Negative pole piece, cylindrical battery and electric device

Abstract

The invention relates to the technical field of batteries, in particular to a negative pole piece, a cylindrical battery and an electric device. The negative pole piece comprises a current collector and a coating arranged on at least one side surface of the current collector, the coating comprises a negative active material, and the negative active material comprises graphite and a silicon-based material; the negative pole piece meets the condition that M-N / M is less than or equal to 5%; wherein M is the predicted hole tortuosity of the negative pole piece, and N is the actually measured hole tortuosity of the negative pole piece; m satisfies the following formula: 0.3 < = M = (5 * lga) + (e8 * (1-b) * c-1) < = 4; wherein a is the apparent density of the negative pole piece; b is the mass percentage content of graphite in the coating; and c is the mass percentage of the silicon-based material in the coating. The cylindrical battery comprises the provided negative pole piece. According to the invention, the problem that the magnification performance of the battery is influenced due to the polarization increase caused by the increase of the tortuosity of the existing cylindrical full-tab battery hole can be relieved, and the high-magnification charging and discharging of the full-tab cylindrical lithium ion battery can be realized.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and in particular, to a negative electrode plate, a cylindrical battery, and an electrical device. Background Art

[0002] In recent years, with the continuous progress of technology and the increasing awareness of environmental protection among humans, the demand for high-efficiency energy storage batteries has also increased. Lithium-ion batteries are currently widely used secondary batteries. At present, as a high-efficiency and environmentally friendly energy storage device, lithium batteries have been widely used in fields such as consumer electronics, power tools, electric vehicles, and energy storage systems. Lithium batteries have the advantages of high energy density, long cycle life, low self-discharge rate, and no memory effect, so they have become a research hotspot in current battery technology. However, there are still some problems to be solved urgently in the existing lithium battery technology. For example, the internal resistance of existing cylindrical battery products is relatively large, resulting in a large amount of heat generated during the charging and discharging process of the battery, and the energy utilization rate is low.

[0003] In addition, for the negative electrode material of the battery, in order to increase the specific capacity of the negative electrode, some silicon is added to the graphite negative electrode plate to obtain a silicon-containing battery cell. In this way, due to the continuous increase in energy density requirements, the surface density of the negative electrode coating also increases accordingly, making the cold pressing difficulty of the electrode plate higher and the pressure required for primary cold pressing greater; under the action of a larger pressure, more closed pores are formed in the negative electrode plate, resulting in a larger pore tortuosity (or pore impedance), which is not conducive to the infiltration of the electrolyte. Moreover, the increase in pore tortuosity (or pore impedance) will increase the polarization, directly affecting the rate performance of the battery. Summary of the Invention

[0004] In view of this, the present invention aims to at least solve one of the technical problems in the related art to some extent. For this reason, the present invention provides a negative electrode plate, a cylindrical battery, and an electrical device, which can make the pore tortuosity of the negative electrode plate within a suitable range, thereby facilitating the improvement of the rate performance of the battery.

[0005] In order to solve the above technical problems, the present application is implemented as follows:

[0006] According to one aspect of the present application, an embodiment of the present application provides a negative electrode plate, the negative electrode plate includes a current collector and a coating provided on at least one surface of the current collector, the coating includes a negative electrode active material, and the negative electrode active material includes graphite and a silicon-based material; the negative electrode plate satisfies:

[0007] |M - N| / M ≤ 5%;

[0008] wherein, M is the predicted pore tortuosity of the negative electrode plate, and N is the measured pore tortuosity of the negative electrode plate;

[0009] The M satisfies:

[0010] 0.3 ≤ M = (5 × lg a) + (e 8×(1-b)×c - 1) ≤ 4;

[0011] where a is the apparent density of the negative electrode plate, with the unit of g / cm 3 ;

[0012] b is the mass percentage of the graphite in the coating;

[0013] c is the mass percentage of the silicon-based material in the coating.

[0014] In some embodiments, the negative electrode plate satisfies: |M - N| / M < 5%.

[0015] In some embodiments, M satisfies: 0.3 < M = (5 × lg a) + (e 8×(1-b)×c - 1) < 4.

[0016] In some embodiments, N satisfies: N = (N1 + N2 + N3 + N4 + N5) / 5; where, when the battery containing the negative electrode plate is in the 0% SOC state, the disassembled negative electrode plate is divided into five equal regions, and the tortuosity of the pores in each region is measured and calculated at the middle positions of the five regions, and are respectively denoted as N1, N2, N3, N4, and N5.

[0017] In some embodiments, N1, N2, N3, N4, and N5 are calculated by the following formula: N i = (R ion × A × ε × σ) / d; where R ion is the pore impedance of the negative electrode plate, A is the area of the electrode plate corresponding to the middle circular hole when measuring the pore impedance of the negative electrode plate, σ is the conductivity of the electrolyte in the battery containing the negative electrode plate, ε is the porosity of the coating, and d is the thickness of the coating on one side.

[0018] In some embodiments, R ion satisfies: 2 ≤ R ion ≤ 10, with the unit of Ω.

[0019] In some embodiments, R ion satisfies: R ion = (R1 + R2 + R3 + R4 + R5) / 5; where, when the battery containing the negative electrode plate is in the 0% SOC state, the disassembled negative electrode plate is divided into five equal regions, and the pore impedance of each region is measured at the middle positions of the five regions, and are respectively denoted as R1, R2, R3, R4, and R5.

[0020] In some of these embodiments, A satisfies: 1 ≤ A ≤ 15, with the unit being cm 2 ;

[0021] When the negative electrode tab is in a wound structure, the tab area A is the tab area of the region corresponding to one tab.

[0022] In some of these embodiments, d satisfies: 20 ≤ d ≤ 150, with the unit being μm.

[0023] In some of these embodiments, 10% ≤ ε ≤ 50%.

[0024] In some of these embodiments, 5 ≤ σ ≤ 20, with the unit being mS / cm.

[0025] In some of these embodiments, the negative electrode tab satisfies at least one of the following characteristics (1) to (9):

[0026] (1) a satisfies: 1.05 ≤ a ≤ 1.8, with the unit being g / cm 3 ;

[0027] (2) b satisfies: 64% ≤ b ≤ 96%;

[0028] (3) c satisfies: 2% ≤ c ≤ 28%;

[0029] (4) The mass percentage content of the negative electrode active material in the coating is x, and x satisfies:

[0030] 92% ≤ x ≤ 98%;

[0031] (5) The mass ratio of the silicon-based material to graphite is (3 to 30):(70 to 97);

[0032] (6) The silicon-based material includes at least one of elemental silicon, silicon oxide, silicon-carbon material, silicon nitride composite, or silicon alloy material;

[0033] (7) The average particle size range of the graphite is 3 μm to 30 μm;

[0034] (8) The average particle size range of the silicon-based material is 3 μm to 30 μm;

[0035] (9) The negative electrode tab is a wound structure tab.

