Tempo‐Spatial Manipulation of Ultrasonics Toward Healing of Solid‐State Batteries

Abstract Solid‐state batteries (SSBs) struggle with poor interface contact and the resulting fast dendrite growth and short circuits. Ultrasonic treatment offers a potential solution to heal SSBs by ultrasonic welding at room temperature to improve interface contact free from side reactions. A significant challenge is the adverse effect of ultrasonics on SSBs, such as severe cracking in brittle electrolytes increasing the risk of dendrite growth and short circuits. Inspired by ultrasonic treatment on patients in hospitals, a tempo‐spatial manipulation of ultrasonics (TSMU) is examined, guided by ultrasonic‐structure interaction simulations, to maximize the propagated energy for ultrasonic welding while mitigating the possibility of electrolyte cracking. The application of TSMU to Li/garnet/Li symmetric cells is found to reduce the interfacial resistance from thousands to tens of Ω cm −2 for poorly formed interfaces, from SSB manufacturing to (dis)charging cycles, which outperforms constant ultrasonic treatment that achieves a resistance minimum of hundreds of Ω cm −2 ; otherwise, a short circuit occurs due to the cracking. Galvanostatic cycling further demonstrates the excellent stability of TSMU‐healed cells over 1,000 cycles at a current density of 0.1 mA cm −2 , which is not attainable by constant ultrasonics with short‐circuiting issues.