Composite negative electrode material and negative electrode and battery using same

Abstract

The application provides a composite negative electrode material and a negative electrode and a battery using the same, the composite negative electrode material comprising a negative electrode active material and a conductive polymer coating the negative electrode active material, and a raw material for preparing the conductive polymer comprising a bithiophene aromatic compound; the chemical structural formula of the bithiophene aromatic compound is as follows: wherein A is independently selected from at least one of H, a thiophene ring, a 2-trimethyltin thiophene ring and a thiazole ring; R1, R2, R3 and R4 are independently selected from at least one of H, a halogen atom, an alkyl group and an alkyl tin group; R5 and R6 are independently selected from at least one of H, a halogen atom and an alkyl group, or R5 and R6 and the atoms connected therewith form at least one of a thiophene ring, a thiazole ring and a 2-trimethyltin thiophene ring. By using a benzo-dithiophene compound to coat the negative electrode active material, the application can not only enhance the conductive performance of the negative electrode active material, but also enhance the mechanical performance of the negative electrode active material and inhibit the expansion of the negative electrode active material.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of batteries, and particularly relates to a composite negative electrode material and a negative electrode and a battery using the same. BACKGROUND

[0002] With the development of science and technology, people's dependence on electronic devices is increasing, and the demand for battery endurance is also increasing. For example, the use frequency of smart phones is very high, and if the battery capacity is small, it needs to be charged frequently, which brings inconvenience to users. Therefore, improving the battery capacity can meet the user's demand for long-time use of electronic devices.

[0003] Since silicon is the second most abundant element in the earth's crust, second only to oxygen, it is widely available, which helps to reduce the cost of the battery. The theoretical specific capacity of silicon is as high as 4200 mAh / g, which is more than 10 times that of traditional graphite materials, which means that using silicon materials can significantly improve the energy density of the battery, thereby improving the endurance of the battery. In addition, the working voltage of silicon is relatively low, which can further improve the energy density of the battery.

[0004] Although the application prospect of silicon materials in batteries is broad, there are also some challenges, such as the volume expansion and contraction of silicon during charging and discharging process reaches 320% (graphite only 12%), which will generate a large mechanical stress, and after multiple cycles, the silicon particles will be broken and pulverized, causing the negative electrode to fail. In addition, the contact between silicon and conductive agent and negative electrode binder is poor, which leads to poor overall conductivity of the electrode, affecting the performance of the battery. SUMMARY

[0005] In order to improve the electrochemical performance of the battery, the application provides a composite negative electrode material and a negative electrode and a battery using the same.

[0006] According to one aspect of the present application, a composite negative electrode material is provided, which comprises a negative electrode active material and a conductive polymer coating the negative electrode active material, and the raw material for preparing the conductive polymer comprises a bithiophene aromatic compound; the chemical structural formula of the bithiophene aromatic compound is: wherein A is independently selected from at least one of H, a thiophene ring, a 2-trimethyltin thiophene ring, and a thiazole ring; R1, R2, R3, and R4 are independently selected from at least one of H, a halogen atom, an alkyl group, and an alkyl tin group; R5 and R6 are independently selected from at least one of H, a halogen atom, and an alkyl group, or R5 and R6 and the atoms to which they are connected form at least one of a thiophene ring, a thiazole ring, and a 2-trimethyltin thiophene ring.

[0007] The present application can not only enhance the conductivity of the negative active material, but also enhance the mechanical properties of the negative active material, and inhibit the expansion of the negative active material by using the benzodithiophene compound coated on the negative active material. This is mainly due to the large conjugated planar structure of the benzodithiophene compound, which is beneficial to the transmission of electrons, thereby improving the energy density and rate performance of the battery. At the same time, the benzodithiophene compound has good rigidity and flexibility, which can enhance the mechanical properties of the negative active material, thereby improving the cycle performance of the battery.

