Preparation method of lithium ion battery and lithium ion battery

Abstract

This invention discloses a method for preparing a lithium-ion battery and the lithium-ion battery itself, relating to the field of lithium-ion battery technology. The method involves preparing a mixture of lithium nickel cobalt manganese oxide, conductive carbon black, polyvinylidene fluoride (PVDF), and alumina nanoparticles, adding N-methylpyrrolidone, and stirring to form a positive electrode slurry. Then, a mixture of graphite, silica nanoparticles, graphene, carbon nanotubes, sodium carboxymethyl cellulose, and styrene-butadiene rubber is prepared, and deionized water is added followed by stirring. During stirring, 0.1% polyethylene glycol dispersant is added to form a negative electrode slurry. The addition of alumina nanoparticles to the positive electrode slurry fills the gaps between lithium nickel cobalt manganese oxide particles, enhancing the structural stability of the positive electrode material. Simultaneously, the addition of silica nanoparticles and polyethylene glycol dispersant to the negative electrode slurry allows silica to form a complementary structure with graphite, ensuring uniform dispersion of the negative electrode components and preventing performance loss due to uneven dispersion or structural instability, thus improving battery stability.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery technology, specifically to a method for preparing a lithium-ion battery and a lithium-ion battery itself. Background Technology

[0002] A lithium-ion battery is a rechargeable battery that primarily functions by the movement of lithium ions between the positive and negative electrodes. A lithium-ion battery consists of a positive electrode, a negative electrode, an electrolyte, a separator, positive and negative leads, a battery casing, and safety devices. During charging and discharging, lithium ions (Li)... + During charging, Li intercalates and deintercalates back and forth between the two electrodes, and during charging... + The lithium is extracted from the positive electrode and inserted into the negative electrode through the electrolyte. The negative electrode is in a lithium-rich state. The opposite occurs during discharge. It is commonly known as a lithium battery and is now widely used in smartphones, smart robots, electric bicycles and electric vehicles.

[0003] In current lithium-ion battery manufacturing processes, the positive and negative electrode slurries are prone to agglomeration, resulting in uneven coating thickness. The current collector and coating have weak adhesion, and the coating contains microbubbles after drying. Misalignment of the stacked cells causes uneven internal stress. The aluminum-plastic film seal is prone to leakage due to lack of protection. Ultimately, this leads to rapid capacity decay, poor rate performance, and high safety risks during battery cycling, making it difficult to meet the requirements of the new energy field for long battery life and high stability. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a method for preparing a lithium-ion battery and a lithium-ion battery in general, thus solving the problems mentioned in the background section.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a method for preparing a lithium-ion battery, comprising the following steps:

[0006] Prepare a mixture of lithium nickel cobalt manganese oxide, conductive carbon black, polyvinylidene fluoride and alumina nanoparticles, add N-methylpyrrolidone, and stir to make a positive electrode slurry for the battery. Then prepare a mixture of graphite, silica nanoparticles, graphene, carbon nanotubes, sodium carboxymethyl cellulose and styrene-butadiene rubber, add deionized water and stir. During the stirring process, add 0.1% polyethylene glycol dispersant to make a negative electrode slurry for the battery.

[0007] The copper foil for the negative electrode and the aluminum foil for the positive electrode are placed in a plasma processor. Argon gas is introduced into the plasma processor to treat the copper foil and the aluminum foil. After treatment, the positive electrode slurry and the negative electrode slurry are injected into a slot coating machine. The slot coating machine coats the positive electrode slurry and the negative electrode slurry onto the surfaces of the copper foil and the aluminum foil respectively, forming a wet coating on the surfaces of the copper foil and the aluminum foil.

[0008] The copper foil and aluminum foil coated with the wet coating are placed in a vacuum drying oven, which is then subjected to low vacuum pre-baking, high vacuum deep baking and high vacuum drying in sequence, so that the wet coating is dried into a dry coating, and a positive electrode sheet and a negative electrode sheet are obtained.

[0009] The positive electrode and the negative electrode are cut into corresponding electrode sizes and rolled. After the rolling process is completed, positioning pins are set on the stacking table. The separator, the positive electrode, the separator and the negative electrode are sequentially placed on the positioning pins and aligned. After alignment, the positioning pins are removed and the cells are stacked. The cells are then formed by hot pressing.

