Zinc deposition and dissolution in methanesulfonic acid onto a carbon composite electrode as the negative electrode reactions in a hybrid redox flow battery

Enhancing Hydrophilicity of Thick Electrodes for High Energy Density Aqueous Batteries

Thick electrodes can substantially enhance the overall energy density of batteries. However, insufficient wettability of aqueous electrolytes toward electrodes with conventional hydrophobic binders severely limits utilization of active materials with increasing the thickness of electrodes for aqueous batteries, resulting in battery performance deterioration with a reduced capacity. Here, we demonstrate that controlling the hydrophilicity of the thicker electrodes is critical to enhancing the overall energy density of batteries. Hydrophilic binders are synthesized via a simple sulfonation process of conventional polyvinylidene fluoride binders, considering physicochemical properties such as mechanical properties and adhesion. The introduction of abundant sulfonate groups of binders (i) allows fast and sufficient electrolyte wetting, and (ii) improves ionic conduction in thick electrodes, enabling a significant increase in reversible capacities under various current densities. Further, the sulfonated binder effectively inhibits the dissolution of cathode materials in reactive aqueous electrolytes. Overall, our findings significantly enhance the energy density and contribute to the development of practical zinc-ion batteries.

A strategy for anode modification for future zinc-based battery application

In the past several years, rechargeable zinc batteries, featuring the merits of low cost, environmental friendliness, easy manufacturing, and enhanced safety, have, attracted much attention. Zinc (Zn) anodes for zinc metal batteries play an important role. In this review, the fundamental understanding of these batteries and modification strategies to deal with the problematic issues for Zn anodes, including dendrite growth, corrosion, and the hydrogen evolution phenomenon will be summarized. The practical application of Zn anodes can still lead to Zn dendrites, various side reactions, and serious safety risks. Therefore, metal-free anodes for "rocking chair" zinc ion batteries to replace Zn anodes are systemically reviewed. The performance and the zinc storage mechanism of metal-free anodes will be discussed. Subsequently, a "rocking chair" zinc ion battery prototype selected as a recent example is assessed to explore the merits and demerits of Zn anodes and metal-free anodes. To conclude, a perspective on the future of zinc metal batteries and "rocking chair" zinc ion batteries is presented. It is hoped that this review may provide for further improvement of commercial rechargeable zinc batteries.

Silver nano-reporter enables simple and ultrasensitive profiling of microRNAs on a nanoflower-like microelectrode array on glass

MicroRNAs (miRNAs) are small non-coding RNAs with ~ 22 nucleotides, playing important roles in the post-transcriptional regulation of gene expression. The expression profiles of many miRNAs are closely related to the occurrence and progression of cancer and can be used as biomarkers for cancer diagnosis and prognosis. However, their intrinsic properties, such as short length, low abundance and high sequence homology, represent great challenges in miRNA detection of clinical samples. To overcome these challenges, we developed a simple, ultrasensitive detection platform of electrochemical miRNAs chip (e-miRchip) with a novel signal amplification strategy using silver nanoparticle reporters (AgNRs) for multiplexed, direct, electronic profiling of miRNAs. A two-step hybridization strategy was used to detect miRNAs, where the target miRNA hybridizes with a stem-loop probe to unlock the probe first, and the opened stem-loop can further hybridize with AgNRs for signaling amplification. To enhance the detection sensitivity, the gold nanoflower electrodes (GNEs) were constructed in the microaperture arrays of the e-miRchips by electroplating. With the optimal size of the GNEs, the e-miRchip showed excellent performance for miR-21 detection with a detection limit of 0.56 fM and a linear range extended from 1 fM to 10 pM. The e-miRchip also exhibited good specificity in differentiating the 3-base mismatched sequences of the target miRNA. In addition, the e-miRchip was able to directly detect miR-21 expression in the total RNA extracts or cell lysates collected from lung cancer cells and normal cells. This work demonstrated the developed e-miRchip as an efficient and promising miniaturized point-of-care diagnostic device for the early diagnosis and prognosis of cancers.

Graphical Abstract

Preparation and Properties of Indium Ion Modified Graphite Felt Composite Electrode

Iron-chromium redox flow batteries (ICRFBs) have the advantages of high safety, long cycle life, flexible design, and low maintenance costs. Polyacrylonitrile-based graphite felt composite material has good temperature resistance, corrosion resistance, large surface area and excellent electrical conductivity, and is often used as the electrode material of ICRFB, but its chemical activity is poor. In order to improve the activity of the graphite felt electrode, In3+ was used for modification in this paper, and the modified graphite felt was used as the electrode material for iron-chromium batteries. The structure and surface morphology of the modified graphite felt were analyzed by the specific surface area analyzer and scanning electron microscope; the electrochemical impedance spectroscopy and cyclic voltammetry experiments were carried out on the electrochemical workstation to study the electro catalytic activity of In3+ modified graphite felt and its performance in ICRFBS. The results show that the graphite felt electrode modified with a concentration of 0.2 M In3+ was activated at 400°C for 2 h, and its surface showed a lot of grooves, and the specific surface area reached 3.889 m2/g, while the specific surface area of the untreated graphite felt was only 0.995 m2/g significantly improved. Electrochemical tests show that the electrochemical properties of graphite felt electrodes are improved after In3+ modification. Therefore, the In3+ modified graphite felt electrode can improve the performance of ICRFB battery, and also make it possible to realize the engineering application of ICRFB battery.

