Battery monomer, negative pole piece, battery device and power utilization device

Abstract

The invention provides a battery monomer, a negative pole piece, a battery device and a power utilization device, the battery monomer comprises the negative pole piece, the negative pole piece comprises a bottom coating arranged on at least one side of a negative current collector, and the bottom coating comprises a plurality of first bulges protruding back to the negative current collector and a first concave part between two adjacent first bulges; the bottom coating layer comprises a first binder; the active material layer is arranged on one side, opposite to the negative electrode current collector, of the bottom coating layer, the active material layer comprises a plurality of second bulges protruding towards the bottom coating layer and second concave parts between two adjacent second bulges, and the active material layer comprises a second binder; the first bulge is coupled with the second concave part, and the second bulge is coupled with the first concave part; the mass content a of the first binder in the undercoat layer is greater than the mass content b of the second binder in the active material layer. The dynamic performance and the cycle life of the battery monomer are relatively good; the battery device and the power utilization device at least have the above beneficial effects.

Description

Technical Field

[0001] This application belongs to the field of battery cell technology, specifically relating to a battery cell, a negative electrode sheet, a battery device, and an electrical device. Background Technology

[0002] In recent years, battery cells have been widely used in energy storage systems such as hydropower, thermal power, wind power, and solar power plants, as well as in power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, and many other fields. With the application and promotion of battery cells, their comprehensive performance has received increasing attention; for example, battery cells need to simultaneously meet requirements such as high reliability and strong charging performance. The negative electrode of the battery cell plays a role in the insertion and extraction of active ions, and it is one of the key factors affecting the performance of the battery cell.

[0003] Therefore, there is an urgent need to provide a battery cell with good overall performance. Summary of the Invention

[0004] This application provides a battery cell with superior kinetic performance and cycle life; the negative electrode sheet of this application has superior bonding stability and good active ion transport effect; the battery device and the power supply device containing this battery cell have at least the above-mentioned beneficial effects.

[0005] In a first aspect, embodiments of this application provide a battery cell and an electrode assembly. The electrode assembly includes a positive electrode, a negative electrode, and a separator. The separator is located between the positive and negative electrode. The negative electrode includes: a negative current collector; a base coating layer disposed on at least one side of the negative current collector, the base coating layer including a plurality of first protrusions protruding away from the negative current collector and a first recess between two adjacent first protrusions; the base coating layer includes a first adhesive; and an active material layer disposed on the side of the base coating layer away from the negative current collector, the active material layer including a plurality of second protrusions protruding towards the base coating layer and a second recess between two adjacent second protrusions, the active material layer including a second adhesive; wherein the first protrusions are coupled to the second recess, and the second protrusions are coupled to the first recess; the relationship between the mass content 'a' of the first adhesive in the base coating layer and the mass content 'b' of the second adhesive in the active material layer satisfies: a > b.

[0006] In this embodiment, the first protrusion is coupled to the second recess, and the second protrusion is coupled to the first recess. This arrangement increases the contact area between the base coating and the active material layer, improves the bonding tightness between the two interfaces, thereby improving the adhesion effect between the base coating and the active material layer and increasing the cycle life of the battery cell. With a good adhesion effect between the base coating and the active material layer, which can be understood as a stable negative electrode structure, in order to reduce the obstruction of the active material layer surface to the transport of active ions, the amount of binder required for the active material layer can be reduced without affecting the peel strength between the base coating and the active material layer, thereby improving the ion conduction effect of the negative electrode and improving the dynamic performance of the battery cell.

[0007] In some alternative embodiments, the mass content 'a' of the first adhesive in the primer layer and the mass content 'b' of the second adhesive in the active material layer satisfy a:b = (2~10):1.

[0008] In this embodiment, the interface between the base coating and the active material layer has an uneven structure. While taking into account the adhesion effect between the base coating and the active material layer, the ratio of the mass content a of the first binder to the mass content b of the second binder is set within the above range. This can further reduce the binder content in the active material layer, improve the active ion transport or deintercalation efficiency in the active material layer, and improve the dynamic performance of the battery cell.

[0009] In some optional embodiments, the thickness ratio of the base coating layer to the active material layer is (1:5) to (1:50). A thickness ratio within this range can reduce the thickness of the base coating and the proportion of the counter electrode, thereby reducing the impact of the high binder content of the base coating on the negative electrode kinetics.

[0010] In some optional embodiments, the base coating layer comprises a first negative electrode active material; the active material layer comprises a second negative electrode active material; and the average volumetric particle size Dv of the first negative electrode active material is... 1 50 and the average volumetric particle size Dv of the second negative electrode active material 2 The ratio c of 50 satisfies: (1:1)≤c≤(1:5).

[0011] In the embodiments of this application, when the ratio c is within the above range, the average volume particle size of the first negative electrode active material in the bottom coating is relatively less than or equal to the average volume particle size of the first negative electrode active material, which is beneficial to the transport of active ions in the active material layer; this indicates that the thickness of the bottom coating is relatively less than or equal to the active material layer, reducing the thickness of the bottom coating and its proportion to the negative electrode sheet, reducing the influence of the bottom coating with a high binder content on the negative electrode dynamics, and improving the dynamic performance of the battery cell.

[0012] In some optional embodiments, the average volumetric particle size Dv of the first negative electrode active material 1 50 is 1 to 20 μm; optionally, it is 3 to 10 μm. The average volumetric particle size of the first negative electrode active material is within the above range, which is beneficial for forming an uneven bottom coating surface, improving the adhesion between the bottom coating and the active material layer, improving the stability of the coating, and improving the cycle life of the battery cell.

[0013] In some optional embodiments, the average volumetric particle size Dv of the second negative electrode active material 2 50 is 2 to 40 μm; optionally, it is 19 to 25 μm. An average volumetric particle size of the second negative electrode active material within the above range is beneficial for forming an uneven undercoating surface, which improves the adhesion between the undercoating and the active material layer, enhances the stability of the coating, and increases the cycle life of the battery cell.

[0014] In some optional embodiments, the bottom coating layer includes a first negative electrode active material; the active material layer includes a second negative electrode active material; the first and second negative electrode active materials include one or more of artificial graphite and natural graphite. Therefore, having the first and second negative electrode active materials of the aforementioned types not only provides an uneven interface between the bottom coating layer and the active material layer, but also provides sites for the insertion and extraction of active ions in the negative electrode sheet, thereby increasing the capacity of the battery cell.

[0015] In some optional embodiments, the bottom coating layer includes a first negative electrode active material; the active material layer includes a second negative electrode active material; the first and second negative electrode active materials respectively further include one or more of silicon-carbon materials, silicon-oxygen materials, silicon-nitrogen materials, silicon alloys, lithium carbonate, titanium dioxide, titanates, amorphous carbon, transition metal oxides, transition metal sulfides, and transition metal phosphides. Therefore, the first and second negative electrode active materials being of the above types not only give the interface between the bottom coating layer and the active material layer an uneven structure, but also provide sites for the insertion and extraction of active ions in the negative electrode sheet, thereby improving the capacity of the battery cell.

[0016] In some optional embodiments, the thickness of the base coating is from 1 μm to 20 μm, optionally from 10 μm to 15 μm.

[0017] By keeping the thickness of the base coating within the above range, the proportion of the base coating thickness in the negative electrode thickness can be reduced, thereby reducing the impact of the base coating with a high binder content on the negative electrode dynamics and improving the dynamic performance of the battery cell.

[0018] In some optional embodiments, the mass content of the first negative electrode active material in the base coating is ≥50%, optionally 85% to 95%. A mass content of the first negative electrode active material within the above range can create an uneven interface between the base coating and the active material layer, increasing the contact area between the base coating and the active material layer and the tightness of the bonding between the two interfaces, improving the adhesion effect between the base coating and the active material layer, and enhancing the structural stability of the negative electrode sheet.

[0019] In some optional embodiments, the mass content 'a' of the first binder in the primer layer is 2% to 10%, optionally 2% to 5%. When the mass content of the binder in the primer layer is within the above range, the bonding effect between the primer layer and the negative electrode current collector can be improved, thereby enhancing the stability of the negative electrode sheet.

[0020] In some optional embodiments, the areal density of the base coating is 0.1 mg / cm³. 2 Up to 2 mg / cm 2 1 mg / cm 2 Up to 1.5 mg / cm 2 A base coating with an areal density within the aforementioned range enhances the bonding strength between the base coating and the negative electrode current collector, as well as the bonding strength between the base coating and the active material layer. This reduces the risk of electrode peeling or detachment during cycling, improving the structural stability of the negative electrode. A base coating with an areal density within the aforementioned range also fills in microscopic irregularities on the current collector surface, resulting in a more uniform application of active material. This optimizes current distribution, reduces electrode polarization, and thus improves the overall consistency of the electrode, enhancing the kinetic performance and reliability of the battery cell.

[0021] In some optional embodiments, the peel strength between the undercoat layer and the active material layer is 5 N / m to 15 N / m, optionally 10 N / m to 12 N / m. Controlling the peel strength between the undercoat layer and the active material layer within the above range is beneficial for improving the stability of the negative electrode sheet and increasing the cycle life and reliability of the battery cell.

[0022] In some optional embodiments, the mass m of the undercoating layer accounts for 1% to 20% of the total mass M of the undercoating layer and the active material layer, optionally 10% to 15%. A mass percentage of the undercoating layer within this range can reduce the mass percentage of the undercoating layer in the negative electrode sheet, reduce the impact of a high binder content in the undercoating layer on the negative electrode dynamics, and improve the dynamic performance of the battery cell.

[0023] In some optional embodiments, the mass content b of the second binder in the active material layer is 0.5% to 3%, optionally 0.5% to 1.5%. When the mass content of the binder in the active material layer is within the above range, the transport or deintercalation efficiency of active ions in the active material layer can be improved while maintaining the stability of the active material layer, thereby enhancing the kinetic performance of the battery cell.

[0024] In some optional embodiments, the thickness of the active material layer is from 10 μm to 200 μm, optionally from 50 μm to 150 μm. A thickness within this range increases the proportion of the active material layer to the total thickness of the negative electrode, reduces the amount of binder in the active material layer, improves the transport efficiency of active ions within the active material layer, and enhances the kinetic performance of the battery cell.

