Method for improving ion conduction in positive electrode of in-situ polymerization battery system

Abstract

The invention relates to an in-situ polymerization polymer battery system, in particular to a method for improving ion conduction in a positive electrode of the in-situ polymerization battery system. A polymerization inhibitor is added into a positive electrode for preparing an in-situ polymerization battery system, and polymerization of an in-situ polymerization electrolyte precursor in the positive electrode is selectively inhibited, so that ion conduction in the positive electrode is improved; and the addition amount is 0.1-5wt% (relative to the total amount of the positive electrode material). The polymerization inhibitor is pre-dispersed in the positive electrode, and the polymerization reaction in the positive electrode is effectively inhibited in the subsequent polymerization process, so that the polymerization degree of a polymer network in the region is selectively reduced, and the ion conduction performance in the positive electrode is improved. According to the invention, the cycling stability of the battery is remarkably improved, and the battery is particularly suitable for application scenes of high-load thick electrodes and shows good application prospects in the field of in-situ polymerization solid-state batteries.

Description

Technical Field

[0001] This invention relates to in-situ cured polymer battery systems, and more particularly to a method for improving ion conduction within the positive electrode of an in-situ polymer battery system. Background Technology

[0002] In recent years, battery safety issues have occurred frequently, making the development of high-safety battery systems crucial for the industry's development. Polymer batteries have received widespread attention due to their high safety. Among them, polymer batteries obtained using in-situ curing strategies are a promising next-generation high-safety battery system due to their simple preparation method and good interfacial compatibility. However, in traditional in-situ curing systems, the significant increase in molecular weight after polymer curing partially "blocks" the ion conduction channels inside the positive electrode, leading to a decrease in ionic conductivity and consequently affecting the battery's rate performance and cycle stability.

[0003] To alleviate this problem, researchers have proposed several strategies. For example, reducing the overall degree of polymerization of the electrolyte can enhance chain segment mobility and improve overall ionic conductivity. However, this method leads to a decrease in the mechanical properties of the polymer electrolyte, reducing battery safety. In addition, some researchers have introduced SiO2, Al2O3, and Li7La3Zr2O into the in-situ polymerization system. 12 Inorganic nanoparticles or lithium fast ion conductors can be used to construct composite ion transport networks. However, this method requires high uniformity of inorganic particle dispersion; if the distribution is uneven, it is difficult to form a continuous ion transport network. Some studies have also attempted to develop condensed polymer electrolytes to improve overall ion conductivity, but the introduction of liquid electrolytes significantly reduces battery safety and poses safety hazards.

[0004] There is currently a lack of effective solutions to the problem of ion conduction within the positive electrode caused by the increased degree of polymerization during the curing process. Summary of the Invention

[0005] In view of this, the present invention provides a method for improving ion conduction within the cathode of an in-situ polymer battery system.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A method for improving ion conduction within the cathode of an in-situ polymer battery system.

[0008] In preparing the in-situ polymerized battery system, a polymerization inhibitor is added to the positive electrode to selectively inhibit the polymerization reaction of the in-situ polymerized electrolyte precursor in the positive electrode region, thereby improving the ion conduction performance of the positive electrode region; the amount of the polymerization inhibitor added is 0.1 to 5 wt% of the total mass of the positive electrode material.

[0009] To elaborate further,

[0010] (a) Dissolve the polymerization inhibitor and binder together in a solvent and allow them to stand for 12-24 hours to achieve molecular-level pre-bonding of the polymerization inhibitor and binder;

[0011] (b) Add the conductive agent and the positive electrode active material to the above solution and mix to form a positive electrode slurry containing a polymerization inhibitor;

[0012] (c) The positive electrode slurry is coated onto the current collector and dried to obtain the positive electrode material;

[0013] (d) Assemble the positive electrode material with the separator, the in-situ polymerized electrolyte precursor and the negative electrode to form a battery, and complete the in-situ polymerization by heating to obtain an in-situ polymerized battery.

