Polymer surfactant for solid-state battery, negative electrode material and preparation method

Abstract

The invention provides a polymer surfactant for a solid-state battery, a negative electrode material and a preparation method. The polymer surfactant has a polyoxyethylene chain segment and a polysiloxane chain segment, the polyoxyethylene chain segment has hydrophilicity, the polysiloxane chain segment has hydrophobicity, and the amphiphilic structure enables the polymer surfactant to form a stable micelle structure in a solution. The polymer surfactant improves the dispersibility of the carbon spheres, can construct a more stable and more efficient electrode structure, increases the contact area between an electrode and an electrolyte, is beneficial to rapid transmission and storage of lithium ions, and improves the overall performance of the all-solid-state battery.

Description

Technical Field

[0001] This invention belongs to the field of lithium-sulfur battery technology, specifically relating to a polymeric surfactant, anode material, and preparation method for solid-state batteries. Background Technology

[0002] All-solid-state battery systems use all-solid-state electrolytes instead of traditional liquid electrolytes, resulting in a significant improvement in safety compared to traditional lithium-ion batteries. This allows for the use of metal-based materials as the anode, significantly reducing the overall battery weight and further increasing energy density. Currently, the main challenges of solid-state battery systems are concentrated in three areas: 1. Interfacial impedance issues caused by poor interfacial contact and volume changes during charge and discharge; 2. Low ionic conductivity of solid-state electrolytes at room temperature; and 3. Capacity decay of the lithium metal anode after multiple cycles due to uneven deposition and lithium dendrite formation.

[0003] To address these issues, various strategies have been employed to improve lithium anodes, including fabricating artificial solid electrolyte interfaces, adding new electrolyte additives, and designing porous conductive substrates as lithium carriers. For example, patent application CN113130881A discloses a method for preparing a lithium-sulfur battery anode material, comprising the following steps: (1) preparing ZIF-8; (2) preparing ZnSA@HPCNF fibers; and (3) preparing Li / ZnSA@HPCNF. The anode material obtained by this method has a large specific surface area and can provide more high-density, uniformly distributed deposition sites, inducing uniform surface nucleation and lithium deposition, thereby effectively improving the electrochemical performance of the battery. However, the three-dimensional framework, due to its limited ability to support Li... + The adsorption capacity is poor, so it is difficult to effectively regulate the Li near the electrode / electrolyte interface. + concentration.

[0004] Patent application CN105374991A discloses the preparation of a framework carbon sphere using spray drying, which is then melted with metallic lithium to obtain a metallic lithium composite anode material. Although this method effectively suppresses the formation of lithium dendrites, the lack of surfactants leads to the following problems: firstly, nanoscale carbon materials are difficult to disperse in aqueous solutions, and the use of organic solvents during spray drying can easily cause safety accidents; secondly, the unbonded carbon materials are difficult to ensure structural stability. Summary of the Invention

[0005] To address the aforementioned technical problems in the prior art, this invention provides a polymeric surfactant, a negative electrode material, and a preparation method for solid-state batteries.

[0006] This invention provides a method for preparing a polymeric surfactant for solid-state batteries, comprising the following steps: (1) By mass, under the protection of an inert gas, 15-30 parts of cyclic siloxane monomer and 0.6-1.2 parts of catalyst are added to 150-200 parts of organic solvent to undergo ring-opening polymerization reaction to obtain mixture 1; (2) Add 30-50 parts of polyethylene glycol and 0.06-0.5 parts of 8-hydroxyquinoline-lithium (CAS: 850918-68-2) to mixture 1 to carry out block copolymerization reaction, and after removing the organic solvent, obtain the polymeric surfactant for solid-state batteries.

[0007] Preferably, in step (1), the cyclic siloxane monomer is octamethylcyclotetrasiloxane (D4) or hexamethylcyclotrisiloxane (D3); in step (2), the polyethylene glycol has a molecular weight of 300-4000 Da, for example, it can be 300, 600, 2000 or 4000 Da, or it can be a mixture of different molecular weights.

[0008] Preferably, in step (1), the organic solvent is dichloromethane and the catalyst is tetramethylammonium hydroxide.

