Regioselective single-step synthesis of 2-aminoimidazole derivatives

Article abstract of DOI:10.1016/j.tetlet.2019.151122

A convenient single-step strategy for the regioselective assembly of 2-aminoimidazole derivatives is herein described. Through a transition metal-free domino addition/cyclization process, the reactions of unsymmetrical carbodiimides with propargylic amines mediated by Cs₂CO₃ selectively afforded the corresponding polysubstituted 2-aminoimidazoles in moderate to good yields under very mild conditions. The regioselectivity was reversed in the presence of TEA at a higher temperature. The obtained 2-(o-iodoaryl)amino imidazoles could be easily converted to 2-(2-biphenyl)amino imidazole, 2-(o-alkynylphenyl)amino imidazole, benzoimidazo[1,2-a]imidazole and N-(imidazol-2-yl)indole derivatives.

Full text of DOI:10.1016/j.tetlet.2019.151122

JOM
https://doi.org/10.1007/s11837-019-03778-0
Ó 2019 The Minerals, Metals & Materials Society
EXTRACTION AND RECYCLING OF BATTERY MATERIALS
Disassembly Automation for Recycling End-of-Life Lithium-Ion
Pouch Cells
LIURUI LI,1 PANNI ZHENG,1 TAIRAN YANG,1 ROBERT STURGES,1
1,2
MICHAEL W. ELLIS,1 and ZHENG LI
1.—Department of Mechanical Engineering, Virginia Tech, Blacksburg, VA 24060, USA.
2.—e-mail: zhengli@vt.edu
Rapid advances in the use of lithium-ion batteries (LIBs) in consumer elec-
tronics, electric vehicles, and electric grid storage have led to a large number
of end-of-life (EOL) LIBs awaiting recycling to reclaim critical materials and
eliminate environmental hazards. This article studies automatic mechanical
separation methodology for EOL pouch LIBs with Z-folded electrode-separator
compounds (ESC). Customized handling tools are designed, manufactured,
and assembled into an automatic disassembly system prototype that consists
of three modules. Verification experiments utilizing dummy cells prove that
the main components of pouch LIBs (cathode sheets, anode sheets, separators,
and polymer-laminated aluminum film housing) can be automatically sepa-
rated and extracted with well-preserved integrity using our proposed disas-
sembly strategy.
packs into cells, and separating materials of single
INTRODUCTION
cells. Metallurgy processes that consist of pyro-,
As governments worldwide have begun to set
timetables for banning the production of internal
combustion engine vehicles, the estimated annual
demand for lithium-ion batteries (LIBs) from elec-
tric vehicles (EVs) in 2025 will reach 408 GWh,
while this number was merely 20 GWh in 2016.1
Previous studies on cycling performance degrada-
tion of battery packs in hybrid electric vehicles
(HEVs) indicate a battery pack lifetime of only 4.5 to
14.5 years depending on their operating condi-
tions.2,3 The foreseen rapid growth of end-of-life
(EOL) LIBs from HEVs and EVs along with
portable electronics and energy storage plants will
cause severe environmental and safety problems if
not treated properly.4 However, EOL LIBs are a
potential source of valuable metals (e.g., Ni, Mn, Li
or Co), and pressures have already been imposed on
the supply chain of these materials.5 Therefore, it is
vitally important to develop recycling methodologies
that are ecologically friendly and economically
feasible for EOL LIBs in the present time and
future.
hydro-, and bio-metallurgy are generally down-
stream procedures of mechanical pretreatments.4
Despite the dominant role of metallurgical pro-
cesses in industry, their hazardous gas emissions,
acid waste, and high-energy consumption issues
have always been barriers to truly sustainable
closed-loop recycling.7 In recent years, a direct
recycling approach that resynthesizes recycled cath-
ode powder with heat treatment has proved to be
feasible in laboratory-scale research.8–10 Although
this approach claimed to be more ecologically
friendly and energy conserving, it also had much
higher requirements for the material separation
technique in mass production.
As the most critical process in mechanical pre-
treatments, the material separation step mainly
refers to multi-level crushing, sorting, and sieving
techniques in the industry because of their high
automation potential. The total coating material
recovery rate following this destructive crushing
strategy is only 75% even in laboratory-scale
research.11 However, if electrode sheets can be
separated and extracted with well-preserved integ-
rity, the coating material recovery rate can reach as
high as 97.4% utilizing an ANVIL (adhesion neu-
tralization via incineration and impact liberation)
The current EOL LIB recycling methods mainly
combine mechanical pretreatments and metallurgy
processes.6 Mechanical pretreatments comprise
steps of discharging battery packs, dismantling

