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

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 (LiCoO 2 ) and inactive material (α-Al 2 O 3 ), electrically conductive additive and binder polymer onto an Al current collector. The resistance components derived from the LiCoO 2 single particles were measured and calculated. Their apparent activation energy ( E a ) 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 LiCoO 2 originated E a could be calculated. Resistance components attributed to LiCoO 2 were also measured and extracted by alternating current impedance measurements using DES. The resistance non-linearly decreased with LiCoO 2 concentration, and the percolation and inhomogeneity of LiCoO 2 particles were suspected. The planful isolation of an active material particle should be critical for the overall information on an electrode particle.