Electrode assembly, battery, and electric device

Abstract

The present application relates to the technical field of batteries, and particularly relates to an electrode assembly, a battery, and an electric device. The electrode assembly comprises a first electrode sheet, a second electrode sheet, a first separator, and a second separator. One of the first separator and the second separator is arranged between the first electrode sheet and the second electrode sheet, and the other one of the first separator and the second separator is arranged on the side of the first electrode sheet or the second electrode sheet facing away from the first separator; one of the first separator and the second separator does not comprise a porous coating, and the other one of the first separator and the second separator comprises a porous coating, wherein the thickness of the porous coating is 0.5 μm-8 μm. The electrode assembly of the present application comprises a specific first separator and a specific second separator, thus effectively improving the cycle performance of the battery.

Description

Electrode assemblies, batteries, and electrical equipment

[0001] Related applications

[0002] This application claims priority to Chinese patent application No. 202310919314.0 filed on July 26, 2023, the entire contents of which are incorporated by reference into this application. Technical Field

[0003] The present application relates to the field of battery technology, and in particular to an electrode assembly, a battery, and an electrical device. Background Art

[0004] Secondary batteries have been widely used in various consumer electronic products and electric vehicles due to their advantages such as high energy density, high output voltage, good safety, no pollution and no memory effect.

[0005] As the application scope of secondary batteries becomes wider and wider, the demand for their use by customers is also increasing. However, how to make secondary batteries have better electrochemical performance is still a difficult point in the current development of secondary batteries.

[0006] Application Contents

[0007] The main purpose of this application is to provide an electrode assembly to improve the cycle performance of the battery.

[0008] To achieve the above-mentioned object, the present application proposes an electrode assembly, comprising a first electrode piece, a second electrode piece, and a first diaphragm and a second diaphragm;

[0009] One of the first diaphragm and the second diaphragm is arranged between the first pole piece and the second pole piece, and the other of the first diaphragm and the second diaphragm is arranged on the side of the first pole piece or the second pole piece away from the first diaphragm; one of the first diaphragm and the second diaphragm does not include a porous coating, and the other of the first diaphragm and the second diaphragm includes a porous coating, and the thickness of the porous coating is 0.5μm-8μm.

[0010] It can be understood that one of the first electrode and the second electrode is a positive electrode, and the other is a negative electrode.

[0011] It can be understood that the setting positions of the first diaphragm and the second diaphragm in the electrode are not limited and can be set as needed. For example, one of the first diaphragm and the second diaphragm is set between the first electrode and the second electrode, and the other of the first diaphragm and the second diaphragm is set on the side of the first electrode or the second electrode away from the first diaphragm.

[0012] One of the first separator and the second separator does not include a porous coating, and the other of the first separator and the second separator includes a porous coating, and the thickness of the porous coating is 0.5μm-8μm. For example, the first separator does not include a porous coating, and the second separator includes a porous coating, or the second separator does not include a porous coating, and the first separator includes a porous coating.

[0013] It can be understood that the design of the first diaphragm and the second diaphragm in this application is different. During the battery cycle, more expansion space is reserved for the battery cell, reducing the squeezing of the shell on the battery cell during the expansion process, improving the phenomenon of active material being damaged by the squeezing force during the squeezing process, and also improving the phenomenon of electrolyte being squeezed out during the squeezing process, so that the battery cell is effectively immersed in the electrolyte during the expansion process, which is conducive to the transmission of ions, thereby effectively improving the cycle performance of the battery.

[0014] Further, the first separator includes a first porous base membrane and a porous coating layer; and / or the second separator includes a second porous base membrane.

[0015] Specifically, the first diaphragm includes a first porous base membrane and a porous coating. The porous coating can be a structure used to perform bonding functions and / or heat-resistant functions, and of course it can also be a structure with other functions. This application is not limited to this. The performance of the electrode assembly is improved by introducing a porous coating; the second diaphragm includes a second porous base membrane. It can be understood that the base membrane refers to the basic material of the diaphragm, such as an organic microporous membrane, that is, the second diaphragm may not include a porous coating.

[0016] It can be understood that the setting position of the porous coating in the first diaphragm is not limited. For example, the porous coating can be set on at least one side of the first porous base membrane, or the porous coating is composited on the first porous base membrane. For example, the material of the porous coating is mixed with the material of the base membrane, and a composite diaphragm is prepared by melt co-extrusion.

[0017] It is also understood that the placement of the first diaphragm and the second diaphragm in this application is not limited and can be arranged according to actual needs. For example, in one case, the first diaphragm is arranged between the first electrode piece and the second electrode piece, and the second diaphragm is arranged on the side of the first electrode piece or the second electrode piece facing away from the first diaphragm. In another case, the second diaphragm is arranged between the first electrode piece and the second electrode piece, and the first diaphragm is arranged on the side of the first electrode piece or the second electrode piece facing away from the first diaphragm.

[0018] It can be understood that when the first diaphragm includes a porous coating and the second diaphragm does not include a porous coating, the preferred solution in this application is the first situation, that is, the first diaphragm including the porous coating is arranged between the first electrode and the second electrode. At this time, the porous coating is arranged close to the electrode, and the porous coating can better protect the electrode and improve the performance of the battery.

[0019] Optionally, the second diaphragm does not include a porous coating, and the second diaphragm is provided on a side of the first pole piece or the second pole piece facing away from the first diaphragm.

[0020] It is understood that when the first separator includes a porous coating and the second separator does not, the preferred solution in this application is to dispose the first separator including the porous coating between the first and second electrode sheets. In this case, the porous coating is disposed close to the electrode sheets, which can better protect the electrode sheets and improve battery performance. For example, when the porous coating includes an adhesive layer, the adhesive directly contacts the electrode sheets, which helps improve the adhesion between the electrode sheets and the separator.

[0021] Optionally, the electrode assembly includes a wound structure, the wound structure includes an inner side and an outer side, and the wound structure includes a negative electrode, a first separator, a positive electrode, and a second separator stacked in sequence from the inner side to the outer side.

[0022] It can be understood that after each electrode and each diaphragm is stacked in sequence, they will be bent and wound along the winding center. The electrode will be bent so that the electrode assembly forms a corner portion, and there is a straight portion between the two corner portions. During the winding process, a structure stacked in circles will be formed. The first circle formed is defined as the inner circle, and then the winding is repeated on the outer surface of the inner circle. The last circle formed by winding is defined as the outer circle. The space enclosed by the inner circle is defined as the inner side, and the area where the outer surface of the outer circle is located is the outer side.

[0023] It can be understood that in the wound electrode assembly, the wound structure includes an inner side and an outer side, and the wound structure includes a negative electrode, a first separator, a positive electrode, and a second separator stacked in sequence from the inner side to the outer side. Taking into account the following problems that may exist in the wound structure, since the negative electrode will expand during the cycle, a gap will be formed between the positive electrode and the negative electrode, resulting in an increase in the corner area of ​​the positive electrode at the corner (it can be understood that the corner refers to the bending part of the wound structure). This structural feature causes the problem of negative electrode lithium plating in the process of lithium ions in the positive electrode (taking lithium secondary batteries as an example) being embedded in the negative electrode. This is mainly because the area of ​​the positive electrode corner increases. Under a certain negative electrode area, the number of lithium ions reaching the negative electrode area increases, and the area of ​​the negative electrode is insufficient to accommodate the increased lithium ions, resulting in lithium plating at the negative electrode. In order to alleviate the above problems, a first diaphragm is arranged between the two pole pieces. The first diaphragm includes a porous coating. When the porous coating includes an adhesive layer, the bonding force of the two pole pieces can be improved, the problem of gap formation between the two pole pieces can be reduced, and the phenomenon of lithium plating can be improved.

[0024] Optionally, the thickness of the second porous base membrane is greater than the thickness of the first porous base membrane.

[0025] Considering that the first diaphragm includes a porous coating, which has the effect of reducing the penetration of lithium dendrites (taking lithium secondary batteries as an example) into the first diaphragm, and the second diaphragm does not include a porous coating, in order to improve the anti-puncture effect of the second diaphragm, the thickness of the second porous base membrane is greater than the thickness of the first porous base membrane to reduce the puncture of the second diaphragm and improve the safety of the battery.

[0026] When the thickness of the second porous base membrane is greater than that of the first porous base membrane, the thickness of the first diaphragm and the thickness of the second diaphragm are not limited. For example, the thickness of the first diaphragm can be greater than that of the second diaphragm, or the thickness of the first diaphragm can be less than that of the second diaphragm, or the thickness of the first diaphragm can be equal to that of the second diaphragm. The design can be made according to the thickness requirements and functional requirements of the electrode assembly. For example, in one case, on the one hand, the thickness of the electrode assembly needs to be reduced, and on the other hand, the risk of the diaphragm being punctured needs to be reduced. At this time, when the thickness of the second porous base membrane is greater than that of the first porous base membrane, the thickness of the first porous base membrane can be reduced, and a porous coating can be provided on the first porous base membrane. In this way, the overall thickness of the base membrane is reduced, thereby helping to reduce the thickness of the electrode assembly and increase the thickness of the second porous base membrane. In addition, a porous coating can be provided on the first porous base membrane to help improve the strength of the diaphragm.

[0027] Of course, there are some cases where it is necessary to set a porous coating on the first porous base membrane. Since the setting of the porous coating will increase the thickness of the first diaphragm, in this case, when the thickness of the first porous base membrane is the same as that of the second porous base membrane, the thickness of the first diaphragm will be greater than that of the second diaphragm. In other cases, when the first diaphragm is set between the two pole pieces, considering that there will be a problem of lithium dendrites (taking lithium secondary batteries as an example) penetrating the first diaphragm between the pole pieces, in order to alleviate this problem, the thickness of the first diaphragm can be made greater than that of the second diaphragm. The increase in thickness can reduce the risk of lithium dendrites piercing the first diaphragm and improve the safety of the electrode assembly.

