Hollow Carbon Spheres and Their Hybrid Nanomaterials in Electrochemical Energy Storage

Electrochemical energy storage is of extraordinary importance for fulfilling the utilization of renewable and sustainable energy sources. There is an increasing demand for energy storage devices with high energy and power densities, prolonged stability, safety, and low cost. In the past decade, numerous research efforts have been devoted to achieving these requirements, especially in the design of advanced electrode materials. Hollow carbon spheres (HCS) derived nanomaterials combining the advantages of 3D HCS and porous structures have been considered as alternative electrode materials for advanced energy storage applications, due to their unique features such as high surface‐to‐volume ratios, encapsulation capability, together with outstanding chemical and thermal stability. In this review, the authors first present a comprehensive overview of the synthetic strategies of HCS, and elucidate the design and synthesis of HCS‐derived nanomaterials including various types of HCS and their nanohybrids. Additionally, their significant roles as electrode materials for supercapacitors, lithium‐ion or sodium‐ion batteries, and sulfur hosts for lithium sulfur batteries are highlighted. Finally, current challenges in the synthesis of HCS and future directions in HCS‐derived nanomaterials for energy storage applications are proposed.     

The Development of Pseudocapacitor Electrodes and Devices with High Active Mass Loading

Pseudocapacitive materials are used for supercapacitor applications due to their exceptionally high capacitance and low cost. Good capacitive performance of the pseudocapacitive materials at high active mass loadings is vital for the development of the next generation of supercapacitor devices. This review describes recent advances in materials and nanotechnologies, which allows the development of advanced pseudocapacitive devices with high active mass. An important breakthrough is the discovery of novel dispersing and capping agents for the colloidal processing of nanoparticles. Particularly important are novel co‐dispersants that exhibit enhanced adsorption on materials of different types, such as inorganic nanoparticles, carbon nanotubes, and graphene. Conceptually new strategies are designed to fabricate coated particles. Recent innovations pave the way for the development of multifunctional redox‐active dopants‐dispersants and dopants‐oxidants to manufacture conductive polymer composites. Among the most important advances in nanotechnology is the development of template methods and heterocoagulation techniques for composite manufacturing. The progress in the design of novel surface modification techniques and materials, discovery of advanced anchoring groups, and development of liquid–liquid extraction allows agglomerate‐free processing of nanomaterials and composites. This review describes fundamental aspects of novel technologies and their applications in the manufacturing of pseudocapacitive devices for energy storage.     

Routes to High Energy Cathodes of Sodium‐Ion Batteries

Sodium‐ion batteries (SIBs) are now being actively developed as low cost and sustainable alternatives to lithium‐ion batteries (LIBs) for large‐scale electric energy storage applications. In recent years, various inorganic and organic Na compounds, mostly mimicked from their Li counterparts, have been synthesized and tested for SIBs, and some of them indeed demonstrate comparable specific capacity to the presently developed LIB electrodes. However, the lack of suitable cathode materials is still a major obstacle to the commercial development of SIBs. Here, we present a brief review on the recent developments of SIB cathodes, with a focus on low cost and high energy density materials (> 450 Wh kg^?1 vs Na) together with discussion of their Na‐storage mechanisms. The considerable differences in the structural requirements for Li‐ and Na‐storage reactions mean that it is not sufficient to design SIB cathode materials by simply mimicking LIB materials, and therefore great efforts are needed to discover new materials and reaction mechanisms to further develop variable cathodes for advanced SIB technology. Some directions for future research and possible strategies for building advanced cathode materials are also proposed here.     

Recent Advances in Design and Fabrication of Electrochemical Supercapacitors with High Energy Densities

In recent years, tremendous research effort has been aimed at increasing the energy density of supercapacitors without sacrificing high power capability so that they reach the levels achieved in batteries and at lowering fabrication costs. For this purpose, two important problems have to be solved: first, it is critical to develop ways to design high performance electrode materials for supercapacitors; second, it is necessary to achieve controllably assembled supercapacitor types (such as symmetric capacitors including double‐layer and pseudo‐capacitors, asymmetric capacitors, and Li‐ion capacitors). The explosive growth of research in this field makes this review timely. Recent progress in the research and development of high performance electrode materials and high‐energy supercapacitors is summarized. Several key issues for improving the energy densities of supercapacitors and some mutual relationships among various effecting parameters are reviewed, and challenges and perspectives in this exciting field are also discussed. This provides fundamental insight into supercapacitors and offers an important guideline for future design of advanced next‐generation supercapacitors for industrial and consumer applications.     

