NaNO2 additive-assisted Li2O2 decomposition for highly efficient cathode prelithiation of lithium-ion batteries

Silicon based anodes are the most attractive candidates for high energy density lithium-ion batteries (LIBs), but their practical applications are hindered by the large initial lithium loss. Cathode prelithiation is an effective method to mitigate the active lithium loss in silicon-based LIBs. However, a cathode prelithiation method enabling suitable cutoff voltage and less residues still remains challenging. Herein, we demonstrate that soluble additive NaNO2 in carbonate-based electrolyte could efficiently reduce the decomposition voltage of Li2O2 to as low as 4.3 V. The liquid-solid synergistic effect of NaNO2 additive and LiNi0.83Co0.07Mn0.1O2 (NCM) cathode on the Li2O2 decomposition is revealed, which enables the highly efficient cathode prelithiation with remarkable Li2O2 decomposition efficiency of 96.7% at the acceptable cutoff voltage 4.4 V. For the addition for 1 wt% Li2O2, a capacity of 14.85 mAh/g could be supplied in the first charge. Besides, NaNO2 could reduce the active lithium loss during the following cycles for its irreversibly decomposing into Li3N and LiNxOy on the anode surface. The full cell assembled with NCM(Li2O2) cathode and silicon-graphite (Si-G) anode delivers 17.3% higher initial specific capacity (218.6 mAh/g) than that without Li2O2 (186.4 mAh/g) at the charge cutoff voltage of 4.4 V. This work provides a novel electrolyte-assisted cathode prelithiation strategy to compensate the initial active lithium loss, which is highly compatible with the current battery fabrication process.