Investigating Pore Microstructure Effects on Sintered Electrode Transport and Rate Capability

Abstract

Lithium-ion (Li-ion) batteries have achieved significant commercial success and found widespread use in numerous applications. To further improve the energy density of Li-ion batteries, reducing the inert material and increasing the electrode thickness are two routes. Recently, electrodes that consist of active material only and fabricated via mild sintering treatment have been explored. These sintered electrodes have greater thickness and thus showed much higher areal capacity than composite electrodes. However, restricted Li+ transport in the electrolyte phase through the porous microstructure of thick electrodes limits the ability to achieve high current densities and rates of charge/discharge with these high energy cells.In this work, cells with sintered LiCoO2 (LCO) and Li4Ti5O12 (LTO) electrodes have been fabricated and tested. Processing routes to mitigate transport restrictions were pursued. For LTO electrodes, comparisons were done between using ice-templating to provide directional porosity and using sacrificial particles during processing to match the geometric pore/void density without pore alignment. The ice-templated electrodes retained much greater discharge capacity at higher rates of cycling, which was attributed to improved transport properties provided by the processing. The electrodes were further characterized using an electrochemical model of the cells and evaluated using neutron imaging. The results indicated that significant improvements can be made to electrochemical cell properties via templating the electrode microstructure for situations where the rate limiting step includes ion transport limitations in the cell.