Utilizing Phosphating Sludge to Synthesize Lithium Iron Phosphate with a Hybrid Coating of Metal Oxides and Carbon

In order to utilize the hazardous phosphating sludge, a novel approach including FeCl 3 solution replacement leaching and MeO (metal oxides) coprecipitation coating is proposed to prepare LiFePO 4 coated with metal oxides and carbon, where FePO 4 is recycled from phosphating sludge and its valuable impurities are utilized as coating materials. The FeCl 3 solution replacement leaching is a process for PO 4 3+ enrichment and FePO 4 purifying. The metal ions (Zn 2+, Ca 2+, Mn 2+, etc.) of the impurity phosphates can be leached into the solution, meanwhile their corresponding PO 4 3– are reprecipitated as FePO 4, whose Fe 3+ come from the FeCl 3 leaching solution. Taking the obtained FePO 4 as the core material, the MeO can be coprecipitated from the leached solution and coated onto the FePO 4 particle uniformly under the critical pH and appropriate concentration. This uniform hybrid coating is helpful to avoid the asymmetrical conductivity both for electron and lithium ion on the surface of the LiFePO 4 particle, and hence improve its electrochemical performance. In result, the phosphating sludge is utilized in a fine and high atom utilization way, which meets the requirements of hazardous waste reusing and LiFePO 4 modification.