A processing method of a functional set fluid, a functional set fluid prepared by applying the method, and a secondary battery

Abstract

The present invention belongs to the technical field of current collectors. The present invention provides a processing method of a functional current collector, a functional current collector prepared by applying the method, and a secondary battery. The above-mentioned functional current collector includes a polymer substrate and a metal layer; the above-mentioned processing method includes a piezoelectric material layer forming process and a metal layer forming process; the piezoelectric material layer forming process includes the following operations of fabricating a piezoelectric material layer on the surface of the polymer substrate; the metal layer forming process includes the following operations of fabricating a metal layer on the surface of the film obtained after the piezoelectric material layer forming process is completed, and during this process, an electric field is applied to the piezoelectric material layer. The functional current collector prepared by using the above-mentioned processing method has good structural stability.

Description

Technical Field

[0001] The present invention belongs to the technical field of current collectors, and specifically relates to a processing method of a functional current collector, a functional current collector prepared by applying the method, and a secondary battery. Background Art

[0002] With the rapid development of the new energy vehicle and energy storage fields, the demand for lithium-ion power batteries has increased rapidly, which in turn has put forward higher requirements for the performance of current collectors. Therefore, current collectors are developing in the direction of being thinner, lighter, and safer. As a new type of current collector material with the most potential for substitution, the functional current collector subverts the traditional current collector with its "metal-polymer composite-metal" sandwich structure, enabling it to improve safety performance while increasing energy density and reducing raw material costs.

[0003] The composite copper current collector has the characteristics of low cost and light weight, can improve the energy density of the battery, and improve the thermal runaway of the battery. Currently, the development of functional current collectors based on polymer substrates is one of the most popular sub-research fields in the power battery industry. However, compared with traditional foil current collectors, in terms of the application of polymer substrates and the thinning of metal conductive layers, the functional current collector shows certain deficiencies in tensile strength and elongation, and due to the interlayer composite of different materials, the internal structural stability of the functional current collector is also not as good as that of traditional foil current collectors. In addition, in the processing technology of functional current collectors, physical vapor deposition, water plating and other processes are generally used to form metal conductive layers. During the forming process, it is easy to cause pressure on the film material to be processed, resulting in deformation, leading to the concentration of residual stress at the processing interface, and easily inducing insufficient interlayer bonding strength or even delamination between the metal conductive layer and the polymer substrate. Local areas in the metal conductive layer may be affected by uneven stress and pressure, increasing the brittleness of the functional current collector or affecting its tensile strength, etc., which seriously affects the structural stability of the functional current collector during battery processing and battery operation. Moreover, in the physical vapor deposition-related solutions, the polymer substrate is prone to breakage in the physical vapor deposition environment (such as winding tension, metal ion bombardment, vacuum pumping, and high temperature generated during sputtering), which has an adverse effect on the quality of the functional current collector.

[0004] In summary, the deficiencies in the structural stability of the functional current collector seriously hinder its further application and development. Summary of the Invention

[0005] In order to improve the structural stability of the functional current collector, the present invention provides a processing method of a functional current collector, a functional current collector prepared by applying the method, and a secondary battery. The functional current collector prepared by using the above processing method has good tensile strength, elongation and interlayer bonding strength, and applying the functional current collector to a secondary battery is beneficial to improving the performance of the secondary battery.

[0006] According to a first aspect of the present invention, there is provided a processing method for a functional current collector: the functional current collector includes a polymer substrate and a metal layer; the processing method includes a piezoelectric material layer forming process and a metal layer forming process; the piezoelectric material layer forming process includes the following operations of fabricating a piezoelectric material layer on the surface of the polymer substrate; the metal layer forming process includes the following operations of fabricating a metal layer on the surface of the film obtained after the completion of the piezoelectric material layer forming process, and during this process, an electric field is applied to the piezoelectric material layer. In this solution, the operation of applying a voltage can be achieved by using common DC power sources on the market such as multi-channel precision voltage sources. In the functional current collector processing method provided in this solution, a piezoelectric material layer is first provided on the surface of the polymer substrate before preparing the metal layer. In the subsequent metal layer forming process, due to the piezoelectric effect, the piezoelectric material in the piezoelectric material layer deforms under the action of an external electric field, and the deformation of the piezoelectric material can be transmitted to the gradually thickening metal layer, thereby affecting the nucleation and growth behavior of the metal grains constituting the metal layer during the formation of the metal layer, realizing the refinement of the metal grains, and further adjusting the residual stress distribution of the metal layer during the formation of the metal layer, fully releasing the residual stress of the metal layer, reducing stress concentration, so that the tensile strength and elongation rate of the functional current collector are both improved. In addition, the refinement of the metal grains improves the density of the metal layer, improves the corrosion resistance of the metal layer, and increases the interlayer adhesion strength of the functional current collector. For the above reasons, the functional current collector prepared by using the processing method of the functional current collector provided by the present invention has good structural stability.

[0007] Optionally, the materials constituting the polymer substrate include at least one of polyethylene terephthalate (PET), polypropylene (PP), polyimide (PI), polyvinyl chloride (PVC), polyamide (PA), polystyrene (PS), polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF).

[0008] Preferably, before preparing the piezoelectric material layer, the surface of the polymer substrate is pretreated by plasma. Using plasma to remove the stains on the surface of the polymer substrate and making the surface of the polymer substrate rough can improve the surface activity of the polymer substrate.

