Battery cell, battery monomer, battery and electric equipment

Abstract

The utility model relates to a battery cell, a battery monomer, a battery and electric equipment. The battery cell comprises a plurality of positive plates and a plurality of negative plates which are arranged in a laminated manner, and the positive plates and the negative plates are alternately arranged; wherein part of the positive plates are first positive plates, the other part of the positive plates are second positive plates, the first positive plates are phosphate positive plates, the second positive plates are ternary positive plates, and the ratio of the porosity epsilon 1 of the first positive plates to the porosity epsilon 2 of the second positive plates meets the condition that epsilon 1 / epsilon 2 is larger than or equal to 1.3 and smaller than or equal to 1.8. Therefore, the ternary material and the phosphate material are separated on the pole piece layer, so that on one hand, relatively large lithium ion concentration gradient and internal stress caused by dynamic difference between the ternary material and the phosphate material are avoided, and the cycle performance of the battery is favorably improved; and on the other hand, weakening of the advantage of the ternary material in the aspect of rate capability due to low conductivity of the phosphate material is avoided, so that the overall rate capability of the battery is improved.

Description

Technical Field

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

[0002] With the development of new energy technologies, the expansion of the new energy market demand has directly driven the rise in the demand for lithium batteries. As an energy storage device that integrates high energy density and high voltage, lithium-ion batteries have been widely used in mobile and wireless electronic devices, power tools, hybrid and electric vehicles, and other fields.

[0003] For ternary lithium batteries, the positive electrode is composed of manganese, cobalt, nickel, etc., which has advantages such as high ionic conductivity and high energy density, but suffers from poor cycle life and safety. For phosphate batteries, the positive electrode material is one or both of lithium manganese iron phosphate or lithium iron phosphate, which has advantages such as high safety and long cycle life, but suffers from lower energy density and ionic conductivity. In order to achieve the advantages of high energy density, high safety, and long cycle life, existing technologies usually mix ternary materials and phosphate materials in the slurry stage or apply double layers to achieve the blending of the two materials. That is, the active material in the same positive electrode sheet contains both ternary materials and phosphate materials.

[0004] However, the scheme of mixing ternary materials and phosphate materials in the same electrode has the following drawbacks: On the one hand, due to the large difference in ionic conductivity between the two materials, mixing them at the electrode level will generate a large lithium ion concentration gradient during charging and discharging, resulting in large internal stress inside the electrode, reducing electrode stability and causing a decrease in cycle performance; on the other hand, since the two materials are in the same electrode, the electrolyte wetting and ion migration paths are the same, and the low conductivity of the phosphate material will weaken the advantage of the ternary material in terms of rate performance, resulting in poor overall rate performance. Utility Model Content

[0005] Therefore, it is necessary to address the problem of poor cycle life and rate performance of batteries in existing technologies that use ternary materials and phosphate materials mixed in the same electrode, and to provide a cell, battery cell, battery and electrical device that improves the above defects.

[0006] On the one hand, this application provides a battery cell, including a plurality of positive electrode plates and a plurality of negative electrode plates stacked together, wherein the positive electrode plates and the negative electrode plates are arranged alternately to each other;

[0007] Among them, a portion of the positive electrode sheet is a first positive electrode sheet, and another portion of the positive electrode sheet is a second positive electrode sheet. The first positive electrode sheet is a phosphate positive electrode sheet, and the second positive electrode sheet is a ternary positive electrode sheet. The ratio of the porosity ε1 of the first positive electrode sheet to the porosity ε2 of the second positive electrode sheet satisfies: 1.3≤ε1 / ε2≤1.8.

[0008] In one embodiment, the ratio N / P of the negative electrode capacity to the positive electrode capacity in adjacent negative electrode plates and the first positive electrode plate is a first preset value.

[0009] In the adjacent negative electrode and the second positive electrode, the ratio of negative electrode capacity to positive electrode capacity, N / P, is a second preset value;

[0010] Wherein, the first preset value is equal to the second preset value.

