A Dendrite-Free Zn Anode Co-modified with In and ZnF2 for Long-Life Zn-Ion Capacitors

Stabilizing zinc anodes with sodium lignosulfonate-doped polypyrrole

Despite zinc-based electrochemical energy storage being considered a safe and efficient energy storage system, problems such as uncontrolled dendrite growth, hydrogen precipitation reactions, and corrosion have seriously hindered its commercialization. Mitigating dendrite growth and other associated issues is crucial for the successful commercialization of these systems. Sodium lignosulfonate is an excellent dopant for conductive polymers, which can endow conductive polymers with abundant functional groups. Herein, we propose a sodium lignosulfonate-doped polypyrrole protective layer for zinc anodes with good hydrophilicity, electrical conductivity, and a porous structure, which can effectively inhibit the growth of zinc dendrites and side reactions. The doping of sodium lignosulfonate introduces numerous zincophilic groups. The sulfonate groups enhance zinc ion interaction and regulate flux, while phenolic hydroxyl groups increase zincophilic sites, aiding in the uniform deposition of zinc.

Dynamically Favorable Ion Channels Enabled by a Hybrid Ionic-Electronic Conducting Film toward Highly Reversible Zinc Metal Anodes

Aqueous zinc ion batteries show great promise for future applications due to their high safety and ecofriendliness. However, nonuniform dendrite growth and parasitic reactions on the Zn anode have severely impeded their use. Herein, a hybrid ionic-electronic conducting ink composed of graphene-like carbon nitride (g-C3N4) and conductive polymers (CP) of poly(3,4ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) is introduced to Zn anode using a scalable spray-coating strategy. Notably, the g-C3N4 promotes a screening effect, disrupting the coulombic interaction between the PEDOT+ segments and PSS- chains within CP, thereby reducing interfacial resistance and homogenizing the surface electric field distribution of the Zn anode. Furthermore, the abundant N-containing species and ─SO3 - groups in g-C3N4/CP exhibit strong zincophilicity, which accelerates the diffusion of Zn2+ and disrupts the solvation structure of Zn(H2O)6 2+, thus improving the Zn2+ transfer capability. Consequently, the g-C3N4/CP can powerfully stabilize the Zn2+ flux and thus enable a high coulombic efficiency of 99.47% for 1500 cycles and smooth Zn plating/stripping behaviors more than 3000 h at a typical current density of 1 mA cm-2. These findings shed new light on the Zn electrodeposition process under the mediation of g-C3N4/CP and offer sustainability considerations in designing more stable Zn-metal anodes with enhanced reversibility.

Engineering a High-Strength and Superior-Electrolyte-Wettability Silk Fibroin-Based Gel Interface Achieving Dendrite-Free Zn Anode

Zn metal anode is confronted with notorious Zn dendrite growth caused by inhomogeneous Zn2+ deposition, rampant dendrite growth, and serious interface side reactions, which significantly hinder their large-scale implication. Interface modification engineering is a powerful strategy to improve the Zn metal anode by regulating Zn2+ deposition behavior, suppressing dendrite formation, and protecting the anode from electrolyte corrosion. Herein, we have designed a high-strength and superior-electrolyte-wettability composite gel protective layer based on silk fibroin (SF) and ionic liquids (ILs) on the Zn anode surface by a straightforward spin-coating strategy. The Zn ion transport kinetics and mechanical properties were further improved by following the incubation process to construct a more well-ordered β-sheet structure. Consequently, the incubated composite gel coating serves as a command station, guiding the Zn ion's preferential growth along the (002) plane, resulting in a smooth and uniform deposition morphology. Driven by these improvements, the zinc anode modified with this composite gel exhibits a remarkably long-term cycling lifespan up to 2200 h at 2 mA cm-2, while also displaying superior rate capability. This study represents a landmark achievement in the realm of electrochemical science, delineating a clear pathway toward the realization of a highly reversible and enduring Zn anode.

Ion Sieve Interface Assisted Zinc Anode with High Zinc Utilization and Ultralong Cycle Life for 61 Wh/kg Mild Aqueous Pouch Battery

The cycling stability of a thin zinc anode under high zinc utilization has a critical impact on the overall energy density and practical lifetime of zinc ion batteries. In this study, an ion sieve protection layer (ZnSnF@Zn) was constructed in situ on the surface of a zinc anode by chemical replacement. The ion sieve facilitated the transport and desolvation of zinc ions at the anode/electrolyte interface, reduced the zinc deposition overpotential, and inhibited side reactions. Under a 50% zinc utilization, the symmetrical battery with this protection layer maintained stable cycling for 250 h at 30 mA cm-2. Matched with high-load self-supported vanadium-based cathodes (18-20 mg cm-2), the coin battery with 50% zinc utilization possessed an energy density retention of 94.3% after 1000 cycles at 20 mA cm-2. Furthermore, the assembled pouch battery delivered a whole energy density of 61.3 Wh kg-1, surpassing the highest mass energy density among reported mild zinc batteries, and retained 76.7% of the energy density and 85.3% (0.53 Ah) of the capacity after 300 cycles.