Texture and surface morphology in zinc electrodeposits

Influence of Electrolyte Choice on Zinc Electrodeposition

Zinc electrodeposition serves as a crucial electrochemical process widely employed in various industries, particularly in automotive manufacturing, owing to its cost effectiveness compared to traditional methods. However, traditional zinc electrodeposition using aqueous solutions faces challenges related to toxicity and hydrogen gas generation. Non-aqueous electrolytes such as ionic liquids (ILs) and deep eutectic solvents (DESs) have gained attention, with choline-chloride-based DESs showing promise despite raising environmental concerns. In this study, zinc electrodeposition on mild steel was investigated using three distinct electrolytes: (i) halide-free aqueous solutions, (ii) chloride-based DES, and (iii) halide-free acetate-based organic solutions. The study examined the influence of deposition time on the growth of Zn on mild steel substrates from these electrolytes using physical characterization techniques, including scanning electron microscopy (SEM) and X-ray diffraction (XRD). The results indicate that glycol + acetate-based non-aqueous organic solutions provide an eco-friendly alternative, exhibiting comparable efficiency, enhanced crystalline growth, and promising corrosion resistance. This research contributes valuable insights into the impact of electrolyte choice on zinc electrodeposition, offering a pathway towards more sustainable and efficient processes. Through a comprehensive comparison and analysis of these methods, it advances our understanding of the practical applications of zinc electrodeposition technology.

Nonepitaxial Electrodeposition of (002)-Textured Zn Anode on Textureless Substrates for Dendrite-Free and Hydrogen Evolution-Suppressed Zn Batteries

Nontoxic and safe aqueous Zn batteries are largely restricted by the detrimental dendrite growth and hydrogen evolution of Zn metal anode. The (002)-textured Zn electrodeposition, demonstrated as an effective approach for solving these issues, is nevertheless achieved mainly by epitaxial or hetero-epitaxial deposition of Zn on pre-textured substrates. Herein, the electrodeposition of (002)-textured and compact Zn on textureless substrates (commercial Zn, Cu, and Ti foils) at a medium-high galvanostatic current density is reported. According to the systematic investigations on Zn nucleation and growth behaviors, this is ascribed to two reasons: i) the promoted nonepitaxial nucleation of fine horizontal (002) nuclei at increased overpotential and ii) the competitive growth advantages of (002)-orientated nuclei. The resulting freestanding (002)-textured Zn film exhibits significantly suppressed hydrogen evolution and prolonged Zn plating-stripping cycling life, achieving over 2100 mAh cm^-2 cumulative capacity under a current density of 10 mA cm^-2 and a high depth of discharge (DOD) of 45.5%. Therefore, this study provides both fundamental and practical insights into long-life Zn metal batteries.

Horizontally arranged zinc platelet electrodeposits modulated by fluorinated covalent organic framework film for high-rate and durable aqueous zinc ion batteries

Rechargeable aqueous zinc-ion batteries (RZIBs) provide a promising complementarity to the existing lithium-ion batteries due to their low cost, non-toxicity and intrinsic safety. However, Zn anodes suffer from zinc dendrite growth and electrolyte corrosion, resulting in poor reversibility. Here, we develop an ultrathin, fluorinated two-dimensional porous covalent organic framework (FCOF) film as a protective layer on the Zn surface. The strong interaction between fluorine (F) in FCOF and Zn reduces the surface energy of the Zn (002) crystal plane, enabling the preferred growth of (002) planes during the electrodeposition process. As a result, Zn deposits show horizontally arranged platelet morphology with (002) orientations preferred. Furthermore, F-containing nanochannels facilitate ion transport and prevent electrolyte penetration for improving corrosion resistance. The FCOF@Zn symmetric cells achieve stability for over 750 h at an ultrahigh current density of 40 mA cm^-2. The high-areal-capacity full cells demonstrate hundreds of cycles under high Zn utilization conditions.

Anion Texturing Towards Dendrite-Free Zn Anode for Aqueous Rechargeable Batteries

The reversibility of metal anode is a fundamental challenge to the lifetime of rechargeable batteries. Though being widely employed in aqueous energy storage systems, metallic zinc suffers from dendrite formation that severely hinders its applications. Here we report texturing Zn as an effective way to address the issue of zinc dendrite. An in-plane oriented Zn texture with preferentially exposed (002) basal plane is demonstrated via a sulfonate anion-induced electrodeposition, noting no solid report on (002) textured Zn till now. Anion-induced reconstruction of zinc coordination is revealed to be responsible for the texture formation. Benchmarking against its (101) textured-counterpart by the conventional sulphate-based electrolyte, the Zn (002) texture enables highly reversible stripping/plating at a high current density of 10 mA cm^-2 , showing its dendrite-free characteristics. The Zn (002) texture-based aqueous zinc battery exhibits excellent cycling stability. The developed anion texturing approach provides a pathway towards exploring zinc chemistry and prospering aqueous rechargeable batteries.

Effect of crystallographic orientation on the tribological behavior of electrodeposited Zn coatings

Tribo/transfer film evolution during sliding wear of steel contact on oriented Zn coatings.