[0011] In one embodiment, the negative electrode includes a first type of negative electrode located between two first positive electrode pieces and a second type of negative electrode located between one first positive electrode piece and one second positive electrode piece;

[0012] The first type of negative electrode includes a first current collector and a first negative electrode active material layer formed on opposite sides of the first current collector. The second type of negative electrode includes a second current collector, the first negative electrode active material layer formed on one side of the second current collector facing the first positive electrode, and a second negative electrode active material layer formed on one side of the second current collector facing the second positive electrode. The negative electrode capacity of the first negative electrode active material layer is not equal to that of the second negative electrode active material layer.

[0013] In one embodiment, the negative electrode further includes a third type of negative electrode located between the two second positive electrodes, the third type of negative electrode including a third current collector and a second negative electrode active material layer formed on opposite sides of the third current collector.

[0014] In one embodiment, the first positive electrode includes a fourth current collector and a first positive active material layer formed on opposite sides of the fourth current collector, wherein the ratio N / P of the negative capacity of the first negative active material layer to the positive capacity of the first positive active material layer is the first preset value.

[0015] The second positive electrode includes a fifth current collector and a second positive electrode active material layer formed on opposite sides of the fifth current collector. The ratio N / P of the negative electrode capacity of the second negative electrode active material layer to the positive electrode capacity of the second positive electrode active material layer is the second preset value.

[0016] In one embodiment, the first positive electrode active material layer is a lithium iron phosphate material layer and / or a lithium manganese iron phosphate material layer, and the second positive electrode active material layer is a ternary active material layer.

[0017] In one embodiment, each of the first positive electrode sheets includes a fourth current collector and a first positive electrode active material layer formed on the fourth current collector, and each of the second positive electrode sheets includes a fifth current collector and a second positive electrode active material layer formed on the fifth current collector;

[0018] The sum of the masses of all the second positive electrode active material layers is the first mass value, and the sum of the masses of all the first positive electrode active material layers and all the second positive electrode active material layers is the second mass value. The ratio of the first mass value to the second mass value is 40% to 70%.

[0019] On the other hand, this application provides a battery cell, including the cell described in any of the above embodiments.

[0020] In another aspect, this application provides a battery comprising a single battery cell as described in any of the above embodiments.

[0021] In another aspect, this application provides an electrical device including the battery described in any of the above embodiments.

[0022] Compared with the prior art, this application has the following beneficial effects:

[0023] The aforementioned battery cells, battery cells, batteries, and electrical devices all employ phosphate cathodes in some of their positive electrode plates and ternary cathodes in others. This separation of ternary and phosphate materials at the electrode level avoids significant lithium-ion concentration gradients and internal stresses caused by kinetic differences between the two materials within the same electrode, thus improving battery cycle performance. Furthermore, it prevents the low conductivity of phosphate materials from weakening the rate performance advantage of ternary materials, which would otherwise be a problem with ternary and phosphate materials sharing the same electrode, thereby enhancing the overall rate performance of the battery. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the arrangement of the positive electrode, separator, and negative electrode of a battery cell in one embodiment of this application;

[0025] Figure 2 This is a schematic diagram of the arrangement of the positive electrode, separator, and negative electrode of the battery cell in another embodiment of this application;

[0026] Figure 3 The graphs showing the rate versus capacity retention obtained from rate testing of the coin cells in Examples 1 to 3 and Comparative Example 1. Detailed Implementation

[0027] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, the specific embodiments of this application are described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of this application. However, this application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of this application. Therefore, this application is not limited to the specific embodiments disclosed below.

[0028] In the description of this application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicating the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, are only for the convenience of describing 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, and therefore should not be construed as a limitation of this application.

[0029] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0030] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "joining," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; 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; they can refer to the internal communication of two components or the interaction between two components, unless otherwise expressly limited. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0031] In 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.

[0032] It should be noted that when an element is referred to as being "fixed to" or "set on" another element, it can be directly on the other element or there may be an intervening element. When an element is considered to be "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only possible implementation.

[0033] Please see Figure 1 One embodiment of this application provides a battery cell including a plurality of positive electrode plates 10 and a plurality of negative electrode plates 20 stacked together, wherein the positive electrode plates 10 and negative electrode plates 20 are alternately arranged. In this battery cell, some of the positive electrode plates 10 are first positive electrode plates 11, and other parts of the positive electrode plates 10 are second positive electrode plates 13. The first positive electrode plate 11 is a phosphate positive electrode plate, and the second positive electrode plate 13 is a ternary positive electrode plate. The ratio of the porosity ε1 of the first positive electrode plate 11 to the porosity ε2 of the second positive electrode plate 13 satisfies: 1.3 ≤ ε1 / ε2 ≤ 1.8.

