S, N Co-Doped Porous Carbon Derived from Metal-Organicframeworks as Cathode for Lithium-Ion Capacitor

Abstract

Lithium-ion capacitors (LICs), which integrate the advantages of lithium ion batteries and supercapacitors, show promising application prospects in sustainable transportation systems. However, the energy density of LICs has been limited due to the low specific capacity of the cathode material. The porous carbon derived from Metal-organic frameworks (MOFs) possesses large specific surface area, abundant pore structure and is convenient for heteroatom doping, which can achieve the high specific capacity. In this work, S, N-co-doped porous carbon (SNC) derived from Co-based MOFs was prepared with a simple method. Thiophene-2,5-dicarboxylic acid (TDA) and 4,4’-dimethyl-2,2’-bipyridine (dmbpy) were mixed as ligand to provide sulfur and nitrogen sources for doping. The SNC shows the best electrochemical performance at the molar ratio of 3:1 for TDA: dmbpy because of the synergistic effect of S and N elements. The specific surface area of SNC is as large as 616.8 m2 g-1. The specific capacitance of the as prepared SNC can achieve 78 mAh g-1 at 0.1 A g-1 and maintain 90% of initial capacity after 5000 cycles. Moreover, a lithium-ion capacitor based on SNC and pre-lithiated hard carbon was assembled, which has shown the maximum energy density of 52 Wh kg-1 and maintains 97% of initial capacity after 2500 cycles.

Keywords: Metal-organic frameworks, Lithium-ion capacitors, Carbon