Ultralong Cycling and Safe Lithium-Sulfur Pouch Cells for Sustainable Energy Storage.

While layered metal oxides remain the dominant cathode materials for the state-of-the-art lithium-ion batteries, conversion-type cathodes such as sulfur present unique opportunities in developing cheaper, safer and more energy-dense next-generation battery technologies. There has been remarkable progress in advancing the laboratory scale lithium-sulfur (Li-S) coin cells to a high level of performance. However, the relevant strategies cannot be readily translated to practical cell formats such as pouch cells and even battery pack. Here we address these key technical challenges by molecular engineering of the Li metal for hydrophobicization, fluorination and thus favorable anode chemistry. The introduced tris(2,4-di-tert-butylphenyl) phosphite (TBP) and tetrabutylammonium fluoride (TBA + F - ) as well as cellulose membrane by rolling enables the formation of a functional thin layer that eliminates the vulnerability of Li metal towards the already demanding environment required (1.55% relative humidity) for cell production and gives rise to LiF-rich solid electrolyte interphase (SEI) to suppress dendrite growth. As a result, Li-S pouch cells assembled at a pilot production line survive 400 full charge/discharge cycles with an average Coulombic efficiency of 99.55% and impressive rate performance of 1.5 C. A cell-level energy density of 417 Wh kg -1 and power density of 2766 W kg -1 are also delivered via multilayer Li-S pouch cell. The Li-S battery pack can even power an unmanned aerial vehicle of 3 kg for a fairly long flight time. Our work represents a big step forward acceleration in Li-S battery marketization for future energy storage featuring improved safety, sustainability, higher energy density as well as reduced cost. This article is protected by copyright. All rights reserved.