Water-in-salt electrolytes for high voltage aqueous electrochemical energy storage devices

If were not by their low electrochemical stability, aqueous electrolytes would be the preferred alternative to be used in electrochemical energy storage devices. Their abundance and nontoxicity are key factors for such application, especially in large scale. The development of highly concentrated aqueous electrolytes, so-called water-in-salt electrolytes, has expanded the electrochemical window of aqueous electrolyte up to 3.0 V (whereas salt-in-water electrolytes normally shows up to 1.6 V), showing that water can be an alternative after all. Many devices, ranging from metal-ion batteries to electrochemical capacitors, have been reported recently, making use of such wider electrochemical stability and enhancing devices energy density. Different salts have also been proposed not only to gain in costs but also to improve physicochemical properties.     

Rapid prototyping of electrochemical energy storage devices based on two dimensional materials

Rapid prototyping methods such as additive manufacturing (three dimensional printing) and laser scribing have attracted much attention for manufacturing next-generation electrochemical energy storage devices because of their simplicity, low cost, medium throughput, and ability to prepare electrodes with unique form factors and multiple functionalities, such as stretchability, flexibility, and wearability. Of the wide array of potential active materials that can be used for energy storage, two dimensional materials such as graphene, MXenes, and MoS₂ have exceptionally high conductive surface areas and are attractive candidates for printing thick, high loading supercapacitors and batteries. In this brief review, we highlight recent progress and major challenges which must be overcome to make these manufacturing approaches and the resulting printed devices commercially viable.     

Single-atom catalysts for electrochemical energy storage and conversion

The expedited consumption of fossil fuels has triggered broad interest in the fabrication of novel catalysts for electrochemical energy storage and conversion.E...     

Ab initio simulations of liquid electrolytes for energy conversion and storage

Understanding physicochemical properties of liquid electrolytes is essential for predicting and optimizing device performance for a wide variety of emerging energy technologies, including photoelectrochemical water splitting, supercapacitors, and batteries. In this work, we review recent progress and open challenges in predicting structural, dynamical, and electronic properties of the liquids using first-principles approaches. We briefly summarize the basic concepts of first-principles molecular dynamics (FPMD), and we discuss how FPMD methods have enriched our understanding of a number of liquids, including aqueous solutions, organic electrolytes and ionic liquids. We also discuss technical challenges in extending FPMD simulations to the study of liquid electrolytes in more complex environments, including the interface between electrolytes and electrodes, which is a key component in many energy storage and conversion systems.     

Nanostructured energy materials for electrochemical energy conversion and storage: A review

Nanostructured materials have received tremendous interest due to their unique mechanical/electrical properties and overall behavior contributed by the complex synergy of bulk and interfacial properties for efficient and effective energy conversion and storage. The booming development of nanotechnology affords emerging but effective tools in designing advanced energy material. We reviewed the significant progress and dominated nanostructured energy materials in electrochemical energy conversion and storage devices, including lithium ion batteries, lithium–sulfur batteries, lithium–oxygen batteries, lithium metal batteries, and supercapacitors. The use of nanostructured electrocatalyst for effective electrocatalysis in oxygen reduction and oxygen evolution reactions for fuel cells and metal–air batteries was also included. The challenges in the undesirable side reactions between electrolytes and electrode due to high electrode/electrolyte contact area, low volumetric energy density of electrode owing to low tap density,and uniform production of complex energy materials in working devices should be overcome to fully demonstrate the advanced energy nanostructures for electrochemical energy conversion and storage. The energy chemistry at the interfaces of nanostructured electrode/electrolyte is highly expected to guide the rational design and full demonstration of energy materials in a working device.     

Characterization of bi-material electrodes for electrochemical hybrid energy storage devices

The hybridization of an electrochemical double layer capacitor and a lithium-ion battery at the electrode level can be realized by combining lithium insertion materials and capacitive materials in bi-material electrodes. A bi-material electrode based on activated carbon and LiMn₂O₄ has been prepared and characterized in the present work. An experimental setup was developed in order to measure the current sharing between the two different active materials in a single segmented bi-material electrode. This setup allows distinguishing the contribution of each material to the overall electrode performance. The characterization consisted of cyclic voltammetry and galvanostatic charge discharge cycling. The behavior of the bi-material electrode is essentially a linear combination of the behaviors of the two materials.     

Graphene from electrochemical exfoliation and its direct applications in enhanced energy storage devices

Graphite was electrochemically exfoliated in mixtures of room temperature ionic liquids and deionized water containing lithium salts to produce functionalized graphenes and such an electrochemical exfoliation technique can be directly used in making primary battery electrodes with significantly enhanced specific energy capacity.     

