2021 Fiscal Year Research-status Report
Low/no-corrosion leaching of spent lithium-ion battery cathode materials in hydrothermal water using amino acid or mixed organic acids as the leachant
| Project/Area Number |
21K12302
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| Research Institution | Tohoku University |
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Principal Investigator |
鄭 慶新 東北大学, 工学研究科, 特任助教 (30835509)
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| Project Period (FY) |
2021-04-01 – 2024-03-31
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| Keywords | Lithium-ion batteries / Metal recovery / Hydrothermal leaching / Acid corrosion / Glycine / Citric acid / Mixed organic acids / Unreacted core model |
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| Outline of Annual Research Achievements |
To achieve high leaching efficiency and avoid acid corrosion during hydrothermal leaching of spent lithium-ion battery (LIB) cathode materials, a screening of new acid leachant was executed. Based on a literature investigation and initial experiments, a kind of amino acid, glycine, was chosen tentatively.
With glycine, hydrothermal leaching of LIB cathode materials including commercial LiCoO2 (LCO), LiNiO2 (LNO), and LiMn2O4 (LMO), and spent LiNixMnyCo1-x-yO2 (NMC) cathode material, was performed at 90-200°C for 5-90 min. The leaching efficiencies of all metals with glycine were lower than those using citric acid under the same conditions, especially for Mn. The aqueous solution during the hydrothermal leaching with glycine exhibited a pH value of 5.8-9.0, close to neutral. The above results indicated that the use of glycine can decrease acid corrosion, although its leaching performance is lower than citric acid.
To combine the advantages of citric acid on leaching performance and glycine on low acid corrosion, a citric acid/glycine mixture was proposed and applied to be the acid leachant for the hydrothermal leaching of spent NMC cathode material at 200°C for 5 min. After a parameter optimization, the best leaching performance was found at the ratio of citric acid/glycine of 10%/90%; the leaching efficiency of each metal achieved >90%, and the pH value during the leaching process changed from 3.6 to 7.0. This was the first time to achieve the acid leaching of spent LIB cathode materials through a green process with high efficiency of about 100% and low/no acid corrosion.
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| Current Status of Research Progress |
Current Status of Research Progress
2: Research has progressed on the whole more than it was originally planned.
Reason
Based on a literature investigation and initial experiments using glycine as the acid leachant, a kind of mixed organic acid, citric acid/glycine mixture, was proposed and applied as a suitable acid leachant to achieve high leaching efficiency and resolve the problem of acid corrosion during hydrothermal leaching of spent lithium-ion battery (LIB) cathode materials. After a parameter optimization, the leaching efficiency of each metal achieved >90% and the pH value during the leaching process changed from 3.6 to 7.0. This result indicated that the acid leaching of spent LIB cathode materials with ~100% efficiency and low/no acid corrosion was firstly realized through a green process.
On the whole, the project is progressing smoothly in line with the research plan, and the obtained results were even better than expected.
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| Strategy for Future Research Activity |
Based on the results of the first fiscal year of this project, a suitable acid leachant, which can achieve high leaching efficiency and resolve the problem of acid corrosion during hydrothermal leaching of spent lithium-ion battery (LIB) cathode materials, has been found to be a citric acid/glycine mixture with the ratio of citric acid/glycine of 10%/90% (referred to "acid X"). As a new acid leachant during hydrothermal leaching of LIB cathode materials, acid X has many blank areas to explore.
In the second fiscal year, acid X will be used to achieve continuous hydrothermal leaching of spent LIB cathode materials using a flow system, and the leaching performance and acid corrosion of acid X will be evaluated. Then, a kinetic study of hydrothermal leaching of commercial and spent LIB cathode materials will be performed by using the unreacted core model. Meanwhile, some papers will be written and submitted to top journals in this area.
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| Causes of Carryover |
There are two main reasons for incurring amount to be used next fiscal year.
The first and the biggest reason is COVID-19. Because of the global epidemic, attending an academic conference in a related area became very difficult. Many international and domestic conferences were canceled or postponed, and even when some were available, they were only held online, which greatly reduced the significance and motivation to participate in the conference. In addition, the epidemic also affected the global manufacturing and transportation, making it very difficult or impossible to order some goods such as specific imported parts used in experiments.
The second reason is the problem caused by the unskilled use of KAKENHI project funding. Since this is the first time to manage a KAKENHI project, it requires time to learn how to use KAKENHI project well.
In the next step, the possible effects of COVID-19 must be taken into consideration, to attend online conferences more positively and ensure that the required items or parts can be bought in advance as far as possible. And, KAKENHI project funding will be managed and used in a more orderly and reasonable way.
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