Flexible Composite Electrolyte Membranes with Fast Ion Transport Channels for Solid-State Lithium Batteries.

Numerous endeavors have been dedicated to the development of composite polymer electrolyte (CPE) membranes for all-solid-state batteries (SSBs). However, insufficient ionic conductivity and mechanical properties still pose great challenges in practical applications. In this study, a flexible composite electrolyte membrane (FCPE) with fast ion transport channels was prepared using a phase conversion process combined with in situ polymerization. The polyvinylidene fluoride-hexafluoro propylene (PVDF-HFP) polymer matrix incorporated with lithium lanthanum zirconate (LLZTO) formed a 3D net-like structure, and the in situ polymerized polyvinyl ethylene carbonate (PVEC) enhanced the interface connection. This 3D network, with multiple rapid pathways for Li+ that effectively control Li+ flux, led to uniform lithium deposition. Moreover, the symmetrical lithium cells that used FCPE exhibited high stability after 1200 h of cycling at 0.1 mA cm-2. Specifically, all-solid-state lithium batteries coupled with LiFePO4 cathodes can stably cycle for over 100 cycles at room temperature with high Coulombic efficiencies. Furthermore, after 100 cycles, the infrared spectrum shows that the structure of FCPE remains stable. This work demonstrates a novel insight for designing a flexible composite electrolyte for highly safe SSBs.

Carbon Deposition Mitigation Strategies in Proton-Conducting Solid Oxide Fuel Cells: A Case Study with Biomass Fuels.

Methanol and ethanol, when used as biomass fuels, demonstrate distinct benefits compared to hydrogen in proton-conducting solid oxide fuel cells (PCFCs) applications. Nevertheless, employing these biomass fuels in PCFCs encounters a significant obstacle due to carbon deposition, adversely affecting the cells' longevity. To mitigate this issue, a dendritic pore channel anode design was implemented to optimize the fuel distribution and utilization efficiency. Additionally, the approach incorporates a co-reforming strategy of fuel and steam, operating the cell under stable output current conditions to mitigate carbon deposition in the cell. Furthermore, the integration of Ru-GDC nanofiber catalysts enhanced the cell's resistance to carbon deposition and improved its stability. Techniques such as argon and oxygen purging, along with thermal regeneration, were investigated for carbon removal. These approaches have proven to be effective in diminishing carbon buildup and restoring cell functionality. Applying these strategies, PCFCs equipped with Ru-GDC fiber catalysts, operating at a stable 700 °C current, demonstrated prolonged stability for 117 h with methanol and 96 h with ethanol, markedly surpassing the performance of untreated cells. These advancements not only alleviate carbon deposition issues in PCFCs utilizing methanol and ethanol but also enhance the potential of biomass fuels in PCFC applications.

Facile Approach for Improving the Interfacial Adhesion of Nanofiber Air Electrodes of Reversible Solid Oxide Cells.

Nanofibers have great promise as a highly active air electrode for reversible solid oxide cells (ReSOCs); however, one thorny issue is how to adhesively stick nanofibers to electrolyte with no damage to the original morphology. Herein, PrBa0.8Ca0.2Co2O5+δ (PBCC) nanofibers are applied as an air electrode by a facile direct assembly approach that leads to the retention of most of the unique microstructure of nanofibers, and firm adhesion of the nanofiber electrode onto the electrolyte is achieved by applying electrochemical polarization. A single cell with the PBCC nanofiber air electrode exhibits excellent maximum power density (1.97 W cm-2), electrolysis performance (1.3 A cm-2 at 1.3 V), and operating stability at 750 °C for 200 h. These findings provide a facile means for the utilization of nanofiber electrodes for high-performance and durable ReSOCs.

Robust Direct Hydrocarbon Solid Oxide Fuel Cells with Exsolved Anode Nanocatalysts.

