Production method of lithium ion supercapacitor

Abstract

The invention discloses a production method of a lithium ion supercapacitor, the lithium ion supercapacitor comprises a shell, a positive plate, a diaphragm and a negative plate are packaged in the shell, and the positive plate and the negative plate both comprise current collectors and coating layers containing active materials and coated on the current collectors. The diaphragm is a polyimide-lithium lanthanum titanium oxide composite nanofiber membrane, the positive plate, the diaphragm and the negative plate are immersed in an organic electrolyte, and the organic electrolyte comprises a lithium salt and an organic solvent. The charge-discharge performance of the capacitor is improved, and meanwhile, the capacitor has good cycle performance.

Description

Technical Field

[0001] The present invention belongs to the technical field of tantalum capacitors, and particularly relates to a production method of a lithium-ion supercapacitor. Background Art

[0002] Lithium-ion batteries and supercapacitors are currently the two most widely used electrochemical energy storage devices. Lithium-ion batteries can usually provide a relatively high energy density (150 Wh·kg -1 ), but they have a relatively low power density and a poor cycle life; traditional supercapacitors have a high power density (10 kW·kg -1 ), a long cycle life, but are limited by a relatively low energy density (<10 Wh·kg -1 ). Lithium-ion capacitors (LIC) combine the advantages of lithium-ion batteries and supercapacitors, can provide a relatively high power density and cycle life while maintaining a high energy density, and are considered to be outstanding representatives of the next-generation supercapacitors, with very broad application and market prospects.

[0003] Lithium-ion capacitors usually consist of a positive electrode, a negative electrode, a separator, and an electrolyte, etc. Among them, the separator is one of the key inner components. The quality of the separator's performance determines the battery's interface structure, internal resistance, etc., directly affecting the battery's capacity, cycle performance, and safety performance, etc. A separator with excellent performance plays an important role in improving the comprehensive performance of the battery. Currently, the commercially available separators for lithium-ion capacitors are mainly polyolefin separators, which have the defect of poor affinity with the electrolyte, resulting in the electrolyte not swelling well with the separator, and the electrolyte is prone to side leakage, making the lithium-ion capacitor have poor cycle stability. Summary of the Invention

[0004] To solve the deficiencies mentioned in the above background art, the purpose of the present invention is to provide a production method of a lithium-ion supercapacitor. The lithium-ion supercapacitor uses a polyimide-lithium lanthanum titanate oxide composite film prepared by electrospinning as the separator, which improves the charge and discharge performance of the capacitor and has good cycle performance at the same time.

[0005] The purpose of the present invention can be achieved through the following technical solutions: A production method of a lithium-ion supercapacitor. The lithium-ion supercapacitor includes a housing, and a positive electrode sheet, a separator, and a negative electrode sheet are encapsulated in the housing. Both the positive electrode sheet and the negative electrode sheet include a current collector and a coating layer containing an active material coated on the current collector. The separator is a polyimide-lithium lanthanum titanate oxide composite nanofiber membrane. The positive electrode sheet, the separator, and the negative electrode sheet are immersed in an organic electrolyte. The organic electrolyte includes a lithium salt and an organic solvent. The production method of the lithium-ion supercapacitor includes the following steps: S1. Prepare perovskite-type lithium lanthanum titanium oxide by the sol-gel method. Then, prepare a polyamic acid solution by the forward feeding method and mix it with lithium lanthanum titanium oxide to prepare a spinning solution. Prepare a polyamic acid-lithium lanthanum titanium oxide composite nanofiber membrane by electrospinning, and finally obtain a polyimide-lithium lanthanum titanium oxide composite nanofiber membrane by thermal imidization; S2. Dissolve the lithium salt in an organic solvent to obtain an organic electrolyte with a lithium ion concentration of 0.1 - 1 mol / L. Then, encapsulate the positive electrode, negative electrode, and separator in a casing, and then encapsulate the electrolyte to obtain a lithium ion supercapacitor.

[0006] Further preferably, the active material of the positive electrode sheet is a porous carbon material and LiNi x Co y Mn z O₂. The porous carbon material is one or more of activated carbon, activated carbon fiber, porous conductive carbon black, graphene, carbon aerogel, or carbon nanotube.

