DESC:FIELD OF THE INVENTION
[001] The present invention relates to an aluminum alloy composition. More particularly, the present invention relates to an aluminum alloy foil based on the aluminum alloy composition, as current collector for energy storage applications, possessing high tensile strength, elongation, and conductivity.

BACKGROUND OF THE INVENTION
[002] Metal alloy is a substance that combines more than one metal or mixes a metal with other non-metallic elements. Metal alloys are useful in advanced energy storage and conversion applications. Both structure and composition can play an important role in determining the resulting materials properties.
[003] Aluminum is well known to have a relatively high electrochemical capacity, and therefore, is highly attractive for use advanced energy storage and conversion applications such Lithium-ion batteries (LIBs), Na-ion batteries, Aluminum-ion batteries, super capacitors etc.
[004] Further, aluminum alloys are widely used in various advanced energy storage and conversion applications. Due to their high strength to weight ratio and conductivity properties, Aluminum (Al) foils are the most widely used current collector for positive electrodes due to electrochemical stability at low cost.
[005] However, Al foil current collectors still face a variety of challenges. The limited contact area and weak adhesion between electrode materials and current collectors lead to increased interface contact resistance and thereby increase the internal resistance of energy storage devices such as LIBs. Further, existing foils available in the market use high purity Aluminum alloys with limited tensile strength properties. Low tensile strength limits the usage of foils in energy storage applications and customers must rely on low conductivity and high strength alloys.
[006] Accordingly, there is a need for improvement in mechanical properties of Aluminum foils with high electrical conductivity for current collector applications and ensure prolonged life and enhanced performance of current collectors.

SUMMARY OF THE INVENTION
[007] One aspect of the present invention an aluminum alloy composition comprising, Silicon (Si), Iron (Fe), Manganese (Mn), Magnesium (Mg), 0.05 to 0.20 wt% Copper (Cu) and equal to or greater than 99.5 wt% Aluminum (Al).
[008] Another aspect of the present invention relates to a foil comprising the aluminum alloy composition: Silicon (Si), Iron (Fe), Manganese (Mn), Magnesium (Mg), 0.05 to 0.20 wt% Copper (Cu) and equal to or greater than 99.5 wt% Aluminum (Al).
[009] Yet another aspect of the present invention relates to method of preparing aluminum alloy foil, comprising the following steps: (a) an aluminum alloy cast ingot is heated to a predetermined temperature, (b) the heated aluminum alloy cast ingot obtained in step (a) is passed through a series of rolling mills which reduce the thickness of the ingot in multiple steps at predetermined reduction to produce hot rolled aluminum alloy coils of predetermined thickness, (c) the hot rolled aluminum alloy coils obtained in step (b) are cooled to room temperature and passed multiple times through a series of rolling mills at predetermined reduction ratios to produce foil of predetermined thickness, wherein the predetermined reduction ratios during each pass in step (c) is between 30 to 70%.

BRIEF DESCRIPTION OF THE DRAWINGS
[010] Reference will be made to embodiments of the invention, examples of which may be illustrated in accompanying figures. These figures are intended to be illustrative, not limiting. Although the invention is generally described in the context of these embodiments, it should be understood that it is not intended to limit the scope of the invention to these particular embodiments.
Figure 1 shows comparison of 15-micron and 12-micron battery foil of the present invention with typical battery foil commercially available

