Electrode assembly and battery

Abstract

The invention discloses an electrode assembly and a battery, the electrode assembly comprises a plurality of pole pieces and an isolating membrane arranged between two pole pieces with opposite polarities, at least one pole piece is provided with a plurality of convex parts, the height H ([mu] m) of each convex part is greater than or equal to 20 and less than or equal to 80, and the convex parts can form good support so as to improve the infiltration effect of electrolyte. The isolating membrane comprises a base membrane and a ceramic layer connected to the base membrane, and the ceramic layer is arranged on one side of the base membrane in the thickness direction. Wherein the puncture resistance strength of the base membrane is C (gf), the thickness of the ceramic layer is D1 (mu m), C is more than or equal to 100 and less than or equal to 500, and D1 is more than or equal to 1 and less than or equal to 6, so that the mechanical strength of the isolating membrane is enough to bear stress generated by powder falling from a pole piece, the condition that the powder punctures the isolating membrane is improved, the risk of short circuit is reduced, the yield of an electrode assembly is improved, and the service life and the stability of a battery are assisted to be improved.

Description

Technical Field

[0001] The present application relates to the technical field of electrochemical devices, and in particular to an electrode assembly and a battery. Background Art

[0002] At present, the electrode assembly inside the secondary battery adopts a winding structure, and the electrolyte is not easy to enter the electrode assembly, which can easily lead to problems such as insufficient electrolyte and poor wetting. In the related art, attempts are made to apply stress to the pole piece to cause it to undergo plastic deformation, thereby forming a convex structure, making it easier for the electrolyte to enter the electrode assembly and optimizing the wetting effect. However, in the process of constructing the convex structure, the pole piece is extended, which increases the risk of microcracks on the surface of the pole piece, and may even cause powder loss and cause the isolation membrane to be punctured, affecting the safety performance of the battery. Summary of the invention

[0003] The embodiments of the present application provide an electrode assembly and a battery, which can solve the problem of poor battery safety performance caused by powder falling off of the electrode piece of the electrode assembly.

[0004] In a first aspect, an embodiment of the present application provides an electrode assembly, the electrode assembly comprising a plurality of pole pieces and an isolation membrane arranged between two pole pieces with opposite polarities, wherein at least one pole piece has a plurality of protrusions, the height of the protrusions is H (μm), and H satisfies: 20≤H≤80; the isolation membrane comprises a base membrane and a ceramic layer connected to the base membrane, and the ceramic layer is arranged on one side of the base membrane along the thickness direction; wherein the puncture resistance of the base membrane is C (gf), the thickness of the ceramic layer is D1 (μm), C satisfies: 100≤C≤500, and D1 satisfies: 1≤D1≤6.

[0005] Based on an electrode assembly of an embodiment of the present application, the puncture resistance C of the base film in the isolation membrane and the thickness D1 of the ceramic layer respectively satisfy the conditions 100≤C≤500, 1≤D1≤6, so that the mechanical strength of the isolation membrane is sufficient to withstand the stress generated by the powder falling from the pole piece, improve the situation of powder puncturing the isolation membrane, thereby allowing the construction of a convex portion on the pole piece, and when the height H of the convex portion is in the range of 20≤H≤80, the convex portion can form a good support to improve the infiltration effect of the electrolyte, thereby improving the cycle performance. If C is too large, the closed-cell temperature of the diaphragm will increase, the heat generation of the battery cell at high temperature will increase, and the high-temperature storage and hot box performance of the battery cell will deteriorate. If C is too small, it is impossible to avoid powder puncturing the diaphragm, reducing the processing advantage rate during the battery cell production process and the battery cell self-discharge performance (K value). If D1 is too large, the energy density of the battery cell will be reduced and the battery impedance will be increased. If D1 is too small, on the one hand, it will be impossible to prevent the powder from piercing the diaphragm, reducing the processing efficiency and self-discharge performance (K value) of the battery cell during production. On the other hand, it will worsen the wetting of the battery cell and the cycle performance.

[0006] In some of the embodiments, the electrode assembly satisfies one of the following conditions: (1) C satisfies: 100≤C<250, H satisfies: 20≤H<60; (2) C satisfies: 250≤C≤500, H satisfies: 60≤H≤80.

[0007] Based on the above embodiment, when the puncture resistance strength C and the protrusion height H are within the above range, the height of the protrusion is adapted to the mechanical strength of the base film, thereby improving the situation where the local pressure of the protrusion on the base film exceeds its tolerance limit, suppressing the puncture risk caused by powder falling of the pole piece, and improving the processing quality rate and self-discharge performance (K value) of the battery cell.

[0008] In some embodiments, the electrode assembly satisfies one of the following conditions: (1) D1 satisfies: 1≤D1<3, H satisfies: 20≤H<60; (2) D1 satisfies: 3≤D1≤6, H satisfies: 60≤H≤80.

[0009] Based on the above embodiment, by controlling the thickness D1 of the ceramic layer and the height H of the protrusion to meet the above range, the height of the protrusion is adapted to the thickness of the ceramic layer. The ceramic layer helps to enhance the mechanical strength of the isolation membrane to resist the stress generated by dendrites and powder particles and reduce the risk of puncture of the isolation membrane.

[0010] In some of the embodiments, the thickness of the base film is D2 (μm), and D2 satisfies: 4≤D2≤14; the porosity of the base film is B (%), and B satisfies: 20≤B≤55.

[0011] Based on the above embodiment, by controlling the thickness D2 and porosity B of the base film to satisfy the conditions 4μm≤D2≤14μm and 20%≤B≤55% respectively, the base film can maintain a certain mechanical strength to withstand the stress caused by the uneven coating and protrusions on the pole piece surface.

[0012] In some of the embodiments, the electrode assembly satisfies one of the following conditions: (1) D2 satisfies: 4≤D2<7, H satisfies: 20≤H<60; (2) D2 satisfies: 7≤D2≤14, H satisfies: 60≤H≤80.

[0013] Based on the above embodiment, the thickness D2 of the base film and the height H of the protrusion satisfy the above range, so that the thickness of the base film matches the height of the protrusion, so that the base film can form an effective barrier, reduce the risk of short circuit due to contact between the positive and negative electrodes, maintain the stability of the battery structure, and make the base film have appropriate internal resistance through gradient matching, avoiding unnecessary loss of energy density and power density of the battery due to matching lower protrusions with thicker base film.

[0014] In some embodiments, the electrode assembly satisfies one of the following conditions: (1) B satisfies: 40≤B≤55, H satisfies: 20≤H<60; (2) B satisfies: 20≤B<40, H satisfies: 60≤H≤80.

[0015] Based on the above embodiments, by controlling the porosity B and the protrusion height H of the base membrane to meet the above ranges, it helps to improve the air permeability of the isolation membrane and thus improve the ion transmission performance. The base membrane serves as a good carrier for electrolyte infiltration and can store electrolyte through pores.

[0016] In some of the embodiments, at least one of the multiple pole pieces is a negative pole piece; the isolation film includes one or two ceramic layers, and along the thickness direction of the base film, at least one ceramic layer is arranged on the side of the base film facing the negative pole piece.

[0017] Based on the above embodiment, a ceramic layer is provided on the side of the base film facing the negative electrode plate. The ceramic layer has a certain liquid absorption capacity and can absorb and retain more electrolyte to enhance the liquid retention capacity of the negative electrode plate, which helps the diffusion and embedding of lithium ions in the negative electrode plate, thereby improving the cycle performance of the battery.

