Piezoresistive Free‐standing Microfiber Strain Sensor for High‐resolution Battery Thickness Monitoring

Abstract

from green electric mobility to all sorts of daily-life personal electronic gadgets. Increasing the lifetime of the Li-ion battery is of utmost importance, not only to prohibit premature capacity fade but also to effectively reduce the hazardous waste stemming from these devices. During the battery operation, several inevitable electrochemical reactions occur between the electrodes and the electrolyte due to Li-ion de/intercalation. On the one hand, lattice expansion, and contractions during charging and discharging, known as breathing cause reversible volume expansion, in the long run leading to gradual structural aging. [1] On the other hand, parasitic reactions such as lithiumplating, gas generation, and solid electrolyte interphase growth, decrease capacity retention over time and cause irreversible expansions known as swelling, leading to lithium inventory loss. [2,3] These reactions, depending on the used electrode and electrolyte chemistry cause relative volume changes ranging from 1% up to 10%. [3] Thus, in a battery management system, real-time monitoring of the volume changes Highly sensitive microfiber strain sensors are promising for the detection of mechanical deformations in applications where limited space is available. In particular for in situ battery thickness monitoring where high resolution and low detection limit are key requirements. Herein, the realization of a highly sensitive strain sensor for in situ lithium-ion (Li-ion) battery thickness monitoring is presented. The compliant fiber-shaped sensor is fabricated by an upscalable wet-spinning method employing a composite of microspherical core-shell conductive particles embedded in an elastomer. The electrical resistance of the sensor changes under applied strain, exhibiting a high strain sensitivity and extremely low strain detection limit of 0.00005 with high durability of 10 000 cycles. To demonstrate the accuracy and ease of applicability of this sensor, the real-time thickness change of a Li-ion battery pouch cell is monitored during the charge and discharge cycles. This work introduces a promising approach with the least material complexity for soft microfiber strain gauges.

High‐Resolution Printed Ethylene Vinyl Acetate Based Strain Sensor for Impact Sensing

“…Previously, we reported a minimum detection limit of 0.005% in a freestanding microfiber sensor by using 4 μm microspheres. [31] As presented in Figure 5a, the EVA-4MS sensor provides a repeatable and hysteresis-free signal for detecting cyclic strains of 0.5%, 1%, 2%, and 3%. The response time evaluation is depicted in Figure 5b when a 0.1% strain is applied.…”

“…Previously, we reported a minimum detection limit of 0.005% in a freestanding microfiber sensor by using 4 µm microspheres. [ 31 ]…”

Methods for Quantifying Expansion in Lithium-Ion Battery Cells Resulting from Cycling: A Review

“…This principle is shown in Figure 1. The electrodes go through a reversible swelling and contraction phases during charge and discharge due to the intercalation of lithium-ions [12][13][14][15].…”

Methods for Quantifying Expansion in Lithium-Ion Battery Cells Resulting from Cycling: A Review

“…This principle is shown in Figure 1. The electrodes go through a reversible swelling and contraction phases during charge and discharge due to the deintercalation and intercalation of lithium ions [27][28][29][30]. Reversible expansion due to thermal effects is also observed during the charging and discharging of lithium-ion cells [31].…”