Lithium-ion battery and electric device

Abstract

Provided in the present application are a lithium-ion battery and an electric device. The lithium-ion battery comprises a positive electrode sheet, a negative electrode sheet, a separator and an electrolyte, wherein the positive electrode sheet comprises a positive electrode current collector and a positive electrode film layer arranged on at least one surface of the positive electrode current collector, and the positive electrode film layer comprises a positive electrode active material and a sustained-release agent; the positive electrode active material comprises lithium-containing olivine phosphate; and the sustained-release agent comprises one or more of lithium nickel cobalt manganese oxide, a lithium-rich manganese-based material, lithium nickel cobalt oxide, lithium nickelate, lithium carbonate, lithium oxalate, Li5FeO4 and Li4SiO4, wherein based on the total weight of the positive electrode active material, the weight percentage of the sustained-release agent is less than or equal to 10%. According to the present application, a sustained-release agent is provided in the positive electrode film layer, such that the lithium loss of the positive electrode active material is compensated during cycling of the lithium-ion battery, thereby facilitating the improvement of the cycle life of the lithium-ion battery.

Description

Lithium-ion batteries and electrical equipment

[0001] This disclosure claims priority to Chinese patent application No. 202411527407X, filed on October 29, 2024, entitled “Lithium-ion Battery and Electrical Device”, which is incorporated herein by reference in its entirety. Technical Field

[0002] This invention relates to the field of lithium-ion battery technology, and more particularly to a lithium-ion battery and electrical equipment. Background Technology

[0003] This section provides only background information relevant to this application and is not necessarily prior art.

[0004] Lithium-ion batteries are currently the most widely used electrochemical energy storage devices in the energy field. However, over time, the energy density of lithium-ion batteries decreases, reducing their cycle life.

[0005] Therefore, this invention is proposed. Summary of the Invention

[0006] In view of the above-mentioned technical problems, this application provides a lithium-ion battery and an electrical device to solve the problem of low cycle life of lithium-ion batteries.

[0007] The first technical solution adopted in this application is: providing a lithium-ion battery, including a positive electrode, a negative electrode, a separator, and an electrolyte; the positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector, the positive electrode film layer including a positive active material and a slow-release agent; the positive active material includes a lithium-containing olivine phosphate; the slow-release agent includes one or more of lithium nickel cobalt manganese oxide, lithium-rich manganese-based material, lithium nickel cobalt oxide, lithium nickel oxide, lithium carbonate, lithium oxalate, Li5FeO4, and Li4SiO4; wherein, based on the total weight of the positive active material, the weight percentage of the slow-release agent is less than or equal to 10%.

[0008] In the technical solution of this application embodiment, the slow-release agent has poorer structural stability compared to the positive electrode active material. During the cycling process of the lithium-ion battery, not all the lithium ions released during delithiation can return to the delithiation site. The active lithium that does not return to the delithiation site of the slow-release agent remains in the positive electrode film layer as a reserve lithium in the positive electrode film layer, compensating for the lithium loss of the positive electrode active material, thereby helping to improve the cycle life of the lithium-ion battery. In addition, the slow-release agent of this application is slowly released at the plateau voltage of the positive electrode active material, without the need for special processing and activation conditions, which simplifies the application conditions of the slow-release agent.

[0009] In some implementations, the weight percentage of the sustained-release agent is 1% to 5% based on the weight of the positive electrode active material.

[0010] In the technical solution of this application embodiment, the weight ratio of the slow-release agent is within the above range, which can play the role of slowly releasing lithium ions, realize the slow replenishment of lithium to the positive electrode active material, improve the degradation of lithium-ion battery during cycling, and improve the cycle life of lithium-ion battery.

[0011] In some implementations, the weight percentage of the positive electrode active material is 88% to 99.5% based on the total weight of the positive electrode film.

[0012] In the technical solution of this application embodiment, the weight ratio of the positive electrode active material is within the above range, which is beneficial to improving the cycle life of the lithium-ion battery.

[0013] In some embodiments, the electrolyte includes additives; the additives account for less than or equal to 10% of the total weight of the electrolyte, and the additives include vinylene carbonate.

[0014] In the technical solution of this application embodiment, an additive is set in the electrolyte and the additive is used within the above-mentioned weight percentage range. The additive includes vinylene carbonate. During the cycling process of the lithium-ion battery, it is beneficial to improve the film formation effect of the negative electrode and reduce the side reactions between the negative electrode film layer and the electrolyte, thereby improving the cycle life of the lithium-ion battery.

[0015] In some embodiments, the electrolyte further includes one or more of the following features:

[0016] (1) The electrolyte includes lithium salt; based on the total weight of the electrolyte, the weight percentage of lithium salt is between 8% and 14%;

[0017] (2) The lithium salt includes one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI);

[0018] (3) The electrolyte also includes a solvent, which includes one or more of ethylene carbonate (EC), dimethyl carbonate (DMC), ethylene methyl carbonate (EMC), and diethyl carbonate (DEC);

[0019] (4) Based on the total weight of the electrolyte, the weight ratio of the solvent is 82% to 87%;

[0020] (5) The conductivity of the electrolyte is between 5 mS / cm and 20 mS / cm;

[0021] (6) The electrolyte injection coefficient is between 3.0 g / Ah and 3.5 g / Ah.

[0022] In the technical solution of this application embodiment, lithium salt is a compound containing lithium ions, which acts as a carrier of lithium ions in the electrolyte and migrates between the positive and negative electrodes. The concentration of lithium salt within the aforementioned range facilitates good liquid-phase transport of lithium ions, enabling the formation of a high-quality SEI film (solid electrolyte interface film) at the negative electrode and improving the cycle life of the battery.

[0023] The solvent in the electrolyte is used to dissolve the lithium salt, serving as a medium to support lithium-ion migration. This supports the formation of a high-quality SEI (solid electrolyte interphase) film at the negative electrode, thereby improving the battery's cycle life. The solvent's weight percentage within the aforementioned range supports the formation of a high-quality SEI film at the negative electrode, further enhancing the battery's cycle life.

[0024] When the conductivity of the electrolyte is within the above range, lithium ions can be transported faster inside the battery, resulting in a faster charge and discharge rate, which is beneficial for improving the fast-charging performance of lithium-ion batteries.

[0025] When the electrolyte injection coefficient is within the above range, the uniformity of electrolyte distribution inside the lithium-ion battery can be improved, which is beneficial to improving the cycle life of the lithium-ion battery.

[0026] In some embodiments, the compaction density of the positive electrode film is 2.5 g / cm³. 3 ~3.0g / cm 3 .

[0027] In the technical solution of this application embodiment, the compaction density of the positive electrode film layer is within the above-mentioned range, which is beneficial to improving the energy density of lithium-ion batteries.

