High Areal Energy Density 3D Lithium-Ion Microbatteries

Three-dimensional (3D) microbatteries offer an opportunity to provide mobile power at dimensions that are comparable with those of the actuators, sensors, and other internet-connected devices that constitute the internet of things (IoT). To overcome the difficulties of assembling these architectures, we developed an entirely new fabrication route based on semiconductor processing methods. The use of partially lithiated (10% of theoretical capacity) silicon as the negative electrode keeps the volume change suitably controlled so that the Si array registry is maintained during charge and discharge. Photopatterning of SU-8 photoresist creates a conformal solid electrolyte coating around the high-aspect-ratio Si arrays. Rechargeable 3D microbatteries prepared on a 3 mm 3 3 mm footprint have an areal capacity of nearly 2 mAh cm(-2), operate at current densities up to 0.66 mA cm(-2), and withstand 100 cycles. The combination of semiconductor-based processing and photopatternable electrolytes holds great promise for the further development of 3D microbatteries for IoT applications.