Intelligent ultrasound to adaptively control interfacial properties and reactions

Project begins in 2022.

Operating future hybrid autonomous vehicles in highly stochastic and uncontrolled environments puts significant demands on their structure and power system. Imagine that (1) parts can be produced at the point of need using additive manufacturing to meet mission requirements; (2) new materials and light weight structures can be joined by advanced methods such as friction stir welding; and (3) vehicles are capable to adaptively use diverse energy sources. Such capabilities are crucial for autonomous vehicles that may be deployed for months before eventually going to a base. These capabilities may be realized by using structures composed of layers of materials, such as

• Metal or composite sheets to be joined,
• Membrane layers in fuel cells,
• Separator and electrode layers in batteries.

These layered structures share a common challenge: to actively and adaptively change interfacial properties in situ during operation.

The capability to change interfacial properties dynamically can lead to major enhancements in the adaptability of structures and power sources of autonomous vehicles. Take batteries as an example. Ultrasound can be used to provide adaptivity by changing reaction kinetics at electrode/electrolyte interfaces. The high internal resistance caused by high intensity usage leads to reduced battery power, low usable capacity, and long charging time. The increase in internal battery resistance is related to the solid-electrolyte interphase (SEI), which is composed of two distinct layers: a thin compact layer of inorganic products, and a porous amorphous outer layer of organic products. The compact layer is beneficial because it protects electrodes from further chemical reaction with the electrolyte. The outer porous layer controls the growth of the SEI which affects the internal resistance. Studies have shown that SEI is the major cause of battery power and capacity degradation.

We propose to create an approach to actively and adaptively change interfacial properties in situ during operation. This study will develop an ultrasound-enabled adaptive interface control for such systems. We aim to address several key fundamental questions to enable this paradigm-shifting technology for the US Army and broader applications: (1) how does ultrasonic waves affect interfacial layers? (2) how to deliver targeted ultrasonic waves to an interface without strongly vibrating the entire structure? (3) how to prove the feasibility in a practical setup? (4) how to intelligently activate ultrasonic waves to provide adaptability when needed? Surrounding these questions, we have formulated four research tasks.

To illustrate the approach, we focus on one example involving the manipulation of the SEI layer in batteries, which was shown in our past work to significantly influence the battery internal resistance and thus power capability and usable capacity (patent pending). However, the same approach and related tasks will be used for the other applications, namely ultrasonic joining and additive manufacturing processes.

#3.19