Suppressing Electrode Crosstalk and Prolonging Cycle Life in High‐Voltage Li Ion Batteries: Pivotal Role of Fluorophosphates in Electrolytes

High-voltage Li ion batteries are compromised by lower cycle life due to enhanced degradation of cathode material, e.g. NCM523. Crucial part is the initiated electrode crosstalk, i.e. transition metal (TM) dissolution from the cathode and subsequent deposition on the anode, as it forces formation of high surface area lithium, capacity losses and risk of Li dendrite penetration, finally leading to an abrupt end-of-life (= rollover failure). Hence, suppression of this failure cascade is the pivotal strategy to prolong cycle life. A pragmatic approach is the electrolyte manipulation towards formation/presence of fluorophosphates, as they effectively suppress electrode crosstalk via TM scavenging. Either, they can be intrinsically formed, e.g. via elimination of ethylene carbonate (EC) solvent (= EC-free electrolyte), or simply externally added, e.g. via (good-soluble) lithium difluorophosphate electrolyte additive. Their effectiveness is demonstrated for conventional EC-based and EC-free electrolytes at limiting conditions (4.5 and 4.6 V, respectively). In parallel to supportive approach combinations ( e.g. coating), also destructive combinations are highlighted, i.e. approaches, which even decrease the fluorophosphate content, e.g. vinylene carbonate additive in EC-free electrolytes. Finally, by demonstrating the value of (concentration-optimized) fluorophosphates, appropriate benchmark electrolyte formulations for high-voltage LIBs are discussed