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

[0002] Secondary batteries have the outstanding features of being lightweight, pollution-free, and having no memory effect, and are therefore widely used in consumer electronic products and electric vehicles. The negative electrode plates of conventional secondary batteries are generally made of silicon-based electrodes. Silicon-based materials have large capacity, but at the same time have large volume effects and poor electrical conductivity. During the charge-discharge cycle, the expansion of the silicon-based materials can cause the adhesive in the electrode plate to fail and powder to fall off from the electrode plate, which can further lead to irreversible loss of capacity of the electrode plate. Summary of the Invention [Means for solving the problem]

[0003] In view of the technical problems in the background art, the present application provides a battery cell, a laminated battery, and an electric device that can improve defects caused by expansion of electrode plates, extend the battery life, and improve the energy density and storage performance of the battery.

[0004] To achieve the above object, a first aspect of the present application provides a battery cell, the battery cell including at least one electrode assembly, the electrode assembly including a positive plate and a negative plate, the negative plate including 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 provided between two adjacent first negative plates, and at least one second negative plate being provided between two adjacent first negative plates.

[0005] The present application has at least the following beneficial effects: Unlike the prior art, the present application provides two types of negative electrode plates with different capacities per unit volume, and provides at least one negative electrode plate with a relatively low capacity per unit volume between two adjacent negative electrode plates with a high capacity per unit volume, thereby improving the volume expansion effect of the plates, reducing the failure of the battery caused by the expansion of the plates, and simultaneously improving 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, where 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. Setting the spacing between the negative electrode plates based on the capacity per unit volume of the two types of negative electrode plates effectively controls plate expansion while significantly increasing the capacity of the battery.

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

[0008] In some 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 plates is equal to or less than the total number of second negative plates, thereby reducing the impact of volume expansion of the plates on the battery life and extending the battery life.

[0010] In some embodiments, the ratio of the capacity areal density of any one positive plate to any one negative plate is 1.01≦C 負 / C 正The capacity surface density is the capacity of the active layer on one side per unit area of ​​the positive / negative plate. By designing the capacity surface density of the negative plate to be greater than that of the positive plate, it is possible to prevent overcharging of the negative electrode, suppress the formation of lithium dendrites, and improve the safety of the battery.

[0011] In some embodiments, the first negative plate has a weight areal density of 2.63 mg / cm 2 ~10.16mg / cm 2 and / or the weight areal density of the second negative electrode plate is 6.06 mg / cm 2 ~13.21mg / cm 2 By controlling the weight area 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, and the mass fraction of the negative electrode active material in the first active layer is 90% to 95.5%. Alternatively, 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 greater. The total content of the active material in the active layer can be determined based on the content of active materials 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 active material content. Because a high silicon content causes a larger volume effect and poorer resistance, more adhesive and conductive agent must be added. A silicon content of 10% to 50% and a total active material content of 90% to 97% in the active layer can effectively control volume expansion. Because the second negative electrode plate does not have a significant volume effect or electrical conductivity issues, the higher the active material content, the better, provided that it does not affect processing performance. The lowest mass fraction is 96%.

[0013] In some embodiments, the first negative plate comprises a silicon-based plate, and the active material in the silicon-based plate comprises one or more of a pure silicon material, a silicon carbon material, and a silicon oxygen material, preferably one or more of a pre-lithiated silicon oxygen material or a pre-magnesiated silicon oxygen material.

[0014] In some embodiments, 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%.

[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, and when combined with a silicon negative electrode plate, it can reduce the volume expansion of the silicon negative electrode plate and improve the electrical conductivity of the battery.

[0016] In some embodiments, the positive plate has a weight areal density of 12 mg / cm 2 ~30mg / cm 2 By providing the electrodes in this manner, the energy density of the battery can be increased.

[0017] In some embodiments, the positive plate has a compressed density of 2.3 g / cm 3 ~4g / cm 3 By providing the electrodes in this manner, 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 plate, a lithium cobalt oxide plate, a lithium nickel cobalt manganese oxide plate, and a lithium iron manganese phosphate plate, which can increase the energy density of the battery.

[0020] In some embodiments, the battery cell further includes a separator that is folded into a Z-shape and is used to separate adjacent positive and negative plates, and the positive and negative plates are alternately inserted into the stacked gaps. This arrangement 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 laminate battery of the present application includes the battery cell provided by the present application, and therefore has at least the same advantages as the 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 the present application includes the laminated battery provided by the present application, and therefore has at least the same advantages as the laminated battery.

[0025] The above description is merely an outline of the technical solution of the present application, and in order to make the technical solution of the present application more clearly understood, it can be implemented according to the content of the specification, and the above and other objectives, features and advantages of the present application more obvious and understandable, the following provides specific embodiments of the present application. [Brief explanation of the drawings]

[0026] In order to more clearly describe the technical solutions of the present application, the following briefly introduces the drawings used in the present application. Obviously, the drawings described below are only some embodiments of the present application, and those skilled in the art can further obtain other drawings based on the drawings without creative efforts. [Figure 1] 1 is a schematic diagram of a three-dimensional structure of an embodiment of a secondary battery of the present invention. [Figure 2] FIG. 1 is a front view of an embodiment of a battery cell of the present application. [Figure 3]FIG. 2 is a schematic diagram showing the layout of an example of a negative electrode plate of a battery cell according to the present invention. [Figure 4] 1 is a schematic diagram of a three-dimensional structure of an embodiment of a battery cell according to the present invention; [Figure 5] 1 is a schematic diagram of the three-dimensional structure of an electrical device according to the present invention; DETAILED DESCRIPTION OF THE INVENTION

[0027] The present application will now be further described with reference to the following detailed description, which should be understood as merely illustrative of the present application and not limiting the scope of the present application.

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

[0029] In the description herein, unless otherwise specified, 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 the description of 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 specified, the terms used herein have the meanings commonly understood by those skilled in the art. Unless otherwise specified, the numerical values ​​of each parameter mentioned herein can be measured by various measurement methods commonly used in the art (for example, they can be tested by the methods given in the examples of the present application).

[0032] The terms used in this specification are merely for the purpose of describing specific embodiments and are not intended to limit the present application. The terms "including," "having," and any variations thereof in the specification, claims, and description of the drawings of this application are intended to cover a non-exclusive "including."

