Battery cell and battery

Abstract

The utility model provides a battery cell and a battery, the battery cell comprises a first pole piece, the first pole piece comprises a first current collector and first active material layers respectively arranged on two opposite sides of the first current collector in a first direction; the second pole piece is located on at least one side of the first pole piece in the first direction of the battery cell, and the second pole piece comprises a second current collector and a second active material layer arranged on the side, facing the first pole piece, of the second current collector; the diaphragm is positioned between the first pole piece and the second pole piece; the first pole piece and the second pole piece have the same polarity, and the thickness of the second active material layer is greater than that of the first active material layer. The problem that the thickness of the battery cell expands abnormally due to lithium separation in the circulation process is avoided, the circulation passing rate of the fast charging battery is greatly increased, and the service life of the fast charging battery is greatly prolonged.

Description

Technical Field

[0001] The present application relates to the technical field of battery cells and batteries, and in particular to battery cells and batteries. Background Art

[0002] Electrochemical devices represented by lithium-ion batteries have been widely used in consumer electronics, electric vehicles, and energy storage. Among them, lithium-ion batteries have the advantages of high energy density, long cycle life, fast charge and discharge, and environmental friendliness, and have become a research hotspot at this stage. In order to reduce the instability inside the battery under high voltage or fast charging chemical systems, it is necessary to improve the long cycle process of the battery. Utility Model Content

[0003] The embodiments of the present application provide a cell and a battery, which avoid the problem of abnormal cell thickness expansion due to lithium plating during the cycle process, and greatly improve the cycle pass rate and service life of the fast-charging battery.

[0004] The present application provides a battery cell, comprising a first pole piece, the first pole piece comprising a first current collector and first active material layers respectively arranged on two opposite sides of the first current collector in a first direction;

[0005] A second pole piece, located along the first direction of the battery cell at least on one side of the first pole piece, the second pole piece comprising a second current collector and a second active material layer disposed on a side of the second current collector facing the first pole piece;

[0006] A diaphragm, the diaphragm being located between the first pole piece and the second pole piece;

[0007] The thickness of the second active material layer is greater than the thickness of the first active material layer.

[0008] Through the above-mentioned arrangement, that is, by making the thickness of the second active material layer greater than that of the first active material layer, the problem of lithium plating in the second electrode due to the large current density of the second electrode can be avoided, and the abnormal thickness expansion of the battery cell due to lithium plating during the cycle process can be avoided, thereby greatly improving the cycle pass rate and service life of the fast charging battery.

[0009] In some optional embodiments, the surface density of the second pole piece is less than the surface density of the first pole piece.

[0010] It should be noted that by setting the surface density of the second pole piece smaller than the surface density of the first pole piece, the problem of lithium plating of the second pole piece due to the large current density of the second pole piece can be avoided during the cycle of the battery cell, and the abnormal thickness expansion of the battery cell due to lithium plating during the cycle can be avoided, thereby greatly improving the cycle pass rate and service life of the fast charging battery.

[0011] In some optional embodiments, the compaction density of the second pole piece is less than the compaction density of the first pole piece.

[0012] It should be noted that by reducing the compaction density of the active material layer on one side of the second electrode sheet, the current density of the second electrode sheet is reduced, thereby reducing the potential for lithium deposition.

[0013] In some optional embodiments, the ratio of the compaction density of the second pole piece to the compaction density of the first pole piece is between 90% and 98%.

[0014] In some optional embodiments, the weight per unit area of ​​the second active material layer is less than the weight per unit area of ​​the first active material layer.

[0015] It should be noted that by reducing the content of the second active material layer on one side of the second electrode sheet, the current density of the second electrode sheet is reduced, thereby reducing the potential for lithium deposition.

[0016] In some optional embodiments, the ratio of the weight per unit area of ​​the second active material layer to the weight per unit area of ​​the first active material layer is between 90% and 97%.

