Multiphysics Modelling of Electrochemical Energy Storage Devices: Li-ion Batteries and Supercapacitors

Abstract

As one of the current and next-generation energy storage devices, lithium-ion batteries and supercapacitors have potential for improved design for lower cost, higher safety and efficiency, compared with recent status. The major development of lithium-ion batteries and supercapacitors is currently driven by the experimental approaches, which cost much time and lack deep insight into interacted multiphysics processes. Multiphysics modelling approach can overcome such drawbacks, and thus be used for investigation and discovery of new materials and device design. For lithium-ion batteries, a novel 3D multiphysics model was developed to discover such heterogeneously physical interactions in a 12Ah pouch cell based on operation principles. The model analyzes the internal interactions of local thermal effects, electrochemical and electric performance on electro-active layers in the pouch cell. It illustrates that the poor heat dissipation and high heat generation causes strong thermal heterogeneity at large currents, which finally results in intense local interactions of electric and electrochemical performance. This 3D multiphysics model is applied into a global sensitivity analysis of the same cell for the utilizable discharge capacity and local maximum temperature at 1C. The sensitivity analysis is efficiently executed for 46 parameters in this 3D model. Consequently, it reveals that the capacity and the local maximum temperature are both most sensitive to geometric parameters of electrodes and their pore structures. Following these results, a large-format prismatic battery was optimized with the detailed 3D geometries and components for upgrading safety prevention of thermal-runaway and maximizing the capacity. For supercapacitors, a novel multiphysics pseudo-2D model is developed to interpret complex faradaic reaction mechanisms and investigate effects of different pore structures on capacitive performance. Symmetric cells of cuprous oxide and hierarchical porous carbon are parameterized respectively, with good agreement between experimental data and simulated results at the room temperature. The simulation results imply that the effective ion size and micropore volume can strongly affect the double layer capacitance due to the change of ion transport in double layers and pores. This multiphysics model is the first to interpret the capacitive behavior in hierarchical pore structures based on attractive force theory and modified Donnan concepts, to my best knowledge.