Pole piece, preparation method thereof, battery cell, battery, battery device and electric equipment

Abstract

The application relates to the technical field of batteries, and relates to a pole piece, a preparation method thereof, a battery cell, a battery, a battery device and a power utilization equipment. The pole piece comprises a pole lug, a current collector and an active material layer; the thickness size of the current collector in a second direction on a side close to the pole lug is smaller than the thickness size of the current collector in the second direction on a side away from the pole lug; the active material layer is arranged on at least one side surface of the current collector in the second direction; the thickness size of the active material layer in the second direction on a side close to the pole lug is greater than the thickness size of the active material layer in the second direction on a side away from the pole lug; and a first direction is arranged to intersect the second direction. In the pole piece of the embodiment, the size of the current collector and the active material layer in the second direction is specifically designed along the first direction, so that the SOC state uniformity of the pole piece in the first direction is improved, the risk of local lithium precipitation when the pole piece is applied to a battery is reduced, and the service life of the battery is improved.

Description

Technical Field

[0001] This application relates to the field of battery technology, and in particular to an electrode sheet and its preparation method, a battery cell, a battery, a battery device, and an electrical device. Background Technology

[0002] Battery electrodes typically consist of a current collector and an active material layer, and their structural design affects the battery's electrochemical behavior and overall performance. When the current collector and active material layer of the battery electrode are of uniform thickness, the impedance characteristics of the current collector along a certain direction during charge and discharge cause lithium insertion / extraction to preferentially occur near the tab compared to the side farther from the tab. This results in the state of charge (SOC) of the electrode region near the tab being higher or lower than other regions. For example, during charging, the SOC of the negative electrode is higher on the side near the tab than on the other side, while the opposite is true for the positive electrode. Related technologies suppress SOC non-uniformity by increasing the thickness of the current collector; however, increasing the current collector thickness obviously occupies more volume and mass, resulting in a loss of battery energy density. Summary of the Invention

[0003] This application provides an electrode sheet and its preparation method, a battery cell, a battery, a battery device, and an electrical device to solve the problem of poor uniformity of SOC state distribution in the electrode sheet of the battery during charging and discharging in the prior art.

[0004] The first aspect of this application provides an electrode sheet, comprising:

[0005] Extreme ear;

[0006] A current collector, connected to the tab, extends away from the tab and along a first direction; the thickness of the current collector in a second direction on the side closer to the tab is smaller than the thickness of the current collector in the second direction on the side farther from the tab; and

[0007] An active material layer is disposed on at least one side surface of the current collector in the second direction; the thickness of the active material layer in the second direction on the side closer to the tab is greater than the thickness of the active material layer in the second direction on the side farther from the tab; the first direction and the second direction are intersecting.

[0008] In one possible implementation, the thickness of the current collector gradually increases in the first direction and gradually decreases in the second direction; the thickness of the active material layer gradually decreases in the second direction.

[0009] In one possible implementation, in the first direction, the thickness difference of the active material layers in the second direction is successively equal for adjacent unit lengths.

[0010] In one possible implementation, the surface of the active material layer away from the current collector is configured as a plane.

[0011] In one possible implementation, the thickness of the active material layer in the second direction gradually changes over adjacent unit lengths in the first direction.

[0012] In one possible implementation, the surface of the active material layer away from the current collector is configured as a concave surface, and the thickness difference of the active material layer in the second direction gradually decreases over adjacent unit lengths.

[0013] In one possible implementation, the surface of the active material layer away from the current collector is configured as a convex surface, and the thickness difference of the active material layer in the second direction gradually increases over adjacent unit lengths.

[0014] In one possible implementation, the active material layer includes a first material layer and a second material layer connected along the first direction, the first material layer being located on the side closer to the tab; wherein the average particle size of the active material in the first material layer is greater than the average particle size of the active material in the second material layer.

[0015] In one possible implementation, the average particle size of the active material in the first material layer is D1, and the average particle size of the active material in the second material layer is D2, satisfying the following relationship: 1 <D1 / D2<10。

[0016] In one possible implementation, D1 and D2 satisfy the following relationship: 2 <D1 / D2<5。

[0017] In one possible implementation, D1 is 50-500 nm, and / or D2 is 20-100 nm.

[0018] In one possible implementation, the active material of the active material layer includes lithium iron phosphate and / or lithium nickel cobalt manganese oxide.

[0019] In one possible implementation, the active material of the active material layer includes graphite.

[0020] In one possible implementation, the active material in the first material layer is secondary graphite particles, and the active material in the second material layer is primary graphite particles.

[0021] In one possible implementation, in the first direction, the length of the active material layer is L1, the length of the first material layer is L5, and the following relationship is satisfied: 0 <L5 / L1<0.5。

[0022] In a possible implementation, the L1 and the L5 satisfy the following relational expression: 0.05 < L5 / L1 < 0.12; or 0.1 < L5 / L1 < 0.2.

[0023] In a possible implementation, the active material layer has a third end portion and a fourth end portion that are oppositely arranged, and the third end portion is located on a side close to the tab; the thickness dimension of the third end portion in the second direction is d7, and the thickness dimension of the fourth end portion on the same side as the third end portion in the second direction is d8, and at least one of the following relational expressions is satisfied:

[0024] 1.0 < d7 / d8 < 5.0.

[0025] In a possible implementation, the electrode sheet is a positive electrode sheet, the active material layer is formed by curing a positive electrode paste, and the positive electrode paste includes, by mass parts:

[0026] 80 to 120 parts of positive electrode active material;

[0027] 12.0 to 14.0 parts of conductive agent;

[0028] 2.0 to 3.0 parts of binder;

[0029] 20 to 200 parts of positive electrode solvent.

[0030] In a possible implementation, the mass parts ratio of the positive electrode active material, the conductive agent, the binder, and the positive electrode solvent in the positive electrode paste is 100:13.2:2.3:52.5.

[0031] In a possible implementation, the electrode sheet is a negative electrode sheet, the active material layer is formed by curing a negative electrode paste, and the negative electrode paste includes, by mass parts:

[0032] 80 to 120 parts of negative electrode active material;

[0033] 1.0 to 2.0 parts of conductive agent;

[0034] 1.0 to 5.0 parts of binder;

[0035] 1.0 to 2.0 parts of thickening agent;

[0036] 50 to 300 parts of negative electrode solvent.

[0037] In a possible implementation, the mass parts ratio of the negative electrode active material, the conductive agent, the binder, the thickening agent, and the negative electrode solvent in the negative electrode paste is 100:1.5:3.0:1.2:115.

[0038] In one possible implementation, the dimension of the current collector on the side away from the tab in the second direction is d6, and the dimension of the active material layer on the side away from the tab in the second direction is d8, satisfying the following relationship:

[0039] 1.0 <d6 / d8<5.0。

[0040] In one possible implementation, the length of the active material layer in the first direction is not greater than the length of the current collector.

[0041] A second aspect of this application provides a method for preparing an electrode sheet as described in any one of the above claims, the method comprising the following steps:

[0042] A current collector is provided, and at least one end of the current collector is provided with a tab;

[0043] An active material slurry is coated on at least one side of the current collector to cure and form an active material layer; wherein the thickness of the active material layer on the side closer to the tab is greater than the thickness on the side farther from the tab.

[0044] In one possible implementation, the step of coating at least one side of the current collector with an active material slurry to cure and form an active material layer includes the following steps:

[0045] The current collector is tilted so that the side of the current collector away from the electrode is higher than the side close to the electrode;

[0046] An active material slurry is coated on at least one side of the current collector so that the active material slurry tends to flow toward the tab under the action of gravity.

[0047] The active material slurry solidifies to form an active material layer; wherein the thickness of the active material layer on the side closer to the tab is greater than the thickness on the side farther from the tab.

[0048] In one possible implementation, the step of coating at least one side of the current collector with an active material slurry to cure and form an active material layer includes the following steps:

[0049] An active substance slurry is coated on at least one side of the current collector, and pressure is applied to the active substance slurry on the side away from the current collector.

[0050] The pressure applied to the active material layer on the side closer to the tab is less than the pressure applied to the active material layer on the side farther from the tab;

[0051] The active material slurry solidifies to form an active material layer; wherein the thickness of the active material layer on the side closer to the tab is greater than the thickness on the side farther from the tab.

