An Environmentally Friendly and Flexible Aqueous Zinc Battery Using an Organic Cathode

Rechargeable batteries have been used to power various electric devices and store energy from renewables, but their toxic components (namely, electrode materials, electrolyte, and separator) generally cause serious environment issues when disused. Such toxicity characteristic makes them difficult to power future wearable electronic devices. Now an environmentally friendly and highly safe rechargeable battery, based on a pyrene‐4,5,9,10‐tetraone (PTO) cathode and zinc anode in mild aqueous electrolyte is presented. The PTO‐cathode shows a high specific capacity (336 mAh g^?1) for Zn²⁺ storage with fast kinetics and high reversibility. Thus, the PTO//Zn full cell exhibits a high energy density (186.7 Wh kg^?1), supercapacitor‐like power behavior and long‐term lifespan (over 1000 cycles). Moreover, a belt‐shaped PTO//Zn battery with robust mechanical durability and remarkable flexibility is first fabricated to clarify its potential application in wearable electronic devices.     

High‐Performance Lithium–Air Battery with a Coaxial‐Fiber Architecture

The lithium–air battery has been proposed as the next‐generation energy‐storage device with a much higher energy density compared with the conventional lithium‐ion battery. However, lithium–air batteries currently suffer enormous problems including parasitic reactions, low recyclability in air, degradation, and leakage of liquid electrolyte. Besides, they are designed into a rigid bulk structure that cannot meet the flexible requirement in the modern electronics. Herein, for the first time, a new family of fiber‐shaped lithium–air batteries with high electrochemical performances and flexibility has been developed. The battery exhibited a discharge capacity of 12 470 mAh g^?1 and could stably work for 100 cycles in air; its electrochemical performances were well maintained under bending and after bending. It was also wearable and formed flexible power textiles for various electronic devices.     

Superoxide Stabilization and a Universal KO2 Growth Mechanism in Potassium–Oxygen Batteries

Rechargeable potassium–oxygen (K‐O₂) batteries promise to provide higher round‐trip efficiency and cycle life than other alkali–oxygen batteries with satisfactory gravimetric energy density (935 Wh kg^?1). Exploiting a strong electron‐donating solvent, for example, dimethyl sulfoxide (DMSO) strongly stabilizes the discharge product (KO₂), resulting in significant improvement in electrode kinetics and chemical/electrochemical reversibility. The first DMSO‐based K‐O₂ battery demonstrates a much higher energy efficiency and stability than the glyme‐based electrolyte. A universal KO₂ growth model is developed and it is demonstrated that the ideal solvent for K‐O₂ batteries should strongly stabilize superoxide (strong donor ability) to obtain high electrode kinetics and reversibility while providing fast oxygen diffusion to achieve high discharge capacity. This work elucidates key electrolyte properties that control the efficiency and reversibility of K‐O₂ batteries.     

Lithium–Sulfur Batteries under Lean Electrolyte Conditions: Challenges and Opportunities

The development of energy‐storage devices has received increasing attention as a transformative technology to realize a low‐carbon economy and sustainable energy supply. Lithium–sulfur (Li–S) batteries are considered to be one of the most promising next‐generation energy‐storage devices due to their ultrahigh energy density. Despite the extraordinary progress in the last few years, the actual energy density of Li–S batteries is still far from satisfactory to meet the demand for practical applications. Considering the sulfur electrochemistry is highly dependent on solid‐liquid‐solid multi‐phase conversion, the electrolyte amount plays a primary role in the practical performances of Li–S cells. Therefore, a lean electrolyte volume with low electrolyte/sulfur ratio is essential for practical Li–S batteries, yet under these conditions it is highly challenging to achieve acceptable electrochemical performances regarding sulfur kinetics, discharge capacity, Coulombic efficiency, and cycling stability especially for high‐sulfur‐loading cathodes. In this Review, the impact of the electrolyte/sulfur ratio on the actual energy density and the economic cost of Li–S batteries is addressed. Challenges and recent progress are presented in terms of the sulfur electrochemical processes: the dissolution–precipitation conversion and the solid–solid multi‐phasic transition. Finally, prospects of future lean‐electrolyte Li–S battery design and engineering are discussed.     

