A hard-soft synergy strategy enables drastic temperature performance of pouch sodium-ion batteries over wide-temperature range of- 30 ° C to 60 ° C

A "hard-soft synergy" strategy is firstly developed to design functional multi-component electrolytes and successfully achieve drastic temperature performance of NaNi0.33Fe0.33Mn0.33O2 (NFM)/hard carbon (HC) sodiumion batteries (SIBs) over a wide range from -30 degrees C to 60 degrees C. Coupling "hard"-sodium difluorophosphate (NaDFP) with "soft"-tris(trimethylsilyl) phosphate (TMSP) or tris(trimethylsilyl) borate (TMSB) reasonably realizes an optimized solvation structure from "solvent dominated" to "anion collaborative" and synergistic-formed tough and multi-component interfacial films. Benefit to these, the cycling stability is considerably improved under the room and cold conditions, the capacity retention after 350 cycles increases from 0 % to 92 % and even stable cycling performance at 1 C (1 C = 900 mA) can be obtained at -10 degrees C. Discharge capacity at -30 degrees C and the capacity retention after storage at 60 degrees C are also greatly improved. Furthermore, the functional mechanisms of different electrolyte combinations under extreme temperature conditions are analyzed. It is demonstrated that the combination of NaDFP and TMSP is more suitable for high-temperature requirements due to its tougher cathode electrolyte interphase (CEI), reduced transition metal dissolution, and minimized cathode phase deviation. In contrast, the combination of NaDFP and TMSB is more suitable for low-temperature requirements, benefiting from the reduced desolvation energy and viscosity. In addition to the obtained functional electrolytes, this work also provides new insight for designing functional multi-component electrolytes of SIBs.