Fast precipitation-induced LiFe0.5Mn0.5PO4/C nanorods with a fine size and large exposure of the (010) faces for high-performance lithium-ion batteries

Olivine-type LiFexMn1-xPO4/C cathode materials are of great interest for lithium-ion batteries because of their higher lithium ion intercalation potential compared with that of LiFePO4. Two types of LiFe0.5Mn0.5PO4/C nanorods with different sizes and crystal structures were synthesized through a facile glycol-based solvothermal process with different precursor feeding sequences. The microstructural investigation revealed that the size and structure of the LiFe0.5Mn0.5PO4 nanorods can be tuned by nucleation and crystal growth rates of the intermediate precipitates, which can be controlled by precursor feeding sequence. The LiFe0.5Mn0.5PO4 nanorods obtained through the first feeding sequence (a solution of transition metal salts was added dropwise into the solution mixture of LiOH and H3PO4) exhibited less exposure of the (010) crystal faces and had bigger sizes compared with those of the LiFe0.5Mn0.5PO4 nanorods obtained through the second feeding sequence (a LiOH solution was added dropwise into the solution mixture of H3PO4 and transition metal salts). Electrochemical investigations indicated that the LiFe0.5Mn0.5PO4 nanorods obtained through the second feeding sequence showed substantially improved electrochemical performance, in which the discharge capacities reached 157 and 119 mAh g−1 at 0.2 and 5 C, respectively. Furthermore, a capacity retention of 89% was obtained after 500 cycles at 1 C, demonstrating excellent cyclic stability.