Anisotropically Electrochemical–Mechanical Evolution in Solid‐State Batteries and Interfacial Tailored Strategy

All‐solid‐state batteries have attracted attention owing to the potential high energy density and safety; however, little success has been made on practical applications of solid‐state batteries, which is largely attributed to the solid–solid interface issues. A fundamental elucidation of electrode–electrolyte interface behaviors is of crucial significance but has proven difficult. The interfacial resistance and capacity fading issues in a solid‐state battery were probed, revealing a heterogeneous phase transition evolution at solid–solid interfaces. The strain‐induced interfacial change and the contact loss, as well as a dense metallic surface phase, deteriorate the electrochemical reaction in solid‐state batteries. Furthermore, the in situ growth of electrolytes on secondary particles is proposed to fabricate robust solid–solid interface. Our study enlightens new insights into the mechanism behind solid–solid interfacial reaction for optimizing advanced solid‐state batteries.     

An All‐Solid‐State Fiber‐Shaped Aluminum–Air Battery with Flexibility,Stretchability, and High Electrochemical Performance

Owing to the high theoretical energy density of metal–air batteries, the aluminum–air battery has been proposed as a promising long‐term power supply for electronics. However, the available energy density from the aluminum–air battery is far from that anticipated and is limited by current electrode materials. Herein we described the creation of a new family of all‐solid‐state fiber‐shaped aluminum–air batteries with a specific capacity of 935 mAh g⁻¹ and an energy density of 1168 Wh kg⁻¹. The synthesis of an electrode composed of cross‐stacked aligned carbon‐nanotube/silver‐nanoparticle sheets contributes to the remarkable electrochemical performance. The fiber shape also provides the aluminum–air batteries with unique advantages; for example, they are flexible and stretchable and can be woven into a variety of textiles for large‐scale applications.     

A Self‐Healing Aqueous Lithium‐Ion Battery

Flexible lithium‐ion batteries are critical for the next‐generation electronics. However, during the practical application, they may break under deformations such as twisting and cutting, causing their failure to work or even serious safety problems. A new family of all‐solid‐state and flexible aqueous lithium ion batteries that can self‐heal after breaking has been created by designing aligned carbon nanotube sheets loaded with LiMn₂O₄ and LiTi₂(PO₄)₃ nanoparticles on a self‐healing polymer substrate as electrodes, and a new kind of lithium sulfate/sodium carboxymethylcellulose serves as both gel electrolyte and separator. The specific capacity, rate capability, and cycling performance can be well maintained after repeated cutting and self‐healing. These self‐healing batteries are demonstrated to be promising for wearable devices.     

An All‐Solid‐State Fiber‐Shaped Aluminum–Air Battery with Flexibility,Stretchability, and High Electrochemical Performance

Owing to the high theoretical energy density of metal–air batteries, the aluminum–air battery has been proposed as a promising long‐term power supply for electronics. However, the available energy density from the aluminum–air battery is far from that anticipated and is limited by current electrode materials. Herein we described the creation of a new family of all‐solid‐state fiber‐shaped aluminum–air batteries with a specific capacity of 935 mAh g^?1 and an energy density of 1168 Wh kg^?1. The synthesis of an electrode composed of cross‐stacked aligned carbon‐nanotube/silver‐nanoparticle sheets contributes to the remarkable electrochemical performance. The fiber shape also provides the aluminum–air batteries with unique advantages; for example, they are flexible and stretchable and can be woven into a variety of textiles for large‐scale applications.     