[0028] Optionally, the porosity of the first porous base membrane is greater than the porosity of the second porous base membrane.

[0029] On the one hand, considering the need to set a porous coating on the first porous base membrane, since the setting of the porous coating will make the porosity of the first diaphragm worse than that of the first porous base membrane, in order to alleviate the problem of poor air permeability of the first diaphragm and ensure that the first diaphragm has good air permeability, the porosity of the first porous base membrane is greater than the porosity of the second porous base membrane.

[0030] On the other hand, when the first separator is disposed between the two electrode sheets, in order to facilitate the transmission of lithium ions between the two electrode sheets through the first separator, the porosity of the first porous base membrane is greater than the porosity of the second porous base membrane.

[0031] Optionally, the air permeability of the first diaphragm is greater than the air permeability of the second diaphragm.

[0032] When the first diaphragm is disposed between the two electrode sheets, in order to facilitate the transmission of lithium ions, the air permeability of the first diaphragm is greater than that of the second diaphragm.

[0033] Optionally, the ratio of the thickness of the first diaphragm to the thickness of the second diaphragm is 1:2-18:5. Optionally, the ratio of the thickness of the first diaphragm to the thickness of the second diaphragm is 1:2-3:1.

[0034] In the present application, after the electrode assembly is compacted, the thickness ratio of the first diaphragm to the second diaphragm is 1:2-18:5, and can be optionally 1:2-3:1.

[0035] In the present application, the thickness of the first diaphragm and the second diaphragm can be comprehensively controlled to ensure that the overall thickness of the electrode assembly meets actual needs. For example, when the overall thickness of the first diaphragm and the second diaphragm remains unchanged, the thickness of the porous coating in the first diaphragm can be increased and the thickness of the second diaphragm can be reduced, thereby ensuring that the overall thickness of the diaphragm remains unchanged.

[0036] For example, considering that secondary batteries require different expansion spaces in different application scenarios, the thickness of the bare cell can be controlled at the same number of winding turns by changing the type and thickness of the first porous base membrane of the first diaphragm, the thickness of the porous coating, the type of functional material, etc.

[0037] Optionally, the thickness of the first diaphragm is 8 μm-18 μm;

[0038] And / or, the thickness of the second separator is 5 μm-16 μm.

[0039] Optionally, the thickness of the first diaphragm is 10 μm-15 μm;

[0040] And / or, the thickness of the second separator is 5 μm-10 μm.

[0041] The thickness of the first diaphragm and the thickness of the second diaphragm are not limited in this application. For example, the thickness of the first diaphragm is 8 μm-18 μm, and can be 10 μm-15 μm. The thickness of the second diaphragm is 5 μm-16 μm, and can be 5 μm-10 μm.

[0042] In some cases, when the first diaphragm includes a porous coating and the second diaphragm does not include a porous coating, when the thickness of the first porous base membrane is the same as that of the second porous base membrane, the first diaphragm includes the first porous base membrane and the porous coating. Since the porous coating has a thickness, there is a case where the thickness of the first diaphragm is greater than that of the second diaphragm. Of course, there are other cases. When the thickness of the first porous base membrane is less than that of the second porous base membrane, a porous coating is set on the first porous base membrane, which can make the thickness of the first diaphragm and the second diaphragm the same. Those skilled in the art can make it according to actual needs.

[0043] Optionally, the porous coating layer has a thickness of 1 μm-5 μm.

[0044] The thickness of the porous coating layer is not limited in the present application, for example, the thickness of the porous coating layer is 0.5 μm-8 μm, and can be optionally 1 μm-5 μm, and can be set by those skilled in the art as needed.

[0045] Optionally, the air permeability of the first diaphragm is 80s / 100cc-250s / 100cc;

[0046] And / or, the air permeability of the second separator is 110s / 100cc-310s / 100cc.

[0047] Optionally, the air permeability of the first diaphragm is 110s / 100cc-210s / 100cc;

[0048] And / or, the air permeability of the second diaphragm is 210s / 100cc-310s / 100cc.

[0049] The air permeability of the first diaphragm and the second diaphragm is not limited in this application. For example, the air permeability of the first diaphragm includes 80s / 100cc-250s / 100cc, and can be optionally 110s / 100cc-210s / 100cc; the air permeability of the second diaphragm includes 110s / 100cc-310s / 100cc, and can be optionally 210s / 100cc-310s / 100cc.

[0050] The air permeability of the first membrane satisfies the above range, which can improve the transmission of ions between the first membranes. The air permeability of the second membrane satisfies the above range, which can improve the transmission of ions between the second membranes.

[0051] Optionally, the porous coating layer is provided on at least one side of the first porous base membrane;

[0052] And / or, the porous coating layer includes at least one of a binder and an inorganic material.

[0053] In the first diaphragm, the porous coating is arranged on at least one side of the first porous base membrane, so that the porous coating is closer to the electrode, effectively playing the role of the porous coating. For example, when the porous coating includes an adhesive, the adhesive directly contacts the electrode, which helps to improve the adhesion between the electrode and the diaphragm.

[0054] Taking into account the expansion, heat generation, gas generation, and even the formation of dendrites in some cases of the electrode assembly during the cycle, in order to solve the above problems, the porous coating may include a binder and / or an inorganic material. The binder can enhance the bonding force between the first electrode and / or the second electrode and the diaphragm, and the inorganic material can enhance the heat resistance and mechanical properties of the diaphragm. Of course, in addition to the binder and / or inorganic material included in the porous coating, other functional materials may also be included, such as lithium supplements (for lithium secondary batteries, this application does not limit the type of secondary batteries), etc., which can be set as needed.

[0055] It is understood that the present application does not limit the particle size of the inorganic material. For example, in one embodiment, the Dv50 of the inorganic material is in a range of 0.5 μm to 2 μm.

[0056] At the same time, the arrangement of the binder and the inorganic material in the porous coating is not limited. For example, the porous coating can include a binder or an inorganic material alone, the porous coating can include both at the same time, the binder and the inorganic material can be directly mixed and arranged in a layer structure, or the binder and the inorganic material can be arranged separately in different layered structures, or the inorganic material can be directly arranged in the first porous base membrane (for example, the base membrane material is mixed with the inorganic material and then a composite membrane is prepared by a co-extrusion device). The specific method is not limited and can be arranged as needed.

[0057] Optionally, the porous coating layer includes at least one of a bonding layer and a heat-resistant layer.

[0058] The bonding layer mainly plays a bonding role, which is used to fix the two pole pieces, or to fix the pole pieces and the diaphragm. In addition, inorganic materials and other substances can be added to the bonding layer to improve the comprehensive performance of the bonding layer. It can be set according to needs.

[0059] The heat-resistant layer primarily enhances the separator's heat resistance and mitigates thermal shrinkage. For example, the heat-resistant layer can include inorganic materials, which can improve the separator's heat resistance, oxidation resistance, puncture resistance, and wettability, thereby enhancing battery safety. Other functional materials can also be added to the heat-resistant layer, allowing for customized configurations.

[0060] Optionally, an adhesive layer is provided on at least one side of the first porous base membrane.

[0061] To improve the interfacial bonding between the separator and the electrode, thereby increasing the hardness of the battery cell and reducing deformation of the battery cell, an adhesive layer is provided on at least one side of the first porous base membrane. It is understood that the adhesive layer can be provided on one side of the first porous base membrane or on both sides of the first porous base membrane, and the arrangement can be as needed.

[0062] Optionally, a heat-resistant layer is provided between the first porous base membrane and the bonding layer.

[0063] In order to improve the heat resistance of the base membrane, a heat-resistant layer is provided between the first porous base membrane and the bonding layer. The heat-resistant layer may include an inorganic material. The inorganic material can enhance the heat resistance, oxidation resistance, puncture resistance and wettability of the separator, which is beneficial to improving the safety of the battery. It is understandable that when a bonding layer is provided on one side of the first porous base membrane, a heat-resistant layer may be provided between the first porous base membrane on that side and the bonding layer. Of course, a heat-resistant layer may also be provided on the other side of the first porous base membrane. Of course, when no bonding layer is provided on both sides of the first porous base membrane, a heat-resistant layer may be provided on both sides or one side of the first porous base membrane. It can be provided according to specific needs.

[0064] It can be understood that when the first porous base membrane is provided with both an adhesive layer and a heat-resistant layer, the interfacial bonding force between the electrode and the diaphragm can be increased, the risk of wrinkling of the electrode can be reduced, and the first diaphragm can be provided with better heat resistance, oxidation resistance, puncture resistance and other functions.

[0065] Optionally, the thickness of the bonding layer is 0.5 μm-5 μm.

[0066] And / or, the thickness of the heat-resistant layer is 0 μm-3 μm.

[0067] Optionally, the thickness of the bonding layer is 1 μm-3 μm;

[0068] And / or, the thickness of the heat-resistant layer is 1 μm-2 μm.

[0069] The porous coating in the present application may include a bonding layer, which may improve the bonding force between the electrode and the diaphragm. The present application does not limit the thickness of the bonding layer. For example, the thickness of the bonding layer may include 0.5 μm-5 μm, and may be optionally 1 μm-3 μm.

[0070] In the present application, the porous coating may include a heat-resistant layer, which may include inorganic materials. The inorganic materials can enhance the heat resistance, oxidation resistance, puncture resistance and wettability of the diaphragm, which is beneficial to improving the safety of the battery. The present application does not limit the thickness of the heat-resistant layer, for example, 0μm-3μm, and can be optionally 1μm-2μm.

