Lithium battery pack with excellent cycle performance and preparation method thereof

Abstract

The invention discloses a lithium battery pack with excellent cycle performance and a preparation method thereof, and belongs to the technical field of lithium battery pack preparation. The preparation method of the lithium battery pack with excellent cycle performance comprises the following steps: step 1, preparing positive electrode slurry by taking polyvinylidene fluoride, N-methyl pyrrolidone, an organic active substance and a modified conductive agent as raw materials, and coating the surface AB of an aluminum current collector with the positive electrode slurry to obtain a positive plate; step 2, graphite, carboxymethyl cellulose and deionized water are used as raw materials to obtain negative electrode slurry, and the AB surface of a copper current collector is coated with the negative electrode slurry to obtain a negative plate; and 3, winding the diaphragm, the positive plate and the negative plate into a roll core, vertically inserting the roll core into the steel shell, drying, injecting electrolyte, welding to obtain lithium batteries, and then connecting the lithium batteries in series to obtain the lithium battery pack. The lithium battery pack prepared by the method has excellent energy density, cycling stability and rate capability.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium battery pack preparation, and in particular relates to a lithium battery pack with excellent cycle performance and a preparation method thereof. Background Art

[0002] Lithium-ion batteries, as a new type of energy storage device with high energy density, long service life and environmental protection, are an important development direction of energy storage technology in the future. Electrode materials are one of the decisive factors for the performance of lithium batteries. Positive electrode materials, such as lithium iron phosphate, lithium manganese oxide, and ternary lithium, each have unique electrochemical properties. For example, lithium iron phosphate has high stability, safety and environmental protection, but its theoretical capacity is relatively low; lithium manganese oxide has a low cost, which is conducive to the production of large and medium-sized batteries, but its high temperature stability is insufficient and its theoretical capacity is not high; ternary lithium batteries combine the advantages of lithium cobalt oxide and lithium manganese oxide, with high energy density and good cycle performance. In terms of negative electrode materials, graphite carbon materials have always been in the mainstream, but the research and development of new materials such as graphene has opened up new paths for improving negative electrode performance. Through reasonable blending of positive and negative electrode materials, carbon coating and surface modification, the conductivity, stability and lithium storage capacity of the electrode can be significantly improved, thereby extending the cycle life of the battery.

[0003] Patent CN118919680A discloses an ultra-high current lithium iron phosphate battery and its preparation method, firstly, by preparing a positive electrode slurry, coating the obtained positive electrode slurry on the surface of aluminum foil to obtain a positive electrode plate, then assembling the positive electrode plate with the negative electrode and the diaphragm, injecting the electrolyte and sealing. Compared with the prior art, this invention improves the charge and discharge capacity of the material under high current by coating lithium iron phosphate with modified carbon nanotubes, and improves the battery rate and cycle performance. However, the energy density, cycle stability and rate performance of the lithium battery prepared by this method still have room for improvement. Summary of the invention

[0004] The object of the present invention is to provide a lithium battery pack with excellent cycle performance and a preparation method thereof, so as to solve the technical problems of poor energy density, cycle stability and rate performance of lithium battery packs in the prior art.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] The present invention provides a method for preparing a lithium battery pack with excellent cycle performance, comprising the following steps:

[0007] Step 1: Add polyvinylidene fluoride to a container containing N-methylpyrrolidone, stir until completely dissolved, mix and grind the organic active material and the modified conductive agent, add them to the container, continue to stir and mix, obtain a positive electrode slurry, and evenly coat the positive electrode slurry on the AB surface of the aluminum current collector, dry, and compact to obtain a positive electrode sheet;

[0008] Step 2: Mix and stir graphite, carboxymethyl cellulose and deionized water to obtain a negative electrode slurry, and then evenly coat the negative electrode slurry on the copper current collector AB surface, dry, and compact to obtain a negative electrode sheet;

[0009] Step 3: Wind the diaphragm, positive electrode sheet and negative electrode sheet into a core through a winding machine, and then insert the core vertically into the steel shell. After drying, inject electrolyte and weld to obtain a lithium battery. Then connect the lithium batteries in series to obtain a lithium battery pack.

[0010] Preferably, in the step 1, the amount ratio of polyvinylidene fluoride, N-methylpyrrolidone, organic active substance and modified conductive agent is (1-2) g: (8-12) mL: (5-8) g: (2-3) g, the mixing and grinding time is 10-15 min, the stirring and mixing time is continued for 4-6 h, first dried at 50-60 ° C for 10-12 h, and then vacuum dried at 80-85 ° C for 8-10 h; in the step 2, graphite, The dosage ratio of carboxymethyl cellulose and deionized water is (3-5) g: (1-2) g: (5-7) mL; in the step three, the diaphragm is composed of a polypropylene film, and the electrolyte is composed of lithium hexafluorophosphate, dimethyl carbonate, diethyl carbonate, cyclohexylbenzene and 1,2-dimethoxy-4,5-dinitrobenzene, and the dosage ratio is (10-12) g: (20-32) g: (12-18) g: (0.2-0.6) g: (0.1-0.4) g.

[0011] Preferably, the method for preparing the organic active substance comprises the following steps:

[0012] Q1: Add tetrachloroperylene anhydride to a container filled with argon, then add propionic acid, then add aminotriglycol monomethyl ether, heat and stir to reflux for reaction, after the reaction is completed, pour into methanol, filter, separate and purify, recrystallize to obtain compound 1; add compound 1 to a container, then add cuprous iodide and L-proline, evacuate and introduce argon, add dimethyl sulfoxide, heat and stir to reflux for reaction, after the reaction is completed, pour into distilled water, stir and mix, filter, wash, rotary evaporate, separate and purify, and settle to obtain compound 2;

[0013] Q2: Compound 2 is added to a container, and then pinacol borate, tris(pentafluorophenyl)phosphine and methoxy(cyclooctadiene) iridium polymer are added in sequence, argon is introduced and then dichlorohexacyclopentane is added, heated and stirred to reflux for reaction, after the reaction is completed, rotary evaporation, separation and purification, and precipitation are performed to obtain compound 3; Compound 3 is added to a container, and then copper bromide is added, argon is introduced, and then a mixed solution of dioxane, methanol and distilled water after aeration and deoxygenation is added to the container, heated and stirred to reflux for reaction, after the reaction is completed, added to distilled water, stirred, filtered, washed, rotary evaporated, recrystallized, dried, and added to a container containing triisopropylsilyl acetylene, argon is introduced and then dimethyl sulfoxide is added, heated and stirred to react, added to distilled water, filtered, washed, rotary evaporated, separated and purified, and precipitated to obtain compound 4;

[0014] Q3: Add compound 4 to a container containing a mixed solution of tetrahydrofuran and deionized water, stir to mix, then add tetrabutylammonium fluoride to a sample bottle containing a mixed solution of tetrahydrofuran and deionized water, mix evenly, add the mixture in the sample bottle to the container with a syringe, react in a closed manner at room temperature, and after the reaction is completed, wash, rotary evaporate, separate and purify, and precipitate to obtain compound 5; add cuprous chloride and tetramethylethylenediamine to a reaction tube containing dichloromethane, stir to mix, add compound 5 to dichloromethane, mix evenly, add to the reaction tube, heat to react, wash, rotary evaporate, separate and purify, and precipitate to obtain an organic active substance.

