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CN-122025780-A - Polymer electrolyte for all-solid-state battery, preparation method of polymer electrolyte and all-solid-state battery

CN122025780ACN 122025780 ACN122025780 ACN 122025780ACN-122025780-A

Abstract

The embodiment of the application provides a polymer electrolyte for an all-solid-state battery, a preparation method of the polymer electrolyte and the all-solid-state battery. The polymer electrolyte for the all-solid-state battery comprises a positive electrode polymer electrolyte film and a negative electrode polymer electrolyte film, wherein the positive electrode polymer electrolyte film comprises a polyester-based polymer, the structural formula of the polyester-based polymer is shown as formula I, m is 0.5-5, n is 5-9.5, j is 5-9.5, k is 0.5-5, the negative electrode polymer electrolyte film comprises a porous base film and a polyether-based polymer embedded in the porous base film, the structural formula of the polyether-based polymer is shown as formula II, o is 5-9.5, p is 0.5-5, and x is 2-6, and the technical problems that in the prior art, an electrochemical window of the polymer electrolyte is lower, and interface stability between an electrode material and an electrolyte membrane is poor are solved.

Inventors

  • SUN YULIANG
  • XU FANGLIN
  • ZHAO FENGDONG
  • YU DA

Assignees

  • 奇瑞汽车股份有限公司

Dates

Publication Date
20260512
Application Date
20260212

Claims (10)

  1. 1. A polymer electrolyte for an all-solid-state battery, comprising a positive electrode terminal polymer electrolyte film and a negative electrode terminal polymer electrolyte film, characterized in that the positive electrode terminal polymer electrolyte film comprises a polyester-based polymer, and the structural formula of the polyester-based polymer is shown as formula I: I is a kind of In the formula I, m is 0.5-5, n is 5-9.5, j is 5-9.5, and k is 0.5-5; the negative electrode end polymer electrolyte film comprises a porous base film and a polyether-based polymer embedded in the porous base film, wherein the structural formula of the polyether-based polymer is shown in a formula II: II (II) In the formula II, o is 5-9.5, p is 0.5-5, and x is 2-6; wherein m, n, j and k represent the mole fraction of the corresponding chain unit in the structure shown in the formula I; and o, p and x respectively represent the mole fraction of the corresponding chain unit in the structure shown in the formula II.
  2. 2. The polymer electrolyte for all-solid-state batteries according to claim 1, wherein the mass ratio of the porous base film to the polyether-based polymer is 1 to 5:25 to 30, and/or the porous base film is selected from any one or more of polypropylene fiber film, polyethylene, polypropylene, polyimide.
  3. 3. The polymer electrolyte for an all-solid battery according to claim 1, wherein the thickness of the positive electrode-side polymer electrolyte film is 23 to 30 μm, and the thickness of the negative electrode-side polymer electrolyte film is 23 to 30 μm.
  4. 4. A production method of the polymer electrolyte for an all-solid battery according to any one of claims 1 to 3, comprising: Step a, carrying out a first prepolymerization reaction on raw materials comprising ethylene carbonate, a first initiator and 4-hydroxybutyl acrylate to obtain a first prepolymerized precursor solution; Step b, adding a first lithium salt into the first pre-polymerized precursor solution, coating the solution on the surface of the positive electrode plate, and then carrying out a first heating copolymerization reaction to form a positive electrode end polymer electrolyte film on the surface of the positive electrode plate; step c, carrying out a second prepolymerization reaction on raw materials comprising polyethylene glycol monomethyl ether monoacrylate, a second initiator and 2, 3-tetrafluoropropyl methacrylate to obtain a second precursor solution after prepolymerization; and d, adding a second lithium salt into the second pre-polymerized precursor solution, and then mixing the second pre-polymerized precursor solution with the porous base film to perform a second heating copolymerization reaction to obtain the negative electrode end polymer electrolyte film.
  5. 5. The method of claim 4, wherein step a satisfies at least one of the following conditions: (1) The molar ratio of the ethylene carbonate to the 4-hydroxybutyl acrylate is 8.5:1.5-9:1; (2) The dosage of the first initiator is 0.8-1 wt% of the mass of the ethylene carbonate; (3) The temperature of the first prepolymerization reaction is 55-70 ℃; (4) The time of the first prepolymerization reaction is 0.5-2.5 h.
  6. 6. The method of claim 4, wherein step b satisfies at least one of the following conditions: (1) The temperature of the first heating copolymerization reaction is 80-100 ℃; (2) The first heating copolymerization reaction time is 8-12 hours; (3) The mass ratio of the first lithium salt to the ethylene carbonate is 0.5:3.5-1:2.5.
  7. 7. The method of claim 4, wherein step c satisfies at least one of the following conditions: (1) The molar ratio of the polyethylene glycol monomethyl ether monoacrylate to the 2, 3-tetrafluoropropyl methacrylate is 8.5:1.5-9:1; (2) The dosage of the second initiator is 0.8-1 wt% of the mass of the polyethylene glycol monomethyl ether monoacrylate; (3) The temperature of the second prepolymerization reaction is 20-30 ℃; (4) The second prepolymerization reaction time is 0.5-2.5 h.
  8. 8. The method of claim 4, wherein step d satisfies at least one of the following conditions: (1) The temperature of the second heating copolymerization reaction is 80-100 ℃; (2) The second heating copolymerization reaction time is 8-12 hours; (3) The mass ratio of the second lithium salt to the polyethylene glycol monomethyl ether monoacrylate is 0.5:3.5-1:2.5.
  9. 9. The method of claim 4, wherein the method of preparation satisfies at least one of the following conditions: (1) The first initiator and the second initiator are respectively and independently selected from any one or more of azodiisobutyronitrile, benzoyl peroxide and azodiisoheptonitrile; (2) The first lithium salt and the second lithium salt are each independently selected from any one or more of lithium bis (trifluoromethane) sulfonyl imide, lithium hexafluorophosphate, lithium difluorosulfonyl imide, lithium difluorooxalato borate, and lithium trifluoromethane sulfonate.
  10. 10. An all-solid-state battery comprising a positive electrode layer, a positive electrode electrolyte film, a negative electrode electrolyte film and a lithium metal negative electrode layer which are sequentially stacked, wherein the positive electrode electrolyte film is a positive electrode polymer electrolyte film in the polymer electrolyte for all-solid-state batteries according to any one of claims 1 to 3 or is prepared by the preparation method according to any one of claims 4 to 9, and the negative electrode electrolyte film is a negative electrode polymer electrolyte film in the polymer electrolyte for all-solid-state batteries according to any one of claims 1 to 3 or is prepared by the preparation method according to any one of claims 4 to 9.

