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
  • H01M10/056—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
  • H01M10/0565—Polymeric materials, e.g. gel-type or solid-type
• • 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
  • H01M10/052—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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  • 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
• • 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
  • H01M10/0569—Liquid materials characterised by the solvents
• • 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
  • H01M4/485—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of mixed oxides or hydroxides for inserting or intercalating light metals, e.g. LiTi2O4 or LiTi2OxFy
• • 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
  • H01M4/48—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
  • 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
  • H01M4/48—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
• • 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
  • H01M4/5825—Oxygenated metallic salts or polyanionic structures, e.g. borates, phosphates, silicates, olivines
• • H—ELECTRICITY
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  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M2300/00—Electrolytes
  • H01M2300/0017—Non-aqueous electrolytes
  • H01M2300/0025—Organic electrolyte
  • H01M2300/0028—Organic electrolyte characterised by the solvent
• • H—ELECTRICITY
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  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M2300/00—Electrolytes
  • H01M2300/0017—Non-aqueous electrolytes
  • H01M2300/0065—Solid electrolytes
  • H01M2300/0082—Organic polymers
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M2300/00—Electrolytes
  • H01M2300/0085—Immobilising or gelification of electrolyte
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
  • Y02E60/10—Energy storage using batteries

Definitions

• the technical field of the invention is that of electrolytes intended for use in electrochemical elements of lithium-ion type, and more particularly electrochemical elements of lithium-ion type comprising a cathodic active material operating at high potential and an anode active material. based on a lithiated oxide of titanium or a titanium oxide capable of lithiation.
• electrochemical element and the term “element” have the same meaning in what follows and will be used in an equivalent manner.
• Lithium-ion type electrochemical elements comprising a cathodic active material operating at high potential and an anodic active material based on a lithiated titanium oxide are known from the state of the art.
• cathode comprising an electrochemically active material based on
• a lithiated titanium oxide in the anode of this type of element is advantageous because it makes it possible to carry out charges and discharges under strong currents.
• a charge under strong current of a lithium-ion element comprising a graphite-based anode can lead to the formation of lithium dendrites at the anode.
• These dendrites can be responsible for the appearance of an internal short circuit. This is explained by the fact that the diffusion of lithium in the graphite is slow and if the current is too strong and the lithium does not insert sufficiently quickly into the structure of the graphite, metallic lithium is formed on the anode. . This lithium deposit can evolve into dendrites.
• lithiated titanium oxide instead of graphite makes it possible to overcome the risk of the appearance of a deposit of lithium on the anode.
• the use of a lithiated titanium oxide therefore makes it possible to improve the safety of use of the element under high current.
• This type of element advantageously uses a cathodic active material operating at high potential, typically at least 4.5 V relative to the Li + / Li pair.
• This high potential indeed makes it possible to partially compensate for the drop in potential of the element of about 1.5 V linked to the fact that the potential of the lithiated titanium oxide is about 1.5 V with respect to the torque Li + / Li while the potential of graphite is about 0.1 V with respect to the Li + / Li couple.
• a lithium-ion type element is therefore sought, the electrolyte of which exhibits increased stability with respect to oxidation and reduction.
• An electrolyte is sought which is stable over the entire potential range during the operation of an electrochemical element comprising a cathodic active material operating at a voltage greater than or equal to 4.5 V with respect to the Li + / Li couple and a material anodic active agent which is a lithiated titanium oxide or a titanium oxide capable of being lithiated.
• a lithium-ion type element is also sought which makes it possible to suppress the migration of chemical species from an electrode to an electrode of opposite polarity.
• the preferred solvents are ethylene carbonate, diethyl carbonate and propylene carbonate.
• a poly (ethylene oxide), such as a polyacrylate contains oxygen atoms which can easily be reduced to a low potential or be oxidized at a high potential. This type of electrolyte is therefore not stable over the entire operating range of the element.
• Document WO 2017/196012 describes a lithium-ion element comprising an electrolyte based on a polymer whose main chain comprises vinylidene fluoride units and whose branched chains comprise sulphonate groups.
• Document WO 2017/168330 describes a lithium-ion element comprising an anode whose active material may be Li 4 Ti 5 O 12 and a cathode whose active material may be lithiated manganese oxide LiMn 2 O 4 . The anode and the cathode are separated by a polymer separator also playing the role of solid electrolyte.
• This polymer is obtained by curing a mixture of a silicone-urethane prepolymer comprising polysiloxane and poly (ethylene oxide) units with the lithium trifluoromethanesulfonimide salt LiN (CF 3 S0 2 ) 2 (LiTFSI) dissolved in a ionic liquid which is butyl N-methylpyrrolidinium bis (trifluoromethylsulfonyl) imide (PYR 14 TFSI).
• the objective of this document is to replace the lithium hexafluophosphate salt LiPF 6 with lithium trifluoromethanesulfonimide LiN (CF 3 SO 2 ) 2 (LiTFSI).
