In situ electrochemo-mechanical coupling of 2D nanomaterial supercapacitor electrodes

Internal stresses that develop during electrochemical cycling can create microstructural electrode damage and capacitance fade. For example, two-dimensional (2D) nanomaterial supercapacitor electrodes can experience damage due to mechanical “breathing” as ions intercalate in and out. However, the coupling between electrochemical and mechanical processes remains extensively unexplored. Here, using a unique instrument designed to measure in situ electrochemo-mechanical coupling, the consequences of stress, strain, and electrochemical charge in 2D supercapacitor electrodes are revealed. Under varying applied tensile strains (up to 1%) on individual electrodes, the capacitance can decrease by as much as 37%. Notably, the in situ development of internal stress in individual electrodes during electrochemical cycling is revealed, in which the total stress changes by about 5% with the adsorption and release of ions. A micromechanics model using an eigenstrain to capture the electrochemical charge explains the resulting coupling. This combined approach provides insight into other 2D nanomaterial electrodes.