[0010] Prepare an aluminum-plastic film, spray zirconium oxide nano-ceramic particles onto the inner side of the heat-sealing layer of the aluminum-plastic film and dry it, put the battery cell into the treated aluminum-plastic film, and perform pre-sealing and main sealing, and then inspect it to obtain the battery body, inject electrolyte into the qualified battery body and seal it, and then obtain the lithium-ion battery through formation treatment, capacity testing and packaging.

[0011] Preferably, the slot coating machine is equipped with an ultrasonic vibration mechanism. During coating, the ultrasonic vibration mechanism has a vibration frequency of 20-30kHz, a power of 50-100W, and a coating speed of 5-8m / min. The coating width of the positive electrode paste on the copper foil is 0.1-0.12mm, and the coating width of the negative electrode paste on the aluminum foil is 0.08-0.1mm.

[0012] Preferably, the low vacuum pre-drying has a vacuum degree of -0.05MPa, a temperature of 60℃, and is combined with infrared heating with a wavelength of 2-5μm and a power of 100-150W, and the drying time is 30min.

[0013] The vacuum degree of the high vacuum deep drying is raised to -0.09MPa and the temperature is raised to 80℃, while the power of the infrared heating is reduced to 80-100W and the drying time is 45min.

[0014] The high-vacuum drying process maintains a vacuum level of -0.09 MPa, raises the temperature to 100°C, and takes 15 minutes.

[0015] Preferably, the electrolyte is a mixed solution of lithium hexafluorophosphate ethylene carbonate, diethyl carbonate and dimethyl carbonate, wherein the volume ratio of lithium hexafluorophosphate ethylene carbonate, diethyl carbonate and dimethyl carbonate is 1:1:1.

[0016] Preferably, the formation process involves charging to 3.6V at 0.1C and letting stand for 1 hour, then charging to 4.2V at 0.2C and letting stand for 0.5 hours.

[0017] Preferably, during plasma processing, the flow rate of argon gas is 10-15 sccm, the processing power of the plasma processor is 300-400W, the processing pressure is 0.1-0.2MPa, and the processing time is 30-60s.

[0018] Preferably, the zirconium oxide nano-ceramic particles have a particle size of 30-50 nm, the coating thickness of the zirconium oxide nano-ceramic particles sprayed onto the surface of the aluminum-plastic film is 5-8 μm, the drying temperature of the aluminum-plastic film sprayed with the zirconium oxide nano-ceramic particles is 75-85℃, and the drying time is 25-35 min.

[0019] Preferably, the pre-sealing temperature of the aluminum-plastic film is 120-130℃, the pre-sealing pressure is 0.2-0.4MPa, and the pre-sealing time is 8-12s; the main sealing temperature of the aluminum-plastic film is 180-190℃, the main sealing pressure is 0.7-0.9MPa, and the main sealing time is 18-22s; and the battery body is inspected using a helium mass spectrometer leak detector.

[0020] Preferably, the mass ratio of the lithium nickel cobalt manganese oxide, the conductive carbon black, the polyvinylidene fluoride and the alumina nanopowder is 96:2:1.5:0.5, and the mass ratio of the graphite, the silica nanoparticles, the graphene, the carbon nanotubes, the sodium carboxymethyl cellulose and the styrene-butadiene rubber is 95:2:1:1:2:1.

[0021] A lithium-ion battery, wherein the lithium-ion battery is prepared using the aforementioned method for preparing a lithium-ion battery.

[0022] This invention provides a method for preparing a lithium-ion battery and a lithium-ion battery itself. It has the following beneficial effects:

[0023] (1) By adding alumina nanopowder to the positive electrode slurry, it can fill the gaps between lithium nickel cobalt manganese oxide particles and enhance the structural stability of the positive electrode material. At the same time, adding silica nanoparticles and polyethylene glycol dispersant to the negative electrode slurry allows silica to form a complementary structure with graphite, while polyethylene glycol can prevent the agglomeration of graphite and carbon nanotubes. This ensures that the components of the negative electrode are evenly dispersed, guaranteeing the coating properties of the slurry and avoiding electrode performance loss due to uneven material dispersion or structural instability. This improves the overall electrode performance stability of the battery, reduces capacity decay caused by electrode material problems during battery cycling, and provides core support for the long life of the battery.