L. Li, Zheng, Yang, Sturges, Ellis, and Z. Li
process.12 Meanwhile, the black mass yielded from
the destructive crushing strategy is a mixture of
anode coating, cathode coating, and metal impuri-
ties. For metallurgical processes that mostly break
down the compounds of the cathode active materi-
als, metal elemental constituents are recycled by
melting or leaching processes. Nevertheless, for
direct recycling processes, the existence of anode
powders and mixed metals in the black mass
increases the complexity of downstream recycling
processes and may even decrease the electrochem-
ical performance of the final product.13
Hence, an automatic disassembly system is
designed and prototyped specifically for dismantling
and separating cathode sheets, anode sheets, sepa-
rators, and polymer-laminated aluminum film hous-
ing from lithium-ion pouch cells.14 Compared with
the destructive crushing strategy widely adopted in
the industry, our proposed system has great poten-
tial to achieve a higher coating material recovery
rate as well as yielded cathode powder with higher
purity for large-scale mechanical pretreatment pro-
cesses in mass production.
Fig. 1. Configuration of a pouch LIB.
DISMANTLING SEQUENCE DESIGN
The shape of lithium-ion secondary cells can be
divided into three main groups: cylindrical, pouch,
and prismatic. Their differences in housing material
and electrode-separator compound (ESC) designs
lead to certain advantages and disadvantages in
manufacturing processes and applications. Rela-
tively low production costs and highly simplified
packaging processes allow deploying pouch cells
extensively on EVs and portable electronics.
The typical structure of pouch LIBs is an ESC
sealed by a stamped polymer-laminated aluminum
film (Fig. 1). Anodes and cathodes are alternately
stacked and electrically isolated by the separator to
form the ESC. Depending on the continuity of
electrode sheets and the separator, ESCs are clas-
sified into three styles: single-sheet stacking, wind-
ing, and Z-folding. The single-sheet stacking style is
commonly used in laboratory cell assembly, while
the winding style has proved to be the most
productive design in industrial applications due to
its continuous electrode and separator feeding
strategy. In recent years, efforts to decrease the
cycle time of the Z-folding process utilizing robots
and customized mechanisms have been made,15,16
which resulted in a rapid technology transition to
the mass production scale. Meanwhile, Z-folded
ESCs with discrete electrodes and continuous sep-
arators require more complicated mechanisms to
disassemble than the other two types. Thus, in this
article, we focused on the recycling of EOL pouch
LIBs with z-folded ESCs.
Fig. 2. Continuous process for recovery of cathode coating from
end-of-life LIBs.
battery disassembly system has great potential to
ensure the automatic separation of polymer-lami-
nated aluminum films, separators, cathode sheets,
and anode sheets with well-preserved integrity.
Before being fed into the disassembly system, EOL
Figure 2 shows the continuous process for direct
recycling of cathode materials recycled from EOL
LIBs in our laboratory-scale production line. As part
of this direct recycling strategy, our proposed single-

