Electrode assembly, battery and electric device

Abstract

The invention relates to the technical field of batteries, in particular to an electrode assembly, a battery and an electric device. The electrode assembly comprises a positive plate, a negative plate and a diaphragm positioned between the positive plate and the negative plate, the positive plate comprises a positive current collector and a positive coating; the positive electrode coating comprises a positive electrode active material region and a positive electrode mixing region which are distributed in a staggered manner in the width direction of the positive plate; the positive electrode active material region comprises a lithium-containing positive electrode active material; the positive electrode mixing region comprises a lithium-containing positive electrode active material and a lithium-free positive electrode non-active material; the negative plate comprises a negative current collector and a negative coating; negative electrode active material areas and negative electrode non-active material areas are distributed on the negative electrode coating in the width direction of the negative electrode sheet in a staggered manner; the negative active material area is opposite to the positive active material area, and the negative non-active material area is opposite to the positive mixing area. According to the electrode assembly provided by the invention, the power density of the battery can be improved, and the lithium precipitation phenomenon on the surface of the negative electrode is reduced, so that the harm caused by overcharge is inhibited to a certain extent.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and more specifically, to an electrode assembly, a battery, and an electrical device. Background Technology

[0002] Lithium-ion batteries play a crucial role in portable electronics, transportation, and large-scale energy storage due to their high energy density, high power density, and long lifespan. They are now ubiquitous in daily life, including in mobile phones, electric vehicles, and grid energy storage. Currently, various high-energy-density lithium-ion batteries can meet the range requirements of electric vehicles to some extent, but charging time remains a bottleneck for widespread adoption compared to traditional gasoline vehicles. During high-current charging, a large number of lithium ions rapidly and simultaneously escape from the positive electrode and embed into the negative electrode, causing polarization. If the negative electrode potential drops below 0V, lithium ions cannot embed into the negative electrode and instead precipitate on its surface, leading to increased irreversible capacity decay and potentially serious safety issues. Therefore, optimizing the structure and material system of the positive and negative electrodes is crucial for improving the diffusion capacity of lithium ions. Summary of the Invention

[0003] In view of this, the present invention aims to address, to a certain extent, the technical problems in the related art. To this end, the present invention provides an electrode assembly, a battery, and an electrical device, which, by improving the structure and composition of the electrode assembly, improves the diffusion capacity of lithium ions, increases the power density of the battery, and reduces lithium deposition on the negative electrode surface, thereby suppressing the hazards caused by overcharging to a certain extent.

[0004] To solve the above-mentioned technical problems, the present invention is implemented as follows: According to one aspect of the present invention, an electrode assembly is provided, comprising a positive electrode, a negative electrode, and a separator located between the positive electrode and the negative electrode; The positive electrode sheet includes a positive current collector and a positive electrode coating disposed on at least one surface of the positive current collector; the positive electrode coating includes a positive active material region and a positive mixed region; the positive active material region and the positive mixed region are staggered along the width direction of the positive electrode sheet; the positive active material region includes a positive active material; the positive mixed region includes a positive active material and a positive inactive material; the positive active material includes lithium, and the positive inactive material does not include lithium; The negative electrode sheet includes a negative electrode current collector and a negative electrode coating disposed on at least one side surface of the negative electrode current collector; the negative electrode coating includes a first sublayer; the first sublayer includes a negative electrode active material region and a negative electrode inactive material region; the negative electrode active material region and the negative electrode inactive material region are staggered in the width direction of the negative electrode sheet; the negative electrode active material region includes a first negative electrode active material; the negative electrode inactive material region includes a negative electrode inactive material; the potential of the first negative electrode active material relative to lithium is <0.5V, and the potential of the negative electrode inactive material relative to lithium is >0.5V; The negative electrode active material region is arranged opposite to the positive electrode active material region, and the negative electrode inactive material region is arranged opposite to the positive electrode mixed region.

[0005] In some embodiments, the positive electrode mixing region is provided on both sides of the positive electrode sheet in the width direction.

[0006] In some embodiments, the negative electrode inactive material regions are provided on both sides of the negative electrode sheet in the width direction.

[0007] In some embodiments, the width of the positive electrode is less than or equal to the width of the negative electrode.

[0008] In some of these embodiments, the total width of the positive electrode active material region is greater than or equal to the total width of the positive electrode mixing region.

[0009] In some of these embodiments, the total width of the negative electrode active material region is greater than or equal to the total width of the negative electrode inactive material region.

[0010] In some of these embodiments, the width of a single negative electrode inactive material region is greater than or equal to the width of a single positive electrode mixing region.

[0011] In some embodiments, the coverage area of ​​the negative electrode coating is greater than or equal to the coverage area of ​​the positive electrode coating.

[0012] In some embodiments, the mass ratio of the positive electrode active material to the positive electrode inactive material in the positive electrode mixing region is ≤3 / 7.

[0013] In some of these embodiments, the positive electrode active material includes at least one of lithium iron phosphate, ternary nickel cobalt manganese, lithium manganese oxide, and lithium cobalt oxide.

[0014] In some embodiments, the positive electrode inactive material and the negative electrode inactive material each independently include at least one of carbon-based materials, transition metal compounds, and conductive polymer materials.

[0015] In some of these embodiments, the first negative electrode active material includes at least one of graphite, silicon oxide, silicon carbon, and pure silicon.

[0016] In some embodiments, the negative electrode coating further includes a second sublayer located between the negative electrode current collector and the first sublayer; the second sublayer includes a second negative electrode active material.

[0017] In some embodiments, the second negative electrode active material includes at least one of graphite, silicon carbide, silicon oxide, and pure silicon.

[0018] In some embodiments, the thickness ratio of the first sublayer to the second sublayer is 0.5 to 1.5.

[0019] In some embodiments, the expansion coefficient of the second negative electrode active material is less than that of the first negative electrode active material.

[0020] In some embodiments, the diaphragm includes a base membrane and a coating disposed on at least one surface of the base membrane; the coating includes at least one of alumina, boehmite, and a solid electrolyte.

[0021] According to another aspect of the present invention, the present invention provides a battery comprising the electrode assembly described above.

[0022] According to another aspect of the present invention, an electrical device is provided, comprising the battery described in the above technical solution.

[0023] Implementing the technical solution of the present invention has at least the following beneficial effects: 1. This invention improves the structure and composition of the electrode assembly by setting a positive active material region and a positive mixed region on the positive electrode sheet, and setting a negative active material region and a negative inactive material region on the negative electrode sheet, thereby achieving better overall interaction. While ensuring that the battery energy density is not excessively sacrificed, the diffusion ability of lithium ions is improved, which can greatly improve the power density of the battery, reduce the lithium deposition phenomenon on the negative electrode surface, and thus suppress the harm caused by overcharging to a certain extent.

