Battery module and electric equipment

Abstract

The invention provides a battery module and electric equipment. The battery module comprises N battery cells arranged in a first direction, the N battery cells comprise a first type of battery cells and a second type of battery cells, and the first type of battery cells are closer to the two ends of the battery module in the first direction than the second type of battery cells; each of the N battery cells comprises a positive pole piece and a negative pole piece, the positive pole piece comprises a positive pole material layer, and the positive pole material layer comprises a positive pole material containing a nickel element; the molar percentage content of the nickel element is W1 based on the mole number of the positive electrode material in the first type of battery cells, and the molar percentage content of the nickel element is W2 based on the mole number of the positive electrode material in the second type of battery cells; and 1% < = W1-W2 < = 10%. The battery module provided by the invention is beneficial to considering the cycling stability and the energy density.

Description

Technical Field

[0001] The present application relates to the field of electrochemical technology, and in particular to a battery module and electrical equipment. Background Art

[0002] Battery modules, such as battery modules composed of lithium-ion batteries, are widely used in portable electronic devices, electric vehicles and other application scenarios due to their advantages such as fast charging speed, high operating voltage and low self-discharge rate. As the market for lithium-ion batteries continues to develop, people's requirements for the energy density of lithium-ion batteries are getting higher and higher.

[0003] In the positive electrode material system of lithium-ion batteries, high-nickel positive electrode materials have relatively high theoretical specific capacity. Therefore, the energy density of lithium-ion batteries can be improved by using high-nickel positive electrode materials. However, when the nickel content increases, the stability of the high-nickel positive electrode materials becomes worse. Especially in a battery module including multiple battery cells, the different voltage differences between different battery cells will aggravate the attenuation of the stability of the high-nickel positive electrode materials and affect the cycle stability of the battery module. Summary of the invention

[0004] The purpose of this application is to provide a battery module and electrical equipment, which balances the nickel content between the cells in the battery module, thereby balancing the voltage difference between the cells, improving the cycle stability of the battery module and taking into account the energy density. The specific technical solution is as follows:

[0005] The first aspect of the present application provides a battery module, which includes: N battery cells arranged in a first direction; the N battery cells include a first type of battery cell and a second type of battery cell, and the first type of battery cell is closer to the two ends of the battery module in the first direction than the second type of battery cell; each of the N battery cells includes a positive electrode plate and a negative electrode plate, and the positive electrode plate includes a positive electrode material layer, and the positive electrode material layer includes a positive electrode material containing a nickel element; based on the molar number of the positive electrode material in the first type of battery cell, the molar percentage of the nickel element is W1, and based on the molar number of the positive electrode material in the second type of battery cell, the molar percentage of the nickel element is W2; 1%≤W1-W2≤10%. In some embodiments of the present application, 3%≤W1-W2≤7%. Through the above-mentioned setting, it is beneficial to reduce the temperature difference between the battery cells in the battery module, thereby alleviating the voltage difference, and taking into account the cycle stability and energy density of the battery module.

[0006] In some embodiments of the present application, 3≤N≤10. In some embodiments of the present application, 3≤N≤5.

[0007] In some embodiments of the present application, 60%≤W2≤95%, 70%≤W1≤99%. By adjusting W1 and W2 within the above range, it is beneficial to balance the voltage difference and energy density between the first type of battery cell and the second type of battery cell, thereby balancing the cycle stability and energy density of the battery module.

[0008] In some embodiments of the present application, the N battery cells also include a third type of battery cell, and in the first direction, the third type of battery cell is located between the first type of battery cell and the second type of battery cell; based on the molar number of the positive electrode material in the third type of battery cell, the molar percentage of the nickel element is W3, W3≥W2, W1≥W3. Such a setting is conducive to reducing the temperature difference between the first type of battery cell, the second type of battery cell and the third type of battery cell, thereby alleviating the voltage difference between the above battery cells, improving the cycle stability of the battery module, and combining the use of the positive electrode material containing the nickel element, taking into account the energy density of the battery module.

[0009] In some embodiments of the present application, the battery module satisfies at least one of the following characteristics: (1) 0% ≤ W3-W2 ≤ 10%; (2) 0% ≤ W1-W3 ≤ 10%. The battery module satisfies at least one of the above characteristics, which is conducive to further alleviating the voltage difference between the cells in the battery module, thereby improving the cycle stability of the battery module and taking into account the energy density of the battery module.

[0010] In some embodiments of the present application, the battery module satisfies at least one of the following characteristics: (1) 3% ≤ W3-W2 ≤ 7%; (2) 3% ≤ W1-W3 ≤ 7%. The battery module satisfies at least one of the above characteristics, which is conducive to further alleviating the voltage difference between the cells in the battery module, thereby improving the cycle stability of the battery module and taking into account the energy density of the battery module.

[0011] In some embodiments of the present application, in the first direction, the size of the first type of battery cell is D1 mm, the size of the second type of battery cell is D2 mm, and D1≤D2. By adjusting D1≤D2, the temperature difference between the first type of battery cell and the second type of battery cell of the obtained battery module is reduced, thereby reducing the voltage difference between the two types of battery cells, thereby improving the cycle stability of the battery module and taking into account the energy density.

[0012] In some embodiments of the present application, the battery module further includes a third type of battery cell, and in the first direction, the third type of battery cell is located between the first type of battery cell and the second type of battery cell; the size of the third type of battery cell is D3 mm, D3≤D2, D1≤D3. The above arrangement is conducive to balancing the temperature difference between the first type of battery cell, the second type of battery cell, and the third type of battery cell, thereby improving the problem of poor cycle stability of the battery module caused by the large voltage difference between the battery cells, and taking into account the energy density.

[0013] In some embodiments of the present application, the coating weight per unit area of ​​the positive electrode material layer in the first type of battery cell is CW1 mg / cm 2 The coating weight per unit area of ​​the positive electrode material layer in the second type of battery is CW2 mg / cm 2 , CW1≤CW2.

[0014] In some embodiments of the present application, the battery module further includes a third type of battery cell, which is located between the first type of battery cell and the second type of battery cell in the first direction; the coating weight per unit area of ​​the positive electrode material layer in the third type of battery cell is CW3 mg / cm 2 , CW3≤CW2, CW1≤CW3. Through the above settings, the temperature difference between the first type of battery cell, the second type of battery cell and the third type of battery cell is balanced, thereby alleviating the voltage difference between the above three types of battery cells, improving the cycle stability of the battery module, and stabilizing the cycle performance of the battery module in a high temperature environment.

[0015] In some embodiments of the present application, the compaction density of the positive electrode material layer in the first type of battery cell is PD1 g / cm 3 The compaction density of the positive electrode material layer in the second type of battery is PD2 g / cm 3 , PD1≤PD2. By adjusting PD1≤PD2, it is beneficial to balance the temperature difference between the first type of battery cell and the second type of battery cell, thereby alleviating the voltage difference between the two types of battery cells and improving the cycle stability of the battery module.

[0016] In some embodiments of the present application, the battery module further includes a third type of battery cell, and in the first direction, the third type of battery cell is located between the first type of battery cell and the second type of battery cell; the compaction density of the positive electrode material layer in the third type of battery cell is PD3 g / cm 3 , PD3≤PD2, PD1≤PD3. The above arrangement is helpful to reduce the heat generated by the second type of battery cells located further inside the battery module, while improving the cycle stability of the first type of battery cells with relatively high nickel content, thereby better balancing the energy density and cycle stability of the battery module.

