Direct Evidence of Charge Transfer upon Anion Intercalation in Graphite Cathodes through New Electronic States: An Experimental and Theoretical Study of Hexafluorophosphate

Tristan De Boer; Jacob G. Lapping; Jeffrey A. Read; Timothy T. Fister; Mahalingam Balasubramanian; Jordi Cabana; Alexander Moewes

doi:10.1021/acs.chemmater.9b05078

Direct Evidence of Charge Transfer upon Anion Intercalation in Graphite Cathodes through New Electronic States: An Experimental and Theoretical Study of Hexafluorophosphate

Tristan De Boer
, Jacob G. Lapping
, Jeffrey A. Read
, Timothy T. Fister
, Mahalingam Balasubramanian
, Jordi Cabana
, Alexander Moewes

Research output: Contribution to journal › Article › peer-review

12 Scopus citations

Abstract

Graphite intercalation compounds continue to be central to technologies for electrochemical energy storage from anodes in established Li-ion batteries to cathodes in beyond Li-ion concepts paired with multivalent anodes. When used as a cathode, graphite intercalates a variety of anions with PF₆ ^- being among the most common. Paired with Li intercalation at the anode, the corresponding dual carbon battery yields high energy and power densities. Given the available choice of anions as intercalants, it is important to elucidate how the graphite structure accommodates them in order to tailor the molecular species to maximize charge and reversibility. However, the changes in electronic structure of the host graphite lattice upon anion intercalation are poorly understood compared to cations, which represent a fundamentally different reaction. In this work, PF₆-intercalated graphite has been studied using techniques sensitive to electronic structure, namely, X-ray Raman spectroscopy (XRS), X-ray absorption near-edge spectroscopy (XANES), and X-ray emission spectroscopy (XES). Complementary full-potential, all-electron density functional theory calculations yielded excellent agreement with the spectra, thus providing insight into charge compensation in the graphite lattice. In particular, a pre-π∗ feature emerged in XRS/XANES, which is direct evidence of the removal of charge from the host lattice to compensate the intercalated anions, leading to an overall lowering of the Fermi energy level. This is expected to be characteristic of many intercalants in anion-intercalated graphite. The unambiguous identification of the origin of the pre-π∗ spectral feature, which is frequently seen in graphitic systems, is of broad interest to the spectroscopy of graphitic systems beyond the practical implications of anion-induced changes in the electronic properties for real devices.

Original language	English
Pages (from-to)	2036-2043
Number of pages	8
Journal	Chemistry of Materials
Volume	32
Issue number	5
DOIs	https://doi.org/10.1021/acs.chemmater.9b05078
State	Published - Mar 10 2020
Externally published	Yes

Funding

We acknowledge support from NSERC and the Canada Research Chair program. Research of J.G.L., J.A.R., and J.C. was sponsored by the Army Research Laboratory and accomplished under Cooperative Agreement no. W911NF-15-2-0010. The views and conclusions contained in this document are those of the authors and should not be interpreted as representing the official policies, either expressed or implied, of the Army Research Laboratory or the U.S. government. The U.S. government is authorized to reproduce and distribute reprints for government purposes notwithstanding any copyright notation herein. This research used resources of the Advanced Photon Source, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by the Argonne National Laboratory under contract no. DE-AC02-06CH11357. This research used resources of the Advanced Light Source, which is a DOE Office of Science User Facility under contract no. DE-AC02-05CH11231. The computational component of this work was enabled by resources provided by Compute Canada Calcul Canada ( www.computecanada.ca ) and the Plato computing cluster at the University of Saskatchewan.

Access to Document

10.1021/acs.chemmater.9b05078

Cite this

De Boer, T., Lapping, J. G., Read, J. A., Fister, T. T., Balasubramanian, M., Cabana, J., & Moewes, A. (2020). Direct Evidence of Charge Transfer upon Anion Intercalation in Graphite Cathodes through New Electronic States: An Experimental and Theoretical Study of Hexafluorophosphate. Chemistry of Materials, 32(5), 2036-2043. https://doi.org/10.1021/acs.chemmater.9b05078

@article{fed6d83365024632a7c5c3acfccc9e2c,

title = "Direct Evidence of Charge Transfer upon Anion Intercalation in Graphite Cathodes through New Electronic States: An Experimental and Theoretical Study of Hexafluorophosphate",

abstract = "Graphite intercalation compounds continue to be central to technologies for electrochemical energy storage from anodes in established Li-ion batteries to cathodes in beyond Li-ion concepts paired with multivalent anodes. When used as a cathode, graphite intercalates a variety of anions with PF6 - being among the most common. Paired with Li intercalation at the anode, the corresponding dual carbon battery yields high energy and power densities. Given the available choice of anions as intercalants, it is important to elucidate how the graphite structure accommodates them in order to tailor the molecular species to maximize charge and reversibility. However, the changes in electronic structure of the host graphite lattice upon anion intercalation are poorly understood compared to cations, which represent a fundamentally different reaction. In this work, PF6-intercalated graphite has been studied using techniques sensitive to electronic structure, namely, X-ray Raman spectroscopy (XRS), X-ray absorption near-edge spectroscopy (XANES), and X-ray emission spectroscopy (XES). Complementary full-potential, all-electron density functional theory calculations yielded excellent agreement with the spectra, thus providing insight into charge compensation in the graphite lattice. In particular, a pre-π∗ feature emerged in XRS/XANES, which is direct evidence of the removal of charge from the host lattice to compensate the intercalated anions, leading to an overall lowering of the Fermi energy level. This is expected to be characteristic of many intercalants in anion-intercalated graphite. The unambiguous identification of the origin of the pre-π∗ spectral feature, which is frequently seen in graphitic systems, is of broad interest to the spectroscopy of graphitic systems beyond the practical implications of anion-induced changes in the electronic properties for real devices.",

