Effect of Li2CO3 additive on gas generation in lithium-ion batteries

To elucidate the mechanism of gas generation during charge–discharge cycling of a lithium-ion cell, the generated gases and passive films on the carbon electrode are examined by means of gas chromatography (GC) and Fourier transform infrared (FTIR) spectroscopy. In ethyl carbonate/dimethyl carbonate and ethyl carbonate/diethyl carbonate 1 M LiPF 6 electrolytes, the detected gaseous products are CO 2 , CO, CH 4 , C 2 H 4 , C 2 H 6 , etc. The FTIR spectrum of the surface of the carbon electrode shows bands which correspond to Li 2 CO 3 , ROCO 2 Li, (ROCO 2 Li) 2 , and RCO 2 Li. These results suggest that gas evolution is caused by electrode decomposition, reactive trace impurities, and electrolyte reduction. The surface of the electrode is composed of electrolyte reduction products. When 0.05 M Li 2 CO 3 is added as an electrolyte additive, the total volume of generated gases is reduced, and the discharge capacity and the conductivity of lithium-ions are increased. These results can be explained by a more compact and thin ‘solid electrolyte interface’ film on the carbon electrode formed by Li 2 CO 3 , which effectively prevents solvent co-intercalation and carbon exfoliation.