Amorphous cobalt phosphide/nanocarbon composite material and preparation method and application thereof

Abstract

The invention belongs to the technical field of new energy materials, and particularly relates to an amorphous cobalt phosphide / nanocarbon composite material and a preparation method and application thereof. The composite material is high in specific surface area, rich in pore structure and excellent in conductivity; the conductive carbon network can provide channels for transmission of electronsand ions. The composite material can realize high sulfur loading capacity and high sulfur utilization rate, and can adapt to huge volume change of sulfur in charging and discharging processes. Compared with cobalt phosphide in a high crystalline state, the amorphous cobalt phosphide nanosheet can effectively physically and chemically adsorb polysulfide, reduce the shuttle effect, expose enough catalytic active sites, provide a large number of defect sites, promote electrochemical conversion of polysulfide to the final discharge product and improve the catalytic kinetics of the reaction.

Description

technical field [0001] The invention belongs to the technical field of new energy materials, and in particular relates to an amorphous cobalt phosphide / nano-carbon composite material, a preparation method and an application thereof. Background technique [0002] Lithium-sulfur batteries have a very high theoretical specific capacity of 1675mAh / g, much higher than traditional lithium-ion secondary batteries. Moreover, the source of sulfur is abundant, cheap, environmentally friendly, and non-toxic, so lithium-sulfur batteries are a new energy system with great development potential. Although lithium-sulfur batteries have great development prospects, there are still many problems: the reactants and products are insulators of electrons and ions; the discharge intermediate product lithium polysulfide can be dissolved in the electrolyte, causing a "shuttle effect"; During the process, the sulfur in the positive electrode will expand and shrink in volume, resulting in the sheddin...

AI Technical Summary

Problems solved by technology

Although lithium-sulfur batteries have great development prospects, there are still many problems: the reactants and products are insulators of electrons and ions; the discharge intermediate product lithium polysulfide can be dissolved in the electrolyte, causing a "shuttle effect"; During the process, the sulfur in the positive electrode will expand and shrink in volume, resulting in the shedding of sulfur and destroying the electrode structure.

However, the above method of synthesizing metal or metal compound and carbon material composite material has high cost and complex production process, and the metal or metal compound is prone to agglomeration, resulting in a decrease in specific surface area, and it is difficult to uniformly combine with carbon material

Moreover, the synthesized metal compounds usually exhibit high crystallinity, few exposed active sites, and cannot provide enough defect sites to promote the effective catalytic conversion of intermediate lithium polysulfides.

At present, crystalline cobalt phosphide (CoP) composite carbon materials synthesized by liquid-phase precipitation or vapor-phase phosphating of cobalt-containing precursors have been used in lithium-sulfur battery cathodes, but crystalline CoP is easy to agglomerate, and the crystalline Due to the periodic arrangement of atoms, there are fewer cobalt active sites that can be exposed, and the adsorption capacity for soluble lithium polysulfide is weak, and the improvement of catalytic conversion kinetics for soluble lithium polysulfide is also limited, resulting in low discharge specific capacity. , low Coulombic efficiency, poor cycle stability, etc.

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