Comparative Study on the Solid Electrolyte Interface Formation by the Reduction of Alkyl Carbonates in Lithium Ion Battery
The reduction products are determined by using ex-situ attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), in the glove box, after employing linear sweep voltammetry (LSV) to certain potential regions. EC/PC/DEC based electrolyte shows better capacity retention and less impedance than the EC/PC system. In all systems, the FTIR results indicate the formation of (CH3CH2OCO2Li)2 and Li2CO3 due to the reduction of PC. EC is reduced to (CH2OCO2Li)2 and Li2CO3 in both the binary and ternary solvent system. The FTIR result at the potential where DEC reduction occurs shows the formation of (CH2=CH-OCO2CH2CH3)Li which is less stable and forms a less-passivating layer in the first cycle. However, this product can further react with another species in the subsequent cycles and form a stable SEI.
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