Electrochemical device and electronic apparatus
By setting a high elongation protective layer on the current collector surface of the lithium-ion battery and performing lithium supplementation treatment, the risk of short-circuiting of the lithium-ion battery during mechanical damage is solved, and the safety performance and energy density are improved.
Patent Information
- Application Number
- CN202510376435.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-27
- Publication Date
- 2025-07-08
AI Technical Summary
Existing lithium-ion batteries are prone to puncture the diaphragm when mechanically damaged, resulting in short-circuit contact between the cathode plate and the anode plate, which has the problem of insufficient safety performance.
A protective layer is provided between the first current collector and the first material layer. The protective layer is made of polymer material with high elongation, and lithium is supplemented with the cathode electrode sheet in combination with the first material to reduce the risk of mechanical damage, while optimizing the thickness ratio of the conductive layer and the protective layer to improve safety performance and energy density.
It effectively reduces the risk of damage to the current collector machinery, reduces the heat generated during short circuit, improves the safety performance and energy density of the electrochemical device, and extends the service life.
Smart Images
Figure CN120280451A_ABST
Abstract
Description
Technical Field
[0001] The embodiments of the present application relate to the technical field of batteries, and in particular, to electrochemical devices and electronic devices. Background Art
[0002] With the rapid development of modern technology, the demand for high-performance energy storage devices in fields such as portable electronic devices and electric vehicles is increasing day by day. As an efficient and environmentally friendly energy storage device, lithium-ion batteries have been widely used in many fields due to their high energy density, long cycle life, low self-discharge rate and other advantages. In the continuous development process of lithium-ion batteries, the requirements for the safety performance of batteries are also getting higher and higher. Summary of the Invention
[0003] An object of the embodiments of the present application is to provide an electrochemical device and an electronic device that can improve the safety performance of the electrochemical device.
[0004] In a first aspect, the embodiments of the present application provide an electrochemical device, including an electrode assembly. The electrode assembly includes a cathode electrode sheet, a separator and an anode electrode sheet. The separator is disposed between the cathode electrode sheet and the anode electrode sheet. The anode electrode sheet includes silicon element. The cathode electrode sheet includes a first current collector, a protective layer and a first material layer. Along the thickness direction of the electrode assembly, the protective layer is disposed on the surface of the first current collector, and the first material layer is disposed on the surface of the protective layer away from the first current collector; the first current collector includes a first base material layer, a first conductive layer and a second conductive layer. The first base material layer is disposed between the first conductive layer and the second conductive layer. The first base material layer includes at least one of polyethylene terephthalate, polyimide, polyamide, polyurethane, polyethylene, and polypropylene; the first material layer includes a first material and a second material, and the first material includes lithium element; the thicknesses of the first conductive layer and the second conductive layer are both H microns, the thickness of the protective layer is B microns, and the mass ratio of the first material in the first material layer is C%, and satisfies: 2 / H ≤ B ≤ 4.
[0005] In the embodiments of the present application, by disposing a protective layer between the first current collector and the first material layer, the protective layer can protect at least one surface of the first current collector, thereby reducing the risk of mechanical damage to the first current collector, and further reducing the risk of burrs or protrusions being generated at the damaged part of the first current collector and piercing the separator, resulting in short circuit due to contact between the cathode electrode and the anode electrode. At the same time, the first current collector includes a first substrate layer, and the first substrate layer includes at least one of polyethylene terephthalate, polyimide, polyamide, polyurethane, polyethylene, and polypropylene. The first substrate layer has a high elongation rate, so that the cathode electrode can extend when subjected to pressure. The first substrate layer can rapidly extend under mechanical stress, causing a significant increase in the sheet resistance of the first current collector, thereby increasing the resistance during short circuit, reducing the heat generation during short circuit, and further improving the safety performance of the electrochemical device; on this basis, the anode electrode includes silicon element, providing a high theoretical specific capacity for the electrochemical device, thereby increasing the capacity of the electrochemical device. At the same time, the first material in the present application is used to supplement lithium to the cathode electrode, thereby reducing the loss of energy density caused by the low initial efficiency of the silicon negative electrode, improving the safety performance of the electrochemical device, and increasing the energy density of the electrochemical device. Furthermore, by setting 2 / H ≤ B ≤ 4, the safety performance of the electrochemical device can be improved, and the energy density and cycle life of the electrochemical device can be taken into account.
[0006] In some embodiments, the first material includes Li5-xFeO 4-y , Li6-xCoO 4-y , Li2-zMnO2 or Li 1.2- r Ni 0.13 Fe 0.13 Mn 0.54 O2, where 4 ≤ x ≤ 5, 2 ≤ y ≤ 4, 1.6 ≤ z ≤ 2, 0.2 ≤ r ≤ 1.2, the mass ratio of the first material in the first material layer is C%, and it satisfies: B ≤ 2*C, which can further increase the energy density of the electrochemical device.
[0007] In some embodiments, 1 ≤ H ≤ 3. Preferably, 1.5 ≤ H ≤ 2. If the thickness of the first conductive layer or the second conductive layer is too small, the sheet resistance of the cathode electrode 1 is too large, the internal resistance of the electrochemical device is too large, and the electrical performance of the electrochemical device is poor; if the thickness of the first conductive layer or the second conductive layer is too thick, on the one hand, the energy density of the electrochemical device will be reduced, and on the other hand, the too thick conductive layer is prone to form large-sized burrs when pierced or squeezed, and is prone to pierce the separator and cause short circuit. Therefore, setting 1 ≤ H ≤ 3 can reduce the internal resistance of the electrochemical device, improve the kinetic performance of the electrochemical device, and take into account the energy density of the electrochemical device and improve the safety performance of the electrochemical device.
[0008] In some embodiments, 1 ≤ B ≤ 4. Preferably, 1.5 ≤ B ≤ 2.5. If the thickness of the protective layer is too small, its protective effect on the first current collector is insufficient, and it is easily pierced by the main cathode material during cold pressing, resulting in lithium deposition and safety risks. In addition, if the thickness of the protective layer is too small, the sheet resistance is relatively large, the conductivity is poor, the charging speed is deteriorated, the charging temperature rise is deteriorated, which is not conducive to the performance of the electrochemical device; if the thickness of the protective layer is too large, the energy density of the electrochemical device is affected. Therefore, setting 1.5 ≤ B ≤ 2.5 can improve the protective effect of the protective layer on the first current collector, reduce the risk of mechanical damage to the first current collector, and take into account the energy density of the electrochemical device.
