Concentration shift experiment with an electrode of active material for precise electrochemical analysis.

Abstract

To precisely evaluate the electrochemical properties of a battery of active material, we proposed a "concentration shift experiment" using single-particle electrochemical measurement (SPEM) and a diluted electrode sheet (DES). SPEM can be used for information, such as the charge-discharge and resistance properties of only the active material (extremely dilute condition: ≈0). DES consists of concentrations varying from 1% to 100% of the active material (LiCoO2) and inactive material (α-Al2O3), electrically conductive additive and binder polymer onto an Al current collector. The resistance components derived from the LiCoO2 single particles were measured and calculated. Their apparent activation energy (Ea) was 27 kJ mol-1, which is relatively low compared with the applied-type sheet electrode (30-60 kJ mol-1). Simple electric/ionic conductive route was analyzed using SPEM cell, and the fundamental LiCoO2 originated Ea could be calculated. Resistance components attributed to LiCoO2 were also measured and extracted by alternating current impedance measurements using DES. The resistance non-linearly decreased with LiCoO2 concentration, and the percolation and inhomogeneity of LiCoO2 particles were suspected. The planful isolation of an active material particle should be critical for the overall information on an electrode particle.