As the demand for lithium-ion batteries for electric vehicles is increasing, it is important to recover valuable metals from waste lithium-ion batteries. In this study, the effects of gas flow rate and hydrogen partial pressure on hydrogen reduction of NCM-based lithium-ion battery cathode materials were investigated. As the gas flow rate and hydrogen partial pressure increased, the weight loss rate increased significantly from the beginning of the reaction due to the reduction of NiO and CoO by hydrogen. At 700 °C and hydrogen partial pressure above 0.5 atm, Ni and Li2O were produced by hydrogen reduction. From the reduction product and Li recovery rate, the hydrogen reduction of NCM-based cathode materials was significantly affected by hydrogen partial pressure. The Li compounds recovered from the solution after water leaching of the reduction products were LiOH, LiOH·H2O, and Li2CO3, with about 0.02 wt% Al as an impurity.

1. Introduction
2. Experimental Procedure
3. Results and Discussion
    3.1. 양극재 수소환원의 열역학
    3.2. 수소환원에 미치는 온도의 영향
    3.3. 수소환원에 미치는 유량과 수소 분압의 영향
    3.4. 환원 생성물의 수침출과 Li 회수
4. Conclusions
References

• 이소영(경북대학교 금속재료공학과) | So-Yeong Lee (Department of Materials Science and Metallurgical Engineering, Kyungpook National University, Daegu 41566, Republic of Korea)
• 이소연(㈜앨앤에프) | So-Yeon Lee (L&F Co., Ltd, Daegu 42620, Republic of Korea)
• 이대현(고려아연) | Dae-Hyeon Lee (Korea Zinc, Ulsan 44997, Republic of Korea)
• 손호상(경북대학교 금속재료공학과) | Ho-Sang Sohn (Department of Materials Science and Metallurgical Engineering, Kyungpook National University, Daegu 41566, Republic of Korea) Corresponding author