[0017] In some embodiments of the present application, the battery cell satisfies at least one of the following characteristics: (1) in the first direction, the size of a single battery cell is D mm, 3≤D≤15; (2) the coating weight per unit area of ​​the positive electrode material layer is CW mg / cm 2 , 8≤CW≤25; (3) The compaction density of the positive electrode material layer is PD g / cm 3 , 3.1≤PD≤3.7. The battery module satisfies at least one of the above characteristics, which is conducive to further balancing energy density and cycle stability.

[0018] A second aspect of the present application provides an electrical device, which includes the battery module in any of the aforementioned embodiments.

[0019] Beneficial effects of this application:

[0020] The present application provides a battery module and an electrical device. During the use of the battery module, the temperature of the battery cells near the inside of the battery module is usually higher, while the temperature of the battery cells relatively close to the two ends of the battery module is lower. The present application balances the temperature difference between the battery cells by arranging a first type of battery cell with a relatively higher nickel content on the outside of a second type of battery cell with a relatively lower nickel content, and based on the molar number of the positive electrode material in the first type of battery cell, the molar percentage of the nickel element is W1; based on the molar number of the positive electrode material in the second type of battery cell, the molar percentage of the nickel element is W2, 1%≤W1-W2≤10%, thereby reducing the voltage difference between the battery cells, improving the cycle stability of the battery module, and taking into account the energy density.

[0021] Of course, implementing any product or method of the present application does not necessarily require achieving all of the advantages described above at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application, and a person skilled in the art can also obtain other embodiments based on these drawings.

[0023] Figure 1 A schematic diagram of the arrangement of cells of a battery module along a first direction according to an embodiment of the present application;

[0024] Figure 2 A schematic diagram of the arrangement of cells of a battery module along a first direction according to another embodiment of the present application;

[0025] Figure 3 This is a schematic diagram of the arrangement of cells of a battery module along a first direction according to another embodiment of the present application;

[0026] Figure 4 This is a schematic diagram of the arrangement of cells of a battery module along a first direction according to another embodiment of the present application;

[0027] Figure 5 This is a schematic diagram of the arrangement of battery cells along a first direction of a battery module according to another embodiment of the present application. DETAILED DESCRIPTION

[0028] The following will be combined with the embodiments of the present application and the accompanying drawings to clearly and completely describe the technical solutions in the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. All other embodiments obtained by those skilled in the art based on the present application belong to the scope of protection of the present application.

[0029] It should be noted that in the specific implementation manner of the present application, the present application is explained by taking a lithium-ion battery as an example of a secondary battery, but the secondary battery of the present application is not limited to a lithium-ion battery.

[0030] As the lithium-ion battery market continues to develop, people have higher and higher requirements for the energy density of lithium-ion batteries. The energy density of traditional lithium iron phosphate batteries and lithium cobalt oxide batteries is relatively low, while high-nickel positive electrode materials are widely used in lithium-ion batteries because of their relatively high energy density. Generally, the higher the nickel content in the positive electrode material, the higher its energy density, but at the same time, the stability of the positive electrode material will deteriorate accordingly, especially in a battery module including multiple cells. Usually, the nickel content in multiple cells is the same, but due to the difference in the heat dissipation environment of the cells, the temperature of the middle cell will be higher and the temperature of the cells on both sides will be lower, resulting in a larger internal resistance difference between the cells in the middle and at both ends of the battery module, which in turn makes the voltage difference between the cells in each part of the battery module larger, and the capacity attenuation degree is different, thereby aggravating the attenuation of the stability of the nickel-containing positive electrode material and affecting the cycle stability of the battery module.

[0031] Based on the above problems, the present application provides a battery module and electrical equipment, which is beneficial to improve the energy density of the battery module while reducing the temperature difference between the battery cells in the battery module, thereby alleviating the voltage difference and taking into account the cycle stability and energy density of the battery module.

[0032] The first aspect of the present application provides a battery module, such as Figure 1As shown, it includes: N battery cells arranged in a first direction, the first direction is the direction of the double-headed arrow in the figure, that is, the stacking direction of the N battery cells; the N battery cells include a first type of battery cell 11 and a second type of battery cell 12, and the first type of battery cell 11 is closer to the two ends of the battery module in the first direction than the second type of battery cell 12. Each of the N battery cells includes a positive electrode plate and a negative electrode plate, the positive electrode plate includes a positive electrode material layer, and the positive electrode material layer includes a positive electrode material containing nickel element; based on the molar number of the positive electrode material in the first type of battery cell, the molar percentage of the nickel element is W1, and based on the molar number of the positive electrode material in the second type of battery cell, the molar percentage of the nickel element is W2; 1%≤W1-W2≤10%. In some embodiments of the present application, 3%≤W1-W2≤7%. For example, W1-W2 can be 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, 10% or a range consisting of any two of these values. When W1-W2 is less than 1%, the nickel content in the first type of battery cell is similar to that in the second type of battery cell, so the heat generated by the first type of battery cell and the second type of battery cell is similar. Since the second type of battery cell is located in the middle of the battery module, the heat generated cannot be well dissipated to the surrounding environment, resulting in the temperature of the second type of battery cell being too high, thereby increasing the temperature difference between the first type of battery cell and the second type of battery cell, and the internal resistance consistency of the two types of battery cells is poor, which leads to a large voltage difference between the two, aggravating the capacity decay of the battery module and reducing the cycle stability of the battery module. When W1-W2>10%, the difference between the nickel content of the first type of battery and the second type of battery is too large, and the heat generated by the second type of battery located in the middle of the battery module cannot be balanced with the heat generated by the first type of battery located at both ends of the battery module, and a large voltage difference will still be generated between the two types of batteries, affecting the cycle stability of the battery module. At the same time, due to the relative decrease in the nickel content of the battery module, the energy density of the battery module will also be reduced, so that the energy density and cycle stability of the battery module cannot be well taken into account. When W1-W2 is adjusted within the scope of this application, the first type of battery with a relatively high nickel content can improve the overall energy density of the battery module, and because it is located at both ends in the first direction, the heat generated can be relatively promptly diffused to the surrounding environment, reducing the temperature of the first type of battery; and the second type of battery has a relatively lower nickel content than the first type of battery, and generates relatively less heat. In combination with the first type of battery, the temperature difference between the first type of battery and the second type of battery can be reduced while improving the energy density of the battery module, thereby reducing the voltage difference between the two, and improving the cycle stability of the battery module, which is conducive to taking into account the energy density and cycle stability of the battery module.

[0033] In the present application, the positive electrode material layer is a positive electrode material containing nickel elements. For example, the positive electrode material containing nickel elements may include but is not limited to at least one of lithium nickel cobalt manganese oxide (such as NCM811, NCM622, NCM523, NCM111), lithium nickel cobalt aluminum oxide, nickel cobalt manganese aluminum quaternary material or nickel manganese binary material.

[0034] In some embodiments of the present application, 3≤N≤10, and N is an integer. For example, N can be 3, 4, 5, 6, 7, 8, 9, or 10. In some embodiments of the present application, 3≤N≤5.

[0035] In some embodiments of the present application, Figure 1 As shown, N=3, and the battery module 10 includes two of the first type battery cells 11 and one of the second type battery cells 12 .

[0036] In some embodiments of the present application, 60% ≤ W2 ≤ 95%, 70 ≤ W1 ≤ 99%. For example, W1 can be 70%, 72%, 75%, 78%, 80%, 82%, 85%, 87%, 90%, 92%, 95%, 99% or a range consisting of any two of them; W2 can be 60%, 63%, 65%, 70%, 75%, 78%, 80%, 85%, 88%, 90%, 95% or a range consisting of any two of them. By regulating W1 and W2 within the above range, it is beneficial to balance the voltage difference and energy density between the first type of battery cell and the second type of battery cell, so as to take into account the cycle stability and energy density of the battery module.

