Negative electrode plate and manufacturing method therefor, electrode assembly, and secondary battery

Abstract

Provided in the present application is a negative electrode plate, comprising: a current collector; a first active substance layer, which is arranged on at least one surface of the current collector; and a second active substance layer, which is arranged on the surface of the first active substance layer away from the current collector, wherein the first active substance layer comprises a first active material, the second active substance layer comprises a second active material, and the lithium intercalation potential and lithium deintercalation potential of the second active material are both higher than the lithium intercalation potential and lithium deintercalation potential of the first active material. The negative electrode plate of the present application can improve the safety and cycle characteristics of a secondary battery.

Description

Negative electrode sheet and manufacturing method thereof, electrode assembly, and secondary battery Technical Field

[0001] The present application relates to the field of batteries, and in particular to a negative electrode plate and a manufacturing method thereof, an electrode assembly having the same, a secondary battery, a battery module, a battery pack and an electrical device. Background Art

[0002] Secondary batteries are widely used due to their reliable performance, pollution-free operation, and lack of memory effects. For example, with increasing attention to environmental protection and the growing popularity of new energy vehicles, demand for power secondary batteries is expected to surge. However, this expanding range of applications also poses significant challenges to their performance.

[0003] However, as the energy density of secondary batteries increases, lithium deposition can occur in certain locations of the negative electrode due to insufficient lithium insertion capacity. As lithium dendrites continue to form, they puncture the separator, causing a short circuit and compromising battery safety. Therefore, there is an urgent need to design and develop a secondary battery that effectively reduces the risk of lithium deposition without sacrificing energy density.

[0004] Summary of the Invention

[0005] The present application is made in view of the above-mentioned problems, and its purpose is to provide a negative electrode plate and its manufacturing method, a secondary battery equipped with the same, as well as a battery module, a battery pack and an electrical device. The negative electrode plate is locally double-layered with different active materials, which can reduce the risk of lithium plating of the secondary battery, improve the safety performance of the secondary battery, extend the battery life, and does not reduce the energy density of the battery.

[0006] In order to achieve the above-mentioned objectives, the first aspect of the present application is to provide a negative electrode plate, comprising: a current collector; a first active material layer, arranged on at least one surface of the current collector; and a second active material layer, arranged on the surface of the first active material layer away from the current collector; the first active material layer includes a first active material, the second active material layer includes a second active material, and the lithium insertion potential and the lithium deintercalation potential of the second active material are both higher than those of the first active material.

[0007] By locally coating a second active material layer with high lithium insertion and delithiation potentials on the first active material layer, the negative electrode lithium plating of the secondary battery can be improved, the safety performance of the secondary battery can be improved, and the battery service life can be extended without reducing the energy density of the battery.

[0008] In some embodiments, the second active material layer is multiple and spaced apart. This allows selective coating of the second active material layer on locations prone to lithium deposition, thereby addressing the safety risk of lithium deposition caused by insufficient lithium insertion capacity in these locations, thereby improving the safety, cycle characteristics, and energy density of the secondary battery.

[0009] In some embodiments, within the range of 0 to 300 mAh / g of lithium insertion capacity of the negative electrode sheet, the second active material has a higher lithium insertion potential than the first active material. By ensuring that the lithium insertion potentials of the second active material and the first active material satisfy the aforementioned relationship within a specific lithium insertion capacity range, lithium from the positive electrode material is ensured to be inserted into the second active material first, thereby reducing the risk of lithium over-insertion in the second active material, lowering the risk of lithium plating at the negative electrode of the secondary battery, and improving the safety performance of the secondary battery.

[0010] In some embodiments, when the delithiation capacity of the negative electrode is in the range of 10 to 300 mAh / g, the delithiation potential of the second active material is higher than that of the first active material. By ensuring that the delithiation potentials of the second active material and the first active material satisfy the above relationship within a specific lithium insertion capacity range, the lithium ions embedded in the second active material can be only partially or not fully released during the subsequent charge and discharge process of the battery. The unreleased lithium ions will not be able to be reduced and form lithium dendrites. That is, the second active material can enrich and lock lithium ions that may have been reduced to form lithium dendrites on the surface of the negative electrode, thereby improving the lithium plating caused by insufficient local lithium insertion capacity of the negative electrode and improving the safety performance of the secondary battery.

[0011] In some embodiments, the second active material has a higher specific capacity than the first active material, thereby further increasing the lithium insertion capacity of the negative electrode, improving the lithium plating improvement effect, and enhancing the safety performance of the secondary battery.

[0012] In some embodiments, the ratio of the mass of the second active material to the mass of the first active material is 0.1 to 2, and can be optionally 0.1 to 1. As a result, the second active material layer is coated with less second active material, and the change in secondary battery mass after adding the second active material layer is negligible, which can improve the safety performance of the secondary battery without reducing the energy density of the secondary battery.

[0013] The second aspect of the present application is to provide an electrode assembly, comprising a negative electrode sheet, a positive electrode sheet, and a separator according to any of the above embodiments; the positive electrode sheet comprises a positive electrode active material layer; wherein the capacity a of the second active material layer, the capacity b of the first active material layer, and the capacity c of the positive electrode active material layer satisfy the formula (1):

[0014] a+b=nc, n=1.07~5 Formula (1)

[0015] The units of a, b, and c in formula (1) are mAh / cm 2 .

