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NB/T 42082-2016: Vanadium flow battery-test method for electrode
NB/T 42082-2016
NB
ENERGY INDUSTRY STANDARD OF
THE PEOPLE’S REPUBLIC OF CHINA
ICS 27.070
K 82
Filing No.: 55691-2016
Vanadium flow battery - Test method for electrode
ISSUED ON: AUGUST 16, 2016
IMPLEMENTED ON: DECEMBER 01, 2016
Issued by: National Energy Administration
Table of Contents
Foreword ... 3
1 Scope ... 4
2 Normative references ... 4
3 Terms, definitions, symbols... 4
4 General requirements ... 5
5 Test preparation ... 6
6 Thickness uniformity test ... 7
7 Resistivity test ... 9
8 Mechanical properties test ... 10
9 Electrochemical activity test ... 12
10 Apparent density test ... 13
11 Surface density test ... 14
12 Flow resistance test ... 15
13 Test preparation and test report ... 15
Appendix A (Informative) Test of the total resistance of the two measuring electrodes
and the contact resistance between the sample and the two measuring electrodes ... 16
Appendix B (Informative) Flow resistance test ... 17
Appendix C (Informative) Test preparation ... 19
Appendix D (Informative) Test report ... 20
References ... 22
Vanadium flow battery - Test method for electrode
1 Scope
This standard specifies the general requirements and test methods for electrodes for
vanadium flow batteries, mainly including thickness uniformity test, resistivity test,
mechanical property test, electrochemical activity test, apparent density test, surface
density test, flow resistance test.
This standard applies to the test methods for vanadium flow battery electrodes.
2 Normative references
The following documents are essential for the application of this document. For all
dated references, only the dated version applies to this document. For all undated
references, the latest version (including all amendments) applies to this document.
GB/T 29840-2013 Vanadium flow battery - Terminology
3 Terms, definitions, symbols
3.1 Terms and definitions
The terms and definitions defined in GB/T 29840-2013, as well as the following terms
and definitions, apply to this document. For ease of use, some terms and definitions in
GB/T 29840 are repeated below.
3.1.1
Electrode
The place where electrochemical reaction occurs.
[GB/T 29840-2013 Definition 2.6]
3.1.2
Electrochemical activity
The ability of the electrode surface to undergo electrochemical reaction.
3.1.3
- Temperature: 25 °C ± 5 °C;
- Air humidity: 5% ~ 95%.
For tests with special requirements for environmental conditions, the test environment
conditions shall be determined by negotiation between the supplier and the buyer.
5 Test preparation
5.1 Sample preparation
Sample preparation is as follows:
- Samples are randomly selected from the same batch or different batches;
- Samples shall be flat and undamaged;
- Soak the samples in acetone for at least 1 hour; then dry them in an oven at 120 °C
for more than 2 hours and set aside.
5.2 Test instruments and apparatus
The instruments and apparatus used in this standard and their accuracy requirements
are as follows:
- Thickness gauge: Used to measure the thickness of the sample, which has an
accuracy of not less than 10 μm;
- Caliper: Used to test the length and width of the sample, which has an accuracy of
not less than 0.1 mm;
- Electronic balance: Used to test the mass of the sample, which has an accuracy of
not less than 0.1 mg;
- Low resistance tester: Used to test the vertical resistance of the sample, which has
an accuracy of not less than 0.01 mΩ;
- Mechanical properties testing machine: Used to test the mechanical strength of the
sample, which has an accuracy of ±0.5% of its full scale;
- Electrochemical tester: Used to test the activity of the sample, which has an
accuracy of not less than 1 mA and a voltage accuracy of not less than 1 mV;
- Precision pressure controller: Pressure accuracy is ±2% of its full scale;
- Stainless steel fixture;
- Flat plate forming machine;
Where:
- The average thickness of the sample under a certain pressure, in millimeters
(mm);
di - The thickness measurement value of a certain point of the sample under a certain
pressure, in millimeters (mm);
n - The number of measurement data points.
6.3.2 The thickness standard deviation is calculated by formula (2).
Where:
σ - The thickness standard deviation of the sample under a certain pressure, in
millimeters (mm);
di - The thickness measurement value of a certain point of the sample under a certain
pressure, in millimeters (mm);
- The average thickness of the sample under a certain pressure, in millimeters
(mm);
n - The number of measurement data points.
