A method for preparing a lithium ion battery and use

Abstract

The application provides a method for preparing a lithium ion battery and application. The method comprises the following steps: (1) soaking a negative electrode sheet in a naphthalene lithium solution, and performing elution after soaking to obtain the negative electrode sheet; (2) mixing positive electrode active material, a conductive agent and a binder to obtain a first mixture, then mixing the first mixture, an additive and an organic solvent to obtain a positive electrode slurry, and coating the positive electrode slurry on at least one side of a positive electrode current collector to obtain a positive electrode sheet after drying; (3) assembling the negative electrode sheet obtained in step (1), the positive electrode sheet obtained in step (2) and a separator, and obtaining the lithium ion battery after injection. On one hand, the application adopts the naphthalene lithium solution to perform pre-lithiation treatment on the negative electrode sheet, and can safely and efficiently supplement lithium ions into the battery system; on the other hand, the application adds an appropriate amount of additive material in the positive electrode sheet, and further improves the electrochemical performance and safety performance of the battery.

Description

Technical Field

[0001] This invention belongs to the field of battery materials technology, specifically relating to a method for preparing lithium-ion batteries and their applications. Background Technology

[0002] Lithium-ion batteries are widely used in portable electronics and electric vehicles due to their high energy density and long cycle life. During the first charge, an SEI film forms on the negative electrode surface, consuming active lithium from the positive electrode material and causing irreversible capacity loss. Currently, the irreversible capacity loss of commercially available graphite anode materials can reach 10%, while for silicon-based and tin-based anode materials with high specific capacity, the irreversible capacity loss can even exceed 30%, significantly reducing the energy density of lithium-ion batteries.

[0003] To address the irreversible capacity issue caused by the formation of the SEI film during the first charge and discharge cycle of lithium-ion batteries, researchers typically employ negative electrode lithium replenishment methods. These methods primarily include lithium foil replenishment and lithium powder replenishment. However, due to the inherent reactivity of lithium metal, it requires stringent storage and manufacturing conditions, posing significant safety and complex processing risks, and resulting in high production costs. Furthermore, while positive electrode lithium replenishment technology offers high safety, the replenishment materials require charging to 4.2V–4.5V to function effectively, and high voltage conditions can easily lead to various problems, such as electrolyte decomposition and gas generation, separator burning due to high temperatures, and battery overcharge failure.

[0004] The "overcharge" test is an important safety indicator for lithium-ion batteries. When a lithium-ion battery is overcharged, the cathode delithiation potential rises rapidly with the degree of overcharge. After exceeding a certain limit, it causes irreversible oxidation and decomposition of the electrolyte inside the battery, producing flammable gases and releasing a large amount of heat. This leads to an increase in the temperature and pressure inside the battery and triggers a series of exothermic reactions, resulting in thermal runaway inside the battery.

[0005] Therefore, there is an urgent need in this field to develop a lithium-ion battery that not only has good electrochemical performance but also good safety performance. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a method for preparing lithium-ion batteries and their applications. On one hand, the present invention employs a lithium naphthalene solution to pre-lithiate the negative electrode, enabling safe and efficient replenishment of lithium ions into the battery system. On the other hand, the present invention adds appropriate additives to the positive electrode, thereby improving the conductivity and overcharge capability of the lithium iron phosphate battery system, thus enhancing the battery's electrochemical and safety performance.

[0007] To achieve this objective, the present invention employs the following technical solution:

[0008] In a first aspect, the present invention provides a method for preparing a lithium-ion battery, the method comprising the following steps:

[0009] (1) The negative electrode sheet is immersed in a lithium naphthalene solution and then rinsed to obtain the negative electrode sheet;

[0010] (2) The positive electrode active material, conductive agent and binder are mixed to obtain a first mixture, and then the first mixture, additives and organic solvent are mixed to obtain a positive electrode slurry, and the positive electrode slurry is coated on at least one side of the positive electrode current collector, and after drying, a positive electrode sheet is obtained.

[0011] (3) Assemble the negative electrode obtained in step (1), the positive electrode obtained in step (2), and the separator, and then inject liquid to obtain the lithium-ion battery.

