The poor stability of the zinc‐metal anode is a main bottleneck for practical application of aqueous zinc‐ion batteries. Herein, a series of molecular sieves with various channel sizes are investigated as an electrolyte host to regulate the ionic environment of Zn2+ on the surface of the zinc anode and to realize separator‐free batteries. Based on the ZSM‐5 molecular sieve, a solid–liquid mixed electrolyte membrane is constructed to uniformize the transport of zinc ions and foster dendrite‐free Zn deposition. Side reactions can also be suppressed through tailoring the solvation sheath and restraining the activity of water molecules in electrolyte. A V2O5||ZSM‐5||Zn full cell shows significantly enhanced performance compared to cells using glass fiber separator. Specifically, it exhibits a high specific capacity of 300 mAh g−1, and a capacity retention of 98.67% after 1000 cycles and 82.67% after 3000 cycles at 1 A g−1. It is attested that zeolites (ZSM‐5, H‐β, and Bate) with channel sizes of 5–7 Å result in best cycle stability. Given the low cost and recyclability of the ZSM and its potent function, this work may further lower the cost and boost the industrial application of AZIBs.

A Molecular‐Sieve Electrolyte Membrane enables Separator‐Free Zinc Batteries with Ultralong Cycle Life

3D zincophilic micro-scaffold enables stable Zn deposition

Rechargeable aqueous zinc‐ion batteries are of great potential as one of the next‐generation energy‐storage devices due to their low cost and high safety. However, the development of long‐term stable electrodes and electrolytes still suffers from great challenges. Herein, a self‐separation strategy is developed for an interface layer design to optimize both electrodes and electrolytes simultaneously. Specifically, the coating with an organometallics (sodium tricyanomethanide) evolves into an electrically responsive shield layer composed of nitrogen, carbon‐enriched polymer network, and sodium ions, which not only modulates the zinc‐ion migration pathways to inhibit interface side reactions but also adsorbs onto Zn perturbations to induce planar zinc deposition. Additionally, the separated ions from the coating can diffuse to the electrolyte to affect the Zn2+ solvation structure and maintain the cathode structural stability by forming a stable cathode–electrolyte interface and sodium ions’ equilibrium, confirmed by in situ spectroscopy and electrochemical analysis. Due to these unique advantages, the symmetric zinc batteries exhibit an extralong cycling lifespan of 3000 h and rate performance at 20 mA cm−2 at wide temperatures. The efficiency of the self‐separation strategy is further demonstrated in practical full batteries with an ultralong lifespan over 10 000 cycles from −35 to 60 °C.

Simultaneously Stabilizing Both Electrodes and Electrolytes by a Self‐Separating Organometallics Interface for High‐Performance Zinc‐Ion Batteries at Wide Temperatures

Constructing fast-ion-conductive disordered interphase for high-performance zinc-ion and zinc-iodine batteries

Constructing stable surface modification layer is an effective strategy to suppress dendrite growth and side reactions of Zinc (Zn) metal anode in aqueous Zn-ion battery. Herein, a multicomponent Cu-Zn alloy interlayer with superior Zn affinity, high toughness and effective inhibition effect on lattice distortion is constructed on Zn foil (Cu-Zn@Zn) to fabricate ultra-stable Zn metal anode. Owning to the advantages of high binding energy of Cu-Zn alloy layer with Zn atoms and less contact area between metallic Zn and electrolyte, the as-prepared Cu-Zn@Zn electrode not only restricts the aggregation of Zn atoms, but also suppresses the pernicious hydrogen evolution and corrosion, leading to homogeneous Zn deposition and outstanding electrochemical performances. Accordingly, the symmetric battery with Cu-Zn@Zn electrode exhibits an ultra-long cycle life of 5496 h at 1 mA cm -2 for 1 mAh cm -2 , and the Cu-Zn@Zn//V 2 O 5 pouch cell demonstrates excellent cycling stability with a capacity retention of 88% after 600 cycles.

Multicomponent Copper-Zinc Alloy Layer Enabling Ultra-Stable Zinc Metal Anode of Aqueous Zn-ion Battery.

The practical application of the Zn‐metal anode for aqueous batteries is greatly restricted by catastrophic dendrite growth, intricate hydrogen evolution, and parasitic surface passivation. Herein, a polyanionic hydrogel film is introduced as a protective layer on the Zn anode with the assistance of a silane coupling agent (denoted as Zn–SHn). The hydrogel framework with zincophilic –SO3− functional groups uniformizes the zinc ions flux and transport. Furthermore, such a hydrogel layer chemically bonded on the Zn surface possesses an anti‐catalysis effect, which effectively suppresses both the hydrogen evolution reaction and formation of Zn dendrites. As a result, stable and reversible Zn stripping/plating at various currents and capacities is achieved. A full cell by pairing the Zn–SHn anode with a NaV3O8·1.5 H2O cathode shows a capacity of around 176 mAh g−1 with a retention around 67% over 4000 cycles at 10 A g−1. This polyanionic hydrogel film protection strategy paves a new way for future Zn‐anode design and safe aqueous batteries construction.

