Preparation of NiCo-LDH/honeycomb turtle shell biochar composites and their supercapacitor performance

The development of renewable, low-cost, and environmentally friendly electrode materials with rapid ion/electron transfer rates and tunable surface chemistry is crucial for advancing energy storage devices. Here, turtle shell biomass waste was transformed into carbon materials with outstanding chemical properties and subsequently combined with nickel-cobalt layered double hydroxide (NiCo-LDH) to form composites. The NiCo-LDH/honeycomb turtle shell biochar (NiCo-LDH/TSHC-5) composite electrode material was synthesized via a straight forward solvothermal method, exhibiting excellent electrochemical performance. NiCo-LDH/TSHC-5 with a microporous structure exhibited a maximum specific capacitance of 1231.4 F·g⁻¹ (615.7 C·g⁻¹) at a current density of 1 A·g⁻¹ and the retention of the initial specific capacitance after 5000 cycles was 84.62%. An asymmetric supercapacitor was assembled using NiCo-LDH/TSHC-5 and TSHC-5 as positive and negative electrodes, respectively, yielding a retention rate of 85% of the initial specific capacitance after 5000 cycles. The maximum energy density was 61.8 W·h·kg⁻¹ and the maximum power density was 800 W·kg⁻¹. Thus, NiCo-LDH/TSHC-5 demonstrates significant potential as an electrode material for supercapacitors.