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Hydrogels hold great promise as electrolytes for emerging aqueous batteries, for which establishing a robust electrode‐hydrogel interface is crucial for mitigating side reactions. Conventional hydrogel electrolytes fabricated by ex situ polymerization through either thermal stimulation or photo exposure cannot ensure complete interfacial contact with electrodes. Herein, we introduce an in situ electropolymerization approach for constructing hydrogel electrolytes. The hydrogel is spontaneously generated during the initial cycling of the battery, eliminating the need of additional initiators for polymerization. The involvement of electrodes during the hydrogel synthesis yields well‐bonded and deep infiltrated electrode‐electrolyte interfaces. As a case study, we attest that, the in situ‐formed polyanionic hydrogel in Zn‐MnO2 battery substantially improves the stability and kinetics of both Zn anode and porous MnO2 cathode owing to the robust interfaces. This research provides insight to the function of hydrogel electrolyte interfaces and constitutes a critical advancement in designing highly durable aqueous batteries. [ABSTRACT FROM AUTHOR]

The practical application of aqueous rechargeable batteries faces several challenges due to the limited stability window of electrolytes and parasitic side reactions, such as corrosion, passivation, gas evolution, and co‐intercalations. The solid electrolyte interphase (SEI) formed at the electrode/electrolyte interface plays a critical role in determining interfacial properties and battery performance. Efforts are being made to develop effective SEIs, functionalize interphase layers, and explore various aqueous hybrid electrolytes that facilitate SEI formation. This review highlights the role of interphasial structures in aqueous batteries. First, common issues encountered by aqueous batteries and specific characteristics of aqueous lithium‐ion, sodium‐ion, zinc‐ion, and aluminum‐ion batteries are outlined. Then the tactics used to improve cycle stability of aqueous batteries are introduced and compared and the working principles and key parameters from the context of interphasial modification are discussed. Finally, constructive insights and suggestions for developing high‐performance batteries are offered, with a focus on SEI formation and interphase layer design. [ABSTRACT FROM AUTHOR]

The practical implementation of aqueous zinc‐iodine batteries (ZIBs) is hindered by the rampant Zn dendrites growth, parasite corrosion, and polyiodide shuttling. In this work, ionic liquid EMIM[OAc] is employed as an all‐round solution to mitigate challenges on both the Zn anode and the iodine cathode side. First, the EMIM+ embedded lean‐water inner Helmholtz plane (IHP) and inert solvation sheath modulated by OAc− effectively repels H2O molecules away from the Zn anode surface. The preferential adsorption of EMIM+ on Zn metal facilitates uniform Zn nucleation via a steric hindrance effect. Second, EMIM+ can reduce the polyiodide shuttling by hindering the iodine dissolution and forming an EMIM+‐I3− dominated phase. These effects holistically enhance the cycle life, which is manifested by both Zn || Zn symmetric cells and Zn‐I2 full cells. ZIBs with EAc deliver a capacity decay rate of merely 0.01 ‰ per cycle after over 18,000 cycles at 4 A g−1, and lower self‐discharge and better calendar life than the ZIBs without ionic liquid EAc additive. [ABSTRACT FROM AUTHOR]

The development of polymer sodium batteries requires cathode materials with stable interfaces to avoid poor interfacial contact and interfacial side reactions during cycling. Here, a co‐engineering strategy is deployed to tailor the cathode internal structure and improve the cathode interface stability through bonding interactions. Internally, the effect of low‐cost Fe substitution in the obtained Na0.67Mn2/3Fe1/3O2 cathode material renders favorable effects in several aspects. First, the increased lattice constant facilitates Na+ intercalation and thereby lowers the diffusion barrier of Na+ ions. Second, it increases the electronic conductivity, thereby improving the reaction reversibility. Third, the MnO bond length is shortened, which alleviates the Jahn‐Taylor effect and improves structural stability. In addition to these internal effects, the FeOB bond interactions due to Fe substitution promote the decomposition of the tris(trimethylsilane)borate additive and the formation of a dense and uniform cathode electrolyte interface film, leading to improved cycling stability. Owing to the co‐engineering of both internal structure and surface modification, the polymer solid‐state sodium battery with a stable interface exhibits a specific capacity of 85.2 mAh g‐1 after 800 cycles at 1 C. [ABSTRACT FROM AUTHOR]

Organic cathodes for aqueous zinc‐ion batteries (AZIBs) feature intrinsic flexibility and favorable kinetics, but they suffer from high solubility. Herein, a partial charge regulation strategy is deployed by designing a small organic molecule with extended π‐conjugated plane, namely benzo[i]benzo[6′,7′]quinoxalino[2′,3′:9,10]phenanthro[4,5‐abc]phenazine‐5,10,16,21‐tetraone (PTONQ). The charge equalization of active sites induced by the extended π‐conjugated plane of the PTONQ molecule combined with high aromaticity renders the molecule low solubility, fast charge transfer, and high structural stability. The fabricated Zn//PTONQ battery cycles more than 500 h at 175 mA g−1 with small capacity reduction, fast charged/discharged kinetics, and anti‐freeze performance (below ‐20°C). By a series of ex situ characterizations, it is attested that the capacity originates mainly from Zn2+ insertion/removal of PTONQ without H+ incorporation, which also accounts for the formation of Znx(CF3SO3)y(OH)2x‐y·nH2O by‐products. This result benefits the understanding of the by‐product formation mechanism of organic cathode and paves a new way to advance the aqueous Zn‐organic batteries. [ABSTRACT FROM AUTHOR]