[0015] In the above process, the synthesis reaction formula of the organic active substance is as follows:

[0016]

[0017] The results of mass spectrometry analysis of compound 1 were: m / z: 820.09 (100.0%), 818.10 (78.2%), 822.09 (48.2%), 821.10 (42.6%), 819.10 (32.8%), 823.09 (20.1%), 822.10 (10.6%), 824.09 (10.4%), 820.10 (8.4%), 824.10 (5.3%), 825.09 (4.3%), 823.10 (2.4%), 826.09 (1.1%), 825.10 (1.0%); the results of mass spectrometry analysis of compound 2 were: m / z: 750.17 (100.0%), 752.17 (63 .9%), 751.18(41.9%), 753.18(28.8%), 752.18(10.9%), 754.17(10.4%), 754.18(6.8%), 755.17(4.3%), 755.18(1.4%), 756.18(1.0%); The results of mass spectrometry analysis of compound 3 were: m / z: 1002.35(100.0%), 1003.35(69.1%), 1004.34(48.8%), 1001.35(37.8%), 1005.35(32.8%), 1004.35(27.9%), 1006.35(11.4%), 1006.34(8.0%), The results of mass spectrometry analysis of compound 4 were as follows: m / z: 1110.44 (100.0%), 1112.44 (78.0%), 1111.44 (75.8%), 1113.44 (54.3%), 1112.45 (23.7%), 1113.36 (54.3%), 1113.36 (23.7%), 1113.36 (23.7%), 1113.36 (23.7%), 1113.36 (23.7%), 1113.36 (23.7%), 1113.36 (23.7%), 1113.36 (23.7%), 1113.36 (23.7%), 1113.36 (23.7%), 1113.36 (23.7%), 1113.36 (23.7%), 1113.36 (23.7%), 1113.36 (23.7%), 1113.36 (23.0%), 1113.36 (23.7%), 1113.36 (23. 4.44 (21.2%), 1114.45 (17.0%), 1115.44 (12.7%), 1113.45 (8.5%), 1115.45 (4.4%), 1116.44 (4.3%), 1116.45 (1.3%), 1111.45 (1.3%), 1117.44 (1.0%); the results of mass spectrometry analysis of compound 5 were as follows: m / z: 798.17 (100.0%), 800.17 (63.9%), 799.18 (46.2%), 801.18 (32.0%), 800.18 (12.8%), 802.17 (10.4%), 802.18 (8.0%), 803.17 (4.8%), 803.18 (1.7%), 804.18 (1.2%); the results of mass spectrometry analysis of organic active substances are: m / z: 1594.32 (100.0%), 1595.32 (68.2%), 1592.32 (57.4%), 1593.32 (53.9%), 1597.32 (35.8%), 1596.31 (35.2%), 1596.32 (35.0%), 1598.32 (16.5%) ,1597.33(10.0%),1595.33(9.5%),1598.31(8.0%),1599.31(7.0%),1599.32(6.0%),1600.32(3.9%),1598.33(3.4%),1596.33(2.8%),1601.32(1.2%),1600.33(1.1%),1595.31(1.1%),1600.31(1.0%). .

[0018] Preferably, in Q1, the amount ratio of tetrachloroperylene anhydride, propionic acid and aminotriglycol monomethyl ether is (8-13) g: (180-220) mL: (9-12) g, the heating stirring reflux reaction temperature is 130-150°C, and the reaction time is 15-18 h; the amount ratio of compound 1, cuprous iodide, L-proline and dimethyl sulfoxide is (3-6) g: (18-20) g: (11-13) g: (100-130) mL, the heating stirring reflux reaction temperature is 110-120°C, the stirring speed is 600-800 rpm, the reaction time is 16-20 h, and the stirring mixing time is 1-2 h.

[0019] Preferably, in Q2, the amount ratio of compound 2, bipyraclostrobin, tris(pentafluorophenyl)phosphine, methoxy(cyclooctadiene) iridium polymer and dichlorohexacyclopentane is (1-1.5) g: (3-3.88) g: (0.081-0.086) g: (0.024-0.027) g: (18-25) mL, the heating stirring reflux reaction temperature is 100-120° C., the stirring speed is 600-700 rpm, and the reaction time is 10-12 h; compound 3, copper bromide, dioxane, The dosage ratio of methanol, triisopropylsilyl acetylene and dimethyl sulfoxide is (1.2-1.8) g: (2.01-2.25) g: (38-42) mL: (14-18) mL: (1.41-1.84) g: (80-120) mL, the heating stirring reflux reaction temperature is 110-130°C, the stirring speed is 600-800 rpm, the reaction time is 10-12h, the stirring reaction time is 1-2h, the heating stirring reaction temperature is 110-120°C, and the reaction time is 3-5h.

[0020] Preferably, in Q3, the dosage ratio of compound 4 and tetrabutylammonium fluoride is (0.3-0.5) g: (0.2-0.4) mL, and the closed reaction time is 10-12 h; the dosage ratio of cuprous chloride, tetramethylethylenediamine and compound 5 is (3-5) mg: (10-13) μL: (35-41.2) mg, the heating reaction temperature is 50-60°C, and the reaction time is 6-8 h.

[0021] Preferably, the method for preparing the modified conductive agent comprises the following steps:

[0022] S1: adding cyclohexane, 2-tert-butylphenol and benzaldehyde into a container, adding diethylamine under stirring, heating to react, then heating under reduced pressure distillation, then adding a mixed solution of anhydrous ethanol and cyclohexane into the container, recrystallizing, filtering, washing and drying to obtain intermediate A;

[0023] S2: Add intermediate A, toluene and tetracycloheptane into a container, heat and stir under reflux, rotary evaporate, purify to obtain a crude product, add the crude product and sodium sulfate into methanol, heat and stir under nitrogen atmosphere, then vacuum concentrate, add ethyl acetate, extract, dry, and filter to obtain intermediate B;

[0024] S3: Add intermediate B, graphene and tetrahydrofuran into a container, then add Grubbs catalyst, react at room temperature, and after the reaction is completed, add to methanol after dilution, stir the reaction, filter, vacuum dry, wash, and dry to obtain a modified conductive agent.