[0009] Preferably, after the metal forming process is completed, there is a conductive layer forming process; in the conductive layer forming process, a conductive layer is fabricated on the surface of the piezoelectric material layer; in the metal layer forming process, the way of applying an electric field to the piezoelectric material layer is to apply a voltage to the conductive layer.

[0010] Preferably, the metal materials constituting the conductive layer include at least one of nickel, platinum, titanium, gold, silver, copper or alloys containing the above metals.

[0011] Preferably, in the process of forming the metal layer, the voltage applied to the conductive layer does not exceed 10V.

[0012] Preferably, in the process of forming the metal layer, the voltage applied to the conductive layer is 1V - 8V.

[0013] Preferably, the metal layer includes a seed copper layer and a thickened copper layer stacked in a direction away from the polymer substrate, and the metal materials constituting the seed copper layer and the thickened copper layer include at least one of metallic copper and copper alloy; in the process of forming the metal layer, a first voltage is applied to the conductive layer during the preparation of the seed copper layer, and a second voltage is applied to the conductive layer during the preparation of the thickened copper layer, and the first voltage is less than the second voltage. The above-mentioned seed copper layer can be deposited and formed by magnetron sputtering, and the above-mentioned thickened copper layer can be plated on the surface of the seed copper layer by electroplating. By forming the seed copper layer, the substrate for forming the thickened copper layer can meet the minimum resistance required for electroplating. Further, during the magnetron sputtering deposition process of forming the seed layer, a first voltage is applied to the piezoelectric material layer, and the piezoelectric material deforms under the action of the first voltage, causing the micro-roughness of the seed copper layer to change accordingly, and then changing the nucleation density of metal grains in the subsequent thickened copper layer, which is beneficial to the formation of the thickened copper layer and improves the interlayer bonding strength of the functional current collector. During the process of forming the thickened copper layer, by setting the second voltage to be greater than the first voltage, the deformation amount of the piezoelectric material can be increased, thereby refining the metal grains in the thickened copper layer and dispersing the concentrated stress of the metal layer, further improving the mechanical properties of the functional current collector. Preferably, 0V < first voltage < 4V, second voltage ≤ 10V.

[0014] Preferably, the difference between the second voltage and the first voltage is 4V - 6V.

[0015] Preferably, the metal layer further includes a conductive layer.

[0016] Preferably, the metal material constituting the conductive layer includes at least one of nickel, platinum, titanium, gold, silver, copper or an alloy containing the above metals.

[0017] Preferably, the thickness of the conductive layer ≤ 10nm.

[0018] Preferably, the particle size of the piezoelectric material is 30μm - 80μm, and the thickness of the piezoelectric material layer ≤ 500nm.

[0019] Preferably, the piezoelectric material includes at least one of lead zirconate titanate (PZT), lead magnesium niobate-titanate (PMN-PT), polyvinylidene fluoride (PVDF), lithium niobate, and lead zirconate niobate-titanate (PZN-PT).

[0020] According to the second aspect of the present invention, there is provided a functional current collector obtained by a processing method of the functional current collector as described above.

[0021] Preferably, the functional set fluid satisfies at least one of the following a, b, c, and d: a. The thickness of the seed copper layer is 100 nm; b. The particle size of the material constituting the seed copper layer is 20 nm to 100 nm; c. The thickness of the thickened copper layer is 800 nm to 1200 nm; d. The particle size of the material constituting the thickened copper layer is 30 nm to 200 nm.

[0022] According to the third aspect of the present invention, a secondary battery is provided, and the secondary battery includes the functional set fluid as described above. Detailed implementation manners

[0023] In order to enable those skilled in the art to better understand the solution of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments.

[0024] In the following examples and comparative examples, the measured results of the grain size are obtained by measuring the specimens using a scanning electron microscope S4800. During the measurement of the grain size, the main parameters set for the scanning electron microscope S4800 are as follows: the acceleration voltage is 0.1 kV to 30 kV, the highest magnification can reach up to eight hundred thousand times, and its resolution is 1 nm when the acceleration voltage is 15 kV.

[0025] Example 1

[0026] In this example, a PET film with a thickness of 4.5 μm is used as the polymer base layer for preparing the functional set fluid, and PZT with an average particle size of 50 nm is selected as the piezoelectric material used in this example, and the functional set fluid is prepared according to the following steps.

[0027] 1. Plasma cleaning

[0028] A roll-to-roll plasma processing device is used to provide plasma for surface cleaning and activation of the polymer base layer to be processed. In this step, the working gas for providing plasma is an 80% Ar + 20% O2 mixed gas, the radio frequency power of the device is 100 W, the cleaning and activation time is 10 min, the working gas flow rate is 150 mL / min, and the winding tension is controlled to be about 70 N (control error < 2%).

