Negative pole piece, battery and electric equipment

Abstract

The invention discloses a negative pole piece, a battery and electric equipment. The negative pole piece comprises a negative current collector, the first negative electrode active material layer is arranged on at least one side of the negative electrode current collector, and the first negative electrode active material layer comprises a first negative electrode active material; the second negative electrode active material layer is arranged on one side, far away from the negative electrode current collector, of the first negative electrode active material layer, and the second negative electrode active material layer comprises a second negative electrode active material; under the pressure of 20000N, the compaction density of the first negative electrode active material is P1, the compaction density of the second negative electrode active material is P2, and P1-P2 is greater than or equal to 0.09 g / cm < 3 >. Therefore, the probability of deformation of the negative current collector can be reduced, and the risk of brittle damage of the negative pole piece in the circulation process is further reduced.

Description

Technical Field

[0001] The present application relates to the field of batteries, and in particular, to negative electrode plates, batteries and electrical equipment. Background Art

[0002] Batteries are not only used in energy storage power systems such as hydropower, thermal power, wind power and solar power stations, but are also widely used in electric vehicles such as electric bicycles, electric motorcycles, electric cars, as well as military equipment and aerospace and other fields. In order to meet the demand for high energy density, the energy density of the battery can be increased by increasing the coating weight per unit area of ​​the negative electrode and the pressure of the negative electrode during cold pressing. When the cold pressing pressure is increased, the brittleness of the negative electrode increases. During the battery cycle, the risk of brittle damage to the negative electrode increases, which reduces the cycle life of the battery. Summary of the invention

[0003] In view of the technical problems existing in the background technology, the present application provides a negative electrode plate, which has a reduced risk of brittle damage to the negative electrode plate, thereby increasing the cycle life of the battery.

[0004] The first aspect of the present application provides a negative electrode sheet, comprising: a negative electrode current collector; a first negative electrode active material layer, the first negative electrode active material layer is arranged on at least one side of the negative electrode current collector, the first negative electrode active material layer comprises a first negative electrode active material; a second negative electrode active material layer, the second negative electrode active material layer is arranged on a side of the first negative electrode active material layer away from the negative electrode current collector, the second negative electrode active material layer comprises a second negative electrode active material; under a pressure of 20000N, the compaction density of the first negative electrode active material is P 1 , the compaction density of the second negative electrode active material is P 2 , and satisfies P 1 -P 2 ≥0.09g / cm 3 Thus, by making the difference in compaction density between the first negative electrode active material and the second negative electrode active material within the above range, the ability of the first negative electrode active material layer to bear external force is improved, and the transmission of external force to the negative electrode current collector is reduced, thereby reducing the risk of brittle damage to the negative electrode sheet during the cycle process, reducing the risk of fracture of the negative electrode sheet during the battery cycle, reducing the probability of falling off of the negative electrode active material, and improving the cycle life of the battery.

[0005] According to some embodiments of the present application, under a pressure of 20000N, 0.09g / cm 3 ≤P 1 -P 2 ≤0.22g / cm 3Thus, by making the difference in compaction density between the first negative electrode active material and the second negative electrode active material within the above range, the ability of the first active material layer to bear external force can be improved, thereby reducing the transmission of force from the first negative electrode active material layer to the negative electrode current collector, thereby reducing the risk of brittle damage to the negative electrode sheet during the cycle.

[0006] According to some embodiments of the present application, under a pressure of 20000N, 0.12g / cm 3 ≤P 1 -P 2 ≤0.20g / cm 3 Thus, by making the difference in compaction density between the first negative electrode active material and the second negative electrode active material within the above range, the ability of the first active material layer to bear external force can be improved, thereby reducing the transmission of force from the first negative electrode active material layer to the negative electrode current collector, thereby reducing the risk of brittle damage to the negative electrode sheet during the cycle.

[0007] According to some embodiments of the present application, under a pressure of 20000N, P 1 and P 2 The value of satisfies one or more of the following conditions: 1.84 g / cm 3 ≤P 1 ≤1.90g / cm 3 ; 1.70g / cm 3 ≤P 2 ≤1.75g / cm 3 Therefore, by making P 1 and P 2 The value of within the above range can reduce the brittleness of the negative electrode sheet and increase the energy density of the battery.

[0008] According to some embodiments of the present application, the compaction density of the negative electrode sheet is 1.75 g / cm 3 -1.85g / cm 3 . Thereby, the energy density of the battery can be improved.

[0009] According to some embodiments of the present application, the coating weight of the negative electrode sheet is 11.0 mg / cm 2 -13.0mg / cm 2 . Thereby, the energy density of the battery can be improved.

[0010] According to some embodiments of the present application, the volume average particle size Dv50 of the first negative electrode active material layer powder satisfies: 15μm≤Dv50≤20μm, and the volume average particle size Dv50 of the second negative electrode active material layer powder satisfies: 13μm≤Dv50≤18μm. Thus, by making the compaction density of the first negative electrode active material greater than the compaction density of the second negative electrode active material, the ability of the first negative electrode active material layer to bear external force can be improved.

