Understanding the crucial roles of natural clinochlore in reinforcing Li–S batteries

Abstract

Random dendrite growth and the severe shuttle effect of lithium polysulfides are major obstacles to exploiting dependable high-capacity Li–S batteries. Conventional polypropylene separators fail to homogenize lithium-ion migration and inhibit polysulfide shuttling, causing dead lithium and side reactions on lithium metal anode surfaces. In this study, natural layered clinochlore is proposed for the first time as a solution to modify polypropylene separators for reinforcing Li–S batteries. The clinochlore surface possessed various polar adsorption sites to immobilize polysulfides via robust O⋯S, Li⋯O, and Si⋯S bonds. It also enabled bidirectional catalysis for sulfur redox reactions in Li–S batteries; that is, it could not only catalyze the reduction reactions of soluble polysulfides upon discharging but also expedite the oxidation reactions of Li₂S upon charging. Moreover, the clinochlore surface with an ultra-low lithium migration energy (0.14 eV) induced uniform ion flux, relieved lithium-ion accumulation, and finally eliminated lithium dendrite growth. As a result, Li–S batteries with clinochlore-modified separators demonstrated an excellent rate performance of 770 mA h g⁻¹ at 5C and a high areal capacity of 5.68 mA h cm⁻² even at a sulfur loading of 6.2 mg cm⁻². This work provides insights into the crucial roles of natural clinochlore in promoting Li–S chemistries and offers a facile method for designing low-cost and multifunctional separators.