Solid-state battery binder, preparation method and application thereof, composite electrolyte membrane and solid-state battery composite positive electrode

Abstract

The invention relates to the technical field of solid-state batteries, and discloses a solid-state battery binder, a preparation method and application thereof, a composite electrolyte membrane and a solid-state battery composite positive electrode, and the solid-state battery binder is a product obtained by grafting a group represented by a formula (I) to non-polar unsaturated rubber. The grafting rate of the group shown in the formula (I) is 5-10%; -S-R-OH is shown in formula (I), and in the formula (I), R is selected from alkylene, phenylene and methylphenylene of C1-C6; the non-polar unsaturated rubber comprises at least one of styrene-butadiene-styrene block copolymer, butadiene rubber, butadiene styrene rubber, isoprene rubber and chloroprene rubber. The battery binding agent provided by the invention is strong in binding property and can be dissolved in a medium-polarity solvent or a weak-polarity solvent, and a solid-state battery prepared by applying the binding agent has more excellent electrochemical performance.

Description

Technical Field

[0001] The present invention relates to the technical field of solid-state batteries, and particularly relates to a solid-state battery binder, a preparation method and application thereof, a composite electrolyte membrane, and a solid-state battery composite positive electrode. Background Art

[0002] All-solid-state batteries use solid electrolytes to replace liquid electrolytes and separators, and can provide better safety performance and higher energy density. They are a very promising new type of battery. Among various solid electrolytes, sulfide-based solid electrolytes have become a research hotspot due to their high room-temperature ionic conductivity, even exceeding that of liquid electrolytes. However, all-solid-state batteries based on sulfides still face the combination problem of solvents and binders in wet manufacturing. In polar solvents, the lattice structure of sulfide electrolytes is damaged, resulting in a decrease in ionic conductivity.

[0003] In commercial liquid lithium-ion batteries, conventional polyvinylidene fluoride (PVDF) has become the main binder due to its mechanical, chemical, and electrochemical stability. Currently, existing PVDF-based binder systems can only dissolve in polar solvents, so they cannot meet the application requirements of sulfide-based solid-state batteries. The slurries for sulfide wet processes are mainly developed based on non-polar or weakly polar solvents. Due to the principle of "like dissolves like", the limitation of solvent selection will also limit the binder system, usually a non-polar or less polar polymer macromolecule system. However, the adhesion of these binders to sulfide electrolyte particles, ternary cathode active materials, and current collectors is relatively weak, resulting in poor processability and poor cycling performance of the battery.

[0004] Therefore, the development of new binders is crucial for achieving high-performance sulfide-based all-solid-state batteries. Summary of the Invention

[0005] The purpose of the present invention is to provide a battery binder with strong adhesion and capable of dissolving in medium-polarity solvents or weakly polar solvents.

[0006] To achieve the above purpose, the first aspect of the present invention provides a solid-state battery binder, which is a product obtained by grafting a non-polar unsaturated rubber with the group shown in formula (I); the grafting rate of the group shown in formula (I) is 5-10%; -S-R-OH formula (I), wherein, R is selected from C1-C6 alkylene, phenylene, or tolylene; The non-polar unsaturated rubber includes at least one of styrene-butadiene-styrene block copolymer, butadiene rubber, styrene-butadiene rubber, isoprene rubber, and chloroprene rubber.

[0007] The second aspect of the present invention provides a method for preparing the solid-state battery binder described in the first aspect above. The method includes: In the presence of a benzene solvent and a photoinitiator, a graft reaction is carried out between a non-polar unsaturated rubber and a compound represented by formula (II) to obtain a solid-state battery binder; the molar ratio of the compound represented by formula (II) to the carbon-carbon double bonds contained in the non-polar unsaturated rubber is 0.5-5:1; HS-R-OH formula (II), wherein, R is selected from C1-C6 alkylene groups, phenylene groups, and tolylene groups.

[0008] The third aspect of the present invention provides the application of the solid-state battery binder described in the first aspect above in a sulfide-based all-solid-state battery.

[0009] The fourth aspect of the present invention provides a composite electrolyte membrane, which contains a sulfide electrolyte and a solid-state battery binder; based on the total mass of the composite electrolyte membrane, the content of the sulfide electrolyte is 80-99 wt%, and the content of the solid-state battery binder is 1-20 wt%; the solid-state battery binder is the solid-state battery binder described in the first aspect above.

[0010] The fifth aspect of the present invention provides a solid-state battery composite positive electrode, which includes: an active material, a conductive agent, a sulfide electrolyte, and a solid-state battery binder; the solid-state battery binder is the solid-state battery binder described in the first aspect above.

[0011] The present invention introduces a hydroxyl group into a non-polar unsaturated rubber, which can significantly improve the adhesion while ensuring solubility in medium and weakly polar solvents.

[0012] The composite electrolyte membrane prepared by using this binder has better mechanical properties and flexibility, and at the same time has a higher room-temperature ionic conductivity.

[0013] The composite positive electrode prepared by using this binder forms more hydrogen bonds on the surface of the nickel cobalt manganese ternary positive electrode material with a coating layer in the composite positive electrode, enhancing the adhesion with the active material. Even when the addition amount of the binder is extremely small (<2%), there will be no powder falling phenomenon, and the coating of the electrode sheet is not easy to break and fall off during bending, optimizing the processing performance. And the hydrogen bond interaction between the solid-state battery binder provided by the present invention and the nickel cobalt manganese ternary active material can inhibit the volume expansion of nickel cobalt manganese particles, thereby reducing the rupture of nickel cobalt manganese particles and improving the cycling performance of the nickel cobalt manganese positive electrode.

