Engineering of a TiO2 anode toward a record high Initial coulombic efficiency enabling high-performance low-temperature Na-ion hybrid capacitors. Issue 45 (1st November 2018)

• Record Type: Journal Article
• Authors: Kang, Meiling; Wu, Yingying; Huang, Xin; Zhou, Kaiqiang; Huang, Zhigao; Hong, Zhengsheng
• Is Part Of: Journal of materials chemistry. Volume 6:Issue 45(2018)
• Page Start: 22840
• Page End: 22850
• Publication Date: 2018-11-01
• Subjects: Materials -- Research -- Periodicals; Chemistry, Analytic -- Periodicals; Environmental sciences -- Research -- Periodicals; 543.0284
• DOI: 10.1039/c8ta07127f
• Languages: English
• ISSNs: 2050-7488

Abstract

Abstract : A high-performance hybrid sodium-ion capacitor was developed through the engineering of a TiO2 anode to achieve record high initial coulombic efficiency. Abstract : Initial coulombic efficiency (ICE) is an important evaluation index to weigh the applicability of electrode materials, but it is not acknowledged by many researchers. Herein, S-doped TiO2 nanosheets with porous and layered structures are utilized as anodes to fabricate hybrid sodium-ion capacitors in an ether electrolyte with high performance, especially through dramatically improved ICE. For Na-ion half cell tests in a DME electrolyte, S-doped TiO2 nanosheets display record high ICE of 88.6%, excellent rate capability and good cycling performance. We also find that TiO2 material with a large surface area is helpful for reducing the first irreversible capacity in an ether electrolyte, which is different from that observed using a traditional ester-based electrolyte. This could be due to excellent electronic conductivity with charge resistance of ∼1 Ω through the construction of an ultrathin solid electrolyte interphase (SEI) layer. Coupling with an Na3 V2 (PO4 )3 cathode, we verify a successful Na-ion hybrid capacitor, delivering high energy and power density values of 158 W h kg −1 and 1075 W kg −1, respectively, at room temperature. Moreover, it also exhibits satisfactory performance of 82 W h kg −1 at −20 °C and outstanding cycling performance with over 95% retention after 800 cycles even at 1 A g −1 charge and discharge rate.