Thickness evolution of graphite-based cathodes in the dual ion batteries via in operando optical observation

Graphite has been currently considered as a promising cathode material in dual ion batteries (DIBs) due to its unique features of sp2 hybridized carbon and stacked two-dimensional layered structures. However, unexpected volume/thickness changes in the graphite cathodes, induced by the intercalation/deintercalation of anions with large molecular size have been known to be a critical problem in designing DIB cells. To understand the volume/thickness changes in the DIB electrodes, in operando optical observing apparatus has been employed to observe the cross-section view of a graphite-based cathode upon cycles in the present work. The observation suggests that the cathode initially presented a huge irreversible thickness change (60%), and such thickness variation was prone to reduce and remain