[0025] In the above process, the synthetic reaction formula of the modified conductive agent is as follows:

[0026]

[0027] Preferably, in S1, the dosage ratio of cyclohexane, 2-tert-butylphenol, benzaldehyde, diethylamine and mixed solution is (80-120) mL: (90-110) g: (62-68) g: (5-6) g: (130-135) mL, the heating reaction temperature is 100-120°C, the reaction time is 20-24h, the heating reduced pressure distillation temperature is 120-125°C, the reduced pressure distillation time is 1-2h, and the volume ratio of anhydrous ethanol to cyclohexane is 3:1.

[0028] Preferably, in S2, the amount ratio of intermediate A, toluene and tetracycloheptane is (14-16) g: (40-60) mL: (9-10.2) g, the heating stirring reflux temperature is 50-65° C., and the reflux time is 72-90 h. The amount ratio of crude product, sodium sulfate, methanol and ethyl acetate is (6-10) g: (8-8.5) g: (80-120) mL: (90-110) mL, the heating stirring temperature is 45-55° C., and the stirring time is 4-6 h. In S3, the amount ratio of intermediate B, graphene, tetrahydrofuran and Grubbs catalyst is (50-70) mg: (30-40) mg: (2-4) mL: (1.2-1.5) mg, the reaction time at room temperature is 2-4 h, and the stirring reaction time is 1-2 h.

[0029] Preferably, a lithium battery pack with excellent cycle performance is prepared by the method according to any one of claims 1 to 9.

[0030] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0031] 1. The present invention first uses tetrachloroperylene anhydride, aminotriglycol monomethyl ether, biboric acid pinacol ester, triisopropylsilyl acetylene, tetrabutylammonium fluoride and tetramethylethylenediamine as raw materials to prepare an organic active substance, and then uses 2-tert-butylphenol, benzaldehyde, tetracycloheptane and graphene as raw materials to prepare a modified conductive agent. The two are applied to a lithium battery pack, which can effectively improve its energy density, cycle stability and rate performance.

[0032] 2. The present invention adds the prepared organic active substance to the preparation process of the lithium battery pack, which can effectively improve its energy density and cycle stability. The conjugated system of the prepared organic active substance is significantly expanded, making the electron cloud distribution wider and the electron transmission efficiency improved, so that more electrons participate in the reaction during the charging and discharging process of the lithium battery, thereby improving the energy density. At the same time, the expansion of the conjugated system enhances the π-π stacking effect between molecules, further improving the charging and discharging efficiency. The stable molecular structure of the organic active substance makes it difficult for the battery to decompose or reconstruct during the charging and discharging process, ensuring the long life and cycle stability of the battery and extending the service life of the lithium battery pack.

[0033] 3. The present invention applies the prepared modified conductive agent to a lithium battery pack, which can effectively improve the cycle stability and rate performance of the battery. The modified conductive agent has a high molecular weight and a complex chemical structure, so that it can remain relatively stable during the battery charging and discharging process and is not prone to decomposition or degradation. The stable structure helps to reduce the shedding and differentiation of electrode materials, thereby extending the service life of the battery. The stable chemical properties of the modified conductive agent are conducive to its chemical stability in the internal environment of the battery, thereby reducing harmful chemical reactions inside the battery and improving the cycle stability of the battery. At the same time, the conjugated structure and electron transmission channel of the modified conductive agent give it excellent conductivity, thereby enabling faster transfer of charges and ions inside the battery and improving the rate performance of the battery. The quinone group contained in it has high redox activity, which can enable the battery pack to quickly carry out charge transfer reactions, reduce polarization inside the battery, and enable the battery to maintain high performance under high rate charging and discharging conditions. At the same time, the presence of the modified conductive agent can also improve the ion transmission rate inside the battery and improve the rate performance of the battery pack. DETAILED DESCRIPTION

[0034] The following will be described clearly and completely in conjunction with the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0035] Example 1: This example discloses a method for preparing an organic active substance, comprising the following steps:

[0036] Q1: 10.5 g of tetrachloroperylene anhydride was added to a container filled with argon, and then 200 mL of propionic acid was added, followed by 10.5 g of aminotriglycol monomethyl ether, and the mixture was heated at 140°C with stirring and reflux for 16 h. After the reaction was completed, the mixture was poured into methanol, filtered, separated and purified, and recrystallized to obtain compound 1; 4.5 g of compound 1 was added to a container, and then 19 g of cuprous iodide and 12 g of L-proline were added. After vacuuming and introducing argon, 120 mL of dimethyl sulfoxide was added, and the mixture was heated at 600 rpm and 120°C with stirring and reflux for 20 h. After the reaction was completed, the mixture was poured into distilled water, stirred and mixed for 1 h, filtered, washed, rotary evaporated, separated and purified, and precipitated to obtain compound 2;

[0037] Q2: 1.25 g of compound 2 was added to a container, and then 3.44 g of bipyraclostrobin, 0.083 g of tris(pentafluorophenyl)phosphine and 0.026 g of methoxy(cyclooctadiene)iridium polymer were added in sequence, argon was introduced, 22 mL of dichlorohexacyclopentane was added, and the mixture was heated, stirred and refluxed at 700 rpm and 110 ° C for 12 h. After the reaction was completed, the mixture was rotary evaporated, separated and purified, and precipitated to obtain compound 3; 1.5 g of compound 3 was added to a container, and then 2.13 g of copper bromide was added, argon was introduced, and then 40 A mixed solution of mL of dioxane, 16 mL of methanol and 8 mL of distilled water was added to a container, heated and stirred at 800 rpm and 130°C for 12 h, and after the reaction was completed, it was added to 500 mL of distilled water, stirred for 1 h, filtered, washed, rotary evaporated, recrystallized, and added to a container containing 1.63 g of triisopropylsilyl acetylene after drying. After argon was introduced, 100 mL of dimethyl sulfoxide was added, heated and stirred at 120°C for 4 h, and then added to distilled water, filtered, washed, rotary evaporated, separated and purified, and precipitated to obtain compound 4;

[0038] Q3: Add 0.4 g of compound 4 to a container containing a mixed solution of 120 mL of tetrahydrofuran and 6 mL of deionized water, stir to mix, then add 0.3 mL of tetrabutylammonium fluoride to a sample bottle containing a mixed solution of 10 mL of tetrahydrofuran and 0.3 mL of deionized water, mix evenly, add the mixture in the sample bottle to the container with a syringe, and react in a closed manner at room temperature for 12 hours. After the reaction is completed, wash, rotary evaporate, separate and purify, and precipitate to obtain compound 5; add 4 mg of cuprous chloride and 11.5 μL of tetramethylethylenediamine to a reaction tube containing 10 mL of dichloromethane, stir to mix, add 38.1 mg of compound 5 to 10 mL of dichloromethane, mix evenly, add to the reaction tube, heat at 50°C for 6 hours, wash, rotary evaporate, separate and purify, and precipitate to obtain an organic active substance.

