GB/T 42161-2022 English PDF (GBT42161-2022)

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GB/T 42161-2022: Electrochemical performance test of lithium iron phosphate -- Test method for the initial discharge specific capacity and the initial efficiency
GB/T 42161-2022
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 77.160
CCS H 21
Electrochemical performance test of lithium iron phosphate
- Test method for the initial discharge specific capacity and
the initial efficiency
ISSUED ON: DECEMBER 30, 2022
IMPLEMENTED ON: APRIL 01, 2023
Issued by: State Administration for Market Regulation;
Standardization Administration of the People’s Republic of China.
Table of Contents
Foreword ... 3
1 Scope ... 4
2 Normative references ... 4
3 Terms and definitions ... 4
4 Test conditions ... 4
5 Reagents and materials ... 4
6 Instruments and equipment ... 5
7 Test steps ... 6
8 Test data processing ... 10
9 Allowable difference ... 11
10 Test report ... 12
Electrochemical performance test of lithium iron phosphate
- Test method for the initial discharge specific capacity and
the initial efficiency
1 Scope
This document describes the test method for the initial discharge specific capacity and
the initial charge-discharge efficiency of lithium iron phosphate, i.e., the cathode
material for lithium-ion batteries.
This document applies to the test for the initial discharge specific capacity and the initial
charge-discharge efficiency of lithium iron phosphate, i.e., the cathode material for
lithium-ion batteries.
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 20252-2014 Lithium cobalt oxide
3 Terms and definitions
For the purpose of this document, the terms and definitions defined in GB/T 20252-
2014 apply.
4 Test conditions
Unless otherwise specified, each test step should be carried out at a relative humidity
not greater than 40.0 % and an ambient temperature of 20 ℃ ~ 30 ℃. The rolling
process should be carried out at a relative humidity not greater than 30.0 % and an
ambient temperature not greater than 30 °C.
5 Reagents and materials
5.1 Lithium iron phosphate: the particle size characteristic value D50 is 0.5 μm ~ 8.0 μm,
and the specific surface area is 6 m2/g ~ 30 m2/g.
5.2 Conductive agent: conductive carbon material.
5.3 Polyvinylidene fluoride (PVDF): battery grade, the weight average molecular
weight is not less than 5 × 105, and the moisture (mass fraction) is not greater than
0.10 %.
5.4 N-methylpyrrolidone (NMP): battery grade, the purity is not less than 99.9 %, and
the moisture (mass fraction) is not greater than 0.02 %.
5.5 Aluminum foil: the thickness is 8 μm ~ 20 μm.
5.6 Ethanol: analytical reagent.
5.7 Lithium-ion battery separator: polyolefin porous membrane, the porosity is 35.0 %
~ 60.0 %, the air permeability is 100 s/100 mL ~ 500 s/100 mL, the average pore size
is not greater than 1.0 μm, the diameter is 16.0 mm ~ 18.0 m, and the thickness is 9.0
μm ~ 32.0 μm.
5.8 Metal lithium sheet: the diameter is 12.0 mm ~ 16.0 mm, and the thickness is 0.40
mm ~ 0.80 mm.
5.9 Battery standard structural parts: model CR2016, CR2025 or CR2032, including
positive electrode case, negative electrode case, gasket, and spring support piece (or
nickel foam sheet).
5.10 Lithium-ion battery electrolyte: lithium-ion battery electrolyte composed of
lithium hexafluorophosphate (LiPF6) and mixed carbonate-based organic solvents
[ethylene carbonate (EC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC),
etc.], the moisture is not greater than 0.002 %, the free acid (HF) is not greater than
0.005 %, and the conductivity (25 ℃) is not less than 7.0 mS/cm.
5.11 Dust-free paper.
5.12 Nitrogen (or argon): the purity (volume fraction) is not less than 99.99 %.
6 Instruments and equipment
6.1 Vacuum oven: 0 ℃ ~ 200 ℃, and the temperature deviation is ± 2 ℃.
6.2 Oven.
6.3 Electronic balance: the accuracy is 0.0001 g.
6.4 Electronic balance: the accuracy is 0.00001 g.
6.5 Dispersing mixer or pulp mixer.
6.6 Small coating machine for lithium-ion battery electrode sheets.
7.2.1 Weighing
Calculate the lithium iron phosphate, conductive agent, and PVDF pretreated in 7.1
according to the mass fractions of 80 % ~ 97 %, 1 % ~ 10 %, and 2 % ~ 10 %
respectively, and weigh them with an electronic balance (6.3). Calculate the amount of
NMP (5.4) according to the design requirements of solid content (mass fraction) of 25 %
~ 65 %, and weigh with an electronic balance (6.3).
7.2.2 Pulping
The pulping process is as follows:
a) Add the weighed NMP into the mixing tank of a dispersing mixer or pulp mixer
(6.5); gradually add the weighed PVDF; disperse and stir until completely
dissolved; to prepare a transparent glue, of which the mass fraction of PVDF is
2 % ~ 10 %;
b) add the weighed conductive agent to the above transparent glue; vacuum, disperse
and stir evenly;
c) gradually add the weighed lithium iron phosphate in portions; vacuum, disperse
and stir evenly;
d) add another NMP according to the designed solid content, to control the slurry
viscosity at 3000 mPa • s ~ 20000 mPa • s; vacuum, disperse and stir evenly;
complete the pulping process.
NOTE: The solid content in this document is the ratio of the mass of the cathode active material
lithium iron phosphate, conductive agent and PVDF to the mass of the cathode slurry.
7.2.3 Coating
Use a small coating machine for lithium-ion battery electrode sheets (6.6) to evenly
coat the cathode slurry mixed in 7.2.2 on one side (matte side) of the aluminum foil
(5.5) or directly on the carbon-coated aluminum foil, and the thickness of wet slurry
coating is 100 μm ~ 300 μm. After the coating is completed, transfer the positive
electrode sheet to a vacuum oven (6.1) for drying. During drying, vacuum or circulate
in a nitrogen (or argon) (5.12) atmosphere, the baking temperature is controlled at 90 ℃
~ 150 ℃, and the baking time is 0.5 h ~ 18 h.
7.2.4 Preparation of positive electrode sheets
Take the electrode sheets that have been dried in 7.2.3 and meet the processability
requirements, use a punching machine (6.7) to punch out positive electrode sheets of
appropriate size; use an electronic balance (6.4) and a desktop digital thickness gauge
(6.8) to measure the mass mc and thickness dc of the positive electrode sheets,
respectively.
vacuum or circulate in a nitrogen (or argon) (5.12) atmosphere. The baking temperature
is controlled at 90 ℃ ~ 120 ℃, and the baking time is 12 h ~ 18 h. Cool down and then
transfer them to an inert atmosphere (or argon) glove box (6.10) for storage.
7.3 Battery assembly
Battery assembly shall be performed in an inert atmosphere (or argon) glove box (6.10).
To assemble a button battery, please refer to the following steps:
a) Place a negative electrode case flatly on a horizontal table with the opening
upward;
b) use an insulated tweezers (6.11) to pick up a metal lithium sheet (5.8) and place
it into the negative electrode case, so that it is in plane contact with the negative
electrode case and lies flat in the center of the negative electrode case;
c) use an insulated tweezers (6.11) to pick up a lithium-ion battery separator (5.7)
and make it completely covers the metal lithium sheet and lies in the center;
d) use an injector (6.12) to inject 50 μL ~ 200 μL of lithium-ion battery electrolyte
(5.10) into the negative electrode case;
e) use an insulated tweezers (6.11) to pick...