Xuejun Lu

Urea, as one of the most sustainable organic solutes, denies the high salt consumption in commercial electrolytes with its peculiar solubility in water. The bi‐mixture of urea‐H ₂ O shows the eutectic feature for increased attention in aqueous Zn‐ion electrochemical energy storage (AZEES) technologies. While the state‐of‐the‐art aqueous electrolyte recipes are still pursuing the high‐concentrated salt dosage with limited urea adoption and single‐anion selection category. Here, a dual‐anion urea‐based (DAU) electrolyte composed of dual‐Zn salts and urea‐H ₂ O‐induced solutions is reported, contributing to a stable electric double‐layer construction and in situ organic/inorganic SEI formation. The optimized ZT ₂ S _0.5 ‐20U electrolytes show a high initial Coulombic efficiency of 93.2% and durable Zn‐ion storage ≈4000 h regarding Zn//Cu and Zn//Zn stripping/plating procedures. The assembled Zn//activated carbon full cells maintain ≈100% capacitance over 50 000 cycles at 4 A g ^–1 in coin cell and ≈98% capacitance over 20 000 cycles at 1 A g ^–1 in pouch cell setups. A 12 × 12 cm ² pouch cell assembly illustrates the practicality of AZEES devices by designing the cheap, antifreezing, and nonflammable DAU electrolyte system coupling proton donor‐acceptor molecule and multi‐anion selection criteria, exterminating the critical technical barriers in commercialization.

The brain‐storm of designing low‐cost and commercialized eutectic electrolytes for zinc (Zn)‐based electrochemical energy storage (ZEES) remains unresolved and attractive, especially when implementing it at low temperatures. Here, we report an appealing layout of advancing chlorine‐functionalized eutectic (Cl‐FE) electrolytes via exploiting Cl anion‐induced eutectic interaction with Zn acetate solutions. This novel eutectic liquid shows high affinity to collaborate with 1,3‐dioxolane (DOL) and is prone to constitute Cl‐FE/DOL‐based electrolytes with a unique inner/outer eutectic solvation sheath for the better regulation of Zn‐solvating neighboring and reconstruction of H‐bonding. The side reactions are effectively restricted on Zn anodes and a high Coulombic efficiency of 99.5 % can be achieved over 1000 cycles at −20 °C with Zn//Cu setups. By prototyping scale‐up Zn‐ion pouch cells using the optimal eutectic liquid of 3ZnOAc_1.2Cl_1.8‐DOL, we obtain improved electrochemical properties at −20 °C with a high capacitance of 203.9 F g⁻¹ at 0.02 A g⁻¹ in a range of 0.20–1.90 V and long‐term cycling ability with 95.3 % capacitance retention at 0.2 A g⁻¹ over 3,000 cycles. Overall, the proposal of ideal Cl‐FE/DOL‐based electrolytes guides the design of sub‐zero and endurable aqueous ZEES devices and beyond.

The brain‐storm of designing low‐cost and commercialized eutectic electrolytes for zinc (Zn)‐based electrochemical energy storage (ZEES) remains unresolved and attractive, especially when implementing it at low temperatures. Here, we report an appealing layout of advancing chlorine‐functionalized eutectic (Cl‐FE) electrolytes via exploiting Cl anion‐induced eutectic interaction with Zn acetate solutions. This novel eutectic liquid shows high affinity to collaborate with 1,3‐dioxolane (DOL) and is prone to constitute Cl‐FE/DOL‐based electrolytes with a unique inner/outer eutectic solvation sheath for the better regulation of Zn‐solvating neighboring and reconstruction of H‐bonding. The side reactions are effectively restricted on Zn anodes and a high Coulombic efficiency of 99.5 % can be achieved over 1000 cycles at −20 °C with Zn//Cu setups. By prototyping scale‐up Zn‐ion pouch cells using the optimal eutectic liquid of 3ZnOAc_1.2Cl_1.8‐DOL, we obtain improved electrochemical properties at −20 °C with a high capacitance of 203.9 F g⁻¹ at 0.02 A g⁻¹ in a range of 0.20–1.90 V and long‐term cycling ability with 95.3 % capacitance retention at 0.2 A g⁻¹ over 3,000 cycles. Overall, the proposal of ideal Cl‐FE/DOL‐based electrolytes guides the design of sub‐zero and endurable aqueous ZEES devices and beyond.

