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Developing advanced electrode architectures through modifying active materials, conductive fillers, binders, and electrolytes as well as processing methods has drawn significant research interest. Due to the insufficient electrical conductivity of many active materials, adding conductive carbon fillers to composite electrodes provides the necessary electrical conductivity. The dimensionality effect among different conductive fillers has a significant impact on electrochemistry, which can be associated with morphological and chemical heterogeneities of electrodes. Here, synchrotron X-ray mosaic nanotomography and X-ray spectroscopy nanoimaging provided direct three-dimensional (3D) visualization and quantification capabilities to investigate the dimensionality effects of Super P (SP) and single-walled carbon nanotube (SWCNT) fillers on the capacity retention of LiNi1/3Mn1/3Co1/3O2 (NMC111). The results indicate that NMC/SWCNT electrodes, with a wrapping effect from the SWCNTs, exhibited more homogeneous particle size distributions, morphological changes, and chemical states than NMC/SP electrodes, without the wrapping effect. This work developed a framework of 3D quantification methods to study the capacity fading behavior associated with morphological and chemical heterogeneities and paved the way toward designing electrodes for high rate energy storage applications.

Aqueous Zn/MnO2 batteries with their environmental sustainability and competitive cost, are becoming a promising, safe alternative for grid-scale electrochemical energy storage.

Aqueous Zn-ion batteries has attracted great attention in recent years, as a promising candidate for grid energy storage applications. An aqueous system offers intrinsic safety, high ionic conductivity contributing improved power capability and raw materials that are more earth abundant and environment friendly. Numerous promising reports haven been focusing on the Zn/MnO2 system owing to its low cost, moderate discharge potentials and with improved reversibility in the mild aqueous electrolyte. However, many questions remain unanswered regarding its reaction mechanism. The different reaction mechanisms including Zn+2 insertion, H+ insertion, chemical conversion reaction including the combined intercalation and conversion reaction mechanism, and the dissolution-deposition of the manganese oxide. In this work, we aim to unravel the reaction mechanism by a systematic multimodal synchrotron characterization. This work discusses the galvano-static charge-discharge process of aqueous Zn-MnO2 batteries using operando measurements, which provides us with a direct insight into the phenomenon and can be directly correlated to the battery's electrochemical response. The multimodal techniques include operando X-ray diffraction to study the structural phase change of the cathode active material, operando X-ray absorption spectroscopy to probe the local structure changes and transmission X-ray microscopy studies to observe the key morphological events. Overall, this multimodal approach gives us an insight into the reaction mechanism enabling us to better design Zn-MnO2 batteries for practical applications.

As batteries revolutionize all technological areas – from miniaturized electronic devices to electric vehicles and to large-scale energy storage, understanding the complex morphological, chemical and structural evolution and their interplays has been at the forefront of the research. Synchrotron X-ray characterization techniques provide insights into the electrochemical reactions and multiscale, multiphysics environments to address the fundamental mechanisms in these systems. The presentation will highlight the application of synchrotron X-ray analysis in two Li-ion battery systems, including both aqueous and non-aqueous systems. X-ray nano-tomography via transmission X-ray microscopy and spectroscopic imaging, complemented by other diffraction, spectroscopy and microscopy techniques, will be discussed. We will present how synchrotron X-ray nano-tomography and quantitative 3D morphological analysis were instrumental in revealing the dimensionality effect of conductive carbon fillers in LiNi 1/3Mn1/3Co1/3O2 (NMC111) cathode [1]. Additionally, we will discuss how a multimodal characterization approach offered insights when probing kinetics of water-in-salt aqueous batteries with thick, porous LiV3O8-LiMn2O4 electrodes [2, 3]. Through the morphological and chemical analyses, the work aims to facilitate the design of future advanced energy storage materials, as well as provide a novel characterization framework for studying a wider range of electrochemical systems. References: [1] "Dimensionality effect of conductive carbon fillers in LiNi 1/3Mn 1/3Co 1/3O 2 cathode", Cheng-Hung Lin, Zhengyu Ju, Xiaoyin Zheng, Xiao Zhang, Nicole Zmich, Xiaoyang Liu, Kenneth J. Takeuchi, Amy C.Marschilok, Esther S.Takeuchi, Mingyuan Ge, Guihua Yu, Yu-chen Karen Chen-Wiegart, Carbon (2021), DOI: https://doi.org/10.1016/j.carbon.2021.11.014 [2] "Probing Kinetics of Water-in-Salt Aqueous Batteries with Thick Porous Electrodes", Cheng-Hung Lin, Lei Wang, Steven T. King, Jianming Bai, Lisa M. Housel, Alison H. McCarthy, Mallory N. Vila, Hengwei Zhu, Chonghang Zhao, Lijie Zou, Sanjit Ghose, Xianghui Xiao, Wah-Keat Lee, Kenneth J. Takeuchi, Amy C. Marschilok, Esther S. Takeuchi, Mingyuan Ge, and Yu-chen Karen Chen-Wiegart, ACS Central Science (2021), DOI: 10.1021/acscentsci.1c00878 [3] "Systems-Level Investigation of Aqueous Batteries for Understanding the Benefit of Water-In-Salt Electrolyte by Synchrotron Nano-Imaging", Cheng-Hung Lin, Ke Sun, Mingyuan Ge, Lisa Housel, Alison McCarthy, Mallory Vila, Chonghang Zhao, Xianghui Xiao, Wah-Keat Lee, Kenneth J. Takeuchi, Esther S. Takeuchi, Amy C. Marschilok, Yu-chen Karen Chen-Wiegart, Science Advances (2020), DOI: 10.1126/sciadv.aay7129