[0036] According to another aspect of the present application, embodiments of the present application provide a cylindrical battery, which includes a cylindrical battery cell. The cylindrical battery cell includes the aforementioned negative electrode tab, and further includes a positive electrode tab, a separator, and an electrolyte. The separator is located between the positive electrode tab and the negative electrode tab.

[0037] In some of these embodiments, the cylindrical battery cell satisfies at least one of the following characteristics (1) to (4):

[0038] (1) The porosity of the separator ranges from 30% to 48%.

[0039] (2) The porosity of the separator ranges from 36% to 45%.

[0040] (3) The cylindrical battery cell includes a full-tab cylindrical winding core formed by interleaved winding of a positive electrode tab, a separator, and a negative electrode tab. One end of the full-tab cylindrical winding core is a negative full-tab end face, and the other end is a positive full-tab end face.

[0041] (4) The diameter of the cylindrical battery cell is 15 mm to 50 mm, and the length of the cylindrical battery cell is 60 mm to 150 mm.

[0042] According to another aspect of the present application, an electrical device provided by an embodiment of the present application includes the aforementioned negative electrode tab or includes the aforementioned cylindrical battery.

[0043] Implementing the technical solutions of the present invention has at least the following beneficial effects:

[0044] In the embodiments of the present application, the provided negative electrode tab can be used as the negative electrode in a battery, such as a cylindrical lithium-ion battery. The present application predicts the pore tortuosity of the negative electrode tab by defining the relationship between the characteristic parameters of the silicon-based material and graphite in the negative electrode tab and the apparent density of the electrode tab, and makes the difference between the predicted pore tortuosity and the measured pore tortuosity not exceed 5%, so that the pore tortuosity of the negative electrode tab is within an appropriate range, thereby avoiding the problem that the increase in pore tortuosity causes an increase in polarization and affects the rate performance of the battery, which is beneficial to improving the rate performance of the negative electrode tab, especially enabling high-rate charge and discharge of a full-tab lithium-ion cylindrical battery.

[0045] The additional aspects and advantages of the present application will be partially given in the following description, partially become apparent from the following description, or be understood through the practice of the present invention. Description of the Drawings

[0046] Figure 1 The figure shows a schematic structural diagram of a cylindrical battery provided by an embodiment of the present invention;

[0047] Figure 2 The figure shows a schematic structural diagram of a cylindrical battery cell provided by an embodiment of the present invention.

[0048] Description of the Reference Numerals

[0049] 10 - positive electrode end; 20 - negative electrode end; 30 - outer casing

[0050] 101 - Positive electrode plate; 102 - Negative electrode plate; 103 - Separator; 104 - Wound core. Detailed implementation manners

[0051] The following further elaborates on this application in combination with specific embodiments. It should be understood that these embodiments of this application are only used to illustrate this application and not to limit the scope of this application.

[0052] In the ranges disclosed herein, the endpoints and any values are not limited to the exact ranges or values. These ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range or individual point values, and between individual point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0053] If there is no special indication, all implementation manners and optional implementation manners of this application can be combined with each other to form new technical solutions. If there is no special indication, all technical features and optional technical features of this application can be combined with each other to form new technical solutions.

[0054] If there is no special indication, the "including" and "comprising" mentioned in this application mean open-ended, and can also be closed-ended. For example, the "including" and "comprising" can mean that other components not listed can also be included or comprised, or only the components listed are included or comprised.

[0055] Generally, a battery includes an electrode assembly and an electrolyte. The electrode assembly includes a separator, a positive electrode plate, and a negative electrode plate. Silicon has become one of the most promising negative electrode active materials at present due to its high theoretical specific capacity. By adding silicon materials to the negative electrode plate, it is beneficial to improve the energy density of the battery. However, in existing silicon-containing battery cores, due to the continuous increase in energy density requirements, the surface density of the negative electrode coating also increases accordingly, making the cold pressing of the electrode plate more difficult and requiring a greater pressure for the first cold pressing; under the action of a larger pressure, more closed pores are formed in the negative electrode plate, resulting in a larger pore tortuosity (or pore impedance), which is not conducive to the infiltration of the electrolyte. In addition, under a larger pressure, the degree of fragmentation of the material particles will be greater, thereby increasing the amount of SEI film formation and reducing the battery efficiency. Moreover, the increase in pore tortuosity (or pore impedance) will increase the polarization, directly affecting the rate performance of the battery.

[0056] Based on this, the inventors have found through research that by limiting the pore tortuosity of the negative electrode plate, the problem that the pore tortuosity of the negative electrode plate is likely to increase and the corresponding battery rate performance or cycle performance is poor after the existing silicon-based material and graphite are compounded can be effectively improved. Next, this application will be described in detail.

[0057] The following specifically describes a negative electrode tab of an embodiment of the present application, a cylindrical battery including the negative electrode tab, and an electrical device.

[0058] In some embodiments, the present application provides a negative electrode tab, which includes: a current collector, and a coating disposed on at least one surface of the current collector along the thickness direction; the coating includes a negative electrode active material, and the negative electrode active material includes graphite and a silicon-based material.

[0059] Among them, the silicon-based material may be granular silicon material, and the graphite may be granular graphite material.

[0060] In an embodiment of the present application, the negative electrode tab includes a current collector and a coating (which may also be referred to as an active material layer) disposed on at least one surface of the current collector along the thickness direction. The above-mentioned "coating disposed on at least one surface of the current collector along the thickness direction" means that the coating may be disposed on one surface of the current collector along its own thickness direction, or may be disposed on two surfaces of the current collector along its own thickness direction. Here, the "surface" may be the entire area of the current collector or a partial area of the current collector. The present application has no special limitation on this, as long as the purpose of the present application can be achieved.

[0061] As an example, the current collector has two surfaces opposite to each other in its own thickness direction, and the coating is disposed on the two opposite surfaces of the current collector. It can be understood that in other embodiments, the coating may also be stacked on any one of the two surfaces of the current collector.

[0062] The active material in the coating of the provided negative electrode tab includes graphite and a silicon-based material, and the relationship between the pore tortuosity of the negative electrode tab, the content of the silicon-based material, the content of the graphite, and the apparent density of the negative electrode tab is defined. It can be applied in batteries such as lithium-ion batteries, further can be applied in cylindrical lithium-ion batteries, and even further can be applied in cylindrical all-pole-ear lithium-ion batteries to alleviate the problems of poor cycle stability or low rate performance of graphite-silicon anodes in existing cylindrical all-pole-ear lithium-ion batteries.

[0063] Particularly prominent is that in an embodiment of the present application, the negative electrode tab satisfies the following relational expression:

[0064] |M - N| / M ≤ 5%;

[0065] Among them, M is the predicted pore tortuosity of the negative electrode tab, and N is the measured pore tortuosity of the negative electrode tab;

[0066] M satisfies:

[0067] 0.3 ≤ M ≤ 4, and M = (5 × lg a) + (e 8×(1-b)×c-1); As an example, M can be any one of the point values such as 0.35, 0.5, 0.8, 1, 1.2, 1.5, 1.8, 2, 2.5, 3, 3.5, 3.8, 3.9, etc. or the range value between any two of them.

