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CN-121983660-A - In-situ curing gel polymer electrolyte with high cycling stability

CN121983660ACN 121983660 ACN121983660 ACN 121983660ACN-121983660-A

Abstract

The invention discloses an in-situ curing gel polymer electrolyte with high cycling stability and application thereof in a lithium ion battery, and belongs to the technical field of lithium ion battery materials. The electrolyte is formed by in-situ polymerization of a precursor mixture containing electrolyte, a main crosslinking agent N, N' -methylene bisacrylamide and a multi-arm crosslinking agent in a battery. The multi-arm crosslinking agent has at least a three-arm structure, the design avoids interface side reaction caused by high-activity double bonds from the molecular level, and the Lewis acidity of the central atom can promote the dissociation of lithium salt. The battery adopting the electrolyte forms a stable and elastic SEI/CEI film at the electrode interface, so that the cycling stability is remarkably improved, and the capacity retention rate is higher than 90% after cycling for 500 times at 25 ℃ and 1 ℃. The invention has simple process, is compatible with the existing production line, and is suitable for lithium ion batteries with high energy density and long service life.

Inventors

  • ZHOU GANG
  • CHEN WENJIE
  • HE ZHIYUAN
  • WANG BINGHUAN
  • HUANG WEIHAO
  • LI MINGZHE
  • CHEN HAO

Assignees

  • 东莞理工学院
  • 东莞市钜大电子有限公司

Dates

Publication Date
20260505
Application Date
20260121

Claims (10)

  1. 1. The high-cycle-stability in-situ curing gel polymer electrolyte is characterized by being prepared by in-situ polymerization of a precursor mixture containing electrolyte, a main crosslinking agent N, N' -methylene bisacrylamide and a multi-arm crosslinking agent in a battery, wherein: the multi-arm crosslinking agent has at least a three-arm structure and a molecular general formula of: Wherein X is a central atom and is selected from one or more of Si, B, P, S, W, mo, m is more than or equal to 1, n is more than or equal to 3, and R is a divalent organic group; The molecular structure of the multi-arm crosslinking agent does not contain X=O double bonds; in the polymer network of the gel polymer electrolyte, the central atom X is connected with the organic polymer framework only through X-O-C single bonds.
  2. 2. The gel polymer electrolyte of claim 1, wherein the multi-arm crosslinking agent is selected from at least one of tripropenyl borate, tetra allyl silicate, triallyl silicate.
  3. 3. The gel polymer electrolyte according to claim 1 or 2, wherein the multi-arm crosslinking agent is 0.05-5wt% in the precursor mixture.
  4. 4. The gel polymer electrolyte according to claim 1, wherein the mass ratio of the main crosslinking agent N, N' -methylenebisacrylamide to the multi-arm crosslinking agent is 1:10-10:1.
  5. 5. The gel polymer electrolyte of claim 1, wherein the electrolyte comprises an organic carbonate solvent and a lithium salt; The organic carbonate solvent is selected from one or more of ethylene carbonate, dimethyl carbonate, diethyl carbonate and methyl ethyl carbonate; The lithium salt is selected from one or more of LiPF 6 、LiBF 4 , liFSI, liTFSI, liDFOB.
  6. 6. The gel polymer electrolyte of claim 1, wherein the precursor mixture further comprises a film forming aid and/or a solid electrolyte filler; The film forming auxiliary agent is selected from one or more of fluorocarbonate, phosphate, sulfone and fluorine-containing ether solvents; The solid electrolyte filler is selected from one or more of LLZO, LAGP, LATP, NASICON type solid electrolyte, fluorine-containing polymer and inorganic oxide.
  7. 7. A lithium ion battery with high cycle life is characterized by comprising a positive electrode, a negative electrode, electrolyte and a diaphragm, wherein the diaphragm is loaded with the in-situ cured gel polymer electrolyte layer according to any one of claims 1-6, or the in-situ cured gel polymer electrolyte layer is contacted with the positive electrode and/or the negative electrode simultaneously to form an interface layer.
  8. 8. The lithium ion battery according to claim 7, wherein the capacity retention rate is not lower than 90% after 500 cycles at 25 ℃ and 1 ℃ and not lower than 85% after 500 cycles at 45 ℃ and 1 ℃.
  9. 9. The lithium ion battery of claim 7 or 8, wherein the in-situ cured gel polymer electrolyte is formed by thermally initiated polymerization at a thermal initiation temperature of 50-80 ℃ for a holding time of 2-10 hours.
  10. 10. The lithium ion battery according to claim 7 or 8, wherein the in-situ cured gel polymer electrolyte is formed by photoinitiated polymerization, and the irradiation light source is ultraviolet light or near ultraviolet light with a wavelength of 320-420 nm, and the irradiation time is 5-20 min.

