The demand for high-energy-density lithium batteries (LBs) that work under a wide temperature range (−40 to 60 °C) has been increasing recently. However, the conventional lithium hexafluorophosphate (LiPF6)-based ester electrolyte with a solvent-based solvation structure has limited the practical application of LBs under extreme temperature conditions. In this work, a novel localized high-concentration electrolyte (LHCE) system is designed to achieve the anion-containing solvation structure with less free solvent molecules using lithium difluorophosphate (LiPO2F2) as a lithium salt, which enables wide-temperature electrolyte for LBs. The optimized solvation structure contributes to the cathode–electrolyte interface (CEI) with abundant LiF and P–O components on the surface of the LiNi0.5Co0.2Mn0.3O2 (NCM523) cathode, effectively inhibiting the decomposition of electrolyte and the dissolution of transition-metal ions (TMIs). Moreover, the weakened Li+–dipole interaction is also beneficial to the desolvation process. Therefore, the 4.3 V Li||NCM523 cell using the modified electrolyte maintains a high capacity retention of 81.0% after 200 cycles under 60 °C. Meanwhile, a considerable capacity of 70.9 mAh g–1 (42.0% of that at room temperature) can be released at an extremely low temperature of −60 °C. This modified electrolyte dramatically enhances the electrochemical stability of NCM523 cells by regulating the solvation structure, providing guidelines for designing a multifunctional electrolyte that works under a wide temperature range.

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Combining the Ni-rich layered cathode (Ni ≥ 80%) with high operating voltage is considered as a feasible solution to achieve high-energy lithium-ion batteries (LIBs). However, the working voltage is limited in practical applications due to the poor interface stability in traditional carbonate electrolytes. Herein, LiBF4 and LiNO3 are added as film-forming additives and 1.0 M LiPF6 in SL/FEC/EMC with 0.5 wt % LiBF4–LiNO3 (HVE) is obtained. A uniform and inorganic-rich cathode electrolyte interphase (CEI) as well as a dense and Li3N–LiF-rich solid electrolyte interphase (SEI) could be in situ generated on LiNi0.8Co0.1Mn0.1O2 (NCM811) and graphite (Gr) electrode in HVE, respectively. The robust interface film with electronic insulation and ionic conductivity effectively stabilizes the NCM811/Gr-electrolyte interfaces and improves the Li+ diffusion kinetics, enabling the high-load NCM811-Gr to maintain 85.2% capacity (∼180 mA h g–1) after 300 cycles under 4.4 V. Besides, the 4.2 V NCM811-Gr retains 90.4% of the initial capacity after 200 cycles at 2 C (∼6 mA h cm–2). Compared with the traditional carbonate electrolyte (LB301), HVE has obvious advantages in terms of high-voltage and fast dynamics performance. Especially, good thermal stability and economy make HVE a promising electrolyte for commercial high-energy LIBs.

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