Supporting Statement

Dear Professor,

My name is Yohandys Alexis Zulueta Leyva. I am a Cuban scholar who obtained a PhD in Chemistry at KU Leuven (Belgium) and PhD in Physics at Havana University (Cuba) in 2018.  I am inspired to apply for the position of Postdoctoral Research Associate in Solid-State Batteries, because I am working on modelling and predicting relevant properties of battery materials by using advanced atomistic simulations. I have always been interested in this kind of opportunity, in which experiments and material modelling can be combined to understand the structure-property relationship of battery materials. My past experience in EIS data analysis, together with the advanced atomistic simulations have given me a firm foundation in the skills required for this position. Moreover, I am open to earning new knowledge, which makes me a good fit.

During my time as a Master and PhDstudent- from EIS data- I developed a code to analyse the relaxation dynamic in time and frequency domain simultaneously, and recently, I developed a new formalism disclosing relaxation dynamic at low and higher frequency and time domains simultaneously. These experimental methods can be used to determine the state of aging or to distinguish different battery components.  Along my PhD scholarship, I gained experience in advanced atomistic simulations applied to battery materials. As a result I was able to continue developing new research in the field of computational material design of battery materials. This experience will enable me to reach at least a TRL 3 to 5 due to the close experimental collaboration provided by this position and the excellence of the research group.

Experience in Density Functional Theory (DFT) computation:

Despite the review literature concerning the role of DFT computational approaches on the material design, synthesis strategies and defects engineering, to the very best of my knowledge, there is no report of a DFT protocol to predict the majority of the main properties required for a battery material. My intention is to use my experience in DFT into:

1. Determination and/or prediction of lattice parameters and electronic structure properties (such as energy gap), density of the states and projected density of the states to disclose the bonding nature of the constituent ions and their contribution to the electronic properties,
2. Exploration of «first-order» thermodynamic stability of the compounds considered (such as the standard molar and standard formation enthalpies),

• Exploration of «second-order» thermodynamic stability, i.e.; the stability upon individual constituent ion during the insertion/disinsertion process, with particular interest on alkali ions,

1. Exploration of open cell voltage and, if it is possible, theoretical capacity, and more importantly
2. Prediction of new battery materials.

Experience in static simulations:

1. My knowledge of defect energetics method will contribute along the objective of the project providing the complete description of vacancy formation, anti-site and substitution energy, including interstitial incorporation, solution, cluster, binding and final solution energies by using forcefield-based method.
2. Force field-based nudged elastic band (NEB) is indeed crucial in the understanding and design of chemical reaction, alkali migration path, and activation energy involved in solid-state electrolytes. This method considers two main data, namely the true transition state structure and the minimum energy migration path, including the activation energy by taking a hypothetical reaction path. The synchronous transit method (Sync) is efficient to predict the transition state structure, whereas the NEB discloses the minimum energy path, the activation energy, and together with the NEB, the diffusion coefficient at ambient temperature of the migrating ion considered. This method can be used to disclose the rate performance of the inorganic solid electrolyte.

• Large-scale Molecular Dynamics Simulations (MD): Force field-based MD approach is used to disclose the alkali transport properties for large systems with defect engineering included. Despite the progress of supercomputer, ab-initio MD protocols commonly cannot be applied for larger systems due to computational cost and timing. It can be used to study the transport properties of monocrystalline and particular grain boundaries in solid-state electrolytes. In polycrystalline samples both grain and grain boundaries are the main conducting regions. Force field-based MD computations constitutes a powerful tool to study the transport properties of individual conducting regions. Properties such as diffusion coefficient, conductivity, diffusion/conduction activation energy and diffusion/conduction at operative temperature of a solid state electrolyte can be predicted by using the MD protocol. This protocol allows a direct comparison of transport properties between conducting regions, elucidating the influence of each region on the overall transport properties, including the defect engineering effect, contrasting the results of transport properties obtained from EIS data.

Experience in EIS data analysis:

Despite the equivalent circuit approach to study the conducting properties of solid-state electrolyte, it is a combination of complex impedance and dielectric modulus formalism that provides with a better understanding concerning individual relaxation regions. The complex impedance formalism allows the hidden relaxation process at low frequency regime to be accessible, whereas the dielectric modulus formalism discloses the relaxation process at high frequency in mixed electronic-ionic conductors [https://doi.org/10.1016/j.mssp.2022.106997]. In the past five years, my scientific activity has led to 16 joint published papers in international journals, 14 of these papers deal with the computational protocols applied to solid-state materials used as electrode and electrolyte in batteries and hybrid supercapacitors.

As for now, I have not gained experience in synthesis of compounds, but my skills and experience in advanced atomistic simulations will help in the development of synthesis strategies of current or new battery materials, while my experience in the EIS data analysis will contribute to understanding their conducting and relaxation properties.

I do have solid experience in international team collaboration. For instance, as a result of manuscript research projects, I collaborate with both experimental and theoretical researchers of different recognized institutions such as James A. Dawson (Newcastle University, UK), Professor Paul Geerlings and Frederik Tielens (General Chemistry (ALGC), Vrije Universiteit Brussel, Belgium), My-Phuong Pham-Ho (Ho Chi Minh City University of Technology, Viet Nam), and continue collaborating with my former Ph. D. supervisor Professor Minh Tho Nguyen (Department of Chemistry, KU Leuven, Leuven, Belgium), including my former Master supervisors Yurimiler Leyet Ruiz and Fidel Guerrero Zayas (Federal University of Amazonas, Manaus, Brazil) among others (see e.g. my CV file submitted). I am also in contact with  Professor Saiful Islam, Academic Staff of Department of Materials, University of Oxford, for sharing ideas about one of my last published paper dealing with modelling mixed halide antiperovskite structures, which are promising inorganic solid electrolytes. By means of this multidisciplinary experience I have earned important skills concerning project management, training bachelor/master students, gender equality, open access policy, and to how to conduct independent research, which constitutes one of the requirement of this position.  

I am excited about the career development this position offers.  I am particularly eager to become a T-Shape researcher in the field of battery materials. I hope that by joining this group, I will be able to work in an interdisciplinary research group and in close contact with the industry.

In conclusion, by applying for this role I hope to further put to use my skills and experience in material modelling and EIS analysis. As a part of Department of Materials at the University of Oxford, I look forward to the opportunity of developing new battery materials.

I sincerely thank you in advance for your consideration, and am looking forward to hearing from you soon.

Expectantly,

Yohandys A. Zulueta

Departamento de Física, Facultad de Ciencias Naturales y Exactas,

Universidad de Oriente, CP- 90500, Santiago de Cuba, Cuba.

Email: [email protected] [email protected]

ORCID: 0000-0003-0491-5817