Secondary battery and electric device

Abstract

The embodiment of the invention provides a secondary battery and electric equipment. The secondary battery comprises a shell, a roll core, a top cover and a connecting piece, the top cover comprises a pole, and the roll core comprises a tab. The connecting piece comprises a base body, a transition layer and an insulating layer. The base body comprises a main body part as well as a first connecting part and a second connecting part which are arranged at the edge of the main body part, the first connecting part is connected to the tab, the second connecting part is connected to the pole, a modified layer is arranged on the surface of the main body part, and one side, deviating from the main body part, of the modified layer is a coupling surface with a rough structure. The transition layer is arranged on the coupling surface of the modified layer, the transition layer comprises deposition particles, the deposition particles comprise an aluminum element and a silicon element, and the number density of particles with the particle size larger than 100 nm in the deposition particles is 103 / cm < 2 >-105 / cm < 2 >. The insulating layer is arranged on the side, away from the base body, of the transition layer and comprises ceramic particles. Therefore, the anti-corrosion performance and the insulating performance of the main body part of the connecting piece can be improved.

Description

Technical Field

[0001] This application generally relates to the field of batteries, and in particular to secondary batteries and electrical equipment. Background Technology

[0002] A connector is a conductive connector adapted between the electrode (e.g., the positive electrode) and external terminals (e.g., terminals) of a secondary battery. The connector can be fixed to the electrode tab and the external terminal respectively by means such as welding, so that the electrode and the external terminal are electrically connected, thereby enabling the secondary battery to perform charging and discharging operations.

[0003] Because of the harsh working environment of the connector, the connector is easily affected by chemical or physical factors, which may lead to increased internal resistance, performance degradation, or even short circuits in the secondary battery. Summary of the Invention

[0004] In a first aspect of this application, a secondary battery is provided. The secondary battery includes a casing, a core, a top cover, and a connecting piece. The casing has a receiving cavity, and the top cover is connected to the casing to close the receiving cavity. The core is disposed within the receiving cavity. The top cover includes an electrode post, and the core includes an electrode tab. Both the electrode tab and the electrode post are connected to the connecting piece. The connecting piece includes a substrate, which includes a main body and a first connecting portion and a second connecting portion disposed at the edge of the main body. The first connecting portion is connected to the electrode tab, and the second connecting portion is connected to the electrode post. A modified layer is disposed on the surface of the main body, and the side of the modified layer facing away from the main body is a coupling surface with a rough structure. A transition layer is disposed on the coupling surface of the modified layer. The transition layer includes deposited particles, which include aluminum and silicon elements. The number density of particles with a diameter greater than 100 nm in the deposited particles is 10. 3 pcs / cm 2 ~10 5 pcs / cm 2 ; and an insulating layer disposed on the side of the transition layer away from the substrate, the insulating layer comprising ceramic particles.

[0005] After the transition layer is bonded to the coupling surface with a rough structure, the contact area between the transition layer and the modified layer can be significantly increased, and the number of adhesion sites between the two layers can be increased. In this way, the adhesion strength between the transition layer and the main body can be improved, and delamination between the transition layer and the substrate due to insufficient interfacial bonding can be avoided. Furthermore, the tight bonding between the transition layer and the main body can also improve the adhesion strength of the insulating layer on the main body. In addition, the high ductility of aluminum in the transition layer can buffer the difference in thermal expansion coefficients between the substrate and the insulating layer (ceramic material, which has high rigidity), so that when the secondary battery experiences temperature fluctuations during charge and discharge cycles, interfacial thermal stress can be effectively released, preventing warping or coating cracking of the connecting piece, and significantly improving the structural stability of the connecting piece under long-term high-temperature conditions.

[0006] By controlling the particle size distribution of the deposited particles in the transition layer, the number density of particles with a particle size greater than 100 nm in the deposited particles is controlled to be 10 3 cm 2 -10 5 cm 2 , which can significantly inhibit particle agglomeration, make the microstructure of the transition layer more uniform and dense, and thus alleviate the problem of interface stress concentration caused by excessive particle spacing.

[0007] The insulation layer can form a continuous and defect-free insulation protective layer with the uniform support of the transition layer. Compared with the protective form of the insulation sticker (or insulation tape) based on polyethylene terephthalate (PET) and polyimide (PI) materials, the ceramic insulation layer can effectively block the accidental conduction path between the connecting tab and the shell of the secondary battery and / or the opposite electrode. Even if the connecting tab is slightly deformed due to vibration and extrusion during the assembly of the secondary battery, or the secondary battery is deformed due to collision during use, the insulation layer can maintain its complete insulation properties and improve the safety performance of the secondary battery.

[0008] The dense ceramic structure of the insulation layer can also reduce the penetration of corrosive media (such as hydrofluoric acid and other corrosive substances generated by the trace hydrolysis of lithium salts in the electrolyte) into the main body of the connecting tab, further delaying the corrosion process of the main body, and avoiding problems such as increased battery resistance and capacity decay caused by corrosion of the connecting tab, thereby effectively extending the service life of the secondary battery.

[0009] Compared with the protective means of pasting insulation tape on the surface of the connecting tab, the multilayer structure of the embodiments of the present application occupies less space after being formed on the surface of the connecting tab. For the same size of the base body, the connecting tab of the embodiments of the present application has a smaller overall volume and is more suitable for the compact space design of the secondary battery, providing convenience for the assembly of the secondary battery. In addition, the first connecting part and the second connecting part of the connecting tab can also retain the metal properties of the base body. The first connecting part can be reliably connected to the tab of the roll core by welding (such as laser welding and ultrasonic welding), and the second connecting part can also be reliably connected to the pole by a similar method, thereby ensuring the reliability of the secondary battery.

