Extreme Fast Charging and Stable Cycling of Lithium Manganese Oxide Batteries by Suppression of Cathode Phase Changes

Abstract Extreme fast charging (XFC, i.e., 80% state of charge within 15 min, 4C rate) remains a high‐desirability criterion for next‐generation lithium batteries. While the anodes, such as, graphite and lithium are historically acknowledged as the critical hurdles toward XFC of Li‐ion batteries, the stability of cathodes under such sustained high rate cycling has not been addressed in literature. In this work, for the first time, the XFC and 4C cycling of cobalt‐free LiMn 2 O 4 (LMO) batteries with practical areal capacity (1 mAh cm −2 ) are investigated. This work demonstrates that the high rate cycling of LMO brings forth a cascade of irreversible phase changes in the bulk of the cathode, which initiates the electrolyte degradation. The electrolyte degradation and cathode irreversibility play a compounding role in the capacity loss during cycling, even with high‐rate compatible anodes, e.g., Li 4 Ti 5 O 12 (LTO). This capacity loss is overcome by combining a micro‐structured LMO cathode and a novel electrolyte containing a novel lithium salt, lithium 1,1,1,3,3,3 (tetrakis) hexafluoroisopropoxy borate. Cycling of the LMO|LTO cells shows 98 mAh g −1 initial discharge capacity at 4C‐4D cycling and 91% capacity retention after 1500 cycles while charging to 90% of total capacity in 10 min.