[0009] Preferably, in step (1), the ring-opening polymerization reaction occurs at a temperature of 80-100℃ for 2-5 hours.

[0010] Preferably, in step (2), the block copolymerization reaction occurs at a temperature of 51-65°C for 2-5 hours.

[0011] The present invention also provides a polymeric surfactant for solid-state batteries prepared by the above preparation method.

[0012] This invention also provides a method for preparing a negative electrode material for solid-state batteries, comprising the following steps: (1) By weight, 50-70 parts of carbon material, 20-30 parts of the polymeric surfactant for solid-state batteries, 10-20 parts of functional additives and 500-1000 ml of water are mixed evenly to obtain a mixture. (2) The mixture is dried to obtain a precursor, and then the precursor is heat-treated under an inert atmosphere to obtain carbon nanospheres; (3) By mass, 20-50 parts of the nanocarbon spheres and 50-80 parts of metallic lithium are reacted in an inert atmosphere and at a temperature of 180-300°C for 1-10 hours to obtain the negative electrode material for solid-state batteries.

[0013] Preferably, in step (1), the carbon material is at least one of Super P, acetylene black, Ketjen black, conductive carbon black, mesophase carbon microspheres, carbon nanotubes, graphene, fullerene and carbon nanofibers.

[0014] Preferably, in step (1), the functional additive is selected from one of the following: nano-fast ion conductors, soluble transition metal salts, inorganic templates, and negative electrode materials with high lithium intercalation potential; the nano-fast ion conductor is Li 10 GeP2S 12 (LGPS), Li7La3Zr2O 12 (LLZO) and Li 1.3 Al 0.3 Ti 1.7 At least one of (PO4)3 (LATP); the soluble transition metal salt is at least one of Ni(OH)2, Ni(NO3)2·6H2O, NiSO4·6(H2O), NiCl2·6H2O, Fe(OH)3, Fe(NO3)3, FeSO4·7H2O, CoCl2, and CoSO4; the inorganic template is at least one of SiO2, Al2O3, Fe2O3, TiO2, and CaCO3; the negative electrode material with a high lithium intercalation potential is Si, SiO2, and Li4Ti5O. 12 At least one of them.

[0015] Preferably, in step (2), the drying is spray drying, and the conditions for spray drying are: inlet temperature 105-350℃, outlet temperature 80-200℃, inlet pressure 0.2-0.6MPa, and flow rate controlled at 3-15ml / min; the conditions for heat treatment are: heating temperature controlled at 500-1000℃, and heat preservation time controlled at 3-12h.

[0016] In a further preferred embodiment, in step (2), in order to prevent the generation of tar, a pre-oxidation treatment is performed before heat treatment. The pre-oxidation treatment temperature is 100-300℃ and the pre-oxidation treatment time is 1-4 hours.

[0017] The present invention also provides a negative electrode material for solid-state batteries prepared by the above preparation method.

[0018] Compared with the prior art, the present invention has the following beneficial effects: (1) The polymeric surfactant used in this invention has polyethylene oxide segments and polysiloxane segments. The polyethylene oxide segments are hydrophilic, while the polysiloxane segments are hydrophobic. This amphiphilic structure enables it to form a stable micelle structure in solution. In the preparation process of lithium metal-carbon sphere composite anode material for all-solid-state batteries, it can reduce the interfacial surface tension and improve the compatibility and dispersibility between the components.

[0019] (2) The polymeric surfactant in this invention introduces lithium ions through lithium doping, giving the copolymer a certain degree of ionic conductivity. In all-solid-state battery systems, lithium ion conduction is crucial to battery performance. This ionicly conductive polymeric surfactant can promote the transport of lithium ions in the electrode material, improving the battery's charge / discharge efficiency and rate performance.

