Efficient pre-lithiation / sodiation method for energy storage devices and applications

Abstract

The application discloses a high-efficiency pre-lithiation / sodiation method of an energy storage device and application, and relates to the technical field of battery pre-lithiation / sodiation. In the application, the negative electrode is subjected to short-circuit treatment, the pre-lithiation / sodiation potential is controlled, the pre-lithiation / sodiation amount can be accurately regulated and controlled, the pre-lithiation / sodiation is more uniform through the positive electrode cooperative pre-lithiation / sodiation, the environmental requirement of the process is reduced, the pre-lithiation / sodiation method in the application is compatible with the preparation process of the battery in the prior art, the battery structure is not changed after packaging, the lithium strip / metal sodium strip in the application can be recycled and reused, the maximum utilization is realized, the cost is reduced, and certain economic benefits are obtained. In the application, a flame-retardant polyacrylonitrile fiber is prepared, the flame-retardant polyacrylonitrile fiber is used as a reinforcing fiber, and the surface of a semi-finished product diaphragm is formed with a silica aerogel, so that the safety of the battery is comprehensively improved.

Description

Technical Field

[0001] This invention relates to the field of battery pre-lithiation / sodium technology, specifically to a highly efficient pre-lithiation / sodiumification method and application for energy storage devices. Background Technology

[0002] Energy storage devices are widely used in new energy vehicles, smart grids and other fields, but the energy density and cycle life of energy storage devices still need to be improved. In order to solve the capacity decay of energy storage devices caused by effective lithium ion loss, the operating potential window can be adjusted by pre-lithiation / sodiumization, thereby improving the cycle life of energy storage devices.

[0003] Traditionally, there are two methods for pre-lithiation / sodiumification of the negative electrode. One method involves coating a mixture of lithium and sodium metal powder onto the negative electrode. However, lithium and sodium metal powders have high activity and require a harsh preparation environment, making them unsuitable for existing processes and large-scale industrial production. The other method involves rolling lithium and sodium metal onto the negative electrode surface. This method also has stringent environmental requirements, and the amount of pre-lithiation / sodium used is difficult to control, making it unsuitable for large-scale production and incompatible with production equipment. Traditionally, pre-lithiation / sodiumification of the positive electrode involves selecting an appropriate amount of positive electrode salt for mixed coating, with a doping amount of approximately 3-5%. However, this method has limited lithium / sodium capacity and affects the battery's energy density (reducing it by about 3-5%). During the entire pre-lithiation / sodium process, the pre-lithiation / sodium agent generates a large amount of gas during the formation stage, affecting battery performance and appearance, requiring additional venting treatment.

[0004] Therefore, we propose an efficient pre-lithiation / sodiumization method for energy storage devices and its application, which solves the problems of difficult operation, high cost and low efficiency in traditional pre-lithiation / sodiumization technologies. Summary of the Invention

[0005] The purpose of this invention is to provide an efficient pre-lithiation / sodiumification method and application for energy storage devices. By adding a third electrode to the existing battery and adopting a strategy of negative electrode short-circuiting, charging and positive electrode synergistic lithium / sodium replenishment for pre-lithiation / sodiumification, the efficiency and uniformity of pre-lithiation / sodiumification are improved.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a highly efficient pre-lithiation method for energy storage devices, comprising the following steps:

[0007] Step A1: Stack the positive electrode, separator, and negative electrode in sequence to form a positive electrode-separator-negative electrode structure, and then wind it to obtain the battery cell;

[0008] Step A2: Fix metallic lithium onto the tab to form a third electrode. Fix the third electrode on the side of the negative electrode away from the positive electrode. Inject electrolyte and seal to obtain a soft-pack battery.

[0009] Step A3: Short-circuit the third electrode and the negative electrode, monitor the potential between the third electrode and the negative electrode, and after fully charging, use the third electrode as the negative electrode and keep the positive electrode unchanged to pre-lithiate the soft pack battery. Then, perform secondary encapsulation, remove excess air pockets, and recover the metallic lithium in the third electrode to obtain the pre-lithiated energy storage device.

[0010] Furthermore, in step A1, the diaphragm is a polyacrylonitrile diaphragm.

[0011] Furthermore, in step A2, the lithium metal is elongated; the tab is an aluminum tab.

[0012] Furthermore, in step A2, the electrolyte includes an electrolyte, an additive, and a solvent;

[0013] The electrolyte is one or a mixture of two of LiPF6 (lithium hexafluorophosphate) and LiBF4 (lithium tetrafluoroborate);

[0014] The additive is one or more of FEC (fluoroethylene carbonate), PS (propane sulfonate lactone), and VC (ethylene carbonate);

[0015] The solvents are PC (propylene carbonate), EMC (ethyl methyl carbonate), DEC (diethyl carbonate), and EC (ethylene carbonate).

[0016] Furthermore, this application also provides a highly efficient pre-sodiuming method for energy storage devices, comprising the following steps:

[0017] Step B1: Stack the positive electrode, separator, and negative electrode in sequence to form a positive electrode-separator-negative electrode structure, and then wind it to obtain the battery cell;

[0018] Step B2: Fix metallic sodium onto the tab to form a third electrode. Fix the third electrode on the side of the negative electrode away from the positive electrode. Inject electrolyte and seal to obtain a soft-pack battery.

[0019] Step B3: Short-circuit the third electrode and the negative electrode, monitor the potential between the third electrode and the negative electrode, and after fully charging, use the third electrode as the negative electrode and keep the positive electrode unchanged to pre-sodium the soft pack battery. Then, perform secondary encapsulation, remove excess air pockets, and recover the metallic sodium in the third electrode to obtain the pre-sodiumized energy storage device.

[0020] Furthermore, in step B1, the diaphragm is a polyacrylonitrile diaphragm.

[0021] Furthermore, in step B2, the metallic sodium is in the shape of a long strip; the electrode tab is an aluminum electrode tab.

[0022] Furthermore, in step B2, the electrolyte includes an electrolyte, an additive, and a solvent;

[0023] The electrolyte is one or a mixture of two of LiPF6 (lithium hexafluorophosphate) and LiBF4 (lithium tetrafluoroborate);

[0024] The additive is one or more of FEC (fluoroethylene carbonate), PS (propane sulfonate lactone), and VC (ethylene carbonate);

[0025] The solvents are PC (propylene carbonate), EMC (ethyl methyl carbonate), DEC (diethyl carbonate), and EC (ethylene carbonate).

[0026] Furthermore, the preparation method of the positive electrode is as follows:

[0027] Sodium iron pyrophosphate, Super-P (super carbon black), single-walled carbon nanotubes, PVDF (polyvinylidene fluoride), and N-methylpyrrolidone are mixed and stirred evenly to obtain a positive electrode slurry. The positive electrode slurry is evenly coated on the upper and lower surfaces of carbon-coated aluminum foil, vacuum dried, then rolled to 0.10~0.12mm, die-cut to form an electrode sheet, and lead strips are welded to the blank parts of the electrode sheet to obtain the positive electrode sheet.

[0028] Furthermore, the mass ratio of sodium iron pyrophosphate, Super-P, single-walled carbon nanotubes, PVDF, and N-methylpyrrolidone is (92~94):(2.4~3.4):(0.4~0.6):(1~2):(28~32).

[0029] The solid content of the positive electrode slurry is 75-78%.

[0030] Furthermore, the surface density of the positive electrode slurry coating is 140~150 g / m². 2 ;

[0031] The coating thickness of the positive electrode slurry is 65~92μm.

[0032] Furthermore, the vacuum drying process conditions are: temperature 110~120℃, time 3~4h.

