Constructing Active BN Sites in Carbon Nanosheets for High‐Capacity and Fast Charging Toward Potassium Ion Storage

• Published in: Small (Weinheim an der Bergstrasse, Germany) Germany), 2023-05, Vol.19 (20), p.e2300440-n/a
• Main Authors: Yang, Liuqian, Cao, Zhen, Yin, Jian, Wang, Chunyan, Ouyang, Dandan, Zhu, Hui, Wang, Yanan, Cavallo, Luigi, Alshareef, Husam N., Yin, Jiao
• Format: Article
• Language: English
• Subjects: Adsorption; Adsorptivity; Boron; B–N sites; Carbon; carbon nanosheets; Charge transfer; Conjugation; Doping; electric conductivity; Electrical resistivity; Energy storage; heteroatom doping; Ion storage; Nanosheets; Nanotechnology; Nitrogen; Potassium; potassium ion storage
• ISSN: 1613-6810; 1613-6829
• DOI: 10.1002/smll.202300440

Nitrogen doping is an effective strategy to improve potassium ion storage of carbon electrodes via the creation of adsorption sites. However, various undesired defects are often uncontrollably generated during the doping process, limiting doping effect on capacity enhancement and deteriorating the electric conductivity. Herein, boron element is additionally introduced to construct 3D interconnected B, N co‐doped carbon nanosheets to remedy these adverse effects. This work demonstrates that boron incorporation preferentially converts pyrrolic N species into BN sites with lower adsorption energy barrier, further enhancing the capacity of B, N co‐doped carbon. Meanwhile, the electric conductivity is modulated via the conjugation effect between the electron‐rich N and electron‐deficient B, accelerating the charge‐transfer kinetics of potassium ions. The optimized samples deliver a high specific capacity, high rate capability, and long‐term cyclic stability (532.1 mAh g−1 at 0.05 A g−1, 162.6 mAh g−1 at 2 A g−1 over 8000 cycles). Furthermore, hybrid capacitors using the B, N co‐doped carbon anode deliver a high energy and power density with excellent cycle life. This study demonstrates a promising approach using BN sites for adsorptive capacity and electric conductivity enhancement in carbon materials for electrochemical energy storage applications. Abundant BN sites are constructed in 3D interconnected carbon nanosheets to comprehensively boosted K+ storage performance. Upon the addition of B, pyrrolic N species are preferentially converted into BN sites with lower adsorption energy barrier, enhancing the capacity of samples. Meanwhile, the electric conductivity is modulated via the conjugation effect between electron‐rich N and electron‐deficient B, accelerating the charge‐transfer kinetics.