Unlike conventional liquid electrolytes used in lithium-ion batteries, gel polymer electrolytes (GPEs) are immobilized within a polymer network, which reduces leakage risks, thereby improving mechanical and thermal stability. However, current methods for GPE fabrication result only in two-dimensional planar films, which can make their application into different battery geometries complex and costly. Researchers from the University of Texas at El Paso (UTEP; www.utep.edu) have now demonstrated a scalable vat photopolymerization (VPP) process that enables the “printing” of GPEs directly into three-dimensional architectures, enabling their use in more complex or application-specific battery configurations. “VPP is a family of additive manufacturing techniques in which a liquid photosensitive resin is selectively cured by light, layer by layer, to produce a three-dimensional object. VPP starts with an entire vat of liquid resin, and the solid object is created by exposing selected regions to ultraviolet or visible light,” explains Alexis Maurel, the study’s lead researcher and a faculty member in UTEP’s Department of Metallurgical, Materials and Biomedical Engineering.
Source: Communications Engineering, “Vat photopolymerization of gel polymer electrolytes with solvent-dependent performance and complex geometries for Li-ion batteries”
The ability to more easily incorporate GPEs into batteries supports the manufacture of rechargeable batteries into nearly any form factor, providing many benefits in specialized applications like aerospace components, drones and wearable devices. Beyond the safety and stability benefits, the GPE’s polymer matrix also improves contact with battery electrodes, notes Maurel: “This lowers interfacial resistance and facilitates efficient ion transport. Processing GPEs into engineered three-dimensional architectures using advanced manufacturing techniques, such as VPP, enables the fabrication of architected batteries with optimized ion-transport pathways and enhanced electrochemical performance.”
The core of the VPP process is a standard 3D printer consisting of a resin vat, a movable build platform and a light source. The GPE resin formulation includes photocurable monomers or oligomers, a photoinitiator and lithium salts and solvents. The team has demonstrated the process at the laboratory scale, printing discs, an open honeycomb lattice and a solid cube, and work is also underway to incorporate the printed GPEs into complete battery cells and apply VPP to additional materials. “Recently, we leveraged VPP-based precursor approaches to fabricate metallic structures, including copper, nickel and refractory metals, such as tungsten. We also extended this approach to complex multicomponent systems, allowing the production of alloys and compositionally graded materials, such as spatially varying tungsten-nickel architectures,” adds Maurel. Details of this work were published in Communications Engineering.