Regulating Crystal Orientation in VO2 for Aqueous Zinc Batteries with Enhanced Pseudocapacitance.

Although aqueous zinc batteries have attracted extensive interest, they are limited by relatively low rate capabilities and poor cyclic stability of cathodes. The crystal orientation of the cathode is one important factor influencing electrochemical properties. However, it has rarely been investigated. Herein, VO2 cathodes with different crystal orientations are developed via tuning the number of hydroxyl groups in polyol, such as using glycerol, erythritol, xylitol, or mannitol. The polyols serve as a reductant as well as a structure-directing agent through a hydrothermal reaction. Xylitol-derived VO2 shows a (110)-orientated crystalline structure and ultrathin nanosheet morphology. Such features greatly enhance the pseudocapacitance to 76.1% at a scan rate of 1.0 mV s-1, which is significantly larger than that (61.6%) of the (001)-oriented VO2 derived from glycerol. The corresponding aqueous zinc batteries exhibit a high energy storage performance with a reversible specific capacity of 317 mAh g-1 at 0.5 A g-1, rate ability of 220 mAh g-1 at 10 A g-1, and capacity retention of 81.0% at 10 A g-1 over 2000 cycles. This work demonstrates a facile method for tailoring VO2 crystal orientations, offers an understanding of the Zn2+ storage mechanism upon different VO2 facets, and provides a novel method to develop cathode materials toward advanced aqueous zinc batteries.

Asymmetric Anion Zinc Salt Derived Solid Electrolyte Interphase Enabled Long-Lifespan Aqueous Zinc Bromine Batteries.

Organic additives with high-reduction potentials are generally applied in aqueous electrolytes to stabilize the Zn anode, while compromise safety and environmental compatibility. Highly concentrated water-in-salt electrolytes have been proposed to realize the high reversibility of Zn plating/stripping; however, their high cost and viscosity hinder their practical applications. Therefore, exploring low-concentration Zn salts, that can be used directly to stabilize Zn anodes, is of primary importance. Herein, we developed an asymmetric anion group, bi(difluoromethanesulfonyl)(trifluoromethanesulfonyl)imide (DFTFSI- )-based novel zinc salt, Zn(DFTFSI)2 , to obtain a high ionic conductivity and a highly stable dendrite-free Zn anode. Experimental tests and theoretical calculations verified that DFTFSI- in the Zn2+ solvation sheath and inner Helmholtz plane would be preferentially reduced to construct layer-structured SEI films, inhibiting hydrogen evolution and side reactions. Consequently, the Zn | | ${||}$ Zn symmetric cell with 1M Zn(DFTFSI)2 aqueous electrolyte delivers an ultralong cycle life for >2500 h outperforming many other conventional Zn salt electrolytes. The Zn | | ${||}$ Br2 battery also exhibits a long lifespan over 1200 cycles at ~99.8 % Coulombic efficiency with a high capacity retention of 92.5 %. Furthermore, this outstanding performance translates well to a high-areal-capacity Zn | | ${||}$ Br2 battery (~5.6 mAh ⋅ cm-2 ), cycling over 320 cycles with 95.3 % initial capacity retained.

Fast Reaction Kinetics and Commendable Low-Temperature Adaptability of Zinc Batteries Enabled by Aprotic Water-Acetamide Symbiotic Solvation Sheath.

Although rechargeable aqueous zinc batteries are cost effectiveness, intrinsicly safe, and high activity, they are also known for bringing rampant hydrogen evolution reaction and corrosion. While eutectic electrolytes can effectively eliminate these issues, its high viscosity severely reduces the mobility of Zn2+ ions and exhibits poor temperature adaptability. Here, we infuse acetamide molecules with Lewis base and hydrogen bond donors into a solvated shell of Zn[(H2 O)6 ]2+ to create Zn(H2 O)3 (ace)(BF4 )2 . The viscosity of 1ace-1H2 O is 0.032 Pa s, significantly lower than that of 1ace-0H2 O (995.6 Pa s), which improves ionic conductivity (9.56 mS cm-1 ) and shows lower freezing point of -45 °C, as opposed to 1ace-0H2 O of 4.04 mS cm-1 and 12 °C, respectively. The acidity of 1ace-1H2 O is ≈2.8, higher than 0ace-1H2 O at ≈0.76, making side reactions less likely. Furthermore, benefiting from the ZnCO3 /ZnF2 -rich organic/inorganic solid electrolyte interface, the Zn || Zn cells cycle more than 1300 hours at 1 mA cm-2 , and the Zn || Cu operated over 1800 cycles with an average Coulomb efficiency of ≈99.8 %. The Zn || PANI cell cycled over 8500 cycles, with a specific capacity of 99.8 mAh g-1 at 5 A g-1 at room temperature, and operated at -40 °C with a capacity of 66.8 mAh g-1 .

