DESC:METHODS FOR WELDING COMPONENTS OF BATTERY MODULE(S)
CROSS REFERENCE TO RELATED APPLICATIONS
The present application claims priority from Indian Provisional Patent Application No. 202421046304 filed on 15/06/2024, the entirety of which is incorporated herein by a reference.
TECHNICAL FIELD
Generally, the present disclosure relates to welding. Particularly, the present disclosure relates to a method of weld quality improvement.
BACKGROUND
The advancement of electric mobility, energy storage systems, and high-power electronic devices has led to an increasing demand for robust and reliable interconnection methods in battery pack assemblies. One critical component of the energy storage devices is the busbar-to-cell terminal connection, which ensures efficient current flow and structural integrity of the battery module.
Conventional methods for welding a busbar to the terminal of an electrical cell, such as resistance welding, ultrasonic welding, and laser welding, have been widely used in battery pack assembly for electric vehicles, consumer electronics, and energy storage systems. The traditional welding methods involve applying pressure and passing a controlled electric current through the interface, generating heat due to electrical resistance. The localized heat melts or softens the material, allowing the busbar and terminal to fuse upon cooling. The resistance welding is highly valued for precision, cleanliness, and the ability to join dissimilar conductive metals. The main types applicable include spot welding (most common in battery tab connections), projection welding (for structured contact points), and seam welding (for continuous joints). The resistance welding typically includes electrodes (usually copper-based), a power supply unit (capable of multi-pulse or waveform-controlled output), a force application mechanism, and a control system to regulate current, pressure, and duration.
However, there are certain problems associated with the existing or above-mentioned welding processes. For instance, the methods include inconsistent weld quality due to uneven heat distribution, high electrical resistance at the joint interface, and weak metallurgical bonding, especially when joining dissimilar or thin materials such as copper and aluminium. The absence of an interface-enhancing medium results in poor contact conformity, increased risk of voids and cracks, and greater thermal stress accumulation, thereby compromising the structural and electrical reliability of the weld joint. Additionally, traditional welding processes are more susceptible to surface contamination and oxidation, leading to premature joint degradation and reduced lifecycle performance in demanding environments such as electric vehicles or grid-scale storage systems.
Therefore, there exists a need for a method of welding a busbar to a terminal of an electrical cell that is efficient, robust, and overcomes one or more problems as mentioned above.
SUMMARY
An object of the present disclosure is to provide a method of welding a busbar to a terminal of an electrical cell.
Another object of the present disclosure is to provide a reliable and efficient method for welding a busbar to the terminal of an electrical cell using a nanoparticle-enhanced interface layer.
In accordance with an aspect of the present disclosure, there is provided a method of welding a busbar to a terminal of an electrical cell, the method comprising:
- positioning the busbar in contact with the terminal of the at least one electrical cell;
- introducing a nanoparticle-enhanced interface layer between the busbar and the terminal;
- pre-weld heating of the nanoparticle-enhanced interface layer between the busbar and the terminal; and
- applying a resistance welding to join the busbar and the terminal by controlling the energy input and contact pressure of the welding.
The method of welding a busbar to a terminal of an electrical cell, as described in the present disclosure, is advantageous in terms of providing a combination of pre-weld heating and uniform welding to ensure a stronger and more reliable bond between the metals. The use of nanoparticles in the welding process enhances the thermal and electrical conductivity at the welding interface. Further, due to the high surface area-to-volume ratio, the nanoparticles facilitate rapid and uniform heat transfer during resistance welding, reducing the risk of localized overheating or cold welds. The uniform heat transfer ensures a more uniform melt and solidification process, leading to stronger metallurgical bonds. Additionally, the nanoparticles improve electrical contact by filling microscopic surface gaps and irregularities, lowering the interfacial resistance and improving overall current flow efficiency. Therefore, the above-mentioned improvements translate into longer-lasting, more reliable battery connections.
Additional aspects, advantages, features, and objects of the present disclosure would be made apparent from the drawings and the detailed description of the illustrative embodiments constructed in conjunction with the appended claims that follow.
It will be appreciated that features of the present disclosure are susceptible to being combined in various combinations without departing from the scope of the present disclosure as defined by the appended claims.
BRIEF DESCRIPTION OF DRAWINGS
The summary above, as well as the following detailed description of illustrative embodiments, is better understood when read in conjunction with the appended drawings. For the purpose of illustrating the present disclosure, exemplary constructions of the disclosure are shown in the drawings. However, the present disclosure is not limited to specific methods and instrumentalities disclosed herein. Moreover, those in the art will understand that the drawings are not to scale. Wherever possible, like elements have been indicated by identical numbers.
