A high voltage cathode of Na2+2xFe2−x(SO4)3 intensively protected by nitrogen-doped graphene with improved electrochemical performance of sodium storage. Issue 10 (16th February 2018)

• Record Type: Journal Article
• Authors: Wang, Wei; Liu, Xiaohao; Xu, Qunjie; Liu, Haimei; Wang, Yong-Gang; Xia, Yongyao; Cao, Yuliang; Ai, Xinping
• Is Part Of: Journal of materials chemistry. Volume 6:Issue 10(2018)
• Page Start: 4354
• Page End: 4364
• Publication Date: 2018-02-16
• Subjects: Materials -- Research -- Periodicals; Chemistry, Analytic -- Periodicals; Environmental sciences -- Research -- Periodicals; 543.0284
• DOI: 10.1039/c7ta11110j
• Languages: English
• ISSNs: 2050-7488

Abstract

Abstract : A high voltage alluaudite sulfate Na2+2x Fe2−x (SO4 )3 composited with nitrogen-doped graphene and the sodium storage performance is remarkably improved. Abstract : As a high-voltage and earth-abundant element, in recent years, alluaudite, Na2+2 x Fe2− x (SO4 )3, has been regarded as a highly promising cathode material of sodium ion batteries with higher energy density. However, the critical environmental sensitivity and limited conductivity of this kind of sulfate-based (SO4 2− ) polyanionic material has led to its poor crystal stability and inferior intercalation ability. Herein, we report the design of nitrogen-doped graphene under low temperature conditions as an evolutionary modification approach to prepare the Na2+2 x Fe2− x (SO4 )3 ; namely, an alluaudite sulfate Na2+2 x Fe2− x (SO4 )3 @N-rGO composite was prepared by a facile co-precipitation method assisted by the nitrogen-doped graphene. It is therefore surprising that the three-dimensional graphene-based network provides continuous electron pathways; thus, the Na2+2 x Fe2− x (SO4 )3 @N-rGO composite exhibits improved electronic conductivity and excellent sodium insertion capability, as well as the electrochemical performance. As a result, it delivers a reversible capacity of 93.2 mA h g −1 with average redox potential of 3.8 V ( vs. Na + /Na) at 0.05C; when the discharge rate increased to 10C, it delivers 56.3 mA h g −1 and an amazing capacity retention of 83% is achieved after 400 cycles. On the other hand, the doped nitrogen species plays a huge role on improving the electron-donating ability of the graphene layer, which effectively protects the easily oxidized host material from deterioration, giving the material longer stability in a normal oxygen-containing atmosphere. We believe that this work may lead to a promising, low cost, suitable sodium ion battery material for next-generation large-scale energy storage devices.