Advancements and Challenges of P2 NaxTMO2 (TM=Mn, Ni, Co, Fe, Cu) Cathodes for High-performance Sodium-ion Battery

Hongrui Yu, Chengping Li, Peng Dong, Jinsong Wang, Zhengfu Zhang, Yingjie Zhang, Jiangzhao Chen

Sodium-ion batteries have become one of the most promising options for large-scale energy storage due to their abundant sodium source, high storage capacity and relatively low price. Among the key components of sodium-ion batteries, cathode materials play a pivotal role and have a significant impact on the energy density and power density of the battery. Advances in cathode materials ultimately determine the practical applications of sodium-ion batteries. The P2-type layered transition metal oxides have open Na⁺ diffusion channels, and Na⁺ can migrate through the adjacent trigonal positions, resulting in high diffusion coefficients, giving them good rate and cyclic properties. However, in P2-type layered transition metal oxide cathode materials, there are several challenges, such as structural distortion, irreversible oxygen atom redox at high voltages, and irreversible phase transitions, which seriously affect the rate and cycling performance of the batteries. As a result, these issues have hindered the widespread application of sodium-ion batteries in large-scale energy storage. It is crucial to optimize the P2-Na_xTMO₂ layered transition metal oxide cathode materials. This review summarizes the challenges and research progress of P2-Na_xTMO₂ layered transition metal oxide cathode materials for the development of P2-Na_xTMO₂ cathodes for high-energy sodium-ion batteries.

A Review of Mechanical Characterization Techniques for Ultrathin Films Beyond Two-Dimensional Materials

Yunfeng Yan, Jiayi He, Wenqi Ji, Zhuorui Hu, Jiaying Xiao, Changlin Li, Hongxi He, Ximing Wang, Jiawen Xu, Yuxuan Gong, Nanlong Sun

Thin films, thinner than the diameter of a human hair (~90µm and below), hold considerable promise across various applications such as flexible electronics, thin film devices, and biomedical applications due to their distinct characteristics. At this juncture, the mechanical properties of these films play a pivotal role as they underpin the stability of these applications. However, evaluating the mechanical properties of these thin films poses a significant technical challenge owing to their minimal thickness, where conventional technologies often prove inadequate. Over the past decade, notable advancements have been made in characterization techniques to surmount this challenge, particularly for ultra-thin films. This review focuses on recently developed experimental techniques used for characterizing the mechanical properties of thin films thinner than the diameter of a human hair, but beyond two-dimensional materials. We introduce these experimental testing techniques, analyze their pros and cons, and discuss their main applications. The mechanical properties of ultrathin films beyond 2D materials discussed in this study include elastic modulus, hardness, in-plane strength, and fracture toughness. We conclude this review article with our perspective on the applications and future research directions of thin films in the current state of the field.

CuO Nanowhiskers Grown from Cu Nanowire Electrode as Highly Efficient Electrocatalysts for Glucose Detection

Zebin Xue, Jihong Liang, Zongjian Liu

Nonenzymatic electrochemical glucose sensors are normally based on an electrode that owns a conductive substrate decorated with nanosized electrocatalysts. However, these sensors often suffer from drawbacks originating from the use of polymer binder or substrate of low specific surface area. In this work, a porous Cu nanowire (CuNW) electrode fabricated by thermal annealing of CuNWs is employed as the conductive substrate, and the electrocatalysts, namely CuO nanowhiskers with a length ranging from 1 μm to 2 μm, are in situ grown from the CuNW electrode via anodic deposition and subsequent calcination. Electrochemical measurements by cyclic voltammetry indicate that the as-formed electrode is stable in alkaline medium and responds well to the addition of glucose. An investigation on the performance of this CuO nanowhiskers/CuNWs electrode as a nonenzymatic glucose sensor via amperometry under optimized conditions reveals a wide linear range of 3 μM to 7135 μM, a high sensitivity of 3506 μA·mM^-1·cm^-2, and a low detection limit of 0.96 μM at a signal-to-noise ratio of 3. Testing the interfering signals produced by Cl^- ions and some easily oxidizable compounds at a level of physiological concentration suggests a strong anti-interference ability of the as-prepared sensor. In addition, this new glucose sensor also possesses good stability and reproducibility and is successfully tested for detection of glucose in human serum sample.

Pore Engineering Enables MOFs to Capture Trace Benzene Vapor

Rui-Biao Lin, Xiao-Ming Chen, Yingguang Li

Structural Modification of Partially Ni-substituted MnHCF Cathode Material for Aqueous Zn-ion Batteries

Mariam Maisuradze, Min Li, Mattia Gaboardi, Giuliana Aquilanti, Jasper Rikkert Plaisier, Marco Giorgetti

The initial capacity fading and electrochemical profile modification of the nickel substituted manganese hexacyanoferrate cathode material in aqueous zinc-ion batteries was investigated. The outcome of the electrochemical tests suggested the structural transformation of the material; therefore, further characterization has been performed with the synchrotron-based x-ray absorption spectroscopy and powder x-ray diffraction. Indeed, the alteration of the structure was evident with both techniques. The dissolution of Mn and Ni was observed, alongside with the substitution of Mn with Zn. Furthermore, a new Zn-containing phase formation, and the modification of Mn species were demonstrated.

Between the Electrodes of a Supercapacitor: An Update on Electrolytes

Rudolf Holze

Performance, in particular power capabilities and stability of the supercapacitor critically depend on the electrolyte: the ionically conducting phase between the electrodes of a supercapacitor. This review provides an overview with particular attention to possible practical perspectives and promising developments. It addresses all studied or suggested electrolyte systems, mentions relevant properties and highlights details possibly important for practical use or posing likely problems.