Battery cells, laminated batteries, and electrical devices

Abstract

The present application provides a battery cell, a laminated battery, and an electric device, the battery cell including at least one electrode assembly, the electrode assembly including a positive plate and a negative plate. The negative plate includes a first negative plate and a second negative plate, the capacity per unit volume of the first negative plate being greater than the capacity per unit volume of the second negative plate, at least one positive plate being disposed between two adjacent first negative plates, and at least one second negative plate being disposed between two adjacent first negative plates. These measures can improve defects due to expansion of the electrode plates, extend the battery's life, and improve the battery's energy density and storage performance.

Description

[Technical Field]

[0001] This application belongs to the field of battery technology and specifically relates to battery cells, laminated batteries, and electrical devices. [Background technology]

[0002] Rechargeable batteries are widely used in mass-market electronic products and electric vehicles due to their notable characteristics such as being lightweight, pollution-free, and having no memory effect. Conventional rechargeable batteries typically use silicon-based negative electrodes. While silicon-based materials have high capacity, they also suffer from significant volumetric effects and poor conductivity. During the charge-discharge cycle, the expansion of the silicon-based material can cause the adhesive on the electrode to fail, leading to powder detachment and potentially irreversible loss of electrode capacity. [Overview of the project] [Means for solving the problem]

[0003] In view of the technical challenges in the background technology, this application provides a battery cell, a laminated battery, and an electrical device that can improve defects caused by plate expansion, extend battery life, and enhance the energy density and storage performance of the battery.

[0004] To achieve the above objective, a first aspect of the present application provides a battery cell comprising at least one electrode assembly, the electrode assembly comprising a positive electrode plate and a negative electrode plate. The negative electrode plate comprises a first negative electrode plate and a second negative electrode plate, wherein the capacity per unit volume of the first negative electrode plate is greater than the capacity per unit volume of the second negative electrode plate, at least one positive electrode plate is provided between two adjacent first negative electrode plates, and at least one second negative electrode plate is provided between two adjacent first negative electrode plates.

[0005] This invention includes at least the beneficial effects described below. Unlike the prior art, this invention improves the volume expansion effect of the electrodes by providing two types of negative electrode plates with different capacities per unit volume, and by providing at least one negative electrode plate with a relatively low capacity per unit volume between two adjacent negative electrode plates with high capacities per unit volume. This reduces battery failure due to electrode expansion and simultaneously improves the energy density and storage performance of the battery.

[0006] In some embodiments, M second negative electrode plates are provided between two adjacent first negative electrode plates. 1 ≤ M ≤ 2.5n, where n = Cs / Cg, where M is an integer greater than or equal to 1, Cs is the capacity per unit volume of the first negative electrode plate, and Cg is the capacity per unit volume of the second negative electrode plate. By setting the spacing between the negative electrode plates considering the capacity per unit volume of the two types of negative electrode plates, plate expansion can be effectively controlled while simultaneously increasing the battery capacity to a greater extent.

[0007] In some examples, n is 1 or greater.

[0008] In several embodiments, the capacity per unit volume of the first negative electrode plate is 0.44 Ah / mL to 2.68 Ah / mL, and the capacity per unit volume of the second negative electrode plate is 0.32 Ah / mL to 1.17 Ah / mL.

[0009] In some embodiments, the total number of first negative electrode plates is less than or equal to the total number of second negative electrode plates. By arranging them in this way, the impact of volume expansion of the electrode plates on the battery life can be reduced, and the battery life can be extended.

[0010] In some embodiments, the ratio of the capacitance surface density of one positive electrode plate to one negative electrode plate is 1.01 ≤ C 負 / C 正The capacitance surface density is ≤1.2 and is the capacitance of the active layer on one side per unit area of ​​the positive / negative electrode plate. By designing the negative electrode plate so that its capacitance surface density is greater than that of the positive electrode plate, overcharging of the negative electrode can be prevented, the formation of lithium dendritic crystals can be suppressed, and the safety of the battery can be enhanced.

[0011] In several examples, the weight-surface density of the first negative electrode plate was 2.63 mg / cm³. 2 ~10.16 mg / cm³ 2 And / or, the weight surface density of the second negative electrode plate is 6.06 mg / cm³. 2 ~13.21 mg / cm³ 2 Therefore, by controlling the weight surface density of the negative electrode plate within a reasonable range, the battery can have a high energy density.

[0012] In some embodiments, the first negative electrode plate includes a first active layer, the mass fraction of the negative electrode active material in the first active layer is 90% to 95.5%, and / or the second negative electrode plate includes a second active layer, the mass fraction of the negative electrode active material in the second active layer is 96% or more. The total content of the active material in the active layer can be determined based on the content of the active material with a small volume expansion effect. For example, the total content of the active material in the active layer can be determined based on the silicon content. The higher the silicon content, the lower the total proportion of the active material. Higher silicon content leads to a greater volume effect and deterioration of resistance, requiring the addition of more adhesive and conductive agent. With a silicon content of 10% to 50%, the total proportion of the active material in the active layer is 90% to 97%, which effectively controls volume expansion. The second negative electrode plate does not have such a large volume effect or conductivity problem, so theoretically, a higher active material content is preferable, assuming it does not affect processing performance, and the lowest mass fraction is 96%.

[0013] In some embodiments, the first negative electrode plate includes a silicon-based electrode plate, and the active material in the silicon-based electrode plate includes one or more of a pure silicon material, a silicon-carbon material, and a silicon-oxygen material. The silicon-oxygen material is preferably one or more of prelithiated silicon oxygen or premagnesiated silicon oxygen.

[0014] In some embodiments, the mass fraction of silicon in the active material of the silicon-based electrode plate is 10% - 50%, and the mass fraction of graphite in the active material of the silicon-based electrode plate is 40% - 85.5%.

[0015] In some embodiments, the second negative electrode plate includes a graphite electrode plate, and the active material in the graphite electrode plate includes artificial graphite and / or natural graphite. The graphite electrode has good electrical conductivity and a small volume effect. When combined with the silicon negative electrode plate, it can relieve the volume expansion of the silicon negative electrode plate and increase the electrical conductivity of the battery.

[0016] In some embodiments, the weight areal density of the positive electrode plate is 12mg / cm 2 ~30mg / cm 2 . By providing it in this way, the energy density of the battery can be increased.

[0017] In some embodiments, the compression density of the positive electrode plate is 2.3g / cm 3 ~4g / cm 3 . By providing it in this way, the energy density of the battery can be increased.

[0018] In some embodiments, the positive electrode plate includes a positive electrode active layer, and the mass fraction of the positive electrode active material in the positive electrode active layer is 97% or more.

[0019] In some embodiments, the positive electrode plate includes one or more of a lithium iron phosphate electrode plate, a lithium cobaltate electrode plate, a lithium nickel cobalt manganese oxide electrode plate, and a lithium manganese iron phosphate electrode plate. By providing it in this way, the energy density of the battery can be increased.

[0020] In some embodiments, the battery cell further includes a Z-shaped foldable separator used to separate adjacent positive and negative electrodes, with the positive and negative electrodes alternately inserted into the gaps between them. This configuration can improve the manufacturing efficiency of the battery.

[0021] A second aspect of the present application provides a laminated battery including a case and a battery cell according to the first aspect of the present application.

[0022] The laminated battery of this application includes a battery cell provided by this application and therefore has at least the same advantages as a battery cell.

[0023] A third aspect of the present application provides an electrical device including a laminated battery according to the second aspect of the present application.

[0024] The electrical device of this application includes a laminated battery provided by this application and therefore has at least the same advantages as a laminated battery.

