Silicon-carbon anode materials and their preparation methods, anode sheets and electrochemical energy storage devices

Abstract

This invention relates to a silicon-carbon anode material, comprising: a silicon-carbon material and a temperature-sensitive polymer coated on the surface of the silicon-carbon material. When the temperature of the silicon-carbon anode material is below the critical dissolution temperature of the temperature-sensitive polymer, the silicon-carbon anode material exhibits hydrophobicity; when the temperature of the silicon-carbon anode material is above the critical dissolution temperature of the temperature-sensitive polymer, the silicon-carbon anode material exhibits hydrophilicity. This invention also relates to a method for preparing the silicon-carbon anode material, an anode sheet, and an electrochemical energy storage device. When using the silicon-carbon anode material of this invention to prepare an anode sheet, when the temperature of the homogenate is below the critical dissolution temperature of the temperature-sensitive polymer, the silicon-carbon anode material exhibits hydrophobicity, which can effectively reduce the contact between silicon and water, reduce the amount of hydrogen gas generated due to the reaction between silicon and water, and make the preparation process safer. At the same time, it can also reduce problems such as pores, scratches, and material shedding in the prepared anode sheet, thereby improving the performance of the anode sheet.

Description

Technical Field

[0001] This invention relates to the field of electrochemical energy storage device technology, and in particular to a silicon-carbon anode material and its preparation method, anode sheet and electrochemical energy storage device. Background Technology

[0002] Silicon-carbon anode materials have become a key focus of research for next-generation lithium-ion battery anode materials due to their high theoretical specific capacity. However, existing mature silicon-carbon anode materials still face many challenges. In particular, during the preparation of anode slurry using silicon-carbon anode materials, the nano-silicon in the silicon-carbon anode material reacts with water to produce hydrogen gas, specifically: Si + 4H₂O = H₄SiO₄ + 2H₂↑. This not only poses a significant safety hazard but also leads to problems such as pores, scratches, and material shedding on the anode sheet, affecting its performance. Summary of the Invention

[0003] Therefore, it is necessary to provide a silicon-carbon anode material, its preparation method, anode sheet, and an electrochemical energy storage device to address the above problems. When the silicon-carbon anode material is used to prepare the anode sheet, not only can the preparation process be made safer, but the performance of the prepared anode sheet is also better.

[0004] A silicon-carbon anode material includes: a silicon-carbon material and a temperature-sensitive polymer coated on the surface of the silicon-carbon material. When the temperature of the silicon-carbon anode material is lower than the critical dissolution temperature of the temperature-sensitive polymer, the silicon-carbon anode material exhibits hydrophobicity; when the temperature of the silicon-carbon anode material is higher than the critical dissolution temperature of the temperature-sensitive polymer, the silicon-carbon anode material exhibits hydrophilicity.

[0005] In one embodiment, the critical dissolution temperature of the thermosensitive polymer is 40°C-65°C.

[0006] In one embodiment, the thermosensitive polymer is obtained by polymerization of at least two monomers from formulas (I), (II), (III), and (IV):

[0007]

[0008] In formula (I), R1-R3 are independently selected from unsubstituted -H, C1-C30 alkyl, C3-C30 cycloalkyl, C3-C30 alkenyl, C3-C30 alkynyl, C6-C30 aromatic, C3-C30 heterocyclic, and C5-C30 heteroaromatic, or selected from C1-C30 alkyl, C3-C30 cycloalkyl, C3-C30 alkenyl, and C3-C30 alkynyl containing at least one heteroatom or having a substituent. The following groups are selected: C6-C30 aromatic groups, C3-C30 heterocyclic groups, and C5-C30 heteroaromatic groups, wherein the heteroatom is selected from at least one of O, S, N, Si, and P, and the substituent is selected from at least one of halogen atoms, C1-C20 straight-chain or branched alkyl groups, C3-C20 cycloalkyl groups, C1-C20 straight-chain or branched alkoxy groups, C6-C30 aromatic groups, and C5-C30 heteroaromatic groups. When R3 is not -H, A is selected from SO3. - COO - PO4 2- HPO4 - any one of them;

