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.

X‐ray Nano‐computed Tomography of Electrochemical Conversion in Lithium‐ion Battery

“…Advanced ex and in situ measurements have promoted fundamental understanding of the structural and morphological modifications along with the effects of metal oxide composition on the conversion reaction features . Among the various investigative approaches, three‐dimensional imaging at the micro‐ and nanoscale may actually shed light on the particle evolution throughout the lithium‐exchange process and reveal crucial morphological parameters for electrode modelling, such as the phase volume fraction and the particle size distribution .…”

A New CuO‐Fe2O3‐Mesocarbon Microbeads Conversion Anode in a High‐Performance Lithium‐Ion Battery with a Li1.35Ni0.48Fe0.1Mn1.72O4 Spinel Cathode

“…According to previous reports on composite conversion anodes, [38,41] the first cycle shows irreversible processes relatedt ot he formation of aS EI and structural rearrangements within the material, in additiont ot he reversible lithiation of CuO, Fe 2 O 3 ,a nd carbon matrix. [26][27][28] This processm ay cause limited reversibility and remarkable changes in particles ize;s ubsequently,t he electrode structure stabilizes throughout cycling. [53] Ac arbon delithiationp rocess at about 0.3 Vv ersus Li + /Li and deconversion reactions above 1Vversus Li + /Li are observed throughout the first anodic scan.…”

“…Thus, the first cathodic scan reveals two peaks at 1.1 and 0.7 Vv ersus Li + /Li, which reflect the reduction of CuO [38] and Fe 2 O 3 [41] to Cu, Fe, and Li 2 O, followed by ab road signal below 0.4 Vv ersus Li + /Li, which suggestsl ithium insertion into carbon. [26][27][28][29] Similarly, electron microscopy,X RD, and X-ray photoelectron spectroscopy (XPS) studies have shown that Fe 2 O 3 exchanges lithium ions through insertion followed by conversion to metallic Fe embedded within aL i 2 Om atrix, which leads to significant electrode swelling upon lithiation. The CV profile stabilizes in subsequent cycles and reveals reversible lithium conversion within the range of 0.7 to 2.5 Vv ersus Li + /Li andl ithium insertion into the carbon matrixb elow 0.3 Vv ersus Li + /Li.…”

“…[16,17] Therefore, several oxides have been recently investigated for battery applications, with promising results. [26][27][28][29][30][31][32] These structuralc hanges lead to electrode pulverization and loss of electric contact after prolonged cycling. Moreover,t hese metal oxides are generally cheap, remarkably safe, and environmentally compatible.…”

Sustainable Method for the Large‐Scale Preparation of Fe3O4 Nanocrystals

“…In this study, the supernatant from a previous process was retained and then used for the subsequent preparation of porous Fe 3 O 4 nanocrystals composed of small grains. When the nanoparticle is interconnected with small grains, this nanoparticle is generally denoted as a porous nanoparticle . A mixture of Fe(acac) 3 (100 g) and the first recycled solvent (the first supernatant) was heated to 300°C and maintained at this temperature for 30 min.…”