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EP-4736253-A1 - ELECTROLYTE, AND LITHIUM ION BATTERY COMPRISING SAME

EP4736253A1EP 4736253 A1EP4736253 A1EP 4736253A1EP-4736253-A1

Abstract

The invention relates to an electrolyte for a lithium-ion battery, comprising, in percent by weight relative to the weight of the electrolyte: - between 8% and 20% lithium salt which comprises at least a mixture of LiFSI and LiPF6, - between 0.5% and 1.5% methylene methane disulfonate, - between 0.25% and 2% ethylene sulfate, - a complementary additive, the weight percentage of which does not exceed 2.5%, - a sufficient quantity of a non-aqueous organic solvent. The invention also relates to a lithium-ion battery comprising said electrolyte.

Inventors

  • LASSAGNE, Adrien
  • PETRISSANS, Xavier
  • DELOBEL, Bruno
  • BARCHASZ, Céline

Assignees

  • Verkor

Dates

Publication Date
20260506
Application Date
20240626

Claims (10)

  1. 1. Electrolyte characterized in that it comprises, in mass percentages expressed relative to the mass of said electrolyte: - between 8% and 20%, preferably between 11% and 16%, of lithium salt which comprises at least one mixture of lithium bis(fluorosulfonyl) imide (hereinafter abbreviated LiFSI) and lithium hexafluorophosphate (hereinafter abbreviated LiPFe), - between 0.5% and 1.5% of methylene methane disulfonate (hereinafter abbreviated MMDS), - between 0.25% and 2%, preferably between 0.5% and 1.5%, of ethylene sulfate (hereinafter abbreviated DTD), - at least one additional additive, the mass percentage of which does not exceed 2.5%, and if the additional additive is fluoroethylene carbonate (hereinafter abbreviated as “FEC”), the mass percentage of FEC is less than 0.5%, preferably less than 0.25%, - Qsp of at least one non-aqueous organic solvent, "Qsp" being the acronym for "Quantity sufficient for" to signify that the mass percentage of solvent in the electrolyte is such that, added to the percentages of all the other constituents of the electrolyte, a total of 100% is obtained.
  2. 2. Electrolyte according to claim 1, characterized in that the additional additive is chosen from the group consisting of 1,3-propane sultone (hereinafter abbreviated PS), vinylene carbonate (hereinafter abbreviated VC), FEC, vinylethylene carbonate, prop-l-ene-1,3-sultone, butane sultone and trimethylene sulfate, taken alone or as a mixture thereof.
  3. 3. Electrolyte according to claim 2, characterized in that the additional additive is PS and/or VC.
  4. 4. Electrolyte according to any one of claims 1 to 3, characterized in that the lithium salt further comprises IJBF4, LilX^SOzCFsh, LiCIO4, LiAsFe, lithium bis(oxalato)borate and lithium difluoro(oxalato)borate, taken alone or as a mixture thereof.
  5. 5. Electrolyte according to claim 1, characterized in that the lithium salt is a mixture of LiFSI and LiPFe.
  6. 6. Electrolyte according to any one of claims 1 to 5, characterized in that the non-aqueous organic solvent is chosen from the group consisting of carbonate ethylene carbonate (hereinafter abbreviated EC), propylene carbonate, 1,2-butylene carbonate, 2,3-butylene carbonate, dimethyl carbonate (hereinafter abbreviated DMC), diethyl carbonate, dipropyl carbonate, dibutyl carbonate, ethyl methyl carbonate (hereinafter abbreviated EMC), methyl propyl carbonate, methyl isopropyl carbonate, methyl butyl carbonate and ethyl propyl carbonate, taken alone or in mixtures thereof.
  7. 7. Electrolyte according to claim 6, characterized in that the non-aqueous organic solvent is chosen from the group consisting of EC, EMC and DMC, taken alone or as a mixture thereof.
  8. 8. Electrolyte according to claim 1, characterized in that the electrolyte comprises, in mass percentages expressed relative to the mass of said electrolyte: - between 8% and 20%, preferably between 11% and 16%, of lithium salt which comprises at least a mixture of LiFSI and LiPFe, - between 0.5% and 1.5% of MMDS, - between 0.25% and 2%, preferably between 0.5% and 1.5%, of DTD, - between 0.25% and 2.5%, preferably between 0.5% and 2%, of at least one complementary additive chosen from PS and VC, - Q.sp of at least one non-aqueous organic solvent chosen from EC, EMC and DMC.
  9. 9. Electrolyte according to claim 1, characterized in that the electrolyte comprises, in mass percentages expressed relative to the mass of said electrolyte: - between 1.5% and 4%, preferably between 2% and 3.5%, of LiFSI, - between 8.5% and 16%, preferably between 10% and 14%, of LiPFe, - between 0.5% and 1.5% of MMDS, - between 0.25% and 2%, preferably between 0.5% and 1.5%, of DTD, - between 0.25% and 2%, preferably between 0.5% and 1.5%, of PS, - between 0.25% and 2%, preferably between 0.5% and 1.5%, of VC, - between 10% and 50%, preferably between 20% and 40%, of EC, - between 10% and 78%, preferably between 60% and 78%, of EMC, - between 0% and 60%, preferably between 0% and 40%, of DMC.
  10. 10. Lithium-ion accumulator comprising an electrolyte according to any one of claims 1 to 9.

