Superstructure control of first-cycle voltage hysteresis in oxygen-redox cathodes.

In conventional intercalation cathodes, alkali metal ions can move in and out of a layered material with the charge being compensated for by reversible reduction and oxidation of the transition metal ions. If the cathode material used in a lithium-ion or sodium-ion battery is alkali-rich, this can increase the battery's energy density by storing charge on the oxide and the transition metal ions, rather than on the transition metal alone. There is a high voltage associated with oxidation of O during the first charge, but this is not recovered on discharge, resulting in reduced energy density.

Oxygen redox chemistry without excess alkali-metal ions in Na[MgMn]O.

The search for improved energy-storage materials has revealed Li- and Na-rich intercalation compounds as promising high-capacity cathodes. They exhibit capacities in excess of what would be expected from alkali-ion removal/reinsertion and charge compensation by transition-metal (TM) ions. The additional capacity is provided through charge compensation by oxygen redox chemistry and some oxygen loss.

One-Pot Synthesis of Lithium-Rich Cathode Material with Hierarchical Morphology.

Lithium-rich transition metal oxides, LiTMO (TM, transition metal), have attracted much attention as potential candidate cathode materials for next generation lithium ion batteries because their high theoretical capacity. Here we present the synthesis of Li[LiNiMn]O using a facile one-pot resorcinol-formaldehyde method. Structural characterization indicates that the material adopts a hierarchical porous morphology consisting of uniformly distributed small pores and disordered large pore structures.

Anion Redox Chemistry in the Cobalt Free 3d Transition Metal Oxide Intercalation Electrode Li[Li0.2Ni0.2Mn0.6]O2.

Conventional intercalation cathodes for lithium batteries store charge in redox reactions associated with the transition metal cations, e.g., Mn(3+/4+) in LiMn2O4, and this limits the energy storage of Li-ion batteries.

Charge-compensation in 3d-transition-metal-oxide intercalation cathodes through the generation of localized electron holes on oxygen.

During the charging and discharging of lithium-ion-battery cathodes through the de- and reintercalation of lithium ions, electroneutrality is maintained by transition-metal redox chemistry, which limits the charge that can be stored. However, for some transition-metal oxides this limit can be broken and oxygen loss and/or oxygen redox reactions have been proposed to explain the phenomenon. We present operando mass spectrometry of (18)O-labelled Li1.

Nanosized LiFePO4-decorated emulsion-templated carbon foam for 3D micro batteries: a study of structure and electrochemical performance.

In this article, we report a novel 3D composite cathode fabricated from LiFePO4 nanoparticles deposited conformally on emulsion-templated carbon foam by a sol-gel method. The carbon foam is synthesized via a facile and scalable method which involves the carbonization of a high internal phase emulsion (polyHIPE) polymer template. Various techniques (XRD, SEM, TEM and electrochemical methods) are used to fully characterize the porous electrode and confirm the distribution and morphology of the cathode active material.

Direct Observation of Active Material Concentration Gradients and Crystallinity Breakdown in LiFePO Electrodes During Charge/Discharge Cycling of Lithium Batteries.

The phase changes that occur during discharge of an electrode comprised of LiFePO, carbon, and PTFE binder have been studied in lithium half cells by using X-ray diffraction measurements in reflection geometry. Differences in the state of charge between the front and the back of LiFePO electrodes have been visualized. By modifying the X-ray incident angle the depth of penetration of the X-ray beam into the electrode was altered, allowing for the examination of any concentration gradients that were present within the electrode.

Evidence for enhanced capacitance and restricted motion of an ionic liquid confined in 2 nm diameter Pt mesopores.

The organised nanostructure of mesoporous platinum deposited from the H(I) phase of a lyotropic liquid crystal template contains a regular, hexagonal array of uniform nanometre diameter cylindrical pores. This structure is ideally suited to the investigation of the interfacial capacitance and properties of ionic liquids confined within small pores of the type found in the high surface area electrodes favoured for supercapacitors and batteries. Cyclic voltammetry experiments for BMIM-PF(6) show a large capacitance for the mesoporous Pt electrode, confirming that the ionic liquid fills the 2 nm pores.

Stripping voltammetry using sequential standard addition calibration with the analytes themselves acting as internal standards.

A novel two-step standard addition calibration procedure for stripping voltammetry, whereby the analytes under investigation act as internal standards for each other, is described. In this way, the benefits of an internal standard for improving precision are obtained, without the requirement to add internal standard solutions. Only the standard solutions used to perform quantification are required.

Systematic error arising from 'Sequential' Standard Addition Calibrations: quantification and correction.

Calibrations involving the sequential addition of aliquots of a standard solution to a solution of unknown analyte content may exhibit a systematic error. We show that this systematic error is related to the ratio of the mass fractions in the standard and unknown solutions. This relationship is consistent with experimental results from the determination of lead in aqueous solution by anodic stripping voltammetry using 'Sequential' Standard Addition Calibration (S-SAC).