Electrodilatometric analysis under applied force: A powerful tool for electrode investigation

A new equipment for in situ electrochemical dilatometry is designed and validated by studying the volumetric changes of a model electrode. The contactless measurement system permit to not influence the dilation of the sample during the tests. In addition, different forces can be applied in a selected range. Graphite is selected as model electrode and electrochemical tests in different electrolytes are carried out under different applied forces. The results of the electrodilatometric tests on graphite in EC:DMC- and in PC-based electrolyte reveal not only lithium insertion/deinsertion process, but also the presence of simultaneous phenomena like solvent evaporation, SEI formation and gas evolution. The latter has been detected by applying different forces that affect the gas uptake and release from porous separator. Controlled hydrogen evolution experiments were carried out at different applied forces in order to assess the gassing detection ability of the dilatometer. We demonstrate that with this new equipment it is possible, from thickness variation, to collect information on processes of different nature. Specifically, different applied forces emphasized gas evolution, which is a worth studying phenomenon for increasing battery safety.