[0009] In formula (II), R4 is selected from unsubstituted -H, C1-C30 alkyl, C3-C30 cycloalkyl, C3-C30 alkenyl, C3-C30 ynyl, C6-C30 aromatic, C3-C30 heterocyclic, C5-C30 heteroaromatic, or selected from C1-C30 alkyl, C3-C30 cycloalkyl, C3-C30 alkenyl, C3-C30 ynyl containing at least one heteroatom or having a substituent. The substituent is selected from at least one of the following groups: C6-C30 aromatic group, C3-C30 heterocyclic group, and C5-C30 heteroaromatic group, wherein the heteroatom is selected from at least one of O, S, N, Si, and P, and the substituent is selected from at least one of the following groups: halogen atom, C1-C20 straight-chain or branched alkyl group, C3-C20 cycloalkyl group, C1-C20 straight-chain or branched alkoxy group, C6-C30 aromatic group, and C5-C30 heteroaromatic group, and R5 is selected from -H or... Wherein, R is selected from -H, C1-C30 alkyl containing an amide group, C3-C30 cycloalkyl containing an amide group, C3-C30 alkenyl containing an amide group, C3-C30 alkynyl containing an amide group, C6-C30 aromatic group containing an amide group, C3-C30 heterocyclic group containing an amide group, or C5-C30 heteroaromatic group containing an amide group.

[0010] In formula (Ⅲ), R6 is selected from cyano or phenyl;

[0011] In formula (Ⅳ), R7 is selected from 1-butenyl or 2-aminohexanoic acid.

[0012] In one embodiment, in formula (I), R1 is selected from -H or methyl, and R2 is selected from NH(CH2). a Or O(CH2) b R3 is selected from (CH2). c A is selected from SO3 - In this case, a and b are 2 or 3 respectively, and c is 2, 3 or 4;

[0013] And / or, in formula (II), R4 is selected from -H or methyl, and R5 is selected from -H,

[0014] And / or, in formula (Ⅲ), R6 is selected from cyano;

[0015] And / or, in formula (Ⅳ), R7 is selected from 2-aminohexanoic acid.

[0016] In one embodiment, the silicon-carbon anode material further includes a binder coated on the surface of the silicon-carbon material, and the temperature-sensitive polymer is coated on the surface of the binder.

[0017] A method for preparing a silicon-carbon anode material as described above includes the following steps:

[0018] Provide temperature-sensitive polymers;

[0019] The silicon-carbon material is mixed with the temperature-sensitive polymer in water and then dried to obtain the silicon-carbon anode material.

[0020] In one embodiment, a binder is also added during the step of mixing the silicon-carbon material with the temperature-sensitive polymer in water.

[0021] In one embodiment, at least two monomers of formula (I), formula (II), formula (III) and formula (IV) are dissolved in an organic solvent, and an initiator is added to carry out a polymerization reaction. After the polymerization reaction is completed, the polymer is dried to obtain the temperature-sensitive polymer.

[0022] In one embodiment, the step of obtaining the thermosensitive polymer also satisfies at least one of the following conditions:

[0023] (1) The polymerization temperature is 30℃-100℃, and the polymerization reaction time is 30min-3000min;

[0024] (2) The organic solvent is selected from at least one of dimethyl sulfoxide and tetrahydrofuran;

[0025] (3) The drying method is selected from vacuum drying or freeze drying.

[0026] In one embodiment, the step of mixing the silicon carbon material with the temperature-sensitive polymer in water and then drying it further satisfies at least one of the following conditions:

[0027] (1) The mass ratio of the silicon carbon material to the thermosensitive polymer is 100:0.1-100:10;

[0028] (2) The mixing speed is 100 rpm / min-5000 rpm / min, and the mixing time is 10 min-300 min;

[0029] (3) The mixing temperature is 30℃-90℃;

[0030] (4) The drying method is selected from vacuum drying, baking or spray drying, and the drying temperature is 80℃-250℃.

[0031] A negative electrode sheet comprising the silicon-carbon negative electrode material described above.

[0032] An electrochemical energy storage device comprising the aforementioned negative electrode.

[0033] Thermosensitive polymers can undergo reversible changes in response to temperature variations. This invention selects thermosensitive polymers whose hydrophilicity / hydrophobicity changes with temperature and coats these polymers onto the surface of a silicon-carbon material. This ensures that the silicon-carbon anode material exhibits hydrophobicity when the temperature is below the critical dissolution temperature of the thermosensitive polymer. Furthermore, when using this silicon-carbon anode material to prepare anode sheets, the hydrophobicity effectively reduces the contact between silicon and water, lowering the amount of hydrogen generated by the reaction between silicon and water. This enhances the safety of the preparation process and reduces problems such as porosity, scratches, and material shedding in the prepared anode sheets, thus improving their performance. Attached Figure Description

[0034] To more clearly illustrate the technical solutions in the embodiments of the present invention 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 the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0035] Figure 1 This is a SEM image of the silicon-carbon anode material prepared in Example 1. Detailed Implementation

[0036] To facilitate understanding of the present invention, it will be described in more detail below. However, it should be understood that the present invention can be implemented in many different forms and is not limited to the embodiments or examples described herein. Rather, these embodiments or examples are provided to make the disclosure of the present invention more thorough and complete.

