Proton Insertion Chemistry of a Zinc–Organic Battery

Proton storage in rechargeable aqueous zinc-ion batteries (ZIBs) is attracting extensive attention owing to the fast kinetics of H⁺ insertion/extraction. However, it has not been achieved in organic materials-based ZIBs with a mild electrolyte. Now, aqueous ZIBs based on diquinoxalino [2,3-a:2′,3′-c] phenazine (HATN) in a mild electrolyte are developed. Electrochemical and structural analysis confirm for the first time that such Zn–HATN batteries experience a H⁺ uptake/removal behavior with highly reversible structural evolution of HATN. The H⁺ uptake/removal endows the Zn–HATN batteries with enhanced electrochemical performance. Proton insertion chemistry will broaden the horizons of aqueous Zn–organic batteries and open up new opportunities to construct high-performance ZIBs.     

A Smart Flexible Zinc Battery with Cooling Recovery Ability

Flexible batteries are essential for wearable electronic devices. To meet practical applications, they need to be mechanically robust and stable. However, strong or multiple bending may sever the interfacial contact between electrode and electrolyte, causing capacity fading or even battery failure. Herein we present a new cooling‐recovery concept for flexible batteries, which involves a temperature‐sensitive sol–gel transition behavior of the thermoreversible polymer hydrogel electrolyte. Once a battery has suffered from strong mechanical stresses, a simple cooling process can refresh the electrode–electrolyte interface. The energy‐storage capability can be recovered with a healing efficiency higher than 98 %. It is believed that this study not only offers new valuable insights, but also opens up new perspectives to develop functional wearable devices.     

Recent Progress in the Electrolytes of Aqueous Zinc-Ion Batteries

Rechargeable aqueous zinc-ion batteries (ZIBs) have garnered tremendous attention in the field of next energy storage devices due to their high safety, low cost, abundant resources, and eco-friendliness. As an important component of the zinc-ion battery, the electrolyte plays a vital role in the electrochemical properties, since it will provide a pathway for the migrations of the zinc ions between the cathode and anode, and determine the ionic conductivity, electrochemically stable potential window, and reaction mechanism. In this Minireview, a brief introduction of electrochemical principles of the aqueous ZIBs is discussed and the recent advances of various aqueous electrolytes for ZIBs, including liquid, gel, and multifunctional hydrogel electrolytes are also summarized. Furthermore, the remaining challenges and future directions of electrolytes in aqueous ZIBs are also discussed, which could provide clues for the following development.     

Photoreversible Gelation of a Triblock Copolymer in an Ionic Liquid

The reversible micellization and sol–gel transition of block copolymer solutions in an ionic liquid (IL) triggered by a photostimulus is described. The ABA triblock copolymer employed, denoted P(AzoMA‐r‐NIPAm)‐b‐PEO‐b‐P(AzoMA‐r‐NIPAm)), has a B block composed of an IL‐soluble poly(ethylene oxide) (PEO). The A block consists of a random copolymer including thermosensitive N‐isopropylacrylamide (NIPAm) units and a methacrylate with an azobenzene chromophore in the side chain (AzoMA). A phototriggered reversible unimer‐to‐micelle transition of a dilute ABA triblock copolymer (1 wt %) was observed in an IL, 1‐butyl‐3‐methylimidazolium hexafluorophosphate ([C₄mim]PF₆), at an intermediate “bistable” temperature (50 °C). The system underwent a reversible sol–gel transition cycle at the bistable temperature (53 °C), with reversible association/fragmentation of the polymer network resulting from the phototriggered self‐assembly of the ABA triblock copolymer (20 wt %) in [C₄mim]PF₆.     

Nonflammable pseudoconcentrated electrolytes for batteries

Electrolyte is essentially important for electrochemical and safety performance of batteries. The pseudoconcentrated electrolyte, with lean solvent but anion-involved solvation sheath and heterogeneous long-range structure, endows the electrolyte with superior interfacial properties and the bulk properties, enabling the high-voltage lithium-ion battery, lithium-metal battery, and sodium battery with outstanding electrochemical performances. Nonflammable solvents as diluent in the pseudoconcentrated electrolyte can reach 30–60% by volume share, making the electrolyte nonflammable and then showing great possibility in mitigating the thermal runaway of the battery. As a new family of liquid electrolyte, nonflammable pseudoconcentrated electrolyte is promising for high safety and high energy density secondary batteries.     