Eutectic electrolytes are emerging to be explored to meet the high demand for aqueous zinc‐ion capacitors (AZICs) due to their high electrochemical stability and environmental‐friendly feature. Notably, a large‐scale requirement for a practical AZIC has been addressed to balance decent performance and increase package size. Thus, a “duet‐insurance” eutectic electrolyte (DIEE) is proposed by introducing successively heavy water (D₂O) and dimethyl sulfoxide in an aqueous chaotropic Zn salt solution, which hindered the severe irreversibility of Zn anodes compared to that lacking this dual‐solvent protection. For example, the optimal DIEE delivered a high capacitance of 352.9 F g⁻¹ at 0.5 A g⁻¹ and excellent capacitance retention of ≈100% over 30,000 cycles at 2 A g⁻¹ implementing in pouch cells and showing the ability to operate at a low temperature. Besides, experimental (e.g., nuclear magnetic resonance spectroscopy, Raman spectroscopy, electric double‐layer capacitance, etc.) and theoretical techniques (e.g., molecular dynamics simulation, density functional theory) illustrate the vital presence of contact ion pairs and aggregates ion species. Ultimately, this efficient DIEE system employing “duet‐insurance” protections provides a promising direction for designing novel eutectic electrolytes for AZICs chemistries.

Aqueous eutectic electrolytes are emerging as the cost-effective and environmentally benign alternatives governing the next-generation electrochemical energy storage (EES) devices. For example, Li-based eutectic (ALE) electrolyte benefits from the strong hydrogen bond (H-bond) interaction with dimethyl sulfoxide (DMSO)–H₂O eutectic mixtures, exhibiting non-flammability and high electrochemical stability compared to conventional aqueous electrolytes. However, the highly concentrated feature raises obstacles to sluggish ions transfer and low-temperature performance, limiting the practical application of ALE electrolytes. Herein, a novel approach regarding organic solvent regulation has been proposed to deal with concentration-related electrochemical-stability issues. For instance, the protic ether of 1,2-dimethoxyethane (DME) in the ALE electrolyte (ALE–DME_6.6) can efficiently occupy the primary solvating shell of Li⁺ and increase H-bond intensity between DME–H₂O and DMSO–H₂O, which ultimately delivers high capacitance of 66.2 F g⁻¹ at 0.5 A g⁻¹ and ∼80% capacitance retention after 20 000 cycles at room temperature. In addition, enhanced low-temperature operation in supercapacitors (SCs) displays high ionic conductivity of 0.62 mS cm⁻¹ and high capacitance retention of 80% (8000 cycles) at −20 °C. The DME regulator in eutectic electrolytes offers appealing prospects and guidance for the advanced design of eutectic electrolytes for diverse EES applications.

Rechargeable zinc batteries (RZBs) have proved to be promising candidates as an alternative to lithium‐ion batteries due to their low cost, inherent safety, and environmentally benign features. While designing cost‐effective electrolyte systems with excellent compatibility with electrode materials, high energy/power density as well as long life‐span challenge their further application as grid‐scale energy storage devices. Eutectic electrolytes as a novel class of electrolytes have been extensively reported and explored taking advantage of their feasible preparation and high tunability. Recently, some perspectives have summarized the development and application of eutectic electrolytes in metal‐based batteries, but their infancy requires further attention and discussion. This review systematically presents the fundamentals and definitions of eutectic electrolytes. Besides, a specific classification of eutectic electrolytes and their recent progress and performance on RZB fields are introduced as well. Significantly, the impacts of various composing eutectic systems are disserted for critical RZB chemistries including attractive features at electrolyte/electrode interfaces and ions/charges transport kinetics. The remaining challenges and proposed perspectives are ultimately induced, which deliver opportunities and offer practical guidance for the novel design of advanced eutectic electrolytes for superior RZB scenarios.