[0028] In some embodiments, the areal density of the positive electrode film is 0.20 g / 1540.25 mm². 2 ~0.30g / 1540.25mm 2 .

[0029] In the technical solution of this application embodiment, the areal density of the positive electrode film is within the above-mentioned range, which is beneficial to improving the energy density of the lithium-ion battery.

[0030] In some embodiments, the negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector; the negative electrode film layer includes a negative electrode active material; the negative electrode active material includes one or both of natural graphite and artificial graphite.

[0031] In the technical solution of this application embodiment, the negative electrode active material includes artificial graphite. Artificial graphite has high purity and a structure suitable for the smooth insertion and extraction of lithium ions. Furthermore, artificial graphite has a highly ordered layered structure, which helps reduce volume expansion during charging and discharging, thus improving the cycle life of the lithium-ion battery. The negative electrode active material may also include natural graphite, which has the characteristics of large reserves and low cost, thus helping to reduce the manufacturing cost of lithium-ion batteries.

[0032] In some embodiments, the compaction density of the negative electrode film is 1.3 g / cm³. 3 ~1.7g / cm 3 .

[0033] In the technical solution of this application embodiment, the compaction density of the negative electrode film layer is within the above range, which is beneficial to improving the energy density of lithium-ion batteries.

[0034] In some embodiments, the areal density of the negative electrode film is 0.1 g / 1540.25 mm². 2 ~0.25g / 1540.25mm 2 .

[0035] In the technical solution of this application embodiment, the areal density of the negative electrode film layer is within the above range, which is beneficial to improving the energy density of lithium-ion batteries.

[0036] In some embodiments, the separator includes one or more of the following characteristics: the thickness of the separator is 5 μm to 7 μm, and the porosity of the separator is 35% to 45%.

[0037] In the technical solution of this application embodiment, the thickness of the separator is within the above-mentioned range, which is beneficial to improving the mechanical strength of the lithium-ion battery.

[0038] When the porosity of the separator is within the above range, the separator has a large electrolyte retention capacity, which reduces the barrier to lithium ion transport through the separator, thereby reducing the internal resistance of the cell and helping to improve the cycle life of the lithium-ion battery.

[0039] In some embodiments, the lithium-ion battery includes a housing that contains a positive electrode, a negative electrode, a separator, and an electrolyte; the housing includes a main body and an edge portion along the axial direction, and the opening of the housing is located at the end of the edge portion away from the main body; in a cross-section of the housing along the axial direction, the wall thickness of the main body is less than the wall thickness of the edge portion.

[0040] In the technical solution of this application embodiment, the wall thickness of the main body of the shell is less than the wall thickness of the edge, which is beneficial to increase the internal capacity of the shell, allowing it to accommodate larger battery cells and improve the capacity of the lithium-ion battery.

[0041] The second technical solution adopted in this application is: to provide an electrical device including any of the above-mentioned lithium-ion batteries.

[0042] Since the electrical equipment of this application includes the lithium-ion battery provided in this application, it has at least the same advantages as the lithium-ion battery. Attached Figure Description

[0043] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiments below. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0044] Figure 1 is a schematic diagram of the vehicle structure provided in an embodiment of this application;

[0045] Figure 2 is an exploded structural diagram of a lithium-ion battery provided in an embodiment of this application;

[0046] Figure 3 is an exploded structural diagram of a battery cell provided in an embodiment of this application;

[0047] Figure 4 is a schematic diagram of the structure of an asymmetric shell provided in an embodiment of this application;

[0048] Figure 5 is a schematic cross-sectional view of the asymmetric shell shown in Figure 4 along the AA direction;

[0049] Figure 6 is a schematic diagram of the structure of a symmetrical shell provided in another embodiment of this application.

[0050] Explanation of reference numerals in the attached diagram: 1000-Vehicle, 100-Lithium-ion battery, 200-Controller, 300-Motor, 10-Box, 20-Battery cell, 11-First part, 12-Second part, 21-End cap, 22-Housing shell, 23-Electrode assembly, 21a-Electrode terminal, 201-Opening, 202-Main body, 203-Edge part, 2021-First wall surface, 2022-Second wall surface, 2031-Third wall surface, 2032-Fourth wall surface, 2023-Fifth wall surface, 2024-Sixth wall surface. Detailed Implementation

[0051] The embodiments of the technical solution of this application will now be described in detail with reference to the accompanying drawings. These embodiments are only used to more clearly illustrate the technical solution of this application and are therefore merely examples, and should not be used to limit the scope of protection of this application.

[0052] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0053] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0054] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0055] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0056] Lithium-ion batteries need to meet the requirements of long life and high energy density. However, as time goes on, lithium-ion batteries suffer from severe degradation in the early stages, which reduces cycle life.

[0057] To address the aforementioned problems, the first technical solution adopted in this application is: to provide a lithium-ion battery, comprising a positive electrode, a negative electrode, a separator, and an electrolyte; the positive electrode comprises a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector, the positive electrode film layer comprising a positive electrode active material and a slow-release agent; the positive electrode active material comprises a lithium-containing olivine phosphate; the slow-release agent comprises one or more of lithium nickel cobalt manganese oxide, lithium-rich manganese-based materials, lithium nickel cobalt oxide, lithium nickel oxide, lithium carbonate, lithium oxalate, Li5FeO4, and Li4SiO4; wherein, based on the total weight of the positive electrode active material, the weight percentage of the slow-release agent is less than or equal to 10%.

[0058] In the technical solution of this application embodiment, the slow-release agent has poorer structural stability compared to the positive electrode active material. During the cycling process of the lithium-ion battery, not all the lithium ions released during delithiation can return to the delithiation site. The active lithium that does not return to the delithiation site of the slow-release agent remains in the positive electrode film layer as a reserve lithium in the positive electrode film layer, compensating for the lithium loss of the positive electrode active material, thereby helping to improve the cycle life of the lithium-ion battery. In addition, the slow-release agent of this application is slowly released at the plateau voltage of the positive electrode active material, without the need for special processing and activation conditions, which simplifies the application conditions of the slow-release agent.

[0059] In some implementations, the weight percentage of the sustained-release agent is 1% to 5% based on the weight of the positive electrode active material.

[0060] The weight percentage of the sustained-release agent can be 1%, 1.2%, 1.5%, 1.6%, 1.8%, 2%, 2.1%, 2.2%, 2.5%, 2.65%, 2.7%, 2.9%, 3%, 3.6%, 4.2%, 5%, or any range of two of the above values, such as 1%–2%, 2%–2.7%, 2.7%–3%, 1.8%–2.5%, etc.

