The emergence of all-solid-state Li batteries (ASSLBs) represents a promising avenue to address critical concerns like safety and energy density limitations inherent in current Li-ion batteries. Solid electrolytes (SEs) show significant potential in curtailing Li dendrite intrusion, acting as natural barriers against short circuits. However, the substantial challenges at the SEs−electrode interface, particularly concerning the anode, pose significant impediments to the practical implementation of ASSLBs. This review aims to delineate the most viable strategies for overcoming anode interfacial hurdles across four distinct categories of SEs: sulfide SEs, oxide SEs, polymer SEs, and halide SEs. Initially, pivotal issues such as anode interfacial side reactions, inadequate physical contact, and Li dendrite formation are comprehensively outlined. Furthermore, effective methodologies aimed at enhancing anode interfacial stability are expounded, encompassing approaches like solid electrolyte interface (SEI) interlayer insertion, SE optimization, and the adoption of Li alloy in lieu of Li metal, each tailored to specific SE categories. Moreover, this review presents novel insights into fostering interfaces between diverse SE types and Li anodes, while also advocating perspectives and recommendations for the future advancement of ASSLBs.
Lithium-ion batteries are limited by the low energy density of graphite anodes and are gradually becoming unable to meet the demand for energy storage development. A further increase in high capacity requires new battery materials and chemistry, such as the innovative lithium metal anodes (LMAs). However, the actual commercialization of LMAs is limited by the unstable Li/electrolyte interface, impeding their progress from the laboratory to industrial production. To address these problems, constructing a Li alloy/Li halide mixed layer upon a Li surface is considered to be an ideal direction because of the combined advantages of Li alloys and Li halides. In this context, by comparing the limitations of self-generated solid electrolyte interfaces, the unique merits of Li alloys and Li halides are discussed in depth with summaries of their respective advances. Accordingly, mixed layers of Li alloy/Li halides are introduced, and the mechanisms of Li deposition behaviors are clearly described, along with their manufacturing strategies and recent progress. Moreover, the emerging techniques for interface characterization are also comprehensively summarized. Furthermore, the necessary considerations and outlooks for the future design of Li alloy/Li halide mixed layers are highlighted, with the aim of elucidating the structure-property relationships and providing rational directions for the attainment of the next-generation high-performance batteries.
Lithium-ion batteries (LIBs) have been extensively used in electronic devices, electric vehicles, and energy storage systems due to their high energy density, environmental friendliness, and longevity. However, LIBs are sensitive to environmental conditions and prone to thermal runaway (TR), fire, and even explosion under conditions of mechanical, electrical, and/or thermal abuse. These unpredictable hazardous consequences significantly limit the commercial applications of LIBs. Thus, these safety issues need to be urgently addressed. In this review, the TR mechanisms and fire characteristics of LIBs are systematically discussed. Battery thermal safety monitoring methods, including the traditional technologies such as temperature, voltage, and gas sensors, as well as the latest new technologies such as optical fiber sensors and ultrasonic imaging, are summarized. A battery thermal management system (BTMS) based on various cooling methods and new insights into the BTMS are briefly presented. According to the fire characteristics of LIBs, nonaqueous and water-based fire extinguishing agents are comprehensively summarized and compared, and the concept of an intelligent fire protection system is discussed. Based on the analysis of the thermal safety issues for preventing possible TRs and for extinguishing an already uncontrollable fire, a complete set of solutions for the thermal safety of LIBs is proposed. In this review, integrated strategies for intelligent detection and fire suppression of LIBs are presented and can provide theoretical guidance for key material design and intellectual safety systems to promote wide application of LIBs.
Thermal safety analysishelps us gain a deep understanding of the causesof LIB safety issues. Monitoring and thermal management prevent and alertpotential safety accidents. Intelligent fire-fighting system effectivelyextinguishes LIB fires that have already occurred. This review proposes acomplete set of solutions for the thermal safety of LIBs.
Lithium-ion batteries (LIBs) are susceptible to mechanical failures that can occur at various scales, including particle, electrode and overall cell levels. These failures are influenced by a combination of multi-physical fields of electrochemical, mechanical and thermal factors, making them complex and multi-physical in nature. The consequences of these mechanical failures on battery performance, lifetime and safety vary depending on the specific type of failure. However, the complex nature of mechanical degradation in batteries often involves interrelated processes, in which different failure mechanisms interact and evolve. Despite extensive research efforts, the detailed mechanisms behind these failures still require further clarification. To bridge this knowledge gap, this review systematically investigates three key aspects: multiscale mechanical failures; their implications for performance, lifetime and safety; and the interconnections between the different types and scales of the mechanical failures. By adopting a multiscale and multidisciplinary perspective, fragmented ideas from current research are integrated into a comprehensive framework, providing a deeper understanding of the mechanical behaviors and interactions within LIBs. We highlight the main characteristics of mechanical failures in LIBs and present valuable insights and prospects in four key areas of theories, materials, designs and applications, for improving the performance, lifetime and safety of LIBs by addressing current challenges in the field. As a valuable resource, this review may serve as a bridge for researchers from diverse disciplines, facilitating their understanding of mechanical failures in LIBs and encouraging further advancements in the field.
