Olivine-type LiMPO₄ (M = Fe, Mn, Co, Ni) has become of great interest as cathodes for next-generation high-power lithium-ion batteries. LiMnPO₄, possessing a moderate working voltage compatible to the present electrolyte systems, can provide a higher energy density than LiFePO₄ on account of its higher redox potential of Mn³⁺/Mn²⁺ (4.1 V) than Fe³⁺/Fe²⁺ (3.5 V). However, the electrochemical performance of LiMnPO₄ is poor due to the slow lithium diffusion kinetics within the grains and the low intrinsic electronic conductivity, even much worse than those of LiFePO₄. Up to now, low electronic conductivity can be successfully overcome by modifying the LiMnPO₄ particles with carbon and minimizing particle size. The mesoporous and hollow sphere structure can further improve the electrochemical performance of olivine-type LiMnPO₄ material.

Here, we synthesized the mesoporous hollow sphere LiMn_0.8Fe_0.2PO₄/C composite by a solvothermal method using spherical Li₃PO₄ as the precursor. The small crystalline size of (~50 nm) LiMn_0.8Fe_0.2PO₄ can reduce the diffusion length for lithium ion transport leading to the enhanced rate capability. The mesoporous and hollow sphere structure offers high surface area, which can enhance the electrochemical performance of LiMn_0.8Fe_0.2PO₄/C composite as show in Figure 1. The material exhibits an ultra-long cycle life exceeding 1000 cycles with an extremely low capacity decay of 0.0068 mAh·g^-1 loss per cycle, which is the best cycling performance to our knowledge. The results exhibit that the mesoporous hollow sphere LiMn_0.8Fe_0.2PO₄/C composite is a promising cathode material for lithium ion batteries.