Embodiments of the present disclosure will now be described, by way of example only, with reference to the following diagrams wherein:
Figure 1 illustrates a flow chart of a method of a busbar to a terminal of an electrical cell, in accordance with an embodiment of the present disclosure.
Figure 2 illustrates a detailed view of a busbar attached to a terminal of an electrical cell, in accordance with another embodiment of the present disclosure.
In the accompanying drawings, an underlined number is employed to represent an item over which the underlined number is positioned or an item to which the underlined number is adjacent. A non-underlined number relates to an item identified by a line linking the non-underlined number to the item. When a number is non-underlined and accompanied by an associated arrow, the non-underlined number is used to identify a general item at which the arrow is pointing.
DETAILED DESCRIPTION
The following detailed description illustrates embodiments of the present disclosure and ways in which they can be implemented. Although some modes of carrying out the present disclosure have been disclosed, those skilled in the art would recognize that other embodiments for carrying out or practicing the present disclosure are also possible.
As used herein, the term “welding” refers to a process of joining materials, such as metals or thermoplastics, by applying heat, pressure, or both. The process involves melting the base material and adding a filler material to form a weld joint that solidifies and cools to form a strong bond. The welding is performed using various techniques, each suited for different materials, joint configurations, and applications. Various types of welding include such as, but not limited to, arc welding (such as Shielded Metal Arc Welding or SMAW, and Gas Metal Arc Welding or GMAW), gas welding (oxy-acetylene welding), Metal Inert Gas (MIG) welding, Tungsten Inert Gas (TIG) welding, laser welding, and spot welding. Each type of welding process utilizes different energy sources, such as electric arcs, gas flames, or lasers, to melt and fuse materials. The basic components of a welding setup include the power supply to generate the heat, the electrode or filler material (used to fill the joint), and the welding torch or gun (to direct the heat and filler material to workpieces). In the welding process, the heat melts the base materials at the joint, and the filler material is added to fill the joint. Subsequently, the heat is removed, and the molten pool solidifies, forming a durable, fused bond between the two pieces. For certain types of welding, such as arc welding, an electrical arc is formed between an electrode and the workpiece, creating the required heat. Different welding processes offer various advantages, such as but not limited to speed, precision, or the ability to weld different materials.
As used herein, the term “busbar” refers to a conductive metal strip or bar that carries and distributes electric current across components within an electrical system, such as in battery modules or power distribution units. Further, the busbar serves as the primary electrical interconnect between individual cells or between cells and external circuitry. The busbars are made from high-conductivity materials such as, but not limited to, copper or aluminium, depending on electrical resistance and current-carrying capacity. The types of busbars are based on form and application, such as solid busbars, laminated busbars, and flexible busbars, each designed to manage space, heat, and mechanical stress effectively in different setups. The components of a busbar system for cell welding include the metal bar, insulating layers, mounting supports, and weldable contact surfaces devised for reliable connections. In the welding process, the busbar is positioned directly over the cell terminal and joined using techniques such as resistance welding or arc welding. Further, once welded, the busbar acts as a durable, low-resistance path for electrical current, ensuring even power distribution and thermal management across the battery pack. The structural role also supports mechanical stability and integrity within the battery module.
As used herein, the terms “electrical cell” and “cell” are used interchangeably and refer to a single energy storage unit, such as a lithium-ion cell or other rechargeable electrochemical cell used in battery modules for electric vehicles, power storage systems, or electronic devices. Specifically, the primary function of the cell is to convert stored chemical energy into electrical energy through redox reactions occurring between the anode and cathode, separated by an electrolyte. The various types of electrical cells used in the assemblies include cylindrical, prismatic, and pouch cells, each offering unique benefits in terms of energy density, thermal management, and packaging efficiency. The key components of an electrical cell include the anode (negative terminal), cathode (positive terminal), electrolyte, separator, and cell casing. Further, during the welding process, the busbars are attached to the terminals to form an electrical connection across multiple cells. The working of the electrical cell involves positioning the busbar over the cell terminal, preparing the interface, and applying resistance welding to create a strong, conductive bond.