• the preferred solvent for improving the contact between the electrodes and the polymer separator is dimethyl carbonate (DMC).
• Document US 2015/0004475 describes a lithium-ion element whose anode contains a lithiated titanium oxide, such as LiTi 2 O 4 and whose cathode contains an active material operating at high potential, such as LiMn 1; 5 Ni 0 , 5 O 4 .
• the separator may be coated with a gel-type electrolyte consisting of poly (ethylene oxide) or poly (vinylidene fluoride) or polyacrylonitrile.
• Document US 2017/0288265 describes a gel-type electrolyte containing a poly (ethylene oxide) which can be used in a lithium-ion element operating at high potential.
• the solvent used in the manufacture of the electrolyte can be chosen from butylene carbonate, butyl sulfoxide, n-methyl-2-pyrrolidone, 1,2-diethoxyethane, ethyl methyl sulfone, dimethyl ether triethylene glycol, dimethyltetraglycol, poly (ethylene glycol) dimethyl ether and g-caprolactone.
• the invention provides a gel-type electrolyte comprising a matrix which is a polymer of poly (vinylidene fluoride-co-hexafluoropropylene) (P (VdF-HFP)) in which is embedded (or incorporated) a liquid mixture comprising at least one lithium salt and a solvent comprising at least one linear carbonate, the polymer matrix of poly (vinylidene fluoride-co-hexafluoropropylene) representing from 5 to 95% by mass relative to the mass of the gel-type electrolyte, the liquid mixture representing from 95 to 5% by mass relative to the mass of the gel-type electrolyte.
• P vinylene fluoride-co-hexafluoropropylene
• a gel-type electrolyte comprising a poly (vinylidene fluoride-co-hexafluoropropylene) matrix impregnated with a liquid mixture comprising a solvent comprising at least one linear carbonate is stable vis-à-vis. oxidation at potentials greater than 4.5 V with respect to Li + / Li and also with respect to reduction at potentials ranging from 1 to 1.5 V with respect to Li + / Li.
• the gel-type electrolyte according to the invention makes it possible to extend the life of the element in cycling. He allows the element to be used in cycling at a temperature ranging from room temperature up to about 60 ° C. It also offers the following advantages:
• the poly (vinylidene fluoride-co-hexafluoropropylene) polymer matrix represents from 5 to 25% by mass of the mass of the gel-type electrolyte.
• the solvent comprises methyl ethyl carbonate (EMC) and optionally another linear carbonate.
• EMC methyl ethyl carbonate
• the solvent comprises dimethyl carbonate (DMC) and optionally another linear carbonate.
• DMC dimethyl carbonate
• optionally another linear carbonate optionally another linear carbonate.
• the solvent consists solely of methyl ethyl carbonate (EMC) or consists solely of dimethyl carbonate (DMC).
• the solvent comprises at least one cyclic carbonate and the proportion of said at least one cyclic carbonate is less than or equal to 10%, preferably less than or equal to 5% by volume relative to the volume of the solvent.
• the solvent does not include cyclic carbonate.
• the solvent comprises at least one non-fluorinated linear carbonate and at least one fluorinated linear carbonate.
• said at least one fluorinated linear carbonate does not represent more than 30% of the volume of linear carbonates, preferably not more than 10%.
• said at least one lithium salt is lithium hexafluorophosphate LiPF 6 .
• the contribution of lithium ions provided by LiPF 6 represents at least 90% of the total quantity of lithium ions in the electrolyte.
