Sub-micro droplet reactors for green synthesis of Li3VO4 anode materials in lithium ion batteries

The conventional solid-state reaction suffers from low diffusivity, high energy consumption, and uncontrolled morphology. These limitations are competed by the presence of water in solution route reaction. Herein, based on concept of combining above methods, we report a facile solid-state reaction conducted in water vapor at low temperature along with calcium doping for modifying lithium vanadate as anode material for lithium-ion batteries. The optimized material, delivers a superior specific capacity of 543.1, 477.1, and 337.2 mAh g−1 after 200 and 1000 cycles at current densities of 100, 1000 and 4000 mA g−1, respectively, which is attributed to the contribution of pseudocapacitance. In this work, we also use experimental and theoretical calculation to demonstrate that the enhancement of doped lithium vanadate is attributed to particles confinement of droplets in water vapor along with the surface and structure variation of calcium doping effect.

Tuning Properties of Partially Reduced Graphene Oxide Fibers upon Calcium Doping

The arrangement of two-dimensional graphene oxide sheets has been shown to influence physico-chemical properties of the final bulk structures. In particular, various graphene oxide microfibers remain of high interest in electronic applications due to their wire-like thin shapes and the ease of hydrothermal fabrication. In this research, we induced the internal ordering of graphene oxide flakes during typical hydrothermal fabrication via doping with Calcium ions (~6 wt.%) from the capillaries. The Ca2+ ions allowed for better graphene oxide flake connections formation during the hydrogelation and further modified the magnetic and electric properties of structures compared to previously studied aerogels. Moreover, we observed the unique pseudo-porous fiber structure and flakes connections perpendicular to the long fiber axis. Pulsed electron paramagnetic resonance (EPR) and conductivity measurements confirmed the denser flake ordering compared to previously studied aerogels. These studies ultimately suggest that doping graphene oxide with Ca2+ (or other) ions during hydrothermal methods could be used to better control the internal architecture and thus tune the properties of the formed structures.

Synergetic Effect of Calcium Doping on Catalytic Activity of Manganese Ferrite: DFT Study and Oxidation of Hydrocarbon

Manganese ferrite (MnFe2O4) and calcium-doped manganese ferrite (Ca-MnFe2O4) were synthesized, characterized, and tested for oxidation of hydrocarbons (CH) in a self-designed gas blow rotating (GBR) reactor. The uniformly sized and thermally stable MnFe2O4 nanoparticles (molar ratio, 1/284.5) showed a reasonable catalytic activity (productivity: 366.17 mmolg−1h−1) with 60% selectivity at 80 °C, which was further enhanced by calcium doping (productivity: 379.38 mmolg−1h−1). The suspicious behavior of Ca-MnFe2O4 was disclosed experimentally and theoretically as well.

Accelerating solid diffusion and suppressing phase transition in LiV3O8via calcium doping at lithium sites

The phase transition of LiV3O8 from α phase to β phase during discharge/charge process leads to drastic structural change and rapid capacity decay, and consequent sluggish Li+ solid diffusion results in serious concentration polarization.