Innovative insertion material of LiAl1/4Ni3/4O2 (R-m) for lithium-ion (shuttlecock) batteries

We report an innovative insertion material of LiAl1/4Ni3/4O2 (R-m) which is a solid solution of LiNiO2 (R—m) and α-LiAlO2 (R—m). LiAl1/4Ni3/4O2 (interlayer distance: ~4.75 Å) shows an overcharge-resistant character due to the formation of an insulator of 3/4Li1/4-Al1/4Ni3/4O2 having ~ 4.8 Å of interlayer distance. Cycle tests of an Li/LiAl1/4Ni3/4O2 cell between 2.5 and 4.5 V show no noticeable loss in rechargeable capacity (~ 150 mAh g−1). The thermal behavior of Li1 −xAl1/4Ni3/4O2 (0 ≤ x <3/4) is also examined by differential scanning calorimetry and shows that the exothermic reaction of Li1 − xAl1/4Ni3/4O2 with electrolyte is remarkably suppressed even for the fully charged state when compared with that of Li1 − xNiO2. From these results we discuss on the possibility of designing reliable high-energy, high-volume, lithium-ion batteries.