Annealed SiO₂ Protective Layer on LiMn₂O₄ for Enhanced Li-Ion Extraction from Brine

In this study, we present a novel approach for selective Li-ion extraction from brine using an LiMn₂O₄ ion sieve coated with a dense silica layer, denoted as LMO@SiO₂. The SiO₂ layer is controllably coated onto the LMO surface, forming passivation layers and ion permeation filters. This design effectively minimizes the acidic corrosion of the LMO and enhances the Li⁺ adsorption capacity. Additionally, the SiO₂ layer undergoes calcination at various temperatures (ranging from 300 to 700 °C) to achieve different compactness levels of the coating layer, providing further protection to the LMO crystal structures. As a result of these improvements, the optimized LMO@SiO₂ adsorbent demonstrates an exceptional Li⁺ adsorption capacity of 18.5 mg/g for brine, and even after seven adsorption-elution cycles, it maintains a capacity of 15.3 mg/g. This outstanding performance makes our material a promising candidate for efficient Li⁺ extraction from brine or other low-concentration Li⁺ solutions in future applications.