Edge Electron Effect Induced High-Entropy SEI for Durable Anode-Free Sodium Batteries

Abstract

Anode-free sodium metal batteries represent great promising as high-energy-density and resource-rich electrochemical energy storage systems. However, the savage growth of sodium metal and continuous consumption hinder its stable capacity output. Herein, ordered flower-edges of zinc on Al substrate can induce high-entropy solid electrolyte interphase (SEI) to adjust sodium uniform deposition and extremely reduce electrolyte consumption with ultrahigh initial Coulombic efficiency (97.05%) for prolong batteries cycling life. Theoretical and experimental studies have demonstrated that the electron-donating property and exposed edge sites between (100) and (101) facets in zinc flower enhance anion adsorption onto the inner Helmholtz plane accelerating its interface decomposition. Additionally, the ordered zinc edges serve as homogeneous-nucleating template, leading to thin and inorganic-rich SEI layer (18 nm, ZnF₂, NaZn₁₃, NaF, and Na₂CO₃) with high-entropy discrete multicomponent distribution, so that fast and high-flux Na ions transport field, thereby reducing the critical nucleation barrier and promoting sodium high density nucleation (7.36 × 10¹³ N cm⁻²) and pyknotic growth (3 mAh cm⁻², 22 µm). The assembled anode-free sodium batteries exhibit high stability (86%, 90 cycles) under ultrahigh cathode loading (32 mg cm⁻²). Moreover, the anode-less single-layer pouch batteries exhibit a durable capacity retention of 99% after 600 cycles.