[0008] Preferably, the bithiophene aromatic compound comprises at least one of a first monomer and a second monomer; wherein the chemical structure of the first monomer is The chemical structure of the second monomer is R1, R2, R3, R4 are independently selected from at least one of a halogen atom and an alkyl group. The conductive polymer obtained by polymerizing the first monomer and the second monomer has both benzodithiazole and benzodithiophene, both of which have a larger conjugated planar structure, which can further improve the transmission of electrons, thereby further enhancing the rate performance of the battery.

[0009] Preferably, the number of carbon atoms of the alkyl group is ≥5.

[0010] Preferably, the molar ratio of the first monomer to the second monomer is 1-4:1-7.

[0011] Preferably, the molecular weight of the conductive polymer is 6000-40000.

[0012] Preferably, the raw material for preparing the conductive polymer further comprises a dibromothiophene compound, and the structural formula of the dibromothiophene compound is wherein R7, R8 are independently selected from at least one of H, a carboxyl group and an alkyl group. The introduction of the dibromothiophene compound can form a hydrogen bond between the conductive polymer and the negative active material, which can further enhance the interface stability of the composite negative material, thereby enhancing the cycle performance of the battery.

[0013] Preferably, the bithiophene aromatic compound comprises monomer I; wherein the chemical structure of monomer I is A is independently selected from at least one of H and a thiophene ring; R5, R6 are independently selected from at least one of H, a halogen atom and an alkyl group. Further, the symmetric 2-trimethyltin thiophene ring is introduced into the bithiophene aromatic compound, which further improves the conductivity of the material.

[0014] Preferably, the molar ratio of the bithiophene aromatic compound to the dibromothiophene compound is 1:1-3.

[0015] Preferably, the molecular weight of the conductive polymer is 5000-30000.

[0016] Preferably, the method for preparing the conductive polymer comprises the following steps: S1. mixing the bithiophene aromatic compound, or the bithiophene aromatic compound and the dibromothiophene compound, with an organic solvent under anhydrous and anaerobic conditions, and then adding a catalyst to reflux at 70-125°C for 6-24 hours to obtain a first solution; S2. then filtering the first solution, and washing the solid part obtained by the filtering with diethyl ether to obtain a diethyl ether washing liquid; S3. mixing the diethyl ether washing liquid with the filtrate obtained by the filtering, adding a saturated potassium fluoride aqueous solution, and obtaining an organic layer after standing; S4. transferring the organic layer, adding a saturated sodium chloride solution to the organic layer for washing, and then drying with anhydrous magnesium sulfate to obtain a crude product; and S5. purifying the crude product by using a neutral aluminum oxide column chromatography method, and using n-hexane as an eluent to obtain the conductive polymer.

[0017] Preferably, the organic solvent is at least one of benzene, toluene, acetone, and N,N-dimethylformamide (DMF).

[0018] Preferably, the catalyst comprises at least one of tetrakis(triphenylphosphine)palladium (Pd(PPh3)4) and dichlorobis(triphenylphosphine)palladium (Pd(PPh3)2Cl2).

[0019] Preferably, in the composite negative electrode material, the D50 of the negative electrode active material is 3-10 μm, and the thickness of the conductive polymer is 5-80 nm. 50 Preferably, in the composite negative electrode material, the D50 of the negative electrode active material is 3-10 μm, and the thickness of the conductive polymer is 5-80 nm.

[0020] Preferably, the negative electrode active material comprises a silicon material.

[0021] Preferably, the silicon material comprises silicon carbon.

[0022] Preferably, the thickness of the silicon layer in the silicon carbon is 1-10 nm.

[0023] Preferably, in the inner pores and the outer pores of the silicon carbon, the proportion of mesopores is 45-88%, and the proportion of micropores is less than 60%, wherein the diameter of the pore mesopore is 3-45 nm, and the pore diameter of the micropore is 1-2 nm.

[0024] Preferably, in the negative electrode active material, the mass content of the silicon element is 30%-80%.