Nanosized zinc oxides-based materials for electrochemical energy storage and conversion: Batteries and supercapacitors

Transition metal oxides(TMO) bring a novel direction for the development of energy store materials due to their excellent stability. They not only have high capacity and good cycle performance, but also are cheap and easily available. Zinc oxide(Zn O) as an important part of TMO have gradually attracted attention in the research of electrochemistry. Zn O, as a metal semiconductor with the advantages of wide band gap, possesses high ion migration rate, good chemical stability, simple preparation ...     

Fluoride based electrode materials for advanced energy storage devices

Energy storage and conversion have become a prime area of research to address both the societal concerns regarding the environment and pragmatic applications such as the powering of an ever increasing cadre of portable electronic devices. This paper reviews the use of fluoride based electrode materials in energy storage devices. The majority of the energy storage and conversion applications for fluorine based materials resides in present and future lithium battery chemistries. The use of fluorides either as coatings or in the formation of oxyfluorides has resulted in a marked increase of the stability and morphological development of electrodes for use in nonaqueous lithium and lithium-ion batteries. Pure fluorides, despite their intrinsic insulative properties, have demonstrated the capability to exhibit exceptional energy densities and have the potential to open the door to future high energy lithium battery technology.     

Light-emitting devices based on solid electrolytes and polyelectrolytes

The properties of light-emitting diodes (LEDs) based on organic layers containing mobile ions, so-called light-emitting electrochemical cells (LECs), are reviewed. These devices have some unique properties: their current–voltage characteristics are antisymmetric with respect to the origin and they emit light under both forward and reverse bias. The physical processes involved in the emission from LECs are discussed in terms of a thermodynamic model. Recent work on blends of luminescent and ion-conducting polymers is summarized. In addition, the properties of novel single-component LECs and polyelectrolyte-based devices are presented. The results show that LECs with performances superior to that of conventional LED devices can be fabricated, but questions concerning the transient behavior and degradation mechanisms persist. © 1998 John Wiley & Sons, Ltd.     

A review of understanding electrocatalytic reactions in energy conversion and energy storage systems via scanning electrochemical microscopy

To address climate change and promote environmental sustainability, electrochemical energy conversion and storage systems emerge as promising alternative to fossil fuels, catering to the escalating demand for energy. Achieving optimal energy efficiency and cost competitiveness in these systems requires the strategic design of electrocatalysts, coupled with a thorough comprehension of the underlying mechanisms and degradation behavior occurring during the electrocatalysis processes. Scanning elec...     

Graphene-based electrochemical energy conversion and storage: fuel cells, supercapacitors and lithium ion batteries

Graphene has attracted extensive research interest due to its strictly 2-dimensional (2D) structure, which results in its unique electronic, thermal, mechanical, and chemical properties and potential technical applications. These remarkable characteristics of graphene, along with the inherent benefits of a carbon material, make it a promising candidate for application in electrochemical energy devices. This article reviews the methods of graphene preparation, introduces the unique electrochemical behavior of graphene, and summarizes the recent research and development on graphene-based fuel cells, supercapacitors and lithium ion batteries. In addition, promising areas are identified for the future development of graphene-based materials in electrochemical energy conversion and storage systems.     

Overview on conducting polymer in energy storage and energy conversion system

Polymer-based electrochemical devices such as supercapacitor, battery, and fuel cell have been developed and advanced for energy related application. In this regard, conducting polymers own several tunable characteristics for energy conversion and energy storage relevance. Consequently, efficient, reliable, low cost, conducting, stable, and environment friendly energy systems have been developed using conducting polymers. To enhance the efficiency and commercialization of energy systems, design, structure, composition, and fabrication technique used for conducting polymers and related composite have been focused. Challenges and future trend associated with current state of the art conducting polymer materials in supercapacitor, battery, and fuel cell are highlighted.     

Solid electrolytes based on CeO<Subscript>2</Subscript> for medium-temperature electrochemical devices

CeO₂-based solid solutions with a fluorite structure are promising materials as electrolytes of medium-temperature electrochemical devices: electrolytic cells, oxygen sensors, and solid oxide fuel cells. In this work, studies are presented of the effect of the dopant cation radius and its concentration on the physico-chemical properties of the Ce_{1 − x} Ln _x O_{2 − δ} solid solutions (x = 0–0.20; Ln = La, Nd, Sm, Eu, Gd, Dy, Ho, Er, Yb) and also of multicomponent solid solutions of Ce_{1 − x} Ln _x/2Ln′ _x/2O_{2 − δ} (x = 0–0.20; Ln = Sm, La, Gd and Ln′ = Dy, Nd, Y) and Ce_{1 − x − y} Sm _x M _y O_{2 − δ} (M = Ca, Sr, Ba) obtained using the solid-phase synthesis technique. Electric properties of the samples were studied in the temperature range of 623–1173 K and in the oxygen partial pressure range of 0.01–10⁻²² MPa. The values of oxygen critical pressure ( p_O2 ^* )\left( {p_{O_2 }^* } \right) are presented, at which the ionic and electron conductivity values are equal. The values were calculated on the basis of experimental dependences at 1023 K at the assumption that the ionic conductivity value is determined only by the dopant concentration and its effective ionic radius and is independent of the oxygen partial pressure.     

