A Hydridoaluminate Additive Producing a Protective Coating on Ni-Rich Cathode Materials in Lithium-Ion Batteries

Abstract

To enhance the energy density of Li-ion batteries, high-capacity and high-voltage cathode materials are needed. Recently, Ni-rich layered oxides have attracted attention as they can offer ≈200 mAh g−1 when cycled up to 4.3 V. However, cycling these materials in their full capacity range often leads to excessive reactivity with the electrolyte, resulting in particle cracking, transition metal dissolution, and oxygen loss. In this study, the use of lithium hydridoaluminates as electrolyte additives is explored for lithium-ion batteries based on nickel-rich cathode materials. Being mild reducing agents, these additives act as HF scavengers, avoiding transition metal dissolution from the cathode. Additionally, their oxidation results in the formation of an Al-rich protective layer on the cathode, which dampens the surface reactivity, preventing surface reconstruction and impedance build-up. This study further stresses the important role of the cathode-electrolyte interface phenomena on the capacity degradation of Ni-rich cathode materials and provides a novel avenue for controlling this reactivity, thus extending their cycling life.