Electrolyte Additives for Room‐Temperature,Sodium‐Based,Rechargeable Batteries

Owing to resource abundance, and hence, a reduction in cost, wider global distribution, environmental benignity, and sustainability, sodium‐based, rechargeable batteries are believed to be the most feasible and enthralling energy‐storage devices. Accordingly, they have recently attracted attention from both the scientific and industrial communities. However, to compete with and exceed dominating lithium‐ion technologies, breakthrough research is urgently needed. Among all non‐electrode components of the sodium‐based battery system, the electrolyte is considered to be the most critical element, and its tailored design and formulation is of top priority. The incorporation of a small dose of foreign molecules, called additives, brings vast, salient benefits to the electrolytes. Thus, this review presents progress in electrolyte additives for room‐temperature, sodium‐based, rechargeable batteries, by enlisting sodium‐ion, Na−O₂/air, Na−S, and sodium‐intercalated cathode type‐based batteries.     

Metal‐containing Ionic Liquid/Polyacrylonitrile‐derived Carbon Nanofibers for Oxygen Reduction Reaction and Flexible Zn–Air Battery

Practical applications of Zn–air batteries are usually limited by sluggish kinetics of oxygen reduction reaction. Replacing Pt‐based catalysts with convenient, efficient and low‐cost materials to boost oxygen reduction reaction is highly desirable. Herein, a class of Fe?N co‐doped carbon nanofibers is successfully synthesized by pyrolysis of polyacrylonitrile/metal‐containing ionic liquid‐based electrospun films. The ionic liquids act as porogen to provide multiscale pores as well as activator to bring carbon nanofibers active sites. The catalyst possessing appropriate active sites and unique 3D porous architecture exhibits remarkable long‐term stability and electrocatalytic activity. Particularly, the catalyst maintains a shape of membrane after carbonization, manifesting its direct use as air electrode without binders. It is notable that an all solid‐state Zn–air battery based on the carbon nanofibers exhibits good flexibility, indicating its promising application as wearable devices.     

An Ultraflexible Silicon–Oxygen Battery Fiber with High Energy Density

To satisfy the rapid development of portable and wearable electronics, it is highly desired to make batteries with both high energy densities and flexibility. Although some progress has been made in recent decades, the available batteries share critical problems of poor energy storage capacity and low flexibility. Herein, we have developed a silicon–oxygen battery fiber with high energy density and ultra‐high flexibility by designing a coaxial architecture with a lithiated silicon/carbon nanotube hybrid fiber as inner anode, a polymer gel as middle electrolyte and a bare carbon nanotube sheet as outer cathode. The fiber showed a high energy density of 512 Wh kg⁻¹ and could effectively work after bending for 20 000 cycles. These battery fibers have been further woven into flexible textiles for a large‐scale application.     

X‐ray Absorption Near‐Edge Structure and Nuclear Magnetic Resonance Study of the Lithium–Sulfur Battery and its Components

Understanding the mechanism(s) of polysulfide formation and knowledge about the interactions of sulfur and polysulfides with a host matrix and electrolyte are essential for the development of long‐cycle‐life lithium–sulfur (Li–S) batteries. To achieve this goal, new analytical tools need to be developed. Herein, sulfur K‐edge X‐ray absorption near‐edge structure (XANES) and ^6,7Li magic‐angle spinning (MAS) NMR studies on a Li–S battery and its sulfur components are reported. The characterization of different stoichiometric mixtures of sulfur and lithium compounds (polysulfides), synthesized through a chemical route with all‐sulfur‐based components in the Li–S battery (sulfur and electrolyte), enables the understanding of changes in the batteries measured in postmortem mode and in operando mode. A detailed XANES analysis is performed on different battery components (cathode composite and separator). The relative amounts of each sulfur compound in the cathode and separator are determined precisely, according to the linear combination fit of the XANES spectra, by using reference compounds. Complementary information about the lithium species within the cathode are obtained by using ⁷Li MAS NMR spectroscopy. The setup for the in operando XANES measurements can be viewed as a valuable analytical tool that can aid the understanding of the sulfur environment in Li–S batteries.     

