Overcoming the Intrinsic Limitations of Fast Charging Lithium‐Ion Batteries Using Integrated Acoustic Streaming

Abstract

A lithium‐ion battery's maximum charge rate and energy density are intrinsically limited by the ion diffusion rate in the electrolyte. Most research focuses on materials science solutions to this problem, with gradual improvement over the years. A mechanical solution is proposed to integrate an MHz‐order frequency surface acoustic wave (SAW) device into an existing 1.8 Ah multilayered Li‐ion pouch cell to enhance the ion diffusion rate and the overall battery performance. Both the charging rate and cycling lifetime are improved from SAW. At a 6C (10 min) charge and C/3 discharge rate, typical of electric vehicle applications, integrating SAW into the Li‐ion cell doubles the energy density and maintains at least 72% of the battery's initial capacity after 2000 cycles. Moreover, using SAW quantifiably reduces battery degradation in these conditions as determined by optical imaging, scanning electron microscopy, X‐ray diffraction, and neutron diffraction. The use of SAW appears to offer a method to avoid undesirable Li metal plating on the graphite anode during charging, and leads to a much longer battery lifetime and good charge capacity, all despite rapid charging.

Acoustofluidics

“…It is also sufficient to drive rapid fluid flows in nanochannels and to transport, split, combine, and even mix 20 to 200 fL droplets within (Zhang et al, 2021b). A notable use of acoustic streaming in confined flows is in rechargeable batteries, where it has been used to rapidly recharge previously unrechargeable lithium metal batteries (Huang et al, 2020) and to make 10-min charging possible in lithium ion batteries for up to 2,000 cycles (Huang et al, 2022). If driven continuously, large amplitude acoustic waves streaming can lead to significant heating in milli-scale and larger frozen and fluid samples (Horesh et al, 2023), but because of the dominance of surface area-driven effects together with the rapid flow, at micro-scale and smaller, the heating is mitigated by rapid conduction into the surrounding materials.…”

Surface Acoustic Wave-Driven Enhancement of Enzyme-Linked Immunosorbent Assays: ELISAW

“…For example, the charging of batteries relies on the diffusion of lithium ions within the electrolyte to replace those ions deposited on the anode and lost from the electrolyte; diffusion is the rate-limiting phenomenon preventing faster charging. Acoustic streaming-driven convection was discovered to convect lithium ions and overcome diffusion limitations, thereby allowing complete and rapid recharging of batteries in only minutes. , The analytes in ELISA likewise must diffuse in order to produce the binding necessary for the assay to complete, again representing the rate-limiting phenomenon preventing improvements in the speed of the assay in every binding step. More generally, surface acoustic waves have already been used for mixing purposes in biosensors, in particular to speed up the process. , …”