An electrochemical device and an electronic device

Abstract

An electrochemical device and an electronic device, by setting a non-active material layer (50) on the second surface (10b) of the single-face area (30) of the positive electrode current collector (10), while matching the electrolyte, the risk of abnormality of the positive electrode sheet (100) of the electrochemical device after the charge and discharge cycle is reduced, the risk of lithium precipitation of the negative electrode sheet (200) is reduced, thereby reducing the risk of failure of the electrochemical device in the charge and discharge cycle.

Description

Technical Field

[0001] This application relates to the field of electrochemical technology, and in particular to an electrochemical device and an electronic device. Background Technology

[0002] Most existing secondary batteries (such as lithium-ion batteries) have exposed positive electrode current collectors (usually aluminum foil), such as wound structures with the positive electrode current collector ending, wound structures with die-cut aluminum tabs, or stacked structures with the positive electrode ending on one side. As the voltage of lithium-ion batteries continues to increase, the oxidation capacity of the positive electrode sheet to the electrolyte during full charging also increases. To reduce the oxidation of the electrolyte by the positive electrode sheet, existing technologies often improve the protection of both the positive and negative electrode sheets under high voltage by continuously increasing the content of fluorine compounds in the electrolyte.

[0003] However, fluorinated compounds, such as fluorinated additives and fluorinated lithium salts, are prone to undergoing a defluorination reaction under the influence of Lewis acids (such as PF5) produced by electrolyte decomposition, generating HF. In this situation, after the lithium-ion battery is filled with electrolyte, the electrolyte comes into contact with the exposed positive electrode current collector. The HF in the electrolyte and the positive electrode current collector easily react to generate impurities. These impurities will diffuse inside the lithium-ion battery with the electrolyte and accumulate in specific areas of the positive electrode (e.g., at the edge of the positive electrode material layer where the positive electrode current collector is located on one side), causing abnormalities in the positive electrode. This will affect the lithium plating on the negative electrode, leading to lithium-ion battery failure during charge-discharge cycles. Therefore, how to reduce the risk of lithium-ion battery failure during charge-discharge cycles has become a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0004] The purpose of this application is to provide an electrochemical device and an electronic device to reduce the risk of failure of the electrochemical device during charge-discharge cycles.

[0005] It should be noted that while this application uses lithium-ion batteries as an example of an electrochemical device to explain the invention, the electrochemical device described herein is not limited to lithium-ion batteries. The specific technical solution is as follows:

[0006] This application provides an electrochemical device comprising an electrode assembly, an electrolyte, and a packaging bag containing the electrode assembly and the electrolyte. The electrolyte includes a fluorinated compound. The electrode assembly includes a positive electrode, a negative electrode, and a separator, with the separator disposed between the positive and negative electrode. The electrode assembly is formed by stacking the positive electrode, the separator, and the negative electrode. The positive electrode includes a positive current collector, a positive active material layer, and an inactive material layer. The positive current collector is aluminum foil and includes silicon, with a silicon content of a% by mass (0.03 ≤ a ≤ 0.13). The positive current collector includes a first surface and a second surface opposite to each other. The positive current collector has a single-sided region, which includes a first portion. The second surface of the first portion is located on the outer surface of the electrode assembly. The first surface of the single-sided region is provided with the positive active material layer, and the second surface of the single-sided region is provided with the inactive material layer. The inactive material layer includes an inactive material, which includes at least one of inorganic oxides or non-metallic elements. By using the positive current collector provided in this application, and setting an inactive material layer on the second surface of the single-sided region of the positive current collector, and in conjunction with the electrolyte of this application, the risk of abnormality of the positive electrode and the risk of lithium plating of the negative electrode are reduced after the electrochemical device has undergone charge-discharge cycles, thereby reducing the risk of failure of the electrochemical device during charge-discharge cycles.

[0007] In some embodiments of this application, an inactive material layer covers the second surface of the single-sided region. It is understood that the entire area of ​​the second surface of the single-sided region is provided with the inactive material layer. Thus, the inactive material layer, acting as an inert layer between the electrolyte and the positive electrode current collector, completely isolates the electrolyte from the positive electrode current collector, further reducing the possibility of contact between them and further reducing the content of byproducts generated by the reaction between the electrolyte and the positive electrode current collector. This reduces the risk of byproducts accumulating in specific areas or other areas of the positive electrode. After charge-discharge cycles, the risk of abnormalities in the positive electrode is reduced, and the risk of lithium plating in the negative electrode is reduced, thereby reducing the risk of failure of the electrochemical device during charge-discharge cycles.

[0008] In some embodiments of this application, the inorganic oxide includes at least one of aluminum oxide, silicon oxide, calcium oxide, boehmite, or calcium carbonate. The non-metallic element includes at least one of silicon, carbon, or boron. By selecting the above-mentioned inorganic oxides and non-metallic elements, the risk of abnormality in the positive electrode is reduced, and the risk of lithium plating in the negative electrode is reduced, thereby reducing the risk of failure of the electrochemical device during charge-discharge cycles.

[0009] In some embodiments of this application, the Dv50 of the inorganic oxide is from 0.1 μm to 30 μm, and the Dv50 of the non-metallic element is from 0.1 μm to 10 μm. Controlling the average particle size Dv50 of the inorganic oxide and non-metallic element within these ranges makes it easier to control the thickness of the inactive material layer within a suitable range, reducing the risk of abnormalities in the positive electrode and the risk of lithium plating in the negative electrode, thereby reducing the risk of failure of the electrochemical device during charge-discharge cycles.

[0010] In some embodiments of this application, the inactive material layer further includes an inactive material layer binder, which includes at least one of polytetrafluoroethylene, chloroprene rubber, nitrile rubber, styrene-butadiene rubber, carboxylated rubber, chlorosulfonated polyethylene rubber, phenolic resin, epoxy resin, or silicone resin. The mass ratio of the inactive material to the inactive material layer binder is (70–98):(2–30). By selecting the above-mentioned binder and controlling the mass ratio of the inactive material to the inactive material layer within the above range, the risk of abnormality in the positive electrode is reduced, and the risk of lithium plating in the negative electrode is reduced, thereby reducing the risk of failure of the electrochemical device during charge-discharge cycles.

[0011] In some embodiments of this application, the fluorinated compound includes a fluorinated additive, and the mass percentage of the fluorinated additive in the electrolyte is c%, where 0.1 ≤ c ≤ 40. The inclusion of the fluorinated additive in the electrolyte, and the control of the mass percentage of the fluorinated additive within the aforementioned range, reduces the risk of abnormalities in the positive electrode, thereby reducing the risk of failure of the electrochemical device during charge-discharge cycles.

[0012] In some embodiments of this application, the thickness of the inactive material layer is b μm, where 3 ≤ b ≤ 20. By controlling the thickness of the inactive material layer within the above range, the risk of abnormality in the positive electrode is reduced, and the risk of lithium plating in the negative electrode is reduced, thereby reducing the risk of failure of the electrochemical device during charge-discharge cycles.