[0020] (3) During the preparation of carbon spheres, polymeric surfactants can be adsorbed onto the surface of the carbon spheres to form a stable protective film, preventing the agglomeration of carbon spheres and enabling the carbon spheres to be uniformly dispersed in the reaction system, thereby improving the quality and performance of the carbon spheres. The uniformly dispersed carbon spheres of this invention can construct a more stable and efficient electrode structure, increase the contact area between the electrode and the electrolyte, which is beneficial for the rapid transport and storage of lithium ions, and improves the overall performance of the all-solid-state battery, such as improving the battery capacity, cycle stability and safety. Detailed Implementation

[0021] Example 1 A method for preparing a lithium metal-carbon sphere composite anode material for solid-state batteries includes the following steps: According to the mass fraction, 50g of carbon nanospheres and 50g of lithium metal were placed in a sealed heater and vacuumed. Under a nitrogen atmosphere, the mixture was heated to 180°C and stirred for 1 hour. After the heater returned to normal pressure, the temperature was lowered to room temperature to obtain the lithium metal-carbon sphere composite anode material. The method for preparing the carbon nanospheres is as follows: According to the mass fractions, 70g of carbon material, 20g of polymeric surfactant, and 10g of functional additives were added to 500ml of deionized water and stirred at 1000rpm for 18h. During the stirring, the mixture was sonicated for 1h to dissolve and disperse the solution. The above mixed solution was spray-dried with the inlet temperature of the spray dryer set to 105℃, the outlet temperature to 80℃, the inlet pressure to 0.2MPa, and the flow rate to 3ml / min to obtain the precursor. The precursor was then heat-treated in an inert atmosphere to obtain carbon nanospheres.

[0022] The carbon material is conductive carbon black.

[0023] The polymeric surfactant is a lithium-doped ethylene oxide-siloxane block copolymer, and its preparation method is as follows: T1: Ring-opening polymerization of siloxanes: Add 15g of cyclic siloxane monomer, 0.6g of tetramethylammonium hydroxide, and 150g of dichloromethane to a three-necked flask, purge with nitrogen, and heat to 80℃ for 2 hours. T2: Polyoxyethylene block copolymerization: After the siloxane polymerization reaction is completed, the reaction system is cooled to 51°C, 30g of polyethylene glycol and 0.06g of 8-hydroxyquinoline-lithium are added, the reaction is continued for 2 hours, and dichloromethane is removed by vacuum distillation to obtain lithium-doped ethylene oxide-siloxane block copolymer.

[0024] The cyclic siloxane monomers include octamethylcyclotetrasiloxane (D4).

[0025] The polyethylene glycol is selected from polyethylene glycol 300 (i.e., the molecular weight of polyethylene glycol is 300 Da).

[0026] The functional additive is a nano-fast ion conductor powder; the nano-fast ion conductor powder is Li 10 GeP2S 12 (LGPS).

[0027] The inert atmosphere is nitrogen, a commonly used inert gas.

[0028] The heat treatment conditions are as follows: the heating temperature is controlled at 500℃, and the holding time is controlled at 3 hours. To prevent tar formation, a pre-oxidation treatment is performed before heat treatment at 100℃ for 1 hour.

[0029] Example 2 A method for preparing a lithium metal-carbon sphere composite anode material for solid-state batteries includes the following steps: According to the mass fraction, 40g of carbon nanospheres and 60g of lithium metal were placed in a sealed heater and evacuated. Under a nitrogen atmosphere, the mixture was heated to 220°C and stirred for 4 hours. After the heater returned to normal pressure, the temperature was lowered to room temperature to obtain the lithium metal-carbon sphere composite anode material. The method for preparing the carbon nanospheres is as follows: According to the mass fractions, 60g of carbon material, 25g of polymeric surfactant, and 15g of functional additives were added to 650ml of deionized water and stirred at 2500rpm for 12h. During the stirring, the solution was ultrasonically treated for 5h to dissolve and disperse the mixture. The above mixed solution was spray-dried with the inlet temperature of the spray dryer set to 180°C, the outlet temperature to 120°C, the inlet pressure to 0.35 MPa, and the flow rate to 7 ml / min to obtain the precursor. The precursor was then heat-treated in an inert atmosphere to obtain carbon nanospheres.

[0030] The carbon material is a mixture of 30g Super P, 10g acetylene black, 10g carbon nanotubes, and 10g graphene.

