Apple Invents Charging Techniques for Solid State Batteries
On July 25, 2013, the US Patent & Trademark Office published a patent application from Apple that reveals charging techniques for Solid State batteries. Solid State batteries fall into low-power density and high-energy density categories. On the latter side of the equation, Toyota is working on a Solid State battery for 2020 vehicles that will deliver 3 to 4 times battery life. Obviously Apple is interested in the low-power side of Solid State batteries for iDevices and likely future wearable computers. According to Wikipedia, Solid Sated batteries "are easy to miniaturize and can be constructed in thin film form," which would be great in context with bendable devices and those with flexible displays. They also eliminate the problem of electrolyte leakage found in traditional batteries. This kind of batteries also tends to have very long shelf lives and usually don't have any abrupt changes in performance with temperature, such as might be associated with electrolyte freezing or boiling. At the end of the day, we'd like to see battery life extended for iDevices in the 3 to 4 times range like the goal Toyota is aiming for. Now that would be great news.
Apple's Patent Background
Rechargeable batteries are presently used to provide power to a wide variety of portable electronic devices, including laptop computers, tablet computers, mobile phones, personal digital assistants (PDAs), digital music players and cordless power tools. The most commonly used type of rechargeable battery is a lithium battery, which can include a lithium-ion or a lithium-polymer battery.
Lithium-polymer batteries often include cells that are packaged in flexible pouches. Such pouches are typically lightweight and inexpensive to manufacture. Moreover, these pouches may be tailored to various cell dimensions, allowing lithium-polymer batteries to be used in space-constrained portable electronic devices such as mobile phones, laptop computers, and/or digital cameras. For example, a lithium-polymer battery cell may achieve a packaging efficiency of 90-95% by enclosing rolled electrodes and electrolyte in an aluminized laminated pouch. Multiple pouches may then be placed side-by-side within a portable electronic device and electrically coupled in series and/or in parallel to form a battery for the portable electronic device.
Recent advances in battery technology have also led to the development of solid-state batteries, in which electrodes and a thin solid electrolyte are layered on top of a non-conducting substrate. Because the solid electrolyte takes up less space and/or weighs less than the liquid electrolyte of a comparable lithium-ion and/or lithium-polymer battery, the solid-state battery may have a higher energy density than the lithium-ion and/or lithium-polymer battery. In addition, the solid-state battery may be safer and/or more reliable than conventional lithium-ion and/or lithium-polymer batteries.
For example, the use of a non-flammable, solid electrolyte in the solid-state battery may allow the solid-state battery to sidestep liquid electrolyte hazards such as spilling, boiling, gassing, and/or fires. Consequently, solid-state batteries may improve the safety, reliability, form factor, and/or runtime of portable electronic devices.
Apple's Invents Charging Techniques for Solid State Batteries
Apple's invention provides a system that manages use of a solid-state battery in portable electronic devices. During operation, the system monitors a temperature of the solid-state battery during use of the solid-state battery with the portable electronic device.
Next, the system modifies a charging technique for the solid-state battery based on the monitored temperature to increase a capacity or a cycle life of the solid-state battery.
To modify the charging technique based on the monitored temperature, the system may increase a charge rate of the solid-state battery if the temperature exceeds a first temperature threshold (e.g., 25.degree. Celsius). On the other hand, the system may maintain the charge rate of the solid-state battery if the temperature does not exceed the first temperature threshold.
In some embodiments, the system further increases the charge rate of the solid-state battery if the temperature exceeds a second temperature threshold such as 45.degree. Celsius.
In some embodiments, increasing the charge rate of the solid-state battery involves at least one of increasing a charge current of the solid-state battery, and increasing a charge voltage of the solid-state battery.
Apple states that the new solid state batteries will apply to such devices as the iPhone, iPad, iPod, MacBooks and more. This would be ideal for bendable and/or wearable computers.
Apple's patent FIG. 1 noted above illustrates a cross-sectional view of a battery cell 100 in accordance with the disclosed embodiments. As shown in FIG. 1, battery cell 100 includes a substrate 102, a cathode current collector 104, a cathode active material 106, an electrolyte 108, an anode active material 110, and an anode current collector 112.
More specifically, FIG. 1 shows a cross-sectional view of a solid-state battery cell. The components of the battery cell may be formed by depositing layers of different materials onto a substrate. For example, the substrate 102 may correspond to a non-conducting substrate such as mica, polyamide, and/or polyether ether ketone (PEEK).
A vacuum deposition technique may be used to deposit the cathode current collector as a layer of platinum and/or gold onto the substrate and the anode current collector as a layer of copper onto the substrate. Next, a sputtering technique may be used to deposit a lithium compound corresponding to the cathode active material onto the cathode current collector along with a thin film of lithium phosphorus oxynitride (LiPON) corresponding to a solid electrolyte over the cathode current collector, the cathode active material, the substrate and/or the anode current collector. A layer of lithium may then be thermally evaporated onto the LiPON to form the anode active material.
Apple credits Ramesh Bhardwaj as the sole inventor of this patent application which was originally filed under serial number 354179 in Q1 2012.
Until we get to solid state batteries, you check out Apple's other invention published today that generally relates to power management for electronic devices here.
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