[0033] Furthermore, the method for preparing the negative electrode sheet is as follows:

[0034] Hard carbon, Super-P, CMC (carboxymethyl cellulose), SBR (styrene-butadiene rubber) and N-methylpyrrolidone are mixed and stirred evenly to obtain a negative electrode slurry. The negative electrode slurry is evenly coated on the upper and lower surfaces of copper foil, vacuum dried, then rolled to 0.05~0.07mm and die-cut to form an electrode sheet. Lead strips are welded to the blank parts of the electrode sheet to obtain the negative electrode sheet.

[0035] Furthermore, the mass ratio of hard carbon, Super-P, CMC, SBR to N-methylpyrrolidone is 95:(1.0~1.5):(2.0~3.0):(0.3~0.5):(115~125).

[0036] The solid content of the negative electrode slurry is 44-46%.

[0037] Furthermore, the surface density of the negative electrode slurry coating is 70~80 g / m². 2 ;

[0038] The coating thickness of the negative electrode slurry is 150~159μm.

[0039] Furthermore, the vacuum drying process conditions are: temperature 110~120℃, time 3~4h.

[0040] Furthermore, the diaphragm can also be prepared by the following process:

[0041] S1: Take polyacrylonitrile composite fiber, cut it into short pieces to obtain polyacrylonitrile composite short-cut fiber, mix it with cellulose acetate and water, perform the first pulping treatment, then add nanocellulose, perform the second pulping treatment, and then perform papermaking to obtain wet fiber sheet, and perform the first drying, hot calendering treatment, and second drying in sequence to obtain semi-finished diaphragm.

[0042] S2: Disperse polyacrylonitrile composite fibers in anhydrous ethanol, add tetraethyl orthosilicate, methacryloyloxypropyltrimethoxysilane and deionized water and stir until homogeneous, adjust the pH value to 3-4, stir until homogeneous, and obtain wet gel.

[0043] S3: Immerse the semi-finished diaphragm in an aqueous sodium hydroxide solution, wash it, then place it in a wet gel for 8-10 hours, remove it, and finally place it in a photoinitiator solution for ultraviolet irradiation to form an aerogel. Dry it to obtain the diaphragm.

[0044] Furthermore, in S1, the mass ratio of polyacrylonitrile composite chopped fiber, cellulose acetate, nanocellulose, and water is (3~5):1:(3~5):(40~50);

[0045] In S1, the length of the polyacrylonitrile composite short-cut fibers is 1~3mm.

[0046] Furthermore, in S1, the process conditions for the first pulping treatment are: pulping speed 10000~12000rpm, pulping time 5~15min;

[0047] In S1, the process conditions for the second pulping treatment are: pulping speed 13000~15000 rpm, pulping time 10~20 min.

[0048] Furthermore, in S1, the process conditions for the first drying are: temperature 40~50℃, time 10~15h;

[0049] In S1, the process conditions for the second drying are: temperature 50~70℃, time 16~24h;

[0050] In S1, the process conditions for hot rolling are: temperature 200~250℃, pressure 12~16MPa.

[0051] Furthermore, in S2, the mass ratio of polyacrylonitrile composite fiber, anhydrous ethanol, tetraethyl orthosilicate, methacryloyloxypropyltrimethoxysilane and deionized water is 10:(200~400):(50~150):(3~5):(100~120).

[0052] Furthermore, in S3, the mass fraction of the sodium hydroxide aqueous solution is 6-8%;

[0053] In S3, the impregnation process conditions are: temperature 50~60℃, time 1.5~2.0h.

[0054] Furthermore, in S3, the photoinitiator solution is prepared by mixing benzoin dimethyl ether and ethyl acetate in a ratio of (3~5) g: 1 L.

[0055] Furthermore, in S3, the process conditions for ultraviolet irradiation are: irradiation intensity 6~10mW / cm². 2 Time: 20-30 minutes; Temperature: 60-70℃;

[0056] In S3, the drying process conditions are: drying at 40~45℃ for 1~2 hours, and drying at 75~85℃ for 2~4 hours.

[0057] Furthermore, the polyacrylonitrile composite fiber is prepared by the following process:

[0058] Step 1: Under a nitrogen atmosphere, 4-methyl-1,3,5-triazine-2-amine, 3,4,5-trihydroxybenzaldehyde and anhydrous ethanol were mixed, p-toluenesulfonic acid was added dropwise, the mixture was heated under reflux, rotary evaporated, and cooled to obtain a nitrogen-containing compound.

[0059] Step 2: Under a nitrogen atmosphere, a nitrogen-containing compound, p-toluenesulfonic acid, hydroquinone, and toluene are mixed, stirred, and heated to 110-120°C. 3-mercaptopropionic acid is added, and the mixture is reacted for 5-7 hours. After cooling and rotary evaporation, the flame-retardant compound is obtained.

[0060] Step 3: Disperse silica in tetrahydrofuran, add flame retardant compound under nitrogen atmosphere, heat and reflux reaction, wash to obtain mercapto-modified silica;

[0061] Step 4: Mix polyacrylonitrile with N,N-dimethylacetamide and stir for 1-2 hours. Add mercapto-modified silica and stir again for 4-6 hours to obtain a spinning solution. Then electrospin and vacuum dry to obtain polyacrylonitrile composite fibers.

[0062] Furthermore, in step 1, the mass ratio of 4-methyl-1,3,5-triazine-2-amine, 3,4,5-trihydroxybenzaldehyde to anhydrous ethanol and p-toluenesulfonic acid is (10~15):10:(50~100):(0.1~0.5).

[0063] Furthermore, in step 1, the process conditions for the heating reflux reaction are: temperature 80~100℃, time 6~8h;

[0064] In step 1, the rotary evaporation temperature is 50~60℃ and the time is 30~50min.

[0065] Furthermore, in step 2, the mass ratio of the nitrogen-containing compound, p-toluenesulfonic acid, hydroquinone, toluene, and 3-mercaptopropionic acid is 10:(0.3~0.5):(0.02~0.10):(50~90):(6~8).

[0066] Furthermore, in step 3, the mass ratio of silicon dioxide, tetrahydrofuran, and flame retardant compound is 10:(50~100):(5~10).

[0067] Furthermore, in step 3, the process conditions for the heating reflux reaction are: temperature 65~68℃, time 6~10h.

[0068] Furthermore, in step 4, the mass ratio of polyacrylonitrile, N,N-dimethylacetamide, and mercaptolated silica is 10:(60~100):(3~5).

[0069] Furthermore, in step 4, the electrospinning process conditions are: voltage 16~18kV, spinneret speed 1.3~1.5mL / h;

[0070] In step 4, the vacuum drying process conditions are: temperature 50~60℃, time 10~12h.

[0071] In the above technical solution, firstly, 4-methyl-1,3,5-triazine-2-amine and 3,4,5-trihydroxybenzaldehyde undergo an aldehyde-amine condensation reaction to obtain a nitrogen-containing compound with multiple hydroxyl groups in its molecular structure. Then, the hydroxyl groups on the compound react with the carboxyl groups of 3-mercaptopropionic acid under the action of an acid catalyst (p-toluenesulfonic acid) to esterify the compound and introduce mercapto groups, thus obtaining a flame-retardant compound. By controlling the amount of 3-mercaptopropionic acid added, the flame-retardant compound retains hydroxyl groups. The residual hydroxyl groups undergo a condensation reaction with the silanol groups on the surface of silica, introducing flame-retardant segments and mercapto groups onto the silica surface, thus obtaining mercapto-modified silica. Finally, polyacrylonitrile and mercapto-modified silica are mixed to form a spinning solution, and electrospinning is performed to obtain polyacrylonitrile composite fibers with mercapto groups. The polyacrylonitrile composite fibers are used as reinforcing fibers to form an aerogel on the surface of the semi-finished membrane through a mercapto-dilute reaction, thus obtaining the membrane.

