Step-by-Step Modification of Graphite Felt Electrode for Vanadium Redox Flow Battery

doi:10.13208/j.electrochem.190714

Abstract

Abstract:

As a well-known electrode material of the vanadium redox flow battery (VRFB),graphite felt electrode is the frequently-used electrode material in VRFB, and its low electrochemical activity is one of the key factors for the low power density of VRFB. In this work, we proposed a step-by-step modification method, which used KMnO₄ to oxidize graphite felt first and then placed in an activation solution to excite its reactivity, to improve the electrochemical performance of the graphite felt electrode. According to the results from cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) characterizations of the treated graphite felts, it was found that the oxidation time and the composition of the activation solution are factors affecting the electrode performance. In this paper, the charge transfer resistance of the electrode treated in the activation solution with a volume ratio of H₂SO₄:H₂O₂ = 3:1 after oxidation in KMnO₄ for 3 days, was significantly lower than that of the electrode treated by other methods, showing the lowest contact resistance (7.33 Ω·cm ²). The redox peak current density ratio (I_pa/I_pc) was closer to 1, which effectively increased the activity and reversibility of the redox reactions. In addition, the XPS data showed that the excellent electrochemical performance of the treated graphite felt might be related to the increase in the number of surface oxygen-containing functional groups. The charge/discharge testing results demonstrated that the all-vanadium redox flow battery employing the modified graphite felt electrodes exhibited the enhanced performance with higher battery efficiency and favorable discharge capacity. Moreover, the all-vanadium redox flow battery with the treated graphite felt as an electrode delivered the energy efficiency of 7.47%, which was higher than that of the untreated electrode at a current density at 100 mA·cm ^-2. Compared with heat treatment, acid treatment and electrochemical oxidation, the step-by-step modification method requires no auxiliary equipment and consumes no energy.

Key words: vanadium redox flow battery, graphite felt, step-by-step modification, activity

CLC Number:

TM911
O646

LOU Jing-yuan, YOU Dong-jiang, LI Xue-jing. Step-by-Step Modification of Graphite Felt Electrode for Vanadium Redox Flow Battery[J]. Journal of Electrochemistry, 2020, 26(6): 876-884.

