Advancing multifunctional Zinc structural batteries through electrochemical surface-modification of carbon fibre

Structural batteries offer a promising route to reducing system-level weight and volume by integrating energy storage directly into load-bearing materials. However, current systems are predominantly based on lithium chemistries, which present challenges in safety, scalability, and compatibility with composite manufacturing. This study presents a scalable approach to redesigning conventional carbon fibre (CF) composites into multifunctional zinc structural batteries (ZnSBs) by integrating surface-functionalized CF and bespoke solid polymer electrolytes (SPEs), offering integrated electrochemical, mechanical, and electromagnetic interference (EMI) shielding capabilities for defence and aerospace platforms. Surface modification of CFs with conformal Zn and MnO 2 nanostructures via a scalable two-step electrochemical surface modification approach enables multifunctional electrodes with enhanced interfacial adhesion. The SPE composed of Zn(TFSI) 2 in propylene carbonate and a photocurable resin, provides a tuneable platform with balanced ionic conductivity (4.31 x 10 -4 S cm −1 ), wide electrochemical stability window (3.75 V) at 25 °C and mechanical properties (flexural modulus of 3.17 ± 0.74 MPa). The ZnSB composites are fabricated in ambient laboratory conditions using established composite fabrication methods, supporting scalability and practical implementation. The composites demonstrate a stable discharge capacity of 13.5 mAh/g at C/4, alongside significant improvements in interlaminar shear strength (up to 0.63 MPa, ∼59%) and toughness (up to 13.46 MPa, 173%) compared to unfunctionalized CF composites. Additionally, the composite exhibits intrinsic EMI shielding, with recycled CF functionalized with MnO 2 and virgin CF functionalized with Zn achieving shielding effectiveness of -43 dB and -62 dB respectively, outperforming unfunctionalized fibres.