An advanced cathode composite design for co-utilization of cations and anions in lithium batteries

Abstract

Anions in the electrolyte are usually ignored in conventional "rocking-chair" batteries because only cationic de-/intercalation is considered. An ingenious scheme combining LiMn0.7Fe0.3PO4 (LMFP@C) and graphite as a hybrid cathode for lithium-ion batteries (LIBs) is elaborately designed in order to exploit the potential value of anions for battery performance. The hybrid cathode has a higher conductivity and energy density than any of the individual components, allowing for the co-utilization of cations and anions through the de-/intercalation of Li+ and PF6− over a wide voltage range. The optimal compound with a weight mix ratio of LMFP@C: graphite= 5: 1 can deliver the highest specific capacity of nearly 140 mA h/g at 0.1 C and the highest voltage plateau of around 4.95 V by adjusting the appropriate mixing ratio. In addition, cyclic voltammetry was used to investigate the electrode kinetics of Li+ and PF6- diffusion in the hybrid compound at various scan rates. In situ X-ray diffraction is also performed to further demonstrate the structural evolution of the hybrid cathode during the charge/discharge process.