Polymer binder containing star structure, preparation method and solid-state battery

Abstract

The invention provides a polymer binder containing a star structure, a preparation method and a solid-state battery. A polymer binder containing a star structure, wherein the binder is obtained by emulsion polymerization; the emulsion polymerization monomer comprises vinyl silane, hydroxyl acrylamide and a star-shaped long-chain monomer; the star-shaped long-chain monomer is obtained by lithiating a product obtained by reacting a carboxylation product of 1, 3, 5-tri (2-thienyl) benzene with sulfamic acid and enamine; one carboxyl group is condensed with enamine to introduce unsaturated alkenyl, and the other two carboxyl groups are condensed with sulfamic acid to introduce a lithium sulfonate group; the polymer is endowed with ionic conductivity; the interfacial compatibility of the binder and a polar base material is improved, and the material has better ion migration ability in an electrochemical system; the multi-amido bond enhances the intermolecular interaction, so that the polymer has high crosslinking degree, strong interface bonding force, good ionic conductivity and chemical stability, and is obviously superior to the conventional technology in high-performance electrode materials or special environment bonding application.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high polymer materials, in particular to a polymer binder containing a star-shaped structure, a preparation method and a solid-state battery. BACKGROUND

[0002] With the rapid development of lithium ion batteries, solid-state batteries and next-generation energy storage devices, the design of electrode materials not only requires high specific capacity and high stability, but also requires excellent mechanical bonding performance and interface stability. In the preparation of electrodes, the binder, as an indispensable component, plays a role in uniformly combining and fixing active material particles, conductive agents and electrolytes on the current collector. The performance of the binder directly affects the integrity of the electrode structure, the impedance of the electrode / electrolyte interface and the cycle life of the battery.

[0003] In traditional liquid electrolyte batteries, the earliest widely used binder is polyvinylidene fluoride (PVDF). PVDF has good chemical stability and film-forming property, but its own ionic conductivity is low, and it needs to use organic solvents such as N-methyl pyrrolidone (NMP), which brings environmental and cost problems. Subsequently, researchers developed water-based binders represented by polyacrylic acid (PAA), polyacrylonitrile (PAN), carboxymethyl cellulose (CMC), polyvinyl alcohol (PVA), etc., which improved the environmental friendliness and the binding ability of polar groups, but still had problems such as limited mechanical strength and insufficient ionic conduction. In solid-state batteries, in order to reduce the interface impedance and improve the flexibility, a binder system containing inorganic fillers such as polyether (such as PEO), polysulfonate, polyimide and composite was also appeared, which to some extent improved the interface stability, but the key problem was that the conductivity was insufficient, and the adhesion and flexibility were difficult to balance.

[0004] In summary, the existing binders generally have the following defects: Insufficient ion / electron conductivity: leading to high electrode interface impedance and reduced cycle efficiency; Limited molecular chain entanglement effect: unable to effectively fix active particles and conductive agents, prone to powder loss during cycling, affecting battery life; Insufficient interface bonding force: especially in solid-state electrolyte systems, poor electrode / electrolyte contact and large interface impedance; Performance difficult to balance: a single polymer often cannot meet the requirements of mechanical strength, conductivity and processability at the same time.

[0005] Therefore, there is an urgent need for a new binder that has conductivity, strong adhesion and flexibility to improve the binding state of electrode particles and interface performance in solid-state batteries. SUMMARY

[0006] Invention purposes: In view of the problems existing in the above-mentioned existing solid-state battery binder, the present application proposes a polymer binder material prepared by copolymerization of long-chain star-shaped compounds as monomers, which has certain electronic / ion conductivity, can reduce the interface impedance, and significantly improves the cycle stability and service life of the battery.

