An ionic polymer binder based on viologen, its preparation method and application

Abstract

The present invention provides a viologen-based ionic polymer binder, a preparation method thereof, and an application thereof, belonging to the technical field of lithium-ion batteries. The binder provided by the present invention is a polymer of viologen-based acrylate, acrylate, and / or methoxypolyethylene glycol acrylate. When preparing a positive electrode sheet of a lithium-ion battery with it, the viologen-based acrylate chain segment can enhance the adhesion between positive electrode active materials, promote the conduction of lithium ions, and improve the capacity retention rate and cycle stability of the battery; the acrylate chain segment can improve the flexibility of the binder and avoid the decrease in battery capacity and cycle performance caused by the absorption of water by the binder; the methoxypolyethylene glycol acrylate chain segment can improve the ion transport performance between the electrode sheet and the electrolyte interface. Therefore, the lithium-ion battery assembled with the positive electrode sheet of the lithium-ion battery prepared by using the ionic polymer binder provided by the present invention has a high capacity retention rate and good cycle stability.

Description

Technical Field

[0001] The invention relates to the technical field of lithium ion batteries, and in particular to an ionic polymer binder based on viologen, and a preparation method and application thereof. Background Art

[0002] In the positive electrode of lithium-ion batteries, the role of the binder is to bond the active material and the conductive agent to the current collector to form a stable positive electrode and maintain the integrity of the electrode structure. The binder has a significant impact on battery performance. When the binding performance of the binder is not good enough, the electrode may fall off, resulting in battery failure; when the electrochemical stability of the binder is not good, some functional groups of the binder may undergo irreversible chemical reactions with lithium ions during the electrode electrochemical process, resulting in a decrease in the reversible capacity of the battery. Therefore, designing high-performance binders is an effective way to solve problems such as active material pulverization and active material shedding from the current collector and to improve the cyclability of lithium-ion batteries.

[0003] At present, common lithium-ion battery binders include polyvinylidene fluoride (PVDF). However, PVDF binders have the following defects: the bonding strength between PVDF and the conductive agent and active material is low; the interface impedance of the lithium-ion battery assembled with the positive electrode sheet prepared by PVDF as a binder is large; the poor electronic conductivity of PVDF limits its application in high-rate charge and discharge environments. In order to overcome the problems of PVDF binders, there have been many studies on positive and negative electrode binders for lithium-ion batteries. For example, Chinese patent CN111180733A discloses a binder containing ethylene carbonate, which gives the polymer binder a certain elasticity, but the bonding of the positive electrode sheet prepared by the binder is still poor, and the peeling strength between the dry slurry coating on the surface of the current collector in the electrode sheet and the current collector is low, which leads to the capacity retention rate of the battery assembled with the electrode sheet being below 70%. Another example is Chinese patent CN111635478A, which discloses a low-impedance binder containing an ionic liquid structural unit. This binder has good ion transmission ability, and when the positive and negative electrode sheets prepared by this binder are respectively applied to lithium-ion batteries, the battery cycle stability can be improved. However, the battery assembled with the electrode sheets prepared by this binder has poor capacity retention and cycle stability under high-rate charge and discharge conditions.

[0004] Therefore, how to improve the bonding performance of the binder to improve the capacity retention and cycle stability of lithium-ion batteries under high-rate charge and discharge conditions has become a technical problem that needs to be solved urgently in this field. Summary of the invention

[0005] The object of the present invention is to provide a viologen-based ionic polymer binder, a preparation method thereof, and an application thereof. The viologen-based ionic polymer binder provided by the present invention has excellent capacity retention and cycle stability under high-rate charge and discharge conditions.

[0006] To achieve the above object of the invention, the present invention provides the following technical solutions:

[0007] The present invention provides a viologen-based ionic polymer binder, which is characterized by having a chemical structure shown in Formula I:

[0008]

[0009] In Formula I, R 1 , R 3 and R 4 are independently hydrogen or methyl; R 2 and R 5 are independently alkyl; X is methylene, methylene ester group or methylene carbamate group; Y is PF 6- , BF 4- , Br - , I - , CH 3 SO 3 - , CF 3 SO 3 - or (CF 3 SO 2 ) 2 N - ; m + n + q = 1, where m ≥ 0, n ≥ 0, q > 0; p = 0 to 40. The present invention also provides a preparation method of the viologen-based ionic polymer binder according to the above technical solution, including: mixing a viologen-based acrylate, an acrylate and / or a methoxypolyethylene glycol acrylate, an initiator and a first solvent, and performing a radical polymerization reaction to obtain a viologen-based ionic polymer binder;

[0010] The viologen-based acrylate has a chemical structure shown in Formula II:

[0011]

[0012] In Formula II, R 4 is hydrogen or methyl; R 5 is alkyl; X is methylene, methylene ester group or methylene carbamate group; Y is PF 6 - , BF 4 - , Br - , I -, CH 3 SO 3 - , CF 3 SO 3 - or (CF 3 SO 2 ) 2 N - .

[0013] Preferably, the preparation method of the viologen-based acrylate includes the following steps:

[0014] (1) Mix 4,4'-bipyridine, an alkylating agent and a second solvent to carry out a first alkylation reaction to obtain an N-alkyl-4,4'-bipyridinium salt;

[0015] (2) Mix the N-alkyl-4,4'-bipyridinium salt obtained in the step (1) with a 1-haloalkyl-1'-alcohol and a third solvent to carry out a second alkylation reaction to obtain a 1-(hydroxyalkyl)-1'-alkyl viologen salt (1);

[0016] (3) Mix the 1-(hydroxyalkyl)-1'-alkyl viologen salt (1) obtained in the step (2) with a salt containing different anions and a fourth solvent to carry out an ion exchange reaction to obtain a 1-(hydroxyalkyl)-1'-alkyl viologen salt (2);

[0017] (4) Mix the 1-(hydroxyalkyl)-1'-alkyl viologen salt (2) obtained in the step (3) with a vinyl carbonyl compound, a catalyst, an inhibitor and a fifth solvent to carry out an esterification reaction to obtain a viologen-based acrylate.

[0018] Preferably, the alkylating agent in the step (1) is at least one of methyl iodide, dimethyl sulfate, dimethyl carbonate, ethyl iodide, diethyl sulfate, diethyl carbonate, propyl iodide, dipropyl sulfate and dipropyl carbonate; the second solvent is at least one of dichloroethane, tetrahydrofuran, dichloromethane, toluene and chloroform; the temperature of the first alkylation reaction is 10-35 °C; the time of the first alkylation reaction is 1-24 h.

[0019] Preferably, the 1-haloalkyl-1'-alcohol in the step (2) is at least one of 2-bromoethanol, 2-chloroethanol, 3-bromo-1-propanol, 3-chloro-1-propanol, 4-bromo-1-butanol, 4-chloro-1-butanol, 5-bromo-1-pentanol, 5-chloro-1-pentanol, 6-bromo-1-hexanol, 6-chloro-1-hexanol, 7-bromo-1-heptanol, 7-chloro-1-heptanol, 8-bromo-1-octanol, and 8-chloro-1-octanol; the third solvent is at least one of acetonitrile, N-methylpyrrolidone, N,N-dimethylformamide, and dimethyl sulfoxide; the temperature of the second alkylation reaction is 50-100 °C; the time of the second alkylation reaction is 30-72 h.

[0020] Preferably, the salts containing different anions in the step (3) are KPF 6 , NaPF 6 , NH 4 PF 6 , NaBF 4 , KBF 4 , NaBr, KBr, NaI, KI, Na 2 SO 4 , Na 2 CO 3 , K 2 CO 3 , CH 3 SO 3 Na, CF 3 SO 3 Na, and (CF 3 SO 2 ) 2 NLi, etc.; the fourth solvent is at least one of deionized water, ethanol, N-methylpyrrolidone, N,N-dimethylformamide, and dimethyl sulfoxide; the temperature of the ion exchange reaction is 10-35 °C; the time of the ion exchange reaction is 1-12 h.

[0021] Preferably, the vinyl carbonyl compound in the step (4) is at least one of 2-isocyanatoethyl acrylate, isocyanatoethyl methacrylate, acrylic acid, methacrylic acid, acryloyl chloride, and methacryloyl chloride; the catalyst is at least one of dibutyltin dilaurate, triethylamine, sodium carbonate, and potassium carbonate; the inhibitor is at least one of p-methoxyphenol, p-benzoquinone, and hydroquinone; the fifth solvent is at least one of N-methylpyrrolidone, N,N-dimethylformamide, tetrahydrofuran, 1,4-dioxane, acetonitrile, and chloroform; the temperature of the esterification reaction is 10-35 °C; the time of the esterification reaction is 1-36 h.

[0022] Preferably, the initiator for the radical polymerization reaction is at least one of azobisisobutyronitrile, azobiscyclohexylcarbonitrile, dimethyl azobisisobutyrate, and benzoyl peroxide; the first solvent is at least one of acetonitrile, toluene, acetone, N-methylpyrrolidone, N,N-dimethylformamide, tetrahydrofuran, 1,4-dioxane, and chloroform; the temperature of the radical polymerization is 50-80 °C; the time of the radical polymerization reaction is 8-12 h.

[0023] The present invention also provides the application of the viologen-based ionic polymer binder described in the above technical solution or the viologen-based ionic polymer binder prepared by the preparation method described in the above technical solution in a lithium-ion battery electrode sheet.

[0024] Preferably, the lithium-ion battery electrode sheet is a positive electrode sheet or a negative electrode sheet.