[0072] Combining aerogel with a membrane can endow the membrane with properties such as high temperature resistance and structural stability, preventing short circuits caused by membrane deformation or thermal runaway at high temperatures. Silica aerogel has a large specific surface area, which can increase the contact area with the electrolyte, improve electrolyte wettability, and enhance ion transport efficiency, thereby comprehensively improving the performance of energy storage devices. Polyacrylonitrile composite fibers, as reinforcing fibers, can improve the tensile strength of the aerogel, and flame-retardant segments are grafted onto the surface of the polyacrylonitrile composite fibers, further enhancing the safety of energy storage devices.

[0073] Compared with the prior art, the beneficial effects of the present invention are:

[0074] 1. In this application, the pre-lithiation / sodium potential is controlled by a negative electrode short circuit, which allows for precise control of the pre-lithiation / sodium amount. The positive electrode synergistic pre-lithiation / sodium method makes the pre-lithiation / sodium more uniform and reduces the environmental requirements of the process. The pre-lithiation / sodiumification method of the battery in this application is compatible with the battery preparation process in the prior art. It does not change the battery structure after packaging. Furthermore, the lithium / sodium metal bars in this application can be recycled and reused, maximizing utilization, reducing costs, and having certain economic benefits.

[0075] 2. In this application, the aerogel is combined with the separator, which can endow the separator with properties such as high temperature resistance and structural stability, avoiding short circuits caused by deformation or thermal runaway of the separator at high temperature. The silica aerogel has a large specific surface area, which can increase the contact area with the electrolyte, improve the wettability of the electrolyte, and improve the ion transport efficiency, thereby comprehensively improving the performance of the energy storage device. The polyacrylonitrile composite fiber, as a reinforcing fiber, can improve the tensile strength of the aerogel, and the surface of the polyacrylonitrile composite fiber is grafted with flame-retardant segments, further improving the safety of the battery. Attached Figure Description

[0076] Figure 1This is a schematic diagram of the structure of the lithium / sodium source fixing position in the soft-pack battery of the present invention;

[0077] In the diagram, ① is the positive electrode, ② is the negative electrode, ③ is the third electrode, and ④ is either lithium metal or sodium metal.

[0078] Figure 2 This is a schematic flowchart of an efficient pre-lithiation method for an energy storage device according to the present invention. Detailed Implementation

[0079] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0080] In the following specific implementation,

[0081] Polyacrylonitrile membrane, thickness 15~25μm;

[0082] Single-walled carbon nanotubes, with a diameter of 1-2 nm and a length of 5-30 μm;

[0083] Super-P, BET specific surface area 62m² 2 / g, ash content 0.01%, particle size 40nm;

[0084] The polyethylene diaphragm has a thickness of 20 μm.

[0085] Silica, with an average particle size of 60 nm and a specific surface area of ​​150–200 m². 2 / g;

[0086] SBR, model HC-W086;

[0087] Hard carbon fiber, model YTL-YKT-037;

[0088] Polyacrylonitrile, molecular weight 50,000;

[0089] Preparation of electrolyte: Mix LiBF4, LiPF6, FEC, VC, DEC, EC and EMC in a mass ratio of 1:1:0.3:0.2:3:4:3 and stir until homogeneous to obtain the electrolyte.

[0090] Example 1: A highly efficient pre-lithiation method for energy storage devices, comprising the following steps:

[0091] Sodium iron pyrophosphate, Super-P, single-walled carbon nanotubes, PVDF, and N-methylpyrrolidone were mixed at a mass ratio of 94:3.4:0.6:2:32 and stirred until homogeneous to obtain a positive electrode slurry. The positive electrode slurry was uniformly coated onto the upper and lower surfaces of a carbon-coated aluminum foil, vacuum dried, rolled to 0.12 mm, and die-cut to form an electrode sheet. Lead strips were welded to the blank areas of the electrode sheet to obtain the positive electrode sheet. The solid content of the positive electrode slurry was 78%, and the coating surface density was 150 g / m³. 2 The coating thickness of the positive electrode slurry is 92 μm; the vacuum drying process conditions are: temperature 120℃, time 4h;

[0092] Hard carbon, Super-P, CMC, SBR, and N-methylpyrrolidone were mixed in a mass ratio of 95:1.5:3.0:0.5:125 and stirred evenly to obtain a negative electrode slurry. The negative electrode slurry was uniformly coated on the upper and lower surfaces of a copper foil, vacuum dried, rolled to 0.07 mm, and die-cut to form an electrode sheet. Lead strips were welded to the blank areas of the electrode sheet to obtain the negative electrode sheet. The solid content of the negative electrode slurry was 46%, and the coating surface density of the negative electrode slurry was 80 g / m³. 2 The coating thickness of the negative electrode slurry is 159 μm; the vacuum drying process conditions are: temperature 120℃, time 4h.

[0093] Step A1: Stack the positive electrode, a 25μm thick polyacrylonitrile separator, and the negative electrode in sequence to form a positive electrode-separator-negative electrode structure, and wind them to obtain a battery cell; Step A2: Fix a strip of metallic lithium on an aluminum tab to form a third electrode. Fix the third electrode on the side of the negative electrode away from the positive electrode, inject electrolyte, and seal to obtain a pouch battery; Step A3: Short-circuit the third electrode and the negative electrode, monitor the potential between the third electrode and the negative electrode, form to full charge, use the third electrode as the negative electrode and keep the positive electrode unchanged, pre-lithiate the pouch battery, then perform secondary encapsulation, remove excess air pockets, and recover the metallic lithium in the third electrode to obtain a pre-lithiated energy storage device.

[0094] Example 2: A highly efficient pre-lithiation method for energy storage devices, comprising the following steps:

[0095] Sodium iron pyrophosphate, Super-P, single-walled carbon nanotubes, PVDF, and N-methylpyrrolidone were mixed at a mass ratio of 93:3.0:0.5:1.5:30 and stirred until homogeneous to obtain a positive electrode slurry. The positive electrode slurry was uniformly coated onto the upper and lower surfaces of a carbon-coated aluminum foil, vacuum dried, rolled to 0.11 mm, and die-cut to form an electrode sheet. Lead strips were welded to the blank areas of the electrode sheet to obtain the positive electrode sheet. The solid content of the positive electrode slurry was 76%, and the coating surface density was 145 g / m³. 2The coating thickness of the positive electrode slurry is 75 μm; the vacuum drying process conditions are: temperature 115℃, time 3.5 h;

[0096] Hard carbon, Super-P, CMC, SBR, and N-methylpyrrolidone were mixed at a mass ratio of 95:1.2:2.5:0.4:120 and stirred evenly to obtain a negative electrode slurry. The negative electrode slurry was uniformly coated on the upper and lower surfaces of a copper foil, vacuum dried, rolled to 0.06 mm, and die-cut to form an electrode sheet. Lead strips were welded to the blank areas of the electrode sheet to obtain the negative electrode sheet. The solid content of the negative electrode slurry was 45%, and the coating surface density of the negative electrode slurry was 75 g / m³. 2 The coating thickness of the negative electrode slurry is 155 μm; the vacuum drying process conditions are: temperature 115℃, time 3.5 h.

[0097] Step A1: Stack the positive electrode, a 20μm thick polyacrylonitrile separator, and the negative electrode in sequence to form a positive electrode-separator-negative electrode structure, and wind them to obtain a battery cell; Step A2: Fix metallic lithium on the aluminum tab to form a third electrode, fix the third electrode on the side of the negative electrode away from the positive electrode, inject electrolyte, and seal to obtain a pouch battery; Step A3: Short-circuit the third electrode and the negative electrode, monitor the potential between the third electrode and the negative electrode, form to full charge, use the third electrode as the negative electrode and keep the positive electrode unchanged, pre-lithiate the pouch battery, then perform secondary encapsulation, remove excess air pockets, and recover metallic lithium from the third electrode to obtain a pre-lithiated energy storage device.