[0018] In some of the embodiments, the isolation film further includes an adhesive layer, which is bonded to the base film or the ceramic layer, and is also used for bonding to the electrode piece; wherein the thickness of the adhesive layer is D3 (μm), and the electrode assembly satisfies one of the following conditions: (1) D3 satisfies: 0.5≤D3<2, and H satisfies: 20≤H<60; (2) D3 satisfies: 2≤D3≤5, and H satisfies: 60≤H≤80.

[0019] Based on the above embodiment, by selecting the thickness D3 of the adhesive layer and the height H of the protrusion to meet the above range, the adhesive layer has an appropriate thickness and good bonding performance to improve the contact interface between the isolation membrane and the pole piece, and the adhesive layer can buffer the local pressure caused by the protrusion, reduce the risk of the isolation membrane being punctured, and ensure good K value performance.

[0020] In some of the embodiments, the bonding layer has a porous structure, the pore size of the bonding layer is P (μm), and the diameter of the protrusion is R (mm); the electrode assembly satisfies one of the following conditions: (1) 100<P≤300, 20≤H<60, 0.3mm≤R<2mm; (2) 0.5≤P≤100, 60≤H≤80, 2mm<R≤10mm.

[0021] Based on the above embodiments, by selecting the pore size P of the adhesive layer, the height H and the diameter R of the protrusion to meet the above ranges, the air permeability and mechanical properties of the adhesive layer are balanced, thereby improving the ion transmission performance and puncture resistance of the isolation membrane, and facilitating the control of the area occupied by the protrusion within an appropriate range to prevent the sharp shape of the protrusion from causing damage to the isolation membrane, and to prevent the protrusion from occupying too large an area resulting in insufficient wetting space after winding.

[0022] In some of the embodiments, the pole piece includes a main body, and the convex portion is formed by a portion of the pole piece protruding toward one side of the thickness direction of the main body; in the thickness direction of the pole piece, all the convex portions are bent toward the same side of the main body; or, in the thickness direction of the pole piece, a portion of the convex portions are bent toward one side of the main body, and another portion of the convex portions are bent toward the other side of the main body.

[0023] Based on the above embodiments, the plurality of protrusions on the pole piece may be arranged on the same side or different sides of the main body, so that the orientation of the protrusions can be set according to the actual structure of the electrode assembly, so that the isolation membrane can be evenly supported.

[0024] In a second aspect, an embodiment of the present application provides a battery, including a housing and an electrode assembly, wherein the electrode assembly is disposed in an internal space of the housing.

[0025] An electrode assembly and a battery based on the embodiments of the present application are configured such that the puncture resistance C (gf) of the base film and the thickness D1 (μm) of the ceramic layer are controlled to satisfy the conditions 100≤C≤500 and 1≤D1≤6 respectively, so that the mechanical strength of the isolation membrane is sufficient to withstand the stress generated by the protrusions and the powder dropped from the pole piece, which helps to improve the puncture situation of the isolation membrane, reduce the risk of short circuit, and improve the quality rate of the electrode assembly, thereby allowing the pole piece to be processed to form a protrusion that meets the use requirements, improve the electrolyte infiltration effect, and help improve the service life and stability of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on these drawings without paying any creative work.

[0027] Figure 1 This is a schematic diagram of the front view structure of a pole piece in an embodiment of the present application in an unfolded state;

[0028] Figure 2 This is a schematic cross-sectional structural diagram of an electrode assembly according to an embodiment of the present application;

[0029] Figure 3This is a schematic diagram of the structure of an isolation membrane according to an embodiment of the present application;

[0030] Figure 4 This is a schematic structural diagram of a convex portion of an embodiment of the present application;

[0031] Figure 5 Another structural diagram of an isolation membrane according to an embodiment of the present application is shown below.

[0032] Reference numerals:

[0033] 10. pole piece; 11. positive pole piece; 12. negative pole piece; 101. convex part; 102. main body;

[0034] 20. isolation film; 21. base film; 22. ceramic layer; 23. bonding layer;

[0035] X, length direction of the pole piece; Y, width direction of the pole piece; Z, thickness direction of the pole piece. DETAILED DESCRIPTION

[0036] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0037] The inventors discovered that the electrode assembly inside the secondary battery adopts a winding structure, and the electrode assembly needs to be hot-pressed after the pole pieces and the isolation membranes are alternately stacked and wound. There is internal stress inside the electrode assembly, resulting in poor electrolyte wettability. In addition, the electrode assembly will expand during the charge and discharge process, and the interlayer extrusion of the electrode assembly will be further aggravated, resulting in insufficient electrolyte, poor wetting, and ultimately deterioration of the interface at the weak position, and even lithium deposition. In order to solve the above problems, it is necessary to create gaps between battery layers. Currently, there are the following methods for creating gaps: (1) sticking adhesive tape at specific positions of the electrode sheets to support the formation of gaps. This method currently improves the wetting ability, but the presence of the adhesive tape occupies the thickness, which increases the thickness of the electrode assembly and causes a certain loss in the energy density of the battery; (2) applying soluble chemicals to form gaps by evenly applying some glue soluble in electrolyte on the electrode sheets, but the improvement effect is limited and has other side effects on battery performance; (3) thickening the isolation membrane. The isolation membrane has a stronger ability to store electrolyte and improves the wetting effect of the electrolyte, but this method will make the battery thicker and greatly lose energy density.

[0038] The inventors also found that by machining a convex portion on the pole piece, the convex portion plays a supporting role during the winding process, so that a gap is formed between the pole piece layers of the electrode assembly, thereby improving the transmission capacity of the electrolyte inside the electrode assembly and improving the cycle performance of the battery. In actual processing, stress is applied to the pole piece to cause it to undergo plastic deformation and form a convexity. At this time, the pole piece is extended, and the greater the elongation rate of the pole piece, the greater the damage to the pole piece, and the pole piece surface is more likely to produce microcracks. The risk of the pole piece falling off and the powder piercing the isolation membrane increases, affecting the safety performance of the battery. Based on this, the embodiment of the present application provides an electrode assembly and a battery, and the isolation membrane is designed to improve the electrode assembly efficiency and safety performance after the convex portion is constructed.

[0039] The battery of the embodiment of the present application includes a housing and an electrode assembly disposed in the inner space of the housing, and an electrolyte filled in the inner space of the housing. The electrode assembly includes two pole pieces with opposite polarities and a separator. Figure 1-Figure 2 , the pole pieces 10 have a length direction X, a width direction Y and a thickness direction Z that are perpendicular to each other, the length directions X, the width direction Y and the thickness direction Z of the two pole pieces 10 of opposite polarity of the electrode assembly are consistent, and the separator 20 is arranged between the two pole pieces 10 of opposite polarity in the thickness direction Z of the pole piece 10. One of the two pole pieces 10 of opposite polarity is a positive pole piece 11, and the other is a negative pole piece 12. The separator 20 has an insulating property and is used to separate the positive pole piece 11 from the negative pole piece 12 to prevent the positive pole piece 11 and the negative pole piece 12 from short-circuiting. In the embodiment of the present application, there is no special limitation on the positive pole piece 11 and the negative pole piece 12, and various pole pieces that can be used as positive and negative poles known in the art are applicable to the present application.

