Co-extruded Integral Battery Structures

We have successfully designed a process that utilizes high-speed co-extrusion to simultaneously fabricate two layers of a functional battery structure (separator and heterogeneous cathode) in a single deposition step. The use of our novel co-extrusion printhead technology enables structuring in battery electrodes - a new design tool that can improve battery energy density and power for a given application. Our co-extrusion process also enables a resulting cost reduction relative to conventional manufacturing processes. Typical state-of-the-art battery manufacturing consists of sequential fabrication and processing of each of the constituent layers: the cathode, separator, and anode. These sequential processing steps drive costs through increased capital equipment, process time, and yield loss. The development of mass markets for large batteries, including electric vehicles (EVs) and grid support, depends on cost reductions to improve their economic viability. Our process removes multiple steps in a conventional battery coating process and has the potential to revolutionize battery manufacturing across most chemistries, significantly lowering end-product cost and shifting the underlying economics to make EVs and other battery applications a reality. To date, we have realized a co-extruded integral battery structure with a silica-based separator and heterogeneous LiNi1/3 Co1/3 Mn1/3O2 (nickel cobalt manganese) cathode fabricated in a single pass at print speeds comparable to conventional roll coating processes. The heterogeneous cathode consists of striped regions of varying LiNi1/3 Co1/3 Mn1/3O2 density, enabling better active material utilization at higher C-rates. Separator and cathode slurry formulations were designed to be compatible with our co-extrusion process. Our co-extrusion process enables a final dried separator thickness of 16-21m with cathode thicknesses ~90-120m. A co-extruded integral battery, when paired with a conventional graphite anode, demonstrated gravimetric and volumetric energy density of 267.4 Wh/kg and 436.4 Wh/L at a C/2 rate. We will present our co-extrusion printhead, constituent material formulations and fabrication processes which enabled our proof-of-principle integral battery structure.