[0033] In the description of the embodiments of the present application, technical terms such as "first," "second," etc. are used only to distinguish different objects, and should not be understood as indicating or implying relative importance, or the number, specific order, or primary-subordinate relationship of the indicated technical features. In the description of the embodiments of the present application, unless otherwise clearly and specifically limited, "plurality" means two or more.

[0034] When an "embodiment" is mentioned in this specification, it means that a particular feature, structure, or characteristic described in connection with the embodiment may be included in at least one embodiment of the present application. Appearances of this phrase in various places in the specification do not necessarily refer to the same embodiment, nor are they mutually exclusive, separate, or alternative embodiments to other embodiments. Those skilled in the art can explicitly and implicitly understand that the embodiments described in this specification can be combined with other embodiments.

[0035] In describing the examples of the present application, the term "plurality" refers to two or more (including two); similarly, "groups" refers to two or more (including two groups); and "plurality" refers to two or more (including two).

[0036] After extensive research, the inventors discovered that the negative electrode plates of conventional batteries are generally made of silicon-based materials and other active materials, which have a large volume effect and poor conductivity, which can cause the negative electrode plate to expand during charge / discharge cycles, leading to the loss of adhesive in the electrode plate and the detachment of powder from the electrode plate, which can further lead to irreversible loss of capacity of the electrode plate.

[0037] Secondary batteries A secondary battery refers to a battery that can be continuously used by activating the active material through charging after the battery has been discharged.

[0038] Typically, a secondary battery consists of a battery cell (positive electrode plate, negative electrode plate, separator), electrolyte, and case. During the battery's charge and discharge process, active ions are repeatedly inserted and removed between the positive and negative electrode plates. The separator is placed between the positive and negative electrode plates to provide isolation. The electrolyte conducts ions between the positive and negative electrode plates.

[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 hard case such as a hard 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, for example, one or more of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0041] Methods for manufacturing the secondary battery of the present application are well 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, the separator, and the negative electrode plate are formed into a battery cell through a winding process and / or a stacking process, the battery cell is placed in a case, baked, and then an electrolyte is injected. A secondary battery can be obtained through processes such as vacuum packaging, standing, chemical formation, and shaping. The secondary battery can include multiple battery cells, which can be connected in series, parallel, or in a series-parallel configuration.

[0042] In one embodiment, the secondary battery of the present example is a laminate battery.

[0043] About battery cells An embodiment of the present application provides a battery cell, the battery cell including at least one electrode assembly, the electrode assembly including a positive plate and a negative plate, the negative plate including 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 provided between two adjacent first negative plates, and at least one second negative plate being provided between two adjacent first negative plates.

[0044] In some embodiments, for example, the number of positive plates may be set to a plurality of numbers, such as two, three, or four, and the number of negative plates may be set to a plurality of numbers, such as two, three, four, five, six, or seven. The number of second negative plates provided between two adjacent first negative plates in the negative plate may be one, two, or three. For example, when the number of negative plates is five, the number of first negative plates is two, the number of second negative plates is three, and one second negative plate is provided between two adjacent first negative plates. The number of positive plates provided between two adjacent first negative plates may be one, two, or three. A single positive electrode plate may be provided between any two adjacent negative electrode plates, i.e., 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 single positive electrode plate is provided therebetween. When the first negative electrode plate is adjacent to the second negative electrode plate, no positive electrode plate may be provided between them.

[0045] As shown in FIG. 2, this is a front view of a battery cell according to one embodiment of the present application. 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 provided between two adjacent first negative electrode plates 21.

[0046] About the positive electrode plate In a secondary battery, a positive electrode plate typically includes a positive electrode current collector and a positive electrode active layer disposed on the positive electrode current collector, the positive electrode active layer including a positive electrode active material. The positive electrode current collector may be a conventional metal foil or a composite current collector, and the composite current collector may be formed by disposing a metal material on a polymer substrate. For example, the positive electrode current collector may be aluminum foil.

[0047] In some embodiments, the positive electrode plate includes one or more of lithium iron phosphate plates, lithium cobalt oxide plates, lithium nickel cobalt manganese oxide plates, and lithium iron manganese phosphate plates. Lithium iron phosphate is a safe positive electrode active material with the chemical formula LiFePO4, which does not contain any heavy metal elements harmful to the human body. It has a theoretical specific capacity of 170 mAh / g and an actual specific capacity of more than 140 mAh / g (0.2 C, 25°C). Lithium cobalt oxide ion batteries are lithium ion batteries that use lithium cobalt oxide as the positive electrode active material and have excellent electrochemical performance. Lithium cobalt oxide has the chemical formula LiCoO2, a capacity fade rate of less than 0.05%, a first discharge specific capacity greater than 135 mAh / g, stable performance, high consistency, easy synthesis, and good safety performance. Lithium nickel cobalt manganese oxide is a commonly used ternary positive electrode active material with the chemical formula LiNi x Co y Mn 1-x-y O2. Lithium nickel cobalt manganese oxide has a high energy density, a theoretical capacity of 280 mAh / g, an actual capacity of over 150 mAh / g, and good cycle performance, with excellent cycle stability at both room temperature and high temperature. Preferably, a ternary lithium nickel cobalt manganese oxide plate is selected as the positive electrode plate.

[0048] In some 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%, or 99% or more. The positive electrode active material in the positive electrode active layer can include any one of the active materials described above. Unlike negative electrode plates, positive electrode plates are less likely to experience volume expansion or electrical conductivity issues. Therefore, theoretically, the higher the content of the active material, the more preferable it is, provided that it does not affect processing performance. 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 some embodiments, the weight areal density of the positive plate is 12.0 mg / cm 2 ~30mg / cm 2 The mass of active material in a plate per unit area is called the plate weight areal density. The plate weight areal density is an important factor in determining the consistency of a battery. For a battery with the same capacity, the higher the weight areal density, the less inactive material (e.g., copper foil, aluminum foil, tab) there is, and the higher the battery's energy density. However, if the weight areal density is too high, the electrolyte will have difficulty permeating the entire electrode, reducing the gram capacity and hindering the improvement of energy density. Therefore, the weight areal density of a positive plate must be controlled within a reasonable range. For example, it can be measured by means of point tracking measurement using an X-ray / beta ray areal density meter. For example, the weight areal density of a positive plate is 18 mg / cm. 2 ~24mg / cm 2 , 19 mg / cm 2 ~25mg / cm 2 , 26 mg / cm 2 ~30mg / cm 2 , 17 mg / cm 2 ~23mg / cm 2 , 12 mg / cm 2 ~16mg / cm 2 By controlling the weight areal density of the positive electrode plate within a predetermined range, it is possible to further increase the energy density of the battery while maintaining the cycle performance and safety performance of the battery.

