Three-dimensional graphene-hollow carbon sphere nanocomposite and preparation method thereof

Abstract

The invention discloses a three-dimensional graphene-hollow carbon sphere nano composite and a preparation method thereof. The three-dimensional graphene-hollow carbon sphere nano composite is prepared from hollow carbon spheres and graphene, wherein the hollow carbon spheres are distributed in a three-dimensional net structure formed by the graphene. The preparation method comprises the following steps: (1) preparing silicon dioxide microspheres coated with phenolic resin; (2) preparing three-dimensionalgraphene-microsphere hydrogel; (3) preparing a three-dimensional graphene-carbon sphere nano composite; and (4) preparing the three-dimensional graphene-hollow carbon sphere nano composite. The three-dimensional graphene-hollow carbon sphere nano composite is good in conductivity, is rich in graded hole structure, can be applied to a positive electrode material of a lithium-sulphur battery so as to supply rapid electron conduction, restrain dissolution and shuttle of polysulfide sulphur and alleviate the volume change of a sulphur positive electrode in a circulating process. The preparation method is simple and convenient and has a good effect.

Description

technical field [0001] The invention relates to the field of nano-carbon materials and preparation thereof, in particular to a three-dimensional graphene-hollow carbon sphere nanocomposite and a preparation method thereof. Background technique [0002] Secondary batteries with high energy density and low cost have promising applications in portable electronic devices, electric vehicles, and smart grids. Lithium-sulfur batteries have high theoretical specific capacity (1672mAh / g) and energy density (2600Wh / kg), which are several times that of ordinary lithium-ion batteries. In addition, sulfur elemental resources are abundant, cheap, and environmentally friendly. These remarkable advantages make lithium-sulfur batteries regarded as one of the most promising power sources for next-generation electric vehicles. [0003] At present, the main problems that restrict the practical application of lithium-sulfur batteries are as follows: (1) The conductivity of sulfur element is po...

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Problems solved by technology

[0003] At present, the main problems that restrict the practical application of lithium-sulfur batteries are as follows: (1) The conductivity of sulfur element is poor (only 5×10 -30 S / cm), it needs to be mixed with a large amount of conductive agent, which seriously reduces the utilization rate of sulfur and the rate performance of the battery; (2) the long-chain polysulfide lithium (Li 2 S x , x=3~8) dissolved in the electrolyte, and "shuttle" back and forth between the positive and negative electrodes, resulting in low Coulombic efficiency and reversible capacity; (3) short-chain polysulfide lithium (Li 2 S. Li 2 S 2 ) Form insoluble deposits on the surface of the positive electrode material, resulting in a decrease in electrochemical activity and a decrease in cycle performance; (4) Large volume changes during the cycle cause the pulverization and shedding of the active material

They are all good carriers for lithium-sulfur battery cathode materials with important application prospects, but each has its own shortcomings: the electronic conductivity of hollow carbon spheres is not as good as that of graphene, the pore structure of graphene is not as rich as that of hollow carbon spheres, and graphene has excellent electrical conductivity but There are problems of dissolution and shuttling of lithium polysulfide when it is used alone as a positive electrode material

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