[0068] Wherein, a is the apparent density of the negative electrode plate, and the unit is g / cm 3 ;

[0069] b is the mass percentage of graphite in the coating;

[0070] c is the mass percentage of the silicon-based material in the coating.

[0071] Thus, in this application, by making the content of the silicon-based material, the content of graphite, and the apparent density of the negative electrode plate satisfy the above function relationship, and using the function relationship formed by the content of the silicon-based material, the content of graphite, and the apparent density of the negative electrode plate to characterize the predicted pore tortuosity of the negative electrode plate, that is, the present invention predicts or estimates the pore tortuosity of the negative electrode plate, and uses the special relationship formed by the content of the silicon-based material, the content of graphite, and the apparent density of the negative electrode plate to characterize the predicted pore tortuosity of the negative electrode plate. Moreover, the pore tortuosity of the negative electrode plate is also measured actually. By making the difference between the predicted pore tortuosity and the actually measured pore tortuosity of the negative electrode plate not exceed 5%, it shows the accuracy of the predicted pore tortuosity of the present invention. Furthermore, by making the pore tortuosity within a suitable range, and making the content of the silicon-based material, the content of graphite, and the apparent density of the negative electrode plate all within suitable ranges, the rate performance or cycle performance of the battery using the negative electrode plate can be improved, and the problem that the pore tortuosity of the negative electrode plate is likely to increase and the corresponding rate performance or cycle performance of the battery is poor after the silicon-based material and graphite are compounded in the existing battery can be avoided.

[0072] The inventors of the present application have found through extensive research that there is a certain correlation between the content of silicon-based materials, the content of graphite, and the apparent density of the negative electrode sheet and the pore tortuosity of the negative electrode sheet. When the content of silicon-based materials in the coating increases, due to the volume change characteristics of silicon-based materials during charge and discharge, it will promote the change of the pore structure inside the negative electrode sheet, resulting in an upward trend in pore tortuosity. This makes the transmission path of lithium ions inside the electrode more complex, and to a certain extent affects the charge and discharge efficiency of the battery. When the content of graphite in the coating increases, while optimizing electron conduction, it will also act on the pore structure of the electrode sheet. Therefore, an appropriate amount of graphite can fill some pores, reduce the pore tortuosity, and improve the smoothness of ion transmission. However, too high a graphite content may prevent the advantages of silicon-based materials from being fully exerted, affecting the overall energy density performance of the battery. In addition, the change in the apparent density of the negative electrode sheet is also closely related to the pore tortuosity. As the apparent density increases, the compaction degree inside the electrode sheet increases, the number of pores decreases and the pore diameter becomes smaller, and the pore tortuosity increases significantly. This not only hinders the diffusion of lithium ions but also increases the internal resistance of the electrode. On the contrary, when the apparent density decreases, the number of pores increases, and although the pore tortuosity decreases, too low an apparent density will result in insufficient loading of active substances, which is also not conducive to improving the battery performance. Therefore, precisely regulating the content of silicon-based materials, the content of graphite, and the apparent density of the negative electrode sheet in the coating to achieve an ideal balance state is of crucial significance for optimizing the pore tortuosity of the negative electrode sheet and then improving the comprehensive performance of the battery, such as energy density, cycle life, and charge and discharge rate, etc.

[0073] The term "pore tortuosity (i.e., tortuosity)" represents the ratio of the transmission path of lithium ions in the coating (active material layer) to the layer thickness.

[0074] It should be understood that the coating in the negative electrode sheet usually has a microporous structure, and this microporous structure has a certain tortuosity. Therefore, the pore tortuosity of the negative electrode sheet in the present application refers to the pore tortuosity of the microporous structure of the coating in the negative electrode sheet, and can also be referred to as the tortuosity of the negative electrode sheet.

[0075] Generally, the smaller the pore tortuosity, the looser the coating is, which is more conducive to the transport of lithium ions. Because a smaller pore tortuosity means a shorter and more direct transport path of lithium ions within the coating, enabling them to move more efficiently within the electrode. When the pore tortuosity is too large, the transport path of lithium ions becomes complex and long, and at the same time, the electronic conductivity will decrease sharply, resulting in an increase in battery impedance and seriously affecting the rate performance of the battery. On the contrary, the coating structure with a large pore tortuosity is relatively dense. Although it is conducive to maintaining structural stability to a certain extent, it is not conducive to the rapid transport of lithium ions. The coating with a small pore tortuosity, due to its relatively loose structure, is more conducive to the solid-phase transport of lithium ions during the battery cycling process, enabling lithium ions to be inserted into and extracted from the electrode material more smoothly. Therefore, it is necessary to control the pore tortuosity of the negative electrode plate within a suitable range, neither too large nor too small. Furthermore, in this application, by making the pore tortuosity of the negative electrode plate within the above-mentioned suitable range and making the difference between the predicted pore tortuosity and the measured pore tortuosity of the negative electrode plate less than 5%, the battery performance can be effectively improved. This can not only make the capacity retention rate of the battery relatively high during cycling at high rates, but also facilitate more uniform lithium intercalation in the negative electrode during battery charging, thereby enabling the battery to have a relatively high capacity and energy density.

[0076] In addition, tortuosity is a parameter for evaluating the microstructure of porous materials. It represents the ratio of the actual length of the transport path of a porous structure with a length of L to the shortest straight-line length, reflecting the complexity of the transport path. Therefore, the degree of complete wetting of the electrolyte can also be indirectly characterized by tortuosity. For example, when different electrolytes are injected into the same battery and the tortuosity reaches a stable value, the smaller the value of the tortuosity, the better the wettability of the corresponding electrolyte. Because a smaller tortuosity means that the electrolyte can penetrate into the porous structure more smoothly, occupy more pore spaces, and achieve more complete wetting.

[0077] The term "apparent density" refers to the ratio of the mass of a material (electrode plate) to its apparent volume.

[0078] In this application, the apparent density of the negative electrode plate can be the apparent density of the negative electrode plate after disassembly. For example, the apparent density of the negative electrode plate after disassembling the battery containing the negative electrode plate at a charging state of 0% SOC.

[0079] As an example, disassemble the battery containing the negative electrode plate at a charging state of 0% SOC, take out the negative electrode plate, clean and dry the negative electrode plate to a constant weight, measure the apparent volume of the negative electrode plate (calculate the volume of the electrode plate by measuring the length, width and height of the electrode plate with a micrometer caliper) and the mass (weigh with an electronic balance), and the apparent density of the negative electrode plate can be obtained.

