Nanocrystalline Magnetite: Synthetic Crystallite Size Control and Resulting Magnetic and Electrochemical Properties

Zhu, Shali; Marschilok, Amy C.; Takeuchi, Esther S.; Yee, Gordon T.; Wang, Guangbin; Takeuchi, Kenneth J.

doi:10.1149/1.3478667

Cited by 53 publications

(87 citation statements)

References 41 publications

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“…1), we hypothesize that heterogeneous nucleation was dominant at low concentration, and homogeneous nucleation was dominant at high concentration. 9 Consistent with our expectations as discussed above, the most significant difference in Fe 3 O 4 electrochemical behavior were observed under higher rate conditions. Specifically, under pulsatile discharge at 5 mA/cm 2 , a 30% Fe 3 O 4 crystallite size reduction improved discharge capacity by 40% (Fig.…”

Section: Control Of Physical Propertiessupporting

confidence: 91%

“…Thus, especially for applications demanding high power output, control of material properties including crystallite size can be especially useful. 8,9 To rationalize our observed bifunctional correlation of Fe 2+ concentration and crystallite size ( Fig. 1), we hypothesize that heterogeneous nucleation was dominant at low concentration, and homogeneous nucleation was dominant at high concentration.…”

Section: Control Of Physical Propertiesmentioning

confidence: 75%

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Secondary Battery Science: At the Confluence of Electrochemistry and Materials Engineering

2012

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Considerations of energy density, power, and calendar life are critical to effectively develop advanced secondary systems. For next generation battery applications requiring multiple features including long life, large cycle count, high energy density and high power, new strategies are needed for the rational design of electroactive materials and electrodes. This article discusses several conceptual approaches under exploration with examples from our research group. The first approach is the systematic synthesis of materials with structures facilitating ion insertion and deinsertion at high voltage and energy density, where we control materials properties such as surface area, particle size and in particular crystallite size. A second approach is the investigation of novel electrode structures and substrates to increase energy density and capacity retention under cycling, where we have developed strategies for minimizing passive components. A third approach is investigation of catalysts for metal air batteries where the cathode active material is drawn from the air rather than carried in the battery.

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Section: Control Of Physical Propertiessupporting

confidence: 91%

Section: Control Of Physical Propertiesmentioning

confidence: 75%

Secondary Battery Science: At the Confluence of Electrochemistry and Materials Engineering

2012

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“…11,12 Larger sized nanocrystalline magnetite, ∼32 nm, was purchased from Alfa Aesar. X-ray diffraction data was collected using a Rigaku Smart Lab diffractometer with Cu Kα radiation.…”

Section: Methods Of Approachmentioning

confidence: 99%

Modeling the Mesoscale Transport of Lithium-Magnetite Electrodes Using Insight from Discharge and Voltage Recovery Experiments

Knehr

Brady

Cama

et al. 2015

J. Electrochem. Soc.

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100

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A multi-scale mathematical model, which accounts for mass transport on the crystal and agglomerate length-scales, is used to investigate the electrochemical performance of lithium-magnetite electrochemical cells. Experimental discharge and voltage recovery data are compared to three sets of simulations, which incorporate crystal-only, agglomerate-only, or multi-scale transport effects. Mass transport diffusion coefficients are determined by fitting the simulated voltage recovery times to experimental data. In addition, a further extension of the multi-scale model is proposed which accounts for the impact of agglomerate size distributions on electrochemical performance. The results of the study indicate that, depending on the crystal size, the low utilization of the active material is caused by transport limitations on the agglomerate and/or crystal length-scales. For electrodes composed of small crystals (6 and 8 nm diameters), it is concluded that the transport limitations in the agglomerate are primarily responsible for the long voltage recovery times and low utilization of the active mass. In the electrodes composed of large crystals (32 nm diameter), the slow voltage recovery is attributed to transport limitations on both the agglomerate and crystal length-scales. Large increases in the use of distributed and intermittent energy sources (i.e., wind and solar) have increased the need for cost effective, reliable, and efficient energy storage technologies.1 To address these needs, significant research efforts have focused on the development of next generation materials for secondary batteries, which can provide inexpensive and long lasting energy storage solutions.2-4 In particular, considerable work has focused on the advancement of magnetite (Fe 3 O 4 ) as an electrode in lithium-ion batteries due to its high theoretical capacity (926 mAh g −1 ), low cost and safety (non-toxic). 5-14Despite these advantages, one of the major challenges limiting the advancement of magnetite electrodes is a considerable difference between the maximum, theoretical capacity and the observed, experimental capacity of the active material. This difference increases the anticipated cost of magnetite batteries because it requires the electrodes to be overdesigned with excess amounts of active material. The difference between the theoretical and experimental capacity is related to the close-packed inverse spinel structure of Fe 3 O 4 , which restricts the transport of lithium in the material. To address this issue, several authors have synthesized Fe 3 O 4 nano-crystallites in attempts to minimize the path length for ion transport.9-14 The smaller path length increases the utilization of the active material by making it possible for ions to penetrate to the center of the crystals, especially at high rates of discharge. Electrodes fabricated with nano-crystalline magnetite have shown significant improvement in capacity; however, the theoretical capacity has still proven difficult to obtain.11 Further improvements in capacity may requir...