[0098] Example 3: A highly efficient pre-lithiation method for energy storage devices, comprising the following steps:

[0099] Sodium iron pyrophosphate, Super-P, single-walled carbon nanotubes, PVDF, and N-methylpyrrolidone were mixed at a mass ratio of 92:2.4:0.4:1:28 and stirred evenly to obtain a positive electrode slurry. The positive electrode slurry was uniformly coated on the upper and lower surfaces of carbon-coated aluminum foil, vacuum dried, rolled to 0.10 mm, and die-cut to form an electrode sheet. Lead strips were welded to the blank areas of the electrode sheet to obtain the positive electrode sheet. The solid content of the positive electrode slurry was 75%, and the coating surface density of the positive electrode slurry was 140 g / m³. 2 The coating thickness of the positive electrode slurry is 65 μm; the vacuum drying process conditions are: temperature 110℃, time 3h;

[0100] Hard carbon, Super-P, CMC, SBR, and N-methylpyrrolidone were mixed at a mass ratio of 95:1.0:2.0:0.3:115 and stirred evenly to obtain a negative electrode slurry. The negative electrode slurry was uniformly coated on the upper and lower surfaces of a copper foil, vacuum dried, rolled to 0.05 mm, and die-cut to form an electrode sheet. Lead strips were welded to the blank areas of the electrode sheet to obtain the negative electrode sheet. The solid content of the negative electrode slurry was 44%, and the coating surface density of the negative electrode slurry was 70 g / m³. 2 The coating thickness of the negative electrode slurry is 150 μm; the vacuum drying process conditions are: temperature 110℃, time 3h.

[0101] Step A1: Stack the positive electrode, a 15μm thick polyacrylonitrile separator, and the negative electrode in sequence to form a positive electrode-separator-negative electrode structure, and wind them to obtain a battery cell; Step A2: Fix a strip of metallic lithium on an aluminum tab to form a third electrode. Fix the third electrode on the side of the negative electrode away from the positive electrode, inject electrolyte, and seal to obtain a pouch battery; Step A3: Short-circuit the third electrode and the negative electrode, monitor the potential between the third electrode and the negative electrode, and after forming to full charge, pre-lithiate the pouch battery with the third electrode as the negative electrode and the positive electrode unchanged. Then, perform secondary encapsulation, remove excess air pockets, and recover the metallic lithium in the third electrode to obtain a pre-lithiated energy storage device.

[0102] Example 4: Compared with Example 1, lithium metal was replaced with sodium metal to pre-sodium the soft-pack battery, while other conditions remained unchanged.

[0103] Example 5: Compared with Example 2, lithium metal was replaced with sodium metal to pre-sodium the soft-pack battery, while other conditions remained unchanged.

[0104] Example 6: Compared with Example 3, lithium metal was replaced with sodium metal to pre-sodium the soft-pack battery, while other conditions remained unchanged.

[0105] Example 7: Compared with Example 1, a highly efficient pre-lithiation method for energy storage devices includes the following steps:

[0106] (1) Preparation of polyacrylonitrile composite fibers:

[0107] Step 1: Under a nitrogen atmosphere, 4-methyl-1,3,5-triazine-2-amine, 3,4,5-trihydroxybenzaldehyde, and anhydrous ethanol were mixed, p-toluenesulfonic acid was added dropwise, and the mixture was heated to 100°C and refluxed for 8 hours. The mixture was then rotary evaporated at 60°C for 50 minutes and cooled to obtain a nitrogen-containing compound. Step 2: Under a nitrogen atmosphere, the nitrogen-containing compound, p-toluenesulfonic acid, hydroquinone, and toluene were mixed, stirred, and heated to 120°C. 3-Mercaptopropionic acid was added, and the mixture was reacted for 7 hours. The mixture was then cooled and rotary evaporated to obtain a flame-retardant compound. Step 3: Silica was dispersed in tetrahydrofuran. Under a nitrogen atmosphere, the flame-retardant compound was added, and the mixture was heated to 68°C and refluxed for 10 hours. The mixture was washed to obtain mercapto-modified silica. Step 4: Polyacrylonitrile and N,N-dimethylacetamide were mixed and stirred for 2 hours. Mercapto-modified silica was then added. The mixture was stirred again for 6 hours to obtain a spinning solution, which was then electrospun and vacuum dried at 60°C for 12 hours to obtain polyacrylonitrile composite fibers. In step 1, the mass ratio of 4-methyl-1,3,5-triazine-2-amine, 3,4,5-trihydroxybenzaldehyde to anhydrous ethanol and p-toluenesulfonic acid was 15:10:100:0.5. In step 2, the mass ratio of nitrogen-containing compound, p-toluenesulfonic acid, hydroquinone, toluene and 3-mercaptopropionic acid was 10:0.5:0.10:90:8. In step 3, the mass ratio of silica, tetrahydrofuran and flame retardant compound was 10:100:10. In step 4, the mass ratio of polyacrylonitrile, N,N-dimethylacetamide and mercaptolated silica was 10:100:5. In step 4, the electrospinning process conditions were: voltage 18kV and spinning speed 1.5mL / h.

[0108] (2) Preparation of the diaphragm:

[0109] S1: Polyacrylonitrile composite fibers are chopped to obtain chopped polyacrylonitrile composite fibers. These are mixed with cellulose acetate and water for a first pulping treatment. Nanocellulose is then added for a second pulping treatment, followed by papermaking to obtain a wet fiber sheet. This sheet is then dried at 50℃ for 15 hours, hot-calendered at 250℃ and 16MPa, and dried again at 70℃ for 24 hours to obtain a semi-finished diaphragm. S2: Polyacrylonitrile composite fibers are dispersed in anhydrous ethanol. Ethyl orthosilicate, methacryloyloxypropyltrimethoxysilane, and deionized water are added and stirred until homogeneous. The pH is adjusted to 4, and the mixture is stirred until homogeneous to obtain a wet gel. S3: The semi-finished diaphragm is immersed in an 8% sodium hydroxide aqueous solution at 60℃ for 2.0 hours, washed, and then placed in the wet gel for 10 hours. Finally, it is placed in a photoinitiator solution for ultraviolet irradiation to form... The aerogel was dried at 45℃ for 2 hours and then at 85℃ for 4 hours to obtain a diaphragm. In S1, the mass ratio of polyacrylonitrile composite chopped fibers, cellulose acetate, nanocellulose, and water was 5:1:5:50. The length of the polyacrylonitrile composite chopped fibers in S1 was 3 mm. The process conditions for the first pulping treatment in S1 were: pulping speed 12000 rpm and pulping time 15 min; the process conditions for the second pulping treatment were: pulping speed 15000 rpm and pulping time 20 min. In S2, the mass ratio of polyacrylonitrile composite fibers, anhydrous ethanol, tetraethyl orthosilicate, methacryloyloxypropyltrimethoxysilane, and deionized water was 10:400:150:5:120. In S3, the photoinitiator solution was prepared by mixing benzoin dimethyl ether and ethyl acetate in a ratio of 5 g:1 L. The process conditions for ultraviolet irradiation in S3 were: irradiation intensity 10 mW / cm². 2 Time: 30 minutes; Temperature: 70℃;

[0110] (3) Preparation of pre-lithiation energy storage device: Same as in Example 1.