[0080] In a preferred embodiment of the present application, the negative electrode sheet satisfies: |M - N| / M < 5%, for example, |M - N| / M can be 4.5%, 4%, 3.5%, 3%, 2.5%, 2%, 1.5%, 1% or less than 1%, etc.

[0081] In a preferred embodiment of the present application, M satisfies: 0.3 < M = (5 × lg a) + (e 8×(1-b)×c - 1) < 4.

[0082] It should be noted that in the coating of the negative electrode sheet, the specific types of the silicon-based material and graphite are not limited and can be set according to the conventional selection in the art.

[0083] As an example, in some embodiments, the graphite can be selected from one or a combination of artificial graphite, natural graphite, and modified graphite. The graphite can be further modified, and there is no specific limitation on the modification method of the graphite. For example: coating modification is carried out on the surface of the graphite.

[0084] As an example, in some embodiments, the silicon-based material can be selected from one or more of elemental silicon, silicon oxide, silicon-carbon material, silicon nitride composite, or silicon alloy material. Among them, the elemental silicon can be, for example, nanosilicon. The silicon-carbon material can be, for example, a silicon-carbon composite of nanosilicon-carbon, or the silicon-carbon material includes a silicon-carbon body and a carbon coating layer coated on the surface of the silicon-carbon body. In some embodiments, the silicon-oxygen material can be, for example, one or more of silicon monoxide, prelithiated silicon monoxide, or premagnesiated silicon monoxide.

[0085] The present invention does not limit the shapes of the graphite and the silicon-based material. As an example, the shapes of the graphite particles and the silicon-based material are selected from one or more of blocky, quasi-spherical, and spherical. The shape of the particles will affect the tap density.

[0086] In some embodiments, the mass percentage content of graphite in the coating is b, and b satisfies: 64% ≤ b ≤ 96%, that is, the range of b is 64% to 96%, preferably 75% to 90%; for example, it can be any point value among 64%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 96% or the range value between any two of them.

[0087] By uniformly mixing the graphite and the silicon-based material, the negative electrode active material can be obtained. The addition amount of graphite in the negative electrode active material is a key factor determining the performance of the negative electrode material. Controlling its dosage can optimize the overall comprehensive performance of the battery. When the proportion content of graphite is too high, the advantages of the silicon-based material are difficult to fully play, and the improvement of the energy density of the battery is limited. On the contrary, when the proportion content of graphite is too low, the stability of the negative electrode material may decrease, and problems such as volume expansion are likely to occur during charge and discharge, resulting in a shortened cycle life of the battery.

[0088] In some embodiments, the mass percentage content of the silicon-based material in the coating is c, and c satisfies: 2% ≤ b ≤ 28%, that is, the range of c is 2% to 28%, preferably 5% to 25%; for example, it can be any one of the point values of 2%, 3%, 4%, 5%, 8%, 10%, 15%, 20%, 25%, 28% or the range value between any two of them.

[0089] Graphite and the silicon-based material are uniformly mixed to obtain the negative electrode active material. The addition amount of the silicon-based material in the negative electrode active material is a key factor determining the performance and application prospects of the negative electrode material. Controlling its dosage can balance the various performance indicators of the battery as a whole. When the proportion content of the silicon-based material is too high, the volume expansion effect of the material during charge and discharge will be significantly enhanced, resulting in easy damage to the electrode structure, thereby reducing the cycle stability and service life of the battery, and may also increase the internal resistance of the battery, affecting the charge and discharge efficiency of the battery. On the contrary, when the proportion content of the silicon-based material is too low, the advantage of the high theoretical specific capacity of the silicon-based material cannot be fully exerted, and the energy density of the battery is not significantly improved, making it difficult to meet the requirements of high energy density battery application scenarios.

[0090] In some embodiments, the mass percentage content of the negative electrode active material in the coating is x, and x satisfies: 92% ≤ x ≤ 98%, that is, the total mass percentage content of graphite and the silicon-based material in the coating is x, and the range of x is 92% to 98%. For example, it can be any one of the point values of 92%, 93%, 94%, 95%, 96%, 97%, 98% or the range value between any two of them.

[0091] In some embodiments, the mass ratio of the silicon-based material to graphite is (3 to 30):(70 to 97); as an example, the mass ratio of the silicon-based material to graphite can be 3:97, 10:90, 15:85, 20:80, 25:75, 30:70, etc. Thus, by making the ratio of the silicon-based material to graphite within the above range, during the process of volume expansion of the negative electrode, the stress can be well released, reducing the possibility of silicon particles cracking, and thus facilitating the improvement of the cycle performance and rate performance of the battery.

[0092] In some embodiments, the average particle size range of graphite is 3 μm to 30 μm; for example, it can be any one of the point values of 3 μm, 5 μm, 6 μm, 8 μm, 10 μm, 12 μm, 15 μm, 18 μm, 20 μm, 25 μm, 30 μm or the range value between any two of them.

[0093] In some embodiments, the average particle size of the silicon-based material ranges from 3 μm to 30 μm; for example, it can be any one of the point values of 3 μm, 5 μm, 6 μm, 8 μm, 10 μm, 12 μm, 15 μm, 18 μm, 20 μm, 25 μm, 30 μm or the range value between any two of them.

[0094] It should be understood that the particle size of the graphite material and the silicon-based material are closely related, which will have a certain impact on the coating structure, the rate performance of the battery, and the cycling performance. Especially for the negative electrode sheet containing a combination of silicon and graphite, if the particle sizes of the graphite material and the silicon-based material are relatively small, it is easy to cause the space between the graphite material and the silicon-based material to be too tight. During the charging and lithium intercalation process, the change in the silicon-based material is large, and the mechanical stress generated by the huge volume expansion cannot be released, resulting in the material being brittle and cracked easily; in addition, if the particle sizes of the graphite material and the silicon-based material are relatively large, the distance between the graphite material and the silicon-based material is too far, which is likely to lead to a decline in the rate performance and cycling performance of the battery.

[0095] In some embodiments, the coating in the negative electrode sheet usually further includes a conductive agent, a binder, and an optional thickener. That is, the coating mainly includes a negative electrode active material, a conductive agent, a binder, and an optional thickener. This application mainly makes improvements to the negative electrode active material, and does not limit the specific types of the conductive agent, the binder, and the thickener. As an example, optionally, the conductive agent can be one or a combination of more than one of, including but not limited to, graphite conductive agents, carbon black conductive agents, polymer conductive agents, polymeric conductive agents, branched conductive agents, one-dimensional chain conductive agents, two-dimensional sheet conductive agents, three-dimensional spherical conductive agents, etc. More specifically, it can be one or a combination of more than one of, including but not limited to, conductive graphite, acetylene black, Ketjen black, superconducting carbon black, carbon nanotubes, carbon fibers, graphene, polyacetylene, polypyrrole, etc. Optionally, the binder and the thickener can be one or a combination of more than one of, including but not limited to, polyvinylidene fluoride, polytetrafluoroethylene, styrene-butadiene rubber, polyvinyl alcohol, polyacrylonitrile, polyimide, polyacrylic acid, polyacrylate, carboxymethyl cellulose (sodium carboxymethyl cellulose), sodium alginate, etc.

