Hierarchically porous carbon materials for advanced Lithium selenium battery

Abstract

Batteries became a welcomed device due to their clean, efficient, removable features. Li-ion batteries have already been successfully applied in the fields of vehicles, electronic equipment, aerospace, etc. The demand for the high environment-friendly, high energy density, small volume, and wide temperature applicability, in turn, promotes the development of new battery storage systems, such as Li-S batteries, Li-O2 batteries, Na-ion batteries, K-ion batteries, Al-ion batteries, etc. Li-Se batteries, due to their high specific capacity (675 mA h g-1) and much higher conductivity of Se than S, became a promising candidate and have achieved significant development in these few decades. Unfortunately, the capacity decay of the battery by the diffusion of the intermediate polyselenides (Sen2-, n≥4) and volume expansion of cathode have limited the commercialization of Li-Se batteries. In addition, the problems of electrolyte leakage and growth of lithium dendrites should also be overcome.
In this thesis, we will first talk about the overview of the Li-Se batteries. In which the development history of batteries, the mechanism of Li-Se battery, the challenges it faces, and the strategies how to solve these problems will be described in detail. Our work mainly focuses on designing and structuring Se cathode host materials to suppress the rapid capacity fading of batteries caused by polyselenide diffusion. The research can be included in the following three parts:
1. The three-dimensional ordered hierarchically micro-meso-macro-porous carbon materials were designed as Se host material. The confinement and rich of reaction sites of Se by the micropores and the rapid electrolyte and ions transfer by the interconnected meso-macropores pathways, ensure the stability of the Li-Se battery and high rate capability. Moreover, the optimized pore size of these three pores range value was explored and achieved the best electrochemical performance.
2. The strong interaction between host materials and Se species of chemisorption tiredly confines the Se species in the cathode, which is beneficial for the long lifespan of Li-Se battery. Combining the advantages of the micro-meso-macroporous frameworks, single-crystal metal-organic framework (MOF)-derived N-doped ordered hierarchically porous carbon was fabricated. Benefiting from the synergy of physical adsorption of micropores and chemisorption of N-doping, combined with the optimized porous design, the capacity of the battery achieved a further improved.
3. In order to break the number of the polar site limitation brought by nitrogen doping, amorphous bimetallic oxides CoSnO3 was introduced to the host system of the interconnected carbon nanotube (CNT). Besides the further enhanced adsorption to polyselenides, the introduced CoSnO3 showed catalytic effect on the redox reactions during the discharge/charge process. The catalytic mechanism was accessed by the density functional theory (DFT) calculation method.

Date of Award	25 Nov 2022
Original language	English
Awarding Institution	University of Namur
Sponsors	China Scholarship Council
Supervisor	BAO LIAN SU (Supervisor), Olivier Deparis (President), Laurence Leherte (Jury), Nikolay Tumanov (Jury), Alexandru Vlad (Jury) & Yu Li (Jury)