Topotactic Transformation Synthesis of 2D Ultrathin GeS<sub>2</sub> Nanosheets toward High-Rate and High-Energy-Density Sodium-Ion Half/Full Batteries.

Li, Cheng Chao; Wang, Bo; Chen, Dong; Gan, Li-Yong; Feng, Yuezhan; Zhang, Yufei; Yang, Yang; Geng, Hongbo et al. · ACS Nano · 2020

basic_science · Level V

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Abstract

Currently, development of metal sulfide anodes for sodium-ion batteries (SIBs) with high capacity, fast charging/discharging, and good cycling performance continues to present a great challenge. Hence, a topochemical conversion strategy is reported to fabricate 2D ultrathin GeS<sub>2</sub> nanosheets (thickness: ∼1.2 nm) as the potential anodes for sodium storage. The 2D ultrathin nanostructure can mitigate the electrode-electrolyte contact issue faced by bulk material and provide shorter transport/diffusion pathways for Na ions and electrons, resulting in excellent rate performance. Impressively, ultrathin GeS<sub>2</sub> nanosheets can bring a large capacity of 515 mAh g<sup>-1</sup> even after 2000 cycles under 10 A g<sup>-1</sup>. Additionally, as revealed by calculations and <i>in situ</i>/<i>ex situ</i> technique analysis, a favorable mechanism of Na<sup>+</sup> intercalation/deintercalation into/from the GeS<sub>2</sub> interlayer region (GeS<sub>2</sub> ↔ Na<sub><i>x</i></sub>GeS<sub>2</sub>) is demonstrated. Furthermore, when coupled with the advanced cathode of Na<sub>3</sub>V<sub>2</sub>(PO<sub>4</sub>)<sub>2</sub>O<sub>2</sub>F, the sodium-ion full cell shows a stable high energy density (213 Wh kg<sup>-1</sup>), which makes our ultrathin GeS<sub>2</sub> nanosheets a promising candidate for SIBs.