[0096] In some embodiments, the apparent density of the negative electrode sheet is a, and a satisfies: 1.05 ≤ a ≤ 1.8, with the unit of g / cm 3 ; as an example, a can be 1.05 g / cm 3 、1.1 g / cm 3 、1.2 g / cm 3 、1.3 g / cm 3 、1.4 g / cm 3 、1.5 g / cm 3 、1.6 g / cm 3 、1.7 g / cm 3 、1.8 g / cm 3Any one of the point values or the range values between any two of them.

[0097] By making the apparent density of the negative electrode sheet within the above range, it is beneficial to the battery performance and the quality of the electrode sheet. If the apparent density is too large, it will lead to: reduced specific capacity, increased internal resistance, deteriorated cycling performance, and poor appearance and mechanical properties of the electrode sheet; if the apparent density is too small, it will lead to: reduced energy density, limited charge-discharge efficiency, poor cycling stability, and increased thickness resulting in assembly problems.

[0098] In some embodiments, N satisfies: N = (N1 + N2 + N3 + N4 + N5) / 5; where, when the battery including the negative electrode sheet is in a charged state of 0% SOC, the disassembled negative electrode sheet is divided into five equal parts, and the middle positions of the five regions are taken to test and calculate the pore tortuosity of each region, which are respectively denoted as N1, N2, N3, N4, and N5.

[0099] As an example, when applying this negative electrode sheet in a battery, the battery using this negative electrode sheet is disassembled to obtain the negative electrode sheet in a charged state of 0% SOC. The disassembled negative electrode sheet is evenly divided into five parts, that is, evenly divided into five regions, such as region 1, region 2, region 3, region 4, and region 5. Then, the middle position of each region is taken for measurement and calculation to obtain the pore tortuosity of each region, and the obtained values are respectively denoted as N1, N2, N3, N4, and N5. Then, by calculating the average value of the pore tortuosity of these five regions, the average pore tortuosity of the entire negative electrode sheet can be obtained, that is, the measured pore tortuosity N of the negative electrode sheet.

[0100] In some embodiments, N1, N2, N3, N4, and N5 are calculated by the following formula: N i = (R ion × A × ε × σ) / d; where, i is 1, 2, 3, 4, 5, R ion is the pore impedance of the negative electrode sheet, A is the area of the electrode sheet corresponding to the middle circular hole (small circular hole) when measuring the pore impedance of the negative electrode sheet, σ is the conductivity of the electrolyte in the battery including the negative electrode sheet, ε is the porosity of the coating, and d is the thickness of the coating on one side.

[0101] In some embodiments, R ion satisfies: 2 ≤ R ion ≤ 10, with the unit of Ω; preferably, 2 < R ion < 10. As an example, R ion can be 3 Ω, 4 Ω, 5 Ω, 6 Ω, 7 Ω, 8 Ω, 9 Ω, etc.

[0102] In some embodiments, R ion satisfies: R ion= (R1 + R2 + R3 + R4 + R5) / 5; where, when the battery including the negative electrode plate is at a state of charge of 0% SOC, the disassembled negative electrode plate is divided into five equal parts, and the middle positions of the five regions are taken to measure the pore impedance of each region, which are respectively denoted as R1, R2, R3, R4, and R5.

[0103] As an example, apply this negative electrode plate in a battery. When the battery using this negative electrode plate is at a state of charge of 0% SOC, disassemble the battery to obtain the negative electrode plate. Divide the disassembled negative electrode plate into five equal parts, that is, divide it into five regions, such as Region 1, Region 2, Region 3, Region 4, and Region 5. Then, take the middle position of each region to measure its pore impedance, and the obtained values are respectively denoted as R1, R2, R3, R4, and R5. Then, by calculating the average value of the pore impedance of these five regions, the average pore impedance R of the entire negative electrode plate can be obtained. ion .

[0104] In some embodiments, A satisfies: 1 ≤ A ≤ 15, with the unit of cm 2 ; for example, A can be 1 cm 2 , 2 cm 2 , 4 cm 2 , 5 cm 2 , 6 cm 2 , 8 cm 2 , 10 cm 2 , 12 cm 2 , 15 cm 2 or any range value between any two of these values.

[0105] When the negative electrode plate is in a wound structure, the electrode plate area A is the electrode plate area of the region corresponding to one tab.

[0106] In some embodiments, d satisfies: 20 ≤ d ≤ 150, with the unit of μm; for example, d can be any one of 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 80 μm, 100 μm, 120 μm, 150 μm or any range value between any two of these values.

[0107] In some embodiments, σ satisfies: 5 ≤ σ ≤ 20, with the unit of mS / cm; for example, σ can be any one of 5 mS / cm, 6 mS / cm, 8 mS / cm, 10 mS / cm, 12 mS / cm, 15 mS / cm, 20 mS / cm or any range value between any two of these values.

[0108] In some embodiments, the porosity of the coating is ε, and ε satisfies: 10%≤ε≤50%, that is, the range of ε is 10% to 50%; for example, it can be any point value among 10%, 20%, 30%, 40%, 50% or a range value between any two of them.

[0109] In the negative electrode sheet, the porosity of the coating will affect the transmission capacity of electrons and ions and the infiltration speed of the electrolyte. When the coating contains more small pores, the transmission path of electrons and ions will increase, the transmission rate will decrease, and the electrode rate performance will decrease. Although the high porosity of the coating can relieve the stress in electrodes with large volume changes such as silicon-based electrodes, the pores will make the proportion of active materials low, resulting in a decrease in the energy density of the battery. In the present application, by making the porosity of the coating within the above range, the energy density of the battery can be increased as much as possible while ensuring the electrode rate performance, and the stress of large volume change electrodes such as silicon-based electrodes during the charging and discharging process can be effectively relieved, thereby improving the overall performance and stability of the battery.

[0110] In some embodiments, the negative electrode plate is a wound structure plate.

[0111] In view of the problems of large internal resistance or poor rate performance of existing cylindrical battery products, the negative electrode plate of the present application is more preferably used in cylindrical batteries, that is, the present application predicts the pore tortuosity of the negative electrode plate by limiting the characteristic parameters of the silicon-based material and graphite in the negative electrode plate of the winding structure and the relationship between the apparent density of the plate, and by ensuring that the difference between the predicted pore tortuosity and the measured pore tortuosity does not exceed 5%, the pore tortuosity of the negative electrode plate is within an appropriate range, thereby avoiding the problem that the increase in pore tortuosity leads to increased polarization and affects the rate performance of the cylindrical battery, which is beneficial to improving the rate performance of the negative electrode plate and realizing high-rate charging and discharging of full-ear lithium-ion cylindrical batteries.