Excessive nitrate (NO3 −) contamination has emerged as a critical environmental issue owing to the widespread use of nitrogen-based fertilizers, fossil fuel combustion, and the discharge of industrial and domestic effluents. Consequently, electrochemical nitrate reduction (eNO3R) to ammonia (NH3) has emerged as a promising alternative to the traditional Haber-Bosch process. However, the industrial implementation of eNO3R is hindered by low catalytic activity, poor selectivity, and limited stability owing to competing hydrogen evolution reactions. This paper provides a comprehensive overview of recent advancements in eNO3R, particularly evaluating the catalytic activity, selectivity, and stability of both noble and non-noble metal catalysts. This review elucidates innovative catalyst design strategies, state-of-the-art developments, and potential directions for future research. Additionally, the paper explores the fundamental mechanisms underlying eNO3R for NH3 production, including electrocatalyst development methodologies, electrolyte effects, in situ characterization techniques, theoretical modeling, and cell design considerations. Moreover, factors influencing NH3 selectivity and catalyst structural composition are thoroughly examined. Finally, this review provides comprehensive insights into optimizing eNO3R processes for synthesizing NH3, which can promote further advancements in this field.
Endowed by high energy density and high conversion efficiency between chemical and electric energy, rechargeable batteries are indispensable in a variety of different energy-level applications, ranging from portable devices (W-level) to electric vehicles (kW-level) and large-scale energy storage systems (MW-level). However, many lingering scientific and technical challenges still inhibit their wide applications, including low Coulombic efficiency, inferior cycle/rate performance, and safety hazards. After decades of extensive research, it is widely accepted that these challenges are largely influenced by the interfacial chemistry occurring at the electrode–electrolyte interface (EEI). EEI includes both the solid electrolyte interphase on the anode and the cathode electrolyte interphase on the cathode, and the great protective capability of the fluorinated interface is gradually unveiled. Although intensive research efforts have been devoted to fabricating various ex situ artificial and in situ interfacial fluorinated layers, the fundamental approaches to the fluorinated interface are still inferior and not systematically categorized and analyzed. In this contribution, we have confined and proposed five principles regarding obtaining fluorinated interfaces from pretreatment, solvent-separated ion pairs, contact ion pairs, aggregates, and feasible decomposition from numerous reports and built up a systematic design framework to guide the construction of the protective fluorinated interfaces for rechargeable batteries, offering target-oriented guidelines to tackle interface issues in secondary batteries.
Lithium metal is considered a highly promising anode material because of its low reduction potential and high theoretical specific capacity. However, lithium metal is prone to irreversible side reactions with liquid electrolytes, resulting in the consumption of metallic lithium and electrolytes due to the high reactivity of lithium metal. The uneven plating/stripping of lithium ions leads to the growth of lithium dendrites and battery safety risks, hindering the further development and commercial application of lithium metal batteries (LMBs). Constructing solid-state electrolyte (SSE) systems with high mechanical strength and low flammability is among the most effective strategies for suppressing dendrite growth and improving the safety of LMBs. However, the structural defects, intrinsic ionic conductivity, redox potential and solid-solid contacts of SSEs can cause new electrochemical problems and solid-phase dendrite growth drawbacks in the application of solid-state batteries (SSBs). In this review, the mechanisms of lithium dendrite growth in SSEs are comprehensively summarized. Strategies to suppress lithium dendrite growth, stabilize the interface, and enhance ion transport in organic, inorganic and composite SSEs are emphasized. We conclude with not only relevant experimental findings but also computational predictions to qualitatively and quantitatively characterize the ionic conductivity, interfacial stability and other properties of SSEs based on both chemical and physical principles. The development direction and urgent problems of SSEs are summarized and discussed.
Rechargeable all-solid-state sodium batteries (ASS-SBs), including all-solid-state sodium-ion batteries and all-solid-state sodium-metal batteries, are considered highly advanced electrochemical energy storage technologies. This is owing to their potentially high safety and energy density and the high abundance of sodium resources. However, these materials are limited by the properties of their solid-state electrolytes (SSEs) and various SSE/Na interfacial challenges. In recent years, extensive research has focused on understanding the interfacial behavior and strategies to overcome the challenges in developing ASS-SBs. In this prospective, the sodium-ion conduction mechanisms in different SSEs and the interfacial failure mechanisms of their corresponding batteries are comprehensively reviewed in terms of chemical/electrochemical stability, interfacial contacts, sodium dendrite growth, and thermal stability. Based on mechanistic analysis, representative interfacial engineering strategies for the interface between SSEs and Na anodes are summarized. Advanced techniques, including in situ/ex situ instrumental and electrochemical measurements and analysis for interface characterization, are also introduced. Furthermore, advanced computer-assisted methods, including artificial intelligence and machine learning (which can complement experimental systems), are discussed. The purpose of this review is to outline the solid-state electrolyte and electrolyte/anode interface challenges, and the potential research directions for overcoming these challenges. This would enable target-oriented research for the development of solid-state electrochemical energy storage devices.