[0009] In some embodiments, 0.5% ≤ C% ≤ 4%. Preferably, 1% ≤ C% ≤ 3%. If the content of the first material is too low, the lithium supplement amount of the cathode electrode sheet 1 will be low, resulting in a low energy density of the electrochemical device; the side reaction in the first material is more than that in the second material. If the content of the first material is too high, it is easy to cause a large increase in side reactions, resulting in a poor cycle charge and discharge ability of the electrochemical device, and the electrical performance of the electrochemical device 100 deteriorates at high temperatures. Therefore, setting 0.5% ≤ C% ≤ 4% can improve the cycle charge and discharge ability of the electrochemical device, improve the high-temperature performance, and take into account the energy density of the electrochemical device.
[0010] In some embodiments, along the thickness direction of the electrode assembly, the protective layer is disposed on opposite surfaces of the first current collector, and the first material layer is disposed on the surface of the protective layer away from the first current collector.
[0011] In this embodiment, by disposing the protective layer on both surfaces of the first current collector 11, the two sides of the first current collector 11 can be protected, which is beneficial to further reducing the risk of mechanical damage to the first current collector, and thus reducing the risk of the first current collector generating a bulge at the damaged part and piercing the separator to cause a short circuit.
[0012] In some embodiments, the second material includes at least one of lithium cobaltate, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminate, lithium iron phosphate, or lithium manganate.
[0013] In some embodiments, the protective layer includes an inorganic material, a conductive agent, and an adhesive. The conductive agent can enhance the conductive ability of the first material layer, and the adhesive is used to bond the particles in the inorganic material and the conductive agent, and to bond the first material layer to the first conductive layer or the second conductive layer.
[0014] In some embodiments, the adhesive includes at least one of metal polyacrylate, polyvinylidene fluoride, and styrene-butadiene rubber.
[0015] In some embodiments, the inorganic material includes at least one of aluminum oxide, boehmite, titanium dioxide, barium titanate, and barium sulfate.
[0016] In some embodiments, the anode current collector includes a second current collector and a second material layer. The second material layer is disposed on at least one surface of the second current collector. The second material layer includes silicon element, and the mass ratio of the silicon element in the second material layer is D%, and it satisfies: 1% ≤ D% ≤ 50%. The increase in the content of silicon element can improve the energy density of the electrochemical device. However, silicon is prone to expansion during the insertion or extraction of lithium ions, resulting in an increase in the volume of the electrochemical device. Therefore, by setting 1% ≤ D% ≤ 50%, it is possible to balance the improvement of the energy density of the electrochemical device and the reduction of volume expansion.
[0017] In some embodiments, the charging specific capacity of the first material is E, and the charging specific capacity of the second material is F, and it satisfies: F < E. With such a setting, it is beneficial to improve the energy density of the electrochemical device.
[0018] In some embodiments, the charging specific capacity E of the first material satisfies: 240 mAh / g ≤ E ≤ 950 mAh / g. With such a setting, it is beneficial to improve the energy density of the electrochemical device.
[0019] In a second aspect, the present application provides an electronic device including the above-mentioned electrochemical device.
[0020] The beneficial effects of the embodiments of the present application are as follows: By disposing the protective layer between the first current collector and the first material layer, the protective layer can protect at least one surface of the first current collector, thereby reducing the risk of mechanical damage to the first current collector, and further reducing the risk that the first current collector generates burrs or protrusions at the damaged part and pierces the separator, resulting in short circuit due to the contact between the cathode current collector and the anode current collector. At the same time, the first current collector includes a first base material layer including at least one of polyethylene terephthalate, polyimide, polyamide, polyurethane, polyethylene, and polypropylene. The first base material layer has a high elongation rate, so that the cathode current collector can extend when subjected to pressure. The first base material layer can quickly extend under mechanical stress, resulting in a significant increase in the sheet resistance of the first current collector, thereby increasing the resistance during short circuit and reducing the heat generation during short circuit, and further improving the safety performance of the electrochemical device; On this basis, the anode current collector includes silicon element, which provides a high theoretical specific capacity for the electrochemical device, thereby increasing the capacity of the electrochemical device. At the same time, the first material in the present application is used to supplement lithium to the cathode current collector, thereby reducing the loss of energy density caused by the low first efficiency of the silicon negative electrode, while improving the safety performance of the electrochemical device and increasing the energy density of the electrochemical device. Furthermore, by setting 2 / H ≤ B ≤ 4 and B ≤ 2*C, the safety performance and energy density of the electrochemical device can be further improved. Description of the Drawings
[0021] One or more embodiments are exemplarily illustrated by pictures in the corresponding drawings. These exemplary illustrations are not configured to limit the embodiments, and elements with the same reference numerals in the drawings represent similar elements.
[0022] Figure 1 It is a schematic structural diagram of the electrode assembly provided in the embodiment of the present application;
[0023] Figure 2 It is a schematic structural diagram of the electrochemical device provided in the embodiment of the present application;
[0024] Figure 3 It is a schematic partial structural diagram of the electrode assembly provided in the embodiment of the present application.
[0025] Explanation of the reference numerals in the drawings
[0026] 100, electrochemical device;
[0027] 10, electrode assembly;
[0028] 1, cathode electrode sheet; 11, first current collector; 111, first base material layer; 112, first conductive layer; 113, second conductive layer; 12, protective layer; 13, first material layer;
[0029] 2, separator;
[0030] 3, anode electrode sheet; 31, second current collector; 311, second base material layer; 312, third conductive layer; 313, fourth conductive layer; 32, second material layer. Detailed implementation manners
[0031] To make the objectives, technical solutions, and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and detailedly described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all of the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application, and are not used to limit the present application.
[0032] It should be noted that when an element is expressed as "connected" to another element, it can be directly connected to the other element, or there can be one or more intermediate elements therebetween. In addition, the technical features involved in the various embodiments of the present application described below can be combined with each other as long as they do not conflict with each other.
[0033] Silicon materials have a relatively high theoretical specific capacity. When applied to anode electrode sheets, the theoretical specific capacity of silicon materials is usually dozens of times that of graphite negative electrode materials. Therefore, electrochemical devices containing silicon materials applied to anode electrode sheets are becoming increasingly popular in the market.
[0034] However, silicon materials will undergo significant expansion during the charge and discharge process, resulting in an increase in the volume of the electrochemical device, and further leading to a decrease in energy density. Additionally, in related technologies, in an electrochemical device with a silicon system, the cathode electrode typically includes a cathode current collector and a cathode active material layer. The cathode current collector is usually aluminum foil, and the cathode active material layer is disposed on at least one surface of the aluminum foil. However, when the electrochemical device is mechanically damaged, the aluminum foil is easily punctured, resulting in a short circuit with the anode electrode, and the safety performance of the electrochemical device is not high.
