1. A separator for energy storage devices, wherein the separator comprising of: a polymer matrix; and metal ferrite nanoparticles wherein the nanoparticles are uniformly dispersed in the polymer matrix to form a nanocomposite membrane.

2. The separator for energy storage devices as claimed in claim 1, wherein polymer matrix is selected as polyvinylidene fluoride (PVDF).

3. The separator for energy storage devices as claimed in claim 1, wherein metal ferrite nanoparticles selected are cobalt ferrite (CoFe₂O₄) nanoparticles.

4. The separator for energy storage devices as claimed in claim 1, wherein cobalt ferrite (CoFe₂O₄) nanoparticles are present in an amount ranging from 5 to 20 weight percent of the total nanocomposite.

5. The separator for energy storage devices as claimed in claim 1, wherein nanocomposite exhibits a bulk electrolyte resistance of less than 25 ohms measured by electrochemical impedance spectroscopy.

6. The separator for energy storage devices as claimed in claim 1, wherein the nanocomposite has a porosity in the range of 30 – 40% and thickness of 76 Microns.

7. The separator for energy storage devices as claimed in claim 1, wherein the nanocomposite exhibits thermal stability upto 500degree C.

8. The separator for energy storage devices as claimed in claim 1, wherein the charge transfer resistance of the nanocomposite is less than 30 ohms, confirming enhanced ionic transport.

9. The separator for energy storage devices as claimed in claim 1, wherein cobalt ferrite nanoparticles are synthesized via a sol-gel auto combustion method before dispersion in PVDF.

10. A method for preparing the separator as claimed in claim 1, wherein the method comprising the steps of: i. synthesizing CoFe₂O₄ nanoparticles by sol-gel auto combustion; ii. preparing a PVDF solution; iii. dispersing CoFe₂O₄ nanoparticles uniformly into the PVDF solution; iv. casting the mixture onto a flat glass petridish and v. drying to form a flexible PVDF-CoFe₂O₄ nanocomposite film.

11. A PVDF-CoFe₂O₄ nanocomposite for use in flexible or wearable energy storage devices, hybrid systems, or sensing applications requiring combined flexibility and electrochemical activity.

Description:FIELD OF INVENTION:
The present invention relates to the field of energy storage, particularly to electrochemical devices such as supercapacitors. More particularly, the present invention relates to a flexible separator based on polyvinylidene fluoride (PVDF)-CoFe2O4 (CFO in short) nanocomposite for use in energy storage devices especially supercapacitors. The present invention further relates to a method of preparation of the PVDF/CoFe2O4 nanocomposite- based separator.

BACKGROUND OF THE INVENTION:
In recent years, the growing demand for advanced energy storage devices, particularly supercapacitors, has highlighted the urgent need for efficient, sustainable, and long-lasting power solutions to meet the requirements of next-generation electronics. Supercapacitors are energy storage devices that bridge the gap between conventional capacitors and batteries. Their increased demand is substantially due to their advantages, including high power density, fast charge/discharge capability, and long operational life. A crucial component in supercapacitor design is the separator, which serves to electrically insulate the electrodes while permitting efficient ionic transport. Conventional separators, such as Whatman filter paper, suffer from high bulk electrolyte resistance and offer no additional functionalities, thereby limiting the overall performance of the device.

Existing separators made from polypropylene (PP) or polyethylene often exhibits limitations such as poor thermal stability, low wettability with electrolytes and insufficient mechanical robustness. Polyvinylidene fluoride (PVDF) emerges as a promising host matrix owing to its excellent chemical stability, mechanical robustness, and favourable dielectric characteristics. However, PVDF alone lacks the necessary electrochemical activity and ionic conductivity for optimal separator functionality.

US9960400B2 discloses a separator that includes a monolayer-type polyolefin-based micro-porous film having a porosity of 40 to 60%, an average pore diameter of 60 nm or less, and an air permeability of 350 s/100 mL or less; and a porous coating layer formed on at least one surface of the micro-porous film and made of a mixture of a plurality of inorganic particles and a binder polymer. It further discloses that electrochemical device having the above separator has excellent thermal stability and allows a high power while minimizing the occurrence of leak current.