[0016] The capacity a of the second active material layer, the capacity b of the first active material layer and the capacity c of the positive electrode active material layer can further increase the lithium insertion capacity of the negative electrode, improve the negative electrode lithium plating of the secondary battery, and enhance the safety performance and cycle characteristics of the secondary battery.

[0017] In some embodiments, the negative electrode sheet, the separator, and the positive electrode sheet are wound along a winding direction to form a coiled structure; the coiled structure includes a planar portion and a corner portion connecting the planar portion; and the second active material layer is at least partially located in the corner portion. This can improve lithium deposition in the corner portion of the secondary battery and enhance the safety of the secondary battery.

[0018] In some embodiments, the corner portions include a first corner portion and a second corner portion near the winding start of the electrode assembly; the second active material layer is located at the first and second corner portions. This can further reduce lithium deposition at the inner corners of the secondary battery, thereby improving the safety of the secondary battery.

[0019] In some embodiments, the current collector of the negative electrode plate further includes a tab portion, and the second active layer is further located on the side of the planar portion that is connected to the tab portion. This can reduce lithium deposition near the tab portion of the negative electrode plate and improve the safety of the secondary battery.

[0020] In some embodiments, the negative electrode sheet, the separator, and the positive electrode sheet are stacked in sequence to form a laminate structure; the laminate structure includes a central portion and edge portions disposed around the central portion; and the second active material layer is at least partially located in the edge portions. This can reduce lithium deposition at the edge of the negative electrode sheet and improve the safety of the secondary battery.

[0021] In some embodiments, the current collector of the negative electrode plate further includes a tab portion, and the second active material layer is further located on the side of the edge portion that is connected to the tab portion. This can reduce lithium deposition near the tab portion of the negative electrode plate and improve the safety of the secondary battery.

[0022] A third aspect of the present application is to provide a method for manufacturing a negative electrode sheet, for use in any of the aforementioned embodiments. The negative electrode sheet manufacturing method of the present application utilizes a double-layer coating method, which provides high process controllability, flexibility, and simplicity. For negative electrode materials of different systems, the use of a double-layer coating method to form a composite negative electrode can avoid process difficulties caused by differences in material systems.

[0023] A fourth aspect of the present application is to provide a secondary battery, which includes the electrode assembly according to the second aspect of the present application.

[0024] A fifth aspect of the present application is to provide a battery module, which includes the secondary battery according to the fourth aspect of the present application.

[0025] The sixth aspect of the present application is to provide a battery pack, which includes the battery module according to the fifth aspect of the present application.

[0026] The seventh aspect of the present application is to provide an electrical device, which includes at least one of the secondary battery according to the fourth aspect of the present application, the battery module according to the fifth aspect of the present application, and the battery pack according to the sixth aspect of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] FIG1 is a schematic cross-sectional view of a negative electrode sheet according to one embodiment of the present application.

[0028] FIG2 is a schematic top view of a negative electrode sheet according to an embodiment of the present application.

[0029] FIG3 is a schematic top view of an electrode assembly according to an embodiment of the present application.

[0030] FIG. 4 is a detailed schematic diagram of a corner portion of the electrode assembly according to an embodiment of the present application shown in FIG. 3 .

[0031] FIG5 is a schematic top view of the negative electrode sheet of the electrode assembly according to one embodiment of the present application.

[0032] FIG6 is a schematic top view of an electrode assembly according to an embodiment of the present application.

[0033] FIG7 is a schematic top view of the negative electrode sheet of the electrode assembly according to one embodiment of the present application shown in FIG6 .

[0034] FIG. 8 is a schematic diagram of a secondary battery according to an embodiment of the present application.

[0035] FIG. 9 is an exploded view of the secondary battery according to the embodiment of the present application shown in FIG. 8 .

[0036] FIG10 is a schematic diagram of a battery module according to an embodiment of the present application.

[0037] FIG11 is a schematic diagram of a battery pack according to an embodiment of the present application.

[0038] FIG. 12 is an exploded view of the battery pack shown in FIG. 11 according to an embodiment of the present application.

[0039] FIG. 13 is a schematic diagram of an electric device using a secondary battery as a power source according to an embodiment of the present application.

[0040] FIG. 14 is a lithium insertion and extraction curve diagram of the first active material and the second active material according to one embodiment of the present application.

[0041] Description of reference numerals:

[0042] 1 Battery pack; 2 Upper case; 3 Lower case; 4 Battery module; 5 Secondary battery; 51 Housing; 52 Electrode assembly; 53 Top cover assembly; 54 Connecting member; 55 Electrode terminal; 6 Positive electrode sheet; 7 Negative electrode sheet; 9 Separator; 100 Current collector; 101 First active material layer; 102 Second active material layer; 111 Plane portion; 112 Corner portion; 112a First corner portion; 112b Second corner portion; 100a Tab portion; DETAILED DESCRIPTION

[0043] Below, the embodiments of the positive electrode active material and its manufacturing method, positive electrode sheet, secondary battery, battery module, battery pack and electrical device of the present application are specifically disclosed in detail with appropriate reference to the drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structure are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0044] The "ranges" disclosed herein are defined in terms of lower and upper limits, where a given range is defined by selecting a lower limit and an upper limit, and the selected lower and upper limits define the boundaries of the particular range. Ranges defined in this manner can be inclusive or exclusive of the end values ​​and can be combined arbitrarily, i.e., any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60 to 120 and 80 to 110 are listed for a particular parameter, it is understood that ranges of 60 to 110 and 80 to 120 are also contemplated. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, the following ranges are all contemplated: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4, and 2 to 5. In this application, unless otherwise indicated, the numerical range "a to b" is a shorthand representation of any combination of real numbers between a and b, where a and b are both real numbers. For example, a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is simply an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0045] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0046] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0047] Unless otherwise specified, the terms "include" and "comprising" used in this application may be open-ended or closed-ended. For example, "include" and "comprising" may mean that other components not listed may also be included or that only the listed components are included.