[0037] In some embodiments of the present application, N=3, 60%≤W2≤95%, 70≤W1≤99%.

[0038] In some embodiments of the present application, N≥4, and the N battery cells also include a third type of battery cell. In the first direction, the third type of battery cell is located between the first type of battery cell and the second type of battery cell; based on the molar number of the positive electrode material in the third type of battery cell, the molar percentage of the nickel element is W3, W3≥W2, and W1≥W3. In this way, the third type of battery cell is located between the first type of battery cell and the second type of battery cell, and the nickel element content of the third type of battery cell is not higher than that of the first type of battery cell and not lower than that of the second type of battery cell. This can improve the problem of increased battery cell temperature caused by the high nickel element content in the positive electrode material, thereby helping to reduce the temperature difference between the first type of battery cell, the second type of battery cell and the third type of battery cell, thereby alleviating the voltage difference between the above-mentioned battery cells, improving the cycle stability of the battery module, and combining the use of positive electrode materials containing nickel elements, taking into account the energy density of the battery module.

[0039] In some embodiments of the present application, the battery module includes the above-mentioned first type of battery cells, the above-mentioned second type of battery cells and the above-mentioned third type of battery cells, and the molar percentage of the nickel element in the third type of battery cells can be the same as the molar percentage of the nickel element in the first type of battery cells, or the molar percentage of the nickel element in the third type of battery cells can be the same as the molar percentage of the nickel element in the second type of battery cells, or the molar percentage of the nickel element in the third type of battery cells can be between the molar percentages of the nickel element in the first type of battery cells and the second type of battery cells, as long as the purpose of the present application can be achieved.

[0040] In some embodiments of the present application, the battery module satisfies at least one of the following characteristics: (1) 0% ≤ W3-W2 ≤ 10%; (2) 0% ≤ W1-W3 ≤ 10%. The battery module satisfies at least one of the above characteristics, which is conducive to further alleviating the voltage difference between the cells in the battery module, thereby improving the cycle stability of the battery module and taking into account the energy density of the battery module.

[0041] In some embodiments of the present application, 0% ≤ W3-W2 ≤ 10%. In some embodiments of the present application, 3% ≤ W3-W2 ≤ 7%. For example, W3-W2 can be 0%, 0.5%, 1%, 1.5%, 2%, 3%, 3.5%, 4%, 5%, 5.5%, 6%, 7%, 7.5%, 8%, 9%, 9.5%, 10% or a range consisting of any two of the values. By regulating W3-W2 within the above range, it is beneficial to balance the energy density and heat generated by the second type of battery cell and the third type of battery cell, thereby improving the overall cycle stability of the battery module while taking into account the energy density.

[0042] In some embodiments of the present application, 0% ≤ W1-W3 ≤ 10%. In some embodiments of the present application, 3% ≤ W1-W3 ≤ 7%. For example, W1-W3 can be 0%, 0.5%, 1%, 1.5%, 2%, 3%, 3.5%, 4%, 5%, 5.5%, 6%, 7%, 7.5%, 8%, 9%, 9.5%, 10% or a range consisting of any two of the values. By regulating W1-W3 within the above range, it is beneficial to balance the temperature difference between the first type of battery cell and the third type of battery cell while taking into account the energy density, thereby reducing the pressure difference between the two types of battery cells and improving the cycle stability of the battery module.

[0043] In some embodiments of the present application, N=5, 70%≤W1≤99%, 60%≤W2≤85%, 65%≤W3≤98%. For example, W3 can be 65%, 68%, 70%, 72%, 75%, 78%, 80%, 82%, 85%, 87%, 90%, 92%, 95%, 98% or a range consisting of any two of the values.

[0044] In some embodiments of the present application, Figure 1 As shown, in the first direction, the size of the first type of battery cell 11 is D1 mm, and the size of the second type of battery cell 12 is D2 mm, and D1≤D2. When D1=D2 is adjusted, if the coating weight of the first type of battery cell and the second type of battery cell is the same, the second type of battery cell has a lower nickel content and a lower battery capacity, and generates relatively less heat. Although the first type of battery cell has a relatively high nickel content and a high battery capacity, it will also generate more heat, but because it is located at both ends of the battery module, the generated heat is easier to conduct away, so that the temperature difference between the first type of battery cell and the second type of battery cell is reduced, the voltage difference is balanced, and the cycle stability of the battery module is improved. By adjusting D1<D2, when the capacity of each battery cell in the battery module is designed to be the same, when the thickness of the battery cell located in the middle of the battery module is usually larger, the heat generated is difficult to dissipate. Therefore, the second type of battery cell with a relatively lower nickel content in this application is used to balance the heat generation, heat dissipation and energy density of the second type of battery cell; the first type of battery cell located at both ends of the battery module has a higher nickel content, generates more heat but has better heat dissipation, and is matched with a lower battery cell thickness. Therefore, the temperature difference between the first type of battery cell and the second type of battery cell of the obtained battery module is reduced, thereby reducing the voltage difference between the two types of battery cells, thereby improving the cycle stability of the battery module while taking into account the energy density.

[0045] In some embodiments of the present application, 3≤D1≤15, 3≤D2≤15. For example, D1 can be 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, or a range consisting of any two of them; D2 can be 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, or a range consisting of any two of them.

[0046] In some embodiments of the present application, Figure 5 As shown, the battery module 10 also includes a third type of battery cell 13. In the first direction, that is, the direction of the double-headed arrow in the figure, the third type of battery cell 13 is located between the first type of battery cell 11 and the second type of battery cell 12; the size of the third type of battery cell 13 is D3 mm, D3≤D2, D1≤D3. The above arrangement is conducive to balancing the temperature difference between the first type of battery cell, the second type of battery cell, and the third type of battery cell, thereby improving the problem of poor cycle stability of the battery module caused by the large voltage difference between the battery cells, and taking into account the energy density.

[0047] In some embodiments of the present application, the coating weight per unit area of ​​the positive electrode material layer in the first type of battery cell is CW1 mg / cm 2 The coating weight per unit area of ​​the positive electrode material layer in the second type of battery is CW2 mg / cm 2, CW1≤CW2. Through the above settings, when CW1<CW2, the second type of battery cells with relatively low nickel content are matched with a higher coating weight per unit area, while the first type of battery cells with relatively high nickel content are matched with a lower coating weight per unit area, so as to balance the energy density, heat generated, and heat dissipated of each battery cell, thereby alleviating the voltage difference between each battery cell, thereby improving the cycle stability of the battery module. When CW1=CW2, the second type of battery cells located in the relatively middle of the battery module have a low nickel content and generate low heat, while the first type of battery cells located at both ends of the battery module have a high nickel content, generate high heat but have better heat dissipation, so the temperature difference between the first type of battery cells and the second type of battery cells is balanced, thereby alleviating the voltage difference between the two types of battery cells, improving the cycle stability of the battery module, and stabilizing the cycle performance of the battery module in a high temperature environment.

[0048] In some embodiments of the present application, 8≤CW1≤25, 8≤CW2≤25. For example, CW1 may be 8, 10, 11, 13, 15, 17, 19, 20, 21, 23, 25, or a range consisting of any two values ​​therein; CW2 may be 8, 10, 11, 13, 15, 17, 19, 20, 21, 23, 25, or a range consisting of any two values ​​therein.

[0049] In some embodiments of the present application, the battery module further includes a third type of battery cell, which is located between the first type of battery cell and the second type of battery cell along the first direction; the coating weight per unit area of ​​the positive electrode material layer in the third type of battery cell is CW3 mg / cm 2 , CW3≤CW2, CW1≤CW3. Through the above settings, different coating weights and nickel content are matched with each other, which is conducive to balancing the energy density and temperature difference between each battery cell, and then balancing the voltage difference, and better taking into account the energy density and cycle stability of the battery module.

