A silicon-doped lithium-supplemented negative electrode sheet, a preparation method thereof, and a lithium-ion battery

Abstract

The present invention belongs to the technical field of lithium ions, and particularly relates to a silicon-doped lithium-supplemented negative electrode sheet, a preparation method thereof, and a lithium ion battery, which sequentially include a first silicon-doped coating, a first negative electrode current collector, a lithium-supplemented layer, a second negative electrode current collector, and a second silicon-doped coating from top to bottom. The silicon-doped lithium-supplemented negative electrode sheet of the present invention is provided with a first silicon-doped coating and a second silicon-doped coating on both outer sides, and a lithium-supplemented layer is provided on the inner side, having high specific capacity, first efficiency, cycle stability, and safety.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium ions, and particularly relates to a silicon-doped lithium-complemented negative electrode sheet, a preparation method thereof, and a lithium ion battery. Background Art

[0002] Lithium ion batteries are widely used in fields such as electronic mobile devices, power transportation networks, and smart grids due to their advantages of high energy density, high output voltage, no memory effect, and environmental friendliness. However, during their repeated charge and discharge processes, it is easy to cause the loss of active substance lithium ions. When the negative electrode of a lithium ion battery is graphite, its initial Coulomb efficiency is generally between 92% and 94%, and the theoretical specific capacity is 372 mAh / g, making it difficult to improve the energy density of the entire battery. If we want to increase the energy density of the battery, the current mainstream is to dope silicon into graphite. Although silicon has a high theoretical specific capacity, after doping silicon, the initial efficiency of the battery cell is relatively low, and the cycle stability is poor. At this time, in order to achieve large-scale application, it is necessary to perform lithium compensation on it.

[0003] Existing lithium compensation technologies emerge in an endless stream, and researchers have proposed various lithium compensation strategies. Chinese Patent CN202010584954.7 proposes a lithium-complemented negative electrode sheet, a lithium ion battery, and a preparation method thereof. After assembling the positive and negative electrodes into a battery and charging and discharging it to a certain cut-off voltage, the battery is disassembled, the positive electrode sheet is removed, and a lithium-complemented negative electrode sheet is obtained. This method is cumbersome and complex to operate. The lithium-complemented negative electrode sheet may have a lot of side reaction products remaining, and discarding the positive electrode sheet leads to an increase in cost, etc. Chinese Patent CN202010238490.4 discloses a lithium compensation method for a silicon-containing negative electrode material, a negative electrode sheet, and a battery. This method has high requirements for equipment technology. Summary of the Invention

[0004] One of the purposes of the present invention is to provide, in view of the deficiencies of the prior art, a silicon-doped lithium-complemented negative electrode with a high specific capacity, initial efficiency, cycle retention rate, and structural stability.

[0005] To achieve the above purpose, the present invention adopts the following technical solutions:

[0006] A silicon-doped lithium-complemented negative electrode sheet, which sequentially includes a first silicon-doped coating, a first negative electrode current collector, a lithium compensation layer, a second negative electrode current collector, and a second silicon-doped coating from top to bottom. The first silicon-doped coating is connected to the second silicon-doped coating, and the first negative electrode current collector is connected to the second negative electrode current collector.

[0007] Preferably, the first silicon-doped coating and the second silicon-doped coating are integrally formed and connected, and the first negative electrode current collector and the second negative electrode current collector are integrally formed and connected. The first negative electrode current collector and the second negative electrode current collector are integrally formed and connected. After forming, the metal form is relatively fixed, making the structure of the composite negative electrode sheet more stable. After lithium supplementation, the structure of the electrode sheet will not be damaged, with better safety, and the preparation process is simpler and easier to automate. Compared with a negative electrode sheet made by directly laminating two independent negative electrode current collector layers and two independent silicon-doped coatings respectively, the first negative electrode current collector and the second negative electrode current collector of the present invention are integrally formed and connected. After forming, the metal form is relatively fixed, making the structure of the composite negative electrode sheet more stable. Even after the lithium supplementation layer in the middle is liquefied by injection, and the lithium supplementation layer dissolves and diffuses, the structures of the upper and lower electrode sheets are not easily displaced, thus avoiding safety problems.

