Realizing Textured Zinc Metal Anodes through Regulating Electrodeposition Current for Aqueous Zinc Batteries

Guiding Zn Uniform Deposition with Polymer Additives for Long-lasting and Highly Utilized Zn Metal Anodes

The parasitic side reaction on Zn anode is the key issue which hinders the development of aqueous Zn-based energy storage systems on power-grid applications. Here, a polymer additive (PMCNA) engineered by copolymerizing 2-methacryloyloxyethyl phosphorylcholine (MPC) and N-acryloyl glycinamide (NAGA) was employed to regulate the Zn deposition environment for satisfying side reaction inhibition performance during long-term cycling with high Zn utilization. The PMCNA can preferentially adsorb on Zn metal surface to form a uniform protective layer for effective water molecule repelling and side reaction resistance. In addition, the PMCNA can guide Zn nucleation and deposition along 002 plane for further side reaction and dendrite suppression. Consequently, the PMCNA additive can enable the Zn//Zn battery with an ultrahigh depth of discharge (DOD) of 90.0 % for over 420 h, the Zn//active carbon (AC) capacitor with long cycling lifespan, and the Zn//PANI battery with Zn utilization of 51.3 % at low N/P ratio of 2.6.

Self-Decoupled Oxygen Electrocatalysis for Ultrastable Rechargeable Zn-Air Batteries with Mild-Acidic Electrolyte

Rechargeable zinc-air batteries (ZABs) have been considered promising as next-generation sustainable energy storage devices; however, their large-scale deployment is hampered by the unsatisfactory cyclic lifespan. Employing neutral and mild-acidic electrolytes is effective in extending the cyclability, but the rapid performance degradation of the bifunctional catalysts owing to different microenvironmental requirements of the alternative oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is still a serious limitation of their cyclic life. Herein, we propose a "self-decoupling" strategy to significantly improve the stability of the bifunctional catalysts by constructing a smart interface in the bifunctional air electrode. This smart interface, containing a resistance-switchable sulfonic acid doped polyaniline nanoarray interlayer, is nonconductive at high potential but conductive at low potential, which enables spontaneous electrochemical decoupling of the bifunctional catalyst for the ORR and OER, respectively, and thus protects it from degradation. The resulting self-decoupled mild-acidic ZAB delivers stable cyclic performances in terms of a negligible energy efficiency loss of 0.015% cycle-1 and 3 times longer cycle life (∼1400 h) compared with the conventional mild-acidic ZAB using a normal bifunctional air electrode and the same low-cost ZnCo phosphide/nitrogen-doped carbon bifunctional catalyst. This work provides an effective strategy for tolerating alternative oxidation-reduction reactions and emphasizes the importance of smart nanostructure design for more sustainable batteries.

Synergistic Cooperation of Zn(002) Texture and Amorphous Zinc Phosphate for Dendrite-Free Zn Anodes

Zn anodes of aqueous Zn metal batteries face challenges from dendrite growth and side reactions. Building Zn(002) texture mitigates the issues but does not eradicate them. Zn(002) still faces severe challenges from corrosive electrolytes and dendrite growth, especially after hundreds of cycles. Therefore, it is necessary to have a passivation layer covering Zn(002). Here, Zn(002) texture and surface coating are achieved on Zn foils by an one-step annealing process, as demonstrated by ZnS, ZnSe, ZnF₂, Zn₃(PO₄)₂ (ZPO), etc. Using ZPO as a model, the coupling between surface coating and Zn(002) is illustrated in terms of dendrite-suppressing ability and diffusion energy barrier of Zn²⁺. The modified Zn foils (Zn(002)@ZPO) exhibit the excellent electrochemical performance, far superior to Zn(002) or ZPO alone. In the full cells, the performance is greatly improved even under harsh conditions, i.e., high areal capacity and limited Zn resource. This work achieves crystal engineering and surface coating on Zn anodes simultaneously and discloses the in-depth insights about the synergy of crystal orientation and passivation layers.

Examining Concentration-Reliant Zn Deposition/Stripping Behavior in Organic Alcohol/Sulfones-Modified Aqueous Electrolytes

The practical application of Zn metal anodes in electronic devices is hindered by dendrite growth and parasitic reactions. Electrolyte optimization, particularly the introduction of organic co-solvents, is widely used to circumvent these challenges. Various organic solvents in a wide range of concentrations have been reported; however, their influences and corresponding working mechanisms at different concentrations are largely unexplored in the same organic species. Herein, economical, low-flammable ethylene glycol (EG) is used as a model co-solvent in aqueous electrolytes to examine the relationship between its concentration, anode-stabilizing effect, and mechanism. Two maximal values are observed for the lifetime of Zn/Zn symmetric batteries under EG concentrations from 0.05 vol% to 48 vol%. Zn metal anodes can stably run for over 1700 h at a low EG content (0.25 vol%) and high EG content (40 vol%). Based on the complementary experimental and theoretical calculations, the enhancements in low- and high-content EG are ascribed to the specific surface adsorption for suppressed dendrite growth and the regulated solvation structure for inhibited side reactions, respectively. Intriguingly, a similar concentration-reliant bimodal phenomenon is observed in other low-flammable organic solvents (e.g., glycerol and dimethyl sulfoxide), thereby suggesting universality of this study and providing insight into electrolyte optimization.