1 Scope
This document specifies the determination method of magnetic impurities content and residual alkali content in cathode materials for lithium ion battery.
This document is applicable to the determination of magnetic impurities content and residual alkali content in cathode materials for lithium ion battery. The determination range of magnetic impurities content is ≥1μg/kg, and that of residual alkali content (mass fraction) is 0.001%~2.500%.
2 Normative references
The following documents contain requirements which, through reference in this text, constitute provisions of this document. For dated references, only the edition cited applies. For undated references, the latest edition (including any amendments) applies.
GB/T 601 Chemical reagent - Preparations of reference titration 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
For the purposes of this document, the following terms and definitions apply.
3.1
magnetic impurities
impurities in cathode materials for lithium ion battery that can be adsorbed by magnetic rods with magnetic induction intensity of not less than 0.5T (5,000 Gauss)
Note: Magnetic impurities usually refer to elementary substances or compounds of iron, chromium, nickel and zinc.
3.2
large particle magnetic impurities
magnetic impurities with a diameter of not less than 10μm under the scanning electron microscope
3.3
residual alkali
alkaline substance attached to the surface of cathode materials for lithium ion battery
Note: The residual alkali mainly exists in the form of lithium hydroxide and lithium carbonate. The residual alkali is expressed by lithium carbonate content after test, and the residual lithium is expressed by lithium content.
4 Determination of magnetic impurities content
4.1 Inductively coupled plasma atomic emission spectrometry
4.1.1 Principle
In a clean environment without magnetic impurities, a magnetic rod is used to adsorb and gather the magnetic impurities in cathode materials. The magnetic rod is washed with water to remove the cathode material attached to the surface, and the magnetic impurities are dissolved with acid solution. The emission intensity of each element is determined at the recommended wavelength by inductively coupled plasma atomic emission spectrometer, and then the mass fraction of each element is calculated according to the standard working curve.
4.1.2 Reagents or materials
Unless otherwise specified, guaranteed reagents and Grade 1 water specified in GB/T 6682 are adopted for the purpose of this method.
4.1.2.1 Nitric acid (ρ=1.42g/mL).
4.1.2.2 Aqua regia ().
4.1.2.3 Iron standard stock solution (100μg/mL), prepared from high purity metals or compounds, or using certified single element standard stock solution.
4.1.2.4 Chromium standard stock solution (100μg/mL), prepared from high purity metals or compounds, or using certified single element standard stock solution.
4.1.2.5 Nickel standard stock solution (100μg/mL), prepared from high purity metals or compounds, or using certified single element standard stock solution.
4.1.2.6 Zinc standard stock solution (100μg/mL), prepared from high purity metals or compounds, or using certified single element standard stock solution.
4.1.2.7 Lithium standard stock solution (100μg/mL), prepared from high purity metals or compounds, or using certified single element standard stock solution.
4.1.2.8 Mixed standard solution A: respectively pipette 10.00mL iron standard stock solution (4.1.2.3), chromium standard stock solution (4.1.2.4), nickel standard stock solution (4.1.2.5) and zinc standard stock solution (4.1.2.6) into a 100mL volumetric flask, add 3mL nitric acid (4.1.2.1), dilute it to the scale with water, mix well and immediately transfer into a dry plastic bottle. This solution has a content of iron, chromium, nickel and zinc of 10μg/mL respectively.
4.1.2.9 Mixed standard solution B: pipette 20.00mL mixed standard solution A (4.1.2.8) into a 100mL volumetric flask, add 3mL nitric acid (4.1.2.1), dilute it to the scale with water, mix well and immediately transfer into a dry plastic bottle. This solution has a content of iron, chromium, nickel and zinc of 2μg/mL respectively.
4.1.2.10 Lithium standard solution A: pipette 10.00mL lithium standard stock solution (4.1.2.7) into a 100mL volumetric flask, add 3mL nitric acid (4.1.2.1), dilute it to the scale with water, mix well and immediately transfer into a dry plastic bottle. This solution has a content of lithium of 10μg/mL.
4.1.2.11 Lithium standard solution B: pipette 20.00mL lithium standard solution A (4.1.2.10) into a 100mL volumetric flask, add 3mL nitric acid (4.1.2.1), dilute it to the scale with water, mix well and immediately transfer into a dry plastic bottle. This solution has a content of lithium of 2μg/mL.
4.1.3 Instruments and apparatus
4.1.3.1 De-ironing rod: with magnetic induction intensity of not less than 0.5T (5,000 Gauss), covered with plastic wrap.
4.1.3.2 Wide-mouth plastic bottle: 500mL.
4.1.3.3 Magnetic rod: with magnetic induction intensity of not less than 0.5T (5,000 Gauss), a size of 17mm×52mm, sealed with PTFE jacket.
4.1.3.4 Magnet: covered with plastic wrap.
4.1.3.5 Ball mill.
Foreword i
Introduction ii
1 Scope
2 Normative references
3 Terms and definitions
4 Determination of magnetic impurities content
5 Determination of residual alkali content
6 Test report
