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

Faced with the strong demand of clean energy, development of lithium source is becoming exceedingly vital. Spinel-type manganese oxide (λ-MnO₂) 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-MnO₂ on 3D reduced graphene oxide (3D-rGO) matrix for Li extraction by capacitive deionization (CDI). The λ-MnO₂ modified rGO (λ-MnO₂/rGO) retained the 3D network structure with uniform distribution of λ-MnO₂ nanosheets on rGO. Electrochemical characterization demonstrated its high conductivity and fast lithium ion diffusion rate. By adjusting the rGO concentration, λ-MnO₂ activity was improved significantly. With λ-MnO₂/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-MnO₂/rGO was attained by thermogravity analysis. With the appropriate rGO content (15.5%), the obtained λ-MnO₂/rGO electrode achieved the optimal Li⁺ adsorption amount. The corresponding λ-MnO₂/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.