Influence of sol–gel derived lithium cobalt phosphate in alkaline rechargeable battery

A lithium cobalt phosphate (LiCoPO₄) cathode was synthesised by citric acid assisted sol?Cgel method and its electrochemical behaviour in alkaline secondary battery (using novel lithium hydroxide as the electrolyte) is reported. The sol?Cgel method using metal acetate precursors with citric acid as a chelating agent influenced the particle size and the homogeneity while yielding a single phase LiCoPO₄ at a considerably lower temperature and shortened heating time, compared to that of the conventional solid state reaction. The cyclic voltammogram of LiCoPO₄ showed a reversible redox process implying that de-intercalation and intercalation of lithium can occur in aqueous electrolyte. This was supported by X-ray diffraction (XRD) and Infra-red (IR) studies. The charge?Cdischarge performance of the Zn/LiCoPO₄ battery showed good capacity retention (after 25 cycles it delivered 90?% of its initial capacity). This enhanced capacity retention was attributed to the synergistic effect of particle homogeneity, reduced Li⁺ diffusion path and stability of the non-reactive aqueous electrolyte between the electrode and the electrolyte interface.     

Interfacial Design of Dendrite-Free Zinc Anodes for Aqueous Zinc-Ion Batteries

Aqueous zinc-ion batteries have rapidly developed recently as promising energy storage devices in large-scale energy storage systems owing to their low cost and high safety. Research on suppressing zinc dendrite growth has meanwhile attracted widespread attention to improve the lifespan and reversibility of batteries. Herein, design methods for dendrite-free zinc anodes and their internal mechanisms are reviewed from the perspective of optimizing the host–zinc interface and the zinc–electrolyte interface. Furthermore, a design strategy is proposed to homogenize zinc deposition by regulating the interfacial electric field and ion distribution during zinc nucleation and growth. This Minireview can offer potential directions for the rational design of dendrite-free zinc anodes employed in aqueous zinc-ion batteries.     

2-Methoxyhydroquinone from Vanillin for Aqueous Redox-Flow Batteries

We show the synthesis of a redox-active quinone, 2-methoxy-1,4-hydroquinone (MHQ), from a bio-based feedstock and its suitability as electrolyte in aqueous redox flow batteries. We identified semiquinone intermediates at insufficiently low pH and quinoid radicals as responsible for decomposition of MHQ under electrochemical conditions. Both can be avoided and/or stabilized, respectively, using H₃PO₄ electrolyte, allowing for reversible cycling in a redox flow battery for hundreds of cycles.     

Rapidly Synthesized Single-Ion Conductive Hydrogel Electrolyte for High-Performance Quasi-Solid-State Zinc-ion Batteries

Single-ion conductive electrolytes can largely eliminate electrode polarization, reduce the proportion of anion migration and inhibit side reactions in batteries. However, they usually suffer from insufficient ion conductivity due to the strong interaction between cations and cationic receptors. Here we report an ultrafast light-responsive covalent organic frameworks (COF) with sulfonic acid groups modification as the acrylamide polymerization initiator. Benefiting from the reduced electrostatic interaction between Zn²⁺ and sulfonic acid groups through solvation effects, the as-prepared COF-based hydrogel electrolyte (TCOF-S-Gel) receives an ion conductivity of up to 27.2 mS/cm and Zn²⁺ transference number of up to 0.89. In addition, sufficient hydrogen bonds endow the single-ion conductive TCOF-S-Gel electrolyte to have good water retention and superb mechanical properties. The assembled Zn||TCOF-S-Gel||MnO₂ full zinc-ion battery exhibits high discharge capacity (248 mAh/g at 1C), excellent rate capability (90 mAh/g at 10C) and superior cycling performance. These enviable results enlist the instantaneously photocured TCOF-S-Gel electrolyte to be qualified to large-scaled flexible high-performance quasi-solid-state zinc-ion batteries.     

Nano-LiCoO2 as cathode material of large capacity and high rate capability for aqueous rechargeable lithium batteries

Crystalline nanoparticles of LiCoO₂ are prepared by a sol–gel method at 550 °C and characterized by X-ray diffraction. Their electrochemical behaviors were characterized by cyclic voltammograms, capacity measurement and cycling performance. Results show that the reversible capacity of the nano-LiCoO₂ can be up to 143 mAh/g at 1000 mA/g and still be 133 mAh/g at 10,000 mA/g (about 70C) in 0.5 mol/l Li₂SO₄ aqueous electrolyte. In addition, their cycling behavior is also very satisfactory, no evident capacity fading during the initial 40 cycles. These data present great promise for the application of aqueous rechargeable lithium batteries.     

