DESC:FORM-2
THE PATENTS ACT, 1970
(39 OF 1970)
&
THE PATENT RULES, 2003
COMPLETE SPECIFICATION
(SECTION 10, RULE 13)

TITLE
“SEPARATOR WITH CLOSER RIBS TO INCREASE THE BATTERY EFFICIENCY”

APPLICANT
EASTMAN AUTO AND POWER LIMITED, a company organized and existing under the laws of India, of the address, 572, Udyog Vihar Phase-V, Gurgaon, 122016, India

The following specification particularly describes the invention and the manner in which it is to be performed
FIELD OF INVENTION :-
The invention is related to the field of battery. More particularly, the present invention is related to a Lead-acid battery separator with closer ribs to increase the battery efficiency.

BACKGROUND OF INVENTION :-
Lead-acid batteries are widely used as a major power source in many applications such as automotive, telecom, electric vehicles, uninterruptible power supply (UPS), traction, etc. Different types of lead-based alloys are used in making grids (current collector) whereas pure lead is used for producing lead oxide (active material) for these batteries based on their application requirements.

A permeable membrane called as separators are placed between the cathode and anode of a battery. Their main function is to prevent the short-circuiting by keeping the electrodes apart. In an electrochemical cell, these separators allow the transport of ion or charge carriers acting as a part of the closed circuit during the current passage. They are usually made of polymeric membrane with microporous structures and hence they act as critical components in batteries that uses liquid electrolytes. The separators should have the high stability with electrodes and electrolytes in both chemical and electrochemical manner. Their mechanical strength should be very high for withstanding the high tension during the battery construction. The impact of their structure and properties will affect the performance of the battery like cycle life, energy and power density, and safety.

In the start, the wooden separators are designed but they got deteriorated inside the electrolyte. After that, they were made of rubber, cellulose, glass fiber mat, and polyethylene plastic. The porous polyolefin films, cellophane or nylon separators were used for nickel-based batteries whereas AGM separators were used in sealed lead-acid batteries. Also, batteries like nickel-cadmium and lead-acid were made with the liquid electrolyte solutions. Since they develop gases, when overcharged, the vent was needed to push out these gases. Later, in 1947, nickel-cadmium of sealed types were developed and in 1970, the maintenance free lead-acid batteries have been introduced. In these kinds of designs, the porous separator will absorb the electrolyte. They are compressed against the electrodes, to reach the chemical reaction, required. In the 70s, the liquid electrolytes were converted into semi-solid paste and used for gelled lead-acid batteries.

In high temperature conditions, due to the melting process, the separator pores gets closed resulting in the shutdown of the battery. Like, the polyethylene (PE) separators melts above 130°C and shuts down the battery. If shutdown is not happening, the heat inside will be increased leading to the thermal runaway of the battery due to the high temperature.

A separator moistened by the electrolyte acts as a catalyst for increasing the movement of ions from one electrode to the other. As we know that, during charging, ions will move from cathode to anode and in the reverse direction during discharging process.

During this time, the separator controls the amount of ionic transfer based on their porosity. It also controls the self-discharge when the battery is in ideal condition. It can be said that even though the separators do not have electrical conductivity, they always acts as an isolator.

The major properties of the separators to be considered for the battery system are mentioned as follows,
i. Chemical Stability: The separator material should not be reactive to either of the electrodes or electrolyte solution. They should be non-degradable and chemically stable.
ii. Thickness & Strength: It should be thin, to facilitate the power and energy density of a battery, with sufficient tensile strength. Their thickness should be designed without compromising the properties of the cell.
iii. Porosity & Pore Size: The porosity volume should be good enough to facilitate the transport of ions between the electrodes. The pore size should not be higher than the active material components used for the electrodes to prevent their escape into the electrolyte. The pores should be uniform with better tortuosity.
iv. Thermal stability and shutdown: The separator should have the wide range of thermal stability without deterioration in their structures. It should be supportive for the shutdown mechanism at higher temperatures for preventing the thermal runaway of the battery.
The impurity presence in the separators has to be thoroughly checked. And the important factor is the maximum allowable amount of elements (impurities) that it may contain and still be suitable for battery use. Based on several works of literature, the impurity levels have been discussed in parts per million count. In lead-acid batteries, the water content plays a major effect in product performance. Water usage should be considered and viewed as a major factor for maximum performance. These contaminants or impurities in the separators play a major role in the water loss leading to an impact in the cycle life and performance of a battery. The gassing effects from charging a storage battery, coupled with evaporation, may leave behind the contaminants in the electrolyte solution. As a result, the impurities will have a cumulative effect on the battery.

