Secondary battery and electrical apparatus

Abstract

Provided in the present application are a secondary battery and an electrical apparatus. A negative electrode sheet in the secondary battery of the present application comprises: a current collector, a first coating layer provided on at least one side surface of the current collector, and a second coating layer provided on the first coating layer; the first coating layer comprises a first silicon negative electrode active material, and the second coating layer comprises a second silicon negative electrode active material; the first silicon negative electrode active material and the second silicon negative electrode active material comprise modified elements, the modified elements comprising element P, element Al and element K, and satisfying the following relationships: the content of the modified elements satisfies: P1<P2, Al1>Al2 and K1>K2. In the present application, the elements P, Al and K are introduced into the silicon negative electrode active materials, and the three modified elements are used together. In addition, specifically designing the distribution of the elements in the silicon negative electrode active materials can suppress lithium plating of the secondary battery, and prolong the service life of the secondary battery.

Description

Secondary battery and electric device

[0001] The present application claims priority to the Chinese patent application No. 202411336486.6, filed on September 24, 2024, and entitled "Secondary battery and electric device", the whole content of which is incorporated herein by reference. TECHNICAL FIELD

[0002] The present application relates to the technical field of battery, in particular to a secondary battery and an electric device. BACKGROUND

[0003] The secondary battery with silicon negative electrode has defects such as easy lithium precipitation and rapid capacity attenuation during the cycle process. Through disassembly analysis of the secondary battery with silicon negative electrode after cycle, it is found that the lithium precipitation interface generally appears at 800-1200 cycle times. At present, the above problems are mainly solved by reducing the compaction density of the negative electrode coating, using soft carbon or hard carbon coating to improve the kinetic performance of the negative electrode and optimizing the electrolyte formula, but the battery obtained by the above modification means gradually increases the polarization of the battery, the overpotential between the positive electrode and the negative electrode gradually increases, and the capacity retention rate of the battery significantly decreases, which greatly shortens the service life of the secondary battery. SUMMARY

[0004] The purpose of the present application is to further improve the service life of the secondary battery. The negative electrode sheet is improved, and a secondary battery with a longer service life is provided.

[0005] To achieve the above purpose, the first aspect of the present application provides a secondary battery, comprising a negative electrode sheet, the negative electrode sheet comprising:

[0006] a current collector, a first coating layer arranged on at least one side surface of the current collector, and a second coating layer coated on the first coating layer;

[0007] The first coating layer comprises a first silicon negative electrode active material, and the second coating layer comprises a second silicon negative electrode active material.

[0008] The first silicon negative electrode active material and the second silicon negative electrode active material contain a modification element, the modification element contains elements P, elements Al and elements K; and satisfy the following relationship:

[0009] The content of the modification element satisfies: P1

[0010] Wherein, P1, Al1 and K1 represent the content of element P, element Al and element K in the first silicon negative electrode active material respectively, and P2, Al2 and K2 represent the content of element P, element Al and element K in the second silicon negative electrode active material respectively.

[0011] As an embodiment of the present application, the negative electrode sheet in the secondary battery satisfies: 1000 ppm ≤ P2-P1 ≤ 2000 ppm.

[0012] As an embodiment of the present application, P1 is 800 ppm to 1200 ppm.

[0013] As an embodiment of the present application, P2 is 1800 ppm to 3200 ppm.

[0014] As an embodiment of the present application, the negative electrode sheet in the secondary battery satisfies: 50 ppm ≤ Al1-Al2 ≤ 1000 ppm.

[0015] As an embodiment of the present application, Al1 is 1000 ppm to 1200 ppm.

[0016] As an embodiment of the present application, Al2 is 100 ppm to 950 ppm.

[0017] As an embodiment of the present application, the negative electrode sheet in the secondary battery satisfies: 50 ppm ≤ K1-K2 ≤ 600 ppm.

[0018] As an embodiment of the present application, the negative electrode sheet in the secondary battery satisfies: K1 is 500 to 700 ppm.