As used herein, the terms “nanoparticle-enhanced interface layer”, “interface layer,” and “layer” are used interchangeably and refer to a thin layer applied at the contact surface between the busbar and the cell terminal, enriched with nanoparticles to improve bonding characteristics. The layer comprises the unique properties of nanoparticles, such as high surface area, thermal conductivity, and reactivity, to enhance the quality and consistency of the weld. The nanoparticles are metallic (such as copper, silver, nickel), ceramic (such as alumina, silica), or carbon-based (such as graphene, carbon nanotubes). Further, the interface layer also exhibits uniform, bimodal, or multimodal particle size distributions and is tailored to serve different functions such as conductivity enhancement, localized heating, or energy control. The components of the nanoparticle-enhanced interface layer include the base carrier medium (such as a paste or coating), embedded nanoparticles, and binders or dispersants used to maintain uniform distribution. During the welding process, the layer is first applied between the busbar and cell terminal and later exposed to controlled pre-weld heating. The nanoparticles promote localized heating and improve current flow paths during resistance welding. As the weld current is applied, the nanoparticle layer enhances heat generation and diffusion at the interface, contributing to superior metallurgical bonding. In some cases, the layer also forms self-assembling structures that improve insulation or energy focusing, ensuring a high-integrity and energy-efficient joint.
As used herein, the term “pre-weld heating” refers to a controlled thermal treatment of the joint interface in the region between the busbar and the cell terminal before the application of the main welding current. The purpose of pre-weld heating is to prepare the interface by reducing thermal gradients, enhancing nanoparticle activation, and improving material flow and bonding during welding. The types of pre-weld heating include inductive heating, resistive heating, laser-based heating, and infrared radiation, depending on the materials involved and the precision required. The pre-weld heating is often applied at temperatures ranging from approximately 100°C to 400°C, depending on the specific configuration and materials. The pre-weld heating system generally comprises a heat source (such as, induction coil or a resistance heater), a temperature control mechanism (sensors or thermocouples), and an energy regulation unit to ensure consistent heat application. In operation, as the nanoparticle-enhanced interface layer is applied between the busbar and terminal, the pre-weld heating step is initiated. The heating activates the nanoparticles, promotes uniform spreading or self-assembly, softens surface oxides, and reduces contact resistance at the interface.
As used herein, the term “resistance welding” refers to a thermo-electric process used to join a busbar to the terminal of an electrical cell by applying pressure and passing a controlled electric current through the interface, generating heat due to electrical resistance. The localized heat melts or softens the material, allowing the busbar and terminal to fuse upon cooling. The resistance welding is highly valued for precision, cleanliness, and the ability to join dissimilar conductive metals. The main types applicable include spot welding (most common in battery tab connections), projection welding (for structured contact points), and seam welding (for continuous joints). The resistance welding typically includes electrodes (usually copper-based), a power supply unit (capable of multi-pulse or waveform-controlled output), a force application mechanism, and a control system to regulate current, pressure, and duration. In operation, the electrodes clamp the busbar and terminal together with a set force. A pulse or sequence of electrical pulses is passed through the joint, generating heat due to resistance at the contact surfaces, especially at the nanoparticle-enhanced interface layer. The nanoparticles aid by enhancing local heating and current flow uniformity. As the materials soften or melt, the maintained pressure ensures intimate contact and fusion. Further, as the current stops, the joint solidifies under pressure, resulting in a durable and conductive weld.
As used herein, the terms “predefined group” and “group” are used interchangeably and refer to a selected category of nanoparticles that possess the required thermal, electrical, and chemical properties to enhance the welding interface. The nanoparticles are selected based on factors such as high electrical and thermal conductivity, stability at elevated temperatures, compatibility with metal substrates, and minimal reactivity with electrode materials. The common types of nanoparticles in this group include metallic nanoparticles (such as silver, copper, nickel), metal oxide nanoparticles (such as zinc oxide, aluminium oxide), and carbon-based nanoparticles (such as graphene, carbon nanotubes). Each type of nanoparticle offers unique benefits, such as metallic nanoparticles provide excellent conductivity, oxides offer thermal stability and controlled insulation, and carbon-based materials provide lightweight reinforcement and high conductivity. The components of the predefined group include a primary nanoparticle material, any surface functionalization agents (to improve dispersion and adhesion), and binders or solvents to apply the nanoparticles uniformly in a layer. Specifically, the nanoparticles are dispersed in a carrier medium and introduced between the busbar and terminal surfaces before welding. Further, the nanoparticles provide heat absorption, diffusion, and bonding enhancement, creating a more reliable and conductive joint.
