A novel fire safety separator decorated by Co₂P/Co/C multifunctional layer for Li-S batteries

Lithium-Sulfur (Li-S) battery is a potential alternative energy storage system owing to its high theoretical capacity, low cost, and eco-friendly features. However, the commercialization of Li-S battery has been hindered by the notorious “shuttle effect”. To overcome the above-mentioned long-standing problem, herein, an advanced separator modified by N and P heteroatoms co-doped carbon frameworks with confined Co₂P nanoparticles (named Co₂P/Co/C) has been successfully prepared. The introduction of functional coating can obviously enhance the thermal stability of separator. To be specific, it showed higher initial decomposition temperature (475 ℃) and lower maximum mass loss rate (1.755%℃⁻¹) values than the Celgard separator (400 ℃ and 2.915%℃⁻¹, respectively). Notably, when kindled separators directly, the modified separator can quench by itself with many residual remains. In addition, the engineered functional layer possesses the capability of capturing lithium polysulfides (LiPSs), and then confines them within the cathode region so that the “shuttle effect” can be restrained effectively. After assembling the modified separator in the Li-S cell, compared with the cell with Celgard separator of low initial specific discharge capacity (730 mAh g⁻¹), the cell with Co₂P/Co/C separator delivered a superior initial discharge capacity of 1310 mAh g⁻¹ at 0.5 C. Also, the modified cell can perform remarkably enhanced rate performances. In addition, As a consequence of these merits, the modified separator with improved thermal stability, preferable fire safety, and satisfied electrochemical performances shows significant guiding value for advancing the practical application of Li-S batteries.