Freeze-Tolerant Hydrogel Electrolyte with High Strength for Stable Operation of Flexible Zinc-Ion Hybrid Supercapacitors.

Constructing ionic conductive hydrogels with diversified properties is crucial for portable zinc-ion hybrid supercapacitors (ZHSCs). Herein, a freeze-tolerant hydrogel electrolyte (AF PVA-CMC/Zn(CF3 SO3 )2 ) is developed by forming a semi-interpenetrating anti-freezing polyvinyl alcohol-carboxymethyl cellulose (AF PVA-CMC) network filled with the ethylene glycol (EG)-containing Zn(CF3 SO3 )2 aqueous solution. The semi-interpenetrating AF PVA-CMC/Zn(CF3 SO3 )2 possesses enhanced mechanical properties, realizes the uniform zinc deposition, and impedes the dendrite growth. Notably, the interaction between PVA and EG suppresses the ice crystal formation and prevents freezing at -20 °C. Due to these advantages, the designed hydrogel owns high ionic conductivity of 1.73/0.75 S m-1 at 20/-20 °C with excellent tensile/compression strength at 20 °C. Impressively, the flexible AF quasi-solid-state ZHSC employing the hydrogel electrolyte achieves a superior energy density at 20/-20 °C (87.9/60.7 Wh kg-1 ). It maintains nearly 84.8% of the initial capacity after 10 000 cycles and a low self-discharge rate (1.77 mV h-1 ) at 20 °C, together with great tolerance to corrosion. Moreover, this device demonstrates a stable electrochemical performance at -20 °C under deformation. The obtained results provide valuable insights for constructing durable hydrogel electrolytes in cold environments.

Zhu X ，Ji C ，Meng Q ，Mi H ，Yang Q ，Li Z ，Yang N ，Qiu J ... -  《-》

Natural Polysaccharide Strengthened Hydrogel Electrolyte and Biopolymer Derived Carbon for Durable Aqueous Zinc Ion Storage.

Ji C ，Wu D ，Liu Z ，Mi H ，Liao Y ，Wu M ，Cui H ，Li X ，Wu T ，Bai Z ... -  《-》

Self-adhesive, freeze-tolerant, and strong hydrogel electrolyte containing xanthan gum enables the high-performance of zinc-ion hybrid supercapacitors.

Hydrogel electrolyte is an ideal candidate material for flexible energy storage devices due to its excellent softness and conductivity properties. However, challenges such as the inherent mechanical weakness, the susceptibility to be frozen in low-temperature environments, and the insufficiency of hydrogel-electrode contact persist. Herein, a "Multi in One" strategy is employed to effectively conquer these difficulties by endowing hydrogels with high strength, freeze-resistance, and self-adhesive ability. Multiple hydrogen bond networks and ion crosslinking networks are constructed within the hydrogel electrolyte (PVA/PAAc/XG) containing polyvinyl alcohol (PVA), acrylic acid (AAc), and xanthan gum (XG), promoting the enhanced mechanical property, and the adhesion to electrode materials is also improved through abundant active groups. The introduction of zinc ions provides the material with superior frost resistance while also promoting electrical conductivity. Leveraging its multifunction of superior mechanical strength, anti-freeze property, and self-adhesive characteristic, the PVA/PAAc/XG hydrogel electrolyte is employed to fabricate zinc ion hybrid supercapacitors (ZHS). Remarkably, ZHS exhibits outstanding electrochemical performance and cycle stability. A remarkable capacity retention rate of 83.86 % after 10,000 charge-discharge cycles can be achieved at high current densities, even when the operational temperature decreases to -60 °C, showing great potential in the field of flexible energy storage devices.

Zhou Y ，Liu H ，Zhou X ，Lin X ，Cai Y ，Shen M ，Huang X ，Liu H ，Xu X ... -  《-》

A safe and robust dual-network hydrogel electrolyte coupled with multi-heteroatom doped carbon nanosheets for flexible quasi-solid-state zinc ion hybrid supercapacitors.

Wu D ，Ji C ，Mi H ，Guo F ，Cui H ，Qiu P ，Yang N ... -  《-》

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 ... -  《-》