Structural batteries take a load off

Amino-acid surface modulation of cobalt-tin sulfide and band broadening in cobalt-iron selenide heterostructure for high-performing asymmetric supercapacitor

Controlled synthesis of hierarchical flowerlike cobalt tin sulfide (SnCoSx) is successfully obtained using the chelation of the biomolecule l-asparagine with cobalt-tin metal cations by a hydrothermal technique. l-asparagine plays a crucial role as an inducer and a good structure-directing activity. Subsequently, pine needle-shaped cobalt iron selenium (FeCoSey) is tightly deposited on the SnCoSx surface to construct cobalt tin sulfide coated with cobalt iron selenide (FeCoSey@SnCoSx) heterostructure, which has exposed more active sites and the most abundant channels for electron/ion transfer. Among all prepared electrodes, the optimized FeCoSey@SnCoSx demonstrates the highest energy storage capacity (1754.65 F/g at 1 A g-1) and excellent cycling steadiness (86.71 % after 10,000 cycles at 15 A g-1). The heterogeneous interface engineering of FeCoSey and SnCoSx enables the FeCoSey@SnCoSx composite to generate outstanding electrochemical performance for supercapacitor devices. As expected, an asymmetric hybrid supercapacitor (AHSC) based on FeCoSey@SnCoSx cathode and nitrogen-doped hierarchy porous activated carbon (NHPC) derived from soybeans anode displays a high energy density of 59.44 Wh kg-1 at 402.09 W kg-1 and a super-long steady presentation with a preliminary capacitance holding ratio of 92.2 % following 10,000 cycles with an 8 A g-1 voltage density. This strategy provides a new approach for the controllable preparation of electrode material morphology, opens up new methods for high-performance heterogeneous interface composite electrode materials, and guides the designing of low-cost energy storage devices.

Structural pseudocapacitors with reinforced interfaces to increase multifunctional efficiency

Structural supercapacitors hold promise to expand the energy capacity of a system by integrating load-bearing and energy-storage functions in a multifunctional structure, resulting in weight savings and safety improvements. Here, we develop strategies based on interfacial engineering to advance multifunctional efficiency. The structural electrodes were reinforced by coating carbon-fiber weaves with a uniquely stable conjugated redox polymer and reduced graphene oxide that raised pseudocapacitive capacitance and tensile strength. The solid polymer electrolyte was tuned to a gradient configuration, where it facilitated high ionic conductivity at the electrode-electrolyte interfaces and transitioned to a composition with high mechanical strength in the bulk for load support. The gradient design enabled the multilayer structural supercapacitors to reach state-of-the-art performance matching the level of monofunctional supercapacitors. In situ electrochemical-mechanical measurements established the device durability under mechanical loads. The structural supercapacitor was made into the hull of a model boat to demonstrate its multifunctionality.

Improving Cycle Life of Zinc-Air Batteries with Calcium Ion Additive in Electrolyte or Separator

The electrolyte carbonation and the resulting air electrode plugging are the primary factors limiting the cycle life of aqueous alkaline zinc-air batteries (ZABs). In this work, calcium ion (Ca²⁺) additives were introduced into the electrolyte and the separator to resolve the above issues. Galvanostatic charge-discharge cycle tests were carried out to verify the effect of Ca²⁺ on electrolyte carbonation. With the modified electrolyte and separator, the cycle life of ZABs was improved by 22.2% and 24.7%, respectively. Ca²⁺ was introduced into the ZAB system to preferentially react with CO₃^2- rather than K⁺ and then precipitated granular CaCO₃ prior to K₂CO₃, which was deposited on the surface of the Zn anode and air cathode to form a flower-like CaCO₃ layer, thereby prolonging its cycle life.

Study on failure mechanism on rechargeable alkaline zinc-Air battery during charge/discharge cycles at different depths of discharge

Background: Zinc-air battery (ZAB) is a promising candidate for energy storage, but the short cycle life severely restricts the wider practical applications. Up to date, no consensus on the dominant factors affecting ZABs cycle life was reached to help understanding how to prolong the ZAB's cycle life. Here, a series of replacement experiments based on the ZAB were conducted to confirm the pivotal factors that influence the cycle life at different depths of discharge (DOD). Method: The morphology and composition of the components of the battery were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and chemical titration analyses. Result: SEM images and XRD results revealed that the failure of the zinc anode gradually deepens with the increase of DOD, while the performance degradation of the tricobalt tetroxide/Carbon Black (Co₃O₄/CB) air cathode depends on the operating time. The concentration of CO₃ ^2- depends on the charge/discharge cycle time. The replacement experiments results show that the dominant factors affecting the ZAB's cycle life is the reduction of active sites on the surface of Co₃O₄/CB air cathode at a shallow DOD, while that is the carbonation of the electrolyte at a deep DOD. The reduction of active sites on the surface of Co₃O₄/CB air cathode is caused by the coverage of K₂CO₃ precipitated by carbonation of the electrolyte, suggesting that the carbonation of the alkaline electrolyte limits ZAB's cycle life. Conclusion: Therefore, this work not only further discloses the failure mechanism of ZAB, but also provides some feasible guidance to design a ZAB with along cycle life.