Connecting piece, battery, battery pack and electric device

Abstract

The application provides a connecting tab, a battery, a battery pack and an electric device. The connecting tab comprises a current collecting layer and a functional layer. The functional layer is arranged on at least part of the surface of the current collecting layer. The absorption rate of the functional layer to laser is greater than that of the current collecting layer to laser. The functional layer is partially soluble in the electrolyte. The connecting tab can solve the technical problem that the absorption intensity of the connecting tab to laser is low in the prior art, and the phenomenon of poor welding such as virtual welding and empty welding easily occurs in the process of laser welding, which leads to poor welding strength between the connecting tab, the tab and the electrode terminal, and greatly affects the safety performance and use reliability of the battery. Meanwhile, the functional layer is soluble in the electrolyte, and the technical problem that the solid impurities formed by the falling of the coating material in the battery have a potential negative impact on the safety performance and reliability of the battery can also be solved.

Description

Technical Field

[0001] This application relates to the field of batteries, specifically to a connector, a battery, a battery pack, and an electrical device. Background Technology

[0002] With the continuous development of lithium-ion battery technology, lithium-ion batteries have advantages over other types of batteries such as lead-acid and nickel-cadmium batteries, including higher specific capacity, no memory effect, higher operating voltage, faster charging speed, wider operating temperature range, longer cycle life, smaller size, and lighter weight. Currently, lithium-ion batteries are widely used in mobile phones, laptops, electric vehicles, energy storage cabinets, and other fields, and their application range is becoming increasingly broad. Connecting tabs are crucial bridges between the battery's tabs and electrode terminals, and laser welding is typically used to connect them. However, current connecting tabs have low laser absorption intensity, making them prone to poor welding, such as incomplete welds or gaps, during laser welding. This results in poor weld strength between the connecting tabs and the tabs and electrode terminals, significantly affecting the battery's safety performance and reliability. Summary of the Invention

[0003] To address the aforementioned issues, this application provides a connecting piece, a battery, a battery pack, and an electrical device to solve the technical problem in the prior art where the connecting piece has low laser absorption intensity, making it prone to poor welding such as incomplete welding and empty welding during laser welding. This results in poor welding strength between the connecting piece and the tabs and electrode terminals, which greatly affects the safety performance and reliability of the battery.

[0004] A first aspect of this application provides a connector for use in a battery, the battery including an electrolyte, the connector including: a current collector layer; and a functional layer disposed on at least a portion of the surface of the current collector layer; the functional layer having a higher absorption rate of laser light than the current collector layer, and the functional layer being partially soluble in the electrolyte.

[0005] It is understandable that by placing the functional layer on the surface of the welding area of ​​the current collector, where the functional layer has a higher laser absorption rate than the current collector, the reflectivity of the connecting piece to the laser can be reduced, and the absorption of laser energy in the welding area can be increased. This improves the welding strength between the connecting piece and the tab after laser welding, ensuring the connection strength between the connecting piece and the tab and reducing the battery resistance, thereby ensuring the battery has a high capacity and good cycle life. By making the functional layer soluble in the electrolyte, on the one hand, the functional layer provides better laser absorption during laser welding, achieving a good connection between the connecting piece and the tab; on the other hand, after the battery is injected with electrolyte, the functional layer is wetted by the electrolyte and soluble in the electrolyte, preventing the coating from falling directly into the battery and existing in the battery system as a solid impurity, reducing self-discharge and preventing internal short circuits, thus ensuring the battery's safety performance and reliability.

[0006] Furthermore, the thickness of the functional layer is 0.2μm≤D≤2μm.

[0007] It is understandable that by setting the thickness of the functional layer to 0.2μm≤D≤2μm, not only can the connecting piece have a high absorption rate for laser, improve the welding strength between the connecting piece and the tab, ensure the current transmission efficiency of the battery and reduce the internal resistance of the battery, but it can also ensure that the concentration of metal cations introduced after the functional layer dissolves in the electrolyte is within a controllable range, thereby ensuring that the battery has a high capacity and a good cycle life.

[0008] Furthermore, the functional layer comprises a metal complex and a resin, wherein the metal complex is dispersed in the resin and is soluble in the electrolyte.

[0009] It is understood that the metal complex in the functional layer covers the welding area of ​​the connecting piece, and the metal complex plays a major role in improving the absorption rate of the connecting piece to the laser. During laser welding, it can reduce the reflection of the connecting piece to the laser and enhance the absorption intensity of the connecting piece to the laser, thereby improving the welding strength of the connecting piece to the tabs after laser welding, reducing the battery resistance, and thus ensuring that the battery has a high capacity and good cycle life. When the battery is injected with electrolyte, the metal complex can dissolve in the electrolyte, preventing the coating from falling directly into the battery and existing in the battery system as a solid impurity, reducing battery self-discharge and preventing internal short circuits, thereby ensuring the battery's safety performance and reliability. The resin in the functional layer can be used to disperse the metal complex, which not only allows the metal complex to be loaded onto the current collector layer, increasing the connection strength between the metal complex and the current collector layer, but also forms a uniform film, thereby better ensuring the adhesion strength and load uniformity of the metal complex on the connecting piece, further ensuring the connection strength between the connecting piece and the tabs after laser welding, and further ensuring that the battery has a high capacity and good cycle life.

[0010] Furthermore, the mass percentage of the metal complex in the functional layer ranges from 80% to W1 to 99%; and the mass percentage of the resin in the functional layer ranges from 1% to W2 to 20%.

[0011] It is understandable that by setting the mass percentage of the metal complex in the functional layer to be 80% ≤ W1 ≤ 99% and the mass percentage of the resin in the functional layer to be 1% ≤ W2 ≤ 20%, on the one hand, the metal complex in the functional layer can reduce the reflection of the connecting piece to the laser, increase the absorption intensity of the connecting piece to the laser, and ensure the connection strength between the connecting piece and the electrode after laser welding, thereby ensuring that the battery has a high capacity and good cycle life; on the other hand, it can ensure that the metal complex is uniformly dispersed in the resin, and the functional layer can be uniformly filmed on the connecting piece, ensuring the adhesion strength and load uniformity of the metal complex on the connecting piece, thereby reducing the battery resistance and improving the reliability of the connecting piece.

[0012] Furthermore, the metal complex comprises a metal cation and a ligand, wherein the metal cation comprises at least one of chromium ions, iron ions, titanium ions, and zinc ions; and the ligand comprises at least one of phthalocyanine, thiodiene polymer, polyurethane, and mordant black.

[0013] It is understood that when the metal cation is at least one of chromium ions, iron ions, titanium ions, and zinc ions, the metal complex is a transition metal complex. The inventors discovered that in transition metal complexes, the d orbitals of the transition metal cations originally have the same energy. Under the influence of the ligand-formed ligand field, the d orbital energy levels of the transition metal cations split. The split orbitals are not filled with electrons, and electrons can transition between the different energy levels of the split orbitals, thus producing an absorption spectrum. By configuring the metal complex to include metal cations and ligands, wherein the metal cations include at least one of chromium ions, iron ions, titanium ions, and zinc ions, during laser welding, the unfilled d orbitals in the metal complex can absorb the laser and achieve transitions between different orbitals, enhancing the absorption intensity of the connecting piece to the laser during laser welding, reducing the reflectivity of the connecting piece to the laser, and the absorbed energy is less likely to be conducted and diffused to the surroundings compared to the current collector layer. This ensures that the welded area forms a highly concentrated heat source zone within a short time, thereby causing the connecting piece and the electrode to partially melt and form a strong weld point and weld seam, ensuring the connection strength between the connecting piece and the electrode, and ensuring that the battery has a high capacity and good cycle life.