[0025] The above description is merely an overview of the technical solution of the present application. In order to better understand the technical means of the present application, and to enable implementation according to the contents of the specification, and to make the above and other objectives, features, and benefits of the present application clearer and easier to understand, specific embodiments of the present application are given below. The present invention provides, for example, the following items: (Item 1) A battery cell comprising at least one electrode assembly, wherein the electrode assembly is Positive plate and A negative electrode plate is included, The battery cell is characterized in that the negative electrode plate includes a first negative electrode plate and a second negative electrode plate, the capacity per unit volume of the first negative electrode plate is greater than the capacity per unit volume of the second negative electrode plate, at least one positive electrode plate is provided between two adjacent first negative electrode plates, and at least one second negative electrode plate is provided between two adjacent first negative electrode plates. (Item 2) The battery cell according to item 1, characterized in that M second negative electrode plates are provided between two adjacent first negative electrode plates, 1 ≤ M ≤ 2.5n, n = Cs / Cg, M is an integer of 1 or more, Cs is the capacity per unit volume of the first negative electrode plates, and Cg is the capacity per unit volume of the second negative electrode plates. (Item 3) The battery cell described in item 2, characterized in that n is 1 or greater. (Item 4) The capacity per unit volume of the first negative electrode plate is 0.44 Ah / mL to 2.68 Ah / mL, and / or A battery cell according to any one of items 1 to 3, characterized in that the capacity per unit volume of the second negative electrode plate is 0.32 Ah / mL to 1.17 Ah / mL. (Item 5) A battery cell according to any one of items 1 to 4, characterized in that the total number of the first negative electrode plates is less than or equal to the total number of the second negative electrode plates. (Item 6) The ratio of the capacitance surface density of either one positive electrode plate to either one negative electrode plate is 1.01 ≤ C 負 / C 正 A battery cell according to any one of items 1 to 5, characterized in that the capacitance surface density is ≤ 1.2 and the capacitance surface density is the capacitance of the active layer on one side per unit area of ​​the positive electrode plate / negative electrode plate. (Item 7) The surface density by weight of the first negative electrode plate is 2.63 mg / cm³. 2 ~10.16 mg / cm³ 2 and / or, The weight-surface density of the second negative electrode plate is 6.06 mg / cm³. 2 ~13.21 mg / cm³ 2 A battery cell as described in any one of items 1 to 6, characterized by being the same as the above. (Item 8) The first negative electrode plate includes a first active layer, the mass fraction of the negative electrode active material in the first active layer is 90% or more and / or 95.5% or less, The battery cell according to any one of items 1 to 7, characterized in that the second negative electrode plate includes a second active layer, and the mass fraction of the negative electrode active material in the second active layer is 96% or more. (Item 9) The battery cell according to any one of items 1 to 8, wherein the first negative electrode plate includes a silicon-based electrode plate, and the active material in the silicon-based electrode plate includes one or more of a pure silicon material, a silicon carbon material, and a silicon oxygen material, preferably the silicon oxygen material includes one or more of prelithiated silicon oxygen or premagnesated silicon oxygen. (Item 10) The battery cell according to item 9, characterized in that the mass fraction of silicon in the active material of the silicon-based electrode plate is 10% to 50%, and the mass fraction of graphite in the active material of the silicon-based electrode plate is 40% to 85.5%. (Item 11) The battery cell according to any one of items 1 to 10, characterized in that the second negative electrode plate includes a graphite electrode plate, and the active material in the graphite electrode plate includes artificial graphite and / or natural graphite. (Item 12) The surface density of the positive electrode plate is 12 mg / cm³. 2 ~30 mg / cm³ 2 A battery cell as described in any one of items 1 to 11, characterized by being the same as the above. (Item 13) The compressed density of the positive electrode plate is 2.3 g / cm³. 3 ~4g / cm 3 A battery cell as described in any one of items 1 to 12, characterized by being the same as the above. (Item 14) The battery cell according to any one of items 1 to 13, characterized in that the positive electrode plate includes a positive electrode active layer, and the mass fraction of the positive electrode active material in the positive electrode active layer is 97% or more. (Item 15) The battery cell according to any one of items 1 to 14, characterized in that the positive electrode plate includes one or more of the following: a lithium iron phosphate electrode plate, a lithium cobalt oxide electrode plate, a lithium nickel cobalt manganese oxide electrode plate, and a lithium manganese iron phosphate electrode plate. (Item 16) A battery cell according to any one of items 1 to 15, further comprising a separator used to separate adjacent positive and negative plates, which is folded in a Z-shape, wherein the positive and negative plates are alternately inserted into the gap between the stacked plates. (Item 17) A laminated battery characterized by including a case and a battery cell as described in any one of items 1 to 16. (Item 18) An electrical device characterized by including a laminated battery as described in item 17. [Brief explanation of the drawing]

[0026] To more clearly explain the technical solution of this application, the drawings used in this application are briefly introduced below. Clearly, the drawings described below represent only a few embodiments of this application, and those skilled in the art can obtain further drawings based on these drawings without any creative effort. [Figure 1] This is a schematic diagram of the three-dimensional structure of one embodiment of the secondary battery of the present invention. [Figure 2] This is a front view of one embodiment of the battery cell of the present invention. [Figure 3] This is a schematic diagram illustrating the arrangement of one embodiment of the negative electrode plate of the battery cell of the present invention. [Figure 4] This is a schematic diagram of the three-dimensional structure of one embodiment of the battery cell of the present invention. [Figure 5] This is a schematic diagram of the three-dimensional structure of the electrical device of the present invention. [Modes for carrying out the invention]

[0027] The present application will be further described below with reference to the embodiments for carrying out the invention. Please understand that these embodiments for carrying out the invention are merely for illustrative purposes and do not limit the scope of the present application.

[0028] For the sake of brevity, only a few numerical ranges are specifically disclosed in this specification. However, any lower limit can be combined with any upper limit to form an unspecified range, and any lower limit can be combined with other lower limits to form an unspecified range, and similarly, any upper limit can be combined with any other upper limit to form an unspecified range. Furthermore, each point or single numerical value disclosed individually can be combined with any other point or single numerical value as a lower or upper limit, or with any other lower or upper limit, to form an unspecified range.

[0029] In this specification, unless otherwise stated, the term "or" is inclusive. That is, the phrase "A or B" means "A, B, or both A and B." More specifically, any one of the following conditions satisfies the condition "A or B": 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).

[0030] In this specification, unless otherwise specified, "greater than or equal to" and "less than or equal to" include the value itself, and "multiple" in "one or more" means two or more.

[0031] Unless otherwise stated, terms used herein have the common meanings generally understood by those skilled in the art. Unless otherwise stated, the numerical values ​​of each parameter mentioned herein can be measured by various measurement methods commonly used in the art (for example, by the methods given in the embodiments of this application).

[0032] The terms used herein are for illustrative purposes only and are not intended to limit this application. The terms “including,” “having,” and any variations thereof in the description of this application, claims, and drawings are intended to cover non-exclusive “including.”

[0033] In the description of embodiments of this application, technical terms such as “first,” “second,” etc., are used solely to distinguish different subjects and should not be understood as indicating or implying relative importance, or suggesting the number, specific order, or primary / secondary relationship of the technical features being referred to. In the description of embodiments of this application, unless otherwise clearly and specifically limited, “plural” means two or more.

[0034] Where the “Examples” are referred to herein, it means that certain features, structures, or properties described in conjunction with the Examples may be included in at least one Example of the Application. The use of this term in each part of the Specification does not necessarily refer to the same Example, nor do they represent mutually exclusive, separate, or alternative Examples. Those skilled in the art will understand, both expressly and implicitly, that the Examples described herein can be combined with other Examples.

[0035] In the description of the embodiments of this application, the term "multiple" refers to two or more (including two), similarly, "multiple groups" refers to two or more groups (including two groups), and "multiple sheets" refers to two or more (including two sheets).

[0036] Through extensive research, the inventor discovered that in conventional batteries, the negative electrode plate is generally manufactured from silicon-based materials and other active materials. These silicon-based materials have a large volume effect and poor conductivity, which can cause the negative electrode plate to expand during the charge-discharge cycle, leading to the loss of adhesive on the electrode plate, the shedding of powder from the electrode plate, and potentially irreversible loss of electrode plate capacity.

[0037] About rechargeable batteries A secondary battery refers to a battery that can be used continuously by recharging after it has been discharged, thereby activating the active material.

[0038] Typically, a secondary battery includes a battery cell (positive electrode, negative electrode, separator), electrolyte, and case. During the charging and discharging process of the battery, active ions are repeatedly inserted into and removed from between the positive and negative electrodes. The separator is placed between the positive and negative electrodes and serves to isolate them. The electrolyte plays a role in conducting ions between the positive and negative electrodes.

[0039] In the embodiments of the present application, the shape of the secondary battery is not particularly limited and may be cylindrical, rectangular, or any other shape. As shown in Figure 1, Figure 1 is a schematic diagram of the three-dimensional structure of one embodiment of the secondary battery of the present application.

[0040] As an example, the secondary battery 100 includes a case. The case is used to package the positive electrode plate, the negative electrode plate, and the electrolyte. As an example, the case of the secondary battery 100 may be a rigid case, such as a rigid plastic case, an aluminum case, or a steel case. The case of the secondary battery 100 may also be a soft pack, such as a bag-type soft pack. The material of the soft pack may be plastic, and may include one or more of the following: polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0041] The method for manufacturing the secondary battery of the present invention is known. In some embodiments, a secondary battery can be formed by assembling a positive electrode plate, a separator, a negative electrode plate, an electrolyte, and a case. For example, the positive electrode plate, separator, and negative electrode plate can be formed as a battery cell by a winding process and / or a lamination process, the battery cell can be placed in a case, the electrolyte can be injected after baking, and a secondary battery can be obtained through processes such as vacuum packaging, standing, chemical formation, and shaping. The secondary battery can include a plurality of battery cells, and the plurality of battery cells may be connected in series, in parallel, or in series-parallel.

[0042] In one embodiment, the secondary battery of the embodiment of the present application is a laminated battery.

[0043] About battery cells Embodiments of the present application provide a battery cell comprising at least one electrode assembly, the electrode assembly comprising a positive electrode plate and a negative electrode plate. The negative electrode plate comprises a first negative electrode plate and a second negative electrode plate, wherein the capacity per unit volume of the first negative electrode plate is greater than the capacity per unit volume of the second negative electrode plate, at least one positive electrode plate is provided between two adjacent first negative electrode plates, and at least one second negative electrode plate is provided between two adjacent first negative electrode plates.

[0044] In some embodiments, for example, the number of positive electrode plates may be set to multiple plates such as 2, 3, or 4, and the number of negative electrode plates may be set to multiple plates such as 2, 3, 4, 5, 6, or 7. The number of second negative electrode plates provided between two adjacent first negative electrode plates may be 1, 2, or 3. For example, if the number of negative electrode plates is 5, the number of first negative electrode plates is 2, the number of second negative electrode plates is 3, and one second negative electrode plate is provided between two adjacent first negative electrode plates. The number of positive electrode plates provided between two adjacent first negative electrode plates may be 1, 2, or 3. A positive electrode plate may be provided between two adjacent negative electrode plates; that is, whether the first negative electrode plate is adjacent to the first negative electrode plate, the first negative electrode plate is adjacent to the second negative electrode plate, or the second negative electrode plate is adjacent to the second negative electrode plate, a positive electrode plate is provided between them. When the first negative electrode plate is adjacent to the second negative electrode plate, a positive electrode plate does not need to be provided between them.

