Silicon-based negative electrode slurry based on amide bond-containing polyimide and application thereof

Abstract

This invention provides a silicon-based anode slurry based on amide-bonded polyimide and its application. The silicon-based anode slurry includes an anode active material and a binder material. The anode active material includes a silicon-containing active material, and the binder material includes polyimide and / or its precursor, wherein the precursor is polyamic acid. The polyamic acid is obtained by polycondensation of a diamine monomer and a dianhydride monomer. The polyimide is obtained by imidization of the polyamic acid. The diamine monomer includes an amide-bonded diamine monomer, and the dianhydride monomer includes an aromatic tetracarboxylic acid dianhydride monomer. This invention introduces an amide-bonded structure into the polyimide backbone to construct a functionalized polyimide binder that combines multiple hydrogen bonding effects with moderate electrolyte compatibility, thereby enhancing the interfacial adhesion between the binder and the silicon active material and inhibiting its swelling in the electrolyte.

Description

Technical Field

[0001] This invention belongs to the field of new energy technology, specifically relating to a silicon-based anode slurry based on polyimide containing amide bonds and its application. Background Technology

[0002] In recent years, the energy crisis and environmental problems caused by traditional fossil fuels have received widespread attention, making the replacement of traditional energy sources with new energy sources an inevitable development trend. Lithium-ion batteries (LIBs) have been widely used in power supply and energy storage devices due to their advantages such as high energy density, long cycle life, low self-discharge rate, and absence of "memory effect".

[0003] Graphite, as the primary anode active material, has a theoretical specific capacity of 372 mAh g⁻¹. -1 However, during battery charging, lithium ions embedded in the graphite anode may form lithium dendrites on the surface, leading to a short circuit and posing a serious safety hazard. In contrast, silicon has a capacity of up to 4200 mAh g⁻¹. -1 With its theoretical specific capacity, silicon is considered a highly promising electrode material for next-generation lithium-ion batteries. However, the drastic volume changes of silicon materials during charging and discharging can cause instability at the solid electrolyte interface and breakage of Si particles, leading to deterioration of the electrode structure, severe pulverization, and ultimately a decrease in coulombic efficiency and rapid capacity decay.

[0004] In the fabrication of silicon-based anodes, binders are required. Traditional binders, such as polyvinylidene fluoride (PVDF), are unsuitable for the role of ideal binders due to their weak adhesion to the silicon surface. While linear polymers such as carboxymethyl cellulose (CMC), polyacrylic acid (PAA), sodium alginate (SA), and chitosan (CS) have been extensively studied, they are prone to slippage when dealing with the large volume changes of silicon electrodes, leading to mechanical failure and battery malfunction. Therefore, they are insufficient in maintaining the long-term cycle performance of silicon electrodes. Summary of the Invention

[0005] To solve all or part of the above-mentioned technical problems, the present invention provides the following technical solutions:

[0006] A first aspect of the present invention provides a silicon-based anode paste based on amide-bonded polyimide, comprising an anode active material and a binder material, wherein the anode active material comprises a silicon-containing active material, and the binder material comprises polyimide and / or its precursor, wherein the precursor is polyamic acid;

[0007] The polyamic acid is prepared by polycondensation of a diamine monomer and a dianhydride monomer; the polyimide is prepared by imidization of the polyamic acid; the diamine monomer includes a diamine monomer containing an amide bond, and the dianhydride monomer includes an aromatic tetracarboxylic acid dianhydride monomer.

[0008] The polyimide containing amide structural units, obtained by reacting the aforementioned amide-bonded diamine monomer with an aromatic tetracarboxylic dianhydride monomer, can form multiple hydrogen bond interactions between polymer molecules and between the polymer and the surface of silicon-containing active materials, thereby enhancing its interfacial bonding strength with the silicon surface. Furthermore, this polyimide binder exhibits suitable wettability and absorbance to carbonate electrolytes, preventing excessive swelling in the electrolyte environment. The silicon-based anode prepared using this slurry maintains good electrode structural stability during charge-discharge cycles, suppresses silicon-based anode volume expansion, regulates the formation and stability of the solid electrolyte interfacial film, and improves the cycle stability of lithium-ion batteries.

