Free-standing single-walled carbon nanotube/SnO ₂ anode paper for flexible lithium-ion batteries

Free-standing single-walled carbon nanotube/SnO ₂ (SWCNT/SnO ₂) anode paper was prepared by vacuum filtration of SWCNT/SnO ₂ hybrid material which was synthesized by the polyol method. From field emission scanning electron microscopy and transmission electron microscopy, the CNTs form a three-dimensional nanoporous network, in which ultra-fine SnO ₂ nanoparticles, which had crystallite sizes of less than 5 nm, were distributed, predominately as groups of nanoparticles on the surfaces of single walled CNT bundles. Electrochemical measurements demonstrated that the anode paper with 34 wt.% SnO ₂ had excellent cyclic retention, with the high specific capacity of 454 mAh g ^-1 beyond 100 cycles at a current density of 25 mA g ^-1, much higher than that of the corresponding pristine CNT paper. The SWCNTs could act as a flexible mechanical support for strain release, offering an efficient electrically conducting channel, while the nanosized SnO ₂ provides the high capacity. The SWCNT/SnO ₂ flexible electrodes can be bent to extremely small radii of curvature and still function well, despite a marginal decrease in the conductivity of the cell. The electrochemical response is maintained in the initial and further cycling process. Such capabilities demonstrate that this model hold great promise for applications requiring flexible and bendable Li-ion batteries.