[0025] The viologen-based ionic polymer binder provided by the present invention is a polymer of viologen-based acrylate, acrylate, and / or methoxypolyethylene glycol acrylate. When it is used to prepare a lithium-ion battery positive electrode sheet, the viologen-based acrylate chain segment has the following functions: First, the quaternary ammonium cation and counter anion in the viologen structure are combined with the positive electrode active material of the lithium-ion battery through electrostatic interaction, which can enhance the adhesion between the positive electrode active materials; Second, the counter anion in the viologen structure can promote the conduction of lithium ions; Third, the viologen has a stable structure and reversible redox characteristics. When the ionic polymer is used as a binder for the lithium-ion battery positive electrode sheet, it is beneficial to improve the capacity retention rate and cycle stability of the battery. The acrylate chain segment can not only improve the flexibility of the binder, soften the electrode sheet, but also enhance the hydrophobicity of the binder, avoiding the decrease of the battery capacity and cycle performance caused by the binder absorbing water. The methoxypolyethylene glycol acrylate chain segment can enhance the flexibility of the binder on the one hand; on the other hand, due to its good lithium ion transport ability, it can improve the ionic transport performance between the electrode sheet and the electrolyte interface and reduce the interface impedance. Therefore, a lithium-ion battery assembled with a lithium-ion positive electrode sheet prepared by using the viologen-based ionic polymer binder provided by the present invention has a lower interface impedance, a higher specific capacity, a higher capacity retention rate, and good cycle stability. The results of the examples show that the glass transition temperature of the viologen-based ionic polymer binder provided by the present invention is -45.3 to -24.5 °C; the peel strength of the surface coating of the positive electrode sheet prepared by using the viologen-based ionic polymer binder provided by the present invention is 120.1 to 145.7 N·m -1 ; the initial discharge specific capacity of the lithium iron phosphate|metal lithium battery assembled with the positive electrode sheet prepared by the viologen-based ionic polymer binder provided by the present invention is 141.5 to 145.2 mAh·g at a cut-off voltage of 2.5 to 4.2 V and a rate of 0.5C-1 After 400 cycles, the discharge specific capacity of the battery is 128.5 - 136.3 mAh·g -1 and the capacity retention rate is 89.17 - 93.87%; the initial interfacial impedance of the lithium iron phosphate|metal lithium battery assembled with the positive electrode sheet prepared from the viologen-based ionic polymer binder provided by the present invention is 204.1 - 211.9 Ω. Description of the Drawings

[0026] Figure 1 1H NMR spectrum of 1-(2-(((2-(acryloyloxy)ethyl)carbamoyl)oxy)ethyl)-1'-methylviologen hexafluorophosphate prepared in Example 1 of the present invention;

[0027] Figure 2 1H NMR spectrum of the viologen-based ionic polymer binder A1 prepared in Example 1 of the present invention;

[0028] Figure 3 1H NMR spectrum of 1-((2-acryloyloxy)ethyl)-1'-methylviologen hexafluorophosphate prepared in Example 3 of the present invention;

[0029] Figure 4 1H NMR spectrum of the viologen-based ionic polymer binder A5 prepared in Example 5 of the present invention;

[0030] Figure 5 Differential scanning calorimetry curve of the viologen-based ionic polymer binder A5 prepared in Example 5 of the present invention;

[0031] Figure 6 Interfacial impedance curves of the lithium iron phosphate|metal lithium batteries D5 and D10 prepared by the present invention at 25°C;

[0032] Figure 7 Long cycle charge and discharge curves of the lithium iron phosphate|metal lithium batteries D5 and D10 prepared by the present invention at 25°C, with a cut-off voltage of 2.5 - 4.2 V and a rate of 0.5C;

[0033] Figure 8 Charge and discharge curves of the lithium iron phosphate|metal lithium battery D5 prepared by the present invention at 25°C, with a cut-off voltage of 2.5 - 4.2 V, at rates of 0.2C, 0.5C, 1C, 2C, and 3C. Detailed Description of the Invention

[0034] The present invention provides a viologen-based ionic polymer binder, which is characterized by having a chemical structure as shown in Formula I:

[0035]

[0036] In the present invention, in the formula I, R 1 , R 3 and R 4 are independently hydrogen or methyl; R 2 and R 5 are independently alkyl groups; X is methylene, methylene ester group or methylene carbamate group; Y is PF 6- , BF 4 - , Br - , I - , CH 3 SO 3 - , CF 3 SO 3 - or (CF 3 SO 2 ) 2 N - ; m + n + q = 1, where m ≥ 0, n ≥ 0, q > 0; p is 0 to 40.

[0037] In the present invention, the alkyl group is preferably a C1 - C4 alkyl group, more preferably including methyl, ethyl or butyl. Further, R 2 is preferably ethyl or butyl, and R 5 is preferably methyl; the p is preferably 0 to 40, more preferably 9 to 30, and further preferably 9, 10, 12, 15, 20 or 30; the m is preferably 0 to 0.9, more preferably 0, 0.62, 0.68, 0.81, 0.86 or 0.9; the n is preferably 0 to 0.75, more preferably 0, 0.05, 0.16, 0.65 or 0.75; the q is preferably 0.10 to 1, more preferably 0.1, 0.14, 0.16, 0.22, 0.25, 0.35 or 1. By adopting the viologen - based ionic polymer binder with the structure of formula I, the present invention can not only endow the binder with good adhesiveness, but also promote the conduction of lithium ions, which is beneficial to improving the capacity retention rate and cycle stability of the battery.

[0038] The present invention also provides a preparation method of the viologen - based ionic polymer binder described in the above technical solution, including: mixing a viologen - based acrylate, an acrylate and / or a methoxypolyethylene glycol acrylate, an initiator and a first solvent, and carrying out a free - radical polymerization reaction to obtain the viologen - based ionic polymer binder;

[0039] The viologen - based acrylate has a chemical structure as shown in formula II:

[0040]

[0041] In the formula II, R4 is hydrogen or methyl; R 5 is an alkyl group; X is a methylene group, a methylene ester group or a methylene carbamate group; Y is PF 6 - 、BF 4 - 、Br - 、I - 、CH 3 SO 3 - 、CF 3 SO 3 - or (CF 3 SO 2 ) 2 N - 。

[0042] In the present invention, unless otherwise specified, the materials used in the present invention can be commercial products well-known to those skilled in the art.

[0043] In the present invention, the preparation method of the viologen-based acrylate preferably includes the following steps:

[0044] (1) Mix 4,4'-bipyridine, an alkylating agent and a second solvent to carry out a first alkylation reaction to obtain an N-alkyl-4,4'-bipyridinium salt;

[0045] (2) Mix the N-alkyl-4,4'-bipyridinium salt obtained in step (1) with a 1-haloalkyl-1'-alcohol and a third solvent to carry out a second alkylation reaction to obtain a 1-(hydroxyalkyl)-1'-alkyl viologen salt (1);

[0046] (3) Mix the 1-(hydroxyalkyl)-1'-alkyl viologen salt (1) obtained in step (2) with a salt containing different anions and a fourth solvent to carry out an ion exchange reaction to obtain a 1-(hydroxyalkyl)-1'-alkyl viologen salt (2);

[0047] (4) Mix the 1-(hydroxyalkyl)-1'-alkyl viologen salt (2) obtained in step (3) with a vinyl carbonyl compound, a catalyst, an inhibitor and a fifth solvent to carry out an esterification reaction to obtain a viologen-based acrylate.

[0048] The present invention preferably mixes 4,4'-bipyridine, an alkylating agent and a second solvent to carry out a first alkylation reaction to obtain an N-alkyl-4,4'-bipyridinium salt.

[0049] In the present invention, the alkylating agent preferably includes at least one of methyl iodide, dimethyl sulfate, dimethyl carbonate, ethyl iodide, diethyl sulfate, diethyl carbonate, propyl iodide, dipropyl sulfate, and dipropyl carbonate. In the present invention, the above alkylating agent is selected to carry out an alkylation reaction with 4,4'-bipyridine to form an N-alkyl-4,4'-bipyridinium salt.

[0050] In the present invention, the second solvent preferably includes at least one of dichloroethane, tetrahydrofuran, dichloromethane, toluene, and chloroform. By selecting the solvents of the above types in the present invention, they have good solubility in 4,4'-bipyridine and the alkylating agent, which is more conducive to the full progress of the first alkylation reaction.

[0051] In the present invention, the mass ratio of 4,4'-bipyridine, the alkylating agent, and the second solvent is preferably (160 - 250):(150 - 240):4000, more preferably (190 - 240):(200 - 230):4000, and most preferably (195 - 235):(210 - 225):4000. By adopting the above mass ratio in the present invention, the formation of N,N-dialkyl-4,4'-bipyridinium salt can be avoided, which is beneficial to the formation of N-alkyl-4,4'-bipyridinium salt.

[0052] The present invention has no special limitation on the method of mixing 4,4'-bipyridine, the alkylating agent, and the second solvent. By using a conventional mixing method, each component can be fully dissolved. In the present invention, the mixing of 4,4'-bipyridine, the alkylating agent, and the second solvent is preferably carried out under stirring conditions.

[0053] In the present invention, the temperature of the first alkylation reaction is preferably 10 - 35 °C, more preferably 15 - 30 °C, and most preferably 20 - 30 °C; the time of the first alkylation reaction is preferably 1 - 24 h, more preferably 8 - 20 h, and most preferably 10 - 13 h. By controlling the temperature and time of the first alkylation reaction in the present invention, the formation of N,N-dialkyl-4,4'-bipyridinium salt can be avoided, which is beneficial to the formation of N-alkyl-4,4'-bipyridinium salt.

[0054] The present invention preferably mixes the product obtained from the first alkylation reaction with a first precipitant, and then filters and dries it in sequence to obtain an N-alkyl-4,4'-bipyridinium salt.

