Negative electrode sheet and silicon-carbon battery

Abstract

In order to overcome the problem of high expansion rate of the silicon-carbon system battery in the prior art affecting the battery performance, the application provides a negative electrode sheet and a silicon-carbon battery; the negative electrode sheet comprises a current collector and an active material layer, the active material layer comprises a first material layer and a second material layer, the first material layer is arranged on the surface of the current collector, the second material layer is arranged on the side of the first material layer away from the current collector, a plurality of first micropores are arranged on the surface of the first material layer, a plurality of second micropores are arranged on the surface of the second material layer, and the plurality of first micropores and the plurality of second micropores are filled with silicon material. The negative electrode sheet provided by the application provides accommodation space for the expansion of the silicon material through the structure of the plurality of first micropores and the plurality of second micropores, improves the expansion problem of the silicon-carbon negative electrode, enables the battery to more efficiently perform electrochemical reactions in the charging and discharging process, and further improves the overall electrical performance of the battery.

Description

Technical Field

[0001] This invention belongs to the field of battery technology, specifically relating to a negative electrode and a silicon-carbon battery. Background Technology

[0002] Silicon anode materials have a high theoretical specific capacity and can play a significant role in improving battery energy density. However, during the charging process of silicon-carbon batteries, the silicon anode material absorbs lithium ions, causing its volume to expand rapidly. This expansion damages the solid electrolyte interphase (SEI) film formed during the initial charging. Once the SEI film is damaged, the anode material reacts again with the electrolyte, forming a new SEI film on the newly exposed surface. This process continuously consumes lithium ions and electrolyte, reducing the amount of active material available for electrochemical reactions within the battery, further decreasing battery capacity, accelerating battery aging, and affecting cycle performance. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to address the issue of the high expansion rate of silicon-carbon batteries affecting battery performance in the prior art, and to provide a negative electrode and a silicon-carbon battery.

[0004] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows:

[0005] A negative electrode is provided, comprising a current collector and an active material layer. The active material layer includes a first material layer and a second material layer. The first material layer is disposed on the surface of the current collector, and the second material layer is disposed on the side of the first material layer facing away from the current collector. The first material layer has a plurality of first micropores, and the second material layer has a plurality of second micropores. The plurality of first micropores and the plurality of second micropores are filled with silicon material.

[0006] Optionally, one end of the first micropore penetrates the first material layer on the side facing the second material layer, and the opening depth of the first micropore is 10%-50% of the thickness of the first material layer;

[0007] One end of the second micropore passes through the second material layer on the side opposite to the first material layer, and the second micropore penetrates the second material layer.

[0008] Optionally, the first micropore and the second micropore extend along the thickness direction of the current collector.

[0009] Optionally, the silicon material filling amount in the first micropore is 5%-50%;

[0010] The silicon material filling amount in the second micropore is 5%-50%.

[0011] Optionally, the amount of silicon material filling the first micropore and the second micropore is the same.

[0012] Optionally, the diameter of the first micropore is smaller than the diameter of the second micropore.

[0013] Optionally, the diameter of the first micropore is 2-4 mm, and the diameter of the second micropore is 5-8 mm.

[0014] Optionally, the pore size of each of the first micropores is the same; and / or,

[0015] The pore size of each of the second micropores is the same.

[0016] Optionally, the spacing between adjacent first micropores is 4-6 mm, and the spacing between adjacent second micropores is 2-4 mm.

[0017] Optionally, the coating thickness of the first material layer is 20-50 mm, and the coating thickness of the second material layer is 5-50 mm.

[0018] Optionally, the ratio of the coating surface density of the first material layer to the coating surface density of the second material layer is 80:20-50:50.

[0019] Optionally, the surface density of the first material layer is 20-100 g / m². 2 The surface density of the second material layer is 10-100 g / m³. 2 .

[0020] Optionally, the particle size of the silicon material filling the first micropore is the same as the particle size of the silicon material filling the second micropore.

[0021] Optionally, the active material in the active material layer includes one or more of graphite, porous carbon, hard carbon, and soft carbon.

[0022] Optionally, the negative electrode slurry for the first material layer is the same as the negative electrode slurry used to form the second material layer.

[0023] On the other hand, the present invention provides a method for preparing a negative electrode sheet, which is used to prepare the aforementioned negative electrode sheet; the preparation method includes the following steps:

[0024] The first material layer is disposed on the current collector to obtain the first negative electrode precursor;

[0025] A first micropore is processed on the first material layer of the first negative electrode precursor, and silicon material is filled into the first micropore to obtain the second negative electrode precursor.

[0026] A second material layer is disposed on the second negative electrode precursor to obtain a third negative electrode precursor;

[0027] A second micropore is processed on the second material layer of the third negative electrode precursor, and silicon material is filled into the second micropore to obtain the negative electrode.

[0028] Optionally, the step of processing a first micropore on the first material layer of the first negative electrode precursor and filling the first micropore with silicon material to obtain the second negative electrode precursor includes:

[0029] A first protective film is applied to the first negative electrode precursor.

[0030] The first negative electrode precursor covered with the first protective film is etched to form the first micropore on the first material layer of the first negative electrode precursor. The first protective film is hollowed out at the position corresponding to the first micropore to obtain the first micropore assembly.

[0031] Silicon material is deposited on the first microporous component, so that the silicon material fills the first micropores; after the deposition is completed, the first protective film on the first microporous component is removed to obtain the second negative electrode precursor.

[0032] Optionally, the deposition raw material for the silicon material is silane;

[0033] The step of depositing silicon material on the first microporous component, such that the silicon material fills the first micropores, includes:

[0034] By holding the temperature at 200-900℃ for 0.5-10 hours, silane is deposited on the surface of the first microporous component and inside the first micropores through vapor deposition and then decomposed to form the silicon material.

[0035] Optionally, the step of processing a second micropore on the second material layer of the third negative electrode precursor and filling the second micropore with silicon material to obtain the negative electrode includes:

[0036] A second protective film is applied to the third negative electrode precursor.

[0037] The third negative electrode precursor covered with the second protective film is etched to form the second micropore on the second material layer of the third negative electrode precursor. The second protective film is hollowed out at the position corresponding to the second micropore to obtain the second micropore assembly.

[0038] Silicon material is deposited on the second microporous component, so that the silicon material fills the second micropores; after the deposition is completed, the second protective film on the second microporous component is removed to obtain the negative electrode sheet.