[0013] In some embodiments of this application, 3 ≤ b ≤ 10. This allows the inactive material layer to have a suitable thickness, meeting the requirement of reducing the risk of failure of the electrochemical device during charge-discharge cycles. It also reduces the impact of the inactive material layer on the energy density of the electrochemical device. Furthermore, it allows the rolling equipment to act on the inactive material layer during the rolling process after electrode coating, reducing the risk of the rolling equipment directly transitioning from the positive electrode active material layer to the positive electrode current collector, which could cause the positive electrode to break.

[0014] In some embodiments of this application, 0.003 ≤ a / b ≤ 0.025. By controlling the value of a / b within this range, the mass percentage of silicon in the positive electrode current collector and the thickness of the inactive material layer work synergistically, further reducing the risk of failure of the electrochemical device during charge-discharge cycles. In some embodiments of this application, 0.003 ≤ a / b ≤ 0.02. This can further reduce the risk of failure of the electrochemical device during charge-discharge cycles.

[0015] In some embodiments of this application, 0.1 ≤ c / b ≤ 13. By controlling the c / b value within this range, the mass percentage of the fluorinated additive in the electrolyte and the thickness of the inactive material layer work synergistically, further reducing the risk of failure of the electrochemical device during charge-discharge cycles. In some embodiments of this application, 0.1 ≤ c / b ≤ 6.7. This can further reduce the risk of failure of the electrochemical device during charge-discharge cycles.

[0016] In some embodiments of this application, the fluorinated additive includes at least one of fluoroethylene carbonate, bis(fluoromethyl)ethylene carbonate, bis(difluoromethyl)ethylene carbonate, bis(trifluoromethyl)ethylene carbonate, bis(2-fluoroethyl)ethylene carbonate, bis(2,2-difluoroethyl)ethylene carbonate, bis(2,2,2-trifluoroethyl)ethylene carbonate, 2-fluoroethylmethylethylene carbonate, 2,2-difluoroethylmethylethylene carbonate, or 2,2,2-trifluoroethylmethylethylene carbonate. Using the above-mentioned types of fluorinated additives is more effective in reducing the oxidizing power of the positive electrode sheet on the electrolyte, forming a uniform and dense protective film on the surfaces of both the positive and negative electrode sheets, thus protecting them.

[0017] In some embodiments of this application, the fluorinated material includes fluorinated lithium salts, which include at least one of lithium hexafluorophosphate, lithium difluorophosphate, lithium bis(trifluoromethane)sulfonylimide, lithium bisfluorosulfonylimide, lithium tetrafluoroborate, lithium difluorooxalate borate, lithium hexafluoroantimonyate, lithium hexafluoroarsenate, lithium perfluorobutylsulfonate, lithium bissulfonylimide, or lithium fluoride. The addition of fluorinated lithium salts further enhances the provision of high ionic conductivity, resulting in faster lithium-ion transport rates.

[0018] In some embodiments of this application, the electrode assembly has a stacked structure; or, the electrode assembly has a wound structure, and the positive current collector further includes a double-sided region, with the double-sided region and the single-sided region connected sequentially along the winding direction.

[0019] A second aspect of this application provides an electronic device that includes the electrochemical device provided in the first aspect of this application. Therefore, the beneficial effects of the electrochemical device provided in the first aspect of this application can be obtained.

[0020] Of course, implementing any product or method of this application does not necessarily require achieving all of the advantages described above at the same time. Attached Figure Description

[0021] To more clearly illustrate the technical solutions of the embodiments of this application and the prior art, the drawings used in the embodiments and the prior art are briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings.

[0022] Figure 1 This is a schematic diagram of the electrode assembly structure of some embodiments of this application;

[0023] Figure 2 for Figure 1 A schematic diagram of the cross-sectional structure of the positive electrode sheet in the electrode assembly in its unfolded state along its own thickness direction;

[0024] Figure 3 for Figure 2 A schematic diagram of the positive electrode sheet as viewed along its own thickness direction;

[0025] Figure 4 This is a schematic diagram of the electrode assembly structure of some embodiments of this application;

[0026] Figure 5 for Figure 4 A schematic diagram of the cross-sectional structure of the positive electrode sheet in the electrode assembly in its unfolded state along its own thickness direction;

[0027] Figure 6 This is a schematic diagram of the structure of the positive electrode sheet in some embodiments of this application;

[0028] Figure 7 This is a schematic diagram of the cross-sectional structure of the positive electrode sheet of Comparative Example 1 in its unfolded state along its own thickness direction. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided with reference to the accompanying drawings and embodiments. Obviously, the described embodiments are merely some embodiments of this application, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments in this application are within the scope of protection of this application.

[0030] It should be noted that, in the specific embodiments of this application, lithium-ion batteries are used as an example of electrochemical devices to explain this application, but the electrochemical devices of this application are not limited to lithium-ion batteries.

[0031] Electrochemical devices (such as lithium-ion batteries) typically have exposed positive electrode current collectors. Current technologies often use aluminum foil with a silicon content of 0.06% to 0.18% by mass, with most silicon existing as silicon dioxide or silicates. As the voltage of electrochemical devices increases, the oxidation of the electrolyte by the positive electrode at full charge also increases. To reduce this oxidation, current technologies often increase the content of fluorine compounds in the electrolyte to improve protection of both the positive and negative electrodes at high voltages.

[0032] However, fluorinated compounds, such as fluorinated additives and fluorinated lithium salts, are prone to undergoing de-fluorination reactions under the action of Lewis acids (such as PF5) produced by electrolyte decomposition, generating HF. In this case, after the electrochemical device is filled with electrolyte, the electrolyte comes into contact with the bare aluminum foil. The HF in the electrolyte may react with components in the aluminum foil, such as silicon dioxide or silicates, to generate byproduct fluorosilicone compounds. These byproduct fluorosilicone compounds diffuse inside the electrochemical device and accumulate in specific areas of the positive electrode (e.g., at the edge of the positive active material layer in the single-sided area of ​​the positive current collector), causing abnormalities in the positive electrode (e.g., obvious color difference in local areas, increased silicon content). The abnormal areas of the positive electrode cannot properly delithiate, and lithium ions escape from the edges of the abnormal areas, resulting in insufficient lithium intercalation sites on the corresponding negative electrode, leading to lithium plating and causing the electrochemical device to fail during charge-discharge cycles. To solve the problem of electrochemical device failure during charge-discharge cycles, this application provides an electrochemical device and an electronic device.