[0040] See also Figure 3 The isolation film 20 includes a base film 21 and a ceramic layer 22 connected to the base film 21, and the ceramic layer 22 is arranged on one side of the base film 21 along the thickness direction. The embodiment of the present application synergistically controls the puncture resistance C of the base film 21 and the thickness D1 of the ceramic layer 22, so that the isolation film 20 has sufficient mechanical strength to block the powder particles that may be caused by the construction of the protrusion 101, and has little effect on the internal resistance of the electrode assembly, so that the protrusion 101 is allowed to be constructed on the pole piece 10, and the infiltration effect of the electrolyte is improved under the premise of ensuring the safety performance of the electrode assembly.

[0041] Among them, the puncture resistance of the base film 21 is C(gf), and C satisfies: 100≤C≤500. For example, C can be 100, 200, 300, 400, 500 or any range of the above two. By selecting the range in which the base film 21 satisfies the above conditional formula, the base film 21 has sufficient mechanical strength. When the isolation film 20 is sandwiched between the uneven pole pieces 10, the base film 21 can withstand the stress generated by the powder falling from the pole pieces 10, thereby reducing the risk of the isolation film 20 being punctured. When C is higher than the upper limit of 500, the base film 21 needs to use high-density materials, and the thickness will increase, and the internal resistance of the electrode assembly will increase accordingly, affecting the electrochemical performance of the battery. When C is lower than the lower limit of 100, the protective effect of the base film 21 on the powder particles is limited, and the probability of local perforation of the isolation film 20 increases, which can easily cause a short circuit.

[0042] The thickness of the ceramic layer 22 is D1 (μm), and D1 satisfies: 1≤D1≤6. For example, D1 can be 1, 3, 5, 6 or any range of the above two. By selecting the range in which the ceramic layer 22 satisfies the above conditional formula, the ceramic layer 22 can prevent the puncture of powder particles. The ceramic layer 22 makes the isolation membrane 20 have a better electrolyte affinity, and helps to improve the thermal stability of the isolation membrane 20, thereby making the battery have good cycle stability. When D1 is higher than the upper limit of 6, the ceramic layer 22 is too thick and the flexibility is reduced, which not only increases the mass and thickness of the isolation membrane 20, which is not conducive to improving the energy density of the battery, but also may increase the probability of wrinkles during processing and winding, affecting the quality rate of the electrode assembly. When D1 is lower than the lower limit of 1, the ceramic layer 22 is too thin, and the mechanical strength of the isolation membrane 20 is limited, and it is difficult to effectively resist the puncture of powder particles dropped from dendrites and pole pieces 10.

[0043] See also Figure 4 , at least one of the positive electrode sheet 11 and the negative electrode sheet 12 has a convex portion 101, wherein the height of the convex portion 101 is H (μm), and H satisfies: 20≤H≤80, for example, H can be 20, 40, 60, 80 or any range of the above two. By selecting the range in which the convex portion 101 satisfies the above conditional expression, the convex portion 101 provides support for the separator 20, so that there is a gap between the separator 20 and the electrode sheet 10, and the electrolyte can flow smoothly between the convex portions 101, so as to achieve better liquid storage, improve the electrolyte infiltration effect, and prevent local lack of liquid. When H is higher than the upper limit of 80, the convex portion 101 is too high, and the electrode sheet 10 is partially over-extended, which can easily cause damage to the structure of the electrode sheet 10, for example, structural defects such as cracks in the active material layer or fracture of the current collector occur; when H is lower than 20, the convex portion 101 is too low, and the supporting capacity of the convex portion 101 is insufficient, and the improvement of the electrolyte infiltration effect is limited.

[0044] In some embodiments, the pole piece 10 includes a main body 102, wherein a portion of the pole piece 10 protrudes toward one side of the main body 102 in the thickness direction to form a protrusion 101. Optionally, in the thickness direction Z of the pole piece 10, all the protrusions 101 provided on a single pole piece 10 are bent toward the same side of the main body 102, for example, all the protrusions 101 provided on a single pole piece 10 are protruded toward the side where the winding center is located, or all the protrusions 101 provided on a single pole piece 10 are protruded toward the side away from the winding center. Optionally, in the thickness direction Z of the pole piece 10, a portion of the protrusions 101 provided on a single pole piece 10 are bent toward one side of the main body 102, and another portion of the protrusions 101 are bent toward the other side of the main body 102, for example, a portion of the protrusions 101 provided on a single pole piece 10 are bent toward the side where the winding center is located, and another portion of the protrusions 101 are bent toward the side away from the winding center.

[0045] The above is only an exemplary introduction. The present application does not limit the orientation of the protrusion 101 of each pole piece 10, and the orientation can be selected according to actual needs.

[0046] In the separator 20, the base film 21 plays a role of physical isolation, preventing the positive and negative electrodes from directly contacting each other and causing a short circuit, while allowing lithium ions to shuttle freely. The base film 21 can resist mechanical deformations such as expansion of the electrode 10 and winding stress, and provide mechanical support for the separator 20. Among them, the puncture resistance strength C of the base film 21 satisfies 100≤C<250, and the height H of the protrusion 101 satisfies 20≤H<60. The base film 21 with a lower puncture resistance strength C matches the protrusion 101 with a lower height H, ensuring that the base film 21 has sufficient mechanical strength to cope with the stress generated by the protrusion 101 and the powder particles, reducing the toughness loss of the base film 21 and reducing the risk of cracking of the base film 21; the puncture resistance strength C of the base film 21 satisfies 250≤C≤500, and the height H of the protrusion 101 satisfies 60≤H≤80. The base film 21 with a higher puncture resistance strength C can cope with the stress concentration generated by the higher protrusion 101, thereby reducing the risk of short circuit.

[0047] By selecting C and H to meet the above range, the height of the protrusion 101 is adapted to the mechanical strength of the base film 21, the situation where the local pressure of the protrusion 101 on the base film 21 exceeds its tolerance limit is improved, and the risk of puncture caused by the powder falling of the pole piece 10 is suppressed. In addition, when C satisfies 100≤C<250 and H is higher than the upper limit of 60, or when C satisfies 250≤C≤500 and H is higher than the upper limit of 80, the pressure of the protrusion 101 exceeds the puncture resistance limit of the base film 21, the risk of rupture of the base film 21 increases, and microcracks may be generated in the base film 21. When C satisfies 100≤C<250 and H is lower than the lower limit of 20, the height of the protrusion 101 is insufficient, an effective gap cannot be formed, the cross-sectional area of ​​the electrolyte flow is reduced, the immersion time is prolonged, and local lithium precipitation is easily caused; when C satisfies 250≤C≤500 and H is lower than the lower limit of 60, the material performance of the base film 21 is wasted and the utilization rate of its compressive resistance is low.

[0048] Optionally, the base film 21 may be a polyolefin film, such as a polyethylene (PE) film, a polypropylene (PP) film, etc. The base film 21 may be a single-layer film or a multi-layer composite film, which is not limited here.

[0049] In the embodiment of the present application, the thickness of the base film 21 is D2 (μm), and D2 satisfies: 4≤D2≤14. For example, D2 can be 4, 8, 12, 14, or any range of the above two. In the above thickness range, the base film 21 can form a barrier between adjacent pole pieces 10, and the base film 21 can maintain a certain mechanical strength to withstand the stress generated by the uneven coating on the surface of the pole piece 10 and the protrusion 101.

