Asymmetric-Layered Tin Thiophosphate: An Emerging 2D Ternary Anode for High-Performance Sodium Ion Full Cell.

Abstract

The emerging sodium ion batteries (SIBs) are believed to be prospective substitutes for lithium ion batteries (LIBs) because of the wide distribution of sodium resources. However, to compensate for the sluggish reaction kinetics and higher intrinsic potential of Na⁺ compared to Li⁺, cost-effective, reliable, and sustainable electrode materials must be explored for practical applications. Herein, 2D ternary tin thiophosphate (SnP₂S₆) nanosheets (∼10 nm thickness) grown on graphene (denoted as SPS/G hybrid) are demonstrated as intriguing anodes for SIBs. The asymmetric-layered structure and ternary composition enable the SPS/G hybrid with a high reversible capacity (1230 mAh g^-1 at 50 mA g^-1), superior rate capability (200 mAh g^-1 at 15 A g^-1), and an exceptional capacity retention of 76% after 1000 cycles at 2.0 A g^-1. More importantly, a prototype sodium-ion full cell constructed by pairing with the Na₃V₂O₂(PO₄)₃F cathode affords a high capacity of 470 mAh g^-1 at 30 mA g^-1 (on the basis of anode weight) and good cyclic capacity of 360 mAh g^-1 at 150 mA g^-1. Such 2D ternary chalcogenides with low-cost elements are promising materials for superior SIBs.