1
|
Allen J, Grey CP. Solution NMR of Battery Electrolytes: Assessing and Mitigating Spectral Broadening Caused by Transition Metal Dissolution. THE JOURNAL OF PHYSICAL CHEMISTRY. C, NANOMATERIALS AND INTERFACES 2023; 127:4425-4438. [PMID: 36925561 PMCID: PMC10009815 DOI: 10.1021/acs.jpcc.2c08274] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/25/2022] [Revised: 02/10/2023] [Indexed: 06/02/2023]
Abstract
NMR spectroscopy is a powerful tool that is commonly used to assess the degradation of lithium-ion battery electrolyte solutions. However, dissolution of paramagnetic Ni2+ and Mn2+ ions from cathode materials may affect the NMR spectra of the electrolyte solution, with the unpaired electron spins in these paramagnetic solutes inducing rapid nuclear relaxation and spectral broadening (and often peak shifts). This work establishes how dissolved Ni2+ and Mn2+ in LiPF6 electrolyte solutions affect 1H, 19F, and 31P NMR spectra of pristine and degraded electrolyte solutions, including whether the peaks from degradation species are at risk of being lost and whether the spectral broadening can be mitigated. Mn2+ is shown to cause far greater peak broadening than Ni2+, with the effect of Mn2+ observable at just 10 μM. Generally, 19F peaks from PF6 - degradation species are most affected by the presence of the paramagnetic metals, followed by 31P and 1H peaks. Surprisingly, when NMR solvents are added to acquire the spectra, the degree of broadening is heavily solvent-dependent, following the trend of solvent donor number (increased broadening with lower solvent donicity). Severe spectral broadening is shown to occur whether Mn is introduced via the salt Mn(TFSI)2 or is dissolved from LiMn2O4. We show that the weak 19F and 31P peaks in spectra of electrolyte samples containing micromolar levels of dissolved Mn2+ are broadened to an extent that they are no longer visible, but this broadening can be minimized by diluting electrolyte samples with a suitably coordinating NMR solvent. Li3PO4 addition to the sample is also shown to return 19F and 31P spectral resolution by precipitating Mn2+ out of electrolyte samples, although this method consumes any HF in the electrolyte solution.
Collapse
Affiliation(s)
- Jennifer
P. Allen
- Yusuf
Hamied Department of Chemistry, University
of Cambridge, Lensfield Road, Cambridge, CB2 1EW, Cambridge, United Kingdom
- The
Faraday Institution, Quad One, Harwell Science and Innovation Campus, Didcot OX11 0RA, United Kingdom
| | - Clare P. Grey
- Yusuf
Hamied Department of Chemistry, University
of Cambridge, Lensfield Road, Cambridge, CB2 1EW, Cambridge, United Kingdom
- The
Faraday Institution, Quad One, Harwell Science and Innovation Campus, Didcot OX11 0RA, United Kingdom
| |
Collapse
|
2
|
Kösters K, Henschel J, Winter M, Nowak S. Online sample pretreatment for analysis of decomposition products in lithium ion battery by liquid chromatography hyphenated with ion trap-time of flight-mass spectrometry or inductively coupled plasma-sector field-mass spectrometry. J Chromatogr A 2021; 1658:462594. [PMID: 34666267 DOI: 10.1016/j.chroma.2021.462594] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2021] [Revised: 09/25/2021] [Accepted: 09/27/2021] [Indexed: 11/30/2022]
Abstract
Lithium ion batteries are essential power sources for mobile electronic devices like cell phones, tablets and increasingly used in the field of electromobility and energy transition. The commonly applied liquid electrolytes in commercial cells contain a conducting salt at relatively high concentration (LiPF6, ≥1 mol/L). For analytical battery electrolyte investigations, it is necessary to protect the column and mass spectrometer from salt precipitation and clogging. Thus, dilution of the sample is necessary which results in higher limits of detection and limits of quantification. In this study, a comprehensive online sample preparation approach for reversed phase liquid chromatography with an online-solid phase extraction was developed, which allows higher injections volumes and lower dilution factors. For the method development of the online-solid phase extraction, pristine electrolytes were used with trimethyl