[0039] Optionally, the deposition raw material for the silicon material is silane;

[0040] The step of depositing silicon material on the second microporous component, such that the silicon material fills the second micropores, includes:

[0041] By holding the temperature at 200-900℃ for 0.5-10 hours, silane is deposited on the surface of the second microporous component and inside the second micropores through vapor deposition and then decomposed to form the silicon material.

[0042] On the other hand, the present invention provides a silicon-carbon battery, comprising a positive electrode, a separator, and a negative electrode or a negative electrode prepared by a method thereof.

[0043] The beneficial effects of this application are as follows:

[0044] In the composite electrode provided by this invention, a first material layer and a second material layer are respectively disposed on the current collector, and a first micropore and a second micropore are respectively disposed on the first material layer and the second material layer. The micropores are filled with silicon material. The micropore structure can provide corresponding space for the expansion of silicon material, reducing the risk of electrode structure damage due to volume change, thereby effectively improving the expansion problem of silicon-carbon anode. In addition, multiple micropores are uniformly distributed on the surface of the first material layer and the second material layer, so that the expansion stress of silicon material can be dispersed at multiple locations. Compared with the case of concentrated distribution of silicon material, the first material layer, the second material layer, and the corresponding multiple micropore structure are beneficial to further reduce the problems of electrode cracking and pulverization due to stress concentration, and improve the structural stability of electrode during charge-discharge cycle. The presence of the first micropore and the second micropore increases the contact area between silicon material and electrolyte. As an active material, full contact between silicon material and electrolyte helps lithium ion transport and insertion / extraction processes between electrode and electrolyte, thereby improving the kinetic performance of electrode reaction, enabling the battery to carry out electrochemical reaction more efficiently during charge-discharge process, and thus improving the overall electrical performance of battery. Attached Figure Description

[0045] Figure 1 This is a schematic diagram of the first material layer structure provided by the present invention;

[0046] Figure 2 This is a schematic cross-sectional view of the first material layer provided by the present invention;

[0047] Figure 3 This is a schematic diagram of the second material layer structure provided by the present invention;

[0048] Figure 4 This is a schematic cross-sectional view of the second material layer provided by the present invention;

[0049] Figure 5 This is a schematic diagram of the negative electrode structure provided by the present invention;

[0050] Figure 6This is a graph showing the relationship between the number of cycles and the expansion rate of silicon-carbon batteries provided in Example 1 and Comparative Example 1.

[0051] The reference numerals in the accompanying drawings are as follows:

[0052] 1. Current collector; 2. Active material layer; 21. First material layer; 211. First micropore; 22. Second material layer; 221. Second micropore; 3. Silicon material; 4. Negative electrode. Detailed Implementation

[0053] To make the technical problems solved, the technical solutions, and the beneficial effects of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0054] In the description of this invention, it should be understood that the terms "longitudinal," "radial," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientation or positional relationships, are based on the orientation or positional relationships shown in the accompanying drawings and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0055] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0056] Reference Figure 1-5 This invention provides a negative electrode 4, including a current collector 1 and an active material layer 2. The active material layer 2 includes a first material layer 21 and a second material layer 22. The first material layer 21 is disposed on the surface of the current collector 1, and the second material layer 22 is disposed on the side of the first material layer 21 facing away from the current collector 1. The first material layer 21 is provided with a plurality of first micropores 211, and the second material layer 22 is provided with a plurality of second micropores 221. The plurality of first micropores 211 and the plurality of second micropores 221 are all filled with silicon material 3.

[0057] Specifically, in the negative electrode 4 provided by the present invention, a first material layer 21 and a second material layer 22 are respectively disposed on the current collector 1, and a first micropore 211 and a second micropore 221 are respectively disposed on the first material layer 21 and the second material layer 22. The micropores are filled with silicon material 3. The micropore structure can provide corresponding space for the expansion of silicon material 3, reducing the risk of electrode structure damage due to volume change, thereby effectively improving the expansion problem of silicon-carbon negative electrode; in addition, multiple micropores are uniformly distributed on the first material layer 21 and the second material layer 22, so that the expansion stress of silicon material 3 can be reduced. The silicon material 3 is dispersed in multiple locations. Compared with the concentrated distribution of silicon material 3, the first material layer 21 and the second material layer 22, as well as the corresponding multiple microporous structures, are conducive to further reducing problems such as cracking and pulverization of the electrode due to stress concentration, and improving the structural stability of the electrode during charge and discharge cycles. The presence of the first micropore 211 and the second micropore 221 increases the contact area between silicon material 3 and electrolyte. As an active material, the full contact between silicon material 3 and electrolyte helps the transport and insertion / extraction of lithium ions between the electrode and electrolyte, thereby improving the kinetic performance of the electrode reaction.

[0058] In the negative electrode 4, the current collector 1 is connected to the silicon material 3 through the first material layer 21, and the second material layer 22 further covers the first material layer 21, so that electrons can be transported in an orderly manner between different material layers, which can reduce the obstruction of electron transport, improve the electron conduction efficiency, thereby improving the charge and discharge efficiency and rate performance of the battery, thus ensuring the stable electrical performance of the battery during long cycle and extending the battery's service life.

[0059] In one embodiment, one end of the first micropore 211 penetrates the side of the first material layer 21 facing the second material layer 22, and the opening depth of the first micropore 211 is 10%-50% of the thickness of the first material layer 21;

[0060] One end of the second micropore 221 penetrates the side of the second material layer 22 away from the first material layer 21, and the second micropore 221 penetrates the thickness of the second material layer 22.

[0061] Specifically, the first micropore 211 extends to the side facing the second material layer 22, which facilitates smoother lithium ion transport between the first material layer 21 and the second material layer 22. Lithium ions can migrate rapidly between the two layers through the first micropore 211, improving ion transport efficiency and thus enhancing the battery's charge and discharge performance. The second micropore 221 extends to the side away from the first material layer 21, allowing for more sufficient contact between the silicon material 3 and the electrolyte. During battery charge and discharge, this helps to form a more stable solid electrolyte interface (SEI) film on the electrode surface, thereby promoting lithium ion transport and improving battery cycle performance.

[0062] The opening depth of the first micropore 211 is set to be 10%-50% of the thickness of the first material layer 21, so that the first micropore 211 occupies a certain proportion of space in the first material layer 21. When the silicon material 3 expands during charging and discharging, the first micropore 211 can provide a certain buffer space. When the expansion of the silicon material 3 is small, the 10% depth of the first micropore can initially accommodate the expansion of the silicon material 3. The second micropore 221 penetrates the second material layer 22, which means that the second micropore 221 provides a larger space for the expansion of the silicon material 3 in the second material layer 22, so that the expansion of the silicon material 3 on the side near the electrode surface can be fully accommodated by the second micropore 221. That is, the expansion of the silicon-carbon battery is improved by the opening depth of the first micropore 211 and the second micropore 221.

