| Lithium ion battery (LIB) is considered as the most promising secondary battery due to its stable discharge potential curve, high-performance at low temperature, environmental friendliness, memoryless effect, high working voltage, long cycle life, low self-discharge and high energy density. LIBs can not only satisfiy the demands in the fields of consumer electronics, electric vehicles and storage devices of clean energy, but also are friendly to envirment. Nowadays, LIBs have been widely used in portable electric devices.The commercial anode material is griphte, which shows a low capacity of 372 mAh/g. Therefore, the development of anodes with higher lithium storage capacities is urgent SnO2 is considered as a potential substitute due to its rich content, low toxicity, low pollution and higher lithium storage capacity. However, the large volume changes iN the lithium ions insertion and exertion processes result in pulverization of the electrode, leading to the rapid capacity decline upon cycling. To solve the above problems, LOts of approachs has been used, and two of them are widely used. One is to design and fabricate SnO2 material in the size of nanometer and the other is to introduce carbonaceous material.In this paper, CNF/SnOx/C, CNF/SnO2/C, SnO2/C NTs and rGO/SnO2 are designed, fabricated and characterizated. The main contents and results are listed as follows.1. CNF/SnO2 networks are fabricated by a facile dipping-coating method and a subsequent calsination process. As anodes for LIBs, CNF/SnO2 shows a high initial capacity. However, with the increasing of the cycle number, the capacities decrease. In order to enhance the electrochemical performance of CNF/SnO2, we fabricate a carbon layer to gain CNF/SnOx/C and CNF/SnO2/C by a CVD growth and a hythermal process, respectively. And, both the CNF/SnOx/C and CNF/SnO2/C show good cyclic performances. After 200 cycles, the CNF/SnOx/C anode shows a high capacity of 512 mAh/g at a current density of 200 mA/g. It only decreases a capacity of ～0.66 mAh/g per cycle from the 50th to the 200th cycles. CNF/SnO2/C anode delieves a capacity of 580 mAh/g at 100 mA/g in the 65th cycle.2. SnO2/C nanotubes are fabricated by calcinating CNF/SnO2 and a subsequent CVD growth process. As anode for LIBs, SnO2/C NTs material shows a high capacity and a good rate performance. At a current density of 400 mA/g, it deliveres a capacity of 653 mAh/g in the 50th cycle. After 15 cycles, there is a peak of SnO2 at 480 cm-1 by the Raman characterization. It conforms that the reaction between SnO2 and Li+ is reversible and the theorical capacity of SnO2 is higher than 781 mAh/g.3. rGO/SnO2 is fabricated by a colloidal coagulation method and a subsequent reduction. As anodes for LIBs, rGO/SnO2 shows an excellent electrochemical performance. At a current density of 1000 mA/g, it delieves a reversible capacity of 796 mAh/g in the 600th cycle, which is even higher than the theorical capcity of SnO2 anodes. At 1600 mA/g, it shows a capacity of 563 mAh/g. XPS is used to characterizate the anode material. After 200 cycles, the peaks of SnO2 are still observed and it informs that the reaction between SnO2 and Li+ is reversible and the reaction should be descreabed as... |
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