[0037] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments or examples only and is not intended to limit the invention. The optional scope of the term "and / or" as used herein includes any one of two or more of the related listed items, as well as any and all combinations of the related listed items, including any two related listed items, any more related listed items, or a combination of all related listed items.

[0038] This invention provides a silicon-carbon anode material, comprising: a silicon-carbon material and a temperature-sensitive polymer coated on the surface of the silicon-carbon material. When the temperature of the silicon-carbon anode material is lower than the critical dissolution temperature of the temperature-sensitive polymer, the silicon-carbon anode material exhibits hydrophobicity; when the temperature of the silicon-carbon anode material is higher than the critical dissolution temperature of the temperature-sensitive polymer, the silicon-carbon anode material exhibits hydrophilicity.

[0039] Thermosensitive polymers can undergo reversible changes in response to temperature variations. This invention selects thermosensitive polymers whose hydrophilicity / hydrophobicity changes with temperature and coats these polymers onto the surface of silicon-carbon materials. This results in the silicon-carbon anode material exhibiting hydrophobicity (i.e., a contact angle greater than 90°) when the temperature of the silicon-carbon anode material is below the critical dissolution temperature of the thermosensitive polymer. Specifically, when the temperature of the silicon-carbon anode material is above the critical dissolution temperature of the thermosensitive polymer, the polymer chains on the surface of the silicon-carbon anode material extend, making the silicon-carbon anode material hydrophilic. When the temperature of the silicon-carbon anode material is below the critical dissolution temperature of the thermosensitive polymer, the polymer chains on the surface of the silicon-carbon anode material collapse, making the silicon-carbon anode material hydrophobic.

[0040] Furthermore, when the silicon-carbon anode material described in this invention is used to prepare anode sheets, the silicon-carbon anode material exhibits hydrophobicity when the temperature of the homogenate is lower than the critical dissolution temperature of the temperature-sensitive polymer. This effectively reduces the contact between silicon and water, lowers the amount of hydrogen generated due to the reaction between silicon and water, and makes the preparation process safer. At the same time, it can also reduce problems such as pores, scratches, and material shedding in the prepared anode sheets, thereby improving the performance of the anode sheets.

[0041] This invention allows for the design of temperature-sensitive polymers, enabling flexible adjustment of the critical dissolution temperature of these polymers based on the temperature during the preparation of the negative electrode slurry. Preferably, the critical dissolution temperature of the temperature-sensitive polymer in this invention is between 40℃ and 65℃, including but not limited to 40℃, 41℃, 42℃, 43℃, 44℃, 45℃, 46℃, 47℃, 48℃, 49℃, 50℃, 51℃, 52℃, 53℃, 54℃, 55℃, 56℃, 57℃, 58℃, 59℃, 60℃, 61℃, 62℃, 63℃, 64℃, and 65℃.

[0042] Optionally, the temperature-sensitive polymer is obtained by polymerization of at least two monomers from formula (I), formula (II), formula (III), and formula (IV). For example, the temperature-sensitive polymer can be obtained by polymerization of formula (I) and formula (II), or by polymerization of formula (I) and formula (III), or by polymerization of formula (I) and formula (IV), or by polymerization of formula (II) and formula (III), or by polymerization of formula (II) and formula (IV), or by polymerization of formula (III) and formula (IV), or by polymerization of formula (I), formula (II), and formula (III), or by polymerization of formula (II), formula (III), and formula (IV), or by polymerization of formula (I), formula (II), formula (III), and formula (IV).

[0043]

[0044] In formula (I), R1-R3 are preferably unsubstituted -H, C1-C30 alkyl, C3-C30 cycloalkyl, C3-C30 alkenyl, C3-C30 alkynyl, C6-C30 aromatic, C3-C30 heterocyclic, or C5-C30 heteroaromatic; or, R1-R3 are preferably C1-C30 alkyl, C3-C30 cycloalkyl, C3-C30 alkenyl, C3-C30 alkynyl, C6-C30 aromatic, C3-C30 heterocyclic, or C5-C30 heteroaromatic containing at least one heteroatom, wherein the heteroatom is preferably O. At least one of S, N, Si, and P; or, R1-R3 are preferably independently substituents of C1-C30 alkyl, C3-C30 cycloalkyl, C3-C30 alkenyl, C3-C30 alkynyl, C6-C30 aromatic, C3-C30 heterocyclic, and C5-C30 heteroaromatic groups, wherein the substituent is selected from at least one of halogen atoms, C1-C20 straight-chain or branched alkyl, C3-C20 cycloalkyl, C1-C20 straight-chain or branched alkoxy, C6-C30 aromatic, and C5-C30 heteroaromatic groups; and when R3 is not -H, A is preferably SO3. - COO - PO4 2- HPO4 - Any one of them.

