In Situ Pt Migration Enabled Resurrection of Electrocatalyst and Fuel Cell Device.

In direct methanol fuel cells (DMFCs), the poisoning of noble metals is considered to be a major impediment to their commercial development. Here, it is found that the loss of surface Pt is one main reason for the attenuation of catalyst performance during long-time methanol oxidation reaction (MOR). A strategy to realize in situ resurrection of the deactivated catalyst by migrating Pt atoms inside to the surface is innovatively proposed. A high-activity Pt-SnO2 is designed, whose MOR activity is resurrected to 97.4% of the initial value. Based on this, the multiple resurrection of a DMFC device is also achieved for the first time. This work provides a new approach for the solution of catalyst deactivation and the development of sustainable catalysts as well as fuel cells.

Rational Design of Dynamically Super-Tough and Super-Stretchable Hydrogels for Deformable Energy Storage Devices.

Hydrogels possess unique polymer networks that offer flexibility/stretchability, high ionic conductivity, and resistance to electrolyte leakage, making them suitable for deformable energy storage devices. Endowing the mechanical functionality of the hydrogel electrolytes focus on either enhancing the stretchability or the toughness. However, the stretchability and the toughness are generally a trade-off that the stretchable gels are intrinsically prone to damage and sensitive to notches and cracks. Here, the regulating strategies on the hydrogel's mechanical properties are provided to develop the designated hydrogel electrolyte, where different polymeric network structures are constructed, including single network structures, semi-interpenetrating network structures, and interpenetrating dual-network structures. A comprehensive comparison of these polymer network structures is conducted to evaluate their mechanical stretchability and toughness. Designing super-tough and super-stretchable hydrogels based on specific application requirements can be realized by striking a balance by regulating the hydrogel structure. In specific, incorporating semi-interpenetrating networks significantly can enhance stretchability to achieve a break elongation up to 1300%, while the interpenetrating dual-networks can largely improve the toughness to realize the extraordinary fracture toughness of 6.843 kJ m-2. These findings offer valuable designing guidance for designated hydrogel electrolytes and the deformable zinc-silver battery is demonstrated with high mechanical stability and electrochemical performance.

Anion-Cation Competition Chemistry for Comprehensive High-Performance Prussian Blue Analogs Cathodes.

The extensively studied Prussian blue analogs (PBAs) in various batteries are limited by their low discharge capacity, or subpar rate etc., which are solely reliant on the cation (de)intercalation mechanism. In contrast to the currently predominant focus on cations, we report the overlooked anion-cation competition chemistry (Cl-, K+, Zn2+) stimulated by high-voltage scanning. With our designed anion-cation combinations, the KFeMnHCF cathode battery delivers comprehensively superior discharge performance, including voltage plateau >2.0 V (vs. Zn/Zn2+), capacity >150 mAh g-1, rate capability with capacity maintenance above 96 % from 0.6 to 5 A g-1, and cyclic stability exceeding 3000 cycles. We further verify that such comprehensive improvement of electrochemical performance utilizing anion-cation competition chemistry is universal for different types of PBAs. Our work would pave a new and efficient road towards the next-generation high-performance PBAs cathode batteries.

Synergistic Modulation of In-Situ Hybrid Interface Construction and pH Buffering Enabled Ultra-Stable Zinc Anode at High Current Density and Areal Capacity.

In aqueous electrolytes, the uncontrollable interfacial evolution caused by a series of factors such as pH variation and unregulated Zn2+ diffusion would usually result in the rapid failure of metallic Zn anode. Considering the high correlation among various triggers that induce the anode deterioration, a synergistic modulation strategy based on electrolyte modification is developed. Benefitting from the unique pH buffer mechanism of the electrolyte additive and its capability to in situ construct a zincophilic solid interface, this synergistic effect can comprehensively manage the thermodynamic and kinetic properties of Zn anode by inhibiting the pH variation and parasitic side reactions, accelerating de-solvation of hydrated Zn2+ , and regulating the diffusion behavior of Zn2+ to realize uniform Zn deposition. Thus, the modified Zn anode can achieve an impressive lifespan at ultra-high current density and areal capacity, operating stably for 609 and 209 hours at 20 mA cm-2 , 20 mAh cm-2 and 40 mA cm-2 , 20 mAh cm-2 , respectively. Based on this exceptional performance, high loading Zn||NH4 V4 O10 batteries can achieve excellent cycle stability and rate performance. Compared with those previously reported single pH buffer strategies, the synergistic modulation concept is expected to provide a new approach for highly stable Zn anode in aqueous zinc-ion batteries.