Dendrite-Free Zinc-Based Battery with High Areal Capacity via the Region-Induced Deposition Effect of Turing Membrane

Zinc-based batteries are promising for use as energy storage devices owing to their low cost and high energy density. However, zinc chemistry commonly encounters serious dendrite issues, especially at high areal capacities and current densities, limiting their application. Herein, we propose a novel membrane featuring ordered undulating stripes called "Turing patterns", which can effectively suppress zinc dendrites and improve ion conductivity. The crests and troughs in the Turing membrane can effectively adjust the Zn(OH)₄^2- distribution and provide more zinc deposition space. The coordinated Cu ions during membrane formation can interact with Zn(OH)₄^2-, further smoothing zinc deposition. Even at a high current density of 80 mA·cm^-2, the Turing membrane enables an alkaline zinc-iron flow battery (AZIFB) to work stably with an ultrahigh areal capacity of 160 mA·h·cm^-2 for approximately 110 cycles, showing an energy efficiency of 90.10%, which is by far the highest value ever reported among zinc-based batteries with such a high current density. This paper provides valid access to zinc-based batteries with high areal capacities based on membrane design and promotes their advancement.

Trust is good, control is better: a review on monitoring and characterization techniques for flow battery electrolytes

Flow batteries (FBs) currently are one of the most promising large-scale energy storage technologies for energy grids with a large share of renewable electricity generation. Among the main technological challenges for the economic operation of a large-scale battery technology is its calendar lifetime, which ideally has to cover a few decades without significant loss of performance. This requirement can only be met if the key parameters representing the performance losses of the system are continuously monitored and optimized during the operation. Nearly all performance parameters of a FB are related to the two electrolytes as the electrochemical storage media and we therefore focus on them in this review. We first survey the literature on the available characterization methods for the key FB electrolyte parameters. Based on these, we comprehensively review the currently available approaches for assessing the most important electrolyte state variables: the state-of-charge (SOC) and the state-of-health (SOH). We furthermore discuss how monitoring and operation strategies are commonly implemented as online tools to optimize the electrolyte performance and recover lost battery capacity as well as how their automation is realized via battery management systems (BMSs). Our key findings on the current state of this research field are finally highlighted and the potential for further progress is identified.

Zn Electrodeposition by an In Situ Electrochemical Liquid Phase Transmission Electron Microscope

Alternative battery technologies are required to meet growing energy demands and to solve the limitations of the present energy technologies. As such, it is necessary to look beyond lithium-ion batteries. Zinc batteries enable high power density while being sourced from abundant and cost-effective materials. In this paper, the effect of the applied current and electrolyte flow rate on the early stage of Zn dendrite formation was characterized by in situ electrochemical liquid phase transmission electron microscopy (EC-LPTEM). For the first time, the square root relation is revealed between time and Zn dendrite growth on the lateral direction, indicating a diffusion-limited growth. It is intriguing that a higher applied current leads to longer incubation time. In situ EC-LPTEM can provide a useful strategy for understanding characteristics of unstable dendritic growth. The finding can help rationalize the electrode engineering design and parameters selection to avoid dendrite formation.

Electrochemical dual-aptamer biosensors based on nanostructured multielectrode arrays for the detection of neuronal biomarkers

Multielectrode arrays (MEAs) have been increasingly used for the development of biosensors due to their capability to record signals from multiple channels, fast mass transfer rates, and high spatial resolution. Alzheimer's disease (AD) is often associated with mitochondrial dysfunction, which is closely related to reduced levels of adenosine triphosphate (ATP). Therefore, simultaneous detection of ATP together with amyloid-β oligomers (AβO), a reliable biomarker for AD, can potentially advance the early detection of Alzheimer's disease. In this work, a dual-aptamer modified MEA chip was developed that consists of microelectrodes modified with electrodeposited 3D nanostructures (3D-GMEs). Electrodeposition methods, deposition potential, and deposition time were systematically altered and the active surface areas as well as the electrode morphologies were characterized by cyclic voltammetry and scanning electron microscopy. The nanostructured microelectrodes were sequentially modified with AβO and ATP specific aptamer receptors. To achieve the modification of different aptamer receptors at different 3D-GMEs of the same MEA chip, electrochemical cleaning was applied to individual 3D-GMEs. Ferrocene labels were attached to the aptamer receptors to enable amperometric signaling after target-aptamer binding. The developed aptasensor showed a linear detection range from 1 pM to 200 nM for the detection of AβO and from 0.01 nM to 1000 nM for the detection of ATP. Finally, ATP and AβO were detected simultaneously in the same analyte solution by the same sensor chip, which could support the early detection of AD, provide comprehensive information about the health status of the patient, and be helpful for pathological studies of neurodegenerative diseases.

