Robust solid/electrolyte interphase on graphite anode to suppress lithium inventory loss in lithium-ion batteries

Lithium inventory loss is the most important reason for capacity decay of commercial lithium ion batteries. To suppress lithium inventory loss and prolong the battery cycle-life, sodium maleate (SM) is coated onto the surface of graphite active materials and act as the starting material for in-situ growth of SEI film. Microscopic studies show that the SM salt is uniformly dispersed on the graphite particles. The SM coating favors the formation of robust solid electrolyte interphase (SEI) due to its abundant carboxyl group and improves the mechanical property due to the polymerization between the unsaturated bonds. With 3.0 wt% SM coating, the first columbic efficiency, cycling stability and rate capability of the graphite anode are simultaneously improved. Electrochemical impedance spectroscopy (EIS) studies and scanning electron microscope (SEM) observations show that continuous lithium deposit on the graphite surface arising from the SEI instability during long-term electrochemical cycles is effectively suppressed. Cycle-life of the full cell assembled with LiFePO4 cathode and 3.0 wt% SM coated graphite anode is thus significantly prolonged.