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We report a new electrochemical capacitor with an aqueous KI-KOH electrolyte that exhibits a higher specific energy and power than the state-of-the-art nonaqueous electrochemical capacitors. In addition to electrical double layer capacitance, redox reactions in this device contribute to charge storage at both positive and negative electrodes via a catholyte of IOx-/I- couple and a redox couple of H2O/Had, respectively. Here, we, for the first time, report utilizing IOx-/I- redox couple for the positive electrode, which pins the positive electrode potential to be 0.4-0.5 V vs Ag/AgCl. With the positive electrode potential pinned, we can polarize the cell to 1.6 V without breaking down the aqueous electrolyte so that the negative electrode potential could reach -1.1 V vs Ag/AgCl in the basic electrolyte, greatly enhancing energy storage. Both mass spectroscopy and Raman spectrometry confirm the formation of IO3- ions (+5) from I- (-1) after charging. Based on the total mass of electrodes and electrolyte in a practically relevant cell configuration, the device exhibits a maximum specific energy of 7.1 Wh/kg, operates between -20 and 50 °C, provides a maximum specific power of 6222 W/kg, and has a stable cycling life with 93% retention of the peak specific energy after 14,000 cycles.

Rechargeable batteries employing ammonium (NH4+) ions have attracted widespread interest owing to the abundant resources, eco-friendliness, and sustainability of NH4+ ions. Herein, an organic–inorganic hybrid is applied to organic NH4+ ion batteries. A poly (3,4-ethylene dioxythiophene) (PEDOT)-intercalated vanadium oxide nanowire (noted as VO-P-x) is applied for organic NH4+ ion storage. VO-P-x with the optimal content of PEDOT showed an interlayer spacing (d-spacing) expanded to 1.82 nm, exhibiting an ultrahigh initial coulombic efficiency of 91% and a reversible capacity of 163 mA h g−1. A significant improvement in NH4+ ion storage was achieved due to the large interlayer spacing and conductive polymer PEDOT. Combining ex situ X-ray photoelectron spectroscopy (XPS) and multi-sweep cyclic voltammetry tests, the NH4+ ion storage mechanism of VO-P-x was clearly revealed. This study provides a new strategy for designing high-performance organic ammonium batteries. [ABSTRACT FROM AUTHOR]

The unsatisfactory conductivity and large volume variation severely handicap the application of SnO2 in sodium‐ion batteries (SIBs). Herein, we design unique three‐layer structured SnO2@C@TiO2 hollow spheres to tackle the above‐mentioned issues. The hollow cavity affords empty space to accommodate the volume variation of SnO2, while the C and TiO2 protecting shells strengthen the structural integrity and enhances the electrical conductivity. As a result, the three‐layer structured SnO2@C@TiO2 hollow spheres demonstrate enhanced Na storage performances. The SnO2@C@TiO2 manifests a reversible capacity two times to that of pristine SnO2 hollow spheres. In addition, Ex situ XRD reveals highly reversible alloying and conversion reactions in SnO2@C@TiO2 hollow spheres. This study suggests the introduction of a hollow cavity and robust protecting shells is a promising strategy for constructing SIB anode materials. [ABSTRACT FROM AUTHOR]

Few‐layered 2D analogs exhibit new physical/chemical properties, leading to a strong research interest and broad areas of application. Recently, lots of methods (such as ultrasonic and electrochemical methods) have already used to prepared 2D materials. However, these methods suffer from the drawbacks of low yield, high cost, or precarious state, which limit the large‐scale applications. Inspired by the famous Scotch tape method, we develop a ball‐milling with polymer "tape" method, fabricating few‐atomic‐layered material, showing the high‐yield, low‐cost, and much stability. As electrode material, ultrathin 2D materials can shorten the ion transfer pathway, contributing to the development of high‐power batteries. Meanwhile, few‐atomic‐layered structure can expose more active sites to increase their capacity, showing special energy storage mechanism. We use the as‐prepared few‐atomic‐layered Bi (FALB) and reduced oxide graphene composites as the anode for potassium/sodium‐ion batteries (KIBs/NIBs). The sample achieves a high reversible capacity of 395 mAh g−1 for KIBs, of which FALB contributes 438 mAh g−1 (higher than the theoretical capacity of Bi, 386 mAh g−1), and it carries outstanding cycle and rate performance in KIBs/NIBs. [ABSTRACT FROM AUTHOR]