Dual-activated shoot shells as three-dimensional mesh materials for all-solid-state supercapacitors

Abstract

The investigation of green carbon precursors and cost-effective activators has become an important area for manufacturing electrode materials. Bamboo shoot shells are carbonized at high temperatures and then dual activated with KOH and K₂CO₃ to create bamboo shoot shell-based porous carbon materials (BSC-X). The obtained porous carbon materials are subjected to electrochemical tests, nitrogen adsorption and desorption (BET), scanning electron microscopy (SEM) and infrared and X-ray diffraction (XRD) analyses. The experimental results show that the BSC-1 porous carbon has a rich pore structure, high specific surface area (2583.75 m² g⁻¹), O content of up to 33.00 % and total pore volume of up to 1.47 cm³ g⁻¹. In the three-electrode test system, the BSC-1 shows the specific capacitance of 459.50 F g⁻¹ at 0.5 A g⁻¹, a capacitance retention of 73.48 % at a current density of 10 A g⁻¹, and a capacitance retention of 99.97 % and a Coulombic efficiency of 94.85 % after 10,000 cycles at a current density of 10 A g⁻¹. The symmetric supercapacitor assembled with BSC-1//BSC-1 exhibits a voltage range of 0–2.0 V in 1 M Na₂SO₄ electrolyte, the specific capacitance of 313.00 F g⁻¹ (at 0.5 A g⁻¹), and a high energy density of up to 43.47 Wh kg⁻¹. The capacitance retention of 94.34 % and the Coulombic efficiency is 94.72 % after 10,000 cycles at 10 A g⁻¹ current density. The supercapacitors with PVA/KOH gel as electrolyte have a specific capacitance of 252.57 F g⁻¹ and a high energy density of up to 17.19 Wh kg⁻¹ at a voltage of 0–1.4 V and a current density of 0.5 A g⁻¹. The capacitance retention of 85.45 % and Coulombic efficiency of 92.37 % after 10,000 cycles at 10 A g⁻¹ current density. This study provides an affordable and renewable strategy for the synthesis of porous carbon materials for supercapacitors.