Biomass-derived carbon prepared through a quadruple-functional-salt approach for application in K-ion capacitors

• Published in: Chemical engineering journal (Lausanne, Switzerland : 1996) Switzerland : 1996), 2022-12, Vol.449, p.137561, Article 137561
• Main Authors: Zhu, Feng, Cao, Weishan, Song, Weihao, Peng, Jiaying, Yang, Na, Niu, Jin, Wang, Feng
• Format: Article
• Language: English
• Subjects: Biomass; heteroatom doping; K-ion capacitor; mechanism study; porous carbon
• ISSN: 1385-8947; 1873-3212
• DOI: 10.1016/j.cej.2022.137561

•A quadruple-functional-salt strategy is firstly proposed for the synthesis of N/P -doped carbons.•The carbonization mechanism of the carbons is revealed by in-situ thermal analysis.•Carbon electrodes show high performance in half-cell/pouch-cell K-ion capacitors.•In-situ Raman/XRD and DFT calculations give insights into the energy storage mechanisms. Heteroatom-doped porous carbons are regarded as promising electrodes for K-ion capacitors. However, current synthetic methods suffer from problems of low efficiency and use unsustainable precursors, and this has restricted wide application of these materials. Moreover, the mechanisms of energy-storage by heteroatom-doped porous carbon electrodes in K-ion capacitors are not well understood. In this work, we prepare porous carbons having honeycomb-like hierarchical structures and doped with P/N heteroatoms by using a low-cost fish scale and K3PO4 as precursor and auxiliary, respectively. K3PO4 and its derivatives not only serve as collagen-hydrolysis reagents during the pre-treatment process, but also act as dopants, templates, and activators during the subsequent carbonization process. Deionized water is the only solvent required in the whole synthesis process. The as-prepared carbons were used as electrodes in K-ion capacitors and their energy-storage mechanisms studied by detailed in-situ characterization methods and DFT calculations. The optimized carbon anode and cathode were used to assemble a pouch K-ion capacitor, which showed high energy density (184.6 Wh kg–1), high power density (4.8 kW kg–1), and long lifetime (retaining 90% of the initial capacity after 10000 cycles).