[0008] Preferably, the thickness of the lithium supplementation layer is 1-100 μm. The thickness of the lithium supplementation layer is 1 μm, 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm; the thickness of the first silicon-doped coating and / or the second silicon-doped coating is 10-50 μm. The thickness of the first silicon-doped coating is 10 μm, 20 μm, 30 μm, 40 μm, 50 μm; the thickness of the second silicon-doped coating is 10 μm, 20 μm, 30 μm, 40 μm, 50 μm.

[0009] The second object of the present invention is to provide a preparation method of a silicon-doped lithium-supplemented negative electrode sheet in view of the deficiencies of the prior art. The preparation method has a simple process, does not require changing the original production line, does not need to redesigned the battery structure, and is suitable for mass production.

[0010] To achieve the above object, the present invention adopts the following technical solutions:

[0011] A preparation method of a silicon-doped lithium-supplemented negative electrode sheet includes the following steps:

[0012] Step S1, prepare a negative electrode silicon-based slurry. Take a negative electrode current collector and coat the negative electrode silicon-based slurry on one surface of the negative electrode current collector to form a negative electrode silicon-based coating to obtain a substrate.

[0013] Step S2, take a lithium supplementation sheet and set the lithium supplementation sheet on the other surface of the substrate away from the negative electrode silicon-based slurry to obtain a composite substrate.

[0014] Step S3, with the lithium supplementation sheet as the inner side, fold the composite substrate so that the lithium supplementation sheet is folded in half to form a lithium supplementation layer, the negative electrode current collector is folded in half to form a first negative electrode current collector and a second negative electrode current collector, and the negative electrode silicon-based coating is folded in half to form a first silicon-doped coating and a second silicon-doped coating.

[0015] Among them, coating can be carried out by gravure coating, printing coating, etc. The first negative electrode current collector and / or the second negative electrode current collector include, but are not limited to, metal foils, etc., and more specifically, may include, but are not limited to, copper foils and aluminum foils. When folding, it can be folded according to the position where the tab is set, can be folded symmetrically left and right according to the tab, or can be folded from the side without a tab to the side with a tab. The thickness of the lithium supplement sheet doubles after folding to form a lithium supplement layer; the negative electrode current collector is located between the lithium supplement sheet and the negative electrode silicon-based coating. After folding, a first negative electrode current collector located on the upper layer and a second negative electrode current collector located on the lower layer are respectively formed, and the first negative electrode current collector and the second negative electrode current collector are connected to each other, thereby forming a semi-surrounding protection structure for the lithium supplement sheet, further improving the structural stability, so that the composite electrode sheet will not shift or deform after the lithium supplement is dissolved. The negative electrode silicon-based coating located outside the negative electrode current collector is respectively formed into a first silicon-doped coating located on the upper layer and a second silicon-doped coating located on the lower layer after folding, thereby forming a first silicon-doped coating, a first negative electrode current collector, a lithium supplement layer, a second negative electrode current collector, and a second silicon-doped coating arranged in sequence from top to bottom. The silicon-doped lithium supplement negative electrode sheet of the present invention has a relatively low cost and will not cause excessive waste. In addition, it can isolate the direct contact between metallic lithium and the positive and negative electrode sheets, improving the safety performance of the battery. It can effectively supplement lithium to the battery, improve the first Coulomb efficiency of the battery, and the lithium metal that is not consumed during the formation stage can continuously provide lithium during subsequent cycling processes, thereby improving the cycling performance of the battery. The process of manufacturing the lithium-ion battery device of the present invention is relatively simple, without changing the original process flow on the production line, etc., and there is no need to re-design the battery structure, which is suitable for mass production.

[0016] Preferably, the negative electrode silicon-based slurry includes graphite, a silicon-based material, conductive carbon, and a binder, and the weight ratio of graphite, the silicon-based material, conductive carbon, and the binder is 50-80:20-40:1-5:1-5. The negative electrode silicon-based slurry further includes an organic solvent, and the organic solvent is methanol, propanol, etc.

