Optimized synthesis conditions and electrochemical performances for novel quaternary cobalt-free spherical cathodes

Although Lithium-rich manganese-based layered oxides (LLOs) cathode containing cobalt has practical ability and stability for commercial purposes, it suffers from the scarcity, toxicity and high cost of cobalt. Here, a novel quaternary cobalt-free Li1.23Fe0.1Ni0.1Mn0.55Al0.015O2 (LFNMA) LLOs cathode is successfully designed and synthesized. In this work, Al3+ with the electrons in low spin state and without the unpaired electrons outside the nucleus, is introduced to induce the reduction of transition metal (TM) ions (especially Ni3+ ions) in LLOs cathode materials, so as to enhance the redox activity of the cations. Besides, the introduction of Al also could enhance the TM-O bonds, stabilize the overall crystal structure, inhibit the phase transition and accelerate Li+ diffusion, thus improving the cycling stability. The optimized quaternary cobalt-free LFNMA cathode exhibits a smaller Brunauer-Emmett-Teller (BET) area of 2.05 m2 g−1 and a higher tap density area of 2.32 g cm−3. The Li1.23Fe0.1Ni0.1Mn0.55Al0.015O2 (LFNMA)||Li cells deliver a discharge specific capacity of 217 mAh g−1 with an initial Coulombic efficiency of 73%. The corresponding capacity retention is 90.4% after 100 cycles at C/10.