Lithium battery binder capable of accelerating redox process and preparation and application thereof

Abstract

The application discloses a lithium battery binder capable of accelerating an oxidation-reduction process and a preparation and application thereof. The binder is a linear polymer PUS containing a disulfide bond, a linear polymer PUSe containing a diselenide bond or a polyurethane type high molecular polymer (PUPEG-2000) based on a diselenide bond; in the preparation, a concept of an oxidation-reduction auxiliary medium is introduced into the binder, cystamine dihydrochloride or selenocystamine dihydrochloride is used as raw material, the PUS or the PUSe is synthesized through one-step polymerization, or the polyurethane type high molecular polymer (PUPEG-2000) based on the diselenide bond is further synthesized, and the binder is used as a lithium battery electrode material binder. The binder can accelerate an oxidation-reduction kinetics process of the electrode, and effectively improves a discharge specific capacity and an electrochemical cycle performance of the lithium battery.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of lithium battery binders. Specifically relates to a preparation and application of a lithium battery binder capable of accelerating the redox process. BACKGROUND

[0002] In recent years, with the rapid development of society, energy consumption is increasing, and the development and utilization of new energy has become the core content of the energy transformation strategy of countries around the world and the main way to cope with climate change. Lithium batteries have attracted widespread attention due to their high voltage, high energy density, long cycle life, and green environmental protection (Nature, 2001, 414, 359-367). Lithium batteries include lithium ion batteries and lithium-sulfur batteries, among which lithium ion batteries have been widely used in various portable electronic devices and electric vehicles; lithium-sulfur batteries have a specific capacity nearly 3-5 times higher than that of lithium ion batteries (1675mA·h·g -1 ) and a high theoretical energy density (2600Wh·kg -1 ), which is a promising energy storage system (Nature Energy, 2016, 1, 16132).

[0003] The binder is a material that connects the electrode active material, the conductive agent and the current collector and makes them have overall continuity and good mechanical properties, its main function is to bond and maintain the active material, stabilize the structure of the battery electrode and reduce the impedance of the electrode, etc. It has a great influence on the performance of the electrode and even the entire battery (internal resistance, capacity, cycle life, specific energy, etc.). Polyvinylidene fluoride (PVDF) is the most widely used lithium battery electrode binder, which has strong electrochemical corrosion resistance and can be applied to positive and negative electrode materials. However, the adhesion of PVDF is mainly generated by relatively weak van der Waals force, and PVDF will swell in the electrolyte during battery testing, resulting in poor adhesion and inability to adapt to the volume change of the electrode, which leads to the destruction of the structure of the electrode material and reduces the charge-discharge specific capacity and cycle stability of the battery (Journal of Energy Chemistry, 2020, 43, 165-172). Therefore, it is very important to design a new type of multifunctional polymer binder to replace PVDF for the next generation of lithium batteries.

[0004] The patent "Preparation method and application of lithium battery adhesive with self-repairing performance (application number 202010715958.4)" is a reaction of a component containing polyamino functional groups and a component containing a bis-thiolactone functional group to generate a new cross-linked network polymer containing a large number of thiol functional group side chains. The disulfide bond generated by the mutual reaction of thiol can repair the positive electrode structure damaged by the pulverization or volume change of active material during the charging and discharging process of lithium battery. Due to the low content of sulfur element in thiolactone, this method has the limitation of less available active functional groups. SUMMARY

[0005] The purpose of the present application is to overcome the shortcomings in the current technology and provide a lithium battery adhesive that can accelerate the oxidation-reduction process and its preparation and application. The adhesive is a linear polymer PUS containing disulfide bonds, a linear polymer PUSe containing diselenide bonds, or a polyurethane-based polymer (PUPEG-2000) based on diselenide bonds. In the preparation, the concept of "redox auxiliary mediator" is introduced into the adhesive. Cystamine dihydrochloride or selenocystamine dihydrochloride is used as the raw material, and PUS or PUSe is synthesized by one-step polymerization, or further synthesis of polyurethane-based polymer (PUPEG-2000) based on diselenide bonds. They are used as lithium battery electrode material adhesives. The adhesive as a redox auxiliary mediator reacts with the negative electrode of lithium ion battery or the sulfur positive electrode of lithium-sulfur battery to generate products with stronger redox mediation ability, thereby accelerating the oxidation-reduction kinetics process of the electrode and effectively improving the discharge specific capacity and electrochemical cycle performance of lithium battery.

[0006] The technical solution of the present application is:

[0007] A lithium battery adhesive that can accelerate the oxidation-reduction process, the adhesive is one of the following three compounds:

[0008] Compound one, PUS, has the following structure:

[0009]

[0010] Wherein, n = 50-100;

[0011] Alternatively, compound two, PUSe, has the following structure:

[0012]

[0013] Wherein, n = 30-70;

[0014] Alternatively, compound three, PUPEG-2000, has the following structure:

[0015]

[0016] wherein n = 40-50, m = 10-30.

