Development of asphaltene-derived hierarchically activated carbon and carbon-coated Li4Ti5O12 for high-performance lithium-ion capacitors

Abstract

Lithium-ion capacitors (LICs), which integrate the complementary characteristics of electric double-layer capacitors (EDLCs) and lithium-ion batteries (LIBs) to achieve high energy density and power capability, have attracted substantial interest. Asphaltene, a challenging byproduct of crude oil extraction, can be transformed into a valuable material for energy storage applications through an appropriate activation process. In this study, undesired asphaltene was utilized as a carbon source to produce hierarchical porous activated carbon (AC) for supercapacitors (SCs) and to form a modified carbon coating on Li₄Ti₅O₁₂ (LTO) anode materials, enhancing rate performance. The asphaltene-derived AC exhibits a specific capacitance of 100.8 F/g at 0.1 A/g, with a retention of 86.7 % after 40,000 cycles in a 1.0 M TEABF₄/PC electrolyte. Moreover, the uniform coating of asphaltene-derived carbon on LTO also enhances the electronic conductivity, delivering a specific capacity of 120.5 mAh/g even at a high current rate of 20C. By integrating the asphaltene-derived capacitive SC and Faradaic LIB electrodes, the resultant LICs reveal excellent electrochemical properties with an energy density of 60.75 W h/kg at a power density of 215 W/kg, along with superior cycling stability. This work presents a viable method for converting the undesirable fraction of crude oil into high-performance energy storage materials.