[0017] It should be noted that the ratio of the weight per unit area of ​​the second active material layer to the weight per unit area of ​​the first active material layer may be 90%, 91%, 92%, 93%, 94%, or 95%, or any value in between.

[0018] In some optional embodiments, the thickness of the diaphragm facing the second pole piece is greater than the thickness of the diaphragm facing the first pole piece; or,

[0019] The thickness of the glue layer of the diaphragm facing the second pole piece is greater than the thickness of the glue layer of the diaphragm facing the first pole piece; or,

[0020] The glue content of the glue layer of the diaphragm facing the second pole piece is greater than the glue content of the glue layer of the diaphragm facing the first pole piece.

[0021] It should be noted that by increasing the adhesion between the separator and the second electrode, the transmission path of lithium ions during the cycle process is reduced.

[0022] In some optional embodiments, the peeling force between the second pole piece and the diaphragm is greater than, or equal to, half of the peeling force between the first pole piece and the diaphragm.

[0023] It should be noted that such a setting can reduce the transmission path of lithium ions during the cycle, so that the problem of lithium plating in the second electrode sheet caused by the high current density of the second electrode sheet can be avoided during the cycle of the battery cell.

[0024] In some optional embodiments, the battery cell further includes a third pole piece, the first pole piece and the second pole piece have the same polarity, the third pole piece and the second pole piece have opposite polarity, the diaphragm is located between the first pole piece and the third pole piece, and the diaphragm is located between the second pole piece and the third pole piece;

[0025] The peeling force between the diaphragm facing the second pole piece and the third pole piece is greater than, or equal to, half of the peeling force between the diaphragm facing the first pole piece and the third pole piece.

[0026] In some optional embodiments, the battery cell further includes an insulating layer, and there are two battery cells, which are located on opposite sides of the insulating layer.

[0027] In some optional embodiments, the thickness of the second current collector in the battery cell located on the first side of the insulating layer is greater than the thickness of the first current collector in the battery cell located on the first side of the insulating layer; and / or,

[0028] The thickness of the second current collector in the battery cell located on the second side of the insulating layer is greater than the thickness of the first current collector in the battery cell located on the second side of the insulating layer.

[0029] It should be noted that such a setting, that is, the total thickness of the diaphragm corresponding to the second active material layer is higher than the total thickness of the diaphragm corresponding to the first active material layer, can improve the adhesion between the diaphragm and the second active material layer, thereby reducing the transmission path of lithium ions during the cycle.

[0030] In some optional embodiments, a ratio of a thickness of the second current collector located on the first side of the insulating layer to a thickness of the first current collector located on the first side of the insulating layer is greater than, or equal to, 1.2.

[0031] It should be noted that by increasing the thickness of the second current collector located on the first side of the insulating layer, the structural strength of the second current collector is improved, thereby buffering the force of the single-sided area expansion and protecting the pole piece in the middle area of ​​the stacked core from being squeezed.

[0032] In some optional embodiments, a ratio between a thickness of the second current collector located on the second side of the insulating layer and a thickness of the first current collector located on the second side of the insulating layer is greater than, or equal to, 1.2.

[0033] It should be noted that by increasing the thickness of the second current collector located on the second side of the insulating layer, the structural strength of the second current collector is improved, thereby buffering the force of the single-sided area expansion and protecting the pole piece in the middle area of ​​the stacked core from being squeezed.

[0034] In some optional embodiments, a difference between a thickness of the second active material layer located on the first side of the insulating layer and a thickness of the second active material layer located on the second side of the insulating layer is less than 0 um-20 um.

[0035] It should be noted that such a setting can avoid the problem of single-sided lithium plating caused by the high current density of the two stacked battery cells. At the same time, it can also ensure that the expansion degree of the two battery cells is close during the cycle process, preventing the problem of abnormal expansion of a single battery cell.

[0036] In some optional embodiments, in the battery cell located on the first side of the insulating layer, the difference between the thickness of the second active material layer away from the insulating layer and the thickness of the second active material layer facing the insulating layer is less than 0um-10um.