Liquid–Solid Interfacial Assemblies of Soft Materials for Functional Freestanding Layered Membrane–Based Devices toward Electrochemical Energy Systems

Freestanding layered membrane–based devices have broad applications in highly efficient energy‐storage/conversion systems. The liquid–solid interface is considered as a unique yet versatile interface for constructing such layered membrane–based devices. In this review, the authors outline recent developments in the fabrication of soft materials to functionalize layered devices from the aspect of liquid–solid interfacial assembly and engineering arts. Seven liquid–solid interfacial assembly strategies, including flow‐directed, superlattice, solvent‐casting, evaporation‐induced, dip‐coating, spinning, and electrospinning assemblies, are comprehensively highlighted with a focus on their synthetic pathways, formation mechanisms, and interface engineering strategies. Meanwhile, recent representative works on layered membrane–based devices for electrochemical energy applications are presented. Finally, challenges and opportunities of this research area are highlighted in order to stimulate future developments. This review not only offers comprehensive and practical approaches to assemble liquid–solid interfaces with soft materials for various important layered electrochemical energy devices but also sheds lights on fundamental insights by thoughtful discussions on performance enhancement mechanisms of these electrochemical energy systems.     

High Performance Thermoelectric Materials: Progress and Their Applications

Thermoelectric (TE) materials have the capability of converting heat into electricity, which can improve fuel efficiency, as well as providing robust alternative energy supply in multiple applications by collecting wasted heat, and therefore, assisting in finding new energy solutions. In order to construct high performance TE devices, superior TE materials have to be targeted via various strategies. The development of high performance TE devices can broaden the market of TE application and eventually boost the enthusiasm of TE material research. This review focuses on major novel strategies to achieve high‐performance TE materials and their applications. Manipulating the carrier concentration and band structures of materials are effective in optimizing the electrical transport properties, while nanostructure engineering and defect engineering can greatly reduce the thermal conductivity approaching the amorphous limit. Currently, TE devices are utilized to generate power in remote missions, solar–thermal systems, implantable or/wearable devices, the automotive industry, and many other fields; they are also serving as temperature sensors and controllers or even gas sensors. The future tendency is to synergistically optimize and integrate all the effective factors to further improve the TE performance, so that highly efficient TE materials and devices can be more beneficial to daily lives.     

Advanced Phosphorus‐Based Materials for Lithium/Sodium‐Ion Batteries: Recent Developments and Future Perspectives

High‐performance and lost‐cost lithium‐ion and sodium‐ion batteries are highly desirable for a wide range of applications including portable electronic devices, transportation (e.g., electric vehicles, hybrid vehicles, etc.), and renewable energy storage systems. Great research efforts have been devoted to developing alternative anode materials with superior electrochemical properties since the anode materials used are closely related to the capacity and safety characteristics of the batteries. With the theoretical capacity of 2596 mA h g^?1, phosphorus is considered to be the highest capacity anode material for sodium‐ion batteries and one of the most attractive anode materials for lithium‐ion batteries. This work provides a comprehensive study on the most recent advancements in the rational design of phosphorus‐based anode materials for both lithium‐ion and sodium‐ion batteries. The currently available approaches to phosphorus‐based composites along with their merits and challenges are summarized and discussed. Furthermore, some present underpinning issues and future prospects for the further development of advanced phosphorus‐based materials for energy storage/conversion systems are discussed.     

Sodium‐Ion Batteries: From Academic Research to Practical Commercialization

Sodium‐ion batteries (SIBs) have been considered as the most promising candidate for large‐scale energy storage system owing to the economic efficiency resulting from abundant sodium resources, superior safety, and similar chemical properties to the commercial lithium‐ion battery. Despite the long period of academic research, how to realize sodium‐ion battery commercialization for market applications is still a great challenge. Thus, from the perspective of future practical application, this review will identify the factors that are restricting commercialization, and evaluate the existing active materials and sodium‐ion‐based full‐cell system. The design and development trends that are needed for SIBs to meet the requirements of practical applications in large‐scale energy storage will also be discussed in detail.     

