Cooperating Effects of Conformal Iron Oxide ALD Coating and Post-Annealing on Li-Rich Layered Cathod

Abstract

Li-rich layered cathode materials draw a wide attention due to their superior Li-storage capability and high energy density, but they suffer capacity degradation and voltage decay due to phase transition and metal dissolution during cycling. To address these problems, iron oxide atomic layer deposition (ALD) was performed on Li-rich layered cathode powders in a fluidized bed reactor, followed by an annealing process for a further improvement. The annealing of iron oxide-coated particles led to the diffusion of iron cation into the structure and a higher structure ordering. After 100 cycles of charge-discharge at a 1C rate and 55 °C, the iron oxide-coated cathode material delivered an initial capacity of ~196 mAh g-1 with a capacity retention of ~49%, while the annealing process improved it to ~221 mAh g-1 and a capacity retention of ~73%. The Fe doping on the surface of cathode facilitated Li+ transport and stabilized cyclic behavior. On the surface, the annealed-coated cathodes suppressed decomposition of electrolyte salt and formed a more stable solid permeable interface layer. In the bulk, a stable spinel phase formed during cycling contributed to the stability of structure; metal dissolution was also suppressed due to the annealing plus coating. These effects enabled a stable- and high-performance Li-ion battery cathode.