Selenium-based Cathode Materials For Rechargeable Magnesium Battery

Rechargeable magnesium batteries are expected to be one of the promising candidates for replacing lithium batteries,owning to the characteristics of low cost,high volume energy density,environmental friendliness and high safety of metallic Mg.Nevertheless,due to the high charge density,small radius and severe solvation of the divalent magnesium ions,they show a low solid phase diffusion rate in host materials,which limits the development of the cathode materials for rechargeable magnesium batteries.Thus,exploration for new kinds of cathode materials which can realize the reversible reaction with magnesium ions without using the insertion mechanism is another direction for current study.Based on the conversion reaction mechanism,selenium,possessing many of the merits of sulfur or even beyond sulfur,is thus proposed as a novel prospective candidate for cathode of magnesium batteries.In this paper,the work of selenium-based cathode materials was carried out,and the electrochemical performances as well as the electrochemical reaction mechanism of copper selenide and selenized polyacrylonitrile cathodes were studied in rechargeable magnesium batteries.?1?Cu₂Se materials with the same crystal form and different morphologies were synthesized by hydrothermal and solvothermal methods.The electrochemical performance and reaction mechanism of the material as cathode were firstly studied in the APC electrolyte(0.4 mol L^-1?PhMgCl?₂-AlCl₃/THF)with Li salt as an additive.In addition,the cycling stability and rate performance of the cathode were further improved by in situ homogeneously anchoring Cu₂Se particles onto the surface of the reduced graphene oxide nanosheets.?2?Selenized polyacrylonitrile?Se/PAN?was designed and finally obtained by optimizing the reaction conditions.The feasibility of the battery containing a Se/PAN cathode,a Mg anode and a typical nucleophilic electrolyte(0.4 mol L^-1?PhMgCl?₂-AlCl₃+1.0 mol L^-1 LiCl/THF)was reported for the first time.Due to the special structure of the Se/PAN composite,the reaction of selenium with the nucleophilic electrolyte and the shuttle effect during cycling are both effectively suppressed.The obtained battery shows relatively high specific capacity,excellent cycling stablility and rate performance.In addition,the interfacial properties of Se/PAN cathode with different electrolytes and their effects on the electrochemical performance were also investigated.