[0009] In some embodiments, the amide-containing diamine monomer contains one or more benzene rings.

[0010] In some embodiments, the amide-containing diamine monomer includes one or a combination of multiple of 4,4'-diaminobenzoylaniline, N,N'-(1,4-phenylene)bis(4-aminobenzamide), N,N′-(1,3-phenylene)bis(4-aminobenzamide), and N,N′-(4,4′-biphenyl)bis(4-aminobenzamide).

[0011] In some embodiments, the aromatic tetracarboxylic acid dianhydride monomer has a biphenyl structure or a polycyclic conjugated structure.

[0012] In some embodiments, the aromatic tetracarboxylic dianhydride monomer includes one or a combination of more of 3,3',4,4'-biphenyltetracarboxylic dianhydride, 2,2',3,3'-biphenyltetracarboxylic dianhydride, and 2,3,3',4-biphenyltetracarboxylic dianhydride.

[0013] Aromatic tetracarboxylic acid dianhydride monomers have biphenyl or polycyclic conjugated structures, which can endow the polyimide backbone with rigidity and thermal stability, further improving the cycle stability and mechanical integrity of silicon-based anodes.

[0014] In some embodiments, the mass ratio of the silicon-containing active material to the binder material is 82~90:8~15.

[0015] In some embodiments, the silicon-based anode slurry further includes a conductive material, wherein the mass ratio of the silicon-containing active material to the conductive material is 41-45:4-8. The conductive material can be any known conductive material for secondary batteries in the art, such as Super P, carbon nanotubes, etc.

[0016] In some embodiments, the silicon-containing active material includes one or a combination of multiple of nano-silicon, silicon oxide, and silicon-carbon composite materials.

[0017] In some embodiments, the preparation method of the polyamic acid includes: reacting a mixed reaction system containing the amide-bonded diamine monomer and the aromatic tetracarboxylic acid dianhydride monomer at a temperature of 25~40°C to obtain the polyamic acid.

[0018] In some embodiments, the amounts of the diamine monomer and the dianhydride monomer are in an equimolar ratio.

[0019] In some embodiments, the mixed reaction system further includes a solvent.

[0020] In some embodiments, the amount of solvent used is such that the solid content of the obtained polyamic acid is 5wt% to 15wt%.

[0021] In some embodiments, the solvent may include, for example, N-methyl-2-pyrrolidone, water, dimethylformamide, dimethylacetamide, methylformamide, dimethyl sulfoxide, but is not limited thereto.

[0022] In some embodiments, the polyamic acid is subjected to heat treatment to imidize it to obtain the polyimide; the heat treatment includes holding at a temperature of 150°C to 350°C for 4 to 5 hours.

[0023] A second aspect of the present invention provides a silicon-based anode comprising a current collector and an anode active material layer formed on the current collector, the anode active material layer being formed from the silicon-based anode slurry described in any of the technical solutions of the present invention.

[0024] A third aspect of the present invention provides a method for preparing a silicon-based anode, comprising:

[0025] Provide a silicon-based anode paste as described in any of the above technical solutions, wherein the binder material is the polyamic acid;

[0026] The silicon-based anode is coated onto the current collector with a slurry, the solvent is removed, and then it is heat-treated to imidize the polyamic acid therein to form polyimide. The mixture is then stamped to obtain a silicon-based anode containing polyimide.

[0027] In some embodiments, the heat treatment includes holding at a temperature of 150℃ to 350℃ for 4 to 5 hours. Preferably, the heat treatment specifically includes performing heat treatment sequentially at 150℃, 200℃, 250℃, 300℃, and 350℃, with a holding time of 40 to 60 minutes at each temperature.

[0028] In some embodiments, the current collector can be made of any material known in the field of secondary batteries, such as one or a combination of copper, aluminum, and nickel, but is not limited thereto. For example, the current collector may be copper foil, aluminum foil, or nickel foil.