[0055] In the present invention, the first precipitant preferably includes at least one of ether, n-hexane, and cyclohexane. In the present invention, when the first precipitant is two or more of the above, the present invention has no special limitation on the proportional relationship between the two or more, and they can be mixed in any ratio. In the present invention, using the first precipitant can separate the N-alkyl-4,4'-bipyridinium salt from the reaction solution.

[0056] In the present invention, the mass ratio of the first precipitating agent to the product obtained from the first alkylation reaction is preferably 4 to 11:1, more preferably 5 to 10:1. By controlling the amount of the first precipitating agent within the above range, the product of the first alkylation reaction can be fully precipitated in the present invention.

[0057] The present invention has no special limitation on the operations of filtration and drying, and the operations well-known to those skilled in the art can be adopted. In the present invention, the drying temperature is preferably 40 to 70 °C, more preferably 50 to 60 °C; the drying time is preferably 8 to 15 h, more preferably 10 to 12 h.

[0058] After obtaining the N-alkyl-4,4'-bipyridinium salt, the present invention preferably mixes the N-alkyl-4,4'-bipyridinium salt with 1-haloalkyl-1'-ol and a third solvent to carry out a second alkylation reaction to obtain 1-(hydroxyalkyl)-1'-alkylviologen salt (1).

[0059] In the present invention, the 1-haloalkyl-1'-ol is preferably at least one of 2-bromoethanol, 2-chloroethanol, 3-bromo-1-propanol, 3-chloro-1-propanol, 4-bromo-1-butanol, 4-chloro-1-butanol, 5-bromo-1-pentanol, 5-chloro-1-pentanol, 6-bromo-1-hexanol, 6-chloro-1-hexanol, 7-bromo-1-heptanol, 7-chloro-1-heptanol, 8-bromo-1-octanol, and 8-chloro-1-octanol. By selecting the above 1-haloalkyl-1'-ol, the present invention can form 1-(hydroxyalkyl)-1'-alkylviologen salt (1) with the N-alkyl-4,4'-bipyridinium salt.

[0060] In the present invention, the third solvent is preferably at least one of acetonitrile, N-methylpyrrolidone, N,N-dimethylformamide, and dimethyl sulfoxide.

[0061] In the present invention, the mass ratio of the N-alkyl-4,4'-bipyridinium salt, 1-haloalkyl-1'-ol, and the third solvent is preferably (390 to 420):(190 to 230):4000, more preferably (390 to 410):(195 to 230):4000.

[0062] The present invention has no special limitation on the mixing of the N-alkyl-4,4'-bipyridinium salt, 1-haloalkyl-1'-ol, and the third solvent. A conventional mixing method can be adopted to fully dissolve the above components.

[0063] In the present invention, the temperature of the second alkylation reaction is preferably 50 to 100 °C, more preferably 70 to 90 °C; the time of the second alkylation reaction is preferably 12 to 72 h, more preferably 40 to 65 h, and most preferably 50 to 63 h.

[0064] The present invention preferably mixes the product obtained from the second alkylation reaction with a second precipitating agent, and then filters and dries it in sequence to obtain 1-(hydroxyalkyl)-1'-alkylviologen salt (1).

[0065] In the present invention, the second precipitating agent is preferably at least one of dichloromethane, dichloroethane, diethyl ether, and n-hexane. When the second precipitating agent is two or more of the above, the present invention has no special limitation on the proportional relationship between the two or more, and they can be mixed in any ratio.

[0066] In the present invention, the mass ratio of the second precipitating agent to the product obtained from the second alkylation reaction is preferably 4-11:1, more preferably 6-11:1. In the present invention, the methods and parameters of the filtration and drying are the same as those of the filtration and drying after the product obtained from the first alkylation reaction is mixed with the first precipitating agent in the above technical solution, and will not be elaborated here.

[0067] After obtaining 1-(hydroxyalkyl)-1'-alkylviologen salt (1), the present invention preferably mixes the 1-(hydroxyalkyl)-1'-alkylviologen salt (1) with a salt containing different anions and a fourth solvent to carry out an ion exchange reaction to obtain 1-(hydroxyalkyl)-1'-alkylviologen salt (2). In the present invention, the salt containing different anions is preferably KPF 6 , NaPF 6 , NH 4 PF 6 , NaBF 4 , KBF 4 , NaBr, KBr, NaI, KI, Na 2 SO 4 , Na 2 CO 3 , K 2 CO 3 , CH 3 SO 3 Na, CF 3 SO 3 Na and (CF 3 SO 2 ) 2 NLi, and when the salt containing different anions is two or more of the above, the present invention has no special limitation on the proportional relationship between the two or more, and they can be mixed in any ratio. By selecting the above types of salts containing different anions, the present invention is more conducive to making the anion bind to the viologen quaternary ammonium salt cation through the ion exchange reaction, thereby forming 1-(hydroxyalkyl)-1'-alkylviologen salt (2).

[0068] In the present invention, the fourth solvent is preferably at least one of deionized water, ethanol, N-methylpyrrolidone, N,N-dimethylformamide, and dimethyl sulfoxide. By using the above solvents, the present invention has good solubility for 1-(hydroxyalkyl)-1'-alkylviologen salt (1) and salts containing different anions, and promotes the full progress of the ion exchange reaction.

[0069] In the present invention, the mass ratio of 1-(hydroxyalkyl)-1'-alkylviologen salt (1), the salt containing different anions, and the fourth solvent is preferably (540 - 700):(470 - 1000):5000, and more preferably (550 - 570):(500 - 900):5000. By controlling the mass ratio of 1-(hydroxyalkyl)-1'-alkylviologen salt (1), the salt containing different anions, and the fourth solvent within the above range, it is more beneficial for the salt containing different anions to fully contact 1-(hydroxyalkyl)-1'-alkylviologen salt (1) and undergo an ion exchange reaction.

[0070] There is no special limitation on the operation of mixing 1-(hydroxyalkyl)-1'-alkylviologen salt (1), the salt containing different anions, and the fourth solvent in the present invention, and the technical solutions for preparing a mixed material well-known to those skilled in the art can be adopted.

[0071] In the present invention, the temperature of the ion exchange reaction is preferably 10 - 35°C, and more preferably 20 - 30°C; the time of the ion exchange reaction is preferably 1 - 12 h, and more preferably 8 - 11 h.

[0072] The present invention preferably mixes the product obtained from the ion exchange reaction with a third precipitant, and then filters and dries in sequence to obtain 1-(hydroxyalkyl)-1'-alkylviologen salt (2).

[0073] In the present invention, the third precipitant is preferably at least one of dichloromethane, dichloroethane, ethanol, ether, deionized water, and methanol. When the third precipitant is two or more of the above, there is no special limitation on the proportional relationship between the two or more, and they can be mixed in any ratio. The present invention uses the third precipitant to separate 1-(hydroxyalkyl)-1'-alkylviologen salt (2) from the reaction solution.

[0074] In the present invention, the mass ratio of the third precipitant to the product obtained from the ion exchange reaction is preferably 4 - 11:1, and more preferably 5 - 10:1.

[0075] In the present invention, the temperature of the drying is preferably 50 - 70°C, and more preferably 55 - 60°C; the time of the drying is preferably 20 - 25 h, and more preferably 24 - 25 h.

[0076] After obtaining 1-(hydroxyalkyl)-1'-alkyl viologen salt (2), the present invention preferably mixes the 1-(hydroxyalkyl)-1'-alkyl viologen salt (2) with a vinyl carbonyl compound, a catalyst, an inhibitor, and a fifth solvent to carry out an esterification reaction to obtain a viologen-based acrylate.

[0077] In the present invention, the vinyl carbonyl compound is preferably at least one of 2-isocyanatoethyl acrylate, isocyanatoethyl methacrylate, acrylic acid, methacrylic acid, acryloyl chloride, and methacryloyl chloride. By selecting the above-mentioned vinyl carbonyl compound, the present invention can form a viologen-based acrylate.

[0078] In the present invention, the catalyst is preferably at least one of dibutyltin dilaurate, triethylamine, sodium carbonate, and potassium carbonate.

[0079] In the present invention, the inhibitor is preferably at least one of p-methoxyphenol, p-benzoquinone, and hydroquinone. When the inhibitor is two or more of the above, the present invention has no special limitation on the proportional relationship between the two or more, and any ratio can be mixed.

[0080] In the present invention, the fifth solvent is preferably at least one of N-methylpyrrolidone, N,N-dimethylformamide, tetrahydrofuran, 1,4-dioxane, acetonitrile, and chloroform. When the solvent is two or more of the above, the present invention has no special limitation on the proportional relationship between the two or more, and any ratio can be mixed.

[0081] In the present invention, the mass ratio of the 1-(hydroxyalkyl)-1'-alkyl viologen salt (2), the vinyl carbonyl compound, the catalyst, the inhibitor, and the fifth solvent is preferably (600-1500):(130-310):(0.5-7.0):(1-2.5):5000, more preferably (610-1400):(140-300):(0.5-5.0):(1-1.5):5000.

[0082] The present invention has no special limitation on the operation of mixing the 1-(hydroxyalkyl)-1'-alkyl viologen salt (2), the vinyl carbonyl compound, the catalyst, the inhibitor, and the fifth solvent. The technical scheme of preparing a mixed material well-known to those skilled in the art can be adopted to fully dissolve each component.

[0083] In the present invention, the temperature of the esterification reaction is preferably 10-35°C, more preferably 20-30°C; the time of the esterification reaction is preferably 1-36 h, more preferably 20-25 h. By controlling the temperature and time of the esterification reaction within the above ranges, the present invention can not only avoid the occurrence of side reactions but also ensure that the raw materials react fully to form a viologen-based acrylate.

