SnP₂O₇ Covered Carbon Nanosheets as a Long‐Life and High‐Rate Anode Material for Sodium‐Ion Batteries

Abstract

SnP 2 O 7 attached to reduced graphene oxide (rGO) is synthesized by a solvothermal reaction, followed by a mild annealing in Ar/H 2 . As an anode material for sodium-ion batteries, this composite is associated with the conversion reaction between Sn and SnP 2 O 7 and the alloy reaction between Sn and Na x Sn, as evidenced by ex situ techniques, such as high-resolution transmission electron microscope images, selected area electron diffraction patterns, and X-ray diffraction patterns. The close contact between SnP 2 O 7 and rGO facilitates the charge transfer upon cycling and benefits the preservation of SnP 2 O 7 on rGO even after pulverization. Therefore, this composite exhibits an extraordinary cycling stability. 99% of the initial capacity is remained after 200 cycles at 0.2 A g −1 and also 99% is kept after 1000 cycles at 1.0 A g −1 . The similar results are also observed in full cells. Quantitative kinetic analysis confirms that sodium storage in this composite is governed by pseudocapacitance, especially at high rates. These results indicate the promising potential of metal pyrophosphates in sodium-ion batteries.

Recent Progress on the Alloy‐Based Anode for Sodium‐Ion Batteries and Potassium‐Ion Batteries

“…The chemical bonds of PS enable intimate contact of above two materials, greatly improving conductivity and forming a robust electrode structure. Owing to effectiveness of nanostrategy, solvothermal method, [ 24 ] including hydrothermal method, has been widely used in the fabrication of nanomaterials, accompanied with three steps: formation of supersaturated solution, crystal nucleation, and growth. It can effectively synthesize different nanomaterials with high crystallinity, phase purity, and accurate particle size distribution.…”

“…Other unique Sn‐based phosphide is also effective to enhance energy storage performance. Yang and co‐workers [ 24 ] reported SnP 2 O 7 attaching to rGO composite prepared by a solvothermal reaction and annealing method. This anode is combined conversion (SnP 2 O 7 to Sn) and alloying reaction (Sn to Na x Sn).…”

Post‐Lithium‐Ion Battery Era: Recent Advances in Rechargeable Potassium‐Ion Batteries

“…Tin has always been an important anode material in LIBs and SIBs due to its high theoretical capacity (990 mAh g −1 in LIBs and 847 mAh g −1 in SIBs), environmental friendliness, abundant reserves, and low prices [47–53] . However, because the radius of K + is larger than that of Li + and Na + , the volume change caused by Sn in the alloying reaction (Sn↔KSn 4 ↔KSn 2 ↔KSn↔K 2 Sn) is much larger than that in LIBs and SIBs, resulting in rapid capacity attenuation [54, 55] .…”

Carbon‐Based Alloy‐Type Composite Anode Materials toward Sodium‐Ion Batteries

“…f) Cycling performance of SnP 2 O 7 /rGO at 0.2 A g −1 . Reproduced with permission . Copyright 2018, Wiley‐VCH.…”

“…Latest research with carbon nanosphere encapsulated Sn 4 P 3 committed to high reversible capacity even after long term cycling which strongly indicating that the volume expansion was significantly reduced after carbon coating . Some interesting Sn‐based host materials have been established between Sn and Na x Sn . More importantly, the presence of carbon decide the improved performance.…”