[0025] In some optional embodiments, the mass content of the second negative electrode active material in the active material layer is 70% to 98%, optionally 85% to 98%. A mass content of the second negative electrode active material within the above range can create an uneven interface between the base coating layer and the active material layer, increasing the contact area between the base coating layer and the active material layer and the tightness of the bonding between the two interfaces, improving the adhesion effect between the base coating layer and the active material layer, and enhancing the structural stability of the negative electrode sheet.

[0026] In some optional embodiments, the areal density of the active material layer is 5 mg / cm³. 2 Up to 20 mg / cm 2 10mg / cm 2 Up to 15 mg / cm 2 A surface density of the active material layer within the above range indicates the presence of a significant amount of active material, which is beneficial for improving the battery's energy density. A surface density within this range can also reduce polarization at high currents, thereby improving charge and discharge efficiency.

[0027] In some optional embodiments, the mass m' of the active material layer accounts for 80% to 99% of the total mass M of the undercoat and the active material layer, optionally 95% to 90%. When the mass m' of the active material layer is within the above range, it can increase the mass ratio of the active material layer in the negative electrode, improve the transport and deintercalation efficiency of active ions in the active material layer, and enhance the kinetic performance of the battery cell.

[0028] In some optional embodiments, the battery cell includes an electrolyte comprising an electrolyte salt, an organic solvent, and a thioester additive, wherein the thioester additive comprises a structure shown in any one or more of formulas (1) to (6):

[0029]

[0030] R1 and R2 each independently include hydrogen atoms and alkyl groups with 1 to 10 unsubstituted or heteroatom-substituted carbon atoms, and n and m are integers, with n being 1 to 4 and m being 0 to 4.

[0031] In the embodiments of this application, the thioester additive is dispersed in the electrolyte formed by the electrolyte salt and organic solvent. The thioester additive can participate in the formation of the solid electrolyte membrane (SEI membrane). That is, the sulfur-containing organic compound is reduced to a sulfur-containing electrolyte salt component and introduced into the SEI. The binding energy ΔE of sulfur element with active ions (e.g., S-Li) is lower than the binding energy of active ions with oxygen element, which reduces the binding energy of elements with active ions in the SEI and also reduces the transport energy barrier of active ions in the SEI membrane, making it easier for active ions to transport in the SEI, reducing the charging impedance Rct, and thus improving the dynamic performance of the battery cell, which is reflected in the charging capacity.

[0032] In some optional embodiments, R1 and R2 independently comprise hydrogen atoms and alkyl groups having 1 to 4 carbon atoms, respectively. The use of these types of groups in R1 and R2, compared to other groups substituted with heteroatoms, reduces side reactions such as corrosion to the battery cell, lowers the probability of the thioester additive releasing toxic gases under extreme conditions such as overheating or overcharging, and improves the reliability and cycle life of the battery cell.

[0033] Furthermore, R1 and R2 utilize the aforementioned types of functional groups, making them more easily degraded in the natural environment and causing less environmental damage.

[0034] In some optional embodiments, the thioester additive comprises the structure shown in any one or more of formulas (I-1) to (I-26):

[0035]

[0036] In the embodiments of this application, the above-mentioned thioester additives can participate in the formation of the SEI film, reduce the transport energy barrier of active ions in the SEI film, make it easier for active ions to be transported in the SEI, and improve the kinetic performance of the battery cell.

[0037] In some optional embodiments, the thioester additive has a mass content of 0.1% to 10% in the electrolyte, optionally 0.5% to 2%. A mass content of the thioester additive in the electrolyte within the above range is beneficial for further reducing the transport energy barrier of active ions in the SEI membrane and improving the kinetic performance of the battery cell.

[0038] In some alternative embodiments, the concentration of the electrolyte salt in the electrolyte is from 0.5 mol / L to 3 mol / L, and optionally from 0.8 mol / L to 1.2 mol / L.

[0039] When the electrolyte salt content is within the above range, the interfacial characteristics between the electrode and the electrolyte can be optimized, the interfacial stability of the battery can be enhanced, and the service life of the battery cell can be increased.

[0040] In some optional embodiments, the organic solvent accounts for 60% to 90% by mass of the electrolyte, optionally 80% to 88%. Therefore, the viscosity and ionic conductivity of the electrolyte can be further controlled, thereby improving the kinetic performance of the battery cell.

[0041] Secondly, embodiments of this application provide a negative electrode sheet, comprising: a negative electrode sheet, the negative electrode sheet including: a negative electrode current collector; a base coating layer disposed on at least one side of the negative electrode current collector, the base coating layer including a plurality of first protrusions protruding away from the negative electrode current collector and a first recess between two adjacent first protrusions; the base coating layer including a first adhesive; an active material layer disposed on the side of the base coating layer away from the negative electrode current collector, the active material layer including a plurality of second protrusions protruding towards the base coating layer and a second recess between two adjacent second protrusions, the active material layer including a second adhesive; wherein, the first protrusions and the second recesses are coupled together, and the second protrusions and the first recesses are coupled together; the relationship between the mass content a of the first adhesive in the base coating layer and the mass content b of the second adhesive in the active material layer satisfies: a > b.

[0042] In this embodiment, the base coating is disposed between the active material layer and the negative electrode current collector. The interface between the base coating and the active material layer has an uneven structure, which can increase the contact area between the base coating and the active material layer, improve the bonding tightness of the two interfaces, thereby improving the adhesion effect between the base coating and the active material layer and improving the cycle life of the battery cell. On the basis of good adhesion between the base coating and the active material layer, that is, on the basis of stable negative electrode structure, in order to reduce the obstruction of the active material layer surface to the active ion transport, the amount of binder required for the active material layer can be reduced, while not affecting the peel strength between the base coating and the active material layer, improving the ion conduction effect of the negative electrode and improving the dynamic performance of the battery cell.

[0043] Thirdly, embodiments of this application provide a battery device comprising a battery cell according to the first aspect or a battery cell formed by preparing a negative electrode sheet according to the second aspect. The battery device of this application comprises a battery cell according to the first aspect or a battery cell prepared from an electrolyte according to the second aspect, and therefore has at least the advantages corresponding to a battery cell or a negative electrode sheet.

[0044] Fourthly, embodiments of this application provide an electrical device that includes the battery device of the third aspect. The electrical device of this application includes the battery device of the third aspect, and therefore has at least the advantages corresponding to the battery device. Attached Figure Description

[0045] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments of this application will be briefly described below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the drawings without creative effort.

[0046] Figure 1 A schematic diagram of one embodiment of the battery cell of this application is shown.

[0047] Figure 2 It shows Figure 1 An exploded view of one embodiment of the battery cell is shown.

[0048] Figure 3 A schematic diagram of the battery pack according to one embodiment of this application is shown.

[0049] Figure 4 An exploded view of a battery pack according to one embodiment of this application is shown.

[0050] Figure 5 A schematic diagram of the cross-section of the negative electrode sheet along the thickness direction according to one embodiment of this application is shown.

[0051] Figure 6 A schematic diagram of the active material layer along the thickness direction of one embodiment of this application is shown.

[0052] Figure 7 A schematic diagram of the structure of the base coating and the negative electrode current collector along the thickness direction of one embodiment of this application is shown.

[0053] Figure 8 The diagram shows the microstructure of the base coating and the negative electrode current collector along the thickness direction of one embodiment of this application.

[0054] Figure 9 A schematic diagram of one embodiment of an electrical device incorporating the battery cell of this application as a power source is shown.

[0055] In the accompanying drawings, the figures may not be drawn to scale. The reference numerals are explained as follows: 1. Battery pack, 2. Upper casing, 3. Lower casing, 4. Battery module, 5. Battery cell, 50. Negative electrode plate, 51. Negative current collector, 52. Undercoating layer, 520. First protrusion, 521. First recess, 53. Active material layer, 531. Second recess, 530. Second protrusion. Detailed Implementation

[0056] The following detailed description, with appropriate reference to the accompanying drawings, specifically discloses embodiments of the battery cell, negative electrode, battery assembly, and power-consuming device of this application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided for the purpose of enabling those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0057] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of the particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60–120 and 80–110 are listed for specific parameters, it is understood that ranges of 60–110 and 80–120 are also expected. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1–3, 1–4, 1–5, 2–3, 2–4, and 2–5. In this application, unless otherwise stated, the numerical range "a–b" represents a shortened representation of any combination of real numbers between a and b, characterized in that a and b are both real numbers. For example, the numerical range "0~5" indicates that all real numbers between "0~5" have been listed in this article; "0~5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0058] Unless otherwise specified, all embodiments and optional embodiments of this application may be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the disclosure of this application.

[0059] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions, and such technical solutions shall be deemed to be included in the disclosure of this application.

[0060] Unless otherwise specified, all steps of this application may be performed sequentially or randomly, preferably sequentially. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, if the method may also include step (c), it means that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0061] Throughout this application, substituents of the compounds are disclosed by groups or ranges. It is expressly intended that such descriptions include each individual sub-combination of members of these ranges. For example, it is expressly intended that the term "C1-C10 alkyl" individually discloses C1, C2, C3, C4, C5, C6, C7, C9, C10, C1-C2, C1-C3, C1-C4, C1-C5, C1-C6, C1-C7, C1-C8, C1-C9, C1-C10, C2-C3, C2-C4, C2-C5, C2-C6, C2-C7, C2-C8, C2-C9, C2-C10, C3-C4, C3-C 5. C3–C6, C3–C7, C3–C8, C3–C9, C3–C10, C4–C5, C4–C6, C4–C7, C4–C8, C4–C9, C4–C10, C5–C6, C5–C7, C5–C8, C5–C9, C5–C10, C6–C7, C6–C8, C6–C9, C6–C10, C7–C8, C7–C9, C7–C10, C8–C9, C8–C10, and C9–C10 alkyl groups. Unless otherwise stated, the term "alkyl" encompasses both straight-chain alkyl and branched-chain alkyl groups.

[0062] Unless otherwise specified, in this application, the terms "first," "second," "third," "fourth," etc., are used to distinguish different objects, rather than to describe a specific order or primary / secondary relationship.

[0063] Unless otherwise specified, in this application, the term "active ion" refers to ions that can be inserted and extracted back and forth between the positive and negative electrodes of a battery cell, including but not limited to lithium ions, sodium ions, etc.

[0064] In this application, "multiple" refers to two or more (including two). Similarly, "several items" or "multiple items" in this application refers to two or more (including two).