[0019] As an embodiment of the present application, the negative electrode sheet in the secondary battery satisfies: K2 is 50 to 500 ppm.

[0020] As an embodiment of the present application, the modifying element is distributed on the surface and / or inside of the first silicon negative electrode active material or the second silicon negative electrode active material.

[0021] As an embodiment of the present application, the negative electrode sheet satisfies: 10 mAh / g ≤ C2-C1 ≤ 21 mAh / g; wherein C1 mAh / g represents the gram capacity of the first silicon negative electrode active material; C2 mAh / g represents the gram capacity of the second silicon negative electrode active material.

[0022] As an embodiment of the present application, the negative electrode sheet satisfies: 15 mAh / g ≤ C2-C1 ≤ 20 mAh / g.

[0023] As an embodiment of the present application, C1 is 1400 mAh / g to 1415 mAh / g.

[0024] As an embodiment of the present application, C2 is 1415 mAh / g to 1432 mAh / g.

[0025] As an embodiment of the present application, the particle size D V50 of the first silicon negative electrode active material is 4.0-7.0 μm, and the particle size D V50 of the second silicon negative electrode active material is 4.0-7.0 μm; wherein the particle size D V50 represents the particle size corresponding to the volume accumulation of 50% of the material particles, and the unit is μm.

[0026] As an embodiment of the present application, the negative electrode sheet satisfies: 0.94≤PD2 / PD1≤1.07, PD1 g / cm 3 represents the tap density of the first coating in the negative electrode sheet, and PD2 g / cm 3 represents the tap density of the second coating in the negative electrode sheet.

[0027] As an embodiment of the present application, PD1 is 1.5 g / cm 3 -1.6 g / cm 3 .

[0028] As an embodiment of the present application, PD2 is 1.5 g / cm 3 -1.6 g / cm 3 .

[0029] In a second aspect of the present application, a power utilization device is provided, which comprises the secondary battery of the first aspect of the present application.

[0030] Compared with the prior art, the present application has the following beneficial effects:

[0031] In the present application, P, Al and K elements are introduced into the silicon negative electrode active material, and the three modified elements are used together. Meanwhile, by specifically designing the element distribution in the silicon negative electrode active material, the specific capacity and structural stability of the silicon negative electrode material are improved, the polarization of the secondary battery prepared therefrom is reduced, and thus the capacity retention rate of the secondary battery after cycling is improved, the lithium precipitation interface of the negative electrode after cycling is improved, and the service life of the secondary battery is improved. BRIEF DESCRIPTION OF DRAWINGS

[0032] FIG. 1 is a structural schematic diagram of the negative electrode sheet of Example 1. DETAILED DESCRIPTION

[0033] For better illustrating the purpose, technical scheme and advantages of the present application, the present application will be further illustrated in combination with specific examples and drawings, but the examples do not limit the present application in any form. Unless otherwise specified, the reagents, methods and devices used in the present application are conventional reagents, methods and devices in the technical field. Unless otherwise specified, the reagents and materials used in the present application are commercially available.

[0034] Embodiments of the present application provide a secondary battery, comprising a negative electrode sheet, the negative electrode sheet comprising:

[0035] a current collector, a first coating layer provided on at least one side surface of the current collector, and a second coating layer provided on the first coating layer;

[0036] the first coating layer comprises a first silicon negative electrode active material, and the second coating layer comprises a second silicon negative electrode active material;

[0037] the first silicon negative electrode active material and the second silicon negative electrode active material contain a modified element, the modified element contains elements P, Al and K; and satisfies the following relationship:

[0038] the content of the modified element satisfies: P1

[0039] wherein P1, Al1 and K1 represent the content of elements P, Al and K in the first silicon negative electrode active material respectively, and P2, Al2 and K2 represent the content of elements P, Al and K in the second silicon negative electrode active material respectively.