US11411281B2 discloses a s multi-layer composite functional separator for lithium-ion battery includes four layers. Layer A is a base separator. Layer B is a porous structural layer composed of insulating inorganic compounds or high temperature resistant polymers. Layer C is a porous layer composed of polymer microspheres with temperature-induced expansion characteristics. Layer D is a thermoplastic resin with a melting point of 80-110° C.

CN111662470A provides a fatigue-resistant cobalt ferrite/PVDF-trifluoro ethylene multilayer composite film and a preparation method thereof, which not only have excellent ferroelectric fatigue properties, but also the cost of the process equipment is low, the process is simple and the controllability is strong.

The National Institute of Technology, Kurukshetra (Patent No. 488083), developed a flexible separator using PVDF/BaTiO₃/NiO nanocomposite films with an approximate thickness of 50 µm, prepared via the solution mixing method. The reported bulk resistance (Rbe) and charge transfer resistance (RCT) were 0.6 Ω and 42 Ω, respectively.

Despite several advancements, the existing separators still fall short in achieving the optimal balance between mechanical strength, flexibility, ionic conductivity, porosity and electrolyte compatibility. To address these shortcomings, inventors explored polymer composite materials embedded with electroactive fillers.

Therefore, the present invention aims to provide a PVDF-CFO nanocomposite with improved ionic conductivity and storage performance, making it ideally suited for next-generation supercapacitor applications.

OBJECT OF THE INVENTION
To address the foregoing problems, in whole or in part, and/or other problems that may have been observed by persons skilled in the art, the present disclosure provides a flexible separator and method of its preparation as described by way of example as set forth below.

Accordingly, the main object of the present invention is to provide a nanocomposite-based multifunctional separator for use in electrochemical energy storage devices, especially supercapacitors.

Another object of the present invention is to provide a PVDF- CoFe₂O₄ nanocomposite-based separator for use in electrochemical energy storage devices, especially supercapacitors.

Yet another object of the present invention is to provide a multifunctional separator that is not merely a passive physical barrier, it also contributes actively to the device's charge storage performance.

Yet another object of the present invention is to provide a PVDF-CoFe₂O₄ separator with significantly reduced bulk electrolyte resistance and improved ionic conductivity.

Yet another object of the present invention is to provide a method of preparation for PVDF-CoFe₂O₄ nanocomposite-based separator.

Yet another object of the present invention is to provide a scalable, cost-effective process for fabricating PVDF-CoFe₂O₄ nanocomposite-based separator.

Yet another object of the present invention is to provide a PVDF-CoFe₂O₄ separator that can be directly applied in high-performance supercapacitors, offering enhanced efficiency and reliability for electric vehicles, renewable energy systems, and portable electronics.

SUMMARY OF THE INVENTION
This summary is intended to introduce, in simplified form, a selection of concepts that are further described in the detailed description. This summary is merely presented as a brief overview of the subject matter described and claimed herein and does not aid in determining the scope of the claimed subject matter.

The present invention provides a PVDF-CoFe₂O₄ nanocomposite-based multifunctional separator for use in energy storage devices especially supercapacitors.

In another aspect, the present invention provides a separator for energy storage devices, wherein the separator comprising of:
a polymer matrix (PVDF); and
metal ferrite nanoparticles (cobalt ferrite nanoparticles)
wherein the cobalt ferrite nanoparticles are uniformly dispersed in the polymer matrix (PVDF) to form a nanocomposite membrane.

In yet another aspect, the present invention provides a PVDF-CoFe₂O₄ nanocomposite-based multifunctional separator wherein the cobalt ferrite (CoFe₂O₄) nanoparticles are present in an amount ranging from 5 to 20 weight percent of total nanocomposite.

In yet another aspect, the present invention provides a PVDF-CoFe₂O₄ nanocomposite-based multifunctional separator wherein the nanocomposite has a porosity in the range of 30 - 40% and thickness of 76 Microns.

In another aspect, the present invention provides a PVDF-CoFe₂O₄ nanocomposite-based separator with significantly reduced bulk electrolyte resistance and improved ionic conductivity.

In another aspect, the present invention provides a PVDF-CoFe₂O₄ nanocomposite-based separator, wherein nanocomposite exhibits a bulk electrolyte resistance of less than 25 ohms measured by electrochemical impedance spectroscopy.

