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GB/T 41704-2022 (GB/T41704-2022, GBT 41704-2022, GBT41704-2022)
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GB/T 41704-2022: PDF in English (GBT 41704-2022)

GB/T 41704-2022
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 77.160
CCS H 16
Test Methods of Cathode Materials for Lithium Ion Battery
- Determination of Magnetic Impurities Content and
Residual Alkali Content
ISSUED ON: OCTOBER 12, 2022
IMPLEMENTED ON: FEBRUARY 1, 2023
Issued by: State Administration for Market Regulation;
Standardization Administration of the People’s Republic of China.
Table of Contents
Foreword ... 3 
Introduction ... 4 
1 Scope ... 5 
2 Normative References ... 5 
3 Terms and Definitions ... 5 
4 Determination of Magnetic Impurities Content ... 6 
5 Determination of Residual Alkali Content ... 13 
6 Test Report ... 17 
Test Methods of Cathode Materials for Lithium Ion Battery
- Determination of Magnetic Impurities Content and
Residual Alkali Content
WARNING---the personnel adopting this document shall have practical experience with
formal laboratory work. This document does not address all possible safety issues. It is
the user’s responsibility to take appropriate safety and health measures.
1 Scope
This document specifies the determination method for magnetic impurities content and residual
alkali content in the cathode materials for lithium ion battery.
This document is applicable to the determination of magnetic impurities content and residual
alkali content in the cathode materials for lithium ion battery. The determination range of the
magnetic impurities content is  1 g/kg; the determination range of residual alkali content
(mass fraction) is 0.001% ~ 2.500%.
2 Normative References
The contents of the following documents constitute indispensable clauses of this document
through the normative references in this text. In terms of references with a specified date, only
versions with a specified date are applicable to this document. In terms of references without a
specified date, the latest version (including all the modifications) is applicable to this document.
GB/T 601 Chemical Reagent - Preparations of Standard Volumetric Solutions
GB/T 6682 Water for Analytical Laboratory Use - Specification and Test Methods
GB/T 8170 Rules of Rounding off for Numerical Values & Expression and Judgement of
Limiting Values
3 Terms and Definitions
The following terms and definitions are applicable to this document.
3.1 Magnetic Impurities
Magnetic impurities refer to impurities in the cathode materials for lithium ion battery that can
be adsorbed by the magnetic bar with a magnetic induction intensity of not less than 0.5 T
(5,000 Gauss).
NOTE: magnetic impurities are usually simple elements or compounds of iron, chromium, nickel
and zinc.
3.2 Large Particle Magnetic Impurities
Large particle magnetic impurities refer to magnetic impurities with a diameter of not less than
10 m under the scanning electron microscope.
3.3 Residual Alkali
Residual alkali refers to alkaline substances attached to the surface of the particles of the
cathode materials for lithium ion battery.
NOTE: residual alkali mainly exists in the form of lithium hydroxide and lithium carbonate. After
the test, all the amounts are expressed in terms of lithium carbonate as residual alkali and
in terms of lithium content as residual lithium.
4 Determination of Magnetic Impurities Content
4.1 Inductively Coupled Plasma Atomic Emission Spectrometry
4.1.1 Principle
In a clean environment free of magnetic impurities, use a magnetic bar to adsorb and enrich the
magnetic impurities in the cathode material. Use water to wash the enriched magnetic bar, so
as to remove the cathode material attached to the surface; use acid solution to dissolve the
magnetic impurities on the magnetic bar. Adopt the inductively coupled plasma atomic
emission spectrometer, at the recommended wavelength of each element, determine its
emission intensity. In accordance with the standard working curve, calculate the mass fraction
of each element.
4.1.2 Reagents or materials
Unless it is otherwise specified, all reagents used in this Method are of guaranteed purity and
Grade-1 water specified in GB/T 6682.
4.1.2.1 Nitric acid ( = 1.42 g/mL).
4.1.2.2 Aqua regia (VHNO3 : VHCl = 1 : 3).
4.1.2.3 Iron standard stock solution (100 g/mL), prepared from high-purity metals or
compounds, or adopt a certified single-element standard stock solution.
4.1.2.4 Chromium standard stock solution (100 g/mL), prepared from high-purity metals or
compounds, or adopt a certified single-element standard stock solution.
4.1.5.4.3 Transfer the magnetic bar (4.1.3.3) to a clean 200 mL beaker; add water, until the
magnetic bar (4.1.3.3) is immersed; prevent the water from directly rushing to the surface of
the magnetic bar (4.1.3.3). Place the magnet (4.1.3.4) on the outer bottom of the beaker; push
the magnetic bar (4.1.3.3) in the adsorption jar back and forth for cleaning, until the impurities
on the surface of the magnetic bar (4.1.3.3) have no obvious visual changes.