[0084] Preferably, in the present invention, the product obtained from the esterification reaction is mixed with a fourth precipitating agent, and then filtered and dried in sequence to obtain a viologen-based acrylate.

[0085] In the present invention, the fourth precipitating agent is preferably at least one of dichloroethane, ethanol, ether, and methanol.

[0086] In the present invention, the mass ratio of the fourth precipitating agent to the product obtained from the esterification reaction is preferably 4 - 11:1, more preferably 5 - 10:1.

[0087] In the present invention, the drying temperature is preferably 20 - 30°C, more preferably 25 - 30°C; the drying time is preferably 15 - 25 h, more preferably 18 - 24 h.

[0088] In the present invention, the acrylate is preferably at least one of ethyl methacrylate, ethyl acrylate, butyl acrylate, and butyl methacrylate. By selecting the above types of acrylates, the present invention can not only improve the flexibility of the binder and soften the electrode sheet, but also enhance the hydrophobicity of the binder and avoid the problem of decreased battery capacity and cycling performance caused by water absorption of the binder.

[0089] In the present invention, on the one hand, the segment of the polyethylene glycol monomethyl ether acrylate can enhance the flexibility of the binder; on the other hand, due to its good lithium ion transport ability, it can improve the ion transport performance between the electrode sheet and the electrolyte interface and reduce the interface impedance.

[0090] In the present invention, the initiator is preferably at least one of azobisisobutyronitrile, azobiscyclohexylcarbonitrile, dimethyl azobisisobutyrate, and benzoyl peroxide. When two or more of the above initiators are used, the present invention has no special limitation on the proportional relationship between the two or more, and they can be mixed in any ratio.

[0091] In the present invention, the mass of the initiator preferably accounts for 0.05 - 0.15% of the sum of the masses of the viologen-based acrylate, acrylate, and / or polyethylene glycol monomethyl ether acrylate. In the present invention, controlling the amount of the initiator within the above range can improve the degree of free radical polymerization reaction.

[0092] In the present invention, the first solvent is preferably at least one of acetonitrile, toluene, acetone, N-methylpyrrolidone, N,N-dimethylformamide, tetrahydrofuran, 1,4-dioxane, and chloroform. When the solvent is two or more of the above, the present invention has no special limitation on the proportion relationship between the two or more, and they can be mixed in any ratio. The present invention has no special limitation on the dosage of the first solvent, as long as the total mass concentration of the viologen-based acrylate, acrylate, and / or methoxypolyethylene glycol acrylate is in the range of 20-40%.

[0093] In the present invention, the mass ratio of the viologen-based acrylate, acrylate, methoxypolyethylene glycol acrylate, initiator, and first solvent in the free radical polymerization reaction is preferably (100-500):(0-600):(0-800):(0.3-1.5):(1000-5000), more preferably (200-500):(0-580):(0-700):(0.4-1.3):(1000-2800). By controlling the components within the above ranges, the present invention is more conducive to forming an ionic polymer binder with excellent adhesion performance.

[0094] In the present invention, the temperature of the free radical polymerization reaction is preferably 50-80°C, more preferably 65-75°C; the time of the free radical polymerization reaction is preferably 8-12 h, more preferably 9-11 h. By controlling the above parameters of the free radical polymerization reaction, the present invention can further improve the degree of the polymerization reaction.

[0095] In the present invention, the free radical polymerization reaction is preferably carried out in an inert atmosphere. In the present invention, the gas of the inert atmosphere is preferably nitrogen and / or argon. In the present invention, the inert gas can avoid the interference of air on the free radical polymerization reaction to ensure that the polymer obtained by free radical polymerization has good performance.

[0096] The present invention preferably mixes the product obtained from the free radical polymerization reaction with a fifth precipitating agent, and then filters and dries it in sequence to obtain a viologen-based ionic polymer binder.

[0097] In the present invention, the fifth precipitating agent is preferably at least one of ether, ethanol, acetone, and methanol. When the fifth precipitating agent is two or more of the above, the present invention has no special limitation on the proportion relationship between the two or more, and they can be mixed in any ratio. In the present invention, the volume ratio of the fifth precipitating agent to the volume of the system obtained from the free radical polymerization reaction is preferably 4-11:1, more preferably 5-10:1.

[0098] In the present invention, the drying temperature is preferably 30 to 60 °C, more preferably 50 to 60 °C; the drying time is preferably 1 to 24 h, more preferably 12 to 24 h.

[0099] The preparation method provided by the present invention is simple to operate and can introduce viologen-based acrylate into the ionic polymer binder. The electrostatic interaction between the quaternary ammonium cation and the counter anion in the viologen structure and the active material can enhance the adhesion between materials; the counter anion can promote the conduction of lithium ions; viologen has a stable structure and reversible redox characteristics, which is beneficial to improving the capacity retention rate and cycle stability of the battery when the ionic polymer is used as the binder for the positive electrode sheet of the lithium-ion battery. Acrylate can not only improve the flexibility of the binder, soften the electrode sheet, but also enhance the hydrophobicity of the binder, avoiding the problems of decreased battery capacity and cycle performance caused by water absorption of the binder. Methoxypolyethylene glycol acrylate can enhance the flexibility of the binder on the one hand; on the other hand, due to its good lithium ion transport ability, it can improve the ion transport performance between the electrode sheet and the electrolyte interface and reduce the interface impedance.

[0100] The present invention also provides the application of the viologen-based ionic polymer binder described in the above technical solution or the viologen-based ionic polymer binder prepared by the preparation method described in the above technical solution in the lithium-ion battery electrode sheet.

[0101] In the present invention, the lithium-ion battery electrode sheet is preferably a positive electrode sheet or a negative electrode sheet.

[0102] In the present invention, the preparation method of the lithium-ion battery electrode sheet preferably includes the following steps:

[0103] 1) Dissolve the viologen-based ionic polymer binder in an organic solvent to obtain a binder solution;

[0104] 2) Mix the electrode active material and the conductive agent to obtain a mixed powder;

[0105] 3) Mix the binder solution obtained in step 1), the mixed powder obtained in step 2) with an organic solvent to obtain an electrode paste;

[0106] 4) Coat the electrode paste obtained in step 3) on a current collector to obtain a lithium-ion battery electrode sheet.

[0107] The present invention preferably dissolves the viologen-based ionic polymer binder in an organic solvent to obtain a binder solution.

[0108] In the present invention, the organic solvent is preferably one or more of N-methylpyrrolidone, N,N-dimethylformamide, dimethyl sulfoxide and acetonitrile.

[0109] The present invention has no special limitation on the dosage of the organic solvent, as long as the viscosity of the binder solution can be within the range of 0.1 to 20 Pa·s, preferably 10 to 15 Pa·s.

[0110] In the present invention, the temperature at which the viologen-based ionic polymer binder dissolves in the organic solvent is preferably 25 °C; the time for the viologen-based ionic polymer binder to dissolve in the organic solvent is preferably 8 to 12 h, more preferably 10 to 12 h.

[0111] The present invention preferably mixes the active material and the conductive agent to obtain a mixed powder.

[0112] In the present invention, the active material is preferably a positive electrode active material, and the positive electrode active material preferably includes one of lithium iron phosphate, lithium cobaltate, lithium manganate, ternary nickel cobalt manganese 811, ternary nickel cobalt manganese 523, ternary nickel cobalt aluminum 811, ternary nickel cobalt manganese 622, ternary nickel cobalt manganese 613 or lithium titanate. By adopting the above types of positive electrode active materials, the lithium ion battery can have good electrochemical performance.

[0113] In the present invention, the conductive agent preferably includes one or more of superconducting carbon black, carbon nanotubes, acetylene black and Ketjen black. By selecting the above types of conductive agents, the lithium ion battery can have good electrochemical performance.

[0114] In the present invention, the method for mixing the positive electrode active material and the conductive agent preferably includes: at room temperature, ball-milling the positive electrode active material and the conductive agent at a rotation speed of 600 to 1200 rpm for 0.5 to 4 h, preferably ball-milling at a rotation speed of 900 to 1100 rpm for 0.5 to 1.5 h. In the present invention, adopting the above mixing method can make the positive electrode active material and the conductive agent mix evenly.

[0115] After obtaining the binder solution and the mixed powder, the present invention preferably mixes the binder solution, the mixed powder and the organic solvent to obtain an electrode paste.

[0116] In the present invention, the organic solvent is preferably one or more of N-methylpyrrolidone, N,N-dimethylformamide, dimethyl sulfoxide and acetonitrile. By adopting the above organic solvents, the electrode paste can be mixed more evenly.

[0117] In the present invention, the mass ratio of the positive electrode active material, the conductive agent and the viologen-based ionic polymer binder in the electrode paste is preferably (60 to 100):(1 to 20):(1 to 20), more preferably (75 to 96):(2 to 15):(2 to 15).

[0118] The present invention has no special limitation on the dosage of the organic solvent, and it can be adjusted as needed. In the present invention, when the mass ratio of the positive active material, the conductive agent and the viologen-based ionic polymer binder in the electrode paste is (60-100):(1-20):(1-20), the total mass concentration of the mixed powder and the binder in the electrode paste is preferably 30-95 wt%, more preferably 30-85 wt%. By controlling the electrode paste within the above concentration range, the present invention can make the electrode paste easier to coat and make the thickness of the obtained positive electrode sheet more uniform.

[0119] The present invention has no special limitation on the method of mixing the binder solution, the mixed powder and the organic solvent. A conventional mixing method can be used as long as a uniform electrode paste can be formed. In the present invention, the mixing of the binder solution, the mixed powder and the organic solvent preferably includes: ball milling the mixed powder and the binder solution in a ball mill at a rotation speed of 900-1100 rpm for 2-4 h, preferably at a rotation speed of 1000-1100 rpm for 2-3 h; then adding the organic solvent and continuing to ball mill for 1-3 h, preferably for 2-3 h. By adopting the above mixing operation and controlling the parameters within the above range, the present invention is more conducive to the uniform mixing of each raw material.