[0017] The preparation method of the lithium battery binder capable of accelerating the redox process comprises one of the following three methods:

[0018] Method one, preparation of PUS:

[0019] Cystamine dihydrochloride is dissolved in anhydrous dimethyl sulfoxide (DMSO), triethylamine is first added, stirred for 1-2 hours, then 2,4-toluene diisocyanate is added, and reacted at 50-100°C for 12-24 hours. After dialysis, freeze-drying is performed to obtain a white powder product (PUS);

[0020] wherein 0.1-0.5 mmol of cystamine dihydrochloride, 1-5 mmol of triethylamine, and 0.1-0.5 mmol of 2,4-toluene diisocyanate are added to 10 ml of anhydrous dimethyl sulfoxide (DMSO).

[0021] Alternatively, method two, preparation of PUSe:

[0022] Selenocystamine dihydrochloride is dissolved in anhydrous dimethyl sulfoxide (DMSO), triethylamine is first added, stirred for 1-2 hours, then 2,4-toluene diisocyanate is added, and reacted at 50-100°C for 12-24 hours. After dialysis, freeze-drying is performed to obtain a light yellow powder product (PUSe);

[0023] wherein 0.1-0.5 mmol of selenocystamine dihydrochloride, 1-5 mmol of triethylamine, and 0.1-0.5 mmol of 2,4-toluene diisocyanate are added to 10 ml of anhydrous dimethyl sulfoxide (DMSO).

[0024] Alternatively, method three, preparation of PUPEG-2000:

[0025] Polyethylene glycol is dried at 50-100°C for 1-2 hours, then anhydrous dimethyl sulfoxide (DMSO) is added to obtain solution A; 2,4-toluene diisocyanate and dibutyltin dilaurate are dissolved in anhydrous dimethyl sulfoxide (DMSO) to obtain solution B, which is added dropwise to solution A. After reacting at 50-100°C for 2-3 hours, a prepolymer is obtained; selenocystamine dihydrochloride and triethylamine are added to anhydrous dimethyl sulfoxide (DMSO) and stirred for 0.1-1 hour to obtain solution C, which is added dropwise to the prepolymer. After reacting at 50-100°C for 2-3 hours, drying is performed in a vacuum to obtain the product PUPEG-2000;

[0026] Wherein, solution A: 0.1-0.5mmol polyethylene glycol (Mn=2000) is added in 5ml anhydrous dimethyl sulfoxide (DMSO); solution B: 1-5mmol 2,4-toluene diisocyanate and 3-4mg dibutyltin dilaurate are added in 5ml anhydrous dimethyl sulfoxide (DMSO); solution C: 0.5-1mmol selenocystamine dihydrochloride and 5-10mmol triethylamine are added in 5ml anhydrous dimethyl sulfoxide (DMSO); the volume ratio is solution A:solution B:solution C=(1-5):(1-5):(1-5).

[0027] The application of the lithium battery binder capable of accelerating the oxidation-reduction process is used in a lithium ion battery negative electrode material or a lithium-sulfur battery positive electrode material.

[0028] The application of the lithium battery binder capable of accelerating the oxidation-reduction process is used in a lithium ion battery negative electrode material or a lithium-sulfur battery positive electrode material.

[0029] The binder is mixed with a conductive agent, a negative electrode active material, a dispersing agent, and a ball mill to form a slurry, which is coated on a copper foil current collector with a coating thickness of 15-20μm; after drying at 60-100℃ for 12 hours, the slurry is used as a lithium ion battery negative electrode material;

[0030] The mass ratio of the binder, the conductive agent, the negative electrode active material, and the dispersing agent is (1-6):(1-5):(90-98):(1-5);

[0031] The negative electrode active material is one of natural graphite, artificial graphite, modified graphite, amorphous carbon material, and nanostructured carbon material;

[0032] The conductive agent is acetylene black, Super P, multi-walled carbon nanotube, or graphene; and the dispersing agent is hydroxymethyl cellulose (CMC) or water (H2O);

[0033] The ball mill rotation speed is 300-600r·min -1 The active material loading is 1.2-2mg·cm -2 ;

[0034] The lithium ion battery specifically uses lithium iron phosphate as a positive electrode, 1M LiPF6 / EC+PC+DEC+EMC (volume ratio 1:0.3:1:1) as an electrolyte, and Celgard-2325 type commercial separator.

[0035] The application of the lithium battery binder capable of accelerating the oxidation-reduction process is used in a lithium ion battery negative electrode material or a lithium-sulfur battery positive electrode material.