[0025] Preferably, the method for preparing the composite negative electrode material comprises the following steps: dissolving the conductive polymer in a tetrahydrofuran (THF) solvent to configure a solution with a mass fraction of 5-30%; adding the negative electrode active material to the solution to stir at 40-80°C for 4-10 hours to obtain a mixed solution; and then performing spray drying on the mixed solution to obtain the composite negative electrode material.

[0026] Preferably, the operating parameters of the spray drying process are: inlet temperature 100-200℃, outlet temperature 50-90℃.

[0027] In a second aspect of the present application, a negative electrode is provided, the negative electrode comprising the composite negative electrode material as described above.

[0028] In a third aspect of the present application, a battery is provided, the battery comprising the negative electrode as described above.

[0029] Preferably, an electrolyte is included in the battery, and the electrolyte includes 1-5% lithium bisfluorosulfonylimide (LiFSI) and 5-10% methyl trifluoroethyl carbonate (FEMC) by mass content. By matching the electrolyte additives described above, the ionic conductivity of the battery can be further improved. DETAILED DESCRIPTION

[0030] In order to enable those skilled in the art to better understand the technical solutions in the present application, the technical solutions of the present application will be described clearly and completely in the following with reference to the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor should be within the scope of protection of the present application.

[0031] Embodiment 1

[0032] 1. Preparation of the composite negative electrode material

[0033] (1) Preparation method of the conductive polymer

[0034] S1. Under anhydrous and anaerobic conditions, 1 mmol of 4,8-bis(5-bromo-4-(2- ethylhexyl)thiophene-2-yl)benzo[1,2-c:4,5-c']bis[1,2,5]thiadiazole (CAS No.: 1401018-41-4) and 1 mmol of (4,8-di(4-chloro-5-(2-ethylhexyl)thiophene-2-yl)benzo[1,2-b:4,5-b']dithiophene-2,6-diyl)bis(trimethyltin) (CAS No.: 2239295-69-1) are mixed with 25 mL of N,N-dimethylformamide (DMF), followed by the addition of tetrakis(triphenylphosphine)palladium (Pd(PPh3)4), and the first solution is obtained by refluxing at 100℃ for 18 hours;

[0035] S2. The first solution is then filtered, and the solid part obtained by the filtration is washed with diethyl ether to obtain a diethyl ether washing liquid;

[0036] S3. The diethyl ether washing liquid is mixed with the filtrate obtained by the above filtration, and a saturated potassium fluoride aqueous solution is added, and the organic layer is obtained after standing treatment;

[0037] S4. The organic layer is transferred and washed with a saturated sodium chloride solution, and then dried with anhydrous magnesium sulfate to obtain a crude product;

[0038] S5. The crude product is purified by neutral aluminum oxide column chromatography, using n-hexane as an eluent, to obtain the conductive polymer.

[0039] (2) Preparation method of composite negative electrode material

[0040] The conductive polymer is dissolved in a tetrahydrofuran (THF) solvent to prepare a solution with a mass fraction of 20%; silicon carbon is added to the solution, and stirring is performed at 60°C for 8 hours to obtain a mixed solution; then the mixed solution is subjected to spray drying treatment to obtain the composite negative electrode material. The operating parameters of the spray drying treatment are: an inlet temperature of 150°C and an outlet temperature of 70°C; the prepared composite negative electrode material has a D 50 value of 6 μm, and a conductive polymer thickness of 60 nm.

[0041] 2. Preparation of lithium ion battery

[0042] (1) Preparation of positive electrode sheet

[0043] A ternary material NCM811 (LiNi 0.8 Co 0.1 Mn 0.1 O2) positive electrode active material, a binder PVDF (polyvinylidene fluoride), and a conductive agent SP (conductive carbon black Super-P) are mixed and stirred uniformly at a mass ratio of 96:2:2 to obtain a positive electrode slurry, and then the positive electrode slurry is coated on an aluminum foil through a coating process, and a positive electrode sheet is obtained after a drying and cold pressing process.

