Du Yang, Huo Hua
State Key Laboratory of Space Power-Sources, School of Chemistry and Chemical Engineering, Harbin Institute of Technology, Harbin, 150001, China.
Magn Reson Lett. 2024 Dec 4;5(2):200172. doi: 10.1016/j.mrl.2024.200172. eCollection 2025 May.
Supercapacitors, comprising electrical double-layer capacitors (EDLCs) and pseudocapacitors, are widely acknowledged as high-power energy storage devices. However, their local structures and fundamental mechanisms remain poorly understood, and suitable experimental techniques for investigation are also lacking. Recently, nuclear magnetic resonance (NMR) has emerged as a powerful tool for addressing these fundamental issues with high local sensitivity and non-invasiveness. In this paper, we first review the limitations of existing characterization methods and highlight the advantages of NMR in investigating mechanisms of supercapacitors. Subsequently, we introduce the basic principle of ring current effect, NMR-active nuclei, and various NMR techniques employed in exploring energy storage mechanisms including cross polarization (CP) magic angle spinning (MAS) NMR, multiple-quantum (MQ) MAS, two-dimensional exchange spectroscopy (2D-EXSY) NMR, magnetic resonance imaging (MRI) and pulsed-field gradient (PFG) NMR. Based on this, recent progress in investigating energy storage mechanisms in EDLCs and pseudocapacitors through various NMR techniques is discussed. Finally, an outlook on future directions for NMR research in supercapacitors is offered.
超级电容器，包括双电层电容器（EDLC）和赝电容器，被广泛认为是高功率储能装置。然而，它们的局部结构和基本机制仍知之甚少，并且也缺乏合适的实验研究技术。最近，核磁共振（NMR）已成为解决这些基本问题的强大工具，具有高局部灵敏度和非侵入性。在本文中，我们首先回顾现有表征方法的局限性，并强调NMR在研究超级电容器机制方面的优势。随后，我们介绍环电流效应的基本原理、NMR活性核以及用于探索储能机制的各种NMR技术，包括交叉极化（CP）魔角旋转（MAS）NMR、多量子（MQ）MAS、二维交换光谱（2D-EXSY）NMR、磁共振成像（MRI）和脉冲场梯度（PFG）NMR。基于此，讨论了通过各种NMR技术在研究EDLC和赝电容器储能机制方面的最新进展。最后，对超级电容器NMR研究的未来方向进行了展望。
