Evolution and Interplay of Lithium Metal Interphase Components Revealed by Experimental and Theoretical Studies.

Lithium metal batteries (LMB) have high energy densities and are crucial for clean energy solutions. The characterization of the lithium metal interphase is fundamentally and practically important but technically challenging. Taking advantage of synchrotron X-ray, which has the unique capability of analyzing crystalline/amorphous phases quantitatively with statistical significance, we study the composition and dynamics of the LMB interphase for a newly developed important LMB electrolyte that is based on fluorinated ether. Pair distribution function analysis revealed the sequential roles of the anion and solvent in interphase formation during cycling. The relative ratio between Li2O and LiF first increases and then decreases during cycling, suggesting suppressed Li2O formation in both initial and long extended cycles. Theoretical studies revealed that in initial cycles, this is due to the energy barriers in many-electron transfer. In long extended cycles, the anion decomposition product Li2O encourages solvent decomposition by facilitating solvent adsorption on Li2O which is followed by concurrent depletion of both. This work highlights the important role of Li2O in transitioning from an anion-derived interphase to a solvent-derived one.

Asymmetric Lithium Extraction and Insertion in High Voltage Spinel at Fast Rate.

Spinel-structured ordered-LiNi0.5Mn1.5O4 (o-LNMO) has experienced a resurgence of interest in the context of reducing scarce elements such as cobalt from the lithium-ion batteries. O-LNMO undergoes two two-phase reactions at slow rates. However, it is not known if such phenomenon also applies at fast rates. Herein, we investigate the rate-dependent phase transition behavior of o-LNMO through in operando time-resolved X-ray diffraction. The results indicate that a narrow region of the solid solution reaction exists for charge and discharge at both slow and fast rates. The overall phase transition is highly asymmetric at fast rates. During fast charge, it is a particle-by-particle mechanism resulting from an asynchronized reaction among the particles. During fast discharge, it is likely a core-shell mechanism involving transition from Li0+xNi0.5Mn1.5O4 to Li1+xNi0.5Mn1.5O4 in the outer layer of particles. The Li0.5Ni0.5Mn1.5O4 phase is suppressed during fast discharge and appears only through Li redistribution upon relaxation.

Bioinspired Neuron-like Adsorptive Networks for Heavy Metal Capture and Tunable Electrochemically Mediated Recovery.

Electrochemical techniques have garnered increasing attention as a heavy metal remediation platform for pollutant mitigation and sustainable recycling. Inspired by the biological signal-transfer mode, biomimic neuron-like hierarchical adsorptive networks were constructed by interweaving one-dimensional manganese oxide nanowires into polyaniline-decorated hollow structural metal-organic frameworks (MOFs). The prepared biomimic neuron adsorbent exhibits good adsorption capacity toward cations (Pb2+) and oxyanions (Cr2O72-) at the neutral state; tunable cation/oxyanion desorption can be electrochemically switched at the oxidized and reduced states, respectively, where the biomimic neuron-like hierarchical adsorptive networks facilitated electron transfer and benefited substantial redox reactions. The combination of simulations and calculations demonstrates that the curvature-induced polarization in a hollow MOF structure enhances the desorption efficiencies by improving the redox processes at the electrode-electrolyte interface, which facilitate the promising implementation in terms of water economy and downstream waste sustainability.