Synergistic interphase modification with dual electrolyte additives to boost cycle stability of high nickel cathode for all-climate battery

Abstract

B-containing electrolyte additives are widely used to enhance the cycle performance at low temperature and the rate capability of lithium-ion batteries by constructing an efficient cathode electrolyte interphase (CEI) to facilitate the rapid Li+ migration. Nevertheless, its wide-temperature application has been limited by the instability of B-derived CEI layer at high temperature. Herein, dual electrolyte additives, consisting of lithium tetraborate (Li2TB) and 2, 4-difluorobiphenyl (FBP), are proposed to boost the wide-temperature performances of LiNi0.6Co0.2Mn0.2O2 (NCM) cathode. Theoretical calculation and electrochemical performances analyses indicate that Li2TB and FBP undergo successive decomposition to form a unique dual-layer CEI. FBP acts as a synergistic filming additive to Li2TB, enhancing the high-temperature performance of NCM cathode while preserving the excellent low-temperature cycle stability and the superior rate capability conferred by Li2TB additive. Therefore, the capacity retention of NCM||Li cells using optimal FBP-Li2TB dual electrolyte additives increases to 100% after 200 cycles at −10 °C, 99% after 200 cycles at 25 °C, and 83% after 100 cycles at 55 °C, respectively, much superior to that of base electrolyte (63%/69%/45%). More surprisingly, galvanostatic charge/discharge experiments at different temperatures reveal that NCM||Li cells using FBP-Li2TB additives can operate at temperatures ranging from −40 °C to 60 °C. This synergistic interphase modification utilizing dual electrolyte additives to construct a unique dual-layer CEI adaptive to a wide temperature range, provides valuable insights to the practical applications of NCM cathodes for all-climate batteries.