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UNIVERSITY OF BUCHAREST
FACULTY OF PHYSICS Guest
2024-11-22 2:23 |
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Conference: Bucharest University Faculty of Physics 2024 Meeting
Section: Physics and Technology of Renewable and Alternative Energy Sources
Title:
Enhancing energy density in Lithium-ion batteries through increased electrode thickness: challenges and limitations
Authors:
Florian POMPIERU
*
Affiliation:
University of Bucharest, Faculty of Physics, 405 Atomiștilor str., PO Box MG-38, Bucharest-Măgurele, Romania
E-mail
florin.pompieru@gmail.com
Keywords:
Abstract:
To enable the development of high energy density lithium-ion batteries (LIBs), one effective method is to increase the thickness of the electrodes. This strategy improves the active to passive material ratio by reducing the number of layers in the cell stack. Thin NMC (Nickel Manganese Cobalt) cathodes are typically referred to as high-power electrodes, capable of operating at high current densities. In contrast, cells with ultra-thick NMC cathodes are known as high-energy electrodes, which are applicable only at lower current densities due to transport limitations. Cells with thick NMC cathodes, however, exhibit significant capacity losses, up to 40%, when cycled at above C/2 rate. The underlying physics-based factors that limit the energy and power density of thick electrodes include increased cell polarisation and the underutilization of active materials. These issues are primarily caused by two factors: Li-ion diffusion in the active materials and Li-ion depletion in the electrolyte phase. The increased cell polarisation results from the difficulty in transporting Li-ions through the thicker electrode structure, which leads to uneven utilisation of the active material and hence reduced overall performance. Increasing the thickness of electrodes in lithium-ion batteries can enhance energy density but comes with several other significant downsides:
1. Thicker electrodes lead to higher internal resistance, causing increased cell polarization. This results in greater voltage drops during discharge and higher voltage spikes during charge, reducing the battery's overall efficiency and performance.
2. The transport of Li-ions becomes more difficult in thicker electrodes. The diffusion paths for Li-ions are longer, leading to slower ion transport. This can cause uneven distribution of lithium, resulting in underutilization of active materials and decreased capacity.
3. Thicker electrodes can lead to higher heat generation due to increased internal resistance. Effective heat dissipation becomes more challenging, potentially leading to thermal management issues and reduced safety.
4. Batteries with thicker electrodes have reduced rate capabilities, meaning they cannot charge or discharge as quickly as those with thinner electrodes. This limits their use in applications requiring high power output or fast charging.
5. Thicker electrodes are more prone to mechanical stress, which can cause cracking, delamination, or other structural failures over repeated charge and discharge cycles. This affects the battery's longevity and reliability.
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