Although Vanadium Redox Flow Battery (VRFB) is well suitable for grid-scale application, their power-related cost must be reduced in order to boost the technology to the market, allowing their widespread commercialization. One effective way to make the VRFB a competitive and viable solution could be through the new strategies for improving the electrocatalytic activity of the electrodes with enhanced electrolyte/electrode interface characteristics. The greatly effective and enhanced-electron transfer could increase the current density with the decrement of the stack size. Herein, we report the synergistic effect demonstrated by N-and WO 3 -decorated carbon-based positive electrode, named HTNW electrode, which demonstrates the feasibility of achieving: i) enhanced electrocatalytic activity, indicating high rate towards VO 2+ /VO 2 + couple (promotion of oxygen and electron transfer processes), ii) decrement of the electron-transfer resistance from 75.62 Ω to 12.4 Ω for the pristine electrode and HTNW electrodes, respectively; iii) 51% of the electrolyte utilization ratio at high rates (i.e. 200 mA cm -2 ) with 70% of energy efficiency ; iv) increment of more than 50% of the power-peak in comparison with HT electrode.
Nickel-rich layered oxides, such as LiNi 0.6 Co 0.2 Mn 0.2 O 2 (NMC622), are high-capacity electrode materials for lithium-ion batteries. However, this material faces issues, such as poor durability at high cut-off voltages (>4.4 V vs Li/Li + ), which mainly originate from an unstable electrode−electrolyte interface. To reduce the side reactions at the interfacial zone and increase the structural stability of the NMC622 materials, nanoscale (<5 nm) coatings of TiO x (TO) and Li x Ti y O z (LTO) were deposited over NMC622 composite electrodes using atomic layer deposition. It was found that these coatings provided a protective surface and also reinforced the electrode structure. Under high-voltage range (3.0−4.6 V) cycling, the coatings enhance the NMC electrochemical behavior, enabling longer cycle life and higher capacity. Cyclic voltammetry, X-ray photoelectron spectroscopy, and X-ray diffraction analyses of the coated NMC electrodes suggest that the enhanced electrochemical performance originates from reduced side reactions. In situ dilatometry analysis shows reversible volume change for NMC-LTO during the cycling. It revealed that the dilation behavior of the electrode, resulting in crack formation and consequent particle degradation, is significantly suppressed for the coated sample. The ability of the coatings to mitigate the electrode degradation mechanisms, illustrated in this report, provides insight into a method to enhance the performance of Ni-rich positive electrode materials under high-voltage ranges.
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