[0010] In some embodiments, the deposited particles include aluminum and nano-silicon, and the mass ratio of aluminum to nano-silicon is (5.5-18.5): 1.

[0011] By employing a hybrid approach of aluminum and nano-silicon, the boundary between the metal interface of the connecting piece (e.g., aluminum connecting piece) and the ceramic interface of the insulating layer can be blurred. This buffers the interfacial thermal stress caused by the difference in thermal expansion coefficients between the substrate (metallic material, such as aluminum) and the insulating layer (ceramic material, with high rigidity) during the charge-discharge cycle of the secondary battery. Aluminum exhibits good compatibility with the substrate (metallic materials such as copper / aluminum), enabling tight adhesion to the coupling surface of the modified layer and enhancing the interfacial bonding between the transition layer and the substrate. Furthermore, nano-silicon can strengthen the interfacial affinity between the transition layer and the insulating layer (containing ceramic particles), promoting the bonding between the two layers.

[0012] Nano-silicon can also enhance the structural strength of the transition layer. By controlling the amount of aluminum and nano-silicon used, and keeping the mass ratio of aluminum to nano-silicon within the range of (5.5~18.5):1, the transition layer can have both ductility and strength, preventing cracking or peeling of the transition layer due to stress concentration, while ensuring the stable support of the transition layer for the substrate and insulation layer.

[0013] A mass ratio of aluminum to nano-silicon of 5.5–18.5:1 can reduce particle agglomeration, resulting in a particle number density of 1010 particles larger than 100 nm. 3 pcs / cm 2 ~10 5 pcs / cm 2 Within a certain range. This makes the microstructure of the transition layer more uniform, further reducing the risk of local stress and improving the overall structural stability of the connecting piece.

[0014] In some embodiments, the mass ratio of metallic aluminum to nano-silicon can be a value of 5.5, 7.5, 9, 12, 15, 17.5, or 18.5, or a range of any two values.

[0015] In some embodiments, the average particle size of aluminum in the transition layer can be controlled within the range of 20 nm to 80 nm.

[0016] In some embodiments, the average particle size of the nano-silicon in the transition layer can be controlled within the range of 5 nm to 20 nm.

[0017] By controlling the average particle size of metallic aluminum and nano-silicon in the transition layer within the aforementioned range, the transition layer can be deposited more densely, allowing for closer contact between the transition layer and the modified layer, thus improving the bonding strength between them. Furthermore, controlling the average particle size of metallic aluminum and nano-silicon in the transition layer within this range also contributes to a more uniform surface roughness structure on the side of the transition layer facing the insulating layer, thereby increasing the contact area between the transition layer and the insulating layer and improving the bonding stability between them.

[0018] In some embodiments, the deposited particles comprise an aluminum-silicon alloy, wherein the mass percentage of aluminum is 84.5% to 95% and the mass percentage of silicon is 5% to 15.5%.

[0019] In some embodiments, at least a portion of the metallic aluminum in the deposited particles may be combined with at least a portion of the nano-silicon in the form of an alloy. Exemplarily, the metallic aluminum and nano-silicon may be combined to form an amorphous or nanocrystalline aluminum-silicon alloy. The aluminum-silicon alloy achieves a gradient transition in thermal expansion coefficient and chemical bonding from the metallic substrate to the ceramic coating. The resistivity of the aluminum-silicon alloy is lower than that of the ceramic layer but still higher than that of pure aluminum, providing a certain degree of intermediate insulation.

[0020] In some embodiments, the mass percentage of aluminum in the aluminum-silicon alloy can be one or a range of any two of the following values: 84.5%, 87%, 89%, 91%, 93%, or 95%.

[0021] In some embodiments, the aluminum-silicon alloy may be composed of silicon and aluminum. In some other embodiments, the aluminum-silicon alloy may also contain other suitable elements, which are not limited in this application.

[0022] In some embodiments, the mass percentage of silicon in the aluminum-silicon alloy can be one of 5%, 7%, 9%, 11%, 13%, or 15.5%, or a range of any two values.

[0023] In some embodiments, magnetically filtered cathodic vacuum arc deposition (FCVA) technology can be used to deposit an aluminum-silicon-containing transition layer on the coupling surface. The transition layer is dense and free of large particles, providing good matching with the subsequent insulating layer. The magnetic filtration device effectively removes macro-particles, resulting in a particle contaminant density (diameter > 100 nm) in the deposited transition layer of less than 10-1. 5 pcs / cm 2 Five randomly selected fields of view at 10,000x magnification using scanning electron microscopy (SEM) showed no particles larger than 100 nm in diameter. This characteristic ensures the extremely high density and smoothness of the transition layer, providing a good foundation for the subsequent processing of the insulating layer.

[0024] In some embodiments, the thickness of the transition layer can be controlled within the range of 50nm to 200nm.

[0025] In some embodiments, the arithmetic mean deviation Ra of the coupling surface profile is 0.8 μm to 1.5 μm.

[0026] The profile arithmetic average deviation Ra reflects the roughness of the coupling surface. By processing the coupling surface of the modified layer, the profile arithmetic average deviation Ra of the coupling surface is controlled in the range of 0.8 μm to 1.5 μm, which can significantly increase the surface area of the coupling surface, improve the bonding strength of the transition layer, and avoid the occurrence of tip discharge or local corrosion caused by excessive roughness.

[0027] In some embodiments, the profile arithmetic average deviation Ra of the coupling surface can be controlled in the range of one value or any two values selected from 0.8 μm, 0.9 μm, 1.0 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, and 1.5 μm.

