Customer Success Story – Professor Seon Yang-guk’s Laboratory at Hanyang University’s Energy Engineering Department

This is a success story of a customer who owns Malvern Panalytical’s XRD equipment ‘Empyrean’.

This is a success story concerning the precise analysis of cathode materials for advanced lithium-ion batteries and next-generation battery systems. We met Researcher Nam-young Park from Professor Seon Yang-guk’s laboratory at Hanyang University’s Energy Engineering Department.

Q. What kind of research are you conducting?

Our laboratory focuses on anode materials for advanced lithium-ion batteries and next-generation battery systems, prioritizing research and development of battery materials with higher capacity, longer cycles, and improved safety. Based on a fundamental understanding of the physical and electrochemical properties of materials, we develop and evaluate innovative cathode materials to enhance the energy density, cycle life, and stability of lithium-ion batteries. We conduct research and development on key technologies with a deep understanding and experience of commercialization technology with domestic and international chemical companies, secondary battery companies, and automobile companies. Additionally, we explore and realize future battery systems. We strive to create a more environmentally friendly world for the future using these innovative battery materials.

Q. What is the most important challenge you face, and what issues need to be addressed?

With the Ni content of Li[Ni_xCo_yMn_1-x-y]O2 (NCM) anodes exceeding 60%, the range of microcracks increases rapidly due to anisotropic deformation caused by sharp lattice volume changes during the H2-H3 phase transition. The resulting microcracks in Ni-rich anode particles can create channels for the electrolyte to infiltrate the particle interior, increasing the surface area exposed to electrolyte attack. To suppress the degradation of Ni-rich anode materials, our laboratory focuses on modifying the microstructure to disperse internal deformation caused by lattice volume changes.

The microstructure of the cathode material is primarily determined by the hydroxide precursor and calcination process. When a mixture of the hydroxide precursor and lithium hydroxide is sintered at high temperatures (700~800^oC), a layered crystal structure capable of (de)inserting Li+ ions is formed. However, the coarsening of primary particles during calcination can weaken the anode’s mechanical stability against microcrack formation by destroying the microstructure. Meanwhile, limiting calcination temperature or soak time to adjust the shape of primary particles prevents complete crystallization of the anode. Subsequent cation mixing can worsen the cycling behavior. Achieving complete crystallization without coarsening of the cathode material is one of the important issues to be addressed.

Q. Can you explain the approaches/solutions considered and the evaluation process and selection?

Generally, there is an optimal temperature during calcination at which the hydroxide precursor fully crystallizes. While high temperatures can anneal structural defects such as antisite defects, excessively high temperatures lead to Li deficiency and cation mixing. Due to the similar radii of Li⁺ (0.076 nm) and Ni²⁺ (0.069 nm), the degree of cation mixing, resulting from Li/Ni site exchange, can be used to assess the crystallinity of the layered structure. By combining microstructure and structural information obtained from scanning electron microscopy (SEM) of anode particles with their respective electrochemical performances, we determine the optimal calcination temperature for the anode material.

Q. What characterization techniques did you use before employing Malvern Panalytical XRD?

Prior to using XRD, we conducted XRD analysis utilizing a particle accelerator in Pohang. We also performed transmission electron microscopy (TEM) analysis to verify atomic-scale crystal structures.

Q. Why did you choose Malvern Panalytical equipment, and how do you see it fitting your manufacturing/research/development processes?

As XRD is a basic analysis providing extensive information on crystal structures, we needed a compact yet powerful XRD analysis device that could be installed in the laboratory. The Malvern Panalytical XRD system can analyze not only powder samples but also pouch cells without disassembly. In-situ XRD analysis of batteries can provide detailed structural changes during battery charging/discharging. Analyzing anode structural changes without disassembling cells is crucial for developing high-energy Ni-rich cathode materials, as the capacity degradation mechanism of Ni-rich cathode is significantly determined by the H2-H3 phase transition involving abrupt structural changes.

Q. How is Malvern Panalytical supporting your research? What equipment from Malvern Panalytical are you using, and what results are you obtaining?

Our laboratory owns the XRD floorstanding ‘Empyrean’, which can analyze in both reflection and transmission modes. Reflection mode is used to analyze anode powder samples for determining lattice parameters and layers. Transmission mode is used to analyze pouch cells composed of many components (electrode, separator, aluminum pouch, etc.). We analyze peak shifts according to structural changes in cathode materials during cell charging and discharging. For instance, changes in lattice parameters according to the chemical composition of cathode materials can be analyzed by Rietveld refinement. Additionally, through the deconvolution of (003) reflections during the H2-H3 phase transition, we can compare the structural reversibility of cathode materials. The structural information of cathode materials obtained from XRD analysis aligns well with our expectations.

Q. What proven practical benefits have you experienced using Malvern Panalytical equipment?

The intuitive interface allows for precise analysis. Additionally, the ability to utilize a variety of accessories according to the purpose is an advantage.

Q. How do you foresee Malvern Panalytical contributing in the future, and do you anticipate further development or expansion of the system applications?

We plan to conduct TR(Time-resolved)-XRD analysis using a high-temperature reactor chamber. Through TR-XRD analysis, we can analyze phase changes in real time during heat treatment similarly to actual calcination processes.

Q. How do you anticipate collaborating with Malvern Panalytical for future work?

We expect it will significantly aid not only in the analysis of cathode materials where crystal structure is closely related to electrochemical performance but also in the analysis of next-generation battery materials (solid-state batteries, lithium-sulfur batteries).

Further Reading

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Ask an expert – Best practices for operando-XRD experiments on batteries on a laboratory instrument

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