Hard carbon with an “adsorption-intercalation/filling” behavior for selective deionization of lithium ions

Lithium extraction from seawater/brine to enrich the available global lithium resources is key to the development of energy storage and water desalination . Understanding the Li + extraction mechanism in hard carbon has been a topic of debate because of its complex structure. In this work, polyimide-based carbon microsphere (PCMs) organized by ultralong nanowires was fabricated for the first time by solvent polarity induced interface self-assembly strategy. Examined as the electrode, the assembled device delivers a high Li + extraction capacity of ~34.55 mg g −1 in LiCl solution and highly selective rapid transport in simulated Qarhan Salt Lake old brine, which is very competitive among the reported data. It is demonstrated that the Li + ion extraction behavior in PCMs is an “adsorption-intercalation/filling” hybrid mechanism, similar to that of in batteries system. The simulation calculations further reveal that specific adsorbed sites and confined channels in PCMs dominate the Li + ion-selective permeation behavior. This work provides a solvent polarity induced interface self-assembly strategy to develop polyimide-based hard carbon for electrochemical desalination and underlies the Li + ion extraction mechanism, offering a general hard carbon design concept.