Composite films of nanobeam V 2 O 5 and poly-3,4-ethylenedioxythiophene (PEDOT) were grown using an electrochemical polymerization method. PEDOT in the composite film connects the isolated V 2 O 5 nanobeams and gives rise to a conductive network, improved Li-ion accessibility and transport pathways in the electrode. The nanobeam-V 2 O 5 /PEDOT composite film cathodes have high capacities, excellent rate capabilities and cycling stabilities at various C rates: their specific capacities were 262 mAh g À1 at 0.1 C, 239 mAh g À1 at 1 C, 186 mAh g À1 at 10 C, and 141 mAh g À1 at 100 C. After testing the battery for more than 150 battery cycles at a rate of 10 C, the degradation rate was found to be approximately 9 %. The diffusion coefficient of the nanobeam-V 2 O 5 crystalline electrode was calculated to be approximately 4.6 10 À8 ; and those of a-, e-, and d-Li x V 2 O 5 crystalline phases, were estimated to be in the range of (2.1-9.8) 10À10 . Under the conditions of PEDOT coating and networking in the composite film, the diffusion coefficients of each phase of Li x V 2 O 5 that reversibly formed during the discharging and charging processes were able to be estimated.

The Li + ion diffusion coefficients (DLi+) in V2O5 (2.12 × 10 -12 cm 2 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 cm 2 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 m 2 g , 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).

Composite films of nanocrystalline V 2 O 5 embedded in a conducting polymer, poly-3,4-ethylenedioxythiophene (PEDOT), were grown using an electrochemical polymerization method. The nanobeam-shaped V 2 O 5 and PEDOT composite film cathodes have high capacities, excellent rate capabilities and cycling stabilities: the specific capacity was 269 mAhg -1 and the degradation rate was only 8% after 100 consecutive cycles at 1 C rate. The charge transfer resistances (R ct ) for the nanobeam-V 2 O 5 /PEDOT composite film cathodes were smaller than that for the nanobeam-V 2 O 5 powder cathode, in the electrochemical impedance measurements. The diffusion coefficient (D Li+ ) in the nanobeam-V 2 O 5 crystallines was calculated to be approximately 4.6 x 10 -8 , and the values of D Li+ for each of α-, ε-, and δ-Li x V 2 O 5 crystalline phases, reversibly formed in the composite films during the discharging and charging processes, were able to be estimated in the range of (2.1~9.8) x 10 -10 .