A polymer precursor and a method for preparing the same, a polymer coating and a method for preparing the same, a negative current collector, and a lithium ion battery

Abstract

The application belongs to the field of batteries, and particularly relates to a polymer precursor and a preparation method thereof, a polymer coating and a preparation method thereof, a negative current collector and a lithium ion battery. The chemical structure of the polymer precursor provided by the application is shown as formula A, wherein X is Br, and R1 and R2 are selected from one or more of a methyl group, a cyano group, an ethynyl group, a hydrogen atom, a fluorine atom and a trifluoromethyl group. The polymer coating formed by the polymer precursor provided by the application has a central structure of an imidazole-like ionic liquid, which is introduced into a lithium ion battery as a surface coating of a negative current collector, can artificially induce the formation of a high-performance solid-state electrolyte interface film at the negative electrode, improves the stability of lithium ion transmission at the interface, and thus improves the electrochemical performance of the lithium ion battery.

Description

Technical Field

[0001] This invention belongs to the field of batteries, and particularly relates to a polymer precursor and its preparation method, a polymer coating and its preparation method, a negative electrode current collector, and a lithium-ion battery. Background Technology

[0002] Since the industrialization of lithium-ion batteries, as a highly efficient energy storage system, they have been involved in the important process of energy ecosystem evolution, from various electronic products to electric vehicles, and further to the expansion of grid-scale energy storage, becoming increasingly intertwined with people's lives. For the past few decades, lithium-ion batteries have occupied a very important and dominant position in technological development, with higher-performance lithium-ion batteries being their main development direction. During the charge-discharge cycle of lithium-ion batteries, a stable electrode-electrolyte interface is crucial. Related research shows that the solid electrolyte interphase (SEI) film formed on the electrode surface plays a significant role in battery performance during the initial charge-discharge process. Therefore, the artificial positive modulation of the SEI film can significantly and effectively improve the electrochemical performance of lithium-ion batteries.

[0003] Currently, the optimal regulation of the SEI membrane often involves adding electrolyte additives with lower LUMO energy levels to the electrolyte. These additives preferentially undergo reduction reactions at the negative electrode surface to form a film, thus protecting the negative electrode interface. Examples of such additives include vinylene carbonate, fluoroethylene carbonate, and ethylene sulfate. However, these functional additives often require specific storage conditions; otherwise, they can lead to electrolyte failure. Furthermore, achieving optimal performance often necessitates the addition of large quantities of additives, which can negatively impact the electrolyte's ionic conductivity, making it unsuitable for fast charging. Summary of the Invention

[0004] In view of this, the purpose of this invention is to provide a polymer precursor and its preparation method, a polymer coating and its preparation method, a negative electrode current collector, and a lithium-ion battery. The polymer coating formed by the polymer precursor provided by this invention has a central structure similar to an imidazole ionic liquid. When introduced as a surface coating for a negative electrode current collector into a lithium-ion battery, the bromide anion in the structure readily combines with lithium ions, inducing the formation of a LiBr phase in the SEI layer. LiBr has a low lithium-ion diffusion barrier in the SEI layer, thereby improving the interfacial lithium-ion transport stability. Simultaneously, the anchored cationic groups can attract and bind the anions in the electrolyte, i.e., PF6, through charge attraction interactions. 6- The ions accumulate at the negative electrode interface, leading to more anions participating in the formation of the negative electrode SEI film. The formed SEI film contains more LiF phase with high mechanical strength and high electrochemical stability. Therefore, lithium-ion batteries containing this SEI film induced by artificial control have achieved excellent electrochemical performance.

[0005] This invention provides a polymer precursor, the chemical structure of which is shown in Formula A:

[0006]

[0007] Where X is Br, and R1 and R2 are selected from one or more of methyl, cyano, ethynyl, hydrogen atom, fluorine atom and trifluoromethyl.

[0008] Preferably, the polymer precursor is at least one of compounds of formula (I) to (VI):

[0009]

[0010] This invention provides a method for preparing a polymer precursor, comprising the following steps:

[0011] a) The o-diamino compound of formula a is reacted with butenidine to obtain the diimidazolium intermediate of formula b;

[0012] b) Grafting the diimidazole intermediate of formula b with chloromethylethyldimethylsilane to obtain the intermediate of formula c;

[0013] c) React the intermediate of the structure of formula c with the haloolefin of the structure of formula d to obtain the polymer precursor of the structure of formula A;

[0014]

[0015] Wherein, X is Br, and R1 and R2 are independently selected from one or more of methyl, cyano, ethynyl, hydrogen atom, fluorine atom and trifluoromethyl.

[0016] The present invention provides a polymer coating, wherein the raw materials for preparing the polymer coating include a polymer precursor and a free radical initiator, wherein the polymer precursor is the polymer precursor described in the above technical solution or the polymer precursor obtained by the preparation method described in the above technical solution.

[0017] Preferably, the free radical initiator is one or more of a peroxide initiator, an azo compound initiator, and a redox initiator; the mass ratio of the polymer precursor to the free radical initiator is 7.5:(0.02-0.1).

[0018] Preferably, the raw materials used in the preparation further include a binder and a conductive agent; the binder is one or more of acrylic binders, polyvinyl alcohol, and sodium carboxymethyl cellulose; the conductive agent is one or more of acetylene black, natural graphite, and artificial graphite; and the mass ratio of the polymer precursor, binder, and conductive agent is 7.5:(3-7):(6-10).

[0019] This invention provides a method for preparing the polymer coating described above, comprising the following steps:

[0020] The raw materials for preparing the polymer coating are mixed with water, coated, and baked to obtain the polymer coating.

[0021] The present invention provides a negative electrode current collector, which includes a negative electrode current collector substrate and a coating coated on the surface of the negative electrode current collector substrate. The coating is a polymer coating as described in the above technical solution or a polymer coating prepared by the preparation method described in the above technical solution.

[0022] Preferably, the negative electrode current collector substrate is made of copper.

[0023] This invention provides a lithium-ion battery, wherein the negative electrode current collector of the lithium-ion battery is the negative electrode current collector described in the above technical solution.

[0024] Compared with existing technologies, this invention provides a polymer precursor and its preparation method, a polymer coating and its preparation method, a negative electrode current collector, and a lithium-ion battery. The chemical structure of the polymer precursor provided by this invention is shown in Formula A, where X is Br, and R1 and R2 are selected from one or more of methyl, cyano, ethynyl, vinyl, fluorine, and trifluoromethyl groups. The polymer coating formed from the polymer precursor provided by this invention has a central structure similar to an imidazole ionic liquid. Introduced as a surface coating for the negative electrode current collector into a lithium-ion battery, the bromide anion in the structure readily combines with lithium ions, inducing the formation of a LiBr phase in the SEI layer. LiBr has a low lithium-ion diffusion barrier in the SEI layer, thereby improving the stability of lithium-ion transport at the interface. Furthermore, due to the abundant cationic groups anchored in the polymer coating structure on the surface of the negative electrode current collector, more anions (PF5) in the electrolyte can be attracted through charge attraction. 6- Enriching the SEI film on the negative electrode surface and participating in its formation helps to further improve the mechanical strength of the SEI film and the electrochemical performance of the lithium-ion battery. The technical solution provided by this invention does not focus on controlling the SEI film by adding additives to the electrolyte, but offers a new approach to the artificial positive control of the SEI film. Detailed Implementation

[0025] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] This invention provides a polymer precursor with the chemical structure shown in Formula A:

[0027]

[0028] Wherein, X is Br, and R1 and R2 are independently selected from one or more of methyl, cyano, ethynyl, hydrogen atom, fluorine atom and trifluoromethyl.

