Tailoring electrolyte to enable high-rate and super-stable Ni-rich NCM cathode materials for Li-ion batteries

The detrimental effects on the electrochemical performances of high-capacity nickel-rich layered oxide cathode LiNi0.8Co0.1Mn0.1O2 (Ni-rich NCM) are continuous irreversible phase transition, particle disintegration, and unstable cathode-electrolyte interface, which are usually induced by deleterious cathode-electrolyte reactions. Here, we report those side reactions are limited by a uniform inorganic/polymer cathode-electrolyte-interface (CEI) formed by in-situ electrochemical oxidation of a trace amount of dual additives in the traditional carbonate-based electrolytes. This CEI film not only eliminates the adverse cathode-electrolyte interface reaction and prevents the electrolyte penetration into the grain boundary but also hinders the formation of inactive rock salt phase on the material surface. More significantly, it is demonstrated that this N, B, O-rich interface layer offers a fast Li+ diffusion kinetic process to ensure a high-rate performance of the cathode, which is still a technical difficulty for the large application of Ni-rich NCM. Here, under the synergistic effect of dual additives containing lithium bis(oxalate)borate (LiBOB) and dopamine, the cell exhibits high-capacity retention over 92% after 200 cycles at 1 C, and also obtain a high specific capacity of 118 mA h g(-1) at the high rate of 20 C. Building a stable and effect Li+-ion conductive interface film by optimizing the electrolyte formula is a facial and effective approach to develop aggressive high-capacity cathodes for high-energy storage applications.