In yet another aspect, the present invention provides a PVDF-CoFe₂O₄ nanocomposite-based separator wherein the charge transfer resistance of the nanocomposite is less than 30 ohms, confirming enhanced ionic transport.
In yet another aspect, the present invention provides a PVDF-CoFe₂O₄ nanocomposite-based multifunctional separator that is not merely a passive physical barrier, it also contributes actively to the device's charge storage performance.

In yet another aspect, the present invention provides a PVDF-CoFe₂O₄ nanocomposite-based multifunctional separator wherein the nanocomposite exhibits thermal stability upto 500degree C. In yet another aspect, the present invention provides a a scalable, cost-effective process for fabricating PVDF-CoFe₂O₄ nanocomposite-based separator.
In yet another aspect, the nanocomposite is fabricated by a solution casting method to form a free-standing flexible film.
In yet another aspect, the present invention provides a method for preparing the separator, wherein the method comprising the steps of:
i. synthesizing CoFe₂O₄ nanoparticles by sol-gel auto combustion;
ii. preparing a PVDF solution;
iii. dispersing CoFe₂O₄ nanoparticles uniformly into the PVDF solution;
iv. casting the mixture onto a flat glass petridish; and
v. drying to form a flexible PVDF-CoFe₂O₄ nanocomposite film.

BRIEF DESCRIPTION OF DRAWINGS:
In order to facilitate a comprehensive understanding and practical implementation of the disclosure, reference will now be made to exemplary embodiments illustrated in the accompanying figures. The figures together with detailed description below, are incorporated into and form part of the specification, and serve to further illustrate the embodiments and explain various principles and advantages, in accordance with the present disclosure:
FIG. 1 illustrates process of synthesis of CFO nanoparticles by sol-gel auto combustion method.
FIG. 2 illustrates process of synthesis of PVDF/CFO nanocomposites by solution casting method.
FIG. 3 illustrates (A-C) CV curves at different scan rates of standard separator and fabricated flexible separators.
FIG. 4 illustrates Nyquist plot of standard and fabricated (PVDF/CFO) separators.

DETAILED DESCRIPTION OF THE INVENTION
Accordingly, the present invention provides a PVDF-CoFe₂O₄ nanocomposite-based multifunctional separator for use in energy storage devices especially supercapacitors
The present disclosure can be understood more readily by reference to the following description, taken in conjunction with the accompanying Figures and Examples, all of which form a part of this disclosure.

At the very outset of the detailed description, it may be understood that the ensuing description only illustrates a particular form of the invention covered in the present disclosure. However, such a particular form is only an exemplary embodiment, and without intending to imply any limitation on the scope of the invention. Accordingly, the description is to be understood as an exemplary embodiment and teaching of invention and not intended to be taken restrictively.

Before the present disclosure or methods of the present disclosure are described in greater detail, it is to be understood that the specific products, methods, processes, conditions or parameters, are not limited to particular embodiments described, as such may, of course, vary. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to be limiting.

Where a range of values is provided, it is understood that each intervening value, to the tenth of the unit of the lower limit unless the context clearly dictates otherwise, between the upper and lower limit of that range and any other stated or intervening value in that stated range, is encompassed within the methods. Where the stated range includes one or both of the limits, ranges excluding either or both of those included limits are also included in the methods. Certain ranges are presented herein with numerical values being preceded by the term “about.” The term “about” is used herein to provide literal support for the exact number that it precedes, as well as a number that is near to or approximately the number that the term precedes. For example, "about" can mean within one or more standard deviations, or within ± 30%, 25%, 20%, 15%, 10% or 5% of the stated value.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the invention belongs. Although any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, preferred methods and materials are described. For the purposes of the present invention, the following terms are defined below.

It is appreciated that certain features of the methods, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the methods, which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable sub-combination. All combinations of the embodiments are specifically embraced by the present invention and are disclosed herein just as if each and every combination was individually and explicitly disclosed, to the extent that such combinations embrace operable processes and/or composites/scaffolds.

The articles "a" and "an" are used herein to refer to one or to more than one (i.e., to at least one) of the grammatical object of the article. By way of example, "an element" means one element or more than one element.

