Tin phosphide-carbon composite as a high-performance anode active material for sodium-ion batteries with high energy density

Tin phosphide (Sn4P3) is a promising anode material for sodium-ion batteries because of its relatively large theoretical capacity, appropriate Na+ alloying potential, and good cyclic stability. Herein, the Sn4P3 embedded into a carbon matrix with good rate performance and long cycle life is reported. The Sn4P3-C composite exhibits excellent rate performance (540 mAh g−1 at 5 A g−1) and the highest reversible capacity (844 mAh g−1 at 0.5 A g−1) among Sn4P3-based anodes reported so far. Its reversible capacity is as high as 705 mAh g−1 even after 100 cycles at 0.5 A g−1. Besides, its initial Coulomb efficiency can reach 85.6%, with the average Coulomb efficiency exceeding 99.75% from the 3rd to 100th cycles. Na2C6O6 is firstly used as a cathode when Sn4P3 acts as anode, and the Na-Sn4P3-C//Na2C6O6 full cell shows excellent electrochemical performance. These results demonstrate that the Sn4P3-C composite prepared in this work displays high-rate capability and superior cyclic performance, and thus is a potential anode for sodium ion batteries.