ISO/DIS 12467-3:2025(en)

ISO TC 333/WG6

Secretariat: SAC

Date:2025-11-26

Chemical analysis of lithium composite oxides—Part 3: Determination of lithium carbonate and lithium hydroxide contents

© ISO 2026

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Contents

Foreword i

1. Scope 1

2. Normative Reference 1

3. Terms and Definitions 1

4. Principle 1

5. Reactions 1

6. Reagents and solutions 2

7. Apparatus 2

8. Preparation and calibration of standard titration solution and indicators 3

9. Sample 3

10. Procedure 3

11. Express of results 4

12. Precision 5

13. Test Report 5

Annex A (informative) Calculation of the residual alkali or residue lithium content 6

Foreword

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This document was prepared by Technical Committee [or Project Committee] ISO/TC [or ISO/PC]333, [Lithium].

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Lithium composite oxides—Part 3: Determination of lithium carbonate and lithium hydroxide contents—Potentiometric titration method

WARNING – The use of this document can involve hazardous materials, operations, and equipment. This document does not purport to address any safety problems associated with its use. It is the responsibility of the user of this document to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

This document describes an analytical procedure for the determination of lithium carbonate and lithium hydroxides content in lithium composite oxides, such as lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium iron phosphate, lithium manganese oxide and so on.

This document specifies a potentiometric titration method for the determination of lithium carbonate and hydroxide content in lithium composite oxides for lithium-ion batteries (LIBs). The method is applicable to lithium composite oxides for LIBs with a mass fraction of lithium carbonate contents in the range from 0,001 % to 1,500 % and lithium hydroxide contents in the range from 0,001 % to 1,000 %.

The following documents are referred to in the text in such a way that some or all of their content constitutes requirements 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.

ISO 1042, Laboratory glassware — One-mark volumetric flasks

ISO 3696, Water for analytical laboratory use — Specification and test methods

ISO 7819, Lithium — Vocabulary^[1]

ISO 23496, Determination of pH value — Reference buffer solutions for the calibration of pH measuring equipment

For the purposes of this document, the terms and definitions given in ISO 7819 apply.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

— ISO Online browsing platform: available at https://www.iso.org/obp

— IEC Electropedia: available at http://www.electropedia.org/

The residual lithium exists on the surface of the materials which can be dissolved in excessive water. By mixing the sample and excessive water, the solution will contain the lithium, carbonate and hydroxide ions. By titration method, we could determine the content of carbonate and hydroxide ions in the filtrated solution. In this standard, potentiometric titration method is adopted. The order of reaction with the acid solution is different for carbonate and hydroxide ions. By locating the potential jump of the solution, the content of carbonate and hydroxide can be calculated from the acid consumption of the two jump point.

The lithium carbonate and lithium hydroxide in the sample are allowed to dissolve in water and then filtered. When the filtrate is subjected to auto-potentiometric titration using a hydrochloric acid standard titration solution, the following reaction occurs:

LiOH+HCl→LiCl+H₂O

Li₂CO₃+HCl→LiHCO₃+LiCl

With the continuous addition of hydrochloric acid standard titration solution, all the lithium hydroxide will be transformed into LiCl and H₂O, and all the lithium carbonate will be transformed into LiHCO₃ and LiCl. At this stage, the pH value is about 8,5 ± 0,5, and the potential of the automatic potentiometric titrator electrode will reach a jump point Ep₁. Then continue to add the drop of hydrochloric acid standard titration solution, the following reaction occurs:

LiHCO₃+HCl→LiCl+CO₂↑+H₂O

Lithium bicarbonate will be completely transformed into LiCl, CO₂ and H₂O. At this stage, the pH value is about 4,5 ± 0,5, and the potential of the automatic potentiometric titrator electrode will reach another jump point Ep₂. By recording the potential jump point Ep1 and Ep₂ corresponding to the consumption of hydrochloric acid standard titration solution, lithium carbonate and lithium hydroxide content in the sample can be calculated respectively.

WARNING – Concentrated mineral acids (6.1) are corrosive, highly reactive and acid vapour is an irritant. Avoid contact with the skin or eyes, or inhalation of the vapour. Use suitable personal protective equipment (e.g., gloves, face shield or safety goggles, etc.) when working with concentrated or dilute acid. Handle open vessels containing concentrated acid in a fume hood. Do not add water to acid, as the reaction is violent. Small aliquots of acid shall be added slowly to larger volumes of water. The vapour pressure of acid is high; therefore beware of pressure build-up in stoppered flasks when preparing acid/water mixtures.

