FIELD OF INVENTION
[0001] The present disclosure broadly relates to the field of battery. Particularly,
the present disclosure relates to a process of preparing an electrode film.
BACKGROUND OF INVENTION
5 [0002] With increasing global demand for batteries, developing more efficient
processes for preparation of electrode composition is a growing focus of the
industry. The conventional electrode preparation for lithium-ion batteries often
involves a wet electrode process. Conventional wet electrode processes include
dissolving the binder in a solvent and dispersing the active material and conductive
10 additive mixture in the binder solution. The resulting slurry is coated over a current
collector and the solvent is removed by heating. The resultant electrode consists of
binder getting coated on the active material. Due to the inconvenience and
impracticality of scaling up such wet processes, the battery manufacturing has
shifted toward dry electrode processes.
15 [0003] Dry processed electrodes permit better ionic conductivity when compared
to wet processed electrodes at a similar electrode density. Electrode engineering
plays a significant role in determining the key performance factors of a lithium-ion
cell such as volumetric energy density and rate performance. While electrode
density, and mass loading of active material play key roles in determining the cell’s
20 energy density. The electron and lithium-ion transport properties of the electrode
determine the rate performance of the cell. One major factor upon which the
electron and ion transportation depend directly on is electrode density. Improving
electrode density of dry electrodes could also enhance the electrode properties like,
peel strength, initial columbic efficiency (ICE), and energy density while
25 maintaining good ionic conductivity of the electrodes. An electrode with high
density with reduced porosity provides a higher volumetric energy density.
However, as a consequence of the reduced porosity in such electrodes, the lithiumion transfer kinetics are severely impeded due to reduced surface area, putting an
upper limit on the electrode density. An electrode with lower density and higher
30 porosity provides a better ion transport. However, loosely bound active materials
impede the electron transport in the electrode, creating a higher polarization resistance on the electrode. Additionally, volume expansion during cycling hampers
structural integrity of the electrode, leading to loss of capacity during cycling. As a
result of this trade off, it is necessary to strike a balance between the electrode
density and transport properties to achieve an optimum cell performance.
5 [0004] Therefore, there exists a need for developing an efficient dry electrode
process to achieve an electrode with optimised porosity and electrode density.
SUMMARY OF THE INVENTION
[0005] In a first aspect of the present disclosure, there is provided a process for
10 preparing an electrode film, the process comprising: a. pre-mixing an active
material with at least one conductive additive and a non-fibrillating binder to obtain
a first mixture; b. adding a fibrillating binder to the first mixture followed by high
shear mixing to obtain a second mixture; c. first calendering the second mixture
through a first set of rollers (101) having a roller gap in a range of 100 to 400 µm,
15 and at a differential roller speed in a range of 40 to 88% to obtain a first film ; and
d. second calendering the first film through a second set of rollers (102) at a roller
force in a range of 12 to 25 kN, at a differential roller speed in a range of 70 to 80%,
to obtain an electrode film, wherein the electrode film has a porosity in a range of
17 to 22% and a density in a range of 1.7 to 3.9 g/cc.
20 [0006] In a second aspect of the present disclosure, there is provided an electrode
film obtained by the process as disclosed herein, the electrode film comprising: a.
an active material; b. at least one conductive additive; and c. at least one binder,
wherein the electrode film that has a porosity in a range of 17 to 22% and a density
in a range of least 1.7 to 3.9g/cc.
25 [0007] In a third aspect of the present disclosure, there is provided an electrode
comprising the electrode film as disclosed herein, laminated on one side or both
sides of a current collector.
[0008] In a fourth aspect of the present disclosure, there is provided a method of
preparing an electrode as disclosed herein, the method comprising:
30 a. obtaining a mixture comprising an active material, at least one
conductive additive, a non-fibrillating binder, and a fibrillating binder;b. allowing a first part of the mixture from input A to pass through a first
set of rollers (101) for first calendering to obtain a first film A, and allowing
a second part of the mixture from input A’ to pass through a third set of
rollers (103) for first calendering to obtain a first film A’;
5 c. second calendering the first film A through a second set of rollers (102)
to obtain a second film B and second calendering the first film A’ through a
fourth set of rollers (104) to obtain a second film B’; and
d. simultaneously laminating the second film B and the second film B’ on a
current collector to obtain the electrode,
10 wherein the electrode has a porosity in a range of 17 to 22% and a density
in a range of 1.7 to 3.9 g/cc.
[0009] In a fifth aspect of the present disclosure, there is provided a first
electrochemical cell comprising: a. a cathode; b. an anode comprising the electrode
film as; and c. an electrolyte.
15 [0010] In a sixth aspect of the present disclosure, there is provided a second
electrochemical cell comprising: a. a cathode comprising the electrode film as
disclosed herein; b. an anode; and an electrolyte.
