Rechargeable zinc-ion batteries (ZIBs) are promising alternatives for large-scale energy storage systems. However, instability of the cathode during operation leads to rapid capacity fading and poor stability. Binders play a crucial role in keeping all components in the cathode intact during cycling. However, the impact of the binders’ chemical structure on the electrochemical reaction in ZIBs is not well understood. Herein, the effect of the chemical structure of a conventional polyvinylidene fluoride (PVDF) and green binders, that is, sodium carboxymethyl cellulose (CMC) and cellulose acetate (CA), on the performance, cyclability, and reaction of Zn/α-MnO2 aqueous batteries is investigated. Results show that a cathode having a PVDF binder yields the highest specific capacity in a full battery. Besides, the CMC-based ZIB is seen to attain superior cycling stability through 500 galvanostatic charge–discharge (GCD) cycles having no irreversible products confirmed by scanning electron microscopy (SEM) and X-ray diffraction (XRD). It is found that the Na+ ion in the CMC structure plays a critical role in promoting prominent battery reactions. The CMC-based ZIB, therefore, is able to maintain its high ionic diffusivity obtained from the galvanostatic intermittent titration technique (GITT) during prolonged operation. Moreover, the interaction between binders and α-MnO2 has been investigated via density-functional theory (DFT) to affirm the high stability of the ZIB/α-MnO2 with the CMC binder. This work highlights the importance of the selection of functional groups on the binder not only to enhance stability but also to control the preferential reactions of batteries. Such findings are ultimate keys for the development of low-cost, stable, and eco-friendly energy storage devices.
This research evaluates the impact of nanowire morphology and transition-metal doping to vanadium oxides as the positive electrode material on the performance of rechargeable aqueous zinc-ion batteries. It was found that both the wire morphology and Cu doping enhanced the cycle stability and specific capacity of the cathode. The improvement is ascribed to the wire morphology and Cu doping for attaining more mechanical stability, less morphology change and fewer parasitic reactions, and more facile Zn2+ insertion/extraction.
Rechargeable aqueous zinc-ion batteries are promising alternatives due to its abundance of active materials, safety, and lower cost. However, development of a suitable cathode that is earth abundance, such as manganese oxide, which can also produce high performance battery needs to be further carried out. Binders play a key role in achieving desirable properties, such as mechanical, electrical, electrochemical etc. of a battery. Specifically, selecting the right binder will promote stability throughout operation and enable tuning the thickness of a cathode to load more active materials to increase the capacity. This work explores three different binders, Carboxymethyl cellulose(CMC), Cellulose acetate (CA), and Polyvinylidene fluoride (PVDF), in aqueous electrolyte with ZnSO4 salt to investigate the effect of hydrophilicity level on performance and stability of the battery. The result shows that a cathode with PVDF as a binder yields the highest specific capacity regardless of charge/discharge rate. While, CA cathode works well at low rate and their performance started to drop at higher rates. CMC based cathode yields the lowest capacity from low to medium rate and starts to excel at higher rates. The relationship between different degree of electrolyte wettability on cyclability of the batteries will also be discussed. Further investigation using the Galvanostatic Intermittent Titration Technique (GITT) shows that there are two regions of ionic diffusion in all samples. During high state-of-charge (SOC) all three cathodes behave the same, while at lower SOC, CA based electrode seems to be limited by ionic diffusion. This explains why CA cathode performance dropped a lot at a higher rate. Our binder selection criteria for zinc-ion batteries can be further adapted in wider rechargeable zinc-based batteries for a variety of applications. Figure 1
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