Confined Fe2VO4⊂Nitrogen‐Doped Carbon Nanowires with Internal Void Space for High‐Rate and Ultrastable Potassium‐Ion Storage

Developing low‐cost, high‐capacity, high‐rate, and robust earth‐abundant electrode materials for energy storage is critical for the practical and scalable application of advanced battery technologies. Herein, the first example of synthesizing 1D peapod‐like bimetallic Fe₂VO₄ nanorods confined in N‐doped carbon porous nanowires with internal void space (Fe₂VO₄?NC nanopeapods) as a high‐capacity and stable anode material for potassium‐ion batteries (KIBs) is reported. The peapod‐like Fe₂VO₄?NC nanopeapod heterostructures with interior void space and external carbon shell efficiently prevent the aggregation of the active materials, facilitate fast transportation of electrons and ions, and accommodate volume variation during the cycling process, which substantially boosts the rate and cycling performance of Fe₂VO₄. The Fe₂VO₄?NC electrode exhibits high reversible specific depotassiation capacity of 380 mAh g^?1 at 100 mA g^?1 after 60 cycles and remarkable rate capability as well as long cycling stability with a high capacity of 196 mAh g^?1 at 4 A g^?1 after 2300 cycles. The first‐principles calculations reveal that Fe₂VO₄?NC nanopeapods have high ionic/electronic conductivity characteristics and low diffusion barriers for K⁺‐intercalation. This study opens up new way for investigating high‐capacity metal oxide as high‐rate and robust electrode materials for KIBs.     

Nanosheets‐Assembled CuSe Crystal Pillar as a Stable and High‐Power Anode for Sodium‐Ion and Potassium‐Ion Batteries

Thanks to low costs and the abundance of the resources, sodium‐ion (SIBs) and potassium‐ion batteries (PIBs) have emerged as leading candidates for next‐generation energy storage devices. So far, only few materials can serve as the host for both Na⁺ and K⁺ ions. Herein, a cubic phase CuSe with crystal‐pillar‐like morphology (CPL‐CuSe) assembled by the nanosheets are synthesized and its dual functionality in SIBs and PIBs is comprehensively studied. The electrochemical measurements demonstrate that CPL‐CuSe enables fast Na⁺ and K⁺ storage as well as the sufficiently long duration. Specifically, the anode delivers a specific capacity of 295 mA h g^?1 at current density of 10 A g^?1 in SIBs, while 280 mA h g^?1 at 5 A g^?1 in PIBs, as well as the high capacity retention of nearly 100% over 1200 cycles and 340 cycles, respectively. Remarkably, CPL‐CuSe exhibits a high initial coulombic efficiency of 91.0% (SIBs) and 92.4% (PIBs), superior to most existing selenide anodes. A combination of in situ X‐ray diffraction and ex situ transmission electron microscopy tests fundamentally reveal the structural transition and phase evolution of CuSe, which shows a reversible conversion reaction for both cells, while the intermediate products are different due to the sluggish K⁺ insertion reaction.     

Refilling Nitrogen to Oxygen Vacancies in Ultrafine Tungsten Oxide Clusters for Superior Lithium Storage

Morphological engineering of nanosized transitional metal oxides shows great promise for performance improvement, yet limited efforts have been attempted to engineer the atomic structure. Oxygen vacancy (V_O) can boost charge transfer leading to enhanced performance; yet excessive V_O may impair the conductivity. Herein, tungsten oxide is atomically tailored by incorporating nitrogen heteroatoms into the oxygen vacancies. The efficient nitrogen‐filling into the oxygen vacancies is evidenced by the electron paramagnetic resonance spectroscopy and X‐ray absorption spectroscopy. The coordinated N atoms play a crucial role in facilitating the charge transfer and maintaining efficient lithium‐ion diffusion. Consequently, the tungsten oxide with N‐filled oxygen vacancies exhibits superior lithium‐ion storage performance.     

Electrochemiluminescence of palmatine being oxidized by electrogenerated hydroxyl radical and its analytical application

A strong electrochemiluminescence (ECL) of palmatine in NaOH medium was observed at a vaseline‐impregnated graphite anode. The ECL production could be described as follows: hydroxyl radical (OH^?) was generated via the oxidation of hydroxyl group (OH^‐) in NaOH medium, and the formed OH^? subsequently oxidized palmatine base converted from palmatine in NaOH medium to the excited state oxypalmatine (oxypalmatine*). As the oxypalmatine* went back to its ground state, a stronger chemiluminescence was produced. Based on the ECL of palmatine, an ECL method for the determination of palmatine was proposed. An ECL signal of palmatine in NaOH solution was obtained by applying direct current of 15 mA to the vaseline‐impregnated graphite anode. The ECL intensity was rectilinear with palmatine concentration in the range of 8.0 × 10^?7 to 2.0 × 10^?5 mol l^?1 and the limit of detection (signal‐to‐noise = 3) was 3 × 10^?7 mol l^?1. The proposed method was applied to the determination of palmatine in pharmaceutical preparations. Copyright © 2010 John Wiley & Sons, Ltd.     