• a subject of the invention is also an electrochemical element comprising:
• the cathode comprises an electrochemically active material capable of operating at a potential of at least 4.5 V with respect to the Li + / Li pair. This can be chosen from the group consisting of:
• M, M ', M "and M are selected from the group consisting of B , Mg, Al, Si, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, W and Mo provided that at least M or M 'or M ” or M, or selected from Mn, Co, Ni, or Fe; M, M ', M "and M,,, are different from each other, and 0.8 ⁇ x ⁇ 1.4; 0 ⁇ y ⁇ 0.5; 0 ⁇ z ⁇ 0.5; 0 ⁇ w ⁇ 0.2 and x + y + z + w ⁇ 2.1;
• a compound of group vi) consisting of the disordered oxides and oxyfluorides, partially or totally, of lithium and transition metals, of cubic structure, of formula Li 1 + x MO 2-y F y
• M represents at least one element selected from the group consisting of Na, K, Mg, Ca, B, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Al, Y, Zr, Nb, Mo, Ru, Ag, Sn,
• the anode comprises an electrochemically active material operating at a potential of approximately 1.5 V with respect to the Li + / Li pair. This can be chosen from the group consisting of:
• M is at least one member selected from the group consisting of Na, K, Mg, Ca, B, Mn, Fe, Co, Cr, Ni, Al, Cu, Ag, Pr, Y and La;
• M ' is at least one member selected from the group consisting of B, Mo, Mn, Ce, Sn, Zr, Si, W, V, Ta, Sb, Nb, Ru, Ag, Fe, Co, Ni, Zn, Al , Cr, La, Pr, Bi, Sc, Eu, Sm, Gd, Ti, Ce, Y and Eu;
• X is at least one member selected from the group consisting of S, F, Cl and Br; such as Li 4/3 Ti 5/3 O 4 (Li 4 Ti 5 O 12 ), Li 8/3 Ti 4/3 O 4 ((Li 2 Ti O 3 ), Li 8/7 Ti 12/7 O 4 (Li 2 Ti 3 7), Li Ti 2 O 4 , (Li x 2i 5 O 4 with 0 ⁇ x ⁇ 2 and Li 4/7 Na 4/7 Ti 12/7 O 4 (Li 2 Na 2 Ti 6 O 14 ) ;
• H x Ti y O 4 where 0 x x 1; 0 ⁇ y ⁇ 2, such as H 8/13 Ti 24/13 O 4 (H 2 Ti 6 O 13 ), H 8/25 Ti 48/25 O 4 (H 2 Ti 12 O 25 ) and Ti 2 O 4 (TiO 2 );
• M and M 'each represent at least one element selected from the group consisting of Li, Na, K, Mg, Ca, B, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Al, Y, Zr, Nb, Mo, Ru, Ag, Sn, Sb, Ta, W, Bi, La, Pr, Eu, Nd and Sm;
• X represents at least one element selected from the group consisting of S, F, Cl and Br, such as TiNb 2 O 7 , Ti 2 Nb 2 O 9 and Ti 2 Nb 10 O 29 ; d) a mixture of several compounds chosen from groups a) to c).
• the liquid mixture comprises lithium hexafluorophosphate LiPF 6 , and methyl ethyl carbonate (EMC) as solvent.
• FIG. 1 represents the variation of the current passing through the elements of type A, B and C during an anodic sweep.
• FIG. 2 shows the variation of the voltage of type D to G cells during formation consisting of a charge at C / 10 followed by a discharge at C / 10, C being the nominal capacity of the cells.
• FIG. 3 represents the variation of the specific capacity of the elements of type D to G during a cycling at 45 ° C according to the number of cycles carried out.
• FIG. 4 shows the variation of the voltage of the elements of type D, F and H during a formation at 60 ° C consisting of a charge at C / 10 followed by a discharge at C / 10.
• FIG. 5 represents the variation of the mass capacity per gram of cathodic active material of elements D and H during a cycling comprising a first series of 10 cycles carried out at 60 ° C, followed by a second series of 22 cycles carried out at 25 ° C.
• FIG. 6 represents the variation of the mass capacity per gram of cathodic active material of elements I and J during cycling at 25 ° C.
• FIG. 7 shows the voltage variation curves of two elements of type J and K during training at a temperature of 60 ° C.
• FIG. 8 represents the variation of the mass capacity per gram of cathodic active material of two elements of type J and K during cycling at 25 ° C.
• FIG. 9 shows the voltage variation curves of L, M and N type elements during training at a temperature of 60 ° C.
• FIG. 10 represents the variation of the mass capacity per gram of cathodic active material of the elements of type L, M and N during a cycling comprising a first series of 40 cycles at 25 ° C, followed by a second series of 20 cycles at 45 ° C and a third series of 25 cycles at 60 ° C.
• the electrolyte according to the invention is a gel type electrolyte. It is obtained by mixing a polymer of poly (vinylidene fluoride-co-hexafluoropropylene) p (VdF-HFP) with a liquid mixture comprising at least one lithium salt and a solvent comprising at least one linear carbonate.
• VdF-HFP Poly (vinylidene fluoride-co-hexafluoropropylene) p (VdF-HFP) has the following formula: where x denotes the number of units of vinylidene fluoride and y denotes the number of units of hexafluoropropy 1 ene.
• the molecular mass by weight of P can vary from 300 Da to 5 MDa. It can be in the range from 300 to 800 Da or in the range from 200 to 400 kDa.
• the matrix of p can represent from 5 to 95% or from 5 to 50%, or from 5 to 20% or from 5 to 10% by mass relative to the mass of the gel-type electrolyte.
• a preferred percentage range is the range from 5 to 25%, more preferably from 10 to 20%. This preferred range makes it possible both to obtain good resistance of the electrolyte to oxidation at high cathode potentials as well as good reversible capacity of the element.
• the resistance of the electrolyte to oxidation may decrease if the gel-type electrolyte contains 5% or less of polymer.
• the reversible capacity of the element containing the electrolyte may decrease if the electrolyte contains a percentage of polymer greater than 25%. In addition, for a percentage of polymer greater than 25%, poorer impregnation of the electrodes by the polymer can be observed.