Stable Zinc Anodes Enabled by a Zincophilic Polyanionic Hydrogel Layer

Ultrathin Smart Energy-Storage Devices for Skin-Interfaced Wearable Electronics

The commercial implementation of aqueous Zn-ion batteries is being impeded by the rampant dendrite growth and exacerbated side reactions on the Zn metal anodes. Herein, a 60 nm artificial protective layer with spatial dielectric–metallic gradient composition (denoted as GZH) is developed via Zn and HfO2 cosputtering. In this design, the top HfO2 layer with high permittivity and low electronic conductivity effectively suppresses hydrogen evolution. The intermediate Zn-rich oxide region promotes the dendrite-free Zn deposition and reinforces the contact between Zn and the sputtered layer. This design allows stable battery operation at high currents. Symmetric cells with Zn-GZH exhibit stable voltage separation over 500 h at 10 mA cm–2 with a cutoff capacity of 5 mAh cm–2. When paired with a vanadate cathode, the full-cell battery delivers a capacity retention of around 75% after 2000 cycles. This design concept may apply to other aqueous metal batteries. 

Dielectric–Metallic Double-Gradient Composition Design for Stable Zn Metal Anodes

A large portion of heat is wasted in the form of low‐grade heat less than 100 °C. There have been various efforts to utilize such energy, such as organic ranking cycles, thermoelectrics, and thermogalvanic cells. The thermally regenerative electrochemical cycle has achieved a noticeable energy conversion efficiency of low‐grade heat harvesting by the thermodynamic cycle of the electrochemical cell that the charging voltage is lower than the discharging voltage. For higher efficiency, this system requires a larger temperature coefficient (α) affected by the change of entropy of electrochemical reaction. Herein, the tuning of the hydration status of cation by mixing acetonitrile in the aqueous electrolyte to improve both negative and positive α of PBAs for highly efficient low‐grade heat harvesting is presented. It largely improves α of cobalt hexacyanoferrate, which are 0.93 mV K−1 at 10–30% state of charge (SOC) in 90% acetonitrile and −0.96 mV K−1 at 70–90% SOC in 10% acetonitrile. A clue to understand the origin of α and to improve it further with various solvents is provided. Eventually, tuning of α using mixing solvent allows building an electrochemical cell with a large positive and negative α of electrode for highly efficient low‐grade heat harvesting.

https://onlinelibrary.wiley.com/doi/pdfdirect/10.1002/aesr.202100176

Tuning the Hydration Entropy of Cations during Electrochemical Intercalation for High Thermopower

Recent advances in wearable devices have enabled noninvasive monitoring for healthcare applications. Smart contact lenses have gained substantial attention for medical diagnosis through the analysis of vital signs in tear fluids. However, previous studies have mostly focused on designs embedded with electronic devices or antennas for wireless transmission, which are power-intensive and require external receivers around the ocular system. Here, the study reports a power-free smart contact lens for noninvasive glucose sensing according to the color changes of multiple electrochromic electrodes to achieve direct data transmission without the external wireless system. The device detects various glucose concentrations, from the ordinary range (0.16–0.5 mm) to abnormally high concentrations (0.9 mm). The multi-electrode design exhibits acceptable accuracy, with a correlation coefficient r = 0.99543 to the controlled sample and allowed low-glucose detections with concentrations down to 0.05 mm. The device shows good reproducibility, with standard deviations of determined glucose levels of 0.0462 and 0.025 for four continuous cycles and for an interval of several days, respectively. It is believed that the reported smart contact lens has the potential for daily health monitoring by ordinary users without a power supply and external devices. Its simple electronics-free structure will allow for immediate application to the market with cost-effective manufacturing. 

Jia Li

Papers

Stable Zinc Anodes Enabled by a Zincophilic Polyanionic Hydrogel Layer

Ultrathin Smart Energy-Storage Devices for Skin-Interfaced Wearable Electronics

Dielectric–Metallic Double-Gradient Composition Design for Stable Zn Metal Anodes

Tuning the Hydration Entropy of Cations during Electrochemical Intercalation for High Thermopower

Power‐Free Contact Lens for Glucose Sensing