An amorphous SnP2O7-carbon architecture with enhanced rate and cyclic stability for sodium-ion batteries

Abstract

The development of advanced anodes for sodium storage with considerable rate capability and cycle performance remains a significant challenge. Herein, an amorphous SnP2O7-carbon (SnP2O7/C) composite is synthesized by one-step pyrolysis using Sn(HPO4)2 nanosheets and phytic acid as precursors. The porous three-dimensional skeleton structure of the SnP2O7/C composite contributes to sodium-ions storage. The SnP2O7/C anode exhibits a considerable reversible capacity of 343.6 mA h/g at 0.1 A/g and outstanding high-current charge/discharge performance with capacities of 156.4 and 120.4 mA h/g at 5 and 10 A/g. Furthermore, the SnP2O7/C anode retains capacity of 248.1 mA h/g after 1000 cycles at 1 A/g, giving an impressive capacity retention rate of 92.5 %. Kinetic analysis further reveals that the pseudocapacitive behavior dominates the process of charge storage. Coupling with Na3V2(PO4)3, a SnP2O7/C||Na3V2(PO4)3 full cell delivers a high-energy density of 143.1 W h kg−1 at 44.3 W kg−1 and retains 61.0 W h kg−1 at a power density of 2191.7 W kg−1. These excellent properties prove the application potential of amorphous SnP2O7-carbon composite in sodium-ion batteries.