• the polymer may be insufficiently in contact with the porosity of the electrodes.
• PVdF-HFP exhibits greater solubility with respect to the liquid mixture comprising said at least one lithium salt and the solvent.
• the matrix can also comprise one or more polymers in combination with p (VdF-HFP).
• This or these other polymers can be chosen from a poly (ethylene oxide), poly (vinylidene fluoride) PVDF, a polyacrylate and a poly (imidine).
• P (VdF-HFP) preferably represents at least 50% by mass of the mixture of polymers.
• the gel makes it possible to avoid the phenomena of crossing of chemical species between the anode and the cathode. These crossings lead to degradation of the anode and the cathode and to a reduction in the service life of the element.
• the liquid mixture comprises at least one lithium salt and a solvent comprising at least one linear carbonate.
• Said at least one linear carbonate may represent from 95 to 5% or from 95 to 50%, or from 95 to 80% or from 95 to 90% by mass relative to the mass of the gel-type electrolyte.
• Said at least one linear carbonate may be selected from the group consisting of dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (EMC) and methyl propyl carbonate (PMC). Particularly preferred are dimethyl carbonate (DMC), methyl ethyl carbonate (EMC).
• the solvent can comprise EMC with optionally one or more other linear carbonates.
• the solvent can comprise EMC optionally in admixture with DMC.
• the solvent can be free from linear carbonates other than EMC and DMC.
• the solvent may consist of EMC only or consist of DMC only.
• the solvent can include at least one linear nonfluorinated carbonate and at least one linear fluorinated carbonate.
• said at least one fluorinated linear carbonate does not represent more than 30% of the volume of linear carbonates, preferably not more than 10%.
• Said at least one linear carbonate can be used in combination with one or more cyclic carbonates.
• cyclic carbonates are reactive with respect to the anode and the cathode under the operating conditions of the element. Therefore, the solvent preferably comprises at most 10% or at most 5% by volume of said one or more cyclic carbonates. Beyond 10% of cyclic carbonate (s), a loss of capacity of the element can be observed.
• the following solvents can be considered:
• the solvent therefore preferably does not contain any cyclic carbonate.
• the solvent does not contain linear ester (s) or cyclic ester (s), also called lactones.
• linear esters tend to degrade in the presence of LiPF 6 .
• lactones can have the effect of increasing the irreversible capacity and causing a strong polarization of the element.
• the solvent does not contain ether (s).
• Lithium hexafluorophosphate may be mentioned LiPF 6, lithium hexafluoroarsenate LiAsF 6, lithium hexafluoroantimonate LiSbF 6, and lithium tetrafluoroborate LiBF4, lithium perchlorate LiClO 4, lithium trifluoromethanesulfonate LiCF 3 SO 3 , lithium bis (fluorosulfonyl) imide Li (FSO 2 ) 2 N (LiFSI), lithium trifluoromethanesulfonimide LiN (CF 3 SO 2 ) 2 (LiTFSI), lithium trifluoromethanesulfonemethide LiC (CF 3 SO 2 ) 3 (LiTFSM), lithium bisperfluoroethylsulfonimide LiN (C 2 F 5 SO 2 ) 2 (LiBETI), lithium 4,5-dicyano-2- (trifluoromethyl) imidazolide (LiTDI), lithium
• said at least one lithium salt is lithium hexafluorophosphate LiPF 6 .
• LiPF 6 can be combined with another lithium salt.
• the lithium ions resulting from this other salt preferably represent at most approximately 10% of the total amount of lithium ions present in the gel-type electrolyte. This applies in particular if this other salt is LiBF 4 . Indeed, it has been observed that LiBF 4 had the effect of increasing the irreversible capacity of the element, which is not desirable. It has also been observed that LiBF 4 causes a faster drop in the performance of the element in cycling than when LiPF 6 is used as the sole salt.
• the gel-type electrolyte contains neither lithium bis (fluorosulfonyl) imide Li (FSO 2 ) 2 N (LiFSI), nor lithium trifluoromethanesulfonimide LiN (CF 3 SO 2 ) 2 (LiTFSI), nor lithium tetrafluoroborate LiBF 4 , nor lithium bis (oxalatoborate) (LiBOB), nor lithium difluoro (oxalato) borate (LiDFOB).
• the gel-type electrolyte does not contain other lithium salt lithium hexafluorophosphate LiPF 6.
• a particularly preferred example of gel-type electrolyte according to the invention comprises the poly (vinylidene fluoride-co-hexafluoropropylene) matrix in which is embedded a liquid mixture comprising LiPF 6 , and a solvent consisting of EMC, the polymer matrix.
• a liquid mixture comprising LiPF 6 , and a solvent consisting of EMC, the polymer matrix.
• poly (vinylidene-co-hexafluoropropylene fluoride) representing from 5 to 25% by mass relative to the mass of the gel-type electrolyte
• the liquid mixture representing from 95 to 75% by mass relative to the mass of the gel-type electrolyte.
