Search

CN-122025777-A - Three-dimensional interpenetrating network composite gel electrolyte and diaphragm-free lithium ion battery

CN122025777ACN 122025777 ACN122025777 ACN 122025777ACN-122025777-A

Abstract

The invention relates to the technical field of electrochemical energy storage, in particular to a three-dimensional interpenetrating network composite gel electrolyte and a diaphragm-free lithium ion battery; the three-dimensional interpenetrating network composite gel electrolyte comprises, by weight, 10-30 parts of a polymer matrix, 1-5 parts of an inorganic filler, 3-8 parts of diethyl (2, 2-trifluoroethoxy) methylphosphonate flame retardant and the balance of a basic electrolyte, and solves the long-standing trade-off problem between the mechanical strength and the ionic conductivity of the gel electrolyte in a synergistic way through the exquisite IPN structural design and the covalent bonding strategy of the inorganic filler, converts the traditional sacrificial additive into a functional component, realizes the ingenious combination of efficient flame retardance and high-performance SEI film in-situ construction, reduces the solid-solid interface impedance to an extremely low level through a diaphragm-free interlocking integrated structure, greatly improves the interface stability and the quick charge-discharge capability of the battery, and prolongs the cycle life.

Inventors

  • ZHAO YUNZHU
  • CAI XIANYU
  • LI ENYU
  • ZHONG YIHUA

Assignees

  • 双登集团股份有限公司

Dates

Publication Date
20260512
Application Date
20260206

Claims (10)

  1. 1. The three-dimensional interpenetrating network composite gel electrolyte is characterized by comprising, by weight, 10-30 parts of a polymer matrix, 1-5 parts of an inorganic filler, 3-8 parts of diethyl (2, 2-trifluoroethoxy) methylphosphonate flame retardant and the balance of a basic electrolyte.
  2. 2. The three-dimensional interpenetrating network composite gel electrolyte of claim 1 wherein said polymer matrix comprises a polyethylene oxide-based crosslinked network and a polycyanoacrylate-based crosslinked network.
  3. 3. The three-dimensional interpenetrating network composite gel electrolyte according to claim 2, wherein the polyethylene oxide-based crosslinked network is formed by ultraviolet light initiated polymerization of polyethylene glycol diacrylate monomers.
  4. 4. The three-dimensional interpenetrating network composite gel electrolyte of claim 2 wherein said polycyanoacrylate-based crosslinked network is polymerized from ethyl cyanoacrylate monomers by thermal initiation.
  5. 5. The three-dimensional interpenetrating network composite gel electrolyte according to claim 1, wherein the inorganic filler is a LLZO/LLTO composite filler, and the composite mass ratio of the LLZO to the LLTO is (1-3): 1.
  6. 6. The three-dimensional interpenetrating network composite gel electrolyte according to claim 5, wherein the surface of the LLZO/LLTO composite filler is treated with a vinyl-containing silane coupling agent and has polymerizable c=c double bonds.
  7. 7. The three-dimensional interpenetrating network composite gel electrolyte according to claim 1, wherein the base electrolyte comprises lithium salt and an organic solvent.
  8. 8. A diaphragm-free lithium ion battery is characterized by comprising a positive electrode, a negative electrode and the three-dimensional interpenetrating network composite gel electrolyte according to any one of claims 1 to 7; wherein, the positive electrode and the negative electrode are porous structures with vertical through pore passages inside, the pore diameter of the vertical through pore passages is 1-10 mu m, and the porosity is 10-30%.
  9. 9. A method of preparing a separator-less lithium-ion battery according to claim 8, comprising the steps of: S1, dissolving lithium salt in an organic solvent, sequentially adding diethyl (2, 2-trifluoro ethoxy) methylphosphonate flame retardant, polyethylene glycol diacrylate monomer, ethyl cyanoacrylate monomer and LLZO/LLTO compound filler, and uniformly mixing to obtain a liquid precursor; S2, vacuum pouring the liquid precursor into a stacked positive electrode-cavity-negative electrode cell structure, and sequentially performing thermal polymerization and ultraviolet polymerization to obtain the diaphragm-free lithium ion battery.
  10. 10. The method according to claim 9, wherein in the step S2, the temperature of the thermal polymerization is 50-70 ℃ and the time is 1-3 hours, and in the ultraviolet polymerization, the ultraviolet wavelength is 365nm and the irradiation time is 5-15 minutes.