As used herein, the term “multimodal distribution” refers to the presence of nanoparticles of varying sizes within a single interface layer, typically arranged in two or more distinct sizes. The multimodal distribution is used to enhance the thermal, electrical, and mechanical behavior of the nanoparticle-enhanced interface layer. The multimodal distribution includes, for example, a mixture of small (such as 20–40 nm) and larger (such as 60–80 nm) nanoparticles. The variation in particle size helps improve packing density, heat distribution, and structural interlocking at the interface. The components of a multimodal nanoparticle system typically include two or more nanoparticle size groups, a carrier medium (such as a conductive or insulating polymer), and optional binders or dispersants to ensure uniform distribution. Further, the multimodal distribution enables efficient thermal conduction and controlled melting at the interface by optimizing the contact points and heat flow. The smaller particles fill voids between larger ones, enhancing density and energy absorption, and the combination creates a functionally graded interfacial zone that transitions more smoothly between the busbar and terminal materials. Therefore, the gradient improves bonding quality, reduces thermal stress, and promotes robust metallurgical fusion during resistance welding.
As used herein, the term “functionally graded interfacial zone” and “FGIZ” are used interchangeably and refer to a transition layer formed between the two materials, in which the composition, structure, or properties vary gradually, achieved using a controlled distribution of nanoparticles. The grading minimizes abrupt changes in material properties (such as thermal expansion, conductivity, or hardness), thereby enhancing the mechanical and electrical integrity of the weld. The types of functional gradients include compositional gradients, size gradients (varying nanoparticle size through the thickness), or density gradients (variation in nanoparticle concentration). The FGIZ typically comprises a mix of nanoparticles such as metals, ceramics, or conductive carbons embedded within a matrix or carrier medium. Further, the nanoparticles are applied such that the concentration or size varies across the layer’s thickness, via processes such as, but not limited to, layer-by-layer deposition, spray coating, and controlled sintering. Furthermore, during resistance welding, the functionally graded layer allows heat to distribute more evenly, reduces thermal mismatch stress, and facilitates gradual bonding across the interface.
As used herein, the terms “self-assembling insulating boundary layer” and “boundary layer” are used interchangeably and refer to a nanoscale interface structure that spontaneously self-organizes into a functional, electrically insulating layer in response to heat, pressure, or environmental triggers. Further, the boundary layer regulates or limits the flow of electric current and heat beyond the targeted weld zone, thereby preventing energy leakage and ensuring localized, efficient bonding. The types of self-assembling layers include thermally activated, pressure-activated, and chemically-triggered assemblies, depending on the nature of the nanoparticle material and the surface functionalization. The key components of the boundary layer include nanoparticles, such as but not limited to silica, alumina, boron nitride, or polymer-coated nanomaterials that enable the nanoparticles to arrange into structured formations upon activation. The nanoparticles are typically dispersed in a carrier medium and applied as part of the interface layer between the busbar and cell terminal. Furthermore, the pre-weld heating or pressure application, the particles to reorient and bind into an organized boundary that exhibits insulating properties. The self-assembled layer during welding acts in containing the energy within the desired fusion region, improving process control and weld quality.
As used herein, the terms “multi-pulse waveform” and “waveform” are used interchangeably and refer to a controlled series of electrical current pulses applied during the resistance welding process. The multi-pulse welding uses several current pulses with varying amplitudes, durations, or intervals to manage heat generation and material flow. The technique allows for fine-tuned thermal control, improved fusion quality, and better accommodation of complex material interfaces, such as surface enhanced with nanoparticles. The types of multi-pulse waveforms include, but not limited to, preheat pulses, main weld pulses, and post-weld cooling pulses, each serving a distinct purpose in the bonding cycle. The delivery of the multi-pulse waveform consists of a programmable welding controller, precision current sources, and real-time feedback sensors for monitoring temperature, resistance, and displacement. In operation, initial low-energy pulses gradually heat the interface, promoting softening and reducing contact resistance. Subsequently, the higher-energy pulses cause localized melting and metallurgical bonding, and end pulses help solidify the joint under pressure and control cooling rates. The multi-pulse waveform reduces spatter, prevents overheating, and improves joint strength and consistency, particularly when joining dissimilar materials.