[0050] In some embodiments of the present application, 8≤CW3≤25. For example, CW3 can be 8, 10, 11, 13, 15, 17, 19, 20, 21, 23, 25, or a range consisting of any two of these values.

[0051] In some embodiments of the present application, the compaction density of the positive electrode material layer in the first type of battery cell is PD1 g / cm 3 The compaction density of the positive electrode material layer in the second type of battery is PD2 g / cm 3, PD1≤PD2. By adjusting PD1<PD2, the first type of battery cell with a higher nickel content is matched with a lower compaction density, and the second type of battery cell with a relatively lower nickel content is matched with a higher compaction density, which is conducive to balancing the temperature between the first type of battery cell and the second type of battery cell, thereby reducing the voltage difference between the first type of battery cell and the second type of battery cell, and thus helping to better balance the energy density and cycle stability of the battery module. In addition, matching the first type of battery cell with a lower compaction density is also conducive to stabilizing the high-temperature cycle stability of the first type of battery cell with a higher nickel content. When PD1=PD2, it is the same as when CW1=CW2, which is conducive to balancing the temperature difference between the first type of battery cell and the second type of battery cell, thereby alleviating the voltage difference between the two types of battery cells and improving the cycle stability of the battery module.

[0052] In some embodiments of the present application, 3.1≤PD1≤3.7, 3.1≤PD2≤3.7. For example, PD1 can be 3.1, 3.15, 3.2, 3.25, 3.3, 3.35, 3.4, 3.45, 3.5, 3.55, 3.6, 3.65, 3.7, or a range consisting of any two of them; PD2 can be 3.1, 3.15, 3.2, 3.25, 3.3, 3.35, 3.4, 3.45, 3.5, 3.55, 3.6, 3.65, 3.7, or a range consisting of any two of them.

[0053] In some embodiments of the present application, the battery module further includes a third type of battery cell, and in the first direction, the third type of battery cell is located between the first type of battery cell and the second type of battery cell; the compaction density of the positive electrode material layer in the third type of battery cell is PD3 g / cm 3 , PD3≤PD2, PD1≤PD3. The above arrangement is helpful to reduce the heat generated by the second type of battery cells located further inside the battery module, while improving the cycle stability of the first type of battery cells with relatively high nickel content, thereby better balancing the energy density and cycle stability of the battery module.

[0054] In some embodiments of the present application, 3.1≤PD3≤3.7. For example, PD3 can be 3.1, 3.15, 3.2, 3.25, 3.3, 3.35, 3.4, 3.45, 3.5, 3.55, 3.6, 3.65, 3.7, or a range consisting of any two of the values.

[0055] In some embodiments of the present application, the battery module satisfies at least one of the following characteristics: (1) in the first direction, the size of a single battery cell is D mm, 3≤D≤15; (2) the coating weight per unit area of ​​the positive electrode material layer is CW mg / cm 2 , 8≤CW≤25; (3) The compaction density of the positive electrode material layer is PD g / cm3 , 3.1≤PD≤3.7. The battery module satisfies at least one of the above characteristics, which is conducive to further balancing energy density and cycle stability.

[0056] In some embodiments of the present application, in the first direction, the size of a single battery cell is D, 3≤D≤15; for example. D can be 3, 4, 5, 6, 7, 8, 9, 11, 12, 13, 14, 15 or a range consisting of any two of these values. By regulating D within the above range, it is beneficial for the heat generated by the battery cell during the charging and discharging process to be transferred to the surrounding environment more promptly, improving the high-temperature cycle performance of the battery module, and taking into account the energy density of the battery module.

[0057] In some embodiments of the present application, the coating weight per unit area of ​​the positive electrode material layer is CW mg / cm 2 , 8≤CW≤25; for example. CW can be 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25 or a range consisting of any two of these values. By adjusting CW within the above range, it is beneficial to improve the high temperature stability of the positive electrode material containing nickel elements, thereby improving the cycle stability of the battery module in a high temperature environment.

[0058] In some embodiments of the present application, the compaction density of the positive electrode material layer is PD g / cm 3 , 3.1≤PD≤3.7. For example, PD can be 3.1, 3.15, 3.2, 3.25, 3.3, 3.35, 3.4, 3.45, 3.5, 3.55, 3.6, 3.65, 3.7 or a range consisting of any two of these values. By adjusting PD within the above range, it is beneficial to take into account both the energy density and kinetic performance of the battery module.

[0059] In some embodiments of the present application, Figure 2 As shown, N=4, the battery module 10 includes the above-mentioned first type battery cell 11 and the above-mentioned second type battery cell 12, wherein the first type battery cell 11 and the second type battery cell 12 are 2 each. The molar percentage of the nickel element in the positive electrode material of the two first type battery cells may be the same or different, but both are greater than the molar percentage of the nickel element in the positive electrode material of the adjacent second type battery cell. The molar percentage of the nickel element in the positive electrode material of the two second type battery cells may be the same or different, but both are less than the molar percentage of the nickel element in the positive electrode material of the adjacent first type battery cell.

[0060] In some embodiments of the present application, N=5, such as Figure 3As shown, the battery module 10 includes the above-mentioned first type battery cell 11 and the above-mentioned second type battery cell 12, wherein there are 2 first type battery cells 11 and 3 second type battery cells 12. The molar percentage of the nickel element in the positive electrode materials of the two first type battery cells may be the same or different, but both are greater than the molar percentage of the nickel element in the positive electrode materials of the second type battery cells adjacent thereto. The molar percentage of the nickel element in the positive electrode materials of the three second type battery cells may be the same or different, but both are less than the molar percentage of the nickel element in the positive electrode materials of the first type battery cells adjacent thereto. In addition, when the molar percentage of the nickel element in the positive electrode materials of the three second type battery cells is different, in the first direction, the battery cell with a higher molar percentage of the nickel element is closer to the two ends.

[0061] In some embodiments of the present application, N=5, such as Figure 4 As shown, the battery module 10 includes the above-mentioned first type battery cell 11 and the above-mentioned second type battery cell 12, wherein there are 4 first type battery cells 11 and 1 second type battery cell 12. The molar percentage of nickel element in the positive electrode materials of the 4 first type battery cells may be the same or different, but are all greater than the molar percentage of nickel element in the positive electrode materials of the second type battery cells. In addition, when the molar percentage of nickel element in the positive electrode materials of the 4 second type battery cells is different, in the first direction, the battery cell with a higher molar percentage of nickel element is closer to both ends.

[0062] In some embodiments of the present application, N=5, such as Figure 5 As shown, the battery module 10 includes the above-mentioned first type battery cell 11, the second type battery cell 12 and the third type battery cell 13, wherein there are 2 first type battery cells 11, 1 second type battery cell 12 and 2 third type battery cells 13. The molar percentage of the nickel element in the positive electrode material of the two first type battery cells may be the same or different, but both are greater than the molar percentage of the nickel element in the positive electrode material of the third type battery cell adjacent thereto. The molar percentage of the nickel element in the positive electrode material of the two third type battery cells may be the same or different, but both are greater than the molar percentage of the nickel element in the positive electrode material of the second type battery cell.