[0071] Optionally, the bonding layer comprises a layered coating, and the layered coating is provided on the first diaphragm;

[0072] Alternatively, the bonding layer includes a dot coating layer, and the dot coating layer is spaced apart from the first diaphragm.

[0073] The layered coating refers to a continuous coating of the adhesive on the surface of the first porous base membrane.

[0074] The dot coating refers to the adhesive being discontinuously disposed on the surface of the first porous base membrane.

[0075] Furthermore, the dot-shaped coating is spaced apart from the first porous base film, ensuring good air permeability of the first diaphragm and facilitating ion transport. Furthermore, the dot-shaped coating increases its contact area with the electrolyte, making it more susceptible to swelling. After swelling, the dot-shaped coating increases in volume, increasing its contact area with the electrode and improving adhesion between the electrode and the diaphragm. The pores of the swollen dot-shaped coating can store electrolyte, increasing the wettability of the first diaphragm to the electrolyte and improving ion transport.

[0076] Optionally, the coverage area of ​​the dot coating is 50%-90% of the surface area of ​​the first diaphragm.

[0077] Optionally, the coverage area of ​​the dot coating is 60%-80% of the surface area of ​​the first diaphragm.

[0078] For example, the area of ​​one side of the first diaphragm is S, and the total coating area of ​​each dot coating on one side of the first diaphragm is s1. Then the ratio of the coverage area of ​​the dot coating to the surface area of ​​the first diaphragm is s1 / S, and the range of s1 / S is 50%-90%, and can be optionally 60%-80%.

[0079] The ratio of the coverage area of ​​the dot-shaped coating to the surface area of ​​the first separator is within the above range, which can improve the adhesion of the adhesive layer.

[0080] Optionally, the bonding layer includes a bonding agent, and the mass percentage of the bonding agent to the total mass of the bonding layer is 80%-95%, and optionally 85%-90%;

[0081] And / or, the heat-resistant layer comprises an inorganic material, and the mass percentage of the inorganic material to the total mass of the heat-resistant layer is 60%-80%, optionally 67%-75%.

[0082] In the present application, the mass percentage of the binder to the total mass of the adhesive layer is 80%-95%, optionally 85%-90%. The heat-resistant layer includes an inorganic material, and the mass percentage of the inorganic material to the total mass of the heat-resistant layer is 60%-80%, optionally 67%-75%. The mass percentage of the binder to the total mass of the adhesive layer falling within the above range can improve the bonding properties of the adhesive layer. The mass percentage of the inorganic material to the total mass of the heat-resistant layer falling within the above range can improve the heat resistance of the heat-resistant layer, further improving the heat resistance and mechanical properties of the first separator.

[0083] Optionally, the binder includes at least one of a copolymer of vinylidene fluoride and hexafluoropropylene, a copolymer of vinylidene fluoride and trichloroethylene, polyacrylate, polyacrylic acid, polyacrylate, polyacrylonitrile, polyvinyl pyrrolidone, polyvinyl acetate, ethylene-vinyl acetate copolymer, polyimide, polyethylene oxide, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethyl pullulan, cyanoethyl polyvinyl alcohol, cyanoethyl cellulose, cyanoethyl sucrose, pullulan, carboxymethyl cellulose, sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, acrylonitrile-styrene-butadiene copolymer, polyvinyl alcohol, a styrene-butadiene copolymer and polyvinylidene fluoride;

[0084] And / or, the inorganic material includes at least one of silicon dioxide, aluminum oxide, titanium oxide, zinc oxide, magnesium oxide, hafnium dioxide, tin oxide, zirconium oxide, yttrium oxide, silicon carbide, boehmite, magnesium hydroxide, aluminum hydroxide, calcium titanate, barium titanate, lithium phosphate, lithium titanium phosphate, and lithium lanthanum titanate.

[0085] The binders in the present application include, but are not limited to, at least one of a copolymer of vinylidene fluoride and hexafluoropropylene, a copolymer of vinylidene fluoride and trichloroethylene, polyacrylates, polyacrylic acids, polyacrylates, polyacrylonitrile, polyvinyl pyrrolidone, polyvinyl acetate, ethylene-vinyl acetate copolymer, polyimide, polyethylene oxide, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethyl pullulan, cyanoethyl polyvinyl alcohol, cyanoethyl cellulose, cyanoethyl sucrose, pullulan, carboxymethyl cellulose, sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, acrylonitrile-styrene-butadiene copolymer, polyvinyl alcohol, a styrene-butadiene copolymer and polyvinylidene fluoride.

[0086] The inorganic materials in the present application include but are not limited to at least one of silicon dioxide, aluminum oxide, titanium oxide, zinc oxide, magnesium oxide, hafnium dioxide, tin oxide, zirconium oxide, yttrium oxide, silicon carbide, boehmite, magnesium hydroxide, aluminum hydroxide, calcium titanate, barium titanate, lithium phosphate, lithium titanium phosphate, and lithium lanthanum titanate.

[0087] It is understandable that the above-mentioned lithium titanium phosphate and lithium lanthanum titanate are a kind of solid electrolyte, and the solid electrolyte material can react with metallic lithium (taking lithium secondary batteries as an example, the present application does not limit the type of battery) to absorb lithium dendrites and prevent lithium dendrites from penetrating the diaphragm. That is, a solid electrolyte can be added to the heat-resistant layer, and the solid electrolyte includes but is not limited to at least one of lithium aluminum titanium phosphate, lithium titanium phosphate, lithium tetrathiophosphate, lithium germanium phosphosulfur sulfide, and lithium phosphosulfur chloride. Furthermore, the solid electrolyte has a certain ionic conductivity and low electronic conductivity. When used as an electrolyte material, it has good ion conductivity and electronic insulation. Therefore, when used as a diaphragm coating, it will not significantly increase the diaphragm impedance and inhibit the transfer of electrons through the diaphragm.

[0088] The present application also provides a battery comprising the electrode assembly.

[0089] The present application also provides an electrical device, which includes the battery.

[0090] The electrode assembly of the present application includes a first electrode piece, a second electrode piece, and a first diaphragm and a second diaphragm; one of the first diaphragm and the second diaphragm is arranged between the first electrode piece and the second electrode piece, and the other of the first diaphragm and the second diaphragm is arranged on the side of the first electrode piece or the second electrode piece away from the first diaphragm; one of the first diaphragm and the second diaphragm does not include a porous coating, and the other of the first diaphragm and the second diaphragm includes a porous coating, and the thickness of the porous coating is 0.5μm-8μm. The design of the first diaphragm and the second diaphragm in the present application is different. During the battery cycle, more expansion space is reserved for the battery cell, reducing the squeezing of the battery cell by the shell during the expansion process, improving the phenomenon of active material being damaged by the squeezing force during the squeezing process, and also improving the phenomenon of electrolyte being squeezed out during the squeezing process, so that the battery cell is effectively immersed in the electrolyte during the expansion process, which is conducive to the transmission of ions and thus effectively improves the cycle performance of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0091] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying any creative work.

[0092] FIG1 is a schematic structural diagram of an embodiment of an electrode assembly of the present application;

[0093] FIG2 is a schematic structural diagram of another embodiment of the electrode assembly of the present application;

[0094] FIG3 is a schematic structural diagram of another embodiment of the electrode assembly of the present application;

[0095] FIG4 is a schematic structural diagram of an embodiment of the first diaphragm of the present application;

[0096] FIG5 is a schematic structural diagram of another embodiment of the first diaphragm of the present application;

[0097] FIG6 is a schematic diagram of a battery cell provided in an embodiment of the present application;

[0098] FIG7 is an exploded view of the battery cell provided by the embodiment of the present application shown in FIG6 ;

[0099] FIG8 is a schematic diagram of a battery module provided in an embodiment of the present application;

[0100] FIG9 is a schematic diagram of a battery pack provided in an embodiment of the present application;

[0101] FIG10 is an exploded view of the battery pack provided by the embodiment of the present application shown in FIG9 ;

[0102] FIG11 is a schematic diagram of an electrical device using a battery cell provided in an embodiment of the present application as a power source.

[0103] Description of Figure Numbers:

[0104] The realization of the objectives, functional features and advantages of this application will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0105] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0106] Below, the embodiments of the electrode assembly, battery, and electrical device of the present application are described in detail with appropriate reference to the accompanying drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there may be cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0107] " range " disclosed in the present application is limited in the form of lower limit and upper limit, and given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of special range. The scope limited in this way can be to include end value or not include end value, and can be arbitrarily combined, that is, any lower limit can form a range with any upper limit combination. For example, if the scope of 60-120 and 80-110 is listed for specific parameters, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range value 1 and 2 are listed, and if the maximum range value 3,4 and 5 are listed, then the following range can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, unless otherwise specified, the numerical range " ab " represents the abbreviation of any real number combination between a and b, wherein a and b are all real numbers. For example, a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is simply an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0108] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0109] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0110] Unless otherwise specified, all steps of the present application 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 may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), indicating that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0111] In the related art, a secondary battery, such as a lithium secondary battery, a sodium secondary battery, etc., is manufactured by housing an electrode assembly including a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode, and an electrolyte in a case.

[0112] Secondary batteries have been widely used in various consumer electronic products and electric vehicles due to their advantages such as high energy density, high output voltage, good safety, no pollution and no memory effect.

[0113] As the application scope of secondary batteries becomes wider and wider, the demand for their use by customers is also increasing. However, how to make secondary batteries have better electrochemical performance is still a difficult point in the current development of secondary batteries.

[0114] In order to solve the above technical problems, the present application provides an electrode assembly, which aims to improve the cycle performance of the battery.

