Ruiyong Chen

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.

Anodic Electrocatalytic Coatings for Electrolytic Chlorine Production: A Review

Abstract Industrial chlor-alkali electrolysis represents one of the most energy- and resource-intensive technological applications of electrocatalysis. Improving process efficiency becomes a critical issue for the sustainable development and for alleviating the energy and environmental crisis. Rational design in the morphology of RuO2-based anodic electrocatalytic coatings and the control in the coating microstructure can contribute to massive energy saving compared to the current commercial Ru0.3Ti0.7O2 coating. This review covers recent developments in the anodic coatings. Performance enhancement for RuO2-based anodic coatings is achieved by using alternative preparation routes of sol-gel and electrodeposition. The target control in the coating surface morphologies and the increase in the utilization of active Ru species are demonstrated.

Lithiation-driven structural transition of VO2F into disordered rock-salt LixVO2F

We synthesize a new vanadium oxyfluoride VO2F (rhombohedral, Rc) through a simple one-step ball-milling route and demonstrate its promising lithium storage properties with a high theoretical capacity of 526 mA h g−1. Similar to V2O5, VO2F transfers into an active disordered rock-salt (Fmm) phase after initial cycling against the lithium anode, as confirmed by diffraction and spectroscopic experiments. The newly formed nanosized LixVO2F remains its crystal structure over further cycling between 4.1 and 1.3 V. A high capacity of 350 mA h g−1 at 2.5 V was observed at 25 °C and 50 mA g−1. Furthermore, superior performance was observed for VO2F in comparison with a commercial crystalline V2O5, in terms of discharge voltage, voltage hysteresis and reversible capacity.

Redox Flow Batteries: Fundamentals and Applications

A redox flow battery is an electrochemical energy storage device that converts chemical energy into electrical energy through reversible oxidation and reduction of working fluids. The concept was initially conceived in 1970s. Clean and sustainable energy supplied from renewable sources in future requires efficient, reliable and cost-effective energy storage systems. Due to the flexibility in system design and competence in scaling cost, redox flow batteries are promising in stationary storage of energy from intermittent sources such as solar and wind. This chapter covers basic principles of electrochemistry in redox flow batteries and provides an overview of status and future challenges. Recent progress in redox couples, membranes and electrode materials will be discussed. New demonstration and commercial development will be addressed.

Li+intercalation in isostructural Li2VO3and Li2VO2F 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 (Fm3̅m) model intercalation materials Li2VO3 and Li2VO2F with O(2-) and mixed O(2-)/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 V(4+/5+) redox reaction, the material Li2VO2F with oxofluoro anions and the partial activity of V(3+/5+) redox reaction favor higher theoretical capacity (460 mA h g(-1)vs. 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) cm(2) s(-1)vs. ∼10(-11) cm(2) 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.