[0048] Unless otherwise specified, the term "or" is used in this application to be inclusive. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, the condition "A or B" is satisfied if any of the following conditions are met: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0049] Currently, market developments indicate that power batteries are becoming increasingly widely used. They are not only used in energy storage systems such as hydropower, thermal, wind, and solar power plants, but are also widely used in electric vehicles like electric bicycles, electric motorcycles, and electric vehicles, as well as in military equipment and aerospace. As power battery applications continue to expand, market demand is also growing.

[0050] The inventors have noted that, during actual use, power batteries experience a problem: lithium dendrites are prone to forming in certain locations on the negative electrode due to insufficient lithium insertion capacity. As lithium dendrites continue to form, they puncture the separator, causing a short circuit and degrading battery safety.

[0051] To mitigate lithium plating in the negative electrode sheet while also improving the battery's energy density, the inventors, after in-depth research, have designed a negative electrode sheet comprising: a current collector, a first active material layer disposed on at least one surface of the current collector, and a second active material layer disposed on a surface of the first active material layer distal from the current collector. The first active material layer comprises a first active material, and the second active material layer comprises a second active material, with both the second active material's lithium insertion and delithiation potentials being higher than those of the first active material.

[0052] The above-mentioned negative electrode plate is coated with a second active material layer with high lithium insertion potential and lithium desorption potential at a position where lithium is easily deposited, which can improve the negative electrode lithium deposition of the secondary battery, improve the safety performance of the secondary battery, extend the battery life, and do not reduce the energy density of the battery.

[0053] The secondary battery disclosed in the embodiments of the present application can be used, but is not limited to, in electrical devices such as vehicles, ships, or aircraft. The embodiments of the present application provide an electrical device that uses a secondary battery as a power source. The electrical device can be, but is not limited to, a mobile phone, a tablet, a laptop computer, an electric toy, an electric tool, a battery-powered vehicle, an electric car, a ship, a spacecraft, and the like. Among them, the electric toy can include fixed or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, and the like. The spacecraft can include airplanes, rockets, space shuttles, and spacecraft, and the like.

[0054] [Pole structure]

[0055] As shown in Figures 1 and 2, in one embodiment of the present application, a negative electrode plate 7 is proposed, including: a current collector 100; a first active material layer 101, arranged on at least one surface of the current collector 100; and a second active material layer 102, arranged on the surface of the first active material layer 101 away from the current collector 100; the first active material layer 101 includes a first active material, and the second active material layer 102 includes a second active material, and the lithium insertion potential and the lithium deintercalation potential of the second active material are both higher than those of the first active material.

[0056] The first active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, and the like.

[0057] The inventors of this application have discovered that by locally coating the first active material layer 101 with a second active material layer 102, which has high lithium insertion and removal potentials, lithium can be first embedded in the second active material coated on the upper layer. This prevents the lithium embedded in the second active material from being released and then reinserted into the first active material, which can cause lithium deposition. This improves lithium deposition at the negative electrode and enhances the safety and cycle stability of the secondary battery. Furthermore, the overall increased lithium insertion capacity of the negative electrode also increases the specific capacity of the battery's positive electrode, thereby improving the battery's energy density.

[0058] In some embodiments, there are multiple second active material layers 102, and the multiple second active material layers 102 are spaced apart. This allows the second active material layer to be selectively applied to locations prone to lithium deposition, thereby improving lithium deposition at the negative electrode of the secondary battery and enhancing the cycle characteristics and energy density of the secondary battery.

[0059] "Interval arrangement" means that there is a gap between at least two second active material layers among the plurality of second active material layers. Depending on actual production needs, the spacing between any two adjacent second active material layers can be equal or unequal, and this application does not impose any limitation on this.

[0060] In some embodiments, within the range of 0 to 300 mAh / g of lithium insertion capacity of the negative electrode plate 7, the second active material has a higher lithium insertion potential than the first active material. By ensuring that the lithium insertion potentials of the second active material and the first active material satisfy the aforementioned relationship within a specific lithium insertion capacity range, lithium from the positive electrode material is first inserted into the second active material, thereby enhancing the lithium insertion capacity of the negative electrode, reducing the risk of lithium plating at the negative electrode of the secondary battery, and improving the safety performance of the secondary battery.

[0061] In some embodiments, within the range of 10 to 300 mAh / g of the lithium desorption capacity of the negative electrode 7, the second active material has a higher lithium desorption potential than the first active material. By ensuring that the lithium desorption potentials of the second active material and the first active material satisfy the aforementioned relationship within a specific lithium insertion capacity range, the lithium ions embedded in the second active material can be partially or not fully released during the subsequent charge and discharge process of the battery. The unreleased lithium ions cannot be reduced and form lithium dendrites. In other words, the second active material can enrich and lock lithium ions that might otherwise be reduced to form lithium dendrites on the surface of the negative electrode, thereby improving the lithium plating of the secondary battery caused by insufficient local lithium insertion capacity of the negative electrode and improving the safety performance of the secondary battery.