[0045] In formula (II), R4 is preferably an unsubstituted -H, a C1-C30 alkyl, a C3-C30 cycloalkyl, a C3-C30 alkenyl, a C3-C30 alkynyl, a C6-C30 aromatic, a C3-C30 heterocyclic, or a C5-C30 heteroaromatic; or, R4 is preferably a C1-C30 alkyl, C3-C30 cycloalkyl, C3-C30 alkenyl, C3-C30 alkynyl, C6-C30 aromatic, C3-C30 heterocyclic, or C5-C30 heteroaromatic containing at least one heteroatom, wherein the heteroatom Preferably, R4 is at least one of O, S, N, Si, and P; or, R4 is preferably a C1-C30 alkyl, C3-C30 cycloalkyl, C3-C30 alkenyl, C3-C30 alkynyl, C6-C30 aromatic, C3-C30 heterocyclic, or C5-C30 heteroaromatic group having a substituent, wherein the substituent is selected from at least one of a halogen atom, a C1-C20 straight-chain or branched alkyl, a C3-C20 cycloalkyl, a C1-C20 straight-chain or branched alkoxy, a C6-C30 aromatic, or a C5-C30 heteroaromatic. R5 is preferably -H or Wherein, R is selected from -H, C1-C30 alkyl containing an amide group, C3-C30 cycloalkyl containing an amide group, C3-C30 alkenyl containing an amide group, C3-C30 alkynyl containing an amide group, C6-C30 aromatic group containing an amide group, C3-C30 heterocyclic group containing an amide group, or C5-C30 heteroaromatic group containing an amide group.

[0046] In formula (Ⅲ), R6 is preferably cyano or phenyl.

[0047] In formula (Ⅳ), R7 is preferably 1-butenyl or 2-aminohexanoic acid.

[0048] To improve atom utilization, in formula (I), R1 is preferably -H or methyl, and R2 is preferably NH(CH2). a Or O(CH2) b R3 is preferably (CH2). c A is preferably SO3 - Wherein, a and b are preferably 2 or 3, and c is preferably 2, 3, or 4; and / or, in formula (II), R4 is preferably -H or methyl, and R5 is preferably -H, And / or, in formula (III), R6 is preferably cyano; and / or, in formula (IV), R7 is preferably 2-aminohexanoic acid.

[0049] The silicon-carbon anode material of the present invention preferably further includes a binder, the binder coating the surface of the silicon-carbon material, and the temperature-sensitive polymer coating the surface of the binder, thereby further enhancing the bonding between the silicon-carbon material and the temperature-sensitive polymer and improving the coating effect of the temperature-sensitive polymer on the silicon-carbon material.

[0050] Optionally, the adhesive is preferably at least one of hydroxypropyl methylcellulose, sodium carboxymethyl cellulose, polyethylene oxide, sodium polyacrylate, and polyvinyl alcohol methylcellulose.

[0051] The silicon-carbon material of this invention comprises silicon-based materials and carbon materials, wherein the silicon-based materials and the carbon materials can be mixed in a suitable manner to form the silicon-carbon material. Preferably, the silicon-carbon material is selected from silicon-based material / graphite composite materials.

[0052] The present invention also provides a method for preparing the silicon-carbon anode material, comprising the following steps:

[0053] S1 provides temperature-sensitive polymers;

[0054] S2, the silicon-carbon material is mixed with the temperature-sensitive polymer in water and dried to obtain the silicon-carbon anode material.

[0055] In step S1, preferably at least two monomers from formulas (I), (II), (III) and (IV) are dissolved in an organic solvent, and an initiator is added to carry out a polymerization reaction. After the polymerization reaction is completed, the polymer is dried to obtain the thermosensitive polymer.

[0056] Optionally, the polymerization temperature is preferably 30℃-100℃, and the polymerization time is preferably 30min-3000min; and preferably, mixing and stirring are carried out during the polymerization process, with the reaction speed preferably 100rpm / min-5000rpm / min.