Fabrication and evaluation of a polymer Li-ion battery with microporous gel electrolyte

This paper introduces an easy method for the fabrication of polymer Li-ion batteries with microporous gel electrolyte (MGE). The MGE is a multiphase electrolyte, which is composed of liquid electrolyte, gel electrolyte, and polymer matrix. The MGE not only has high ionic conductivity and good adhesion to the electrodes at low temperatures, but also retains good mechanical strength at elevated temperatures. Therefore, the MGE batteries are able to operate over a wide temperature range. During battery fabrication, the MGE is formed in situ by introducing liquid electrolyte into a swellable microporous polymer membrane and then heating or cycling the battery. In this work, the chemical compatibility of MGE with metal lithium during 60 °C storage and with LiMn₂O₄ cathode during cycling was studied. In addition, graphite/MGE/LiMn₂O₄ Li-ion batteries were made and evaluated.     

Xylene as a New Polymerizable Additive for Overcharge Protection of Lithium Ion Batteries

The electrochemical properties and overcharge protection mechanism of xylene as a new polymerizable electrolyte additive for overcharge protection of lithium ion batteries were studied by cyclic voltammetry tests, charge- discharge performance and battery power capacity measurements. It was found that when the battery was overcharged, xylene could electrochemically polymerize at the overcharge potential of 4.3—4.7 V (vs. Li/Li＋) to form a thin polymer film on the surface of the cathode, thus preventing voltage runaway. On the other hand, the use of xylene as an overcharge protection electrolyte additive did not influence the normal performance of lithium ion batteries.     

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.     

水系锌离子电池电解液添加剂的研究进展

电解液添加剂能有效缓解锌金属阳极的不可控枝晶生长和固有副反应,大幅提升锌金属阳极的循环稳定性和可逆性,对水系锌离子电池的发展和商业化应用具有重要意义。本文通过对近期水系锌离子电池电解液添加剂的研究进展进行了系统总结和分析,简要介绍了锌金属阳极目前面临的主要挑战及其相关机理,重点阐述了电解液添加剂对锌金属阳极界面的作用机制,包括改变溶剂化结构、调节沉积方式、构筑界面保护层。此外,还对不同类型电解液添加剂进行了分类讨论,包括离子添加剂、无机添加剂和有机添加剂。最后,我们进一步对电解液添加剂策略在提升水系锌离子电池电化学性能中存在的科学问题和未来的研究方向进行了总结与展望。     

金属锂电池的热失控与安全性研究进展

锂离子电池在便携式储能器件及电动汽车领域得到了广泛应用,然而频繁发生的电池起火爆炸事故,使热失控和热安全问题备受人们关注,目前已有多篇综述报道了缓解锂离子电池热失控的措施。相比于已经接近理论比能极限的锂离子电池,金属锂负极具有更高的比容量、更低的电势和高反应活性,但是不可控的锂枝晶生长,使得金属锂电池的热失控问题更为复杂和严重。针对金属锂电池的热失控问题,本文首先介绍了热失控的诱因及基本过程和阶段,其次从材料层面综述了提高电池热安全性的多种策略,包括使用阻燃性电解质、离子液体电解质、高浓电解质和局域高浓电解质等不易燃液态电解质体系,开发高热稳定性隔膜、热响应隔膜、阻燃性隔膜和具有枝晶检测预警与枝晶消除功能的新型智能隔膜,以及研究热响应聚合物电解质,最后对金属锂电池热失控在未来的进一步研究进行了展望。     

A study on structure-performance relationship of overcharged 18650-size Li4Ti5O12/LiMn2O4 battery

The electrochemical properties and thermal generation behavior of 18650 Li₄Ti₅O₁₂/LiMn₂O₄ batteries were tested before and after overcharge. The experimental results showed that after overcharge, the specific capacity decreased obviously. The higher the current density was, the more obvious the capacity decreased. For instance, the overcharged battery had almost no capacity when the current density increased to 5C. At the same time, the overcharged battery presented a much more apparent thermal runaway trend compared to the normal battery. After measuring the electrochemical impedance spectroscopy of the batteries and characterizing the crystal structure/nanostructure of the electrode materials, these phenomena could be attributed to the following two reasons: (1) the decomposition of the electrolyte arisen from the overcharge process resulted in increased internal resistance; (2) the thermal runaway due to the increased internal resistance resulted in the damage to crystal structure/nanostructure and aggregation of the electrode materials, thus leading to the secondary decrease in capacity.     