[0014] The polymerization inhibitor is selected from organic polymerization inhibitors and / or inorganic polymerization inhibitors.

[0015] The solvent in step (a) is one or a combination of N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, tetrahydrofuran, acetone, water, and ethanol.

[0016] The adhesive is selected from one or more combinations of polyvinylidene fluoride, polytetrafluoroethylene, sodium carboxymethyl cellulose, styrene-butadiene rubber, polyacrylic acid, polyvinyl alcohol, polyacrylonitrile, polyurethane or polymethyl methacrylate.

[0017] The conductive agent is selected from one or more of graphite, carbon black, graphene, carbon nanotubes or carbon fibers.

[0018] The current collector is one or a combination of several of the following: metal foil, metal layer, porous metal foil, foam metal, graphite plate, graphene layer, and carbon nanotube layer.

[0019] The polymerization inhibitor is selected from organic polymerization inhibitors and / or inorganic polymerization inhibitors.

[0020] The organic polymerization inhibitor is selected from one or more combinations of hydroquinone, 2,6-di-tert-butyl-p-cresol, 4-hydroxy-2,2,6,6-tetramethylpiperidine, p-benzoquinone, methyl p-benzoquinone, nitrobenzene, p-nitrotoluene, N-nitrosodiphenylamine, nitrosobenzene, diphenyl sulfide, and 2,2,6,6-tetramethylpiperidine oxide; the inorganic polymerization inhibitor is selected from one or more combinations of chromium trioxide, manganese dioxide, sodium nitrite, potassium nitrite, molybdenum disulfide, sodium sulfide, copper chloride, copper sulfate, ferric chloride, ferrous sulfate, cerium oxide, trisodium phosphate, and sodium pyrophosphate.

[0021] The areal loading of the positive electrode material is preferably 5-40 mg / cm³. 2 .

[0022] The positive electrode active material is selected from one or a combination of lithium iron phosphate, lithium cobalt oxide, lithium manganese oxide, lithium nickel cobalt manganese, or lithium manganese silicate.

[0023] An application of the method, specifically its application in the preparation of in-situ polymeric battery systems.

[0024] An in-situ polymer battery includes a positive electrode, a negative electrode, a separator, and an electrolyte between the positive and negative electrodes, characterized in that: the positive electrode is a positive electrode prepared by the method described above.

[0025] The negative electrode is selected from one or more combinations of graphite negative electrode, hard carbon negative electrode, soft carbon negative electrode, lithium titanium oxide negative electrode, silicon negative electrode, silicon suboxide negative electrode, and silicon carbon negative electrode.

[0026] An in-situ polymerization battery includes a positive electrode, a negative electrode, a separator, and an electrolyte between the positive and negative electrodes. The positive electrode contains 0.1-5 wt% of a polymerization inhibitor added to the positive electrode material, thereby selectively inhibiting the polymerization reaction of the in-situ polymerization electrolyte precursor in the positive electrode to improve the ion conduction performance of the positive electrode region.

[0027] Furthermore, according to the above description, a negative electrode containing a polymerization inhibitor can also be prepared, thereby achieving the final objective. The beneficial effects of this invention are as follows:

[0028] This invention pre-mixes a binder and a polymerization inhibitor, then disperses them inside the electrode. During in-situ curing, it selectively inhibits excessive polymerization of the polymer within the electrode region, thereby forming a polymer network with low polymerization degree and high ionic conductivity inside the electrode. This ensures sufficient ionic conductivity within the high-capacity electrode, improving battery rate performance and cycle stability. Furthermore, the pre-mixing and aging process of the binder and polymerization inhibitor results in pre-bonding between molecules through entanglement or electrostatic interactions. This ensures that the polymerization inhibitor is confined within the electrode region and does not diffuse into the electrolyte, affecting its polymerization. In addition, the preparation process of this invention is simple, compatible with existing battery manufacturing processes, and easy to industrialize. This invention also has broad applicability and is suitable for electrode preparation in other in-situ polymerized battery systems (sodium battery systems, magnesium battery systems, zinc battery systems, etc.). Detailed Implementation

[0029] The present invention will be further described in detail below through specific embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0030] This invention addresses the ion conductivity problem caused by increased polymerization degree during the curing process by pre-dispersing a certain amount of polymerization inhibitor inside the cathode material. Due to the presence of the inhibitor, the polymer network formed inside the cured cathode has a lower degree of polymerization, ensuring high ion conductivity within the cathode. This method significantly improves the overall battery performance, is particularly suitable for high-load cathodes, and shows promising application prospects in in-situ cured polymer battery systems.

