Achieving stable Na metal cycling via polydopamine/multilayer graphene coating of a polypropylene separator

Sodium metal batteries are considered one of the most promising low-cost high-energy-density electrochemical energy storage systems. However, the growth of unfavourable Na metal deposition and the limited cell cycle life hamper the application of this battery system at a large scale. Here, we propose the use of polypropylene separator coated with a composite material comprising polydopamine and multilayer graphene to tackle these issues. The oxygen- and nitrogen- containing moieties as well as the nano- and meso- porous network of the coating allow cycling of Na metal electrodes in symmetric cell configuration for over 2000 h with a stable 4 mV overpotential at 1 mA cm(-2). When tested in full Na || Na3V2(PO4)(3) coin cell, the coated separator enables the delivery of a stable capacity of about 100 mAh g(-1) for 500 cycles (90% capacity retention) at a specific current of 235 mA g(-1) and satisfactory rate capability performances (i.e., 75 mAh g(-1) at 3.5 A g(-1)). The development of future Na metal batteries relies on the cycling stability of the metallic anode. Here, the authors propose a polypropylene separator functionalized with polydopamine and multilayer graphene to enable stable and prolonged Na metal cell cycling.

Automated summary

The use of a polypropylene separator coated with a composite material comprising polydopamine and multilayer graphene helps address issues related to unfavorable Na metal deposition and limited cell cycle life in sodium metal batteries. The coated separator enables stable cycling of Na metal electrodes for over 2000 hours with a stable overpotential. Testing in coin cells shows stable capacity retention and satisfactory rate performance.