[0062] In some embodiments, the second active material has a higher specific capacity than the first active material. Specifically, the second active material has a higher specific capacity than the first active material at a potential > 0.5 V (vs Li / Li + ) potential range is higher than that of the first active material. This can further increase the lithium insertion capacity of the negative electrode, improve lithium plating caused by insufficient local lithium insertion capacity of the negative electrode, and enhance the safety performance of the secondary battery. The second active material includes, but is not limited to, one or more transition metal oxides, lithium titanate, and the like.

[0063] In some embodiments, the ratio of the mass of the second active material to the mass of the first active material is 0.1 to 2, and can be optionally 0.1 to 1. As a result, the second active material layer is coated with less second active material, and the change in secondary battery mass after adding the second active material layer is negligible, which can improve the safety performance of the secondary battery without reducing the energy density of the secondary battery.

[0064] In addition, the negative electrode active material of the present application adopts a double-layer coating method, which has high process controllability, flexibility and simplicity. For negative electrode materials of different systems, the double-layer coating method is used to form a composite negative electrode to avoid the process difficulties caused by differences in material systems.

[0065] [Electrode assembly]

[0066] As shown in Figures 3 to 6, in one embodiment of the present application, an electrode assembly 52 is provided, including a negative electrode sheet 7, a positive electrode sheet 6, and a separator 9; the positive electrode sheet 7 includes a positive electrode active material layer; wherein the capacity a of the second active material layer, the capacity b of the first active material layer, and the capacity c of the positive electrode active material layer satisfy the formula (1):

[0067] a+b=nc, n=1.07~5 Formula (1)

[0068] The units of a, b and c in formula (1) are mAh / cm2.

[0069] Here, the capacity is calculated as follows: Capacity = active material gram capacity (mAh / g) * mass of active material in the active material layer (g / cm2)

[0070] When n is less than 1.07, the lithium insertion capacity provided by the second active material is insufficient and cannot effectively reduce the risk of lithium plating. When n is greater than 5, although the risk of lithium plating of the secondary battery can be reduced, the second active material is enriched with excessive lithium, which can easily cause lithium loss. At the same time, the battery mass increases, resulting in a decrease in battery energy density.

[0071] By keeping the positive and negative electrode capacity ratio within the above range, the lithium insertion capacity of the negative electrode can be further increased, the negative electrode lithium plating of the secondary battery can be improved, and the safety performance, cycle characteristics and energy density of the secondary battery can be improved.

[0072] As shown in Figure 3, the electrode assembly 52 can be a wound structure. Specifically, the positive electrode sheet 6 and the negative electrode sheet 7 are each a single piece, and the positive electrode sheet 6 and the negative electrode sheet 7 are in a strip-shaped structure. The positive electrode sheet 6, the separator 9, and the negative electrode sheet 7 are stacked in sequence and wound two or more times to form the electrode assembly 52. ​​The electrode assembly 52 can be flat.

[0073] In some embodiments, as shown in FIG3 , the negative electrode sheet 7 , separator 9 , and positive electrode sheet 6 are wound along a winding direction to form a wound structure; the wound structure includes a planar portion 111 and a corner portion 112 connecting the planar portion 111 ; and the second active material layer 102 is at least partially located in the corner portion 112 . This can improve lithium deposition in the corners of the secondary battery and enhance the safety of the secondary battery.

[0074] In some embodiments, as shown in FIG4 , the corner portion 112 includes a first corner portion 112a and a second corner portion 112b near the winding start of the electrode assembly; the second active material layer 102 is located at the first corner portion 112a and the second corner portion 112b. This can further improve lithium deposition at the inner corners of the secondary battery.

[0075] In some embodiments, as shown in FIG5 , the current collector 100 of the negative electrode plate 7 further includes a tab portion 100a , and the second active material layer 102 is further located on the side of the planar portion 111 that is connected to the tab portion 100a . This can reduce lithium deposition near the negative electrode tab portion of the secondary battery, thereby improving the safety of the secondary battery.

[0076] Alternatively, as shown in FIG6 , the electrode assembly 52 may also be a laminated structure. Specifically, a plurality of positive electrode sheets 6 and a plurality of negative electrode sheets 7 are provided, wherein the plurality of positive electrode sheets 6 and negative electrode sheets 7 are alternately stacked, and a separator 9 separates the positive electrode sheets 6 and the negative electrode sheets 7.

[0077] In some embodiments, as shown in FIG7 , a negative electrode sheet 7 , a separator 9 , and a positive electrode sheet 9 are stacked in sequence to form a laminate structure; the laminate structure includes a central portion and edge portions disposed around the central portion; the second active material layer is at least partially located in the edge portions. This can improve lithium deposition at the edge of the negative electrode sheet, which is located opposite the positive electrode sheet of the secondary battery and lacks an active material layer.

[0078] In some embodiments, as shown in FIG7 , the current collector of the negative electrode sheet 7 further includes a tab portion 100a , and the second active material layer 102 is further located on the side of the edge portion that is connected to the tab portion. This can reduce lithium deposition near the negative electrode tab portion of the secondary battery, thereby improving the safety of the secondary battery.

[0079] [Secondary battery]

[0080] Figure 8 shows a secondary battery 5 with a square structure. In this application, secondary batteries include lithium-ion batteries, lithium-sulfur batteries, sodium-lithium-ion batteries, sodium-ion batteries, or magnesium-ion batteries. The following description primarily uses lithium-ion batteries as an example to describe the concepts of this application. It should be understood that any other appropriate type of rechargeable battery is also applicable.

