Self-Derived Stress-Release Phase Enables High-Performance Self-Healing Sodium Anodes

Self-healing anodes, enabled by liquid metals, stand out among alkali-ion storage materials due to their spontaneous repairing capability. Nevertheless, a fundamental understanding of the underlying self-healing mechanism, particularly from the perspective of stress evolution, remains elusive. Herein, a self-derived stress-release phase strategy is proposed to elucidate the intrinsic role of liquid gallium (Ga) in achieving self-healing behavior and high-performance sodium storage. Specifically, Ga₂Se₃ is selected as a model system, where liquid Ga is self-derived during the conversion reaction, as confirmed by theoretical calculations and in situ XRD analysis. Abnormal peak shifts of Na₂Se observed during cycling are explained by a unit-cell "breathing" mechanism induced by the liquid Ga, which functions as a stress-release phase. This process not only heals cracks but also alleviates misfit strains, thereby mitigating structural degradation and enabling long-term electrochemical stability. As anticipated, Ga₂Se₃ demonstrates superior cycling performance in both half (≈200 mAh g^-1 at 10 A g^-1) and full cells (a high-capacity retention of 91.5% after 150 cycles), highlighting its potential for practical sodium-ion batteries. The findings provide direct evidence that self-derived stress-release phases are key to self-healing electrodes, offering a new paradigm for designing high-performance sodium storage systems.