Depending on the type of impurity, the physical characteristics as well as the performance of the battery will be affected. The presence of impurities can hinder both the positive and negative plates. Various kinds of reactions will happen due to the presence of the impurities inside the battery and so their behavioural characteristics will be different. Some impurities affect the electrode characteristics. This scenario will lead to a performance drop.

In existing art, the improper usage of separators leads to the secondary reactions such as corrosion, water decomposition, and oxygen recombination which are the main cause of the self- discharge of lead-acid batteries. Maintaining the charge of standby batteries is necessary to compensate for self-discharge. However, if the maintaining charge current is too high, it can accelerate the side reactions, which can thus become the cause of several failures of standby batteries. An appreciated method of maintaining the charge for stationary lead-acid batteries is a trade-off between their state of charge and state of health.

The problem associated with broader ribs is that the materials of the active mass may settle on the ribs if it is broader and results in the destruction of the separators leading to the possibility of the thermal-runaway in a battery.

If the ribs of the separator are broader, the settling of active materials over the separators is highly possible during shedding process. Therefore, there is a need to overcome the aforesaid drawbacks.

SUMMARY OF THE INVENTION :-
The effects of the separators in the electrochemical reactions inside the lead-acid batteries have been explored and their role play was discussed in this work. This invention provides some measures that help in improving the ionic mobility by adjusting the specifications of the separators. It’s been expressed that the increase in the movement of ions increases the electrical conductivity resulting in higher efficiency of the battery. This phenomenon also results in increased capacity and higher backup characteristics of a battery. The separators helps in preventing the escape of the impurities or the other components of the electrode into the system to get in contact with the electrolyte which may become active centers for the electrochemical reaction of hydrogen evolution and decreases the water loss in the battery. These separators with the closer ribs proved to be more efficient in the ionic diffusion.

Therefore such as herein described there us provided a separator for Lead-Acid Battery comprising of a polyethylene membrane having a backweb with a first surface, a plane second surface, and a backweb thickness defined as the distance between said first surface and said second surface; a first array of major ribs with straight profile ribs with a defined first pitch extending from said first surface, and a second array of minor ribs with straight profile ribs with a defined second pitch extending in adjacent position below the negative plate from said first surface; said first array of ribs having a first height, and said second array of ribs having a second height; wherein said first pitch of major ribs is more than the second pitch of the minor ribs; and wherein said first height of major ribs is equal to the second height of the minor ribs.

In an embodiment, the thickness and back-web thickness of the separators are fixed at 1.6 ± 0.1 mm and 0.35 ± 0.05 mm respectively, hold their deterioration because of the acid and electrochemical effects resulting in a long life for a battery. Same type of design construction is used for different separators of thickness 1.6, 1.8 and 2.0 mm with back-web thickness of 0.35, 0.45 and 0.45 mm respectively. Total thickness comes with a tolerance of ± 0.1 mm and back-web thickness with a tolerance of ± 0.05 mm.

In an embodiment, the tortuosity in a separator is responsible for the rate of charge transfer and the path flow of an acid. The separators with closer ribs with straight profile are chosen for the better diffusion of ions.

In an embodiment, the elongation is fixed at more than 200% and puncture strength is fixed at holding the minimum weight of 8 kg such that the separators should hold the battery operations and the disruptions caused by the presence of impurities from the electrode components.

In an embodiment, the electrical resistance is fixed at the range of less than 1.8 m? for area of 10cm2 such that the separators should not impact the ionic flow between the electrodes and the electrolyte.

In an embodiment, reducing the impurities content in the separators is very important because the separators will starts to deteriorate if they are not resistant enough to withstand the oxidation effect. So, each of the element presence such as herein described is important. Apart from them, no other impurities can be present.

