Preventing Sudden Death of High‐Energy Lithium‐Ion Batteries at Elevated Temperature Through Interfacial Ion‐Flux Rectification

Abstract Lithium‐ion batteries commonly exhibit a gradual loss of Li‐storage capacity during operation and storage. However, they can also abruptly lose much of their capacity in a rollover fashion (i.e., “sudden death”) under aggressive but practically relevant conditions, such as high‐voltage operation or cycling at elevated temperatures. Here the origin of rollover failure is investigated in high‐energy LiNi 0.80 Co 0.15 Al 0.05 O 2 ‐graphite (NCA‐Gr) batteries cycled at 55 °C. A combined chemical, structural, and electrochemical studies revealed that severe Li plating at the anode surface is the major reason causing the capacity rollover. The Li plating at elevated temperature is triggered by temperature hotspots resulting from inhomogeneous Li‐ion flux, which is a thermodynamic‐driven mechanism different from the kinetically limited one at low temperature and/or under fast‐charging conditions. A Zr(OH) 4 ‐coated, ion‐rectifying separator is further designed to enable an NCA‐Gr pouch cell with a stable cycle performance for 600 cycles and without a sudden death at 55 °C.