[0014] Furthermore, the average particle size range of the metal complex is 5 nm ≤ D 50 ≤20nm.

[0015] It is understandable that by setting the average particle size range of the metal complex to 5nm≤D50≤20nm, the particle size of the metal complex is moderate, which can not only ensure the uniformity of dispersion of the metal complex in the resin, but also help control the thickness of the functional layer and the uniformity of distribution of the metal complex, provide more active sites for absorbing laser, reduce the difficulty of uniformly attaching the coating to the current collector layer, and ensure the absorption intensity of the laser by the connecting piece, thereby improving the connection strength between the connecting piece and the tab, thus ensuring that the battery has high capacity and good cycle life.

[0016] Furthermore, the reflectivity of the functional layer to laser light ranges from 5% to R to 70%, and the absorption rate of the functional layer to laser light ranges from 30% to A to 95%.

[0017] Understandably, by selecting metallic complexes with dark or even black colors, the functional layer primarily absorbs and reflects laser light, with virtually no transmission. In other words, the sum of the functional layer's laser absorption rate (A) and its laser reflection rate (R) is approximately 100%. By setting the functional layer's laser absorption rate within the range of 30% ≤ A ≤ 95% and its laser reflection rate within the range of 5% ≤ R ≤ 70%, the absorption intensity of the functional layer can be guaranteed, while reducing the reflectivity of the connecting piece. Furthermore, the absorbed energy is less likely to diffuse to the surrounding environment compared to the current collector layer, causing localized melting of the connecting piece and the electrode tab to form strong weld points and seams. This ensures the connection strength between the connecting piece and the electrode tab, thereby guaranteeing the battery's high capacity and good cycle life.

[0018] Furthermore, the resin includes at least one of rosin ester, ketone resin, xylene resin, acrylic resin, polyamide resin, ethylene resin, alkylphenol resin, maleic acid resin, and cellulose resin.

[0019] It is understandable that using the above-mentioned substances as resins for dispersing metal complexes can reduce the time required for uniform dispersion of metal complexes, improve the uniformity of coating slurry film formation and ensure the adhesion strength of functional layers, further improve the absorption intensity of laser on the connecting piece, and better ensure the connection strength between the connecting piece and the tab after laser welding, thereby better ensuring that the battery has a higher capacity and a better cycle life.

[0020] A second aspect of this application provides a battery comprising: an electrolyte; an electrode assembly; and a connecting piece as described in the embodiments of this application, wherein the electrode assembly is at least partially immersed in the electrolyte, and the electrode assembly is electrically connected to the connecting piece.

[0021] Furthermore, the functional layer comprises a metal complex and a resin, the metal complex being soluble in the electrolyte, the metal complex comprising a metal cation and a ligand, and the metal cation having a mass content of 1 ppm ≤ C ≤ 70 ppm in the electrolyte.

[0022] It is understandable that when the mass content (C) of the metal cation in the electrolyte is greater than 70 ppm, the concentration of the metal cation in the electrolyte is relatively high. During battery charge-discharge cycles, it may react with other substances in the battery system, and excessive side reactions and byproducts will affect the battery's cycle performance. By setting the mass content of the metal cation in the electrolyte to 1 ppm ≤ C ≤ 70 ppm, it is possible to ensure that the connector has a high absorption rate for laser light, improve the welding strength between the connector and the tab, ensure the current transmission efficiency of the battery, and reduce the battery's internal resistance. Moreover, by setting the mass content of the metal cation in the electrolyte to 1 ppm ≤ C ≤ 70 ppm, it is also possible to ensure that the concentration of metal cations introduced after the functional layer dissolves in the electrolyte is within a controllable range, thereby better ensuring that the battery has a high capacity and a good cycle life.

[0023] A third aspect of this application provides a battery pack comprising:

[0024] Box;

[0025] The batteries described in the embodiments of this application are housed in the casing and are electrically connected, wherein the electrical connection of the batteries includes at least one of series and parallel connection.

[0026] A fourth aspect of this application provides an electrical appliance, comprising:

[0027] The electrical equipment body and the battery described in the embodiments of this application, wherein the battery supplies power to the electrical equipment body. Attached Figure Description

[0028] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 This is a schematic diagram of the structure of a connecting piece according to an embodiment of this application.

[0030] Figure 2 yes Figure 1 The diagram shows a cross-sectional view of the connecting piece along the CC direction.

[0031] Figure 3 This is a schematic diagram of the connecting piece according to another embodiment of this application.

[0032] Figure 4 yes Figure 3 The diagram shows a cross-sectional view of the connecting piece along the CC direction.

[0033] Figure 5 This is a schematic diagram of the structure of a battery according to an embodiment of this application.

[0034] Figure 6 This is an exploded view of a battery according to an embodiment of this application.

[0035] Figure 7 This is a schematic diagram of the structure of a battery pack according to an embodiment of this application.

[0036] Figure 8 This is a schematic diagram of the structure of an electrical device according to an embodiment of this application, when the device body and battery are not assembled.

[0037] Explanation of reference numerals in the attached figures:

[0038] 100-Connecting piece, 110-Current collector layer, 111-Body, 112-Welding area, 120-Functional layer, 200-Battery, 210-End cap assembly, 220-Electrode assembly, 230-Housing, 300-Battery pack, 310-Box, 311-Accommodation cavity, 400-Electrical device, 410-Electrical device body. Detailed Implementation

[0039] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present application.

[0040] The terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish different objects, not to describe a specific order. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps or units is not limited to the listed steps or units, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to these processes, methods, products, or apparatuses.

[0041] The technical solutions in the embodiments of this application will now be described with reference to the accompanying drawings.

[0042] It should be noted that, for ease of explanation, the same reference numerals denote the same components in the embodiments of this application, and for the sake of brevity, detailed descriptions of the same components are omitted in different embodiments.

[0043] With the continuous development of lithium-ion battery technology, lithium-ion batteries have advantages over other types of batteries such as lead-acid and nickel-cadmium batteries, including higher specific capacity, no memory effect, higher operating voltage, faster charging speed, wider operating temperature range, longer cycle life, smaller size, and lighter weight. Currently, lithium-ion batteries are widely used in mobile phones, laptops, electric vehicles, energy storage cabinets, and other fields, and their application range is becoming increasingly broad. Connecting tabs are crucial bridges between the battery's tabs and electrode terminals, and laser welding is typically used to connect them. However, current connecting tabs have low laser absorption intensity, making them prone to poor welding, such as incomplete welds or gaps, during laser welding. This results in poor weld strength between the connecting tabs and the tabs and electrode terminals, significantly affecting the battery's safety performance and reliability.