As used herein, the term "comprises", "comprising", or “comprising of” is generally used in the sense of include, that is to say permitting the presence of one or more features or components. The term "comprises", "comprising", or “comprising of” when placed before the recitation of steps in a process or method means that the process or method encompasses one or more steps that are additional to those expressly recited, and that the additional one or more steps may be performed before, between, and/or after the recited steps.

Reference throughout this specification to “certain embodiments”, “further embodiments”, “specific embodiments”, “further specific embodiment”, “one embodiment”, “a non-limiting embodiment”, “an exemplary embodiment”, “some instances”, or “further instances”, means that a particular feature, structure or characteristic described in connection with the embodiment may be included in at least one embodiment of the present disclosure.

As used herein, the terms ‘include’, ‘have’, ‘comprise’, ‘contain’ etc. or any form of said terms such as ‘having’, ‘including’, ‘containing’, ‘comprising’ or ‘comprises’ are inclusive and will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.

The use of any and all examples, or exemplary language (e.g., “such as”) provided with respect to certain embodiments herein is intended merely to better illustrate the disclosure and does not pose a limitation on the scope of the disclosure otherwise claimed.

As used herein, the term “invention”, “present invention”, “disclosure” or “present disclosure” as used herein is a non-limiting term and is not intended to refer to any single embodiment of the particular invention but encompasses all possible embodiments as described in the specification.

The terms “process(es)” and “method(s)” are considered interchangeable within this disclosure.

For convenience, certain terms used in the specification and examples are collected in this section below:

PVDF: polyvinylidene fluoride
CoFe₂O₄: cobalt ferrite
CFO: cobalt ferrite
P5CFO: 5 wt% CFO in PVDF
P10CFO: 10 wt% CFO in PVDF
P20CFO: 20 wt% CFO in PVDF
DMF: N, N Dimethylformamide
Rb: Bulk resistance
RCT: Charge transfer resistance
Ω: ohms (unit of resistance)

In one specific embodiment, the present invention provides a PVDF-CoFe₂O₄ nanocomposite-based multifunctional separator for use in energy storage devices especially supercapacitors.
In another embodiment, the cobalt ferrite (CoFe₂O₄) nanoparticles are present in an amount ranging from 5 to 20 weight percent of total nanocomposite.

In yet another embodiment, the nanocomposite has a porosity in the range of 30 – 40% and thickness of 76 Microns.

In yet another embodiment, the present invention provides a PVDF-CoFe₂O₄ nanocomposite-based separator with significantly reduced bulk electrolyte resistance and improved ionic conductivity.

In yet another embodiment, the present invention discloses that incorporation of CoFe₂O₄ into the PVDF matrix enhances the overall performance of the separator, contributing to improved energy efficiency and device stability.

In yet another embodiment, the present invention provides a PVDF-CoFe₂O₄ nanocomposite-based separator, wherein nanocomposite exhibits a bulk electrolyte resistance of less than 25 ohms measured by electrochemical impedance spectroscopy.
In yet another embodiment, the present invention provides a PVDF-CoFe₂O₄ nanocomposite-based separator wherein the charge transfer resistance of the nanocomposite is less than 30 ohms, confirming enhanced ionic transport.
In yet another embodiment, the present invention provides a PVDF-CoFe₂O₄ nanocomposite-based multifunctional separator that is not merely a passive physical barrier, it also contributes actively to the device's charge storage performance.

In yet another embodiment, the present invention provides a PVDF-CoFe₂O₄ nanocomposite-based multifunctional separator wherein the nanocomposite exhibits thermal stability upto 500 degree C.

In yet another embodiment, the present invention provides a scalable, cost-effective process for fabricating PVDF-CoFe₂O₄ nanocomposite-based separator.
In yet another embodiment, the nanocomposite is fabricated by a solution casting method to form a free-standing flexible film.
In yet another embodiment, the present invention provides a method for preparing the separator, wherein the method comprising the steps of:
i. synthesizing CoFe₂O₄ nanoparticles by sol-gel auto combustion;
ii. preparing a PVDF solution;
iii. dispersing CoFe₂O₄ nanoparticles uniformly into the PVDF solution;
iv. casting the mixture onto a flat glass petridish; and
v. drying to form a flexible PVDF-CoFe₂O₄ nanocomposite film.