4.1.5.4.4 There are two optional modes for dissolution:
a) Add 10 mL of aqua regia (4.1.2.2) to the beaker containing the magnetic bar (4.1.3.3);
add water, until the magnetic bar (4.1.3.3) is immersed; use a watch glass to cover it,
then, place it on an electric hot plate to heat for 30 min;
b) Put the magnetic bar (4.1.3.3) into a 100 mL colorimetric tube; add 10 mL of aqua
regia (4.1.2.2), then, add water, until the magnetic bar (4.1.3.3) is immersed; use a
stopper to cover it. Then, place it in 95 C water bath to heat for 30 min.
4.1.5.4.5 Remove the beaker or colorimetric tube. After cooling, transfer all the solution to a 50
mL volumetric flask. Use a small amount of water to rinse the magnetic bar (4.1.3.3); repeat
for 3 times. Then, transfer all the washing solution to a volumetric flask and use water to reach
a constant volume; record the volume as V.
4.1.5.5 Preparation of standard series solutions
4.1.5.5.1 Iron, chromium, nickel and zinc standard series solution: respectively transfer-take 0
mL, 2.50 mL, 5.00 mL and 25.00 mL of the mixed standard solution B (4.1.2.9); 10.00 mL and
20.00 mL of the mixed standard solution A (4.1.2.8) in six 100 mL volumetric flasks. Add 3 mL
of nitric acid (4.1.2.1); use water to dilute to the scale and mix it well.
4.1.5.5.2 Lithium standard series solution: respectively transfer-take 0 mL, 2.50 mL, 5.00 mL
and 25.00 mL of lithium standard solution B (4.1.2.11); 10.00 mL and 20.00 mL of lithium
standard solution A (4.1.2.10) in six 100 mL volumetric flasks. Add 3 mL of nitric acid (4.1.2.1);
use water to dilute to the scale and mix it well.
4.1.5.6 Determination
4.1.5.6.1 When the main element of the sample does not contain iron or nickel, adopt the
inductively coupled plasma atomic emission spectrometer (4.1.3.6), at the selected wavelength
of each element, use the iron, chromium, nickel and zinc standard series solution (4.1.5.5.1) to
determine the emission spectrum intensity of iron, chromium, nickel and zinc. Respectively
take the mass concentration of the tested element as the x-coordinate and the emission intensity
as the y-coordinate; the computer automatically draws the working curve. Determine the
emission spectrum intensity of the sample solution and blank solution; the computer
automatically calculates the mass concentration of the tested element through the working curve.
4.1.5.6.2 When the main element of the sample contains iron, adopt the inductively coupled
plasma atomic emission spectrometer (4.1.3.6), at the selected wavelength of each element, use
the iron, chromium, nickel and zinc standard series solution (4.1.5.5.1) to determine the
to collect the magnetic impurities. After drying, collect the magnetic impurities on the carbon
conductive tape. On a scanning electron microscope - energy disperse spectrometer, measure
the number of large particle magnetic impurities.
4.2.2 Reagents or materials
Unless it is otherwise specified, the water used in this Method is Grade-1 water that complies
with the stipulations in GB/T 6682.
4.2.2.1 Plastic spoon, plastic tweezers, ceramic scissors.
4.2.2.2 Sealing film.
4.2.2.3 Filter film: cellulose acetate with a pore size of 0.45 m.
4.2.2.4 Carbon conductive tape.
4.2.3 Instruments and equipment
4.2.3.1 Environmental iron removing rod: magnetic induction intensity  0.5 T (5,000 Gauss),
wrapped with plastic wrap.
4.2.3.2 Magnetic ring sleeve: magnetic induction intensity 0.5 T ( 5,000 Gauss)
4.2.3.3 Plastic jar: 500 mL.
4.2.3.4 Ball mill.
4.2.3.5 Oven.
4.2.3.6 Vacuum filtration device: the diameter of the sand core is 20 mm.
4.2.3.7 Scanning electron microscope - energy disperse spectrometer.
4.2.3.8 Petri dish with a lid.
4.2.4 Sample
The particle of the sample shall be not greater than 0.154 mm.
4.2.5 Test procedures
4.2.5.1 Use the environmental iron removing rod (4.2.3.1) to carry out meticulous iron removal
treatment on all instruments and supplies used in the test. Use water to wash the test supplies
for 2 or 3 times.
