Ice as Solid Electrolyte To Conduct Various Kinds of Ions

Regulating Frozen Electrolyte Structure with Colloidal Dispersion for Low Temperature Aqueous Batteries

Electrolyte freezing under low temperatures is a critical challenge for the development of aqueous batteries (ABs). While lowering the freezing point of the electrolyte has caught major research efforts, limited attention has been paid to the structural evolution during the electrolyte freezing process and regulating the frozen electrolyte structure for low temperature ABs. Here, we reveal the formation process of interconnected liquid regions for ion transport in frozen electrolytes with various in situ variable-temperature technologies. More importantly, the low-temperature performance of ABs was significantly improved with the colloidal electrolyte design using graphene oxide quantum dots (GOQDs), which effectively inhibits the growth of ice crystals and expands the interconnected liquid regions for facial ion transport. This work provides new insights and a promising strategy for the electrolyte design of low-temperature ABs.

Optimization Strategies of Electrolytes for Low-temperature Aqueous Batteries

Aqueous rechargeable batteries (ARBs) are considered promising electrochemical energy storage systems for grid-scale applications due to their low cost, high safety, and environmental benignity. With the demand for a wide range of application scenarios, batteries are required to work in various harsh conditions, especially the cold weather. Nevertheless, electrolytes would freeze at extremely low temperatures, resulting in dramatically sluggish kinetics and severe performance degradation. Here, we discuss the behaviors of hydrogen bonds and basic principles of anti-freezing mechanisms in aqueous electrolytes. Then, we present a systematical review of the optimization strategies of electrolytes for low-temperature aqueous batteries. Finally, the challenges and promising routes for further development of aqueous low-temperature electrolytes are provided. This review can serve as a comprehensive reference to boost the further development and practical applications of advanced ARBs operated at low temperatures.

Eutectic Crystallization Activates Solid-State Zinc-Ion Conduction

Solid-state zinc (Zn) batteries offer a new candidate for emerging applications sensitive to volume, safety and cost. However, current solid polymeric or ceramic electrolyte structures remain poorly conductive for the divalent Zn²⁺ , especially at room temperature. Constructing a heterogeneous interface which allows Zn²⁺ percolation is a viable option, but this is rarely involved in multivalent systems. Herein, we construct a solid Zn²⁺ -ion conductor by inducing crystallization of tailored eutectic liquids formed by organic Zn salts and bipolar ligands. High-entropy eutectic-networks weaken the ion-association and form interfacial Zn²⁺ -percolated channels on the nucleator surfaces, resulting in a solid crystal with exceptional selectivity for Zn²⁺ transport (t Zn 2 + =0.64) and appreciable Zn²⁺ conductivity (σ Zn 2 + =3.78×10^-5  S cm^-1 at 30 °C, over 2 orders of magnitude higher than conventional polymers), and finally enabling practical ambient-temperature Zn/V₂ O₅ metal solid cells. This design principle leveraged by the eutectic solidification affords new insights on the multivalent solid electrochemistry suffering from slow ion migration.

Hydrous Nickel-Iron Turnbull's Blue as a High-Rate and Low-Temperature Proton Electrode

Proton batteries are emerging as a promising solution for energy storage; however, their development has been hindered by the lack of suitable cathode materials. Herein, a hydrous Turnbull's blue analogue (TBA) of Ni[Fe(CN)₆]_2/3·4H₂O has been investigated as a viable proton cathode. Particularly, it shows an extremely high rate performance up to 6000 C (390 A g^-1) at room temperature and delivers good capacity values at a low temperature of -40 °C in an aqueous electrolyte. The excellent rate capability is also amenable to high mass loadings of 10 mg cm^-2. Such fast and low-temperature rate behavior likely stems from the fast proton conduction that is afforded by the Grotthuss mechanism inside the TBA structure. Furthermore, advanced characterization, including in operando synchrotron X-ray diffraction (XRD), and X-ray absorption near-edge structure (XANES) were employed to understand the changes of crystal structures and the oxidation-states of metal elements of the electrodes.