Three-dimensional N,P co-doped graphene hydrogel cathode for zinc-ion hybrid capacitor with high specific capacitance and excellent rate performance

• Published in: Journal of power sources 2024-12, Vol.623, p.235509, Article 235509
• Main Authors: Zhou, Qinqin, Lv, Guanlin, Li, Hongzheng, Hu, Shaokang, Liu, Hexiong, Li, Ling, He, Lixing, Li, Hongyi, Hu, Peng, Wang, Jinshu
• Format: Article
• Language: English
• Subjects: Co-doping; Graphene hydrogel; Rate capability; Size effect; Zinc-ion hybrid capacitor
• ISSN: 0378-7753
• DOI: 10.1016/j.jpowsour.2024.235509

Zinc-ion hybrid capacitor (ZHSC) is recognized as a favorable energy storage device due to the combined advantages of battery-type anode and capacitor-type cathode. However, it still remains a huge challenge to achieve a high-specific-capacitance cathode without compromising the rate capability for high-performance ZHSC. Here, a three-dimensional hierarchical nitrogen and phosphorus co-doped reduced graphene oxide hydrogel (NPGH) is synthesized with small-sized graphene oxide precursors via one-step hydrothermal reduction and in-situ doping, which is firstly used as cathode for ZHSC without adding extra conductive additives and binders. In this case, small-sized graphene sheets can increase and shorten ions diffusion channels for the efficient utilization of active surface compared with commonly-used large-sized counterparts. Moreover, nitrogen and phosphorus co-doping can synergistically enhance the conductivity, provide additional active sites, and promote the adsorption of zinc ions, which is well demonstrated by electrochemical analysis, ex situ characterization and DFT theoretical calculation. Attributed to the synergy, NPGH-based ZHSC displays large specific capacitance (251.3 F g−1, 0.5 A g−1), outstanding rate performance (79 %, 50 A g−1) and excellent cycle stability. This work proposes a novel strategy of tailoring rGO cathode by simultaneous size effect and doping engineering, which shows a great promise of constructing high-performance rGO based ZHSC. [Display omitted] •RGO hydrogel cathode for ZHSC was firstly modulated by size and doping engineering.•Small-sized rGO can enhance and shorten ions transport channels.•N,P co-doping can provide extra active sites and promote the Zn2+ adsorption.•The ZHSC shows high specific capacitance even at high rate and long cycle life.