[0014] The preparation method of the binder provided by the present invention is simple and effective, the reaction conditions are mild, the required product can be obtained only through one-step reaction, and the yield is high, which is of great significance for industrial production. Description of the Drawings

[0015] Figure 1It is the bond-line formula of the structural fragment of the solid-state battery binder synthesized in the present invention; Figure 2 It is the infrared spectrogram of the binders of each example and comparative example of the present invention; Figure 3 It is the 1H NMR spectra of SBS binder and SBS-OH binder; Figure 4 It is the 1H NMR spectra of BR binder and BR-OH binder; Figure 5 It is the 1H NMR spectra of SBR binder and SBR-OH binder; Figure 6 It is the cycling performance graph of the battery assembled with Application Example 1-B and Application Comparative Example 1-B of the present invention at a current of 0.1C and 25°C; Figure 7 It is the impedance graph of the battery assembled with Application Example 1-B and Application Comparative Example 1-B of the present invention after 100 cycles at a current of 0.1C, 25°C; Figure 8 It is the impedance graph of the corresponding composite electrolyte membranes of each application example and application comparative example of the present invention at 25°C; Figure 9 It is the cycling performance graph of the battery assembled with Application Comparative Example 5-B at a current of 0.1C and 25°C; Figure 10 It is the impedance graph of the battery assembled with Application Comparative Example 5-B after 100 cycles at a current of 0.1C and 25°C; Figure 11 It is the impedance graph of the composite electrolyte membrane corresponding to Application Comparative Example 5-A at 25°C. Detailed implementation mode

[0016] The endpoints and any values within the ranges disclosed herein are not limited to the exact ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0017] The "C1-C6 alkylene group" described in the present invention means an alkylene group with a total of 1-6 carbon atoms, such as -CH2-, -CH2CH2-, -CH2CH(CH3)CH2-, including linear alkylene groups and branched alkylene groups.

[0018] The "phenylene group" described in the present invention refers to the group formed after removing two H atoms at any position on the benzene ring.

[0019] As used in the present invention, "tolylene" refers to a group formed by removing two H atoms from any position on the benzene ring of toluene.

[0020] It should be noted that in various aspects of the present invention, for the same components or terms in each aspect, the present invention only describes them once in one aspect without repeating the description. Those skilled in the art should not consider this as a limitation of the present invention.

[0021] As mentioned above, the first aspect of the present invention provides a solid-state battery binder, which is a product obtained by grafting a non-polar unsaturated rubber with the group represented by formula (I); the grafting rate of the group represented by formula (I) is 5-10%; -S-R-OH formula (I), wherein, R is selected from C1-C6 alkylene, phenylene, tolylene.

[0022] The non-polar unsaturated rubber includes at least one of styrene-butadiene-styrene block copolymer (SBS), butadiene rubber (BR), styrene-butadiene rubber (SBR), isoprene rubber (IR), chloroprene rubber (CR).

[0023] Preferably, in formula (I), R is selected from -CH2-, -CH2CH2-, -CH2CH2CH2-.

[0024] Preferably, the weight-average molecular weight of the non-polar unsaturated rubber is 50,000-300,000, preferably 120,000-200,000.

[0025] In some embodiments, the solid-state battery binder is a product obtained by grafting styrene-butadiene-styrene block copolymer with -S-CH2CH2-OH. Preferably, the weight-average molecular weight of the styrene-butadiene-styrene block copolymer is 100,000-200,000. Preferably, the content of styrene structural units in the styrene-butadiene-styrene block copolymer is 25-35 wt%.

[0026] In some embodiments, the solid-state battery binder is a product obtained by grafting butadiene rubber with -S-CH2CH2-OH. Preferably, the weight-average molecular weight of the butadiene rubber is 200,000-300,000.

[0027] In some embodiments, the solid-state battery binder is a product obtained by grafting styrene-butadiene rubber with -S-CH2CH2-OH. Preferably, the weight-average molecular weight of the styrene-butadiene rubber is 50,000-80,000. Preferably, the content of styrene structural units in the styrene-butadiene rubber is 20-30 wt%.

[0028] According to a preferred embodiment 1, the solid-state battery binder is a product obtained by grafting styrene-butadiene-styrene block copolymer with -S-CH2CH2-OH, and the molecular formula of the solid-state battery binder is (C8H8) m (CH2CH=CHCH2) n (C8H8) k (C6H 11 SOH) h [CH2CH(CH=CH2)] j , where the value of m + k is 430 - 450, and the value of n + h + j is 2500 - 2700.

[0029] It should be noted that (C8H8), (CH2CH=CHCH2), (C8H8), (C6H 11 SOH), and [CH2CH(CH=CH2)] in the molecular formula of the solid-state battery binder refer to the structural units contained in the solid-state battery binder. The aforementioned arrangement order of each structural unit does not represent the connection relationship order. m, n, k, h, and j represent the number of repeating units of each structural unit. The present invention exemplarily provides partial structural fragments of the solid-state battery binder, specifically as shown in the left figure of Figure 1 .

[0030] According to a preferred embodiment 2, the solid-state battery binder is a product obtained by grafting butadiene rubber with -S-CH2CH2-OH, and the molecular formula of the solid-state battery binder is (CH2CH=CHCH2) m (C6H 11 SOH) n , where the value of m + n is 6100 - 6300.

[0031] It should be noted that (CH2CH=CHCH2) and (C6H 11 SOH) in the molecular formula of the solid-state battery binder refer to the structural units contained in the solid-state battery binder. The aforementioned arrangement order of each structural unit does not represent the connection relationship order. m and n represent the number of repeating units of each structural unit. The present invention exemplarily provides partial structural fragments of the solid-state battery binder, specifically as shown in the middle figure of Figure 1 .

[0032] According to a preferred embodiment 3, the solid-state battery binder is a product obtained by grafting styrene-butadiene rubber with -S-CH2CH2-OH, and the molecular formula of the solid-state battery binder is (C8H8) m (CH2CH=CHCH2) n (C6H 11 SOH) k [CH2CH(CH=CH2)]h where the value of m ranges from 100 to 150, and the value of n + k + h ranges from 900 to 1000.

[0033] It should be noted that (C8H8), (CH2CH=CHCH2), (C6H 11 SOH), and [CH2CH(CH=CH2)] in the molecular formula of the solid-state battery binder refer to the structural units contained in the solid-state battery binder. The aforementioned arrangement order of each structural unit does not represent the connection relationship order. m, n, k, and h represent the number of repeating units of each structural unit. The present invention exemplarily provides partial structural fragments of the solid-state battery binder, specifically as shown in the right figure of Figure 1 as follows.

