Seth Reed, Arumugam Manthiram
LiMnxFe1-xPO4 (LMFP) cathodes for lithium-ion batteries provide a balance of chemical stability and high energy density when compared to LiFePO4. Due to its low electronic conductivity, LMFP must be coated with conductive carbon to achieve optimal electrochemical performance. While a plethora of carbon coating precursors and methods have been pursued, the effectiveness of coating in an LMFP full cell with a graphite anode has not been examined. Herein, six unique carbon coating methods are implemented to synthesize LMFP with 60 mol% Mn and doped with 2 mol% V. X-ray photoelectron spectroscopy examines the C 1s peaks with and without charge neutralization applied, providing context to the conductivity and uniformity of carbon coating. Full cell cycling at 21°C and 45°C demonstrates that LMFP cathodes with uniform carbon coatings achieve higher discharge capacity and superior capacity retention. In these cells, solid-electrolyte interface growth and transition metal deposition of Mn onto graphite anode are minimized as confirmed by inductively coupled plasma-optical emission spectroscopy. While Fe deposition is abundant in some cells, its impact on cycling performance is unsubstantiated. Optimizing the carbon coating of LMFP cathodes can protect both the cathode and anode from degradation and enhance the electrochemical performance.