[0036] The binder is mixed with a conductive agent, a positive active material, a dispersing agent, and a ball mill to form a slurry, which is coated on a carbon aluminum foil current collector with a coating thickness of 15-20 microns; after drying at 60-100 DEG C for 12 hours, the positive electrode material is prepared for a lithium-sulfur battery;

[0037] The mass ratio is binder: conductive agent: positive active material: dispersing agent = 1:1:(5-9):(30-60).

[0038] The positive active material is an S / C composite material prepared by a "sulfur filling method" from elemental sulfur and multi-walled carbon nanotubes.

[0039] The conductive agent is acetylene black, Super P, multi-walled carbon nanotubes, or graphene; the dispersing agent is N-methyl pyrrolidone (NMP), N,N'-dimethylformamide (DMF), or water (H2O).

[0040] The ball mill rotation speed is 300-600 r / min. -1 The active material loading is 1.2-2 mg / cm -2 .

[0041] The lithium-sulfur battery specifically uses metal lithium as a negative electrode, Celgard-2400 type polypropylene film as a separator, and a mixed solution of dimethoxyethane (DME) and 1,3 dioxolane (DOL) with a volume ratio of 1:1 as an electrolyte, wherein lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and 0.1M LiNO3 are used as additives.

[0042] The substantial features of the present application are:

[0043] The present application introduces the concept of "redox auxiliary mediator" into the binder to make the binder act as a redox auxiliary mediator and react with the lithium ion battery negative electrode or the sulfur positive electrode of the lithium-sulfur battery to generate a product with stronger redox mediation ability, thereby accelerating the redox kinetics process of the electrode and making the electrode have excellent electrochemical performance.

[0044] The present application has the following advantages:

[0045] The application synthesizes two kinds of high molecular linear binders (PUS and PUSe) by one-step polymerization method with cystamine dihydrochloride, selenocystamine dihydrochloride and 2,4-toluene diisocyanate as raw materials, and synthesizes polyurethane type binder (PUPEG-2000) with multiple functions with polyethylene glycol (Mn=2000), selenocystamine dihydrochloride and 2,4-toluene diisocyanate as raw materials, which are used as lithium battery electrode material binders. Compared with the commercial PVDF binder, the disulfide bond contained in PUS and the diselenide bond contained in PUSe and PUPEG-2000 can react with the lithium ion battery negative electrode or the sulfur positive electrode of the lithium-sulfur battery to generate products with stronger redox ability, thereby accelerating the redox kinetics of the electrode.

[0046] Compared with the lithium ion battery prepared by the traditional lithium battery binder PVDF, the initial specific capacity of the lithium ion battery prepared by the binder of the application is increased by about 4.0%, and the capacity retention rate is about 98.8% (the capacity retention rate of the lithium ion battery prepared by the PVDF is 95.1%); compared with the lithium-sulfur battery prepared by the traditional lithium battery binder PVDF, the initial specific capacity of the lithium-sulfur battery prepared by the binder of the application is increased by about 14.1%, and the capacity retention rate is about 86.7% (the capacity retention rate of the lithium-sulfur battery prepared by the PVDF is 71.4%), so the binder of the application has a significant improvement on the specific capacity and cycle stability of the lithium battery. BRIEF DESCRIPTION OF DRAWINGS

[0047] Fig. 1 is the nuclear magnetic resonance hydrogen spectrum of PUS obtained in examples 1 and 4.

[0048] Fig. 2 is the nuclear magnetic resonance hydrogen spectrum of PUSe obtained in examples 2 and 5.

[0049] Fig. 3 is the nuclear magnetic resonance hydrogen spectrum of PUPEG-2000 obtained in examples 3 and 6. DETAILED DESCRIPTION

[0050] In order to make the purpose, technical scheme and advantages of the application more clear and explicit, the application will be further described in detail below in combination with the drawings and examples. It should be understood that the specific implementation described here is only used to explain the application, and is not used to limit the application.

[0051]

[0052] As shown in reaction formula 1: two kinds of linear polymers (PUS and PUSe) are synthesized by reacting cystamine dihydrochloride, selenocystamine dihydrochloride and 2,4-toluene diisocyanate respectively, and they are used as lithium battery binders.

[0053]

[0054] A polyurethane type polymer (PUPEG-2000) was synthesized by reacting 2,4-toluene diisocyanate with polyethylene glycol (Mn=2000) and cystamine disulfide dihydrochloride as shown in Reaction 2, and used as a lithium battery binder.

[0055] The lithium battery binder capable of accelerating the redox process of the present application is applied to the negative electrode of a lithium ion battery and the positive electrode of a lithium-sulfur battery. Examples 1 to 3 are applied to the preparation of a lithium ion battery; and Examples 4 to 6 are applied to the preparation of a lithium-sulfur battery.

