多晶型MnO_(2)改善富锂锰基正极材料的电化学性能

Electrochemical Performance of Lithium-Rich Manganese-Based Cathode Materials Improved by Polymorphic MnO_(2)

富锂锰基正极材料由于具有较高的理论比容量,被认为是下一代锂电池最有前途的正极材料之一。但在循环过程中存在比容量低、倍率性能差、衰减速度快等问题。基于此,本文采用水热法制备了多晶型MnO_(2)材料,并利用湿化学研磨法结合热处理工艺对商业富锂锰基正极材料进行了表面包覆改性。通过循环伏安、恒流充放电及电化学阻抗谱对所得材料进行电化学性能测试,并通过包覆前后材料电化学性能的变化研究了多晶型MnO_(2)对富锂锰基正极材料电化学性能的影响。结果表明,β-MnO_(2)的电化学性能最佳,其初始比容量在0.1 C下达到292.2 mAh·g^(-1),在0.1~5.0 C的倍率下容量保持率为56.3%,在1 C下循环50次后容量保持率为81.6%。通过EIS测试得出β-MnO_(2)的包覆改善了原样品电化学反应过程中的电化学动力学。

Lithium-rich manganese-based cathode materials are known as one of the most promising cathode materials for next-generation lithium batteries due to their high theoretical specific capacity.However,there are problems in the cycle process,such as low specific capacity,poor magnification performance,and fast decay rate.Based on this,polymorphic MnO_(2) materials were prepared by hydrothermal method,and the lithium-rich manganese-based cathode materials were modified of surface coating by wet chemical grinding combined and heat treatment.Electrochemical performance of the obtained materials was tested by cyclic voltammetry,constant current charge and discharge and electrochemical impedance spectroscopy,and the effect of polymorphic MnO_(2) on electrochemical performance of lithium-rich manganese-based cathode materials was studied by the changes of electrochemical performances of the materials before and after coating.The results show that β-coated has the best electrochemical performance,and its initial specific capacity reaches 292.2 mAh·g^(-1) at 0.1 C,the capacity retention rate is 56.3% at 0.1~5.0 C,and the capacity retention rate is 81.6% at 1 C for 50 times cycles.The coating of β-MnO_(2) by EIS test improves electrochemical kinetics of original sample during the electrochemical reaction.