Interface solvation regulation stabilizing the Zn metal anode in aqueous Zn batteries

Guiding uniform Zn deposition with a multifunctional additive for highly utilized Zn anodes

The practical applications of aqueous zinc-ion batteries (AZIBs) have been restricted by the fast growth of Zn dendrites and severe side reactions at the Zn/electrolyte interface. Herein, a multifunctional additive, L-leucine (Leu), is incorporated into a mild acidic electrolyte to stabilize the Zn anode. The Leu molecule, featuring both carboxyl and amino groups, exhibits strong interactions with Zn2+, which can reshape the solvation structure of Zn2+ and facilitate the uniform electrodeposition of Zn. Simultaneously, the Leu molecule exhibits preferential adsorption onto the Zn surface, effectively isolating it from direct contact with water, thus suppressing unwanted side reactions. Consequently, the Zn∥Cu asymmetric cell exhibits a high and stable coulombic efficiency of 99.5% at a current density of 5 mA cm-2 for 1100 h. Importantly, the capacity retention of the Zn∥NH4V4O10 full cell based on the Leu electrolyte reaches 80% after 1200 cycles at a current density of 2 A g-1. The successful application of the low-cost Leu effectively enhances the cycling stability of the AZIBs and accelerates their applications.

Easy-to-Lay Poly-N Heterocyclic Additives Enable Long-Term Stabilization of Zinc-Ion Capacitor Anodes under Deep Plating/Stripping

Addition of organic compounds containing O/N heteroatoms to aqueous electrolytes such as ZnSO4 (ZS) solutions is one of the effective strategies to inhibit Zn anode dendrites and side reactions. However, addressing the stability of Zn plating/stripping at high current densities and areal capacities by this method is still a challenge, especially in capacitors known for high power and long life. Herein, an organic heterocyclic compound of 1, 4, 7, 10-tetraazacyclododecane (TC) containing four symmetrically distributed N atoms is employed as ZS additive, expanding the life of Zn anodes from ≈ 30 h to 1000 and 240 h at deep plating/stripping conditions of 10 and 20 mA cm-2/mAh cm-2, respectively; the cumulative capacity is as high as 5.0 Ah cm-2 with 99% Coulombic efficiency, far exceeding reported additives. TC with higher binding energies than H2O for Zn species tends to adsorb to Zn (002) in a lying manner and participate in the solvation shell of Zn2+, thus avoiding Zn dendrites and side-reaction damage, especially at high current densities. The TC-endowed Zn anode's stability under such extreme conditions is verified in Zn-ion capacitors (i.e., > 94.6% capacity retention after 28 000 cycles), providing new insights into the development of high-power Zn-based energy storage devices.

Rescuing zinc anode-electrolyte interface: mechanisms, theoretical simulations and in situ characterizations

The research interest in aqueous zinc-ion batteries (AZIBs) has been surging due to the advantages of safety, abundance, and high electrochemical performance. However, some technique issues, such as dendrites, hydrogen evolution reaction, and corrosion, severely prohibit the development of AZIBs in practical utilizations. The underlying mechanisms regarding electrochemical performance deterioration and structure degradation are too complex to understand, especially when it comes to zinc metal anode-electrolyte interface. Recently, theoretical simulations and in situ characterizations have played a crucial role in AZIBs and are exploited to guide the research on electrolyte engineering and solid electrolyte interphase. Herein, we present a comprehensive review of the current state of the fundamental mechanisms involved in the zinc plating/stripping process and underscore the importance of theoretical simulations and in situ characterizations in mechanism research. Finally, we summarize the challenges and opportunities for AZIBs in practical applications, especially as a stationary energy storage and conversion device in a smart grid.

Interface regulation of the Zn anode by using a low concentration electrolyte additive for aqueous Zn batteries

The Zn metal anode in aqueous Zn batteries faces a number of challenges including instable deposition and corrosion issues. Here, we present an interface environment regulation for a Zn electrode with a low concentration electrolyte additive of 0.1 m 3-aminobenzenesulfonic acid (ASA). ASA prefers to adsorb on the Zn surface over water and creates an ASA-rich interface. It further enters the Zn2+ solvation sheath locally, which shifts the lowest unoccupied molecular orbital from solvated water to ASA. The hydrogen evolution reaction from solvated water reduction is inhibited, and the reduction of solvated ASA generates a stable solid-electrolyte interphase composed of the ion conductor ZnS covered by organic-inorganic mixed components. With the resulting homogenized Zn deposition, continuous Zn stripping in symmetric cells reaches 99.7% depth of discharge (DOD) at a current density of 2 mA cm-2, whereas cell short-circuit takes place at 11.4% DOD in the ASA free ZnSO4 electrolyte. The repeated stripping/plating also realizes 1100 h cycle life at 2 mA cm-2, and a 99.54% stabilized coulombic efficiency is obtained for 500 cycles at 10 mA cm-2.