[0040] The negative electrode sheet of the present application introduces P, Al and K elements in the silicon negative electrode active material, which can improve the interlayer spacing of the silicon negative electrode active material, improve the lithium ion diffusion coefficient, and reduce polarization; the P element can improve the gram capacity of the silicon negative electrode active material, and the K and Al elements can improve the structural stability of the silicon negative electrode active material and reduce the free energy of lithium intercalation. The three modified elements are used together, and at the same time, the distribution of elements in the silicon negative electrode active material is specifically designed, which improves the gram capacity and structural stability of the silicon negative electrode material, reduces the polarization of the secondary battery prepared therefrom, thereby improving the capacity retention rate of the secondary battery after cycling, improving the lithium precipitation interface of the negative electrode after cycling, and improving the service life of the secondary battery.

[0041] In the present application, the modified element can be distributed on the surface of the first silicon negative electrode active material or the second silicon negative electrode active material, or can be distributed in the interior of the first silicon negative electrode active material or the second silicon negative electrode active material. When the modified element is distributed on the surface and in the interior of the negative electrode active material, the stability of the negative electrode active material can be optimized, and the negative electrode material has more electrochemical active sites.

[0042] In the first silicon negative electrode active material and the second silicon negative electrode active material of some embodiments of the present application, the K and Al elements can improve the structural stability of the silicon negative electrode active material and reduce the free energy of lithium intercalation. At the same time, the K element and the Al element loaded into the silicon negative electrode active material can also act together with the P element to improve the crystallization performance of the material, thereby significantly improving the cycle stability of the battery and prolonging the service life of the battery.

[0043] In some embodiments, 1000 ppm ≤ P2-P1 ≤ 2000 ppm is satisfied. Exemplarily, the value of P2-P1 can be any one of 1000 ppm, 1500 ppm, 2000 ppm or a range value between any two of them. When the above condition is satisfied, the initial discharge capacity and cycle performance of the battery can be further improved.

[0044] In some embodiments, P1 is in the range of 800 ppm to 1200 ppm. Exemplarily, the value of P1 can be any one of 800 ppm, 1000 ppm, 1200 ppm or a range value between any two of them.

[0045] In some embodiments, P2 is in the range of 1800 ppm to 3200 ppm. Exemplarily, the value of P2 can be any one of 1800 ppm, 2000 ppm, 2900 ppm, 3000 ppm, 3200 ppm or a range value between any two of them.

[0046] In some embodiments, 50 ppm ≤ Al1-Al2 ≤ 1000 ppm is satisfied. Exemplarily, the value of Al1-Al2 can be any one of 50 ppm, 300 ppm, 400 ppm, 500 ppm, 700 ppm, 950 ppm or a range value between any two of them. When the above condition is satisfied, the cycle capacity retention rate of the battery can be improved.

[0047] In some embodiments, Al1 is in the range of 1000 ppm to 1200 ppm. Exemplarily, the value of Al1 can be any one of 1000 ppm, 1050 ppm, 1200 ppm or a range value between any two of them.

[0048] In some embodiments, Al2 is in the range of 100 ppm to 950 ppm. Exemplarily, the value of Al2 can be any one of 100 ppm, 300 ppm, 500 ppm, 700 ppm, 800 ppm, 950 ppm or a range value between any two of them.

[0049] In some embodiments, 50 ppm ≤ K1-K2 ≤ 600 ppm is satisfied. Exemplarily, the value of K1-K2 can be any one of 50 ppm, 200 ppm, 300 ppm, 400 ppm, 500 ppm, 600 ppm or a range value between any two of them. When the above condition is satisfied, the cycle capacity retention rate of the battery can be improved.

[0050] In some embodiments, K1 is in the range of 500 ppm to 700 ppm, and exemplarily, K1 can be any one of 500 ppm, 550 ppm, 700 ppm, or a range value between any two of them.

[0051] In some embodiments, K2 is in the range of 50 ppm to 500 ppm, and exemplarily, K2 can be any one of 50 ppm, 100 ppm, 200 ppm, 300 ppm, 450 ppm, or a range value between any two of them.

