In situ formation of GeSe nanocrystals in carbon nanofiber network supports for ultra-thick sodium ion storage anodes via enhanced carrier transport

Abstract

Metallic selenides are considered as a promising class of alternative anodes for sodium ion batteries due to the high capacity conferred by their hybrid sodium storage mechanism. However, the low reversible volume expansion induced by larger size sodium ion storage greatly limits their cycle life, theoretical capacity mining and electrode thickness enhancement. Herein, a germanium selenide/carbon nanofibers (GeSe/CNFs) sodium storage anode is first reported by taking advantage of the encapsulation and dispersion of electrostatic spinning technology, i.e., GeO2 is first mixed with polyacrylonitrile and electrospun to form a wrapped structure, followed by in situ pre-oxidation, carbonization, and selenization. For the optimized electrode, it delivers a high capacity up to 567 mAh g−1 based on the mass of GeSe (320 mAh g−1 based on GeSe/CNFs), reaching > 80% of its theoretical capacity, with a > 2300 cycles cycling stability at 1.0 A g−1. In addition, its capacity barely decays after 700 cycles at near commercial electrode thickness (115 µm, the capacity retention > 47–63% even at the ultrahigh thickness of 187–219 µm). This study opens up new possibilities for the development of Se-based sodium storage anode materials with long life, high capacity and ultra-thick electrode that are expected to meet practical needs.