Overview of Carbon Felt Electrode Modification in Liquid Flow Batteries (IV) Carbon Felt Body Doping Modification

Classification:Industrial News

 - Author:Luo Xuan

 - Release time:Jun-08-2022

【 Summary 】Carbon felt also exhibits excellent long-term stability after 1000 cycles, showing great potential in practical liquid flow battery applications

     This series of content will mainly summarize the surface activity improvement process and related research of carbon felt electrodes in all vanadium flow batteries, which are currently widely cited. In the previous article, we introduced the improvement of electrode performance through surface functionalization of carbon felt in the first article, and then demonstrated the modification of carbon felt electrodes through the introduction of carbon nanotubes in the second article. In the previous chapter, we also reviewed some processes for modifying carbon felt electrodes by depositing metals or metal oxides on the surface of carbon felt electrodes. These three methods are all important and effective means to modify carbon felt electrodes for flow batteries, which can effectively improve the operational efficiency and overall performance of all vanadium flow batteries. This content is the final installment of the four series, mainly focusing on the surface modification of carbon felt electrodes by doping the carbon felt electrode body.




Huang et al. [1] reported a simple preparation process for N, O double doped carbon felt (CF) as an electrode for all vanadium redox flow batteries. It uses nitrogen and oxygen plasma to treat carbon felt, directly doping nitrogen and oxygen atoms into the felt to improve the electrocatalytic activity during battery operation and enhance the interaction between electrolytes in the felt. At a current density of 50 mA cm-2, the energy efficiency of the assembled all vanadium flow battery increased from 65% (original) to 78% (doped), and exhibited excellent cycling stability. In addition, it reported that oxygen nitrogen co doped carbon felt exhibits better battery performance than original undoped carbon felt or single atom doped carbon felt (O-CF and N-CF). This is mainly due to the introduction of a large number of functional groups such as carbonyl and pyridine-N by N and O doping, which can increase the active sites of vanadium ion reaction and the conductivity of the material.

Dixon et al. [2] applied oxygen plasma treatment to carbon felt electrodes based on artificial silk and polyacrylonitrile. The results showed that the surface area of the artificial silk and PAN based carbon felt electrodes treated with oxygen plasma did not significantly increase, but both plasma treated electrodes showed significantly enhanced V2+/V3+redox activity compared to the original electrode. The reason for this should be the introduction of surface active functional groups, which can be observed as an overall improvement in the single cell performance of all vanadium flow batteries.

Zhang et al. [3] proposed a novel two-step in-situ interface copolymerization process strategy to directly construct microvilliform nitrogen doped carbon on carbon felt. This method has the characteristics of good uniformity, high doping content, and controllable nitrogen type conversion. By adding polyethyleneimine in the polymerization reaction, the aggregation effect of polydopamine was reduced, and more firmly bonded nitrogen atoms were introduced. Generate layered electrode interfaces with high pyridine-N content through covalent interactions. The results indicate that the prepared electrodes exhibit excellent reaction kinetics for both VO2+/VO2+and V2+/V3+redox pairs, and can achieve simple mass transfer processes. The all vanadium flow battery assembled with the prepared electrodes showed an energy efficiency of 73.6% at 300 mA cm-2 and achieved long-term cycling stability of over 600 cycles at 200 mA cm-2, with extremely low energy efficiency decay, only a percentage of 0.006 per cycle.

Zhang et al. [4] combined carbon nanofiber networks onto carbon felt substrates through the self-assembly process of polyaniline and used them as electrodes for vanadium redox flow batteries. The specific surface area of the adhesive free carbon nanonetwork wrapped carbon felt produced by this process is 161 m2 g-1, which is much higher than the original carbon felt (0.4 m2 g-1) and heat-treated carbon felt (1.0 m2 g-1). In addition, it also optimized the surface composition of carbon nanofibers through co doping of sulfur and nitrogen to selectively catalyze the redox reaction of vanadium. The results indicate that the optimized N-S co doping effect and graded porous structure provide abundant active sites and effective mass transfer pathways for the reaction, promoting the process of convection diffusion reaction. At the same time, the nanofiber network also improves the interconnectivity between micrometer sized fibers of carbon felt, reduces the internal resistance of the battery, and enables the electrode to have an energy efficiency of 82.4% in the vanadium redox flow battery system at a very high current density of 320 mA cm-2, which is much higher than the energy efficiency of heat-treated carbon felt (66.8%). In addition, carbon felt wrapped in carbon nanonetworks also exhibits excellent long-term stability after 1000 cycles, showing great potential in practical liquid flow battery applications.

Hosseini et al. [5] have successfully co modified N - and WO3- on the surface of carbon felt using a low-cost, easily scalable, and environmentally friendly hydrothermal method. Compared with the individually modified carbon felt electrode, the combined modified carbon felt electrode exhibits higher electrocatalytic activity (i.e. reverse polarity and high current density), promoting high electron and oxygen transfer rates and mass transfer diffusion characteristics. The resistance of the interface electrode and electrolyte has been reduced from 76.18 Ω to 13 Ω. In addition, the results indicate that it has a high capacity value under the applied high current density (200 mA/cm2), and achieves an electrolyte utilization rate of 51%, an energy efficiency value of up to 70%, and a power density increase of more than twice, thereby reducing the size of the battery stack and battery cost.