Perovskite anodes with in situ exsolved nanocatalysts have been proven to overcome carbon deposition and increase anode catalytic activity as an alternative to conventional Ni/YSZ anodes for direct hydrocarbon solid oxide fuel cells (SOFCs). This study, for the first time, demonstrates the state-of-the-art exsolution over cathode-supported SOFCs, which achieve the highest cell performance compared to conventional electrolyte-supported SOFCs with perovskite anodes using CH4 as a fuel. The dendritic channel structure of cathode supports retains a high active surface during high-temperature electrolyte sintering. Sr2Ti0.8Co0.2FeO6-δ perovskite ceramic is employed as anodes, and Co-Fe alloy nanoparticles are exsolved after reduction, which increases the cell power output by about 40%. The peak power densities of the cells are 0.82, 0.59, 0.43, and 0.33 W cm-2 at 800 °C using hydrogen, methane, methanol, and ethanol, respectively. The SOFCs with the exsolved nanocatalysts demonstrate stable power generation up to 110 h using methane, methanol, and ethanol fuels. Interestingly, the perovskite anodes show high methane fuel utilization by the complete oxidation of methane, which is in contrast to the partial oxidation over Ni catalysts. Robust hydrocarbon SOFCs have been developed by coupling anode catalyst exsolution with dendritically channeled cathode supports.

Medium-Entropy SrV1/3Fe1/3Mo1/3O3 with High Conductivity and Strong Stability as SOFCs High-Performance Anode.

Perovskite oxides using solid oxide fuel cells (SOFCs) anodes should possess high chemical stability, adequate electronic conductivity and excellent catalytic oxidation for fuel gas. In this work, the medium-entropy SrV1/3Fe1/3Mo1/3O3 (SVFMO) with Fe, V and Mo co-existing in the B site of a perovskite structure was fabricated in reducing 5% H2/Ar mixed gas: (1) SVFMO demonstrates more stable physicochemical properties when using SOFCs anodes in a reducing environment; (2) the co-existence of Fe, V and Mo in SVFMO forms more small-polaron couples, demonstrating greatly enhanced electronic conductivity. With SVFMO in a porous structure (simulating the porous anode layer), its electronic conductivity can also reach 70 S cm-1 when testing at 800 °C in an H2 atmosphere; (3) SVFMO with more oxygen vacancies achieves higher catalytic ability for fuel gas, as an SOFCs anode layer demonstrates 720 mW cm-2 at 850 °C.

Fe, B, and N Codoped Carbon Nanoribbons Derived from Heteroatom Polymers as High-Performance Oxygen Reduction Reaction Electrocatalysts for Zinc-Air Batteries.

For zinc-air batteries, it is of great importance to heighten the oxygen reduction reaction (ORR) activity of cathode electrocatalysts. Herein, we synthesized carbon nanoribbons doped with Fe, B, and N as high-activity ORR electrocatalysts by a templating method. Benefiting from the melamine fiber (MF) and B doping, the as-prepared carbon nanoribbon has a high specific surface area, and the improved turnover frequency of Fe sites increases the ORR activity. The as-synthesized Fe-B-N-C electrocatalyst shows an improved half-wave potential and limited current density compared to Fe-N-C, B-N-C, and N-C. Moreover, zinc-air batteries with the Fe-B-N-C electrocatalyst exhibit a higher specific capacity and better long-term durability compared to those with commercial Pt/C. This work provides an effective strategy to synthesize noble-metal-free electrocatalysts for wide applications of zinc-air batteries.

Robust Anode-Supported Cells with Fast Oxygen Release Channels for Efficient and Stable CO2 Electrolysis at Ultrahigh Current Densities.

High-temperature electrolysis using solid oxide electrolysis cells (SOECs) provides a promising way for the storage of renewable energy into chemical fuels. During the past, nickel-based cathode-supported thin-film electrolyte configuration was widely adopted. However, such cells suffer from the serious challenge of anode delamination at high electrolysis currents due to enormous gaseous oxygen formation at the anode-electrolyte interface with insufficient adhesion caused by low sintering temperatures for ensuring high anode porosity and cathode pulverization because of potential nickel redox reaction. Here, the authors propose, fabricate, and test asymmetric thick anode-supported SOECs with firm anode-electrolyte interface and graded anode gas diffusion channel for realizing efficient and stable electrolysis at ultrahigh currents. Such a specially structured anode allows the co-sintering of anode support and electrolyte at high temperatures to form strong interface adhesion while suppressing anode sintering. The mixed oxygen-ion and electron conducting anode with graded channel structure provides a fast oxygen release pathway, large anode surface for oxygen evolution reaction, and excellent support for depositing nanocatalysts, to further improve oxygen evolution activity. As a result, the as-prepared cells demonstrate both high performance, comparable or even higher than state-of-the-art cathode-supported SOECs, and outstanding stability at a record current density of 2.5 A cm-2 .