[0052] In one possible implementation, the step of coating at least one side of the current collector with an active material slurry to cure and form an active material layer includes the following steps:

[0053] An active substance slurry is coated on at least one side of the current collector, and pressure is applied to the active substance slurry on the side away from the current collector by a pressure mechanism.

[0054] The distance between the pressure mechanism and the active material layer on the side closer to the tab is greater than the distance between the pressure mechanism and the active material layer on the side farther from the tab.

[0055] The active material slurry solidifies to form an active material layer; wherein the thickness of the active material layer on the side closer to the tab is greater than the thickness on the side farther from the tab.

[0056] A third aspect of this application provides a battery cell, comprising:

[0057] Diaphragm; and

[0058] A positive electrode and a negative electrode are respectively disposed on opposite sides of the separator, and at least one of the positive electrode and the negative electrode adopts the electrode described in any one of the above descriptions.

[0059] A fourth aspect of this application provides a battery, comprising:

[0060] The battery casing is filled with electrolyte; and

[0061] The battery cell described in any of the above embodiments is housed within the battery casing and is in contact with the electrolyte.

[0062] The fifth aspect of this application provides a battery device comprising: a plurality of batteries as described in any one of the foregoing claims.

[0063] The sixth aspect of this application provides an electrical appliance, comprising:

[0064] Electrical appliances; and

[0065] The battery device, the battery, or the cell described in any of the preceding claims is electrically connected to the electrical device and is used to supply power to the electrical device.

[0066] Implementing the embodiments of this application has the following beneficial effects:

[0067] In the electrode of this embodiment, by specifically designing the dimensions of the current collector and the active material layer in the second direction along the first direction, the SOC state uniformity of the electrode in the first direction can be improved, thereby reducing the risk of local lithium plating when the electrode is applied to the battery, and thus improving the battery life. Attached Figure Description

[0068] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0069] Figure 1 A schematic diagram of the electrode structure in an embodiment of the present invention is shown.

[0070] Figure 2 A schematic diagram of the electrode structure in Embodiment 1 of the present invention is shown;

[0071] Figure 3 A schematic diagram of the electrode structure in Embodiment 2 of the present invention is shown;

[0072] Figure 4 A schematic diagram of the electrode sheet in Embodiment 3 of the present invention is shown;

[0073] Figure 5 A schematic diagram of the electrode sheet in Embodiment 4 of the present invention is shown;

[0074] Figure 6 A schematic diagram of the battery cell structure in one embodiment of the present invention is shown;

[0075] Figure 7 A schematic diagram of the battery cell structure is shown in another embodiment of the present invention;

[0076] Figure 8 A schematic flowchart of the electrode preparation method of the present invention is shown;

[0077] Figure label:

[0078] 100-cell;

[0079] 110 - Electrode; 111 - Tab; 112 - Current collector; 1121 - First end; 1122 - Second end; 113 - Active material layer; 1131 - Third end; 1132 - Fourth end; 1133 - First material layer; 1134 - Second material layer;

[0080] 120-diaphragm;

[0081] 130 - Protective tape. Detailed Implementation

[0082] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0083] For ease of description, please refer to Figure 2 As shown, the definition Figure 2 The X direction in the equation is the first direction, defined as follows: Figure 2 The Y direction in the equation is the second direction, such as... Figure 2 In the illustrated embodiment, the X direction is perpendicular to the Y direction. The first direction can be the length or width direction of the electrode 110, and the second direction can be the thickness direction of the electrode 110. Specifically, the first direction can be the length or width direction of the current collector 112, and the second direction can be the thickness direction of the current collector 112. Of course, in some embodiments, the first and second directions can intersect at an angle, specifically 0-90°. The angle between the first and second directions is determined by the design requirements of the electrode 110 and is not uniquely limited here.

[0084] Battery electrodes typically consist of a current collector and an active material layer, and their structural design affects the battery's electrochemical behavior and overall performance. In particular, when the current collector and active material layer of the battery electrode are of uniform thickness, the impedance characteristics of the current collector along a certain direction during charge and discharge cause lithium insertion / extraction to preferentially occur near the tab compared to the side farther from the tab. This results in the state of charge (SOC) of the electrode region near the tab being higher or lower than other regions. For example, during charging, the SOC of the negative electrode is higher on the side near the tab than on the other side, while the opposite is true for the positive electrode.

[0085] To address these issues, related technologies typically employ two methods: controlling the ratio of electrode length to width and increasing the thickness of the current collector. While these methods can alleviate the non-uniformity of the state of charge (SOC) to some extent, they inherently have limitations and trade-offs. For example, reducing the ratio of electrode length to width can decrease ohmic losses and improve overall performance, but it risks reducing the battery's energy density; while increasing the current collector thickness can improve conductivity, it increases the battery's volume and mass, thus sacrificing energy density.

[0086] For the above technical issues, please refer to Figures 1 to 7 As shown, an embodiment of the present invention provides an electrode 110, which includes an electrode tab 111, a current collector 112, and an active material layer 113. The current collector 112 is connected to the electrode tab 111, and extends away from the electrode tab 111 along a first direction. The thickness of the current collector 112 in a second direction on the side near the electrode tab 111 is smaller than the thickness of the current collector 112 in a second direction on the side away from the electrode tab 111. The active material layer 113 is disposed on at least one surface of the current collector 112 in a second direction. The thickness of the active material layer 113 in a second direction on the side near the electrode tab 111 is larger than the thickness of the active material layer 113 in a second direction on the side away from the electrode tab 111. The first direction and the second direction are intersecting.

[0087] In this embodiment, since the size of the active material layer 113 gradually decreases in the second direction along the first direction, the current distribution in the active material layer 113 can be made more uniform. When the current passes through the electrode 110, the thicker active material layer 113 can provide more reaction area, which helps to reduce the phenomenon of excessively high local current density, thereby reducing the occurrence of problems such as local overheating and lithium plating, so as to improve the current density distribution.

[0088] Meanwhile, by designing the current collector 112 to gradually increase in size in the second direction along the first direction, it helps to optimize the electron transport path from the current collector 112 to the active material layer 113. The wider end of the current collector 112 can provide better conductivity, while the narrower end reduces unnecessary material usage, while ensuring the electron transport efficiency of the entire electrode 110. This structural design helps to maintain a relatively uniform current density across the entire electrode 110, further improving the uniformity of SOC.

[0089] In addition, the combined structure design of the active material layer 113 and the current collector 112 can effectively reduce the edge effect, that is, improve the phenomenon of abnormally high or low current density in the edge region of the electrode 110 due to physical structure. By gradually changing the thickness of the active material layer 113, the difference in current density between the edge and the center region can be balanced to a certain extent, thereby improving the electrical performance of the entire electrode 110 and making the electrode 110 have a more uniform size in the second direction.

[0090] In the electrode 110 of this embodiment, by specifically designing the dimensions of the current collector 112 and the active material layer 113 in the second direction along the first direction, the SOC uniformity of the electrode 110 in the first direction can be improved, thereby reducing the risk of local lithium plating when the electrode 110 is applied in the battery, and thus improving the battery life.

[0091] It should be noted that, for reference Figure 1As shown, in some embodiments, the current collector 112 can be a plate-like structure or a columnar structure. When the current collector 112 is, for example, a plate-like rectangular structure, the dimension of the current collector 112 in the first direction can be the length or width dimension, and the dimension of the current collector 112 in the second direction can be the thickness dimension. When the current collector 112 is a columnar structure, the dimension of the current collector 112 in the second direction can be the diameter or width dimension. Of course, in some embodiments, the active material layer 113 can also be disposed on opposite sides of the current collector 112, or multiple active material layers 113 can be disposed on the same side of the current collector 112; this is not a unique limitation.

