Poly(ethylene oxide)- lithium zirconium phosphate sulfophenylphosphonate nanocomposites for solid polymer electrolyte and their application in lithium polymer batteries
Date Issued
2016
Date
2016
Author(s)
Yang, Meng-Zhe
Abstract
Poly(ethylene oxide)-based solid polymer electrolytes (SPE) have been the most studied solid state electrolyte system for lithium batteries because of good chemical stability and low cost. Nevertheless, low ion conductivity, low lithium transference number (tLi+) and the need of operating at elevated temperatures severely challenged the success of this system. Introducing ceramic nanofillers into PEO matrix to form nanocomposites has been the most adopted approach to enhance the transport properties of PEO-based SPEs by suppressing the crystallinity of PEO. In this research, lithium zirconium phosphate sulfophenylphosphonate (ZrSPPLi) is synthesized and incorporated into PEO for the first time . ZrSPPLi is an amorphous nanoparticle containing lithium sulfonate groups both within and at the surface of the globular particles with an average diameter of 30nm. The PEO-ZrSPPLi nanocomposites with different ZrSPPLi loading and EO/Li ratio are prepared by solvent-casting from the solution mixture of as-synthesized ZrSPPLi, PEO (Mn ~ 600k) and lithium perchlorate (LiClO4). Systematic studies regarding the loading amount of ZrSPPLi on ion conductivity, lithium transfer number( tLi+), mechanical property, thermal property as well as the performance of lithium metal battery and electrochemical stability are performed. The composite with 1 wt% ZrSPPLi loading in EO/Li = 12/1 matrix exhibits the best transport property and cell performance among all composites. Comparing to the reference SPE without ZrSPPLi, the ion conductivity at room temperature is 2 times higher due to significantly suppressed crystallinity of PEO. With the addition of 1 wt% ZrSPPLi, tLi+ at 60oC would increase to 0.37 from 0.25 of the pristine PEO SPE and the composite exhibits a stable electrochemical window of 4.8V. The LiFePO4 /(PEO)12LiClO4-1wt%ZrSPPLi /Li battery operating at 60oC demonstrates good capacity retention and columbic efficiency at various discharge rate. The discharge capacity could reach 138 mAh g-1 at 0.8C.
Subjects
solid polymer electrolyte
lithium metal battery
Poly(ethylene oxide)PEO
lithium zirconium phosphate sulfophenylphosphonate (ZrSPPLi)
composite polymer electrolyte
Type
thesis
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