Mesh-Like Carbon Nanosheets with High-Level Nitrogen Doping for High-Energy Dual-Carbon Lithium-Ion Capacitors

Li-ion capacitors (LICs) have demonstrated great potential for bridging the gap between lithium-ion batteries and supercapacitors in electrochemical energy storage area. The main challenge for current LICs (contain a batterytype anode as well as a capacitor-type cathode) lies in circumventing the mismatched electrode kinetics and cycle degradation. Herein, a mesh-like nitrogen (N)-doped carbon nanosheets with multiscale pore structure is adopted as both cathode and anode for a dual-carbon type of symmetric LICs to alleviate the above mentioned problems via a facile and green synthesis approach. With rational design, this dual-carbon LICs exhibits a broad high working voltage window (0-4.5 V), an ultrahigh energy density of 218.4 Whkg(-1) electrodes (229.8 WhL(-1) electrodes), the highest power density of 22.5kWkg(-1) electrodes (23.7 kWL(-1) electrodes) even under an ultrahigh energy density of 97.5Whkg(-1) electrodes (102.6 WhL(-1) electrodes), as well as reasonably good cycling stability with capacity retention of 84.5% (only 0.0016% capacity loss per cycle) within 10 000 cycles under a high current density of 5 A g(-1). This study provides an efficient method and option for the development of high performance LIC devices.