[0065] The battery device mentioned in the embodiments of this application may include one or more battery cell assemblies for providing voltage and capacity. A battery cell assembly may include multiple battery cells, which are connected in series, parallel, or mixed connections via a busbar.

[0066] In some embodiments, a battery cell assembly is typically formed by arranging multiple battery cells; as an example, a battery cell assembly can be a battery module, which is formed by arranging and fixing multiple battery cells into a single module. As an example, a battery module can be formed by bundling multiple battery cells together with cable ties.

[0067] A single battery cell is the smallest unit that makes up a battery device, and it can independently perform the functions of charging and discharging. A single battery cell can be cylindrical, cuboid, or other shapes, and the embodiments of this application are not limited in this respect. Figure 1 The example shown is a rectangular battery cell 5.

[0068] In some embodiments, individual battery cells can be assembled into a battery module, and the number of individual battery cells contained in the battery module can be multiple, the specific number of which can be adjusted according to the application and capacity of the battery module. Figure 2 This is a schematic diagram of battery module 4 as an example. Figure 2 As shown, in battery module 4, multiple battery cells 5 can be arranged sequentially along the length of battery module 4. Of course, they can also be arranged in any other manner. Furthermore, these multiple battery cells 5 can be fixed in place using fasteners.

[0069] Optionally, the battery module 4 may also include a housing with a receiving space in which multiple battery cells 5 are received.

[0070] In some embodiments, the battery modules described above can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be adjusted according to the application and capacity of the battery pack.

[0071] Figure 3 and Figure 4 This is a schematic diagram of battery pack 1 as an example. Figure 3 and Figure 4 As shown, the battery pack 1 may include a housing and multiple battery modules 4 disposed within the housing. The housing includes an upper housing 2 and a lower housing 3. The upper housing 2 covers the lower housing 3, forming a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the housing.

[0072] In some embodiments, the battery device may be an energy storage device. Energy storage devices include energy storage containers, energy storage cabinets, etc.

[0073] In this embodiment of the application, the battery cell can be a secondary battery, which refers to a battery cell that can be recharged to activate the active materials and continue to be used after the battery cell has been discharged.

[0074] The battery cell can be a lithium-ion battery cell, a sodium-ion battery cell, a sodium-lithium-ion battery cell, a lithium metal battery cell, a sodium metal battery cell, a lithium-sulfur battery cell, a magnesium-ion battery cell, a nickel-metal hydride battery cell, a nickel-cadmium battery cell, a lead-acid battery cell, etc., but the embodiments of this application are not limited to this.

[0075] The battery cell may also include an outer packaging, which can be used to encapsulate the electrode assembly. The outer packaging can be a rigid shell, such as a hard plastic shell, aluminum shell, or steel shell. The outer packaging can also be a flexible package, such as a pouch-type flexible package. The material of the flexible package can be plastic, such as one or more of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0076] The battery cell includes an electrode assembly. The electrode assembly can be a wound structure or a stacked structure, and the embodiments of this application are not limited to this.

[0077] The electrode assembly includes a positive electrode, a negative electrode, and a separator, with the separator located between the positive and negative electrode.

[0078] [Negative electrode plate]

[0079] This application provides a negative electrode sheet, comprising: a negative current collector; a base coating layer disposed on at least one side of the negative current collector, the base coating layer including a plurality of first protrusions protruding away from the negative current collector and a first recess between two adjacent first protrusions; the base coating layer including a first adhesive; and an active material layer disposed on the side of the base coating layer away from the negative current collector, the active material layer including a plurality of second protrusions protruding towards the base coating layer and a second recess between two adjacent second protrusions, the active material layer including a second adhesive; wherein the first protrusions are coupled to the second recess, and the second protrusions are coupled to the first recess; the relationship between the mass content 'a' of the first adhesive in the base coating layer and the mass content 'b' of the second adhesive in the active material layer satisfies: a > b.

[0080] In related technologies, the negative electrode sheet needs a certain amount of binder to ensure the bonding effect with the current collector. However, a high amount of binder covering the surface of the negative electrode active material hinders ion transport and affects the charging capability of the negative electrode.

[0081] In this embodiment, the first protrusion is coupled to the second recess, and the second protrusion is coupled to the first recess. This can be understood as the interface between the base coating and the active material layer having an uneven structure. This arrangement increases the contact area between the base coating and the active material layer, improves the bonding tightness between the two interfaces, thereby improving the adhesion effect between the base coating and the active material layer and increasing the cycle life of the battery cell. On the basis of good adhesion between the base coating and the active material layer, i.e., stable negative electrode structure, in order to reduce the obstruction of the active material layer surface to the transport of active ions, the amount of binder required for the active material layer can be reduced without affecting the peel strength between the base coating and the active material layer, improving the ion conduction effect of the negative electrode and improving the dynamic performance of the battery cell.

[0082] It is understood that coupling setups typically refer to the interconnection or interaction of two or more structures or components. In this application, a mutually cooperating structure is formed between the first protrusion and the second recess, as well as between the second protrusion and the first recess, to enhance the overall performance or stability of the negative electrode sheet and improve the bonding force of the negative electrode sheet material.

[0083] The components and their contents in the negative electrode can be determined according to conventional methods in this field. For example, they can be detected using methods such as gas chromatography-mass spectrometry (GC-MS), ion chromatography (IC), liquid chromatography (LC), inductively coupled plasma optical emission spectrometry (ICP-OES), infrared spectroscopy, differential scanning thermogravimetric analysis (TG), Raman spectroscopy, and nuclear magnetic resonance.

[0084] As an example, the method for detecting the mass content of binder in the base coating or active material layer is as follows: cut along the thickness of the negative electrode sample to obtain a cross-section of the negative electrode along the thickness direction, polish the cross-section, and observe the base coating and active material layer with a microscope or scanning electron microscope. It can be observed that the material in the base coating is more dense and the active material layer is more porous. Take samples of the base coating and the active material layer respectively, and detect the binder content in them.

[0085] For example, infrared spectroscopy can be used to determine the characteristic peaks of CH bonds in saturated hydrocarbons of binders, such as styrene-butadiene rubber latex (SBR), at cm⁻¹. -1 The composition can be determined by high-resolution gas chromatography-high-resolution mass spectrometry (HPLC-MS / MS), which can separate different components in the electrolyte and obtain high-precision molecular weights, thereby determining the atomic composition. Then, the specific molecular structure of each component can be confirmed through nuclear magnetic resonance (NMR) spectroscopy. The mass fraction of the binder can be determined by differential scanning gravimetric analysis (TG).

[0086] An exemplary detection method for the first protrusion, first concave portion, second protrusion, and second concave portion of the negative electrode sheet is as follows: Take a negative electrode sheet sample with a length of 500 mm and a width of 100 mm; cut along the thickness of the negative electrode sheet sample to obtain a cross-section of the negative electrode sheet along the thickness direction; polish the cross-section; and observe the base coating layer and active material layer using a microscope or scanning electron microscope (SEM). It can be observed that the material in the base coating layer is denser, while the active material layer is more porous. The interface between the base coating layer and the active material layer has an uneven structure. The base coating layer has multiple first protrusions, with a first concave portion between two adjacent first protrusions; the active material layer has multiple second protrusions, with a second concave portion between two adjacent protrusions. The thickness of the base coating layer and the active material layer can be tested using the above method, and multiple points can be measured, with the average thickness taken.

[0087] Please refer to Figures 5 to 9 , Figure 5 A schematic diagram of the cross-section of a negative electrode sheet along the thickness direction according to an embodiment of this application is shown. As can be seen from the figure, the negative electrode sheet 50 includes: a negative current collector 51; a base coating layer 52 disposed on at least one side of the negative current collector 51; and an active material layer 53 disposed on the side of the base coating layer 52 facing away from the negative current collector 51, the active material layer including a second binder; wherein, a first protrusion 520 is coupled to a second recess 531, and the second protrusion 530 is coupled to the first recess 521.

[0088] Figure 6 A schematic diagram of the active material layer along the thickness direction of one embodiment of this application is shown. As can be seen from the figure, the active material layer 53 includes a plurality of second protrusions 530 protruding toward the base coating layer 52 and a second recess 531 between two adjacent second protrusions 530.

[0089] Figure 7 A schematic diagram of the base coating and negative electrode current collector along the thickness direction of one embodiment of this application is shown. As can be seen from the figure, the base coating 52 includes a plurality of first protrusions 520 protruding away from the negative electrode current collector 51 and a first recess 521 between two adjacent first protrusions 520.

[0090] Figure 8 A microstructure diagram along the thickness direction of the base coating and the negative electrode current collector according to an embodiment of this application is shown. As can be seen from the figure, the gray area in the middle is the negative electrode current collector. After the base coating is prepared, it is observed that the base coating is disposed on both sides of the negative electrode current collector. The surface of the base coating is uneven, including the first recess 521 between the first protrusions 520.

[0091] In some alternative embodiments, the mass content 'a' of the first adhesive in the primer layer and the mass content 'b' of the second adhesive in the active material layer satisfy a:b = (2~10):1.

[0092] Optionally, the ratio of a:b can be any ratio or a range thereof from 2:1, 2.5:1, 3:1, 3.5:1, 4:1, 4.5:1, 5:1, 5.5:1, 6:1, 6.5:1, 7:1, 7.5:1, 8:1, 8.5:1, 9:1, 9.5:1, and 10:1.

[0093] In this embodiment, the interface between the base coating and the active material layer has an uneven structure. While taking into account the adhesion effect between the base coating and the active material layer, the ratio of the mass content a of the first binder to the mass content b of the second binder is set within the above range. This can further reduce the binder content in the active material layer, improve the active ion transport or deintercalation efficiency in the active material layer, and improve the dynamic performance of the battery cell.

[0094] In some optional embodiments, the thickness ratio of the base coating layer to the active material layer is (1:5) to (1:50). A thickness ratio within this range can reduce the thickness of the base coating and the proportion of the counter electrode, thereby reducing the impact of the high binder content of the base coating on the negative electrode kinetics.

[0095] Optionally, the thickness ratio of the base coating layer to the active material layer can be any ratio or a range of its components from 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, 1:15, 1:20, 1:25, 1:30, 1:35, 1:40, 1:45, and 1:50.

