Molecular isolation layer constructed by planar conjugated organic molecules for highly durable Na/K metal anodes

The uncontrollable growth of Na/K dendrites and the instability of the solid electrolyte interphase (SEI) layer pose significant challenges for the practical application of Na/K metal batteries. Herein, we propose the use of a protective layer constructed by using a novel copper hexadecafluorophthalocyanine (C 32 CuF 16 N 8 , denoted as CuPcF) electrolyte additive to address these issues. Both experimental and theoretical calculations reveal that the CuPcF molecule, with its planar conjugated ring structure and polar groups (−CF, −CN), can preferentially absorb onto the Na/K surface to construct a stable self-regulating protective layer. This layer aids in the redistribution of Na + /K + flux, promotes rapid Na/K desolvation and transport kinetics, and encourages uniform Na/K deposition. The synergistic effect of the CuPcF additive enabled the Na symmetrical cell to cycle selectively for over 1600 h at 1.0 mA cm −2 , while the high-voltage Na 3 V 2 (PO 4 ) 2 F 3 (NVPF)||Na full cell achieved an ultra-high energy density of 432.9 Wh kg −1 at 180.7 W kg −1 . The effectiveness of CuPcF additive was also confirmed in K symmetric cell and the well-designed full cell. The relevant K symmetric cells maintained over 1000 h at 0.5 mA cm −2 , and the K full cell exhibited excellent cycling stability (82 mAh g −1 over 1180 cycles at 10C). This work provides valuable insights for the development of protective layers to prevent dendrite formation in Na/K anodes. A protective layer is constructed using a novel electrolyte additive, copper hexadecafluorophthalocyanine (C 32 CuF 16 N 8 , denoted as CuPcF), to address the notorious growth of Na/K dendrites. This layer stabilizes the Na/K anode interface, promotes rapid Na/K desolvation and transport kinetics, thereby achieving uniform Na/K deposition. • An effective additive is screened from various MPcF (M = Cu, Co, Fe, Ni) molecules. • The CuPcF molecule can absorb onto the Na surface to construct a stable layer. • The CuPcF-induced interface layer effectively regulates Na/K deposition behaviors. • The protective layer can boost the cycling stability of Na/K metal batteries. • The Na/K full cells with CuPcF electrolyte demonstrate superior service life.