Preparation and application of manganese dioxide@sulfur@carbon sphere cathode composite with yolk-shell structure

Abstract

The invention provides a manganese dioxide@sulfur@carbon sphere positive electrode composite material with a yolk-shell structure as well as a preparation method and application thereof. According tothe manganese dioxide@sulfur@carbon sphere composite material, manganese dioxide of a flaky structure serves as a core and is distributed in a cavity with a carbon sphere serving as a shell, sulfur isdistributed between the manganese dioxide core and the carbon shell, and the composite material comprises 10%-30% of carbon, 10%-30% of manganese dioxide and 40%-80% of sulfur. The hollow carbon spheres provide sufficient sulfur loading space; moreover, the rich point-to-point contact among the carbon spheres ensures the rapid transmission of electrons, the flaky manganese dioxide core layer in the carbon sphere cavity has a strong chemical adsorption conversion effect on polysulfide, the shuttle effect can be effectively inhibited by combining the physical limitation effect of the carbon layer, and the capacity retention ratio, the cycling stability and the rate capability of the battery are improved.

Description

technical field [0001] The invention belongs to the technical field of new energy, and specifically relates to the preparation and application of a manganese dioxide@sulfur@carbon sphere cathode composite material with a yolk-shell structure. Background technique [0002] With the consumption of non-renewable resources such as fossils, people have accelerated the development and utilization of new energy sources. Among them, secondary batteries are playing an increasingly important role as an important energy carrier. At present, lithium-ion batteries have been widely used in energy storage fields such as small mobile power supplies and power batteries due to their good safety, cycle stability, and low cost. However, due to its low theoretical specific capacity (<300mAh g -1 ) has been unable to meet people's demand for high specific energy batteries, therefore, it is of great significance to develop a new type of secondary battery with high specific energy, long cycle l...

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Problems solved by technology

In addition, sulfur reacts complexly with lithium ions during the discharge process, undergoing a process from long-chain polysulfides (Li 2 S x ,4<x<8) to the process of short-chain lithium sulfide, in which long-chain polysulfide is easily soluble in ether electrolyte, and will shuttle through the separator to the metal lithium negative electrode side to be reduced during the battery cycle, resulting in relatively Low capacity retention, coulombic efficiency, and poor cycle stability, so how to alleviate the shuttle effect of polysulfides is a fundamental scientific problem that still exists in lithium-sulfur batteries

[0004] In the Chinese invention patent with the authorized publication number CN104916828 A, it is mentioned that the carbon-sulfur positive electrode material prepared with hollow carbon spheres as the sulfur carrier solves the problem of cycle performance caused by lithium polysulfide shuttling by confining sulfur in the cavity of the carbon spheres. bad question

However, the physical interaction between non-polar carbon spheres and polar lithium polysulfides in this patent is weak, and it is difficult to efficiently adsorb the dissolved lithium polysulfides, which cannot effectively inhibit the occurrence of the shuttle effect.

At the same time, in the Chinese invention patent with the authorized publication number CN107887605 A, it is proposed to prepare a sulfur positive electrode with nano-sulfur powder, manganese dioxide powder, carbon fiber, and carbon nanotubes as a slurry. Lithium plays an anchoring role, and the battery can achieve good cycle stability in the first 80 cycles, but manganese dioxide with poor conductivity tends to lose electrical contact with the insulating active material sulfur during the cycle, and thus cannot effectively inhibit polysulfide. The dissolution of lithium makes the battery's long-term cycle performance poor

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