[0111] Example 8: Compared with Example 2, a highly efficient pre-lithiation method for energy storage devices includes the following steps:

[0112] (1) Preparation of polyacrylonitrile composite fibers:

[0113] Step 1: Under a nitrogen atmosphere, 4-methyl-1,3,5-triazine-2-amine, 3,4,5-trihydroxybenzaldehyde, and anhydrous ethanol were mixed, and p-toluenesulfonic acid was added dropwise. The mixture was heated to 90°C and refluxed for 7 hours. The mixture was then rotary evaporated at 55°C for 40 minutes and cooled to obtain a nitrogen-containing compound. Step 2: Under a nitrogen atmosphere, the nitrogen-containing compound, p-toluenesulfonic acid, hydroquinone, and toluene were mixed, stirred, and heated to 115°C. 3-Mercaptopropionic acid was added, and the mixture was reacted for 6 hours. The mixture was then cooled and rotary evaporated to obtain a flame-retardant compound. Step 3: Silica was dispersed in tetrahydrofuran. Under a nitrogen atmosphere, the flame-retardant compound was added, and the mixture was heated to 66°C and refluxed for 8 hours. The mixture was washed to obtain mercapto-modified silica. Step 4: Polyacrylonitrile and N,N-dimethylacetamide were mixed and stirred for 1.5 hours. Mercapto-modified silica was added... Silicon was stirred again for 5 hours to obtain a spinning solution, which was then electrospun and vacuum dried at 55°C for 11 hours to obtain polyacrylonitrile composite fibers. In step 1, the mass ratio of 4-methyl-1,3,5-triazine-2-amine, 3,4,5-trihydroxybenzaldehyde to anhydrous ethanol and p-toluenesulfonic acid was 13:10:75:0.3. In step 2, the mass ratio of nitrogen-containing compound, p-toluenesulfonic acid, hydroquinone, toluene and 3-mercaptopropionic acid was 10:0.4:0.06:70:7. In step 3, the mass ratio of silica, tetrahydrofuran and flame retardant compound was 10:70:8. In step 4, the mass ratio of polyacrylonitrile, N,N-dimethylacetamide and mercaptolated silica was 10:80:4. In step 4, the electrospinning process conditions were: voltage 17kV and spinneret speed 1.4mL / h.

[0114] (2) Preparation of the diaphragm:

[0115] S1: Polyacrylonitrile composite fibers are chopped to obtain chopped polyacrylonitrile composite fibers. These are mixed with cellulose acetate and water for a first pulping treatment. Nanocellulose is then added for a second pulping treatment, followed by papermaking to obtain a wet fiber sheet. This sheet is then dried at 45℃ for 12 hours, hot-calendered at 240℃ and 14MPa, and dried again at 60℃ for 20 hours to obtain a semi-finished diaphragm. S2: Polyacrylonitrile composite fibers are dispersed in anhydrous ethanol. Ethyl orthosilicate, methacryloyloxypropyltrimethoxysilane, and deionized water are added and stirred until homogeneous. The pH is adjusted to 3, and the mixture is stirred until homogeneous to obtain a wet gel. S3: The semi-finished diaphragm is immersed in a 7% sodium hydroxide aqueous solution at 55℃ for 1.8 hours, washed, and then placed in the wet gel for 9 hours. Finally, it is placed in a photoinitiator solution for ultraviolet irradiation to form... Aerogel was dried at 43℃ for 1.5 h and then at 80℃ for 3 h to obtain a diaphragm. In S1, the mass ratio of polyacrylonitrile composite chopped fibers, cellulose acetate, nanocellulose, and water was 4:1:4:45. The length of the polyacrylonitrile composite chopped fibers in S1 was 2 mm. The process conditions for the first pulping treatment in S1 were: pulping speed 11000 rpm and pulping time 10 min; the process conditions for the second pulping treatment were: pulping speed 14000 rpm and pulping time 15 min. In S2, the mass ratio of polyacrylonitrile composite fibers, anhydrous ethanol, tetraethyl orthosilicate, methacryloyloxypropyltrimethoxysilane, and deionized water was 10:300:100:4:110. In S3, the photoinitiator solution was prepared by mixing benzoin dimethyl ether and ethyl acetate in a ratio of 4 g:1 L. The process conditions for ultraviolet irradiation in S3 were: irradiation intensity 8 mW / cm². 2 Time: 25 minutes; Temperature: 65℃;

[0116] (3) Preparation of pre-lithiation energy storage device: Same as in Example 2.

[0117] Example 9: Compared with Example 3, a highly efficient pre-lithiation method for energy storage devices includes the following steps:

[0118] (1) Preparation of polyacrylonitrile composite fibers:

[0119] Step 1: Under a nitrogen atmosphere, 4-methyl-1,3,5-triazine-2-amine, 3,4,5-trihydroxybenzaldehyde, and anhydrous ethanol were mixed, and p-toluenesulfonic acid was added dropwise. The mixture was heated to 80°C and refluxed for 6 hours. After rotary evaporation at 50°C for 30 minutes, the mixture was cooled to obtain a nitrogen-containing compound. Step 2: Under a nitrogen atmosphere, the nitrogen-containing compound, p-toluenesulfonic acid, hydroquinone, and toluene were mixed, stirred, and heated to 110°C. 3-Mercaptopropionic acid was added, and the mixture was reacted for 5 hours. After cooling and rotary evaporation, a flame-retardant compound was obtained. Step 3: Silica was dispersed in tetrahydrofuran. Under a nitrogen atmosphere, the flame-retardant compound was added, and the mixture was heated to 65°C and refluxed for 6 hours. After washing, mercapto-modified silica was obtained. Step 4: Polyacrylonitrile and N,N-dimethylacetamide were mixed and stirred for 1 hour. Mercapto-modified silica was then added. The mixture was stirred again for 4 hours to obtain a spinning solution, which was then electrospun and vacuum dried at 50°C for 10 hours to obtain polyacrylonitrile composite fibers. In step 1, the mass ratio of 4-methyl-1,3,5-triazine-2-amine, 3,4,5-trihydroxybenzaldehyde to anhydrous ethanol and p-toluenesulfonic acid was 10:10:50:0.1. In step 2, the mass ratio of nitrogen-containing compound, p-toluenesulfonic acid, hydroquinone, toluene and 3-mercaptopropionic acid was 10:0.3:0.02:50:6. In step 3, the mass ratio of silica, tetrahydrofuran and flame retardant compound was 10:50:5. In step 4, the mass ratio of polyacrylonitrile, N,N-dimethylacetamide and mercaptolated silica was 10:60:3. In step 4, the electrospinning process conditions were: voltage 16kV and spinning speed 1.3mL / h.

[0120] (2) Preparation of the diaphragm:

[0121] S1: Polyacrylonitrile composite fibers are chopped to obtain chopped polyacrylonitrile composite fibers. These fibers are mixed with cellulose acetate and water for a first pulping treatment. Then, nanocellulose is added for a second pulping treatment, followed by papermaking to obtain a wet fiber sheet. This sheet is then dried at 40℃ for 10 hours, hot-calendered at 200℃ and 12MPa, and dried again at 50℃ for 16 hours to obtain a semi-finished diaphragm. S2: Polyacrylonitrile composite fibers are dispersed in anhydrous ethanol. Tetraethyl orthosilicate, methacryloyloxypropyltrimethoxysilane, and deionized water are added and stirred until homogeneous. The pH is adjusted to 3, and the mixture is stirred until homogeneous to obtain a wet gel. S3: The semi-finished diaphragm is immersed in a 6% sodium hydroxide aqueous solution at 50℃ for 1.5 hours, washed, and then placed in the wet gel for 8 hours. Finally, it is placed in a photoinitiator solution for ultraviolet irradiation. An aerogel was formed and dried at 40℃ for 1 hour and then at 75℃ for 2 hours to obtain a diaphragm. In S1, the mass ratio of polyacrylonitrile composite chopped fibers, cellulose acetate, nanocellulose, and water was 3:1:3:40. The length of the polyacrylonitrile composite chopped fibers in S1 was 1 mm. The process conditions for the first pulping treatment in S1 were: pulping speed 10000 rpm and pulping time 5 min; the process conditions for the second pulping treatment were: pulping speed 13000 rpm and pulping time 10 min. In S2, the mass ratio of polyacrylonitrile composite fibers, anhydrous ethanol, tetraethyl orthosilicate, methacryloyloxypropyltrimethoxysilane, and deionized water was 10:200:50:3:100. In S3, the photoinitiator solution was prepared by mixing benzoin dimethyl ether and ethyl acetate in a ratio of 3 g:1 L. The process conditions for ultraviolet irradiation in S3 were: irradiation intensity 6 mW / cm². 2 Time: 20 minutes; Temperature: 60℃;

[0122] (3) Preparation of pre-lithiation energy storage device: Same as in Example 4.

