Lithium difluoro(oxalato)borate/ethylene carbonate + propylene carbonate + ethyl(methyl) carbonate electrolyte for LiMn2O4 cathode

Lithium difluoro(oxalato)borate (LiODFB) was investigated as a lithium salt for non-aqueous electrolytes for LiMn₂O₄ cathode in lithium-ion batteries. Linear sweep voltammetry (LSV) tests were used to examine the electrochemical stability and the compatibility between the electrolytes and LiMn₂O₄ cathode. Through inductively coupled plasma (ICP) analysis, we compared the amount of Mn²⁺ dissolved from the spinel cathode in 1 mol L⁻¹ LiPF₆/EC + PC + EMC (1:1:3 wt.%) and 1 mol L⁻¹ LiODFB/EC + PC + EMC (1:1:3 wt.%). AC impedance measurements and scanning electron microscopy (SEM) analysis were used to analyze the formation of the surface film on the LiMn₂O₄ cathode. These results demonstrate that ODFB anion can capture the dissolution manganese ions and form a denser and more compact surface film on the cathode surface to prevent the continued Mn²⁺ dissolution, especially at high temperature. It is found that LiODFB, instead of LiPF₆, can improve the capacity retention significantly after 100 cycles at 25 °C and 60 °C, respectively. LiODFB is a very promising lithium salt for LiMn₂O₄ cathode in lithium-ion batteries.