[0052] In some embodiments, the negative electrode tab satisfies: 0.94≤PD2 / PD1≤1.07, and further preferably, 1.0≤PD2 / PD1≤1.07. Exemplarily, PD2 / PD1 can be any one of 0.94, 0.97, 1.00, 1.03, 1.07, or a range value between any two of them. PD1 g / cm 3 represents the compacted density of the first coating in the negative electrode tab, and PD2 g / cm 3 represents the compacted density of the second coating in the negative electrode tab. When PD2 / PD1 is in the above range, the cycle capacity retention rate of the battery can be improved.

[0053] In some embodiments, PD1 is in the range of 1.5 g / cm 3 to 1.6 g / cm 3 , and exemplarily, PD1 can be any one of 1.5 g / cm 3 , 1.6 g / cm 3 , or a range value between any two of them.

[0054] In some embodiments, PD2 is in the range of 1.5 g / cm 3 to 1.6 g / cm 3 , and exemplarily, PD2 can be any one of 1.5 g / cm 3 , 1.55 g / cm 3 , 1.6 g / cm 3 , or a range value between any two of them.

[0055] In some embodiments, PD1 is 1.5 g / cm 3 , and PD2 is 1.55 g / cm 3 , and thus the cycle capacity retention rate of the battery can be improved.

[0056] In some embodiments, the negative electrode sheet satisfies: 10 mAh / g≤C2-C1≤21 mAh / g; further preferably 15 mAh / g≤C2-C1≤20 mAh / g. Exemplarily, the value of C2-C1 can be any one of 10 mAh / g, 11 mAh / g, 14 mAh / g, 15 mAh / g, 20 mAh / g, 21 mAh / g or a range value between any two of them. Wherein, C1 mAh / g represents the gram capacity of the first silicon negative electrode active material; C2 mAh / g represents the gram capacity of the second silicon negative electrode active material. When the above condition is satisfied, the cycle capacity retention rate of the battery can be improved.

[0057] In some embodiments, C1 is in the range of 1400 mAh / g~1415 mAh / g, exemplarily, the value of C1 can be any one of 1408 mAh / g, 1409 mAh / g, 1410 mAh / g, 1412 mAh / g, 1413 mAh / g, 1415 mAh / g or a range value between any two of them.

[0058] In some embodiments, C2 is in the range of 1415 mAh / g~1432 mAh / g, exemplarily, the value of C2 can be any one of 1418 mAh / g, 1420 mAh / g, 1423 mAh / g, 1424 mAh / g, 1425 mAh / g, 1430 mAh / g, 1432 mAh / g or a range value between any two of them.

[0059] In some embodiments, C1 is 1420 mAh / g and C2 is 1425 mAh / g, which can improve the lithium precipitation of the negative electrode, and further improve the cycle capacity retention rate of the battery.

[0060] In some embodiments, the particle size D V50 of the first silicon negative electrode active material is 4.0~7.0 μm. Exemplarily, the particle size D V50 of the first silicon negative electrode active material can be any one of 4 μm, 5 μm, 6 μm, 7 μm or a range value between any two of them.

[0061] In some embodiments, the particle size D V50 of the second silicon negative electrode active material is 4.0~7.0 μm. Exemplarily, the particle size D V50 of the second silicon negative electrode active material can be any one of 4 μm, 5 μm, 6 μm, 7 μm or a range value between any two of them.

[0062] In this application, the particle size D V50 represents the particle size corresponding to the volume accumulation of 50% of the material particles, and the unit is μm.

[0063] The particle size of the silicon negative electrode active material is within the above range, which can further improve the compaction density of the coating and the capacity of the battery; meanwhile, the proportion of the particle sizes of the two silicon negative electrode active materials is within the above range, which can form good ion channels on the basis of high compaction density and improve the ion transmission performance, thereby further improving the cycle capacity retention rate of the battery.