[0033] The first aspect of this application provides an electrochemical device, comprising an electrode assembly, an electrolyte, and a packaging bag containing the electrode assembly and the electrolyte. The electrolyte includes a fluorinated compound. The electrode assembly includes a positive electrode, a negative electrode, and a separator, with the separator disposed between the positive and negative electrode. The electrode assembly is composed of a positive electrode, a separator, and a negative electrode stacked together. The positive electrode includes a positive current collector, a positive active material layer, and an inactive material layer. The positive current collector is aluminum foil and includes silicon, with a silicon content of a% by mass (0.03 ≤ a ≤ 0.13). The positive current collector includes a first surface and a second surface opposite to each other. The positive current collector includes aluminum and silicon, with a silicon content of a% by mass (0.03 ≤ a ≤ 0.13). The positive electrode current collector has a single-sided region located at its end along its length. This single-sided region includes a first portion, the second surface of which is located on the outer surface of the electrode assembly. The first surface of the single-sided region is provided with a positive active material layer, and the second surface is provided with an inactive material layer. The inactive material layer includes at least one of an inorganic oxide or a non-metallic element. The length direction of the positive electrode current collector is along the winding direction of the wound electrode assembly.

[0034] It can be understood that the single-sided region is a segment of the positive electrode current collector. Therefore, the first surface of the single-sided region is the first surface of the positive electrode current collector, and the second surface of the single-sided region is the second surface of the positive electrode current collector. The first part is a segment or all of the single-sided region, that is, it is also a segment of the positive electrode current collector. Therefore, the first surface of the first part is the first surface of the positive electrode current collector, and the second surface of the first part is the second surface of the positive electrode current collector.

[0035] For example, the value of 'a' can be 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.10, 0.11, 0.12, 0.13, or any value between any two of the above ranges. If the mass percentage of silicon in the positive electrode current collector is too small (i.e., 'a' is less than 0.03), the aluminum foil will have insufficient strength and poor wear resistance, increasing the risk of cold-pressing breakage during the preparation of the positive electrode sheet. If the mass percentage of silicon in the positive electrode current collector is too large (i.e., 'm' is greater than 0.13), the positive electrode current collector will have excessive strength, leading to poor ductility and increasing the risk of breakage during subsequent winding processes (such as winding the positive electrode current collector, winding the positive electrode sheet, and winding during the preparation of electrode components). Simultaneously, the conductivity of the positive electrode current collector will decrease. By controlling the mass percentage of silicon in the positive electrode current collector within the above-mentioned range, the manufacturing abnormalities of the positive electrode current collector can be reduced, ensuring that the strength and toughness of the positive electrode current collector meet the requirements of its manufacturing process, and that it has good conductivity.

[0036] The single-sided region includes a first part, and the second surface of the first part is located on the outer surface of the electrode assembly. An inactive material layer is provided on the second surface of the single-sided region, so that the inactive material layer acts as an inert layer between the electrolyte and the positive electrode current collector, physically isolating the electrolyte and reducing the possibility of the electrolyte reacting with the positive electrode current collector to generate byproducts, thereby reducing the content of byproducts and reducing the risk of byproducts accumulating in specific areas or other areas of the positive electrode sheet.

[0037] Overall, by using the positive current collector provided in this application and setting an inactive material layer on the second surface of the single-sided region of the positive current collector, and in conjunction with the electrolyte of this application, the risk of abnormality of the positive electrode and the risk of lithium plating of the negative electrode are reduced after the electrochemical device has undergone charge-discharge cycles, thereby reducing the risk of failure of the electrochemical device during charge-discharge cycles.

[0038] This application does not specifically limit the type of aluminum foil; it can be any aluminum foil known in the art, as long as it can achieve the purpose of this application.

[0039] This application does not impose any particular restrictions on the method for controlling the mass percentage of silicon in the positive electrode current collector, as long as it achieves the purpose of this application. For example, it can be achieved by adjusting the ratio and type of each component in the positive electrode current collector.

[0040] Exemplary examples, in some embodiments of this application, such as Figures 1 to 5 As shown, the electrode assembly 001 has a wound structure, with the winding direction indicated by W. The electrode assembly 001 includes a positive electrode 100, a negative electrode 200, and a separator 300 disposed between the positive electrode 100 and the negative electrode 200. The positive electrode 100 includes a positive current collector 10, a positive active material layer 20, and an inactive material layer 50. The positive current collector 10 includes opposing first surfaces 10a and second surfaces 10b, and includes a single-sided region 30. The first surface 10a of the single-sided region 30 is provided with the positive active material layer 20, and the second surface 10b of the single-sided region 30 is provided with the inactive material layer 50. The single-sided region 30 includes a first portion 301, and the second surface 10b of the first portion 301 is located on the outer surface of the electrode assembly 001. Figures 1 to 3 As shown, the positive current collector 10 also includes a double-sided region 40, a first double-sided empty foil region 61 and a second double-sided empty foil region 62. The portion of the single-sided region 30 other than the first part 301 is not located on the outer surface of the electrode assembly 001, and the second surface 10b of the first part 301 is located on the outer surface of the electrode assembly 001. Figure 4 The positive current collector in the electrode assembly shown does not include the second double-sided empty foil region 62, which includes a double-sided region 40, a single-sided region 30, and a first double-sided empty foil region 61, as shown. Figure 4 and Figure 5As shown, the first part 301 can be understood as a single-sided area 30, and the second surface 10b of the first part 301 can also be understood as the second surface 10b of the single-sided area 30, that is, the second surface 10b of the single-sided area 30 is located on the outer surface of the electrode assembly 001.

[0041] Exemplary, in some embodiments of this application, the electrode assembly has a stacked structure, consisting of a positive electrode, a negative electrode, and a separator between the positive and negative electrode layers. The two outermost layers of the electrode assembly along its thickness direction are both single-sided positive electrode sheets. Specifically, as shown... Figure 6 As shown, a single-sided positive electrode includes a positive current collector 10, which includes a first surface 10a and a second surface 10b facing each other. The positive current collector 10 includes a single-sided region 30. The first surface 10a of the single-sided region 30 is provided with a positive active material layer 20, and the second surface 10b of the single-sided region 30 is provided with an inactive material layer 50. The single-sided region 30 includes a first portion 301, and the second surface 10b of the first portion 301 is located on the outer surface of the electrode assembly 001. The first portion 301 can be understood as the single-sided region 30, and the second surface 10b of the first portion 301 can also be understood as the second surface 10b of the single-sided region 30, meaning the second surface 10b of the single-sided region 30 is located on the outer surface of the electrode assembly. Typically, a positive electrode not located on the outer surface of the electrode assembly is a double-sided positive electrode. A double-sided positive electrode includes a positive current collector, which includes a first surface and a second surface facing each other, both of which are provided with a positive active material layer.

[0042] In some embodiments of this application, an inactive material layer covers the second surface of the single-sided region. It is understood that the entire area of ​​the second surface of the single-sided region is provided with the inactive material layer. Thus, the inactive material layer, acting as an inert layer between the electrolyte and the positive electrode current collector, completely isolates the electrolyte from the positive electrode current collector, further reducing the possibility of contact between them and further reducing the content of byproducts generated by the reaction between the electrolyte and the positive electrode current collector. This reduces the risk of byproducts accumulating in specific areas or other areas of the positive electrode. After charge-discharge cycles, the risk of abnormalities in the positive electrode is reduced, and the risk of lithium plating in the negative electrode is reduced, thereby reducing the risk of failure of the electrochemical device during charge-discharge cycles.