[0035] To solve at least some of the above problems, in a first aspect, the present application provides an electrochemical device. By providing a protective layer between the first current collector and the first material layer, the risk of mechanical damage (such as being punctured) to the cathode electrode is reduced, and further the risk of contact short circuit between the cathode electrode and the anode electrode due to mechanical damage is reduced.
[0036] The following details the specific solutions of the present application.
[0037] Please refer to Figure 1 and Figure 2 , the electrochemical device 100 includes an electrode assembly 10. The electrode assembly 10 includes an anode electrode 3, a separator 2, and a cathode electrode 1. The separator 2 is disposed between the anode electrode 3 and the cathode electrode 1. Among them, the anode electrode 3 includes silicon elements.
[0038] In some embodiments, the electrochemical device 100 includes a housing 4. The above-mentioned electrode assembly 10 is housed in the housing 4 so that the housing 4 can protect the electrode assembly 10.
[0039] In some embodiments, the anode electrode 3 includes a second current collector 31 and a second material layer 32. The second material layer 32 is disposed on the surface of the second current collector 31. Among them, the second material layer 32 includes silicon elements.
[0040] It should be noted that the second material layer 32 includes silicon elements or the anode electrode 3 includes silicon elements. Here, "includes" means that the second material layer 32 includes silicon-containing materials, such as pure silicon, silicon oxide, silicon carbide, etc. The silicon-containing materials serve as the main carriers for lithium ions to embed or escape, rather than existing in the second material layer 32 or the anode electrode 3 in the form of impurities.
[0041] In some embodiments, the second current collector 31 may be copper foil.
[0042] It is understandable that the second current collector 31 can also be a composite current collector, that is, the second current collector 31 includes a second substrate layer 311, a third conductive layer 312, and a fourth conductive layer 313. The third conductive layer 312 and the fourth conductive layer 313 are respectively disposed on both sides of the second substrate layer 311. The second material layer 32 as described above can be disposed on the surface of the third conductive layer 312 facing away from the second substrate layer 311 and the surface of the fourth conductive layer 313 facing away from the second substrate layer 311.
[0043] In some embodiments, the mass percentage of silicon element in the second material layer 32 is D%, and it satisfies: 1% ≤ D% ≤ 50%. In some embodiments, the value of D can be 1, 3, 5, 8, 10, 13, 15, 18, 20, 23, 25, 28, 30, 33, 35, 38, 40, 43, 45, 48, 50, or a range composed of any two of these values, or a value within the range composed of any two of these values. The increase in the content of silicon element can improve the energy density of the electrochemical device 100. However, silicon is prone to expansion during the insertion or extraction of lithium ions, resulting in an increase in the volume of the electrochemical device 100. Therefore, by setting 1% ≤ D% ≤ 50%, the improvement of the energy density of the electrochemical device 100 and the reduction of volume expansion can be taken into account.
[0044] The electrochemical device 100 can be arranged in a wound form, that is, after the separator 2 is disposed between the anode electrode sheet 3 and the cathode electrode sheet 1, the anode electrode sheet 3, the separator 2, and the cathode electrode sheet 1 are wound and formed.
[0045] The electrochemical device 100 can also be arranged in a stacked form, that is, the anode electrode sheet 3, the separator 2, and the cathode electrode sheet 1 are alternately stacked, and the separator 2 is disposed between the anode electrode sheet 3 and the cathode electrode sheet 1. The separator 2 is used to electrically isolate the first anode electrode sheet 3 and the cathode electrode sheet 1, reducing the risk of short circuit of the electrochemical device 100. Among them, the stacking direction of the anode electrode sheet 3, the separator 2, and the cathode electrode sheet 1 is the thickness direction of the electrode assembly 10.
[0046] In some embodiments, the number of the anode electrode sheet 3, the separator 2, and the cathode electrode sheet 1 can be multiple. Multiple anode electrode sheets 3, multiple separators 2, and multiple cathode electrode sheets 1 are alternately stacked in sequence, and a separator 2 is disposed between an anode electrode sheet 3 and a cathode electrode sheet 1.
[0047] This application will be described by taking the stacked electrochemical device 100 as an example.
[0048] Please refer to Figure 1, the cathode electrode sheet 1 includes a first current collector 11, a protective layer 12, and a first material layer 13. Along the thickness direction of the electrode assembly 10, the protective layer 12 is disposed on the surface of the first current collector 11, and the first material layer 13 is disposed on the surface of the protective layer 12 away from the first current collector 11. The first current collector 11 includes a first conductive layer 112, a first base material layer 111, and a second conductive layer 113. The first base material layer 111 is disposed between the first conductive layer 112 and the second conductive layer 113, that is, the first conductive layer 112 and the second conductive layer 113 are respectively disposed on two opposite surfaces of the first base material layer 111. The first material layer 13 is disposed on the surface of the first conductive layer 112 facing away from the first base material layer 111, or the first material layer 13 is disposed on the surface of the second conductive layer 113 facing away from the first base material layer 111. The first material layer 13 includes a first material and a second material, and the first material and the second material are mixed with each other. The first material includes lithium element. In some embodiments, the first material includes at least one of Li5-xFeO4-y, Li6-xCoO4-y, Li2-zMnO2, or Li1.2-rNi0.13Fe0.13Mn0.54O2, where 4 ≤ x ≤ 5, 2 ≤ y ≤ 4, 1.6 ≤ z ≤ 2, 0.2 ≤ r ≤ 1.2. When the silicon-based anode material is first charged, a large amount of SEI (Solid Electrolyte Interface) film will be generated, consuming a large amount of active lithium, resulting in a low first Coulomb efficiency and a low battery energy density. The first material can be used as a lithium supplement agent to supplement lithium ions in the cathode electrode sheet 1, thereby increasing the battery capacity and energy density of the electrochemical device 100, replacing the consumption of active lithium in the cathode main material, and improving the utilization rate of the cathode main material; in addition, the protective layer 12 can reduce the risk of mechanical damage to the first current collector 11. When the first current collector 11 is damaged and generates a sharp protrusion that pierces the separator 2 and contacts the anode electrode sheet 3, the first current collector 11 is insulated from the anode electrode sheet 3, reducing the risk of short circuit of the electrochemical device 100 and improving the safety performance of the electrochemical device 100.
[0049] In some embodiments, the second material includes at least one of lithium cobaltate, lithium nickel cobalt manganate, lithium nickel cobalt aluminate, lithium iron phosphate, or lithium manganate.
