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 the National Technical Committee on Flow Battery in Energy Industry of Standardization Administration of China (NEA/TC 23).
This standard is formulated for the first time.
Ion conductive membrane for vanadium flow battery - Test method
1 Scope
This standard specifies the sampling method and general conditions of ion conductive membrane for vanadium flow battery, and the test methods of membrane thickness uniformity, moisture content, dimensional change rate, tensile performance, conductivity, membrane area resistance, ion selectivity coefficient, oxidation resistance, etc.
This standard is applicable to various types of ion conductive membranes for vanadium flow battery.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
GB/T 601-2002 Chemical reagent - Preparations of reference titration solutions
GB/T 1040.3 Plastics - Determination of tensile properties - Part 3: Test conditions for films and sheets
GB/T 6672 Plastics film and sheeting - Determination of thickness by mechanical scanning
GB/T 20103 Technical terms for membrane separation
GB/T 29840-2013 Vanadium flow battery - Terminology
3 Terms and definitions
For the purposes of this standard, the terms and definitions given in GB/T 29840-2013 and GB/T 20103 and the following apply.
3.1
ion conductive membrane
membrane that separates the positive and negative electrolytes and selectively conducts ions
Note 1: Both ion exchange membrane and porous ion conductive membrane belong to ion conductive membrane, and the mechanisms of conducting ions are ion exchange mechanism and sieving mechanism respectively.
Note 2: It is revised from Definition 2.2 in GB/T 29840-2013.
3.2
ion exchange membrane
ion conductive membrane with ion exchange group, which may selectively permeate ions
3.3
porous ion conductive membrane
ion conductive membrane for sieving and conducting hydrogen ions and vanadium ions by nano-aperture
3.4
membrane resistance
resistance in the membrane thickness direction at given temperature and solution composition
Note: The unit of membrane resistance is Ω.
3.5
effective area
geometric area of ion conductive membrane realizing ion conduction, perpendicular to current direction
3.6
membrane area resistance
product of membrane resistance and the effective area of membrane during determination
Note: The unit of membrane area resistance is Ω·cm2.
3.7
membrane conductivity
capability of membrane to pass ions, which is equal to the ratio of membrane thickness to membrane area resistance
Note: The unit of membrane conductivity is S/cm.
3.8
ion diffusion coefficient
flux of given ion passing through an ion conductive membrane under given conditions
Note: The unit of diffusion coefficient is cm2/s.
3.9
ion permeation selectivity
characteristic of selective permeation of different ions by ion conductive membrane, which is equal to the ratio of ion diffusion coefficients of different ions determined under given conditions
3.10
bursting strength
measured maximum pressure intensity when continuously pressurizing the sample by introducing liquid or air until it busts
Note: The unit of bursting strength is MPa.
4 Sampling methods and general conditions
Samples are randomly selected from the same batch or different batches.
Unless otherwise specified, the test shall be carried out in the environment specified in this standard. Ion conductive membranes with special environmental requirements shall be determined according to the requirements of the tested materials or through negotiation between the supplier and the demander.
The test environmental conditions in this standard are as follows:
——temperature: 25±5℃;
——relative humidity: 5%~95%.
Each test shall be conducted for at least 3 times (to ensure that 3 effective values are obtained).
5 Measurement methods
5.1 Sample requirements
Sampling shall be conducted according to the requirements of Clause 4. Visual inspection is adopted, and an optical box shall be provided if necessary; in this case, the ion conductive membrane shall be free of folds, apparent defects and damage. At least 3 samples are randomly selected from the same batch of ion conductive membranes for test.
5.2 Requirements for instrument precision
The instruments used hereof shall meet the following precision requirements:
——thickness gauge, used to measure the thickness of ion conductive membrane, with a precision of not less than 0.1μm;
——length gauge, used to measure the length and width of ion conductive membrane, with a precision of not less than 0.1mm;
——ordinary oven, with a temperature control precision of not less than 1℃;
——analytical balance, with a precision of not lower than 0.1mg;
——thermostat, with a temperature control precision of not less than 0.5℃;
——pH meter, with a precision of not lower than 0.01 grade.
——UV-visible spectrophotometer, with a photometric accuracy of not less than 0.5%T.
