Synthesis And Performanc Of Cathode Materials For Zinc-ion Batteries

Recently,aqueous zinc ion batteries（AZIBs）have attracted more and more attention from scientific researchers due to their high theoretical specific capacity and low cost.AZIBs using aqueous electrolyte are safer and more environmentally friendly than batteries using organic electrolyte.However,compared with lithium ions,Zn²⁺has two positive charges,the radius ratio of hydrated ions is large,and the electrostatic repulsion between Zn²⁺and the cathode material is large,which affects the diffusion kinetics of Zn²⁺in the material,so the stability of the cathode material is extremely important.Manganese oxides are considered to be one of the most promising cathode materials for AZIBs due to their low cost,rich valence,high specific capacity and operating voltage.Prussian blue analogues are also used as AZIBs cathode materials due to their easy synthesis and unique three-dimensional open-framework structure that enables rapid insertion/extraction of Zn²⁺.Therefore,this paper will focus on the manganese-based and Prussian blue analogue cathode materials of AZIBs,and improve their electrochemical performance by synthesizing and modifying manganese oxides and Prussian blue analogue cathode materials.（1）Ca_xMn₈O₁₆ cathode material was synthesized by hydrothermal method,and the optimum process conditions were obtained.When the hydrothermal temperature is 120°C and the molar ratio of Ca and Mn is 15%,the obtained Ca_xMn₈O₁₆/CNT composite electrode material has the best electrochemical performance.When the current density is 100 m A g^-1,the discharge specific capacity is still 252.40 m Ah g^-1 after 100 cycles.Even at a current density of 500 m A g^-1,the initial discharge specific capacity is still 175.75 m Ah g^-1.After500 cycles,the discharge specific capacity is 140.93 m Ah g^-1,and the capacity retention rate is 80.19%.（2）Based on the above preparation process of Ca_xMn₈O₁₆,Ca_xMn₈O₁₆/C composites were synthesized by hydrothermal method.When the content of graphitized carbon spheres is 0.15 g,the obtained Ca_xMn₈O₁₆/C composite cathode material has the best performance.When the current density is 100 m A g^-1,the initial discharge specific capacity is 388.52 m Ah g^-1.After 40 cycles,the discharge specific capacity is 407.17 m Ah g^-1.Even if the current density increases to 500 m A g^-1,the discharge specific capacity is still 102.98 m Ah g^-1 after500 cycles.（3）The Mn₂O₃/Co₃O₄ cathode material was synthesized by hydrothermal method,and the cathode material prepared when the molar ratio of Co to Mn was 15%had the best electrochemical performance.Co₃O₄ composite can further improve the conductivity of the material,so that zinc ions can be quickly embedded/removed.At a current density of 100 m A g^-1,the discharge specific capacity is 179.14 m Ah g^-1 after 60 cycles,and the initial discharge specific capacity is still 304.62 m Ah g^-1 at a current density of 500 m A g^-1.（4）The Mn HCF@PPy cathode material was synthesized by direct reaction.The cathode material prepared when K₃Fe（CN）₆ and Mn Cl₂ molar ratio of 1:1 and the amount of pyrrole was 400μL had the best electrochemical performance.At a current density of 100 m A g^-1,it can still reach 130.24 m Ah g^-1 after 150 cycles.At a current density of 500 m A g^-1,the discharge specific capacity after 300 cycles is 63.68 m Ah g^-1.