The team used the recovered material from end-of-life EV batteries to synthesize compounds with a disordered rocksalt (DRX) structure.
DRX materials are seen as a promising alternative to the regular layered structure of conventional cathode materials, as they increase the capacity of the cathode, allowing development of higher energy density rechargable Lithium ion batteries.
The researchers believe this is the first time such materials have been made from recycled EV battery feedstock.
Results of electrochemical testing showed high performance, that is comparable to materials prepared from conventional high purity reagents, demonstrating the applicability of this new approach.
The cathode, which is the part of batteries that supply electrical current, is the primary limitation for achieving the high-energy, low-cost lithium ion (LI) batteries needed for the transition to zero emissions at tailpipe that will be required to reduce global CO2 emissions and mitigate global warming.
For electric vehicle (EV) batteries, the challenge is to design a high energy battery cathode that will maintain its ability to discharge electricity over a large number of charge-discharge cycles. For recycling experts, the challenge is to design recycling processes for lithium-ion batteries when they reach the end of their useful life.
Researchers at the University of Birmingham have taken these challenges one step further, by tasking themselves with the objective of ‘upcycling’ recovered battery materials, so the waste streams from current EV batteries can be used to manufacture new high-performance batteries.
The research, which is published in ChemRxiV, is a development of previous work demonstrating ascorbic acid (Vitamin C) can be used as a leaching agent, replacing the need for hazardous chemicals in cathode recycling.
The research team led by Professor Peter Slater has now shown recycled material from a cathode containing lithium manganese oxide (LMO) and nickel-rich ‘layered’ oxide (LO), can be upcycled to lithium manganese nickel oxides (LMNO) – a high voltage cathode material, which is attracting high levels of commercial interest.
For the current study the researchers used citric acid (a natural component of citrus fruits) as a leaching agent to further reduce the number of steps in the process, which they applied to cathodes from an end-of-life Gen 1 Nissan Leaf (2011 model, 40,000 miles), and used the recovered LMO as a starting point for LMNO synthesis.
They then used the recovered material to synthesize compounds with a DRX structure.
Professor Slater said: “The challenge is no longer about recycling. Battery chemistry has moved on considerably in the last decade, and, as first-generation EV batteries reach the end of their lives, their components need to be upcycled to deliver chemistries that can be reused in the newer batteries.”
The research team is working on a number of methods for recycling and upcycling battery cathode materials, and is looking for long-term partners for pilot studies, deliver technologies to existing infrastructure, or collaborate on further research to develop novel approaches.
