2D crumpled nitrogen-doped carbon nanosheets anode with capacitive-dominated behavior for ultrafast-charging and high-energy-density Li-ion capacitors

Abstract

Li-ion capacitors (LICs) are promising to simultaneously achieve battery-level energy density and supercapacitor-level power density, but the slow kinetics of diffusion-controlled battery anodes lead to unmatched two-electrode kinetics at the device level. Herein, we report a capacitive-dominated anode of two-dimensional (2D) crumpled nitrogen-doped carbon nanosheets (N-CNS) with tailored nitrogen incorporation and abundant mesopore distribution, exhibiting large capacities and superior rate performance. The optimized N-CNS delivers large reversible capacities of 620 and 121 mA h g⁻¹ at 0.1 and 100 A g⁻¹, respectively. The introduced nitrogen is found to contribute to providing additional pseudocapacity and high Li⁺ diffusion coefficients in the medium–high voltage region and enhancing the capacitive-dominated charge storage process. The structural reversibility and “adsorption-intercalation” mechanism are supported by in situ and ex situ measurements. Furthermore, it is theoretically revealed that N-CNS with superior electrochemical properties benefits from the increase in Li⁺ adsorption energy and the decline in the Li⁺ diffusion barrier. A LIC coupling the N-CNS anode with a porous carbon cathode outputs a high energy density of 75 W h kg⁻¹ at an ultrahigh power density of 65 kW kg⁻¹. This study provides a novel and effective approach to developing high-performance carbon-based anodes for constructing advanced LICs featuring high energy and power density.