[0012] This invention employs a lithium naphthalene solution to pre-lithiate the negative electrode, which can safely and efficiently replenish lithium ions into the battery system, compensating for irreversible capacity loss caused by the formation of the SEI film, and significantly improving the battery's initial coulombic efficiency and cycle performance. Furthermore, this invention adds appropriate amounts of additive materials to the positive electrode, which not only possesses good conductivity but also excellent overcharge protection, effectively improving the lithium ion transport rate, reducing gases generated by electrolyte decomposition at high temperatures, and effectively enhancing the aforementioned performance of the lithium iron phosphate battery system. This comprehensively improves the battery's charge-discharge capability, cycle performance, and safety performance at high rates.

[0013] Furthermore, the naphthalene lithium solution in the negative electrode and the additive materials in the positive electrode have a synergistic effect, which can effectively reduce the internal resistance of the battery, reduce the waste gas caused by side reactions, and improve the battery's initial coulombic efficiency and cycle performance.

[0014] Preferably, the preparation method of the naphthalene-lithium solution in step (1) includes the following steps: mixing naphthalene and solvent in a glove box with water content <1ppm and oxygen content <1ppm to obtain a naphthalene solution; then adding lithium sheets to the obtained naphthalene solution and reacting to obtain the naphthalene-lithium solution.

[0015] Preferably, the solvent includes any one or a combination of at least two of tetrahydrofuran, ethanol, or diethyl ether.

[0016] Preferably, the concentration of the naphthalene solution is 0.1 mol / L to 0.5 mol / L, for example, it can be 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, etc.

[0017] Preferably, the area of ​​the lithium sheet is 4 cm². 2 -100cm 2 For example, it can be 4cm 2 8cm 2 16cm 2 24cm 2 40cm 2 60cm 2 80cm 2 100cm 2 The thickness ranges from 10μm to 400μm, for example, it can be 10μm, 50μm, 80μm, 100μm, 200μm, 300μm, 400μm, etc.

[0018] Preferably, the soaking time in step (1) is 1-2 hours.

[0019] Preferably, the rinsing in step (1) is performed using dimethyl carbonate solvent.

[0020] Preferably, the additive in step (2) includes any one or a combination of at least two of polynaphthalene, nitrated polynaphthalene, or sulfide polynaphthalene.

[0021] Preferably, the additive in step (2) includes any one or a combination of at least two of 1,4-dinitronaphthalene, 1,5-dinitronaphthalene, 1,4-diaminonaphthalene, or 1,5-diaminonaphthalene.

[0022] In this invention, the additive can be added to the positive or negative electrode slurry of a lithium battery; by selecting the above-mentioned specific types of additives, it has the advantages of good conductivity and reliable safety.

[0023] Preferably, based on the total mass of the first mixture as 100%, the mass percentage of the additive in step (2) is 2 to 5%, for example, it can be 2%, 2.2%, 2.5%, 2.8%, 3%, 3.2%, 3.5%, 3.8%, 4%, 4.2%, 4.5%, 4.8%, 5%, etc.

[0024] In this invention, by controlling the mass percentage content of the additive, the first mixture and the additive can play a good synergistic role. If the content is too low, it will cause a decrease in high-rate charge and discharge performance, an increase in gas production, and a weakening of electrical performance and safety. Conversely, it will lead to insufficient lithium replenishment and a decrease in battery cycle performance.

[0025] Preferably, the positive electrode active material in step (2) includes lithium iron phosphate.

[0026] Preferably, the conductive agent in step (2) includes any one or a combination of at least two of carbon nanotubes, conductive carbon black, or graphene.

[0027] Preferably, the adhesive in step (2) comprises polyvinylidene fluoride.

[0028] Preferably, the first mixture in step (2) further includes a dispersant.

[0029] Preferably, the dispersant comprises any one or a combination of at least two of polyvinylpyrrolidone, polyacrylamide, or polyacrylamide.

[0030] Preferably, the organic solvent in step (2) includes N-methylpyrrolidone.

