Battery cell and battery pack

Abstract

The utility model relates to the technical field of batteries, and discloses a battery cell and a battery pack, comprising: a positive electrode comprising a positive electrode active material layer, the positive electrode active material layer comprising a high-nickel ternary material layer; the thickness a of the positive electrode active material layer is 50 [mu] m to 70 [mu] m; the negative electrode comprises a negative electrode active material layer, and the negative electrode active material layer comprises a silicon carbon compound and a graphite composite material layer, or a Si (at) SiOx (at) C compound and a graphite composite material layer; the thickness b of the negative electrode active material layer is 40 [mu] m to 60 [mu] m. According to the utility model, the high-nickel ternary material is used as the positive electrode active material, the silicon carbon compound and the graphite or the Si (at) SiOx (at) C compound and the graphite are used as the negative electrode material, and the thicknesses of the positive electrode active material layer and the negative electrode active material layer are limited, so that the energy density of the battery cell is improved while the battery cell is ensured not to be broken when being fully charged.

Description

Technical Field

[0001] The utility model relates to the technical field of batteries, in particular to a battery cell and a battery pack. Background Art

[0002] With the increasing prominence of energy and environmental issues and the continuous development of new technologies, the demand for the application of secondary batteries in portable electronic devices and electric vehicles with high mileage and high power performance is increasing. The development of high energy density batteries has become the focus of secondary battery development. As the market's requirements for electric vehicle endurance are getting higher and higher, the graphite negative electrode has basically reached its gram capacity limit and can no longer meet the future demand for high energy density batteries. Utility Model Content

[0003] In view of this, the utility model provides a battery cell and a battery pack to solve the problem that the existing battery cells cannot meet the requirements of high energy density.

[0004] In the first aspect, the utility model provides a battery cell, comprising: a positive electrode, the positive electrode comprising a positive electrode active material layer, the positive electrode active material layer comprising a high-nickel ternary material layer; the thickness a of the positive electrode active material layer is 50μm to 70μm; a negative electrode, the negative electrode comprising a negative electrode active material layer, the negative electrode active material layer comprising a silicon-carbon composite and a graphite composite material layer, or a Si@SiOx@C composite and a graphite composite material layer; the thickness b of the negative electrode active material layer is 40μm to 60μm.

[0005] Beneficial effects: High nickel ternary material is used as the positive electrode active material, silicon carbon composite and graphite or Si@SiOx@C composite and graphite are used as the negative electrode material, and the thickness of the positive electrode active material layer and the negative electrode active material layer are limited, while ensuring that the battery cell does not rupture when fully charged, the energy density of the battery cell is improved.

[0006] In an optional embodiment, the high-nickel ternary material layer includes a Ni90 ternary material layer, or a Ni91 ternary material layer, or a Ni92 ternary material layer, or a Ni93 ternary material layer, or a Ni94 ternary material layer, or a Ni95 ternary material layer, or a Ni96 ternary material layer, or a Ni97 ternary material layer, or a Ni98 ternary material layer, or a Ni99 ternary material layer.

[0007] Beneficial effect: The high-nickel ternary material layer Ni90-Ni99 is used as the positive electrode active material layer, which further ensures that the battery cell has a higher energy density and ensures the structural stability of the high-nickel ternary material layer.

[0008] In an optional embodiment, the positive electrode further includes a positive electrode current collector, the positive electrode current collector is an aluminum foil, and the positive electrode active material layer is coated on the positive electrode current collector.

[0009] In an optional implementation, the thickness c of the aluminum foil is 9 μm-15 μm.

[0010] Beneficial effect: While facilitating the processing of aluminum foil, it prevents thicker foil from occupying the space of active materials, making it easier to achieve high energy density of the battery cell.

[0011] In an optional embodiment, the negative electrode further includes a negative electrode current collector, the negative electrode current collector is copper foil, and the negative electrode active material layer is coated on the negative electrode current collector.

[0012] In an optional implementation, the thickness d of the copper foil is 3 μm-8 μm.

[0013] Beneficial effect: While facilitating copper foil processing, it prevents thicker foil from occupying the space of active materials, making it easier to achieve high energy density of the battery cell.

[0014] In an optional embodiment, the battery cell includes an electrode group, the electrode group is formed by winding the positive electrode and the negative electrode, and the number of winding turns of the positive electrode and the negative electrode is 60 to 70.

[0015] Beneficial effect: While ensuring that the battery cell has a high energy density, it avoids the battery cell steel shell from being easily broken due to too many winding turns.

