Manufacturing‐Driven Programming of Carbon Interfaces via Controlled Densification for Solid‐State Sodium Storage

Interfacial instability in solid‐state sodium storage is largely dictated by uneven ion flux and localized degradation, while its control through manufacturing parameters remains limited. Here, controlled densification is employed to regulate interfacial structure and sodium‐ion behavior in nitrogen‐doped bio‐derived carbon electrodes. Increasing pressure leads to a transition from porous and discontinuous interfaces to compact and continuous pathways, which moderates ion flux and suppresses local Na⁺ accumulation. Electrochemical impedance measurements show a reduction in interfacial resistance from 320 to 140 Ω, accompanied by restrained resistance evolution during extended cycling. Structural and post‐cycling analyses indicate that this stabilization is associated with more uniform ion redistribution and reduced defect formation at the interface. Nitrogen functionalities further contribute by tuning the interfacial electronic environment, supporting more stable ion transport. The optimized electrodes maintain capacity retention above 90% with consistent rate behavior. These observations reveal a direct link between densification, ion redistribution, and interfacial stability, indicating that ion transport can be regulated through manufacturing‐controlled structural design. This work highlights a practical route for stabilizing solid‐state interfaces through process‐driven control of material architecture.