[0037] It should be noted that such a configuration, while avoiding the problem of lithium deposition on one side, ensures that the expansion degree of the upper and lower sides of the battery cell is the same, thus preventing excessive squeezing of the electrode in the middle area of ​​the battery cell.

[0038] In addition, the present application also provides a battery, including a battery casing and the above-mentioned battery cell, wherein the battery cell is located in the battery casing.

[0039] The battery cell and battery provided in the present application include a battery shell and a battery cell, wherein the battery cell is located in the battery shell; the battery cell includes a first pole piece, the first pole piece includes a first current collector and a first active material layer respectively arranged on two opposite sides of the first current collector in a first direction; a second pole piece, along the first direction of the battery cell, the second pole piece is located on at least one side of the first pole piece, the second pole piece includes a second current collector and a second active material layer arranged on a side of the second current collector facing the first pole piece; a diaphragm, the diaphragm is located between the first pole piece and the second pole piece; the thickness of the second active material layer is greater than the thickness of the first active material layer.

[0040] By making the thickness of the second active material layer greater than that of the first active material layer, the problem of lithium plating in the second electrode due to the large current density of the second electrode can be avoided, and the abnormal thickness expansion of the battery cell due to lithium plating during the cycle process can be avoided, thereby greatly improving the cycle pass rate and service life of the fast charging battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, a brief introduction will be given below to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0042] Figure 1 A schematic diagram of the structure of the first battery cell provided in an embodiment of the present application;

[0043] Figure 2 A schematic diagram of the structure of a second battery cell provided in an embodiment of the present application;

[0044] Figure 3 A schematic diagram of the structure of a third battery cell provided in an embodiment of the present application;

[0045] Figure 4 A schematic diagram of the structure of the fourth battery cell provided in an embodiment of the present application.

[0046] Description of reference numerals:

[0047] 100-battery cell;

[0048] 110- first pole piece;

[0049] 111- a first current collector;

[0050] 112- first active material layer;

[0051] 120- second pole piece;

[0052] 121- second fluid collector;

[0053] 122- second active material layer;

[0054] 130-third pole piece;

[0055] 131-third collector;

[0056] 132- third active material layer;

[0057] 140 - diaphragm;

[0058] 150-Insulation layer. DETAILED DESCRIPTION

[0059] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiment is a one-cavity embodiment of the present application, rather than an embodiment of the whole cavity. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present application. All other embodiments obtained are within the scope of protection of the present application. In the absence of conflict, the following embodiments and features in the embodiments can be combined with each other.

[0060] In the description of the present application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0061] In this application, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected, or indirectly connected through an intermediate medium, it can be the communication of the inner cavities of two components or the interaction relationship between two components. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0062] It should be noted that in the description of this application, the terms "first", "second", and "third" are only used to facilitate the description of different chambers, and cannot be understood as indicating or implying a sequential relationship, relative importance, or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first", "second", and "third" may explicitly or implicitly include at least one of the features.

[0063] At present, the laminated battery includes a positive electrode sheet, a negative electrode sheet, and a separator disposed between the positive electrode sheet and the negative electrode sheet. The positive electrode sheet includes a single-sided positive electrode sheet and a double-sided positive electrode sheet, wherein the single-sided positive electrode sheet is located at the edge of the battery along the first direction of the battery. However, due to the large thickness of the current collector of the single-sided positive electrode sheet, the impedance is small, and the current density flowing through is large, it is easier to reach the lithium plating potential, thereby causing long-cycle failure.

[0064] In order to overcome the defects in the prior art, the battery cell and battery provided in the present application, by setting the surface density of the second pole piece smaller than the surface density of the first pole piece, can avoid the problem of lithium plating of the second pole piece due to the large current density of the second pole piece during the cycle of the battery cell, and avoid the abnormal thickness expansion of the battery cell due to lithium plating during the cycle process, thereby greatly improving the cycle pass rate and service life of the fast charging battery.