[0096] Method for detecting the thickness of the base coating and active material layer: The negative electrode sample is cut along its thickness direction to obtain a cross-section. The cross-section is polished, and the base coating and active material layer are observed using a microscope or scanning electron microscope. It can be observed that the material in the base coating is denser, while the active material layer is more porous. The interface between the base coating and the active material layer has an uneven structure. The base coating has multiple first protrusions, with a first recess between adjacent first protrusions; the active material layer has multiple second protrusions, with a second recess between adjacent protrusions. The thickness between the top and the other side of 10 protrusions in the base coating is measured to obtain a first average value. The thickness between the top and the other side of 10 recesses in the base coating is measured to obtain a second average value. The average of the first and second average values ​​is the thickness of the base coating. The thickness of the active material layer can also be determined using the same method as the base coating thickness test.

[0097] In some optional embodiments, the base coating layer comprises a first negative electrode active material; the active material layer comprises a second negative electrode active material; and the average volumetric particle size Dv of the first negative electrode active material is... 1 50 and the average volumetric particle size Dv of the second negative electrode active material 2The ratio c of 50 satisfies: (1:1)≤c≤(1:5).

[0098] Optionally, the average volumetric particle size Dv of the first negative electrode active material is... 1 50 and the average volumetric particle size Dv of the second negative electrode active material 2 The ratio c of 50 can be any ratio or a range of ratios among 1:1, 1:1.01, 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5, 1:2, 1:2.5, 1:3, 1:3.5, 1:4, 1:4.5, and 1:5.

[0099] In the embodiments of this application, the average volumetric particle size Dv of the first negative electrode active material 1 50 and the average volumetric particle size Dv of the second negative electrode active material 2 When the ratio of 50 is within the above range, the average volume particle size of the first negative electrode active material in the bottom coating is relatively less than or equal to the average volume particle size of the first negative electrode active material, which is beneficial to the transport of active ions in the active material layer. This indicates that the thickness of the bottom coating is relatively less than or equal to that of the active material layer, which reduces the thickness of the bottom coating and its proportion to the negative electrode sheet, reduces the influence of the bottom coating with high binder content on the negative electrode dynamics, and improves the dynamic performance of the battery cell.

[0100] The average volumetric particle size Dv of the first negative electrode active material 1 50 and the average volumetric particle size Dv of the second negative electrode active material 2 The value of 50 is known in the art and represents the particle size corresponding to a cumulative volume distribution percentage of 50%. This value can be determined during the preparation of the negative electrode sheet by separately measuring the first and second negative electrode active materials using instruments and methods known in the art. For example, it can be conveniently measured using a laser particle size analyzer, such as the Mastersizer 2000E laser particle size analyzer from Malvern Instruments Ltd., UK, according to GB / T 19077-2016, Particle Size Distribution by Laser Diffraction.

[0101] The average volumetric particle size Dv of the first negative electrode active material 1 50 and the average volumetric particle size Dv of the second negative electrode active material 2 50 can also separate the base coating and active material layer in the negative electrode sheet, remove other substances in the base coating and active material layer respectively, remove binders, etc. with solvents, and conveniently measure the first negative electrode active material or the second negative electrode active material obtained separately using a laser particle size analyzer.

[0102] In some optional embodiments, the bottom coating layer includes a first negative electrode active material; the active material layer includes a second negative electrode active material; the first and second negative electrode active materials include one or more of artificial graphite and natural graphite. Therefore, having the first and second negative electrode active materials of the aforementioned types not only provides an uneven interface between the bottom coating layer and the active material layer, but also provides sites for the insertion and extraction of active ions in the negative electrode sheet, thereby increasing the capacity of the battery cell.

[0103] In some alternative embodiments, the base layer includes a first negative electrode active material; the active material layer includes a second negative electrode active material; the second negative electrode active material includes artificial graphite and natural graphite, and the first negative electrode active material includes natural graphite.

[0104] In this embodiment, the porous structure of artificial graphite makes the active material layer, primarily composed of artificial graphite, relatively porous, facilitating the transport of active ions within the active material layer. Conversely, the denser structure of natural graphite makes the undercoat layer, primarily composed of artificial and natural graphite, relatively denser than the active material layer. This arrangement promotes the transport of active ions from the active material layer to the undercoat layer, improving the ion-conducting effect of the negative electrode and enhancing the kinetic performance of the battery cell. Furthermore, the second negative electrode active material includes artificial graphite, and the first negative electrode active material includes both artificial and natural graphite. This increases the contact area between the undercoat layer and the active material layer and strengthens the bonding between the two interfaces, thereby improving the adhesion between the undercoat layer and the active material layer.

[0105] In some optional embodiments, the bottom coating layer includes a first negative electrode active material; the active material layer includes a second negative electrode active material; the first and second negative electrode active materials respectively further include one or more of silicon-carbon materials, silicon-oxygen materials, silicon-nitrogen materials, silicon alloys, lithium carbonate, titanium dioxide, titanates, amorphous carbon, transition metal oxides, transition metal sulfides, and transition metal phosphides. Therefore, the first and second negative electrode active materials being of the above types not only give the interface between the bottom coating layer and the active material layer an uneven structure, but also provide sites for the insertion and extraction of active ions in the negative electrode sheet, thereby improving the capacity of the battery cell.

[0106] In some optional embodiments, the thickness of the base coating is from 1 μm to 20 μm, optionally from 10 μm to 15 μm.

[0107] Optionally, the thickness of the base coating is any value or a range of combinations thereof from 1μm, 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, 16μm, 17μm, 18μm, 19μm, and 20μm.

[0108] By keeping the thickness of the base coating within the above range, the proportion of the base coating thickness in the negative electrode thickness can be reduced, thereby reducing the impact of the base coating with a high binder content on the negative electrode dynamics and improving the dynamic performance of the battery cell.

[0109] In some optional embodiments, the mass content of the first negative electrode active material in the undercoat is ≥50%, optionally 85% to 95%.

[0110] The mass content of the first negative electrode active material in the base coating can be any value or range of its composition from 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, and 95%.

[0111] When the mass content of the first negative electrode active material is within the above range, it can create an uneven interface between the base coating layer and the active material layer, increasing the contact area between the base coating layer and the active material layer and the tightness of the bonding between the two interfaces, thereby improving the adhesion effect between the base coating layer and the active material layer and enhancing the structural stability of the negative electrode sheet.

[0112] In some optional embodiments, the mass content 'a' of the first adhesive in the primer layer is 2% to 10%, optionally 2% to 5%.

[0113] The mass content 'a' of the first adhesive in the primer layer can be any value or a range of combinations thereof from 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, and 10%.

[0114] When the mass content of the binder in the primer layer is within the above range, the bonding effect between the primer layer and the negative electrode current collector can be improved, thereby enhancing the stability of the negative electrode sheet.

[0115] In some optional embodiments, the areal density of the base coating is 0.1 mg / cm³. 2 Up to 2 mg / cm 2 1 mg / cm 2 Up to 1.5 mg / cm 2 .

[0116] Optionally, the areal density of the base coating can be 0.1 mg / cm³. 2 0.2 mg / cm 2 0.3 mg / cm 2 0.4 mg / cm 2 0.5 mg / cm 2 1.0 mg / cm 2 1.5 mg / cm 2 2.0 mg / cm2 Any value in or a range thereof.

[0117] A base coating with an areal density within the aforementioned range enhances the bonding strength between the base coating and the negative electrode current collector, as well as the bonding strength between the base coating and the active material layer. This reduces the risk of electrode peeling or detachment during cycling, improving the structural stability of the negative electrode. A base coating with an areal density within the aforementioned range also fills in microscopic irregularities on the current collector surface, resulting in a more uniform application of the active material. This optimizes current distribution, reduces electrode polarization, and thus improves the overall consistency of the electrode, enhancing the kinetic performance and reliability of the battery cell.

[0118] The areal density of the undercoating layer has a well-known meaning in the art and can be measured using instruments and methods known in the art. For example, take a negative electrode sheet that has been coated on one side and cold-pressed (if it is a double-coated negative electrode sheet, the coating on one side can be wiped off first), cut it into small circular pieces with an area of ​​S1, remove the active material layer on the surface under a microscope, weigh it, and record it as M1. Then wipe off the undercoating layer of the negative electrode sheet after weighing, weigh the negative current collector, and record it as M0. The areal density of the undercoating layer = (weight of the negative electrode sheet after removing the active material layer M1 - weight of the negative current collector M0) / S1.

[0119] In some optional embodiments, the compaction density of the undercoat layer is greater than that of the active material layer. Therefore, while taking into account the bonding effect of the undercoat layer and the active material layer, the transport rate of active ions in the active material layer can be further improved, thereby further enhancing the kinetic performance of the battery cell.

[0120] In some optional embodiments, the mass m of the base coating layer accounts for 1% to 20% of the total mass M of the base coating layer and the active material layer, optionally 10% to 15%.

[0121] Optionally, the proportion of the mass m of the primer layer in the sum M of the masses of the primer layer and the active material layer can be any value or a range of combinations of 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, and 20%.

[0122] When the mass percentage of the base coating is within the above range, the mass percentage of the base coating in the negative electrode sheet can be reduced, thereby reducing the impact of the high binder content in the base coating on the dynamics of the negative electrode and improving the dynamic performance of the battery cell.

[0123] As an example, take a negative electrode sheet that has been coated on one side and cold-pressed (if it is a double-sided coated negative electrode sheet, the coating on one side can be wiped off first), and cut it into a small circular sheet with an area of ​​S1. Weigh the negative electrode sheet with the coating on one side as M2. Remove the active material layer on the surface under a microscope and weigh it, recording the weight as M1. Then wipe off the bottom coating of the weighed negative electrode sheet and weigh the negative current collector, recording the weight as M0. The mass of the bottom coating m = (the weight of the negative electrode sheet after removing the active material layer M1 - the weight of the negative current collector M0), and the sum of the masses of the bottom coating and the active material layer M = (the weight of the negative electrode sheet with the coating on one side M1 - the weight of the negative current collector M0). 2- The weight M0 of the negative electrode current collector.

[0124] In some optional embodiments, the mass content b of the second adhesive in the active material layer is 0.5% to 3%, optionally 0.5% to 1.5%.

[0125] The mass content b of the second binder in the active material layer can be any value or a range of its composition from 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, and 3.0%.