[0050] In some embodiments, D2 satisfies: 4≤D2<7, H satisfies: 20≤H<60, and the base film 21 is guaranteed to have sufficient mechanical strength to cope with the protrusions 101 and powder particles. By selecting a thinner base film 21, the energy density of the battery can be improved; D2 satisfies: 7≤D2≤14, H satisfies: 60≤H≤80, and the base film 21 has a higher mechanical strength, thereby allowing a higher protrusion 101 to be constructed on the pole piece 10, further improving the infiltration effect of the electrolyte. By selecting D2 and H to meet the above range, the thickness of the base film 21 matches the height of the protrusion 101, so that the base film 21 can form an effective barrier, reduce the risk of short circuit due to contact between the positive and negative pole pieces, maintain the stability of the battery structure, and make the base film 21 have an appropriate internal resistance through gradient matching, avoiding unnecessary loss of energy density and power density of the battery due to the lower protrusion 101 matching the thicker base film 21. When D2 satisfies 4≤D2<7, H is lower than the lower limit of 20, or when D2 satisfies 7≤D2≤14, H is lower than the lower limit of 60, the thickness of the base film 21 is highly redundant with respect to the convex portion 101, which increases the internal resistance of the battery, deteriorates the chemical properties of the battery, and is not conducive to improving the energy density of the battery. When D2 satisfies 4≤D2<7, H is higher than the upper limit of 60, or when D2 satisfies 7≤D2≤14, H is higher than the upper limit of 80, the base film 21 is relatively too thin and easily pierced by dendrites and powder particles.

[0051] In the embodiment of the present application, the porosity of the base film 21 is B (%), and B satisfies: 20≤B≤55. For example, B can be 20, 30, 40, 50, 55, or any range of the above two. The porosity of the base film 21 is within the above range, which can improve the air permeability of the isolation film 20 and thus improve the ion transmission performance. The base film 21 is a good carrier for electrolyte infiltration and can store the electrolyte through the pores.

[0052] In some embodiments, B satisfies: 40≤B≤55, H satisfies: 20≤H<60, and the base film 21 has good air permeability to improve the electrochemical performance of the battery while ensuring that the base film 21 has sufficient mechanical strength to cope with the protrusions 101 and powder particles. B satisfies: 20≤B<40, H satisfies: 60≤H≤80, and the base film 21 has higher mechanical strength, thereby allowing a higher protrusion 101 to be constructed on the pole piece 10. By selecting B and H to meet the above range, the uniform distribution of pores in the base film 21 can promote uniform transmission of ions, ensure the consistency of the interface performance between the pole piece 10 and the electrolyte, reduce the generation of lithium dendrites, and thus improve the safety of the battery. When B satisfies 40≤B≤55 and H is higher than the upper limit of 60, or when B satisfies 20≤B<40 and H is higher than the upper limit of 80, the porosity of the base film 21 is relatively too high, resulting in a decrease in the mechanical strength of the base film 21, which has an adverse effect on the safety of the battery. When B satisfies 40≤B≤55 and H is lower than the lower limit of 20, or when B satisfies 20≤B<40 and H is lower than the lower limit of 60, the porosity of the base film 21 is relatively too low, resulting in low absorption rate of the electrolyte, large internal resistance of the battery, and unfavorable transmission of lithium ions.

[0053] In the isolation membrane 20, the ceramic layer 22 is used to prevent powder particles or dendrites from piercing the base membrane 21 to strengthen the mechanical properties of the isolation membrane 20. At the same time, the ceramic layer 22 can inhibit the shrinkage of the base membrane 21 at high temperatures to prevent thermal runaway. The introduction of the ceramic layer 22 can improve the mechanical strength and thermal stability of the isolation membrane 20, thereby improving the safety performance of the battery. In some embodiments, the thickness D1 (μm) of the ceramic layer 22 satisfies 1≤D1<3, and the height of the protrusion 101 satisfies 20≤H<60. The thickness D1 (μm) of the ceramic layer 22 satisfies 4≤D2≤14, and the height of the protrusion 101 satisfies 60≤H≤80. By selecting D1 and H to meet the above range, the height of the protrusion 101 is adapted to the thickness of the ceramic layer 22, and the ceramic layer 22 helps to enhance the mechanical strength of the isolation membrane 20 to resist the stress generated by dendrites and powder particles and reduce the risk of the isolation membrane 20 being punctured. In addition, when D1 satisfies 1≤D1<3, H is higher than the upper limit of 60, or D1 satisfies 4≤D2≤14, H is higher than the upper limit of 80, it is difficult for the ceramic layer 22 to form effective protection, and the protrusion 101 squeezes the ceramic layer 22, and the local stress generated by it easily causes the ceramic layer 22 to fall off, resulting in deterioration of the interface contact. When D1 satisfies 1≤D1<3, H is lower than the lower limit of 20, the lower protrusion 101 cannot form an effective gap, the flow of electrolyte is blocked, and the risk of local lithium precipitation increases; D1 satisfies 4≤D2≤14, H is lower than the lower limit of 60, the thicker ceramic layer 22 does not match the high protrusion 101, and its compressive capacity utilization rate is low, and the excessive thickness of the ceramic layer 22 is not conducive to the improvement of the energy density of the battery.

[0054] Optionally, the material of the ceramic layer 22 includes at least one of aluminum oxide, titanium oxide, zinc oxide, zirconium oxide, magnesium oxide, titanium dioxide, silicon oxide, and calcium oxide.

[0055] In some of the embodiments, the isolation film 20 includes one or two ceramic layers 22. Along the thickness direction of the base film 21, at least one ceramic layer 22 is arranged on the side of the base film 21 facing the negative electrode plate 12. The ceramic layer 22 has a certain liquid absorption capacity and can absorb and retain more electrolyte to enhance the liquid retention capacity of the negative electrode plate 12, which helps the diffusion and embedding of lithium ions in the negative electrode plate 12, thereby improving the cycle performance of the battery. It can be understood that the ceramic layer 22 has a certain thermal insulation and insulation property. The ceramic layer 22 is arranged on the side of the base film 21 facing the negative electrode plate 12, which can reduce the risk of lithium deposition in the battery under overcharge conditions and alleviate the process of excessive embedding and extraction of lithium ions. During the long-term cycle of the battery, lithium dendrites may form on the surface of the negative electrode plate 12. The ceramic layer 22 can reduce the formation and puncture risk of lithium dendrites.

[0056] Optionally, the separator 20 is provided with a ceramic layer 22, and along the thickness direction of the base film, the ceramic layer 22 is provided on the side of the base film 21 facing the negative electrode plate 12. Figure 5 As shown, the isolation membrane 20 is provided with two ceramic layers 22 , and along the thickness direction of the base membrane, the two ceramic layers 22 are arranged on opposite sides of the base membrane 20 .

[0057] In some embodiments, the ceramic layer 22 includes ceramic particles, the particle size of the ceramic particles is E (μm), and the electrode assembly satisfies one of the following conditions:

[0058] (1) E satisfies: 1<E≤2, H satisfies: 20≤H<60;

[0059] (2) E satisfies: 0.1≤E≤1, H satisfies: 60≤H≤80.

[0060] By selecting E and H to meet the above range, the ceramic particles are stacked to form a high-strength ceramic layer 22 to resist the local stress caused by the protrusion 101 and the mechanical penetration of the powder particles, reducing the risk of failure of the separator 20. In addition, the ceramic particles are evenly arranged to form a uniform ceramic layer, which is conducive to the uniform distribution of heat in the electrode assembly, and the thermal stability of the separator 20 is better. The uniform pore size distribution will bring more uniform lithium flux and lithium deposition, and reduce the generation of lithium dendrites. On this basis, when E meets: 1<E≤2, the particle size of the ceramic particles is larger, and the rough surface morphology of the ceramic layer 22 helps to improve the electrolyte wettability of the separator 20, which is beneficial to the improvement of battery performance. When E meets: 0.1≤E≤1, the particle size of the ceramic particles is smaller and the stacking density is relatively higher, thereby forming a dense and high-strength ceramic layer 22, which helps to improve the mechanical strength of the ceramic layer 22, thereby allowing the construction of a higher height protrusion 101.

