Diffusion-Kinetically Dormant Ni-Rich Cathode at High Potentials

Abstract

High energy-density Ni-rich layered cathodes suffer a long-standing challenge of severe performance deterioration at high potentials. Besides, it is of great challenge to develop a universal mitigation strategy to address numerous deterioration causes. Herein, to probe the dominant deterioration root for guiding rational development, we perform an in-depth investigation of LiNi0.83Mn0.1Co0.07O2 in full cells with graphite anode for 1000 cycles at different state-of-charges. Intriguingly, severe capacity retention of harvest cathodes (like 54% at 4.6 V) is inconsistent with insignificant material degradation via synchrotron-based X-ray characterizations. To unpuzzle this, we deconvolute the overall performance deterioration of cycled cathode into irreversible and reversible losses. Our evaluation unveils Ni-rich cathodes are mostly alive (like 88% at 4.6 V) but kinetically inhibited in long-term cycling at high potentials. The evolution of Li+ diffusion is of greater significance than that of electrical impedance. The exacerbated cathode-electrolyte interface, mainly rock-salt phase, is speculated experimentally and analytically as the predominant root for severe chemical diffusion and performance deterioration. Our findings highlight the upmost importance of stabilizing the cathode-electrolyte interface for deploying Ni-rich cathodes at higher potentials to awaken more energy and longer lifespan.