Introduction of Carbonyl Groups: An Approach to Enhance Electrochemical Performance of Conjugated Dicarboxylate for Li-Ion Batteries

A rational functionalization of conjugated dicarboxylate is reported here to enhance the cyclability and rate capability for Li-ion batteries. Introduction of carbonyl groups between aromatic rings is explored as an alternative way to extend π-conjugation. For the proof of concept, 4,4'-bis(lithiooxycarbonyl)benzil (Li2-BZL) was synthesized and compared its lithium storage performance against lithium [1,1'-biphenyl]-4,4'-dicarboxylate (Li2-BPDC). The Li2-BZL electrode delivers a stable capacity of 165 mAh g−1 even after 50 cycles at current density of 50 mAh g−1 whereas, rapid capacity fading was observed in the case of Li2-BPDC. Density functional theory (DFT) studies confirmed that the carbonyl groups in the Li2-BZL to reduce the bandgap, thereby improving the elctrochemical lithium storage performance of Li2-BZL electrode in comparision to that of Li2-BPDC.