To Avoid a Potential Fire Hazard, Apple Invents Pressure-Relief Battery Pouches for Portable Devices
On May 26, 2011, the US Patent & Trademark Office published a patent application from Apple that reveals various concepts behind a newly devised pressure-relief battery pouch for portable devices using rechargeable lithium-polymer battery cells. Gas buildup found in most chargeable battery designs could potentially cause the battery cell to swell or explode and even cause a fire. Apple's invention introduces a new series of designs to remedy this potential fire hazard.
The Problem to Solve
Rechargeable batteries are presently used to provide power to a wide variety of portable electronic devices, including laptop computers, cell phones, PDAs, digital music players and cordless power tools. The most commonly used type of rechargeable battery is a lithium battery, which could include a lithium-ion or a lithium-polymer battery – which is currently used in Apple MacBook.
A potential safety issue could arise if there is a gas buildup within a rechargeable lithium battery cell. This could occur, for example, if the cell is overcharged, if there is a short within the cell, or if the cell is left uncharged for a significant period of time. This type of gas buildup could potentially cause the battery cell to swell or even to explode, which could seriously damage the portable electronic device, and may even start a fire.
To alleviate this problem, cylindrical lithium-ion battery cells are often equipped with a vent valve to release the internal pressure in the battery cell when a gas buildup occurs. However, there exist no comparable pressure-relief mechanisms for lithium-polymer batteries, which are becoming increasingly popular in portable electronic devices. A lithium-polymer battery is typically enclosed in a flexible pouch, which is lightweight and inexpensive to manufacture. However, no pressure-relief mechanism has been developed for these pouches so far.
Apple's patent application outlines a battery cell which includes a weakness for relieving pressure. This battery cell may include a jelly roll comprising layers which are wound together, including a cathode with an active coating, a separator, and an anode with an active coating. The jelly roll may also include a first conductive tab coupled to the cathode and a second conductive tab coupled to the anode. The jelly roll, according to Apple, is enclosed in a flexible pouch, wherein the first and second conductive tabs extend through seals in the pouch to provide terminals for the battery cell. This pouch includes a weakness which yields when internal pressure in the pouch exceeds a threshold to create a hole which releases the internal pressure.
In some embodiments, the pouch includes multiple weaknesses at different locations on the pouch.
In some embodiments, the weakness could include: a V-shaped notch cut into a seal for the pouch; a half-circle cut into a seal for the pouch; a pattern of tiny holes formed in a seal for the pouch; and a thinned region of the pouch material.
In some embodiments, the weakness could be located on: a side seal for the pouch; a terrace seal for the pouch; a corner of the pouch; a fold in the pouch material; and a location on a surface of the pouch which is not part of a seal.
In some embodiments, the pouch is comprised of a layer of aluminum and a layer of polypropylene. In some embodiments, the battery cell is a lithium-polymer battery cell, or a silver-zinc battery cell.
Apple's patent application was originally filed in Q4 2009 by inventors Ramesh Bhardwaj, Taisup Hwang and Richard Mank.
Other Noteworthy Patent Applications Published Today
Other noteworthy patent applications published today include patent application 20110125929 which covers the iPod shuffle's one-button design form factor and functionality that works with minimal touch and voice commands. Apple's new iPod shuffle design was granted a patent this week. Two continuation patents have also surfaced covering the topic of "Invisible, Light Transmissive Display System." Apple has already been granted a patent on this technology. Additional information on how Apple could apply this technology in the future could be found here. Another patent application (20110123186) that surfaced today titled "Electro-Mechanical Shutter Control" was actually granted this past Tuesday. Hmm, that seems to be a bit backwards in the greater scheme of things: But we'll take it as another win for Apple.
Another oldie patent gets re-entered for "Display that Emits Circularly-Polarized Light" which is related to two original filings dating back to 2006 and 2010. In fact, you could read about Apple's technology in our March 2010 report titled "Apple Patent May Shed Light on Recent Protective Film Ban." Last year's patent report provided a basic overview of Apple's engineering team's use of retardation film on media displays so that you could continue to enjoy crisp imagery even when we're wearing sunglasses.The bottom line is that there’s nothing new in today’s patent application on this matter worth reporting on.
And finally, another continuation patent application (20110120850) has been filed relating to the 2007 iPhone's "Home" and other buttons which are also now incorporated into their iPod touch.
Notice: Patently Apple presents only a brief summary of patents with associated graphic(s) for journalistic news purposes as each such patent application is revealed by the U.S. Patent & Trade Office. Readers are cautioned that the full text of any patent application should be read in its entirety for further details. Patents shouldn't be digested as rumors or fast-tracked according to rumor time tables. Apple patents represent true research that could lead to future products and should be understood in that light. About Comments: Patently Apple reserves the right to post, dismiss or edit comments.
Update May 28, 2011 from Engadget: HP Expands Laptop Battery Recall, Doesn't Want you to Feel the Burn. One of the reasons for Apple's patent presented above is likely to avoid such a recall. A tid bit worth noting.
Community Sites Covering our Original Report
MacSurfer, Apple Investor News, Google Reader, UpgradeOSX, TechWatching, Macnews, iPhone World Canada, Cliqz, Lithium Battery Blog, CBS MarketWatch, 9to5 Mac, Gizmodo Australia, Gizmodo Mobile, Gizmodo UK, IT Avisen Norway, MacBidouille France, Slide to Mac Italy, Mela Blog Italy, MacMagazine Brazil, Gadget Reviews UK, and more.
The battery related photos came from iFixit.