author = "\{De Boer\}, Tristan and Lapping, \{Jacob G.\} and Read, \{Jeffrey A.\} and Fister, \{Timothy T.\} and Mahalingam Balasubramanian and Jordi Cabana and Alexander Moewes",

note = "Publisher Copyright: Copyright {\textcopyright} 2020 American Chemical Society.",

year = "2020",

month = mar,

day = "10",

doi = "10.1021/acs.chemmater.9b05078",

language = "English",

volume = "32",

pages = "2036--2043",

journal = "Chemistry of Materials",

issn = "0897-4756",

publisher = "American Chemical Society",

number = "5",

}

De Boer, T, Lapping, JG, Read, JA, Fister, TT, Balasubramanian, M, Cabana, J & Moewes, A 2020, 'Direct Evidence of Charge Transfer upon Anion Intercalation in Graphite Cathodes through New Electronic States: An Experimental and Theoretical Study of Hexafluorophosphate', Chemistry of Materials, vol. 32, no. 5, pp. 2036-2043. https://doi.org/10.1021/acs.chemmater.9b05078

Direct Evidence of Charge Transfer upon Anion Intercalation in Graphite Cathodes through New Electronic States: An Experimental and Theoretical Study of Hexafluorophosphate. / De Boer, Tristan; Lapping, Jacob G.; Read, Jeffrey A. et al.
In: Chemistry of Materials, Vol. 32, No. 5, 10.03.2020, p. 2036-2043.

Research output: Contribution to journal › Article › peer-review

TY - JOUR

T1 - Direct Evidence of Charge Transfer upon Anion Intercalation in Graphite Cathodes through New Electronic States

T2 - An Experimental and Theoretical Study of Hexafluorophosphate

AU - De Boer, Tristan

AU - Lapping, Jacob G.

AU - Read, Jeffrey A.

AU - Fister, Timothy T.

AU - Balasubramanian, Mahalingam

AU - Cabana, Jordi

AU - Moewes, Alexander

PY - 2020/3/10

Y1 - 2020/3/10

N2 - Graphite intercalation compounds continue to be central to technologies for electrochemical energy storage from anodes in established Li-ion batteries to cathodes in beyond Li-ion concepts paired with multivalent anodes. When used as a cathode, graphite intercalates a variety of anions with PF6 - being among the most common. Paired with Li intercalation at the anode, the corresponding dual carbon battery yields high energy and power densities. Given the available choice of anions as intercalants, it is important to elucidate how the graphite structure accommodates them in order to tailor the molecular species to maximize charge and reversibility. However, the changes in electronic structure of the host graphite lattice upon anion intercalation are poorly understood compared to cations, which represent a fundamentally different reaction. In this work, PF6-intercalated graphite has been studied using techniques sensitive to electronic structure, namely, X-ray Raman spectroscopy (XRS), X-ray absorption near-edge spectroscopy (XANES), and X-ray emission spectroscopy (XES). Complementary full-potential, all-electron density functional theory calculations yielded excellent agreement with the spectra, thus providing insight into charge compensation in the graphite lattice. In particular, a pre-π∗ feature emerged in XRS/XANES, which is direct evidence of the removal of charge from the host lattice to compensate the intercalated anions, leading to an overall lowering of the Fermi energy level. This is expected to be characteristic of many intercalants in anion-intercalated graphite. The unambiguous identification of the origin of the pre-π∗ spectral feature, which is frequently seen in graphitic systems, is of broad interest to the spectroscopy of graphitic systems beyond the practical implications of anion-induced changes in the electronic properties for real devices.

AB - Graphite intercalation compounds continue to be central to technologies for electrochemical energy storage from anodes in established Li-ion batteries to cathodes in beyond Li-ion concepts paired with multivalent anodes. When used as a cathode, graphite intercalates a variety of anions with PF6 - being among the most common. Paired with Li intercalation at the anode, the corresponding dual carbon battery yields high energy and power densities. Given the available choice of anions as intercalants, it is important to elucidate how the graphite structure accommodates them in order to tailor the molecular species to maximize charge and reversibility. However, the changes in electronic structure of the host graphite lattice upon anion intercalation are poorly understood compared to cations, which represent a fundamentally different reaction. In this work, PF6-intercalated graphite has been studied using techniques sensitive to electronic structure, namely, X-ray Raman spectroscopy (XRS), X-ray absorption near-edge spectroscopy (XANES), and X-ray emission spectroscopy (XES). Complementary full-potential, all-electron density functional theory calculations yielded excellent agreement with the spectra, thus providing insight into charge compensation in the graphite lattice. In particular, a pre-π∗ feature emerged in XRS/XANES, which is direct evidence of the removal of charge from the host lattice to compensate the intercalated anions, leading to an overall lowering of the Fermi energy level. This is expected to be characteristic of many intercalants in anion-intercalated graphite. The unambiguous identification of the origin of the pre-π∗ spectral feature, which is frequently seen in graphitic systems, is of broad interest to the spectroscopy of graphitic systems beyond the practical implications of anion-induced changes in the electronic properties for real devices.

UR - https://www.scopus.com/pages/publications/85081934046

U2 - 10.1021/acs.chemmater.9b05078

DO - 10.1021/acs.chemmater.9b05078

M3 - Article

AN - SCOPUS:85081934046

SN - 0897-4756

VL - 32

SP - 2036

EP - 2043

JO - Chemistry of Materials

JF - Chemistry of Materials

IS - 5

ER -

Direct Evidence of Charge Transfer upon Anion Intercalation in Graphite Cathodes through New Electronic States: An Experimental and Theoretical Study of Hexafluorophosphate

Abstract

Funding

Access to Document

Other files and links

Fingerprint

Cite this