Partial substitution of Mn/Si with V, Cr or Al in Li2MnSiO4 nanoparticle: Dependence of the physical and electrochemical properties on the substitution strategy

Partial substitution of Mn/Si with V, Cr or Al is employed to modify Li2MnSiO4 nanoparticles. The dependence of the physical and chemical properties on the substitution strategy is clarified. In comparison with partial substitution of Mn, partial substitution of Si with the same substituent usually results in larger lattice volume, lower O–Si–O bridging linkage and higher specific surface area with smaller particle size, which contributes to lower charge transfer resistance and higher lithium ion diffusion coefficient. Li2.05MnSi0.95Al0.05O4 delivers a discharge capacity as high as 108 mA h g−1 at the current density of 660 mA g−1. However, partial substitution of Si leads to faster capacity fading in comparison with partial substitution of Mn with the same substituent, which can be attributed to the absence of the pillar effect when Si is substituted. Substitution of Si with Al, V or Cr is a promising strategy to break through the insulation effect of (SiO4)4− polyanion and thus improves the high rate capability of Li2MnSiO4.