6.3.3 The thickness dispersion coefficient is calculated by formula (3).
Where:
δ - Coefficient of dispersion, reflecting the degree of dispersion on the unit mean;
σ - Standard deviation of the thickness of the sample under a certain pressure, in
millimeters (mm);
The sample shall not be larger than the cross-sectional size of the flat fixture of the
mechanical properties tester. The recommended sample is round, which has a diameter
of 50 mm. The number of samples shall not be less than 3 (to ensure that 3 valid values
are obtained).
8.2 Compression rate test
8.2.1 Measure the initial average thickness d0 of the sample when the pressure is close
to zero according to the method in Chapter 6.
8.2.2 Install the sample between two smooth flat fixtures; fix the position of the lower
clamp; calibrate the corresponding position of the upper clamp when the pressure is
close to zero as the displacement origin; the positive direction of the displacement
movement is calibrated as vertically downward.
8.2.3 During the test, apply pressure to the outside of the two fixtures. For every
increase of 0.01 MPa, record the displacement value lp corresponding to the downward
movement of the upper fixture, until the measured displacement value is less than or
equal to 5% of the displacement value measured at the previous pressure, it is
considered to have reached the minimum value and the test is stopped.
Note: The recommended measurement pressure range is less than 1.0 MPa.
8.3 Data processing
Calculate the compression rate of the sample under different pressures according to
formula (5).
Where:
γ - Compression rate of the sample under a certain pressure, in percentage (%);
lp - Thickness of the sample reduced by compression under a certain pressure, in
millimeters (mm);
d0 - Initial thickness of the sample, i.e. thickness when the pressure is close to zero,
in millimeters (mm).
Take 3 valid samples as a group and calculate the average value as the test result. Plot
the results calculated under different pressures into a compression rate-pressure curve.
9 Electrochemical activity test
9.1 Sample preparation
9.1.1 The sample size (effective area) is 1 cm2 (1 cm × 1 cm); the number of samples is
not less than 3 (to ensure 3 valid values). The sample shape and size can also be
determined by negotiation between the supplier and the buyer.
9.1.2 Place the sample in two hollow frames of the same size; the size of the hollow
part of the frame is 1 cm × 1 cm. Connect the sample to the gold-plated copper sheet,
to make a test electrode with airtight edges.
9.2 Test method
9.2.1 Positive electrode activity test process
9.2.1.1 Test the battery assembled with the sample using the test electrode as the
working electrode, the saturated calomel electrode (SCE) as the reference electrode, the
platinum sheet or platinum wire as the auxiliary electrode.
9.2.1.2 Use an electrochemical tester to scan the cyclic voltammetry curve of the sample.
The electrolyte is a solution containing 0.05 mol/L VO2+, 0.05 mol/L VO2+, 3 mol/L
H2SO4. The scan rate is 20 mV/s; the scan range is 0.2 V ~ 1.6 V (relative to the voltage
value of the saturated calomel electrode).
Note: The recommended amount of electrolyte is not less than 100 mL.
9.2.2 Negative electrode activity test process
9.2.2.1 Test the battery assembled with the sample using the test electrode as the
working electrode, the saturated calomel electrode (SCE) as the reference electrode, the
platinum sheet or platinum wire as the auxiliary electrode.
9.2.2.2 Use an electrochemical tester, to scan the cyclic voltammetry curve of the
sample. The electrolyte is a solution containing 0.05 mol/L V2+, 0.05 mol/L V3+, 3 mol/L
H2SO4. The scanning rate is 20 mV/s and the scanning range is -1.0 V ~ 0.2 V (relative
to the voltage value of the saturated calomel electrode).
Note 1: The test process must be carried out under the protection of an inert atmosphere.
Note 2: The recommended amount of electrolyte is not less than 100 mL.
9.3 Data processing
9.3.1 The double peak electrode potential difference of the redox couple is calculated
according to formula (6).
Appendix A
(Informative)
Test of the total resistance of the two measuring electrodes and the contact
resistance between the sample and the two measuring electrodes
The total resistance of the two measuring electrodes and the contact resistance between
the sample and the two electrodes can be calculated according to formula (A.1).