Potassium-ion batteries (PIBs) have attracted tremendous attention during the past several years due to their abundant reserves, wide distribution, fast ionic conductivity, and high operating voltage. The primary obstacle impeding the commercialization of rechargeable PIBs is the lack of suitable high-performance anode materials. Carbon materials, known for their environmental friendliness, abundant availability, and outstanding comprehensive performance, have received extensive attention because they can be utilized directly as anodes or serve as a constrained matrix for conversion-/alloying-type anodes to enhance the electrochemical performance. Structural tuning and morphological modulation are two common strategies for modifying carbon materials. In this review, the recent progress in carbon materials aimed at enhancing the performance of PIBs through the utilization of these two strategies is systematically summarized. First, the effects of structural tuning and morphological modulation on the electrochemical properties of carbon materials and the corresponding storage mechanisms are reviewed. Second, the performance improvement mechanisms of conversion-/alloying-type anodes utilizing carbon scaffolds based on these two strategies are systematically discussed. Third, the application of carbon materials based on various modification strategies in various advanced K+ storage devices is reviewed. Finally, the challenges and perspectives for the further development of carbon-based materials for PIBs are highlighted.
With the proposal of the global carbon neutrality target, lithium-ion batteries (LIBs) are bound to set off the next wave of applications in portable electronic devices, electric vehicles, and energy-storage grids due to their unique merits. However, the growing LIB market poses a severe challenge for waste management during LIB recycling after end-of-life, which could cause serious environmental pollution and resource waste without proper treatment. Pyrometallurgical, hydrometallurgical, and direct recycling of spent LIBs have been developed, guided by the “waste to wealth” principle, and were applied to LIB remanufacturing. However, some spent LIB materials with low values or great direct regeneration difficulties may not be suitable for the above options, necessitating expanded application ranges of spent LIBs. Considering their unique compositions, using waste electrode materials directly or as precursors to prepare advanced catalysts has been proposed as another promising disposal technology for end-of-life LIBs. For example, transition metal elements in the cathode, like Ni, Co, Mn, and Fe, have been identified as catalytic active centers, and graphite anodes can serve as the catalyst loading matrix. This scheme has been adopted in various catalysis applications, and preliminary progress has been made. Therefore, this review summarizes and discusses the application of spent LIB recycling materials in catalysis and classified it into three aspects: environmental remediation, substance conversion, and battery-related catalysis. Moreover, the existing challenges and possible foci of future research on spent LIB recycling are also discussed. This review is anticipated to mark the start of close attention to the high-value-added applications of spent LIB products, enhancing economic efficiency and sustainable development.
Continuing global growth in consumer electronics, electric vehicles and new energy power generation has caused tremendous demand for lithium ion batteries (LIBs), and the recycling of end-of-life LIBs has become a priority for sustainable development. In addition to the remanufacturing of LIBs, spent LIB products with high value-added components have received more attention in catalysis. Catalysts prepared from spent LIB electrode materials exhibit superior performance in the field of environmental remediation, substance conversion, and batteries-related catalysis, which are summarized and discussed in this review.
Atomically precise metal nanocluster and ultrasmall nanoparticle catalysts have garnered significant interest in electrocatalysis applications due to their unique geometric and electronic structures. As an intermediate state between single-atom catalysts (SACs) and nanoparticles in size, nanoclusters with specific low nuclearity provide designated metallic states with multiple atoms or surface sites for the adsorption and transformation of reactants/intermediates. The unique catalytic properties of nanoclusters offer a novel platform for designing effective and efficient electrocatalysts, potentially surpassing the SACs in certain catalytic reactions. This review summarizes and discusses the latest progress of nanoclusters and ultrasmall nanoparticles for various electrocatalysis applications, including oxygen reduction reaction (ORR), oxygen evolution reaction (OER), CO2 reduction reaction (CO2RR), nitrogen reduction reaction (NRR), hydrogen evolution reaction (HER), various chemicals oxidation reaction (COR), etc. Specifically, this review highlights surface/interface chemical modification strategies and structure-properties relationships, drawing from the atomic-level insights to determine electrocatalytic performance. Lastly, we present the challenges and opportunities associated with nanocluster or ultrasmall nanoparticle electrocatalysts.
Biomass, which is derived from abundant renewable resources, is a promising alternative to fossil-fuel-based carbon materials for building a green and sustainable society. Biomass-based carbon materials (BCMs) with tailored hierarchical pore structures, large specific surface areas, and various surface functional groups have been extensively studied as energy and catalysis-related materials. This review provides insights from the perspectives of intrinsic physicochemical properties and structure-property relationships for discussing several fundamental yet significant issues in BCMs and their consequences. First, the synthesis, properties, and influencing factors of BCMs are discussed. Then, the causes and effects of the poor mechanical properties of biochar are explored. The factors affecting the properties of BCMs are presented, and the approaches for tuning these properties of biochar are summarized. Further, the applications of BCMs in energy storage and conversion are highlighted, including hydrogen storage and production, fuel cells, supercapacitors, hybrid electrodes, catalytic reforming, oxygen and CO2 reduction, and acetylene hydrochlorination. Finally, the future trends and prospects for biochar are proposed. This review aims to serve as a useful, up-to-date reference for future studies on BCMs for energy and catalytic applications.
