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Novel electrolytes for high-voltage and high-stability aqueous rechargeable batteries
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Chen, Shigang (2021) Novel electrolytes for high-voltage and high-stability aqueous rechargeable batteries. PhD thesis, University of Warwick.
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Official URL: http://webcat.warwick.ac.uk/record=b3750940
Abstract
Aqueous rechargeable batteries (ARBs) are superior in terms of safety and power density, while facing the challenges of low energy density, short cyclic lifespan, and narrow working temperature windows. The challenges are originated from narrow electrochemical stability windows (ESWs), electrode dissolution/side reaction, and instability upon temperature variation of aqueous electrolytes. Therefore, routes upon ameliorating aqueous electrolytes like additive, pH adjusting, salt concentrating, gelling, solvent hybridizing, interface tuning and beyond concentrating are developed, while salt concentrating is a simply processed and highly effective method for ameliorating aqueous electrolytes.
In this thesis, salt-concentrated electrolytes were developed based on inexpensive salts from acetates, perchlorates to nitrates, which enhanced electrolyte stability thus battery cyclic lifespan, and improved working voltage thus energy density of whole cells. In acetate concentrated system, Zn//MnO2 and VO2//LiNi0.5Mn1.5O4 redox pairs delivered working voltages of 2.0 (overcharged state for Zn//MnO2) and 2.5 V, coupling cyclic lifespans of 600 and 1200 cycles, respectively. Moreover, “oversaturated gel electrolyte” (OSGE) was proposed to break the limitation of salt solubility, bringing more low-solubility salts into salt-concentrated system, while further extending ESWs in comparison of “room-temperature saturated gel electrolyte” (RTSGE). OSGE endowed Zn//MnO2 and VO2//LiNi0.5Mn1.5O4 redox couples with high voltages of 2.0 and 2.5 V, and lengthened charge/discharge lifespan to 2000 and 700 cycles, respectively. Furthermore, OSGE enabled the stable operation of correlated ARBs up to 80 °C, which revealed the wide working temperature windows of OSGE-based ARBs. In order to realize stability of ARBs with relatively diluted electrolytes, and simplify battery assembly processing, N,N-dimethylacetamide (DMA) was employed to dilute nitrate concentrated electrolyte, which obtained desired performance for Zn//LiMn2O4 battery. The overall route of this thesis is from salt concentrating to beyond concentrating, and back to diluting with simple battery assembly procedures, which implement high-voltage and high-stability ARBs with industrially appliable potentials
The research method here can be basically classified into liquid study (especially solvation structure) on electrolytes by spectroscopy and molecular dynamics (MD) simulation; material characterization on electrodes by X-ray, spectroscopy, and microscope; electrochemical characterization on electrolytes, electrodes and assembled batteries by voltammetry, a.c. impedance and galvanostatic.
Item Type: | Thesis (PhD) | ||||
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Subjects: | T Technology > TK Electrical engineering. Electronics Nuclear engineering | ||||
Library of Congress Subject Headings (LCSH): | Storage batteries -- Design and construction, Electrolyte solutions, Acetates | ||||
Official Date: | October 2021 | ||||
Dates: |
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Institution: | University of Warwick | ||||
Theses Department: | School of Engineering | ||||
Thesis Type: | PhD | ||||
Publication Status: | Unpublished | ||||
Supervisor(s)/Advisor: | Tao, Shanwen | ||||
Sponsors: | China Scholarship Council | ||||
Format of File: | |||||
Extent: | xxiii, 218 leaves : illustrations | ||||
Language: | eng |
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