Asymmetric Electrolytes Design for Aqueous Multivalent Metal Ion Batteries.

With the rapid development of portable electronics and electric road vehicles, high-energy-density batteries have been becoming front-burner issues. Traditionally, homogeneous electrolyte cannot simultaneously meet diametrically opposed demands of high-potential cathode and low-potential anode, which are essential for high-voltage batteries. Meanwhile, homogeneous electrolyte is difficult to achieve bi- or multi-functions to meet different requirements of electrodes. In comparison, the asymmetric electrolyte with bi- or multi-layer disparate components can satisfy distinct requirements by playing different roles of each electrolyte layer and meanwhile compensates weakness of individual electrolyte. Consequently, the asymmetric electrolyte can not only suppress by-product sedimentation and continuous electrolyte decomposition at the anode while preserving active substances at the cathode for high-voltage batteries with long cyclic lifespan. In this review, we comprehensively divide asymmetric electrolytes into three categories: decoupled liquid-state electrolytes, bi-phase solid/liquid electrolytes and decoupled asymmetric solid-state electrolytes. The design principles, reaction mechanism and mutual compatibility are also studied, respectively. Finally, we provide a comprehensive vision for the simplification of structure to reduce costs and increase device energy density, and the optimization of solvation structure at anolyte/catholyte interface to realize fast ion transport kinetics.

Pillar[5]arene based water-soluble [3]pseudorotaxane with enhanced fluorescence emission for cell imaging and both type I and II photodynamic cancer therapy.

Water-soluble [3]pseudorotaxane with enhanced fluorescence emission was successfully constructed and applied in cell imaging and photodynamic cancer therapy.

An asymmetric electrolyte to simultaneously meet contradictory requirements of anode and cathode.

One of the major obstacles hindering the application of zinc metal batteries is the contradictory demands from the Zn metal anode and cathodes. At the anode side, water induces serious corrosion and dendrite growth, remarkably suppressing the reversibility of Zn plating/stripping. At the cathode side, water is essential because many cathode materials require both H+ and Zn2+ insertion/extraction to achieve a high capacity and long lifespan. Herein, an asymmetric design of inorganic solid-state electrolyte combined with hydrogel electrolyte is presented to simultaneously meet the as-mentioned contrary requirements. The inorganic solid-state electrolyte is toward the Zn anode to realize a dendrite-free and corrosion-free highly reversible Zn plating/stripping, and the hydrogel electrolyte enables consequent H+ and Zn2+ insertion/extraction at the cathode side for high performance. Therefore, there is no hydrogen and dendrite growth detected in cells with a super high-areal-capacity up to 10 mAh·cm-2 (Zn//Zn), ~5.5 mAh·cm-2 (Zn//MnO2) and ~7.2 mAh·cm-2 (Zn//V2O5). These Zn//MnO2 and Zn//V2O5 batteries show remarkable cycling stability over 1000 cycles with 92.4% and over 400 cycles with 90.5% initial capacity retained, respectively.

Aqueous Zinc Batteries with Ultra-Fast Redox Kinetics and High Iodine Utilization Enabled by Iron Single Atom Catalysts.

Rechargeable aqueous zinc iodine (ZnǀǀI2) batteries have been promising energy storage technologies due to low-cost position and constitutional safety of zinc anode, iodine cathode and aqueous electrolytes. Whereas, on one hand, the low-fraction utilization of electrochemically inert host causes severe shuttle of soluble polyiodides, deficient iodine utilization and sluggish reaction kinetics. On the other hand, the usage of high mass polar electrocatalysts occupies mass and volume of electrode materials and sacrifices device-level energy density. Here, we propose a "confinement-catalysis" host composed of Fe single atom catalyst embedding inside ordered mesoporous carbon host, which can effectively confine and catalytically convert I2/I- couple and polyiodide intermediates. Consequently, the cathode enables the high capacity of 188.2 mAh g-1 at 0.3 A g-1, excellent rate capability with a capacity of 139.6 mAh g-1 delivered at high current density of 15 A g-1 and ultra-long cyclic stability over 50,000 cycles with 80.5% initial capacity retained under high iodine loading of 76.72 wt%. Furthermore, the electrocatalytic host can also accelerate the [Formula: see text] conversion. The greatly improved electrochemical performance originates from the modulation of physicochemical confinement and the decrease of energy barrier for reversible I-/I2 and I2/I+ couples, and polyiodide intermediates conversions.