Description

DESCRIPTION ELECTROLYTE AND LITHIUM-ION ACCUMULATOR COMPRISING IT [0001] The present invention relates to an electrolyte and a lithium-ion accumulator comprising this electrolyte. [0002] In the context of the present invention, a lithium-ion accumulator is a device used for the electrochemical storage of energy and the restitution of the latter as and when needed. With reference to the English term "battery", the term "lithium-ion battery" is also used to designate this type of electric accumulator. It is an electric generator consisting of two electrical conductors (namely the electrodes) in contact with an ionic conductor (the electrolyte) which can be in the form of a liquid, gel or solid. [0003] The principle of the lithium-ion accumulator is based on the reversible exchange of the lithium ion between a cathode (generally a lithiated transition metal oxide such as cobalt or manganese dioxide) and an anode (generally graphite) during the charge and discharge cycles, and this with very good cycling performance. The electrolyte is aprotic (generally a dissolved lithium hexafluorophosphate salt, hereinafter abbreviated to "LiPFe") to passivate the anode and avoid degrading the highly reactive electrodes. [0004] The lithium-ion accumulator has the following advantages in particular: - high energy density thanks to the properties of lithium, - low self-discharge, - good cyclability. [0005] This is why the lithium-ion accumulator is widely acclaimed for mobile applications (telephony, automobile) and in systems using renewable energies (solar, wind). [0006] More specifically, with the increase in the consumption of portable electronic devices, electric vehicles and the storage of renewable energies, the development of lithium-ion accumulators with high energy density and power, safe and at low costs has become essential. Research and development has therefore mainly focused on the development of new materials. electrodes but also new electrolyte compositions to obtain ever more efficient lithium-ion accumulators. [0007] Over time and with the number of charge and discharge cycles, the capacity of a lithium-ion battery tends to degrade and its internal resistance to increase, so much so that it becomes unusable. [0008] The physicochemical phenomenon causing this aging of the lithium-ion accumulator is as follows: when the graphite of the electrode is in contact with the electrolyte, in particular during the first charge of the accumulator, a layer of lithium is deposited on the electrode, naturally reducing the available quantity of lithium ions in solution in the electrolyte. This so-called "passivation" layer electrically insulates the electrode from the electrolyte, which prevents and/or restricts a subsequent reaction of the electrode with the electrolyte. This slightly reduces the capacity of the accumulator and increases its internal resistance. This passivation layer thickens with time and the number of cycles, which increases the internal resistance and reduces the capacity of the lithium-ion accumulator accordingly. [0009] Thus, the alteration of the capacity, compared to its nominal value, is one of the visible effects of the aging of a lithium-ion accumulator and contributes to reducing the performance of said accumulator. In this regard, in the context of the present invention, the capacity of a lithium-ion accumulator is defined as being the quantity of charges that can be provided by the accumulator during discharge. This is the integral of the current that can be delivered during one hour (Ah) and which allows the accumulator to go from a fully charged state to a 0% charge state. The capacity measurement is carried out by galvanostatic cycling at a constant current density. [0010] The inventors of the present invention have sought to overcome this drawback by developing a new lithium-ion battery electrolyte composition for which the retention of its capacity during charge and discharge cycles or during storage of the latter at high temperature is greater than that of lithium-ion batteries known from the state of the art. [0011] In the context of the disclosure of the present invention, the following abbreviations are used: - BS for butane sultone; - CMC for carboxymethylcellulose; - DEC for diethyl carbonate; - DMC for dimethyl carbonate; - DTD for ethylene sulfate; - EC for ethylene carbonate; - EMC for ethyl and methyl carbonate; - FEC for fluoroethylene carbonate; - LCO for LiCoO 2 ; - LiBOB for lithium bis(oxalato)borate; - LiDFOB for lithium difluoro(oxalato)borate; - LFP for LiFePO4; - LiFSI for lithium bis(fluorosulfonyl) imide; - LiPFe for lithium hexafluorophosphate; - LiTFSI for LiN(SO 2 CF 3 ) 2 ; - LMO for LiMn 2 O4; - MMDS for methylene methane disulfonate; - NCA for Li(Ni,Co,AI)O 2 ; - NMC for Li(Ni,Mn,Co)O 2 ; - NMP for N-methyl-2-pyrrolidone; - PC for propylene carbonate; - PES for prop-l-ene-l,3-sultone; - PS for 1,3-propane sultone; - PVDF for polyvinylidene fluoride; - SBR fo