[0057] Optionally, the organic solvent is preferably at least one of dimethyl sulfoxide and tetrahydrofuran.

[0058] Optionally, the initiator may be selected from oil-soluble initiators, and more preferably at least one of azobisisobutyronitrile, azobisisoheptanenitrile, benzoyl peroxide, dodecyl peroxide, and diisopropyl peroxide.

[0059] Optionally, the drying method is preferably at least one of vacuum drying and freeze drying.

[0060] In step S2, the temperature-sensitive polymer and the silicon-carbon material are mixed in water, and the temperature-sensitive polymer comes into contact with the silicon-carbon material. The temperature-sensitive polymer coats the surface of the silicon-carbon material through chemical bonding and physical entanglement.

[0061] Optionally, the mass ratio of the silicon carbon material to the thermosensitive polymer is preferably 100:0.1-100:10, for example, 100:0.1, 100:0.2, 100:0.5, 100:1, 100:2, 100:3, 100:4, 100:5, 100:6, 100:7, 100:8, 100:9, 100:10.

[0062] In the step of mixing silicon carbon materials and temperature-sensitive polymers, the mixing speed is preferably 100 rpm / min-5000 rpm / min, the mixing time is preferably 10 min-300 min, and the mixing temperature is preferably 0℃-70℃, which is beneficial to improving the coating effect of temperature-sensitive polymers.

[0063] After mixing, the mixture is dried. The preferred drying methods are vacuum drying, oven drying, or spray drying, and the preferred drying temperature is 80℃-250℃.

[0064] In the step of mixing the silicon-carbon material with the temperature-sensitive polymer in water, it is preferable to add a binder to further enhance the bonding between the silicon-carbon material and the temperature-sensitive polymer. The preparation steps preferably include the following steps: preparing a binder slurry, for example, first placing the binder in water to form a binder slurry; then adding the silicon-carbon material to the binder slurry to form a silicon-carbon material slurry; finally adding the temperature-sensitive polymer to the silicon-carbon material slurry, mixing evenly, and drying to obtain the silicon-carbon anode material.

[0065] The present invention also provides a negative electrode sheet, wherein the negative electrode sheet comprises the aforementioned silicon-carbon negative electrode material.

[0066] The present invention also provides an electrochemical energy storage device, wherein the electrochemical energy storage device includes the aforementioned negative electrode.

[0067] Optionally, the electrochemical energy storage device is preferably a lithium-ion battery, a sodium-ion battery, a supercapacitor, a fuel cell, or a solar cell.

[0068] The following specific embodiments will further illustrate the silicon-carbon anode material, its preparation method, the anode sheet, and the electrochemical energy storage device.

[0069] Example 1

[0070] 0.5 g of methacrylamide and 1.9 g of allyl urea were dissolved in 20 mL of dimethyl sulfoxide. Nitrogen gas was introduced and the rotation speed was set to 500 rpm / min. 0.03 g of azobisisobutyronitrile initiator was added dropwise. The temperature was raised to 70 °C and the reaction was carried out for 12 h. After the reaction was completed, the reaction solution was poured into 50 mL of chloroform, and a solid was precipitated and dried under vacuum to obtain a thermosensitive polymer. The critical dissolution temperature of the thermosensitive polymer was 62 °C.

[0071] 2g of hydroxypropyl methylcellulose was dissolved in 1400mL of water and stirred at 650rpm / min for 1.5h to obtain an adhesive slurry. Then, 100g of silicon-based / graphite composite material was slowly added to the adhesive slurry and stirred at 1200rpm / min for 2h to obtain a silicon-carbon material slurry.

[0072] A temperature-sensitive polymer was added to a silicon-carbon material slurry, the temperature was raised to 60°C, and the mixture was stirred for 1.5 hours at a speed of 1200 rpm / min to obtain a mixed slurry. The mixed slurry was then spray-dried at 120°C to obtain the silicon-carbon anode material.

[0073] The SEM image of the silicon-carbon anode material prepared in this embodiment is shown below. Figure 1 As shown in Table 1, the gas production of the silicon-carbon anode material in this embodiment was tested, and the test data are shown in Table 1.

[0074] Example 2

[0075] 0.8 g of acryloylglycine and 1.9 g of allyl urea were dissolved in 20 mL of dimethyl sulfoxide. Nitrogen gas was introduced and the rotation speed was set to 500 rpm / min. 0.03 g of azobisisobutyronitrile initiator was added dropwise. The temperature was raised to 70 °C and the reaction was carried out for 12 h. After the reaction was completed, the reaction solution was poured into 50 mL of chloroform, and a solid was precipitated and dried under vacuum to obtain a thermosensitive polymer slurry. The critical dissolution temperature of the thermosensitive polymer was 60 °C.

