Go-encapsulated La-doped lithium manganese oxide assemblies to enhance lithium extraction performance in capacitive deionization

Abstract

The electrochemical lithium extraction technique from brine has emerged as a key strategy in addressing the issue of lithium resource scarcity. Lithium manganese oxide (LMO) stands out as a typical lithium-ion selective material. Nevertheless, its lithium extraction application is restricted by inadequate conductivity and limited cycling stability. In this report, through a simple electrostatic self-assembling method, a 3-dimensional (3D) GO/La-LMO hybrid was fabricated wherein La-doped LMO (La-LMO) was enveloped by graphene oxide (GO) nanosheets. The resultant GO/La-LMO exhibited a significantly improved electrochemical behavior with fast Li+ diffusion rate and high conductivity. The GO/La-LMO hybrid demonstrated outstanding selectivity for the electrochemical intercalation/de-intercalation of Li+. As a Li+-selective cathode in capacitive deionization (CDI) device, the GO/La-LMO electrode achieved a high Li+ adsorption capacity of 1.33 mmol g−1 (10 mM LiCl) and superior selectivity with a separation factor of 126 (Mg2+/Li+ = 30, molar ratio) in Mg2+/Li+ mixed solution. The Li+ extraction percentage reached 80.4 % in the simulated salt-lake brine. Crucially, the GO/La-LMO electrode substantiated prominent structural stability and low Mn dissolution over 100 cycles, attributed to the synergistic effect of La-doping and GO capsulation to mitigate Jahn-Teller distortion. In addition, the selective adsorption–desorption mechanism of Li+ was confirmed. This work introduces a facile approach for the fabrication of robust carbon-based LMO hybrids, demonstrating the potential applications as high-performance lithium-selective materials.