Xianmin Mai

Improved extraction of cobalt and lithium by reductive acid from spent lithium-ion batteries via mechanical activation process

Cobalt (Co) and lithium (Li) were extracted from pure LiCoO2 powders and actual cathode material powders from the spent lithium-ion batteries (LIBs) after l-ascorbic acid dissolution via a mechanical activation process. The influences of activation time and rotation speed on the leaching were discussed. The mechanism of the improved leaching yield was proposed based on the characterization analysis including X-ray diffraction, scanning electron microscope, BET-specific surface area and particle size analyzer. The reduced particle size, increased specific surface area of activated samples, destroyed crystal structure and amorphous state of LiCoO2 contributed to the improved leaching efficiencies of Co and Li. With the activated process, about 99% Co and 100% Li were extracted from actual spent LIBs after 60-min grinding at 500xa0rpm with mild conditions. This effective process would be of great importance for recovering valuable metals from the spent LIBs at room temperature.

Constructing efficient mixed-ion perovskite solar cells based on TiO2 nanorod array

Oriented TiO2 nanorod array (TiO2 NA) is very attractive in the fields of halide perovskite solar cells (PSCs) due to its fewer grain boundaries and high crystallinity for effective charge collection. The optimization of TiO2 nanostructures has been proved to be an effective approach for efficient PSCs. On the other hand, tuning the crystallization of perovskite films on top of the TiO2 NA is very important for efficient TiO2-NA based PSCs. Herein, scanning electron microscopy (SEM) and X-ray powder diffraction (XRD) were used to study the crystallization of different mixed-ion Cs0.1(FA0.83MA0.17)0.9Pb(I0.83Br0.17)3 perovskite (in which MAu202f=u202fCH3NH3+, and FAu202f=u202fCH(NH2)2+) films, from different perovskite precursor concentrations, on the TiO2 nanorod arrays. A mechanism was proposed to reveal the inherent connection between the precursor concentration and the crystallite growth of the perovskite film prepared with anti-solvent quenching process. Meanwhile, both faster charge separation at perovskite/TiO2 NA interface and longer charge transport were observed on thicker perovskite film with larger grains, revealed by the time-resolved method. However, atomic force microscopy (AFM) results indicated that too thick perovskite film impaired the charge collection owing to the increased recombination. By balancing the charge collection and film thickness, highly efficient PSCs were prepared with a champion power conversion efficiency (PCE) of 19.33% with little hysteresis. The study highlights a great potential of incorporating oriented one-dimensional electron extraction materials in high-performance PSCs and other applications.