A binder, a positive electrode sheet, and a preparation method and application thereof

Abstract

The application belongs to the technical field of all-solid-state batteries, and particularly relates to a binder, a positive electrode sheet and a preparation method and application thereof. The binder provided by the application comprises a polycarboxylic acid water reducing agent and MXene. The application utilizes covalent bonding of the polycarboxylic acid water reducing agent and MXene material to prepare an integrated binder, realizes uniform dispersion of the MXene material in a non-polar solvent, and thus can be used as a binder of a sulfide solid-state electrolyte positive electrode. The binder can improve the stability of the positive electrode on one hand, and can reduce the interface impedance of the sulfide solid-state electrolyte / positive electrode material on the other hand, and finally improves the overall performance of the all-solid-state battery.

Description

Technical Field

[0001] This invention belongs to the field of all-solid-state battery technology, specifically relating to a binder, a positive electrode sheet, its preparation method, and its application. Background Technology

[0002] On the road to carbon neutrality, the rapid development of industries such as new energy vehicles is continuously contributing to carbon emission reduction. However, the frequent electric vehicle fires are hindering the large-scale popularization of electric vehicles. The main reasons for the frequent electric vehicle safety accidents include overheating, overcharging, internal short circuits or mechanical abuse of the power battery, and battery management system malfunction. For lithium batteries themselves, the use of unsafe organic electrolytes is the root cause of battery fires. In contrast, solid electrolytes have higher safety. Therefore, as the next generation of energy storage devices, the development of all-solid-state batteries has received high attention from all sectors. Among them, sulfide electrolytes have become the most promising solid electrolyte materials due to their high ionic conductivity and high deformability, which can be tightly contacted with active materials through cold pressing to achieve low interfacial resistance. However, severe interfacial side reactions between the electrolyte and the oxide cathode restrict the long-cycle performance of sulfide electrolyte-based all-solid-state batteries. To date, preparing sulfide solid electrolyte-based cathodes with high cathode material loading and excellent mechanical properties (binder content <5wt%) remains a challenge. In addition, high electrode / electrolyte interfacial impedance is one of the key issues limiting the commercial application of solid-state batteries.

[0003] The high conductivity of MXene two-dimensional materials and the strong attractive interaction between them and active material particles enable effective encapsulation, thereby providing an electronic conduction path, achieving rapid ion transfer, and contributing to the capacitance of stored charge. Due to the excellent mechanical properties of MXene and the attractive forces between its oxygen and hydroxyl-terminated 2D sheets, films with high electronic conductivity can be easily fabricated. Gogotsi et al. used MXene materials to prepare a sodium-ion battery binder for NaTi2(PO3)4(NTP) cathodes. Compared with electrodes prepared using traditional PVDF, the integrated NTP / MXene electrode exhibits superior electrochemical performance in terms of capacity, rate capability, and long-term stability (Nano Energy 79(2021)105433). CN115602850A discloses a surface modification of an active material and the use of MXene as a conductive agent to achieve cross-linking bonding between the conductive agent, the active material, and the binder, forming a three-dimensional network structure Si-APS-M-SA electrode combining point-line-surface. This three-dimensional network structure significantly improves the overall stability of the electrode, filling a technological gap in enhancing electrode stability from the perspective of conductive agents. CN113292139A discloses a sub-titanium oxide / MXene / Co3O4 composite electrode and its preparation method. The unique structure of MXene promotes the dispersion of nano-Co3O4, while the intercalation of Co3O4 within MXene inhibits MXene stacking. The sub-titanium oxide peptide acts as a substrate, functioning as a binder under high temperature and pressure. The Co-O-Ti bonds formed by the sub-titanium oxide peptide, MXene, and Co3O4 fix cobalt onto the sub-oxide substrate, enhancing the stability of the composite electrode.

[0004] Although MXene materials have been widely used in the battery industry, there are no reports of their application in sulfide solid electrolyte composite electrodes. This is attributed to the fact that sulfide solid electrolytes are highly sensitive to polar solvents such as water and ethanol, and that MXene materials prepared using conventional methods reported in the literature often have a solubility of less than 0.5 mg / ml in non-polar solvents, which cannot meet the requirements of sulfide solid-state batteries. Summary of the Invention

[0005] The present invention aims to at least partially solve one of the technical problems in the related art. To this end, embodiments of the present invention provide a binder that enables uniform dispersion of MXene materials in nonpolar solvents, thereby serving as a binder for sulfide solid electrolyte cathodes.

