The hydrophobic internal cavity and hydrophilic external surface of cyclodextrins (CDs) render promising electrochemical applications. Here, we report a comparative and mechanistic study on the use of CD molecules (α-, β-, and γ-CD) as electrolyte additives for rechargeable Zn batteries. The addition of α-CD in aqueous ZnSO 4 solution reduces nucleation overpotential and activation energy of Zn plating and suppresses H 2 generation. Computational, spectroscopic, and electrochemical studies reveal that α-CD preferentially adsorbs in parallel on the Zn surface via secondary hydroxyl groups, suppressing water-induced side reactions of hydrogen evolution and hydroxide sulfate formation. Additionally, the hydrophilic exterior surface of α-CD with intense electron density simultaneously facilitates Zn 2+ deposition and alleviates Zn dendrite formation. A formulated 3 M ZnSO 4 + 10 mM α-CD electrolyte enables homogenous Zn plating/stripping (average Coulombic efficiency ∼ 99.90%) at 1 mA cm −2 in Zn|Cu cells and a considerable capacity retention of 84.20% after 800 cycles in Zn|V 2 O 5 full batteries. This study provides insight into the use of supramolecular macrocycles to modulate and enhance the interface stability and kinetics of metallic anodes for aqueous battery chemistry.

Engineering a stable solid electrolyte interphase (SEI) is one of the critical maneuvers in improving the performance of a lithium anode for high-energy-density rechargeable lithium batteries. Herein, we build a fluorinated lithium/ sodium hybrid interphase via a facile electroless electrolyte-soaking approach to stabilize the repeated plating/stripping of lithium metal. Jointed experimental and computational characterizations reveal that the fluorinated hybrid SEI mainly consisting of NaF, LiF, Li x PO y F z , and organic components features a mosaic polycrystalline structure with enriched grain boundaries and superior interfacial properties toward Li. This LiF/NaF hybrid SEI exhibits improved ionic conductivity and mechanical strength in comparison to the SEI without NaF. Remarkably, the fluorinated hybrid SEI enables an extended dendrite-free cycling of metallic Li over 1300 h at a high areal capacity of 10 mAh cm −2 in symmetrical cells. Furthermore, full cells based on the LiFePO 4 cathode and hybrid SEI-protected Li anode sustain long-term stability and good capacity retention (96.70% after 200 cycles) at 0.5 C. This work could provide a new avenue for designing robust multifunctional SEI to upgrade the metallic lithium anode.

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Metallic zinc (Zn) is an attractive anode material to use for building an aqueous battery but suffers from dendritic growth and waterinduced corrosion. Herein, we report the use of vanillin as a bifunctional additive in aqueous electrolyte to stabilize the Zn electrochemistry. Computational, spectroscopic, and electrochemical studies suggest that vanillin molecules preferentially absorb in parallel on the Zn surface to homogenize the Zn 2+ plating and favorably coordinate with Zn 2+ to weaken the solvation interaction between H 2 O and Zn 2+ , resulting in a compact, dendrite-free Zn deposition and a stable electrode−electrolyte interface with suppressed hydrogen evolution and hydroxide sulfate formation. In the formulated 2 M ZnSO 4 electrolyte with 5 mM vanillin, the Zn anode sustains high areal capacity (10 mAh cm −2 at 1 mA cm −2 ) and remarkable cycling stability (1 mAh cm −2 for 1000 h) in a Zn|Zn cell and high average Coulombic efficiency (99.8%) in a Zn|Cu cell, significantly outperforming the cells without vanillin. Furthermore, the vanillin additive supports stable operation of full Zn|V 2 O 5 batteries and is readily generalized to a Zn(CF 3 SO 3 ) 2based electrolyte. This work offers a facile and cost-effective strategy of electrolyte design to enable high-performance aqueous Zn batteries.