(298b) Processing and Characterization of Thick All Active Material Lithium-Ion Electrodes

In general, increasing electrode thickness in a battery system will increase energy density at the cell level, because less relative volume is contributed by other inactive but necessary components such as current collectors and separators. While increasing electrode thickness increases volumetric energy density there will be tradeoffs with regards to accessible capacity at increasing rate of charge/discharge and cell overpotential due to the increased ion and electron transport distances for the thicker electrodes. For organic electrolyte systems, such as with lithium-ion batteries, ionic transport limitations are typically more significant, although electronic transport/conduction can also be a factor depending on the specific system and materials involved.

Within our research group, we have developed methods to fabricate thick lithium-ion battery electrodes comprised of only electroactive material. Electrode processing includes thermal treatment to maintain porosity sufficient for percolated ionic transport. While in general the large electrode thickness still results in long ion diffusion paths which limits charge/discharge rate for these electrodes, dramatic reduction of inactive additives provides a relative advantage in effective ionic transport properties. There are also mechanical advantages to processing electrodes with the targeted thicknesses, which can exceed 2 mm.

In this presentation, recent progress for all active material electrode batteries from our group will be discussed. In particular, incorporation of new materials with increased gravimetric and more importantly volumetric energy density will be described. In some cases, the alternative materials have lower electronic conductivity than previously used electroactive materials for all active material electrodes, and processing strategies for alleviating electronic conductivity limitations will be discussed. Incorporation of modified materials and processing results in very high energy density small form factor battery cells, though with significant tradeoffs in terms of rate of charge/discharge.