As used herein, the term “resistance value” refers to electrical resistance measured at the interface between the two components during the welding process. The resistance value directly influences the amount of heat generated through Joule heating (I²R), where I is the current and R is the resistance. In welding, the resistance value ensures consistent heat generation, optimal fusion, and minimal defects. The types of resistance values considered include initial contact resistance, dynamic resistance during welding, and post-weld resistance, each providing insights into interface condition, material behavior, and weld quality. The key components influencing the resistance value include the surface roughness and cleanliness of the busbar and terminal, the presence and properties of the nanoparticle-enhanced interface layer, and the applied pressure during welding. Further, the sensors integrated with the resistance welding systems continuously monitor the resistance in real-time. As the busbar and cell terminal are pressed together and current is applied, the resistance value changes dynamically. Further, monitoring and controlling the resistance profile is essential for optimizing energy input, preventing overheating, and ensuring a strong, defect-free weld joint.
In accordance with an aspect of the present disclosure, there is provided a method of welding a busbar to a terminal of an electrical cell, the method comprising:
- positioning the busbar in contact with the terminal of the at least one electrical cell;
- introducing a nanoparticle-enhanced interface layer between the busbar and the terminal;
- pre-weld heating of the nanoparticle-enhanced interface layer between the busbar and the terminal; and
- applying a resistance welding to join the busbar and the terminal by controlling energy input and contact pressure of the welding.
Figure 1 describes a method 100 of welding a busbar 202 to a terminal 204 of an electrical cell 206. The method 100 starts at a step 102. At the step 102, the method 100 comprises positioning the busbar 202 in contact with the terminal 204 of the at least one electrical cell 206. At a step 104, the method 100 comprises introducing a nanoparticle-enhanced interface layer between the busbar 202 and the terminal 204. At a step 106, the method 100 comprises pre-weld heating of the nanoparticle-enhanced interface layer between the busbar 202 and the terminal 206. At a step 108, the method 100 comprises applying a resistance welding to join the busbar 202 and the terminal 204 by controlling energy input and contact pressure of the welding.
The above-mentioned method aims to weld a busbar 202 to a terminal 204 of an electrical cell 206 with accurately positioning the busbar 202 in contact with the terminal 204. The physical alignment ensures that the intended contact area is uniform, allowing for optimal current flow and minimal resistance. Further, the surfaces of the busbar 202 and the terminal 204 are prepared to remove oxides or contaminants that impede conductivity or interfere with the welding process. Further, the nanoparticle-enhanced interface layer is introduced between the busbar 202 and the terminal 204. The layer typically consists of metallic nanoparticles, such as but not limited to copper, silver, or nickel, suspended in a carrier medium. The nanoparticles serve to enhance the thermal and electrical conductivity at the interface, reduce localized thermal gradients, and promote uniform melting during welding. Subsequently, the interface layer is subjected to the pre-weld heating process, which activates the nanoparticles by removing any volatile substances in the medium and initiates diffusion bonding at the microscopic level. The pre-heating also helps to reduce thermal mismatch stress between the busbar 202 and terminal materials, ensuring a smoother transition during resistance welding. The welding step involves resistance welding, where controlled electric current and pressure are applied across the interface. Specifically, the energy input is regulated to ensure that sufficient localized heat is generated at the contact point, enabling the materials and the nanoparticle interface to melt and fuse under applied pressure. The precise control over energy and pressure minimizes the risk of overheating, spatter, or cold welds. The above-mentioned method is advantageous in terms of enhanced thermal and electrical conductivity at the welding interface. Further, due to the high surface area-to-volume ratio, the nanoparticles facilitate rapid and uniform heat transfer during resistance welding, reducing the risk of localized overheating or cold welds. The uniform heat transfer ensures a more uniform melt and solidification process, leading to stronger metallurgical bonds. Additionally, the nanoparticles improve electrical contact by filling microscopic surface gaps and irregularities, lowering the interfacial resistance and improving overall current flow efficiency. Furthermore, the use of functionally graded nanoparticle layers allows for stress mitigation and improved mechanical integrity. By tailoring the concentration and type of nanoparticles across the thickness of the interface, the joint can better absorb thermal expansion differences between the busbar 202 and terminal materials, reducing the cracking, delamination, or fatigue over time. The nanoparticles also serve as a barrier to oxidation and contamination, preserving the quality of the joint over extended service life. The improvements translate into longer-lasting, more reliable battery connections, especially in high-demand applications like electric vehicles, where safety, thermal stability, and power delivery consistency are critical.
