Long-term cycling behavior of Mg-doped LiCoO2 materials investigated with the help of laboratory scale X-ray absorption near-edge spectroscopy

Katja Lahtinen; Maximilian Labmayr; Ville Mäkelä; Hua Jiang; Jouko Lahtinen; Lide Yao; Ekaterina O. Fedorovskaya; Samuli Räsänen; Simo Huotari; Tanja Kallio

doi:10.1016/j.mtener.2022.101040

Long-term cycling behavior of Mg-doped LiCoO₂ materials investigated with the help of laboratory scale X-ray absorption near-edge spectroscopy

Katja Lahtinen
, Maximilian Labmayr
, Ville Mäkelä
, Hua Jiang
, Jouko Lahtinen
, Lide Yao
, Ekaterina O. Fedorovskaya
, Samuli Räsänen
, Simo Huotari
, Tanja Kallio^*

^*Corresponding author for this work

Aalto University
University of Helsinki
Umicore Finland Oy

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

20 Citations (Scopus)

149 Downloads (Pure)

Abstract

The use of Li-ion batteries is increasing rapidly. Understanding the processes behind active material aging helps to enhance the materials, and therefore, development of new in situ methods for structural studies is important. In addition, understanding the effect of different synthesis methods on the active material properties is necessary to optimize the material cycle life. In this work, the performance of LiCoO₂ doped with Mg during the lithiation step is compared to LiCoO₂ prepared using an Mg-doped Co₃O₄ precursor. In situ laboratory-scale X-ray absorption near-edge spectroscopy is used to analyze the Co valence changes in LiCoO₂ to understand the electrochemical behavior of the investigated materials. The maximum reachable Co valence state is found to decrease upon aging, a small decrease indicating a good cycle-life, and this is attributed to the enhanced stacking order, better Mg distribution in the lattice, and fine primary particle size in the material. In the synthesis conditions used in this study, Mg doping during the lithiation step is shown to perform better compared to the precursor doping. Overlithiation is shown to reduce the electrochemical performance of nondoped and precursor-doped LiCoO₂ materials but not to affect the cyclability of lithiation-doped LiCoO₂.

Original language	English
Article number	101040
Number of pages	14
Journal	Materials Today Energy
Volume	27
Early online date	17 Jun 2022
DOIs	https://doi.org/10.1016/j.mtener.2022.101040
Publication status	Published - Jul 2022
MoE publication type	A1 Journal article-refereed

Funding

The high-frequency semicircle (active material/current collector interface resistance, RI) increases in the pouch cells upon cycling. The initial values vary between 0.07 Ω and 0.18 Ω for all materials except for o-P-LCO, for which the initial resistance is 0.27 Ω. After the cycling the resistance increases typically with 0.20–0.25 Ω. There are no notable differences between the materials. The increasing interface resistance indicates that contact between the particles and the current collector worsens with cycling. This could be caused by the loss of the particle contacts caused by volume changes during charge and discharge or formation of surface layers, such as solid electrolyte interphase (SEI) layer on the graphite particles. The second semicircle (RN) is attributed to the charge-transfer resistance of the negative electrode. It overlaps strongly with the third semicircle attributed to the charge-transfer resistance of the positive electrode (RP) and therefore it is difficult to analyze. However, the sum of RP and RN charge transfer resistances in the pouch cells is in agreement with the three-electrode measurements presented in Supporting information, and based on this, the EIS analysis of the pouch cells focuses on the positive electrode.This work made use of the Aalto University Otanano and RAMI infrastructures. The authors thank Dr. Eeva-Leena Rautama for the instruction and help with the modelling of XRD data. The authors also thank Dr. Juho Välikangas and Mr. Tuomo Vähätiitto from University of Oulu for optimizing and preparing the pouch cells. We acknowledge the University of Helsinki Center for X-ray Spectroscopy for providing the XANES experiments with the Hel-XAS spectrometer under Proposal number 2021–0007. Financial support from Academy of Finland (Strategic Research Counsil, the Profi 5 project) and the Grant No. 295696, and Business Finland (the BatCircle project No 2117574) is also greatly acknowledged. This work made use of the Aalto University Otanano and RAMI infrastructures. The authors thank Dr. Eeva-Leena Rautama for the instruction and help with the modelling of XRD data. The authors also thank Dr. Juho Välikangas and Mr. Tuomo Vähätiitto from University of Oulu for optimizing and preparing the pouch cells. We acknowledge the University of Helsinki Center for X-ray Spectroscopy for providing the XANES experiments with the Hel-XAS spectrometer under Proposal number 2021–0007. Financial support from Academy of Finland (Strategic Research Counsil, the Profi 5 project) and the Grant No. 295696, and Business Finland (the BatCircle project No 2117574 ) is also greatly acknowledged.

UN SDGs

This output contributes to the following UN Sustainable Development Goals (SDGs)

SDG 7 Affordable and Clean Energy

Keywords

Doping
Li-ion battery
Overlithiation
Synthesis
Valence state
XANES

Access to Document

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Cite this

Lahtinen, K., Labmayr, M., Mäkelä, V., Jiang, H., Lahtinen, J., Yao, L., Fedorovskaya, E. O., Räsänen, S., Huotari, S., & Kallio, T. (2022). Long-term cycling behavior of Mg-doped LiCoO₂ materials investigated with the help of laboratory scale X-ray absorption near-edge spectroscopy. Materials Today Energy, 27, Article 101040. https://doi.org/10.1016/j.mtener.2022.101040

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abstract = "The use of Li-ion batteries is increasing rapidly. Understanding the processes behind active material aging helps to enhance the materials, and therefore, development of new in situ methods for structural studies is important. In addition, understanding the effect of different synthesis methods on the active material properties is necessary to optimize the material cycle life. In this work, the performance of LiCoO2 doped with Mg during the lithiation step is compared to LiCoO2 prepared using an Mg-doped Co3O4 precursor. In situ laboratory-scale X-ray absorption near-edge spectroscopy is used to analyze the Co valence changes in LiCoO2 to understand the electrochemical behavior of the investigated materials. The maximum reachable Co valence state is found to decrease upon aging, a small decrease indicating a good cycle-life, and this is attributed to the enhanced stacking order, better Mg distribution in the lattice, and fine primary particle size in the material. In the synthesis conditions used in this study, Mg doping during the lithiation step is shown to perform better compared to the precursor doping. Overlithiation is shown to reduce the electrochemical performance of nondoped and precursor-doped LiCoO2 materials but not to affect the cyclability of lithiation-doped LiCoO2.",

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AU - Lahtinen, Jouko

AU - Yao, Lide

AU - Fedorovskaya, Ekaterina O.

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