钠离子电池Na2MnSiO4正极材料的合成、结构及其电化学性能研究

首次采用溶胶-凝胶法制备Na₂MnSiO₄/C纳米复合正极材料. X射线衍射（XRD）和Rietveld结构精修结果表明,合成的Na₂MnSiO₄材料为单斜晶系、Pn空间群. 红外光谱（FTIR）结果证实材料中不含有Na₂SiO₃和SiO₂等杂质. 电化学测试结果表明，该材料在1 mol·L^-1 NaClO₄/PC电解液中，电流密度为14 mA·g^-1、电压范围为1.5 ~4.2 V（vs. Na⁺/Na）测试条件下，其首次可逆放电比容量高达113 mAh·g^-1.

Synthesis,Structure and Electrochemical Performance of Na2MnSiO4/C Cathode Material for Na-Ion batteries

As a promising cathode material for sodium ion batteries, pure phase Na₂MnSiO₄/C nanocomposite was successfully synthesized by a sol-gel method with a citric acid as a complex agent. The as prepared material was characterized by XRD, FTIR, SEM and TEM techniques. XRD and Rietveld refinement results indicated that the sample was indexed as monoclinic structure with space group of Pn. It was observed by SEM and TEM that the obtained product consisted of micro-scaled secondary particles, which were composed of NaMnSiO4 nanocrystallites and amorphous carbon network. More importantly, the uniform carbon network in the nanocomposite greatly enhanced the electronic conductivity of the material, thus, resulted in the impressive electrochemical performance. The electrochemical tests showed that the Na₂MnSiO₄/C could deliver a reversible capacity of 113 mAh·g^-1 (vs. Na⁺/Na) at a current density of 14 mA·g^-1 within 1.5 ~ 4.2 V when 1 mol·L^-1 NaClO₄ + PC was used as the electrolyte.