Interplay of Interfacial Adhesion and Mechanical Degradation in Anode-Free Solid-State Batteries

Anode-free solid-state batteries (AFSSBs) with an Ag-C interlayer are an innovative architecture because of their high energy density compared to conventional Li metal solid-state batteries. This work introduces simple methods to enhance the interfacial adhesion strength between the Ag-C interlayer and the solid electrolyte (SE) for better initial capacity of the cell, by controlling the cell assembling pressure to place together all components of the cell. Through contact angle experiments, our study unveils how the variation in the assembling pressure can significantly influence the contact angle between SE (at different assembling pressures) and Li metal, affecting their adhesion energy. Our electrochemical tests evidence that raising the assembling pressure from 350 to 530 MPa outcomes an increment of more than 50% in initial capacity due to higher adhesion energies, with the corresponding energy density of 410 Wh kg⁻¹. Nonetheless, SE separator tends to crack beyond a critical assembling pressure of 530 MPa that might cause a dramatic decrease of the cell performance. Our findings show that increasing the interfacial adhesion through different methods can prevent interface degradation and increase energy density of AFSSBs, affirming the vital role of interfacial adhesion between the Ag-C interlayer and SE separators, holding significant advances in anode free architectures.