[0076] 2g of polyethylene oxide was dissolved in 1400mL of water and stirred at 650rpm / min for 1.5h to obtain an adhesive slurry. Then, 100g of silicon-based / graphite composite material was slowly added to the adhesive slurry and stirred at 1200rpm / min for 2h to obtain a silicon-carbon material slurry.

[0077] A temperature-sensitive polymer was added to a silicon-carbon material slurry, the temperature was raised to 60°C, and the mixture was stirred for 1.5 hours at a speed of 1200 rpm / min to obtain a mixed slurry. The mixed slurry was then spray-dried at 120°C to obtain the silicon-carbon anode material.

[0078] The gas production of the silicon-carbon anode material in this embodiment was tested, and the test data are shown in Table 1.

[0079] Example 3

[0080] 0.8 g of acryloylglycine and 1.0 g of acrylonitrile were dissolved in 20 mL of dimethyl sulfoxide. Nitrogen gas was introduced, and the rotation speed was set to 500 rpm / min. 0.03 g of azobisisobutyronitrile initiator was added dropwise. The temperature was raised to 70 °C and the reaction was carried out for 12 h. After the reaction was completed, the reaction solution was poured into 50 mL of methanol, and a solid was precipitated and dried under vacuum to obtain a thermosensitive polymer slurry. The critical dissolution temperature of the thermosensitive polymer was 57 °C.

[0081] Dissolve 2g of sodium carboxymethyl cellulose in 1400mL of water and stir at 650rpm / min for 1.5h to obtain an adhesive slurry. Then, slowly add 100g of silicon-based / graphite composite material to the adhesive slurry and stir at 1200rpm / min for 2h to obtain a silicon-carbon material slurry.

[0082] A temperature-sensitive polymer was added to a silicon-carbon material slurry, the temperature was raised to 60°C, and the mixture was stirred for 1.5 hours at a speed of 1200 rpm / min to obtain a mixed slurry. The mixed slurry was then spray-dried at 120°C to obtain the silicon-carbon anode material.

[0083] The gas production of the silicon-carbon anode material in this embodiment was tested, and the test data are shown in Table 1.

[0084] Example 4

[0085] The difference between Example 4 and Example 1 is that the monomers used to prepare the thermosensitive polymer are acrylamide, allyl urea and acrylonitrile, and the critical dissolution temperature of the thermosensitive polymer is 48°C.

[0086] The gas production of the silicon-carbon anode material in this embodiment was tested, and the test data are shown in Table 1.

[0087] Example 5

[0088] The difference between Example 5 and Example 1 is that the monomers used to prepare the thermosensitive polymer are sulfobetaine, allyl urea and acrylonitrile, and the critical dissolution temperature of the thermosensitive polymer is 53°C.

[0089] The gas production of the silicon-carbon anode material in this embodiment was tested, and the test data are shown in Table 1.

[0090] Example 6

[0091] The difference between Example 6 and Example 1 is that the monomers used to prepare the thermosensitive polymer are methacrylamide, sulfobetaine, acrylonitrile and acryloylglycamide, and the critical dissolution temperature of the thermosensitive polymer is 50°C.

[0092] The gas production of the silicon-carbon anode material in this embodiment was tested, and the test data are shown in Table 1.

[0093] Example 7

[0094] The difference between Example 7 and Example 1 is that the monomers used to prepare the thermosensitive polymer are acryloylglycine, acrylamide, and acrylonitrile, and the critical dissolution temperature of the thermosensitive polymer is 45°C.

[0095] The gas production of the silicon-carbon anode material in this embodiment was tested, and the test data are shown in Table 1.

[0096] Example 8

[0097] 0.8 g of acryloylglycine and 1.9 g of allyl urea were dissolved in 20 mL of dimethyl sulfoxide. Nitrogen gas was introduced and the rotation speed was set to 500 rpm / min. 0.03 g of azobisisobutyronitrile initiator was added dropwise. The temperature was raised to 70 °C and the reaction was carried out for 12 h. After the reaction was completed, the reaction solution was poured into 50 mL of chloroform, and a solid was precipitated and dried under vacuum to obtain a thermosensitive polymer. The critical dissolution temperature of the thermosensitive polymer was 60 °C.

