Deciphering The Interfacial Chemistry and Degradation Pathway of Layered Cathode Materials

The ever-increasing demand for renewable energy and electric vehicles calls for high-energy-density rechargeable batteries. Cathode materials such as layered oxides play a crucial role in determining batteries' energy density and safety. LiNi_xMn_yCo_zO₂ (NMC), as the dominating cathode, has been successfully commercialized for many years. In addition, there is a consensus that integrating NMC cathodes into all-solid-state batteries (ASSBs) is an effective way to achieve high energy densities. However, NMC cathodes are still facing many challenges, particularly, during the perusing of the high Ni concentration and high cut-off voltages. In the presentation, we will discuss the interface degradation of the NMC cathode at multiple length scales. By comprehensive imaging and spectroscopic techniques, we could bridge the degradation phenomenon from the electrode scale to the atomic scale. We will present the challenges of characterizing the surface properties of the cycled layered cathode and summarize our strategies that can enhance the surface stability of NMCs. Our fundamental understanding will inform the design principles at multiple length scales in batteries. Shifting our focus to solid-state batteries (SSBs), there is a growing body of research on SSBs incorporating NMC cathodes and argyrodite solid electrolytes (SEs). However, these advanced ASSBs face significant challenges in terms of low initial Coulombic efficiency and rapid capacity degradation. Therefore, we will also explore the interfacial degradation mechanisms in composite SE-NMC cathodes utilizing the NMC/Li₆PS₅Cl combination as a platform.