Critical aspects in the development of lithium–air batteries

Intensive research has been done on lithium–air batteries, especially in the last few years. Due to their very high theoretical specific energy, lithium–air batteries are one of the most promising candidates to power future electric vehicles. However, this new technology is in a very early stage of development, and several challenges must be overcome before there will be a commercially viable product. This review describes the most important critical aspects in the development of lithium–air batteries: the electrocatalysis of the oxygen electrode reactions, the degradation of the electrolyte and the oxygen electrode components, the structure of the oxygen electrode, and the passivation of the oxygen electrode during the discharge of the battery. Recent works in these areas are critically reviewed, and suitable research strategies to address these issues are discussed.     

Dynamically Resettable Electrode-Electrolyte Interface through Supramolecular Sol-Gel Transition Electrolyte for Flexible Zinc Batteries

Flexible batteries based on gel electrolytes with high safety are promising power solutions for wearable electronics but suffer from vulnerable electrode-electrolyte interfaces especially upon complex deformations, leading to irreversible capacity loss or even battery collapse. Here, a supramolecular sol-gel transition electrolyte (SGTE) that can dynamically accommodate deformations and repair electrode-electrolyte interfaces through its controllable rewetting at low temperatures is designed. Mediated by the micellization of polypropylene oxide blocks in Pluronic and host-guest interactions between α-cyclodextrin (α-CD) and polyethylene oxide blocks, the high ionic conductivity and compatibility with various salts of SGTE afford resettable electrode-electrolyte interfaces and thus constructions of a series of highly durable, flexible aqueous zinc batteries. The design of this novel gel electrolyte provides new insights for the development of flexible batteries.     

Halide‐Based Materials and Chemistry for Rechargeable Batteries

Rechargeable batteries are considered one of the most effective energy storage technologies to bridge the production and consumption of renewable energy. The further development of rechargeable batteries with characteristics such as high energy density, low cost, safety, and a long cycle life is required to meet the ever‐increasing energy‐storage demands. This Review highlights the progress achieved with halide‐based materials in rechargeable batteries, including the use of halide electrodes, bulk and/or surface halogen‐doping of electrodes, electrolyte design, and additives that enable fast ion shuttling and stable electrode/electrolyte interfaces, as well as realization of new battery chemistry. Battery chemistry based on monovalent cation, multivalent cation, anion, and dual‐ion transfer is covered. This Review aims to promote the understanding of halide‐based materials to stimulate further research and development in the area of high‐performance rechargeable batteries. It also offers a perspective on the exploration of new materials and systems for electrochemical energy storage.     

Full Dissolution of the Whole Lithium Sulfide Family (Li2S8 to Li2S) in a Safe Eutectic Solvent for Rechargeable Lithium–Sulfur Batteries

The lithium–sulfur battery is an attractive option for next‐generation energy storage owing to its much higher theoretical energy density than state‐of‐the‐art lithium‐ion batteries. However, the massive volume changes of the sulfur cathode and the uncontrollable deposition of Li₂S₂/Li₂S significantly deteriorate cycling life and increase voltage polarization. To address these challenges, we develop an ?‐caprolactam/acetamide based eutectic‐solvent electrolyte, which can dissolve all lithium polysulfides and lithium sulfide (Li₂S₈–Li₂S). With this new electrolyte, high specific capacity (1360 mAh g^?1) and reasonable cycling stability are achieved. Moreover, in contrast to conventional ether electrolyte with a low flash point (ca. 2 °C), such low‐cost eutectic‐solvent‐based electrolyte is difficult to ignite, and thus can dramatically enhance battery safety. This research provides a new approach to improving lithium–sulfur batteries in aspects of both safety and performance.     

锂电池电极过程的原位电化学原子力显微镜研究进展

随着人类对能源的使用与存储需求不断增加,高能量密度和高安全性能的二次锂电池体系正在被不断地开发与完善.深入理解充放电过程中锂电池内部电极/电解质界面的电化学过程以及微观反应机理,有利于指导电池材料的优化设计.原位电化学原子力显微镜将原子力显微镜的高分辨表界面分析优势与电化学反应装置相结合,能够在电池运行条件下实现对电极/电解质界面的原位可视化研究,并进一步从纳米尺度上揭示界面结构的演化规律与动力学过程.本文总结了原位电化学原子力显微镜在锂电池电极过程中的最新研究进展,主要包括基于转化型反应的正极过程、固体电解质中间相的动态演化以及固态电池界面演化与失效分析.     

