Negative electrode and preparation method and application thereof

Abstract

The invention discloses a negative electrode and a preparation method and application thereof. The negative electrode comprises a current collector and a negative electrode material layer combined on the current collector, the negative electrode material layer comprises a plurality of separation layers and a plurality of active layers, the plurality of active layers are combined on the current collector, and the plurality of active layers are separated through the plurality of separation layers; the spacer layer is used for buffering volume expansion of the active layer. The problems of shedding, powder falling, wrinkling, breakage and the like caused by volume expansion of the active material contained in the negative electrode are solved, the structural stability of the whole negative electrode material layer is improved, and the cycle performance of the negative electrode is improved. The preparation method of the negative electrode comprises the following steps: respectively preparing the separation layer slurry and the active layer slurry, and then carrying out film forming treatment on the surface of the current collector. The negative electrode can be applied to the battery, and the safety and the cycling stability of the battery are improved.

Description

Negative electrode and its preparation method and application Technical Field

[0001] The present application relates to the field of battery technology, and in particular to a negative electrode and a preparation method and application thereof. Background Art

[0002] In the context of energy conservation and emission reduction, new energy technologies are developing rapidly, among which the research breakthroughs and applications of battery technology are the most significant, and lithium-ion batteries are the battery with the most prominent development momentum.

[0003] In lithium-ion batteries, the negative electrode is the primary lithium storage site, allowing lithium ions to be inserted and removed during the charge and discharge processes. Therefore, the performance of the negative electrode is a key factor influencing battery performance. Currently, there are several types of negative electrode materials: carbon negative electrode materials, such as natural graphite and soft carbon, and non-carbon negative electrode materials, such as silicon-based materials, alloys, and tin-gold materials.

[0004] However, the currently widely used carbon and silicon-based negative electrodes are prone to shedding, wrinkling, and even breaking in severe cases, significantly impacting electrode quality and cycling performance. One reason for this is the volume expansion of the main materials used in these electrodes. Existing technologies primarily address this issue by focusing on material design and process improvements, while addressing improvements to the electrode design itself is less effective.

[0005] Summary of the Invention

[0006] In view of the above problems, the embodiments of the present application provide a negative electrode and a preparation method and application thereof to solve the technical problem of volume expansion of existing negative electrode sheets.

[0007] In a first aspect, embodiments of the present application provide a negative electrode. The negative electrode in embodiments of the present application includes a current collector and a negative electrode material layer bonded to the current collector. The negative electrode material layer includes several separator layers and several active layers. The several active layers are bonded to the current collector and separated by several separator layers. The separator layers are used to buffer the volume expansion of the active layers.

[0008] Through the above-mentioned arrangement, the separator layer of the negative electrode in the embodiment of the present application can absorb the volume expansion of the active layer, solve the problem of shedding and powdering caused by volume expansion, avoid the generation of wrinkles and electrode breakage, improve the structural stability of the entire negative electrode material layer, improve the cycle performance of the negative electrode, and can also block the growth of large-scale shedding, penetrating wrinkles, and cracks.

[0009] In some embodiments, the separator layers and the active layers are alternately arranged side by side along the length direction of the current collector.

[0010] Or in some embodiments, the separator layers and the active layers are alternately arranged side by side along the width direction of the current collector.

[0011] Or in some embodiments, the separation layer is bonded to the surface of the current collector in a grid structure, and the active layer is filled in the grid structure.

[0012] With these arrangements, when the active material contained in the active layer expands in volume, the separator layer can effectively play a buffering or volume absorption role, buffering or absorbing the volume expansion of the active layer, thereby effectively reducing the volume expansion effect of the negative electrode material layer during charging and discharging, and reducing problems such as shedding, powdering, cracking, and breakage caused by the volume expansion of the active layer.

[0013] In some embodiments, when the separator layer and the active layer are alternately arranged side by side along the length of the current collector, the outermost layer of the negative electrode material layer in the length direction is the separator layer. This can improve the overall structural stability and electrochemical performance stability of the negative electrode material layer.

[0014] In some embodiments, the width of a single active layer is 5 μm to 15 μm.

[0015] In some embodiments, the width ratio of the spacer layer to the active layer is 1:2 to 1:7.

[0016] These width designs can take into account the stability of the negative electrode material layer structure and electrochemical performance as well as the high capacity of the negative electrode.

[0017] In some embodiments, the porosity of the separator layer is greater than the porosity of the active layer.

[0018] In some embodiments, when subjected to the same force, the deformation of the separation layer is greater than the deformation of the active layer.

[0019] These designs can enhance the buffering effect of the separator layer on the volume expansion of the active layer, and improve the stability of the negative electrode material layer structure and electrochemical performance.

[0020] In some embodiments, the material of the separation layer includes the following components in parts by weight:

[0021]

[0022] In a further embodiment, the porous skeleton material includes at least one of metal organic matter, porous metal oxide, metal, MXene material, graphite, graphene, amorphous carbon, lithium titanium composite oxide, and carbon nanotubes.

[0023] In a further embodiment, the pore size of the porous framework material is 1 nm to 10 nm.

[0024] In a further embodiment, the ratio of the pore size of the porous framework material to the pore size of the graphite is greater than 1.

[0025] In a further embodiment, the ratio of the pore size of the porous framework material to the pore size of the silicon-based material is ≥2.

[0026] The use of these porous skeleton materials can give the separator layer a porous structure, which can accommodate a large amount of lithium, withstand large deformation and stress, and buffer the volume expansion of the active material contained in the active layer.

[0027] In a further embodiment, the metal organic compound includes at least one of a metal organic framework material and a metal organic framework derivative.

[0028] In a further embodiment, the metal center of the metal organic framework material includes at least one of Ti, Fe, Cu, Zr, Zn, and Cr.

[0029] The porous skeleton material uses these metal organics, especially metal organic framework materials, so that the separator layer has a better buffering effect on volume expansion, ensures the stability of the structure and chemical properties of the separator layer, improves the conductivity of the separator layer and reduces the internal resistance of the entire negative electrode.

[0030] In a further embodiment, the conductive agent includes at least one of carbon black SP, superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. These conductive agents can increase the conductivity of the separator layer and reduce the internal resistance of the entire negative electrode.

[0031] In a further embodiment, the binder includes at least one of styrene-butadiene latex, styrene-butadiene rubber, polyacrylic acid, sodium polyacrylate, polyacrylamide, polyvinyl alcohol, polymethacrylic acid, and carboxymethyl chitosan. These binders can bond the components in the separator layer and shape the separator layer.

[0032] In some embodiments, the active material contained in the active layer includes at least one of silicon-based materials, graphite, amorphous carbon materials, and tin-based materials.

[0033] In some embodiments, the active layer further includes a solid electrolyte, and the solid electrolyte accounts for a mass percentage of the active layer that is greater than 0 and less than or equal to 1%.

[0034] In a further embodiment, the solid electrolyte includes at least one of polyethylene oxide, polymethyl methacrylate, polyacrylonitrile, polyvinyl chloride, pentaerythritol tetraacrylate, and nano-ceramic composite polymer.

