Polysaccharide hydrogel electrolytes with robust interfacial contact to electrodes for quasi-solid state flexible aqueous zinc ion batteries with efficient suppressing of dendrite growth.

Flexible aqueous zinc-ion batteries (AZIBs) require high conductive and adhesive hydrogel electrolytes. However, high adhesion tends to hinder ion conduction rate. Herein, we designed a water/glycerol binary solvent coordinating the hydrophilic polymers to reconstruct the water molecules' environment in the hydrogel. As a consequence, the interface adhesion strength between Zn and the hydrogel reached 3.0 kPa and the ionic conductivity was up to 16.8 mS cm-1. In addition, inspired by the slurry electrode preparation method, we developed a simple blade coating technique using a non-Newtonian polysaccharide liquid solution to construct an ultra-thin hydrogel electrolyte in situ on the cathode. The thickness of the obtained hydrogel reached 70 μm, and the ultrathin flexible AZIBs were easily constructed by pasting a Zn anode directly on the adhesive hydrogel, showing the potential of flexible AZIBs scalable assembly. In addition, the Zn//Zn symmetrical cells with the hydrogel electrolyte provided stable cycling performance for over 400 h at 0.1 mA cm-2 with suppressed dendrite growth. The assembled Zn//Polyaniline battery and Zn//V2O5 battery also exhibited excellent capacity retention after cycles. This work has realized the hydrogel electrolyte with high adhesion and conductivity, which has good adaptability to metal electrodes and opened up a new practical way for large-scale assembly of flexible energy storage devices.

Deng Y ，Wu Y ，Wang L ，Zhang K ，Wang Y ，Yan L ... -  《-》

Realizing an All-Round Hydrogel Electrolyte toward Environmentally Adaptive Dendrite-Free Aqueous Zn-MnO(2) Batteries.

Flexible energy storage devices are at the forefront of next-generation power supplies, one of the most important components of which is the gel electrolyte. However, shortcomings exist, more or less, for all the currently developed hydrogel electrolytes. Herein, a facile and cost-effective method is developed to construct an all-round hydrogel electrolyte by using cotton as the raw material, tetraethyl orthosilicate as the crosslinker, and glycerol as the antifreezing agent. The obtained hydrogel electrolyte has high ionic conductivity, excellent mechanical properties (e.g., high tensile strength and elasticity), ultralow freezing point, good self-healing ability, high adhesion, and good heat-resistance ability. Remarkably, this hydrogel electrolyte can provide a record-breaking high ionic conductivity of 19.4 mS cm-1 at -40 °C compared with previously reported aqueous electrolytes for zinc-ion batteries. In addition, this hydrogel electrolyte can significantly inhibit zinc dendritic growth and parasitic side reactions from -40 to 60 °C. With this hydrogel electrolyte, a flexible quasi-solid-state Zn-MnO2 battery is assembled, which shows remarkable energy densities from -40 to 60 °C. The battery also exhibits outstanding cycling durability and has high endurance under various harsh conditions. This work opens new opportunities for the development of hydrogel electrolytes.

Chen M ，Chen J ，Zhou W ，Han X ，Yao Y ，Wong CP ... -  《-》

Mild synthesis of superadhesive hydrogel electrolyte with low interfacial resistance and enhanced ionic conductivity for flexible zinc ion battery.

Flexible aqueous battery is considered to be one of the most promising energy storage devices for powering flexible electronics. However, inferior interfacial compatibility in electrode-electrolyte interfaces and inefficient ionic channel of electrolytes usually result in potential troubles when applied in practical applications. Herein, we report a mild synthetic route to a sodium lignosulfonate-polyacrylamide hydrogel electrolyte with a high adhesiveness to achieve low electrode-electrolyte interfacial resistance and fast ionic conduction. Comprehensive experiments show that the catechol groups from sodium lignosulfonate demonstrate strong interactions with both cathode and anode materials, and thus greatly reduce the contact resistances across the electrodes. Meanwhile, the existence of sulfonate groups significantly enhances the ionic conductivity of the hydrogel electrolyte. Benefiting from this design, a low ohmic resistance of 3.8 Ω (i.e., 11.4 Ω cm2 ), a low charge transfer resistance of 22.5 Ω (i.e., 67.5 Ω cm2 ), a high ionic conductivity of 31.1 mS cm-1 as well as a 100% capacity retention upon harsh bending deformation can be realized in the flexible zinc ion battery, which are significantly superior to those in the traditional candidates. The present investigation provides new insight into addressing the interfacial issue plaguing flexible energy storage devices.

Li J ，Yu P ，Zhang S ，Wen Z ，Wen Y ，Zhou W ，Dong X ，Liu Y ，Liang Y ... -  《-》

Stable zinc anode interface and environmentally adaptable hydrogel electrolytes for stable operation of zinc-ion hybrid supercapacitors.

Hydrogel-based zinc ion hybrid supercapacitors (ZIHS) have stood out from many energy storage device candidates due to their battery-level energy density, inherent flexibility, and safety. Nevertheless, the inevitable dendrite growth of Zn anodes and sharp capacity degradation at low-temperature seriously hinder their practical application. Herein, a dense ZnF2 solid electrolyte interface protective layer was constructed in situ on the Zn electrode surface by a simple chemical deposition method, effectively isolating the water molecules and alleviating the water-induced dendrite growth and parasitic reaction. To achieve the flexible ZIHS with environmental adaptability, a self-adhesion and anti-freezing zwitterionic hydrogel electrolyte was fabricated to afford superior ionic conductivity (97.1 mS cm-1), excellent anti-drying ability, and robust interfacial adhesion. Benefitting from the integrated merits of the as-designed electrolyte and electrode, the ZIHS delivered excellent mechanical adaptability, favorable energy density (103.9 Wh kg-1 at 270.1 W kg-1), broad operating temperature range (-40 to 40 °C), along with long-term cycling stability (12,000 cycles) with 90.3 % capacity retention at -25 °C. Notably, the unencapsulated ZIHS achieved exceptional electrochemical stability in an open environment. This finding provides valuable insights for constructing durable, flexible, and environmentally adaptable zinc-based energy storage systems.

Zhang Z ，Gao Y ，Gao Y ，Jia F ，Gao G ... -  《-》

Salting-Out Effect Realizing High-Strength and Dendrite-Inhibiting Cellulose Hydrogel Electrolyte for Durable Aqueous Zinc-Ion Batteries.

Quan Y ，Ma H ，Chen M ，Zhou W ，Tian Q ，Han X ，Chen J ... -  《-》