Waste to wealth: calcium-magnesium mud-coated polypropylene separator for lithium-ion battery

Polyolefins like polypropylene (PP) and polyethylene (PE)-based separators are widely used in the lithium-ion batteries (LIBs). However, applying polyolefin separators is limited in high-performance batteries due to poor electrolyte wettability and thermal stability. In this study, on the basis of the concept of “waste to wealth,” a novel approach has been proposed by utilizing waste raw materials of calcium-magnesium mud (CM), incorporating in a slurry coating method applied to a commercial PP separator for enhanced performance surpassing that of the traditional separator. The CM-coated PP (CM@PP) separator demonstrated better thermal stability and electrolyte compatibility, higher Li-ion conductivity, and lower interfacial resistance than the uncoated PP separator. Cycling and rate performance of CM@PP separator assembled battery were higher compared to those of the uncoated PP separator assembled battery. The LiFePO₄|Li battery with the CM@PP separator rendered a high discharge capacity of 154 mAh g⁻¹ at 1 C and a capacity retention rate of 93.0% after 200 cycles. These results indicate that CM-coated PP separator is a promising strategy to improve the safety and electrochemical performance of LIBs. The low cost of CM emphasized the superiority of this facile separator modification method.