[0029] For example, the method for preparing the silicon-based anode specifically includes:

[0030] Weigh the silicon-containing active material, the above-mentioned polyamic acid, Super P, and carbon nanotubes in a weight ratio of 82~90:10~15:6~8:2~4, add solvent to adjust the solid content to 5wt%~15wt%, and place in a degassing machine at 1000~3000 rmin. -1 Degas for 1-5 minutes, then sonicate in an ultrasonic machine for 20-60 minutes to form a uniform silicon-based anode slurry;

[0031] The above slurry is coated onto the current collector and then dried to remove the solvent (e.g., in a vacuum oven at 100-120°C for 12-18 hours). After the solvent has completely evaporated, it is pressed into a sheet to obtain a silicon-based anode containing polyamic acid.

[0032] Silicon-based anode sheets containing polyamic acid were heat-treated sequentially at 150 ℃, 200 ℃, 250 ℃, 300 ℃, and 350 ℃ for 40~60 min to obtain silicon-based anodes containing polyimide.

[0033] A fourth aspect of the present invention provides a secondary battery comprising a positive electrode, a negative electrode, a separator, and an electrolyte, wherein the negative electrode is a silicon-based negative electrode as described in any of the technical solutions.

[0034] In some embodiments, the electrolyte is a carbonate-based electrolyte. The silicon-based anode based on the polyimide binder of the present invention is suitable for use in secondary batteries with carbonate-based electrolyte systems. It exhibits moderate wettability and absorbency in carbonate-based electrolytes, preventing excessive swelling in the electrolyte environment and thus maintaining good electrode structural stability during charge-discharge cycles. The carbonate-based electrolyte may include any carbonate known in the field of secondary batteries, such as dimethyl carbonate, ethylene carbonate, and fluoroethylene carbonate, but is not limited thereto.

[0035] Compared with existing technologies, the present invention has at least some or all of the following beneficial effects: The present invention constructs a functionalized polyimide binder that combines multiple hydrogen bonding interactions with moderate electrolyte compatibility by introducing an amide bond structure into the polyimide backbone. The amide bonds in this polyimide can form a multi-point, reversible hydrogen bond interaction network with the silicon surface, enhancing its interfacial adhesion with silicon-containing active materials; simultaneously, it exhibits suitable wettability and absorbency in carbonate electrolyte systems, effectively suppressing excessive swelling in the electrolyte. When this polyimide binder is applied to the preparation of silicon-based anodes for lithium-ion batteries, it facilitates the construction of a dense and LiF-rich solid electrolyte interfacial film, alleviating the volume expansion of the silicon-based anode during charge and discharge processes, maintaining the integrity of the electrode structure, and thus improving the cycle stability of lithium-ion batteries. Attached Figure Description

[0036] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0037] Figure 1 These are the infrared spectra of the polyimide materials prepared in Example 1 and Comparative Example 2;

[0038] Figure 2 These are TGA images of the polyimide materials prepared in Example 1 and Comparative Example 2;

[0039] Figure 3 This is a SEM image of the surface of the silicon-based anode prepared in Example 1 under conditions of 4.0 kV × 1.0 kV;

[0040] Figure 4 This is a SEM image of the surface of the silicon-based anode prepared in Example 1 under conditions of 4.0 kV × 70.0 k.

[0041] Figure 5 This is a photograph of the silicon-based negative electrode containing amide bonds prepared in Example 1 after 200 cycles;

[0042] Figure 6 The diagram shows the cycle stability of the polyimide batteries based on Example 1 and Comparative Example 2.

[0043] Figure 7 This is a peeling force diagram of the negative electrode active material layer of polyimide in Example 1 and Comparative Example 2 being peeled off from the current collector. Detailed Implementation

[0044] The invention will be more fully understood through the following detailed description, which should be read in conjunction with the accompanying drawings. Detailed embodiments of the invention are disclosed herein; however, it should be understood that the disclosed embodiments are merely exemplary of the invention, which may be embodied in various forms. Therefore, the specific functional details disclosed herein should not be construed as limiting, but rather as the basis for the claims and as intended to teach those skilled in the art to employ the representative basis of the invention in different ways in any suitable detailed embodiment.