[0031] The polymeric surfactant is a lithium-doped ethylene oxide-siloxane block copolymer, and its preparation method is as follows: T1: Ring-opening polymerization of siloxanes: 20g of cyclic siloxane monomer, 0.8g of tetramethylammonium hydroxide, and 165g of dichloromethane were added to a three-necked flask, nitrogen gas was introduced, and the temperature was raised to 90℃ for 3 hours. T2: Polyoxyethylene block copolymerization: After the siloxane polymerization reaction is completed, the reaction system is cooled to 55°C, 40g of polyethylene glycol and 0.15g of 8-hydroxyquinoline-lithium are added, the reaction is continued for 3 hours, and dichloromethane is removed by vacuum distillation to obtain lithium-doped ethylene oxide-siloxane block copolymer.

[0032] The cyclic siloxane monomer is hexamethylcyclotrisiloxane (D3).

[0033] The polyethylene glycol is polyethylene glycol 600.

[0034] The functional additive is a soluble transition metal salt; the soluble transition metal salt is obtained by mixing 5g Ni(OH)2, 5g Fe(OH)3, and 5g CoCl2.

[0035] The inert atmosphere is argon, a commonly used inert gas.

[0036] The heat treatment conditions are as follows: heating temperature controlled at 650℃, holding time controlled at 6 hours. To prevent tar formation, pre-oxidation treatment can be performed before heat treatment at 160℃ for 2 hours.

[0037] Example 3 A method for preparing a lithium metal-carbon sphere composite anode material for solid-state batteries includes the following steps: According to the mass fraction, 30g of carbon nanospheres and 70g of lithium metal were placed in a sealed heater and vacuumed. Under a nitrogen atmosphere, the mixture was heated to 260°C and stirred for 8 hours. After the heater returned to normal pressure, the temperature was lowered to room temperature to obtain the lithium metal-carbon sphere composite anode material. The method for preparing the carbon nanospheres is as follows: According to the mass fractions, 55g of carbon material, 28g of polymeric surfactant, and 17g of functional additives were added to 800ml of deionized water and stirred at 4000rpm for 20h. During the stirring, the solution was ultrasonically treated for 8h to dissolve and disperse the mixture. The above mixed solution was spray-dried with the inlet temperature of the spray dryer set to 280℃, the outlet temperature to 160℃, the inlet pressure to 0.5MPa, and the flow rate to 12ml / min to obtain the precursor. The precursor was then heat-treated in an inert atmosphere to obtain carbon nanospheres.

[0038] The carbon material is a mixture of 30g mesophase carbon microspheres, 15g fullerene, and 10g carbon nanofibers.

[0039] The polymeric surfactant is a lithium-doped ethylene oxide-siloxane block copolymer, and its preparation method is as follows: T1: Ring-opening polymerization of siloxanes: Add 25g of cyclic siloxane monomer, 1.0g of tetramethylammonium hydroxide, and 180g of dichloromethane to a three-necked flask, purge with nitrogen, and heat to 95℃ for 4 hours. T2: Polyoxyethylene block copolymerization: After the siloxane polymerization reaction is completed, the reaction system is cooled to 60°C, 45g of polyethylene glycol and 0.3g of 8-hydroxyquinoline-lithium are added, and the reaction is continued for 4 hours. Dichloromethane is removed by vacuum distillation to obtain lithium-doped ethylene oxide-siloxane block copolymer.

[0040] The cyclic siloxane monomer is octamethylcyclotetrasiloxane (D4).

[0041] The polyethylene glycol is a mixture of polyethylene glycol 4000 and polyethylene glycol 2000 in a mass ratio of 1:1.

[0042] The functional additive is an inorganic template, and the inorganic template is SiO2.

[0043] The inert atmosphere is nitrogen, a commonly used inert gas.

[0044] The heat treatment conditions are as follows: heating temperature controlled at 800℃, holding time controlled at 9 hours. To prevent tar formation, pre-oxidation treatment can be performed before heat treatment at 230℃ for 3 hours.

