Ultra-fast recycling of used lithium-ion battery cathodes

Recently, the team of associate professor Wan Jiayu of Southern University of Science and Technology reported the latest work results on the ultrafast recovery of cathode materials in the field of lithium-ion battery recycling. The ultra-fast repair method developed by the team can efficiently and directly repair the cathode material (LCO) of waste batteries within 8s, and the electrochemical performance of the repaired cathode material is comparable to that of the newly prepared cathode material. This research on the repair of cathode materials for lithium-ion batteries provides an efficient and energy-saving method for the renewable development and resource reuse of lithium-ion batteries.

On June 14, 2023, the results were published in the journal ACS Energy Letter under the title “Rapid, Direct Regeneration of Spent LiCoO2 Cathodes for Li-Ion Batteries”. The corresponding author of the paper is Associate Professor Wan Jiayu, and the co-first authors are Yin Yunchao and Li Chao.

Lithium-ion batteries (LIBs) are characterized by high voltage, high energy density and long cycle life, and are widely used in various electronic products, electric vehicles and portable electronic devices. With the rapid development of new energy technology and electronics industry, the consumption of LIBs has increased explosively. Due to the limited lifespan of LIBs, a large number of scrapped LIBs will be generated in the near future. Therefore, there is an urgent need to recycle used LIBs in order to achieve sustainable development of resources and environment.

Inspired by the ultrafast high temperature synthesis synthesis method of Joule heat in Hu Liangbing’s research group, the researchers proposed an ultrafast repair method that proved for the first time that the cathode material S-LCO of waste batteries can be regenerated in seconds. Compared to traditional metallurgical processes and direct repair processes based on high-temperature furnaces, this ultrafast repair method utilizes direct current to generate Joule heat, which has the advantages of high heating rate, adjustable temperature and high cooling rate, which can greatly reduce the inevitable heat dissipation. Notably, the reaction temperature of URM is relatively higher than that of other traditional recovery methods, allowing S-LCO to be quickly repaired within 8 seconds. The rapid process not only minimizes the volatilization loss of the lithium source at high temperatures, but also avoids the melting process of the lithium source and the possible corrosion reaction with the container. Despite the rapid reaction process, the crystal structure of the waste cathode material can be fully restored, and the spinel Co3O4 formed in long-term cycling has all been converted into LCO with layered structure. The electrochemical performance of recycled lithium cobalt oxide is comparable to that of commercial cathode materials. The developed method is an efficient and potentially universal method for battery cathode regeneration.

1) Advantages of ultra-fast repair method

In Figure 1, the researchers developed a novel ultrafast repair method to quickly repair cathode materials. Compared with the traditional repair method, this method can realize the repair of the cathode material within 8s, which effectively reduces unnecessary energy consumption and operation time. At the same time, due to the short reaction time, the problem of lithium volatilization at high temperature for a long time is well avoided.

Figure 1: (a) Schematic diagram of the ultrafast repair process and (b) the furnace repair method; (c) Schematic diagram of the regeneration process; (d) Schematic diagram of the S-LCO repair process; (e) SEM diagram of S-LCO; (f) XRD plots of S-LCO and URM-LCO; (g) Energy consumption and operating time of different regeneration processes.

2) Repair of cathode material structure

In Figure 2, the structural characterization of the cathode material before and after repair was found that due to the long-term electrochemical cycle, the structure of the cathode material changed, and the spinel phase Co3O4 was partially formed. The cathode material obtained by the ultrafast repair method is completely restored to a perfect layered structure.

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Figure 2: Structural characterization of cathode materials before and after repair.

3) Defect type analysis

Figure 3 shows the researchers optimizing the temperature during the repair process. As the reaction temperature increases, all samples with lithium source exhibit a layered structure, and no other impurity peaks appear. When the temperature is 1440K, the electrochemical properties show optimal performance. It is noted that the temperature used in the ultrafast repair method is significantly higher than that used by the traditional method, which is beneficial to shorten the reaction time. In addition, current studies have shown that LCOs with layered structures have lower free energy at all temperatures. These conclusions show that lithium cobalt oxide can withstand high temperatures for a short period of time.

Figure 3: (a) Temperature change during the experiment; (b) XRD patterns of R-LCO with Li2CO3 as lithium source at different temperatures; (c) XRD pattern of lithium-free regeneration of LiCO2 at different temperatures; (d) toLi2CO3The rate performance of R-LCO of lithium source at different temperatures; (e) Charge-discharge curves of R-LCO-Li-1440 (solid line) and R-LCO-1440 (dashed line) at different currents; (f) R-LCO-LI-T IIS curve; (g) Cycling performance of S-LCO, R-LCO-LI-1440 and R-LCO-Li-1440 at 0.2 C; (h) dQ/dV curves for S-LCO and R-LCO-Li-1440.

4) Comparison between ultra-fast repair method and traditional repair method

Figure 4: The researchers compared ultrafast repair with conventional repair. Compared with the ultra-fast repair method of complete repair, the traditional repair method improves the electrochemical performance of waste cathode materials to a limited extent. The specific capacity, rate performance, cycle stability, interfacial resistance and diffusion coefficient of lithium ions of the cathode materials repaired by the ultrafast repair method were better than those obtained by the traditional repair method.

Figure 4: (a) Charge-discharge curves for S-LCO, R-LCO-1173, R-LCO-Li-1173, R-LCO-1440 and R-LCO-Li-1440; (b) Rate performance of different samples; (c) Long-term performance of S-LCO, R-LCO-LI-1173 and R-LCO-Li-1440; (d) EIS curves for S-LCO, R-LCO-LI-1173 and R-LCO-LI-1440; (e) GITT curves for S-LCO and (f) R-CO-Li-1440 over time; (g) GITT curves when S-LCO and R-LCO-Li-1440 are charged; Chemical diffusion coefficient of Li+ (DLi+) charged and (i) discharged.

5) Large-scale generation process based on ultrafast repair method

Figure 5: The researchers imagined an ultra-fast, roll-to-roll manufacturing method for the regeneration of cathode materials. In this process, the homogeneous mixed precursor composed of the cathode material and the lithium source continuously passes through the heating zone, so that the cathode material recovers its original crystal structure and electrochemical properties after rapid high-temperature treatment. This design offers great potential for ultra-fast and efficient roll-to-roll regeneration of cathode materials.

Figure 5. Schematic diagram of large-scale repair of cathode material by ultrafast repair method.

In this paper, the authors demonstrate that waste lithium cobalt oxide materials can be directly recycled in as little as 8s using ultrafast repair methods. The system characterization showed that the phase structure of the waste lithium cobalt oxide could be completely restored to the original layered structure, and the electrochemical performance of the repaired lithium cobalt oxide was comparable to that of the original material. After optimizing the repaired lithium cobaltate, the initial discharge specific capacity at 0.1 C was restored to 133.0 mAh/g with excellent cycling performance. In addition, the repaired lithium cobalt oxide exhibits better rate performance than the traditional repair method to repair the sample. In addition, the ultrafast repair method shows high time and energy efficiency, making it suitable for the actual direct regeneration of lithium cobalt oxide cathodes in lithium-ion batteries. The ultrafast repair method has opened up a new way for the ultrafast and efficient repair of lithium-ion battery cathode materials. (Source: Science Network)

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