5:40 PM - EN09.04.02
Rational Design of Sulfur Cathode for High-Energy Lithium-Sulfur Batteries
Shuo Feng1,2,Lili Shi1,Cassidy Anderson1,Yuehe Lin2,Jie Xiao1,Jun Liu1,Dongping Lu1
Pacific Northwest National Laboratory1,Washington State University2
A crucial prerequisite for a high energy lithium-sulfur (Li-S) battery is the integration of a high-loading sulfur cathode, a lean amount of electrolyte, and a limited Li anode 1-4. However, simultaneous application of these parameters often leads to the rapid deterioration of the cell performance. Fundamental mechanisms of the cell failure are still not very clear; materials that can fulfill both high energy density and long cycle life of the Li-S batteries are still facing significant challenges. Highly porous and nanosized carbon materials are widely explored as effective sulfur hosts to improve Li-S battery’s performance. However, these nano materials tend to form extremely porous and thick sulfur cathodes which require a large amount of electrolyte for pore filling, and thus a very high electrolyte to sulfur ratio (E/S ratio > 10 µL/mgs) is usually used for cell test. To address those issues, rational designs for both materials and electrode structures are urgently needed to enable the operation of low porosity sulfur cathodes (<50%) under lean electrolyte condition (E/S ratio < 4 µL/mgs), conserving more proportion of electrolyte for cell cycling. In this research, sulfur/carbon composite with controllable secondary particle sizes were synthesized and used as example materials to understand the impacts of materials and electrodes on sulfur reactions at realistic conditions. It is found that the larger sulfur/carbon particles (> 90 µm) demonstrate significant superiorities over the smaller ones (< 20 µm) in terms of electrolyte permeability, sulfur utilization rate, electrochemical polarization, and shuttling effect. As a result, at an extremely low electrode porosity of 45%, the high loading sulfur cathode (>4 mg/cm2) can deliver a high initial discharge capacity of 1001 mAh/g under lean electrolyte conditions (E/S ratio = 4 µL/mgs) with a much improved cycling stability. New findings of the research will be presented and discussed at the symposium.
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