[0011] According to some embodiments of the present application, the first negative electrode active material includes at least one of a first artificial graphite or a natural graphite, and the second negative electrode active material includes a second artificial graphite. Thus, the energy density and fast charging performance of the battery can be improved.

[0012] According to some embodiments of the present application, the first artificial graphite and the second artificial graphite both include secondary graphite particles, thereby improving the energy density and fast charging performance of the battery.

[0013] According to some embodiments of the present application, the negative electrode sheet satisfies one or more of the following conditions: the volume average particle size Dv50 of the second artificial graphite satisfies: 13μm≤Dv50≤18μm; the volume average particle size Dv50 of the first artificial graphite satisfies: 13μm≤Dv50≤17μm; the volume average particle size Dv50 of the natural graphite satisfies: 15μm≤Dv50≤25μm. Thus, by making the compaction density of the first negative electrode active material greater than the compaction density of the second negative electrode active material, the ability of the first negative electrode active material layer to bear external forces can be improved, thereby reducing the risk of brittle damage to the negative electrode current collector.

[0014] The second aspect of the present application provides a battery, comprising the negative electrode plate provided in the first aspect of the present application. Thus, the battery has excellent fast charging capability, high energy density and excellent cycle performance.

[0015] The third aspect of the present application provides an electrical device, including the negative electrode plate provided in the first aspect of the present application or the battery provided in the second aspect of the present application.

[0016] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become apparent from the description below, or will be learned through the practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present application. Moreover, the same reference numerals are used throughout the drawings to represent the same components. In the drawings:

[0018] Figure 1 It is a schematic structural diagram of a negative electrode sheet according to an embodiment of the present application;

[0019] Figure 2 is a schematic diagram of a battery according to one embodiment of the present application.

[0020] Figure 3 yes Figure 2 An exploded view of a battery according to an embodiment of the present application is shown.

[0021] Figure 4 is a schematic diagram of a battery module according to an embodiment of the present application.

[0022] Figure 5 It is a schematic diagram of a battery pack according to one embodiment of the present application.

[0023] Figure 6 yes Figure 5 An exploded view of a battery pack according to an embodiment of the present application is shown.

[0024] Figure 7 It is a schematic diagram of an electrical device using a battery as a power source according to an embodiment of the present application.

[0025] Description of reference numerals:

[0026] 10 negative electrode plate; 11 negative electrode current collector; 12 first negative electrode active material layer; 13 second negative electrode active material layer;

[0027] 1 battery pack; 2 upper box; 3 lower box; 4 battery module; 5 battery; 51 shell; 52 electrode assembly; 53 top cover assembly. DETAILED DESCRIPTION

[0028] The following is a detailed description of the embodiments of the technical solution of the present application. The following embodiments are only used to more clearly illustrate the technical solution of the present application, and are therefore only used as examples, and cannot be used to limit the scope of protection of the present application.

[0029] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0030] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0031] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0032] If there is no special explanation, all steps of the present application can be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), which means that step (c) may be added to the method in any order. For example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0033] At present, from the perspective of market development, the application of batteries is becoming more and more extensive. Batteries are not only used in energy storage power systems such as hydropower, thermal power, wind power and solar power stations, but also widely used in electric vehicles such as electric bicycles, electric motorcycles, electric cars, as well as military equipment and aerospace and other fields. With the continuous expansion of battery application areas, its market demand is also constantly expanding.

[0034] In order to meet the demand for high energy density of batteries, the energy density of batteries can be increased by increasing the coating weight of negative electrode sheets. As the energy density of negative electrode sheets increases, the cold pressing pressure increases during the cold pressing process, and the brittleness of negative electrode sheets increases after cold pressing. Due to the limited space in the battery shell, after the battery is fully charged, the sheets may be squeezed, resulting in brittle damage to the negative electrode sheets. For example, when preparing the battery, the positive electrode sheets, negative electrode sheets, and diaphragms can be wound around a winding needle of a certain shape and then loaded into a shell of a fixed size. If the negative electrode sheets are relatively brittle, after the battery is fully charged, the corners of the inner circle negative electrode sheets are prone to brittle damage.

[0035] During the cold pressing process of the pole piece, there is force distribution in different film layers on the pole piece. The negative pole piece proposed in this application improves the ability of the first negative active material layer to bear external force by making the compaction density difference between the first negative active material and the second negative active material meet a certain range. When the battery is fully charged, even if the pole pieces are squeezed, the transmission of external force to the negative current collector can be reduced, and the probability of brittle damage to the negative current collector can be reduced. The risk of fracture of the negative pole piece is reduced during the battery cycle, and the probability of shedding of the negative active material is reduced, thereby improving the cycle life of the battery.

[0036] The negative electrode plate proposed in the present application can be used for lithium-ion batteries, and the battery disclosed in the embodiments of the present application can be used for electrical equipment using batteries as power sources or various energy storage systems using batteries as energy storage elements. Electrical equipment may include, but is not limited to, mobile phones, tablets, laptops, electric toys, electric tools, battery cars, electric cars, ships, spacecraft, and the like. Among them, electric toys may include fixed or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, and the like, and spacecraft may include airplanes, rockets, space shuttles, and spacecraft, and the like.