CAS 7647-01-0, specific gravity 1,19 g/ml.

CAS 7732-18-5, complying with Grade 2 as defined in ISO 3696.

CAS 497-19-8, reference grade, purity ≧99,9 % (mass fraction), used for HCl standardization.

CAS 77-86-1, reference grade, purity ≧99,88 % (mass fraction), used for HCl standardization.

Concentration of 0,1 mol/l (0,10 N), preferably obtained commercially with certificate of analysis.

Meet the requirements of ISO 23496.

Use volumetric flasks with graduation markings that conform to the requirements of ISO 1042, Class A.

Readable to the nearest 0,000 1 g.

Generally, propeller and magnetic stirrers are recommended. Magnetic stirrer will require a magnetic stirrer bar. Speed should be set to sufficient to ensure rapid mixing of the solution without vortexing around the electrode or dosing tips.

With pH glass acid-base electrode. The pH electrode of the potentiometric titrator shall be calibrated in accordance with ISO 23496 before titration. The potentiometer shall have 2,0 mV sensitivity, covering the range −1,0 V to +1,0 V.

Operate in air, and temperature range and control shall meet the drying requirements which is 110 ± 5 °C.

Readable to the nearest 0,001 g.

It is advised to use certified commercially available titrants in the form of ready-for-use solutions whose concentration has been standardized by the manufacturer. Standard titration solutions with a calibration certificate or self-prepared and calibrated solutions shall be used, and the calibrated concentration before use shall prevail.

If no certified HCl solution is available, the following procedure is recommended.

Add 8,3 ml HCl (6.1) to a clean 1,000 ml volumetric flask (7.1) and dilute it to volume with water (6.2) at (20 ± 2) °C, or apply volumetric correction if performed under different temperature condition.

Both anhydrous sodium carbonate (6.3) and hydroxymethyl aminomethane (6.4) are suitable for the calibration of HCl standard titration solution, the following procedure is recommended.

Anhydrous sodium carbonate (6.3) is dried in a furnace (7.2) at 270 °C to 300 °C for 2 h and allowed cool down to room temperature in a desiccator (7.3).

Approximately 0,1 g of dried anhydrous sodium carbonate (6.3) is weighed out into the titration beaker (7.4) with an accuracy of 0,1 mg and dissolved in approx. 50 mL water (6.2). After adding water (6.2) the dissolution must be stirred for at least 1 hour to ensure homogeneity. Record the mass of anhydrous sodium carbonate (6.3) as m.

Place the titration beaker (7.4) on the titration stand. Place the combined glass pH electrode and the dispensing tube tip into the beaker (7.4). The diaphragm of the pH electrode and the dispensing tube tip shall be immersed. Stir the solution with a magnetic stirrer (7.6).

Titrate the solution with HCl standard reference solution using the potentiometric titrator (7.7). The end point is detected automatically until second equivalent point is observed. The pH range of the second equivalent point should be in the range from 3,5 to 5,5. Record the volume of second equivalent point as V.

Carry out the analysis three times. The relative range of molarity of the HCl standard reference solution consumed for calibration should not exceed 1,0 % .

Carry out a blank test using water (6.2), omitting the solid sodium carbonate. The titration should be performed until the second equivalent point. Record the volume as V₀.

The actual concentration of HCl standard reference solution is calculated using the following equation (1):

(1)

where

C is the actual concentration of the HCl standard titration solution, in mol/l;

m is the mass of anhydrous sodium carbonate reference material, in g;

52,99 is the molar mass with (1/2 Na₂CO₃) as the basic unit, in g/mol;

V is the volume of HCl standard solution consumed by titrated sodium carbonate, in ml;

V0 is the volume of the HCl standard reference solution consumed by titration blank solution, in ml.

Prior to drying, the test sample shall be stored in a sealed and moisture-free environment at ambient laboratory conditions. 20 g of test sample is dried in an oven (7.8) at 11 °C ± 5 °C for 2 hours. And cool down to room temperature in a desiccator (7.3).

Weigh 5,0 g of test portion using an analytical balance (7.5), accurate to 0,000 1 g, and record the mass as m₁.

Carry out the determinations in triplicate at least, as far as possible under repeatability conditions, on each sample.

