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2. Lithium-ion intercalation by coupled ion-electron transfer

Author

Zhang, Yirui, primary, Fraggedakis, Dimitrios, additional, Gao, Tao, additional, Pathak, Shakul, additional, Zhuang, Debbie, additional, Grosu, Cristina, additional, Samantaray, Yash, additional, Neto, Armando R.C., additional, Duggirala, Sravani R., additional, Huang, Botao, additional, Zhu, Yun Guang, additional, Giordano, Livia, additional, Tatara, Ryoichi, additional, Agarwal, Harsh, additional, Stephens, Ryan M., additional, Bazant, Martin Z., additional, and Shao-Horn, Yang, additional

Published
2024
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10. Quantifying Interfacial Ion Transfer at Operating Potassium-Insertion Battery Electrodes within Highly Concentrated Aqueous Solutions

Author

Gossage, Zachary T., Tatara, Ryoichi, Hosaka, Tomooki, and Komaba, Shinichi

Abstract

Electrode/electrolyte interfacial ion transfer is a fundamental process occurring during insertion-type redox reactions at battery electrodes. The rate at which ions move into and out of the electrode, as well as at interphase structures, directly impacts the power performance of the battery. However, measuring and quantifying these ion transfer phenomena can be difficult, especially at high electrolyte concentrations as found in batteries. Herein, we report a scanning electrochemical microscope method using a common ferri/ferrocyanide (FeCN) redox mediator dissolved in an aqueous electrolyte to track changes in alkali ions at high electrolyte concentrations (up to 3 mol dm–3). Using voltammetry at a platinum microelectrode, we observed a reversible E1/2shift of ∼60 mV per decade change in K+concentrations. The response showed high stability in sequential measurements and similar behavior in other aqueous electrolytes. From there, we used the same FeCN mediator to position the microelectrode at the surface of a potassium-insertion electrode. We demonstrate tracking of local changes in the K+concentration during insertion and deinsertion processes. Using a 2D axisymmetric, finite element model, we further estimate the effective insertion rates. These developments enable characterization of a key parameter for improving batteries, the interfacial ion transfer kinetics, and future work may show mediators appropriate for molar concentrations in nonaqueous electrolytes and beyond.

Published
2024
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11. Application of Na2CO3 as a Sacrificial Electrode Additive in Na‐ion Batteries to Compensate for the Sodium Deficiency in Na2/3[Fe1/2Mn1/2]O2.

Author

Matsuzaki, Masayoshi, Tatara, Ryoichi, Kubota, Kei, Kuroki, Kazutoshi, Hosaka, Tomooki, Umetsu, Kazuteru, Okada, Nobuhiro, and Komaba, Shinichi

Subjects
NEGATIVE electrode, ELECTRIC batteries, PROCESS capability, TRANSITION metal oxides, ELECTRODES, ETHYLENE carbonates
Abstract

Owing to their high discharge capacities, P2‐type transition metal layered oxides have attracted attention for use as positive electrode materials in Na‐ion batteries. However, owing to the Na‐deficient compositions of these oxides, additional Na+ must be supplied using a Na‐metal negative electrode to attain a high capacity in a half‐cell configuration. In this study, solid Na2CO3 powder was introduced into the P2−Na2/3Fe1/2Mn1/2O2 composite positive electrode as a sacrificial salt to compensate for the Na deficiency. Na+ was supplied through the electrochemical oxidative decomposition of Na2CO3 during the initial charging process; the decomposition mechanism responsible for this process was investigated in detail. Online electrochemical mass spectrometry confirmed that Na2CO3 was oxidatively decomposed in combination with the decomposition of the ethylene carbonate electrolyte. This reaction produced CO2, wherein the carbon source was derived from both Na2CO3 and the electrolyte. Consequently, Na+ supplementation improved the reversible capacity of the Na‐ion full cell. This study offers practical insights and a mechanistic understanding of the pre‐doping technique for Na‐free negative electrodes. This approach also compensates for the irreversible reductive capacity in a process that can be easily applied to practical sodium‐ and lithium‐ion batteries and capacitors. [ABSTRACT FROM AUTHOR]

Published
2024
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23. In situ Observation of Evolving H2 and Solid Electrolyte Interphase Development at Potassium Insertion Materials within Highly Concentrated Aqueous Electrolytes.

