Micro-Architected Lithium Cobalt Oxide Electrodes Via Hydrogel Infusion Additive Manufacturing

Abstract

Additive manufacturing frees up the structural design of battery electrode materials from traditional slurry electrodes, enabling three-dimensional free-standing structures with micro-architected features, which provides a promising pathway toward 3D solid-state batteries with high power and high energy density. In this work, lithium cobalt oxide (LCO) is fabricated into 3D micro-lattice through a novel hydrogel infusion additive manufacturing (HIAM) process. A blank 3D architected organogel is fabricated through photopolymerization-based 3D printing and soaked in water to form a blank hydrogel micro-lattice, where lithium and cobalt ions in an aqueous solution are then swelled into the hydrogel. A free-standing LCO micro-lattice is synthesized from the ion-containing hydrogel during the post-printing calcination process. 50 μm beam diameter is obtained, giving a crucial lithium-ion diffusion length of 25 μm into LCO lattice beams. Structural, electrochemical, and mechanical properties of the LCO microlattice are investigated. HIAM technique utilizes photopolymerization of a UV-curable photoresin to create 3D structures with well-controlled form factors. Compared to traditional extrusion-based additive manufacturing techniques, photopolymerization stands out for its ability to fabricate materials with higher resolution. The main challenge with photopolymerization to fabricate non-polymeric functional materials is the complex photoresin design. A standard approach is to introduce active material nanoparticles into the photoresin, which often sacrifices print resolution due to the presence of light-scattering nanoparticles. HIAM technique overcomes the difficulties during the resin design by using a single photoresin to fabricate a large variety of functional materials. Without presence of nanoparticles, even higher resolution can be achieved. With this technique, LCO cathodes can be flexibly architected into 3D geometries for optimization of their electrochemical performance. It also enables the fabrication of various electrode materials into 3D structures with well-controlled form factors, and their incorporation into customizable batteries and microbatteries of any shape.