Morphology controlled Si-modified LiNi0.5Mn1.5O4 microspheres as high performance high voltage cathode materials in lithium ion batteries

Well-crystallized, microspherical LiNi0.5Mn1.5−nSinO4 (0.05 < n < 0.2) is successfully synthesized by a template directed approach in combination with the partial substitution of manganese by silicon. Structural and electrochemical characteristics are investigated through FE-SEM, XRD, EDX, cyclic voltammetry and galvanostatic charge/discharge testing. Spherical shape and incorporation of silicon into the crystal leads to higher proportion of the disordered Fd-3m phase, and electrochemical performance is significantly improved. High capacity retention of 99.4% after 100 cycles at 1 C rate for LiNi0.5Mn1.45Si0.05O4 microspheres is achieved, which is superior compared to 93.1% capacity retention of the pristine LiNi0.5Mn1.5O4 microspheres. Since the SiO bond exhibits higher dissociation energy compared to the dissociation energies of the MnO or NiO bonds, the excellent electrochemical performance might be associated with an increased structural and chemical stability caused by incorporation of silicon into the oxygen rich crystal lattice.