[0034] As described above, the second aspect of the present invention provides a method for preparing the solid-state battery binder described in the first aspect above. The method includes: Performing a graft reaction on the non-polar unsaturated rubber and the compound represented by formula (II) in the presence of a benzene solvent and a photoinitiator to obtain a solid-state battery binder; the molar ratio of the compound represented by formula (II) to the carbon-carbon double bonds contained in the non-polar unsaturated rubber is 0.5 - 5:1; HS-R-OH Formula (II), wherein, R is selected from C1-C6 alkylene, phenylene, and tolylene.

[0035] Preferably, the compound represented by formula (II) includes at least one of mercaptoethanol, 3-mercapto-1-propanol, 4-mercapto-1-butanol, 3-mercapto-2-methylpentanol, 6-mercaptohexan-1-ol, p-hydroxythiophenol, 2-hydroxythiophenol, 3-hydroxythiophenol, 4-hydroxy-3-methylthiophenol; particularly preferably mercaptoethanol.

[0036] Preferably, the molar ratio of the compound represented by formula (II) to the carbon-carbon double bonds contained in the non-polar unsaturated rubber is 1 - 2.5:1.

[0037] In some embodiments of the present invention, the photoinitiator includes at least one of phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, 1-hydroxycyclohexyl phenyl ketone, 2,2-dimethoxy-2-phenylacetophenone, ethyl 2,4,6-trimethylbenzoylphosphinate, 2-benzyl-2-dimethylamino-1-(4-morpholinobenzylphenyl)butanone; particularly preferably 1-hydroxycyclohexyl phenyl ketone.

[0038] In some embodiments of the present invention, the benzene solvent includes at least one of benzene, toluene, o-xylene, m-xylene, p-xylene, and anisole.

[0039] Preferably, the molar ratio of the photoinitiator to the carbon-carbon double bonds contained in the non-polar unsaturated rubber is 0.01-0.05:1, preferably 0.01-0.02:1.

[0040] Preferably, the grafting reaction is carried out under ultraviolet light irradiation, and the conditions of the grafting reaction include: the temperature is 10-50 °C, preferably 20-35 °C; the time is 10 min to 5 h, preferably 1-2 h.

[0041] Preferably, the wavelength of the ultraviolet light irradiation for the grafting reaction is 365-380 nm.

[0042] According to a preferred specific embodiment of the present invention, the method for preparing the solid-state battery binder includes: S1: In the presence of a benzene solvent, the non-polar unsaturated rubber and the compound shown in formula (II) are subjected to a first mixing to obtain an intermediate mixture; S2: In the presence of a photoinitiator, under ultraviolet light irradiation, the intermediate mixture is subjected to the grafting reaction to obtain the solid-state battery binder.

[0043] The present invention does not particularly limit the conditions of the first mixing, as long as the non-polar unsaturated rubber can be dissolved in the benzene solvent and the compound shown in formula (II) can be evenly dispersed in the mixing system. The present invention will not elaborate here, and those skilled in the art should not understand it as a limitation of the present invention.

[0044] The method of the present invention may further include post-treatment means known in the art such as extraction, washing, and drying. Exemplarily, the product in the mixing system after the grafting reaction is extracted with methanol, redissolved in a benzene solvent, repeated three times, and the unreacted small molecules are washed away. The obtained product is placed in a freeze dryer and dried for 24 h to remove the solvent completely to obtain the solid-state battery binder. The present invention will not elaborate here, and those skilled in the art should not understand it as a limitation of the present invention.

[0045] As described above, the third aspect of the present invention provides the application of the solid-state battery binder described in the first aspect in a sulfide-based all-solid-state battery.

[0046] Preferably, the sulfide-based all-solid-state battery is a sulfide-based all-solid-state lithium-ion battery.

[0047] As described above, the fourth aspect of the present invention provides a composite electrolyte membrane, which contains a sulfide electrolyte and a solid-state battery binder; based on the total mass of the composite electrolyte membrane, the content of the sulfide electrolyte is 80-99 wt%, and the content of the solid-state battery binder is 1-20 wt%; the solid-state battery binder is the solid-state battery binder described in the first aspect above.

[0048] Preferably, the thickness of the composite electrolyte membrane is 20-40 μm.

[0049] According to a preferred embodiment of the present invention, the sulfide electrolyte includes at least one of Li7P2S8I, αLi2S-(100-α)P2S5, Li 6-X5-X6 P 1-X6 T X6 S 5-X5-X7 G X7 Z X5+1 and the like; wherein, 70≤α≤80, 0≤X5<1, 0≤X6<1, 0≤X7<1; T is selected from at least one of Ge, Si, Sn, Sb, and As; G is O and / or Se; Z is selected from at least one of Cl, Br, and I.

[0050] According to a preferred specific embodiment of the present invention, the preparation method of the composite electrolyte membrane includes: In the presence of organic solvent I, the sulfide electrolyte and the solid-state battery binder are dispersed to obtain a dispersion; then the dispersion is cast and dried in sequence to obtain the composite electrolyte membrane.

[0051] Preferably, the organic solvent I is selected from at least one of toluene, p-xylene, and anisole.

[0052] Preferably, relative to 100 mL of the organic solvent I, the dosage of the solid-state battery binder is 0.5-5 g.

[0053] Preferably, the method further includes: subjecting the product obtained after the drying to hot pressing to obtain the composite electrolyte membrane.

[0054] The present invention has no particular requirements on the ways of the dispersion treatment, casting, drying, and hot pressing, and those skilled in the art can adopt the known methods in the art.

[0055] As described above, the fifth aspect of the present invention provides a solid-state battery composite positive electrode, which includes: an active material, a conductive agent, a sulfide electrolyte, and a solid-state battery binder; the solid-state battery binder is the solid-state battery binder described in the first aspect above.