[0050] In some embodiments, the first material and the second material are mixed with each other. By means of mixing, the process is simple and the cost is low.
[0051] It should be noted that the particle size of the second material is relatively large (usually greater than 5 μm), while the particle size of the first material is relatively small. By mixing the first material with the second material, when the cathode electrode sheet 1 is cold-pressed, the first material can fill the gaps between the particles of the second material, making the pressure more uniform, thereby reducing the risk of large-particle-size particles (such as lithium cobaltate particles) in the second material piercing through the first current collector 11, which is beneficial to reducing the risk of lithium deposition at the pierced part of the electrochemical device 100.
[0052] Furthermore, the impedance of the protective layer 12 is greater than that of the first conductive layer 112 and the second conductive layer 113. Therefore, even if the first current collector 11 undergoes mechanical damage and comes into contact with the anode electrode sheet 3 to cause a short circuit, the joule heat generated by the short circuit can be significantly reduced, thereby reducing the probability of failure of the electrochemical device 100 and further improving the safety performance of the electrochemical device 100.
[0053] In some embodiments, the first base layer 111 is made of at least one material selected from polyethylene terephthalate, polyimide, polyamide, polyurethane, polyethylene, and polypropylene. That is to say, the first base layer 111 is made of a polymer material. Therefore, the first base layer 111 has a relatively high resistance, and the first base layer 111 has a relatively high elongation. Especially in the case of high elongation, the resistance of the first base layer 111 increases exponentially, that is, the sheet resistance of the first current collector 11 increases. Even if a short circuit occurs, the joule heat generated by the short circuit can be reduced, thereby further improving the safety performance of the electrochemical device 100.
[0054] In some embodiments, please refer to Figure 3 , the thicknesses of both the first conductive layer 112 and the second conductive layer 113 are H microns, and the thickness of the protective layer 12 is B microns, and 2 / H ≤ B ≤ 4 is satisfied. In some embodiments, the mass percentage of the first material in the first material layer 13 is C%, and B ≤ 2*C. If the thickness of the protective layer 12 is too small, its protection effect on the first current collector 11 is insufficient, and it is easily pierced by the main cathode material during cold pressing, posing risks of lithium deposition and safety. At the same time, if the thickness of the protective layer 12 is too small, its protection effect on the cathode current collector is insufficient in the mechanical safety test, the internal short-circuit impedance is small, and the risk of fire and explosion is high; if the thickness of the protective layer 12 is too large, it affects the energy density of the electrochemical device 100. In addition, if the thickness of the protective layer 12 is too large, the sheet resistance is relatively large, the conductivity is poor, the charging speed is deteriorated, the charging temperature rise is deteriorated, which is not conducive to the performance of the electrochemical device; therefore, setting 2 / H ≤ B ≤ 4, B ≤ 2*C can improve the protection ability of the protective layer 12 on the first current collector 11, thereby improving the safety performance of the electrochemical device 100 and taking into account the energy density of the electrochemical device 100.
[0055] In some embodiments, 3 / H ≤ B ≤ 3. Setting 3 / H ≤ B can further enhance the protection ability of the protective layer 12 for the first current collector 11 and further improve the safety performance of the electrochemical device 100. Setting B ≤ 3 can further improve the energy density of the electrochemical device 100 and can extend the service life of the electrochemical device 100.
[0056] In some embodiments, B ≤ C. The content of the lithium supplement agent can be increased to further improve the energy density of the electrochemical device 100.
[0057] In some embodiments, both the first conductive layer 112 and the second conductive layer 113 are metals. The metal material has good electrical conductivity, which is beneficial to improving the charge-discharge performance of the electrochemical device 100.
[0058] In some embodiments, the thicknesses of the first conductive layer 112 and the second conductive layer 113 are equal. If the thicknesses of the first conductive layer 112 and the second conductive layer 113 are inconsistent, it is likely to cause uneven current distribution inside the electrochemical device 100, thereby reducing the charge-discharge rate of the electrochemical device 100. By defining that the thicknesses of the first conductive layer 112 and the second conductive layer 113 are equal, it is beneficial to improve the uniformity of the current inside the electrochemical device 100 and beneficial to improve the charge-discharge rate of the electrochemical device 100. It can be understood that, on the premise of not affecting the inventive purpose of the present application, due to reasons such as production and processing precision, when the error between the thickness of the first conductive layer 112 and the thickness of the second conductive layer 113 does not exceed 10%, the thicknesses of the first conductive layer 112 and the second conductive layer 113 can also be considered equal.
[0059] In some embodiments, the thickness of the first conductive layer 112 or the second conductive layer 113 is H microns and satisfies: 0.5 ≤ H ≤ 4. Preferably, 1 ≤ H ≤ 3. In some embodiments, H can be 0.5, 0.8, 0.9, 1, 1.2, 1.5, 1.8, 2, 2.2, 2.4, 2.8, 3, 3.2, 3.4, 3.6, 3.8, 4 or a value within the range formed by any two of these values or a value within the range formed by any two of these values. If the thickness of the first conductive layer 112 or the second conductive layer 113 is too small, the sheet resistance of the cathode electrode 1 is too large, the internal resistance of the electrochemical device 100 is too large, and the electrical performance of the electrochemical device 100 is poor; if the thickness of the first conductive layer 112 or the second conductive layer 113 is too thick, on the one hand, the energy density of the electrochemical device 100 will be reduced, and on the other hand, the too thick conductive layer is likely to form large-sized burrs when pierced or squeezed, and is likely to pierce the separator 2 and cause a short circuit. Therefore, setting 1 ≤ H ≤ 3 can reduce the internal resistance of the electrochemical device 100, improve the kinetic performance of the electrochemical device 100, and take into account the energy density of the electrochemical device 100 and improve the safety performance of the electrochemical device 100. It can also reduce the risk of the cathode electrode 1 being pierced during cold pressing, thereby reducing the risk of lithium plating in the electrochemical device 100.
[0060] Furthermore, the thickness of the first conductive layer 112 or the second conductive layer 113 satisfies: 1.5 ≤ H ≤ 2. Setting 1.5 ≤ H can further reduce the internal resistance of the electrochemical device 100, improve the energy density of the electrochemical device 100, and further reduce the risk of the cathode electrode 1 being pierced during cold pressing, thereby reducing the risk of lithium plating in the electrochemical device 100. Setting H ≤ 2 can further improve the energy density and safety performance of the electrochemical device 100.