[0044] The inventors discovered that, at the same temperature, the lower the resistivity of a material, the lower its absorption rate of laser light. To reduce the internal resistance of a battery, metallic conductors with low resistivity and good conductivity, such as copper, aluminum, nickel, or their composites, are typically used as the battery's connecting pieces. Because the electric field of light waves on the surface of a metallic conductor always forms standing wave nodes (standing waves are two waves with the same frequency but opposite directions of propagation; a standing wave node is the point of minimum amplitude in a standing wave), free electrons are forced to vibrate by the electromagnetic field of the light wave, generating secondary waves. These secondary waves cause strong reflected waves, reflecting most of the laser light. Furthermore, connecting pieces are usually manufactured through processes such as stamping, resulting in a relatively smooth surface. The material and smooth surface of the connecting pieces lead to a very low absorption rate of laser light, and the absorbed heat is quickly conducted and diffused to the surrounding area, easily causing poor welding phenomena such as incomplete soldering or open soldering, affecting the welding strength and efficiency between the connecting piece and the electrode tabs. When the welding between the connector and the tab is poor, the battery's internal resistance is high. Under high current conditions, the connection point between the connector and the tab is more prone to overheating due to excessive temperature rise, significantly impacting the battery's safety and reliability. Furthermore, when laser light strikes these highly reflective materials, most of the energy is reflected back. This reflected laser light may return to the laser itself, causing unstable or stopped light emission during processing, and even damaging the laser, shortening its lifespan and reducing its reliability.

[0045] Please see Figures 1 to 4 This application provides a connector 100 for use in a battery, the battery including an electrolyte, the connector 100 including: a current collector layer 110; and a functional layer 120, the functional layer 120 being disposed on at least a portion of the surface of the current collector layer 110; the absorption rate of the functional layer 120 to laser light is greater than the absorption rate of the current collector layer 110 to laser light, and the functional layer 120 is partially soluble in the electrolyte.

[0046] For example, please see Figure 1 and Figure 2 , Figure 1 This is a schematic diagram of the structure of a connecting piece according to an embodiment of this application. Figure 2 for Figure 1 The diagram shows a cross-sectional view of the connecting piece 100 along the CC direction. Figure 2 In this embodiment, the connecting piece 100 includes a current collector layer 110 and a functional layer 120. The current collector layer 110 includes a body 111 and a welding area 112. The welding area 112 is connected to the body 111 and protrudes from the body 111 along the thickness direction of the body 111. The functional layer 120 is disposed on the surface of the welding area 112. The absorption rate of the functional layer 120 to laser light is greater than that of the current collector layer 110 to laser light, and the functional layer 120 is partially soluble in the electrolyte. The functional layer 120 can be coated onto the surface of the current collector layer 110 by methods such as roller coating, spraying, or brushing.

[0047] For example, please see Figure 3 and Figure 4 , Figure 3 This is a schematic diagram of the connecting piece according to another embodiment of this application. Figure 4 for Figure 3 The diagram shows a cross-sectional view of the connecting piece 100 along the CC direction. This is to simplify the operation of the functional layer 120 loaded on the current collector layer 110. Figure 3 In this process, the functional layer 120 is disposed on the entire surface of the connecting piece 100. That is to say, in addition to being disposed on the surface of the welding area 112, the functional layer 120 can also be disposed on the surface of the body 111.

[0048] By placing the functional layer 120 on the surface of the welding area 112 of the current collector 110, the functional layer 120 has a higher laser absorption rate than the current collector 110, which reduces the laser reflectivity of the connecting piece 100 and increases the laser energy absorption of the welding area 112. This improves the welding strength between the connecting piece 100 and the tab after laser welding, ensuring the connection strength between the connecting piece 100 and the tab and reducing the battery resistance, thereby ensuring the battery has a high capacity and good cycle life. By making the functional layer 120 soluble in the electrolyte, on the one hand, the functional layer 120 provides better laser absorption for the connecting piece 100 during laser welding, achieving a good connection between the connecting piece 100 and the tab; on the other hand, after the battery is injected with electrolyte, the functional layer 120 is wetted by the electrolyte and soluble in the electrolyte, preventing the coating from falling directly into the battery and existing in the battery system as a solid impurity, reducing battery self-discharge and preventing internal short circuits, thereby ensuring the battery's safety performance and reliability.

[0049] In some embodiments, the thickness of the functional layer 120 is 0.2 μm ≤ D ≤ 2 μm. Specifically, the thickness of the functional layer 120 can be, but is not limited to, 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1.0 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm, or 2.0 μm. When the thickness D of the functional layer 120 is less than 0.2 μm, the functional layer 120 covers the current collector layer 110 too thinly. When the laser irradiates the connecting piece 100, most of the laser energy will be reflected back by the current collector layer 110. The connecting piece 100 has a low absorption rate of laser, which leads to the risk of poor welding and a large internal resistance of the battery, affecting the welding strength of the connecting piece 100 and the tab, as well as the performance of the battery. When the thickness D of the functional layer 120 is greater than 2 μm, the functional layer 120 covers the current collector layer 110 too thickly. During laser welding, the functional layer 120 is located between the current collector layer 110 and the tab. The thicker functional layer 120 not only affects the welding strength between the current collector layer 110 and the tab, but also affects the current transmission efficiency between the tab and the current collector layer 110, resulting in a large resistance of the battery. At the same time, when the metal complex dissolves in the electrolyte, the concentration of metal cations in the electrolyte is too high, which may lead to more side reactions in the battery system, thereby deteriorating the cycle performance of the battery. By setting the thickness of the functional layer 120 to 0.2μm≤D≤2μm, not only can the connecting piece 100 have a high absorption rate for laser, improve the welding strength between the connecting piece 100 and the electrode, ensure the current transmission efficiency of the battery and reduce the internal resistance of the battery, but it can also ensure that the concentration of metal cations introduced after the functional layer 120 dissolves in the electrolyte is within a controllable range, thereby ensuring that the battery has a high capacity and a good cycle life.

[0050] Furthermore, the thickness of the functional layer 120 is 0.5μm≤D≤1μm. By setting the thickness of the functional layer 120 to 0.5μm≤D≤1μm, it is possible to further ensure that the connecting piece 100 has a high absorption rate for laser, improve the welding strength between the connecting piece 100 and the electrode, better ensure the current transmission efficiency of the battery and reduce the internal resistance of the battery, further reduce the current transmission efficiency between the connecting piece 100 and the electrode, and further ensure that the concentration of metal cations introduced after the functional layer 120 dissolves in the electrolyte is within a controllable range, thereby better ensuring that the battery has a high capacity and good cycle life.

[0051] In some embodiments, the functional layer 120 comprises a metal complex and a resin, the metal complex being dispersed in the resin and soluble in the electrolyte. Understandably, the metal complex in the functional layer 120 covers the welding area 112 of the connecting piece 100, and the metal complex plays a major role in improving the absorption rate of the connecting piece 100 to the laser. During laser welding, it can reduce the reflection of the connecting piece 100 to the laser and enhance the absorption intensity of the connecting piece 100 to the laser, thereby improving the welding strength of the connecting piece 100 to the tabs, etc., after laser welding, reducing the battery resistance, and thus ensuring that the battery has a high capacity and good cycle life. When the battery is injected with electrolyte, the metal complex can dissolve in the electrolyte, preventing the coating from falling directly into the battery and existing in the battery system as a solid impurity, reducing battery self-discharge and preventing internal short circuits, thereby ensuring the battery's safety performance and reliability. The resin in the functional layer 120 can be used to disperse the metal complex, which not only allows the metal complex to be loaded onto the current collector layer 110, increasing the connection strength between the metal complex and the current collector layer 110, but also allows for uniform film formation, thereby better ensuring the adhesion strength and load uniformity of the metal complex on the connecting piece 100, further ensuring the connection strength between the connecting piece 100 and the tab after laser welding, and further ensuring that the battery has a high capacity and good cycle life.

