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A foldable battery with high flexibility provides great potential in various wearable electronic devices for health and fitness tracking, chronic disease management, performance monitoring, navigation tracking, and portable gears for soldiers. We report a highly flexible, self‐healing Zn‐ion battery with a free‐standing cathode that is composed of a 3D gear‐like NH4V4O10@C composite on carbon paper. The battery retained a capacity of up to 102.4 mAh g−1 even after being folded 60 times with a high angle of 180°. An aqueous hydrogel consisting polyvinyl alcohol, glycerin and Zn(CF3SO3)2 was used as electrolyte, which showed as high as 580 % tensile strain under a loading weight of 78 N. The battery exhibited a better capacity retention of over 100 mAh g−1 and Coulombic efficiency of over 99.8 % after cutting and twisting to 90°, thereby indicating a great self‐healing performance. The gear‐like geometry greatly improved the volume accommodation due to the increased interval space between the blades and the outward configuration. Meanwhile the Zn2+ ionic conductivity was improved by rapid re‐binding of many existing hydroxy groups from the electrolyte and the enhanced contact surface area and diffusion route from the cathode material. The highly flexible, safe aqueous Zn‐ion battery opens a practical way to power various carry‐on electronics under mechanical agitation. [ABSTRACT FROM AUTHOR]

Self‐healing secondary batteries have attracted great attention for constructing stable energy‐storage systems. Herein, a novel self‐healing rechargeable magnesium battery cathode is developed using self‐healing microcapsules in a vanadium pentoxide microflower‐based cathode. The microcapsules are prepared through a microfluidic approach. The core of the microcapsule contains a conductive hydrogel and carbon nanospheres, and the shell composes of a UV‐curved polymer. When the self‐healing Mg battery cathode cracks, the microcapsules break and release the core into the cracks, rebuilding the pathways for the electron transport and enabling a stable electrochemical performance. The presented cathode displays a good capacity of 105 mAh g−1 after 500 cycles at 100 mA g−1 and it delivers a stable capacity of 98.3 mAh g−1 after long‐term cycling 1000 times at 200 mA g−1. A recoverable rate‐performance and a good temperature tolerance are also achieved. It is expected that the general preparation approach of the self‐healing microcapsules and the long‐term stable Mg battery will find broad applications for developing many emerging energy‐storage systems. [ABSTRACT FROM AUTHOR]

Self‐healing and flexibility are significant for many emerging applications of secondary batteries, which have attracted broad attention. Herein, a self‐healing flexible quasi‐solid Zn‐ion battery composing of flexible all‐in‐one cathode (VS2 nanosheets growing on carbon cloth) and anode (electrochemically deposited Zn nanowires), and a self‐healing hydrogel electrolyte, is presented. The free‐standing all‐in‐one electrodes enable a high capacity and robust structure during flexible transformation of the battery, and the hydrogel electrolyte possesses a good self‐healing performance. The presented battery remains as a high retention potential even after healing from being cut into six pieces. When bending at 60°, 90°, and 180°, the battery capacities remain 124, 125, and 114 mAh g−1, respectively, cycling at a current density of 50 mA g−1. Moreover, after cutting and healing twice, the battery still delivers a stable capacity, indicating a potential use of self‐healing and wearable electronics. [ABSTRACT FROM AUTHOR]

Microencapsulated materials are receiving broad attention for applications as diverse as energy storage and conversion, biomedicine, self‐healing materials, and electronics. Here, a general microfluidic approach is presented to prepare phase‐change material‐infilled microcapsules with unique thermal and mechanical properties. Aqueous sodium acetate solutions are encapsulated by an acrylate‐based shell via a microfluidic method. To understand and optimize microcapsule formation, flow behavior during the encapsulation is numerically simulated. When the microcapsules are embedded in an acrylate matrix (same composition as the shell wall material), the microcapsules exhibit a significant 46.6 ºC difference between the crystallization and melting temperatures as determined by differential scanning calorimetry at a rate of 10 ºC per min. Variable temperature dynamic mechanical analysis over the range of 50 to ‐90 ºC reveals up to a 50% change in the composite's elastic modulus at a given temperature, depending on if the sample is being cooled or heated, due to significant undercooling of the core material crystallization as shown by X‐ray diffraction. [ABSTRACT FROM AUTHOR]