[0028] In some embodiments, the average ten-point height Rz of the coupling surface is 3 μm to 8 μm.

[0029] The average ten-point height Rz is also an important parameter for evaluating the roughness of the coupling surface, which reflects the extreme fluctuation of the peaks and valleys of the coupling surface. By controlling the average ten-point height Rz of the coupling surface, the surface microfluctuation (e.g., peak and valley distribution) of the coupling surface can be made smoother. Thus, the coupling surface can be kept in contact with the transition layer, and the adhesion strength of the transition layer on the coupling surface can be improved.

[0030] In some embodiments, the average ten-point height Rz of the coupling surface can be controlled in the range of one value or any two values selected from 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, and 8 μm.

[0031] In some embodiments, the ratio of the profile arithmetic average deviation Ra to the average ten-point height Rz of the coupling surface is less than 0.3.

[0032] By controlling the ratio of the profile arithmetic average deviation Ra to the average ten-point height Rz of the coupling surface to be less than 0.3, the coupling surface can be kept rough enough, and the peak and valley distribution of the coupling surface can be relatively uniform. This helps to increase the contact area of the coupling surface with the transition layer, and the transition layer can be as close to the coupling surface as possible, thereby improving the bonding strength of the transition layer and the modified layer.

[0033] In the above embodiments, the profile arithmetic average deviation Ra refers to the arithmetic average value of the absolute value of the distance of each point on the measured profile to the profile center line within a set sampling length. The average ten-point height Rz refers to the sum of the average value of 5 maximum profile peak heights and the average value of 5 maximum profile valley depths. The profile arithmetic average deviation Ra and the average ten-point height Rz can be measured by a stylus surface profiler (refer to GB / T 10610 standard).

[0034] In some embodiments, the surface of the main body portion can be treated by plasma immersion ion implantation or low-temperature plasma bombardment technology. Under the condition of low energy and high beam current without causing thermal deformation of the substrate, the surface of the main body portion is nanocrystallized and activated to form a nanometer modified layer metallurgically combined with the substrate. The treatment process is isotropic bombardment, which does not form obvious directional scratches or concave-convex.

[0035] The surface layer of the modified layer (i.e., the coupling surface on the side away from the main body portion) is formed with an equiaxed nanocrystalline structure with a grain size of 20-50 nm. The modified layer is metallurgically combined with the substrate without a clear interface. The profile arithmetic average deviation Ra of the coupling surface is controlled to be between 0.8-1.5 μm. The ratio (Ra / Rz) of the profile arithmetic average deviation Ra to the average ten-point height Rz is less than 0.3.

[0036] The ratio (Ra / Rz) of the profile arithmetic average deviation (Ra) to the ten-point height (Rz) is less than 0.3, indicating that the surface peak-valley distribution is uniform and the flatness is good. Due to the formation of nanocrystals and the increase in surface roughness, the specular reflectivity of the coupling surface to visible light (e.g., 550 nm) is reduced by 60%-80% compared to the original polished aluminum surface, and the overall coupling surface presents a uniform matte gray appearance, which is an intuitive sign of surface activation.

[0037] In some embodiments, the modified layer can be made to have the desired performance by changing the voltage, pulse width, processing time, and other parameters during plasma immersion ion implantation. In some embodiments, the voltage can be controlled in the range of 10 kV-30 kV. In some embodiments, the pulse width can be controlled in the range of 20 μs-100 μs. In some embodiments, the event of plasma immersion ion implantation treatment can be controlled in the range of 5 min-30 min.

[0038] In some embodiments, the modified layer can also be machined on the surface of the connecting piece by chemical etching, mechanical grinding, and other machining methods, and the coupling surface of the modified layer can have a suitable rough structure. This application does not limit this.

[0039] In some embodiments, the ceramic particles include at least one of aluminum oxynitride or chromium oxynitride.

[0040] In some embodiments, a reactive magnetron sputtering technique can be employed to deposit a ceramic coating layer as the insulating layer on the surface of the transition layer. The ceramic coating layer can be deposited at a low temperature (e.g., below 150 °C) in an atmosphere of Ar, N2, and O2. The ceramic particles formed by the reactive magnetron sputtering technique can be aluminum oxynitride-based ceramic or chromium oxynitride-based ceramic, depending on the target material used in the reactive magnetron sputtering technique. In some embodiments, the target material can also be an aluminum-chromium alloy, and the ceramic particles formed by the deposition can include both aluminum oxynitride-based ceramic and chromium oxynitride-based ceramic.

[0041] By precisely controlling the flow ratio of N2 / O2, the nitrogen-to-oxygen ratio of the ceramic particles can be adjusted to obtain ceramic coating layers with different properties. Specifically, increasing the flow ratio of N2 can increase the nitrogen content of the ceramic particles, thereby making the insulating layer harder. Increasing the flow ratio of O2 can increase the oxygen content of the ceramic particles, thereby making the insulating layer have good insulating properties.

[0042] In some embodiments, the thickness of the insulating layer can be controlled to be between 1 and 5 μm.

[0043] In some embodiments, the thickness of the insulating layer can be 1 μm, 2 μm, 3 μm, 4 μm, or 5 μm, or a range defined by any two of the values.

[0044] In some embodiments, the ceramic particles contain at least one of yttrium and silicon.

[0045] In some embodiments, the ceramic particles can contain yttrium by doping the target material with yttrium. Specifically, an aluminum-based target material or a chromium-based target material containing yttrium can be selected to deposit the insulating layer on the surface of the transition layer. The content of yttrium in the ceramic particles can be controlled by adjusting the content of yttrium in the target material. In some embodiments, the molar percentage of yttrium in the ceramic particles is between 1 and 4%.