All solid-state lithium batteries (ASSLBs) overcome the safety concerns associated with traditional lithium-ion batteries and ensure the safe utilization of high-energy-density electrodes, particularly Li metal anodes with ultrahigh specific capacities. However, the practical implementation of ASSLBs is limited by the instability of the interface between the anode and solid-state electrolyte (SSE). To mitigate this, considerable research has been dedicated to achieving enhanced stability at the anode/SSE interface. Among the current strategies for enhancing interface performance, the concept of Li-alloy materials is extensively used and well functionalized in various scenarios, including Li alloys as anodes, Li-alloy interlayers and Li alloys in the anode. Despite the notable achievements of Li-alloy materials in ASSLBs, the functionality, practicality and working mechanism of Li-alloys have not been fully elucidated. This review commences by providing an exhaustive and in-depth examination of the fundamental kinetics, thermodynamics, and mechanics, highlighting Li-alloy materials. Subsequently, through a systematic interconnection of material properties and their practical applications, we undertake a comprehensive analysis of the operative principles governing Li alloys. This analytical approach allows a thorough evaluation of the viability and utility of Li alloys within the context of ASSLBs. Finally, this review concludes by succinctly summarizing the future prospects and inherent potential of Li-alloy materials for further advancing the field of ASSLBs.
Unsustainable fossil fuel energy usage and its environmental impacts are the most significant scientific challenges in the scientific community. Two-dimensional (2D) materials have received a lot of attention recently because of their great potential for application in addressing some of society’s most enduring issues with renewable energy. Transition metal-based nitrides, carbides, or carbonitrides, known as “MXenes”, are a relatively new and large family of 2D materials. Since the discovery of the first MXene, Ti3C2 in 2011 has become one of the fastest-expanding families of 2D materials with unique physiochemical features. MXene surface terminations with hydroxyl, oxygen, fluorine, etc., are invariably present in the so far reported materials, imparting hydrophilicity to their surfaces. The current finding of multi-transition metal-layered MXenes with controlled surface termination capacity opens the door to fabricating unique structures for producing renewable energy. MXene NMs-based flexible chemistry allows them to be tuned for energy-producing/storage, electromagnetic interference shielding, gas/biosensors, water distillation, nanocomposite reinforcement, lubrication, and photo/electro/chemical catalysis. This review will first discuss the advancement of MXenes synthesis methods, their properties/stability, and renewable energy applications. Secondly, we will highlight the constraints and challenges that impede the scientific community from synthesizing functional MXene with controlled composition and properties. We will further reveal the high-tech implementations for renewable energy storage applications along with future challenges and their solutions.
Owing to their advantages, such as a high energy density, low operating potential, high abundance, and low cost, rechargeable silicon (Si) anode lithium-ion batteries (LIBs) have attracted considerable interest. Significant advancements in Si-based LIBs have been made over the past decade. Nevertheless, because the cycle instability is a crucial factor in the half/full-battery design and significantly affects the consumption of active components and the weight of the assembled battery, it has become a concern in recent years. This paper presents a thorough analysis of the recent developments in the enhancement methods for the stability of LIBs. Comprehensive in situ and operando characterizations are performed to thoroughly evaluate the electrochemical reactions, structural evolution, and degradation processes. Approaches for enhancing the cycle stability of Si anodes are systematically divided from a design perspective into several categories, such as the structural regulation, interfacial design, binder architecture, and electrolyte additives. The advantages and disadvantages of several methods are emphasized and thoroughly evaluated, offering insightful information for the logical design and advancement of cutting-edge solutions to address the deteriorating low-cycle stability of silicon-based LIBs. Finally, the conclusions and potential future research perspectives for promoting the cycling instability of silicon-based LIBs are presented.
Organic material electrodes are regarded as promising candidates for next-generation rechargeable batteries due to their environmentally friendliness, low price, structure diversity, and flexible molecular structure design. However, limited reversible capacity, high solubility in the liquid organic electrolyte, low intrinsic ionic/electronic conductivity, and low output voltage are the main problems they face. A lot of research work has been carried out to explore comprehensive solutions to the above problems through molecular structure design, the introduction of specific functional groups and specific molecular frameworks, from small molecules to polymer molecules, metal-organic frameworks (MOFs), covalent organic frameworks (COFs) and heterocyclic molecules; from simple organic materials to organic composites; from single functional groups to multi-functional groups; etc. The inevitable relationship between various molecular structure design and enhanced electrochemical properties has been illustrated in detail. This work also specifically discusses several approaches for the current application of organic compounds in batteries, including interfacial protective layer of inorganic metal oxide cathode, anode (metal lithium or silicon) and solid-state electrolyte, and host materials of sulfur cathode and redox media in lithium-sulfur batteries. This overview provides insight into a deep understanding of the molecular structure of organic electrode materials (OEMs) and electrochemical properties, broadens people’s research ideas, and inspires researchers to explore the advanced application of electroactive organic compounds in rechargeable batteries.
