Graphene nanoscrolls-wrapped oxygen-deficient ZnSb2O6-x nanospheres for enhanced lithium-ion storage

Abstract

Although polyantimonic acid (PAA, H2Sb2O6·nH2O) possesses a high theoretical specific capacity for lithium-ion storage, its development is hindered by ultralow intrinsic electrical conductivity (∼10−10 S cm−1). In addition, the existence of proton/crystal water and large volume change during electrochemical reaction will impair its cycling stability. Here, oxygen-deficient zinc antimonate (ZnSb2O6-x) nanospheres were designed and synthesized by a facile precipitation-calcination method and then wrapped/confined in 1D graphene nanoscrolls (GS) through graphene self-scrolling strategy. The change from “acid” to “salt” can not only endow zinc antimonate with a higher electrical conductivity (∼1.9 × 10−3 S cm−1) but also remove the proton/crystal water. The encapsulation of GS can accommodate the volume expansion of internal ZnSb2O6-x nanospheres, prevent the loss of active species and further accelerate the transport of electrons (23 S cm−1). Therefore, the resultant ZnSb2O6-x@GS shows high reversible capacity (755 mAh g−1 at 0.1 A g−1), good rate capability (401 and 331 mAh g−1 at 5 and 10 A g−1), and long cycling performance (727 mAh g−1 after 800 cycles at 1 A g−1). These results exhibit the application potential of the ZnSb2O6-x@GS anode material and prove the effectiveness of the composition and structure design.