[0061] In some of the embodiments, the ceramic layer 22 also includes an adhesive, which enables the ceramic layer 22 to form a tight connection with the base film 21. It should be noted that the ceramic layer 22 is not limited to the above components, and those skilled in the art can select other components for preparing the ceramic layer 22 in related technologies according to actual conditions, that is, the ceramic layer 22 can also include other additives, such as dispersants (organic acids), etc.

[0062] In the embodiment of the present application, the isolation film 20 also includes an adhesive layer 23, which is bonded to the base film 21 or the ceramic layer 22, and the adhesive layer 23 is also used to bond the pole piece 10. The adhesive layer 20 is formed on the outermost layer of the isolation film 20 so that the isolation film 20 and the pole piece 10 are closely connected to prevent the two from being delaminated during the winding process. For example, the isolation film 20 is provided with a ceramic layer 22 and two adhesive layers 23, the ceramic layer 22 is arranged on the side of the base film 21 facing the negative pole piece 12 in the thickness direction of the base film 21, one adhesive layer 23 is bonded between the ceramic layer 22 and the negative pole piece 12, and the other adhesive layer 23 is bonded between the base film 21 and the positive pole piece 11. For another example, the isolation film 20 is provided with two ceramic layers 22 and two adhesive layers 23, and the base film 21 is provided with a ceramic layer 22 on both sides along the thickness direction, and the adhesive layer 23 is used to bond the ceramic layer 22 and the pole piece 10.

[0063] Optionally, the material of the adhesive layer 23 includes at least one of polyvinylidene fluoride, polyacrylonitrile, polyacrylic acid, and polystyrene.

[0064] In some embodiments, the thickness of the adhesive layer 23 is D3 (μm), and the electrode assembly satisfies one of the following conditions:

[0065] (1) D3 satisfies: 0.5≤D3<2, H satisfies: 20≤H<60;

[0066] (2) D3 satisfies: 2≤D3≤5, and H satisfies: 60≤H≤80.

[0067] By selecting D3 and H to meet the above range, the thickness of the adhesive layer 23 is appropriate and has good bonding properties to improve the contact interface between the separator 20 and the pole piece 10, improve the consistency of the battery, and the adhesive layer 23 can buffer the local pressure caused by the protrusion 101, and reduce the risk of the separator 20 being punctured. When D3 satisfies 0.5≤D3<2, H is lower than the lower limit of 20, or D3 satisfies: 2≤D3≤5, H is lower than the lower limit of 60, the adhesive layer 23 is relatively thick, which hinders the infiltration of the electrolyte, resulting in a decrease in ionic conductivity, and the adhesive layer 23 is too thick, which can easily lead to loose cross-section fit between the pole piece 10 and the separator 20, deterioration of interface contact, and increased impedance. When D3 satisfies 0.5≤D3<2 and H is higher than the upper limit of 60, or D3 satisfies: 2≤D3≤5 and H is higher than the upper limit of 80, the bonding layer 23 is relatively thin and it is difficult to ensure the bonding effect. Failure of the bonding layer 23 may cause damage to the pole piece 10, accelerate the expansion of microcracks in the pole piece 10, and lead to more serious powder loss problems.

[0068] In some embodiments, the bonding layer 23 has a porous structure, the pore size of the bonding layer 23 is P (μm), and the diameter of the protrusion 101 is R (mm). The electrode assembly satisfies one of the following conditions:

[0069] (1) 100<P≤300, 20≤H<60, 0.3≤R<2;

[0070] (2)0.5≤P≤100, 60≤H≤80, 2<R≤10.

[0071] By selecting P, H, and R within the above range, the air permeability and mechanical properties of the adhesive layer 23 are balanced, thereby improving the ion transmission performance and puncture resistance of the isolation membrane 20. In addition, within the above range, it is easy to control the area occupied by the protrusion 101 within an appropriate range to prevent the area occupied by the protrusion 101 from being too large or too small, making it difficult to take into account the electrolyte infiltration and support strength requirements. In combination with the height of the protrusion 101, it is also possible to prevent the sharp shape of the protrusion 101 from causing damage to the isolation membrane 20, and to prevent the protrusion 101 from occupying an area too large to cause insufficient wetting space after winding.

[0072] In some embodiments, the bonding layer 23 includes bonding particles, the particle size of the bonding particles is G (μm), and the electrode assembly satisfies one of the following conditions:

[0073] (1) G satisfies: 0.2≤G<1, H satisfies: 20≤H<40;

[0074] (2) G satisfies: 1≤G≤5, H satisfies: 40≤H<60;

[0075] (3) G satisfies: 5<G≤30, H satisfies: 60≤H≤80.

[0076] The bonding layer 23 includes a copolymer, which is in a granular form, namely the above-mentioned bonding particles. By selecting G and H to meet the above-mentioned range, the copolymer can form particle bumps in the bonding layer 23, and form a certain gap when the isolation film 20 and the pole piece 10 are in contact, so as to buffer the expansion and deformation of the battery during use. When G satisfies 0.2≤G<1, H is lower than the lower limit of 20, or G satisfies 1≤G≤5, H is lower than the lower limit of 40, or G satisfies: 5<G≤30, H is lower than the lower limit of 60, the particle size of the bonding particles is relatively large, which not only affects the bonding effect of the bonding layer 23, but also causes the bonding layer 23 to be too thick, increases the space occupied by the isolation film 20, and reduces the energy density of the battery. When G satisfies 0.2≤G<1 and H is higher than the upper limit of 40, or G satisfies 1≤G≤5 and H is higher than the upper limit of 60, or G satisfies: 5<G≤30 and H is higher than the upper limit of 80, the particle size of the bonding particles is relatively small, and it is difficult to form a gap between the isolation membrane 20 and the pole piece 10. When the battery is charged and discharged, the pole piece 10 expands and lacks buffer space. The interface pressure is directly transmitted to the isolation membrane 20, accelerating the fatigue rupture of the membrane material.

[0077] The present application also provides a battery, including a housing and an electrode assembly as described above, wherein the electrode assembly is disposed in the inner space of the housing. The battery also includes an electrolyte, which is filled in the inner space of the housing and infiltrates the electrode assembly. The present application also does not particularly limit the electrolyte, and various materials known in the art that can be used as electrolytes are applicable to the present application.

[0078] The present application is further described below by taking the electrode assembly of a lithium-ion battery as an example and combining specific embodiments. It should be understood that these embodiments are only used to illustrate the present application and are not used to limit the scope of the present application.

[0079] In each embodiment and comparative example of the present application, the following method is used to prepare a lithium ion battery and test the lithium ion battery:

[0080] (1) 25℃ / 50℃ cycle test

[0081] In an environment of 25℃ / 45℃, the electrode assembly is charged at a constant current of 3C to the full charge voltage (the battery design maximum voltage is 4.53V), and then charged at a constant voltage at the maximum voltage until the current is 0.02C, and then discharged at a constant current of 0.5C until the final voltage is 3.0V, and the discharge capacity of the first cycle is recorded. After that, the above steps are repeated for 1000 / 800 charge and discharge cycles, and the discharge capacity of the lithium-ion battery after 1000 / 800 charge and discharge cycles is recorded.