[0046] In some embodiments, the molar percentage of yttrium in the ceramic particles is 1%, 2%, 3%, or 4%, or a range defined by any two of the values.

[0047] In some embodiments, silane (SiH4) gas can be mixed into the atmosphere of Ar, N2, and O2 to make the deposited ceramic particles contain silicon. The molar percentage of silicon in the ceramic particles can be adjusted by controlling the flow rate of the silane gas.

[0048] In some embodiments, the molar percentage of silicon in the ceramic particles is between 2 and 8%.

[0049] In some embodiments, the molar percentage of silicon in the ceramic particles is 2%, 3%, 4%, 5%, 6%, 7%, or 8%, or a range defined by any two of the values.

[0050] The yttrium element can refine the grain size, plug the grain boundary, and significantly reduce the through defects in the coating; the silicon element can form amorphous SiO x The network further blocks the ion migration channel.

[0051] In a second aspect of the present application, a power consuming device is provided. The power consuming device comprises the secondary battery provided in the first aspect of the present application, and the secondary battery serves as a power supply for the power consuming device.

[0052] In some embodiments, the power consuming device can be a vehicle, a mobile phone, a portable device, a notebook computer, a ship, a spacecraft, an electric toy, and an electric tool, etc. The vehicle can be a new energy vehicle, which can be a pure electric vehicle, a hybrid electric vehicle, or an extended range vehicle, etc. The spacecraft includes an airplane, a rocket, a space shuttle, a spacecraft, etc. The electric toy includes a fixed or mobile electric toy, such as a game console, an electric car toy, an electric ship toy, and an electric plane toy, etc. The electric tool includes a metal cutting electric tool, a grinding electric tool, an assembling electric tool, and a railway electric tool, such as an electric drill, an electric grinder, an electric wrench, an electric screwdriver, an electric hammer, an impact drill, a concrete vibrator, and an electric planer, etc. The embodiments of the present application do not specially limit the above devices.

[0053] It should be understood that the content described in this part is not intended to limit the key features or important features of the embodiments of the present application, nor is it used to limit the scope of the present application. Other features of the present application will become apparent through the following description. BRIEF DESCRIPTION OF DRAWINGS

[0054] The above and other features, advantages, and aspects of the embodiments of the present application will become more apparent by describing in detail the following embodiments with reference to the attached drawings. In the drawings, the same or similar reference numerals refer to the same or similar elements, in which: Figure 1 A structural schematic diagram of a secondary battery according to some embodiments of the present application is shown; Figure 2 A schematic diagram of the overall structure of a connecting piece according to some embodiments of the present application is shown; and Figure 3 A schematic diagram of the layer structure of a connecting piece according to an embodiment of the present application is shown. DETAILED DESCRIPTION

[0055] Embodiments of the present application will be described in more detail below with reference to the accompanying drawings. While certain embodiments of the present application are shown in the drawings, it is understood that the present application can be embodied in various forms and should not be construed as limited to the embodiments set forth herein, but rather, should be construed broadly. It should be further understood that the drawings and embodiments described herein are for illustrative purposes only and are not intended to limit the scope of the present application.

[0056] It is noted that the headings provided herein are not limitations of various embodiments. Various embodiments are described throughout this document and can be included under any heading. Moreover, embodiments described in any heading can be combined with any other embodiment described in the same heading and / or a different heading in any manner.

[0057] In the description of embodiments of the present application, the term "includes" and its derivatives are open-ended, meaning "including but not limited to". The term "based on" is intended to mean "based, at least in part, on" The term "one embodiment" or "an embodiment" means "at least one embodiment". The term "some embodiments" means "at least some embodiments". Other explicit or implicit definitions can also be included below. The terms "first", "second", etc. can refer to different or the same objects. Other explicit and implicit definitions can also be included below.

[0058] Due to the compact internal space of the secondary battery, during assembly and use of the battery, the connecting tab can come into contact with the adjacent opposite electrode or battery case (usually steel or aluminum) due to physical vibration, extrusion or process deviation, etc., causing a short circuit of the secondary battery, and thus triggering thermal runaway. In addition, the electrolyte of the lithium ion battery usually contains lithium salts such as LiPF6, which can decompose to produce corrosive substances such as HF in the presence of trace amounts of moisture. The connecting tab is exposed to an acidic environment at high pressure and high temperature for a long time, which can cause pitting, corrosion, etc., thus increasing the internal resistance of the secondary battery, degrading the battery performance, and even causing failure.

[0059] In some cases, the connecting tab is protected from corrosion and insulation by sticking a tape made of materials such as polyethylene terephthalate (PET) and polyimide (PI) on the connecting tab. However, the tape has problems such as aging, adhesion failure, poor electrolyte resistance, and poor high-temperature resistance, which affect the long-term use of the connecting tab.

[0060] This application provides a secondary battery and electrical device to solve or at least partially solve the technical problems mentioned above or other potential technical problems. According to the connecting piece provided in this application, by providing a transition layer on the main body of the substrate and an insulating layer on the side of the transition layer facing away from the substrate, the insulating layer can be stably attached to the surface of the main body through the transition layer. The dense, insulating, and corrosion-resistant properties of the insulating layer can protect the connecting piece, improve its insulation and corrosion resistance, thereby increasing its service life and ensuring the reliability of the secondary battery during long-term use. The transition layer, arranged between the substrate and the insulating layer, can effectively release the interfacial stress between the substrate and the insulating layer, avoiding warping of the thin sheet workpiece and coating peeling.

