Lithium-sulfur battery

Abstract

The invention discloses a lithium-sulfur battery. The lithium-sulfur battery comprises three-dimensional porous graphene covalence fixing nanometer lithium sulfide as a composite positive electrode, a polyolefin membrane coated with graphene oxide as a modified membrane, and a lithium sheet negative electrode and an electrolyte which are generally adopted. The particle size of lithium sulfide in the composite positive electrode is between 1 nm and 100 nm, and the lithium sulfide is combined with oxygen-containing functional groups on the surface of three-dimensional porous graphene in the form of a C-O-S covalent bond. The modified membrane is prepared from graphene oxide with the thickness of 0.1 to 10 microns uniformly deposited on the surface of a traditional polyolefin membrane; and the graphene oxide can be coated on both sides of the polyolefin membrane, and can also be coated on the side facing the lithium sulfide positive electrode when the battery is assembled. According to the lithium-sulfur battery disclosed by the invention, the dissolution of the sulfur positive electrode can be effectively prevented, the shuttle effect is inhibited, the overpotential of the battery is reduced, the structural damage generated by positive electrode volume expansion is avoided, and the rate characteristic and cycle performance of the lithium-sulfur battery are substantially improved.

Description

technical field [0001] The invention relates to a secondary battery, in particular to a rechargeable lithium battery, which is applied in the technical field of electrochemical energy storage devices. Background technique [0002] With the rapid development of new energy technologies, especially with the potential market demand in the field of intelligent communication and electric vehicles, the task of developing a secondary battery system with higher energy density is very urgent. With the existing lithium battery technology, the specific energy of commercial lithium-ion batteries is difficult to exceed 300 Wh / kg, which cannot meet the needs of the new energy industry for high-performance batteries. [0003] The theoretical energy density of lithium-sulfur batteries is as high as 2600 Wh / kg, which is 7 times that of commercial lithium cobalt oxide / graphite lithium-ion batteries, and the positive electrode active material elemental sulfur has the advantages of abundant reso...

AI Technical Summary

Problems solved by technology

However, the electronic conductivity of the sulfur cathode is poor, and the polysulfide ion shuttle effect also exists in Li 2 In the S positive electrode, it is hoped that the three-dimensional porous graphene can be synthesized to chemically immobilize nano-lithium sulfide, so that the lithium-sulfur battery provides a good dispersion, and has efficient electron and ion transport channels, strong polysulfide ion binding force, and load capacity. Composite cathode material with high sulfur content

But generally, when the lithium sulfide / carbon composite electrode is charged for the first time, it will nucleate and generate new polysulfides, resulting in a potential barrier of about 1 V. Usually, Li 2 S-based cathodes are first charged to 4 V for activation, but lead to decomposition of ether-based electrolytes and deterioration of electrochemical performance

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