[0024] 2. By further optimizing the positional relationship and material composition of the positive electrode active material region and the positive electrode mixed region, as well as the negative electrode active material region and the negative electrode inactive material region, on the one hand, electrochemical reactions can be effectively reduced, active lithium loss can be reduced, and battery life can be extended; on the other hand, after lithium ions are extracted from the positive electrode active material region and the positive electrode mixed region, they can be rapidly responded to in the corresponding negative electrode layer. In addition to the active main material, the high specific surface area and porous structure of the carbon-based material in the inactive region can quickly accommodate a large number of lithium ions. At the same time, the positive and negative electrode sheets are equipped with carbon-based materials, transition metal compounds or conductive polymer materials, which can store a large amount of charge. During discharge, the ions stored in the carbon-based material return to the electrolyte and the positive electrode through the reverse reaction of the redox reaction, and the stored charge is released through the external circuit, improving the battery discharge rate performance; during charging, the charging requirements can also be quickly met.

[0025] 3. By setting a functional coating on the separator, the free energy of the separator surface is higher than that of the negative electrode material, thereby forming a self-built electric field, accelerating the migration of lithium ions, and further improving the performance of the battery.

[0026] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0027] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0028] Figure 1 This is a schematic diagram of the positive electrode structure of an electrode assembly provided by the present invention.

[0029] Figure 2 This is a schematic diagram of the negative electrode structure of an electrode assembly provided by the present invention.

[0030] Figure 3 This is a schematic diagram of the positive electrode plate in the electrode assembly provided in Example 1.

[0031] Figure 4 This is a schematic diagram of the structure of the positive electrode in the electrode assembly provided in Example 11.

[0032] Explanation of reference numerals in the attached figures: 10 - Positive electrode sheet; 110 - Positive electrode current collector; 120 - Positive electrode coating; 121 - Positive electrode mixing region; 122 - Positive electrode active material region.

[0033] 20 - Negative electrode sheet; 210 - Negative electrode current collector; 220 - Negative electrode coating; 2210 - First sublayer of negative electrode; 2201 - Active material region of negative electrode; 2202 - Inactive material region of negative electrode; 2220 - Second sublayer of negative electrode.

[0034] The accompanying drawings have illustrated specific embodiments of the invention, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the invention in any way, but rather to illustrate the concept of the invention to those skilled in the art through reference to particular embodiments. Detailed Implementation

[0035] The present application will be further described below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the present application.

[0036] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges or individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0037] In the description of this application, "same chemical composition" should be interpreted broadly, that is, the main components of the two have the same chemical composition, or the two have substantially the same chemical composition, but may have errors or impurities within the acceptable range that can be understood by those skilled in the art.

[0038] In the description of this application, "A and / or B" can include any of the cases of A alone, B alone, or A and B, where A and B are merely examples and can be any technical feature connected by "and / or" in this application.

[0039] Unless otherwise specified, the terms "comprising" and "including" as used in this invention can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0040] Unless otherwise specified, all embodiments and optional embodiments of the present invention can be combined with each other to form new technical solutions.

[0041] Unless otherwise specified, all technical features and optional technical features of this invention can be combined to form new technical solutions.

[0042] Unless otherwise specified, all steps of the present invention may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order; for example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0043] Currently, in traditional lithium-ion batteries, high-current charging leads to the formation of lithium dendrites and intensifies internal polarization, resulting in a reduced proportion of lithium ions actually entering the electrode materials. This causes irreversible capacity decay, decreases battery performance, significantly impairs battery life, and poses safety risks. Therefore, optimizing the structure and material system of the positive and negative electrodes to improve the diffusion capacity of lithium ions in the battery has become a pressing technical challenge for those skilled in the art.

[0044] Based on this, the inventors of this invention have obtained an electrode assembly with dual-reaction characteristics by improving the structure and composition of the electrode assembly. This assembly can improve the diffusion ability of lithium ions, increase the power density of the battery, and reduce lithium deposition on the negative electrode surface, thereby suppressing the hazards caused by overcharging to a certain extent. Specifically, this invention adopts the following technical solution: According to one aspect of the present invention, an electrode assembly is provided, see [link to previous invention]. Figures 1-2 As shown, the electrode assembly includes a positive electrode 10, a negative electrode 20, and a separator located between the positive electrode 10 and the negative electrode 20; The positive electrode sheet 10 includes a positive current collector 110 and a positive electrode coating 120 disposed on at least one side surface of the positive current collector 110; the positive electrode coating 120 includes a positive electrode active material region 122 and a positive electrode mixing region 121; the positive electrode active material region 122 and the positive electrode mixing region 121 are staggered in the width direction of the positive electrode sheet 10; the positive electrode active material region 122 includes a positive electrode active material; the positive electrode mixing region 121 includes a positive electrode active material and a positive electrode inactive material; the positive electrode active material includes lithium, and the positive electrode inactive material does not include lithium; The negative electrode sheet 20 includes a negative electrode current collector 210 and a negative electrode coating 220 disposed on at least one side surface of the negative electrode current collector 210; the negative electrode coating 220 includes a first sub-layer 2210; the first sub-layer 2210 includes a negative electrode active material region 2201 and a negative electrode inactive material region 2202; the negative electrode active material region 2201 and the negative electrode inactive material region 2202 are staggered in the width direction of the negative electrode sheet 20; the negative electrode active material region 2201 includes a first negative electrode active material; the negative electrode inactive material region 2202 includes a negative electrode inactive material; the potential of the first negative electrode active material relative to lithium is <0.5V, and the potential of the negative electrode inactive material relative to lithium is >0.5V; The negative electrode active material region 2201 is disposed opposite to the positive electrode active material region 122, and the negative electrode inactive material region 2202 is disposed opposite to the positive electrode mixing region 121.

[0045] In a specific embodiment of the present invention, the positive electrode sheet 10 includes a positive electrode current collector 110 and a positive electrode coating 120 disposed on at least one surface of the positive electrode current collector 110; wherein, the positive electrode current collector 110 has two surfaces opposite each other in its own thickness direction, and the positive electrode coating 120 is disposed on either or both of the two opposite surfaces of the positive electrode current collector 110. The positive electrode current collector 110 may be a metal foil or a composite current collector, for example, aluminum foil may be used as a metal foil; the composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer; the composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.). The present invention does not have any special restrictions on the source of the positive current collector 110, and commercially available products or self-made products well known to those skilled in the art can be used.

[0046] In a specific embodiment of the present invention, the thickness of the positive current collector 110 is preferably 8µm to 16µm, specifically it can be 8µm, 9µm, 10µm, 11µm, 12µm, 13µm, 14µm, 15µm, 16µm or any value between the two.

[0047] In a specific embodiment of the present invention, the positive electrode coating 120 includes a positive electrode active material region 122 and a positive electrode mixing region 121; the positive electrode active material region 122 and the positive electrode mixing region 121 are staggered in the width direction of the positive electrode sheet 10; by Figure 1It can be seen that there is a positive electrode mixing region 121 between two adjacent positive electrode active material regions 122, and a positive electrode active material region 122 between two adjacent positive electrode mixing regions 121. In a preferred embodiment of the present invention, the positive electrode mixing region 121 is provided on both sides of the positive electrode sheet 10 in the width direction. The reason for this arrangement is that the edges of the positive electrode sheet 10 are prone to lithium ion deposition due to differences in current density and coating control. When the edges of the positive electrode sheet 10 are positive electrode mixing regions 121 containing both positive electrode active material and positive electrode inactive material, the number of lithium ions in the edges of the positive electrode sheet 10 can be significantly reduced. At the same time, because the proportion of inactive material is increased, it can provide physical adsorption capacity to adsorb the deposited lithium ions, thereby further reducing lithium ion deposition and ultimately improving the cycle stability of the battery.