[0050] In some embodiments, the positive plate has a compressed density of 2.3 g / cm 3 ~4g / cm 3 Generally, within the allowable compression range of the material, the higher the compressed density of the positive plate, the higher the battery capacity can be, so the compressed density is also regarded as one of the reference indicators of energy density. However, if the compressed density is too high, not only will it be impossible to improve the specific capacity of the battery, but it will also seriously reduce the specific capacity and cycle performance of the battery. Therefore, the compressed density of the positive plate must be set within a reasonable range. For example, the compressed density of the positive plate is 2.4 g / cm 3 ~3.5g / cm 3 , 2.5g / cm3 ~3.4g / cm 3 , 2.6g / cm 3 ~3.3g / cm 3 , 2.7g / cm 3 ~3.2g / cm 3 , 2.8g / cm 3 ~3.8g / cm 3 , 3.1g / cm 3 ~3.6g / cm 3 By controlling the compression density of the positive electrode plate within a predetermined range, it is possible to further increase the energy density of the battery while maintaining the cycle performance and safety performance of the battery.

[0051] About the negative electrode In a secondary battery, the negative electrode plate usually 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 may be a conventional metal foil or a composite current collector (e.g., a composite current collector may be formed by providing a metal material on a polymer substrate). For example, the negative electrode current collector may be copper foil. The negative electrode active layer may further include an adhesive, a conductive agent, and other optional additives. For 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. For 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). For example, other optional additives may be thickeners and dispersants (e.g., sodium carboxymethyl cellulose (CMC-Na)) and PTC thermistor materials.

[0053] The negative electrode plate provided by the present 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 disposed 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, which can lead to significant expansion during charge / discharge cycles and the plate failure. Similarly, when the capacity per unit volume of a negative electrode plate is small, its volume expansion rate is also small. In the present application, by disposing 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 battery failure due to plate volume expansion and simultaneously improving the battery's energy density and storage performance.

[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 90% or more and 95.5% or less. 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. A high silicon content causes a larger volume effect and a deterioration in resistance, so more adhesive and conductive agent must be added, thereby reducing the silicon content in the first negative electrode plate. When the silicon content is 10% to 50%, the total proportion of the active material in the active layer is 90% or more and 97% or less, which can accommodate volume expansion. Controlling the content of the negative electrode active material in the first active layer within a predetermined range can further increase the energy density of the battery while controlling the volume effect.

[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 a pure silicon material, a silicon carbon material, and a silicon oxygen material. The silicon oxygen material is preferably one or more of a pre-lithiated silicon oxygen material or a pre-magnesiated silicon oxygen material. A silicon carbon material (a silicon carbon material using a porous hard carbon as a skeleton and deposited by silane) is preferred. Silicon-based negative electrodes have advantages such as high energy density, wide raw material distribution, and a suitable discharge plateau, and are recognized as promising negative electrode active materials. Silicon alone, as an active material for negative electrodes, has a high theoretical specific capacity of 4200 mAh / g, more than 10 times that of negative electrodes using graphite as the active material. Silicon carbon negative electrodes and silicon oxygen negative electrodes also have theoretical specific capacities much higher than those of graphite negative electrodes. Silicon-based plates have the advantages of high gram capacity, high energy density, high volumetric energy density, and small battery volume, making silicon carbon plates the preferred first negative plate.

[0056] In some embodiments, 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 be referred to as a silicon-carbon anode material, which is a novel anode material with graphite as the dispersed matrix and silicon as the active material. While silicon-based electrodes have high specific capacity, they undergo volume expansion and contraction during charging and discharging (the volume expansion and contraction rate of silicon during charging and discharging reaches 320%), resulting in significant mechanical stress. This causes silicon particles to fracture and pulverize after multiple cycles, leading to anode failure. Therefore, silicon-based electrodes with a porous graphite skeleton are preferred, as they can further increase the energy density of batteries by adjusting the volume effect. 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. Controlling the silicon content and graphite content in the silicon-based electrode plate within a predetermined range limits the expansion during charging to the pores of the hard carbon, further reducing the expansion effect of the silicon-based electrode plate. Because silicon is deposited within the pores of the porous hard carbon, this silicon-carbon material has strong pressure resistance and does not fracture during cold pressing. Therefore, expansion during charging occurs within 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 skeleton 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 electrodes, graphite electrodes are less susceptible to volume expansion and electrical conductivity issues. Therefore, the theoretically higher the active material content, provided that it does not affect processing performance, is preferable, 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 plate, and the active material in the graphite plate includes artificial graphite and / or natural graphite. Graphite negative electrode materials have advantages such as widespread supply, abundant reserves, high tap density after modification, stable electrochemical performance, and an actual specific capacity density close to the theoretical specific capacity. Therefore, selecting a graphite plate as the second negative electrode plate can reduce manufacturing costs and improve efficiency.