[0063] Specifically, when etching the second micro-hole 221 on the second material layer 22, the areal density ratio of the first material layer 21 and the second material layer 22 is pre-designed during the coating operation. The electrode sheet after coating and baking has a certain thickness. At this time, the thickness of the first material layer 21 can be determined. Then, by subtracting the thickness of the first material layer 21 from the total thickness, the thickness of the second material layer 22 can be obtained. Thus, when etching the second micro-hole 221 that penetrates the second material layer 22, the etching of the first material layer 21 can be avoided, thus avoiding damage to the structure of the first material layer 21. Furthermore, if laser etching is used, the required etching depth can be achieved by controlling the power of the laser during etching.

[0064] Further, in a preferred embodiment, the opening depth of the first micropore 211 is 25%-50% of the thickness of the first material layer 21, that is, the opening depth of the first micropore 211 can be 25%, 28%, 30%, 35%, 40%, 45% or 50% of the thickness of the first material layer 21.

[0065] In one embodiment, the first micropore 211 and the second micropore 221 extend along the thickness direction of the negative electrode 4 of the current collector 1.

[0066] On the one hand, during charging and discharging, the first micropore 211 and the second micropore 221, extending along the thickness direction, can quickly intercalate and deintercalate between the current collector 1 and the silicon active material, greatly improving lithium-ion transport efficiency and thus enhancing the battery's charging and discharging performance, enabling faster charging speeds and higher discharge power. Simultaneously, due to the large volume change of the silicon material 3 during charging and discharging, the micropores extending along the thickness direction provide space for the expansion of the silicon material 3 in the electrode thickness direction, better dispersing the stress generated by the expansion and enhancing the structural stability of the electrode during charge-discharge cycles. Furthermore, the micropores along the thickness direction facilitate uniform penetration of the electrolyte into the active material layer 2. From the electrode surface to the interior, the electrolyte can fully contact the silicon material 3 through the micropores, allowing the electrochemical reaction to occur more uniformly throughout the entire active material layer 2, thereby improving the overall battery performance.

[0067] In one embodiment, the amount of silicon material 3 filling the first micropore 211 and the second micropore 221 is the same.

[0068] Specifically, when the amount of silicon material 3 filling the first micropore 211 and the second micropore 221 is the same, the volume expansion of silicon material 3 in the two layers of material is similar during the charging and discharging process, making the expansion of the electrode sheet in the thickness direction more uniform, avoiding the problem of excessive expansion of a certain layer of silicon material 3, which could cause the electrode sheet to bend or delaminate.

[0069] In addition, the amount of silicon material 3 filling in the first micropore 211 and the second micropore 221 is the same, which means that the number of active sites for lithium ion insertion and extraction provided by the silicon material 3 in the two layers is similar. During charging, lithium ions can be inserted into the silicon material 3 of the first material layer 21 and the second material layer 22 at a relatively uniform rate, and can also be extracted at a relatively uniform rate during discharge. This is beneficial to optimizing the transport dynamics of lithium ions in the entire active material layer 2, making the transport of lithium ions more stable and efficient, and improving the charge and discharge performance of the battery.

[0070] In one embodiment, the diameter of the first micropore 211 is smaller than the diameter of the second micropore 221.

[0071] The first micropore 211 has a smaller pore size than the second micropore 221, forming a gradient buffer structure. The first micropore 211, which is closer to the current collector 1, has a smaller pore size, which limits the expansion of the silicon material 3. This helps to limit the excessive expansion of the silicon material 3 in the region near the current collector 1 and ensures a tight connection between the current collector 1 and the active material. Meanwhile, the second micropore 221 of the second material layer 22 has a larger pore size, which provides more space for the silicon material 3 to expand further. This forms a gradient buffer mechanism from the inside out, which more effectively copes with the volume change of silicon during charging and discharging and alleviates the expansion of the silicon-carbon anode.

[0072] In one embodiment, the diameter of the first micropore 211 is 2-4 mm, and the diameter of the second micropore 221 is 5-8 mm.

[0073] Specifically, the diameter of the first micropore 211 can be 2mm, 2.5mm, 3mm, 3.5mm or 4mm; the diameter of the second micropore 221 can be 5mm, 5.5mm, 6mm, 6.5mm, 7mm, 7.5mm or 8mm.

[0074] On the one hand, the pore size of the first micropore (2-4 mm) provides adequate expansion space for the silicon material 3 on the side near the current collector 1. This pore size range is neither too small, which would cause excessive compression of the silicon material 3 during initial expansion, nor too large, which would make the silicon material 3 too loose near the current collector 1, affecting the stability of the electrical connection with the current collector 1. The pore size of the second micropore (5-8 mm) provides more sufficient expansion space for the silicon material 3 on the side away from the current collector 1. As the volume expansion of the silicon material 3 intensifies during charging and discharging, the larger pore size of the second micropore 221 can effectively accommodate further volume changes of the silicon material 3. On the other hand, if the pore size is too large, the silicon material 3 is prone to aggregate within the micropores, resulting in excessively high local expansion stress. The appropriate pore size limits the range of motion of the silicon material 3, making it relatively uniformly distributed within the micropores, thereby evenly distributing the expansion stress throughout the entire active material layer 2, avoiding the cracking or detachment of the electrode due to stress concentration, and extending the service life of the electrode.

[0075] Reference Figure 1 and Figure 3 In one embodiment, the pore size of each of the first micropores 211 is the same; and / or, the pore size of each of the second micropores 221 is the same.

[0076] Specifically, multiple first micropores 211 have the same pore size, and multiple second micropores 221 have the same pore size. This uniform pore size is beneficial for the transport of lithium ions within the micropores. The uniform pore size makes the diffusion path and resistance of lithium ions within each micropore more similar, thereby improving the consistency and efficiency of lithium ion transport. In addition, the uniform pore size helps the active material to be distributed more evenly within the micropores, thereby optimizing the electron conduction path. In the first material layer 21 and the second material layer 22, since the silicon material 3 is evenly distributed within the micropores with the same pore size, the conduction of electrons in the active material is smoother and more uniform, reducing the resistance difference caused by poor local electron conduction and improving the overall electron conduction efficiency.

