In situ TEM study of lithiation into a PPy coated α-MnO 2 /graphene foam freestanding electrode

Mohammad Akbari Garakani, Sara Abouali, Jiang Cui, Jang Kyo Kim

Research output: Contribution to journalArticlepeer-review

17 Scopus citations

Abstract

Even with the many desirable properties, natural abundance and low cost of α-MnO 2 , its application as the anode in lithium-ion batteries has been limited because of its low intrinsic electrical conductivity and large volume expansion occurring during charge/discharge cycles. In this work, a ternary composite electrode consisting of MnO 2 -polypyrrole (PPy) core-shell arrays is grown on graphene foam (GF) to address the above critical issues. The freestanding MnO 2 -PPy/GF electrode exhibits a high reversible capacity of 945 mA h g -1 at 0.1 A g -1 after 150 cycles with a coulombic efficiency of over 98%, far better than 550 mA h g -1 for the uncoated counterpart. An in situ TEM examination reveals several functional features of the PPy coating that ameliorate the MnO 2 conversion reaction kinetics, and thus the electrochemical performance of the electrode. The PPy coated MnO 2 nanowires have a lithiation speed three times faster than that of the uncoated MnO 2 along with improved electronic conduction and a stable structure against volume expansion. Such a rational design of an electroactive core and a highly conductive polymer shell on a GF conductive substrate offers a potential solution to developing novel MnO 2 -based electrodes with enhanced electrochemical performance.

Original languageBritish English
Pages (from-to)1481-1488
Number of pages8
JournalMaterials Chemistry Frontiers
Volume2
Issue number8
DOIs
StatePublished - Aug 2018

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