LAUSR

Abstract K-ion hybrid capacitors (KIHCs) have been attracted extensive attention. However, the large radius of K-ion impedes the exploration of electrode materials for KIHCs. Herein, we demonstrate a one-step calcination of mango seed shuck to prepare the natural N/O co-doped hard carbon (NOHC) as the excellent anode for KIHCs. The NOHC shows a capacity retention of 93.5% of initial reversible capacity (186.3 mA h g−1) after 500 cycles at 0.1 A g−1 with a superior rate performance (103 mA h g−1 at 2 A g−1). Further, the K-ion intercalation mechanism and the stable solid electrolyte interphase layer are revealed by ex-situ X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) techniques, clarifying the excellent electrochemical performance of the NOHC anode for KIHCs. Consequently, the fabricated KIHCs by NOHC anode and activated carbon cathode deliver acceptable energy and power densities (68 W h kg−1 and 2000 W kg−1) as well as long cycling stability with a retention of 80% over 1000 cycles at 1 A g−1. This study offers the practical preparation of natural NOHC by a low-cost mass production route, which would advance the biomass application and energy materials preparation for practical KIHCs and beyond.