[0063] In some embodiments of the present application, the positive electrode material layer also includes a conductive agent and a binder. The present application does not particularly limit the types of conductive agents and binders, as long as the purpose of the present application can be achieved. For example, the conductive agent may include but is not limited to at least one of conductive carbon black (Super P), carbon nanotubes (CNTs), carbon fibers, flake graphite, graphene, metal materials or conductive polymers, and the conductive carbon black may include but is not limited to at least one of acetylene black or Ketjen black. The above-mentioned carbon nanotubes may include but are not limited to single-walled carbon nanotubes and / or multi-walled carbon nanotubes. The above-mentioned carbon fibers may include but are not limited to vapor-grown carbon fibers (VGCF) and / or nano-carbon fibers. The above-mentioned metal materials may include but are not limited to metal powders and / or metal fibers. Specifically, the metal may include but is not limited to at least one of copper, nickel, aluminum or silver. The above-mentioned conductive polymers may include but are not limited to at least one of polyphenylene derivatives, polyaniline, polythiophene, polyacetylene or polypyrrole. The present application has no particular restrictions on the binder, as long as the purpose of the present application can be achieved. For example, the binder may include but is not limited to at least one of polyacrylic acid, sodium polyacrylate, potassium polyacrylate, lithium polyacrylate, polyimide, polyvinyl alcohol, carboxymethyl cellulose, sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, polyimide, polyamide-imide, styrene-butadiene rubber or polyvinylidene fluoride. The present application has no particular restrictions on the mass ratio of the conductive agent and the binder in the positive electrode material layer. Those skilled in the art can choose according to actual needs, as long as the purpose of the present application can be achieved.

[0064] In the present application, the positive electrode sheet includes a positive electrode current collector and a positive electrode material layer disposed on at least one surface of the positive electrode current collector. The above-mentioned "positive electrode material layer disposed on at least one surface of the positive electrode current collector" means that the positive electrode material layer can be disposed on one surface of the positive electrode current collector along its own thickness direction, or it can be disposed on two surfaces of the positive electrode current collector along its own thickness direction. It should be noted that the "surface" here can be the entire area of ​​the surface of the positive electrode current collector, or it can be a partial area of ​​the surface of the positive electrode current collector. This application has no special restrictions, as long as the purpose of this application can be achieved.

[0065] The present application has no particular limitation on the positive electrode current collector, as long as the purpose of the present application can be achieved. For example, it may include aluminum foil, aluminum alloy foil or a composite current collector (such as an aluminum-carbon composite current collector).

[0066] The present application has no particular limitation on the thickness of the positive electrode current collector and the positive electrode material layer, as long as the purpose of the present application can be achieved. For example, the thickness of the positive electrode current collector is 5 μm to 20 μm, and the thickness of the positive electrode material layer is 30 μm to 120 μm.

[0067] In the present application, each battery cell also includes a negative electrode plate, and the negative electrode plate includes a negative electrode current collector and a negative electrode material layer disposed on at least one surface of the negative electrode current collector. The above-mentioned "negative electrode material layer is disposed on at least one surface of the negative electrode current collector" means that the negative electrode material layer can be disposed on one surface of the negative electrode current collector along its own thickness direction, or it can be disposed on two surfaces of the negative electrode current collector along its own thickness direction. It should be noted that the "surface" here can be the entire area of ​​the surface of the negative electrode current collector, or it can be a partial area of ​​the surface of the negative electrode current collector. This application has no special restrictions, as long as the purpose of this application can be achieved.

[0068] The present application has no particular limitation on the negative electrode current collector, as long as the purpose of the present application can be achieved. For example, it may include copper foil, copper alloy foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam or a composite current collector. For example, the composite current collector may be a lithium-copper composite current collector, a carbon-copper composite current collector, a nickel-copper composite current collector, a titanium-copper composite current collector, etc.

[0069] The negative electrode material layer includes a negative electrode active material. The present application has no particular limitation on the negative electrode active material as long as the purpose of the present application can be achieved. For example, the negative electrode active material may include but is not limited to natural graphite, artificial graphite, mesophase microcarbon beads, hard carbon, soft carbon, silicon, silicon-carbon composite, Li-Sn alloy, Li-Sn-O alloy, Sn, SnO, SnO2, spinel structured lithiated TiO2-Li4Ti5O 12 Or at least one of Li-Al alloy.

[0070] In some embodiments of the present application, the negative electrode material layer may further include a conductive agent and a binder. The present application does not particularly limit the types of the conductive agent and the binder, as long as the purpose of the present application can be achieved. For example, it may be at least one of the above conductive agent and the above binder. The present application does not particularly limit the mass ratio of the negative electrode active material, the conductive agent, and the binder in the negative electrode material layer. Those skilled in the art may select according to actual needs, as long as the purpose of the present application can be achieved.

[0071] The present application has no particular limitation on the thickness of the negative electrode material layer, as long as the purpose of the present application can be achieved. For example, the thickness of the negative electrode material layer is 30 μm to 120 μm.

[0072] The present application has no particular limitation on the thickness of the negative electrode current collector, as long as the purpose of the present application can be achieved. For example, the thickness of the negative electrode current collector is 4 μm to 15 μm.

[0073] Optionally, the negative electrode plate may further include a conductive layer, and the conductive layer is located between the negative electrode current collector and the negative electrode material layer. The present application has no particular restrictions on the composition of the conductive layer, and it may be a conductive layer commonly used in the art. For example, the conductive layer includes a conductive agent and a binder. The present application has no particular restrictions on the conductive agent and the binder in the conductive layer, and it may be at least one of the above conductive agent and the above binder.

[0074] In the present application, the battery cell also includes a diaphragm. The present application has no particular restrictions on the diaphragm, as long as the purpose of the present application can be achieved. For example, the material of the diaphragm may include, but is not limited to, polyethylene (PE), polypropylene (PP)-based polyolefins (PO), polyesters (e.g., polyethylene terephthalate (PET) films), cellulose, polyimide (PI), polyamide (PA), spandex or at least one of aramid. The type of diaphragm may include at least one of a woven membrane, a non-woven membrane, a microporous membrane, a composite membrane, a rolled membrane or a spun membrane.

[0075] In some embodiments of the present application, the diaphragm may include a substrate layer and a surface treatment layer. The substrate layer may be a nonwoven fabric, a film or a composite film having a porous structure, and the material of the substrate layer may include at least one of polyethylene, polypropylene, polyethylene terephthalate or polyimide. Optionally, a polypropylene porous film, a polyethylene porous film, a polypropylene nonwoven fabric, a polyethylene nonwoven fabric or a polypropylene-polyethylene-polypropylene porous composite film may be used.

[0076] Optionally, a surface treatment layer is disposed on at least one surface of the substrate layer. The surface treatment layer may be a polymer layer or an inorganic layer, or a layer formed by mixing a polymer and an inorganic layer.

[0077] In some embodiments of the present application, the inorganic layer includes inorganic particles and a binder. The present application is not particularly limited to inorganic particles, such as inorganic particles can include at least one of aluminum oxide, silicon oxide, magnesium oxide, titanium oxide, hafnium dioxide, tin oxide, cerium dioxide, nickel oxide, zinc oxide, calcium oxide, zirconium oxide, yttrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide or barium sulfate. The present application is not particularly limited to binders, such as binders can be at least one of the above-mentioned binders. In some embodiments of the present application, the polymer layer includes polymers, and the material of the polymer includes at least one of polyamide, polyacrylonitrile, acrylate polymers, polyacrylic acid, polyacrylates, polyvinyl pyrrolidone, polyvinyl ether or polyvinylidene fluoride or poly (vinylidene fluoride-hexafluoropropylene).

[0078] In the present application, there is no particular limitation on the thickness of the separator as long as the purpose of the present application can be achieved. For example, the thickness of the separator may be 3 μm to 30 μm.