[0048] In a specific embodiment of the present invention, the positive electrode active material region 122 includes a positive electrode active material; the elements in the positive electrode active material include lithium, preferably including at least one of lithium iron phosphate, ternary nickel cobalt manganese, lithium manganese oxide, and lithium cobalt oxide, more preferably ternary nickel cobalt manganese (NCM). The present invention does not impose any special restrictions on the source of the positive electrode active material; commercially available products well known to those skilled in the art can be used.

[0049] In a specific embodiment of the present invention, the positive electrode mixing region 121 includes a positive electrode active material and a positive electrode inactive material; wherein, the positive electrode active material is the same as that in the above technical solution, and will not be described again here; the elements in the positive electrode inactive material do not include lithium, and preferably include at least one of carbon-based materials, transition metal compounds and conductive polymer materials, wherein, the carbon-based materials include, but are not limited to, activated carbon (AC) and / or graphene, the transition metal compounds include, but are not limited to, at least one of cobaltates, molybdates, ferrates, manganates, tungstates, and vanadates, and the conductive polymer materials include, but are not limited to, at least one of polyaniline (PANI), polythiophene (PTh), and polypyrrole (PPy); in a preferred embodiment of the present invention, the positive electrode inactive material is selected from activated carbon (AC), MnO2, or polypyrrole (PPy). The present invention does not have any special restrictions on the source of the positive electrode inactive material, and commercially available products well known to those skilled in the art can be used.

[0050] In a specific embodiment of the present invention, in the positive electrode mixing region 121, the mass ratio of the positive electrode active material to the positive electrode inactive material is preferably ≤3 / 7. When the mass ratio exceeds 3 / 7, there will be insufficient inactive material to provide physical adsorption for lithium ions and solvent molecules in the electrolyte, affecting the cycle life of the battery. However, the mass ratio must be at least greater than 0; otherwise, there will not be enough positive electrode active material to provide lithium ions, which will affect energy release to some extent and reduce energy density.

[0051] In a specific embodiment of the present invention, in the positive electrode coating 120: the total width of the positive electrode active material region 122 is preferably greater than or equal to the total width of the positive electrode mixing region 121, and more preferably greater than the total width of the positive electrode mixing region 121. Based on this, a sufficient range of the positive electrode active material region 122 can be ensured, thereby guaranteeing sufficient lithium ion insertion / extraction, thus achieving a balance between improving some performance using the positive electrode mixing region 121 without sacrificing the area where the chemical reaction occurs. In a preferred embodiment of the present invention, the ratio of the total width of the positive electrode active material region 122 to the total width of the positive electrode mixing region 121 is (2~4):1.

[0052] In a specific embodiment of the present invention, the thickness of the positive electrode coating 120 is preferably 50µm to 150µm, specifically it can be 50µm, 60µm, 70µm, 80µm, 90µm, 100µm, 110µm, 120µm, 130µm, 140µm, 150µm or any value between the two.

[0053] The present invention does not impose any special restrictions on the preparation method of the positive electrode sheet 10. The positive electrode slurry (including the positive electrode active material region slurry and the positive electrode mixing region slurry) is coated on the positive electrode current collector 110 by means of methods known to those skilled in the art. After drying, cold pressing and other processes, the positive electrode sheet 10 can be obtained. For the special structural setting of the present invention, the two slurries are coated alternately.

[0054] In a specific embodiment of the present invention, the slurry in the positive electrode active material region preferably includes, in addition to the positive electrode active material described in the above technical solution, a binder, a conductive agent, and a solvent; similarly, the slurry in the positive electrode mixing region preferably includes, in addition to the positive electrode active material and the positive electrode inactive material described in the above technical solution, a binder, a conductive agent, and a solvent; the binder may include one or more of polyvinylidene fluoride (PVDF), sodium alginate, polyvinyl alcohol, polymethyl methacrylate, hydrogenated nitrile rubber, polytetrafluoroethylene, and polyacrylic acid, thereby improving the bonding strength between the positive electrode coating 120 and the positive electrode current collector 110; the conductive agent may include one or more of superconducting carbon (SP), acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers; the present invention does not have any special restrictions on the type and source of the solvent, such as commercially available N-methylpyrrolidone (NMP) well known to those skilled in the art.

[0055] In a specific embodiment of the present invention, the negative electrode sheet 20 includes a negative electrode current collector 210 and a negative electrode coating 220 disposed on at least one surface of the negative electrode current collector 210; wherein, the negative electrode current collector 210 has two surfaces opposite each other in its own thickness direction, and the negative electrode coating 220 is disposed on either or both of the two opposite surfaces of the negative electrode current collector 210. The negative electrode current collector 210 may be a metal foil or a composite current collector, for example, copper foil may be used as a metal foil; the composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer; the composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.). The present invention does not have any special restrictions on the source of the negative electrode current collector 210, and commercially available products or self-made products well known to those skilled in the art can be used.

[0056] In a specific embodiment of the present invention, the thickness of the negative electrode current collector 210 is preferably 4µm to 10µm, specifically it can be 4µm, 5µm, 6µm, 7µm, 8µm, 9µm, 10µm or any value between the two.

[0057] In a specific embodiment of the present invention, the negative electrode coating 220 includes a first sub-layer 2210; the first sub-layer 2210 includes a negative electrode active material region 2201 and a negative electrode inactive material region 2202; the negative electrode active material region 2201 and the negative electrode inactive material region 2202 are staggered in the width direction of the negative electrode sheet 20; by Figure 2 It can be seen that there is a negative electrode inactive material region 2202 between two adjacent negative electrode active material regions 2201, and a negative electrode active material region 2201 between two adjacent negative electrode inactive material regions 2202. In a preferred embodiment of the present invention, the negative electrode inactive material regions 2202 are provided on both sides of the negative electrode sheet 20 in the width direction. The purpose is to ensure that the negative electrode inactive material regions 2202 are positioned opposite to the positive electrode mixing region 121. On this basis, lithium plating is prevented and the safety of the battery is improved. During the charging and discharging process of the battery, due to the uneven distribution of current density at the edge (usually higher), lithium ions are easily over-deposited at the edge, forming lithium dendrites. At the same time, through the corresponding arrangement of the negative electrode inactive material regions 2202 and the positive electrode mixing region 121, even if the edges of the negative electrode sheet 20 and the positive electrode sheet 10 are in direct contact due to some reasons (such as assembly deviation), the negative electrode inactive material regions 2202, which include negative electrode inactive materials, are provided on the edge of the negative electrode sheet 20, which can also act as a buffer zone to reduce local chemical reactions and thus reduce the impact of the deviation.