[0031] Preferably, the viscosity of the positive electrode slurry in step (2) is 7000–15000 mPa·s. -1 For example, it can be 7000 mPa·s -1 9000mpa·s -1 11000mpa·s -1 13000mpa·s -1 15000mpa·s -1 wait.

[0032] Preferably, the drying process in step (2) further includes cold pressing and die-cutting.

[0033] Preferably, step (3) further includes standing, formation and volume separation treatment after liquid injection.

[0034] In a second aspect, the present invention provides a lithium-ion battery, which is prepared by the method for preparing a lithium-ion battery according to the first aspect.

[0035] Thirdly, the present invention provides an electronic device comprising the lithium-ion battery according to the second aspect.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] This invention provides a method for preparing lithium-ion batteries. On one hand, it uses a lithium naphthalene solution to pre-lithiate the negative electrode, which can safely and efficiently replenish lithium ions into the battery system, compensate for the irreversible capacity loss caused by the formation of the SEI film, and significantly improve the battery's initial coulombic efficiency and cycle performance. On the other hand, this invention adds an appropriate amount of additive material to the positive electrode, which not only has good conductivity but also good overcharge protection, effectively improving the lithium ion transport rate, reducing the gas generated by electrolyte decomposition at high temperatures, and effectively improving the aforementioned performance of the lithium iron phosphate battery system. Thus, it comprehensively improves the battery's charge-discharge capacity, cycle performance, and safety performance at high rates. Detailed Implementation

[0038] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0039] Example 1

[0040] This embodiment provides a lithium-ion battery and its preparation method, which includes the following steps:

[0041] (1) In a glove box with a water content <1ppm and an oxygen content <1ppm, naphthalene and tetrahydrofuran were mixed to obtain a naphthalene solution with a concentration of 0.5mol / L; then, a container with an area of ​​25cm² was placed in the obtained naphthalene solution. 2 A lithium sheet with a thickness of 400 μm was reacted for 1 hour to obtain a naphthalene-lithium solution. Graphite, conductive carbon black, sodium carboxymethyl cellulose, and styrene-butadiene rubber binder were mixed and stirred evenly in a mass ratio of 94:2:2:2. Deionized water was added to prepare a negative electrode slurry, which was then evenly coated on the surface of copper foil, dried, and cold-pressed to obtain a negative electrode sheet. The negative electrode sheet was immersed in the above naphthalene-lithium solution for 2 hours and then rinsed with dimethyl carbonate solvent to obtain the negative electrode sheet.

[0042] (2) Lithium iron phosphate positive electrode active material, conductive carbon black, polyvinylidene fluoride binder, and polyvinylpyrrolidone dispersant are mixed in a mass ratio of 93:3:3.5:0.5 to obtain a first mixture. Then, the first mixture, polynaphthalene (with a mass percentage of 3.5% based on the total mass of the first mixture being 100%), and N-methylpyrrolidone solvent are mixed to obtain a positive electrode slurry with a viscosity of 11000 mPa·s. -1 The positive electrode slurry is then coated onto the surface of aluminum foil and dried to obtain the positive electrode sheet.

[0043] (3) Assemble the negative electrode obtained in step (1), the positive electrode obtained in step (2), and the polypropylene separator. Use 1 mol / L LiPF6 as the lithium salt and ethylene carbonate / diethyl carbonate / methyl ethyl carbonate (volume ratio of 1:1:1) as the electrolyte. Under negative pressure, inject the electrolyte into the cell. After sufficient settling, encapsulate, form, and capacity test to obtain a lithium-ion battery.

[0044] Example 2

[0045] This embodiment provides a lithium-ion battery and its preparation method, which includes the following steps:

[0046] (1) In a glove box with a water content <1ppm and an oxygen content <1ppm, naphthalene and tetrahydrofuran were mixed to obtain a naphthalene solution with a concentration of 0.3mol / L; then, a 50cm² area was placed in the obtained naphthalene solution. 2 A lithium sheet with a thickness of 200 μm was reacted for 1.5 h to obtain a naphthalene-lithium solution. Graphite, conductive carbon black, sodium carboxymethyl cellulose, and styrene-butadiene rubber binder were mixed and stirred evenly in a mass ratio of 94:2:2:2. Deionized water was added to prepare a negative electrode slurry, which was then uniformly coated on the surface of copper foil, dried, and cold-pressed to obtain a negative electrode sheet. The negative electrode sheet was immersed in the above naphthalene-lithium solution for 2 h and then rinsed with dimethyl carbonate solvent to obtain a negative electrode sheet.