[0065] The contents of the present application will be described in detail below in conjunction with the accompanying drawings so that those skilled in the art can understand the contents of the present application more clearly and in detail.

[0066] Figure 1This is a schematic diagram of the structure of the first battery cell provided in the embodiment of the present application. Figure 2 This is a schematic diagram of the structure of the second battery cell provided in the embodiment of the present application. Figure 3 A schematic diagram of the structure of the third battery cell provided in an embodiment of the present application.

[0067] like Figure 1 and Figure 2 As shown, the embodiment of the present application provides a battery cell 100, including:

[0068] A first pole piece 110, the first pole piece 110 comprises a first current collector 111 and a first active material layer 112, there are two first active material layers 112, and the two first active material layers 112 are respectively arranged on two opposite sides of the first current collector 111 in a first direction;

[0069] A second pole piece 120, located along the first direction of the battery cell 100 on at least one side of the first pole piece 110, the second pole piece 120 comprises a second current collector 121 and a second active material layer 122, the second active material layer 122 is disposed on a side of the second current collector 121 facing the first pole piece 110;

[0070] A diaphragm 140 , wherein the diaphragm 140 is located between the first pole piece 110 and the second pole piece 120 ;

[0071] The first pole piece 110 and the second pole piece 120 have the same polarity, and the surface density of the second pole piece 120 is smaller than that of the first pole piece 110 .

[0072] It should be noted that the first direction of the first current collector 111 is consistent with the first direction of the battery cell 100. Figure 1 and Figure 2 The first direction of the first current collector 111 may be a thickness direction of the first current collector 111 , or may be a thickness direction of the battery cell 100 .

[0073] It should be noted that the first electrode sheet 110 and the second electrode sheet 120 may be positive electrode sheets, the first current collector 111 and the first current collector 111 are both positive current collectors, and the first active material layer 112 and the second active material layer 122 are both positive active material layers.

[0074] It can be understood that the first pole piece 110 is a positive pole piece having a double-sided active material layer, and the second pole piece 120 is a positive pole piece having a single-sided active material layer.

[0075] There are multiple first pole sheets 110, which are arranged at intervals, and the diaphragm 140 is located between the multiple first pole sheets 110. Along the first direction of the battery cell 100, at least two second pole sheets 120 are located on opposite sides of the first pole sheet 110, and the diaphragm 140 is located between the first pole sheet 110 and the second pole sheet 120.

[0076] It should be noted that the surface density of the first electrode sheet 110 and the second electrode sheet 120 in the battery refers to the mass or capacity of the positive electrode material per unit area. Surface density is one of the important parameters for measuring battery performance, affecting the energy density, power density and overall performance of the battery.

[0077] Areal density is usually expressed as weight or capacity per unit area, such as grams per square centimeter (g / cm2), milliampere hours per square centimeter (mAh / cm2), etc. The higher the areal density, the more battery material content per unit area, and the battery can store more electrical energy or provide higher power output.

[0078] The surface density is affected by many factors, including the type, formula, and preparation process of the cathode material. Generally speaking, increasing the surface density can increase the energy density of the battery, thereby improving the battery's endurance and performance.

[0079] Through the above-mentioned setting, that is, by setting the surface density of the second pole piece 120 to be smaller than the surface density of the first pole piece 110, the problem of lithium deposition of the second pole piece 120 due to the large current density of the second pole piece 120 can be avoided during the cycle of the battery cell 100, and the abnormal thickness expansion problem of the battery cell 100 due to lithium deposition during the cycle process can be avoided, thereby greatly improving the cycle pass rate and service life of the fast charging battery.

[0080] It should be understood that the battery cell 100 can be any type of battery cell 100. For example, in some embodiments, the battery cell 100 is a wound battery cell 100. In other embodiments, the battery cell 100 is a laminated battery cell 100. For ease of understanding, in the subsequent embodiments, the battery cell 100 will be described as a laminated battery cell 100.

