Amorphous VO : A Pseudocapacitive Platform for High-Rate Symmetric Batteries.

Among the various VO polymorphs, the layered compound, VO (B), has been the most widely investigated lithium-ion battery electrode material. For sodium-ion electrodes, however, an amorphous solid may be more advantageous as a result of the open framework to facilitate ion insertion and the ability to tolerate volumetric changes. Herein, it is shown that the Na insertion properties of amorphous VO (a-VO ) are superior to those of crystalline VO (B).

Fast-Charging Cathodes from Polymer-Templated Mesoporous LiVPOF.

Fast-charging cathodes with high operating voltages are critical to the development of high energy and power density lithium-ion batteries. One route to fast-charging battery materials is through the formation of nanoporous networks, but these methods are often limited by the high calcination temperatures required for synthesis. Here, we report the synthesis of carbon-coated nanoporous LiVPOF with excellent rate capabilities that can be stably cycled up to 4.

Differentiating Double-Layer, Psuedocapacitance, and Battery-like Mechanisms by Analyzing Impedance Measurements in Three Dimensions.

Electrochemical energy storage arises from processes that are broadly categorized as capacitive, pseudocapacitive, or battery-like. Advanced charge-storing materials that are designed to deliver high capacity at a high rate often exhibit a multiplicity of such mechanisms, which complicates the understanding of their charge-storage behavior. Herein, we apply a "3D Bode analysis" technique to identify key descriptors for fast Li-ion storage processes, where AC impedance data, such as the real capacitance (') or phase angle (ϕ), are represented versus the frequency () and a third independent variable, the applied DC cell voltage.

Irreversibility at macromolecular scales in the flake graphite of the lithium-ion battery anode.

Charging a commercial lithium-ion battery intercalates lithium into the graphite-based anode, creating various lithium carbide structures. Despite their economic importance, these structures and the dynamics of their charging-discharging transitions are not well-understood. We have videoed single microcrystals of high-quality, natural graphite undergoing multiple lithiation-delithiation cycles.

Designing Pseudocapacitance for NbO/Carbide-Derived Carbon Electrodes and Hybrid Devices.

Composite structures for electrochemical energy storage are prepared on the basis of using the high-rate lithium ion insertion properties of NbO. The NbO is anchored on reduced graphene oxide (rGO) by hydrothermal synthesis to improve the charge-transfer properties, and by controlling the surface charge, the resulting NbO-rGO particles are attached to a high-surface-area carbide-derived carbon scaffold without blocking its exfoliated layers. The electrochemical results are analyzed using a recently published multiscale physics model that provides significant insights regarding charge storage kinetics.