[0092] Specifically, the side of the current collector 112 closest to the tab 111 is the first end 1121, and the second end 1122 is located on the side of the current collector 112 furthest from the tab 111. The first end 1121 and the second end 1122 are arranged sequentially along a first direction. The side of the active material layer 113 closest to the tab 111 is the third end 1131, and the fourth end 1132 is located on the side of the active material layer 113 furthest from the tab 111. In the first direction, the thickness of the current collector 112 gradually increases in the second direction; in the first direction, the thickness of the active material layer 113 gradually decreases in the second direction. Of course, in some embodiments, the second end 1122 may not be the end of the current collector 112 furthest from the tab 111, but may be a segment of the current collector 112 furthest from the tab 111; this is not a unique limitation. Similarly, the fourth end 1132 can be the end of the inactive material layer 113 away from the tab 111, or it can be a local structure of the active material layer 113 away from the tab 111. It is not limited to a single end here.

[0093] In traditional electrode designs, the thickness of the current collector and active material layer is usually uniform. This design causes the current density to be unevenly distributed at different locations on the electrode when the current passes through it. In particular, the current density is often higher at the edge of the electrode, which can lead to local overcharging or over-discharging, i.e., the state of charge (SOC) is too high or too low. In this embodiment, the current collector 112 and the active material layer 113 in the electrode 110 have a gradually changing thickness. When the electrode 110 of this embodiment is applied in a battery, during charging, the negative electrode 110 can improve the situation where the SOC state is too high on the side near the tab 111 of the electrode 110, and at the same time improve the situation where the SOC state is too low on the side near the tab 111 of the positive electrode 110. Conversely, during discharging, the negative electrode 110 can improve the situation where the SOC state is too low on the side near the tab 111 of the electrode 110, and at the same time improve the situation where the SOC state is too high on the side near the tab 111 of the positive electrode 110. This can improve the power performance, energy density and lifespan of the battery.

[0094] Specifically, refer to Figure 1 As shown, in one embodiment, the current collector 112 has a length dimension L1 in the first direction, and L1 = 10~2000mm; the current collector 112 has a thickness dimension L2 in the second direction, and L2 = 10~2000mm; the tab 111 has a thickness dimension L3 in the second direction, and L3 = 10~2000mm; the tab 111 has a length L4 in the first direction, and L4 = 10~2000mm. Specifically, in one embodiment, when the electrode 110 is applied to the positive electrode, L1 = 450mm, L2 = 50mm, L3 = 30mm, and L4 = 50mm; when the electrode 110 is applied to the negative electrode, L1 = 455mm, L2 = 53mm, L3 = 25mm, and L4 = 50mm.

[0095] See Figure 2 As shown, specifically in Embodiment 1, in the first direction, the thickness difference of the active material layer 113 in the second direction is successively equal in the second direction among adjacent unit lengths.

[0096] In this embodiment, the thickness of the active material layer 113 gradually decreases in the first direction, so that the thickness of the active material layer 113 at the third end 1131 is greater than the thickness of the fourth end 1132, and the active material layer 113 has different thicknesses in the first direction, so as to improve the non-uniform state of the SOC state of the electrode 110 during the charging and discharging process.

[0097] In one embodiment, the size of the current collector 112 increases linearly in the second direction. With this arrangement, the size of the current collector 112 gradually increases from the first end 1121 to the second end 1122 in the first direction. By cooperating with the active material layer 113, the SOC state distribution of the electrode sheet 110 can be made more uniform. Further, when the current collector 112 and the active material layer 113 have opposite thickness change structures in the first direction, the thickness dimension or the diameter dimension of the electrode sheet 110 formed by the combination of the current collector 112 and the active material layer 113 can be kept uniform in the first direction as a whole, so that the structure of the electrode sheet 110 is flat in the second direction, facilitating the electrode sheet 110 to make the battery cell 100 have a more regular outer shape structure when forming the battery cell 100.

[0098] Referring to Figure 2 As shown, in the first embodiment, optionally, the thickness dimension of the first end 1121 in the second direction is d5, and d5 = 2 - 20 μm, the thickness dimension of the second end 1122 in the second direction is d6, and d6 = 2 - 20 μm, the thickness dimension of the third end 1131 in the second direction is d7, and d7 = 10 - 200 μm, the thickness dimension of the fourth end 1132 in the second direction is d8, and d8 = 10 - 200 μm. Optionally, 1.0 < d7 / d8 < 5.0, specifically it can be 2.0, 3.0, 4.0; optionally, 1.0 < d6 / d8 < 5.0, specifically it can be 2.0, 3.0, 4.0, which is determined according to the actual design requirements of the electrode sheet 110 and is not uniquely limited here. By limiting the thickness of the third end 1131 and the fourth end 1132 in the second direction, it can be ensured that the overall thickness of the active material layer 113 changes uniformly, and the overall structure of the electrode sheet 110 is flat by cooperating with the thickness dimension of the current collector 112.

[0099] Specifically, in one embodiment, when the electrode sheet 110 is applied to the positive electrode sheet, d5 = 10 μm, d6 = 16 μm, d7 = 83 μm, d8 = 77 μm. When the electrode sheet 110 is applied to the negative electrode sheet, d5 = 5 μm, d6 = 11 μm, d7 = 53 μm, d8 = 47 μm.

[0100] Further, the surface of the active material layer 113 away from the current collector 112 is configured as a plane.

[0101] In this embodiment, by configuring the surface of the active material layer 113 away from the current collector 112 as a plane, the thickness change of the active material layer 113 along the first direction can be made more uniform and the outer surface of the electrode sheet 110 can be made flush, so as to ensure the consistency of the outer surface of the electrode sheet 110.

[0102] Referring to Figure 3 and Figure 4As shown, in some embodiments, in the first direction, the thickness difference of the active material layer 113 per unit length varies sequentially in the second direction, that is, the thickness of the active material layer 113 along the first direction is non-linear. This configuration allows for the selection of a corresponding structural layout based on the design requirements of the electrode 110. It should be noted that the thickness change of the active material layer 113 can be slow or rapid; specific implementations can include gradual thickening, gradual thinning, or a gradient design. The advantage of this non-linear thickness distribution is that it effectively improves the uniformity of current distribution, reduces hot spots, and thus improves the battery's discharge efficiency and safety. Furthermore, this design improves the full utilization rate of the active material, contributing to an increase in the overall energy density of the battery.

[0103] For details, please refer to [link / reference]. Figure 3 As shown, in Embodiment 2, the surface of the active material layer 113 away from the current collector 112 is constructed as a concave surface, and the thickness difference of the active material layer 113 in the second direction gradually decreases per unit length. It should be noted that the concave structure of the active material layer 113 not only helps improve the current distribution characteristics but also effectively reduces heat accumulation in the electrode 110 during charging and discharging, thereby improving battery safety and cycle life. This concave shape allows electrons and ions to flow more smoothly, reducing unnecessary resistance and improving the battery's charging and discharging efficiency. Specifically, in this embodiment, the thickness d of the active material layer 113 can be selected as d = 2~200 μm.

[0104] In one embodiment, the thickness of the active material layer 113 at six points in the first direction, excluding d7 and d8, is denoted as d9 to d14. When the electrode 110 is applied to the positive electrode, d7 = 83 μm, d9 = 80 μm, d10 = 78 μm, d11 = 76.6 μm, d12 = 75.6 μm, d13 = 74.8 μm, d14 = 74.1 μm, and d8 = 73.4 μm. When the electrode 110 is applied to the negative electrode, d7 = 77 μm, d9 = 74 μm, d10 = 72 μm, d11 = 70.6 μm, d12 = 69.6 μm, d13 = 68.8 μm, d14 = 68.1 μm, and d8 = 67.4 μm. Of course, in one embodiment, the size of the current collector 112 in the second direction can also be increased exponentially and adapted to the structure of the active material layer 113 to make the overall surface of the electrode 110 flat.

[0105] See Figure 4As shown, in Embodiment 3, the surface of the active material layer 113 away from the current collector 112 is constructed as a convex surface, and the thickness difference of the active material layer 113 in the second direction gradually increases per unit length. This design optimizes the current distribution and the reaction interface of the active material by gradually increasing the thickness, which is beneficial to improving the overall performance and charge / discharge efficiency of the electrode 110. Specifically, in this embodiment, the thickness of the active material layer 113 along the first direction varies non-linearly, and the thickness d of the active material layer 113 can be selected as d = 2 to 200 μm.

