Native lattice strain induced structural earthquake in sodium layered oxide cathodes

Gui-Liang Xu,Xiang Liu,Zonghai Chen,Yang Ren,Amine Daali,Inhui Hwang,Chen Zhao,Yuzi Liu,Zhenzhen Yang,Xinwei Zhou,Khalil Amine,Cheng-Jun Sun

doi:10.1038/s41467-022-28052-x

Abstract

High-voltage operation is essential for the energy and power densities of battery cathode materials, but its stabilization remains a universal challenge. To date, the degradation origin has been mostly attributed to cycling-initiated structural deformation while the effect of native crystallographic defects induced during the sophisticated synthesis process has been significantly overlooked. Here, using in situ synchrotron X-ray probes and advanced transmission electron microscopy to probe the solid-state synthesis and charge/discharge process of sodium layered oxide cathodes, we reveal that quenching-induced native lattice strain plays an overwhelming role in the catastrophic capacity degradation of sodium layered cathodes, which runs counter to conventional perception—phase transition and cathode interfacial reactions. We observe that the spontaneous relaxation of native lattice strain is responsible for the structural earthquake (e.g., dislocation, stacking faults and fragmentation) of sodium layered cathodes during cycling, which is unexpectedly not regulated by the voltage window but is strongly coupled with charge/discharge temperature and rate. Our findings resolve the controversial understanding on the degradation origin of cathode materials and highlight the importance of eliminating intrinsic crystallographic defects to guarantee superior cycling stability at high voltages.

Highlights

High-voltage operation is essential for the energy and power densities of battery cathode materials, but its stabilization remains a universal challenge
Instead, using advanced transmission electron microscopy (TEM), we discovered that the native high lattice strain plays an overwhelming role in triggering the destructive structural earthquake of sodium-layered cathodes, which spontaneously relaxed due to local strain heterogeneity and led to severe breakdown/fragmentation of layered structure during prolonged cycling
Researchers leveraged in situ synchrotron X-ray diffraction (SXRD) and computational modeling to investigate the evolution of nonequilibrium kinetic intermediates and the formation of thermodynamic equilibrium phases during these processes[37,38]

Summary

Introduction

High-voltage operation is essential for the energy and power densities of battery cathode materials, but its stabilization remains a universal challenge. Mu et al have reported that the cathode–electrolyte interfacial reaction can trigger transition metal reduction/dissolution, heterogeneous surface reconstruction, and nanocracks[29] To address these concerns, surface coating[30,31,32,33] and high-voltage electrolytes[34,35,36] have been widely developed to enhance the high-voltage cycling stability of layered cathodes. Surface coating[30,31,32,33] and high-voltage electrolytes[34,35,36] have been widely developed to enhance the high-voltage cycling stability of layered cathodes These valuable findings are acknowledged, but the aforementioned degradation mechanism has been mainly attributed to the dynamic structural changes (e.g., phase transition, interfacial reactions, and mechanical cracks) that nucleated and evolved during cycling. Cathode materials with tailor-made defects through precise synthetic control could serve as a model structure to probe their explicit role in battery performance

Methods

Results

Conclusion