[0017] Preferably, the silicon-based material includes one or a mixture of several of elemental silicon, silicon oxide materials, silicon carbide materials, and alloy silicon materials.

[0018] Preferably, the graphite includes one or a mixture of several of artificial graphite, natural graphite, hard carbon, and soft carbon.

[0019] Preferably, step S1 further includes baking the substrate until the water content is below 150 ppm.

[0020] Preferably, the dew point of the preparation environment for step S1 and step S2 is below -35°C.

[0021] The third object of the present invention is to provide a lithium-ion battery aiming at the deficiencies of the prior art, which has high specific capacity, first efficiency, cycle stability, and safety.

[0022] To achieve the above object, the present invention adopts the following technical solutions:

[0023] A lithium-ion battery includes the above-mentioned silicon-doped and lithium-supplemented negative electrode sheet. Specifically, a lithium-ion battery includes a positive electrode sheet, a negative electrode sheet, a separator, an electrolyte, and a housing. The negative electrode sheet is the silicon-doped and lithium-supplemented negative electrode sheet prepared above. After assembling the above-mentioned silicon-doped and lithium-supplemented electrode sheet with the positive electrode sheet and the separator into an electrode core, injecting the electrolyte, and standing still for 1-6 days, there is a certain potential difference between the lithium metal and the silicon-doped negative electrode, and lithium ions can diffuse onto the silicon-doped electrode sheet to achieve the effect of lithium supplementation. In addition, during the subsequent formation and cycling processes, metallic lithium can be gradually dissolved into the electrolyte to supplement lithium for the lithium-ion battery.

[0024] Among them, the active material layer coated on the current collector of the positive electrode sheet can be one or more combinations of compounds including but not limited to those with chemical formulas such as Li a Ni x Co y M z O 2-b N b (where 0.95 ≤ a ≤ 1.2, x > 0, y ≥ 0, z ≥ 0, and x + y + z = 1, 0 ≤ b ≤ 1, M is selected from one or more combinations of Mn and Al, and N is selected from one or more combinations of F, P, and S), and the positive electrode active material can also be one or more combinations including but not limited to LiCoO 2 , LiNiO 2 , LiVO 2 , LiCrO 2 , LiMn 2 O 4 , LiCoMnO 4 , Li 2 NiMn 3 O 8 , LiNi 0.5 Mn 1.5 O 4 , LiCoPO 4 , LiMnPO 4 , LiFePO 4 , LiNiPO 4 , LiCoFSO 4 , CuS 2 , FeS 2 , MoS 2 , NiS, TiS 2A combination of one or more of the above. The positive electrode active material can also be modified. The methods for modifying the positive electrode active material should be known to those skilled in the art. For example, methods such as coating and doping can be used to modify the positive electrode active material. The materials used for the modification treatment can be a combination of one or more of, including but not limited to, Al, B, P, Zr, Si, Ti, Ge, Sn, Mg, Ce, W, etc. The positive electrode current collector is usually a structure or part that collects current. The positive electrode current collector can be various materials suitable for use as the positive electrode current collector of a lithium-ion battery in the art. For example, the positive electrode current collector can be, including but not limited to, a metal foil, and more specifically, including but not limited to, an aluminum foil, etc.

[0025] The separator can be various materials suitable for use as a separator of a lithium-ion battery in the art. For example, it can be a combination of one or more of, including but not limited to, polyethylene, polypropylene, polyvinylidene fluoride, aramid, polyethylene terephthalate, polytetrafluoroethylene, polyacrylonitrile, polyimide, polyamide, polyester, and natural fibers, etc.