[0106] In one embodiment, the thickness of the active material layer 113 at six points in the first direction, excluding d7 and d8, is denoted as d9 to d14. When the electrode 110 is applied to the positive electrode, d7 = 83 μm, d9 = 82.3 μm, d10 = 81.6 μm, d11 = 80.8 μm, d12 = 79.8 μm, d13 = 78.4 μm, d14 = 76.4 μm, and d8 = 73.4 μm. When the electrode 110 is applied to the negative electrode, d7 = 77 μm, d9 = 76.3 μm, d10 = 75.6 μm, d11 = 74.8 μm, d12 = 73.8 μm, d13 = 72.4 μm, d14 = 70.4 μm, and d8 = 67.4 μm.

[0107] See Figure 5 As shown, in Embodiment 5, the active material layer 113 includes a first material layer 1133 and a second material layer 1134 connected along a first direction. The first material layer 1133 is located on the side close to the tab 111. The particle size of the material in the first material layer 1133 is larger than the average particle size of the active material in the second material layer 1134.

[0108] This design allows different layers of the active material layer 113 to possess different physical properties. For example, smaller particle size active material layers (such as the second material layer 1134) can more effectively accelerate ion diffusion, thereby improving the battery's charge and discharge efficiency; while larger particle size active material layers (such as the first material layer 1133) help improve the material's electrical conductivity and mechanical strength. Through this ingenious combination of particle sizes, the advantages of different material layers can be fully utilized, thereby providing a more balanced performance during battery operation and ensuring the battery's stability and durability under high load and high cycle frequency conditions.

[0109] In this embodiment, the average particle size of the active material in the first material layer 1133 is D1, the average particle size of the active material in the second material layer 1134 is D2, and the active material layer 113 is divided along the first direction into a first material layer 1133 near the first end 1121 and a second material layer 1134 near the second end 1122.

[0110] In these two regions, the slurry in the active material layer 113 can be selected as graphite, lithium iron phosphate, or lithium nickel cobalt manganese oxide. When the electrode 110 is applied to the positive electrode, the length dimension of the first material layer 1133 in the first direction is defined as L5, and the length dimension of the second material layer 1134 in the first direction is defined as L6, satisfying the following relationship: optionally, L5 / L1 = 0~0.5, D1 = 50~500nm, D2 = 20~100nm; specifically in one embodiment, L5 / L1 = 0.1; the average particle size D1 of lithium iron phosphate in the L5 region can be selected as D1 = 100nm; the average particle size D2 of lithium iron phosphate in the L6 region is 50nm.

[0111] Of course, in some embodiments, the material of the active material layer 113 includes a mixture of lithium iron phosphate and lithium nickel cobalt manganese oxygen particles. However, in the application process, in order to ensure the performance of the battery, it is necessary to conduct experiments on the electrochemical compatibility, performance balance and manufacturing process of the active material after the two are mixed.

[0112] Additionally, it should be noted that the average particle size mentioned in this application refers to the particle size value where 50% of the particles in the particle distribution have a diameter less than or equal to the average particle size. Image analysis can be used to analyze particle images using image processing technology to measure and statistically analyze particle size. The specific detection process is as follows: First, the electrode 110 is cross-sectionally cut using ion milling (CP), and then the cross-section is characterized using scanning electron microscopy (SEM). At least five different regions are selected and SEM images are taken at different magnifications (e.g., 100,000, 50,000, 20,000, 10,000, 5,000, 2,000, 1,000, etc., including but not limited to the above magnifications). The obtained images are processed to make the particle boundaries clearer, such as brightness and contrast. After the particle size is statistically analyzed manually or using image analysis software, the results can be processed to obtain detailed particle size distribution results, thereby obtaining indicators such as average particle size. Of course, in other embodiments, the electrode 110 can also be tested using other methods commonly used in the art, such as laser particle size analysis, sieving, microscopic observation, sedimentation, dynamic light scattering, and resistance methods, without being limited to a single method.

[0113] In one embodiment, the average particle size of the active material in the first material layer 1133 is D1, and the average particle size of the active material in the second material layer 1134 is D2, satisfying the following relationship: 1 <D1 / D2<10。

[0114] This difference in particle size between the first material layer 1133 and the second material layer 1134 not only optimizes the battery's conductivity but also enhances ion transport capabilities. Specifically, larger particle sizes of active materials (such as D1) help improve the electrode's mechanical strength and electrical conductivity, while smaller particle sizes of active materials (such as D2) enhance the battery's reaction rate and ion transport efficiency. This combination effectively improves the overall performance of the electrode 110, especially under high-rate charge-discharge conditions.

[0115] It should be noted that when the ratio of D1 to D2 is not within the preferred range, for example, if D1 / D2≤1 or D1 / D2≥10, it may lead to uneven internal reactions in the battery, thereby affecting the battery's charging and discharging efficiency and lifespan. Preferably, D1 and D2 satisfy the following relationship: 2 <D1 / D2<5。

[0116] In one embodiment, when the electrode 110 is applied to the negative electrode, the material of the active material layer 113 includes graphite.

[0117] Specifically, the active material in the first material layer 1133 is secondary graphite particles, and the active material in the second material layer 1134 is primary graphite particles.

[0118] It should be noted that secondary particles refer to larger particles formed by secondary granulation of smaller primary particles, which usually have better kinetic properties than primary particles.

[0119] Specifically, in the first direction, the length of the active material layer 113 is L1, the length of the first material layer 1133 is L5, and they satisfy the following relationship: 0 <L5 / L1<0.5。

[0120] It should be noted that in this embodiment, L5 can be 5%, 10%, 15%, etc., of L1, ensuring that the ratio is maintained between 0.1 and 0.5. With this configuration, the length of the first material layer 1133 is relatively short, and the conduction path of ions and electrons can be optimized through a higher area ratio, thereby improving the charging and discharging efficiency of the battery.

[0121] For the first material layer 1133, which has a larger average particle size of active material, its length ratio relative to the active material layer 113 is limited. This choice is made because the size distribution of secondary graphite particles is closely related to battery performance. A larger particle size reduces the resistance to the movement of electrons and lithium ions in the electrode, but if the particle size is too large, it may cause ion diffusion restriction, thus affecting cycle stability. Therefore, appropriately selecting the particle size can further improve the overall performance of the battery. By controlling the ratio of the length of the first material layer 1133 to the length of the active material layer 113, and ensuring its relatively reasonable boundary, the reaction surface area during battery charging and discharging can be effectively optimized.

[0122] Further, L1 and L5 satisfy the following relational expressions: 0.05 < L5 / L1 < 0.12; or 0.1 < L5 / L1 < 0.2.

[0123] It should be noted that when the electrode sheet 110 is applied to the positive electrode sheet, 0.05 < L5 / L1 < 0.12 to ensure the stability of the electrode sheet and the overall performance of the battery at a high charging rate; when the electrode sheet 110 is applied to the negative electrode sheet, 0.1 < L5 / L1 < 0.2, which can improve the ionic conductivity and structural strength of the negative electrode.

[0124] In this embodiment, by selecting a shorter first material layer 1133 in the positive electrode sheet, the reaction time of the electrode can be effectively reduced, thereby improving the energy output ability of the battery during rapid charge and discharge. At the same time, the shorter first material layer 1133 can reduce the internal resistance of the electrode and improve the overall charging efficiency and energy density. Selecting a longer first material layer 1133 in the negative electrode sheet compared to the positive electrode sheet is to enhance the insertion and extraction reactions of ions, thereby improving the cycle stability and rate performance of the battery. In addition, the longer first material layer also helps to improve the durability of the electrode during repeated charge and discharge processes and reduce material fatigue.

[0125] In one embodiment, the electrode sheet 110 is the positive electrode sheet 110, and the active material layer 113 is formed by curing a positive electrode slurry, and the positive electrode slurry includes, by mass parts:

[0126] 80 to 120 parts of positive electrode active material;

[0127] 12.0 to 14.0 parts of conductive agent;

[0128] 2.0 to 3.0 parts of binder;

[0129] 20 to 200 parts of positive electrode solvent.