Place part of the test portion (9.2) in a 150 ml glass beaker (7.4), add 100 g of water at a temperature of 25 °C ± 2 °C, If performed under different conditions, the temperature shall be recorded and appropriate compensation or correction shall be applied based on the instrument specifications, and record the water mass as m₂. After sealing with preservative film or covering with a lid, place it on the magnetic stirrer (7.6), mix it at 800 r/min for 5 min. Use the vacuum filtration device (7.9) to separate the sample from water immediately after mixing.

Transfer the liquid filtrate into a 250 ml beaker, weigh using a balance (7.10) and seal it with a preservative film, and record the mass of the filtrate as m₃. Place the filtrate in the potentiometric titrator (7.7) and titrate with 0,1 mol/L HCl standard titration solution (6.4). Record the volume of HCl standard titration solution (6.4) consumed at two equivalence points Ep₁ and Ep₂ as V₁ and V₂, respectively.

Carry out a blank test (see 10.2) until the second equivalent point Ep₂. Record the volume as V*.

The mass fraction of lithium carbonate in the test portion, wLi₂CO₃, expressed as a percentage, is given by the following equation (2):

(2)

where

C is the actual concentration of HCl standard titration solution, in mol/L;

V₂ is the volume of HCl standard titration solution consumed before the second equivalence point, in ml;

V₁ is the volume of HCl standard titration solution consumed before the first equivalence point, in ml;

V* is the volume of HCl standard titration solution consumed in the blank titration, in ml;

m₂ is the mass of the water, in g;

73,89 is the molar mass of lithium carbonate, in g/mol;

m₁ is the mass of the test portion, in g;

m₃ is the mass of the filtrate, in g.

The mass fraction of lithium hydroxide in the test portion (wLiOH), expressed as a percentage, is given by the following equation (3):

(3)

where

C is the concentration of HCl standard titration solution, in mol/L;

V₁ is the volume of HCl standard titration solution consumed before the first equivalence point, in ml;

V₂ is the volume of HCl standard titration solution consumed before the second equivalence point, in ml;

V* is the volume of HCl standard titration solution consumed in the blank titration, in ml;

m₂ is the mass of the water, in g;

23,95 is the molar mass of lithium hydroxide, in g/mol;

m₁ is the mass of the test portion, in g;

m₃ is the mass of the filtrate, in g.

Calculate the results to the third decimal place.

NOTE The content of lithium carbonate and lithium hydroxide is usually converted into residual alkali content or residual lithium content, and the calculation of residual alkali content and residual lithium content is shown in Annex A.

The Repeatability limit of this analytical method is ±0,05 %. The calculation of residual alkali content and residual lithium content is shown in Annex A

The test report shall include the following information:

a) identification and characteristics of the sample;

b) identification of the laboratory carrying out;

c) the receival date of the sample;

d) the date and method of sampling, if known;

e) the mean values of the analyte content of the sample as results; The results of the analyte content of the sample are shown as a percentage to the third decimal places.

f) method used by reference to this document;

g) issue date of test report;

h) results and their expression;

i) any deviations from the procedure specified;

j) any unusual features, events or anomaly observed during the test;

k) identification of the laboratory manager and operator.

1. 
   (informative)
   
   Calculation of the residual alkali or residual lithium content
   1. Calculation of the residual alkali content

The mass fraction of residual alkali in the test portion (w_ra), expressed as a percentage, is given by equation (A.1):

(A.1)

where

1,543 is the conversion coefficient, ratio of relative molecular weight of lithium carbonate to 2 times of relative molecular weight of lithium hydroxide;

w_LiOH is mass fraction of the lithium hydroxide, in %;

w_Li2CO3 is mass fraction of the lithium carbonate, in %.

• 1. Calculation of the residual lithium content

The mass fraction of residual lithium in the test portion (w_rl), expressed as a percentage, is given by equation (A.2) :

(A.2)

where

0,188 is the conversion coefficient, ratio of 2 times of relative molecular weight of lithium to relative molecular weight of lithium carbonate;

w_ra is the mass fraction of the residual alkali content, in %.

Calculate the results to the third decimal place.

1. 
   (informative)
   
   Results of interlaboratory test

An interlaboratory test was undertaken between fifteen collaborating laboratories. The target samples consisted of NMC and LFP, and both were provided by China. The original data are shown in Table B.1 and B.2.

Table B.1 — Analytical results of the interlaboratory test (NMC)<Tbl_--></Tbl_-->

Table B.2 — Analytical results of the interlaboratory test (LFP)<Tbl_--></Tbl_-->

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