High performance HASEL actuators as self-healing trigger devices for lithium-ion batteries

Lithium-ion batteries (LIB) are part of our modern life and they enable the operation of numerous devices, in general without complications. The possibility for fast recharging ensures high comfort for mobile devices and electric vehicles. Nevertheless, also advanced cell chemistries may cause problems over time, which could lead to damages of battery cells before their regular end of lifetime. Since a few years, research work on self-healing mechanisms aims to extend the lifetime of used batteries or tries to repair the battery directly in the used system. To enable these self-healing mechanisms, an outer trigger mechanism such as pressure or temperature is necessary, usually driven by an additional device. The authors of this work present a device for generating pressure on lithium-ion battery pouch cells, where the device is based on HASEL (hydraulically amplified self-healing electrostatic) actuators. The HASEL actuator itself has an overall thickness of only 0.3 mm and is able to generate a continuously rising active pressure of up to 70 kPa depending on the applied electric field strength. With the active HASEL area of 100 mm x 60 mm, this pressure corresponds to a force of 450 N, where a field strength of 140 kV/mm is required. For optimum pressure generation, the device was placed in a special arrangement with the battery cell. Various mechanical prestress loads on the battery cell between 20 and 30 kPa were tested. This extremely thin pressure generating HASEL actuator offers the possibility for triggering self-healing mechanisms in lithium-ion batteries for single cells, battery modules and packs and offers high integration potential.