[0047] (2) Lithium iron phosphate positive electrode active material, conductive carbon black, polyvinylidene fluoride binder, and polyvinylpyrrolidone dispersant are mixed in a mass ratio of 93:3:3.5:0.5 to obtain a first mixture. Then, the first mixture, polynaphthalene (based on the total mass of the first mixture, the mass percentage of polynaphthalene is 3%), and N-methylpyrrolidone solvent are mixed to obtain a positive electrode slurry with a viscosity of 9000 mPa·s. -1 The positive electrode slurry is then coated onto the surface of aluminum foil and dried to obtain the positive electrode sheet.

[0048] (3) Assemble the negative electrode obtained in step (1), the positive electrode obtained in step (2), and the polypropylene separator. Use 1 mol / L LiPF6 as the lithium salt and ethylene carbonate / diethyl carbonate / methyl ethyl carbonate (volume ratio of 1:1:1) as the electrolyte. Under negative pressure, inject the electrolyte into the cell. After sufficient settling, encapsulate, form, and capacity test to obtain a lithium-ion battery.

[0049] Example 3

[0050] This embodiment provides a lithium-ion battery and its preparation method, which includes the following steps:

[0051] (1) In a glove box with a water content <1ppm and an oxygen content <1ppm, naphthalene and tetrahydrofuran were mixed to obtain a naphthalene solution with a concentration of 0.4 mol / L; then, a 60 cm² area was placed in the obtained naphthalene solution. 2 A lithium sheet with a thickness of 300 μm was reacted for 1 hour to obtain a naphthalene-lithium solution. Graphite, conductive carbon black, sodium carboxymethyl cellulose, and styrene-butadiene rubber binder were mixed and stirred evenly in a mass ratio of 94:2:2:2. Deionized water was added to prepare a negative electrode slurry, which was then evenly coated onto the surface of a copper foil, dried, and cold-pressed to obtain a negative electrode sheet. The negative electrode sheet was then immersed in the above naphthalene-lithium solution for 2 hours and rinsed with dimethyl carbonate solvent to obtain the negative electrode sheet.

[0052] (2) Lithium iron phosphate positive electrode active material, conductive carbon black, polyvinylidene fluoride binder, and polyvinylpyrrolidone dispersant are mixed in a mass ratio of 93:3:3.5:0.5 to obtain a first mixture. Then, the first mixture, polynaphthalene (with a mass percentage of 4.5% based on the total mass of the first mixture being 100%), and N-methylpyrrolidone solvent are mixed to obtain a positive electrode slurry with a viscosity of 13000 mPa·s. -1 The positive electrode slurry is then coated onto the surface of aluminum foil and dried to obtain the positive electrode sheet.

[0053] (3) Assemble the negative electrode obtained in step (1), the positive electrode obtained in step (2), and the polypropylene separator. Use 1 mol / L LiPF6 as the lithium salt and ethylene carbonate / diethyl carbonate / methyl ethyl carbonate (volume ratio of 1:1:1) as the electrolyte. Under negative pressure, inject the electrolyte into the cell. After sufficient settling, encapsulate, form, and capacity test to obtain a lithium-ion battery.

[0054] Example 4

[0055] This embodiment provides a lithium-ion battery and its preparation method, which includes the following steps:

[0056] (1) In a glove box with a water content <1ppm and an oxygen content <1ppm, naphthalene and tetrahydrofuran were mixed to obtain a naphthalene solution with a concentration of 0.1mol / L; then, a 10cm² area was placed in the obtained naphthalene solution. 2 A lithium sheet with a thickness of 10 μm was reacted for 2 hours to obtain a naphthalene-lithium solution. Graphite, conductive carbon black, sodium carboxymethyl cellulose, and styrene-butadiene rubber binder were mixed in a mass ratio of 94:2:2:2 and stirred evenly. Deionized water was added to prepare a negative electrode slurry, which was then uniformly coated on the surface of copper foil, dried, and cold-pressed to obtain a negative electrode sheet. The negative electrode sheet was immersed in the above naphthalene-lithium solution for 2 hours and then rinsed with dimethyl carbonate solvent to obtain the negative electrode sheet.

