Lithium ion sieve modified three-dimensional graphene electrode for selective extraction of lithium by capacitive deionization.

Faced with the strong demand of clean energy, development of lithium source is becoming exceedingly vital. Spinel-type manganese oxide (λ-MnO) is a typical lithium ion sieve material. Herein, the conductive three-dimensional (3D) lithium ion sieve electrode material was fabricated by in-situ growth of λ-MnO on 3D reduced graphene oxide (3D-rGO) matrix for Li extraction by capacitive deionization (CDI). The λ-MnO modified rGO (λ-MnO/rGO) retained the 3D network structure with uniform distribution of λ-MnO nanosheets on rGO. Electrochemical characterization demonstrated its high conductivity and fast lithium ion diffusion rate. By adjusting the rGO concentration, λ-MnO activity was improved significantly. With λ-MnO/rGO as a positive electrode (activated carbon as negative electrode), the corresponding CDI system was successfully applied for the selective extraction of Li. The final rGO content in the λ-MnO/rGO was attained by thermogravity analysis. With the appropriate rGO content (15.5%), the obtained λ-MnO/rGO electrode achieved the optimal Li adsorption amount. The corresponding λ-MnO/rGO-based CDI cell showed good selectivity and high cycle stability. When applied to the extraction of lithium from synthetic salt lake brine, the electrode also obtained high Li adsorption amount with good selectivity.