[0058] In a specific embodiment of the present invention, the negative electrode active material region 2201 includes a first negative electrode active material; the negative electrode inactive material region 2202 includes a negative electrode inactive material; the first negative electrode active material has a potential relative to lithium <0.5V, preferably including at least one of graphite, silicon oxide, silicon carbon, and pure silicon, more preferably pure silicon; the negative electrode inactive material has a potential relative to lithium >0.5V, preferably including at least one of carbon-based materials, transition metal compounds, and conductive polymer materials, wherein the carbon-based materials include, but are not limited to, activated carbon (AC) and / or graphene, and the transition metal compounds include, but are not limited to, at least one of cobaltates, molybdates, ferrates, manganates, tungstates, and vanadates. One embodiment of the invention provides that the conductive polymer material includes, but is not limited to, at least one of polyaniline (PANI), polythiophene (PTh), and polypyrrole (PPy). In a preferred embodiment, the negative electrode inactive material is selected from activated carbon (AC), MnO2, or polypyrrole (PPy). This is because the negative electrode inactive material has a higher lithium intercalation potential and a larger potential difference, resulting in a higher reserved lithium plating potential during charging, thus preventing lithium plating. Simultaneously, the negative electrode inactive material also exhibits good thermal stability. Therefore, through the above structural design, the occurrence of lithium plating can be reduced through the negative electrode inactive material region 2202, while ensuring that the battery's electrical performance and safety are not significantly affected. The invention does not impose any special restrictions on the source of the negative electrode inactive material; commercially available products well-known to those skilled in the art can be used.

[0059] In specific embodiments of the present invention, the positive electrode inactive material and the negative electrode inactive material each independently include at least one of carbon-based materials, transition metal compounds, and conductive polymer materials. It should be further noted that "each independently includes" indicates that in the electrode assembly of the present invention, the positive electrode inactive material and the negative electrode inactive material can be different materials or the same material; preferably, they are the same material. By selecting specific positive electrode inactive materials and negative electrode inactive materials, the present invention facilitates better construction of the electron conduction network, regulates interfacial reactions, ensures efficient lithium-ion migration, and improves the overall performance of the battery. Specifically, this invention optimizes the material composition of the positive electrode active material region 122 and the positive electrode mixed region 121, the negative electrode active material region 2201 and the negative electrode inactive material region 2202. On the one hand, it can effectively reduce electrochemical reactions, reduce active lithium loss, and extend battery life. On the other hand, after lithium ions are extracted from the positive electrode active material region 122 and the positive electrode mixed region 121, they can be rapidly responded to in the corresponding negative electrode layer. In addition to the active main material, the high specific surface area and porous structure of the carbon-based material in the inactive region can quickly accommodate a large number of lithium ions. At the same time, the positive and negative electrode sheets are provided with carbon-based materials, transition metal compounds or conductive polymer materials, which can store a large amount of charge. During discharge, the ions stored in the carbon-based material return to the electrolyte and the positive electrode through the reverse reaction of the redox reaction, and the stored charge is released through the external circuit, improving the battery discharge rate performance. During charging, it can also quickly meet the charging requirements.

[0060] In a specific embodiment of the present invention, in the first sublayer 2210 of the negative electrode coating 220: the total width of the negative electrode active material region 2201 is preferably greater than or equal to the total width of the negative electrode inactive material region 2202, and more preferably greater than the total width of the negative electrode inactive material region 2202. Based on this, a sufficient range of the negative electrode active material region 2201 can be ensured, thereby guaranteeing sufficient lithium ion insertion / extraction, thus achieving a balance between improving some performance using the negative electrode inactive material region 2202 without sacrificing the area where the chemical reaction occurs.

[0061] In a specific embodiment of the present invention, the negative electrode coating 220 preferably further includes a second sub-layer 2220, which is located between the negative electrode current collector 210 and the first sub-layer 2210. The second sub-layer 2220 includes a second negative electrode active material, which preferably includes at least one of graphite, silicon carbon, silicon oxide, and pure silicon, more preferably graphite (Gr). The present invention does not have any special restrictions on the source of the second negative electrode active material, and commercially available products well known to those skilled in the art can be used. The purpose of introducing the above-mentioned second sub-layer 2220 is to avoid excessive sacrifice of energy density caused by the introduction of non-active negative electrode material in the first sub-layer 2210. That is, through a balanced design, a second sub-layer 2220 is set between the negative electrode current collector 210 and the first sub-layer 2210, which improves the charge and discharge capacity of the battery, thereby meeting the required lifespan and power performance, and also has a certain energy density. Moreover, the design of the second sub-layer 2220 located between the negative electrode current collector 210 and the first sub-layer 2210 can effectively meet the actual requirements for lithium ion adsorption and intercalation.

[0062] In a specific embodiment of the present invention, the expansion coefficient of the second negative electrode active material is preferably smaller than that of the first negative electrode active material. Based on this, the battery performance is significantly improved. The reason for this is that the first sub-layer 2210 is on the surface of the negative electrode sheet 20 (the outermost layer), and a first negative electrode active material with a larger expansion coefficient is used. The second sub-layer 2220 is between the negative electrode current collector 210 and the first sub-layer 2210 of the negative electrode sheet 20, and a second negative electrode active material with a smaller expansion coefficient is used. This can alleviate the overall volume expansion, reduce structural stress, and make the overall structure more stable. Simultaneously, the outermost layer, which is in direct contact with the electrolyte, mainly undertakes the lithium-ion storage function. A larger expansion coefficient provides a larger expansion space, reducing the overall diffusion resistance of lithium ions and facilitating lithium-ion migration. In a preferred embodiment of the present invention, the first negative electrode active material is pure silicon, and the second negative electrode active material is graphite.

[0063] In a specific embodiment of the present invention, the thickness ratio of the first sub-layer 2210 and the second sub-layer 2220 is preferably 0.5 to 1.5, specifically it can be 0.5, 0.75, 1, 1.25, 1.5 or any value between the two. When the first sublayer 2210 is too thick, the proportion of the highly expandable first negative electrode active material is too high, and the overall volume expansion will increase significantly, resulting in greater overall electrode deformation. This can lead to current collector breakage, electrode peeling, or separator puncture, exacerbating safety risks. At the same time, the increased thickness of the first sublayer 2210 also leads to a significant increase in the amount of inactive negative electrode material, excessively sacrificing the battery's energy density, resulting in a lower discharge platform and affecting the total discharge energy. When the thickness of the first sublayer 2210 is too thin, the proportion of the low-expansion second negative electrode active material in the second sublayer 2220 increases, reducing the overall expansion space of the negative electrode sheet 20. This reduces the lithium-ion storage function, affects the ion adsorption space, and impacts cycle life. Therefore, choosing an appropriate thickness range ensures that the negative electrode sheet 20 will not experience uncontrolled expansion due to an excessively thick first sublayer 2210, increasing risks and reducing battery energy density, nor will an excessively thick second sublayer 2220 affect the ion adsorption space and thus cycle life. Simultaneously, it can reduce interfacial stress, optimize mass transfer efficiency, and improve the overall performance of the battery.

[0064] In a specific embodiment of the present invention, the thickness of the negative electrode coating 220 is preferably 50µm to 120µm, specifically it can be 50µm, 60µm, 70µm, 80µm, 90µm, 100µm, 110µm, 120µm or any value between the two.

