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CN-122025837-A - Plasticizer synergistic modified low-temperature polymer electrolyte and low-temperature silicon-based negative lithium ion battery using same

CN122025837ACN 122025837 ACN122025837 ACN 122025837ACN-122025837-A

Abstract

The invention discloses a plasticizer synergistically modified low-temperature polymer electrolyte and a low-temperature silicon-based negative electrode lithium ion battery using the same. The precursor solvent at least comprises one low-freezing point organic solvent capable of dissolving the polymer matrix, and the plasticizer is composed of two organic solvents with different lithium ion coordination capacities. The invention provides a synergistic modification strategy of a dual plasticizer based on intermolecular interaction, which regulates and controls the interaction and interface stability between lithium ions and a polymer matrix through optimizing ether and ester solvents with different coordination capacities and different oxidation-reduction resistances of the ether and the ester solvents, promotes desolvation of the lithium ions and realizes the performance of a polymer electrolyte at a low temperature. Meanwhile, the preferred volatile organic solvent with low freezing point is beneficial to industrial production, reduces energy consumption and can still ensure stable circulation of the silicon anode in a small amount of residual.

Inventors

  • LI QIAN
  • MING JUN
  • CAI TAO
  • ZHAO FEI
  • MA ZHENG

Assignees

  • 中国科学院长春应用化学研究所

Dates

Publication Date
20260512
Application Date
20260126
Priority Date
20250930

Claims (10)

  1. 1. A low-temperature polymer electrolyte cooperatively modified by a plasticizer is characterized by comprising, (I) The lithium ion battery is prepared from a polymer matrix, a precursor solvent, lithium salt and a plasticizer by a solution casting method; (ii) The precursor solvent comprises at least one low freezing point organic solvent that can dissolve the polymer matrix; (iii) The plasticizer is composed of two organic solvents with different coordination capacities with lithium ions, and the mass ratio of the two organic solvents is 4:1-1:4.
  2. 2. The low-temperature polymer electrolyte cooperatively modified by the plasticizer according to claim 1, wherein the low-freezing point organic solvent comprises one or more of tetrahydrofuran, acetone and dimethyl carbonate, and the mass ratio of the precursor solvent to the polymer matrix is 5-15:1.
  3. 3. The low-temperature polymer electrolyte cooperatively modified by the plasticizer according to claim 1, wherein the lithium salt comprises one or more of lithium difluorooxalato borate, lithium hexafluorophosphate, lithium bis (fluorosulfonyl) imide, lithium bis (trifluoromethanesulfonyl) imide, lithium dioxaoxalato borate and lithium difluorodioxaato phosphate, and the mass ratio of the lithium difluorooxalato borate to the polymer matrix is 1:4-1.
  4. 4. The low-temperature polymer electrolyte cooperatively modified by the plasticizer according to claim 1, wherein the two organic solvents with different coordination abilities with lithium ions are an organic solvent I with stronger coordination ability with lithium ions and stronger reduction resistance and an organic solvent II with weaker coordination ability with lithium ions and capable of forming a stable SEI film on the surface of a silicon-based negative electrode; wherein the organic solvent I comprises one or more of ethylene glycol dimethyl ether, ethylene glycol dibutyl ether, diethylene glycol dimethyl ether, diethylene glycol methyl ethyl ether, diethylene glycol isopropyl methyl ether and tetraethylene glycol dimethyl ether; the organic solvent II comprises one or more of fluoroethylene carbonate, bifluoroethylene carbonate, trifluoropropylene carbonate, methyl trifluoroethyl carbonate, ethyl trifluoroethyl carbonate and di (2, 2, 2-trifluoroethyl) carbonate.
  5. 5. The low-temperature polymer electrolyte cooperatively modified by the plasticizer according to claim 1, wherein the mass percentage of the plasticizer is 10% -60% of the total mass of the polymer electrolyte, and the polymer matrix comprises one of polyvinylidene fluoride-hexafluoropropylene, polyethylene oxide, polyacrylonitrile, polyvinylidene fluoride and polymethyl methacrylate.
  6. 6. The method for preparing a plasticizer synergistically modified low temperature polymer electrolyte according to any one of claims 1 to 5, comprising, Adding a polymer matrix and lithium salt which are dried in vacuum into a precursor solvent, heating and stirring vigorously to obtain a uniform viscous solution, adding a plasticizer, and stirring to obtain a film-making solution; And preparing an electrolyte membrane by the membrane preparation liquid through a solution pouring method, and drying to obtain the plasticizer synergistically modified low-temperature polymer electrolyte.
  7. 7. The method for preparing a plasticizer synergistic modified low temperature polymer electrolyte as claimed in claim 6, wherein the heating temperature of the heating and vigorous stirring is 55 o C~75 o ℃ and the stirring time is 0.5 h-6 h.
  8. 8. The method for preparing a plasticizer synergistically modified low temperature polymer electrolyte according to claim 6, wherein the thickness of the polymer electrolyte membrane obtained by the solution casting method is 50-300 μm.
  9. 9. The application of the plasticizer synergistically modified low-temperature polymer electrolyte in preparation of a low-temperature silicon-based negative electrode lithium ion battery according to any one of claims 1-5.
  10. 10. A low-temperature silicon-based negative electrode lithium ion battery is characterized by comprising the plasticizer synergistically modified low-temperature polymer electrolyte as set forth in claim 1, and further comprising a silicon negative electrode serving as a working electrode and a lithium sheet serving as a counter electrode and a reference electrode.