[0130] In one embodiment, the mass parts ratio of the positive electrode active material, conductive agent, binder, and positive electrode solvent in the positive electrode slurry is 100:13.2:2.3:52.5. Specifically, when the electrode sheet 110 is applied to the positive electrode sheet, the positive electrode active material can be lithium iron phosphate, the conductive agent can be carbon black, the binder can be polyvinylidene fluoride, and the positive electrode solvent can be N-methylpyrrolidone.

[0131] In this embodiment, the tab 111 and the current collector 112 can be aluminum foil, and the active material layer 113 is formed by curing the above-mentioned positive electrode slurry on the current collector 112. In this embodiment, the mass ratio of each component in the slurry can be lithium iron phosphate: carbon black: polyvinylidene fluoride: N-methylpyrrolidone = 100:13.2:2.3:52.5. Of course, the lithium iron phosphate in the slurry in this embodiment can also be replaced by lithium nickel cobalt manganese oxide. Optionally, the mass ratio of N-methylpyrrolidone can also be 20 to 200.

[0132] In one embodiment, the electrode 110 is a negative electrode 110, and the active material layer 113 is formed by curing a negative electrode slurry, wherein the negative electrode slurry comprises, by weight parts:

[0133] 80 to 120 parts of negative electrode active material;

[0134] 1.0 to 2.0 parts of conductive agent;

[0135] 1.0 to 5.0 parts of adhesive;

[0136] Thickener 1.0 to 2.0 parts;

[0137] 50 to 300 parts of negative electrode solvent.

[0138] In one embodiment, the mass ratio of the negative electrode active material, conductive agent, binder, thickener, and negative electrode solvent in the negative electrode slurry is 100:1.5:3.0:1.2:115. Specifically, when the electrode 110 is applied to the negative electrode, the negative electrode active material can be graphite powder, the conductive agent can be carbon black, the binder can be styrene-butadiene rubber, the thickener can be sodium carboxymethyl cellulose, and the negative electrode solvent can be deionized water.

[0139] In this embodiment, the tab 111 and the current collector 112 can be copper foil, and the active material layer 113 is formed by curing the aforementioned negative electrode slurry on the current collector 112. In this embodiment, the mass ratio of the slurry components can be graphite powder: carbon black: styrene-butadiene rubber: sodium carboxymethyl cellulose: deionized water = 100:1.5:3.0:1.2:115. In some embodiments, carbon black can also be replaced by carbon nanotubes, and optionally, the mass ratio of deionized water can be 50-300. Of course, in actual processing, the components and their proportions of the slurry can be adjusted according to the actual situation on site, with the goal of ultimately obtaining a uniform and stable active material layer 113.

[0140] Specifically, the dimension of the current collector 112 on the side away from the tab 111 in the second direction is d6, and the dimension of the active material layer 113 on the side away from the tab 111 in the second direction is d8, satisfying the following relationship: 1.0 <d6 / d8<5.0。

[0141] In this embodiment, by limiting the ratio of the thickness of the second end 1122 to the thickness of the fourth end 1132, the battery design is optimized, improving its performance and durability. In this embodiment, by further limiting the ratio of the thickness of the second end 1122 to the thickness of the fourth end 1132, the current distribution and thermal management characteristics of the current collector 112 and the active material layer 113 can be effectively controlled. Specifically, the thickness of the second end 1122 can be selected as 30%, 50%, or 70% of the thickness of the active material layer 113, thereby optimizing the battery's charge and discharge efficiency while ensuring structural stability. Through a reasonable thickness configuration, better battery cycle performance can be achieved, reducing the heat generated during charging and discharging, thereby improving battery safety and lifespan.

[0142] Specifically, in the first direction, the length of the active material layer 113 is not greater than the length of the current collector 112.

[0143] In this embodiment, the active material layer 113 can be coated on the current collector 112 in a way that avoids the current collector 112 from forming tabs 111 at its end. This prevents the active material layer 113 from covering the tabs 111 and affecting the electrical performance of the electrode 110. If the active material layer 113 excessively covers the tabs 111, it may lead to a decrease in current collection efficiency, affecting the overall performance and charge / discharge capability of the battery.

[0144] In one embodiment, the length of the active material layer 113 in the first direction is less than the length of the current collector 112. Specifically, the length of the active material layer 113 can be selected to be 90%, 80%, or 70% of the length of the current collector 112 to ensure that the active material layer 113 functions within the effective reaction area while avoiding interference with the normal function of the tab 111. With this design, the battery can maintain good stability and safety at higher power outputs.

[0145] In other embodiments, the length of the active material layer 113 in the first direction may also be equal to the length of the current collector 112. This design is suitable for certain special needs, such as those requiring higher energy density or specific battery performance requirements.

[0146] In some embodiments, the electrode 110 may be provided with two tabs 111, which are respectively connected to opposite sides of the current collector 112. This design not only improves the energy output efficiency of the battery but also optimizes the uniform distribution of current, thereby improving the overall performance of the battery. In this embodiment, the thickness of the current collector 112 gradually increases in a second direction away from the tabs 111, reaching its maximum thickness at the middle part of the current collector 112, i.e., between the two tabs 111. This gradually thickening design enhances the mechanical strength of the current collector 112, making it stable during high-current operation, thereby effectively preventing battery deformation or damage.

[0147] In this embodiment, the thickness of the current collector 112 can be equal at both ends. This design helps ensure that the electrode 110 maintains good symmetry during manufacturing and use, thereby optimizing the assembly accuracy and performance of the battery. The thickness of the active material layer 113 gradually decreases in the second direction away from the tab 111, reaching its minimum thickness in the middle. This configuration effectively increases the specific surface area of ​​the active material layer 113 in the important electrochemical reaction region, improving reaction efficiency and capacity. The specific form of the electrode 110 is determined according to its design requirements and is not uniquely limited here.

[0148] Additionally, it should be noted that the reference... Figures 1 to 7 As shown, the tab 111 can be directly formed on the current collector 112, and the thickness dimension of the first end 1121 described above in the second direction can be only the thickness dimension of the part where the current collector 112 is connected to the tab 111, or it can be the thickness dimension of the end of the tab 111 away from the current collector 112. In this application, no further limitation is made on the specific combination form between the tab 111 and the current collector 112. Whether the tab 111 is directly formed from the first end 1121 of the current collector 112, or the tab 111 and the current collector 112 are separate structures and are combined by processing to form an integral structure, they all fall within the protection scope of this application.

[0149] See Figure 8 As shown, the present invention also provides a method for preparing an electrode sheet 110 in any of the above embodiments. This method includes the following steps:

[0150] Step S100: Provide a current collector 112, and at least one end of the current collector 112 is provided with a tab 111;

[0151] Step S200: Apply an active material slurry to at least one side of the current collector 112 to cure and form an active material layer 113; wherein the thickness of the active material layer 113 on the side closer to the tab 111 is greater than the thickness on the side farther from the tab 111.

[0152] The electrode prepared by the method of this embodiment can improve the SOC uniformity of the electrode in the first direction by specifically designing the size of the active material layer in the second direction along the first direction. This reduces the risk of local lithium plating when the electrode is applied to the battery, thereby improving the battery life.

[0153] Specifically, in one embodiment, step S200 includes the following steps:

[0154] The current collector 112 is tilted so that the side of the current collector 112 away from the tab 111 is higher than the side close to the tab 111. This tilted arrangement can not only effectively guide the flow direction of the active material slurry, but also help to increase the uniformity of the slurry coating on the surface of the current collector 112.

[0155] An active material slurry is coated on at least one side of the current collector 112 so that the active material slurry tends to flow toward the tab 111 under the action of gravity; thereby the active material slurry flows toward the side of the current collector 112 near the tab 111 before curing, so that the active material slurry accumulates here, so that the active material layer 113 can have a larger thickness on the side near the tab 111.

[0156] After the active material slurry is cured, an active material layer 113 is formed; wherein, the thickness of the active material layer 113 on the side closer to the tab 111 is greater than the thickness on the side farther from the tab 111.

[0157] In one embodiment, the first end 1121 may have a height difference relative to the second end 1122 in a second direction, and the active material slurry tends to flow towards the first end 1121 before curing under the influence of gravity, causing the thickness of the active material layer 113 to vary along the first direction. Optionally, H = 0~100cm, specifically 5cm, 20cm, 30cm, 80cm, 100cm, depending on the design requirements of the electrode 110, and is not limited to a single value here.

