Past exam of the MPhil in micro- and nanotechnology enterprise course of the University of Cambridge / 2023 / Paper 1 / Section B / 11 / iii / Solution

Make a composite positive electrode containing the active graphite fluoride, a connected conductive-carbon network and a binder, supported on a suitable current collector. Carbon black provides electronic pathways to distributed reaction sites; the binder maintains cohesion and contact.

Electrolyte-filled porosity provides ionic access, while particle dimensions and intimate mixing limit the distance electrons and lithium ions must traverse. Excess conductive additive or binder dilutes the capacity per gram of composite. The reaction can also alter the electronic network as carbon forms, but that does not remove the need for adequate initial connectivity or prevent insulating LiF from obstructing transport.