In this work, we present a simple and cost-effective method to form different types of dual-scale porous electrodes via KOH activation of the fibers of different carbon materials, including carbon felts/papers/clothes. As shown in Fig. 1, the large pores (~10 μm), formed between carbon fibers, serve as the macroscopic pathways for high electrolyte flow rates, while the small pores (~5 nm), formed on carbon fiber surfaces, act as active sites for rapid electrochemical reactions. Hence, the dual-scale porous electrode is expected to deliver high surface area without any sacrificing in electrolyte permeability. Our preliminary results showed that Brunauer-Emmett-Teller specific surface area of these carbon materials is increased by more than 10 times and the battery assembled with dual-scale carbon-paper/cloth electrodes can even operate at 400 mA cm-2 with energy efficiency over 80%. Moreover, the dual-scale carbon-felt electrode showed stable efficiencies during more than 1000 cycles. Further characterizations and optimizations of these dual-scale electrodes and comparisons between them will be disclosed at the meeting.
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