[0037] The first aspect of the present application provides a negative electrode plate, referring to Figure 1 The negative electrode sheet 10 includes: a negative electrode current collector 11; a first negative electrode active material layer 12, the first negative electrode active material layer 12 is arranged on at least one side of the negative electrode current collector 11, and the first negative electrode active material layer 12 includes a first negative electrode active material; a second negative electrode active material layer 13, the second negative electrode active material layer 13 is arranged on a side of the first negative electrode active material layer 12 away from the negative electrode current collector 11, and the second negative electrode active material layer 13 includes a second negative electrode active material; under a pressure of 20000N, the compaction density of the first negative electrode active material is P 1 , the compaction density of the second negative electrode active material is P 2 , and satisfies P 1 -P 2 ≥0.09g / cm 3 .

[0038] The negative electrode plate proposed in the present application, even if a relatively high pressure is used to cold press the plate, when the negative electrode plate is subjected to external force during the cold pressing process, the degree of deformation that the first negative electrode active material layer 12 can withstand can be increased by making the compaction density difference between the first negative electrode active material and the second negative electrode active material within the above range. The external force during cold pressing mainly acts on the first negative electrode active material and causes it to deform, thereby reducing the probability of the external force being transmitted to the negative electrode collector 11 through the first negative electrode active material layer 12, reducing the force on the negative electrode collector 11, and further reducing the probability of deformation of the negative electrode collector 11, reducing the risk of brittle damage of the negative electrode plate 10 during the cycle, reducing the probability of microcracks in the negative electrode collector 11 or the detachment of the negative electrode active material, and thereby improving the cycle life of the battery.

[0039] In the present application, the first negative electrode active material layer 12 and the second negative electrode active material layer 13 are layered as follows: the overall thickness of the negative electrode active material layer is recorded as H, the thickness range from the surface of the negative electrode active material layer away from the negative electrode current collector to 0.3H can be regarded as the second negative electrode active material layer, and the film layer with a thickness of 0.3H from the surface of the negative electrode current collector 11 to the negative electrode current collector 11 can be regarded as the first negative electrode active material layer, and the powders of the second negative electrode active material layer and the first negative electrode active material layer are scraped off in turn, and the powders are sintered at a sintering temperature greater than or equal to 400°C, and the binder in the powders of the first negative electrode active material layer and the second negative electrode active material layer is removed. The remaining powders of the first negative electrode active material layer and the second negative electrode active material layer are tested for compaction density, which can represent the compaction density of the first negative electrode active material and the second negative electrode active material.

[0040] In the present application, the testing method for the compaction density of the first negative electrode active material layer powder and the second negative electrode active material layer powder is: take a certain amount of powder and place it in a compaction mold, apply a pressure of 20000N, record the thickness of the powder after pressure relief, and the compaction density of the powder under a pressure of 20000N can be calculated by ρ=m / v.

[0041] According to some embodiments of the present application, under a pressure of 20000N, 0.09g / cm 3 ≤P 1 -P 2 ≤0.22g / cm 3 For example, P 1 -P 2 ≤0.09g / cm 3 , 0.1g / cm 3 , 0.11g / cm 3 , 0.12g / cm 3 , 0.13g / cm 3 , 0.14g / cm 3 , 0.15g / cm 3 , 0.16g / cm 3 , 0.17g / cm 3 , 0.18g / cm 3 , 0.19g / cm 3 , 0.2g / cm 3 or 0.22g / cm 3 According to some specific embodiments of the present application, under a pressure of 20000N, 0.12g / cm 3 ≤P 1 -P 2 ≤0.20g / cm 3 .

[0042] According to some embodiments of the present application, under a pressure of 20000N, 1.84g / cm 3 ≤P 1 ≤1.90g / cm 3 , for example, can be 1.84 g / cm 3 , 1.85g / cm 3 , 1.86g / cm 3 , 1.87g / cm 3 、1.88g / cm 3 、1.89g / cm 3 or 1.90g / cm 3 The above-mentioned arbitrary numerical ranges may also be used.

[0043] According to some embodiments of the present application, under a pressure of 20000N, 1.70g / cm 3 ≤P 2 ≤1.75g / cm 3 For example, it can be 1.70 g / cm 3 , 1.71g / cm 3 , 1.72g / cm 3 , 1.73g / cm 3 , 1.74g / cm 3 or 1.75g / cm 3 The above-mentioned arbitrary numerical ranges may also be used.

[0044] Therefore, due to P 1 Greater than P 2 , by making P 1 and P 2 When the value of is within the above range, the energy density of the battery can be increased while the ability of the first negative electrode active material layer 12 to bear external forces is increased.