[0007] Technical scheme of the present application: In a first aspect, the present application provides a polymer binder containing a star-shaped structure, which is obtained by emulsion polymerization. The emulsion polymerization monomers include vinyl silane, hydroxy acrylamide and star-shaped long-chain monomers. The star-shaped long-chain monomer is obtained by reacting the carboxylation product of 1,3,5-tris(2-thienyl)benzene with aminosulfonic acid and enamine, and then lithiation.

[0008] In some embodiments, the vinyl silane is selected from one or more combinations of vinyl triethoxysilane, vinyl trimethoxysilane, and vinyl triisopropoxysilane.

[0009] In some embodiments, the hydroxy acrylamide is selected from one or more combinations of 2-hydroxyethyl methacrylamide or N-hydroxyethyl acrylamide; the hydroxy acrylamide contains -NH (donor) and carbonyl (acceptor), has stronger hydrogen bonding ability and polarity, forms stable hydrogen bonds with amide / sulfonic acid groups, and can improve adhesion and improve interface conductivity / ion transmission.

[0010] In some embodiments, the aminosulfonic acid is selected from one or more combinations of 4-aminopentane-1-sulfonic acid, 5-aminopentane-1-sulfonic acid, and 6-aminohexane-1-sulfonic acid.

[0011] In some embodiments, the enamine is selected from one or more combinations of 3-buten-1-amine, 3-methyl-3-buten-1-amine, and 4-penten-2-amine.

[0012] In some embodiments, the preparation method of the star-shaped long-chain monomer comprises the following steps: S1. Add solvent, then add diisopropylamine, then add n-BuLi, and stir; add ligand and continue stirring; slowly add 1,3,5-tris(2'-thienyl)benzene dissolved in solvent, stir and react; then add dry ice to the reactor, continue to react at low temperature, then slowly raise the temperature to room temperature, and continue to react; add dilute acid, extract, wash, dry, concentrate, and crystallize to separate the intermediate 1; S2. Add solvent, intermediate 1 and coupling agent to the second reactor to activate and obtain an activated solution; dissolve the enamine in solvent in another reactor, add base to form a free base solution; slowly drop the activated solution into the free base solution under low temperature stirring, after the reaction is completed, extract, wash, dry, filter and concentrate to obtain intermediate 2; S3. Add sulfamic acid and deionized water to the flask, add LiOH H2O solution under stirring, freeze-dry to obtain lithium salt solid; disperse the lithium salt solid in dry DMF, add base to form a free amine solution; S4. Add intermediate 2 and solvent to the reactor, cool, add coupling agent to activate; slowly drop the free amine solution obtained in step 3 into the above solution under low temperature stirring, monitor the reaction; after the reaction is completed, extract, wash, dry, filter and concentrate; collect by chromatography to obtain the star-shaped long-chain monomer.

[0013] In some embodiments, the molar ratio of the added diisopropylamine, 1,3,5-tris(2'-thiophene)benzene and n-BuLi is 3-6:1:3-6.

[0014] In some embodiments, the low temperature temperature for continuing the reaction in step 1 is -70~-80℃; the dilute acid is dilute hydrochloric acid.

[0015] In some embodiments, the coupling agent in step 2 is 2-(7-azabenzotriazole)-N,N,N',N'-tetramethyluronium hexafluorophosphate (HATU); the molar ratio of intermediate 1, coupling agent and enamine is 3-3.1:3.1-3.5:3-3.1; the base in step 2 is N,N-diisopropyl ethylamine (DIPEA); the molar ratio of enamine and base is 1:1-1.2.

[0016] In some embodiments, the molar ratio of sulfamic acid and LiOH H2O in step 3 is 1:1-1.2.

[0017] In some embodiments, the coupling agent in step 4 is 2-(7-azabenzotriazole)-N,N,N',N'-tetramethyluronium hexafluorophosphate (HATU); the molar ratio of intermediate 2, coupling agent and sulfamic acid is 3-3.1:6.1-6.5:6.1-6.5.

[0018] In some embodiments, the mass fraction of each component in the emulsion polymerization monomer is: vinyl silane 40-70 parts, hydroxy acrylamide 10-30 parts and star-shaped long-chain monomer 10-30 parts.