In an embodiment, due to the presence of closer ribs, the positive plate will not rest on the back-web of the separators directly and hence it will not allow the dendrites (active material) to be in contact with the separators reducing the water loss. So, short- circuiting can be prevented.

In an embodiment, the problem related to settling can be avoided due to the closer ribs as used.

Brief Description of the accompanying drawing:-

Figure 1 illustrates the Section view of new PE separators (3D Image) in accordance with the present invention;

Figure 2 illustrates the Magnified section view of PE separator with negative plate in accordance with the present invention;

Figure 3 illustrates the Dimensional Representation of newly designed PE separators in accordance with the present invention;

Figure 4 illustrates (a) Positive plate between PE separators (closer ribs) on both sides (3D Image), (b) Bottom view in accordance with the present invention;

Figure 5 illustrates the Impurities settled on old PE separators with diagonal ribs;

Figure 1 illustrates the Acid effect on PE separators in accordance with the present invention;

Figure 7 illustrates the Mossing Formation above the negative plates in accordance with the present invention;

Figure 8 illustrates the Life cycle comparison between the batteries with old and new PE separators in accordance with the present invention;

Figure 2 illustrates the Voltage difference at each unit with respect to number of cycles in accordance with the present invention;

Figure 3 illustrates the charge acceptance graph for battery with new PE separator at higher temperature in accordance with the present invention.
Description of the invention :-

A permeable membrane called as separators are placed between the cathode and anode of a battery. Their main function is to prevent the short-circuiting by keeping the electrodes apart. In an electrochemical cell, these separators allow the transport of ion or charge carriers acting as a part of the closed circuit during the current passage. They are usually made of polymeric membrane with micro-porous structures and hence they act as critical components in batteries that uses liquid electrolytes. The separators should have the high stability with electrodes and electrolytes in both chemical and electrochemical manner. Their mechanical strength should be very high for withstanding the high tension during the battery construction. The impact of their structure and properties will affect the performance of the battery like cycle life, energy and power density, and safety.

The instant invention provides the way for increasing the diffusion of ions from the electrodes into the electrolyte resulting in the improvement of charge transfer. Due to the porosity control in the separators, the impurities cannot enter the electrolyte solution and helps in the non-destruction of the system. The overall parameters control in the separators is controlled in an efficient way by the instant invention, so that the flow of ions and electrons becomes smoother enhancing the overall efficiency and product life. They also give the better results in reduced water loss replacing the need for a regular top-up of the battery. And also, overheating inside the cell and the harmfulness of a battery can be escaped because of the shutdown mechanism by separators. The dendrites of the active mass will rest on the back-web of the separators, if the wider ribs and the gauntlets are of the fitting dimensions. This will have a higher impact on the separators and hence short-circuiting is highly possible. To overcome this, separators with the closer ribs have been designed. And also, the materials of the active mass will settle on the ribs if the broader ribs are present and results in the destruction of the separators leading to the possibility of the thermal-runaway in a battery.

The invention also relates to the importance of separators in lead-acid batteries and their role towards the battery system. They help in preventing the contact of the positive electrode and the negative electrode inside the cell. This is because, if the electrodes are not separated, it results in short-circuiting and collapses the whole system. Separators play a major role in the diffusion of ions into the electrolyte solution and prevent the other elements (impurities) from the electrodes to involve in the electrochemical reaction. Our invention provides the parameters for the separators to prevent their own deterioration inside the system and for increasing the overall efficiency of the battery. High maintenance is always a major concern for every customer in lead-acid batteries with Sb Alloy. The usage of well- designed separators gives the benefit to any brand to receive the title of ‘Less Maintenance & Highly Value Added’ product in the market and helps in the market growth with their uses in various applications

In an embodiment, the thickness and back-web thickness of the separators are fixed at 1.6 ± 0.1 mm and 0.35 ± 0.05 mm respectively (Fig. 1), hold their deterioration because of the acid and electrochemical effects resulting in a long life for a battery. Total thickness comes with a tolerance of ± 0.1 mm and back-web thickness with a tolerance of ± 0.05 mm. Same type of design construction is used for different separators of thickness 1.6, 1.8 and 2.0 mm with back-web thickness of 0.35, 0.45 and 0.45 mm respectively