[0052] In some embodiments, the mass percentage of the metal complex in the functional layer 120 ranges from 80% ≤ W1 ≤ 99%; the mass percentage of the resin in the functional layer 120 ranges from 1% ≤ W2 ≤ 20%. Specifically, the mass percentage W1 of the metal complex in the functional layer 120 can be, but is not limited to, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 99.5%, or 99.9%. The mass percentage W2 of the resin in the functional layer 120 can be, but is not limited to, 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, or 20%. When the mass percentage W1 of the metal complex in the functional layer 120 is less than 80% and the mass percentage W2 of the resin in the functional layer 120 is greater than 20%, the proportion of the metal complex in the functional layer 120 is too small and the proportion of the resin in the functional layer 120 is too large. Not only is the amount of the metal complex too small, which has a limited effect on enhancing the absorption intensity of the laser by the connecting piece 100, but the amount of the resin too large will also increase the contact resistance between the current collector layer 110 and the electrode, affecting the current transmission efficiency between the current collector layer 110 and the electrode, resulting in a large internal resistance of the battery, and thus affecting the battery's capacity and cycle life. When the mass percentage W1 of the metal complex in the functional layer 120 is greater than 99% and the mass percentage W2 of the resin in the functional layer 120 is less than 1%, the resin has a high difficulty in dispersing the metal complex and is not conducive to the uniform film formation of the functional layer 120 on the connecting piece 100. This affects the bonding force between the functional layer 120 and the current collector layer 110 and the absorption intensity of the functional layer 120 to the laser, thereby affecting the connection strength between the connecting piece 100 and the tab, and consequently affecting the performance and reliability of the battery. By setting the mass percentage of the metal complex in the functional layer 120 to be 80% ≤ W1 ≤ 99% and the mass percentage of the resin in the functional layer 120 to be 1% ≤ W2 ≤ 20%, on the one hand, the metal complex in the functional layer 120 can reduce the reflection of the connecting piece 100 to the laser, increase the absorption intensity of the connecting piece 100 to the laser, and ensure the connection strength between the connecting piece 100 and the electrode after laser welding, thereby ensuring that the battery has a high capacity and good cycle life; on the other hand, it can ensure that the metal complex is uniformly dispersed in the resin, and the functional layer 120 can be uniformly filmed on the connecting piece 100, ensuring the adhesion strength and load uniformity of the metal complex on the connecting piece 100, thereby reducing the battery resistance and improving the reliability of the connecting piece 100.

[0053] Furthermore, the mass percentage of the metal complex in the functional layer 120 ranges from 95% ≤ W1 ≤ 99%; the mass percentage of the resin in the functional layer 120 ranges from 1% ≤ W2 ≤ 5%. By setting the mass percentage of the metal complex in the functional layer 120 to 95% ≤ W1 ≤ 99% and the mass percentage of the resin in the functional layer 120 to 1% ≤ W2 ≤ 5%, the reflection of the connecting piece 100 to the laser can be further reduced, the absorption intensity of the connecting piece 100 to the laser can be increased, and the connection strength between the connecting piece 100 and the electrode after laser welding can be better guaranteed, thereby further ensuring that the battery has a high capacity and a good cycle life. While ensuring the adhesion strength and load uniformity of the metal complex on the connecting piece 100, further reducing the resin content can further reduce the contact resistance between the current collector layer 110 and the electrode, improve the current transmission efficiency of the battery, thereby further ensuring that the battery has a high capacity and a good cycle life.

[0054] In some embodiments, the metal complex comprises a metal cation and a ligand, wherein the metal cation comprises at least one selected from chromium ions, iron ions, titanium ions, and zinc ions. Optionally, the metal cation is a transition metal cation, and when the metal cation is at least one selected from chromium ions, iron ions, titanium ions, and zinc ions, the metal complex is a transition metal complex. The inventors have discovered that in transition metal complexes, the d orbitals of the transition metal cation originally have the same energy. Under the influence of the ligand-formed ligand field, the d orbital energy levels of the transition metal cation split. The split orbitals are not filled with electrons, and electrons can transition between energy levels of the different split orbitals, thereby generating an absorption spectrum. By setting the metal complex to include metal cations and ligands, wherein the metal cations include at least one of chromium ions, iron ions, titanium ions, and zinc ions, during laser welding, the unfilled d orbitals in the metal complex can absorb the laser and achieve transitions between different orbitals, thereby enhancing the absorption intensity of the laser by the connecting piece 100 during laser welding, reducing the reflectivity of the connecting piece 100 to the laser, and making the absorbed energy less likely to be conducted and diffused to the surroundings compared to the current collector layer 110. This ensures that the welding area 112 forms a highly concentrated heat source area at the welded site in a short time, thereby causing the connecting piece 100 and the electrode to partially melt and form a strong weld point and weld seam, ensuring the connection strength between the connecting piece 100 and the electrode, and ensuring that the battery has a high capacity and good cycle life.

[0055] In some embodiments, the ligand includes at least one of phthalocyanine, a thiodiene polymer, polyurethane, and medium black. The number-average molecular weight of the thiodiene polymer is 500 ≤ M1 ≤ 5000; the number-average molecular weight of the polyurethane is 500 ≤ M2 ≤ 5000; and the medium black can be at least one of acidic medium black A, medium black 3, acidic medium black P2B, acidic medium black PV, acidic medium black T, and medium black 17. When the above substances are used as ligands for metal cations, the metal complex formed with the metal cation is dark in color. Further, a substance that can form a black metal complex with the metal cation is selected as the ligand. When the metal complex is black, it indicates that the electronic energy level of the metal complex is relatively low, requiring only low photon energy to achieve energy level transitions. In other words, the metal complex can better absorb the incident laser energy, further enhance the absorption intensity of the laser by the connecting piece 100, reduce the reflectivity of the laser by the connecting piece 100, and the absorbed energy is less likely to be conducted and diffused to the surroundings compared to the current collector layer 110. This allows the connecting piece 100 and the electrode to melt locally and form a strong weld point and weld seam, further ensuring the connection strength between the connecting piece 100 and the electrode, thereby further ensuring that the battery has a high capacity and good cycle life.

[0056] In some embodiments, the average particle size of the metal complex is in the range of 5 nm ≤ D 50 ≤20nm. The average particle size D of the metal complex. 50 The possible sizes are, but not limited to: 5nm, 6nm, 7nm, 8nm, 9nm, 10nm, 11nm, 12nm, 13nm, 14nm, 15nm, 16nm, 17nm, 18nm, 19nm, and 20nm. When the average particle size D of the metal complex... 50 When the particle size is less than 5 nm, the metal complex particles are too small, and the metal complex is prone to agglomeration, making it difficult for the resin to disperse the metal complex. This results in poor uniformity of the metal complex distribution in the functional layer 120, affecting the bonding force between the functional layer 120 and the current collector layer 110, as well as the absorption intensity of the functional layer 120 to the laser. Consequently, the connection strength between the connecting piece 100 and the electrode tab is low, affecting the performance and reliability of the battery. When the average particle size D of the metal complex... 50 When the particle size is greater than 20 nm, the metal complex particles are too large. This not only makes it difficult to control the thickness of the functional layer 120, resulting in a higher contact resistance between the connecting piece 100 and the electrode, but also reduces the number of active sites for laser absorption in the metal complex, leading to a lower laser absorption intensity in the functional layer 120. This affects the connection strength between the connecting piece 100 and the electrode, thereby impacting the battery's performance and reliability. By setting the average particle size range of the metal complex to 5 nm ≤ D...50 With a particle size of ≤20nm, the metal complex has a moderate size, which can ensure the uniform dispersion of the metal complex in the resin, and is also conducive to controlling the thickness of the functional layer 120 and the uniform distribution of the metal complex. It provides more active sites for absorbing laser, reduces the difficulty of uniformly attaching the coating to the current collector layer 110, and ensures the absorption intensity of the laser by the connecting piece 100. It also improves the connection strength between the connecting piece 100 and the tab, thereby ensuring that the battery has a high capacity and good cycle life.

