Na-Mn共掺对磷酸铁锂正极材料结构与性能的影响

Effect of Na-Mn Co-Doping on the Structure and Performance of LiFePO_(4)Cathode Materials

利用碳热还原法成功制备了Li_(0.97)Na_(0.03)Fe_(7/8)Mn_(1/8)PO_(4)正极材料,运用XRD、SEM、EDS和电化学测试等手段对其晶体结构、形貌、元素分布和电化学性能进行研究,并结合第一性原理计算分析材料性能提升的机理。结果表明,Na-Mn掺杂一方面导致LiFePO_(4)晶格畸变,晶格体积增大,扩大了锂离子迁移通道,为锂离子嵌入/脱出提供更大的空间;另一方面使材料在电化学性能上表现出优异的高倍率性能和循环稳定性。Na-Mn掺杂有利于提高材料的锂离子扩散系数和电导率,从而提高其电化学性能。基于第一性原理计算结果表明,Na-Mn共掺杂使LiFePO_(4)晶格膨胀,晶格体积增大,并促使带隙宽度减小,增强了费米能级附近的电子态密度,提高了材料的电子电导率和锂离子迁移率。

Li_(0.97)Na_(0.03)Fe_(7/8)Mn_(1/8)PO_(4)cathode materials were successfully prepared by carbothermal reduction method.The crystal structure,morphology,elemental distribution,and electrochemical performance of the material were studied by XRD,SEM,EDS,and electrochemical tests,with first-principle calculation being used to analyze the mechanism of the material′s improved performance.The results show that on the one hand,Na-Mn doping leads to the lattice distortion in LiFePO_(4)and the expansion of lattice volume,expanding the lithium ion migration channels and providing more space for lithium ion insertion and extraction.On the other hand,the material exhibits excellent high-rate performance and cycle stability in electrochemical performance.Na-Mn doping is advantageous in improving the lithium-ion diffusion coefficient and conductivity of the material,thereby improving its electrochemical performance.The first-principle calculation results show that Na-Mn co-doping induces lattice expansion of LiFePO_(4),increases lattice volume,narrows energy band gap,enhances electronic density of states near Fermi level,and improves the electronic conductivity and lithium ion mobility of the material.