Structural Origin of Suppressed Voltage Decay in Single-Crystalline Li-Rich Layered Li[Li Ni Mn ]O Cathodes.

Lithium- and manganese-rich layered oxides (LMLOs, ≥ 250 mAh g ) with polycrystalline morphology always suffer from severe voltage decay upon cycling because of the anisotropic lattice strain and oxygen release induced chemo-mechanical breakdown. Herein, a Co-free single-crystalline LMLO, that is, Li[Li Ni Mn ]O (LLNMO-SC), is prepared via a Li /Na ion-exchange reaction. In situ synchrotron-based X-ray diffraction (sXRD) results demonstrate that relatively small changes in lattice parameters and reduced average micro-strain are observed in LLNMO-SC compared to its polycrystalline counterpart (LLNMO-PC) during the charge-discharge process.