Preparation And Performance Of Bi₂MoO₆-based Anode Materials For Aqueous Aluminum Ion Batteries

Aqueous rechargeable aluminum ion batteries have attracted a lot of attention due to their low cost,safety and high capacity.However,in aqueous electrolytes,metallic aluminum negative electrodes tend to form a protective oxide layer on the surface,which hinders the redox reaction,and are prone to hydrogen precipitation side reactions,limiting the cycle life and operating voltage of the battery.Therefore,the use of non-metallic aluminum materials as negative electrodes is of great significance for the further development of aqueous aluminum ion batteries.Currently these non-metallic aluminum negative electrode materials still exhibit low discharge capacity,poor multiplicity performance and a short cycle life.In this thesis,bismuth molybdate（Bi₂MoO₆）with a high theoretical capacity(791 m Ah g^-1)and low discharge potential was selected as the target of this study.The electrochemical performance of Bi₂MoO₆negative electrode for aqueous aluminum ion batteries was investigated,and its aluminum storage mechanism was analysed.Moreover,the performance of aqueous aluminum ion batteries was initially explored by matching it with the positive electrode.The main research contents are as follows:（1）Bi₂MoO₆electrodes were prepared by in situ growing Bi₂MoO₆on the exfoliated graphite foil collector using a one-step solvothermal method.To improve the electrical conductivity and electrochemical performance of the Bi₂MoO₆electrode,the Bi₂MoO₆-polyaniline（PANI）composite electrode was prepared by coating a layer of PANI on the surface of Bi₂MoO₆microspheres through chemical oxidative polymerization of aniline.The electrochemical performances of the prepared electrodes were tested and analysed using an aqueous electrolyte of 0.5 M Al₂（SO₄）₃+0.5 M Na Cl under a three-electrode system.The results showed that the Bi₂MoO₆-PANI electrode exhibited a low discharge voltage plateau-0.57 V（vs.Ag/Ag Cl）and a high initial discharge capacity of 579.1 m Ah g^-1at 5 A g^-1,as well as good cycling stability(maintaining discharge capacity of 281 m Ah g^-1after 300cycles).Subsequently,the reaction kinetics and the aluminum storage mechanism were analysed.（2）To evaluate the feasibility of Bi₂MoO₆-PANI composite electrode application,Al_xMn O₂,potassium nickel ferricyanate（KNHCF）and tetrachloro-1.4-benzoquinone（TCQ）were selected as positive electrode materials to construct an aqueous aluminum ion full battery.The results showed that the Al_xMn O₂//Bi₂MoO₆-PANI aqueous full battery exhibited a high discharge plateau（close to 1.0 V）,a high initial discharge capacity(112.3 m Ah g^-1at 50 m A g^-1),and a capacity retention rate of over 70%after100 cycles.This study provides a reference for the development of high-performance cathode materials for aqueous aluminum ion battery and full battery.