[0019] The present application needs to achieve a balance of various properties, such as electrical conductivity, enhanced adhesion, powder prevention and flexibility of the adhesive, and if the content of a certain component is too high, too much emphasis is placed on a certain performance, which will lead to a decline in other performances.

[0020] In a second aspect, the present application provides a preparation method of the star-shaped structure polymer adhesive, comprising the following steps: The initiator, vinyl silane, hydroxy acrylamide, star-shaped long-chain monomer, emulsifier and water are weighed and mixed, heated and polymerized, and after demulsification, water washing and drying, the polymer adhesive is obtained.

[0021] In a third aspect, the present application also provides a solid-state battery comprising the star-shaped structure polymer adhesive.

[0022] Advantages: The adhesive designed by the present application takes a star as the core structure, introduces an unsaturated alkenyl group through condensation of one carboxyl group with an enamine, and introduces a lithium sulfonate group through condensation of the other two carboxyl groups with a sulfamic acid. The lithium sulfonate group on the structure endows ionic conductivity; can improve the interfacial compatibility of the adhesive with a polar substrate, and also enables the material to have better ion migration ability in an electrochemical system; the multiple carboxyl groups + amide bond enhances intermolecular interaction, improving the adhesion of the adhesive to inorganic substrates, and the amide bond itself has high chemical stability, acid and alkali resistance and heat resistance; the adhesive provided by the present application has high crosslinking degree, strong interfacial bonding force, good ionic conductivity and chemical stability, and is obviously superior to conventional technology in high-performance electrode material or special environment bonding applications. DETAILED DESCRIPTION

[0023] The present application will be described below in conjunction with specific embodiments. It should be noted that the following examples are examples of the present application and are only used to illustrate the present application, but not to limit the present application. Other combinations and various modifications within the concept of the present application can be made without departing from the spirit or scope of the present application.

[0024] The chemical reagents used in the present application are commercially available and of analytical purity unless otherwise specified. EGCG is purchased from Aladdin with the item number E107404; polydimethylsiloxane is purchased from Yikang Chemical with the item number 9016-00-6.

[0025] Preparation example of star-shaped long-chain monomer 1 S1. Add 100 mL of tetrahydrofuran to the reactor, add 9.3 mmol of diisopropylamine, cool to -75°C, then add 9.3 mmol of n-BuLi, stir for 2 h; add 9.3 mmol of TMEDA, continue stirring; slowly add 50 mL of tetrahydrofuran dissolved in 3.1 mmol of 1,3,5-tris(2'-thiophene)benzene, stir for 1 h at -75°C; then add dry ice to the reactor and continue stirring for 2 h, then slowly raise the temperature to room temperature, continue stirring for 2 h; add dilute hydrochloric acid, extract, wash, dry, concentrate, crystallize and separate to obtain intermediate 1; S2. Add 100 mL of DMF to the reactor, add 3.1 mmol of intermediate 1 and 3.1 mmol of HATU at 0°C, stir for 10 min to activate, and obtain an activated solution; dissolve 3.2 mmol of 3-buten-1-amine in 20 mL of DMF in another reactor, add 3.2 mmol of DIPEA at 0°C to form a free base solution; slowly add the activated solution to the free base solution at 0°C, stir for 1 h, and after the reaction is completed, extract with solvent, wash, dry, filter and concentrate to enrich intermediate 2; S3. Add 6.2 mmol of 6-amino hexane-1-sulfonic acid and 20 mL of deionized water to the flask, add 6.5 mmol of LiOH·H2O solution under stirring, stir until pH=7, and freeze-dry to obtain lithium salt solid; disperse the lithium salt solid in 20 mL of dry DMF, add 12 mmol of DIPEA to form a free amine solution; S4. Add 3.1 mmol of intermediate 2 and 100 mL of DMF to the reactor, cool to 0°C, add 6.2 mmol of HATU and stir for 10 min at 0°C to activate; slowly add the free amine solution obtained in step 3 to the above solution, keep stirring at 0°C for 1 h, raise the temperature to room temperature and continue stirring for 2 h; after the reaction is completed, extract with solvent, wash, dry, filter and concentrate; separate by chromatography to obtain star-shaped long-chain monomer 1.

