Synthesis And Electrochemical Performance Of Biochar-Based Porous Carbon And Cobalt-based Selenide

Currently,lithium ion batteries?LIBs?can be considered to be the most successfully developed electrochemical technology,which have been widely used in portable electronic devices.This is mainly due to their high energy density,long cycle life and superior security.At the same time,LIBs are regarded as the best choice for the electric vehicles.Thus,the development of high-performance LIBs has always been the focus of scientific researchers.However,the limited lithium resources will be the bottleneck in the process.Hence,people are also looking for new alternative energy storage system while optimizing the LIBs.Compared with lithium,sodium has similar physical and chemical properties.What is more,sodium is very abundant in the earth.Especially,energy density is not a critical issue in the field of large-scale energy storage system.Thus,Na ion battery is a reasonable alternative.Electrode material is a key aspect in the Li/Na ion battery system,so people have always been looking for new electrode material to further improve overall battery performance.In this thesis,we mainly do some research on the anode of the Li/Na ion battery.Firstly,porous carbon derived from the prawn was successfully fabricated by a simple“curing method”,followed by an annealing process.The electrochemical performance as anode for LIBs was investigated.Secondly,nanoflower-like Co_0.7Fe_0.3Se₂ was synthesized by a solvothermal method.The synergistic effect of multi-metal was studied when envalued Co_0.7Fe_0.3Se₂ as anode for Na ion battery.Porous carbon derived from the prawn was successfully obtained via a simple“curing method”,followed by an annealing process under the reducing atmosphere.In the“curing”process,NaCl evenly infiltrates into the tissue of the prawn.It was found that nanocrystal NaCl can be as green“corrosive agent”during the annealing and washing process,which is favorable for the subsequent formation of rich porous structures.The residual NaCl can be removed easily and completely by using distilled water.Benefitting from rich porous structures,porous carbon material derived from the prawn display good lithium storage properties.Nanoflower-like Co_0.7Fe_0.3Se₂ anode was synthesized by a solvothermal method and investigated in Na ion battery.Compared to the single-metal CoSe₂ and FeSe₂,multi-metal Co_0.7Fe_0.3Se₂ had better electrochemical performance,especially in the high current density test.Moreover,for the cobalt based selenide,ether-based electrolyte is beneficial to achieve better performance than carbonate-based electrolyte.