Cylindrical battery with pole pieces with concave-convex structures and preparation method of cylindrical battery

Abstract

The invention discloses a cylindrical battery with a pole piece with a concave-convex structure and a preparation method of the cylindrical battery, and belongs to the technical field of cylindrical batteries. According to the invention, the concave-convex pole piece is designed, so that the pore structure and porosity of the diaphragm cannot be changed due to internal stress in the charging process, and the performance of the battery cannot be degraded. Through reasonable calculation, the depths, the widths and the distances of the convex points and the concave pits meet a specific relational expression, and the length change caused by expansion is reasonably compensated by utilizing the thickness change caused by expansion of the pole piece to be matched with the depths and the widths of the convex points, so that the length margin of the diaphragm is proper, diaphragm wrinkles caused by relatively large diaphragm margin are avoided, and the service life of the diaphragm is prolonged. And the change of the pore structure and the porosity caused by small margin can be avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of cylindrical batteries, and in particular to a cylindrical battery having a pole piece with a concave-convex structure and a preparation method thereof. Background Art

[0002] Lithium-ion batteries have been widely used. As people's requirements for performance increase, the demand for long-cycle lithium-ion batteries is getting higher and higher. Among them, cylindrical batteries, as the earliest commercialized lithium-ion batteries, have always been favored by the market.

[0003] As we all know, during the charge and discharge process of lithium-ion batteries, the volume of lithium-ion batteries will change due to the release and embedding of lithium ions in the positive and negative electrodes. The volume of the core in the cylindrical battery will change, especially during the first charge, when the diameter of the core changes greatly. Due to the unique winding structure, the number of turns of the core will not change during the charge and discharge process. As the diameter of the core changes, the length of the positive and negative electrodes and the diaphragm will change subtly. Due to the poor elastic deformation and elastic modulus of the diaphragm, the change in length will cause changes in its own pore structure and porosity, thereby affecting the shuttling of lithium ions during the charge and discharge process. In addition, due to the poor mechanical strength of the diaphragm itself, the diaphragm will wrinkle, thus affecting the battery interface and greatly reducing the battery life.

[0004] In view of this, the present invention is proposed. Summary of the invention

[0005] The object of the present invention is to provide a cylindrical battery having a pole piece with a concave-convex structure and a preparation method thereof, aiming to solve the problem of battery performance degradation caused by changes in the volume of the winding core.

[0006] The present invention is achieved in that:

[0007] In a first aspect, the present invention provides a cylindrical battery having a pole piece with a concave-convex structure, comprising a winding core, the winding core comprising a negative pole piece, a separator and a positive pole piece;

[0008] Multiple convex points are arranged at intervals on both sides of the negative electrode sheet, and multiple concave pits matching the convex points are arranged at intervals on both sides of the positive electrode sheet. The distance between two adjacent convex points and two adjacent concave pits is L0, so that the convex points on the negative electrode sheet fall into the corresponding concave pits on the positive electrode sheet;

[0009] The width of the pit is W1, and the depth of the pit is h1;

[0010] The width of the bump is W2, and the height of the bump is h2;

[0011] h1, h2, W1, W2 and L0 satisfy the following relationship:

[0012] h2=k1×h1;

[0013] W2=k2×W1;

[0014] L0=k3*L / ((2*π*(λ*H)*n) / (h2*2));

[0015] Where:

[0016] k1, k2 and k3 all represent coefficients, k1 is 60%-90%, k2 is 70%-95%, k3 is 80%-120%, and the units of h1, h2, W1 and W2 are all μm;

[0017] L represents the length of the pole piece, in mm;

[0018] λ represents the expansion rate of the negative electrode sheet at 100% SOC state;

[0019] H represents the thickness of the negative electrode sheet at 0% SOC, in μm;

[0020] n represents the number of windings of the winding core.

[0021] In an optional embodiment, k1 is 60%-90%, preferably 75%-85%;

[0022] and / or, k2 is 70%-95%, preferably 75%-85%;

[0023] and / or, k3 is 80%-120%, preferably 95%-105%;

[0024] And / or, the length of the pit of the positive electrode sheet is equal to the width of the positive electrode sheet, and the length of the convex cell of the negative electrode sheet is equal to the width of the negative electrode sheet.

[0025] In an optional implementation, the value of h1 is 2 μm-10 μm.

[0026] In an optional embodiment, the value of W1 is 3 μm-30 μm.

[0027] In an optional embodiment, the expansion rate λ of the negative electrode sheet at 100% SOC state is 8%-35%.

