Unlocking Zinc-Ion Energy Storage Performance of Onion-Like Carbon by Promoting Heteroatom Doping Strategy

Abstract

Onion-like carbon (OLC) is one kind of a quasi-nanosphere with a concentric graphite shell structure and abundant mesopores, which is appropriate for a high rate of charging/discharging and long-lifespan cycling. However, the moderate specific surface area seriously impeded its capacitance performance in comparison with activated carbon and porous carbon. Herein, we have unlocked the Zn ion storage performance of OLC material through introducing N and P dopants. Benefitting from the fabricated N,P-OLC with a fully accessible external surface area for ion adsorption, high proportion of mesopores for fast ion migration, and synergistic effect of N and P co-doping in a carbon matrix favoring chemical adsorption of Zn 2+ ions, when applied as a cathode electrode for Zn ion hybrid supercapacitors (ZHSCs), such a device can deliver a high specific capacitance of 420.3 F g −1 (184.5 mA h g −1 ) at 0.5 A g −1 , an outstanding capacitance retention capability of 262.7 F g −1 even at 20 A g −1 (∼63% capacitance retention), a high energy density of 149.5 W h kg −1 , and a high power density of 26.7 kW kg −1 . Furthermore, this N,P-OLC material can in situ tightly integrate with a carbon cloth (CC) or carbon fiber to construct a freestanding and flexible electrode. The fabricated Zn//N,P-OLC@CC device achieved a high energy density of 85.3 mW h cm −2 , a high power density of 24.3 W cm −2 , and a long-term cycling lifespan (77.8% after 50 000 cycles). At last, the assembled quasi-solid-state fiber-shaped ZHSCs also present excellent flexibility and practicality. Our study exhibits that OLC can act as a promising carbon electrode for ZHSCs.

Mechanical Insights into the Electrochemical Properties of Thornlike Micro-/Nanostructures of PDA@MnO2@NMC Composites in Aqueous Zn Ion Batteries

“…In addition, the incorporation of carbons into MnO 2 has been previously reported to effectively improve its electrical conductivity. , Onion-like carbons are reported to modify α-MnO 2 nanorods with ultrasonic treatment, achieving increased capacity retention from 81 to 93% at 246 mA g –1 for 100 cycles . Another way to decorate α-MnO 2 nanorods with graphene oxide by a hydrothermal method can also realize a high energy density of 406.6 Wh kg –1 and a high specific capacity of 382.2 mAh g –1 at 300 mA g –1 .…”

Carbon fiber reinforced structural Zn-ion battery composites with enhanced mechanical properties and energy storage performance

“…), which enables the integrity of the composite electrodes under external mechanical load. Besides, the high specic capacity of the PANI and MXene composite cathodes, 38,39 far exceeding those of carbon materials, 40 demonstrates high energy storage ability with a thinner coating. Therefore, the optimized structural cathode avoids the delamination of the active materials because of the few in situ grown electrode materials connected by chemical bonds.…”

Zinc‐ion hybrid supercapacitors: Design strategies, challenges, and perspectives

“…The LDC electrodes with high surface area, abundant electroactive sites, and hierarchical porosity exhibited excellent electrochemical performance, mainly due to their short ion/electron transfer pathways, fast kinetics, and increased electroactivity. Besides O/N and N/B co‐doping, N/P co‐doped PC materials are also widely used as cathode materials for Zn‐ion hybrid capacitors, such as cross‐linked PC nanosheets, [ 74 ] N, P co‐doped carbon hollow nanospheres (PN‐CHoNS), [ 75 ] N, P co‐doped onion‐like carbon, [ 76 ] and N/P co‐doped graphene. [ 77 ] When P element was doped into the carbon electrode, the larger radius of P (195 pm) would generate more structural defects, thereby enhancing the energy storage capacity.…”