Three different V6O13-based cathodes have been incorporated into thin-film polymer electrolyte cells : single-phase V6O13, and V6O13 containing 10 molar percent (m/o) VO2 or V2O5. In situ x-ray diffraction (XRD) reveals four phases, identified as Li0.5V6O13, Li1.5V6O13, Li3V6O13, and Li6V6O13. Cells containing single-phase V6O13 were cycled between 3.0 and 1.8 V at three different rates (1000, 30, and 7(A). Weight analysis and titration data gave Li6V6O13 as the final phase. In situ XRD could identify lithium intercalated phases as the same as those obtained from chemical lithiation. Phase-pure V6O13 batteries exhibited no significant capacity loss during cycling (up to 60 cycles). With VO2 or V2O5 present, the capacity was lower and the cyclability poor, particularly in the case of V2O5.