| Olivine-type lithium manganese phosphate is regarded as a very potential cathode materials for Li-ion battery because of its low cost, environmentally benign, good compatibility with most liquid electrolytes presently used, as well as the optimal value of its redox potential (4.1 V vs. Li+/Li) which exhibits a higher energy density, is about 20% larger than that of LiFePO4. However, the extremely low electronic conductivity and sluggish Li-ion diffusion rate of LiMnPO4 make it a great challenge to achieve prominent electrochemical capability.LiMnPO4/C prepared in this work by a microwave solvothermal method were use MnSO4·H2O and Li3PO4 precursor as source materials and the mixture of water and diethylene glycol as reaction solvents. The effects of pH, volume ratio of water and diethylene glycol, reaction temperature, reaction time on the structures, morphologies and electrochemical performances of samples were investigated by XRD, SEM, TEM, EDS, CV, EIS and charge/discharge tests.The results show that flaky LiMnPO4 with a diameter of 40～80 nm and a thickness of 15 nm can be formed in a short reaction time when the reaction between Li3PO4 and MnSO4 is carried out under the microwave solvothermal conditions. LiMnPO4/C composite material with ordered olivine structure is synthesized by microwave assisted solvothermal process in 2:5(v/v) water-DEG mixed solvents at pH=6.8 and 190 ℃ for 5 min. The prepared LiMnPO4/C exhibits a discharge capacity of 131.1 and 85.2 mAh·g-1 at 0.1 C and 5 C, severally. Moreover, this sample delivers a discharge capacity of 108.3 mAh·g-1 and maintains about 99% of the capacity after 50 cycles at 1 C.The synthesis method used in this work takes advantages of both the mixture solvent to influence the crystal growth orientation as a soft template and the microwave effect to reduce the reaction time in high temperature and pressure state. This method can be applied to the microwave synthesis of other LiMPO4 olivine-type materials. |
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