An Organic Carboxylate Host for Stable Sodium Metal Batteries

Sodium metal batteries (SMBs) hold great promise for the development of high‐energy, sustainable energy storage solutions, but their practical deployment is hampered by unstable solid electrolyte interphases, uncontrollable sodium dendrite growth, and low Coulombic efficiency (CE) during repeated Na plating/stripping cycles. To address these challenges, we introduce an organic interlayer, containing perylenetetracarboxylic dianhydride sodium salt (Na 4 PT), on the surface of Cu current collector. This interlayer forms a sodiophilic organic interphase that lowers the nucleation barriers for sodium deposition and guides the formation of the interphase through polar carbonyl/carboxylate sites and a π ‐conjugated organic framework. A dendrite‐free sodium metal anode is achieved using Na 4 PT coated Cu current collector. Under capacity‐limited Na plating/stripping, Na||Na 4 PT@Cu half‐cells deliver reversible capacities of 500 and 1,000 mAh g −1 at 0.1 and 1 A g −1 for 500 cycles with average CE above 99%. Post‐cycling scanning electron microscopy and X‐ray photoelectron spectroscopy measurements confirm that Na 4 PT@Cu promotes compact and uniform Na deposits and supports the formation of a stable interphase with reduced parasitic decomposition, directly correlating interfacial chemistry/morphology with high plating/stripping reversibility. These results highlight organic carboxylate coating as a practical interface engineering strategy for dendrite‐free SMBs.