A High Energy‐Density, Cobalt‐Free, Low‐Nickel LiNi_0.7Mn_0.25Al_0.05O₂ Cathode with a High‐Voltage Electrolyte for Lithium‐Metal Batteries

Abstract 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 LiNi_0.7Mn_0.25Al_0.05O₂ (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 ≈100 cycles 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.