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SYNTHESIS AND CHARACTERIZATION OF INORGANIC FRAMEWORK MATERIALS AND GEL POLYMER ELECTROLYTES FOR LITHIUM-SULFUR BATTERIES

Sumeng, Chen (2018) SYNTHESIS AND CHARACTERIZATION OF INORGANIC FRAMEWORK MATERIALS AND GEL POLYMER ELECTROLYTES FOR LITHIUM-SULFUR BATTERIES. Master's Thesis, University of Pittsburgh. (Unpublished)

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Abstract

Lithium sulfur batteries have been the focus of much attention in recent years due to the high
theoretical capacity (~1675 mAh/g) of sulfur as compared to the traditional oxide-based cathode
materials. However, sulfur-based cathodes suffer from rapid capacity fade and low
charge/discharge capacities due to the formation of soluble polysulfides (PS), consequent PS
shuttling and low electronic conductivity of sulfur hindering its transition to commercial lithium
ion batteries (LIBs). Inorganic framework materials (IFM) are used in this study as host due to
their high temperature stability to contain the PS, reduce the ensuing PS dissolution/transport and
accordingly improve the Li conductivity of the sulfur-based cathodes. Sulfur was successfully
entrapped into the IFM by employing moderate temperature vacuum infiltration technique and the
formation of the IFM-Sulfur (IFM-S) composite was confirmed by XRD, SEM and TEM analysis.
The Li-ion conductivity of these IFM-sulfur (Li-IFM-S) composites was further improved by ion
exchange methods leading to improvement in the specific capacity with also reducing the fade rate
as compared to IFM-S when tested in LIBs using liquid electrolyte. Electrospun composites of
PVdF-HFP, polyacrylonitrile (PAN), Bis(trifluoromethane)sulfonimide lithium salt (LiTFSI) and
Na/Ti - IFM were used to replace the traditional liquid-based electrolytes and further prevent PS
dissolution/shuttling. The electrospun membranes served as suitable host matrices for generating iv
v
composite polymer electrolytes (CPEs) activated with 1M LiTFSI, 0.1M LiNO3 in
Dioxolane/Dimethoxyethane (50:50 vol.%). The PAN/PVdF-HFP/Na-IFM based CPE with
commercial sulfur cathode showed improved performance in LIBs by suppressing PS dissolution,
with an initial discharge capacity of 944.74 mAh∙g-1 at C/8 rate. The combination of Na-IFM
incorporated as fillers into CPE membrane as electrolyte, Li-IFM-S as the corresponding sulfur
cathode and surface engineered lithium (SE-Li) anode showed improved electrochemical
performance in LIB, when compared to commercial sulfur cathode/pristine Li anode/liquid
electrolyte system due to entrapment of PS and suppressed PS dissolution/shuttling. The hybrid
composite system showed a first cycle discharge capacity of ~925 mAh∙g-1 at ~ C/14 rate and a
very low fade rate of 3.33 mAh∙g-1 cycle-1 (~0.0036 % loss per cycle) at the end of 25 cycles. This
high electrochemical performance is the consequence of a combination of novel CPEs and Li
IFM-S. This improved cycling performance demonstrates the promise of Li-IFM-S cathode, PAN
+ PVdF-HFP with 10 wt. % Na-IFM electrolyte and SE-Li warranting further studies as a high
performance system for high energy density Li-S rechargeable batteries.


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Details

Item Type: University of Pittsburgh ETD
Status: Unpublished
Creators/Authors:
CreatorsEmailPitt UsernameORCID
Sumeng, Chensuc71@pitt.edusuc71
ETD Committee:
TitleMemberEmail AddressPitt UsernameORCID
Committee ChairKumta, Prashant
Committee MemberEnick, Robert
Committee MemberBaled, Hseen
Date: 20 September 2018
Date Type: Publication
Defense Date: 26 July 2018
Approval Date: 20 September 2018
Submission Date: 27 July 2018
Access Restriction: 3 year -- Restrict access to University of Pittsburgh for a period of 3 years.
Number of Pages: 56
Institution: University of Pittsburgh
Schools and Programs: Swanson School of Engineering > Chemical Engineering
Degree: MS - Master of Science
Thesis Type: Master's Thesis
Refereed: Yes
Uncontrolled Keywords: Lithium sulfur battery; composite polymer electrolyte; nanofillers; engineering lithium anode; inorganic framework cathode
Date Deposited: 20 Sep 2018 18:19
Last Modified: 20 Sep 2018 18:19
URI: http://d-scholarship.pitt.edu/id/eprint/35039

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