For energy storage technologies, secondary batteries have the merits of environmental friendliness, long cyclic life, high energy conversion efficiency and so on, which are considered to be hopeful large-scale energy storage technologies. Among them, rechargeable lithium-ion batteries (LIBs) have been commercialized and occupied an important position as secondary batteries due to their high energy density and long cyclic life. Nevertheless, the uneven distribution of lithium resources and a large number of continuous consumptions result in a price increase for lithium. So, it is very crucial to seek and develop alternative batteries with abundant reserves and low cost. As one of the best substitutes for widely commercialized LIBs, sodium-ion batteries (SIBs) display gorgeous application prospects. However, further improvements in SIB performance are still needed in the aspects of energy/power densities, fast-charging capability and cyclic stability. Electrode materials locate at a central position of SIBs. In addition to electrode materials, electrolytes, conductive agents, binders and separators are imperative for practical SIBs. In this review, the latest progress and challenges of applications of SIBs are reviewed. Firstly, the anode and cathode materials for SIBs are symmetrically summarized from aspects of the design strategies and synthesis, electrochemical active sites, surrounding environments of active sites, reaction mechanisms and characterization methods. Secondly, the influences of electrolytes, conductive agents, binders and separators on the electrochemical performance are elucidated. Finally, the technical challenges are summarized, and the possible future research directions for overcoming the challenges are proposed for developing high performance SIBs for practical applications.
Flexible energy storage systems are promising and efficient technologies for realizing large-scale application of portable, bendable, and wearable electronic devices. Among these systems, aqueous hybrid supercapacitors (AHSs) fabricated using redox-active materials with a positive voltage window in aqueous electrolytes and capacitive carbon materials have attracted enormous attention due to their advantages, including a wide operating voltage, a high energy density, a high power density, a long cycling lifespan, and low cost. Thus far, considerable efforts have been made to develop flexible AHSs constructed from various free-standing and flexible electrodes. However, optimizing the configurations of flexible electrodes and the interfacial interaction between flexible substrates and electroactive materials to fully develop the performance through their synergistic effects remains a major challenge. Herein, we have reviewed and summarized recent advances in flexible electrode materials with a variety of configurations based on porous metal supports, carbon substrates, including carbon nanotube networks, graphene and wearable carbon (carbon fibers, carbon cloth, carbon fabric, etc.), and other flexible materials for high-performance AHSs. These flexible electrodes show unique configurations and optimized interfacial structures, resulting in excellent electrochemical performance and superior mechanical stability in AHSs under various harsh conditions, and have great potential for practical applications. Furthermore, the future directions and perspectives for constructing flexible electrodes with novel configurations and AHSs are outlined and discussed, including (1) fabrication of compressible, ultralight, or transparent flexible electrodes for special needs; (2) tailoring and tuning of interfacial properties with robust adhesion between electroactive materials and flexible substrates; (3) development of advanced in situ characterization techniques to uncover the structure evolution rules of flexible electrodes under the operation conditions; (4) matching and optimization of flexible positive and negative electrode materials to assemble advanced AHS devices; (5) design of multifunctional flexible electrodes and AHSs by integrating other specific functions, etc. This timely review is believed to provide deep insights into the intensive research on flexible aqueous energy storage devices.
The recent advances in flexible electrodes with a variety of configurations based on porous metal supports, carbon substrates, and other flexible materials for advanced aqueous hybrid supercapacitors (AHSs) are summarized. The future prospects and directions for constructing flexible electrodes and AHSs are further outlined.
Water electrolysis for hydrogen production holds great promise as an energy conversion technology. The electrolysis process contains two necessary electrocatalytic reactions, one is the hydrogen evolution reaction (HER) at the cathode, and the other is the oxygen evolution reaction (OER) at the anode. In general, the kinetics of OER is much slower than that of HER, dominating the overall of performance electrolysis. As identified, the slow kinetics of catalytic OER is mainly resulted from multiple electron transfer steps, and the catalysts often undergo compositional, structural, and electronic changes during operation, leading to complicated dynamic reaction mechanisms which have not been fully understood. Obviously, this challenge presents formidable obstacles to the development of highly efficient OER electrocatalysts. To address the issue, it is crucial to unravel the origins of intrinsic OER activity and stability and elucidate the catalytic mechanisms across diverse catalyst materials. In this context, in-situ/operando characterization techniques would play a pivotal role in understanding the catalytic reaction mechanisms by enabling real-time monitoring of catalyst structures under operational conditions. These techniques can facilitate the identification of active sites for OER and provide essential insights into the types and quantities of key reaction intermediates. This comprehensive review explores various catalyst design and synthesis strategies aimed at enhancing the intrinsic OER activity and stability of catalysts and examines the application of advanced in-situ/operando techniques for probing catalyst mechanisms during the OER process. Furthermore, the imperative need for developing innovative in-situ/operando techniques, theoretical artificial intelligence and machine learning and conducting theoretical research to better understand catalyst structural evolution under conditions closely resembling practical OER working states is also deeply discussed. Those efforts should be able to lay the foundation for the improved fabrication of practical OER catalysts.