[0056] Example 1

[0057] The preparation of the lithium battery binder capable of accelerating the redox process and its application, characterized in that it comprises the following steps:

[0058] (1) Synthesis of the binder: 0.045 g of cystamine disulfide dihydrochloride (0.2 mmol) was added to a 50 ml flask, and the gas was replaced with nitrogen. Then 10 ml of anhydrous dimethyl sulfoxide (DMSO) and 2 g of triethylamine (2 mmol) were added in turn, and a clear solution was obtained after stirring for 1 hour. Then 0.0348 g of 2,4-toluene diisocyanate (0.2 mmol) was added to the flask, and the reaction was continued at 50°C for 24 hours. The reaction solution was dialyzed with a dialysis bag (molecular weight cut-off 7000), and freeze-dried to obtain a white powder product (PUS, as shown in the following structural formula), with a yield of about 75%.

[0059]

[0060] wherein n = 76.99;

[0061] By Fig. 1 It can be seen that, due to the presence of disulfide bonds in the structural formula, the target product is obtained.

[0062] (2) Preparation of the negative electrode material of a lithium ion battery: Artificial graphite, Super P, binder, hydroxymethyl cellulose (CMC) were mixed in a mass ratio of 95:1.2:1.5:1.2 under the condition of a ball mill rotation speed of 400 r / min for 6 hours to form a slurry. The slurry was coated on a copper foil with a coating thickness of 15 μm, and a wet electrode sheet was prepared. After drying in a vacuum drying oven at 80°C for 12 hours, the electrode sheet was cut into an electrode sheet with a diameter of 10 mm, which was used as the negative electrode material of a lithium ion battery.

[0063] (3) Assembling lithium ion battery device: In the glove box filled with argon, the electrode piece prepared in step (2) is used as negative electrode, lithium iron phosphate as positive electrode, 1M LiPF6 / EC+PC+DEC+EMC (volume ratio 1:0.3:1:1) as electrolyte, and Celgard-2325 type commercial diaphragm is assembled into CR2025 type standard button cell.

[0064] Example 2

[0065] The preparation of the lithium battery binder capable of accelerating the redox process and its application, characterized in that it comprises the following steps:

[0066] (1) Synthesis of binder: 0.064 g of selenocystamine dihydrochloride (0.2 mmol) is added to a 50 ml flask, and the gas is replaced with nitrogen. Then 10 ml of anhydrous dimethyl sulfoxide (DMSO) and 2 g of triethylamine (2 mmol) are added in turn, and a clear solution is obtained after stirring for 1 hour. Then 0.0348 g of 2,4-toluene diisocyanate (0.2 mmol) is added to the flask, and the reaction is continued at 50°C for 24 hours. The reaction solution is dialyzed with a dialysis bag (molecular weight cutoff 7000), and freeze-dried to obtain a light yellow powder (PUSe, as shown in the following structural formula), with a yield of about 70%.

[0067]

[0068] wherein n = 54.42;

[0069] By Fig. 2 It can be seen that, due to the presence of diselenium bond in the structural formula, the target product is obtained.

[0070] (2) Preparation of negative electrode material for lithium ion battery: Artificial graphite, Super P, binder, hydroxymethyl cellulose (CMC) are mixed at a mass ratio of 95:1.2:1.5:1.2 under the condition of ball milling at a speed of 400 r / min for 6 hours to form a slurry. The slurry is coated on a copper foil with a coating thickness of 15 μm, and the wet electrode piece is dried in a vacuum drying oven at 80°C for 12 hours. Then the electrode piece is cut into an electrode piece with a diameter of 10 mm, which is used as the negative electrode material for lithium ion battery.

[0071] (3) Assembling lithium ion battery device: In the glove box filled with argon, the electrode piece prepared in step (2) is used as negative electrode, lithium iron phosphate as positive electrode, 1M LiPF6 / EC+PC+DEC+EMC (volume ratio 1:0.3:1:1) as electrolyte, and Celgard-2325 type commercial diaphragm is assembled into CR2025 type standard button cell.

[0072] Example 3

[0073] The preparation of lithium battery binder capable of accelerating the redox process and its application, characterized in that it comprises the following steps:

[0074] (1) Synthesis of binder: 0.8 g of polyethylene glycol (Mn = 2000, 0.4 mmol) was added to a 50 ml flask, and the gas was replaced with nitrogen. After drying at 100°C for 1 hour, 5 ml of anhydrous DMSO was added. 0.174 g of 2,4-toluene diisocyanate (1 mmol) and 3.9 mg of dibutyltin dilaurate were dissolved in 5 mL of anhydrous DMSO, and the resulting solution was added dropwise to the flask. After reacting at 80°C for 3 hours, a prepolymer was obtained. Then 0.192 g of selenocystamine dihydrochloride (0.6 mmol) and 0.6 g of triethylamine (6 mmol) were added to 5 ml of anhydrous DMSO, and after stirring for 0.5 hours, a light yellow clear solution was obtained. The light yellow clear solution was added dropwise to the flask containing the prepolymer, and the reaction was continued at 80°C for 3 hours. After the reaction was completed, the final solution was poured into a culture dish, and after drying in a vacuum oven at 90°C for 24 hours, the product PUPEG-2000 was obtained, as shown in the following structural formula, with a yield of about 70%.

