Improving the electrochemical properties of lithium iron(II) phosphate through surface modification with manganese ion(II) and reduced graphene oxide

摘要

Lithium iron(II) phosphate (LiFePO4) particles were simultaneously modified via reduced graphene oxide (rGO) and manganese ion(II) (Mn2+) through a facile one-step method. X-ray photoelectron spectroscopy unravels that the formation of Mn-O bond originated from Mn2+ ion and fringe oxygen atoms of LiFePO4, which is beneficial for the rate capability of cathode. As cathode for lithium-ion battery, the as-prepared rGO/Mn-LiFePO4 composite exhibits excellent electrochemical properties. Its discharge-specific capacity is 159 mAh g(-1) at 1 C after 800 cycles with capacity retention of 92%. Even at a high rate of 10 C, the rGO/Mn-LiFePO4 composite is still capable of delivering 140 mAh g(-1) of discharge-specific capacity, indicating its excellent rate capability and cycle stability. It was demonstrated that the simultaneous modification of Mn2+ and rGO does not destroy the olivine structure of LiFePO4, but it can stabilize the crystal structure, decrease the electrode polarization, enhance the electronic conductivity and Li+ diffusion coefficient, and thus improve its cycling and high-rate capability.