[0061] In the technical solution of this application embodiment, the weight ratio of the slow-release agent is within the above range, which can play the role of slowly releasing lithium ions, realize the slow replenishment of lithium to the positive electrode active material, improve the degradation of lithium-ion battery during cycling, and improve the cycle life of lithium-ion battery.

[0062] In some implementations, the weight percentage of the positive electrode active material is 88% to 99.5% based on the total weight of the positive electrode film.

[0063] In the technical solution of this application embodiment, the weight ratio of the positive electrode active material is within the above range, which is beneficial to improving the cycle life of the lithium-ion battery.

[0064] Based on the total weight of the positive electrode film, the weight percentage of the positive electrode active material can be 88%, 90%, 91%, 92.5%, 93%, 94.2%, 95%, 97%, 98%, 99%, 99.5%, or a range of any two of the above values, such as 88%–94.2%, 94.2%–99.5%, 91%–97%, etc.

[0065] In some embodiments, the electrolyte includes additives; the additives account for less than or equal to 10% of the total weight of the electrolyte, and the additives include vinylene carbonate.

[0066] In the technical solution of this application embodiment, an additive is set in the electrolyte and the additive is used within the above-mentioned weight percentage range. The additive includes vinylene carbonate. During the cycling process of the lithium-ion battery, it is beneficial to improve the film formation effect of the negative electrode and reduce the side reactions between the negative electrode film layer and the electrolyte, thereby improving the cycle life of the lithium-ion battery.

[0067] The weight percentage of vinylene carbonate can be 0.02%, 0.1%, 0.2%, 0.5%, 1%, 2%, 2.5%, 3%, 4.5%, 5%, 5.5%, 6.6%, 7.5%, 8%, 10%, or any range of two of the above values, such as 0.02%–4.5%, 4.5%–7.5%, 7.5%–10%, 2.5%–7.5%, 5%–8%, etc.

[0068] In some embodiments, the electrolyte further includes one or more of the following features:

[0069] (1) The electrolyte includes lithium salt; based on the total weight of the electrolyte, the weight percentage of lithium salt is between 8% and 14%;

[0070] (2) The lithium salt includes one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI);

[0071] (3) The electrolyte also includes a solvent, which includes one or more of ethylene carbonate (EC), dimethyl carbonate (DMC), ethylene methyl carbonate (EMC), and diethyl carbonate (DEC);

[0072] (4) Based on the total weight of the electrolyte, the weight ratio of the solvent is 82% to 87%;

[0073] (5) The conductivity of the electrolyte is between 5 mS / cm and 20 mS / cm;

[0074] (6) The electrolyte injection coefficient is between 3.0 g / Ah and 3.5 g / Ah.

[0075] In the technical solution of this application embodiment, lithium salt is a compound containing lithium ions, which acts as a carrier of lithium ions in the electrolyte and migrates between the positive and negative electrodes. The concentration of lithium salt within the aforementioned range facilitates good liquid-phase transport of lithium ions, enabling the formation of a high-quality SEI film (solid electrolyte interface film) at the negative electrode and improving the cycle life of the battery.

[0076] The solvent in the electrolyte is used to dissolve the lithium salt, serving as a medium to support lithium-ion migration and enabling the formation of a high-quality SEI (solid electrolyte interphase) film at the negative electrode, thereby improving the battery's cycle life. The solvent's weight percentage within the aforementioned range supports the formation of a high-quality SEI film at the negative electrode, enhancing the battery's cycle life. The solvent's weight percentage can be 82%, 83.5%, 83.8%, 84%, 84.5%, 85%, 86.4%, 86.8%, 87%, etc., or any combination of two of the above values, for example, 82%–84.5%, 84.5%–87%, 83.5%–85%, 83.5%–84.5%, etc.

[0077] When the electrolyte conductivity is within the above-mentioned range, lithium ions are transported faster within the battery, resulting in a faster charge and discharge rate, which is beneficial for improving the fast-charging performance of lithium-ion batteries. The electrolyte conductivity can be 5 mS / cm, 6.8 mS / cm, 7.5 mS / cm, 8 mS / cm, 10 mS / cm, 14 mS / cm, 16 mS / cm, 18.5 mS / cm, 20 mS / cm, or any range of two of the above values, such as 5 mS / cm~10 mS / cm, 10 mS / cm~20 mS / cm, 6.8 mS / cm~14 mS / cm, 7.5 mS / cm~18.5 mS / cm, etc.

[0078] When the electrolyte filling coefficient is within the above range, the uniformity of electrolyte distribution within the lithium-ion battery can be improved, which is beneficial for increasing the cycle life of the lithium-ion battery. The electrolyte filling coefficient can be 3.0 g / Ah, 3.1 g / Ah, 3.2 g / Ah, 3.3 g / Ah, 3.4 g / Ah, 3.5 g / Ah, or any range of two of the above values, such as 3.0 g / Ah to 3.2 g / Ah, 3.2 g / Ah to 3.5 g / Ah, 3.1 g / Ah to 3.4 g / Ah, etc.

[0079] In some embodiments, the compaction density of the positive electrode film is 2.5 g / cm³. 3 ~3.0g / cm 3 .

[0080] In the technical solution of this application embodiment, the compaction density of the positive electrode film layer is within the above-mentioned range, which is beneficial to improving the energy density of lithium-ion batteries.

[0081] The compaction density of the positive electrode film can be 2.5 g / cm³. 3 2.6g / cm 3 2.7g / cm 3 2.8g / cm 3 2.9g / cm3 2.95g / cm 3 3.0g / cm 3 etc., or a range consisting of any two of the above values, for example, 2.5 g / cm³. 3 ~2.7g / cm 3 2.7g / cm 3 ~3.0g / cm 3 2.6g / cm 3 ~2.95g / cm 3 wait.

[0082] In some embodiments, the areal density of the positive electrode film is 0.20 g / 1540.25 mm². 2 ~0.30g / 1540.25mm 2 .

[0083] In the technical solution of this application embodiment, the areal density of the positive electrode film is within the above-mentioned range, which is beneficial to improving the energy density of the lithium-ion battery.

[0084] The areal density of the positive electrode film can be 0.20 g / 1540.25 mm. 2 0.22g / 1540.25mm 2 0.25g / 1540.25mm 2 0.265g / 1540.25mm 2 0.27g / 1540.25mm 2 0.275g / 1540.25mm 2 0.28g / 1540.25mm 2 0.286g / 1540.25mm 2 0.291g / 1540.25mm 2 0.30g / 1540.25mm 2 etc., or a range consisting of any two of the above values, for example, 0.20g / 1540.25mm. 2 ~0.27g / 1540.25mm 2 0.27g / 1540.25mm 2 ~0.286g / 1540.25mm 2 0.286g / 1540.25mm 2 ~0.3g / 1540.25mm 2 0.22g / 1540.25mm 2 ~0.275g / 1540.25mm 2 wait.

