Groundbreaking study reveals impact of calendering on electrochemical-mechanical performance of silicon-based composite electrodes

Source: Beijing Institute of Technology Press

The super volume changes and severe mechanical degradation have been a hindrance in the wide application of silicon based composite electrodes in commercial lithium-ion batteries (LIBs). A recent breakthrough study presented by researchers from the University of Shanghai for Science and Technology reveals effects of calendering state on coupled electrochemical-mechanical performance of silicon based composite electrodes. These findings can help understand how the calendering process could affect the capacity dissipating and lifetime of Si based electrodes.

Silicon (Si), known for its exceptionally high intrinsic gravimetric and volumetric capacities, is considered a highly promising anode material for next-generation lithium-ion batteries (LiBs). However, its widespread commercial use has been hindered by limited cycle life and significant volumetric expansion, which can reach up to 300% during full lithiation. These challenges have so far prevented Si-based electrodes from achieving broad commercialization.

The study focuses on the effects of the calendering process on the cyclic stability and particles/electrode structures in LIBs. Calendering, one procedure in producing LIBs' electrodes, is indispensable to ensure low porosity and energy density.

Using in-situ measurement system, the study tracked changes in lithium-ion concentration and corresponding curvature variations during the lithiation process. The findings show that electrodes with higher degrees of calendering experience greater deformation and more pronounced cracking compared to those with lower calendering levels. For instance, the heavily calendered electrode, CAL2, displayed a maximum curvature of approximately 0.27 mm⁻¹, while the less calendered CAL1 exhibited a smaller curvature of around 0.23 mm⁻¹.

The incorporation of lithium ions engenders a progressive augmentation in the elastic modulus while the partial molar volume exhibits periodic variations contingent upon diverse SOC. All the modulus of silicon-based decreases in the charging process, which is because of soften of Si particles. During the discharge process, the modulus is further decreased due to the formation of cracks. The elastic modulus of the silicon-based electrodes is tremendously involved in the calendering process. During the calendering process, the roller can apply a large tension on the outer face of the Si based electrode, which can decrease the porosity and increase the density of solid materials.

Optimizing the calendering state of silicon-based composite electrodes can unlock new possibilities for high-performance batteries across industries, ranging from consumer electronics to electric vehicles, renewable energy storage, and beyond. It can lead to advancements in battery safety. Better understanding of mechanical strain and cracking in silicon-based composite electrodes can reduce the risk of failure, thermal runaway, or other safety hazards.

In conclusion, the study offers invaluable insights for electro-mechanical process modeling and the advancement of robust, long-lasting silicon-based electrodes. However, the research also acknowledges that further analysis is needed to fully explore the connection between microstructural changes, macroscopic deformation, crack propagation, and electrode resistance. The team is actively working on this to better understand how these factors influence electrochemical kinetics and overall battery performance.

Reference

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Author: Dawei Li, Hongfei Wan, Jiahui Liu, Hainan Jiang, Yikai Wang, Junqian Zhang, Yuejiu Zheng

Title of original paper: Effects of calendering state on coupled electrochemical-mechanical performance of silicon based composite electrodes

Article link: https://doi.org/10.1016/j.geits.2024.100154

Journal: Green Energy and Intelligent Transportation

https://www.sciencedirect.com/science/article/pii/S2773153724000069