[0077] In one embodiment, the spacing between adjacent first micropores 211 is 4-6 mm, and the spacing between adjacent second micropores 221 is 2-4 mm.

[0078] Specifically, the spacing of the first micropore 211 can be 4mm, 4.5mm, 5mm, 5.5mm or 6mm; the spacing of the second micropore 221 can be 2mm, 2.5mm, 3mm, 3.5mm or 4mm.

[0079] As described above, the spacing between the second micropores 221 is smaller than that between the first micropores 211, meaning that the silicon material 3 is more densely distributed in the second material layer 22, increasing the reaction sites for the active material. During the electrochemical reaction, lithium ions can more quickly find reaction sites for insertion and extraction, accelerating the electrochemical reaction rate on the electrode surface. Simultaneously, the relatively large micropore spacing of the first material layer 21 complements the smaller micropore spacing of the second material layer 22, effectively addressing the volume changes of the silicon-carbon anode during charging and discharging.

[0080] In addition, the reasonable micropore spacing helps to maintain the overall structure of the active material layer 2. After multiple expansion and contraction cycles of the silicon material 3, the electrode will not collapse due to stress accumulation, thus ensuring good contact between the silicon material 3 and the current collector 1 and each material layer, which is conducive to improving the stability of the battery.

[0081] In one embodiment, the coating thickness of the first material layer 21 is 20-50 mm, and the coating thickness of the second material layer 22 is 5-50 mm.

[0082] Specifically, the coating thickness of the first material layer 21 in this application is set to 20-50 mm. If the thickness is too thin, the first material layer 21 may not be able to effectively support the silicon material 3 and the second material layer 22 filled in the micropores. During the charging and discharging process of the battery, the stress generated by the expansion and contraction of the silicon material 3 can easily cause the first material layer 21 to crack, thereby affecting the overall structural stability of the electrode. If the thickness is too thick, although the mechanical stability may be enhanced, it will increase the transport distance of lithium ions in the first material layer 21, reduce the ion transport efficiency, and cause the charging and discharging performance of the battery to decline.

[0083] The second material layer 22 is in contact with the electrolyte, and its coating thickness also affects the surface performance of the battery. In this application, the coating thickness of the second material layer 22 is set to 5-50 mm, which is beneficial for the second material layer 22 to form a stable SEI film in the electrolyte, thereby improving the safety and cycle stability of the battery.

[0084] Specifically, in a preferred embodiment, the coating thickness of the first material layer 21 is 25-45 mm, and further, the coating thickness of the first material layer 21 can be 25 mm, 30 mm, 35 mm, 40 mm or 45 mm; in a preferred embodiment, the coating thickness of the second material layer 22 can be 15-30 mm, and further, the coating thickness of the second material layer 22 can be 15 mm, 20 mm, 25 mm or 30 mm.

[0085] In one embodiment, the ratio of the coating surface density of the first material layer 21 to the coating surface density of the second material layer 22 is 80:20-50:50.

[0086] A suitable areal density ratio helps to improve the bonding force between the first material layer 21 and the second material layer 22. The areal densities of the two materials are matched to each other, ensuring that lithium ions can be smoothly transported between the two layers during charging and discharging, and maintaining the stability of the negative electrode 4.

[0087] By setting the coating density according to this ratio, the first material layer 21 and the second material layer 22 can work together to cope with the volume change of silicon material 3. When the first material layer 21 bears a relatively large amount of active material (the ratio is close to 80:20), it can buffer the stress generated by the expansion of silicon material 3 to a certain extent and disperse some of the stress to the second material layer 22. As the ratio changes to 50:50, the ability of the two materials to share the stress is further enhanced, making the stress distribution of the entire negative electrode 4 more uniform. This effectively reduces the risk of electrode breakage and pulverization caused by stress concentration and ensures the structural integrity of the negative electrode 4 during the charge and discharge cycle.

[0088] In one embodiment, the surface density of the first material layer 21 is 20-100 g / m². 2 The surface density of the second material layer 22 is 10-100 g / m³. 2 .

[0089] It should be noted that if the coating density is too high and the active material is too thick, the lithium-ion diffusion path will become longer and the resistance will increase, thus reducing the battery's charging and discharging efficiency and power density.

[0090] The inventors previously verified that when the surface density of the first material layer 21 is 20-100 g / m², 2 The surface density of the second material layer 22 is 10-100 g / m³. 2 At the same time, the structure and porosity of the first material layer 21 and the second material layer 22 can be maintained in a good state, providing a smooth transport channel for lithium ions and realizing fast charging and stable discharge.

[0091] Specifically, in a preferred embodiment, the surface density of the first material layer 21 is 35-80 g / m². 2 Furthermore, the surface density of the first material layer 21 can be 35 g / m². 2 40g / m 2 45g / m 2 50g / m 2 55g / m 2 60g / m 2 65g / m 2 70g / m 2 75g / m 2 Or 80g / m 2 ;

[0092] In a preferred embodiment, the surface density of the second material layer 22 is 20-40 g / m². 2 Furthermore, the surface density of the first material layer 21 can be 20 g / m². 2 25g / m 2 30g / m 2 35g / m 2 or 40g / m 2 .

[0093] In one embodiment, the active material of the active material layer 2 includes one or more of graphite, porous carbon, hard carbon, and soft carbon.

[0094] In one embodiment, the negative electrode slurry of the first material layer 21 is the same as the negative electrode slurry used to form the second material layer 22.

[0095] The use of the same negative electrode slurry to prepare the first material layer 21 and the second material layer 22 indicates that the first material layer 21 and the second material layer 22 are highly similar in chemical composition and physical properties. During the charging and discharging process, the performance differences between different regions inside the battery are reduced, and the consistency and stability of the overall battery performance are improved. Since the two material layers have similar properties, the interface characteristics and transport resistance encountered by lithium ions during the process of lithium ions traveling from the current collector 1 through the first material layer 21 to the second material layer 22, or in the reverse direction, are more uniform. This helps to optimize the transport path of lithium ions in the negative electrode sheet 4, and further improves the charging and discharging efficiency and rate performance of the battery.

[0096] In another embodiment of this application, a method for preparing a negative electrode sheet is provided, comprising the following steps:

[0097] The first material layer 21 is disposed on the current collector 1 to obtain the first negative electrode precursor;

[0098] A first micropore 211 is processed on the first material layer 21 of the first negative electrode precursor, and silicon material 3 is filled into the first micropore 211 to obtain the second negative electrode precursor.

