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Aqueous Zn-ion batteries present a low cost, safe, and high-energy battery technology, but suffer from the lack of suitable cathode materials because of the sluggish intercalation kinetics associated with the large size of hydrated zinc ions. Herein we report an effective and general strategy to transform inactive intercalation hosts into efficient Zn 2+ storage materials through intercaltion energy tuning. Using MoS 2 as a model system, we show both experimentally and theoretically that even hosts with originally poor Zn 2+ diffusivity can allow fast Zn 2+ diffusion. Through simple interlayer spacing and hydrophilicity engineering that can be experimentally achieved by oxygen incorporation, the Zn 2+ diffusivity is boosted by 3 orders of magnitude, effectively enabling the otherwise barely active MoS 2 to achieve a high capacity of 232 mAh g -1 that is 10 times as its pristine form. The strategy developed in our work can be generally applied for enhancing the ion Experimental details and additional supporting data as noted in the main text (PDF).

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Sulfurized polyacrylonitrile (SPAN) is the most promising cathode for next-generation lithium−sulfur (Li−S) batteries due to the much improved stability. However, the molecular structure and reaction mechanism have not yet been fully understood. Herein, we present a new take on the structure and mechanism to interpret the electrochemical behaviors. We find that the thiyl radical is generated after the cleavage of the S−S bond in molecules in the first cycle, and then a conjugative structure can be formed due to electron delocalization of the thiyl radical on the pyridine backbone. The conjugative structure can react with lithium ions through a lithium coupled electron transfer process and form an ion-coordination bond reversibly. This could be the real reason for the superior lithium storage capability, in which the lithium polysulfide may not be formed. This study refreshes current knowledge of SPAN in Li−S batteries. In addition, the structural analysis is applicable to analyze the current organic cathodes in rechargeable batteries and also allows further applications in Al−S batteries to achieve high performance.

Graphite anodes are not stable in most noncarbonate solvents (e.g., ether, sulfoxide, sulfone) upon Li ion intercalation, known as an urgent issue in present Li ions and next-generation Li−S and Li−O 2 batteries for storage of Li ions within the anode for safety features. The solid electrolyte interphase (SEI) is commonly believed to be decisive for stabilizing the graphite anode. However, here we find that the solvation structure of the Li ions, determined by the electrolyte composition including lithium salts, solvents, and additives, plays a more dominant role than SEI in graphite anode stability. The Li ion intercalation desired for battery operation competes with the undesired Li + −solvent co-insertion, leading to graphite exfoliation. The increase in organic lithium salt LiN(SO 2 CF 3 ) 2 concentration or, more effectively, the addition of LiNO 3 lowers the interaction strength between Li + and solvents, suppressing the graphite exfoliation caused by Li + −solvent co-insertion. Our findings refresh the knowledge of the well-known SEI for graphite stability in metal ion batteries and also provide new guidelines for electrolyte systems to achieve reliable and safe Li−S full batteries.

The interface structure between room temperature ionic liquids, 1-butyl-3-methylimidazolium hexafluorophosphate (BMIM+/PF6 −) and 1-octyl-3-methylimidazolium hexafluorophosphate (OMIM+/PF6 −), and the graphite (0001) surface has been studied by classical molecular dynamic simulations. It is found that the density of IL is much enhanced at the interfacial region and the density oscillation extends to ∼15 Å into the bulk with three layers. The results also demonstrate that the polar groups tend to aggregate forming a polar network, while the nonpolar groups fill up the rest of the vacancy. The imidazolium rings and the side chains preferentially lie flat at the graphite surface with the alkyl side chains of the cations elongated at the interfacial region, and the cations are closer to the graphite surface (ca. 3.6−3.7 Å) than the anions. The surface potential drop across the interface is more profound for OMIM+/PF6 − than for BMIM+/PF6 −, due to relatively larger local density of the anions for OMIM+/PF6 − near the graphite surface.

The photocatalytic water splitting technique is a promising alternative to produce hydrogen using a facile and proficient method. In the current Review, recent progress made in photocatalytic hydrogen evolution reaction (HER) using 2D nanomaterials (NMs) and composite heterostructures is described. The strong in-plane chemical bonds along with weak van der Waals interaction make these materials lucrative for surface-related applications. State-of-the-art protocols designed for the synthesis of 2D NMs is discussed in detail. The Review illustrates density functional theory (DFT)-based studies against the new set of 2D NMs, which also highlights the importance of structural defects and doping in the electronic structure. Additionally, the Review describes the influence of electronic, structural, and surface manipulation strategies. These impact the electronic structures, intrinsic conductivity, and finally output toward HER. Moreover, this Review also provides a fresh perspective on the prospects and challenges existing behind the application and fabrication strategies.

Aqueous zinc-ion batteries and capacitors are potentially competitive grid-scale energy storage devices because of their great features such as safety, environmental friendliness, and low cost. Herein, a completely new phenanthroline covalent organic framework (PA-COF) was synthesized and introduced in zinc-ion supercapatteries (ZISs) for the first time. Our as-synthesized PA-COF shows a high capacity of 247 mAh g −1 at a current density of 0.1 A g −1 , with only 0.38% capacity decay per cycle during 10 000 cycles at a current density of 1.0 A g −1 . Although covalent organic frameworks (COFs) are attracting great attention in many fields, our PA-COF has been synthesized using a new strategy involving the condensation reaction of hexaketocyclohexanone and 2,3,7,8-phenazinetetramine. Detailed mechanistic investigations, through experimental and theoretical methods, reveal that the phenanthroline functional groups in PA-COF are the active zinc ion storage sites. Furthermore, we provide evidence for the cointercalation of Zn 2+ (60%) and H + (40%) into PA-COF using inductively coupled plasma atomic emission spectroscopy and deuterium solid-state nuclear magnetic resonance (NMR). We believe that this study opens a new avenue for COF material design for zinc-ion storage in aqueous ZISs.