Decorating carbon quantum dots onto VO2 nanorods to boost electron and ion transport kinetics for high–performance zinc–ion batteries

• Published in: Journal of energy storage 2023-12, Vol.74, p.109340, Article 109340
• Main Authors: Wu, Tzu-Ho, Chen, Jheng-An, Su, Jia-He, Ting, Yuan-Hong
• Format: Article
• Language: English
• Subjects: Aqueous zinc–ion battery; Carbon quantum dots; Heterogeneous interface; Promoted electron/ion transport; Vanadium oxide
• ISSN: 2352-152X; 2352-1538
• DOI: 10.1016/j.est.2023.109340

Rechargeable aqueous Zn–ion batteries (RAZIBs) are regarded as attractive alternatives for large–scale energy storage. V–based cathode materials have gained great attention due to the merits of rich valence states, controllable morphology, diverse crystal structures, and controllable chemical compositions. However, the development of high–performance V–based cathode is still impeded by sluggish electron/ion transport kinetics. To address this issue, this work reveals that the electrochemical performance of the VO2 cathode can be significantly boosted by decorating carbon quantum dots (CQDs) onto the VO2 nanorods via a facile hydrothermal reaction. The VO2/CQDs sample is characterized to have strong interface interaction with the presence of CO bond. Compared to the CQD–free counterpart, the obtained VO2/CQDs sample exhibits higher specific surface area (18.7 vs 4.4 m2 g−1), better electrolyte wettability (53° vs 114° for contact angle), reduced charge–transfer resistance (1.8 vs 19.9 Ω), and facilitated ion diffusion coefficient (1.66 × 10−10 vs 4.56 × 10−11 cm2 s−1). Benefiting from these features, a high attainable capacity of 427 mAh g−1 at 0.2 A g−1 can be reached for VO2/CQDs, corresponding to the specific energy of 333 Wh kg−1 (based on the mass of VO2/CQDs). When the current density increases to 8 A g−1, VO2/CQDs can still deliver 309 mAh g−1, showing great promise for high–rate capability. Moreover, the VO2/CQDs cathode renders stable cycle performance with retaining 229 mAh g−1 after 2000 cycles. By contrast, the unmodified sample demonstrates moderate electrochemical performance (373 and 186 mAh g−1 at 0.2 and 8 A g−1, respectively). The results highlight the importance of the CQDs decoration strategy, which can effectively boost electron/ion transport in oxide–based cathodes for high–performance RAZIBs. [Display omitted] •CQDs can be derived from citric acid via a facile and scalable pyrolysis approach.•CQDs engineering endows vanadium oxide with efficient electron/ion transport kinetics.•VO2/CQDs possesses strong interface interaction to keep structural integrity.•Zn2+ and H+ dual–cation insertion mechanism is found for VO2/CQDs.