Recently, many studies have been conducted on the materialization of spent batteries. In conventional cases, lithium is recovered from an acidic solution through the leaching and separation of valuable metals; however, it is difficult to remove impurities because lithium is recovered in the last step. Cathode active materials of lithium-ion batteries comprise oxides with lithium, such as LiNi_xCo_yMn_zO₂ and LiCoO₂. Thus, lithium should be converted into a compound that can be leached in deionized water for selective lithium leaching. Recent studies on the leaching and recovery of Li₂CO₃ through a carbon reduction reaction show low economic efficiency, due to the solubility of Li₂CO₃ at room temperature being as low as 13 g/L. This paper proposes a method of roasting after nitric acid deposition for selective lithium leaching and recovery to LiNO₃. Based on experiments involving the varying of the amount of nitric acid, roasting temperature, and solid–liquid ratio, optimal values were found to be dipping in 10 M HNO₃ 2 mL/g, roasting at 275 °C, and deionized water with a solid–liquid ratio of 10 mL/g, respectively. Over 80% Li leaching was possible under these conditions. IC analysis confirmed that the purity was 97% lithium nitrate.

A complete recycling process for the cathode material of spent lithium-ion batteries is demonstrated with a simple two-step process comprised of one-pot cobalt recovery to nanostructured materials and single step synthesis of LiCoO₂. For the facile and efficient recovery of cobalt, we employ malic acid as a leaching agent and oxalic acid as a precipitating agent, resulting in nanostructured cobalt oxalate. X-ray diffraction and Fourier transform infrared spectroscopy (FT-IR) analysis clearly show that cobalt species are simultaneously leached and precipitated as cobalt oxalate with a high yield of 99.28%, and this material can then be used as a reactant for the synthesis of LiCoO₂ for use as a cathode material. In addition to its advantages in simplifying the process, the proposed method allows for not only enhancing the efficiency of cobalt recovery, but also enabling reaction without a reducing agent, H₂O₂. Through successive single-step reaction of the obtained cobalt oxalate without any purification process, LiCoO₂ is also successfully synthesized. The effect of the annealing temperature during synthesis on the nanostructure and charge–discharge properties is also investigated. Half-cell tests with recycled LiCoO₂ exhibit a high discharge capacity (131 mA·h·g⁻¹) and 93% charge–discharge efficiency.

In this study, a fabrication method of tapered microstructures with high aspect ratio was proposed by deep X-ray lithography. Tapered microstructures with several hundred micrometers and high aspect ratio are demanded owing to the high applicability in the fields of various microelectromechanical systems (MEMS) such as optical components and microfluidic channels. However, as the pattern and gap size were downsized to smaller micro-scale with higher aspect ratio over 5, microstructures were easily deformed or clustered together due to capillary force during the drying process. Here, we describe a novel manufacturing process of tapered microstructures with high aspect ratio. To selectively block the deep X-ray irradiation, an X-ray mask was prepared via conventional ultraviolet (UV) lithography. A double X-ray exposure process with and without X-ray mask was applied to impose a two-step dose distribution on a photoresist. For the clear removal of the exposed region, the product was developed in the downward direction, which encourages a gravity-induced pulling force as well as a convective transport of the developer. After a drying process with the surface additive, tapered microstructures were successfully fabricated with a pattern size of 130 μm, gap size of 40 μm, and aspect ratio over 7.

Cyanex 301 and 5,8-diethyl-7-hydroxyldodecane-6-oxime (LIX 63) can selectively extract Pd(II) over Pt(IV) from concentrated hydrochloric acid solutions. Therefore, solvent extraction experiments have been performed by extractant mixtures containing either Cyanex 301 or LIX 63, and the extraction behavior of Pd(II) was compared. Among the mixtures of Cyanex 301, the highest synergistic enhancement coefficient was achieved by mixing Cyanex 301 and trioctylphosphine oxide (TOPO). However, it was very difficult to strip the Pd(II) from the loaded mixture phase. Among the mixtures of LIX 63, the mixture of LIX 63 and alamine 336/TOPO enhanced the extraction of Pd(II). Although the synergistic coefficient by Cyanex 301 + TOPO was higher than that by LIX 63 + Alamine 336, the Pd(II) in the loaded mixture phase of LIX 63 and alamine 336 was easily stripped by thiourea.