Wen-Jia Zhou

Preparation and Electrochemistry of SWNT/PANI Composite Films for Electrochemical Capacitors

Single-walled carbon nanotube/polyaniline (SWNT/PANI) composite films were prepared by in situ electrochemical polymerization of an aniline solution containing different SWNT contents. Surface morphology and structural properties of these PANI-based films were examined by a scanning electron microscope and X-ray photoelectron spectroscopy. The electrochemical capacitance properties of these films were investigated with cyclic voltammetry, charge-discharge tests, and ac impedance spectroscopy. The composite film, based on the charge-transfer complex between well-dispersed SWNT and PANI matrixes, shows much higher specific capacitance, better power characteristics, and is more promising for applications in capacitors than a pure PANI film electrode.

Electrodeposition of ordered mesoporous cobalt hydroxide film from lyotropic liquid crystal media for electrochemical capacitors

A novel ordered mesoporous cobalt hydroxide film (designated HI-e Co(OH)2) has been successfully electrodeposited on titanium substrate from the hexagonal lyotropic liquid crystalline phase using surfactant Brij 56 as the structure-directing agent. Low-angle X-ray diffraction (XRD) and transmission electron microscopy (TEM) studies indicate that the film electrodeposited from the liquid crystal template has a regular nanostructure consisting of a hexagonal array of cylindrical pores. Cyclic voltammeter (CV) and galvanostatic charge/discharge measurements show that the ordered mesoporous HI-e Co(OH)2 film electrode has excellent electrochemical capacitance between a potential range of –0.1–0.45 V, and a maximum specific capacitance as high as 1084 F g–1 could be achieved in 2 M KOH solution at a charge–discharge current density of 4 A g–1. Meanwhile, the properties of Co(OH)2 film electrodeposited from aqueous solution without templates (designated Aq-e Co(OH)2) are also discussed for comparison.

One-Step, Low-Temperature Route for the Preparation of Spinel LiMn2O4 as a Cathode Material for Rechargeable Lithium Batteries

A new low-temperature synthetic route has been developed and demonstrated for the production of spinel LiMn 2 O 4 as a cathode material for Li-ion batteries. The process involves the insertion of lithium into electrolytic manganese dioxide with glucose as a mild reductant in an autoclave. The material resulting from hydrothermal treatment is a spinel-structured Li 0 . 9 2 LiMn 2 O 4 with reasonable crystallinity. It exhibits promising electrochemical behavior in nonaqueous liquid electrolyte. The influence of hydrothermal temperature and the effect of glucose in determining the final structural integrity and electrochemical performance have also been systemically explored. Furthermore, the capacity degradation of low-temperature synthesized spinels was studied by cyclic voltammetry and X-ray diffraction. This capacity fading can be mainly attributed to the factors of structural degradation and loss of active materials.