Highly [010]-oriented, gradient Co-doped LiMnPO4 with enhanced cycling stability as cathode for Li-ion batteries

LiMnPO4 has been attracting attention for high energy density (701 Wh kg−1) and excellent safety. However, LiMnPO4 suffers from the cycling instability coming from the fragile solid electrolyte interface, besides the Jahn-Teller effect of Mn3+, the poor electrical conductivity and the sluggish ionic conductivity. The substitution of cation with less ionic radius for Mn2+ is conducive to stabilize the solid-electrolyte interface and retard the erosion from electrolyte; therefore, the gradient Co-doped LiMn0.98Co0.02PO4 was synthesized with 25.93 (mol) % Co on the surface by the secondary solvothermal method, and the permeated depth reaches more than 20 nm because of the coprecipitation and cation exchange of Co2+ and Mn2+. LiMn0.98Co0.02PO4/Li cell that demonstrates the cycling performance is remarkably enhanced with 87% capacity retention after 380 cycles at room temperature, even 87% after 100 cycles at 60 °C. Meanwhile, the preferential growth along the a–c plane results in the highly [010]-oriented LiMnPO4 by the solvothermal, which afford more channels for Li+ migration by exposing more reaction sites, and the infrared spectrum also reflects the less Mn2+-Li+ antisite defects in the crystal. So the samples show the superior rate performance as well.