[0158] Specifically, in another embodiment, step S200 includes the following steps:

[0159] An active material slurry is coated on at least one side of the current collector 112, and pressure is applied to the active material slurry on the side away from the current collector 112. By applying pressure, the adhesion between the active material slurry and the current collector 112 can be effectively improved, ensuring that the active material layer 113 is uniformly and firmly attached to the current collector 112.

[0160] The pressure applied to the active material layer 113 on the side near the tab 111 is less than the pressure applied to the active material layer 113 on the side away from the tab 111; this different pressure application method can make the film thickness uneven on the side near the tab 111 and the side away from the tab 111, thereby forming a difference in thickness size.

[0161] After the active material slurry is cured, an active material layer 113 is formed; wherein, the thickness of the active material layer 113 on the side closer to the tab 111 is greater than the thickness on the side farther from the tab 111.

[0162] In this embodiment, after the slurry is applied to the current collector 112, a pressure mechanism can be used to apply pressure to the cured electrode 110. Optionally, a pressure P1 = 7500 kgf is applied on the side near the first end 1121, while a pressure P2 = 8000 kgf is applied on the side away from the first end 1121.

[0163] During the application of pressure, the pressure difference causes the thickness of the active material layer 113 to change along the L1 direction. Furthermore, the pressures P1 and P2 can range from 1000 to 100000 kgf. Within this range, applying different pressures allows for more flexible adjustment of the film thickness. If the pressure is too low, the active material layer 113 may not solidify sufficiently, thus affecting the overall performance of the battery; while excessive pressure may cause the film to rupture or peel off, leading to battery failure.

[0164] Specifically, in another embodiment, step S200 includes the following steps:

[0165] An active material slurry is coated on at least one side of the current collector 112, and pressure is applied to the active material slurry on the side away from the current collector 112 by a pressure mechanism; by applying pressure, the adhesion between the active material slurry and the current collector 112 can be effectively improved, ensuring that the active material layer 113 is uniformly and firmly attached to the current collector 112.

[0166] The distance between the pressure mechanism and the active material layer 113 on the side closer to the tab 111 is greater than the distance between the pressure mechanism and the active material layer 113 on the side farther from the tab 111; by setting the first end 1121 and the second end 1122 to have a height difference with respect to the pressure mechanism, active material layers 113 with different thicknesses can be formed.

[0167] After the active material slurry is cured, an active material layer 113 is formed; wherein, the thickness of the active material layer 113 on the side closer to the tab 111 is greater than the thickness on the side farther from the tab 111.

[0168] Specifically, when electrode 110 is applied to the positive electrode, the height near the first end 1121 can be set to h1 = 81 μm, while the height near the second end 1122 is h2 = 75 μm; when electrode 110 is applied to the negative electrode, the height near the first end 1121 is 51 μm, while the height near the second end 1122 is 45 μm. It should be noted that h1 can range from 10 to 200 μm, and h2 can also be adjusted within the range of 10 to 200 μm. In this design, the ratio of h1 / h2 is preferably greater than 1, and the specific range can be selected as h1 / h2 = 1.0 to 5.0. This height difference setting enables uniform flow of the coated active material slurry and optimizes the formation of the film layer, thereby improving the overall performance of the battery.

[0169] For specific implementations of the fixed pressure structure, the pressure device can be pneumatic, electric, or mechanical. Each pressure mechanism has its advantages: pneumatic devices can achieve efficient and uniform pressure application, electric devices can provide precise pressure control, and mechanical devices are suitable for mass production and can reduce production costs. These different structural forms provide flexibility in the implementation process, allowing different types of battery electrodes to be optimized according to actual needs.

[0170] The present invention also provides a battery cell 100, which includes a positive electrode, a negative electrode and a separator 120; the positive electrode and the negative electrode are respectively disposed on opposite sides of the separator 120, and at least one of the positive electrode and the negative electrode adopts the electrode 110 in any of the above embodiments.

[0171] It is understood that in the cell 100 of this embodiment, by setting the electrode 110 in any of the above embodiments, the electrode 110 of this embodiment can improve the SOC uniformity of the electrode 110 in the first direction by specifically designing the dimensions of the current collector 112 and the active material layer 113 in the second direction along the first direction, thereby reducing the risk of local lithium plating when the electrode 110 is applied in the battery, and thus improving the battery life.

[0172] Specifically, the diaphragm 120 can be made of materials including polypropylene (PP) and polyethylene (PE); in some embodiments, the diaphragm 120 can also be coated with ceramics, such as alumina (AL5O3), magnesium hydroxide (MgOH), and silicon oxide (SiO2); the surface of the diaphragm 120 can be coated with an adhesive layer, such as PVDF, acrylic resin, and polyurethane resin.

[0173] In one embodiment, the cell 100 further includes a protective tape 130, which is wrapped around the ends of the positive electrode to protect the positive electrode.

[0174] The present invention also provides a battery comprising a battery casing and a cell 100 as described in any of the above embodiments; the battery casing is filled with an electrolyte; the cell 100 is housed within the battery casing and is in contact with the electrolyte.

[0175] It is understood that in the battery of this embodiment, by providing a cell 100 having the electrode 110 of any of the above embodiments, the electrode 110 of this embodiment can improve the SOC uniformity of the electrode 110 in the first direction by specifically designing the dimensions of the current collector 112 and the active material layer 113 in the second direction along the first direction, thereby reducing the risk of local lithium plating when the electrode 110 is applied in the battery, and thus improving the battery life.

[0176] Specifically, in some embodiments, the electrolyte comprises a lithium salt and a solvent. Optional lithium salts include lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(oxalateborate)borate (LiBOB), and lithium difluorooxalateborate (LiODFB); optional solvents include ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), diethyl carbonate (DEC), and 1,2-dimethoxyethane (DME). The metal casing can be aluminum or steel, and composite films commonly include those formed from aluminum, polypropylene (PP), etc. It should be noted that any publicly disclosed materials that can be used to prepare lithium-ion batteries can be used as substitutes for the aforementioned materials.

[0177] See Figure 6 and Figure 7 As shown, the battery is a stacked cell or a cylindrical cell.

[0178] Specifically, such as Figure 6 In the embodiment shown, the cell 100 is a stacked cell 100, in which the positive electrode and the negative electrode are arranged alternately and separated by the separator 120 to form a stacked structure. When the cell 100 of this embodiment is assembled with the battery casing, a stacked battery can be formed.

[0179] See Figure 7 In the illustrated embodiment, the cell 100 has a wound structure. The positive and negative electrode plates are separated by a separator 120, and the entire cell 100 is wound to form a wound structure. Once the cell 100 is assembled with the corresponding battery casing, a cylindrical battery is formed, optionally a cylindrical battery. Of course, in other embodiments, the cell 100 can also be molded according to the actual design requirements of the battery to form a battery with a corresponding structure. Specifically, after the cell 100 is assembled with the battery casing, the battery casing can be sealed with a composite film.

[0180] The present invention also provides a battery device comprising a plurality of batteries according to any of the above embodiments.

[0181] It is understood that in the battery of this embodiment, by setting up a battery having any of the above embodiments, the electrode 110 in the battery can improve the SOC uniformity of the electrode 110 in the first direction by specifically designing the dimensions of the current collector 112 and the active material layer 113 in the second direction along the first direction. This reduces the risk of local lithium plating when the electrode 110 is applied in the battery, thereby improving the lifespan of the battery device. Specifically, multiple batteries can be electrically connected to output electrical energy, and the battery device can be a battery pack, battery cluster, or battery module.

[0182] Specifically, experiments were conducted on the electrode 110 in the above embodiments, and the materials and key processes used are as follows:

[0183] The mass ratio of the negative electrode slurry formulation is: graphite powder: carbon black: styrene-butadiene rubber: sodium carboxymethyl cellulose: deionized water = 100: 1.5: 3.0: 1.2: 115.

[0184] Positive electrode slurry formulation: Lithium iron phosphate: Carbon black: Polyvinylidene fluoride: N-methylpyrrolidone = 100: 13.2: 2.3: 52.5.