[0026] The electrolyte of the lithium-ion battery includes an organic solvent, an electrolyte lithium salt, and an additive. Among them, the electrolyte lithium salt can be LiPF used in a high-temperature electrolyte 6 and / or LiBOB; it can also be at least one of LiBF used in a low-temperature electrolyte 4 , LiBOB, LiPF 6 ; it can also be at least one of LiBF used in an overcharge-preventing electrolyte 4 , LiBOB, LiPF 6 , LiTFSI; it can also be at least one of LiClO 4 , LiAsF 6 , LiCF 3 SO 3 , LiN(CF 3 SO 2 ) 2 . The organic solvent can be a cyclic carbonate, including PC, EC; it can also be a chain carbonate, including DFC, DMC, or EMC; it can also be a carboxylic acid ester, including MF, MA, EA, MP, etc. The additive includes at least one of, including but not limited to, a film-forming additive, a conductive additive, a flame retardant additive, an overcharge-preventing additive, an additive for controlling the content of H 2 O and HF in the electrolyte, an additive for improving low-temperature performance, and a multifunctional additive.

[0027] The material of the housing is one of an aluminum-plastic film, stainless steel, and an aluminum plate. Preferably, the material of the housing is an aluminum-plastic film.

[0028] Compared with the prior art, the beneficial effects of the present invention are as follows: The two outer sides of the silicon-doped lithium-supplemented negative electrode sheet of the present invention are provided with a first silicon-doped coating and a second silicon-doped coating, and the inner side is provided with a lithium-supplemented layer, which has high specific capacity, first efficiency, cycle retention rate, and structural stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 is a front view of the left-right folding substrate of the present invention.

[0030] Figure 2 is a rear view of the left-right folding substrate of the present invention.

[0031] Figure 3 is a front view of the up-down folding substrate of the present invention.

[0032] Figure 4 is a rear view of the up-down folding substrate of the present invention.

[0033] Figure 5 is a schematic structural diagram of the silicon-doped lithium-supplemented negative electrode sheet of the present invention.

[0034] Figure 6 is an assembly schematic diagram of a composite negative electrode sheet formed by laminating a first silicon-doped coating, a first negative electrode current collector, a lithium-supplemented layer, a second negative electrode current collector, and a second silicon-doped layer that are independent of each other from top to bottom.

[0035] Figure 7 is a schematic structural diagram of the negative electrode sheet prepared in Comparative Example 1.

[0036] Wherein: 1. First silicon-doped coating; 2. First negative electrode current collector; 3. Lithium-supplemented layer; 4. Second negative electrode current collector; 5. Second silicon-doped coating; 6. Composite substrate; 7. Tab; 8. Negative electrode silicon-based coating; 9. Negative electrode current collector. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0037] The present invention will be further described in detail below in conjunction with the specific embodiments and the drawings, but the embodiments of the present invention are not limited thereto.

[0038] Example 1

[0039] Graphite:SiOx:acetylene black:styrene-butadiene rubber (SBR) = 76:20:2:2 were mixed and stirred to form a uniform slurry, i.e., the negative electrode silicon-based slurry, which was coated on one side of a 6-μm copper foil (negative electrode current collector 9), rolled to form a negative electrode silicon-based coating 8, the tabs 7 were cut, and it was die-cut into a certain size (depending on the battery model) such as Figure 1 shown substrate. It was baked in an oven until the water content was below 150 ppm, and a 5-μm metal lithium foil of a certain area was rolled onto the copper foil side of the above substrate in a drying room (dew point below -35°C) as Figure 2The composite substrate 6 shown is then folded left and right along the dashed line to form a silicon-doped lithium-compensated negative electrode sheet, that is, a silicon-doped lithium-compensated negative electrode sheet including a first silicon-doped coating 1, a first negative electrode current collector 2, a lithium-compensating layer 3, a second negative electrode current collector 4, and a second silicon-doped coating 5 from top to bottom is obtained as Figure 5 shown. Among them, the thickness of the lithium-compensating layer 3 is 5 μm, and the thicknesses of the first silicon-doped coating 1 and the second silicon-doped coating 5 are 30 μm. After assembling the negative electrode sheet with the positive electrode sheet and the separator into a stacked electrode cell, it is filled with electrolyte and encapsulated into a lithium-ion battery. After standing for 2 days, electrochemical performance tests are carried out.

