Widespread recycling of lithium-ion batteries, especially from electric cars, will sustainably ensure the supply of critical raw materials in the future. Today’s recycling processes recover only some metals, lithium is partially lost, graphite even completely. A new process could now change this: In the RecycleMat project, the Center for Solar Energy and Hydrogen Research Baden- Württemberg (ZSW) has developed a recycling process by which active materials from used lithium-ion batteries can be reprocessed and used directly in new batteries. This is done in relatively simple chemical processes. Material powders reactivated with the new process reach 95 percent of their initial capacity. This is true both for the metal oxides in the positive pole of the batteries and, surprisingly, for the graphite of the negative pole. The researchers have already produced new battery cells from such recycled material and measured them electrochemically.
In the development project “Cathode and anode materials from recycled lithium-ion batteries (RecycleMat)”, which has been funded by the Baden-Württemberg Ministry of Economics, Labor and Tourism with 870,000 euros since August 2020, ZSW has developed a resource-saving process to mechanically separate the active materials from the cathode, the positive pole of the battery, and the anode, the negative pole, from used or defective battery electrodes, clean them and process them into as-new powders via heat treatment.
“The new recycling process makes it possible to reactivate discarded battery electrodes with a cathode structure made of the lithium-nickel-manganese-cobalt oxides commonly used today and an anode made of graphite, and then use them directly in new cells,” explains Dr. Marilena Mancini, scientific director of the project. “Unlike conventional processes, the new process preserves the active materials as such and reuses them directly in new batteries after restoring their original functionality. This approach avoids the currently common and energy-intensive dissolution and recovery of the metallic components with simultaneous loss of the graphite.”
“Recycling batteries is not only desirable, but absolutely necessary. The transition to a climate-neutral economy requires a comprehensive expansion of the circular economy — especially for batteries, which contain various critical raw materials. With high-quality recycling, however, we not only help the environment, but also reduce our dependence on raw material imports in the long term. In view of the current challenges posed by disrupted supply chains, we are thus increasing the resilience and competitiveness of Baden-Württemberg as a business location. The research results of the ZSW make an important contribution to achieving these ambitious goals and show how recycling is feasible in an efficient and resource-saving way,” says Economics Minister Dr. Nicole Hoffmeister-Kraut.
Recycling of cathode and anode masses
As part of the project, new approaches and processes had to be developed in particular for recycling the graphite from the negative terminal of the battery, since graphite is not typically recycled today but is usually simply incinerated. The solution to the problem was a complex temperature treatment that both frees the surface of the particles from impurities and restores the crystalline material structure. The graphite powder treated in this way has 95 percent of the specific energy content of the original material and can be used directly in new batteries.
The materials with the highest value content in the battery are the cathode masses in the positive pole of the battery, as they contain expensive metals such as nickel, manganese, cobalt (NMC) and lithium, among others. Current recycling processes therefore focus on these cathode materials by dissolving them completely in acid during the process and then converting them back into battery raw materials step by step. However, these recycling processes consume a lot of energy and ideally require proximity to a chemical site.
The ZSW process for recycling cathode materials is essentially the same as for graphite and thus avoids precisely these energy-intensive chemical steps. After only two relatively simple process steps, the cathode materials can be directly reused in new batteries and also show significantly more than 90% of their original capacity.
Recovering metals pays off
Over the past decade, scientific and industrial development of lithium-ion batteries has focused on increasing energy density while reducing costs. With the increasing success of electromobility and the mass production of batteries, the end-of-life discussion — recycling — is now also coming to the fore. On the one hand, this discussion is driven by legal framework conditions that, depending on the respective region or country, require a recycling rate of up to 80 percent for the scrapping of electric cars. On the other hand, there are calculations according to which large quantities of recycled metals will be necessary in order to be able to build sufficient batteries for electric vehicles at all in the future.
Although lithium-ion batteries do not contain precious metals, the materials used are far too valuable not to be recycled: It is the large quantities of metals such as copper, nickel, cobalt, aluminum and the lithium that already make battery recycling economical and lucrative due to their metal values: For example, one ton of nickel-bearing rock from a nickel mine contains only about 20 kilograms of nickel.
However, a battery of the type needed for a mid-size car already contains 60 kilograms of nickel. With a battery weight of 500 kilograms, this corresponds to a fivefold enrichment of this metal compared to the mine. In the case of lithium, this factor is much higher: six kilograms of lithium in a battery save the processing of several thousand cubic meters of lithium-containing salt solution when successfully recycled.