Freeze‐Drying‐Assisted Synthesis of Porous SnO₂/rGO Xerogels as Anode Materials for Highly Reversible Lithium/Sodium Storage

Abstract

Three‐dimensional porous SnO2/rGO xerogels with superior cycling performance in lithium‐ion batteries (LIBs) and sodium‐ion batteries (SIBs) are fabricated through a freeze‐drying‐assisted method. SnO2 nanoparticles (5 nm in diameter) are homogeneously attached to the surface of graphene sheets without self‐aggregation. The heterostructured SnO2/rGO xerogel possesses numerous micron‐sized pores that can efficiently buffer the volumetric change of SnO2 during the charge/discharge process and provide multidimensional channels, improving the conductivity between active materials and electrolyte. The SnO2/rGO xerogel exhibits excellent electrochemical performance, both in LIBs and SIBs, owing to its particular porous structure. For LIBs, it delivers a high initial discharge capacity of 1670.5 mAh g−1 in the first cycle and remains at 1139.4 mAh g−1 after 166 cycles at a current density of 0.1 A g−1. The SnO2/rGO xerogel also delivers a high discharge capacity of 189.4 mAh g−1 without capacity loss over 266 cycles at a current density of 0.5 A g−1 for SIBs. The SnO2/rGO xerogel can be used as an electrode material in both LIBs and SIBs, and can maintain an excellent rate performance and cyclic performance, owing to the abundant porosity and high conductivity.

SnO2 Nanoflake Arrays Coated with Polypyrrole on a Carbon Cloth as Flexible Anodes for Sodium-Ion Batteries

“…Figure d represents the Sn 3d spectrum with two peaks at 486.73 and 495.14 eV, which are associated with Sn 3d 5/2 and Sn 3d 3/2 , respectively . As shown in Figure e, the O 1s spectrum contains different O bonds including Sn–O (530.57 eV), Sn–O–C (531.57 eV), and CO (532.45 eV) . Moreover, the N 1s spectrum in Figure f contains two peaks of pyrrolic N (399.85 eV) and C–N + (401.79 eV), confirming the existence of PPy. , …”

“…However, SnO 2 faces two challenges, that is, unsatisfactory rate and cyclic performance causing by poor conductivity as well as large volume expansion during cycling. , Many efforts have been made to solve the problems. One strategy is designing particular shapes including hollow nanoparticles, − nanosheets, , nanotubes, etc., which can enhance the electron/ion transport and relieve the volume expansion. − Although the above-mentioned nanosizing can inhibit pulverization, it is not enough since the intrinsic poor conductivity limits the electron transfer rate in the SnO 2 electrode. , Another strategy is proposed to combine SnO 2 with conductive materials such as metals, , carbon, , and conducting polymers, which can not only strengthen the conductivity but also reduce the volume change. , In addition, introducing a dopant such as a metal and nitrogen is also a common strategy to adjust the lattice constant, thus improving the sodium storage. , …”

Synthesis Strategies and Structural Design of Porous Carbon‐Incorporated Anodes for Sodium‐Ion Batteries

“…The macro‐/mesosized hierarchical pores not only facilitated interfacial electrode–electrolyte interaction, but also provided efficient electron pathways (Figure h–k). Ma et al explored the freeze‐drying‐assisted synthesis approach to fabricate porous SnO 2 / rGO xerogels as anode for sodium‐ion batteries . The as‐obtained heterostructured material with numerous micron‐sized pores could efficiently buffer the volumetric changes and provide multidimensional channels.…”

Binary-Metal Mn2SnO4 Nanoparticles and Sn Confined in a Cubic Frame with N-Doped Carbon for Enhanced Lithium and Sodium Storage

“…The enhanced rate capability and cyclic performance of the Sn@Mn 2 SnO 4 -NC electrode in Li + storage can be assigned to the rapid transfer of charge, which can be verified by the EIS measurements. As displayed in Figure g, the depressed semicircles in the high- and medium-frequency regions represent SEI impedance ( R SEI ) and charge transfer resistance ( R ct ), respectively. , To observe the EIS profiles of electrodes more clearly, the enlarged EIS spectra are displayed in Figure h. The R SEI and R ct of Sn@Mn 2 SnO 4 -NC and Sn@SnO 2 -NC electrodes are summarized in the inset of Figure h.…”

“…As displayed in Figure 4g, the depressed semicircles in the high-and medium-frequency regions represent SEI impedance (R SEI ) and charge transfer resistance (R ct ), respectively. 46,47 To observe the EIS profiles of electrodes more clearly, the enlarged EIS spectra are displayed in Figure 4h. The R SEI and R ct of Sn@Mn 2 SnO 4 -NC and Sn@ SnO 2 -NC electrodes are summarized in the inset of Figure 4h.…”