[0029] In this invention, the polymer precursor may specifically be at least one of the compounds of formula (I) to (VI):

[0030]

[0031] The present invention also provides a method for preparing the polymer precursor described in the above technical solution, comprising the following steps:

[0032] a) The o-diamino compound of formula a is reacted with butenidine to obtain the diimidazolium intermediate of formula b;

[0033] b) Grafting the diimidazole intermediate of formula b with chloromethylethyldimethylsilane to obtain the intermediate of formula c;

[0034] c) React the intermediate of the structure of formula c with the haloolefin of the structure of formula d to obtain the polymer precursor of the structure of formula A;

[0035]

[0036] Wherein, X is Br, and R1 and R2 are independently selected from one or more of methyl, cyano, ethynyl, vinyl, fluorine, and trifluoromethyl.

[0037] In the preparation method provided by the present invention, in step a), the molar ratio of the ortho-diamino compound of formula a to butenedialdehyde is preferably (1.5-2.5):1, specifically 2:1.

[0038] In the preparation method provided by the present invention, in step a), the addition reaction is preferably carried out in a protective gas atmosphere, and the protective gas is preferably nitrogen; the addition reaction is preferably carried out in the presence of a catalyst, and the catalyst is preferably p-benzoquinone, and the molar ratio of p-benzoquinone to the ortho-diamino compound of formula a is preferably 1:(0.5-2), specifically 1:1; the addition reaction is preferably carried out in an organic solvent, and the organic solvent is preferably ethanol.

[0039] In the preparation method provided by the present invention, in step a), the specific process of the addition reaction preferably includes: reacting at a first temperature for a period of time, and then reacting at a second temperature for a period of time; wherein, the first temperature is preferably 70-90°C, specifically 80°C; the reaction time at the first temperature is preferably 2-6 hours, specifically 4 hours; the second temperature is preferably 15-35°C, specifically 25°C (room temperature); the reaction time at the second temperature is preferably 2-6 hours, specifically 4 hours.

[0040] In the preparation method provided by the present invention, in step a), after the addition reaction is completed, the product is post-processed. The post-processing process preferably includes: vacuum distillation, washing, extraction, drying and rotary evaporation in sequence.

[0041] In the preparation method provided by the present invention, in step b), the molar ratio of the diimidazole intermediate of formula b to chloromethylethyldimethylsilane is preferably 1:(1.5-2.5), specifically 1:2.

[0042] In the preparation method provided by the present invention, in step b), the grafting reaction is preferably carried out in a protective gas atmosphere, preferably nitrogen; the grafting reaction is preferably carried out in the presence of an alkali metal hydroxide, preferably potassium hydroxide, and the molar ratio of the alkali metal hydroxide to the diimidazole intermediate of formula b is preferably (7-9):3, specifically 8.2:3; the grafting reaction is preferably carried out in an organic solvent, preferably dimethyl sulfoxide (DMSO).

[0043] In the preparation method provided by the present invention, in step b), the temperature of the grafting reaction is preferably 15-35°C, specifically 25°C (room temperature); the time of the grafting reaction is preferably 1-5 hours, specifically 3 hours.

[0044] In the preparation method provided by the present invention, in step b), after the grafting reaction is completed, the product is post-processed. The post-processing process preferably includes: low-temperature extraction, vacuum distillation and chromatographic purification in sequence.

[0045] In the preparation method provided by the present invention, in step c), the molar ratio of the intermediate of formula c to the haloalkene of formula d is preferably 50:(70-130), specifically 50:105.

[0046] In the preparation method provided by the present invention, in step c), the reaction is preferably carried out in a protective gas atmosphere, preferably nitrogen; the reaction is preferably carried out in an organic solvent, preferably acetonitrile.

[0047] In the preparation method provided by the present invention, in step c), the reaction temperature is preferably 50-80°C, specifically 60°C; the reaction time is preferably 12-48h, specifically 24h.

[0048] In the preparation method provided by the present invention, in step c), after the reaction is completed, the product is post-processed, and the post-processing preferably includes: vacuum distillation, washing and drying in sequence.

[0049] The present invention also provides a polymer coating, wherein the raw materials for preparing the polymer coating include a polymer precursor and a free radical initiator, wherein the polymer precursor is the polymer precursor described in the above technical solution or the polymer precursor obtained by the preparation method described in the above technical solution.

[0050] In the polymer coating provided by the present invention, the free radical initiator is preferably one or more of a peroxide initiator, azo compound initiator, and redox initiator, more preferably benzoyl peroxide; the mass ratio of the polymer precursor to the free radical initiator is preferably 7.5:(0.02-0.1), specifically 7.5:0.02, 7.5:0.03, 7.5:0.04, 7.5:0.05, 7.5:0.06, 7.5:0.07, 7.5:0.08, 7.5:0.09, or 7.5:0.1.

[0051] In the polymer coating provided by the present invention, the raw materials preferably further include a binder, which is preferably one or more of acrylic binders, polyvinyl alcohol, and sodium carboxymethyl cellulose; the mass ratio of the polymer precursor to the binder is preferably 7.5:(3-7), specifically 7.5:3, 7.5:3.2, 7.5:3.5, 7.5:3.7, 7.5:4, 7.5:4.2, 7.5:4.5, 7.5:4.7, 7.5:5, 7.5:5.2, 7.5:5.5, 7.5:5.7, 7.5:6, 7.5:6.2, 7.5:6.5, 7.5:6.7, or 7.5:7.

[0052] In the polymer coating provided by the present invention, the raw materials preferably further include a conductive agent, which is preferably one or more of acetylene black, natural graphite and artificial graphite; the mass ratio of the polymer precursor to the conductive agent is preferably 7.5:(6-10), specifically 7.5:6, 7.5:6.2, 7.5:6.5, 7.5:6.7, 7.5:7, 7.5:7.2, 7.5:7.5, 7.5:7.7, 7.5:8, 7.5:8.2, 7.5:8.5, 7.5:8.7, 7.5:9, 7.5:9.2, 7.5:9.5, 7.5:9.7 or 7.5:10.

[0053] The present invention also provides a method for preparing the polymer coating described above, comprising the following steps:

[0054] The raw materials for preparing the polymer coating are mixed with water, coated, and baked to obtain the polymer coating.

[0055] In the preparation method provided by the present invention, the solid content of the slurry after mixing the raw materials with water is preferably 5-20 wt%, specifically 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, 11 wt%, 12 wt%, 13 wt%, 14 wt%, 15 wt%, 16 wt%, 17 wt%, 18 wt%, 19 wt%, or 20 wt%.

