Investigation of defects in cathode materials for lithium-ion batteries

13TH INTERNATIONAL RESEARCH SCHOOL

Physics, Photonics, Numerical modeling

Development of advanced rechargeable Li-ion batteries is one of the most important challenges of modern technology. This type of batteries is the most perspective due to their high energy density, enhanced rate capabilities and superior safety features. In fact, the electric vehicle (EV) revolution and renewable energy sources development depend on the research and development success of new generation Li ion batteries. The project is aimed to investigate the possible cathode materials and defects within them.

Fig.1: Li(Fe, Mn)PO₄ crystal structure

A number of materials can be considered as a next generation of cathode materials for Li-ion batteries after expensive LiCoO₂: LiFePO₄, LiMnPO₄, LiCoPO₄ and mixed metal phosphates like LiFe_0.33Mn_0.33Co_0.33PO₄. Hydrothermal reactions give the possibilities to produce these electrochemically active materials. But the influence of synthesis on defect structure and their impact on the electrochemical properties is not fully clear.

Fig.2: Structure of LiFePO4 with substitutional hydrogen in the iron atom vacancy position

Recently, it was experimentally observed that PO₄ polyanions can be substituted by up to four OH groups in hydrothermal synthesis of LiFePO₄. However, due to the light nature of hydrogen the crystal structure of this defect was not fully resolved. In order to optimize synthesis conditions it is important to understand the mechanisms of PO₄/OH defect formation and its influence on electrochemical properties. We will use the computer simulation for that.

Fig.3: Structure of LiFePO₄ with phosphorus vacancy in tetrahedral position and substitutional "cloud" of hydrogen defects

Therefore, in this project we will define the crystal structure of OH defects in LiFePO₄ using computer simulation methods. Firstly, we will visualize the ideal structures of cathodes under investigation. We will find the possible locations of defects and the energy of their formation. To understand the formation mechanism of such defects the migration of hydrogen will be studied. Finally, the stability of the defects and their formation conditions will be considered. For this work we will use the programs like Jmol and Python.

If you are eager to understand how batteries work and you have basic programming skills, we will be very glad to welcome you in our project team!

Technical requirements
- Stable internet connection
- Laptop with Intel Core i5 CPU, SSD 256Gb memory, NVIDIA GeForce GPU, Operation System doesn't matter.
Some useful links:
http://jmol.sourceforge.net/download/
https://www.teamviewer.com/ru/?utm_source=google&u...|b|pr|19|mar|exact-sn|free|t0|0&utm_content=Exact_Download&utm_term=%D1%82%D0%B8%D0%BC%20%D0%B2%D0%B8%D0%B2%D0%B5%D1%80%20%D1%81%D0%BA%D0%B0%D1%87%D0%B0%D1%82%D1%8C&gclid=CjwKCAjw6qqDBhB-EiwACBs6x9NsYaLwefE5maS44J-pgbTeS8qE_eyy7EiSiAt2MFvEntzosa-ZyBoCmf8QAvD_BwE

Tutor

Irina Varlamova

Moscow, Russia

Irina, Irina works at the Skolkovo Institute of Science and Technology. She is interested in transistors, semiconductor devices, renewable energy sources and electrochemical energy storage technologies. She got her Master degree in Physics at the Kazan Federal University, 2017 and a Master degree in Materials Science at the Skolkovo Institute of Science and Technology, 2020. She holds a special scholarship of the Russian government for her scientific achievements. Among other things Irina likes travelling, snowboarding and yoga.