Ferroelectric Polarization Orientation Enables Exceptional Capacitive Deionization via Vertical Local Electric Field Enhancement

ABSTRACT The controlled alignment of polarization fields in electrode materials presents a critical yet underexplored opportunity to enhance capacitive deionization performance. While heterogeneous electrodes naturally develop local polarization under applied electric field, the typically disordered orientation of these field leads to mutual cancellation effects that impair ion transport and electric double layer (EDL) formation. In response, this work demonstrates a new strategy through vertical local electric field enhancement (V‐LEFE), achieved by precisely engineering the polarization characteristics of ferroelectric materials. Our systematic investigation reveals that the designed V‐LEFE facilitates directional electron migration to the electrode surface, simultaneously accelerating ion diffusion kinetics (evidenced by a 74% increase in Na + diffusion coefficient to 3.47 × 10 −9 cm 2 /s) and reconstructing more efficient EDL structures. The resulting V‐LEFE electrode achieves exceptional desalination performance, including a high Na + adsorption capacity of 2.49 mmol/g (154% higher than pristine electrode) at 1.2 V in 400 mg/L NaCl solution, while maintaining outstanding cycling stability (95.5% retention after 100 cycles) and fast salt adsorption rate (3.60 mg/g/min). These findings not only elucidate the fundamental role of polarization alignment in interfacial processes but also establish a new design approach for developing high‐efficiency and sustainable desalination systems.