[0099] The second material layer 22 is disposed on the second negative electrode precursor to obtain the third negative electrode precursor;

[0100] A second micropore 221 is processed on the second material layer 22 of the third negative electrode precursor, and silicon material 3 is filled into the second micropore 221 to obtain the negative electrode 4.

[0101] The preparation of the slurry for the first material layer 21 and / or the second material layer 22 specifically includes the following operations:

[0102] 22 kg of graphite, 1 kg of CMC and 10.5 kg of water were added sequentially and stirred at 200 rpm for 30 min. Then, 1 kg of SBR, 12.5 kg of water and 0.3 kg of NMP were added sequentially and stirred at 400 rpm for 4 h to prepare a uniformly dispersed slurry, which is the slurry of the first material layer 21 and / or the second material layer 22. The slurry has a solid content of 49% (the solid content ratio of graphite, CMC and SBR is 98%, 1% and 1% respectively).

[0103] In one embodiment, the step of processing a first micropore 211 on the first material layer 21 of the first negative electrode precursor and filling the first micropore 211 with silicon material 3 to obtain the second negative electrode precursor includes:

[0104] A first protective film is applied to the first negative electrode precursor.

[0105] The first negative electrode precursor covered with the first protective film is etched to form the first micropore 211 on the first material layer 21 of the first negative electrode precursor. The first protective film is hollowed out at the position corresponding to the first micropore 211 to obtain the first micropore 211 assembly.

[0106] Silicon material 3 is deposited on the first micropore 211 component, so that the silicon material 3 fills the first micropore 211; after the deposition is completed, the first protective film on the first micropore 211 component is removed to obtain the second negative electrode precursor.

[0107] Specifically, a first protective film is covered on the first negative electrode precursor. The purpose of this film is to protect the areas that do not need to be etched, thereby providing a shielding effect and ensuring that subsequent etching is carried out only in specific areas, thus precisely forming the required first micropore 211 structure.

[0108] The first negative electrode precursor covered with the first protective film is etched. The etching can remove part of the first material layer 21, thereby precisely forming a predetermined first micropore 211 on the first material layer 21, and obtaining the first micropore 211 assembly.

[0109] The first protective film is a high-temperature resistant protective film, including a ceramic film layer.

[0110] In one embodiment, the deposition raw material for the silicon material 3 is silane;

[0111] The step of depositing silicon material 3 on the first micropore 211 component, such that the silicon material 3 fills the first micropore 211, includes:

[0112] By holding the temperature at 200-900℃ for 0.5-10 hours, silane is deposited on the surface of the first micropore 211 component and inside the first micropore 211 through vapor deposition and then decomposed to form the silicon material 3.

[0113] Specifically, a temperature range of 150-350℃ and a holding time of 60-120 minutes are used. This temperature range provides sufficient energy for the vapor deposition and pyrolysis reaction of silane, allowing silane molecules to effectively deposit and pyrolyze on the surface and within the micropores of the first micropore 211 component, forming silicon material 3. If the temperature is too low, the silane may not be able to fully pyrolyze and deposit, resulting in insufficient filling or failure to form silicon material 3; if the temperature is too high, it may cause thermal damage to the first micropore 211 component, current collector 1, other material layers, and other structures, affecting the overall performance and structural stability of the electrode. On the other hand, a holding time of 60-120 minutes is sufficient to ensure that the silane has enough time to undergo deposition and pyrolysis reactions, allowing silicon material 3 to fill the first micropore 211 relatively uniformly. The expansion of the silicon material 3 filled in the micropores can be buffered to a certain extent within the micropores, reducing the risk of electrode structure damage caused by volume change, further improving the expansion problem of silicon-carbon anode. Moreover, the uniformly filled silicon material 3 is conducive to smoother transport and insertion / extraction of lithium ions between the electrode and the electrolyte, thereby improving the kinetic performance of the electrode reaction and enhancing the overall electrical performance of the battery.

[0114] Silane was chosen as the deposition raw material for silicon material 3 because it is a relatively reactive compound that readily undergoes gas-phase reactions. Under suitable temperature conditions, it can easily decompose to form silicon material 3. Consequently, the preparation process does not require overly harsh reaction conditions or complex equipment, reducing production difficulty and cost. Furthermore, the purity and quality of silane are relatively easy to control, which helps ensure the purity and performance of the final silicon material 3, thereby guaranteeing the stability of the quality and performance of the negative electrode 4.

[0115] In one embodiment, the step of processing a second micropore 221 on the second material layer 22 of the third negative electrode precursor and filling the second micropore 221 with silicon material 3 to obtain the negative electrode 4 includes:

[0116] A second protective film is applied to the third negative electrode precursor.

[0117] The third negative electrode 4 precursor covered with the second protective film is etched to form the second micropore 221 on the second material layer 22 of the third negative electrode precursor. The second protective film is hollowed out at the position corresponding to the second micropore 221 to obtain the second micropore 221 assembly.

[0118] Silicon material 3 is deposited on the second micropore 221 component, so that the silicon material 3 fills the second micropore 221; after the deposition is completed, the second protective film on the second micropore 221 component is removed to obtain the negative electrode 4.

[0119] When the second protective film is covered on the third negative electrode precursor, the protective film can protect the area except for the area where the second micropore 221 needs to be formed, and avoid unnecessary damage during subsequent etching. This is the same as the function of the first protective film on the first negative electrode precursor. The second protective film is the same as the first protective film, both of which are high temperature resistant protective films.

[0120] In one embodiment, the step of depositing silicon material 3 on the second micropore 221 component, such that the silicon material 3 fills the second micropore 221, includes:

[0121] By holding the temperature at 200-900℃ for 0.5-10 hours, silane is deposited on the surface of the second micropore 221 component and inside the second micropore 221 through vapor deposition and then decomposed to form the silicon material 3.

[0122] In another embodiment of this application, a silicon-carbon battery is provided, including a positive electrode, a separator, and a negative electrode 4 or a negative electrode 4 prepared by the method of preparing the negative electrode.

[0123] Specifically, the specific preparation operations of the negative electrode sheet include:

[0124] 1) Add 22kg of graphite, 1kg of CMC and 10.5kg of water to the mixing tank in sequence, stir at 200rpm for 30min, then add 1kg of SBR, 12.5kg of water and 0.3kg of NMP in sequence, stir at 400rpm for 4h to make a uniformly dispersed slurry with a solid content of 49% (the solid content ratio of graphite, CMC and SBR is 98%, 1% and 1% respectively).

