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The recycling and treatment of wastewater using microbial fuel cells (MFCs) has been attracting significant attention as a way to control energy crises and water pollution simultaneously. Despite all efforts, MFCs are unable to produce high energy or efficiently treat pollutants due to several issues, one being the anode’s material. The anode is one of the most important parts of an MFC. Recently, different types of anode materials have been developed to improve the removal rate of pollutants and the efficiency of energy production. In MFCs, carbon-based materials have been employed as the most commonly preferred anode material. An extensive range of potentials are presently available for use in the fabrication of anode materials and can considerably minimize the current challenges, such as the need for high quality materials and their costs. The fabrication of an anode using biomass waste is an ideal approach to address the present issues and increase the working efficiency of MFCs. Furthermore, the current challenges and future perspectives of anode materials are briefly discussed.

A comprehensive understanding of the solid–electrolyte interphase (SEI) composition is crucial to developing high-energy batteries based on lithium metal anodes. A particularly contentious issue concerns the presence of LiH in the SEI. Here we report on the use of synchrotron-based X-ray diffraction and pair distribution function analysis to identify and differentiate two elusive components, LiH and LiF, in the SEI of lithium metal anodes. LiH is identified as a component of the SEI in high abundance, and the possibility of its misidentification as LiF in the literature is discussed. LiF in the SEI is found to have different structural features from LiF in the bulk phase, including a larger lattice parameter and a smaller grain size (<3 nm). These characteristics favour Li + transport and explain why an ionic insulator, like LiF, has been found to be a favoured component for the SEI. Finally, pair distribution function analysis reveals key amorphous components in the SEI. X-ray diffraction and Rietveld refinement analysis confirm the presence of LiH in the solid–electrolyte interphase of lithium metal anodes.

Improving the anode properties, including increasing its capacity, is one of the basic necessities to improve battery performance. In this paper, high-capacity anodes with alloy performance are introduced, then the problem of fragmentation of these anodes and its effect during the cyclic life is stated. Then, the effect of reducing the size to the nanoscale in solving the problem of fragmentation and improving the properties is discussed, and finally the various forms of nanomaterials are examined. In this paper, electrode reduction in the anode, which is a nanoscale phenomenon, is described. The negative effects of this phenomenon on alloy anodes are expressed and how to eliminate these negative effects by preparing suitable nanostructures will be discussed. Also, the anodes of the titanium oxide family are introduced and the effects of Nano on the performance improvement of these anodes are expressed, and finally, the quasi-capacitive behavior, which is specific to Nano, will be introduced. Finally, the third type of anodes, exchange anodes, is introduced and their function is expressed. The effect of Nano on the reversibility of these anodes is mentioned. The advantages of nanotechnology for these electrodes are described. In this paper, it is found that nanotechnology, in addition to the common effects such as reducing the penetration distance and modulating the stress, also creates other interesting effects in this type of anode, such as capacitive quasi-capacitance, changing storage mechanism and lower volume change.

HighlightsRepresentative methods for calculating the depth of discharge of different Zn anodes are introduced.Recent advances of aqueous Zn metal batteries with high Zn utilization are reviewed and categorized according to Zn anodes with different structures.The working mechanism of anode-free aqueous Zn metal batteries is introduced in detail, and different modification strategies for anode-free aqueous Zn metal batteries are summarized.Aqueous zinc metal batteries (AZMBs) are promising candidates for next-generation energy storage due to the excellent safety, environmental friendliness, natural abundance, high theoretical specific capacity, and low redox potential of zinc (Zn) metal. However, several issues such as dendrite formation, hydrogen evolution, corrosion, and passivation of Zn metal anodes cause irreversible loss of the active materials. To solve these issues, researchers often use large amounts of excess Zn to ensure a continuous supply of active materials for Zn anodes. This leads to the ultralow utilization of Zn anodes and squanders the high energy density of AZMBs. Herein, the design strategies for AZMBs with high Zn utilization are discussed in depth, from utilizing thinner Zn foils to constructing anode-free structures with theoretical Zn utilization of 100%, which provides comprehensive guidelines for further research. Representative methods for calculating the depth of discharge of Zn anodes with different structures are first summarized. The reasonable modification strategies of Zn foil anodes, current collectors with pre-deposited Zn, and anode-free aqueous Zn metal batteries (AF-AZMBs) to improve Zn utilization are then detailed. In particular, the working mechanism of AF-AZMBs is systematically introduced. Finally, the challenges and perspectives for constructing high-utilization Zn anodes are presented.