• LiPF 6 is used as the only salt and the solvent consists only of EMC.
• the concentration of said at least one lithium salt can range from 0.75 to 1.5 mol.L -1 . Preferably, it ranges from 1 to 1.5 mol.L -1 . More preferably, it is approximately equal to 1 mol.L -1 .
• a low concentration of lithium salt would increase the fluidity of the gel-type electrolyte, provide better pore imbibition of the cathode and anode active material, and improve the function of the gel. 'element.
• the gel-type electrolyte is dissolved in the solvent.
• the poly (vinylidene fluoride-co-hexafluoropropylene) polymer is incorporated.
• the mixture is stirred for several minutes. It can be heated to a temperature not exceeding 50 ° C in order to accelerate the swelling of the polymer.
• the gel-type electrolyte is free from additives such as vinylene carbonate VC.
• the additives can be reactive in which case, the products resulting from the reaction could carry out a crossing movement between the anode and the cathode leading to a degradation of the anode and the cathode and to a reduction of the duration of element life.
• the anode active material is characterized by an operating voltage of approximately 1.5 V with respect to the Li + / Li pair.
• the characteristic according to which the anode active material exhibits an operating voltage of approximately 1.5 V with respect to the potential of the electrochemical pair Li + / Li is an intrinsic characteristic of the active material. It can be easily measured by routine tests for a person skilled in the art. To do this, a person skilled in the art makes an electrochemical element comprising a first electrode consisting of metallic lithium and a second electrode comprising the active material, the potential of which is to be determined with respect to the electrochemical pair Li + / Li.
• Electrodes are separated by a microporous polyolefin membrane, typically polyethylene, impregnated with electrolyte, usually a mixture of ethylene carbonate and dimethyl carbonate, in which LiPF 6 is dissolved, at a concentration of 1 mol. L -1 .
• electrolyte usually a mixture of ethylene carbonate and dimethyl carbonate, in which LiPF 6 is dissolved, at a concentration of 1 mol. L -1 .
• the potential measurement is carried out at 25 ° C.
• Negative active materials exhibiting an operating potential of approximately 1.5 V relative to the potential of the electrochemical pair Li + / Li are also described in the literature.
• the anodic active material may be a lithiated titanium oxide or a titanium oxide capable of being lithiated. It can be chosen from the group consisting of:
• M is at least one member selected from the group consisting of Na, K, Mg, Ca, B, Mn, Fe, Co, Cr, Ni, Al, Cu, Ag, Pr, Y and La;
• M ' is at least one member selected from the group consisting of B, Mo, Mn, Ce, Sn, Zr, Si, W, V, Ta, Sb, Nb, Ru, Ag, Fe, Co, Ni, Zn, Al , Cr, La, Pr, Bi, Sc, Eu, Sm, Gd, Ti, Ce, Y and Eu;
• X is at least one member selected from the group consisting of S, F, Cl and Br;
• This compound of group a) includes the examples Li 4 Ti 5 O 12 , Li 2 Ti O 3 , Li 2 Ti 3 O 7 , LiTi 2 O 4 , Li x Ti 2 O 4 with 0 ⁇ x ⁇ 2 and Li 2 Na 2 Ti 6 O 14 .
• b 0.25;
• M and M 'each represent at least one element selected from the group consisting of Li, Na, K, Mg, Ca, B, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Al, Y, Zr, Nb, Mo, Ru, Ag, Sn, Sb, Ta, W, Bi, La, Pr, Eu, Nd and Sm;
• X represents at least one element selected from the group consisting of S, F, Cl and Br.
• M and M's are chosen from Ti, V, Nb, Mo, Ta and W.
• X is chosen from F and S.
• M and M ′ are chosen from Ti, V, Nb, Mo, Ta and W and X is chosen from F and S and d ⁇ 0.5.
• Examples of compound of group c) are TiNb 2 O 7 , Ti 2 Nb 2 O 9 and Ti 2 Nb 10 O 29 .
• the anode active material is preferably at least one compound of group a) or at least one compound of group c). In one embodiment, it comprises a mixture of at least one compound of group a) with at least one compound of group c). This mixture can be Li 4 Ti 5 O 12 with TiNb 2 O 7 .
• the cathodic electrochemically active material is preferably an active material operating at “high potential”, that is to say having an open circuit potential of at least about 4.5 V with respect to the Li + / Li pair.
• the measurement of the potential of the cathodic active material can be carried out under the same conditions as those described for the measurement of the operating potential of the anode active material.