[0035] Adding a solid electrolyte to the active layer can increase the lithium ion migration rate of the active layer; can enhance the bonding force between the active layer material and the current collector; can increase the cohesion of the active material and inhibit the volume expansion of the active layer.

[0036] In a second aspect, an embodiment of the present application provides a method for preparing a negative electrode. The preparation method of the embodiment of the present application comprises the following steps:

[0037] Prepare separation layer slurry and active layer slurry;

[0038] The separator slurry and the active layer slurry are subjected to film-forming treatment on the surface of the current collector to form a negative electrode material layer, and the negative electrode material layer includes several separator layers and several active layers, and the several active layers are separated by several separator layers.

[0039] The separator layer produced by the preparation method of the present invention can buffer the volume expansion and stress of the active layer, thereby solving the problem of negative electrode volume expansion. The preparation method has controllable process parameters and produces a high-quality negative electrode with stable performance and good electrochemical performance.

[0040] In some embodiments, the spacer layer slurry includes a solvent and the following components dispersed in the solvent in parts by weight:

[0041]

[0042] In some embodiments, the viscosity of the separation layer slurry is 6000 mPa·s to 25000 mPa·s.

[0043] In some embodiments, the solid content of the separation layer slurry is 50% to 70%.

[0044] The setting of these process parameters can ensure that the separator layer formed by the separator layer slurry has good quality and improve the effect of the separator layer in buffering the volume expansion of the active layer.

[0045] In some embodiments, the active layer slurry contains a solid electrolyte, and the solid electrolyte accounts for a mass percentage of the active layer formed by the active layer slurry that is greater than 0 and less than or equal to 1%.

[0046] The setting of these process parameters can ensure that the active layer formed by the active layer slurry has good quality and good electrochemical performance and stability.

[0047] Thirdly, embodiments of the present application provide a battery comprising the negative electrode of the aforementioned embodiments, or comprising a negative electrode prepared using the preparation method of the aforementioned embodiments. This can alleviate the volume expansion of the negative electrode, and mitigate issues such as wrinkling, peeling, and even fracture caused by volume expansion, thereby ensuring the safety and good cycling stability of the battery of this embodiment.

[0048] Fourthly, the present invention provides an electrical device, which includes the battery of the present invention, and is used to provide electrical energy. The electrical device of the present invention has good safety and long standby or battery life.

[0049] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiment below. The accompanying drawings are for illustration purposes only and are not to be considered as limiting the present application. The same reference numerals are used throughout the drawings to represent the same components. In the drawings:

[0051] FIG1 is a schematic structural diagram of an embodiment of a negative electrode of the present application;

[0052] FIG2 is a schematic perspective structural diagram of the negative electrode of the embodiment of the present application shown in FIG1 ;

[0053] FIG3 is a schematic structural diagram of another embodiment of the negative electrode of the present application;

[0054] FIG4 is a schematic structural diagram of another embodiment of the negative electrode of the present application;

[0055] FIG5 is a schematic flow chart of a method for preparing a negative electrode according to an embodiment of the present application;

[0056] FIG6 is a schematic structural diagram of an embodiment of a secondary battery according to an embodiment of the present application;

[0057] FIG7 is an exploded schematic diagram of the secondary battery shown in FIG6 ;

[0058] FIG8 is a schematic structural diagram of an embodiment of a battery module according to the present application;

[0059] FIG9 is a schematic structural diagram of an embodiment of a battery pack according to the present application;

[0060] FIG10 is a schematic diagram of the exploded structure of the battery pack shown in FIG9 ;

[0061] FIG11 is a schematic diagram of an embodiment of an electric device including a secondary battery according to an embodiment of the present application as a power source.

[0062] The accompanying drawings in the specific implementation manner are as follows:

[0063] 10. Current collector;

[0064] 20. Negative electrode material layer, 21. Separator layer, 22. Active layer;

[0065] 30. Secondary battery cell, 31. Housing, 32. Electrode assembly, 33. Cover plate;

[0066] 40. Battery module;

[0067] 50. Battery pack, 51. Box, 52. Lower box. DETAILED DESCRIPTION

[0068] The following embodiments of the technical solution of the present application will be described in detail with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present application and are therefore only examples and are not intended to limit the scope of protection of the present application.

[0069] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in the specification and claims of this application and the above-mentioned figure descriptions are intended to cover non-exclusive inclusions.

[0070] In the description of the embodiments of this application, the technical terms "first" and "second" are used only to distinguish different objects and should not be understood to indicate or imply relative importance or implicitly specify the quantity, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, the meaning of "plurality" is more than two, unless otherwise clearly and specifically defined.

[0071] References herein to "embodiments" mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0072] In the description of the embodiments of this application, the term "and / or" is simply a description of the association relationship between associated objects, indicating that three relationships can exist. For example, A and / or B can represent three situations: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " in this document generally indicates that the associated objects are in an "or" relationship.

[0073] In the description of the embodiments of the present application, the term "multiple" refers to more than two (including two). Similarly, "multiple groups" refers to more than two groups (including two groups), and "multiple pieces" refers to more than two pieces (including two pieces).

[0074] In the description of the embodiments of the present application, the technical terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the embodiments of the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the embodiments of the present application.

[0075] In the description of the embodiments of the present application, unless otherwise expressly specified or limited, technical terms such as "installed," "connected," "connected," and "fixed" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integration; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; internal connections between two components or interactions between two components. Those skilled in the art can understand the specific meanings of the above terms in the embodiments of the present application based on specific circumstances.

[0076] In the context of energy conservation and emission reduction, new energy technologies are developing rapidly, among which the research breakthroughs and applications of battery technology are the most significant, and lithium-ion batteries are the battery with the most prominent development momentum.

[0077] In lithium-ion batteries, the negative electrode is the primary storage site for lithium, allowing lithium ions to be inserted and removed during the charge and discharge process. Therefore, the quality and performance of the negative electrode are crucial factors affecting battery performance. Currently, a wide variety of negative electrode materials are available, including carbon, silicon-based, and metal materials.

[0078] For example, lithium-ion batteries using carbon materials as negative electrode materials have certain safety and stability properties. These carbon materials mainly include graphite-based carbon materials, non-graphite-based carbon materials, doped carbon materials, and coated carbon materials. Among them, graphite materials, especially artificial graphite, are currently the most commonly used negative electrode materials in lithium batteries due to their low price, high reversible capacity, low charge and discharge voltage platform, no voltage hysteresis, excellent conductivity, good cycle performance and rate performance, and good electrolyte selectivity.

[0079] Silicon-based materials are also ideal negative electrode materials for lithium-ion batteries. Silicon-based materials can form Li4.4Si alloys with lithium, with a theoretical lithium storage capacity of up to 4200mAh / g, which is more than 10 times the specific capacity of graphite. Silicon has a higher lithium insertion potential (0.5V) than graphite, and is less likely to form lithium dendrites during charging, with a much smaller risk of lithium precipitation and better safety than graphite-based negative electrode materials. Silicon has low reactivity with electrolytes and will not co-intercalate with organic solvents. It can provide channels for lithium ion insertion and extraction from all directions, with excellent fast charging performance. In addition, it has abundant reserves and low cost. Therefore, silicon-based materials are also very promising negative electrode materials for lithium batteries. In practical applications, silicon-based materials can also be incorporated into materials such as graphite as negative electrode materials.