[0123] Example 10: Compared with Example 4, a highly efficient pre-sodiuming method for energy storage devices includes the following steps:

[0124] Step 1: Under a nitrogen atmosphere, 4-methyl-1,3,5-triazine-2-amine, 3,4,5-trihydroxybenzaldehyde, and anhydrous ethanol were mixed, p-toluenesulfonic acid was added dropwise, and the mixture was heated to 100°C and refluxed for 8 hours. The mixture was then rotary evaporated at 60°C for 50 minutes and cooled to obtain a nitrogen-containing compound. Step 2: Under a nitrogen atmosphere, the nitrogen-containing compound, p-toluenesulfonic acid, hydroquinone, and toluene were mixed, stirred, and heated to 120°C. 3-Mercaptopropionic acid was added, and the mixture was reacted for 7 hours. The mixture was then cooled and rotary evaporated to obtain a flame-retardant compound. Step 3: Silica was dispersed in tetrahydrofuran. Under a nitrogen atmosphere, the flame-retardant compound was added, and the mixture was heated to 68°C and refluxed for 10 hours. The mixture was washed to obtain mercapto-modified silica. Step 4: Polyacrylonitrile and N,N-dimethylacetamide were mixed and stirred for 2 hours. Mercapto-modified silica was then added. The mixture was stirred again for 6 hours to obtain a spinning solution, which was then electrospun and vacuum dried at 60°C for 12 hours to obtain polyacrylonitrile composite fibers. In step 1, the mass ratio of 4-methyl-1,3,5-triazine-2-amine, 3,4,5-trihydroxybenzaldehyde to anhydrous ethanol and p-toluenesulfonic acid was 15:10:100:0.5. In step 2, the mass ratio of nitrogen-containing compound, p-toluenesulfonic acid, hydroquinone, toluene and 3-mercaptopropionic acid was 10:0.5:0.10:90:8. In step 3, the mass ratio of silica, tetrahydrofuran and flame retardant compound was 10:100:10. In step 4, the mass ratio of polyacrylonitrile, N,N-dimethylacetamide and mercaptolated silica was 10:100:5. In step 4, the electrospinning process conditions were: voltage 18kV and spinning speed 1.5mL / h.

[0125] (2) Preparation of the diaphragm:

[0126] S1: Polyacrylonitrile composite fibers are chopped to obtain chopped polyacrylonitrile composite fibers. These are mixed with cellulose acetate and water for a first pulping treatment. Nanocellulose is then added for a second pulping treatment, followed by papermaking to obtain a wet fiber sheet. This sheet is then dried at 50℃ for 15 hours, hot-calendered at 250℃ and 16MPa, and dried again at 70℃ for 24 hours to obtain a semi-finished diaphragm. S2: Polyacrylonitrile composite fibers are dispersed in anhydrous ethanol. Ethyl orthosilicate, methacryloyloxypropyltrimethoxysilane, and deionized water are added and stirred until homogeneous. The pH is adjusted to 4, and the mixture is stirred until homogeneous to obtain a wet gel. S3: The semi-finished diaphragm is immersed in an 8% sodium hydroxide aqueous solution at 60℃ for 2.0 hours, washed, and then placed in the wet gel for 10 hours. Finally, it is placed in a photoinitiator solution for ultraviolet irradiation to form... The aerogel was dried at 45℃ for 2 hours and then at 85℃ for 4 hours to obtain a diaphragm. In S1, the mass ratio of polyacrylonitrile composite chopped fibers, cellulose acetate, nanocellulose, and water was 5:1:5:50. The length of the polyacrylonitrile composite chopped fibers in S1 was 3 mm. The process conditions for the first pulping treatment in S1 were: pulping speed 12000 rpm and pulping time 15 min; the process conditions for the second pulping treatment were: pulping speed 15000 rpm and pulping time 20 min. In S2, the mass ratio of polyacrylonitrile composite fibers, anhydrous ethanol, tetraethyl orthosilicate, methacryloyloxypropyltrimethoxysilane, and deionized water was 10:400:150:5:120. In S3, the photoinitiator solution was prepared by mixing benzoin dimethyl ether and ethyl acetate in a ratio of 5 g:1 L. The process conditions for ultraviolet irradiation in S3 were: irradiation intensity 10 mW / cm². 2 Time: 30 minutes; Temperature: 70℃;

[0127] (3) Preparation of pre-sodium energy storage device: Same as in Example 4.

[0128] Example 11: Compared with Example 5, a highly efficient pre-sodiuming method for energy storage devices includes the following steps:

[0129] (1) Preparation of polyacrylonitrile composite fibers:

[0130] Step 1: Under a nitrogen atmosphere, 4-methyl-1,3,5-triazine-2-amine, 3,4,5-trihydroxybenzaldehyde, and anhydrous ethanol were mixed, and p-toluenesulfonic acid was added dropwise. The mixture was heated to 90°C and refluxed for 7 hours. The mixture was then rotary evaporated at 55°C for 40 minutes and cooled to obtain a nitrogen-containing compound. Step 2: Under a nitrogen atmosphere, the nitrogen-containing compound, p-toluenesulfonic acid, hydroquinone, and toluene were mixed, stirred, and heated to 115°C. 3-Mercaptopropionic acid was added, and the mixture was reacted for 6 hours. The mixture was then cooled and rotary evaporated to obtain a flame-retardant compound. Step 3: Silica was dispersed in tetrahydrofuran. Under a nitrogen atmosphere, the flame-retardant compound was added, and the mixture was heated to 66°C and refluxed for 8 hours. The mixture was washed to obtain mercapto-modified silica. Step 4: Polyacrylonitrile and N,N-dimethylacetamide were mixed and stirred for 1.5 hours. Mercapto-modified silica was added... Silicon was stirred again for 5 hours to obtain a spinning solution, which was then electrospun and vacuum dried at 55°C for 11 hours to obtain polyacrylonitrile composite fibers. In step 1, the mass ratio of 4-methyl-1,3,5-triazine-2-amine, 3,4,5-trihydroxybenzaldehyde to anhydrous ethanol and p-toluenesulfonic acid was 13:10:75:0.3. In step 2, the mass ratio of nitrogen-containing compound, p-toluenesulfonic acid, hydroquinone, toluene and 3-mercaptopropionic acid was 10:0.4:0.06:70:7. In step 3, the mass ratio of silica, tetrahydrofuran and flame retardant compound was 10:70:8. In step 4, the mass ratio of polyacrylonitrile, N,N-dimethylacetamide and mercaptolated silica was 10:80:4. In step 4, the electrospinning process conditions were: voltage 17kV and spinneret speed 1.4mL / h.

