Analytical modeling of a multilayer, multimorph lithium-ion battery actuator

Silicon-anode based lithium-ion batteries can provide large actuation strain and actuator strain energy through their novel electrochemical actuation mechanism. Battery actuators have strong potential as multifunctional actuators due to their ability to store energy, actuate, and self-sense. This paper presents a generic multilayer model that can predict the following actuator metrics for a multimorph: free deflection, blocked deflection, blocked force, actuator force, and actuator strain energy. Two case studies are explored including an experimentally validated case study with a 13-layer multimorph and a 33-layer multimorph. These case studies are investigated for a range of coating layer thicknesses and for two prevailing assumptions. The first assumes perfect bonding of all layers within the multimorph, and the second is a novel method where some layer interfaces in a multimorph are assumed be in slip. Results under the perfect bonding assumption indicate that the stiffer 33-layer performs better than the 13-layer in blocked force and actuator strain energy per active material volume. The 13-layer multimorph performs better in free deflection due to its larger compliance. When some layers are assumed to slip, the free and blocked deflection increase, due to the increased compliance, relative to all the perfectly bonded case studies.