[0056] In the present invention, the sulfide electrolyte preferably used in the solid-state battery composite positive electrode has the same definition as that in the foregoing fourth aspect, and will not be elaborated here.

[0057] Preferably, the active material includes at least one of the compounds represented by formula (1), the compounds represented by formula (2), the compounds represented by formula (3), the compounds represented by formula (4), and the compounds represented by formula (5); Formula (1): LiCoO2; Formula (2): LiNi x1 Mn y1 Co 1-x1-y1 O2; Formula (3): LiNi 1-x2-y2 Co x2 Al y2 O2; Formula (4): LiNi x3 Mn 1-x3 O2; Formula (5): Li 1+x4 EO2; Wherein, x1, x2, x3, x4, y1, y2 are each independently selected from any value of 0-1; E is selected from any one of Mn, Ni, Co, and Al.

[0058] The "any value of 0-1" in the present invention includes the endpoint values of 0 and 1.

[0059] Preferably, the conductive agent is selected from at least one of conductive carbon black super-P, acetylene black, conductive carbon black Super C65, carbon fiber (VGCF), multi-walled carbon nanotube (MWCNT), single-walled carbon nanotube (SWCNT), and graphene.

[0060] Preferably, the solid-state battery composite positive electrode further includes a positive electrode current collector.

[0061] According to a preferred specific embodiment of the present invention, the preparation method of the solid-state battery composite positive electrode includes: SS1: In the presence of organic solvent II, the active material, the conductive agent, the sulfide electrolyte, and the solid-state battery binder are contacted and mixed to obtain a positive electrode slurry; SS2: The positive electrode slurry is coated on the surface of the positive electrode current collector, and after drying and rolling, the solid-state battery composite positive electrode is obtained.

[0062] Preferably, the mass ratio of the amounts of the active material, the sulfide electrolyte, the conductive agent, and the solid-state battery binder is (75-95):(5-25):(0.5-5):(0.5-3).

[0063] Preferably, the organic solvent II is a benzene-based solvent, and the organic solvent II is selected from at least one of benzene, toluene, o-xylene, m-xylene, p-xylene, and anisole.

[0064] The present invention will be described in detail below by way of examples. In the following examples, unless otherwise specified, the raw materials are commercially available products. Unless otherwise specified, room temperature means 25 ± 2 °C.

[0065] The anhydrous xylene used in the following examples is a mixture of commercially available o-xylene, m-xylene, and p-xylene.

[0066] Styrene-butadiene-styrene block copolymer (SBS): The weight-average molecular weight Mw = 150,000, and the content of styrene structural units is 30 wt%.

[0067] Butadiene rubber (BR): The weight-average molecular weight Mw = 250,000.

[0068] Styrene-butadiene rubber (SBR): The weight-average molecular weight Mw = 50,000, and the content of styrene structural units is 25 wt%.

[0069] The test or calculation method of the grafting rate involved in the following examples is as follows: The intensities of the peaks in the 1H NMR spectrum are related to the number of hydrogen atoms in the molecule. The integral represents the area ratio of different peaks, thus reflecting the number of hydrogen atoms, corresponding to the hydrogen atoms at different positions in the molecular structure, and calculating the grafting rate.

[0070] Example 1 Preparation of solid-state battery binder SBS-OH (1) Weigh 1 g of SBS and add it to a reaction vessel, then add 30 mL of anhydrous xylene, and stir for 1 h to completely dissolve it until it is uniformly dispersed without precipitation; (2) Add 30 mg of 1-hydroxycyclohexyl phenyl ketone and 1 mL of mercaptoethanol to the reaction solution, stir for 2 h, and after stirring evenly, carry out a grafting reaction under ultraviolet light irradiation for 1 h, the reaction temperature is 25 °C, and the ultraviolet light wavelength is 380 nm; (3) After the reaction is completed, pour the reaction solution into methanol, dissolve the obtained precipitate in xylene again, repeat three times, and then place the obtained precipitate in a freeze dryer and dry it for 24 h to obtain a solid-state battery binder (SBS-OH).

[0071] The molecular formula of SBS-OH is (C8H8) m (CH2CH=CHCH2) n (C8H8) k (C6H 11 (SOH) h[CH2CH(CH=CH2)] j ; where m + k ≈ 440, n + h + j ≈ 2600; the grafting rate is 8.3%.

[0072] Figure 1 The left figure in shows a partial structural fragment of SBS-OH. The infrared spectrum is as shown in Figure 2 (a) in, characterized by: an -OH peak near 3300 cm -1 position, and the 1H NMR spectrum is as shown in Figure 3 , characterized by: two sets of peaks at 2.7 and 3.7 ppm.

[0073] Application Example 1-A Application of the binder SBS-OH in the composite electrolyte membrane in Example 1 Dissolve 1 g of the SBS-OH binder in 300 mL of p-xylene solution, and add 99 g of Li 5.5 PS 4.5 Cl 0.75 Br 0.75 (LPSCB) sulfide electrolyte into the solution, stir to make the sulfide electrolyte uniformly dispersed, and finally cast it onto a polytetrafluoroethylene plate to evaporate the solvent to obtain the LPSCB-(SBS-OH) composite electrolyte membrane.

[0074] Application Comparative Example 1-A Application of the binder SBS in the composite electrolyte membrane Dissolve 1 g of the SBS binder in 300 mL of p-xylene solution, and add 99 g of Li 5.5 PS 4.5 Cl 0.75 Br 0.75 sulfide electrolyte into the solution, stir to make the sulfide electrolyte uniformly dispersed, and finally cast it onto a polytetrafluoroethylene plate to evaporate the solvent to obtain the LPSCB-SBS composite electrolyte membrane.