[0081] 9 , a secondary battery 5 according to an embodiment of the present application includes an outer shell (including a shell 51 and a cover plate 53) and an electrode assembly 52. ​​The shell 51 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 present application has no particular restrictions on the shape of the shell 51, which may be cylindrical, square or any other shape. The shell 51 has an opening connected to the receiving cavity, and the cover plate 53 can be covered on the opening to close the receiving cavity. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is immersed in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the secondary battery 5 may be one or more, and those skilled in the art can select according to specific actual needs.

[0082] There are two electrode terminals 55 provided on the cover plate 53 . There are two connecting members 54 , one connecting member 54 connecting one electrode terminal 55 and the positive electrode tab 6 of the electrode assembly 52 , and the other connecting member 54 connecting the other electrode terminal 55 and the negative electrode tab 7 of the electrode assembly 52 .

[0083] In addition, the secondary battery, battery module, battery pack, and electric device of the present application will be described below with reference to the drawings as appropriate.

[0084] In one embodiment of the present application, a secondary battery is provided.

[0085] Typically, a secondary battery consists of a positive electrode, a negative electrode, an electrolyte, and a separator. During the battery's charge and discharge processes, active ions are inserted and removed between the positive and negative electrodes. The electrolyte conducts ions between the positive and negative electrodes. The separator, located between the positive and negative electrodes, primarily prevents short circuits between the positive and negative electrodes while allowing ions to pass through.

[0086] [Positive electrode]

[0087] The positive electrode sheet includes a positive electrode current collector and a positive electrode film layer arranged on at least one surface of the positive electrode current collector, wherein the positive electrode film layer includes the positive electrode active material of the first aspect of the present application.

[0088] As an example, the positive electrode current collector has two surfaces opposite to each other in its thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive electrode current collector.

[0089] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer material base and a metal layer formed on at least one surface of the polymer material base. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0090] In some embodiments, the positive electrode active material may adopt the positive electrode active material for batteries that is well known in the art. As an example, the positive electrode active material may include at least one of the following materials: lithium-containing phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, the present application is not limited to these materials, and other traditional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides may include, but are not limited to, lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), lithium manganese oxide (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also referred to as NCM 333 ), LiNi 0.5 Co 0.2 Mn 0.3 O2 (also referred to as NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25 O2 (also referred to as NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2 O2 (also referred to as NCM 622 ), LiNi 0.8 Co 0.1 Mn 0.1 O2 (also referred to as NCM 811 ), lithium nickel cobalt aluminum oxide (such as LiNi 0.85 Co 0.15 Al 0.05 O2) and its modified compounds. Examples of olivine-structured lithium-containing phosphates may include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO4), a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon.

[0091] In some embodiments, the positive electrode film layer may further optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylate resin.

[0092] In some embodiments, the positive electrode film layer may further include a conductive agent. For example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0093] In some embodiments, the positive electrode sheet can be prepared by the following method: the components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode current collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0094] [Negative electrode]

[0095] The negative electrode sheet includes a negative electrode current collector and a negative electrode film layer provided on at least one surface of the negative electrode current collector, wherein the negative electrode film layer includes a negative electrode active material.

[0096] As an example, the negative electrode current collector has two surfaces opposite to each other in its thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0097] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer base layer and a metal layer formed on at least one surface of the polymer base material. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer base material (such as a base material of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0098] In some embodiments, the first negative electrode active material may be a negative electrode active material for a battery known in the art. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, etc. The silicon-based material may be selected from at least one of elemental silicon, silicon oxides, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. However, the present application is not limited to these materials, and other conventional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0099] In some embodiments, the second active material of the negative electrode may include at least one of the following materials: one or more of transition metal oxides (eg. Fe2O3, Fe3O4, Mn2O3, Co3O4, NiO, ZnO), lithium-containing transition metal oxides (eg. Li4Ti5O12), etc. It can be understood that any one of the above substances alone or any combination of substances can be used as the second negative electrode active material layer material to achieve a lithium insertion potential higher than that of the first active material in the range of 0 to 300 mAh / g for the negative electrode lithium insertion capacity, and a lithium delithiation potential higher than that of the first active material in the range of 10 to 300 mAh / g for the negative electrode lithium desorption capacity. Preferably, the gram capacity of the second negative electrode active material layer material may be greater than that of the first negative electrode active material layer material. However, the present application is not limited to these materials, and other traditional materials that can be used as battery negative electrode active materials may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0100] In some embodiments, the negative electrode film layer may further include a binder. The binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), carboxymethyl chitosan (CMCS), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin.

[0101] In some embodiments, the negative electrode film layer may further include a conductive agent, which may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0102] In some embodiments, the negative electrode film layer may optionally further include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0103] In some embodiments, a negative electrode sheet containing a first active material can be prepared by the following method: the components for preparing a negative electrode slurry containing a first active material, such as a first negative electrode active material, a conductive agent, a binder, and any other components, are dispersed in a solvent (such as deionized water) to form a negative electrode slurry of the first active material; the negative electrode slurry is coated on a negative electrode current collector, and after drying, cold pressing, and other processes, a negative electrode sheet containing a first active coating can be obtained.

[0104] In some embodiments, a negative electrode sheet comprising the first and second active materials can be prepared in the following manner: the components for preparing the second active material negative electrode slurry, such as the second active material, the conductive agent, the binder and any other components, are dispersed in a solvent (such as N-methylpyrrolidone) to form a second active material negative electrode slurry; the second active material negative electrode slurry is coated on the negative electrode sheet comprising the first active coating, and after drying and other processes, a positive electrode sheet can be obtained.