[0045] As shown in Figure 2, Figure 2 is a front view of a battery cell according to one embodiment of the present invention. The battery cell 10 specifically includes four positive electrode plates 1 and four negative electrode plates 2, with each positive electrode plate 1 and each negative electrode plate 2 separated by a separator 3. There are two first negative electrode plates 21 and two second negative electrode plates 22, with two second negative electrode plates 22 provided between two adjacent first negative electrode plates 21. In another embodiment, for example, there may be five positive electrode plates 1 and five negative electrode plates 2, with two first negative electrode plates 21 and three second negative electrode plates 22, with three second negative electrode plates 22 provided between two adjacent first negative electrode plates 21.

[0046] Regarding the positive electrode plate In a secondary battery, the positive electrode plate typically includes a positive electrode current collector and a positive electrode active layer provided on the positive electrode current collector, the positive electrode active layer containing a positive electrode active material. The positive electrode current collector can be a conventional metal foil or a composite current collector, and a composite current collector can be formed by providing a metal material on a polymer substrate. As an example, an aluminum foil can be used as the positive electrode current collector.

[0047] In some embodiments, the positive electrode plate includes one or more of the following: lithium iron phosphate plate, lithium cobalt oxide plate, lithium nickel cobalt manganese oxide plate, and lithium manganese iron phosphate plate. Lithium iron phosphate is a safe positive electrode active material, with the chemical formula LiFePO4, containing no heavy metal elements harmful to the human body, with a theoretical specific capacity of 170 mAh / g and an actual specific capacity that may exceed 140 mAh / g (0.2C, 25℃). Lithium cobalt oxide ion batteries are lithium-ion batteries that use lithium cobalt oxide as the positive electrode active material, exhibiting excellent electrochemical performance. Lithium cobalt oxide has the chemical formula LiCoO2, a capacity decay rate of less than 0.05%, an initial discharge specific capacity greater than 135 mAh / g, and the battery exhibits stable performance, high consistency, ease of synthesis in the process, and good safety performance. Lithium nickel cobalt manganese oxide is a conventional ternary positive electrode active material, with the chemical formula LiNi x Co y Mn 1-x-y It is O2. Lithium nickel-cobalt manganese oxide has a high energy density, a theoretical capacity of 280 mAh / g, a product capacity exceeding 150 mAh / g, and good cycle performance, exhibiting excellent cycle stability at both room temperature and high temperature. Preferably, a ternary nickel-cobalt manganese oxide lithium electrode plate is selected as the positive electrode plate.

[0048] In several embodiments, the mass fraction of the positive electrode active material in the positive electrode active layer is 97% or more. For example, the mass fraction of the positive electrode active material in the positive electrode active layer is 97%, 98%, 99% or more. The positive electrode active material in the positive electrode active layer may include any of the active materials described in one of the above items. Unlike the negative electrode plate, volume expansion and conductivity problems are less likely to occur in the positive electrode plate, so theoretically, a higher active material content is preferable, provided that it does not affect processing performance, and the lowest weight percentage is 97%. By controlling the positive electrode active material in the positive electrode active layer within a predetermined range, the energy density of the battery can be further increased while maintaining the battery's cycle performance and safety performance.

[0049] In several examples, the surface density of the positive electrode plate was 12.0 mg / cm³. 2 ~30 mg / cm³ 2 The mass of the active material per unit area of ​​the electrode plate is called the gravimetric density of the electrode plate. The gravimetric density of the electrode plate is an important factor in determining the consistency of a battery. For batteries of the same capacity, the higher the gravimetric density, the less inert material (e.g., copper foil, aluminum foil, tab) there is, and the higher the energy density of the battery. However, if the gravimetric density is too high, the electrolyte does not penetrate the entire electrode easily, the gram capacity decreases, and this is unfavorable for improving energy density. Therefore, the gravimetric density of the positive electrode plate needs to be controlled within a reasonable range. For example, it can be measured using an X / β-ray surface densimeter by means of typographic tracking. For example, the gravimetric density of the positive electrode plate is 18 mg / cm³. 2 ~24 mg / cm³ 2 , 19 mg / cm³ 2 ~25 mg / cm³ 2 , 26 mg / cm³ 2 ~30 mg / cm³ 2 , 17 mg / cm³ 2 ~23 mg / cm³ 2 , 12 mg / cm³ 2 ~16 mg / cm³ 2 This may also be the case. By controlling the weight surface density of the positive electrode plate within a predetermined range, the energy density of the battery can be further increased while maintaining the battery's cycle performance and safety performance.

[0050] In several examples, the compressed density of the positive electrode plate was 2.3 g / cm³. 3 ~4g / cm 3 Generally, within the allowable compression range of the material, a higher compressive density of the positive electrode plate allows for a higher battery capacity, and therefore, compressive density is considered one of the reference indicators of energy density. However, if the compressive density is too high, it not only fails to improve the specific capacity of the battery, but also severely degrades the specific capacity and cycle performance of the battery. Therefore, the compressive density of the positive electrode plate needs to be set within a reasonable range. For example, the compressive density of the positive electrode plate is 2.4 g / cm³. 3 ~3.5g / cm 3 2.5 g / cm³3 ~3.4g / cm 3 2.6 g / cm³ 3 ~3.3g / cm 3 2.7 g / cm³ 3 ~3.2g / cm 3 2.8 g / cm³ 3 ~3.8g / cm 3 3.1 g / cm³ 3 ~3.6g / cm 3 This may also be the case. By controlling the compression density of the positive electrode plate within a predetermined range, the energy density of the battery can be further increased while maintaining the battery's cycle performance and safety performance.

[0051] Regarding the negative electrode plate In a secondary battery, the negative electrode plate typically includes a negative electrode current collector and a negative electrode active layer provided on the negative electrode current collector, and the negative electrode active layer includes a negative electrode active material.

[0052] The negative electrode current collector can be a conventional metal foil or a composite current collector (for example, a composite current collector can be formed by providing a metal material on a polymer substrate). As an example, the negative electrode current collector can be copper foil. The negative electrode active layer may further selectively contain an adhesive, a conductive agent, and other selective auxiliary agents. As an example, the conductive agent may be one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. As an example, the adhesive may be one or more of styrene-butadiene rubber (SBR), water-based acrylic resin, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), ethylene-vinyl acetate copolymer (EVA), polyvinyl alcohol (PVA), and polyvinyl butyral (PVB). As an example, other selective auxiliary agents may be thickeners and dispersants (e.g., sodium carboxymethylcellulose CMC-Na), PTC thermistor materials.

[0053] The negative electrode plate provided in this application includes a first negative electrode plate and a second negative electrode plate, wherein the capacity per unit volume of the first negative electrode plate is greater than the capacity per unit volume of the second negative electrode plate, and at least one second negative electrode plate is provided between two adjacent first negative electrode plates. Generally, when the capacity per unit volume of a negative electrode plate is large, its volume expansion rate is also large, so it may expand significantly during the charge-discharge cycle process and the electrode plate may fail. Similarly, when the capacity per unit volume of a negative electrode plate is small, its volume expansion rate is also small. In this application, by providing a negative electrode plate with a small capacity per unit volume between negative electrode plates with a large capacity per unit volume, the volume expansion of the large capacity negative electrode plate can be mitigated, reducing the failure of the battery due to the volume expansion of the electrode plate, and at the same time, the energy density and storage performance of the battery can be improved.

[0054] In some embodiments, the first negative electrode plate includes a first active layer, and the mass fraction of the negative electrode active material in the first active layer is between 90% and 95.5%. For example, the mass fraction of the negative electrode active material in the first active layer is 91%, 92%, 93%, 94%, 95%, etc. The negative electrode active material in the first active layer can include silicon-based materials, selenium-based materials, etc. The total content of the active material in the active layer can be determined based on the silicon content. Higher silicon content leads to greater volumetric effects and deterioration of resistance, requiring the addition of more adhesives and conductive agents, which results in a relatively lower silicon content in the first negative electrode plate. With a silicon content of 10% to 50%, the total content of the active material in the active layer is between 90% and 97%, which can accommodate volumetric expansion. By controlling the content of the negative electrode active material in the first active layer within a predetermined range, the energy density of the battery can be further increased, provided that the volumetric effect is adjusted.

[0055] In some embodiments, the first negative electrode plate includes a silicon-based electrode plate, and the active material in the silicon-based electrode plate includes one or more of pure silicon material, silicon carbon material, and silicon oxygen material, wherein the silicon oxygen material is preferably one or more of pre-lithium-reinforced silicon oxygen or pre-magnesium-reinforced silicon oxygen. A silicon carbon material (a silicon carbon material that uses porous hard carbon as a framework and is deposited with silane) is preferred. Silicon-based negative electrodes have advantages such as high energy density, wide raw material distribution, and appropriate discharge plateaus, and are considered promising negative electrode active materials. As an active material for a negative electrode, pure silicon has a high theoretical specific capacity of 4200 mAh / g, more than 10 times that of a negative electrode using graphite as the active material. Similarly, silicon carbon negative electrodes and silicon oxygen negative electrodes have theoretical specific capacities that are far higher than those of graphite negative electrodes. Because silicon-based electrodes have a high gram capacity, they offer advantages such as a high energy density and volumetric energy density, and a small battery volume; therefore, silicon-carbon electrodes are preferred as the first negative electrode.

