Structural Regulation Of Manganese-Based Cathode For High-Performance Zinc-Ion Batteries

Lithium-ion batteries（LIBs）have the advantages of high energy density,long cycle life and good mobility,which are widely used in mobile electronic devices and electric vehicles.However,the shortage of lithium resources and high safety risks hinder the application of LIBs in the field of large-scale energy storage.Aqueous zinc-ion batteries（ZIBs）have the merits of low cost,stable chemical property and high safety,holding great potential in large-scale energy storage devices.Currently,manganese-based material has become a research hotspot for the cathodes of ZIBs due to its high energy density and abundant resources.This thesis aims to develop manganese-based cathode materials with high specific capacity,long cycle life and excellent rate performance,and improve their reaction kinetics behavior and zinc storage performance through the strategies of crystal plane regulation and alkali-metal ion pre-intercalation.The specific research contents and conclusions are listed as follows:（1）β-Mn O₂ materials exposed with different crystal planes have been prepared by controlling the concentration of KCl in the reaction solution.The scientific connection between the zinc storage performance ofβ-Mn O₂and its exposed crystal planes has been revealed.The experimental results show that exposing the（100）crystal plane can accelerate the activation process in the initial reaction stage and induce an in-situ phase transition reaction from tunnel-structuredβ-Mn O₂ to layered-structure Zn Mn₃O₇·3H₂O,guaranteeing excellent cycling stability.Meanwhile,DFT calculation results suggest that the differential charge distribution of（100）plane in theβ-Mn O₂ crystal structure is uneven,indicating its higher electrochemical reactivity.Additionally,the Zn²⁺diffusion path along the（100）plane has a lower energy barrier.Therefore,β-Mn O₂ cathode exposed（100）plane also holds superior diffusion kinetics.As a result,it exhibits a high capacity of 275 m Ah g^-1 at 100 m A g^-1,and still has a reversible capacity of 95.5 m Ah g^-1 after 1000 cycles at 1000 m A g^-1,demonstrating that regulating crystal plane is feasible to improve zinc storage performance of manganese-based cathode materials.（2）A series of Li⁺pre-intercalated layered manganese-based cathode materials(Li_0.1-NMO,Li_0.2-NMO and Li_0.4-NMO)have been prepared by solid-phase sintering method.The effects of different Li⁺intercalation amount on zinc storage performance of layered manganese-based cathode has been explored.XRD results show that the more Li⁺intercalation,the more significant the electrostatic shielding effect between the Li⁺ions within interlayer,resulting in the constriction of layered structure and the reduction of interlayer spacing.XPS results indicate that Li⁺pre-intercalation introduces different degrees of oxygen defects,and the more Li⁺intercalation,the more accompanying oxygen defects.Appropriate amount of Li⁺intercalation can effectively increase the interlayer spacing,support the layered structure and improve the reaction kinetics.However,excessive Li⁺intercalation will seriously damage the structural stability during cycling.Thanks to these merits,Li_0.2-NMO cathode maintains high zinc storage capacity of 248.3 m Ah g^-1 after 100 cycles at 100 m A g^-1.Additionally,its reversible capacity is 188,141.46 and 93.3 m Ah g^-1 after170,300 and 1000 cycles at 200,500 and 1000 m A g^-1,respectively,suggesting excellent cycling stability and rate capability.There are 31 pictures,6 tables and 127 references.