[0044] (2) Preparation of negative electrode sheet

[0045] A composite negative electrode material, a conductive agent SP (conductive carbon black Super-P), SWCNT (single-walled carbon nanotube), and a binder PAA (polyacrylic acid) are mixed and stirred uniformly at a mass ratio of 80:9:1:10 to obtain a negative electrode slurry, and the solid content is controlled at 30%, and then the negative electrode slurry is coated on a copper foil through a coating process, and a negative electrode sheet is obtained after a vacuum drying and cold pressing process.

[0046] (3) Selection of electrolyte

[0047] EC: DMC: DEC: FEC = 20:40:30:10, LiPF6 1 mol / L to prepare a lithium ion battery.

[0048] (4) Selection of separator film

[0049] Polyethylene (PE) and ceramic are selected as the separator of lithium ion battery.

[0050] (5) Preparation of lithium ion battery

[0051] The above positive electrode sheet, separator and negative electrode sheet are stacked in order, with the separator between the positive electrode sheet and the negative electrode sheet to play a separating role, and then wound to obtain a bare battery cell; the bare battery cell is placed in an outer packaging shell, dried, and then injected with electrolyte, and then subjected to vacuum packaging, standing, formation, shaping and other processes to obtain a lithium ion battery.

[0052] Example 2

[0053] In this embodiment, the composite negative electrode material is prepared by using 2,5-dibromo thiophene-3,4-dicarboxylic acid (CAS No.: 190723-12-7) instead of 4,8-bis(5-bromo-4-(2-ethylhexyl) thiophene-2-yl) benzo[1,2-c:4,5-c'] bis[1,2,5] thiadiazole (CAS No.: 1401018-41-4). The operation steps of preparing the composite negative electrode material and the negative electrode and the battery using the same in this embodiment are strictly consistent with those in Example 1. Specifically, the steps of preparing the composite negative electrode material in this embodiment are as follows:

[0054] S1. Under anhydrous and anaerobic conditions, 1 mmol of 2,5-dibromo thiophene-3,4-dicarboxylic acid (CAS No.: 190723-12-7) and 1 mmol of 5,6-difluoro-4,7-bis(5-(trimethylstannyl) thiophene-2-yl) benzo[c][1,2,5] thiadiazole (CAS No.: 1421762-30-2) are mixed with 25 mL of benzene, followed by the addition of dichlorobis(triphenylphosphine) palladium (Pd(PPh3)2Cl2), and then refluxed at 110°C for 18 hours to obtain a first solution;

[0055] The operation steps of S2-S5 are strictly consistent with those in Example 1. The composite negative electrode material D prepared in this embodiment has a thickness of 6 μm, and the thickness of the conductive polymer is 65 nm. 50

[0056] Example 3

[0057] In this embodiment, the composite negative electrode material is prepared by using 2,5-dibromo thiophene-3,4-dicarboxylic acid (CAS No.: 190723-12-7) instead of 4,8-bis(5-bromo-4-(2-ethylhexyl) thiophene-2-yl) benzo[1,2-c:4,5-c'] bis[1,2,5] thiadiazole (CAS No.: 1401018-41-4). The operation steps of preparing the composite negative electrode material and the negative electrode and the battery using the same in this embodiment are strictly consistent with those in Example 1. Specifically, the steps of preparing the composite negative electrode material in this embodiment are as follows: ​

[0058] S1. Under anhydrous and anaerobic conditions, 1 mmol of 2,5-dibromothiophene-3,4-dicarboxylic acid (CAS No.: 190723-12-7) and 1 mmol of (4,8-di(4-chloro-5-(2- ethylhexyl)thiophen-2-yl)benzo[l,2-b:4,5-b']dithiophene-2,6-diyl)bis(trimethyltin) (CAS No.: 2239295-69-1) were mixed with 25 mL of N,N-dimethylformamide (DMF), followed by the addition of dichlorobis(triphenylphosphine) palladium (Pd(PPh3)2Cl2), and the first solution was obtained by refluxing at 100 °C for 18 hours;

[0059] The operation steps of S2-S5 were strictly consistent with those of Example 1. Among them, the prepared composite negative electrode material D 50 was 5 pm, and the thickness of the conductive polymer was 58 nm.

