Additive-free synthesis of Li₄Ti₅O₁₂ nanowire arrays on freestanding ultrathin graphite as a hybrid anode for flexible lithium ion batteries

Interest in high-power, lightweight, and flexible lithium-ion batteries (FLIBs) to fulfill the energy requirements of future flexible electronic devices is increasing. To fabricate a thin FLIB, which consists of flexible components, we herein describe, as a model study, a hybrid electrode structure that includes no binders, conductive agents or metal current collectors. A freestanding ultrathin graphite (FSG) film was used as both the current collector and the anode, over which vertically aligned Li₄Ti₅O₁₂ (LTO) nanowire (NW) arrays were grown. For comparison, two different additive-free electrodes consisting of an LTO NW array on titanium (LTO-Ti) and an LTO NW array on FSG (LTO-FSG) were prepared; they exhibited discharge capacities of 158 and 154 mA h g^-1, respectively. The capacities remained approximately stable even after 500 cycles at a 20C charge/discharge rate, revealing outstanding cycling stability of the electrodes. The high-rate performance of the additive-free LTO-FSG electrode revealed excellent rate capability. Finally, the flexible LTO-FSG electrode was used to assemble an FLIB. This novel approach of preparing an additive-free and flexible hybrid electrode enabled the fabrication of a high-power, thin, and lightweight FLIB that exhibited no physical deterioration or performance loss.