[0043] In some embodiments of this application, the inorganic oxide includes at least one of aluminum oxide, silicon oxide, calcium oxide, boehmite, or calcium carbonate, and the non-metallic element includes at least one of silicon, carbon, or boron. Using the aforementioned inorganic oxides and non-metallic elements better utilizes the inertness of the non-active material layer, physically isolating the electrolyte from the positive electrode current collector, thereby reducing the possibility of byproducts generated from the reaction between the electrolyte and the positive electrode current collector, and reducing the content of byproducts. This reduces the risk of byproducts accumulating in specific areas or other areas of the positive electrode. Consequently, after charge-discharge cycles, the risk of abnormalities in the positive electrode and the risk of lithium plating in the negative electrode are reduced, thus lowering the risk of failure of the electrochemical device during charge-discharge cycles.

[0044] In this application, there are no particular restrictions on the form in which non-metallic elements are added to the inactive material layer, as long as the purpose of this application can be achieved. For example, silicon can be added in the form of silicon powder, carbon in the form of conductive carbon, and boron in the form of elemental boron powder.

[0045] In some embodiments of this application, the Dv50 of the inorganic oxide is from 0.1 μm to 30 μm, and the Dv50 of the non-metallic element is from 0.1 μm to 10 μm. For example, the Dv50 of the inorganic oxide is 0.1 μm, 1 μm, 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, or any value between any two of the above ranges. The Dv50 of the non-metallic element is 0.1 μm, 1 μm, 5 μm, 10 μm, or any value between any two of the above ranges. Controlling the average particle size Dv50 of the inorganic oxide and non-metallic element within the above ranges makes it easier to control the thickness of the inactive material layer within a suitable range. This allows the inactive material layer to physically isolate the electrolyte and the positive electrode current collector, reducing the possibility of the electrolyte reacting with the positive electrode current collector to generate byproducts and reducing the content of byproducts. Thus, the risk of byproducts accumulating in specific areas or other areas of the positive electrode sheet is reduced. Therefore, after charge-discharge cycles, the risk of abnormality in the positive electrode and the risk of lithium plating in the negative electrode are reduced, thereby reducing the risk of failure of the electrochemical device during charge-discharge cycles.

[0046] In this application, Dv50 represents the particle size that, from the smallest particle size side, reaches 50% of the total volumetric particle size distribution of an inorganic oxide or non-metallic element on a volume-based basis.

[0047] In some embodiments of this application, the inactive material layer further includes an inactive material layer binder, which includes at least one of polytetrafluoroethylene, chloroprene rubber, nitrile rubber, styrene-butadiene rubber, carboxylated rubber, chlorosulfonated polyethylene rubber, phenolic resin, epoxy resin, or silicone resin. The mass ratio of the inactive material to the inactive material layer binder is (70–98):(2–30). For example, the mass ratio of the inactive material to the binder is 70:30, 75:25, 80:20, 85:15, 90:10, 95:5, 98:2, or any value between any two of the above ranges. By selecting the above-mentioned inactive material layer binder and controlling the mass ratio of the inactive material to the inactive material layer within the above range, it is more conducive to preparing an inactive material layer with good insulation effect, physically isolating the electrolyte from the positive electrode current collector, further reducing the possibility of contact between the electrolyte and the positive electrode current collector, and further reducing the content of by-products generated by the reaction between the electrolyte and the positive electrode current collector. This reduces the risk of byproducts accumulating in specific or other areas of the positive electrode. After charge-discharge cycles, the risk of abnormalities in the positive electrode and the risk of lithium plating in the negative electrode are reduced, thereby lowering the risk of failure of the electrochemical device during charge-discharge cycles.

[0048] In some embodiments of this application, the fluorinated compound includes a fluorinated additive, and the mass percentage of the fluorinated additive in the electrolyte is c%, where 0.1 ≤ c ≤ 40. For example, the value of c is 0.1, 2.0, 5.0, 10.0, 15.0, 20.0, 25.0, 30.0, 35.0, 40.0, or any value between any two of the above ranges. The inclusion of a fluorinated additive in the electrolyte, and the control of the mass percentage of the fluorinated additive in the electrolyte within the above range, can enhance the electrolyte's protective ability against the negative electrode, forming a uniform and dense protective film on the surface of the negative electrode, thereby improving the cycle performance of the electrochemical device. Simultaneously, it reduces the content of fluorosilicone compounds, byproducts generated from the reaction of HF in the electrolyte and silicon in the positive electrode current collector. This reduces the risk of abnormalities in the positive electrode, thereby reducing the risk of failure of the electrochemical device during charge-discharge cycles.

[0049] In some embodiments of this application, the thickness of the inactive material layer is b μm, where 3 ≤ b ≤ 20. For example, the value of b is 3, 4, 6, 8, 10, 12, 14, 16, 18, 20, or any value within any two of the above ranges. Controlling the thickness of the inactive material layer within the above range, without increasing the volume of the electrochemical device or affecting its energy density, makes it more advantageous for the inactive material layer to act as an inert layer between the electrolyte and the positive electrode current collector, isolating the electrolyte from the positive electrode current collector and reducing the possibility of contact between them. This reduces the content of byproducts generated by the reaction between the electrolyte and the positive electrode current collector. Consequently, the risk of byproducts accumulating in specific areas or other areas of the positive electrode is reduced. After charge-discharge cycles, the risk of abnormalities in the positive electrode and the risk of lithium plating in the negative electrode are reduced, thereby reducing the risk of failure of the electrochemical device during charge-discharge cycles. In some embodiments of this application, 3 ≤ b ≤ 10. This allows the inactive material layer to have a suitable thickness, meeting the need to reduce the risk of failure of the electrochemical device during charge-discharge cycles. It can also reduce the impact of the inactive material layer on the energy density of the electrochemical device. At the same time, it can also reduce the risk of the positive electrode sheet breaking due to the direct transition of the rolling equipment from the positive active material layer to the positive current collector during the rolling process after electrode coating.

[0050] This application does not impose any particular restrictions on the method for controlling the thickness of the inactive material layer, as long as it achieves the purpose of this application. For example, it can be achieved by controlling the Dv50 of the inactive material or the coating weight of the inactive material layer slurry.

[0051] In some embodiments of this application, 0.003 ≤ a / b ≤ 0.025. In some embodiments of this application, 0.003 ≤ a / b ≤ 0.02. For example, the value of a / b is 0.003, 0.005, 0.01, 0.015, 0.02, 0.025, or any value between any two of the above ranges. By controlling the value of a / b within the above ranges, the mass percentage of silicon in the positive electrode current collector and the thickness of the inactive material layer work synergistically. The thickness of the inactive material, without increasing the volume of the electrochemical device and affecting its energy density, fully exerts its insulating effect, isolating the electrolyte from the positive electrode current collector, reducing the possibility of the electrolyte reacting with the positive electrode current collector to produce byproducts, reducing the content of byproducts, and reducing the risk of byproducts accumulating in specific areas or other areas of the positive electrode sheet, thereby further reducing the risk of failure of the electrochemical device during charge-discharge cycles.

