Cu?Co Bimetallic Oxide Quantum Dot Decorated Nitrogen‐Doped Carbon Nanotubes: A High‐Efficiency Bifunctional Oxygen Electrode for Zn–Air Batteries

The large‐scale production of metal–air batteries, an appealing solution for next‐generation energy storage, requires low‐cost, earth‐abundant, and efficient oxygen electrode materials, yet insights into active catalyst structures and synergistic reactivity remain largely unknown. Here, a new bifunctional oxygen electrode based on nitrogen‐doped carbon nanotubes decorated by spinel CuCo₂O₄ quantum dots (CuCo₂O₄/N‐CNTs) is reported, outperforming the benchmark of state‐of‐the‐art noble metal catalysts. Combining spectroscopic characterization and electrochemical studies, a prominent synergetic effect between CuCo₂O₄ and N‐doped carbon nanotubes is uncovered: the high conductivity, large active surface area, and increase in the number of catalytic sites induced by Cu doping (i.e., Cu²⁺ and Cu? N) can be beneficial to the overall electrocatalytic activities. Remarkably, the native flexibility of CuCo₂O₄/N‐CNTs allows its direct use as reversible oxygen electrodes in Zn–air batteries either with liquid alkaline electrolyte or in the all‐solid‐state configuration. The prepared devices demonstrate excellent discharging/charging performance, large energy density (83.83 mW cm^?2 in liquid state, 1.86 W g^?1 in all‐solid‐state), and long lifetime (48 h in liquid state, 9 h in all‐solid‐state), holding great promise in the practical application of rechargeable metal–air batteries and other fuel cells.     

Large‐Scale Li?O2 Pouch Type Cells for Practical Evaluation and Applications

Due to their high theoretical specific capacity and energy density, Li? O₂ batteries are considered as candidates for next‐generation battery systems in place of conventional Li‐ion batteries for advanced applications such as electric vehicles. However, low energy efficiency, poor cycle life, and Li‐metal safety issues make the use of Li? O₂ batteries yet impractical. In addition, actual cell capacities are very low, and since only small‐scale electrodes are currently tested, it is hard to predict the properties of large‐size electrodes and cells, thus evaluating and judging real practical challenges related to this battery technology. In this work, the behavior of pouch‐type Li? O₂ cells using 3 × 5 cm² sized electrodes is investigated and it is confirmed that Li‐metal is a key issue for the upscale of Li? O₂ cells. This study can help to determine which parameters are the most important for developing practical Li? O₂ batteries.     

How Does Moisture Affect the Physical Property of Memristance for Anionic–Electronic Resistive Switching Memories?

Memristors based on anionic–electronic resistive switches represent a promising alternative to transistor‐based memories because of their scalability and low power consumption. To date, studies on resistive switching have focused on oxygen anionic or electronic defects leaving protonic charge‐carrier contributions out of the picture despite the fact that many resistive switching oxides are well‐established materials in resistive humidity sensors. Here, the way memristance is affected by moisture for the model material strontium titanate is studied. First, characterize own‐processed Pt|SrTiO_3‐δ|Pt bits via cyclic voltammetry under ambient conditions are thoroughly characterized. Based on the high stability of a non‐volatile device structures the impact of relative humidity to the current–voltage profiles is then investigated. It is found that Pt|SrTiO_3‐δ|Pt strongly modifies the resistance states by up to 4 orders of magnitude as well as the device's current–voltage profile shape, number of crossings, and switching capability with the level of moisture exposure. Furthermore, a reversible transition from classic memristive behavior at ambient humidity to a capacitively dominated one in dry atmosphere for which the resistive switching completely vanishes is demonstrated for the first time. The results are discussed in relation to the changed Schottky barrier by adsorbed surface water molecules and its interplay with the charge transfer in the oxide.     

Design of Hierarchical Ni?Co@Ni?Co Layered Double Hydroxide Core–Shell Structured Nanotube Array for High‐Performance Flexible All‐Solid‐State Battery‐Type Supercapacitors

A novel hierarchical nanotube array (NTA) with a massive layered top and discretely separated nanotubes in a core–shell structure, that is, nickel–cobalt metallic core and nickel–cobalt layered double hydroxide shell (Ni? Co@Ni? Co LDH), is grown on carbon fiber cloth (CFC) by template‐assisted electrodeposition for high‐performance supercapacitor application. The synthesized Ni? Co@Ni? Co LDH NTAs/CFC shows high capacitance of 2200 F g^?1 at a current density of 5 A g^?1, while 98.8% of its initial capacitance is retained after 5000 cycles. When the current density is increased from 1 to 20 A g^?1, the capacitance loss is less than 20%, demonstrating excellent rate capability. A highly flexible all‐solid‐state battery‐type supercapacitor is successfully fabricated with Ni? Co LDH NTAs/CFC as the positive electrode and electrospun carbon fibers/CFC as the negative electrode, showing a maximum specific capacitance of 319 F g^?1, a high energy density of 100 W h kg^?1 at 1.5 kW kg^?1, and good cycling stability (98.6% after 3000 cycles). These fascinating electrochemical properties are resulted from the novel structure of electrode materials and synergistic contributions from the two electrodes, showing great potential for energy storage applications.     

Are Electrospun Fibrous Membranes Relevant Electrode Materials for Li‐Ion Batteries? The Case of the C/Ge/GeO2 Composite Fibers

Self‐supporting paper‐like membranes consisting of carbon/germanium dioxide (C/GeO₂) fibers are prepared via electrospinning of solutions with different germanium load (2.50?4.25 wt%), followed by carbonization at 550?700 °C, and are evaluated as anode materials in lithium ion batteries. The investigation of the physicochemical properties of the membranes by several characterization techniques shows that, as expected, with increasing carbonization temperature better graphitized and less nitrogen‐rich C fibers are obtained, containing Ge⁰ and/or reduced oxide phases along with GeO₂ nanoparticles. These characteristics, combined with the cold pressing of the as‐spun membrane that noticeably reduces the hollow space within the fibres giving rise to a more compact and tight structure, lead to initial discharge volumetric capacities (≈1390–3580 mAh cm^?3) much higher than commercial graphite anodes. In particular, the membrane prepared from solution with 4.25 wt% Ge‐load by cold‐pressing and carbonization at 700 °C, is able to deliver ≈1500 mAh cm^?3 after 50 cycles at 50 mA g^?1 with a Coulombic efficiency close to 100%. Nevertheless, the anodes exhibit poor rate capability. This is because the carbonization at high temperature promotes outward diffusion and subsequent coalescence of Ge‐clusters in larger particles, with the structure of the fibers made fragile by the formation of voids within them.