Porous MXenes enable high performance potassium ion capacitors

Fangwang Ming, Hanfeng Liang, Wenli Zhang, Jun Ming, Yongjiu Lei, Abdul-Hamid M. Emwas, Husam N. Alshareef

Research output: Contribution to journalArticlepeer-review

71 Scopus citations

Abstract

High power K+ ion capacitors have great potential in various large-scale applications because of the cost advantages and the low redox potential of K/K+. However, the large ionic radius of potassium brings huge challenges for the development of suitable electrode materials. Here we demonstrate a general strategy for preparing porous MXene electrodes that can significantly enhance K+ storage performance. Using V2C MXene as a model system, we show that the K+ ion storage capacity can be greatly boosted by a simple sequential acid/alkali treatment. The resulting product, K–V2C, not only delivers a capacity of 195 mAh g−1 (in contrast to 98 mAh g−1 of pristine V2C) at 50 mA g−1, but also good rate performance. The charge storage mechanism was carefully studied and is shown to involve a solvent co-intercalation process. In addition, full cells were fabricated by coupling the K–V2C anode and Prussian blue analogous (KxMnFe(CN)6) cathode, which can work at a high average operating voltage of ~3.3 V within a wide range (0.01 V–4.6 V). Moreover, the devices can achieve a high energy density of 145 Wh kg−1 at a power density of 112.6 W kg−1, suggesting that K–V2C, and other porous MXenes prepared by our approach, are promising electrodes in mobile ion capacitors.
Original languageEnglish (US)
Pages (from-to)853-860
Number of pages8
JournalNano Energy
Volume62
DOIs
StatePublished - Jun 12 2019

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