[0039] This embodiment discloses a method for preparing a modified conductive agent, comprising the following steps:

[0040] S1: 100 mL of cyclohexane, 100 g of 2-tert-butylphenol and 66 g of benzaldehyde were added to a container, 5.5 g of diethylamine was added under stirring, the temperature was raised to 110°C for reaction for 24 h, and then the mixture was heated to 125°C for reduced pressure distillation for 1 h, and then 132 mL of a mixed solution (composed of anhydrous ethanol and cyclohexane in a volume ratio of 3:1) was added to the container, and the mixture was recrystallized, filtered, washed, and dried to obtain intermediate A;

[0041] S2: 15 g of intermediate A, 50 mL of toluene and 9.6 g of tetracycloheptane were added to a container, heated at 65 ° C with stirring and reflux for 72 h, rotary evaporated and purified to obtain a crude product, 8 g of the crude product and 8.25 g of sodium sulfate were added to 100 mL of methanol, heated at 50 ° C with stirring for 6 h under a nitrogen atmosphere, then vacuum concentrated, 100 mL of ethyl acetate was added, extracted, dried, and filtered to obtain intermediate B;

[0042] S3: Add 60 mg of intermediate B, 35 mg of graphene and 3 mL of tetrahydrofuran into a container, then add 1.35 mg of Grubbs' catalyst, react at room temperature for 4 hours, and after the reaction is completed, add to methanol after dilution, stir and react for 1 hour, filter, vacuum dry, wash, and dry to obtain a modified conductive agent.

[0043] This embodiment discloses a method for preparing a lithium battery pack with excellent cycle performance, comprising the following steps:

[0044] Step 1: Add 1.5g of polyvinylidene fluoride to a container containing 10mL of N-methylpyrrolidone and stir until completely dissolved. Mix and grind 6.5g of organic active material and 2.5g of modified conductive agent for 15min and add them to the container. Continue stirring and mixing for 6h to obtain positive electrode slurry. Evenly coat the positive electrode slurry on the AB surface of the aluminum current collector, first dry at 55°C for 12h, then vacuum dry at 85°C for 9h, and compact to obtain a positive electrode sheet.

[0045] Step 2: 4 g of graphite, 1.5 g of carboxymethyl cellulose and 6 mL of deionized water are mixed and stirred to obtain a negative electrode slurry, and then the negative electrode slurry is evenly coated on the copper current collector AB surface, dried, and compacted to obtain a negative electrode sheet;

[0046] Step 3: Wind the polypropylene film, positive electrode sheet and negative electrode sheet into a core by a winding machine, and then insert the core vertically into the steel shell. After drying, inject electrolyte (consisting of 11g lithium hexafluorophosphate, 26g dimethyl carbonate, 15g diethyl carbonate, 0.4g cyclohexylbenzene and 0.25g 1,2-dimethoxy-4,5-dinitrobenzene), weld, and obtain a lithium battery. Then connect the lithium batteries in series to obtain a lithium battery pack.

[0047] Example 2: This example discloses a method for preparing an organic active substance, comprising the following steps:

[0048] Q1: 8 g of tetrachloroperylene anhydride was added to a container filled with argon, and then 180 mL of propionic acid was added, followed by 9 g of aminotriglycol monomethyl ether, and the mixture was heated at 140°C with stirring and reflux for 16 h. After the reaction was completed, the mixture was poured into methanol, filtered, separated and purified, and recrystallized to obtain compound 1; 3 g of compound 1 was added to a container, and then 18 g of cuprous iodide and 11 g of L-proline were added. After vacuuming and introducing argon, 110 mL of dimethyl sulfoxide was added, and the mixture was heated at 600 rpm and 120°C with stirring and reflux for 20 h. After the reaction was completed, the mixture was poured into distilled water, stirred and mixed for 1 h, filtered, washed, rotary evaporated, separated and purified, and precipitated to obtain compound 2;

[0049] Q2: 1.5 g of compound 2 was added to a container, and then 3 g of bipyraclostrobin, 0.081 g of tris(pentafluorophenyl)phosphine and 0.024 g of methoxy(cyclooctadiene)iridium polymer were added in sequence, argon was introduced, 18 mL of dichlorohexacyclopentane was added, and the mixture was heated, stirred and refluxed at 700 rpm and 110 ° C for 12 h. After the reaction was completed, the mixture was rotary evaporated, separated and purified, and precipitated to obtain compound 3; 1.2 g of compound 3 was added to a container, and then 2.01 g of copper bromide was added, argon was introduced, and then 38 mL of deoxygenated copper bromide was added. A mixed solution of 1 mL of dioxane, 14 mL of methanol and 8 mL of distilled water was added to a container, heated and stirred at 800 rpm and 130°C for 12 h, and after the reaction was completed, added to 500 mL of distilled water, stirred for 1 h, filtered, washed, rotary evaporated, recrystallized, dried, added to a container containing 1.41 g of triisopropylsilyl acetylene, purged with argon, added with 80 mL of dimethyl sulfoxide, heated and stirred at 120°C for 4 h, added to distilled water, filtered, washed, rotary evaporated, separated and purified, and precipitated to obtain compound 4;

[0050] Q3: Add 0.3 g of compound 4 to a container containing a mixed solution of 120 mL of tetrahydrofuran and 6 mL of deionized water, stir to mix, then add 0.2 mL of tetrabutylammonium fluoride to a sample bottle containing a mixed solution of 10 mL of tetrahydrofuran and 0.3 mL of deionized water, mix evenly, add the mixture in the sample bottle to the container with a syringe, and react in a closed manner at room temperature for 12 hours. After the reaction is completed, wash, rotary evaporate, separate and purify, and precipitate to obtain compound 5; add 3 mg of cuprous chloride and 10 μL of tetramethylethylenediamine to a reaction tube containing 10 mL of dichloromethane, stir to mix, add 35 mg of compound 5 to 10 mL of dichloromethane, mix evenly, add to the reaction tube, heat at 50°C for 6 hours, wash, rotary evaporate, separate and purify, and precipitate to obtain an organic active substance.

