Reversible cationic-anionic redox in disordered rocksalt cathodes enabled by fluorination-induced integrated structure design

Cation-disordered rocksalt oxides(DRX)have been identified as promising cathode materials for high energy density applications owing to their variable elemental composition and cationic-anionic redox activity.However,their practical implementation has been impeded by unwanted phenomena such as irrepressible transition metal migration/dissolution and O_(2)/CO_(2)evolution,which arise due to parasitic reactions and densification-degradation mechanisms during extended cycling.To address these issues,a micron-sized DRX cathode Li_(1.2)Ni_(1/3)Ti_(1/3)W_(2/15)O_(1.85)F_(0.15)(SLNTWOF)with F substitution and ultrathin LiF coating layer is developed by alcohols assisted sol-gel method.Within this fluorination-induced integrated structure design(FISD)strategy,in-situ F substitution modifies the activity/reversibility of the cationic-anionic redox reaction,while the ultrathin LiF coating and single-crystal structure synergistically mitigate the cathode/electrolyte parasitic reaction and densification-degradation mechanism.Attributed to the multiple modifications and size effect in the FISD strategy,the SLNTWOF sample exhibits reversible cationic-anionic redox chemistry with a meliorated reversible capacity of 290.3 mA h g^(-1)at 0.05C(1C=200 mA g^(-1)),improved cycling stability of 78.5%capacity retention after 50 cycles at 0.5 C,and modified rate capability of 102.8 mA h g^(-1)at 2 C.This work reveals that the synergistic effects between bulk structure modification,surface regulation,and engineering particle size can effectively modulate the distribution and evolution of cationic-anionic redox activities in DRX cathodes.

Synthesis of nitrocarbazole compounds and their electrocatalytic oxidation of alcohol

Three compounds with nitrocarbazole frameworks were synthesized and their electrochemical reversibility as organic electrocatalysts was studied by cyclic voltammetry. The electrochemical reversibility and oxidation‐reduction potential of the compounds were greatly affected by their substituents. The oxidation‐reduction potential of the compound with an electron‐donating group was negative, while that of the compound with an electron‐withdrawing group on the carbazole framework was positive. The electrocatalytic oxidation activities of the nitrocarbazole compounds were investigated through cyclic voltammetry and controlled potential electrolysis at room tem‐perature. The electrocatalysts showed excellent selectivity for p‐methoxybenzyl alcohol, converting it to the corresponding aldehyde through electro‐oxidation with just 2.5 mol%of the electrocata‐lysts presented. The electrocatalysts maintained their excellent electroredox activity following re‐cycling.

Nanoparticles Modified Electrodes: Synthesis, Modification, and Characterization—A Review

Nanoparticles offer unique features such as a larger surface area and enhanced electrochemical performance compared to their contemporary matters. These properties make them suitable to be considered in bridging the lacunae associated with the use of bare electrodes in electrochemical sensors. Nanomaterials enhance the redox reversibility on the electrodes’ surfaces, hence, improving the reproducibility, sensitivity, and limit of detection of the electrodes/sensors. Their methods of synthesis (top-to-bottom and bottom-to-to-top) are tailored toward manipulating their sizes, shapes, and preventing their agglomeration. This review paper provides a synopsis on research done in synthesizing nanoparticles, modifying electrodes, and pinpointing the improved performances of the modified electrodes via known characteristic techniques, namely: cyclic voltammetry, differential pulse voltammetry, and electrochemical impedance spectroscopy. In addition, a perspective is given in terms of increasing the lifespan of the working electrodes and the need for non-faradaic sensors.

Enhanced Reversible Zinc Ion Intercalation in Deficient Ammonium Vanadate for High-Performance Aqueous Zinc-Ion Battery

Ammonium vanadate with bronze structure(NH_(4)V_(4)O_(10))is a promising cathode material for zinc-ion batteries due to its high specific capacity and low cost.However,the extraction of NH^(+)_(4) at a high voltage during charge/discharge processes leads to irreversible reaction and structure degradation.In this work,partial NH^(+)_(4) ions were pre-removed from NH_(4)V_(4)O_(10) through heat treatment;NH_(4)V_(4)O_(10) nanosheets were directly grown on carbon cloth through hydrothermal method.Defi-cient NH_(4)V_(4)O_(10)(denoted as NVO),with enlarged interlayer spacing,facilitated fast zinc ions transport and high storage capacity and ensured the highly reversible electrochemical reaction and the good stability of layered structure.The NVO nanosheets delivered a high specific capac-ity of 457 mAh g^(−1) at a current density of 100 mA g^(−1) and a capacity retention of 81%over 1000 cycles at 2 A g^(−1).The initial Coulombic efficiency of NVO could reach up to 97%compared to 85%of NH_(4)V_(4)O_(10) and maintain almost 100%during cycling,indicating the high reaction reversibility in NVO electrode.