Boosting Superior Lithium Storage Performance of Alloy‐Based Anode Materials via Ultraconformal Sb Coating–Derived Favorable Solid‐Electrolyte Interphase

Alloy materials such as Si and Ge are attractive as high‐capacity anodes for rechargeable batteries, but such anodes undergo severe capacity degradation during discharge–charge processes. Compared to the over‐emphasized efforts on the electrode structure design to mitigate the volume changes, understanding and engineering of the solid‐electrolyte interphase (SEI) are significantly lacking. This work demonstrates that modifying the surface of alloy‐based anode materials by building an ultraconformal layer of Sb can significantly enhance their structural and interfacial stability during cycling. Combined experimental and theoretical studies consistently reveal that the ultraconformal Sb layer is dynamically converted to Li₃Sb during cycling, which can selectively adsorb and catalytically decompose electrolyte additives to form a robust, thin, and dense LiF‐dominated SEI, and simultaneously restrain the decomposition of electrolyte solvents. Hence, the Sb‐coated porous Ge electrode delivers much higher initial Coulombic efficiency of 85% and higher reversible capacity of 1046 mAh g^?1 after 200 cycles at 500 mA g^?1, compared to only 72% and 170 mAh g^?1 for bare porous Ge. The present finding has indicated that tailoring surface structures of electrode materials is an appealing approach to construct a robust SEI and achieve long‐term cycling stability for alloy‐based anode materials.     

Syntrophic interactions among anode respiring bacteria (ARB) and Non‐ARB in a biofilm anode: electron balances

We demonstrate that the coulombic efficiency (CE) of a microbial electrolytic cell (MEC) fueled with a fermentable substrate, ethanol, depended on the interactions among anode respiring bacteria (ARB) and other groups of micro‐organisms, particularly fermenters and methanogens. When we allowed methanogenesis, we obtained a CE of 60%, and 26% of the electrons were lost as methane. The only methanogenic genus detected by quantitative real‐time PCR was the hydrogenotrophic genus, Methanobacteriales, which presumably consumed all the hydrogen produced during ethanol fermentation (～30% of total electrons). We did not detect acetoclastic methanogenic genera, indicating that acetate‐oxidizing ARB out‐competed acetoclastic methanogens. Current production and methane formation increased in parallel, suggesting a syntrophic interaction between methanogens and acetate‐consuming ARB. When we inhibited methanogenesis with 50 mM 2‐bromoethane sulfonic acid (BES), the CE increased to 84%, and methane was not produced. With no methanogenesis, the electrons from hydrogen were converted to electrical current, either directly by the ARB or channeled to acetate through homo‐acetogenesis. This illustrates the key role of competition among the various H₂ scavengers and that, when the hydrogen‐consuming methanogens were present, they out‐competed the other groups. These findings also demonstrate the importance of a three‐way syntrophic relationship among fermenters, acetate‐consuming ARB, and a H₂ consumer during the utilization of a fermentable substrate. To obtain high coulombic efficiencies with fermentable substrates in a mixed population, methanogens must be suppressed to promote new interactions at the anode that ultimately channel the electrons from hydrogen to current. Biotechnol. Bioeng. 2009;103: 513–523. © 2009 Wiley Periodicals, Inc.     

Si‐Encapsulating Hollow Carbon Electrodes via Electroless Etching for Lithium‐Ion Batteries

Remarkable improvements in the electrochemical performance of Si materials for Li‐ion batteries have been recently achieved, but the inherent volume change of Si still induces electrode expansion and external cell deformation. Here, the void structure in Si‐encapsulating hollow carbons is optimized in order to minimize the volume expansion of Si‐based anodes and improve electrochemical performance. When compared to chemical etching, the hollow structure is achieved via electroless etching is more advanced due to the improved electrical contact between carbon and Si. Despite the very thick electrodes (30 ～ 40 μm), this results in better cycle and rate performances including little capacity fading over 50 cycles and 1100 mA h g^?1 at 2C rate. Also, an in situ dilatometer technique is used to perform a comprehensive study of electrode thickness change, and Si‐encapsulating hollow carbon mitigates the volume change of electrodes by adoption of void space, resulting in a small volume increase of 18% after full lithiation corresponding with a reversible capacity of about 2000 mA h g^?1.     

Carbon Coated ZnFe2O4 Nanoparticles for Advanced Lithium‐Ion Anodes

The preparation and electrochemical characterization of a new material consisting of carbon coated ZnFe₂O₄ nanoparticles is presented. This material, which offers an interesting combination of alloying and conversion mechanisms, is capable of hosting up to nine equivalents of lithium per unit formula, corresponding to an exceptional specific capacity, higher than 1000 mAh g^?1. Composite electrodes of such a material, prepared using environmentally friendly sodium carboxymethyl cellulose as binder, showed the highest, ever reported, specific capacity and high rate performance upon long‐term testing. Furthermore, in situ X‐ray diffraction analysis allowed identifying the reduction process occurring upon initial lithiation.