Thermal-healing of lattice defects for high-energy single-crystalline battery cathodes

Shaofeng Li,Yang Yang,Piero Pianetta,Xiaojing Huang,Zhisen Jiang,Jieshan Qiu,Wei-Na Wang,Yijin Liu,Dechao Meng,Xiaomei He,Linsen Li,Kejie Zhao,Zi-Feng Ma,Jun-Sik Lee,Guannan Qian,Sang-Jun Lee,Chang Yu,Yong S Chu

doi:10.1038/s41467-022-28325-5

Abstract

Single-crystalline nickel-rich cathodes are a rising candidate with great potential for high-energy lithium-ion batteries due to their superior structural and chemical robustness in comparison with polycrystalline counterparts. Within the single-crystalline cathode materials, the lattice strain and defects have significant impacts on the intercalation chemistry and, therefore, play a key role in determining the macroscopic electrochemical performance. Guided by our predictive theoretical model, we have systematically evaluated the effectiveness of regaining lost capacity by modulating the lattice deformation via an energy-efficient thermal treatment at different chemical states. We demonstrate that the lattice structure recoverability is highly dependent on both the cathode composition and the state of charge, providing clues to relieving the fatigued cathode crystal for sustainable lithium-ion batteries.

Highlights

Single-crystalline nickel-rich cathodes are a rising candidate with great potential for highenergy lithium-ion batteries due to their superior structural and chemical robustness in comparison with polycrystalline counterparts
A set of single-crystalline NMC materials with pre-set stresses as a model system were investigated to reveal how the thermal treatment modulates the structural evolution at the atomic scale and its implications for electrochemical performance
The experimental work is guided by a systematic density functional theory (DFT) modeling that has provided a high-level predictive overview of the thermal effects

Summary

Introduction

Single-crystalline nickel-rich cathodes are a rising candidate with great potential for highenergy lithium-ion batteries due to their superior structural and chemical robustness in comparison with polycrystalline counterparts. The shortened diffusion length is advantageous to lithium transport and the close packing of the primary grains is beneficial to the energy density These polycrystalline NMC materials, have abundant grain boundaries and, suffer from the broadly observed structure degradations, e.g., intergranular and intragranular cracks[6,7], inhomogeneous mechanical strain[8,9], local phase transformation and segregation[10,11]. The anisotropic lattice breathing during the repeated cycling of the energy devices leads to an accumulation of lattice strain and defects, which could be released via particle cracking, to the detriment of the composite cathode electrode’s multiscale structural integrity These cracks create more solid-liquid interfaces that aggravate unwanted side reactions and further exacerbate structural degradation and performance decay. Combined with a suite of state-of-art synchrotron techniques and theoretical approaches, we demonstrate a thermalhealing of lattice defects in single-crystalline cathodes caused by the thermal-induced release of lattice strain and the structured ordering, which contribute to the capacity restoration

Methods

Results

Conclusion