Stabilizing Cobalt-Free Cathodes with Lithium-Stoichiometry Control for Sustainable Lithium-ion Batteries

Abstract

Lithium-ion batteries are essential to decarbonizing transportation and power grids, but their reliance on high-cost earth-scarce cobalt in nickel-manganese-cobalt (NMC) based cathodes raises significant supply chain and sustainability concerns. Despite numerous attempts to address these issues, eliminating Co has remained elusive, yet to be commercially realized because doing so detrimentally affects the layering and cycling stability of NMC cathodes. We report here an alternative solution using Co free high-Ni Li1 xNi0.95Mn0.05O2 (NM9505) with a Li-deficient composite structure that outperforms the stoichiometric layer-structured counterparts. Through correlated synchrotron X-ray characterization and multiscale modeling, we show that Li-deficiency plays a predominant role in hindering crystallization and interparticle fusion during calcination, resulting in intergrown rocksalt and layered phases within the composite. As such, the anisotropic lattice expansion and contraction is suppressed in Li-deficient NM9505 upon cycling, offering 90% first-cycle Coulombic efficiency, 90% capacity retention, and close-to-zero voltage fade for 100 cycles up to 4.4 V. Our findings represent an important step forward in addressing the critical Co-reliance issues, and offer new opportunities for designing high-performing Co-free cathodes for sustainable Li-ion batteries.