Magnetic Field-Driven Ion Selectivity Boosts LiF-Rich SEI Formation for Enhanced Lithium Metal Battery Performance Across Temperatures

Lithium metal anodes are considered highly promising electrode materials due to their exceptional theoretical capacity and low reduction potential. However, their path to large-scale commercialization has been obstructed by significant challenges such as uncontrolled volume expansion, severe side reactions, and dendrite formation. To tackle these issues, our study introduces a covalent modification of separators using tannic acid (TA) and Co²⁺, coupled with the application of an external magnetic field. This innovative approach promotes the adsorption of CO₃^2- ions while inhibiting the uptake of F^- ions on the TA-Co/PP separators, leading to the formation of a LiF-rich solid electrolyte interface on the anode surface. Such modifications significantly enhance the electrochemical performance of lithium metal batteries. Remarkably, with the aid of the magnetic field, batteries featuring these modified separators maintained a Coulombic efficiency of 90% over 650 cycles at 1 mA cm^-2. Additionally, under challenging conditions at 60 °C and 4 mA cm^-2, the polarization voltage of Li symmetric cells utilizing TA-Co/PP separators is maintained at just 20 mV. This successful demonstration underlines the potential of our method to catalyze the broader adoption and commercialization of lithium metal batteries across varied temperature spectra.