Electrode Microstructure and Electrolyte Conductivity Modifications to Improve Thick Sintered Electrode Rate Capability

Abstract

Increasing the electrode thickness and/or reducing the inert content in a cell are routes to improve the energy density of lithium-ion batteries (Li-ion battery). Sintered electrodes have been pursued towards achieving both of those routes to increase energy density at the cell level. These electrodes are fabricated by sintering of pure active material pellets and thus do not contain any inert additives such as conductive carbon and polymer binder. The greater thickness of sintered electrodes compared to composite electrodes increases the energy density and areal capacity at the cell level. However, a limitation is that Li-ion transport in thick porous electrodes is restricted and impacts the charge/discharge capacity at high rate/current density.In this work, different approaches to mitigate transport restrictions have been investigated with sintered electrode system. First, electrolytes with different Li+ concentration and conductivity were investigated. The highest conductivity electrolyte had the highest retention of capacity at high cycling rates and was combined with pellets with directional porosity which were fabricated via ice-templating. Ice-templating alone also improved the rate capability of the electrodes in the cells, and the combined system with higher conductivity electrolyte and a directional porosity electrode demonstrated substantive retention of capacity at increasing rates. These results showed limitations of thick battery electrodes, and demonstrate possible design improvements in the context of molecular transport properties.