STTR Phase II: Advanced Li-S Battery System for Unmanned Air Vehicles

This award is funded in whole or in part under the American Rescue Plan Act of 2021 (Public Law 117-2).

The broader impact/commercial potential of this Small Business Technology Transfer Research (STTR) project includes reducing the US dependence on foreign-sourced materials for the production and supply of battery systems. There are increased concerns about the shortage of materials for lithium ion batteries (LIB) as the number of electric vehicles increases.

Lithium Sulfur (Li-S) batteries use sulfur which is more readily available, lower cost, and environment-friendly. Li-S batteries do not require the use of sulfuric acid or other more harmful chemicals, which allows them to be disposed of easily or recycled. This project will advance knowledge in addressing challenges to the development of practical and commercially viable (Li-S) batteries.

The Global Lithium-Sulfur (Li-S) Battery Market was valued at $696 Million in 2019 and is anticipated to reach $6,686 Million by 2028, with a CAGR of 29.6% during the forecast period. Li-S batteries are mainly used in aviation, automotive, electronic device, and power & energy sector due to the growing demand for environmentally friendly energy with higher energy density than other battery types. Li-S technology has potential to enhance safer battery manufacturing in the US.

This STTR Phase II project proposes to address important technical challenges against the development of practical Li-S batteries. These challenges include limited cycle life, high self-discharge rates and over-heating at end of charge. These are thought to be caused by the shuttle, where cathode species diffuse to the anode and react directly with the metallic lithium.

A system approach will be employed to develop practical high performance Li-S Cells by focusing on: Performance (high energy density, large temperature range, and considerable cycle life); safety; and manufacturability. The project combines experimental and electrochemical modeling approaches to achieve a Li-S cell with 400-600 Wh/kg; ≥200 cycles; - 20oC to 60oC @ 1C.

The project will use advanced trilayer multifunctional separator and lithium metal anode to solve the problems associated with the shuttling effect. Simulation tools will be used to study and optimize the design and performance of the Li-S cells. The technical objectives for Phase 2 include the design, fabrication and characterization of progressively larger pouch cells (from 50 mAh to 500 mAh/1000 mAh).

The development path will focus on achieving high energy density Li-S cells first and increasing the temperature range at a reasonable number of cycles.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.