Co/Li2S of chemical confinement decorated electrochemically stable Co(OH)F nanoarrays enabling dendrite-free flexible 3D Li anodes

Abstract

Lithium (Li) metal is regarded as a promising anode for high-energy-density Li-ion batteries because of its high theoretical specific capacity and low potential. Unfortunately, the safety issues derived from Li dendrite formation have hindered their commercialization. Thus, fabricating a flexible, three-dimensional (3D) composite Li anode is an effective strategy to suppress Li dendrite growth. Lithiophilic nanoarrays are commonly constructed on a 3D skeleton to increase its surface area and lithiophilicity. However, the lithiophilic nanoarrays are unstable due to the conversion reaction during Li plating/stripping. Therefore, designing composite nanoarrays with an electrochemically stable inner core and a lithiophilic outer shell is conducive to providing a large surface area and promoting uniform Li deposition. Herein, CoS₂ shell–Co(OH)F core composite nanowire arrays were prepared on carbon cloth (CoS₂–Co(OH)F/CC) to fabricate a flexible 3D composite Li anode (Li@CoS₂–Co(OH)F/CC), in which the electrochemically stable Co(OH)F core ensures the stability of the nanoarray and the lithiophilic CoS₂ shell facilitates uniform Li adsorption. Moreover, the Co/Li₂S configuration derived from the lithiation of CoS₂ could promote homogeneous Li deposition, in which the lithiophilic Li₂S phase and electron-conductive Co phase jointly facilitate uniform Li nucleation and charge transfer. Consequently, the symmetric cells and full cells paired with a LiFePO₄ (LFP) cathode based on the flexible Li@CoS₂–Co(OH)F/CC anode presented superior cycling stability.