Nondestructive testing of defects in adhesive joints

Novel nanocomposite polymer electrolytes based on electrospun poly(vinylidene
fluoride-co-hexafluoropropylene) for lithium batteries
Prasanth Raghavan, Xiaohui Zhao, James Manuel, Jou-Hyeon Ahn , *
Department of Chemical and Biological Engineering and Engineering Research Institute, Gyeongsang
National University, 900, Gajwa-dong, Jinju 660-701, Korea
Abstract
Email: jhahn@gnu.ac.kr
A series of nanocomposite polymer electrolytes (NCPE) based on poly(vinylidene fluoride-cohexafluoropropylene)
[P(VdF-HEP)] comprising nanoparticles of BaTiO3, Al2O3 or SiO2 were prepared
by electrospinning technique. The presence of the ceramic nanoparticles has positive effect on the
electrolyte uptake, relative absorption ratio and mechanical properties of the membranes. The ionic
conductivity and the electrochemical stability window of the PEs were enhanced by the presence of the
fillers. The prototype cell Li/LiFePO4 based on the NCPE containing BaTiO3 delivers a discharge
capacity of 164 mAh/g, which corresponds to 96.5% utilization of the active material. In comparison, the
performance of Li/LiFePO4 cells with NCPEs containing Al2O3 and SiO2 was observed to be lower with
respective discharge capacities of 153 mAh/g and 156 mAh/g.
Keywords: Lithium batteries; Composite polymer electrolyte; Electrospinning; Fibrous membrane;
Ceramic filler
1. Introduction
The high crystallinity of polymer membranes
is one of the major factors of the low ionic
conductivity of polymer electrolytes (PE), which
limits their use in lithium batteries [1]. This
problem can be addressed to a certain extent by
the addition of nano-sized ceramic fillers to PEs.
The addition of ceramic filler reduce the
crystallinity of the host polymer. Even a small
amount of these fillers can affect the mechanical
strength and ionic conductivity of PEs. Apart
from ionic conductivity, the ceramic filler
nanoparticles also enhance interfacial stability
between the PE and lithium electrode. The
reduced capacity fading and improved cycling
performance of the cell are other positive effects
of the added nanoparticles [2].
Among many of polymers P(VdF-HFP)
membranes prepared by electrospinning are
suitable host polymers for preparing NCPEs due
to the high affinity to the electrolyte, good
electrochemical stability and desirable adhesion
with the electrode.
- 1 -
In the present article, we report preparation,
characterization and evaluation of the
electrochemical properties of electrospun P(VdF-
HFP) based NCPEs prepared with nanoparticles
of three ceramic fillers, SiO2, BaTiO3 and Al2O3.
The electrochemical properties of the NCPEs
have been studied and the results have been
compared with the PE prepared without the
ceramic filler.
2. Experimental
2.1. Preparation of electrospun P(VdF-HFP)
nanocomposite membranes
16% solution of P(VdF-HFP) (Kynar Flex
280) was prepared in a mixture of
acetone/DMAc (7:3, w/w) at room temperature.
To prepare the electrospun membranes with 6%
ceramic fillers, 14% solution of P(VdF-HFP)
was used. Al2O3, SiO2 and BaTiO3 (Aldrich),
with a particle size range of 30-50 nm was used
as nanoparticles. The resulting solutions were
electrospun at 25 ºC as published elsewhere [3].