[0056] In the preparation method provided by the present invention, the coating thickness is preferably 1.5 to 3 μm, specifically 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm, 2 μm, 2.1 μm, 2.2 μm, 2.3 μm, 2.4 μm, 2.5 μm, 2.6 μm, 2.7 μm, 2.8 μm, 2.9 μm or 3 μm.

[0057] In the preparation method provided by the present invention, the baking temperature is preferably 80-100℃, specifically 80℃, 85℃, 90℃, 95℃ or 100℃; the baking time is preferably 30-60s, specifically 30s, 35s, 40s, 45s, 50s, 55s or 60s.

[0058] The present invention also provides a negative electrode current collector, comprising a negative electrode current collector substrate and a coating coated on the surface of the negative electrode current collector substrate, wherein the coating is a polymer coating as described in the above technical solution or a polymer coating prepared by the preparation method described in the above technical solution.

[0059] In the negative electrode current collector provided by the present invention, the material of the negative electrode current collector substrate is preferably copper; the coating is preferably applied to both sides of the negative electrode current collector substrate.

[0060] The present invention also provides a method for preparing the negative electrode current collector described in the above technical solution, comprising the following steps:

[0061] The raw materials for preparing the polymer coating are mixed with water and then coated onto the surface of the negative electrode current collector substrate. After baking, the polymer coating is obtained. The solid content of the slurry after mixing the raw materials with water, the coating thickness, and the baking conditions can be referred to the previous text and will not be repeated here.

[0062] The present invention also provides a lithium-ion battery, comprising a positive electrode, a negative electrode, a separator, and an electrolyte, wherein the current collector of the negative electrode is the negative electrode current collector described in the above technical solution.

[0063] In the lithium-ion battery provided by the present invention, the positive electrode includes a positive electrode current collector and a positive electrode coating coated on the surface of the positive electrode current collector; the positive electrode current collector includes, but is not limited to, aluminum foil; the positive electrode coating comprises a positive electrode active material, a conductive agent, and a binder. In the present invention, the positive electrode active material is preferably lithium cobalt oxide, lithium manganese oxide, ternary nickel-cobalt-manganese lithium, nickel-manganese lithium oxide, lithium iron phosphate, or manganese iron phosphate, more preferably ternary nickel-cobalt-manganese lithium (Ni:Co:Mn=9:0.5:0.5); the conductive agent is preferably conductive carbon black (SuperP) and / or carbon nanotubes (CNTs), the molar ratio of the conductive carbon black to carbon nanotubes is preferably 0.7:(0.5~1), more preferably 0.7:0.8; the binder is preferably polyvinylidene fluoride (PVDF); the mass ratio of the positive electrode active material, conductive agent, and binder is preferably 97:(0.5~3):(0.5~3), more preferably 97:1.5:1.5.

[0064] In the lithium-ion battery provided by the present invention, the negative electrode includes a negative electrode current collector and a negative electrode coating coated on the surface of the negative electrode current collector; the negative electrode current collector is the negative electrode current collector described in the above technical solution; the components of the negative electrode coating include a negative electrode active material, a conductive agent, a thickener, and a binder. In the present invention, the negative electrode active material is preferably artificial graphite, natural graphite, lithium titanate, lithium metal, silicon-carbon composite material, or silicon suboxide, more preferably silicon suboxide; the conductive agent is preferably conductive carbon black (SuperP); the thickener is preferably sodium carboxymethyl cellulose; the binder is preferably polyacrylic acid; the mass ratio of the negative electrode active material, conductive agent, thickener, and binder is preferably 95:(0.5~1.5):(1~2):(2~4), more preferably 95:1:1.5:2.5.

[0065] In the lithium-ion battery provided by the present invention, the separator is preferably a polypropylene separator, a polyethylene separator, or a polyethylene separator coated with alumina on one side, and more preferably a polyethylene separator coated with alumina on one side.

[0066] In the lithium-ion battery provided by the present invention, the electrolyte preferably comprises lithium salt, non-aqueous organic solvent and electrolyte additives.

[0067] In the lithium-ion battery provided by the present invention, the lithium salt in the electrolyte is preferably one or more of lithium hexafluorophosphate (LiPF6), lithium perchlorate (LiClO4), lithium tetrafluoroborate (LiBF4), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), and lithium bis(fluorosulfonyl)imide (LiFSI), and more preferably lithium hexafluorophosphate.

[0068] In the lithium-ion battery provided by this invention, the non-aqueous organic solvent in the electrolyte is preferably an organic ester solvent and / or an ether solvent. The organic ester solvent is preferably at least one selected from ethylene carbonate, propylene carbonate, butenyl carbonate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, ethyl formate, ethyl acetate, propyl acetate, propyl propionate, fluoroethylene carbonate, and methyl trifluoroethyl carbonate. The ether solvent is preferably at least one selected from dimethyl ether, diethyl ether, methyl ethyl ether, ethylene glycol dimethyl ether, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, and 1H,1H,5H-octafluoropentyl-1,1,2,2-tetrafluoroethyl ether. More preferably, ethylene carbonate, propylene carbonate, dimethyl carbonate and ethyl methyl carbonate are selected, and the volume ratio of ethylene carbonate, propylene carbonate, dimethyl carbonate and ethyl methyl carbonate is preferably 5:(8-12):(35-45):(40-50), more preferably 5:10:40:45.

[0069] In the lithium-ion battery provided by this invention, the additives in the electrolyte are preferably vinylene carbonate, ethylene ethylene carbonate, fluoroethylene carbonate, di(2,2,2-trifluoroethyl) carbonate, vinyl sulfate, vinyl disulfate, propylene sulfate, 1,3-propanesulfonyl lactone, 1,3-propenesulfonyl lactone, 1,4-butanesulfonyl lactone, 2,4-butanesulfonyl lactone, phenyl methanesulfonate, methanedisulfonate, N-phenylbis(trifluoromethanesulfonyl)imide, triallyl phosphate, tris(trimethylsilane) phosphate, and trimethyl phosphite. The following are some of the following: triphenyl phosphite, tetramethylmethylene diphosphate, propargyl phosphate, (2-allylphenoxy)trimethylsilane, tris(trimethylsilane)borate, 1,3,5-triallyl isocyanurate, isocyanoethyl methacrylate, hexamethylene diisocyanate, terephthalic diisocyanate, 2,4-toluene diisocyanate, adiponitrile, succinic anhydride, glutaronitrile, 1,3,6-hexanetrionitrile, 1,2-bis(cyanethoxy)ethane, lithium difluorophosphate, lithium bis(oxalate)borate, lithium difluorooxalateborate, and lithium difluorodi(oxalate)phosphate. More preferably, one or more of lithium difluorophosphate, 1,3-propanesulfonate lactone, and tris(trimethylsilane) phosphate are selected, and the mass ratio of lithium difluorophosphate, 1,3-propanesulfonate lactone, and tris(trimethylsilane) phosphate is preferably 1:(2-6):(0.5-2), specifically 1:4:1.

