Recycling and upcycling of cathode materials from lithium-ion batteries

Madge, Rosie ORCID: 0000-0001-7588-6772 (2024). Recycling and upcycling of cathode materials from lithium-ion batteries. University of Birmingham. Ph.D.

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Abstract

In the past decade there has been a significant increase in the number of electric vehicles (EVs) globally. In turn, this has led to increased amounts of end-of-life (EOL) lithium-ion batteries (LIBs). These EOL LIBs must be recycled to allow the materials from them to be reused. Ideally, closed-loop recycling methods should be used to allow recovered materials to be directly used in the manufacture of materials for new LIBs.
This work investigates recycling of cathode material from a Gen 1 Nissan Leaf which contains a mixture of spinel LiMn2O4 (LMO) and a Ni-rich layered oxide (LO). Both EOL and quality control (QC) rejected material was investigated in this thesis as they are representative of EOL batteries and manufacturing scrap that is likely to be present in the LIB recycling market.

This work develops a method which allows for separation of the LMO and LO phases. Citric acid was employed as a leaching agent to selectively leach the LMO component into solution while leaving the LO phase in the cathode. Citric acid also acts as a delamination agent to remove the remaining LO from the Al current collector. The optimal conditions for allowing facile separation with the best selectivity were 10 mL of 1 M acid at 50 °C with 0.3 g of cathode for 20 mins. The LMO and LO phases were recovered and then utilised in new LIBs. However, LMO is no longer used commercially and has a lower value than Ni/Co containing cathodes therefore this work investigated upcycling it into new cathode materials.

Firstly, LMO was upcycled into Ni-doped spinels. LiMn1.5Ni0.5O4 (LMNO) is attracting commercial interest due its high operating voltage and high energy density. Both EOL and QC LMO were upcycled into LMNO. This work investigates improving the electrochemical performance of upcycled LMNO by changing the composition, synthesis temperature, and synthesis atmosphere. EOL and QC LMNO were shown to have an improved capacity retention compared to pristine LMNO.

This work also investigates upcycling LMO into Mn-containing cation disordered rocksalt (DRS) materials. Firstly, work was done to prevent degradation and improve the electrochemical performance of Li4Mn2O5 using coatings and alternative electrochemical testing procedures. F, Ni, Zn and Na doping were also investigated as ways to improve the capacity retention. Na doping was found to provide the best capacity retention of 78.9% after 20 cycles. Finally, EOL and QC LMO were upcycled into Li4Mn2O5 and Li2MnO2.25F which performed with a comparable electrochemical performance to DRS made using pristine starting materials.

This work details a method for the separation of mixed cathodes containing LMO and LO. It also demonstrates a method to upcycle lower value cathode materials, such as LMO, into current and next generation cathode materials, such as LMNO and DRS materials.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):