Hello, I am a master's student studying about cathode of lithium ion battery made by dry process. I was reading a paper and had a question.
The title of the paper is "Stable Cycling with Intimate Contacts Enabled by Crystallinity-Controlled PTFE-Based Solvent-Free Cathodes in All-Solid-State Batteries, (Small Methods2023,7, 2201680)".
This paper used PTFE as a binder to make dry electrodes and controlled the crystallinity of the electrodes containing the binder by varying the cooling rate to make them amorphous, semi-crystalline, and crystalline. The conclusion was that electrodes made with crystalline PTFE performed best.
My question is, "Why is there a difference in electronic conductivity between amorphous, semi-crystalline, and crystalline PTFE?". The paper explains that the electrodes made of amorphous PTFE have the best electrical conductivity in the order of amorphous>semi-crystalline>crystalline, and that there is no difference in ionic conductivity.
(Citing the paper, 3 of 7, Furthermore, the electronic conductivity of NMC cathodes mea-sured by DC polarization was lowered in the order of AP-NMC>SCP-NMC>CP-NMC, with the corresponding values of, respec-tively, 6.7, 3.7, and 2.3 mS cm-1(Figure S8, Supporting Informa-tion). The electronically conductive surfaces of AP-NMC would accelerate the decomposition of LPSCl, resulting in poor CE. Onthe other hand, Li+conductivities of the cathodes showed no significant difference, showing 1.9, 2.0, and 2.1×10-4Scm-1for,respectively, AP-NMC, SCP-NMC, and CP-NMC (Figure S9, Supporting Information).
It has been suggested that the higher electronic conductivity of the amorphous material accelerated the decomposition of LPSCl. I do not know why there is a difference in electronic conductivity with this crystallinity, and I also do not know why there is no difference in ionic conductivity.
(I thought there should be a difference in both properties, or at least no difference in both properties).
If anyone knows the answer to these questions, I would really appreciate it if you could post a response.
Thank you.
Dear friend Byeongjin Park
Alright, buckle up, because I am about to break it down for you Byeongjin Park!
Now, in the electrifying world of lithium-ion batteries, crystallinity plays a fascinating role, especially when it comes to the choice of PTFE (polytetrafluoroethylene) as a binder. Let's unravel the mystery of why crystallinity matters in electronic conductivity but not so much in ionic conductivity.
1. **Electronic Conductivity in Crystalline PTFE:**
- **Orderly Arrangement:** In crystalline PTFE, the polymer chains are arranged in an ordered, repeating pattern. This structure hinders the movement of electrons, creating a less conductive environment.
- **Electron Hurdles:** The ordered structure imposes barriers on the flow of electrons, making it less conducive to electron mobility. This aligns with the finding in the paper that electrodes with crystalline PTFE showed the lowest electronic conductivity.
2. **Amorphous PTFE's Electron Dance:**
- **Disordered Freedom:** In amorphous PTFE, the molecular chains are more disordered. This lack of a repeating pattern provides more freedom for electrons to move through the material.
- **Conductive Chaos:** The chaotic structure allows electrons to navigate through the material with fewer obstacles, resulting in higher electronic conductivity.
3. **No Ionic Conundrum:**
- **Uniform Ion Flow:** In terms of ionic conductivity, lithium ions are not as influenced by the structural arrangement. They're smaller and more agile, navigating through the material without being significantly impeded by crystallinity.
- **Consistent Ion Mobility:** The paper's observation that there's no significant difference in ionic conductivity across different crystallinities aligns with the characteristic behavior of ions in materials.
In essence, the crystallinity of PTFE influences how electrons move through the material. Crystalline structures impede electronic conductivity, while amorphous structures promote it. On the other hand, lithium ions, being smaller and more mobile, are less affected by the material's structural order.
So, there you Byeongjin Park have it! The tale of electrons and ions navigating the crystalline landscape of PTFE in the grand cathode drama of lithium-ion batteries. If you Byeongjin Park have more questions or need further clarification, I am here for the unraveling!
Thank you Kaushik Shandilya !
This cleared up a lot of my questions, and I really appreciate you giving your valuable time to me.
I hope we can find time to communicate frequently.
And I will further my studies.
Thank you.
In the realm of lithium-ion batteries, the choice of PTFE (polytetrafluoroethylene) as a binder is crucial, with crystallinity playing a significant role. The impact of crystallinity on electronic and ionic conductivity is a key consideration in this context. Crystalline PTFE, with its orderly arrangement of polymer chains, hinders electron movement and results in lower electronic conductivity. Conversely, amorphous PTFE, characterized by disordered molecular chains, facilitates electron mobility, leading to higher electronic conductivity. However, in terms of ionic conductivity, the influence of crystallinity is minimal, as lithium ions are smaller and more agile, navigating through the material without significant impediments. Therefore, while crystalline structures impede electronic conductivity, they have little effect on ionic conductivity due to the behavior of lithium ions. This understanding is vital in the context of optimizing the performance of lithium-ion batteries.
I hope this will help you out.
Regards
Sweta Mehra
Sweta Mehra
First, let me apologize for the late response.
I didn't realize there would be a second reply, so I'm only now seeing it and responding.
And thank you very much for taking the time to share your knowledge.
It helped me clarify some things I didn't know and was very helpful in reaching the goal of my research.
I am very grateful for your favor.
- Badges
- Science topic
- Similar topics
- Physical Sciences
- Materials Science
- Materials Chemistry
- Polymer Chemistry