Photochemical conversion and storage of solar energy

The possibilities for the photochemical storage of solar energy are examined from the standpoint of maximum efficiency and mechanism. Loss factors are considered for a general endergonic photochemical reaction and it is concluded that a realistic maximum solar energy storage efficiency for any photochemical system is 15–16%. The natural process of photochemical solar energy storage, namely, photosynthesis, is analyzed and it is found that the maximum solar energy storage efficiency of photosynthesis is 9.5 ± 0.8%. Kinetic and thermodynamic limitations on a photochemical energy storage process are identified and it is shown that the desirable production of hydrogen and oxygen from water probably cannot be sensitized with visible light if only one photochemical step is employed. However, by analogy with the mechanism of photosynthesis, two photochemical reactions operating in series permit a full utilization of the photochemically active part of the solar spectrum. A possible scheme is described and analyzed as to its possibilities and potential difficulties. Finally, some practical considerations are presented not only for the photochemical production of hydrogen but also for solid state photovoltaic devices.     

Perspective on antiferroelectrics for energy storage and conversion applications

As a close relative of ferroelectricity,antiferroelectricity has received a recent resurgence of interest driven by technological aspirations in energy-efficient applications,such as energy storage capacitors,solid-state cooling devices,explosive energy conversion,and displacement transducers.Though prolonged efforts in this area have led to certain progress and the discovery of more than 100 antiferroelectric materials over the last 70 years,some scientific and technological issues remain unresolved.Herein,we provide perspectives on the development of antiferroelectrics for energy storage and conversion applications,as well as a comprehensive understanding of the structural origin of antiferroelectricity and field-induced phase transitions,followed by design strategies for new lead-free antiferroelectrics.We also envision unprecedented challenges in the development of promising antiferroelectric materials that bridge materials design and real applications.Future research in these directions will open up new possibilities in resolving the mystery of antiferroelectricity,provide opportunities for comprehending structure-property correlation and developing antiferroelectric/ferroelectric theories,and suggest an approach to the manipulation of phase transitions for real-world applications.     

Ti3C2Tx MXene compounds for electrochemical energy storage

Since their discovery in 2011, MXene compounds, and in particular the Ti₃C₂-based phases, have gained increasing interest from researchers leading to over 2000 scientific works in 2020. The peculiar morphological, charge transport, and surface properties make the MXenes ideal materials for energy storage applications such as active material in alkaline ion batteries and supercapacitors, as conductive or buffer agent in composite electrodes for high energy applications, and as electrocatalytic materials for oxygen evolution or redox flow batteries. Among this almost endless literature, this work focuses on 5 recent articles (2019/2020) that summarize the potential of MXenes in different energy storage applications, also resuming the most promising preparatory routes regarding industrial scalability.     

Recent advances in multifunctional electrochromic energy storage devices and photoelectrochromic devices

Multifunctional devices integrated with electrochromism and energy storage or energy production functions are attractive because these devices can be used as an effective approach to address the energy crisis and environmental pollution in society today. In this review, we explain the operation principles of electrochromic energy storage devices including electrochromic supercapacitors, electrochromic batteries, and the photoelectrochromic devices. Furthermore, the material candidates and structure types of these multifunctional devices are discussed in detail. The major challenges of these devices along with a further outlook are highlighted at the end.     

2020 roadmap on two-dimensional materials for energy storage and conversion

Energy storage and conversion have attained significant interest owing to its important applications that reduce CO₂ emission through employing green energy. Some promising technologies are included metal-air batteries, metal-sulfur batteries, metal-ion batteries, electrochemical capacitors, etc. Here, metal elements are involved with lithium, sodium, and magnesium. For these devices, electrode materials are of importance to obtain high performance. Two-dimensional (2D) materials are a large kind of layered structured materials with promising future as energy storage materials, which include graphene, black phosporus, MXenes, covalent organic frameworks (COFs), 2D oxides, 2D chalcogenides, and others. Great progress has been achieved to go ahead for 2D materials in energy storage and conversion. More researchers will join in this research field. Under the background, it has motivated us to contribute with a roadmap on ‘two-dimensional materials for energy storage and conversion.