[0031] Example 1:

[0032] PVDF (2.5 wt% of the total positive electrode slurry) and hydroquinone (0.5 wt% of the total positive electrode slurry) were co-dissolved in N-methylpyrrolidone and allowed to stand for 12 hours for aging. Then, lithium iron phosphate (95 wt% of the total positive electrode slurry) and Super P (2 wt% of the total positive electrode slurry) were also dispersed in the above solution and mixed evenly to form the positive electrode slurry. The slurry was then uniformly coated onto an aluminum foil current collector and dried to obtain a positive electrode containing a polymerization inhibitor, with a positive electrode loading of 20 mg / cm³. 2 .

[0033] Polyethylene glycol methyl ether methacrylate (Mn = 500 g / mol) was selected as the polymerization monomer; LiTFSI was selected as the lithium salt, wherein the lithium salt content accounted for 30 wt% of the total electrolyte mass; and azobisisobutyronitrile was selected as the initiator, wherein the amount of the initiator accounted for 1 wt% of the polymerization monomer mass. The above monomers, lithium salts and initiators were mixed evenly to obtain the electrolyte precursor.

[0034] The above-mentioned positive electrode containing polymerization inhibitor, polyolefin separator, lithium metal negative electrode and electrolyte precursor are assembled into a battery assembly according to conventional steps.

[0035] The assembled battery was placed in a 60°C oven and left to stand for 24 hours for in-situ curing to form a solid electrolyte system.

[0036] The battery's charge-discharge performance at a 0.5C rate was tested, and its capacity retention after 100 cycles was 95%. The battery was disassembled, and the polymers in the positive electrode and electrolyte were separated and subjected to coagulation-permeation chromatography. The number-average molecular weight of the polymer in the electrolyte was found to be Mn = 43000 g / mol, while the number-average molecular weight of the polymer in the positive electrode was Mn = 5000 g / mol.

[0037] Example 2:

[0038] PVDF (2.5 wt% of the total positive electrode slurry) and tert-butylated hydroxytoluene (0.5 wt% of the total positive electrode slurry) were co-dissolved in N-methylpyrrolidone and allowed to stand for 12 hours for aging. Then, lithium iron phosphate (95 wt% of the total positive electrode slurry) and Super P (2 wt% of the total positive electrode slurry) were also dispersed in the above solution and mixed evenly to form the positive electrode slurry. The slurry was then uniformly coated onto an aluminum foil current collector and dried to obtain a positive electrode containing a polymerization inhibitor, with a positive electrode loading of 23 mg / cm³. 2 .

[0039] Polyethylene glycol methyl ether methacrylate (Mn = 500 g / mol) was selected as the monomer; LiTFSI was used as the lithium salt, with the lithium salt content accounting for 30 wt% of the total electrolyte mass; and azobisisobutyronitrile (AIOBR) was used as the initiator, with the initiator accounting for 1 wt% of the monomer mass. The monomer, lithium salt, and initiator were mixed uniformly to obtain the electrolyte precursor. The above-mentioned positive electrode containing the polymerization inhibitor, polyolefin separator, lithium metal negative electrode, and electrolyte precursor were assembled into a battery assembly according to conventional procedures.

[0040] The assembled battery was placed in a 60°C oven and left to stand for 24 hours for in-situ curing to form a solid electrolyte system.