[0080] However, in existing lithium-ion batteries, negative electrodes often have the problem of volume expansion, especially negative electrodes made of the above-mentioned carbon materials or silicon-based materials. For example: carbon material negative electrodes represented by graphite often begin to expand in volume after coating and compaction; silicon-based negative electrodes will also expand in volume during the lithium insertion process. The volume expansion of silicon-based negative electrodes in a charged state can reach 300%. This phenomenon is also called the rebound phenomenon of the negative electrode pole piece and can be expressed by thickness changes. Huge volume changes can easily cause uneven stress inside the negative electrode material layer, and the active materials squeeze each other and fall off the current collector or even lose powder, thereby reducing the electrical contact between the active material and the current collector, causing the electrode cycle performance to decline rapidly; in addition, the volume expansion of the material can easily cause the negative electrode to wrinkle or even break. The above problems hinder the application of these negative electrode materials, especially silicon-based materials, in negative electrodes.

[0081] In the existing technology, the problem of product quality and performance degradation caused by the expansion of negative electrode materials is generally alleviated through solutions such as material design and process improvement. For example, parameters such as slurry, coating speed, guide roller tension, drying temperature, and battery cell design are optimized to improve problems such as powder shedding, wrinkling and breakage of the negative electrode. However, since the root cause of the problem lies in the negative electrode itself, the existing technology has not made effective optimization and design of the negative electrode itself.

[0082] Based on the inventor's research on the shortcomings of existing negative electrodes, the inventor found that if a layer of negative electrode material contained in the negative electrode is creatively broken down into smaller pieces, that is, divided into several negative electrode active layer intervals, and a volume buffer is added between adjacent active layer intervals. In this way, when the volume of each active layer interval expands during the charge and discharge process, the buffer can effectively absorb the volume expansion of each active layer interval, thereby effectively increasing the volume expansion of the entire negative electrode material layer. Based on the inventor's new optimization and design of the negative electrode, the following negative electrode and its preparation method and application are proposed, which alleviate the volume expansion of the active material in the negative electrode and avoid uneven stress inside the negative electrode material layer, thereby solving the problem of volume expansion of the negative electrode and reducing the impact on the quality and cycle performance of the negative electrode.

[0083] negative electrode

[0084] In a first aspect, embodiments of the present application provide a negative electrode. As some embodiments of the present application, the structure of the negative electrode of the present application is shown in Figures 1 to 4, including a current collector 10 and a negative electrode material layer 20 bonded to the current collector 10. The negative electrode material layer 20 may include several separator layers 21 and several active layers 22, wherein the several active layers 22 are bonded to the surface of the current collector 10 and separated by the several separator layers 21; the separator layers 21 are used to buffer the volume expansion of the active layers 22.

[0085] In the negative electrode of the present embodiment, the negative electrode material layer 20 includes several active layers 22 bonded to the current collector 10, and adjacent active layers 22 are separated by several separator layers 21. In other words, each separator layer 21 is disposed between two adjacent active layers 22 to absorb the volume expansion of the corresponding active layer 22 during charge and discharge, thereby improving the structural stability of the entire negative electrode material layer 20 and the cycle performance of the negative electrode. The term "several" refers to a number of two or more.

[0086] Therefore, the active layers 22 contained in the negative electrode material layer 20 of the negative electrode of the present embodiment are separated, and the separator layer 21 can timely buffer or absorb the volume expansion of several active layers 22 and buffer stress, thereby solving the problem of negative electrode volume expansion, thereby solving the problem of active material volume expansion, including shedding and powdering, which affects cycle performance, and also suppressing the occurrence of wrinkles and electrode fractures. In addition, compared with conventional negative electrodes containing a single layer of negative electrode material, the negative electrode of the present embodiment can divide the stress it is subjected to into several relatively small active layers 22, and the active layers 22 are separated from each other by the separator layer 21, which can prevent the growth of localized shedding, penetrating wrinkles, and cracks.

[0087] It should be noted that the names of the separation layer 21 and the active layer 22 do not limit their shapes to layered, but rather indicate the aggregation state of the materials contained in the separation layer 21 and the active layer 22. The active layer 22 can be arranged on the current collector 10 in a variety of shapes, such as a long strip, a grid, etc. In addition, several adjacent active layers 22 can be completely separated, or they can be partially connected, such as being connected on one side of the surface of the current collector 10 and separated at the part away from the current collector 10. As long as the active layer 22 is separated and arranged on the current collector 10, it should be included in the present application. Based on the distribution and arrangement of the separation layer 21 and the active layer 22 on the current collector 10, the combination and distribution of the separation layer 21 and the active layer 22 on the current collector 10 at least includes the methods shown in the following embodiments.

[0088] In one example, the separator layer 21 and the active layer 22 may be arranged alternately side by side along the length direction of the current collector 10 (ie, the length direction of the negative electrode, specifically the x-axis direction shown in FIG. 1 ), as shown in FIG. 1 and FIG. 2 .

[0089] In another example, the separator layer 21 and the active layer 22 may also be alternately arranged side by side along the width direction of the current collector 10 (ie, the width direction of the negative electrode, specifically the y-axis direction shown in FIG3 ), as shown in FIG3 .

[0090] In another example, the separation layers 21 are staggered to form a grid structure and bonded to the current collector 10 , and a plurality of active layers 22 are filled in the grids of the grid structure, as shown in FIG. 4 .

[0091] Figures 1 to 4 are merely examples of how the separator layer 21 and active layer 22 included in the negative electrode of an embodiment of the present application are arranged on the current collector 10. When the active layer 22 is arranged in accordance with at least the separation shown in Figures 1 to 4, when the volume of the active material contained in the active layer 22 expands, the separator layer 21 can effectively play a buffering or volume absorption role, buffering or absorbing the volume expansion of the active layer 22. This effectively reduces the volume expansion effect of the negative electrode material layer 20 during charge and discharge, thereby preventing the negative electrode material layer 20 from shedding powder. In addition, the stress of the active layer 22 is evenly stretched in all directions, thereby reducing or avoiding problems such as wrinkling and breaking in the negative electrode of the embodiment of the present application.

[0092] In some embodiments, when the separator layer 21 and the active layer 22 are alternately arranged side by side along the length of the current collector 10 as shown in Figures 1 and 2, the outermost layer of the negative electrode material layer 20 in the length direction is the separator layer 21. In this way, the outermost separator layer 21 can effectively protect the stability of the active layers 22 arranged on both sides of the length direction of the current collector 10, thereby improving the overall structural stability and electrochemical performance stability of the negative electrode material layer 20.

[0093] In some embodiments, the porosity of the separator layer 21 can be greater than the porosity of the active layer 22. This design allows the active material contained in the active layer 22 to partially fill the pores of the separator layer 21 when the volume expands, thereby enhancing the buffering effect of the separator layer 21, improving the stability of the structure and electrochemical performance of the negative electrode material layer 20, and alleviating or preventing problems such as shedding, powdering, cracking, and breakage of the negative electrode material layer 20.

