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CN-122025826-A - Wide-temperature-range lithium battery electrolyte and preparation method thereof

CN122025826ACN 122025826 ACN122025826 ACN 122025826ACN-122025826-A

Abstract

The invention discloses a wide-temperature-range lithium battery electrolyte and a preparation method thereof, and relates to the technical field of lithium battery electrolytes, wherein the electrolyte is used for low-temperature quick charge and high Wen Man electric storage, and comprises a component A to a component E, wherein the component A is linear carbonate and low-condensation-point carboxylate, the component B is nitrile solvent and phosphate solvent, the component C is a multi-lithium salt system, the component D is ethylene sulfite, the component E is an acid-triggered crosslinking self-repairing interface enhancer, the electrolyte comprises a multifunctional epoxy unit, latent polyol capable of being triggered by acidic species to release hydroxyl groups and a borate dynamic modulation unit, moisture is controlled in an inert atmosphere during preparation, solvent mother liquor is prepared, salt is dissolved step by step, then the component D and the component E are sequentially added, the electrolyte maintains low viscosity and ion transmission at low temperature, lithium separation risk is reduced, gas production and interface degradation are inhibited under a high-temperature charge state, the phase is avoided, and the circulation and storage stability is improved.

Inventors

  • LI XU
  • LI YONGWEI
  • CHEN XIAORONG

Assignees

  • 安徽兴锂新能源有限公司

Dates

Publication Date
20260512
Application Date
20260313

Claims (10)

  1. 1. The wide-temperature-range lithium battery electrolyte is characterized by comprising, The solvent system comprises linear carbonate, low-condensation-point carboxylic ester, nitrile solvent and phosphate solvent, wherein the lithium salt is lithium hexafluorophosphate, lithium bis (fluorosulfonyl) imide, lithium difluorooxalato borate and lithium difluorophosphate, the total lithium salt concentration is 0.9-1.3 mol/liter, the component E comprises 0.2-2.5 mass percent of a multifunctional epoxy unit, 0.05-1.2 mass percent of 1, 4-butanediol bis (tert-butyldimethylsilyl) ether and 0.05-0.6 mass percent of tributyl borate, the multifunctional epoxy unit comprises polyethylene glycol diglycidyl ether and 1, 3-bis (3-glycidyl) propyl) tetramethyl disiloxane, and the ratio of the epoxy equivalent of the multifunctional epoxy unit to the hydroxy equivalent released by the 1, 4-butanediol bis (tert-butyldimethylsilyl) ether is 0.7-2.5.
  2. 2. The wide temperature range lithium battery electrolyte according to claim 1, wherein: Based on the total mass of the solvent, the linear carbonate is 35 mass percent of ethyl methyl carbonate and 20 mass percent of diethyl carbonate, the low-condensation-point carboxylic ester is 10 mass percent of ethyl propionate, the nitrile solvent is 25 mass percent of 3-methoxy propionitrile, and the phosphate solvent is 10 mass percent of triethyl phosphate.
  3. 3. The wide temperature range lithium battery electrolyte according to claim 1, wherein: lithium hexafluorophosphate was 0.65 mol/liter, lithium bis (fluorosulfonyl) imide was 0.25 mol/liter, lithium difluorooxalato borate was 0.08 mol/liter, and lithium difluorophosphate was 0.03 mol/liter.
  4. 4. The wide temperature range lithium battery electrolyte according to claim 1, wherein: Ethylene sulfite is 0.6 to 1.5 mass percent.
  5. 5. The wide temperature range lithium battery electrolyte according to claim 1, wherein: The polyethylene glycol diglycidyl ether is added in an amount of 0.5 to 1.0 mass% and has an epoxy equivalent of 250 to 320 grams per equivalent.
  6. 6. The wide temperature range lithium battery electrolyte according to claim 1, wherein: The 1, 3-bis (3-glycidylether propyl) tetramethyldisiloxane is added in an amount of 0.1 to 0.6 mass% and has two epoxy groups in its molecule.
  7. 7. The wide temperature range lithium battery electrolyte according to claim 1, wherein: The 1, 4-butanediol bis (t-butyldimethylsilyl) ether is added in an amount of 0.15 to 0.40 mass% and contains at least two silyl ether linkages in the molecule.
  8. 8. The wide temperature range lithium battery electrolyte according to claim 1, wherein: Tributyl borate is 0.10 to 0.25 mass% and the ratio of the molar number of boron centers of tributyl borate to the hydroxyl equivalent released by 1, 4-butanediol bis (t-butyldimethylsilyl) ether is 0.05 to 0.4.
  9. 9. The preparation method of the wide-temperature-range lithium battery electrolyte is characterized by comprising the following steps of: Mixing the solvent system and stirring under an inert atmosphere to a water content of not more than 20 mg/kg; mixing solvent system under inert atmosphere and cooling to 0-20 ℃, adding lithium hexafluorophosphate in batches under stirring, adding lithium difluoroborate and lithium difluorophosphate at 20-30 ℃, adding lithium bis (fluorosulfonyl) imide, finally stirring until the mixture is clear, sequentially adding ethylene sulfite, a multifunctional epoxy unit and 1, 4-butanediol bis (tert-butyl dimethylsilyl) ether, then diluting tributyl borate with the solvent system in advance, then dripping, filtering and sealing for storage.
  10. 10. A method for preparing the same according to claim 9, wherein: stirring for at least 20 min after adding the above materials, filtering with polytetrafluoroethylene filter membrane with pore size of 0.2 μm, filtering, filling into aluminum bottle or fluoride bottle, sealing with argon, and storing at 0-10deg.C in dark place.