Referring to figure 2, in accordance with an embodiment, there is described the nanoparticle-enhanced interface layer formed between the busbar 102 and the terminal 104. The nanoparticle-enhanced interface layer comprises a multimodal distribution of nanoparticles formed by varying the concentration of the nanoparticles across the thickness of the interface layer. Further, the multimodal distribution of the nanoparticle sizes comprises a plurality of functionally graded interfacial zones formed by introducing a higher concentration of nanoparticles near the terminal 204 and a lower concentration of nanoparticles near the busbar 202. Furthermore, the interface layer comprises a self-assembling insulating boundary layer formed by graded pre-heating of the interface layer near the busbar 202.
In an embodiment, the nanoparticle-enhanced interface layer comprises at least one nanoparticle selected from a predefined group and wherein the particle size of the at least one nanoparticle ranges between 20 and 80 nanometres. The nanoparticle-enhanced interface layer comprises nanoparticles with a particle size in the range of 20 to 80 nanometers, which balances surface reactivity, thermal conductivity, and process stability. The nanoparticles within the above-mentioned size range exhibit high surface area-to-volume ratios, enabling enhanced surface energy and promoting stronger interfacial bonding between the busbar and terminal. The particles are incorporated using techniques such as, but not limited to, colloidal suspension deposition, inkjet printing, or aerosol spraying, followed by drying and mild pre-weld sintering. Further, the small size allows for better dispersion and uniform coating across the contact area, leading to a more consistent and controllable welding interface. Additionally, the size range is effective in minimizing agglomeration and provides sufficient contact points for conductive bridging during resistance welding. The nanoparticles in the 20–80 nm range provide significant improvement in heat transfer and current flow at the weld interface. Further, the nanoparticles facilitate rapid thermal conduction and uniform heating, ensuring a stable melt zone during resistance welding and reducing localized overheating or cold spots. The reduced localized overheating results in stronger metallurgical bonds, lower electrical resistance, and reduced defect rates such as voids or cracks. Furthermore, the enhanced diffusion and bonding provided by the nanoparticles improve the mechanical integrity and lifespan of the welded joint, especially under dynamic load or thermal cycling conditions.
In an embodiment, the nanoparticle-enhanced interface layer comprises a multimodal distribution of nanoparticles formed by varying the concentration of the nanoparticles across the thickness of the interface layer. Specifically, the nanoparticle-enhanced interface layer is refined by employing a multimodal distribution of nanoparticles, which involves varying the concentration and size of the nanoparticles across the thickness of the interface layer. Further, the multimodal distribution is achieved through techniques such as, but not limited to, layer-by-layer deposition, gradient mixing, and controlled spraying, as higher concentrations of smaller nanoparticles are positioned closer to the terminal surface, and larger particles or lower concentrations are placed toward the busbar side. The purpose of the graded distribution is to optimize thermal and electrical conductivity while managing thermal expansion mismatches between dissimilar metals. Furthermore, the smaller nanoparticles near the terminal enhance interfacial diffusion and bonding, and larger or sparser particles on the busbar side maintain mechanical strength and improve load transfer during welding. The multimodal distribution is the creation of a functionally graded interface that accommodates both thermal and mechanical stress during and after welding. Furthermore, the gradient layer ensures smoother heat propagation and prevents abrupt thermal spikes, reducing the microcracks or delamination. The gradient layer facilitates controlled melting and bonding yields, enhancing the wetting and metallurgical fusion between the busbar and terminal. The advantages of the gradient layer include improved joint integrity, reduced interfacial resistance, and longer service life of the welded structure. Further, the graded nanoparticle interface enhances thermal stability, minimizes degradation over charge-discharge cycles, and contributes to safer, more efficient energy distributions.
In an embodiment, the multimodal distribution of the nanoparticle sizes comprises a plurality of functionally graded interfacial zones formed by introducing a higher concentration of nanoparticles near the terminal 204 and a lower concentration of nanoparticles near the busbar 202. The multimodal distribution of nanoparticle sizes creates a plurality of functionally graded interfacial zones, achieved by introducing a higher concentration of nanoparticles near the terminal 204 and a lower concentration near the busbar 202. Specifically, the gradient is formed using techniques, such as but not limited to electrophoretic deposition, controlled dip-coating, and spray coating with variable feed rates. Further, by concentrating smaller, more reactive nanoparticles near the terminal, the method encourages stronger interfacial diffusion and metallurgical bonding at that critical junction, and the sparser, larger particles near the busbar 202 maintain structural stability without promoting excessive melting or warping. The above-mentioned tailored gradient leads to the formation of a thermally and mechanically optimized bond zone that reduces the formation of hotspots and minimizes stress concentrations during resistance welding and thermal cycling. Furthermore, the homogeneity of the weld is enhanced, and the probability of failure due to fatigue or thermal expansion mismatches is reduced. The advantages of the graded interfacial zone include improved weld quality, higher resistance to delamination, and increased electrical efficiency due to the more intimate and uniform contact at the interface. In battery packs for electric vehicles or power grids, the interfacial zone in the welding results in a more robust, reliable connection that supports extended life cycles, reduced maintenance needs, and better overall battery performance.