Nature‐Inspired Electrochemical Energy‐Storage Materials and Devices

Currently, tremendous efforts are being devoted to develop high‐performance electrochemical energy‐storage materials and devices. Conventional electrochemical energy‐storage systems are confronted with great challenges to achieve high energy density, long cycle‐life, excellent biocompatibility and environmental friendliness. The biological energy metabolism and storage systems have appealing merits of high efficiency, sophisticated regulation, clean and renewability, and the rational design and fabrication of advanced electrochemical energy‐storage materials and smart devices inspired by nature have made some breakthrough progresses, recently. In this review, we summarize the latest developments in the field of nature‐inspired electrochemical energy‐storage materials and devices. Specifically, the nature‐inspired exploration, preparation and modification of electrochemical energy‐storage related materials including the active materials, binders, and separators are introduced. Furthermore, nature‐inspired design and fabrication of smart energy‐storage devices such as self‐healing supercapacitors, supercapacitors with ultrahigh operating voltage, and self‐rechargeable batteries are also discussed. The review aims to provide insights and expanded research perspectives for further study in this exciting field based on our comprehensive discussions.     

3D Nanostructures for the Next Generation of High‐Performance Nanodevices for Electrochemical Energy Conversion and Storage

Among the different nanostructures that have been demonstrated as promising materials for various applications, 3D nanostructures have attracted significant attention as building blocks for constructing high‐performance nanodevices. Particularly over the last decade, considerable research efforts have been devoted to designing, fabricating, and evaluating 3D nanostructures as electrodes for electrochemical energy conversion and storage devices. Although remarkable progress has been achieved, the performance of electrochemical energy devices based on 3D nanostructures in terms of energy conversion efficiency, energy storage capability, and device reliability still needs to be significantly improved to meet the requirements for practical applications. Rather than simply outlining and comparing different 3D nanostructures, this article systematically summarizes the general advantages as well as the existing and future challenges of 3D nanostructures for electrochemical energy conversion and storage, focusing on photoelectrochemical water splitting, photoelectrocatalytic solar‐to‐fuels conversion from nitrogen and carbon dioxide, rechargeable metal‐ion batteries, and supercapacitors. A comprehensive understanding of these advantages and challenges shall provide valuable guidelines and enlightenments to facilitate the further development of 3D nanostructured materials, and contribute to the achieving more efficient energy conversion and storage technologies toward a sustainable energy future.     

Engineering Mixed Ionic Electronic Conduction in La0.8Sr0.2MnO3+δ Nanostructures through Fast Grain Boundary Oxygen Diffusivity

Nanoionics has become an increasingly promising field for the future development of advanced energy conversion and storage devices, such as batteries, fuel cells, and supercapacitors. Particularly, nanostructured materials offer unique properties or combinations of properties as electrodes and electrolytes in a range of energy devices. However, the enhancement of the mass transport properties at the nanoscale has often been found to be difficult to implement in nanostructures. Here, an artificial mixed ionic electronic conducting oxide is fabricated by grain boundary (GB) engineering thin films of La_0.8Sr_0.2MnO_3+δ. This electronic conductor is converted into a good mixed ionic electronic conductor by synthesizing a nanostructure with high density of vertically aligned GBs with high concentration of strain‐induced defects. Since this type of GBs present a remarkable enhancement of their oxide‐ion mass transport properties (of up to six orders of magnitude at 773 K), it is possible to tailor the electrical nature of the whole material by nanoengineering, especially at low temperatures. The presented results lead to fundamental insights into oxygen diffusion along GBs and to the application of these engineered nanomaterials in new advanced solid state ionics devices such are micro‐solid oxide fuel cells or resistive switching memories.     