[0115] An electrode assembly includes a first electrode piece, a second electrode piece, and a first diaphragm and a second diaphragm; one of the first diaphragm and the second diaphragm is arranged between the first electrode piece and the second electrode piece, and the other of the first diaphragm and the second diaphragm is arranged on the side of the first electrode piece or the second electrode piece away from the first diaphragm; one of the first diaphragm and the second diaphragm does not include a porous coating, and the other of the first diaphragm and the second diaphragm includes a porous coating, and the thickness of the porous coating is 0.5μm-8μm.

[0116] It can be understood that one of the first electrode and the second electrode is a positive electrode, and the other is a negative electrode.

[0117] It can be understood that the setting positions of the first diaphragm and the second diaphragm in the electrode are not limited and can be set as needed. For example, one of the first diaphragm and the second diaphragm is set between the first electrode and the second electrode, and the other of the first diaphragm and the second diaphragm is set on the side of the first electrode or the second electrode away from the first diaphragm.

[0118] One of the first separator and the second separator does not include a porous coating, and the other of the first separator and the second separator includes a porous coating, and the thickness of the porous coating is 0.5μm-8μm. For example, the first separator does not include a porous coating, and the second separator includes a porous coating, or the second separator does not include a porous coating, and the first separator includes a porous coating.

[0119] It can be understood that the design of the first diaphragm and the second diaphragm in this application is different. During the battery cycle, more expansion space is reserved for the battery cell, reducing the squeezing of the shell on the battery cell during the expansion process, improving the phenomenon of active material being damaged by the squeezing force during the squeezing process, and also improving the phenomenon of electrolyte being squeezed out during the squeezing process, so that the battery cell is effectively immersed in the electrolyte during the expansion process, which is conducive to the transmission of ions, thereby effectively improving the cycle performance of the battery.

[0120] In the above 0.5μm-8μm, the values ​​include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Specific examples include but are not limited to the point values ​​in the embodiments and 0.5μm, 1μm, 3μm, 5μm, 7μm, 8μm, etc., as well as the range values ​​between any two of the above point values.

[0121] In one embodiment, the first separator includes a first porous base membrane and a porous coating layer; and / or the second separator includes a second porous base membrane.

[0122] It is understandable that the materials of the first porous base membrane and the second porous base membrane can be the same or different, and the thicknesses of the first porous base membrane and the second porous base membrane can be the same or different, which can be set according to needs.

[0123] Specifically, the present application includes a first diaphragm and a second diaphragm. The first diaphragm includes a first porous base membrane and a porous coating. The porous coating can be a structure used to perform bonding functions or heat-resistant functions, and of course it can also be a structure with other functions. The present application is not limited to this. The performance of the electrode assembly is improved by introducing a porous coating; the second diaphragm includes a second porous base membrane. It can be understood that the base membrane refers to the basic material of the diaphragm, such as an organic microporous membrane, that is, the second diaphragm may not include a porous coating.

[0124] It can be understood that the setting position of the porous coating in the first diaphragm is not limited. For example, the porous coating can be set on at least one side of the first porous base membrane, or the porous coating is composited on the first porous base membrane. For example, the material of the porous coating is mixed with the material of the base membrane, and a composite diaphragm is prepared by melt co-extrusion.

[0125] It is also understood that the placement of the first diaphragm 100 and the second diaphragm 300 in this application is not limited and can be placed according to actual needs. For example, as shown in FIG1 , which is a schematic structural diagram of an electrode assembly 1000, in one case, the first diaphragm 100 is placed between the first electrode piece 20 and the second electrode piece 40, and the second diaphragm 300 is placed on the side of the first electrode piece 20 or the second electrode piece 40 facing away from the first diaphragm. In another case, the second diaphragm is placed between the first electrode piece and the second electrode piece, and the first diaphragm is placed on the side of the first electrode piece or the second electrode piece facing away from the first diaphragm.

[0126] It can be understood that when the first diaphragm includes a porous coating and the second diaphragm does not include a porous coating, the preferred solution in this application is the first situation, that is, the first diaphragm including the porous coating is arranged between the first electrode and the second electrode. At this time, the porous coating is arranged close to the electrode, and the porous coating can better protect the electrode and improve the performance of the battery.

[0127] In one embodiment, the second diaphragm does not include a porous coating layer, and the second diaphragm is disposed on a side of the first electrode piece or the second electrode piece facing away from the first diaphragm.

[0128] It is understood that when the first separator includes a porous coating and the second separator does not, the preferred solution in this application is to dispose the first separator including the porous coating between the first and second electrode sheets. In this case, the porous coating is disposed close to the electrode sheets, which can better protect the electrode sheets and improve battery performance. For example, when the porous coating includes an adhesive layer, the adhesive directly contacts the electrode sheets, which helps improve the adhesion between the electrode sheets and the separator.

[0129] In one embodiment, the electrode assembly includes a wound structure including an inner side and an outer side, and the wound structure includes a negative electrode, a first separator, a positive electrode, and a second separator stacked in sequence from the inner side to the outer side.

[0130] The inner and outer sides can refer to those shown in FIG2 . After the pole pieces 15 and the diaphragms 14 are stacked in sequence, they will be bent and wound along the winding center 50 . The pole pieces will be bent so that the electrode assembly forms a corner portion 80 , and there is a straight portion 90 between the two corner portions 80 . During the winding process, a structure stacked in circles will be formed. The first circle formed is defined as the inner circle 60 , and then the winding is repeated on the outer surface of the inner circle 60 . The last circle formed by the winding is defined as the outer circle 70 . The space enclosed by the inner circle 60 is defined as the inner side 61 , and the area where the outer surface of the outer circle 70 is located is defined as the outer side 71 .

[0131] It can be understood that in the electrode assembly of the wound structure, the wound structure includes an inner side and an outer side. For example, Figure 3 is a schematic diagram of a wound structure. The wound structure includes a negative electrode 22, a first diaphragm 100, a positive electrode 24, and a second diaphragm 300 stacked in sequence from the inner side to the outer side. Taking into account the following problems that may exist in the wound structure, since the negative electrode will expand during the cycle, a gap will be formed between the positive electrode and the negative electrode, resulting in an increase in the corner area of ​​the positive electrode at the corner (it can be understood that the corner refers to the bending part of the wound structure). This structural feature causes the problem of negative electrode lithium plating in the process of lithium ions in the positive electrode (taking lithium secondary batteries as an example) being embedded in the negative electrode. This is mainly because the area of ​​the positive electrode corner increases. Under a certain negative electrode area, the number of lithium ions reaching the negative electrode area increases, and the area of ​​the negative electrode is insufficient to accommodate the increased lithium ions, resulting in lithium plating at the negative electrode. In order to alleviate the above problems, a first diaphragm is arranged between the two pole pieces. The first diaphragm includes a porous coating. When the porous coating includes an adhesive layer, the bonding force of the two pole pieces can be improved, the problem of gap formation between the two pole pieces can be reduced, and the phenomenon of lithium plating can be improved.

[0132] In one embodiment, the thickness of the second porous base membrane is greater than the thickness of the first porous base membrane.

[0133] Considering that the first diaphragm includes a porous coating, for example, when the porous coating includes an inorganic material, it has the effect of reducing the penetration of lithium dendrites (taking lithium secondary batteries as an example) through the first diaphragm, and the second diaphragm does not include a porous coating. In order to improve the anti-puncture effect of the second diaphragm, the thickness of the second porous base membrane is greater than the thickness of the first porous base membrane to reduce the puncture of the second diaphragm and improve the safety of the battery.

[0134] When the thickness of the second porous base membrane is greater than that of the first porous base membrane, the thickness of the first diaphragm and the thickness of the second diaphragm are not limited. For example, the thickness of the first diaphragm can be greater than that of the second diaphragm, or the thickness of the first diaphragm can be less than that of the second diaphragm, or the thickness of the first diaphragm can be equal to that of the second diaphragm. The design can be made according to the thickness requirements and functional requirements of the electrode assembly. For example, in one case, on the one hand, the thickness of the electrode assembly needs to be reduced, and on the other hand, the risk of the diaphragm being punctured needs to be reduced. At this time, when the thickness of the second porous base membrane is greater than that of the first porous base membrane, the thickness of the first porous base membrane can be reduced, and a porous coating can be provided on the first porous base membrane. In this way, the overall thickness of the base membrane is reduced, thereby helping to reduce the thickness of the electrode assembly and increase the thickness of the second porous base membrane. In addition, a porous coating can be provided on the first porous base membrane to help improve the strength of the diaphragm.

[0135] Of course, there are some cases where it is necessary to set a porous coating on the first porous base membrane. Since the setting of the porous coating will increase the thickness of the first diaphragm, in this case, when the thickness of the first porous base membrane is the same as that of the second porous base membrane, the thickness of the first diaphragm will be greater than that of the second diaphragm. In other cases, when the first diaphragm is set between the two pole pieces, considering that there will be a problem of lithium dendrites (taking lithium secondary batteries as an example) penetrating the first diaphragm between the pole pieces, in order to alleviate this problem, the thickness of the first diaphragm can be made greater than that of the second diaphragm. The increase in thickness can reduce the risk of lithium dendrites piercing the first diaphragm and improve the safety of the electrode assembly.

[0136] In one embodiment, the porosity of the first porous base membrane is greater than the porosity of the second porous base membrane.

[0137] On the one hand, considering the need to set a porous coating on the first porous base membrane, since the setting of the porous coating will make the porosity of the first diaphragm worse than that of the first porous base membrane, in order to alleviate the problem of poor air permeability of the first diaphragm and ensure that the first diaphragm has good air permeability, the porosity of the first porous base membrane is greater than the porosity of the second porous base membrane.

