The interfacial stability is highly responsible for the longevity and safety of sodium ion batteries (SIBs). However, the continuous solid‐electrolyte interphase(SEI) growth would deteriorate its stability. Essentially, the SEI growth is associated with the electron leakage behavior, yet few efforts have tried to suppress the SEI growth, from the perspective of mitigating electron leakage. Herein, we built two kinds of SEI layers with distinct growth behaviors, via the additive strategy. The SEI physicochemical features (morphology and componential information) and SEI electronic properties (LUMO level, band gap, electron work function) were investigated elaborately. Experimental and calculational analyses showed that, the SEI layer with suppressed growth delivers both the low electron driving force and the high electron insulation ability. Thus, the electron leakage is mitigated, which restrains the continuous SEI growth, and favors the interface stability with enhanced electrochemical performance. We have given insights into the electron leakage behavior that underlies the distinct SEI growth, by investigating the specific SEI component type/distribution in detail. The uniform SEI layer with favorable component and distribution is found to have both low electron driving force and high electron insulation. Therefore, the electron leakage causing SEI growth is largely restrained.