[0185] In some embodiments, the positive electrode slurry formulation may also be: lithium nickel cobalt manganese oxide: carbon black: polyvinylidene fluoride: N-methylpyrrolidone = 100: 13.2: 1.5: 15.

[0186] Positive current collector: 13μm aluminum foil; negative current collector: 6μm copper foil.

[0187] Electrolyte: LiPF6 lithium salt at a concentration of 1M, solvent EC:DMC = 3:7 (volume ratio). The positive electrode, negative electrode, and separator 120 can be stacked together and sealed externally by an aluminum shell. Implementation details can be found in any lithium-ion battery manufacturing process.

[0188] Example 1

[0189] The mass ratio of the negative electrode slurry formulation is: graphite powder: carbon black: styrene-butadiene rubber: sodium carboxymethyl cellulose: deionized water = 100: 1.5: 3.0: 1.2: 115.

[0190] The mass ratio of the positive electrode slurry formulation is: lithium iron phosphate: carbon black: polyvinylidene fluoride: N-methylpyrrolidone = 100: 13.2: 2.3: 52.5.

[0191] Positive current collector: 13μm aluminum foil; negative current collector: 6μm copper foil.

[0192] Electrolyte: LiPF6 lithium salt at a concentration of 1M, solvent EC:DMC = 3:7 (volume ratio). The positive electrode, negative electrode, and separator 120 can be stacked together and sealed externally by an aluminum shell. Implementation details can be found in any lithium-ion battery manufacturing process.

[0193] In this example, the positive electrode size L1 is adjusted while maintaining a 5mm margin between the negative electrode and the positive electrode. Other parameters remain unchanged, as shown in Examples 1-1, 1-2, and 1-3.

[0194] Example 2

[0195] In this example, the positive electrode size L5 is adjusted while maintaining a 3mm margin between the negative electrode and the positive electrode. Other parameters remain unchanged, as shown in Examples 2-1, 2-2, and 2-3.

[0196] Example 3

[0197] In this example, the thickness d7 of the third end 1131 of the positive electrode is adjusted. Other parameters remain unchanged, as shown in Examples 3-1, 3-2, and 3-3.

[0198] Example 4

[0199] In this example, the thickness d8 of the fourth end 1132 of the positive electrode is adjusted. Other parameters remain unchanged, as shown in Examples 4-1, 4-2, and 4-3.

[0200] Example 5

[0201] In this example, the thickness d7 of the third end 1131 of the positive electrode is adjusted. Other parameters remain unchanged, as shown in Examples 5-1, 5-2, and 5-3.

[0202] Example 6

[0203] In this example, the thickness d8 of the fourth end 1132 of the positive electrode is adjusted. Other parameters remain unchanged, as shown in Examples 6-1, 6-2, and 6-3.

[0204] Example 7

[0205] In this example, the average particle size of the first material layer 1133 of the positive electrode is adjusted. Other parameters remain unchanged, as shown in Examples 7-1, 7-2, and 7-3.

[0206] Example 8

[0207] In this example, the average particle size of graphite within the first material layer 1133 of the positive electrode is adjusted. Other parameters remain unchanged, as shown in Examples 8-1, 8-2, and 8-3.

[0208] Example 9

[0209] In this example, the average particle size of graphite and LFP in the first material layer 1133 of the positive electrode is adjusted. Other parameters remain unchanged, as shown in Examples 9-1, 9-2, and 9-3.

[0210] Control group -1

[0211] This example uses a conventional electrode design, i.e., d7 / d8 = 1. For the positive electrode, d7 = d8 = 80 μm; for the negative electrode, d7 = d8 = 50 μm. See Control Group-1 for details.

[0212] Control group -2

[0213] This example uses an unconventional electrode design, i.e., d7 / d8 < 1. Specifically, for the positive electrode, d7 = 83 μm and d8 = 77 μm; for the negative electrode, d7 = 53 μm and d8 = 47 μm.

[0214] The cycle life test of the secondary battery in this experiment was conducted according to GB / T31484-2015 "Requirements and Test Methods for Cycle Life of Power Batteries for Electric Vehicles" to test the capacity retention rate of the above-mentioned cells after 500 cycles at 45℃.

[0215] The comparison results between the control group and each embodiment of the present invention are shown in Table 1 below:

[0216] Table 1

[0217]

[0218]

[0219] Comparing the capacity retention data in Table 1, it can be seen that by adjusting the thickness of the active material layer 113 of the positive and negative electrodes, a thickness difference is created in the electrode 110 in the first direction, which significantly improves the cycle life of the secondary battery. Specifically, as seen in Examples 1-2, an increase in L1 / L5 initially shows a stronger trend in lifespan improvement, but a further increase in L1 / L5 leads to a deterioration in the lifespan of the electrode 110. This may be because, after L1 increases to a certain extent, the resulting non-uniformity cannot be changed by adjusting the thickness of the active material layer 113. As seen in Examples 3-6, an increase in d7 / d8 initially shows a stronger trend in lifespan improvement, but a further increase in d7 / d also leads to a deterioration in the lifespan of the electrode 110. This may be because, after d7 / d8 increases to a certain extent, it leads to additional uneven stress.

[0220] Furthermore, in the positive and negative electrode slurries, as the average particle size of lithium iron phosphate in the first material layer 1133 (L5 / L1 = 0.1) of the positive electrode increased from 85 nm to 200 nm, the results of Example 7 showed that the capacity retention rate increased from 97.3% to 97.9%; and as the graphite in the first material layer 1133 (L5 / L1 = 0.1) of the negative electrode changed from secondary particles to three types of primary particles, the results of Example 8 showed that the capacity retention rate increased from 97.3% to 98.0%.

[0221] Specifically, after optimizing the distribution of positive and negative electrode materials in the first material layer 1133, the results of Example 9 show that there is a synergistic effect between the improvement brought about by the thickness design of the active material layer 113 in the first direction and the improvement brought about by the distribution of positive and negative electrode materials in the first material layer 1133. In the above experiments, the known optimal solution is Example 9-2, which improves the capacity retention rate from 95.3% corresponding to the conventional electrode design (control group-1) to 98.8%.

[0222] The present invention also provides an electrical device, which includes an electrical device and a battery in any of the above embodiments, and a cell 100 or an electrode 110 in any of the above embodiments; the battery or cell 100 is electrically connected to the electrical device and is used to supply power to the electrical device.

[0223] It is understood that the electrical device provided in this application embodiment can improve the uniformity of the distribution of the SOC state of the electrode 110 during the charging and discharging process by using the battery in any of the above embodiments to power the device, thereby reducing the risk of local lithium plating during the charging and discharging process and improving the life and safety of the device.

[0224] In this embodiment, the electrical device can also be a smart wearable device, such as a smartwatch. The electrical device can also be a mobile phone, tablet computer, or laptop computer. In some embodiments, the electrical device can also be a vehicle, which can be a new energy vehicle, such as a pure electric vehicle (PEV / BEV), a range-extended electric vehicle (REEV), a hybrid electric vehicle (HEV), or a fuel cell electric vehicle. The vehicle can also be any vehicle equipped with a battery. The electrical device can also be an energy storage station.

[0225] In the description of the embodiments of this application, it should be noted that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this application. In addition, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0226] In the description of the embodiments of this application, it should be noted that, unless otherwise explicitly specified and limited, the terms "connected" and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of this application based on the specific circumstances.

[0227] In the embodiments of this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0228] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the embodiments of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0229] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. An electrode (110), characterized in that, include: Polar ear (111); A current collector (112) is connected to the tab (111), the current collector (112) being opposite to the tab (111) and extending along a first direction; the thickness of the current collector (112) in a second direction on the side near the tab (111) is smaller than the thickness of the current collector (112) in the second direction on the side away from the tab (111); and An active material layer (113) is disposed on at least one side surface of the current collector (112) in the second direction; the thickness of the active material layer (113) in the second direction on the side near the tab (111) is greater than the thickness of the active material layer (113) in the second direction on the side away from the tab (111); the first direction and the second direction are intersected.