[0057] In some embodiments, the reflectivity of the functional layer 120 to laser light ranges from 5% ≤ R ≤ 70%, and the absorptivity of the functional layer 120 to laser light ranges from 30% ≤ A ≤ 95%. Specifically, the reflectivity R of the functional layer 120 to laser light can be, but is not limited to, 5%, 8%, 10%, 12%, 15%, 18%, 20%, 22%, 25%, 28%, 30%, 32%, 35%, 38%, 40%, 42%, 45%, 48%, 50%, 52%, 55%, 58%, 60%, 62%, 65%, 68%, and 70%. The absorption rate A of the functional layer 120 to laser light can be, but is not limited to, 30%, 32%, 35%, 38%, 40%, 42%, 45%, 48%, 50%, 52%, 55%, 58%, 60%, 62%, 65%, 68%, 70%, 72%, 75%, 78%, 80%, 82%, 85%, 88%, 90%, 92%, and 95%. By selecting a dark-colored or even black metal complex, the functional layer 120 mainly absorbs and reflects laser light, with virtually no transmission. In other words, the sum of the absorption rate A and the reflectivity R of the functional layer 120 to laser light is approximately equal to 100%. By setting the absorption rate of the functional layer 120 to the laser within the range of 30% ≤ A ≤ 95% and the reflectivity of the functional layer 120 to the laser within the range of 5% ≤ R ≤ 70%, the absorption intensity of the functional layer 120 to the laser can be guaranteed, the reflectivity of the connecting piece 100 to the laser can be reduced, and the absorbed energy is less likely to be conducted and diffused to the surroundings compared to the current collector layer 110. This causes the connecting piece 100 and the electrode to partially melt and form a strong solder joint and weld, ensuring the connection strength between the connecting piece 100 and the electrode, thereby ensuring that the battery has a high capacity and good cycle life.

[0058] In some embodiments, when laser welding is performed on the connecting piece 100, the wavelength range of the laser is 1050nm≤λ≤1070nm, specifically, the wavelength λ is 1064nm. The laser welding power is 1500W≤P≤4000W, and the laser welding speed is 50mm / s≤v≤200mm / s. By setting the laser welding power to 1500W≤P≤4000W, higher power during laser welding can ensure higher welding energy, allowing the welding area 112 to form a highly concentrated heat source area at the welded site in a shorter time. This results in localized melting of the connecting piece 100 and the electrode tab, forming a strong weld point and weld seam. This avoids poor welding strength due to excessively low welding power, or increased energy consumption due to excessively high welding power, thus ensuring the connection strength and welding efficiency between the connecting piece 100 and the electrode tab. By setting the laser welding speed to 50mm / s≤v≤200mm / s, the laser's interaction time with the connecting piece 100 and the electrode can be guaranteed during laser welding. This avoids welding efficiency being too slow due to excessively slow welding speed, or welding defects such as incomplete welds or empty welds due to excessively fast welding speed, thus ensuring the connection strength and welding efficiency between the connecting piece 100 and the electrode.

[0059] In some embodiments, the resin includes at least one selected from rosin ester, ketone resin, xylene resin, acrylic resin, polyamide resin, ethylene resin, alkylphenol resin, maleic acid resin, and cellulose resin. Using the above substances as resins for dispersing metal complexes can reduce the time required for uniform dispersion of the metal complexes, improve the film uniformity of the coating slurry and ensure the adhesion strength of the functional layer 120, further enhance the absorption intensity of the laser by the connecting piece 100, and better ensure the connection strength between the connecting piece 100 and the electrode tab after laser welding, thereby better ensuring that the battery has a higher capacity and a better cycle life.

[0060] In some embodiments, the mass content of the metal cation in the electrolyte is 1 ppm ≤ C ≤ 70 ppm. Specifically, the mass content C of the metal cation in the electrolyte can be, but is not limited to, 1 ppm, 5 ppm, 8 ppm, 10 ppm, 15 ppm, 18 ppm, 20 ppm, 25 ppm, 28 ppm, 30 ppm, 35 ppm, 38 ppm, 40 ppm, 45 ppm, 48 ppm, 50 ppm, 55 ppm, 58 ppm, 60 ppm, 65 ppm, 68 ppm, or 70 ppm. When the mass content C of the metal cation in the electrolyte is greater than 70 ppm, the concentration of the metal cation in the electrolyte is relatively high. During battery charge-discharge cycles, it may react with other substances in the battery system, and excessive side reactions and byproducts will affect the battery's cycle performance. By setting the mass content of the metal cation in the electrolyte to 1ppm≤C≤70ppm, it is possible to ensure that the connecting piece 100 has a high absorption rate for laser light, improve the welding strength between the connecting piece 100 and the electrode, ensure the current transmission efficiency of the battery, and reduce the internal resistance of the battery. Furthermore, by setting the mass content of the metal cation in the electrolyte to 1ppm≤C≤70ppm, it is also possible to ensure that the concentration of metal cations introduced after the functional layer 120 dissolves in the electrolyte is within a controllable range, thereby better ensuring that the battery has a high capacity and good cycle life.

[0061] The connecting piece 100 of this application will be further described below through specific embodiments.

[0062] 1. Preparation of the connecting piece 100 in Examples 1 to 17 and Comparative Example 1:

[0063] The substrate material of the connector 100 is aluminum. Using 1,2-butanediol as an organic solvent, a certain mass percentage of resin is mixed with the organic solvent and stirred until homogeneous. Then, a certain mass percentage of metal complex is added, and the mixture is stirred at 800 r / min for 60 min until homogeneous, resulting in a coating slurry. The coating slurry is applied to the welding area 112 surface of the positive electrode connector 100, and after drying, a positive electrode connector 100 with a functional layer 120 is obtained. The differences in the thickness of the functional layer 120, the mass percentage of the metal complex, and the material of the metal complex in Examples 1 to 17 are detailed in Table 1.

[0064] Unlike Examples 1 to 17, Comparative Example 1 did not coat the functional layer 120 on the connecting piece 100.

[0065] 2. The batteries of Examples 1 to 17 and Comparative Example 1 were prepared by the following steps:

[0066] 1) Preparation of the positive electrode sheet:

[0067] The positive electrode active material, conductive agent, and binder are dispersed in a solvent and mixed evenly to obtain a positive electrode slurry. The positive electrode slurry is coated onto a current collector aluminum foil, and after drying, cold pressing, slitting, and cutting, a positive electrode sheet is obtained.

[0068] 2) Preparation of the negative electrode sheet:

[0069] The positive electrode active material, conductive agent, and binder are dispersed in a solvent and mixed evenly to obtain a positive electrode slurry. The positive electrode slurry is coated onto a current collector copper foil, and after drying, cold pressing, slitting, and cutting, a negative electrode sheet is obtained.

