High-Capacity, Aliovalently Doped Olivine LiMn1鈥?x/2Vx鈻?sub>x/2PO4 Cathodes without Carbon Coating

详细信息    查看全文

• 作者：Arturo Gutierrez ; Ruimin Qiao ; Liping Wang ; Wanli Yang ; Feng Wang ; Arumugam Manthiram
• 刊名：Chemistry of Materials
• 出版年：2014
• 出版时间：May 13, 2014
• 年：2014
• 卷：26
• 期：9
• 页码：3018-3026
• 全文大小：602K
• 年卷期：v.26,no.9(May 13, 2014)
• ISSN：1520-5002

文摘

A substantial amount of Mn²⁺ has been aliovalently substituted by V³⁺ in cation-deficient LiMn_1鈥?x/2V_x鈻?sub>x/2PO₄ (0 鈮?x 鈮?0.20) by a low-temperature (<300 掳C) microwave-assisted solvothermal (MW-ST) process. The necessity of a low-temperature synthesis to achieve higher levels of doping is demonstrated as the solubility of vanadium decreases with the formation of impurity phases on heating the samples to 鈮?75 掳C. Soft X-ray absorption spectroscopy reveals enhanced Mn鈥揙 hybridization in the vanadium-doped samples, which is believed to facilitate an increase in capacity with increasing vanadium content in the lattice. For example, a high capacity of 155 mAh/g is achieved above a cutoff voltage of 3 V without any carbon coating for the x = 0.2 sample. The vanadium substitution enhances the overall kinetics of the material by lowering the charge-transfer impedance and increasing the lithium-diffusion coefficient.