[0070] In the lithium-ion battery provided by the present invention, the lithium salt preferably accounts for 11-16% of the electrolyte by weight, more preferably 12.5%; the non-aqueous organic solvent preferably accounts for 72-85% of the electrolyte by weight, more preferably 84.5%; and the electrolyte additive preferably accounts for 2-5% of the electrolyte by weight, more preferably 3%.

[0071] Compared with the prior art, the technical solution provided by the present invention has at least the following beneficial effects:

[0072] (1) The polymer coating developed in this invention, as a surface modification coating for negative electrode current collector, contains anion and cation pairs in the polymer structure, in which bromide anion is easy to combine with lithium ion, which can make the SEI film on the negative electrode surface rich in LiBr component, thereby having a lower lithium ion diffusion barrier at the interface, thereby improving the stability of lithium ion transport at the interface.

[0073] (2) The negative electrode current collector developed in this invention has a surface coating polymer structure in which the anchored cationic groups can attract more anions in the electrolyte to accumulate on the negative electrode surface and participate in the formation of the negative electrode film. This results in the SEI film containing more inorganic LiF components. The high Young's modulus of LiF greatly improves the mechanical strength of the SEI film, making it less likely for the SEI film on the silicon-oxygen negative electrode surface with a large volume expansion coefficient to break during charging and discharging. This avoids the continuous growth and reaction of the SEI film caused by the secondary exposure of the active material, thereby alleviating the thickening of the battery gas production and the increase of internal resistance, and thus improving the electrochemical performance of the lithium-ion battery.

[0074] For clarity, the following examples and comparative models will be used to provide a detailed description.

[0075] Example 1

[0076] The specific steps for preparing compound (I) are as follows:

[0077] (1) Preparation of intermediate product 1, the chemical reaction formula is shown below:

[0078]

[0079] The preparation process was as follows: Under a nitrogen atmosphere, butenedialdehyde (0.34 g, 4.00 mmol), 100 mL of anhydrous ethanol, and p-benzoquinone (0.86 g, 8.00 mmol) were added to a clean, dry 150 mL three-necked flask equipped with a magnetic rotor and a reflux condenser. Then, 4,5-dimethyl-1,2-phenylenediamine (1.09 g, 8.00 mmol) was added, and the mixture was heated to 80 °C and refluxed for 4 h. The reaction mixture was then cooled to room temperature and stirred for another 4 h. The solvent was then removed by vacuum distillation, and the residual product was washed with 100 mL of 1 mol / L hydrochloric acid aqueous solution. The mixture was then extracted three times with 100 mL of chloroform. The organic phases were combined, dried over anhydrous magnesium sulfate, and the solvent was removed by rotary evaporation to obtain intermediate product 1, with a yield of 79.2%. HRMS (m / z): calcd.for C 22 H 24N4,344.20,found 344.37.

[0080] (2) Preparation of intermediate product 2, the chemical reaction formula is shown below:

[0081]

[0082] The preparation process was as follows: Under a nitrogen atmosphere, intermediate 1 (10.33 g, 30.00 mmol), chloromethylethyl dimethylsilane (8.08 g, 60.00 mmol), potassium hydroxide (4.60 g, 82.00 mmol), and DMSO (300 mL) were added sequentially to a clean, dry 500 mL three-necked flask equipped with a magnetic rotor. Stirring was started, and the mixture was reacted at room temperature for 3 h. After the reaction was complete, 300 mL of distilled water pre-cooled to 0 °C was added. The mixture was then extracted with chloroform (3 × 100 mL). The organic phases were combined, the solvent was removed by vacuum distillation, and the solution was purified using n-hexane as the eluent via rapid silica gel chromatography to obtain intermediate 2, with a yield of 78.6%. HRMS (m / z): calcd.for C 32 H 44 N4Si2, 540.31, found 540.43.

[0083] (3) Preparation of compound (I), the chemical reaction formula is shown below:

[0084]

[0085] The preparation process was as follows: Under a nitrogen atmosphere, intermediate compound 2 (27.02 g, 50.00 mmol) and 200 mL of anhydrous acetonitrile were added to a clean, dry 500 mL three-necked flask equipped with a magnetic rotor. Stirring was started, and then 100 mL of anhydrous acetonitrile solution containing 12.60 g, 105.00 mmol of 3-bromopropene was slowly added through a constant-pressure dropping funnel. After the addition was complete, the reaction temperature was raised to 60 °C, and the reaction was continued with stirring for 24 h. After the reaction was complete, the acetonitrile was removed by vacuum distillation. The mixture was washed three times with ethyl acetate (3 × 20 mL), and finally dried under vacuum to obtain compound (I) in 97.5% yield. EIMS (m / z): calcd.for C 38 H 54 N4Si2 2+ ,311.19,found 311.31.

[0086] The specific steps for preparing the composite modified copper current collector sample 1 are as follows:

[0087] The aforementioned polymer precursor compound (I) was mixed with the free radical initiator benzoyl peroxide (BPO), the binder sodium carboxymethyl cellulose (CMC), and the conductive agent acetylene black at a mass ratio of 7.5:0.05:5:8. Deionized water was then added at a solid content of 10%, and the mixture was dispersed evenly using a dual planetary mixer to obtain a slurry. The slurry was then coated onto both sides of a 6 μm copper foil using gravure coating, with a single-sided coating thickness of 1.5 μm. The foil was baked at 100°C for 30 seconds to obtain a composite modified copper current collector. The prepared composite modified copper current collector was then stored in a drying room with a dew point of -35°C.

[0088] The specific steps for preparing standard electrolyte samples are as follows:

[0089] In an argon glove box with a water and oxygen content ≤0.1ppm, ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) were uniformly mixed at a volume ratio of 5:10:40:45 to obtain an organic solvent. Lithium hexafluorophosphate (LiPF6) was then slowly added to the organic solvent, maintaining the mixture temperature <38℃. Subsequently, lithium difluorophosphate (LiPO2F2), 1,3-propanesulfonyl lactone (PS), and tris(trimethylsilane) phosphate (TMSP) were added, and the mixture was stirred until homogeneous to obtain a standard electrolyte. The amounts of LiPF6, organic solvent, LiPO2F2, PS, and TMSP used were 12.5%, 84.5%, 0.5%, 2%, and 0.5% of the total electrolyte mass, respectively.

[0090] The specific steps for preparing experimental battery sample 1 are as follows:

[0091] Preparation of the positive electrode: The positive electrode material is lithium nickel cobalt manganese oxide (Ni... 0.9 Co 0.05 Mn 0.05 Li), conductive carbon black (SuperP), carbon nanotubes (CNTs, in a 5% NMP solution by mass), and polyvinylidene fluoride (PVDF, in a 5% NMP solution by mass) were weighed and mixed at a mass ratio of 97:0.7:0.8:1.5 (excluding solvent). After mixing, an appropriate amount of NMP was added to control the theoretical solid content to 65%. The mixture was homogenized using a planetary homogenizer to obtain a positive electrode slurry. The positive electrode slurry was then uniformly coated onto a 13μm thick aluminum foil. After drying, rolling, and cutting, a 50mm×70mm positive electrode sheet was obtained.

