Morphology controlled Si-modified LiNi_0.5Mn_1.5O₄ microspheres as high performance high voltage cathode materials in lithium ion batteries

Well-crystallized, microspherical LiNi_0.5Mn_1.5−nSi_nO₄(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 LiNi_0.5Mn_1.45Si_0.05O₄microspheres is achieved, which is superior compared to 93.1% capacity retention of the pristine LiNi_0.5Mn_1.5O₄microspheres. Since the Si[sbnd]O bond exhibits higher dissociation energy compared to the dissociation energies of the Mn[sbnd]O or Ni[sbnd]O 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.