title: In Situ Transmission Electron Microscopy Observation of the Lithiation-Delithiation Conversion Behavior of CuO/Graphene Anode.
abstract: The electrochemical conversion behavior of metal oxides as well as its influence on the lithium-storage performance remains unclear. In this paper, we studied the dynamic electrochemical conversion process of CuO/graphene as anode by in situ transmission electron microscopy. The microscopic conversion behavior of the electrode was further correlated with its macroscopic lithium-storage properties. During the first lithiation, the porous CuO nanoparticles transformed to numerous Cu nanograins (2-3 nm) embedded in Li2O matrix. The porous spaces were found to be favorable for accommodating the volume expansion during lithium insertion. Two types of irreversible processes were revealed during the lithiation-delithiation cycles. First, the nature of the charge-discharge process of CuO anode is a reversible phase conversion between Cu2O and Cu nanograins. The delithiation reaction cannot recover the electrode to its pristine structure (CuO), which is responsible for about ∼55% of the capacity fading in the first cycle. Second, there is a severe nanograin aggregation during the initial conversion cycles, which leads to low Coulombic efficiency. This finding could also account for the electrochemical behaviors of other transition metal oxide anodes that operate with similar electrochemical conversion mechanism.
authors.affiliation: Institute of Physical Chemistry, Zhejiang Normal University , Jinhua 321004, China.
authors.forename: Qingmei
authors.initials: Q
authors.lastname: Su
authors.affiliation: Institute of Physical Chemistry, Zhejiang Normal University , Jinhua 321004, China.
authors.forename: Libing
authors.initials: L
authors.lastname: Yao
authors.affiliation: Institute of Physical Chemistry, Zhejiang Normal University , Jinhua 321004, China.
authors.forename: Jun
authors.initials: J
authors.lastname: Zhang
authors.affiliation: Institute of Physical Chemistry, Zhejiang Normal University , Jinhua 321004, China.|Research Centre of Advanced Materials Science and Technology, Taiyuan University of Technology , Taiyuan, 030024 Shanxi, China.
authors.forename: Gaohui
authors.initials: G
authors.lastname: Du
authors.affiliation: Research Centre of Advanced Materials Science and Technology, Taiyuan University of Technology , Taiyuan, 030024 Shanxi, China.
authors.forename: Bingshe
authors.initials: B
authors.lastname: Xu
keywords: conversion mechanism; lithium-ion battery; metal oxide; nanograin aggregation; transmission electron microscopy