[0075]

[0076] wherein n = 45, m = 19.62;

[0077] By Fig. 3 It can be seen that, due to the presence of diselenide bond in the structural formula, the target product is obtained.

[0078] (2) Preparation of negative electrode material for lithium ion battery: Artificial graphite, Super P, binder, hydroxymethyl cellulose (CMC) were mixed in a mass ratio of 95:1.2:1.5:1.2 under the condition of ball milling at a speed of 400 r / min for 6 hours to form a slurry. The slurry was coated on a copper foil with a coating thickness of 15 μm to prepare a wet electrode sheet. After drying in a vacuum drying oven at 80°C for 12 hours, the electrode sheet was cut into an electrode sheet with a diameter of 10 mm as a negative electrode material for lithium ion battery.

[0079] (3) Assembly of lithium ion battery device: In an argon-filled glove box, the electrode sheet prepared in step (2) was used as the negative electrode, lithium iron phosphate was used as the positive electrode, and 1M LiPF6 / EC+PC+DEC+EMC (volume ratio 1:0.3:1:1) was used as the electrolyte. Celgard-2325 type commercial separator was assembled into a standard CR2025 type button cell.

[0080] Example 4

[0081] The preparation of lithium battery binder capable of accelerating the redox process and its application, characterized in that it comprises the following steps:

[0082] (1) Synthesis of binder: In a 50 ml vial, 0.045 g of cystamine dihydrochloride (0.2 mmol) was added and the vial was purged with nitrogen. Then, 10 ml of anhydrous dimethyl sulfoxide (DMSO) and 2 g of triethylamine (2 mmol) were added sequentially. After stirring for 1 h, a clear solution was obtained. Then, 0.0348 g of 2,4-toluene diisocyanate (0.2 mmol) was added to the vial and the reaction was continued at 50 °C for 24 h. The reaction solution was dialyzed using a dialysis bag (MWCO 7000) and freeze-dried to obtain the product (PUS) as a white powder with a yield of about 75%.

[0083] (2) Preparation of S / C composite: Elemental sulfur and multi-walled carbon nanotubes were weighed in a mass ratio of 3:1 and were ground in an agate mortar for 1 h to mix them thoroughly. The ground powder was transferred to a reaction kettle, which was purged with a glove box, and the kettle was placed in an oven at 155 °C for 24 h to obtain the S / C composite.

[0084] (3) Preparation of sulfur cathode: The S / C composite, multi-walled carbon nanotubes, and binder were weighed in a mass ratio of 8:1:1 and were ground in an agate mortar for 1 h. After adding an appropriate amount of DMSO, the grinding was continued until a uniform slurry was obtained. The slurry was uniformly coated on an aluminum foil using an adjustable film applicator, and the aluminum foil was placed in a forced air drying oven at 50 °C for 12 h. The aluminum foil was cut into a circular patch with a diameter of 8 mm, and a sulfur loading of 1.4 mg cm -2 was obtained.

[0085] (4) Assembly of lithium-sulfur battery: A metal lithium was used as the anode, and a Celgard-2400 type polypropylene membrane was used as the separator. The electrolyte was a mixture of dimethoxyethane (DME) and 1,3-dioxolane (DOL) in a volume ratio of 1:1, with lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and 0.1 M LiNO3 as additives. The battery was assembled in a glove box in the order of positive electrode shell, positive electrode patch, electrolyte (2-3 drops), separator, lithium sheet, gasket, spring sheet, and negative electrode shell.

[0086] Example 5

[0087] The preparation of a lithium battery binder that can accelerate the redox process and its application, characterized by the following steps:

[0088] (1) Synthesis of binder: In a 50 ml vial, 0.064 g of selenocystamine dihydrochloride (0.2 mmol) was added and the vial was purged with nitrogen. Then, 10 ml of anhydrous dimethyl sulfoxide (DMSO) and 2 g of triethylamine (2 mmol) were added sequentially. After stirring for 1 h, a clear solution was obtained. Then, 0.0348 g of 2,4-toluene diisocyanate (0.2 mmol) was added to the vial and the reaction was continued at 50 °C for 24 h. The reaction solution was dialyzed using a dialysis bag (cut-off molecular weight 7000) and freeze-dried to obtain the product (PUSe) as a light yellow powder with a yield of about 70%.