5.3 Thickness uniformity
5.3.1 Test method
Test the membrane thickness by reference to the method in GB/T 6672, Express the thickness uniformity of a sample by the average thickness, the difference between the maximum thickness and the minimum thickness (i.e. the maximum deviation) and the average thickness deviation. Specific test requirements are as follows:
Take a membrane sample with an effective area of at least 10cm×10cm. Measure the thickness of at least 9 uniformly distributed points at four corners and middle part of the sample, and keep the distance from the sample edge to be more than 2.5mm.
5.3.2 Data processing
Express the thickness uniformity of ion conductive membrane by average thickness, maximum thickness deviation and average thickness deviation.
a) The average thickness is calculated using Equation (1):
(1)
Where,
d——the average thickness of membrane, μm;
di——the measured thickness of membrane at a certain point, i=1, 2, 3, …n, μm;
n——the number of data measuring points.
b) The maximum deviation, i.e., the difference between the maximum and minimum values, is calculated using Equation (2):
△d=dmax-dmin (2)
Where,
△d——the maximum deviation, i.e., the difference between the maximum thickness and the minimum thickness of membrane, μm;
dmax——the maximum thickness of membrane, μm;
dmin——the minimum thickness of membrane, μm.
c) The average thickness deviation is calculated using Equation (3):
(3)
Where,
△dave——the average thickness deviation of membrane, μm;
di——the measured thickness of membrane at a certain point, i=1, 2, 3, … n, μm;
d——the average thickness of membrane, μm.
The average thickness d, maximum thickness deviation △d and average thickness deviation △dave are calculated respectively. Take three samples as a group and calculate the average as the test result.
5.4 Moisture content
5.4.1 Reagents
Measuring reagents include:
——deionized water: with a conductivity of less than 10μS/cm at 25℃;
——1mol/L sodium hydroxide solution;
——1mol/L sulfuric acid aqueous solution;
——3mol/L sulfuric acid aqueous solution.
The solution shall be prepared according to the relevant detailed rules given in GB/T 601-2002, 4.3.
5.4.2 Test method
Pretreat ion conductive membrane (area not less than 10cm×10cm) according to the specific method in Annex A, and then test according to the following steps:
a) take out the sample membrane from deionized water, absorb the moisture on the membrane surface with absorbent paper, quickly put it into a weighing bottle with constant weight, weigh the mass with an analytical balance, record the mass as m1, and seal it immediately;
b) unseal the weighing bottle, dry it in an ordinary oven at 100~105℃ for 1h, and then weigh again until the mass difference between two adjacent weighings is less than 1mg;
c) take out the sample and put it in the dryer to cool it to room temperature, and weigh it with the analytical balance. After the reading is stable, record the mass as m2.
5.4.3 Data processing
The moisture content of ion conductive membrane is calculated using Equation (4):
(4)
Where,
Cw——the moisture content of ion conductive membrane, %;
m1——the mass of ion conductive membrane after absorbing surface moisture and before drying, mg;
m2——the mass of ion conductive membrane after drying, mg.
5.5 Dimensional change rate
5.5.1 Test method
Conduct the test at a relative humidity of (50±10)%.
Test the dimensional change rate of membrane according to the following steps:
a) put the sample membrane in the test environment for 24h;
b) thickness measurement: measure the thickness according to 5.3.2 to obtain the average membrane thickness doz;
c) length and width measurement: take another 10cm×20cm rectangular sample membrane, mark x and y in the length and width directions of the membrane, and measure the distance between the marks as lox and loy;
d) pretreat the above two sample membranes according to the method in Annex A;
e) take the pretreated sample membrane out, measure the thickness of the four corners and the middle part, and take the average value thereof as dwz;
f) take the pretreated sample membrane out, and measure the length and width in the same marking direction as that before pretreatment, wherein the distance between marks is lwx and lwy.
Foreword i
1 Scope
2 Normative references
3 Terms and definitions
4 Sampling methods and general conditions
5 Measurement methods
Annex A (Informative) Pretreatment method of ion conductive membrane
Annex B (Informative) Test method of bursting strength
Annex C (Informative) Test preparation method of ion permeation selectivity coefficient
Annex D (Informative) Derivation method of equation for ion apparent diffusion coefficient
Annex E (Informative) Calculation examples for selectivity coefficient of ion conductive membrane for H+ and VO2+