[0007] Further preferably, the active material of the negative electrode sheet is one or more of graphite, mesophase carbon microspheres, hard carbon, soft carbon, lithium titanate, titanium oxide, tin oxide, or silicon oxide.

[0008] Further preferably, the preparation method of lithium lanthanum titanium oxide includes the following steps: (1) Dissolve citric acid in deionized water to prepare a citric acid solution with a mass concentration of 50 wt%. Divide it into two parts. Dissolve tetrabutyl titanate in one part of the citric acid solution, continuously stir it at room temperature to hydrolyze it, and then slowly titrate it with ammonia water to adjust the pH value close to neutral. Then let it stand for layering, and take out the lower layer of light yellow clear liquid to obtain titanium citrate. Dissolve lanthanum nitrate hexahydrate and lithium nitrate in the other part of the citric acid solution, stir until completely dissolved, and slowly titrate it with ammonia water to adjust the pH value close to neutral to obtain a mixed solution of lanthanum citrate and lithium citrate; (2) Pour titanium citrate into the mixed solution of lithium citrate and lanthanum citrate and mix well. Measure an appropriate amount of ethylene glycol and add it to the above mixed solution, stir well, put the prepared solution into a water bath at 70 - 90 °C and heat it with magnetic stirring for about 8 - 10 h to obtain a clear and transparent coagulant gel. Then put the wet gel into an oven at 140 - 160 °C for about 3 - 5 h to make it completely dry and obtain a black precursor; (3) Finally, put the black precursor into an electric furnace at 300 - 400 °C and heat it in air for 3 - 5 h, and then calcine it at 850 - 1000 °C for 1 - 3 h, and cool it with the furnace to obtain lithium lanthanum titanium oxide powder.

[0009] Further preferably, in step (1), the molar ratio of tetrabutyl titanate, lanthanum nitrate hexahydrate, lithium nitrate, and citric acid is 5:3:2:10.

[0010] Further preferably, the molar amount of ethylene glycol added in step (2) is 3 to 5 times the total amount of citric acid.

[0011] Further preferably, the method for preparing the separator includes the following steps: A. Weigh a certain amount of lithium lanthanum titanium oxide powder, add it to N,N-dimethylformamide, and ultrasonically disperse it to obtain a lithium lanthanum titanium oxide suspension. In a nitrogen atmosphere, while stirring, add p-phenylenediamine and 4,4'-diaminodiphenyl ether; B. Add 3,3',4,4'-biphenyltetracarboxylic dianhydride to the above suspension in four batches, with an interval of 20 to 30 minutes between each addition. After the addition is completed, continuously stir the reaction system for 20 to 24 hours to obtain a polyamic acid-lithium lanthanum titanium oxide spinning solution; C. Add the polyamic acid-lithium lanthanum titanium oxide spinning solution into the syringe of an electrospinning device, prepare a polyamic acid-lithium lanthanum titanium oxide composite nanofiber membrane by electrospinning, and then dry the polyamic acid-lithium lanthanum titanium oxide composite nanofiber membrane in a vacuum oven at 50 to 60 °C for 6 to 12 hours to completely volatilize the remaining solvent; D. Place the polyamic acid-lithium lanthanum titanium oxide composite nanofiber membrane in a high-temperature tube furnace. Under an argon atmosphere, heat it at a heating rate of 3 to 5 °C / min to 240 to 260 °C and hold for 1 to 2 hours, then heat it at a heating rate of 0.5 to 1.5 °C / min to 330 to 350 °C and hold for 1 to 2 hours, and then naturally cool to room temperature to obtain the separator.

[0012] Further preferably, the molar ratio of p-phenylenediamine, 4,4'-diaminodiphenyl ether, and 3,3',4,4'-biphenyltetracarboxylic dianhydride is 1:1:2.

[0013] Further preferably, the lithium salt is one or more of LiN(SO3CF3)2, LiSO3CF3, LiPF6, and LiBOB.