[0045] According to some embodiments of the present application, the compaction density of the negative electrode sheet 10 can be 1.75 g / cm 3 -1.85g / cm 3 For example, it can be 1.75 g / cm 3 , 1.76g / cm 3 , 1.77g / cm 3 , 1.78g / cm 3 , 1.79g / cm 3 , 1.80g / cm 3 、1.81g / cm 3 , 1.82g / cm 3 , 1.83g / cm 3 , 1.84g / cm 3 or 1.85g / cm3 etc., or can be any range of the above values. Thus, the compaction density of the negative electrode sheet 10 is relatively large, and by making P 1 Greater than P 2 , which can improve the ability of the first negative electrode active material layer 12 to bear external forces, thereby reducing the transmission of force from the first negative electrode active material layer 12 to the negative electrode current collector 11, thereby reducing the risk of brittle damage to the negative electrode plate 10 during the cycle, reducing the risk of the negative electrode plate breaking during the battery cycle, reducing the probability of active material on the negative electrode plate falling off, and improving the cycle life of the battery.

[0046] In the present application, the compaction density of the negative electrode sheet refers to the compaction density of the negative electrode active material layer (including the first negative electrode active material layer and the second negative electrode active material layer).

[0047] In the present application, the test method of the compaction density of the negative electrode plate 10 is as follows: the coated area and the empty foil area in the electrode plate are punched into fixed sizes, and the thickness of the electrode plate is measured by using a micrometer. 1 , the thickness of the negative electrode current collector is H 0 ; Weigh the weight of the cut negative electrode sheet as M 1 , the weight of the negative electrode collector is M 0 , the compaction density of the negative electrode sheet can be calculated as (M 1 -M 0 ) / (H 1 -H 0 ).

[0048] According to some embodiments of the present application, the volume average particle size Dv50 of the powder of the first negative active material layer 12 satisfies: 15μm≤Dv50≤20μm, for example, the Dv50 of the powder of the first negative active material layer 12 may be 15μm, 16μm, 17μm, 18μm, 19μm or 20μm, etc., or may be a range composed of any of the above numerical values; the volume average particle size Dv50 of the powder of the second negative active material layer 13 satisfies: 13μm≤Dv50≤18μm, for example, the Dv50 of the powder of the second negative active material layer 13 may be 13μm, 14μm, 15μm, 16μm, 17μm or 18μm, etc., or may be a range composed of any of the above numerical values. Thus, the fast charging capability of the battery is improved.

[0049] In this application, the volume average particle size Dv50 refers to the particle size corresponding to the cumulative volume distribution percentage reaching 50%, for example, with reference to the standard GB / T 19077-2016 / ISO 13320:2009, using a laser particle size analyzer (MalvernMaster Size2000) for measurement. The specific test process is: scrape off the powder of the first negative electrode active material layer 12, take an appropriate amount of sample (the sample concentration is guaranteed to be 8%-12% shading), add 20ml of deionized water, and ultrasonicate for 5min (53KHz / 120W) at the same time to ensure that the sample is completely dispersed, and then measure the sample according to the GB / T19077-2016 / ISO 13320:2009 standard.

[0050] According to some embodiments of the present application, the coating weight of the negative electrode sheet 10 can be 11.0 mg / cm 2 -13.0mg / cm 2 For example, it can be 11.0 mg / cm 2 、11.5mg / cm 2 、12.0mg / cm 2 , 12.5mg / cm 2 or 13.0 mg / cm 2 etc., or can be any range of the above values. Thus, the negative electrode sheet is coated thickly to improve the energy density of the battery.

[0051] According to some embodiments of the present application, the compaction density of the negative electrode sheet can be 1.75 g / cm 3 -1.85g / cm 3 ， The coating weight of the negative electrode plate 10 can be 11.0 mg / cm 2 -13.0mg / cm 2 That is, the negative electrode plate adopts high pressure density and thick coating. When the negative electrode plate is subjected to external force during the cold pressing process, since the compaction density of the second negative electrode active material is less than the compaction density of the first negative electrode active material, the deformation degree that the first negative electrode active material layer 12 can withstand can be increased. The external force during cold pressing mainly acts on the first negative electrode active material and causes it to deform, thereby reducing the probability of the external force being transmitted to the negative electrode current collector 11 through the first negative electrode active material layer 12, reducing the force on the negative electrode current collector 11, and further reducing the probability of deformation of the negative electrode current collector 11, reducing the risk of brittle damage of the negative electrode plate 10 during the cycle, and reducing the probability of microcracks in the negative electrode current collector 11 or the falling off of the negative electrode active material.

[0052] In the present application, the method for testing the coating weight of the negative electrode sheet 10 is to punch the coating area and the empty foil area in the negative electrode sheet into fixed sizes, and weigh the weight of the cut negative electrode sheet as M.1 , the weight of the negative electrode collector is M 0 , the coating weight of the negative electrode sheet can be calculated as: (M 1 -M 0 ) / pole area after punching.

[0053] According to some embodiments of the present application, the ratio of the coating weight of the first negative electrode active material layer 12 to the coating weight of the second negative electrode active material layer 13 can be 0.65-1.5, for example, it can be 0.65, 0.75, 0.85, 0.95, 1.05, 1.15, 1.25, 1.35, 1.45 or 1.5, etc., or can be a range consisting of any of the above numerical values.

[0054] According to some embodiments of the present application, the coating weight of the first negative electrode active material layer 12 and the coating weight of the second negative electrode active material layer 13 may be the same.

