The recovery of valuable elements in the cathode of decommissioned lithium-ion batteries is very important. The effective separation of cathode active material from cathode current collector and binder (PVDF)is the key step in the recovery of valuable elements. Mechanical crushing, thermal separation and solvent dissolution have problems of high environmental risks or high separation costs. Hence, this paper proposes a new method that aluminum foil vaporization by pulse discharge in water to vaporize the cathode current collector of lithium-ion batteries. An equipment for the vaporization of aluminum foil by pulse discharge in water was built, and 1060 aluminum foil with a thickness of 10 μm was used to replace the positive current collector of the lithium-ion battery，which was coated with PVDF. In the experiment, the initial discharge voltage was set to 1 kV and gradually increased in steps of 1 kV. When the discharge voltage is 4 kV, the aluminum foil is partially vaporized; and when the discharge voltage is 5 kV, the aluminum foil is completely vaporized. The pH test paper was used to detect the pH value of the liquid after the vaporization of the aluminum foil, and the result showed weak acidity. The results show that the pulse discharge in water realizes the vaporization of aluminum foil and the dissolution of PVDF, which meets the expectations. This paper can provide theoretical and experimental support for the separation of cathode active materials and recovery of cathode valuable elements for decommissioned lithium-ion batteries.