TY - JOUR
T1 - Simple and Cost-Effective Approach to Dramatically Enhance the Durability and Capability of a Layered δ-MnO2 Based Electrode for Pseudocapacitors
T2 - A Practical Electrochemical Test and Mechanistic Revealing
AU - Yao, Minghai
AU - Ji, Xu
AU - Chou, Tsung Fu
AU - Cheng, Shuang
AU - Yang, Lufeng
AU - Wu, Peng
AU - Luo, Haowei
AU - Zhu, Yuanyuan
AU - Tang, Lujie
AU - Wang, Jenghan
AU - Liu, Meilin
N1 - Funding Information:
This work was supported by the Fundamental Research Funds for Central Universities of SCUT, China (Grant No. 2018ZD20), the National Science Foundation for Young Scientists of China (Grant No. 21403073), the National Science Foundation for Key Support Major Research project of China (Grant No. 91745203), Guangdong Innovative and Entrepreneurial Research Team Program (Grant No. 2014ZT05N200), and Guangzhou Science and Technology Program (Grant No. 20181002SF0115).
Publisher Copyright:
© 2019 American Chemical Society.
PY - 2019/4/22
Y1 - 2019/4/22
N2 - 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.
AB - 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.
KW - DFT computation
KW - in situ Raman
KW - layered δ-MnO/NaMnO
KW - pseudocapacitor
KW - tunnel structure modification/preaccommodation of exotic ions
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U2 - 10.1021/acsaem.9b00075
DO - 10.1021/acsaem.9b00075
M3 - Article
AN - SCOPUS:85064820612
SN - 2574-0962
VL - 2
SP - 2743
EP - 2750
JO - ACS Applied Energy Materials
JF - ACS Applied Energy Materials
IS - 4
ER -