[0040] Example 2

[0041] Graphite:SiOx:acetylene black:styrene-butadiene rubber (SBR)=65:30:2.5:2.5 are mixed to form a uniform slurry, that is, a negative electrode silicon-based slurry, which is coated on a 6-μm copper foil (negative electrode current collector 9) on one side, and rolled to obtain a negative electrode silicon-based coating 8. The tab 7 is cut, and it is die-cut into a certain size (depending on the battery model) as Figure 3 shown substrate. It is baked in an oven until the water content is below 150 ppm. In a drying room (dew point below -35 °C), a certain area of 10-μm metal lithium foil is rolled onto the copper foil side of the above substrate as Figure 4 shown composite substrate 6, and then folded up and down along the dashed line to form a silicon-doped lithium-compensated negative electrode sheet, that is, a silicon-doped lithium-compensated negative electrode sheet including a first silicon-doped coating 1, a first negative electrode current collector 2, a lithium-compensating layer 3, a second negative electrode current collector 4, and a second silicon-doped coating 5 from top to bottom is obtained as Figure 5 shown. Among them, the thickness of the lithium-compensating layer 3 is 5 μm, and the thicknesses of the first silicon-doped coating 1 and the second silicon-doped coating 5 are 30 μm. After assembling the negative electrode sheet with the positive electrode sheet and the separator into a stacked electrode cell, it is filled with electrolyte and encapsulated into a lithium-ion battery. After standing for 4 days, electrochemical performance tests are carried out.

[0042] Example 3

[0043] Graphite:SiOx:acetylene black:(polyacrylic acid) PAA=54:40:2:4 are mixed to form a uniform slurry, that is, a negative electrode silicon-based slurry, which is coated on a 6-μm copper foil on one side, and after rolling, a negative electrode silicon-based coating 8 is formed. The tab 7 is cut, and it is die-cut into a certain size (depending on the battery model) as Figure 1 shown substrate. It is baked in an oven until the water content is below 150 ppm. In a drying room (dew point below -35 °C), a certain area of 20-μm metal lithium foil is rolled onto the copper foil side of the above negative electrode sheet as Figure 2 shown, and then folded left and right along the dashed line to form a silicon-doped lithium-compensated negative electrode sheet, that is, a silicon-doped lithium-compensated negative electrode sheet including a first silicon-doped coating 1, a first negative electrode current collector 2, a lithium-compensating layer 3, a second negative electrode current collector 4, and a second silicon-doped coating 5 from top to bottom is obtained as Figure 5As shown. Among them, the thickness of the lithium supplement layer 3 is 5 μm, and the thicknesses of the first silicon-doped coating 1 and the second silicon-doped coating 5 are 30 μm. After assembling the negative electrode sheet with the positive electrode sheet and the separator into a stacked cell, it is filled with electrolyte and encapsulated into a lithium-ion battery. After standing for 6 days, electrochemical performance tests are carried out.

[0044] Example 4

[0045] The difference from Example 1 is that the weight ratio of the graphite, silicon-based material, conductive carbon, and binder is 50:20:5:5.

[0046] The rest is the same as in Example 1 and will not be elaborated here.

[0047] Example 5

[0048] The difference from Example 1 is that the weight ratio of the graphite, silicon-based material, conductive carbon, and binder is 55:25:5:5.

[0049] The rest is the same as in Example 1 and will not be elaborated here.

[0050] Example 6

[0051] The difference from Example 1 is that the weight ratio of the graphite, silicon-based material, conductive carbon, and binder is 65:30:3:3.

[0052] The rest is the same as in Example 1 and will not be elaborated here.

[0053] Example 7

[0054] The difference from Example 1 is that the weight ratio of the graphite, silicon-based material, conductive carbon, and binder is 70:40:2:4.

[0055] The rest is the same as in Example 1 and will not be elaborated here.

[0056] Example 8

[0057] The difference from Example 1 is that the thickness of the lithium supplement layer 3 is 5 μm, and the thicknesses of the first silicon-doped coating 1 and the second silicon-doped coating 5 are 20 μm.

[0058] The rest is the same as in Example 1 and will not be elaborated here.