Description

Three-dimensional interpenetrating network composite gel electrolyte and diaphragm-free lithium ion battery Technical Field The invention relates to the technical field of electrochemical energy storage, in particular to a three-dimensional interpenetrating network composite gel electrolyte and a diaphragm-free lithium ion battery. Background Currently, conventional lithium ion batteries with liquid electrolytes and polyolefin separators as cores face intrinsic safety hazards of easy leakage of electrolytes, flammability, and explosiveness. In addition, the electrochemically inert separator occupies space and weight inside the cell, limiting further energy density. Gel polymer electrolytes are considered to be extremely potential solutions that combine the high ionic conductivity of liquid electrolytes with the high safety of solid electrolytes. However, the existing GPE technology generally has a series of contradictions which are difficult to reconcile, and are often called as a 'teetertotter effect', wherein the introduction of a large amount of liquid plasticizer for realizing high ionic conductivity often leads to significant deterioration of mechanical strength, so that the penetration of lithium dendrites cannot be effectively inhibited, and the design of canceling a diaphragm faces extremely high risks. And the GPE is in physical contact with the electrode, so that the interface impedance is high and unstable, and the performance of the battery is accelerated and attenuated. In addition, flame retardants (e.g., organic phosphorus compounds) conventionally added for improving flame retardancy may seriously impair the ionic conductivity, electrochemical stability, and compatibility with an electrode of an electrolyte, resulting in opposition of "safety" and "performance". Therefore, a novel GPE system which can cooperatively consider mechanical strength, ion transmission, interface stability and intrinsic safety is developed, and a battery structure which is matched with the novel GPE system is designed, so that the novel GPE system becomes a technical bottleneck to be broken through in the field. Disclosure of Invention The invention aims at overcoming the defects in the prior art and provides a three-dimensional interpenetrating network composite gel electrolyte with excellent comprehensive performance and a corresponding diaphragm-free lithium ion battery. The system can effectively unify the characteristics of high ion conductivity, excellent mechanical property, excellent interface stability, intrinsic safety and the like. In order to achieve the above purpose, the technical scheme adopted by the invention is as follows: The invention provides a three-dimensional interpenetrating network composite gel electrolyte, which comprises, by weight, 10-30 parts of a polymer matrix, 1-5 parts of an inorganic filler, 3-8 parts of diethyl (2, 2-trifluoroethoxy) methylphosphonate flame retardant and the balance of a base electrolyte. The flame retardant skillfully fuses phosphorus, fluorine and ethoxy chain segments, and realizes the cooperative promotion of flame retardance and electrochemical performance through a triple cooperative mechanism of gas phase-condensed phase-interfacial phase: The gas-phase flame-retarding mechanism is that in the initial stage of heat abuse of the battery, the flame retardant is heated to decompose and release phosphorus-containing free radicals (such as PO and HPO) and fluorine free radicals (F), so that H and OH active free radicals required by combustion chain reaction can be quenched efficiently, and open fire can be extinguished rapidly. The condensed phase/interface flame retardance and SEI regulation mechanism has moderate coordination capacity to lithium ions of P=O groups and C-F bonds in molecules, and can take part in forming a layer of solid electrolyte interface film rich in high-stability and high-ion conductivity inorganic components such as LiF, li xPOyFz and the like in preference to reduction decomposition of carbonate solvents on the surface of a negative electrode such as graphite and the like. The composite SEI film constructed in situ is like an interface armor, is compact and stable, can effectively prevent continuous side reaction, can homogenize lithium ion flow, and can fundamentally inhibit the generation of lithium dendrites. Electrochemical compatibility because it functions primarily by participating in the construction of a stable SEI film, rather than physically impeding ion migration, its impact on the ionic conductivity of the electrolyte body is minimized, and even indirectly improves the rate performance and cycle life of the battery by significantly improving interface stability. Preferably, the polymer matrix comprises a polyethylene oxide-based crosslinked network and a polycyanoacrylate-based crosslinked network. More preferably, the polyethylene oxide-based crosslinked network is polymerized by ultraviolet light initiation of polyethyl