[0034] Thus, in the aforementioned battery cell, some positive electrode sheets 10 use phosphate positive electrode sheets, while others use ternary positive electrode sheets. This allows the ternary material and the phosphate material to be separated at the electrode level. On the one hand, this avoids the large lithium-ion concentration gradient and internal stress caused by the kinetic differences between the ternary material and the phosphate material in the same electrode, which is beneficial to improving the cycle performance of the battery. On the other hand, it avoids the situation where the low conductivity of the phosphate material weakens the advantage of the ternary material in terms of rate performance due to the ternary material and the phosphate material being in the same electrode, which is beneficial to improving the overall rate performance of the battery.

[0035] It should be noted that the ratio of the porosity ε1 of the first positive electrode 11 to the porosity ε2 of the second positive electrode 13 in the above-mentioned battery cell satisfies 1.3≤ε1 / ε2≤1.8, which makes the kinetic difference between the first positive electrode 11 and the second positive electrode 13 small, and their rate performance is matched. On the one hand, this makes the overall rate of the battery cell better; on the other hand, it greatly reduces the polarization of the phosphate electrode during high current charging and discharging, thereby avoiding particle breakage and helping the battery maintain a long cycle life, that is, it helps to improve the rate performance and cycle performance of the battery.

[0036] Preferably, the ratio of the porosity ε1 of the first positive electrode 11 to the porosity ε2 of the second positive electrode 13 satisfies: ε1 / ε2 = 1.5. Of course, in other embodiments, ε1 / ε2 can also be 1.3, 1.4, 1.6, 1.7 or 1.8, etc., and is not limited here.

[0037] Specifically, the porosity ε1 of the first positive electrode 11 (i.e., the phosphate positive electrode) can be increased by creating pores in the first positive electrode 11, thereby reducing the difference between the porosity ε1 of the first positive electrode 11 and the porosity ε2 of the second positive electrode 13, and thus achieving the goal of controlling the value of ε1 / ε2 between 1.3 and 1.8. Optionally, pores can be created in the first positive electrode 11 using processes such as laser etching, mechanical drilling, needle roller punching, or adding a pore-forming agent.

[0038] It should be noted that when the value of ε1 / ε2 is less than 1.3, the rate performance difference between the first positive electrode 11 and the second positive electrode 13 is significant, which will increase the internal stress of the cell, reduce the stability of the electrode, and cause a decrease in the cycle performance of the battery. When the value of ε1 / ε2 is greater than 1.8, the porosity ε1 of the first positive electrode 11 is too high, resulting in a smaller amount of active material in the first positive electrode 11, which in turn leads to a decrease in the energy density of the battery. Therefore, in this application, controlling the value of ε1 / ε2 between 1.3 and 1.8 can improve the rate performance, cycle performance, and energy density of the battery.

[0039] It should be noted that in the battery cell, the arrangement of each first positive electrode 11 and each second positive electrode 13 can be either alternating between the first positive electrode 11 and the second positive electrode 13, or the number of first positive electrode 11 between every two adjacent second positive electrode 13 can be equal (see [reference]). Figure 1 Alternatively, the first positive electrode plates 11 can be arranged first, followed by the second positive electrode plates 13 (see...). Figure 2 Of course, other arrangements can also be used, and no restrictions are imposed here.

[0040] It should be noted that, in order to prevent a short circuit caused by direct electrical connection between adjacent positive electrode 10 and negative electrode 20, a diaphragm 30 is provided between each adjacent positive electrode 10 and negative electrode 20 to serve as an insulator.

[0041] In the embodiments of this application, in any adjacent negative electrode 20 and first positive electrode 11, the ratio N / P of the negative electrode capacity to the positive electrode capacity is a first preset value. In any adjacent negative electrode 20 and second positive electrode 13, the ratio N / P of the negative electrode capacity to the positive electrode capacity is a second preset value, and the first preset value and the second preset value are equal.

