Deciphering the lithium ion movement in lithium ion batteries: determination of the isotopic abundances of <sup>6</sup>Li and <sup>7</sup>Li

Diehl, Marcel; Evertz, Marco; Winter, Martin; Nowak, Sascha

doi:10.1039/c9ra02312g

Cited by 14 publications

(124 citation statements)

References 52 publications

(92 reference statements)

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“…Each sample was measured at least three times. The typical drift in the 7 Li/ 6 Li ratio was 0.1‰ to 0.2‰, as observed by two consecutive bracketing standard measurements of LSVEC during the sequences.…”

Section: General Proceduresmentioning

confidence: 52%

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High-Resolution Atomic Absorption Spectrometry Combined With Machine Learning Data Processing for Isotope Amount Ratio Analysis of Lithium

et al. 2021

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An alternative method for lithium isotope amount ratio analysis based on a combination of high-resolution atomic absorption spectrometry and spectral data analysis by machine learning (ML) is proposed herein. It is based on the well-known isotope shift of approximately 15 pm for the electronic transition 2 2 P←2 2 S at around the wavelength of 670.8 nm, which can be measured by state-of-the-art high-resolution continuum source graphite furnace atomic absorption spectrometry. For isotope amount ratio analysis, a scalable tree boosting ML algorithm (XGBoost) was employed and calibrated using a set of samples with 6 Li isotope amount fractions ranging from 0.06 to 0.99 mol mol −1 , previously determined by multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS). The calibration ML model was validated with two certified reference materials (LSVEC and IRMM-016). The procedure was applied to the isotope amount ratio determination of a set of stock chemicals (Li 2 CO 3 , LiNO 3 , LiCl, and LiOH) and a BAM candidate reference material, that is, LiNi 1/3 Mn 1/3 Co 1/3 O 2 (NMC111) cathode material. The results of these determinations were compared with those obtained by MC-ICP-MS and found to be metrologically comparable and compatible. The residual bias was −1.8‰ and the precision obtained ranged from 1.9‰ to 6.2‰. This precision was sufficient to resolve naturally occurring variations, as demonstrated for samples ranging from approximately −3‰ to +15‰. To assess its suitability to technical applications, the NMC111 cathode candidate reference material was analyzed using high-resolution continuum source molecular absorption spectrometry with and without matrix purification. The results obtained were metrologically compatible with each other. File list (2) download file view on ChemRxiv Manuscript_Preprint_20210115.pdf (703.18 KiB) download file view on ChemRxiv ESI_Manuscript_20210115.pdf (210.73 KiB)High-resolution atomic absorption spectrometry combined with machine learning data processing for isotope amount ratio analysis of lithium

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Section: General Proceduresmentioning

confidence: 52%

“…4 It is crucial for the understanding of the aging mechanisms and therefore leading to the improved design of long-lasting batteries. 5,6 Presently, mass spectrometry (MS) is considered the standard technique for Li isotope ratio analysis.…”

Section: Introductionmentioning

confidence: 99%

High-Resolution Atomic Absorption Spectrometry Combined With Machine Learning Data Processing for Isotope Amount Ratio Analysis of Lithium

et al. 2021

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“…For the operability of LIBs, transition metals (TMs) play a fundamental role as reversible lithium insertion hosts for positive electrodes in form of layered lithium metal oxides (L M O 2 , M = Ni, Co, Mn, (Al)), spinel type LiMn 2 O 4 (LMO), or olivine type LiFePO 4 (LFP) materials [6–10]. TM dissolution from these materials and redeposition on the electrodes can accelerate electrolyte side reactions leading to a loss of active lithium and thus to a lower battery lifetime [11–22]. Also Al dissolution from the Al current collector at the positive electrode (cathode) can take place [23–26].…”

Section: Introductionmentioning

confidence: 99%

Accessing copper oxidation states of dissolved negative electrode current collectors in lithium ion batteries