[0045] In addition, unless otherwise specified, all raw materials used in the following embodiments can be purchased from the market or other sources, and all production and testing equipment used are known in the art, as are the testing methods used.

[0046] Example 1

[0047] This embodiment provides a polyamic acid and its preparation method, and uses the polyamic acid to prepare a slurry for silicon-based anodes and to prepare silicon-based anodes.

[0048] The preparation method of polyamic acid specifically includes the following steps:

[0049] 1.3636 g of 4,4'-diaminobenzoylaniline (DABA, 6 mmol) solid was added to a 50 mL three-necked flask purged with N2. 6.7 mL of N-methyl-2-pyrrolidone (NMP) solution was added to dissolve the solid. Then, 1.7653 g of 3,3',4,4'-biphenyltetracarboxylic acid dianhydride (BPDA, 6 mmol) was added to the same three-necked flask in two batches. Specifically, at 25°C, 1.5 g of BPDA and 2 mL of NMP solvent were added first. After the solid dissolved, 0.2653 g of BPDA and 2.7 mL of NMP solvent were added. After all the solid was completely dissolved, the solution was diluted to 10 wt% solids while stirring to obtain a polyamic acid (PAA) solution containing amide bonds.

[0050] The preparation of silicon-based anodes using the above-mentioned polyamic acid specifically includes the following steps:

[0051] Nano-silicon powder (particle size approximately 100 nm), the aforementioned polyamic acid containing amide bonds, Super P, and carbon nanotubes (CNTs) were mixed at a mass ratio of 82:10:6:2. NMP was added to adjust the solid content to 10 wt%, and then the mixture was placed in a degassing machine at 2000 r / min. -1 Degas for 2 minutes, then sonicate in an ultrasonic machine for 30 minutes to form a uniform slurry.

[0052] Using a doctor blade method, the above slurry was coated onto a 5 μm thick copper foil and dried at 80 °C. It was then transferred to a vacuum drying oven and dried at 120 °C for 12 h to remove the solvent, forming a precursor layer with a thickness between 20 and 30 μm. This precursor layer was then pressed into sheets to obtain an active material with a density of 2 mg / cm³. 3 Electrode plates.

[0053] The electrode sheets were heat-treated at 150 ℃, 200 ℃, 250 ℃, 300 ℃ and 350 ℃ respectively, with a holding time of 1 h at each temperature, so that the polyamic acid in them would undergo imidization to generate polyimide, thus obtaining a silicon-based negative electrode with polyimide as a binder.

[0054] The specific steps for assembling a button cell using the aforementioned silicon-based anode are as follows:

[0055] In an argon glove box (O2 < 0.01 ppm, H2O < 0.01 ppm), using the silicon-based negative electrode prepared in this example as the negative electrode, Celgard 2500 as the separator, and lithium foil as the counter electrode, 5.0 wt.% of fluoroethylene carbonate was added to a mixture containing 1 M LiPF6 and ethylene carbonate / diethyl carbonate (1 / 1 volume ratio) to prepare an electrolyte, and a button cell (CR2032) was assembled.

[0056] Examples 2 to 6

[0057] Examples 2 through 6 are essentially the same as Example 1, except that the amounts of the amide-containing diamine monomer or aromatic tetracarboxylic acid dianhydride monomer used in Examples 2 through 6, as shown in Table 1, are the same as in Example 1. The rest of the procedures are the same as in Example 1 and will not be repeated here.

[0058] Table 1. Diamine monomers and dianhydride monomers used in Examples 1-6

[0059]

[0060] Comparative Example 1

[0061] The only difference between Comparative Example 1 and Example 1 is that the diamine monomer used in Comparative Example 1 is p-phenylenediamine, and the amount of p-phenylenediamine is 6 mmol. The rest of the procedures are the same as in Example 1, and will not be repeated here.

[0062] Comparative Example 2

[0063] The only difference between Comparative Example 1 and Example 1 is that the diamine monomer used in Comparative Example 2 is p-aminobenzoic acid p-phenyl ester, and its amount is 6 mmol. The rest of the procedures are the same as in Example 1, and will not be repeated here.

