Sustainable construction of multistage porous LiMn2O4 thick electrode by 3D printing for enhanced electrochemical lithium extraction from brine

Electrochemical liquid lithium extraction technology has attracted much attention because of its high selectivity, good efficiency, and eco-friendliness. However, the low energy density per unit area and poor stability of traditional thin film electrodes (F-LMO), as well as manganese dissolution loss induced by the Jahn-Teller distortion of LiMn2O4, hinder their industrial scalability. Herein, a durable and high-efficiency multistage porous LiMn2O4 thick electrode was prepared sustainably by 3D printing technology (3DP-LMO) for enhancing lithium recovery from salt lake brine. The multistage porous structure reduced the mass transfer resistance and shortened the ion diffusion path, which was conducive to accelerating the diffusion rate of Li+. Simultaneously, the three-dimensional conductive networks composed of reduced graphene oxide (rGO) and carbon nanotubes (CNT) synergized with the multistage pores effectively weakened the polarization phenomenon of the electrode and improved the stability of 3DP-LMO. The 3DP-LMO exhibited a 5.5-fold higher extraction capacity per unit area and the Mn dissolution loss rate was only 1/15 compared with the F-LMO. Notably, the capacity retention rate of 3DP-LMO was 87.6 %, significantly better than that of F-LMO (66.3 %). Based on the quasi-in situ X-ray Diffraction results, the mechanism of lithium intercalation and deintercalation in 3DP-LMO was elucidated. Furthermore, lithium extraction parameters were optimized using response surface method-center composite design (RSM-CCD), resulting in an increase in lithium extraction capacity to 15.66 mg g−1 and a reduction in energy consumption to only 12.33 Wh mol−1. The results show that 3DP-LMO has significantly improved lithium extraction performance and stability, and has considerable prospects in practical application.