posted on 2021-03-16, 20:04authored byWeiping Liu, Bingqian Zheng, Xuechen Yin, Xiaoxi Yu, Yugang Zhang, Lutz Wiegart, Andrei Fluerasu, Beth L. Armstrong, Gabriel M. Veith, Surita R. Bhatia
X-ray
photon correlation spectroscopy (XPCS) microrheology and
conventional bulk rheology were performed on silica nanoparticle dispersions
associated with battery electrolyte applications to probe the properties
of these specific complex materials and to explore the utility of
XPCS microrheology in characterizing nanoparticle dispersions. Sterically
stabilized shear-thickening electrolytes were synthesized by grafting
poly(methyl methacrylate) chains onto silica nanoparticles. Coated
silica dispersions containing 5–30 wt % nanoparticles dispersed
in propylene carbonate were studied. In general, both XPCS microrheology
and conventional rheology showed that coated silica dispersions were
more viscous at higher concentrations, as expected. The complex viscosity
of coated silica dispersions showed shear-thinning behavior over the
frequency range probed by XPCS measurements. However, measurements
using conventional mechanical rheometry yielded a shear viscosity
with weak shear-thickening behavior for dispersions with the highest
concentration of 30% particles. Our results indicate that there is
a critical concentration needed for shear-thickening behavior, as
well as appropriate particle size and surface polymer chain length,
for this class of nanoparticle-based electrolytes. The results of
this study can provide insights for comparing XPCS microrheology and
bulk rheology for related complex fluids and whether XPCS microrheology
can capture expected macroscopic rheological properties by probing
small-scale particle dynamics.