[0126] When the mass content of the binder in the active material layer is within the above range, the transport or deintercalation efficiency of active ions in the active material layer can be improved while taking into account the stability of the active material layer, thereby improving the kinetic performance of the battery cell.

[0127] In some optional embodiments, the thickness of the active material layer is from 10 μm to 200 μm, and optionally from 50 μm to 150 μm.

[0128] Optionally, the thickness of the active material layer can be any value or a range of combinations thereof from 10μm, 15μm, 20μm, 30μm, 40μm, 50μm, 60μm, 70μm, 80μm, 90μm, 100μm, 110μm, 120μm, 130μm, 140μm, 150μm, 160μm, 170μm, 180μm, 190μm, and 200μm. A thickness within the above range increases the proportion of the active material layer thickness in the negative electrode sheet thickness, reduces the amount of binder in the active material layer, improves the transport efficiency of active ions in the active material layer, and enhances the kinetic performance of the battery cell.

[0129] In some optional embodiments, the average volumetric particle size Dv of the first negative electrode active material 150 is 1 to 20 μm; it can be selected as 3 to 10 μm.

[0130] For example, the average volumetric particle size Dv of the first negative electrode active material 1 50 can be any value or a range of combinations thereof from 1μm, 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, 16μm, 17μm, 18μm, 19μm, and 20μm.

[0131] The average volume particle size of the first negative electrode active material is within the above range, which is beneficial for forming an uneven bottom coating surface, improving the bonding force between the bottom coating and the active material layer, improving the stability of the coating, and improving the cycle life of the battery cell.

[0132] In some optional embodiments, the average volumetric particle size Dv of the second negative electrode active material 2 50 is 2 to 40 μm; 19 to 25 μm is also available.

[0133] For example, the average volumetric particle size Dv of the second negative electrode active material 2 50 can be any value or a range of combinations thereof from 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, 16μm, 17μm, 18μm, 19μm, 20μm, 21μm, 22μm, 23μm, 24μm, 25μm, 26μm, 27μm, 28μm, 29μm, 30μm, 31μm, 32μm, 33μm, 34μm, 35μm, 36μm, 37μm, 38μm, 39μm, and 40μm.

[0134] The average volume particle size of the second negative electrode active material is within the above range, which is beneficial for forming an uneven bottom coating surface, improving the bonding force between the bottom coating and the active material layer, improving the stability of the coating, and increasing the cycle life of the battery cell.

[0135] In some optional embodiments, the mass content of the second negative electrode active material in the active material layer is 70% to 98%, optionally 85% to 98%.

[0136] Optionally, the mass content of the second negative electrode active material in the active material layer can be any value or a range thereof from 70%, 75%, 80%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, and 98%. A mass content of the second negative electrode active material within the above range can create an uneven interface between the base coating layer and the active material layer, increasing the contact area between the base coating layer and the active material layer, as well as the bonding tightness between the two interfaces, improving the adhesion effect between the base coating layer and the active material layer, and enhancing the structural stability of the negative electrode sheet.

[0137] In some optional embodiments, the peel strength of the base coating and the active material layer is 5 N / m to 15 N / m, optionally 10 N / m to 12 N / m.

[0138] Optionally, the peel strength between the undercoat layer and the active material layer can be any value or a combination thereof from 5 N / m, 6 N / m, 7 N / m, 8 N / m, 9 N / m, 10 N / m, 11 N / m, 12 N / m, 13 N / m, 14 N / m, and 15 N / m. Controlling the peel strength between the undercoat layer and the active material layer within the above range is beneficial for improving the stability of the negative electrode sheet and increasing the cycle life and reliability of the battery cell.

[0139] The peel strength between the primer layer and the active material layer is a concept well-known in the art and can be tested using instruments and methods known in the art. An exemplary test method is as follows: Remove the negative current collector from the negative electrode sheet and adhere the tape to the surface of the primer layer; then cut it into a 15mm width w; peel the primer layer and the active material layer at 180° at 50mm / min; based on the tensile force and displacement data graph, read the maximum tensile force x (N), and calculate the peel strength F' (N / m) between the primer layer and the active material layer according to F' = x / w. The tensile testing equipment can be a tensile testing machine from a high-speed rail testing instrument company, such as the AI-3000-S model.

[0140] In some optional embodiments, the areal density of the active material layer is 5 mg / cm³. 2 Up to 20 mg / cm 2 10mg / cm 2 Up to 15 mg / cm 2 .

[0141] Optionally, the areal density of the active material layer can be 5 mg / cm³. 2 6mg / cm 2 7mg / cm 2 8mg / cm 2 9mg / cm 2 10mg / cm 211mg / cm 2 12mg / cm 2 13mg / cm 2 14mg / cm 2 15mg / cm 2 16mg / cm 2 17mg / cm 2 18mg / cm 2 19mg / cm 2 20mg / cm 2 The areal density of the active material layer falls within any of the specified values ​​or ranges. An areal density within this range indicates the presence of a significant amount of active material, which is beneficial for improving the battery's energy density. Furthermore, an areal density within this range can reduce polarization at high currents, thereby improving charge and discharge efficiency.

[0142] The areal density of the active material layer has a well-known meaning in the art and can be measured using instruments and methods known in the art. For example, take a negative electrode sheet that has been coated on one side and cold-pressed (if it is a double-coated negative electrode sheet, the coating on one side can be wiped off first), cut it into small circular pieces with an area of ​​S1, weigh the negative electrode sheet under a microscope, and record the weight as M2. Referring to the test method for the areal density of the reference base coating, M1 and M0, the areal density of the active material layer = (weight of the negative electrode sheet M2 - weight of the negative electrode sheet after removing the active material layer M1) / S1.

[0143] In some optional embodiments, the mass m' of the active material layer accounts for 80% to 99% of the total mass M of the undercoat and the active material layer, and may be 85% to 90%.

[0144] Optionally, the mass m' of the active material layer relative to the sum M of the masses of the undercoating layer and the active material layer can be any value or a range thereof from 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, and 99%. A mass m' ratio within the above range can increase the mass proportion of the active material layer in the negative electrode, improve the transport and deintercalation efficiency of active ions in the active material layer, and enhance the kinetic performance of the battery cell.

[0145] As an example, take a negative electrode sheet that has been coated on one side and cold-pressed (if it is a double-sided coated negative electrode sheet, the coating on one side can be wiped off first), and cut it into a small circular sheet with an area of ​​S1. Weigh the negative electrode sheet with the coating on one side as M2. Remove the active material layer on the surface under a microscope and weigh it, recording the weight as M1. Then wipe off the bottom coating of the weighed negative electrode sheet and weigh the negative current collector, recording the weight as M0. The mass of the active material layer m' = (the weight of the negative electrode sheet with the coating on one side is M2 - the weight of the negative electrode sheet after removing the active material layer is M1), and the sum of the masses of the bottom coating and the active material layer M = (the weight of the negative electrode sheet with the coating on one side is M0 - the weight of the negative electrode sheet after removing the active material layer is M1). 2- The weight M0 of the polar current collector.

[0146] As an example, the negative electrode current collector has two surfaces opposite each other in its thickness direction, and the negative electrode active material film layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector. The negative electrode current collector can be made of materials such as metal foil, carbon-coated metal foil, or porous metal plate, and copper foil can be selected as an option.

[0147] As an example, the primer layer and the active material layer may each include an optional conductive agent, an optional binder, and an optional thickener. The conductive agent is used to improve the conductivity of the negative electrode active material film layer, and the binder is used to firmly bond the negative electrode active material and the binder to the negative electrode current collector. This application does not specifically limit the types of conductive agents and binders, which can be selected according to actual needs.

[0148] As an example, the conductive agent may be one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers; the binder may be one or more of styrene-butadiene rubber (SBR), styrene-butadiene rubber (SBCs), water-based acrylic resin, and carboxymethyl cellulose (CMC).

[0149] As an example, the first and second anode active materials can also be one or more of mesophase microcarbon spheres (MCMB), hard carbon, and soft carbon.

[0150] As an example, a thickener such as carboxymethyl cellulose (CMC) can be used. However, this application is not limited to this, and other thickener materials that can be used as negative electrode sheets of battery cells can also be used.

[0151] In some optional embodiments, the method for preparing the negative electrode sheet includes:

[0152] A primer slurry is applied to at least one side of the negative electrode current collector to obtain a primer layer, wherein the primer slurry includes a first adhesive and the primer layer includes a plurality of first protrusions protruding away from the negative electrode current collector and a first recess between two adjacent first protrusions.

[0153] An active material slurry is coated on the side of the base coating away from the negative electrode current collector to obtain the negative electrode sheet containing the active material layer; wherein, the active material layer includes a second binder, the active material layer includes a plurality of second protrusions protruding toward the base coating and a second recess between two adjacent second protrusions, the first protrusions are coupled to the second recesses, the second protrusions are coupled to the first recesses, and the relationship between the mass content a of the first binder in the base coating and the mass content b of the second binder in the active material layer satisfies: a > b;

[0154] In some optional embodiments, the primer slurry includes a first negative electrode active material, etc. In some optional embodiments, the active material slurry includes a second negative electrode active material, etc.

[0155] The aforementioned base coating layer and active material layer are formed by sequentially applying the base coating slurry and active material slurry to the negative electrode current collector, followed by drying and cold pressing. These negative electrode slurries, such as the base coating slurry and active material slurry, are typically formed by dispersing the negative electrode active material, optional conductive agent, optional binder, and other optional additives in a solvent and stirring until homogeneous. The solvent can be N-methylpyrrolidone (NMP) or deionized water, but is not limited to these.

[0156] The negative electrode sheet does not exclude additional functional layers besides the base coating and active material layer. For example, in some embodiments, the negative electrode sheet of the present application may further include a negative electrode conductive layer sandwiched between the negative electrode current collector and the negative electrode film layer and disposed on the surface of the negative electrode current collector. In other embodiments, the negative electrode sheet of the present application may further include a protective layer covering the surface.

[0157] Electrolyte

[0158] A single battery cell includes an electrolyte. The electrolyte acts as a conductor of ions between the positive and negative electrodes.

[0159] In some optional embodiments, the battery cell includes an electrolyte comprising an electrolyte salt, an organic solvent, and a thioester additive, wherein the thioester additive comprises a structure shown in any one or more of formulas (1) to (6):

[0160]

[0161] R1 and R2 each independently include hydrogen atoms and alkyl groups with 1 to 10 unsubstituted or heteroatom-substituted carbon atoms, and n and m are integers, with n being 1 to 4 and m being 0 to 4.