[0094] In some embodiments, when subjected to the same stress, the deformation of the separator layer 21 can be greater than that of the active layer 22. This design ensures that when the active material contained in the active layer 22 undergoes volume expansion and generates stress, the separator layer 21 can deform sufficiently to buffer the volume expansion of the active layer 22, thereby providing a sufficient volume buffering effect, improving the stability of the structure and electrochemical performance of the negative electrode material layer 20, and alleviating or preventing problems such as shedding, powdering, cracking, and breakage of the negative electrode material layer 20.

[0095] In some embodiments, each active layer 22 necessarily contains active materials, and may further contain at least one of a conductive agent, a binder, a thickener, a dispersant, etc. The type and content of the conductive agent, binder, thickener, and dispersant can be selected as needed.

[0096] In the exemplary embodiment, the active material may include at least one of a silicon-based material, graphite, an amorphous carbon material, and a tin-based material. When the active material includes a silicon-based material and graphite, the active layer 22 has a high capacity, a low risk of lithium plating, and excellent safety. Furthermore, during the charge and discharge process of the negative electrode in the embodiment of the present application, the separator layer 21 can effectively mitigate the volume expansion of the active layer 22, thereby providing the negative electrode in the embodiment of the present application with high energy density while maintaining high structural stability and electrochemical performance stability.

[0097] In some embodiments, the active layer 22 may further include a solid electrolyte. The solid electrolyte may comprise a mass percentage of the active layer 22 greater than 0 and less than or equal to 1%, and may further comprise 0.1% to 1%. In exemplary embodiments, this mass percentage may be 0.2%, 0.5%, 1.0%, or other typical, non-limiting percentages. Adding a solid electrolyte to the active layer 22 not only effectively improves the ionic conductivity and electrical conductivity of the active layer 22, but also enhances the active layer 22's resistance to volume expansion.

[0098] For example, when the active material contained in the active layer 22 includes a silicon-based material, the inventors have discovered that after mixing the solid electrolyte with the silicon-based material, the hydrocarbon groups and carboxyl groups on the surface of the silicon-based material can be grafted onto the solid electrolyte, generating a bonding effect that inhibits the lattice structure of the polymer, improves the ionic conductivity of the solid electrolyte, and thus improves the ionic conductivity of the active layer 22. Specifically, the silicon-based material can disrupt the orderly arrangement of the polymer chains contained in the solid electrolyte. Chemical and mechanical bonding promotes the formation of amorphous particles, thereby forming a large number of amorphous regions at the interface between the polymer and silicon oxide. This inhibits crystallization, thereby promoting the segmental motion of lithium ion conduction in the solid electrolyte and increasing the lithium ion migration rate.

[0099] The inventors also discovered that adding a solid electrolyte can increase the cohesion of the active material and inhibit the volume expansion of the active layer 22; it can also enhance the adhesion between the active material and the current collector 10; and the solid electrolyte is an organic polymer, which can reduce the breakage of the negative electrode during the winding process; during battery charging, the solid electrolyte filling area can also provide space for the volume expansion of the negative electrode and quickly release the expansion stress, thereby improving the wrinkling of the negative electrode. In an exemplary embodiment, the solid electrolyte can include at least one of polyethylene oxide, polymethyl methacrylate, polyacrylonitrile, polyvinyl chloride, pentaerythritol tetraacrylate (PETEA), and a nano-ceramic composite polymer. Among them, the nano-ceramic composite polymer can include, but is not limited to, aluminum oxide, silicon oxide, lithium aluminum oxide, and polymer solid electrolytes.

[0100] In some embodiments, the width ratio of the separator layer 21 to the active layer 22 can be 1:2 to 1:7. In exemplary embodiments, the width ratio can be 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, and other typical, non-limiting ratios. The inventors discovered that as the width ratio of the separator layer 21 to the active layer 22 increases, the volume expansion and rebound ratio of the negative electrode plate decrease, but this results in a decrease in the proportion of the active layer 22, affecting the capacity of the negative electrode. Setting the width ratio of the separator layer 21 to the active layer 22 to the above ratio effectively balances the stability of the structure and electrochemical performance of the negative electrode material layer 20 contained in the negative electrode of the embodiment of the present application, as well as the high capacity of the negative electrode.

[0101] For example, in some embodiments, the width of a single active layer is 5 mm to 50 mm. In this case, in some embodiments, the width of the separator layer 21 can be a width that is lower than the ratio of the width of the separator layer 21 to the width of the active layer 22. Separator layers 21 within this width range can enhance the separation and buffering effect on the active layer 22, further buffering the volume expansion and stress changes of the active layer 22.

[0102] In some embodiments, the material of the separation layer 21 may include the following components in parts by weight:

[0103]

[0104] In some embodiments, when the amount of porous skeleton material contained in the separator layer 21 is not zero, the presence of the porous skeleton material imparts a rich porous structure to the separator layer 21, giving the separator layer 21 a three-dimensional porous structure, which has the ability to absorb the volume expansion of the active material contained in the active layer 22, thereby improving the stability of the structure and electrochemical performance of the negative electrode material layer 20, and alleviating or preventing problems such as shedding, powdering, cracking, and breakage of the negative electrode material layer 20. In some embodiments, the mass fraction of the porous skeleton material contained in the separator layer 21 can be 90.5-95.35 parts. In exemplary embodiments, the mass fraction of the porous skeleton material can be 90.5 parts, 91 parts, 92 parts, 93 parts, 94 parts, 95.25 parts, 95.35 parts, 95.45 parts, and other typical but non-limiting mass fractions. The use of porous skeleton materials with this content can improve the porous structure of the separation layer 21, which can accommodate a large amount of lithium and improve the separation layer 21 to have a three-dimensional buffer space, so that it can better withstand larger deformation and stress. When the volume of the active material contained in the active layer 22 expands, some particles can be filled into the separation layer 21, thereby better buffering the volume expansion of the active layer 22.

[0105] When the content of the porous skeleton material is 0 parts, that is, the separation layer 21 does not contain a porous skeleton material, then the separation layer 21 has good deformation properties. For example, when subjected to the same stress, the deformation of the separation layer 21 can be greater than the deformation of the active layer 22, so that when the active material contained in the active layer 22 expands in volume and generates stress, the separation layer 21 has sufficient deformation to buffer the volume expansion of the active layer 22, thereby achieving sufficient volume buffering effect.

[0106] In some embodiments, the pore size of the porous framework material may be 1 nm to 10 nm. In exemplary embodiments, the pore size may be 1 nm, 3 nm, 5 nm, 7 nm, 8 nm, 9 nm, 10 nm, and other typical, but non-limiting, pore sizes. For porous framework materials with such pore sizes, the separator layer 21 can already meet the corresponding buffering requirements for volume expansion of common negative electrode active materials, thereby absorbing the volume expansion of the active layer 22.

[0107] In some embodiments, the pore size ratio of the porous framework material to the graphite is ≥ 1. In exemplary embodiments, the pore size ratio to the graphite can be 1, 1.5, 2, 2.5, 3, 5, and other typical, non-limiting ratios. With a porous framework material having such a pore size, the separator layer 21 can already meet the corresponding buffering requirements for volume expansion of common negative electrode active materials. In particular, it can buffer the graphite material, which has the highest usage rate in the negative electrode, thereby absorbing the volume expansion of the active layer 22 and preventing cracking of the graphite material due to high stress caused by deformation.