[0064] Figure 1 These are the infrared spectra of the polyimide materials prepared in Example 1 and Comparative Example 2. From... Figure 1 As can be seen, all materials exhibit the characteristic peaks of polyimide, proving the successful synthesis of the polyimide materials. Specifically, the polyimide in Example 1 shows a peak at 3375 cm⁻¹. -1 and 1660 cm -1 The characteristic peaks of NH and C=O with amide bonds are present.

[0065] Figure 2 These are TGA images of the polyimide materials prepared in Example 1 and Comparative Example 2. From... Figure 2 It can be seen that the polyimides prepared in Example 1 all have good thermal stability.

[0066] Figure 3 This is a SEM image of the surface of the silicon-based anode prepared in Example 1 under conditions of 4.0 kV × 1.0 kV; Figure 4 This is a SEM image of the surface of the silicon-based anode prepared in Example 1 under conditions of 4.0 kV × 70.0 k. Figure 5 This is a photograph of the silicon-based anode containing amide bonds, prepared in Example 1, after 200 cycles. From... Figure 4 It can be seen that in the prepared silicon-based anode, the surface of the silicon nanoparticles is uniformly coated and bonded together by polyimide, without agglomeration, which is beneficial to the stability of the silicon anode during charge and discharge. Furthermore... Figure 5 The electrode condition in the experiment showed that the silicon-based negative electrode did not detach after 200 cycles, indicating that the polyimide in Example 1 has good bonding properties.

[0067] The electrolyte wettability of the silicon-based anodes prepared in Examples 1, 2, 3, 4, Comparative Example 1, and Comparative Example 2 was tested. The electrolyte composition was as follows: 5.0 wt.% of fluoroethylene carbonate was added to a mixture containing 1 M LiPF6 and ethylene carbonate / diethyl carbonate (1 / 1 volume ratio). The test method was as follows: the polyamic acid solutions prepared in Examples 1, 2, Comparative Example 1, and Comparative Example 2 were cast into polyamic acid films using a casting method, and then subjected to thermal imidization treatment to obtain polyimide films. These films were then immersed in the electrolyte for 24 h, and the immersed films were weighed. The test results are shown in Table 2.

[0068] Table 2. Electrolyte wetting properties of the silicon-based anodes prepared in the above embodiments and comparative examples.

[0069]

[0070] As shown in Table 2, the silicon-based anode prepared in Example 1 exhibits suitable electrolyte wettability, with its absorbance remaining stable in the range of approximately 12.9% to 18.8%. Moderate electrolyte wettability facilitates the full penetration and uniform distribution of the electrolyte within the electrode, thereby improving the lithium-ion transport kinetics in the silicon-based anode and promoting the formation of a stable and uniform SEI film, ultimately enhancing the battery's cycle stability and rate performance. In contrast, the silicon-based anode prepared in Comparative Example 1 exhibits poor electrolyte wettability, with an absorbance of only approximately 2.9% to 5.7%, indicating that the electrolyte struggles to fully penetrate the electrode. This insufficient wettability can lead to inadequate contact between the electrode active material and the electrolyte, resulting in limited interfacial reactions, increased polarization, and ultimately affecting the battery's capacity and cycle performance. The silicon-based anode prepared in Comparative Example 2, however, exhibits excessively high electrolyte wettability, with an absorbance as high as approximately 28.1% to 36.7%. Excessive electrolyte adsorption may lead to local expansion of the electrode structure and a decrease in mechanical stability. It also exacerbates the side reactions of the electrolyte and the repeated rupture and reconstruction of the SEI film, which is detrimental to the long-term cycle stability of silicon-based anodes.

[0071] The modulus, tensile strength, and elongation at break of the silicon-based anodes prepared in the above embodiments and comparative examples were tested on a 1 kN universal testing machine before and after electrolyte wetting. The test results are shown in Table 3.

[0072] Table 3. Mechanical strength of the silicon-based anode in the above embodiments and comparative examples before and after electrolyte wetting.