[0125] 2) Coat the prepared slurry from step 1) onto the copper foil as the first material layer (area density 46.9 g / m²). 2 The coated electrode sheet is baked at 180°C until the moisture is dried, thus obtaining the first negative electrode precursor.

[0126] A first protective film is covered on the first negative electrode precursor, and the first negative electrode precursor covered with the first protective film is etched to form a first micropore (the aperture is adjusted according to the power of the laser, the aperture is 2-4mm, the depth is 50% of the thickness of the first material layer 21, and the aperture spacing is 4-6mm), thereby obtaining the first micropore 211 component.

[0127] The first microporous 211 component is subjected to formation vapor deposition and kept at 200-900℃ for 0.5-10h. The vapor deposition fills the first microporous 211 with silane gas. After the deposition is completed, the first protective film on the first microporous 211 component is removed to obtain the second negative electrode precursor.

[0128] 3) Coat the slurry prepared in step 1) onto the precursor of the second negative electrode (area density 20.1 g / m³). 2 The sample is baked at 180°C for 7 minutes until the moisture is dried, thus obtaining the precursor for the third negative electrode.

[0129] A second protective film is covered on the third negative electrode precursor. The third negative electrode precursor covered with the second protective film is etched to form a second micropore 221 (the aperture is adjusted according to the laser power, the aperture is 4-7mm, the depth is 30% of the thickness of the third negative electrode precursor, and the aperture spacing is 2-4mm) to obtain the second micropore 221 assembly.

[0130] The second micropore 221 component was subjected to formation vapor deposition at 150-350℃ for 60-120 min. Vapor deposition allowed silane gas to fill the second micropore 221. After deposition, the first protective film on the second micropore 221 component was removed to obtain the negative electrode. Figure 5 ).

[0131] 4) Assemble the obtained negative electrode 4 with the positive electrode and the separator to obtain a silicon-carbon battery.

[0132] The first micropore 211 and the second micropore 221 can also be obtained by mechanical drilling or chemical etching; the graphite can also be one or more of porous carbon, hard carbon, and soft carbon.

[0133] The present invention will be further illustrated by the following examples.

[0134] Example 1

[0135] This embodiment illustrates a negative electrode sheet and a silicon-carbon battery disclosed in this invention, including the following operational steps:

[0136] Preparation of slurry:

[0137] Add 22 kg of graphite, 1 kg of CMC and 10.5 kg of water to a mixing tank in sequence, and stir at 200 rpm for 30 min. Then add 1 kg of SBR, 12.5 kg of water and 0.3 kg of NMP in sequence, and stir at 400 rpm for 4 h to make a uniformly dispersed slurry with a solid content of 49% (the solid content ratio of graphite, CMC and SBR is 98%, 1% and 1% respectively).

[0138] Preparation of negative electrode:

[0139] The slurry was coated onto copper foil as the first material layer (area density 46.9 g / m²). 2 The coated electrode sheet is baked at 180°C until the moisture is dried, thus obtaining the first negative electrode precursor.

[0140] A first protective film is covered on the first negative electrode precursor. The first negative electrode precursor covered with the first protective film is laser etched to form a first micropore with a diameter of 3 mm, a depth of 50% of the thickness of the first material layer, and a hole spacing of 4 mm, thus obtaining a first micropore assembly.

[0141] The first microporous component was subjected to formation vapor deposition and kept at 450°C for 5 hours. The vapor deposition caused silane gas to fill the first micropores (filling amount was 10%). After the deposition was completed, the first protective film on the first microporous component was removed to obtain the second negative electrode precursor.

[0142] The slurry prepared above is coated onto the second negative electrode precursor as the second material layer (area density 20.1 g / m²). 2 Bake at 180℃ for 7 minutes. After baking, the precursor of the third negative electrode is obtained.

[0143] A second protective film is covered on the third negative electrode precursor, and the third negative electrode precursor is laser etched to form a second micropore. The second micropore penetrates the third negative electrode precursor. The diameter of the second micropore is 7 mm and the spacing between the pores is 2 mm, thus obtaining the second micropore assembly.

[0144] The second microporous component was subjected to formation vapor deposition and held at 200°C for 100 min. Vapor deposition allowed silane gas to fill the second micropores (filling amount was 10%). After deposition, the first protective film on the second microporous component was removed to obtain the negative electrode.

[0145] Preparation of silicon-carbon batteries:

[0146] The obtained negative electrode sheet is assembled with the positive electrode sheet and the separator to obtain a silicon-carbon battery.

[0147] Example 2

[0148] This embodiment illustrates a negative electrode and silicon-carbon battery disclosed in this invention, including most of the operations in Embodiment 1, with the following differences:

[0149] The opening depth of the first micropore is 25% of the thickness of the first material layer.

[0150] Example 3

[0151] This embodiment illustrates a negative electrode and silicon-carbon battery disclosed in this invention, including most of the operations in Embodiment 1, with the following differences:

[0152] The opening depth of the first micropore is 40% of the thickness of the first material layer.

[0153] Example 4

[0154] This embodiment illustrates a negative electrode and silicon-carbon battery disclosed in this invention, including most of the operations in Embodiment 1, with the following differences:

[0155] The opening depth of the first micropore is 10% of the thickness of the first material layer.

[0156] Example 5

[0157] This embodiment illustrates a negative electrode and silicon-carbon battery disclosed in this invention, including most of the operations in Embodiment 1, with the following differences:

[0158] The silicon material filling amount in the first micropore is 10%, and the silicon material filling amount in the second micropore is 20%.

[0159] Example 6

[0160] This embodiment illustrates a negative electrode and silicon-carbon battery disclosed in this invention, including most of the operations in Embodiment 1, with the following differences:

[0161] The silicon material filling amount in the first micropore is 20%, and the silicon material filling amount in the second micropore is 10%.

[0162] Example 7

[0163] This embodiment illustrates a negative electrode and silicon-carbon battery disclosed in this invention, including most of the operations in Embodiment 1, with the following differences:

[0164] The diameter of the first micropore is 4 mm, and the diameter of the second micropore is 8 mm.

[0165] Example 8

[0166] This embodiment illustrates a negative electrode and silicon-carbon battery disclosed in this invention, including most of the operations in Embodiment 1, with the following differences:

[0167] The diameter of the first micropore is 2 mm, and the diameter of the second micropore is 5 mm.

[0168] Example 9

[0169] This embodiment illustrates a negative electrode and silicon-carbon battery disclosed in this invention, including most of the operations in Embodiment 1, with the following differences:

[0170] The spacing between adjacent first micropores is 5 mm, and the spacing between adjacent second micropores is 3 mm.