[0082] 25° C. 3C charge / 0.5C discharge cycle capacity retention rate=(discharge capacity at the 1000th cycle / discharge capacity at the first cycle)×100%.

[0083] 45° C. 3C charge / 0.5C discharge cycle capacity retention rate=(discharge capacity at the 800th cycle / discharge capacity at the first cycle)×100%.

[0084] 55° C. 3C charge / 0.5C discharge cycle capacity retention rate=(discharge capacity at the 800th cycle / discharge capacity at the first cycle)×100%.

[0085] 65° C. 3C charge / 0.5C discharge cycle capacity retention rate=(discharge capacity at the 800th cycle / discharge capacity at the first cycle)×100%.

[0086] (2) Winding quality

[0087] After the bare cell winding production is completed, use an X-Ray detector to detect the overhang of the bare cell (the width of the negative electrode edge exceeding the positive electrode edge in the width direction of the positive electrode). If the excess width is greater than 0.2mm, it is a good product. The total number of samples tested is 100, and the winding quality rate = number of good products / total number of samples.

[0088] (3) K value test method

[0089] After the battery cell is produced, use an open circuit voltage tester to measure the battery cell open circuit voltage OCV1 first, and then re-measure the battery cell open circuit voltage OCV2 after an interval of 48 hours. K value = (OCV1-OCV2)mv / 48h.

[0090] The K value can characterize the self-discharge performance of the battery cell. When the K value is larger, it means that the battery loses power quickly, that is, the battery power decreases quickly when it is at rest. When the K value is smaller, it means that the battery loses power slowly and the battery stability is good, that is, the battery power decreases slowly when it is at rest.

[0091] (4) Puncture resistance test method

[0092] The prepared basement membrane was flattened and clamped in a fixture, and a puncture needle with a diameter of 1 mm and a spherical tip and a ball diameter of 0.5 mm was used to puncture the membrane at a rate of (100±10) mm / min. The force F measured when the basement membrane was punctured was recorded. 0 After completion, take out the sample and test the thickness at four points around the pinhole and take the average value. Calculate the puncture strength C:

[0093] (5) Porosity test method

[0094] Cut three samples from the base film at a distance of 150 mm in the longitudinal direction. The sample size is 100 mm × 80 mm. Measure the length L1, width L2, and thickness L3 of the sample. Use an analytical balance with a resolution of 0.0001 g to weigh the mass M of the sample and calculate the surface density р of the sample. 1 and porosity B:

[0095] р=M / (L1·L2);

[0096] B=(1-р 1 / (L3·р 0 ))×100%;

[0097] Among them, 0 is the density of the raw material.

[0098] Example 1-1

[0099] Preparation of lithium-ion batteries

[0100] (1) Preparation of positive electrode sheet

[0101] The positive electrode active material is lithium cobalt oxide LiCoO 2 , conductive carbon black, and binder polyvinylidene fluoride PVDF are mixed in a mass ratio of 97.9:0.9:1.2, and N-methylpyrrolidone NMP is added as a solvent. The mixture is stirred evenly under the action of a vacuum mixer to obtain a positive electrode slurry with a solid content of 75wt%. The positive electrode slurry is evenly coated on one surface of a positive electrode current collector aluminum foil with a thickness of 9μm, and dried and cold pressed at 85°C to obtain a positive electrode with a single-sided coating of a positive electrode material layer with a thickness of 95μm. Thereafter, the above steps are repeated on the other surface of the aluminum foil to obtain a positive electrode with a double-sided coating of a positive electrode material layer. After cutting and welding the positive electrode aluminum pole ears, a positive electrode sheet with a specification of 74mm×851mm is obtained. The compaction density of the positive electrode material layer of the positive electrode sheet is 4.20g / cm 3 .

[0102] (2) Preparation of negative electrode sheet

[0103] The negative electrode active material artificial graphite, the binder styrene butadiene rubber SBR, and the thickener sodium carboxymethyl cellulose CMC are mixed in a mass ratio of 97.4:1.4:1.2, and then deionized water is added as a solvent, and the mixture is stirred evenly under the action of a vacuum mixer to obtain a negative electrode slurry with a solid content of 50wt%. The negative electrode slurry is evenly coated on one surface of a negative electrode current collector copper foil with a thickness of 10μm, and dried and cold pressed at 85°C to obtain a negative electrode with a negative electrode material layer coated on one side with a thickness of 130μm. After that, the above steps are repeated on the other surface of the copper foil to obtain a negative electrode with a negative electrode material layer coated on both sides. After cutting and welding the negative electrode tab nickel tab, a negative electrode sheet with a specification of 76mm×867mm is obtained, and the compaction density of the negative electrode material layer of the negative electrode sheet is 1.80g / cm 3 .

[0104] (3) Preparation of isolation membrane

[0105] The polypropylene raw material is melt extruded and hot stretched to prepare a polypropylene base film with a thickness D1 of 5 μm. A ceramic layer 22 with a thickness D2 of 2 μm is coated on both sides of the base film 21. After coating, a bonding layer 23 is coated on the side of the ceramic layer 22 away from the base film 21. The thickness D3 of the bonding layer 23 is 1 μm. The obtained isolation film is cut to obtain an isolation film with a specification of 80 mm×880 mm. The ceramic layer 22 and the bonding layer 23 both extend from the starting end of the isolation film 20 toward the terminal opposite to the starting end. The puncture resistance C of the base film 21 is 100 gf, the porosity B is 50%, the particle size of the ceramic particles in the ceramic layer 22 is 1.5 μm, the pore size P of the bonding layer 23 is 150 μm, and the particle size G of the bonding particles is 1 μm.

[0106] (4) Preparation of electrolyte

[0107] In an argon atmosphere glove box with a water content of less than 10 ppm, ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), ethyl propionate (EP), and propyl propionate (PP) were uniformly mixed in a mass ratio of 1:1:1:1:1. Ethylene carbonate: dimethyl carbonate: ethyl methyl carbonate = 1:1:1 was mixed to obtain a base solvent, and lithium hexafluorophosphate (LiPF 6 ) is dissolved in the above non-aqueous solvent and mixed evenly to obtain an electrolyte. Wherein, based on the total mass of the electrolyte, LiPF 6 The mass percentage is 12.5%.

[0108] (5) Assembly of lithium-ion batteries

[0109] The insulating protective adhesive is pasted on the positive electrode sheet, and the positive electrode tab is installed on the edge area of ​​the positive electrode sheet 11. The convex portion 101 is rolled out on the negative electrode sheet 12 by a roller, and the height H of the convex portion 101 is 40 μm and the diameter is 1 μm, and the negative electrode tab is installed on the edge area of ​​the negative electrode sheet 12.

[0110] The positive electrode sheet 11 with the positive electrode ear, the separator 20, and the negative electrode sheet 12 with the negative electrode ear are stacked in order, so that the separator 20 is located between the positive electrode sheet 11 and the negative electrode sheet 12 to play an isolating role, and then wound to obtain the electrode body. The electrode assembly is placed in an outer packaging aluminum plastic film, after dehydration at 80°C, the above electrolyte is injected and packaged, and a lithium-ion battery is obtained through a process of formation, degassing, trimming, etc. The test method of each parameter of each embodiment of the present application is described below.