[0011] In a seventh aspect of the present disclosure, there is provided a third
electrochemical cell comprising: a. the electrode as disclosed herein as cathode; b.
20 the electrode as disclosed herein as anode; and c. an electrolyte.
[0012] In an eighth aspect of the present disclosure, there is provided a use of the
electrode film as disclosed herein or the electrode as disclosed herein, as a working
electrode in an electrochemical cell
[0013] These and other features, aspects, and advantages of the present subject
25 matter will be better understood with reference to the following description. This
summary is provided to introduce a selection of concepts in a simplified form. This
summary is not intended to identify key features or essential features of the claimed
subject matter, nor is it intended to be used to limit the scope of the claimed subject
matter.

I/We Claim:
1. A process for preparing an electrode film, the process comprising:
a. pre-mixing an active material with at least one conductive additive and a
non-fibrillating binder to obtain a first mixture;
5 b. adding a fibrillating binder to the first mixture followed by high shear
mixing to obtain a second mixture;
c. first calendering the second mixture through a first set of rollers (101)
having a roller gap in a range of 100 to 400 µm, and at a differential roller
speed in a range of 40 to 88% to obtain a first film ; and
10 d. second calendering the first film through a second set of rollers (102) at a
roller force in a range of 12 to 25 kN, at a differential roller speed in a
range of 70 to 80%, to obtain an electrode film,
wherein the electrode film has a porosity in a range of 17 to 22% and a density
in a range of 1.7 to 3.9 g/cc.
15 2. The process as claimed in claim 1, wherein the first set of rollers (101)
comprises ‘m’ number of rollers wherein each pair of rollers has a
progressively decreasing roller gap; the second set of rollers (102) comprises
‘n’ number of rollers wherein each roller rotates in a progressively increasing
roller speed; ‘m’ is in a range of 2 to 5; and ‘n’ is in a range of 2 to 10.
20 3. The process as claimed in claim 1, wherein the first set of rollers (101) and
the second set of rollers (102), independently rotate at a speed in a range of at
a roller speed in a range of 0.5 to 25 m/min.
4. The process as claimed in claim 1, wherein the first set of rollers (101) and
the second set of rollers (102) have a roller temperature in a range of 100 to
25 200 °C.
5. The process as claimed in claim 1, wherein the active material is in a weight
range of 96 to 99% (w/w) and is selected from natural graphite, synthetic
graphite, silicon, silicon-graphite, nickel-manganese-cobalt oxide (NMC),
lithium-nickel-cobalt-aluminium oxides (NCA), lithium iron phosphate
30 (LFP), or lithium-manganese-rich (LMR).
6. The process as claimed in claim 1, wherein the at least one conductive
additive is in a weight range of 0.5 to 2% (w/w) and is selected from carbon
black, graphene, mesoporous carbon, acetylene black, activated carbon, super
P, carbon nanofiber, vapour grown carbon nanofiber, carbon nanotube, or
5 combinations thereof.
7. The process as claimed in claim 1, wherein the fibrillating binder is in a
weight range of 0.5 to 3% (w/w) and is selected from polytetrafluoroethylene
(PTFE), fluoroethylene vinyl ether (FEVE), fluoroethylene polymer (FEP),
or combinations thereof.
10 8. The process as claimed in claim 1, wherein the non-fibrillating binder is in a
weight range of 0.5 to 3% (w/w) and is selected from polyvinylidene fluoride
(PVDF), hydroxypropyl methyl cellulose (HPMC), hydroxypropyl cellulose
(HPC), hydroxyethyl cellulose (HEC), sodium carboxymethyl cellulose (NaCMC), carboxymethyl cellulose (CMC), styrene butadiene rubber,
15 polyethylene glycol (PEG), polyacrylic acid (PAA), polyethylene oxide
(PEO), poly vinyl pyrrolidone (PVP), poly(vinylidene fluoride-cohexafluoropropylene) (PVDF-HFP), or combinations thereof.
9. The process as claimed in claim 1, wherein high shear mixing is carried out
at a tip speed in a range of 30 to 41m/s, for a period in a range of 5 to 60
20 minutes, until temperature of the mixture is in a range of 65 to 85 °C.
10. The process as claimed in claim 1, wherein the second mixture is cooled to a
temperature below 19°C followed by jet milling, prior to first calendering.
11. The process as claimed in claim 1, wherein the process further comprises
laminating the electrode film upon a current collector to obtain an electrode.
25 12. An electrode film obtained by the process as claimed in claim 1, the electrode
film comprising:
a. an active material;
b. at least one conductive additive; and
c. at least one binder,
30 wherein the electrode film has a porosity in a range of 17 to 22% and a density
in a range of 1.7 to 3.9 g/cc.
3413. The electrode film as claimed in claim 12, wherein at least one binder is
selected from a fibrillating binder, a non-fibrillating binder or combinations
thereof.
