Millimeter scale thin film batteries for integrated high energy density storage

for the first time, we experimentally demonstrated thin film batteries (TFBs) with very high electrochemical energy density storage of 0.89 mAh.cm
⁻²
at the device level. The 3.1×1.7 mm² TFBs of 95μm total thickness show a discharge capacity of 25μAh and maintain 60% of this value at 0.25mA. Upon cycling, TFBs exhibit excellent capacity retention, with an average loss of 0.05% per cycle. Results at 37°C present similar performance, thus highlighting the great potential of these TFBs as integrated energy storage solution in particular for medical implantable, injectable and wearable solutions