[0085] In some embodiments, the negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector; the negative electrode film layer includes a negative electrode active material; the negative electrode active material includes one or both of natural graphite and artificial graphite.

[0086] In the technical solution of this application embodiment, the negative electrode active material includes artificial graphite. Artificial graphite has high purity and a structure suitable for the smooth insertion and extraction of lithium ions. Furthermore, artificial graphite has a highly ordered layered structure, which helps reduce volume expansion during charging and discharging, thus improving the cycle life of the lithium-ion battery. The negative electrode active material may also include natural graphite, which has the characteristics of large reserves and low cost, thus helping to reduce the manufacturing cost of lithium-ion batteries.

[0087] In some embodiments, the compaction density of the negative electrode film is 1.3 g / cm³. 3 ~1.7g / cm 3 .

[0088] In the technical solution of this application embodiment, the compaction density of the negative electrode film layer is within the above range, which is beneficial to improving the energy density of lithium-ion batteries.

[0089] The compaction density of the negative electrode film can be 1.3 g / cm³. 3 1.32g / cm 3 1.35g / cm 3 1.38g / cm 3 1.4g / cm 3 1.45g / cm 3 1.5g / cm 3 1.56g / cm 3 1.62g / cm 3 1.68g / cm 3 1.7g / cm 3 etc., or a range consisting of any two of the above values, for example, 1.3 g / cm³. 3 ~1.4g / cm 3 1.4g / cm 3 ~1.56g / cm 3 1.56g / cm 3 ~1.7g / cm 3 1.35g / cm 3 ~1.62g / cm 3 wait.

[0090] In some embodiments, the areal density of the negative electrode film is 0.1 g / 1540.25 mm². 2 ~0.25g / 1540.25mm 2 .

[0091] In the technical solution of this application embodiment, the areal density of the negative electrode film layer is within the above range, which is beneficial to improving the energy density of lithium-ion batteries.

[0092] The areal density of the negative electrode film can be 0.1 g / 1540.25 mm. 2 0.16g / 1540.25mm 2 0.18g / 1540.25mm 2 0.2g / 1540.25mm 2 0.21g / 1540.25mm 2 0.22g / 1540.25mm 2 0.23g / 1540.25mm 2 0.24g / 1540.25mm 2 0.25g / 1540.25mm 2 etc., or a range consisting of any two of the above values, for example, 0.1g / 1540.25mm. 2 ~0.2g / 1540.25mm 2 0.2g / 1540.25mm 2 ~0.25g / 1540.25mm 2 0.16g / 1540.25mm 2 ~0.21g / 1540.25mm 2 0.18g / 1540.25mm 2 ~0.24g / 1540.25mm 2 wait.

[0093] In some embodiments, the separator includes one or more of the following characteristics: the thickness of the separator is 5 μm to 7 μm, and the porosity of the separator is 35% to 45%.

[0094] In the technical solution of this application embodiment, the thickness of the separator within the above-mentioned range is beneficial to improving the mechanical strength of the lithium-ion battery. The thickness of the separator can be 5μm, 5.2μm, 5.5μm, 5.6μm, 5.8μm, 6.0μm, 6.2μm, 6.3μm, 6.5μm, 6.8μm, 7.0μm, etc., or a range composed of any two of the above values, for example, 5μm~6.0μm, 6.0μm~7.0μm, 5.5μm~6.3μm, 5.6μm~6.5μm, etc.

[0095] When the porosity of the separator is within the aforementioned range, the separator retains a large amount of electrolyte, reducing the barrier to lithium-ion transport and thus lowering the internal resistance of the cell, which helps improve the cycle life of the lithium-ion battery. The porosity of the separator can be 35%, 35.5%, 36%, 37%, 37.8%, 38%, 38.5%, 40%, 41%, 42%, 45%, or any range of two of the above values, such as 35%–37%, 37%–38%, 38%–45%, 36%–41%, 37.8%–42%, etc.

[0096] In some embodiments, the lithium-ion battery includes a housing that contains a positive electrode, a negative electrode, a separator, and an electrolyte; the housing includes a main body and an edge portion along the axial direction, and the opening of the housing is located at the end of the edge portion away from the main body; in a cross-section of the housing along the axial direction, the wall thickness of the main body is less than the wall thickness of the edge portion.

[0097] Referring to FIG4, along the axial direction x of the housing, the housing 22 includes a main body portion 202 and an edge portion 203, and the opening 201 of the housing 22 is located at the end of the edge portion 203 away from the main body portion 202; in the cross section of the housing 22 along the axial direction x, the wall thickness of the main body portion 202 is less than the wall thickness of the edge portion 203.

[0098] In the technical solution of this application embodiment, the wall thickness of the main body 202 of the housing 22 is less than the wall thickness of the edge portion 203, which is beneficial to increase the internal capacity of the housing 22, allowing it to accommodate larger battery cells and improve the capacity of the lithium-ion battery.

[0099] The second technical solution adopted in this application is: to provide an electrical device including any of the above-mentioned lithium-ion batteries.

[0100] The electrical devices provided by the embodiments of this application have at least the same advantages as lithium-ion batteries, which can improve the battery life of the electrical devices.

[0101] For ease of explanation, the following embodiments will be described using a vehicle 1000 as an example of an electrical device according to an embodiment of this application.

[0102] Please refer to Figure 1, which is a structural schematic diagram of a vehicle provided in an embodiment of this application.

[0103] Referring to Figure 1, vehicle 1000 can be a gasoline-powered vehicle, a natural gas-powered vehicle, or a new energy vehicle. New energy vehicles can be pure electric vehicles, hybrid electric vehicles, or range-extended electric vehicles, etc. A lithium-ion battery 100 is installed inside vehicle 1000, which can be located at the bottom, front, or rear of vehicle 1000. The lithium-ion battery 100 can be used to power vehicle 1000; for example, it can serve as the operating power source for vehicle 1000. Vehicle 1000 may also include a controller 200 and a motor 300. The controller 200 controls the lithium-ion battery 100 to supply power to the motor 300, for example, to meet the power needs of vehicle 1000 during startup, navigation, and driving.

[0104] In some embodiments of this application, the lithium-ion battery 100 can not only serve as the operating power source for the vehicle 1000, but also as the driving power source for the vehicle 1000, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 1000.

[0105] Please refer to Figure 2, which is a schematic diagram of the exploded structure of a lithium-ion battery provided in an embodiment of this application.