[0112] like Figure 1 and Figure 2 As shown, in some embodiments, the present application provides a cylindrical battery, which includes a cylindrical battery cell, the cylindrical battery cell includes the aforementioned negative electrode plate 102, and also includes a positive electrode plate 101, a diaphragm 103 and an electrolyte, and the diaphragm 103 is located between the positive electrode plate 101 and the negative electrode plate 102.

[0113] Optionally, the cylindrical battery is a lithium-ion battery with a cylindrical structure.

[0114] It should be noted that, in the specific implementation manner, the present application is explained by taking a lithium-ion battery as an example of a secondary battery, but the battery of the present application is not limited to a lithium-ion battery.

[0115] Since the cylindrical battery provided in the second aspect of the embodiments of the present invention adopts all the technical solutions of the negative electrode tab in the first aspect, it has at least all the beneficial effects brought by the technical solutions of the above embodiments, which will not be elaborated one by one herein.

[0116] In some embodiments, the porosity of the separator 103 ranges from 30% to 48%; preferably, the porosity of the separator ranges from 33% to 48%; more preferably, the porosity of the separator ranges from 36% to 45%. For example, the porosity of the separator can be any one of the point values of 30%, 33%, 35%, 36%, 38%, 40%, 45%, 48% or the range value between any two of them. A separator with a reasonable porosity is beneficial to improving the cycle and safety performance of the battery. When the porosity of the separator is too low, the ion diffusion impedance will increase, causing cycle deterioration; when the porosity of the separator is too high, the diffusion rate of metal ions will increase, and the mechanical reliability of the separator will be reduced, resulting in cycle deterioration and safety failure.

[0117] In some embodiments, the positive electrode tab 101, the separator 103 and the negative electrode tab 102 can be wound in sequence to form a core 104; as an example, the cylindrical battery core includes a full-tab cylindrical core 104 formed by interleaved winding of the positive electrode tab 101, the separator 103 and the negative electrode tab 102. One end of the full-tab cylindrical core 104 is the negative full-tab end face, and the other end is the positive full-tab end face.

[0118] Optionally, the above cylindrical battery further includes a housing 30, with a positive terminal 10 provided at one end of the housing 30 and a negative terminal 20 provided at the other end of the housing 30.

[0119] In this embodiment, for the positive electrode tab, the specific materials, structures, etc. of the positive current collector and the positive active material layer are not limited, and the positive electrode tab structures and components known to those skilled in the art and applicable to secondary batteries can be selected.

[0120] In the present application, the electrolyte may include organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes or molten inorganic electrolytes that can be used to manufacture lithium secondary batteries, but are not limited thereto. As an example, the electrolyte is an electrolyte solution, which may include organic solvents and lithium salts. The present application has no special restrictions on the organic solvents, electrolyte salts, etc. in the electrolyte solution. Those skilled in the art can select according to actual needs as long as the purpose of the present application can be achieved.

[0121] In some embodiments, the diameter of the cylindrical battery core is 15 mm to 50 mm, and the length of the cylindrical battery core is 60 mm to 150 mm.

[0122] In some embodiments, the present application provides an electrical device, which includes the aforementioned negative electrode sheet or the aforementioned cylindrical battery.

[0123] Optionally, the electrical device may be an Electric Vertical Take off and Landing (EVTOL) aircraft.

[0124] It should be understood that the battery provided by the present invention can be applied in EVTOLs, but is not limited thereto. Other electrical devices with the same or similar requirements can also use the battery provided by the present invention. For example, the electrical device can also be a mobile phone, a tablet computer, a laptop computer, an e-book player, an electric toy, an electric tool, a lighting fixture, a vehicle such as a battery car, an electric vehicle, an electric bicycle, an electric truck, etc., a ship, other aircraft, an energy storage system, and other electrical devices.

[0125] To further illustrate the present invention, the battery of the present invention will be described in detail below in conjunction with embodiments. All reagents used in the following embodiments are commercially available.

[0126] Example 1

[0127] 1. Preparation of the negative electrode sheet

[0128] Mix the negative electrode active material artificial graphite, silicon-based material (silicon-oxygen material), conductive agent acetylene black, thickening agent carboxymethyl cellulose (CMC), and binder polyacrylic acid (PAA) in a mass ratio of 90:6:1:1:2, add deionized water and stir to form a uniformly mixed and stable negative electrode paste, and the solid content of the negative electrode paste is 40%; uniformly coat the negative electrode paste on the negative electrode current collector copper foil, and then obtain the negative electrode sheet after drying and cold pressing.

[0129] In the negative electrode sheet, the mass percentage content b of graphite in the coating is 90%; the mass percentage content c of the silicon-based material in the coating is 6%; the apparent density a of the negative electrode sheet is 1.5 g / cm 3 .

[0130] 2. Preparation of the positive electrode sheet

[0131] Mix the positive electrode active material high-nickel ternary material, conductive agent conductive carbon black (SP), and binder polyvinylidene fluoride (PVD) in a mass ratio of 96:1:3, then add N-methylpyrrolidone (NMP), stir and mix evenly to form a stable positive electrode paste, and the solid content of the positive electrode paste is 68%; uniformly coat the positive electrode paste on the positive electrode current collector aluminum foil with a thickness of 12 μm, and then obtain the positive electrode sheet after drying and cold pressing.

[0132] 3. Preparation of the electrolyte

[0133] In a glove box filled with inert gas, EC:FEC:EMC:DMC = 15:15:20:50 was mixed in proportion to obtain an organic solvent. Then, the fully dried lithium salt LiPF 6 was dissolved in the mixed organic solvent to prepare an electrolyte solution with a concentration of 1 mol / L.

[0134] 4. Separator

[0135] A polyethylene porous separator with a thickness of 12 μm was used.

[0136] 5. Preparation of lithium-ion battery

[0137] After the positive and negative electrode sheets were respectively roll-pressed and slit, they were wound together with the separator to obtain a 21700 cylindrical battery cell. Subsequently, after the cylindrical battery cell was welded to the connecting piece, it was installed in the battery case. After the processes of injecting electrolyte, sealing, and formation were completed, an experimental test battery was obtained. The size of the cylindrical battery case was: diameter 50 mm, length 150 mm.

[0138] Example 2

[0139] The preparation of the battery in Example 2 was basically the same as that in Example 1, except that:

[0140] In the negative electrode sheet, the mass percentage content b of graphite in the coating was 70%; the mass percentage content c of the silicon-based material in the coating was 26%.

[0141] The rest were the same as those in Example 1.

[0142] Example 3

[0143] The preparation of the battery in Example 3 was basically the same as that in Example 1, except that:

[0144] In the negative electrode sheet, the mass percentage content b of graphite in the coating was 80%; the mass percentage content c of the silicon-based material in the coating was 16%.

[0145] The rest were the same as those in Example 1.

