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LiNixCoyMnzO2 (x+y+z=1)||graphite lithium‐ion battery (LIB) chemistry promises practical applications. However, its low‐temperature (≤ −20 °C) performance is poor because the increased resistance encountered by Li+ transport in and across the bulk electrolytes and the electrolyte/electrode interphases induces capacity loss and battery failures. Though tremendous efforts have been made, there is still no effective way to reduce the charge transfer resistance (Rct) which dominates low‐temperature LIBs performance. Herein, we propose a strategy of using low‐polarity‐solvent electrolytes which have weak interactions between the solvents and the Li+ to reduce Rct, achieving facile Li+ transport at sub‐zero temperatures. The exemplary electrolyte enables LiNi0.8Mn0.1Co0.1O2||graphite cells to deliver a capacity of ≈113 mAh g−1 (98 % full‐cell capacity) at 25 °C and to remain 82 % of their room‐temperature capacity at −20 °C without lithium plating at 1/3C. They also retain 84 % of their capacity at −30 °C and 78 % of their capacity at −40 °C and show stable cycling at 50 °C. [ABSTRACT FROM AUTHOR]

The instability of sulfide solid electrolytes to Li anode and high‐voltage LiNi0.8Mn0.1Co0.1O2 (NMC811) cathodes limits the cyclic performance of all‐solid‐state lithium battery (ASSLB). Herein, the stability of Li6PS5Cl against Li anode is enhanced by mixing a small amount (0.32 wt%) of CuF2‐LiNO3 (CL) into Li6PS5Cl electrolyte layer to in‐situ form a mixed‐conductive‐lithiophobic and self‐healing LiF‐Li3N‐Cu solid electrolyte interphase (SEI) at Li6PS5Cl‐CL/Li interface. The critical current density (CCD) of Li6PS5Cl‐CuF2‐LiNO3 increases to 1.4 mA cm–2/1.4 mAh cm–2 at room temperature, which is much higher than that of pristine Li6PS5Cl (0.4 mA cm–2/0.4 mAh cm–2) even though mixing 0.32 wt% CL into Li6PS5Cl slightly reduces the ionic conductivity from 2.9 × 10–3 to 1.5 × 10–3 S cm–1. The compatibility of Li6PS5Cl‐CL electrolyte to single‐crystalline NMC811 (S‐NMC811) is further enhanced by adding a small amount (0.02 wt%) of AlF3 into Li6PS5Cl‐CL forming Li6PS5Cl‐CuF2‐LiNO3‐AlF3 (Li6PS5Cl‐CLA) as a cathode electrolyte and by doing Cl– on S‐NMC811 (Cl@S‐NMC811) surface. The Cl@S‐NMC811‐Li6PS5Cl‐CLA|Li6PS5Cl‐CL|Li cells with areal capacity of 2.55 mAh cm‐2 achieve a capacity retention of 69.4% after 100 cycles at 1C (1C = 200 mAh g‐1). Adding a small amount of SEI and cathode/electrolyte interphase (CEI) former into the sulfide electrolytes with minimal reduction (48.3%) of ionic conductivity is an effective method to enhance the performance of ASSLB. [ABSTRACT FROM AUTHOR]