[0075] Application Example 1-B Application of the binder SBS-OH in all-solid-state lithium-ion batteries in Example 1 According to the mass ratio of LiNi 0.83 Co 0.11 Mn 0.06 O2:LPSCB:Super P:SBS-OH = 80:20:2:1 for pulping. First dissolve the SBS-OH binder in anhydrous toluene, and then add LiNi 0.83 Co 0.11 Mn 0.06O2, LPSCB sulfide electrolyte, and carbon fiber VGCF were added to the above mixed system and stirred at a speed of 800 rpm for 4 h to obtain a homogeneous slurry. Then, it was cast onto an aluminum foil and subsequently dried in a vacuum oven at 70 °C for 12 h to obtain a composite positive electrode sheet. The dried positive electrode sheet was cut into positive electrode sheets with a diameter of 10 mm on a manual slicing machine. The composite electrolyte membrane in Application Example 1-A was used as the intermediate electrolyte separator layer, and a lithium-indium alloy was selected as the negative electrode to assemble a battery, and cyclic tests were carried out in a glove box.

[0076] Apply Comparative Example 1-B Application of Binder SBS in All-Solid-State Lithium-Ion Batteries According to LiNi 0.83 Co 0.11 Mn 0.06 O2:LPSCB:Super P:SBS = 80:20:2:1 by mass ratio for pulping. First, the SBS binder was dissolved in anhydrous toluene, and then LiNi 0.83 Co 0.11 Mn 0.06 O2, LPSCB sulfide solid electrolyte, and carbon fiber VGCF were added to the above mixed system and stirred at a speed of 800 rpm for 4 h to obtain a homogeneous slurry. Then, it was cast onto an aluminum foil and subsequently dried in a vacuum oven at 70 °C for 12 h to obtain a composite positive electrode sheet.

[0077] The dried electrode sheet was cut into positive electrode sheets with a diameter of 10 mm on a manual slicing machine. The composite electrolyte membrane in Application Example 1-A was selected as the intermediate electrolyte separator layer, and a lithium-indium alloy was selected as the negative electrode to assemble a battery, and cyclic tests were carried out in a glove box.

[0078] Example 2 Preparation of Solid-State Battery Binder BR-OH (1) Weigh 2 g of BR and add it to a reaction vessel, then add 50 mL of anhydrous xylene, and stir for 30 min until it is completely dissolved and dispersed evenly without precipitation. (2) Add 210 mg of phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide and 5.5 mL of mercaptoethanol to the reaction solution, stir for 3 h. After stirring evenly, carry out a grafting reaction under ultraviolet light irradiation for 2 h, the reaction temperature is 25 °C, and the ultraviolet light wavelength is 380 nm. (3) After the reaction is completed, pour the reaction solution into methanol. The obtained precipitate is redissolved in xylene, repeated three times, and then the obtained precipitate is placed in a freeze dryer and dried for 24 h to obtain modified hydroxylated butadiene rubber (BR-OH).

[0079] The molecular formula of BR-OH is (CH2CH=CHCH2) m (C6H 11 SOH) n ; where m + n ≈ 6240; the grafting rate is 6.2%.

[0080] Figure 1 The middle diagram in shows a partial structural fragment of BR-OH. The infrared spectrum is as shown in (b) in Figure 2 , featuring an -OH peak near 3300 cm -1 . The 1H NMR spectrum is as shown in Figure 4 , featuring two sets of peaks at 2.7 and 3.7 ppm.

[0081] Application Example 2-A Application of the binder BR-OH in the composite electrolyte membrane in Example 2 Dissolve 1 g of the BR-OH binder in 300 mL of p-xylene solution, and add 99 g of Li 5.5 PS 4.5 Cl 1.5 sulfide electrolyte into the solution, stir to make the sulfide electrolyte disperse evenly, and finally cast it onto a polytetrafluoroethylene plate and evaporate the solvent to obtain a Li 5.5 PS 4.5 Cl 1.5 -(BR-OH) composite electrolyte membrane.

[0082] Application Comparative Example 2-A Application of the binder BR in the composite electrolyte membrane Dissolve 1 g of the BR binder in 300 mL of p-xylene solution, and add 99 g of Li 5.5 PS 4.5 Cl 1.5 sulfide electrolyte into the solution, stir to make the sulfide electrolyte disperse evenly, and finally cast it onto a polytetrafluoroethylene plate and evaporate the solvent to obtain a Li 5.5 PS 4.5 Cl 1.5 -BR composite electrolyte membrane.

[0083] Application Example 2-B Application of the binder BR-OH in all-solid-state lithium-ion batteries in Example 2 Prepare a slurry according to the mass ratio of LiNi 0.9 Co 0.06 Mn 0.04 O2:LPSC:MWCNT:BR-OH = 75:25:1.5:1. First, dissolve the BR-OH binder in anhydrous toluene, and then add LiNi 0.9 Co 0.06 Mn0.04 O2, Li 5.5 PS 4.5 Cl 1.5 O2, Li, PS, Cl, and multi-walled carbon nanotubes (MWCNT) were added to the above-mentioned mixed system, stirred at a speed of 500 rpm for 4 h to obtain a homogeneous slurry, then cast onto an aluminum foil, and subsequently placed in a vacuum oven at 70 °C for 12 h to obtain a composite positive electrode sheet. The dried positive electrode sheet was cut into positive electrode sheets with a diameter of 10 mm on a manual slicing machine. The electrolyte membrane in Application Example 2-A was selected as the intermediate electrolyte separator layer, and a lithium-indium alloy was selected as the negative electrode to assemble a battery, and cyclic testing was carried out in a glove box.

[0084] Application of Comparative Example 2-B Application of Binder BR in All-Solid-State Lithium-Ion Batteries According to the mass ratio of LiNi 0.9 Co 0.06 Mn 0.04 O2:LPSCB:MWCNT:BR = 75:25:1.5:1, pulping was carried out. First, the BR binder was dissolved in anhydrous toluene, and then LiNi 0.9 Co 0.06 Mn 0.04 O2, Li 5.5 PS 4.5 Cl 1.5 Sulfide solid electrolyte, multi-walled carbon nanotubes (MWCNT) were added to the above-mentioned mixed system, stirred at a speed of 500 rpm for 4 h to obtain a homogeneous slurry, then cast onto an aluminum foil, and subsequently placed in a vacuum oven at 70 °C for 12 h to obtain a composite positive electrode sheet.