Solid Interhalogen Compounds with Effective Br0 Fixing for Stable High-energy Zinc Batteries.

Though massive efforts have been devoted to exploring Br-based batteries, the highly soluble Br2 /Br3 - species causing rigorous "shuttle effect", leads to severe self-discharge and low Coulombic efficiency. Conventionally, quaternary ammonium salts such as methyl ethyl morpholinium bromide (MEMBr) and tetrapropylammonium bromide (TPABr) are used to fix Br2 and Br3 - , but they occupy the mass and volume of battery without capacity contribution. Here, we report an all-active solid interhalogen compound, IBr, as a cathode to address the above challenges, in which the oxidized Br0 is fixed by iodine (I), thoroughly eliminating cross-diffusing Br2 /Br3 - species during the whole charging and discharging process. The Zn||IBr battery delivers remarkably high energy density of 385.8 Wh kg-1 , which is higher than those of I2 , MEMBr3 , and TPABr3 cathodes. Our work provides new approaches to achieve active solid interhalogen chemistry for high-energy electrochemical energy storage devices.

Inducing Fe 3d Electron Delocalization and Spin-State Transition of FeN4 Species Boosts Oxygen Reduction Reaction for Wearable Zinc-Air Battery.

Transition metal-nitrogen-carbon materials (M-N-Cs), particularly Fe-N-Cs, have been found to be electroactive for accelerating oxygen reduction reaction (ORR) kinetics. Although substantial efforts have been devoted to design Fe-N-Cs with increased active species content, surface area, and electronic conductivity, their performance is still far from satisfactory. Hitherto, there is limited research about regulation on the electronic spin states of Fe centers for Fe-N-Cs electrocatalysts to improve their catalytic performance. Here, we introduce Ti3C2 MXene with sulfur terminals to regulate the electronic configuration of FeN4 species and dramatically enhance catalytic activity toward ORR. The MXene with sulfur terminals induce the spin-state transition of FeN4 species and Fe 3d electron delocalization with d band center upshift, enabling the Fe(II) ions to bind oxygen in the end-on adsorption mode favorable to initiate the reduction of oxygen and boosting oxygen-containing groups adsorption on FeN4 species and ORR kinetics. The resulting FeN4-Ti3C2Sx exhibits comparable catalytic performance to those of commercial Pt-C. The developed wearable ZABs using FeN4-Ti3C2Sx also exhibit fast kinetics and excellent stability. This study confirms that regulation of the electronic structure of active species via coupling with their support can be a major contributor to enhance their catalytic activity.

Alkaline Tolerant Antifreezing Additive Enabling Aqueous Zn||Ni Battery Operating at -60 °C.

Alkaline aqueous batteries such as the Zn||Ni batteries have attracted substantial interests due to their merits of high energy density, high safety and low cost. However, the freeze of aqueous electrolyte and the poor cycling stability in alkaline condition have hindered their operation in subzero conditions. Herein, we construct a stable aqueous electrolyte with lowest freezing point down to -90 °C by adding dimethyl sulfoxide (DMSO) as alkaline tolerant antifreezing additive into 1 M KOH solution. Meanwhile, we find the DMSO can also retard Zn anode corrosion and prevent Zn dendrite formation in alkaline condition, which enables the Zn plating/stripping over 700 h cycle at 1 mA cm-2 and 0.5 mAh cm-2 . The fabricated Zn||Ni battery can endure low working temperature even down to -60 °C and its dischage capacity retains 84.1 % at -40 °C, 60.6 % at -60 °C at 0.5 C. Meanwhile, it can maintain 600 cycles with a specific capacity retention of 86.5 % at -40 °C at 2 C.

Solid Electrolyte Interface in Zn-Based Battery Systems.