[0092] Preparation of the diaphragm: A polyethylene diaphragm coated with alumina on one side was used as the isolation membrane and was left to stand in a dry room with a dew point of -35°C for 72 hours before use.

[0093] Preparation of the negative electrode: Silicon suboxide (specific capacity 650 mAh g) is used as the negative electrode material.-1 The following ingredients were mixed: conductive agent SuperP, thickener sodium carboxymethyl cellulose (CMC, 1.5% solids content deionized aqueous solution), and binder polyacrylic acid (PAA, 6% solids content deionized aqueous solution), at a mass ratio of 95:1:1.5:2.5 (excluding solvent). After mixing, deionized water was added, and the theoretical solids content was controlled to be 55%. The mixture was homogenized using a planetary homogenizer to obtain a negative electrode slurry. The negative electrode slurry was then uniformly coated onto the composite modified copper foil prepared above. After drying, rolling, and cutting, a 52mm × 72mm negative electrode sheet was obtained. The N / P ratio of the positive and negative electrodes was 1.1.

[0094] Battery fabrication: The battery was fabricated in a dry room with an ambient dew point ≤ -35℃. The separator was folded in a Z-shape, with the positive and negative electrodes placed on opposite sides. There were 12 layers of positive electrode and 13 layers of negative electrode. The positive electrode, separator, and negative electrode were stacked in sequence and aligned. The positive electrode was coated with an alumina-coated separator to obtain the electrode assembly. The electrode assembly was then fixed with polyimide tape and the tabs were welded. The battery was then placed in an aluminum-plastic film and vacuum-baked at 90℃ for 12 hours. After cooling, the prepared standard electrolyte was injected at an injection coefficient of 4.0 g / Ah. Finally, after vacuum sealing, high-temperature wetting, formation, aging, secondary sealing, and capacity testing, an experimental battery 1 with a capacity of approximately 2.5Ah was obtained.

[0095] Example 2

[0096] The specific steps for preparing compound (II) are as follows:

[0097] (1) Preparation of intermediate product 3, the chemical reaction formula is shown below:

[0098]

[0099] The preparation process was as follows: Under a nitrogen atmosphere, butenedialdehyde (0.34 g, 4.00 mmol), 100 mL of anhydrous ethanol, and p-benzoquinone (0.86 g, 8.00 mmol) were added to a clean, dry 150 mL three-necked flask equipped with a magnetic rotor and a reflux condenser. Then, 4,5-diamino-o-dibenzonitrile (1.26 g, 8.00 mmol) was added, and the mixture was heated to 80 °C and refluxed for 4 h. The reaction mixture was then cooled to room temperature and stirred for another 4 h. The solvent was then removed by vacuum distillation, and the residual product was washed with 100 mL of 1 mol / L hydrochloric acid aqueous solution. The mixture was then extracted three times with 100 mL of chloroform. The combined organic phases were dried over anhydrous magnesium sulfate, and the solvent was removed by rotary evaporation to obtain intermediate product 3, with a yield of 76.4%. HRMS (m / z): calcd.forC 22 H 12 N8,388.12,found 388.25.

[0100] (2) Preparation of intermediate product 4, the chemical reaction formula is shown below:

[0101]

[0102] The preparation process was as follows: Under a nitrogen atmosphere, intermediate 3 (11.64 g, 30.00 mmol), chloromethylethyl dimethylsilane (8.08 g, 60.00 mmol), potassium hydroxide (4.60 g, 82.00 mmol), and DMSO (300 mL) were added sequentially to a clean, dry 500 mL three-necked flask equipped with a magnetic rotor. Stirring was started, and the mixture was reacted at room temperature for 3 h. After the reaction was complete, 300 mL of distilled water pre-cooled to 0 °C was added. The mixture was then extracted with chloroform (3 × 100 mL). The organic phases were combined, the solvent was removed by vacuum distillation, and n-hexane was used as the eluent. After purification by rapid silica gel chromatography, intermediate 4 was obtained with a yield of 77.8%. HRMS (m / z): calcd.for C 32 H 32 N8Si2,584.23,found 584.39.

[0103] (3) Prepare compound (II) using the following chemical reaction formula:

[0104]

[0105] The preparation process was as follows: Under a nitrogen atmosphere, intermediate compound 4 (29.21 g, 50.00 mmol) and 200 mL of anhydrous acetonitrile were added to a clean, dry 500 mL three-necked flask equipped with a magnetic rotor. Stirring was started, and then 100 mL of anhydrous acetonitrile solution containing 12.60 g, 105.00 mmol of 3-bromopropene was slowly added through a constant-pressure dropping funnel. After the addition was complete, the reaction temperature was raised to 60 °C, and the reaction was continued with stirring for 24 h. After the reaction was complete, the acetonitrile was removed by vacuum distillation. The mixture was washed three times with ethyl acetate (3 × 20 mL), and finally dried under vacuum to obtain compound (II) in 97.0% yield. EIMS (m / z): calcd.for C 38 H 42 N8Si2 2+ ,333.15,found 333.23.

[0106] The composite modified copper current collector 2 sample was prepared according to the method of Example 1, except that the polymer precursor compound (II) was used in the composite modified copper current collector 2 sample.

[0107] The standard electrolyte was prepared according to the method in Example 1.

[0108] Experimental battery 2 was prepared according to the method of Example 1, except that the current collector used for the negative electrode was the composite modified copper current collector 2 prepared above.

[0109] Example 3

[0110] (1) Preparation of intermediate product 5, the chemical reaction formula is shown below:

[0111]

[0112] The preparation process was as follows: Under a nitrogen atmosphere, butenedialdehyde (0.34 g, 4.00 mmol), 100 mL of anhydrous ethanol, and p-benzoquinone (0.86 g, 8.00 mmol) were added to a clean, dry 150 mL three-necked flask equipped with a magnetic rotor and a reflux condenser. Then, 4,5-diamino-2-trifluoromethylbenzonitrile (1.61 g, 8.00 mmol) was added. The mixture was heated to 80 °C and refluxed for 4 h. The reaction mixture was then cooled to room temperature and stirred for another 4 h. The solvent was then removed by vacuum distillation, and the residual product was washed with 100 mL of 1 mol / L hydrochloric acid aqueous solution. The mixture was then extracted three times with 100 mL of chloroform. The combined organic phases were dried over anhydrous magnesium sulfate, and the solvent was removed by rotary evaporation to give intermediate product 5, with a yield of 75.3%. HRMS (m / z): calcd.for C 22 H 12 F6N6,474.10,found474.20.