The effects of the separators in the electrochemical reactions inside the lead-acid batteries have been explored and improvement in their role play is discussed in this work. This invention relates to some measures that helps in improving the ionic mobility by adjusting the specifications of the separators. It’s been expressed that the increase in the movement of ions increases the electrical conductivity resulting in higher efficiency of the battery. This phenomenon also results higher backup characteristics of a battery. The separators helps in preventing the escape of the impurities or the other components of the electrode into the system to get in contact with the electrolyte which may become active centers for the electrochemical reaction of hydrogen evolution and decreases the water loss in the battery. The separators with the closer ribs proved to be more efficient in the ionic diffusion. The separators with closer ribs are represented in Figure.2.

Because of the oxidation process happening in the positive plates, over time, PE separators will have the effect of oxidation on themselves by deterioration in their properties. This is because there is a possibility of a structural change in a PE molecule which can results in a formation of carbonyl and carboxyl groups. This will reduce the molecular weight of PE resulting in the loss of their mechanical strength.

From time to time, the thickness of the separators gets degraded because of the acid and the other electrochemical effects explaining the consumption of PE in a slow manner. Also, the charging process results in the cutting of PE molecular chain because of dehydrogenation process explaining the decrease in the mechanical strength. Hence, at the initial stage, the physical and chemical properties of the separators should be designed for their better support in the overall efficiency of a battery. In Eastman Auto & Power Limited, we have designed such parameters required for long-life of the separators with the better diffusivity of ions. The tests were performed along with the separators taken from the failure batteries came from the field. The data from the failure batteries and the incoming source have been analyzed and based on the screening determinations, specifications are made which have been illustrated in Table.1. The dimensional representation of the separator with closer ribs is shown in Figure.3.

The dendrites of the active mass will rest on the back-web of the separators, if the wider ribs and the gauntlets are of the fitting dimensions. This will have a higher impact on the separators and hence short-circuiting is highly possible. To overcome this, separators with the closer ribs have been designed. And also, the materials of the active mass will settle on the ribs if the broader ribs are present and results in the destruction of the separators leading to the possibility of the thermal-runaway in a battery.

The current improvement in the separators provides the way for increasing the diffusion of ions from the electrodes into the electrolyte resulting in the improvement of charge transfer. Due to the porosity control in the separators, the impurities cannot enter the electrolyte solution and helps in the non-destruction of the system. The overall parameters control in the separators is designed in an efficient way by Eastman Auto & Power Limited, so that the flow of ions becomes smoother enhancing the overall efficiency and product life. They also gives the better results in reduced water loss replacing the need for a regular top-up of the battery. And also, overheating inside the cell and the harmfulness of a battery like thermal-runaway can be escaped.

LIFE CYCLE TEST PROCEDURE:
As referred in Fig 8 - 10, the life cycle test procedure of the of the battery includes:
1. Discharge the battery @ 400 W till 10.8 V.
2. Charge the battery with 15.00 A till 14.80 V for 9hrs.
3. Repeat the cycling.
4. Test Temperature @ Ambient condition.

In an embodiment, the tortuosity in a separator is responsible for the rate of charge transfer and the path flow of an acid. The separators with closer ribs with straight profile are chosen for the better diffusion of ions.

In an embodiment, the elongation is fixed at more than 200% and puncture strength is fixed at holding the minimum weight of 8 kg such that the separators should hold the battery operations and the disruptions caused by the presence of impurities from the electrode components.

In an embodiment, the electrical resistance is fixed at the range of less than 1.8 m? for area of 10cm2 such that the separators should not impact the ionic flow between the electrodes and the electrolyte.

In an embodiment, reducing the impurities content in the separators is very important because the separators will starts to deteriorate if they are not resistant enough to withstand the oxidation effect. So, each of the parameter as stated in Table 1 is important.

In an embodiment, due to the presence of closer ribs, the positive plate will not rest on the back-web of the separators directly and hence it will not allow the dendrites (active material) to be in contact with the separators reducing the water loss. So, short- circuiting can be prevented.

In an embodiment, the problem related to settling can be avoided due to the closer ribs as used.