[0060] Example 4

[0061] This example prepared a composite negative electrode material and a negative electrode and a battery using the same according to the formula and method provided in Example 1, which was different from Example 1 in that 5,6-difluoro-4,7-bis(5-(trimethylstannyl)thiophen-2-yl)benzo[c][l,2,5]thiadiazole (CAS No.: 1421762-30-2) was used instead of (4,8-di(4-chloro-5-(2- ethylhexyl)thiophen-2-yl)benzo[l,2-b:4,5-b']dithiophene-2,6-diyl)bis(trimethyltin) (CAS No.: 2239295-69-1) in the preparation of the composite negative electrode material. Except for the above difference, the operation steps of the preparation of the composite negative electrode material and the negative electrode and the battery using the same in this example were strictly consistent with those of Example 1. Specifically, the steps for preparing the composite negative electrode material in this example were as follows:

[0062] S1. Under anhydrous and anaerobic conditions, 1 mmol of 2,5-dibromothiophene-3,4-dicarboxylic acid (CAS No.: 190723-12-7) and 1 mmol of (4,8-di(4-chloro-5-(2- ethylhexyl)thiophen-2-yl)benzo[l,2-b:4,5-b']dithiophene-2,6-diyl)bis(trimethyltin) (CAS No.: 2239295-69-1) were mixed with 25 mL of N,N-dimethylformamide (DMF), followed by the addition of dichlorobis(triphenylphosphine) palladium (Pd(PPh3)2Cl2), and the first solution was obtained by refluxing at 100 °C for 18 hours;

[0063] The operation steps of S2-S5 were strictly consistent with those of Example 1. Among them, the prepared composite negative electrode material D 505 pm, and the thickness of the conductive polymer was 55 nm.

[0064] Example 5

[0065] In this example, the composite negative electrode material was prepared according to the formula and method provided in Example 1, and the negative electrode and battery using the same were prepared. The difference between this example and Example 1 is that the thickness of the conductive polymer of the composite negative electrode material prepared in this example was 83 nm (achieved by adjusting the operation parameters of the spray drying process), and the thickness of the conductive polymer of the composite negative electrode material prepared in Example 1 was 55 nm. 50 In addition to the above difference, the operation steps for preparing the composite negative electrode material and the negative electrode and battery using the same in this example were strictly consistent with those in Example 1.

[0066] Example 6

[0067] In this example, the composite negative electrode material was prepared according to the formula and method provided in Example 2, and the negative electrode and battery using the same were prepared. The difference between this example and Example 2 is that the thickness of the conductive polymer of the composite negative electrode material prepared in this example was 83 nm (achieved by adjusting the operation parameters of the spray drying process), and the thickness of the conductive polymer of the composite negative electrode material prepared in Example 2 was 55 nm. 50 In addition to the above difference, the operation steps for preparing the composite negative electrode material and the negative electrode and battery using the same in this example were strictly consistent with those in Example 2.

[0068] Example 7

[0069] In this example, the composite negative electrode material was prepared according to the formula and method provided in Example 2, and the negative electrode and battery using the same were prepared. The difference between this example and Example 2 is that the thickness of the conductive polymer of the composite negative electrode material prepared in this example was 83 nm (achieved by adjusting the operation parameters of the spray drying process), and the thickness of the conductive polymer of the composite negative electrode material prepared in Example 2 was 55 nm.

