Mode optimization of self-electrical-energy recuperation in a Li1-xMn2O4-polypyrrole coupled system for efficient electrochemical Li+/Na+ separation

Efficient recovery of residual lithium from lithium precipitation brine has always been a major challenge. A stable and efficient lithium extraction system and a driven mode need to be constructed. This study presents an innovative coupled electrochemical system combining a chlorine-doped polypyrrole (PPy−Cl) electrode with the LiMn 2 O 4 electrode. In this system, the LiMn 2 O 4 film electrode and chlorine-doped polypyrrole were synchronized to remove lithium and chlorine ions, and complete de-intercalation of LiMn 2 O 4 could be achieved at the cell voltage of 1.1 V, which greatly reduces energy consumption. No manganese ions were detected in the solution compared to the 1.43 % manganese dissolution loss after 10 tests on the graphite plate (GP) used as an auxiliary electrode. In addition, self-electrical-energy recuperation can be achieved by utilizing the low potential difference between Li 1-x Mn 2 O 4 and polypyrrole. The performances of the self-driven(SD) mode and the constant-current(CC) mode were compared to achieve externally controlled energy release. The intercalation capacity reached 33.82 mg g −1 at 0.4 mA cm −2 , and the intercalation efficiency was maintained at 88.12 % after 10 tests. During the first discharge, the discharge efficiency of the SD mode was only 54.08 % of the CC mode. Furthermore, the system exhibited high selectivity (51.3) in the lithium-precipitated brine with a high concentration of Na + and Li + (Na + /Li +  = 8.47). These results indicate that the proposed strategy has significant potential in Li + resource recovery and can be used in a variety of Li + resource recovery applications.