Figures/Tables 10

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References 28

[1]	Guarnieri M, Mattavelli P, Petrone G , et al. Vanadium redox flow batteries: Potentials and challenges of an emerging storage technology[J]. IEEE Industrial Electronics Magazine, 2016,10(4):20-31.
[2]	Perry M L . Expanding the chemical space for redox flow batteries[J]. Science, 2015,349(6255):1452-1452.
[3]	Zeng Y( 曾艳), Lv Z S( 吕早生), Liu Y C( 刘俞辰 ), et al. Recent progress on graphite felt as electrode materials in vanadium redox flow battery[J]. Plating & Finishing( 电镀与精饰), 2019,41(1):15-21.
[4]	Kim K J, Park M S, Kim Y J , et al. A technology review of electrodes and reaction mechanisms in vanadium redox flow batteries[J]. Journal of Materials Chemistry, 2015,3(33):16913-16933.
[5]	Li B, Gu M, Nie Z M , et al. Bismuth nanoparticle decorating graphite felt as a high performance electrode for an all vanadium redox flow battery[J]. Nano Letters, 2013,13(3):1330-1335.
[6]	Lin D( 林顿), Zhang X Y( 张熙悦), Zeng Y X( 曾银香 ), et al. Recent advances on carbon and transition metallic compound electrodes for high-performance supercapacitors[J]. Journal of Electrochemistry( 电化学), 2017,23(5):560-580.
[7]	Zhang Y M, Wang F, Zhu H , et al. Preparation of nitrogen-doped biomass-derived carbon nanofibers/graphene aerogel as a binder-free electrode for high performance supercapacitors[J]. Applied Surface Science, 2017,426(44):99-106.
[8]	Mehboob S, Mehmood A, Lee J Y , et al. Excellent electrocatalytic effects of tinthrough in situ electrodeposition on the performance of all-vanadium redox flow batteries[J]. Journal of Materials Chemistry A, 2017,5(33): 17388-17400.
[9]	Ye J L( 叶江林), Zhu Y W( 朱彦武 ). Porous carbon materials produced by KOH activation for supercapacitor electrodes[J]. Journal of Electrochemistry( 电化学), 2017,23(5):548-559.
[10]	Zhou Y, Liu L, Shen Y , et al. Carbon dots promoted vanadium flow batteries for all climate energy storage[J]. Chemical Communications, 2017,53(54):7565-7568.
[11]	Li W Y, Liu J G, Yan C W . Multi-walled carbon nanotubes used as an electrode reaction catalyst for VO ²+/VO ²+ for avanadium redox flow battery [J]. Carbon, 2011,49(11):3463-3470.
[12]	Kabtamu D M, Chen J Y, Chang Y C , et al. Electrocatalytic activity of Nb-doped hexagonal WO₃ nanowire-modified graphite felt as a positive electrode for vanadium redox flow batteries[J]. Journal of Materials Chemistry A, 2016,4(29):11472-11480.
[13]	Liu H J, Yang L X, Xu Q , et al. An electrochemically activated graphite electrode with excellent kinetics for electrode processes of V(II)/V(III) and V(IV)/V(V) couples in a vanadium redox flow battery[J]. RSC Advances, 2014,4(98):55666-55670.
[14]	Wang G( 王刚), Chen J W( 陈金伟), Zhu S F( 朱世富 ), et al. Activation of carbon electrodes for all-vanadium redox flow battery[J]. Progress in Chemistry( 化学进展), 2015,27(10):1343-1355.
[15]	Jing M H, Zhang X S, Fan X Z , et al. CeO₂ embedded electrospun carbon nanofibers as the advanced electrode with high effective surface area for vanadium flow battery[J]. Electrochimica Acta, 2016,215:57-65.
[16]	Liu S Q( 刘素琴), Guo X Y( 郭小义), Huang K L( 黄可龙 ), et al. Research on the graphite felt of vanadium battery electrode materials[J]. Battery( 电池), 2005,35(3):183-184.
[17]	Sun H( 孙红), Liu H R( 刘浩然), Li J( 李洁 ), et al. Effects of the graphite felt electrode acid or thermal treatment on characteristics of all vanadium flow battery[J]. Journal of Shenyang Jianzhu University( 沈阳建筑大学学报), 2018,34(6):1110-1117.
[18]	Liu D( 刘迪), Tan N( 谭宁), Huang K L( 黄可龙 ), et al. The electrochemical treatment of the graphite felt electrode materials used in vanadium redox flow battery[J]. Power Technology( 电源技术), 2006,30(3):224-226.
[19]	Mazúr P, Mrlík J, Beneš J , et al. Performance evaluation of thermally treated graphite felt electrodes for vanadium redox flow battery and their four-point single cell characterization[J]. Journal of Power Sources, 2018,380:105-114.
[20]	Zhang W G, Xi J Y, Li Z H , et al. Electrochemical activation of graphite felt electrode for VO ²+/VO ²+ redox couple application [J]. Electrochimica Acta, 2013,89(1):429-435.
[21]	Zhao T S( 赵天寿), Jiang H R( 蒋浩然 ). 液流电池电极及其制备方法和液流电池[P]. 中国专利: CN108346806A
	2018-07-31.
[22]	Liu Y C, Shen Y, Yu L H , et al. Holey-engineered electrodes for advanced vanadium flow batteries[J]. Nano Energy, 2018,43:55-62.
[23]	Jing M H, Wei Z F, Su W , et al. Improved electrochemical performance for vanadium flow battery by optimizing the concentration of the electrolyte[J]. Journal of Power Sources, 2016,324:215-223.
[24]	Wei G J, Su W, Wei Z F , et al. Effect of the graphitization degree for electrospun carbon nanofibers on their electrochemical activity towards VO ²+/VO ²+ redox couple [J]. Electrochimica Acta, 2016,199:147-153.
[25]	Tan N( 谭宁), Huang K L( 黄可龙), Liu S Q( 刘素琴 ), et al. Activation mechanism study of electrochemical treated graphite felt for vanadium redox cell by electrochemical impedance spectrum[J]. Acta Chimica Sinica( 化学学报), 2006,64(6):584-588.
[26]	Hu G J, Jing M H, Wang D W , et al. A gradient bi-functional graphene-based modified electrode for vanadium redox flow batteries[J]. Energy Storage Materials, 2018,13:66-71.
[27]	Su X L( 苏秀丽), Yang L L( 杨霖霖), Zhou Y( 周禹 ), et al. Developments of electrodes for vanadium redox flow battery[J]. Energy Storage Science and Technology( 储能科学与技术), 2019,8(1):65-74.
[28]	Abbas S, Lee H, Hwang J , et al. A novel approach for forming carbon nanorods on the surface of carbon felt electrode by catalytic etching for high-performance vanadium redox flow battery[J]. Carbon, 2018,128:31-37.

Sample	Oxidation time in KMnO₄/day	Mixed activation solution ratio/(V:V)
N	0	0
A1	1	3:1
A2	1	2:1
A3	1	1:1
B1	3	3:1
B2	3	2:1
B3	3	1:1

Sample	I_pa/(mA·cm^-2)	I_pc/(mA·cm^-2)	E_pa/V	E_pc/V	I_pa/I_pc
N	12.06	5.02	0.94	0.86	2.40
A1	36.60	24.50	0.94	0.88	1.49
A2	21.20	12.90	0.93	0.89	1.64
A3	17.96	7.48	0.93	0.87	2.39
B1	39.70	28.50	0.93	0.87	1.39
B2	36.15	25.78	0.92	0.82	1.40
B3	20.5	13.8	0.94	0.86	1.49

Sample	R_s/(Ω·cm²)	R₁/(Ω·cm²)	R₂/(Ω·cm²)
N	0.40	21.06	299.60
A1	0.32	10.64	255.90
A2	0.32	9.41	273.30
A3	0.33	11.41	266.50
B1	0.38	7.33	198.30
B2	0.34	10.64	203.30
B3	0.38	10.95	253.10

Sample	Atomic concentration/%		O1s/C1s
Sample	O1s	O1s	O1s/C1s
N	93.20	6.86	0.07
A1	73.12	27.88	0.39
A3	84.87	15.13	0.18
B1	58.60	41.40	0.71
B3	75.06	24.94	0.33

Current density/ (mA·cm^-2)	N			B1
Current density/ (mA·cm^-2)	CE/%	VE/%	EE/%	CE/%	VE/%	EE/%
50	92.61	80.55	74.59	95.93	84.27	80.84
80	94.58	69.67	65.90	96.61	74.84	72.30
100	95.19	61.90	58.92	97.33	68.21	66.39
150	-	-	-	98.55	52.82	52.05