[0089] (2) Preparation of S / C composite: Elemental sulfur and multi-walled carbon nanotubes were weighed in a mass ratio of 3:1 and were ground in an agate mortar for 1 h to mix them thoroughly. The ground powder was poured into a reaction kettle, which was purged with a glove box, and the reaction kettle was placed in an oven at 155 °C for 24 h to obtain the S / C composite.

[0090] (3) Preparation of sulfur cathode: The S / C composite, multi-walled carbon nanotubes, and binder were weighed in a mass ratio of 8:1:1 and were ground in an agate mortar for 1 h. After adding an appropriate amount of DMSO, the grinding was continued until a uniform slurry was obtained. The slurry was uniformly coated on an aluminum foil using an adjustable film applicator, and the aluminum foil was placed in a forced air drying oven at 50 °C for 12 h. The aluminum foil was cut into a circular piece with a diameter of 8 mm, and a cathode piece with a sulfur loading of 1.4 mg cm -2 was obtained.

[0091] (4) Assembly of lithium-sulfur battery: A metal lithium was used as the anode, and a Celgard-2400 type polypropylene film was used as the separator. The electrolyte was a mixed solution of dimethoxyethane (DME) and 1,3-dioxolane (DOL) in a volume ratio of 1:1, with lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and 0.1 M LiNO3 as additives. The battery was assembled in a glove box in the order of positive electrode shell, cathode piece, electrolyte (2-3 drops), separator, lithium piece, gasket, spring piece, and negative electrode shell.

[0092] Example 6

[0093] The preparation of a lithium battery binder that can accelerate the redox process and its application, characterized by comprising the following steps:

[0094] (1) Synthesis of binder: In a 50 ml flask, 0.8 g of polyethylene glycol (Mn = 2000, 0.4 mmol) was taken and degassed, purged with nitrogen and dried at 100 °C for 1 h. Then 5 ml of dry DMSO was added. Separately, 0.174 g of 2,4-toluene diisocyanate (1 mmol) and 3.9 mg of dibutyltin dilaurate were dissolved in 5 mL of dry DMSO and the resulting solution was added dropwise to the flask. The pre-polymer was obtained after 3 h of reaction at 80 °C. Then 0.192 g of selenocystamine dihydrochloride (0.6 mmol) and 0.6 g of triethylamine (6 mmol) were added in 5 ml of dry DMSO and a light yellow clear solution was obtained after 0.5 h of stirring. The light yellow clear solution was added dropwise to the flask containing the pre-polymer and the reaction was continued at 80 °C for 3 h. After completion of the reaction, the final solution was poured into a petri dish and the product PUPEG-2000 was obtained after drying in a vacuum oven at 90 °C for 24 h with a yield of about 70%.

[0095] (2) Preparation of S / C composite: Elemental sulfur and multi-walled carbon nanotubes were weighed in a mass ratio of 3:1 and were ground in an agate mortar for 1 h to mix them thoroughly. The ground powder was poured into a reaction kettle and was degassed using a glove box. The reaction kettle was then placed in an oven at 155 °C for 24 h to obtain the S / C composite.

[0096] (3) Preparation of sulfur cathode: The S / C composite, multi-walled carbon nanotubes and the binder were weighed in a mass ratio of 8:1:1 and were ground in an agate mortar for 1 h. The grinding was continued after adding an appropriate amount of DMSO until a homogeneous slurry was obtained. The slurry was uniformly coated on an aluminum foil using an adjustable film applicator. The aluminum foil was then placed in a forced air drying oven at 50 °C for 12 h. The aluminum foil was cut into a circular patch of 8 mm in diameter to obtain a cathode patch with a sulfur loading of 1.4 mg cm -2 .

[0097] (4) Assembly of lithium-sulfur battery: The lithium metal was used as the anode and Celgard-2400 type polypropylene membrane was used as the separator. The electrolyte was a mixture of dimethoxyethane (DME) and 1,3-dioxolane (DOL) in a volume ratio of 1:1, with lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and 0.1 M of LiN03 as additives. The battery was assembled in a glove box in the order of cathode shell, cathode patch, electrolyte (2-3 drops), separator, lithium patch, gasket, spring piece, and anode shell.

[0098] Comparative Example 1

[0099] A method of preparing a lithium ion battery, comprising the steps of

[0100] (1) Artificial graphite, Super P, PVDF, hydroxymethyl cellulose (CMC) were mixed in a mass ratio of 95:1.2:1.5:1.2 under the condition of ball milling rotation speed 400 r / min for 6 hours to slurry. The slurry was coated on a copper foil with a coating thickness of 15 μm, and the wet electrode sheet was dried in a vacuum drying oven at 80°C for 12 hours. The electrode sheet was cut into a diameter of 10 mm, and used as a negative electrode material for lithium ion batteries.