[0138] On the other hand, when the first separator is disposed between the two electrode sheets, in order to facilitate the transmission of lithium ions between the two electrode sheets through the first separator, the porosity of the first porous base membrane is greater than the porosity of the second porous base membrane.

[0139] In one embodiment, the air permeability of the first membrane is greater than the air permeability of the second membrane.

[0140] When the first diaphragm is disposed between the two electrode sheets, in order to facilitate the transmission of lithium ions, the air permeability of the first diaphragm is greater than that of the second diaphragm.

[0141] In the first diaphragm, the porous coating is arranged on at least one side of the first porous base membrane, so that the porous coating is closer to the electrode, effectively playing the role of the porous coating. For example, when the porous coating includes an adhesive, the adhesive directly contacts the electrode, which helps to improve the adhesion between the electrode and the diaphragm.

[0142] In one embodiment, the porous coating layer is disposed on at least one side of the first porous base membrane; and / or the porous coating layer includes at least one of a binder and an inorganic material.

[0143] In the first diaphragm, the porous coating is arranged on at least one side of the first porous base membrane, so that the porous coating is closer to the electrode, effectively playing the role of the porous coating. For example, when the porous coating includes an adhesive, the adhesive directly contacts the electrode, which helps to improve the adhesion between the electrode and the diaphragm.

[0144] Taking into account the expansion, heat generation, gas generation, and even the formation of dendrites in some cases of the electrode assembly during the cycle, in order to improve the above problems, the porous coating may include a binder and / or an inorganic material. The binder can enhance the bonding force between the first electrode and / or the second electrode and the diaphragm, and the inorganic material can enhance the heat resistance and mechanical properties of the diaphragm. Of course, in addition to the binder and / or inorganic material included in the porous coating, other functional materials may also be included, such as lithium supplements (for lithium secondary batteries, this application does not limit the type of secondary batteries), etc., which can be set as needed.

[0145] It is understood that the present application does not limit the particle size of the inorganic material. For example, in one embodiment, the Dv50 of the inorganic material is in a range of 0.5 μm to 2 μm.

[0146] At the same time, the arrangement of the binder and the inorganic material in the porous coating is not limited. For example, the porous coating can include a binder or an inorganic material alone, the porous coating can include both at the same time, the binder and the inorganic material can be directly mixed and arranged in a layer structure, or the binder and the inorganic material can be arranged separately in different layered structures, or the inorganic material can be directly arranged in the first porous base membrane (for example, the base membrane material is mixed with the inorganic material and then a composite membrane is prepared by a co-extrusion device). The specific method is not limited and can be arranged as needed.

[0147] In one embodiment, the porous coating layer includes at least one of a bonding layer and a heat-resistant layer.

[0148] The bonding layer mainly plays a bonding role, which is used to fix the two pole pieces, or to fix the pole pieces and the diaphragm. In addition, inorganic materials and other substances can be added to the bonding layer to improve the comprehensive performance of the bonding layer. It can be set according to needs.

[0149] The heat-resistant layer primarily enhances the separator's heat resistance, addressing the issue of thermal shrinkage. For example, the heat-resistant layer can include inorganic materials, which can improve the separator's heat resistance, oxidation resistance, puncture resistance, and wettability, thereby enhancing battery safety. Other functional materials can also be added to the heat-resistant layer, allowing for customized configurations.

[0150] In one embodiment, a bonding layer is provided on at least one side of the first porous base membrane.

[0151] To improve the interfacial bonding between the separator and the electrode, thereby increasing the hardness of the battery cell and reducing deformation of the battery cell, an adhesive layer is provided on at least one side of the first porous base membrane. It is understood that the adhesive layer can be provided on one side of the first porous base membrane or on both sides of the first porous base membrane, and the arrangement can be as needed.

[0152] In one embodiment, a heat-resistant layer is provided between the first porous base membrane and the adhesive layer.

[0153] In order to improve the heat resistance of the base membrane, a heat-resistant layer is provided between the first porous base membrane and the bonding layer. The heat-resistant layer may include an inorganic material. The inorganic material can enhance the heat resistance, oxidation resistance, puncture resistance and wettability of the separator, which is beneficial to improving the safety of the battery. It is understandable that when a bonding layer is provided on one side of the first porous base membrane, a heat-resistant layer may be provided between the first porous base membrane on that side and the bonding layer. Of course, a heat-resistant layer may also be provided on the other side of the first porous base membrane. Of course, when no bonding layer is provided on both sides of the first porous base membrane, a heat-resistant layer may be provided on both sides or one side of the first porous base membrane. It can be provided according to specific needs.

[0154] It can be understood that when the first porous base membrane is provided with both an adhesive layer and a heat-resistant layer, the interfacial bonding force between the electrode and the diaphragm can be increased, the risk of wrinkling of the electrode can be reduced, and the first diaphragm can be provided with better heat resistance, oxidation resistance, puncture resistance and other functions.

[0155] For example, in one embodiment, as shown in FIG1 , a first diaphragm 100 has adhesive layers 11 disposed on both sides of the first porous base membrane 10, and a heat-resistant layer 12 disposed between the first porous base membrane 10 and the adhesive layer 11 to form a composite first diaphragm 100. The diaphragm includes both an adhesive layer and a heat-resistant layer, and the first diaphragm is disposed between the two pole pieces. The first diaphragm separates the positive pole piece from the negative pole piece, which is beneficial to the shaping of the electrode assembly and the release of corner stress, thereby suppressing the deformation of the electrochemical device.

[0156] In one embodiment, the ratio of the thickness of the first diaphragm to the thickness of the second diaphragm is 1:2-18:5, and can be optionally 1:2-3:1.

[0157] In the present application, after the electrode assembly is compacted, the thickness ratio of the first diaphragm to the second diaphragm is 1:2-18:5, and can be optionally 1:2-3:1.

[0158] In the present application, the thickness of the first diaphragm and the second diaphragm can be comprehensively controlled to ensure that the overall thickness of the electrode assembly meets actual needs. For example, when the overall thickness of the first diaphragm and the second diaphragm remains unchanged, the thickness of the porous coating in the first diaphragm can be increased and the thickness of the second diaphragm can be reduced, thereby ensuring that the overall thickness of the diaphragm remains unchanged.

[0159] For example, considering that secondary batteries require different expansion spaces in different application scenarios, the thickness of the bare cell can be controlled at the same number of winding turns by changing the type and thickness of the first porous base membrane of the first diaphragm, the thickness of the porous coating, the type of functional material, etc.

[0160] In the above 1:2-18:5, the values ​​include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Specific examples include but are not limited to the point values ​​in the embodiments and 1:2, 1:1, 2.5:1, 3:1, 3.5:1, 18:5, etc., as well as the range values ​​between any two of the above point values.

[0161] In one embodiment, the thickness of the first diaphragm is 8 μm-18 μm, and may be 10 μm-15 μm; and / or the thickness of the second diaphragm is 5 μm-16 μm, and may be 5 μm-10 μm.

[0162] The thickness of the first diaphragm and the thickness of the second diaphragm are not limited in this application. For example, the thickness of the first diaphragm is 8 μm-18 μm, and can be 10 μm-15 μm. The thickness of the second diaphragm is 5 μm-16 μm, and can be 5 μm-10 μm.

[0163] In some cases, when the first diaphragm includes a porous coating and the second diaphragm does not include a porous coating, when the thickness of the first porous base membrane is the same as that of the second porous base membrane, the first diaphragm includes the first porous base membrane and the porous coating. Since the porous coating has a thickness, there is a case where the thickness of the first diaphragm is greater than that of the second diaphragm. Of course, there are other cases. When the thickness of the first porous base membrane is less than that of the second porous base membrane, a porous coating is set on the first porous base membrane, which can make the thickness of the first diaphragm and the second diaphragm the same. Those skilled in the art can make it according to actual needs.

[0164] In the above-mentioned 8μm-18μm, the values ​​include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Specific examples include but are not limited to the point values ​​in the embodiments and 8μm, 10μm, 12μm, 15μm, 17μm, 18μm, etc., as well as the range values ​​between any two of the above-mentioned point values.

[0165] In the above 5μm-16μm, the values ​​include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Specific examples include but are not limited to the point values ​​in the embodiments and 5μm, 7μm, 9μm, 10μm, 12μm, 13μm, 14μm, 15μm, 16μm, etc., as well as the range values ​​between any two of the above point values.

[0166] In one embodiment, the porous coating layer has a thickness of 1 μm-5 μm.

[0167] The thickness of the porous coating layer is not limited in the present application, for example, the thickness of the porous coating layer is 1 μm-5 μm, and those skilled in the art can set the thickness as needed.

[0168] In the above 1μm-5μm, the values ​​include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Specific examples include but are not limited to the point values ​​in the embodiments and 1μm, 2μm, 3μm, 4μm, 5μm, etc., as well as the range values ​​between any two of the above point values.

[0169] In one embodiment, the thickness of the adhesive layer is 0.5 μm-5 μm, and may be 1 μm-3 μm; and / or the thickness of the heat-resistant layer is 0 μm-3 μm, and may be 1 μm-2 μm.

[0170] The porous coating in the present application may include a bonding layer, which may improve the bonding force between the electrode and the diaphragm. The present application does not limit the thickness of the bonding layer. For example, the thickness of the bonding layer may include 0.5 μm-5 μm, and may be optionally 1 μm-3 μm.

[0171] In the present application, the porous coating may include a heat-resistant layer, which may include inorganic materials. The inorganic materials can enhance the heat resistance, oxidation resistance, puncture resistance and wettability of the diaphragm, which is beneficial to improving the safety of the battery. The present application does not limit the thickness of the heat-resistant layer, for example, 0μm-3μm, and can be optionally 1μm-2μm.

