Issue 2, 2023

Introducing lignin as a binder material for the aqueous production of NMC111 cathodes for Li-ion batteries

Abstract

By enabling water-based cathode processing, the energy-intensive N-methyl-2-pyrrolidone (NMP) recovery step can be eliminated, reducing the cost and environmental impact of LIBs. Aqueous processing of high capacity Ni-containing LiNixMn1−xyCoyO2 (NMC) cathodes is problematic due to lithium-ion(Li+) leaching, corrosion of the aluminum (Al) current collector, and the lack of aqueous soluble bio-derived binders. The present study investigates the potential of substituting and fully replacing the commonly used polyvinylidene fluoride (PVDF) and carboxymethyl cellulose (CMC) binders with abundant, bio-derived kraft lignin. This paper gives a holistic overview of the optimal conditions when employing these binders. For the first time, we demonstrate that NMC111 cathodes of comparable specific capacities to NMP/PVDF-based ones over 100 cycles or at high C-rates (5C) can be formulated in water using lignin or CMC/lignin as binder materials. Cyclic voltammetry (CV) revealed that kraft lignin undergoes a redox reaction with the electrolyte between 2.8 and 4.5 V, which diminishes upon subsequent cycles. Differential scanning calorimetry (DSC) revealed that lignin is thermally stable up to 152 °C. Rheology measurements showed that replacing NMP with water allows for a solvent reduction. The cathodes fabricated using an aqueous slurry should be dried at 50 °C, as extensive surface cracks detected using scanning electron microscopy (SEM) diminish. Li+ leaching from NMC111 and NaOH species from kraft lignin caused an increase in pH during aqueous slurry fabrication. A carbon-coated Al foil (C-Al) prevented Al corrosion and increased the lignin cathode's mechanical strength revealing lignin's exceptional binding abilities to carbon. The electrolyte wettability decreased for calendered lignin-containing cathodes with low porosity and a large carbon black/lignin matrix.

Graphical abstract: Introducing lignin as a binder material for the aqueous production of NMC111 cathodes for Li-ion batteries

Supplementary files

Article information

Article type
Paper
Submitted
01 8 2022
Accepted
23 10 2022
First published
04 11 2022
This article is Open Access
Creative Commons BY license

Mater. Adv., 2023,4, 523-541

Introducing lignin as a binder material for the aqueous production of NMC111 cathodes for Li-ion batteries

S. N. Bryntesen, I. Tolstorebrov, A. M. Svensson, P. Shearing, J. J. Lamb and O. S. Burheim, Mater. Adv., 2023, 4, 523 DOI: 10.1039/D2MA00850E

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