Where:
Rc - The sum of the body resistance of the two measuring electrodes and the contact
resistance between the sample and the two measuring electrodes, in milliohms
square centimeters (mΩ • cm2);
Rm1 - The measured value of the sample resistance when the thickness is , that is,
the sum of the vertical resistance of the sample per unit area, the body resistance of
the two measuring electrodes, the contact resistance between the sample and the two
measuring electrodes, in milliohms (mΩ);
- The average thickness of sample 1, in centimeters (cm);
Rm2 - The measured value of the sample resistance when the thickness is , that is,
the sum of the vertical resistance of the sample per unit area, the body resistance of
the two measuring electrodes, the contact resistance between the sample and the two
measuring electrodes, in milliohms (mΩ);
- The average thickness of sample 2, in centimeters (cm);
S - The contact area between the sample and the two measuring electrodes, in square
centimeters (cm2).
Note: Take at least 3 samples of different thicknesses for testing. For each sample thickness,
3 valid samples shall be taken as a group; the average value shall be calculated as the test
result under the corresponding thickness.
Appendix B
(Informative)
Flow resistance test
B.1 Sample preparation
B.1.1 The sample size is 100 cm2 (10 cm × 10 cm); the number of samples is not less
than 3 (to ensure 3 valid values). The sample shape and size can also be determined by
negotiation between the supplier and the buyer.
B.1.2 Place the sample in two hollow frames of the same size; the size of the hollow
part of the frame is 10 cm × 10 cm; make a test electrode with airtight edges.
B.2 Test method
B.2.1 Assemble the test electrode between a fixture with a sealant line and a liquid inlet
and outlet on one side; apply a certain pressure on the two fixtures, to ensure that there
is no leakage at the edge of the fixture, as shown in Figure B.1.
B.2.2 Inject liquid into the side with liquid inlet and outlet; measure the inlet and outlet
pressure difference of the liquid flowing through the fixture at a certain liquid inlet flow
rate and inlet pressure, recorded as Δp1.
B.2.3 Take out the test electrode; repeat B.2.1 and B.2.2; measure the inlet and outlet
pressure difference of the liquid flowing through the fixture, recorded as Δp2. Under
this condition, the difference between Δp1 and Δp2 is the net flow resistance of the liquid
flowing through the sample.
B.2.4 Gradually increase the applied inlet pressure; repeat B.2.2 and B.2.3 for each
increase of 0.1 MPa; record the net flow resistance value under different pressures.
Note: The recommended inlet pressure difference range is 0.05 MPa ~ 1.0 MPa.
B.2.5 Stop the test, when the change rate of the current measured sample net flow
resistance value and the net flow resistance value measured last time is no more than
5%.
Appendix D
(Informative)
Test report
D.1 Overview
Based on the test conducted, the test report shall provide enough correct, clear, objective
data for analysis and reference. There are three types of reports: summary, detailed,
complete. Each type of report shall contain the same title page and table of contents.
D.2 Report content
D.2.1 Title page
The title page shall introduce the following information:
a) National standard code;
b) Sample name, material composition, specifications;
c) Sample state conditioning and test standard environment;
d) Test machine model;
e) Results of each test and the average value of the results;
f) Test date and personnel.
The title page shall also include the following:
- Report number (optional);
- Type of report (summary, detailed, complete);
- Report author;
- Tester;
- Report date;
- Test site;
- Test name;
- Test date and time;
- Test application organization.
D.2.2 Table of contents
Each type of report shall provide a table of contents.
D.3 Report types
D.3.1 Summary report
The summary report shall include the following data:
- Purpose of the test;
- Test type, instruments and equipment;
- All test results;
- Uncertainties and certainties of each test result;
- Summary conclusions.
D.3.2 Detailed report
In addition to the contents of the summary report, the detailed report shall also include
the following data:
- Test operation method and test flow chart;
- Description of the arrangement, layout, operating conditions of the instruments and
equipment;
- Calibration of the instruments and equipment;
- Description of the test results in the form of graphs or tables;
- Discussion and analysis of the test results.
D.3.3 Complete report
In addition to the contents of the detailed report, the complete report shall also include
a copy of the original data.