phosphate and triethyl phosphate as model substances for organo(fluoro)phosphates with weak and strong retention on the extraction column. Organo(fluoro)phosphates are potential hazardous decomposition products, due to their structural similarity to chemical warfare agents like sarin, and therefore their quantification is beneficial for toxicological assessment. The optimization of chromatographic parameters was performed using electrochemically aged electrolytes. For substance independent quantification with a plasma-based technique, an isocratic separation method was implemented. Using optimized conditions, LiPF6 could be removed quantitatively and the injection volume was increased up to a factor of 50, while the dilution factor could be decreased up to a factor of ten. Eleven different organo(fluoro)phosphates with an overall concentration of 133 mg/kg were found. Therefore, limit of detection and limit of quantification were improved significantly (LOQ: ≤100 µg kg-1 phosphorus content, LOD: ≤35 µg kg-1 phosphorus content). In summary, a fast online sample preparation for liquid chromatographic investigations of lithium ion battery electrolytes was implemented, validated on electrochemically aged lithium ion battery electrolyte.
Collapse
Affiliation(s)
- Kristina Kösters
- University of Münster, MEET Battery Research Center, Corrensstraße 46, 48149 Münster, Germany
| | - Jonas Henschel
- University of Münster, MEET Battery Research Center, Corrensstraße 46, 48149 Münster, Germany
| | - Martin Winter
- University of Münster, MEET Battery Research Center, Corrensstraße 46, 48149 Münster, Germany; Helmholtz-Institute Münster, IEK-12, FZ Jülich, Corrensstraße 46, 48149 Münster, Germany
| | - Sascha Nowak
- University of Münster, MEET Battery Research Center, Corrensstraße 46, 48149 Münster, Germany.
| |
Collapse
|
3
|
A facile synthesis of non-aqueous LiPO2F2 solution as the electrolyte additive for high performance lithium ion batteries. CHINESE CHEM LETT 2020. [DOI: 10.1016/j.cclet.2020.05.006] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
|
4
|
Kösters K, Henschel J, Lürenbaum C, Diehl M, Nowak L, Winter M, Nowak S. Fast sample preparation for organo(fluoro)phosphate quantification approaches in lithium ion battery electrolytes by means of gas chromatographic techniques. J Chromatogr A 2020; 1624:461258. [PMID: 32540083 DOI: 10.1016/j.chroma.2020.461258] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2020] [Revised: 05/15/2020] [Accepted: 05/16/2020] [Indexed: 11/25/2022]
Abstract
Lithium ion batteries are essential power sources in portable electronics, electric vehicles and as energy storage devices for renewable energies. During harsh battery cell operation as well as at elevated temperatures, the electrolyte decomposes and inter alia organo(fluoro)phosphates are formed due to hydrolysis of the conducting salt lithium hexafluorophosphate (LiPF6). Since these phosphorus-containing decomposition products possess a potential toxicity based on structural similarities compared to chemical warfare agents, quantification is of high interest regarding safety estimates. In this study, two comprehensive approaches for the precipitation of highly concentrated PF6¯ were investigated, allowing the separation from target analytes (organo(fluoro)phosphates) and improving mass spectrometry-based quantification techniques. Trimethyl phosphate was used as a polar, non-acidic organophosphate reference substance for method development via liquid chromatography-mass spectrometry. Six solvents were examined regarding precipitation reaction and selectivity. Thermally degraded electrolytes were analyzed after precipitation by means of gas chromatography-flame ionization detector, demonstrating the applicability of the developed sample preparations. The optimized method was applied successfully without influencing any volatile and non-acidic decomposition products. Using optimized conditions, a precipitation rate of 98% PF6¯ was achieved. Consequently, a fast and easy sample preparation for gas chromatographic investigations on lithium ion battery electrolytes was implemented, applicable for routine analysis.
