Comparative study of LiMnPO4 cathode materials synthesized by solvothermal methods using different manganese salts

The effects of anions on the particle size, phase impurity, crystal structural, and crystal growth orientation of olivine LiMnPO 4 prepared via the solvothermal synthesis method are systematically studied. LiMnPO 4 cannot be obtained for the precursor containing NO 3 − anions due to its strong oxidizing ability in acid environment. The SO 4 2− anion may facilitate the growth of high-index planes of the LiMnPO 4 crystals owing to its higher charge number. The Ac − anion with larger volume may have a significant atomic-scale template effect, thus the particle size of LiMnPO 4 is greatly limited and the crystal growth is inclined to the equilibrium state. The LiMnPO 4 samples, prepared from MnSO 4 , MnCl 2 and Mn(Ac) 2 , deliver an initial capacity of 145, 129 and 81 mAh g −1 , respectively. Among them, the sample synthesized from MnCl 2 can maintain 91% of its initial capacity after 200 cycles at 2 C, due to its high purity and crystal orientation growth with ac planes. Different anions will lead to distinguishable differences in the phase impurity, particle size and morphology of LiMnPO 4 under solvothermal conditions.