Mechanical Weekly

Recycling of Lithium Ion Batteries


Reapplication of the Recovered Materials as Lithium Ion Battery
Materials

Lithium ion batteries (LIBs) are used in modern day portable consumer
electronics like laptops, smartphones or tablets due to their high energy
density and high specific energy. Furthermore, as the most interesting
battery technology for pure and hybrid electric vehicles, there exists a
widespread application of LIBs in private and industrial processes.
Overall, this is directly related to the recycling of LIBs and the respective
components. As an example, Ni and Co are used as transition metal oxides in
cathode materials and due to their price, an economic driven necessity arises.
While there are existing recycling procedures for these metals, the high purity
requirements of the manufacturers diminishes the approach to directly reuse the
recycling materials as cathode materials. Furthermore, recycling itself is
encouraged by the legislation due to several reasons. The demand of lithium,
without any actual replacement, due to the growing application can exceed the
global production already in the 2020s. Especially for the EU, where only two
lithium sites are available, a recycling process is mandatory. Because of this reason,
the European Parliament and Council of the European Union issued several
directives like the Waste of Electrical and Electronic Equipment (WEEE)
2012/19/EU and the End of Life Vehicles (ELV) 2000/53/EC which focuses on the
recycling of batteries from electronic products and electric vehicles. Beginning
from 2006, at least 45 wt% of electrical and electronic equipment need to be
collected by the EU member and the reuse/recovery rate for end of life vehicles is
set to at least 85% weight per vehicle and year. Furthermore, the Battery Directive
2006/66/EC [1] was released to be instituted as the most advanced battery
recycling legislation worldwide. Therefore, each EU member state has to meet a
collection rate of 45% and at least a recycling efficiency of 50 wt% for non-lead-acid
or nickel-cadmium batteries. So far, all processes either on the lab-scale or
commercial are specialized on the metals like nickel, cobalt, manganese and the
lithium from the cathode material or aluminum and copper from the current
collectors.
The electrolyte, with other organic components like the binder, is normally burned
or disposed. However, due to the newest EU Battery Directive, recycling of more
components like the electrolyte or the anode graphitic material is getting more
attention.

LithoRec Process
One recent approach is the LithoRec process (fig. 1). This mechanicalhydrometallurgical
process aims to meet the demands of the EU directive by the
utilization of most materials from a LIB which is a central key of this process.
Battery packs, which are deep discharged by either external resistance or power,
are dismantled and the individual cells are afterwards shredded under an inert
atmosphere. The electrolyte, normally consisting of a mixture of linear and cyclic
carbonates and a conducting salt, which evaporates during this step, is
condensated and collected. In the following step, the remaining electrolyte is
recovered by one of several possible methods. A thermal drying step can be applied
with the disadvantage of losing the conducting salt LiPF6, which is the most costly
part of the electrolyte. One other way is to use dimethyl carbonate (DMC) as a
liquid extractant for electrolyte recovery including LiPF6. Another extraction
method is the use of subcritical or supercritical carbon dioxide (scCO2) to
efficiently recover the organic carbonate solvents. With additional co-solvents
added to the extractant also a high yield of the conductive salt can be obtained.
Subsequently iron parts are removed via magnetic separation and transferred to
scrap metal recycling. The residual non-magnetic material is fed to a zig-zag air
classifier. Here, the shredded material is further separated into two fractions
containing the current collectors and active materials and a fraction consisting of
the separator and plastic foils. The binder is removed by heating up to 400 – 600°C
which additionally causes the detachment of the current collectors from the active
material particles. Due to the application of additional air jet sieves the active
materials are separated from the current collectors. Furthermore, at this stage,
graphite is taken out of the recycling process. Lithium is leached out of the cathode
material, while the active material is dissolved in an acidic mixture, which is further
refined by a hydrometallurgical step.

Electrolyte Recovery
On a lab-scale, the recovered graphite, electrolyte and the cathode material was
chemical and electrochemical characterized and reutilized in lithium ion battery
cells. The proof of principle electrolyte recovery was proven by a static extraction in
an autoclave setup with different electrolytes and separators. Afterwards
commercial 18650er cells were extracted with good results for the organic solvents.
However, only small amounts of the conducting salt could be recovered [2].
Therefore, a flow-through setup was chosen (fig. 2) [3]. By applying either
subcritical or supercritical carbon dioxide with additional solvents, it was
demonstrated that nearly 90% of the electrolyte, including the conducting salt and
aging products, could be recovered from commercial LiNi0.33Co0.33Mn0.33O2
(NMC)/graphite 18650 cells. For the resynthesis of the cathode material,
commercial spent lithium-ion pouch-bag cells, containing a NCM cathode, a
graphite anode and a LiPF6 / organic carbonate solvent based electrolyte, as well as
production rejects of the NCM electrode fabrication were taken as source for the
recycling process [4]. The cells were dissembled and the cathode active material
was dissolved in 10% sulphuric acid. Afterwards, the transition metal oxides were
separated by precipitation as hardly soluble carbonate salts under alkaline
conditions. The actual resynthesis was a hydrometallurgical-precursor synthesis
which produced NCM active material with an electrochemical performance close to
material synthesized from pure solutions. Finally, the two aforementioned
procedures were combined with the graphitic anode material recycling [5]. By
applying subcritical carbon dioxide for electrolyte extraction, in the best case the
electrochemical performance of recycled graphite exceeded the benchmark
consisting of a newly synthesized graphite anode including a 90% recovery of the
electrolyte.

Summary
Overall, it is possible to reutilize nearly the entire components from a spent LIB,
which is of great benefit with regard to the recycling efficiency. Furthermore, the
recycled material is comparable with pristine material. In addition, the removal of
the electrolyte is beneficial not only for the recycling efficiency, but also for
environmental concerns and pilot plant equipment, since the fluorinated
compounds inside a electrolyte represent a risk for both.

Authors
Sascha Nowak1 and Martin Winter

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