Formation of the Secondary Phase Domain by Multi-Cation Substitution for the Superior Electrochemical Performance of Spinel Cathodes for High-Voltage Li-Ion Batteries

Disorder-structured spinel oxides are opening frontiers for high-capacity/high-voltage cathodes to meet the challenges of independence on cobalt-containing cathodes toward cheap and sustainable energy storage sources in Li-ion batteries (LIBs). In the present work, a series of Co-free materials: LiMn2-x-y-zNixFeyAlzO4 (x = 0.8–0.5, y = 0.1–0.25, and z = 0.1–0.25) with spinel/rock salt disordered structures are reported. The refinement studies confirmed that the materials synthesized are of mixed phase, and the I311/I400 peaks ratio confirms that the synthesized materials are stable enough for electrochemical applications. This article addresses the influence of the secondary phase on the electrochemical activity and the reduction of the Mn3+ ratio to alleviate the Mn dissolution issue for bettered stability. The optimized LiMnNi0.7Fe0.1Al0.2O4 is appraised as a cathode material in the voltage range between 3.5 and 5 V (vs. Li+/Li) with an initial discharge capacity of 148.7 mA h g–1 at a rate of 1 C. This material showed very good cycling stability with a capacity retention of 79.5% after 1000 cycles. The cyclic voltammetry studies showed that the material can be a potential candidate for 5 V applications.