Abstract: Lithium-ion batteries are widely used in communications, new energy sources, and electric vehicles due to their high energy density. However, the decay of battery capacity will lead to lithium-ion batteries reaching end-of-life after a few years’ usage. Therefore, recycling lithium-ion batteries for sustainable energy storage is imminent. In this paper, we reviewed the technical methods for separating and purifying the valuable metal ions from the cathode materials of spent lithium-ion batteries, including multicomponent system and lithium iron phosphate cathode materials. This paper also compared the reagents used in terms of economy, environmental protection, efficiency, and operational complexity to examine the advantages and shortcomings of each method. In addition, the latest technology at this stage was summarized and the future development of spent lithium-ion battery recycling technology was expected to maximize its resource utilization.