Description

In-situ curing gel polymer electrolyte with high cycling stability Lithium ion battery Technical Field The invention relates to the technical field of lithium ion battery materials, in particular to an in-situ cured gel polymer electrolyte with high cycling stability and a lithium ion battery. Background The invention belongs to the technical field of lithium ion battery materials, and particularly relates to an in-situ cured gel polymer electrolyte with high cycling stability and application thereof in a lithium ion battery. With the rapid development of new energy automobiles and large-scale energy storage systems, lithium ion batteries are increasingly demanded for high energy density, high safety and long cycle life. Although the traditional liquid electrolyte has higher ionic conductivity, the traditional liquid electrolyte has the problems of easy leakage, flammability and the like, and is easy to decompose under the conditions of high temperature and high voltage, so that the battery cycle stability is reduced and the safety risk is increased. For this reason, gel polymer electrolytes are one of the current research hotspots due to their combination of high ion conductivity of liquid electrolytes and mechanical stability and safety of solid electrolytes. At present, researchers generally adopt an in-situ polymerization method to form a gel polymer electrolyte network inside a battery so as to improve interface contact between an electrode and an electrolyte and improve overall performance of the battery. The common technical routes mainly comprise the following categories: One method is to introduce polymerizable monomers containing multifunctional groups and crosslinking agents (such as polyacrylate, methacrylate and the like) into electrolyte, and build a three-dimensional crosslinked network at an electrode/membrane interface through thermal or photoinitiated polymerization. However, the crosslinker molecules commonly used in such systems typically contain a large number of carbonyl groups (c=o) or x=o bonds formed by other higher inorganic central atoms (e.g. p= O, S =o, etc.). During the charge and discharge of the battery, these highly reactive groups are susceptible to electrochemical reduction or oxidative decomposition, especially under high pressure or high temperature conditions, and participate in the formation of unstable solid electrolyte interfacial films (SEIs) or positive electrode electrolyte interfacial films (CEIs). Continuous rupture and reconstruction of the interfacial film can lead to continuous consumption of electrolyte and gradual increase of interfacial impedance, ultimately leading to rapid decay of battery capacity. Another class of improvements is the addition of inorganic or organic-inorganic hybrid fillers, such as nano-oxides, metal-organic framework materials, etc., to the electrolyte system in an effort to improve ionic conductivity, mechanical strength, and thermal stability. Although this type of method improves the overall performance of the electrolyte to some extent, there are problems of uneven dispersion of the filler, easy agglomeration, poor interfacial compatibility with the polymer matrix, etc., and a high content of filler may introduce additional interfacial resistance. More importantly, the technology cannot fundamentally solve the problem of side reaction activity of the crosslinking agent molecules at the electrochemical interface, and most of the crosslinking agents still are traditional multifunctional compounds containing C=O or X=O structures. In addition, there have been studies to optimize electrolyte composition by introducing deep eutectic solvents, fluorine-containing solvents or functional film-forming additives to widen electrochemical window and improve interface stability. However, these systems often still rely on cross-linking agents with higher oxidation states to build networks, the interfaces of which still face challenges of insufficient chemical and electrochemical stability over long-term cycles. In summary, although the existing in-situ curing gel polymer electrolyte technology has advanced in terms of improving ionic conduction and mechanical properties, the highly reactive groups such as c=o or x=o commonly existing in the molecular structure of the crosslinking agent still remain key factors that cause frequent side reactions at the electrode/electrolyte interface, unstable interfacial film structure and limited battery cycle life. Therefore, from the aspect of molecular design, a novel cross-linking agent which does not contain a reactive double bond structure, can construct a stable interface and has good ion conductivity is developed, and has important scientific significance and practical value for realizing high-cycle stability gel polymer electrolyte and long-service-life lithium ion batteries. Disclosure of Invention The invention aims to provide an in-situ curing gel polymer electrolyte with high cycle stability and