Ultrasound-Induced Impedance Reduction in Lithium Ion Batteries

We report a discovery that the internal impedance of pouch-type lithium ion batteries with polymer electrolytes can be significantly reduced by ultrasound waves applied at constant temperature. By precluding any temperature effect from ultrasound heating, the observation reveals an innovative mechanism to dynamically improve battery performance in operando. The reduction is 16.9% at room temperature, highlighting the great potential for extending lifespan and enhancing energy efficiency. The reduced impedance also increases the usable capacity by 16.3% at room temperature and 53.4% at low temperature, enabling accelerated charging without overheating. The increased effectiveness of ultrasound at low temperatures improves the performance of batteries that degrade under such conditions. This impedance reduction is reversible and can be tuned by the ultrasound power. A potential mechanism is proposed to understand the process, which is supported by molecular dynamics simulations.