The mechanical properties of batteries and supercapacitors

Abstract

Batteries and electrochemical capacitor (Supercapacitors) play significant roles amongst the Electrochemical energy storage systems and are driven electrochemically by adsorption (electrosorption) and insertion of ions into solid materials. These process often lead to significant volume changes during electrochemical measurements. These large volume-change causes mechanical fracture and pulverization of active electrode materials, degradation and failure of the lithium ion batteries which have detrimental effects on battery performance and cycle life. Detailed experimental analysis of reaction-induced transformations in these materials has revealed the importance of mechanics in controlling volume changes and mechanical degradation, as significant reaction-induced stresses and deformation processes are typical. This article focused on recent studies dedicated to understanding of the structural integrity, maximum capacity and the mechanics-related aspects of these transformations, including mechanical properties of active materials, reaction- and diffusion-induced stress evolution, and chemo-mechanical processes. The article is divided in to two sections, Section I discusses Lithium ion batteries with emphasis on lithiation-induced expansion as thermal expansion, the evolution of stress and deformation upon lithiation with various techniques, while section II describe the electrochemical capacitors with emphasis on deformation of solid electrolytes using indentation techniques.