[0065] The present invention does not impose any special restrictions on the preparation method of the negative electrode sheet 20. The negative electrode slurry (including the negative electrode active material region slurry, the negative electrode inactive material region slurry, and the second sub-layer slurry in the preferred embodiment) is coated onto the negative electrode current collector 210 using a method known to those skilled in the art. After drying, cold pressing and other processes, the negative electrode sheet 20 can be obtained. For the special structural setting of the present invention, the second sub-layer slurry is first coated and dried to form the second sub-layer 2220, and then the remaining two slurries are coated alternately and dried to form the first sub-layer 2210.

[0066] In a specific embodiment of the present invention, the slurry in the negative electrode active material region preferably includes, in addition to the first negative electrode active material, a binder, a conductive agent, a solvent, and other additives (such as thickeners); the slurry in the negative electrode inactive material region preferably includes, in addition to the negative electrode inactive material, a binder, a solvent, and other additives (such as thickeners); the second sublayer slurry preferably includes, in addition to the second negative electrode active material, a binder, a conductive agent, a solvent, and other additives (such as thickeners); the binder may include one or more of polyvinylidene fluoride (PVDF), styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS); the conductive agent may include one or more of superconducting carbon (SP), acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers; the present invention does not impose any special restrictions on the type and source of the solvent, such as deionized water well known to those skilled in the art.

[0067] In a specific embodiment of the present invention, the negative electrode active material region 2201 is disposed opposite to the positive electrode active material region 122, and the negative electrode inactive material region 2202 is disposed opposite to the positive electrode mixing region 121. It should be further noted that "relatively disposed" means that the two regions at least partially overlap and cannot be completely offset, thereby ensuring that the battery's CB value (cell balance, which is the excess capacity of the opposite negative electrode over the positive electrode under the same conditions in the same stage) meets design requirements. Through the above-mentioned positional constraints, the present invention can alleviate the problem of lithium dendrite formation in the battery: lithium plating is less likely to occur during battery charge-discharge cycles, including further reducing the phenomenon of lithium plating that is very likely to occur at the battery edges; simultaneously, it reduces the intercalation electrochemical reactions involving the electrolyte inside the battery, and allows the positive electrode active material region 122 and the negative electrode active material region 2201 to store lithium ions through physical adsorption, improving charging and discharging capabilities and extending battery life.

[0068] In a specific embodiment of the present invention, the width of the positive electrode 10 is preferably less than or equal to the width of the negative electrode 20. This prevents lithium dendrite short circuits and improves safety. During battery charging and discharging, lithium ions escape from the positive electrode and embed into the negative electrode. If the width of the positive electrode is greater than that of the negative electrode, some lithium ions may not be effectively received by the negative electrode during charging and will precipitate at the edge or surface of the negative electrode, forming lithium dendrites. Therefore, a wider negative electrode provides sufficient "accommodation space" for lithium ions, preventing lithium dendrite precipitation and reducing the risk of short circuits at the source. Furthermore, the performance difference between the prepared batteries is not significant. Also, when the widths of the positive electrode 10 and the negative electrode 20 are the same, thinning of the coating process is unnecessary, reducing the difficulty of controlling the coating process.

[0069] In a specific embodiment of the present invention, the width of a single negative electrode inactive material region 2202 is preferably greater than or equal to the width of a single positive electrode mixing region 121, and more preferably, the width of the negative electrode inactive material region 2202 at the edge is greater than the width of the positive electrode mixing region 121 at the opposite edge. Based on this, since the negative electrode inactive material region 2202 on the negative electrode sheet 20 and the positive electrode mixing region 121 on the positive electrode sheet 10 have a one-to-one correspondence in the electrode assembly of the present invention, this width setting ensures sufficient effective lithium storage space in the corresponding area on the negative electrode sheet 20. In a preferred embodiment of the present invention, the width of a single negative electrode inactive material region 2202 exceeds the width of a single positive electrode mixing region 121 by 1mm to 3mm, specifically 1mm, 2mm, 3mm, or any value between the two.

[0070] In a specific embodiment of the present invention, the coverage area of ​​the negative electrode coating 220 is preferably greater than or equal to the coverage area of ​​the positive electrode coating 120, and more preferably greater than the coverage area of ​​the positive electrode coating 120. The larger area of ​​the negative electrode coating 220 compared to the positive electrode coating 120 ensures that the overall negative electrode can accommodate a certain surplus of lithium ions, preventing lithium ion deposition due to long-term cycling.

[0071] In a specific embodiment of the present invention, the diaphragm includes a base film and a coating disposed on at least one surface of the base film; wherein the base film includes, but is not limited to, at least one of polyethylene (PE), polypropylene (PP), polyimide (PI), and polypropylene-polyethylene composite film, preferably polypropylene. The present invention does not impose any special restrictions on the source of the base film; commercially available products well known to those skilled in the art can be used.

[0072] In a specific embodiment of the present invention, the base membrane has a coating on at least one side surface, preferably the surface facing the negative electrode. The present invention, by providing a functional coating on the separator, makes the free energy of the separator surface higher than that of the negative electrode material, thereby forming a built-in electric field, accelerating the migration of lithium ions, and further improving battery performance. In the present invention, the coating preferably includes at least one of alumina, boehmite, and a solid electrolyte, more preferably a solid electrolyte, thereby forming an electrolyte layer on the separator surface; the solid electrolyte is preferably lithium aluminum titanium phosphate (LATP). In a preferred embodiment of the present invention, the separator is a separator with an electrolyte layer on one side, facing the negative electrode. Because the free energy of the electrolyte is higher than that of negative electrode materials such as graphite, a built-in electric field is formed, accelerating the migration of lithium ions.

[0073] The present invention does not impose any particular limitation on the preparation method of the diaphragm; conventional methods for preparing diaphragms well known to those skilled in the art can be used. In a preferred embodiment of the present invention, after the coating material is mixed evenly, it is coated onto the base membrane of the diaphragm and cured to obtain the corresponding diaphragm. As an example, the preparation method of the diaphragm includes the following steps: adding lithium aluminum titanium phosphate (LATP) to a polyvinylidene fluoride (PVDF) adhesive solution and dispersing it evenly to obtain a diaphragm coating; then coating the diaphragm coating onto a polypropylene base membrane; and drying to form an LATP electrolyte coating to obtain the diaphragm.

[0074] According to another aspect of the present invention, a battery is provided, comprising the electrode assembly described in the above-described technical solution. Thus, the battery possesses all the features and advantages of the electrode assembly described in the above-described technical solution, which will not be repeated here. Specifically, the electrode assembly can be manufactured from a positive electrode, a negative electrode, and a separator through a winding process or a stacking process. The battery may include an outer packaging that can be used to encapsulate the aforementioned electrode assembly and electrolyte.

[0075] The electrolyte acts as a conductor of ions between the positive and negative electrodes. This invention does not impose specific limitations on the type of electrolyte; it can be selected according to requirements. For example, the electrolyte can be liquid, gel, or entirely solid.

[0076] In a specific embodiment of the present invention, the electrolyte is an electrolyte solution; the electrolyte solution comprises an electrolyte salt and a solvent; wherein, the electrolyte salt preferably comprises one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate, more preferably lithium hexafluorophosphate; the solvent preferably comprises one or more of ethylene carbonate (EC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC), more preferably a mixed solvent of EC, DMC, and EMC. The present invention does not impose any special restrictions on the source of the solvent; commercially available products of the above-mentioned cyclic and chain carbonates well known to those skilled in the art can be used.