DETAILED DESCRIPTION OF THE INVENTION
[011] Before the compositions and formulations of the present invention are described, it is understood that this invention is not limited to particular compositions and formulations described, since such compositions and formulations may, of course, vary. It is also to be understood that the terminology used herein is not intended to be limiting since the scope of the present invention will be limited only by the appended claims.
[012] The terms “comprising”, “comprises” and “comprised of” as used herein are synonymous with “including”, “includes” or “containing”, “contains”, and are inclusive or open-ended and do not exclude additional, non-recited members, elements, or method steps. It will be appreciated that the terms “comprising”, “comprises” and “comprised of” as used herein comprise the terms “consisting of”, “consists” and “consists of”.
[013] Furthermore, the terms “first”, “second”, “third” or “(a)”, “(b)”, “(c)”, “(d)” etc. and the like in the description and in the claims, are used for distinguishing between similar elements and not necessarily for describing a sequential or chronological order. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein. In case the terms “first”, “second”, “third” or “(A)”, “(B)” and “(C)” or “(a)”, “(b)”, “(c)”, “(d)”, “i”, “ii” etc. relate to steps of a method or use or assay there is no time or time interval coherence between the steps, that is, the steps may be carried out simultaneously or there may be time intervals of seconds, minutes, hours, days, weeks, months or even years between such steps unless otherwise indicated in the application as set forth herein above or below.
[014] In the following passages, different aspects of the present invention are defined in more detail. Each aspect so defined may be combined with any other aspect or aspects unless clearly indicated to the contrary. In particular, any feature indicated as being preferred or advantageous may be combined with any other feature or features indicated as being preferred or advantageous.
[015] Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, the appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment but may. Furthermore, the particular features, structures or characteristics may be combined in any suitable manner, as would be apparent to a person skilled in the art from this disclosure, in one or more embodiments. Furthermore, while some embodiments described herein include some, but not other features included in other embodiments, combinations of features of different embodiments are meant to be within the scope of the invention and form different embodiments, as would be understood by those in the art. For example, in the appended claims, any of the claimed embodiments can be used in any combination.
[016] Furthermore, the ranges defined throughout the specification include the end values as well, i.e., a range of 1 to 10 implies that both 1 and 10 are included in the range. For the avoidance of doubt, the applicant shall be entitled to any equivalents according to applicable law.
[017] In an aspect, the present disclosure relates to an aluminum alloy composition comprising Silicon (Si), Iron (Fe), Manganese (Mn), Magnesium (Mg), Copper (Cu), Titanium (Ti) and equal to or greater than 99.5% Aluminium (Al).
[018] In an embodiment, the aluminum alloy composition comprises: Silicon (Si), Iron (Fe), Manganese (Mn), Magnesium (Mg), Titanium (Ti), 0.05-0.20 wt% of Copper (Cu) and a minimum of 99.5 wt% Aluminum (Al).
[019] In an embodiment, the aluminum alloy composition comprises:
- 0.05-0.1 wt% of Silicon (Si),
- 0.2 -0.3 wt% of Iron (Fe),
- <0.01 wt% of Manganese (Mn),
- <0.01 wt% of Magnesium (Mg),
- 0.05-0.20 wt% of Copper (Cu),
- <0.1 wt% of Titanium (Ti), and
- equal to or greater than 99.5% Aluminium (Al).
[020] In an embodiment, the aluminum alloy composition comprises:
%Si %Fe %Mn %Mg %Cu %Ti %Zn %Al
Min 0.05 0.20 - - 0.05 - - >99.5
Max 0.10 0.30 0.01 0.01 0.20 0.1 0.01

[021] In an embodiment, the aluminum alloy composition is prepared by casting of the alloy using continuous casting or direct chill (DC) casting route, hot rolling of the cast ingots in case of a DC casting and cold rolling of the hot rolled coil to the desired thickness.
[022] Another aspect of the invention relates to aluminum alloy foil based on the aluminum alloy composition of the present disclosure.
[023] In an embodiment, the thickness of the foil is in the range of 9 to 20 µm, preferably 10 to 15 µm.
[024] In an embodiment, the aluminum alloy composition or the aluminum foil prepared therefrom demonstrates a high tensile strength > 250MPa, % elongation of > 2.5% and electrical conductivity of > 58% as per International Annealed copper standard (IACS).
[025] In an embodiment, 0.05-0.20 wt% addition of Copper (Cu) is done for solute strengthening of alloy.
[026] Yet another aspect of the invention relates to a method of preparing aluminum alloy foil comprises the following steps:
(a) Hot rolling of aluminum alloy cast ingots down to a predetermined thickness,
(b) cold reductions (in thickness) of hot rolled aluminum alloy cast ingots to foil gauges of predetermined thickness.
[027] In an embodiment, the method of preparing aluminum alloy foil comprises the following steps:
(a) casting of aluminium alloy cast ingots as per specified chemical composition,
(b) hot rolling of the aluminum alloy cast ingots in multiple steps to a predetermined minimum thickness,
(c) cold reductions in multiple passes from predetermined minimum thickness of hot rolled aluminum alloy cast ingots to foil gauges of predetermined thickness,
wherein each pass during cold reduction is limited to between 30 to 60%.
[028] In an embodiment, the method of preparing aluminum alloy foil, comprises the following steps:
(a) an aluminum alloy cast ingot is heated to a predetermined temperature,
(b) the heated aluminum alloy cast ingot obtained in step (a) is passed through a series of rolling mills which reduce the thickness of the ingot in multiple steps at predetermined reductions to produce hot rolled aluminum alloy coils of predetermined thickness,
(c) the hot rolled aluminum alloy coils obtained in step (b) are cooled to room temperature and passed multiple times through a series of rolling mills at predetermined reduction ratios to produce foil of predetermined thickness,
wherein the predetermined reduction ratios during each pass in step (c) is between 30 to 70%.
[029] In an embodiment of the method, the predetermined temperature range is between 400 to 550 oC, followed by hot rolling process and further rolling at room temperatures. The aluminum alloy cast ingot is heated preferably in case of direct chill (DC) casting route.
[030] In an embodiment, the heated aluminum alloy cast ingot obtained in step (a) is passed through a series of rolling mills in step (b) which reduce the thickness of the ingot in multiple steps involving predetermined reductions (hot rolled in 10 to 18 passes with reduction of 20 to 50mm per pass).

