리튬이온이차전지용 양극활물질 Li[Ni0.55Co0.15Mn0.30]O2 의 고전압에서의 특성에 관한 연구

Abstract

The electrochemical properties and thermal stabilities of a new positive electrode material for Li-ion batteries, Li[Ni0.55Co0.15Mn0.30]O2, were investigated over a wide potential window. This electrode material was synthesized via a co-precipitation method. X-ray diffraction studies indicated that the synthesized material crystallized into an α-NaFeO2 layered structure (R3m). The Li[Ni0.55Co0.15Mn0.30]O2 positive electrode has a discharge capacity of 202 mAh/g in the voltage range of 2.7-4.5 V. This high capacity was retained throughout 50 cycling (93% at 55 oC). The thermal stability of Li[Ni0.55Co0.15Mn0.30]O2 was measured by differential thermal calorimetry and found to be comparable to that of Li[Ni1/3Co1/3Mn1/3]O2. This positive electrode material was also characterized in a full cell configuration (graphite negative electrode) by the hybrid pulse power characterization tests following the FreedomCAR battery test manual for plug-in hybrid electric vehicles (PHEVs). Most of the pulse power data exceed the PHEV-10 and PHEV-40 goals, except for the discharge pulse power at 70% DOD (0.98 kW/kg module) and regenerative pulse power at 10% DOD (0.57 kW/kg module) and 20% DOD (0.91 kW/kg module) for high-current (10 C rate, 1700 mA/g) HPPC test. Furthermore, the Li[Ni0.55Co0.15Mn0.30]O2 material meets the optimal power-to-energy (P/E) ratio for the PHEV-10 (90 /h) and PHEV-40 (126 /h) batteries.