Template‐free preparation of porous Co microfibers from spent lithium‐ion batteries as a promising microwave absorber

Abstract

Abstract In order to take full advantage of the secondary resources, in this paper, we reported a template‐free process to prepare porous Co microfibers from spent lithium‐ion batteries (LIBs). First, the waste LiCoO 2 powders were leached by oxalic acid at a suitable temperature, and rod‐like cobalt oxalate powders were obtained. Second, the porous Co microfibers were prepared by using the cobalt oxalate as precursors through a thermal decomposition at 420 °C under nitrogen atmosphere. The prepared Co microfibers possess diameters of 1–2 μm, and each microfiber consists of small particles with size of 100–200 nm. The Co microfibers (25 wt%)/paraffin composite exhibited excellent microwave absorption performance. When the sample thickness is 4.5 mm, the reflection losses reach − 36.14 and − 38.20 dB at 4.16 and 17.60 GHz, respectively, and the effective bandwidth reaches up to 5.52 GHz. This indicates that the Co microfibers can be used as a promising microwave absorber. Therefore, this paper demonstrates a novel process to make a high value‐added product through recycling from the spent lithium‐ion batteries. In addition, it is advantageous to eliminate the hazard of spent lithium‐ion batteries and electromagnetic radiation to environment and human health.