Preparation And Improvement Of Manganese-based Oxide Cathode Materials For Aqueous Zinc Ion Batteries

As one of the emerging and highly promising alternative energy storage technologies,aqueous zinc ion batteries have many advantages such as high safety,abundant resources and high energy density.At present,the cathode materials for aqueous zinc ion batteries are mainly manganese oxide,vanadium oxide and Prussian blue analogues,while manganese-based cathode materials(such as manganese oxide,manganate,etc.)have great potential for application because of their rich crystal type,high operating voltage and low cost.However,their low capacity,low ionic conductivity and performance degradation caused by easy dissolution make it difficult to meet the requirements of practical applications.Therefore,on the one hand,there is an urgent need to develop more potential cathode materials,and on the other hand,it is extremely important to investigate the intrinsic electrochemical reaction mechanism for the further development and largescale application of aqueous zinc ion batteries.Thesis take typical manganese oxide cathode materials as the research target,design and construct novel structures with different characteristics by unique synthesis methods and different modification perspectives.Furthermore,their electrochemical properties and intrinsic electrochemical reaction mechanism were systematically study.The details are as follows:(1)An oxygen-defect-rich Mn3O4 nanomaterial was synthesized by an electrochemical oxidative etching preparation method,and four sets of Mn3O4 with different oxygen vacancy concentrations were obtained by tuning the oxygen vacancy concentration.used as AZIBs cathodes,the electrochemical characterization results concluded that the introduction of an appropriate amount of oxygen vacancies could achieve the best electrochemical performance.A high specific capacity of 440 m Ah·g-1 at 0.1 A·g-1 and a capacity retention of 94% after 2000 cycles(1.0 A·g-1)were exhibited.In addition,the H+/Zn2+ co-embedded storage mechanism of the Mn3O4 electrode was demonstrated by in-situ characterization analysis.(2)Further,the Mn O@CNFs composite nanofibers were synthesized as the cathode of AZIBs by introducing carbon nanofibers through an in situ strategy of electrostatic spinning technology.By unique coating of carbon material,forming a unique structural framework,the electrode achieves a high specific capacity of 430 m Ah·g-1 at 0.1 A·g-1 and a capacity retention rate of 81% after 2500 cycles at 1.0 A·g-1,and the electrode has excellent multiplicative performance.In addition,the H+/Zn2+ coembedding electrochemical reaction mechanism of the Mn O@CNFs electrode was verified by ion diffusion kinetics experiments and characterization after charge/discharge cycles(3)The ZMO/Mn O@C two-component metal oxides were further synthesized by MOF derivatization.By realizing the synergistic effect between the binary metal atoms through the bimetallic MOF,the obtained ZMO/Mn O@C cathode achieves excellent electrochemical performance,reaching a high specific capacity of 460 m Ah·g-1 at 0.1 A·g-1 and providing specific capacity of 170 m Ah·g-1 at 2.0 A·g-1 with 95% capacity retention after 3000 cycles,and the electrode has excellent The electrode has excellent multiplicative rate performance.In addition,further analysis of the phase transition mechanism,the intrinsic electrochemical reaction mechanism as well as the kinetic properties were demonstrated to be a H+/Zn2+ co-embedding mechanism similar to that of MnO.