[0098] Then, 100g of silicon-based / graphite composite material and thermosensitive polymer were mixed in water, heated to 60℃, and stirred for 1.5h at a speed of 1200rpm / min to obtain a mixed slurry. The mixed slurry was then spray-dried at 120℃ to obtain silicon-carbon anode material.

[0099] The gas production of the silicon-carbon anode material in this embodiment was tested, and the test data are shown in Table 1.

[0100] Comparative Example 1

[0101] The difference between Comparative Example 1 and Example 1 is that the silicon-carbon anode material is a silicon-based / graphite composite material, without the addition of binders and temperature-sensitive polymers.

[0102] The gas production of the silicon-carbon anode material in this comparative example was tested, and the test data are shown in Table 1.

[0103] Comparative Example 2

[0104] Dissolve 2g of sodium carboxymethyl cellulose in 1400mL of water and stir at 650rpm / min for 1.5h to obtain an adhesive slurry. Then, slowly add 100g of silicon-based / graphite composite material to the adhesive slurry and stir at 1200rpm / min for 2h to obtain a silicon-carbon material slurry.

[0105] Silicon-carbon material slurry is spray-dried at 120°C to obtain silicon-carbon anode material.

[0106] The gas production of the silicon-carbon anode material in this comparative example was tested, and the test data are shown in Table 1.

[0107] The gas generation test methods for the silicon-carbon anode materials prepared in the above embodiments and comparative examples are as follows:

[0108] Add 5g of silicon-carbon anode material and 50g of water to a sealed bottle and dissolve it completely by centrifugation. Then, place the bottle in a constant temperature room at 25℃ and test the gas production (H2) in the sealed bottle after 24h, 72h, 120h, and 168h. The test data are shown in Table 1.

[0109] Table 1

[0110]

[0111] As shown in Table 1, when the temperature conditions of the silicon-carbon anode material are lower than the critical dissolution temperature of the thermosensitive polymer, the gas production of the silicon-carbon anode materials in Examples 1-8 is 1.3CC / kg-4.13CC / kg. This indicates that when the temperature conditions of the silicon-carbon anode material are lower than the critical dissolution temperature of the thermosensitive polymer, the silicon-carbon anode material exhibits hydrophobicity, thereby more effectively preventing silicon from contacting water and reducing the amount of hydrogen gas generated by the reaction between silicon and water during the preparation of the anode slurry.

[0112] The silicon-carbon anode materials in Comparative Examples 1-2 have a higher gas production rate than those in Examples 1-8 because they do not contain temperature-sensitive polymers.

[0113] As shown in Examples 1-8 and Comparative Examples 1-2, at 25°C, within the same time period, the gas production of the silicon-carbon anode materials prepared in Examples 1-8 is less than that in Comparative Examples 1-2. Furthermore, since the binder in Comparative Example 2 is a hydrophilic substance, it further increases the hydrophilicity of the silicon-carbon anode material, leading to an increase in gas production. Therefore, this indicates that using the silicon-carbon anode materials of Examples 1-8 to prepare the anode slurry can effectively reduce gas production.