[0059] In some embodiments, M second negative plates are disposed between two adjacent first negative plates. 1≦M≦2.5n, n=Cs / Cg, where M is an integer greater than or equal to 1, Cs is the capacitance per unit volume of the first negative plate, and Cg is the capacitance per unit volume of the second negative plate. In one preferred embodiment, M satisfies 1≦M≦2n. For example, the number M of second negative plates may be 1, 2, 3, etc. The inclusion of first negative plates in a battery cell allows for high energy density. Furthermore, the first and second negative plates are stacked together. This design firstly improves the plate expansion effect, reduces battery cell failure due to plate expansion, and maximizes 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 volumetric capacity of the silicon-based electrode plate, the higher the proportion of silicon-based material contained therein, which may result in a greater expansion effect. However, by stacking the two electrodes, the graphite negative electrode plate can mitigate the degree of expansion and pulverization of the silicon-based negative electrode plate, thereby improving the electrochemical performance of the battery of the present application, particularly in terms of cycle and storage performance, compared to conventional methods. Therefore, by stacking the second negative electrode plate between the two silicon-based electrodes in accordance with 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 FIG. 3, this is a schematic diagram of an embodiment of the negative electrode plate arrangement of a battery cell of the present application. In this embodiment, the first negative electrode plates 21 are silicon-based electrode plates, and there are three of them, and the second negative electrode plates 22 are graphite electrode plates, and there are four of them. From left to right, two graphite electrode plates are provided between the first silicon-based electrode plate and the second silicon-based electrode plate, and one graphite electrode plate is provided between the second silicon-based electrode plate and the third silicon-based electrode plate, and one positive electrode plate (not shown) is provided between each negative electrode plate. In other embodiments, the number of graphite electrode plates provided between two silicon-based electrode plates may be different, for example, one, two, three, four, etc., and one positive electrode plate is also 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. The silicon-containing negative electrode plate and the graphite negative electrode plate are stacked, and the battery has a silicon-containing negative electrode plate, which can increase the energy density. Furthermore, by stacking the two electrodes, the expansion effect of the silicon-based electrode plate can be improved, which can reduce the battery failure caused by the volume expansion of the electrode plate, and extend the battery life. In this design, the energy density can be significantly improved, and the storage performance can also be improved.

[0062] In some 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 the first negative plates is equal to or less than the total number of the second negative plates, which can improve the volume expansion effect of the negative plates, reduce the failure of battery cells due to the expansion of the negative plates, and simultaneously increase the capacity of the battery.

[0064] In some embodiments, the ratio of the capacity areal density of any one positive plate to any one negative plate is 1.01≦C 負 / C 正 ≦1.2, and the capacity areal density is the capacity of the active layer on one side per unit area of ​​the positive / negative plate. Capacity areal density = weight areal density × gram capacity of active material × mass fraction of active material in the active layer. C 負 is the capacity (mAh / cm) of the coating layer (active layer) on one side of the negative electrode plate per unit area. 2 ) and C 正 is the capacity of the coating layer on one side per unit area of ​​the positive electrode plate (mAh / cm 2 For example, in one preferred embodiment, 1.03≦C 負 / C 正 In another preferred embodiment, 1.05≦C 負 / C 正≦1.1. By designing the capacity of the active layer on one side per unit area of ​​the negative electrode plate to be greater than the capacity of the active layer on one side per unit area of ​​the positive electrode plate, it is possible to prevent overcharging of the negative electrode, suppress the formation of lithium dendrites, and improve the safety of the battery cell.

[0065] In some embodiments, the first negative plate has a weight areal density of 2.63 mg / cm 2 ~10.16mg / cm 2 and the weight areal density of the second negative electrode plate is 6.06 mg / cm 2 ~13.21mg / cm 2 As mentioned above, the weight areal density of the electrode plate is an important factor in determining the consistency of the battery. For a battery with the same capacity, the higher the weight areal density, the less inactive material (e.g., copper foil, aluminum foil, tab) is used, resulting in a higher energy density. However, if the weight areal density is too high, the electrolyte will have difficulty permeating the entire electrode, reducing the gram capacity and hindering the improvement of energy density. Therefore, the weight areal density of the negative electrode plate must also be controlled within a reasonable range. The weight areal density of the negative electrode plate can be measured using multi-tracking measurement techniques, laser line integrated microspot areal density measurement meters, beta line areal density meters, etc. For example, the weight areal density of the first negative electrode plate is 3.95 mg / cm. 2 ~9.4mg / cm 2 , 4.25 mg / cm 2 ~8.5mg / cm 2 , 5.74 mg / cm 2 ~7.64mg / cm 2 For example, the weight areal density of the second negative electrode plate is 7.96 mg / cm 2 ~11.10mg / cm 2 , 8.50 mg / cm 2 ~9.89mg / cm 2 , 9.12 mg / cm 2 ~10.91mg / cm 2 By controlling the weight surface density of the first negative electrode plate and the second negative electrode plate within a predetermined range, the energy density of the battery can be further increased while maintaining the cycle performance and safety performance of the battery.

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

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

[0068] About the electrolyte The secondary battery includes an electrolyte, which serves to conduct ions between the positive electrode and the negative electrode, and may include an electrolyte salt and a solvent.

[0069] By way of example, the electrolyte salt may be selected from one or more of lithium hexafluorophosphate (LiPF), lithium tetrafluoroborate (LiBF), lithium perchlorate (LiClO), lithium hexafluoroarsenate (LiAsF), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluoro(oxalato)borate (LiDFOB), lithium bisoxalatoborate (LiBOB), lithium difluorophosphate (LiPOF), lithium difluorodioxalatophosphate (LiDFOP), and lithium tetrafluorooxalatophosphate (LiTFOP).

[0070] By way of example, the solvent may be selected from one or more of 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 solution may further contain additives, such as a negative electrode film-forming additive, a positive electrode film-forming additive, or an additive capable of improving specific battery performance, such as an additive for improving the overcharge performance of the battery, an additive for improving the high-temperature performance of the battery, or an additive for improving the low-temperature performance of the battery.

[0072] About the device The present application further provides an electric device including the secondary battery of the present application. The battery cell or secondary battery may be used as a power source for the electric device or as an energy storage unit for the electric device. The electric device may be, but is not limited to, a mobile device (e.g., a mobile phone, a laptop), an electric vehicle (e.g., a battery electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric motorcycle, an electric scooter, an electric golf cart, an electric truck), an electric car, a ship, a satellite, or an energy storage system.

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

[0074] 5 shows an example of an electric device. The electric device may be a battery electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of the secondary batteries of the electric device, multiple secondary batteries may be employed.

[0075] Another example of an electrical device may be a mobile phone, a tablet, or a laptop, which typically requires light weight and thinness and may employ a battery cell as a power source.

[0076] The beneficial effects of the present invention will be further explained below with reference to examples.

