Cyclable Micron‐Sized Silicon‐Based Lithium‐Ion Batteries at −40 °C Enabled by Temperature‐Dependent Solvation Regulation

Abstract Micron‐sized silicon (µSi) anodes hold great promise for high‐energy lithium‐ion batteries (LIBs). However, the rechargeable cyclability of µSi anodes at sub‐zero Celsius, especially below −20 °C remains challenging, caused by the severe volume change and cracking of solid electrolyte interphase (SEI) during cycling. Here, the low‐temperature cyclability of µSi‐based LIBs is realized by using an electrolyte featured with temperature‐adaptive ion‐dipole interactions. The synergistic effect of the methyl group as a weak electron donor and the electronegative fluorine atoms endows methyl difluoroacetate (MDFA) with a weak binding affinity for Li + . Moreover, the affinity between Li + and the oxygen atoms in both MDFA and fluoroethylene carbonate (FEC) decreases at lower temperatures, accompanied by a temperature‐responsive enhancement of Li + ‐anion coordination. Thus, the MDFA/FEC electrolyte exhibits an extraordinary contact ion pairs‐dominated solvation structure at subzero temperatures, which facilitates Li + desolvation and the formation of a thin, robust inorganic‐rich SEI. As expected, µSi anodes show a record‐breaking capacity of 786 mAh g −1 after 100 cycles at −40 °C under 0.1 A g −1 , and µSi‐based full cells display impressive rechargeability at −40 °C. This work paves the way for extending the applications of µSi anodes to extreme cold conditions.