  It is generally believed that silicon-based anodes for Li-ion batteries would
benefit from stronger binders, as cyclic volume changes would not disrupt the
cohesion of the composite electrode. Here, we put this belief to the proof by
testing electrodes containing SiOx particles and an aromatic polyimide binder.
We observe that the electrodes can stretch laterally by as much as 6% during
the first cycle, indicating that internal stresses are high enough to induce
plastic deformation on the copper current collector. Remarkably, no coating
delamination is observed. Additional consequences were size-dependent: while
pouch-cell-sized electrodes developed wrinkles, coin-cell-sized ones remained
mostly smooth. We demonstrate that wrinkling of the current collector damages
the electrode coating, inactivating SiOx domains and accelerating capacity
fade. This size-dependent performance decay indicates that, in extreme cases,
testing outcomes are highly dependent on scale. Novel battery materials may
require testing at larger cell formats for complete validation.