[0056] In several examples, the mass fraction of silicon in the active material of the silicon-based electrode plate is 10% to 50%, and the mass fraction of graphite in the active material of the silicon-based electrode plate is 40% to 85.5%. The active material containing silicon and graphite may also be called a silicon-carbon anode material, and is a novel anode material that uses graphite as a dispersion matrix and silicon as the active material. Although silicon-only electrode plates have a high specific capacity, volume expansion and contraction changes occur during the charge and discharge process (the rate of volume expansion and contraction change during the charge and discharge process of silicon alone reaches 320%), generating large mechanical stresses, which cause silicon particles to break and pulverize after several cycles, leading to anode failure. Therefore, silicon-based electrode plates with porous graphite as a framework are preferred, and the energy density of the battery can be further increased, provided that the volume effect is adjusted. In these embodiments, for example, the mass fraction of silicon in the active material of the silicon-based electrode plate may be 11%, 15%, 19%, 29%, 30%, 35%, 38%, 42%, 45%, etc., and the mass fraction of graphite in the active material of the silicon-based electrode plate may be 77%, 71%, 67%, 61%, 53%, 51%, 49%, 45%, 43%, 41%, etc. By controlling the silicon content and graphite content in the silicon-based electrode plate within predetermined ranges, expansion during the charging process is controlled to occur inside the pores of the hard carbon, further reducing the expansion effect of the silicon-based electrode plate. Since silicon is deposited inside the pores of porous hard carbon, the silicon-carbon material has strong pressure resistance and does not crumble during the cold pressing process, and expansion during the charging process occurs inside the pores of the hard carbon, reducing the expansion effect of the silicon-based electrode plate. Therefore, a silicon-carbon material with a porous hard carbon framework is preferred.

[0057] In some embodiments, the second negative electrode plate includes a second active layer, and the mass fraction of the negative electrode active material in the second active layer is 96% or more. For example, the mass fraction of the negative electrode active material in the second active layer is 97%, 98%, or 99% or more. The negative electrode active material in the second active layer may include graphite. Unlike silicon-based electrode plates, graphite electrode plates are less prone to volume expansion and conductivity problems, so theoretically, a higher active material content is preferable, provided that it does not affect processing performance, with the lowest weight percentage being 96%. By controlling the negative electrode active material in the second active layer within a predetermined range, the energy density of the battery can be further increased while maintaining the battery's cycle performance and safety performance.

[0058] In some embodiments, the second negative electrode plate includes a graphite electrode plate, and the active material in the graphite electrode plate includes artificial graphite and / or natural graphite. Graphite negative electrode material has advantages such as a wide supply source, abundant reserves, high tap density after modification, stable electrochemical performance, and a specific capacitance density close to the theoretical specific capacitance. Therefore, selecting a graphite electrode plate as the second negative electrode plate can reduce manufacturing costs and increase efficiency.

[0059] In some embodiments, M second negative electrode plates are provided between two adjacent first negative electrode plates. 1 ≤ M ≤ 2.5n, n = Cs / Cg, where M is an integer greater than or equal to 1, Cs is the capacity per unit volume of the first negative electrode plate, and Cg is the capacity per unit volume of the second negative electrode plate. In one preferred embodiment, M can satisfy 1 ≤ M ≤ 2n. For example, the number M of the second negative electrode plates may be 1, 2, 3, etc. Because the battery cell includes first negative electrode plates, it can have a high energy density. Furthermore, by adopting a configuration in which the first and second negative electrode plates are mixed and laminated, such a design can first improve the expansion effect of the electrode plates, reduce the failure of the battery cell due to electrode plate expansion, and maximize the battery capacity. For example, if the first negative electrode plate is a silicon-based electrode plate and the second negative electrode plate is a graphite electrode plate, the higher the volume capacity of the silicon-based electrode plate, the higher the proportion of silicon-based material it contains, and the greater the expansion effect. However, by stacking the two electrode plates, the graphite negative electrode plate can mitigate the degree of expansion and powdering of the silicon-based negative electrode plate. Therefore, the electrochemical performance of the battery of this application is superior to that of conventional methods, particularly in terms of cycle and storage performance. Accordingly, by stacking the second negative electrode plate between the two silicon-based electrode plates according to the rule 1 ≤ M ≤ 2.5n, the expansion effect of the first negative electrode plate is dispersed and mitigated. In some embodiments, n is 1 or greater.

[0060] As shown in Figure 3, Figure 3 is a schematic diagram of the arrangement of one embodiment of the negative electrode plates of the battery cell of the present invention. In this embodiment, the first negative electrode plates 21 are silicon-based plates, and there are three of them, and the second negative electrode plates 22 are graphite plates, and there are four of them. In the direction from left to right, two graphite plates are provided between the first silicon-based plate and the second silicon-based plate, one graphite plate is provided between the second silicon-based plate and the third silicon-based plate, and one positive electrode plate (not shown) is provided between each negative electrode plate. In other embodiments, the number of graphite plates provided between two silicon-based plates may differ, for example, one, two, three, or four, and similarly, one positive electrode plate is provided between each negative electrode plate.

[0061] For example, in one embodiment, the first negative electrode plate is a silicon-based electrode plate, and the second negative electrode plate is a graphite electrode plate. By stacking the silicon-containing negative electrode plate and the graphite negative electrode plate, the energy density can be increased because the battery has a silicon-containing negative electrode plate. Furthermore, by stacking the two electrodes, the expansion effect of the silicon-based electrode plate is improved, reducing battery failure due to the volume expansion of the electrodes and extending the battery life. With this design, the energy density can be significantly improved, and storage performance can also be improved.

[0062] In several embodiments, the capacity per unit volume of the first negative electrode plate is 0.44 Ah / mL to 2.68 Ah / mL, and the capacity per unit volume of the second negative electrode plate is 0.32 Ah / mL to 1.17 Ah / mL.

[0063] In some embodiments, the total number of first negative electrode plates is less than or equal to the total number of second negative electrode plates. By setting the total number of first negative electrode plates to be less than or equal to the total number of second negative electrode plates, the volume expansion effect of the negative electrode plates is improved, the failure of the battery cell due to negative electrode plate expansion is reduced, and at the same time the battery capacity can be increased.

[0064] In some embodiments, the ratio of the capacitance surface density of one positive electrode plate to one negative electrode plate is 1.01 ≤ C 負 / C 正 Since ≤ 1.2, the capacitance surface density is the capacity of the active layer on one side per unit area of ​​the positive / negative electrode plate. Capacitance surface density = gravimetric surface density × gram capacity of the active material × mass fraction of the active material in the active layer. C 負 This is the capacity (mAh / cm³) of the coating layer (active layer) on one side per unit area of ​​the negative electrode plate. 2 ) represents C 正 This is the capacity (mAh / cm³) of the coating layer on one side per unit area of ​​the positive electrode plate. 2 This represents ). For example, as one preferred embodiment, 1.03 ≤ C 負 / C 正 ≤ 1.1. Another preferred embodiment is 1.05 ≤ C 負 / C 正The value is ≤1.1. By designing the negative electrode plate so that the capacity of the active layer on one side per unit area is greater than the capacity of the active layer on one side per unit area of ​​the positive electrode plate, overcharging of the negative electrode can be prevented, the formation of lithium dendritic crystals can be suppressed, and the safety of the battery cell can be enhanced.

[0065] In several examples, the weight-surface density of the first negative electrode plate was 2.63 mg / cm³. 2 ~10.16 mg / cm³ 2 The weight-surface density of the second negative electrode plate is 6.06 mg / cm³. 2 ~13.21 mg / cm³ 2 As mentioned above, the gravimetric density of the electrode plates is an important factor in determining the consistency of the battery. For batteries of the same capacity, the higher the gravimetric density, the less inert material (e.g., copper foil, aluminum foil, tabs) there is, and the higher the energy density of the battery. However, if the gravimetric density is too high, the electrolyte does not easily penetrate the entire electrode, the gram capacity decreases, and this is detrimental to improving energy density. Therefore, the gravimetric density of the negative electrode plate also needs to be controlled within a reasonable range. The gravimetric density of the negative electrode plate can be measured using multi-tracking measurement techniques, laser beam integrated microspot gravimetric meters, beta-ray gravimetric meters, etc. For example, the gravimetric density of the first negative electrode plate is 3.95 mg / cm³. 2 ~9.4 mg / cm³ 2 , 4.25 mg / cm³ 2 ~8.5 mg / cm³ 2 5.74 mg / cm³ 2 ~7.64 mg / cm³ 2 For example, the surface density by weight of the second negative electrode plate is 7.96 mg / cm³. 2 ~11.10 mg / cm³ 2 8.50 mg / cm³ 2 ~9.89 mg / cm³ 2 , 9.12 mg / cm³ 2 ~10.91 mg / cm³ 2 Therefore, by controlling the weight surface density of the first and second negative electrode plates within a predetermined range, the energy density of the battery can be further increased while maintaining the battery's cycle performance and safety performance.

[0066] In some embodiments, the separator is folded into a Z-shape, and the positive and negative plates are alternately inserted into the stacking gap. By folding the separator into a Z-shape and alternately inserting the positive and negative plates into the stacking gap, the manufacturing efficiency of the battery can be increased.

[0067] As shown in Figure 4, Figure 4 is a schematic diagram of the three-dimensional structure of another embodiment of the battery cell of the present invention. The positive electrode plate 1 and the negative electrode plate 2 are alternately inserted into the gaps of the Z-shaped separator 3.