Description

Plasticizer synergistic modified low-temperature polymer electrolyte and low-temperature silicon-based negative lithium ion battery using same Technical Field The invention belongs to the technical field of lithium ion batteries, and particularly relates to a plasticizer synergistically modified low-temperature polymer electrolyte and a low-temperature silicon-based negative electrode lithium ion battery using the same. Background The lithium ion battery has the advantages of high working voltage, high energy density, good cycle stability, low self-discharge rate, no memory effect, environmental friendliness and the like, and is widely applied to the fields of portable electronic equipment, aerospace, new energy automobiles, large-scale energy storage devices and the like. However, with the technological innovation, the development of lithium ion batteries faces two major challenges, namely, how to increase the energy density of the battery and how to increase the safety of the battery. The theoretical specific capacity of the commercial graphite cathode is 372 mAh/g only, and the commercial graphite cathode cannot meet the increasing market demand. The theoretical specific capacity of the silicon negative electrode is up to 4200 mAh/g, which is 10 times of that of graphite, and the silicon negative electrode is considered to be an ideal negative electrode material of the next-generation lithium ion battery. Meanwhile, the lithium intercalation potential of silicon is higher than that of a graphite negative electrode, so that the formation of lithium dendrite in the battery cycle process can be effectively relieved, and the safety of the battery is improved. However, the use of silicon cathodes still faces some challenges. During lithiation, the silicon negative electrode can undergo a significant volume expansion (about 400%) resulting in pulverization of the silicon particles and collapse of the negative electrode structure, losing the electron or ion conductivity of the silicon negative electrode, leading to cell failure. At present, most of silicon-based negative electrode lithium ion batteries adopt traditional liquid electrolyte, so that the newly exposed surface of the silicon negative electrode can have serious side reaction with the electrolyte, the electrolyte is continuously consumed, and a new solid electrolyte interface film (SEI) is continuously formed. In particular, organic solvents such as Ethylene Carbonate (EC), dimethyl carbonate (DMC), ethylmethyl carbonate (EMC) and diethyl carbonate (DEC) commonly used in liquid electrolytes have defects of easy volatilization, easy leakage, high flammability and the like, and may cause safety problems such as fire or explosion under the conditions of collision, thermal runaway and the like. With the increase of safety awareness, the problem of liquid electrolyte is getting more and more attention. Solid Polymer Electrolyte (SPE) has the advantages of wide electrochemical window, no inflammable or leakage risk, good thermal stability and the like, and becomes an important direction for the development of lithium ion battery electrolyte. However, SPE has poor contact with the electrode, resulting in increased interface impedance, and most solid electrolytes have low ionic conductivity, which cannot meet the application requirements of lithium ion batteries. In order to solve the above problems, a liquid electrolyte and a solid electrolyte are fused to form a semi-solid Gel Polymer Electrolyte (GPE) as an intermediate product for transition of the liquid electrolyte to the solid electrolyte. GPE embeds electrolyte salts into a network of polymer matrices, giving them high ion transport capacity and mechanical strength. In such electrolytes, the polymer matrix serves as a support for the solid state structure and the electrolyte salt serves as a key for providing ions in the polymer matrix. In other words, GPE combines the advantages of liquid electrolytes and solid-state electrical electrolytes, with high ionic conductivity and solid-like mechanical stability. The residual solvent in GPE also plays a key role, and the small molecule solvent, as the main salt dissolving agent, can promote dissociation of lithium salt, thereby increasing the number of free lithium ions available for charge transport, and at the same time plays a role as a plasticizer, increasing the segmental motion of the polymer, providing a high entropy medium for ion migration, reducing crystallinity and increasing free volume. However, higher levels of liquid electrolyte (or plasticizer) within the GPE can provide higher ionic conductivity, but inevitably detract from the mechanical strength of the electrolyte. Therefore, how to ensure the mechanical stability of the electrolyte while improving the ion transport capability becomes a key challenge in the current solid polymer electrolyte research. In particular, at low temperatures, freezing of solvents and kinetic limitations of ion