Design of fluorinated carbonaceous triazine-based network for dendrite-free Na metal batteries

Sodium metal batteries are promising next-generation energy-dense rechargeable batteries but are severely obstructed by uneven Na nucleation and subsequent dendritic Na growth, leading to the use of highly excessive Na in anode. Herein, a molecular-designed fluorinated carbonaceous triazine-based network (F-CTN) has been employed as the seeding/hosting coating layer to realize high interface stability with limited-excess Na source. The well-defined F functionality acts as uniform sodiophilic sites, effectively reducing the nucleation barrier, suppressing the growth of Na dendrite, and meanwhile promoting the formation of robust solid electrolyte interphase. Accordingly, a low nucleation overpotential of 12 mV, a high average Coulombic efficiency of 99.5 % for 600 cycles in half cells, and long-term interfacial durability of 5000 h in symmetric cells are realized using the F-CTN coating layer, far exceeding the control sample without fluorination. Moreover, the symmetric cell demonstrates stable cycling of 3300 h under a high depth of discharge. Eventually, the proof-of-concept pouch cells deliver a robust lifespan of 500 cycles with negligible capacity fading and energy density of 253 Wh kg−1 under low negative to positive capacity ratio of 2.5, proving the viability of the fluorinated carbonaceous coating layer in the practical deployment of dendrite-free Na metal batteries.