[0108] In some embodiments, the pore size ratio of the porous framework material to the silicon-based material is ≥ 2. In exemplary embodiments, the pore size ratio to the silicon-based material can be 2, 2.5, 3, 4, 5, or other typical, non-limiting ratios. With a porous framework material having such a pore size, the separator layer 21 can also provide a buffering effect on the silicon-based material, which experiences significant volume expansion during charging, thereby absorbing the volume expansion of the active layer 22.

[0109] In some examples, the porous framework material can be at least one of a metal organic compound, a porous metal oxide, a metal, a MXene material, graphene, amorphous carbon, a lithium-titanium composite oxide, and carbon nanotubes. The MXene can be a two-dimensional transition metal carbide, nitride, or carbonitride.

[0110] After research, the inventors selected these porous skeleton materials. First, these materials have a high porosity, which can fully buffer the expansion of the active material contained in the active layer 22; second, these materials have good stability and will not react with the electrolyte or the materials contained in the active layer 22 during use; third, these materials have good electrical conductivity, which can improve the conductivity of the separator 21, thereby forming a conductive network structure with the active layer 22, reducing the internal resistance of the entire negative electrode, and improving the rate performance. For example, MXene and graphite composite materials have excellent above-mentioned effects.

[0111] In some embodiments, when the porous framework material is a metal organic compound, the metal organic compound may include at least one of a metal organic framework material and a metal organic framework derivative (a metal organic compound obtained by calcining a metal organic framework).

[0112] In some embodiments, the metal center of the metal organic framework material may include at least one of Ti, Fe, Cu, Zr, Zn, and Cr. In an exemplary embodiment, it may be a Ti-centered metal organic framework material (hereinafter referred to as MIL-125), an Fe-centered metal organic framework material (MIL-100), and the like.

[0113] After research, the inventors selected the porous skeleton materials of these materials, which have the above-mentioned excellent high porosity, chemical stability and conductivity. When used in the separation layer 21, they can achieve good conductive effect and inhibit the volume expansion of the active layer 22.

[0114] In some embodiments, the conductive agent contained in the separator layer 21 of the aforementioned embodiments can be at least one of carbon black (sp), superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. These conductive agents can improve the electrical conductivity of the separator layer 21, thereby increasing the conductivity of the separator layer 21 and reducing the internal resistance of the negative electrode. In exemplary embodiments, the weight percentage of the conductive agent can be 1 part, 1.2 parts, 1.3 parts, 1.4 parts, 1.5 parts, and other typical but non-limiting parts.

[0115] In some embodiments, the binder contained in the separator layer 21 of the above-described embodiments can be at least one of styrene-butadiene latex (SBR), styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS). These binders can serve to bond the components and shape the separator layer 21. In exemplary embodiments, the binder weight percentages can be 2 parts, 2.1 parts, 2.3 parts, 2.4 parts, 2.5 parts, and other typical but non-limiting weight percentages.

[0116] In some embodiments, the mass fraction of the dispersant contained in the separator layer 21 of the above-mentioned embodiments can be 0 parts, 0.5 parts, 1.0 parts, 1.1 parts, 1.2 parts, 1.3 parts, 1.4 parts, 1.5 parts, and other typical but non-limiting mass fractions. When the dispersant content in the separator layer 21 is not zero, the presence of the dispersant can fully disperse the various components, especially the fine solid particles, to prevent these particles from aggregating to form large secondary particles, which would affect the function of the various components and cause the local performance of the separator layer 21 to weaken, thereby improving the stability and uniformity of the performance of the separator layer 21.

[0117] Negative electrode preparation method

[0118] In a second aspect, the present invention provides a method for preparing a negative electrode. The process flow of the method for preparing a negative electrode in the present invention is shown in FIG5 . In combination with FIG1 to FIG4 , the method for preparing a negative electrode in the present invention may include the following steps:

[0119] S01: Prepare separation layer slurry and active layer slurry;

[0120] S02: The separator slurry and the active layer slurry are subjected to film-forming treatment on the surface of the current collector 10 to form a negative electrode material layer 20, and the negative electrode material layer 20 includes a plurality of separator layers 21 and a plurality of active layers 22, and the plurality of active layers 22 are separated by the plurality of separator layers 21.

[0121] This method can be used to prepare a negative electrode, which is also the negative electrode described in the above-mentioned application embodiment. This preparation method can form a separate active layer 22. At the same time, the separator layer 21 can timely buffer the volume expansion of the active layer 22 and buffer stress, thereby solving the problem of negative electrode volume expansion. The preparation method has controllable process parameters, and the resulting negative electrode is of high quality, stable performance, and excellent electrochemical performance.

[0122] Step S01:

[0123] The separator layer slurry in step S01 can include the components described above in parts by weight for the separator layer 21 and a solvent. For example, by controlling the amount of solvent added, the viscosity of the separator layer slurry can be controlled to 6000 mPa·s to 25000 mPa·s; or the solids content of the separator layer slurry can be further controlled to 50% to 70%. By controlling the viscosity and solids content of the separator layer slurry, the separator layer 21 formed from the separator layer slurry is of high quality, thereby enhancing the separator layer 21's ability to mitigate the volume expansion of the active layer 22.

[0124] In exemplary embodiments, the separator slurry solvent can be, but is not limited to, deionized water, N-methylpyrrolidone (NMP), or other aqueous or oily solvents for the negative electrode. The slurry can be prepared by premixing dry materials, adding a binder, and then vacuum-dispersing the mixture with water, followed by degassing, to obtain a separator slurry with an appropriate solid content, viscosity, and fineness.

[0125] The active layer slurry may include the components contained in the active layer 22 of each embodiment above and a solvent. The concentration of the active layer slurry may be controlled and adjusted as needed.

[0126] Step S02:

[0127] The film forming process in step S02 can be to evenly coat the above-mentioned separator slurry and active layer slurry on the current collector 10 through a coating device, and obtain a negative electrode sheet with suitable surface density and thickness after drying, which can be further cold pressed and cut to obtain a negative electrode. In addition, since several active layers 22 need to be separated by several separators 21, corresponding coating equipment and appropriate coating methods can be selected. In the exemplary embodiment, the separator 21 and the active layer 22 can be arranged alternately and side by side along the length direction of the current collector 10, and the opening of the coating gasket of the coating equipment can be adjusted so that the two slurries can be coated on the current collector 10 at the same time along the length direction of the current collector 10, forming alternating strips similar to zebra stripes, and can achieve a variety of coating effects such as one out of four, six out of eight, etc. The coating process parameters are controllable, the speed is fast, the uniformity is high, and the stability is good.

[0128] Battery

[0129] In a third aspect, the present invention provides a battery. The battery comprises the negative electrode of the present invention, or comprises the negative electrode prepared by the preparation method described above.

[0130] Since the battery of the embodiment of the present application contains the negative electrode of the embodiment of the above-mentioned application, even when a negative electrode active material with high capacity and high volume expansion is selected, it is not prone to wrinkling or even peeling and breaking, thereby ensuring the safety and good cycle stability of the battery.