[0016] In an optional embodiment, the battery core further includes a steel shell, the electrode group is disposed in the steel shell, and the ratio of the diameter of the electrode group to the inner diameter of the steel shell is 98%-99.5%.

[0017] Beneficial effect: While ensuring that the battery cell has a high energy density, it prevents the electrode group from occupying too much space inside the steel shell, which may cause the steel shell to easily break.

[0018] In an optional embodiment, the shell thickness of the steel shell is 0.38mm-0.55mm.

[0019] Beneficial effect: While ensuring that the steel shell has sufficient strength, it avoids the steel shell being too large and causing the battery cell to be too heavy.

[0020] In a second aspect, the utility model also provides a battery pack, comprising the above-mentioned battery cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the specific implementation methods of the utility model or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the utility model. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0022] Figure 1 This is a schematic diagram of the overall structure of the battery cell of an embodiment of the utility model;

[0023] Figure 2 A schematic diagram of the structure of the positive electrode current collector and the positive electrode active material layer of an embodiment of the utility model;

[0024] Figure 3 It is a schematic structural diagram of the negative electrode current collector and the negative electrode active material layer of an embodiment of the utility model.

[0025] Description of reference numerals:

[0026] 1. Positive electrode active material layer; 2. Negative electrode active material layer; 3. Positive electrode current collector; 4. Negative electrode current collector; 5. Steel shell; 10. Battery cell. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solution and advantages of the embodiment of the utility model clearer, the technical solution in the embodiment of the utility model will be clearly and completely described below in conjunction with the drawings in the embodiment of the utility model. Obviously, the described embodiment is a part of the embodiment of the utility model, not all the embodiments. Based on the embodiment of the utility model, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the utility model.

[0028] According to the following Figures 1 to 3 The embodiments of the present invention are described.

[0029] According to an embodiment of the utility model, on the one hand, a battery cell is provided, comprising: a positive electrode, the positive electrode comprising a positive electrode active material layer, the positive electrode active material layer comprising a high-nickel ternary material layer; the thickness a of the positive electrode active material layer is 50 μm to 70 μm; a negative electrode, the negative electrode comprising a negative electrode active material layer, the negative electrode active material layer comprising a silicon-carbon composite and a graphite composite material layer, or a Si@SiOx@C composite and a graphite composite material layer; the thickness b of the negative electrode active material layer is 40 μm to 60 μm.

[0030] The battery cell of this embodiment uses a high-nickel ternary material as the positive electrode active material, and uses a silicon-carbon composite and graphite or a Si@SiOx@C composite and graphite as the negative electrode material. In addition, the thickness of the positive electrode active material layer and the negative electrode active material layer are limited, thereby improving the energy density of the battery cell while ensuring that the battery cell does not rupture when fully charged.

[0031] Furthermore, in the silicon-carbon composite and graphite composite layer or the Si@SiOx@C composite and graphite composite layer, the content of the silicon-carbon composite or the Si@SiOx@C composite is 25%-30%.

[0032] That is, the negative electrode active material includes 25%-30% of a silicon-carbon and graphite composite material, or 25%-30% of a silicon-oxygen and graphite composite material.

[0033] When the silicon-carbon and graphite composite material or silicon-oxygen and graphite composite material is less than 25%, it cannot meet the design requirements of the battery cell energy density; when the silicon-carbon and graphite composite material or silicon-oxygen and graphite composite material is higher than 30%, due to the high expansion performance of high-silicon materials, the material expansion will break the steel shell. Therefore, the range of silicon doping content in the negative electrode active material layer is limited to ensure that the battery cell does not break when fully charged, while improving the energy density of the battery cell.

[0034] It is worth noting that graphite has a low gram capacity, and the negative electrode active material layer of the high energy density battery cell adopts a silicon-doped solution. The silicon-doped material used can be carbon-coated silicon particles, or a Si@SiOx@C composite.

[0035] In one embodiment, the high nickel ternary material layer includes a Ni90 ternary material layer, or a Ni91 ternary material layer, or a Ni92 ternary material layer, or a Ni93 ternary material layer, or a Ni94 ternary material layer, or a Ni95 ternary material layer, or a Ni96 ternary material layer, or a Ni97 ternary material layer, or a Ni98 ternary material layer, or a Ni99 ternary material layer.

[0036] That is, in this embodiment, the positive electrode active material includes a high-nickel ternary material, and the high-nickel ternary material includes Li(Ni a Co b Mn c )O2, where 0.9≤a≤0.99, a+b+c=1.