[0029] 2. Piezoelectric material layer forming process

[0030] The piezoelectric material layer is fabricated on the surface of the polymer substrate by spraying, which specifically includes the following operations: The polymer substrate is spray-treated with a plasma precision spraying device. The PZT powder is fed into the powder feeder of the plasma precision spraying device, heated, and then accelerated by the plasma jet, and subsequently sprayed onto the surface of the polymer substrate pretreated by plasma cleaning to form the piezoelectric material layer. In this step, the working gas for providing plasma is Ar + O2, the Ar flow rate is 110 SCCM, the O2 flow rate is 20 SCCM, the powder feeding rate is 10 g / min, the spraying distance is 90 mm, the spraying current is 200 A, the spraying voltage is 80 V, and the finally prepared coating thickness is 300 nm. During spraying, the film is cooled by a cooling roller, and the cooling temperature is -30°C.

[0031] The film material composed of the polymer substrate and the piezoelectric material layer obtained after this step is used as the piezoelectric substrate.

[0032] 3. Sputtering to form the conductive layer

[0033] The conductive layer is fabricated on the surface of the piezoelectric substrate by magnetron sputtering, which specifically includes the following operations: The piezoelectric substrate is magnetron sputtered with a roll-to-roll magnetron sputtering device, and a conductive layer with a thickness of 10 nm is sputtered on the surface of the piezoelectric material layer. In this step, the relevant materials and parameters involved in magnetron sputtering are as follows: Silver is used as the target. Before sputtering, pre-sputtering is carried out for 10 min to remove impurities on the target surface. The working gas for magnetron sputtering is Ar, the flow rate is 90 SCCM, the sputtering power is 7 kW, the tape running speed of the device is 5 m / min, and the cooling temperature of the main drum is -15°C.

[0034] 4. Metal layer forming process

[0035] (1)Sputtering to form the seed copper layer

[0036] The seed copper layer is fabricated on the surface of the conductive layer by magnetron sputtering, which specifically includes the following operations: The conductive layer is magnetron sputtered with a roll-to-roll magnetron sputtering device, and a seed copper layer with a thickness of 100 nm is sputtered on the surface of the conductive layer. The copper grain size of the seed copper layer is 80 nm, and thus the semi-finished product of the functional current collector is obtained. In this step: Parallel plate electrodes are arranged on the surface of the main drum for contacting the conductive layer, and a first voltage is applied to the conductive layer by a DC power supply during magnetron sputtering. The first voltage is 1 V. The relevant materials and parameters involved in magnetron sputtering are as follows: Copper is used as the target. The working gas for magnetron sputtering is Ar, the flow rate is 90 SCCM, the sputtering power is 15 kW, and the tape running speed of the device is 10 m / min.

[0037] (2)Hydro-plating to form the thickened copper layer

[0038] The thickened copper layer is fabricated on the surface of the seed copper layer by means of electroplating with water, specifically including the following operations: electroless copper plating is carried out on the surface of the seed copper layer by using a bilateral sandwich roll type horizontal continuous coating equipment. During the electroless copper plating process, a second voltage is continuously applied to the conductive layer, and the second voltage is 5V. After the electroless copper plating is completed, the plating solution on the film surface is washed with deionized water and then heated and dried, and the heating temperature is 90°C. Thus, thickened copper layers with a thickness of 1μm are formed on the upper and lower surfaces of the seed copper layer respectively, and the copper crystal grain size of the formed thickened copper layer is 113nm, and the finished product of the functional current collector is obtained accordingly. In the electroless copper plating process involved in this step: the electroplating bath of the bilateral sandwich roll type horizontal continuous coating equipment used is 10L, the pH of the electroplating solution used is 12, the plating solution temperature is 35°C, the electroplating tape running speed is 3m / min, and the deposition voltage is controlled within 10V.

[0039] Example 2

[0040] In this example, a PET film with a thickness of 4.5μm is used as the polymer base layer for preparing the functional current collector, and PZT with an average particle size of 50nm is selected as the piezoelectric material used in this example, and the functional current collector is prepared with reference to Example 1. The difference from Example 1 is that: the first voltage set during the sputtering to form the seed copper layer in this example is 1V, and the second voltage set during the electroplating with water to form the thickened copper layer is 8V. Except for the above differences, other raw materials required for preparing the functional current collector in this example and the corresponding operation steps are strictly the same as those in Example 1.

[0041] Based on the above operation differences from Example 1, in the finished product of the functional current collector obtained in this example: the thickness of the seed copper layer is 100nm, and the copper crystal grain size of the formed seed copper layer is 80nm; the thickened copper layer is formed with a thickness of 1μm on both the upper and lower surfaces, and the copper crystal grain size of the formed thickened copper layer is 105nm.

[0042] Example 3

[0043] In this example, a PET film with a thickness of 4.5μm is used as the polymer base layer for preparing the functional current collector, and PZT with an average particle size of 50nm is selected as the piezoelectric material used in this example, and the functional current collector is prepared with reference to Example 1. The difference from Example 1 is that: the first voltage set during the sputtering to form the seed copper layer in this example is 2V, and the second voltage set during the electroplating with water to form the thickened copper layer is 7V. Except for the above differences, other raw materials required for preparing the functional current collector in this example and the corresponding operation steps are strictly the same as those in Example 1.

[0044] Based on the above-mentioned operational differences from Example 1, in the functional current collector finished product obtained in this example: the thickness of the seed copper layer is 100 nm, and the copper grain size constituting the seed copper layer is 65 nm; the thickened copper layer is formed with a thickness of 1 μm on each of the upper and lower surfaces, and the copper grain size constituting the thickened copper layer is 102 nm.

