Ni-rich cathode materials with enhanced kinetics and hydrophobicity endowed by reactive silane coating

Abstract

Intimate conformal coating with well-controlled thickness and rational-designed composition could work as an artificial cathode electrolyte interphase (CEI) to greatly enhance the cycle stability, moisture tolerance and even kinetics performance of Ni-rich layered oxides (NROs). While complicated treatment is usually required in coating thickness control. Inspired by the amphipathicity and monolayer self-assembling properties of silane coupling agent, herein two kinds of silanes with short hydrophobic functional group, allyltrimethoxysilane (ALTS) and propyltrimethoxysilane (PRTS), are adopted in NRO modification. We find that the silanes could form a conformal coating with self-limited thickness controlled by its reaction with the inevitable –OH or lithium residues on NRO surface. The optimal material, CGAP, not only shows enhanced cycle stability and rate performance, but also impressive moisture tolerance. It retains 93.9% of its capacity in 200 cycles at 25°C, and a high reversible capacity of 192.8 mAh g−1 even after 7 days of exposure in the environment with 60% humidity.