Multilayered SnP₂O₇/Reduced Graphene Oxide Architecture with High-Rate Lithium- and Sodium-Ion Storage

Based on the conversion/alloying reaction mechanism, SnP2O7 is a potential high-capacity lithium- and sodium-ion storage material. However, the inherent poor conductivity suppresses its rate capability. Herein, the SnP2O7/reduced graphene oxide (rGO) composite is synthesized by a liquid nitrogen rapid freezing method and subsequent annealing. The loose and wrinkled multilayered architecture is constructed by SnP2O7 sheets attached to rGO. During the lithiation/delithiation process, rGO enhances the redox reactivity between SnP2O7 and Sn, electron transport kinetics, and lithium-ion diffusion rate, so the SnP2O7/rGO exhibits superior rate capability with capacities of 532.3, 496.4, and 458.3 mA h g(-1) at 0.5, 1, and 2 A g(-1), respectively. The lithium storage mechanism of SnP2O7 is related to the conversion reaction and alloying reaction at the voltage range of 0.01-3 V, as evidenced by cyclic voltammetry curves and ex situ X-ray photoelectron spectroscopy. Moreover, the SnP2O7/rGO anode for sodium storage also demonstrates superior reversibility and cyclability, indicating that the multilayered architecture helps maintain SnP2O7 attached to rGO upon cycling. Furthermore, kinetic analysis reveals that the multilayered structure promotes the pseudocapacitive behavior of the SnP2O7-based anodes. This strategy delivers significant capability advantages, providing inspiration for the development of high-performance SnP2O7-based anodes.