[0041] The battery's charge-discharge performance at a 0.5C rate was tested, and its capacity retention after 100 cycles was 90%. The battery was disassembled, and the polymers in the positive electrode and electrolyte were separated and subjected to coagulation-permeation chromatography. The number-average molecular weight of the polymer in the electrolyte was found to be Mn = 56000 g / mol, while the number-average molecular weight of the polymer in the positive electrode was Mn = 6000 g / mol.

[0042] Example 3:

[0043] PVDF (2.5 wt% of the total positive electrode slurry) and hydroxyphenyl sulfonate (0.5 wt% of the total positive electrode slurry) were co-dissolved in N-methylpyrrolidone and allowed to stand for 12 hours for aging. Then, lithium iron phosphate (95 wt% of the total positive electrode slurry) and Super P (2 wt% of the total positive electrode slurry) were also dispersed in the above solution and mixed evenly to form the positive electrode slurry. The slurry was then uniformly coated onto an aluminum foil current collector and dried to obtain a positive electrode containing a polymerization inhibitor, with a positive electrode loading of 16 mg / cm³. 2 .

[0044] Polyethylene glycol methyl ether methacrylate (Mn = 500 g / mol) was selected as the monomer; LiTFSI was used as the lithium salt, with the lithium salt content accounting for 30 wt% of the total electrolyte mass; and azobisisobutyronitrile (AIOBR) was used as the initiator, with the initiator accounting for 1 wt% of the monomer mass. The monomer, lithium salt, and initiator were mixed uniformly to obtain the electrolyte precursor. The above-mentioned positive electrode containing the polymerization inhibitor, polyolefin separator, lithium metal negative electrode, and electrolyte precursor were assembled into a battery assembly according to conventional procedures.

[0045] The assembled battery was placed in a 60°C oven and left to stand for 24 hours for in-situ curing to form a solid electrolyte system.

[0046] The battery's charge-discharge performance at a 0.5C rate was tested, and its capacity retention after 100 cycles was 92%. The battery was disassembled, and the polymers in the positive electrode and electrolyte were separated and subjected to coagulation-permeation chromatography. The number-average molecular weight of the polymer in the electrolyte was found to be Mn = 32000 g / mol, while the number-average molecular weight of the polymer in the positive electrode was Mn = 4000 g / mol.

[0047] Example 4:

[0048] PVDF (2.5 wt% of the total positive electrode slurry) and o-benzoquinone (0.5 wt% of the total positive electrode slurry) were co-dissolved in N-methylpyrrolidone and allowed to stand for 12 hours for aging. Then, lithium iron phosphate (95 wt% of the total positive electrode slurry) and Super P (2 wt% of the total positive electrode slurry) were also dispersed in the above solution and mixed evenly to form the positive electrode slurry. The slurry was then uniformly coated onto an aluminum foil current collector and dried to obtain a positive electrode containing a polymerization inhibitor, with a positive electrode loading of 25 mg / cm³. 2 .

[0049] Polyethylene glycol methyl ether methacrylate (Mn = 500 g / mol) was selected as the monomer; LiTFSI was used as the lithium salt, with the lithium salt content accounting for 30 wt% of the total electrolyte mass; and azobisisobutyronitrile (AIOBR) was used as the initiator, with the initiator accounting for 1 wt% of the monomer mass. The monomer, lithium salt, and initiator were mixed uniformly to obtain the electrolyte precursor. The above-mentioned positive electrode containing the polymerization inhibitor, polyolefin separator, lithium metal negative electrode, and electrolyte precursor were assembled into a battery assembly according to conventional procedures.

[0050] The assembled battery was placed in a 60°C oven and left to stand for 24 hours for in-situ curing to form a solid electrolyte system.

[0051] The battery's charge-discharge performance at a 0.5C rate was tested, and its capacity retention after 100 cycles was 94%. The battery was disassembled, and the polymers in the positive electrode and electrolyte were separated and subjected to coagulation-permeation chromatography. The number-average molecular weight of the polymer in the electrolyte was found to be Mn = 36000 g / mol, while the number-average molecular weight of the polymer in the positive electrode was Mn = 4500 g / mol.