Aqueous zinc‐ion batteries (ZIBs) have been intensively investigated as potential energy storage devices on account of their low cost, environmental benignity, and intrinsically safe merits. With the exploitation of high‐performance cathode materials, electrolyte systems, and in‐depth mechanism investigation, the electrochemical performances of ZIBs have been greatly enhanced. However, there are still some challenges that need to be overcome before its commercialization. Among them, the obstinate dendrites, corrosion, and hydrogen evolution reaction (HER) on Zn anodes are critical issues that severely limit the practical applications of ZIBs. To address these issues, various strategies have been proposed, and tremendous progress has been achieved in the past few years. In this article, we analyze the origins and effects of the dendrites, corrosion, and HER on Zn anodes in neutral and mildly acid aqueous solutions at first. And then, a scientific understanding of the fundamental design principles and strategies to suppress these problems are emphasized. Apart from these, this article also puts forward some requirements for the practical applications of Zn anodes as well as several cost‐effective‐modifying strategies. Finally, perspectives on the future development of Zn anodes in aqueous solutions are also briefly anticipated. This article provides pertinent insights into the challenges on anodes for the development of high‐performance ZIBs, which will greatly contribute to their practical applications. This article summarizes the causes and effects of Zn dendrites, corrosion, and hydrogen evolution reaction (HER) in aqueous zinc‐ion batteries (ZIBs). Moreover, recent advances in tackling these three issues toward zinc anode are systematically analyzed. Finally, several perspectives for the overall performance of zinc anodes have been put forward.

A solid-state electrolyte is expected to suppress lithium (Li) dendrite penetration with high mechanical strength 1 – 4 . However, in practice it still remains challenging to realise a lithium metal anode for batteries, because micrometre- or submicrometre-sized cracks in ceramic pellets can frequently be generated during battery assembly or long-time cycling 3 , 5 . Once cracks form, lithium dendrite penetration is inevitable 6 , 7 . Here we describe a solid-state battery design with a hierarchy of interface stabilities (to lithium metal responses), to achieve an ultrahigh current density with no lithium dendrite penetration. Our multilayer design has the structure of a less-stable electrolyte sandwiched between more-stable solid electrolytes, which prevents any lithium dendrite growth through well localized decompositions in the less stable electrolyte layer. A mechanism analogous to the expansion screw effect is proposed, whereby any cracks are filled by dynamically generated decompositions that are also well constrained, probably by the ‘anchoring’ effect the decompositions induce. The cycling performance of the lithium metal anode paired with a LiNi 0.8 Mn 0.1 Co 0.1 O 2 cathode is very stable, with an 82 per cent capacity retention after 10,000 cycles at a 20C rate (8.6 milliamps per centimetre squared) and 81.3 per cent capacity retention after 2,000 cycles at a 1.5C rate (0.64 milliamps per centimetre squared). Our design also enables a specific power of 110.6 kilowatts per kilogram and specific energy up to 631.1 watt hours per kilogram at the micrometre-sized cathode material level. A multi-layered electrolyte, in which a less stable electrolyte is sandwiched between two electrolyte layers that are more stable, can inhibit the growth of lithium dendrites in highly pressurized solid-state lithium metal batteries.