[0162] The heteroatom can be one or more of the following: halogen atom, sulfur atom, nitrogen atom, phosphorus atom, oxygen atom, and boron atom. When M is 0, the expression (6) is a 5-membered ring, and the carbon atom in the parentheses is either absent or empty.

[0163] In the embodiments of this application, the thioester additive is dispersed in the electrolyte formed by the electrolyte salt and organic solvent. The thioester additive can participate in the formation of the solid electrolyte membrane (SEI membrane). That is, the sulfur-containing organic compound is reduced to a sulfur-containing electrolyte salt component and introduced into the SEI. The binding energy ΔE of sulfur element with active ions (e.g., S-Li) is lower than the binding energy of active ions with oxygen element, which reduces the binding energy of elements with active ions in the SEI and also reduces the transport energy barrier of active ions in the SEI membrane, making it easier for active ions to transport in the SEI, reducing the charging impedance Rct, and thus improving the dynamic performance of the battery cell, which is reflected in the charging capacity.

[0164] In the embodiments of this application, the types and contents of inorganic components / electrolyte salts in the electrolyte are of a well-known nature in the art and can be detected using equipment and methods known in the art. For example, the concentration of inorganic components / electrolyte salts in the electrolyte can be qualitatively or quantitatively analyzed by ion chromatography analysis method with reference to standard JY / T020-1996 "General Rules for Ion Chromatography Analysis". In the embodiments of this application, freshly prepared electrolyte can be used as a sample, the free electrolyte of a fresh battery can be used as a sample, or a battery that has been completely discharged (discharged to the lower limit cutoff voltage so that the battery's state of charge is about 0% SOC) can be disassembled in reverse and the free electrolyte obtained from the battery can be used as a sample for detection by ion chromatography analysis method.

[0165] In the embodiments of this application, the types and contents of organic components in the electrolyte are defined in the art and can be detected using equipment and methods known in the art. For example, the organic components in the electrolyte can be qualitatively and quantitatively analyzed by gas chromatography using GB / T9722-2006 "General Rules for Gas Chromatography of Chemical Reagents". In the embodiments of this application, freshly prepared electrolyte can be used as a sample, the free electrolyte of a fresh battery can be used as a sample, or a battery that has been completely discharged (discharged to the lower limit cutoff voltage so that the battery's state of charge is approximately 0% SOC) can be disassembled in reverse, and the free electrolyte obtained from the battery can be used as a sample for detection using ion chromatography.

[0166] In some optional embodiments, R1 and R2 independently comprise hydrogen atoms, alkyl groups having 1 to 4 carbon atoms substituted or unsubstituted with non-halogen atoms. This improves the reliability and cycle life of the battery cell.

[0167] In some optional embodiments, R1 and R2 independently comprise hydrogen atoms and alkyl groups having 1 to 4 carbon atoms, respectively.

[0168] R1 and R2 use the aforementioned groups, which, compared to other groups substituted with heteroatoms, reduce side reactions such as corrosion to battery cells, reduce the probability of thioester additives releasing toxic gases under extreme conditions such as overheating or overcharging, and improve the reliability and cycle life of battery cells.

[0169] Furthermore, R1 and R2 utilize the aforementioned types of functional groups, making them more easily degraded in the natural environment and causing less environmental damage.

[0170] In some optional embodiments, the thioester additive comprises the structure shown in any one or more of formulas (I-1) to (I-26):

[0171]

[0172] In the embodiments of this application, the above-mentioned thioester additives can participate in the formation of the SEI film, reduce the transport energy barrier of active ions in the SEI film, make it easier for active ions to be transported in the SEI, and improve the kinetic performance of the battery cell.

[0173] For example, a solid electrolyte membrane exists at the interface between the negative electrode and the electrolyte. The solid electrolyte membrane includes sulfur-containing products that participate in the formation of the SEI membrane with thioester additives, which further improves the kinetic performance of the battery cell.

[0174] In some optional embodiments, the thioester additive is present in the electrolyte at a mass content of 0.1% to 10%, optionally 0.5% to 2%.

[0175] Optionally, the mass content of the thioester additive in the electrolyte can be any value or a range thereof from 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, and 10%. A mass content of the thioester additive in the electrolyte within the above range is beneficial for further reducing the transport energy barrier of active ions in the SEI film and improving the kinetic performance of the battery cell.

[0176] In some alternative embodiments, the concentration of the electrolyte salt in the electrolyte is from 0.5 mol / L to 3 mol / L, and optionally from 0.8 mol / L to 1.2 mol / L.

[0177] The concentration of the electrolyte salt in the electrolyte solution can be any value or range of the following: 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, 1.0 mol / L, 1.5 mol / L, 2.0 mol / L, 2.5 mol / L, 3.0 mol / L.

[0178] When the electrolyte salt content is within the above range, the interfacial characteristics between the electrode and the electrolyte can be optimized, the interfacial stability of the battery can be enhanced, and the service life of the battery cell can be increased.

[0179] In some optional embodiments, the organic solvent accounts for 60% to 90% by mass in the electrolyte, optionally 80% to 90%.

[0180] Optionally, the mass content of the organic solvent in the electrolyte can be any value or range of the following: 60%, 65%, 70%, 75%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%.

[0181] Therefore, the viscosity and ionic conductivity of the electrolyte can be further controlled, thereby improving the kinetic performance of the battery cell.

[0182] In some embodiments, the electrolyte includes anion, which may include bis(fluorosulfonyl)imide anion (FSI). - ), bis(trifluoromethanesulfonyl)imide anion (TFSI) - ), dioxaborate anion (BOB) - ), difluorooxalate borate anion (DFOB) - ), difluorodioxanol phosphate anion (DFOP) - ), tetrafluorooxalate phosphate anion (TFOP) - ), difluorophosphate anion (PO2F2) - ), hexafluorophosphate anion (PF6) - ), tetrafluoroborate anion (BF4) - ), hexafluoroarsenate anion (AsF6) - ), trifluoromethanesulfonate anion (CF3SO3) - One or more of the following.

[0183] In some embodiments, the electrolyte includes cations, which may include lithium ions, sodium ions, etc. In some optional embodiments, to balance the electrolyte cost and kinetic performance of the battery cell, the high-temperature storage performance of the battery cell is also improved. The battery cell includes an electrolyte, which may also include, but is not limited to, one or more solvents selected from esters, ethers, sulfones, nitriles, etc. Esters may include, but is not limited to, one or more solvents selected from carbonates, phosphate esters, carboxylic esters, sulfate esters, sulfonates, etc. Carbonates may include cyclic carbonates and / or chain carbonates; optionally, carbonates may include both cyclic and chain carbonates. Chain carbonates may include low-viscosity polar chain carbonates, aliphatic branched carbonates, etc.

[0184] As an example, organic solvents may include, but are not limited to, ethylene carbonate (EC), propylene carbonate (PC), butene carbonate, ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS), diethyl sulfone (ESE), dimethyl ether tetraethylene glycol (TEGDME), ethylene glycol dimethyl ether (DME), 1,3-dioxolane (DOL), trimethyl phosphate, 3-methoxypropionitrile, H(CF2)2OCH3, C4F9O CH3, H(CF2)2OCH2CH3, H(CF2)2OCH2CF3, H(CF2)2CH2O(CF2)2H, CF3CHFCF2OCH3, CF3CHFCF2OCH2CH3, 2-trifluoromethylhexafluoropropyl methyl ether, 2-trifluoromethylhexafluoropropyl ethyl ether, 2-trifluoromethylhexafluoropropyl propyl ether, 3-trifluoromethyloctafluorobutyl methyl ether, 3-trifluoromethyloctafluorobutyl ethyl ether, 3-trifluoromethyloctafluorobutyl propyl ether, 4-trifluoromethyl One or more of the following: decafluoropentyl methyl ether, 4-trifluoromethyl decafluoropentyl ethyl ether, 4-trifluoromethyl decafluoropentyl propyl ether, 5-trifluoromethyl dodecylfluorohexyl methyl ether, 5-trifluoromethyl dodecylfluorohexyl ethyl ether, 5-trifluoromethyl dodecylfluorohexyl propyl ether, 6-trifluoromethyl tetradecafluoroheptyl methyl ether, 6-trifluoromethyl tetradecafluoroheptyl ethyl ether, 6-trifluoromethyl tetradecafluoroheptyl propyl ether, 7-trifluoromethyl hexadecylfluorooctyl methyl ether, 7-trifluoromethyl hexadecylfluorooctyl ethyl ether, and 7-trifluoromethyl hexadecylfluorooctyl propyl ether.

[0185] The type of electrolyte salt is not specifically limited and can be selected according to actual needs. For example, electrolyte salts include one or more of lithium salts used in lithium battery cells and sodium salts used in sodium battery cells. As an example, lithium salts include one or more selected from lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalate borate (LiDFOB), lithium dioxalate borate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorodioxalate phosphate (LiDFOP), and lithium tetrafluorooxalate phosphate (LiTFOP). As an example, sodium salts include one or more selected from NaPF6, NaClO4, NaBCl4, NaSO3CF3, and Na(CH3)C6H4SO3.

[0186] In some embodiments, the electrolyte may optionally include other additives. For example, other additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature performance, additives that improve battery low-temperature power performance, etc.

[0187] The preparation methods for electrolytes are well known. For example, an electrolyte salt, a solvent, and optional additives can be mixed evenly to obtain an electrolyte. There are no particular restrictions on the order in which the materials are added during the preparation process; they can be added simultaneously or in batches.

[0188] [Positive electrode plate]

[0189] In some alternative embodiments, the positive electrode may include a positive current collector and a positive active material disposed on at least one surface of the positive current collector.

[0190] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive active material is disposed on either or both of the two opposite surfaces of the positive current collector.

[0191] As an example, the positive current collector can be a metal foil, a conductive polymer material, a carbon material, or a composite current collector. For example, as a metal foil, pure metals, alloys, or surface-treated metals can be used, including but not limited to stainless steel, copper, aluminum, nickel, titanium, or silver. The composite current collector may include a polymer material base layer and a metal layer. The composite current collector can be formed by forming a metal material (aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys, etc.) on a polymer material substrate (such as a substrate of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.).