[0052] Comparative Example 1

[0053] Lithium iron phosphate, the positive electrode material for lithium-ion batteries, was dispersed in N-methylpyrrolidone at a mass ratio of 95:2:2.5 with a conductive agent (Super P) and a polymer binder (PVDF) to form a positive electrode slurry. After thorough mixing, the slurry was coated onto an aluminum foil current collector and dried to obtain the positive electrode with a loading of 19 mg / cm³. 2 .

[0054] Polyethylene glycol methyl ether methacrylate (Mn = 500 g / mol) was selected as the monomer; LiTFSI was used as the lithium salt, with the lithium salt content accounting for 30 wt% of the total electrolyte mass; and azobisisobutyronitrile (AIOBR) was used as the initiator, with the initiator accounting for 1 wt% of the monomer mass. The monomer, lithium salt, and initiator were mixed uniformly to obtain the electrolyte precursor. The above-mentioned positive electrode containing the polymerization inhibitor, polyolefin separator, lithium metal negative electrode, and electrolyte precursor were assembled into a battery assembly according to conventional procedures.

[0055] The assembled battery was placed in a 60°C oven and left to stand for 24 hours for in-situ curing to form a solid electrolyte system.

[0056] The battery's charge-discharge performance at a 0.5C rate was tested, and its capacity retention after 100 cycles was 75%. The battery was disassembled, and the polymers in the positive electrode and electrolyte were separated and subjected to coagulation-permeation chromatography. The number-average molecular weight of the polymer in the electrolyte was found to be Mn = 46000 g / mol, while the number-average molecular weight of the polymer in the positive electrode was Mn = 39000 g / mol.

[0057] The experimental results of Example 1 and Comparative Example 1 demonstrate that pre-dispersing a certain amount of polymerization inhibitor inside the positive electrode can effectively suppress the polymerization reaction inside the positive electrode during the subsequent polymerization process, thereby selectively reducing the degree of polymerization of the polymer network inside the positive electrode and improving the cycle stability of the battery.

[0058] Comparative Example 2

[0059] Lithium iron phosphate (95 wt% of total cathode material), PVDF binder (2.5 wt% of total cathode slurry), Super P conductive agent (2 wt% of total cathode slurry), and hydroquinone (0.5 wt% of total cathode slurry) were dispersed in N-methylpyrrolidone and mixed evenly to form a cathode slurry. The slurry was then uniformly coated onto an aluminum foil current collector and dried to obtain a cathode containing a polymerization inhibitor, with a cathode loading of 21 mg / cm³. 2 .

[0060] Polyethylene glycol methyl ether methacrylate (Mn = 500 g / mol) was selected as the polymerization monomer; LiTFSI was selected as the lithium salt, wherein the lithium salt content accounted for 30 wt% of the total electrolyte mass; and azobisisobutyronitrile was selected as the initiator, wherein the amount of the initiator accounted for 1 wt% of the polymerization monomer mass. The above monomers, lithium salts and initiators were mixed evenly to obtain the electrolyte precursor.

[0061] The above-mentioned positive electrode containing polymerization inhibitor, polyolefin separator, lithium metal negative electrode and electrolyte precursor are assembled into a battery assembly according to conventional steps.

[0062] The assembled battery was placed in a 60°C oven and left to stand for 24 hours for in-situ curing to form a solid electrolyte system.

[0063] The battery's charge-discharge performance at a 0.5C rate was tested, and its capacity retention after 100 cycles was 80%. The battery was disassembled, and the polymers in the positive electrode and electrolyte were separated and subjected to coagulation-permeation chromatography. The number-average molecular weight of the polymer in the electrolyte was found to be Mn = 30000 g / mol, while the number-average molecular weight of the polymer in the positive electrode was Mn = 18000 g / mol.