The oxygen-evolving IrO2-Ta2O5/Ti anode (OEA), primarily used in electrolyzers for plating, metal powder production, electrowinning (EW), and water electrolysis, is analyzed. This study focuses on the distribution of oxygen evolution reaction (OER) activity and the associated operational loss over the randomized OEA texture. The OER activity and its distribution across the IrO2-Ta2O5 coating surface are key factors that influence EW operational challenges and the lifecycle of OEA in EW processes. To understand the OER activity distribution over the coating’s randomized texture, we performed analyses using anode polarization in acid solution at both low and high (EW operation relevant) overpotentials and electrochemical impedance spectroscopy (EIS) during the OER. These measurements were conducted on anodes in both their as-prepared and deactivated states. The as-prepared anode was deactivated using an accelerated stability test in an acid solution, the EW simulating electrolyte. The obtained data are correlated with fundamental electrochemical properties of OEA, such as structure-related pseudocapacitive responses at open circuit potential in the same operating environment. OER and Ir dissolution kinetics, along with the physicochemical anode state upon deactivation, are clearly characterized based on current and potential dependent charge transfer resistances and associated double layer capacitances obtained by EIS. This approach presents a useful tool for elucidating, and consequently tailoring and predicting, anode OER activity and electrolytic operational stability in industrial electrochemical applications.

Chlorine (Cl 2 ) is one of the most important chemicals produced by the electrolysis of brine solutions and is a key raw material for many areas of industrial chemistry. For nearly half a century, dimensionally stable anode (DSA) made from a mixture of RuO 2 and TiO 2 solid oxides coated on Ti substrate has been the most widely used electrode for chlorine evolution reaction (CER). In harsh operating environments, the stability of DSAs remains a major challenge greatly affecting their lifetime. The deactivation of DSAs significantly increases the cost of the chlor-alkali industry due to the corrosion of Ru and the formation of the passivation layer TiO 2 . Therefore, it is urgent to develop catalysts with higher activity and stability, which requires a thorough understanding of the deactivation mechanism of DSA catalysts. This paper reviews existing references on the deactivation mechanisms of DSA catalysts, including both experimental and theoretical studies. Studies on how CER selectivity affects electrode stability are also discussed. Furthermore, studies on the effects of the preparation process, elemental composition, and surface/interface structures on the DSA stability and corresponding improvement strategies are summarized. The development of other non-DSA-type catalysts with comparable stability is also reviewed, and future opportunities in this exciting field are also outlined.

Lithium batteries are key components of portable devices and electric vehicles due to their high energy density and long cycle life. To meet the increasing requirements of electric devices, however, energy density of Li batteries needs to be further improved. Anode materials, as a key component of the Li batteries, have a remarkable effect on the increase of the overall energy density. At present, various anode materials including Li anodes, high‐capacity alloy‐type anode materials, phosphorus‐based anodes, and silicon anodes have shown great potential for Li batteries. Composite‐structure anode materials will be further developed to cater to the growing demands for electrochemical storage devices with high‐energy‐density and high‐power‐density. In this review, the latest progress in the development of high‐energy Li batteries focusing on high‐energy‐capacity anode materials has been summarized in detail. In addition, the challenges for the rational design of current Li battery anodes and the future trends are also presented. The increasing development of battery‐powered vehicles for exceeding 500 km endurance has stimulated the exploration of lithium‐ion batteries with high‐energy‐density and high‐power‐density. In this review, proximate developments in various types of high specific energy lithium‐ion batteries are screened, focusing on silicon‐based anode, phosphorus‐based anode, lithium metal anode, and hybrid anode systems.

Lithium-ion batteries have had a profound impact on our daily life, but inherent limitations make it difficult for Li-ion chemistries to meet the growing demands for portable electronics, electric vehicles and grid-scale energy storage. Therefore, chemistries beyond Li-ion are currently being investigated and need to be made viable for commercial applications. The use of metallic Li is one of the most favoured choices for next-generation Li batteries, especially Li–S and Li–air systems. After falling into oblivion for several decades because of safety concerns, metallic Li is now ready for a revival, thanks to the development of investigative tools and nanotechnology-based solutions. In this Review, we first summarize the current understanding on Li anodes, then highlight the recent key progress in materials design and advanced characterization techniques, and finally discuss the opportunities and possible directions for future development of Li anodes in applications.