A winding core structure and a lithium ion battery

Abstract

The utility model discloses a kind of roll core structure and lithium ion battery;Roll core structure includes negative plate, and the first capacity type active material layer and the second capacity type active material layer of negative plate are respectively arranged in the two sides of negative current collector, and the first capacity type active material layer is located in the winding outside of negative plate, and the second capacity type active material layer is located in the winding inside of negative plate;First rate type active material layer is arranged on the side of the first capacity type active material layer away from negative current collector, and second rate type active material layer is arranged or not arranged on the side of the second capacity type active material layer away from negative current collector;The thickness ratio of first rate type active material layer and first capacity type active material layer is greater than the thickness ratio of second rate type active material layer and second capacity type active material layer.The roll core structure provided by the utility model reduces the lithium precipitation problem of negative electrode, can better adapt to the requirement of rate capability when winding outside contacts with positive plate in charge and discharge process, and improves the overall performance of battery.

Description

Technical Field

[0001] This utility model belongs to the field of battery manufacturing technology, specifically relating to a core structure and a lithium-ion battery. Background Technology

[0002] Lithium-ion batteries have become the most widely used energy storage system due to their high energy density and stability. In the fabrication of wound lithium-ion battery cells, the negative electrode is typically wound first, followed by the positive electrode. At this stage, the outer side (B-side) of the wound negative electrode is wrapped by the positive electrode. Figure 1 Compared to the inner side (A side) of the negative electrode, the arc of the outer side of the winding is larger than that of the positive electrode, resulting in insufficient negative electrode and easy lithium plating, which is not conducive to improving the battery's electrical performance. Utility Model Content

[0003] The technical problem to be solved by this utility model is that in the prior art, the arc area where the negative electrode sheet of the wound battery is wrapped by the positive electrode sheet is prone to lithium deposition, which makes it impossible to balance the battery capacity and charge / discharge rate. This utility model provides a wound core structure and a lithium-ion battery.

[0004] The technical solution adopted by this utility model to solve the above-mentioned technical problems is as follows:

[0005] A wound core structure is provided, including a positive electrode sheet, a separator, and a negative electrode sheet. The negative electrode sheet includes a negative current collector, a capacity-type active material layer, and a rate-type active material layer. The capacity-type active material layer includes a first capacity-type active material layer and a second capacity-type active material layer. The rate-type active material layer includes a first rate-type active material layer and a second rate-type active material layer.

[0006] The first capacity-type active material layer and the second capacity-type active material layer are respectively disposed on both sides of the negative electrode current collector. The first capacity-type active material layer is located on the outer side of the winding of the negative electrode sheet, and the second capacity-type active material layer is located on the inner side of the winding of the negative electrode sheet.

[0007] The first rate-type active material layer is disposed on the side of the first capacity-type active material layer that is away from the negative electrode current collector, and the second rate-type active material layer is disposed or not disposed on the side of the second capacity-type active material layer that is away from the negative electrode current collector.

[0008] The thickness ratio of the first rate-type active material layer to the first capacity-type active material layer is greater than the thickness ratio of the second rate-type active material layer to the second capacity-type active material layer.

[0009] Optionally, a first rate-type active material layer is provided on the side of the first capacity-type active material layer facing away from the negative electrode current collector, and a second rate-type active material layer is provided on the side of the second capacity-type active material layer facing away from the negative electrode current collector.

[0010] The thickness of the first rate-type active material layer is 6-20 μm, the thickness of the first capacity-type active material layer is 20-35 μm, the thickness of the second rate-type active material layer is 6-15 μm, and the thickness of the second capacity-type active material layer is 25-35 μm.

[0011] Optionally, a first rate-type active material layer is provided on the side of the first capacity-type active material layer facing away from the negative electrode current collector, and a second rate-type active material layer is not provided on the side of the second capacity-type active material layer facing away from the negative electrode current collector.

[0012] The thickness of the first rate-type active material layer is 10-25 μm, and the thickness of the first capacity-type active material layer is 15-30 μm.

[0013] Optionally, a first rate-type active material layer is provided on the side of the first capacity-type active material layer facing away from the negative electrode current collector, and a second rate-type active material layer is provided on the side of the second capacity-type active material layer facing away from the negative electrode current collector.