[0057] (2) Lithium iron phosphate positive electrode active material, conductive carbon black, polyvinylidene fluoride binder, and polyvinylpyrrolidone dispersant are mixed in a mass ratio of 93:3:3.5:0.5 to obtain a first mixture. Then, the first mixture, polynaphthalene (based on the total mass of the first mixture, the mass percentage of polynaphthalene is 2%), and N-methylpyrrolidone solvent are mixed to obtain a positive electrode slurry with a viscosity of 7000 mPa·s. -1 The positive electrode slurry is then coated onto the surface of aluminum foil and dried to obtain the positive electrode sheet.

[0058] (3) Assemble the negative electrode obtained in step (1), the positive electrode obtained in step (2), and the polypropylene separator. Use 1 mol / L LiPF6 as the lithium salt and ethylene carbonate / diethyl carbonate / methyl ethyl carbonate (volume ratio of 1:1:1) as the electrolyte. Under negative pressure, inject the electrolyte into the cell. After sufficient settling, encapsulate, form, and capacity test to obtain a lithium-ion battery.

[0059] Example 5

[0060] This embodiment provides a lithium-ion battery and its preparation method, which includes the following steps:

[0061] (1) In a glove box with a water content <1ppm and an oxygen content <1ppm, naphthalene and tetrahydrofuran were mixed to obtain a naphthalene solution with a concentration of 0.5mol / L; then, a container with an area of ​​100cm² was placed in the obtained naphthalene solution. 2 A lithium sheet with a thickness of 380 μm was reacted for 1 hour to obtain a naphthalene-lithium solution. Graphite, conductive carbon black, sodium carboxymethyl cellulose, and styrene-butadiene rubber binder were mixed and stirred evenly in a mass ratio of 94:2:2:2. Deionized water was added to prepare a negative electrode slurry, which was then uniformly coated on the surface of copper foil, dried, and cold-pressed to obtain a negative electrode sheet. The negative electrode sheet was immersed in the above naphthalene-lithium solution for 2 hours and then rinsed with dimethyl carbonate solvent to obtain the negative electrode sheet.

[0062] (2) Lithium iron phosphate positive electrode active material, conductive carbon black, polyvinylidene fluoride binder, and polyvinylpyrrolidone dispersant are mixed in a mass ratio of 93:3:3.5:0.5 to obtain a first mixture. Then, the first mixture, polynaphthalene (based on the total mass of the first mixture, the mass percentage of polynaphthalene is 5%), and N-methylpyrrolidone solvent are mixed to obtain a positive electrode slurry with a viscosity of 15000 mPa·s. -1 The positive electrode slurry is then coated onto the surface of aluminum foil and dried to obtain the positive electrode sheet.

[0063] (3) Assemble the negative electrode obtained in step (1), the positive electrode obtained in step (2), and the polypropylene separator. Use 1 mol / L LiPF6 as the lithium salt and ethylene carbonate / diethyl carbonate / methyl ethyl carbonate (volume ratio of 1:1:1) as the electrolyte. Under negative pressure, inject the electrolyte into the cell. After sufficient settling, encapsulate, form, and capacity test to obtain a lithium-ion battery.

[0064] Example 6

[0065] The difference between this embodiment and embodiment 1 is that in step (2), polynaphthalene is replaced with 1,4-dinitronaphthalene, while everything else is the same as in embodiment 1.

[0066] Example 7

[0067] The difference between this embodiment and Example 1 is that the concentration of the naphthalene solution in step (1) is 0.05 mol / L, while all other aspects are the same as in Example 1.

[0068] Example 8

[0069] The difference between this embodiment and Example 1 is that the concentration of the naphthalene solution in step (1) is 1 mol / L, while all other aspects are the same as in Example 1.