[0077] In order to clarify the technical problems, technical solutions, and beneficial effects of the embodiments of the present application, the present application will be described in more detail below in conjunction with the embodiments and drawings. Obviously, the described embodiments are only some of the embodiments of the present application, and not all of the embodiments. The following description of at least one exemplary embodiment is merely for illustrative purposes and does not limit the present application and its applications in any way. All other embodiments obtained based on the embodiments of the present application without the need for creative efforts by those skilled in the art are within the scope of protection of the present 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), conductive carbon black (Super P), and binder polyvinylidene fluoride (PVDF) were mixed in a weight ratio of 97.5:1.5:1 with an appropriate amount of N-methylpyrrolidone (NMP) and stirred thoroughly to obtain a positive electrode slurry. The positive electrode slurry was then applied to the surface of the aluminum foil positive electrode current collector, followed by baking, cold pressing, slitting, and cutting to obtain a positive electrode plate. The compressed density of the positive electrode plate was 3.5 g / cm. 3 and the capacitance areal density is 2.36mAh / cm2 and the gravimetric areal density is 12.07 mg / cm 2 It was.

[0079] (2) Manufacturing of negative electrodes First, manufacturing of negative electrode plates The negative electrode active materials, artificial graphite, silicon-based material (gram capacity 1800-2300mAh / g), single-walled carbon nanotubes, conductive agent acetylene black, thickener sodium carboxymethyl cellulose (CMC), and binder styrene butadiene rubber (SBR) were mixed in a mass ratio of 82.5:13:0.3:1:1.2:2, 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 10μm-thick copper foil negative electrode current collector containing a conductive carbon undercoat layer, dried at 110°C for 20 minutes, and the electrode plate was cold-pressed after drying to a weight areal density of 4.53mg / cm. 2 and the compressed density is 1.7 g / cm 3 and the capacitance area density is 2.6mAh / cm 2 The negative electrode plate had a thickness of 63.3 μm and a capacity per unit volume of 0.82 Ah / mL.

[0080] Regarding the production of the second negative plate The negative electrode active material, artificial graphite, the conductive agent, acetylene black, the thickener, sodium carboxymethyl cellulose (CMC), and the binder (SBR) were mixed in a mass ratio of 97:0.5:1:1.5, and deionized water was added as the solvent. The mixture was stirred using a vacuum mixer until the system was homogeneous. The mixture was 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 the electrode plate was cold-pressed after drying to produce a sheet with a weight areal density of 7.05 mg / cm. 2 and the compressed density is 1.7 g / cm 3 and the capacitance area density is 2.6mAh / cm 2 The negative electrode plate had a thickness of 92.9 μm and a capacity per unit volume of 0.56 Ah / mL.

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

[0082] (4) Separator manufacturing A polyethylene film with a thickness of 12 μm was used as the separator.

[0083] (5) Manufacturing of laminated batteries Positive plates, separators, and negative plates were alternately stacked, and the electrode arrangement of at least one electrode assembly was first negative plate / positive plate / second negative plate / positive plate / first negative plate (i.e., one second negative plate was placed between two first negative plates, and one positive plate was placed between two adjacent negative plates). Separators were alternately stacked continuously in a Z-shape between the positive and negative plates. After stacking was complete, the battery was placed in a case, tab-welded, vacuum-dried at 100°C for 24 hours, and then injected with electrolyte. Chemical formation and capacity tests were conducted to 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. The method for manufacturing a laminate battery in Example 2 is similar to that in Example 1, but the differences are as follows.

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

[0086] Regarding the manufacturing of laminated batteries Positive plates, separators, and negative plates were alternately stacked. The electrode plates of at least one electrode assembly were arranged in a first negative plate / positive plate / second negative plate / positive plate / second negative plate / positive plate / first negative plate configuration. That is, two second negative plates were placed between two first negative plates, and one positive plate was placed between two adjacent negative plates. Separators were alternately stacked in a Z-shape between the positive and negative plates. After stacking was complete, the battery was placed in a case, tab-welded, vacuum-dried at 100°C for 24 hours, and then injected with electrolyte. Chemical and capacity tests were conducted to produce a hard-case battery with a voltage range of 2.5V to 4.25V and a capacity of 65Ah.

[0087] Example 3 is as follows. The manufacturing method of the laminate battery in Example 3 is similar to that in Example 1, but the differences are as follows.

[0088] Regarding the production of the first negative electrode plate The negative electrode active materials, artificial graphite, silicon-based material (gram capacity 1800-2300mAh / g), single-walled carbon nanotubes, conductive agent acetylene black, thickener sodium carboxymethyl cellulose (CMC), and binder SBR were mixed in a mass ratio of 85.5:10:0.3:1:1.2:2, deionized water was added as a solvent, and the mixture was stirred using a vacuum mixer until the system was homogeneous. The mixture was then applied to two surfaces of a 10μm-thick copper foil negative electrode current collector containing a conductive carbon undercoat layer, dried at 110°C for 20 minutes, and the electrode plate was cold-pressed after drying to a weight areal density of 4.95mg / cm. 2 and the compressed density is 1.7 g / cm 3 and the capacitance area density is 2.6mAh / cm 2The negative electrode plate had a thickness of 68.2 μm and a capacity per unit volume of 0.76 Ah / mL.

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

[0090] Regarding the manufacturing of laminated batteries Positive plates, separators, and negative plates were stacked alternately. The electrode arrangement of at least one electrode assembly was 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 stacked alternately in a Z-shape between the positive and negative plates. After stacking was complete, the battery was placed in a case, tab-welded, vacuum-dried at 100°C for 24 hours, and then injected with electrolyte. Chemical formation and capacity tests were conducted to 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. The manufacturing method of the laminate battery in Example 4 is similar to that in Example 1, but the differences are as follows.

[0092] Regarding the production of the first negative electrode plate The negative electrode active materials, artificial graphite, silicon-based material (gram capacity 1800-2300mAh / g), single-walled carbon nanotubes, conductive agent acetylene black, thickener sodium carboxymethyl cellulose (CMC), and binder SBR were mixed in a mass ratio of 85.5:10:0.3:1:1.2:2, 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 10μm-thick copper foil negative electrode current collector containing a conductive carbon undercoat layer, dried at 110°C for 20 minutes, and the electrode plate was cold-pressed after drying to a final weight areal density of 5.42mg / cm. 2 and the compressed density is 1 g / cm 3 and the capacitance area density is 2.6mAh / cm 2 The negative electrode plate had a thickness of 118.4 μm and a capacity per unit volume of 0.44 Ah / mL.

