Ingenious double-modified strategy to prepare “hexagonal warrior” separator for lithium metal batteries

Abstract

Lithium metal batteries (LMBs) represent the favorable option for the new-generation high-energy-density batteries. Nevertheless, LMBs utilizing the merchant separators consistently encounter some issues including the irregular development of lithium dendrites, bulk fluctuation of lithium anode, and excessive electrolyte consumption. In this study, we innovatively coat the double-side of commercial polypropylene (PP) separator with an electrostatically assembled composite of CoMo-layered double hydroxide (CoMo-LDH) hollow polyhedra and high crystallinity graphitic carbon nitride to enhance the electrochemical properties of separator. The CoMo-LDH has a certain effect on accommodating the bulk variation throughout Li deposition/stripping procedure. Additionally, the triazine-based structure of graphitic carbon nitride synthesized by the molten salt assisted approach introduces Cl– to regulate the ion selectivity in separator and promotes the uniform plating of Li+. Satisfactorily, it is demonstrated that the double-modified PP (DMP) separator exhibits a significantly improved ionic conductivity (1.11 mS cm–1) and Li+ transference number (0.75) compared to conventional PP separator. In-situ puncture experiment of lithium dendrites reveals that the DMP separator withstands a lithium deposition capacity of 17 mAh cm–2. Furthermore, the DMP-equipped Li//LFP full-cell delivers a primary discharge capacity of 149 mAh g–1 and maintains 96.6% for the capacity retaining rate after 100 cycles at 0.2 C. Fortunately, after 500 cycles at 1 C, a retention rate of 94.1% is still achieved. Meantime, Li//NCM523 full-cell assembled with DMP separator exhibits a good electrochemical performance at 0.2 C. This work exhibits the universality and practicality of DMP separator as well as offers a dependable solution for restraining the development of lithium dendrites for LMBs. Furthermore, this solution would also be used to other alkali metal anodes.