[0037] The capacity of high-nickel ternary materials below Ni90 is low and does not meet the design requirements of battery cell capacity; while the structure of high-nickel ternary materials above Ni99 is unstable. Therefore, the high-nickel ternary material layer Ni90-Ni99 is used as the positive electrode active material layer to further ensure that the battery cell has a higher energy density and ensure the structural stability of the high-nickel ternary material layer.

[0038] It is worth noting that the high nickel ternary material Ni90 is Li(Ni 0.9 Co 0.05 Mn 0.05 )O2.

[0039] It should be noted that the high-nickel ternary material Ni90-Ni99 adopts a mixture of polycrystalline and single crystal. Specifically, polycrystalline refers to large spherical particles formed by small single crystal particles bonded together by a binder.

[0040] It is worth noting that the energy density of the battery cell of this embodiment can reach 350wh / kg, and the battery cell is guaranteed not to rupture when fully charged.

[0041] In one embodiment, Figure 2 As shown, the positive electrode further includes a positive electrode current collector, which is an aluminum foil, and the positive electrode active material layer is coated on the positive electrode current collector. That is, the positive electrode active material is coated on the positive electrode current collector to form the positive electrode active material layer.

[0042] In one embodiment, Figure 2 As shown, the thickness c of the aluminum foil is 9 μm-15 μm. While facilitating the processing of the aluminum foil, it prevents the thicker foil from occupying the space of the active material, thus facilitating the realization of high energy density of the battery cell.

[0043] It is worth mentioning that aluminum foil with a thickness of less than 9μm is not easy to process with existing technology and is difficult to produce; aluminum foil with a thickness of more than 15μm is too thick and occupies the space for the active material, which is contrary to the original intention of designing high energy density battery cells.

[0044] It should be noted that the two opposite sides of the positive electrode current collector are coated with positive electrode active materials.

[0045] In one embodiment, Figure 3 As shown, the negative electrode further includes a negative electrode current collector, the negative electrode current collector is a copper foil, and the negative electrode active material layer is coated on the negative electrode current collector. That is, the negative electrode active material is coated on the negative electrode current collector to form the negative electrode active material layer.

[0046] In one embodiment, Figure 3 As shown, the thickness d of the copper foil is 3 μm-8 μm. While facilitating the processing of the copper foil, it prevents the thicker foil from occupying the space of the active material, thus facilitating the realization of high energy density of the battery cell.

[0047] It is worth noting that copper foil with a thickness of less than 3 μm is not easy to process with existing technology and is difficult to produce; copper foil with a thickness of more than 8 μm is too thick and occupies the space for the active material, which is contrary to the original intention of designing high energy density battery cells.

[0048] It should be noted that the two opposite sides of the negative electrode current collector are coated with negative electrode active materials.

[0049] In one embodiment, the battery cell includes an electrode group, which is formed by winding a positive electrode and a negative electrode, and the number of windings of the positive electrode and the negative electrode is 60 to 70. While ensuring that the battery cell has a high energy density, it is prevented that the battery cell steel shell is prone to rupture due to too many windings.

[0050] It is worth noting that when the number of windings of the positive and negative electrodes is too small, it is not easy to improve the energy density of the battery cell; when the number of windings of the positive and negative electrodes is too large, it is easy to cause the steel shell of the battery cell to rupture when the battery cell is charged, and the safety performance of the battery cell is low. Furthermore, the expansion of silicon-based materials gradually accumulates and increases with the increase in the number of windings. Therefore, controlling the number of windings is conducive to curbing the increase in expansion.

[0051] It should be noted that, in the present embodiment, the electrode group is the winding core, and the positive electrode and the negative electrode are both material strips, and the material strips are wound to form the winding core.

[0052] In one embodiment, Figure 1 As shown, the battery cell also includes a steel shell, the pole group is arranged in the steel shell, and the ratio of the pole group diameter to the inner diameter of the steel shell is 98%-99.5%. While ensuring that the battery cell has a high energy density, it is prevented that the pole group occupies too much space inside the steel shell, which may cause the steel shell to be easily broken.

[0053] It is worth noting that the ratio of the diameter of the pole group to the inner diameter of the steel shell is the assembly ratio of the battery cell, that is, in this embodiment, the assembly ratio is 98%-99.5%.

[0054] It should be further explained that if the assembly ratio of the battery cell is too small, the internal space of the steel shell cannot be fully utilized, and it is not easy to increase the energy density of the battery cell; if the assembly ratio of the battery cell is too large, the steel shell of the battery cell may easily rupture when the battery cell is charged, and the safety performance of the battery cell is low.

