Towards sustainable electrochemical energy storage: solution-based processing of polyquinone composites

Continuous adoption of renewable energy sources and the proliferation of electric transportation technologies push towards sustainable energy storage solutions. Consequently, a solution-based up-scalable synthesis approach is developed for polymeric quinone composites with graphene. Cellulose nanocrystals play a vital role in achieving greener processing and improving the composite electrochemical energy storage performance. The synthesis method emphasizes using aqueous reaction media, incorporates low-cost and biomass-derived feedstocks, avoids critical or scarce materials, and maintains temperatures below 200 °C. Stable aqueous graphene dispersions were obtained by hydrothermal reduction of electrochemically exfoliated graphene oxide in the presence of cellulose nanocrystals. Dispersions served as a reaction medium for quinone cationic polymerization, leading to core-shell type structures of polymer-covered mono-to-few layer graphene, thanks to the nanosheet restacking prevention effect provided by cellulose nanocrystal dispersions. A sample consisting of 5 wt% cellulose nanocrystals and 5 wt% graphene achieved storage metrics of 720.5 F g^-1 and 129.6 mA h g^-1 at 1 A g^-1, retaining over 70% of the performance after 1000 charge/discharge cycles.