[0006] The adhesive in this embodiment of the invention includes a polycarboxylate superplasticizer and MXene.

[0007] The advantages and technical effects of the binder in this invention are as follows: 1. In this invention, an integrated binder is prepared by covalent bonding of polycarboxylate superplasticizer and MXene material, thereby achieving uniform dispersion of MXene material in non-polar solvents and serving as a binder for solid-state batteries; 2. In this invention, the sulfide solid electrolyte-based cathode prepared with this binder has low interfacial impedance, high interfacial stability, and high compatibility with high-voltage cathode active materials, which can significantly improve the electrochemical performance of sulfide all-solid-state batteries.

[0008] In some embodiments, the polycarboxylate superplasticizer accounts for 10-40% by mass, and the MXene accounts for 60-90% by mass.

[0009] In some embodiments, the structure of the polycarboxylate superplasticizer is as shown in formula (1):

[0010]

[0011] In formula (1), R0 is selected from carboxylic acid group or sulfonic acid group; R1, R2, R3, R4, R5, and R6 are independently selected from hydrogen, halogen, carbamoyl, alkoxy, alkyl, alkylamino, alkylthio, alkoxysilyl, alkanoyl, sulfonyl, aryl, or heteroaryl; x is 0 to 1000, y is 100 to 1000, and z is 0 to 100.

[0012] In some embodiments, the chemical formula of the MXene is M n+1 X n T x Wherein, n = 1 to 3, x = 0 to 1, M includes at least one of Sc, Ti, Zr, Hf, V, Nb, Ta, Cr, and Mo, X includes at least one of carbon or nitrogen, and T includes at least one of -OH, -O, or -F.

[0013] The present invention also provides the application of the above-mentioned binder in the positive electrode sheet.

[0014] This embodiment also provides a positive electrode sheet, including the binder described above.

[0015] The positive electrode sheet provided in this embodiment of the invention can effectively buffer the volume change of the positive electrode active material during the charging and discharging process, so that the battery has good interface contact throughout the entire charging and discharging cycle. Furthermore, the low interface impedance can ensure good ion transport performance at the electrode interface, thereby improving the cycle stability and rate performance of the battery.

[0016] This invention also provides a method for preparing a positive electrode sheet, comprising the following steps:

[0017] (1) The above-mentioned polycarboxylate superplasticizer and MXene are dispersed in water and then freeze-dried to obtain a mixed powder of polycarboxylate superplasticizer and MXene. The mixed powder is then dispersed in an organic solvent to obtain an adhesive colloid.

[0018] (2) Mix the sulfide solid electrolyte, the positive electrode material and the binder colloid obtained in step (1), and then coat it onto the current collector for heat treatment.

[0019] In some embodiments, in step (1), the organic solvent is a nonpolar solvent or a weakly polar solvent, and the organic solvent includes any one of toluene, benzene, petroleum ether, and n-hexane;

[0020] And / or, the mass fraction of the adhesive in the adhesive colloid is 1-50%.

[0021] In some embodiments, in step (2), the mass ratio of the positive electrode material, the sulfide solid electrolyte, and the binder is 80-99%, 0.5-10%, and 0.5-10%, respectively.

[0022] And / or, the temperature of the heat treatment is 130–170°C, and the time of the heat treatment is 10–15 h;

[0023] The present invention also provides the application of the above-described positive electrode sheet or the positive electrode sheet prepared by the above-described preparation method in all-solid-state batteries. Attached Figure Description

[0024] Figure 1 The LiNi assembled in Example 1 and Comparative Example 1 0.8 Co 0.1 Mn 0.1 Plot of long-cycle performance of O2 / Li all-solid-state battery at room temperature;

[0025] Figure 2 These are graphs showing the long-cycle performance of the Sb2S3 / Na all-solid-state batteries assembled in Example 2 and Comparative Example 2 at room temperature.

