Device and reagent names

Purity/Model

Manufacturer

Electrode material

聚丙烯腈毛毡

KD-WD220^[3]

凯盾新材料科技有限公司

石墨毡

厚度5 mm^[3]

辽宁金谷碳材料股份有限公司

聚丙烯腈基碳毡

孔隙率90%^[2]

辽宁金谷炭材料股份有限公司

聚丙烯腈基碳毡

厚度3 mm/4 mm

辽宁金谷炭材料股份有限公司

碳毡电极

/^[4]

甘肃宏伟碳

Diaphragm Material

质子交换膜

Nafion 212^[2,3]

美国杜邦公司（美国科慕化学）

全氟磺酸离子膜

55 μm^[4]

朝阳华鼎有限公司

聚醚醚酮SPEEK

55.0μm^[1]

英国Victrex公司

聚砜

P3500^[4]

Solvay Advanced Polymers

聚苯并咪唑PBI

99%^[1]

苏州友群塑化有限公司

聚苯并咪唑PBI

AR^[6]

上海盛钧塑胶科技有限公司

electrolyte

VOSO4·6H2O

99.9 %^[3]

默克Sigma-Aldrich公司

VOSO4·6H2O

99.9 %^[2,4]、97%^[1]

沈阳市海中天精细化工厂

浓硫酸

AR，98%^[2,3]

国药集团化学试剂有限公司

浓硫酸

98%

大连海运试剂厂

浓盐酸

AR^[4]

天津市富宇精细化工有限公司

Bipolar plate

高纯石墨板

HP-100^[3]

沈阳化学品有限公司

高密度石墨板

1.9 g cm^-3[3]

上海弘俊有限公司

Battery testing system

CT-3008^[2,3]

深圳市新威尔电子有限公司

Electrochemical workstation

Ref 600^[2,3]

美国Gamry公司

Single battery

(1) Parameters: The electrolyte composition is 1.7 M total vanadium ions+3 M sulfuric acid, with a flow rate of 40 mL/min; The volume of half cell electrolyte is 45 mL; The flow frame is made of polyvinyl chloride and PVC;
(2) Constant current charging and discharging: The charging and discharging current during constant current charging and discharging is 2.8 A (100 mA/cm2), and the charging and discharging voltage range is 1.1 V-1.65 V (Shenzhen Newell Electronics Co., Ltd., CT-4008-5V10A) [5].

(1) Parameters: Using graphite plate as the current collector and graphite felt as the electrode, the effective area of the membrane is 14 cm2. The initial electrolytes for both positive and negative electrodes are the same, consisting of H2SO4 solutions containing 1.7 mol · L-1 of VN+(where the molar ratio of V3+/V4+is 1:1) and 4.5 mol · L-1 of SO42-. The volume of both positive and negative electrolytes is 50 ml, and the electrolyte flow rate is 30 ml · min-1.
(2) Constant current charging and discharging: The charging and discharging current densities are 40, 60, 80, and 100 mA · cm-2, respectively. To reduce corrosion on graphite plates and carbon felt electrodes, the charging and discharging cut-off voltage range is set to 0.8 V-1.65 V (Shenzhen Newell Electronics Co., Ltd., CT-4008-5V6A).
(3) Self discharge test: Use OCV to evaluate the degree of self discharge of VRB. Charge the battery with a constant current at a current density of 60 mA · cm-2 to a state of charge of 75%, and then set it for a long time with a lower voltage limit of 0.8 V. The recorded idle time is the self discharge time.
(4) Cyclic performance test: Set the voltage range to 1.65 V-0.8 V and conduct 100 cycles of charging and discharging tests at a current density of 80 mA · cm-2. Evaluate the stability of the charging and discharging process through the efficiency change and capacity retention rate of the battery. [6]

(1) For self discharge testing, a single battery with Nafion 115 as the exchange membrane takes approximately 41 hours.
(2) For cycle performance testing: The efficiency of a single battery fluctuates only within a small range during 100 cycles, without significant degradation.
(3) For the cyclic discharge capacity, the capacity retention rate of a single battery with Nafion 115 as the exchange membrane is 67.2%.

(1) Parameters: In a single battery, two graphite felt pieces have a size of 30 mm x 30 mm x 2.2 mm. Two graphite bipolar plates and two copper plates together serve as the current collector, and all components are clamped by two carbon steel plates with bolts. The electrolyte for the positive and negative electrodes is 25 mL of 1.65 M VO2+/V3+(VO2+/V3+=1:1) in a 3 M H2SO4 solution, with a circulating flow rate of 40 mL · min-1.
(2) Cyclic stability test: The current density range is 100-500 mA · cm-2, and long-term cycling tests are conducted at a fixed current density. (Shenzhen Xinweier Electronics Co., Ltd., CT-3008-5V6A) [1].

(1) For self discharge testing, a single battery with Nafion 212 as the exchange membrane takes approximately 19.5 hours.
(2) For the discharge capacity after 100 cycles, the capacity retention rate of a single battery with Nafion 212 as the exchange membrane is 26.9%.

Laboratory Small Module

(1) Parameters: Electrolyte volume 180 mL, flow rate 160 mL/min; The electrical connection is two series and two parallel (series x parallel=2 x 2);
(2) Charging and discharging test: The charging and discharging current during constant current charging and discharging is 5.6A (100 mA/cm2), and the charging and discharging voltage range is 2.2 V-3.3 V (Shenzhen Newell Electronics Co., Ltd., CT-4008-5V10A) [5].

Under different arrangements of internal resistance batteries, the charging capacities are 1.79Ah and 1.56Ah, respectively.

Fuel cell stack

(1) Parameters: Electrolyte volume 160 L (32 kW stack), flow rate 5 m3/h; Number of monomers 60; (2) Charging and discharging test: The charging process adopts a stepped current method, and the discharging process adopts a constant power method. Firstly, the initial current of 405 A is used to charge the stack to a voltage of 96 V, and then the current is reduced to 155 A to continue charging until the voltage rises again to 96 V, and the charging is cut off; Discharge at a constant power of 32 kW to a voltage of 66 V, with discharge cut-off (Jiangsu Jinfan Power Technology Co., Ltd., KC-XCF08) [5].

Energy storage module

(1) Parameters: Electrolyte volume 8 m3 (250 kW energy storage module), flow rate 40 m3/h; The number of stack assemblies is 8; The electrical connection of the fuel cell stack is four series and two parallel (series x parallel=4 x 2);
(2) Charging and discharging test: The charging process adopts a two-stage method of constant power and constant voltage. The discharging process adopts a constant power method. Firstly, the module is charged to a voltage of 375 V with an initial power of 250 kW, and then the constant voltage of 375 V continues to charge until the module power drops to 150 kW, and the charging is cut off; Discharge at a constant power of 250 kW to a module voltage of 264 V, with discharge cut-off (Rongxin Power Electronics Co., Ltd., RXSV-T-160/250) [5].

The charging capacity varies significantly among different stack arrangements, with a maximum of 1491 Ah and a minimum of 1341 Ah, with a difference of nearly 10%.