Enabling Stable High-Voltage LiNi 0.5 Mn 1.5 O 4 Operation with 1,3,6-Hexanetricarbonitrile as an Electrolyte Additive

Spinel LiNi 0.5 Mn 1.5 O 4 (LNMO) has attracted extensive attention as a high-voltage cathode material due to its large specific capacity, high operating voltage (∼4.7 V vs Li + /Li), excellent rate capability, and low cost. However, its practical application is limited by poor interfacial stability between the cathode and conventional carbonate-based electrolytes under high-voltage conditions, leading to electrolyte decomposition and rapid capacity fading. In this work, 1,3,6-hexanetricarbonitrile (HTCN) is introduced as an electrolyte additive, which significantly improves the cycle and rate performance. HTCN can contribute to forming a robust, nitrogen-rich cathode–electrolyte interphase that suppresses electrolyte oxidative decomposition and inhibits HF corrosion, thereby mitigating Mn dissolution. Additionally, HTCN participates in the formation of an N-containing solid–electrolyte interphase on the graphite anode, which effectively reduces the deposition of dissolved Mn species. As a result, Li||LNMO cells using the electrolyte with 1 wt % HTCN retain 98.6% of their capacity after 100 cycles at 1C, and LNMO||graphite pouch cells exhibit a capacity retention of 82.8% after 170 cycles, much higher than 72.5% for the cells using the electrolyte without HTCN. This highlights the great potential of HTCN as a highly effective electrolyte additive for advanced high-voltage lithium-ion batteries