Understanding and Engineering Interfacial Adhesion in Solid‐State Batteries with Metallic Anodes

Abstract

High performance alkali metal anode solid‐state batteries require solid/solid interfaces with fast ion transfer that are morphologically and chemically stable upon electrochemical cycling. Void formation at the alkali metal/solid‐state electrolyte interface during alkali metal stripping is responsible for constriction resistances and hotspots that can facilitate dendrite propagation and failure. Both externally applied pressures (35–400 MPa) and temperatures above the melting point of the alkali metal have been shown to improve the interfacial contact with the solid electrolyte, preventing the formation of voids. However, the extreme pressure and temperature conditions required can be difficult to meet for commercial solid‐state battery applications. In this review, we highlight the importance of interfacial adhesion or ‘wetting’ at alkali metal/solid electrolyte interfaces for achieving solid‐state batteries that can withstand high current densities without cell failure. The intrinsically poor adhesion at metal/ceramic interfaces poses fundamental limitations on many inorganics solid‐state electrolyte systems in the absence of applied pressure. Suppression of alkali metal voids can only be achieved for systems with high interfacial adhesion (i. e. ‘perfect wetting’) where the contact angle between the alkali metal and the solid‐state electrolyte surface goes to θ=0°. We identify key strategies to improve interfacial adhesion and suppress void formation including the adoption of interlayers, alloy anodes and 3D scaffolds. Computational modeling techniques have been invaluable for understanding the structure, stability and adhesion of solid‐state battery interfaces and we provide an overview of key techniques. Although focused on alkali metal solid‐state batteries, the fundamental understanding of interfacial adhesion discussed in this review has broader applications across the field of chemistry and material science from corrosion to biomaterials development.

Grain‐growth Inhibitor with Three‐section‐sintering for Highly Dispersed Single‐crystal NCM90 Cubes

“…To explain this phenomenon, the work of adhesions (Wads) of SC-NCM90 and MSC-NCM90 were calculated by DFT (Figure 3g-h). [22] The Wad of the pristine NCM90 surface was calculated to be À 0.99 J m À 2 , which was changed to À 0.60 J m À 2 after the surface Mo doping, indicating the reduced tendency of grain fusion for MSC-NCM90. According to the atomic force microscope (AFM) test, the average adhesion force on the surface of MSC-NCM90 (91 nN) is also obviously lower…”

Grain‐growth Inhibitor with Three‐section‐sintering for Highly Dispersed Single‐crystal NCM90 Cubes

“…To explain this phenomenon, the work of adhesions (Wads) of SC-NCM90 and MSC-NCM90 were calculated by DFT (Figure 3g-h). [22] The Wad of the pristine NCM90 surface was calculated to be À 0.99 J m À 2 , which was changed to À 0.60 J m À 2 after the surface Mo doping, indicating the reduced tendency of grain fusion for MSC-NCM90. According to the atomic force microscope (AFM) test, the average adhesion force on the surface of MSC-NCM90 (91 nN) is also obviously lower than that of undoped RSC-NCM90 (293 nN), verifying the suppressed surface adhesion and so the improved particles dispersity in MSC-NCM90 (Figure S14).…”

Pressure Effects and Countermeasures in Solid‐State Batteries: A Comprehensive Review

“…For example, Ga, Al‐doped LLZO‐based SSE, exhibit W ad of 0.691, 0.716, and 0.615 J m −2 , higher than the bare LLZO (0.67 J m −2 ). [ 122,123 ] Similarly, surface termination of SSE such as Zr‐rich LLZO (001) surface has an interfacial energy of 0.76 J m −2 , compared with 0.48 J m −2 for the Zr‐poor surface (Figure 13c); [ 116 ] the Cl‐terminated SSE shows an order lower W ad than the O‐terminated SSE interface. [ 124 ]…”