[0042] It is understandable that the positive / negative electrode capacity ratio (N / P) directly affects the energy density of the battery, and the design of the N / P needs to take into account the specific application scenario and material system of the battery. Since the cell in this embodiment contains two types of positive electrode plates 10 (i.e., the first positive electrode plate 11 and the second positive electrode plate 13), the N / P of the first positive electrode plate 11 and its adjacent negative electrode plate 20 and the N / P of the second positive electrode plate 13 and its adjacent negative electrode plate 20 are designed to be of equal size to avoid two different N / P values. This reduces the difficulty of adjusting the overall N / P of the cell and helps to ensure that the energy density of the battery is at a high level.

[0043] Specifically, in this embodiment, the negative electrode 20 includes a first type of negative electrode 21 located between two first positive electrode 11s and a second type of negative electrode 23 located between one first positive electrode 11 and one second positive electrode 13. The first type of negative electrode 21 includes a first current collector 211 and a first negative electrode active material layer 212 formed on opposite sides of the first current collector 211. The second type of negative electrode 23 includes a second current collector 231, a first negative electrode active material layer 212 formed on one side of the second current collector 231 facing the first positive electrode 11, and a second negative electrode active material layer 232 formed on one side of the second current collector 231 facing the second positive electrode 13. The negative electrode capacity of the first negative electrode active material layer 212 is not equal to the negative electrode capacity of the second negative electrode active material layer 232 to ensure that the aforementioned first preset value is equal to the second preset value.

[0044] In other words, since the positive electrode capacity of the first positive electrode 11 and the second positive electrode 13 is not equal due to the different materials, in order to ensure that the first preset value is equal to the second preset value, it is necessary to change the negative electrode capacity of the two negative electrode active material layers of the corresponding negative electrode 20, thereby forming a first type of negative electrode 21 containing two layers of first negative electrode active material 212 and a second type of negative electrode 23 containing one layer of first negative electrode active material 212 and one layer of second negative electrode active material 232, so that the N / P of the first type of negative electrode 21 or the second type of negative electrode 23 with the adjacent first positive electrode 11 is the first preset value, and the N / P of the second type of negative electrode 23 with the adjacent second positive electrode 13 is the second preset value (the first preset value is equal to the second preset value).

[0045] Please see Figure 2 As shown, in a specific embodiment, the negative electrode 20 further includes a third type of negative electrode 25 located between the two second positive electrode 13s. The third type of negative electrode 25 includes a third current collector 251 and a second negative electrode active material layer 232 formed on opposite side surfaces of the third current collector 251, thereby ensuring that the N / P ratio of the third type of negative electrode 25 to its adjacent second positive electrode 13 is the aforementioned second preset value (the second preset value is equal to the aforementioned first preset value).

[0046] It is understood that the first type of negative electrode 21 includes a first current collector 211 and two layers of first negative electrode active material 212; the second type of negative electrode 23 includes a second current collector 231, one layer of first negative electrode active material 212, and one layer of second negative electrode active material 232; and the third type of negative electrode 25 includes a third current collector 251 and two layers of second negative electrode active material 232. The first current collector 211, the second current collector 231, and the third current collector 251 can be made of the same material, for example, copper foil. The first negative electrode active material layer 212 and the second negative electrode active material layer 232 can be made of the same material. By designing their masses to be different, their negative electrode capacities are different, thus ensuring that the N / P ratio between the first negative electrode active material layer 212 and its adjacent first positive electrode 11 or second positive electrode 13, and the N / P ratio between the second negative electrode active material layer 232 and its adjacent first positive electrode 11 or second positive electrode 13, are both equal. In other words, by adjusting the mass of the negative electrode active material layer on the current collector to form the above three types of negative electrode sheets 20 (i.e., the first type of negative electrode sheet 21, the second type of negative electrode sheet 23 and the third type of negative electrode sheet 25), the N / P ratio between each adjacent negative electrode sheet 20 and the positive electrode sheet 10 is equal.

[0047] Optionally, the first negative electrode active material layer 212 and the second negative electrode active material layer 232 can be made of one or more of graphite, hard carbon, soft carbon, silicon oxide, silicon, and silicon carbon.