Proton exchange membrane fuel cells (PEMFCs) have demonstrated their viability as a promising candidate for clean energy applications. However, performance of conventional PEMFC electrodes, especially the cathode electrode, suffers from low catalyst utilization and sluggish mass transport due to the randomly distributed components and tortuous transport pathways. Development of alternative architectures in which the electrode structure is controlled across a range of length scales provides a promising path toward overcoming these limitations. Here, we provide a comprehensive review of recent research and development of advanced electrode structures, organized by decreasing length-scale from the millimeter-scale to the nanometer-scale. Specifically, advanced electrode structures are categorized into five unique architectures for specific functions: (1) macro-patterned electrodes for enhanced macro-scale mass transport, (2) micro-patterned electrodes for enhanced micro-scale mass transport, (3) electrospun electrodes with fiber-based morphology for enhanced in-plane proton transport and through-plane O2 transport, (4) enhanced-porosity electrodes for improved oxygen transport through selective inclusion of void space, and (5) catalyst film electrodes for elimination of carbon corrosion and ionomer poisoning. The PEMFC performance results achieved from each alternative electrode structure are presented and tabulated for comparison with conventional electrode architectures. Moreover, analysis of mechanisms by which new electrode structures can improve performance is presented and discussed. Finally, an overview of current limitations and future research needs is presented to guide the development of electrode structures for next generation PEMFCs.
Development of improved electrode architectures with the control of structure on length scales ranging from millimeters to nanometers could enable a new generation of fuel cells with increased performance and reduced cost. This paper presents an in-depth review and critical analysis of recent developments and future outlook on the design of advanced electrode structures.
Single-atom catalysts (SACs) have emerged as promising materials in energy conversion and storage systems due to their maximal atom utilization, unique electronic structure, and high efficiency. Among them, main-group metal-based SACs (the s-block and p-block metals) are emerging extraordinary materials and have attracted particular interest in the past few years but are still confronted with several challenges. Initiating with a critical overview of the fundamentals and unique advantages associated with main-group metals, the review proceeds to highlight several types of main-group metal-based SACs. These include s-block metals such as Mg and Ca, and p-block metals such as In, Bi, Al, Ga, Sb, Se, and Sn. The applications of these SACs in diverse chemical energy conversion processes are thoroughly explored. Finally, to promote the future development of highly efficient main-group metal SACs, the critical challenges and prospects in this emerging field are proposed. This review presents a fresh impetus and solid platform for the rational design and synthesis of high-performance main-group metal SAC catalysts for chemical energy conversion fields.
Main-group metal-based SACs are emerging extraordinary materials and have attracted particular interest in the past few years. In this review, several types of main-group metal SACs and their applications in energy storage and conversion are summarized, with the emphasis on the correlation between catalytic activities and geometric structures to guide the construction of novel main-group metal SACs with unrivaled performance
The explosive growth and widespread applications of lithium-ion batteries in energy storage, transportation and portable devices have raised significant concerns about the availability of raw materials. The quantity of spent lithium-ion batteries increases as more and more electronic devices depend on them, increasing the risk of environmental pollution. Recycling valuable metals in these used batteries is an efficient strategy to solve the shortage of raw materials and reduce environmental pollution risks. Pyrometallurgy, hydrometallurgy and direct repair have been extensively studied to achieve these goals. The latter is considered an ideal recycling method (for lithium-ion cathode materials) due to its low cost, energy consumption, short duration and environmental friendliness, and it is nondestructive towards the cathode material itself. However, the direct repair is still in its earlier development stages, and a series of challenges must be tackled to succeed in commerce. This work summarizes the process, its effect and the mechanism of different direct repair methods. Moreover, the energy consumption, greenhouse gas emissions, costs and benefits of different methods will be discussed from economic and environmental perspectives. Feasible strategies are also proposed to address existing challenges, providing an insightful overview of the direct reparation of spent lithium-ion cathode materials.
Lithium-ion batteries (LIBs) are considered to be one of the most promising power sources for mobile electronic products, portable power devices and vehicles due to their superior environmental friendliness, excellent energy density, negligible memory effect, good charge/discharge rates, stable cycling life, and efficient electrochemical energy conversion, which distinguish it from other power devices. However, the flammable and volatile organic solvents in carbonate-containing liquid electrolytes can leach, resulting in thermal runaway and interface reactions, thus significantly limiting its application. The use of polymer solid electrolytes is an effective way to solve this safety issues, among which poly (ethylene oxide) (PEO)-based solid polymer electrolytes (SPEs) have attracted much attention because of their stable mechanical properties, ease of fabrication, excellent electrochemical and thermal stability. Unfortunately, PEO-SPEs with their low room-temperature ionic conductivity, narrow electrochemical windows, poor interface stability, and uncontrollable growth of lithium dendrites cannot meet the demand for high energy density in future LIBs. Therefore, this review firstly describes the ion transport mechanisms and challenges that are crucial for PEO-SPEs, and then provides a comprehensive review of current approaches to address the challenges, including novel and efficient lithium salts, additives, composite electrolytes, stable solid electrolyte interfaces, 3-D lithium metals and alloys, cathode protection layers and multi-layer electrolytes. Finally, future research directions are proposed for the stable operation of PEO-SPEs at room temperature and high voltage, which is imperative for the commercialization of safe and high energy density LIBs.