[0101] (2) In an argon-filled glove box, the electrode sheet prepared in step (1) was used as a negative electrode, lithium iron phosphate was used as a positive electrode, and 1M LiPF6 / EC+PC+DEC+EMC (volume ratio 1:0.3:1:1) was used as an electrolyte. A standard button cell of CR2025 type was assembled with a commercial separator of Celgard-2325 type.

[0102] Comparative Example 2

[0103] A method for preparing a lithium-sulfur battery, comprising the following steps

[0104] (1) Elemental sulfur and multi-walled carbon nanotubes were weighed in a mass ratio of 3:1 and poured into an agate mortar for grinding for 1 hour to fully mix the two. The ground powder was poured into a reaction kettle and the glove box was replaced with air, and then the reaction kettle was placed in an oven at 155°C for 24 hours to obtain an S / C composite material. The S / C composite material, multi-walled carbon nanotubes, and PVDF were weighed in a mass ratio of 8:1:1 and poured into an agate mortar for grinding for 1 hour. After adding an appropriate amount of DMSO, the grinding was continued until a uniformly mixed slurry was obtained. The slurry was uniformly coated on aluminum foil paper by an adjustable film coater, and then the aluminum foil paper was placed in a 50°C air drying oven for 12 hours. The aluminum foil paper was cut into a circular piece with a diameter of 8 mm, and finally a positive electrode sheet with a sulfur loading of 1.4 mg cm -2 was obtained.

[0105] (2) Lithium metal was used as a negative electrode, and a Celgard-2400 type polypropylene film was used as a separator. The electrolyte was a mixture of dimethoxyethane (DME) and 1,3-dioxolane (DOL) in a volume ratio of 1:1, with lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and 0.1M LiNO3 as additives. The battery was assembled in the glove box in the order of positive electrode shell, positive electrode sheet, electrolyte (2-3 drops), separator, lithium sheet, gasket, spring sheet, and negative electrode shell.

[0106] Examples 1-3 are to apply the lithium battery binder capable of accelerating the redox process of the present application to the preparation of lithium ion batteries, Comparative Example 1 is to use the conventional PVDF binder to prepare lithium ion batteries. The lithium ion batteries prepared in Examples 1-3 and Comparative Example 1 are exactly the same in other preparation materials and preparation processes except for the type of binder.

[0107] Examples 4-6 are to apply the lithium battery binder capable of accelerating the redox process of the present application to the preparation of lithium-sulfur batteries, Comparative Example 2 is to use the conventional PVDF binder to prepare lithium-sulfur batteries. The lithium-sulfur batteries prepared in Examples 4-6 and Comparative Example 2 are exactly the same in other preparation materials and preparation processes except for the type of binder.

[0108] In order to verify the properties of the materials obtained in Examples 1-6 and Comparative Examples 1-2 above, the following related characterization and performance tests are carried out.

[0109] (I) Nuclear magnetic hydrogen spectrum

[0110] The PUS, PUSe and PUPEG-2000 prepared in Examples 1-6 are tested using the AVANCE400 nuclear magnetic resonance spectrometer of Brucker Company. Figs. 1-3 The nuclear magnetic resonance hydrogen spectra of PUS, PUSe and PUPEG-2000 respectively show that they are all successfully synthesized.

[0111] (II) Battery cycle performance test

[0112] The lithium ion batteries prepared in Examples 1-3 and Comparative Example 1, and the lithium-sulfur batteries prepared in Examples 4-6 and Comparative Example 2 are respectively subjected to cycle performance test under the condition of 0.2C. It can be found from Table 1 and Table 2 that, whether it is lithium ion battery or lithium-sulfur battery, the discharge specific capacity and cycle stability of the lithium battery prepared by using the lithium battery binder capable of accelerating the redox process of the present application are more excellent than those of the battery prepared by using PVDF as the binder.

[0113] Table 1 Electrochemical cycle test of lithium ion battery corresponding to lithium battery binder capable of accelerating redox process of the present application or PVDF

[0114]

[0115] Table 2 Electrochemical cycle test of lithium-sulfur battery corresponding to lithium battery binder capable of accelerating redox process of the present application or PVDF

[0116]

[0117] Compared with the lithium ion battery prepared by the traditional lithium battery binder PVDF, the initial specific discharge capacity of the lithium ion battery prepared by the binder is increased by about 4.0%, and the capacity retention is increased by about 3.9%; compared with the lithium-sulfur battery prepared by the traditional lithium battery binder PVDF, the initial specific discharge capacity of the lithium-sulfur battery prepared by the binder is increased by about 14.1%, and the capacity retention is increased by about 21.4%.

