Theoretical Insights into High-Entropy Ni-Rich Layered Oxide Cathodes for Low-Strain Li-Ion Batteries

Abstract

Ni-rich, Co-free layered oxide cathode materials are promising candidates for next-generation Li-ion batteries due to their high energy density. However, these cathode materials suffer from rapid capacity fading during electrochemical cycling. To overcome this shortcoming, so-called high-entropy (HE) materials, which are obtained by incorporating multiple dopants, have been suggested. Recent experimental work has shown that HE Ni-rich cathode materials can offer excellent capacity retention on cycling, although a thorough rationale for this has yet to be provided. Here, we present classical and first-principles calculations to elucidate the salient features of HE layered oxides as cathode materials in Li-ion batteries. We suggest that a combination of five prime factors may be responsible for the enhanced performance of HE Ni-rich layered oxide cathode materials over other Ni-rich cathodes: (1) low crystal lattice variation, (2) invariant local crystal field environment, (3) strong metal–oxygen bonding, (4) low degree of antisite defects, and (5) low operational voltage.

Microstructures of layered Ni-rich cathodes for lithium-ion batteries

“…A key question is how will the number and type of introduced foreign elements influence NRLO cathode's stability? For example, high-entropy NRLO cathodes have recently shown a possible advantage of high stability, 309,310 while more mechanistic investigations are necessary to realize their full potential. (6) The effect of other battery components on the NRLO cathode' stability is not very clear.…”

Porous High-Entropy Oxide Anode Materials for Li-Ion Batteries: Preparation, Characterization, and Applications

“…Unlike transition metal oxides, in which the structure collapses after several cycles of the electrode, HEOs have an excellent structural stability. The high-entropy lattice provides a spatial network for the embedded lithium/de-lithium, which ensures the structural stability of HEOs during cycling, resulting in an excellent cycling stability [102,103]. In order to investigate the phase transition of HEO anodes during cycling, various types of in situ as well as ex situ detection techniques have been applied.…”