[0172] In the above 0.5μm-5μm, the values ​​include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Specific examples include but are not limited to the point values ​​in the embodiments and 0.5μm, 0.7μm, 1μm, 2μm, 3μm, 4μm, 5μm, etc., as well as the range values ​​between any two of the above point values.

[0173] In the above 0μm-3μm, the values ​​include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Specific examples include but are not limited to the point values ​​in the embodiments and 0μm, 1μm, 1.5μm, 2μm, 2.5μm, 3μm, etc., as well as the range values ​​between any two of the above point values.

[0174] In one embodiment, the bonding layer includes a layered coating, which is disposed on the first diaphragm; or, the bonding layer includes a dotted coating, which is disposed at intervals on the first diaphragm.

[0175] The layered coating refers to a continuous coating of the adhesive on the surface of the first porous base membrane, presenting a structure as shown in FIG4 . FIG4 is an embodiment of the first separator 100 , in which the adhesive layer 11 is provided on the surface of the first porous base membrane 10 .

[0176] The dot coating refers to a discontinuous arrangement of the adhesive on the surface of the first porous base membrane, presenting a structure as shown in FIG5 . FIG5 is another embodiment of the first separator 100 , in which the dot coating 11 is arranged on the surface of the first porous base membrane 10 .

[0177] Furthermore, the dot-shaped coating is spaced apart from the first porous base film, ensuring good air permeability of the first diaphragm and facilitating ion transport. Furthermore, the dot-shaped coating increases its contact area with the electrolyte, making it more susceptible to swelling. After swelling, the dot-shaped coating increases in volume, increasing its contact area with the electrode and improving adhesion between the electrode and the diaphragm. The pores of the swollen dot-shaped coating can store electrolyte, increasing the wettability of the first diaphragm to the electrolyte and improving ion transport.

[0178] In one embodiment, the coverage area of ​​the dot coating is 50%-90%, and optionally 60%-80%, of the surface area of ​​the first diaphragm.

[0179] For example, the area of ​​one side of the first diaphragm is S, and the total coating area of ​​each dot coating on one side of the first diaphragm is s1. Then the ratio of the coverage area of ​​the dot coating to the surface area of ​​the first diaphragm is s1 / S, and the range of s1 / S is 50%-90%, and can be optionally 60%-80%.

[0180] The ratio of the coverage area of ​​the dot-shaped coating to the surface area of ​​the first separator is within the above range, which can improve the adhesion of the adhesive layer.

[0181] In the above 50%-90%, the values ​​include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Specific examples include but are not limited to the point values ​​in the embodiments and 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, etc., as well as the range values ​​between any two of the above point values.

[0182] In one embodiment, the bonding layer includes a bonding agent, the mass percentage of the bonding agent to the total mass of the bonding layer is 80%-95%, optionally 85%-90%; and / or, the heat-resistant layer includes an inorganic material, the mass percentage of the inorganic material to the total mass of the heat-resistant layer is 60%-80%, optionally 67%-75%.

[0183] In the present application, the mass percentage of the binder to the total mass of the adhesive layer is 80%-95%, optionally 85%-90%. The heat-resistant layer includes an inorganic material, and the mass percentage of the inorganic material to the total mass of the heat-resistant layer is 60%-80%, optionally 67%-75%. The mass percentage of the binder to the total mass of the adhesive layer falling within the above range can improve the bonding properties of the adhesive layer. The mass percentage of the inorganic material to the total mass of the heat-resistant layer falling within the above range can improve the heat resistance of the heat-resistant layer, further improving the heat resistance and mechanical properties of the first separator.

[0184] In the above-mentioned 80%-95%, the values ​​include the minimum and maximum values ​​of the range, as well as every value between such minimum and maximum values. Specific examples include but are not limited to the point values ​​in the embodiments and 80%, 83%, 85%, 87%, 90%, 93%, 95%, etc., as well as the range values ​​between any two of the above-mentioned point values.

[0185] In the above 60%-80%, the values ​​include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Specific examples include but are not limited to the point values ​​in the embodiments and 60%, 65%, 70%, 75%, 80%, etc., as well as the range values ​​between any two of the above point values.

[0186] In one embodiment, the air permeability of the first diaphragm is 80s / 100cc-250s / 100cc, optionally 110s / 100cc-210s / 100cc; and / or the air permeability of the second diaphragm is 110s / 100cc-310s / 100cc, optionally 210s / 100cc-310s / 100cc.

[0187] It's understandable that the battery separator's air permeability is a key indicator of battery internal resistance, reflecting the separator's permeability. According to GB / T36363-2018, the air permeability test requires the time it takes for 100ml of air to pass through a 6.45 square centimeter membrane under a pressure of 1.21 kPa applied by the test instrument, at the test temperature, humidity, and normal pressure. Better air permeability indicates greater ion flow through the membrane, leading to lower membrane resistance.

[0188] The air permeability of the first diaphragm and the second diaphragm is not limited in this application. For example, the air permeability of the first diaphragm includes 80s / 100cc-250s / 100cc, and can be optionally 110s / 100cc-210s / 100cc; the air permeability of the second diaphragm includes 110s / 100cc-310s / 100cc, and can be optionally 210s / 100cc-310s / 100cc.

[0189] The air permeability of the first membrane satisfies the above range, which can improve the transmission of ions between the first membranes. The air permeability of the second membrane satisfies the above range, which can improve the transmission of ions between the second membranes.

[0190] In the above-mentioned 80s / 100cc-250s / 100cc, the values ​​include the minimum and maximum values ​​of the range, as well as every value between such minimum and maximum values. Specific examples include but are not limited to the point values ​​in the embodiments and 80s / 100cc, 90s / 100cc, 100s / 100cc, 120s / 100cc, 140s / 100cc, 160s / 100cc, 180s / 100cc, 200s / 100cc, 220s / 100cc, 240s / 100cc, 250s / 100cc, etc., as well as the range values ​​between any two of the above-mentioned point values.

[0191] In the above-mentioned 110s / 100cc-310s / 100cc, the values ​​include the minimum and maximum values ​​of the range, and every value between such minimum and maximum values. Specific examples include but are not limited to the point values ​​in the embodiments and 110s / 100cc, 120s / 100cc, 140s / 100cc, 160s / 100cc, 180s / 100cc, 200s / 100cc, 220s / 100cc, 240s / 100cc, 250s / 100cc, 270s / 100cc, 290s / 100cc, 300s / 100cc, 310s / 100cc, etc., as well as the range values ​​between any two of the above-mentioned point values.

[0192] In one embodiment, the binder includes at least one of a copolymer of vinylidene fluoride and hexafluoropropylene, a copolymer of vinylidene fluoride and trichloroethylene, polyacrylate, polyacrylic acid, polyacrylate, polyacrylonitrile, polyvinyl pyrrolidone, polyvinyl acetate, a copolymer of ethylene and vinyl acetate, polyimide, polyethylene oxide, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethyl pullulan, cyanoethyl polyvinyl alcohol, cyanoethyl cellulose, cyanoethyl sucrose, pullulan, carboxymethyl cellulose, sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, acrylonitrile-styrene-butadiene copolymer, polyvinyl alcohol, a copolymer of styrene-butadiene, and polyvinylidene fluoride; and / or the inorganic material includes at least one of silicon dioxide, aluminum oxide, titanium oxide, zinc oxide, magnesium oxide, hafnium dioxide, tin oxide, zirconium oxide, yttrium oxide, silicon carbide, boehmite, magnesium hydroxide, aluminum hydroxide, calcium titanate, barium titanate, lithium phosphate, lithium titanium phosphate, and lithium lanthanum titanate.

[0193] The binders in the present application include, but are not limited to, at least one of a copolymer of vinylidene fluoride and hexafluoropropylene, a copolymer of vinylidene fluoride and trichloroethylene, polyacrylates, polyacrylic acids, polyacrylates, polyacrylonitrile, polyvinyl pyrrolidone, polyvinyl acetate, ethylene-vinyl acetate copolymer, polyimide, polyethylene oxide, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethyl pullulan, cyanoethyl polyvinyl alcohol, cyanoethyl cellulose, cyanoethyl sucrose, pullulan, carboxymethyl cellulose, sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, acrylonitrile-styrene-butadiene copolymer, polyvinyl alcohol, a styrene-butadiene copolymer and polyvinylidene fluoride.

[0194] The inorganic materials in the present application include but are not limited to at least one of silicon dioxide, aluminum oxide, titanium oxide, zinc oxide, magnesium oxide, hafnium dioxide, tin oxide, zirconium oxide, yttrium oxide, silicon carbide, boehmite, magnesium hydroxide, aluminum hydroxide, calcium titanate, barium titanate, lithium phosphate, lithium titanium phosphate, and lithium lanthanum titanate.

[0195] It is understandable that the above-mentioned lithium titanium phosphate and lithium lanthanum titanate are a kind of solid electrolyte, and the solid electrolyte material can react with metallic lithium (taking lithium secondary batteries as an example, the present application does not limit the type of battery) to absorb lithium dendrites and prevent lithium dendrites from penetrating the diaphragm. That is, a solid electrolyte can be added to the heat-resistant layer, and the solid electrolyte includes but is not limited to at least one of lithium aluminum titanium phosphate, lithium titanium phosphate, lithium tetrathiophosphate, lithium germanium phosphosulfur sulfide, and lithium phosphosulfur chloride. Furthermore, the solid electrolyte has a certain ionic conductivity and low electronic conductivity. When used as an electrolyte material, it has good ion conductivity and electronic insulation. Therefore, when used as a diaphragm coating, it will not significantly increase the diaphragm impedance and inhibit the transfer of electrons through the diaphragm.

[0196] The present application also provides a battery, including an electrode assembly. The battery includes a battery cell, a battery module and a battery pack.