[0064] In some embodiments, the active substance in the first silicon negative electrode active material and the second silicon negative electrode active material includes at least one of silicon oxide (SiO x x = 1 or 2), Si alloy, Si-C. It should be noted that in the present application, the silicon negative electrode active material includes the active substance and the modifying element.

[0065] In some embodiments, in addition to containing the silicon negative electrode active material, the first coating and the second coating also contain a conductive agent, a binder, and a thickening agent.

[0066] In the present application, the secondary battery further includes a positive electrode sheet, an electrolyte, and a separator.

[0067] In some embodiments, the positive electrode sheet includes a positive electrode current collector and a positive electrode active coating arranged on at least one side surface of the positive electrode current collector; the positive electrode active coating includes a positive electrode active substance, which includes but is not limited to at least one of lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and lithium iron phosphate.

[0068] In some embodiments, the positive electrode sheet can further include a conductive agent, a binder, and a thickening agent.

[0069] The conductive agent includes but is not limited to at least one of conductive carbon black, acetylene black, ketjen black, carbon nanotubes, and graphene.

[0070] The binder includes but is not limited to at least one of styrene butadiene rubber, styrene-acrylic emulsion, polyacrylic acid, and sodium alginate.

[0071] The thickening agent includes but is not limited to at least one of sodium carboxymethyl cellulose and lithium carboxymethyl cellulose.

[0072] The present application also provides a power consumption device including the above-mentioned secondary battery.

[0073] The following are specific embodiments of the present application, which further describe the technical solutions of the present application in conjunction with the embodiments, but the present application is not limited to these embodiments. The reagents, methods, and equipment used in the present application are conventional reagents, methods, and equipment in the technical field, unless otherwise specified.

[0074] Embodiment 1

[0075] The embodiment provides a secondary battery, and a preparation method thereof.

[0076] Preparation of negative electrode sheet

[0077] The negative electrode active material (a mixture of the first silicon negative electrode active material and graphite at a mass ratio of 10:90), the conductive agent (the conductive carbon black and the carbon nanotube are mixed at a weight ratio of 1:1), the thickening agent (sodium carboxymethyl cellulose), and the binder (polyacrylic acid) are mixed at a mass ratio of 96:1.5:0.5:2, and deionized water is added, so that the first negative electrode slurry is obtained under the action of a vacuum stirrer.

[0078] The negative electrode active material (a mixture of the second silicon negative electrode active material and graphite at a mass ratio of 10:90), the conductive agent (the conductive carbon black and the carbon nanotube are mixed at a weight ratio of 1:1), the thickening agent (sodium carboxymethyl cellulose), and the binder (polyacrylic acid) are mixed at a mass ratio of 96:1.5:0.5:2, and deionized water is added, so that the second negative electrode slurry is obtained under the action of a vacuum stirrer.

[0079] The first negative electrode slurry is uniformly coated on the two side surfaces of the negative electrode current collector (copper foil) to form the first coating layer on the two side surfaces respectively; then the second negative electrode slurry is coated on the first coating layer to form the second coating layer; and then the coated electrode sheet is transferred to an oven for drying, and then is subjected to cold pressing and slitting to obtain the negative electrode sheet.

[0080] The first silicon negative electrode active material and the second silicon negative electrode active material are obtained by mixing and grinding silicon dioxide (or Si-C material) and metal salts AlPO4 and K3PO4 of modified elements, and then sintering.

[0081] Other parameters of the negative electrode sheet and the silicon negative electrode active material are shown in Tables 1 and 2.

[0082] Preparation of positive electrode sheet

[0083] The positive electrode active material (high-nickel ternary material, chemical formula: LiNi 0.9 Co 0.05 Mn 0.05 O2), the binder (polyvinylidene fluoride (PVDF)), and the conductive agent (the conductive carbon black and the carbon nanotube are mixed at a weight ratio of 1:1) are mixed at a mass ratio of 97:1.5:1.5, and a solvent (N-methyl pyrrolidone) is added; then the mixture is stirred in a vacuum stirrer until the system is uniform, so that the positive electrode slurry is obtained; the positive electrode slurry is uniformly coated on the double side surfaces of the positive electrode current collector (carbon-coated aluminum foil); and the coated electrode sheet is subjected to oven drying, and then cold pressing and slitting to obtain the positive electrode sheet.