[0048] It should be noted that the third type of negative electrode 25 is not essential. Whether the cell includes a third type of negative electrode 25 depends on the arrangement of the first positive electrode 11 and the second positive electrode 13, and is not specifically limited here. For some embodiments, please refer to... Figure 1 The battery cell may contain only the first type of negative electrode 21 and the second type of negative electrode 23, but not the third type of negative electrode 25. In other embodiments, please refer to... Figure 2 In addition to the first type of negative electrode 21 and the second type of negative electrode 23, the battery cell also contains a third type of negative electrode 25.

[0049] Furthermore, the first positive electrode 11 includes a fourth current collector 111 and a first positive electrode active material layer 112 formed on opposite sides of the fourth current collector 111. The ratio N / P of the negative electrode capacity of the first negative electrode active material layer 212 to the positive electrode capacity of the first positive electrode active material layer 112 is the aforementioned first preset value.

[0050] The second positive electrode 13 includes a fifth current collector 131 and a second positive electrode active material layer 132 formed on opposite sides of the fifth current collector 131. The ratio N / P of the negative electrode capacity of the second negative electrode active material layer 232 to the positive electrode capacity of the second positive electrode active material layer 132 is the aforementioned second preset value. Thus, since the first positive electrode active material layer 112 and the second positive electrode active material layer 132 are made of different materials, their positive electrode capacities are also not equal. To ensure that the N / P ratios of adjacent first negative electrode active material layer 212 and first positive electrode active material layer 112, and adjacent second negative electrode active material layer 232 and second positive electrode active material layer 132 are equal, since the positive electrode capacities of the first positive electrode active material layer 112 and second positive electrode active material layer 132 are not equal, it is necessary to adjust the mass of the first negative electrode active material layer 212 and second negative electrode active material layer 232. This achieves the purpose of adjusting the negative electrode capacities of the first negative electrode active material layer 212 and second negative electrode active material layer 232, ultimately ensuring that the N / P ratios of adjacent first negative electrode active material layer 212 and first positive electrode active material layer 112, and adjacent second negative electrode active material layer 232 and second positive electrode active material layer 132 are equal.

[0051] Optionally, the first positive electrode active material layer 112 can be a lithium iron phosphate material layer and / or a lithium manganese iron phosphate material layer.

[0052] Optionally, the second positive electrode active material layer 132 can be a ternary active material layer. Further, the material of the ternary active material layer can be one or more of the 6-series to 9-series ternary materials, such as lithium nickel cobalt manganese oxide, whether it is monocrystalline or polycrystalline.

[0053] Optionally, the fourth current collector 111 and the fifth current collector 131 can be made of the same material, for example, both of them are aluminum foil.

[0054] Specifically, in a specific embodiment, in a battery cell, the sum of the masses of all the second positive electrode active material layers 132 is a first mass value, and the sum of the masses of all the first positive electrode active material layers 112 and all the second positive electrode active material layers 132 is a second mass value. The ratio of the first mass value to the second mass value is 40% to 70%. That is, in a battery cell, the mass proportion of the second positive electrode active material layer 132 in all the positive electrode materials is 40% to 70%. Preferably, the ratio of the first mass value to the second mass value is 50%.

[0055] The embodiments 1 to 6 of this application are compared with comparative examples 1 to 2 below to illustrate the beneficial effects of the technical solutions of this application:

[0056] In Example 1, a phosphate material slurry was coated onto a 10 μm thick aluminum foil (i.e., the fourth current collector 111) to obtain a first positive electrode 11 with a thickness of 80 μm. Laser etching was then used to create pores in the first positive electrode 11, increasing its porosity ε1 to 31.6%. A ternary material slurry was coated onto a 10 μm thick aluminum foil (i.e., the fifth current collector 131) to obtain a second positive electrode 13 with a thickness of 80 μm and a porosity ε2 of 24.3%, i.e., ε1 / ε2 = 1.3. A graphite slurry was coated onto an 8 μm thick copper foil (i.e., the first current collector 211, the second current collector 231, or the third current collector 251), and the mass of the graphite coated on the copper foil was adjusted to obtain a first type of negative electrode 21, a second type of negative electrode 23, and a third type of negative electrode 25. The first positive electrode 11, the separator 30, the second positive electrode 13, the lithium sheet and the electrolyte are assembled into a coin cell.

