Poly(phenanthrenequinone) as a conductive binder for nano-sized silicon negative electrodes

3,6-Poly(phenanthrenequinone) (PPQ) is synthesized and tested as a conductive binder. The PPQ binder, formulated with nano-sized Si powder without conductive carbon, is n-doped by accepting electrons and Li+ ions to become a mixed conductor in the first charging period. The resulting n-doped PPQ binder remains conductive thereafter within the working potential of Si (0.0-0.5 V vs. Li/Li+). Within the composite electrode, the PPQ binder is uniformly dispersed to effectively convey electrons from the current collector to the Si particles. Namely, the PPQ binder by itself plays the roles of conductive carbon and a polymer binder that are loaded in the conventional composite electrodes. Due to the highly conductive nature, the loading of the PPQ binder can be minimized down to 10 wt%, which is close to that used for practical electrode formulation, with reasonable rate and cycle performances of the nano-Si electrode.