[0026] The star-shaped long-chain monomer 1 is analyzed by infrared spectroscopy by pressing it with KBr, and according to the infrared spectrogram analysis, it can be obtained that: at 3400 cm -1 : ν(N–H), N-H absorption peak of triple amide, broadened by hydrogen bonding, three shoulder peaks can be seen; 2950 cm -1 : ν(C–H), stretching of aliphatic CH2 / CH3; 3050 cm -1 : ν(=C–H) terminal alkenyl group; 1680 cm -1 : ν(C=O), main peak of amide; 1225 cm -1: v as (S03-), asymmetric stretching of sulfonate; 1600 cm -1 : aromatic ring skeleton; 1025 cm -1 : v s (S03-), symmetric stretching of sulfonate; 990 cm -1 : terminal vinyl group =CH2. No 1710-1725 free carboxylic acid C=0 and 2500-3300 wide OH, indicating that the tricarboxylic acid has been completely amidated; from the above analysis, the infrared spectrum data confirms that the star-shaped long-chain monomer 1 is successfully prepared.

[0027] Star-shaped long-chain monomer 2 The preparation example is basically the same as that of the star-shaped long-chain monomer 1, except that S3 and S4 are omitted.

[0028] Star-shaped long-chain monomer 3 The preparation example is basically the same as that of the star-shaped long-chain monomer 1, except that the enamine in S2 is 3-methyl-3-butene-1-amine, and the aminosulfonic acid in S3 is 4-aminopentane-1-sulfonic acid.

[0029] Star-shaped long-chain monomer 4 The preparation example is basically the same as that of the star-shaped long-chain monomer 1, except that the enamine in S2 is 4-penten-2-amine, and the aminosulfonic acid in S3 is 5-aminopentane-1-sulfonic acid.

[0030] Example Ammonium persulfate, sodium bisulfite, vinyl silane, hydroxy acrylamide, star-shaped long-chain monomer, sodium hexadecyl sulfonate, and water were weighed into a flask, vacuumed and replaced with nitrogen, heated to 35°C and polymerized for 2 hours, then emulsion broken, washed with water and dried to obtain the polymer.

[0031] The formulations of each group of examples are shown in Table 1 (unit: mass parts).

[0032] Table 1

[0033] Comparative example Ammonium persulfate, sodium bisulfite, vinyl silane, hydroxy acrylamide, star-shaped long-chain monomer, sodium hexadecyl sulfonate, and water were weighed into a flask, vacuumed and replaced with nitrogen, heated to 35°C and polymerized for 2 hours, then emulsion broken, washed with water and dried to obtain the polymer.

[0034] The formulations of each group of comparative examples are shown in Table 2 (unit: mass parts).

[0035] Table 2

[0036] Performance test Take 0.49 g of positive active material NCM811, 0.14 g of solid-state electrolyte LPSC651, 0.035 g of conductive agent VGCF and 0.35 g of the above prepared binder polymer, then mix the slurry in a swing ball mill at a speed of 1000 rpm for 30 min, then coat it on an aluminum foil with a 300 um SQZ four-sided preparation device, dry at 50℃ for 12h. Get the positive electrode sheet.

[0037] Take 0.476 g of negative active material Si / C-450, 0.126 g of solid-state electrolyte LPSC651, 0.035 g of conductive agent VGCF and 0.63 g of glue solution, then mix the slurry in a swing ball mill at a speed of 1000 rpm for 30 min, then coat it on a stainless steel foil with a 300 um SQZ four-sided preparation device, dry at 50℃ for 12h. Get the negative electrode sheet.

