Stable nickel-substituted spinel cathode material (LiMn1.9Ni0.1O4) for lithium-ion batteries obtained by using a low temperature aqueous reduction technique
A nickel substituted spinel cathode material (LiMn1.9Ni0.1O4) with enhanced electrochemical performance was successfully synthesized by using a locally-sourced, low-cost manganese precursor, electrolytic manganese dioxide (EMD), and NiSO4·6H2O as a nickel source by means of a low temperature aqueous reduction synthesis technique. This synthesis protocol is convenient to scale up the production of the spinel cathode material, with minimal nickel content (Ni = 0.1) in the structure, for lithium-ion battery applications. Ni-ions substituting Mn-ions was confirmed using XRD, EDS, XPS and electrochemical performance studies. LiMn1.9Ni0.1O4 materials showed an octahedral shape with clearly exposed (111) facets that enhanced the Li-ion kinetics and improved the cycling performance compared to the pristine spinel sample (LiMn2O4). The LiMn1.9Ni0.1O4 sample exhibited superior capacity retention by retaining 84% of its initial capacity (128 mA h g−1) whereas pristine LiMn2O4 retained only 52% of its initial capacity (137 mA h g−1). XPS confirmed that the Mn3+/Mn4+ ratio changed with nickel substitution and favored the suppression of capacity fading. The study clearly suggests that the integration of small amounts of Ni into the spinel structure is able to eliminate the disadvantageous Jahn–Teller effects in the LiMn2O4.