• the cathodic active material can be chosen from the group consisting of:
• a compound of group vi) consisting of the disordered oxides and oxyfluorides, partially or totally, of lithium and transition metals, of cubic structure, of formula Li 1 + x MO 2-y F y
• M represents at least one element selected from the group consisting of Na, K, Mg, Ca, B, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Al, Y, Zr, Nb, Mo, Ru, Ag, Sn,
• the compound of group i) can have the formula LiMn 2-xy Ni x M y O 4 with 0 ⁇ x ⁇ 0.5; 0 ⁇ y ⁇ 0.1 where M is at least one element selected from Fe, Co and Al. Preferably, M is Al. Preferably, 0 ⁇ y ⁇ 0.05.
• Examples of compounds of group i) are LiMn 1.5 Ni 0.5 O 4 and LiMn 1.55 Ni 0.41 Al 0.04 O 4 .
• the compound of group ii) may have the formula LiMnPO 4 .
• the compound of group iii) may have the formula LiNiPO 4 .
• the compound of group iv) can have the formula LiCoPO 4 .
• the compound of group v) may have the formula Li x M 1-yzw M ' y M " z M'" w O 2 , where 1 x 1.15; M denotes Ni; M 'denotes Mn; M "denotes Co and M '" is at least an element selected from the group consisting of B, Mg, Al, Si, Ca, Ti, V, Cr, Fe, Cu, Zn, Y, Zr, Nb and Mo; 1-yzw>0;y>0;z>0; w ⁇ 0.
• An example of compound v) is Li 1/3 Mn 1/3 Co 1/3 O 2.
• the compound of group v) can also have the formula Li x M 1-yzw M ' y M " z M'" w O 2 , where 1 x 1.15; M denotes Ni; M 'denotes Co; M "denotes Al and M '" is at least one member selected from the group consisting of B, Mg, Si, Ca, Ti, V, Cr, Fe, Cu, Zn, Y, Zr, Nb and Mo; 1-yzw>0;y>0;z>0; w ⁇ 0.
• An example of compound v) is LiNi 0.8 Co 0.15 Al 0.05 O 2 .
• the compound of group v) can also be chosen from LiNiO 2 , LiCoO 2 , LiMnO 2 , Ni, Co and Mn which may be substituted by one or more of the elements chosen from the group consisting of Mg, Mn (except for LiMnO 2 ), Al, B, Ti, V, Si, Cr, Fe, Cu, Zn and Zr.
• the cathodic active material can be covered at least partially by a carbon layer.
• cathodic active material and anodic active material are preferred:
• At least one compound of group i) at the cathode and at least one compound of group a) at the anode for example LiMn 1.5 Ni 0.5 O 4 at the cathode and Li 4 Ti 5 O 12 at the 'anode;
• At least one compound of group i) at the cathode and at least one compound of group c) at the anode for example LiMn 1.5 Ni 0.5 O 4 at the cathode and TiNb 2 O 7 at the anode or LiMn 1.55 Ni 0.41 Al 0.04 O 4 at the cathode and TiNb 2 O 7 at the anode;
• - at least one compound of group ii) at the cathode and at least one compound of group a) at the anode for example LiMnPO 4 at the cathode and Li 4 Ti 5 O 12 at the anode;
• At least one compound of group iv) at the cathode and at least one compound of group a) at the anode for example LiCoPO 4 at the cathode and Li 4 Ti 5 O 12 at the anode.
• a compound of group i) is advantageous over a compound of group v) in that it releases two to three times less energy during thermal runaway of the element.
• the cathodic and anodic active materials of the lithium-ion electrochemical element are generally mixed with one or more binder (s), the function of which is to bind the particles of active material together as well as to bind them to the current collector on which they are deposited.
• binder the function of which is to bind the particles of active material together as well as to bind them to the current collector on which they are deposited.
• the binder can be chosen from carboxymethylcellulose (CMC), a butadiene-styrene (SBR) copolymer, polytetrafluoroethylene (PTFE), polyamideimide (P AI), polyimide (PI), styrene-butadiene rubber (SBR), polyvinyl alcohol, polyvinylidene fluoride (PVDF) and a mixture thereof.
• CMC carboxymethylcellulose
• SBR butadiene-styrene copolymer
• PTFE polytetrafluoroethylene
• P AI polyamideimide
• PI polyimide
• SBR styrene-butadiene rubber
• PVDF polyvinyl alcohol
• PVDF polyvinylidene fluoride
• the cathode and anode current collector is in the form of a solid or perforated metal strip.
• the strap can be made from different materials. Mention may be made of copper or copper alloys, aluminum or aluminum alloys, nickel or nickel alloys, steel and stainless steel.
• the current collector of the cathode is generally an aluminum strip or an alloy mainly comprising aluminum.
• the current collector of the anode can be a copper strip or an alloy mainly comprising copper. It can also be an aluminum strip or an alloy predominantly comprising aluminum.
• At the operating potential of the anode (around 1.5 V relative to Li + / Li), there is in fact no possibility of inserting Li into the aluminum, nor of creating a LiAl alloy.
• the thickness of the cathode strip may be different from that of the anode strip.
