Lithium–Sulfur Batteries: A Sustainable High-Energy Technology

Dear colleague,

Li-ion batteries are currently used as rechargeable batteries in almost all applications, ranging from portable electronics to electric vehicles. There is no doubt they will continue to dominate the market for the next few years. Nevertheless, the need for a beyond Li-ion battery technology has never been greater with energy requirements exceeding the capabilities of Li-ion batteries and with key materials, including mainly cobalt and nickel, being limited resources, causing serious concerns regarding both their supply chains and rising costs.  Battery technology offering higher specific energy at a lower cost and with sustainable raw materials would be the solution to fulfill the needs of the rapidly expanding electric vehicle market and mitigate climate change.

Sulfur is an attractive cathode material with a high specific capacity; it is the fifth most abundant element and is very inexpensive. Paired with a lithium metal anode in a lithium cell, it can potentially offer twice the specific energy and, hence, a longer range compared to current batteries. It is projected to be the only battery technology that can meet the cost target of <$60/kWh, which is essential for the widespread use of EVs. Preliminary safety tests at various laboratories have indicated that it these batteries have an adequate abuse tolerance for large-scale systems. Li–S batteries, however, are not a new technology. They have been studied sporadically over the last three decades, but have yet to be implemented successfully. The Achilles heel of Li–S cells is the polysulfide shuttle caused by the dissolution of sulfur intermediates in conventional liquid electrolytes, which limits their cycle life to less than 100 cycles. The use of Li–S batteries has therefore been restricted to applications that need high specific energy for fewer cycles, e.g., unmanned aerial vehicles (UAVs).

There is a resurgence of the study of Li–S technology with newer materials, i.e., hierarchically porous carbon hosts of different types, carbon–sulfur polymers, Li-based anodes with various protective coatings, electrolytes that control the degree of polysulfide solvation, and gel and solid electrolyte systems and separators with selective coatings that function as polysulfide barriers. With these ongoing developments, it is reasonable to expect that the Li–S technology will emerge as a viable high-energy option for a partial replacement of Li-ion batteries in aerospace and transportation markets. This Special Issue is aimed at capturing some of these developments that are paving the way for the transition of Li-S technology from small-niche uses to large-scale broad-based applications.

Potential topics include, but are not limited to:

1. Overview of Current Li–S Technology;
2. Porous Carbons as a Sulfur Host;
3. Non-carbon Sulfur Hosts (ceramic and MOF);
4. Li Metal Anode for Li–S Cells;
5. Carbon–Sulfur Polymers, SPAN, etc.  (Inverse Vulcanization), and ϒ-Sulfur;
6. Liquid Electrolytes: How Far can they Take Li-S Technology?;
7. Sulfur Kinetics and Catalysts;
8. Separators and Inner Layers;
9. Solid Electrolytes: Prospects and Comparison with Li/NMC SSBs;
10. Safety Implications of S Cathodes and Li Metal Anodes;
11. Cost Analysis and Environmental Impact Analysis;
12. Application Mapping (year-wise)

Dr. Bugga V. Ratnakumar
Dr. Leela Mohana Reddy Arava
Guest Editors

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• lithium-sulfur cells
• sulfur cathode
• metallic Li anode
• polysulfide shuttle
• carbon–sulfur cathodes
• hierarchical porous carbon