[0079] In the present application, the battery module also includes a shell for accommodating the battery cell and the electrolyte, as well as other components known in the field of secondary batteries, and the present application does not limit the above-mentioned other components. The present application does not particularly limit the shell, and it can be a shell known in the art, as long as the purpose of the present application can be achieved. For example, the shell can be a hard shell or a flexible shell. The material of the hard shell can be metal, and the present application does not limit the type of metal. A metal hard shell known in the art can be used, as long as the purpose of the present application can be achieved. The flexible shell can be a metal plastic film, such as an aluminum plastic film, a steel plastic film, etc. The present application does not limit the electrolyte, and an electrolyte known in the art can be used, as long as the purpose of the present application can be achieved.

[0080] The preparation process of the battery module of the present application is well known to those skilled in the art, and there is no particular limitation in the present application. For example, the preparation process of the battery module may include but is not limited to the following steps: stacking the positive electrode sheet, the separator and the negative electrode sheet in order, and winding, folding and other operations as needed to obtain a battery cell with a wound structure, placing the battery cell in a shell, injecting the electrolyte into the shell and sealing it to obtain a battery cell. Alternatively, stacking the positive electrode sheet, the separator and the negative electrode sheet in order, and then fixing the four corners of the entire laminated structure with tape to obtain a battery cell with a laminated structure, placing the battery cell in a shell, injecting the electrolyte into the shell and sealing it to obtain a battery cell, and then stacking the obtained battery cell in the shell as needed, and then welding and assembling it to obtain a battery module. In addition, overcurrent protection elements, guide plates, etc. may also be placed in the shell as needed to prevent the pressure inside the battery module from rising and overcharging and discharging.

[0081] The second aspect of the present application provides an electric device, which includes a battery module in any of the aforementioned embodiments, and the obtained electric device has good performance. The present application does not particularly limit the type of electric device, and it can be used for any electric device known in the prior art. In some embodiments of the present application, the electric device may include but is not limited to computers, smart phones, backup power supplies, two-wheeled vehicles, drones, power tools or energy storage devices.

[0082] Example

[0083] The following examples and comparative examples are given to more specifically describe the embodiments of the present application. Various tests and evaluations were performed according to the following methods. In addition, unless otherwise specified, "parts" and "%" are based on mass.

[0084] Test methods and equipment:

[0085] Capacity retention rate:

[0086] At 25°C, the lithium-ion battery module is charged at a constant current of 1.0C to a voltage of 12.9V, then charged at a constant voltage of 12.9V to 0.05C, and left to stand for 10 minutes; then discharged at a constant current of 4.0C to a voltage of 7.5V, and left to stand for 15 minutes. The above is one cycle. According to the above cycle to 500 cycles, the first cycle discharge capacity is recorded as the initial capacity Q0, and the discharge capacity of the 500th cycle lithium-ion battery is recorded as Q1. The 500th cycle capacity retention rate of the lithium-ion battery is calculated by the following formula: Cycle capacity retention rate (%) = Q1 / Q0×100%.

[0087] Charging terminal voltage difference:

[0088] The lithium-ion battery is charged and discharged according to the cycle process in the above-mentioned "capacity retention rate" test method, and the maximum voltage and minimum voltage of the three cells in the lithium-ion battery module after 500 cycles and 10 minutes of rest at the charging terminal are recorded respectively. The difference between the maximum voltage and the minimum voltage is the charging terminal voltage difference.

[0089] Energy density test:

[0090] At 25°C, the lithium-ion battery module is charged at a constant current of 0.2C to a voltage of 12.9V, then charged at a constant voltage of 12.9V to a current of 0.05C, and left to stand for 5 minutes; then discharged at a constant current of 0.2C to a voltage of 7.5V, and left to stand for 5 minutes. The discharge energy at this time is recorded as the energy Q Wh of the lithium-ion battery module; and the mass of the lithium-ion battery pack is measured and recorded as m kg. The energy density ED of the lithium-ion battery module is calculated by the following formula: ED = Q / m.

[0091] Test of molar percentage of nickel in positive electrode material:

[0092] Sample preparation: At 25°C ambient temperature, disassemble the lithium-ion battery, take out the positive electrode sheet, scrape the positive electrode material layer powder from the positive electrode sheet, and calcine it in a nitrogen atmosphere at 500°C for 2h to obtain a positive electrode material layer sample containing positive electrode active materials. Then take 0.4g of the sample and dissolve it in 10mL of aqua regia (concentrated hydrochloric acid (HCl) and concentrated nitric acid (HNO3) in a volume ratio of 3:1), dissolve it at 180°C for 30min, cool it to room temperature, and adjust the sample volume to 100mL.

[0093] Standard curve: prepare a series of nickel standard solutions, cobalt standard solutions and manganese standard solutions with different concentrations, use an inductively coupled plasma mass spectrometer (ICP-MS) instrument to measure the mass numbers of the standard solutions, and draw standard curves for nickel, cobalt and manganese.

[0094] Sample test: Introduce the prepared sample solution into the ICP-MS instrument to measure the nickel content, cobalt content, and manganese content. According to the standard curve, the mass concentration of nickel, the mass concentration of cobalt, and the mass concentration of manganese are obtained, and the mass of nickel, the mass of cobalt, and the mass of manganese are converted to obtain the molar number of nickel n1, the molar number of cobalt n2, and the molar number of manganese n3. With n1+n2+n3 as the molar number of the positive electrode active material, the molar percentage of nickel in the positive electrode active material = n1 / (n1+n2+n3)×100%. The above-mentioned positive electrode active material can be the positive electrode active material in the first type of battery cell, the positive electrode active material in the second type of battery cell, or the positive electrode active material in the third type of battery cell.

[0095] Test of cell size in the first direction:

[0096] The size of the battery cell in the first direction is measured three times with a micrometer, and the average of the three test results is the size of the battery cell in the first direction.

[0097] Coating weight per unit area, compaction density test:

[0098] At 25°C, the lithium-ion battery was disassembled, the positive electrode was taken out, and placed in an oven and dried at 80°C for 12 h. The area of ​​the positive electrode material layer coating was measured and recorded as S cm 2 , and then the cross section of the positive electrode sheet along the thickness direction is ion polished, and the cross section of the positive electrode sheet is observed under a VHX5000 microscope at a magnification of 500 to measure the thickness d of the positive electrode material layer, in cm. Then the entire positive electrode material layer is scraped off and its mass mm mg is measured using an analytical balance. The coating weight per unit area can be calculated by the following formula: CW = m / S; the compaction density can be calculated by the following formula: PD = m / (S×d).

[0099] Example 1

[0100] <Preparation of positive electrode sheet of the first type of battery cell>

[0101] The positive electrode active material LiNi 0.91 Co 0.05 Mn 0.04 O2, conductive carbon black (Super P), and binder polyvinylidene fluoride (PVDF) were mixed in a mass ratio of 97:2:1, and N-methylpyrrolidone (NMP) was added as a solvent to prepare a slurry with a solid content of 75wt%. The positive electrode slurry was evenly coated on one surface of a positive electrode current collector aluminum foil with a thickness of 10μm, and dried at 120°C to obtain a positive electrode sheet with a single-sided positive electrode material layer. The coating weight of the positive electrode material layer was 13mg / cm 2Then repeat the above steps on the other surface of the aluminum foil to obtain the first type of battery positive electrode sheet with double-sided positive electrode material layer. After drying at 120°C, cold pressing, cutting and welding the tabs, a positive electrode sheet with a specification of 50mm×80mm is obtained for standby use. Among them, the thickness of the single-sided positive electrode material layer is 70μm.