[0014] The areal density of the first rate-adjustable active material layer is 10-38 g / m³. 2 The areal density of the second rate-adjustable active material layer is 10-20 g / m³. 2 .

[0015] Optionally, a first rate-type active material layer is provided on the side of the first capacity-type active material layer facing away from the negative electrode current collector, and a second rate-type active material layer is not provided on the side of the second capacity-type active material layer facing away from the negative electrode current collector.

[0016] The areal density of the first rate-adjustable active material layer is 15-35 g / m³. 2 .

[0017] Optionally, a first rate-type active material layer is provided on the side of the first capacity-type active material layer facing away from the negative electrode current collector, and a second rate-type active material layer is provided on the side of the second capacity-type active material layer facing away from the negative electrode current collector.

[0018] The areal density of the first capacity-type active material layer is 30-60 g / m³. 2 The areal density of the second capacity-type active material layer is 35-60 g / m³. 2 .

[0019] Optionally, a first rate-type active material layer is provided on the side of the first capacity-type active material layer facing away from the negative electrode current collector, and a second rate-type active material layer is not provided on the side of the second capacity-type active material layer facing away from the negative electrode current collector.

[0020] The areal density of the first capacity-type active material layer is 30-60 g / m³. 2 The areal density of the second capacity-type active material layer is 55-75 g / m³. 2 .

[0021] Optionally, the first rate-type active material layer has a rate of 3C-8C, and the second rate-type active material layer has a rate of 3C-8C.

[0022] Optionally, the rate-type active material layer is a rate-type graphite layer, and the capacity-type active material layer is a capacity-type graphite layer.

[0023] On the other hand, this application provides a lithium-ion battery including the aforementioned winding structure.

[0024] The beneficial effects of this application are as follows:

[0025] In the core structure provided in this application, the first capacity-type active material layer of the capacity-type active material layer is disposed on the outer side of the negative electrode sheet, which increases the active material content on the outer side of the winding and makes up for the relatively insufficient amount of negative electrode on the outer side of the negative electrode sheet, thereby alleviating the situation of insufficient negative electrode, reducing the occurrence of lithium plating problems, and improving the battery's electrical performance. In addition, this application provides a rate-type active material layer, and the thickness ratio of the first rate-type active material layer to the first capacity-type active material layer is greater than the thickness ratio of the second rate-type active material layer to the second capacity-type active material layer. Since the first capacity-type active material layer is located on the outer side of the negative electrode sheet, this arrangement makes the rate-type active material layer on the outer side of the negative electrode sheet relatively thicker, which can better adapt to the rate performance requirements during charging and discharging when the outer side of the winding contacts the positive electrode sheet, further optimizing the battery's performance under different charging and discharging conditions and improving the overall performance of the battery. Attached Figure Description

[0026] Figure 1 This is a cross-sectional diagram of a wound battery cell in the existing technology;

[0027] Figure 2 This is a schematic diagram of the negative electrode structure provided in one embodiment of the present invention;

[0028] Figure 3 This is a schematic diagram of the negative electrode structure provided in another embodiment of the present invention.

[0029] The reference numerals in the accompanying drawings are as follows:

[0030] 1. Negative electrode current collector; 2. Capacity-type active material layer; 21. First capacity-type active material layer; 22. Second capacity-type active material layer; 3. Rate-type active material layer; 31. First rate-type active material layer; 32. Second rate-type active material layer; 100. Negative electrode sheet. Detailed Implementation

[0031] To make the technical problems solved, technical solutions, and beneficial effects of this utility model clearer, the present utility model will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present utility model and are not intended to limit the present utility model.

[0032] In the description of this utility model, it should be understood that the terms "longitudinal," "radial," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the accompanying drawings and are only for the convenience of describing this utility model 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, and therefore should not be construed as a limitation of this utility model. In the description of this utility model, unless otherwise stated, "a plurality of" means two or more.

[0033] In the description of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" 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; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.

