Molten‐Salt Synthesis of Anthracite‐Based Porous Carbon for Microscale Supercapacitors and Strain Sensors

Abstract The molten‐salt synthesis and electrochemical capacitive behaviors of porous carbon are reported using anthracite as the precursor. Upon synthesis, the binary KCl/K ₂ CO ₃ molten salt not only exfoliates bulky anthracite to carbon nanosheets but also creates rich micro‐ and mesopores in the structure. The resulting porous carbon shows a large surface area of 1399.7 m ² g ⁻¹ and a total pore volume of 1.50 cm ³ g ⁻¹ . In 6.0 mol L ⁻¹ KOH aqueous electrolyte, it delivers a high specific capacitance of 245.6 F g ⁻¹ at a current density of 0.5 A g ⁻¹ . Flexible micro‐supercapacitors with this porous carbon are assembled following an interdigitated design. The micro‐supercapacitor affords an area capacitance of 18.0 mF cm ⁻² and an energy density of 1.58 µWh cm ⁻² at a power density of 20 µW cm ⁻² , and sustains 89.6% of the capacitance after 2000 cycles. Furthermore, the strain sensor fabricated by replacing the current‐collecting fluid at both ends of the electrode provides consistent and stable signal output, regardless of the degree of bending and the number of cycles. This study demonstrates the great potential of anthracite‐based porous carbon in flexible energy and electronic microdevices.