In yet another embodiment, bulk electrolyte resistance (Rb) of the PVDF-CFO separator is significantly reduced to 8 Ω, compared to 750 Ω for conventional Whatman paper.

In yet another embodiment, the present invention discloses that low resistance and enhanced electrochemical performance confirm the multifunctionality of the PVDF-CFO nanocomposite, making it highly suitable for use in supercapacitor applications.

In yet another embodiment, the present invention discloses that integration of electroactive filler (CFO) within a flexible polymer matrix to enhance capacitive characteristics without compromising mechanical integrity.
In an embodiment, the present invention discloses a process of synthesis of CFO nanoparticles by sol-gel auto combustion method (refer figure 1). The method involves steps of:
i. Dissolving iron nitrate (Fe(NO₃)₃) and cobalt nitrate (Co(NO₃)₂) in water. These provide the Fe³⁺ and Co²⁺ ions needed for CoFe₂O₄ formation;
ii. Introducing citric acid as a chelating agent. It coordinates with the metal ions, forming a homogenous citrate complex which helps in producing fine, uniform nanoparticles;
iii. Heating the mixture to about 110 °C, converting it into a thick, viscous brown sol or gel;
iv. adding ammonia solution (NH₄OH) slowly; and
v. drying or mild heating, the gel undergoes an auto-combustion process.

In yet another embodiment, the present invention discloses that the PVDF-CFO nanocomposite-based separator has potential for dual functionality in both energy storage and complementary applications such as sensing and energy harvesting, highlighting the material’s versatility as a key component for next-generation supercapacitors.

In yet another embodiment, the present invention discloses that PVDF-CFO nanocomposite as a separator in the field of energy storage is novel. Its unique combination of structural integrity, thermal stability, and excellent electrochemical properties makes it highly suitable for supercapacitor applications.

It is noted that PVDF is a semi-crystalline polymer known for its mechanical strength, thermal and chemical stability, and good dielectric properties. However, PVDF alone does not possess sufficient electrochemical activity or ionic conductivity to serve as an active separator. To overcome this, the present invention incorporates CoFe₂O₄ nanoparticles—magnetic, electroactive ferrite particles with excellent electronic and dielectric properties into the PVDF matrix. The CoFe₂O₄ is uniformly dispersed within the PVDF using a controlled solution casting process, leading to the formation of a flexible, robust, and electrochemically active separator film. The PVDF-CoFe₂O₄ composite separator exhibits several remarkable features:
Reduced Electrolyte Resistance: The bulk electrolyte resistance (Rb) is drastically reduced to 8 Ω compared to 750 Ω for Whatman paper, indicating enhanced ion transport through the separator.
Improved Electrochemical Behaviour: The separator shows quasi-rectangular cyclic voltammetry (CV) curves over a range of scan rates, demonstrating capacitive characteristics typically observed in electrode materials. This unusual behaviour confirms the electrochemical contribution of the separator to energy storage.
Mechanical Integrity: Despite its electrochemical activity, the composite retains the mechanical flexibility and durability of PVDF, making it suitable for integration into flexible and portable energy devices.
Multifunctionality: Beyond serving as a passive separator, the PVDF-CoFe₂O₄ composite can actively participate in energy storage and possibly other applications such as sensing or energy harvesting.

It is further noted that the simplicity of the solution casting fabrication process disclosed in the present invention allows for easy scalability and cost-effective production, positioning this material as a competitive and sustainable alternative to existing separator technologies. Its multifunctional nature not only enhances supercapacitor performance but also opens up avenues for its use in emerging technologies like hybrid energy storage systems, wearable electronics, and next-generation flexible devices. The invention thus offers a novel solution that merges structural support, ionic conductivity, and electrochemical activity within a single material platform.

Even though we have explained the invention of the present disclosure using specific examples, this explanation is not meant to limit how you understand it. People who are skilled in this field may think of various changes and different versions of the invention after reading this description. We expect that such changes can be made without straying from the main idea or purpose of the invention as defined in the claims.

The present disclosure is further described with reference to the following examples, which are only illustrative in nature and should not be construed to limit the scope of the present disclosure in any manner.