[0077] In a specific embodiment of the present invention, the electrolyte preferably further includes film-forming additives, such as negative electrode film-forming additives and positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance and additives that improve battery high-temperature or low-temperature performance.

[0078] This invention does not impose any particular limitation on the preparation method of the electrolyte; conventional methods well-known to those skilled in the art can be used. In a preferred embodiment of this invention, the electrolyte is obtained by uniformly mixing the various components. As an example, the preparation method of the electrolyte includes the following steps: in an argon glove box, the solvent components are first mixed to form a homogeneous solvent system, and then a lithium salt electrolyte is slowly added to avoid local overheating and decomposition of the lithium salt; after complete dissolution, trace particulate impurities are removed by pressure filtration through a 0.2 μm PTFE filter membrane to obtain the electrolyte.

[0079] In a specific embodiment of the present invention, the outer packaging of the battery can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc., or it can be a soft pack, such as a pouch-type soft pack; the material of the soft pack can be plastic, and examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0080] The present invention does not impose any particular restrictions on the shape of the battery; it can be cylindrical, square, or any other arbitrary shape, and those skilled in the art can choose according to specific practical needs.

[0081] According to another aspect of the present invention, an electrical device is provided, comprising the battery described in the above-described technical solution. Thus, the electrical device possesses all the features and advantages of the battery described in the above-described technical solution, which will not be repeated here. Specifically, the battery can serve as a power source for the electrical device, or as an energy storage unit for the electrical device. The electrical device may include, but is not limited to, mobile devices (e.g., mobile phones, laptops), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks), electric trains, ships and satellites, and energy storage systems.

[0082] The present application will be described in detail below with reference to the accompanying drawings and embodiments. However, the implementation and protection of the present invention are not limited thereto. The following embodiments are only some embodiments of the present application and are not intended to limit the present application. In the context of the specification, including the following embodiments and comparative examples, performance tests were performed according to the following method: (1) Film resistance: Take the freshly coated and dried electrode and test the electrode resistance using the ACCFILM film resistance test system. Select ten measurement points and obtain the average value as the resistance value.

[0083] (2) Tortuousness: Represents the degree of tortuosity of the lithium ion transport path in the porous electrode, that is, the ratio of the actual transport path ∆L of lithium ions in the electrode coating to the coating thickness ∆x. The effective ionic conductivity is inversely proportional to the tortuousness.

[0084] (3) 10Ah soft package test: First, perform a 1C charge and a 1C discharge, then mark the battery capacity.

[0085] 5C charging constant current ratio: Using 5C constant current and constant voltage charging, cutoff at 0.05C, the ratio of constant current / (constant current + constant voltage) is the charging constant current ratio.

[0086] 10C discharge capacity: Using 10C constant current discharge as a benchmark, the 10C discharge capacity retention rate is calculated.

[0087] Capacity retention after 2000 cycles: The capacity retention was calculated after 2000 cycles of constant current and constant voltage charging at 1C and constant current discharging at 1C, with a voltage range of 2.8V to 4.2V.

[0088] Example 1 (1) Preparation of the positive electrode: Positive electrode active material slurry: First, polyvinylidene fluoride (PVDF) is dissolved in N-methylpyrrolidone (NMP) solvent and dispersed at high speed (dispersion speed is 17 m / s, the same below) for 4 hours to obtain PVDF gel. Then, conductive agent SP and ternary nickel-cobalt-manganese (NCM) are added sequentially and dispersed at high speed for 3 hours to obtain positive electrode active material slurry. The mass ratio of PVDF, SP and NCM is 3:1.5:95.5.

[0089] Positive electrode mixing zone slurry: First, PVDF is dissolved in NMP solvent and dispersed at high speed for 4 hours to obtain PVDF gel. Then, activated carbon AC and NCM are added sequentially and dispersed at high speed for 4 hours to obtain positive electrode mixing zone slurry. The mass ratio of PVDF, AC and NCM is 5:76:19.

[0090] The two slurries described above are applied alternately to the surface of the aluminum foil. See [link to relevant documentation]. Figure 3 As shown, a positive electrode sheet is obtained after drying; the total width of the coating area in the positive electrode sheet is 110 mm, and the specific data is shown in Table 1.

[0091] (2) Preparation of negative electrode: Second sublayer slurry for negative electrode: First, sodium carboxymethyl cellulose (CMC) is dissolved in deionized water and dispersed at medium speed (10 m / s, the same below) for 4 hours to obtain an aqueous solution of CMC. Then, SP and graphite are added sequentially and dispersed at high speed for 3 hours. Finally, styrene-butadiene rubber (SBR) is added and dispersed at high speed for 30 minutes to obtain the second sublayer slurry for negative electrode. The mass ratio of CMC, SP, graphite and SBR is 1.6:1.5:95.1:1.8.

[0092] The slurry for the negative electrode active material region of the first sublayer of the negative electrode: SP and Si are added sequentially to the polyacrylic acid PAA adhesive solution and dispersed at high speed for 3 hours. Then SBR is added and dispersed at high speed for another 30 minutes to obtain the slurry for the negative electrode active material region of the first sublayer of the negative electrode. The mass ratio of SP, Si, PAA and SBR is 1.5:95:2:1.5.

[0093] The slurry of the non-active material region of the first sublayer of the negative electrode: Activated carbon AC was added to CMC aqueous solution and dispersed at high speed for 5 hours to obtain the slurry of the non-active material region of the first sublayer of the negative electrode; wherein the mass ratio of AC to CMC was 98:2.

[0094] The negative electrode second sublayer paste is coated onto the copper foil surface and dried to form the second sublayer. Then, two other pastes are alternately coated onto the surface of the second sublayer. (See [link to previous section]). Figure 2 As shown, after drying, the first sub-layer is formed, and the negative electrode sheet is obtained; wherein, the thickness ratio of the first sub-layer to the second sub-layer is 1, and the total width of the coating area in the negative electrode sheet is 114mm. For specific data, please refer to Table 2.

[0095] (3) Preparation of the diaphragm: Diaphragm coating: Prepared using an oil-based system, 5 wt% PVDF is dissolved in NMP solvent and dispersed at high speed for 4 h to obtain PVDF solution, then 5 wt% LATP is added to the above PVDF solution and dispersed at medium speed for 2 h to obtain LATP diaphragm coating.

[0096] The LATP membrane coating is applied to a polypropylene base membrane and dried to form an LATP electrolyte coating, thus obtaining the membrane.

[0097] (4) Battery assembly: 10Ah Soft Pack Manufacturing: The separator is placed between the positive and negative electrode plates and wound to form a core with a thickness of about 10mm. After the core is dried, it is placed in an aluminum-plastic film and sealed. Then, 30g of electrolyte is injected. The electrolyte formula is: lithium hexafluorophosphate (LiPF6) solution (the solvent is a mixture of EC, DMC and EMC in a mass ratio of 1:1:1). After standing for 48 hours, it is fully charged to 4.2V for formation and degassing. After secondary sealing, a complete soft pack battery is obtained.