Disassembly Automation for Recycling End-of-Life Lithium-Ion Pouch Cells
LIBs need to be fully discharged in saltwater to
avoid any explosions or fire hazards. Although the
saltwater shorting process may introduce HF and
salt impurities, the proposed disassembling process
will still function well to sort the electrodes and
benefit the separation efficiency in the downstream
processing with fewer impurities introduced to the
cathode recycling process. Then, three sealed edges
along with metal tabs are sequentially cut off from
the core area. The remaining folded polymer-lami-
nated aluminum film housing film needs to be
stretched from both sides by external forces to
extract the ESC. Separators need to be unfolded and
continuously fed forward. Minimum human inter-
vention is required after this step for removing
adhesion tapes at the endpoint of continuous sepa-
rators. Supplementary Figure S-1 gives a few
examples of the taping patterns. The tape-peeling
module (see supplementary Figure S-1b) aims at
skiving off these tapes automatically. For EOL
LIBs, electrode sheets tend to attach on the sepa-
rator because of the surface tension of the elec-
trolyte or the natural bond due to aging. Thus,
specialized skiving tools are needed to scrape cath-
ode and anode sheets off from opposite sides of the
separator.
The clearance between the trimming blades and
edges of the lower trimming base is controlled
at< 0.3 mm, while edges of the upper trimming
base keep a 0.5-mm distance from the trimming
blades to protect ESCs and avoid unnecessary
cutting resistance force. Two conveyor roller sets,
each consisting of five power train gears and three
25A polyurethane rollers, are assembled inside both
the lower and upper trimming bases along with
rotary shafts and ball bearings. These rollers with a
rough surface texture can hold the pouch cell in
position as well as transport the pouch without
slipping.
The handling scenario of the pouch trimming
process is as follows:
1. Feed fully discharged pouch cell into the trim-
ming base.
2. Conveyor roller sets transport the pouch into
the trimming position.
3. The trimming toolset moves down toward the
trimming base and cuts off three edges of the
housing.
4. Linear motion stage transports the trimming
base forward.
5. Conveyor rollers deliver the trimmed pouch
toward the next module.
A modularization design is adopted to increase
the flexibility of the disassembly system. The sys-
tem is physically designed and built into three
modules: pouch trimming, housing removal, and
electrode sorting. These modules should finish three
key steps encircled correspondingly in Fig. 2. Each
module contains several customized key appara-
tuses to achieve the desired motions. The proto-
typed disassembly system was then tested with
dummy cells assembled by a semi-automated bat-
tery manufacturing line (Figure S2).
Housing Removal Module
In this module, the remaining polymer-laminated
aluminum film housing is peeled off from the
trimmed pouch. Hence, the recovery of polymer-
laminated aluminum film from the EOL LIBs is
accomplished in this module. Figure 4a demon-
strates the key procedure to stretch the housing
and extract the ESC, while Fig. 4b shows the
prototype of this module.
The housing removal module consists of a three-
part gripping apparatus with specialized function-
alities: the transporting grip, vacuum grip, and
clamping grip. The transporting grip installed on a
rotary base is designed to hold and transport the
trimmed pouch and the ESC. The distance between
two flat arms at their parallel position equals the
thickness of the targeted pouch core. The vacuum
grip is equipped with a height-adjusting vacuum
cup on each arm driven by 12 V DC air pumps.
These bellows suction cups are made of translucent
silicone, which provides sufficient adaptivity to the
uneven surface of the polymer-laminated aluminum
film housing. The clamping grip is a fixture with a
stationary flat base and vertically movable top
clamp. The width and depth of the groove on the
movable top clamp are compatible with the size of
targeted pouch cells in order to support and guide
the ESC while the vacuum grip peels off the
trimmed housing.
SYSTEM DESIGN AND VERIFICATION
Pouch Trimming Module
In this module, the front edge of the pouch that
carries the electrode tabs is cut off, thus separating
each of the electrode layers from the current
collecting structure. The opposing side edge seals
are also removed so that the polymer-laminated
aluminum film housing can be fully separated from
the compound.
As shown in Fig. 3, the pouch trimming module
consists of three main components: the trimming
blade set, trimming base set, and conveyor roller
set. The trimming blade set is a triple-way alu-
minum frame with heavy duty breakaway blades
fixed correspondingly in their grooves. Each blade is
tilted 25 degrees from the horizontal direction to
decrease the cutting resistance force as well as
maintain the cutting speed. The lower trimming
base cooperates with the trimming toolset in the
trimming process by providing solid support to the
double-layered polymer-laminated aluminum film.
The handling scenario of the pouch removal
process is as follows:

L. Li, Zheng, Yang, Sturges, Ellis, and Z. Li
Fig. 3. (a) CAD design and (b) prototype of the pouch removal module.
Fig. 4. (a) Schematic and (b) prototype of the pouch removal module.