[0131] (2) Preparation of the diaphragm:

[0132] S1: Polyacrylonitrile composite fibers are chopped to obtain chopped polyacrylonitrile composite fibers. These are mixed with cellulose acetate and water for a first pulping treatment. Nanocellulose is then added for a second pulping treatment, followed by papermaking to obtain a wet fiber sheet. This sheet is then dried at 45℃ for 12 hours, hot-calendered at 240℃ and 14MPa, and dried again at 60℃ for 20 hours to obtain a semi-finished diaphragm. S2: Polyacrylonitrile composite fibers are dispersed in anhydrous ethanol. Ethyl orthosilicate, methacryloyloxypropyltrimethoxysilane, and deionized water are added and stirred until homogeneous. The pH is adjusted to 3, and the mixture is stirred until homogeneous to obtain a wet gel. S3: The semi-finished diaphragm is immersed in a 7% sodium hydroxide aqueous solution at 55℃ for 1.8 hours, washed, and then placed in the wet gel for 9 hours. Finally, it is placed in a photoinitiator solution for ultraviolet irradiation to form... Aerogel was dried at 43℃ for 1.5 h and then at 80℃ for 3 h to obtain a diaphragm. In S1, the mass ratio of polyacrylonitrile composite chopped fibers, cellulose acetate, nanocellulose, and water was 4:1:4:45. The length of the polyacrylonitrile composite chopped fibers in S1 was 2 mm. The process conditions for the first pulping treatment in S1 were: pulping speed 11000 rpm and pulping time 10 min; the process conditions for the second pulping treatment were: pulping speed 14000 rpm and pulping time 15 min. In S2, the mass ratio of polyacrylonitrile composite fibers, anhydrous ethanol, tetraethyl orthosilicate, methacryloyloxypropyltrimethoxysilane, and deionized water was 10:300:100:4:110. In S3, the photoinitiator solution was prepared by mixing benzoin dimethyl ether and ethyl acetate in a ratio of 4 g:1 L. The process conditions for ultraviolet irradiation in S3 were: irradiation intensity 8 mW / cm². 2 Time: 25 minutes; Temperature: 65℃;

[0133] (3) Preparation of pre-sodium energy storage device: Same as in Example 5.

[0134] Example 12: Compared with Example 6, a highly efficient pre-sodiuming method for energy storage devices includes the following steps:

[0135] (1) Preparation of polyacrylonitrile composite fibers:

[0136] Step 1: Under a nitrogen atmosphere, 4-methyl-1,3,5-triazine-2-amine, 3,4,5-trihydroxybenzaldehyde, and anhydrous ethanol were mixed, and p-toluenesulfonic acid was added dropwise. The mixture was heated to 80°C and refluxed for 6 hours. After rotary evaporation at 50°C for 30 minutes, the mixture was cooled to obtain a nitrogen-containing compound. Step 2: Under a nitrogen atmosphere, the nitrogen-containing compound, p-toluenesulfonic acid, hydroquinone, and toluene were mixed, stirred, and heated to 110°C. 3-Mercaptopropionic acid was added, and the mixture was reacted for 5 hours. After cooling and rotary evaporation, a flame-retardant compound was obtained. Step 3: Silica was dispersed in tetrahydrofuran. Under a nitrogen atmosphere, the flame-retardant compound was added, and the mixture was heated to 65°C and refluxed for 6 hours. After washing, mercapto-modified silica was obtained. Step 4: Polyacrylonitrile and N,N-dimethylacetamide were mixed and stirred for 1 hour. Mercapto-modified silica was then added. The mixture was stirred again for 4 hours to obtain a spinning solution, which was then electrospun and vacuum dried at 50°C for 10 hours to obtain polyacrylonitrile composite fibers. In step 1, the mass ratio of 4-methyl-1,3,5-triazine-2-amine, 3,4,5-trihydroxybenzaldehyde to anhydrous ethanol and p-toluenesulfonic acid was 10:10:50:0.1. In step 2, the mass ratio of nitrogen-containing compound, p-toluenesulfonic acid, hydroquinone, toluene and 3-mercaptopropionic acid was 10:0.3:0.02:50:6. In step 3, the mass ratio of silica, tetrahydrofuran and flame retardant compound was 10:50:5. In step 4, the mass ratio of polyacrylonitrile, N,N-dimethylacetamide and mercaptolated silica was 10:60:3. In step 4, the electrospinning process conditions were: voltage 16kV and spinning speed 1.3mL / h.

[0137] (2) Preparation of the diaphragm:

[0138] S1: Polyacrylonitrile composite fibers are chopped to obtain chopped polyacrylonitrile composite fibers. These fibers are mixed with cellulose acetate and water for a first pulping treatment. Then, nanocellulose is added for a second pulping treatment, followed by papermaking to obtain a wet fiber sheet. This sheet is then dried at 40℃ for 10 hours, hot-calendered at 200℃ and 12MPa, and dried again at 50℃ for 16 hours to obtain a semi-finished diaphragm. S2: Polyacrylonitrile composite fibers are dispersed in anhydrous ethanol. Tetraethyl orthosilicate, methacryloyloxypropyltrimethoxysilane, and deionized water are added and stirred until homogeneous. The pH is adjusted to 3, and the mixture is stirred until homogeneous to obtain a wet gel. S3: The semi-finished diaphragm is immersed in a 6% sodium hydroxide aqueous solution at 50℃ for 1.5 hours, washed, and then placed in the wet gel for 8 hours. Finally, it is placed in a photoinitiator solution for ultraviolet irradiation. An aerogel was formed and dried at 40℃ for 1 hour and then at 75℃ for 2 hours to obtain a diaphragm. In S1, the mass ratio of polyacrylonitrile composite chopped fibers, cellulose acetate, nanocellulose, and water was 3:1:3:40. The length of the polyacrylonitrile composite chopped fibers in S1 was 1 mm. The process conditions for the first pulping treatment in S1 were: pulping speed 10000 rpm and pulping time 5 min; the process conditions for the second pulping treatment were: pulping speed 13000 rpm and pulping time 10 min. In S2, the mass ratio of polyacrylonitrile composite fibers, anhydrous ethanol, tetraethyl orthosilicate, methacryloyloxypropyltrimethoxysilane, and deionized water was 10:200:50:3:100. In S3, the photoinitiator solution was prepared by mixing benzoin dimethyl ether and ethyl acetate in a ratio of 3 g:1 L. The process conditions for ultraviolet irradiation in S3 were: irradiation intensity 6 mW / cm². 2 Time: 20 minutes; Temperature: 60℃;

[0139] (3) Preparation of pre-sodium-based energy storage devices: Same as in Example 6.

[0140] Comparative Example 1: Compared with Example 1, the energy storage device was not pre-lithiated, and all other conditions remained the same.

[0141] Comparative Example 2: Compared with Example 4, the energy storage device was not pre-sodium-treated, and all other conditions remained the same.

[0142] Comparative Example 3: Compared with Example 7, no aerogel was prepared on the surface of the polyacrylonitrile composite fiber, while the other conditions remained unchanged.

[0143] Comparative Example 4: Compared with Example 10, no aerogel was prepared on the surface of the polyacrylonitrile composite fiber, while the other conditions remained unchanged.

[0144] Experiment: The pre-lithiated batteries obtained in the examples and comparative examples were subjected to electrochemical tests. Specifically, the pre-lithiated batteries were discharged at 25°C with a discharge cutoff voltage of 1.5V. The first efficiency, discharge voltage plateau, and energy density were recorded.