[0120] After obtaining the electrode paste, the present invention preferably coats the electrode paste on a current collector to obtain a lithium-ion battery electrode sheet.

[0121] In the present invention, the current collector is preferably aluminum foil. The present invention has no special limitation on the size of the aluminum foil, and it can be adjusted according to actual needs.

[0122] The present invention has no special limitation on the coating method, and a conventional coating method can be used. In the present invention, the coating is preferably doctor blade coating. The present invention has no special limitation on the model of the doctor blade used for doctor blade coating, and an instrument well-known to those skilled in the art can be used.

[0123] The present invention has no special limitation on the dosage of the electrode paste coated on the current collector, and it can be adjusted according to needs. In the present invention, the dosage of the electrode paste can make the thickness of the paste layer on the obtained positive electrode sheet reach 60-250 μm.

[0124] The present invention preferably dries, rolls and cuts the product obtained by coating in sequence to obtain a lithium-ion battery electrode sheet. By drying, rolling and cutting, the present invention can obtain a flat and appropriately sized positive electrode sheet.

[0125] In the present invention, the drying preferably includes atmospheric drying or vacuum drying; the temperature of the atmospheric drying is preferably 50-90°C, more preferably 60-80°C; the time of the atmospheric drying is preferably 6-10h, more preferably 8-9h; the temperature of the vacuum drying is preferably 70-90°C, more preferably 80-90°C; the time of the vacuum drying is preferably 8-15h, more preferably 9-12h. By controlling the drying temperature and time within the above ranges, the present invention is conducive to the full volatilization of the organic solvent and can avoid problems such as cracking and curling of the positive electrode plate of the lithium-ion battery caused by the volatilization of the organic solvent.

[0126] The present invention has no special limitation on the operations of rolling and cutting, and the operations well-known to those skilled in the art can be adopted.

[0127] The ionic polymer binder based on viologen provided by the present invention can enable the lithium-ion battery assembled with the positive electrode plate prepared by using it to have a lower interfacial impedance, a higher specific capacity, a higher capacity retention rate, and good cycle stability due to having viologen-based acrylate segments, acrylate segments, and methoxypolyethylene glycol acrylate segments.

[0128] Next, the technical solutions in the present invention will be clearly and completely described in conjunction with the embodiments in the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present invention without making creative efforts shall fall within the protection scope of the present invention.

[0129] Example 1

[0130] An ionic polymer binder based on viologen has a chemical structure shown in Formula I, and for R in Formula I 1 , R 3 , R 4 are all hydrogen, R 2 is butyl, R 5 is methyl, X is ethylenedicarbamate group, Y is PF 6 - , m = 0.68, n = 0.16, q = 0.16, p = 9;

[0131] The preparation method of the above ionic polymer binder based on viologen is as follows:

[0132] Under a nitrogen atmosphere, 500 g of viologen phosphate acrylate, 420 g of butyl acrylate, 373 g of methoxypolyethylene glycol acrylate, 1.29 g of azobisisobutyronitrile, and 3000 g of acetonitrile were mixed in a reaction kettle, and then radical polymerization was carried out at 70 °C. After reacting for 10 h, the above ionic polymer solution was precipitated into 45000 g of ethanol, filtered, and the filter cake was dried in a vacuum drying oven at 50 °C for 12 h to obtain 1150 g of a viologen-based ionic polymer binder, named A1;

[0133] The above viologen phosphate acrylate is 1-(2-(((2-(acryloyloxy)ethyl)carbamoyl)oxy)ethyl)-1'-methylviologen hexafluorophosphate, and its structural formula is:

[0134]

[0135] The preparation method of the above viologen phosphate acrylate is as follows:

[0136] (1) 200 g of 4,4'-bipyridine and 218 g of iodomethane were dissolved in 4000 g of dichloromethane, and then the first alkylation reaction was carried out by stirring at 25 °C for 12 h. After the reaction, the mixed system was precipitated into 44180 g of n-hexane, filtered, and the filter cake was vacuum dried at 50 °C for 12 h to obtain 395 g of a yellow solid, which is N-methyl-4,4'-bipyridine iodide;

[0137] (2) The N-alkyl-4,4'-bipyridine salt obtained in the step (1) was mixed and dissolved with 199 g of 2-bromoethanol and 4000 g of acetonitrile, and then the second alkylation reaction was carried out at 80 °C for 60 h. The mixed system was precipitated into 51000 g of dichloromethane, filtered, and the filter cake was vacuum dried at 50 °C for 12 h to obtain 552 g of a yellow solid, which is 1-(hydroxyalkyl)-1'-alkylviologen salt (1), that is, 1-(2-hydroxyethyl)-1'-methylviologen salt;

[0138] (3) 1-(hydroxyalkyl)-1'-alkylviologen salt (1) obtained in the step (2) was mixed and dissolved with 510 g of ammonium hexafluorophosphate and 5000 g of deionized water, and then the ion exchange reaction was carried out by stirring at 25 °C for 10 h. After the reaction, the mixed system was precipitated into 60620 g of deionized water, filtered, and the filter cake was vacuum dried at 60 °C for 24 h to obtain 620 g of a white solid, which is 1-(hydroxyalkyl)-1'-alkylviologen salt (2), that is, 1-(2-hydroxyethyl)-1'-methylviologen hexafluorophosphate;

[0139] (4) Under a nitrogen atmosphere, 1-(hydroxyalkyl)-1'-alkyl viologen salt (2) obtained in the step (3) is mixed and dissolved with 208 g of 2-isocyanatoethyl acrylate, 0.77 g of dibutyltin dilaurate, 1.32 g of p-benzoquinone, and 5000 g of 1,4-dioxane, and then stirred at 25 °C for 24 h for an esterification reaction. After the reaction, the mixed system is precipitated into 58300 g of ethanol, filtered, and the filter cake is dried in vacuo at 25 °C for 24 h to obtain 719 g of a white solid, which is viologen phosphate acrylate, that is, 1-(2-(((2-(acryloyloxy)ethyl)carbamoyl)oxy)ethyl)-1'-methyl viologen hexafluorophosphate;

[0140] The nuclear magnetic resonance hydrogen spectrum of 1-(2-(((2-(acryloyloxy)ethyl)carbamoyl)oxy)ethyl)-1'-methyl viologen hexafluorophosphate prepared in this example is as Figure 1 shown;

[0141] The nuclear magnetic resonance hydrogen spectrum of the viologen-based ionic polymer binder A1 prepared in this example is as Figure 2 shown.

[0142] Example 2

[0143] A viologen-based ionic polymer binder has a chemical structure shown in Formula I, where R 1 , R 3 , R 4 are all hydrogen, R 2 is butyl, R 5 is methyl, X is ethylenedicarbamate group, Y is (CF 3 SO 2 ) 2 N - , m = 0.68, n = 0.16, q = 0.16, p = 9;

[0144] The preparation method of the above viologen-based ionic polymer binder is as follows:

[0145] Under a nitrogen atmosphere, 500 g of viologen bis(trifluoromethanesulfonyl)imide salt acrylate, 277 g of butyl acrylate, 246 g of methoxypolyethylene glycol acrylate, 1.02 g of azobisisobutyronitrile, and 2377 g of acetonitrile are mixed in a reaction kettle, and then subjected to free radical polymerization at 70 °C. After reacting for 10 h, the above ionic polymer solution is precipitated into 10230 g of ethanol, filtered, and the filter cake is dried in a vacuum drying oven at 50 °C for 12 h to obtain 950 g of a viologen-based ionic polymer binder, named A2;

[0146] The above-mentioned viologen bis(trifluoromethanesulfonyl)imide acrylate is 1-(2-(((2-(acryloyloxy)ethyl)carbamoyl)oxy)ethyl)-1'-methylviologen bis(trifluoromethanesulfonyl)imide, and its structural formula is:

[0147]

[0148] The preparation steps of the above-mentioned viologen bis(trifluoromethanesulfonyl)imide acrylate are as follows:

[0149] (1) After mixing and dissolving 552 g of 1-(hydroxyalkyl)-1'-alkyl viologen salt (1), 898 g of lithium bis(trifluoromethanesulfonyl)imide and 5000 g of deionized water, stir at 25 °C for 10 h for an ion exchange reaction. After the reaction, precipitate the mixed system into 82800 g of deionized water, filter, and vacuum dry the filter cake at 60 °C for 24 h to obtain 1370 g of a white solid, which is 1-(hydroxyalkyl)-1'-alkyl viologen salt (2), namely 1-(2-hydroxyethyl)-1'-methylviologen bis(trifluoromethanesulfonyl)imide; (2) Under a nitrogen atmosphere, mix and dissolve the 1-(hydroxyalkyl)-1'-alkyl viologen salt (2) obtained in step (1) with 293 g of 2-isocyanatoethyl acrylate, 0.85 g of dibutyltin dilaurate, 1.43 g of p-benzoquinone and 5000 g of 1,4-dioxane, and stir at 25 °C for 24 h for an esterification reaction. After the reaction, precipitate the mixed system into 16700 g of ethanol, filter, and vacuum dry the filter cake at 25 °C for 24 h to obtain 1532 g of a white solid, which is viologen bis(trifluoromethanesulfonyl)imide acrylate, namely 1-(2-(((2-(acryloyloxy)ethyl)carbamoyl)oxy)ethyl)-1'-methylviologen bis(trifluoromethanesulfonyl)imide.