[0014] Further preferably, the organic solvent is at least two mixtures of diethyl carbonate, dimethyl carbonate, ethylene carbonate, propylene carbonate, ethyl propyl carbonate, ethyl isopropyl carbonate, methyl butyl carbonate, dibutyl carbonate, ethyl butyl carbonate, γ-valerolactone, tetrahydrofuran, dimethyltetrahydrofuran, ethylene glycol dimethyl ether, dimethoxymethane, and 1,2-dimethoxyethane.

[0015] The beneficial effects of the present invention: The separator of the lithium-ion supercapacitor of the present invention uses a polyimide-lithium lanthanum titanate composite film prepared by electrospinning. This film can not only balance the secondary current distribution on the surface of the lithium negative electrode, but also achieve pre-storage of lithium ions before massive lithium deposition, buffer the concentration gradient of lithium ions, and redistribute the non-uniform lithium ion flux, thereby achieving uniform lithium deposition, improving the charge and discharge performance of the capacitor, and having good cycle performance at the same time. Detailed implementation mode

[0016] Next, in combination with the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work belong to the scope of protection of the present invention.

[0017] Example 1 A lithium lanthanum titanate, and its preparation method includes the following steps: (1) Dissolve 1.2 mol of citric acid in deionized water to prepare a citric acid solution with a mass concentration of 50 wt%, and divide it into two parts. Dissolve 0.6 mol of tetrabutyl titanate in one part of the citric acid solution, continuously stir it at room temperature to hydrolyze it, and then slowly titrate it with ammonia water to adjust the pH value to be close to neutral. Then let it stand for stratification, and take out the lower pale yellow clear liquid to obtain titanium citrate. Dissolve 0.36 mol of lanthanum nitrate hexahydrate and 0.24 mol of lithium nitrate in the other part of the citric acid solution, stir until completely dissolved, and slowly titrate it with ammonia water to adjust the pH value to be close to neutral to obtain a mixed solution of lanthanum citrate and lithium citrate; (2) Pour titanium citrate into the mixed solution of lithium citrate and lanthanum citrate and mix well. Measure 5 mol of ethylene glycol and add it to the above mixed solution, stir well, put the prepared solution into an 80 °C water bath and heat it with magnetic stirring for about 10 h to obtain a clear and transparent coagulant gel. Then put the wet gel into an oven at 150 °C for about 4 h to make it completely dry to obtain a black precursor; (3) Finally, put the black precursor into an electric furnace at 350 °C and heat it for decomposition in air for 4 h, and then calcine it at 900 °C for 2 h, and cool it with the furnace to obtain lithium lanthanum titanate powder.

[0018] Example 2 A separator, which is a polyimide-lithium lanthanum titanate composite nanofiber membrane, and its preparation method includes the following steps: A. Weigh 3.2 g of the lithium lanthanum titanate powder prepared in Example 1 and add it to 200 ml of N,N-dimethylformamide for ultrasonic dispersion to obtain a lithium lanthanum titanate suspension. In a nitrogen atmosphere, while stirring, add 10.8 g of p-phenylenediamine and 20 g of 4,4'-diaminodiphenyl ether; B. Add 58.8 g of 3,3',4,4'-biphenyltetracarboxylic dianhydride to the above suspension in four batches, with an interval of 20 min between each addition. After the addition is completed, continuously stir the reaction system for 24 h to obtain a polyamic acid-lithium lanthanum titanate oxide spinning solution; C. Add the polyamic acid-lithium lanthanum titanate oxide spinning solution into the syringe of the electrospinning equipment, and prepare a polyamic acid-lithium lanthanum titanate oxide composite nanofiber membrane by electrospinning. Then dry the polyamic acid-lithium lanthanum titanate oxide composite nanofiber membrane in a vacuum oven at 50 °C for 12 h to completely volatilize the residual solvent; D. Place the polyamic acid-lithium lanthanum titanate oxide composite nanofiber membrane in a high-temperature tubular furnace. Under an argon atmosphere, heat it at a heating rate of 3 °C / min to 260 °C and hold for 1 h, then heat it at a heating rate of 1.5 °C / min to 330 °C and hold for 2 h, and then naturally cool to room temperature to obtain a separator.