[0081] In some optional embodiments, the thickness of the second active material layer 122 is greater than the thickness of the first active material layer 112 .

[0082] It should be noted that by making the thickness of the second active material layer 122 greater than that of the first active material layer 112, the problem of lithium plating of the second electrode sheet 120 due to the high current density of the second electrode sheet 120 can be avoided, and the abnormal thickness expansion of the battery cell 100 due to lithium plating during the cycle process can be avoided, thereby greatly improving the cycle pass rate and service life of the fast-charging battery.

[0083] In some optional embodiments, the compaction density of the second pole piece 120 is less than the compaction density of the first pole piece 110 .

[0084] It should be noted that the compaction density of the first pole piece 110 and the second pole piece 120 refers to the density of the positive electrode material after being well compacted during the battery manufacturing process. The compaction density is one of the important parameters for measuring the quality and performance of the first pole piece 110 and the second pole piece 120 of the battery, and affects the energy density, cycle life and power output of the battery.

[0085] The compaction density of the first pole piece 110 and the second pole piece 120 is usually expressed as mass or capacity per unit volume, such as grams per cubic centimeter (g / cm3), milliampere hours per cubic centimeter (mAh / cm3), etc. The higher the compaction density, the more densely packed the active materials in the first pole piece 110 and the second pole piece 120 are, and more charge can be stored, thereby improving the energy density and performance of the battery.

[0086] During the battery manufacturing process, the compaction density of the first pole piece 110 and the second pole piece 120 can be achieved by controlling the preparation process, adjusting the parameters of the compactor, selecting an appropriate good binder, etc. A high compaction density helps to improve the performance and cycle life of the battery, but an excessively high compaction density may cause deformation or damage to the internal structure of the battery, affecting the safety and stability of the battery.

[0087] Therefore, in battery design and manufacturing, it is necessary to balance the compaction density and other performance indicators of the first pole sheet 110 and the second pole sheet 120 to achieve optimal performance and safety of the battery.

[0088] It should be noted that by reducing the compaction density of the active material layer on one side of the second electrode sheet 120 , the current density of the second electrode sheet 120 is reduced, thereby reducing the potential for lithium deposition.

[0089] In some optional embodiments, the ratio of the compaction density of the second pole piece 120 to the compaction density of the first pole piece 110 is between 90% and 98%.

[0090] It should be noted that the ratio of the compaction density of the second pole piece 120 to the compaction density of the first pole piece 110 can be 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97% or 98%, or any value in between.

[0091] In some optional embodiments, the weight per unit area of ​​the second active material layer 122 is less than the weight per unit area of ​​the first active material layer 112 .

[0092] It should be noted that by reducing the content of the second active material layer 122 on one side of the second electrode sheet 120 , the current density of the second electrode sheet 120 is reduced, thereby reducing the potential for lithium deposition.

[0093] In some optional embodiments, the ratio of the weight per unit area of ​​the second active material layer 122 to the weight per unit area of ​​the first active material layer 112 is between 90% and 97%.

[0094] It should be noted that the ratio of the weight per unit area of ​​the second active material layer 122 to the weight per unit area of ​​the first active material layer 112 may be 90%, 91%, 92%, 93%, 94%, or 95%, or any value therebetween.

[0095] In some optional embodiments, the thickness of the diaphragm 140 facing the second pole piece 120 is greater than, or equal to, the thickness of the diaphragm 140 facing the first pole piece 110; or,

[0096] The thickness of the glue layer of the diaphragm 140 facing the second pole piece 120 is greater than, or equal to, the thickness of the glue layer of the diaphragm 140 facing the first pole piece 110; or,

[0097] The glue content of the glue layer of the diaphragm 140 facing the second pole piece 120 is greater than, or equal to, the glue content of the glue layer of the diaphragm 140 facing the first pole piece 110 .

[0098] It should be noted that by improving the adhesion between the separator 140 and the second electrode sheet 120 , the transmission path of lithium ions during the cycle process is reduced.