[0105] [Electrolytes]

[0106] The electrolyte plays the role of conducting ions between the positive electrode and the negative electrode. This application has no specific restrictions on the type of electrolyte, and it can be selected according to needs.

[0107] In some embodiments, the electrolyte is an electrolyte solution comprising an electrolyte salt and a solvent.

[0108] In some embodiments, the electrolyte salt may be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalatoborate, lithium dioxalatoborate, lithium difluorodioxalatophosphate, and lithium tetrafluorooxalatophosphate.

[0109] In some embodiments, the solvent can be selected from at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.

[0110] In some embodiments, the electrolyte may further include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, and additives that improve battery high or low temperature performance.

[0111] [Isolation film]

[0112] In some embodiments, the secondary battery further includes a separator. The present application has no particular limitation on the type of separator, and any known porous separator with good chemical and mechanical stability can be selected.

[0113] In some embodiments, the material of the separator can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0114] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be formed into an electrode assembly through a winding process or a lamination process.

[0115] In some embodiments, the secondary battery may include an outer packaging that can be used to encapsulate the electrode assembly and the electrolyte.

[0116] In some embodiments, the outer packaging of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. Alternatively, the outer packaging of the secondary battery can be a soft shell, such as a pouch-type soft shell. The soft shell can be made of plastic, such as polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0117] The present application has no particular limitation on the shape of the secondary battery, which may be cylindrical, square, or any other shape.

[0118] In some embodiments, secondary batteries can be assembled into a battery module. The number of secondary batteries contained in the battery module can be one or more. The specific number can be selected by those skilled in the art according to the application and capacity of the battery module.

[0119] Figure 10 shows an example battery module 4. Referring to Figure 10 , within the battery module 4, multiple secondary batteries 5 may be arranged sequentially along the length of the battery module 4. Of course, any other arrangement is also possible. Furthermore, the multiple secondary batteries 5 may be secured together using fasteners.

[0120] Optionally, the battery module 4 may further include a housing having a receiving space, and the plurality of secondary batteries 5 are received in the receiving space.

[0121] In some embodiments, the battery modules described above may also be assembled into a battery pack. The battery pack may contain one or more battery modules, and the specific number may be selected by those skilled in the art based on the application and capacity of the battery pack.

[0122] Figures 11 and 12 illustrate an example battery pack 1. Referring to Figures 11 and 12 , the battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box comprises an upper case 2 and a lower case 3. The upper case 2 can be positioned over the lower case 3 to form an enclosed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0123] In addition, the present application also provides an electric device, which includes at least one of the secondary battery, battery module, or battery pack provided in the present application. The secondary battery, battery module, or battery pack can be used as a power source for the electric device, and can also be used as an energy storage unit for the electric device. The electric device may include mobile devices (such as mobile phones, 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., but is not limited thereto.

[0124] As the electrical device, a secondary battery, a battery module or a battery pack can be selected according to its usage requirements.

[0125] Figure 13 shows an example of an 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 the secondary battery, a battery pack or battery module can be used.

[0126] Another example device may be a mobile phone, a tablet computer, a notebook computer, etc. Such a device is generally required to be lightweight and thin, and may use a secondary battery as a power source.

[0127] Example

[0128] 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.

[0129] Preparation of 1. Secondary Battery

[0130] <Example 1>

[0131] (1) Preparation of negative electrode materials

[0132] Graphite, the first negative electrode active material, was mixed with Super P (a conductive agent), CMC (a thickener), and SBR (a binder) in deionized water to create a first negative electrode slurry. The slurry had a solids content of 53% by weight, and the mass ratio of graphite, Super P, CMC, and SBR was 96:2:1:1.

[0133] NiO, the second negative electrode active material, was mixed with a conductive agent, Super P, and a binder, polyvinylidene fluoride (PVDF), in N-methylpyrrolidone (NMP) to create a second negative electrode slurry. The solid content of the negative electrode slurry was 43% by weight, and the mass ratio of NiO, Super P, CMC, and the binder, styrene-butadiene rubber (SBR), was 92:6:2.

[0134] (2) Preparation of negative electrode sheet

[0135] The first negative electrode slurry is applied to the current collector copper foil and dried at 85°C to form the first negative electrode active material layer. The second negative electrode slurry is then applied to the first negative electrode active material layer at the specified position and dried at 85°C. The negative electrode sheets are then cold pressed, trimmed, cut, and slit, and then dried at 120°C under vacuum for 12 hours.

[0136] (3) Preparation of positive electrode sheet

[0137] A positive electrode slurry consisting of lithium iron phosphate (LiFePO4), a conductive agent Super P, and a binder polyvinylidene fluoride (PVDF) was prepared in N-methylpyrrolidone (NMP). The solids content of the slurry was 64% by weight, with a mass ratio of lithium iron phosphate, Super P, and PVDF of 97:1:2. The slurry was then coated onto a current collector aluminum foil, dried at 85°C, and cold-pressed. The sheet was then trimmed, cut, and slit, and then dried at 85°C under vacuum for 4 hours to form the positive electrode sheet.

