Li+ intercalation in isostructural Li2VO3 and Li2VO2 with O2- and mixed O2-/F- anions

Mixed-anion materials for Li-ion batteries have been attracting attention in view of their tunable electrochemical properties. Herein, we compare two isostructural (Fm3m) model intercalation materials Li2VO3 and Li2VO2F with O2- and mixed O2-/F- anions, respectively. Synchrotron X-ray diffraction and pair distribution function data confirm large structural similarity over long-range and at the atomic scale for these materials. However, they show distinct electrochemical properties and kinetic behaviour arising from the different anion environments and the consequent difference in cationic electrostatic repulsion. In comparison with Li2VO3 with an active V4+/5+ redox reaction, the material Li2VO2F with oxofluoro anions and the partial activity of V3+/5+ redox reaction favor higher theoretical capacity (460 mA h g-1vs. 230 mA h g-1), higher voltage (2.5 V vs. 2.2 V), lower polarization (0.1 V vs. 0.3 V) and faster Li+ chemical diffusion (~10-9 cm2 s-1vs. ~10-11 cm2 s-1). This work not only provides insights into the understanding of anion chemistry, but also suggests the rational design of new mixed-anion battery materials

Improved voltage and cycling for Li⁺ intercalation in high-capacity disordered oxyfluoride cathodes

New high-capacity intercalation cathodes of Li2VxCr1−xO2F with a stable disordered rock salt host framework allow a high operating voltage up to 3.5 V, good rate performance (960 Wh kg−1 at ≈1 C), and cycling stability

3D-printed microfluidic system for the in situ diagnostics and screening of nanoparticles synthesis parameters

Fine tuning of the material properties requires many trials and errors during the synthesis. The metal nanoparticles undergo several stages of reduction, clustering, coalescence and growth upon their formation. Resulting properties of the colloidal solution thus depend on the concentrations of the reagents, external temperature, synthesis protocol and qualification of the researcher determines the reproducibility and quality. Automatized flow systems overcome the difficulties inherent for the conventional batch approaches. Microfluidic systems represent a good alternative for the high throughput data collection. The recent advances in 3D-printing made complex topologies in microfluidic devices cheaper and easily customizable. However, channels of the cured photopolymer resin attract metal ions upon synthesis and create crystallization centers. In our work we present 3D-printed system for the noble metal nanoparticle synthesis in slugs. Alternating flows of oil and aqueous reaction mixtures prevent metal deposition on the channel walls. Elongated droplets are convenient for optical and X-ray diagnostics using conventional methods. We demonstrate the work of the system using Ag nanoparticles synthesis for machine-learning assisted tuning of the plasmon resonance frequency