Three-dimensional reconstruction and computational analysis of a structural battery composite electrolyte

Abstract

Structural batteries are multifunctional composite materials that can carry mechanical load and store electrical energy. Their multifunctionality requires an ionically conductive and stiff electrolyte matrix material. For this purpose, a bi-continuous polymer electrolyte is used where a porous solid phase holds the structural integrity of the system, and a liquid phase, which occupies the pores, conducts lithium ions. To assess the porous structure, three-dimensional topology information is needed. Here we study the three-dimensional structure of the porous battery electrolyte material using combined focused ion beam and scanning electron microscopy and transfer into finite element models. Numerical analyses provide predictions of elastic modulus and ionic conductivity of the bi-continuous electrolyte material. Characterization of the three-dimensional structure also provides information on the diameter and volume distributions of the polymer and pores, as well as geodesic tortuosity.

Advancing Structural Battery Composites: Robust Manufacturing for Enhanced and Consistent Multifunctional Performance

“…Additionally, the SBE's unique morphology, where the electrolyte is confined to the polymer percolating pores, directly affects the ionic conductivity. [ 20 ] This restricted distribution of liquid electrolyte limits the available pathways for ion transport and hinders the connectivity between the electrode materials. Consequently, the confinement of the liquid electrolyte within small compartments in the porous structure creates localized regions with lower ion mobility, leading to an overall decrease in ionic conductivity.…”

Low-Temperature Structural Battery Electrolytes Produced by Polymerization-Induced Phase Separation

“…These SBE systems should simultaneously possess high ionic conductivity, high mechanical stiffness/strength, safe operation, and electrode compatibility. PIPS based on SBEs consist of two coexisting phases (bicontinuous): a solid phase that provides high mechanical stiffness and a liquid phase that provides high ionic conductivity. − The mass or volume fraction of the solid phase can be used to tune the ionic conductivity and mechanical properties in which a trade-off exists between the two properties. − , Mechanical stiffness implies rigid polymer chains while ionic conductivity is facilitated by polymer flexibility . One early example of a bicontinuous electrolyte was applied to supercapacitors; specifically, a commercial epoxy resin cured in the presence of lithium bis­(trifluoromethanesulfonyl)­imide (LiTFSI) and an ionic liquid electrolyte resulted in a conductivity of 4.00 × 10 –5 to 1.30 × 10 –4 S/cm at 30 °C and a modulus of 0.19 to 0.15 GPa, depending on the relative mass fraction .…”