Offsetting Initial Lithium Loss By Pre-Forming SEI Layer on Graphite Surface

Abstract

The irreversible lithium loss due to the formation of solid electrolyte interphase (SEI) in the initial cycle greatly reduced the overall cell energy density of lithium ion batteries. Cathode prelithiation methods have been widely explored to compensate this lithium loss. However, these cathode additives with high lithium contents inevitable lower the active cathode materials loading. Here we report a facile graphite prelithiation method by pre-forming SEI layers on graphite surface (Pre-SEI graphite) in a flow cell. The Li accommodation in graphite anode could be controlled by the operation of the time and current density in flow cell for the electrochemical SEI formation. As a result, we demonstrate a 10% initial Columbic efficiency increase of the LiFePO4 electrode in a full cell configuration with our Pre-SEI graphite. The electrochemical pre-formation of SEI on graphite offers a novel route to offset initial lithium loss without a sacrifice of active cathode loading.