[0070] 3) Preparation of the diaphragm:

[0071] A 16μm polypropylene film was used as the diaphragm.

[0072] 4) Preparation of electrolyte:

[0073] In an argon atmosphere glove box with a moisture content ≤1ppm, lithium hexafluorophosphate is used as the solute and an ester-based organic solvent is used as the solvent. The dried solute is dissolved in the solvent and stirred until the solute is completely dissolved and homogeneous to obtain the electrolyte.

[0074] 5) Battery assembly:

[0075] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrode to act as an insulator. Then, they are wound together to form an electrode assembly.

[0076] Laser welding was used to weld the positive electrode connecting piece 100 to the positive electrode tab of the electrode assembly, and the negative electrode connecting piece 100 to the negative electrode tab of the electrode assembly. The wavelength of the laser was 1064nm, the welding power was 2200W, and the welding speed was 120mm / s.

[0077] The electrode assembly was placed in an outer packaging shell, dried, and then injected with electrolyte. After vacuum sealing, settling, formation, and shaping, the battery was finally prepared. The positive electrode connector 100 was the connector 100 used in Examples 1 to 17 and Comparative Example 1, while the negative electrode connector 100 was a conventional copper-based connector 100. After assembly, the batteries of Examples 1 to 17 and Comparative Example 1 were obtained, respectively.

[0078] Coating solubility test: The connecting pieces 100 of Examples 1 to 17 were immersed in 100g of electrolyte for 12 hours. The electrolyte after immersion was analyzed using an inductively coupled plasma atomic emission spectrometer (ICP-AES) of Thermo Fisher iCAP7400, and the concentration of the corresponding metal cations dissolved after the coating was analyzed (i.e., the mass content of metal cations in the electrolyte).

[0079] Welding condition test: Use a metallographic microscope to observe whether there are defects such as incomplete penetration, cracks, and porosity in the welding area 112 of the connecting piece 100.

[0080] Charge-discharge cycle performance test: The batteries obtained in Examples 1 to 17 and Comparative Example 1 were subjected to constant current charge-discharge cycle tests on a charge-discharge apparatus. The test temperature was 25°C, the charge-discharge rate was 0.5C (the magnitude of the charge-discharge current is usually expressed by the charge-discharge rate, and the calculation formula for the charge-discharge current is: charge-discharge current = charge-discharge rate × battery rated capacity), and the charge-discharge voltage window was 2.0V to 3.65V (that is, the battery's charging cut-off voltage is 3.65V, and the battery's discharging cut-off voltage is 2.0V). One complete charge-discharge cycle is usually called one charge-discharge cycle, which means that the battery is first charged to 3.65V, left to rest, and then discharged from 3.65V to 2.0V, thus forming one charge-discharge cycle. N cycles are performed, meaning the above process is repeated N times.

[0081] Battery internal resistance test: After one charge-discharge cycle, the battery's state of charge (SOC) is adjusted to 27%, the test temperature is 25℃, the discharge rate is 1C, and the discharge time is 30s. The battery voltages U1 and U2 before and after discharge are recorded respectively. The formula for calculating the battery's internal resistance is: DCR=(U1-U2) / I.

[0082] Capacity testing: The discharge capacity of a battery after one charge-discharge cycle is calibrated as its capacity.

[0083] The formula for calculating capacity retention rate is: Capacity retention rate = Capacity of battery in Nth cycle / Initial capacity of battery × 100%.

[0084] Table 1: Parameter control and performance comparison of each embodiment and comparative example

[0085]

[0086] As shown in Table 1:

[0087] 1) The connecting pieces 100 in Examples 1 to 17 all have a functional layer 120, while the connecting piece 100 in Comparative Example 1 does not have a functional layer 120. Test results show that the reflectivity of the connecting pieces 100 in Examples 1 to 17 to the laser is all below 70%, and the welding area 112 of the connecting pieces 100 has no defects such as incomplete penetration, cracks, or pores. The internal resistance of the batteries in Examples 1 to 17 is all below 0.75 mΩ, and the capacity of the batteries is all above 49.4 Ah. After 500 cycles, the capacity retention rate of the batteries in Examples 1 to 17 is all 80% or higher. In contrast, the reflectivity of the connecting piece 100 in Comparative Example 1 to the laser is 76%, and the welding area 112 of the connecting piece 100 has defects such as incomplete penetration, cracks, and pores. The internal resistance of the battery in Comparative Example 1 is 0.78 mΩ, and the capacity of the battery is only 49.2 Ah. After 500 cycles, the capacity retention rate of the battery in Comparative Example 1 is only 74%. Therefore, the functional layer 120 on the connecting piece 100 has a significant impact on the laser welding effect of the connecting piece 100 and the performance of the battery. By placing the functional layer 120 on the surface of the welding area 112 of the current collector layer 110, the absorption rate of the functional layer 120 to the laser is greater than that of the current collector layer 110. This reduces the reflectivity of the connecting piece 100 to the laser and increases the absorption of laser energy in the welding area 112. Consequently, it improves the welding strength between the connecting piece 100 and the electrode after laser welding, ensuring the connection strength between the connecting piece 100 and the electrode and reducing the battery resistance, thus ensuring that the battery has a high capacity and a good cycle life.

[0088] 2) As can be seen from Examples 1 to 6, the thickness of the functional layer 120 in Examples 2 to 5 all falls within the range of 0.2μm≤D≤2μm, while the thickness of the functional layer 120 in Examples 1 and 6 exceeds the range of 0.2μm≤D≤2μm. The test results show that the reflectivity of the connecting piece 100 to laser light in Examples 2 to 5 is all below 25%, the internal resistance of the battery in Examples 1 to 17 is all below 0.65mΩ, and the capacity of the battery is all above 50.3Ah. After 500 cycles, the capacity retention rate of the batteries in Examples 1 to 17 is all 92% or higher. Among Examples 2 to 5, Example 4 exhibits the best overall performance. In Example 1, the reflectivity of the connecting piece 100 to laser is as high as 67%, the internal resistance of the battery is 0.74 mΩ, and the capacity of the battery is only 49.5 Ah. After 500 cycles, the capacity retention rate of the battery is only 82%. In Example 6, the internal resistance of the battery is 0.71 mΩ, the capacity of the battery is only 50.1 Ah, the concentration of metal cations in the electrolyte is as high as 106 ppm, and after 500 cycles, the capacity retention rate of the battery is only 78%. Therefore, when the mass percentage of the metal complex in the functional layer 120 and the type of metal complex remain unchanged, the thickness of the functional layer 120 has a significant impact on the laser welding effect of the connecting piece 100 and the performance of the battery. When the thickness D of the functional layer 120 is less than 0.2 μm, the functional layer 120 covers the current collector layer 110 too thinly. When the laser irradiates the connecting piece 100, most of the laser energy will be reflected back by the current collector layer 110. The connecting piece 100 has a low absorption rate of laser, which leads to the risk of poor welding and a large internal resistance of the battery, affecting the welding strength of the connecting piece 100 and the tab, as well as the performance of the battery. When the thickness D of the functional layer 120 is greater than 2 μm, the functional layer 120 covers the current collector layer 110 too thickly. During laser welding, the functional layer 120 is located between the current collector layer 110 and the tab. The thicker functional layer 120 not only affects the welding strength between the current collector layer 110 and the tab, but also affects the current transmission efficiency between the tab and the current collector layer 110, resulting in a large resistance of the battery. At the same time, when the metal complex dissolves in the electrolyte, the concentration of metal cations in the electrolyte is too high, which may lead to more side reactions in the battery system, thereby deteriorating the cycle performance of the battery. By setting the thickness of the functional layer 120 to 0.2μm≤D≤2μm, not only can the connecting piece 100 have a high absorption rate for laser, improve the welding strength between the connecting piece 100 and the electrode, ensure the current transmission efficiency of the battery and reduce the internal resistance of the battery, but it can also ensure that the concentration of metal cations introduced after the functional layer 120 dissolves in the electrolyte is within a controllable range, thereby ensuring that the battery has a high capacity and a good cycle life.