[0070] Example 9

[0071] The difference between this embodiment and embodiment 1 is that, taking the total mass of the first mixture as 100%, the mass percentage of polynaphthalene in step (2) is 1%, and everything else is the same as in embodiment 1.

[0072] Example 10

[0073] The difference between this embodiment and Embodiment 1 is that, taking the total mass of the first mixture as 100%, the mass percentage of polynaphthalene in step (2) is 10%, and all other aspects are the same as in Embodiment 1.

[0074] Comparative Example 1

[0075] The difference between this comparative example and Example 1 is that the negative electrode is not pre-lithiated in step (1), while all other steps are the same as in Example 1.

[0076] Comparative Example 2

[0077] The difference between this comparative example and Example 1 is that no polynaphthalene is added in step (2), while everything else is the same as in Example 1.

[0078] Comparative Example 3

[0079] The difference between this comparative example and Example 1 is that the negative electrode is not pre-lithiated in step (1), and polynaphthalene is not added in step (2). Everything else is the same as in Example 1.

[0080] Test conditions

[0081] The lithium-ion batteries provided in Examples 1 to 10 and Comparative Examples 1 to 3 were tested using the following methods:

[0082] (1) Initial Coulomb Efficiency: The initial Coulomb efficiency is calculated according to the following formula: Initial Coulomb Efficiency = (Initial Discharge Specific Capacity / Initial Charge Specific Capacity) × 100%;

[0083] (2) 45℃@3C rate discharge:

[0084] a) Place the battery at room temperature and perform a 0.5C charge-discharge cycle for a total of 5 cycles. Record the discharge capacity of the last cycle as the rated capacity Q1. Charge the battery to 3.65V at a constant current and constant voltage of 0.5C, with a cutoff current of 0.05C.

[0085] b) Place the battery at a temperature of 45±2℃ for 2±0.5h, and discharge it at a constant current of 0.5C to 2.5V. Record the discharge capacity as Q2.

[0086] c) Capacity retention rate at 45℃@3C = Q2 / Q1;

[0087] (3) Cyclic performance: The battery is placed under the appropriate temperature conditions and subjected to charge and discharge treatment;

[0088] Charging: Charge to 3.65V at a constant current and constant voltage of 0.5C, cut-off current: 0.05C;

[0089] Discharge: Discharge to 2.5V with a constant current of 0.5C;

[0090] The cell charge-discharge cycle test was performed using the above steps, and the capacity retention rate after 500 cycles / 2000 cycles was compared. The calculation formula is as follows:

[0091] X-week capacity retention rate = (X-week capacity / first-week discharge capacity) × 100%, where X can be any number of weeks.

[0092] (4) Battery gas production: Gas volume was measured using the water displacement method, as shown in the following test method:

[0093] ①Testing equipment: a beaker filled with 3 / 4 pure water, a 50cm long piece of insulating tape, and a weighing balance.

[0094] ② Seal the battery tabs with insulating tape, wrap the battery with insulating tape, maintain the same tension, and immerse the battery in water, ensuring the battery tabs are level with the water surface. Record the weight after the balance stabilizes. During the test, the tension and the battery immersion position must remain consistent.

[0095] The test results are shown in Table 1:

[0096] Table 1

[0097]

[0098]

[0099] From the data in Table 1, we can draw the following conclusions:

[0100] 1. Examples 1-6 show that using naphthalene-lithium solution to pre-lithiate the negative electrode can significantly improve the first coulombic efficiency and cycle performance of the battery. This is mainly because a certain amount of lithium ions are added to the system to compensate for the irreversible capacity loss caused by the formation of the SEI film in the first cycle of the battery.

[0101] 2. Examples 1-6 show that after adding polynaphthalene or its derivatives, the high-temperature high-rate charge-discharge cycle performance of the battery is improved and the gas production is significantly reduced. This is mainly because polynaphthalene or its derivatives have good conductivity and overcharge resistance, which can effectively improve the lithium-ion transport rate and reduce the gas generated by electrolyte decomposition at high temperature and high rate and at the end of the cycle.