2. The electrode (110) according to claim 1, characterized in that, In the first direction, the thickness of the current collector (112) gradually increases in the second direction; in the first direction, the thickness of the active material layer (113) gradually decreases in the second direction.

3. The electrode (110) according to claim 2, characterized in that, In the first direction, the thickness difference of the active material layer (113) in the second direction is successively equal in adjacent unit lengths.

4. The electrode (110) according to claim 3, characterized in that, The surface of the active material layer (113) away from the current collector (112) is constructed as a plane.

5. The electrode (110) according to claim 2, characterized in that, In the first direction, the thickness of the active material layer (113) in the second direction gradually changes within adjacent unit lengths.

6. The electrode (110) according to claim 5, characterized in that, The surface of the active material layer (113) away from the current collector (112) is constructed as a concave surface, and the thickness difference of the active material layer (113) in the second direction gradually decreases in adjacent unit lengths.

7. The electrode (110) according to claim 5, characterized in that, The surface of the active material layer (113) away from the current collector (112) is constructed as a convex surface, and the thickness difference of the active material layer (113) in the second direction gradually increases in adjacent unit lengths.

8. The electrode (110) according to claim 1, characterized in that, The active material layer (113) includes a first material layer (1133) and a second material layer (1134) connected along the first direction, wherein the first material layer (1133) is located on the side close to the tab (111); wherein the average particle size of the active material in the first material layer (1133) is greater than the average particle size of the active material in the second material layer (1134).

9. The electrode (110) according to claim 8, characterized in that, The average particle size of the active material in the first material layer (1133) is D1, and the average particle size of the active material in the second material layer (1134) is D2, satisfying the following relationship: 1 <D1 / D2<10。 10. The electrode (110) according to claim 9, characterized in that, The D1 and the D2 satisfy the following relationship: 2 <D1 / D2<5。 11. The electrode (110) according to claim 9, characterized in that, The D1 is 50-500nm, and / or the D2 is 20-100nm.

12. The electrode (110) according to claim 9, characterized in that, The active material in the active material layer (113) includes lithium iron phosphate and / or lithium nickel cobalt manganese oxide.

13. The electrode (110) according to claim 8, characterized in that, The active material in the active material layer (113) includes graphite.

14. The electrode (110) according to claim 13, characterized in that, The active material in the first material layer (1133) is secondary graphite particles, and the first material layer (1134) contains primary graphite particles.

15. The electrode (110) according to any one of claims 8-14, characterized in that, In the first direction, the length of the active material layer (113) is L1, and the length of the first material layer (1133) is L5, satisfying the following relationship: 0 < L5 / L1 < 0.

5.

16. The electrode (110) according to claim 15, characterized in that, The L1 and L5 satisfy the following relationship: 0.05 < L5 / L1 < 0.12; or 0.1 < L5 / L1 < 0.

2.

17. The electrode (110) according to any one of claims 1-14, characterized in that, The active material layer (113) has a relatively arranged third end (1131) and a fourth end (1132), and the third end (1131) is located on the side close to the tab (111); the thickness dimension of the third end (1131) in the second direction is d7, and the thickness dimension of the fourth end (1132) on the same side as the third end (1131) in the second direction is d8, satisfying at least one of the following relationships: 1.0 < d7 / d8 < 5.

0.

18. The electrode (110) according to any one of claims 1-14, characterized in that, The electrode sheet (110) is a positive electrode sheet (110), the active material layer (113) is formed by curing a positive electrode slurry, and the positive electrode slurry includes, by mass parts: 80 to 120 parts of positive electrode active material; 12.0 to 14.0 parts of conductive agent; 2.0 to 3.0 parts of binder; 20 to 200 parts of positive electrode solvent.

19. The electrode (110) according to claim 18, characterized in that, The mass part ratio of the positive electrode active material, the conductive agent, the binder, and the positive electrode solvent in the positive electrode slurry is 100:13.2:2.3:52.

5.

20. The electrode (110) according to any one of claims 1-14, characterized in that, The electrode sheet (110) is a negative electrode sheet (110), the active material layer (113) is formed by curing a negative electrode slurry, and the negative electrode slurry includes, by mass parts: 80 to 120 parts of negative electrode active material; 1.0 to 2.0 parts of conductive agent; 1.0 to 5.0 parts of binder; 1.0 to 2.0 parts of thickening agent; 50 to 300 parts of negative electrode solvent.

21. The electrode (110) according to claim 20, characterized in that, The mass part ratio of the negative electrode active material, the conductive agent, the binder, the thickening agent, and the negative electrode solvent in the negative electrode slurry is 100:1.5:3.0:1.2:

115.

22. The electrode (110) according to any one of claims 1-14, characterized in that, The dimension of the side of the current collector (112) away from the tab (111) in the second direction is d6, and the dimension of the side of the active material layer (113) away from the tab (111) in the second direction is d8, satisfying the following relationship: 1.0 < d6 / d8 < 5.

0.

23. The electrode (110) according to any one of claims 1-14, characterized in that, In the first direction, the length of the active material layer (113) is not greater than the length of the current collector (112).

24. A method for preparing an electrode sheet, used to prepare an electrode sheet (110) as described in any one of claims 1-23, characterized in that, The method for preparing the electrode sheet includes the following steps: Providing a current collector (112), and at least one end of the current collector (112) is provided with a tab (111); Coating an active material slurry on at least one side of the current collector (112) to cure and form an active material layer (113); wherein, the thickness dimension of the side of the active material layer (113) close to the tab (111) is greater than the thickness dimension of the side away from the tab (111).

25. The electrode preparation method according to claim 24, characterized in that, The step of coating an active material slurry onto at least one side of the current collector (112) to cure and form an active material layer (113) includes the following steps: The current collector (112) is tilted so that the side of the current collector (112) away from the electrode (111) is higher than the side close to the electrode (111); An active material slurry is coated on at least one side of the current collector (112) so that the active material slurry tends to flow toward the tab (111) under the action of gravity; After the active material slurry is cured, an active material layer (113) is formed; wherein, the thickness of the active material layer (113) on the side closer to the tab (111) is greater than the thickness on the side farther away from the tab (111).

26. The electrode preparation method according to claim 24, characterized in that, The step of coating an active material slurry onto at least one side of the current collector (112) to cure and form an active material layer (113) includes the following steps: An active substance slurry is coated on at least one side of the current collector (112), and pressure is applied to the active substance slurry on the side away from the current collector (112). The pressure applied to the active material layer (113) on the side closer to the tab (111) is less than the pressure applied to the active material layer (113) on the side farther from the tab (111); After the active material slurry is cured, an active material layer (113) is formed; wherein, the thickness of the active material layer (113) on the side closer to the tab (111) is greater than the thickness on the side farther away from the tab (111).

27. The electrode preparation method according to claim 24, characterized in that, The step of coating an active material slurry onto at least one side of the current collector (112) to cure and form an active material layer (113) includes the following steps: An active substance slurry is coated on at least one side of the current collector (112), and pressure is applied to the active substance slurry on the side away from the current collector (112) by a pressure mechanism. The distance between the pressure mechanism and the active material layer (113) on the side closer to the tab (111) is greater than the distance between the pressure mechanism and the active material layer (113) on the side farther from the tab (111); After the active material slurry is cured, an active material layer (113) is formed; wherein, the thickness of the active material layer (113) on the side closer to the tab (111) is greater than the thickness on the side farther away from the tab (111).

28. A battery cell (100), characterized in that, include: Diaphragm (120); as well as A positive electrode (110) and a negative electrode (110) are respectively disposed on opposite sides of the separator (120), and at least one of the positive electrode (110) and the negative electrode (110) adopts the electrode (110) according to any one of claims 1-23.

29. A battery, characterized in that, include: The battery casing is filled with electrolyte. as well as The cell (100) as claimed in claim 28 is housed within the battery casing and in contact with the electrolyte.

30. A battery device, characterized in that, include: Multiple batteries as described in claim 29.

31. An electrical appliance, characterized in that, include: Electrical appliances; as well as The battery device as claimed in claim 30, or the battery as claimed in claim 29, or the cell (100) as claimed in claim 28, is electrically connected to the electrical device and is used to supply power to the electrical device.

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