[0034] Reference Figure 2-3 This utility model provides a wound core structure, including a positive electrode sheet, a separator, and a negative electrode sheet 100. The negative electrode sheet 100 includes a negative current collector 1, a capacity-type active material layer 2, and a rate-type active material layer 3. The capacity-type active material layer 2 includes a first capacity-type active material layer 21 and a second capacity-type active material layer 22. The rate-type active material layer 3 includes a first rate-type active material layer 31 and a second rate-type active material layer 32.

[0035] The first capacity-type active material layer 21 and the second capacity-type active material layer 22 are respectively disposed on both sides of the negative electrode current collector 1. The first capacity-type active material layer 21 is located on the outer side of the winding of the negative electrode sheet 100, and the second capacity-type active material layer 22 is located on the inner side of the winding of the negative electrode sheet 100.

[0036] The first rate-type active material layer 31 is provided on the side of the first capacity-type active material layer 21 that is away from the negative electrode current collector 1, and the second rate-type active material layer 32 is provided or not provided on the side of the second capacity-type active material layer 22 that is away from the negative electrode current collector 1.

[0037] The thickness ratio of the first rate-type active material layer 31 to the first capacity-type active material layer 21 is greater than the thickness ratio of the second rate-type active material layer 32 to the second capacity-type active material layer 22.

[0038] Specifically, in the core structure provided in this application, the first capacity-type active material layer 21 of the capacity-type active material layer 2 is disposed on the outer side of the winding of the negative electrode sheet 100, which increases the active material content on the outer side of the winding, makes up for the relatively insufficient negative electrode amount on the outer side of the winding of the negative electrode sheet 100, thereby alleviating the situation of insufficient negative electrode, reducing the occurrence of lithium plating problem, and helping to improve the electrical performance of the battery; in addition, a rate-type active material layer is provided in this application, and the thickness ratio of the first rate-type active material layer 31 to the first capacity-type active material layer 21 is greater than that of the second rate-type active material layer. The thickness ratio of the first capacity active material layer 21 to the second capacity active material layer 22 is such that, since the first capacity active material layer 21 is located on the outer side of the negative electrode 100, the rate active material layer 3 on the outer side of the negative electrode 100 is relatively thicker. This allows it to better adapt to the rate performance requirements during charging and discharging when the outer side of the winding contacts the positive electrode, further optimizing the battery performance under different charging and discharging conditions. The capacity active material layer on the inner side of the negative electrode 100 is relatively thicker, which is beneficial to improving the energy density of the battery, thereby helping to balance the battery capacity and charging and discharging rate.

[0039] Reference Figure 3 In one embodiment, a first rate-type active material layer 31 is provided on the side of the first capacity-type active material layer 21 facing away from the negative electrode current collector 1, and a second rate-type active material layer 32 is provided on the side of the second capacity-type active material layer 22 facing away from the negative electrode current collector 1.

[0040] The thickness of the first rate-type active material layer 31 is 6-20 μm, the thickness of the first capacity-type active material layer 21 is 20-35 μm, the thickness of the second rate-type active material layer 32 is 6-15 μm, and the thickness of the second capacity-type active material layer 22 is 25-35 μm.

[0041] Specifically, by controlling the thickness of the first rate-adjustable active material layer 31 within the range of 10-25 μm, the insertion and extraction of lithium ions on the outer side of the negative electrode 100 during charging and discharging are smoother, thus improving the charging and discharging efficiency of the battery. The setting of the thickness range of the second rate-adjustable active material layer 32 ensures that the inner side of the negative electrode 100 also has good rate performance. Combined with the performance improvement on the outer side, the battery as a whole can maintain stable performance output at different charging and discharging rates, thus improving the situation where the overall battery performance is reduced due to the performance difference between the inner and outer sides.

[0042] When the thickness of the first rate-adjustable active material layer 31 is set in the range of 6-20 μm, problems such as local overheating and overcharging caused by excessively rapid lithium ion insertion and extraction on the outer side of the negative electrode sheet 100 can be avoided, and the occurrence of side reactions such as lithium plating and gas generation can be reduced, thereby improving the safety and stability of the battery. The reasonable setting of the thickness of the second rate-adjustable active material layer 32 can enable the negative electrode material on the inner side of the winding to maintain good structural stability during long-term charge and discharge cycles, reduce the shedding of active material and damage to the electrode structure, and thus extend the service life of the battery.