[0055] According to some embodiments of the present application, the first negative electrode active material includes at least one of a first artificial graphite or a natural graphite, and the second negative electrode active material includes a second artificial graphite. Thus, while improving the energy density of the battery, the fast charging performance of the battery can be improved. According to some specific embodiments of the present application, both the first artificial graphite and the second artificial graphite can include secondary graphite particles.

[0056] According to some embodiments of the present application, the first negative electrode active material includes a first artificial graphite and a natural graphite, and the second negative electrode active material includes a second artificial graphite, wherein the first artificial graphite and the second artificial graphite are both secondary graphite particles.

[0057] According to some embodiments of the present application, when the first negative electrode active material layer 12 includes a first artificial graphite and a natural graphite, the ratio of the mass of the first artificial graphite to the mass of the natural graphite can be 1-1.5, for example, it can be 1, 1.1, 1.2, 1.3, 1.4 or 1.5, etc., or it can be a range composed of any of the above numerical values.

[0058] According to some embodiments of the present application, based on the total mass of the first negative electrode active material layer 12, the mass proportion of the first artificial graphite may be 50%-60%. For example, it may be 50%, 52%, 54%, 56%, 58% or 60%, etc., or may be a range of any of the above values.

[0059] According to some embodiments of the present application, the mass proportion of the natural graphite may be 40%-50% based on the total mass of the first negative electrode active material layer 12. For example, it may be 40%, 42%, 44%, 46%, 48% or 50%, etc., or may be a range consisting of any of the above values.

[0060] It should be noted that when the first negative electrode active material layer 12 includes both the first artificial graphite and the natural graphite, the compaction density of the first negative electrode active material can be calculated according to the content of the first artificial graphite and the natural graphite. For example, the compaction density of the first negative electrode active material = X 1 ×P 11 +X 2 ×P 12 , where X 1 is the mass proportion of the first artificial graphite based on the total mass of the first artificial graphite and the natural graphite, in %; P 11 is the compacted density of the first artificial graphite, in g / cm 3 ;X 2 is the mass proportion of natural graphite based on the total mass of the first artificial graphite and natural graphite, in %; P 12 is the compacted density of natural graphite, in g / cm 3 .

[0061] According to some embodiments of the present invention, under a pressure of 20000N, the compaction density of the first artificial graphite may be 1.84 g / cm 3 ≤P 1 ≤1.90g / cm 3 , for example, can be 1.84 g / cm 3 , 1.85g / cm 3 , 1.86g / cm 3 , 1.87g / cm 3 、1.88g / cm 3 、1.89g / cm 3 or 1.90g / cm 3 etc., or can be within the range of any of the above numerical values. Thus, the energy density of the battery can be increased.

[0062] According to some embodiments of the present invention, the compaction density of natural graphite can be 1.84 g / cm2 under a pressure of 20,000 N. 3 ≤P 1 ≤1.90g / cm 3 , for example, can be 1.84 g / cm 3 , 1.85g / cm 3 , 1.86g / cm 3 , 1.87g / cm 3 、1.88g / cm 3 、1.89g / cm 3 or 1.90g / cm 3 etc., or can be within the range of any of the above numerical values. Thus, the energy density of the battery can be increased.

[0063] According to some embodiments of the present application, the volume average particle size Dv50 of the second artificial graphite satisfies: 13 μm ≤ Dv50 ≤ 18 μm, for example, it can be 13 μm, 15 μm, 17 μm or 18 μm, or can be a range of any of the above values. Thus, the energy density of the battery can be improved.

[0064] According to some embodiments of the present application, the volume average particle size Dv50 of the first artificial graphite satisfies: 13 μm ≤ Dv50 ≤ 17 μm, for example, it can be 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, etc., or can be a range of any of the above values. Thus, the energy density of the battery is improved.

[0065] According to some embodiments of the present application, the volume average particle size Dv50 of the natural graphite satisfies: 15 μm ≤ Dv50 ≤ 25 μm, for example, it can be 15 μm, 17 μm, 19 μm, 21 μm, 23 μm or 25 μm, or can be a range of any of the above values. Thus, the energy density of the battery is improved.

[0066] The second aspect of the present application provides a battery, comprising the negative electrode plate 10 provided in the first aspect of the present application. Thus, during the battery cycle, the probability of brittle damage to the negative electrode plate 10 can be reduced, thereby increasing the cycle life of the battery.

[0067] Generally, a battery includes a positive electrode sheet, a negative electrode sheet 10, an electrolyte and a separator. During the charge and discharge process of the battery, active ions are embedded and extracted back and forth between the positive electrode sheet and the negative electrode sheet 10. The electrolyte plays a role in conducting ions between the positive electrode sheet and the negative electrode sheet 10. The separator is arranged between the positive electrode sheet and the negative electrode sheet 10, mainly to prevent the positive and negative electrodes from short-circuiting, while allowing ions to pass through.

[0068] [Positive electrode]

[0069] The positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer arranged on at least one surface of the positive electrode current collector, wherein the positive electrode active material layer includes the positive electrode active material of the first aspect of the present application.

