An aerosol delivery device or electronic cigarette generates an aerosol or vapor for consumption by a consumer. The device may include a cartridge holding an aerosol precursor substance or fluid that is turned into the aerosol or vapor. The fluid may be stored in reservoir that allows for the fluid to be passed to an atomizer for generating the aerosol. The reservoir may be a flexible bladder that equalizes pressure inside the cartridge to reduce leakage, such as with an internal valve to activate fluid transfer. Alternatively, the reservoir may include one or more capsules that can be broken or melted to release the fluid.