Lithium is an important raw material for new energy-powered vehicles, and ensuring its supply is of great significance for global green and sustainable development. Salt lake brine is the main lithium resource, but the separation of Li⁺ from coexisting metals poses a major challenge. In this work, a lithium-storing metal oxide SnO₂ nanoparticle island-modified LiMn₂O₄ electrode material is designed to endow LiMn₂O₄ with higher lithium extraction capacity and cycling stability. The SnO₂ nanoparticle islands effectively mitigate stress during the charge–discharge process of LiMn₂O₄, thereby enhancing cycling stability and promoting the diffusion of Li⁺. The lithium adsorption capacity of the LiMn₂O₄ electrode material modified with SnO₂ nanoparticles reaches 19.76 mg g⁻¹ within 1 hour, which is 1.7 times higher than that of LiMn₂O₄ (11.45 mg g⁻¹). The LiMn₂O₄ electrode material modified with SnO₂ nanoparticles shows good selectivity and cycling stability for the separation of lithium ions.

Since the advantages of simple preparation, low-priced, environmental friendliness, and high absorption capacity, deep eutectic solvents (DESs) are considered to have eminent application potential in terms of SO₂ absorption. However, the absorption rate, selectivity, and reversibility of DESs urgently need to be further improved to meet the requirements of industrialization. In this work, five purine-based DESs were designed and synthesized through the use of 1-ethyl-3-methylimidazolium chloride (EmimCl) as hydrogen bond acceptors (HBAs) plus 6-aminopurine (6-AmP), 6-hydroxypurine (6-HoP), and 6-chloropurine (6-ChP) as hydrogen bond donors (HBDs), respectively. The results indicated that the optimal molar ratio of HBAs to HBDs is 7:1, and the absorption capacity of EmimCl + 6-AmP-7 can reach up to 18.118 mol/kg, at 298.15 K and 1.0 bar. Notably, the present purine-based DESs not only achieve gas-liquid equilibrium within 40 s, but also exhibit outstanding reversibility (absorb-desorb more than 30 times) and remarkable selectivity of SO₂/CO₂. Furthermore, a reaction equilibrium thermodynamic model (RETM) equation was employed to investigate the absorption behavior by combining the absorption data under different SO₂ partial pressures and temperatures. Finally, Fourier-transform infrared (FT-IR) spectroscopy and ¹H nuclear magnetic resonance (NMR) were conducted to explore further the formation and SO₂ absorption mechanism of purine-based DESs. It is revealed that the former is mainly hydrogen bonding interaction among HBAs and HBDs, and the latter is mainly Lewis acid-base interaction plus strong charge-transfer interaction among DESs and SO₂. Based on the obtained data, it could be confirmed that the SO₂ absorption includes both physical and chemical absorption.

With more and more lithium-ion batteries (LIBs) being put into production and application, precious metals such as lithium and cobalt are scarce, so it is imminent to recover various strategic metal resources from spent LIBs. Meanwhile, the complex and difficult problem of separating and recovering metals from leaching solutions has been an urgent question that needs to be resolved. In this work, a phosphoric acid-based deep eutectic solvent (DES) was developed for extracting metals from spent LIBs and one-step selectively separating and efficiently recovering transition metal. The prepared DES shows excellent extraction performance for Li (100%) and Co (92.8%) at 100 ℃. In addition, the extraction system can effectively separate and precipitate Co through its own components, avoiding the introduction of new precipitants and the destruction of the original composition structure of DES. This also contributes to the good cycle stability of the extraction system with excellent extraction performance for Li (94.3%) and Co (80.8%) after 5 cycles. This work proposes a green method for one-step selectively separating and recovering valuable metals from spent LIBs.