Design And Preparation Of Manganese Dioxide Cathode Material For High Performance Zinc Ion Batteries

Zinc manganese dioxide（Zn-MnO₂）battery shows a broad development prospect in the field of energy storage because of its advantages of high security and environmental friendliness.However,problems such as dissolution and structural collapse of cathode materials during battery cycle lead to poor stability of charge and discharge,which limit its practical application.In view of this,this paper takes the synthesis of manganese dioxide（MnO₂）as the starting point,by optimizing the preparation process ofβ-MnO₂,and applying potassium ion（K⁺）pre-embedding strategy to modify MnO₂,to explore the strategy of high performance and long cycling stability of MnO₂ cathode method.The main research work includes two aspects:（1）Using K₂S₂O₈ and MnSO₄·H₂O as raw materials,the influence of hydrothermal reaction conditions on the crystal structure of MnO₂nanoparticles was investigated.The effect ofβ-MnO₂ structure on charge/discharge process was revealed.The results showed that the lattice plane spacing of 12h-β-MnO₂ is larger,which is conducive to the ion embedding/ejection during charge and discharge.The stable tunnel structure can avoid the collapse of the cathode in the high rate cycling.The presence of hydration water can improve the reversibility of ion embedding/ejection.The regulated structure of network can provide more active sites for redox reaction.The 12h-β-MnO₂ cathode achieved a high specific capacity of 216.2 m Ah g^-1 for the first discharge process at a high rate of 5 C,and the capacity retention rate can still reach 77.7%after 100cycles.（2）By controlling the concentration of K₂S₂O₈ in hydrothermal synthesis,K_xMnO₂ with different embedding amount of K⁺was obtained.The study revealed the influence of K⁺embedding amount on the structural and electrochemical performance of MnO₂.When the addition amount of K₂S₂O₈ is over 5%,K_0.07MnO₂ can be obtained,and it can realize not only good structural stability of the material,but also the enlarged the lattice-plane spacing of the material,which is conductive to improve the cycling stability of the battery and accelerate the embedding/ejection process of zinc ion(Zn²⁺).Hollow structure can not only provide more active sites,but also help to mitigate the volume change of cathode material during the cycling.The large specific surface area and abundant microporous and mesoporous structures contribute to the efficient electrons and ions transportation.K_0.07MnO₂ cathode still maintained a high specific capacity of 199.2 m Ah g^-1 at 10 C and a low average fading rate per cycle,of 0.06%after 500 cycles.