Li(Ni1/3Co1/3Mn1/3)O2 as a suitable cathode for high power application

초록

Since its introduction in 1990, the rechargeable Lithium-ion battery with high energy density and capability has become an important power source for portable electronic devices, such as cellular phones and laptop computers and, more recently, hybrid elecric vehicles(HEV). In this workthe electrochemical performance of the layered Li(Ni1/3Co1/3Mn1/3)O2 material have been investigated as a promising cathode for a hybrid electric vehicle (HEV)) application. A C/Li(Ni1/3Co1/3Mn1/3)O2 cell, cycled between 2.9 and 4.1V at 1.5C rate, dose not show any sign of capasity fade up to 100cycles, whereas at the 5C rate, a loss of only 18% of capacity is obtained after 200 cycles. The Li(Ni1/3Co1/3Mn1/3)O2 host cathode converts from the hexagonal to a monoclinic symmetry at a high state of charge. The cell pulse power capability on charge and discharge were found to exceed thr requirement for powering a hybrid HEV. The accelerated calendar life tests performed on C/Li(Ni1/3Co1/3Mn1/3)O2 cells charged at 4.1V and stored at 50oC have shown a limited area specific impedence (ASI) increase unlike C/Li(Ni0.8Co0.2)O2 bases-cells. A differential scanning calorimetry (DSC) comparative study clearly showed that the thermal stability of Li(Ni1/3Co1/3Mn1/3)O2 is much better than that of Li(Ni0.8Co0.2)O2 and Li(Ni0.8Co0.15Al0.05)O2 cathode. Also, DSC data of Li(Ni1/3Co1/3Mn1/3)O2 cathode charged at 4.1, 4.3, and 4.6V are presented and their corresponding exothermic heat flow peaks are discussed.