[0055] In one embodiment, the thickness of the steel shell is 0.38 mm to 0.55 mm, so as to ensure that the steel shell has sufficient strength while preventing the steel shell from being too thick and causing the battery cell to be too heavy.

[0056] It is worth mentioning that if the thickness of the steel shell is too small, the structural strength of the steel shell itself is poor, and the steel shell is easily broken when the battery cell is charged; if the thickness of the steel shell is too large, the weight of the steel shell itself is large, which makes the overall weight of the battery cell too large, making it difficult to achieve lightweight battery cells.

[0057] It should be noted that during the production of battery cells, the battery cells need to be divided into different capacities. During the division, a sleeve is added to the periphery of the battery cell, and the inner diameter of the sleeve is 0-0.5 mm larger than the diameter of the battery cell, so as to evenly distribute the stress after the battery cell expands. Furthermore, the sleeve can be an aluminum alloy sleeve.

[0058] Table 1 shows the specific conditions of different battery cell embodiments and comparative examples, wherein the embodiments refer to battery cells that meet the requirements of the embodiments, and correspondingly, the comparative examples refer to battery cells that do not meet the requirements of the embodiments.

[0059] Table 1: Battery cell information of the embodiment and the comparative example

[0060]

[0061] As shown in Table 1, the battery cell shown in Example 1 uses high-nickel ternary material Ni95 as the positive electrode active material, 27% silicon-carbon and artificial graphite composite material as the negative electrode active material, 6μ copper foil, 12μ aluminum foil, 70 windings, 99.2% assembly ratio, and 0.4mm steel shell thickness. The energy density of the battery cell reaches 350wh / kg, and the steel shell does not break when the battery cell is fully charged.

[0062] Relative to Example 1, please refer to Comparative Example 1 in Table 1. The battery shown in Comparative Example 1 is relative to the battery shown in Example 1. The negative electrode active material uses 5% silicon-carbon and artificial graphite composite materials. The other setting conditions are the same as those in Example 1, that is, the positive electrode active material uses high-nickel ternary material Ni95, the copper foil uses 6μ thick copper foil, the aluminum foil uses 12μ thick aluminum foil, the number of windings is 70, the assembly ratio is 99.2%, and the steel shell thickness is 0.4mm. Although the steel shell of the battery shown in Comparative Example 1 does not break after full charging, the energy density of the battery is only 260wh / kg.

[0063] As shown in Table 1, the battery cell shown in Example 2 uses high-nickel ternary material Ni90 as the positive electrode active material, 30% silicon-carbon and artificial graphite composite material as the negative electrode active material, 6μ thick copper foil, 12μ thick aluminum foil, 68 turns, 99% assembly ratio, and 0.4mm thickness of the steel shell. The energy density of the battery cell reaches 350wh / kg, and the steel shell does not break when the battery cell is fully charged.

[0064] Relative to Example 2, please refer to Comparative Example 2 in Table 1. The battery cell shown in Comparative Example 2 has 90 winding turns relative to the battery cell shown in Example 2, and the other setting conditions are the same as those in Example 2, that is, the positive electrode active material uses high-nickel ternary material Ni90, the negative electrode active material uses 30% silicon-carbon and artificial graphite composite materials, the copper foil uses 6μ thick copper foil, the aluminum foil uses 12μ thick aluminum foil, the assembly ratio is 99%, and the steel shell thickness is 0.4mm. Although the battery cell energy density of Comparative Example 2 reaches 350wh / kg, the steel shell of the battery cell is cracked when it is fully charged.

[0065] As shown in Table 1, the battery cell shown in Example 3 uses high-nickel ternary material Ni93 as the positive electrode active material, 30% silicon oxide and artificial graphite composite material as the negative electrode active material, 6μ thick copper foil, 12μ thick aluminum foil, 67 turns, 99% assembly ratio, and 0.5mm thickness of the steel shell. The energy density of the battery cell reaches 350wh / kg, and the steel shell does not break when the battery cell is fully charged.

[0066] Relative to Example 3, please refer to Comparative Example 3 in Table 1. The battery cell shown in Comparative Example 3 has an assembly ratio of 99.7% relative to the battery cell shown in Example 3, and the other setting conditions are the same as those in Example 3, that is, the positive electrode active material uses high-nickel ternary material Ni93, the negative electrode active material uses 30% silicon oxide and artificial graphite composite material, the copper foil uses 6μ thick copper foil, the aluminum foil uses 12μ thick aluminum foil, the number of windings is 67, and the steel shell thickness is 0.5mm. Although the battery cell energy density of Comparative Example 3 reaches 350wh / kg, the steel shell of the battery cell is cracked when it is fully charged.