[0019] The molar ratio of p-phenylenediamine, 4,4'-diaminodiphenyl ether and 3,3',4,4'-biphenyltetracarboxylic dianhydride is 1:1:2

[0020] Example 3 A separator, which is a polyimide-lithium lanthanum titanate oxide composite nanofiber membrane, and its preparation method includes the following steps: A. Weigh 5.6 g of the lithium lanthanum titanate oxide powder prepared in Example 1 and add it to 200 ml of N,N-dimethylformamide, and ultrasonically disperse to obtain a lithium lanthanum titanate oxide suspension. Under a nitrogen atmosphere, add 10.8 g of p-phenylenediamine and 20 g of 4,4'-diaminodiphenyl ether while stirring; B. Add 58.8 g of 3,3',4,4'-biphenyltetracarboxylic dianhydride to the above suspension in four batches, with an interval of 20 min between each addition. After the addition is completed, continuously stir the reaction system for 24 h to obtain a polyamic acid-lithium lanthanum titanate oxide spinning solution; C. Add the polyamic acid-lithium lanthanum titanate oxide spinning solution into the syringe of the electrospinning equipment, and prepare a polyamic acid-lithium lanthanum titanate oxide composite nanofiber membrane by electrospinning. Then dry the polyamic acid-lithium lanthanum titanate oxide composite nanofiber membrane in a vacuum oven at 60 °C for 12 h to completely volatilize the residual solvent; D. Place the polyamic acid-lithium lanthanum titanate oxide composite nanofiber membrane in a high-temperature tubular furnace. Under an argon atmosphere, heat it at a heating rate of 5 °C / min to 250 °C and hold for 1 h, then heat it at a heating rate of 1 °C / min to 340 °C and hold for 1 h, and then naturally cool to room temperature to obtain a separator.

[0021] Example 4 A separator, which is a polyimide-lithium lanthanum titanate oxide composite nanofiber membrane, and its preparation method includes the following steps: A. Weigh 9.5 g of the lithium lanthanum titanium oxide powder prepared in Example 1 and add it to 200 ml of N,N-dimethylformamide. Ultrasonically disperse it to obtain a lithium lanthanum titanium oxide suspension. Under a nitrogen atmosphere, while stirring, add 10.8 g of p-phenylenediamine and 20 g of 4,4'-diaminodiphenyl ether; B. Add 58.8 g of 3,3',4,4'-biphenyltetracarboxylic dianhydride to the above suspension in four batches, with an interval of 30 min between each addition. After the addition is completed, continuously stir the reaction system for 20 h to obtain a polyamic acid-lithium lanthanum titanium oxide spinning solution; C. Add the polyamic acid-lithium lanthanum titanium oxide spinning solution into the syringe of an electrospinning device. Prepare a polyamic acid-lithium lanthanum titanium oxide composite nanofiber membrane by electrospinning. Then dry the polyamic acid-lithium lanthanum titanium oxide composite nanofiber membrane in a vacuum oven at 60 °C for 6 h to completely volatilize the residual solvent; D. Place the polyamic acid-lithium lanthanum titanium oxide composite nanofiber membrane in a high-temperature tube furnace. Under an argon atmosphere, heat it at a heating rate of 5 °C / min to 240 °C and hold for 2 h. Then heat it at a heating rate of 0.5 °C / min to 350 °C and hold for 1 h, and then naturally cool to room temperature to obtain a separator.

[0022] Example 5 A production method of a lithium-ion supercapacitor. The lithium-ion supercapacitor includes a housing. Inside the housing, a positive electrode sheet, a separator, and a negative electrode sheet are encapsulated. Both the positive electrode sheet and the negative electrode sheet include a current collector and a coating layer containing an active material coated on the current collector. The active material of the positive electrode sheet is activated carbon, porous conductive carbon black, and LiNi x Co y Mn z O2. The separator is the polyimide-lithium lanthanum titanium oxide composite nanofiber membrane prepared in Example 2. The active material of the negative electrode sheet is graphite. The positive electrode sheet, the separator, and the negative electrode sheet are immersed in an organic electrolyte. The organic electrolyte includes LiN(SO3CF3)2, diethyl carbonate, and dimethyl carbonate.