[0106] Referring to Figure 2, the lithium-ion battery 100 includes a housing 10 and a battery cell 20, with the battery cell 20 housed within the housing 10. The housing 10 provides a space for the battery cell 20 and can have various structures. In some embodiments, the housing 10 may include a first portion 11 and a second portion 12, which overlap each other, collectively defining a space for accommodating the battery cell 20. The second portion 12 can be a hollow structure with one open end, and the first portion 11 can be a plate-like structure, covering the open side of the second portion 12 so that the first portion 11 and the second portion 12 together define the space. Alternatively, both the first portion 11 and the second portion 12 can be hollow structures with one open side, with the open side of the first portion 11 covering the open side of the second portion 12. Of course, the housing 10 formed by the first portion 11 and the second portion 12 can have various shapes, such as a cylinder, a cuboid, etc.

[0107] In the lithium-ion battery 100, there can be multiple battery cells 20, which can be connected in series, parallel, or in a mixed manner. A mixed connection means that multiple battery cells 20 are connected in both series and parallel configurations. Multiple battery cells 20 can be directly connected in series, parallel, or in a mixed manner, and then the entire assembly of the multiple battery cells 20 is housed within the casing 10. Alternatively, the lithium-ion battery 100 can also consist of multiple battery cells 20 first connected in series, parallel, or in a mixed manner to form a battery module, and then these battery modules are connected in series, parallel, or in a mixed manner to form a whole, which is also housed within the casing 10. The lithium-ion battery 100 may also include other structures; for example, it may include a busbar component for electrical connection between the multiple battery cells 20.

[0108] Among them, the battery cell 20 can be in the form of a cylinder, a flat shape, a cuboid, or other shapes.

[0109] Please refer to Figure 3, which is an exploded structural diagram of a battery cell provided in an embodiment of this application.

[0110] Referring to Figure 3, the battery cell 20 refers to the smallest unit that makes up the lithium-ion battery 100. The battery cell 20 includes an end cap 21, a housing 22, an electrode assembly 23, and other functional components.

[0111] End cap 21 refers to a component that covers the opening of housing 22 to isolate the internal environment of battery cell 20 from the external environment. The shape of end cap 21 can be adapted to the shape of housing 22 to fit it. Optionally, end cap 21 can be made of a material with certain hardness and strength (such as aluminum alloy), so that end cap 21 is not easily deformed under pressure and impact, giving battery cell 20 higher structural strength and improved safety performance. Functional components such as electrode terminals 21a can be provided on end cap 21. Electrode terminals 21a can be used for electrical connection with electrode assembly 23 for outputting or inputting electrical energy to battery cell 20. In some embodiments, end cap 21 can also be provided with a pressure relief mechanism for releasing internal pressure when the internal pressure or temperature of battery cell 20 reaches a threshold. The material of end cap 21 can also be various, including but not limited to copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc. In some embodiments, an insulating element may be provided on the inner side of the end cap 21. The insulating element can be used to isolate the electrical connection components within the housing 22 from the end cap 21 to reduce the risk of short circuits. For example, the insulating element may be made of plastic, rubber, etc.

[0112] The housing 22 is a component used to cooperate with the end cap 21 to form the internal environment of the battery cell 20. This internal environment can accommodate the electrode assembly 23, electrolyte, and other components. The housing 22 and the end cap 21 can be independent components. An opening can be provided on the housing 22, and the end cap 21 closes the opening to form the internal environment of the battery cell 20. Alternatively, the end cap 21 and the housing 22 can be integrated. Specifically, the end cap 21 and the housing 22 can form a common connecting surface before other components are inserted into the housing. When it is necessary to encapsulate the interior of the housing 22, the end cap 21 closes the housing 22. The housing 22 can be of various shapes and sizes, such as cuboid, cylindrical, hexagonal prism, etc. Specifically, the shape of the housing 22 can be determined according to the specific shape and size of the electrode assembly 23. The housing 22 can be made of various materials, including but not limited to copper, iron, aluminum, stainless steel, aluminum alloy, and plastic.

[0113] Electrode assembly 23 is the component in the battery cell 20 where electrochemical reactions occur. The casing 22 may contain one or more electrode assemblies 23. The electrode assembly 23 is mainly formed by winding or stacking positive and negative electrode sheets, and typically a separator is provided between the positive and negative electrode sheets. The portions of the positive and negative electrode sheets containing active material constitute the main body of the cell assembly, while the portions of the positive and negative electrode sheets without active material each constitute a tab. The positive and negative tabs may be located together at one end of the main body or separately at both ends of the main body. During the charging and discharging process of the battery cell 20, the positive and negative active materials react with the electrolyte, and the tabs connect to the electrode terminals to form a current loop.

[0114] In one embodiment, the positive electrode film layer further includes a positive electrode conductive agent and a positive electrode binder.

[0115] A positive electrode conductive agent imparts conductivity to the positive electrode. The positive electrode conductive agent can include any conductive material, as long as it does not cause a chemical change. Positive electrode conductive agents include, but are not limited to: carbon-based materials (e.g., natural graphite, conductive graphite, carbon black, acetylene black, Ketjen black, carbon fiber, etc.), metal-based materials (e.g., metal powders, metal fibers, such as copper, nickel, aluminum, silver, etc.), conductive polymers (e.g., polyphenylene derivatives), and mixtures thereof.

[0116] Positive electrode binders improve the adhesion stability of the positive electrode film and reduce the probability of powder shedding. Positive electrode binders may include one or more of polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), and polytetrafluoroethylene (PTFE).

[0117] In some embodiments, the negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector.

[0118] In some embodiments, the negative electrode film layer includes a negative electrode active material. The negative electrode active material may be any negative electrode active material known in the art for use in batteries. As an example, the negative electrode active material may include, but is not limited to, at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. Silicon-based materials may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. These negative electrode active materials may be used alone or in combination of two or more.

[0119] In some embodiments, the negative electrode film layer may further include a negative electrode binder, a negative electrode conductive agent, and other optional additives. For example, the negative electrode conductive agent may be one or more of superconducting carbon, carbon black (examples may include acetylene black, Ketjen black, Super P, etc.), carbon dots, carbon nanotubes, graphene, and carbon nanofibers. For example, the negative electrode binder may be one or more of styrene-butadiene rubber (SBR), water-based acrylic resin, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), ethylene-vinyl acetate copolymer (EVA), polyacrylic acid (PAA), lithium-ionized polyacrylic acid (PAALi), carboxymethyl cellulose (CMC), polyvinyl alcohol (PVA), and polyvinyl butyral (PVB). For example, other optional additives may be thickeners and dispersants (e.g., sodium carboxymethyl cellulose CMC-Na) and PTC thermistor materials.

[0120] In some embodiments, the material of the separator can be selected from one or more of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film. When the separator is a multi-layer composite film, the materials of each layer can be the same or different.

[0121] The beneficial effects of this application are further illustrated below with reference to the embodiments.

