Codeofchina.com is in charge of this English translation. In case of any doubt about the English translation, the Chinese original shall be considered authoritative.
This standard is developed in accordance with the rules given in GB/T 1.1-2009 Directives for standardization — Part 1: Structure and drafting of standards.
This standard was proposed by China Electrical Equipment Industry Association.
This standard is under the jurisdiction of National Technical Committee on Flow Battery of Standardization Administration of China (NEA/TC 23).
Vanadium flow battery — test method for electrode
1 Scope
This standard specifies the general requirements and test methods of electrodes for vanadium flow batteries, mainly including thickness uniformity test, resistivity test, mechanical property test, electrochemical activity test, apparent density test, surface density test and flow resistance test.
This standard is applicable to the test methods of electrodes of vanadium flow batteries.
2 Normative references
The following referenced document is indispensable for the application of this document. For dated reference, only the edition cited applies. For undated reference, the latest edition of the referenced documents (including any amendments) applies.
GB/T 29840-2013 Vanadium flow battery —Terminology
3 Terms, definitions and symbols
3.1
Terms and definitions
For the purposes of this document, the terms and definitions given in GB/T 29840-2013 and the following apply. For the convenience of application, some terms and definitions in GB/T 29840 are listed repeatedly as follows.
3.1.1
electrode
place where electrochemical reaction takes place
[GB/T 29840-2013, Definition 2.6]
3.1.2
electrochemical activity
capacity of generating electrochemical reactions on the electrode surface
3.1.3
electrode area
geometric area of electrode where electrochemical reaction takes place
[GB/T 29840-2013, Definition 2.12]
3.2 Symbols
See Table 1 for symbols, their meanings and units used in this standard.
Table 1 Symbols and their meanings and the units used in this standard
Symbol Meaning Unit
Average thickness of the sample under certain pressure mm
di Measured values of sample thickness at a certain point under certain pressure mm
σ Thickness standard deviation of sample under certain pressure mm
δ Dispersion coefficient, reflecting the degree of dispersion on unit average
ρt Through-plane resistivity of sample mΩ·cm
Rm The measured resistance value of the sample, i.e., the sum of the through-plane resistance of the sample per unit area, the body resistance of two measured electrodes, the contact resistance between sample and two measured electrodes mΩ
Rc The sum of the body resistance of the two measured electrodes and the contact resistance between the sample and two measured electrodes mΩ·cm2
γ Compression ratio of sample under certain pressure ％
lp Thickness of the sample reduced by compression under certain pressure mm
d0 The initial thickness of the sample, that is, the thickness when the pressure approaches zero mm
Δη Absolute value of bimodal electrode potential difference of redox couple mV
η1 Electrode potential value of oxidation peak mV
η2 Electrode potential value of reduction peak mV
θ Bimodal height ratio of redox couple
iop Peak current of oxidation peak mA
irp Peak current of reduction peak mA
ρ0 Apparent density of the sample g/cm3
m Mass of sample g
V0 Apparent volume of the sample cm3
ρs Surface density of the sample g/cm2
S Contact area between sample and the two measured electrodes cm2
A Electrode area of the sample cm2
Δp Net flow resistance MPa
Δp1 Pressure difference between the inlet and outlet of liquid flowing through sample clamp MPa
Δp2 Pressure difference between the inlet and outlet of the clamp through which the liquid flows without sample. MPa
4 General requirements
Test ambient conditions:
— Temperature: 25°C ± 5°C;
— Humidity of air: 5% ~ 95%.
The test that has special requirements for the ambient conditions, the test environment shall be determined by the supplier and the purchaser through negotiation.
5 Test preparation
5.1 Sample preparation
Sample preparation shall be as follows:
— Samples shall be randomly taken from the same batch or different batches;
— Samples shall be smooth and undamaged;
— Soak the sample in acetone for at least 1 h, and then dry it in an oven at 120°C for more than 2 h for later use.
5.2 Test instrument and appliance
The instruments and appliances used in this standard and their precision requirements are as follows:
— Thickness gauge: used to measure the thickness of the sample, the precision shall not be less than 10 μm;
— Calipers: used to test the length and width of the sample, the precision shall not be less than 0.1 mm;
— Electronic balance: used to test the mass of samples, the precision shall not be less than 0.1 mg;
— Low resistance tester: used to test the through-plane resistance of the sample, the precision shall not be less than 0.01 mΩ.
— Mechanical property tester: used to test the mechanical strength of the sample, with the precision of ±0.5% of its full scale;
— Electrochemical tester: used to test the activity of the sample, with current accuracy not less than 1 mA and voltage accuracy not less than 1 mV;
— Precision pressure controller: the pressure accuracy is ±2% of its full scale;
— Stainless steel clamp;
— Plate moulding machine;
— Electrochemical test cell.
6 Thickness uniformity test
6.1 Sample preparation
The sample dimension shall be 100 cm2 (10 cm × 10 cm), the sample quantity shall not less than 3 (3 r.m.s values are guaranteed), and the shape and dimension of the sample may also be determined through negotiation between the supplier and the purchaser.
6.2 Test methods
The test of the electrode thickness shall be carried out according to the following steps:
a) The zero point of the thickness gauge shall be calibrated before each measurement, and it shall be rechecked after each measurement of the sample;
b) Gently lower the measuring head of the thickness gauge to avoid deformation and damage of the sample and conduct the test;
c) Maintain a certain pressure between the measuring head of the thickness gauge and the sample, and record the thickness value;
Note: The recommended pressure is 1.8 × 10-4 Pa. The test pressure may also refer to ISO 5084 and GB/T 3820, or be determined through consultation between the supplier and the purchaser.
d) There shall be no less than 9 test points for each sample, and the test points shall be evenly distributed, as shown in Figure 1.
Foreword i
1 Scope
2 Normative reference
3 Terms, definitions and symbols
4 General requirements
5 Test preparation
6 Thickness uniformity test
7 Resistivity test
8 Mechanical property test
9 Electrochemical activity test
10 Apparent density test
11 Surface density test
12 Flow resistance test
13 Test preparation and test report
Annex A (Informative) Test for the sum of the body resistance of the two measured electrode and the contact resistance between the sample and the two measured electrodes
Annex B (Informative) Flow resistance test
Annex C (Informative) Test preparation
Annex D (Informative) Test report
Bibliography