Due to its high theoretical capacity (820 mAh g-1), low standard electrode potential (- 0.76 V vs. SHE), excellent stability in aqueous solutions, low cost, environmental friendliness and intrinsically high safety, zinc (Zn)-based batteries have attracted much attention in developing new energy storage devices. In Zn battery system, the battery performance is significantly affected by the solid electrolyte interface (SEI), which is controlled by electrode and electrolyte, and attracts dendrite growth, electrochemical stability window range, metallic Zn anode corrosion and passivation, and electrolyte mutations. Therefore, the design of SEI is decisive for the overall performance of Zn battery systems. This paper summarizes the formation mechanism, the types and characteristics, and the characterization techniques associated with SEI. Meanwhile, we analyze the influence of SEI on battery performance, and put forward the design strategies of SEI. Finally, the future research of SEI in Zn battery system is prospected to seize the nature of SEI, improve the battery performance and promote the large-scale application.

Nano-Theranostics Constructed from Terpyridine-Modified Pillar [5]arene-Based Supramolecular Amphiphile and Its Application in Both Cell Imaging and Cancer Therapy.

Theranostics play an important role in cancer treatment due to its realized real-time tracking of therapeutic efficacy in situ. In this work, we have designed and synthesized a terpyridine-modified pillar [5]arenes (TP5). By the coordination of terpyridine and Zn2+, the complex TP5/Zn was obtained. Then, supramolecular amphiphile can be constructed by using host-guest complexation between a polyethylene glycol contained guest (PM) and TP5/Zn. Combining the fluorescence properties from the terpyridine group and the amphiphilicity from the system, the obtained TP5/Zn/PM can further be self-assembled into fluorescent particles with diameters of about 150 nm in water. The obtained particles can effectively load anti-cancer drugs and realize living cell imaging and a precise release of the drugs.

Segmented Structure Design of Carbon Ring In-Plane Embedded in g-C3 N4 Nanotubes for Ultra-High Hydrogen Production.

The photocatalytic water splitting capability of metal-free graphitic carbon nitride (g-C3 N4 ) photocatalyst is determined by its microstructure and photoexcited electrons transfer. Herein, a segmented structure was developed, consisting of alternant g-C3 N4 nanotubes and graphitic carbon rings (denoted as Cr -CN-NT). The Cr -CN-NT showed ordered structure and ultralong length/diameter ratio of 150 nm in diameter and a few microns in lengths, which promoted electron transport kinetics and elongated photocarrier diffusion length and lifetime. Meanwhile, the local in-plane π-conjugation was formed and extended in Cr -CN-NT, which could improve charge carrier density and prohibit electron-hole recombination. Accordingly, the average hydrogen evolution rate of Cr -CN-NT reached 9245 µmol h-1 g-1 , which was 61.6 times that of pristine CN, and the remarkable apparent quantum efficiency (AQE) of Cr -CN-NT reached up to 12.86 % at 420 nm. This work may provide a pathway for simultaneous morphology regulation and in-plane modification of high-performance photocatalysts.

Pillar[5]arene-based [1]rotaxanes with salicylaldimine as the stopper: synthesis, characterization and application in the fluorescence turn-on sensing of Zn2+ in water.

Two pillar[5]arene-based [1]rotaxanes with salicylaldimine as the stopper were synthesized and characterized fully, and could be further applied in the fluorescence turn-on sensing of Zn2+ in water.

Construction and Property Investigation of Serial Pillar[5]arene-Based [1]Rotaxanes.

Although the construction and application of pillar[5]arene-based [1]rotaxanes have been extensively studied, the types of stoppers for them are limited. In this work, we designed and prepared three series of pillar[5]arene-based [1]rotaxanes (P5[1]Rs) with pentanedione derivatives, azobenzene derivatives, and salicylaldehyde derivatives as the stoppers, respectively. The obtained P5[1]Rs were fully characterized by NMR (1H, 13C, and 2D), mass spectra, and single-crystal X-ray analysis. We found that the synergic C-H···π, C-H···O interactions and N-H···O, O-H···N hydrogen bonding are the key to the stability of [1]rotaxanes. This work not only enriched the diversity of pillar[n]arene family but also gave a big boost to the pillar[n]arene-based mechanically interlocked molecules.

Recent Advances in Electrolytes for "Beyond Aqueous" Zinc-Ion Batteries.