[0131] In an exemplary embodiment, the battery of the present application can be a secondary battery, comprising a positive electrode, a separator, and a negative electrode. Specifically, the negative electrode of the secondary battery is the negative electrode described in the embodiment of the present application. Therefore, the negative electrode of the battery of the present application, specifically the secondary battery, is less prone to volume expansion, has a low rebound rate, exhibits good cycling stability, and is less prone to wrinkling or fracture.

[0132] In an embodiment, the secondary battery of the present application may include any one of a battery cell, a battery module, and a battery pack.

[0133] A battery cell is a battery housing and a cell encapsulated within the housing. The shape of a battery cell is not particularly limited and can be cylindrical, square, or any other shape. A secondary battery cell 30 with a square structure is shown in FIG6 .

[0134] In some embodiments, as shown in Figure 7, the outer packaging of the secondary battery cell 30 may include a shell 31 and a cover plate 33. The shell 31 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 31 has an opening connected to the receiving cavity, and the cover plate 33 is used to cover the opening to close the receiving cavity. The positive electrode, diaphragm and negative electrode contained in the secondary battery of the embodiment of the present application can be formed into an electrode assembly 32 through a winding process and / or a lamination process. The electrode assembly 32 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 32. The number of electrode assemblies 32 contained in the secondary battery cell 30 can be one or more, which can be adjusted according to actual needs.

[0135] The preparation method of the secondary battery cell 30 is well known. In some embodiments, the positive electrode, separator, negative electrode, and electrolyte can be assembled to form the secondary battery cell 30. As an example, the positive electrode, separator, and negative electrode can be wound or laminated to form the electrode assembly 32. The electrode assembly 32 is then placed in an outer package, dried, and then injected with electrolyte. The secondary battery cell 30 is then vacuum packaged, allowed to stand, formed, and shaped.

[0136] A battery module is assembled from the secondary battery cells 30 , that is, it may contain a plurality of the secondary battery cells 30 , and the specific number can be adjusted according to the application and capacity of the battery module.

[0137] In some embodiments, FIG8 is a schematic diagram of an exemplary battery module 40. As shown in FIG8 , in the battery module 40, multiple secondary battery cells 30 may be arranged sequentially along the length of the battery module 40. Of course, any other arrangement is also possible. Furthermore, the multiple secondary battery cells 30 may be secured using fasteners.

[0138] Optionally, the battery module 40 may further include a housing having an accommodation space in which the plurality of secondary battery cells 30 are accommodated.

[0139] A battery pack is assembled from the aforementioned secondary battery cells 30, and can contain multiple secondary battery cells 30, wherein multiple secondary battery cells 30 can be assembled into the aforementioned battery module 40. The specific number of secondary battery cells 30 or battery modules 40 contained in the battery pack can be adjusted according to the application and capacity of the battery pack.

[0140] In the embodiment, Figures 9 and 10 are schematic diagrams of an exemplary battery pack 50. The battery pack 50 may include a battery box and multiple battery modules 40 disposed within the battery box. The battery box includes an upper box body 51 and a lower box body 52. ​​The upper box body 51 covers the lower box body 52 and forms an enclosed space for accommodating the battery modules 40. The multiple battery modules 40 may be arranged in any manner within the battery box.

[0141] Electrical devices

[0142] In a sixth aspect, embodiments of the present application further provide an electrical device comprising the battery of the aforementioned embodiments. The battery can serve as both a power source and an energy storage unit for the electrical device. Thus, the electrical device of the embodiments of the present application has excellent safety performance and a long standby or battery life.

[0143] Electrical devices may include, but are not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships, satellites, energy storage systems, etc. These electrical devices may use secondary batteries, battery modules, or battery packs based on their usage requirements.

[0144] Figure 11 is a schematic diagram of an exemplary electric device. This device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of this device, a battery pack or battery module may be used.

[0145] As another example, the electric device may be a mobile phone, a tablet computer, a laptop computer, etc. Such an electric device is usually required to be lightweight and thin, and may use a secondary battery as a power source.

[0146] Example

[0147] Below, the embodiment of the present application is described. The embodiment described below is exemplary and is only used to explain the present application, and is not to be construed as limiting the present application. Where specific techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. Reagents or instruments used that do not specify the manufacturer are conventional products that can be obtained commercially.

[0148] 1. Negative Electrode and Preparation Method Example

[0149] Example A1

[0150] This embodiment provides a negative electrode and a method for preparing the same. The negative electrode includes a current collector, which is a copper foil. Multiple separator layers and multiple active layers are bonded to the copper foil. The separator layers and active layers are alternately arranged in parallel along the length of the copper foil. The width of each separator layer is 3 mm, and the width of each active layer is 21 mm. The ratio of the widths of the separator layers to the active layers is 1:7.

[0151] The separator layer includes the following components in parts by weight:

[0152]

[0153] The active layer includes the following components in parts by weight:

[0154]

[0155] The negative electrode preparation method of this embodiment includes the following steps:

[0156] S1. Preparation of separation layer slurry:

[0157] S11: dry-mixing 95.35 parts by mass of MIL-125 and 2.45 parts by mass of conductive carbon black sp contained in the above-mentioned separator layer;

[0158] S12: Add the dry mixture in step S11 to 2.2 parts by mass of the binder styrene-butadiene latex contained in the above-mentioned separator and an appropriate amount of deionized water, stir, mix and disperse, measure the solid content and adjust until a separator slurry with a solid content of 95.35% is obtained.

[0159] S2. Preparation of active layer slurry:

[0160] S21: dry-mixing 94.85 parts by mass of the nano-silicon material, 0.5 parts by mass of polyoxyethylene (solid electrolyte), and 1.25 parts by mass of conductive carbon black sp contained in the active layer;

[0161] S22: Add the dry mixture in step S21 to 2.2 parts by mass of the binder styrene-butadiene latex, 1.25 parts by mass of the dispersant and an appropriate amount of deionized water contained in the above-mentioned active layer, stir, mix and disperse, measure the solid content and adjust until a separation layer slurry with a solid content of 94.85% is obtained.

[0162] S3. Preparation of negative electrode:

[0163] By adjusting the opening of the coating gasket of the coating equipment, the two slurries prepared in step S1 and step S2 are coated on the current collector at the same time, and the active layer slurry and the spacer layer slurry are arranged alternately to form alternating strips similar to zebra stripes, and double-sided coating is performed, wherein the surface density of each single side is 0.131g / 1540.25mm 2 After drying at 100°C, the negative electrode is obtained by cold pressing and cutting.

[0164] Example A2

[0165] This embodiment provides a negative electrode and a method for preparing the same. This embodiment differs from Embodiment A1 in that the width ratio of the single separator layer to the single active layer is 1:10, and the active layer does not contain polyethylene oxide.

[0166] The negative electrode preparation method was also adjusted in this way.

[0167] Example A3

[0168] This embodiment provides a negative electrode and a method for preparing the same. The difference between this embodiment and embodiment A1 is that the active layer does not contain polyethylene oxide.

