FlexPower II: Flexible Interdigitated Battlet Li-ion Battery on FlexTrateTM for Wearables

To overcome the structural shortcomings of stacked electrode battery design and improve the flexibility of Li-ion batteries for powering wearables, we develop a chiplet-inspired coplanar-interdigitated flexible Li-ion battery using lithium iron phosphate LFP/ lithium titanate (LTO) electrode in ionic liquid electrolyte on FlexTrate ${}^{\text{TM.}}$ This enables efficient packaging scheme for power delivery for wearables. This single layer thin film battery of thickness $<300 \mu \mathrm{m}$ delivers $0.1 \text{mAh} / \text{cm}^{2}$ specific areal capacity at C/10 charge/discharge rate with 5 mm bending radius. We show that 3D stacking approach may allow us to increase this to our target capacity of $1 \text{mAh} / \text{cm}^{2}$.