Realizing Lean-Leachate Recycling of Spent Lithium Nickel Oxides by Dynamically Stabilizing the Hole-Mediated Diffusion Kinetics.

While hydrometallurgy is the primary technology for recycling spent lithium-ion batteries due to various advantages, it still involves substantial consumption of chemical reagents and poses challenges in wastewater emission. Herein, we report the realization of cathode recycling under lean-leachate conditions by dynamically stabilizing hole-mediated diffusion kinetics, which is enabled by synchronizing the extraction step during the leaching stage, thus continuously removing the dissolved ions out of the leachate. Theoretical molecular dynamics simulations predict that preventing the accumulation of the dissolved ions is efficient for keeping the leaching process proceeding. Experimentally, even with a small dosage of leachate (0.5 mL), a 94.51% leaching efficiency can be achieved (90 °C, 40 min) for spent LNO materials. Considering that our strategy is not limited to a specific materials system, it could be extended to recycle other valuable materials (including LCO or NCM 811) with minimal leachate usage.

Mechanism Study of Imidazole-Type Deep Eutectic Solvents for Efficient Absorption of CO2.

Deep eutectic solvents (DESs) are a new class of green solvents that exhibit unique properties in various process applications. In this regard, this study evaluated imidazole-type DESs as solvents for carbon dioxide (CO2) capture. A series of imidazole-type DESs with different ratios was prepared through one-step synthesis. The absorption capacity of CO2 in imidazole-type DESs was measured through weighing, and the effects of temperature, hydrogen bond acceptors, hydrogen bond donors, and water content were discussed. DESs absorbed the effects of CO2. Im-MEA (1:2) was selected to linearly fit lnη and 1/T using the Arrhenius equation under variable temperature conditions, and a good linear relationship was found. The results show the best absorption effect for Im-MEA (1:4). At 303.15 K and 0.1 MPa, the absorption capacity of Im-MEA (1:4) was as high as 0.323 g CO2/g DES; through five times of absorption-desorption after the cycle, the absorption capacity of DES was almost unchanged. Finally, the mechanism of CO2 absorption was studied using Fourier transform infrared and nuclear magnetic resonance spectroscopy. The absorption mechanism of imidazole-type DESs synthesized using imidazole salt and an amine-based solution was chemical absorption, and the reaction formed carbamate (-NHCOO) to absorb CO2.