[0098] Example 2 The positive electrode, negative electrode, separator and battery were obtained by the preparation method provided in Example 1, with the only difference being that the activated carbon AC in the positive electrode mixing zone slurry was replaced with MnO2.

[0099] Example 3 The positive electrode, negative electrode, separator and battery were obtained by the preparation method provided in Example 1, with the only difference being that the mass ratio of PVDF, AC and NCM in the positive electrode mixing zone slurry was adjusted to 5:85.5:9.5.

[0100] Example 4 The positive electrode, negative electrode, separator and battery were obtained by the preparation method provided in Example 1, with the only difference being that the mass ratio of PVDF, AC and NCM in the positive electrode mixing zone slurry was adjusted to 5:66.5:28.5.

[0101] Example 5 The positive electrode, negative electrode, separator and battery were obtained by the preparation method provided in Example 1, with the only difference being that the total width of the coating area in the negative electrode is exactly the same as the total width of the coating area in the positive electrode, which is 110 mm.

[0102] Example 6 The positive electrode, negative electrode, separator and battery were obtained by the preparation method provided in Example 1, the only difference being that the negative electrode did not have a second sub-layer.

[0103] Example 7 The positive electrode, negative electrode, separator and battery were obtained by the preparation method provided in Example 1, with the only difference being that the thickness ratio of the first sublayer to the second sublayer is 0.5.

[0104] Example 8 The positive electrode, negative electrode, separator and battery were obtained by the preparation method provided in Example 1, with the only difference being that the thickness ratio of the first sublayer to the second sublayer is 1.5.

[0105] Example 9 The positive electrode, negative electrode, separator and battery were obtained by the preparation method provided in Example 1, with the only difference being that the separator did not have an LATP electrolyte coating.

[0106] Example 10 The positive electrode, negative electrode, separator and battery were obtained by the preparation method provided in Example 1, with the only difference being that the inactive material of the positive electrode was replaced by polyaniline instead of activated carbon, and the inactive material of the negative electrode was replaced by polyaniline instead of activated carbon.

[0107] Example 11 The positive electrode, negative electrode, separator, and battery were obtained using the preparation method provided in Example 1, with the only difference being that the slurry for the positive electrode active material region and the slurry for the positive electrode mixing region were alternately coated on the surface of the aluminum foil. See [link to example]. Figure 4 As shown, the slurry of the positive electrode active material region is located on both sides of the positive electrode sheet in the width direction.

[0108] Comparative Example 1 The positive electrode sheet, negative electrode sheet, separator and battery were obtained by the preparation method provided in Example 1, with the only difference being that the positive electrode mixing region is not provided in the positive electrode sheet, that is, the positive electrode mixing region in Example 1 is covered by the positive electrode active material region.

[0109] Comparative Example 2 The positive electrode, negative electrode, separator and battery were obtained by the preparation method provided in Example 1. The only difference is that the first sub-layer of the negative electrode does not have a negative electrode inactive material region, that is, the negative electrode inactive material region in Example 1 is covered by the negative electrode active material region.

[0110] Comparative Example 3 The positive electrode, negative electrode, separator and battery were obtained by the preparation method provided in Example 1, with the only difference being that the first negative electrode active material in the negative electrode active material region of the first sub-layer of the negative electrode is graphite, and the second negative electrode active material in the second sub-layer is silicon.

[0111] Comparative Example 4 The positive electrode sheet, negative electrode sheet, separator and battery were obtained by the preparation method provided in Example 1, with the only difference being that: no positive electrode mixing region was set in the positive electrode sheet, that is, the positive electrode mixing region in Example 1 was covered by the positive electrode active material region; at the same time, no negative electrode inactive material region was set in the first sub-layer of the negative electrode sheet, that is, the negative electrode inactive material region in Example 1 was covered by the negative electrode active material region.

[0112] The condition parameters and test results data of Examples 1-11 and Comparative Examples 1-4 are shown in Tables 1-3 below.

[0113] Table 1. Conditional parameter data for positive electrode and separator coatings Note: The mass percentage of the data in the "Active Material + Inactive Material" item in Table 1 represents the ratio of the two materials, active material and inactive material.

[0114] Table 2. Conditional parameter data for negative electrode sheets Table 3 Test results data for 10Ah pouch batteries The test results of Examples 1-11 and Comparative Examples 1-4 show that the electrode assembly provided by the present invention enables the battery to maintain structural stability and excellent electrochemical performance under rapid charge-discharge and long-cycle conditions: a 5C charging constant current ratio of 95%-99%, a 10C discharge retention rate of 94%-98%, and a capacity decay rate of 5%-10% after 2000 cycles. The reason for this is that the present invention improves the structure of the positive and negative electrodes by setting a positive active material region and a positive mixed region on the positive electrode, and adding a negative inactive material region on the negative electrode. This significantly increases the power density, i.e., improves charging and discharging capabilities, without excessively sacrificing battery energy density, reduces the intercalation electrochemical reactions involving the electrolyte inside the battery, and stores lithium ions through physical adsorption outside the positive active material region, thus extending battery life. By systematically controlling the selection of inactive materials on the positive and negative electrodes, the ratio of positive active materials to positive inactive materials in the positive electrode mixing region of the positive electrode, the coating width of the positive and negative electrodes, the structural composition of the negative electrode, the optimization of the separator, and the positional relationship between the positive electrode mixing region of the positive electrode and the negative electrode inactive material region of the negative electrode, a better overall technical effect is achieved at both the electrode assembly and battery levels. This significantly improves the overall performance of the battery under fast charge and discharge and long cycle conditions, achieving a balance between high specific capacity, fast charging capability, and long cycle life, and has good prospects for commercial application.

[0115] Specifically: As can be seen from Examples 1, 2, and 10 (examination of the types of inactive materials in the positive and negative electrodes), the battery performance of Example 2 is slightly lower than that of Example 1, that is, the performance of activated carbon is better than that of manganese dioxide. The energy density of the battery in Example 10 is higher than that of Example 1. The performance of all three batteries meets the purpose of this invention, indicating that the addition of inactive materials in the positive and negative electrodes can improve some of the battery performance to a certain extent.

[0116] Through Examples 1, 3-4, and Comparative Example 1 (examination of the ratio of active and inactive materials in the positive electrode mixing region), it can be seen that under the same negative electrode conditions, the design of the positive electrode mixing region affects the discharge rate capability. The higher the proportion of inactive materials, the better it is to improve the discharge capability. However, when the positive electrode does not have a positive electrode mixing region, although the battery energy density increases, the cycle stability of the battery (capacity retention rate after 2000 cycles) decreases significantly because the inactive materials in the positive electrode mixing region do not participate in the physical adsorption of lithium ions, thus affecting the overall cycle life of the battery.

[0117] As can be seen from Examples 1 and 5 (examination of the coating width of the positive and negative electrode sheets), when the coating width of the negative electrode sheet is greater than or equal to the coating width of the positive electrode sheet, the performance difference of the prepared battery is not significant and the impact on cycle life is small. At the same time, when the coating widths of the positive and negative electrode sheets are equal, the thinning area does not need to be removed during the process preparation, reducing the difficulty of coating process control.