[0043] The thickness of the first rate-type active material layer 31 can be 6μm, 10μm, 15μm or 20μm, the thickness of the first capacity-type active material layer 21 can be 20μm, 25μm, 30μm or 35μm, the thickness of the second rate-type active material layer 32 can be 6μm, 10μm or 15μm, and the thickness of the second capacity-type active material layer 22 can be 25μm, 30μm or 35μm.

[0044] Reference Figure 2 In one embodiment, a first rate-type active material layer 31 is provided on the side of the first capacity-type active material layer 21 that is away from the negative electrode current collector 1, and a second rate-type active material layer 32 is not provided on the side of the second capacity-type active material layer 22 that is away from the negative electrode current collector 1.

[0045] The thickness of the first rate-type active material layer 31 is 10-25 μm, and the thickness of the first capacity-type active material layer 21 is 15-30 μm.

[0046] Specifically, since the first rate-type active material layer 31 is disposed on the first capacity-type active material layer 21 on the outer side of the negative electrode sheet 100, by setting a specific thickness range for the first rate-type active material layer 31, the lithium-ion transport capability of the outer side of the winding during charging and discharging can be specifically improved, so that this area can better adapt to the matching with the larger arc positive electrode surface, thereby improving the overall charging and discharging efficiency and performance of the battery; the second rate-type active material layer 32 is located on the inner side of the negative electrode sheet 100 winding, and its dynamics are better than those of the outer side of the negative electrode sheet 100 where the first rate-type active material layer 31 is located. Therefore, under the condition that the first rate-type active material layer 31 can improve or solve the lithium plating problem, the second rate-type active material layer 32 may not be disposed on the side of the second capacity-type active material layer 22 facing away from the negative electrode current collector 1.

[0047] A suitable thickness range of the first rate-type active material layer 31 helps improve the rate performance of the outer winding, enabling faster lithium-ion insertion and extraction during high-rate charging and discharging, and reducing lithium plating problems caused by insufficient negative electrode.

[0048] The thickness of the first rate-type active material layer 31 can be 10μm, 15μm, 20μm or 25μm, and the thickness of the first capacity-type active material layer 21 can be 15μm, 20μm, 25μm or 30μm.

[0049] In one embodiment, a first rate-type active material layer 31 is provided on the side of the first capacity-type active material layer 21 facing away from the negative electrode current collector 1, and a second rate-type active material layer 32 is provided on the side of the second capacity-type active material layer 22 facing away from the negative electrode current collector 1.

[0050] The areal density of the first rate-adjustable active material layer 31 is 10-38 g / m³. 2 The areal density of the second rate-adjustable active material layer 32 is 10-20 g / m³. 2 .

[0051] Specifically, the areal density of the first rate-adjustable active material layer 31 is 15-35 g / m³. 2 The first rate-type active material layer 31 has an areal density that ensures more efficient insertion and extraction of lithium ions during charging and discharging, reducing polarization and improving the battery's charging and discharging efficiency. Similarly, the second rate-type active material layer 32 can also improve the lithium-ion transport performance on the inner side of the winding, making the overall ion conduction of the battery smoother. When the first and second rate-type active material layers 32 are set within the corresponding areal density ranges mentioned above, it helps the battery maintain good performance at different charge and discharge rates.

[0052] The areal density of the first rate-adjustable active material layer 31 can be 10 g / m³. 215g / m 2 20g / m 2 25g / m 2 30g / m 2 35g / m 2 Or 38g / m 2 The areal density of the second rate-adjustable active material layer 32 can be 10 g / m³. 2 12g / m 2 15g / m 2 18g / m 2 Or 20g / m 2 .

[0053] In one embodiment, a first rate-type active material layer 31 is provided on the side of the first capacity-type active material layer 21 facing away from the negative electrode current collector 1, and a second rate-type active material layer 32 is not provided on the side of the second capacity-type active material layer 22 facing away from the negative electrode current collector 1.

[0054] The areal density of the first rate-adjustable active material layer 31 is 15-35 g / m³. 2 .