[0051] This embodiment discloses a method for preparing a modified conductive agent, comprising the following steps:

[0052] S1: 80 mL of cyclohexane, 90 g of 2-tert-butylphenol and 62 g of benzaldehyde were added to a container, 5 g of diethylamine was added under stirring, the temperature was raised to 110°C for reaction for 24 h, and then the mixture was heated to 125°C for reduced pressure distillation for 1 h, and then 130 mL of a mixed solution (composed of anhydrous ethanol and cyclohexane in a volume ratio of 3:1) was added to the container, and the mixture was recrystallized, filtered, washed and dried to obtain intermediate A;

[0053] S2: 14 g of intermediate A, 40 mL of toluene and 10.2 g of tetracycloheptane were added to a container, heated at 65 ° C with stirring and reflux for 72 h, rotary evaporated and purified to obtain a crude product, 6 g of the crude product and 8 g of sodium sulfate were added to 80 mL of methanol, heated at 50 ° C with stirring for 6 h under a nitrogen atmosphere, then vacuum concentrated, 90 mL of ethyl acetate was added, extracted, dried, and filtered to obtain intermediate B;

[0054] S3: Add 50 mg of intermediate B, 30 mg of graphene and 2 mL of tetrahydrofuran into a container, then add 1.2 mg of Grubbs' catalyst, react at room temperature for 4 hours, and after the reaction is completed, add to methanol after dilution, stir and react for 1 hour, filter, vacuum dry, wash, and dry to obtain a modified conductive agent.

[0055] This embodiment discloses a method for preparing a lithium battery pack with excellent cycle performance, comprising the following steps:

[0056] Step 1: Add 1g of polyvinylidene fluoride to a container containing 8mL of N-methylpyrrolidone and stir until completely dissolved. Mix and grind 5g of organic active material and 2g of modified conductive agent for 15min and add them to the container. Continue stirring and mixing for 6h to obtain positive electrode slurry. Evenly coat the positive electrode slurry on the AB surface of the aluminum current collector, first dry at 55°C for 12h, then vacuum dry at 85°C for 9h, and compact to obtain a positive electrode sheet.

[0057] Step 2: 3 g of graphite, 1 g of carboxymethyl cellulose and 5 mL of deionized water are mixed and stirred to obtain a negative electrode slurry, and then the negative electrode slurry is evenly coated on the AB surface of the copper current collector, dried, and compacted to obtain a negative electrode sheet;

[0058] Step 3: Wind the polypropylene film, positive electrode sheet and negative electrode sheet into a core by a winding machine, and then insert the core vertically into the steel shell. After drying, inject electrolyte (consisting of 10g lithium hexafluorophosphate, 20g dimethyl carbonate, 12g diethyl carbonate, 0.2g cyclohexylbenzene and 0.1g 1,2-dimethoxy-4,5-dinitrobenzene), weld, and obtain a lithium battery. Then connect the lithium batteries in series to obtain a lithium battery pack.

[0059] Example 3: This example discloses a method for preparing an organic active substance, comprising the following steps:

[0060] Q1: 13 g of tetrachloroperylene anhydride was added to a container filled with argon, and then 220 mL of propionic acid was added, followed by 12 g of aminotriglycol monomethyl ether, and the mixture was heated at 140°C with stirring and reflux for 16 h. After the reaction was completed, the mixture was poured into methanol, filtered, separated and purified, and recrystallized to obtain compound 1; 6 g of compound 1 was added to a container, and then 20 g of cuprous iodide and 13 g of L-proline were added. After vacuuming and introducing argon, 130 mL of dimethyl sulfoxide was added, and the mixture was heated at 600 rpm and 120°C with stirring and reflux for 20 h. After the reaction was completed, the mixture was poured into distilled water, stirred and mixed for 1 h, filtered, washed, rotary evaporated, separated and purified, and precipitated to obtain compound 2;

[0061] Q2: 2g of compound 2 was added to a container, and then 3.88g of bipyraclostrobin, 0.086g of tri(pentafluorophenyl)phosphine and 0.027g of methoxy(cyclooctadiene)iridium polymer were added in sequence, argon was introduced, 25mL of dichlorohexacyclopentane was added, and the mixture was heated, stirred and refluxed at 700rpm and 110℃ for 12h. After the reaction was completed, the mixture was rotary evaporated, separated and purified, and precipitated to obtain compound 3; 1.8g of compound 3 was added to a container, and then 2.25g of copper bromide was added, argon was introduced, and then 42m A mixed solution of 1 mL of dioxane, 18 mL of methanol and 8 mL of distilled water was added to a container, heated and stirred at 800 rpm and 130°C for 12 h, and after the reaction was completed, it was added to 500 mL of distilled water, stirred for 1 h, filtered, washed, rotary evaporated, recrystallized, dried, and added to a container containing 1.84 g of triisopropylsilyl acetylene, argon was introduced, 120 mL of dimethyl sulfoxide was added, heated and stirred at 120°C for 4 h, and then added to distilled water, filtered, washed, rotary evaporated, separated and purified, and precipitated to obtain compound 4;

[0062] Q3: Add 0.5 g of compound 4 to a container containing a mixed solution of 120 mL of tetrahydrofuran and 6 mL of deionized water, stir to mix, then add 0.4 mL of tetrabutylammonium fluoride to a sample bottle containing a mixed solution of 10 mL of tetrahydrofuran and 0.3 mL of deionized water, mix evenly, add the mixture in the sample bottle to the container with a syringe, and react in a closed manner at room temperature for 12 hours. After the reaction is completed, wash, rotary evaporate, separate and purify, and precipitate to obtain compound 5; add 5 mg of cuprous chloride and 13 μL of tetramethylethylenediamine to a reaction tube containing 10 mL of dichloromethane, stir to mix, add 41.2 mg of compound 5 to 10 mL of dichloromethane, mix evenly, add to the reaction tube, heat at 50°C for reaction for 6 hours, wash, rotary evaporate, separate and purify, and precipitate to obtain an organic active substance.