[0024] (2) Prepare aluminum-plastic film and add zirconium oxide nano-ceramic coating to the inner side of the heat-sealing layer of aluminum-plastic film. This coating has a dense structure and can form a protective barrier on the surface of the heat-sealing layer of aluminum-plastic film, blocking the direct contact between the electrolyte and the aluminum-plastic film substrate. At the same time, the dried coating is tightly bonded to the heat-sealing layer of aluminum-plastic film. In conjunction with the subsequent pre-sealing and main sealing processes, a tight protective layer is formed, avoiding the cracking and leakage problems that are easy to occur when the traditional aluminum-plastic film is sealed by the heat-sealing layer alone. It can effectively prevent electrolyte leakage, ensure the stability of the internal environment of the battery, reduce the performance degradation caused by electrolyte loss, and extend the battery life.

[0025] (3) The slurry of positive and negative electrodes is coated and dried on copper foil and aluminum foil. Low vacuum pre-baking, high vacuum deep baking and high vacuum drying are carried out in sequence in a vacuum drying oven. This can fully remove the solvent in the wet coating and avoid the formation of micro bubbles by residual solvent. When the electrode sheets are stacked, the positioning pins are used to ensure that the separator, positive electrode sheet and negative electrode sheet are precisely aligned, reducing stacking misalignment. This makes the drying density and stacking regularity more effective, improves the density of the coating and the regularity of the internal structure of the cell, avoids uneven internal stress, reduces the resistance of lithium ion migration inside the cell, improves the rate performance of the battery, reduces the safety hazards caused by internal structural problems, and allows the battery to work stably in different charging and discharging scenarios. Detailed Implementation

[0026] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. 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 of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0027] Example 1

[0028] Lithium nickel cobalt manganese oxide, conductive carbon black, polyvinylidene fluoride, and alumina nanoparticles were added to a mixer and dry-mixed for 30 minutes until uniform. Then, N-methylpyrrolidone was slowly added, and the mixer was turned on and stirred at 2000 rpm for 2 hours. During this period, the mixer was stopped every 30 minutes to observe the slurry state to ensure that there were no lumps. Finally, a uniform and non-agglomerated positive electrode slurry was obtained.

[0029] Add graphite to a mixer, add deionized water, and pre-stir at 1500 rpm for 1 hour. Then add silica nanoparticles and graphene in sequence, and continue stirring for 30 minutes. Next, add carbon nanotubes and stir for another 30 minutes. Then add 0.1% polyethylene glycol dispersant in three portions, and continue stirring for 10 minutes after each addition. Finally, add sodium carboxymethyl cellulose and styrene-butadiene rubber, and add deionized water to make the solid-liquid mass ratio 1:1.3. Maintain stirring at 1500 rpm for 1.5 hours to obtain a uniformly dispersed negative electrode slurry.

[0030] Cut the copper and aluminum foils into rolls of the corresponding size, place them in the plasma processor, close the processor door, evacuate to 0.05 MPa, introduce argon gas at a flow rate of 5 sccm, adjust the processing power to 300 W and the pressure to 0.1 MPa, and continue processing for 60 seconds. After processing, remove the copper and aluminum foils and place them in a clean and dry environment for later use.

[0031] Positive and negative electrode slurries are injected into the hopper of the slot coating machine. Ultrasonic vibration is turned on at a frequency of 20kHz and a power of 100W. The aluminum foil roll is installed at the unwinding end of the coating machine. The slot width is adjusted to 0.12mm, and the positive electrode slurry is coated onto the aluminum foil surface at a speed of 8m / min to form a continuous wet coating. Similarly, the copper foil roll is installed in place, the slot width is adjusted to 0.1mm, and the negative electrode slurry is coated to form a wet coating. The thickness of the wet coating is monitored in real time during the coating process to ensure no missed coating or accumulation.

[0032] Copper foil coated with negative electrode wet coating and aluminum foil coated with positive electrode wet coating were respectively sent into a vacuum drying oven. In the first stage, the vacuum degree was set to -0.05MPa and the temperature to 60℃. An infrared heating lamp with a wavelength of 2μm and a power of 150W was turned on and dried continuously for 30 minutes.