[0055] For a wound battery structure, the side of the first capacity active material layer 21, where the first rate-type active material layer 31 is located, that faces away from the negative electrode current collector 1 is usually the outer side of the winding, which has a different electrochemical environment from the inner side. When the second capacity active material layer 22 is not located on the other side, the areal density of the first rate-type active material layer 31 can be adjusted to optimize the overall performance of the wound battery and reduce the performance degradation caused by the difference between the inner and outer sides. Specifically, when the second capacity active material layer 22 is not located on the side facing away from the negative electrode current collector 1, the areal density of the first rate-type active material layer 31 is set to 15-35 g / m³. 2 This can avoid the problem of decreased electrical performance caused by differences between the inner and outer sides.

[0056] The areal density of the first rate-adjustable active material layer 31 can be 15 g / m³. 2 20g / m 2 25g / m 2 30g / m 2 Or 35g / m 2 .

[0057] In one embodiment, a first rate-type active material layer 31 is provided on the side of the first capacity-type active material layer 21 facing away from the negative electrode current collector 1, and a second rate-type active material layer 32 is provided on the side of the second capacity-type active material layer 22 facing away from the negative electrode current collector 1.

[0058] The areal density of the first capacity-type active material layer 21 is 30-60 g / m³. 2 The areal density of the second capacity-type active material layer 22 is 35-60 g / m³. 2 .

[0059] Specifically, the first rate-type active material layer 31 and the second rate-type active material layer 32 are tightly bonded to the corresponding capacity-type active material layer 2, which can give full play to the advantages of rate-type active materials in improving charging and discharging speed, while the capacity-type active material layer 2 provides sufficient lithium-ion storage capacity, thus achieving a good balance between capacity and rate performance.

[0060] When the areal density of the first capacity-type active material layer 21 is 30-60 g / m³ 2 The areal density of the second capacity-type active material layer 22 is 55-75 g / m³. 2 At this time, the electrical performance of lithium-ion batteries can be better utilized.

[0061] In one embodiment, a first rate-type active material layer 31 is provided on the side of the first capacity-type active material layer 21 facing away from the negative electrode current collector 1, and a second rate-type active material layer 32 is not provided on the side of the second capacity-type active material layer 22 facing away from the negative electrode current collector 1.

[0062] The areal density of the first capacity-type active material layer 21 is 30-60 g / m³. 2 The areal density of the second capacity-type active material layer 22 is 55-75 g / m³. 2 .

[0063] Similarly, since the second capacity-type active material layer 22 does not have a second rate-type active material layer 32 on the side facing away from the negative electrode current collector 1, the areal density of the first capacity-type active material layer 21 needs to be set to 35-55 g / m³. 2 The areal density of the second capacity-type active material layer 22 is set to 60-70 g / m³. 2 This is to achieve a balance between the capacity and rate performance of lithium-ion batteries.

[0064] The areal density of the first capacity-type active material layer 21 can be 30 g / m³. 2 35g / m 2 40g / m 2 45g / m 2 50g / m 2 Or 60g / m 2 ;

[0065] The areal density of the second capacity-type active material layer 22 can be 35 g / m³. 240g / m 2 45g / m 2 50g / m 2 Or 60g / m 2 .

[0066] In one embodiment, the first rate-adjustable active material layer 31 has a rate of 3C-8C, and the second rate-adjustable active material layer 32 has a rate of 3C-8C.

[0067] In one embodiment, the rate-type active material layer is a rate-type graphite layer, and the capacity-type active material layer 2 is a capacity-type graphite layer.

[0068] Rate-type graphite layers typically possess small particle size, high specific surface area, or crystalline structure. These characteristics enable lithium ions to be inserted and extracted more rapidly within the rate-type graphite layer, thus improving the battery's charge and discharge speed. During high-rate charge and discharge, rate-type graphite layers can effectively reduce the battery's internal resistance and polarization, ensuring that the battery can still stably output high power under high current conditions, meeting the requirements of fast charge and discharge applications. Capacity-type graphite layers generally have large interlayer spacing and good crystallinity, which is beneficial for the large-scale storage of lithium ions, providing a higher theoretical specific capacity and increasing the battery's energy density.