[0067] As shown in Table 1, the battery cell shown in Example 4 uses high-nickel ternary material Ni92 as the positive electrode active material, 27% silicon-carbon and artificial graphite composite material as the negative electrode active material, 6μ thick copper foil, 12μ thick aluminum foil, 65 turns, 98.7% assembly ratio, and 0.4mm steel shell thickness. The energy density of the battery cell reaches 350wh / kg, and the steel shell does not break when the battery cell is fully charged.

[0068] As shown in Table 1, the battery cell shown in Example 5 uses high-nickel ternary material Ni95 as the positive electrode active material, 27% silicon oxide and artificial graphite composite material as the negative electrode active material, 6μ copper foil, 12μ aluminum foil, 70 windings, 98.8% assembly ratio, and 0.35mm steel shell thickness. The energy density of the battery cell reaches 350wh / kg, and the steel shell does not break when the battery cell is fully charged.

[0069] As shown in Table 1, the battery cell shown in Comparative Example 4 uses high-nickel ternary material Ni95 as the positive electrode active material, 5% silicon oxide and artificial graphite composite material as the negative electrode active material, 6μ thick copper foil, 12μ thick aluminum foil, 70 turns, 99.2% assembly ratio, and 0.4mm steel shell thickness. Although the steel shell of the battery cell does not break after full charge, the energy density of the battery cell does not meet 350wh / kg.

[0070] It is worth noting that when the silicon-carbon and graphite composite material or the silicon-oxygen and graphite composite material exceeds 30%, the steel shell of the battery cell will crack when it is fully charged.

[0071] It is worth noting that the battery cell of this embodiment is a large cylindrical battery cell with high energy density to prevent the steel shell from cracking.

[0072] According to an embodiment of the present invention, on the other hand, a battery pack is provided, comprising the above-mentioned battery cell.

[0073] Although the embodiments of the present invention are described in conjunction with the accompanying drawings, those skilled in the art may make various modifications and variations without departing from the spirit and scope of the present invention, and such modifications and variations are all within the scope defined by the appended claims.

Claims

1. A battery cell, characterized in that: include: A positive electrode, the positive electrode comprising a positive electrode active material layer, the positive electrode active material layer comprising a high-nickel ternary material layer; the thickness a of the positive electrode active material layer is 50 μm to 70 μm; The negative electrode comprises a negative electrode active material layer, wherein the negative electrode active material layer comprises a silicon-carbon composite and a graphite composite material layer, or a Si@SiOx@C composite and a graphite composite material layer; the thickness b of the negative electrode active material layer is 40 μm to 60 μm.

2. The battery cell according to claim 1, characterized in that: The high-nickel ternary material layer includes a Ni90 ternary material layer, a Ni91 ternary material layer, a Ni92 ternary material layer, a Ni93 ternary material layer, a Ni94 ternary material layer, a Ni95 ternary material layer, a Ni96 ternary material layer, a Ni97 ternary material layer, a Ni98 ternary material layer, or a Ni99 ternary material layer.

3. The battery cell according to claim 1 or 2, characterized in that: The positive electrode further includes a positive electrode current collector, which is an aluminum foil, and the positive electrode active material layer is coated on the positive electrode current collector.

4. The battery cell according to claim 3, characterized in that: The thickness c of the aluminum foil is 9 μm-15 μm.

5. The battery cell according to claim 1 or 2, characterized in that: The negative electrode further includes a negative electrode current collector, the negative electrode current collector is a copper foil, and the negative electrode active material layer is coated on the negative electrode current collector.

6. The battery cell according to claim 5, characterized in that: The thickness d of the copper foil is 3 μm-8 μm.

7. The battery cell according to claim 1 or 2, characterized in that: The battery cell includes an electrode group, which is formed by winding the positive electrode and the negative electrode. The number of winding turns of the positive electrode and the negative electrode is 60 to 70.

8. The battery cell according to claim 7, characterized in that: The battery core further comprises a steel shell, the pole group is arranged in the steel shell, and the ratio of the diameter of the pole group to the inner diameter of the steel shell is 98%-99.5%.

9. The battery cell according to claim 8, characterized in that: The shell thickness of the steel shell is 0.38mm-0.55mm.

10. A battery pack, characterized in that: A battery cell comprising the battery cell according to any one of claims 1 to 9.

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