Core-shell structure LiNi_1/3Mn_1/3Co_1/3O₂@ ultrathin δ-MnO₂ nanoflakes cathode material with high electrochemical performance for lithium-ion batteries

Due to the high energy density and low cost, LiNi_1/3Co_1/3Mn_1/3O₂ is wildly explored as a promising cathode material for lithium-ion batteries. However, this material suffers from the destruction of surface structure in the electrolyte and the reacting of electrode with the electrolyte during cycles in highly voltage. Herein, we rationally designed core-shell nanostructure LiNi_1/3Mn_1/3Co_1/3O₂@ ultrathin δ-MnO₂ nanoflakes cathode material with excellent capacity retention and rate capacity by a liquid-phase precipitation method. The unique ultrathin δ-MnO₂ nanoflakes shell nanostructure plays a key role in effectively improving rate performance and cycle life of LiNi_1/3Co_1/3Mn_1/3O₂. The electrode with the coating amount of 3 wt% exhibits excellent cycle performance and superior rate capacity compared with bare electrode. The δ-MnO₂ nanoflakes-coated layer can react with Li⁺ during cycling and convert to spinel phase, resulting in a reversibly de/lithiation coating layer to improve its specific capacity compared with other inactive coating layer, and the spinel phase can also provide a three-dimensional lithium ions diffusion channels and thus promote lithium ions diffusion. Judging from the discussion, it can be concluded that the role of δ-MnO₂-nanoflakes coating layer not only acts as a protective layer to impede the electrode directly contact with electrolyte but also accelerates lithium ions diffusion and improve its specific capacity.