[0023] The production method of the lithium-ion supercapacitor includes the following steps: Dissolve LiN(SO3CF3)2 in diethyl carbonate and dimethyl carbonate to obtain an organic electrolyte with a lithium ion concentration of 0.1 mol / L. Then encapsulate the positive electrode, the negative electrode, and the separator in the housing, and then encapsulate the electrolyte to obtain the lithium-ion supercapacitor.

[0024] Example 6 A production method of a lithium-ion supercapacitor. The lithium-ion supercapacitor includes a housing. Inside the housing, a positive electrode sheet, a separator, and a negative electrode sheet are encapsulated. Both the positive electrode sheet and the negative electrode sheet include a current collector and a coating layer containing an active material coated on the current collector. The active material of the positive electrode sheet is activated carbon fiber, carbon aerogel, and LiNi x Co y Mnz O2, the separator is the polyimide-lithium lanthanum titanate composite nanofiber membrane prepared in Example 3. The active material of the negative electrode sheet is mesophase carbon microspheres and lithium titanate. The positive electrode sheet, the separator and the negative electrode sheet are immersed in an organic electrolyte. The organic electrolyte includes LiPF6, LiBOB, propylene carbonate and dibutyl carbonate.

[0025] The production method of the lithium-ion supercapacitor includes the following steps: Dissolve LiPF6 and LiBOB in propylene carbonate and dibutyl carbonate to obtain an organic electrolyte with a lithium ion concentration of 1 mol / L. Then, encapsulate the positive electrode, the negative electrode and the separator in a housing, and then encapsulate the electrolyte to obtain the lithium-ion supercapacitor.

[0026] Example 7 A production method of a lithium-ion supercapacitor. The lithium-ion supercapacitor includes a housing. Inside the housing, a positive electrode sheet, a separator and a negative electrode sheet are encapsulated. Both the positive electrode sheet and the negative electrode sheet include a current collector and a coating layer containing an active material coated on the current collector. The active material of the positive electrode sheet is porous conductive carbon black, carbon nanotubes and LiNi x Co y Mn z O2, the separator is the polyimide-lithium lanthanum titanate composite nanofiber membrane prepared in Example 4. The active material of the negative electrode sheet is mesophase carbon microspheres. The positive electrode sheet, the separator and the negative electrode sheet are immersed in an organic electrolyte. The organic electrolyte includes a lithium salt and an organic solvent. The lithium salt is LiSO3CF3, dibutyl carbonate and ethylene glycol dimethyl ether.

[0027] The production method of the lithium-ion supercapacitor includes the following steps: Dissolve LiSO3CF3 in dibutyl carbonate and ethylene glycol dimethyl ether to obtain an organic electrolyte with a lithium ion concentration of 0.5 mol / L. Then, encapsulate the positive electrode, the negative electrode and the separator in a housing, and then encapsulate the electrolyte to obtain the lithium-ion supercapacitor.

[0028] Comparative Example 1 A production method of a lithium-ion supercapacitor. The lithium-ion supercapacitor includes a housing. Inside the housing, a positive electrode sheet, a separator and a negative electrode sheet are encapsulated. Both the positive electrode sheet and the negative electrode sheet include a current collector and a coating layer containing an active material coated on the current collector. The active material of the positive electrode sheet is porous conductive carbon black, carbon nanotubes and LiNi x Co y Mn z O2, the separator is a commercially available polypropylene lithium battery separator. The active material of the negative electrode sheet is mesophase carbon microspheres. The positive electrode sheet, the separator and the negative electrode sheet are immersed in an organic electrolyte. The organic electrolyte includes a lithium salt and an organic solvent. The lithium salt is LiSO3CF3, dibutyl carbonate and ethylene glycol dimethyl ether.

[0029] The production method of the lithium-ion supercapacitor includes the following steps: Dissolve LiSO3CF3 in dibutyl carbonate and ethylene glycol dimethyl ether to obtain an organic electrolyte with a lithium-ion concentration of 0.5 mol / L. Then, encapsulate the positive electrode, negative electrode, and separator in a casing, and then encapsulate the electrolyte to obtain a lithium-ion supercapacitor.