[0085] The dried electrode sheet was cut into positive electrode sheets with a diameter of 10 mm on a manual slicing machine. The electrolyte membrane in Application Example 2-A was selected as the intermediate electrolyte separator layer, and a lithium-indium alloy was selected as the negative electrode to assemble a battery, and cyclic testing was carried out in a glove box.

[0086] Example 3 Preparation of Solid-State Battery Binder SBR-OH (1) Weigh 2 g of SBR and add it to a reaction vessel, then add 100 mL of anhydrous xylene, stir for 1 h to completely dissolve it, and disperse it evenly until there is no precipitate. (2) Add 100 mg of 2,2-dimethoxy-2-phenylacetone and 3.6 mL of mercaptoethanol to the reaction solution, stir for 1 h. After stirring evenly, carry out a grafting reaction for 1 h under ultraviolet light irradiation. The reaction temperature is 25 °C, and the ultraviolet light wavelength is 380 nm. (3) After the reaction is completed, pour the reaction solution into methanol. Dissolve the obtained precipitate in xylene and repeat this process three times. Then, place the obtained precipitate in a freeze dryer and dry it for 24 h to obtain modified hydroxylated styrene-butadiene rubber (SBR-OH).

[0087] The molecular formula of SBR-OH is: (C8H8) m (CH2CH=CHCH2) n (C6H 11 SOH) k [CH2CH(CH=CH2)] h ; where m ≈ 120, n + k + h ≈ 940; the grafting rate is 6.9%.

[0088] Figure 1 The right figure in... shows a partial structural fragment of SBR-OH. The infrared spectrum is as shown in Figure 2 (c) in..., characterized by an -OH peak near 3300 cm -1 position. The nuclear magnetic resonance hydrogen spectrum is as shown in Figure 5 ..., characterized by two sets of peaks at 2.7 and 3.7 ppm.

[0089] Application Example 3-A Application of the binder SBR-OH in the composite electrolyte membrane in Example 3 Dissolve 1 g of the SBR-OH binder in 300 mL of p-xylene solution. Add 99 g of Li 5.6 PS 4.6 Cl 1.4 sulfide electrolyte into the solution and stir to make the sulfide electrolyte disperse evenly. Finally, cast it onto a polytetrafluoroethylene plate and evaporate the solvent to obtain the Li 5.6 PS 4.6 Cl 1.4 -(SBR-OH) composite electrolyte membrane.

[0090] Application Comparative Example 3-A Application of the binder SBR in the composite electrolyte membrane Dissolve 1 g of SBR in 300 mL of p-xylene solution. Add 99 g of Li 5.6 PS 4.6 Cl 1.4 sulfide electrolyte into the solution and stir to make the sulfide electrolyte disperse evenly. Finally, cast it onto a polytetrafluoroethylene plate and evaporate the solvent to obtain the Li 5.6 PS 4.6 Cl 1.4 -SBR composite electrolyte membrane.

[0091] Application Example 3-B Application of Binder SBR-OH in All-Solid-State Lithium-Ion Batteries in Example 3 According to LiNi 0.93 Co 0.03 Mn 0.04 O2:LPSC:C65:SBR-OH = 85:15:1:0.5 by mass ratio for pulping. First, dissolve the SBR-OH binder in anhydrous toluene, and then add LiNi 0.93 Co 0.03 Mn 0.04 O2, Li 5.6 PS 4.6 Cl 1.4 sulfide solid electrolyte, conductive carbon black C65 into the above mixing system, stir at a speed of 500 rpm for 4 h to obtain a homogeneous slurry, then cast it onto an aluminum foil, and then place it in a vacuum oven at 80 °C for drying for 12 h to obtain a composite positive electrode sheet; The dried positive electrode sheet is cut into positive electrode sheets with a diameter of 10 mm on a manual slicing machine, select the electrolyte membrane in Application Example 3-A as the intermediate electrolyte separator layer, select lithium indium alloy as the negative electrode, assemble the battery, and conduct a cycle test in a glove box.

[0092] Application of Comparative Example 3-B Application of Binder SBR in All-Solid-State Lithium-Ion Batteries According to LiNi 0.93 Co 0.03 Mn 0.04 O2:LPSC:C65:SBR = 85:15:1:0.5 by mass ratio for pulping.

[0093] First, dissolve the SBR binder in anhydrous toluene, and then add LiNi 0.93 Co 0.03 Mn 0.04 O2, Li 5.6 PS 4.6 Cl 1.4 sulfide electrolyte, conductive carbon black C65 into the above solvent, stir at a speed of 500 rpm for 4 h to obtain a homogeneous slurry, then cast it onto an aluminum foil, and then place it in a vacuum oven at 80 °C for drying for 12 h to obtain a composite positive electrode sheet; The dried electrode sheet is cut into positive electrode sheets with a diameter of 10 mm on a manual slicing machine, select the electrolyte membrane in Application Example 3-A as the intermediate electrolyte separator layer, select lithium indium alloy as the negative electrode, assemble the battery, and conduct a cycle test in a glove box.

[0094] Comparative Example 1 Preparation of Solid-State Battery Binder SBS-COOH (1) Weigh 1 g of SBS and add it to the reaction vessel. Then add 30 mL of anhydrous xylene and stir for 1 h until it is completely dissolved and evenly dispersed without precipitation. (2) Add 30 mg of 1-hydroxycyclohexyl phenyl ketone and 1 mL of mercaptoacetic acid to the reaction solution, stir for 2 h. After stirring evenly, carry out the grafting reaction under ultraviolet light irradiation for 1 h. The reaction temperature is 25 °C and the ultraviolet light wavelength is 380 nm. (3) After the reaction is completed, pour the reaction solution into methanol. The obtained precipitate is redissolved in xylene and repeated three times. Then place the obtained precipitate in a freeze dryer and dry for 24 h to obtain the solid-state battery binder (SBS-COOH).

[0095] The molecular formula of SBS-COOH is (C8H8) m (CH2CH=CHCH2) n (C8H8) k (C5H 11 SCOOH) h [CH2CH(CH=CH2)] j ; where m + k ≈ 440, n + h + j ≈ 2600; the grafting rate is 8.2%.

