High-efficiency zinc thermal charging supercapacitors enabled by hierarchical porous carbon electrodes

High value-added utilization of ubiquitous low-grade heat shows great importance to energy regulation. liquid thermocell is considered as promising candidate for converting heat into electricity due to its high Seebeck coefficient and facile operation. However, the challenging integration of dozens of tiny devices is still required to generate a useful voltage, which greatly blocks the development of thermocells. Here, a well-defined nitrogen-doped hierarchical porous carbon (NHPC) obtained by self-template carbonization and alkaline activation is employed to construct high-performance zinc ion thermal charging supercapacitors (ZTSC) for the integration of energy conversion and storage. Significantly, continuous architecture of NHPC can enlarge the electrochemical active surface and shorten the diffusion pathways of electrolyte ions. Consequently, a high energy/power density of 71.8 Wh kg−1/10.3 kW kg−1 can be achieved. Moreover, NHPC based ZTSC can output an attractive voltage of 1.16 V, a high thermopower of 31.4 mV K−1, and a superior normalized power density of 15.3 mW m−2 K−2 with a temperature difference of 27 K. This work not only provides a facile strategy to prepare promising carbon materials, but also demonstrates the possibility of hybrid supercapacitors for heat-to-current conversion and storage.