Disassembly Automation for Recycling End-of-Life Lithium-Ion Pouch Cells
1. The transporting grip extracts the trimmed
pouch out of the trimming base.
2. The rotary base spins 90 degrees to feed the
trimmed pouch into the clamping grip.
3. The clamping grip clamps the untrimmed side
of the pouch core.
4. The rotary base spins 45 degrees to move the
clamping grip away from the operation path of
the vacuum grip.
5. The vacuum grip closes the jaw, and the
vacuum cups secure the upper and lower side
of the polymer-laminated aluminum film hous-
ing.
while stainless steel guiding posts and break-away
skiving blades work as pairs to scrape electrodes off
from the separator. After the first guiding post
presses down on the soft separator, the front edge of
the electrode sheets will detach from the separator
because of the cathode sheets’ lower compliance to
deformation. As the separator is still rolling for-
ward, the first skiving blade will seek its way
through the gap between the front edge of the
cathode sheets and the separator. The cathode
sheets will then fall into the collecting bin because
of gravity. Anode sheets attached on the upper
surface of the separator are scraped off by the
second guiding post and skiving blade in a similar
sequence.
6. The jaws of the vacuum grip peel back the
upper and lower side of the polymer-laminated
aluminum film housing until the front edge of
the ESC is fully exposed.
The handling scenario of the pouch removal
process is as follows:
7. The rotary base spins back 45 degrees.
8. The transporting grip grasps the ESC.
9. The jaws of the vacuum grip the polymer-
laminated aluminum film housing further
open to its 180-degree configuration while the
untrimmed side of the housing pushes the
electrode-separator compound into the trans-
porting grip.
10. The polymer-laminated aluminum film hous-
ing falls to a waste-recycling stream after the
12-V DC pump shuts down.
11. The transporting grip delivers the ESC into
the next module.
1. The vacuum conveyor secures the top layer of
the Z-folded separator and delivers it through
the pinch roller set.
2. The pinch roller set squeezes the top layer of the
separator as the vacuum conveyor releases the
vacuum.
3. The first guiding post and second skiving blade
drop vertically to press down the separator.
4. The pinch roller set continuously feeds the
separator forward until the separator film is
fully paid off.
5. Components of the electrode-separator com-
pound get separated into three collecting bins
correspondingly for further treatments.
Electrode Sorting Module
The separation of cathodes, anodes, and separators
is a critical process for any LIB recycling processes.
It directly influences the purity and recovery rate of
the black mass. Our proposed electrode sorting
strategy extracts cathode sheets and anode sheets
respectively without applying destructive forces. By
automatically stretching and feeding the Z-folded
separator, cathode and anode sheets attached on
opposite sides of the separator are scraped off by
specialized toolsets as in the schematic shown in
Fig. 5a. Since a commonly used polyvinylidene
fluoride (PVDF) binder can be removed by either
dissolving in organic solvents or decomposing at
temperatures > 400°C,11 multiple combinations of
chemical, thermal, and mechanical treatments are
then available for breaking the adhesion between
the Al foil and cathode coating. The prototype of this
module is shown in Fig. 5b.
The electrode sorting module consists of four
apparatuses: the vacuum conveyor, guiding posts,
skiving blades, and pinch roller set. The vacuum
conveyor is a height-adjusting vacuum cup inte-
grated on an X–Y motion platform. The 12-V DC air
pump enables the vacuum cup to carry the top layer
of the separator longitudinally to the pinch rollers.
These urethane pinch rollers with a 35A durometer
are able to feed the separator forward continuously
Control Architecture
A total of 11 stepper motors, 22 limit switches, 3
servo motors, and 3 pumps were installed in the
prototyped disassembly system. The realization of
this designed handling scenario for all three mod-
ules highly depends on an integrated control archi-
tecture. Therefore, a LabVIEW platform was chosen
to automate stepper motors, limit switches, servo
motors, and vacuum systems. This system-design
platform offers great flexibility for design modifica-
tions, which will benefit the future optimization of
this project. The derived control architecture of the
prototyped automatic disassembly system is as
shown in Fig. 6.
Stepoko motion control boards (MCD) with GRBL
firmware were used as local controllers for stepper
motors and limit switches. Each module was
equipped with one to two MCDs to achieve the
designed linear motion as well as relocate toolsets to
their initial position. Meanwhile, all three servo
motors and three DC vacuum pumps were con-
trolled by one Arduino Mega 2560 R3 board. Lab-
VIEW, which served as a system controller for the
ensemble shown in Fig. 7, was able to supervise the
hand-off functions between modules and to indicate
event timing for system data collection.