[0061] The connecting piece provided in the embodiments of this application will now be described in more detail with reference to the accompanying drawings.

[0062] Figure 1 A schematic diagram of the structure of a secondary battery according to some embodiments of this application is shown. For example... Figure 1 As shown, the secondary battery generally includes a core, terminals 3, and connecting pieces 1. The core is formed by winding multiple electrodes in a stacked manner, and the connecting pieces 1 are arranged between the electrodes and terminals 3 to electrically connect the tabs 2 of the electrodes to the terminals 3. In some embodiments, the electrodes of the secondary battery include at least one positive electrode and at least one negative electrode. Accordingly, the connecting pieces 1 include a positive electrode connecting piece connected to the positive electrode and a negative electrode connecting piece connected to the negative electrode. That is, the connecting pieces 1 are used to connect the tabs 2 and terminals 3 of the same electrode. Taking the positive electrode connecting piece as an example, the positive electrode connecting piece is used to connect the tabs of the positive electrode and the positive terminal. In some embodiments, the positive electrode connecting piece can be connected to the positive electrode and the positive terminal by welding. In some embodiments, the positive electrode connecting piece can be connected to the tabs of the positive electrode by ultrasonic welding. In some embodiments, the positive electrode connecting piece can be connected to the positive terminal by laser welding.

[0063] Figure 2 A schematic diagram of the overall structure of the connecting piece 1 according to some embodiments of this application is shown. Figure 2 As shown, the connecting piece 1 includes a substrate. The substrate is a sheet-like structure and includes a main body 11 and a first connecting part 12 and a second connecting part 13 arranged on the edge of the main body 11. The first connecting part 12 is connected to the tab 2 of the electrode (e.g., the positive electrode) of the secondary battery, and the second connecting part 13 is connected to the post 3.

[0064] In some embodiments, multiple first connecting portions 12 are provided, and the multiple first connecting portions 12 are arranged on the edge of the connecting piece 1 along the width direction. In some embodiments, two first connecting portions 12 are provided on the connecting piece 1, and the two first connecting portions 12 are respectively arranged on two opposite sides of the main body portion 11 along the width direction. The two first connecting portions 12 can be connected to the tabs 2 of the pole pieces corresponding to the two cores, respectively. In some embodiments, one first connecting portion 12 can also be connected to the tabs 2 of the pole pieces of the two cores. That is, one connecting piece 1 can connect the pole pieces corresponding to four cores to the pole post 3. The first connecting portions 12 can be provided on the side of the base along the length direction perpendicular to the width direction.

[0065] Figure 3 A schematic diagram of the layer structure of the connecting piece 1 according to an embodiment of this application is shown. Figure 3 As shown, to provide insulation and corrosion protection for the connecting piece 1, a modified layer 14 is formed on the surface of the main body 11 of the connecting piece 1. A transition layer 4 and an insulating layer 5 are sequentially deposited from the inside to the outside along the thickness direction of the connecting piece 1 on the coupling surface of the modified layer 14 away from the main body 11. The insulating layer 5 includes ceramic particles, which can construct a dense protective barrier on the surface of the main body 11 of the connecting piece 1. While establishing insulation on the surface of the main body 11 of the connecting piece 1, the ceramic particles also improve the corrosion resistance of the connecting piece 1. The transition layer 4 provides a transition between the insulating layer 5 and the modified layer 14, weakening the interface boundary between the insulating layer 5 and the modified layer 14, improving the adhesion of the insulating layer 5, reducing the interfacial stress exerted by the insulating layer 5 on the connecting piece 1, and reducing the possibility of bending of the connecting piece 1 after coating deposition.

[0066] Neither the first connecting portion 12 nor the second connecting portion 13 of the connecting piece 1 has any coating to ensure the conductivity of the connecting piece 1, so that the first connecting portion 12 and the second connecting portion 13 can be welded to the tab 2 and the post 3, respectively. In some embodiments, during the processing of the main body portion 11, the connecting piece 1 can be protected by means of applying protective tape to the first connecting portion 12 and the second connecting portion 13, covering with a mask plate, etc., to prevent the transition layer 4 and the insulating layer 5 from depositing on the surfaces of the first connecting portion 12 and the second connecting portion 13. The connecting piece provided in the embodiments of this application will be described in more detail below with reference to specific embodiments.

[0067] Example 1 The S1 substrate pretreatment uses aluminum sheets as the processing raw material. The substrate is obtained by cutting the aluminum sheets into a predetermined shape. The aluminum sheet material is 1060 aluminum with a thickness of 0.8 mm, according to the Aluminum Association (AA) standard. A laser-etched stainless steel mask is used to cover the joints of the substrate.

[0068] S2 modification layer treatment, the covered substrate is placed in a plasma immersion ion implantation device (Model-3 multifunctional plasma immersion ion implantation device developed by Southwest Jiaotong University Surface Engineering Institute), in an argon atmosphere, a voltage of 10 kV, a pulse width of 50 μs, and a treatment time of 5 minutes, to form a modification layer on the surface of the main body of the substrate.

[0069] S3 transition layer treatment, the substrate with the modification layer is placed in a filtered cathode vacuum arc deposition (FCVA) device, which is a composite coating system equipped with a double-bent filtered cathode arc source, to form a transition layer on the coupling surface of the modification layer by deposition. The first target material used in the filtered cathode vacuum arc deposition is a silicon-aluminum composite target material, and the aluminum-silicon mass ratio of aluminum and silicon in the silicon-aluminum composite target material is 5.5:1. The control current of the filtered cathode vacuum arc deposition device is 80 A, the axial magnetic field strength of the filter conduit is 50 mT, the substrate temperature is maintained below 80°C by a cooling system during the deposition process, and the deposition time is 13 minutes.

