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Lithium polysulfide battery with improved capacity and cycle performance using carbon black coated free-standing carbon cloth
Title
Lithium polysulfide battery with improved capacity and cycle performance using carbon black coated free-standing carbon cloth.
Creator
Wei, Zhen, Kushima, Akihiro, Yang, Yang, Feng, Xiaofeng, University of Central Florida
Abstract / Description
Lithium ion batteries (LIBs) have been used in various applications such as portable electronics, grid storages, and electric vehicles (EVs). Despite its commercial success, further advancement of the battery is necessary to satisfy the increasing demands for low-cost and high- performance energy storage devices as LIB is reaching its theoretical limits. Lithium sulfur battery (LSB) is one of the promising candidates for the next generation energy storage technologies. LSB uses sulfur cathode...
Show moreLithium ion batteries (LIBs) have been used in various applications such as portable electronics, grid storages, and electric vehicles (EVs). Despite its commercial success, further advancement of the battery is necessary to satisfy the increasing demands for low-cost and high- performance energy storage devices as LIB is reaching its theoretical limits. Lithium sulfur battery (LSB) is one of the promising candidates for the next generation energy storage technologies. LSB uses sulfur cathode which is a low-cost and earth abundant material with an extremely high theoretical capacity of 2600 Wh kg-1. Although there have been numerous researches aiming to establish the LSB technology, it is still in a development stage. Some of the major challenges are; low-electric conductivity, dissolution of the intermediate lithium-polysulfide reactants, and the low Coulombic efficiency. These issues must be overcome before LSBs can become practical.The objective of this work is to develop an LSB cathode that solves the above issues and contributes to advancing the development of the LSB technology. We focus on improving the electrical conductivity while reducing the shuttle effect, a parasitic reaction of the polysulfides at the anode lithium surface. To achieve this goal, we developed a carbon black coated free-standing carbon cloth. It is infiltrated with a Li2S8-containing catholyte as an active material, and its carbon framework serves as an entrapment of the polysulfides. The electrode composite enabled high- sulfur-loading, and its high surface area increased the reaction sites allowing the effective utilization of the sulfur that lead to the high capacity. It also showed high capacity retention by successfully trapping the polysulfides within the electrode. This facile and low-cost solution contributes to the realization of the LSBs.
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Date Issued
2019
Identifier
CFE0007873, ucf:52791
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0007873
Fundamental core effects in Co-Cr-Fe-Ni based high entropy alloys
Title
Fundamental core effects in Co-Cr-Fe-Ni based high entropy alloys.
Creator
Mehta, Abhishek, Sohn, Yongho, Coffey, Kevin, Kushima, Akihiro, Jiang, Tengfei, Stolbov, Sergey, University of Central Florida
Abstract / Description
High entropy alloys (HEAs) are near equiatomic multi-principal-element-alloys (MPEAs) which are different from traditional solvent-based multicomponent alloys. Based on initial work by Yeh and Co-workers, they were proposed to exhibit four (")core(") effects: high entropy, sluggish diffusion, lattice distortion, and cocktail effect. Present work investigates two of the four (")core(") effects, i.e. high entropy and sluggish diffusion effects, in Co-Cr-Fe-Ni based transition metal high entropy...
Show moreHigh entropy alloys (HEAs) are near equiatomic multi-principal-element-alloys (MPEAs) which are different from traditional solvent-based multicomponent alloys. Based on initial work by Yeh and Co-workers, they were proposed to exhibit four (")core(") effects: high entropy, sluggish diffusion, lattice distortion, and cocktail effect. Present work investigates two of the four (")core(") effects, i.e. high entropy and sluggish diffusion effects, in Co-Cr-Fe-Ni based transition metal high entropy alloys. Solid-to-solid diffusion couple approach was adopted to investigate, these core effects. Experimental results contradicts the (")high entropy(") effect based on thermodynamics analysis: that the HEAs with low entropy of mixing may be thermodynamically more stable than the HEA of similar constituent elements with high entropy of mixing. In such cases, enthalpy of mixing can also play a vital role in stabilizing the HEA with lower entropy of mixing. Measurement of diffusion coefficients (i.e. both interdiffusion and tracer diffusion coefficients) in HEAs and its comparison with conventional solvent-based multicomponent alloys suggests that diffusion is not always sluggish in high entropy alloys. Contrary to previous findings, larger fluctuations in lattice potential energy (LPE) of an alloy may not always result in anomalously slow diffusion, in comparison to alloy systems which exhibits smaller fluctuation in LPE. Findings from his dissertation provide a (")controversial(") understanding of high entropy alloys, and alloy development strategies in the future for the most aggressive applications such as those found in gas turbines and nuclear reactors. As these applications will certainly require the knowledge of high temperature stability and nature of diffusion under extreme application environment.
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Date Issued
2019
Identifier
CFE0007501, ucf:52645
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0007501