A kind of electrolyte solution for lithium metal secondary battery and lithium metal secondary battery

Abstract

An electrolyte solution for a lithium metal secondary battery, comprising an organic solvent, an electrolyte salt, and an electrolyte additive, the electrolyte additive comprising a component A and a component B, and the component A is obtained by polymerization of a first monomer and a second monomer, The first monomer is selected from 2,2,2‑trifluoroethyl (meth)acrylate, hexafluorobutyl (meth)acrylate, octafluoropentyl (meth)acrylate and 2‑(trifluoromethyl) One or more of acrylic acid; the second monomer is selected from (meth)acrylic acid C 1 -C 6 One or more of alkyl esters and dimethacrylates; component B is selected from one or more of fluoroethylene carbonate, vinylene carbonate and lithium nitrate. The present invention also relates to a lithium metal secondary battery, comprising a positive electrode, a negative electrode, a diaphragm and the aforementioned electrolyte solution for the lithium metal secondary battery. The electrolyte solution of the present invention can effectively improve the deposition morphology of metallic lithium, induce uniform deposition of lithium ions, suppress the generation of lithium dendrites, and significantly improve the utilization efficiency of metallic lithium in lithium metal secondary batteries.

Description

technical field [0001] The invention relates to the field of energy storage devices, and in particular to an electrolyte solution for a lithium metal secondary battery and the lithium metal secondary battery. Background technique [0002] Due to its ultra-high energy density (3860mAh / g), low electrode potential (-3.040V vs. SHE) and low density (0.53g / cm 3 ), has been considered as an ideal anode for constructing high-energy-density lithium batteries. However, due to the inhomogeneity of lithium ion diffusion from the electrolyte body and deposition on the surface of the electrode, lithium dendrites are generated. On the contrary, the generation of lithium dendrites further leads to the inhomogeneity of lithium ion deposition, which repeatedly makes metal lithium batteries The solid-liquid electrolyte film (SEI film) on the electrode surface continues to grow, crack, and peel off, resulting in continuous consumption of the electrolyte and low utilization efficiency of lithi...

AI Technical Summary

Problems solved by technology

One way to improve performance is to coat a solid polymer layer on the surface of the lithium negative electrode to create an "artificial SEI film" for the lithium sheet. This solid polymer layer is conducive to reducing the direct contact between the lithium negative electrode and the organic electrolyte and reducing the lithium The occurrence of an irreversible chemical reaction between the negative electrode and the electrolyte, however, the solid polymer layer will largely retard the migration of electron ions, and cannot fundamentally solve many problems of the lithium metal negative electrode in the liquid electrolyte

Recently, some researchers can increase the coulombic efficiency of carbonate electrolyte to 99.2% by adding electrolyte additives, but it is still not enough to meet the demand for metal lithium utilization efficiency (99.8%) in practical applications.

From many literatures on lithium metal anodes in recent years, the coulombic efficiency of half-cell lithium metal anodes is generally low, but the method of pre-depositing a large amount of metal lithium on the anode in the full battery covers up the disadvantage of low metal lithium utilization.

The coulombic efficiency of lithium metal in ether electrolyte is high, 1M LiTFSI / EC:EMC (volume ratio=1:1) contains 1wt% LiNO 3 The coulombic efficiency of the additive electrolyte is 98%, and the cycle performance is also good, but its voltage window is low, so many research papers use the ether electrolyte in the half-cell and the carbonate electrolyte in the full battery. Get inflated battery performance

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