[0102] 3. The synergistic effect of the above two factors can effectively reduce battery internal resistance, reduce waste gas caused by side reactions, and improve initial coulombic efficiency and cycle performance;

[0103] 4. Examples 7-8 show cases where the concentration of the naphthalene solution is too low or too high, which affects the pre-lithiation of the naphthalene-lithium solution into the negative electrode, and the overall performance of the battery is reduced accordingly; Examples 9-10 show cases where the mass percentage of polynaphthalene is too low or too high, which increases the high-temperature gas production of the battery.

[0104] 5. Comparative Examples 1-3 show that the overall performance of batteries obtained without any treatment of the positive or negative electrodes is poor.

[0105] The applicant declares that the present invention is illustrated by the above embodiments, but the present invention is not limited to the above process steps, that is, it does not mean that the present invention must rely on the above process steps to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions of the raw materials used in the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for preparing a lithium-ion battery, characterized in that, The method includes the following steps: (1) The negative electrode sheet is immersed in a lithium naphthalene solution and then rinsed to obtain the negative electrode sheet; (2) The positive electrode active material, conductive agent and binder are mixed to obtain a first mixture, and then the first mixture, additives and organic solvent are mixed to obtain a positive electrode slurry, and the positive electrode slurry is coated on at least one side of the positive electrode current collector, and after drying, a positive electrode sheet is obtained; (3) Assemble the negative electrode obtained in step (1), the positive electrode obtained in step (2), and the separator, and then inject liquid to obtain the lithium-ion battery; The positive electrode active material mentioned in step (2) includes lithium iron phosphate; The additives mentioned in step (2) include any one or a combination of at least two of 1,4-dinitronaphthalene, 1,5-dinitronaphthalene, 1,4-diaminonaphthalene or 1,5-diaminonaphthalene; Based on the total mass of the first mixture being 100%, the mass percentage of the additives mentioned in step (2) is 2-5%.

2. The method according to claim 1, characterized in that, The preparation method of the naphthalene-lithium solution in step (1) includes the following steps: mixing naphthalene and solvent in a glove box with water content <1ppm and oxygen content <1ppm to obtain a naphthalene solution; then putting lithium sheets into the obtained naphthalene solution, and reacting to obtain the naphthalene-lithium solution.

3. The method according to claim 2, characterized in that, The solvent includes any one or a combination of at least two of tetrahydrofuran, ethanol, or diethyl ether.

4. The method according to claim 2, characterized in that, The concentration of the naphthalene solution is 0.1 mol / L to 0.5 mol / L.

5. The method according to claim 2, characterized in that, The area of ​​the lithium sheet is 4 cm². 2 -100cm 2 The thickness ranges from 10μm to 400μm.

6. The method according to claim 1, characterized in that, The soaking time in step (1) is 1-2 hours.

7. The method according to claim 1, characterized in that, The rinsing in step (1) is performed using dimethyl carbonate solvent.

8. The method according to claim 1, characterized in that, The conductive agent mentioned in step (2) includes any one or a combination of at least two of carbon nanotubes, conductive carbon black, or graphene.

9. The method according to claim 1, characterized in that, The adhesive mentioned in step (2) includes polyvinylidene fluoride.

10. The method according to claim 1, characterized in that, The first mixture in step (2) also includes a dispersant.

11. The method according to claim 10, characterized in that, The dispersant includes any one or a combination of at least two of polyvinylpyrrolidone, polyacrylpyrrolidone, or polyacrylamide.

12. The method according to claim 1, characterized in that, The organic solvent mentioned in step (2) includes N-methylpyrrolidone.

13. The method according to claim 1, characterized in that, The viscosity of the positive electrode slurry mentioned in step (2) is 7000~15000 mPa·s. -1 .

14. The method according to claim 1, characterized in that, The drying process described in step (2) also includes cold pressing and die-cutting.

15. The method according to claim 1, characterized in that, Step (3) includes a settling, formation and volume separation process after the injection.

16. A lithium-ion battery, characterized in that, The lithium-ion battery is prepared by the method for preparing a lithium-ion battery according to any one of claims 1-15.

17. An electronic device, characterized in that, The electronic device includes the lithium-ion battery according to claim 16.

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