[0111] In Examples 1-1 to 1-20 and Comparative Examples 1-1 to 1-4, except for adjusting the puncture resistance C of the base film 21 in the preparation of the isolation film and the height H of the protrusion 101 in the assembly of the lithium-ion battery, the rest is the same as Example 1-1.

[0112] In Examples 1-1 to 1-20 and Comparative Examples 1-1 to 1-4, the parameters of the lithium-ion batteries and the performance test results of the lithium-ion batteries are shown in Table 1.

[0113] Table 1

[0114]

[0115] It can be seen from Examples 1-1 to 1-4, Examples 1-11 to 1-16, Comparative Examples 1-1 and 1-3 in Table 1 that when the lithium ion battery satisfies the puncture resistance C of 100≤C≤500, the lithium ion battery has good charge and discharge cycle performance at 25°C and 45°C, and can take into account the winding yield, ensure the K value performance, and ensure the K value performance.

[0116] It can be seen from Examples 1-5 to 1-10 and Comparative Examples 1-2 to 1-3 in Table 1 that when the lithium-ion battery satisfies 100≤C<250 and 20≤H<60, the puncture resistance C of the base film 21 matches the height H of the protrusion 101, so that the mechanical strength of the base film 21 is sufficient to withstand the stress generated by the powder dropped from the pole piece 10, improve the situation of the powder puncturing the isolation film 20, and the protrusion 101 can provide sufficient support for the isolation film 20, the electrolyte can flow smoothly between the protrusions 101, achieve better liquid storage, improve the wetting effect of the electrolyte, the lithium-ion battery has better charge and discharge cycle performance at 25°C and 45°C, and can take into account the winding yield, ensure the K value performance, and ensure the K value performance.

[0117] It can be seen from Examples 1-11 to 1-16 and Comparative Example 1-3 in Table 1 that when the lithium-ion battery satisfies 250≤C≤500 and 60≤H≤80, the base film 21 has higher mechanical strength to cope with the stress concentration caused by the higher protrusions 101, thereby improving the stability of the lithium-ion battery, making the lithium-ion battery have better charge and discharge cycle performance at 25°C and 45°C, and improving the winding superiority of the lithium-ion battery to ensure the K value performance.

[0118] In Examples 2-1 to 2-20 and Comparative Examples 2-1 to 2-3, except for adjusting the thickness D1 of the ceramic layer 22 in the preparation of the isolation membrane and the height H of the protrusion 101 in the assembly of the lithium-ion battery, the rest is the same as Example 1-8.

[0119] In Examples 1-8, Examples 2-1 to 2-20, and Comparative Examples 2-1 to 2-3, the parameters of the lithium-ion batteries and the performance test results of the lithium-ion batteries are shown in Table 2.

[0120] Table 2

[0121]

[0122]

[0123] It can be seen from Examples 2-1 to 2-5, Examples 2-12 to 2-16, Comparative Examples 2-1 and 2-2 in Table 2 that the thickness D1 of the ceramic layer 22 of the lithium-ion battery satisfies 1≤D1≤6, the lithium-ion battery has good charge and discharge cycle performance at 25°C and 45°C, and can take into account the winding yield and ensure the K value performance.

[0124] It can be seen from Examples 2-6 to 2-11 and Comparative Examples 2-2 to 2-3 in Table 2 that when the lithium-ion battery satisfies 1≤D1<3 and 20≤H<60, the base film 21 can form an effective barrier, reduce the risk of short circuit due to contact between the positive and negative electrodes, maintain the stability of the battery structure, and make the lithium-ion battery have better charge and discharge cycle performance at 25°C and 45°C, and improve the winding efficiency of the lithium-ion battery to ensure the K value performance.

[0125] It can be seen from Examples 2-12 to 2-16 and Comparative Example 2-3 in Table 2 that when the lithium-ion battery satisfies 3≤D1≤6 and 60≤H≤80, the base film 21 has higher mechanical strength to cope with the stress concentration caused by the higher protrusions 101, so that the lithium-ion battery has better charge and discharge cycle performance at 25°C and 45°C, and improves the winding quality of the lithium-ion battery to ensure the K value performance.

[0126] Examples 3-1 to 3-27 are the same as Example 1-1 except for adjusting the thickness D2 of the base film 21 in the preparation of the separator and the height H of the protrusion 101 in the assembly of the lithium-ion battery.

[0127] Examples 1-8, 3-1 to 3-27, the parameters of the lithium-ion batteries and the performance test results of the lithium-ion batteries are shown in Table 3.

[0128] Table 3

[0129]

[0130]

[0131] It can be seen from Examples 3-1 to 3-4 and 3-15 to 3-18 in Table 3 that the thickness D2 of the base film 21 of the lithium-ion battery satisfies 4≤D2≤14, and the lithium-ion battery has good charge and discharge cycle performance at 25°C and 45°C, and can take into account the winding yield and ensure the K value performance.

[0132] It can be seen from Examples 3-5 to 3-9 and 3-10 to 3-14 in Table 3 that when the lithium-ion battery satisfies 4≤D2<7 and 20≤H<60, the lower convex portion 101 matches the thinner base film 21, so that the base film 21 has an appropriate internal resistance to avoid unnecessary loss of the energy density and power density of the battery. It can be seen from Examples 3-19 to 3-21 and 3-22 to 3-27 in Table 3 that when the lithium-ion battery satisfies 7≤D2≤14 and 60≤H≤80, the base film 21 has higher mechanical strength to cope with the stress concentration generated by the higher convex portion 101. By selecting D2 and H in the above range, the charge and discharge cycle performance of the lithium-ion battery at 25°C and 45°C is better, and the winding superiority of the lithium-ion battery is improved to ensure the K value performance.

[0133] In Examples 4-1 to 4-16, except for adjusting the porosity B of the base film 21 in the preparation of the separator and the height H of the protrusion 101 in the assembly of the lithium ion battery, the rest is the same as that of Example 1-1.

[0134] In Examples 1-8 and 4-1 to 4-16, the parameters of the lithium-ion batteries and the performance test results of the lithium-ion batteries are shown in Table 4.

[0135] Table 4

[0136]

[0137]

[0138] It can be seen from Examples 4-1 to 4-5, 4-10 to 4-12, and 1-8 in Table 4 that the porosity B of the base film 21 of the lithium-ion battery satisfies: 20%≤B≤55%, and the lithium-ion battery has good charge and discharge cycle performance at 25°C and 45°C, and can take into account the winding yield and ensure the K value performance.

[0139] It can be seen from Examples 4-6 to 4-10 in Table 4 that when the lithium-ion battery satisfies 40%≤B≤55% and 20≤H<60, it can be seen from Examples 4-14 to 4-16 in Table 4 that the lithium-ion battery satisfies 20%≤B<40% and 60≤H≤80. By selecting D2 and H within the above range, the uniform distribution of pores in the base film 21 can promote the uniform transmission of ions, ensure the consistency of the interface performance between the electrode 10 and the electrolyte, reduce the generation of lithium dendrites, and thus improve the safety of the battery, so that the charge and discharge cycle performance of the lithium-ion battery at 25°C and 45°C is better, and the winding advantage of the lithium-ion battery is improved to ensure the K value performance.

[0140] In Examples 5-1 to 5-18, except for adjusting the thickness D3 of the adhesive layer 23 in the preparation of the separator and the height H of the protrusion 101 in the assembly of the lithium-ion battery, the rest is the same as that of Example 1-1.

[0141] In Examples 1-8 and 5-1 to 5-18, the parameters of the lithium-ion batteries and the performance test results of the lithium-ion batteries are shown in Table 5.