[0028] In an optional embodiment, the thickness H of the negative electrode sheet at 0% SOC is 70 μm-300 μm.

[0029] In an optional embodiment, the number of rolls n of the winding core is 5-300;

[0030] And / or, the length L of the electrode sheet is calculated based on the thickness of the positive electrode sheet, the negative electrode sheet and the separator and the number of winding turns.

[0031] In an optional embodiment, the shape of the protrusions on the negative electrode sheet is n-type, and each protrusion extends from one end in the width direction of the negative electrode sheet to the other opposite end;

[0032] The shape of the pits on the positive electrode sheet is U-shaped, and each pit extends from one end of the positive electrode sheet in the width direction to the other opposite end.

[0033] In an optional embodiment, the negative electrode sheet includes a negative electrode current collector and a negative electrode active coating attached to both sides of the negative electrode current collector, and the active material in the negative electrode active coating is selected from at least one of graphite, silicon-based negative electrode and lithium titanate;

[0034] And / or, the positive electrode sheet includes a positive electrode current collector and a positive electrode active coating attached to both sides of the positive electrode current collector, and the active material in the positive electrode active coating is selected from at least one of lithium cobalt oxide, lithium nickel cobalt manganese oxide and lithium iron phosphate.

[0035] In a second aspect, the present invention provides a method for preparing a cylindrical battery according to any one of the aforementioned embodiments, comprising:

[0036] A negative electrode sheet having a convex point and a positive electrode sheet having a concave point are provided; the distance between two adjacent convex points and two adjacent concave points is L0, the width of the concave point is W1, and the depth of the concave point is h1; the width of the convex point is W2, and the height of the convex point is h2;

[0037] h1, h2, W1, W2 and L0 satisfy the following relationship:

[0038] h2=k1×h1;

[0039] W2=k2×W1;

[0040] L0=k3*L / ((2*π*(λ*H)*n) / (h2*2));

[0041] Where:

[0042] k1, k2 and k3 all represent coefficients, k1 is 60%-90%, k2 is 70%-95%, k3 is 80%-120%, and the units of h1, h2, W1 and W2 are all μm;

[0043] L represents the length of the pole piece, in mm;

[0044] λ represents the expansion rate of the negative electrode sheet at 100% SOC state;

[0045] H represents the thickness of the negative electrode sheet at 0% SOC, in μm;

[0046] n represents the number of rolls of the core;

[0047] The negative electrode sheet, separator and positive electrode sheet are wound to form a winding core, so that the protrusions on the negative electrode sheet fall into the corresponding pits on the positive electrode sheet.

[0048] The present invention has the following beneficial effects: the present invention designs a "concave-convex" shaped pole piece, so that the diaphragm will not change its pore structure and porosity due to internal stress during the charging process, causing battery performance degradation. Through reasonable calculation, the depth, width and spacing of the convex points and the concave points meet a specific relationship, and the thickness change caused by the expansion of the pole piece is used to match the depth and width of the convex points to reasonably compensate for the change in the length of the diaphragm caused by the expansion, so that the margin of the diaphragm length is appropriate, and the diaphragm will not be wrinkled due to a large margin, and the pore structure and porosity will not change due to a small margin. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0050] Figure 1 A schematic diagram of a negative electrode sheet provided in an embodiment of the present invention;

[0051] Figure 2 A schematic diagram of a positive electrode sheet provided in an embodiment of the present invention;

[0052] Figure 3 It is a schematic diagram of the basic unit of the winding core after winding;

[0053] Figure 4 This is a schematic diagram of the diaphragm in the winding core after winding;

[0054] Figure 5 This is a schematic diagram of the basic unit of the winding core when the battery cell is fully charged for the first time. DETAILED DESCRIPTION

[0055] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention will be described clearly and completely below. If the specific conditions are not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be purchased commercially.

[0056] The embodiment of the present invention provides a cylindrical battery having a concave-convex structure of a pole piece, including a winding core, the winding core including a negative pole piece, a separator and a positive pole piece, such as Figure 1 and Figure 2As shown, a plurality of convex points are arranged at intervals on both sides of the negative electrode sheet, and a plurality of concave pits matching the convex points are arranged at intervals on both sides of the positive electrode sheet. The spacing between two adjacent convex points and two adjacent concave pits is L0. The convex points on the negative electrode sheet in the winding core fall into the corresponding concave pits on the positive electrode sheet. The basic unit of the winding core is as follows: Figure 3 shown.