[0069] Specifically, since insufficient negative electrode and lithium plating problems are prone to occur on the outer side of the wound negative electrode sheet 100 of the wound lithium-ion battery, the rate-type graphite layer is set on the side of the first capacity-type graphite layer away from the negative electrode current collector 1 (i.e., the outer side of the wound negative electrode sheet 100). This can increase the total amount of active material on the outer side of the winding, make the matching between the negative electrode and the positive electrode more reasonable, alleviate the situation of insufficient negative electrode, improve the lithium plating problem, and improve the stability and safety of the battery.

[0070] Another embodiment of this application provides a lithium-ion battery including the aforementioned winding structure.

[0071] The lithium-ion battery provided in this application includes the aforementioned core structure. In the core structure, the first capacity-type active material layer 21 of the capacity-type active material layer 2 is disposed on the outer side of the negative electrode sheet 100, increasing the active material content on the outer side of the winding and supplementing the relatively insufficient negative electrode amount on the outer side of the negative electrode sheet 100, thereby alleviating the situation of insufficient negative electrode, reducing the occurrence of lithium plating problems, and improving the battery's electrical performance. In addition, this application provides a rate-type active material layer 3, and the thickness ratio of the first rate-type active material layer 31 to the first capacity-type active material layer 21 is greater than the thickness ratio of the second rate-type active material layer 32 to the second capacity-type active material layer 22. Since the first capacity-type active material layer 21 is located on the outer side of the negative electrode sheet 100, this arrangement makes the rate-type active material layer on the outer side of the negative electrode sheet 100 relatively thicker, which can better adapt to the rate performance requirements during charging and discharging when the outer side of the winding contacts the positive electrode sheet, further optimizing the battery's performance under different charging and discharging conditions and improving the overall performance of the battery.

[0072] The present invention will be further described below through embodiments.

[0073] Example 1

[0074] This embodiment illustrates the core structure and lithium-ion battery disclosed in this utility model, including:

[0075] Step 1: Add 22kg of graphite 1 (5C fast charging type, capacity 350g / mAh), 1kg of CMC and 10.5kg of water to the stirring bar in sequence, stir at 200rpm for 30min, then add 1kg of SBR, 12.5kg of water and 0.3kg of NMP in sequence, stir at 400rpm for 4h to make a uniformly dispersed slurry (slurry of first-rate active material layer and second-rate active material layer), the slurry solid content is 49% (the solid content ratio of graphite, CMC and SBR is 98%, 1% and 1% respectively).

[0076] Step 2: Add 22kg of graphite 2 (2C, capacity 358g / mAh), 1kg of CMC and 10.5kg of water to the stirring bar in sequence, stir at 200rpm for 30min, then add 1kg of SBR, 12.5kg of water and 0.3kg of NMP in sequence, stir at 400rpm for 4h to prepare a uniformly dispersed slurry (slurry of the first capacity type active material layer and the second capacity type active material layer), the slurry has a solid content of 49% (the solid content ratio of graphite, CMC and SBR is 98%, 1% and 1% respectively).

[0077] Step 3: Apply the slurry prepared in Step 2 onto the copper foil using an extrusion coating machine and roll it around the outer side to form the first volumetric active material layer slurry with an areal density of 35 g / m³. 2Then, the slurry prepared in step 1 is coated onto the surface of the first volumetric active material layer slurry using an extrusion coating machine, serving as the first rate-type active material layer with a surface density of 15 g / m³. 2 (The thickness ratio of the first rate-type active material layer to the first capacity-type active material layer is 30%:70%).

[0078] The slurry prepared in step 2 is coated onto the inner side of the copper foil roll using an extrusion coating machine as the second capacity-type active material layer, with an areal density of 40 g / m³. 2 Then, the slurry prepared in step 1 is coated onto the surface of the second capacity-type active material layer slurry using an extrusion coating machine, serving as the second rate-type active material layer with an areal density of 10 g / m³. 2 (The thickness ratio of the second rate-type active material layer to the second capacity-type active material layer is 20%:80%); the coated copper foil is dried to obtain the negative electrode sheet.

[0079] Step 4: Take the positive electrode, separator and the above-mentioned negative electrode and assemble them into a lithium-ion battery.