[0099] In some optional embodiments, the peeling force between the second electrode piece 120 and the diaphragm 140 is greater than, or equal to, half of the peeling force between the first electrode piece 110 and the diaphragm 140 .

[0100] It should be noted that the peeling force between the second electrode sheet 120 and the separator 140 refers to the adhesion force or peeling force between the positive electrode sheet of the battery and the separator 140 .

[0101] The greater the peeling force, the stronger the adhesion between the electrode and the diaphragm 140, and the more stable the battery structure, which can prevent the electrode and the diaphragm 140 from accidentally peeling off during use and reduce the risk of internal short circuit in the battery.

[0102] However, if the peeling force is too large, it may cause stress concentration inside the battery, increase the internal stress of the battery during the charge and discharge process, and thus reduce the cycle life and performance of the battery.

[0103] Therefore, in battery design and manufacturing, it is necessary to reasonably control the peeling force between the positive electrode sheet and the separator 140 to ensure the safety, stability and cycle life of the battery. The peeling force can usually be adjusted by optimizing the materials, surface treatment, and preparation process of the positive electrode sheet and the separator 140.

[0104] It should be noted that such a configuration further reduces the transmission path of lithium ions during the cycle, so that during the cycle of the battery cell 100, the problem of lithium deposition in the second electrode sheet 120 caused by the high current density of the second electrode sheet 120 can be avoided.

[0105] like Figures 1 to 3 As shown, in some optional embodiments, the battery cell 100 further includes a third pole piece 130, the third pole piece 130 has a polarity opposite to that of the second pole piece 120, the diaphragm 140 is located between the first pole piece 110 and the third pole piece 130, and the diaphragm 140 is located between the second pole piece 120 and the third pole piece 130;

[0106] The peeling force between the diaphragm 140 facing the second pole piece 120 and the third pole piece 130 is greater than, or equal to, half of the peeling force between the diaphragm 140 facing the first pole piece 110 and the third pole piece 130 .

[0107] It should be noted that the third electrode sheet 130 may be a negative electrode sheet.

[0108] In some embodiments, the third electrode sheet 130 includes a third current collector 131 and at least one third active material layer 132 , wherein the third positive current collector is a negative current collector, and the third active material layer 132 is a negative active material layer.

[0109] It should be noted that the third current collector 131 is a high-strength copper foil current collector with a tensile strength of 300MPa-700MPa, an elongation of 2.0%-11%, and a surface density of 30g / m2-65g / m2. The purpose is to effectively improve the problem of the third current collector 131 breaking due to the stress difference generated during welding melting; at the same time, it can also effectively reduce the burrs on the solder joints and reduce the risk of puncture. At the same time, it can also increase the tensile force value at the solder joint, reduce the contact impedance, and reduce the internal resistance of the battery cell 100.

[0110] Figure 4 A schematic diagram of the structure of the fourth battery cell provided in the embodiment of the present application is shown in FIG. Figure 4 As shown, in some optional embodiments, the battery cell 100 further includes an insulating layer 150 , and there are two battery cells 100 , which are respectively located on opposite sides of the insulating layer 150 .

[0111] In some optional embodiments, the thickness of the second current collector 121 in the battery cell 100 located on the first side of the insulating layer 150 is greater than the thickness of the first current collector 111 in the battery cell 100 located on the first side of the insulating layer 150; and / or,

[0112] The thickness of the second current collector 121 in the battery cell 100 located on the second side of the insulating layer 150 is greater than the thickness of the first current collector 111 in the battery cell 100 located on the second side of the insulating layer 150 .

[0113] The first side of the insulating layer 150 is the upper side of the insulating layer 150 , and the second side of the insulating layer 150 is the lower side of the insulating layer 150 .

[0114] It should be noted that such a setting, i.e. the total thickness of the second active material layer 122 corresponding to the diaphragm 140 is higher than the total thickness of the first active material layer 112 corresponding to the diaphragm 140, can improve the adhesion between the diaphragm 140 and the second active material layer 122, thereby reducing the transmission path of lithium ions during the cycle.

