A magnetically tuneable piezoresistive sensor for direct, in situ strain measurements in Li-ion batteries

Abstract

This paper demonstrates the first example of using generic Li-ion battery components (nickel, carboxymethylcellulose and styrene-butadiene rubber) to prepare piezoresistive materials (PRMs) which detect the strain of lithiating Sn in operando. The PRM was prepared by mixing the three components and molding it into a desired shape. Three different types of Ni microparticle arrangement strategies were investigated to study their effects on the piezoresistive performance: an alignment parallel to or perpendicular to the direction of strain, and no alignment (control and random dispersion). The alignment was directed by an external magnetic field during sample preparation and confirmed using cross-sectional SEM images. Significant differences were found between the different alignments, with the parallel alignment resulting in the lowest percolation threshold of 4 vol% Ni and perpendicular alignment the highest of 11 vol% Ni. For a fixed fraction of Ni microparticles at 4 vol%, the difference in alignment resulted in a difference in the gauge factor by three orders of magnitude. The stress-strain curve of the prepared PRMs showed a typical response seen for porous structures, which was consistent with the SEM images. The PRM samples are compatible with the low operating potential and the organic Li-ion electrolyte, and its porous structure allows electrolyte infusion that ensures the ionic conductivity of the material. Lithiation of Sn was successfully detected as a change in resistance using a parallelly aligned PRM with no additional treatment. The method described here offers significant merits over conventional approaches: the ability to directly monitor the strain without complex modelling, the simple low cost setup that does not require specialized equipment, and the ability to easily control the PRM performance by magnetically directed assembly.

Revisit to three-dimensional percolation theory: Accurate analysis for highly stretchable conductive composite materials

“…If there is directional anisotropy in the Poisson’s ratios or reorganization of composite due to the deformation, strain-dependent percolation threshold must be appropriately adjusted. Several researches have mentioned possibility of these effects 31 32 33 and verified them with the experimental results 15 27 34 . In previous research 15 , the strain-dependent percolation threshold was only described by tensile strain.…”

High-Fidelity Strain and Temperature Measurements of Li-Ion Batteries Using Polymer Optical Fiber Sensors

“…potential windows, rate dependencies, etc). Indeed, the importance of observing package expansion has been tried in many forms including dilatometry, [15][16][17] digital image correlation, 18 piezosensors, 19 strain gauges, 6 and others. 20 Looking ahead, strain measurements are slated to be essential for use in the monitoring of future solid-state batteries which have no fluids in their interior, and preliminary reports of such efforts are very encouraging thus far.…”