[0063] This embodiment discloses a method for preparing a modified conductive agent, comprising the following steps:

[0064] S1: 120 mL of cyclohexane, 110 g of 2-tert-butylphenol and 68 g of benzaldehyde were added to a container, 6 g of diethylamine was added under stirring, the temperature was raised to 110°C for reaction for 24 h, and then the mixture was heated to 125°C for reduced pressure distillation for 1 h, and then 135 mL of a mixed solution (composed of anhydrous ethanol and cyclohexane in a volume ratio of 3:1) was added to the container, and the mixture was recrystallized, filtered, washed and dried to obtain intermediate A;

[0065] S2: 16 g of intermediate A, 60 mL of toluene and 9 g of tetracycloheptane were added to a container, heated at 65 ° C with stirring and reflux for 72 h, rotary evaporated, purified to obtain a crude product, 10 g of the crude product and 8.5 g of sodium sulfate were added to 120 mL of methanol, heated at 50 ° C with stirring for 6 h under a nitrogen atmosphere, then vacuum concentrated, 110 mL of ethyl acetate was added, extracted, dried, and filtered to obtain intermediate B;

[0066] S3: 70 mg of intermediate B, 40 mg of graphene and 4 mL of tetrahydrofuran were added to a container, and then 1.5 mg of Grubbs' catalyst was added, and the reaction was carried out at room temperature for 4 hours. After the reaction was completed, the mixture was diluted and added to methanol, and the reaction was stirred for 1 hour. The mixture was filtered, vacuum dried, washed, and dried to obtain a modified conductive agent.

[0067] This embodiment discloses a method for preparing a lithium battery pack with excellent cycle performance, comprising the following steps:

[0068] Step 1: Add 2g of polyvinylidene fluoride to a container containing 12mL of N-methylpyrrolidone and stir until completely dissolved. Mix and grind 8g of organic active material and 3g of modified conductive agent for 15min and add them to the container. Continue stirring and mixing for 6h to obtain positive electrode slurry. Evenly coat the positive electrode slurry on the AB surface of the aluminum current collector, first dry at 55°C for 12h, then vacuum dry at 85°C for 9h, and compact to obtain a positive electrode sheet.

[0069] Step 2: 5 g of graphite, 2 g of carboxymethyl cellulose and 7 mL of deionized water are mixed and stirred to obtain a negative electrode slurry, and then the negative electrode slurry is evenly coated on the AB surface of the copper current collector, dried, and compacted to obtain a negative electrode sheet;

[0070] Step 3: Wind the polypropylene film, positive electrode sheet and negative electrode sheet into a core through a winding machine, and then insert the core vertically into the steel shell. After drying, inject electrolyte (consisting of 12g lithium hexafluorophosphate, 32g dimethyl carbonate, 18g diethyl carbonate, 0.6g cyclohexylbenzene and 0.4g 1,2-dimethoxy-4,5-dinitrobenzene), weld, and obtain a lithium battery. Then connect the lithium batteries in series to obtain a lithium battery pack.

[0071] Example 4: This example discloses a method for preparing an organic active substance, comprising the following steps:

[0072] Q1: 9 g of tetrachloroperylene anhydride was added to a container filled with argon, and then 190 mL of propionic acid was added, followed by 10 g of aminotriglycol monomethyl ether, and the mixture was heated at 140°C with stirring and reflux for 16 h. After the reaction was completed, the mixture was poured into methanol, filtered, separated and purified, and recrystallized to obtain compound 1; 4 g of compound 1 was added to a container, and then 18.5 g of cuprous iodide and 11.5 g of L-proline were added. After vacuuming and introducing argon, 115 mL of dimethyl sulfoxide was added, and the mixture was heated at 600 rpm and 120°C with stirring and reflux for 20 h. After the reaction was completed, the mixture was poured into distilled water, stirred and mixed for 1 h, filtered, washed, rotary evaporated, separated and purified, and precipitated to obtain compound 2;

[0073] Q2: 1.1 g of compound 2 was added to a container, and then 3.22 g of bipyraclostrobin, 0.082 g of tris(pentafluorophenyl)phosphine and 0.025 g of methoxy(cyclooctadiene)iridium polymer were added in sequence, argon was introduced, 19 mL of dichlorohexacyclopentane was added, and the mixture was heated, stirred and refluxed at 700 rpm and 110 ° C for 12 h. After the reaction was completed, the mixture was rotary evaporated, separated and purified, and precipitated to obtain compound 3; 1.3 g of compound 3 was added to a container, and then 2.08 g of copper bromide was added, argon was introduced, and then the 39 A mixed solution of mL of dioxane, 15 mL of methanol and 8 mL of distilled water was added to a container, heated and stirred at 800 rpm and 130°C for 12 h, and after the reaction was completed, it was added to 500 mL of distilled water, stirred for 1 h, filtered, washed, rotary evaporated, recrystallized, dried, and added to a container containing 1.52 g of triisopropylsilyl acetylene, argon was introduced, 90 mL of dimethyl sulfoxide was added, heated and stirred at 120°C for 4 h, and then added to distilled water, filtered, washed, rotary evaporated, separated and purified, and precipitated to obtain compound 4;

[0074] Q3: Add 0.35 g of compound 4 to a container containing a mixed solution of 120 mL of tetrahydrofuran and 6 mL of deionized water, stir to mix, then add 0.25 mL of tetrabutylammonium fluoride to a sample bottle containing a mixed solution of 10 mL of tetrahydrofuran and 0.3 mL of deionized water, mix evenly, add the mixture in the sample bottle to the container with a syringe, and react in a closed manner at room temperature for 12 hours. After the reaction is completed, wash, rotary evaporate, separate and purify, and precipitate to obtain compound 5; add 3.5 mg of cuprous chloride and 11 μL of tetramethylethylenediamine to a reaction tube containing 10 mL of dichloromethane, stir to mix, add 36 mg of compound 5 to 10 mL of dichloromethane, mix evenly, add to the reaction tube, heat at 50°C for 6 hours, wash, rotary evaporate, separate and purify, and precipitate to obtain an organic active substance.

[0075] This embodiment discloses a method for preparing a modified conductive agent, comprising the following steps:

[0076] S1: 90 mL of cyclohexane, 95 g of 2-tert-butylphenol and 64 g of benzaldehyde were added to a container, 5.2 g of diethylamine was added under stirring, the temperature was raised to 110°C for reaction for 24 h, and then the mixture was heated to 125°C for reduced pressure distillation for 1 h, and then 131 mL of a mixed solution (composed of anhydrous ethanol and cyclohexane in a volume ratio of 3:1) was added to the container, and the mixture was recrystallized, filtered, washed and dried to obtain intermediate A;

[0077] S2: 14.5 g of intermediate A, 45 mL of toluene and 9.2 g of tetracycloheptane were added to a container, heated at 65 ° C with stirring and reflux for 72 h, rotary evaporated and purified to obtain a crude product, 9 g of the crude product and 8.1 g of sodium sulfate were added to 90 mL of methanol, heated at 50 ° C with stirring for 6 h under a nitrogen atmosphere, then vacuum concentrated, 95 mL of ethyl acetate was added, extracted, dried, and filtered to obtain intermediate B;

[0078] S3: Add 55 mg of intermediate B, 32 mg of graphene and 2.5 mL of tetrahydrofuran into a container, then add 1.3 mg of Grubbs' catalyst, react at room temperature for 4 hours, and after the reaction is completed, add to methanol after dilution, stir and react for 1 hour, filter, vacuum dry, wash, and dry to obtain a modified conductive agent.

