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Polyacrylamide hydrogel electrolytes with highly concentrated salt solutions have been developed for solid-state supercapacitors of slow self-discharge. When the supercapacitors are charged by a triboelectric nanogenerator, a much enhanced charging efficiency has been obtained.

As the most promising next-generation lithium-ion battery anode materials, porous silicon-based materials are attracting great attention nowadays, mainly because of silicon's exceptionally high lithium storage capacity. However, how to realize the large-scale manufacture of these materials at low cost still remains a big challenge. In this work, we report the direct preparation of porous Si materials from metallurgical-grade Si in an autoclave, which is the most environmentally friendly route to produce alkoxysilane monomers in the organic silicon industry. In this reaction, Cu-based catalysts catalyze the reaction of Si particles with alcohols to create a porous structure within Si, followed by carbon deposition via the chemical vapor deposition method. The micro-morphology and -structure of the porous Si materials can be well tuned by adjusting the synthesis conditions. When used as the anode materials for lithium ion batteries, the charge capacity of the obtained porous Si/C materials was 1240 mA h g(-1) at a current density of 50 mA g(-1) after 50 cycles, much higher than that of the commercial graphite. This work provides an economic and scalable approach to the preparation of porous Si/C anode materials from commercial Si powders for lithium ion batteries.

We report the preparation of porous silicon/carbon microspheres (GPSCMs) by the ball milling and spray drying methods followed by carbonization and chemical vapor deposition processes, in which, the waste fine graphitized needle coke and silicon nanoparticles were employed as the carbon and silicon sources respectively, and sucrose as the binder. The samples were characterized by X-ray diffraction, transmission electron microscopy, scanning electron microscopy, nitrogen adsorption, thermogravimetric analysis, and Raman spectroscopy. It was found that GPSCMs had spherical sizes of 8–30 μm and surface areas between 20 and 90 m2 g−1. When used as the anode materials for lithium ion batteries, the average charge capacity was 589 mA h g−1 at a current density of 50 mA g−1, much higher than that of the commercial graphite microspheres (GMs). Furthermore, GPSCMs exhibited much better rate performance than the commercial GMs, making them promising for use as the next generation anode materials in lithium ion batteries.

We report the facile preparation of graphitized porous carbon microspheres (GPCMs) by the spray drying technique using carbon black (CB) nanoparticles as the primary carbon resource and sucrose as the binder, followed by graphitization at 2800 °C. The samples were characterized by X-ray diffraction, transmission electron microscopy, scanning electron microscopy, nitrogen adsorption, thermogravimetric analysis, and Raman spectroscopy. It is found that the GPCMs with a size of 5–20 μm delivered a reversible capacity of 459 mA h g−1 at the current density of 50 mA g−1 after 100 cycles, much higher than that of the commercial graphite microspheres (GMs) (372 mA h g−1). More importantly, GPCMs exhibited excellent rate performances with a capacity of 338 and 300 mA h g−1 at the current densities of 500 and 1000 mA g−1 respectively, superior to those of GMs (200 and 100 mA h g−1). The excellent electrochemical properties of GPCMs originate from its unique structure, which is composed of core–shell nanoparticles with the graphitized carbon core derived from CB nanoparticles and the hard carbon shell generated from sucrose, providing more lithium ion storage sites, higher electronic conductivity, and fast ion diffusion. This work opens a simple way to large-scale production of new carbon anode materials with a low cost and good performance for Li-ion batteries.

We report the synthesis and characterization of mesoporous cobalt ferrite (CoFe2O4, named CFO) nanospheres cross-linked by carbon nanotubes (CNTs) as anode nanocomposites (CFO/CNT) for Li-ion batteries. CFO/CNT nanocomposites were synthesized by a facile one-pot solvothermal method using Co(CH3COO)2 and FeCl3 as the metal precursors in the presence of CH3COOK, CH3COOC2H5, HOCH2CH2OH, and CNTs. The obtained samples were characterized by X-ray diffraction, thermogravimetric analysis, nitrogen adsorption, transmission electron microscopy, and scanning electron microscopy. It is found that most CFO nanospheres are interconnected with CNTs forming a network composite possibly due to the presence of defects at the open ends and on the external surface of CNTs. These defects may act as nucleation centers for growth of CFO nanospheres. Compared with the bare CFO nanospheres and the physically mixed CFO nanospheres with CNTs, the CFO/CNT composite containing 16.5 wt% CNTs shows much higher capacities of 1137.6, 1003.4, 867.3, and 621.7 mA h g−1 at the current densities of 200, 500, 1000, and 2000 mA g−1 after 10 charge–discharge cycles, respectively, and even after 100 cycles, it still maintains a high capacity of 1045.6 mA h g−1 at 200 mA g−1. The super electrochemical properties of the CFO/CNT composite should originate from the formed network structure with the intimate interconnection between CFO nanospheres and CNTs, which not only provides stable electrical and ionic transfer channels but also significantly shortens the diffusion length of the Li+ ions. This work opens a new way for fabrication and utilization of metal oxide–CNT composites as anode materials for Li-ion batteries.