Abstract Massive deployment of lithium-ion battery inevitably causes a large amount of solid waste. To be sustainably implemented, technologies capable of reducing environmental impacts and recovering resources from spent lithium-ion battery have been an urgent task. The electrochemical reduction of LiNiO2 to metallic nickel has been reported, which is a typical cathode material of lithium-ion battery. In this paper, the electrochemical reduction behavior of LiNiO2 is studied at 750 °C in the eutectic NaCl-CaCl2 molten salt, and the constant cell voltage electrolysis of LiNiO2 is carried out. The results show that Ni(III) is reduced to metallic nickel by a two-step process, Ni(III) → Ni(II) → Ni, which is quasi-reversible controlled by diffusion and electron transfer. After electrolysis for 6 h at 1.4 V, the surface of LiNiO2 cathode is reduced to metallic nickel, with NiO and a small amount of Li0.4Ni1.6O2 detected inside the partially reduced cathode. After prolonging the electrolysis time to 12 h, LiNiO2 is fully electroreduced to metallic nickel, achieving a high current efficiency of 98.60%. The present work highlights that molten salt electrolysis could be an effective protocol for reclamation of spent lithium-ion battery.

中文翻译：

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废锂离子电池熔盐中金属镍的电化学回收

摘要 锂离子电池的大规模部署不可避免地造成了大量的固体废物。为了可持续地实施，能够减少环境影响和从废锂离子电池中回收资源的技术一直是一项紧迫的任务。已有报道将 LiNiO2 电化学还原为金属镍，这是一种典型的锂离子电池正极材料。本文研究了LiNiO2在750℃共晶NaCl-CaCl2熔盐中的电化学还原行为，并对LiNiO2进行了恒压电解。结果表明，Ni(III)通过两步过程被还原为金属镍，Ni(III)→Ni(II)→Ni，这是由扩散和电子转移控制的准可逆过程。在 1.4 V 电解 6 h 后，LiNiO2 阴极表面被还原为金属镍，在部分还原的阴极内部检测到 NiO 和少量 Li0.4Ni1.6O2。将电解时间延长至 12 小时后，LiNiO2 被完全电还原为金属镍，电流效率高达 98.60%。目前的工作强调熔盐电解可能是回收废锂离子电池的有效方案。