[0030] Performance detection The alternating current impedance method is used to test the ionic conductivity of the separator materials in Examples 5 to 7 and Comparative Example 1 infiltrated with the electrolyte; the linear sweep voltammetry is used to test the electrochemical stability window of the separator materials in Examples 5 to 7 and Comparative Example 1 infiltrated with the electrolyte; the Arbin automatic battery tester is used to test the cycle performance of the lithium-ion supercapacitors in Examples 5 to 7 and Comparative Example 1 at a current rate of 0.2C within a charge-discharge range of 2.5 - 4.2V, and calculate the discharge capacity retention rate after 50 weeks of cyclic charge and discharge at room temperature. The results are shown in Table 1 below: Table 1 Performance test results of the separator and lithium-ion supercapacitor

[0031] It can be seen from the data in the above table that the separator materials in Examples 4 to 7 of the present invention have a relatively high lithium-ion conductivity (10 -3 S / cm), because the polyimide-lithium lanthanum titanate oxide composite film prepared by the electrospinning method in the present invention has a relatively high porosity, can absorb and store more electrolyte, and at the same time, due to the presence of lithium lanthanum titanate oxide, the La in the crystal structure of the perovskite-type lithium fast ion conductor ceramic particle lithium lanthanum titanate oxide 3+ The position in the crystal phase is conducive to the formation of pores with a relatively large radius, so that the lithium-ion transmission bottleneck is relatively large, which is conducive to the migration of Li + . At the same time, the perovskite-type lithium ion conductor ceramic particle lithium lanthanum titanate oxide plays a stabilizing role in the system, improving the stability of the composite fiber membrane infiltrated with the electrolyte, so the electrochemical stability window increases. The lithium-ion supercapacitor encapsulated with the polyimide-lithium lanthanum titanate oxide composite film of the present invention has a slower decline in discharge capacity and a relatively stable amplitude, and has good cycle performance.

[0032] In the description of this specification, the description referring to terms such as "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0033] The foregoing has shown and described the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments, and what is described in the above embodiments and the specification is only to illustrate the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention will also have various changes and improvements, and these changes and improvements fall within the scope of the present invention claimed.

Claims

1. A production method of a lithium-ion supercapacitor, characterized in that, The lithium-ion supercapacitor includes a housing, in which a positive electrode sheet, a separator, and a negative electrode sheet are encapsulated. Both the positive electrode sheet and the negative electrode sheet include a current collector and a coating film layer containing active materials coated on the current collector. The separator is a polyimide-lithium lanthanum titanate composite nanofiber membrane. The positive electrode sheet, the separator, and the negative electrode sheet are immersed in an organic electrolyte. The organic electrolyte includes a lithium salt and an organic solvent. The production method of the lithium-ion supercapacitor includes the following steps: S1. Prepare perovskite-type lithium lanthanum titanate by the sol-gel method, then prepare a polyamic acid solution by the forward feeding method and mix it with lithium lanthanum titanate to prepare a spinning solution. Prepare a polyamic acid-lithium lanthanum titanate composite nanofiber membrane by electrospinning, and finally obtain a polyimide-lithium lanthanum titanate composite nanofiber membrane by thermal imidization; S2. Dissolve the lithium salt in an organic solvent to obtain an organic electrolyte with a lithium ion concentration of 0.1~1 mol / L. Then encapsulate the positive electrode, the negative electrode, and the separator in the housing, and then encapsulate the electrolyte to obtain a lithium-ion supercapacitor.

2. The production method of the lithium-ion supercapacitor according to claim 1, characterized in that The active material of the positive electrode sheet is a porous carbon material and LiNi x Co y Mn z O2, and the porous carbon material is one or more of activated carbon, activated carbon fiber, porous conductive carbon black, graphene, carbon aerogel or carbon nanotube.

3. The production method of the lithium-ion supercapacitor according to claim 1, characterized in that, The active material of the negative electrode sheet is one or more of graphite, mesophase carbon microspheres, hard carbon, soft carbon, lithium titanate, titanium oxides, tin oxides, and silicon oxides.

