Coordination modulation of hydrated zinc ions to enhance redox reversibility of zinc batteries.

The dendrite growth of zinc and the side reactions including hydrogen evolution often degrade performances of zinc-based batteries. These issues are closely related to the desolvation process of hydrated zinc ions. Here we show that the efficient regulation on the solvation structure and chemical properties of hydrated zinc ions can be achieved by adjusting the coordination micro-environment with zinc phenolsulfonate and tetrabutylammonium 4-toluenesulfonate as a family of electrolytes. The theoretical understanding and in-situ spectroscopy analysis revealed that the favorable coordination of conjugated anions involved in hydrogn bond network minimizes the activate water molecules of hydrated zinc ion, thus improving the zinc/electrolyte interface stability to suppress the dendrite growth and side reactions. With the reversibly cycling of zinc electrode over 2000 h with a low overpotential of 17.7 mV, the full battery with polyaniline cathode demonstrated the impressive cycling stability for 10000 cycles. This work provides inspiring fundamental principles to design advanced electrolytes under the dual contributions of solvation modulation and interface regulation for high-performing zinc-based batteries and others.

A highly conductive gel electrolyte with favorable ion transfer channels for long-lived zinc-iodine batteries.

Aqueous rechargeable zinc-iodine batteries (ARZIBs), as a powerful energy alternative, have inherent advantages, such as low cost, good safety and environmental friendliness. Unfortunately, uneven Zn deposition with dendrite growth and undesirable side reactions seriously compromises the safety and stability of ARZIBs. Herein, a novel strategy is demonstrated to fabricate highly conductive iota-carrageenan (IC) gel electrolyte. The unique double helix structure with good mechanical properties provides favorable Zn2+ channels guided by sulfate groups, which enables confinement effect and orderly guidance of Zn deposition. Additionally, the activity of water molecules confined in the gel electrolyte is reduced, thus inhibiting the corrosion reactions of the zinc electrode. As a result, the gel electrolyte with remarkable ionic conductivity (42.95 mS cm-1) showed a good cycling stability over 1000 h. Importantly, the Zn-I2 batteries with the IC-Zn gel electrolyte demonstrated remarkable reversibility with an impressive capacity retention (91.9%) over 5000 cycles and high average coulombic efficiency (99.86%). This work provides a reliable strategy to develop natural polymer gel electrolytes to regulate the Zn deposition for advanced rechargeable Zn-I2 batteries.

Physicochemical Confinement Effect Enables High-Performing Zinc-Iodine Batteries.

Zinc-iodine batteries are promising energy storage devices with the unique features of aqueous electrolytes and safer zinc. However, their performances are still limited by the polyiodide shuttle and the unclear redox mechanism of iodine species. Herein, a single iron atom was embedded in porous carbon with the atomic bridging structure of metal-nitrogen-carbon to not only enhance the confinement effect but also invoke the electrocatalytic redox conversion of iodine, thereby enabling the large capacity and good cycling stability of the zinc-iodine battery. In addition to the physical trapping effect of porous carbon with good electronic conductivity, the in situ experimental characterization and theoretical calculation reveal that the metal-nitrogen-carbon bridging structure modulates the electronic properties of carbon and adjusts the intrinsic activity for the reversible conversion of iodine via the thermodynamically favorable pathway. This work demonstrates that the physicochemical confinement effect can be invoked by the rational anchoring of a single metal atom with nitrogen in a porous carbon matrix to enhance the electrocatalytic redox conversion of iodine, which is crucial to fabricating high-performing zinc-iodine batteries and beyond by applying the fundamental principles.

Interface Coordination Stabilizing Reversible Redox of Zinc for High-Performance Zinc-Iodine Batteries.

Aqueous Zn batteries (AZBs) have attracted extensive attention due to good safety, cost-effectiveness, and environmental benignity. However, the sluggish kinetics of divalent zinc ion and the growth of Zn dendrites severely deteriorate the cycling stability and specific capacity. The authors demonstrate modulation of the interfacial redox process of zinc via the dynamic coordination chemistry of phytic acid with zinc ions. The experimental results and theoretical calculation reveal that the in-situ formation of such inorganic-organic films as a dynamic solid-electrolyte interlayer is efficient to buffer the zinc ion transfer via the energy favorable coordinated hopping mechanism for the reversible zinc redox reactions. Especially, along the interfacial coating layer with porous channel structure is able to regulate the solvation structure of zinc ions along the dynamic coordination of the phytic acid skeleton, efficiently inhibiting the surface corrosion of zinc and dendrite growth. Therefore, the resultant Zn anode achieves low voltage hysteresis and long cycle life at rigorous charge and discharge circulation for fabricating highly robust rechargeable batteries. Such an advanced strategy for modulating ion transport demonstrates a highly promising approach to addressing the basic challenges for zinc-based rechargeable batteries, which can potentially be extended to other aqueous batteries.

Atomic Bridging Structure of Nickel-Nitrogen-Carbon for Highly Efficient Electrocatalytic Reduction of CO2.

To meet strategic applications, electrochemical reduction of CO2 into value-added chemical molecules would be improved by the rational design of advanced electrocatalysts with atomically dispersed active sites. Herein an electrospun-pyrolysis cooperative strategy is presented to not only modulate the porous structure of the carbon support for favorable charge and mass transfer, but also adjust the bridging structure of atomically dispersed metal species. Typically, the experimental results and theoretical calculations revealed that the unique chemical structure of binuclear nickel bridging with nitrogen and carbon atoms (namely Ni2 -N4 -C2 ) tunes the electronic nature of the d-states for the optimal adsorption of carbon dioxide and intermediates, thus inducing the substantial enhancement of CO2 reduction via the thermodynamically more favorable pathway. The identification of such a structure demonstrates the large space to modulate the atomic bridging status for optimizing electrocatalysis.

Metal-Organic Framework/Polythiophene Derivative: Neuronlike S-Doped Carbon 3D Structure with Outstanding Sodium Storage Performance.

Herein, a metal-organic framework (MOF)/polythiophene (PTh)-derived S-doped carbon is successfully designed and prepared employing zeolitic imidazolate frameworks (ZIF-8/ZIF-67) and thiophene (Th) as precursors. The S-doped carbon presents a neuronlike three-dimensional network structure (3DSC). The 3DSC delivers extra-high capacities (225 mAh/g at 5000 mA/g after 3000 cycles) and excellent endurance ability of current changes when applied in Na-ion batteries (SIBs). Moreover, when the 3DSC-700 anode is coupled with a sodium vanadium phosphate cathode to construct a Na-ion full cell, after 50 cycles, a high capacity of ∼229.64 mAh/g is obtained at 100 mA/g. Electrochemical impedance spectroscopy analysis, density functional theory calculations, and pseudocapacitance contributions are adopted to investigate the excellent sodium storage mechanism of the 3DSC electrode. A new idea has been provided in this work to open up the possibility of MOF materials and carbon-based materials applications in SIBs in the future.