[0115] In some optional embodiments, a ratio between a thickness of the second current collector 121 located on the first side of the insulating layer 150 and a thickness of the first current collector 111 located on the first side of the insulating layer 150 is greater than, or equal to, 1.2.

[0116] It should be noted that by increasing the thickness of the second current collector 121 located on the first side of the insulating layer 150, the structural strength of the second current collector 121 is improved, thereby buffering the force of the single-sided area expansion and protecting the pole piece in the middle area of ​​the stacked core from being squeezed.

[0117] It should be noted that the specific values ​​can be adjusted according to actual conditions and are not overly restricted here.

[0118] In some optional embodiments, a ratio between a thickness of the second current collector 121 located on the second side of the insulating layer 150 and a thickness of the first current collector 111 located on the second side of the insulating layer 150 is greater than, or equal to, 1.2.

[0119] It should be noted that by increasing the thickness of the second current collector 121 located on the second side of the insulating layer 150, the structural strength of the second current collector 121 is improved, thereby buffering the force of the single-sided area expansion and protecting the pole piece in the middle area of ​​the stacked core from being squeezed.

[0120] It should be noted that the specific values ​​can be adjusted according to actual conditions and are not overly restricted here.

[0121] In some optional embodiments, the difference between the thickness of the second active material layer 122 located on the first side of the insulating layer 150 and the thickness of the second active material layer 122 located on the second side of the insulating layer 150 is less than 0 um-20 um.

[0122] It should be noted that such a configuration can avoid the problem of single-sided lithium plating due to high current density in the two stacked battery cells 100. At the same time, it can also ensure that the expansion degrees of the two battery cells 100 during the cycle are close, thereby preventing the problem of abnormal expansion of a single battery cell 100.

[0123] In some optional embodiments, in the battery cell 100 located on the first side of the insulating layer 150 , the difference between the thickness of the second active material layer 122 away from the insulating layer 150 and the thickness of the second active material layer 122 facing the insulating layer 150 is less than 0um-10um.

[0124] It should be noted that such a configuration avoids the problem of lithium deposition on one side while ensuring that the upper and lower sides of the battery cell 100 expand to the same extent, thereby preventing excessive compression of the electrode in the middle area of ​​the battery cell 100.

[0125] The battery cell provided in the embodiment of the present application includes a first pole piece, the first pole piece includes a first current collector and a first active material layer respectively arranged on two opposite sides of the first current collector in a first direction; a second pole piece, along the first direction of the battery cell, the second pole piece is located on at least one side of the first pole piece, the second pole piece includes a second current collector and a second active material layer arranged on a side of the second current collector facing the first pole piece; a diaphragm, the diaphragm is located between the first pole piece and the second pole piece; the thickness of the second active material layer is greater than the thickness of the first active material layer.

[0126] By making the thickness of the second active material layer greater than that of the first active material layer, the problem of lithium plating in the second electrode due to the large current density of the second electrode can be avoided, and the abnormal thickness expansion of the battery cell due to lithium plating during the cycle process can be avoided, thereby greatly improving the cycle pass rate and service life of the fast charging battery.

[0127] In addition, an embodiment of the present application also provides a battery, including a battery shell and the above-mentioned battery cell, wherein the battery cell is located in the battery shell. By having the thickness of the second active material layer be greater than the thickness of the first active material layer, the problem of lithium plating of the second electrode sheet due to the large current density of the second electrode sheet can be avoided, and the abnormal thickness expansion of the battery cell due to lithium plating during the cycle process can be avoided, thereby greatly improving the cycle pass rate and service life of the fast-charging battery.

[0128] The specific structure, working principle and function of the battery cell 100 have been described in detail in the aforementioned embodiments and will not be repeated here.

