Defect Engineering Modification Of Manganese Based Oxide For High Performance Zinc Ion Battery

Energy shortage and environmental pollution problems have prompted mankind to develop efficient energy storage devices.High safe,environment friendly,and high ionic conductivity aqueous rechargeable zinc ion batteries have received much attention due to the high specific capacity,low redox voltage,and low cost of zinc.Manganese-based materials are considered as promising cathode materials for zinc ion batteries due to their simple synthesis technology,low price,and a variety of crystalline forms suitable for Zn²⁺embedding.However,due to the strong electrostatic interaction forces between Zn²⁺and the lattice of the host material,the cathode materials usually exhibit poor reversibility and slow kinetic processes.Therefore,modifying and optimizing the Zn storage capacity of Mn-based cathode materials using reasonable means plays an important role for realizing the application of Zn ion energy storage system.In this work,the Mn-based cathode material is modified by defect engineering to further enhance its zinc storage capacity.The main research results are as follows:（1）Porous hollow cubic blocks of MnOOH with well maintained skeletons were obtained by ion exchange using solid microcubes as templates,and then hollow cubic O_d-Mn₃O₄ with oxygen defects were prepared by calcination process.It was shown that oxygen vacancies could improve the electrical conductivity and reduce the internal electric field strength,thus improving the cationic body diffusion and stabilizing the crystal structure of O_d-Mn₃O₄.The vacancies also facilitate the subsequent insertion process by enhancing the binding of Zn²⁺and H⁺between the main body and the exterior.Thanks to the hollow structure and oxygen vacancies,O_d-Mn₃O₄ battery exhibit high specific capacity(325.4mAhg^-1 at 0.3Ag^-1)and remarkable cycling performance(151.3mAhg^-1 after 1100 cycles at 3Ag^-1).The energy storage mechanisms of H⁺and Zn²⁺co-embedding/de-embedding and Mn dissolution/deposition were verified.（2）The anode using structural modification strategies and vacancy engineering to introduce nitrogen and oxygen vacancies into mesoporous N-ZMO cubes exhibits unique advantages.The porous surface facilitates electrolyte penetration and accelerates ion and electron transport.The robust open cubic framework alleviates the intercalation/de-intercalation stress of zinc ions.The coupling of anion doping and oxygen vacancies increases the conductivity and reduces the local charge density,leading to rapid ion diffusion.N-ZMO electrodes exhibit high reversible discharge capacity(225.4mAhg^-1 at 0.3Ag^-1),good rate(80.5mAhg^-1 at 3.0Ag^-1)and stable cycling performance(88.4mAhg^-1 after 1000 cycles at 3Ag^-1).of 88.4mAhg^-1).Various in situ characterization tools were used to characterize the reaction mechanism of H⁺/Zn²⁺co-insertion/extraction.In addition,a flexible quasi-solid device with high energy density(261.6 Wh kg^-1)was assembled,showing long-lasting durability.（3）Hollow porous microspheres MnO_x/Co₃O₄ heterojunctions were prepared by the Kirkendall effect.Lattice cation defects are activated using an in situ electrochemical induction strategy,and the resulting product serves as a cathode for ultrafast zinc ion intercalation/deintercalation.Cation vacancies can serve as sacrificial sites for zinc ion intercalation and provide a channel for the rapid diffusion of zinc ions,while reducing the internal electrostatic force to alleviate the volume expansion during zinc ion intercalation.The heterostructured MnO_x/Co₃O₄ exhibits a high capacity of404.8mAhg^-1 and excellent rate performance(167.5mAhg^-1 at 3Ag^-1).