Collapse
Affiliation(s)
- Kristina Kösters
- University of Münster, MEET Battery Research Center, Corrensstraße 46, 48149Münster, Germany
| | - Jonas Henschel
- University of Münster, MEET Battery Research Center, Corrensstraße 46, 48149Münster, Germany
| | - Constantin Lürenbaum
- University of Münster, MEET Battery Research Center, Corrensstraße 46, 48149Münster, Germany
| | - Marcel Diehl
- University of Münster, MEET Battery Research Center, Corrensstraße 46, 48149Münster, Germany
| | - Laura Nowak
- University of Münster, MEET Battery Research Center, Corrensstraße 46, 48149Münster, Germany
| | - Martin Winter
- University of Münster, MEET Battery Research Center, Corrensstraße 46, 48149Münster, Germany; Helmholtz-Institute Münster, IEK-12, FZ Jülich, Corrensstraße 46, 48149Münster, Germany
| | - Sascha Nowak
- University of Münster, MEET Battery Research Center, Corrensstraße 46, 48149Münster, Germany.
| |
Collapse
|
5
|
Henschel J, Wiemers-Meyer S, Diehl M, Lürenbaum C, Jiang W, Winter M, Nowak S. Preparative hydrophilic interaction liquid chromatography of acidic organofluorophosphates formed in lithium ion battery electrolytes. J Chromatogr A 2019; 1603:438-441. [PMID: 31301799 DOI: 10.1016/j.chroma.2019.07.008] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2019] [Accepted: 07/05/2019] [Indexed: 10/26/2022]
Abstract
The expansion of lithium ion battery (LIB) application is accompanied by the growth of battery pack sizes. This progression emphasizes the consideration of electrolyte safety as well as environmental aspects in case of abuse, accident, or recycling. Hexafluorophosphate is one of the most commonly used conducting salt anions in electrolytes. It has great potential to degrade to various acidic and non-acidic organo(fluoro)phosphates with presence of water and during battery cell operation. Consequently, toxicological investigation on these organo(fluoro)phosphates has emerged because they either have structural similarities as chemical warfare agents or play a widespread physiological role as phosphates in the human body. This circumstance underlines the need of isolated examination of these compounds for safety assessment. In this work, we used hydrophilic interaction liquid chromatography for the extraction of acidic organofluorophosphates from thermally aged LIB electrolytes. The developed two-step fractionation method provided high separation selectivity towards acidic head groups, which allowed the separation of undesired matrix and target compounds. These findings facilitate isolated toxicological investigations on organofluorophosphates that are beneficial for environmental and safety research, the battery cell industry, and human safety surveillance in regard to aged LIB electrolytes.
Collapse
Affiliation(s)
- Jonas Henschel
- University of Münster, MEET Battery Research Center, Corrensstraße 46, 48149 Münster, Germany
| | - Simon Wiemers-Meyer
- University of Münster, MEET Battery Research Center, Corrensstraße 46, 48149 Münster, Germany
| | - Marcel Diehl
- University of Münster, MEET Battery Research Center, Corrensstraße 46, 48149 Münster, Germany
| | - Constantin Lürenbaum
- University of Münster, MEET Battery Research Center, Corrensstraße 46, 48149 Münster, Germany
| | - Wen Jiang
- HILICON AB, Tvistevägen 48, 907 36 Umeå, Sweden
| | - Martin Winter
- University of Münster, MEET Battery Research Center, Corrensstraße 46, 48149 Münster, Germany; Helmholtz-Institute Münster, IEK-12, FZ Jülich, Corrensstraße 46, 48149 Münster, Germany
| | - Sascha Nowak
- University of Münster, MEET Battery Research Center, Corrensstraße 46, 48149 Münster, Germany.
| |
Collapse
|