Composite solid electrolyte and its preparation method and application

Abstract

The invention discloses a composite solid electrolyte, comprising a first solid electrolyte layer and a second solid electrolyte layer, wherein the first solid electrolyte layer is a polymer solid electrolyte layer, and the second solid electrolyte layer includes a polymer solid electrolyte and an inorganic solid electrolyte , the mass content of the second solid electrolyte layer in the composite solid electrolyte is 50-90%, and the mass content of the inorganic solid electrolyte in the second solid electrolyte layer is 10-70%; the invention also discloses the composite solid electrolyte Preparation method and application thereof; the composite solid electrolyte disclosed in the present invention combines the advantages of inorganic solid electrolyte and polymer solid electrolyte, has high electrical conductivity, wide electrochemical window, can effectively inhibit the growth of lithium dendrites, and prevent the pulverization of metal negative electrodes. The preparation method is simple and easy for industrialized production.

Description

technical field [0001] The invention belongs to the technical field of lithium ion batteries, and in particular relates to a composite solid electrolyte and its preparation method and application. Background technique [0002] At present, commercialized lithium batteries use organic liquid electrolytes, which have problems such as easy leakage, flammability, and poor safety. In recent years, with the application of lithium batteries in electric vehicles and chemical energy storage fields, the safety of batteries has become more and more serious. important. Replacing the organic liquid electrolyte with a solid electrolyte can effectively improve the safety of lithium-ion batteries. [0003] In order to meet the performance requirements of all-solid-state batteries, the research focus of solid electrolytes mainly includes two aspects, improving the room temperature lithium ion conductivity of solid electrolytes and improving the mechanical strength of solid electrolytes. [...

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Problems solved by technology

[0004] At present, the solid electrolytes that have been widely studied mainly include polymer electrolytes and inorganic electrolytes. Polymers have high ion conductivity under high temperature conditions, and have high stability to metal lithium, and are easy to form films and process. Low conductivity at room temperature (about 10 -5 S / cm~10 -7 S / cm) and narrow electrochemical window, it is not suitable for battery systems with higher working voltage than lithium iron phosphate; inorganic electrolytes are divided into oxide and sulfide types. Compared with polymers, inorganic electrolytes have higher room temperature conductivity, at 10 -3 ~10 -4 About S / cm, some even exceed the conductivity of the organic electrolyte, and the working voltage window is wide, but the interface resistance with the positive and negative materials is larger and the stability is insufficient, and because of the lack of toughness, it is difficult to prepare an all-solid-state battery. Cracks are prone to occur in the medium, especially because of the preparation process problem, when the relative density of the inorganic solid electrolyte is lower than 95%, the bulk phase ionic conductivity will be greatly reduced

In order to solve the problem of low interface resistance and ionic conductivity, most researchers choose to add about 5% organic liquid electrolyte, which can be called a quasi-solid-state battery, but this system still has liquid electrolyte leakage and limited operating voltage. question

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