[0114] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0115] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A silicon-carbon anode material, characterized in that, include: The silicon-carbon material and the thermosensitive polymer coated on the surface of the silicon-carbon material exhibit hydrophobicity when the temperature conditions of the silicon-carbon anode material are lower than the critical dissolution temperature of the thermosensitive polymer, and hydrophilicity when the temperature conditions of the silicon-carbon anode material are higher than the critical dissolution temperature of the thermosensitive polymer. The thermosensitive polymer is obtained by polymerization of at least two monomers from formulas (I), (II), (III), and (IV): In formula (I), R1-R3 are independently selected from unsubstituted -H, C1-C30 alkyl, C3-C30 cycloalkyl, C3-C30 alkenyl, C3-C30 alkynyl, C6-C30 aromatic, C3-C30 heterocyclic, and C5-C30 heteroaromatic, or selected from C1-C30 alkyl, C3-C30 cycloalkyl, C3-C30 alkenyl, and C3-C30 alkynyl containing at least one heteroatom or having a substituent. The following groups are selected: C6-C30 aromatic groups, C3-C30 heterocyclic groups, and C5-C30 heteroaromatic groups, wherein the heteroatom is selected from at least one of O, S, N, Si, and P, and the substituent is selected from at least one of halogen atoms, C1-C20 straight-chain or branched alkyl groups, C3-C20 cycloalkyl groups, C1-C20 straight-chain or branched alkoxy groups, C6-C30 aromatic groups, and C5-C30 heteroaromatic groups. When R3 is not -H, A is selected from SO3. - COO - PO4 2- HPO4 - any one of them; In formula (II), R4 is selected from unsubstituted -H, C1-C30 alkyl, C3-C30 cycloalkyl, C3-C30 alkenyl, C3-C30 ynyl, C6-C30 aromatic, C3-C30 heterocyclic, C5-C30 heteroaromatic, or selected from C1-C30 alkyl, C3-C30 cycloalkyl, C3-C30 alkenyl, C3-C30 ynyl containing at least one heteroatom or having a substituent. The substituent is selected from at least one of the following groups: C6-C30 aromatic group, C3-C30 heterocyclic group, and C5-C30 heteroaromatic group; wherein the heteroatom is selected from at least one of O, S, N, Si, and P; the substituent is selected from at least one of the following groups: halogen atom, C1-C20 straight-chain or branched alkyl group, C3-C20 cycloalkyl group, C1-C20 straight-chain or branched alkoxy group, C6-C30 aromatic group, and C5-C30 heteroaromatic group; R5 is selected from -H or... Wherein, R is selected from -H, C1-C30 alkyl containing an amide group, C3-C30 cycloalkyl containing an amide group, C3-C30 alkenyl containing an amide group, C3-C30 alkynyl containing an amide group, C6-C30 aromatic group containing an amide group, C3-C30 heterocyclic group containing an amide group, or C5-C30 heteroaromatic group containing an amide group. In formula (Ⅲ), R6 is selected from cyano or phenyl; In formula (Ⅳ), R7 is selected from 1-butenyl or 2-aminohexanoic acid.

2. The silicon-carbon anode material according to claim 1, characterized in that, The critical dissolution temperature of the thermosensitive polymer is 40℃-65℃.

3. The silicon-carbon anode material according to any one of claims 1-2, characterized in that, In formula (I), R1 is selected from -H or methyl, and R2 is selected from NH(CH2). a Or O(CH2) b R3 is selected from (CH2). c A is selected from SO3 - In this case, a and b are 2 or 3 respectively, and c is 2, 3 or 4; And / or, in formula (II), R4 is selected from -H or methyl, and R5 is selected from -H, And / or, in formula (Ⅲ), R6 is selected from cyano; And / or, in formula (Ⅳ), R7 is selected from 2-aminohexanoic acid.

4. The silicon-carbon anode material according to any one of claims 1-2, characterized in that, The silicon-carbon anode material also includes a binder, which coats the surface of the silicon-carbon material, and the temperature-sensitive polymer coats the surface of the binder.

5. A method for preparing the silicon-carbon anode material as described in any one of claims 1-4, characterized in that, Includes the following steps: Provide temperature-sensitive polymers; The silicon-carbon material is mixed with the temperature-sensitive polymer in water and then dried to obtain the silicon-carbon anode material.

6. The method for preparing the silicon-carbon anode material according to claim 5, characterized in that, In the step of mixing the silicon carbon material with the temperature-sensitive polymer in water, a binder is also added.

7. The method for preparing the silicon-carbon anode material according to claim 5 or 6, characterized in that, At least two monomers from formulas (I), (II), (III), and (IV) are dissolved in an organic solvent, and an initiator is added to carry out a polymerization reaction. After the polymerization reaction is completed, the polymer is dried to obtain the thermosensitive polymer.

8. The method for preparing the silicon-carbon anode material according to claim 7, characterized in that, In the step of obtaining the thermosensitive polymer, at least one of the following conditions must also be met: (1) The polymerization temperature is 30℃-100℃, and the polymerization reaction time is 30min-3000min; (2) The organic solvent is selected from at least one of dimethyl sulfoxide and tetrahydrofuran; (3) The drying method is selected from vacuum drying or freeze drying.

9. The method for preparing the silicon-carbon anode material according to claim 5, characterized in that, In the step of mixing the silicon carbon material with the temperature-sensitive polymer in water and then drying it, at least one of the following conditions must also be met: (1) The mass ratio of the silicon carbon material to the thermosensitive polymer is 100:0.1-100:10; (2) The mixing speed is 100 rpm / min-5000 rpm / min, and the mixing time is 10 min-300 min; (3) The mixing temperature is 30℃-90℃; (4) The drying method is selected from vacuum drying, baking or spray drying, and the drying temperature is 80℃-250℃.

10. A negative electrode sheet comprising the silicon-carbon negative electrode material according to any one of claims 1-4.

11. An electrochemical energy storage device comprising the negative electrode sheet of claim 10.

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