Inhibition of Zinc Dendrites in Zinc-Based Flow Batteries

Zinc-based flow batteries have gained widespread attention and are considered to be one of the most promising large-scale energy storage devices for increasing the utilization of intermittently sustainable energy. However, the formation of zinc dendrites at anodes has seriously depressed their cycling life, security, coulombic efficiency, and charging capacity. Inhibition of zinc dendrites is thus the bottleneck to further improving the performance of zinc-based flow batteries, but it remains a major challenge. Considering recent developments, this mini review analyzes the formation mechanism and growth process of zinc dendrites and presents and summarizes the strategies for preventing zinc dendrites by regulating the interfaces between anodes and electrolytes. Four typical strategies, namely electrolyte modification, anode engineering, electric field regulation, and ion transfer control, are comprehensively highlighted. Finally, remaining challenges and promising directions are outlined and anticipated for zinc dendrites in zinc-based flow batteries.

Advanced Materials for Zinc-Based Flow Battery: Development and Challenge

Zinc-based flow batteries (ZFBs) are well suitable for stationary energy storage applications because of their high energy density and low-cost advantages. Nevertheless, their wide application is still confronted with challenges, which are mainly from advanced materials. Therefore, research on advanced materials for ZFBs in terms of electrodes, membranes, and electrolytes as well as their chemistries are of the utmost importance. Herein, the focus is on the scientific understandings of the fundamental design of these advanced materials and their chemistries in relation to the battery performance. The principles of using different materials in different ZFB technologies, the functions and structure of the materials, and further material improvements are discussed in detail. Finally, the challenges and prospects of ZFBs are summarized as well. This review provides valuable instruction on how to design and develop new materials as well as new chemistries for ZFBs.

An Electrolytic Zn-MnO2 Battery for High-Voltage and Scalable Energy Storage

Zinc-based electrochemistry is attracting significant attention for practical energy storage owing to its uniqueness in terms of low cost and high safety. However, the grid-scale application is plagued by limited output voltage and inadequate energy density when compared with more conventional Li-ion batteries. Herein, we propose a latent high-voltage MnO₂ electrolysis process in a conventional Zn-ion battery, and report a new electrolytic Zn-MnO₂ system, via enabled proton and electron dynamics, that maximizes the electrolysis process. Compared with other Zn-based electrochemical devices, this new electrolytic Zn-MnO₂ battery has a record-high output voltage of 1.95 V and an imposing gravimetric capacity of about 570 mAh g^-1 , together with a record energy density of approximately 409 Wh kg^-1 when both anode and cathode active materials are taken into consideration. The cost was conservatively estimated at <US$ 10 per kWh. This result opens a new opportunity for the development of Zn-based batteries, and should be of immediate benefit for low-cost practical energy storage and grid-scale applications.

Inhibition of Zinc Dendrite Growth in Zinc-Based Batteries

Zinc deposition and dissolution is a significant process in zinc-based batteries. During this process, the formation of zinc dendrites is pervasive, which leads to the loss of efficiency and capacity of batteries. The continually growing dendrites will finally pierce the separator and cause the batteries to short circuit. Thus, employing effective methods to inhibit the formation and growth of zinc dendrites is vital for the practical application of zinc-based batteries. This Minireview first clarifies the formation and growth principles of zinc dendrites. Then, the research and development of methods to solve the problem of zinc dendrites are reviewed, including ways to suppress the further formation and growth of dendrites as far as possible, to minimize the adverse effects of dendrites, along with ways to produce dendrite-free deposition processes. The mechanisms, advantages, drawbacks, and perspectives of these methods are illustrated. Thus, this overview of these methods will aid understanding of the formation process of zinc dendrites and provide an extensive, comprehensive, and professional reference to resolve the problem of zinc dendrites completely.

Redox-Flow Batteries: From Metals to Organic Redox-Active Materials

Research on redox-flow batteries (RFBs) is currently experiencing a significant upturn, stimulated by the growing need to store increasing quantities of sustainably generated electrical energy. RFBs are promising candidates for the creation of smart grids, particularly when combined with photovoltaics and wind farms. To achieve the goal of "green", safe, and cost-efficient energy storage, research has shifted from metal-based materials to organic active materials in recent years. This Review presents an overview of various flow-battery systems. Relevant studies concerning their history are discussed as well as their development over the last few years from the classical inorganic, to organic/inorganic, to RFBs with organic redox-active cathode and anode materials. Available technologies are analyzed in terms of their technical, economic, and environmental aspects; the advantages and limitations of these systems are also discussed. Further technological challenges and prospective research possibilities are highlighted.

Evaluation of the catalytic effect of non-noble bismuth on the lead half-cell reaction for lead-based redox flow batteries

Bi³⁺ ions can serve as high-performance additives for lead-based redox flow batteries.