Hexabutylcyclohexane‐1,2,3,4,5,6‐hexaimine Additive‐Assisted Commercial Ester Electrolyte for 4.7 V Highly‐Stable Li‐Metal Batteries

Abstract The development of high‐energy density batteries is of utmost importance for various applications. However, the utilization of numerous high‐capacity materials is impeded by the inadequate stability of electrolytes beyond 4.5 V. This research proposes a straightforward yet highly efficient strategy to overcome this limitation and enhance the stability of interfaces in high‐voltage Li metal batteries when employing commercial ester electrolytes. A series of electrolyte additives is designed with the aim of gradually extending the length of the terminal alkyl groups of cyclohexane‐1,2,3,4,5,6‐hexaimine (CHHI). Among these additives, hexabutylcyclohexane‐1,2,3,4,5,6‐hexaimine (HBCHHI) demonstrate exceptional performance due to the synergistic complementarity of n‐butyl and imino groups. This synergistic effect leads to the formation of a thinner, denser, and Li x N‐rich solid/cathode‐electrolyte interface. Accordingly, the electrolyte‐electrode interactions are suppressed, enabling Li||LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811) battery operation at a high‐voltage of 4.7 V with alleviated structural degradation of cathode and even Li deposition at the anode. The capacity retention of high‐voltage Li||NCM811 cells is improved by ≈250% after 500 cycles at a rate of 5C. The lifespan of full cells is also prolonged at quasi‐practical conditions of high cathode loading of ≈2.5 mAh cm −2 .