Semi-anchored percolation networks for low-threshold and selective desalination in FCDI

Flow electrode capacitive deionization (FCDI) holds great promise for next-generation desalination, yet its advancement is fundamentally constrained by sluggish electron conduction and poor ion selectivity under multivalent interference. Herein, we conceive a semi-anchoring strategy that covalently binds polymeric ionic liquids (PILs) onto ultra-microporous carbon nanospheres (UCNs), constructing a UCNs@PILs composite featuring an ion-selective charge percolation network. This design unlocks dual-functionality: it not only enhances electron mobility via continuous conductive pathways, but also enables sodium-preferred transport through a synergistic “push-pull” effect, as revealed by DFT and COMSOL simulations. Strikingly, this strategy allows the carbon slurry loading to be reduced from the conventional 5-15 wt% [1] to just 3.33 wt% without conductive additives, approaching the lowest value ever reported in FCDI. As a result, the system delivers a 28.00 % increase in desalination efficiency, an 18.26 % reduction in energy consumption, and a 39.40 % enhancement in ion selectivity, while its ion selectivity matches that of state-of-the-art carbon-based materials. This work not only overcomes electron conduction discontinuity and ion transport limitations, but also establishes the semi-anchoring framework for achieving ultra-low percolation thresholds with high ion selectivity, offering a new paradigm for the scalable design of advanced FCDI electrodes.