[0146] Example 4

[0147] The preparation of the battery in Example 4 was basically the same as that in Example 1, except that:

[0148] The apparent density of the silicon negative electrode sheet was 1.2 g / cm 3 .

[0149] The rest were the same as those in Example 1.

[0150] Example 5

[0151] The preparation of the battery of Example 5 is basically the same as that of Example 1, except that:

[0152] The apparent density of the silicon negative electrode sheet is 1.3 g / cm 3 .

[0153] The rest are the same as those of Example 1.

[0154] Example 6

[0155] The preparation of the battery of Example 6 is basically the same as that of Example 1, except that:

[0156] The apparent density of the silicon negative electrode sheet is 1.7 g / cm 3 .

[0157] The rest are the same as those of Example 1.

[0158] Example 7

[0159] The preparation of the battery of Example 7 is basically the same as that of Example 1, except that:

[0160] In the negative electrode sheet, the mass percentage content b of graphite in the coating is 65%; the mass percentage content c of the silicon-based material in the coating is 31%.

[0161] The rest are the same as those of Example 1.

[0162] Example 8

[0163] The preparation of the battery of Example 8 is basically the same as that of Example 1, except that:

[0164] In the negative electrode sheet, the mass percentage content b of graphite in the coating is 94%; the mass percentage content c of the silicon-based material in the coating is 2%.

[0165] The rest are the same as those of Example 1.

[0166] Comparative Example 1

[0167] The difference between this comparative example and Example 1 is that the apparent density c of the silicon negative electrode sheet is 1.0 g / cm 3 ;

[0168] The others are the same as those of Example 1.

[0169] Comparative Example 2

[0170] The difference between this comparative example and Example 1 is that the apparent density c of the silicon negative electrode sheet is 1.9 g / cm 3 ;

[0171] The others are the same as those of Example 1.

[0172] Comparative Example 3

[0173] The difference between this comparative example and Example 1 is that the mass percentage b of artificial graphite added during the preparation of the silicon negative electrode sheet is 50%, and the mass percentage c of the silicon-based material is 46%;

[0174] Others are the same as those in Example 1.

[0175] The main difference parameters of the above examples and comparative examples are shown in Table 1 below.

[0176] Performance Test

[0177] Perform relevant performance tests on the above negative electrode sheets and batteries, specifically including:

[0178] (1) Test of the content of graphite and silicon-based materials:

[0179] Analyze by using inductively coupled plasma mass spectrometry (ICP-MS). Convert the sample into plasma to ionize the elements, and then determine the element types and contents by analyzing the ion mass-to-charge ratio and intensity with a mass spectrometer.

[0180] (2) Apparent density test of the negative electrode sheet:

[0181] Measurement of the sheet mass: Weigh the mass of the negative electrode sheet of a certain size 5 times with an electronic balance and take the average value, denoted as m1 (unit: g). After wiping off the coating on the surface of the sheet with deionized water, measure the mass of the same-sized foil 5 times and take the average value, denoted as m2 (unit: g).

[0182] Measurement of the sheet size: Cut the sheet into a rectangle and measure its length L (unit: cm), width W (unit: cm), and thickness T (unit: cm) with a vernier caliper.

[0183] Calculate its apparent density according to the formula apparent density = (m1 - m2) / (L × W × T), and the unit is g / cm 3 .

[0184] (3) Pore tortuosity test and calculation method:

[0185] The pore tortuosity is calculated using the following formula: N = (R ion × A × ε × σ) / d;

[0186] where N is the pore tortuosity; R ion is the pore impedance of the sheet; A is the sheet area; ε is the sheet porosity; σ is the electrolyte conductivity; d is the single-sided thickness of the sheet. The measurement temperature of the pore impedance of the sheet and the electrolyte conductivity is 25 ± 2 °C.

[0187] The R of the above examples and comparative examples ion, The specific numerical values of A, ε, σ, and d are shown in Table 2 below.

[0188] (4) Preparation of symmetric soft-pack batteries:

[0189] Cut a circular hole with a diameter of 14 mm in the middle of the high-temperature insulating tape. Stack the negative electrode sheet, separator, high-temperature insulating tape, and negative electrode sheet in sequence, weld the negative electrode tab, and obtain an electrode assembly. Among them, the number of layers of the negative current collector is 2, the number of layers of the separator is 1, and the number of layers of the high-temperature insulating tape is 1. Place the electrode assembly in the outer packaging aluminum-plastic film, inject the electrolyte, and obtain a symmetric soft-pack battery.

[0190] (5) Hole impedance test method:

[0191] Use an electrochemical workstation to test the electrochemical impedance spectrum (EIS) of the above symmetric soft-pack battery in the test frequency range of 1 Hz - 100 kHz, and obtain the hole impedance of the above symmetric soft-pack battery through EIS.

[0192] (6) Rate performance test method:

[0193] Place the cylindrical battery in a 25°C constant temperature oven for 4 h and test it according to the following steps:

[0194] 1) Constant current charge to 4.2 V under the condition of 0.1C and stand for 10 min; 2) Constant current discharge to 2.5 V cut-off under the condition of 0.1C and stand for 10 min; 3) Constant current charge to 4.2 V under the condition of 0.5C and stand for 10 min; 4) Constant current discharge to 2.5 V cut-off under the condition of 0.1C and stand for 10 min; 5) Constant current charge to 4.2 V under the condition of 1C and stand for 10 min; 6) Constant current discharge to 2.5 V cut-off under the condition of 0.1C and stand for 10 min; 7) Constant current charge to 4.2 V under the condition of 2C and stand for 10 min; 8) Constant current discharge to 2.5 V cut-off under the condition of 0.1C and stand for 10 min; 9) Constant current charge to 4.2 V under the condition of 3C and stand for 10 min; 10) Constant current discharge to 2.5 V cut-off under the condition of 0.1C and stand for 10 min; 11) Constant current charge to 4.2 V under the condition of 4C and stand for 10 min; 12) Constant current discharge to 2.5 V cut-off under the condition of 0.1C and stand for 10 min; 13) Constant current charge to 4.2 V under the condition of 5C and stand for 10 min; 14) Constant current discharge to 2.5 V cut-off under the condition of 0.1C and stand for 10 min; 15) Constant current charge to 4.2 V under the condition of 6C and stand for 10 min; 16) Constant current discharge to 2.5 V cut-off under the condition of 0.1C and stand for 10 min.

[0195] The rate performance test results of the above embodiments and comparative examples are shown in Table 3 below.

