Speaker
Description
Over the past few decades, the global community has become increasingly concerned about the effects of climate change and the urgent need for sustainable energy solutions. One key area of focus has been the development of high-energy-density batteries for use in e-transportation, as they can potentially reduce carbon emissions. The incorporation of silicon (Si) as an anode material in lithium-ion batteries (LIBs) has garnered significant interest due to its high theoretical capacity, surpassing traditional graphite-based anodes. Despite its potential advantages, commercialization of the Si-based anode in LIBs has been impeded by several critical drawbacks, including low coulombic efficiency resulting in the depletion of active lithium and the pulverization of particles induced by drastic volume changes during charging and discharging [1], [2]. Due to these factors, the battery cell that exploits Si-based material as an anode generally shows poorer capacity retention and, therefore, their superior initial energy density cannot be maintained long. This study introduces a counter-intuitive design for a battery cell to overcome this quandary with the help of prelithiation technology.
In the design of a battery cell, the N/P ratio, representing the ratio of areal capacities of the anode and cathode, must be well balanced, usually slightly above 1.0. Setting the N/P ratio too high can decrease the coulombic efficiency and waste the remaining areal capacity of the anode, leading to reduced energy density. Conversely, setting the ratio too low can result in a safety hazard due to lithium plating [3]. The N/P ratio was purposefully increased in this research based on rigorous experiment-based calculations. This adjustment aims to partially utilize the Si particle until its critical point in terms of fragmentation, which might be below the yield strength [4], but not to diminish the energy density significantly and not to incur additional costs. In order to validate this safety limit, the degradation of Si under different depth-of-discharge (DoD) conditions was measured, and the fragmentation patterns of Si particles were also observed.
The primary disadvantage of using a Si-containing anode with a high N/P ratio is a low coulombic efficiency. During the initial charging process, a considerable amount of lithium ions becomes irreversible due to the high-areal-capacity anode requiring a substantial amount of solid electrolyte interphase (SEI) on its surface. This is where prelithiation plays a crucial role. Prelithiation is a technique whereby active material is lithiated before being integrated into the battery cell, thereby compensating for the loss of lithium. The electrochemical prelithiation technique allows for easy control of prelithiation parameters, such as prelithiation capacity, as demonstrated in previous studies [5], [6]. By employing electrochemical prelithiation, it becomes possible to introduce additional lithium ions to offset the amount of lithium consumed during SEI formation.
Combining the partially-utilized Si caused by a high N/P ratio and well-controlled electrochemical prelithiation, the battery cell achieved 80% capacity retention after more than 200 cycles with a coin cell configuration, although only including Si as an active material. Additionally, the energy density remained high enough due to its excellent gravimetric capacity. These findings demonstrate that pure Si anodes can indeed exhibit excellent cycling stability and provide valuable insights into the design of Li-ion battery cells containing Si.
References
[1] G. G. Eshetu et al., “Production of high-energy Li-ion batteries comprising silicon-containing anodes and insertion-type cathodes,” Nature Communications, vol. 12, no. 1, pp. 1–14, 2021.
[2] X. Feng et al., “Facile approach to SiOx/Si/C composite anode material from bulk SiO for lithium ion batteries,” Physical Chemistry Chemical Physics, vol. 15, no. 34, pp. 14420–14426, 2013.
[3] M. Luo et al., “Examining Effects of Negative to Positive Capacity Ratio in Three-Electrode Lithium-Ion Cells with Layered Oxide Cathode and Si Anode,” ACS Appl. Energy Mater., vol. 5, no. 5, pp. 5513–5518, 2022
[4] S. Poetke et al., “Partially Lithiated Microscale Silicon Particles as Anode Material for High-Energy Solid-State Lithium-Ion Batteries,” Energy Technology., vol 11, 2201330, 2023.
[5] H. J. Kim et al., “Controlled Prelithiation of Silicon Monoxide for High Performance Lithium-Ion Rechargeable Full Cells,” Nano Letters, vol. 16, no. 1, pp. 282–288, 2016
[6] D. I. Lee, H.-W. Yang, W. S. Kang, J. Kim, and S.-J. Kim, “Optimal Condition of Solid-Electrolyte-Interphase Prepared by Controlled Prelithiation for High Performance Li-Ion Batteries,” Journal of The Electrochemical Society, vol. 166, no. 4, pp. A787–A792, 2019
| Keywords | e-transportation, Li-ion batteries, Si-based anode, Cell design, N/P ratio, Prelithiation, High energy density, Long driving range electric vehicle |
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