Carlos M. Ramos-Castillo

Gel polymer electrolytes (GPEs) for rechargeable zinc–air batteries (ZABs) are commonly stabilized through chemical crosslinking or thermal treatments, which increase processing complexity and may compromise electrolyte transport. Herein, we demonstrate an alternative stabilization strategy based on hydrogen‐bond engineering through the incorporation of low‐molecular‐weight polyols into poly(vinyl alcohol)–poly(acrylic acid) (PVA–PAA) matrices. Glycerol (G) and ethylene glycol (EG) were incorporated to produce crosslinker‐free GPEs without thermal curing (PP‐G and PP‐EG), which were compared with thermally treated PVA–PAA (PP‐T). PP‐G exhibited a higher degree of local chain ordering, a larger electrostatic potential ( μ = 13.64 D), the highest KOH uptake (1080%), and the highest ionic conductivity (208 mS cm ⁻¹ ). Although glycerol reduced the strain at break from 121% (PP‐T) to 82%, the resulting polymer network maintained excellent structural integrity while significantly improving electrochemical performance. Rechargeable ZABs assembled with PP‐G delivered a power density of 54 mW cm ⁻² , an areal capacity of 10 mAh cm ⁻² , and stable cycling over 500 charge–discharge cycles (80 h). More importantly, the enhanced electrolyte retention enabled stable battery operation at temperatures up to 85 °C, demonstrating that multifunctional additive‐induced stabilization provides a simple route toward high‐temperature ZABs capable of exploiting low‐grade waste heat.

Developing bifunctional oxygen electrocatalysts that simultaneously provide catalytic activity, electronic transport, and operational durability remains a major challenge in the development of rechargeable zinc–air batteries (RZABs). Here, thermally reconstructed Ni–MoS₂/Ni₂Mo₆S₈ heterostructures supported on N-doped CNT/graphene were investigated to clarify how defect-rich MoS₂ domains, conductive Ni–Mo–S interfacial species, and catalyst–support coupling collectively govern the bifunctional air-electrode behavior. Structural analyses revealed that thermal treatment regulates the balance between accessible defect-rich lamellae and more consolidated heterostructures containing Chevrel-type Ni₂Mo₆S₈ domains. Compared to the 900 °C sample (N9N), the 800 °C material (N8N) retained a more open lamellar architecture, a higher surface abundance of Ni–Mo–S species, and more favorable interfacial accessibility. This structural state translates into the best overall bifunctional response within the studied series, with an ORR limiting current density of 5.65 mA cm^–2, OER potential of 1.572 V at 10 mA cm^–2, and a bifunctional gap of 909 mV. When implemented as the air electrode in RZABs, N8N delivered a maximum power density of 90 mW cm^–2 and sustained superior cycling durability relative to Pt/C + IrO₂/C under repeated charge–discharge operations. The results show that durable RZAB performance is dictated not only by electrochemically active surface area or phase conductivity but also by the cooperative integration of catalytically accessible sulfide domains, conductive interfacial phases, and transport-compatible electrode architecture.

Metal‐air batteries have attracted attention due to their high energy density and low cost compared to conventional ion batteries. One of the primary challenges for metal‐air devices is the development of air electrodes using a fast, easily controlled, and mild‐condition methodology. In this work, bifunctional electrocatalysts for oxygen reduction and evolution reactions (ORR/OER) based on metal‐organic frameworks (MOFs) were prepared using terephthalic acid as ligand and Ni, Co, and Fe as metal centers onto carbon cloths through a quick and easy method, such as electrodeposition. Fe incorporation into Co‐Ni terephthalate drives a remarkable electrocatalytic improvement, decreasing the overpotential for OER (@ 10 mA cm ⁻² ) and exhibiting a Tafel slope value of 28 mV dec ⁻¹ . Meanwhile, incorporating Fe also improves the electrocatalytic behavior towards ORR, achieving a Tafel slope of 157 mV dec ⁻¹ and a 4 e ⁻ pathway. Introducing Fe modifies the electronic structure, changing the electronic density of neighboring metals (Ni and Co) and promoting these active sites. Finally, an aqueous zinc‐air battery assembled using NiCoFe‐MOF films as the positive electrode exhibited a constant cell voltage of 1.2 V under open‐circuit conditions. The battery remained stable during the galvanostatic charging‐discharging process at 5 mA cm ⁻² (0.83 mAh cm ⁻² ) for 9 days with a round‐trip efficiency of around 52%, delivering a maximum energy density of 8 Whm ⁻² with an energetic efficiency of up to 66%. These results demonstrate the viability of using a fast and economical approach to construct ready‐to‐use oxygen electrodes for metal‐air batteries in 10 min.

