Molybdenum Substitution for Improving the Charge Compensation and Activity of Li 2 MnO 3

Lithium‐rich layer‐structured oxides x Li 2 MnO 3 ⋅ (1− x )LiMO 2 (0< x <1, M=Mn, Ni, Co, etc.) are interesting and potential cathode materials for high energy‐density lithium ion batteries. However, the characteristic charge compensation contributed by O 2− in Li 2 MnO 3 leads to the evolution of oxygen during the initial Li + ion extraction at high voltage and voltage fading in subsequent cycling, resulting in a safety hazard and poor cycling performance of the battery. Molybdenum substitution was performed in this work to provide another electron donor and to enhance the electrochemical activity of Li 2 MnO 3 ‐based cathode materials. X‐ray diffraction and adsorption studies indicated that Mo 5+ substitution expands the unit cell in the crystal lattice and weakens the LiO and MnO bonds, as well as enhancing the activity of Li 2 MnO 3 by lowering its delithiation potential and suppressing the release of oxygen. In addition, the chemical environment of O 2− ions in molybdenum‐substituted Li 2 MnO 3 is more reversible than in the unsubstituted sample during cycling. Therefore molybdenum substitution is expected to improve the performances of the Li 2 MnO 3 ‐based lithium‐rich cathode materials.