Carbyne is one of the allotropes of sp-carbon with a one-dimensional chain, but its physicochemical properties have not yet been clarified. We produced a carbyne-like carbon (carbon containing sp bond) electrode by electrochemical reduction in an organic electrolyte (1.0 mol dm(-3) LiClO4/propylene carbonate) using a poly(tetrafluoroethylene) (PTFE) film electrode coated with a thin gold layer. The Li+ ion can be doped/undoped in the carbyne-like carbon film by electrochemical reduction/oxidation. The stoichiometry of the electrochemically reduced PTFE is estimated to be CLi(0.48)(.)2LiF which corresponds to a lithium ion battery negative electrode with approximate to 1100 mAh g(-1) (of carbon) capacity.