N,Se co-doped strategy to boost the K+ storage performance of metal organic framework-derived 3D amorphous carbon

Abstract

In view of the cost-effective, tunable interlayer spacing, and high electrical conductivity, carbonaceous materials are regarded as the most promising anodes for potassium-ion energy storage devices. Whereas, the poor diffusion kinetics, substantial volume changes caused by large-sized potassium ions (K+), and insufficient active sites limit its rate capability and cycling stability. Herein, N, Se co-doped porous carbon octahedron (NSeC) has been successfully synthesized by integrating microstructure engineering and surface modification strategies, using UiO-66-NH2 (Zr-based MOF) as the precursor. The resultant NSeC features high content of edge N (pyrrolic N and pyridinic N) and abundant micropores, which ensures plentiful active sites and defects for K+ storage, enhancing the diffusion kinetics of K+ and providing additional capacitive storage capacity. Accordingly, the NSeC anode displays a high reversible capacity (228.8 mAh g−1 at 0.5 A g−1 after 1000 cycles), long cycling stability (195.6 mAh g−1 at 2.0 A g−1 over 3300 cycles) and excellent rate performance (158.4 mAh g−1 at 10 A g−1), which are superior to the C and NC anodes. Especially, the CV, charge/discharge curves and in-situ Raman measurements are further performed to reveal the high structural stability of NSeC and its “adsorption-intercalation” mechanism for K+ storage. Moreover, the successful assembly of full cell also confirms its potential for practical applications. This work could provide us with a greener, lower energy-consuming and more facile method for developing high-performance carbon material anodes applicable to potassium-ion batteries.