[0093] Regarding the production of the second negative plate The negative electrode active material, artificial graphite, the conductive agent, acetylene black, the thickener, sodium carboxymethyl cellulose (CMC), and the binder (SBR) were mixed in a mass ratio of 97:0.5:1:1.5, and deionized water was added as the solvent. The mixture was stirred using a vacuum mixer until the system was homogeneous. The mixture was 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 the electrode plate was cold-pressed after drying to produce a weight areal density of 7.65 mg / cm. 2 and the compressed density is 1 g / cm 3 and the capacitance area density is 2.6mAh / cm 2 The negative electrode plate had a thickness of 163 μm and a capacity per unit volume of 0.32 Ah / mL.

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

[0095] Regarding the manufacturing of positive electrodes Lithium Nickel Cobalt Manganese Oxide LiNi 0.8 Co 0.1 Mn 0.1 O2 (NCM811), conductive carbon black (Super P), and binder PVDF were mixed in a weight ratio of 97.5:1.5:1 with an appropriate amount of N-methylpyrrolidone (NMP) and stirred thoroughly to obtain a positive electrode slurry. The positive electrode slurry was then applied to the surface of the aluminum foil positive electrode current collector, followed by baking, cold pressing, slitting, and cutting to obtain a positive electrode plate. The compressed density of the positive electrode plate was 3.5 g / cm. 3 and the capacitance area density is 4.43mAh / cm 2 and the gravimetric areal density is 22.59 mg / cm 2 It was.

[0096] First, manufacturing of negative electrode plates The negative electrode active materials, artificial graphite, silicon-based material (gram capacity 2800-3500mAh / g), single-walled carbon nanotubes, conductive agent acetylene black, thickener sodium carboxymethyl cellulose (CMC), and binder SBR were mixed in a mass ratio of 85.5:10:0.3:1:1.2:2, 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 10μm-thick copper foil negative electrode current collector containing a conductive carbon undercoat layer, dried at 110°C for 20 minutes, and the electrode plate was cold-pressed after drying to a weight areal density of 10.16mg / cm. 2 and the compressed density is 1.7 g / cm 3 and the capacitance area density is 4.87mAh / cm 2 The negative electrode plate had a thickness of 129.5 μm and a capacity per unit volume of 0.75 Ah / mL.

[0097] Regarding the production of the second negative plate The negative electrode active material, artificial graphite, the conductive agent, acetylene black, the thickener, sodium carboxymethyl cellulose (CMC), and the binder (SBR) were mixed in a mass ratio of 97:0.5:1:1.5, and deionized water was added as the solvent. The mixture was stirred using a vacuum mixer until the system was homogeneous. The mixture was 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 the electrode plate was cold-pressed after drying to produce a weight areal density of 13.21 mg / cm. 2 and the compressed density is 1.7 g / cm 3 and the capacitance area density is 4.87mAh / cm 2 The negative electrode plate had a thickness of 165.4 μm and a capacity per unit volume of 0.59 Ah / mL.

[0098] Example 6 is as follows. The method for producing a laminate battery in Example 6 is similar to that in Example 1, but the differences are as follows.

[0099] Regarding the manufacturing of positive electrodes Lithium Nickel Cobalt Manganese Oxide LiNi 0.8 Co 0.1 Mn 0.1 O2 (NCM811), conductive carbon black (Super P), and binder PVDF were mixed in a weight ratio of 97.5:1.5:1 with an appropriate amount of N-methylpyrrolidone (NMP) and stirred thoroughly to obtain a positive electrode slurry. The positive electrode slurry was then applied to the surface of the aluminum foil positive electrode current collector, followed by baking, cold pressing, slitting, and cutting to obtain a positive electrode plate. The compressed density of the positive electrode plate was 3.5 g / cm. 3 and the capacitance area density is 4.43mAh / cm 2 and the gravimetric areal density is 22.59 mg / cm 2 It was.

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

[0101] Regarding the production of the second negative plate The negative electrode active material, artificial graphite, the conductive agent, acetylene black, the thickener, sodium carboxymethyl cellulose (CMC), and the binder (SBR) were mixed in a mass ratio of 97:0.5:1:1.5, and deionized water was added as the solvent. The mixture was stirred using a vacuum mixer until the system was homogeneous. The mixture was 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 the electrode plate was cold-pressed after drying to produce a weight areal density of 13.21 mg / cm. 2 and the compressed density is 1.7 g / cm 3 and the capacitance area density is 4.87mAh / cm 2 The negative electrode plate had a thickness of 165.4 μm and a capacity per unit volume of 0.76 Ah / mL.

[0102] Regarding the manufacturing of laminated batteries Positive plates, separators, and negative plates were alternately stacked. The electrode plates of at least one electrode assembly were arranged in a first negative plate / positive plate / second negative plate / positive plate / second negative plate / positive plate / first negative plate configuration. That is, two second negative plates were placed between two first negative plates, and one positive plate was placed between two adjacent negative plates. Separators were alternately stacked in a Z-shape between the positive and negative plates. After stacking was complete, the battery was placed in a case, tab-welded, vacuum-dried at 100°C for 24 hours, and then injected with electrolyte. Chemical and capacity tests were conducted to 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. The method for producing a laminate battery in Example 7 is similar to that in Example 1, but the differences are as follows.

[0104] Regarding the manufacturing of positive electrodes Lithium Nickel Cobalt Manganese Oxide LiNi 0.8 Co 0.1 Mn 0.1 O2 (NCM811), conductive carbon black (Super P), and binder PVDF were mixed in a weight ratio of 97.5:1.5:1 with an appropriate amount of N-methylpyrrolidone (NMP) and stirred thoroughly to obtain a positive electrode slurry. The positive electrode slurry was then applied to the surface of the aluminum foil positive electrode current collector, followed by baking, cold pressing, slitting, and cutting to obtain a positive electrode plate. The final compressed density of the positive electrode plate was 3.5 g / cm. 3 and the capacitance area density is 4.43mAh / cm 2 and the gravimetric areal density is 22.59 mg / cm 2 It was.