[0080] Comparative Example 1

[0081] This scale is used to compare and illustrate the core structure and lithium-ion battery disclosed in this utility model, including most of the operations in Example 1, the difference being:

[0082] The first capacity-type active material layer does not have a first rate-type active material layer, and the second capacity-type active material layer does not have a second rate-type active material layer. Furthermore, the areal density of both the first and second capacity-type active material layers is 50 g / m³. 2 .

[0083] Comparative Example 2

[0084] This scale is used to compare and illustrate the core structure and lithium-ion battery disclosed in this utility model, including most of the operations in Example 1, the difference being:

[0085] No first capacity-type active material layer and no second capacity-type active material layer are provided on both sides of the copper foil. The areal density of both the first rate-type active material layer and the second rate-type active material layer is 50 g / m³. 2 .

[0086] Comparative Example 3

[0087] This scale is used to compare and illustrate the core structure and lithium-ion battery disclosed in this utility model, including most of the operations in Example 1, the difference being:

[0088] The slurry prepared in step 2 is coated onto the outer side of a copper foil using an extrusion coating machine, serving as the first volumetric active material layer slurry with an areal density of 15 g / m³.2 Then, the slurry prepared in step 1 is coated onto the surface of the first volumetric active material layer slurry using an extrusion coating machine, serving as the first rate-type active material layer with an areal density of 35 g / m³. 2 (The thickness ratio of the first rate-type active material layer to the first capacity-type active material layer is 70%:30%).

[0089] The slurry prepared in step 2 is coated onto the inner side of the copper foil roll using an extrusion coating machine as the second capacity-type active material layer, with an areal density of 10 g / m³. 2 Then, the slurry prepared in step 1 is coated onto the surface of the second capacity-type active material layer slurry using an extrusion coating machine, serving as the second rate-type active material layer with a surface density of 40 g / m³. 2 (The thickness ratio of the second rate-type active material layer to the second capacity-type active material layer is 80%:20%)

[0090] The overall electrical performance of the lithium-ion batteries prepared in Example 1 and Comparative Examples 1-3 was tested:

[0091] Test method:

[0092] 1. Charge the battery to 4.5V using constant current and constant voltage at charging currents of 1C, 2C, and 3C respectively, with a cutoff current of 0.05C.

[0093] 2. Let it sit for 10 minutes;

[0094] 3. Discharge to 3V at 0.5C, repeat steps 1-3 20 times, then charge to 4.5V and disassemble the battery at full charge.

[0095] Table 1

[0096]

[0097] As shown in Table 1, no lithium plating problem occurred in Example 1 during the charge and discharge test. Comparative Example 1 did not exhibit lithium plating during 20 cycles of 1C charge / 0.5C discharge, but lithium plating occurred during 2C and 3C charge / 0.5C discharge for 20 cycles. This indicates that setting a rate-type active material layer on the capacity-type active material layer (as in Example 1) can effectively reduce the lithium plating problem, while the absence of a rate-type active material layer (Comparative Example 1) increases the risk of lithium plating during high-rate charge and discharge.

[0098] Although no lithium plating occurred in Comparative Examples 2 and 3 during the entire charge-discharge test, the energy density of Comparative Example 2 was only 660Wh / L and that of Comparative Example 3 was 689Wh / L, both lower than that of Example 1. Compared with Example 1, Comparative Example 2 did not have a capacity-type active material layer, which could not effectively store lithium ions, resulting in a low energy density. Comparative Example 3 changed the proportion of the active material layer, and it is speculated that the unreasonable proportion of the active material layer affected the improvement of energy density.

[0099] Considering both lithium plating and energy density, the core structure prepared in Example 1 (with a suitable proportion of rate-type active material layer set on the capacity-type active material layer, and the first capacity-type active material layer located on the outer side of the negative electrode sheet) performs well in suppressing lithium plating and ensuring energy density, indicating that the core structure provided by this utility model can effectively improve the overall performance of lithium-ion batteries.

