Lithium sulfur battery based on modification of graphene oxide thin film

Abstract

The invention discloses a lithium sulfur battery. The lithium sulfur battery comprises a sulfur electrode, a metallic lithium electrode and a diaphragm and an electrolyte which are arranged between the sulfur electrode and the metallic lithium electrode. The lithium sulfur battery is characterized in that the sulfur electrode is modified by a graphene oxide thin film, and the sulfur electrode is prepared according to the following steps of: grinding and mixing a carbon sulfur compound, a conductive agent and an adhesive according to proportions, dissolving the obtained materials in N-methyl pyrrolidone to prepare paste, applying the paste onto a current collector, and drying the current collector to prepare the sulfur electrode for modification; preparing graphene oxide, and dissolving the graphene oxide in ethanol, wherein the concentration is 0.5-5 mg / mL; and uniformly adding the ethanol solution of the graphene oxide onto the surface of the modified sulfur electrode dropwise, and drying the surface of the modified sulfur electrode. By the graphene oxide thin film prepared according to the invention, polysulfide ions can be effectively bound and are greatly prevented from diffusing to the outside of the sulfur electrode, meanwhile, lithium ion transmission cannot be blocked, thus, oxidation shuttle effect in the lithium sulfur battery is suppressed, and the problem that the capacity is reduced dramatically due to the loss of active substance sulfur is solved.

Description

technical field [0001] The invention relates to a lithium-sulfur battery, in particular to a lithium-sulfur battery with a sulfur electrode modified by a graphene oxide film and a preparation method thereof. Background technique [0002] Compared with the mainstream lithium-ion batteries on the market, lithium-sulfur batteries have 2 to 5 times the theoretical energy density of the former, so research on lithium-sulfur batteries continues to deepen. However, lithium-sulfur batteries still suffer from severe capacity decline and low energy efficiency. problem, the main reason is the loss of active substance sulfur; on the one hand, in the charging and discharging process, there is an inevitable "oxidative shuttle effect", that is, the polysulfides generated at the sulfur electrode will diffuse into the electrolyte, resulting in a capacity loss. drop; when polysulfides diffuse to the lithium anode, they react with lithium metal to form Li 2 S x , meanwhile, the partial reduc...

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Problems solved by technology

[0002] Compared with the mainstream lithium-ion batteries on the market, lithium-sulfur batteries have 2 to 5 times the theoretical energy density of the former, so research on lithium-sulfur batteries continues to deepen. However, lithium-sulfur batteries still suffer from severe capacity decline and low energy efficiency. problem, the main reason is the loss of active substance sulfur; on the one hand, in the charging and discharging process, there is an inevitable "oxidative shuttle effect", that is, the polysulfides generated at the sulfur electrode will diffuse into the electrolyte, resulting in a capacity loss. drop; when polysulfides diffuse to the lithium anode, they react with lithium metal to form Li 2 S x , meanwhile, the partial reduction product Li 2 S 4 will diffuse back to the sulfur electrode and react further; on the other hand, the final reduction product Li 2 S 2 and Li 2 S 2 None of them are conductive, and some products will be deposited on the surface of lithium metal, thus losing electrochemical activity to form "dead lithium", resulting in the loss of part of sulfur; limited by the "oxidation shuttle effect" and "dead lithium", lithium-sulfur batteries The capacity drops sharply, and it is difficult to maintain a high specific capacity after 300 cycles. Therefore, the lithium-sulfur battery has poor cycle stability, low energy efficiency, and short service life. The root cause of the short service life is the loss of active material sulfur. An important reason why it is difficult to market

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