Apple looking to sweeten battery life with redesigned 'jelly rolls'

Jelly rolls, also known as Swiss rolls, are found in cylindrical, rechargeable batteries, like a typical AA, AAA or D batteries. In the design, anode and cathode material is laid down and divided by a separator, and then rolled up into a hollow cylinder.

Apple is now looking to expand on the jelly roll design, according to a new patent application discovered this week by AppleInsider. The filing, dubbed "Battery with Multiple Jelly Rolls in a Single Pouch," aims to improve the existing lithium batteries found in most electronic devices, including the iPhone, iPad and portable Macs.

The application notes that lithium-polymer batteries are convenient, because they include cells that are packaged in flexible pouches that can be tailored to fit into small portable electronic devices.

A lithium-polymer battery can achieve a packaging efficiency of between 90 percent and 95 percent if a jelly roll is enclosed in a foil pouch. Multiple pouches can be placed side by side in order to form a battery.

But to further improve the efficiency of batteries, making them smaller and even more efficient, Apple has proposed a new kind of battery cell with a set of jelly rolls found in a foil pouch, rather than just one.

Just like in a rechargeable AA, Apple's concept includes a cathode and anode divided by a separator. Conductive tabs within the battery cell would connect cathodes and anodes from the jelly rolls found in the pouches.

"The use and placement of multiple jelly rolls of different lengths and thicknesses within a pouch may allow the creation of a custom battery cell that maximizes the use of free space within a portable electronic device and provides greater capacity, packing efficiency, and/or voltage than battery cells that contain only one jelly roll per pouch," the application reads.

This kind of custom battery could be designed to specifically fit the needs of the device in which it is found. In one example, Apple describes a laptop with a battery pouch and multiple thin jelly rolls housed behind the display of a laptop computer.

"Along the same lines, jelly rolls of various thicknesses and lengths may be sealed in a pouch to create an asymmetric battery cell that fits around other components (e.g., processors, printed circuit boards (PCBs), memory, storage, etc.) inside the enclosure of a mobile phone," it states.

The application made public this week by the U.S. Patent and Trademark Office was first filed by Apple on Jan. 26, 2010. The proposed invention is credited to Ramesh C. Bhardwaj, Taisup Hwang, and Richard M. Mank.

Apple's interest in improving batteries is not new. Earlier this year, a separate filing described a concept for dense lithium cells that could increase the capacity of rechargeable batteries without increasing their size.

The company has also expressed interest in building its own external battery pack that would allow for recharging when a power outlet may not be available. In one example, the company described a battery pack built into its standard charging cable for devices like an MacBook Pro or iPhone.