[0070] As an example, the positive electrode current collector has two surfaces facing each other in its thickness direction, and the positive electrode active material layer is disposed on any one or both of the two facing surfaces of the positive electrode current collector.

[0071] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer material base and a metal layer formed on at least one surface of the polymer material base. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0072] In some embodiments, when the battery is a lithium-ion battery, the positive electrode active material may adopt a positive electrode active material for lithium-ion batteries known in the art. As an example, the positive electrode active material may include at least one of the following materials: a lithium-containing phosphate with an olivine structure, a lithium transition metal oxide, and their respective modified compounds. However, the present application is not limited to these materials, and other traditional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more. Among them, examples of lithium transition metal oxides may include, but are not limited to, lithium cobalt oxides (such as LiCoO 2 ), lithium nickel oxide (such as LiNiO 2 ), lithium manganese oxide (such as LiMnO 2 、LiMn 2 O 4 ), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O 2 (Also referred to as NCM 333 )、LiNi 0.5 Co 0.2 Mn 0.3 O 2 (Also referred to as NCM 523 )、LiNi 0.5 Co 0.25 Mn 0.25 O 2 (Also referred to as NCM 211 )、LiNi 0.6 Co 0.2 Mn 0.2 O 2 (Also referred to as NCM 622 )、LiNi 0.8 Co 0.1 Mn 0.1 O 2 (Also referred to as NCM 811), lithium nickel cobalt aluminum oxide (such as LiNi 0.8 Co 0.15 Al 0.05 O 2 ) and its modified compounds, etc. Examples of lithium phosphates containing olivine structures may include, but are not limited to, lithium iron phosphate (such as LiFePO 4 (also referred to as LFP), composite materials of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO 4 ), at least one of a composite material of lithium manganese phosphate and carbon, a composite material of lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon.

[0073] The modified compounds of the above materials may be doping-modified and / or surface-coated modified materials.

[0074] In some embodiments, the positive electrode active material layer may further optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin.

[0075] In some embodiments, the positive electrode active material layer may further include a conductive agent, which may include, for example, at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0076] In some embodiments, the positive electrode sheet can be prepared in the following manner: the components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0077] [Negative electrode]

[0078] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, as the metal foil, copper foil may be used. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0079] In some embodiments, the first negative electrode active material layer and the second negative electrode active material layer may further optionally include a binder. The binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA) and carboxymethyl chitosan (CMCS).

[0080] In some embodiments, the first negative electrode active material layer and the second negative electrode active material layer may further include a conductive agent, which may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.

[0081] In some embodiments, the first negative electrode active material layer and the second negative electrode active material layer may further optionally include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0082] [Electrolytes]

[0083] The electrolyte plays a role in conducting ions between the positive electrode and the negative electrode. The present application has no specific restrictions on the type of electrolyte, which can be selected according to needs.

[0084] In some embodiments, the electrolyte is an electrolyte solution, which includes an electrolyte salt and a solvent.

[0085] In some embodiments, the electrolyte salt may include at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bisfluorosulfonyl imide, lithium bistrifluoromethanesulfonyl imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalatoborate, lithium dioxalatoborate, lithium difluorodioxalatophosphate, and lithium tetrafluorooxalatophosphate.

[0086] In some embodiments, the solvent can be selected from at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane sulfone, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.

[0087] In some embodiments, the electrolyte may further include additives, such as negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high or low temperature performance, etc.

[0088] [Isolation film]

[0089] In some embodiments, the battery further includes a separator. The present application has no particular limitation on the type of separator, and any known porous separator with good chemical stability and mechanical stability can be selected.

[0090] In some embodiments, the material of the isolation membrane can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride. The isolation membrane can be a single-layer film or a multi-layer composite film, without particular limitation. When the isolation membrane is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0091] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator may be formed into an electrode assembly by a winding process or a lamination process.

[0092] In some embodiments, the battery may include an outer packaging, which may be used to encapsulate the electrode assembly and the electrolyte.

[0093] In some embodiments, the outer packaging of the battery may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer packaging of the battery may also be a soft package, such as a bag-type soft package. The material of the soft package may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0094] The present application has no particular limitation on the shape of the battery, which may be cylindrical, square or any other shape. For example, Figure 2 The battery 5 is a square structure as an example.

[0095] In some embodiments, reference Figure 3 , the outer packaging may include a shell 51 and a cover plate 53. Among them, the shell 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 51 has an opening connected to the receiving cavity, and the cover plate 53 can be covered on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the isolation membrane can form an electrode assembly 52 through a winding process or a lamination process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the battery 5 can be one or more, and those skilled in the art can select according to specific actual needs.

[0096] In some embodiments, batteries may be assembled into a battery module. The number of batteries contained in the battery module may be one or more. The specific number may be selected by those skilled in the art according to the application and capacity of the battery module.

[0097] Figure 4 4 is an example of a battery module. Figure 4In the battery module 4, the multiple batteries 5 can be arranged in sequence along the length direction of the battery module 4. Of course, they can also be arranged in any other manner. Further, the multiple batteries 5 can be fixed by fasteners.

[0098] Optionally, the battery module 4 may further include a housing having a receiving space, and the plurality of batteries 5 are received in the receiving space.

