Abstract

Low-temperature operation of lithium-ion batteries (LIBs) is severely limited by sluggish Li+ transport, aggravated interfacial polarization, and structural degradation of layered oxide cathodes. Herein, a multifunctional Li2O-B2O3-Li2SO4 composite coating, denoted as LBLS, was constructed on LiNi0.6Co0.2Mn0.2O2 (NCM622) through a simple wet-mixing/calcination strategy. Structural and surface characterizations confirm that the LBLS-derived layer is successfully introduced onto NCM622 while the layered α-NaFeO2 framework is well preserved. Benefiting from the regulated surface chemistry and improved interfacial kinetics, NCM622@LBLS exhibits significantly enhanced electrochemical performance, especially under subzero conditions. At −20 °C, the charge-transfer resistance decreases from 160 Ω for pristine NCM622 to 110 Ω after LBLS modification. Moreover, after 500 cycles at −20 °C, NCM622@LBLS maintains 101.57 mAh g−1 with a capacity retention of 80.60%, which compares favorably with representative coated NCM622 cathodes evaluated under comparable subzero conditions. In situ XRD reveals suppressed lattice breathing, while ex situ EIS, DRT and GITT confirm reduced interfacial polarization and faster Li+ diffusion. Depth-profiling XPS further demonstrates that LBLS promotes an inorganic-reinforced CEI containing Li–O, B–O/B–F, and SOx-containing species, thereby stabilizing the cathode/electrolyte interface during low-temperature cycling.

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