Towards High‐Performance Zinc‐Based Hybrid Supercapacitors via Macropores‐Based Charge Storage in Organic Electrolytes

Abstract

Zn‐based aqueous supercapacitors are attracting extensive attention. However, most of the reported long‐life and high‐power performances are achieved with low Zn‐utilization (<0.6 %) and low mass loading in cathode (<2 mg cm−2). And, many obtained high energy densities are generally evaluated without considering the mass of Zn‐anode. Herein, we propose a Zn‐based hybrid supercapacitor, involving a metal organic framework derived porous carbon cathode, a Zn‐anode and an N, N‐dimethylformamide (DMF)‐based electrolyte containing Zn2+. We demonstrate that the charge storage of cathode mainly occurs in macropores, showing high rate performance at high mass loading (40 mg cm−2). Furthermore, the aprotic nature of electrolyte and formation of Zn2+‐DMF complex avoid the Zn‐corrosion and dendrite formation. Therefore, the supercapacitor shows a long‐life (9,000 cycles) with a high Zn‐utilization (2.2 %). When calculated with the total mass of cathode (40 mg cm−2) and Zn‐anode, the energy density reaches 25.9 Wh kg−1.

Biochar for Supercapacitor Electrodes: Mechanisms in Aqueous Electrolytes

“…35 Wang et al successfully clarify the charge storage mechanism of the MOF-PC (metal organic framework derived porous carbon) cathode of Zn-based hybrid SC (i.e., MOF-PC//Zn) by using in situ ATR-IR analysis in a nonaqueous electrolyte (0.5 M Zn-TFMS in dimethylformamide solution), which is found that the charge storage mechanism mainly based on the anions/cations adsorption and exchange in macropores. 36 These studies are based on the ionic kinetic mechanism of EDLCs with organic or ionic liquids as electrolytes. However, so far, the reports on the ionic dynamics mechanism of biomass carbon materials containing N and O functional groups in SCs in aqueous electrolytes and the chemical changes at the molecular level in electrochemical energy storage have not been revealed in detail.…”