Freestanding film formed with Sb-nanoplates embedded in flexible porous carbon nanofibers as a binder-free anode for high-performance wearable potassium-ion battery

Antimony-based materials are considered as promising anodes for potassium ion batteries due to their high theoretical capacity and low electrode potential. However, the aggregation and bulk expansion of Sb particles in cycling will cause capacity attenuation and poor rate performance. In this paper, Sb nanoplates were designed to be embedded in flexible porous N-dopped carbon nanofibers (Sb@PCNFs) by a simple electrospinning deposition (ESD) method. In this structural design, Sb nanoplates of high capacity were employed as active materials, N-dopped carbon nanofibers were used to improve conductivity and structural stability. The introduction of pore-forming agent enables the nanofibers to possess porous structure, thus buffering the huge volume change and promoting the transfer of electrolyte/ions. More importantly, the freestanding film can be directly used as a working electrode, reducing the redundancy in the battery and the cost. Benefitting from the favorable structure, the freestanding flexible Sb@PCNFs electrode shows excellent potassium storage performance with a capacity of 314 mAh/g after 2000 cycles at 500 mA/g. This strategy of employing active material with high capacity in porous and conductive flexible nanofibers represents an effective method of achieving binder-free electrode with good electrochemical performance towards wearable energy storage devices.     

Preliminary study of single flow zinc–nickel battery

A novel redox flow battery–single flow Zn/NiOOH battery is proposed. The electrolyte of this battery for both negative electrode and positive electrode is high concentration solutions of ZnO in aqueous KOH, the negative electrode is inert metal such as nickel foil, and the positive electrode is nickel oxide for secondary alkaline batteries. Typically, there is no requirement for a membrane in the battery. Ni(OH)₂ is oxidized to NiOOH at positive electrode and the zincate ions is reduced to zinc and electroplated onto the negative electrode during charge. The reverse occurs during discharge. Results obtained with a small laboratory cell show that high efficiencies can be achieved with an average coulombic efficiency of 96% and energy efficiency of 86% over 1000 cycles. High performance obtained indicates that the single flow zinc/nickel battery is a promising battery.     

Nonaqueous magnesium electrochemistry and its application in secondary batteries

A revolution in modern electronics has led to the miniaturization and evolution of many portable devices, such as cellular telephones and laptop computers, since the 1980s. This has led to an increasing demand for new and compatible energy storage technologies. Furthermore, a growing awareness of pollution issues has provided a strong impetus for the science and technology community to develop alternatives with ever-higher energy densities, with the ultimate goal of being able to propel electric vehicles. Magnesium's thermodynamic properties make this metal a natural candidate for utilization as an anode in high-energy-density, rechargeable battery systems. We report herein on the results of extensive studies on magnesium anodes and magnesium insertion electrodes in nonaqueous electrolyte solutions. Novel, rechargeable nonaqueous magnesium battery systems were developed based on the research. This work had two major challenges: one was to develop electrolyte solutions with especially high anodic stability in which magnesium anodes can function at a high level of cycling efficiency; the other was to develop a cathode that can reversibly intercalate Mg ions in these electrolyte systems. The new magnesium batteries consist of Mg metal anodes, an electrolyte with a general structure of Mg(AlX(3-n)R(n)R')(2) (R',R = alkyl groups, X = halide) in ethereal solutions (e.g., tetrahydrofuran, polyethers of the "glyme" family), and Chevrel phases of MgMo(3)S(4) stoichiometry as highly reversible cathodes. With their practical energy density expected to be >60 Wh/Kg, the battery systems can be cycled thousands of times with almost no capacity fading. The batteries are an environmentally friendly alternative to lead-acid and nickel-cadmium batteries and are composed of abundant, inexpensive, and nonpoisonous materials. The batteries are expected to provide superior results in large devices that require high-energy density, high cycle life, a high degree of safety, and low-cost components. Further developments in this field are in active progress.