[0113] (2) Preparation of intermediate product 6, the chemical reaction formula is shown below:

[0114]

[0115] The preparation process was as follows: Under a nitrogen atmosphere, intermediate 5 (14.10 g, 30.00 mmol), chloromethylethyl dimethylsilane (8.08 g, 60.00 mmol), potassium hydroxide (4.60 g, 82.00 mmol), and DMSO (300 mL) were added sequentially to a clean, dry 500 mL three-necked flask equipped with a magnetic rotor. Stirring was started, and the mixture was reacted at room temperature for 3 h. After the reaction was complete, 300 mL of distilled water pre-cooled to 0 °C was added. The mixture was then extracted with chloroform (3 × 100 mL). The organic phases were combined, the solvent was removed by vacuum distillation, and n-hexane was used as the eluent. After purification by rapid silica gel chromatography, intermediate 6 was obtained with a yield of 78.4%. HRMS (m / z): calcd.forC 32 H 32 F6N6Si2,670.21, found 670.33.

[0116] (3) Prepare compound (III) using the following chemical reaction:

[0117]

[0118] The preparation process was as follows: Under a nitrogen atmosphere, intermediate compound 6 (33.51 g, 50.00 mmol) and 200 mL of anhydrous acetonitrile were added to a clean, dry 500 mL three-necked flask equipped with a magnetic rotor. Stirring was started, and then 100 mL of anhydrous acetonitrile solution containing 12.60 g, 105.00 mmol of 3-bromopropene was slowly added through a constant-pressure dropping funnel. After the addition was complete, the reaction temperature was raised to 60 °C, and the reaction was continued with stirring for 24 h. After the reaction was complete, the acetonitrile was removed by vacuum distillation. The mixture was washed three times with ethyl acetate (3 × 20 mL), and finally dried under vacuum to obtain compound (III) in a yield of 96.3%. EIMS (m / z): calcd.for C 38 H 42 F6N6Si2 2+ ,376.15,found 376.19.

[0119] The composite modified copper current collector 3 sample was prepared according to the method of Example 1, except that the polymer precursor compound (III) was used in the composite modified copper current collector 3 sample.

[0120] The standard electrolyte was prepared according to the method in Example 1.

[0121] Experimental battery 3 was prepared according to the method of Example 1, except that the current collector used for the negative electrode was the composite modified copper current collector 3 prepared above.

[0122] Example 4

[0123] (1) Preparation of intermediate product 7, the chemical reaction formula is shown below:

[0124]

[0125] The preparation process was as follows: Under a nitrogen atmosphere, butenedialdehyde (0.34 g, 4.00 mmol), 100 mL of anhydrous ethanol, and p-benzoquinone (0.86 g, 8.00 mmol) were added to a clean, dry 150 mL three-necked flask equipped with a magnetic rotor and a reflux condenser. Then, 4-acetylenephenyl-1,2-diamine (1.06 g, 8.00 mmol) was added. The mixture was heated to 80 °C and refluxed for 4 h. The reaction mixture was then cooled to room temperature and stirred for another 4 h. The solvent was then removed by vacuum distillation, and the residual product was washed with 100 mL of 1 mol / L hydrochloric acid aqueous solution. The mixture was then extracted three times with 100 mL of chloroform. The organic phases were combined, dried over anhydrous magnesium sulfate, and the solvent was removed by rotary evaporation to obtain intermediate product 7, with a yield of 78.4%. HRMS (m / z): calcd.forC 22 H 16 N4,336.14,found 336.28.

[0126] (2) Preparation of intermediate product 8, the chemical reaction formula is shown below:

[0127]

[0128] The preparation process was as follows: Under a nitrogen atmosphere, intermediate 7 (10.08 g, 30.00 mmol), chloromethylethyl dimethylsilane (8.08 g, 60.00 mmol), potassium hydroxide (4.60 g, 82.00 mmol), and DMSO (300 mL) were added sequentially to a clean, dry 500 mL three-necked flask equipped with a magnetic rotor. Stirring was started, and the mixture was reacted at room temperature for 3 h. After the reaction was complete, 300 mL of distilled water pre-cooled to 0 °C was added. The mixture was then extracted with chloroform (3 × 100 mL). The organic phases were combined, the solvent was removed by vacuum distillation, and n-hexane was used as the eluent. After purification by rapid silica gel chromatography, intermediate 8 was obtained with a yield of 78.9%. HRMS (m / z): calcd.for C 32 H 36 N4Si2, 532.25, found 532.42.

[0129] (3) Preparation of compound (IV), the chemical reaction formula is shown below:

[0130]

[0131] The preparation process was as follows: Under a nitrogen atmosphere, intermediate compound 8 (26.61 g, 50.00 mmol) and 200 mL of anhydrous acetonitrile were added to a clean, dry 500 mL three-necked flask equipped with a magnetic rotor. Stirring was started, and then 100 mL of anhydrous acetonitrile solution containing 12.60 g, 105.00 mmol of 3-bromopropene was slowly added through a constant-pressure dropping funnel. After the addition was complete, the reaction temperature was raised to 60 °C, and the reaction was continued with stirring for 24 h. After the reaction was complete, the acetonitrile was removed by vacuum distillation. The mixture was washed three times with ethyl acetate (3 × 20 mL), and finally dried under vacuum to obtain compound (IV) in 96.9% yield. EIMS (m / z): calcd.for C 38 H 46 N4Si2 2+ ,307.16,found 307.21.

[0132] The composite modified copper current collector 4 sample was prepared according to the method of Example 1, except that the polymer precursor compound (IV) was used in the composite modified copper current collector 4 sample.

[0133] The standard electrolyte was prepared according to the method in Example 1.

[0134] Experimental battery 4 was prepared according to the method of Example 1, except that the current collector used for the negative electrode was the composite modified copper current collector 4 prepared above.

[0135] Example 5

[0136] (1) Preparation of intermediate product 9, the chemical reaction formula is shown below:

[0137]

[0138] The preparation process was as follows: Under a nitrogen atmosphere, butenedialdehyde (0.34 g, 4.00 mmol), 100 mL of anhydrous ethanol, and p-benzoquinone (0.86 g, 8.00 mmol) were added to a clean, dry 150 mL three-necked flask equipped with a magnetic rotor and a reflux condenser. Then, 4,5-difluorophenyl-1,2-diamine (1.15 g, 8.00 mmol) was added, and the mixture was heated to 80 °C and refluxed for 4 h. The reaction mixture was then cooled to room temperature and stirred for another 4 h. The solvent was then removed by vacuum distillation, and the residual product was washed with 100 mL of 1 mol / L hydrochloric acid aqueous solution. The mixture was then extracted three times with 100 mL of chloroform. The combined organic phases were dried over anhydrous magnesium sulfate, and the solvent was removed by rotary evaporation to obtain intermediate product 9, with a yield of 75.1%. HRMS (m / z): calcd.forC 18 H 12 F4N4,360.10,found 360.23.

