One-Dimensional RuO₂/Mn₂O₃ Hollow Architectures as Efficient Bifunctional Catalysts for Lithium–Oxygen Batteries

Abstract

Rational design and massive production of bifunctional catalysts with fast oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) kinetics are critical to the realization of highly efficient lithium-oxygen (Li-O2) batteries. Here, we first exploit two types of double-walled RuO2 and Mn2O3 composite fibers, i.e., (i) phase separated RuO2/Mn2O3 fiber-in-tube (RM-FIT) and (ii) multicomposite RuO2/Mn2O3 tube-in-tube (RM-TIT), by controlling ramping rate during electrospinning process. Both RM-FIT and RM-TIT exhibited excellent bifunctional electrocatalytic activities in alkaline media. The air electrodes using RM-FIT and RM-TIT showed enhanced overpotential characteristics and stable cyclability over 100 cycles in the Li-O2 cells, demonstrating high potential as efficient OER and ORR catalysts.

A General Electrode Design Strategy for Flexible Fiber Micro‐Pseudocapacitors Combining Ultrahigh Energy and Power Delivery

“…The rapid advances in portable/wearable electronics have stimulated ever‐increasing demand in flexible miniature power modules 1, 2, 3. Solid‐state flexible fiber micro‐supercapacitors (m‐SCs) have gained a surge of attentions 1, 2, 3, 4, 5, 6.…”

“…Solid‐state flexible fiber micro‐supercapacitors (m‐SCs) have gained a surge of attentions 1, 2, 3, 4, 5, 6. As for practical applications with microscale fiber devices, the areal performance is becoming an increasingly important evaluation metric, since the active material mass and the device volume are usually negligible 7.…”

“…As for practical applications with microscale fiber devices, the areal performance is becoming an increasingly important evaluation metric, since the active material mass and the device volume are usually negligible 7. However, the major bottleneck for the existing fiber m‐SCs lies in their much lower areal energy density relative to routine planar SCs8 or batteries 2. In this context, considerable efforts were concentrated on exploring proper fiber electrode materials with large capacitance for improving the energy density, while maintaining high power density 1, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17.…”

“…This undoubtedly restricted allowable active material loading, since thicker active material layer may cause poor adhesion, inferior mechanical stability, and high resistivity. In principle, ideal 1D pseudocapactive fiber electrode should consist of high‐surface‐area, conductive and porous framework and concurrently render: (1) efficient long‐range electronic transport; (2) fast ion transport/diffusion; (3) a large fraction of active materials 1, 2. However, as mentioned above, those existing fiber electrodes using 1D metallic wires/or carbonaceous fibers failed to simultaneously satisfy the above three key requirements, thereby resulting in limited areal energy densities and inferior power output 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36.…”

“…As shown in Figure 2d–f, scanning electron microscopy (SEM) observation for the plated metal wire reveals interconnected porous metallic skeletons consisting of a thin conformal coating of nanostructured metal oxides (denoted as MnO 2 /porous Ni wire). Such unique microarchitecture design favors fast electron transport with shortened solid‐state ion diffusion path 2. The cross‐sectional SEM image indicates that the porous Ni “sheath” possesses a thickness of around 100 µm (Figure 2g,h).…”