Effect of aluminum on the potentiometric determination of fluorine in spent lithium-ion battery black mass

S. Malik; A. Tanash; S. Uskov; A. Tazhibayeva; T. Kan; F. Malchik

doi:10.15328/cb2026_166

Authors

S. Malik Al-Farabi Kazakh National University, Laboratory of Electrochemical Production Technologies, Center of Physical-Chemical Methods of Research and Analysis, Almaty, Kazakhstan https://orcid.org/0009-0000-0662-6950 (unauthenticated)
A. Tanash Al-Farabi Kazakh National University, Laboratory of Electrochemical Production Technologies, Center of Physical-Chemical Methods of Research and Analysis, Almaty, Kazakhstan https://orcid.org/0009-0007-9268-7063 (unauthenticated)
S. Uskov Al-Farabi Kazakh National University, Laboratory of Electrochemical Production Technologies, Center of Physical-Chemical Methods of Research and Analysis, Almaty, Kazakhstan https://orcid.org/0009-0001-3776-8991 (unauthenticated)
A. Tazhibayeva Al-Farabi Kazakh National University, Laboratory of Electrochemical Production Technologies, Center of Physical-Chemical Methods of Research and Analysis, Almaty, Kazakhstan https://orcid.org/0000-0002-4680-5846 (unauthenticated)
T. Kan Al-Farabi Kazakh National University, Laboratory of Electrochemical Production Technologies, Center of Physical-Chemical Methods of Research and Analysis, Almaty, Kazakhstan https://orcid.org/0000-0002-1945-8471 (unauthenticated)
F. Malchik Al-Farabi Kazakh National University, Laboratory of Electrochemical Production Technologies, Center of Physical-Chemical Methods of Research and Analysis, Almaty, Kazakhstan https://orcid.org/0000-0001-6381-0738 (unauthenticated)

DOI:

https://doi.org/10.15328/cb2026_166

Keywords:

lithium-ion batteries, black mass, fluorine, fluoride-selective electrode, direct potentiometry, alkaline fusion, PVDF, LiPF6, recycling

Abstract

Fluorine is a significant component of the black mass of spent lithium-ion batteries (LIBs), occurring in residual electrolyte salts, their transformation products, fluorine-containing additives, and the polyvinylidene fluoride (PVDF) binder. The differing chemical nature of these components complicates quantitative fluorine determination in industrial black mass. In this work we examined the feasibility of separately assessing the water-extractable and residual, water-non-extractable fluorine fractions by direct potentiometry with a fluoride-selective electrode. Industrial black mass containing a mixture of cathode materials predominantly of the LiNi1−x−yCoxAlyO2 (NCA) type was treated by water leaching, acid leaching, and direct alkaline fusion in a NaOH–KOH mixture. The water-extractable fraction amounted to (2.33 ± 0.06) wt.%, whereas acid leaching and direct alkaline fusion of the as-received material both underestimated the fluorine content, indicating a matrix effect of aluminium during sample preparation. On a model sample of pure PVDF, alkaline fusion efficiently converted covalently bound fluorine into a form accessible to potentiometric determination. The critical factor proved to be the transfer of Al into solution followed by its possible precipitation upon pH adjustment, which partially removes fluoride from the dissolved, measurable form. The water-extractable fraction can therefore be determined with good repeatability, whereas quantification of the water-non-extractable fraction after alkaline decomposition is substantially compromised by Al-induced fluoride loss during neutralisation. This effect of aluminium – present in real black mass both within the cathode material and as metallic impurities – must be taken into account when developing analytical protocols for fluorine determination in LIB black mass.

Author Biographies

S. Malik, Al-Farabi Kazakh National University, Laboratory of Electrochemical Production Technologies, Center of Physical-Chemical Methods of Research and Analysis, Almaty, Kazakhstan

PhD-student, Junior Researcher at al-Farabi Kazakh National University, Almaty, Kazakhstan; seilbekmalik@gmail.com
A. Tanash, Al-Farabi Kazakh National University, Laboratory of Electrochemical Production Technologies, Center of Physical-Chemical Methods of Research and Analysis, Almaty, Kazakhstan

bachelor student at al-Farabi Kazakh National University, Almaty, Kazakhstan; tanashaltynai@gmail.com
S. Uskov, Al-Farabi Kazakh National University, Laboratory of Electrochemical Production Technologies, Center of Physical-Chemical Methods of Research and Analysis, Almaty, Kazakhstan

bachelor student at al-Farabi Kazakh National University, Almaty, Kazakhstan; uskov_spiridon@live.kaznu.kz
A. Tazhibayeva, Al-Farabi Kazakh National University, Laboratory of Electrochemical Production Technologies, Center of Physical-Chemical Methods of Research and Analysis, Almaty, Kazakhstan

PhD-student, Junior Researcher at al-Farabi Kazakh National University, Almaty, Kazakhstan; tazhibayeva.aigerim1995@gmail.com
T. Kan, Al-Farabi Kazakh National University, Laboratory of Electrochemical Production Technologies, Center of Physical-Chemical Methods of Research and Analysis, Almaty, Kazakhstan

MSc, Junior Researcher at al-Farabi Kazakh National University, Almaty, Kazakhstan; tatyana.qan@gmail.com
F. Malchik, Al-Farabi Kazakh National University, Laboratory of Electrochemical Production Technologies, Center of Physical-Chemical Methods of Research and Analysis, Almaty, Kazakhstan

PhD, Assoc. Professor, Head of the Laboratory of Electrochemical Production Technologies, al-Farabi Kazakh National University, Almaty, Kazakhstan; frodo-007@mail.ru

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