[0096] Application Comparative Example 4-A It is carried out using a process similar to that of Application Example 1-A. The difference is that the SBS-OH binder is replaced with an equal mass of SBS-COOH binder, and the rest remain unchanged to prepare a composite electrolyte membrane.

[0097] Application Comparative Example 4-B It is carried out using a process similar to that of Application Example 1-B. The difference is that the SBS-OH binder is replaced with an equal mass of SBS-COOH binder, and the rest remain unchanged to prepare a solid-state battery.

[0098] Comparative Example 2 Preparation of the solid-state battery binder SBS-OH It is carried out using a process similar to that of Example 1. The difference is that the molar ratio of mercaptoethanol to the carbon-carbon double bonds contained in SBS is adjusted to prepare a solid-state battery binder SBS-OH with a grafting rate of 11.9%. The specific method is as follows: (1) Weigh 1 g of SBS and add it to the reaction vessel. Then add 30 mL of anhydrous xylene and stir for 1 h until it is completely dissolved and evenly dispersed without precipitation. (2) Add 30 mg of 1-hydroxycyclohexyl phenyl ketone and 5 mL of mercaptoethanol to the reaction solution, stir for 2 h. After stirring evenly, carry out the grafting reaction under ultraviolet light irradiation for 1 h. The reaction temperature is 25 °C and the ultraviolet light wavelength is 380 nm. (3) After the reaction was completed, the reaction solution was poured into methanol, and it was found that the obtained precipitate could no longer dissolve in xylene.

[0099] The product prepared in this comparative example had poor solubility in xylene, which did not meet the requirement that the binder for sulfide solid-state batteries should be soluble in medium and low polarity solvents.

[0100] Comparative Example 3 It was carried out using a process similar to that of Example 1. The difference was that the molar ratio of mercaptoethanol to the carbon-carbon double bonds in SBS was adjusted to prepare a solid-state battery binder SBS-OH with a grafting rate of 3.6%. The specific method was as follows: (1) Weigh 1 g of SBS and add it to a reaction vessel, then add 30 mL of anhydrous xylene, and stir for 1 h to completely dissolve it and disperse it evenly until there is no precipitate; (2) Add 30 mg of 1-hydroxycyclohexyl phenyl ketone and 0.5 mL of mercaptoethanol to the reaction solution, stir for 2 h, and after stirring evenly, carry out a grafting reaction under ultraviolet light irradiation for 1 h. The reaction temperature is 25 °C, and the ultraviolet light wavelength is 380 nm; (3) After the reaction was completed, the reaction solution was poured into methanol, and the obtained precipitate was redissolved in xylene, repeated three times, and then the obtained precipitate was placed in a freeze dryer and dried for 24 h.

[0101] This comparative example prepared an SBS-OH binder with a low grafting rate.

[0102] Application of Comparative Example 5-A It was carried out using a process similar to that of Application Example 1-A. The difference was that the SBS-OH binder prepared in Example 1 was replaced with an equal mass of the SBS-OH binder prepared in Comparative Example 3, and the rest remained unchanged to prepare a composite electrolyte membrane.

[0103] Application of Comparative Example 5-B It was carried out using a process similar to that of Application Example 1-B. The difference was that the SBS-OH binder prepared in Example 1 was replaced with an equal mass of the SBS-OH binder prepared in Comparative Example 3, and the rest remained unchanged to prepare a solid-state battery.

[0104] Test Example 1 The ionic conductivity and impedance of the sulfide composite electrolyte membrane prepared in the above examples were tested. The impedance diagram of the composite electrolyte membrane at 25 °C was as shown in Figure 8 and Figure 11 shown, where in Figure 8Among them, (a) shows the impedance diagram of the composite electrolyte membrane of Application Example 1-A and Application Comparative Example 1-A; (b) shows the impedance diagram of the composite electrolyte membrane of Application Example 2-A and Application Comparative Example 2-A; (c) shows the impedance diagram of the composite electrolyte membrane of Application Example 3-A and Application Comparative Example 3-A. Figure 11 It is the impedance diagram of the corresponding composite electrolyte membrane of Application Comparative Example 5-A at 25 °C.

[0105] The ionic conductivity was tested according to the following method: (i) Take a sulfide composite electrolyte membrane with a diameter of Φ = 10 mm; (ii) Stick stainless steel on both sides of the sulfide composite electrolyte membrane as a current collector, and press it at 150 MPa to obtain the sample I to be tested; (iii) Use an electrochemical workstation to test the impedance of the sample I to be tested, obtain the AC impedance spectrum diagram, obtain the impedance of the sulfide composite electrolyte membrane, and calculate the room-temperature ionic conductivity σ of the sulfide composite electrolyte membrane according to the formula σ = L / R 1 S where L is the thickness of the sulfide composite electrolyte membrane (in mm), R1 is the impedance of the sulfide composite electrolyte membrane (in Ω), and S is the contact area (in cm 2 ).

[0106] The physical and chemical property parameters of the composite electrolyte membrane are shown in Table 1.

[0107] Table 1

[0108] It can be seen from the above results that the composite electrolyte membrane prepared by using the solid-state battery binder provided by the present invention has low impedance and high ionic conductivity, and has better application prospects.

[0109] Test Example 2 The electrochemical performance of the batteries assembled in each application example and application comparative example was tested by the constant current charge and discharge method. The test conditions were constant temperature at 25 °C, voltage range of 2.4 - 3.7 V, and cycling at a rate of 0.1 C. All battery tests were carried out in a glove box.

[0110] Constant current charge and discharge can control the current and voltage during the charging and discharging processes, simulate the charging and discharging behavior of the battery in actual use, evaluate performance indicators such as the capacity, energy density, and Coulomb efficiency of the battery, and predict the cycle life of the battery.

[0111] The specific results are shown in Table 2.