[0045] Example 4

[0046] In this example, a PET film with a thickness of 4.5 μm is used as the polymer base layer for preparing the functional current collector, and PZT with an average particle size of 50 nm is selected as the piezoelectric material used in this example, and the functional current collector is prepared with reference to Example 1. The difference from Example 1 is that: in this example, the first voltage set during the sputtering forming of the seed copper layer is 5 V, and the second voltage set during the electroplating forming of the thickened copper layer is 9 V. Except for the above differences, other raw materials required for preparing the functional current collector in this example and the corresponding operation steps are strictly the same as those in Example 1.

[0047] Based on the above-mentioned operational differences from Example 1, in the functional current collector finished product obtained in this example: the thickness of the seed copper layer is 100 nm, and the copper grain size constituting the seed copper layer is 90 nm; the thickened copper layer is formed with a thickness of 1 μm on each of the upper and lower surfaces, and the copper grain size constituting the thickened copper layer is 98 nm.

[0048] Example 5

[0049] In this example, a PET film with a thickness of 4.5 μm is used as the polymer base layer for preparing the functional current collector, and PZT with an average particle size of 50 nm is selected as the piezoelectric material used in this example, and the functional current collector is prepared with reference to Example 1. The difference from Example 1 is that: in this example, the first voltage set during the sputtering forming of the seed copper layer is 3 V, and the second voltage set during the electroplating forming of the thickened copper layer is 9 V. Except for the above differences, other raw materials required for preparing the functional current collector in this example and the corresponding operation steps are strictly the same as those in Example 1.

[0050] Based on the above-mentioned operational differences from Example 1, in the functional current collector finished product obtained in this example: the thickness of the seed copper layer is 100 nm, and the copper grain size constituting the seed copper layer is 45 nm; the thickened copper layer is formed with a thickness of 1 μm on each of the upper and lower surfaces, and the copper grain size constituting the thickened copper layer is 40 nm.

[0051] Example 6

[0052] In this embodiment, a PET film with a thickness of 4.5 μm is used as the polymer substrate for preparing the functional current collector, PZT with an average particle size of 50 nm is selected as the piezoelectric material used in this embodiment, and the functional current collector is prepared with reference to Embodiment 1. The difference from Embodiment 1 is that: in this embodiment, the first voltage set during the sputtering forming of the seed copper layer is 2 V, and the second voltage set during the electroplating with water to form the thickened copper layer is 2 V. Except for the above differences, other raw materials required for preparing the functional current collector in this embodiment and the corresponding operation steps are strictly consistent with those in Embodiment 1.

[0053] Based on the above operation differences from Embodiment 1, in the finished product of the functional current collector obtained in this embodiment: the thickness of the seed copper layer is 100 nm, and the copper grain size forming the seed copper layer is 70 nm; the thickness of the thickened copper layer is 1 μm formed on each of the upper and lower surfaces, and the copper grain size forming the thickened copper layer is 125 nm.

[0054] Embodiment 7

[0055] In this embodiment, a PET film with a thickness of 4.5 μm is used as the polymer substrate for preparing the functional current collector, PZT with an average particle size of 50 nm is selected as the piezoelectric material used in this embodiment, and the functional current collector is prepared with reference to Embodiment 1. The difference from Embodiment 1 is that: in this embodiment, the first voltage set during the sputtering forming of the seed copper layer is 7 V, and the second voltage set during the electroplating with water to form the thickened copper layer is 2 V. Except for the above differences, other raw materials required for preparing the functional current collector in this embodiment and the corresponding operation steps are strictly consistent with those in Embodiment 1.

[0056] Based on the above operation differences from Embodiment 1, in the finished product of the functional current collector obtained in this embodiment: the thickness of the seed copper layer is 100 nm, and the copper grain size forming the seed copper layer is 92 nm; the thickened copper layer is 1 μm formed on each of the upper and lower surfaces, and the copper grain size forming the thickened copper layer is 139 nm.

[0057] Embodiment 8

[0058] In this embodiment, a PET film with a thickness of 4.5 μm is used as the polymer substrate for preparing the functional current collector, PZT with an average particle size of 50 nm is selected as the piezoelectric material used in this embodiment, and the functional current collector is prepared with reference to Embodiment 1. The difference from Embodiment 1 is that: in this embodiment, the first voltage set during the sputtering forming of the seed copper layer is 1 V, and the second voltage set during the electroplating with water to form the thickened copper layer is 7 V. Except for the above differences, other raw materials required for preparing the functional current collector in this embodiment and the corresponding operation steps are strictly consistent with those in Embodiment 1.

[0059] Based on the above-mentioned operational differences from Example 1, in the functional current collector product obtained in this example: the thickness of the seed copper layer is 100 nm, and the copper grain size constituting the seed copper layer is 80 nm; the thickened copper layer is formed on each of the upper and lower surfaces with a thickness of 1 μm, and the copper grain size constituting the thickened copper layer is 112 nm.

[0060] Example 9

[0061] In this example, a PET film with a thickness of 4.5 μm is used as the polymer base layer for preparing the functional current collector, and PZT with an average particle size of 50 nm is selected as the piezoelectric material used in this example, and the functional current collector is prepared with reference to Example 1. The difference from Example 1 is that: in this example, the first voltage set during the sputtering forming of the seed copper layer is 1 V, and the second voltage set during the electroplating forming of the thickened copper layer is 0 V. Except for the above differences, other raw materials required for preparing the functional current collector in this example and the corresponding operation steps are strictly the same as those in Example 1.