[0129] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit it. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A battery cell, characterized in that: include: A first pole piece, the first pole piece comprising a first current collector and first active material layers respectively arranged on two opposite sides of the first current collector in a first direction; A second pole piece, located along the first direction of the battery cell, the second pole piece is located on at least one side of the first pole piece, the second pole piece comprises a second current collector and a second active material layer arranged on a side of the second current collector facing the first pole piece; a diaphragm, the diaphragm being located between the first pole piece and the second pole piece; The second active material layer has a thickness greater than that of the first active material layer.

2. The battery cell according to claim 1, characterized in that: The surface density of the second pole piece is less than the surface density of the first pole piece.

3. The battery cell according to claim 1, characterized in that: The compaction density of the second pole piece is less than the compaction density of the first pole piece.

4. The battery cell according to claim 1, characterized in that: The ratio of the compaction density of the second pole piece to the compaction density of the first pole piece is between 90% and 98%.

5. The battery cell according to claim 1, characterized in that: The weight per unit area of ​​the second active material layer is smaller than the weight per unit area of ​​the first active material layer.

6. The battery cell according to claim 2, characterized in that: The ratio of the weight per unit area of ​​the second active material layer to the weight per unit area of ​​the first active material layer is between 90% and 97%.

7. The battery cell according to claim 1, characterized in that: The thickness of the diaphragm facing the second pole piece is greater than the thickness of the diaphragm facing the first pole piece; or, The thickness of the glue layer of the diaphragm facing the second pole piece is greater than the thickness of the glue layer of the diaphragm facing the first pole piece; or, The glue content of the glue layer of the diaphragm facing the second pole piece is greater than the glue content of the glue layer of the diaphragm facing the first pole piece.

8. The battery cell according to claim 1, characterized in that: The peeling force between the second pole piece and the diaphragm is greater than, or equal to, half of the peeling force between the first pole piece and the diaphragm.

9. The battery cell according to claim 1, characterized in that: The battery cell further includes a third pole piece, the first pole piece and the second pole piece have the same polarity, the third pole piece and the second pole piece have opposite polarity, the diaphragm is located between the first pole piece and the third pole piece, and the diaphragm is located between the second pole piece and the third pole piece; The peeling force between the diaphragm facing the second pole piece and the third pole piece is greater than, or equal to, half of the peeling force between the diaphragm facing the first pole piece and the third pole piece.

10. The battery cell according to any one of claims 1 to 9, characterized in that: The battery core further includes an insulating layer. There are two battery cores, and the two battery cores are respectively located on two opposite sides of the insulating layer in a first direction.

11. The battery cell according to claim 10, characterized in that: The thickness of the second current collector in the battery cell located on the first side of the insulating layer is greater than the thickness of the first current collector in the battery cell located on the first side of the insulating layer; and / or, The thickness of the second current collector in the battery cell located on the second side of the insulating layer is greater than the thickness of the first current collector in the battery cell located on the second side of the insulating layer.

12. The battery cell according to claim 11, characterized in that: A ratio between a thickness of the second current collector located on the first side of the insulating layer and a thickness of the first current collector located on the first side of the insulating layer is greater than, or equal to, 1.

2.

13. The battery cell according to claim 11, characterized in that: A ratio between a thickness of the second current collector located on the second side of the insulating layer and a thickness of the first current collector located on the second side of the insulating layer is greater than, or equal to, 1.

2.

14. The battery cell according to claim 11, characterized in that: A difference between a thickness of the second active material layer located on the first side of the insulating layer and a thickness of the second active material layer located on the second side of the insulating layer is less than 0 um-20 um.

15. The battery cell according to claim 11, characterized in that: In the battery cell located on the first side of the insulating layer, a difference between a thickness of the second active material layer away from the insulating layer and a thickness of the second active material layer facing the insulating layer is less than 0 um-10 um.

16. A battery, characterized in that: The invention comprises a battery casing and a battery cell as claimed in any one of claims 1 to 15, wherein the battery cell is located in the battery casing.

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