[0142] Table 5

[0143]

[0144]

[0145] It can be seen from Examples 5-1 to 5-5 and 5-11 to 5-14 in Table 5 that the thickness D3 of the adhesive layer 23 of the lithium-ion battery satisfies 0.5≤D3≤5, and the lithium-ion battery has good charge and discharge cycle performance at 25°C and 55°C, and can take into account the winding yield and ensure the K value performance.

[0146] It can be seen from Examples 5-5 to 5-10 in Table 5 that the lithium-ion battery satisfies 0.5≤D3<2 and 20≤H<60. It can be seen from Examples 5-15 to 5-18 in Table 5 that the lithium-ion battery satisfies 2≤D3≤5 and 60≤H≤80. By selecting D2 and H within the above range, the height of the protrusion 101 matches the thickness of the adhesive layer 23, and the adhesive layer 23 has good bonding properties to improve the contact interface between the isolation film 20 and the pole piece 10 and improve the consistency of the battery. The adhesive layer 23 can buffer the local pressure caused by the protrusion 101 and reduce the risk of the isolation film 20 being punctured, so that the lithium-ion battery has better charge and discharge cycle performance at 25°C and 55°C, and improves the winding superiority of the lithium-ion battery to ensure the K value performance.

[0147] In Examples 1-8 and 6-1 to 6-36, except for adjusting the pore size P of the adhesive layer in the preparation of the isolation membrane and the height H and diameter R of the protrusion 101 in the assembly of the lithium-ion battery, the rest is the same as that of Example 1-1.

[0148] In Examples 1-8 and 6-1 to 6-36, the parameters of the lithium-ion batteries and the performance test results of the lithium-ion batteries are shown in Table 6.

[0149] Table 6

[0150]

[0151]

[0152] It can be seen from Examples 6-1 to 6-6 and 6-19 to 6-25 in Table 6 that when the pore size P of the adhesive layer 23 of the lithium-ion battery meets the scope of the present application, the lithium-ion battery has good charge and discharge cycle performance at 25°C and 65°C, and can take into account the winding yield and ensure the K value performance.

[0153] It can be seen from Table 6 that the lithium-ion battery satisfies 100<P≤300, 20≤H<60, 0.3mm≤R<2mm, or the lithium-ion battery satisfies 0.5≤P≤100, 60≤H≤80, 2<R≤10, and the air permeability and mechanical properties of the adhesive layer 23 are balanced, thereby improving the ion transmission performance and puncture resistance of the isolation membrane 20. Within the above range, it is convenient to control the area occupied by the protrusion 101 within a suitable range to prevent the area occupied by the protrusion 101 from being too large or too small, so that the protrusion 101 takes into account both the electrolyte infiltration and the support strength requirements, so that the lithium-ion battery has better charge and discharge cycle performance at 26°C and 66°C, and improves the winding superiority of the lithium-ion battery to ensure the K value performance.

[0154] It can be seen from the embodiments of Table 6 that, in combination with the height of the protrusion 101 and the diameter of the protrusion 10, the sharp shape of the protrusion 101 is prevented from causing damage to the isolation membrane 20, and the protrusion 101 is prevented from occupying too large an area, resulting in insufficient wetting space after winding, so that the charge and discharge cycle performance of the lithium-ion battery at 25°C and 65°C is better, the winding advantage of the lithium-ion battery is improved, and the K value performance is guaranteed.

[0155] The same or similar numbers in the drawings of this embodiment correspond to the same or similar parts; in the description of this application, it should be understood that if the terms "upper", "lower", "left", "right", etc. indicate an orientation or position relationship based on the orientation or position relationship shown in the drawings, it is only for the convenience of describing this application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, the terms describing the position relationship in the drawings are only used for illustrative purposes and cannot be understood as a limitation on this patent. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0156] The above are only preferred embodiments of the present application and are not intended to limit the present application. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. An electrode assembly, characterized in that: The electrode assembly comprises a plurality of pole pieces and a separation membrane disposed between two pole pieces with opposite polarities, wherein at least one of the pole pieces has a plurality of protrusions, the height of the protrusions is H (μm), and H satisfies: 20≤H≤80; The isolation membrane includes a base membrane and a ceramic layer connected to the base membrane, and the ceramic layer is arranged on one side of the base membrane along the thickness direction; wherein the puncture resistance of the base membrane is C (gf), the thickness of the ceramic layer is D1 (μm), C satisfies: 100≤C≤500, and D1 satisfies: 1≤D1≤6.

2. The electrode assembly according to claim 1, characterized in that: The electrode assembly satisfies one of the following conditions: (1) C satisfies: 100 ≤ C < 250, H satisfies: 20 ≤ H < 60; (2) C satisfies: 250≤C≤500, and H satisfies: 60≤H≤80.

3. The electrode assembly according to claim 1, characterized in that: The electrode assembly satisfies one of the following conditions: (1) D1 satisfies: 1≤D1<3, H satisfies: 20≤H<60; (2) D1 satisfies: 3≤D1≤6, and H satisfies: 60≤H≤80.

4. The electrode assembly according to claim 1, characterized in that: The thickness of the base film is D2 (μm), and D2 satisfies: 4≤D2≤14; The porosity of the base film is B (%), and B satisfies: 20≤B≤55.

5. The electrode assembly according to claim 4, characterized in that: The electrode assembly satisfies one of the following conditions: (1) D2 satisfies: 4≤D2<7, H satisfies: 20≤H<60; (2) D2 satisfies: 7≤D2≤14, and H satisfies: 60≤H≤80.

6. The electrode assembly according to claim 4, characterized in that: The electrode assembly satisfies one of the following conditions: (1) B satisfies: 40≤B≤55, H satisfies: 20≤H<60; (2) B satisfies: 20≤B<40, and H satisfies: 60≤H≤80.

7. The electrode assembly according to claim 1, characterized in that: At least one of the plurality of pole pieces is a negative pole piece; The isolation film includes one or two ceramic layers, and along the thickness direction of the base film, at least one ceramic layer is arranged on a side of the base film facing the negative electrode plate.

8. The electrode assembly according to claim 1, characterized in that: The isolation film further comprises an adhesive layer, the adhesive layer is bonded to the base film or the ceramic layer, and the adhesive layer is also used for bonding and connecting to the pole piece; The thickness of the adhesive layer is D3 (μm), and the electrode assembly satisfies one of the following conditions: (1) D3 satisfies: 0.5≤D3<2, H satisfies: 20≤H<60; (2) D3 satisfies: 2≤D3≤5, and H satisfies: 60≤H≤80.

9. The electrode assembly according to claim 8, characterized in that: The adhesive layer has a porous structure, the pore size of the adhesive layer is P (μm), and the diameter of the protrusion is R (mm); The electrode assembly satisfies one of the following conditions: (1) 100<P≤300, 20≤H<60, 0.3≤R<2; (2)0.5≤P≤100, 60≤H≤80, 2<R≤10.

10. The electrode assembly according to claim 1, characterized in that: The pole piece includes a main body, and the convex portion is formed by a portion of the pole piece protruding toward one side of the main body in the thickness direction; In the thickness direction of the pole piece, all the protrusions are bent toward the same side of the main body; or, In the thickness direction of the pole piece, a portion of the protrusion is bent toward one side of the main body, and another portion of the protrusion is bent toward the other side of the main body.

11. A battery, characterized in that: include: shell; and The electrode assembly as described in any one of claims 1 to 10 is arranged in the inner space of the shell.

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