[0122] To make the technical problems, technical solutions, and beneficial effects solved by the embodiments of this application clearer, the following will provide a more detailed description in conjunction with the embodiments and accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. The following description of at least one exemplary embodiment is merely illustrative. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0123] Example 1

[0124] The preparation of a lithium-ion battery includes the following steps:

[0125] (1) Provide positive electrode: LiFePO4 active material, sustained-release agent LiNi 0.8 Co 0.1 Mn 0.1 O2, Super-P, and polyvinylidene fluoride powder were mixed in a mass ratio of 96%:2%:1%:1% to prepare a slurry with a solid solution content of 45%. The slurry was then applied to one side of aluminum foil using a coating machine and rolled. Finally, the prepared positive electrode sheet was dried in a 70℃ vacuum drying oven for later use. The areal density of the positive electrode sheet film was 0.30 g / 1540.25 mm². 2 The compaction density of the positive electrode film is 2.6 g / cm³. 3 .

[0126] (2) Providing the negative electrode sheet: A slurry with a solid solution content of 69% was prepared by mixing artificial graphite (Gr), conductive agent (CNT), and binder (CMC) powder in a mass ratio of 96%:2%:2%. Subsequently, the slurry was applied to one side of copper foil using a coating machine and rolled. Finally, the prepared negative electrode sheet was dried in a 70℃ vacuum drying oven for later use. The areal density of the negative electrode slurry and negative electrode sheet film was 0.15 g / 1540.25 mm². 2 The compaction density of the negative electrode film is 1.65 g / cm³. 3 .

[0127] (3) Provide a separator: The thickness of the porous polymer separator is 7 μm and the porosity of the separator is 40%.

[0128] (4) Provide electrolyte: lithium salt is LiPF6, solvent is DEC / EC / EMC (volume ratio is 1:2:7), additive is vinylene carbonate, wherein the weight ratio of solvent: lithium salt: additive is 85%:12%:3%; the conductivity of electrolyte is 10.3mS / cm.

[0129] (5) Following the conventional liquid injection process, vacuum is first applied followed by liquid injection, with an injection coefficient of 3.3 g / Ah, ensuring thorough wetting and absorption to provide channels for ion migration. The electrodes are placed in the order of "separator-negative electrode-separator-positive electrode," with one end of the positive electrode, negative electrode, and two separators fixed to the discharge roller, and the other ends stacked together and fixed to the winding shaft. A motor is used to rotate the winding shaft, winding the positive electrode, negative electrode, and two separators to obtain lithium-ion battery 1, which has an asymmetric structure.

[0130] Referring to Figures 4 and 5, Figure 4 shows an asymmetric lithium-ion battery, and Figure 5 is a cross-sectional view of the asymmetric casing shown in Figure 4 along the AA direction. The asymmetric lithium-ion battery includes a main body 202 and an edge portion 203. The main body 202 includes a first wall surface 2021 and a second wall surface 2022. The first wall surface 2021 has a first wall thickness of 0.8 mm, and the second wall surface 2022 has a second wall thickness of 0.6 mm. The edge portion 203 has a third wall surface 2031 and a fourth wall surface 2032. The third wall surface 2031 has a third wall thickness of 0.9 mm, and the fourth wall surface 2032 has a fourth wall thickness of 0.7 mm.

[0131] Example 2

[0132] Similar to Example 1, the difference is:

[0133] The positive electrode in step (1) of Example 1 is adjusted to contain: LiFePO4 active material and LiNi slow-release agent. 0.8 Co 0.1 Mn 0.1 O2, Super-P, and polyvinylidene fluoride powder were mixed in a mass ratio of 97%:1%:1%:1% to prepare a slurry with a solid solution content of 45%.

[0134] Step (5) of Example 1 is adjusted as follows: following the conventional liquid injection process, vacuum is first applied followed by liquid injection, with an injection coefficient of 3.3 g / Ah, ensuring full immersion and absorption to provide a channel for ion migration. The electrodes are placed in the order of "separator-negative electrode-separator-positive electrode," with one end of the positive electrode, negative electrode, and two separators fixed to the discharge roller, and the other ends stacked together and fixed to the winding shaft. The winding shaft is rotated using a motor to wind the positive electrode, negative electrode, and two separators, resulting in lithium-ion battery 2, which has a symmetrical casing structure.

[0135] Referring to Figure 6, the casing of the symmetrical lithium-ion battery has a uniform thickness. The casing includes a fifth wall 2023 and a sixth wall 2024. In Embodiment 2, the fifth wall thickness of the fifth wall 2023 is 0.9 mm, and the sixth wall thickness of the sixth wall 2024 is 0.7 mm.

[0136] Example 3

[0137] Similar to Example 1, the difference is:

[0138] The positive electrode in step (1) of Example 1 is adjusted to contain: LiFePO4 active material and LiNi slow-release agent. 0.8 Co 0.1 Mn 0.1 A slurry with a solid solution content of 45% was prepared by mixing O2, Super-P, and polyvinylidene fluoride powder in a mass ratio of 93%:5%:1%:1%.

[0139] Example 4

[0140] Similar to Example 1, the difference is:

[0141] The positive electrode in step (1) of Example 1 is adjusted to contain: LiFePO4 active material and LiNi slow-release agent. 0.8 Co 0.1 Mn 0.1 O2, Super-P, and polyvinylidene fluoride powder were mixed in a mass ratio of 88%:10%:1%:1% to prepare a slurry with a solid solution content of 45%.

[0142] Example 5

[0143] Similar to Example 1, the difference is:

[0144] The positive electrode sheet provided in step (1) of Example 1 is adjusted to be: LiFePO4 active material, Li2CO3 slow release agent, Super-P, and polyvinylidene fluoride powder are prepared into a slurry with a solid solution content of 45% in a mass ratio of 96%:2%:1%:1%.

[0145] The negative electrode sheet provided in step (2) of Example 1 is adjusted to have an areal density of 0.2 g / 1540.25 mm for the negative electrode slurry and negative electrode sheet film. 2 .

[0146] Example 6

[0147] Similar to Example 1, the difference is:

[0148] The positive electrode sheet provided in step (1) of Example 1 is adjusted to be: LiFePO4 active material, slow release agent Li1.2Mn0.54Ni0.13Co0.13O2, Super-P, and polyvinylidene fluoride powder are prepared in a mass ratio of 96%:2%:1%:1% to prepare a slurry with a solid solution content of 45%.

[0149] The electrolyte provided in step (4) of Example 1 was adjusted to be: lithium salt LiPF6, solvent DEC / EC / EMC (volume ratio 1:2:7), and additive vinylene carbonate, wherein the weight ratio of solvent:lithium salt:additive was 85%:5%:10%; the conductivity of the electrolyte was 11.2 mS / cm.