• the strip of the cathode or of the anode has a thickness generally between 6 and 30 ⁇ m.
• the aluminum collector of the cathode is covered with a conductive coating, such as, for example, carbon black or graphite.
• the anode active material is mixed with one or more binders mentioned above and optionally a good electronic conductor compound, such as carbon black.
• a good electronic conductor compound such as carbon black.
• composition of the ink deposited on the anode can be as follows:
• binder (s) from 2 to 15% of binder (s), preferably 5%;
• the procedure is carried out in the same way as for obtaining the anode, but starting from cathodic active material.
• composition of the ink deposited on the cathode can be as follows:
• cathodic active material preferably from 80 to 90%
• a separator is generally interposed between an anode and a cathode to avoid possible short circuits.
• the material of the separator can be chosen from the following materials: a polyolefin, for example polypropylene PP, polyethylene PE, a polyester, glass fibers bonded together by a polymer, polyimide, polyamide, polyaramid, polyamideimide and cellulose.
• the polyester can be chosen from polyethylene terephthalate (PET) and polybutylene terephthalate (PBT).
• the polyester or polypropylene or polyethylene contains or is coated with a material selected from the group consisting of a metal oxide, a carbide, a nitride, a boride, a silicide and a sulfide.
• This material can be SiO 2 or Al 2 O 3 .
• the separator can be coated with an organic coating, for example comprising an acrylate or PVDF or P (VdF-HFP).
• a preferred separator is made of polyethylene or is made from the combination of three layers which are polypropylene PP / polyethylene PE / polypropylene PP.
• the gel-type electrolyte is deposited in contact with the composition of cathodic active material.
• a separator is then deposited on the composition of cathodic active material impregnated with the gel-type electrolyte.
• the face of the separator intended to be in contact with the composition of anodic active material is coated with gel-type electrolyte.
• An anode is then applied in contact with the gel-type electrolyte.
• the gel-type electrolyte is deposited on the one hand on the cathodic active material composition and on the other hand on the active material composition. anodic.
• a separator is interposed between the composition of cathodic active material and the composition of anode active material impregnated with gel-type electrolyte.
• the two faces of the separator are imbibed with gel-type electrolyte and the separator is inserted between a cathode and an anode.
• an assembly is obtained in which the gel-type electrolyte and the separator are sandwiched between an anode and a cathode.
• a separator is not necessary if the mass of P (VdF-HFP) represents at least 50% of the mass of the gel-type electrolyte.
• the gel-type electrolyte in this case acts both as a separator and as an electrolyte.
• the element Before starting the “formation” of the electrodes, that is to say carrying out a first charge / discharge cycle of the element, it may be useful to let the element stand at a temperature above room temperature. , for example 50 or 60 ° C, for several hours, for example 5 to 15 hours, so as to promote the impregnation of the active material of the electrodes by the gel-type electrolyte.
• the formation of the element can be carried out at a temperature less than or equal to 50 ° C, for example ranging from 20 to 50 ° C.
• An increase in the formation temperature allows better imbibition of the pores of the electrodes by the gel-type electrolyte.
• the separator is a Celgard® 2325 PP / PE / PP three-layer separator (PP: polypropylene; PE: polyethylene).
• cathode comprising carbon (LiTX TM 200, Cabot) and PTFE deposited on an aluminum current collector,
• the cathode of these elements is devoid of electrochemically active material so as to evaluate only the effect of the increase in potential on the stability of the electrolyte.
• the elements have first undergone an impregnation phase with the electrolyte at 60 ° C. for 6 hours. The anodic sweep was carried out at 60 ° C. at a rate of 0.1 mV.s -1 . The results are shown in Figure 1. This shows a sharp increase in current when the potential exceeds 4.5 V vs. Li + / Li for type A elements comprising a liquid electrolyte based on cyclic carbonates (EC, PC).
• cathode comprising carbon (LiTX TM 200, Cabot) and PTFE deposited on a copper current collector
• the gel-type electrolyte according to the invention exhibits good stability with respect to oxidation and reduction. It increases the life of the element in cycling. A possible drop in the conductivity of the gel electrolyte observed with respect to a liquid electrolyte is compensated for by the increase in stability provided by the association of poly (vinylidene fluoride-co-hexafluoropropylene) with the linear carbonate. b) Effect of the electrolyte according to the invention on the irreversible capacity of lithium-ion elements comprising a cathodic active material at high potential:
• Elements comprising LiMn 1.55 Ni 0.41 Al 0.04 O 4 as cathodic active material operating at high potential have been manufactured. These are the elements of types D to G described in Table 1 above.
• the elements have undergone a phase of impregnation of the electrodes with the electrolyte for 12 hours at 60 ° C, the electrolyte being either in liquid form (elements D and E), or in gelled form based on P (VdF-HFP ) (elements F and G).
• the cells then underwent a formation consisting of a charge at C / 10 followed by a discharge at the rate of C / 10, C being the nominal capacity of the cells.