[031] In an embodiment of the method, during rolling process at room temperature, the predetermined reduction ratios range between 30% to 60 %.

[032] In an embodiment of the method, the number of passes through rolling mills in step (c) is between 9 to 10.
[033] In an embodiment of the method, the predetermined thickness of hot rolled aluminum alloy cast ingots is in the range of 4 to 7 mm.
[034] In an embodiment of the method, the predetermined thickness of foil is in the range of 9 to 20 µm, preferably 10 to 15 µm.
[035] In an embodiment of the method, cold reduction in step (c) up to 1 mm thickness is between 40 to 60 %.
[036] In an embodiment of the method, cold reduction in step (c) below 1 mm thickness is between 30 to 50%.
[037] In an embodiment, the aluminium alloy with a minimum of 99.5 wt% Aluminum (Al) in the composition when used as current collector in energy storage applications achieve tensile strength of >250 MPa and elongation >2.5% with minimum electrical conductivity of 58% IACS.
[038] In an embodiment, the aluminum alloy composition and aluminum foil prepared therefrom are used as current collectors preferably for lithium-ion batteries (LIBs), Na-ion batteries, Aluminum-ion batteries and super capacitors.

EXAMPLES
[039] The following experimental examples are illustrative of the invention but not limitative of the scope thereof:
[040] Example 1: 12-micron Battery foil (HIL1X-HC-12µ): Aluminum foil having a thickness of 12 µm with the specified composition (Table 1) was produced from 6 mm hot rolled thickness in ten cold reduction passes with following reduction set (Table 2).
Table 1: Aluminum Foil composition (12 µm)
%Wt %Si %Fe %Mn %Mg %Cu %Zn %Cr %Zr %Ti %B %Al
Min 0.050 0.200 0.000 0.000 0.080 - - 0.000 - 0.000 99.500
Max 0.10 0.300 0.01 0.01 0.130 - - 0.000 0.020 0.000

Table 2: Reduction % for each pass
Pass 1 Pass 2 Pass 3 Pass 4 Pass 5 Pass 6 Pass 7 Pass 8 Pass 9 Pass 10
54% 50% 53% 50% 49% 42% 49% 35% 43% 40%

[041] Example 2: 15-micron Battery foil (HIL1X-HC-15µ): Aluminum foil having a thickness of 15 µm with the specified composition (Table 3) was produced from over 6 mm thick hot rolled sheet after nine passes with following reduction set (Table 4).