[0068] About the electrolyte A secondary battery contains an electrolyte, which acts as a conductor of ions between the positive and negative electrodes. The electrolyte may contain an electrolyte salt and a solvent.

[0069] As an example, the electrolyte salt can be selected from one or more of the following: lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluoro(oxalato)borate (LiDFOB), lithium bisoxalatoborate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorodioxalatophosphate (LiDFOP), and lithium tetrafluorooxalatophosphate (LiTFOP).

[0070] As an example, the solvent can be selected from one or more of the following: ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS), and diethyl sulfone (ESE).

[0071] For example, the electrolyte may further contain additives. For instance, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve specific battery performance, such as additives that improve the battery's overcharge performance, additives that improve the battery's high-temperature performance, and additives that improve the battery's low-temperature performance.

[0072] About the device The present invention further provides an electrical device including a secondary battery. The battery cell, secondary battery may serve as a power source for the electrical device or as an energy storage unit for the electrical device. The electrical device may be, but is not limited to, mobile devices (e.g., mobile phones, laptop computers), electric vehicles (e.g., battery-powered electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric motorcycles, electric scooters, electric golf carts, electric trucks), electric vehicles, ships and satellites, or energy storage systems.

[0073] As an electrical device, battery cells and rechargeable batteries can be selected according to the specific needs of its use.

[0074] Figure 5 shows an example of an electrical device. This electrical device may be a battery-powered electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. Multiple secondary batteries can be used to meet the high power and high energy density requirements for the secondary batteries of this electrical device.

[0075] Other examples of electrical devices may include mobile phones, tablets, and laptop computers. These devices typically require lightweight and thin designs, and can utilize battery cells as their power source.

[0076] The beneficial effects of this application will be further explained below in accordance with the examples provided.

[0077] To further clarify the technical problems, technical solutions, and beneficial effects that the embodiments of this application aim to solve, they will be described in more detail below in conjunction with the embodiments and drawings. Clearly, the embodiments described are only a selection of the embodiments of this application, not all of them. The description of at least one exemplary embodiment below is for illustrative purposes only and does not limit the invention or its application in any way. All other embodiments obtained by a person skilled in the art based on the embodiments of this application without any creative effort are all within the scope of protection of this application.

[0078] 1. Battery manufacturing Example 1 is as follows. (1) Manufacturing of positive electrode plates Lithium nickel cobalt manganese oxide (LiNi) 0.8 Co 0.1 Mn 0.1 O2 (NCM811), the conductive agent carbon black (Super P), and the binder polyvinylidene fluoride (PVDF) were thoroughly mixed with an appropriate amount of N-methylpyrrolidone (NMP) in a weight ratio of 97.5:1.5:1 to obtain a positive electrode slurry. This slurry was then applied to the surface of the aluminum foil of the positive electrode current collector, and a positive electrode plate was obtained by baking, cold pressing, slitting, and cutting. The compressed density of the positive electrode plate was 3.5 g / cm³. 3 The capacitance density is 2.36 mAh / cm³.2 The surface density is 12.07 mg / cm³. 2 That was the case.

[0079] (2) Manufacturing of the negative electrode plate Regarding the manufacturing of the first negative electrode plate The negative electrode active material consists of artificial graphite, silicon-based material (gram capacity 1800-2300 mAh / g), single-walled carbon nanotubes, conductive agent acetylene black, thickener sodium carboxymethylcellulose (CMC), and binder styrene-butadiene rubber (SBR). These are mixed in a mass ratio of 82.5:13:0.3:1:1.2:2, deionized water is added as a solvent, and the mixture is stirred using a vacuum mixer until the system is homogeneous. This mixture is then applied to two surfaces of a 10 μm thick copper foil negative electrode current collector containing a conductive carbon undercoat layer. The mixture is dried at 110°C for 20 minutes, and after drying, the electrode plates are cold-pressed to obtain a surface density of 4.53 mg / cm³. 2 The compressed density is 1.7 g / cm³. 3 The capacitance density is 2.6 mAh / cm³. 2 Thus, a negative electrode plate with a thickness of 63.3 μm was obtained. The capacity per unit volume of the obtained negative electrode plate was 0.82 Ah / mL.

[0080] Regarding the manufacturing of the second negative electrode plate The negative electrode active material, artificial graphite, the conductive agent, acetylene black, the thickener, sodium carboxymethylcellulose (CMC), and the binder (SBR) were mixed in a mass ratio of 97:0.5:1:1.5. Deionized water was added as a solvent, and the mixture was stirred using a vacuum mixer until the system was homogeneous. This mixture was then applied to two surfaces of a 10 μm thick copper foil negative electrode current collector containing a conductive carbon undercoat layer. The mixture was dried at 110°C for 20 minutes, and after drying, the electrode plates were cold-pressed to obtain a surface density of 7.05 mg / cm³. 2 The compressed density is 1.7 g / cm³. 3 The capacitance density is 2.6 mAh / cm³. 2 Thus, a negative electrode plate with a thickness of 92.9 μm was obtained. The capacity per unit volume of the obtained negative electrode plate was 0.56 Ah / mL.

[0081] (3) Manufacturing of electrolyte Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a 1:1:1 volume ratio to obtain an organic solvent. A thoroughly dried lithium salt, LiPF6, was dissolved in the above organic solvent, resulting in a lithium salt concentration of 1 mol / L. The mixture was then prepared to obtain an electrolyte.

[0082] (4) Manufacturing of separators A 12 μm thick polyethylene film was used as the separator.

[0083] (5) Manufacturing of laminated batteries Positive plates, separators, and negative plates were stacked alternately, and the arrangement of the electrode plates in at least one electrode assembly satisfies the pattern of first negative plate / positive plate / second negative plate / positive plate / first negative plate, that is, one second negative plate was placed between two first negative plates, and one positive plate was placed between two adjacent negative plates. Separators were continuously and alternately stacked in a Z-shape between the positive and negative plates. After the stacking was completed, the assembly was placed in a case, tab welding was performed, vacuum drying was carried out at 100°C for 24 hours, liquid was injected, and chemical conversion tests and capacity tests were performed to finally produce a hard-case battery with a voltage range of 2.5V to 4.25V and a capacity of 65Ah.

[0084] Example 2 is as follows. Example 2 is similar to the manufacturing method of the laminated battery in Example 1, but the differences are as follows.

[0085] Regarding the manufacturing of the first negative electrode plate The negative electrode active material consists of artificial graphite, silicon-based material (gram capacity 1800-2300 mAh / g), single-walled carbon nanotubes, conductive agent acetylene black, thickener sodium carboxymethylcellulose (CMC), and binder SBR, which are mixed in a mass ratio of 69.5:26:0.3:1:1.2:2. Deionized water is added as a solvent, and the mixture is stirred using a vacuum mixer until the system becomes homogeneous. This mixture is then applied to two surfaces of a 10 μm thick copper foil negative electrode current collector containing a conductive carbon undercoat layer. The mixture is dried at 110°C for 20 minutes, and after drying, the electrode plates are cold-pressed to obtain a surface density of 3.38 mg / cm³.2 , with a compression density of 1.7 g / cm 3 and a areal capacity density of 2.6 mAh / cm 2 , a negative electrode plate with a thickness of 49.8 μm was obtained. The capacity per unit volume of the obtained negative electrode plate was 1.04 Ah / mL.

[0086] Regarding the manufacture of laminated batteries The positive electrode plate, separator, and negative electrode plate were alternately laminated. The arrangement of the electrode plates in at least one electrode assembly satisfied the condition of the first negative electrode plate / positive electrode plate / second negative electrode plate / positive electrode plate / second negative electrode plate / positive electrode plate / first negative electrode plate. That is, two second negative electrode plates were provided between two first negative electrode plates, and one positive electrode plate was provided between two adjacent negative electrode plates. The separator was continuously laminated alternately in a zigzag pattern between the positive electrode plate and the negative electrode plate. After the lamination was completed, it was placed in a case, tab welding was performed, vacuum drying was carried out at 100 °C for 24 h, electrolyte was injected, a formation test and a capacity test were performed, and finally, a hard case battery with a voltage range of 2.5 V to 4.25 V and a capacity of 65 Ah was manufactured.

[0087] Example 3 is as follows. Example 3 is similar to the method for manufacturing the laminated battery of Example 1, but the differences are as follows.

[0088] Regarding the manufacture of the first negative electrode plate Artificial graphite of the negative electrode active material, silicon-based material (gram capacity 1800 - 2300 mAh / g), single-layer carbon nanotubes, acetylene black as the conductive agent, sodium carboxymethyl cellulose (CMC) as the thickening agent, and SBR as the binder were mixed at a mass ratio of 85.5:10:0.3:1:1.2:2, deionized water as the solvent was added, and stirring was carried out by the action of a vacuum mixer until the system became uniform. Then, it was applied to both surfaces of a copper foil of a negative electrode current collector with a thickness of 10 μm including a conductive carbon undercoat layer, dried at 110 °C for 20 min, and after drying, the electrode plate was cold-pressed, with a weight areal density of 4.95 mg / cm 2 and a compression density of 1.7 g / cm 3 and a areal capacity density of 2.6 mAh / cm 2Thus, a negative electrode plate with a thickness of 68.2 μm was obtained. The capacity per unit volume of the obtained negative electrode plate was 0.76 Ah / mL.

