Improving electrochemical performances of LiNi0.5Mn1.5O4 by the strategy of oxygen vacancy doping

Despite the dazzling potential to be utilized as a high energy density lithium-ion battery cathode, the practical application of LiNi0.5Mn1.5O4 (LNMO) is hampered by the structural distortion related to Jahn-Teller effect of Mn3+ and the capacity degradation related to Mn2+ dissolution at high voltage. Herein, LNMO cathode materials doped with different contents of oxygen vacancies are synthesized by directly adjusting the oxygen ratio in the calcination atmosphere. Experimental and theoretical calculation results show that doping an appropriate amount of oxygen vacancies can regulate the electronic structure of Mn and Ni around oxygen vacancy, adjust the relative amount of Mn3+/Mn4+, increase the degree of disorder, and improve the electronic and ionic conductivity of LNMO, thereby enhancing its electrochemical performance. Especially, the modified LNMO exhibits a high capacity of 121.2 mAh g−1 at 0.5 C, a good capacity retention of 87.6 % after 100 cycles, and an excellent rate performance when the content of oxygen vacancies is about 20.60 %, corresponding to the oxygen ratio of 50 % in the calcination atmosphere. This study emphasizes the influence of doping oxygen vacancies on LNMO performance, enhancing its electrochemical properties without the introduction of additional elements. Moreover, these findings offer a fresh approach to enhancing the electrochemical performance of advanced batteries.