Nickel‐Rich and Lithium‐Rich Layered Oxide Cathodes: Progress and Perspectives

TLDR

Ni‑rich and Li‑rich layered oxides are attractive Li‑ion battery cathodes because of their low cost and high discharge capacities, yet they face synthesis difficulties, poor cyclability, moisture sensitivity, thermal runaway, surface degradation, oxygen loss, irreversible capacity loss, low tap density, and voltage decay. The review surveys recent developments and performance gains of Ni‑rich and Li‑rich layered oxide cathodes and outlines future research directions. It focuses on recent efforts to optimize composition and processing of Ni‑rich oxides to control bulk and surface chemistry, on studies of Li‑rich oxides to understand and eliminate surface and bulk defects, and on summarizing performance gains and future research directions.

Abstract

Ni‐rich layered oxides and Li‐rich layered oxides are topics of much research interest as cathodes for Li‐ion batteries due to their low cost and higher discharge capacities compared to those of LiCoO 2 and LiMn 2 O 4 . However, Ni‐rich layered oxides have several pitfalls, including difficulty in synthesizing a well‐ordered material with all Ni 3+ ions, poor cyclability, moisture sensitivity, a thermal runaway reaction, and formation of a harmful surface layer caused by side reactions with the electrolyte. Recent efforts towards Ni‐rich layered oxides have centered on optimizing the composition and processing conditions to obtain controlled bulk and surface compositions to overcome the capacity fade. Li‐rich layered oxides also have negative aspects, including oxygen loss from the lattice during first charge, a large first cycle irreversible capacity loss, poor rate capability, side reactions with the electrolyte, low tap density, and voltage decay during extended cycling. Recent work on Li‐rich layered oxides has focused on understanding the surface and bulk structures and eliminating the undesirable properties. Followed by a brief introduction, an account of recent developments on the understanding and performance gains of Ni‐rich and Li‐rich layered oxide cathodes is provided, along with future research directions.