[0145]

[0146] Based on the data in the table above, the following conclusions can be drawn:

[0147] Compared with Examples 1 and 4, the electrochemical performance of the energy storage devices obtained in Examples 2, 3, 5, and 6 all decreased to varying degrees. It can be seen that the pre-lithiation / sodiumification method used in this application can promote the improvement of the electrochemical performance of the energy storage devices. Compared with Examples 1 and 4, the membranes with flame retardancy and surface-deposited aerogel prepared in Examples 7 and 10 have improved electrochemical performance of the energy storage devices. This is because the silica aerogel has a large specific surface area, which can increase the contact area with the electrolyte, improve the wettability of the electrolyte, and improve the ion transport efficiency, thus comprehensively improving the electrochemical performance of the energy storage devices.

[0148] Compared with Examples 1 and 4, Comparative Examples 1 and 2 did not perform pre-lithiation / sodium-lithiation on the energy storage devices, resulting in a significant decrease in the electrochemical performance of the energy storage devices. Compared with Examples 7 and 10, Comparative Examples 3 and 4 did not prepare aerogels on the surface of polyacrylonitrile composite fibers, and their electrochemical performance also decreased. This indicates that in this application, both the pre-lithiation / sodium-lithiation method and the membrane preparation process can improve the performance of the prepared energy storage devices.

[0149] The performance of the diaphragms from Examples 1, 7-9, and Comparative Example 3 was tested.

[0150] Flame retardancy test: The diaphragm was cut into 1*5cm samples, and the oxygen index of the samples was tested in accordance with GB / T2406.2-2009 to characterize its flame retardancy.

[0151] Ionic conductivity test: The separator and lithium foil are assembled into a symmetrical battery in the order of lithium foil, separator, lithium foil, and after standing for a period of time, its ionic conductivity is measured.

[0152]

[0153] Based on the data in the table above, the following conclusions can be drawn:

[0154] In Example 1, the diaphragm was a commercially available polyacrylonitrile diaphragm, which had the worst flame retardancy and ionic conductivity. In Example 7, the flame retardancy and ionic conductivity were the best. Compared with Example 7, the flame retardancy of Comparative Example 3 did not change much, but the ionic conductivity decreased significantly. In Example 1, the diaphragm was a commercially available polyacrylonitrile diaphragm that did not have flame retardancy and did not have aerogel on its surface.

[0155] As can be seen from the above, the diaphragm prepared in this application has better flame retardancy and ionic conductivity than commercially available polyacrylonitrile diaphragms, which can comprehensively improve the safety and electrochemical performance of the energy storage device.

[0156] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

Claims

1. A highly efficient pre-lithiation / sodiumification method for energy storage devices, characterized in that: Includes the following steps: Step A1: Stack the positive electrode, separator, and negative electrode in sequence to form a positive electrode-separator-negative electrode structure, and then wind it to obtain the battery cell; Step A2: Fix metallic lithium or metallic sodium onto the tab to form a third electrode. Fix the third electrode on the side of the negative electrode away from the positive electrode. Inject electrolyte and seal to obtain a soft-pack battery. Step A3: Short-circuit the third electrode and the negative electrode, monitor the potential between the third electrode and the negative electrode, and after the battery is fully charged, use the third electrode as the negative electrode and keep the positive electrode unchanged to pre-lithiate or pre-sodiumize the soft pack battery. Then, perform secondary packaging, remove excess air pockets, and recover the metallic lithium or metallic sodium in the third electrode to obtain a pre-lithiate or pre-sodiumized energy storage device. The preparation process of the diaphragm is as follows: S1: Take polyacrylonitrile composite fiber, cut it into short pieces to obtain polyacrylonitrile composite short-cut fiber, mix it with cellulose acetate and water, perform the first pulping treatment, then add nanocellulose, perform the second pulping treatment, and then perform papermaking to obtain wet fiber sheet, and perform the first drying, hot calendering treatment, and second drying in sequence to obtain semi-finished diaphragm. S2: Disperse polyacrylonitrile composite fibers in anhydrous ethanol, add tetraethyl orthosilicate, methacryloyloxypropyltrimethoxysilane and deionized water and stir until homogeneous, adjust the pH value to 3-4, stir until homogeneous, and obtain wet gel. S3: Immerse the semi-finished diaphragm in an aqueous sodium hydroxide solution, wash it, then place it in a wet gel for 8-10 hours, take it out, and finally place it in a photoinitiator solution for ultraviolet irradiation to form an aerogel. Dry it to obtain the diaphragm. The polyacrylonitrile composite fiber is obtained by the following process: Step 1: Under a nitrogen atmosphere, 4-methyl-1,3,5-triazine-2-amine, 3,4,5-trihydroxybenzaldehyde and anhydrous ethanol were mixed, p-toluenesulfonic acid was added dropwise, the mixture was heated under reflux, rotary evaporated, and cooled to obtain a nitrogen-containing compound. Step 2: Under a nitrogen atmosphere, a nitrogen-containing compound, p-toluenesulfonic acid, hydroquinone, and toluene are mixed, stirred, and heated to 110-120°C. 3-mercaptopropionic acid is added, and the mixture is reacted for 5-7 hours. After cooling and rotary evaporation, the flame-retardant compound is obtained. Step 3: Disperse silica in tetrahydrofuran, add flame retardant compound under nitrogen atmosphere, heat and reflux reaction, wash to obtain mercapto-modified silica; Step 4: Mix polyacrylonitrile with N,N-dimethylacetamide and stir for 1-2 hours. Add mercapto-modified silica and stir again for 4-6 hours to obtain a spinning solution. Then electrospin and vacuum dry to obtain polyacrylonitrile composite fibers.

2. The efficient pre-lithiation / sodiumification method for an energy storage device according to claim 1, characterized in that: In step A2, the lithium metal or sodium metal is in the shape of a strip; the tab is an aluminum tab.

3. The efficient pre-lithiation / sodiumification method for an energy storage device according to claim 1, characterized in that: The positive electrode sheet is prepared as follows: Sodium iron pyrophosphate, Super-P, single-walled carbon nanotubes, PVDF and N-methylpyrrolidone are mixed and stirred evenly to obtain a positive electrode slurry. The positive electrode slurry is evenly coated on the upper and lower surfaces of carbon-coated aluminum foil, vacuum dried, then rolled to 0.10~0.12mm, die-cut to form an electrode sheet, and lead strips are welded to the blank parts of the electrode sheet to obtain the positive electrode sheet.

4. The efficient pre-lithiation / sodiumification method for an energy storage device according to claim 1, characterized in that: The method for preparing the negative electrode sheet is as follows: Hard carbon, Super-P, CMC, SBR and N-methylpyrrolidone are mixed and stirred evenly to obtain a negative electrode slurry. The negative electrode slurry is evenly coated on the upper and lower surfaces of copper foil, vacuum dried, then rolled to 0.05~0.07mm, die-cut to form an electrode sheet, and lead strips are welded to the blank part of the electrode sheet to obtain the negative electrode sheet.

5. The efficient pre-lithiation / sodiumification method for an energy storage device according to claim 3, characterized in that: The surface density of the positive electrode slurry coating is 140~150 g / m2; The coating thickness of the positive electrode slurry is 65~92μm.

6. The efficient pre-lithiation / sodiumification method for an energy storage device according to claim 4, characterized in that: The surface density of the negative electrode slurry coating is 70~80 g / m2; The coating thickness of the negative electrode slurry is 150~159μm.

7. The efficient pre-lithiation / sodiumification method for an energy storage device according to claim 3, characterized in that: The mass ratio of sodium iron pyrophosphate, Super-P, single-walled carbon nanotubes, PVDF, and N-methylpyrrolidone was (92~94):(2.4~3.4):(0.4~0.6):(1~2):(28~32). The solid content of the positive electrode slurry is 75-78%.

8. The application of the efficient pre-lithiation / sodiumification method for an energy storage device according to any one of claims 1 to 7, characterized in that: It is used in the fabrication of energy storage devices.

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