Constructing Co3 O4 Nanowires on Carbon Fiber Film as a Lithiophilic Host for Stable Lithium Metal Anodes.

Lithium metal has been considered as the most promising anode electrode for substantially improving the energy density of next-generation energy storage devices. However, uncontrollable lithium dendrite growth, an unstable solid electrolyte interface (SEI), and infinite volume variation severely shortens its service lifespan and causes safety hazards, thus hindering the practical application of lithium metal electrodes. Here, carbon fiber film (CFF) modified by lithiophilic Co3 O4 nanowires (denoted as Co3 O4 Nws) was proposed as a matrix for prestoring lithium metal through a thermal infusion method. The homogeneous needle-like Co3 O4 nanowires can effectively promote molten lithium to infiltrate into the CFF skeleton. The post-formed Co-Li2 O nanowires produced by the reaction of Co3 O4 Nws and molten lithium can homogeneously distribute lithium ions flux and efficaciously increase the adsorption energy with lithium ions proved by density functional theory (DFT) calculation, boosting a uniform lithium deposition without dendrite growth. Therefore, the obtained composite anode (denoted as CFF/Co-Li2 O@Li) exhibits superior electrochemical performance with high stripping/plating capacities of 3 mAh cm-2 and 5 mAh cm-2 over long-term cycles in symmetrical batteries. Moreover, in comparison with bare lithium anode, superior Coulombic efficiencies coupled with copper collector and full battery behaviors paired with LiFePO4 cathode are achieved when CFF/Co-Li2 O@Li composite anode was employed.

Computational investigation of Zn-doped and undoped SrEu2Fe2O7 as potential mixed electron and proton conductors.

Understanding the electrode properties at the atomistic level is of great benefit to the evaluation of electrode performance and design of better electrode materials in solid oxide fuel cells. In this work, density functional theory (DFT) calculations are employed to investigate the formation and conducting behaviors of oxygen vacancies and proton defects in Ruddlesden-Popper oxide SrEu2Fe2O7 (SEFO), which has been experimentally characterized as a promising cathode. The calculation results suggest both oxygen vacancies and proton defects can be formed in SEFO, and especially, the formation of these defects is largely dependent on oxygen sites in the special crystal structure with alternative stacking of rock-salt layers and double-layered perovskite slabs. The oxygen vacancies within the perovskite slabs have very low formation energies, but demonstrate high energy barriers for migration and low hydration properties; while in the case of those in the rock salt layers, it's contrary. Interestingly, protons have similar migration abilities in the perovskite slabs and rock salt layers. And therefore, increasing the vacancy concentration of the rock salt layer is beneficial to increase the concentration of proton defects and to improve the proton conductivity. DFT calculations also indicate that substituting Zn for Fe in SEFO can largely depress the oxygen vacancy formation energy, which helps to increase the concentration of both defects. Importantly, the energy barriers for migration of both oxygen ions and protons are barely enhanced, implying a negligible trapping effect of the Zn dopant.