In Situ Construction of Protective Films on Zn Metal Anodes via Natural Protein Additives Enabling High-Performance Zinc Ion Batteries

Abstract

The strong activity of water molecules causes a series of parasitic side reactions on Zn anodes in the aqueous electrolytes. Herein, we introduce silk fibroin (SF) as a multifunctional electrolyte additive for aqueous zinc-ion (Zn-ion) batteries. The secondary structure transformation of SF molecules from α-helices to random coils in the aqueous electrolytes allows them to break the hydrogen bond network among free water molecules and participate in Zn2+ ion solvation structure. The SF molecules released from the [Zn­(H2O)4(SF)]2+ solvation sheath appear to be gradually adsorbed on the surface of Zn anodes and in situ form a hydrostable and self-healable protective film. This SF-based protective film not only shows strong Zn2+ ion affinity to promote homogeneous Zn deposition but also has good insulating behavior to suppress parasitic reactions. Benefiting from these multifunctional advantages, the cycle life of the Zn||Zn symmetric cells reaches over 1600 h in SF-containing ZnSO4 electrolytes. In addition, by adopting a potassium vanadate cathode, the full cell shows excellent cycling stability for 1000 cycles at 3 A g–1. The in situ construction of a protective film on the Zn anode from natural protein molecules provides an effective strategy to achieve high-performance Zn metal anodes for Zn-ion batteries.

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

“…Previously, it has been demonstrated that adding a small amount of additives to the aqueous electrolytes, such as glucose, [25] saccharin, [26] silk fibroin, [27] and diamine tetraacetic acid tetrasodium salt (Na 4 EDTA), [28] are able to preferentially adsorb on the Zn surface and form a protective layer, which not only has good insulating behavior to inhibit the corrosion of Zn-metal but also shows superior Zn affinity to promote homogeneous Zn deposition. Unfortunately, those physically absorbed layers can be easily detached from the Zn surface…”

Interface Reversible Electric Field Regulated by Amphoteric Charged Protein-Based Coating Toward High-Rate and Robust Zn Anode

“…According to Fick’s law and Poisson's equation, the diffusion flux of ions was relative to the concentration gradient of ions and the distribution of the electric field [ 27 ]. The liquid-phase ion transport (57 mS cm −1 ) in the electrolyte was much faster than the solid-state diffusion in the coating (2 mS cm −1 ), so the solid-state ion transport inside the coating could be crucial for anodic polarization (Zn anode with coating usually had higher overpotential than those of bare Zn due to stronger chemisorption of coating toward Zn 2+ ) [ 11 , 23 , 46 ]. Therefore, an enhanced interface electric field by SF coating could expedite Zn2 + flux and further homogenize the ion transport to form the even ion flux, finally realizing the enhanced transport kinetics [ 47 ].…”

“…Compared to the reports using silk fibroin as an electrolyte additive, the electric field generated additional driving force. Therefore, the Zn-SF anodes showed a lower voltage hysteresis than those of electrolyte additive-based Zn anodes [ 29 , 46 ]. In contrast, the bare Zn anode displayed similar voltage at the low rate but rapid growth (206 mV, 40C) with unstable stripping/plating at the high rate.…”

Development of Proteins for High‐Performance Energy Storage Devices: Opportunities, Challenges, and Strategies

“…The development of electrolyte additives that can improve electrochemical performances over the existing electrolyte systems has become increasingly attractive recently. [59][60][61][62][63][64] The advantages of using additives are low preparation cost, easy processing, and minimum influence on the battery's interior environment. For example, in 2021, Han et al investigated the influence of adding gelatin into an aqueous electrolyte in Zn-ion batteries.…”