[0057] A battery cell is formed by assembling a first positive electrode 11, a second positive electrode 13, a separator 30, and a negative electrode 20 (i.e., a first type of negative electrode 21, a second type of negative electrode 23, and / or a third type of negative electrode 25). In a battery cell, the number of first positive electrodes 11 between every two adjacent second positive electrodes 13 is equal (see...). Figure 1 The N / P ratio of the first negative electrode active material layer 212 to the first positive electrode active material layer 112 is 1.08, and the N / P ratio of the second negative electrode active material layer 232 to the second positive electrode active material layer 132 is also 1.08. By controlling the number of the first positive electrode sheet 11 and the second positive electrode sheet 13 in the cell, the mass proportion of the second positive electrode active material layer 132 in all positive electrode active materials is made to be 40%. Finally, this cell is used to assemble a battery.

[0058] In Example 2, the difference from Example 1 is that ε1 / ε2 = 1.5, that is, ε1 = 36.5%, ε

[0059] 2 = 24.3%. The rest remains the same as in Example 1.

[0060] In Example 3, the difference from Example 1 is that ε1 / ε2 = 1.8, that is, ε1 = 43.7%, ε

[0061] 2 = 24.3%. The rest remains the same as in Example 1.

[0062] In Example 4, the difference from Example 1 is that each of the first positive electrode plates 11 and each of the second positive electrode plates 13 in the battery cell are arranged separately (see Example 1). Figure 2 The rest remains the same as in Example 1.

[0063] In Example 5, the difference from Example 1 is that the second positive electrode active material layer 132 accounts for 50% of the total mass of all positive electrode active materials in the cell. The rest remains the same as in Example 1.

[0064] In Example 6, the difference from Example 1 is that the second positive electrode active material layer 132 accounts for 70% of the total mass of all positive electrode active materials in the cell. The rest remains the same as in Example 1.

[0065] In Comparative Example 1, the difference from Example 1 is that ε1 / ε2 = 1.0, that is, ε1 = 24.3%, ε

[0066] 2 = 24.3%. The rest remains the same as in Example 1.

[0067] In Comparative Example 2, the difference from Example 1 is that a slurry of phosphate material and ternary material is mixed to form a mixed slurry, in which the mass percentage of ternary material is 40%. This mixed slurry is coated on a 10 μm aluminum foil to form a positive electrode 10 with a thickness of 80 μm and a porosity of 24.3%.

[0068] Figure 3 The figure shows the rate and capacity retention curves obtained from rate tests of the coin cells in Examples 1 to 3 and Comparative Example 1, respectively. The rate test method for the coin cells is as follows: at 25°C, they are charged at a constant current of 0.33C to 4.4V, then charged at a constant voltage of 4.4V until the current cutoff is 0.05C; and discharged at a constant current of 0.33 / 2 / 3 / 4 / 6C to 2.8V, and the discharge capacity is recorded.

[0069] from Figure 3As can be seen, when 1.3 ≤ ε1 / ε2 ≤ 1.8, the capacity retention rate of the first positive electrode 11 is similar to that of the second positive electrode 13, meaning their rate performance is comparable. When ε1 / ε2 is 1.0, the capacity retention rate of the first positive electrode 11 differs significantly from that of the second positive electrode 13, indicating a mismatch in their rate performance.

[0070] Table 1 shows the 4C discharge capacity retention data obtained from rate tests of the batteries in Examples 1 to 6 and Comparative Examples 1 to 2, respectively. The rate test method for the batteries was as follows: at 25°C, charging was performed at a constant current of 0.33C to 4.25V, followed by constant voltage charging at 4.25V until the current cutoff point of 0.05C; then discharging was performed at a constant current of 0.33C to 2.5V, and the charge / discharge capacity was recorded. The battery was then charged at a constant current of 0.33C to 4.25V, followed by constant voltage charging at 4.25V until the current cutoff point of 0.05C; finally, discharging was performed at a constant current of 4C to 2.5V, and the discharge capacity was recorded.