[0171] Example 10

[0172] This embodiment illustrates a negative electrode and silicon-carbon battery disclosed in this invention, including most of the operations in Embodiment 1, with the following differences:

[0173] The spacing between adjacent first micropores is 6 mm, and the spacing between adjacent second micropores is 4 mm.

[0174] Example 11

[0175] This embodiment illustrates a negative electrode and silicon-carbon battery disclosed in this invention, including most of the operations in Embodiment 1, with the following differences:

[0176] The surface density of the first material layer is 34.8 g / m². 2 The surface density of the second material layer is 34.8 g / m². 2 .

[0177] Example 12

[0178] This embodiment illustrates a negative electrode and silicon-carbon battery disclosed in this invention, including most of the operations in Embodiment 1, with the following differences:

[0179] The surface density of the first material layer is 20.1 g / m². 2 The surface density of the second material layer is 46.9 g / m². 2 .

[0180] Comparative Example 1

[0181] This comparative example is used to illustrate a negative electrode sheet and silicon-carbon battery disclosed in this invention, including most of the operations in Example 1, except that:

[0182] In Comparative Example 1, the same amount of silicon material as that deposited in Example 1 was directly added during the preparation of the slurry. The resulting slurry was coated on the surface of the current collector without the first and second micropores being provided.

[0183] The performance of the silicon-carbon batteries prepared in Examples 1-12 and Comparative Example 1 was tested:

[0184] Test conditions: The batteries from Example 1 and Comparative Example 1 were tested respectively;

[0185] At 25℃, the battery cell was charged to 4.50V with a constant current and constant voltage of 1C, with a cutoff current of 0.05C, and left to rest for 5 minutes. Then, it was discharged to 3.0V with a constant current of 0.2C. The discharge capacity of the third cycle and the thickness after 50, 100, 150, and 200 cycles were taken to obtain the following results. Figure 6 The graphs showing the relationship between the number of cycles and the expansion rate for Example 1 and Comparative Example 1 are shown.

[0186] The batteries from Examples 1-12 and Comparative Example 1 were tested:

[0187] At 25℃, the battery cell is charged to 4.50V with a constant current and constant voltage of 1C, cut off current of 0.05C, rested for 5 minutes, and then discharged to 3.0V with a constant current of 0.2C. The cycle is repeated for 50 times, and the thickness and thickness change rate data are taken at the 50th cycle.

[0188] Depend on Figure 6 It can be seen that, in the battery charge-discharge cycle, Example 1 (Experimental Group 1, Experimental Group 2) performs better than Comparative Example 1 (Control Group 1, Control Group 2) in controlling electrode expansion and maintaining stable battery performance, further demonstrating that the negative electrode sheet provided in this application can effectively improve the problem of large expansion of silicon-carbon negative electrodes.

[0189] The test results are entered into Table 1.

[0190] Table 1

[0191]

[0192] As can be seen from the test results in Table 1, the thickness and thickness change rate of Examples 1-12 after 50 cycles are lower than those of Comparative Example 1. Comparative Example 1 did not use the first and second micropores as described in this application, and the thickness change rate of the cell prepared by it after cycling is higher. This indicates that the silicon-carbon battery prepared by Comparative Example 1 is prone to volume expansion in application. Therefore, the comparison shows that the silicon-carbon battery prepared using the negative electrode sheet provided in this application is more conducive to improving or solving the problem of silicon-carbon negative electrode expansion.

[0193] In Examples 2-4, the opening depth of the first micropore in Example 2 is 25% of the thickness of the first material layer, the opening depth of the first micropore in Example 3 is 40% of the thickness of the first material layer, and the opening depth of the first micropore in Example 4 is 10% of the thickness of the first material layer. Further, the test data of Examples 2-4 show that the test results of Examples 2, 3, and 4 are quite similar with no significant differences, but all are better than Comparative Example 1. Therefore, it can be concluded that when the opening depth of the first micropore is 10%-50% of the thickness of the first material layer, it is beneficial to improve the problem of silicon-carbon anode expansion and enhance its electrical performance.

[0194] The test results of Examples 1 and 5-6 show that Example 1 has a lower thickness change rate and a higher cell capacity. It is speculated that the reason is that the silicon material filling amount in the first and second micropores in Example 1 is the same (10%), while the silicon material filling amount in the first and second micropores in Examples 5 and 6 is different (10% / 20% and 20% / 10%, respectively). This leads to uneven distribution of expansion stress and a decrease in the stability of the electrode structure. Therefore, Examples 5-6 have a higher thickness change rate (8.07% and 8.12%) and a lower cell capacity. This shows that it is more conducive to balancing expansion stress and improving the electrical performance of silicon-carbon batteries when the silicon material filling amount in the first and second micropores is the same.

[0195] Compared with the test data of Example 1, there was no significant difference in the thickness change rate and cell capacity test results between Example 1 and Example 7-8. The negative electrode sheets of both Example 1 and Example 7-8 adopt the structure of first micropore and second micropore, which can effectively disperse expansion stress, and the pore size is within a reasonable range (the first micropore provides moderate support and the second micropore accommodates expansion). Therefore, their expansion change rate and cell capacity are similar.

[0196] Compared with the test results of Examples 9-10, the thickness change rate of Example 1 is relatively low, that is, the expansion rate of Example 1 is lower than that of Examples 9-10. It is speculated that the reason is that the micropore spacing of Example 1 is smaller (the first micropore spacing is 4 mm and the second micropore spacing is 2 mm), the silicon material is more densely and uniformly distributed, and the stress is more fully dispersed. In contrast, the spacing of Examples 9-10 is slightly larger, which increases the risk of local stress concentration. Therefore, the expansion rate of Examples 9-10 is slightly higher.

[0197] Compared with Examples 11-12, Example 1 has a lower thickness change rate and slightly higher cell capacity after cycling. After 50 cycles, the thickness of Example 11 is 4.182 mm with a thickness change rate of 5.84%, which is close to that of Example 1. After 50 cycles, the thickness of Example 12 is 4.177 mm with a thickness change rate of 5.80%, which is relatively low among all examples. From the perspective of the surface density of the material layer coating, the density difference between the two layers in Example 12 is large. It is possible that during the cycling process, the uneven expansion and contraction of the material is more obvious. Although the overall thickness change rate is low, the changes in its internal structure are not conducive to the improvement of performance.