[0026] Figure 3 The Li assembled in Example 4 and Comparative Example 4 1.17 Mn 0.55 Ni 0.23 Co 0.05 Plot of long-cycle performance of O2 / Li all-solid-state battery at room temperature;

[0027] Figure 4 The LiNi assembled in Example 5 and Comparative Example 5 0.8 Co 0.1 Mn 0.1 The graph shows the long-cycle performance of O2 / Si all-solid-state batteries at room temperature. Detailed Implementation

[0028] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0029] The adhesive in this embodiment of the invention includes a polycarboxylate superplasticizer and MXene.

[0030] The binder in this embodiment of the invention utilizes the covalent bonding of polycarboxylate superplasticizer and MXene material to prepare an integrated binder, thereby achieving uniform dispersion of MXene material in non-polar solvents and serving as a binder for solid-state batteries. In this embodiment of the invention, the sulfide solid electrolyte-based cathode prepared with this binder has low interfacial impedance, high interfacial stability, and high compatibility with high-voltage cathode active materials, which can significantly improve the electrochemical performance of sulfide all-solid-state batteries.

[0031] In some embodiments, preferably, the polycarboxylate superplasticizer accounts for 10-40% by mass, and the MXene accounts for 60-90% by mass.

[0032] In this embodiment of the invention, the preferred mass ratio of carboxylic acid water-reducing agent and MXene not only ensures the uniform dispersion of MXene during the preparation process, but also reduces the interfacial impedance of the sulfide solid electrolyte / cathode material. If the content of polycarboxylic acid water-reducing agent is too high, it may lead to excessively high electrolyte / cathode interfacial impedance; if the content of polycarboxylic acid water-reducing agent is too low, MXene cannot achieve uniform dispersion.

[0033] In some embodiments, preferably, the polycarboxylate superplasticizer has the structure shown in formula (1):

[0034]

[0035] In formula (1), R0 is selected from carboxylic acid group or sulfonic acid group; R1, R2, R3, R4, R5, and R6 are independently selected from hydrogen, halogen, carbamoyl, alkyl, alkoxy, alkylamino, alkylthio, alkoxysilyl, alkanoyl, sulfonyl, aryl, or heteroaryl; x is 0 to 1000, y is 100 to 1000, and z is 0 to 100.

[0036] In some embodiments, preferably, the chemical formula of the MXene is M n+1 X n T xWherein, n = 1 to 3, x = 0 to 1, M includes at least one of Sc, Ti, Zr, Hf, V, Nb, Ta, Cr, and Mo, X includes at least one of carbon or nitrogen, and T includes at least one of -OH, -O, or -F.

[0037] The present invention also provides the application of the above-mentioned binder in the positive electrode sheet.

[0038] This embodiment also provides a positive electrode sheet, including the binder described above.

[0039] The positive electrode sheet provided in this embodiment of the invention can effectively buffer the volume change of the positive electrode active material during the charging and discharging process, so that the battery has good interface contact throughout the entire charging and discharging cycle. Furthermore, the low interface impedance can ensure good ion transport performance at the electrode interface, thereby improving the cycle stability and rate performance of the battery.

[0040] This invention also provides a method for preparing a positive electrode sheet, comprising the following steps:

[0041] (1) The above-mentioned binder polycarboxylate superplasticizer and MXene are dispersed in water and then freeze-dried to obtain a mixed powder of polycarboxylate superplasticizer and MXene. The mixed powder is then dispersed in an organic solvent to obtain a binder colloid.

[0042] (2) Mix the sulfide solid electrolyte, the positive electrode material and the binder colloid obtained in step (1), and then coat it onto the current collector for heat treatment.

[0043] In some embodiments, preferably, in step (1), the organic solvent is a nonpolar solvent or a weakly polar solvent, and the organic solvent includes any one of toluene, benzene, petroleum ether, and n-hexane.

[0044] In some embodiments, preferably, the mass fraction of the adhesive in the adhesive colloid is 1% to 50%, for example, 1%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, etc.

[0045] In some embodiments, preferably, in step (2), the mass ratio of the positive electrode material, the sulfide solid electrolyte, and the binder is 80-99%, 0.5-10%, and 0.5-10%, respectively.

