Capacity Fading of Lithium-Ion Cells Having Li[Li1/3Ti5/3]O₄(LTO)-Negative Electrodes for the First- and Second-Generation 12 V Lead-Free Batteries

Lithium-ion cells consisting of Li[Li 1/3 Ti 5/3 ]O 4 (LTO) and Li[Li 0.1 Al 0.1 Mn 1.8 ]O 4 (LAMO) or Li[Ni 1/2 Mn 3/2 ]O 4 (LiNiMO) were examined at currents higher than 1 mA cm −2 at room temperature. Capacity fading was observed for both LTO/LAMO and LTO/LiNiMO cells during the continuous charge and discharge at 1, 2, and 4 mA cm −2 when a microporous membrane usually used so far was applied. In order to understand the capacity fading, Li/LAMO and Li/LTO cells together with zero-volt lithium-ion cells consisting of LTO or LAMO were fabricated and examined. Among these cells, the rechargeable capacity of a zero-volt lithium-ion cell of LTO with a microporous membrane faded cycle by cycle, while the other cells did not show such obvious capacity fading. From these results, a possible source of capacity fading was discussed in terms of a mass transport problem due to the "zero-strain" insertion electrode combined with a microporous membrane. A solution of the problem is also given in such a way that a non-woven cloth is substituted for the microporous membrane as a separator in LTO/LAMO and LTO/LiNiMO cells for the first- and second-generation 12 V lead-free batteries, respectively.