Natural halloysite nanotubes-coated polypropylene membrane as dual-function separator for highly safe Li-ion batteries with improved cycling and thermal stability

Abstract

Abstract Developing low-cost functional separator is urgently needed by high safety and high energy lithium-ion batteries (LIBs), especially for the electric vehicles application. In this work, we present a new type of dual-function separator (HNTs@PP) by coating natural halloysite nanotubes (HNTs) on both sides of a polypropylene (PP) separator to improve battery safety and electrochemical performance. HNTs@PP separators exhibited better electrolyte uptake, wettability, and high ionic conductivity. Compared with traditional ceramic coating, the low-cost and natural abundant halloysite with unique nano hollow tube structure can improve the thermal stability of separators and significantly enhance the cycle and rate performance. Furthermore, the HNTs@PP shows higher lithium anode stability. The three-dimensional network structure of HNTs on membrane surfaces and their ability to react with electrolytes to obtain the additive, LiPO2F2, improve the cycle stability of LIBs greatly. At 1 C and after 300 cycles, the capacity retention rate of the assembled LiCoO2/Li half-cell using HNTs@PP composite separators was 44.42% higher in comparison with LIBs with bare PP separators. Moreover, at the rates of 0.5, 1, 2, and 3 C, the discharge specific capacities when using HNTs@PP separators were 1.77%, 2.63%, 5.80%, and 9.71%, respectively, higher than when using bare PP separators. As a result, the as-prepared HNTs@PP separator is a promising candidate as low-cost functional separator for highly safe and high-energy LIBs.