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Among many candidates, silicon anode materials have been considered as one of the most promising materials for the next generation Li-ion batteries to replace widely used graphite anode materials, due to its high capacity, abundant source, environmental friendly and potential low cost. However, practical applications of silicon anode materials are still quite challenge due to large volume change and serious interfacial side reactions. Many strategies have been purposed and evaluated over last two decades. It seems that SiO x , Si-M alloy and nano-Si/C composite are more promising materials. In this review, scientific and technological problems and possible solutions of nano-Si/C composite anode for Li-ion batteries are summarized.Lithium-ion batteries have the advantages of high energy density, good rate capability, long cycle life, low self-discharge rate. [1][2][3][4] Since the first commercial application in the portable electronic devices market in 1991, 5 three generations of Li-ion batteries have been developed, as listed in Figure 1.The energy density of commercial Li-ion batteries has been improved from 90 Wh kg −1 to 245 Wh kg −1 . 6 (note: a prototype of 30 Ah Li-ion battery using Si-based anode material and Ni-riched cathode material achieved 330 Wh kg −1 , as claimed by Hitachi Chemical in November 18, 2014, Japanese Battery Symposium). The applications of lithium-ion batteries have been extended to many emerging markets, including electric bikes and vehicles, large scale energy storage, back-up power sources and power tools. 7 For most of applications, the energy densities of the advanced Li-ion batteries are still far from satisfactory. The calls for battery revolutionary have been heard every day.According to theoretical energy density calculations based on thermodynamic data, 6 the rechargeable batteries using metallic lithium as anode could achieve the highest energy densities for electrochemical energy storage devices, as shown in Figure 2. 8,9 Currently, metallic lithium anodes in nonaqueous batteries suffer from the formation of lithium dendrites and holes, growth of the instable solid electrolyte interphase (SEI) and exhaustion of electrolyte caused by the side reactions. Great efforts are needed to solve these problems. 10 In view of short term targets, it is more practical to develop the third generation Li-ion batteries, in which Si-based materials are used in anodes.Silicon is the most attractive choice as anode material in lithiumion batteries to replace graphite. It has a theoretical capacity of 4200 mAh g −1 for forming Li 22 Si 5 and 3580 mAh g −1 for forming Li 15 Si 4 , 11,12 which is 10 times higher than 350-365 mAh g −1 of commercial graphitic anode materials. Si is environmental friendly and has abundant source and low cost for precursors. However, after 20 years R&D, it is realized that the use of the high capacity Si-based anode materials is still very difficult in full Li-ion batteries. In this short review, the main scientific and technoligical problems of the nano-Si/C compo...

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A reduction of Fe3O4 nanowires in nanoscopic reactors of amorphous C:H nanotubes (a-CNTs) was taken to understand features of the chemical reaction mechanism in nanoscale reactors. Fe3O4 nanowires encapsulated in a-CNTs were reduced into iron at a relatively low temperature of 570 degrees C, producing iron nanoparticles encapsulated in CNTs accompanied by the crystallization of the a-CNT shell. It was found that carbon in the a-CNT shell rather than hydrogen (5.5 wt % in it) reduced Fe3O4, showing features different from those in a macroscopic system. The possible mechanisms behind this phenomenon are discussed.