[0038] Cut the prepared positive or negative electrode into a small round piece of 10 mm in diameter, weigh 85 mg of LPSC651 into the mold, press twice at a pressure of 300Mpa, then add the electrode at one end, press twice under the same conditions, then add a 10 mm diameter In piece and an 8 mm lithium piece, seal, then use a 3.5N torque wrench to tighten the mold frame, and get the test solid-state battery.

[0039] Test the sample materials prepared in the above examples and comparative examples as follows: 1. Ion conductivity test method: The obtained positive electrode small round piece is tested by EIS using a Wantong electrochemical workstation, with an amplitude of 5mV and a frequency of 0.01-107Hz. According to the test results, the R value is obtained, the thickness of the electrolyte film is measured to obtain the L value, and the S value is obtained by calculating the area of the small round piece. According to the formula, the ion conductivity of the electrolyte film is calculated: σ Li+ =L / RS.

[0040] 2. Peeling strength test: A KT-PSA-1056 peeling force tester is used to test the peeling strength of the prepared dried positive and negative electrode sheets.

[0041] First charge-discharge test: 3. First charge-discharge test: Place the assembled mold battery in a 45℃ constant temperature box for 12h, then perform 0.05C charge-discharge test on the positive electrode in the voltage range of 2.4-3.7V, and the theoretical specific capacity is 200mAh·g -1 . Perform 0.05C charge-discharge test on the negative electrode in the voltage range of -0.6-0.9V, and the theoretical specific capacity is 200mAh·g -1 , calculate the efficiency.

[0042] The test results are shown in Table 3.

[0043] Table 3 Test results

[0044] The binder provided by the application takes a long-chain star compound as a core structure, introduces an unsaturated alkenyl group through condensation of one carboxyl group with an alkenyl amine, facilitates subsequent grafting, and introduces a lithium sulfonate group through condensation of the other two carboxyl groups with an amino sulfonic acid, thereby improving the electrical conductivity. The molecular structure has obvious advantages in performance compared with the prior art.

[0045] As can be seen from the comparison between the examples and Comparative Example 1, the long-chain structure of the star compound is conducive to improving the bonding strength and peeling strength of the binder, provides flexibility and ductility, significantly improves the overall interface stability, and improves the Li + The migration environment. At the same time, the polymer has a large number of amide groups, and the amide group provides a hydrogen bond donor (N-H) and acceptor (C=O) at the same time, which can form a large number of hydrogen bonds between the polymer chains and the surface of the electrode particles, so that the film layer is more dense, avoiding the pulverization and interface shedding of the active material during the charging and discharging process.

[0046] At the same time, as can be seen from the examples and the comparative example, the lithium sulfonate group endows ionic conductivity and hydrophilicity, and the star polymer has a conjugated structure, which reduces the potential and further improves the ionic conductivity and charging and discharging efficiency.

[0047] The application can also be embodied in other various embodiments without departing from the spirit and essence of the application, and those skilled in the art can make various corresponding changes and modifications according to the application, but these corresponding changes and modifications should all belong to the protection scope of the claims attached to the application.

Claims

1. A polymer binder containing a star-shaped structure, wherein the binder is obtained by emulsion polymerization; The emulsion polymerization monomers include vinyl silane, hydroxy acrylamide and star-shaped long-chain monomers; The star-shaped long-chain monomer is obtained by reacting a carboxylation product of 1,3,5-tri(2-thienyl)benzene with aminosulfonic acid and enamine, and then performing lithiation.

2. The polymer binder containing a star-shaped structure according to claim 1, characterized in that: The vinyl silane is selected from one or more combinations of vinyl triethoxysilane, vinyl trimethoxysilane and vinyl triisopropoxysilane.

3. The polymer binder containing a star-shaped structure according to claim 1, characterized in that: The hydroxyacrylamide is selected from one or more combinations of 2-hydroxyethylmethacrylamide and N-hydroxyethylacrylamide.

