A series of LiMn2O4 cathodes with different Mn3+ contents are synthesized by a hydrothermally assisting method combined with a high-temperature solid phase process based on manganese-based metal organic frameworks (MOFs). The effect of NaOH addition on the morphology, structure and electrochemical properties of the LiMn2O4 cathode is investigated. The obtained samples all exhibit obvious octahedral morphology, corresponding to the cubic spinel structure with high crystallinity. Sample LMO-3 prepared with three times the molar amount of NaOH as PTA has the highest Mn3+ content, approximately 46.02%. The (100) and (110) crystal planes are exposed due to the higher Mn3+ content and the special truncated octahedral morphology, which endows LMO-3 with higher capacity and excellent rate performance. Specifically, the first specific capacity of LMO-3 is 140.6 mAh·g−1 at a rate of 1 C, and the capacity retention is 102.82% after 500 cycles. The corresponding capacity retention is 90.2% after 1000 cycles at 10 C. The spinel LiMn2O4 cathode synthesized by taking manganese-based MOFs as a precursor has great potential in practical applications.