Simple and Cost-Effective Approach to Dramatically Enhance the Durability and Capability of a Layered δ-MnO2 Based Electrode for Pseudocapacitors: A Practical Electrochemical Test and Mechanistic Revealing

Minghai Yao, Xu Ji, Tsung Fu Chou, Shuang Cheng, Lufeng Yang, Peng Wu, Haowei Luo, Yuanyuan Zhu, Lujie Tang, Jenghan Wang, Meilin Liu

Research output: Contribution to journalArticle

6 Citations (Scopus)

Abstract

Inadequate capacity and poor durability of MnO2 based pseudocapacitive electrodes have long been stumbling blocks in the way of their commercial use. Though layered δ-MnO2 has higher potential to be used due to its proton-free energy storage reactions, its durability is still far away from carbon based electrodes associated with structure deformation caused by interlayer spacing change and Jahn-Teller effect. Here we report an effective approach to dramatically enhance not only the stability but also the capacity of δ-MnO2 based electrode through a simple incorporation of exotic cations, hydrated Zn2+, in the tunnel of the material. Even at a very fast charge/discharge rate (50 A g-1), the capacity of the electrode is gradually increased from 268 to 348 F g-1 after ∼3,000 cycles and then remains relatively constant in the subsequent ∼17,000 cycles, which means ∼128% of the initial capacity is maintained after 20,000 cycles. In contrast, the capacity of bare δ-MnO2 electrode without modification is degraded gradually along the cycling, retaining only ∼74% of the initial value after 20,000 cycles. To reveal the basic chemistry between them, synchrotron X-ray diffraction and Raman spectroscopy were performed to explore the structural evolution of the modified δ-MnO2 during cycling; DFT computation was used to estimate the energetics and vibration modes associated with the hydrated Zn2+. The performance enhancement is attributed largely to the preaccommodation of [Zn (H2O)n]2+, which effectively suppresses the interlayer spacing change during cycling and thus benefits the stability.

Original languageEnglish
Pages (from-to)2743-2750
Number of pages8
JournalACS Applied Energy Materials
Volume2
Issue number4
DOIs
Publication statusPublished - 2019 Apr 22

Keywords

  • DFT computation
  • in situ Raman
  • layered δ-MnO/NaMnO
  • pseudocapacitor
  • tunnel structure modification/preaccommodation of exotic ions

ASJC Scopus subject areas

  • Chemical Engineering (miscellaneous)
  • Energy Engineering and Power Technology
  • Electrochemistry
  • Materials Chemistry
  • Electrical and Electronic Engineering

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