Table 3: Aluminum Foil composition (15 µm)
%Wt %Si %Fe %Mn %Mg %Cu %Zn %Cr %Zr %Ti %B %Al
Min 0.050 0.200 0.000 0.000 0.080 - - - - 0.000 99.5
Max 0.10 0.300 0.01 0.01 0.130 - - - 0.020 0.000

Table 4: Reduction % for each pass
Pass 1 Pass 2 Pass 3 Pass 4 Pass 5 Pass 6 Pass 7 Pass 8 Pass 9
50% 50% 53% 50% 49% 42% 49% 48% 46%

[042] The tensile strength of the 12 µm and 15 µm aluminium foils prepared above were measured using ASTM E345-16. Standard testing parameters for ASTM E345 are as follows:
Gauge Length (G)- 125mm
Sample Width (W)-15 mm
Overall Length (L)- 230mm
Sample Thickness (T)- At actuals (checked by weighing method or by micrometer gauge)
Test Parameters
Speed of testing - 7.5mm/min (0.06 in/in/min)
Grips- Smooth Faced pneumatic grips
Grips pressure- 1.5 to 2 Bar
[043] The ultimate tensile strength (UTS) of the resulting 12 µm aluminum foil was found to be 275 MPa and the % elongation was found to be 2.87% and the ultimate tensile strength (UTS) of the resulting 15 µm aluminum foil was found to be 267 MPa and the % elongation was found to be 2.94% (Figure 1).
[044] Further, conductivity of 12 µm and 15 µm aluminium foils were measured using bench top probe type conductivity measurement unit. Minimum conductivity observed was 58% (%IACS).
[045] Furthermore, the conductivity (%IACS), ultimate tensile strength (UTS) and the % elongation of 15 µm and 12 µm aluminium foils of the present invention were compared with a 12 µm typical battery foils (AA1060 and AA1100) commercially available. The 12 µm aluminium foil of the present invention demonstrates a significant enhancement in tensile strength along with improved electrical conductivity (Table 5 and Figure 1).

Table 5: Comparison 12 µm aluminium foil of present invention with 12 µm regular market foils
Material Conductivity (%IACS) UTS (MPa) %Elongation
AA1060 foil (12 µm) (Regular market foil) >58% 169 3.0
AA1100 Foil (12 µm)
(Regular market foil)
>55% 260 2.50
HIL1X-HC (12 µm) >58% 273 2.95

[046] The foregoing description of the invention has been set merely to illustrate the invention and is not intended to be limited. Since the modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to the person skilled in the art, the invention should be construed to include everything within the scope of the disclosure.

,CLAIMS:1. An aluminum alloy composition comprising, Silicon (Si), Iron (Fe), Manganese (Mn), Magnesium (Mg), 0.05 to 0.20 wt% Copper (Cu) and equal to or greater than 99.5 wt% Aluminum (Al).
2. The aluminum alloy composition as claimed in claim 1, comprising
- 0.05 to 0.1 wt% of Silicon (Si),
- 0.2 to 0.3 wt% of Iron (Fe),
- less than 0.01 wt% of Manganese (Mn),
- less than 0.01 wt% of Magnesium (Mg),
- 0.05 to 0.20 wt% of Copper (Cu),
- less than 0.1 wt% of Titanium (Ti), and
- equal to or greater than 99.5 wt% Aluminium (Al).
3. A foil comprising aluminum alloy composition as claimed in claims 1 and 2.
4. The foil as claimed in claim 3, wherein the thickness of the foil is in the range of
9 to 20 µm, preferably between 10 to 15 µm.
5. A method of preparing aluminum alloy foil, comprising the following steps:
(a) an aluminum alloy cast ingot is heated to a predetermined temperature,
(b) the heated aluminum alloy cast ingot obtained in step (a) is passed through a series of rolling mills which reduce the thickness of the ingot in multiple steps at predetermined reduction to produce hot rolled aluminum alloy coils of predetermined thickness,
(c) the hot rolled aluminum alloy coils obtained in step (b) are cooled to room temperature and passed multiple times through a series of rolling mills at predetermined reduction ratios to produce foil of predetermined thickness,
wherein the predetermined reduction ratios during each pass in step (c) is between 30 to 70%.
6. The method as claimed in claim 5, wherein the range of predetermined temperature is between 400 to 550 oC.
7. The method as claimed in claim 5, during rolling process at room temperature, the predetermined reduction ratios range between 30% to 60 %.
8. The method as claimed in claim 5, wherein the number of passes through rolling mills in step (c) is between 9 to 10.
9. The method as claimed in claim 5, wherein the predetermined thickness of hot rolled aluminum alloy cast ingots is in the range of 4 to 7 mm.
10. The method as claimed in claim 5, wherein the predetermined thickness of foil is in the range of 9 to 20 µm, preferably between 10 to 15 µm.