[0150] Example 7

[0151] Similar to Example 1, the difference is:

[0152] The positive electrode sheet provided in step (1) of Example 1 is adjusted to be: LiFePO4 active material, slow release agent Li1.26Mn0.592Co0.074Ni0.074O2, Super-P, and polyvinylidene fluoride powder are prepared into a slurry with a solid solution content of 45% in a mass ratio of 96%:2%:1%:1%.

[0153] The electrolyte provided in step (4) of Example 1 was adjusted to be: lithium salt LiPF6, solvent DEC / EC / EMC (volume ratio 1:2:7), and additive vinylene carbonate, wherein the weight ratio of solvent:lithium salt:additive was 85%:8%:7%; the conductivity of the electrolyte was 9.8 mS / cm.

[0154] Example 8

[0155] Similar to Example 1, the difference is:

[0156] The electrolyte provided in step (4) of Example 1 was adjusted to be: lithium salt LiPF6, solvent DEC / EC / EMC (volume ratio 1:2:7), and additive vinylene carbonate, wherein the weight ratio of solvent:lithium salt:additive was 85%:14%:1%; the conductivity of the electrolyte was 10.9 mS / cm.

[0157] Example 9

[0158] Similar to Example 1, the difference is:

[0159] The positive electrode sheet provided in Example (1) was adjusted as follows: the prepared positive electrode sheet was dried in a vacuum drying oven at 70°C for later use, and the areal density of the positive electrode sheet film was 0.20 g / 1540.25 mm. 2 The compaction density of the positive electrode film is 2.5 g / cm³. 3 .

[0160] The negative electrode sheet provided in Example (1) was adjusted to have an areal density of 0.1 g / 1540.25 mm. 2 .

[0161] Example 10

[0162] Similar to Example 1, the difference is:

[0163] The positive electrode sheet in step (1) of Example 1 was adjusted as follows: the prepared positive electrode sheet was dried in a vacuum drying oven at 70°C for later use. The areal density of the positive electrode sheet film was 0.20 g / 1540.25 mm. 2 The compaction density of the positive electrode film is 3 g / cm³. 3 .

[0164] The negative electrode sheet of Example (1) was adjusted to have an areal density of 0.1 g / 1540.25 mm. 2 .

[0165] Example 11

[0166] Similar to Example 1, the difference is:

[0167] The positive electrode sheet in step (1) of Example 1 was adjusted to be: LiFePO4 active material, Li5FeO4 slow release agent, Super-P, and polyvinylidene fluoride powder were prepared into a slurry with a solid solution content of 45% in a mass ratio of 96%:2%:1%:1%.

[0168] The negative electrode sheet in step (2) of Example 1 is adjusted to have a compaction density of 1.3 g / cm³. 3 .

[0169] Step (4) of Example 1 is adjusted as follows: the lithium salt is LiPF4, the solvent is DEC / EC / EMC (volume ratio is 1:2:7), and the additive is vinylene carbonate, wherein the weight ratio of solvent: lithium salt: additive is 85%:12%:3%; the conductivity of the electrolyte is 11.3 mS / cm.

[0170] Example 12

[0171] Similar to Example 1, the difference is:

[0172] The positive electrode sheet in step (1) of Example 1 was adjusted to be: LiFePO4 active material, Li4SiO4 slow release agent, Super-P, and polyvinylidene fluoride powder were prepared into a slurry with a solid solution content of 45% in a mass ratio of 96%:2%:1%:1%.

[0173] The negative electrode sheet in step (2) of Example 1 was adjusted to have a compaction density of 1.7 g / cm³. 3 .

[0174] Step (4) of Example 1 is adjusted as follows: the lithium salt is LiPF4, the solvent is DEC / EC / EMC (volume ratio is 1:2:7), and the additive is vinylene carbonate, wherein the weight ratio of solvent: lithium salt: additive is 87%:10%:3%; the conductivity of the electrolyte is 10.1 mS / cm.

[0175] Comparative Example 1

[0176] Similar to Example 1, the difference is:

[0177] The positive electrode sheet in step (1) of Example 1 is adjusted as follows: no slow-release agent is added, and a slurry with a solid solution content of 45% is prepared by mixing LiFePO4 active material, Super-P and polyvinylidene fluoride powder in a mass ratio of 98%:1%:1%.

[0178] Comparative Example 2

[0179] Similar to Example 1, the difference is:

[0180] The positive electrode in step (1) of Example 1 is adjusted to contain: LiFePO4 active material and LiNi slow-release agent. 0.8 Co 0.1 Mn 0.1 A slurry with a solid solution content of 45% was prepared by mixing O2, Super-P, and polyvinylidene fluoride powder in a mass ratio of 78%:20%:1%:1%.

[0181] The lithium-ion batteries prepared in Examples 1-12 and Comparative Examples 1 and 2 were tested for cycle life, energy density, and fast charging performance. The test results are shown in Table 1.

[0182] (1) Cyclic life test:

[0183] The prepared lithium-ion battery was charged at 25℃ with a constant current of 1C to the charging cutoff voltage of 3.8V, then charged with a constant voltage to a current of 0.05C, allowed to stand for 5 minutes, and then discharged at a constant current of 0.33C to the discharge cutoff voltage of 2.0V. Its actual capacity was recorded as C0. Then, it was discharged at a rate of 1C followed by a discharge at 0.33C, and the discharge capacity C of each cycle was recorded. n Until the battery's capacity retention rate reaches 80%, capacity retention rate = C n / C0*100%, records the number of cycles at this point. The more cycles, the better the cycle performance of the secondary battery.

[0184] (2) Charging performance test:

[0185] At 25°C, the prepared lithium-ion battery was charged at a constant current of 0.33C to the charging cutoff voltage of 3.8V, then charged at a constant voltage to a current of 0.05C, left to stand for 5 minutes, and then discharged at a constant current of 0.33C to the discharge cutoff voltage of 2.0V. Its actual capacity was recorded as C0.

[0186] Then, the lithium-ion battery was sequentially charged at constant currents of 0.5C0, 1C0, 1.5C0, 2C0, 2.5C0, 3C0, 3.5C0, 4C0, and 4.5C0 until the full-cell charging cutoff voltage or the 0V negative electrode cutoff potential (whichever comes first). After each charge, it was discharged at 1C0 until the full-cell discharge cutoff voltage. The negative electrode potentials corresponding to 10%, 20%, 30%, 40%, 50%, 60%, 70%, and 80% SOC (State of Charge) were recorded at different charging rates. The rate-negative electrode potential curves under different SOC states were plotted. After linear fitting, the charging rate corresponding to the negative electrode potential of 0V under different SOC states was obtained. This charging rate is the charging window under that SOC state, denoted as C. 10％SOC C 20％SOC C 30％SOC C 40％SOC C 50％SOC C 60％SOC C 70％SOC C 80％SOC According to the formula (60 / C) 10％SOC +60 / C 20％SOC +60 / C 30％ SOC +60 / C 40％SOC +60 / C 50％SOC +60 / C 60％SOC +60 / C 70％SOC +60 / C 80％SOC The charging time T for the secondary battery to charge from 10% SOC to 80% SOC is calculated by multiplying the value by 10%. The shorter the charging time, the better the charging performance.