I3 - /I- Redox Reaction-mediated Organic Zinc-Air Batteries with Accelerated Kinetics and Long Shelf Lives.

The storage time of Zn-air batteries (ZABs) for practical implementation have been neglected long-lastingly. ZABs based on organic solvents promise long shelf lives but suffer from sluggish kinetics. Here, we report a longly storable ZAB with accelerated kinetics mediated by I3 - /I- redox. In the charge process, the electrooxidation of Zn5 (OH)8 Cl2 ⋅H2 O is accelerated by I3 - chemical oxidation. In the discharge process, I- adsorbed on the electrocatalyst changes the energy level of oxygen reduction reaction (ORR). Benefitting from these advantages, the prepared ZAB shows remarkably improved round-trip efficiency (56.03 % vs. 30.97 % without the mediator), and long-term cycling time (>2600 h) in ambient air without replacing any components or applying any protective treatment to Zn anode and electrocatalyst. After resting for 30 days without any protection, it can still directly discharge continuously for 32.5 h and charge/discharge very stably for 2200 h (440 cycles), which is evidently superior to aqueous ZABs (only 0/0.25 h, and 50/25 h (10/5 cycles) by mild/alkaline electrolyte replenishment). This study provides a strategy to solve both storage and sluggish kinetics issues that have been plaguing ZABs for centuries, opening up a new avenue to the industrial application of ZABs.

S-Doping Promotes Pyridine Nitrogen Conversion and Lattice Defects of Carbon Nitride to Enhance the Performance of Zn-Air Batteries.

The efficient operation of Zn-air batteries (ZABs) requires highly active and stable reversible air catalysts. Studies have shown that heteroatom-doped carbonaceous nanomaterials are effective metal-free electrocatalysts for the oxygen evolution reaction (OER) and the oxygen reduction reaction (ORR). Herein, we design a facile and scalable catalyst doping scheme to manufacture S-doped carbon nitride (S-C3N4). Surprisingly, this metal-free catalyst exhibits excellent OER and ORR electrocatalytic activities in alkaline electrolytes, being comparable to those of commercial Pt/C. For the first time, it is proved by experiments that S doping can not only effectively increase the lattice defects of C3N4 but also promote the conversion of pyrrolic nitrogen to pyridine nitrogen, thereby enhancing the bifunctional catalytic activity (OER and ORR). When the catalyst is used as an air electrode for rechargeable ZABs, its performance is obviously better than that provided by commercial Pt/C. Our findings and material design strategies are expected to provide new ideas for the synthesis of various high-performance carbon-based electrocatalysts.

A polyaniline surface-modified Prussian blue analogue cathode for flexible aqueous Zn-ion batteries.

Aqueous Zn-ion batteries have gained popularity due to their low cost and high safety, but their low energy density limits their application scenarios. Although the Prussian blue analogue (PBA) has the characteristics of high redox potential, the poor capacity and cycling performance restrict its further development. Here, we propose a modification strategy of a polyaniline (PANI) coating on zinc ferricyanide (ZnHCF). The PANI coating inhibits the dissolution of ZnHCF and enables the Zn-ion battery to present two long-flat discharge voltage platforms as well as a high capacity of 150 mA h g-1, which provides a new idea for the development of high-performance PBA battery materials. Meanwhile, owing to the spring-like structure, the battery has a high stretchability of 600% and maintains stable electrochemical properties during stretching.

Ultra-High-Capacity and Dendrite-Free Zinc-Sulfur Conversion Batteries Based on a Low-Cost Deep Eutectic Solvent.

Traditional cathodes for aqueous Zn-ion batteries are afflicted by a limited specific capacity and fearful Zn dendrites. Herein, these troubles are disposed of with a conversion-type Zn-S battery and low-cost deep eutectic solvent (DES). By utilizing the optimized electrolyte, the symmetrical Zn battery can stably cycle over 3920 h, which also confers on the Zn-S battery an ultrahigh specific capacity of ∼846 mA h gS-1 and energy density of 259 W h kg-1 at 0.5 A g-1. Importantly, the conversion chemistry of S and ZnS is responsible for the superior anti-self-discharge behavior (capacity retention: 94.58 and 68.58% after standing for 72 and 288 h versus Zn//VO2 battery: 76.82 and 47.80% after resting for 24 and 72 h versus Zn//MnO2 battery: 95.96 and 91.57% after resting for 24 and 72 h, respectively). This work is the first authentication of Zn-S batteries based on a newly developed low-cost DES-based electrolyte, which meanwhile settles the deep-rooted low specific capacity and infamous Zn dendrite issues in conventional (de)intercalation Zn-ion batteries.