FlexEnergy LLC is developing a safe, flexible, thin film battery that can achieve novel form factors for wearables that traditional Li-ion battery technologies cannot provide. The enabling component is a flexible but mechanically robust uniform separator membrane (trade marked as Pyrolux™) with tunable and hierarchal nanoporosity, with electrochemical performance equivalent to or better than polyolefin-based systems, and with substantially improved thermal stability and performance (compared to commercially available separators like Celgard).
This Air Force technology enables batteries that can flex and handle higher temperatures. This is achieved by using a printable ink with additive direct write manufacturing approach. Direct write manufacturing techniques are an effective method to create complex, multifunctional structures. And, unlike most printing techniques commonly adopted for batteries (such as stencil printing, screen printing, and spray printing), direct write printing does not require masking or material removal, and is a scalable ready technology.
These template-free printing techniques offer an economical, scalable approach to rapid prototyping of battery electrodes and architectures that can be patterned to fit a specific application or even directly printed on a device enabling direct integration of a power source into its corresponding device. Printing also offers the utilization of confined or nonplanar substrates as power sources.
The FlexEnergy battery could be used in a variety of small factors and is able to be competitive at scale by using a printing process for custom shapes.
Embedded energy has remained elusive for wearables without installing “bricks into clothing” that cannot be laundered or be integrated into the natural contours of clothing. The lack of batteries for clothing has pushed the limits for wrist-based wearables and ignores the possibility to extend IoT to body worn tech and embedded harnesses that could be invisible inside of clothing.
Clothing is not able to be “smart” nor offer self-actuating baffles to open up for ventilation nor can it be used to embed electronics that could be used in monitoring. The best the current market offers are embedded resistive heating but nothing that enables IoT or other advances in sensing.
The key gap for these technologies is the ability to embed a power source that fits in the traditional expectations of clothing (feel, look, movement) with the allure of embedded future tech. For wearables, embedded power and storage for clothing (e.g., washable/dryer stable storage) is expected to experience massive growth, and some estimates place the market to achieve ~$5.4Bil by 2024, with a huge increase in materials applications applied to clothing.
The major issues for clothing companies to integrate storage is that they simply do not have systems that can handle low level wash/dryer cycles safely (due to traditional Li-ion electrolytes) and do not have access to batteries that are as flexible/conformable as the clothing they are part of. A major limiting factor in these systems is a high temperature separator that can handle these temperatures and work with new electrolytes at higher temperatures with surface/interface stability.
As a result of these limitations, instead of being able to embed extra power into clothing that are universally worn, the market has gone to external power bricks, constant charging, and limited smart clothing. Several other applications outside wearables will also be benefited with improved thermal stability and safety by use of nonflammable membrane/separator.