Lithium nitrate as a surplus lithium source for anode-free cell with Ni-rich (NMC811) cathode

Anode-free lithium metal batteries (AFLMBs) consisting of the copper current collector, carbonated-based electrolytes, and Ni-rich cathodes can be considered potential candidates for coming-generation energy storage devices. However, the capacity fade of Ni-rich (NMC811) cathode is very fast in carbonate electrolyte. It is essential to find way to increase the lithium inventory on the cathode side so that the issue of short cycle life associated with limited lithium can be addressed for AFLMBs. Here, we introduce lithium nitrate (LiNO3) as a cathode additive to modify the Ni-rich cathode. The additive is supposed to supply lithium inventory to compensate irreversible lithium loss and simultaneously result in the formation of stable solid electrolyte interphase (SEI) layers on the plated lithium surface. Interestingly in our AFLMBs configuration, we observe that the LiNO3 decomposes during the high voltage operation and strongly favors formation of a good solid-electrolyte interphase (LiF and Li3N) and cathodic-electrolyte interphase (CEI). The result also demonstrates that the cell with lithium nitrate additive exhibits much better Coulombic efficiency (CE) (97.69% after 30 cycles) compared to the cell with no additive (89.25% after 30 cycles). This work provides a new approach to extend the cycle life of anode-free lithium metal batteries.