[0112] Table 2

[0113] Figure 6 Figure 1 shows the cycle performance graph of the batteries assembled with Application Example 1-B and Application Comparative Example 1-B of the present invention at a current of 0.1C and 25°C.

[0114] Figure 7 Figure 2 shows the impedance graph of the batteries assembled with Application Example 1-B and Application Comparative Example 1-B of the present invention after 100 cycles at a current of 0.1C, 25°C.

[0115] Figure 9 Figure 3 shows the cycle performance graph of the battery assembled with Application Comparative Example 5-B of the present invention at a current of 0.1C and 25°C; Figure 10 Figure 4 shows the impedance graph of the battery assembled with Application Comparative Example 5-B of the present invention after 100 cycles at a current of 0.1C and 25°C.

[0116] It can be seen from the above results that the sulfur-based solid-state battery prepared by using the solid-state battery binder provided by the present invention has a capacity retention rate far superior to that of the comparative example after the first efficiency and 100 cycles, and has more excellent electrochemical performance.

[0117] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, including any other suitable combination of each technical feature. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. A solid-state battery binder, characterized in that, The solid-state battery binder is a product obtained by grafting a non-polar unsaturated rubber with a group represented by formula (I); the grafting rate of the group represented by formula (I) is 5-10%; -S-R-OH formula (I), wherein, R is selected from C1-C6 alkylene groups, phenylene groups, and tolylene groups; The non-polar unsaturated rubber includes at least one of styrene-butadiene-styrene block copolymer, butadiene rubber, styrene-butadiene rubber, isoprene rubber, and chloroprene rubber.

2. The solid-state battery binder according to claim 1, wherein In formula (I), R is selected from -CH2-, -CH2CH2-, -CH2CH2CH2-.

3. The solid-state battery binder according to claim 1 or 2, characterized in that, The weight-average molecular weight of the non-polar unsaturated rubber is 50,000-300,000; And / or, the solid-state battery binder is a product obtained by grafting styrene-butadiene-styrene block copolymer with -S-CH2CH2-OH, and the molecular formula of the solid-state battery binder is (C8H8) m (CH2CH=CHCH2) n (C8H8) k (C6H 11 SOH) h [CH2CH(CH=CH2)] j , where the value of m + k is 430 - 450, and the value of n + h + j is 2500 - 2700; And / or, the solid-state battery binder is a product obtained by grafting butadiene rubber with -S-CH2CH2-OH, and the molecular formula of the solid-state battery binder is (CH2CH=CHCH2) m (C6H 11 SOH) n , where the value of m + n is 6100 - 6300; And / or, the solid-state battery binder is a product obtained by grafting styrene-butadiene rubber with -S-CH2CH2-OH, and the molecular formula of the solid-state battery binder is (C8H8) m (CH2CH=CHCH2) n (C6H 11 SOH) k [CH2CH(CH=CH2)] h , where m ranges from 100 to 150, and n + k + h ranges from 900 to 1000.

4. A method for preparing the solid-state battery binder according to any one of claims 1-3, characterized in that, The method includes: In the presence of a benzene solvent and a photoinitiator, a non-polar unsaturated rubber and a compound represented by formula (II) are subjected to a grafting reaction to obtain a solid-state battery binder; the molar ratio of the compound represented by formula (II) to the carbon-carbon double bonds contained in the non-polar unsaturated rubber is 0.5-5:1; HS-R-OH formula (II), wherein, R is selected from C1-C6 alkylene groups, phenylene groups, and tolylene groups.

5. The method according to claim 4, wherein The compound represented by formula (II) includes at least one of mercaptoethanol, 3-mercapto-1-propanol, 4-mercapto-1-butanol, 3-mercapto-2-methylpentanol, 6-mercaptohexan-1-ol, p-hydroxythiophenol, 2-hydroxythiophenol, 3-hydroxythiophenol, and 4-hydroxy-3-methylthiophenol; and / or, the photoinitiator includes at least one of phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, 1-hydroxycyclohexyl phenyl ketone, 2,2-dimethoxy-2-phenylacetophenone, ethyl 2,4,6-trimethylbenzoylphosphinate, and 2-benzyl-2-dimethylamino-1-(4-morpholinobenzylphenyl)butanone; and / or, the benzene solvent includes at least one of benzene, toluene, o-xylene, m-xylene, p-xylene, and anisole.

6. The method according to claim 4 or 5, characterized in that The molar ratio of the photoinitiator to the carbon-carbon double bonds contained in the non-polar unsaturated rubber is 0.01-0.05:1; and / or, the grafting reaction is carried out under ultraviolet light irradiation, and the conditions of the grafting reaction include: the temperature is 10-50°C, and the time is 10 min to 5 h.

7. Use of the solid-state battery binder according to any one of claims 1-3 in a sulfide-based all-solid-state battery.

8. A composite electrolyte membrane, characterized in that, The composite electrolyte membrane contains a sulfide electrolyte and a solid-state battery binder; based on the total mass of the composite electrolyte membrane, the content of the sulfide electrolyte is 80-99 wt%, and the content of the solid-state battery binder is 1-20 wt%; The solid-state battery binder is the solid-state battery binder according to any one of claims 1-3.

9. A composite cathode for a solid-state battery, characterized in that, The solid-state battery composite positive electrode includes: active material, conductive agent, sulfide electrolyte, solid-state battery binder; The solid-state battery binder is the solid-state battery binder according to any one of claims 1-3.

10. The composite positive electrode of the solid-state battery according to claim 9, characterized in that, The active material includes at least one of the compounds represented by formula (1), the compounds represented by formula (2), the compounds represented by formula (3), the compounds represented by formula (4), and the compounds represented by formula (5); Formula (1): LiCoO2; Formula (2): LiNi x1 Mn y1 Co 1-x1-y1 O2; Formula (3): LiNi 1-x2-y2 Co x2 Al y2 O2; Formula (4): LiNi x3 Mn 1-x3 O2; Formula (5): Li 1+x4 EO2; wherein, x1, x2, x3, x4, y1, and y2 are each independently selected from any value between 0 and 1; E is selected from any one of Mn, Ni, Co, and Al.

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