[0033] Second stage: Gradually increase the vacuum to -0.09MPa, rapidly increase the temperature to 80℃, reduce the infrared heating power to 100W, and continue drying for 45 minutes;

[0034] Third stage: Maintain vacuum of -0.09MPa, raise temperature to 100℃, turn off infrared heating lamp, and continue drying for 15 minutes; after drying, take out copper foil and aluminum foil, and let them cool naturally to room temperature to obtain positive electrode roll and negative electrode roll with dry coating.

[0035] The positive and negative electrode rolls are placed into a laser cutting machine and cut into individual electrode sheets. The cut positive electrode sheets are then placed into a roller press, and the roller pressing density is adjusted to 3.8 g / cm³. 3 The negative electrode sheet undergoes a rolling process, with a rolling density of 1.8 g / cm³. 3 Roll pressing; after rolling, check the uniformity of electrode thickness and discard electrode sheets with excessive thickness deviation.

[0036] Make positioning holes with a diameter of 2mm and a spacing of 50mm on the surface of the stacking table, insert stainless steel positioning pins with a height of 5mm, take a polyethylene and polypropylene composite diaphragm, put it into the positioning pin and fix it, place a positive electrode plate on the diaphragm, ensure that the edge of the electrode plate is aligned with the diaphragm, then cover it with another diaphragm, put in the positioning pin, and finally place a negative electrode plate. After aligning, gently press to make the layers adhere, remove the positioning pin, put the stacked electrode core into the hot press, set the temperature to 80℃, the pressure to 0.5MPa, and hot press for 30s. After hot pressing is completed, take it out to obtain a neat battery cell.

[0037] Weigh out the corresponding amount of zirconia nano-ceramic particles, add a small amount of solvent to make a spraying liquid, lay the aluminum-plastic film flat, and spray the zirconia spraying liquid evenly on the inner side of its heat-sealing layer with a spray gun, controlling the coating thickness to 5μm. Place the sprayed aluminum-plastic film in an 80℃ oven and dry for 30min. Place the hot-pressed battery cell into the prepared aluminum-plastic film, centering the battery cell, fold the edges of the aluminum-plastic film, and put it into a heat-sealing machine. First, perform pre-sealing at a temperature of 130℃ and a pressure of 0.3MPa for 10s. Then, perform main sealing at a temperature of 190℃ and a pressure of 0.8MPa for 20s. After sealing, use a helium mass spectrometer to detect leaks to ensure no leakage, and obtain the battery body.

[0038] In a glove box, a mixed electrolyte of carbonate containing lithium hexafluorophosphate is injected into the leak-tested battery body. The box is then sealed, and the injected battery is left to stand for 24 hours. It is then placed in a formation device, charged at 0.1C to 3.6V, left to stand for 1 hour, and then charged at 0.2C to 4.2V, left to stand for 0.5 hours to complete the formation. After formation, capacity testing is performed (charge and discharge at 0.5C at 25℃, and the capacity is recorded). Batteries with qualified capacity are screened out. Finally, visual inspection and packaging are performed to obtain the finished lithium-ion battery.

[0039] Example 2

[0040] In the positive electrode slurry preparation step, alumina nanopowder was mixed with N-methylpyrrolidone and treated in a 40kHz, 300W ultrasonic disperser for 20 minutes to obtain an alumina pre-dispersion. Then, lithium nickel cobalt manganese oxide, conductive carbon black, polyvinylidene fluoride and the pre-dispersion were added to a mixer and dry-mixed for 30 minutes until uniform. The remaining N-methylpyrrolidone was then slowly added, and the mixer was turned on and stirred at 2000rpm for 2 hours. During this period, the mixer was stopped every 30 minutes to observe the slurry state to ensure that there were no lumps. Finally, a uniform and non-agglomerated positive electrode slurry was obtained. The other steps were completely consistent with those in Example 1. The difference from Example 1 was the pretreatment and dispersion of alumina nanopowder and N-methylpyrrolidone.