Developing electrochemical energy storage and conversion devices (e.g., water splitting, regenerative fuel cells and rechargeable metal-air batteries) driven by intermittent renewable energy sources holds a great potential to facilitate global energy transition and alleviate the associated environmental issues. However, the involved kinetically sluggish oxygen evolution reaction (OER) severely limits the entire reaction efficiency, thus designing high-performance materials toward efficient OER is of prime significance to remove this obstacle. Among various materials, cost-effective perovskite oxides have drawn particular attention due to their desirable catalytic activity, excellent stability and large reserves. To date, substantial efforts have been dedicated with varying degrees of success to promoting OER on perovskite oxides, which have generated multiple reviews from various perspectives, e.g., electronic structure modulation and heteroatom doping and various applications. Nonetheless, the reviews that comprehensively and systematically focus on the latest intellectual design strategies of perovskite oxides toward efficient OER are quite limited. To bridge the gap, this review thus emphatically concentrates on this very topic with broader coverages, more comparative discussions and deeper insights into the synthetic modulation, doping, surface engineering, structure mutation and hybrids. More specifically, this review elucidates, in details, the underlying causality between the being-tuned physiochemical properties [e.g., electronic structure, metal–oxygen (M–O) bonding configuration, adsorption capacity of oxygenated species and electrical conductivity] of the intellectually designed perovskite oxides and the resulting OER performances, coupled with perspectives and potential challenges on future research. It is our sincere hope for this review to provide the scientific community with more insights for developing advanced perovskite oxides with high OER catalytic efficiency and further stimulate more exciting applications.
Ni-rich layered oxide cathode materials hold great promise for enhancing the energy density of lithium-ion batteries (LIBs) due to their impressive specific capacity. However, the chemical and structural stability issues associated with the materials containing a high Ni content have emerged as a primary safety concern, particularly in the context of traction batteries for electric vehicles. Typically, when these materials are in a highly charged state, their metastable layered structure and highly oxidized transition metal ions can trigger detrimental phase transitions. This leads to the generation of oxygen gas and the degradation of the material’s microstructure, including the formation of cracks, which can promote the interactions between Ni-rich materials and electrolytes, further generating flammable gases. Consequently, various strategies have been devised at the material level to mitigate potential safety hazards. This review begins by providing an in-depth exploration of the sources of instability in Ni-rich layered oxides, drawing from their crystal and electronic structures, and subsequently outlines the safety issues that arise as a result. Subsequently, it delves into recent advancements and approaches aiming at modifying Ni-rich cathode materials and electrolytes to enhance safety. The primary objective of this review is to offer a concise and comprehensive understanding of why Ni-rich cathode materials are susceptible to safety incidents and to present potential methods for improving the safety of Ni-rich cathode materials in high-density LIBs.
Safety risk origin of Ni-rich cathode materials, potential safety issues, and possible measures to improve safety are summarized.
The electrochemical reduction of carbon dioxide (CO2RR) stands as an enticing approach for the production of essential chemicals and feedstocks, storing clean electric energy and mitigating greenhouse gas emissions. Recent years have witnessed remarkable breakthroughs in CO2RR, enhancing its performance and transitioning related research from laboratory settings toward industrial realization. However, the journey of CO2RR development is not devoid of challenges, including issues like mass transfer limitation, salt accumulation, and flooding phenomena. Remarkably, recent studies have unveiled a promising avenue by conducting CO2RR in an acidic environment, effectively circumventing these challenges and presenting novel opportunities. In this review, we embark on a reassessment of H-cells and flow cells, delving into their opportunities, challenges, strengths, and weaknesses. Additionally, we compile recent advancements in CO2RR under acidic conditions, elucidating the performance metrics and strategies embraced by pertinent research. Subsequently, we propose three pivotal concerns in acidic CO2RR: ① balancing the competition between CO2RR and hydrogen evolution reaction (HER), ② enhancing the selectivity, and ③ exploring industrial applications. And finally, we delve into the core factors influencing the performance of CO2RR in acid: local pH, cation effects, and catalyst design. Building upon these strategies, challenges, and insights, prospects are proposed for the future trajectory of CO2RR development.
Redox flow batteries (RFBs) that employ sustainable, abundant, and structure-tunable redox-active species are of great interest for large-scale energy storage. As a vital class of redox-active species, metal coordination complexes (MCCs) possessing the properties of both the organic ligands and transition metal ion centers are attracting increasing attention due to the advantages of multielectron charge transfer, high structural tailorability, and reduced material crossover. Herein, we present a critical overview of RFBs that employ MCCs as redox-active materials in both aqueous and nonaqueous mediums. The progress is comprehensively summarized, including the design strategies, solubility characteristics, electrochemical properties, and battery cycling performance of MCCs. Emphasis is placed on the ligand selection and modification strategies used to tune the critical properties of MCCs, including their redox potential, solubility, cycling stability, and electron transfer redox reactions, to achieve stable cycled RFBs with a high energy density. Furthermore, we discuss the current challenges and perspectives related to the development of MCC-based RFBs for large-scale energy storage implementations.