[0046] In this embodiment of the invention, the preferred mass ratio of positive electrode material, sulfide solid electrolyte and binder is selected to ensure good ion transport performance at the electrode interface, which is beneficial to improving the cycle stability and rate performance of the battery.

[0047] In some embodiments, preferably, in step (2), the temperature of the heat treatment is 130-170°C, such as 130°C, 135°C, 140°C, 145°C, 150°C, 155°C, 160°C, 165°C, 170°C, etc., and the time of the heat treatment is 10-15h, such as 10h, 11h, 12h, 13h, 14h, 15h, etc.

[0048] In some embodiments, preferably, in step (2), the sulfide solid electrolyte includes Li6PS5X, Li 10 D x P 3-x S 12 , Li2S: (1-x)P2S5, Li3PS4, Na3QS4, Na 10 D x P 3-x S 12 Or at least one of Na2S:(1-x)P2S5, wherein X in Li6PS5X includes at least one of Cl, Br, or I; the Li 10 D x P 3-x S 12 In the case of Li₂S:(1-x)P₂S₅, 0 ≤ x ≤ 2, and D includes at least one of Si, Ge, or Sn; in the case of Li₂S:(1-x)P₂S₅, x = 0.7–0.8; in the case of Na₃QS₄, Q includes at least one of P or Sb; in the case of Na… 10 D x P 3-x In S1, 0 ≤ x ≤ 2, and D includes at least one of Si, Ge, or Sn; in Na2S:(1-x)P2S5, x = 0.7 to 0.8;

[0049] It is understandable that, for all-solid-state lithium batteries, the sulfide solid electrolyte includes Li6PS5X and Li 10 D x P 3- x S 12 At least one of Li₂S:(1-x)P₂S₅ or Li₃PS₄; for all-solid-state sodium batteries, the sulfide solid electrolyte includes Na₃QS₄, Na 10 D x P 3-x S 12 Or at least one of Na2S:(1-x)P2S5.

[0050] In some embodiments, preferably, the cathode material includes lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium manganese oxide, lithium nickel manganese oxide, lithium cobalt manganese oxide, lithium-rich manganese-based materials, nickel manganese spinel, or Na. xAt least one of EG(CN)6, sodium vanadium phosphate, sulfur, sodium ferric sulfate, elemental sulfur, elemental selenium, titanium disulfide, molybdenum disulfide, sodium fluorophosphate, sodium vanadium fluorophosphate, sodium ferric fluorophosphate, sodium manganese oxide, and sodium cobalt oxide, wherein Na x In EG(CN)6, E and G are each independently selected from at least one of Fe, Co, Ni or Mn.

[0051] The present invention also provides the application of the above-described positive electrode sheet or the positive electrode sheet prepared by the above-described preparation method in all-solid-state batteries.

[0052] The technical solution of the present invention will now be described in detail with reference to specific embodiments and accompanying drawings.

[0053] Example 1

[0054] (1) Polycarboxylate superplasticizer E1 and MXene material Ti3C2T x The MXene / E1 mixed powder was prepared by uniformly dispersing it in water at a mass ratio of 2:5 and then freeze-drying it for 12 hours. The mixed powder was then dissolved in toluene to prepare an A1 binder colloid with a mass fraction of 20%.

[0055] (2) The cathode material (LiNi) 0.8 Co 0.1 Mn 0.1 O2), sulfide solid electrolyte particles (Li8GeS6), and Al binder colloid were mixed in a glove box at a ratio of 88wt%, 10wt%, and 2wt% for 12 hours. The uniformly mixed slurry was then evenly coated onto aluminum foil with a scraper and dried at 150°C for 12 hours to obtain the sulfide solid electrolyte composite cathode.

[0056] The structural formula of polycarboxylate superplasticizer E1 is:

[0057] Where x = 1000, y = 100, z = 50, and m = 10.

[0058] In this embodiment, the cathode material loading in the composite cathode based on polycarboxylate superplasticizer / MXene integrated binder is 10 mg / cm³. 2 The ionic conductivity at room temperature is 0.8 mS / cm. -1 .