L. Li, Zheng, Yang, Sturges, Ellis, and Z. Li
Fig. 5. (a) Schematic and (b) prototype of the electrode sorting module.
Fig. 7. Prototyped disassembly system overview.
Concept Verification
To assure the safety of the operators at the
current prototyping stage, dummy pouch cells were
used to verify the feasibility of the designed disas-
sembly system. In dummy pouch cells, non-toxic
materials replaced key components of functional
Fig. 6. Control architecture of the prototyped automatic recycling
system.

Disassembly Automation for Recycling End-of-Life Lithium-Ion Pouch Cells
Fig. 8. Twelve key frames corresponding to (a) handling scenario 2, 3, 4, and 5 of the trimming module, (b) handling scenario 1, 4, 8, and 11 of
the housing removal module, and (c) handling scenario 1, 3, 4, and 5 of the electrode sorting module.
LIBs with similar physical properties. The outer
dimensions of the dummy pouch cells were
50.0 mm 9 60.0 mm 9 5.8 mm with tolerance of
0.5 mm. These values followed the size of H605060
2000mAh LIBs, which will be our test subjects for
the future development of this system.
Recycling of the polymer-laminated aluminum film
is accomplished in the fourth frame of Fig. 8b. The
Al film housing falls off from the bellows cup after
the DC pump releases the vacuum. The four frames
in Fig. 8c correspond to handling scenario 1, 3, 4,
and 5 of the electrode sorting module. As shown in
the fourth frame of Fig. 8c, it is clear that the blue
cardboards representing cathode sheets, the green
cardboards representing anode sheets, and the
separator have been successfully separated and
stored in three positions. Future research activities
will focus on testing the existing prototyped disas-
sembly system with H605060 2000 mAh LIBs under
an inert atmosphere and designing the unwinding
module for the pouch cells with wound ESCs (see
supplementary Figure S-3).
Finally, we want to point out the limitations of the
designed disassembly automation. For example, the
current prototype lacks flexibility to process the
heavily deformed cells present in the battery recy-
cling stream. In addition, for certain battery
designs, the battery electrode and separator sheet
layers are glued together, which poses challenges
for the electrode skiving and sorting process. Addi-
tional treatment steps or more flexible and smarter
designs are needed to address these challenges.
A pneumatic semiautomated Z-folded LIB assem-
bly line used to assemble dummy cells is shown in
supplementary Figure S-2; 0.3-mm-thick card-
boards were trimmed by a die cut machine to
replace the double-coated current collectors. The
folding machine then stacked these cardboards with
a continuous separator to form the dummy ESC,
which was contained inside the polymer-laminated
aluminum film stamped by the pouch-forming
machine. After two side edges of the stamped
housing had been sealed up by the heat-sealing
machine, diluted 3 M liquid glue was filled inside
the dummy cells to mimic the adhesion between the
electrodes and separator. The polymer-laminated
aluminum film housing was finally evacuated and
sealed up in the chamber of the vacuum sealing
machine.
Sealed dummy cells were then disassembled by
the prototyped automatic disassembly system. Fig-
ure 8 shows four key frames from the testing
records of each module. Handling of scenario 2, 3,
4, and 5 of the trimming module is sequentially
shown in Fig. 8a. The material flow of the single
frame in Fig. 8b and c is from the right-hand side to
the left-hand side for clearer interpretation. Four
frames in Fig. 8b correspond to handling scenario 1,
4, 8, and 11 of the housing removal module.
CONCLUSION
An automated disassembly system for EOL Z-
folded pouch LIBs has been introduced and proto-
typically realized. Customized tool sets aiming at
automatic material handling are designed in each
module. Success in treating dummy cells proved the

L. Li, Zheng, Yang, Sturges, Ellis, and Z. Li
effectiveness of the proposed disassembly strategy.
Within this automated disassembly system, cathode
sheets, anode sheets, separators, and polymer-lam-
inated aluminum film housing are automatically
separated. The integrity of cathode sheets can be
well preserved. Compared with the destructive
crushing strategy, such improvement will greatly
benefit downstream recycling processes, especially
for the direct recycling of LIBs.
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