The power capability of Li-ion batteries has become increasingly limiting for the electrification of transport on land and in the air. The specific power of Li-ion batteries is restricted to a few thousand W kg−1due to the required cathode thickness of a few tens of micrometers. We present a design of monolithically-stacked thin-film cells that has the potential to increase the power ten-fold. We demonstrate an experimental proof-of-concept consisting of two monolithically stacked thin-film cells. Each cell consists of a silicon anode, a solid-oxide electrolyte, and a lithium cobalt oxide cathode. The battery can be cycled for more than 300 cycles between 6 and 8 V. Using a thermo-electric model, we predict that stacked thin-film batteries can achieve specific energies >250 Wh kg−1at C-rates above 60, resulting in a specific power of tens of kW kg−1needed for high-end applications such as drones, robots, and electric vertical take-off and landing aircrafts.