[0197] The present application also provides an electrical device, including a battery.

[0198] In addition, the electrode assembly, battery cell, battery, and electric device of the present application will be described below with reference to the accompanying drawings as appropriate.

[0199] In one embodiment of the present application, an electrode assembly is provided.

[0200] Typically, an electrode assembly includes a positive electrode sheet, a negative electrode sheet, an electrolyte, and a separator. During the battery's charge and discharge process, active ions are embedded in and released from the positive and negative electrodes. The electrolyte conducts ions between the positive and negative electrodes. The separator is located between the positive and negative electrodes, primarily preventing a short circuit between the positive and negative electrodes while allowing ions to pass through. The separator is the separator described above in this application.

[0201] The positive electrode sheet includes a positive electrode current collector and a positive electrode film layer arranged on at least one surface of the positive electrode current collector.

[0202] As an example, the positive electrode current collector has two surfaces opposite to each other in its thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive electrode current collector.

[0203] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer material base and a metal layer formed on at least one surface of the polymer material base. 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.).

[0204] In some embodiments, when the electrode assembly is a lithium-ion battery, the positive electrode active material may be a positive electrode active material known in the art for lithium-ion batteries. As an example, the positive electrode active material may include at least one of the following materials: an olivine-structured lithium-containing phosphate, a lithium transition metal oxide, and modified compounds thereof. However, this application is not limited to these materials; other conventional materials that can be used as battery positive electrode active materials may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides include, but are not limited to, lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), lithium manganese oxide (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi1 / 3Co1 / 3Mn1 / 3O2 (also referred to as NCM333), LiNi0.5Co0.2Mn0.3O2 (also referred to as NCM523), LiNi0.5Co0.25Mn0.25O2 (also referred to as NCM211), LiNi0.6Co At least one of 0.2Mn0.2O2 (also referred to as NCM622), LiNi0.8Co0.1Mn0.1O2 (also referred to as NCM811), lithium nickel cobalt aluminum oxide (such as LiNi0.85Co0.15Al0.05O2) and modified compounds thereof. Examples of lithium-containing phosphates with an olivine structure may include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO4), a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon.

[0205] The battery's charge and discharge processes involve the intercalation and deintercalation of lithium, leading to different molar Li contents at different discharge states. The molar Li contents listed in this application for cathode materials refer to the initial state of the material, i.e., the state before addition of the materials. When the cathode material is used in a battery system, the molar Li content will change after charge and discharge cycles.

[0206] In the list of positive electrode materials in this application, the molar content of O is only a theoretical value. Lattice oxygen release will cause the molar content of oxygen to change, and the actual molar content of O will fluctuate.

[0207] In some embodiments, the positive electrode film layer may further optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylate resin.

[0208] In some embodiments, the positive electrode film layer may further include a conductive agent. For example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0209] In some embodiments, the positive electrode sheet can be prepared by the following method: the components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode current collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0210] The negative electrode sheet includes a negative electrode current collector and a negative electrode film layer provided on at least one surface of the negative electrode current collector, wherein the negative electrode film layer includes a negative electrode active material.

[0211] As an example, the negative electrode current collector has two surfaces opposite to each other in its thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0212] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer base layer and a metal layer formed on at least one surface of the polymer base material. 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 base material (such as a base material of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0213] In some embodiments, the negative electrode active material may be a negative electrode active material for a battery that is well known in the art. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate. The silicon-based material may be selected from at least one of elemental silicon, silicon oxides, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxides, and tin alloys. However, the present application is not limited to these materials, and other traditional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0214] In some embodiments, the negative electrode film layer may further include a binder. The binder may be selected from at least one of 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).

[0215] In some embodiments, the negative electrode film layer may further include a conductive agent, which may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0216] In some embodiments, the negative electrode film layer may optionally include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0217] In some embodiments, the negative electrode sheet can be prepared by the following method: the components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode current collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.

[0218] The electrolyte plays the role of conducting ions between the positive electrode and the negative electrode. This application has no specific restrictions on the type of electrolyte, and it can be selected according to needs.

[0219] In some embodiments, the electrolyte is an electrolyte solution, which includes an electrolyte salt and a solvent.

[0220] In some embodiments, the electrolyte salt may be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalatoborate, lithium dioxalatoborate, lithium difluorodioxalatophosphate, and lithium tetrafluorooxalatophosphate.

[0221] In some embodiments, the solvent can be selected from at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.

[0222] In some embodiments, the electrolyte may optionally include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, and additives that improve battery high or low temperature performance.

[0223] In some embodiments, the electrode assembly further includes a separator. The present application has no particular limitation on the type of separator, and any known porous separator with good chemical and mechanical stability can be selected.

[0224] In some embodiments, the material of the separator can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0225] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator may be formed into an electrode assembly by a winding process or a lamination process.

[0226] In some embodiments, the electrode assembly may include an outer packaging that can be used to encapsulate the electrode assembly and the electrolyte.

[0227] In some embodiments, the outer packaging of the electrode assembly may be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. Alternatively, the outer packaging of the electrode assembly may be a soft shell, such as a bag-type soft shell. The soft shell may be made of plastic, such as polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0228] The present application has no particular limitation on the shape of the electrode assembly, which may be cylindrical, square, or any other shape. For example, FIG6 shows a battery cell 5 having a square structure as an example.

[0229] In some embodiments, referring to Figure 7, the outer packaging may include a shell 51 and a cover plate 53. The shell 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 51 has an opening connected to the receiving cavity, and the cover plate 53 can be covered on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the diaphragm can be formed into a battery cell 52 through a winding process or a lamination process. The battery cell 52 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the battery cell 52. The number of battery cells 52 contained in the battery cell 5 can be one or more, and those skilled in the art can select according to specific actual needs.

[0230] In some embodiments, the electrode assemblies may be assembled into a battery module. The number of electrode assemblies contained in the battery module may be one or more. The specific number may be selected by those skilled in the art based on the application and capacity of the battery module.

[0231] Figure 8 shows an example battery module 4. Referring to Figure 8 , within the battery module 4, multiple battery cells 5 may be arranged sequentially along the length of the battery module 4. Of course, they may also be arranged in any other manner. Furthermore, the multiple battery cells 5 may be secured together using fasteners.

[0232] Optionally, the battery module 4 may further include a housing having an accommodation space, and the plurality of battery cells 5 are accommodated in the accommodation space.

[0233] In some embodiments, the battery modules described above may also be assembled into a battery pack. The battery pack may contain one or more battery modules, and the specific number may be selected by those skilled in the art based on the application and capacity of the battery pack.

[0234] Figures 9 and 10 illustrate an example battery pack 1. Referring to Figures 9 and 10 , the battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box comprises an upper case 2 and a lower case 3. The upper case 2 can be placed over the lower case 3 to form an enclosed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0235] In addition, the present application also provides an electrical device, which includes at least one of the electrode assembly, battery module, or battery pack provided in the present application. The electrode assembly, battery module, or battery pack can be used as a power source for the electrical device, or as an energy storage unit for the electrical device. The electrical device may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but is not limited thereto.

[0236] As an electrical device, an electrode assembly, battery module or battery pack can be selected according to its usage requirements.

[0237] Figure 11 shows an example of an electric device. This device can be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of the electrode assembly, a battery pack or battery module can be used.

[0238] Another example device may be a mobile phone, a tablet computer, a notebook computer, etc. Such a device is generally required to be lightweight and thin, and may use an electrode assembly as a power source.

[0239] Example

[0240] Example 1

[0241] Preparation of the first diaphragm:

[0242] A first porous base membrane was prepared, which had a thickness of 7 μm, was made of polyethylene, had a porosity of 36%, and an air permeability of 160 s / 100 cc.

[0243] Alumina, binder polyvinylidene fluoride, and dispersant acrylic block polymer are mixed in a mass ratio of 7:2:1, dispersed in a solvent (deionized water) to form an inorganic coating slurry, and evenly coated on a single surface of the first substrate. The thickness of the heat-resistant layer is 2 μm.

[0244] The adhesive components polyethylene-vinylidene fluoride copolymer, N-dodecyldimethylamine, and polydimethylsiloxane are then mixed in a mass ratio of 8:1:1 to obtain a mixture, and the mixture is then dissolved in acetone to obtain an adhesive slurry with a solid content of 40%; the adhesive slurry is evenly sprayed on both surfaces of the first substrate to form a bonding layer. After the electrode assembly is compacted, the thickness of the single-layer polymer bonding layer is 1 μm.

[0245] After the electrode assembly is compacted, the thickness of the first separator is 7 μm+2 μm+(2×1 μm)=11 μm, the porosity is 30%, and the air permeability is 130 s / 100 cc.

[0246] Preparation of the second diaphragm:

[0247] Prepare a second porous base membrane with a thickness of 10 μm, made of polypropylene, a porosity of 40%, and an air permeability of 250 s / 100 cc.

[0248] Preparation of negative electrode sheet:

[0249] Graphite, conductive agent acetylene black, binder styrene-butadiene rubber (SBR), and thickener sodium carboxymethyl cellulose (CMC-Na) were added to the solvent deionized water in a mass ratio of 96.2:1.0:1.6:1.2, and the mixture was thoroughly stirred and mixed to prepare a negative electrode slurry. The negative electrode slurry was coated on the negative electrode current collector copper foil, and then dried, cold pressed, and cut to obtain the negative electrode sheet.

[0250] Preparation of positive electrode sheet:

[0251] The positive electrode active material (NCM811), binder (polyvinylidene fluoride (PVDF), and conductive agent (carbon black) are added to the solvent N-methylpyrrolidone (NMP) in a mass ratio of 98:1:1 to obtain a slurry. The slurry is coated on the current collector aluminum foil, and then dried, cold pressed, and cut to obtain the positive electrode sheet.