With the growing demands for large-scale energy storage, Zn-ion batteries (ZIBs) with distinct advantages, including resource abundance, low-cost, high-safety, and acceptable energy density, are considered as potential substitutes for Li-ion batteries. Although numerous efforts are devoted to design and develop high performance cathodes and aqueous electrolytes for ZIBs, many challenges, such as hydrogen evolution reaction, water evaporation, and liquid leakage, have greatly hindered the development of aqueous ZIBs. Developing "beyond aqueous" electrolytes can be able to avoid these issues due to the absence of water, which are beneficial for the achieving of highly efficient ZIBs. In this review, the recent development of the "beyond aqueous" electrolytes, including conventional organic electrolytes, ionic liquid, all-solid-state, quasi-solid-state electrolytes, and deep eutectic electrolytes are presented. The critical issues and the corresponding strategies of the designing of "beyond aqueous" electrolytes for ZIBs are also summarized.

Battery-Sensor Hybrid: A New Gas Sensing Paradigm with Complete Energy Self-Sufficiency.

Fully autonomous operation has long been an ultimate goal in environmental sensing. Although self-powered gas sensors based on energy harvesting have been widely reported to provide power for autonomous operation, these sensors rely on external sources of harvestable energy, thus are not completely self-sufficient. Herein, a battery-sensor hybrid device that can simultaneously function as both a power source and a gas sensor is presented. The battery-sensor consists of a cathode that reduces NO2 to NO2- via a catalyst with Fe-Nx species distributed on highly graphitic porous nitrogen-doped carbon. On the basis of the efficient and selective electrocatalytic activity of the catalyst, the battery-sensor is capable of sensing NO2 and does so without any external power, overcoming the long-standing grand challenge to achieve complete energy self-sufficiency. Furthermore, through controlling the working current the sensing range can be significantly expanded and electronically tuned, which is not only unprecedented for gas sensors but also of remarkable commercial practicality. The proposed battery-sensor hybrid architecture represents a new paradigm toward sensors with complete energy self-sufficiency.

Toward a Practical Zn Powder Anode: Ti3C2Tx MXene as a Lattice-Match Electrons/Ions Redistributor.

The renaissance of aqueous Zn ion batteries has drawn intense attention to Zn metal anode issues, including dendrites growth, dead Zn, low efficiency, and other parasitic reactions. However, against the widely used 2D Zn foil, in fact, the Zn powder anode is a more practical choice for Zn-based batteries in industrial applications, but the related solutions are rarely investigated. Herein, we focus on the Zn powder anode and disclose its unknown failure mechanism different from Zn foils. By utilization of 2D flexible conductive Ti3C2Tx MXene flakes with hexagonal close-packed lattice as electrons and ions redistributor, a stable and highly reversible Zn powder anode without dendrite growth and low polarization is constructed. Low lattice mismatch (∼10%) enables a coherent heterogeneous interface between the (0002) plane of deposited Zn and (0002) plane of the Ti3C2Tx MXene. Thus, the Zn2+ ions are induced to undergo rapid uniform nucleation and sustained reversible stripping/plating with low energy barriers via the internally bridged shuttle channels. Paired with cyano group iron hexacyanoferrate (FeHCF) cathode, the FeHCF//MXene@Zn full battery delivers superior cycle durability and rate capability, whose service life with a CE of near 100% touches 850% of bare Zn powder counterparts. The proposed Ti3C2Tx MXene redistributor strategy concerning high-speed electrons/ions channel, low-barrier heterogeneous interface, is expected to be widely applied to other alkali metal anodes.

Manipulating anion intercalation enables a high-voltage aqueous dual ion battery.

Aqueous graphite-based dual ion batteries have unique superiorities in stationary energy storage systems due to their non-transition metal configuration and safety properties. However, there is an absence of thorough study of the interactions between anions and water molecules and between anions and electrode materials, which is essential to achieve high output voltage. Here we reveal the four-stage intercalation process and energy conversion in a graphite cathode of anions with different configurations. The difference between the intercalation energy and hydration energy of bis(trifluoromethane)sulfonimide makes the best use of the electrochemical stability window of its electrolyte and delivers a high intercalation potential, while BF4- and CF3SO3- do not exhibit a satisfactory potential because the graphite intercalation potential of BF4- is inferior and the graphite intercalation potential of CF3SO3- exceeds the voltage window of its electrolyte. An aqueous dual ion battery based on the intercalation behaviors of bis(trifluoromethane)sulfonimide anions into a graphite cathode exhibits a high voltage of 2.2 V together with a specific energy of 242.74 Wh kg-1. This work provides clear guidance for the voltage plateau manipulation of anion intercalation into two-dimensional materials.