[0059] Example 9

[0060] The difference from Example 1 is that the thickness of the lithium supplement layer 3 is 5 μm, and the thicknesses of the first silicon-doped coating 1 and the second silicon-doped coating 5 are 40 μm.

[0061] The rest is the same as in Example 1 and will not be elaborated here.

[0062] Example 10

[0063] The difference from Example 1 is that the thickness of the lithium compensation layer 3 is 10 μm, and the thicknesses of the first silicon-doped coating 1 and the second silicon-doped coating 5 are 50 μm.

[0064] The rest is the same as in Example 1 and will not be elaborated here.

[0065] Comparative Example 1

[0066] Graphite:SiOx:acetylene black:SBR = 76:20:2:2 was mixed to form a uniform slurry, which was single-sidedly coated on a 6-μm copper foil. After rolling, it was die-cut into a negative electrode sheet of a certain size (depending on the battery model) as Figure 7 shown. It was baked in an oven until the water content was below 150 ppm, and then folded along the dotted line to form an uncompensated lithium and silicon-doped negative electrode sheet. Then, this negative electrode sheet was assembled with a positive electrode sheet and a separator into a stacked cell, and after injecting electrolyte and encapsulating, it was made into a lithium-ion battery. After standing for 2 days, electrochemical performance tests were carried out. The performance data are shown in Table 1.

[0067] Comparative Example 2

[0068] Graphite:SiOx:acetylene black:PAA = 65:30:2.5:2.5 was mixed to form a uniform slurry, which was single-sidedly coated on a 6-μm copper foil. After rolling, it was die-cut into a negative electrode sheet of a certain size (depending on the battery model). It was baked in an oven until the water content was below 150 ppm, and then folded along the dotted line to form an uncompensated lithium and silicon-doped negative electrode sheet. Then, this negative electrode sheet was assembled with a positive electrode sheet and a separator into a stacked cell, and after injecting electrolyte and encapsulating, it was made into a lithium-ion battery. After standing for 4 days, electrochemical performance tests were carried out, and the performance data are shown in Table 1.

[0069] Comparative Example 3

[0070] Graphite:SiOx:acetylene black:PAA = 54:40:2:4 was mixed to form a uniform slurry, which was single-sidedly coated on a 6-μm copper foil. After rolling, it was die-cut into a negative electrode sheet of a certain size (depending on the battery model). It was baked in an oven until the water content was below 150 ppm, and then folded along the dotted line to form an uncompensated lithium and silicon-doped negative electrode sheet. Then, this negative electrode sheet was assembled with a positive electrode sheet and a separator into a stacked cell, and after injecting electrolyte and encapsulating, it was made into a lithium-ion battery. After standing for 6 days, electrochemical performance tests were carried out. The performance data are shown in Table 1.

[0071] Comparative Example 4 uses a composite negative electrode sheet formed by laminating, from top to bottom, an independent first silicon-doped coating 1, a first negative electrode current collector 2, a lithium compensation layer 3, a second negative electrode current collector 4, and a second silicon-doped layer, as Figure 6 shown.

[0072] Performance test: The negative electrode sheets and lithium-ion batteries prepared in the above Examples 1-10 and Comparative Examples 1-4 were subjected to performance tests, and the test results are recorded in Table 1.

[0073] Table 1

[0074]