The search for cost‐effective, high‐performance bifunctional catalysts for Zn‐air batteries (ZABs) requires extensive research into precious‐metal‐free materials. This study provides insight into the synergy between nickel cobaltite and P,N‐doped carbon modified through interface engineering by inducing oxygen vacancies in the spinel and non‐metallic heteroatoms in the carbon material. NiCo₂O₄ with various oxygen vacancy levels was synthesized via an ethylene glycol‐assisted solvothermal route. This resulted in significant changes in the structural and morphological properties, such as reduced crystallite size, lattice distortion, and increased oxygen vacancies, as observed from the physicochemical results. This was further verified by X‐ray photoelectron spectroscopy (XPS) and high‐resolution transmission electron microscopy (HR‐TEM), which showed a homogeneous dispersion of nickel cobaltite nanorods on the carbonaceous matrix, along with an increased concentration of pyridinic nitrogen and the formation of P−N and P−C bonds, both of which enhance electrocatalytic activity. NiCo₂O₄DI/P,N−C exhibited superior discharge polarization behavior, achieving power and current densities of 124.4 mW cm⁻² and 215.8 mA cm⁻². Stability tests revealed that the catalyst had excellent performance, lasting up to 100 h, while Pt‐IrO₂/C lasted only up to 21 h. These results demonstrate the great potential of tailoring surface defects and heteroatom doping via interface engineering, resulting in high‐performance precious‐metal‐free electrocatalysts for long‐lasting and high‐efficiency ZABs.

Cathodic materials significantly influence the performance, durability, and sustainability of primary zinc‐air batteries (ZABs). This study focuses on the rational design of highly active metal‐free composites by tailoring the content of N and S heteroatoms in carbon nanotube‐graphene (CNTG) composites. The oxygen reduction reaction (ORR) tests showed onset potentials (E_o) of 0.88 V (N‐CNT) and 0.89 V (N‐graphene) for individual materials and 0.92 V for the N‐CNTG composite, highlighting the advantage of using a composite materialThe N content varied with dicyandiamide and urea, displaying changes in the surface area and N content (7.09 vs. 5.30 at. %), and in pyridinic and quaternary N species. The N content varied with dicyandiamide and urea, showing changes in the surface area and N content (7.09 vs. 5.30 at. %), and in pyridinic and quaternary N species. The abundance of pyridinic‐N species in N‐CNTG using urea enabled a higher ORR activity (E_o=0.92 V). The S incorporation through thiourea improved the E_o to 0.94 V (Pt/C=1.03 V). And, the combination of urea and thiourea resulted in a highly active and durable N,S‐CNTG material, displaying a E_o of 0.96 V, and an activity loss of 8.7 % (Pt/C=25.4 %) after 2000 cycles. In ZAB mode, this material displayed a voltage of 1.35 V, a power density of 107 mW cm⁻², and a specific capacity of 1060 mA h g⁻¹.

Zinc‐air batteries (ZABs) with metal‐free cathodes are considered environmentally friendly and cost‐effective. However, more active and durable catalysts are required for this purpose. Herein, polyaniline (PANI)‐derived carbon materials were obtained to boost the oxygen reduction reaction (ORR) and, consequently, the performance of a primary ZAB. The developed porous N‐doped carbon (NDC) materials were engineered by varying the polymerization time and calcination temperature (500–900 °C). SEM micrographs and BET surface areas showed that the polymerization of aniline under cold conditions (5 °C) at 6, 8, or 24 h did not have a significant effect on the morphology or surface area. The fibrous structure of PANI was engineered by temperature, resulting in a progressive increase in the surface area until a three‐dimensional porous structure was achieved at 900 °C with the highest area of 601.9 m² g⁻¹. The surface doping of nitrogen species shifted from PANI‐rich N species to enriched graphitic N from 12.69 % (500 °C) to 24.26 % at 900 °C. The NDC 900 °C presented a voltage of 1.4 V and power density of 56 mW cm⁻² (only 7 mW cm⁻² lower than that of Pt/C). The results demonstrate that this material is an excellent candidate for high‐performance primary ZABs.