Colloid Electrolyte with Changed Li⁺ Solvation Structure for High-Power, Low-Temperature Lithium-Ion Batteries.

Abstract

Lithium-ion batteries currently suffer from low capacity and fast degradation under fast charging and/or low temperatures. In this work, a colloid liquid electrolyte (CLE) is designed, where the trace amount of lithium thiocarbonate (LTC) colloids in commercial carbonate electrolyte (1 m LiPF₆ in ethylene carbonate/dimethyl carbonate) not only boosts up σ_Li+ but also improves the Li⁺ transfer kinetics at LiNi_0.8 Co_0.15 Al_0.05 O₂ (NCA) cathode/electrolyte interface. The competitive coordination of LTCs with anions and solvents facilitates the dissociation of lithium salts and Li⁺ decoupling, dramatically enhancing the σ_Li+ (15 to 4.5 mS cm^-1 at 30 and -20 °C, respectively); meanwhile, the desolvation process is accelerated. It demonstrates that LTC colloids induce an ≈5 nm ultrathin Li₂ CO₃ -rich cathode electrolyte interface and infuse the grain boundary of NCA particles, enhancing interfacial Li⁺ transfer and inhibiting the particle cracks during cycling. Consequently, the Li||CLE||NCA battery delivers a maximum capacity of 135 mAh g^-1 at a 10 C rate with 80% retention after 2000 cycles. Moreover, the fast-charging capability under a sub-zero environment is proved (122 mAh g^-1 with 90% retention after 400 cycles at 2 C and -10 °C). This strategy for tailoring the interfacial charge transfer appears generalizable and can practically be extended to next-generation energy-storage systems.