Description

Polymer electrolyte for all-solid-state battery, preparation method of polymer electrolyte and all-solid-state battery Technical Field The embodiment of the invention relates to the technical field of lithium batteries, in particular to a polymer electrolyte for an all-solid-state battery, a preparation method of the polymer electrolyte and the all-solid-state battery. Background In order to fully release the energy density of the battery, it is necessary to couple the low electrode potential lithium metal negative electrode with the high voltage positive electrode. In this battery system, the solid polymer electrolyte film Solid Polymer Electrolytes (SPEs) employed should be compatible with both high voltage positive and lithium metal negative electrodes, i.e., its highest occupied molecular orbital Highest Occupied Molecular Orbital (HOMO) value should be lower than that of high voltage positive electrodes, and the lowest unoccupied orbital Lowest Unoccupied Molecular Orbital (LUMO) value should be higher than that of lithium metal, or stable cathode-electrolyte interphase (CEI) and solid-state State Electrolyte Interface (SEI) should be produced simultaneously on solid-state batteries. However, few single SPEs currently have such a wide energy level window. Polyether-based SPEs are generally capable of forming stable SEI layers with lithium metal, but are continuously oxidized at high pressure, rarely forming stable CEI passivation layers. And high-voltage end-stabilized polymers such as polycarbonate and polyoxalate are easily reduced by lithium metal negative electrodes, and a stable SEI layer cannot be formed. Chinese patent application publication No. CN108963334a, publication No. 2020, 23, discloses a multi-layer polymer electrolyte and battery using separately prepared first electrolyte layer (e.g. poly (N-methylmalonamide, PMA)) and second electrolyte layer (e.g. polyethylene oxide, PEO) laminated to form a double layer solid electrolyte membrane. According to the method, the stability of the anode and the cathode is optimized respectively by selecting the polymer and the lithium salt with specific structures, so that the electrochemical window is effectively widened, and the interface resistance is reduced. However, the method involves independent film forming and subsequent superposition processes, which may cause problems of large interface contact resistance between layers, complex process, large-scale production efficiency and the like. For another example, the invention discloses an in-situ polymerization solid-state battery with a multilayer structure electrolyte and a preparation method thereof, wherein the in-situ polymerization solid-state battery is disclosed in China patent application with a publication number of CN114335716A and a publication date of 2024, 12 and 10. The technology comprises the steps of pre-doping a monomer or an initiator capable of forming an oxidation-resistant or reduction-resistant polymer into positive electrode or negative electrode slurry to prepare a composite electrode, after assembling a battery core, injecting electrolyte containing the corresponding reaction monomer, heating to initiate in-situ polymerization reaction inside the battery, and finally forming an oxidation-resistant polymer layer on the positive electrode side and forming a reduction-resistant polymer layer on the negative electrode side. The method aims to realize a tighter integrated interface between the electrolyte and the electrode material and reduce interface impedance. However, the technical scheme depends on the injection of the liquid electrolyte and the subsequent polymerization process, the process control requirement is high, and the polymerization reaction degree and uniformity may influence the overall performance and consistency of the final electrolyte. In summary, although the adoption of the multi-layer structure design is an effective direction for solving the contradiction between the stability of the positive electrode and the stability of the negative electrode in the solid-state battery, the prior art still has the problems that a single-layer solid-state polymer electrolyte is difficult to simultaneously optimize two key interfaces, and low-voltage stable SPEs (such as polyether-based solid-state electrolyte) are easy to be oxidized and decomposed under high pressure, and SPEs with good oxidation resistance (such as polyester-based solid-state electrolyte) are easy to be reduced when contacting with a lithium metal negative electrode, so that the battery is invalid. Because the compatibility of SPEs with positive and negative electrodes depends on their electrochemical window or whether stable SEI and CEI can be formed. SPE has the ability to inhibit oxidative decomposition and is stable with the positive electrode when its Highest Occupied Molecular Orbital (HOMO) is below the positive electrode potential or forms a stable CEI. Also, for low voltage anode sides, t