Flexible Integrated Battery on System-in-Package (SiP) for Internet of Things (IoT) and Smart Wearables

The emergence of advanced electronic products has resulted in more and more devices being interconnected to communicate with each other. Next generations of electronic devices, especially IoTs and smart wearable devices are expected to have smaller from factor, higher reliability, better flexibility, and lower power consumption. Flexible battery emerges as one promising solution considering the miniaturized form factor that typically requires mechanical bending or even folding, which are not achievable by conventional Li ion battery (LIB). In this paper, we demonstrate a unique flexible battery that can be embedded on flexible printed circuit (FPC), along assembled ICs and passive components to form System-in-Package (SiP) module for smart IoT device. The formulation of UV curable amorphous PEO-based solid state electrolyte (SSE) not only offers high ionic conductivity to achieve better cell performance, but also good mechanical properties to support the flexibility. Various characterizations are performed to evaluate the battery performance including charging/discharging capacity, retention capacity, and safety. The flexible battery demonstrated achieved final thickness of only 200 $\mu \text{m}$, it can be charged and discharged in a wide range of temperature of -20°C to 60°C owing to the amorphous structure of the PEO-based electrolyte.