[0138] (4) Preparation of lithium-ion batteries:

[0139] Using polyethylene film (PE) as a separator, the prepared positive electrode sheet, separator, and negative electrode sheet are stacked in order, with the separator placed between the positive and negative electrodes to separate them. The cells are wound to form a bare cell, and the tabs are welded. The bare cell is then placed in an outer package. The prepared electrolyte is injected into the dried cell, and the cell is packaged, left to rest, formed, shaped, and tested for capacity to complete the lithium-ion battery production process.

[0140] <Example 2> to <Example 11>, <Comparative Examples 1 to 3>

[0141] The secondary batteries of Examples 2 to 11 and Comparative Examples 1 to 3 were prepared in a similar manner to the secondary battery of Example 1, except that the composition of the second active material and the mass ratio of the second active material to the first active material were adjusted. The different product parameters are detailed in Table 1.

[0142] Next, the testing process of the relevant parameters of the electrode assembly is described.

[0143] [1] Method for determining the lithium insertion potential of the first and second active materials

[0144] After the negative electrode material powder is made into an electrode according to a specific formula, it is assembled into a half-button battery consisting of an electrode and a lithium sheet. The total charge and discharge capacity of the negative electrode material at different potentials is calculated through low-rate charge and discharge. The total charge and discharge capacity of the second cycle is then divided by the mass of the active material in the electrode to obtain the material's potential-charge-discharge capacity curve. Here, the lithium insertion potential is the potential value corresponding to the corresponding capacity of the potential-capacity curve during the second discharge cycle.

[0145] [2] Method for determining the delithiation potential of the first and second active materials

[0146] After the negative electrode material powder is made into an electrode according to a specific formula, it is assembled into a half-button battery consisting of an electrode and a lithium sheet. The total charge and discharge capacity of the negative electrode material at different potentials is measured through low-rate charge and discharge. The total charge and discharge capacity of the second cycle is then divided by the mass of the active material in the electrode to obtain the material's potential-charge-discharge capacity curve. Here, the delithiation potential is the potential value corresponding to the corresponding capacity of the potential-capacity curve during the second charge cycle.

[0147] [3] Capacity measurement method for the first and second negative electrode active material layers

[0148] After the material powder is made into an electrode according to a certain formula, it is assembled into a semi-button battery of an electrode-lithium sheet and the button capacity is obtained through low-rate charge and discharge. The capacity is then divided by the mass of the active material in the electrode to obtain the gram capacity parameter. Here, the capacity is calculated as follows: Capacity (mAh / cm2) = Gram capacity of active material (mAh / g) * Mass of active material in the active material layer (g / cm2).

[0149] [4] Method for measuring the capacity of the positive electrode active material layer

[0150] After the material powder is made into an electrode according to a certain formula, it is assembled into a semi-button battery of an electrode-lithium sheet and the button capacity is obtained through low-rate charge and discharge. The capacity is then divided by the mass of the active material in the electrode to obtain the gram capacity parameter. Here, the capacity is calculated as follows: Capacity (mAh / cm2) = Gram capacity of active material (mAh / g) * Mass of active material in the active material layer (g / cm2).

[0151] 2. Battery performance test

[0152] The secondary batteries prepared in [1] to [4] were tested for performance using the following method. The results are shown in Table 2.

[0153] [1] Lithium deposition at negative electrode

[0154] The formed battery was charged at 25°C at a constant current of 2C to 3.65V, then charged at a constant voltage of 3.65V to a current less than 0.05C, and then discharged at 1C to 2.5V. After 10 cycles, it was charged at a constant current of 0.33C to 3.65V, and then charged at a constant voltage of 3.65V to a current less than 0.05C to obtain a fully charged battery.

[0155] Disassemble the battery after 10 cycles, observe the lithium deposition on the negative electrode convex surface, and record it in the "Lithium deposition on the negative electrode convex surface" column in the table below.

[0156] The evaluation criteria after observation are as follows.

[0157] No lithium deposition: The surface of the negative electrode in the corner area is golden yellow when fully charged. When wiped with dust-free paper, there is no gray metallic lithium powder on the paper.

[0158] Slight lithium deposition: The surface of the fully charged negative electrode in the corner area is dark yellow. When wiped with dust-free paper, there is gray metallic lithium powder on the paper.

[0159] Gray spots: The surface of the fully charged negative electrode in the corner area is partially gray, with no golden color showing through.

[0160] Severe lithium plating: The surface of the fully charged negative electrode in the corner area is all gray, with no golden color showing through.

[0161] In the present application, the preferred order of lithium deposition on the negative electrode convex surface is no lithium deposition > gray spots > slight lithium deposition > severe lithium deposition.

[0162] [Table 1]

[0163]

[0164] In Table 1, the lithium insertion or delithiation potential refers to the potential corresponding to a lithium insertion or delithiation capacity of 100mAh / g. Specifically, as shown in Figure 14, the lithium insertion potential of the first active material refers to the potential corresponding to a specific capacity of 100mAh / g on the lithium insertion curve of the first active material. The delithiation potential of the first active material refers to the potential corresponding to a specific capacity of 100mAh / g on the delithiation curve of the first active material. Similarly, the lithium insertion or delithiation potential of the second active material can be obtained. The above potentials are all relative to Li / Li + , in V. In addition, it can be seen from FIG14 that, in the range of lithium insertion capacity of 0 to 300 mAh / g, the lithium insertion potential of the second active material is higher than that of the first active material, and in the range of lithium desorption capacity of 10 to 300 mAh / g, the lithium desorption potential of the second active material is higher than that of the first active material.