et al. 2020

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A novel capillary electrophoresis (CE) method with ultraviolet-visible spectroscopy (UV-Vis) detection for the investigation of dissolved Cu + and Cu 2+ in lithium ion battery (LIB) electrolytes was developed. This method is of relevance, as the current collector at the anode of LIBs may dissolve under certain operation conditions. In order to preserve the actual oxidation states of dissolved copper in the electrolytes and to prevent any precipitation during sample preparation and CE measurements, neocuproine (NC) and ethylenediamine tetraacetic (EDTA) were effectively applied as complexing agents for both ionic copper species. However, precipitation and loss of the Cu +-NC-complex for quantification occurred in presence of the commonly applied conducting salt lithium hexafluorophosphate (LiPF 6). Therefore, acetonitrile (ACN) was added to the sample in order to suppress this precipitation. Dissolution experiments with copper-based negative electrode current collectors in a LIB electrolyte were conducted at 60°C under non-oxidizing atmosphere. First findings regarding the copper species via CE revealed dissolved Cu + and mainly Cu 2+. However, primarily Cu + dissolved from the passivating oxide layer (Cu 2 O and CuO) of the current collector due to the formation of acidic electrolyte decomposition products. Due to the instability of Cu + in the electrolyte a further disproportionation reaction to Cu 0 and Cu 2+ occurred. The results show the high potential of this CE method for prospective investigations regarding the current collector stability in new battery electrode formulations and correlations of dissolution events with dissolution mechanisms and battery cell operation conditions.

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“…However, LFP‐based cells also show ongoing capacity loss with increasing cycle number. The capacity loss is mainly associated with side reactions of the electrolyte, resulting in the loss of active lithium and finally to a lower battery lifetime [14–21]. As for other transition metal ions like nickel, cobalt, and manganese, deposited iron on the negative electrode could accelerate these side reactions [22–29].…”

Section: Introductionmentioning

confidence: 99%

Investigating the oxidation state of Fe from LiFePO₄‐based lithium ion battery cathodes via capillary electrophoresis

et al. 2020

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A capillary electrophoresis (CE) method with ultraviolet/visible (UV-Vis) spectroscopy for iron speciation in lithium ion battery (LIB) electrolytes was developed. The complexation of Fe 2+ with 1,10-phenantroline (o-phen) and of Fe 3+ with ethylenediamine tetraacetic acid (EDTA) revealed effective stabilization of both iron species during sample preparation and CE measurements. For the investigation of small electrolyte volumes from LIB cells, a sample buffer with optimal sample pH was developed to inhibit precipitation of Fe 3+ during complexation of Fe 2+ with o-phen. However, the presence of the conducting salt lithium hexafluorophosphate (LiPF 6) in the electrolyte led to the precipitation of the complex [Fe(o-phen) 3 ](PF 6) 2. Addition of acetonitrile (ACN) to the sample successfully redissolved this Fe 2+-complex to retain the quantification of both species. Further optimization of the method successfully prevented the oxidation of dissolved Fe 2+ with ambient oxygen during sample preparation, by previously stabilizing the sample with HCl or by working under counterflow of argon. Following dissolution experiments with the positive electrode material LiFePO 4 (LFP) in LIB electrolytes under dry room conditions at 20°C and 60°C mainly revealed iron dissolution at elevated temperatures due to the formation of acidic electrolyte decomposition products. Despite the primary oxidation state of iron in LFP of +2, both iron species were detected in the electrolytes that derive from oxidation of dissolved Fe 2+ by remaining molecular oxygen in the sample vials during the dissolution experiments.

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Deciphering the lithium ion movement in lithium ion batteries: determination of the isotopic abundances of ⁶Li and ⁷Li

Abstract: Different aging experiments were performed on NMC622/graphite cells with a 6Li enriched electrolyte to unravel the lithium distribution.

Cited by 14 publications

References 52 publications

High-Resolution Atomic Absorption Spectrometry Combined With Machine Learning Data Processing for Isotope Amount Ratio Analysis of Lithium

High-Resolution Atomic Absorption Spectrometry Combined With Machine Learning Data Processing for Isotope Amount Ratio Analysis of Lithium

Accessing copper oxidation states of dissolved negative electrode current collectors in lithium ion batteries

Investigating the oxidation state of Fe from LiFePO₄‐based lithium ion battery cathodes via capillary electrophoresis

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Deciphering the lithium ion movement in lithium ion batteries: determination of the isotopic abundances of 6Li and 7Li

Abstract: Different aging experiments were performed on NMC622/graphite cells with a 6Li enriched electrolyte to unravel the lithium distribution.

Cited by 14 publications

References 52 publications

High-Resolution Atomic Absorption Spectrometry Combined With Machine Learning Data Processing for Isotope Amount Ratio Analysis of Lithium

High-Resolution Atomic Absorption Spectrometry Combined With Machine Learning Data Processing for Isotope Amount Ratio Analysis of Lithium

Accessing copper oxidation states of dissolved negative electrode current collectors in lithium ion batteries

Investigating the oxidation state of Fe from LiFePO4‐based lithium ion battery cathodes via capillary electrophoresis

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Deciphering the lithium ion movement in lithium ion batteries: determination of the isotopic abundances of ⁶Li and ⁷Li

Investigating the oxidation state of Fe from LiFePO₄‐based lithium ion battery cathodes via capillary electrophoresis