A simple approach to synthesizing γ-Fe2O3 nanoparticles encapsulated by reduced graphene oxide (RGO) sheets is demonstrated for the first time.

No abstract

Lithium–sulfur batteries (Li‐S batteries) are promising next‐generation energy storage systems because of their high‐theoretical energy density. However, the commercialization of Li‐S batteries is still impeded by the aggregation of sulfur, low‐sulfur utilization, shuttling of dissolved polysulfides and sluggish reaction kinetics. Herein, we designed a hierarchically maple leaf‐like structured sulfur electrodes by in‐situ growth of ultrathin sulfur microcrystal on two‐dimensional MXene‐graphene‐cellulose nanofiber (MGN) matrice (denoted as IS‐MGN@S). The sulfur microcrystal as cathode can achieve improved kinetics than bulk sulfur due to its few layers of sulfur atoms, which is proved by the density functional theory calculations. The MXene not only confines polysulfides through strong chemisorption but also promotes the catalytic conversion of polysulfides. The introduction of graphene improves the conductivity and boosts the immobilization and conversion of polysulfides. As a result, the IS‐MGN@S cathode demonstrates remarkable electrochemical properties with a high‐initial capacity (1229 mAh g−1 at 0.2C), substantial improvement in rate capability (770 mAh g−1 at 2C), and stable long‐term cycling capacity. Moreover, the pouch cells with IS‐MGN@S cathode and gel electrolyte demonstrate excellent mechanical properties under mechanical damage (nail & cut tests, severe deformations), suggesting their promising applications for wearable electronic devices.

Rational structure and morphology design of catalytic cathode materials is the key to realize excellent performances of lithium-oxygen batteries (LOBs). Herein, a three-dimensional (3D) open-structured Co 3 O 4 @MnO 2 heteromatrix has been designed through a facile two-step hydrothermal method. Unexpectedly, when it serves as oxygen reduction reaction/oxygen evolution reaction bifunctional catalytic cathodes for lithiumoxygen cells, the 3D open-structured Co 3 O 4 @MnO 2 heteromatrix-catalyzed LOBs exhibit outstanding electrochemical performances (a high specific capacity of 12,980 mA h g −1 during the initial discharge and long cycle life of 331, 197, and 14 times with specific capacities fixed at 500, 1000, and even 3000 mA h g −1 , respectively), obviously superior to reported batteries based on low-dimensional and closed-ended catalysts. We find that the enhanced electrochemical performances are ascribed to the bifunctional catalyst and the 3D open structure of the Co 3 O 4 @MnO 2 heteromatrix, which can guide the homogeneous and fluffy deposition of discharge products Li 2 O 2 , demonstrating a promising application in both LOBs and flexible/wearable Li-air batteries.