[0070] S4 insulation layer treatment, the substrate with the transition layer is transferred to a magnetron sputtering device as a substrate, and the second target material used in the magnetron sputtering is an aluminum target. An insulation layer is formed by magnetron sputtering deposition in a mixed atmosphere. The magnetron sputtering device is a PVD500 type high vacuum magnetron sputtering thin film deposition system produced by Shenyang Scientific Instrument Co., Ltd., Chinese Academy of Sciences. During the reactive sputtering deposition, the sputtering power is 3-8 W / cm 2 , and the substrate temperature is 120°C. The working gas is a mixed gas of Ar, N2 and O2, and the total gas flow is maintained at 100 sccm. The molar ratio of Ar:N2:O2 in the mixed gas can be controlled by the flow controller at 6:2:1.

[0071] S5 remove the laser-etched stainless steel mask plate to obtain the connecting piece.

[0072] Examples 2-5 The difference from Example 1 is that the aluminum-silicon mass ratio of the first target material in step S3 is different Examples 6 and 7 The difference from Example 3 is that the control current and the axial magnetic field strength of the filtered cathode vacuum arc deposition device in step S3 are different.

[0073] Examples 8-12 The difference from Example 3 is that the voltage, pulse width, and treatment time in step S2 are different.

[0074] Example 13 The difference from Example 10 is that the second target material used in step S4 is a chromium target.

[0075] Example 14 The difference from Example 10 is that the second target material used in step S4 is an aluminum-yttrium composite target, and the molar percentage of yttrium element in the aluminum-yttrium composite target is 1%.

[0076] Example 15 The difference from Example 10 is that the mixed gas atmosphere in step S4 further includes silane gas, and the molar ratio of Ar:N2:O2:SiH4 in the mixed gas atmosphere is 2:1:1:0.02. Examples 16-20 The difference from Example 10 is that the second target material used in step S4 is an aluminum-yttrium composite target, and the molar percentage of aluminum element and yttrium element in the aluminum-yttrium composite target is different. In addition, the mixed gas atmosphere in step S4 further includes silane gas, and the molar percentage of silane gas in the mixed gas atmosphere is different.

[0077] Table 1

[0078] Note: 1) In Table 1, X(a%) in the target material composition represents the molar percentage of the total amount of the second target material occupied by the X element. For example, Al(100%) indicates that the second target material is a pure aluminum target, and Al(a%), Y(b%) indicates that the second target material is an aluminum-yttrium composite target, and the molar percentage of aluminum element is a%, and the molar percentage of yttrium element is b%.

[0079] 2) In Table 1, the molar ratio of Ar:N2:O2:SiH4 in the mixed gas atmosphere is represented by “-” in the example, which means that SiH4 is not used, i.e. silane gas does not exist.

[0080] Comparative Example 1 An aluminum sheet is used as a processing raw material, and after cutting, a substrate is obtained, wherein the aluminum sheet is an aluminum material with a grade of 1060 under the standard of The Aluminum Association (AA) and a thickness of 0.8 mm. A PET tape is pasted on the main body of the substrate, and the thickness of the PET tape is 100 um and the width is 20 mm.

[0081] Comparative Example 2 An aluminum sheet is used as a processing raw material, and after cutting, a substrate is obtained, wherein the aluminum sheet is an aluminum material with a grade of 1060 under the standard of The Aluminum Association (AA) and a thickness of 0.8 mm. A laser engraving stainless steel mask plate is used to cover the connecting part of the substrate.

[0082] The covered substrate was placed in a magnetron sputtering device, and an insulating layer was formed by reactive sputtering deposition using an aluminum target in an Ar / N2 / O2 atmosphere. During the sputtering process, the total gas flow was maintained at 100 sccm. The molar ratio of Ar:N2:O2 in the mixed gas can be controlled by the flow controller at 6:2:1.

[0083] Comparative Example 3 The difference from Example 3 is that the current of the magnetic filter cathode vacuum arc deposition device in step S3 is controlled at 40 A, and the axial magnetic field strength of the filter conduit is 100 mT.

[0084] Performance test Detection content 1) Property detection of the modified layer The surface roughness (Ra and Rz) detection equipment is a TR200 high-precision roughness meter. The detection steps and parameters are as follows: the substrate after the modified layer treatment is fixed on the sample table, the contact mode is used (diamond stylus is used to draw across the surface), the sampling length is set to 0.8 mm, the evaluation length is set to 4 mm (i.e. 5 sampling lengths), and the driving speed is set to 0.5 mm / s. The values of Ra and Rz are measured at least 5 different areas in the middle of the sample, and Ra / Rz is calculated therefrom.

[0085] 2) Property detection of the transition layer The thickness of the transition layer, the mass ratio of aluminum and silicon in the transition layer, and the number of particle contaminants (particle size greater than 100 nm) of the substrates of Examples 1-20 after the transition layer treatment were detected.

[0086] 2.1) The thickness of the transition layer was observed and calculated using a scanning electron microscope (SEM).

[0087] 2.2) The mass ratio of aluminum and silicon in the transition layer was analyzed using an energy dispersive X-ray spectrometer (EDS) in combination with a scanning electron microscope (SEM).

[0088] 2.3) Five random fields of view of the transition layer were observed under 10000 times using a scanning electron microscope (SEM), the number of particles with a diameter greater than 100 nm in the field of view was checked, and the density of particles with a diameter greater than 100 nm was calculated.

[0089] 3) Property detection of the insulating layer 3.1) The thickness of the insulating layer of the substrates of Examples 1-20 after the insulating layer treatment was observed and calculated using a scanning electron microscope (SEM).