4. The polymer binder containing a star-shaped structure according to claim 1, characterized in that: The aminosulfonic acid is selected from one or more combinations of 4-aminopentane-1-sulfonic acid, 5-aminopentane-1-sulfonic acid, and 6-aminohexane-1-sulfonic acid.

5. The polymer binder containing a star-shaped structure according to claim 1, characterized in that: The enamine is selected from one or more combinations of 3-butene-1-amine, 3-methyl-3-butene-1-amine, and 4-pentene-2-amine.

6. The polymer binder containing a star-shaped structure according to claim 1, characterized in that: The preparation method of the star-shaped long-chain monomer comprises the following steps: S1. Add solvent to a reactor, add diisopropylamine, then add n-BuLi, and stir; add ligand and continue stirring; slowly add 1,3,5-tri(2'-thiophene)benzene dissolved in the solvent and stir to react; then add dry ice to the reactor and continue the reaction at low temperature, then slowly warm to room temperature and continue the reaction; add dilute acid, extract, wash, dry, concentrate, and crystallize to obtain intermediate 1; S2 then added to the reactor solvent, the intermediate 1 and the coupling agent were added for activation to obtain an activated solution; in another reactor, the enamine was dissolved in a solvent, a base was added to form a free base solution; The activated solution is slowly added dropwise to the free base solution with stirring at low temperature. After the reaction is completed, the intermediate 2 is extracted, washed, dried, filtered and concentrated to enrich the intermediate 2; S3. Add sulfamic acid and deionized water to a flask, add LiOH·H2O solution under stirring, and freeze-dry to obtain a lithium salt solid; disperse the lithium salt solid in dry DMF, add a base to form a free amine solution; S4. Intermediate 2 and a solvent were added to the reactor, the temperature was lowered, and a coupling agent was added for activation; The free amine solution obtained in step 3 is slowly added dropwise to the above solution and stirred at low temperature while monitoring the reaction; after the reaction is completed, the solution is extracted with a solvent, washed, dried, filtered and concentrated; The star-shaped long-chain monomer is collected by chromatography separation.

7. The polymer binder containing a star-shaped structure according to claim 5, characterized in that: The low temperature for continuing the reaction at a low temperature in step 1 is -70 to -80°C; the dilute acid is dilute hydrochloric acid; the coupling agent in step 2 is 2-(7-azabenzotriazole)-N,N,N',N'-tetramethyluronium hexafluorophosphate (HATU); the molar ratio of intermediate 1, coupling agent, and enamine is 3-3.1:3.1-3.5:3-3.1; the base in step 2 is N,N-diisopropylethylamine (DIPEA); the molar ratio of enamine and base is 1:1-1.2; the molar ratio of aminosulfonic acid and LiOH·H2O in step 3 is 1:1-1.2; the coupling agent in step 4 is 2-(7-azabenzotriazole)-N,N,N',N'-tetramethyluronium hexafluorophosphate (HATU); and the molar ratio of intermediate 2, coupling agent, and aminosulfonic acid is 3-3.1:6.1-6.5:6.1-6.

5.

8. The polymer binder containing a star-shaped structure according to claim 1, characterized in that: The mass proportions of the components in the emulsion polymerization monomer are: 40-70 parts of vinyl silane, 10-30 parts of hydroxyacrylamide and 10-30 parts of star-shaped long-chain monomer.

9. The method for preparing a polymer binder containing a star structure according to any one of claims 1 to 8, characterized in that: The steps include: An initiator, vinyl silane, hydroxyacrylamide, a star-shaped long-chain monomer, an emulsifier and water are weighed and mixed, heated for polymerization, demulsified, washed with water and dried to obtain a polymer binder.

10. A solid-state battery, characterized in that: The invention comprises the polymer binder containing a star-shaped structure according to any one of claims 1 to 8.

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