[0073]

[0074] As shown in Table 3, the silicon-based anode based on amide-containing polyimide in the embodiments of the present invention exhibits minimal changes in mechanical properties before and after electrolyte wetting. This is because the amide bonds of its hydrogen bond donors (-NH-) and acceptors (C=O) can construct a multi-point hydrogen bond network to enhance its resistance to electrolyte swelling and suppress the mechanical property decay caused by electrolyte adsorption. This structural feature is beneficial for maintaining electrode integrity and mitigating volume changes in the silicon-based anode during charge and discharge. The silicon-based anodes of Comparative Examples 1 and 2 both exhibited significant changes in mechanical properties before and after electrolyte wetting, especially large fluctuations in elongation at break and tensile strength, indicating that their bonding system lacks structural stability under the action of the electrolyte and is difficult to maintain the overall mechanical integrity of the electrode during long-term cycling.

[0075] Constant current charge-discharge tests were conducted using the button cells assembled in the above embodiments and comparative examples. The test conditions were as follows: the button cells were connected to the battery testing system, and charge-discharge tests were performed at room temperature with a voltage range of 0.005–1.00 V (relative to Li / Li⁺). The test temperature was 25 °C, and cyclic charge-discharge tests were conducted using a constant current of 0.2 C. Capacity retention (%) = Discharge capacity after N cycles ÷ Initial discharge capacity × 100. The test results are shown in Table 4.

[0076] Table 4. Relevant battery performance in the above embodiments and comparative examples.

[0077]

[0078] Figure 6 The graph shows the cycle stability of the polyimide batteries based on Example 1 and Comparative Example 2. The polyimide battery based on Example 1 retains 76.3% capacity after 200 charge-discharge cycles, demonstrating superior cycle stability.

[0079] Figure 7 This is a peeling force diagram showing the peeling of the negative electrode active material layer of polyimide from the current collector based on Example 1 and Comparative Example 2. Figure 7 It can be seen that the adhesive used in Example 1 exhibits higher interfacial adhesion (5.32 N cm). -1 The concentration was significantly higher than that of control example 2 (1.10 N cm⁻¹). -1 This demonstrates that the polyimide containing amide bonds of the present invention has superior adhesion properties. This is because the imide and amide groups can form hydrogen bonds and dipole-dipole interactions with the surface of silicon particles, thereby achieving strong adhesion of the composite electrode and improving adhesion performance during battery cycling.

[0080] Furthermore, as shown in Tables 2-4, compared to Example 1, the increased number of amide bonds in the polyimide of Example 2 leads to slightly greater electrolyte wettability of the silicon-based anode; and the elongation at break is lower than that of Example 1, only about 7.5% and 5.9% before and after wetting, respectively, indicating slightly poorer flexibility and deformation adaptability. Therefore, the scheme using 4,4'-diaminobenzoylaniline as the diamine monomer is a more preferred scheme. However, as shown in Table 4, although the battery performance of Example 2 is slightly worse than that of Example 1, it is still better than Comparative Example 1 and Comparative Example 2.

[0081] In addition, the inventors of this case also conducted experiments with other raw materials, process operations and process conditions described in this specification, referring to the aforementioned embodiments. For example, they controlled the mass ratio of silicon-containing active material to binder material in the slurry to be 90:8 and 82:15, and used silicon oxide compounds and silicon-carbon composite materials as active materials, and obtained relatively ideal results in all cases.

[0082] In summary, the diamine monomer used in this invention has one or more amide bonds, and the aromatic tetracarboxylic dianhydride monomer has a biphenyl or polycyclic conjugated structure. This allows for the introduction of polar sites that function as both hydrogen bond donors (–NH–) and acceptors (C=O) while ensuring the rigidity and thermal stability of the polyimide backbone, thereby constructing a multi-point, reversible hydrogen bond interaction network at the molecular level. This structural feature not only enhances the interfacial bonding strength between the polyimide binder and the silicon-based active material surface, but also effectively buffers stress concentration caused by volume changes during repeated lithium insertion / extraction processes, suppressing electrode structural damage and interfacial instability, thereby improving the cycle stability and mechanical integrity of the silicon-based anode.

