Design Of One-dimensional Carbon And Application In Improving The Electrochemical Properties Of Lithium-Selenium Batteries

Lithium-ion batteries have been widely studied due to their long cycle life,non-toxic and environmental friendliness.As an anode electrode material for lithium-ion batteries,carbon materials are widely used in commercial applications.Although they have good cycle stability and rate performance,the actual specific capacity is not high,which limits their application.The one-dimensional core-shell nano-carbon material with special structure design has higher active sites,higher electron conductivity and shorter ion diffusion path,which is beneficial to the anode material of lithium battery.In this paper,a novel one-dimensional core-shell structured porous carbon material was studied and prepared,revealing the relationship between its lithium storage performance and the structure of carbon materials.In this guide,we choose a suitable carbon matrix to load the elemental selenium.By studying the mechanism of using carbon matrix for relieving the volume expansion of selenium as a positive electrode and the shuttle effect of polyselenide during the cyclic process,it is revealed that the multi-porous structure of carbon material and the non-carbon component play an important role in improving the stability of selenium cathode.Therefore,a carbon/selenium composite cathode material was designed and prepared for the cathode material of lithium selenium batteries.At the same time,in order to solve the shuttle effect of the traditional lithium selenium batteries,a new one-dimensional porous carbon was designed as a barrier layer to improve the electrochemical properties of lithium selenium batteries.(1)A method combining electrospinning and thermal oxidation reaction was used,using a mixed solution of polyvinylpyrrolidone and stannous octoate as a precursor,and controlling parameters such as spinning voltage and flow rate.The polymer solution is stretched into a wire under electrostatic force to overcome the surface tension,and calcined at a low temperature(not higher than 400?)to obtain Sn02/C nanofibers.(2)Dopamine is used as the outer carbon source.A certain amount of SnO2/C nanofibers are uniformly dispersed in tris-buffer buffer(pH?8.5),and dopamine is dissolved in the suspension.Then dopamine turns out self polymerization,covered with the outer layer of nanofibers.The finally obtained composites are carbonized under the protection of nitrogen.When carbonized,SnO2 will react with surrounding carbon to become elemental Sn,and dissolve as a liquid form at high temperature.The carbon material is finally etched by hydrochloric acid to finally obtain a one-dimensional core-shell structured porous carbon(1DC-CCNFs).At a current density of 200 mAg-1,the reversible capacity obtained after circulating for 100 cycles is 976 mAhg'1 and exhibits excellent rate performance..(3)The elemental selenium and the obtained one-dimensional core-shell structured porous carbon were mixed and heat-treated under the seal to obtain a composite material.Under the current density of 200 mAg-1,the reversible capacity obtained after 100 cycles was 137.1 mAhg-1,indicating that this composite can be used for the cathode material of lithium selenium batteries.(4)Considering the adsorption of porous carbon to polyselenide,a one-dimensional porous carbon obtained by electrospinning and pore-forming method was used as a barrier layer of the lithium selenium batteries to improve its electrochemical performance.At a current density of 200 mAg-1,the reversible capacity obtained after 100 cycles was 666.7 mAg-1,and it exhibited excellent rate performance.