A High Energy-Density, Cobalt-Free, Low-Nickel LiNi0.7Mn0.25Al0.05O2 Cathode with a High-Voltage Electrolyte for Lithium-Metal Batteries

Cobalt-free cathode materials have garnered increased attention for applications in next-generation batteries for electric vehicles, as cobalt is considered to have at a high supply chain risk. Here, the use of a localized saturated electrolyte (LSE) to enable stable cycling of a cobalt-free, low-nickel layered-oxide cathode LiNi0.7Mn0.25Al0.05O2 (NMA-70) to higher voltages (4.6 V) in a lithium-metal battery is demonstrated. Compared to the baseline LP57 electrolyte, the LSE extends the cycle life from approximate to 100 cycles to approximate to 400 cycles before reaching 80% capacity retention. Visual indicators of cell degradation, such as product deposition, are observed on electrodes cycled in LP57. It is shown that cycling NMA-70 in LSE reduces the overall active material loss and overpotential growth during extended cycling. This is attributed to the formation of a beneficial fluorinated interphase layer, a lower degree of rock-salt phase formation, and a reduction in the gas evolution from the cathode surface. The decrease in gas evolution from the cathode cycled in LSE reflects a lower degree of electrolyte reactivity and an overall improvement in the safety characteristics of the cell. This study highlights the importance of a stable electrolyte to enable the high-voltage cycling of alternative, lower nickel, and cobalt-free cathodes.