A novel red phosphorescent iridium complex containing a carbazole‐functionalized β‐diketonate, Ir(DBQ)2(CBDK) (bis(dibenzo[f,h]quinoxalinato‐N,C2) iridium (1‐(carbazol‐9‐yl)‐5,5‐dimethylhexane‐2,4‐diketonate)) is designed, synthesized, and characterized. The electrophosphorescence properties of a nondoped device using the title complex as an emitter with a device configuration of indium tin oxide (ITO)/N,N′‐diphenyl‐N,N′‐bis(1‐naphthyl)‐1,1′‐diphenyl‐4,4′‐diamine (NPB; 20 nm)/iridium complex (20 nm)/2,9‐dimethyl‐4,7‐diphenyl‐1,10‐phenanthroline (BCP; 5 nm)/tris(8‐hydroxyquinoline) (AlQ; 30 nm)/Mg0.9Ag0.1 (200 nm)/Ag (80 nm) are examined. The results show that the nondoped device achieves a maximum lumen efficiency as high as 3.49 lm W–1. To understand this excellent result observed, two reference complexes Ir(DBQ)2(acac), where acac is the acetyl acetonate anion, and Ir(DBQ)2(FBDK), [bis(dibenzo[f,h]quinoxalinato‐N,C2) iridium (1‐(9‐methyl‐fluoren‐9‐yl)‐6,6‐dimethylheptane‐3,5‐diketonate)], have also been synthesized, and as emitters they were examined under the same device configuration. The maximum lumen efficiency of the former compound is found to be 0.26 lm W–1 while that for the latter is 0.37 lm W–1, suggesting that the excellent performance of Ir(DBQ)2(CBDK) can be attributed mainly to an improved hole‐transporting property that benefits the exciton transport. In addition, a bulky diketonate group separates the emitter centers from each other, which is also important for organic light‐emitting diodes.

A hybrid Li−air battery uses a protected lithium anode and a porous air cathode in an aqueous electrolyte, based on a 4-e oxygen reduction reaction/oxygen evolution reaction (ORR/OER). It avoids the insoluble and insulating Li 2 O 2 product in a typical nonaqueous Li−air battery, and it owns unique advantages. A bifunctional cathode catalyst is crucial to battery performance. Here, we synthesize an ultrathin N-doped grapheneencapsulated nanosphere Co−Ni alloy (Co−Ni@NG). It has hierarchical architecture consisting of a uniform Co−Ni nanoalloy coated with a thin layer of N-doped graphene, showing high activity, high stability, and lower overpotential between the ORR and OER (0.55 V between onset potentials). It exhibited a discharge/charge voltage gap of 0.55 V at a current density of 1.4 mA cm −2 , which is much smaller than the commercial Pt/C catalyst. It delivered an energy density of 3158 Wh kg −1 and a power density as high as 134.2 W m −2 at a current density of 7 mA cm −2 . The graphene shells protect the alloy catalyst and improve the durability of the catalyst. One hundred cycles were demonstrated without significant deterioration. It was testified as a promising energy storage system with high energy density, efficiency, reliability, and durability.

No abstract

No abstract

Battery separators play a vital role in the safety, sustainability, and electrochemical performance of lithium ion batteries (LIBs). In this work, thermally resistant composite membranes were fabricated by a wet-laid process using northern bleached softwood kraft (NBSK) fibers, polysulfonamide (PSA) fibers, and nanofibrillated cellulose (NFC), for lithium ion battery applications. NFC functioned as a mediator to control and optimize pore size in the composite membranes, while the PSA fibers provided superior heat resistance to the membranes. The as-prepared composite separator membranes have more uniform micropores and superior thermal stability and electrolyte absorption in comparison with a commercial separator membrane (Celgard 2350).