A Ferroelectric Nanofiber Composite Anode for Stable Potassium Metal Batteries

ABSTRACT Potassium metal batteries (KMBs) are promising for large‐scale energy storage but are plagued by dendrite growth and unstable interfaces, hindering their practical application. Here, we introduce a ferroelectric polarization field regulation strategy by fabricating a 3D ferroelectric barium titanate nanofibers (BTONFs) network for a composite BTONFs/K anode. The rapid response and uniform spontaneous polarization field, generated by the anisotropic multi‐domain structure of the BTONFs, effectively homogenizes the local electric field and K + ion flux, lowering the nucleation barrier to guide uniform, dendrite‐suppressed K deposition. Benefiting from this design, the BTONFs/K anode exhibits good stability, cycling for over 690 h at 1 mA cm −2 /1 mAh cm −2 in symmetric cells. Furthermore, full cells paired with a Prussian blue cathode achieve a long lifespan of 1000 cycles at a high rate of 10 C with 81.8% capacity retention. Multi‐scale investigations, including in situ optical microscopy, piezoelectric force microscopy (PFM), and phase‐field simulations, collectively corroborate the dominant role of the ferroelectric polarization field in suppressing dendrite growth and stabilizing the interface. This work pioneeringly utilizes the microstructure and dimensions of ferroelectric materials to regulate the polarization field, providing a new paradigm for modulating electrochemical processes based on ferroelectric fields in KMBs.