Nitrile-Additive-Enabled Solvation Regulation and Cathode Interphase Stabilization for High-Voltage Ni-Rich Layered Oxide Cathodes

Ni-rich layered oxides, such as LiNi_0.835Co_0.113Mn_0.052O₂, are promising cathodes for high-energy-density lithium-ion batteries owing to their high theoretical specific capacity, elevated operating voltage, and reduced Co content. However, their practical application is hindered by severe interfacial instability, including continuous electrolyte decomposition, dissolution of transition-metal (TM) ions, and surface structural degradation during cycling. Meanwhile, conventional carbonate electrolytes exhibit limited oxidative stability at high voltages and tend to form an unstable cathode electrolyte interphase (CEI), which aggravates interfacial side reactions and capacity fading. Herein, 1,3,6-hexanetricarbonitrile (HTCN) is introduced as an electrolyte additive to regulate the cathode/electrolyte interphase of NCM cathodes. HTCN modifies the local solvation environment and promotes the formation of a thin, robust, and homogeneous CEI, thereby suppressing electrolyte decomposition and mitigating TM dissolution. As a result, the NCM||Li half-cell with 1.0 vol % HTCN exhibits the best electrochemical performance, delivering a capacity retention of 75.40% after 250 cycles at 1 C and a specific capacity of 207.1 mA h g⁻¹ after 200 cycles at 0.2 C. This work clarifies the role of nitrile additives in interfacial stabilization and provides an effective electrolyte-design strategy for high-voltage Ni-rich cathodes.