Titanium dioxide colloidal modified diaphragm for lithium-sulfur battery, preparation method thereof, and lithium-sulfur battery

Abstract

The invention discloses a titanium dioxide colloid modified separator for lithium-sulfur batteries, a preparation method thereof and a lithium-sulfur battery, comprising a polypropylene separator and a nano-scale dense and uniform membrane with a thickness of 1-4 μm coated on both surfaces of the polypropylene separator. Titanium dioxide colloidal layer, simple preparation method, uniform and dense TiO 2 The colloidal layer and the formation of Ti-S bonds to capture polysulfides can not only effectively inhibit the diffusion of polysulfides to the negative electrode and react with lithium metal, but also reduce the loss of active materials and the capacity loss caused by the loss of active materials, and inhibit the shuttle effect in lithium-sulfur batteries to improve The cycle stability of the battery.

Description

Technical field: [0001] The invention relates to a lithium-sulfur battery, in particular to a titanium dioxide colloid-modified diaphragm for a lithium-sulfur battery, a preparation method thereof, and a lithium-sulfur battery. Background technique: [0002] At present, due to the limitation of the theoretical specific capacity of lithium-ion batteries, which are widely used at present, the further development of lithium-ion whose performance improvement tends to the limit has encountered a certain bottleneck. However, with the development of clean energy storage, electronic equipment, and electric vehicles, people There is an urgent need to develop a new generation of batteries with high specific capacity and high specific energy. In lithium-sulfur batteries, due to the high theoretical specific capacity of sulfur (1675mAh g -1 ) and high theoretical energy density (2600Wh kg), as well as the low cost and environmental friendliness of sulfur, have been widely favored by re...

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Problems solved by technology

Although lithium-sulfur batteries have the above advantages, the following three problems need to be solved to maintain the cycle stability of the battery: 1) sulfur and the product Li 2 S / Li 2 S 2 The electrical conductivity of the electrode is extremely poor, which seriously affects the surface density and rate performance of the active material of the electrode; 2) The densities of sulfur and lithium sulfide are 2.07g cm -3 and 1.66g cm -3 , there is a volume change of up to about 79% during the charging and discharging process, which easily causes the active material to detach from the conductive carrier, thereby seriously affecting the cycle life of the battery; 3) Shuttle effect: the positive electrode is linked by 8 sulfur atoms during the discharge process The existing S will continue to break bonds to form intermediate products (polysulfides) with fewer sulfur atoms. These products can be dissolved in the electrolyte and diffuse to the lithium negative electrode and react with the surface of the lithium negative electrode. However, the polysulfide formed during charging Under the action of diffusion, it migrates to the lithium negative electrode and reacts with lithium, which not only reduces the active material sulfur, but also reduces the Coulombic efficiency and destroys the lithium metal surface.

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