Intercalation chemistry engineering strategy enabled high mass loading and ultrastable electrodes for High-Performance aqueous electrochemical energy storage devices.

Aqueous electrochemical energy storage devices (AEESDs) are considered one of the most promising candidates for large-scale energy storage infrastructure due to their high affordability and safety. Developing electrodes with the merits of high energy density and long lifespan remains a challenging issue toward the practical application of AEESDs. Research attempts at electrode materials, nanostructure configuration, and electronic engineering show the limitations due to the inherent contradictions associated with thicker electrodes and ion-accessible kinetics. Herein, we propose an intercalation chemistry engineering strategy to enhance the electrolyte ion (de)intercalation behaviors during the electrochemical charge-discharge. To validate this strategy, the prototypical model of a high-mass-loading MnO2-based electrode is used with controlled intercalation of Na+ and H2O. Theoretical and experimental results reveal that an optimal content of Na+ and H2O on the MnO2-based electrode exhibits superior electrochemical performance. Typically, the resultant electrode exhibits an impressive areal capacitance of 1551 mF/cm2 with a mass loading of 9.7 mg/cm2 (at 1 mA/cm2). Furthermore, the assembled full-cell with obtained MnO2-based electrode delivers a high energy density of 0.12 mWh/cm2 (at 20.02 mW/cm2) and ultra-high cycling stability with a capacitance retention percentage of 89.63 % (345 mF/cm2) even after 100,000 cycles (tested over 72 days).

Three-Dimensional Polypyrrole-Decorated CuCo2S4 Nanowires Anchored on Nickel Foam: A Promising Electrode for High-Performance Supercapacitors.

The exploitation of high-performance supercapacitors is crucial to promote energy storage technologies. Benefiting from the three-dimensional conductive micronanostructures and high specific capacity of the PPy@CuCo2S4@NF (polypyrrole/copper cobalt sulfide/nickel foam) composite electrode, this electrode exhibits a high specific capacity of 1403.21 C g-1 at 1 A g-1 and a capacitance retention of 85.79% after 10,000 cycles at 10 A g-1. The assembled PPy@CuCo2S4@NF//AC aqueous hybrid supercapacitor (AHSC) reveals a wide operating potential window of 1.5 V and achieves a high specific capacity of 322.52 C g-1 at 1 A g-1 and a capacitance retention of 86.84% after 15,000 cycles at 10 A g-1. The AHSC also exhibits a high power density of 733.69 W kg-1 at an energy density of 67.19 W h kg-1, surpassing those of previously reported spinel-based supercapacitors. Ex situ X-ray diffraction and X-ray photoelectron spectroscopy results show that the CuCo2S4 spinel structure changes to CuS2 and CoS2 cube structures, and the oxidation states of Cu and Co increase during charging and discharging processes. Density functional theory calculations suggest a superior conductivity for CuCo2S4 compared to that for CuCo2O4, demonstrating that CuCo2S4 has superior electrochemical performance. These findings attest to the considerable potential of the spinel materials for advanced energy storage applications.

Ferroelectric-Enhanced cathode kinetics toward High-Performance aqueous Zinc-Ion batteries.

Rechargeable aqueous zinc ion batteries (AZIBs) offer promising potential for large-scale energy storage systems due to their high affordability and safety. However, their practical applications are hindered by the undesired rate capability and cycling stability of the used cathode, attributed to sluggish ions kinetics during charge-discharge process. Herein, we propose an electric field balancing strategy to regulate the electrolyte ions behavior by constructing a ferroelectric interface on the cathode surface using a prototypical of MnO2-based cathode. An appropriate thickness coating of ferroelectric materials coating (i.e., ß-PVDF) on the MnO2 surface is theoretically and experimentally demonstrated to enhance the ion kinetics due to the optimized electrical distribution during electrochemical operations. Further comprehensive electrochemical mechanism studies reveal that the ferroelectric interface on the MnO2@ß-PVDF not only promotes the diffusion of Zn2+ but also reduces the electrochemical overpotential (17.6 mV), resulting in improved electrochemical reversibility and capacity performance. The resultant MnO2@ß-PVDF cathode exhibits the highest capacity of 277.6 mAh g-1 (at 0.1 A g-1) and capacity retention of 68.6% after 120 cycles, surpassing both the pristine MnO2 and non-ferroelectric materials coated MnO2 electrodes. This success presents a new approach to enhance the overall electrochemical performance of the cathodes for the practical application of AZIBs.

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.

Electrolyte additives inhibit the surface reaction of aqueous sodium/zinc battery.

In aqueous zinc-based batteries, the reaction by-product Zn4SO4(OH)6·xH2O is commonly observed when cycling vanadium-based and manganese-based cathodes. This by-product obstructs ion transport paths, resulting in enhanced electrochemical impedance. In this work, we report a hybrid aqueous battery based on a Na0.44MnO2 cathode and a metallic zinc foil anode. The surfactant sodium lauryl sulfate is added to the electrolyte as a modifier, and the performance before and after modification is compared. The results show that sodium lauryl sulfate can generate an artificial passivation film on the electrode surface. This passivation film reduces the generation of Zn4SO4(OH)6·xH2O and inhibits the dissolution of Na0.44MnO2 in the electrolyte. Therefore, the reaction kinetics and cycle stability of the battery are significantly enhanced. A battery with this electrolyte additive delivers an initial discharge capacity of 235 mA h g-1 at a current density of 0.1 A g -1. At the same time, the battery has excellent rate performance. Under the high-rate condition of 1 A g-1, the battery still maintains a capacity retention rate of 93% after 1500 cycles. Finally, the functional mechanism of by-product inhibition by the electrolyte additive is discussed.

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.