4.2.5.2 Weigh-take 200.0 g of the sample, accurate to 0.1 g. Place the sample in a 500 mL plastic
jar (4.2.3.3); add water to the shoulder of the jar; tighten the lid, then, use the sealing film to
seal it. Manually mix the water and the sample, so that there is no precipitation at the bottom of
the jar. Put the jar into the magnetic ring sleeve (4.2.3.2); use the heat sealing film to seal it.
Place it on the ball mill (4.2.3.4); after mixing it for 30 min, remove it.
4.2.5.3 After removing it, with the magnetic ring sleeve (4.2.3.2), pour out the water and
material in the plastic jar (4.2.3.3); use water to repeatedly rinse the wall of the jar for more
than 5 times, so as to ensure that there is no precipitation of sample at the bottom of the jar.
4.2.5.4 After assembling the filter film (4.2.2.3) and vacuum filtration device (4.2.3.6), remove
the magnetic ring sleeve (4.2.3.2); use water to rinse the wall of the plastic jar (4.2.3.3) for more
than 3 times. Pour the washing solution into the vacuum filtration device (4.2.3.6); use water to
rinse the wall of the suction and filtration cup for more than 3 times.
4.2.5.5 After the suction and filtration is completed, use plastic tweezers (4.2.2.1) to take out
the filter film (4.2.2.3), put it into the petri dish (4.2.3.8) and use a lid to cover it. Dry it, or use
the oven (4.2.3.5) to perform low-temperature drying.
4.2.5.6 After drying is completed, cut the carbon conductive tape (4.2.2.4) into a size of 5 mm
 6 mm; use the plastic tweezers (4.2.2.1) to clamp the properly cut carbon conductive tape;
thoroughly paste the impurities on the filter film (4.2.2.3) to avoid omission.
4.2.5.7 Fix the carbon conductive tape for collecting impurities on the sample stage. Put it into
the scanning electron microscope - energy disperse spectrometer (4.2.3.7); switch to the
backscattered electron mode; adjust the angle and focal length. From top to bottom, in a zigzag
path, move the selected area and confirm the impurities. Conduct the energy spectrum analysis
on the particles suspected of impurities and record the number.
4.2.6 Processing of test data
Count the number of large particle magnetic impurities. Respectively count the number of iron
and stainless steel (iron-chromium-nickel).
5 Determination of Residual Alkali Content
5.1 Principle
Use a certain volume of water to dissolve the residual alkali on the surface of the sample with
a certain mass. After filtration, take the filtrate; use the standard titration solution of
hydrochloric acid to perform titration. Through the potential jump in the reaction process,
determine the titration end point; calculate its content; through conversion, obtain the residual
alkali content and residual lithium content.
5.2 Reagents or Materials
Unless it is otherwise specified, all reagents used in this Method are of guaranteed purity and
Grade-1 water specified in GB/T 6682.
5.2.1 Standard titration solution of hydrochloric acid: 0.1 mol/L. Adopt a nationally recognized
V2---the volume of hydrochloric acid corresponding to the equivalence point of pH approximate
to 4.5, expressed in (mL);
V1---the volume of hydrochloric acid corresponding to the equivalence point of pH approximate
to 8.5, expressed in (mL);
m2---the mass of added water, expressed in (g);
73.89---the relative molecular mass of lithium carbonate, expressed in (g/mol);
m1---the mass of the weighed sample, expressed in (g);
m3---the mass of the weighed filtrate, expressed in (g).
5.6.2 The residual lithium hydroxide content in the sample, in mass fraction wLiOH, shall be
calculated in accordance with Formula (5):
Where,
wLiOH---the mass fraction of the residual lithium hydroxide in the sample;
c---the concentration of hydrochloric acid, expressed in (mol/L);
V2---the volume of hydrochloric acid corresponding to the equivalence point of pH approximate
to 4.5, expressed in (mL);
V1---the volume of hydrochloric acid corresponding to the equivalence point of pH approximate
to 8.5, expressed in (mL);
m2---the mass of added water, expressed in (g);
23.95---the relative molecular mass of lithium hydroxide, expressed in (g/mol);
m1---the mass of the weighed sample, expressed in (g);
m3---the mass of the weighed filtrate, expressed in (g).
5.6.3 The residual alkali content in the sample, in mass fraction wra, shall be calculated in
accordance with Formula (6):
Where,
wra---the mass fraction of the residual alkali in the sample;
1.54---the conversion factor, the ratio of the relative molecular mass of lithium carbonate to
......
 
Source: Above contents are excerpted from the PDF -- translated/reviewed by: www.chinesestandard.net / Wayne Zheng et al.