Electrochemical In Situ Na Doping to Construct High-Performance Lithium-Rich Cathode

Lithium-rich layered oxides are regarded as the next generation of cathode materials for lithium ion batteries. However, the irreversible release of oxygen during cycling can lead to serious failure problems. In order to solve the above problems, this paper proposes an electrochemical in situ Na doping method with ultrahigh content, homogenization, and no residual alkali. The traditional solid-phase sintering method has low doping content (<10%), no obvious expansion of layer spacing, more residual alkali and multiphase interface, which will lead to serious structural and interface failure problems during charging and discharging. The ultrahigh Na content (30%) leads to the extra-large layer spacing (0.547 nm), and the integration of nonbonded O 2p orbitals is effectively inhibited by coulomb repulsion, which greatly improves the electrochemical performance of cathode materials. The mechanism of electrochemical doping was investigated by a series of in-situ/ex-situ characterizations and density functional theory. This study provides a new way to improve the performance of Li-rich cathode materials.