[0118] The above only describes several preferred embodiments of the present application, but the present application is not limited to the above several specific embodiments. The above specific embodiments are illustrative rather than restrictive, and researchers in the field can make improvements and refinements under the inspiration of the present application, as long as the spirit and principles of the present application are followed, and all fall within the scope of protection of the present application.

[0119] The details of the present application are well known.

Claims

1. A lithium battery binder that can accelerate the redox process, characterized in that the binder has the following structural formula: ； wherein n=40~50, m=10~30.

2. The method of claim 1, wherein the lithium battery binder for accelerated redox process is prepared by mixing the lithium battery binder for accelerated redox process of claim 1 with a solvent. Its characteristic is that the method includes the following steps: After drying polyethylene glycol at 50-100 °C for 1-2 hours, anhydrous dimethyl sulfoxide was added to obtain solution A. Then, 2,4-toluene diisocyanate and dibutyltin dilaurate were dissolved in anhydrous dimethyl sulfoxide to obtain solution B, which was added dropwise to solution A. After reacting at 50-100 °C for 2-3 hours, a prepolymer was obtained. Selenocysteine ​​dihydrochloride and triethylamine were added to anhydrous dimethyl sulfoxide and stirred for 0.1-1 hours to obtain solution C. This solution was added dropwise to the prepolymer and reacted at 50-100 °C for 2-3 hours, then dried under vacuum to obtain the product PUPEG-2000. In solution A: 0.1-0.5 mmol of polyethylene glycol is added to every 5 ml of anhydrous dimethyl sulfoxide; in solution B: 1-5 mmol of 2,4-toluene diisocyanate and 3-4 mg of dibutyltin dilaurate are added to every 5 ml of anhydrous dimethyl sulfoxide; in solution C: 0.5-1 mmol of selenocysteine ​​dihydrochloride and 5-10 mmol of triethylamine are added to every 5 ml of anhydrous dimethyl sulfoxide; the volume ratio of solutions A, B and C is (1-5):(1-5):(1-5).

3. The application of the lithium battery binder that can accelerate the redox process as described in claim 1, characterized in that it is used to prepare a lithium-ion battery anode or a lithium-sulfur battery cathode.

4. The application of the lithium battery binder that can accelerate the redox process as described in claim 3, characterized in that when used to prepare the negative electrode of a lithium-ion battery, it specifically includes the following steps: The binder, conductive agent, negative electrode active material, and dispersant are ball-milled and mixed into a slurry. The slurry is then coated onto a copper foil current collector with a coating thickness of 15-20 μm. After drying at 60-100 °C for 12 hours, it is used as the negative electrode for lithium-ion batteries. wherein The mass ratio of binder, conductive agent, negative electrode active material and dispersant is (1~6):(1~5):(90~98):(1~5); The negative electrode active material is one of natural graphite, artificial graphite, modified graphite, amorphous carbon materials, and nanostructured carbon materials. The conductive agent is acetylene black, Super P, multi-walled carbon nanotubes, or graphene; the dispersant is hydroxymethyl cellulose or water. The ball milling rotation speed is 300-600 r·min -1 under the conditions for 4-8 hours; the active substance loading is 1.2-2 mg·cm -2 ; The lithium-ion battery specifically uses lithium iron phosphate as the positive electrode, 1 M LiPF6 / EC+PC+DEC+EMC as the electrolyte, and Celgard-2325 commercial separator as the separator, with the volume ratio of EC, PC, DEC and EMC being 1:0.3:1:

1.

5. The application of the lithium battery binder that can accelerate the redox process as described in claim 3, characterized in that, when used to prepare the positive electrode of a lithium-sulfur battery, it specifically includes the following steps: The binder, conductive agent, positive electrode active material, and dispersant are ball-milled and mixed into a slurry. The slurry is then coated onto a carbon aluminum foil current collector with a coating thickness of 15-20 μm. After drying at 60-100 °C for 12 hours, it is used as the positive electrode for lithium-sulfur batteries. wherein The mass ratio of binder, conductive agent, positive electrode active material and dispersant is 1:1:(5~9):(30~60); The positive electrode active material is an S / C composite material prepared by the "sulfur infusion method" of elemental sulfur and multi-walled carbon nanotubes; The conductive agent is acetylene black, Super P, multi-walled carbon nanotubes, or graphene; the dispersant is N-methylpyrrolidone, N,N'-dimethylformamide, or water. The ball milling rotation speed is 300-600 r·min -1 under the conditions for 4-8 hours; the active substance loading is 1.2-2 mg·cm -2 ; The lithium-sulfur battery specifically uses lithium metal as the negative electrode, a Celgard-2400 polypropylene membrane as the separator, and a mixed solution of dimethoxyethane and 1,3-dioxolane in a volume ratio of 1:1 as the electrolyte, wherein lithium bis(trifluoromethanesulfonyl)imide and 0.1 M LiNO3 are used as additives.

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