of the battery B and the battery C are similar after about 1 80 cycles. Indeed, a specific discharge capacity of about 150 mAh / g is measured for the 2 cells.
• the analysis of FIG. 1 therefore firstly shows that by using the cycling method according to the invention, a clear improvement in the electrochemical performances is observed. It further results from the analysis of Figure 1 that it is no longer necessary to put excess graphite in a Li-ion battery cell. As a result, the energy density of the cell is increased.

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