[0150] Example 3

[0151] A viologen-based ionic polymer binder has a chemical structure as shown in Formula I, and for R in Formula I 1 , R 3 , R 4 are all hydrogen, R 2 is ethyl, R 5 is methyl, X is dimethylene, Y is PF 6 - , m = 0.62, n = 0.16, p = 9, q = 0.22;

[0152] The preparation method of the above-mentioned viologen-based ionic polymer binder is as follows:

[0153] Under an argon atmosphere, 450 g of viologen phosphate acrylate, 94 g of ethyl acrylate, 277 g of polyethylene glycol monomethyl ether acrylate, 0.82 g of azobisisobutyronitrile, and 1860 g of N-methylpyrrolidone were mixed in a reaction kettle, and then radical polymerization was carried out at 70 °C. After reacting for 10 h, the above ionic polymer solution was precipitated into 32000 g of ethanol, filtered, and the filter cake was dried in a vacuum drying oven at 50 °C for 12 h to obtain 805 g of a viologen-based ionic polymer binder, named A3;

[0154] The above viologen phosphate acrylate is 1-((2-acryloyloxy)ethyl)-1'-methylviologen hexafluorophosphate, and its structural formula is:

[0155]

[0156] The preparation method of the above viologen phosphate acrylate is as follows:

[0157] (1) 230 g of 4,4'-bipyridine and 223 g of dimethyl sulfate were dissolved in 4000 g of dichloromethane, and then the first alkylation reaction was carried out by stirring at 25 °C for 12 h. After the reaction ended, the mixed system was precipitated into 44530 g of n-hexane, filtered, and the filter cake was dried in a vacuum at 50 °C for 12 h to obtain 405 g of a pale yellow solid, which is N-methyl-4,4'-bipyridine sulfate;

[0158] (2) The N-alkyl-4,4'-bipyridinium salt obtained in the step (1) was mixed and dissolved with 227 g of 2-bromoethanol and 4000 g of N-methylpyrrolidone, and then the second alkylation reaction was carried out by reacting at 90 °C for 60 h. The mixed system was precipitated into 51000 g of dichloromethane, filtered, and the filter cake was dried in a vacuum at 50 °C for 12 h to obtain 563 g of a pale yellow solid, which is 1-(hydroxyalkyl)-1'-alkylviologen salt (1), that is, 1-(2-hydroxyethyl)-1'-methylviologen salt;

[0159] (3) 1-(hydroxyalkyl)-1'-alkylviologen salt (1) obtained in the step (2) was mixed and dissolved with 557 g of ammonium hexafluorophosphate and 5000 g of deionized water, and then stirred at 25 °C for 10 h to carry out an ion exchange reaction. After the reaction ended, the mixed system was precipitated into 60000 g of deionized water, filtered, and the filter cake was dried in a vacuum at 60 °C for 24 h to obtain 690 g of a white solid, which is 1-(hydroxyalkyl)-1'-alkylviologen salt (2), that is, 1-(2-hydroxyethyl)-1'-methyl-viologen hexafluorophosphate;

[0160] (4) Under a nitrogen atmosphere, 1-(hydroxyalkyl)-1'-alkyl viologen salt (2) obtained in step (3) is mixed and dissolved with 149 g of acryloyl chloride, 4.9 g of triethylamine, 1.49 g of p-benzoquinone, and 5000 g of 1,4-dioxane, and then stirred at 25 °C for 24 h for an esterification reaction. After the reaction, the mixed system is precipitated into 58500 g of ethanol, filtered, and the filter cake is dried in vacuo at 25 °C for 24 h to obtain 839 g of a white solid, which is viologen phosphate acrylate, i.e., 1-((2-acryloyloxy)ethyl)-1'-methyl viologen hexafluorophosphate;

[0161] The 1H NMR spectrum of 1-((2-acryloyloxy)ethyl)-1'-methyl viologen hexafluorophosphate prepared in this example is as Figure 3 shown.

[0162] Example 4

[0163] An ionomeric polymer binder based on viologen has a chemical structure as shown in Formula I, where R 1 , R 3 , R 4 are all hydrogen, R 2 is butyl, R 5 is methyl, X is ethylenedicarbamate group, Y is PF 6 - , m = 0.81, n = 0.05, p = 9, q = 0.14;

[0164] The preparation method of the above ionomeric polymer binder based on viologen is as follows:

[0165] Under a nitrogen atmosphere, 500 g of viologen phosphate acrylate (the same as the reactant in Example 1), 573 g of butyl acrylate, 134 g of methoxypolyethylene glycol acrylate, 1.21 g of azobis(cyclohexanecarbonitrile), and 2800 g of acetonitrile are mixed in a reaction kettle, and then radical polymerization is carried out at 70 °C. After 10 h of reaction, the above ionomeric polymer solution is precipitated into 42000 g of ethanol, filtered, and the filter cake is dried in a vacuum drying oven at 50 °C for 12 h to obtain 1050 g of an ionomeric polymer binder based on viologen, named A4.

[0166] Example 5

[0167] An ionomeric polymer binder based on viologen has a chemical structure as shown in Formula I, where R 1 , R 4 are all hydrogen, R 2 is butyl, R 5 is methyl, X is ethylenedicarbamate group, Y is PF 6 -, m = 0.9, n = 0, p = 0, q = 0.1;

[0168] The preparation method of the above-mentioned viologen-based ionic polymer binder is as follows:

[0169] Under a nitrogen atmosphere, 200 g of viologen phosphate acrylate (the same reactant as in Example 1), 356 g of butyl acrylate, 0.56 g of azobisisobutyronitrile, and 1280 g of acetonitrile were mixed in a reaction kettle, and then radical polymerization was carried out at 70 °C. After reacting for 10 h, the above-mentioned ionic polymer solution was precipitated into 16000 g of ethanol, filtered, and the filter cake was dried in a vacuum drying oven at 50 °C for 12 h to obtain 530 g of a viologen-based ionic polymer binder, named A5;

[0170] The 1H NMR spectrum of the viologen-based ionic polymer binder A5 prepared in this example is as Figure 4 shown.

[0171] Example 6

[0172] A viologen-based ionic polymer binder has a chemical structure as shown in Formula I, where R corresponding to Formula I 1 , R 4 are both hydrogen, R 2 is butyl, R 5 is methyl, X is ethylenedicarbamate group, Y is PF 6 - , m = 0.86, n = 0, p = 0, q = 0.14;

[0173] The preparation method of the above-mentioned viologen-based ionic polymer binder is as follows:

[0174] Under a nitrogen atmosphere, 200 g of viologen phosphate acrylate (the same reactant as in Example 1), 243 g of butyl acrylate, 0.44 g of azobisisobutyronitrile, and 1008 g of acetonitrile were mixed in a reaction kettle, and then radical polymerization was carried out at 70 °C. After reacting for 10 h, the above-mentioned ionic polymer solution was precipitated into 15000 g of ethanol, filtered, and the filter cake was dried in a vacuum drying oven at 50 °C for 12 h to obtain 429 g of a viologen-based ionic polymer binder, named A6.

[0175] Example 7

[0176] A viologen-based ionic polymer binder has a chemical structure as shown in Formula I, where R corresponding to Formula I 3 and R 4 are both hydrogen, R 5 is methyl, X is ethylenedicarbamate group, Y is PF 6 -, m = 0, n = 0.65, p = 9, q = 0.35;

[0177] The preparation method of the above-mentioned viologen-based ionic polymer binder is as follows:

[0178] Under an argon atmosphere, 500 g of viologen phosphate acrylate (the same as the reactant in Example 1), 696 g of polyethylene glycol monomethyl ether acrylate, 1.19 g of azobisisobutyronitrile, and 2790 g of N-methylpyrrolidone were mixed in a reaction kettle, and then radical polymerization was carried out at 70 °C. After reacting for 10 h, the above ionic polymer solution was precipitated into 35000 g of ethanol, filtered, and the filter cake was dried in a vacuum drying oven at 50 °C for 12 h to obtain 1100 g of a viologen-based ionic polymer binder, named A7.

[0179] Example 8

[0180] A viologen-based ionic polymer binder has a chemical structure as shown in Formula I. For R in Formula I 3 , R 4 are both hydrogen, R 5 is methyl, X is ethylenedicarbamate group, Y is PF 6 - , m = 0, n = 0.75, p = 9, q = 0.25;

[0181] The preparation method of the above-mentioned viologen-based ionic polymer binder is as follows:

[0182] Under an argon atmosphere, 250 g of viologen phosphate acrylate (the same as the reactant in Example 1), 562 g of polyethylene glycol monomethyl ether acrylate, 0.81 g of azobisisobutyronitrile, and 1815 g of N-methylpyrrolidone were mixed in a reaction kettle, and then radical polymerization was carried out at 70 °C. After reacting for 10 h, the above ionic polymer solution was precipitated into 37500 g of ethanol, filtered, and the filter cake was dried in a vacuum drying oven at 50 °C for 12 h to obtain 758 g of a viologen-based ionic polymer binder, named A8.

[0183] Example 9

[0184] A viologen-based ionic polymer binder has a chemical structure as shown in Formula I. For R in Formula I 4 is hydrogen, R 5 is methyl, X is ethylenedicarbamate group, Y is PF 6 - , m = 0, n = 0, p = 0, q = 1;

[0185] The preparation method of the above-mentioned viologen-based ionic polymer binder is as follows:

[0186] Under an argon atmosphere, 500 g of viologen phosphate acrylate (the same reactant as in Example 1), 0.5 g of azobisisobutyronitrile, and 1166 g of N,N-dimethylformamide were mixed in a reaction kettle, and then radical polymerization was carried out at 70 °C. After reacting for 10 h, the above ionic polymer solution was precipitated into 17000 g of ethanol, filtered, and the filter cake was dried in a vacuum drying oven at 50 °C for 12 h to obtain 460 g of a viologen-based ionic polymer binder, named A9.

