Electrochemical lithiation and delithiation of LiMnPO4: Effect of cation substitution

The electrochemical lithiation–delithiation reaction was examined for LiMnPO4 in which different cations were substituted for part of Mn. The X-ray diffraction analysis indicated that LiMnPO4 is tolerant, to some extent, to substitution of Mg2+, Ca2+ and Zr4+. The substitution of Mg2+ and/or Zr4+ led to an increased reversible capacity and a reduced polarization, whereas Ca2+ substitution had a detrimental effect on the electrochemical properties. The potential transient analysis showed that LiMn0.88Mg0.1Zr0.02PO4 has higher lithium diffusivities than pure LiMnPO4, indicating facilitated diffusion kinetics in the substituted material. Upon the first charge–discharge cycle, LiMn0.88Mg0.1Zr0.02PO4 suffered less irreversible capacity loss when compared with LiMnPO4, and smaller amounts of electrolyte salt-based species were detected on the electrode surface of LiMn0.88Mg0.1Zr0.02PO4.