Achieving high-rate and durable aqueous rechargeable Zn-Ion batteries by enhancing the successive electrochemical conversion reactions.

The mild electrolyte working environment of rechargeable aqueous Zn-ion batteries (AZIBs) features its promising characteristic and potential application for large-scale energy storage system. However, the poor cycling stability significantly hinders the broad application of AZIBs due to the complex electrochemical conversion reactions during charge-discharge process. Herein, we propose a strategy to improve the electrochemical performance of AZIB by enhancing the successive electrochemical conversion reactions. With a rational design of electrode, an even homogeneous electric field can be achieved in the cathode side, resulting to significantly enhanced efficiency of successive electrochemical conversion reactions. Charge storage mechanism studies reveal that the reversibility behaviors of byproducts alkaline zinc sulfate (ZHS) can dramatically determine the H+/Zn2+ de/intercalation process, and a high reversibility characteristic ensures the facilitated electrochemical kinetics. As expected, the resultant AZIB possesses outstanding electrochemical performance with a high specific capacity of 425.08 mAh⋅g-1 at 0.1 A⋅g-1, an excellent rate capacity of about 60% (246.6 mAh⋅g-1 at 1 A⋅g-1) and superior cycling stability of 93.7% after 3000 cycles (at 3 A⋅g-1). This effective strategy and thinking proposed here may open a new avenue for the development of high-performing AZIBs.

Wearable and Fully Biocompatible All-in-One Structured ″Paper-Like″ Zinc Ion Battery.

A power supply with the characteristics of portability and safety will be one of the dominating mainstreams for future wearable electronics and implantable biomedical devices. The conventional energy storage devices with typical sandwich structures have complicated components and low mechanical properties, suffering from the apparent performance degradation during deformation and hindering the possibility of implanting biomedical units. Herein, a novel all-in-one structure ″paper-like″ zinc ion battery (ZIB) was designed and assembled from an electrospun polyacrylonitrile (PAN) nanomembrane (as the separator) with in situ deposited anode (zinc nanosheets) and cathode (MnO2 nanosheets), which ensures the monolith under different bending states by avoiding the relative sliding and detaching between the integrated layers. Benefiting from the well-designed all-in-one construction and electrodes, the resultant all-in-one ZIB (AZIB) features an ultrathin thickness (about 97 µm), superior specific capacity of 353.8 mAh g-1 (at 0.1 mA cm-2), and outstanding cycling stability (98.7% capacity retention after 500 cycles at 1 A cm-2). And the achieved volumetric energy density is as high as 17.5 mWh cm-3 at a power density of 116.4 mW cm-3. Impressively, the concept of wearable electronic applications of the obtained AZIB was fully demonstrated with excellent flexibility and remarkable temperature resistance under various severe conditions. Our AZIB may provide a versatile strategy for applying and developing flexible wearable electronics and implantable biomedical devices.

New Insight into the Mechanism of Multivalent Ion Hybrid Supercapacitor: From the Effect of Potential Window Viewpoint.

Multivalent ion hybrid supercapacitors have been developed as the novel electrochemical energy storage systems due to their combined merits of high energy density and high power density. Nevertheless, there are still some challenges due to the limited understanding of the electrochemical behaviors of multivalent ions in the electrode materials, which greatly hinders the large scale applications of its based hybrid supercapacitors. Herein, the long-term electrochemical behaviors of MnO2 -based electrode in the divalent Mg2+ ions electrolyte are systematically studied and linked with the morphological and electronic evolution of MnO2 by cycling at different potential windows (spanning to 1.2 V). It reveals that the different potential windows result in the different electrochemical behaviors, which can be divided into two ranges (below and above -0.2 V). And, the electrode cycled at a potential window of 0-1.2 V delivers the highest capacitance of 967 F g-1 at a scan rate of 10 mV s-1 , in which the MnO2 is transformed into a uniformly distributed and nonagglomerated nanoflake morphology promoting the intercalation and deintercalation of Mg2+ ions. This study will enrich the understanding of the charge storage mechanism of multivalent ions and provide significant guidance on the performance improvement of the hybrid supercapacitors.