[0079] This embodiment discloses a method for preparing a lithium battery pack with excellent cycle performance, comprising the following steps:

[0080] Step 1: Add 1.2g of polyvinylidene fluoride to a container containing 9mL of N-methylpyrrolidone and stir until completely dissolved. Mix and grind 6g of organic active material and 2.2g of modified conductive agent for 15min and add them to the container. Continue stirring and mixing for 6h to obtain positive electrode slurry. Evenly coat the positive electrode slurry on the AB surface of the aluminum current collector, first dry at 55°C for 12h, then vacuum dry at 85°C for 9h, and compact to obtain a positive electrode sheet.

[0081] Step 2: 3.5 g of graphite, 1.2 g of carboxymethyl cellulose and 5.5 mL of deionized water are mixed and stirred to obtain a negative electrode slurry, and then the negative electrode slurry is evenly coated on the copper current collector AB surface, dried, and compacted to obtain a negative electrode sheet;

[0082] Step 3: Wind the polypropylene film, positive electrode sheet and negative electrode sheet into a core by a winding machine, and then insert the core vertically into the steel shell. After drying, inject electrolyte (consisting of 10.5g lithium hexafluorophosphate, 22g dimethyl carbonate, 14g diethyl carbonate, 0.3g cyclohexylbenzene and 0.2g 1,2-dimethoxy-4,5-dinitrobenzene), weld, and obtain a lithium battery. Then connect the lithium batteries in series to obtain a lithium battery pack.

[0083] Comparative Example 1: Compared with Example 1, in the process of preparing the organic active substance in Comparative Example 1, no tetrachloroperylene anhydride is added, and other conditions remain unchanged.

[0084] Comparative Example 2: Compared with Example 1, in Comparative Example 2, during the preparation of the modified conductive agent, no 2-tert-butylphenol was added, and other conditions remained unchanged.

[0085] Experimental Example: The lithium battery packs prepared in Examples 1-4 and Comparative Examples 1-2 were subjected to performance tests, and the energy density and cycle performance of the samples were tested according to IEC62660-1-2018. Under room temperature, the samples were charged to 4.35V at a constant current of 1C, and then charged to a current of ≤0.05C at a constant voltage of 4.35V. After standing for 5 minutes, they were discharged at a constant current of 0.2C to a cut-off voltage of 3V. At this time, the actual discharge capacity was recorded as D0, and then charged to 4.35V at a constant current of 1C, and then charged to a current of ≤0.05C at a constant voltage of 4.35V, and finally discharged to a cut-off voltage of 3V at 2C. The actual discharge capacity at this time was recorded as D1, and the rate performance = [(D1-D0) / D0] × 100%. The test results are shown in Table 1:

[0086] Table 1

[0087]

[0088]

[0089] From the test results in Table 1, it can be seen that the lithium battery packs prepared in Examples 1-4 of the present invention have excellent energy density, cycle stability and rate performance. From the comparison between Comparative Example 1 and Examples 1-4, it can be seen that the addition of tetrachloroperylene anhydride can effectively improve the energy density and cycle stability of the lithium battery pack; from the comparison between Comparative Example 2 and Examples 1-4, it can be seen that the addition of 2-tert-butylphenol can effectively improve the cycle stability and rate performance of the lithium battery pack.

[0090] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

[0091] The preferred embodiments of the present invention disclosed above are only used to help explain the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to only specific implementation methods. Obviously, many modifications and changes can be made according to the content of this specification. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can understand and use the present invention well. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method for preparing a lithium battery pack with excellent cycle performance, characterized in that: The following steps are involved: Step 1: Add polyvinylidene fluoride to a container containing N-methylpyrrolidone, stir until completely dissolved, mix and grind the organic active material and the modified conductive agent, add them to the container, continue to stir and mix, obtain a positive electrode slurry, and evenly coat the positive electrode slurry on the AB surface of the aluminum current collector, dry, and compact to obtain a positive electrode sheet; Step 2: Mix and stir graphite, carboxymethyl cellulose and deionized water to obtain a negative electrode slurry, and then evenly coat the negative electrode slurry on the copper current collector AB surface, dry, and compact to obtain a negative electrode sheet; Step 3: Wind the diaphragm, positive electrode sheet and negative electrode sheet into a core through a winding machine, and then insert the core vertically into the steel shell. After drying, inject electrolyte and weld to obtain a lithium battery. Then connect the lithium batteries in series to obtain a lithium battery pack.

2. The method for preparing a lithium battery pack with excellent cycle performance according to claim 1, characterized in that: In the step 1, the amount ratio of polyvinylidene fluoride, N-methylpyrrolidone, organic active substance and modified conductive agent is (1-2) g: (8-12) mL: (5-8) g: (2-3) g, the mixing and grinding time is 10-15 min, the stirring and mixing time is continued for 4-6 h, first dried at 50-60 ° C for 10-12 h, and then vacuum dried at 80-85 ° C for 8-10 h; in the step 2, graphite, carboxymethyl The dosage ratio of cellulose and deionized water is (3-5) g: (1-2) g: (5-7) mL; in the step three, the diaphragm is composed of a polypropylene film, and the electrolyte is composed of lithium hexafluorophosphate, dimethyl carbonate, diethyl carbonate, cyclohexylbenzene and 1,2-dimethoxy-4,5-dinitrobenzene, and the dosage ratio is (10-12) g: (20-32) g: (12-18) g: (0.2-0.6) g: (0.1-0.4) g.