[0252] Electrolyte:

[0253] At 25° C., ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) are mixed in a volume ratio of 1:1:1 to obtain a mixed solvent, but are not limited to this ratio and solvent. LiPF6 is then dissolved in the mixed solvent to obtain an electrolyte, wherein the concentration of LiPF6 is 1 mol / L.

[0254] Preparation of electrode assembly:

[0255] The negative electrode, first separator, positive electrode, and second separator prepared in the embodiment are stacked in sequence for winding, wherein the first separator is located between the negative electrode and the positive electrode, and the second separator is located on the side of the positive electrode facing away from the first separator. During the winding process, the negative electrode is wound around the winding center. During the winding process, the distance between the stacked negative electrode and the winding center is less than the distance between the stacked positive electrode and the winding center, so that the positive electrode covers the negative electrode in the stacked structure during the winding process, so that the cross-section of the electrode assembly of the lithium-ion battery includes a first electrode sheet (negative electrode), a first separator, a second electrode sheet (positive electrode), and a second separator stacked in sequence, a plurality of first tabs arranged on the first electrode sheet (negative electrode), and a plurality of second tabs arranged on the second electrode sheet (positive electrode). When the porous coatings of the electrode assembly are wound to the end, the second separator is located on the outermost side. It is also necessary to understand that since the outermost circle of the electrode assembly requires negative electrode protection, the length of the negative electrode is extended so that the negative electrode is wrapped around the outer circle one more time, and the surface of the negative electrode wrapped one more time is provided with a first diaphragm.

[0256] Preparation of lithium-ion batteries:

[0257] The wound electrode assembly is then placed in an aluminum casing through ultrasonic welding and top cover welding, leaving a liquid injection port. Electrolyte is poured through the injection port, packaged, and then undergoes formation, aging, and capacity testing to produce a lithium-ion battery.

[0258] Example 2 to Example 8

[0259] On the basis of Example 1, the thickness ratio of the first diaphragm to the second diaphragm, the material of the binder, the inorganic material, etc. were adjusted to obtain Examples 2 to 8.

[0260] Example 9. Based on Example 1, the bonding layer is one layer, and the bonding layer and the heat-resistant layer are located on both sides of the first porous base membrane. After the electrode assembly is compacted, the thickness of the first porous base membrane is 7μm, the thickness of the bonding layer is 0.5μm, and the thickness of the inorganic coating is 1μm. Then the thickness of the first diaphragm is 7μm+1μm+(1×0.5μm)=8.5μm.

[0261] Example 10: Based on Example 1, the adhesive layer and heat-resistant layer are each two layers. The two adhesive layers are located on both sides of the first porous base membrane, and the two heat-resistant layers are located between the adhesive layers on both sides and the first porous base membrane. After the electrode assembly is compacted, the thickness of the first porous base membrane is 5μm, the thickness of the adhesive layer is 2.5μm, and the thickness of the inorganic coating is 2μm. The thickness of the first separator is 5μm + (2×2μm) + (2×2.5μm) = 14μm. The thickness of the second separator is 5μm.

[0262] Comparative Example 1

[0263] On the basis of Example 8, the first diaphragm is the same as the first diaphragm in Example 8, and the second diaphragm is the same as the first diaphragm in Example 8, that is, the first diaphragm and the second diaphragm in Comparative Example 1 are the same.

[0264] Cyclic performance test:

[0265] At 25°C, charge the lithium-ion battery at a constant current of 1 / 3C to 4.25V, then charge it at a constant voltage of 4.25V to a current of 0.05C. After 5 minutes of rest, discharge it at a rate of 1 / 3C to 2.5V. This constitutes one charge-discharge cycle. The discharge capacity is the discharge capacity of the first cycle. Repeat these steps for a charge-discharge cycle test on the lithium-ion battery, and take the discharge capacity of the 500th cycle.

[0266] The capacity retention rate of the lithium-ion battery after 500 cycles = (discharge capacity at the 500th cycle / discharge capacity at the first cycle) × 100%.

[0267] In the examples and comparative examples of the present application, a greater capacity retention rate means a better cycle performance of the battery cell.

[0268] Table 1 List of Examples

[0269] It can be seen from the experimental data in Table 1 above that the first diaphragm and the second diaphragm in the embodiment are designed differently. During the battery cycle, more expansion space is reserved for the battery cell, reducing the squeezing of the battery cell by the shell during the expansion process, improving the phenomenon of active material being damaged by the squeezing force during the squeezing process, and also improving the phenomenon of electrolyte being squeezed out during the squeezing process, so that the battery cell is effectively immersed in the electrolyte during the expansion process, which is conducive to the transmission of ions, thereby effectively improving the cycle performance of the battery.

[0270] The above is only a preferred embodiment of the present application and does not limit the patent scope of the present application. All equivalent structural transformations made based on the contents of the present application specification and drawings, or direct / indirect application in other related technical fields, are included in the patent protection scope of the present application.

Claims

1. An electrode assembly, wherein: It includes a first pole piece, a second pole piece, a first diaphragm and a second diaphragm; One of the first diaphragm and the second diaphragm is arranged between the first pole piece and the second pole piece, and the other of the first diaphragm and the second diaphragm is arranged on the side of the first pole piece or the second pole piece away from the first diaphragm; one of the first diaphragm and the second diaphragm does not include a porous coating, and the other of the first diaphragm and the second diaphragm includes a porous coating, and the thickness of the porous coating is 0.5μm-8μm.

2. The electrode assembly according to claim 1, wherein: The first separator includes a first porous base membrane and a porous coating layer; and / or the second separator includes a second porous base membrane.

3. The electrode assembly according to claim 1 or 2, wherein: The second diaphragm does not include a porous coating layer, and the second diaphragm is disposed on a side of the first pole piece or the second pole piece facing away from the first diaphragm.

4. The electrode assembly according to any one of claims 1 to 3, wherein: The electrode assembly includes a wound structure, the wound structure includes an inner side and an outer side, and the wound structure includes a negative electrode, a first separator, a positive electrode, and a second separator stacked in sequence from the inner side to the outer side.

5. The electrode assembly according to any one of claims 2 to 4, wherein: The second porous base membrane has a thickness greater than that of the first porous base membrane.

6. The electrode assembly according to any one of claims 2 to 5, wherein: The porosity of the first porous base membrane is greater than the porosity of the second porous base membrane.

7. The electrode assembly according to any one of claims 1 to 6, wherein: The air permeability of the first diaphragm is greater than the air permeability of the second diaphragm.

8. The electrode assembly according to any one of claims 1 to 7, wherein: The ratio of the thickness of the first diaphragm to the thickness of the second diaphragm is 1:2-18:

5.

9. The electrode assembly according to any one of claims 1 to 8, wherein: The ratio of the thickness of the first diaphragm to the thickness of the second diaphragm is 1:2-3:

1.

10. The electrode assembly according to any one of claims 1 to 9, wherein: The thickness of the first diaphragm is 8 μm-18 μm; And / or, the thickness of the second separator is 5 μm-16 μm.

11. The electrode assembly according to any one of claims 1 to 10, wherein: The thickness of the first diaphragm is 10 μm-15 μm; And / or, the thickness of the second separator is 5 μm-10 μm.

12. The electrode assembly according to any one of claims 1 to 11, wherein: The thickness of the porous coating layer is 1 μm-5 μm.

13. The electrode assembly according to any one of claims 1 to 12, wherein: The air permeability of the first diaphragm is 80s / 100cc-250s / 100cc; And / or, the air permeability of the second diaphragm is 110s / 100cc-310s / 100cc.

14. The electrode assembly according to any one of claims 1 to 13, wherein: The air permeability of the first diaphragm is 110s / 100cc-210s / 100cc; And / or, the air permeability of the second diaphragm is 210s / 100cc-310s / 100cc.

15. The electrode assembly according to any one of claims 2 to 14, wherein: The porous coating layer is disposed on at least one side of the first porous base membrane; And / or, the porous coating layer includes at least one of a binder and an inorganic material.

16. The electrode assembly according to any one of claims 1 to 15, wherein: The porous coating layer includes at least one of a bonding layer and a heat-resistant layer.

17. The electrode assembly according to any one of claims 2 to 16, wherein: At least one side of the first porous base membrane is provided with a bonding layer.

18. The electrode assembly according to claim 17, wherein: A heat-resistant layer is provided between the first porous base film and the adhesive layer.

19. The electrode assembly according to claim 18, wherein: The thickness of the bonding layer is 0.5 μm-5 μm; And / or, the thickness of the heat-resistant layer is 0 μm-3 μm.

20. The electrode assembly according to claim 18 or 19, wherein: The thickness of the bonding layer is 1 μm-3 μm; And / or, the thickness of the heat-resistant layer is 1 μm-2 μm.

21. The electrode assembly according to any one of claims 17 to 20, wherein: The bonding layer includes a layered coating, and the layered coating is disposed on the first diaphragm; Alternatively, the bonding layer includes a dot coating, and the dot coating is arranged at intervals on the first diaphragm.

22. The electrode assembly according to any one of claims 17 to 20, wherein: The bonding layer includes a dot-shaped coating, and the coverage area of ​​the dot-shaped coating is 50%-90% of the surface area of ​​the first diaphragm.

23. The electrode assembly according to claim 22, wherein: The coverage area of ​​the dot-shaped coating is 60%-80% of the surface area of ​​the first diaphragm.

24. A battery, wherein: Comprising the electrode assembly as claimed in any one of claims 1 to 23.

25. An electrical device, wherein: The electrical device comprises a battery as claimed in claim 24.

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