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

Abstract

Based on the conversion/alloying reaction mechanism, SnP 2 O 7 is a potential high-capacity lithium-and sodium-ion storage material. However, the inherent poor conductivity suppresses its rate capability. Herein, the SnP 2 O 7 /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 SnP 2 O 7 sheets attached to rGO. During the lithiation/delithiation process, rGO enhances the redox reactivity between SnP 2 O 7 and Sn, electron transport kinetics, and lithium-ion diffusion rate, so the SnP 2 O 7 /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 SnP 2 O 7 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 SnP 2 O 7 /rGO anode for sodium storage also demonstrates superior reversibility and cyclability, indicating that the multilayered architecture helps maintain SnP 2 O 7 attached to rGO upon cycling. Furthermore, kinetic analysis reveals that the multilayered structure promotes the pseudocapacitive behavior of the SnP 2 O 7 -based anodes. This strategy delivers significant capability advantages, providing inspiration for the development of highperformance SnP 2 O 7 -based anodes.