[0187] Comparative Example 1

[0188] 300 g of dry polyvinylidene fluoride (PVDF) (HSV900) powder and 2700 g of N-methylpyrrolidone were mixed in a reaction kettle and stirred at 25 °C for 10 h to prepare a PVDF binder solution, denoted as B1.

[0189] Comparative Example 2

[0190] 400 g of sodium carboxymethyl cellulose powder (Shenzhen Kejing, MAC500LC), 1712 g of styrene-butadiene rubber latex (Shenzhen Kejing, S2919, mass fraction of polymer is 35%), and 9000 g of pure water (resistivity greater than 0.1 MΩ·cm) were mixed in a reaction kettle and stirred at 25 °C for 10 h to obtain a binder solution, denoted as B2.

[0191] Application Examples 1-9

[0192] Lithium-ion battery positive electrode sheets were respectively prepared using the viologen-based ionic polymer binders prepared in Examples 1-9. The specific steps are as follows:

[0193] 1) Add 10 g of the viologen-based ionic polymer binder and 90 g of N-methylpyrrolidone into a container, and stir at 25 °C for 10 h until the polymer is completely dissolved to obtain a binder solution;

[0194] 2) Ball-mill 80 g of lithium iron phosphate and 10 g of superconducting carbon black at a rotation speed of 1032 rpm for 1 h to obtain a mixed powder;

[0195] 3) Add the 100 g of binder solution obtained in step 1) to the mixed powder obtained in step 2), ball-mill at a rotation speed of 1032 rpm for 3 h, then add 80 g of N-methylpyrrolidone, and continue to ball-mill for 2 h to obtain an electrode slurry;

[0196] 4) Apply the electrode slurry obtained in step 3) onto the aluminum foil using a doctor blade. First, dry it at 60 °C under normal pressure for 8 h, then dry it at 80 °C under normal pressure for 8 h, and finally dry it at 80 °C under vacuum for 12 h. Then, roll press and cut it successively to prepare lithium iron phosphate positive electrode sheets C1 to C9 (the positive electrode sheet prepared with the viologen-based ionic polymer binder A1 in Example 1 is denoted as C1, and so on).

[0197] Comparative Application Example 1

[0198] Prepare a lithium-ion battery positive electrode sheet using the PVDF binder B1 prepared in Comparative Example 1. The difference from Application Example 1 is that B1 prepared in Comparative Example 1 is used as the binder solution, and the remaining steps are the same as those in Application Example 1. A lithium iron phosphate positive electrode sheet is prepared and denoted as C10.

[0199] Comparative Application Example 2

[0200] Prepare a lithium-ion battery artificial graphite negative electrode sheet using the binder B2 prepared in Comparative Example 2. The specific steps are as follows: Ball mill 188 g of artificial graphite and 6 g of superconducting carbon black at a rotation speed of 1032 rpm for 1 h to obtain a mixed powder; Ball mill the obtained mixed powder with 60 g of the binder solution B2 prepared in Comparative Example 2 at a rotation speed of 1032 rpm for 3 h, add 136 g of pure water (resistivity greater than 0.1 MΩ·cm), and continue to ball mill for 2 h to obtain a negative electrode slurry; Use the method in step 4) of Application Example 1 for coating and drying to obtain a lithium-ion battery artificial graphite negative electrode sheet, numbered C11.

[0201] Test Example 1

[0202] Conduct the following performance tests on the viologen-based ionic polymer binders prepared in Examples 1 to 9 and the binder prepared in Comparative Example 1:

[0203] Viscosity-average molecular weight M η Determined according to the test method of GB / T 10247-2008;

[0204] The thermal decomposition temperature is determined by a thermogravimetric analyzer (Netzsch, Germany, TG209). Under a nitrogen atmosphere, it is heated from 25 °C to 600 °C at a heating rate of 10 °C·min -1 ;

[0205] The glass transition temperature is measured by a differential scanning calorimeter (TA DSC Q100). Under a nitrogen atmosphere, the temperature range is from -80 °C to 180 °C, and the heating / cooling rate is ±10 °C·min -1 . The test results of the binder performance are shown in Table 1.

[0206] Table 1 Performance indicators of the binder

[0207] Binder <![CDATA[M η (Da)]]> <![CDATA[T d (℃)]]> <![CDATA[T g (℃)]]> A1 <![CDATA[3.9×10 4 > 318.7 -43.5 A2 <![CDATA[4.0×10 4 > 317.8 -45.3 A3 <![CDATA[3.3×10 4 > 323.5 -44.6 A4 <![CDATA[2.8×10 4 > 322.5 -44.7 A5 <![CDATA[3.3×10 4 > 326.3 -45.1 A6 <![CDATA[3.2×10 4 > 324.2 -43.8 A7 <![CDATA[4.1×10 4 > 326.3 -44.4 A8 <![CDATA[3.8×10 4 > 325.7 -43.2 A9 <![CDATA[2.0×10 4 > 325.5 24.5 B1 <![CDATA[5.0×10 5 > 316.0 -47.0

[0208] Figure 5 Differential scanning calorimetry curve of the viologen-based ionic polymer binder A5 prepared in Example 5. It can be seen from Figure 5 Table 1 that the viscosity-average molecular weight of the viologen-based ionic polymer binder prepared in the present invention is lower than that of the commercial PVDF molecular weight. Therefore, it can be expected that under the same conditions, the slurry prepared with the viologen-based ionic polymer binder of the present invention has a lower viscosity and is easier to coat; the thermal decomposition temperature of the viologen-based ionic polymer binder prepared in the present invention is slightly higher than that of PVDF (316.0 °C). Therefore, the prepared positive electrode sheet has good heat resistance and meets the needs of the battery to operate under high temperature conditions; the glass transition temperature of the viologen-based ionic polymer binder prepared in the present invention is similar to that of PVDF (-47.0 °C) (except for binder A5, whose glass transition temperature is 24.5 °C). Therefore, the prepared positive electrode sheet has good flexibility.

[0209] Test Example 2

[0210] The method for assembling a battery using the LiFePO₄ electrode sheets C1 to C10 is as follows: Lithium hexafluorophosphate (LiPF 6 ) is dissolved in a solution composed of ethylene carbonate (EC), dimethyl carbonate (DMC), and diethyl carbonate (EMC) with a volume ratio of 1:1:1 as the electrolyte (where the concentration of LiPF 6 is 1 mole / liter); a polypropylene microporous membrane (Celgard 2325) is used as the separator; a lithium metal is used as the counter electrode to assemble a lithium-ion battery; among them, the LiFePO₄ electrode sheet is the positive electrode of the battery, and the lithium metal is the negative electrode of the battery. Place the stainless steel gasket, lithium metal, electrolyte, separator, electrolyte, LiFePO₄ positive electrode sheet, stainless steel gasket, and stainless steel spring piece in the center position of the CR2032 type negative electrode case in sequence, and place the CR2032 type positive electrode case on the top. Then, put the battery into an MSK 110 type battery encapsulation machine, apply pressure to 50 psi for encapsulation in the locked state, and obtain a LiFePO₄|metal lithium battery after unlocking. The electrolyte dosage in each LiFePO₄|metal lithium battery is 40 μL, and it is required to be dropped equally on both sides of the separator to fully wet the separator. The battery assembled with the LiFePO₄ electrode sheets C1 to C10 is the LiFePO₄|metal lithium battery, which is denoted as D1 to D10 respectively (the LiFePO₄|metal lithium battery assembled with the positive electrode material C1 prepared in Application Example 1 is denoted as D1, and so on to D10).

[0211] The specific capacity of the battery refers to the initial discharge specific capacity and the 400th cycle discharge specific capacity of the assembled lithium iron phosphate / metal lithium battery at a current density of 0.5C. The test instrument is a battery cycle tester (Wuhan Blue Electric, CT3002A), the cut-off voltage is 2.5 - 4.2V, the test temperature is 25°C, the rate is 0.5C, and the standard specific capacity of the active material is 170 mAh / g; an electrochemical workstation (Princeton, USA, VersaSTAT3) is used to test the initial interfacial impedance of the assembled lithium iron phosphate / metal lithium battery. The test parameters are as follows: the test temperature is 25°C, the frequency is 1,000,000 Hz, and the amplitude is 5 mV; the results of the surface density, peel strength, initial discharge specific capacity, initial interfacial impedance, 400th cycle discharge specific capacity, and capacity retention rate (the ratio of the discharge specific capacity to the initial discharge specific capacity) of the lithium iron phosphate electrode sheet obtained by testing are shown in Table 2; among them, the peel strength between the dry coating on the surface of the current collector in the electrode sheet and the current collector is measured according to the test method of GB / T 2791 - 1995, and the surface density of the active material of the electrode sheet is the mass of lithium iron phosphate per unit area, which is obtained by calculation.

[0212] Table 2 Performance indicators of lithium iron phosphate / metal lithium battery

[0213]

[0214] Figure 6 It is the interfacial impedance curve of lithium iron phosphate / metal lithium batteries D5 and D10 at 25°C.

[0215] Figure 7 It is the long-cycle charge and discharge curve of lithium iron phosphate / metal lithium batteries D5 and D10 at 25°C, a cut-off voltage of 2.5 - 4.2V, and a rate of 0.5C.