[0196] Table 1 Parameters related to a, b, c, M, and N in Examples 1-8 and Comparative Examples 1-3

[0197]

[0198]

[0199] Table 2 R in Examples 1-8 and Comparative Examples 1-3 ion , A, ε, σ, d related parameters

[0200]

[0201]

[0202] Table 3 Electrical properties of various embodiments and comparative examples

[0203]

[0204]

[0205] From the data in Tables 1 and 3 above, it can be seen that |MN| / M=1.37% in Example 1, |MN| / M=2.63% in Example 2, |MN| / M=2.94% in Example 3, |MN| / M=1.47% in Example 4, |MN| / M=1.04% in Example 5, |MN| / M=0.53% in Example 6, |MN| / M=4.42% in Example 7, and |MN| / M=2.25% in Example 8. However, |MN| / M=800% in Comparative Example 1, |MN| / M=102.78% in Comparative Example 2, and |MN| / M=59.40% in Comparative Example 3. It can be seen that the negative electrode sheets in Examples 1-8 of the present invention all satisfy |MN| / M≤5%, so that the battery containing the negative electrode sheet obtains good rate performance and cycle performance. However, the |MN| / M of the negative electrode plates in Comparative Examples 1-3 far exceeds 5%, resulting in poor rate performance or cycle performance of the corresponding batteries.

[0206] Parts of the present invention that are not described in detail are well known to those skilled in the art.

[0207] The basic principles of the present invention have been described above in connection with specific embodiments. However, it should be noted that the advantages, benefits, effects, etc. mentioned in the present invention are merely examples and not limitations. It cannot be considered that these advantages, benefits, effects, etc. are essential for each embodiment of the present invention. In addition, the above-disclosed specific details are only for illustrative purposes and for ease of understanding, rather than limitations. The above details do not limit the present invention to necessarily adopt the above specific details for implementation.

[0208] It should be noted that the term "and / or" or " / " used herein is merely a description of the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B may mean: A exists alone, A and B exist simultaneously, and B exists alone. The singular forms "a", "the", and "said" used in the embodiments of the present invention and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise.

[0209] In the specific embodiments and the claims, a list of items connected by the terms "at least one of", "at least one in", "at least one kind in", or other similar terms may mean any combination of the listed items. For example, if items A and B are listed, then the phrase "at least one of A and B" means only A; only B; or A and B. In another example, if items A, B, and C are listed, then the phrase "at least one of A, B, and C" means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C. Item A may include a single element or multiple elements. Item B may include a single element or multiple elements. Item C may include a single element or multiple elements.

[0210] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A negative electrode plate, characterized in that: The negative electrode plate comprises a current collector and a coating disposed on at least one side of the current collector, wherein the coating comprises a negative electrode active material, wherein the negative electrode active material comprises graphite and a silicon-based material; the negative electrode plate satisfies: |MN| / M≤5%; Wherein, M is the predicted pore tortuosity of the negative electrode pole piece, and N is the measured pore tortuosity of the negative electrode pole piece; The M satisfies: 0.3≤M=(5×lg a)+(e 8×(1-b)×c -1)≤4; Wherein, a is the apparent density of the negative electrode sheet, in g / cm 3 ; b is the mass percentage of the graphite in the coating; c is the mass percentage of the silicon-based material in the coating.

2. The negative electrode sheet according to claim 1, characterized in that: The negative electrode sheet satisfies: |MN| / M<5%; and / or, The M satisfies: 0.3<M=(5×lg a)+(e 8×(1-b)×c -1)<4。 3. The negative electrode sheet according to claim 1, characterized in that: The N satisfies: N = (N1 + N2 + N3 + N4 + N5) / 5; Among them, when the battery containing the negative electrode plate is in the state of 0% SOC, the disassembled negative electrode plate is divided into five equal areas, and the middle positions of the five areas are taken for testing and the hole tortuosity of each area is calculated, which are respectively recorded as N1, N2, N3, N4 and N5.

4. The negative electrode sheet according to claim 3, characterized in that: The N1, N2, N3, N4 and N5 are calculated by the following formula: N i =(R ion ×A×ε×σ) / d; Among them, R ion is the hole impedance of the negative electrode plate, A is the plate area corresponding to the middle circular hole when measuring the hole impedance of the negative electrode plate, σ is the conductivity of the electrolyte in the battery containing the negative electrode plate, ε is the porosity of the coating, and d is the thickness of the coating on one side.

5. The negative electrode sheet according to claim 4, characterized in that: The R ion satisfy: 2≤R ion ≤10; and / or, The R ion satisfy: R ion =(R1+R2+R3+R4+R5) / 5; Among them, when the battery containing the negative electrode plate is in the state of 0% SOC, the disassembled negative electrode plate is divided into five equal areas, and the middle positions of the five areas are taken to test to obtain the hole impedance of each area, which are respectively recorded as R1, R2, R3, R4 and R5.

6. The negative electrode sheet according to claim 4, characterized in that: The A satisfies: 1≤A≤15, unit: cm 2 ; When the negative electrode plate is a winding structure, the plate area A is the plate area corresponding to one pole ear; and / or, The d satisfies: 20≤d≤150, in μm; and / or, The ε satisfies: 10%≤ε≤50%; and / or, The σ satisfies: 5≤σ≤20, and the unit is mS / cm.

7. The negative electrode sheet according to any one of claims 1 to 6, characterized in that: The negative electrode plate satisfies at least one of the following characteristics (1) to (9): (1) a satisfies: 1.05≤a≤1.8, unit is g / cm 3 ; (2) b satisfies: 64%≤b≤96%; (3) c satisfies: 2%≤c≤28%; (4) The mass percentage of the negative electrode active material in the coating is x, and x satisfies: 92％≤x≤98％； (5) The mass ratio of the silicon-based material to graphite is (3-30): (70-97); (6) The silicon-based material includes at least one of elemental silicon, silicon oxide, silicon-carbon material, silicon-nitrogen composite or silicon alloy material; (7) The average particle size of the graphite is in the range of 3 μm to 30 μm; (8) The average particle size of the silicon-based material is in the range of 3 μm to 30 μm; (9) The negative electrode plate is a wound structure plate.

8. A cylindrical battery, comprising a cylindrical cell, characterized in that: The cylindrical battery cell comprises the negative electrode sheet according to any one of claims 1 to 7, and further comprises a positive electrode sheet, a separator and an electrolyte, wherein the separator is located between the positive electrode sheet and the negative electrode sheet.

9. The cylindrical battery according to claim 8, characterized in that: The cylindrical battery cell satisfies at least one of the following characteristics (1) to (4): (1) The porosity of the diaphragm is in the range of 30% to 48% (2) The porosity of the diaphragm is in the range of 36% to 45%; (3) The cylindrical battery cell comprises a full-pole lug cylindrical winding core formed by staggered winding of a positive electrode sheet, a separator and a negative electrode sheet, wherein one end of the full-pole lug cylindrical winding core is a negative electrode full-pole lug end face, and the other end is a positive electrode full-pole lug end face; (4) The diameter of the cylindrical battery core is 15 mm to 50 mm, and the length of the cylindrical battery core is 60 mm to 150 mm.

10. An electrical device, characterized in that: The electrical device comprises the negative electrode sheet as described in any one of claims 1 to 7, or comprises the cylindrical battery as described in any one of claims 8 to 9.

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