Tailoring nitrogen content in doped carbon by a facile synthesis with ionic liquid precursors for lithium ion batteries

Abstract

Ionic liquids have been intensively explored as precursors for doped carbons used as the anode materials in lithium ion batteries. Thanks to the vast number of potential ionic liquids, the types and contents of heteroatoms in the derived carbons can be tailored by appropriately choosing the ionic liquid precursors. In this work, nitrogen-doped carbons are synthesized through facile pyrolysis of ionic liquids with different nitrogen contents. Three types of nitrogen-doped carbons with a nitrogen content of 13.99 at.%, 11.79 at.% and 10.75 at.% were derived from [EMIm]N(CN)2, [BMIm]N(CN)2 and [HMIm]N(CN)2 ionic liquids, respectively. It was found that increase of nitrogen content leads to decrease of charge transfer resistance and increase of capacity. The improved cell performance is related to the change of nitrogen-bonding configuration, microstructure, defect density and surface area of the derived carbons induced by the increased nitrogen content. Eventually, an appropriate selection of ionic liquids can achieve to tailor the nitrogen content of doped carbons and optimize the performance of lithium ion batteries.