[0057] It should be noted that by designing the "concave and convex" shape of the electrode, the winding tension can be used to press the diaphragm well between the positive and negative electrode sheets during the winding process, thereby increasing the length of each circle of the diaphragm (the schematic diagram of the diaphragm in the winding core after winding is shown in Figure 4 As shown). During the first charging process, the thickness of the negative electrode sheet changes due to expansion. At the same time, the expansion of the negative electrode sheet is affected by the larger force of the winding structure, which makes the expansion rate of the negative electrode sheet at the convex point and the non-convex point inconsistent, but the thickness of the two is consistent in macroscopic performance. Through the subtle change of the thickness of the electrode sheet, the length of the diaphragm is effectively released to adapt to the change of the diaphragm length caused by the change of the winding core diameter. In this way, the diaphragm will not change its pore structure and porosity due to internal stress during the charging process, causing the battery performance to decay.

[0058] Furthermore, the width of the pit on the positive electrode sheet is W1, and the depth of the pit is h1. Specifically, each pit extends from one end of the positive electrode sheet in the width direction to the other opposite end, that is, the pits are spaced apart in the length direction of the positive electrode sheet, so the "width" of the pit refers to the distance that a single pit extends in the length direction of the electrode sheet. The "depth" of the pit refers to the depth of the depression of a single pit, which refers to the distance between the deepest point and the surface of the electrode sheet. In some embodiments, the length of the pit of the positive electrode sheet can be controlled to be equal to the width of the positive electrode sheet.

[0059] Furthermore, the width of the bump on the negative electrode sheet is W2, and the height of the bump is h2. Specifically, each bump extends from one end of the negative electrode sheet in the width direction to the other opposite end, that is, the bumps are spaced apart in the length direction of the negative electrode sheet, so the "width" of the bump refers to the distance that a single bump extends in the length direction of the electrode sheet. The "height" of the bump refers to the degree to which a single bump protrudes, and refers to the distance between the highest point and the surface of the electrode sheet. In some embodiments, the length of the negative electrode sheet convex cell can be controlled to be equal to the width of the negative electrode sheet.

[0060] h1, h2, W1, and W2 satisfy the following relations (1) and (2):

[0061] Relationship (1): h2 = k1 × h1;

[0062] Relationship (2): W2 = k2 × W1;

[0063] Explain each parameter in the formula:

[0064] k1 and k2 both represent coefficients, k1 is 60%-90%, such as 60%, 65%, 70%, 75%, 80%, 85%, 90%, etc.; k2 is 70%-95%, such as 70%, 75%, 80%, 85%, 90%, 95%, etc.; h1, h2, W1, W2 are all in μm. h1 can be 2μm-10μm, such as 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, etc.; W1 can be 3μm-30μm, such as 3μm, 5μm, 10μm, 15μm, 20μm, 25μm, 30μm, etc.

[0065] It should be noted that, from equation (1), it can be seen that the height h2 of the convex point is slightly smaller than the depth h1 of the concave pit, and the ratio of the two needs to be adjusted so that the value of k1 meets the requirements; from equation (2), it can be seen that the width W2 of the convex point is slightly smaller than the width W1 of the concave pit, and the ratio of the two needs to be adjusted so that the value of k2 meets the requirements.

[0066] The distance L0 between two adjacent convex points and two adjacent concave pits satisfies the following relationship:

[0067] Relationship (3): L0 = k3*L / ((2*π*(λ*H)*n) / (h2*2));

[0068] k3 represents a coefficient, and its value ranges from 80% to 120%, such as 80%, 85%, 90%, 95%, 100%, 105%, 110%, 115%, 120%, etc.

[0069] L represents the length of the electrode, which is calculated from the thickness of the positive electrode, negative electrode and diaphragm and the number of windings, in mm. π represents the circumference of a circle, and its value is 3.14.

[0070] λ represents the expansion rate of the negative electrode sheet at 100% SOC state, and the value of λ can be 8%-35%, such as 8%, 10%, 15%, 20%, 25%, 30%, 35%, etc. The expansion rate of the negative electrode sheet at 100% SOC state is a parameter marked on commercially available negative electrode sheet products, which refers to the thickness increase value when reaching 100% SOC state divided by the thickness value of the negative electrode sheet before charging.

[0071] H represents the thickness of the negative electrode sheet at 0% SOC, in μm; the value of H can be 70μm-300μm, such as 70μm, 100μm, 130μm, 150μm, 180μm, 200μm, 230μm, 250μm, 280μm, 300μm, etc. The thickness of the negative electrode sheet at 0% SOC is the parameter marked on commercially available negative electrode sheet products.

