Template-oriented synthesis of boron/nitrogen-rich carbon nanoflake superstructure for high-performance Zn-ion hybrid capacitors

Abstract

The rise of Zn-ion hybrid capacitor (ZHC) has imposed high requirements on carbon cathodes, including reasonable configuration, high specific surface area, multiscale pores, and abundant defects. To achieve this objective, a template-oriented strategy coupled with multi-heteroatom modification is proposed to precisely synthesize a three-dimensional boron/nitrogen-rich carbon nanoflake-interconnected micro/nano superstructure, referred to as BNPC. The hierarchically porous framework of BNPC shares short channels for fast Zn²⁺ transport, increased adsorption-site accessibility, and structural robustness. Additionally, the boron/nitrogen incorporation effect significantly augments Zn²⁺ adsorption capability and more distinctive pseudocapacitive nature, notably enhancing Zn-ion storage and transmission kinetics by performing the dual-storage mechanism of the electric double-layer capacitance and Faradaic redox process in BNPC cathode. These merits contribute to a high capacity (143.7 mAh g⁻¹ at 0.2 A g⁻¹) and excellent rate capability (84.5 mAh g⁻¹ at 30 A g⁻¹) of BNPC-based aqueous ZHC, and the ZHC still shows an ultrahigh capacity of 108.5 mAh g⁻¹ even under a high BNPC mass loading of 12 mg cm⁻². More critically, the BNPC-based flexible device also sustains notable cyclability over 30,000 cycles and low-rate self-discharge of 2.13 mV h⁻¹ along with a preeminent energy output of 117.15 Wh kg⁻¹ at a power density of 163.15 W kg⁻¹, favoring a creditable applicability in modern electronics. In/ex-situ analysis and theoretical calculations elaborately elucidate the enhanced charge storage mechanism in depth. The findings offer a promising platform for the development of advanced carbon cathodes and corresponding electrochemical devices.