[0139] (2) Preparation of intermediate product 10, the chemical reaction formula is shown below:

[0140]

[0141] The preparation process was as follows: Under a nitrogen atmosphere, intermediate 7 (10.80 g, 30.00 mmol), chloromethylethyl dimethylsilane (8.08 g, 60.00 mmol), potassium hydroxide (4.60 g, 82.00 mmol), and DMSO (300 mL) were added sequentially to a clean, dry 500 mL three-necked flask equipped with a magnetic rotor. Stirring was started, and the mixture was reacted at room temperature for 3 h. After the reaction was complete, 300 mL of distilled water pre-cooled to 0 °C was added. The mixture was then extracted with chloroform (3 × 100 mL). The organic phases were combined, the solvent was removed by vacuum distillation, and n-hexane was used as the eluent. After purification by rapid silica gel chromatography, intermediate compound 10 was obtained, with a yield of 76.7%. HRMS (m / z): calcd.for C 28 H 32 F4N4Si2,556.21, found 556.37.

[0142] (3) Prepare compound (V) using the following chemical reaction formula:

[0143]

[0144] The preparation process was as follows: Under a nitrogen atmosphere, intermediate compound 10 (27.81 g, 50.00 mmol) and 200 mL of anhydrous acetonitrile were added to a clean, dry 500 mL three-necked flask equipped with a magnetic rotor. Stirring was started, and then 100 mL of anhydrous acetonitrile solution containing 12.60 g, 105.00 mmol of 3-bromopropene was slowly added through a constant-pressure dropping funnel. After the addition was complete, the reaction temperature was raised to 60 °C, and the reaction was continued with stirring for 24 h. After the reaction was complete, the acetonitrile was removed by vacuum distillation. The mixture was washed three times with ethyl acetate (3 × 20 mL), and finally dried under vacuum to obtain compound (V) in 94.9% yield. EIMS (m / z): calcd.for C 34 H 42 F4N4Si2 2+ ,319.14,found 319.28.

[0145] The composite modified copper current collector 5 sample was prepared according to the method of Example 1, except that the polymer precursor compound (V) was used in the composite modified copper current collector 5 sample.

[0146] The standard electrolyte was prepared according to the method in Example 1.

[0147] Experimental battery 5 was prepared according to the method of Example 1, except that the current collector used for the negative electrode was the composite modified copper current collector 5 prepared above.

[0148] Example 6

[0149] (1) Preparation of intermediate product 9, the chemical reaction formula is shown below:

[0150]

[0151] The preparation process was as follows: Under a nitrogen atmosphere, butenedialdehyde (0.34 g, 4.00 mmol), 100 mL of anhydrous ethanol, and p-benzoquinone (0.86 g, 8.00 mmol) were added to a clean, dry 150 mL three-necked flask equipped with a magnetic rotor and a reflux condenser. Then, 4,5-bis(trifluoromethyl)phenyl-1,2-diamine (1.95 g, 8.00 mmol) was added. The mixture was heated to 80 °C and refluxed for 4 h. The reaction mixture was then cooled to room temperature and stirred for another 4 h. The solvent was then removed by vacuum distillation, and the residual product was washed with 100 mL of 1 mol / L hydrochloric acid aqueous solution. The mixture was then extracted three times with 100 mL of chloroform. The organic phases were combined, dried over anhydrous magnesium sulfate, and the solvent was removed by rotary evaporation to obtain intermediate 11, with a yield of 72.8%. HRMS (m / z): calcd.for C 22 H 12 F 12 N4,560.09,found 560.26.

[0152] (2) Preparation of intermediate product 11, the chemical reaction formula is shown below:

[0153]

[0154] The preparation process was as follows: Under a nitrogen atmosphere, intermediate 11 (16.80 g, 30.00 mmol), chloromethylethyl dimethylsilane (8.08 g, 60.00 mmol), potassium hydroxide (4.60 g, 82.00 mmol), and DMSO (300 mL) were added sequentially to a clean, dry 500 mL three-necked flask equipped with a magnetic rotor. Stirring was started, and the mixture was reacted at room temperature for 3 h. After the reaction was complete, 300 mL of distilled water pre-cooled to 0 °C was added. The mixture was then extracted with chloroform (3 × 100 mL). The organic phases were combined, the solvent was removed by vacuum distillation, and n-hexane was used as the eluent. After purification by rapid silica gel chromatography, intermediate 12 was obtained with a yield of 74.3%. HRMS (m / z): calcd.for C 32 H 32 F 12N4Si2, 756.20, found 756.39.

[0155] (3) Preparation of compound (VI), the chemical reaction formula is shown below:

[0156]

[0157] The preparation process was as follows: Under a nitrogen atmosphere, intermediate compound 12 (37.81 g, 50.00 mmol) and 200 mL of anhydrous acetonitrile were added to a clean, dry 500 mL three-necked flask equipped with a magnetic rotor. Stirring was started, and then 100 mL of anhydrous acetonitrile solution containing 3-bromopropene (12.60 g, 105.00 mmol) was slowly added through a constant-pressure dropping funnel. After the addition was complete, the reaction temperature was raised to 60 °C, and the reaction was continued with stirring for 24 h. After the reaction was complete, acetonitrile was removed by vacuum distillation. The mixture was washed three times with ethyl acetate (3 × 20 mL), and finally dried under vacuum to obtain compound (VI) in 92.5% yield. EIMS (m / z): calcd.for C 38 H 42 F 12 N4Si2 2+ ,419.14,found419.24.

[0158] The composite modified copper current collector 6 sample was prepared according to the method of Example 1, except that the polymer precursor compound (VI) was used in the composite modified copper current collector 6 sample.

[0159] The standard electrolyte was prepared according to the method in Example 1.

[0160] Experimental battery 6 was prepared according to the method of Example 1, except that the current collector used for the negative electrode was the composite modified copper current collector 6 prepared above.

[0161] Example 7

[0162] The composite modified copper current collector 7 sample was prepared according to the method of Example 1, except that the composite modified copper current collector 7 sample used a polymer precursor compound (V). The mass ratio of compound (V) to free radical initiator BPO, binder CMC and conductive agent acetylene black was 7.5:0.02:3:6. The solid content of the coating slurry was 5wt%, and the single-sided coating thickness was 2.0μm.

[0163] The standard electrolyte was prepared according to the method in Example 1.

[0164] The experimental battery 7 was prepared according to the method of Example 1, except that the current collector used for the negative electrode was the composite modified copper current collector 7 prepared above.

[0165] Example 8

[0166] The composite modified copper current collector 8 sample was prepared according to the method of Example 1, except that the composite modified copper current collector 8 sample used a polymer precursor compound (V). The mass ratio of compound (V) to free radical initiator BPO, binder CMC and conductive agent acetylene black was 7.5:0.1:7:10. The solid content of the coating slurry was 15wt%, and the single-sided coating thickness was 2.5μm.

[0167] The standard electrolyte was prepared according to the method in Example 1.

[0168] The experimental battery 8 was prepared according to the method of Example 1, except that the current collector used for the negative electrode was the composite modified copper current collector 8 prepared above.

[0169] Example 9

[0170] The composite modified copper current collector 9 sample was prepared according to the method of Example 1, except that the composite modified copper current collector 9 sample used a polymer precursor compound (V), the coating slurry solid content was 20wt%, the single-sided coating thickness was 3μm, the baking temperature was 80℃, and the baking time was 60s.

