MEAM Seminar: “Strategies for Approaching One Hundred Percent Dense Lithium-Ion Battery Cathodes”

Creating thick electrodes with low porosity can dramatically increase the available energy in a single cell and decrease the number of electrode stacks needed in a full battery, which results in higher energy, lower cost, and easier to manufacture batteries. However, existing electrode architectures cannot simultaneously achieve thick electrodes with high active material volume fractions and good power. These particle-based architectures rely on electrolyte transport within the pores of the cathode to fully lithiate active material particles during discharge. As cathode solid volume fractions approach 100%, batteries experience electrolyte depletion which leads to inaccessible cathode reaction sites. The additional theoretical capacity that comes from increased cathode density, therefore, is impractical if that energy cannot be fully extracted.

We combine experiments and simulations of high density and high thickness cathodes to understand the transport and performance trade-offs of LIBs as the cathode solid volume fraction approaches 100%, which we use to reveal the cathode properties needed to achieve high performance at high relative density and thickness. We use one- and two-dimensional simulations to compare the discharge performance of two cathode architectures, a traditional particle-based architecture and a continuous cathode architecture created via electrodeposition. We show that there is a large opportunity space for improved energy density at high relative densities by using new electrode manufacturing techniques to create continuous diffusion pathways and high diffusivities.

This work uses a comparative analysis of cathode architectures to explore the interdependent impact of solid volume fraction, solid-diffusivity, cathode thickness, and discharge rate on lithium-ion battery areal capacity. We should how a combination of high diffusivity and continuous solid-state diffusion pathways provides an exciting path for realizing ultra-dense and thick cathodes with high energy density.