ZnF2-Riched Inorganic/Organic Hybrid SEI: in situ-Chemical Construction and Performance-Improving Mechanism for Aqueous Zinc-ion Batteries

Uncontrolled dendrites growth and serious parasitic reactions in aqueous electrolytes, greatly hinder the practical application of aqueous zinc-ion battery. On the basis of in situ-chemical construction and performance-improving mechanism, multifunctional fluoroethylene carbonate (FEC) is introduced into aqueous electrolyte to construct a high-quality and ZnF₂-riched inorganic/organic hybrid SEI (ZHS) layer on Zn metal anode (ZMA) surface. Notably, FEC additive can regulate the solvated structure of Zn²⁺ to reduce H₂O molecules reactivity. Additionally, the ZHS layer with strong Zn²⁺ affinity can avoid dendrites formation and hinder the direct contact between the electrolyte and anode. Therefore, the dendrites growth, Zn corrosion, and H₂ evolution reaction on ZMA in FEC-included ZnSO₄ electrolyte are highly suppressed. Thus, ZMA in such electrolyte realize a long cycle life over 1000 h and deliver a stable coulombic efficiency of 99.1 % after 500 cycles.     

Liquid‐Free Lithium–Oxygen Batteries

Non‐aqueous lithium–oxygen batteries are considered as most advanced power sources, albeit they are facing numerous challenges concerning almost each cell component. Herein, we diverge from the conventional and traditional liquid‐based non‐aqueous Li–O₂ batteries to a Li–O₂ system based on a solid polymer electrolyte (SPE‐) and operated at a temperature higher than the melting point of the polymer electrolyte, where useful and most applicable conductivity values are easily achieved. The proposed SPE‐based Li‐O₂ cell is compared to Li–O₂ cells based on ethylene glycol dimethyl ether (glyme) through potentiodynamic and galvanostatic studies, showing a higher cell discharge voltage by 80 mV and most significantly, a charge voltage lower by 400 mV. The solid‐state battery demonstrated a comparable discharge‐specific capacity to glyme‐based Li–O₂ cells when discharged at the same current density. The results shown here demonstrate that the safer PEO‐based Li–O₂ battery is highly advantageous and can potentially replace the contingent of liquid‐based cells upon further investigation.     

Thermal runaway and fire behavior investigation of lithium ion batteries using modified cone calorimeter

The lithium ion battery has been widely used, but it has high fire risk due to its flammable materials. In this study, a series of combustion tests are conducted on the 18650-type lithium ion batteries using the modified cone calorimeter. The temperature and voltage variation of the battery, heat release rate and gas generation during combustion are measured in this study. The battery is heated evenly by the self-made heater, and the reliable trigger temperatures of thermal runaway are obtained for different states of charge (SOCs) batteries in this study. The fire behavior of the 100% SOC batteries is shown in this paper. The net heat absorption by the battery before thermal runaway is calculated based on the heat transfer theory. It ranges from 56.81 to 64.05 kJ for 0 to 100% SOC batteries, which shows a decreasing trend as SOC increases. The peak combustion heat release rate of 100% SOC batteries is 3.747?±?0.858 kW. CH₄ and CO gases are detected before and after thermal runaway. The generation of CO shows an increasing trend as SOC increases. Some suggestions on the early warning system of battery thermal runaway are proposed based on this study.

     

Rechargeable Room‐Temperature Na–CO2 Batteries

Developing rechargeable Na–CO₂ batteries is significant for energy conversion and utilization of CO₂. However, the reported batteries in pure CO₂ atmosphere are non‐rechargeable with limited discharge capacity of 200 mAh g^?1. Herein, we realized the rechargeability of a Na–CO₂ battery, with the proposed and demonstrated reversible reaction of 3 CO₂+4 Na?2 Na₂CO₃+C. The battery consists of a Na anode, an ether‐based electrolyte, and a designed cathode with electrolyte‐treated multi‐wall carbon nanotubes, and shows reversible capacity of 60000 mAh g^?1 at 1 A g^?1 (≈1000 Wh kg^?1) and runs for 200 cycles with controlled capacity of 2000 mAh g^?1 at charge voltage <3.7 V. The porous structure, high electro‐conductivity, and good wettability of electrolyte to cathode lead to reduced electrochemical polarization of the battery and further result in high performance. Our work provides an alternative approach towards clean recycling and utilization of CO₂.