Lithium-sulfur flow battery and positive electrode electrolyte for lithium-sulfur flow battery and its preparation

Abstract

The invention relates to a lithium-sulfur flow battery and a positive electrode electrolyte thereof, as well as a preparation method of the positive electrode electrolyte. The lithium-sulfur flow battery comprises a battery module, the positive electrode electrolyte, a negative electrode electrolyte, a positive electrode electrolyte storage tank, a circulating pump and a circulation line, wherein the battery module is formed by connecting a single cell or more than two single cells in series, the single cell comprises a negative electrode current collector, a lithium negative electrode, a diaphragm, a positive electrode, a positive electrode current collector and a sealing element, and the positive electrode electrolyte which is a mixed solution of Li2S8 containing nano sulfur powder and lithium trifluoromethanesulfonate or trifluoromethane sulfonic acid lithium imide is filled in the positive electrode electrolyte storage tank, wherein the solvent is a mixed solvent which comprises tetraethylene glycol dimethyl ether or glycol dimethyl ether and 1,3-dioxolane at a volume ratio is (1:5)-(5:1) is taken as a solvent. Compared with a traditional lithium-sulfur battery, the lithium-sulfur flow battery has the advantages that the cycle life and the charge and discharge power are improved; an independent positive electrode electrolyte storage tank structure is adopted, so that the capacity is not controlled by an electrode area.

Description

technical field [0001] The invention relates to the field of lithium-sulfur batteries, in particular to a lithium-sulfur flow battery and a cathode electrolyte for the lithium-sulfur flow battery and its preparation. Background technique [0002] With the increasing consumption of chemical power products by portable devices, the development of secondary batteries has also received more and more attention. Due to high energy density, operating voltage, cycle life and low self-discharge performance, lithium-ion batteries have become the most widely used chemical energy storage system. However, as we all know, the energy density of lithium-ion batteries is limited to 250Wh / Kg (theoretical value), which cannot be surpassed, which greatly limits its application in the field of electric vehicles. Moreover, currently commercialized lithium-ion batteries contain metal elements such as cobalt and nickel, which will pollute the environment and cost a lot. The safety of these layered ...

AI Technical Summary

Problems solved by technology

Since the reaction of the lithium-sulfur battery is that the active material enters the liquid phase first, a large amount of sulfur obtains electrons to generate long-chain polysulfide anions and enters the electrolyte, which will inevitably cause the concentration and viscosity of the electrolyte on the positive side to increase, which limits the lithium polysulfide. The further dissolution in the electrolyte will also cause concentration polarization due to the influence of mass transfer, which limits the progress of the last two steps of the reaction.

[0010] At present, in order to solve this problem, many researchers use macroporous materials or make holes in electrodes, such as CN100346523C, etc., trying to provide more channels for the dissolution of sulfur by these methods, so that as much lithium polysulfide can be dissolved as much as possible. However, these methods can only alleviate the problem to a certain extent, and cannot fundamentally solve the problem

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