V á zquez Galv á n et al. [6] designed a high-performance electrode preparation process for all vanadium redox flow batteries. This process involves nitriding carbon felt using ammonolysis at 900 ° C and modifying it with TiO2 rutile nanoparticles. The results indicate that due to the synergistic effect of N and O functional groups on the carbon felt produced, as well as the partial formation of TiN (metal conductor) phase, it can promote the catalytic progress of the redox reaction in all vanadium flow batteries and simultaneously inhibit the hydrogen evolution reaction. The electrode loaded with it achieves a high output power peak of 700 mW cm-2, and the battery exhibits low ohmic loss (overpotential) and excellent redox single cell reversibility under high current density constant current conditions (i.e. 150 mA cm-2), with an energy efficiency of 71%.

Seong et al. [7] successfully introduced boron functional groups into carbon felt by treating it with NH4BF4. By incorporating boron functional groups, the hydrophobicity of carbon felt can be transformed into hydrophilicity, thereby improving affinity with the electrolyte of all vanadium flow batteries and exhibiting excellent wettability. The results showed that the all vanadium flow battery containing boron doped carbon felt electrode exhibited higher energy efficiency (80.56%) than the original carbon felt battery (63.40%) at a current density of 100 mA cm-2. This is mainly because the boron doped carbon felt electrode provides strong active sites for the redox reactions of VO2+/VO2+and V2+/V3+, thereby improving the quality and charge transfer rate, and enhancing its electrocatalytic performance. In particular, the introduction of boron functional groups promotes the serious asymmetric behavior caused by the slow kinetics of V2+/V3+in the anode electrolyte. Therefore, boron doped carbon felt electrode batteries exhibit excellent voltage efficiency and energy efficiency in 100 cycles, while minimizing performance degradation.

Xu et al. [8] produced carbon modified carbon felt for all vanadium flow batteries by using waste asphalt as an efficient and low-cost precursor. Through thermal decomposition treatment, the waste asphalt is transformed into highly active pyrolysis carbon and deposited on the surface of the carbon felt. The carbon felt with high active sites and outstanding hydrophilicity prepared by it exhibits excellent performance in the redox reaction of VO2+/VO2+, especially in terms of electrochemical reversibility and reaction kinetics. Moreover, the results showed that the all vanadium flow battery with carbon felt modified with waste asphalt carbon as the cathode exhibited an energy efficiency of 85%, which was 9% higher than the original carbon felt cathode. Meanwhile, during the battery cycling process, both energy efficiency and voltage efficiency are stable. This strategy can not only increase the value of waste asphalt, but also improve the performance of all vanadium flow batteries by modifying carbon felt electrodes, providing insights for the commercial application of large-scale energy storage.

At present, the scientific community and enterprises have never stopped researching the high-performance and stable carbon felt process for all vanadium flow batteries, and will continue to accelerate their pace to achieve faster improvement of carbon felt electrode performance, thereby improving the overall performance of all vanadium flow batteries and promoting their rapid development in the field of large-scale energy storage. We also look forward to it.



Reference materials

[1] Huang Y, Deng Q, Wu X, et al. N, O Co dropped carbon felt for high performance all advanced redox flow battery [J] International Journal of Hydrogen Energy, 2017, 42 (10): 7177-7185

[2] Dixon D, Babu D J, Langner J, et al. Effect of oxygen plasma treatment on the electrochemical performance of the radiation and polyacrylonitrile based carbon felt for the advanced redox flow battery application [J] Journal of Power Sources, 2016, 332: 240-248.

[3] Zhang K, Yan C, Tang A. Interactive co polymerization derived nitrogen doped carbon enablements high performance carbon felt for advanced flow batteries [J] Journal of Materials Chemistry A, 2021, 9 (32): 17300-17310

[4] Zhang X, Wu Q, Lv Y, et al. Binder free carbon nano network wrapped carbon felt with optimized heteroatom doping for advanced redox flow batteries [J] Journal of Materials Chemistry A, 2019, 7 (43): 25132-25141

[5] Hosseini M G, Mousavihashemi S, Murcia-L ó pez S, et al. High power positive electrode based on synergistic effect of N - and WO3 decorated carbon felt for advanced redox flow batteries [J] Carbon, 2018, 136: 444-453.

[6] V á zquez Galv á n J, Flox C, Jervis J R, et al. High power nitrated TiO2 carbon felt as the negative electrode for all advanced redox flow batteries [J] Carbon, 2019, 148: 91-104.

[28] Fetyan A, El Nagar G A, Derr I, et al. A neodymium oxide nanoparticle doped carbon felt as promising electrode for advanced redox flow batteries [J] Electrochimica Acta, 2018, 268: 59-65.

[7] Park S E, Yang S Y, Kim K J. Boron functionalized carbon felt electrode for enhancing the electrochemical performance of advanced redox flow batteries [J] Applied Surface Science, 2021, 546: 148941.

[8] Xu Z, Xu H, Hu Z, et al. Carbon Felt Decorated with Carbon Derived from Spent Asphalt as a Low cost and High performance Electrode for Vacuum Redox Flow Batteries [J] ChemNanoMat, 2022, 8 (4): e202200027



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