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“…19,20 The electrochemical results indicated less polarization and higher delivered energy during discharge/ charge cycling for the smaller crystallite size material with comparable agglomerate size and distribution. This provided new insights into the agglomerate sizes and discharge progress of nanocrystalline materials when incorporated into electrodes.…”

Section: ■ Introductionmentioning

confidence: 96%

2D Cross Sectional Analysis and Associated Electrochemistry of Composite Electrodes Containing Dispersed Agglomerates of Nanocrystalline Magnetite, Fe₃O₄

Bock

Kirshenbaum

Wang

et al. 2015

ACS Appl. Mater. Interfaces

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When electroactive nanomaterials are fully incorporated into an electrode structure, characterization of the crystallite sizes, agglomerate sizes, and dispersion of the electroactive materials can lend insight into the complex electrochemistry associated with composite electrodes. In this study, composite magnetite electrodes were sectioned using ultramicrotome techniques, which facilitated the direct observation of crystallites and agglomerates of magnetite (Fe3O4) as well as their dispersal patterns in large representative sections of electrode, via 2D cross sectional analysis by Transmission Electron Microscopy (TEM). Further, the electrochemistry of these electrodes were recorded, and Transmission X-ray Microscopy (TXM) was used to determine the distribution of oxidation states of the reduced magnetite. Unexpectedly, while two crystallite sizes of magnetite were employed in the production of the composite electrodes, the magnetite agglomerate sizes and degrees of dispersion in the two composite electrodes were similar to each other. This observation illustrates the necessity for careful characterization of composite electrodes, in order to understand the effects of crystallite size, agglomerate size, and level of dispersion on electrochemistry.

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Nanocrystalline Magnetite: Synthetic Crystallite Size Control and Resulting Magnetic and Electrochemical Properties

Cited by 53 publications

References 41 publications

Secondary Battery Science: At the Confluence of Electrochemistry and Materials Engineering

Secondary Battery Science: At the Confluence of Electrochemistry and Materials Engineering

Modeling the Mesoscale Transport of Lithium-Magnetite Electrodes Using Insight from Discharge and Voltage Recovery Experiments

2D Cross Sectional Analysis and Associated Electrochemistry of Composite Electrodes Containing Dispersed Agglomerates of Nanocrystalline Magnetite, Fe₃O₄

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Nanocrystalline Magnetite: Synthetic Crystallite Size Control and Resulting Magnetic and Electrochemical Properties

Cited by 53 publications

References 41 publications

Secondary Battery Science: At the Confluence of Electrochemistry and Materials Engineering

Secondary Battery Science: At the Confluence of Electrochemistry and Materials Engineering

Modeling the Mesoscale Transport of Lithium-Magnetite Electrodes Using Insight from Discharge and Voltage Recovery Experiments

2D Cross Sectional Analysis and Associated Electrochemistry of Composite Electrodes Containing Dispersed Agglomerates of Nanocrystalline Magnetite, Fe3O4

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Product

Resources

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2D Cross Sectional Analysis and Associated Electrochemistry of Composite Electrodes Containing Dispersed Agglomerates of Nanocrystalline Magnetite, Fe₃O₄