Protection of Cobalt-Free LiNiO₂ from Degradation with Localized Saturated Electrolytes in Lithium-Metal Batteries

High-nickel layered oxide cathode materials are the most promising candidates for developing lithium-metal batteries (LMBs) because of their high energy density and low cost. Herein, we present a localized saturated electrolyte (LSE) based on readily available, low-cost LiPF6 salt with limited solubility in carbonate solvents for developing LiNiO2 cathodes. Compared to the conventional electrolyte that retains only 55% of the initial capacity after 200 cycles, the LSE retains a record 81% of the initial capacity after 600 deep cycles at 4.4 V (versus Li/Li+). The LSE protects the LiNiO2 surface from degrading into rock-salt and spinel phases during cycling and helps form a robust Li morphology on the Li-metal anode that is covered by an inorganic-rich solid-electrolyte interphase. The drastically enhanced cycling stability with LSE demonstrates the importance of developing robust electrolytes compatible with both high-Ni cathodes and Li-metal anodes.