Lithium-sulfur battery functional composite diaphragm and preparation method therefor

Abstract

The invention relates to a lithium-sulfur battery functional composite diaphragm and a preparation method therefor, and belongs to the technical field of a battery material. The lithium-sulfur batteryfunctional composite diaphragm comprises a diaphragm substrate and a functional coating layer which coats the diaphragm substrate; the functional coating layer is a mixture of nitrogen-cobalt-doped graphitized carbon material and a binder; the functional coating layer is 5-15[mu]m in thickness; the preparation method comprises the steps of performing calcining on the obtained BMZIF material in inert atmosphere at a temperature of 900-1,000 DEG C for 3-5h to obtain the nitrogen-cobalt-doped graphitized carbon material; performing uniform mixing on the nitrogen-cobalt-doped graphitized carbon material and the binder to obtain the functional coating layer; and the coating the diaphragm substrate with the functional coating layer and then performing drying to obtain the lithium-sulfur batteryfunctional composite diaphragm. By virtue of the lithium-sulfur battery diaphragm, the positive electrode impedance of the lithium-sulfur battery can be lowered, and the shuttle effect of the polysulfide ions can be suppressed effectively.

Description

technical field [0001] The invention relates to a lithium-sulfur battery functional composite diaphragm and a preparation method thereof, belonging to the technical field of battery materials. Background technique [0002] With the continuous improvement of human beings' requirements for energy density and environmental protection of new energy systems, lithium-sulfur batteries have a capacity of up to 1675mAh·g -1 Theoretical capacity and 2600Wh·kg -1 The energy density has attracted extensive attention of researchers. As a cathode material for lithium batteries, elemental sulfur has the highest theoretical specific capacity. In addition, elemental sulfur also has many advantages such as large storage capacity, low toxicity, and low price. Despite these advantages, there are many problems and challenges in the actual working process. First, the cathode material has poor conductivity and reduces the end product Li 2 S and Li 2 S 2 is an electronic insulator. Second, ...

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Problems solved by technology

Despite these advantages, there are many problems and challenges in the actual working process

First, the cathode material has poor conductivity and reduces the end product Li 2 S and Li 2 S 2 is an electronic insulator

Second, the long-chain polysulfide ions generated during the charge-discharge reaction will dissolve into the electrolyte and migrate back and forth between the positive and negative electrodes to produce a "polysulfide ion shuttle effect", resulting in poor cycle stability and low Coulombic efficiency

Third, the solid electrolyte interface film on the surface of the metal lithium negative electrode is not stable enough and is easy to pulverize; at the same time, there is a problem of dendrite growth on the lithium negative electrode, which affects the safety of the battery

The research group of Zhou Haoshen, Japan Institute of Industrial Technology and Nanjing University proposed a graphene oxide composite functional separator with metal organic framework (MOF) as the basic material, using Cu 3 (BTC) 2 Type MOF (HKUST-1) as an "ion sieve" (Bai Song Y, Liu Xi Z, Zhu Kai, et al. Metal–organic framework-based separator for lithium–sulfurbatteries[J].Nature Energy, 2016, 1, 16094 ), but the preparation process of the diaphragm is cumbersome, the cost of the materials used is high, and a vacuum environment is required, which is not conducive to large-scale preparation

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