Paul K. Andersen

High Capacity MoO2/Graphite Oxide Composite Anode for Lithium-Ion Batteries.

Nanostructured MoO2/graphite oxide (GO) composites are synthesized by a simple solvothermal method. X-ray diffraction and transmission electron microscopy analyses show that with the addition of GO and the increase in GO content in the precursor solutions, MoO3 rods change to MoO2 nanorods and then further to MoO2 nanoparticles, and the nanorods or nanoparticles are uniformly distributed on the surface of the GO sheets in the composites. The MoO2/GO composite with 10 wt % GO exhibits a reversible capacity of 720 mAh/g at a current density of 100 mA/g and 560 mAh/g at a high current density of 800 mA/g after 30 cycles. The improved reversible capacity, rate capacity, and cycling performance of the composites are attributed to synergistic reaction between MoO2 and GO.

Two-Dimensional V2O5 Sheet Network as Electrode for Lithium-Ion Batteries

Two-dimensional V2O5 and manganese-doped V2O5 sheet network were synthesized by a one-step polymer-assisted chemical solution method and characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, thermal-gravimetric analysis, and galvanostatic discharge-charge analysis. The V2O5 particles were covered with thin carbon layers, which remained after decomposition of the polymer, forming a network-like sheet structure. This V2O5 network exhibits a high capacity of about 300 and 600 mA·h/g at a current density of 100 mA/g when it was used as a cathode and anode, respectively. After doping with 5% molar ratio of manganese, the capacity of the cathode increases from 99 to 165 mA·h/g at a current density of 1 A/g (∼3 C). This unique network structure provides an interconnected transportation pathway for lithium ions. Improvement of electrochemical performance after doping manganese could be attributed to the enhancement of electronic conductivity.

Nickel substituted LiMn2O4 cathode with durable high-rate capability for Li-ion batteries

Spinel LiMn2−xNixO4 (x = 0, 0.1, 0.2) nanoparticles were prepared through a simple one-step polymer-assisted chemical solution method. When x = 0.1, the cathode exhibited the best durable rate capability, with 100% of the capacity retained (∼100 mAh g−1) after 400 cycles at 10 C current rate. The excellent cyclability and rate capability originate from the thin carbon layer automatically formed from incomplete depolymerisation of polymers and the improved conductivity due to the nickel dopant. The improved conductivity was confirmed by less polarization at high current rate.

A prediction model of mass transfer through an electrodialysis cell

AbstractThe purpose of this work is to develop a mass transfer model that incorporates all relevant factors—migration, diffusion, and convection—to predict ion transfer in electrodialysis cells more completely than conventional models, which neglect convection. As a demonstration of this approach, the study develops a three-dimensional model that incorporates the factor of convection to predict NaCl mass transport through a rectangular electrodialysis cell. The equations used in the model—the complete Navier–Stokes, continuity, and steady-state Nernst–Planck equations—are solved by the finite difference numerical method in the particular control volumes. The equations in the dilute chamber are numerically solved using techniques from computational fluid dynamics (CFD). In order to evaluate the reliability and accuracy of the model, the results are compared with theory as calculated by the Nernst–Planck equation. We discovered that the developed model is capable of predicting the velocity distribution, sep...