[0070] Example 8

[0071] In this example, the composite negative electrode material was prepared according to the formula and method provided in Example 2, and the negative electrode and battery using the same were prepared. The difference between this example and Example 2 is that the thickness of the conductive polymer of the composite negative electrode material prepared in this example was 83 nm (achieved by adjusting the operation parameters of the spray drying process), and the thickness of the conductive polymer of the composite negative electrode material prepared in Example 2 was 55 nm.

[0072] Comparative Example 1

[0073] The negative electrode, lithium ion battery of the present comparative example was prepared according to the formulation and method provided in Example 1, except that the negative electrode active material used in the preparation of the negative electrode was silicon-carbon. The steps of preparing the composite negative electrode material and the negative electrode and lithium ion battery using the same were strictly consistent with those of Example 1, except for the above difference.

[0074] Comparative Example 2

[0075] The composite negative electrode material and the negative electrode and lithium ion battery using the same of the present comparative example were prepared according to the formulation and method provided in Example 1, except that poly-3,4-ethylenedioxythiophene was used instead of the bis-thiophene aromatic compound in the preparation of the composite negative electrode material. The steps of preparing the composite negative electrode material and the negative electrode and lithium ion battery using the same were strictly consistent with those of Example 1, except for the above difference.

[0076] Test Example

[0077] 1. Test Object

[0078] The composite negative electrode material and the negative electrode and lithium ion battery using the same of Examples 1-8 and Comparative Examples 1-2.

[0079] 2. Test Method

[0080] (1) First coulombic efficiency: the lithium ion battery was charged at a rate of 0.33C to 4.2V under the condition of 25°C, and then rested for 10 minutes. Subsequently, the lithium ion battery was discharged at a rate of 0.33C to 2.5V, and then rested for 10 minutes. The first coulombic efficiency of the lithium ion battery was calculated. The first coulombic efficiency (first efficiency) was calculated according to the following formula:

[0081] First coulombic efficiency (%) = total capacity of the first discharge of the lithium ion battery at 0.33C / total capacity of the first charge of the lithium ion battery at 0.33C x 100%

[0082] (2) Capacity retention rate after 1200 cycles at room temperature at 1C / 1C: the lithium ion battery was charged at a rate of 1C to 4.2V under the condition of 25°C, and then rested for 10 minutes. Subsequently, the lithium ion battery was discharged at a rate of 1C to 2.5V, and then rested for 10 minutes. This was one cycle of charging and discharging. The lithium ion battery was subjected to 1200 cycles of charging and discharging according to the above method. The capacity retention rate after 1200 cycles of charging and discharging of the lithium ion battery at 1C / 1C was calculated. The capacity retention rate was calculated according to the following formula:

[0083] Capacity retention rate (%) after N cycles of the lithium ion battery = (discharge capacity of the Nth cycle / first discharge capacity) x 100%, N is the number of cycles of the lithium ion battery

[0084] (3) 1C / 10C discharge capacity retention: the lithium ion battery after the capacity test was charged at 1C rate to 4.2V at 25℃ with constant current and constant voltage, the cutoff current was 0.05C; standing for 10min; then discharged at 1C rate to 2.5V, recording its discharge capacity Q1C as the initial discharge capacity; then the lithium ion battery was charged at 1C rate to 4.2V at 25℃ with constant current and constant voltage, the cutoff current was 0.05C; standing for 10min; then the fully charged battery was discharged at 10C rate to 2.5V with constant current, recording its discharge capacity Q10C. The discharge capacity retention of the lithium ion battery at 1C / 10C rate was calculated according to the following formula:

[0085] Discharge capacity retention (%) = discharge capacity at 10C rate Q10C / discharge capacity at 1C rate Q1C x 100%

[0086] (4) Normal temperature 6C rate performance-constant current charge ratio: the lithium ion battery was discharged at 1C rate to 2.5V at 25℃ with constant current, standing for 10min, then charged at 6C rate to 4.2V with constant current and constant voltage, the cutoff current was 0.05C, standing for 10min, recording the constant current charge capacity Q1 and the total constant current and constant voltage charge capacity Q2 of the lithium ion battery, and the 6C rate charge constant current charge ratio was calculated according to the following formula:

[0087] 6C rate charge constant current charge ratio = constant current charge capacity Q1 / total constant current and constant voltage charge capacity Q2 x 100%

[0088] 3. Test results and analysis

[0089] The test results of the test examples are shown in Table 1.