[0052] In some embodiments of this application, 0.1 ≤ c / b ≤ 13. In some embodiments of this application, 0.1 ≤ c / b ≤ 6.7. For example, the value of c / b is 0.1, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, or any value between any two of the above ranges. The inactive material layer, as an inert layer between the electrolyte and the positive electrode current collector, can physically isolate the electrolyte and control the value of c / b within the above range. The mass percentage of the fluorinated additive in the electrolyte and the thickness of the inactive material layer work synergistically to further reduce the possibility of the electrolyte reacting with the positive electrode current collector to produce byproducts, further reducing the content of byproducts and further reducing the risk of byproducts accumulating in specific areas or other areas of the positive electrode sheet, thereby further reducing the risk of failure of the electrochemical device during charge-discharge cycles.

[0053] In some embodiments of this application, the fluorinated additive includes at least one of fluoroethylene carbonate (FEC), bis(fluoromethyl)ethylene carbonate (DFEC), bis(difluoromethyl)ethylene carbonate, bis(trifluoromethyl)ethylene carbonate, bis(2-fluoroethyl)ethylene carbonate, bis(2,2-difluoroethyl)ethylene carbonate, bis(2,2,2-trifluoroethyl)ethylene carbonate, 2-fluoroethylmethylethylene carbonate, 2,2-difluoroethylmethylethylene carbonate, or 2,2,2-trifluoroethylmethylethylene carbonate. Using the above-mentioned types of fluorinated additives is more effective in reducing the oxidizing power of the positive electrode sheet on the electrolyte, forming a uniform and dense protective film on the surfaces of both the positive and negative electrode sheets, thus protecting them.

[0054] In some embodiments of this application, the fluorinated substances include fluorinated lithium salts, including lithium hexafluorophosphate, lithium difluorophosphate (LiPF2), lithium bis(trifluoromethane)sulfonylimide (LiTFSI), lithium bis(fluorosulfonylimide) (LiTSI), lithium tetrafluoroborate (LiBF4), lithium difluorooxalate borate (LiBF2(C2O4), LiDFOB), lithium hexafluoroantimonyate (LiSbF6), lithium hexafluoroarsenate (LiAsF6), lithium perfluorobutyl sulfonate (LiC4F9SO3), and lithium bis(sulfonylimide) (LiN(C x F 2x+1 SO2)(C y F 2y+1SO2), where x and y are positive integers and x≤10, y≤10), or at least one of lithium fluoride (LiF). The addition of fluorinated lithium salts is more conducive to providing high ionic conductivity, resulting in faster lithium-ion transport rates. Preferably, the fluorinated lithium salt includes at least one of LiPF6, LiTFSI, or LiTSI, which is more conducive to reducing the production cost of electrochemical devices. This application does not impose any particular limitation on the mass percentage of fluorinated lithium salt in the electrolyte, as long as the purpose of this application is achieved. For example, the mass percentage of fluorinated lithium salt in the electrolyte is 8% to 20%.

[0055] In some embodiments of this application, the electrode assembly has a stacked structure.

[0056] In some embodiments of this application, such as Figure 1 and Figure 2 As shown, the electrode assembly has a wound structure, and the positive electrode current collector 10 also includes a double-sided region 40. Along the winding direction W, the double-sided region 40 is sequentially connected to the single-sided region 30. A positive electrode active material layer 20 is disposed on both the first surface 10a and the second surface 10b of the double-sided region 40.

[0057] This application does not impose any particular limitation on the thickness of the positive electrode current collector, as long as it achieves the purpose of this application. For example, the thickness of the positive electrode current collector can be from 8 μm to 20 μm.

[0058] This application does not impose any particular restrictions on the preparation method of the positive electrode current collector. Any preparation method known in the art can be used, as long as it can achieve the purpose of this application.

[0059] This application does not impose any particular limitation on the compaction density of the positive and negative electrode sheets after cold pressing, as long as the purpose of this application can be achieved. For example, the compaction density of the positive and negative electrode sheets after cold pressing is 3.9 g / cm³. 3 Up to 4.3 g / cm 3 .

[0060] The positive electrode active material layer of this application includes a positive electrode active material. This application does not impose any particular limitation on the type of positive electrode active material, as long as it achieves the purpose of this application. For example, the positive electrode active material may include at least one of lithium nickel cobalt manganese oxide (e.g., common NCM811, NCM622, NCM523, NCM111), lithium nickel cobalt aluminum oxide, lithium iron phosphate, lithium-rich manganese-based materials, lithium cobalt oxide (LiCoO2), lithium manganese oxide, lithium manganese iron phosphate, or lithium titanate. In this application, the positive electrode active material may also include non-metallic elements, such as fluorine, phosphorus, boron, chlorine, silicon, sulfur, etc., which can further improve the stability of the positive electrode active material. Optionally, the positive electrode active material layer also includes a conductive agent and a binder. This application does not impose any particular limitation on the types of conductive agents and binders in the positive electrode active material layer, as long as they achieve the purpose of this application. This application does not impose any particular limitation on the mass ratio of the positive electrode active material, conductive agent, and binder in the positive electrode active material layer; those skilled in the art can choose according to actual needs, as long as the purpose of this application is achieved. For example, the mass ratio of positive electrode active material, conductive agent and binder in the positive electrode active material layer is (97.5~97.9):(0.9~1.7):(1.0~2.0).

[0061] This application does not impose any particular limitation on the thickness of the positive electrode active material layer, as long as it achieves the purpose of this application. For example, the thickness of the positive electrode active material layer can be from 30 μm to 120 μm.

[0062] The negative electrode sheet of this application includes a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector. The aforementioned "negative electrode active material layer disposed on at least one surface of the negative electrode current collector" means that the negative electrode active material layer can be disposed on one surface of the negative electrode current collector along its thickness direction, or on two surfaces of the negative electrode current collector along its thickness direction. It should be noted that the "surface" here can be the entire area of ​​the negative electrode current collector or only a part of it; this application has no particular limitation, as long as the purpose of this application is achieved. This application has no particular limitation on the negative electrode current collector, as long as the purpose of this application is achieved. For example, the negative electrode current collector can include copper foil, copper alloy foil, nickel foil, titanium foil, nickel foam, or copper foam, etc. The negative electrode active material layer includes a negative electrode active material. This application has no particular limitation on the type of negative electrode active material, as long as the purpose of this application is achieved. For example, the negative electrode active material may include at least one of natural graphite, artificial graphite, soft carbon, hard carbon, mesophase carbon microspheres, tin-based materials, silicon-based materials, lithium titanate, transition metal nitrides, or natural flake graphite. Optionally, the negative electrode active material layer may also include at least one of a conductive agent, a stabilizer, and a binder. This application does not impose any particular limitation on the types of conductive agents, stabilizers, and binders in the negative electrode active material layer, as long as the purpose of this application is achieved. This application does not impose any particular limitation on the mass ratio of the negative electrode active material, conductive agent, stabilizer, and binder in the negative electrode active material layer, as long as the purpose of this application is achieved. For example, the mass ratio of the negative electrode active material, conductive agent, stabilizer, and binder in the negative electrode active material layer may be (97–98):(0.5–1.5):(0.5–1.5):(1.0–1.9).