[0061] In some embodiments, the thickness of the protective layer 12 is B microns and satisfies 0.5 ≤ B ≤ 4.5. Preferably, 1 ≤ B ≤ 4. In some embodiments, the value of B can be 0.5, 0.8, 1, 1.2, 1.4, 1.5, 1.8, 2, 2.2, 2.4, 2.5, 2.7, 2.9, 3, 3.2, 3.4, 3.5, 3.7, 3.9, 4, 4.3, 4.5 or a range formed by any two of these values or a value within the range formed by any two of these values. If the thickness of the protective layer 12 is too small, its protective effect on the first current collector 11 is insufficient, and it is easily pierced by the main cathode material during cold pressing, resulting in lithium deposition and safety risks. At the same time, if the thickness of the protective layer 12 is too small, its protective effect on the cathode current collector is insufficient in the mechanical safety test, the internal short-circuit impedance is small, and the risk of fire and explosion is high; if the thickness of the protective layer 12 is too large, it will affect the energy density of the electrochemical device 100. In addition, if the thickness of the protective layer 12 is too large, the sheet resistance is relatively large, the conductivity is poor, the charging speed is deteriorated, the charging temperature rise is deteriorated, which is not conducive to the performance of the electrochemical device; therefore, setting 1 ≤ B ≤ 4 can improve the protective effect of the protective layer 12 on the first current collector 11, reduce the risk of mechanical damage to the first current collector 11, and take into account the energy density of the electrochemical device 100. In addition, it can also extend the service life of the electrochemical device 100.
[0062] Further, 1.5 ≤ B ≤ 2.5. Setting 1.5 ≤ B can further increase the passing rate of the nail penetration test, thereby improving the safety performance of the electrochemical device and can further extend the service life; setting B ≤ 2.5 is beneficial to further improving the energy density of the electrochemical device.
[0063] In some embodiments, the mass percentage of the first material in the first material layer 13 is C% and satisfies 0.5% ≤ C% ≤ 4%. Preferably, 1% ≤ C% ≤ 3%. In some embodiments, the value of C can be 0.5, 0.8, 1, 1.2, 1.5, 1.7, 2, 2.2, 2.5, 2.7, 3, 3.2, 3.5, 3.7, 4 or a range formed by any two of these values or a value within the range formed by any two of these values. If the content of the first material is too low, the lithium supplementation amount of the cathode electrode sheet 1 will be low, resulting in a low energy density of the electrochemical device 100; the side reaction in the first material is more than that in the second material. If the content of the first material is too high, it is easy to cause a large increase in side reactions, making the cycle charge and discharge ability of the electrochemical device 100 poor, and the electrical performance of the electrochemical device 100 deteriorates at high temperatures. Therefore, setting 0.5% ≤ C% ≤ 4% can improve the cycle charge and discharge ability of the electrochemical device 100, improve the high-temperature performance, extend the service life of the electrochemical device 100, and take into account the energy density of the electrochemical device 100, and reduce the risk of the cathode electrode sheet 1 being pierced during cold pressing.
[0064] Further, the mass percentage of the first material in the first material layer 13 satisfies 1% ≤ C% ≤ 3%. Setting 1% ≤ C% can further improve the energy density of the electrochemical device 100 and further extend the service life of the electrochemical device; setting C% ≤ 3% can further improve the charge-discharge cycling ability of the electrochemical device 100, improve the high-temperature performance, and is beneficial to further reducing the risk of the cathode electrode sheet being pierced during cold pressing, and further improving the safety performance of the electrochemical device.
[0065] Further, the mass percentage of the first material in the first material layer 13 satisfies 1.5% ≤ C% ≤ 2.5%. Setting 1.5% ≤ C% can further improve the energy density of the electrochemical device 100; setting C% ≤ 2.5% can further improve the charge-discharge cycling ability of the electrochemical device 100 and improve the high-temperature performance.
[0066] In some embodiments, please refer to Figure 1 , along the thickness direction of the electrode assembly 10, the protective layer 12 is disposed on both opposite surfaces of the first current collector 11, and the first material layer 13 is disposed on the surface of the protective layer 12 away from the first current collector 11. In this embodiment, by disposing the protective layer 12 on both surfaces of the first current collector 11, the two sides of the first current collector 11 can be protected, which is beneficial to further reducing the risk of mechanical damage to the first current collector 11, thereby reducing the risk of the first current collector 11 generating a bulge at the damaged part and piercing the separator 2 to cause a short circuit.
[0067] In some embodiments, the first material layer 13 may be disposed on the surface of one of the protective layers 12 facing away from the first current collector 11, or the above-mentioned first material layer 13 may be disposed on the surfaces of both protective layers 12 facing away from the first current collector 11. That is to say, the cathode electrode sheet 1 may be provided with active substances on only one side or on both sides, and the present application does not make any limitation thereto.
[0068] In some embodiments, the protective layer 12 includes an inorganic material, a conductive agent, and an adhesive. The conductive agent can enhance the conductivity of the first material layer 13, and the adhesive is used to bond the particles in the inorganic material and the conductive agent, and to bond the first material layer 13 to the first conductive layer 112 or the second conductive layer 113.
[0069] In some embodiments, the adhesive includes at least one of metal polyacrylate, polyvinylidene fluoride, and styrene-butadiene rubber.
[0070] In some embodiments, the above-mentioned inorganic material includes at least one of aluminum oxide, boehmite, titanium dioxide, barium titanate, and barium sulfate.
[0071] In some embodiments, the charge capacity per gram of the first material is E, and the charge capacity per gram of the second material is F, and the following is satisfied: F < E. With such a setting, it is beneficial to improve the energy density of the electrochemical device 100.
[0072] In some embodiments, the charge capacity per gram E of the first material satisfies 240 mAh / g ≤ E ≤ 1000 mAh / g. Preferably, 240 mAh / g ≤ E ≤ 950 mAh / g. In some embodiments, E can be 240 mAh / g, 250 mAh / g, 300 mAh / g, 350 mAh / g, 400 mAh / g, 450 mAh / g, 500 mAh / g, 550 mAh / g, 600 mAh / g, 650 mAh / g, 700 mAh / g, 750 mAh / g, 800 mAh / g, 850 mAh / g, 900 mAh / g, 950 mAh / g, 1000 mAh / g, or a value within the range formed by any two of these values, or a value within the range formed by any two of these values. With such a setting, it is beneficial to improve the energy density of the electrochemical device 100.
[0073] In some embodiments, the charge capacity per gram E of the first material satisfies 300 mAh / g ≤ E ≤ 700 mAh / g, so as to further improve the energy density of the electrochemical device 100.
