Three Birds with One Stone: Tetramethylurea as Electrolyte Additive for Highly Reversible Zn‐Metal Anode

Abstract

Aqueous Zn‐metal batteries are the most promising system for large‐scale energy storage due to their high capacity, high safety, and low cost. The Zn‐metal anode, however, suffers from continuous parasitic reactions, random dendrite growth, and sluggish kinetics in aqueous electrolytes. Herein, a high donor number solvent, tetramethylurea (TMU), is introduced as electrolyte additive to enable highly reversible Zn‐metal anode, where the TMU can 1) preferentially adsorb on the Zn surface to inhibit Zn corrosion and suppress parasitic reaction, 2) solvate with Zn2+ and exclude the H2O from Zn2+ solvation sheath to weaken water activity significantly, and 3) contribute to form an inorganic‐organic bilayer solid electrolyte interphase to enable homogeneous and rapid Zn2+ transport kinetic for dendrite‐free Zn deposition. Benefiting from these three merits, the resulting aqueous electrolyte demonstrates a highly reversible Zn plating/stripping cycling in a Zn||Ti asymmetric cell for over 1200 cycles and in a Zn||Zn symmetric cell for over 4000 h. As a proof‐of‐concept, the aqueous Zn‐metal full cells assembled with various state‐of‐the‐art cathodes also deliver excellent cycling performance even with a 10 µm thin Zn anode, favoring the practical application.

Diminishing Space-Charge Layer Effect of Zinc Anodes by an Anion-Immobilized Electrolyte Membrane

“…In addition, a prolonged lifespan of 1500 h was also achieved at a high current density of 5 mA cm –2 for the KevlarH electrolyte (Figure S8). Besides, the KevlarH electrolyte also delivered an impressive CE improvement (99.87%) over 2500 cycles (Figure b), which is superior to most, if not all, recently reported electrolyte regulation studies for Zn metal anodes (Figure c). ,− Inspired by the exceptional Zn deposition/stripping reversibility and interface stability with the KevlarH electrolyte, Zn||V 2 O 5 full batteries were fabricated to probe its feasibility in full cells. As shown in Figures d and S9, the Zn||V 2 O 5 full cell using a thin Zn foil (thickness of 20 μm) with a limited N/P ratio of 4.3 in the KevlarH electrolyte exhibited a high areal capacity of ∼1.2 mAh cm –2 after 1500 cycles at 5 A g –1 with good interfacial stability (Figure S10), thereby demonstrating a certain predominance over the routine liquid electrolyte.…”

3D Printing of Electron/Ion‐Flux Dual‐Gradient Anodes for Dendrite‐Free Zinc Batteries

“…As the Raman spectrum is shown in Figure S15 (Supporting Information), the peak at 3224 cm −1 corresponding to the O-H group of cellulose shifts to a lower wavenumber after adding Zn(OTF) 2 electrolyte, indicating the strong coordination of CNF with Zn 2+ . The CNF is preferentially solvated with Zn 2+ and thereby excludes part of H 2 O from the Zn 2+ solvation sheath, [42] which can significantly weaken the activity of water molecules. Meanwhile, free water molecules in the electrolyte are tethered by the abundant hydrogen bonding networks existing in cellulose, which further suppresses the side reactions.…”

Simultaneous tailoring of hydrogen evolution and dendrite growthviaa fertilizer-derived additive for the stabilization of the zinc anode interface

“…As one of the various inorganic and organic additives, including organic gelatin, polyethylene glycol, thiourea, and ionic liquids, for Zn electrodeposition, the easily available and inexpensive MTU acts in a manner similar to leveling and brightening agents in Zn electroplating baths to improve the physicochemical properties of Zn deposits. 39,40 It reduces the grain size, changes the default growth direction of Zn crystals, and inhibits the formation of Zn nucleation on the electrode surface by readily adsorbing to rapidly grow the number of active sites through the coordination of sulfur atoms. This implies that MTU could potentially be used as a functional additive to change the Zn electrodeposition behavior.…”