• the charge / discharge curves are shown in figure 2.
• the irreversible capacity is measured in the figure. 2 by calculating the difference between the capacity charged during the charging step and the capacity discharged during the next discharging step. It gives an indication of the quantity of lithium which no longer participates in the charge / discharge reactions during cycling.
• the irreversible capacity is approximately 30 to 40 mAh / g for type D and E cells, while it is approximately 20 mAh / g for type F and G cells.
• FIG. 3 represents the variation of the mass capacity per gram of anodic active material of these elements as a function of the number of cycles carried out. It can be seen that from the start of cycling, the elements F and G comprising the gel-type electrolyte according to the invention have a capacity markedly greater than that of the elements D and E comprising a liquid electrolyte. We note moreover elements F and G experience a much slower decrease in capacity than elements D and E. d) Effect of the content of PfVdF-HFP) in the gel-type electrolyte on the irreversible capacity and the reversible capacity of elements:
• Elements of type D, F and H have undergone a phase of impregnation of their electrodes with the electrolyte for 12 hours at 60 ° C, the electrolyte being either in liquid form (elements D) or in gelled form based on P (VdF -HFP) (elements F and H).
• the cells were then "formed" consisting of a charge at C / 10 followed by a discharge at the rate of C / 10, C being the nominal capacity of the cells.
• the charge / discharge curves are shown in FIG. 4.
• the use of the gel-type electrolyte according to the invention makes it possible to significantly reduce the irreversible capacity in the first cycle.
• FIG. 5 represents the variation of the mass capacity per gram of anode active material for elements D and H during cycling comprising a first series of 10 cycles carried out at a temperature of 60 ° C followed by a second series of 22 cycles performed at a temperature of 25 ° C. Each cycle consists of a charge at C / 5 rate followed by a discharge at C / 5 rate. Two discharges at C / 10 were performed at the start of the first series of 10 cycles and at the start of the second series of 22 cycles. It can be seen that from the start of the cycling, the element H comprising the gel-type electrolyte according to the invention has a capacity markedly greater than that of the element D comprising a liquid electrolyte.
• FIG. 6 represents the variation of the mass capacity per gram of cathodic active material of elements I and J during this cycling. It is noted that the capacity of element J according to the invention decreases much less quickly than that of element I which contains a liquid electrolyte.
• Two J-type elements contain LiPF 6 , at a concentration of 1 mol.L -1 .
• Two K-type elements contain LiPF 6 , at a concentration of 0.7 mol.L -1 .
• the curves of variation of the voltage of these elements during training were recorded. They are represented in figure 7. It is noted that the charged capacity of the elements of type J which contain LiPF 6 , at the concentration of 1 mol.L -1 is greater than that of elements of type K which contains LiPF 6 , at the concentration of 0. , 7 mol.L -1 .
• the irreversible capacities are comparable.
• FIG. 8 represents the variation in the mass capacity per gram of cathodic active material of the elements of type J and K during this cycling.
• the first two cycles include a discharge phase at a rate of C / 10. It can be seen that from the start of cycling, the discharged capacity of the type J element containing LiPF 6 , at a concentration of 1 mol.L -1, is greater than that of the type K element containing LiPF 6 , at the concentration of 0.7 mol.L -1 . This result is surprising.
• the charged capacity, the discharged capacity and the irreversible capacity of type L elements not containing EC are close to those of type M elements containing 10% EC. It is also noted that the discharged capacity of type N elements whose electrolyte solvent contains 30% EC is reduced compared to L-type and M-type elements.
• the polarization of N-type elements increases slightly. The increase in the reactivity of the gel-like electrolyte of the N-type elements can be explained by the increase in the concentration of EC, which is reactive towards the cathode and the anode.
• FIG. 10 represents the variation in the mass capacity per gram of cathodic active material of these elements during this cycling.
• the first two cycles of each series include a discharge phase at a rate of C / 10 at 60 ° C. It can be seen that during the first series of cycles at 25 ° C., the cycling performances of the elements L, M and N are comparable from the point of view of the discharged capacity.
• the drops in discharged capacities of type L and M cells whose solvent contains 0% and 10% EC, respectively, are similar.
• the drop in the discharged capacity of the type N element whose solvent contains 30% EC is markedly faster than that of the type L and M elements.
• the discharged capacities of the elements of type M and N are very low.
• the addition of ethylene carbonate does not seem to provide any benefit over the cycle life. On the contrary, it has a tendency to react with the cathode and the anode and to cause an increase in the impedance of the element.
• Impedance measurements taken after cycling on the elements indicate that the type N element, whose solvent contains 30% EC, has a higher impedance than the type L and M elements.
• the temperature increase to 45 ° C and 60 ° C amplifies the instability of EC towards the cathode and the anode.
• their volume percentage is preferably less than 10%, or even less than 5%.

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