[0062] Based on the above-mentioned operational differences from Example 1, in the functional current collector product obtained in this example: the thickness of the seed copper layer is 100 nm, and the copper grain size constituting the seed copper layer is 80 nm; the thickened copper layer is formed on each of the upper and lower surfaces with a thickness of 1 μm, and the copper grain size constituting the thickened copper layer is 135 nm.

[0063] Example 10

[0064] In this example, a PET film with a thickness of 4.5 μm is used as the polymer base layer for preparing the functional current collector, and PZT with an average particle size of 50 nm is selected as the piezoelectric material used in this example, and the functional current collector is prepared with reference to Example 1. The difference from Example 1 is that: in this example, the first voltage set during the sputtering forming of the seed copper layer is 0 V, and the second voltage set during the electroplating forming of the thickened copper layer is 4 V. Except for the above differences, other raw materials required for preparing the functional current collector in this example and the corresponding operation steps are strictly the same as those in Example 1.

[0065] Based on the above-mentioned operational differences from Example 1, in the functional current collector product obtained in this example: the thickness of the seed copper layer is 100 nm, and the copper grain size constituting the seed copper layer is 95 nm; the thickened copper layer is formed on each of the upper and lower surfaces with a thickness of 1 μm, and the copper grain size constituting the thickened copper layer is 143 nm.

[0066] Example 11

[0067] In this embodiment, a PET film with a thickness of 4.5 μm is used as the polymer substrate for preparing the functional current collector, and the functional current collector is prepared with reference to Example 5. The difference from Example 5 is that: in this embodiment, PMN-PT with an average particle size of 50 nm is used to replace PZT used in Example 5 in equal mass as the piezoelectric material to participate in the preparation of the functional current collector. Except for the above differences, other raw materials required for preparing the functional current collector in this embodiment and the corresponding operation steps are strictly the same as those in Example 1.

[0068] Based on the above operation differences from Example 5, in the finished product of the functional current collector prepared in this embodiment: the thickness of the seed copper layer is 100 nm, and the copper grain size forming the seed copper layer is 55 nm; the thickened copper layer is formed with a thickness of 1 μm on each of the upper and lower surfaces, and the copper grain size forming the thickened copper layer is 60 nm.

[0069] Example 12

[0070] In this embodiment, a PET film with a thickness of 4.5 μm is used as the polymer substrate for preparing the functional current collector, and the functional current collector is prepared with reference to Example 5. The difference from Example 5 is that: in this embodiment, lithium niobate with an average particle size of 50 nm is used to replace PZT used in Example 5 in equal mass as the piezoelectric material to participate in the preparation of the functional current collector. Except for the above differences, other raw materials required for preparing the functional current collector in this embodiment and the corresponding operation steps are strictly the same as those in Example 1.

[0071] Based on the above operation differences from Example 5, in the finished product of the functional current collector prepared in this embodiment: the thickness of the seed copper layer is 100 nm, and the copper grain size forming the seed copper layer is 57 nm; the thickened copper layer is formed with a thickness of 1 μm on each of the upper and lower surfaces, and the copper grain size forming the thickened copper layer is 62 nm.

[0072] Comparative Example 1

[0073] In this comparative example, a PET film with a thickness of 4.5 μm is used as the polymer substrate for preparing the functional current collector, PZT with an average particle size of 50 nm is selected as the piezoelectric material used in this comparative example, and the functional current collector is prepared according to the following steps.

[0074] 1. Plasma cleaning

[0075] It is strictly the same as the plasma cleaning operation involved in Example 1.

[0076] 2. Metal layer forming process

[0077] (1) Sputtering to form the seed copper layer

[0078] A seed copper layer is fabricated on the surface of a polymer substrate by magnetron sputtering, which specifically includes the following operations: Using a roll-to-roll magnetron sputtering equipment to perform magnetron sputtering on the surface of the polymer substrate, sputtering a seed copper layer with a thickness of 100 nm on the surface of the polymer substrate. The copper grain size constituting the seed copper layer is 95 nm, thereby obtaining a semi-finished product of the functional current collector. In this step, the relevant materials and parameters involved in magnetron sputtering are specifically as follows: using copper as the target, the working gas for magnetron sputtering is Ar, the flow rate is 90 SCCM, the sputtering power is 15 kW, and the equipment tape running speed is 10 m / min.

[0079] (2)Hydroelectroplating to form a thickened copper layer

[0080] A thickened copper layer is fabricated on the surface of the seed copper layer by hydroelectroplating, which specifically includes the following operations: Using a double-sided clamping roll type horizontal continuous coating equipment to perform electroless copper plating on the surface of the seed copper layer. After the electroless copper plating is completed, use deionized water to wash the plating solution on the film surface, and then heat and dry it. The heating temperature is 90 °C. Thus, thickened copper layers with a thickness of 1 μm are formed on both the upper and lower surfaces of the seed copper layer. The copper grain size constituting the thickened copper layer is 150 nm, thereby obtaining a finished product of the functional current collector. In the electroless copper plating process involved in this step: the double-sided clamping roll type horizontal continuous coating equipment, electroplating solution, plating solution temperature, electroplating tape running speed, and deposition voltage used are all the same as those in Example 1.

