Preparation And Doping Of Layered Oxide Cathode Materials For Na-Ion Batteries

With society’s continuous development,non-renewable fuels such as oil and natural gas have become the main energy source supply.Large-scale exploitation of fossil fuels will cause a series of serious environmental pollution problems.Therefore,it is imperative to find and develop new renewable energy sources.Lithium-ion batteries have been widely used in various electronic devices due to their high energy density and long cycle life.However,due to the crust’s uneven distribution of lithium resources and limited reserves.Na-ion batteries with the same properties and working principles have become an important alternative.The layered oxides with high energy density and theoretical specific capacity have been widely studied.High-performance layered oxide cathode materials are vital to the industrialization of NIBs due to their high theoretical capacity and facile production.These materials,however,suffer from sluggish kinetics,complicated phase transitions,and poor capacity retention cycling.The modifying impacts of classic strategies,such as doping and coating,are generally restricted as well as the problem of structural instability and the lattice distortion to at high voltage.This paper proposes several reasonable designs of Sodium-ion layered oxide materials,and their structural characteristics and electrochemical performance are analyzed to achieve the required performance.The specific research contents are as follows:（1）A rational four-in-one strategy to boost the overall performance of Na_x[Ni,Mn]O₂ materials by innovative composition design and elegant synthesis management is provided.Ti-doped materials were synthesized by coprecipitation with the wet chemistry method and investigated the electrochemistry,structural evolution,and charge compensation.The half-cell capacity retention rate increases from 45%to77%after 250 cycles at 1C.The capacity of the full cells is maintained at 83%after 300cycles at 0.5C.This four-in-one strategy,which encompasses optimization of the energy band structure,ion diffusion,crystal structure,and particle morphology,sheds new insight on the overall optimization of cathode materials for NIBs.（2）The lattice structure and cycle performance were adjusted through the doping of Ti and Mg elements.The O3-Na Ni_0.4Mn_0.4Ti_0.1Mg_0.1O₂ material were synthesized by coprecipitation and the wet chemistry method,which electrochemical properties,charge compensation,and structural evolution processes were investigated in different voltage ranges.The modified material broadened the lattice spacing,suppressed the irreversible phase change in the high-voltage and enhanced structural stability.After200 cycles at 1C,the capacity retention rate increases from 54%to 74%,enhancing cycle performance and structural stability.