EXAMPLES
Exceptional Ionic Conductivity and Electrolyte Permeability:
The bulk electrolyte resistance (Rb) of the PVDF-CFO separator is reduced to 8 Ω, which is nearly two orders of magnitude lower than that of Whatman paper (750 Ω), and significantly lower than other reported polymeric or ceramic composite separators. This is direct evidence of enhanced ion transport pathways, enabled by:
i. The nanoscale percolation channels introduced by CFO.
ii. The synergistic interface formed between PVDF chains and CFO nanoparticles, which facilitates better ionic dissociation and mobility within the electrolyte medium.
No previous literature on PVDF/ferrite composites, has demonstrated such electrolyte transport efficiency or separator functionality. For the sake of convenience, the nanocomposite films having 5, 10, and 20 wt% CFO in PVDF is abbreviated as P5CFO, P10CFO, and P20CFO, respectively, and these will be used throughout herein.

Nyquist plot of standard and fabricated (PVDF/CFO) separators:
Figure 4 shows Nyquist plots comparing a standard separator and fabricated (PVDF/CFO) separators. The fabricated separators exhibit smaller semicircle in the high frequency region, indicating lower charge-transfer resistance and bulk resistance. This implies improved interfacial contact with the electrolyte and enhanced ionic conductivity.
The results are shown in table 2 below:

Table 2. Represents the Bulk resistance and charge transfer resistance of standard and fabricated separators.
S. No. Sample code Rb (Bulk resistance)
(Ω) RCT (Charge transfer resistance) (Ω)
1 Standard separator 750.386 22549.644
2 P5CFO 8.362 28.456
3 P10CFO 21.534 1.517
4 P20CFO 22.784 1.14
Active Charge Storage from the Separator Layer (Electrochemical Participation):
The PVDF/CFO separator demonstrates quasi-rectangular cyclic voltammetry (CV) profiles, indicating capacitive charge storage behavior intrinsic to the separator itself. This is a major departure from the standard supercapacitor architecture, where energy storage is solely confined to the electrodes. This is a major departure from the standard supercapacitor architecture, where energy storage is solely confined to the electrodes. The electrochemical activity of the separator is attributed to:
ii. The interfacial polarization facilitated by the semiconducting and ferrimagnetic CFO nanoparticles.
iii. The enhanced dielectric constant and ionic mobility within the PVDF matrix due to uniform nanoparticle dispersion.
Such electrochemical engagement of the separator layer enhances total device capacitance, improves charge propagation kinetics, and paves the way for hybrid configurations where both separator and electrode contribute to energy storage.
The nanocomposite demonstrates quasi-rectangular cyclic voltammetry curves over varying scan rates, indicative of capacitive electrochemical behaviour as shown in figure 3. The appearance of stable quasi-rectangular cyclic voltammetry curves indicates active participation of the separator in charge storage - a functionality not typically associated with separators. This unusual behaviour confirms the electrochemical contribution of the separator to energy storage.
The results are summarized in table 1 below:

Table 1. Illustrates the area of standard separator and fabricated piezoelectric flexible separators:
Sample Scan rate (mV/s) Area
Standard separator 10 1.0889899158428
50 1.1683062211887
100 1.2471274203563
P5CFO 10 266.43371582031
50 285.76487028493
100 426.6964001766
P10CFO 10 282.0299422884
50 285.65858214827
100 315.10049283802
P20CFO 10 429.98416054518
50 534.2883299361
100 1860.5175888275

Simplicity of Processing with High Functional Integration:
The nanocomposite is synthesized via a single-step solution casting method, offering:
1. Homogeneous dispersion of CFO nanoparticles, critical for both ionic conduction and mechanical uniformity.
2. Mechanical flexibility, allowing for integration into next-generation wearable and bendable energy devices.

Process of synthesis of PVDF/CFO nanocomposites by solution casting method comprises steps of:
i. Adding PVDF powder to N,N Dimethylformamide (DMF) and stir (at around 45–70 °C) for 1-2 hr;
ii. Introducing CoFe₂O₄ (CFO) nanoparticles into the PVDF/DMF solution and continue stirring for an extended period of 12-15 hr;
iii. Pouring or casting the homogeneous PVDF–CFO mixture onto a flat glass petridish and
iv. Drying the mixture at around 70 °C for 24 h to evaporate the DMF, forming a solid PVDF/CFO nanocomposite film.
Refer figure 2.