[0187] (3) Energy density test:

[0188] The lithium-ion batteries prepared in each embodiment and comparative example were placed at 25°C and charged to 3.8V with a constant current of 0.33C, allowed to stand for 1 minute, and then charged to 0.05C with a constant voltage of 3.8V, allowed to stand for 30 minutes. They were then discharged to 2.0V with a constant current of 0.33C, and the discharge capacity A0 was recorded at this point, in Ah. The length, width, and height of the outer surface of the lithium-ion battery were measured using calipers, and the volume of a single cell V0 was calculated, in L. The volumetric energy density of the lithium-ion battery, VED, is calculated as (A0 × discharge plateau voltage of the lithium-ion battery) / V0, in Wh / L. It should be understood that the discharge plateau voltage of lithium-ion batteries with different positive and negative electrode systems varies, and can be obtained by testing their charge-discharge curves or referring to existing literature.

[0189] Table 1. Performance test results of lithium-ion batteries in the examples and comparative examples.

[0190] Table 1 (continued) Performance test results of lithium-ion batteries in the examples and comparative examples

[0191] Table 1 (continued) Performance test results of lithium-ion batteries in the examples and comparative examples

[0192] As shown in Table 1, the lithium-ion batteries of Examples 1-12 all contained a slow-release agent with a weight percentage of less than or equal to 10% in the positive electrode film layer, while the lithium-ion battery of Comparative Example 1 did not contain a slow-release agent. The cycle life of the lithium-ion batteries of Examples 1-12 was higher than that of Comparative Example 1. Among them, the lithium-ion battery of Comparative Example 2 contained a slow-release agent with a weight percentage of more than 10% in the positive electrode film layer, and its cycle life was lower than that of the lithium-ion batteries of Examples 1-12. This indicates that the lithium-ion batteries of this application contain a slow-release agent with a weight percentage of less than or equal to 10% in the positive electrode film layer. Compared with the positive electrode active material, the slow-release agent has poor structural stability. During the cycling process of the lithium-ion battery, not all the lithium ions released by delithiation can return to the delithiation site. The active lithium that does not return to the delithiation site of the slow-release agent remains in the positive electrode film layer as a stock lithium of the positive electrode film layer, compensating for the lithium loss of the positive electrode active material, thereby helping to improve the cycle life of the lithium-ion battery.

[0193] In the several embodiments provided in this application, it should be understood that the disclosed systems, apparatuses, and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces, or indirect coupling or communication connection between apparatuses or units, and may be electrical, mechanical, or other forms.

[0194] Furthermore, the functional units in the various embodiments of this application can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0195] The above description is merely an embodiment of this application and does not limit the patent scope of this application. Any equivalent structural or procedural transformations made using the content of this application's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of this application.

Claims

A lithium-ion battery, wherein, The device includes a positive electrode, a negative electrode, a separator, and an electrolyte. The positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector. The positive electrode film layer includes a positive electrode active material and a slow-release agent. The positive electrode active material includes a lithium-containing olivine phosphate. The slow-release agent includes one or more of lithium nickel cobalt manganese oxide, lithium-rich manganese-based materials, lithium nickel cobalt oxide, lithium nickel oxide, lithium carbonate, lithium oxalate, Li5FeO4, and Li4SiO4. The weight percentage of the slow-release agent is less than or equal to 10% based on the weight of the positive electrode active material. According to claim 1, the lithium-ion battery, wherein, Based on the weight of the positive electrode active material, the weight percentage of the sustained-release agent is between 1% and 5%. The lithium-ion battery according to claim 1 or 2, wherein, Based on the total weight of the positive electrode film, the weight percentage of the positive electrode active material is 88% to 99.5%. The lithium-ion battery according to any one of claims 1 to 3, wherein, The electrolyte includes additives; based on the total weight of the electrolyte, the weight percentage of the additives is less than or equal to 10%, and the additives include vinylene carbonate. The lithium-ion battery according to any one of claims 1 to 4, wherein, The electrolyte further includes one or more of the following characteristics: (1) The electrolyte includes lithium salt; based on the total weight of the electrolyte, the weight percentage of the lithium salt is between 8% and 14%; (2) The lithium salt includes one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, and bis(trifluoromethanesulfonyl)imide; (3) The electrolyte further includes a solvent, which includes one or more of ethylene carbonate, dimethyl carbonate, ethylene methyl carbonate, and diethyl carbonate; (4) Based on the total weight of the electrolyte, the weight percentage of the solvent is between 82% and 87%; (5) The conductivity of the electrolyte is between 5 mS / cm and 20 mS / cm; (6) The electrolyte injection coefficient is between 3.0 g / Ah and 3.5 g / Ah. The lithium-ion battery according to any one of claims 1 to 5, wherein, The compaction density of the positive electrode film is 2.5 g / cm³. 3 ~3.0g / cm 3 . The lithium-ion battery according to any one of claims 1 to 6, wherein, The areal density of the positive electrode film is 0.20 g / 1540.25 mm. 2 ~0.30g / 1540.25mm 2 . The lithium-ion battery according to any one of claims 1 to 7, wherein, The negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector; the negative electrode film layer includes a negative electrode active material; the negative electrode active material includes one or both of natural graphite and artificial graphite. The lithium-ion battery according to claim 8, wherein, The compaction density of the negative electrode film is 1.3 g / cm³. 3 ~1.7g / cm 3 . The lithium-ion battery according to claim 8 or 9, wherein, The areal density of the negative electrode film is 0.1 g / 1540.25 mm. 2 ~0.25g / 1540.25mm 2 . The lithium-ion battery according to any one of claims 1 to 10, wherein, The isolation membrane includes one or more of the following characteristics: (1) The thickness of the isolation membrane is 5μm to 7μm; (2) The porosity of the isolation membrane is 35% to 45%. The lithium-ion battery according to any one of claims 1 to 11, wherein, The lithium-ion battery includes a housing that accommodates the positive electrode, the negative electrode, the separator, and the electrolyte; along the axial direction of the housing, the housing includes a main body and an edge portion, and the opening of the housing is located at the end of the edge portion away from the main body; in the cross section of the housing along the axial direction, the wall thickness of the main body is less than the wall thickness of the edge portion. An electrical appliance, wherein, Including the lithium-ion battery as described in any one of claims 1 to 12.

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