14. The electrode film as claimed in claim 12, wherein the electrode film has an
aerial loading in a range of 10 to 30 mg/cm2
5 .
15. The electrode film as claimed in claim 12, wherein the electrode film has a
porosity in a range of 18 to 22% and a density in a range of 1 to 2 g/cc, when
the electrode film is an anode film.
16. The electrode film as claimed in claim 15, wherein the electrode film exhibits
10 a specific capacity in a range of 340 to 360 mAh/g.
17. The electrode film as claimed in claim 12, wherein the electrode film has a
porosity in a range of 17 to 21% and a density in a range of 3 to 4 g/cc, when
the electrode film is a cathode film.
18. The electrode film as claimed in claim 17, wherein the electrode film exhibits
15 a specific capacity in a range of 205 to 215 mAh/g.
19. An electrode comprising the electrode film as claimed in any one of the claims
12 to 18, laminated on one side or both sides of a current collector.
20. A method of preparing an electrode as claimed in claim 19, the method
comprising:
20 a. obtaining a mixture comprising an active material, at least one conductive
additive, a non-fibrillating binder, and a fibrillating binder;
b. allowing a first part of the mixture from input A to pass through a first set
of rollers (101) for first calendering to obtain a first film A, and allowing
a second part of the mixture from input A’ to pass through a third set of
25 rollers (103) for first calendering to obtain a first film A’;
c. second calendering the first film A through a second set of rollers (102) to
obtain a second film B and second calendering the first film A’ through a
fourth set of rollers (104) to obtain a second film B’; and
d. simultaneously laminating the second film B and the second film B’ on a
30 current collector to obtain the electrode,
wherein the electrode has a porosity in a range of 17 to 22% and a density in
a range of 1.7 to 3.9 g/cc.
21. The method as claimed in claim 20, wherein the first set of rollers (101) is
placed at input A near proximal end; the second set of rollers (102) is placed
5 successive to the first set of rollers (101); the third set of rollers (103) is placed
at input A’ near distal end; the fourth set of rollers (104) is placed successive
to the third set of rollers (103); and the last roller of the second set of rollers
(102) meet the last roller of the fourth set of rollers (104) at the center.
22. The method as claimed in claim 20, wherein the first set of rollers (101) and
10 the third set of rollers (103) have a roller gap in a range of 100 to 400 µm and
rotate at a differential roller speed in a range of 40 to 88%.
23. The method as claimed in claim 20, wherein the second set of rollers (102)
and the fourth set of rollers (104) exert a roller force upon the first film in a
range of 12 to 25 kN and rotate at a differential roller speed in a range of 70
15 to 80%.
24. The method as claimed in claim 20, wherein the first set of rollers (101)
comprises ‘m’ number of rollers wherein each pair of rollers has a
progressively decreasing roller gap; the second set of rollers (102) comprises
‘n’ number of rollers wherein each roller rotates in a progressively increasing
20 roller speed; the third set of rollers (103) comprises ‘o’ number of rollers
wherein each pair of rollers has a progressively decreasing roller gap; the
fourth set of rollers (104) comprises ‘p’ number of rollers wherein each roller
rotates in a progressively increasing roller speed; ‘m’ and ‘o’ are in a range of
2 to 5; and ‘n’ and ‘p’ are in a range of 2 to 10.
25 25. The method as claimed in claim 20, wherein the mixture is obtained by premixing an active material with at least one conductive additive and a nonfibrillating binder followed by high shear mixing with a fibrillating binder.
26. The method as claimed in claim 20, wherein the last roller of the second set
of rollers (102) and the last roller of the fourth set of rollers (104) rotate in the
30 same rotating speed, in a range of 0.5 to 25 m/min.
27. A first electrochemical cell comprising:
a. a cathode;
b. an anode comprising the electrode film as claimed in claim 15; and
c. an electrolyte.
28. A second electrochemical cell comprising:
5 a. a cathode comprising the electrode film as claimed in claim 17;
b. an anode; and
c. an electrolyte.
29. A third electrochemical cell comprising:
a. an anode comprising the electrode film as claimed in claim 15;
10 b. a cathode comprising the electrode film as claimed in claim 17; and
c. an electrolyte.
30. The electrochemical cell as claimed in any one of the claims 27 to 29, wherein
the electrolyte is selected from LiPF6 or LiBF4 dissolved in a solvent selected
from ethyl carbonate (EC), dimethyl carbonate (DMC), ethyl methyl
15 carbonate (EMC), vinylene carbonate (VC), 1, 3-propane sultone (PS),
succinonitrile (SN), or combinations thereof.
31. Use of the electrode film as claimed in any one of the claims 12 to 18 or the
electrode as claimed in claim 19, as a working electrode in an electrochemical
cell.