An electrolyte containment structure for an electrode jelly roll and electrolyte in a portable power source is described. The electrolyte containment structure comprises metal foil, such as metal foil sleeve, coupled to and partially surrounding a rigid frame. The rigid frame can protect the electrode jelly roll edges from crush events. To prevent shorts, the metal foil can be coated in plastic, which can insulate the metal foil from the electrode jelly roll. Further, the plastic can serve as a bonding and sealing agent. For instance, the metal foil can be coupled to the rigid frame using a thermal bonding method involving melting of the plastic. The rigid frame can provide a platform for connector pads and safety circuitry associated with the portable power source. The connector pads and safety circuitry can be assembled as modular components, which can simplify the assembly process The containment structure provides features associated with a pouch cell battery design, such as a light-weight metal foil pouch, but can be utilized in a portable computing device without being enclosed in a hard casing traditionally associated with pouch cell battery designs.