Zinc-ion batteries (ZIB) present great potential in energy storage due to low cost and high safety. However, the poor stability, dendrite growth, and narrow electrochemical window limit their practical application. Herein, we develop a new eutectic electrolyte consisting of ethylene glycol (EG) and ZnCl 2 for dendrite-free and long-lifespan ZIBs. The EG molecules participate in the Zn 2 + solvation via coordination and hydrogen-bond interactions. Optimizing the ZnCl 2 /EG molar ratio (1 : 4) can strengthen intermolecular interactions to form [ZnCl(EG)] + and [ZnCl(EG) 2 ] + cations. The dissociation-reduction of these complex cations enables the formation of a Cl-rich organic-inorganic hybrid solid electrolyte interphase film on a Zn anode, realizing highly reversible Zn plating/stripping with long-term stability of � 3200 h. Furthermore, the polyaniline j j Zn cell manifests decent cycling performance with � 78 % capacity retention after 10 000 cycles, and the assembled pouch cell demonstrates high safety and stable capacity. This work opens an avenue for developing eutectic electrolytes for high-safety and practical ZIBs.

Metal-ion batteries (MIBs) are promising for large-scale energy storage because they can alleviate the inherent intermittency of renewable energy. As an indispensable part of MIBs, electrolytes influence the electrochemical performance. Recently, the new concept of eutectic electrolytes has aroused extensive research attention in the field of MIBs due to their simple synthesis and eco-friendly features. Nevertheless, the development of eutectic electrolytes is still in its infancy and deserves further attention. This review focuses on the systematic understanding of the relationship between eutectic electrolytes and the corresponding performances of MIBs. First, fundamentals of eutectic electrolytes are described. Then, recent progress in the use of eutectic electrolytes in MIBs is introduced, including the correlations between structure and properties, the chemistry at the electrode interface, and the ion/charge transport mechanism. Finally, the challenges and prospects related to eutectic electrolytes are discussed. This Focus Review will provide better directions to devise advanced eutectic electrolytes for high-performance MIBs.

Mn‐based layered oxides are one of the most appealing cathodes for potassium‐ion batteries (PIBs) because of their high theoretical capacity. However, the Jahn–Teller effect of Mn3+ induces detrimental structural disorder and irreversible phase transition, leading to inferior cycling stability. Herein, an efficient strategy to suppress the Jahn–Teller effect in Mn‐based layered oxides by regulating the Mn average valence is demonstrated. To verify this strategy, Ti4+ and Mg2+ ions are chosen and introduced into the layered oxides (K0.5Mn0.7Co0.2Fe0.1O2), which can enhance the structural stability but have opposite effects on the regulation of Mn3+/4+ valence. The K0.5Mn0.6Co0.2Fe0.1Mg0.1O2 with a higher Mn valence (4+) exhibits long‐term cycling stability as a PIB cathode compared to the K0.5Mn0.6Co0.2Fe0.1Ti0.1O2 with a lower Mn valence (3.667+). Meanwhile, the detrimental phase transition from P3 to O3 caused by Jahn–Teller effect is completely suppressed, and is replaced by a highly reversible single‐phase solid solution reaction for K0.5Mn0.6Co0.2Fe0.1Mg0.1O2. The enhanced cycling stability and single‐phase reaction are attributed to the suppressed Jahn–Teller effect via Mn valence regulation, confirmed by first‐principles calculations. Therefore, this discovery paves the way for the development of advanced layered cathodes for the next‐generation high‐performance PIBs.

No abstract

No abstract