Addressing voltage decay in Li-rich cathodes by broadening the gap between metallic and anionic bands

Jicheng Zhang,Yang Yu,Xiangfeng Liu,Qinghua Zhang,Deniz Wong,Christian Schulz,Guoxi Ren,Lin Gu,Lunhua He,Nian Zhang

doi:10.1038/s41467-021-23365-9

Abstract

Oxygen release and irreversible cation migration are the main causes of voltage fade in Li-rich transition metal oxide cathode. But their correlation is not very clear and voltage decay is still a bottleneck. Herein, we modulate the oxygen anionic redox chemistry by constructing Li2ZrO3 slabs into Li2MnO3 domain in Li1.21Ni0.28Mn0.51O2, which induces the lattice strain, tunes the chemical environment for redox-active oxygen and enlarges the gap between metallic and anionic bands. This modulation expands the region in which lattice oxygen contributes capacity by oxidation to oxygen holes and relieves the charge transfer from anionic band to antibonding metal–oxygen band under a deep delithiation. This restrains cation reduction, metal–oxygen bond fracture, and the formation of localized O2 molecule, which fundamentally inhibits lattice oxygen escape and cation migration. The modulated cathode demonstrates a low voltage decay rate (0.45 millivolt per cycle) and a long cyclic stability.

Highlights

Oxygen release and irreversible cation migration are the main causes of voltage fade in Li-rich transition metal oxide cathode
House et al reported that lattice oxygen in alkali-rich transition metal oxide is oxidized to localized oxygen molecules during charging, and Mn migration occurs at the same time[26]
The key to the synthesis of LSLR is the selection of oxalate and Zr4+ as precipitator and Zr source, respectively

Summary

Introduction

Oxygen release and irreversible cation migration are the main causes of voltage fade in Li-rich transition metal oxide cathode. Their correlation is not very clear and voltage decay is still a bottleneck. The improvement space for traditional cathode materials based on transition metal (M) cationic redox is limited to the gradually approached energy-density ceiling[1] Such limitation is foreseen to be transcended by Li-rich Mn-based oxides, which exhibit both M and O redox activities and a high reversible capacity (>250 mA h g−1)[2]. These uncertainties and divergences are the critical issues that prevent OAR from being fully understood and hinder voltage fade from being fundamentally resolved

Methods

Results

Conclusion