Heteroatomic dopants derived from coal fly-ash for the synthesis of nickel-rich Li-ion battery cathode material

Abstract

Fly ashes often become an environmental problem and are difficult to process. Utilizing coal fly ash as a product is a promising approach to overcoming it. In response to this problem, the metal content in fly ash waste in the form of Al2O3 and Fe2O3 can be utilized by applying them as dopants on the nickel-rich cathode material to achieve LiNixCoyAlzFe(1-x-y-z)O2 (NCAF) which is a modified form of nickel-based cathode material or NCA. In this study, NCAF material was made in 3 stages: (i) Recovery of valuable metals Al and Fe from fly ash by leaching and precipitation processes to obtain Aluminum-iron (AF) precursor; (ii) Nickel-cobalt (NC) containing precursors were prepared by mixing nickel and cobalt salts using the coprecipitation method. This NC precursor and AF were mixed at a mass ratio of 90:10; (iii) Lithiation through heat treatments under an O2 atmosphere to form NCAF cathode material. The results of the NCAF material characterization are: (i) The XRD test showed the same diffraction pattern as the JCPDS 87-1562 reference; (ii) FTIR test of NCAF material showed that the storage condition affects the surface of NCAF powder; (iii) SEM-EDX test showed that the NCAF material has an agglomerated morphology and crystal-shape with a primary particle size of around 140 nm; (iv) Electrochemical test of Li-ion battery with NCAF cathode using graphite as anode showed charge and discharge capacity of 172 mAh/g and 144 mAh/g, respectively. Based on the results, implementing Al and Fe from fly ash as materials for Li-ion batteries should be considered for future energy storage technology developments.