Preparation And Properties Of Aqueous Zn-ion Battery Cathode Materials Based On CuHCF And Mn₂O₃

With the increasingly serious environmental pollution in today’s society,aqueous zinc-ion batteries have received more and more attention as an environmentally friendly energy storage device.We mainly study two materials:copper ferricyanide（CuHCF）and manganese trioxide（Mn₂O₃）.The unique framework structure of CuHCF is conducive to the intercalation of Zn²⁺,but its capacity is low（<100 mAh/g）;Mn₂O₃ has a high specific capacity,but faces the problems of poor long-cycle stability and easy dissolution in the electrolyte.Therefore,in this paper,a series of methods are used to improve the discharge capacity of CuHCF、improve the stability of Mn₂O₃ and ease its dissolution in the electrolyte.The specific content and main conclusions are as follows:（1）Preparation of CuHCF@PEDOT composites by in-situ polymerization and their battery performance:in order to improve the specific discharge capacity of CuHCF,in this paper,PEDOT with high conductivity was grown on the surface of CuHCF by in-situ polymerization to prepare CuHCF@PEDOT composite.The optimal performance of the battery based on the system is 38.9 mAh/g at the current density of 0.02 A/g for the first cycle discharge capacity and 7.9 mAh/g after 100 cycles,compared with the initial discharge specific capacity of 29 mAh/g of CuHCF and its discharge specific capacity of 9 mAh/g after 100 cycles,the addition of PEDOT effectively increased the initial discharge specific capacity of the battery.（2）Preparation of Mn₂O₃ material by high temperature calcination and its battery performance:in order to obtain Mn₂O₃ with high stability,α-MnO₂ is first prepared by co-precipitation method,thenα-MnO₂ is recrystallized,and finally calcined at high temperature to prepare Mn₂O₃ with high stability.The results show that the electrochemical performance of Mn₂O₃ calcined at 600℃is the best,the initial discharge capacity of Mn₂O₃ is 197.1 mAh/g when the current density is 0.2 A/g for long cycle test,after 100 cycles,the specific capacity is still as high as 102.3 mAh/g.This method is simple and can obtain Mn₂O₃ with high stability,and is also easy to achieve large-scale production.（3）Preparation of Mn₂O₃@PPy composites by in-situ polymerization and their battery performance:in order to alleviate the dissolution of Mn₂O₃ in the electrolyte,the in-situ polymerization method was used to grow PPy on Mn₂O₃and prepare Mn₂O₃@PPy complex to prevent the dissolution of cathode material caused by direct contact of Mn₂O₃ and the electrolyte.The results show that the initial discharge capacity of the battery based on the system is 169.1mAh/g,and the discharge capacity after 100 cycles is 70.6 mAh/g.At the same time,the related exploration of composite electrolyte was also carried out.MnSO₄ was added to the electrolyte to supplement the Mn²⁺reduced by the dissolution of the cathode material.When the composite electrolyte of 0.5M Zn SO₄+0.1M MnSO₄ was used for buckle test,the specific discharge capacity reached 241.1 mAh/g at 0.2A/g current density,and the specific discharge capacity was still 107 mAh/g after 100 cycles of charge and discharge.This study indicates that the composite electrolyte in manganese battery has a potential application prospect.