[0089] 3) As can be seen from Examples 4, 7 to 10, the mass percentage of the metal complex in the functional layer 120 in Examples 4, 8 and 9 all falls within the range of 80% ≤ W1 ≤ 99%, while the mass percentage of the metal complex in the functional layer 120 in Examples 7 and 10 exceeds the range of 80% ≤ W1 ≤ 99%. The test results show that the reflectivity of the connecting piece 100 to laser light in Examples 4, 8 and 9 is all below 25%, the internal resistance of the battery in Examples 4, 8 and 9 is all below 0.64 mΩ, and the capacity of the battery is all above or equal to 50.3 Ah. After 500 cycles, the capacity retention rate of the batteries in Examples 4, 8 and 9 is all 90% or higher. Among Examples 4, 8 and 9, Example 9 exhibits the best overall performance. In Example 7, the reflectivity of the connecting piece 100 to the laser is 47%, the internal resistance of the battery is 0.72 mΩ, and the capacity of the battery is only 49.4 Ah. After 500 cycles, the capacity retention rate of the battery is only 81%. In Example 10, the internal resistance of the battery is 0.65 mΩ, and the capacity of the battery is only 50.1 Ah. After 500 cycles, the capacity retention rate of the battery is only 89%. Therefore, when the thickness of the functional layer 120 and the type of metal complex remain unchanged, the mass percentage of the metal complex in the functional layer 120 has a significant impact on the laser welding effect of the connecting piece 100 and the performance of the battery. When the mass percentage W1 of the metal complex in the functional layer 120 is less than 80% and the mass percentage W2 of the resin in the functional layer 120 is greater than 20%, the proportion of the metal complex in the functional layer 120 is too small and the proportion of the resin in the functional layer 120 is too large. Not only is the amount of the metal complex too small, which has a limited effect on enhancing the absorption intensity of the laser by the connecting piece 100, but the amount of the resin too large will also increase the contact resistance between the current collector layer 110 and the electrode, affecting the current transmission efficiency between the current collector layer 110 and the electrode, resulting in a large internal resistance of the battery, which in turn affects the battery's capacity utilization and cycle life. When the mass percentage W1 of the metal complex in the functional layer 120 is greater than 99% and the mass percentage W2 of the resin in the functional layer 120 is less than 1%, the resin has a high difficulty in dispersing the metal complex and is not conducive to the uniform film formation of the functional layer 120 on the connecting piece 100. This affects the bonding force between the functional layer 120 and the current collector layer 110 and the absorption intensity of the functional layer 120 to the laser, thereby affecting the connection strength between the connecting piece 100 and the tab, and consequently affecting the performance and reliability of the battery.By setting the mass percentage of the metal complex in the functional layer 120 to be 80% ≤ W1 ≤ 99% and the mass percentage of the resin in the functional layer 120 to be 1% ≤ W2 ≤ 20%, on the one hand, the metal complex in the functional layer 120 can reduce the reflection of the connecting piece 100 to the laser, increase the absorption intensity of the connecting piece 100 to the laser, and ensure the connection strength between the connecting piece 100 and the electrode after laser welding, thereby ensuring that the battery has a high capacity and good cycle life; on the other hand, it can ensure that the metal complex is uniformly dispersed in the resin, and the functional layer 120 can be uniformly filmed on the connecting piece 100, ensuring the adhesion strength and load uniformity of the metal complex on the connecting piece 100, thereby reducing the battery resistance and improving the reliability of the connecting piece 100.

[0090] 4) As can be seen from Examples 9, 11 to 17, when the thickness of the functional layer 120 and the mass percentage of the metal complex in the functional layer 120 remain unchanged, the type of the metal complex also has a significant impact on the laser welding effect of the connecting piece 100 and the performance of the battery. Wherein:

[0091] As shown in Examples 11 to 13, the reflectivity of the connecting piece 100 in Example 13 to laser light is 16%, the internal resistance of the battery is 0.61 mΩ, and the capacity of the battery is 50.4 Ah. After 500 cycles, the capacity retention rate of the battery in Example 13 is 91%. Among Examples 11 to 13, Example 13 has the best overall performance. Therefore, when the thickness of the functional layer 120 and the mass percentage of the metal complex in the functional layer 120 remain constant, the selection of the metal cation has a significant impact on the laser welding effect of the connecting piece 100 and the performance of the battery. Compared to zinc phthalocyanine and iron phthalocyanine, using chromium phthalocyanine as the metal complex is more beneficial for improving the laser welding effect of the connecting piece 100 and the performance of the battery. In other words, when phthalocyanine is used as the ligand of the metal complex, compared to iron ions and zinc ions, using chromium ions as the metal cation of the metal complex is more beneficial for improving the laser welding effect of the connecting piece 100 and the performance of the battery.

[0092] As shown in Examples 14 and 15, the reflectivity of the connecting piece 100 to laser light in Example 14 is 19%, the internal resistance of the battery is 0.64 mΩ, and the capacity of the battery is 50.3 Ah. After 500 cycles, the capacity retention rate of the battery in Example 14 is 90%. In contrast, the reflectivity of the connecting piece 100 to laser light in Example 15 is as high as 69%, the internal resistance of the battery is 0.75 mΩ, and the capacity of the battery is only 49.4 Ah. After 500 cycles, the capacity retention rate of the battery in Example 15 is only 83%. The overall performance of Example 14 is significantly better than that of Example 15. Therefore, when the thickness of the functional layer 120 and the mass percentage of the metal complex in the functional layer 120 remain constant, the selection of the metal cation has a significant impact on the laser welding effect of the connecting piece 100 and the performance of the battery. Compared to thiodiene titanium, using thiodiene chromium as the metal complex is more beneficial for improving the laser welding effect of the connecting piece 100 and the performance of the battery. In other words, when using thiodiene polymers as ligands for metal complexes, using chromium ions as the metal cations of the metal complexes is more beneficial to improving the laser welding effect of the connector 100 and the performance of the battery than using titanium ions.

[0093] As shown in Examples 9 and 16, the reflectivity of the connecting piece 100 to laser light in Example 9 is 12%, lower than the 17% reflectivity in Example 16. Furthermore, in Example 9, the battery internal resistance is 0.59 mΩ and the battery's capacity is 50.5 Ah; after 500 cycles, the battery's capacity retention rate is 96%. In the other example, the battery internal resistance is 0.63 mΩ and the battery's capacity is 50.4 Ah; after 500 cycles, the battery's capacity retention rate is 91%. Therefore, when the thickness of the functional layer 120 and the mass percentage of the metal complex in the functional layer 120 remain constant, the selection of the metal cation has a significant impact on the laser welding effect of the connecting piece 100 and the performance of the battery. Compared to acidic medium black T-iron, using acidic medium black T-chromium as the metal complex is more beneficial for improving the laser welding effect of the connecting piece 100 and the performance of the battery. In other words, when acidic medium black T is used as the ligand for the metal complex, using chromium ions to act as the metal cation of the metal complex is more beneficial to improving the laser welding effect of the connector 100 and the performance of the battery than using iron ions.