Description

Wide-temperature-range lithium battery electrolyte and preparation method thereof Technical Field The invention relates to the technical field of lithium battery electrolyte, in particular to a wide-temperature-range lithium battery electrolyte and a preparation method thereof. Background With the large-scale application of electric vehicles and electrochemical energy storage systems in cold regions, outdoor charging in winter, and high Wen Zhuche/storage in summer, power and energy storage batteries are required to maintain available power, efficiency and life in a wide ambient temperature range, particularly to realize higher-rate charging under low temperature conditions and bear high-charge state storage without excessive flatulence under high temperature conditions. In the industrialized lithium ion battery at present, a nonaqueous liquid electrolyte system is mostly adopted, and lithium hexafluorophosphate is generally used as lithium salt, carbonic ester is used as solvent and a small amount of additive is matched to form an interfacial film so as to support a graphite negative electrode, a high-nickel positive electrode and other material systems. With the improvement of working voltage of a high-nickel positive electrode, the improvement of negative electrode capacity of a silicon-based component and the design of 'less liquid amount', higher requirements are put on infiltration and transmission, and bulk phase transmission and interface stability of electrolyte under a wide temperature range are easier to become limiting factors. In low temperature (e.g., -20 ℃ and below) environments, solvent viscosity increases, salt dissociation and diffusion slow down, resulting in reduced ionic conductivity and desolvation/charge transfer kinetics and thus increased polarization, and in fast charge processes, the local potential of the negative electrode may cross the lithium precipitation threshold, creating metallic lithium deposition and uneven growth, inducing irreversible lithium loss, impedance rise and potential safety risks. In contrast, at high temperatures (e.g., 55-60 ℃) and high charge conditions, the electrolyte is more susceptible to oxidative decomposition and salt-related side reactions, trace amounts of moisture can promote acidic species generation and accelerate dissolution/regeneration of the anode-cathode interfacial film, transition metal dissolution and gas byproduct accumulation, manifested as soft-pack swelling, internal pressure rise, capacity fade acceleration and consistency degradation. The existing improvement means generally improve low-temperature transmission or high-temperature stability respectively by introducing a low-condensation point cosolvent, increasing salt concentration or configuring a multifunctional additive, but the adjustment is often accompanied by side effects of the other end temperature region, namely, a low-temperature friendly solvent/additive can improve high-temperature reactivity and gas production tendency, a high-temperature stability guiding system can improve viscosity and interface impedance, so that low-temperature quick filling is more limited, and meanwhile, the unavoidable trace water/acid and material differences in manufacturing and use can enlarge the contradiction. Therefore, the core problems to be solved in the prior art are: In practical application of the high-nickel positive electrode and the graphite/silicon-based negative electrode, the same electrolyte can simultaneously meet the requirements of lithium precipitation inhibition and low impedance under the low-temperature high-rate charging condition, and the requirements of gas production control and interface stability under the high-temperature high-charge state storage or circulation condition, and can also meet the requirements of infiltration transmission and manufacturing repeatability under the condition of less liquid amount. Disclosure of Invention (One) solving the technical problems Aiming at the defects of the prior art, the invention provides a wide-temperature-range lithium battery electrolyte and a preparation method thereof, wherein the component A is linear carbonate and low-condensation-point carboxylate; the electrolyte is prepared by preparing a solvent mother solution and dissolving salt step by step, sequentially adding the component D and the component E, filtering and sealing, maintaining low viscosity and ion transmission of the electrolyte at low temperature, reducing lithium precipitation risk, inhibiting gas production and interface degradation and avoiding bulk thickening under a high-temperature charged state, and solving the technical problems recorded in the background technology. (II) technical scheme In order to achieve the above purpose, the invention is realized by the following technical scheme: A wide-temperature-range lithium battery electrolyte comprises a solvent system, a lithium salt, ethylene sulfite and a component E, wherein the solvent