Effect of <i>p</i> -Toluenesulfonyl Isocyanate on Interface Construction of Hard Carbon Anode Solid Electrolyte Interphases and Lithium-Ion Charge Transfer Behavior at Low Temperature

Propylene carbonate (PC)-based electrolyte system has the advantages of a wide liquid range and good Li⁺ migration kinetics, and therefore has excellent low-temperature application potential in the hard carbon (HC) anode system of lithium-ion batteries (LIBs). However, the slow charge transfer behavior of Li⁺ at low temperature seriously limits the practical application of hard carbon LIBs. Here, we use <i>p</i>-toluenesulfonyl isocyanate (PTSI) as an additive to improve the SEI structure and optimize the charge transfer behavior of Li⁺ at the interface. The results show that after adding 1% PTSI, PFHC-1 exhibits higher specific capacity (180.25 mAh/g at -20 °C, 94.83 mAh/g at -40 °C) and lower charge transfer impedance at low temperature. The NCO group in PTSI induces the uniform deposition of Li⁺; the larger ionic radius of S^2- controls the growth of the inorganic structure in the SEI and forms an interface layer with a smaller grain boundary size, which provides a migration path for Li⁺ at low temperature, facilitating the rapid migration of Li⁺ and accelerating the charge transfer behavior of Li⁺ at the interface. This work provides guidance for the commercialization of HC anodes for LIBs and the selection and design of low-temperature electrolytes in the future.