Rational Design of Advanced Thermoelectric Materials

Advanced thermoelectric technologies can drastically improve energy efficiencies of industrial infrastructures, solar cells, automobiles, aircrafts, etc. When a thermoelectric device is used as a solid‐state heat pump and/or as a power generator, its efficiency depends pivotally on three fundamental transport properties of materials, namely, the thermal conductivity, electrical conductivity, and thermopower. The development of advanced thermoelectric materials is very challenging because these transport properties are interrelated. This paper reviews the physical mechanisms that have led to recent material advances. Progresses in both inorganic and organic materials are summarized. While the majority of the contemporary effort has been focused on lowering the lattice thermal conductivity, the latest development in nanocomposites suggests that properly engineered interfaces are crucial for realizing the energy filtering effect and improving the power factor. We expect that the nanocomposite approach could be the focus of future materials breakthroughs.     

Governing the Interplay between Industrial Ecosystems and Environmental Regulation

Many scholars of industrial ecology have focused on the institutional and organizational challenges of building and maintaining regional industrial symbiosis through the synergistic integration of material and energy flows. Despite the promise that these intellectual developments hold for the future dematerialization of industrial production, they rarely address the actual regulatory obstacles of turning wastes into raw materials. In this article we introduce a potential future industrial symbiosis around the Gulf of Bothnia between Finland and Sweden, and assess the regulatory bottlenecks related to waste by‐product consideration. We find that although the Gulf of Bothnia region has technological and economic potential for industrial symbiosis, the regulatory support for this is insufficient. We suggest a common pool resource‐based governance system that could utilize market and regulatory mechanisms in a regional‐level cross‐border system of governance. Importantly, the suggested governance system would protect the users of potential raw materials from unpredictable waste regulation, market risks related to large‐scale material flows, and societal risks of hazardous waste treatment.     

Emerging Materials and Strategies for Personal Thermal Management

In this decade, the demands of energy saving and diverse personal thermoregulation requirements along with the emergence of wearable electronics and smart textiles give rise to the resurgence of personal thermal management (PTM) technologies. PTM, including personal cooling, heating, insulation, and thermoregulation, are far more flexible and extensive than the traditional air/liquid cooling garments for the human body. Concomitantly, many new advanced materials and strategies have emerged in this decade, promoting the thermoregulation performance and the wearing comfort of PTM simultaneously. In this review, an overview is presented of the state‐of‐the‐art and the prospects in this burgeoning field. The emerging materials and strategies of PTM are introduced, and classed by their thermal functions. The concept of infrared‐transparent visible‐opaque fabric (ITVOF) is first highlighted, as it triggers the work on advanced PTM by combining it with radiative cooling, and the corresponding implementations and realizations are subsequently introduced, followed by wearable heaters, flexible thermoelectric devices, and sweat‐management Janus textiles. Finally, critical considerations on the challenges and opportunities of PTM are presented and future directions are identified, including thermally conductive polymers and fibers, physiological/psychological statistical analysis, and smart PTM strategies.     

Smart Windows: Electro‐, Thermo‐, Mechano‐, Photochromics,and Beyond

A smart window that dynamically modulates light transmittance is crucial for building energy efficiently, and promising for on‐demand optical devices. The rapid development of technology brings out different categories that have fundamentally different transmittance modulation mechanisms, including the electro‐, thermo‐, mechano‐, and photochromic smart windows. In this review, recent progress in smart windows of each category is overviewed. The strategies for each smart window are outlined with particular focus on functional materials, device design, and performance enhancement. The advantages and disadvantages of each category are summarized, followed by a discussion of emerging technologies such as dual stimuli triggered smart window and integrated devices toward multifunctionality. These multifunctional devices combine smart window technology with, for example, solar cells, triboelectric nanogenerators, actuators, energy storage devices, and electrothermal devices. Lastly, a perspective is provided on the future development of smart windows.     

Bioprocessing in the Digital Age: The Role of Process Models

In this age of technology, the vision of manufacturing industries built of smart factories is not a farfetched future. As a prerequisite for Industry 4.0, industrial sectors are moving towards digitalization and automation. Despite its tremendous growth reaching a sales value of worth $188 billion in 2017, the biopharmaceutical sector distinctly lags in this transition. Currently, the challenges are innovative market disruptions such as personalized medicine as well as increasing commercial pressure for faster and cheaper product manufacturing. Improvements in digitalization and data analytics have been identified as key strategic activities for the next years to face these challenges. Alongside, there is an emphasis by the regulatory authorities on the use of advanced technologies, proclaimed through initiatives such as Quality by Design (QbD) and Process Analytical Technology (PAT). In the manufacturing sector, the biopharmaceutical domain features some of the most complex and least understood processes. Thereby, process models that can transform process data into more valuable information, guide decision‐making, and support the creation of digital and automated technologies are key enablers. This review summarizes the current state of model‐based methods in different bioprocess related applications and presents the corresponding future vision for the biopharmaceutical industry to achieve the goals of Industry 4.0 while meeting the regulatory requirements.     