[0102] <Preparation of positive electrode sheet for the second type of battery cell>

[0103] The positive electrode active material LiNi 0.87 Co 0.08 Mn 0.05 O2, conductive agent SP, and binder PVDF are mixed in a mass ratio of 97:2:1, and N-methylpyrrolidone (NMP) is added as a solvent to prepare a slurry with a solid content of 75wt%. After vacuum stirring, the positive electrode slurry is obtained. The positive electrode slurry is evenly coated on one surface of a positive electrode current collector aluminum foil with a thickness of 10μm, and dried at 120°C to obtain a positive electrode sheet with a single-sided positive electrode material layer. Then repeat the above steps on the other surface of the aluminum foil to obtain a first type of battery cell positive electrode sheet with a double-sided positive electrode material layer. After drying at 120°C, cold pressing is performed, and then cutting and welding of the pole ears are performed to obtain a positive electrode sheet with a specification of 50mm×70mm for standby use. Among them, the thickness of the single-sided positive electrode material layer is 70μm.

[0104] <Preparation of negative electrode sheet>

[0105] The negative electrode active material artificial graphite, silicon carbide, binder polyacrylic acid (PAA), and conductive agent carbon nanotube (CNT) were mixed in a mass ratio of 74:20:5:1, and deionized water was added as a solvent to prepare a slurry with a solid content of 40wt%. The negative electrode slurry was evenly coated on one surface of a negative electrode current collector copper foil with a thickness of 6μm, and dried at 120°C to obtain a negative electrode sheet with a negative electrode material layer coated on one side. The coating weight of the negative electrode material layer was 8mg / cm 2 Then repeat the above steps on the other surface of the copper foil to obtain a negative electrode sheet coated with a negative electrode material layer on both sides. After drying at 120°C, cold pressing, cutting and welding the tabs, a negative electrode sheet with a specification of 55mm×75mm is obtained for standby use. The thickness of the single-sided negative electrode material layer is 50μm.

[0106] <Preparation of Electrolyte>

[0107] In an environment with a water content of less than 10ppm, ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC): ethyl methyl carbonate (EMC) are mixed in a mass ratio of 20:30:40:10 to obtain an organic solvent, and then electrolyte salt LiPF6 is added to the organic solvent and mixed evenly to obtain an electrolyte. Among them, based on the mass of the electrolyte, the mass percentage of the electrolyte salt is 12.5%, and the rest is the organic solvent.

[0108] <Diaphragm>

[0109] A porous polyethylene film with a thickness of 7 μm (provided by Celgard Company) was used as a separator.

[0110] <Preparation of lithium-ion batteries>

[0111] The positive electrode sheet, separator and negative electrode sheet of the first type of battery cell prepared above are stacked in order, so that the separator is located between the positive electrode sheet and the negative electrode sheet to play an isolating role, and then the four corners of the entire laminated structure are fixed with tape to obtain the first type of battery cell of the laminated structure. Then take the positive electrode sheet of the second type of battery cell prepared above and repeat the above steps to obtain the second type of battery cell. Then place the first type of battery cell at both ends of the second type of battery cell, and put it into an aluminum-plastic film packaging bag, and remove the moisture at 80°C, inject the electrolyte prepared above, and obtain a lithium-ion battery after vacuum packaging, standing, formation, degassing, trimming and other processes. Among them, the formation upper limit voltage is 4.15V, the formation temperature is 70°C, and the formation standing time is 2h.

[0112] Example 2 to Example 32

[0113] Except for adjusting the relevant preparation parameters according to Table 1, the rest is the same as Example 1-1. Among them, in Example 19 and Example 20, the thickness of the battery cell is shown in Table 1 by changing the number of layers of the stacked structure of the battery cell; in Example 12 to Example 16, Example 29 to Example 32, the unit area coating mass of the positive electrode material layer is shown in Table 1 by changing the cold pressing pressure of the positive electrode plate during the preparation process; in Example 17 and Example 18, the compaction density of the positive electrode material layer is shown in Table 1 by changing the cold pressing pressure of the positive electrode plate during the preparation process.

[0114] Comparative Example 1 to Comparative Example 3

[0115] Except for adjusting the relevant preparation parameters according to Table 1, the rest is the same as Example 1.

[0116]

[0117]

[0118] It is understandable that the voltage difference, cycle stability and energy density of lithium-ion batteries vary greatly when the nickel content per unit weight is different. Therefore, when the nickel content per unit weight of lithium-ion batteries is the same, similar or equivalent, that is, the weight energy density of the lithium-ion batteries is similar or equivalent, on this basis, the voltage difference and / or cycle stability and / or energy density of the lithium-ion batteries are improved, which means that the voltage difference, cycle stability and energy density of the lithium-ion batteries are taken into account. Among them, the nickel content per unit weight of lithium-ion batteries is mainly related to the nickel content in the positive electrode materials of various types of battery cells in the battery and the number of such battery cells. The number of the first type of battery cells is defined as N1, the number of the second type of battery cells is defined as N2, and the number of the third type of battery cells is defined as N3. That is, the nickel content in lithium-ion batteries is mainly related to W1, W2, W3, N1, N2, and N3. Here, the nickel content per unit weight of lithium-ion batteries is defined as M = (W1×N1+W2×N2+W3×N3) / (N1+N2+N3)×100%. In addition, the influence of the unit area coating weight CW and the compaction density PD of the positive electrode material layer in the battery cell on the nickel content per unit weight of the lithium-ion battery should also be comprehensively considered, thereby affecting the voltage difference, cycle stability, and energy density of the lithium-ion battery. In addition, the influence of the total number of battery cells on the voltage difference, cycle stability, and energy density of the lithium-ion battery should also be considered.

[0119] It can be seen from Examples 1 to 32 and Comparative Examples 1 to 3 that the embodiments include a first type of battery cell and a second type of battery cell, the nickel content W1 of the first type of battery cell is different from the nickel content W2 of the second type of battery cell, and 1% ≤ W1-W2 ≤ 10%, and the obtained lithium ion battery can simultaneously have a higher energy density and better cycle performance, and a lower voltage difference between various types of battery cells. Although the lithium ion battery in Comparative Example 1 has a higher energy density, its cycle performance is poor and the voltage difference between the battery cells is higher. Although the nickel content in the battery cell of Comparative Example 2 is close to that in Example 1, its energy density, cycle performance and voltage difference performance between the battery cells are all poor. Although the lithium ion battery in Comparative Example 3 has a higher energy density, it cannot take into account the cycle performance and the voltage difference between different types of battery cells. This shows that the lithium ion battery that meets the present application can better balance the voltage difference between the battery cells, improve the cycle stability of the lithium ion battery and take into account the energy density.

[0120] Specifically, the nickel content of the lithium ion battery in Example 4 is similar to that in Comparative Example 1, that is, the weight energy density of the lithium ion battery is similar, the capacity retention rate of Comparative Example 1 is lower, and the voltage difference is larger. The nickel content in the lithium ion battery in Comparative Example 2 is close to that in Example 2 and Example 3, that is, the weight energy density of the lithium ion battery is similar, but the lithium ion battery in Comparative Example 2 has a lower capacity retention rate and a higher voltage difference. The nickel content in the lithium ion battery in Example 7 is close to that in Comparative Example 3, that is, the weight energy density of the lithium ion battery is similar, the capacity retention rate of the lithium ion battery in Comparative Example 3 is lower, and the voltage difference is also larger. None of the above comparative examples can take into account the energy density, voltage difference and capacity retention rate of the lithium ion battery well. It is thus shown that the lithium ion battery that meets the present application can better take into account the energy density, voltage difference and cycle stability.

[0121] At the same time, when the lithium-ion battery also includes a third type of battery cell, and W3≥W2, W1≥W3, it can be seen from Examples 24 to 33 that when W1, W2, and W3 meet the above ranges, the obtained lithium-ion battery has a higher energy density and capacity retention rate and a smaller voltage difference. This shows that the lithium-ion battery provided by the present application can take into account energy density, voltage difference, and cycle stability.

