Corona-Poled Piezoelectric Polymer Separators for Suppressing Sodium Dendrites

Sodium-ion batteries (SIBs) have emerged as a cost-effective and sustainable alternative for low-speed electric vehicles and large-scale energy storage, driven by the abundance and safety of sodium. Despite significant advancements in electrode materials, their practicability is severely hindered by the availability of a well-suited separator with dendrite suppression capability and compatibility with electrolytes. This study explores the development of ultrathin (10 μm) advanced polyvinylidene fluoride (PVDF) separators via a simple and scalable casting method followed by corona poling to suppress sodium dendrites and achieve homogeneous deposition. The PVDF separators exhibited uniform nanopore distribution (50-200 nm), high electrolyte uptake (225%), low contact angle (5.31°), reliable tensile strength (19.8 MPa with a strain of 33.3%), and excellent thermal stability, contributing to extended cycling stability and improved rate performance. The piezoelectric properties of poled PVDF separators were found to be effective in suppressing sodium dendritic growth, as demonstrated through a comprehensive electrochemical testing in sodium symmetric (2000 h), asymmetric (2200 cycles), and full cells (1000 cycles). Comparison with conventional separators and microglass fiber further supports the potential of PVDF separators for practical SIB applications.