[0083] All aspects, embodiments, features, and examples of this invention should be considered illustrative and used to explain and illustrate the invention, but not to limit the invention. The scope of the invention is defined only by the claims.

[0084] Although the invention has been described with reference to illustrative embodiments, those skilled in the art will understand that various other changes, omissions, and / or additions can be made without departing from the spirit and scope of the invention, and that elements of the described embodiments can be substituted with substantially equivalents. Furthermore, many modifications can be made without departing from the scope of the invention to adapt particular situations or materials to the teachings of the invention. Therefore, this invention is not intended to be limited to the specific embodiments disclosed for carrying out the invention, but rather is intended to encompass all embodiments falling within the scope of the appended claims.

Claims

1. A slurry for a silicon-based negative electrode based on an amide bond-containing polyimide, characterized by, It includes a negative electrode active material and a binder material, wherein the negative electrode active material includes a silicon-containing active material, and the binder material includes polyimide and / or its precursor, wherein the precursor is polyamic acid; The polyamic acid is prepared by polycondensation reaction of diamine monomer and dianhydride monomer; The polyimide is prepared by imidizing the polyamic acid; wherein the diamine monomer includes an amide-containing diamine monomer, and the amide-containing diamine monomer contains multiple benzene rings; the dianhydride monomer includes an aromatic tetracarboxylic dianhydride monomer, and the aromatic tetracarboxylic dianhydride monomer has a biphenyl structure.

2. The silicon-based anode paste according to claim 1, characterized in that: The amide-containing diamine monomer includes one or a combination of multiple of 4,4'-diaminobenzoylaniline, N,N'-(1,4-phenylene)bis(4-aminobenzamide), N,N′-(1,3-phenylene)bis(4-aminobenzamide), and N,N′-(4,4′-biphenyl)bis(4-aminobenzamide).

3. The silicon-based anode paste according to claim 1, characterized in that: The aromatic tetracarboxylic dianhydride monomer includes one or a combination of more of the following: 3,3',4,4'-biphenyltetracarboxylic dianhydride, 2,2',3,3'-biphenyltetracarboxylic dianhydride, and 2,3,3',4'-biphenyltetracarboxylic dianhydride.

4. The silicon-based anode paste according to claim 1, characterized in that: The mass ratio of the silicon-containing active material to the binder material is 82~90:8~15.

5. The silicon-based anode paste according to claim 1, characterized in that: The silicon-based anode paste also includes a conductive material, wherein the mass ratio of the silicon-containing active material to the conductive material is 41~45:4~8.

6. The silicon-based anode paste according to claim 1, characterized in that: The silicon-containing active material includes one or a combination of multiple of nano-silicon, silicon oxides, and silicon-carbon composite materials.

7. The silicon-based anode paste according to claim 1, characterized in that: The method for preparing the polyamic acid includes: reacting a mixed reaction system containing the amide-bonded diamine monomer and the aromatic tetracarboxylic acid dianhydride monomer at a temperature of 25-40°C to obtain the polyamic acid.

8. The silicon-based anode paste according to claim 7, characterized in that: The polyamic acid is subjected to heat treatment to imidize it to obtain the polyimide; the heat treatment includes holding at a temperature of 150°C to 350°C for 4 to 5 hours.

9. A silicon-based negative electrode, characterized in that, It includes a current collector and a negative electrode active material layer formed on the current collector, the negative electrode active material layer being formed from the silicon-based negative electrode slurry according to any one of claims 1-8.

10. A method for preparing a silicon-based anode, characterized in that, include: A slurry for a silicon-based negative electrode according to any one of claims 1-8 is provided, wherein the binder material is the polyamic acid; The silicon-based anode is coated onto a current collector with a slurry, the solvent is removed, and then it is heat-treated to imidize the polyamic acid to form polyimide. The mixture is then stamped to obtain a silicon-based anode containing polyimide.

11. A secondary battery, comprising a positive electrode, a negative electrode, a separator, and an electrolyte, characterized in that, The negative electrode is the silicon-based negative electrode according to claim 9.

12. The secondary battery according to claim 11, characterized in that: The electrolyte is a carbonate-based electrolyte.

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