Impact of Amorphous LiF Coating Layers on Cathode‐Electrolyte Interfaces in Solid‐State Batteries

• Published in: Advanced functional materials 2024-09, Vol.34 (39), p.n/a
• Main Authors: Hu, Taiping, Xu, Linhan, Dai, Fuzhi, Zhou, Guobing, Fu, Fangjia, Wang, Xiaoxu, Li, Linsen, Ai, Xinping, Xu, Shenzhen
• Format: Article
• Language: English
• Subjects: amorphous LiF coating; Amorphous materials; Cathodes; cathode‐electrolyte interface; Chemical reactions; Coating effects; deep potential molecular dynamics; Diffusion coating; Diffusion layers; Electrolytes; Interface reactions; interfacial reconstructions; Ion diffusion; Lithium fluoride; Lithium-ion batteries; Li‐ion diffusion; Machine learning; Molecular dynamics; Protective coatings; Reconstruction; Solid electrolytes; Tetrahedra; Thickness
• ISSN: 1616-301X; 1616-3028
• DOI: 10.1002/adfm.202402993

High interfacial resistance between electrodes and solid‐state electrolyte is the major cause for the failure of all‐solid‐state Li‐ion batteries. Spontaneous (electro)chemical reactions and poor Li‐ion diffusion at the interfaces are closely related to this increased impedance. Although introducing a coating layer can mitigate interfacial reactions and structural reconstruction, it may also lead to poor Li‐ion diffusion. Balancing this trade‐off therefore is crucial for the design of coating layer materials. In this study, the impact of the amorphous LiF (a‐LiF) coating layer on interfacial structural reconstruction and Li‐ion diffusion at the LiCoO2/Li6PS5Cl solid‐state interface is explicitly elucidated via machine‐learning‐assisted molecular dynamics (MD) simulations. It is found that the a‐LiF can effectively protect the P‐S tetrahedron local structures in Li6PS5Cl but cannot suppress the formation of side product S2 dimers. It is further discovered that once the a‐LiF coating exceeds a certain critical thickness, emergence of ordered local structures will inhibit Li‐ion diffusion. The simulations propose that the optimal thickness of the coating layer is around 1 nm. Overall, the work provides a microscopic understanding for effects of the a‐LiF coating layer on the structural and kinetic properties of cathode‐solid electrolyte interfaces and can guide the design of interfacial coating materials for solid‐state batteries. This research elucidates the impact of the amorphous LiF coating layer on interfacial structural reconstructions and Li‐ion diffusion in the LiCoO2/Li6PS5Cl solid‐state interface via large‐scale machine‐learning‐assisted molecular dynamics simulations, which can guide the design of interfacial coating materials for solid‐state batteries.