[0216] From Table 2, Figure 6 and Figure 7 it can be seen that under the condition of similar surface density of lithium iron phosphate, the positive electrode sheets C1 - C9 have higher peel strength compared to C10, indicating that the viologen-based ionic copolymer binder has stronger adhesion; in addition, the initial interfacial impedance of the lithium iron phosphate / metal lithium batteries D1 - D9 assembled with the positive electrode sheets C1 - C9 is lower than that of the lithium iron phosphate / metal lithium battery D10 assembled with the positive electrode sheet C10 prepared with PVDF binder, indicating that the ionic copolymer binder has better lithium ion transport ability; the initial discharge specific capacity of the lithium iron phosphate / metal lithium batteries D1 - D9 assembled with C1 - C9 is similar to that of the lithium iron phosphate / metal lithium battery D10 assembled with the electrode sheet C10 prepared with PVDF binder, but D1 - D9 has higher discharge specific capacity and capacity retention rate after 400 cycles at a current density of 0.5C compared to D10.

[0217] Figure 8 Charge-discharge curves of the lithium iron phosphate / metal lithium battery D5 at 25 °C with a cut-off voltage of 2.5 - 4.2 V under the conditions of 0.2C, 0.5C, 1C, 2C and 3C rates. From Figure 8 it can be seen that the lithium iron phosphate / metal lithium battery can exhibit a high discharge specific capacity at various current densities. Even at a high current density of 3C, it still shows a discharge specific capacity of 110.8 mAh·g -1 ; when the current density returns to 0.2C again, the specific capacity also smoothly returns to the initial value.

[0218] Test Example 3

[0219] Characterization of the parameters of the lithium iron phosphate / artificial graphite full battery: The lithium iron phosphate positive electrode C5 provided in Application Example 5 and the lithium iron phosphate positive electrode C10 provided in Comparative Application Example 1 were used as the positive electrode plates, and the artificial graphite negative electrode C11 provided in Comparative Application Example 2 was used as the negative electrode plate to assemble a lithium iron phosphate / artificial graphite full battery; among them, the lithium iron phosphate / artificial graphite full battery assembled with the lithium iron phosphate positive electrode C5 provided in Application Example 5 was denoted as E1, and the lithium iron phosphate / artificial graphite full battery assembled with the lithium iron phosphate positive electrode C10 provided in Comparative Application Example 1 was denoted as E2.

[0220] The specific method for assembling the lithium iron phosphate / artificial graphite full battery is as follows: Lithium hexafluorophosphate (LiPF 6 ) dissolved in a solution composed of ethylene carbonate (EC), dimethyl carbonate (DMC) and diethyl carbonate (EMC) with a volume ratio of 1:1:1 was used as the electrolyte (where the concentration of LiPF 6 was 1 mole / liter); a polypropylene microporous membrane (Celgard 2325) was used as the separator; C1 or C10 was used as the positive electrode plate; and an artificial graphite electrode plate was used as the negative electrode plate. They were sequentially placed at the central position of the CR2032 type negative electrode case in the order of stainless steel gasket, artificial graphite negative electrode plate, electrolyte, separator, electrolyte, lithium iron phosphate positive electrode plate, stainless steel gasket and stainless steel spring piece. The CR2032 type positive electrode case was placed on the top, and then the whole was put into an MSK 110 type battery encapsulation machine. The pressure was applied to 50 psi for encapsulation in the locked state, and the lithium iron phosphate / artificial graphite batteries E1 - E2 were obtained after unlocking. The electrolyte dosage for each lithium iron phosphate / artificial graphite battery was 40 μL, and it was required to be evenly dropped on both sides of the separator to fully infiltrate the separator.

[0221] The assembled lithium iron phosphate|artificial graphite full battery was subjected to battery cycling tests in a battery cycling tester (Wuhan Blue Electric, CT3002A). Among them, the cut-off voltage was 2.5 - 4.2 V, the test temperature was 25 °C, the rate was 0.5 C, and the standard specific capacity of the active material was 170 mAh / g. The results of the initial specific capacity of the battery cycle test, the discharge specific capacity at the 500th cycle, and the capacity retention rate (the ratio of the discharge specific capacity to the initial discharge specific capacity) are shown in Table 3.

[0222] Table 3 Performance indicators of lithium iron phosphate|artificial graphite batteries

[0223]

[0224] As can be seen from Table 3, the lithium iron phosphate|artificial graphite full battery assembled with the positive electrode plate C5 prepared from the viologen-based ionic polymer binder provided by the present invention has a higher specific capacity and capacity retention rate at a current density of 0.5 C compared to the lithium iron phosphate|artificial graphite full battery assembled with the positive electrode plate C10 prepared using a PVDF binder.

[0225] In summary, the present invention provides a viologen-based ionic polymer binder of viologen-based acrylate, acrylate, and / or methoxypolyethylene glycol acrylate, and uses it in the preparation of the positive electrode plate of a lithium-ion battery. The assembled lithium-ion battery has the advantages of low interfacial impedance, high specific capacity, high capacity retention rate, and good cycle stability.

[0226] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A method for preparing a viologen-based ionic polymer binder, comprising: Mixing viologen-based acrylate, acrylate and / or polyethylene glycol monomethyl ether acrylate, an initiator and a first solvent, and performing a free radical polymerization reaction to obtain a viologen-based ionic polymer binder; The viologen acrylate has a chemical structure as shown in Formula II: Formula II; In the formula II, R4 is hydrogen or methyl; R5 is alkyl; X is dimethylene or dimethylene carbamate; Y is PF6 - 、BF4 - Br - ,I - 、CH3SO3 - CF3SO3 - or (CF3SO2)2N - ; The preparation method of the viologen acrylate comprises the following steps: (1) mixing 4,4'-bipyridine, an alkylating agent and a second solvent to perform a first alkylation reaction to obtain an N-alkyl-4,4'-bipyridine salt; (2) mixing the N-alkyl-4,4'-bipyridyl salt obtained in step (1) with 1-haloalkyl-1'-alcohol and a third solvent to carry out a second alkylation reaction to obtain a 1-(hydroxyalkyl)-1'-alkyl viologen salt (1); (3) mixing the 1-(hydroxyalkyl)-1'-alkyl viologen salt (1) obtained in step (2) with a salt containing different anions and a fourth solvent to carry out an ion replacement reaction to obtain a 1-(hydroxyalkyl)-1'-alkyl viologen salt (2); (4) The 1-(hydroxyalkyl)-1'-alkyl viologen salt (2) obtained in step (3) is mixed with a vinyl carbonyl compound, a catalyst, a polymerization inhibitor and a fifth solvent to carry out an esterification reaction to obtain viologen acrylate.

2. The preparation method according to claim 1, characterized in that: The alkylating agent in step (1) is at least one of methyl iodide, dimethyl sulfate, dimethyl carbonate, ethyl iodide, diethyl sulfate, diethyl carbonate, propyl iodide, dipropyl sulfate and dipropyl carbonate; the second solvent is at least one of dichloroethane, tetrahydrofuran, dichloromethane, toluene and chloroform; the temperature of the first alkylation reaction is 10-35° C.; and the time of the first alkylation reaction is 1-24 hours.

3. The preparation method according to claim 1, characterized in that: The 1-haloalkyl-1'-alcohol in step (2) is one of 2-bromoethanol and 2-chloroethanol; the third solvent is at least one of acetonitrile, N-methylpyrrolidone, N,N-dimethylformamide and dimethyl sulfoxide; the temperature of the second alkylation reaction is 50-100° C.; and the time of the second alkylation reaction is 30-72 hours.

4. The preparation method according to claim 1, characterized in that: The salt containing different anions in step (3) is at least one of KPF6, NaPF6, NH4PF6, NaBF4, KBF4, NaBr, KBr, NaI, KI, CH3SO3Na, CF3SO3Na and (CF3SO2)2NLi; the fourth solvent is at least one of deionized water, ethanol, N-methylpyrrolidone, N,N-dimethylformamide and dimethyl sulfoxide; the temperature of the ion exchange reaction is 10~35°C; the time of the ion exchange reaction is 1~12h.

5. The preparation method according to claim 1, characterized in that: The vinyl carbonyl compound in step (4) is at least one of 2-isocyanatoethyl acrylate, isocyanoethyl methacrylate, acrylic acid, methacrylic acid, acryloyl chloride and methacryloyl chloride; the catalyst is at least one of dibutyltin dilaurate, triethylamine, sodium carbonate and potassium carbonate; the inhibitor is at least one of p-methoxyphenol, p-benzoquinone and hydroquinone; the fifth solvent is at least one of N-methylpyrrolidone, N,N-dimethylformamide, tetrahydrofuran, 1,4-dioxane, acetonitrile and chloroform; the temperature of the esterification reaction is 10-35°C; and the time of the esterification reaction is 1-36h.

6. The preparation method according to claim 1, characterized in that: The initiator of the free radical polymerization reaction is at least one of azobisisobutyronitrile, azobiscyclohexylcarbonitrile, dimethyl azobisisobutyrate and dibenzoyl peroxide; the first solvent is at least one of acetonitrile, toluene, acetone, N-methylpyrrolidone, N,N-dimethylformamide, tetrahydrofuran, 1,4-dioxane and chloroform; the temperature of the free radical polymerization reaction is 50-80° C.; and the time of the free radical polymerization reaction is 8-12 hours.

7. Application of the viologen-based ionic polymer binder prepared by the preparation method according to any one of claims 1 to 6 in lithium-ion battery pole pieces; The viologen-based ionic polymer binder has a chemical structure as shown in Formula I: Formula I; In the formula I, R1, R3 and R4 are independently hydrogen or methyl; R2 and R5 are independently alkyl; X is dimethylene or dimethylene carbamate; Y is PF6 - 、BF4 - Br - ,I - 、CH3SO3 - CF3SO3 - or (CF3SO2)2N - ; m+n+q=1, where m≥0, n≥0, q>0; p is 0~40.

8. The use according to claim 7, characterized in that: The lithium-ion battery pole piece is a positive pole piece or a negative pole piece.

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