[0045] Example 4 A method for preparing a lithium metal-carbon sphere composite anode material for solid-state batteries includes the following steps: According to the mass fraction, 20g of carbon nanospheres and 80g of lithium metal were placed in a sealed heater and vacuumed. Under a nitrogen atmosphere, the mixture was heated to 300°C and stirred for 10 hours. After the heater returned to normal pressure, the temperature was lowered to room temperature to obtain the lithium metal-carbon sphere composite anode material. The method for preparing the carbon nanospheres is as follows: According to the mass fractions, 50g of carbon material, 30g of polymeric surfactant, and 20g of functional additives were added to 1000ml of deionized water and stirred at 6000rpm for 24h. During the stirring, the mixture was ultrasonically treated for 12h to obtain a mixed solution. The above mixed solution was spray-dried with the inlet temperature of the spray dryer set to 350°C, the outlet temperature to 200°C, the inlet pressure to 0.6 MPa, and the flow rate to 15 ml / min to obtain the precursor. The precursor was then heat-treated in an inert atmosphere to obtain carbon nanospheres.

[0046] The carbon material is carbon nanofiber.

[0047] The polymeric surfactant is a lithium-doped ethylene oxide-siloxane block copolymer, and its preparation method is as follows: T1: Ring-opening polymerization of siloxanes: Add 30g of cyclic siloxane monomer, 1.2g of tetramethylammonium hydroxide, and 200g of dichloromethane to a three-necked flask, purge with nitrogen, and heat to 100℃ for 5 hours. T2: Polyoxyethylene block copolymerization: After the siloxane polymerization reaction is completed, the reaction system is cooled to 65°C, 50g of polyethylene glycol and 0.5g of 8-hydroxyquinoline-lithium are added, and the reaction is continued for 5 hours. Dichloromethane is removed by vacuum distillation to obtain lithium-doped ethylene oxide-siloxane block copolymer.

[0048] The cyclic siloxane monomer is hexamethylcyclotrisiloxane (D3).

[0049] The polyethylene glycol is polyethylene glycol 2000.

[0050] The functional additive is one of the anode materials with a high lithium intercalation potential, and the anode material with a high lithium intercalation potential is Li4Ti5O. 12 .

[0051] The inert atmosphere is argon, a commonly used inert gas.

[0052] The heat treatment conditions are as follows: heating temperature controlled at 1000℃, holding time controlled at 12h. To prevent tar formation, pre-oxidation treatment can be performed before heat treatment at 300℃ for 4 hours.

[0053] Comparative Example 1 The difference from Example 1 is that the polymeric surfactant used is polyvinylpyrrolidone.

[0054] Comparative Example 2 The difference from Example 1 is that 8-hydroxyquinoline-lithium is not added during the preparation of the polymeric surfactant.

[0055] Detection Example 1 Solid-state battery fabrication: Lithium iron phosphate, acetylene black, and PVD were mixed in a mass ratio of 8:1:1, with N-methylpyrrolidone as the solvent, to form a slurry. This slurry was then coated onto a 10 μm aluminum foil surface and dried to obtain the positive electrode. Solid electrolyte Li3PS4 and binder polytetrafluoroethylene (PTFE) were mixed at a mass ratio of 99:1 and rolled into a film to obtain a solid electrolyte film with a thickness of 20 μm. The above-mentioned positive electrode and solid electrolyte membrane were pressed and bonded together with the negative electrode materials prepared in Examples 1-4 and Comparative Examples 1-3 to form a 2032 button battery.

[0056] The electrochemical performance of each 2032 button cell assembled above was tested, and the test results are shown in Table 1.

[0057] Table 1 As can be seen from Table 1, Examples 1-4 using the scheme of the present invention all have higher discharge specific capacity and capacity retention rate than Comparative Examples 1-2, among which Example 4 has the best performance test results.

Claims

1. A method for the preparation of a polymeric surfactant for solid-state batteries, characterized by, The method comprises the following steps: (1) under the protection of inert gas, 15-30 parts of cyclic siloxane monomer and 0.6-1.2 parts of catalyst are added into 150-200 parts of organic solvent to generate ring-opening polymerization reaction, and mixture 1 is obtained; (2) 30-50 parts of polyethylene glycol and 0.06-0.5 parts of 8-hydroxyquinoline-lithium are added into the mixture 1 to generate block copolymerization reaction, and the polymer surfactant for solid-state battery is obtained after removing the organic solvent.