In an embodiment, the pre-weld heating of the nanoparticle-enhanced interface layer is performed within a temperature range of 100°C and 300°C. The pre-weld heating of the nanoparticle-enhanced interface layer is conducted within a temperature range of 100°C to 300°C that activates the interface without causing premature melting or degradation. Specifically, the heating step is performed using techniques such as, but not limited to, localized infrared heaters, resistive heating plates, and laser preheating systems. Further, within the above-mentioned temperature range, the surface energy of the nanoparticles increases, promoting partial sintering and enhanced adhesion to both the terminal and busbar surfaces. Essentially, the temperature value is high enough to evaporate any residual solvents or volatile components from the nanoparticle coating and also adequately low to avoid thermal distortion or oxidation of the underlying conductive metals. The pre-weld heating in the controlled temperature range provides a more uniform and reactive interface layer, which improves energy transfer during the subsequent resistance welding step. Further, by stabilizing the nanoparticle layer and enhancing the bonding characteristics, the pre-heating step reduces the risk of delamination or void formation at the weld site. The advantages of the pre-weld heating include improved interfacial contact, enhanced joint strength, and more consistent weld quality. Additionally, the pre-conditioning minimizes thermal shock during the main welding process and contributes to better repeatability and reliability, particularly beneficial in automated battery manufacturing for improved precision and durability.
In an embodiment, the interface layer comprises a self-assembling insulating boundary layer formed by graded pre-heating of the interface layer near the busbar 202. The interface layer comprises a self-assembling insulating boundary layer formed by graded pre-heating near the busbar 202. Specifically, the graded pre-heating involves gradually increasing the temperature in a controlled manner at the busbar 202 side of the interface using localized thermal sources such as, but not limited to, precision IR lamps or laser scanning systems. Further, the thermal gradient induces differential reactions within the nanoparticle-enhanced layer, as components such as organic binders or doped insulating materials migrate and selectively accumulate near the busbar interface. Consequently, a thin, self-organized insulating boundary forms that acts as a thermal and electrical buffer. The layer limits excessive current flow or heat transfer into the busbar during resistance welding, preventing over-penetration or thermal damage. The above-mentioned self-assembling insulating boundary provides enhanced control over current distribution and thermal flow during the welding process. Furthermore, by partially insulating the busbar 202, the weld energy is more effectively concentrated at the terminal side with strong metallurgical bonding. The selective energy focusing leads to cleaner weld zones, minimized thermal distortion of the busbar, and improved interface uniformity. The advantages of the boundary layer include better weld localization, reduced risk of busbar overheating, and overall improved durability and electrical isolation in the energy systems.
In an embodiment, the energy input is applied via a multi-pulse waveform with a variable amplitude and frequency based on the multimodal distribution of the nanoparticle layer. The energy input during resistance welding is applied using a multi-pulse waveform with variable amplitude and frequency based on the multimodal distribution of the nanoparticle-enhanced interface layer. The approach involves programming the welding system to deliver a sequence of electrical pulses starting with low-energy pulses to pre-condition the interface, followed by higher-energy pulses for fusion, and concluding with tapering pulses for controlled solidification. The pulse characteristics are adjusted with the graded structure of the interface. The multi-pulse waveform optimizes energy distribution and improves weld control, particularly over complex, non-uniform interfaces. The multi-pulse waveform reduces thermal stress and minimizes microstructural defects by preventing overheating and promoting uniform fusion across the graded nanoparticle interface. Additionally, the multi-phase input waveform allows finer control over the melting and re-solidification phases, which is crucial in preserving the functionality of delicate insulating or functional layers. The advantages of multi-phase waveforms include higher weld strength, lower electrical resistance, reduced Heat-Affected Zones (HAZ), and better process repeatability.
