"Self-doping" defect engineering in SnP3@gamma-irradiated hard carbon anode for rechargeable sodium storage.

Reasonable design of defect engineering in the electrode materials for sodium-ion batteries (SIBs) can significantly optimize battery performance. Here, compared with the traditional "foreign-doping" defects method, we report an innovative gamma-irradiation technique to introduce the "self-doping" defects in the popcorn hard carbon (HC). Considering the advantages of adsorption-intercalation-alloying sodium storage mechanism, the defect-rich HC-coated alloy structure (SnP3@HC-γ) was integrated. Due to the high energy and strong penetrability of γ-rays, the constructed "self-doping" defect engineering effectively expands the interlayer structure of HC and forms the irregular ring structure. Simultaneously, the exposed large number of coordination unsaturated sites can accelerate the reaction kinetics on the surface. Based on the synergistic effect of the SnP3@HC-γ, the composites exhibit an excellent reversible capacity of 668 mAh g-1 at 0.1 A g-1 in SIBs. Even, after 400 cycles at 1.0 A g-1, an exceptional cyclability with 88% capacity retention (430 mAh g-1) can be maintained. We envision that the γ-irradiation technology used in this research not only overturns the general perception that "self-doping" defects will reduce performance, but also provides reliable technical support for large-scale construction of high-defect, high-capacity and stable sodium-ion anode materials.