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Abstract Silicon is regarded as one of the most promising anode materials for lithium-ion batteries. Its high theoretical capacity (4000 mAh/g) has the potential to meet the demands of high-energy density applications, such as electric air and ground vehicles. The volume expansion of Si during lithiation is over 300%, indicating its promise as a large strain electrochemical actuator. A Si-anode battery is multifunctional, storing electrical energy and actuating through volume change by lithium-ion insertion. To utilize the property of large volume expansion, we design, fabricate, and test two types of Si anode cantilevers with bi-directional actuation: (a) bimorph actuator and (b) insulated double unimorph actuator. A transparent battery chamber is fabricated, provided with NCM cathodes, and filled with electrolyte. The relationship between state of charge and electrode deformation is measured using current integration and high-resolution photogrammetry, respectively. The electrochemical performance, including voltage versus capacity and Coulombic efficiency versus cycle number, is measured for several charge/discharge cycles. Both configurations exhibit deflections in two directions and can store energy. In case (a), the largest deflection is roughly 35% of the cantilever length. Twisting and unexpected bending deflections are observed in this case, possibly due to back-side lithiation, non-uniform coating thickness, and uneven lithium distribution. In case (b), the single silicon active coating layer can deflect 12 passive layers.
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EXPERIMENTAL STUDY OF MULTIFUNCTIONAL NCM-SI BATTERIES WITH SELF-ACTUATION
Among anode materials for lithium ion batteries, silicon (Si) in known for high theoretical capacity and low cost. Si exhibits over 300% volume change during cycling, potentially providing large displacement. In this paper, we present the design, fabrication and testing of a multifunctional NCM-Si battery that not only stores energy, but also utilizes the volume change of Si for actuation. The battery is transparent, thus allowing the visualization of the actuation process during cycling. This paper shows Si anode design that stores energy and actuates through volume change associated with lithium insertion. Experimental results from a transparent battery show that a Cu current collector single-side coated with Si nanoparticles can store 10:634mWh (charge)/ 2:074mWh (discharge) energy and bend laterally with over 40% beam length displacement. The unloaded anode is found to remain circular shape during cycling. Using a unimorph cantilever model, the Si coating layer actuation strain is estimated to be 30% at 100% SOC.
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- Award ID(s):
- 1662055
- PAR ID:
- 10165900
- Date Published:
- Journal Name:
- SMASIS 2018
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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