[0099] In some embodiments, the battery modules described above may also be assembled into a battery pack. The battery pack may contain one or more battery modules, and the specific number may be selected by those skilled in the art according to the application and capacity of the battery pack.

[0100] Figure 5 and Figure 6 1 is a battery pack 1 as an example. Figure 5 and Figure 6 The battery pack 1 may include a battery box and a plurality of battery modules 4 disposed in the battery box. The battery box includes an upper box body 2 and a lower box body 3. The upper box body 2 can cover the lower box body 3 and form a closed space for accommodating the battery modules 4. The plurality of battery modules 4 can be arranged in the battery box in any manner.

[0101] The third aspect of the present application provides an electric device, which includes at least one of the batteries, battery modules, or battery packs provided in the present application. The battery, battery module, or battery pack can be used as a power source for the electric device, and can also be used as an energy storage unit for the electric device. The electric device may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but are not limited thereto.

[0102] As the electrical device, a battery, a battery module or a battery pack can be selected according to its usage requirements.

[0103] Figure 7 The power consumption device is taken as an example. The power consumption device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. In order to meet the power consumption device's requirements for high power and high energy density of the battery, a battery pack or a battery module can be used.

[0104] As another example, the device may be a mobile phone, a tablet computer, a notebook computer, etc. The device is usually required to be light and thin, and a battery may be used as a power source.

[0105] In order to make the technical problems, technical solutions and beneficial effects solved by the embodiments of the present application clearer, the following will be further described in detail with reference to the embodiments and the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present application and its applications. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present application.

[0106] Example 1

[0107] 1. Preparation of positive electrode sheet

[0108] The positive electrode active material LiNi 0.5 Co 0.2 Mn 0.3 O 2 (NCM523), conductive agent carbon black (Super P), and binder polyvinylidene fluoride (PVDF) are fully stirred and mixed in a proper amount of solvent N-methylpyrrolidone (NMP) at a mass ratio of 80:15:5 to form a uniform positive electrode slurry; the positive electrode slurry is evenly coated on the surface of the positive electrode current collector aluminum foil, and after drying and cold pressing, a positive electrode sheet is obtained.

[0109] 2. Preparation of negative electrode sheet

[0110] The negative electrode active materials artificial graphite and natural graphite (the mass ratio of artificial graphite to natural graphite is 1:1), the conductive agent Super P, the thickener CMC, and the binder styrene butadiene rubber are mixed in a mass ratio of 96.4:1:1.2:1.4, and the solvent deionized water is added. The mixture is stirred evenly under the action of a vacuum mixer, coated on the negative electrode current collector copper foil, and dried in an oven to form a first negative electrode active material layer.

[0111] The negative electrode active material artificial graphite, conductive agent Super P, thickener CMC, and binder styrene butadiene rubber are mixed in a mass ratio of 96.4:1:1.2:1.4, and deionized water solvent is added. The mixture is stirred evenly under the action of a vacuum mixer, and coated on the side of the first negative electrode active material layer away from the copper foil. The mixture is dried in an oven and cold pressed to obtain a negative electrode sheet.

[0112] 3. Preparation of electrolyte

[0113] In an argon atmosphere glove box (H 2 O<0.1ppm, O 2 <0.1ppm), 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 the fully dried electrolyte salt LiPF6 Dissolve in the above solvent, mix well to obtain an electrolyte with a concentration of 1 mol / L.

[0114] 4. Isolation film

[0115] A porous polyethylene membrane was used as the separator.

[0116] 5. Preparation of batteries

[0117] The positive electrode sheet, the separator, and the negative electrode sheet are stacked in order, so that the separator is between the positive and negative electrode sheets to play an isolating role, and then they are wound to obtain an electrode assembly; the electrode assembly is placed in an outer package, and the prepared electrolyte is injected into the dried lithium-ion battery. After vacuum packaging, standing, forming, and shaping processes, a lithium-ion battery is obtained.

[0118] The preparation methods of the batteries in Examples 2 to 13 and Comparative Example 1 are the same as those in Example 1, and the differences are detailed in Table 1.

[0119] In the present application, the compaction density of the negative electrode sheet can be adjusted by adjusting the pressure of the roller during the cold pressing process.

[0120] In the present application, the coating weight of the negative electrode sheet can be adjusted by adjusting the gap between the coating blades during the coating process.

[0121] Table 1

[0122]

[0123] Performance Testing

[0124] 1. Pole brittle damage test

[0125] After fully charging the battery obtained above, disassemble it and separate the fully charged negative electrode. Fold the electrode in the radial direction, and fold it completely by squeezing a 35cm×15cm glass plate with a mass of about 600g. After opening, observe whether the electrode is broken. The degree of lithium precipitation is determined by the ratio of light leakage or fracture length at the crease to the entire length. Complete fracture is first-level brittle damage, light leakage or fracture ratio greater than 1 / 2 is second-level brittle damage, light leakage or fracture ratio between 1 / 4 and 1 / 2 is third-level brittle damage, light leakage or fracture ratio less than 1 / 4 is fourth-level brittle damage, and no light leakage or fracture is zero-level damage. In addition, for the electrode that is not completely broken, fold it back and forth until the electrode breaks, and record the number of times it is completely broken, where one positive fold and one reverse fold of the electrode is counted as one time.