[0075] As can be seen from Table 1 above, the silicon-doped lithium-supplemented negative electrode sheet prepared by the present invention has a higher first efficiency and capacity retention rate compared to Comparative Examples 1-3. The first efficiency reaches 88.7%, and it remains 94.5% after 100 charge-discharge cycles. By comparing Examples 1-7, it is found that when the weight ratio of the graphite, silicon-based material, conductive carbon, and binder is set to 76:20:2:2, the performance of the lithium-ion battery prepared is better. This is because the silicon-based negative electrode slurry prepared with this ratio has better performance. By comparing Examples 1, 8-10, it is found that when the thickness of the lithium-supplementing layer 3 is set to 5 μm and the thicknesses of the first silicon-doped coating 1 and the second silicon-doped coating 5 are set to 30 μm, that is, when the thickness ratio of the lithium-supplementing layer 3 to the first silicon-doped coating 1 and the second silicon-doped coating 5 is 1:6, the lithium-supplementing effect is the best, and the lithium foil can be completely dissolved and supplemented into the electrolyte, thereby improving the first efficiency. By comparing Examples 1-3 and Comparative Examples 1-3, it is found that using a lithium-supplementing sheet for lithium supplementation effectively improves the initial efficiency, and the prepared lithium-ion battery has good capacity cycle stability. By comparing Examples 1-10 and Comparative Example 4, it is found that the lithium-ion battery prepared by the preparation method of the present invention has better structural stability. Even after the lithium-supplementing sheet is dissolved, it will not delaminate, ensuring the structure of the electrode sheet, and having the effect of improving the initial efficiency and capacity cycle retention rate of the electrode sheet.

[0076] According to the disclosure and teachings of the above specification, those skilled in the art to which the present invention pertains can also make changes and modifications to the above embodiments. Therefore, the present invention is not limited to the above specific embodiments. Any obvious improvements, substitutions, or variations made by those skilled in the art based on the present invention fall within the protection scope of the present invention. In addition, although some specific terms are used in this specification, these terms are only for convenience of description and do not constitute any limitation to the present invention.

Claims

1. A preparation method of a silicon-doped lithium-supplemented negative electrode sheet, characterized in that, the silicon-doped lithium-supplemented negative electrode sheet sequentially includes a first silicon-doped coating, a first negative electrode current collector, a lithium-supplemented layer, a second negative electrode current collector, and a second silicon-doped coating from top to bottom. The first silicon-doped coating is connected to the second silicon-doped coating, and the first negative electrode current collector is connected to the second negative electrode current collector; the preparation method of the silicon-doped lithium-supplemented negative electrode sheet includes the following steps: Step S1, prepare a negative electrode silicon-based slurry. Take a negative electrode current collector and coat the negative electrode silicon-based slurry on one surface of the negative electrode current collector to form a negative electrode silicon-based coating to obtain a substrate; Step S2, take a lithium-supplemented sheet and set the lithium-supplemented sheet on the other surface of the substrate away from the negative electrode silicon-based slurry to obtain a composite substrate; Step S3, with the lithium-supplemented sheet as the inner side surface, fold the composite substrate so that the lithium-supplemented sheet is folded in half to form a lithium-supplemented layer, the negative electrode current collector is folded in half to form a first negative electrode current collector and a second negative electrode current collector, and the negative electrode silicon-based coating is folded in half to form a first silicon-doped coating and a second silicon-doped coating.

2. The preparation method according to claim 1, characterized in that, the first silicon-doped coating and the second silicon-doped coating are integrally formed and connected, and the first negative electrode current collector and the second negative electrode current collector are integrally formed and connected.

3. The preparation method according to claim 1 or 2, characterized in that, the thickness of the lithium-supplemented layer is 1-100 μm, and the thickness of the first silicon-doped coating and / or the second silicon-doped coating is 10-50 μm.

4. The preparation method according to claim 1, characterized in that, the negative electrode silicon-based slurry includes graphite, a silicon-based material, conductive carbon, and a binder, and the weight ratio of graphite, the silicon-based material, conductive carbon, and the binder is 50-80:20-40:1-5:1-5.

5. The preparation method according to claim 4, characterized in that, the silicon-based material includes one or several mixtures of elemental silicon, silicon oxide material, silicon carbide material, and alloy silicon material.

6. The preparation method according to claim 4, characterized in that, the graphite includes one or several mixtures of artificial graphite, natural graphite, hard carbon, and soft carbon.

7. The preparation method according to claim 1, characterized in that, Step S1 further includes baking the substrate until the water content is below 150 ppm.

8. The preparation method according to claim 1, characterized in that, the dew point of the preparation environment in Step S1 and Step S2 is below -35°C.

9. A lithium-ion battery, characterized in that, it includes a silicon-doped lithium-supplemented negative electrode sheet prepared by the preparation method according to any one of claims 1 to 8.

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