Long life-span of Li-metal anode enabled by a protective layer based on the pyrolyzed N-doped binder network
The attempts to utilize Lithium metal in secondary batteries are seriously restricted by its uncontrollable side reactions with electrolyte solvent. Here we tend to utilize a protective porous structure based on pyrolyzed PAN binder to stabilize the electrolyte/lithium interface to prolong its working life. As the increase of pyrolysis temperatures, the treated PAN fibers possess two mutational points in mechanical-properties located at ~300 & ~700 ℃, and exhibit carbon-like characteristics at ~400 ℃ and higher temperatures. Compared to the control electrode, the cyclic life-span of the treated electrodes can extend 1.8 times at the first mutational point, and surprisingly rise to 12 & 7 times for the samples pyrolyzed at 400 & 500 ℃, then fall back to 1.6 times at the second mutational point. These results reveal that the stable operation of lithium plating/stripping could be tightly provided by the internal interwoven SEI layer grown on the carbon-like binder network with appropriate rigidity. Among the investigated systems, the protective structure treated at 400 ℃ can stably operate for 350 cycles with an average columbic efficiency as high as ~98%, which represents the best record in the carbonate-based electrolytes.