[0126] It should be noted that graphite negative electrode materials have good flexibility. After cold pressing, the negative electrode sheet is unfolded after extrusion, and it is difficult for the current collector to break or separate from the active material. This application is to avoid possible brittle damage during the cycle, so the fully charged electrode sheet (strong brittleness) is used as the research object.

[0127] The test results of Examples 1 to 13 and Comparative Example 1 are shown in Table 2.

[0128] Table 2

[0129] Damage level Fold times Comparative Example 1 First degree injury 0 Example 1 Grade 3 injury 6 Example 2 Grade 3 injury 9 Example 3 Grade 3 injury 16 Example 4 Grade 3 injury 30 Example 5 Grade 3 injury 28 Example 6 Grade 3 injury 18 Example 7 Grade 4 injury 33 Example 8 Grade 3 injury 10 Example 9 Grade 3 injury 8 Example 10 Grade 3 injury 12 Embodiment 11 Grade 3 injury 25 Example 12 Grade 3 injury 40 Embodiment 13 Grade 4 injury 15

[0130] Conclusion: Compared with Example 1, it can be seen that the present invention uses P 1 -P 2 ≥0.09g / cm 3 , which can reduce the degree of damage to the negative electrode plate, thereby reducing the risk of the negative electrode plate breaking during the battery cycle, reducing the probability of the negative electrode active material falling off, and increasing the cycle life of the battery.

[0131] It can be seen from Examples 1 to 13 of the present application that when the negative electrode plate adopts high pressure density and high coating, by using P 1 -P 2 ≥0.09g / cm 3 , which can reduce the degree of damage to the negative electrode plate, thereby reducing the risk of the negative electrode plate breaking during the battery cycle, reducing the probability of the negative electrode active material falling off, and increasing the cycle life of the battery.

[0132] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them; although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application, and they should all be included in the scope of the claims and specification of the present application. In particular, as long as there is no structural conflict, the various technical features mentioned in the various embodiments can be combined in any way. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions that fall within the scope of the claims.

Claims

1. A negative electrode plate, characterized in that: include: Anode current collector; a first negative electrode active material layer, the first negative electrode active material layer being disposed on at least one side of the negative electrode current collector, the first negative electrode active material layer comprising a first negative electrode active material; a second negative electrode active material layer, the second negative electrode active material layer being disposed on a side of the first negative electrode active material layer away from the negative electrode current collector, the second negative electrode active material layer comprising a second negative electrode active material; Under a pressure of 20000N, the compaction density of the first negative electrode active material is P1, the compaction density of the second negative electrode active material is P2, and P1-P2≥0.09g / cm 3 .

2. The negative electrode sheet according to claim 1, characterized in that: 0.09g / cm2 under 20000N pressure 3 ≤P1-P2≤0.22g / cm 3 .

3. The negative electrode sheet according to claim 1 or 2, characterized in that: 0.12g / cm2 under 20000N pressure 3 ≤P1-P2≤0.20g / cm 3 .

4. The negative electrode sheet according to any one of claims 1 to 3, characterized in that: Under a pressure of 20000N, the values ​​of P1 and P2 meet one or more of the following conditions: 1.84g / cm 3 ≤P1≤1.90g / cm 3 ; 1.70g / cm 3 ≤P2≤1.75g / cm 3 。 5. The negative electrode sheet according to any one of claims 1 to 4, characterized in that: The compaction density of the negative electrode plate is 1.75 g / cm 3 -1.85g / cm 3 .

6. The negative electrode sheet according to any one of claims 1 to 5, characterized in that: The coating weight of the negative electrode sheet is 11.0 mg / cm 2 -13.0mg / cm 2 .

7. The negative electrode sheet according to any one of claims 1 to 6, characterized in that: The volume average particle size Dv50 of the first negative electrode active material layer powder satisfies: 15 μm≤Dv50≤20 μm, and the volume average particle size Dv50 of the second negative electrode active material layer powder satisfies: 13 μm≤Dv50≤18 μm.

8. The negative electrode sheet according to any one of claims 1 to 7, characterized in that: The first negative electrode active material includes at least one of a first artificial graphite or a natural graphite, and the second negative electrode active material includes a second artificial graphite.

9. The negative electrode sheet according to claim 8, characterized in that: The first artificial graphite and the second artificial graphite both include secondary graphite particles.

10. The negative electrode sheet according to claim 9, characterized in that: Meet one or more of the following conditions: The volume average particle size Dv50 of the second artificial graphite satisfies: 13 μm≤Dv50≤18 μm; The volume average particle size Dv50 of the first artificial graphite satisfies: 13 μm≤Dv50≤17 μm; The volume average particle size Dv50 of the natural graphite satisfies: 15 μm≤Dv50≤25 μm.

11. A battery, characterized in that: The invention comprises the negative electrode sheet according to any one of claims 1 to 10.

12. An electrical equipment, characterized in that: Comprising the battery of claim 11.

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