Application of electrolyte using novel ionic liquid to Si thick film anode of Li-ion battery

An applicability of a novel ionic liquid, consisting of 1-methoxyethoxymethyl(tri-n-butyl)phosphonium cation and bis(trifluoromethanesulfonyl)amide anion, was investigated as an electrolyte of Li-ion battery using a thick film electrode of Si prepared by a gas-deposition method. The electrochemical properties in the novel ionic liquid were compared to those in a commercial ionic liquid and a typical organic solvent of propylene carbonate. The initial discharge capacity of 3450 mAh g−1 and excellent cycling performance were achieved in the novel ionic liquid. The novel ionic liquid was confirmed to effectively suppress a collapse and an electrical isolation of the Si thick film induced by pulverization during charge–discharge cycling. The excellent performance is possibly attributed to more effective desolvation of Li ions from the anions due to its lower dielectric constant compared with the propylene carbonate solvent.

Research highlights▶ An applicability of a novel ionic liquid was investigated as an electrolyte of Li-ion battery. ▶ We studied anode property of Si thick-film electrodes prepared by a gas-deposition method. ▶ The novel ionic liquid achieved large initial capacity and excellent cycling performance. ▶ Influence of cation structure on charge-transfer in electrode reaction was discussed.