Commercialization of Lithium Battery Technologies for Electric Vehicles

The currently commercialized lithium‐ion batteries have allowed for the creation of practical electric vehicles, simultaneously satisfying many stringent milestones in energy density, lifetime, safety, power, and cost requirements of the electric vehicle economy. The next wave of consumer electric vehicles is just around the corner. Although widely adopted in the vehicle market, lithium‐ion batteries still require further development to sustain their dominating roles among competitors. In this review, the authors survey the state‐of‐the‐art active electrode materials and cell chemistries for automotive batteries. The performance, production, and cost are included. The advances and challenges in the lithium‐ion battery economy from the material design to the cell and the battery packs fitting the rapid developing automotive market are discussed in detail. Also, new technologies of promising battery chemistries are comprehensively evaluated for their potential to satisfy the targets of future electric vehicles.     

Opening Two‐Dimensional Materials for Energy Conversion and Storage: A Concept

The development of two‐dimensional (2D) materials is experiencing a renaissance since the adventure of graphene. 2D materials typically exhibit strong in‐plane covalent bonding and weak out‐of‐plane van der Waals interactions through the interlayer gap. Opening 2D materials is an effective way to alter the physical and chemical properties, such as band gap, conductivity, optical property, thermoelectric property, photovoltaic property and superconductivity. A larger interlayer distance means more accessible active sites for catalysis, an ion‐accessible surface in the interlayer space, which may greatly enhance the performance of 2D materials for energy conversion and storage. Moreover, opening 2D materials by intercalation can change the band filling state and the Fermi level. This review mainly focuses on the opening of 2D materials and their subsequent applications in energy conversion and storage fields, expecting to promote the development of such a new class of materials, namely expanded 2D materials. The exciting progresses of these expanded materials made in both energy conversion and storage devices including solar cells, thermoelectric devices, electrocatalyst, supercapacitors and rechargeable batteries, is presented and discussed in depth. Furthermore, prospects and further developments in these exciting fields of the expanded 2D materials are also commented.     

Design Considerations for Unconventional Electrochemical Energy Storage Architectures

Batteries have become fundamental building blocks for the mobility of modern society. Continuous development of novel battery chemistries and electrode materials has nourished progress in building better batteries. Simultaneously, novel device form factors and designs with multi‐functional components have been proposed, requiring batteries to not only integrate seamlessly to these devices, but to also be a multi‐functional component for a multitude of applications. Thus, in the past decade, along with developments in the component materials, the focus has been shifting more and more towards novel fabrication processes, unconventional configurations, and additional functionalities. This work attempts to critically review the developments with respect to emerging electrochemical energy storage configurations, including, amongst others, paintable, transparent, flexible, wire or cable shaped, ultra‐thin and ultra‐thick configurations, as well as hybrid energy storage‐conversion, or graphene‐incorporated batteries and supercapacitors. The performance requirements are elaborated together with the advantages, but also the limitations, with respect to established electrochemical energy storage technologies. Finally, challenges in developing novel materials with tailored properties that would allow such configurations, and in designing easier manufacturing techniques that can be widely adopted are considered.     

Energy Applications of Magnetocaloric Materials

The need for energy‐efficient and environmentally friendly refrigeration, heat pumping, air conditioning, and thermal energy harvesting systems is currently more urgent than ever. Magnetocaloric energy conversion is among the best available alternatives for achieving these technological goals and has been the subject of substantial basic and applied research over the last two decades. The subject is strongly interdisciplinary, requiring proper understanding and efficient integration of knowledge in different specialized fields. This review article presents a historical and up‐to‐date account of the energy‐related applications of magnetocaloric materials and information about their processing and magnetic fields, thermodynamics, heat transfer, and other relevant characteristics. The article also discusses the conceptual design of magnetocaloric refrigeration and power generation systems and some guidelines for future research in the field.