[0059] Example 2

[0060] (1) Polycarboxylate superplasticizer E2 and MXene material Ti2CT xThe MXene / E2 mixed powder was prepared by uniformly dispersing it in water at a mass ratio of 1:5 and then freeze-drying it for 12 hours. The mixed powder was then dissolved in toluene to prepare an A2 binder colloid with a mass fraction of 10%.

[0061] (2) Under a dry atmosphere, the positive electrode material (Sb2S3), sulfide solid electrolyte particles (Na3PS4), and A2 binder colloid were stirred and mixed in a glove box at a ratio of 87wt%, 8wt%, and 5wt% for 12 hours. The uniformly stirred slurry was evenly coated onto aluminum foil with a scraper and dried at 150°C for 12 hours to obtain the sulfide solid electrolyte composite positive electrode.

[0062] The structural formula of polycarboxylate superplasticizer E2 is:

[0063] Where x = 2000, y = 200, z = 100, and m = 10.

[0064] In this embodiment, the cathode material loading in the composite cathode based on polycarboxylate superplasticizer / MXene integrated binder is 8 mg / cm³. 2 The ionic conductivity at room temperature is 0.5 mS / cm. -1 .

[0065] Example 3

[0066] (1) Polycarboxylate superplasticizer E3 and MXene material Ti3C2T x The MXene / E3 mixed powder was prepared by uniformly dispersing the powder in water at a mass ratio of 3:7 and then freeze-drying it for 12 hours. The mixed powder was then dissolved in toluene to prepare an A3 binder colloid with a mass fraction of 15%.

[0067] (2) Under a dry atmosphere, the positive electrode material (LiNi) 0.6 Co 0.2 Mn 0.2 O2), sulfide solid electrolyte particles (Li7SnS) 5.5 The A3 binder colloid was mixed in a glove box at a ratio of 87 wt%, 10 wt%, and 3 wt% for 12 hours. The uniformly mixed slurry was then evenly coated onto aluminum foil with a scraper and dried at 150°C for 12 hours to obtain a sulfide solid electrolyte composite positive electrode.

[0068] The structural formula of polycarboxylate superplasticizer E3 is:

[0069] x=1000, y=400, z=200, m=20.

[0070] In this embodiment, the cathode material loading in the composite cathode based on polycarboxylate superplasticizer / MXene integrated binder is 20 mg / cm³. 2 The ionic conductivity at room temperature is 1 mS / cm. -1 .

[0071] Example 4

[0072] (1) Polycarboxylate superplasticizer E4 and MXene material Ti3C2F x The MXene / E4 mixed powder was prepared by uniformly dispersing it in water at a mass ratio of 1:9 and then freeze-drying it for 12 hours. The mixed powder was then dissolved in n-hexane to prepare an A4 binder colloid with a mass fraction of 5%.

[0073] (2) Under a dry atmosphere, the positive electrode material (Li) 1.17 Mn 0.55 Ni 0.23 Co 0.05 O2), sulfide solid electrolyte particles (Li7SnS) 5.5 The A4 binder colloid was mixed in a glove box at proportions of 89 wt%, 8 wt%, and 3 wt% for 12 hours. The uniformly mixed slurry was then evenly coated onto aluminum foil with a scraper and dried at 150°C for 12 hours to obtain a sulfide solid electrolyte composite positive electrode.

[0074] The structural formula of polycarboxylate superplasticizer E4 is:

[0075] x=500, y=300, z=100, m=10.

[0076] In this embodiment, the cathode material loading in the composite cathode based on polycarboxylate superplasticizer / MXene integrated binder is 6 mg / cm³. 2 The ionic conductivity at room temperature is 1.1 mS / cm. -1 .

[0077] Example 5

[0078] (1) is the same as step (1) in Example 3;

[0079] (2) Under a dry atmosphere, the positive electrode material (LiNi) 0.8 Co 0.1 Mn 0.1 O2), sulfide solid electrolyte particles (Li7P3S) 11 The A3 binder colloid was mixed in a glove box at proportions of 89 wt%, 9 wt%, and 2 wt% for 12 hours. The uniformly mixed slurry was then evenly coated onto aluminum foil with a scraper and dried at 150°C for 12 hours to obtain a sulfide solid electrolyte composite cathode.