[0084] Preparation of electrolyte

[0085] The organic solvent is a mixed solution containing ethylene carbonate (EC), methyl ethyl carbonate (EMC) and diethyl carbonate (DEC), wherein the volume ratio of EC, EMC and DEC is 20:20:60. In an argon atmosphere glove box with a water content <10 ppm, a fully dried lithium salt lithium hexafluorophosphate (LiPF6), lithium bisfluorosulfonylimide (LiFSI) (mixed in a molar ratio of 1:1), and an additive (fluoroethylene carbonate (FEC), tris(trimethylsilyl) phosphate (TMSP), vinyl sulfate (DTD) mixed in a mass ratio of 1:1:1) are dissolved in the organic solvent, mixed uniformly to obtain an electrolyte; in the electrolyte of the present embodiment, the concentration of lithium salt is 1.2 mol / L, and the concentration of additive is 5 wt%.

[0086] Secondary battery assembly

[0087] The positive electrode sheet, the separator (PE-based film + [ceramic & PVDF coating]), and the negative electrode sheet are stacked in order, with the separator film between the positive and negative electrode sheets to serve as a separator, and then wound into a square bare cell, which is then loaded into a shell. After baking at 100°C to remove water, electrolyte is injected, sealed, and subjected to processes such as standing, hot and cold pressing, formation, and capacity distribution, to obtain a secondary battery.

[0088] Examples 2-23 and Comparative Examples 1-4

[0089] A series of secondary batteries were prepared according to the method of Example 1, with the negative electrode sheet being slightly different from that of Example 1. The differences are shown in the parameters in Tables 1 and 2. In the silicon negative electrode active material of Comparative Example 4, the first and second silicon negative electrode materials were not doped with a modifying element.

[0090] Table 1

[0091] Table 2 Note: In the table, P1 represents the content of element P in the first silicon negative electrode active material; P2 represents the content of element P in the second silicon negative electrode active material; Al1 represents the content of element Al in the first silicon negative electrode active material; Al2 represents the content of element Al in the second silicon negative electrode active material; K1 represents the content of element K in the first silicon negative electrode active material; and K2 represents the content of element K in the second silicon negative electrode active material.

[0092] Performance test

[0093] The performance of the secondary batteries obtained in the above examples and comparative examples was tested, including the following steps:

[0094] (1) 45℃ standing for 30 minutes; (2) 0.02C constant current discharge to 2.5V; (3) standing for 30 minutes; (4) 0.02C constant current charge to 4.2V, constant voltage charge to current 0.05C; (5) standing for 30 minutes; (6) 0.02C constant current discharge to 2.5V; (7) 45℃ standing for 180 minutes; (8) 1C constant current charge to 4.25V, constant voltage charge to current 0.05C; (9) standing for 60 minutes; (10) 1C constant current discharge to 2.5V; (11) standing for 120 minutes; record the discharge gram capacity at this time as the initial discharge gram capacity; (12) repeat steps (8) to (10) for 1500 times, stop the test, and record the discharge gram capacity at this time as the discharge gram capacity after 1500 cycles.

[0095] wherein the 1500 cycle capacity retention rate (%) = the discharge gram capacity after 1500 cycles / the initial discharge gram capacity*100%.

[0096] After 1500 cycles, the charged battery was further disassembled to observe whether lithium was precipitated on the negative electrode sheet, and the lithium precipitation area was calculated. The lithium precipitation conditions are shown in Table 3.