[0071] Table 1 also shows the full-cell cycle life data obtained from cycle tests of the batteries in Examples 1 to 6 and Comparative Examples 1 to 2, respectively. The battery cycle test method was as follows: the battery was placed in a 25°C constant temperature chamber for 1 hour, charged at a constant current of 1C to 4.25V, charged at a constant voltage of 4.25V to a current of 0.05C, allowed to stand for 30 minutes, and then discharged at a constant current of 1C to 2.5V, allowed to stand for 30 minutes. This cycle test was performed until the capacity dropped to 80% of the initial capacity, and the number of cycles was recorded.

[0072] As can be seen from Table 1, the porosity ε1 of the first positive electrode 11 was increased in Examples 1 to 3, i.e., satisfying 1.3≤ε1 / ε2≤1.8, making the rate performance of the first positive electrode 11 and the second positive electrode 13 similar, thus significantly improving the rate performance of the battery cell. Furthermore, the cycle performance of Examples 1-3 is also better than that of Comparative Examples 1-2. This is because in Comparative Example 1, due to the large kinetic difference between the phosphate positive electrode and the ternary positive electrode, their rate performance is mismatched, resulting in greater polarization of the phosphate material during high-current charging and discharging, which easily leads to particle breakage, thus resulting in poor cycle performance. In Comparative Example 2, since the phosphate material and the ternary material are located within the same electrode, the uneven stress distribution within the electrode is further aggravated, leading to electrode structure damage and active material shedding, thus resulting in even worse cycle performance.

[0073] As can be seen from the data of Examples 1 and 4 in Table 1, the different arrangement of the first positive electrode 11 and the second positive electrode 13 does not affect the performance of the battery.

[0074] As can be seen from the quantities of Examples 1 and 5 to 6 in Table 1, when the mass percentage of the second positive electrode active material layer 132 in all positive electrode active materials is between 40% and 70%, the first positive electrode sheet 11 and the second positive electrode sheet 13 achieve synergistic performance, which is beneficial to improving the cycle performance of the battery.

[0075] Table 1: Statistical data of rate test and cycle test of batteries in Examples 1 to 6 and Comparative Examples 1 to 2.

[0076] 4C discharge capacity retention rate / % Full battery cycle life / cycles Example 1 92.6 2586 Example 2 94.8 2632 Example 3 95.5 2658 Example 4 92.8 2540 Example 5 92.4 2705 Example 6 92.1 2445 Comparative Example 1 84.7 1987 Comparative Example 2 85.9 1532

[0077] Based on the aforementioned battery cell, this application also provides a single battery cell. The single battery cell includes the battery cell described in any of the above embodiments. Optionally, the single battery cell further includes a housing, a top cover assembly, and an electrolyte. The battery cell and electrolyte are housed within the housing, which has an opening. The top cover assembly is sealed at the opening of the housing, thereby sealing the battery cell and electrolyte within the housing. The top cover assembly has terminals, and the battery cell's tabs are electrically connected to the terminals to enable the input or output of electrical energy.

[0078] Based on the aforementioned battery cells, this application also provides a battery. This battery refers to a single physical module comprising one or more battery cells to provide a certain voltage and capacity. For example, the battery mentioned in this application may include a battery module or a battery pack, etc. Specifically, a battery generally includes a casing for encapsulating one or more battery cells. The casing can prevent liquids or other foreign matter from affecting the charging or discharging of the battery cells. Specifically, in a battery, there may be one or more battery cells. If there are multiple battery cells, they can be connected in series, parallel, or a combination thereof. A combination thereof means that multiple battery cells are connected in both series and parallel. Multiple battery cells may first be connected in series, parallel, or a combination thereof to form a battery module, and then multiple battery modules may be connected in series, parallel, or a combination thereof to form a whole, which is then housed in the casing. Alternatively, all battery cells may be directly connected in series, parallel, or a combination thereof, and then the whole consisting of all battery cells is housed in the casing; no special limitation is made here.

[0079] Based on the aforementioned battery, this application also provides an electrical device. This electrical device includes the battery described in any of the above embodiments, and utilizes the battery as a power source. Specifically, the electrical device can be a vehicle, mobile phone, portable device, laptop computer, ship, spacecraft, electric toy, and power tool, etc. Vehicles can be gasoline-powered vehicles, natural gas-powered vehicles, or new energy vehicles; new energy vehicles can be pure electric vehicles, hybrid electric vehicles, or range-extended electric vehicles, etc.; spacecraft include airplanes, rockets, space shuttles, and spacecraft, etc.; electric toys include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc.; power tools include metal cutting power tools, grinding power tools, assembly power tools, and railway power tools, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators, and electric planers, etc. This application does not impose any special limitations on the aforementioned electrical device.