Revealing the Intrinsic Origin for Performance-Enhancing V2O5 Electrode Materials.

Revealing the intrinsic origin is critical for developing performance-enhancing V2O5 battery-type electrode materials. In this work, ultralong single-crystal V2O5 wires (W-V2O5) and V2O5 plate particles (P-V2O5) with similar physicochemical properties were compared to investigate the possible stimulative factors for pseudocapacitive enhancement. Our results indicate that besides the most-discussed specific surface area (or nanostructure), the enhanced electronic conductivity, the controllable interlamellar spacing distance, and the ion-transporting route as intrinsic origin also greatly affect their pseudocapacitive enhancement. First, the ultralong single-crystal wire structure can apparently enhance the electrons transport; second, the unique [001] facet orientation along the wire direction enlarges the interlamellar spacing distance and shortens the Li+ inserting route, thus facilitating the redox reactions by providing fast channels for charge carrier intercalation. Thus W-V2O5 showed much higher capacitance, better rate, and cycling capability than those of P-V2O5. This new insight presented here provides guidance for the design of V2O5 electrode materials and opens new opportunities in the development of high-performance battery-type electrode materials.

Optimization of Cathode Functional Layers of Solid Oxide Electrolysis Cells.

Sluggish CO2 reduction on the cathodes of solid oxide electrolysis cells greatly affects electrolysis performance. However, there is no study systematically investigating the cathode functional layer (CFL), where the reduction occurs. Cathode supports equipped with fast gas diffusion channels were employed as a platform to investigate the CFL, including porosity, NiO/(Y2O3)0.08Zr0.92O2 (YSZ) ratio, and thickness. The porosity was adjusted by pore former content, and a higher porosity generated a higher electrolysis current density, while the porosity improvement is limited by the fabrication process. The three-dimensional microstructure of the CFL with different NiO/YSZ ratios was reconstructed by distance correlation functions to estimate three-phase boundary density, which can explain the optimal NiO/YSZ weight ratio of 60:40 for CO2 electrolysis. Increasing CFL thickness can provide more active sites until the optimal thickness of 35 µm. Further increasing the thickness results in gas diffusion limitation. Based on the channeled cathode supports, the CFL was optimized according to CO2 electrolysis performance.

Composite fuel electrode La(0.2)Sr(0.8)TiO(3-δ)-Ce(0.8)Sm(0.2)O(2-δ) for electrolysis of CO2 in an oxygen-ion conducting solid oxide electrolyser.

Composite Ni-YSZ fuel electrodes are able to operate only under strongly reducing conditions for the electrolysis of CO(2) in oxygen-ion conducting solid oxide electrolysers. In an atmosphere without a flow of reducing gas (i.e., carbon monoxide), a composite fuel electrode based on redox-reversible La(0.2)Sr(0.8)TiO(3+δ) (LSTO) provides a promising alternative. The Ti(3+) was approximately 0.3% in the oxidized LSTO (La(0.2)Sr(0.8)TiO(3.1)), whereas the Ti(3+) reached approximately 8.0% in the reduced sample (La(0.2)Sr(0.8)TiO(3.06)). The strong adsorption of atmospheric oxygen in the form of superoxide ions led to the absence of Ti(3+) either on the surface of oxidized LSTO or the reduced sample. Reduced LSTO showed typical metallic behaviour from 50 to 700 °C in wet H(2); and the electrical conductivity of LSTO reached approximately 30 S cm(-1) at 700 °C. The dependence of [Ti(3+)] concentration in LSTO on P(O(2)) was correlated to the applied potentials when the electrolysis of CO(2) was performed with the LSTO composite electrode. The electrochemical reduction of La(0.2)Sr(0.8)TiO(3+δ) was the main process but was still present up to 2 V at 700 °C during the electrolysis of CO(2); however, the electrolysis of CO(2) at the fuel electrode became dominant at high applied voltages. The current efficiency was approximately 36% for the electrolysis of CO(2) at 700 °C and a 2 V applied potential.

Contra-diffusion synthesis of ZIF-8 films on a polymer substrate.

ZIF-8 films were successfully prepared on a flexible nylon substrate with a contra-diffusion synthesis method, and gas permeation experiments indicated that the films were continuous and compact.