[0081] Based on the above steps, the functional current collector prepared in this comparative example does not have the piezoelectric material layer and conductive layer provided in the functional current collector prepared in other embodiments.

[0082] Comparative Example 2

[0083] This comparative example uses a PET film with a thickness of 4.5 μm as the polymer base for preparing the functional current collector, and prepares the functional current collector according to the following steps.

[0084] 1. Plasma cleaning

[0085] It is strictly consistent with the plasma cleaning operation involved in Example 1.

[0086] 2. Sputtering to form a conductive layer

[0087] A conductive layer is fabricated on the surface of a polymer substrate by magnetron sputtering, which specifically includes the following operations: A roll-to-roll magnetron sputtering equipment is used to perform magnetron sputtering on the polymer substrate, and a conductive layer with a thickness of 10 nm is sputtered on the surface of the polymer substrate. In this step, the relevant materials and parameters involved in magnetron sputtering are as follows: Silver is used as the target material, and pre-sputtering is carried out for 10 min before sputtering to remove impurities on the surface of the target material. The working gas for magnetron sputtering is Ar, with a flow rate of 90 SCC, a sputtering power of 7 kW, a tape running speed of the equipment of 5 m / min, and a main drum cooling temperature of -15°C.

[0088] 3. Metal layer forming process

[0089] (1) Sputtering to form a seed copper layer

[0090] A seed copper layer is fabricated on the surface of the conductive layer by magnetron sputtering, which specifically includes the following operations: A roll-to-roll magnetron sputtering equipment is used to perform magnetron sputtering on the surface of the conductive layer, and a seed copper layer with a thickness of 100 nm is sputtered on the surface of the conductive layer. The copper grain size constituting the seed copper layer is 95 nm, and thus a semi-finished product of the functional current collector is obtained. In this step: Parallel plate electrodes are arranged on the surface of the main drum for contacting the conductive layer, and a first voltage is applied to the conductive layer by a DC power supply during magnetron sputtering. The first voltage is 1 V; The relevant materials and parameters involved in magnetron sputtering are as follows: Copper is used as the target material, the working gas for magnetron sputtering is Ar, with a flow rate of 90 SCC, a sputtering power of 15 kW, and a tape running speed of the equipment of 10 m / min.

[0091] (2) Electroplating with water to form a thickened copper layer

[0092] A thickened copper layer is fabricated on the surface of the seed copper layer by electroplating with water, which specifically includes the following operations: A double-sided sandwich roll-type horizontal continuous coating equipment is used to perform electroless copper plating on the surface of the seed copper layer. During the electroless copper plating process, a second voltage is continuously applied to the conductive layer. The second voltage is 2 V. After the electroless copper plating is completed, the membrane surface electroplating solution is washed with deionized water and then heated and dried. The heating temperature is 90°C. Thus, thickened copper layers with a thickness of 1 μm are formed on both the upper and lower surfaces of the seed copper layer. The copper grain size constituting the thickened copper layer is 148 nm, and thus the finished product of the functional current collector is obtained. In the electroless copper plating process involved in this step: The double-sided sandwich roll-type horizontal continuous coating equipment, electroplating solution, plating solution temperature, electroplating tape running speed, and deposition voltage used are all consistent with those in Example 1.

[0093] Based on the above steps, the functional current collector prepared in this comparative example does not have the piezoelectric material layer provided in the functional current collectors prepared in other embodiments.

[0094] Comparative Example 3

[0095] In this comparative example, a PET film with a thickness of 4.5 μm was used as the polymer substrate for preparing the functional current collector, PZT with an average particle size of 50 nm was selected as the piezoelectric material used in this comparative example, and the functional current collector was prepared according to the following steps.

[0096] 1. Plasma cleaning

[0097] It was strictly consistent with the plasma cleaning operation involved in Example 1.

[0098] 2. Piezoelectric material layer forming process

[0099] It was strictly consistent with the piezoelectric material layer forming operation involved in Example 1.

[0100] 3. Sputtering to form a conductive layer

[0101] It was strictly consistent with the conductive layer forming operation involved in Example 1.

[0102] 4. Metal layer forming process

[0103] (1) Sputtering to form a seed copper layer

[0104] A seed copper layer was fabricated on the surface of the polymer substrate by means of magnetron sputtering, which specifically included the following operations: using a roll-to-roll magnetron sputtering device to perform magnetron sputtering on the surface of the conductive layer, sputtering a seed copper layer with a thickness of 100 nm on the surface of the conductive layer, and the copper grain size constituting the seed copper layer was 95 nm, thereby obtaining a semi-finished product of the functional current collector. In this step, the relevant materials and parameters involved in magnetron sputtering were specifically as follows: using copper as the target, the working gas for magnetron sputtering was Ar, the flow rate was 90 SCCM, the sputtering power was 15 kW, and the tape running speed of the device was 10 m / min.

