Session: 01-02-01: Adaptive and Multifunctional Structures

Paper Number: 121680

121680 - A New Thermodynamics Framework for All-Solid-State Batteries 

All-solid-state batteries (ASSBs) provide a viable alternative to traditional lithium-ion batteries (LIBs) and have become highly desirable for important applications in electric vehicles, consumer electronics, renewable energy storage, medical devices, and aerospace structures. ASSBs operate with solid-state electrolytes that are stable at high temperatures and non-flammable, unlike traditional LIBs based on liquid electrolytes that are associated with significant safety issues such as leakage and flammability. ASSBs hold a promising potential for revolutionizing the battery industry by offering improved battery performance with better safety, longer lifetime, higher energy density, and shorter charging time.

An effective thermodynamics framework capable of describing the various thermomechanical and electrochemical processes in ASSBs is essential for identifying an optimal compromise between different conflicting physical mechanisms influencing the battery performance. However, very limited studies have been conducted on such frameworks.

In the current study, a new thermodynamics framework that accounts for coupling among the thermal, mechanical, electrostatic, and chemical processes existing in ASSBs is proposed. In this framework, an ASSB is treated as a multi-layered structure, with each layer modeled as an open thermodynamic system undergoing reversible thermomechanical deformations and electrochemical processes involving ion transport through its boundary. A Helmholtz free energy function containing mechanical, thermal, diffusional, thermal-mechanical coupling, diffusion-mechanical coupling, and diffusion-thermal coupling energy terms is considered for each layer. Through the thermo-mechanical coupling term, the influence of the thermal expansion mismatch between adjacent layers in the battery stack is incorporated. In addition, the diffusion-mechanical coupling term accounts for the local stresses arising from the ion interdiffusion, electrostatic potential of transported ions and excessive electrochemical potentials caused by mechanical strains. The latter is important in tailoring the electrochemical kinetics at the interfaces between the solid electrolyte and electrodes.

To demonstrate the new thermodynamic framework, an analytical model is developed for an ASSB stack containing multiple layers of dissimilar materials. Each layer is kinematically regarded as a Kirchhoff plate, accounting for stresses due to various factors, including (1) thermal and mechanical loads acting on the layer, (2) electrochemical ionic influx or efflux through the layer boundaries, (3) volume changes in the battery layers due to ion transport, and (4) mismatch in the mechanical and thermal properties of the layers. Additionally, interfacial stresses are included by treating interfaces as imperfect [1].

References

[1] Shaat, M., Gao, X.-L., Li, K. and Littlefield, A. G. (2023). New analytical model for thermomechanical responses of multi-layered structures with imperfect interfaces. Acta Mech. (published online on Aug. 30, 2023) (https://doi.org/10.1007/s00707-023-03659-3)

Presenting Author: Xin-Lin Gao Southern Methodist University

Presenting Author Biography: Dr. Xin-Lin Gao is currently a professor of mechanical engineering at Southern Methodist University, Dallas, TX. He is a fellow of ASME and a former chair of the Aerospace Division of ASME.