context: Flexible lithium-ion batteries have attracted extensive attentions in electronics. However, their practical applications are primarily limited by low open-circuit voltage and energy density. Herein, we report a novel surface/interface modification strategy to obtain electrolyte-phobic carbon nanotube film as the flexible current collector for foldable lithium-ion batteries. The as-assembled battery exhibits a high open-circuit voltage of 4.04 V and energy density of ~293 Wh kg-1 with excellent flexibility and stable cycle performance. The outstanding performance is ascribed to the electrolyte-phobic surface/interfacial layer of carbon nanotube film, which restrains the intercalation of lithium ions into carbon-based current collector. This work not only demonstrates a practical solution to appreciably revamp the voltage and energy density of flexible lithium-ion batteries, but more importantly, offers valuable insights in modifying the surface/interface chemistry of carbon-based current collectors for high-performance energy storage devices.