[0097] Table 3

[0098] From the above results, it can be seen that:

[0099] By introducing P, Al and K elements into the silicon negative electrode active material, the three modified elements are used together, and at the same time, by specifically designing the element distribution in the silicon negative electrode active material, the capacity retention rate of the secondary battery prepared therefrom after cycling can be significantly improved, the lithium precipitation interface of the negative electrode after cycling can be improved, and thus the service life of the secondary battery can be significantly improved.

[0100] Finally, it should be noted that the above examples are only used to illustrate the technical solutions of the present application and not to limit the protection scope of the present application. Although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of the present application.

Claims

1. A secondary battery comprising a negative electrode sheet, wherein, The negative electrode plate comprises: a current collector, a first coating layer arranged on at least one side surface of the current collector, and a second coating layer arranged on the first coating layer; the first coating layer comprises a first silicon negative electrode active material, and the second coating layer comprises a second silicon negative electrode active material; the first silicon negative electrode active material and the second silicon negative electrode active material contain a modified element, the modified element contains elements P, Al and K, and satisfies the following relationship: the content of the modified element satisfies P1 wherein P1, Al1 and K1 represent the content of elements P, Al and K in the first silicon negative electrode active material respectively, and P2, Al2 and K2 represent the content of elements P, Al and K in the second silicon negative electrode active material respectively.

2. The secondary battery according to claim 1, wherein satisfies 1000 ppm≤P2-P1≤2000 ppm.

3. The secondary battery according to claim 2, wherein P1 is 800 ppm-1200 ppm.

4. The secondary battery according to claim 2, wherein P2 is 1800 ppm-3200 ppm.

5. The secondary battery according to claim 1, wherein satisfies 50 ppm≤Al1-Al2≤1000 ppm.

6. The secondary battery according to claim 5, wherein Al1 is 1000 ppm-1200 ppm.

7. The secondary battery according to claim 5, wherein Al2 is 100 ppm-950 ppm.

8. The secondary battery according to claim 1, wherein satisfies 50 ppm≤K1-K2≤600 ppm.

9. The secondary battery according to claim 1, wherein the modified element is distributed on the surface and / or inside of the first silicon negative electrode active material or the second silicon negative electrode active material.

10. The secondary battery according to claim 1, characterized by the negative electrode plate satisfies 10 mAh / g≤C2-C1≤21 mAh / g; C1 mAh / g represents the gram capacity of the first silicon negative electrode active material; C2 mAh / g represents the gram capacity of the second silicon negative electrode active material.

11. The secondary battery according to claim 10, wherein the negative electrode plate satisfies 15 mAh / g≤C2-C1≤20 mAh / g.

12. The secondary battery according to claim 10, wherein C1 is 1400 mAh / g-1415 mAh / g.

13. The secondary battery according to claim 10, wherein C2 is 1415 mAh / g-1432 mAh / g.

14. The secondary battery according to claim 8, wherein K1 is 500-700 ppm, and K2 is 50-500 ppm.

15. The secondary battery according to claim 1, wherein The negative electrode sheet satisfies: 0.94 ≤ PD2 / PD1 ≤ 1.07, PD1 g / cm 3 represents the compacted density of the first coating in the negative electrode sheet, PD2 g / cm 3 represents the compacted density of the second coating in the negative electrode sheet.

16. The secondary battery according to claim 15, wherein PD1 is 1.5 g / cm 3 ~ 1.6 g / cm 3 .

17. The secondary battery according to claim 15, wherein PD2 is 1.5 g / cm 3 ~ 1.6 g / cm 3 .

18. The secondary battery according to claim 1, wherein The particle size D of the first silicon negative electrode active material is 4.0 to 7.0 μm V50 The particle size D of the second silicon negative electrode active material is 4.0 to 7.0 μm V50 The particle size D of the second silicon negative electrode active material is 4.0 to 7.0 μm wherein the particle size D V50 The volume cumulative 50% corresponds to the particle size of the material particles, and the unit is μm.

19. An electrical device, comprising: a secondary battery comprising any one of the negative electrode plates according to claims 1-18.

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