Structure and Electrochemical Behavior of Minor Mn-Doped Olivine LiMnxFe1−xPO₄

In the recent years, olivine LiFePO 4 has been considered as a prospective cathode material for lithium-ion batteries. However, low conductivity is an obstacle to the commercialization of LiFePO 4 ; doping the transition metal such as Mn and Ni is one of the solutions for this issue. This work aimed to synthesize the Mn-doped olivines LiMn x Fe 1− x PO 4 at low content of Mn ( x = 0.1, 0.2) via the hydrothermal route followed by pyrolyzed carbon coating. The synthesized olivines were well crystallized in olivine structure, with larger lattice parameters compared with LiFePO 4 . The EXD and TGA results confirmed the coated carbon of 4.14% for LiMn 0.1 Fe 0.9 PO 4 and 6.86% for LiMn 0.2 Fe 0.8 PO 4 . Both of Mn-doped olivines showed higher diffusion coefficients of Li + intercalation than those of LiFePO 4 that led a good performance in the cycling test. LiMn 0.2 Fe 0.8 PO 4 exhibited a higher specific capacity (160 mAh/g) than LiMn 0.1 Fe 0.9 PO 4 (155 mAh/g), and the Mn content is beneficial for the cycling performance as well as ionic conductivity.