In an embodiment, a resistance value is computed at the nanoparticle-enhanced interface layer based on the variable amplitude and frequency of the multiphase energy input waveform. The dynamic measurement of the resistance value is done via monitoring of the voltage and current signals during each phase of the input pulse sequence. Further, as different pulse amplitudes and frequencies are applied, the interface’s electrical response varies due to changes in temperature, material diffusion, and nanoparticle behavior. The variations are captured using embedded sensors or inline monitoring systems, which compute the instantaneous resistance of the interface at different stages of the welding process. The real-time resistance computation enhances the ability to precisely characterize and control the welding process, ensuring consistent weld quality. Further, by interpreting the resistance feedback in correlation with energy input parameters, the system identifies incomplete bonding, overheating, or material degradation. The identification enables closed-loop control, as welding parameters are automatically adjusted to optimize bonding conditions. The advantages of the resistance computation include improved process stability, defect detection, adaptive quality assurance, and enhanced repeatability.
Based on the above-mentioned embodiments, the present disclosure provides significant advantages such as (but not limited to) ensures a stronger and a reliable bond between the two metals, optimization of the welding process, eliminates any micro voids or inconsistencies in the weld, strengthening the material at the joint interface and predicts the weld joint performance.
In the description of the present invention, it is also to be noted that, unless otherwise explicitly specified or limited, the terms “disposed,” “mounted,” and “connected” are to be construed broadly, and may for example be fixedly connected, detachably connected, or integrally connected, either mechanically or electrically. They may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meaning of the above terms in the present invention can be understood in specific cases to those skilled in the art.
Modifications to embodiments and combinations of different embodiments of the present disclosure described in the foregoing are possible without departing from the scope of the present disclosure as defined by the accompanying claims. Expressions such as “including”, “comprising”, “incorporating”, “have”, and “is” used to describe and claim the present disclosure are intended to be construed in a non-exclusive manner, namely allowing for items, components, or elements not explicitly described also to be present. Reference to the singular is also to be construed to relate to the plural where appropriate.
Although embodiments have been described with reference to a number of illustrative embodiments thereof, it should be understood that numerous other modifications and embodiments can be devised by those skilled in the art that will fall within the spirit and scope of the principles of this disclosure. More particularly, various variations and modifications are possible in the component parts and/or arrangements of the subject combination arrangement within the scope of the present disclosure, the drawings, and the appended claims. In addition to variations and modifications in the component parts and/or arrangements, alternative uses will also be apparent to those skilled in the art.
,CLAIMS:WE CLAIM:
1. A method (100) of welding a busbar (202) to a terminal (204) of an electrical cell (206), the method (100) comprising:
- positioning the busbar (202) in contact with the terminal (204) of at least one electrical cell (206);
- introducing a nanoparticle-enhanced interface layer between the busbar (202) and the terminal (204);
- pre-weld heating of the nanoparticle-enhanced interface layer between the busbar (202) and the terminal (204); and
- applying a resistance welding to join the busbar (204) and the terminal (204) by controlling the energy input and contact pressure of the welding.

2. The method (100) as claimed in claim 1, wherein the nanoparticle-enhanced interface layer comprises at least one nanoparticle selected from a predefined group, and wherein the particle size of the at least one nanoparticle ranges between 20 and 80 nanometres.

3. The method (100) as claimed in claim 1, wherein the nanoparticle-enhanced interface layer comprises a multimodal distribution of nanoparticles formed by varying the concentration of the nanoparticles across the thickness of the interface layer.

4. The method (100) as claimed in claim 3, wherein the multimodal distribution of the nanoparticle sizes comprises a plurality of functionally graded interfacial zones formed by introducing a higher concentration of nanoparticles near the terminal (204) and a lower concentration of nanoparticles near the busbar (202).

5. The method (100) as claimed in claim 1, wherein the pre-weld heating of the nanoparticle-enhanced interface layer is performed within a temperature range of 100°C and 300°C.

6. The method (100) as claimed in claim 1, wherein the nanoparticle-enhanced interface layer comprises a self-assembling insulating boundary layer formed by graded pre-heating of the interface layer near the busbar (202).

7. The method (100) as claimed in claim 1, wherein the energy input is applied via a multi-pulse waveform with a variable amplitude and frequency based on the multimodal distribution of the nanoparticle layer.

8. The method (100) as claimed in claim 1, wherein a resistance value is computed at the nanoparticle-enhanced interface layer based on the variable amplitude and frequency of the multiphase energy input waveform.