Abstracto

Layered/Spinel Heterostructured Li-Rich Cathode Materials without Oxygen Loss in Lithium-ion Battery

Shan Xu1,2*, Jingcheng Xu3

Lithium-excess manganese layered oxides, which are commonly described by the chemical formula xLiMnO3·(1-x) LiMO2 (M=Co, Ni, Mn, etc.), are of great importance as cathode materials for rechargeable lithium batteries. A mechanism involving simultaneous Li and O removal is often proposed. Oxygen loss and MnO2 formation appear when first charging across a voltage plateau at 4.5 V vs Li/Li+, which is bottleneck of industrialization for the resulting security problems. In our recent findings, layered/spinel hetero structured Li-rich material Li1.2Ni0.2Mn0.6O2 consist of Li2MnO3, LiNiMnO2 and LiNi0.5Mn1.5O4 without oxygen loss was desired. After assembling it into lithium-ion battery, CV curves have no oxygen evolution peak and no oxygen appears in situ Differential Electrochemical Mass Spectrometry (DEMS). According to the first principle, Li+ ions in Li2MnO3 de-intercalate then Ni2+ ions of LiNi0.5Mn1.5O4 migrate into the sites when first charging, which avoids the oxygen loss from the collapse of Li2MnO3. The exist of spinel phase make the phase transition process of circulation stable, which contributed to the high cycling performance for lithium-ion battery (300 and 220 mAh g-1 after 200th cycles at 0.1 and 0.5C-rate (1C=250 mA g-1).