Characterization of Lithium Insertion Electrodes and Its Verification: Prototype 18650 Batteries Consisting of LTO and LAMO

Abstract

The insertion electrodes of lithium titanium oxide (LTO) and lithium aluminum manganese oxide (LAMO) are characterized in terms of the area-specific capacity (ASC) in mAh cm−2, area-specific impedance (ASI) in Ω cm2, and area-specific deformation (ASD) in μm/(mAh cm−2). The prototype 18650-batteries consisting of LTO and LAMO electrodes characterized in this way are fabricated and examined in their performance in order to verify the basic concepts of the characterization of the lithium insertion electrodes. The rechargeable capacity, 1.05 Ah, calculated from ASC and the active electrode area agrees with the nominal capacity of 1.0 Ah determined at the 5-h rate of discharge. The impedance estimated from ASI and the active electrode area also agrees well with the observed impedance spectra for a prototype battery except a high frequency region due to inductance derived from a spirally wounded electrode configuration. The internal resistance of the battery is calculated to be ca. 30 mΩ from the results on the rate capability tests at 1/5, 1/2, 1, 2, 3, 4, and 5 C-rate for both charge and discharge, and an understanding on the internal resistance of a battery is discussed in relation to ASI and ASD.