[0089] Regarding the manufacturing of the second negative electrode plate The negative electrode active material consists of artificial graphite, silicon-based material (gram capacity 1800-2300 mAh / g), single-walled carbon nanotubes, conductive agent acetylene black, thickener sodium carboxymethylcellulose (CMC), and binder SBR, which are mixed in a mass ratio of 91.8:3.7:0.3:1:1.2:2. Deionized water is added as a solvent, and the mixture is stirred using a vacuum mixer until the system becomes homogeneous. This mixture is then applied to two surfaces of a 10 μm thick copper foil negative electrode current collector containing a conductive carbon undercoat layer. The mixture is dried at 110°C for 20 minutes, and after drying, the electrode plates are cold-pressed to obtain a surface density of 6.14 mg / cm³. 2 The compressed density is 1.7 g / cm³. 3 The capacitance density is 2.6 mAh / cm³. 2 Thus, a negative electrode plate with a thickness of 82.3 μm was obtained. The capacity per unit volume of the obtained negative electrode plate was 0.63 Ah / mL.

[0090] Regarding the manufacturing of laminated batteries Positive plates, separators, and negative plates were stacked alternately, and the arrangement of the electrode plates in at least one electrode assembly was such that first negative plate / positive plate / second negative plate / positive plate / second negative plate / positive plate / second negative plate / positive plate / first negative plate, that is, three second negative plates were placed between two first negative plates, and one positive plate was placed between two adjacent negative plates. Separators were continuously and alternately stacked in a Z-shape between the positive and negative plates. After stacking was completed, the assembly was placed in a case, tab welding was performed, vacuum drying was carried out at 100°C for 24 hours, liquid was injected, and chemical conversion tests and capacity tests were performed to finally produce a hard-case battery with a voltage range of 2.5V to 4.25V and a capacity of 65Ah.

[0091] Example 4 is as follows. Example 4 is similar to the manufacturing method of the laminated battery in Example 1, but the differences are as follows.

[0092] Manufacture of the first negative electrode plate Artificial graphite of negative electrode active material, silicon-based material (gram capacity 1800 - 2300 mAh / g), single-layer carbon nanotube, acetylene black as conductive agent, sodium carboxymethyl cellulose (CMC) as thickening agent, SBR as binder are mixed at a mass ratio of 85.5:10:0.3:1:1.2:2, deionized water as solvent is added, and it is stirred by the action of a vacuum mixer until the system becomes uniform. Then it is applied to two surfaces of a copper foil of a negative electrode current collector with a thickness of 10 μm including a conductive carbon undercoat layer, dried at 110 °C for 20 min, the electrode plate is cold-pressed after drying, and finally the areal weight density is 5.42 mg / cm 2 and the compression density is 1 g / cm 3 and the volumetric capacity density is 2.6 mAh / cm 2 and a negative electrode plate with an electrode plate thickness of 118.4 μm is obtained. The capacity per unit volume of the obtained negative electrode plate was 0.44 Ah / mL.

[0093] Manufacture of the second negative electrode plate Artificial graphite of negative electrode active material, acetylene black as conductive agent, sodium carboxymethyl cellulose (CMC) as thickening agent, binder (SBR) are mixed at a mass ratio of 97:0.5:1:1.5, deionized water as solvent is added, and it is stirred by the action of a vacuum mixer until the system becomes uniform. Then it is applied to two surfaces of a copper foil of a negative electrode current collector with a thickness of 10 μm including a conductive carbon undercoat layer, dried at 110 °C for 20 min, the electrode plate is cold-pressed after drying, and the areal weight density is 7.65 mg / cm 2 and the compression density is 1 g / cm 3 and the volumetric capacity density is 2.6 mAh / cm 2 and a negative electrode plate with an electrode plate thickness of 163 μm is obtained. The capacity per unit volume of the obtained negative electrode plate was 0.32 Ah / mL.

[0094] Example 5 is as follows. Example 5 is similar to the manufacturing method of the laminate battery in Example 1, but the differences are as follows.

[0095] Regarding the manufacturing of positive electrode plates Lithium nickel cobalt manganese oxide (LiNi) 0.8 Co 0.1 Mn 0.1 O2 (NCM811), the conductive agent carbon black (Super P), and the binder PVDF were thoroughly mixed with an appropriate amount of N-methylpyrrolidone (NMP) in a weight ratio of 97.5:1.5:1 to obtain a positive electrode slurry. This slurry was then applied to the surface of the aluminum foil of the positive electrode current collector, and a positive electrode plate was obtained by baking, cold pressing, slitting, and cutting. The compressed density of the positive electrode plate was 3.5 g / cm³. 3 The capacitance density is 4.43 mAh / cm³. 2 The surface density is 22.59 mg / cm³. 2 That was the case.

[0096] Regarding the manufacturing of the first negative electrode plate The negative electrode active material consists of artificial graphite, silicon-based material (gram capacity 2800-3500 mAh / g), single-walled carbon nanotubes, conductive agent acetylene black, thickener sodium carboxymethylcellulose (CMC), and binder SBR, which are mixed in a mass ratio of 85.5:10:0.3:1:1.2:2. Deionized water is added as a solvent, and the mixture is stirred using a vacuum mixer until the system becomes homogeneous. This mixture is then applied to two surfaces of a 10 μm thick copper foil negative electrode current collector containing a conductive carbon undercoat layer. The mixture is dried at 110°C for 20 minutes, and after drying, the electrode plates are cold-pressed to obtain a surface density of 10.16 mg / cm³. 2 The compressed density is 1.7 g / cm³. 3 The capacitance density is 4.87 mAh / cm³. 2 Thus, a negative electrode plate with a thickness of 129.5 μm was obtained. The capacity per unit volume of the obtained negative electrode plate was 0.75 Ah / mL.

[0097] Regarding the manufacturing of the second negative electrode plate The negative electrode active material, artificial graphite, the conductive agent, acetylene black, the thickener, sodium carboxymethylcellulose (CMC), and the binder (SBR) were mixed in a mass ratio of 97:0.5:1:1.5. Deionized water was added as a solvent, and the mixture was stirred using a vacuum mixer until the system was homogeneous. This mixture was then applied to two surfaces of a 10 μm thick copper foil negative electrode current collector containing a conductive carbon undercoat layer. The mixture was dried at 110°C for 20 minutes, and after drying, the electrode plates were cold-pressed to obtain a surface density of 13.21 mg / cm³. 2 The compressed density is 1.7 g / cm³. 3 The capacitance density is 4.87 mAh / cm³. 2 Thus, a negative electrode plate with a thickness of 165.4 μm was obtained. The capacity per unit volume of the obtained negative electrode plate was 0.59 Ah / mL.

[0098] Example 6 is as follows. Example 6 is similar to the manufacturing method of the laminated battery in Example 1, but the differences are as follows.

[0099] Regarding the manufacturing of positive electrode plates Lithium nickel cobalt manganese oxide (LiNi) 0.8 Co 0.1 Mn 0.1 O2 (NCM811), the conductive agent carbon black (Super P), and the binder PVDF were thoroughly mixed with an appropriate amount of N-methylpyrrolidone (NMP) in a weight ratio of 97.5:1.5:1 to obtain a positive electrode slurry. This slurry was then applied to the surface of the aluminum foil of the positive electrode current collector, and a positive electrode plate was obtained by baking, cold pressing, slitting, and cutting. The compressed density of the positive electrode plate was 3.5 g / cm³. 3 The capacitance density is 4.43 mAh / cm³. 2 The surface density is 22.59 mg / cm³. 2 That was the case.

[0100] Regarding the manufacturing of the first negative electrode plate The negative electrode active material consists of artificial graphite, silicon-based material (gram capacity 2800-3500 mAh / g), single-walled carbon nanotubes, conductive agent acetylene black, thickener sodium carboxymethylcellulose (CMC), and binder SBR, which are mixed in a mass ratio of 40:50:0.6:1:2:8.4, resulting in a final mass surface density of 2.63 mg / cm³. 2 The compressed density is 1.7 g / cm³. 3 The capacitance density is 4.87 mAh / cm³. 2 Thus, a negative electrode plate with a thickness of 40.9 μm was obtained. The capacity per unit volume of the obtained negative electrode plate was 2.38 Ah / mL.

[0101] Regarding the manufacturing of the second negative electrode plate The negative electrode active material, artificial graphite, the conductive agent, acetylene black, the thickener, sodium carboxymethylcellulose (CMC), and the binder (SBR) were mixed in a mass ratio of 97:0.5:1:1.5. Deionized water was added as a solvent, and the mixture was stirred using a vacuum mixer until the system was homogeneous. This mixture was then applied to two surfaces of a 10 μm thick copper foil negative electrode current collector containing a conductive carbon undercoat layer. The mixture was dried at 110°C for 20 minutes, and after drying, the electrode plates were cold-pressed to obtain a surface density of 13.21 mg / cm³. 2 The compressed density is 1.7 g / cm³. 3 The capacitance density is 4.87 mAh / cm³. 2 Thus, a negative electrode plate with a thickness of 165.4 μm was obtained. The capacity per unit volume of the obtained negative electrode plate was 0.76 Ah / mL.

[0102] Regarding the manufacturing of laminated batteries Positive plates, separators, and negative plates were stacked alternately, and the arrangement of the electrode plates in at least one electrode assembly was such that first negative plate / positive plate / second negative plate / positive plate / second negative plate / positive plate / first negative plate, i.e., two second negative plates were placed between two first negative plates, and one positive plate was placed between two adjacent negative plates. Separators were continuously and alternately stacked in a Z-shape between the positive and negative plates. After stacking was completed, the assembly was placed in a case, tab welding was performed, vacuum drying was carried out at 100°C for 24 hours, liquid was injected, and chemical conversion tests and capacity tests were performed to finally produce a hard-case battery with a voltage range of 2.5V to 4.25V and a capacity of 65Ah.

