Improving Li Anode Reversibility in Li-S Batteries by ZnO Coated Separators Using Atomic Layer Deposition

Lithium-sulfur batteries (LSB) are considered a very attractive alternative to lithium-ion batteries due to their high theoretical capacity and low cost of the active materials. However, the realization of LSB is hostage to many challenges associated with the cathode and anode response to the electrochemical conditions inside the battery cell. While working with LSB, elemental sulfur undergoes multielectron reduction reactions until it is reduced to Li₂S. The intermediate long chain lithium-polysulfide (LiPS) species are soluble, hence diffuse through the electrolyte solution from the cathode side to the anode. This “shuttle” phenomenon considered to be one of the main issues of LSB. Most effort in investigating LSB focused on the cathode side while only few considered the importance of the lithium anode reversibility and the separator role in preventing the “shuttle” phenomenon. In the current work, we use Atomic Layer Deposition (ALD) to successfully coat a standard polypropylene separator with an additional layer of metal oxides thin film. We show that surface treatment of the separator facilitated improved electrochemical response, and suppressed the shuttling of LiPS to the anode.