[0080] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0081] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the utility model patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this utility model, and these all fall within the protection scope of this utility model. Therefore, the protection scope of this utility model patent should be determined by the appended claims.

Claims

1. A battery cell, characterized in that, It includes multiple positive electrode plates (10) and multiple negative electrode plates (20) stacked together, and the positive electrode plates (10) and the negative electrode plates (20) are arranged alternately to each other; Among them, part of the positive electrode (10) is the first positive electrode (11), and the other part of the positive electrode (10) is the second positive electrode (13). The first positive electrode (11) is a phosphate positive electrode, and the second positive electrode (13) is a ternary positive electrode. The ratio of the porosity ε1 of the first positive electrode (11) to the porosity ε2 of the second positive electrode (13) satisfies: 1.3≤ε1 / ε2≤1.

8.

2. The battery cell according to claim 1, characterized in that, In the adjacent negative electrode (20) and the first positive electrode (11), the ratio N / P of the negative electrode capacity to the positive electrode capacity is a first preset value; In the adjacent negative electrode (20) and the second positive electrode (13), the ratio of negative electrode capacity to positive electrode capacity N / P is a second preset value; Wherein, the first preset value is equal to the second preset value.

3. The battery cell according to claim 2, characterized in that, The negative electrode (20) includes a first type of negative electrode (21) located between two first positive electrode (11) and a second type of negative electrode (23) located between one first positive electrode (11) and one second positive electrode (13); The first type of negative electrode (21) includes a first current collector (211) and a first negative electrode active material layer (212) formed on opposite sides of the first current collector (211). The second type of negative electrode (23) includes a second current collector (231), the first negative electrode active material layer (212) formed on the side surface of the second current collector (231) facing the first positive electrode (11), and a second negative electrode active material layer (232) formed on the side surface of the second current collector (231) facing the second positive electrode (13). The negative electrode capacity of the first negative electrode active material layer (212) is not equal to the negative electrode capacity of the second negative electrode active material layer (232).

4. The battery cell according to claim 3, characterized in that, The negative electrode (20) also includes a third type of negative electrode (25) located between the two second positive electrode (13), the third type of negative electrode (25) including a third current collector (251) and a second negative electrode active material layer (232) formed on opposite sides of the third current collector (251).

5. The battery cell according to claim 3 or 4, characterized in that, The first positive electrode (11) includes a fourth current collector (111) and a first positive active material layer (112) formed on opposite sides of the fourth current collector (111). The ratio N / P of the negative capacity of the first negative active material layer (212) to the positive capacity of the first positive active material layer (112) is the first preset value. The second positive electrode (13) includes a fifth current collector (131) and a second positive active material layer (132) formed on opposite sides of the fifth current collector (131). The ratio N / P of the negative capacity of the second negative active material layer (232) to the positive capacity of the second positive active material layer (132) is the second preset value.

6. The battery cell according to claim 5, characterized in that, The first positive electrode active material layer (112) is a lithium iron phosphate material layer and / or a lithium manganese iron phosphate material layer, and the second positive electrode active material layer (132) is a ternary active material layer.

7. The battery cell according to claim 1, characterized in that, Each of the first positive electrode sheets (11) includes a fourth current collector (111) and a first positive electrode active material layer (112) formed on the fourth current collector (111), and each of the second positive electrode sheets (13) includes a fifth current collector (131) and a second positive electrode active material layer (132) formed on the fifth current collector (131); The sum of the masses of all the second positive electrode active material layers (132) is the first mass value, and the sum of the masses of all the first positive electrode active material layers (112) and all the second positive electrode active material layers (132) is the second mass value. The ratio of the first mass value to the second mass value is 40% to 70%.

8. A single battery cell, characterized in that, Includes the battery cell as described in any one of claims 1 to 7.

9. A battery, characterized in that, Includes the battery cell as described in claim 8.

10. An electrical appliance, characterized in that, Includes the battery as described in claim 9.

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