2. The method for preparing a polymer surfactant for a solid-state battery according to claim 1, characterized by, In step (1), the cyclic siloxane monomer is octamethylcyclotetrasiloxane or hexamethylcyclotrisiloxane; and the catalyst is tetramethylammonium hydroxide. In step (2), the molecular weight of the polyethylene glycol is 300-4000 Da.

3. The method of claim 1, wherein the polymer surfactant is prepared by the process comprising: (a) dissolving a polymer in a solvent; (b) adding a surfactant to the polymer solution; (c) adding a base to the polymer solution; and (d) removing the solvent from the polymer solution. In step (1), the ring-opening polymerization reaction is carried out at a temperature of 80-100℃ for 2-5h.

4. The method of claim 1, wherein the polymer surfactant is prepared by the process comprising: (a) dissolving a polymer in a solvent; (b) adding a surfactant to the polymer solution; (c) adding a base to the polymer solution; and (d) removing the solvent from the polymer solution. In step (2), the block copolymerization reaction is carried out at a temperature of 51-65℃ for 2-5h.

5. A polymeric surfactant for use in a solid state battery, characterized in that, The polymer surfactant for solid-state battery is prepared by the method of any one of claims 1-4.

6. A method for the preparation of a negative electrode material for a solid-state battery, characterized by, The polymer surfactant for solid-state battery is used in the method for preparing the negative electrode material for solid-state battery, which comprises the following steps: (1) 50-70 parts of carbon material, 20-30 parts of the polymer surfactant for solid-state battery, 10-20 parts of functional additive and 500-1000ml of water are uniformly mixed to obtain a mixed solution; (2) the precursor is obtained by drying the mixed solution, and then the precursor is heat-treated in an inert atmosphere to obtain nanocarbon spheres; (3) 20-50 parts of the nanocarbon spheres are reacted with 50-80 parts of metallic lithium under the conditions of inert atmosphere and temperature of 180-300℃ for 1-10h to obtain the negative electrode material for solid-state battery.

7. The method of claim 6, wherein the method further comprises, In step (1), the carbon material is at least one of Super P, acetylene black, ketjen black, conductive carbon black, mesocarbon microbeads, carbon nanotube, graphene, fullerene and nanocarbon fiber; The functional additive is selected from one of nano fast ionic conductor, soluble transition metal salt, inorganic template and negative electrode material with high lithium intercalation potential; The nano-fast-ion conductor is Li 10 GeP2S 12 , Li7La3Zr2O 12 and Li 1.3 Al 0.3 Ti 1.7 (PO4)3 The soluble transition metal salt is at least one of Ni(OH)2, Ni(NO3)2·6H2O, NiSO4·6(H2O), NiCl2·6H2O, Fe(OH)3, Fe(NO3)3, FeSO4·7H2O, CoCl2 and CoSO4; The inorganic template is at least one of SiO2, Al2O3, Fe2O3, TiO2 and CaCO3; The negative electrode material with a higher lithium intercalation potential is at least one of Si, SiO2, and Li4Ti5O12. 12 ​ 8. The method of claim 6, wherein the method is performed in a glove box. In step (2), the drying is spray drying, and the conditions of the spray drying are that the inlet temperature is 105-350℃, the outlet temperature is 80-200℃, the inlet pressure is 0.2-0.6MPa, and the flow rate is controlled at 3-15ml / min; The heat treatment conditions are that the heating temperature is controlled at 500-1000℃, and the holding time is controlled at 3-12h.

9. The method of claim 8, wherein the method is performed in a glove box. In step (2), the pre-oxidation treatment is performed before the heat treatment, the pre-oxidation treatment temperature is 100-300 DEG C, and the pre-oxidation treatment time is 1-4 hours.

10. A negative electrode material for solid-state batteries, characterized in that, The negative electrode material for solid-state batteries is prepared by the method of any one of claims 6-9.

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