[0169] The negative electrode preparation method was also adjusted in this way.

[0170] Example A4

[0171] This embodiment provides a negative electrode and a method for preparing the same. This embodiment differs from Example A1 in that the width of a single separator layer is 3 mm, the width of a single active layer is 15 mm, and the ratio of the separator layer to the active layer width is 1:5. The active layer does not contain polyethylene oxide.

[0172] The negative electrode preparation method was also adjusted in this way.

[0173] Example A5

[0174] This embodiment provides a negative electrode and a method for preparing the same. This embodiment differs from Embodiment A1 in that the width of a single separator layer is 3 mm, the width of a single active layer is 6 mm, and the ratio of the separator layer to the active layer width is 1:2. The active layer does not contain polyethylene oxide.

[0175] The negative electrode preparation method was also adjusted in this way.

[0176] Example A6

[0177] This embodiment provides a negative electrode and a method for preparing the same. The difference between this embodiment and embodiment A5 is that the MIL-125 contained in the separator layer is replaced with the same mass fraction of porous metal oxide as the porous skeleton material.

[0178] The negative electrode preparation method was also adjusted in this way.

[0179] Example A7

[0180] This embodiment provides a negative electrode and a method for preparing the same. The difference between this embodiment and embodiment A5 is that the separator layer does not contain MIL-125.

[0181] The negative electrode preparation method was also adjusted in this way.

[0182] Comparative Example A1

[0183] This comparative example provides a negative electrode and its preparation method. This comparative example differs from Example A1 in that the negative electrode material layer does not include a separator layer; instead, the active layer forms a monolithic coating on the current collector. The active layer contains 0.2 parts by weight of polyethylene oxide.

[0184] The negative electrode preparation method of this comparative example includes the following steps:

[0185] An active layer slurry was prepared according to step S2 of Example A1, wherein the mass portion of polyoxyethylene was adjusted to 0.2 parts, and the active layer slurry was formed into an overall coating on the current collector.

[0186] Comparative Example A2

[0187] This comparative example provides a negative electrode and a preparation method thereof. The difference between this comparative example and comparative example A1 is that the weight percentage of polyoxyethylene in the active layer is 0.5 parts.

[0188] The negative electrode preparation method of this comparative example was also adjusted in this way.

[0189] Comparative Example A3

[0190] This comparative example provides a negative electrode and a preparation method thereof. The difference between this comparative example and comparative example A1 is that the weight portion of polyoxyethylene in the active layer is 1.0 part.

[0191] The negative electrode preparation method of this comparative example was also adjusted in this way.

[0192] Comparative Example A4

[0193] This comparative example provides a negative electrode and a preparation method thereof. The difference between this comparative example and comparative example A1 is that the weight percentage of polyoxyethylene in the active layer is 1.5 parts.

[0194] The negative electrode preparation method of this comparative example was also adjusted in this way.

[0195] Comparative Example A5

[0196] This comparative example provides a negative electrode and a preparation method thereof. The difference between this comparative example and comparative example A1 is that the active layer does not contain polyethylene oxide, that is, does not contain a solid electrolyte.

[0197] The negative electrode preparation method of this comparative example was also adjusted in this way.

[0198] 2. Secondary Battery Cell Example

[0199] Example B1 to Example B7 and Comparative Examples B1 to Comparative Examples B5;

[0200] The present embodiment B1 to embodiment B7 and comparative examples B1 to comparative examples B5 respectively provide a secondary battery cell, each of which comprises a battery cell formed by a positive electrode, a separator and a negative electrode, and also comprises an electrolyte.

[0201] The negative electrodes provided in Examples A1 to A7 and Comparative Examples A1 to A5 were used as the negative electrodes of secondary battery Examples B1 to B7 and Comparative Examples B1 to B5, respectively. The negative electrode in Example A1 was used as the negative electrode in secondary battery Example B1, the negative electrode in Example A2 was used as the negative electrode in secondary battery Example B2, and so on. The negative electrode in Comparative Example A1 was used as the negative electrode in battery Comparative Example B1.

[0202] The positive electrode was prepared as follows:

[0203] Using methyl pyrrolidone (NMP) as solvent, LiNi 0.8 Co 0.1 Mn 0.1 O2, carbon nanotubes (CNT), and binder (PVDF) were mixed in a mass ratio of 97:2:1 to prepare a positive electrode slurry with a solid content of 97.44%. The positive electrode slurry was evenly coated on aluminum foil, with a double-sided coating, where the surface density of each single side was 0.131g / 1540.25mm 2 After being fully dried, cold pressed and cut, the positive electrode sheet is obtained as the positive electrode.

[0204] Electrolyte: Ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed at a volume ratio of 1:1 at room temperature, and LiPF6 was added to the mixed solution to obtain a solution with a concentration of 1 mol / L as the electrolyte;

[0205] Release membrane: Celgard 2300.

[0206] Secondary battery assembly: In a low-humidity constant temperature room, the positive and negative electrode sheets prepared as above are stacked and wound in the order of "positive electrode-separator-negative electrode", and then filled with electrolyte to assemble a lithium-ion secondary battery.

[0207] Negative electrode and secondary battery cell related data testing

[0208] The negative electrodes and secondary battery cells provided in the above embodiments and comparative examples were tested respectively.

[0209] 1. Negative electrode rebound rate test

[0210] The thickness h0 of the negative electrode pole piece that has not been subjected to the cycle test is measured with a micrometer, and then a lithium-ion secondary battery is prepared using the pole piece.

[0211] A newly manufactured lithium-ion secondary battery is charged at a constant current of 1 / 3C to 4.25V, and then charged at a constant voltage of 4.25V to a current of 0.1C. At this point, the battery is fully charged (voltage window is 2.5V to 4.25V). The battery is then disassembled, and the fully charged negative electrode plate is removed. The thickness of the negative electrode plate at this time is measured with a micrometer (h1). The rebound rate of the negative electrode plate = (h1 / h0-1) × 100%;

[0212] 2-cycle capacity retention test

[0213] At 25°C, charge a newly made lithium-ion secondary battery at a constant current of 1 / 3C to 4.25V, then charge it at a constant voltage of 4.25V to a current of 0.05C, let it sit for 5 minutes, and then discharge it at 1 / 3C to 2.5V. The measured capacity is recorded as the initial capacity C0. Repeat the above steps for the same battery and record the discharge capacity C0 of the battery after the nth cycle. n , then the battery capacity retention rate P after n cycles (i.e., n laps (cls)) n =C n / C0×100%.

[0214] The battery capacity retention rate data in Table 1 is the data measured after 100 cycles under the above test conditions, that is, the P100 value.

[0215] The test results are shown in Table 1 below.

[0216] Table 1

[0217]

[0218] From Table 1 we can see that:

[0219] 1. Comparison of the test results of Examples A2 / B2 through A7 / B7 with Comparative Examples A5 / B5 reveals that by providing multiple active layers and multiple separators, with the active layers separated by the separators, the full charge rebound ratio of the negative electrode plate is reduced and the cycle capacity retention rate is improved, compared to the prior art in which only the active layer serves as the integral coating in Comparative Examples A5 / B5. Therefore, the negative electrode of the present invention can suppress the volume expansion of the active material and improve the cycling stability of the negative electrode.

