Entrapping electrode materials within ultrathin carbon nanotube network for flexible thin film lithium ion batteries

A novel design of a flexible thin film electrode for lithium ion batteries is reported. We employ ordered carbon nanotube (CNT) film, directly pulled from aligned CNT arrays, as a flexible skeleton. The functional electrode material is introduced by a one-step spray-painting approach. The electrode is self-sustained as a result of the strong interactions among CNTs. In such an electrode configuration, the CNT network acts as micro electron pathways and its excellent mechanical properties also ensure flexibility. The electrodes fabricated in this way are electrochemically and mechanically superior in comparison with those prepared by the traditional slurry cast method. A full battery that contains a LiFePO4 cathode and a Li4Ti5O12 anode exhibits a high areal capacity over 200 mu A h cm(-2), a stable output voltage of 1.82 V, excellent reversibility, high flexibility, and light polarization in both flat and bent conditions. As a result, we suggest such electrodes hold great promise for thin film lithium ion batteries to satisfy energy storage demand in revolutionary portable electronics.