[0122] The content of nickel in various types of battery cells usually affects the energy density, cycle stability and voltage difference between various types of battery cells of the lithium-ion battery. It can be seen from Examples 1 to 11 that the content of nickel in the first type of battery cell W1 and the content of nickel in the second type of battery cell W2 are within the scope of this application, and the obtained lithium-ion battery can take into account the voltage difference, capacity retention rate and energy density. When the lithium-ion battery also includes a third type of battery cell, it can be seen from Examples 23 to 28 that W1, W2, and W3 are all within the scope of this application, and the obtained lithium-ion battery can take into account higher energy density and capacity retention rate, and lower voltage difference. This shows that the content of nickel in various types of battery cells is within the scope of this application, and the obtained lithium-ion battery can take into account higher energy density and better cycle stability.

[0123] The coating weight per unit area CW usually affects the energy density, cycle stability and voltage difference of the lithium-ion battery. It can be seen from Example 1 and Example 12 to Example 16 that the coating weight per unit area CW1 of the first type of battery cell and the coating weight per unit area CW2 of the second type of battery cell are within the scope of the present application, and the obtained lithium-ion battery has a higher energy density, better cycle performance and a lower pressure difference. At the same time, when the lithium-ion battery also includes a third type of battery cell, it can be seen from Example 29 to Example 32 that CW1, CW2, and CW3 are all within the scope of the present application, and the obtained lithium-ion battery can take into account a higher energy density and capacity retention rate as well as a lower voltage difference. Thus, when the coating weight per unit area CW of each type of battery cell is within the scope of the present application, the obtained lithium-ion battery can take into account a higher energy density, a smaller pressure difference and a better cycle performance.

[0124] The compaction density PD usually affects the energy density, cycle stability and voltage difference of the lithium-ion battery. It can be seen from Example 1, Example 17 and Example 18 that the compaction density PD1 of the first type of battery cell and the compaction density PD2 of the second type of battery cell are within the scope of this application, and the obtained lithium-ion battery has a higher energy density, a higher capacity retention rate and a lower voltage difference. Therefore, when the compaction density PD of each type of battery cell is within the scope of this application, the obtained lithium-ion battery can better balance the energy density, voltage difference and cycle stability.

[0125] The thickness D of the battery cell usually affects the energy density, cycle stability and voltage difference of the lithium-ion battery. It can be seen from Example 1, Example 19 and Example 20 that when the thickness D1 of the first type of battery cell and the thickness D2 of the second type of battery cell are within the scope of this application, the obtained lithium-ion battery has a higher energy density, a better capacity retention rate and a lower voltage difference. Therefore, when the thickness D of each type of battery cell is within the scope of this application, the obtained lithium-ion battery can better balance the energy density, voltage difference and cycle stability.

[0126] The number of cells in a lithium-ion battery usually affects the energy density, cycle stability and voltage difference of the lithium-ion battery. The lithium-ion battery in Examples 1 to 20 includes 3 cells, and the cells arranged in the first direction are the first type of cell, the second type of cell, and the first type of cell respectively; the lithium-ion battery in Example 21 includes 4 cells, and the cells arranged in the first direction are the first type of cell, the second type of cell, the second type of cell, and the first type of cell respectively; the lithium-ion battery in Example 22 includes 5 cells, and the cells arranged in the first direction are the first type of cell, the first type of cell, the second type of cell, the first type of cell, and the first type of cell respectively; the lithium-ion battery in Examples 23 to 32 includes 5 cells, and the cells arranged in the first direction are the first type of cell, the third type of cell, the second type of cell, the third type of cell, and the first type of cell respectively. The number of cells in the above embodiments is within the scope of this application, and the obtained lithium-ion battery has a higher energy density, a higher capacity retention rate and a lower voltage difference at the same time. This shows that when the number of cells in the lithium-ion battery is within the scope of the present application, the obtained lithium-ion battery can better balance energy density, voltage difference and cycle stability.

[0127] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method or article including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method or article.

[0128] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application shall be included in the scope of protection of the present application.

Claims

1. A battery module, characterized in that: include: N battery cells arranged in a first direction; The N battery cells include a first type of battery cell and a second type of battery cell, and the first type of battery cell is closer to two ends of the battery module in the first direction than the second type of battery cell; Each of the N battery cells includes a positive electrode sheet and a negative electrode sheet, the positive electrode sheet includes a positive electrode material layer, and the positive electrode material layer includes a positive electrode material containing nickel element; Based on the molar number of the positive electrode material in the first type of battery cell, the molar percentage of the nickel element is W1, and based on the molar number of the positive electrode material in the second type of battery cell, the molar percentage of the nickel element is W2; 1%≤W1-W2≤10%.

2. The battery module according to claim 1, wherein: 3≤N≤10。 3. The battery module according to claim 1, wherein: 3%≤W1-W2≤7%.

4. The battery module according to any one of claims 1 to 3, wherein: 3≤N≤5, 60%≤W2≤95%, 70%≤W1≤99%.

5. The battery module according to claim 1, wherein: The N battery cells further include a third type of battery cell, and in the first direction, the third type of battery cell is located between the first type of battery cell and the second type of battery cell; Based on the molar number of the positive electrode material in the third type of battery cell, the molar percentage of the nickel element is W3, W3≥W2, W1≥W3.

6. The battery module according to claim 5, which satisfies at least one of the following characteristics: (1) 0% ≤ W3-W2 ≤ 10%; (2)0%≤W1-W3≤10%.

7. The battery module according to claim 5, which satisfies at least one of the following characteristics: (1) 3% ≤ W3-W2 ≤ 7%; (2) 3% ≤ W1-W3 ≤ 7%.

8. The battery module according to any one of claims 1 to 7, wherein: In the first direction, the size of the first type of battery cell is D1 mm, the size of the second type of battery cell is D2 mm, and D1≤D2.

9. The battery module according to claim 8, wherein: The battery module also includes a third type of battery cell. In the first direction, the third type of battery cell is located between the first type of battery cell and the second type of battery cell. The size of the third type of battery cell is D3 mm, D3≤D2, D1≤D3.

10. The battery module according to any one of claims 1 to 7, wherein: The coating weight per unit area of ​​the positive electrode material layer in the first type of battery cell is CW1 mg / cm 2 The coating weight per unit area of ​​the positive electrode material layer in the second type of battery cell is CW2 mg / cm 2 , CW1≤CW2.

11. The battery module according to claim 10, wherein: The battery module further includes a third type of battery cell, which is located between the first type of battery cell and the second type of battery cell in the first direction; the coating weight per unit area of ​​the positive electrode material layer in the third type of battery cell is CW3 mg / cm 2 , CW3≤CW2, CW1≤CW3.

12. The battery module according to any one of claims 1 to 7, wherein: The compaction density of the positive electrode material layer in the first type of battery cell is PD1 g / cm 3 The compaction density of the positive electrode material layer in the second type of battery is PD2g / cm 3 , PD1≤PD2.

13. The battery module according to claim 12, wherein: The battery module further includes a third type of battery cell, and in the first direction, the third type of battery cell is located between the first type of battery cell and the second type of battery cell; The compaction density of the positive electrode material layer in the third type of battery cell is PD3 g / cm 3 , PD3≤PD2, PD1≤PD3.

14. The battery module according to any one of claims 1 to 13, wherein: The battery cell meets at least one of the following characteristics: (1) In the first direction, the size of a single battery cell is D mm, 3≤D≤15; (2) The coating weight per unit area of ​​the positive electrode material layer is CW mg / cm 2 , 8≤CW≤25; (3) The compaction density of the positive electrode material layer is PD g / cm 3 , 3.1≤PD≤3.

7.

15. An electrical device comprising the battery module according to any one of claims 1 to 14.

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