[0105] (2) Electroplating with water to form a thickened copper layer

[0106] A thickened copper layer was fabricated on the surface of the seed copper layer by means of electroplating with water, which specifically included the following operations: using a double-sided sandwich roll-type horizontal continuous coating device to perform electroless copper plating on the surface of the seed copper layer. After the electroless copper plating was completed, the film surface plating solution was washed with deionized water and then heated and dried, and the heating temperature was 90 °C. Thus, thickened copper layers with a thickness of 1 μm were formed on each of the upper and lower surfaces of the seed copper layer, and the copper grain size constituting the thickened copper layer was 145 nm, thereby obtaining the finished product of the functional current collector. In the electroless copper plating process involved in this step: the double-sided sandwich roll-type horizontal continuous coating device, the electroplating solution, the plating solution temperature, the electroplating tape running speed, and the deposition voltage were all consistent with Example 1.

[0107] Test example

[0108] 1. Test object

[0109] During the preparation of the functional current collectors in Examples 1-12 and Comparative Examples 1-3, after the formation of the seed copper layer, samples were taken from the semi-finished functional current collectors, and after the completion of the preparation of the functional current collectors, samples were taken from the finished functional current collectors. The samples obtained in the above process were used as the test objects in this test example.

[0110] 2. Test items and corresponding test methods

[0111] (1) Tensile strength test

[0112] Tensile strength test: The finished product prepared by the present invention was used as a sample, and an MTS Criterion42 type tensile testing machine was used to measure the tensile strength of the film. Parameter settings: The clamp spacing on the tensile testing machine was 100 mm, the test speed was (250±25) mm / min, and the tensile strength was obtained by testing.

[0113] (2) Elongation test

[0114] Elongation at break test: The finished product prepared by the present invention was used as a sample, and an MTS Criterion42 type tensile testing machine was used to measure the elongation at break of the film. Parameter settings: The clamp spacing on the tensile testing machine was 100 mm, the test speed was (250±25) mm / min, and the elongation at break was obtained by testing.

[0115] (3) Residual stress test

[0116] The residual stress of the metal layer on the surface of the sample was measured by Bruker D8 type X-ray diffraction method (XRD). XRD test conditions: 40 kV, 40 mA, scanning speed 0.08 s / Step, step size set to 0.01°, grazing incidence angle set to 3°.

[0117] 3. Test results

[0118] The voltage setting conditions of the test objects in the preparation process and the characteristic parameters of the finished product structure of this test example are shown in Table 1, and the test results of this test example are shown in Table 2. In the process of preparing the functional current collector in Examples 1 to 12, the step of setting a piezoelectric material layer on the surface of the polymer substrate is included. After the preparation of the piezoelectric material layer is completed, the metal layer is then prepared. Based on the presence of the piezoelectric material layer, in the metal layer forming process, applying an electric field to the piezoelectric material layer can trigger the piezoelectric effect, so that the piezoelectric material in the piezoelectric material layer is deformed under the action of the external electric field. The deformation of the piezoelectric material can be transmitted to the gradually thickening metal layer, thereby affecting the nucleation and growth behavior of the metal grains constituting the metal layer during the metal layer forming process, achieving the refinement of the metal grains, and then adjusting the residual stress distribution of the metal layer during the metal layer forming process, fully releasing the residual stress of the metal layer, reducing stress concentration, and improving the tensile strength and elongation of the functional current collector. In addition, the refinement of the metal grains improves the density of the metal layer, improves the corrosion resistance of the metal layer, and improves the interlayer bonding strength of the functional current collector. Therefore, the functional current collectors prepared in Examples 1 to 12 were able to measure relatively low residual stress of the seed copper layer and the residual stress of the thickened copper layer, good tensile strength and good elongation in this test. Compared with the above embodiments, Comparative Examples 1 and 2 omitted the preparation of the piezoelectric material layer in the process of making the functional current collector. Among them, Comparative Example 1 does not involve the operation of applying voltage to the processing object in the metal layer forming process, while Comparative Example 2 applies voltage to the processing object in the metal layer forming process. However, without the piezoelectric material layer, it is impossible to control the particle size of the metal layer grains through the piezoelectric effect in the metal layer forming process. Although Comparative Example 3 also includes the step of setting a piezoelectric material layer on the surface of the polymer substrate in the process of making the functional current collector, no voltage is applied to the processing object in the metal layer forming process, thereby failing to exert the piezoelectric effect of the piezoelectric material layer, and thus it is difficult to effectively control the particle size of the metal layer grains. Combined with the test results of this test example, it can be seen that compared with the functional current collectors provided in Examples 1 to 12, the functional current collectors prepared in Comparative Examples 1 to 3 have the problems of larger particle size of the metal layer grains, larger residual stress of the metal layer, lower tensile strength and lower elongation.

[0119] Example 3 and Example 6 were compared. The first voltage applied to the processing object during the preparation of the seed copper layer in both cases was 2V. In Example 3, the second voltage applied to the processing object during the preparation of the thickened copper layer was 7V, which was greater than the first voltage applied during the preparation of the seed copper layer. In Example 6, the second voltage applied to the processing object during the preparation of the thickened copper layer was equal to the first voltage applied during the preparation of the seed copper layer, both being 2V. The test results showed that the tensile strength and elongation rate of the functional current collector measured in Example 3 were higher than those of the functional current collector in Example 6. Further, when Example 3 was compared with Example 7, the first voltage value and the second voltage value applied to the processing object during the preparation of the metal layer were in a swapped relationship. The first voltage applied in Example 3 was equal to the second voltage applied in Example 7, both being 2V, and the second voltage applied in Example 3 was equal to the first voltage applied in Example 7, both being 7V. The test results showed that the tensile strength and elongation rate of the functional current collector measured in Example 3 were higher than those of the functional current collector in Example 7. Based on the above comparison results of Example 3 with Example 6 and Example 7 respectively, it was thus shown that based on the application of piezoelectric materials to the processing of functional current collectors, by applying the first voltage and the second voltage to the processing object during the step-by-step formation of the seed copper layer and the thickened copper layer respectively, with the first voltage being less than the second voltage, it was more conducive to improving the tensile strength and elongation rate of the functional current collector.