The development of aprotic alkali metal-oxygen batteries has shown promise due to their high theoretical specific energy, which is supported by the exergonic oxygen electrochemistry. However, practical realization of these batteries has been impeded by parasitic reactions that compromise their rechargeability, efficiency, and cycle life. Recent research has identified highly reactive singlet oxygen (1O2) as the main cause of degradation, which has led to a focus on understanding and harnessing this reactive species. This review provides a summary of current knowledge on the formation mechanisms of 1O2, identifies knowledge gaps that need to be addressed in the future, and discusses the implications of contaminants and battery components for 1O2 formation. The review also covers recent advances in deactivating and taming 1O2, and explains the mechanisms that underpin these strategies. We conclude with perspectives on the remaining challenges and future research opportunities in the field of 1O2-related (electro)chemistry in metal-oxygen batteries.
Biomass is a low-cost, abundant and renewable resource that can be used to manufacture porous carbon-based materials for a variety of applications. Different mesoporous carbon supports can be obtained from the various synthetic approaches that are aimed at increasing the specific surface area and functionalization. Currently, most of the biomass is used for energy recovery. The circular economy approach could lead to the development of cheap and sustainable materials, and turning of wastes into a precious resource. In this review, we provide the recent advances in the field of electrochemistry for porous carbon materials derived from biomass, which offers wider applications in proton exchange membrane fuel cells (PEMFCs), anion exchange membrane fuel cells (AEMFCs) and Zn-air batteries (ZABs). The focus is on understanding the required properties of the materials and the role of synthetic pathways in platinum group metal (PGM) free electrocatalysts. The most promising materials are evaluated towards the oxygen reduction reaction (ORR) in PEMFC, AEMFC, and ZAB. The results achieved showed that the expected performances on these energy conversion devices still lack for deployment in practice, especially if compared with commercially available PGM-free electrocatalysts. This review article provides insights on how to improve the actual electrocatalytic activity of biomass-derived materials.
Because sodium-ion batteries are relatively inexpensive, they have gained significant traction as large-scale energy storage devices instead of lithium-ion batteries in recent years. However, sodium-ion batteries have a lower energy density than lithium-ion batteries because sodium-ion batteries have not been as well developed as lithium-ion batteries. Solid-state batteries using solid electrolytes have a higher energy density than liquid batteries in regard to applications with sodium-ion batteries, making them more suitable for energy storage systems than liquid batteries. Due to their low ionic conductivity, solid electrolytes are currently unable to achieve comparable performance to liquid electrolytes at room temperature. In this review, we discuss the advancements in SSEs applied to sodium-ion batteries in recent years, including inorganic solid electrolytes, such as Na–β-Al2O3, NASICON and Na3PS4, polymer solid electrolytes based on PEO, PVDF-HFP and PAN, and plastic crystal solid electrolytes mainly composed of succinonitrile. Additionally, appropriate solutions for low ionic conductivity, a narrow electrochemical stability window and poor contact with electrodes, which are the significant flaws in current SSEs, are discussed in this review.
Electrochemical CO2 reduction technology could solve the CO2-induced climate warming by electrochemically converting atmospheric CO2 back into fuel, essentially recycling it and building a low carbon emission economy. However, the electrochemical CO2 reduction reaction (CO2RR) poses a significant challenge due to the highly stable and linear CO2 molecules, in addition to a proton-coupled multi-electron transfer process. Thus, highly active catalysts, placed on activity bolstering materials, and permeable electrodes are crucial for CO2RR. Single-atom catalysts (SACs) have recently garnered increasing interest in the electrocatalysis community due to their potentially high mass efficiency and cost benefits (every atom is an active center, resulting in nearly 100% utilization) and adjustable selectivity (higher uniformity of the active sites compared to nanoparticles). However, preserving the accessibility and activity of the SACs inside the electrode poses major materials development and electrode design challenges. A conventional layered structure SAC electrode typically consists of a gas diffusion layer (GDL), a microporous layer (MPL) and a SAC catalyst layer (SACCL), fabricated by using a powder bonding process. However, this process usually encounters issues such as delamination and instability of SACs due to the weak binder-catalyst-support interface. Conversely, the free-standing SAC electrode design has the potential to overcome these issues by eliminating the GDL, MPL, and need of a binder, in contrast to the powder bonding process. This work first reviews the latest developments in experimental and modeling studies of powdered SAC electrode by the traditional powder bonding process. Next, it examines the development towards the free-standing SAC electrode for high-performance electrochemical reduction of CO2. The synthesis-structure-fabrication-performance relationships of SAC-based materials and associated electrodes are analyzed. Furthermore, the article presents future challenges and perspectives for high-performance SAC electrodes for CO2RR.
Electrochemical energy storage technologies have a profound influence on daily life, and their development heavily relies on innovations in materials science. Recently, high-entropy materials have attracted increasing research interest worldwide. In this perspective, we start with the early development of high-entropy materials and the calculation of the configurational entropy. Then, we summarize the recent progress in material design and application using the high-entropy strategy, especially highlighting rechargeable battery materials. Finally, we discuss the potential directions for the future development of high-entropy energy materials.