[0103] Example 7 is as follows. Example 7 is similar to the manufacturing method of the laminated battery in Example 1, but the differences are as follows.

[0104] Regarding the manufacturing of positive electrode plates Lithium nickel cobalt manganese oxide (LiNi) 0.8 Co 0.1 Mn 0.1 O2 (NCM811), the conductive agent carbon black (Super P), and the binder PVDF were thoroughly mixed with an appropriate amount of N-methylpyrrolidone (NMP) in a weight ratio of 97.5:1.5:1 to obtain a positive electrode slurry. This slurry was then applied to the surface of the aluminum foil of the positive electrode current collector, and a positive electrode plate was obtained through baking, cold pressing, slitting, and cutting. The compressed density of the final obtained positive electrode plate was 3.5 g / cm³. 3 The capacitance density is 4.43 mAh / cm³. 2 The surface density is 22.59 mg / cm³. 2 That was the case.

[0105] Regarding the manufacturing of the first negative electrode plate The negative electrode active material consists of artificial graphite, silicon-based material (gram capacity 2800-3500 mAh / g), single-walled carbon nanotubes, conductive agent acetylene black, thickener sodium carboxymethylcellulose (CMC), and binder SBR, which are mixed in a mass ratio of 40:50:0.6:1:2:8.4. Deionized water is added as a solvent, and the mixture is stirred using a vacuum mixer until the system is homogeneous. This mixture is then applied to two surfaces of a 10 μm thick copper foil negative electrode current collector containing a conductive carbon undercoat layer. The mixture is dried at 110°C for 20 minutes, and after drying, the electrode plates are cold-pressed to obtain a surface density of 2.63 mg / cm³. 2 Therefore, the compressed density is 2 g / cm³. 3 The capacitance density is 4.87 mAh / cm³. 2 Thus, a negative electrode plate with a thickness of 36.3 μm was obtained. The capacity per unit volume of the obtained negative electrode plate was 2.68 Ah / mL.

[0106] Regarding the manufacturing of the second negative electrode plate The negative electrode active material consists of artificial graphite, silicon-based material (gram capacity 2800-3500 mAh / g), single-walled carbon nanotubes, conductive agent acetylene black, thickener sodium carboxymethylcellulose (CMC), and binder SBR, which are mixed in a mass ratio of 85.5:10:0.3:1:1.2:2. Deionized water is added as a solvent, and the mixture is stirred using a vacuum mixer until the system becomes homogeneous. This mixture is then applied to two surfaces of a 10 μm thick copper foil negative electrode current collector containing a conductive carbon undercoat layer. The mixture is dried at 110°C for 20 minutes, and after drying, the electrode plates are cold-pressed to obtain a surface density of 7.32 mg / cm³. 2 Therefore, the compressed density is 2 g / cm³. 3 The capacitance density is 4.87 mAh / cm³. 2 Thus, a negative electrode plate with a thickness of 83.2 μm was obtained. The capacity per unit volume of the obtained negative electrode plate was 1.17 Ah / mL.

[0107] Regarding the manufacturing of laminated batteries Positive plates, separators, and negative plates were stacked alternately, and the arrangement of the electrode plates in at least one electrode assembly was such that first negative plate / positive plate / second negative plate / positive plate / second negative plate / positive plate / second negative plate / positive plate / first negative plate, that is, three second negative plates were placed between two first negative plates, and one positive plate was placed between two adjacent negative plates. Separators were continuously and alternately stacked in a Z-shape between the positive and negative plates. After stacking was completed, the assembly was placed in a case, tab welding was performed, vacuum drying was carried out at 100°C for 24 hours, liquid was injected, and chemical conversion tests and capacity tests were performed to finally produce a hard-case battery with a voltage range of 2.5V to 4.25V and a capacity of 65Ah.

[0108] Comparative Example 1 is as follows: The distinction from Example 1 is that the battery has only one type of negative electrode plate, which is manufactured by a method for manufacturing silicon-containing negative electrode plates. Specifically, artificial graphite as the negative electrode active material, silicon-based material (gram capacity 1800-2300 mAh / g), single-walled carbon nanotubes, acetylene black as the conductive agent, sodium carboxymethylcellulose (CMC) as the thickener, and SBR as the binder are mixed in a mass ratio of 91.5:4:0.3:1:1.2:2, deionized water as the solvent is added, and the system is stirred using a vacuum mixer until it becomes homogeneous. This mixture is then applied to two surfaces of copper foil negative electrode current collectors with a thickness of 10 μm, including a conductive carbon undercoat layer, dried at 110°C for 20 min, and after drying, the electrode plates are cold-pressed to obtain a surface density of 6.07 mg / cm³. 2 The capacitance density is 2.6 mAh / cm³. 2 The compressed density is 1.7 g / cm³. 3 Thus, a negative electrode plate with a plate thickness of 81.3 μm was obtained.

[0109] Regarding the manufacturing of laminated batteries Positive plates, separators, and negative plates were stacked alternately, and the arrangement of the plates in at least one electrode assembly satisfies the negative plate / positive plate / negative plate pattern, i.e., two adjacent negative plates were similar. The separators were continuously and alternately stacked in a Z-shape between the positive and negative plates. After stacking was complete, the assembly was placed in a case, tab welding was performed, vacuum drying was carried out at 100°C for 24 hours, liquid was injected, and chemical conversion tests and capacity tests were performed to finally produce a hard-case battery with a voltage range of 2.5V to 4.25V and a capacity of 65Ah.

[0110] Comparative Example 2 is as follows. The distinction from Example 5 is that the battery has only one type of negative electrode plate, which is manufactured by a method for manufacturing silicon-containing negative electrode plates. Specifically, the negative electrode active material consists of artificial graphite, silicon-based material (gram capacity 2800-3500 mAh / g), single-walled carbon nanotubes, conductive agent acetylene black, thickener sodium carboxymethylcellulose (CMC), and binder SBR, which are mixed in a mass ratio of 91.5:4:0.3:1:1.2:2. Deionized water is added as a solvent, and the mixture is stirred using a vacuum mixer until the system becomes homogeneous. This mixture is then applied to two surfaces of a 10 μm thick copper foil negative electrode current collector containing a conductive carbon undercoat layer, dried at 110°C for 20 minutes, and after drying, the electrode plate is cold-pressed to obtain a surface density of 10.07 mg / cm³. 2 The capacitance density is 4.87 mAh / cm³. 2 The compressed density is 1.7 g / cm³. 3 Thus, a negative electrode plate with a plate thickness of 128.4 μm was obtained.

[0111] Regarding the manufacturing of laminated batteries Positive plates, separators, and negative plates were stacked alternately, and the arrangement of the plates in at least one electrode assembly satisfies the negative plate / positive plate / negative plate pattern, i.e., two adjacent negative plates were similar. The separators were continuously and alternately stacked in a Z-shape between the positive and negative plates. After stacking was complete, the assembly was placed in a case, tab welding was performed, vacuum drying was carried out at 100°C for 24 hours, liquid was injected, and chemical conversion tests and capacity tests were performed to finally produce a hard-case battery with a voltage range of 2.5V to 4.25V and a capacity of 65Ah.

[0112] Comparative Example 3 is as follows. The distinction from Comparative Example 2 lies in the manufacturing of the negative electrode plate. Specifically, the negative electrode active material consists of artificial graphite, silicon-based material (gram capacity 2800-3500 mAh / g), single-walled carbon nanotubes, conductive agent acetylene black, thickener sodium carboxymethylcellulose (CMC), and binder SBR, which are mixed in a mass ratio of 81.5:14:0.3:1:1.2:2. Deionized water is added as a solvent, and the mixture is stirred using a vacuum mixer until the system becomes homogeneous. This mixture is then applied to two surfaces of a 10 μm thick copper foil negative electrode current collector containing a conductive carbon undercoat layer. It is dried at 110°C for 20 minutes, and after drying, the electrode plate is cold-pressed to achieve a surface density of 6.2 mg / cm³. 2 The capacitance density is 4.87 mAh / cm³. 2 The compressed density is 1.7 g / cm³. 3 Thus, a negative electrode plate with a thickness of 83 μm was obtained.

[0113] 3. Performance Test (1) Performance testing of the electrode plates (1) Volume test per unit volume 1. The electrode plate was punched out into a small circular disc with area S (a small circular disc with a diameter of 14 mm), its thickness H was tested using a 1 / 100th micrometer, and the volume V = SH was calculated. 2. Using an electronic balance with a test accuracy of 0.01 mg, the weight W1 of the above-mentioned small disc was weighed, the active layers on both sides were scraped off leaving the current collector, its weight W2 was weighed, and the total weight W3 = W1 - W2 was calculated. 3. The active layer on one side of 1 was scraped off, leaving the active layer on the other side and the current collector. Using the electronic balance of 2, the weight W4 was weighed, and the weight of the active layer on the other side W5 = W4 - W2 was calculated. 4. The electrode plates 3 and 4 were assembled into a pair of lithium button-type half-cells in a glove box, and the capacity C1 was tested using equipment from Wuhan Blue Cell Corporation. The gram capacity C2 of the active layer was calculated as C1 ÷ W5. 5. The total volume of the small disk, C3 = C2 × W3, was calculated, and the volume per unit volume of the small disk, C4 = C3 ÷ V, was calculated.

