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

Abstract

Lithium-excess manganese layered oxides, which are commonly described by the chemical formula xLi₂MnO₃· (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 heterostructured Li-rich material Li_1.2Ni_0.2Mn_0.6O₂ consist of Li₂MnO₃, LiNiMnO₂ and LiNi_0.5Mn_1.5O₄ 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 LiNi_0.5Mn_1.5O₄ 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)).