4. The production method of the lithium-ion supercapacitor according to claim 1, characterized in that, The preparation method of the lithium lanthanum titanate includes the following steps: (1) Dissolve citric acid in deionized water to prepare a citric acid solution with a mass concentration of 50 wt%, and divide it into two parts. Dissolve tetrabutyl titanate in one part of the citric acid solution, continuously stir it at room temperature to hydrolyze it, and then slowly titrate it with ammonia water to adjust the pH value to be close to neutral. Then let it stand and layer, and take out the lower layer of light yellow clear liquid to obtain titanium citrate. Dissolve lanthanum nitrate hexahydrate and lithium nitrate in the other part of the citric acid solution, stir until completely dissolved, and slowly titrate it with ammonia water to adjust the pH value to be close to neutral to obtain a mixed solution of lanthanum citrate and lithium citrate; (2) Pour titanium citrate into the mixed solution of lithium citrate and lanthanum citrate and mix well. Measure an appropriate amount of ethylene glycol and add it to the above-mentioned mixed solution, stir well, place the prepared solution in a water bath at 70~90 °C and heat it with magnetic stirring for about 8~10 h to obtain a clear and transparent coagulant gel. Then place the wet gel in an oven at 140~160 °C for about 3~5 h to make it completely dry and obtain a black precursor; (3) Finally, place the black precursor in an electric furnace at 300~400 °C and heat it in air for 3~5 h, and then calcine it at 850~1000 °C for 1~3 h, and cool it with the furnace to obtain lithium lanthanum titanate powder.

5. The production method of the lithium-ion supercapacitor according to claim 4, characterized in that, In the step (1), the molar ratio of tetrabutyl titanate, lanthanum nitrate hexahydrate, lithium nitrate, and citric acid is 5:3:2:

10.

6. The production method of the lithium-ion supercapacitor according to claim 4, characterized in that, In the step (2), the molar amount of ethylene glycol added is 3~5 times the total amount of citric acid.

7. The production method of the lithium-ion supercapacitor according to claim 1, characterized in that, The preparation method of the separator includes the following steps: A. Weigh a certain amount of lithium lanthanum titanate powder and add it to N,N-dimethylformamide for ultrasonic dispersion to obtain a lithium lanthanum titanate suspension. In a nitrogen atmosphere, add p-phenylenediamine and 4,4'-diaminodiphenyl ether while stirring; B. Add 3,3',4,4'-biphenyltetracarboxylic dianhydride to the above suspension in four batches, with an interval of 20 - 30 minutes between each addition. After the addition is completed, continuously stir the reaction system for 20 - 24 hours to obtain a polyamic acid-lithium lanthanum titanate oxide spinning solution; C. Add the polyamic acid-lithium lanthanum titanate oxide spinning solution into the syringe of the electrospinning equipment, and prepare a polyamic acid-lithium lanthanum titanate oxide composite nanofiber membrane by electrospinning. Then, dry the polyamic acid-lithium lanthanum titanate oxide composite nanofiber membrane in a vacuum oven at 50 - 60 °C for 6 - 12 hours to completely volatilize the residual solvent; D. Place the polyamic acid-lithium lanthanum titanate oxide composite nanofiber membrane in a high-temperature tube furnace. Under an argon atmosphere, heat it at a heating rate of 3 - 5 °C / min to 240 - 260 °C and hold for 1 - 2 hours. Then, heat it at a heating rate of 0.5 - 1.5 °C / min to 330 - 350 °C and hold for 1 - 2 hours, and then naturally cool to room temperature to obtain the separator.

8. The production method of the lithium-ion supercapacitor according to claim 7, characterized in that, The molar ratio of p-phenylenediamine, 4,4'-diaminodiphenyl ether and 3,3',4,4'-biphenyltetracarboxylic dianhydride is 1:1:

2.

9. The production method of the lithium-ion supercapacitor according to claim 1, characterized in that The lithium salt is one or more of LiN(SO3CF3)2, LiSO3CF3, LiPF6, LiBOB.

10. The production method of the lithium-ion supercapacitor according to claim 1, characterized in that, The organic solvent is a mixture of at least two of diethyl carbonate, dimethyl carbonate, ethylene carbonate, propylene carbonate, ethyl propyl carbonate, ethyl isopropyl carbonate, methyl butyl carbonate, dibutyl carbonate, ethyl butyl carbonate, γ-valerolactone, tetrahydrofuran, dimethyltetrahydrofuran, ethylene glycol dimethyl ether, dimethoxymethane, 1,2-dimethoxyethane.

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