Prelithiating Si-Based Anodes using Li-Excess Layered Positive Electrode Materials

Abstract With the increasing commercialization of silicon-based anodes, their high first-cycle irreversible capacity becomes a critical issue to address. Future cycles may also require additional lithium due to the evolution of the anode's solid electrolyte interphase. This work introduces Li-excess layered Li1.11(Ni0.5Mn0.5)0.89O2 (Li-excess NMC550) as suitable cathode choice to provide additional lithium reserves to the cell. The excess lithium can be removed from the cathode structure irreversibly when the cell is subjected to voltages greater than 4.4V, making it a good choice for prelithiating Si-based cells without requiring any additional processing. In addition, the Li-excess NMC550 does not display voltage fade typical of Li-rich and Mn-rich materials with more Mn than Ni atoms in the structure. This strategy is shown in this work well in NMC550: silicon/carbon (Si/C) cells. Cells were cycled to an initial upper cutoff of 4.6 V to transfer excess lithium from the cathode to the Si-based anode, followed by typical cycling within a stable voltage window. An 11% excess lithium reserve enhances cell energy density and prevents early capacity loss associated with lithium inventory depletion.