Sulfonic Acid-Functionalized Graphdiyne for Effective Li–S Battery Separators

Lithium-sulfur (Li-S) batteries enable a promising high-energy-storage system while facing practical challenges regarding lithium dendrites and lithium polysulfides (LiPSs) shuttling. Herein, a fascinating SO₃H-functionalized graphdiyne (SOGDY) was developed by grafting SO₃H onto GDY to modify the separator in Li-S batteries. It realizes structure-retained material transformation, that is, SOGDY retains the crystalline all-carbon network and uniform subnanopores from the initial GDY. The abundant SO₃H and uniform pores create a rapid Li⁺ transport relay station, benefit rapid Li⁺ transport and even lithium deposition, and prevent lithium dendrite growth. The spatial obstruction and strong polar adsorption sites from SO₃H effectively inhibit LiPS shuttling. Additionally, SOGDY establishes a fast electron-transfer pathway to facilitate the LiPS conversion. The SOGDY/PP separator exhibited steady cycling at 1 mA cm^-2 over 3500 h in the Li∥Li symmetric battery and achieved outstanding low-temperature and high-rate performance in the Li-S battery with a high initial specific capacity of 804.5 mA h g^-1 and a final capacity of 504.9 mA h g^-1 after 500 cycles at 3 C and -10 °C. This work demonstrates that introducing a stable all-carbon network and uniform functionalized nanopores is an effective strategy to modify the Li-S battery separator.