Study On Controllable Synthesis And Interface Regulation Of Micro-Nano Structure Lithium-Rich Materials

The specific energy density of lithium-rich manganese-based cathode materials with high energy density can reach 1380Wh kg-1,which is ideal for the new generation of lithium-ion batteries.The materials have a wider voltage window and a higher manganese content compared with traditional commercial cathode materials,which is conducive to the reduction of the overall cost of the battery.Therefore,the materials have attracted great attention from researchers.However,there are still many problems in the practical application of lithium-manganese rich cathode materials,such as low initial coulomb efficiency,poor cycle performance and multiplier performance.Therefore,many problems need to be solved in order to put lithium-manganese rich cathode materials into practical application.In this paper,the modification of lithium-rich materials is studied from the aspects of material synthesis and surface interface regulation of lithium-manganese rich cathode materials.In-situ dispersion coprecipitation of PAAM was used to synthesize lithium-manganese-based anode materials.The effect of reaction time and pH value on the shape of the precursor was studied.The precursor with high sphericity and uniform particle size distribution was successfully prepared.By XRD and elemental contents analysis,it was confirmed that the precursor conformed to the expected theoretical setting.Through the optimization of sintering process,the lithium-manganese-based anode materials with high crystallinity,good sphericity and good electrochemical properties were prepared.Polydopamine(PDA)was used to self-assemble different oxide coatings on the surface of Lithium-manganese rich cathode materials.The effects of different zirconia coatings and oxide coatings on the structure and electrical properties of lithium-rich materials were investigated.It is found that the coating layer was very thin with no effect on the main structure of materials,and improved the cyclic performance of materials in different degrees.After the modification of ZrO2 on the first layer,the material had the best cycling performance.After 150 cycles at 0.1C,the capacity retention rate of the modified material was still 82.35%and the discharge capacity was 242.2mAh g-1,while the discharge capacity of the original material was only 167.4 mAh g-1 and the capacity retention rate dropped to 55.74%.XRD,TEM,XPS and other testing methods were used to characterize the crystal structure and surface morphology of the samples before and after coating,which proved that after coating,the structure and interface stability of the material were improved,and the dissolution of Mn in the cycling process was inhibited.A novel aqueous binder(lithium poly(acrylic acid),Li-PAA)is introduced for stabilized cyclic performance of lithium-rich manganese-based cathode materials.The comparison with traditional poly vinylidene fluoride(PVDF)electrochemical performance proved that the Li-PAA binder can effectively improve the cycle performance of lithium-rich materials.After 200 cycles at 0.1C,the capacity retention rate of PVDF electrode was 76.21%and the discharge specific capacity was 223.6 mAh g-1,while the capacity retention rate of Li-PAA electrode is as high as 90.77%and the discharge specific capacity is increased to 254.7 mAh g-1.The experimental results show that the Li-PAA binder is more conducive to adhesion between the active material and the current collector,which provides a more stable positive pole-electrolyte interface membrane and inhibits the phase transition during the material cycle.Li-PAA binder is more environmentally-friendly and has lower requirements for workshop environment,so it provides a new idea for practical application of lithium-rich materials.