[0118] As can be seen from Examples 1, 6-8, and Comparative Examples 2-3 (examination of the negative electrode structure), in Example 6, no second sublayer was introduced, and its energy density was significantly improved compared to Example 1. However, its cycle stability and charge / discharge capability were slightly lower than those of Example 1. The main reason for this is that the purpose of introducing the second sublayer is to avoid the introduction of inactive materials and excessive sacrifice of energy density. That is, through a balanced design, both the required lifespan and power performance are met, while also having a certain energy density. Moreover, the design of the upper inactive layer and the lower active layer can effectively meet the actual requirements for lithium ion adsorption and intercalation. In Comparative Example 2, since no negative electrode inactive material region was set on the first sublayer of the negative electrode, its charge / discharge capability and battery cycle stability were significantly reduced. By comparing the thickness ratios of the first and second sublayers in Examples 7-8 and Example 1, it can be seen that a thickness ratio of 0.5 to 1.5 for both the first and second sublayers can achieve the objective of this invention. Comparing Comparative Example 3 with Example 1, it can be seen that when the active material of the first sublayer is replaced by graphite instead of silicon, the film resistance increases, the tortuosity increases, and the charge / discharge performance and cycle stability of the battery significantly decrease. This may be because silicon has a larger coefficient of thermal expansion, which reduces the overall diffusion resistance of the first sublayer, making it more conducive to ion migration and thus improving the overall performance of the battery. In Comparative Example 4, no positive electrode mixing region is provided on the positive electrode sheet, and no negative electrode inactive material region is provided in the first sublayer of the negative electrode. The results show that its 5C charge constant current ratio, 10C discharge retention rate, and capacity retention rate after 2000 cycles are significantly lower than those of the examples.

[0119] A comparison of the results from Examples 1 and 9 (regarding the membrane structure) shows that coating the membrane with functional materials is more beneficial to improving the overall performance of the battery. The main reason for this is that by coating the membrane with functional materials, such as solid electrolytes, the free energy of the solid electrolytes is higher than that of negative electrode materials such as graphite, thus forming a self-built electric field, which further accelerates the migration rate of lithium ions and improves the performance of the battery.

[0120] A comparison of the results from Examples 1 and 11 (regarding the location of the positive electrode mixing region) shows that when the edge of the positive electrode sheet is set as the positive electrode mixing region, the cycle stability of the battery is significantly reduced. The main reason for this is that lithium ion deposition is more likely to occur at the edge of the electrode sheet due to differences in current density and coating control. When the edge of the positive electrode sheet is adjusted to a mixing region of positive electrode active material and positive electrode inactive material, the number of lithium ions at the edge is significantly reduced. Furthermore, due to the increased proportion of positive electrode inactive material, the occurrence of lithium deposition is significantly reduced, thereby further improving the cycle stability of the battery.

[0121] The parts of this invention not described in detail are techniques known to those skilled in the art.

[0122] The basic principles of the present invention have been described above with reference to specific embodiments. However, it should be noted that the advantages, benefits, and effects mentioned in the present invention are merely examples and not limitations, and should not be considered as essential features of each embodiment of the present invention. Furthermore, the specific details disclosed above are for illustrative and facilitative purposes only, and are not limitations. These details do not limit the present invention to the necessity of employing the aforementioned specific details.

[0123] In the foregoing description of this specification, references to terms such as "one embodiment," "another embodiment," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment is included in at least one embodiment of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples, without contradiction. Additionally, it should be noted that in this specification, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features.

[0124] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An electrode assembly, characterized in that, It includes a positive electrode, a negative electrode, and a separator located between the positive electrode and the negative electrode; The positive electrode sheet includes a positive current collector and a positive electrode coating disposed on at least one surface of the positive current collector; the positive electrode coating includes a positive active material region and a positive mixed region; the positive active material region and the positive mixed region are staggered along the width direction of the positive electrode sheet; the positive active material region includes a positive active material; the positive mixed region includes a positive active material and a positive inactive material; the positive active material includes lithium, and the positive inactive material does not include lithium; The negative electrode sheet includes a negative electrode current collector and a negative electrode coating disposed on at least one side surface of the negative electrode current collector; the negative electrode coating includes a first sublayer; the first sublayer includes a negative electrode active material region and a negative electrode inactive material region; the negative electrode active material region and the negative electrode inactive material region are staggered in the width direction of the negative electrode sheet; the negative electrode active material region includes a first negative electrode active material; the negative electrode inactive material region includes a negative electrode inactive material; the potential of the first negative electrode active material relative to lithium is <0.5V, and the potential of the negative electrode inactive material relative to lithium is >0.5V; The negative electrode active material region is arranged opposite to the positive electrode active material region, and the negative electrode inactive material region is arranged opposite to the positive electrode mixed region.

2. The electrode assembly according to claim 1, characterized in that, The positive electrode and / or the negative electrode satisfy at least one of the following characteristics (1) to (7): (1) The positive electrode mixing region is provided on both sides of the positive electrode sheet in the width direction; (2) The negative electrode non-active material region is provided on both sides of the negative electrode sheet in the width direction; (3) The width of the positive electrode plate is less than or equal to the width of the negative electrode plate; (4) The total width of the positive electrode active material region is greater than or equal to the total width of the positive electrode mixing region; (5) The total width of the negative electrode active material region is greater than or equal to the total width of the negative electrode inactive material region; (6) The width of a single negative electrode inactive material region is greater than or equal to the width of a single positive electrode mixing region; (7) The coverage area of ​​the negative electrode coating is greater than or equal to the coverage area of ​​the positive electrode coating.

3. The electrode assembly according to claim 1, characterized in that, In the positive electrode mixing region, the mass ratio of the positive electrode active material to the positive electrode inactive material is ≤3 / 7.

4. The electrode assembly according to claim 1, characterized in that, The positive electrode active material includes at least one of lithium iron phosphate, ternary nickel cobalt manganese, lithium manganese oxide, and lithium cobalt oxide. And / or, the positive electrode inactive material and the negative electrode inactive material each independently include at least one of carbon-based materials, transition metal compounds and conductive polymer materials; And / or, the first negative electrode active material includes at least one of graphite, silicon oxide, silicon carbon, and pure silicon.

5. The electrode assembly according to claim 1, characterized in that, The negative electrode coating further includes a second sub-layer, which is located between the negative electrode current collector and the first sub-layer; the second sub-layer includes a second negative electrode active material.

6. The electrode assembly according to claim 5, characterized in that, The second negative electrode active material includes at least one of graphite, silicon carbide, silicon oxide, and pure silicon; And / or, the thickness ratio of the first sublayer to the second sublayer is 0.5 to 1.

5.

7. The electrode assembly according to claim 5, characterized in that, The expansion coefficient of the second negative electrode active material is less than that of the first negative electrode active material.

8. The electrode assembly according to claim 1, characterized in that, The diaphragm includes a base membrane and a coating disposed on at least one surface of the base membrane; the coating includes at least one of alumina, boehmite, and solid electrolyte.

9. A battery, characterized in that, Includes the electrode assembly as described in any one of claims 1 to 8.

10. An electrical device, characterized in that, Includes the battery as described in claim 9.

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