[0120] Example 4 and Example 5 were compared. During the preparation of the functional current collector in both cases, the first voltage was applied to the processing object during the step-by-step formation of the seed copper layer, and the second voltage less than the first voltage was applied to the processing object during the thickening of the copper layer, and the applied second voltages were equal. The difference between the above two examples was the different first voltage values applied to the processing object. Based on this difference, the performance test results of the functional current collectors provided by the two were different. The test results showed that the tensile strength and elongation rate of the functional current collector measured in Example 5 were higher than those of the functional current collector in Example 4. Based on the above comparison results and combined with the analysis of other experimental results: when the magnitude of the first voltage was in the range of 0V < first voltage < 4V, with the increase of the first voltage, the grain size of the metal grains constituting the seed copper layer decreased, but the value of the first voltage should not be too high. When the first voltage exceeded 4V and the first voltage was further increased, the grain size of the metal grains in the seed copper layer would instead increase; when the second voltage ≤ 10V and the first voltage was less than the second voltage, with 0V < first voltage < 4V, it was more conducive to improving the tensile strength and elongation rate of the functional current collector. Similarly, when comparing the operations of preparing the functional current collectors in Example 7 and Example 8 and the structures and performances of the obtained functional current collectors, the above conclusion was also consistent.

[0121] Comparing Example 1, Example 2, and Example 8, the first voltage values used for forming the seed copper layer during the preparation of the functional current collector are equal for all three. The difference among them lies in the different second voltage values used for forming the thickened copper layer. Among the functional current collectors provided by the above three examples respectively, the tensile strength and elongation rate measured for the functional current collector of Example 2 are the lowest. This shows that when the second voltage meets the condition of second voltage ≤ 10V, it is not that the larger the value of the second voltage is, the better. Through experiments, it is proved that the selection of the second voltage is related to the first voltage. When the first voltage and the second voltage satisfy that the difference between the second voltage and the first voltage is 4V - 6V, it is beneficial to improve the tensile strength and elongation rate of the functional current collector.

[0122] Table 1. Voltage setting during the preparation of the test object in this test example and the structural characteristics of the finished product

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[0124] Table 2. Statistical situation of the test results in this test example

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[0126] The above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the protection scope of the present invention. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced, but these modifications or replacements are all within the protection scope of the present invention.

Claims

1. A processing method for a functional integrated fluid, characterized in that: The functional integrated fluid includes a polymer substrate, a conductive layer, and a metal layer. The metal layer includes a seed copper layer and a thickened copper layer stacked in a direction away from the polymer substrate. The metal materials constituting the seed copper layer and the thickened copper layer include at least one of metallic copper and copper alloy; The processing method includes a piezoelectric material layer forming process, a conductive layer forming process, and a metal layer forming process; The piezoelectric material layer forming process includes the following operations: fabricating a piezoelectric material layer on the surface of the polymer substrate; In the conductive layer forming process, a conductive layer is fabricated on the surface of the piezoelectric material layer; The metal layer forming process includes the following operations: fabricating the metal layer on the surface of the film obtained after the piezoelectric material layer forming process is completed. During this process, a voltage is applied to the conductive layer, thereby applying an electric field to the piezoelectric material layer; In the metal layer forming process, a first voltage is applied to the conductive layer during the preparation of the seed copper layer, and a second voltage is applied to the conductive layer during the preparation of the thickened copper layer. The first voltage is less than the second voltage, and 0V < the first voltage < 4V, and the second voltage ≤ 10V.

2. The processing method of the functional fluid collector according to claim 1, characterized in that: The difference between the second voltage and the first voltage is 4V - 6V.

3. The processing method of the functional set fluid according to claim 1, characterized in that: The particle size of the piezoelectric material is 30nm - 80nm, and the thickness of the piezoelectric material layer ≤ 500nm.

4. The processing method of the functional set fluid according to claim 3, characterized in that: The piezoelectric material includes at least one of lead zirconate titanate, lead magnesium niobate-titanate, polyvinylidene fluoride, lithium niobate, and lead niobium zinc titanate.

5. A functional integrated fluid obtained by using the processing method for a functional integrated fluid according to any one of claims 1 to 4.

6. A functional integrated fluid obtained by a processing method using the functional integrated fluid described in any one of claims 1 or 2, characterized in that, The functional integrated fluid satisfies at least one of the following a, b, c, and d: a. The thickness of the seed copper layer is 50nm - 100nm; b. The particle size of the material constituting the seed copper layer is 20nm - 100nm; c. The thickness of the thickened copper layer is 800nm - 1200nm; d. The particle size of the material constituting the thickened copper layer is 30nm - 200nm.

7. A secondary battery, characterized in that: The secondary battery includes the functional integrated fluid according to any one of claims 5 or 6.

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