Na‐ion battery has the potential to be one of the best types of next‐generation energy storage devices by virtue of their cost and sustainability advantages. With the demand for high safety, the replacement of traditional organic electrolytes with polymer electrolytes can avoid electrolyte leakage and thermal instability. Polymer electrolytes, however, suffer from low ionic conductivity and large interfacial impedance. Gel polymer electrolytes (GPEs) represent an excellent balance that combines the advantages of high ionic conductivity, low interfacial impedance, high thermal stability, and flexibility. This short review summarizes the recent progress on gel polymer Na‐ion batteries, focusing on different preparation approaches and the resultant physical and electrochemical properties. Reasons for the differences in ionic conductivity, mechanical properties, interfacial properties, and thermal stability are discussed at the molecular level. This Review may offer a deep understanding of sodium‐ion GPEs and may guide the design of intermolecular interactions for high‐performance gel polymer Na‐ion batteries. [ABSTRACT FROM AUTHOR]

In recent years, the increasing demand for high‐capacity and safe energy storage has focused attention on zinc batteries featuring high voltage, high capacity, or both. Despite extensive research progress, achieving high‐energy‐density zinc batteries remains challenging and requires the synergistic regulation of multiple factors including reaction mechanisms, electrodes, and electrolytes. In this Review, we comprehensively summarize the rational design strategies of high‐energy‐density zinc batteries and critically analyze the positive effects and potential issues of these strategies in optimizing the electrochemistry, cathode materials, electrolytes, and device architecture. Finally, the challenges and perspectives for the further development of high‐energy‐density zinc batteries are outlined to guide research towards new‐generation batteries for household appliances, low‐speed electric vehicles, and large‐scale energy storage systems. [ABSTRACT FROM AUTHOR]

Paper electronics offer an environmentally sustainable option for flexible and wearable systems and perfectly fit the available printing technologies for high manufacturing efficiency. As the heart of energy‐consuming devices, paper‐based batteries are required to be compatible with printing processes with high fidelity. Herein, hydrogel reinforced cellulose paper (HCP) is designed to serve as the separator and solid electrolyte for paper batteries. The HCP can sustain higher strain than pristine papers and are biodegradable in natural environment within four weeks. Zinc‐metal (Ni and Mn) batteries printed on the HCP present remarkable volumetric energy density of ≈26 mWh cm–3, and also demonstrate the feature of cuttability and compatibility with flexible circuits and devices. As a result, self‐powered electronic system could be constructed by integrating printed paper batteries with solar cells and light‐emitting diodes. The result highlights the feasibility of hydrogel reinforced paper for ubiquitous flexible and eco‐friendly electronics. [ABSTRACT FROM AUTHOR]

Efficient thermal protection is essential to battery safety. Here, a self‐adaptive strategy is demonstrated to circumvent the thermal runaway of aqueous zinc‐ion batteries, by using a zinc chloride‐enriched hygroscopic hydrogel electrolyte. At high temperatures, water inside the hydrogel can quickly evaporate to dissipate the heat generated. Concurrently, excessive water evaporation causes a sudden drop in the ion diffusion of the hydrogel electrolyte, thereby effectively restricting the migration of ions and shutting down the battery. When the temperature lowers, the hydrogel absorbs water from the air and the battery recovers its function. The evaporation and regeneration of water in the hydrogel electrolytes are highly reversible, thus realizing intelligent and efficient thermal self‐protection of zinc‐ion batteries. By properly designing and engineering the hygroscopic hydrogel electrolytes, it is believed that other thermal self‐protective aqueous batteries with faster response can be abricated, which shows promise for a safe power supply in both consumable electronics and electric vehicles. [ABSTRACT FROM AUTHOR]

Li–O2 batteries (LOB) potentially have the highest specific capacity among all types of metal‐ion batteries but suffer severely from cycle instability and low energy efficiency. In this work, an integrated cathode is fabricated that contains an amorphous MoS2 thin layer deposited on a 3D conductive carbon scaffold to improve the energy efficiency to ≈83% and cycle life up to 190 cycles. An advanced pressure‐tuned stop‐flow atomic layer deposition (ALD) method is employed to deposit a ≈5 nm thick amorphous MoS2 layer on carbon nanotube forest‐covered graphite foam. It is established that this integrated 3D cathode exhibits high catalytic activity for both oxygen reduction reaction and oxygen evolution reaction. The benefit of the ALD MoS2 in lowering the energy barrier is also supported by first‐principles calculations. Finally, quasi‐solid state flexible LOBs are also assembled that can be stably discharged up to 6 d. This new and rational design of cathode may provide a new direction for achieving high‐performance flexible Li–O2 batteries. [ABSTRACT FROM AUTHOR]

Abstract: Multifunctional energy devices with various energy forms in different operation modes are under current research focus toward the new‐generation smart and self‐powered electronics. In this review, the recent progress made in developing integrated/joint multifunctional energy devices, with a focus on electrochromic batteries/supercapacitors, and solar cells powered batteries/supercapacitors, is summarized. The different integration modes and design strategies are highlighted and their merit/demerits are also discussed. The authors' opinions on future research toward smart multifunctional energy devices are provided at the end. [ABSTRACT FROM AUTHOR]