[0100] The above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A core structure, characterized in that, It includes a positive electrode, a separator, and a negative electrode (100). The negative electrode includes a negative current collector (1), a capacity-type active material layer, and a rate-type active material layer (3). The capacity-type active material layer (2) includes a first capacity-type active material layer (21) and a second capacity-type active material layer (22). The rate-type active material layer (3) includes a first rate-type active material layer (31) and a second rate-type active material layer (32). The first capacity-type active material layer (21) and the second capacity-type active material layer (22) are respectively disposed on both sides of the negative electrode current collector (1). The first capacity-type active material layer (21) is located on the outer side of the winding of the negative electrode sheet (100), and the second capacity-type active material layer (22) is located on the inner side of the winding of the negative electrode sheet (100). The first rate-type active material layer (31) is provided on the side of the first capacity-type active material layer (21) facing away from the negative electrode current collector (1), and the second rate-type active material layer (32) is provided or not provided on the side of the second capacity-type active material layer (22) facing away from the negative electrode current collector (1). The thickness ratio of the first rate-type active material layer (31) to the first capacity-type active material layer (21) is greater than the thickness ratio of the second rate-type active material layer (32) to the second capacity-type active material layer (22).

2. The core structure according to claim 1, characterized in that, A first rate-type active material layer (31) is provided on the side of the first capacity-type active material layer (21) facing away from the negative electrode current collector (1), and a second rate-type active material layer (32) is provided on the side of the second capacity-type active material layer (22) facing away from the negative electrode current collector (1). The thickness of the first rate-type active material layer (31) is 6-20 μm, the thickness of the first capacity-type active material layer (21) is 20-35 μm, the thickness of the second rate-type active material layer (32) is 6-15 μm, and the thickness of the second capacity-type active material layer (22) is 25-35 μm.

3. The core structure according to claim 1, characterized in that, A first rate-type active material layer (31) is provided on the side of the first capacity-type active material layer (21) facing away from the negative electrode current collector (1), and a second rate-type active material layer (32) is not provided on the side of the second capacity-type active material layer (22) facing away from the negative electrode current collector (1). The thickness of the first rate-type active material layer (31) is 10-25 μm, and the thickness of the first capacity-type active material layer (21) is 15-30 μm.

4. The core structure according to claim 1, characterized in that, A first rate-type active material layer (31) is provided on the side of the first capacity-type active material layer (21) facing away from the negative electrode current collector (1), and a second rate-type active material layer (32) is provided on the side of the second capacity-type active material layer (22) facing away from the negative electrode current collector (1). The areal density of the first rate-adjustable active material layer (31) is 10-38 g / m³. 2 The areal density of the second rate-adjustable active material layer (32) is 10-20 g / m². 2 .

5. A core structure according to claim 1, characterized in that, A first rate-type active material layer (31) is provided on the side of the first capacity-type active material layer (21) facing away from the negative electrode current collector (1), and a second rate-type active material layer (32) is not provided on the side of the second capacity-type active material layer (22) facing away from the negative electrode current collector (1). The areal density of the first rate-adjustable active material layer (31) is 15-35 g / m³. 2 .

6. The core structure according to claim 1, characterized in that, A first rate-type active material layer (31) is provided on the side of the first capacity-type active material layer (21) facing away from the negative electrode current collector (1), and a second rate-type active material layer (32) is provided on the side of the second capacity-type active material layer (22) facing away from the negative electrode current collector (1). The areal density of the first capacity-type active material layer (21) is 30-60 g / m³. 2 The areal density of the second capacity-type active material layer (22) is 35-60 g / m³. 2 .

7. A core structure according to claim 1, characterized in that, A first rate-type active material layer (31) is provided on the side of the first capacity-type active material layer (21) facing away from the negative electrode current collector (1), and a second rate-type active material layer (32) is not provided on the side of the second capacity-type active material layer (22) facing away from the negative electrode current collector (1). The areal density of the first capacity-type active material layer (21) is 30-60 g / m³. 2 The areal density of the second capacity-type active material layer (22) is 55-75 g / m³. 2 .

8. A core structure according to claim 1, characterized in that, The first rate-type active material layer (31) has a rate of 3C-8C, and the second rate-type active material layer (32) has a rate of 3C-8C.

9. A core structure according to claim 1, characterized in that, The rate-type active material layer is a rate-type graphite layer, and the capacity-type active material layer (2) is a capacity-type graphite layer.

10. A lithium-ion battery, characterized in that, Includes the core structure as described in any one of claims 1-9.

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