[0090] 3.2) Using energy dispersive X-ray spectroscopy (EDS) and in conjunction with scanning electron microscopy (SEM), detect the proportion of yttrium elements and silicon elements in the insulating layer of examples 14~20.

[0091] 4) Insulation performance detection of the connecting piece Volume resistivity: Detection equipment: ZST-212 volume surface resistivity tester, which has an integrated three-electrode system (main electrode, protection ring, measurement electrode) and a high-precision power supply. The output voltage of ZST-212 can be continuously adjusted within the range of 1~1500V, and the upper limit of resistance testing reaches 10^16 Ω, which can meet the high resistance testing needs of insulating coatings.

[0092] Detection steps: ① Put the sample into the shielding box of the instrument; ② Switch the test mode to the "volume resistance" position and set the test voltage to 1000V; ③ Set the electrochemical time (charging time) to 60 seconds to allow the sample to be fully polarized and the current to be stable; ④ Input the accurate thickness of the coating of the sample 1~5μm; ⑤ Start the test. The instrument will directly display the volume resistance (Ω) and the calculated volume resistivity (Ω·cm) readings after the electrochemical time ends.

[0093] Breakdown voltage Breakdown voltage test steps: The detection equipment is the same as the volume resistivity detection equipment, using a high-voltage module and a step-up voltage mode. Start from a lower voltage (such as 500V) and increase the voltage at a constant rate (such as 100V / s) until a sharp increase in current is monitored (breakdown occurs), and the voltage value at this instant is recorded as the breakdown voltage.

[0094] 5) Bonding force detection between the insulating layer and the substrate in the connecting piece Scratch critical load test: Detection equipment: scratch test module of MFT-4000 multifunctional material surface performance tester.

[0095] Detection steps: ① Firmly fix the connecting piece sample with coating, according to the hardness of the coating (ceramic coating is harder), select a diamond indenter with a cone angle of 120° and a tip radius of 0.2mm; ② Set the scratch length to 3~5mm, set the load range to 0N to 50N, set the loading rate (50N / min) to make the load increase linearly to the maximum value within the scratch length, and set the scratch head moving speed (3mm / min); ③ Start the test, the equipment automatically completes the scratch, after the test, the first significant increase in acoustic emission signal or the first sharp fluctuation point in the friction force curve in the software corresponds to the critical load (Lc) of the first crack in the coating.

[0096] 6) Electrolyte resistance test of the connecting piece The connecting tab was immersed in an electrolyte environment at 85°C, with Li + / Li as the standard reference electrode at a test voltage of 4.2V for 1000 hours. The surface state of the connecting tab was observed.

[0097] The connecting tab was rated according to the surface state of the connecting tab. The rating criteria included: Level 1: No blistering or peeling of the connecting tab coating area, no attenuation of the insulation resistance. Obvious corrosion pits appeared in the uncoated area.

[0098] Level 2: Local blistering and partial peeling of the connecting tab coating area, attenuation of the insulation resistance.

[0099] Level 3: Extensive blistering and sheet peeling of the connecting tab coating area, obvious corrosion pits appeared in the coating area.

[0100] The results of the property detection of the modified layer, transition layer, and insulation layer of Examples 1-20 and Comparative Examples 1-3 are shown in Table 2.

[0101] Table 2

[0102] Note: 1) In Table 2, " / " indicates that it was not detected; 2) In Table 2, X(a%) in the coating composition of the insulation layer indicates the mole percentage of the total amount of the target material of the X element in the insulation layer. For example, Y(a%) indicates that the mole percentage of the yttrium element in the insulation layer is a%, Y(a%), Si(b%) indicates that the mole percentage of the yttrium element in the insulation layer is a%, and the mole percentage of the silicon element is b%.

[0103] The insulation performance, bonding force performance, and electrolyte resistance performance of Examples 1-20 and Comparative Examples 1-3 are shown in Table 3.

[0104] Table 3

[0105] Referring to Table 3 in combination with Tables 1 and 2, it can be seen that the connecting tab prepared in Examples 1-20 provides protection to the connecting tab by processing a transition layer and an insulation layer on the surface of the main body portion of the connecting tab. This improves the insulation performance of the surface of the connecting tab and also improves the corrosion resistance of the main body portion. This reduces damage to the connecting tab during assembly, transportation, and use, and improves the safety performance and service life of the secondary battery. In addition, the transition layer is arranged between the insulation layer and the modified layer, which improves the adhesion strength of the insulation layer, thereby avoiding peeling of the insulation layer due to external forces or temperature changes, and further improving the protection ability of the insulation layer to the connecting tab.

[0106] Referring to Examples 1-20 and Comparative Examples 1-3, the connecting pieces provided in this application have advantages such as good insulation performance, strong corrosion resistance, and high adhesion strength. Comparative Example 1 uses PET tape to protect the connecting piece, but the bonding stability between the PET tape and the connecting piece is insufficient, and the critical scratch load is low. After long-term use, the PET tape is prone to peeling and damage, thus affecting the protective performance of the connecting piece and consequently leading to insufficient electrolyte resistance. In the connecting pieces provided in Examples 1-20, the insulation layer is formed directly on the outside of the main body. The insulation layer has high bonding strength with the main body and a high critical scratch load; therefore, the insulation layer can provide long-lasting and durable protection for the connecting piece.

[0107] Compared to Comparative Example 2, Examples 1-20 show better compatibility between the insulation layer and the main body due to the use of modified and transition layers to transition the insulation layer. The critical scratch load of Examples 1-20 is significantly higher than that of Comparative Example 2. In addition, the addition of the transition and modified layers also improves the insulation performance of the connecting piece surface to a certain extent, and the breakdown voltage of Examples 1-20 is significantly higher than that of Comparative Example 2.