[0192] As an example, when the battery cell is a lithium-ion battery cell or a lithium metal battery cell, the positive electrode active material may include at least one of the following materials: lithium phosphate, lithium transition metal oxide, and their respective modified compounds. However, this application is not limited to these materials, and other conventional materials that can be used as battery positive electrode active materials may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium phosphate include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), lithium iron phosphate and carbon composites, lithium manganese phosphate (such as LiMnPO4), lithium manganese phosphate and carbon composites, lithium iron manganese phosphate, and lithium iron manganese phosphate and carbon composites.

[0193] Examples of lithium transition metal oxides may include, but are not limited to, lithium cobalt oxides (such as LiCoO2), lithium nickel oxides (such as LiNiO2), lithium manganese oxides (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, and lithium nickel cobalt manganese oxides, such as LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also known as NCM) 333 LiNi 0.5 Co 0.2 Mn 0.3 O2 (also known as NCM) 523 LiNi 0.5 Co 0.25 Mn 0.25 O2 (also known as NCM) 211 LiNi 0.6 Co 0.2 Mn 0.2 O2 (also known as NCM) 622 LiNi 0.8 Co 0.1 Mn 0.1 O2 (also known as NCM) 811 ), lithium nickel cobalt aluminum oxide (such as LiNi)0.8 Co 0.15 Al 0.05 At least one of O2 and its modified compounds. Modified compounds refer to substances obtained by modification methods such as doping or coating based on the above-mentioned substances.

[0194] When the battery cell is a sodium-ion battery cell or a sodium metal battery cell, the positive electrode active material may include, but is not limited to, one or more of the following: sodium-containing transition metal oxides, polyanionic materials (such as phosphates, fluorophosphates, pyrophosphates, sulfates, etc.), and Prussian blue materials.

[0195] As an example, positive electrode active materials may include NaFeO2, NaCoO2, NaCrO2, NaMnO2, NaNiO2, and NaNi 1 / 2Ti 1 / 2 O2, NaNi 1 / 2 Mn 1 / 2 O2, Na 2 / 3 Fe 1 / 3 Mn 2 / 3 O2, NaNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, NaFePO4, NaMnPO4, NaCoPO4, Prussian blue materials and materials with the general formula X p M' q (PO4) r O x Y 3-x One or more of the materials. In general formula X p M' q (PO4) r O x Y 3-x In the given condition, 0 < p ≤ 4, 0 < q ≤ 2, 1 ≤ r ≤ 3, 0 ≤ x ≤ 2, and X includes elements selected from H. + Li + Na + K + and NH4 + One or more of the following, M' is a transition metal cation, which may be selected from one or more of V, Ti, Mn, Fe, Co, Ni, Cu and Zn, and Y is a halide anion, which may be selected from one or more of F, Cl and Br.

[0196] The modified compounds for the above-mentioned positive electrode active materials can be obtained by doping and / or surface coating of the positive electrode active materials.

[0197] During the charging and discharging process, battery cells undergo Li or Na insertion / extraction and consumption, resulting in varying molar contents of Li or Na at different discharge states. In the examples of positive electrode active materials in this disclosure, the molar contents of Li or Na represent the initial state of the material, i.e., the state before material addition. After charge-discharge cycles, the molar contents of Li or Na will change when the positive electrode active material is applied to the battery cell. Similarly, the molar contents of oxygen (O) in the examples of positive electrode active materials in this disclosure are only theoretical values. Lattice oxygen release will cause changes in the molar contents of O, and the actual molar contents of O will also fluctuate.

[0198] In some alternative embodiments, the positive electrode can be a foamed metal. The foamed metal can be foamed nickel, foamed copper, foamed aluminum, foamed alloy, or foamed carbon, etc. When foamed metal is used as the positive electrode, the surface of the foamed metal may or may not contain a positive electrode active material. As an example, a positive electrode active material is filled and / or deposited within the foamed metal.

[0199] [Isolation membrane]

[0200] The separator is located between the positive and negative electrodes and mainly serves to prevent internal short circuits.

[0201] This application does not impose any particular restrictions on the type of separator membrane; any known porous separator membrane with good chemical and mechanical stability can be selected.

[0202] In some embodiments, the material of the separator may include, but is not limited to, one or more of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may 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 may be the same or different.

[0203] Methods for preparing battery cells are well known. In some embodiments, a positive electrode, a separator, a negative electrode, and an electrolyte can be assembled to form a battery cell. As an example, the positive electrode, separator, and negative electrode can be formed into an electrode assembly through a winding process and / or a stacking process. The electrode assembly is placed in an outer packaging, dried, and then injected with the electrolyte. After vacuum sealing, settling, and formation processes, a battery cell is obtained.

[0204] Electrical appliances

[0205] This application also provides an electrical device, which includes the battery device provided in this application. The battery device can be used as the power source for the electrical device or as the energy storage unit of the electrical device. The electrical device can be, but is not limited to, mobile devices (such as mobile phones, tablets, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0206] Electrical devices can choose the type of battery device according to their usage needs, such as individual battery cells, battery modules, or battery packs.

[0207] Figure 9 This is a schematic diagram of an example electrical device. The device could be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the device's requirements for high power and high energy density, a battery pack or battery module can be used.

[0208] Another example of an electrical device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a single battery cell as their power source.

[0209] Example

[0210] The following embodiments describe the disclosure of this application in more detail. These embodiments are merely illustrative, as various modifications and variations will be apparent to those skilled in the art within the scope of the disclosure of this application. Unless otherwise stated, all parts, percentages, and ratios reported in the following embodiments are based on mass, and all reagents used in the embodiments are commercially available or synthesized by conventional methods and can be used directly without further processing, and the instruments used in the embodiments are commercially available.

[0211] Example 1

[0212] Preparation of negative electrode sheet:

[0213] 1) Preparation of current collectors with graphite undercoat:

[0214] Natural graphite, conductive agent (Super-P), and aqueous dispersant sodium carboxymethyl cellulose (CMC-Na) were mixed evenly at a mass ratio of 93:1:1 to obtain mixture A; mixture A was mixed with water and stirred evenly to obtain mixture B. The average volume particle size Dv50 of the natural graphite was 10 micrometers.

[0215] Add water-based binder styrene-butadiene latex (SBR) to mixture B, wherein the mass fraction ratio of natural graphite: Super-P: CMC: SBR = 93:1:1:5, and stir to obtain a primer slurry with a solid content of 20%.

[0216] Take a copper foil substrate with a thickness of 5μm for the negative electrode current collector, coat the above-mentioned base coating slurry onto the surface of the copper foil substrate, and after drying, form a copper foil current collector with a base coating. The thickness of the base coating on each side is 15 micrometers, so that the surface of the base coating has an uneven structure.

[0217] 2) Preparation of the active substance layer:

[0218] Graphite, conductive carbon black, aqueous dispersant sodium carboxymethyl cellulose (CMC-Na), and aqueous binder styrene-butadiene latex (SBR) were uniformly mixed at a weight ratio of 97:1:1:1. The graphite included both natural and artificial graphite in a 1:1 mass ratio. Water was added to prepare an active material slurry with a solid content of 50%. The active material slurry was coated on both sides of a copper foil current collector with a base coating. After cold pressing and cutting, a negative electrode sheet was obtained with an active material layer thickness of 150 micrometers.

[0219] Preparation of battery cells:

[0220] Preparation of positive electrode sheet: Lithium iron phosphate: conductive carbon black: polyvinylidene fluoride PVDF = 8:1:1 by mass ratio, and then N-methylpyrrolidone solvent is added to prepare positive electrode slurry. The solid content of positive electrode slurry is 50%. It is coated on both sides of aluminum foil with a thickness of 15μm, and after cold pressing and cutting, positive electrode sheet is obtained.

[0221] Preparation of the diaphragm: A polyethylene film with a thickness of 12 μm was used as the diaphragm.

[0222] Negative electrode sheet: The negative electrode sheet prepared above;

[0223] Electrolyte preparation:

[0224] Ethylene carbonate, diethyl carbonate, and dimethyl carbonate were mixed in a volume ratio of 1:1:1. LiPF6 was then dissolved in this solution to obtain an electrolyte. The concentration of LiPF6 in this electrolyte was 1 mol / L.

[0225] Assembly: Place the electrodes in the order of "positive electrode - separator - negative electrode - separator - positive electrode", inject 0.5g of the prepared electrolyte, vacuum heat seal the aluminum-plastic film bag, and let it stand at room temperature for at least 6 hours to obtain the stacked battery.

[0226] Examples 2 to 5

[0227] The preparation method is similar to that of Example 1, except that the content of the first or second binder is different. See Table 1.

[0228] Examples 6 to 8

[0229] The preparation method is similar to that in Example 1, except that the thickness of the base coating or the active material layer is different, as shown in Table 1.

[0230] Examples 9 to 13

[0231] The preparation method is similar to that in Example 1, except that the average volume particle size Dv of the first negative electrode active material is... 1 50 or the average volumetric particle size Dv of the second negative electrode active material 2 50 different, the average volumetric particle size Dv of the first negative electrode active material 1 50 and the average volume particle size Dv of the second negative electrode active material 2 The ratio c of 50 varies, as shown in Table 1.

[0232] Example 14

[0233] The preparation method is similar to that in Example 1, except that a thioester additive with the structural formula I-1 is added to the electrolyte, and the mass content of the thioester additive in the electrolyte is 2%.

[0234] Example 15

[0235] The preparation method is similar to that in Example 1, except that a thioester additive with the structural formula I-1 is added to the electrolyte, and the mass content of the thioester additive in the electrolyte is 4%.

[0236] Example 16

[0237] The preparation method is similar to that in Example 1, except that a thioester additive with the structural formula I-14 is added to the electrolyte. The mass content of the thioester additive in the electrolyte is 2%.

[0238] Example 17

[0239] The preparation method is similar to that in Example 1, except that a thioester additive with the structural formula I-17 is added to the electrolyte. The mass content of the thioester additive in the electrolyte is 2%.