[0072] n represents the number of rolls of the winding core, and the value range can be 5-300, such as 5, 10, 30, 50, 80, 100, 130, 150, 180, 200, 230, 250, 280, 300, etc.

[0073] It should be noted that the spacing L0 between two adjacent bumps and two adjacent pits is calculated by the length of the pole piece L, the width of the bump W2, the expansion rate λ of the negative pole piece at 100% SOC, the thickness H of the negative pole piece at 0% SOC, and the number of turns n. L0 is proportional to L and W2, and inversely proportional to λ, H, and n. The thickness change caused by the expansion of the pole piece is used to match the depth and width of the bump to reasonably compensate for the change in the length of the diaphragm caused by the expansion.

[0074] In a preferred embodiment, k1 is 60%-90%, preferably 75%-85%; k2 is 70%-95%, preferably 75%-85%; k3 is 80%-120%, preferably 95%-105%. By adjusting the value range of the coefficients in the three relationship equations, the battery performance degradation caused by internal stress can be further reduced and the battery cycle life can be improved.

[0075] In some embodiments, the shape of the convex point on the negative electrode sheet is "n-type", and the shape of the corresponding concave pit on the positive electrode sheet is "U-type". In actual operation, the coated positive electrode sheet is rolled to form a "concave" electrode sheet, and the coated negative electrode sheet is rolled to form a "convex" electrode sheet. The convex points and concave pits can be formed by adjusting the shape of the roller used during rolling.

[0076] In some embodiments, the negative electrode sheet includes a negative electrode current collector and a negative electrode active coating attached to both sides of the negative electrode current collector, the active material in the negative electrode active coating is selected from at least one of graphite, silicon-based negative electrode and lithium titanate, and the negative electrode active material can be any one or more of the above. The negative electrode current collector can be copper foil, but is not limited thereto. Specifically, the negative electrode sheet can be a commercially available product.

[0077] In some embodiments, the positive electrode sheet includes a positive electrode current collector and a positive electrode active coating attached to both sides of the positive electrode current collector, the active material in the positive electrode active coating is selected from at least one of lithium cobalt oxide, lithium nickel cobalt manganese oxide and lithium iron phosphate, and the positive electrode active material can be any one or more of the above. The positive electrode current collector can be aluminum foil, but is not limited thereto. Specifically, the positive electrode sheet can be a commercially available product.

[0078] In some embodiments, the cylindrical battery further includes an electrolyte and a structural member. The specific composition of the electrolyte is not limited, and a common electrolyte for lithium batteries can be used. It can also include a shell, which can be a steel shell or an aluminum shell. The type of the diaphragm is not limited, and can be a PP, PE diaphragm or a diaphragm with a functional coating.

[0079] The present invention provides a method for preparing a cylindrical battery, and the steps are as follows:

[0080] S1. Provide a negative electrode sheet with convex points and a positive electrode sheet with concave pits

[0081] The distance between two adjacent convex points and two adjacent concave points is L0, the width of the concave point is W1, and the depth of the concave point is h1; the width of the convex point is W2, and the height of the convex point is h2;

[0082] h1, h2, W1, W2 and L0 satisfy the following relationship:

[0083] h2=k1×h1;

[0084] W2=k2×W1;

[0085] L0=k3*L / ((2*π*(λ*H)*n) / (h2*2));

[0086] Where:

[0087] k1, k2 and k3 all represent coefficients, k1 is 60%-90%, k2 is 70%-95%, k3 is 80%-120%, and the units of h1, h2, W1 and W2 are all μm;

[0088] L represents the length of the pole piece, in mm;

[0089] λ represents the expansion rate of the negative electrode sheet at 100% SOC state;

[0090] H represents the thickness of the negative electrode sheet at 0% SOC, in μm;

[0091] n represents the number of windings of the winding core.

[0092] It should be noted that the specific meanings and value ranges of the above parameters can be found in the above description and will not be repeated here.

[0093] S2, Winding

[0094] The negative electrode sheet, separator and positive electrode sheet are wound to form a winding core, so that the convex points on the negative electrode sheet fall into the corresponding concave pits on the positive electrode sheet. When winding, separators are set on both sides of the positive electrode sheet. The shape of the separator after winding is as follows: Figure 4 shown.