[0198] Based on the test results of the above embodiments, it is shown that the negative electrode sheet provided in this application can effectively play a positive role in solving the problem of silicon-carbon negative electrode expansion, reducing the risk of electrode structure damage caused by expansion. At the same time, good cycle stability is of great significance for improving the overall performance and service life of the battery, providing a more feasible technical solution for the application of silicon-carbon composite electrodes in the field of lithium batteries.

[0199] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A negative electrode sheet, characterized in that, The device includes a current collector (1) and an active material layer (2). The active material layer (2) includes a first material layer (21) and a second material layer (22). The first material layer (21) is disposed on the surface of the current collector (1), and the second material layer (22) is disposed on the side of the first material layer (21) away from the current collector (1). The first material layer (21) has a plurality of first micropores (211), and the second material layer (22) has a plurality of second micropores (221). The plurality of first micropores (211) and the plurality of second micropores (221) are filled with silicon material (3). One end of the first micropore (211) penetrates the side of the first material layer (21) facing the second material layer (22), and the opening depth of the first micropore (211) is 10%-50% of the thickness of the first material layer (21); The second micropore (221) penetrates the second material layer (22); The first micropore (211) and the second micropore (221) extend along the thickness direction of the current collector (1).

2. The negative electrode sheet according to claim 1, characterized in that, In the first micropore (211), the filling amount of the silicon material (3) is 5%-50%; In the second micropore (221), the amount of silicon material (3) is 5%-50%.

3. A negative electrode sheet according to claim 2, characterized in that, The amount of silicon material (3) filling the first micropore (211) and the second micropore (221) is the same.

4. The negative electrode sheet according to claim 1, characterized in that, The diameter of the first micropore (211) is smaller than the diameter of the second micropore (221).

5. The negative electrode sheet (4) according to claim 1, characterized in that, The diameter of the first micropore (211) is 2-4 mm, and the diameter of the second micropore (221) is 5-8 mm.

6. A negative electrode sheet according to claim 1, characterized in that, The pore size of each of the first micropores (211) is the same; and / or, The pore size of each of the second micropores (221) is the same.

7. A negative electrode sheet according to claim 1, characterized in that, The spacing between adjacent first micropores (211) is 4-6 mm, and the spacing between adjacent second micropores (221) is 2-4 mm.

8. A negative electrode sheet according to claim 1, characterized in that, The coating thickness of the first material layer (21) is 20-50 mm, and the coating thickness of the second material layer (22) is 5-50 mm.

9. A negative electrode sheet according to claim 1, characterized in that, The ratio of the surface density of the first material layer (21) to the surface density of the second material layer (22) is 80:20-50:

50.

10. A negative electrode sheet according to claim 1, characterized in that, The surface density of the first material layer (21) is 20-100 g / m². 2 The surface density of the second material layer (22) is 10-100 g / m². 2 .

11. A negative electrode sheet according to any one of claims 1-10, characterized in that, The particle size of the silicon material (3) filling the first micropore (211) is the same as the particle size of the silicon material (3) filling the second micropore (221).

12. A negative electrode sheet according to claim 1, characterized in that, The active material of the active material layer (2) includes one or more of graphite, porous carbon, hard carbon, and soft carbon.

13. A negative electrode sheet according to claim 1, characterized in that, The negative electrode slurry of the first material layer (21) is the same as the negative electrode slurry used to form the second material layer (22).

14. A method for preparing a negative electrode sheet, characterized in that, The method is used to prepare the negative electrode sheet according to any one of claims 1-13; the preparation method includes the following steps: The first material layer (21) is disposed on the current collector (1) to obtain the first negative electrode precursor; A first micropore (211) is processed on the first material layer (21) of the first negative electrode precursor, and silicon material (3) is filled into the first micropore (211) to obtain the second negative electrode precursor; The second material layer (22) is disposed on the second negative electrode precursor to obtain the third negative electrode precursor; A second micropore (221) is processed on the second material layer (22) of the third negative electrode precursor, and silicon material (3) is filled into the second micropore (221) to obtain the negative electrode (4).

15. The method for preparing a negative electrode sheet according to claim 14, characterized in that, The steps of processing a first micropore (211) on the first material layer (21) of the first negative electrode precursor and filling the first micropore (211) with silicon material (3) to obtain the second negative electrode precursor include: A first protective film is applied to the first negative electrode precursor. The first negative electrode precursor covered with the first protective film is etched to form the first micropore (211) on the first material layer (21) of the first negative electrode precursor. The first protective film is hollowed out at the position corresponding to the first micropore (211) to obtain the first micropore (211) component. Silicon material (3) is deposited on the first micropore (211) component, so that the silicon material (3) fills the first micropore (211); after the deposition is completed, the first protective film on the first micropore (211) component is removed to obtain the second negative electrode precursor.

16. The method for preparing a negative electrode sheet according to claim 15, characterized in that, The deposition material for the silicon material (3) is silane; The step of depositing silicon material (3) on the first micropore (211) component, such that the silicon material (3) fills the first micropore (211), includes: By holding the temperature at 200-900℃ for 0.5-10h, silane is deposited on the surface of the first micropore (211) component and inside the first micropore (211) through vapor deposition and then pyrolyzed to form the silicon material (3).

17. The method for preparing a negative electrode sheet according to claim 14, characterized in that, The step of processing a second micropore (221) on the second material layer (22) of the third negative electrode precursor and filling the second micropore (221) with silicon material (3) to obtain the negative electrode includes: A second protective film is applied to the third negative electrode precursor. The third negative electrode precursor covered with the second protective film is etched to form the second micropore (221) on the second material layer (22) of the third negative electrode precursor. The second protective film is hollowed out at the position corresponding to the second micropore (221) to obtain the second micropore (221) assembly. Silicon material (3) is deposited on the second micropore (221) component, so that the silicon material (3) fills the second micropore (221); after the deposition is completed, the second protective film on the second micropore (221) component is removed to obtain the negative electrode (4).

18. The method for preparing a negative electrode sheet according to claim 17, characterized in that, The deposition material for the silicon material (3) is silane; The step of depositing silicon material (3) on the second micropore (221) component, such that the silicon material (3) fills the second micropore (221), includes: By holding the temperature at 200-900℃ for 0.5-10h, silane is deposited on the surface of the second micropore (221) component and inside the second micropore (221) through vapor deposition and then decomposed to form the silicon material (3).

19. A silicon-carbon battery, characterized in that, The negative electrode (4) includes a positive electrode, a separator, and a negative electrode (4) as described in any one of claims 1-13 or the negative electrode (4) prepared by any one of claims 14-18.

Images