[0165] [Table 2]

[0166]

[0167] In Table 2, the unit of gram capacity is mAh / g, and the unit of capacity is mAh / cm 2 .

[0168] 3. Analysis of test results of various embodiments and comparative examples

[0169] From Table 1 above, we can see that:

[0170] A comparison of Examples 1 to 11 and Comparative Example 1 shows that by including both a first active material layer and a second active material layer in the negative electrode material, and by having the second active material have higher lithium insertion and delithiation potentials than the first active material, negative electrode lithium deposition can be significantly improved. However, in Comparative Example 1, which lacks a second active material layer, slight lithium deposition occurred in the negative electrode.

[0171] Comparison of Examples 1 to 6 with Comparative Example 2 shows that increasing the mass ratio of the second active material in the negative electrode material to a certain content or above significantly improves negative electrode lithium deposition. However, excessive amounts of the second active material in Comparative Example 2 increase the battery mass. To ensure battery energy density, the mass ratio of the second active material to the first active material is preferably 2 or less, and more preferably 1 or less.

[0172] Comparison of Examples 1 to 6 with Comparative Example 3 shows that increasing the mass ratio of the second active material in the negative electrode material to a certain level or higher can further improve negative electrode lithium deposition. However, in Comparative Example 3, the mass of the second active material is relatively low, resulting in gray spots on the negative electrode.

[0173] From Table 2 above, we can see that:

[0174] According to the comparison between Examples 1 to 11 and Comparative Examples 1 to 3, it can be seen that the capacity a of the second active material layer, the capacity b of the first active material layer and the capacity c of the positive electrode active material layer satisfy a+b=nc, n=1.07~5, which can greatly improve the negative electrode lithium plating.

[0175] According to the results of Examples 1 to 11, it can be seen that the lithium plating improvement effect can be enhanced by making the gram capacity of the second negative electrode active material greater than the gram capacity of the first negative electrode active material.

[0176] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and any embodiments having substantially the same structure and effect as the technical concept within the scope of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the present application, any other embodiments that can be conceived by those skilled in the art and that combine some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A negative electrode plate, whereinthe negative electrode plate comprises:a current collector;a first active material layer arranged on at least one surface of the current collector; anda second active material layer arranged on a surface of the first active material layer away from the current collector;wherein the first active material layer comprises a first active material, the second active material layer comprises a second active material, and the second active material has a lithiation potential and a delithiation potential higher than those of the first active material;wherein there are a plurality of the second active material layers, and the plurality of the second active material layers are spaced.

2. The negative electrode plate according to claim 1, whereina lithiation potential of the second active material is higher than a lithiation potential of the first active material when a lithiation capacity of the negative electrode plate is within a range of 0-300 mAh / g.

3. The negative electrode plate according to claim 1 or 2, whereina delithiation potential of the second active material is higher than a delithiation potential of the first active material when a delithiation capacity of the negative electrode plate is within a range of 10-300 mAh / g.

4. The negative electrode plate according to any one of claims 1 to 3, whereinthe second active material has a gram capacity higher than that of the first active material.

5. The negative electrode plate according to any one of claims 1 to 4, wherein2022465135   26 Nov 2025a mass ratio of the second active material to the first active material is 0.1-2, and is optionally 0.1-1.

6. An electrode assembly, whereinthe electrode assembly comprises the negative electrode plate according to any one of claims 1 to 5, a positive electrode plate, and a separator; and the positive electrode plate comprises a positive electrode active material layer;wherein a capacity a of the second active material layer, a capacity b of the first active material layer, and a capacity c of the positive electrode active material layer satisfy formula (1)a+b=nc, n=1.07-5         formula (1)and in the formula (1), a, b, and c are in a unit of mAh / cm2.

7. The electrode assembly according to claim 6, whereinthe negative electrode plate, the separator, and the positive electrode plate are winded into a winding structure along a winding direction; the winding structure comprises a planar portion and a corner portion connected to the planar portion; and the second active material layer is at least partially located at the corner portion.

8. The electrode assembly according to claim 7, whereinthe corner portion comprises a first corner portion and a second corner portion close to a winding start end of the electrode assembly; and the second active material layer is located at the first corner portion and the second corner portion.

9. The electrode assembly according to claim 7 or 8, wherein the current collector of the negative electrode plate further comprises a tab portion; and the second active material layer is further located on one side of the planar portion connected to the tab portion.

10. The electrode assembly according to claim 6, whereinthe negative electrode plate, the separator, and the positive electrode plate are successively stacked to form a stacked structure; the stacked structure comprises a center portion and an edge 322022465135   26 Nov 2025portion arranged around the center portion; and the second active material layer is at least partially located at the edge portion.

11. The electrode assembly according to claim 10, wherein the current collector of the negative electrode plate further comprises a tab portion; and the second active material layer is further located on one side of the edge portion connected to the tab portion.

12. A method for manufacturing a negative electrode plate, according to any one of claims 1 to 5.

13. A secondary battery, whereinthe secondary battery comprises the electrode assembly according to any one of claims 6 to 11.

14. A battery module, whereinthe battery module comprises the secondary battery according to claim 13.

15. A battery pack, whereinthe battery pack comprises the battery module according to claim 14.

16. An electrical apparatus, whereinthe electrical apparatus comprises at least one of the secondary battery according to claim 13, the battery module according to claim 14, and the battery pack according to claim 15.Contemporary Amperex Technology (Hong Kong) Limited Patent Attorneys for the Applicant / Nominated Person SPRUSON & FERGUSON

Images