Insufficient ionic conductivity and freezing of the electrolyte are considered the main problems for electrochemical energy storage at low temperatures (low T). Here, an electrolyte with a freezing point lower than −130 °C is developed by using dimethyl sulfoxide (DMSO) as an additive with molar fraction of 0.3 to an aqueous solution of 2 m NaClO4 (2M‐0.3 electrolyte). The 2M‐0.3 electrolyte exhibits sufficient ionic conductivity of 0.11 mS cm−1 at −50 °C. The combination of spectroscopic investigations and molecular dynamics (MD) simulations reveal that hydrogen bonds are stably formed between DMSO and water molecules, facilitating the operation of the electrolyte at ultra‐low T. Using DMSO as the electrolyte additive, the aqueous rechargeable alkali‐ion batteries (AABs) can work well even at −50 °C. This work provides a simple and effective strategy to develop low T AABs.

Aqueous batteries (ABs) have attracted increasing attention because of their inherent safety and low cost. Nevertheless, hydrogen evolution reaction (HER) at the anode presents severe challenges for stable and safe operation of ABs. Instead of passivating the anode surface to hinder HER kinetics, a novel design strategy is proposed here to suppress the HER via alternating its thermodynamics pathway. By adding a hydrogen bond acceptor, dimethyl sulfoxide (DMSO), the onset potential of HER can be delayed by as much as 1.0 V (on titanium mesh). Spectral characterization and molecular dynamics simulation confirm that the formation of hydrogen bonds between DMSO and water molecules can reduce the water activity, thereby suppressing the HER. This strategy has proven to be universal in expanding the electrochemical window of aqueous electrolytes. For instance, unconventional V 2+ ↔V 3+ redox processes in Na 3 V 2 (PO 4 ) 3 (-1.2 V versus Ag/AgCl) and highly stable Zn plating/stripping processes can be realized in ABs.

Aqueous zinc‐ion batteries are promising candidates for grid‐scale energy storage because of their intrinsic safety, low cost, and high energy intensity. However, lack of suitable cathode materials with both excellent rate performance and cycling stability hinders further practical application of aqueous zinc‐ion batteries. Here, a nanoflake‐self‐assembled nanorod structure of Ca0.28MnO2·0.5H2O as Zn‐insertion cathode material is designed. The Ca0.28MnO2·0.5H2O exhibits a reversible capacity of 298 mAh g−1 at 175 mA g−1 and long‐term cycling stability over 5000 cycles with no obvious capacity fading, which indicates that the per‐insertion of Ca ions and water can significantly improve reversible insertion/extraction stability of Zn2+ in Mn‐based layered type material. Further, its charge storage mechanism, especially hydrogen ions, is elucidated. A comprehensive study suggests that the intercalation of hydrogen ions in the first discharge plat is controled by both pH value and type of anion of electrolyte. Further, it can stabilize the Ca0.28MnO2·0.5H2O cathode and facilitate the following insertion of Zn2+ in 1 m ZnSO4/0.1 m MnSO4 electrolyte. This work can enlighten and promote the development of high‐performance rechargeable aqueous zinc‐ion batteries.

The issues of inherent low anodic stability and high flammability hinder the deployment of the etherbased electrolytes in practical high-voltage lithium metal batteries. Here, we report a rationally designed etherbased electrolyte with chlorine functionality on ether molecular structure to address these critical challenges. The chloroether-based electrolyte demonstrates a high Li Coulombic efficiency of 99.2 % and a high capacity retention > 88 % over 200 cycles for Ni-rich cathodes at an ultrahigh cut-off voltage of 4.6 V (stable even up to 4.7 V). The chloroether-based electrolyte not only greatly improves electrochemical stabilities of Ni-rich cathodes under ultrahigh voltages with interphases riched in LiF and LiCl, but possesses the intrinsic nonflammable safety feature owing to the flame-retarding ability of chlorine functional groups. This study offers a new approach to enable ether-based electrolytes for high energy density, long-life and safe Li metal batteries.

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Due to the merits of low cost, safety, environmental friendliness, and abundant sodium reserves, non-aqueous and aqueous sodium-ion batteries are wonderful alternatives for large-scale energy storage.

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