[0064] The experimental results of Example 1 and Comparative Example 2 demonstrate that if the binder and inhibitor are not pre-mixed and allowed to stand for aging, but instead the positive electrode active material, conductive agent, binder and inhibitor are mixed together, the inhibitor dispersed in the positive electrode will partially diffuse and enter the electrolyte, failing to achieve the purpose of selectively reducing the degree of polymerization in the positive electrode, and the effect on improving the cycle stability of the battery is limited.

[0065] Example 5:

[0066] PVDF (2.5 wt% of the total positive electrode slurry) and hydroquinone (0.5 wt% of the total positive electrode slurry) were co-dissolved in N-methylpyrrolidone and allowed to stand for 12 hours for aging. Then, lithium cobalt oxide (95 wt% of the total positive electrode slurry) and Super P (2 wt% of the total positive electrode slurry) were also dispersed in the above solution and mixed evenly to form the positive electrode slurry. The slurry was then uniformly coated onto an aluminum foil current collector and dried to obtain a positive electrode containing a polymerization inhibitor, with a positive electrode loading of 23 mg / cm³. 2 .

[0067] Polyethylene glycol methyl ether methacrylate (Mn = 500 g / mol) was selected as the monomer; LiTFSI was used as the lithium salt, with the lithium salt content accounting for 30 wt% of the total electrolyte mass; and azobisisobutyronitrile (AIOBR) was used as the initiator, with the initiator accounting for 1 wt% of the monomer mass. The monomer, lithium salt, and initiator were mixed uniformly to obtain the electrolyte precursor. The above-mentioned positive electrode containing the polymerization inhibitor, polyolefin separator, lithium metal negative electrode, and electrolyte precursor were assembled into a battery assembly according to conventional procedures.

[0068] The assembled battery was placed in a 60°C oven and left to stand for 24 hours for in-situ curing to form a solid electrolyte system.

[0069] The battery's charge-discharge performance at a 0.5C rate was tested, and its capacity retention after 100 cycles was 88%. The battery was disassembled, and the polymers in the positive electrode and electrolyte were separated and subjected to coagulation-permeation chromatography. The number-average molecular weight of the polymer in the electrolyte was found to be Mn = 52000 g / mol, while the number-average molecular weight of the polymer in the positive electrode was Mn = 6500 g / mol.

[0070] Example 6:

[0071] PVDF (2.5 wt% of the total positive electrode slurry) and hydroquinone (0.5 wt% of the total positive electrode slurry) were co-dissolved in N-methylpyrrolidone and allowed to stand for 12 hours for aging. Then, lithium nickel cobalt manganese (95 wt% of the total positive electrode slurry) and Super P (2 wt% of the total positive electrode slurry) were also dispersed in the above solution and mixed evenly to form the positive electrode slurry. The slurry was then uniformly coated onto an aluminum foil current collector and dried to obtain a positive electrode containing a polymerization inhibitor, with a positive electrode loading of 26 mg / cm³. 2 .

[0072] Polyethylene glycol methyl ether methacrylate (Mn = 500 g / mol) was selected as the monomer; LiTFSI was used as the lithium salt, with the lithium salt content accounting for 30 wt% of the total electrolyte mass; and azobisisobutyronitrile (AIOBR) was used as the initiator, with the initiator accounting for 1 wt% of the monomer mass. The monomer, lithium salt, and initiator were mixed uniformly to obtain the electrolyte precursor. The above-mentioned positive electrode containing the polymerization inhibitor, polyolefin separator, lithium metal negative electrode, and electrolyte precursor were assembled into a battery assembly according to conventional procedures.

[0073] The assembled battery was placed in a 60°C oven and left to stand for 24 hours for in-situ curing to form a solid electrolyte system.

[0074] The battery's charge-discharge performance at a 0.5C rate was tested, and its capacity retention after 100 cycles was 90%. The battery was disassembled, and the polymers in the positive electrode and electrolyte were separated and subjected to coagulation-permeation chromatography. The number-average molecular weight of the polymer in the electrolyte was found to be Mn = 46000 g / mol, while the number-average molecular weight of the polymer in the positive electrode was Mn = 3500 g / mol.