[0080] In this embodiment, the cathode material loading in the composite cathode based on polycarboxylate superplasticizer / MXene integrated binder is 20 mg / cm³. 2 The ionic conductivity at room temperature is 1.2 mS / cm. -1 .

[0081] Example 6

[0082] (1) is the same as step (1) in Example 4;

[0083] (2) Under a dry atmosphere, the positive electrode material (LiCoO2) sulfide solid electrolyte particles (Li 9.54 Si 1.74 P 1.44 S 11.7 Cl 0.3 The A4 binder colloid was mixed in a glove box at proportions of 87 wt%, 10 wt%, and 3 wt% for 12 hours. The uniformly mixed slurry was then evenly coated onto aluminum foil with a scraper and dried at 150°C for 12 hours to obtain a sulfide solid electrolyte composite positive electrode.

[0084] In this embodiment, the cathode material loading in the composite cathode based on polycarboxylate superplasticizer / MXene integrated binder is 25 mg / cm³. 2 The ionic conductivity at room temperature is 1.2 mS / cm. -1 .

[0085] Comparative Example 1

[0086] The comparative example and Example 1 are the same in method, except that step (1) is omitted and PTFE is used as a binder to prepare the composite positive electrode in step (2).

[0087] Comparative Example 2

[0088] The comparative example and Example 2 are the same in method, except that step (1) is omitted and PTFE is used as a binder to prepare the composite positive electrode in step (2).

[0089] Comparative Example 3

[0090] The comparative example and Example 3 are the same in method, except that step (1) is omitted and PTFE is used as a binder to prepare the composite positive electrode in step (2).

[0091] Comparative Example 4

[0092] The comparative example and Example 4 use the same method, except that step (1) is omitted and PTFE is used as a binder to prepare the composite cathode in step (2).

[0093] Comparative Example 5

[0094] The comparative example and Example 5 use the same method, except that step (1) is omitted and PTFE is used as a binder to prepare the composite cathode in step (2).

[0095] Comparative Example 6

[0096] The comparative example and Example 6 are the same in method, except that step (1) is omitted and PTFE is used as a binder to prepare the composite positive electrode in step (2).

[0097] The composite cathodes prepared in Examples 1-6 and Comparative Examples 1-6 were subjected to performance tests.

[0098] (1) According to 0.1C rate, 2.7-4.5V (vs. Li + The composite cathodes prepared in Example 1 and Comparative Example 1 were subjected to charge-discharge tests within the / Li voltage range, and the results are as follows: Figure 1 As shown, from Figure 1 It can be seen that a composite cathode LiNi based on polycarboxylate superplasticizer / MXene integrated binder is used. 0.8 Co 0.1 Mn 0.1 The O2 / Li all-solid-state battery retains 98% of its capacity after 50 cycles, while the composite cathode / Li all-solid-state battery with PTFE as the binder retains only 65%.

[0099] (2) According to 0.1C multiplier, 0.1-2.5V (vs. Na + The composite cathodes prepared in Example 2 and Comparative Example 2 were subjected to charge-discharge tests within the / Na voltage range, and the results are as follows: Figure 2 As shown, the capacity retention rate of the composite cathode Sb2S3 / Na all-solid-state battery using polycarboxylate superplasticizer / MXene integrated binder is 98% after 50 cycles, while the capacity retention rate of the composite cathode Sb2S3 / Na all-solid-state battery using PTFE as binder is only 94%.

[0100] (3) According to 0.1C rate, 2.7-4.5V (vs. Li + The composite cathodes prepared in Example 3 and Comparative Example 3 were subjected to charge-discharge tests within the voltage range of / Li, using a composite cathode LiNi based on polycarboxylate superplasticizer / MXene integrated binder. 0.6 Co 0.2 Mn 0.2 The O2 / Li all-solid-state battery retains 90% of its capacity after 200 cycles, while the composite cathode / Li all-solid-state battery with PTFE as a binder retains only 50%.

[0101] (4) According to 0.2C rate, 2.7-4.9V (vs. Li + The composite cathodes prepared in Example 4 and Comparative Example 4 were subjected to charge-discharge tests within the / Li voltage range, such as Figure 3 As shown, a composite positive electrode Li using polycarboxylate superplasticizer / MXene integrated binder 1.17 Mn 0.55 Ni 0.23 Co 0.05 The O2 / Li all-solid-state battery retains 95% of its capacity after 150 cycles, while the composite cathode / Li all-solid-state battery with PTFE as the binder retains only 75%.

