A High-Capacity O2-Type Li-Rich Cathode Material with a Single-Layer Li2MnO3 Superstructure

Abstract

A high capacity cathode is the key to the realization of high-energy-density lithium-ion batteries. The anionic oxygen redox induced by activation of the Li₂MnO₃ domain has previously afforded an O3-type layered Li-rich material used as the cathode for lithium-ion batteries with a notably high capacity of 250–300 mAh g⁻¹. However, its practical application in lithium-ion batteries has been limited due to electrodes made from this material suffering severe voltage fading and capacity decay during cycling. Here, it is shown that an O2-type Li-rich material with a single-layer Li₂MnO₃ superstructure can deliver an extraordinary reversible capacity of 400 mAh g⁻¹ (energy density: ≈1360 Wh kg⁻¹). The activation of a single-layer Li₂MnO₃ enables stable anionic oxygen redox reactions and leads to a highly reversible charge–discharge cycle. Understanding the high performance will further the development of high-capacity cathode materials that utilize anionic oxygen redox processes.

A new O2-Li-rich cathode Li_1.25Co_0.25Mn_0.5O₂ is prepared by a simple ion-exchange reaction. This promoted phase shows attractive electrochemical performances with a high capacity of 400 mAh g⁻¹ and a perfect first coulomb efficiency near 100%. In addition, the unique geometry structure of O2-Li-rich cathode can inhibit the migration of transition-metal ions, indicating that this cathode can avoid suffering voltage decay.

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