Glassy Metal-Organic Frameworks Enabling Durable Anode-Free Sodium Metal Batteries

Anode-free sodium metal batteries (AFSMBs) exhibit high energy density and low cost but suffer from notorious dendrite growth. Crystalline metal–organic frameworks (MOFs) can stabilize the anode interface, yet their grain boundaries and weak anion/cation interactions cause anisotropic ion transport and high energy barriers. Herein, we propose glassy MOFs as seeding/hosting interphases to enable highly reversible sodium plating/stripping. Unlike their crystalline counterpart, glassy MOFs eliminate grain boundaries, promoting isotropic ion transport with higher conductivity. Their partially dissociated coordination bonds expose abundant unsaturated metal sites that immobilize anions, boosting Na⁺ transference number. This design yields inorganic-rich interphases and dendrite‑free plating/stripping. Consequently, the glassy MOFs interphase achieves an ultralow nucleation overpotential of 1 mV and an average Coulombic efficiency of 99.8% over 1100 cycles in half cells. Anode-free coin-type cells (cathode loading ~ 14 mg cm⁻²) maintain 70.7% capacity after 100 cycles. A proof-of-concept anode-free pouch cell delivers an energy density of 280.6 Wh kg⁻¹ with 83.7% retention over 150 cycles, whereas the crystalline counterpart retains 33.2% after 30 cycles. In situ strain measurements reveal that the glassy interphase suppresses irreversible strain evolution by 78.7% relative to the crystalline counterpart. This work establishes a versatile glassy MOFs platform for high-performance AFSMBs.