[0220] 2. Based on the comparison of the test results of Example A1 / B1 and Comparative Example A2 / B2, the same conclusion as the first point can be drawn.

[0221] 3. Comparison of the test results of Examples A5 / B5 with those of Examples A6 / B6 and A7 / B7, respectively, reveals that the addition of a porous framework material to the separator layer reduces the full charge rebound ratio of the negative electrode and improves the cycle capacity retention rate. The metal-organic framework material also has a more pronounced effect. Therefore, the separator layer containing the porous framework material can more effectively mitigate the volume expansion of the active material contained in the active layer, improving the cycling stability of the negative electrode.

[0222] 4. According to the comparison of the test results of Examples A1 / B1 and A3 / B3, it can be seen that after the solid electrolyte is added to the active layer, the full charge rebound ratio of the negative electrode plate decreases and the cycle capacity retention rate increases.

[0223] 5. Comparing the test results of Comparative Examples A1 / B1 to A4 / B4 with Comparative Example A5 / B5, respectively, yields the same conclusion as in Point 4. Therefore, adding a solid electrolyte to the active layer helps suppress volume expansion of the negative electrode sheet and improves the cycling stability of the negative electrode.

[0224] VI. Comparing the test results of Comparative Examples A1 / B1 through A4 / B4, we can see that increasing the amount of solid electrolyte added to the active layer decreases the full charge rebound ratio of the negative electrode, but also reduces the cycle capacity retention. Therefore, increasing the solid electrolyte content in the active layer can suppress volume expansion, but it also affects cycle performance. Therefore, a higher solid electrolyte content is not necessarily better; there is an appropriate range for its addition.

[0225] VII. Comparing the test results of Examples A2 / B2 through A5 / B5, we can see that increasing the width ratio of a single separator layer to a single active layer decreases the full charge rebound ratio of the negative electrode sheet, but also reduces the cycle capacity retention rate. Therefore, the width and ratio of the separator layer to the active layer should be appropriately set in the examples of this application.

[0226] In summary, the negative electrode provided in the embodiments of the present application can effectively buffer the volume expansion of the negative electrode active material, reduce the rebound of the electrode sheet, inhibit wrinkling, breakage and other phenomena, has good cycle performance, and can effectively improve the electrochemical performance of the battery when used in the battery.

[0227] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, a person of ordinary skill in the art should understand that the technical solutions described in the aforementioned embodiments can still be modified, or some or all of the technical features therein can be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application, and they should all be included in the scope of the claims and specification of the present application. In particular, as long as there is no structural conflict, the various technical features mentioned in each embodiment can be combined in any way. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions that fall within the scope of the claims.

Claims

1. A negative electrode, comprising a current collector and a negative electrode material layer bonded to the current collector, characterized in that: The negative electrode material layer includes a plurality of separation layers and a plurality of active layers, wherein the plurality of active layers are combined on the current collector and the plurality of active layers are separated and arranged by the plurality of separation layers; the separation layers are used to buffer the volume expansion of the active layers.

2. The negative electrode according to claim 1, characterized in that The separation layer and the active layer are alternately arranged side by side along the length direction of the current collector; or The separation layer and the active layer are alternately arranged side by side along the width direction of the current collector; or The separation layer is combined on the surface of the current collector in a grid structure, and the active layer is filled in the grid structure.

3. The negative electrode according to claim 2, characterized in that The separation layer and the active layer are alternately arranged side by side along the length direction of the current collector, and the outermost layer of the negative electrode material layer in the length direction is the separation layer.

4. The negative electrode according to any one of claims 1 to 3, characterized in that The width of a single active layer is 5 μm to 15 μm; and / or The width ratio of the separation layer to the active layer is 1:2 to 1:

7.

5. The negative electrode according to any one of claims 1 to 4, characterized in that The porosity of the separation layer is greater than the porosity of the active layer; and / or When subjected to the same force, the deformation amount of the separation layer is greater than the deformation amount of the active layer.

6. The negative electrode according to any one of claims 1 to 5, characterized in that The material of the separation layer includes the following components in parts by mass:

7. The negative electrode according to claim 6, characterized in that The porous skeleton material includes at least one of metal organic matter, porous metal oxide, metal, MXene material, graphite, graphene, amorphous carbon, lithium titanium composite oxide, and carbon nanotube; and / or The pore size of the porous skeleton material is 1 nm to 10 nm; and / or The pore size ratio of the porous skeleton material to the pore size of graphite is greater than 1; and / or The ratio of the pore size of the porous skeleton material to the pore size of the silicon-based material is ≥ 2; and / or The conductive agent includes at least one of carbon black sp, superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers; and / or The binder includes at least one of styrene-butadiene latex, styrene-butadiene rubber, polyacrylic acid, sodium polyacrylate, polyacrylamide, polyvinyl alcohol, polymethacrylic acid, and carboxymethyl chitosan.

8. The negative electrode according to claim 7, characterized in that The metal organic compound includes at least one of a metal organic framework material and a metal organic framework derivative.

9. The negative electrode according to claim 8, characterized in that The metal center of the metal organic framework material includes at least one of Ti, Fe, Cu, Zr, Zn, and Cr.

10. The negative electrode according to any one of claims 1 to 9, characterized in that The active material contained in the active layer includes at least one of silicon-based materials, graphite, amorphous carbon materials, and tin-based materials.

11. The negative electrode according to any one of claims 1 to 10, characterized in that: The active layer further comprises a solid electrolyte, and the solid electrolyte accounts for a mass percentage of the active layer greater than 0 and less than or equal to 1%.

12. The negative electrode according to claim 11, characterized in that The solid electrolyte includes at least one of polyethylene oxide, polymethyl methacrylate, polyacrylonitrile, polyvinyl chloride, pentaerythritol tetraacrylate, and nano-ceramic composite polymer.

13. A method for preparing a negative electrode, characterized in that: The steps include: Preparing separation layer slurry and active layer slurry; The separator slurry and the active layer slurry are subjected to film-forming treatment on the surface of the current collector to form a negative electrode material layer, and the negative electrode material layer includes a plurality of separator layers and a plurality of active layers, and the plurality of active layers are separated and arranged by the plurality of separator layers.

14. The preparation method according to claim 13, characterized in that: The separator slurry comprises a solvent and the following components in parts by weight dispersed in the solvent:

15. The preparation method according to claim 13 or 14, characterized in that: The viscosity of the separation layer slurry is 6000mPa·s to 25000mPa·s; and / or The solid content of the separation layer slurry is 50% to 70%.

16. The preparation method according to any one of claims 13 to 15, characterized in that: The active layer slurry contains a solid electrolyte, and the solid electrolyte accounts for a mass percentage of the active layer formed by the active layer slurry that is greater than 0 and less than or equal to 1%.

17. A battery, characterized in that: The negative electrode comprises the negative electrode according to any one of claims 1 to 12, or the negative electrode prepared by the preparation method according to any one of claims 13 to 16.

18. An electrical device, characterized in that: The electrical device comprises the battery as claimed in claim 17, wherein the battery is used to provide electrical energy.

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