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

[0106] Regarding the production of the second negative plate The negative electrode active materials, artificial graphite, silicon-based material (gram capacity 2800-3500mAh / g), single-walled carbon nanotubes, conductive agent acetylene black, thickener sodium carboxymethyl cellulose (CMC), and binder SBR were mixed in a mass ratio of 85.5:10:0.3:1:1.2:2, 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 10μm-thick copper foil negative electrode current collector containing a conductive carbon undercoat layer, dried at 110°C for 20 minutes, and the electrode plate was cold-pressed after drying to a weight areal density of 7.32mg / cm. 2 and the compressed density is 2 g / cm 3 and the capacitance area density is 4.87mAh / cm 2 The negative electrode plate had a thickness of 83.2 μm and a capacity per unit volume of 1.17 Ah / mL.

[0107] Regarding the manufacturing of laminated batteries Positive plates, separators, and negative plates were stacked alternately. The electrode arrangement of at least one electrode assembly was 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 stacked alternately in a Z-shape between the positive and negative plates. After stacking was complete, the battery was placed in a case, tab-welded, vacuum-dried at 100°C for 24 hours, and then injected with electrolyte. Chemical formation and capacity tests were conducted to 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 difference from Example 1 is that the battery only has one type of negative electrode plate, which is manufactured by the manufacturing method of a silicon-containing negative electrode plate. Specifically, the negative electrode active material artificial graphite, silicon-based material (gram capacity 1800-2300mAh / g), single-walled carbon nanotubes, conductive agent acetylene black, thickener sodium carboxymethyl cellulose (CMC), and binder SBR are mixed in a mass ratio of 91.5:4:0.3:1:1.2:2, deionized water as a solvent is added, and the system is stirred by a vacuum mixer until it becomes homogeneous. The mixture is then applied to two surfaces of a 10μm-thick copper foil negative electrode current collector with a conductive carbon undercoat layer, dried at 110°C for 20 minutes, and the plate is cold-pressed after drying to have a weight areal density of 6.07mg / cm. 2 and the capacitance area density is 2.6mAh / cm 2 and the compressed density is 1.7 g / cm 3 A negative electrode plate having a thickness of 81.3 μm was obtained.

[0109] Regarding the manufacturing of laminated batteries Positive electrodes, separators, and negative electrodes were stacked alternately, and the electrode arrangement of at least one electrode assembly was negative / positive / negative, i.e., two adjacent negative electrodes were identical. Separators were stacked alternately between the positive and negative electrodes in a Z-shape. After stacking was complete, the battery was placed in a case, tab-welded, vacuum-dried at 100°C for 24 hours, and then injected with electrolyte. Chemical formation and capacity tests were conducted 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 difference from Example 5 is that the battery only has one type of negative electrode plate, which is manufactured by the manufacturing method of a silicon-containing negative electrode plate. Specifically, the negative electrode active material artificial graphite, silicon-based material (gram capacity 2800-3500mAh / g), single-walled carbon nanotubes, conductive agent acetylene black, thickener sodium carboxymethyl cellulose (CMC), and binder SBR are mixed in a mass ratio of 91.5:4:0.3:1:1.2:2, deionized water as a solvent is added, and the system is stirred by a vacuum mixer until it becomes homogeneous. The mixture is then applied to two surfaces of a 10μm-thick copper foil negative electrode current collector with a conductive carbon undercoat layer, dried at 110°C for 20 minutes, and the plate is cold-pressed after drying to have a weight areal density of 10.07mg / cm. 2 and the capacitance area density is 4.87mAh / cm 2 and the compressed density is 1.7 g / cm 3 A negative electrode plate having a thickness of 128.4 μm was obtained.

[0111] Regarding the manufacturing of laminated batteries Positive electrodes, separators, and negative electrodes were stacked alternately, and the electrode arrangement of at least one electrode assembly was negative / positive / negative, i.e., two adjacent negative electrodes were identical. Separators were stacked alternately between the positive and negative electrodes in a Z-shape. After stacking was complete, the battery was placed in a case, tab-welded, vacuum-dried at 100°C for 24 hours, and then injected with electrolyte. Chemical formation and capacity tests were conducted 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 difference from Comparative Example 2 is in the manufacture of the negative electrode plate. Specifically, the negative electrode active materials artificial graphite, silicon-based material (gram capacity 2800-3500mAh / g), single-walled carbon nanotubes, conductive agent acetylene black, thickener sodium carboxymethyl cellulose (CMC), and binder SBR were mixed in a mass ratio of 81.5:14:0.3:1:1.2:2, deionized water as a solvent was added, and the mixture was stirred using a vacuum mixer until the system became homogeneous. The mixture was then applied to two surfaces of a 10μm-thick copper foil negative electrode current collector containing a conductive carbon undercoat layer, dried at 110°C for 20 minutes, and the plate was cold-pressed after drying to a weight areal density of 6.2mg / cm. 2 and the capacitance area density is 4.87mAh / cm 2 and the compressed density is 1.7 g / cm 3 A negative electrode plate having a thickness of 83 μm was obtained.

[0113] 3. Performance testing (1) Performance test of electrode plates (1) Capacity test per unit volume 1. The electrode plate was punched out into a small disk (14 mm diameter) with an area of ​​S, and its thickness H was measured using a ten-thousandth 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 small disk was measured. The active layers on both sides were scraped off, leaving the current collector, and the weight W2 was measured. The total weight W3 of the active layers on both sides was calculated as W1 - W2. 3. The active layer on one side of 1 was scraped off to leave the active layer and current collector on one side, and its weight W4 was measured using the electronic balance 2, and the weight of the active layer on one side W5 = W4 - W2 was calculated. 4. The three plates 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 Electronics Co., Ltd., and the gram capacity of the active layer C2=C1÷W5 was calculated. 5. The capacity of the entire small disk, C3 = C2 × W3, was calculated, and the capacity per unit volume of the small disk, C4 = C3 ÷ V, was calculated.

[0114] (2) Battery performance test (1) First cycle capacity test of secondary batteries The battery was charged at 0.02C for 10 hours at 45°C, then charged at 0.33C to 4.25V at 25°C, 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) Secondary battery cycle performance test The following steps were carried out in a 45°C environment. The battery was left standing for 5 minutes, discharged to 2.5 V at 0.33D0, left standing for 5 minutes, charged to 4.25 V at 0.33D0, charged to 0.05C at a constant voltage of 4.25 V, left standing for 5 minutes, and discharged to 2.5 V at 0.33C, and the capacity at this time was recorded as C0.

