Design of bi-continuous structural battery electrolyte using a virtual temperature constrained topology optimization

Abstract Structural Battery Composites (SBC) are a new class of multifunctional materials that simultaneously provide structural load bearing capabilities as well as electrochemical energy storage. By combining these functionalities, the weight and volume of energy storage systems can be reduced. In this work, a multiphysics, multi-objective topology optimization framework is used to design the Structural Battery Electrolyte (SBE) of the SBC. The objectives considered are the minimization of compliance and maximization of effective ionic conductivity. The multi-objective formulation is implemented using the Normalized-Normal Constraint method. This framework uses the finite element method to evaluate the structural and thermal responses and ResNet, a reduced order model, to find the effective ionic conductivity. The sensitivities of all physics are determined analytically using the adjoint sensitivity method. Previous studies have implemented topology optimization for designing SBE; however, these methodologies do not guarantee a bi-continuous design. Bi-continuous domains of the SBE are necessary for efficient ion transport. In this study, a virtual temperature constraint is used in conjunction with the topology optimization framework to prevent electrolyte islands from forming in the design domain. By doing so, bi-continuous behavior of the SBE microstructure can be enforced. Several numerical studies are conducted to demonstrate the capabilities of this framework.