Hierarchical Interfacial Engineering of Boehmite‐Coated Separators via Silane Functionalization and Electron‐Beam Irradiation

ABSTRACT

Interfacial instability at the ceramic–polymer interface in ceramic‐coated separators remains a critical challenge, as weak adhesion can cause coating delamination and compromise lithium‐ion battery safety and electrochemical performance. Here, we report a dual strategy combining (3‐aminopropyl)triethoxysilane (APTES)‐functionalized boehmite (AlOOH) with electron‐beam (EB) irradiation to reinforce ceramic‐coated high‐density polyethylene (HDPE) separators. APTES promotes coupling between AlOOH and the poly(acrylic acid) binder, while EB irradiation strengthens the interfacial network. APTES functionalization increases tensile strength from 136.13 to 167.78 MPa and elongation at break from 37.52% to 72.84%. Irradiation at 50 kGy further raises tensile strength to 171.72 MPa while retaining 66.28% elongation. The combined treatments increase peel strength from 118.27 to 257.68 N m ^{− 1} . At 150°C and 160°C, shrinkage decreases from 83.23% and 95.21% for HDPE to 2.46% and 9.52% at 50 kGy, and 0.70% and 7.74% at 75 kGy, respectively. Ionic conductivity increases from 0.166 ± 0.005 mS cm ⁻¹ for HDPE to 0.635 ± 0.030 and 0.823 ± 0.028 mS cm ⁻¹ at 50 and 75 kGy, respectively. The 75 kGy separator achieves a Li ⁺ transference number of 0.68% and 98.97% capacity retention after 200 cycles. This approach enables thermally stable, mechanically robust separators through coupled chemical and radiation‐driven interface engineering.