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 Aug 2022
Accepted
23 Oct 2022
First published
04 Nov 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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