[0075] Example 7:

[0076] PVDF (2.5 wt% of the total positive electrode slurry) and hydroquinone (0.5 wt% of the total positive electrode slurry) were co-dissolved in N-methylpyrrolidone and allowed to stand for 12 hours for aging. Then, lithium iron phosphate (95 wt% of the total positive electrode slurry) and Super P (2 wt% of the total positive electrode slurry) were also dispersed in the above solution and mixed evenly to form the positive electrode slurry. The slurry was then uniformly coated onto an aluminum foil current collector and dried to obtain a positive electrode containing a polymerization inhibitor, with a positive electrode loading of 30 mg / cm³. 2 .

[0077] Polyethylene glycol methyl ether methacrylate (Mn = 500 g / mol) was selected as the monomer; LiTFSI was used as the lithium salt, with the lithium salt content accounting for 30 wt% of the total electrolyte mass; and azobisisobutyronitrile (AIOBR) was used as the initiator, with the initiator accounting for 1 wt% of the monomer mass. The monomer, lithium salt, and initiator were mixed uniformly to obtain the electrolyte precursor. The above-mentioned positive electrode containing the polymerization inhibitor, polyolefin separator, silicon anode, and electrolyte precursor were assembled into a battery assembly according to conventional procedures.

[0078] The assembled battery was placed in a 60°C oven and left to stand for 24 hours for in-situ curing to form a solid electrolyte system.

[0079] The battery's charge-discharge performance at a 0.5C rate was tested, and its capacity retention after 100 cycles was 89%. The battery was disassembled, and the polymers in the positive electrode and electrolyte were separated and subjected to coagulation-permeation chromatography. The number-average molecular weight of the polymer in the electrolyte was found to be Mn = 41000 g / mol, while the number-average molecular weight of the polymer in the positive electrode was Mn = 4800 g / mol.

[0080] Example 8:

[0081] PVDF (2.5 wt% of the total positive electrode slurry) and hydroquinone (0.5 wt% of the total positive electrode slurry) were co-dissolved in N-methylpyrrolidone and allowed to stand for 12 hours for aging. Then, lithium iron phosphate (95 wt% of the total positive electrode slurry) and Super P (2 wt% of the total positive electrode slurry) were also dispersed in the above solution and mixed evenly to form the positive electrode slurry. The slurry was then uniformly coated onto an aluminum foil current collector and dried to obtain a positive electrode containing a polymerization inhibitor, with a positive electrode loading of 18 mg / cm³. 2 .

[0082] Ethyl acrylate was selected as the polymerization monomer; LiTFSI was used as the lithium salt, with the lithium salt content accounting for 30 wt% of the total electrolyte mass; and azobisisobutyronitrile (AIBN) was used as the initiator, with the initiator accounting for 1 wt% of the polymerization monomer mass. The monomers, lithium salt, and initiator were mixed uniformly to obtain the electrolyte precursor. The above-mentioned positive electrode containing the polymerization inhibitor, polyolefin separator, lithium metal negative electrode, and electrolyte precursor were assembled into a battery assembly according to conventional procedures.

[0083] The assembled battery was placed in a 60°C oven and left to stand for 24 hours for in-situ curing to form a solid electrolyte system.

[0084] The battery's charge-discharge performance at a 0.5C rate was tested, and its capacity retention after 100 cycles was 91%. The battery was disassembled, and the polymers in the positive electrode and electrolyte were separated and subjected to coagulation-permeation chromatography. The number-average molecular weight of the polymer in the electrolyte was found to be Mn = 82000 g / mol, while the number-average molecular weight of the polymer in the positive electrode was Mn = 6500 g / mol.

[0085] Table 1. Battery parameters and cycle conditions for each embodiment and comparative example.