[0095] The schematic diagram of the basic unit of the winding core when the battery cell is fully charged for the first time is as follows Figure 5As shown, the subtle change in the thickness of the electrode sheet can be used to effectively release the length of the diaphragm so as to adapt to the change in the length of the diaphragm caused by the change in the core diameter. In this way, the pore structure and porosity of the diaphragm will not change due to internal stress during the charging process, causing battery performance degradation.

[0096] The features and performance of the present invention are further described in detail below in conjunction with the embodiments.

[0097] Example 1

[0098] This embodiment provides a method for preparing a cylindrical battery, the steps are as follows:

[0099] (1) Provide negative electrode sheets, positive electrode sheets, and separators

[0100] Positive electrode sheet: The positive electrode active slurry is coated on both sides of the aluminum foil with a thickness of 13μm, and the double-sided surface density of the coating is 30mg / cm 2 After drying, a "concave" pole piece is formed by rolling, the depth of the pit is h1 = 3μm, the pit spacing L0 = 6.0mm, the shape of the pit is "U" type, and the width of the pit W1 = 3μm. Among them, the preparation process of the positive electrode active slurry: lithium iron phosphate, PVDF, and carbon black are mixed in a mass ratio of 96%: 2%: 2%, and NMP is added to homogenize. After cutting, a positive electrode sheet with a length of 6000mm, a width of 120, and a thickness of 140μm is obtained.

[0101] Negative electrode sheet: Negative electrode active slurry is coated on both sides of a 6μm thick copper foil, and the double-sided surface density of the coating is 16mg / cm 2 After drying, a "convex" type pole piece is formed by rolling, the height of the convex point h2 = 2.4μm, the convex point spacing L0 = 6.0mm, the shape of the convex point is "n" type, and the convex point width W2 = 2.4μm. Among them, the preparation process of the negative electrode active slurry: graphite, CMC, SBR, and carbon black are mixed according to the mass ratio of 95%: 1.5%, 1.8%, and 1.7%, and deionized water is added to homogenize. After cutting, a negative electrode sheet with a length of 6100mm, a width of 124mm, and a thickness of 116μm is obtained.

[0102] According to the test, the thickness H of the negative electrode sheet at 0% SOC is 120 μm, and the expansion rate λ of the negative electrode sheet at 100% SOC is 14%.

[0103] The material of the separator is commercially available PP film with a thickness of 16 μm.

[0104] According to the relationship (1): h2 = k1 × h1, k1 = 80%;

[0105] According to the relationship (2): W2 = k2 × W1, k2 = 80%.

[0106] The parameters of the positive electrode sheet and the negative electrode sheet satisfy equations (1) and (2).

[0107] (2) Winding

[0108] The negative electrode sheet, separator, positive electrode sheet and separator are arranged in sequence and wound. The outer diameter of the central axis used in the winding is 6 μm, and the number of winding turns n is 50 turns. After the soft winding is completed, the central axis is removed.

[0109] After calculation, the pole piece length L = 6000mm.

[0110] According to the relationship (3): L0 = (k3×L×W2) / (λ×H×n), k3 = 110%, which satisfies the relationship (3).

[0111] (3) Liquid injection and formation

[0112] The intermediate product obtained in step (2) is packaged to form a steel shell, and then liquid is injected and formed.

[0113] Among them, the injected electrolyte composition is as follows: 13% LiPF6, 30% EC, 20% EMC, 50% DMC, 2% VC, 1.5DTD, and 3% FEC.

[0114] Embodiment 2-4

[0115] The only difference from Example 1 is that the values ​​of the parameters in step (1) and step (2) are different, see Table 1 for details.

[0116] Comparative Example 1

[0117] The only difference from Example 1 is that no pits and convex spots are formed in step (1), and the other steps and parameters refer to Example 1.

[0118] Comparative Examples 2-5

[0119] The only difference from Example 1 is that the values ​​of the parameters in step (1) and step (2) are different, see Table 2 for details.

[0120] Among them, the designs of K3 and K2 in comparative example 2 are unreasonable; the design of K2 in comparative example 3 is unreasonable; the value of K3 in comparative example 4 leads to unreasonable design of L0; the value of K1 in comparative example 5 leads to unreasonable design of L0.

[0121] Table 1 Parameter values ​​of the embodiments and comparative examples

[0122]

[0123] Test Example 1

[0124] The performance of the cylindrical batteries prepared in the test examples and comparative examples is shown in Table 3.

[0125] Table 3 Performance of cylindrical batteries prepared in Examples and Comparative Examples

[0126]

[0127]

[0128] It can be seen from Table 3 that the cycle performance of the cylindrical battery prepared in the embodiment of the present invention is significantly better than that of the comparative example.