[0074] In the embodiments of the present application, by disposing the protective layer 12 between the first current collector 11 and the first material layer 13, the protective layer 12 can protect at least one surface of the first current collector 11, thereby reducing the risk of mechanical damage to the first current collector 11, and further reducing the risk that the first current collector 11 generates burrs or protrusions at the damaged part and pierces the separator 2, resulting in a short circuit due to the contact between the cathode electrode sheet 1 and the anode electrode sheet 3. At the same time, the first current collector 11 includes a first base layer 111 including at least one of polyethylene terephthalate, polyimide, polyamide, polyurethane, polyethylene, and polypropylene. The first base layer 111 has a high elongation rate, so that the cathode electrode sheet 1 can extend when subjected to pressure. The first base layer 111 can rapidly extend under mechanical stress, resulting in a significant increase in the sheet resistance of the first current collector 11, thereby increasing the resistance during short circuit and reducing the heat generation during short circuit, and further improving the safety performance of the electrochemical device 100; on this basis, the anode electrode sheet 3 includes silicon elements, providing a high theoretical specific capacity for the electrochemical device 100, thereby increasing the capacity of the electrochemical device 100. At the same time, the first material in the present application is used to supplement lithium to the cathode electrode sheet 1, thereby reducing the loss of energy density caused by the low initial efficiency of the silicon negative electrode, while improving the safety performance of the electrochemical device 100 and increasing the energy density of the electrochemical device 100. Furthermore, by setting 2 / H ≤ B ≤ 4 and B ≤ 2*C, the safety performance and energy density of the electrochemical device 100 can be further improved.
[0075] In a second aspect, the present application provides an electronic device, which includes the above-mentioned electrochemical device. For the specific structure and function of the electrochemical device, please refer to the above embodiments and will not be elaborated herein one by one.
[0076] To help readers better understand the concept of the present application, experimental proofs are provided below.
[0077] The preparation of the electrochemical device in Example 1 is as follows:
[0078] <Preparation of the cathode electrode sheet>
[0079] Mix aluminum oxide (inorganic material), sodium polyacrylate (conductive agent), and conductive carbon black (conductive agent) in a mass ratio of 88:10:2, add water as a solvent, and stir evenly with a vacuum mixer to obtain a protective layer slurry with a solid content of 50 wt%. Coat the protective layer slurry evenly on the surfaces on both sides of the first current collector. The first current collector is a composite current collector, which includes a first conductive layer, a polymer layer, and a second conductive layer. The polymer layer is made of polyethylene terephthalate, and both the first conductive layer and the second conductive layer are made of aluminum. Dry it at 120 °C to obtain a cathode electrode sheet with a double-sided coated protective layer. The single-sided coating weight of the first material layer is 8 mg / 1540 mm 2 .
[0080] Mix lithium cobaltate (the second material, i.e., the positive electrode material), lithium ferrite (the first material supplementing lithium, i.e., the first material), polyvinylidene fluoride (the first binder), and conductive carbon black (the first conductive agent) in a mass ratio of 95:2:1.6:1.4, add N-methylpyrrolidone (NMP) as a solvent, and stir evenly with a vacuum mixer to obtain a first material layer slurry with a solid content of 75 wt%. Coat the first material layer slurry evenly on the surfaces on both sides of the cathode with the protective layer already coated, and dry it at 120 °C to obtain a cathode electrode sheet with a double-sided coated first material layer. The single-sided coating weight of the first material layer is 260 mg / 1540 mm 2 . At 25 °C, use a pressure of 40 - 80 t to compact the cathode electrode sheet to reach the set thickness specification of 84 μm. Then, after cutting and welding the electrode tabs, a cathode electrode sheet with a specification of 74 mm × 867 mm is obtained for use.
[0081] <Preparation of the anode electrode sheet>
[0082] Mix artificial graphite as the anode material, silicon carbide, the second binder styrene-butadiene rubber (SBR), and carboxymethyl cellulose (CMC) in a mass ratio of 87.7∶10∶1∶1.3. Then add deionized water as a solvent to formulate a slurry with a solid content of 70 wt%, and obtain the second material layer slurry after stirring evenly with a vacuum mixer. Coat the second material layer slurry evenly on one surface of a copper foil with a thickness of 6 μm as the anode current collector (i.e., the second current collector), and dry it at 120 °C to obtain an anode with a single-sided coated second material layer. The single-sided coating weight of the second material layer is 95 mg / 1540 mm 2 。Then repeat the above steps on the other surface of the copper foil to obtain an anode with a double-sided coated second material layer. After drying at 120 °C, perform cold pressing, and then through die cutting and welding the tab, obtain a negative electrode plate with a specification of 78 mm × 875 mm for use. Among them, the thickness of the double-sided second material layer is 93 μm.
[0083] <Preparation of the electrolyte>
[0084] In an argon atmosphere glove box with a water content of less than 10 ppm, evenly mix ethylene carbonate (EC), propylene carbonate (PC), and diethyl carbonate (DEC) as carbonate compounds in a mass ratio of 10∶30∶60 to obtain a basic solvent, and add lithium salt LiPF6 and stir evenly to obtain the electrolyte. Among them, based on the total mass of the electrolyte, the mass percentage content of lithium salt LiPF6 is 12.5%, and the balance is the basic solvent.
[0085] <Separator>
[0086] Use a polyethylene porous polymer film with a thickness of 8 μm (manufacturer: Celgard Separator Co., Ltd., USA) as the separator.
[0087] <Preparation of the electrochemical device>
[0088] Stack the cathode plate, separator, and anode plate in sequence, with the separator in the middle of the cathode plate and the anode plate to play an isolation role, and wind them to obtain an electrode assembly. Put the electrode assembly into an aluminum-plastic film packaging bag, remove moisture at 80 °C, inject the prepared electrolyte, and obtain the electrochemical device through vacuum packaging, standing, formation, and shaping processes. Among them, the upper limit voltage of formation is 4.53 V, the formation temperature is 85 °C, and the formation time is 45 min to 60 min.
[0089] Different from Example 1, the first current collector in Comparative Example 1 is aluminum foil, and the cathode plate does not include a protective layer and the first material;
[0090] Different from Comparative Example 1, the first current collector in Comparative Example 2 includes a first conductive layer, a polymer layer, and a second conductive layer;
[0091] Different from Comparative Example 1, the cathode current collector in Comparative Example 3 includes a protective layer;
[0092] Different from Comparative Example 1, the cathode current collector in Comparative Example 4 includes a first material;
[0093] Different from Comparative Example 2, the cathode current collector in Comparative Example 5 includes a first material;
[0094] Different from Comparative Example 2, the cathode current collector in Comparative Example 6 includes a protective layer;
[0095] Different from Comparative Example 3, the cathode current collector in Comparative Example 7 includes a first material;
[0096] Different from Example 1, the parameters in Comparative Examples 8 to 12 and Examples 2 to 20 are different. For specific parameter differences, please refer to Table 1.