[0094] As shown in Examples 9, 13, 14, and 17, Example 9 exhibits the best overall performance among these three examples. This demonstrates that when the thickness of the functional layer 120 and the mass percentage of the metal complex in the functional layer 120 remain constant, the choice of ligand has a significant impact on the laser welding effect of the connector 100 and the performance of the battery. Compared to phthalocyanine chromium, thiodiene chromium, and polyurethane chromium, using acidic medium black T-chromium as the metal complex is more beneficial for improving the laser welding effect of the connector 100 and the performance of the battery. In other words, when chromium ions act as the metal cation of the metal complex, compared to phthalocyanine, thiodiene polymers, and polyurethane, using acidic medium black T-chromium as the ligand of the metal complex is more beneficial for improving the laser welding effect of the connector 100 and the performance of the battery.

[0095] Please see Figure 5 and Figure 6 This application also provides a battery 200, which includes an end cap assembly 210, a connecting piece 100, an electrode assembly 220, an electrolyte (not shown), and a housing 230. The electrode assembly 220 is located within the housing 230 and is at least partially immersed in the electrolyte. The electrode assembly 220 is electrically connected to the connecting piece 100. The end cap assembly 210 is electrically connected to the electrode assembly 220 through the connecting piece 100 and seals the housing 230. It is understood that the battery 200 of this application can have a cylindrical, rectangular, or other structural shape. In the illustrations of this application embodiment, a cylindrical structure is used as an example for illustration and should not be construed as a limitation on the battery 200 of this application.

[0096] The battery 200 of this application embodiment can be applied to electrical devices such as automobiles, mobile phones, computers, tablets, toys, and home appliances to provide power to these devices.

[0097] Please see Figure 7 This application also provides a battery pack 300, which includes a housing 310 and a plurality of batteries 200 as described in this application embodiment. The plurality of batteries 200 are housed within the housing 310 and are electrically connected. The electrical connection of the plurality of batteries 200 includes at least one of series and parallel connection. The term "plural" means two or more.

[0098] Understandably, the multiple batteries 200 of the battery pack 300 can be connected in parallel, or in series, or partially in parallel and partially in series (i.e., mixed connection). This application does not make specific limitations on the connection method of the multiple batteries 200 of the same battery pack 300.

[0099] Understandably, the housing 310 has a receiving cavity 311 in which a plurality of batteries 200 are received. In some embodiments, each receiving cavity 311 receives one battery 200. In other embodiments, each receiving cavity 311 receives a plurality of batteries 200.

[0100] It is understood that the battery pack 300 described in this embodiment is merely one form of the battery pack 300 used by the battery 200, and should not be construed as a limitation on the battery pack 300 provided in this application, nor should it be construed as a limitation on the battery 200 provided in various embodiments of this application.

[0101] Please see Figure 8 This application embodiment also provides an electrical device 400, which includes: an electrical device body 410 and a battery 200 as described in this application embodiment, wherein the battery 200 is used to supply power to the electrical device body 410.

[0102] The electrical device 400 in this application embodiment can be, but is not limited to, portable electronic devices such as mobile phones, tablets, laptops, desktop computers, smart toys, smart bracelets, smartwatches, e-readers, game consoles, and toys; it can also be large equipment such as electric vehicles, electric cars, ships, and spacecraft.

[0103] It is understood that the electrical device 400 described in this embodiment is merely one form of the electrical device 400 used by the battery 200, and should not be construed as a limitation on the electrical device 400 provided in this application, nor should it be construed as a limitation on the battery 200 provided in various embodiments of this application.

[0104] The terms "embodiment" and "implementation" used in this application mean that a specific feature, structure, or characteristic described in connection with an embodiment can be included in at least one embodiment of this application. The appearance of these phrases in various locations throughout the specification does not necessarily refer to the same embodiment, nor are they independent or alternative embodiments mutually exclusive with other embodiments. Those skilled in the art will understand, explicitly and implicitly, that the embodiments described in this application can be combined with other embodiments. Furthermore, it should be understood that the features, structures, or characteristics described in the various embodiments of this application can be arbitrarily combined to form yet another embodiment that does not depart from the spirit and scope of the technical solution of this application, provided there is no contradiction between them.

[0105] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application and are not intended to limit it. Although this application has been described in detail with reference to the above preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions to the technical solutions of this application should not depart from the spirit and scope of the technical solutions of this application.

Claims

1. A connecting piece, characterized in that, Applied to a battery, the battery including an electrolyte, the connecting piece includes: The flow layer; and A functional layer is disposed on at least a portion of the surface of the current collector layer; the absorption rate of the functional layer for laser light is greater than that of the current collector layer for laser light, and some components of the functional layer are soluble in the electrolyte.

2. The connecting piece according to claim 1, characterized in that, The thickness of the functional layer is 0.2μm≤D≤2μm.

3. The connecting piece according to claim 1, characterized in that, The functional layer comprises a metal complex and a resin, wherein the metal complex is dispersed in the resin and is soluble in the electrolyte.

4. The connecting piece according to claim 3, characterized in that, The mass percentage of the metal complex in the functional layer ranges from 80% to 99% (W1 ≤ 99%); the mass percentage of the resin in the functional layer ranges from 1% to 20% (W2 ≤ 20%).

5. The connecting piece according to claim 4, characterized in that, The metal complex comprises a metal cation and a ligand, wherein the metal cation comprises at least one of chromium ion, iron ion, titanium ion, and zinc ion; and the ligand comprises at least one of phthalocyanine, thiodiene polymer, polyurethane, and mordant black.

6. The connecting piece according to any one of claims 3-5, characterized in that, The average particle size range of the metal complex is 5 nm ≤ D 50 ≤20nm.

7. The connecting piece according to claim 1, characterized in that, The reflectivity of the functional layer to laser light is in the range of 5% ≤ R ≤ 70%, and the absorption rate of the functional layer to laser light is in the range of 30% ≤ A ≤ 95%.

8. The connecting piece according to claim 3, characterized in that, The resin includes at least one of rosin ester, ketone resin, xylene resin, acrylic resin, polyamide resin, ethylene resin, alkylphenol resin, maleic acid resin, and cellulose resin.

9. A battery, characterized in that, include: Electrolyte; Electrode assembly; and The connecting piece according to any one of claims 1-8, wherein the electrode assembly is at least partially immersed in the electrolyte, and the electrode assembly is electrically connected to the connecting piece.

10. The battery according to claim 9, characterized in that, The functional layer comprises a metal complex and a resin. The metal complex is soluble in the electrolyte. The metal complex comprises a metal cation and a ligand. The mass content of the metal cation in the electrolyte is 1 ppm ≤ C ≤ 70 ppm.

11. A battery pack, characterized in that, include: Box; The battery according to any one of claims 9-10, wherein the plurality of batteries are housed in the housing and are electrically connected, wherein the electrical connection of the plurality of batteries includes at least one of series and parallel connection.

12. An electrical appliance, characterized in that, include: The main body of the electrical equipment; and The battery according to any one of claims 9-10, wherein the battery supplies power to the main body of the electrical device.

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