Cellulose-assisted electrodeposition of zinc for morphological control in battery metal recycling

Cellulose nanofibers (CNF) are demonstrated as an effective tool for converting electrodeposits into more easily detachable dendritic deposits useful in recycling zinc ion batteries via electrowinning. The incorporation of CNF at concentrations ranging from 0.01 to 0.5 g/L revealed a progressively extensive formation of a nacre-like dendritic zinc structure that did not form in its absence. Increasing CNF-concentrations from 0.01 to 0.5 g/L resulted in more extensive dendritic structures forming. The explanation to the observed phenomenon is the CNFs ability to strongly interact with the metal ions, i.e., restricting the mobility of the ions towards the electrowinning electrode. At the highest concentration of CNF (0.5 g/L), in combination with the lowest current density (150 A/m2), the electrodeposition was limited to the extent that formed deposits were almost non-existent. The electrodeposition in the presence of CNF was further evaluated at different temperatures: 20, 40 and 60°C. The dendritic formation was increasingly suppressed with increasing temperatures, and at a temperature of 60°C, the electrodeposited morphologies could not be differentiated from the morphologies formed in the absence of the cellulose. The results stemmed from a greater mobility of the metal ions at elevated temperatures, while at the same time suggests an inability of the CNF to strongly associate the metal ions at the elevated temperatures. High-pressure blasted titanium electrodes were used a reference material for accurate comparisons, and electron microscopy (FE-SEM) and X-ray diffraction were used to characterize the zinc morphologies and crystallite sizes, respectively. The article reports the first investigation on how dispersions of highly crystalline cellulose nanofibers can be used as a renewable and functional additive during the recycling of battery metal ions. The metal-ion/cellulose interactions may also allow for structural control in electrodeposition for other applications. Correction in DOI 10.1039/D3MA90041JQC 20220503