[0041] Example 3

[0042] In the negative electrode slurry preparation stage, graphite was added to a mixer, deionized water was added, and the mixture was pre-stirred at 1500 rpm for 1 hour. Simultaneously, carbon nanotubes were mixed with 0.1% polyethylene glycol as a dispersant, deionized water was added, and the mixture was treated with a 30 kHz, 200 W ultrasonic disperser for 15 minutes to obtain a pre-mixed dispersion of carbon nanotubes and polyethylene glycol. Subsequently, silica nanoparticles and graphene were added sequentially to the graphite dispersion, and the mixture was stirred for another 30 minutes. Then, the above carbon nanotube-dispersant pre-mixed mixture was added, and the mixture was stirred for another 30 minutes. Finally, sodium carboxymethyl cellulose and styrene-butadiene rubber were added, and deionized water was added to bring the solid-liquid mass ratio to 1:1.3. The mixture was stirred at 1500 rpm for 1.5 hours to obtain a uniformly dispersed negative electrode slurry. The other steps were completely consistent with those in Example 1. The difference from Example 1 was that the polyethylene glycol dispersant, which was added in three separate batches, was changed to a mixture of carbon nanotubes and polyethylene glycol dispersant, which was ultrasonically pre-mixed and then added as a whole.

[0043] Example 4

[0044] In the plasma processor environment, copper and aluminum foils are cut into rolls of the corresponding size, placed in the plasma processor, the processor door is closed, and the vacuum is evacuated to 0.05 MPa. Argon gas is introduced at a flow rate of 5 sccm, gradually increasing to 8 sccm over 10 seconds. The processing power is adjusted to 300 W and the pressure to 0.1 MPa, and the processing is continued for 60 seconds. After the processing is completed, the copper and aluminum foils are removed and placed in a clean and dry environment for later use. The remaining steps are the same as in Example 1, except that the flow rate of argon gas is dynamically introduced.

[0045] Example 5

[0046] In the drying process of the vacuum drying oven, copper foil coated with a negative electrode wet coating and aluminum foil coated with a positive electrode wet coating are respectively sent into the vacuum drying oven:

[0047] First stage: Set the vacuum degree to -0.05MPa and the temperature to 60℃, turn on the infrared heating lamp with a wavelength of 2μm and a power of 150W, and continue drying for 30 minutes;

[0048] Second stage: Raise the temperature to 80℃ at a slow rate of 5℃ / 10min, while simultaneously gradually increasing the vacuum to -0.09MPa, reducing the infrared heating power to 100W, and continue drying for 45min;

[0049] Third stage: Maintain a vacuum of -0.09MPa, raise the temperature to 100℃, turn off the infrared heating lamp, and continue drying for 15 minutes;

[0050] After drying, remove the copper foil and aluminum foil and allow them to cool naturally to room temperature to obtain positive electrode rolls and negative electrode rolls with dry coating.

[0051] The remaining steps are the same as in Example 1, except that the heating method in the second stage is changed from rapid heating to slow heating.

[0052] Comparative Example 1

[0053] Lithium nickel cobalt manganese oxide, conductive carbon black, and polyvinylidene fluoride were added to a mixer and dry-mixed for 30 minutes until uniform. Then, N-methylpyrrolidone was slowly added, and the mixer was turned on and stirred at 2000 rpm for 2 hours. During this period, the mixer was stopped every 30 minutes to observe the slurry state to ensure that there were no lumps, and the positive electrode slurry was obtained. The remaining steps were the same as in Example 1, except that aluminum oxide nanopowder was not added.

[0054] Comparative Example 2

[0055] Graphite was added to a mixer, followed by deionized water. The mixture was pre-stirred at 1500 rpm for 1 hour. Silica nanoparticles and graphene were added sequentially, and the mixture was stirred for another 30 minutes. Carbon nanotubes were then added, and the mixture was stirred for another 30 minutes. Finally, sodium carboxymethyl cellulose and styrene-butadiene rubber were added, and deionized water was added to bring the solid-liquid mass ratio to 1:1.3. The mixture was stirred at 1500 rpm for 1.5 hours to obtain a uniformly dispersed negative electrode slurry. The remaining steps were the same as in Example 1, except that 0.1% polyethylene glycol dispersant was not added.

[0056] Comparative Example 3

[0057] The copper and aluminum foils were cut into rolls of the corresponding size and stored directly for later use. The remaining steps were the same as in Example 1, except that the plasma processor was not used.

