Faculty Advisor or Committee Member

Yan Wang, Advisor

Identifier

etd-3761

Abstract

Lithium-ion batteries (LIBs) play a significant role in our highly electrified world and will continue to lead technology innovations. Millions of vehicles are equipped with or directly powered by LIBs, mitigating environmental pollution and reducing energy use. This rapidly increasing use of LIBs in vehicles will introduce a large quantity of spent LIBs within an 8- to10-year span and proper handling of end-of-life (EOL) vehicle LIBs is required. Over the last several years, the Worcester Polytechnic Institute (WPI) team in the Department of Mechanical Engineering has developed a closed-loop lithium ion battery recycling process and it has been demonstrated that the recovered NMC 111 has similar or better electrochemical properties than the commercial control powder with both coin cells and pouch cells, which have been independently tested by A123 Systems and Argonne National Laboratory. In addition, the different chemical compositions of the incoming recycling streams were shown to have little observed effects on the recovered precursor and resultant cathode material. Therefore, the WPI-developed process applies to different spent Li-ion battery waste streams and is, therefore, general. During the last few years, industry has the tendency to employ higher-nickel and lower-cobalt cathode material since it can provide higher capacity and energy density and lower cost. However, higher-nickel cathode material has the intrinsic unstable properties and surface modifications can be applied to slow down its degradation. Here, two facile scalable Al2O3 coating methods (dry coating and wet coating) were applied to recycled NMC 622 and the resultants were systematically studied. The Al-rich layer from the dry coating process imparted improved structural and thermal stability in accelerated cycling performed at 45 °C between 3.0 and 4.3 V, and the capacity retention of pouch cells with dry coated NMC 622 (D-NMC) cathode increased from 83% to 91% compared to Al-free NMC 622 after 300 cycles. However, for wet coated NMC 622 (W-NMC), the increased surface area accompanying by formation of NiO rock-salt like structure could have negative impacts on the cycling performance. There exist three challenges for current LIBs’ recycling research. First of all, most of the research is done in lab-scale and the scale-up ability needs to be proven. The scale-up ability of our recycling process has been verified by our scale-up experiments. The second challenge resides in the flexibility, here once again, with our intentionally designed experiments that having various incoming chemistries, the flexibility is validated. The last challenge is the lack of reliable testing because most of the testing is conducted with coin cells. Coin cells are relatively simple format and lacks persuasion. Here, with various industrial-level cell formats that ranging from coin cell, single layer pouch cell, 1Ah cell and 11Ah cell, a reliable and trustworthy testing is established. With this validation, the hesitation of recruiting recycled materials into industry shouldn’t exist.

Publisher

Worcester Polytechnic Institute

Degree Name

PhD

Department

Materials Science & Engineering

Project Type

Dissertation

Date Accepted

2020-05-12

Accessibility

Restricted-WPI community only

Subjects

Lithium-ion batteries

Available for download on Friday, May 12, 2023

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