2024 AIChE Annual Meeting

(735d) Silicon-Vanadium Carbide Based Composite Anodes and Liquid Electrolytes for High-Performance Li-Ion Batteries

As the global demand for energy continues to rise, it is imperative to advance renewable energy technologies and integrate them with energy storage systems to ensure consistent power supply. Over the past few decades, significant research efforts have been directed towards enhancing the energy density of lithium-ion batteries (LIBs) [1]. Currently, graphite is the standard anode material in commercial LIBs. However, its relatively low theoretical capacity (372 mAh g-1) limits its application in high-energy devices. Silicon (Si), on the other hand, presents a promising alternative due to its high theoretical capacity (4200 mAh g-1), abundant availability, and suitable lithium uptake potential (0.4 V vs Li/Li+) [2]. However, the practical application of silicon as an anode material is hindered by its substantial volume expansion (400-500%) during operation [3].

In the present investigation, we intend to primarily mitigate the volume expansion issue of silicon (Si) leading to the fabrication of high-performance LIBs. For realising this, Si, in micro (commercial) and nano size (synthesized using magnesiothermic reduction) have been used. At first, Si particles are amalgamated with graphite to form a finely ground mixture (Si-G). This mixture is then combined with a polymer solution to produce pyrolytic carbon, which serves to buffer the mechanical stresses induced by the volumetric expansion of Si. This process also prevents the direct contact of Si with the electrolyte, thereby stabilizing the solid electrolyte interphase (SEI). The incorporation of a dopant enhances the inherent conductivity of the material, leading to an increase in capacity by facilitating the transport of electrons and lithium ions. To further enhance the performance of the composite, synthesized Mxene vanadium carbide (V2C) is introduced, which promotes charge transport among the Si particles and helps to increase the lithium-ion diffusion through the material. Density Functional Theory (DFT) simulations are performed to show that addition of V2C increases the mobility of Li+ ions through the structure. The morphology and structure of the composite are examined using a range of techniques, including SEM-EDS, TEM, XRD, Raman, and XPS spectroscopy. These analyses reveal the intricate structure of the materials with a uniform distribution of Si, C, and Mxene sheets, with the sheet architecture being preserved.

We also tested different liquid electrolytes (along with additives) with a Si-C composite material as anode. Galvanostatic Charge/Discharge (GCD) tests, thermal analysis at different temperatures and other electrochemical characterizations are performed to study the electrolytes’ behaviour and how their individual components affect the overall electrochemical performance of the cell.

The Si-Mxene composite, when employed as an anode, demonstrates exceptional electrochemical performance. This is substantiated by its remarkable lithium storage specific capacity of 2003 mAh g-1 (calculated on the basis of Si weight), for micron Si and ~3100 mAhg-1 (for nano Si) which it retains even after prolonged cycling at a high current density. The volume change was reduced from 420% to 150% (for micron Si) and 33% (for nano Si). Furthermore, the composite exhibits superior rate performance, delivering a specific capacity of 2439 mAh g-1 at a 10 C rate, underscoring its suitability for high-power applications. Additionally, the electrode showcases a low charge transfer impedance and rapid electron transport, contributing to its enhanced electrochemical performance. This improvement can be attributed to the unique structure of the composite, which comprises Mxene and doping. This structure significantly augments the diffusion of Li ions and the number of active sites. Consequently, this study presents a viable strategy for the development of high-capacity lithium-ion batteries (LIBs) based on silicon.

References

  1. Liu, L. Kang, J. Hu, E. Jung, J. Zhang, S.C. Jun, Y. Yamauchi, ACS Energy Lett. 6 (2021) 3011–3019.
  2. Zhou, Y. Liu, C. Du, Y. Ren, T. Mu, P. Zuo, G. Yin, Y. Ma, X. Cheng, Y. Gao, Journal of Power Sources. 381 (2018) 156–163.
  1. Yi, F. Dai, M.L. Gordin, S. Chen, D. Wang, Advanced Energy Materials 3 (2013) 295-300.