[0090] Among them, through the test results of Examples 1-4 and Comparative Examples 1-2, it can be known that by matching different double thiophene aromatic compounds or introducing dibromothiophene compounds, the electrochemical performance of the lithium ion battery can be significantly enhanced. This is mainly because the benzo dithiophene compound has a larger conjugated planar structure, which is beneficial to the transmission of electrons, thereby improving the energy density and rate performance of the battery. Further, when the conductive polymer obtained by polymerization of the first monomer and the second monomer has both benzo bis thiadiazole and benzo dithiophene, both of which have a larger conjugated planar structure, the transmission of electrons can be further improved, thereby further enhancing the rate performance of the battery. Further, by introducing the dibromothiophene compound, a hydrogen bond can be formed between the conductive polymer and the negative active material, which can further enhance the interface stability of the composite negative electrode material, thereby enhancing the cycle performance of the battery.

[0091] On the other hand, the data of Example 1 and Examples 5-6 can prove that the D 50The cycle performance and rate performance of the battery will be affected, which is likely to be caused by the D 50 The example transmission performance of the battery; the data of example 1 and example 7 can show that by adjusting the thickness of the conductive polymer in the composite negative electrode material, the interface stability of the composite negative electrode material can be improved, thereby improving the overall electrochemical performance of the battery.

[0092] In addition, the data of example 8 can prove that by introducing double fluorosulfonyl imide lithium, methyl trifluoroethyl carbonate (FEMC), the ionic conductivity of the battery can be further improved.

[0093] Table 1. Test results of this test example

[0094]

[0095] The above examples are only used to illustrate the technical solutions of the present application and not to limit the protection scope of the present application. Although the present application has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that the technical solutions of the present application can be modified or replaced equivalently without departing from the essence and scope of the technical solutions of the present application.

Claims

1. A composite negative electrode material, characterized by, The composite negative electrode material includes a negative electrode active material including a silicon material and a conductive polymer coating the negative electrode active material, a first monomer for preparing the conductive polymer includes at least one of 4,8-bis(5-bromo-4-(2-ethylhexyl)thiophene-2-yl)benzo[1,2-c:4,5-c']bis[1,2,5]thiadiazole and 2,5-dibromothiophene-3,4-dicarboxylic acid; and a second monomer for preparing the conductive polymer includes at least one of (4,8-di(4-chloro-5-(2-ethylhexyl)thiophene-2-yl)benzo[1,2-b:4,5-b']dithiophene-2,6-diyl)bis(trimethyltin) and 5,6-difluoro-4,7-bis(5-(trimethyltinyl)thiophene-2-yl)benzo[c][1,2,5]thiadiazole.

2. The composite negative material of claim 1, wherein, The conductive polymer has a molecular weight of 6000 to 40000.

3. The composite negative material of claim 1, wherein the carbon-based material is selected from the group consisting of graphite, carbon black, carbon nanotubes, and carbon nanofibers. The conductive polymer has a molecular weight of 5000 to 30000.

4. The composite negative material according to any one of claims 1 to 3, wherein the carbon material is a carbon material having a graphitization degree of 50% or more. In the composite negative electrode material, the negative electrode active material has a D50 of 3 to 10 µm, and the conductive polymer has a thickness of 5 to 80 nm.

5. A negative electrode characterized by comprising: The negative electrode includes the composite negative electrode material according to any one of claims 1 to 4.

6. A battery, characterized by The battery includes the negative electrode according to claim 5.

Images