[0063] This application does not impose any particular limitations on the thickness of the negative electrode current collector and the negative electrode active material layer, as long as the purpose of this application can be achieved. For example, the thickness of the negative electrode current collector can be 5 μm to 20 μm, and the thickness of the negative electrode active material layer can be 30 μm to 120 μm.

[0064] The electrolyte of this application also includes non-aqueous solvents. This application does not have any particular limitation on non-aqueous solvents, as long as they can achieve the purpose of this application. For example, the non-aqueous solvent may include, but is not limited to, at least one of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), methyl ethyl carbonate (MEC), ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), ethyl acetate, n-propyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, or propyl propionate.

[0065] This application does not impose any particular limitation on the mass percentage of non-aqueous solvents in the electrolyte, as long as the purpose of this application can be achieved. For example, the mass percentage of non-aqueous solvents in the electrolyte can be 70% to 99%.

[0066] This application does not impose any particular restrictions on the diaphragm and packaging bag; they can be any diaphragm and packaging bag known in the art, as long as they can achieve the purpose of this application.

[0067] The electrochemical device described in this application is not particularly limited and may include any device in which an electrochemical reaction occurs. In some embodiments, the electrochemical device may include, but is not limited to, lithium metal secondary batteries, lithium-ion secondary batteries, sodium-ion secondary batteries, lithium polymer secondary batteries, or lithium-ion polymer secondary batteries.

[0068] This application does not impose any particular restrictions on the preparation method of the electrochemical device; any preparation method known in the art can be used, as long as it can achieve the purpose of this application.

[0069] A second aspect of this application provides an electronic device that includes the electrochemical device provided in the first aspect of this application. Therefore, the beneficial effects of the electrochemical device provided in the first aspect of this application can be obtained.

[0070] The electronic device described in this application is not particularly limited and can be any electronic device known in the prior art. In some embodiments, the electronic device may include, but is not limited to: laptop computers, pen input computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, stereo headphones, video recorders, LCD TVs, portable cleaners, portable CD players, mini CDs, transceivers, electronic notebooks, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, electric bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, large household batteries, lithium-ion capacitors, etc.

[0071] Example

[0072] The embodiments and comparative examples provided below illustrate the implementation of this application in more detail. Various tests and evaluations were conducted according to the methods described below.

[0073] Test methods and equipment:

[0074] Detection of different element contents:

[0075] The lithium-ion batteries of each embodiment and comparative example were fully discharged and disassembled. The positive electrode active material layer on the surface of the positive electrode current collector was washed away with N-methylpyrrolidone, and finally the positive electrode current collector was cleaned with DMC. After cleaning, the positive electrode current collector was tested by inductively coupled plasma optical emission spectrometry (ICP) to obtain the content of aluminum and silicon elements.

[0076] Detection of fluorine additive content:

[0077] Lithium-ion batteries from each example and comparative example were centrifuged to obtain 10 mL of electrolyte. The mass percentage of fluorinated additives in the electrolyte could be obtained by gas chromatography.

[0078] Test of average particle size Dv50:

[0079] Dv50 was determined using a laser particle size analyzer (such as Malvern Master Size 3000) in accordance with the national standard GB / T 19077-2016 (Laser Diffraction Method for Particle Size Distribution).

[0080] Detection of abnormalities in the positive electrode:

[0081] After fully discharging and disassembling the lithium-ion batteries of each embodiment and comparative example, the positive electrode was visually inspected. An abnormal appearance (also called an abnormal area) with discolored markings was observed, meaning a significant color difference between the localized area and its surrounding area. X-ray energy dispersive spectroscopy (EDS) was performed on the positive electrode in the abnormal area. If the silicon content in the abnormal area was >2 wt%, the positive electrode was considered abnormal. If no discolored markings were observed on the positive electrode, it was considered normal, and EDS testing was not performed.

[0082] An abnormal appearance of the positive electrode and a silicon content >2wt% in the abnormal area are used to characterize the failure of the electrochemical device during charge-discharge cycles.

[0083] Determining whether there are any abnormalities in the manufacturing of the positive electrode:

[0084] In the <Preparation of Positive Electrode Sheet> of each embodiment or comparative example, during the cold pressing process of the positive electrode sheet, it is determined whether the positive current collector breaks, the positive electrode sheet breaks, the positive active material layer falls off, or the laser positioning of the positive electrode sheet fluctuates greatly.

[0085] Example 1-1

[0086] <Preparation of the positive electrode>

[0087] The inactive material inorganic oxide alumina and the inactive material layer binder polytetrafluoroethylene (weight average molecular weight 500,000) were mixed at a mass ratio of 70:30 to obtain the inactive material layer slurry. The Dv50 of the inorganic oxide was 0.1 μm.

[0088] The positive electrode active material LiCoO2, conductive agent conductive carbon black, and binder polyvinylidene fluoride (PVDF) were mixed in a mass ratio of 96:2:2. N-methylpyrrolidone (NMP) was added, and the mixture was stirred evenly under vacuum to obtain a positive electrode slurry with a solid content of 70 wt%.

[0089] The positive electrode slurry is uniformly coated onto... Figure 5 The positive electrode current collector 10, as shown, has a double-sided region 40 and a single-sided region 30 on its first surface 10a, which is then dried at 120°C for 1 hour. The above steps are repeated on the second surface 10b of the double-sided region 40 of the positive electrode current collector 10. An inactive material layer slurry is then coated onto the second surface 10b of the single-sided region 30 of the positive electrode current collector 10, so that the inactive material layer 50 covers the second surface 10b of the single-sided region 30, thus obtaining the following... Figure 5 The positive electrode sheet shown is dried at 120°C for 1 hour, then cold-pressed, cut, and slit to obtain a positive electrode sheet with dimensions of 78mm × 875mm. Specifically, the dimensions of the first surface 10a of the double-sided region 40 are 78mm × 780mm, the dimensions of the first surface 10a of the single-sided region 30 are the same as those of the first surface 10a of the first portion 31, which is 78mm × 80mm, and the dimensions of the first empty foil region 61 are 78mm × 15mm. The thickness of the positive active material layer 20 is 100μm, the thickness of the inactive material layer 50 is bμm = 3μm, and the thickness of the positive current collector 10 is 10μm. The mass percentage of silicon in the positive current collector 10 is a% = 0.03%.

