Bimetal phosphide inlaid carbon hollow nanocage as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of lithium-sulfur batteries, and particularly relates to a bimetallic phosphide embedded carbon hollow nanocage and a preparation method and application thereof. The preparation method comprises the following steps: dispersing a nickel-cobalt Prussian blue derivative in a liquid medium, preparing dispersion liquid, adding dopamine hydrochloride into the dispersion liquid, and preparing nickel-cobalt prussian blue wrapped by the polydopamine; calcining the nickel-cobalt Prussian blue derivative wrapped by the polydopamine to prepare a nickel-cobalt bimetallic particle embedded carbon hollow nanocage; taking hydrogen phosphide as a phosphating agent, and carrying out one-step phosphating on the carbon hollow nanocage inlaid with the bimetallic particles to prepare the carbon hollow nanocage inlaid with the bimetallic phosphide; preparing a dispersion liquid from a bimetallic phosphide embedded carbon hollow nanocage, carbon black and polyvinylidene fluoride, then coating a polypropylene diaphragm with the dispersion liquid, and performing drying to prepare a multifunctional diaphragm. The comprehensive performance of the lithium-sulfur battery is remarkably improved.

Description

technical field [0001] The invention belongs to the technical field of lithium-sulfur batteries, and in particular relates to a double-metal phosphide-embedded carbon hollow nanocage and a preparation method and application thereof. Background technique [0002] Lithium-sulfur batteries are generally composed of four parts: metal lithium negative electrode, sulfur positive electrode, electrolyte and separator. It is a type of high-energy-density battery system that realizes the conversion of electrical energy and chemical energy by breaking the sulfur-sulfur bond. It has a low cost , environmental friendliness and other advantages, the theoretical specific capacity and energy density are 1675mAh h -1 and 2600Wh kg -1 , which is more than five times the theoretical energy density of commercialized lithium-ion batteries. [0003] However, lithium-sulfur batteries still have some problems: [0004] (1) S and Li 2 S 2 / Li 2 S is an electronic insulating material, so it wil...

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Problems solved by technology

[0004] (1) S and Li 2 S 2 /Li 2 S is an electronic insulating material, so it will generate a large internal resistance during the battery charge and discharge cycle, which will reduce the activity of the reaction; the current solution is mainly to compound S with various carbon materials with good conductivity. To a certain extent, it will also greatly reduce the loading of S; in addition, due to Li 2 S has poor conductivity, and it is difficult to completely convert S on the electrode into Li 2 S, so it is usually difficult to obtain the theoretical specific capacity;

[0005] (2) Since S (2.03g cm -3 ) and Li 2 S (1.66g cm -3 ) There is a density difference between them, so in a fully discharged state, sulfur will experience a volume expansion of up to 80%. Severe volume expansion will lead to the shedding and failure of the electrode material, which will cause a sharp decline in battery performance and limit the capacity of the battery. Further application of high-loaded sulfur cathodes;

[0006] (3) The working mechanism of lithium-sulfur batteries is a "solid-liquid-solid" process. Polysulfide intermediates usually have good solubility in organic solvents, which makes the positive electrode materials continuously flow into the electrolyte during the cycle. Dissolut

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