Author

Gossage, Zachary T., Ito, Nanako, Hosaka, Tomooki, Tatara, Ryoichi, and Komaba, Shinichi

Subjects
SOLID electrolytes, SCANNING electrochemical microscopy, AQUEOUS electrolytes, NEGATIVE electrode, CHARGE exchange, POTASSIUM
Abstract

The solid‐electrolyte interphase (SEI) is key to stable, high voltage lithium‐ion batteries (LIBs) as a protective barrier that prevents electrolyte decomposition. The SEI is thought to play a similar role in highly concentrated water‐in‐salt electrolytes (WISEs) for emerging aqueous batteries, but its properties remain unknown. In this work, we utilized advanced scanning electrochemical microscopy (SECM) and operando electrochemical mass spectrometry (OEMS) techniques to gain deeper insight into the SEI that occurs within highly concentrated WISEs. As a model, we focus on a 55 mol/kg K(FSA)0.6(OTf)0.4 electrolyte and a 3,4,9,10‐perylenetetracarboxylic diimide negative electrode. For the first time, our work showed distinctly passivating structures with slow apparent electron transfer rates alike to the SEI found in LIBs. In situ analyses indicated stable passivating structures when PTCDI was stepped to low potentials (≈−1.3 V vs. Ag/AgCl). However, the observed SEI was discontinuous at the surface and H2 evolution occurred as the electrode reached more extreme potentials. OEMS measurements further confirmed a shift in the evolution of detectable H2 from −0.9 V to <−1.4 V vs. Ag/AgCl when changing from dilute to concentrated electrolytes. In all, our work shows a combined approach of traditional battery measurements with in situ analyses for improving characterization of other unknown SEI structures. [ABSTRACT FROM AUTHOR]

Published
2023
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39. Highly concentrated LiN(SO2CF3)2/dinitrile electrolytes: Liquid structures, transport properties, and electrochemistry.

Author

Ugata, Yosuke, Tatara, Ryoichi, Ueno, Kazuhide, Dokko, Kaoru, and Watanabe, Masayoshi

Subjects
*SOLID state batteries, *ELECTROCHEMISTRY, *ELECTROLYTES, *ELECTRIC batteries, *LIQUID mixtures, *MELTING points, *ION exchange (Chemistry)
Abstract

Liquid structures, transport properties, and electrochemical properties of binary mixtures of lithium bis(trifluoromethanesulfonyl)amide (LiTFSA) and dinitrile solvents [succinonitrile (SN), glutaronitrile (GN), and adiponitrile (ADN)] were investigated. In the LiTFSA/SN and LiTFSA/ADN systems, the stable crystalline solvates of LiTFSA–(SN)1.5 [melting point (Tm): 59 °C] and LiTFSA–(ADN)1.5 (Tm: 50 °C) were formed, respectively. In contrast, the LiTFSA/GN mixtures of a wide range of compositions were found to be glass-forming liquids at room temperature. Raman spectroscopy of LiTFSA/GN liquid mixtures revealed that increasing the LiTFSA concentration results in the formation of the solvent-bridged network structure Li+–GN–Li+. In addition, the considerable formation of contact ion pairs and ionic aggregates was observed in highly concentrated electrolytes. In the liquids, the Li+ ion dynamically exchanged ligands (GN and TFSA) and higher LiTFSA concentrations led to an increase in the ratio of the self-diffusion coefficients of Li+ and TFSA−, DLi/DTFSA, as determined by pulsed field gradient NMR spectroscopy. The Li+ transference number ( t L i + ) of the [LiTFSA]/[GN] = 1/1.5 electrolyte in an electrochemical cell under anion-blocking conditions was estimated to be as high as 0.74. Furthermore, electrochemical measurements revealed that the reductive stability of the LiTFSA/GN electrolyte increases with increasing LiTFSA concentration. A [LiTFSA]/[GN] = 1/1.5 electrolyte is stable against the Li metal electrode, provided that the polarization is relatively small. Owing to high t L i + , a Li–S battery with the [LiTFSA]/[GN] = 1/1.5 electrolyte showed a high rate discharge capability despite its low ionic conductivity (0.21 mS cm−1) at room temperature. [ABSTRACT FROM AUTHOR]

Published
2020
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44. Hydrate Melt Electrolyte for Aqueous K-Ion Batteries

Author

Takahashi, Rie, primary, Hosaka, Tomooki, additional, Chiguchi, Kento, additional, Kubota, Kei, additional, Tatara, Ryoichi, additional, Matsuda, Yuki, additional, Ida, Kazuhiko, additional, Ohkubo, Tsuyoshi, additional, and Komaba, Shinichi, additional

Published
2021
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