[0090] <Preparation of Negative Electrode Sheets>

[0091] Graphite (anode active material), styrene-butadiene rubber (binder), and sodium carboxymethyl cellulose (thickener) were mixed in a mass ratio of 97.4:1.4:1.2. Deionized water was added, and the mixture was stirred evenly under vacuum to obtain a cathode slurry with a solid content of 75 wt%. The cathode slurry was uniformly coated onto one surface of a 12 μm thick copper foil current collector and then dried at 120 °C for 1 hour to obtain a cathode with a single-sided coating of 130 μm thick and a cathode active material layer. The above steps were repeated on the other surface of the cathode current collector to obtain a cathode sheet with a double-sided coating of cathode active material. After drying at 120 °C for 1 hour, the cathode sheet was cold-pressed, cut, and slit to obtain a cathode sheet with a size of 74 mm × 867 mm.

[0092] <Preparation of Electrolyte>

[0093] In an argon-atmospheric glove box with a water content of <10 ppm, EC, PC, and DEC were mixed in a mass ratio of 1:1:1 to obtain an organic solvent. Then, a fluorinated lithium salt, LiPF6, was added to the organic solvent to obtain a basic electrolyte. A fluorinated additive, FEC, was added to the basic electrolyte to obtain the final electrolyte. The mass percentage of the fluorinated lithium salt, LiPF6, in the electrolyte was 13.8%, and the mass percentage of the fluorinated additive, FEC, was c% = 38%.

[0094] <Preparation of the diaphragm>

[0095] A porous polyethylene film with a thickness of 7μm is used.

[0096] <Preparation of Lithium-ion Batteries>

[0097] The positive electrode, separator, and negative electrode prepared above are stacked in sequence, with the separator positioned between the positive and negative electrode to provide separation. The electrodes are then wound to obtain the desired shape. Figure 4 The electrode assembly with the spiral wound structure shown is then placed in an aluminum-plastic film packaging bag, dried, and injected with electrolyte. After vacuum sealing, settling, formation, degassing, and edge trimming, a lithium-ion battery is obtained.

[0098] Examples 1-2 to Examples 1-9

[0099] Except for adjusting the relevant preparation parameters according to Table 1, the rest is the same as in Example 1-1.

[0100] Examples 2-1 to 2-6

[0101] Except for adjusting the relevant preparation parameters according to Table 2, the rest is the same as in Examples 1-1.

[0102] Comparative Example 1

[0103] Besides the positive electrode sheet preparation, the positive current collector, such as... Figure 7 As shown in the positive current collector 10, the first part, i.e., the second surface of the single-sided region, does not have a non-active material layer, and the resulting positive electrode sheet is as follows. Figure 7 Except for the above, the rest is the same as in Example 1.

[0104] Comparative Examples 2 to 3

[0105] Except for adjusting the relevant preparation parameters according to Table 1, the rest is the same as in Example 1-1.

[0106] Comparative Example 4

[0107] Except for adjusting the relevant preparation parameters according to Table 1, the rest are the same as Comparative Example 1. The relevant preparation parameters and performance tests of each example and comparative example are shown in Tables 1 and 2.

[0108] Table 1

[0109]

[0110]

[0111] Note: In Table 1, “N” represents the mass ratio of inactive material to inactive material layer binder; “\” in Table 1 indicates no corresponding parameter; “-” in Table 1 indicates that the positive electrode sheet has no abnormalities and there is no need to test the Si content.

[0112] As can be seen from Examples 1-1 to 1-9 and Comparative Examples 1 to 4, lithium-ion batteries using a positive electrode current collector with a silicon content of a% within the scope of this application, a non-active material layer on the second surface of a single-sided region of the positive electrode current collector, and an electrolyte of this application, exhibit no abnormal appearance of the positive electrode after charge-discharge cycles. This indicates that the risk of failure during charge-discharge cycles is reduced, and the positive electrode does not exhibit manufacturing abnormalities or only large laser positioning fluctuations, thus not affecting its performance. However, in Comparative Examples 1 to 4, lithium-ion batteries using a positive electrode current collector without a non-active material layer on the second surface of a single-sided region, and / or with a silicon content of a% outside the scope of this application, exhibit abnormal appearance of the positive electrode, a Si content greater than 2 wt% in the abnormal area, large laser positioning fluctuations, and / or cold-pressing fracture. This indicates that the risk of failure during charge-discharge cycles is not reduced.

[0113] The mass percentage (a%) of silicon in the positive electrode current collector typically affects the probability of lithium-ion battery failure during charge-discharge cycles. As can be seen from Examples 1-1 to 1-3, Comparative Examples 2 and 3, lithium-ion batteries using a silicon mass percentage (a%) in the positive electrode current collector within the scope of this application exhibit no abnormal appearance on the positive electrode, indicating a reduced risk of failure during charge-discharge cycles. Furthermore, the positive electrode only suffers from large fluctuations in laser positioning, which does not affect its performance.

[0114] The type of inactive material typically affects the probability of lithium-ion battery failure during charge-discharge cycles. As can be seen from Examples 1-2 and 1-4, and Examples 1-5 and 1-7, the lithium-ion batteries using inactive materials within the scope of this application do not exhibit abnormal appearances on the positive electrode, indicating a reduced risk of failure during charge-discharge cycles. Furthermore, the positive electrode does not exhibit manufacturing abnormalities or only large laser positioning fluctuations, thus not affecting its performance. In Examples 1-5 and 1-7, when non-metallic elements, particularly carbon (added as conductive carbon), were used as the inactive material, no large laser positioning fluctuations occurred during the positive electrode manufacturing process. This means that during continuous production of the positive electrode, after the inactive material layer is coated onto the surface of the positive current collector, the laser accurately positions itself at the edge of the inactive material layer, coating to form the positive active material layer, thereby reducing fluctuations in the initial coating position of the positive active material layer. This simplifies the continuous production process of the positive electrode and reduces the cost of manually adjusting the laser positioning of the positive active material layer.

[0115] The Dv50 of inorganic oxides and the Dv50 of non-metallic elements typically affect the probability of failure of lithium-ion batteries during charge-discharge cycles. As can be seen from Examples 1-2, 1-5 to 1-7, the lithium-ion batteries using Dv50 of inorganic oxides and Dv50 of non-metallic elements within the scope of this application exhibit no abnormal appearance of the positive electrode, indicating that the risk of failure during charge-discharge cycles is reduced. Furthermore, the positive electrode does not exhibit manufacturing abnormalities or only large fluctuations in laser positioning, thus not affecting the performance of the positive electrode.

[0116] The mass ratio of inactive materials to the inactive material layer binder typically affects the probability of lithium-ion battery failure during charge-discharge cycles. As can be seen from Examples 1-2, 1-8, and 1-9, the lithium-ion batteries within the scope of this application using the appropriate mass ratio of inactive materials to the inactive material layer binder exhibit no abnormal appearance on the positive electrode, indicating a reduced risk of failure during charge-discharge cycles. Furthermore, the positive electrode shows no manufacturing abnormalities and does not affect its performance.

