Nanostructured TiO sub(2)/carbon nanosheet hybrid electrode for high-rate thin-film lithium-ion batteries

Heterogeneous nanostructured electrodes using carbon nanosheets (CNS) and TiO sub(2) exhibit high electronic and ionic conductivity. In order to realize the chip level power sources, it is necessary to employ microelectronic compatible techniques for the fabrication and characterization of TiO sub(2)-CNS thin-film electrodes. To achieve this, vertically standing CNS grown through a catalytic free approach on a TiN/SiO sub(2)/Si substrate by plasma enhanced chemical vapour deposition (PECVD) was used. The substrate-attached CNS is responsible for the sufficient electronic conduction and increased surface-to-volume ratio due to its unique morphology. Atomic layer deposition (ALD) of nanostructured amorphous TiO sub(2) on CNS provides enhanced Li storage capacity, high rate performance and stable cycling. The amount of deposited TiO sub(2) masks the underlying CNS, thereby controlling the accessibility of CNS, which gets reflected in the total electrochemical performance, as revealed by the cyclic voltammetry and charge/discharge measurements. TiO sub(2) thin-films deposited with 300, 400 and 500 ALD cycles on CNS have been studied to understand the kinetics of Li insertion/extraction. A large potential window of operation (3-0.01 V); the excellent cyclic stability, with a capacity retention of 98% of the initial value; and the remarkable rate capability (up to 100 C) are the highlights of TiO sub(2)/CNS thin-film anode structures. CNS with an optimum amount of TiO sub(2) coating is proposed as a promising approach for the fabrication of electrodes for chip compatible thin-film Li-ion batteries.