Nitridation-boosted V eg occupation of a VN@CNT flexible electrode for high-rate Zn-ion hybrid supercapacitors

• Published in: Journal of materials chemistry. A, Materials for energy and sustainability Materials for energy and sustainability, 2024-06, Vol.12 (47), p.32895-32903
• Main Authors: Cao, Yuyang, Wei, Shiqiang, Xia, Yujian, Zhou, Quan, Wang, Yixiu, Xu, Wenjie, Wang, Changda, Chen, Shuangming, Li, Song
• Format: Article
• Language: English
• Subjects: Absorption spectroscopy; Bending; Capacitance; Electrode materials; Electrodes; Flexibility; Flexible components; Metallicity; Soft x rays; Supercapacitors; X ray absorption; X-ray absorption spectroscopy
• ISSN: 2050-7488; 2050-7496
• DOI: 10.1039/d4ta02102a

Flexible zinc-ion hybrid supercapacitors (f-ZHSCs), with their inherent safety, combine the advantages of the high power density of supercapacitors and the high energy density of zinc-ion batteries, making them a promising energy supply device for wearable and implantable devices. However, commonly used rigid cathode materials and fracture-prone metallic current collectors encounter significant challenges, such as inadequate flexibility and compromised cycling stability, which impede the further development of f-ZHSCs. Herein, we design a free-standing flexible membrane electrode VN@CNT for f-ZHSCs through a nitridation strategy. Soft X-ray absorption spectroscopy (s-XAS) reveals the boosted occupation of electrons in the V eg orbital 3dx2−y2 state after nitridation, leading to enhanced metallicity and conductivity. As a result, the VN@CNT flexible electrode exhibits an excellent specific capacitance of 314.44 F g−1 at 0.5 A g−1. Moreover, it demonstrates exceptional rate capability, retaining 80.17% of its capacitance at a high current density of 10 A g−1 compared to that of 0.5 A g−1. Importantly, it also shows excellent flexibility, enduring bending angles of 0 to 180° and showing no detectable degradation in capacitance after 1200 bending cycles. By design and in-depth study of the local structure of the flexible electrode, this work provides insight into the development of flexible electronics.