[0097] Regarding the test method as follows:
[0098] Stud Test
[0099] Take 10 electrochemical devices in each example and comparative example, and fully charge them in an environment of 25 ± 3°C. The specific steps are as follows: charge at a constant current of 0.5C until 4.53V, and then charge at a constant voltage of 4.53V until the current is cut off at 0.05C.
[0100] Conduct a stud test on the electrochemical device under the condition of 25 ± 3°C. Use a steel nail with a diameter of 4mm, made of carbon steel, a taper of 16.5mm, and a total length of 100mm. The stud insertion speed is set to 30 ± 1mm / s, and the stud insertion depth is based on the taper of the steel nail passing through the electrochemical device. Observe the state of the electrochemical device during the test. If the electrochemical device does not catch fire or explode, it is judged as passing the stud test, and record the number of electrochemical devices passing the stud test. Evaluate the safety performance of the electrochemical device through the passing rate of the stud test. The higher the passing rate of the stud test, the better the safety performance of the electrochemical device; the lower the passing rate of the stud test, the worse the safety performance of the electrochemical device.
[0101] Cycle Number Test:
[0102] At 25°C, charge the electrochemical device at a constant current of 2C until 4.53V, then charge at a constant voltage until the current is less than or equal to 0.05C, and then discharge at a constant current of 0.5C until 3V. This is one charge-discharge cycle, and record the discharge capacity of the first cycle of the electrochemical device. Charge and discharge the electrochemical device according to the above method, record the discharge capacity of each cycle until the discharge capacity of the electrochemical device decays to 80% of the discharge capacity of the first cycle, and record the number of charge-discharge cycles.
[0103] Transmittance Test of Cathode Current Collector:
[0104] At room temperature of 25 °C, place the cathode electrode sheet after drying the double-sided coating film in a cold press, set the compaction pressure at 40 t to 80 t, and use the equipment to cold press the electrode sheet to the set target value. This process can pass through different pressures or multiple cold presses, and finally reach the set target value of the electrode sheet. Randomly select three places on the cold-pressed double-sided electrode sheet, fold the electrode sheet once at 180°, use a 5 kg roller to naturally press the folded part, and then open it at 180°, which is one fold; next, fold it at 180° in the opposite direction, use a 5 kg roller to naturally press the folded part, and then open it at 180°, which is two folds. Each electrode sheet is repeatedly folded four times, and record the number n of light-transmitting points at the folded part of the electrode sheet after each fold. When n is 0, it is opaque; when n is 1 to 3, it is slightly light-transmitting; when n is greater than or equal to 4, it is severely light-transmitting.
[0105] Cathode electrode sheet penetration test:
[0106] At room temperature of 25 °C, place the cathode electrode sheet after drying the double-sided coating film in a cold press, set the compaction pressure at 40 t to 80 t, and use the equipment to cold press the electrode sheet to the set target value. This process can pass through different pressures or multiple cold presses, and finally reach the set target value of the electrode sheet. Randomly select three cold-pressed double-sided electrode sheets and place them on white paper. Drop red mercurochrome on the electrode sheets, and after standing for 4 h, observe whether the white paper under the electrode sheets is dyed red by the red mercurochrome. If at least one piece of white paper of the electrode sheet is dyed red, the cathode electrode sheet is penetrated; otherwise, the cathode electrode sheet is not penetrated.
[0107] Electrode assembly energy density test:
[0108] Place the electrochemical device in an incubator at 25 °C and let it stand for 30 minutes to make the electrochemical device reach a constant temperature. Charge the electrochemical device that has reached a constant temperature at a constant current of 0.5 C until the voltage reaches 4.53 V, then charge it at a constant voltage of 4.53 V until the current reaches 0.05 C, and then discharge it at 0.5 C until the voltage reaches 3.0 V. Record the discharge energy. The energy density of the electrode assembly = discharge energy / (length × width × thickness of the electrochemical device), and the unit is Wh / L. Among them, the length, width, and thickness all refer to the length, width, and thickness of the packaged electrochemical device.
[0109] Table 1
[0110]
[0111]
[0112] Please refer to Table 1. From the comparison between Comparative Examples 1 to 9 and Example 1, it can be seen that compared with using aluminum foil as the first current collector, the composite current collector can improve the passing rate of the nail penetration test of the electrochemical device 100 and reduce the risk of brittle fracture of the cathode electrode sheet; by setting the first material in the cathode electrode sheet for lithium compensation, the energy density of the electrochemical device 100 can be improved; by setting a protective layer on the surface of the cathode current collector (i.e., the first current collector), the risk of the cathode electrode sheet being pierced can be reduced, and the passing rate of the nail penetration test can be further improved, thereby improving the safety performance of the electrochemical device 100. Therefore, in this application, the first current collector includes a first substrate layer, a first conductive layer, and a second conductive layer, a protective layer is provided on the surface of the first current collector, and the first material layer includes the first material, which can balance the improvement of the energy density and safety performance of the electrochemical device. In addition, compared with Example 1, in Comparative Example 8, when 2 / H > B, the passing rate of the nail penetration test is low, and the electrode sheet is pierced, indicating that the protective layer has a weak protection ability for the first current collector; compared with Example 1, in Comparative Example 9, when B > 4, the protective layer is too thick, the energy density of the electrochemical device 100 is low, and at the same time, the too thick protective layer affects electron transport, the impedance of the electrochemical device 100 is large, and the number of cycles of the electrochemical device 100 is low. Therefore, setting 2 / H ≤ B ≤ 4 can improve the protection ability of the protective layer 12 for the first current collector 11, thereby improving the safety performance of the electrochemical device 100, and balancing the energy density and number of cycles of the electrochemical device 100.
[0113] From the comparison between Example 1 and Example 2, it can be seen that when B > 2*C, the energy density of the electrochemical device 100 is low. Therefore, setting B ≤ 2*C can improve the energy density of the electrochemical device 100.