[0108] Referring to Examples 1-5, by controlling the aluminum-silicon mass ratio of the first target material forming the transition layer, the aluminum-silicon mass ratio of the transition layer can be affected. This alters the coupling strength between the transition layer and the modified layer and the insulating layer, thus affecting the adhesion strength of the insulating layer on the main body of the connecting piece. In Examples 1-5, the critical load for the first crack to occur can reach 35N or more. In Example 3, the aluminum-silicon mass ratio of the first target material is 12, and the aluminum-silicon mass ratio in the resulting transition layer is 12.5. The critical scratch load of the coating on the surface of the main body of Example 3 (i.e., the transition layer and insulating layer located on the main body of the connecting piece) can reach 40N.

[0109] Referring to Examples 1-20 and Comparative Example 3, by adjusting the control current of the magnetic filter cathode vacuum arc deposition equipment and the axial magnetic field strength of the filter conduit during the transition layer treatment process, the density of particles with a diameter greater than 100 nm in the transition layer of the connecting piece in Examples 1-20 can be controlled to be within 10. 3 pcs / cm 2 ~10 5 pcs / cm 2 Within this range. This makes the microstructure of the transition layer more uniform and dense, allowing the transition layer to bond more stably with the insulating layer. In Comparative Example 3, the density of particles with a diameter greater than 100 nm is 2.8 × 10⁻⁶. 6 pcs / cm 2 The critical load for scratch resistance is 18N, which is significantly lower than that of Examples 1-20.

[0110] With reference to Embodiments 3, 8-12, by adjusting the voltage, pulse width, processing time, etc. of the plasma immersion ion implantation during the modification layer processing, the surface structure of the coupling surface of the modification layer can be changed, so that the profile arithmetic average deviation Ra of the coupling surface is in the range of 0.8 μm-1.5 μm, the average ten-point height Rz is in the range of 3 μm-8 μm, and the ratio of the profile arithmetic average deviation Ra to the average ten-point height Rz of the coupling surface is lower than 0.3. In this way, the contact area of the coupling surface with the transition layer can be increased, so as to improve the adhesion strength of the transition layer with the coupling surface, and further improve the scratch critical load of the surface coating of the main body. The scratch critical load of the surface coating of the main body of Embodiment 9 can reach 45 N or higher.

[0111] As can be seen from Reference Embodiments 9, 14 and Embodiments 16-18, the second target material is selected as an aluminum-yttrium alloy during the processing of the insulation layer, so that the insulation layer obtained contains aluminum and yttrium elements. The incorporation of yttrium elements can improve the volume resistivity of the surface coating of the main body, and further improve the insulation performance of the insulation layer. It should be noted that since the second target material used in Embodiments 1-13 is an aluminum target, the main body of the insulation layer obtained is aluminum oxynitride (AlON) based ceramic.

[0112] In addition, the insulation layer can also be doped with silicon elements. As can be seen from Reference Embodiments 16-20, silicon elements can play a compounding role with yttrium elements, so as to improve the scratch critical load of the surface coating of the main body while maintaining high volume resistivity.

[0113] The above has described various implementations of the present application, and the above description is exemplary, not exhaustive, and is not limited to the disclosed implementations. Many modifications and changes are obvious to those skilled in the art without departing from the scope and spirit of the described implementations. The choice of terms used herein is intended to best explain the principles of the implementations, practical applications, or improvements to the technology in the market, or to enable other ordinary skilled persons in the art to understand the various implementations disclosed herein.

Claims

1. A secondary battery characterized by comprising: The connection sheet comprises: The base body comprises a main body part and first and second connecting parts arranged at the edges of the main body part, the first connecting part being connected to the tab, and the second connecting part being connected to the pole post, a modified layer being arranged on the surface of the main body part, the modified layer on the side away from the main body part being a coupling surface with a rough structure; An insulating layer is arranged on the side of the transition layer away from the base body, the insulating layer comprising ceramic particles. A transition layer is disposed on the coupling surface of the modified layer. The transition layer comprises deposited particles, which include aluminum and silicon elements. The number density of particles with a diameter greater than 100 nm in the deposited particles is 10. 3 pcs / cm 2 ~10 5 pcs / cm 2 ;as well as The deposited particles comprise aluminum and nano-silicon, the mass ratio of the aluminum and nano-silicon being (5.5-18.5):

1.

2. The secondary battery according to claim 1, characterized by The deposited particles comprise aluminum-silicon alloy.

3. The secondary battery according to claim 2, characterized by The profile arithmetic mean deviation Ra of the coupling surface is 0.8 μm-1.5 μm.

4. The secondary battery according to claim 1, characterized by The average ten-point height Rz of the coupling surface is 3 μm-8 μm.

5. The secondary battery according to claim 4, characterized by The ratio of the profile arithmetic mean deviation Ra to the average ten-point height Rz of the coupling surface is lower than 0.

3.

6. The secondary battery according to claim 5, characterized by The ceramic particles comprise at least one of aluminum oxynitride or chromium oxynitride.

7. The secondary battery according to claim 1, characterized by The ceramic particles contain at least one of yttrium and silicon.

8. The secondary battery according to claim 7, characterized by In the ceramic particles, the molar percentage of yttrium is 1-4%, and the molar percentage of silicon is 2-8%.

9. The secondary battery according to claim 8, characterized by The secondary battery of any one of claims 1-9 is used as a power supply for the electric device.

10. An electric device, characterized by ​

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