3. The method for preparing a lithium battery pack with excellent cycle performance according to claim 1, characterized in that: The method for preparing the organic active substance comprises the following steps: Q1: Add tetrachloroperylene anhydride to a container filled with argon, then add propionic acid, then add aminotriglycol monomethyl ether, heat and stir to reflux for reaction, after the reaction is completed, pour into methanol, filter, separate and purify, recrystallize to obtain compound 1; add compound 1 to a container, then add cuprous iodide and L-proline, evacuate and introduce argon, add dimethyl sulfoxide, heat and stir to reflux for reaction, after the reaction is completed, pour into distilled water, stir and mix, filter, wash, rotary evaporate, separate and purify, and settle to obtain compound 2; Q2: Compound 2 is added to a container, and then pinacol borate, tris(pentafluorophenyl)phosphine and methoxy(cyclooctadiene) iridium polymer are added in sequence, argon is introduced and then dichlorohexacyclopentane is added, heated and stirred to reflux for reaction, after the reaction is completed, rotary evaporation, separation and purification, and precipitation are performed to obtain compound 3; Compound 3 is added to a container, and then copper bromide is added, argon is introduced, and then a mixed solution of dioxane, methanol and distilled water after aeration and deoxygenation is added to the container, heated and stirred to reflux for reaction, after the reaction is completed, added to distilled water, stirred, filtered, washed, rotary evaporated, recrystallized, dried, and added to a container containing triisopropylsilyl acetylene, argon is introduced and then dimethyl sulfoxide is added, heated and stirred to react, added to distilled water, filtered, washed, rotary evaporated, separated and purified, and precipitated to obtain compound 4; Q3: Add compound 4 to a container containing a mixed solution of tetrahydrofuran and deionized water, stir to mix, then add tetrabutylammonium fluoride to a sample bottle containing a mixed solution of tetrahydrofuran and deionized water, mix evenly, add the mixture in the sample bottle to the container with a syringe, react in a closed manner at room temperature, and after the reaction is completed, wash, rotary evaporate, separate and purify, and precipitate to obtain compound 5; add cuprous chloride and tetramethylethylenediamine to a reaction tube containing dichloromethane, stir to mix, add compound 5 to dichloromethane, mix evenly, add to the reaction tube, heat to react, wash, rotary evaporate, separate and purify, and precipitate to obtain an organic active substance.

4. The method for preparing a lithium battery pack with excellent cycle performance according to claim 3, characterized in that: In the Q1, the amount ratio of tetrachloroperylene anhydride, propionic acid and aminotriglycol monomethyl ether is (8-13) g: (180-220) mL: (9-12) g, the heating stirring reflux reaction temperature is 130-150° C., and the reaction time is 15-18 h. The amount ratio of compound 1, cuprous iodide, L-proline and dimethyl sulfoxide is (3-6) g: (18-20) g: (11-13) g: (100-130) mL, the heating stirring reflux reaction temperature is 110-120° C., the stirring speed is 600-800 rpm, the reaction time is 16-20 h, and the stirring mixing time is 1-2 h.

5. The method for preparing a lithium battery pack with excellent cycle performance according to claim 3, characterized in that: In Q2, the amount ratio of compound 2, bipyraclostrobin, tris(pentafluorophenyl)phosphine, methoxy(cyclooctadiene) iridium polymer and dichlorohexacyclopentane is (1-1.5) g: (3-3.88) g: (0.081-0.086) g: (0.024-0.027) g: (18-25) mL, the heating stirring reflux reaction temperature is 100-120° C., the stirring speed is 600-700 rpm, and the reaction time is 10-12 h; compound 3, copper bromide, dioxane, methanol, The dosage ratio of triisopropylsilyl acetylene and dimethyl sulfoxide is (1.2-1.8) g: (2.01-2.25) g: (38-42) mL: (14-18) mL: (1.41-1.84) g: (80-120) mL, the heating stirring reflux reaction temperature is 110-130°C, the stirring speed is 600-800 rpm, the reaction time is 10-12h, the stirring reaction time is 1-2h, the heating stirring reaction temperature is 110-120°C, and the reaction time is 3-5h.

6. The method for preparing a lithium battery pack with excellent cycle performance according to claim 3, characterized in that: In Q3, the dosage ratio of compound 4 and tetrabutylammonium fluoride is (0.3-0.5) g: (0.2-0.4) mL, and the closed reaction time is 10-12 h; the dosage ratio of cuprous chloride, tetramethylethylenediamine and compound 5 is (3-5) mg: (10-13) μL: (35-41.2) mg, the heating reaction temperature is 50-60°C, and the reaction time is 6-8 h.

7. The method for preparing a lithium battery pack with excellent cycle performance according to claim 1, characterized in that: The preparation method of the modified conductive agent comprises the following steps: S1: adding cyclohexane, 2-tert-butylphenol and benzaldehyde into a container, adding diethylamine under stirring, heating to react, then heating under reduced pressure distillation, then adding a mixed solution of anhydrous ethanol and cyclohexane into the container, recrystallizing, filtering, washing and drying to obtain intermediate A; S2: Add intermediate A, toluene and tetracycloheptane into a container, heat and stir under reflux, rotary evaporate, purify to obtain a crude product, add the crude product and sodium sulfate into methanol, heat and stir under nitrogen atmosphere, then vacuum concentrate, add ethyl acetate, extract, dry, and filter to obtain intermediate B; S3: Add intermediate B, graphene and tetrahydrofuran into a container, then add Grubbs catalyst, react at room temperature, and after the reaction is completed, add to methanol after dilution, stir the reaction, filter, vacuum dry, wash, and dry to obtain a modified conductive agent.

8. The method for preparing a lithium battery pack with excellent cycle performance according to claim 7, characterized in that: In S1, the dosage ratio of cyclohexane, 2-tert-butylphenol, benzaldehyde, diethylamine and mixed solution is (80-120) mL: (90-110) g: (62-68) g: (5-6) g: (130-135) mL, the heating reaction temperature is 100-120° C., the reaction time is 20-24 h, the heating reduced pressure distillation temperature is 120-125° C., the reduced pressure distillation time is 1-2 h, and the volume ratio of anhydrous ethanol to cyclohexane is 3:

1.

9. The method for preparing a lithium battery pack with excellent cycle performance according to claim 7, characterized in that: In S2, the amount ratio of intermediate A, toluene and tetracycloheptane is (14-16) g: (40-60) mL: (9-10.2) g, the heating stirring reflux temperature is 50-65° C., and the reflux time is 72-90 h. The amount ratio of crude product, sodium sulfate, methanol and ethyl acetate is (6-10) g: (8-8.5) g: (80-120) mL: (90-110) mL. The heating stirring temperature is 45-55° C., and the stirring time is 4-6 h. In S3, the amount ratio of intermediate B, graphene, tetrahydrofuran and Grubbs' catalyst is (50-70) mg: (30-40) mg: (2-4) mL: (1.2-1.5) mg. The reaction time at room temperature is 2-4 h, and the stirring reaction time is 1-2 h.

10. A lithium battery pack with excellent cycle performance, characterized in that: Prepared by the method according to any one of claims 1 to 9.

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