Analytical Sciences

Abstract − Analytical Sciences, 29(11), 1083 (2013).

Determination of Li+ Diffusion Coefficients in the LixV2O5 (x = 0 – 1) Nanocrystals of Composite Film Cathodes
Dah-Yeon YOO,*1 In-Hyeong YEO,*2 Won Il CHO,*3 Yongku KANG,*4 and Sun-il MHO*1
*1 Division of Energy Systems Research, Ajou University, Suwon 443-749, Korea
*2 Department of Chemistry, Dongguk University, Seoul 100-715, Korea
*3 Energy Storage Research Center, Korea Institute of Science and Technology, Seoul 130-650, Korea
*4 Division of Advanced Materials, Korea Research Institute of Chemical Technology, Daejeon 305-600, Korea
The Li+ ion diffusion coefficients (DLi+) in V2O5 (2.12 × 10−12 cm2 s−1) and in the intermediate α-, ε-, and δ-LixV2O5 phases (1.6 × 10−14, 8.0 × 10−15, and 8.5 × 10−15 cm2 s−1, respectively), reversibly formed during charging/discharging processes of the crystalline-V2O5 and PEDOT (poly-3,4-ethylenedioxythiophene) composite-film electrode, are precisely determined by the galvanostatic intermittent titration technique. The specific surface area of the composite film is estimated to be 13.600 m2 g−1, where the external surface area and the nanopore area are 10.704 and 2.896 m2 g−1, respectively. The V2O5 crystals are coated and interconnected by a conductive polymer network in the composite film, thereby improving the electrode characteristics. V2O5 and PEDOT composite-film cathodes showed high specific capacities (290 mA h g−1 at a 1 C rate), excellent rate capabilities (178 mA h g−1 at a 10 C rate), and superior cycling stabilities (ca. 15% degradation after 500 consecutive cycles).