Laser-induced breakdown spectroscopy for studying the electrochemical impact of porosity variations in composite electrode materials

Abstract

The porosity in composite electrode materials can vary on micro-and nanometer scale and has a great impact on electrochemical performance in lithium-ion cells. Liquid electrolyte has to penetrate into the entire porous electrodes in order to enable lithium-ion diffusion. For studying the electrochemical impact of porosity variations in composite lithium-nickel-manganese-cobalt-oxide thick films (Li(Ni1/3Mn1/3Co1/3)O2, NMC), laser-induced breakdown spectroscopy (LIBS) was applied. A rapid chemical screening of the complete electrode after electrochemical cycling and cell degradation was performed. This rather new technological approach was used to obtain post-mortem critical information about surface and bulk phenomena that define and control the performance of lithium-ion batteries. The influence of porosity variations along NMC electrode surfaces was studied regarding capacity retention, life-time, and lithium distribution. For this purpose, different geometrical arrangements of porosity distribution were generated by embossing. Using LIBS, elemental mapping of lithium was obtained with a lateral resolution of 100 μm. A correlation between porosity distribution, cell degradation and local lithium plating could be identified.