Herein, high-content N-doped carbon nanotube (CNT) microspheres (HNCMs) are successfully synthesized through simple spray drying and one-step pyrolysis. HNCM possesses a hierarchically porous architecture and high-content N-doping. In particular, HNCM800 (HNCM pyrolyzed at 800 °C) shows high nitrogen content of 12.43 at%. The porous structure derived from well-interconnected CNTs not only offers a highly conductive network and blocks diffusion of soluble lithium polysulfides (LiPSs) in physical adsorption, but also allows sufficient sulfur infiltration. The incorporation of N-rich CNTs provides strong chemical immobilization for LiPSs. As a sulfur host for lithium-sulfur batteries, good rate capability and high cycling stability is achieved for HNCM/S cathodes. Particularly, the HNCM800/S cathode delivers a high capacity of 804 mA h g −1 at 0.5 C after 1000 cycles corresponding to low fading rate (FR) of only 0.011% per cycle. Remarkably, the cathode with high sulfur loading of 6 mg cm −2 still maintains high cyclic stability (capacity of 555 mA h g −1 after 1000 cycles, FR 0.038%). Additionally, CNT/Co 3 O 4 microspheres are obtained by the oxidation of CNTs/Co in the air. The as-prepared CNT/Co 3 O 4 microspheres are employed as an anode for lithium-ion batteries and present excellent cycling performance.

rGO/g-C 3 N 4 and rGO/g-C 3 N 4 /CNT microspheres are synthesized through the simple ethanol-assisted spray-drying method. The ethanol, as the additive, changes the structure of the rGO/g-C 3 N 4 or rGO/g-C 3 N 4 /CNT composite from sheet clusters to regular microspheres. In the microspheres, the pores formed by reduced graphene oxide (rGO), g-C 3 N 4 , and carbon nanotube (CNT) stacking provide physical confinement for lithium polysulfides (LiPSs). In addition, enriched nitrogen (N) atoms of g-C 3 N 4 offer strong chemical adhesion to anchor LiPSs. The dual immobilization mechanism can effectively alleviate the notorious "shuttle effect" of the lithium−sulfur battery. Meanwhile, the cathode with high cyclic stability can be achieved. The rGO/g-C 3 N 4 /CNT/S cathode delivers a discharge capacity of 620 mA h g −1 after 500 cycles with a low capacity fading rate of only 0.03% per cycle at 1 C. Even, the cathode shows a retained capacity of 712 mA h g −1 over 300 cycles with a high sulfur loading (4.2 mg cm −2 ) at 0.2 C. KEYWORDS: rGO/g-C 3 N 4 /CNT microspheres, ethanol-assisted spray drying, high nitrogen content, lithium−sulfur battery

In this work, a new effective and low-cost binder applied in porous silicon anode is designed through blending of low-cost poly(acrylic acid) (PAA) and poly-(ethylene-co-vinyl acetate) (EVA) latex (PAA/EVA) to avoid pulverization of electrodes and loss of electronic contact because of huge volume changes during repeated charge/ discharge cycles. PAA with a large number of carboxyl groups offers strong binding strength among porous silicon particles. EVA with high elastic property enhances the ductility of the PAA/EVA binder. The high-ductility PAA/EVA binder tolerates the huge silicon volume variations and keeps the electrode integrity during the charge/discharge cycle process. EVA colloids acting as host materials for electrolytes increase the electrolyte uptake of electrodes. The porous silicon electrode with the PAA/EVA binder exhibits a reversible capacity of 2120 mA h g −1 at 500 mA g −1 after 140 cycles because of the excellent ductility and lithium-ion transport properties of the PAA/EVA binder.

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MXenes have great application prospect in energy storage fields due to a series of special physicochemical properties. However, the application of MXenes is greatly limited due to low intrinsic capacity. Here, through spray drying and vapor deposition methods, N-doped Ti3C2T x and phosphorus composites (N–Ti3C2T x /P) were prepared for the first time. The red phosphorus particles were absorbed to a walnut-like N–Ti3C2T x matrix, facilitating the transport of Li+ and electrons. When used as anodes for lithium-ion batteries, the battery can cycle up to 1040 cycles with a high stable capacity of 801 mAh/g at 500 mA/g. Impressively, there is an obvious increase of capacity in the subsequent cycles at higher current density due to the increment of interlayer spacing of Ti3C2T x nanosheets. XPS measurements confirm that the Ti–O–P bond was formed in the composites, granting the robust structure of the composites and leading to superior performances during cycling. The facile synthesis method of red phosphorus by vapor deposition will facilitate the development of other 2D materials combined with high-capacity red phosphorus for energy storage.