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Title:Investigation of alternative batteries systems beyond lithium-ion batteries
Author(s):Zhang, Ruixian
Director of Research:Gewirth, Andrew A.
Doctoral Committee Chair(s):Gewirth, Andrew A.
Doctoral Committee Member(s):Murphy, Catherine J.; Nuzzo, Ralph R.; Rodríguez-López, Joaquín
Department / Program:Chemistry
Degree Granting Institution:University of Illinois at Urbana-Champaign
Next Generation Batteries
Sulfur Batteries
Zinc Batteries
Water-in-Salt Electrolytes.
Abstract:The growing market for portable electronic devices and electric vehicles has created an increasing demand for state-of-the-art Li-ion batteries. Meanwhile, alternatives to current Li-ion batteries are proposed to improve battery safety, energy density, C-rate, etc. Approaches towards such alternatives include the utilization of novel electrolytes, anode and cathode materials, and metal ion charge carriers in the battery system. The work presented here covers the investigation of several alternative battery systems. Double Layer Structure in Water-in-Salt Electrolytes. Water-in-Salt Electrolytes (WiSE) are highly concentrated aqueous electrolytes that are of great interest due to their application potential in batteries. The double-layer structure of this LiTFSI-based aqueous system is investigated on a charged electrode surface. Potential dependent atomic force microscopy (AFM) reveals the presence of layers, the structure of which changes with applied potential. Larger layers (6.4 Å and 6.7 Å) are observed at positive potentials, associated with [Li(H2O)x]+([TFSI]-)y ion pairs, while smaller layers (2.8 Å and 3.3 Å) are found at negative potentials and associated with [Li(H2O)x]+ alone. Vibrational spectroscopy shows the potential-dependent compositional change in the double layer, where [TFSI]- is enriched at positive and [Li(H2O)x]+ enriched at negative potentials, respectively. Electrochemical measurements using macroelectrodes and ultramicroelectrodes (UME) reveal a surface-confinement effect for a ferricyanide redox species at the electrode/WiSE interface. Catalytic Effect of Co Nanoparticles in a Sodium-Sulfur Battery. Room-temperature sodium-sulfur (Na-S) batteries have aroused great interest due to their high energy density and high natural abundance. A new room-temperature Na-S battery system is developed in this work. A MOF-derived Co-containing nitrogen-doped porous carbon (CoNC) is utilized as a catalytic sulfur cathode host. A concentrated sodium electrolyte based on sodium bis(fluorosulfonyl)imide (NaFSI), dimethyoxyethane (DME) and bis(2,2,2-trifluoroethyl) ether (BTFE) is used to facilitate reversible Na electrodepostion and mitigate polysulfide dissolution. The amount of Co present in the CoNC carbon host is tuned by acid-washing. Significant improvement in reversible sulfur conversion and capacity retention is observed with higher Co-content in CoNC, with 600 mAh/g and 77% capacity retention for CoNC, and 261 mAh/g and 56% capacity retention for acid-washed CoNC at cycle 50 at 80 mAh/g. The catalytic mechanism of Co is investigated. Postmortem XPS, TEM and selected area electron diffraction (SAED) reveals that CoS is formed during cycling in place of Co nanoparticles. Raman spectroscopy suggests that CoS exhibits a catalytic effect on the oxidation of Na2S. CoS2 as a Cathode Material for a Non-Aqueous Zn Battery. CoS2 is investigated as a cathode material for a non-aqueous Zn battery. A maximum capacity of 283 mAh/g is obtained from a Zn/CoS2 coin cell. Compositional study reveals a reversible Zn2+ intercalation process. X-Ray photoelectron spectroscopy (XPS) reveals an anionic redox activity mediated by reversible interconversions between 2S2- (sulfide) and S22- (disulfide), which is the first such known case operating in a multivalent system. X-Ray diffraction (XRD) reveals an irreversible phase change upon Zn2+ insertion.
Issue Date:2021-04-19
Rights Information:Copyright 2021 Ruixian Zhang
Date Available in IDEALS:2021-09-17
Date Deposited:2021-05

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