The short-process recycling of valuable metals in waste lithium-ion batteries is a key challenge for ensuring the supply of raw materials for the new energy industry. With the development of the new energy industry, achieving the short-process recycling of valuable metals in waste lithium-ion batteries is an important link in the new energy industry chain. Based on the basic principle of the sulfurization method, the thermodynamic analysis of the sulfurization of LiCoO2 positive electrode materials with three typical sulfurizing agents [S8, SO2, sulfide minerals (FeS, CuFeS2, ZnS)] was carried out using Factsage 7.3 thermodynamic software. The effects of sulfurization temperature and sulfurizing agent dosage on the sulfurization products were studied. Through software simulation calculations, it was proved that all sulfurizing agents can thermodynamically sulfurize LiCoO2. Li in LiCoO2 was sulfurized into water-soluble Li2S or Li2SO4, while Co generates sulfides or oxides that were insoluble in water. Through leaching separation experiments, efficient separation of Li and Co was achieved. The results of the sulfurization recovery experiment showed that the three types of sulfurizing agents can achieve different degrees of sulfurization on LiCoO2. Among them, S8 was affected by reaction kinetics and had the worst sulfurization effect, with a sulfurization rate of only 2.51%; SO2 had a poor sulfurization effect when used as a sulfurizing agent, with a sulfurization rate of 34.07%, while when SO2 and the reducing agent C synergistically sulfurize, the sulfurization rate increased significantly to 72.03%. When sulfide minerals were used as sulfurizing agents, ZnS showed the best sulfurization effect, with a sulfurization rate of 96.14%, while the sulfurization effects of both CuFeS2 and FeS were quite poor. This study can provide new ideas for the short-process recovery of valuable metals in waste Li-ion batteries.