Revolutionizing multifunctional electrolyte additive design and synthesis for high-voltage nickel-rich batteries in diverse climates

Abstract

The high-voltage LiNi0.6Co0.2Mn0.2O2 (NCM622) cathode presents a promising avenue for advancing the energy density of lithium-ion batteries. Nevertheless, current limitations primarily arise from electrolyte systems unable to meet stringent criteria, including stable performance under elevated temperatures and efficient discharge at low temperatures. In this study, we address these challenges by designing a molecular structure incorporating boron oxygen functional groups, phenyl-, and fluorine moieties to simultaneously enhance ion conductivity and thermal stability under extreme voltages. A multifunctional electrolyte additive, 3, 4, 5-trifluorophenylboronic anhydride (TFPBA), has been successfully developed via synthesis. TFPBA plays a pivotal role in promoting the formation of a hierarchical cathode electrolyte interphase (CEI) through its preferential decomposition and oxidation processes. This CEI features a mechanically stable inner layer enriched with fluorophenyl- groups, crucial for high-temperature cycling, alongside an outer layer concentrated with BxOyFz complexes that significantly improve Li+ conductivity, ensuring superior performance under low-temperature conditions and at elevated rates. Moreover, TFPBA acts as an HF scavenger within the electrolyte, mitigating corrosive effects on the cathode surface, thereby curtailing CEI reformation and the transition metal dissolution. The Li/NCM622 half cells with TFPBA exhibit impressive capacity retention rates of 92.58%, 80.09%, and 81.77% after extensive cycling at temperatures of −20 °C, 25 °C, and 55 °C, respectively. Moreover, NCM622/graphite full cells with TFPBA achieve a remarkable capacity retention of 97.97% after 150 cycles at room temperature. Our findings highlight the exceptional electrochemical performance of NCM622 cathodes at elevated voltages across a wide temperature range, providing valuable insights for the development of advanced electrolytes in high-demand applications.