[0102] (5) According to 0.1C rate, 2.7-4.5V (vs. Li + The composite cathodes prepared in Example 5 and Comparative Example 5 were subjected to charge-discharge tests within the / Li voltage range, and the results are as follows: Figure 4 As shown, a composite cathode LiNi using polycarboxylate superplasticizer / MXene integrated binder 0.8 Co 0.1 Mn 0.1 The O2 / Si all-solid-state battery retains 99% of its capacity after 50 cycles, while the composite cathode / Li all-solid-state battery with PTFE as the binder retains only 78%.

[0103] (6) According to 0.5C rate, 2.7-4.4V (vs. Li + The composite cathodes prepared in Example 6 and Comparative Example 6 were subjected to charge-discharge tests within the voltage range of / Li. The composite cathode LiCoO2 / Li all-solid-state battery using polycarboxylate superplasticizer / MXene integrated binder had a capacity retention rate of 88% after 300 cycles, while the composite cathode / Li all-solid-state battery using PTFE as binder had a capacity retention rate of only 60%.

[0104] The mechanism by which the battery cycle performance is improved in this embodiment of the invention is that the polycarboxylate superplasticizer / MXene integrated binder can ensure good interfacial contact of the battery throughout the entire charge and discharge cycle, and the low interfacial impedance can ensure good ion transport performance at the electrode interface, thereby improving the cycle stability of the battery.

[0105] In this invention, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0106] Although the above embodiments have been shown and described, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Any changes, modifications, substitutions and variations made to the above embodiments by those skilled in the art are within the protection scope of the present invention.

Claims

1. A binder, characterized by The polycarboxylic acid water reducing agent and MXene are included. The polycarboxylic acid water reducing agent accounts for 10-40% by mass, and the MXene accounts for 60-90% by mass. The polycarboxylic acid water reducing agent has any one of the structures of Formula I, Formula II, Formula III or Formula IV, Formula I, wherein x=1000, y=100, z=50, and m=10; Formula II, wherein x=2000, y=200, z=100, and m=10; Formula III, wherein x=1000, y=400, z=200, and m=20; Formula IV, wherein x=500, y=300, z=100, and m=10.

2. The binder of claim 1, wherein The chemical formula of the MXene is M n+1 X n T x ; wherein, n=1~3, x=0~1, M includes at least one of Sc, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, X includes at least one of carbon or nitrogen, and T includes at least one of -OH, -O or -F.

3. Use of the binder of claim 1 or 2 in a positive electrode sheet.

4. A positive electrode sheet characterized by comprising: The binder of claim 1 or 2 is included in a sulfide solid-state electrolyte, a positive electrode material, and a binder.

5. The method of producing a cathode electrode piece according to claim 4, characterized by, The method comprises the following steps: (1) The polycarboxylic acid water reducing agent and MXene of claim 1 or 2 are dispersed in water and then subjected to freeze-drying treatment to obtain a mixed powder of the polycarboxylic acid water reducing agent and MXene, and the mixed powder is dispersed in an organic solvent to obtain a binder colloid; (2) The sulfide solid-state electrolyte and the positive electrode material are mixed with the binder colloid obtained in step (1), and then coated on a current collector and subjected to heating treatment.

6. The method of producing a positive electrode sheet according to claim 5, characterized by, In step (1), the organic solvent is a non-polar solvent or a weakly polar solvent, and the organic solvent includes any one of toluene, benzene, petroleum ether, and n-hexane. And / or, the mass fraction of the binder in the binder colloid is 1-50%.

7. The method of producing a cathode electrode piece according to claim 5, characterized by, In step (2), the mass ratio of the positive electrode material, the sulfide solid-state electrolyte, and the binder is 80-99%, 0.5-10%, and 0.5-10%, respectively. And / or, the temperature of the heating treatment is 130-170℃, and the time of the heating treatment is 10-15h.

8. Use of the positive electrode sheet of claim 4 or the positive electrode sheet prepared by the method of any one of claims 5-7 in a full-solid-state battery.

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