[0117] Table 2

[0118]

[0119] Note: The “-” in Table 2 indicates that there is no abnormality in the positive electrode and there is no need to test the Si content.

[0120] The thickness 'b' of the inactive material layer typically affects the probability of failure of lithium-ion batteries during charge-discharge cycles. As can be seen from Examples 1-2, 2-1 to 2-2, lithium-ion batteries using an inactive material layer thickness 'b' within the scope of this application exhibit no abnormal appearance on the positive electrode, or have abnormal appearance but with Si content in the abnormal area less than 2 wt%. This indicates that the risk of failure of the lithium-ion battery during charge-discharge cycles is reduced, and the positive electrode does not exhibit any manufacturing abnormalities.

[0121] The a / b ratio typically affects the probability of lithium-ion battery failure during charge-discharge cycles. As can be seen from Examples 1-2, 2-1 to 2-3, lithium-ion batteries using a / b ratios within the scope of this application exhibit no abnormal appearance on the positive electrode, or if the positive electrode does have an abnormal appearance, the Si content in the abnormal area is less than 2wt%. This indicates that the risk of lithium-ion battery failure during charge-discharge cycles is reduced, and the positive electrode does not exhibit any manufacturing abnormalities.

[0122] The mass percentage (c%) of fluorinated additives in the electrolyte typically affects the probability of lithium-ion battery failure during charge-discharge cycles. As can be seen from Examples 1-2, 2-4, and 2-5, lithium-ion batteries using fluorinated additives at a mass percentage (c%) within the scope of this application exhibit no abnormal appearance on the positive electrode, or have abnormal appearance but with Si content in the abnormal area less than 2 wt%. This indicates that the risk of lithium-ion battery failure during charge-discharge cycles is reduced, and the positive electrode does not exhibit any manufacturing abnormalities.

[0123] The type of fluorinated additives typically affects the probability of lithium-ion battery failure during charge-discharge cycles. As can be seen from Examples 1-2 and Examples 2-6, when fluorinated additives are selected for lithium-ion batteries within the scope of this application, the positive electrode plate exhibits no abnormal appearance, or the positive electrode plate has an abnormal appearance but the Si content in the abnormal area is less than 2 wt%. This indicates that the risk of lithium-ion battery failure during charge-discharge cycles is reduced, and the positive electrode plate does not exhibit any manufacturing abnormalities.

[0124] The above description is only a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. An electrochemical device comprising an electrode assembly, an electrolyte, and a packaging bag containing the electrode assembly and the electrolyte, wherein the electrolyte comprises a fluorine-containing compound, and the electrode assembly comprises a positive electrode, a negative electrode, and a separator, the separator being disposed between the positive electrode and the negative electrode; The positive electrode sheet includes a positive current collector, a positive active material layer, and an inactive material layer. The positive current collector is an aluminum foil and includes silicon. The mass percentage of silicon in the positive current collector is a%, and 0.03 ≤ a ≤ 0.

13. The positive current collector includes a first surface and a second surface opposite to each other; the positive current collector has a single-sided region, the single-sided region includes a first portion, the second surface of the first portion is located on the outer surface of the electrode assembly, the first surface of the single-sided region is provided with the positive active material layer, and the second surface of the single-sided region is provided with the inactive material layer; the inactive material layer includes an inactive material, which includes at least one of inorganic oxides or non-metallic elements; The fluorinated compound includes a fluorinated additive, and the fluorinated additive has a mass percentage of c% in the electrolyte, where 0.1 ≤ c ≤ 40.0%.

2. The electrochemical device according to claim 1, wherein, The inactive material layer covers the second surface of the single-sided region.

3. The electrochemical device according to claim 1, wherein, The inorganic oxide includes at least one of aluminum oxide, silicon dioxide, calcium oxide, boehmite, or calcium carbonate; and / or, The non-metallic element includes at least one of silicon, carbon, or boron.

4. The electrochemical device according to claim 1, wherein, The inorganic oxide has a Dv50 of 0.1 μm to 30 μm, and / or the nonmetallic element has a Dv50 of 0.1 μm to 10 μm.

5. The electrochemical device according to claim 1, wherein, The inactive material layer further includes an inactive material layer adhesive, which includes at least one of polytetrafluoroethylene, chloroprene rubber, nitrile rubber, styrene-butadiene rubber, carboxylated rubber, chlorosulfonated polyethylene rubber, phenolic resin, epoxy resin, or silicone resin. The mass ratio of the inactive material to the adhesive of the inactive material layer is (70~98):(2~30).

6. The electrochemical device according to claim 1, wherein, The negative electrode sheet includes a negative current collector and a negative active material layer disposed on at least one surface of the negative current collector. The negative active material layer includes a negative active material, which includes a silicon-based material.

7. The electrochemical device according to claim 1, wherein, The thickness of the inactive material layer is b μm, where 3 ≤ b ≤ 20.

8. The electrochemical device according to claim 7, wherein, 3≤b≤10。 9. The electrochemical device according to claim 7, wherein, 0.003≤a / b≤0.

025.

10. The electrochemical device according to claim 7, wherein, 0.003≤a / b≤0.

02.

11. The electrochemical device according to claim 7, wherein, 0.1≤c / b≤13.

12. The electrochemical device according to claim 7, wherein, 0.1≤c / b≤6.

7.

13. The electrochemical device according to claim 1, wherein, The fluorinated additive includes at least one of fluoroethylene carbonate, bis(fluoromethyl)ethylene carbonate, bis(difluoromethyl)ethylene carbonate, bis(trifluoromethyl)ethylene carbonate, bis(2-fluoroethyl)ethylene carbonate, bis(2,2-difluoroethyl)ethylene carbonate, bis(2,2,2-trifluoroethyl)ethylene carbonate, 2-fluoroethylmethylethylene carbonate, 2,2-difluoroethylmethylethylene carbonate, or 2,2,2-trifluoroethylmethylethylene carbonate.

14. The electrochemical device according to claim 1, wherein, The fluorinated compound includes fluorinated lithium salts, which include at least one of lithium hexafluorophosphate, lithium difluorophosphate, lithium bis(trifluoromethane)sulfonylimide, lithium bis(fluorosulfonylimide), lithium tetrafluoroborate, lithium difluorooxalate borate, lithium hexafluoroantimonyate, lithium hexafluoroarsenate, lithium perfluorobutyl sulfonate, or lithium fluoride.

15. The electrochemical device according to claim 1, wherein, The electrode assembly has a stacked structure; or... The electrode assembly has a wound structure, and the positive current collector further includes a double-sided region. Along the winding direction, the double-sided region and the single-sided region are connected in sequence.

16. An electronic device comprising the electrochemical device according to any one of claims 1 to 15.

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