The gap between major ribs is reduced in the new PE separators which makes them closer, so that the gauntlets will not directly touch on the back-web directly. This is because, the direct contact of the dendrites on the positive plate deteriorates the structure of the separators causing a direct contact with a negative active material which leads to short circuiting of the battery.

The gaps between the minor ribs are also adjusted so that the negative active material from inside the separator will not stick directly on the back-web and so the material loss can be prevented.

The diagonal ribs in the old separators will results in the settling of particles over the ribs restricting their bottom settling. But, the new design of PE separators comes with the straight profile of major ribs which will not allow the leaked particles from the electrodes to settle on the ribs allowing their way to the bottom.

From Figure.8, it can be seen that the life-cycle of the battery is improved more than 300 cycles when the PE separators with closer ribs are used. From Figure.10, it can be seen the charge acceptance is consistent in the battery that uses newly designed PE separators explaining their suitability for ion transfer.
Table 1: Controlled specifications for the separators

S. No Parameters Range
1. Weight loss in p-xylene (%) 5 (maximum)
2. Weight loss in peroxide solution (%) 5 (maximum)
3. Moisture (%) 1.5 (maximum)
4. Electrical resistance (m?) for 10 cm2 area <1.8
5. Elongation (%) 200 (minimum)
6. Puncture Strength (kg) 0.8 (minimum)
7. Thickness (mm) (1.6 - 1.8) ± 0.1
8. Back-web thickness (mm) (0.35 – 0.45) ± 0.05
0.05
9. Design type Straight profile
10. Ribs type Closer ribs

11. Porosity (%) 60 ± 5
12. Oil content (%) 12-19
13. Copper content (%) 0.0003
(maximum)
14. Iron content (%) 0.0110
(maximum)
15. Manganese content (%) 0.0003
(maximum)
16. Chloride content (%) 0.0200
(maximum)

Although the foregoing description of the present invention has been shown and described with reference to particular embodiments and applications thereof, it has been presented for purposes of illustration by way of examples and description and is not intended to be exhaustive or to limit the invention to the particular embodiments and applications disclosed. The particular embodiments and applications were chosen and described to provide the best illustration of the principles of the invention and its practical application to thereby enable one of ordinary skill in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. All such changes, modifications, variations, and alterations should therefore be seen as being within the scope of the present invention as determined by the appended claims when interpreted in accordance with the breadth to which they are fairly, legally, and equitably entitled.

,CLAIMS:We Claim:-

1. A separator for Lead-Acid Battery comprising of :
a polyethylene membrane having a backweb with a first surface, a plane second surface, and a backweb thickness defined as the distance between said first surface and said second surface;
a first array of major ribs with straight profile ribs with a defined first pitch extending from said first surface, and a second array of minor ribs with straight profile ribs with a defined second pitch extending in adjacent position below the negative plate from said first surface;
said first array of ribs having a first height, and said second array of ribs having a second height;
wherein said first pitch of major ribs is more than the second pitch of the minor ribs; and
wherein said first height of major ribs is equal to the second height of the minor ribs.

2. The separator for Lead-Acid Battery as claimed in claim 1, wherein back web thickness is 0.35mm-0.45mm, first height is 1.0mm and the second height is 0.25mm.

3. The separator for Lead-Acid Battery as claimed in claim 1, wherein the first pitch at top edge is 3.8mm and the first pitch base is 2.0mm.

4. The separator for Lead-Acid Battery as claimed in claim 1, wherein the ribs are conical with rounded top edges; and
wherein the base width is 0.8mm and the top width is 0.4mm.

5. The separator for Lead-Acid Battery as claimed in claim 1, wherein the total thickness and back-web thickness of the separators are fixed at 1.6 ± 0.05 mm and 0.35 ± 0.05 mm respectively, configured to hold their deterioration because of the acid and electrochemical effects resulting in a long life for a battery.

6. The separator for Lead-Acid Battery as claimed in claim 1, wherein due to the presence of closer ribs, the positive plate does not rest on the back-web of the separators directly and therefore does not allow the dendrites (active material) to be in contact with the separators reducing the water loss and short- circuiting is prevented.

Dated this 20th day of May, 2022

To,
The Controller of Patents,
The Patent Office
Delhi

Arghya Ashis Roy Patent Agent (IN/PA 2346)
For the Applicant