[0114] From the comparison between Comparative Example 10, Example 2, Examples 3 to 7, it can be seen that as H increases, the energy density of the electrochemical device gradually decreases, and the passing rate of the nail penetration test gradually decreases. However, when H < 1, there is a serious light transmission in three folds, the electrode sheet is pierced, and the number of cycles is small. When H > 3, the passing rate of the nail penetration test is low. Therefore, setting 1 ≤ H can reduce the risk of the cathode electrode sheet being pierced and brittle fracture, is beneficial to reducing lithium deposition in the electrochemical device, and can also extend the service life of the electrochemical device 100; setting H ≤ 3 is beneficial to improving the energy density of the electrochemical device 100 and the safety performance of the electrochemical device.
[0115] Furthermore, setting 1.5 ≤ H can further reduce the risk of the cathode electrode sheet being pierced during cold pressing, is beneficial to reducing lithium deposition in the electrochemical device, and can also further extend the service life of the electrochemical device 100; setting H ≤ 2 is beneficial to further improving the energy density of the electrochemical device 100 and the safety performance of the electrochemical device.
[0116] From the comparison of Comparative Example 11, Example 2, and Examples 8 to 13, it can be seen that as B increases, the energy density of the electrochemical device gradually decreases, while the passing rate of the nail penetration test gradually increases. And when B > 4 or B < 1, the number of cycles of the electrochemical device is relatively small. Therefore, setting B ≥ 1 can increase the passing rate of the nail penetration test, thereby improving the safety performance of the electrochemical device and extending its service life; setting B ≤ 4 is beneficial to improving the energy density of the electrochemical device and extending its service life.
[0117] Furthermore, setting 1.5 ≤ B can further increase the passing rate of the nail penetration test, thereby improving the safety performance of the electrochemical device and further extending its service life; setting B ≤ 2.5 is beneficial to further improving the energy density of the electrochemical device.
[0118] From the comparison of Comparative Example 12 and Examples 14 to 20, it can be seen that as the percentage C% of the first material in the first material layer increases, the energy density of the electrochemical device gradually increases, and the light transmittance of the cathode electrode sheet also gradually increases. When C% < 0.5%, the number of cycles is relatively small. When C% > 4%, the number of cycles is relatively small and the passing rate of the nail penetration test is low. Therefore, setting C% ≥ 0.5% is beneficial to improving the energy density of the electrochemical device and extending its service life; setting C% ≤ 4% is beneficial to reducing the risk of the cathode electrode sheet being pierced and brittle broken, while reducing the side reaction with the electrolyte, extending the service life of the electrochemical device, and taking into account the improvement of the safety performance of the electrochemical device.
[0119] Furthermore, setting C% ≥ 1% is beneficial to further improving the energy density of the electrochemical device and further extending its service life; setting C% ≤ 3% is beneficial to further reducing the risk of the cathode electrode sheet being pierced and brittle broken and further improving the safety performance of the electrochemical device.
[0120] The above-disclosed are only the preferred embodiments of the present application. Of course, the scope of rights of the present application cannot be limited thereby. Therefore, equivalent changes made according to the claims of the present application still fall within the scope covered by the present application.
Claims
1. An electrochemical device includes an electrode assembly, the electrode assembly includes a cathode current collector, a separator, and an anode current collector, the separator is disposed between the cathode current collector and the anode current collector, the anode current collector includes silicon element, and it is characterized in that, The cathode current collector includes a first current collector layer, a protective layer, and a first material layer. Along the thickness direction of the electrode assembly, the protective layer is disposed on the surface of the first current collector layer, and the first material layer is disposed on the surface of the protective layer away from the first current collector layer; The first current collector layer includes a first substrate layer, a first conductive layer, and a second conductive layer. The first substrate layer is disposed between the first conductive layer and the second conductive layer. The first substrate layer includes at least one of polyethylene terephthalate, polyimide, polyamide, polyurethane, polyethylene, and polypropylene; The first material layer includes a first material and a second material, and the first material includes lithium element; The thicknesses of the first conductive layer and the second conductive layer are both H microns, the thickness of the protective layer is B microns, and it satisfies: 2 / H ≤ B ≤ 4.
2. The electrochemical device according to claim 1, wherein the first material comprises at least one of Li5-xFeO 4-y , Li6-xCoO 4-y , Li2-zMnO2 or Li 1.2-r Ni 0.13 Fe 0.13 Mn 0.54 O2, wherein 4 ≤ x ≤ 5, 2 ≤ y ≤ 4, 1.6 ≤ z ≤ 2, 0.2 ≤ r ≤ 1.
2. The mass ratio of the first material in the first material layer is C%, and it satisfies: B ≤ 2*C.
3. The electrochemical device according to claim 1, characterized in that, 1≤H≤3。 4. The electrochemical device according to claim 3, characterized in that, 1.5≤H≤2。 5. The electrochemical device according to claim 1, characterized in that, 1≤B≤4。 6. The electrochemical device according to claim 5, characterized in that, 1.5≤B≤2.5。 7. The electrochemical device according to claim 1, characterized in that, 0.5％≤C％≤4％。 8. The electrochemical device according to claim 7, characterized in that, 1％≤C％≤3％。 9. The electrochemical device according to claim 1, characterized in that, Along the thickness direction of the electrode assembly, the protective layer is simultaneously disposed on the opposite two surfaces of the first current collector layer, and the first material layer is disposed on the surface of the protective layer away from the first current collector layer.
10. The electrochemical device according to claim 1, characterized in that, The second material includes at least one of lithium cobaltate, lithium nickel cobalt manganate, lithium nickel cobalt aluminate, lithium iron phosphate, or lithium manganate.
11. The electrochemical device according to claim 1, characterized in that, The protective layer includes an inorganic material, a conductive agent, and an adhesive.
12. The electrochemical device according to claim 11, characterized in that, The adhesive includes at least one of metal polyacrylate, polyvinylidene fluoride, and styrene-butadiene rubber.
13. The electrochemical device according to claim 11, characterized in that, The inorganic material includes at least one of aluminum oxide, boehmite, titanium dioxide, barium titanate, and barium sulfate.
14. The electrochemical device according to claim 1, characterized in that, The anode current collector includes a second current collector layer and a second material layer. The second material layer is disposed on at least one surface of the second current collector layer. The second material layer includes the silicon element, and the mass ratio of the silicon element in the second material layer is D%, and it satisfies: 1% ≤ D% ≤ 50%.
15. The electrochemical device according to claim 1, characterized in that, The charge capacity per gram of the first material is E, and the charge capacity per gram of the second material is F, and it satisfies: F < E.
16. The electrochemical device according to claim 15, characterized in that, The charge capacity per gram E of the first material satisfies: 240 mAh / g ≤ E ≤ 950 mAh / g.
17. An electronic device, characterized in that, Including the electrochemical device according to any one of claims 1-16.