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

Tin phosphide(Sn_(4)P_(3))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 Sn_(4)P_(3) embedded into a carbon matrix with good rate performance and long cycle life is reported.The Sn_(4)P_(3)-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.Na_(2)C_(6)O_(6) is firstly used as a cathode when Sn_(4)P_(3) acts as anode,and the Na-Sn_(4)P_(3)-C//Na_(2)C_(6)O_(6) full cell shows excellent electrochemical performance.These results demonstrate that the Sn_(4)P_(3)-C composite prepared in this work displays high-rate capability and superior cyclic performance,and thus is a potential anode for sodium ion batteries.