[0086]

[0087] In summary, this invention selectively controls the degree of polymerization of the polymer in the positive electrode region during in-situ curing by adding a polymerization inhibitor to the positive electrode material and pre-dispersing the inhibitor in a specific order. This results in the formation of a polymer network with a low degree of polymerization and high ionic conductivity within the positive electrode, effectively improving the rate performance and cycle stability of the battery. This invention is simple and easy to implement, applicable to the manufacture of various in-situ cured polymer batteries, and has high practical value and promising prospects for widespread application. Furthermore, this invention can also be extended to the preparation of negative electrode materials containing polymerization inhibitors, demonstrating its universality.

Claims

1. A method for improving ion conduction within the cathode of an in-situ polymer battery system, characterized in that: In preparing the in-situ polymerized battery system, a polymerization inhibitor is added to the positive electrode to selectively inhibit the polymerization reaction of the in-situ polymerized electrolyte precursor in the positive electrode region, thereby improving the ion conduction performance of the positive electrode region; the amount of the polymerization inhibitor added is 0.1 to 5 wt% of the total mass of the positive electrode material.

2. The method for improving ion conduction within the cathode of an in-situ polymer battery system according to claim 1, characterized in that: (a) Dissolve the polymerization inhibitor and binder together in a solvent and allow them to stand for 12-24 hours to achieve molecular-level pre-bonding of the polymerization inhibitor and binder; (b) Add the conductive agent and the positive electrode active material to the above solution and mix to form a positive electrode slurry containing a polymerization inhibitor; (c) The positive electrode slurry is coated onto the current collector and dried to obtain the positive electrode material; (d) Assemble the positive electrode material with the separator, the in-situ polymerized electrolyte precursor and the negative electrode to form a battery, and complete the in-situ polymerization by heating to obtain an in-situ polymerized battery.

3. The method for improving ion conduction within the cathode of an in-situ polymer battery system according to claim 1 or 2, characterized in that: The polymerization inhibitor is selected from organic polymerization inhibitors and / or inorganic polymerization inhibitors.

4. The method for improving ion conduction in polymer batteries according to claim 3, characterized in that: The organic polymerization inhibitor is selected from one or more combinations of hydroquinone, 2,6-di-tert-butyl-p-cresol, 4-hydroxy-2,2,6,6-tetramethylpiperidine, p-benzoquinone, methyl p-benzoquinone, nitrobenzene, p-nitrotoluene, N-nitrosodiphenylamine, nitrosobenzene, diphenyl sulfide, and 2,2,6,6-tetramethylpiperidine oxide; The inorganic polymerization inhibitor is selected from one or more combinations of chromium trioxide, manganese dioxide, sodium nitrite, potassium nitrite, molybdenum disulfide, sodium sulfide, copper chloride, copper sulfate, ferric chloride, ferrous sulfate, cerium oxide, trisodium phosphate, and sodium pyrophosphate.

5. The method for improving ion conduction within the cathode of an in-situ polymer battery system according to claim 1 or 2, characterized in that: The positive electrode active material is selected from one or a combination of lithium iron phosphate, lithium cobalt oxide, lithium manganese oxide, lithium nickel cobalt manganese, or lithium manganese silicate.

6. The application of the method as described in any one of claims 1 to 5 in the preparation of in-situ polymeric cells.

7. An in-situ polymerization battery, comprising a positive electrode, a negative electrode, a separator, and an electrolyte between the positive and negative electrodes, characterized in that: The positive electrode is prepared according to the method described in claim 1.

8. The in-situ polymerization battery according to claim 7, characterized in that: The negative electrode is selected from one or more combinations of graphite negative electrode, hard carbon negative electrode, soft carbon negative electrode, lithium titanium oxide negative electrode, silicon negative electrode, silicon suboxide negative electrode, and silicon carbon negative electrode.

9. An in-situ polymerization battery, comprising a positive electrode, a negative electrode, a separator, and an electrolyte between the positive and negative electrodes, characterized in that: The positive electrode is to add 0.1-5 wt% of a polymerization inhibitor to the positive electrode material, thereby selectively inhibiting the polymerization reaction of the in-situ polymerized electrolyte precursor in the positive electrode, so as to improve the ion conduction performance of the positive electrode region.

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