Eutectic salt induced self-activation technique for porous graphene-like carbon nanosheets as the high-capacity cathodes for Zn-ion hybrid supercapacitors

The exploration of a non-corrosive and sustainable strategy to produce thin graphene-like porous carbon nanosheets with large specific surface area for electrochemical energy storage applications is highly desired yet a huge challenge. Herein, we report a eutectic salt induced self-activation process for the synthesis of a serials of porous carbon nanosheets with well-controlled microstructures just by simply changing the type of eutectic salt. The experiment results illustrated that the in-situ formed Na2CO3, which is usually “inert” when serves as a chemical activation reagent at relatively low temperature, display a significant enhanced chemical activation in eutectic salt medium. Specifically, thin graphene-like porous carbon nanosheets with a large specific surface of 1739.5 m2/g can be obtained in CsCl-NaCl eutectic salt. When acts as a cathode for Zn-ion hybrid supercapacitors (ZSCs), a high specific capacity of 169.1 mAh/g (at 0.1 A/g), large specific energy of 62.24 W h kg−1 (at an ultrahigh specific power of 16 kW g−1) and cyclic stability of 91.7 % after 10,000 cycles. In addition, a quasi-solid-state ZSC device, which can freely realize series to increase the working voltage, demonstrated its hold a potential for practical application. This strategy combines the advantages of the in-situ chemical activation with the advantages of the eutectic salt medium, which offers an alternative way for the producing of various functional nanocarbons for a variety of applications including electrochemical energy storage.