A High-Performance Li-Mn-O Li-rich Cathode Material with Rhombohedral Symmetry via Intralayer Li/Mn Disordering.

Abstract

The search for new high-performance and low-cost cathode materials for Li-ion batteries is a challenging issue in materials research. Commonly used cobalt- or nickel-based cathodes suffer from limited resources and safety problems that greatly restrict their large-scale application, especially for electric vehicles and large-scale energy storage. Here, a novel Li-Mn-O Li-rich cathode material with <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><mi>R</mi> <mover><mn>3</mn> <mo>¯</mo></mover> <mi>m</mi></mrow> </math> symmetry is developed via intralayer Li/Mn disordering in the Mn-layer. Due to the special atomic arrangement and higher <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><mi>R</mi> <mover><mn>3</mn> <mo>¯</mo></mover> <mi>m</mi></mrow> </math> symmetry with respect to the C2/m symmetry, the oxygen redox activity is modulated and the Li in the Li-layer is preferentially thermodynamically extracted from the crystal structure instead of Li in the Mn-layer. The as-obtained material delivers a reversible capacity of over 300 mAh g^-1 at 25 mA g^-1 and rate capability of up to 260 mAh g^-1 at 250 mA g^-1 within 2.0-4.8 V. The excellent performance is attributed to its highly structural reversibility, mitigation of Jahn-Teller distortion, lower bandgap, and faster Li-ion 2D channels during the lithium-ion de/intercalation process. This material is not only a promising cathode material candidate but also raises new possibilities for the design of low-cost and high-performance cathode materials.