[0114] (ii) Battery performance testing (1) Initial cycle capacity test of secondary battery The battery was charged at 45°C for 10 hours at a multiplier of 0.02C, then charged at 25°C at a multiplier of 0.33C to 4.25V, charged at a constant voltage of 4.25V to 0.05C, and finally discharged at 0.33C to 2.5V. The measured capacity was recorded as D0.

[0115] (2) Cycle performance test of secondary batteries The following steps were performed in a 45°C environment. The battery was left standing for 5 minutes, discharged to 2.5V at 0.33D0, left standing for 5 minutes, charged to 4.25V at 0.33D0, charged to 0.05C at a constant voltage of 4.25V, left standing for 5 minutes, discharged to 2.5V at 0.33C, and the capacitance at this time was recorded as C0.

[0116] After letting the secondary battery stand for 5 minutes, a charge-discharge cycle was performed according to the following steps: Let it stand for 20 minutes, charge to 4.25V at 1D0, charge to 0.05D0 at a constant voltage of 4.25V, let it stand for 5 minutes, discharge to 2.5V at 1D0, and let it stand for 5 minutes. The discharge capacity Cm of each cycle was recorded, where m represents the number of cycles, and the reversible capacity retention rate F1 was calculated when m=1000, where F1=C m The formula is ÷C0 × 100%, and the higher the reversible capacity retention rate, the better the cycle performance.

[0117] (3) Storage performance test of secondary batteries In Step 1, the battery was discharged to 2.5V at 25°C with 0.33D0, left to stand for 5 minutes, charged to 4.25V with 0.33D0, charged to 0.05D0 at a constant voltage of 4.25V, left to stand for 5 minutes, and discharged to 2.5V with 0.33C. The capacity at this time was recorded as C0 (after storage, the battery capacity in this step is the reversible capacity, C t (Note: t is the storage time). The battery was charged to 4.25V at 0.33D0, then charged to 0.05D0 at a constant voltage of 4.25V, at which point the battery was fully charged.

[0118] In Step 2, the fully charged secondary battery is placed in a 60°C environment, stored periodically for a certain period of time, then removed and tested according to the flow in Step 1. The fully charged secondary battery is then placed in a 60°C environment, and the above operations are repeated until t=180 days, and the reversible capacity retention rate F2 is calculated as F2=C t It was ÷C0 × 100%.

[0119] (4) Expansion force and expansion displacement test of secondary batteries Using steel plate clamps, the battery cells were fixed between the press plates, and the positions of the upper and lower press plates were fixed with bolts. A force sensor was attached to the upper press plate to monitor the pressure. Before charging the battery cells, the pitch h0 of the upper and lower press plates was tested, and the corresponding pressure was recorded when the battery cells reached a fully charged state. Simultaneously, the pitch h1 of the upper and lower press plates after full charge was tested, and the expansion rate of the battery cells = (h1 ÷ h0 - 1) × 100% was calculated.

[0120] Tables 1 and 2 show the electrode plate parameters of the battery cells of each example and comparative example measured, and Table 3 shows the battery performance of each example and comparative example measured.

[0121] [Table 1]

[0122] [Table 2]

[0123] [Table 3]

[0124] From Tables 1, 2, and 3, the following conclusions can be drawn. The difference between Comparative Example 1 and Examples 1-4 is that Comparative Example 1 has only one type of negative electrode plate in its battery. As shown by the results, the battery expansion force and the expansion rate of the negative electrode plates of Examples 1-4 when the battery is fully charged are both lower than those of Comparative Example 1, and the reversible capacity retention rate after 180 days of storage at 60°C in a fully charged state, and the reversible capacity retention rate after 1000 cycles at 45°C are both superior to those of Comparative Example 1.

[0125] The difference between Comparative Example 2 and Examples 5 and 6 is that Comparative Example 2 has only one type of negative electrode plate in the battery. As shown in the results, the battery expansion force and the expansion rate of the negative electrode plates in Examples 5 and 6 when the battery is fully charged are both lower than those of Comparative Example 2. Furthermore, the reversible capacity retention rate after 180 days of storage at 60°C in a fully charged state, and the reversible capacity retention rate after 1000 cycles at 45°C are both superior to those of Comparative Example 2.

[0126] The difference between Comparative Example 3 and Example 7 lies in the fact that Comparative Example 3 has only one type of negative electrode plate in its battery. As shown in the results, the battery expansion force of the negative electrode plate in Example 7 and the expansion rate when the battery is fully charged are both lower than those of Comparative Example 3. Furthermore, the reversible capacity retention rate after 180 days of storage at 60°C in a fully charged state and the reversible capacity retention rate after 1000 cycles at 45°C are both superior to those of Comparative Example 3.

[0127] In summary, the battery cell defined by this application includes a plurality of positive electrode plates and a plurality of negative electrode plates, and adjacent positive and negative electrode plates are separated by a separator. The negative electrode plates include a first negative electrode plate and a second negative electrode plate with two different capacities, and at least one negative electrode plate with a relatively low capacity is provided between two adjacent negative electrode plates with higher capacities. Therefore, the expansion effect of the negative electrode plates can be improved, and battery failure due to negative electrode plate expansion can be reduced.

[0128] The above description is merely a specific embodiment of the present application, and the scope of protection of the present application is not limited thereto. A person skilled in the art can easily conceive of various equivalent modifications and substitutions within the technical scope disclosed herein, and all such modifications and substitutions are included within the scope of protection of the present application. Accordingly, the scope of protection of the present application is based on the scope of protection defined in the claims. [Explanation of Symbols]

[0129] 100 Secondary battery 10 battery cells 1 Positive plate 2 Negative plates 3 Separators 21 First negative plate 22 Second negative plate

Claims

1. A battery cell comprising at least one electrode assembly, wherein the electrode assembly is Positive plate and A negative electrode plate is included, The negative electrode plate includes a first negative electrode plate and a second negative electrode plate, wherein the capacity per unit volume of the first negative electrode plate is greater than the capacity per unit volume of the second negative electrode plate, at least one positive electrode plate is provided between two adjacent first negative electrode plates, and at least one second negative electrode plate is provided between two adjacent first negative electrode plates. The capacity per unit volume of the first negative electrode plate is 0.44 Ah / mL to 2.68 Ah / mL, and / or A battery cell characterized in that the capacity per unit volume of the second negative electrode plate is 0.32 Ah / mL to 1.17 Ah / mL.

2. The battery cell according to claim 1, characterized in that M second negative electrode plates are provided between two adjacent first negative electrode plates, 1 ≤ M ≤ 2.5n, n = Cs / Cg, M is an integer of 1 or more, Cs is the capacity per unit volume of the first negative electrode plates, and Cg is the capacity per unit volume of the second negative electrode plates.

3. The battery cell according to claim 2, characterized in that n is 1 or greater.

4. The battery cell according to claim 1, characterized in that the total number of the first negative electrode plates is less than or equal to the total number of the second negative electrode plates.

5. The battery cell according to claim 4, characterized in that the ratio of the capacitance surface density of either one positive electrode plate to either one negative electrode plate is 1.01 ≤ C-negative / C-positive ≤ 1.2, and the capacitance surface density is the capacitance of the active layer on one side per unit area of ​​the positive electrode plate / negative electrode plate.

6. The surface density by weight of the first negative electrode plate is 2.63 mg / cm² to 10.16 mg / cm², and / or The battery cell according to claim 5, characterized in that the weight surface density of the second negative electrode plate is 6.06 mg / cm² to 13.21 mg / cm².

7. The first negative electrode plate includes a first active layer, the mass fraction of the negative electrode active material in the first active layer is 90% or more and / or 95.5% or less, The battery cell according to claim 6, characterized in that the second negative electrode plate includes a second active layer, and the mass fraction of the negative electrode active material in the second active layer is 96% or more.

8. The battery cell according to claim 7, characterized in that the first negative electrode plate includes a silicon-based electrode plate, and the active material in the silicon-based electrode plate includes one or more of a pure silicon material, a silicon carbon material, and a silicon oxygen material.

9. The battery cell according to claim 8, characterized in that the silicon oxygen material comprises one or more of prelithiated silicon oxygen or premagnesated silicon oxygen.

10. The battery cell according to claim 8, characterized in that the mass fraction of silicon in the active material of the silicon-based electrode plate is 10% to 50%, and the mass fraction of graphite in the active material of the silicon-based electrode plate is 40% to 85.5%.

11. The battery cell according to claim 10, characterized in that the second negative electrode plate includes a graphite electrode plate, and the active material in the graphite electrode plate includes artificial graphite and / or natural graphite.

12. The battery cell according to claim 11, characterized in that the weight surface density of the positive electrode plate is 12 mg / cm² to 30 mg / cm².

13. The battery cell according to claim 12, characterized in that the compressed density of the positive electrode plate is 2.3 g / cm³ to 4 g / cm³.

14. The battery cell according to claim 13, characterized in that the positive electrode plate includes a positive electrode active layer, and the mass fraction of the positive electrode active material in the positive electrode active layer is 97% or more.

15. The battery cell according to claim 14, characterized in that the positive electrode plate includes one or more of the following: a lithium iron phosphate electrode plate, a lithium cobalt oxide electrode plate, a lithium nickel cobalt manganese oxide electrode plate, and a lithium manganese iron phosphate electrode plate.

16. The battery cell according to claim 15, further comprising a separator used to separate adjacent positive and negative plates, which is folded in a Z-shape, wherein the positive and negative plates are alternately inserted into the gap between the stacked plates.

17. A laminated battery characterized by comprising a case and a battery cell according to any one of claims 1 to 16.

18. An electrical device characterized by including the laminated battery described in claim 17.

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