Employing nanoscale surface morphologies to improve interfacial adhesion between solid electrolytes and Li ion battery cathodes

Solid state Li ion batteries are particularly susceptible to deleterious mechanical responses at interfaces, because the electrochemically driven volume changes must be accommodated by deformation of the solid electrolyte. In the current study, this was investigated with PEO electrolyte and V2O5 electrodes, using different morphologies (e.g. patterned films, plasma roughened surfaces, etc). Detailed finite element modeling of the experimental configuration was also used to analyze the results. Methods for improving the adhesion of this critical interface were also demonstrated. Relatively small improvements were attributed to plasma roughening. However, the introduction of large, thin sheets of material normal to the primary decohesion surface lead to unexpected large increases in the adhesive energy. For example, with patterned islands that were 800nm tall, the increase in adhesion was approximately 8 times larger than the corresponding surface area increase. A finite element simulation of the decohesion process shows good agreement with the experimental values. Based on this analysis, it appears that thin elastic sheets in a much softer matrix can reduce stresses at the delamination front. This shielding effect provides a novel approach for improving the failure resistance of PEO electrolyte/V2O5 interfaces in solid state batteries.