A pH Buffer Additive for Aqueous Processing of Spinel and Layered Li‐Ion Positive Electrodes
(2025) ChemElectroChem — (2025)
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ChemElectroChem-2025-Maffre-ApHBufferAdditiveforAqueousProcessingofSpinelandLayeredLiIonPositive.pdf
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- Aqueous processing of cathodes offers a lower-cost, greener alternative to poly(vinylidene fluoride)/N-methyl-2-pyrrolidone routes, but contact with water elevates slurry pH and drives metal leaching, causing Al current-collector corrosion and electrode voids. Strong acids (e.g., H3PO4) can curb corrosion yet often disrupt rheology, increase leaching, and weaken adhesion. Herein, lithium dihydrogen phosphate (LiH2PO4) is introduced as a lithium-containing pH buffer (H2PO4−/HPO42− near-neutral pH) for water-based processing of LiNi0.6Co0.2Mn0.2O2 (NMC622) and Li[Ni0.5Mn1.45Al0.05]O4 (LNMO). Slurry pH evolution and transition-metal dissolution under H3PO4 versus LiH2PO4 dosing are quantified and showing that LiH2PO4 more effectively stabilizes pH and suppresses leaching. Electrodes cast with LiH2PO4 additives display reduced Al pitting, crack-free coatings with good adhesion, and improved cycling stability. X-ray photoelectron spectroscopy detects surface phosphorus species consistent with a thin phosphate passivation layer. These results establish LiH2PO4 as a simple, scalable additive that enables robust aqueous processing of high-voltage cathodes without the side effects associated with strong acids.
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Maffre, M., Liu, X., Markowski, R., Pal, S., Tie, D., Melinte, A., Zaulet, A., Buga, M., & Vlad, A. (2025). A pH Buffer Additive for Aqueous Processing of Spinel and Layered Li‐Ion Positive Electrodes. ChemElectroChem. Published. https://doi.org/10.1002/celc.202500327 (Original work published 2025)