Synthesis of lithium vanadate/reduced graphene oxide with strong coupling for enhanced capacitive extraction of lithium ions

Capacitive deionization (CDI) is proposed to be one of the most promising techniques for removal of charged species from brackish water. In this work, a robust CDI electrode is designed by synthesizing Li3VO4 on reduced graphene oxide (LVO/rGO) to extract Li+ with enhanced capacity. The LVO/rGO exhibits the orthorhombic-phase crystal structure. Further, as compared to pure LVO, the optimized LVO/rGO composite realizes the improved specific surface area (SSA) and electrochemical performance. It is suggested that the aggregation of rGO can be alleviated by coupling with LVO, resulting in high SSA. Meanwhile, the LVO provides a large number of active sites to intercalate Li+. Benefiting from this structure, the LVO/rGO parallel to Activated carbon (AC) device demonstrates high Li+ extraction capacity of similar to 39.53 mg/g in LiCl solution with an initial concentration of 610.42 mg/L under the cell voltage of 1.2 V, which is the highest among the reported data. Moreover, the Li+ extraction behavior of LVO/rGO parallel to AC in various electrolytes containing OH- and Cl- is explored, illustrating that the AC electrode has priority in Cl- and thus leading to high Li+ removal capacity. Beyond that, the Li+ removal capacity of the LVO/rGO-20 electrode after 20 cycles is measured as similar to 30.84 mg/g, which is 78.02% of the initial value.