[0129] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A cylindrical battery with a pole piece having a concave-convex structure, characterized in that: The invention comprises a winding core, wherein the winding core comprises a negative electrode sheet, a separator and a positive electrode sheet; A plurality of convex points are arranged at intervals on both sides of the negative electrode sheet, and a plurality of concave pits matching the convex points are arranged at intervals on both sides of the positive electrode sheet, and the distance between two adjacent convex points and two adjacent concave pits is L0, so that the convex points on the negative electrode sheet fall into the corresponding concave pits on the positive electrode sheet; The width of the pit is W1, and the depth of the pit is h1; The width of the convex point is W2, and the height of the convex point is h2; h1, h2, W1, W2 and L0 satisfy the following relationship: h2=k1×h1; W2=k2×W1; L0=k3*L / ((2*π*(λ*H)*n) / (h2*2)) Where: k1, k2 and k3 all represent coefficients, k1 is 60%-90%, k2 is 70%-95%, k3 is 80%-120%, and the units of h1, h2, W1 and W2 are all μm; L represents the length of the pole piece, in mm; λ represents the expansion rate of the negative electrode sheet at 100% SOC; H represents the thickness of the negative electrode sheet at 0% SOC, in μm; n represents the number of windings of the winding core.

2. The cylindrical battery according to claim 1, characterized in that: k1 is 60%-90%, preferably 75%-85%; and / or, k2 is 70%-95%, preferably 75%-85%; and / or, k3 is 80%-120%, preferably 95%-105%; And / or, the length of the pit of the positive electrode sheet is equal to the width of the positive electrode sheet, and the length of the convex cell of the negative electrode sheet is equal to the width of the negative electrode sheet.

3. The cylindrical battery according to claim 1, characterized in that: The value of h1 is 2μm-10μm.

4. The cylindrical battery according to claim 1, characterized in that: The value of W1 is 3μm-30μm.

5. The cylindrical battery according to claim 1, characterized in that: The expansion rate λ of the negative electrode sheet at 100% SOC state is 8%-35%.

6. The cylindrical battery according to claim 1, characterized in that: The thickness H of the negative electrode sheet at 0% SOC is 70 μm-300 μm.

7. The cylindrical battery according to claim 1, characterized in that: The number of rolls n of the roll core is 5-300; And / or, the length L of the electrode sheet is calculated based on the thickness of the positive electrode sheet, the negative electrode sheet and the separator and the number of winding turns.

8. The cylindrical battery according to claim 1, characterized in that: The shape of the protrusions on the negative electrode sheet is n-type, and each of the protrusions extends from one end of the negative electrode sheet in the width direction to the other opposite end; The shape of the pits on the positive electrode sheet is U-shaped, and each of the pits extends from one end in the width direction of the positive electrode sheet to the other opposite end.

9. The cylindrical battery according to claim 1, characterized in that: The negative electrode sheet comprises a negative electrode current collector and a negative electrode active coating attached to both sides of the negative electrode current collector, wherein the active material in the negative electrode active coating is selected from at least one of graphite, silicon-based negative electrode and lithium titanate; And / or, the positive electrode sheet includes a positive electrode current collector and a positive electrode active coating attached to both sides of the positive electrode current collector, and the active material in the positive electrode active coating is selected from at least one of lithium cobalt oxide, lithium nickel cobalt manganese oxide and lithium iron phosphate.

10. A method for preparing a cylindrical battery according to any one of claims 1 to 9, characterized in that: include: Providing a negative electrode sheet having the protrusions and a positive electrode sheet having the pits; The distance between two adjacent protrusions and two adjacent pits is L0, the width of the pit is W1, and the depth of the pit is h1; the width of the protrusion is W2, and the height of the protrusion is h2; h1, h2, W1, W2 and L0 satisfy the following relationship: h2=k1×h1; W2=k2×W1; L0=k3*L / ((2*π*(λ*H)*n) / (h2*2)); Where: k1, k2 and k3 all represent coefficients, k1 is 60%-90%, k2 is 70%-95%, k3 is 80%-120%, and the units of h1, h2, W1 and W2 are all μm; L represents the length of the pole piece, in mm; λ represents the expansion rate of the negative electrode sheet at 100% SOC; H represents the thickness of the negative electrode sheet at 0% SOC, in μm; n represents the number of rolls of the core; The negative electrode sheet, the separator and the positive electrode sheet are wound to form the winding core, so that the protrusions on the negative electrode sheet fall into the corresponding pits on the positive electrode sheet.

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