Porous materials for lithium-sulfur batteries - mechanochemical synthesis and performance probed by in situ and operando techniques

Author(s)

Breno Luiz de Souza

• Document type: Doctoral Thesis
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Conjunto das Químicas (IQ e FCF) (CQ/DBDCQ)
• Defense date: 2024-01-23

Examining board members

Roberto Manuel Torresi; Luiz Henrique Dall'Antonia; Gabriel Negrão Meloni; Lucia Helena Mascaro Sales

• Advisor: Roberto Manuel Torresi; Paulo Filho Marques de Oliveira

Abstract

Lithium-Sulfur Batteries (LiSBs) represent a promising solution for nextgeneration energy storage, boasting an exceptional theoretical capacity of 1675 mA h g-1, a feat nearly five times higher than traditional transition metal oxides and phosphates. The 16-electron transfer during the de/lithiation process at a working voltage of ~1.7-3.0 V vs Li+/Li enables a theoretical density of 2600 Wh Kg-1. However, the substantial challenges faced by LiSBs, primarily rapid capacity fading due to sulfur electrode pulverization and the shuttle effect caused by the dissolution of long-chain polysulfides (LiPSs) in organic solvents, have prompted extensive investigation. This work systematically addresses these challenges through the synthesis and characterization of diverse porous compounds, each detailed in the following chapters. Chapter 2 introduces a novel mechanochemical approach for crafting Zeolitic Imidazole Framework ZIF-8-based composites as sulfur hosts in positive electrodes for LiSBs. Exploring various techniques for integrating conductive carbon and substituting Zn2+ with other bivalent metals (Cu2+, Co2+, and Ni2+), alternative ZIF-8-derived materials are obtained. The ZIF-8/C/S8 positive electrode, Mechanochemically Mixed, showcases a remarkable 54% performance improvement over traditional ZIF-8/S8 slurry preparation, underscoring the advantages of direct mechanochemical synthesis during the initial charge/discharge cycles. Chapter 3 focuses on a 3D polypyrrole-based sponge (PPY) synthesized as a sulfur host for positive electrodes in LiSBs. Optimized PPY:S8 exhibits compelling electrochemical performance, including a cycle lifetime exceeding 200 cycles. Electrochemical impedance spectroscopy (EIS) indicates a minimal shuttle effect through an unchanged solution resistance, and operando Raman spectroscopy reveals the stability of the bipolaronic state and the \"neutralization\" of LiPSs. These findings underscore PPY\'s potential as an effective sulfur host, mitigating the shuttle effect and enhancing the charge storage capacity of LiSBs. Chapter 4 delves into understanding degradation mechanisms within LiSBs, focusing on a porous organic polymer (POP), MTP-1. Synthesized using eco-friendly methods (mechanochemistry), MTP-1 is thoroughly characterized, exhibiting robust performance with over 70% capacity retention across 100 cycles. Operando techniques, including electrochemical impedance spectroscopy (EIS) and X-ray radiography (in lab and Synchrotron), reveal superior sulfur confinement and stability. The synergy of environmentally friendly synthesis, extensive characterization, and advanced in situ and operando techniques positions MTP-1 as a promising sulfur host material. Overall, these diverse approaches collectively underscore the significance of tailored materials and advanced techniques in overcoming LiSBs challenges. Each chapter contributes valuable insights, collectively advancing LiSBs technology and our understanding of degradation mechanisms. This work holds promise for the widespread implementation of LiSBs, addressing critical issues and contributing to the development of advanced materials for energy storage systems. (AU)

• FAPESP's process: 19/09341-1 - Lithium-sulfur batteries: development of new generation of positive electrodes based on composites of MOFs/sulfur
• Grantee: Breno Luiz de Souza
• Support Opportunities: Scholarships in Brazil - Doctorate