[0171] The standard electrolyte was prepared according to the method in Example 1.

[0172] The experimental battery 9 was prepared according to the method of Example 1, except that the current collector used for the negative electrode was the composite modified copper current collector 9 prepared above.

[0173] Comparative Example 1

[0174] Experimental battery 10 was prepared according to the method of Example 1, except that the negative electrode current collector of experimental battery 10 sample was a commercially available 9μm carbon-coated copper foil.

[0175] Comparative Example 2

[0176] Experimental battery 11 was prepared according to the method of Example 1, except that the negative electrode current collector of experimental battery 11 sample was a commercially available 9μm smooth copper foil.

[0177] Performance testing

[0178] The lithium-ion batteries prepared in Examples 1-9 and Comparative Examples 1-2 were subjected to high-temperature long-cycle performance tests and rate-cycle performance tests, respectively, under the following test conditions:

[0179] Battery high temperature long cycle test

[0180] The prepared lithium-ion batteries were first tested using an internal resistance tester to measure the initial internal resistance R0. They were then placed in an explosion-proof oven at an ambient temperature of 45°C and charged under constant current and constant voltage conditions at 1C and 4.2V until the cutoff current reached 0.05C. Next, they were discharged under constant current conditions at 1C until the voltage reached 3V, cycling for 1000 cycles. The capacity retention rate was recorded as follows: Capacity retention rate (%) on the nth cycle = (Discharge capacity on the nth cycle / Discharge capacity on the first cycle) × 100%. After testing, the batteries were cooled to room temperature, and the internal resistance R1 was measured. The internal resistance (ACR) growth rate (%) was calculated as follows: (R1 - R0) × 100% / V0. Four batteries were tested in each group, and the average value was taken.

[0181] Ratio Performance Test

[0182] Before testing, the battery was initially charged and discharged at room temperature at 0.2C. Then, it was charged at room temperature with a constant current and constant voltage of 0.2C and 4.2V until the cutoff current was 0.05C. Then, it was discharged at a constant current of 5C to 3V. The 5C discharge capacity retention rate (%) = (5C discharge capacity / 0.2C discharge capacity) × 100%.

[0183] Before testing, the batteries were initially charged and discharged at room temperature at 0.2C. Then, they were charged at room temperature with a constant current of 5C until the cutoff voltage of 4.2V. Next, they were discharged at a constant current of 0.2C until 3V. The 5C charging capacity retention rate (%) = (5C charging capacity / 0.2C charging capacity) × 100%. Four batteries were tested in each group, and the average value was taken.

[0184] Table 1. Negative electrode current collectors and corresponding battery performance for each embodiment and comparative example

[0185]

[0186]

[0187] High-nickel lithium-ion batteries were prepared using the electrolytes prepared in Examples 1-9 and Comparative Examples 1-2. The battery performance test results are shown in Table 1. It can be seen that the negative electrode current collector prepared by the modification method of the negative electrode current collector provided by this invention, when applied to high-nickel lithium-ion batteries, achieved the expected excellent high-temperature performance and rate performance. Compared with commercially available negative electrode copper current collectors that are not modified or coated with conductive carbon black, the battery performance is significantly improved. Furthermore, the battery internal resistance remains stable or only increases slightly during cycling, which can be attributed to the high stability of the SEI at the negative electrode interface during high-temperature cycling. Thanks to the modified negative electrode current collector provided by this invention, the SEI film contains more inorganic LiF components, resulting in higher mechanical strength. This makes the SEI film on the silicon-oxygen negative electrode surface, which has a large volume expansion coefficient, less prone to rupture during charging and discharging. This avoids the continuous proliferation and stress of the SEI film caused by secondary exposure of the active material, thereby alleviating the thickening of the battery due to gas production and the increase in internal resistance, and thus improving the electrochemical performance of the lithium-ion battery.

[0188] Meanwhile, by comparing Examples 1-6 and Examples 7-9, it can be seen that the modification method for the negative electrode current collector should not have too high a solid content in the coating slurry, nor should the coating thickness be too thick. Too high a solid content will result in excessive viscosity of the coating slurry during actual production and preparation, leading to uneven coating. Too thick a coating thickness will not bring more significant performance improvement, and may even have a negative impact. Therefore, the optimal solid content of the coating slurry is 10%, and the optimal coating thickness is 1.5 μm, which can balance the production and preparation of the modified negative electrode current collector with its performance in lithium-ion batteries.

[0189] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A polymer precursor, characterized in that, The chemical structure of the polymer precursor is shown in Formula A: Where X is Br, and R1 and R2 are selected from one or more of methyl, cyano, ethynyl, hydrogen atom, fluorine atom and trifluoromethyl.

2. The polymer precursor according to claim 1, characterized in that, The polymer precursor is at least one of the compounds of formula (I) to (VI):

3. A method for preparing a polymer precursor, characterized in that, Includes the following steps: a) The o-diamino compound of formula a is reacted with butenidine to obtain the diimidazolium intermediate of formula b; b) Grafting the diimidazole intermediate of formula b with chloromethylethyldimethylsilane to obtain the intermediate of formula c; c) React the intermediate of the structure of formula c with the haloolefin of the structure of formula d to obtain the polymer precursor of the structure of formula A; Wherein, X is Br, and R1 and R2 are independently selected from one or more of methyl, cyano, ethynyl, hydrogen atom, fluorine atom and trifluoromethyl.

4. A polymer coating, characterized in that, The raw materials for preparing the polymer coating include a polymer precursor and a free radical initiator. The polymer precursor is the polymer precursor described in claim 1 or 2, or the polymer precursor obtained by the preparation method described in claim 3.

5. The polymer coating according to claim 4, characterized in that, The free radical initiator is one or more of peroxide initiators, azo compound initiators, and redox initiators; the mass ratio of the polymer precursor to the free radical initiator is 7.5:(0.02-0.1).

6. The polymer coating according to claim 4, characterized in that, The raw materials used in the preparation also include a binder and a conductive agent; the binder is one or more of acrylic binders, polyvinyl alcohol, and sodium carboxymethyl cellulose; the conductive agent is one or more of acetylene black, natural graphite, and artificial graphite; the mass ratio of the polymer precursor, binder, and conductive agent is 7.5:(3-7):(6-10).

7. A method for preparing the polymer coating according to any one of claims 4 to 6, characterized in that, Includes the following steps: The raw materials for preparing the polymer coating are mixed with water, coated, and baked to obtain the polymer coating.

8. A negative electrode current collector, characterized in that, The negative electrode current collector includes a negative electrode current collector substrate and a coating applied to the surface of the negative electrode current collector substrate. The coating is a polymer coating as described in any one of claims 4 to 6 or a polymer coating prepared by the preparation method described in claim 7.

9. The negative electrode current collector according to claim 8, characterized in that, The substrate of the negative electrode current collector is made of copper.

10. A lithium-ion battery, characterized in that, The negative electrode current collector of the lithium-ion battery is the negative electrode current collector as described in claim 8 or 9.

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