We report the synthesis, characterization and cellulose dissolution properties of a series of ionic liquids bearing alkyl and hydroxyl-functionalized imidazolium and pyrrolidinium cations, and dial...

Binary mixtures of ionic liquids (ILs) were prepared and characterized to obtain ILs with viscosity and conductivity properties optimized for use in energy storage devices such as supercapacitors. The bis(trifluoromethylsulfonyl)amide anion (NTf2 -) was the common anion for both ILs in the mixture. Ethoxyethyl was the common substituent on the solute and solvent, as ether substituents have been shown to produce low viscosity ILs. N-Ethoxyethyl-N-methylpyrrolidinium NTf2 was used as the solvent for all of the IL mixtures. The solutes were either monocationic or dicationic and made up 10% of the binary mixture by weight. We report here on the physical properties of the individual ILs and their binary mixtures.

Ionic liquids (ILs) are attractive alternative solvents in a variety of applications such as in supercapacitors, batteries, solar energy conversion and for the storage and clean-up of nuclear waste. However, their high viscosities impede their adoption in many large scale processes. Ether side chains have been shown to lower the viscosity of ILs. In this work, we have synthesized a series of ten pyrrolidinium ionic liquids and ten imidazolium ionic liquids bearing ether and alkyl side chains of varying lengths (4 to 10 atoms in length). Their physical properties, such as viscosity, conductivity and thermal profile were measured and compared. Results reveal a dramatic decrease in viscosity with the substitution of alkoxy (ether) side chains for alkyl side chains on the pyrrolidinium cation. However, as the length of the ether chain increases there is negligible change in the viscosity (of about 50 cP). In contrast, a consistent increase in the viscosity was observed as the length of the alkyl side chain increases. Preliminary results of the imidazolium series show a similar trend. These results provide significant insight on the choice of starting materials for researchers designing ILs for specific applications. The work at BNL was supported by the BNL Office of Educational Programs and the U.S. Department of Energy, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences and Biosciences under contract DE- SC0012704.

The need for improved energy storage capability in supercapacitors has prompted the use of ionic liquids as alternatives to acetonitrile based solvents. Despite the advantages of supercapacitors, their use in transportation is not favorable because of the deterioration of organic solvents with increasing temperatures and their high vapor pressures. We report here on the synthesis and characterization of ionic liquids optimized for use in supercapacitors. The cations were designed to bear ether substituents which are known to lower the viscosity of ILs. ILs and binary mixtures of ILs based on pyrrolidinium, imidazolium and dicationic ammonium cations bearing ether substituents and bis(trifluoromethylsulfonyl)amide [NTf2 -] anions have been synthesized, purified and characterized. The halide salts were synthesized by reaction of the amine with 2-bromoethylethylether. They were then converted to the NTf2 salts after purification. The structures of the salts were confirmed using H-1 and C-13 Nuclear Magnetic Resonance spectroscopy. The dicationic ILs were used as the solutes in the binary IL mixyures. The binary IL mixtures have been analyzed for their transport properties using NMR. The work at BNL was supported by the BNL Office of Educational Programs and the DOE Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences, and Biosciences under contract # DE-AC02-98CH10886.