Composite electrolyte membrane based on functional polymer and preparation method thereof, and lithium-sulfur secondary cell

Abstract

The invention discloses a composite electrolyte membrane based on a functional polymer. The composite electrolyte membrane is mainly composed of a polymer porous diaphragm, a lithium perfluoro-sulfonamide single-lithium ion type polymer electrolyte coating which coats one side of the polymer porous diaphragm and a gel polymer coating which coats the other side of the polymer porous diaphragm, is stable to a lithium negative electrode and has a free radical capture function. A preparation method for the composite electrolyte membrane comprises the following steps: reacting a perfluoro-sulfuryl fluoride resin with lithium methide containing double electron-withdrawing groups so as to obtain a lithium perfluoro-sulfonamide polymer; carrying out washing and dissolving, then coating one side of the polymer porous diaphragm with the lithium perfluoro-sulfonamide polymer and adding a non-solvent for secondary film formation; and coating the other side of the polymer porous diaphragm with a gel polymer system which is stable to the lithium negative electrode, contains an additive and comprises a mixed liquor of a polymer, a solvent, a free radical annihilation effect additive and a nanometer filling material, and then carrying out drying so as to prepare the composite electrolyte membrane. The composite electrolyte membrane can improve cycling stability of a lithium-sulfur secondary cell.

Description

technical field [0001] The invention belongs to the related technical field of rechargeable lithium-sulfur batteries, and in particular relates to a rechargeable lithium-sulfur battery, an electrolyte membrane used in the rechargeable lithium-sulfur battery and a related preparation process. Background technique [0002] Li-S secondary batteries based on Li metal anode and sulfur cathode represent one of the highest energy density combinations of known chemically reversible systems. The theoretical energy density of the lithium-sulfur system is 2600Wh / kg, and the actual energy density that can be expected to be achieved is 700Wh / kg, which is three times that of the existing lithium-ion batteries. Although the achievable energy density of lithium-sulfur batteries has reached 300-400Wh / kg, the sulfur positive electrode is not conductive, the electrochemical reaction process is complicated, and the lithium negative electrode has high activity. The intermediate product lithium p...

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Problems solved by technology

[0006] From the analysis of the working mechanism of the lithium-sulfur battery, during the cycle of the battery, not only the lithium polysulfide, the discharge product of the positive electrode, diffuses to the negative electrode through the diaphragm, and the electrolyte solution in the positive electrode continuously diffuses to the negative electrode through the diaphragm. The reaction product will also diffuse to the positive electrode through the separator. With the loss of electrolyte and active material and the intensification of the passivation of the positive and negative electrodes, the cycle performance of lithium-sulfur batteries will gradually deteriorate.

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