[0240] Comparative Example 1

[0241] The stacked lithium-ion battery in this comparative example has the same assembly structure and materials as the actual design, with the following differences: ① The copper foil of the negative electrode current collector does not have a graphite undercoat; ② The preparation of the negative electrode sheet: graphite, conductive carbon black, aqueous dispersant sodium carboxymethyl cellulose (CMC-Na), and binder styrene-butadiene latex (SBR) are uniformly mixed at a mass ratio of 95:1:1:3:100. The graphite includes natural graphite and artificial graphite at a mass ratio of 1:1 to obtain the positive electrode slurry. The solid content of the negative electrode slurry is 50%. The negative electrode slurry is coated on both sides of a 5-micrometer-thick copper foil current collector. After cold pressing and cutting, the negative electrode sheet is obtained, with an active material layer thickness of 165 micrometers.

[0242] Comparative Example 2

[0243] The stacked lithium-ion battery in this comparative example has the same assembly structure and materials as the actual solution. The difference is that no active material layer is prepared, and the thickness of the bottom coating on the copper foil of the negative electrode current collector is 165 micrometers.

[0244] Test section

[0245] 1) Battery cell cycle life test: The ambient temperature for cell cycling is set to 25℃, and charge / discharge cycles are performed using a 1 / 3C rate. The cut-off voltages for charging and discharging are set to 3.8V and 2.0V, respectively. The number of cycles completed by the battery cell when the discharge capacity decays to 80% of the first discharge capacity is the cycle life of the battery cell.

[0246] 2) Battery cell charging rate test: At temperatures of 25℃ and -10℃, with the negative electrode potential of 0mV as the cutoff condition, the maximum charge capacity (SOC) that can be achieved under different charging rates is tested. The charging time under different SOC ranges is obtained by dividing by different charging rates. The total charging time T is obtained by summing the charging times. The equivalent charging rate = SOC / T. The charging capability is evaluated by the magnitude of the equivalent charging rate.

[0247] The test results are shown in Tables 1 and 2.

[0248]

[0249] In Table 1, the content 'a' of the first adhesive represents the mass content 'a' of the first adhesive in the primer layer; and the content 'b' of the second adhesive represents the mass content 'b' of the second adhesive in the active material layer.

[0250] As shown in Table 1, the bottom coating and active material layer in Examples 1-4 use negative electrode active materials with different particle sizes, namely the first negative electrode active material and the second negative electrode active material. Different amounts of binder are added to the bottom coating and active material layer to make a > b, so that the battery cell obtains better cycle life and charging capability. Compared with Comparative Example 2, the battery cell in Example 1 obtains better charging capability. Compared with Comparative Example 1, the battery cell in Example 1 obtains better cycle life.

[0251] Compared with Example 1, Examples 2 to 5 show differences in the content of the first or second binder, which affects the cycle life and charging capacity of the battery cells to varying degrees. Compared with Example 1, Examples 6 to 8 show differences in the thickness of the undercoat layer or the active material layer, which affects the cycle life and charging capacity of the battery cells to varying degrees. Compared with Example 1, Examples 9 to 13 show differences in the average volume particle size Dv of the first negative electrode active material. 1 50 and the average volume particle size Dv of the second negative electrode active material 2 Different ratios of 50 (c) affect the cycle life and charging capacity of individual battery cells to varying degrees.

[0252] Compared with Example 1, Examples 14 to 17 added different types or amounts of thioester additives to the electrolyte, which improved the charging capacity of the battery cells and also improved the cycle life of the battery cells or kept the cycle life of the battery cells at a comparable level.

[0253] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A battery cell, characterized in that, The electrode assembly includes a positive electrode, a negative electrode, and a separator, wherein the separator is located between the positive electrode and the negative electrode, and the negative electrode includes: Negative electrode current collector; A base coating layer is disposed on at least one side of the negative electrode current collector, the base coating layer including a plurality of first protrusions protruding away from the negative electrode current collector and a first recess between two adjacent first protrusions; the base coating layer includes a first adhesive; An active material layer is disposed on the side of the base coating layer facing away from the negative electrode current collector. The active material layer includes a plurality of second protrusions protruding toward the base coating layer and a second recess between two adjacent second protrusions. The active material layer includes a second binder. Wherein, the first protrusion is coupled to the second recess, and the second protrusion is coupled to the first recess; the relationship between the mass content a of the first adhesive in the base coating and the mass content b of the second adhesive in the active material layer satisfies: a > b.

2. The battery cell according to claim 1, characterized in that, The mass content 'a' of the first adhesive in the base layer and the mass content 'b' of the second adhesive in the active material layer satisfy the relationship a:b = (2~10):

1.

3. The battery cell according to claim 1 or 2, characterized in that, The thickness ratio of the base coating layer to the active material layer is (1:5) to (1:50).

4. The battery cell according to any one of claims 1 to 3, characterized in that, The base coating layer includes a first negative electrode active material; the active material layer includes a second negative electrode active material; the first negative electrode active material and the second negative electrode active material satisfy one or more of the following conditions: 1) The average volumetric particle size Dv of the first negative electrode active material 1 50 and the average volume particle size Dv of the second negative electrode active material 2 The ratio c of 50 satisfies: (1:1)≤c≤(1:5); 2) The average volumetric particle size Dv of the first negative electrode active material 1 50 represents 1 to 20 μm; 3) The average volumetric particle size Dv of the second negative electrode active material 2 50 is 2 to 40 μm; 4) The first negative electrode active material and the second negative electrode active material include one or more of artificial graphite and natural graphite; 5) The first negative electrode active material and the second negative electrode active material further include one or more of silicon-carbon materials, silicon-oxygen materials, silicon-nitrogen materials, silicon alloys, lithium carbonate, titanium dioxide, titanates, amorphous carbon, transition metal oxides, transition metal sulfides, and transition metal phosphides.

5. The battery cell according to claim 4, characterized in that, The peel strength of the base coating and the active material layer is 5 N / m to 15 N / m.

6. The battery cell according to any one of claims 1 to 5, characterized in that, The base coating layer satisfies one or more of the following conditions: 1) The thickness of the base coating is 1 μm to 20 μm; 2) The mass content of the first negative electrode active material in the base coating is ≥50%; 3) The mass content (a) of the first adhesive in the base coating is 2% to 10%; 4) The areal density of the base coating is 0.1 mg / cm³. 2 Up to 2 mg / cm 2 ; 5) The mass m of the base coating layer accounts for 1% to 20% of the total mass M of the base coating layer and the active material layer.

7. The battery cell according to any one of claims 1 to 6, characterized in that, The base coating layer satisfies one or more of the following conditions: 1) The thickness of the base coating is 5 μm to 15 μm; 2) The mass content of the first negative electrode active material in the base coating is 85% to 95%; 3) The mass content (a) of the first adhesive in the base coating is 2% to 5%; 4) The areal density of the base coating is 1 mg / cm³. 2 Up to 1.5 mg / cm 2 ; 5) The mass m of the base coating layer accounts for 10% to 15% of the total mass M of the base coating layer and the active material layer.

8. The battery cell according to any one of claims 1 to 7, characterized in that, The active material layer satisfies one or more of the following conditions: 1) The mass content b of the second adhesive in the active material layer is 0.5% to 3%; 2) The thickness of the active material layer is 10 μm to 200 μm; 3) The mass content of the second negative electrode active material in the active material layer is 70% to 98%; 4) The areal density of the active substance layer is 5 mg / cm³. 2 Up to 20 mg / cm 2 ; 5) The mass m' of the active material layer accounts for 80% to 99% of the total mass M of the base layer and the active material layer.

9. The battery cell according to any one of claims 1 to 8, characterized in that, The active material layer satisfies one or more of the following conditions: 1) The mass content b of the second adhesive in the active material layer is 0.5% to 1.5%; 2) The thickness of the active material layer is 50 μm to 150 μm; 3) The mass content of the second negative electrode active material in the active material layer is 85% to 98%; 4) The areal density of the active substance layer is 10 mg / cm³. 2 Up to 15 mg / cm 2 ; 5) The mass m' of the active material layer accounts for 85% to 90% of the total mass M of the base layer and the active material layer.

10. The battery cell according to any one of claims 1 to 9, characterized in that, The battery cell includes an electrolyte, which comprises an electrolyte salt, an organic solvent, and a thioester additive, wherein the thioester additive comprises any one or more of the structures shown in formulas (1) to (6): R1 and R2 each independently include hydrogen atoms and alkyl groups with 1 to 10 unsubstituted or heteroatom-substituted carbon atoms, and n and m are integers, with n being 1 to 4 and m being 0 to 4.

11. The battery cell according to claim 10, characterized in that, R1 and R2 each independently include hydrogen atoms and alkyl groups having 1 to 4 carbon atoms.

12. The battery cell according to claim 10 or 11, characterized in that, The thioester additive comprises the structure shown in any one or more of formulas (I-1) to (I-26):

13. The battery cell according to any one of claims 10 to 12, characterized in that, The electrolyte meets one or more of the following conditions: 1) The thioester additive in the electrolyte has a mass content of 0.1% to 10%; 2) The concentration of the electrolyte salt in the electrolyte solution is from 0.5 mol / L to 3 mol / L; 3) The organic solvent in the electrolyte contains 60% to 90% by mass.

14. The battery cell according to any one of claims 10 to 13, characterized in that, The electrolyte meets one or more of the following conditions: 1) The thioester additive in the electrolyte has a mass content of 0.5% to 2%; 2) The concentration of the electrolyte salt in the electrolyte solution is from 0.8 mol / L to 1.2 mol / L; 3) The organic solvent in the electrolyte contains 80% to 88% by mass.

15. A negative electrode sheet, characterized in that, include: Negative electrode current collector; A base coating layer is disposed on at least one side of the negative electrode current collector, the base coating layer including a plurality of first protrusions protruding away from the negative electrode current collector and a first recess between two adjacent first protrusions; the base coating layer includes a first adhesive; An active material layer is disposed on the side of the base coating layer facing away from the negative electrode current collector. The active material layer includes a plurality of second protrusions protruding toward the base coating layer and a second recess between two adjacent second protrusions. The active material layer includes a second binder. Wherein, the first protrusion is coupled to the second recess, and the second protrusion is coupled to the first recess; the relationship between the mass content a of the first adhesive in the base coating and the mass content b of the second adhesive in the active material layer satisfies: a > b.

16. A battery device, characterized in that, The battery cell includes any one of the battery cells described in claims 1 to 14, or the negative electrode sheet described in claim 15 is used to form the battery cell.

17. An electrical device, characterized in that, Includes the battery device as described in claim 16.

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