Advantages
1) Enhanced Electrochemical Performance: The PVDF-CoFe₂O₄ separator significantly reduces bulk electrolyte resistance (8 Ω), improving ionic conductivity and overall device efficiency compared to conventional separators like Whatman paper (750 Ω).
2) Multifunctionality: Unlike traditional passive separators, this composite actively contributes to energy storage by exhibiting capacitive behaviour, enabling dual functionality within supercapacitor systems.
3) Simple and Scalable Fabrication: The solution casting method used for preparing the separator is low-cost, easy to scale, and suitable for industrial manufacturing.
4) Mechanical Flexibility and Durability: The PVDF matrix maintains the mechanical integrity of the separator, making it compatible with flexible and wearable electronic devices.
5) Material Versatility: The integration of electroactive cobalt ferrite within PVDF enables potential application beyond energy storage, such as in sensing and energy harvesting technologies.

It is to be noted that the present invention introduces a paradigm-shifting innovation in the field of energy storage materials, specifically supercapacitor separators, through the development of a flexible, electrochemically active nanocomposite separator composed of polyvinylidene fluoride (PVDF) and cobalt ferrite nanoparticles (CoFe₂O₄, CFO). This multifunctional separator is not merely a passive physical barrier; rather, it actively contributes to the device's charge storage performance, an unprecedented feature in conventional or even polymer-based separator technologies.

The inventors have developed the invention, so that advantage can be achieved in an economical, practical, and facile manner. While preferred aspects and example configurations have been shown and described, it is to be understood that various further modifications and additional configurations will be apparent to those skilled in the art. It is intended that the specific embodiments and configurations herein disclosed are illustrative of the preferred nature of the invention and should not be interpreted as limitations on the scope of the invention.
, Claims:We claim
1. A separator for energy storage devices, wherein the separator comprising of:
a polymer matrix; and
metal ferrite nanoparticles
wherein the nanoparticles are uniformly dispersed in the polymer matrix to form a nanocomposite membrane.

2. The separator for energy storage devices as claimed in claim 1, wherein polymer matrix is selected as polyvinylidene fluoride (PVDF).

3. The separator for energy storage devices as claimed in claim 1, wherein metal ferrite nanoparticles selected are cobalt ferrite (CoFe₂O₄) nanoparticles.

4. The separator for energy storage devices as claimed in claim 1, wherein cobalt ferrite (CoFe₂O₄) nanoparticles are present in an amount ranging from 5 to 20 weight percent of the total nanocomposite.

5. The separator for energy storage devices as claimed in claim 1, wherein nanocomposite exhibits a bulk electrolyte resistance of less than 25 ohms measured by electrochemical impedance spectroscopy.

6. The separator for energy storage devices as claimed in claim 1, wherein the nanocomposite has a porosity in the range of 30 – 40% and thickness of 76 Microns.

7. The separator for energy storage devices as claimed in claim 1, wherein the nanocomposite exhibits thermal stability upto 500degree C.

8. The separator for energy storage devices as claimed in claim 1, wherein the charge transfer resistance of the nanocomposite is less than 30 ohms, confirming enhanced ionic transport.

9. The separator for energy storage devices as claimed in claim 1, wherein cobalt ferrite nanoparticles are synthesized via a sol-gel auto combustion method before dispersion in PVDF.

10. A method for preparing the separator as claimed in claim 1, wherein the method comprising the steps of:
i. synthesizing CoFe₂O₄ nanoparticles by sol-gel auto combustion;
ii. preparing a PVDF solution;
iii. dispersing CoFe₂O₄ nanoparticles uniformly into the PVDF solution;
iv. casting the mixture onto a flat glass petridish and
v. drying to form a flexible PVDF-CoFe₂O₄ nanocomposite film.

11. A PVDF-CoFe₂O₄ nanocomposite for use in flexible or wearable energy storage devices, hybrid systems, or sensing applications requiring combined flexibility and electrochemical activity.