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

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

[0118] In step 2, the fully charged secondary battery is placed in a 60°C environment and stored periodically for a certain period of time. Then, the battery is removed and tested according to the flow in step 1. The fully charged secondary battery is 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. F2 = C t ÷C0×100%.

[0119] (4) Secondary battery expansion force and expansion displacement test The battery cell was fixed between the press plates using steel plate clamps, the upper and lower press plates were fixed in position with bolts, a force sensor was attached to the upper press plate to monitor the pressure, the pitch h0 of the upper and lower press plates was tested before charging the battery cell, and the corresponding pressure was recorded when the battery cell reached a fully charged state. At the same time, the pitch h1 of the upper and lower press plates was tested after full charging, and the expansion rate of the battery cell = (h1 ÷ h0 - 1) × 100% was calculated.

[0120] Tables 1 and 2 show the measured parameters of the electrode plates of the battery cells of each of the Examples and Comparative Examples, and Table 3 shows the measured battery performance of each of the Examples and Comparative Examples.

[0121] [Table 1]

[0122] [Table 2]

[0123] [Table 3]

[0124] The following conclusions can be drawn from Tables 1, 2, and 3. Comparative Example 1 is distinguished from Examples 1 to 4 in that the battery contains only one type of negative electrode plate. As shown by the results, the battery expansion force and expansion rate of the negative electrode plates of Examples 1 to 4 when the battery is fully charged are both lower than those of Comparative Example 1. Furthermore, the reversible capacity retention rate after storage in a fully charged state at 60°C for 180 days 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 the battery contains only one type of negative electrode plate. As shown by the results, the battery expansion force and expansion rate of the negative electrode plates of Examples 5 and 6 when fully charged are both lower than those of Comparative Example 2. Furthermore, the reversible capacity retention rate after 180 days of storage in a fully charged state at 60°C 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 is that the battery contains only one type of negative plate. As shown by the results, the battery expansion force of the negative plate of Example 7 and the expansion rate of the battery when fully charged are both lower than those of Comparative Example 3. Furthermore, the reversible capacity retention rate after 180 days of storage in a fully charged state at 60°C 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 the present application includes a plurality of positive plates and a plurality of negative plates, with adjacent positive and negative plates separated by a separator. The negative plates include a first negative plate and a second negative plate with two different capacities, with at least one relatively low-capacity negative plate disposed between two adjacent high-capacity negative plates. This improves the negative plate expansion effect and reduces battery failure due to negative plate expansion.

[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. Those skilled in the art can easily think of various equivalent modifications and substitutions within the technical scope disclosed in the present application, and all of these modifications and substitutions shall be included in the scope of protection of the present application. Therefore, the scope of protection of the present application shall be determined based on the scope of protection defined by the claims. [Explanation of symbols]

[0129] 100 Secondary battery 10 battery cells 1 positive electrode plate 2 negative plates 3 Separator 21 First negative electrode plate 22 Second negative electrode plate

Claims

1. A battery cell including at least one electrode assembly, the electrode assembly comprising: A positive electrode plate; a negative electrode plate, a battery cell characterized in that the negative electrode plates include a first negative electrode plate and a second negative electrode plate, the capacity per unit volume of the first negative electrode plate being greater than the capacity per unit volume of the second negative electrode plate, at least one positive electrode plate being provided between two adjacent first negative electrode plates, and at least one second negative electrode plate being provided between two adjacent first negative electrode plates.

2. 2. The battery cell according to claim 1, wherein 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 greater, Cs is a capacity per unit volume of the first negative electrode plates, and Cg is a capacity per unit volume of the second negative electrode plates.

3. 3. The battery cell according to claim 2, wherein n is 1 or greater.

4. The capacity per unit volume of the first negative electrode plate is 0.44 Ah / mL to 2.68 Ah / mL, and / or 4. The battery cell according to claim 1, wherein the capacity per unit volume of the second negative electrode plate is 0.32 Ah / mL to 1.17 Ah / mL.

5. 5. The battery cell according to claim 1, wherein the total number of the first negative electrode plates is equal to or less than the total number of the second negative electrode plates.

6. The ratio of the capacity surface density of any one of the positive electrode plates to that of any one of the negative electrode plates is 1.01≦C 負 / C 正 6. The battery cell according to claim 1, wherein the capacity surface density is the capacity of the active layer on one side per unit area of ​​the positive electrode plate / negative electrode plate.

7. The weight surface density of the first negative electrode plate is 2.63 mg / cm ２ ~10.16mg / cm ２ and / or The weight areal density of the second negative electrode plate is 6.06 mg / cm ２ ~13.21mg / cm ２ The battery cell according to any one of claims 1 to 6, wherein:

8. 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 90% or more and 95.5% or less; and / or The battery cell according to any one of claims 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.

9. 9. The battery cell of claim 1, wherein the first negative electrode plate comprises a silicon-based electrode plate, and the active material in the silicon-based electrode plate comprises one or more of a pure silicon material, a silicon carbon material, and a silicon oxygen material, and preferably the silicon oxygen material comprises one or more of a pre-lithiated silicon oxygen material or a pre-magnesiated silicon oxygen material.

10. The battery cell according to claim 9, wherein 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 any one of claims 1 to 10, wherein 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 weight surface density of the positive electrode plate is 12 mg / cm ２ ~30 mg / cm ２ The battery cell according to any one of claims 1 to 11, wherein

13. The compressed density of the positive electrode plate is 2.3 g / cm ３ ~4g / cm ３ The battery cell according to any one of claims 1 to 12, wherein

14. 14. The battery cell according to claim 1, wherein 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 any one of claims 1 to 14, wherein the positive electrode plate includes one or more of a lithium iron phosphate electrode plate, a lithium cobalt oxide electrode plate, a lithium nickel cobalt manganese oxide electrode plate, and a lithium iron manganese phosphate electrode plate.

16. The battery cell according to any one of claims 1 to 15, further comprising a separator folded in a Z-shape to separate adjacent positive and negative plates, the positive and negative plates being alternately inserted into the stacked gaps.

17. A laminate battery comprising a case and the battery cell according to any one of claims 1 to 16.

18. An electrical device comprising the laminate battery of claim 17.

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