[0058] Comparative Example 4

[0059] Instead of creating positioning holes or inserting positioning pins on the stacking table, a polyethylene and polypropylene composite diaphragm is directly laid flat. A positive electrode sheet is placed on top of the diaphragm, then another diaphragm is covered, and finally a negative electrode sheet is placed. The layers are gently pressed together, and the stacked electrode core is placed in a hot press to obtain the battery cell. The remaining steps are the same as in Example 1, except that a common electrode sheet stacking method is used.

[0060] Comparative Example 5

[0061] The copper foil coated with the negative electrode wet coating and the aluminum foil coated with the positive electrode wet coating were respectively sent into a vacuum drying oven with a vacuum degree of -0.09MPa and a temperature of 120°C for 50 minutes. The remaining steps were the same as in Example 1. The difference from Example 1 was that the multi-stage drying and infrared drying process was not used.

[0062] Example 6

[0063] The aluminum-plastic film is laid flat and dried in an 80°C oven for 30 minutes. The hot-pressed battery cell is placed in the aluminum-plastic film, centered. The edges of the aluminum-plastic film are folded and placed in a heat-sealing machine. The film is pre-sealed and then fully sealed. After sealing, the leak is detected by a helium mass spectrometer to obtain the battery body. The remaining steps are the same as in Example 1. The difference from Example 1 is that the inner side of the heat-sealing layer of the aluminum-plastic film is not coated with a zirconium oxide nano-ceramic coating.

[0064] Test case

[0065] Cycle life test: The batteries prepared in each example and comparative example were charged to 4.2V at 0.5C and discharged to 2.75V at 0.5C in a constant temperature environment of 25℃, and the cycle was repeated 1000 times. The initial discharge capacity and the capacity retention rate after the cycle were recorded.

[0066] Rate performance test: The batteries prepared in each example and comparative example were discharged at 0.2C to 2.75V and the capacity was recorded at 25°C. After standing for 1 hour, they were discharged at 1C to 2.75V and the capacity was recorded. The rate performance ratio was calculated.

[0067] Sealing performance test: The batteries prepared in each embodiment and comparative example were placed in a constant temperature aging chamber at 50°C and stored for 200 hours. The mass of the batteries before and after aging was weighed, the mass loss rate was calculated, and the presence of electrolyte leakage traces on the inner side of the aluminum-plastic film was observed.

[0068] Coating adhesion test: The batteries prepared in each embodiment and comparative example were subjected to a 180° peel test on the positive and negative electrode sheets using a peel tester at a test speed of 50 mm / min. The average peel strength between the coating and the current collector was recorded, and the average tensile force during the peel process was recorded using a tensile tester, which is the coating adhesion force (N / cm). Three electrode samples were taken for each test group, and the average value of the results was taken.

[0069] Table 1 shows the performance test results of lithium-ion batteries:

[0070]

[0071] Based on the above tests and the performance test results in Table 1, Comparative Example 1, due to the lack of alumina nanopowder, could not fill the gaps between lithium nickel cobalt manganese oxide particles, resulting in easy lattice distortion and poor structural stability during cycling, with a capacity retention rate of only 74.8%, far lower than Example 1. Example 2, through ultrasonic pre-dispersion of alumina and N-methylpyrrolidone, further improved the particle dispersion uniformity, resulting in a better filling effect and a certain improvement in capacity retention rate compared to Example 1, proving that alumina nanopowder can enhance the structural stability of the cathode, and further pre-dispersion process can further optimize its performance.

[0072] In Comparative Example 2, due to the absence of polyethylene glycol dispersant, carbon nanotubes and graphite easily agglomerated, resulting in breakage of the conductive network. The 1C rate performance ratio was only 81.3%, and the bonding strength of the negative electrode coating was significantly lower than that of Example 1 due to uneven dispersion. In Example 3, carbon nanotubes and dispersant were ultrasonically premixed before being added, resulting in a continuous and intact conductive network. The 1C rate performance ratio increased to 97.5%, and the bonding strength was slightly improved compared to Example 1. This indicates that polyethylene glycol dispersant is the key to ensuring the conductivity and structural stability of the negative electrode, and the premixing process can optimize the dispersion effect.

[0073] In Comparative Example 3, the copper and aluminum foils were not treated with plasma, resulting in high surface tension and low roughness. The bonding strength of the positive and negative electrode coatings was only 0.32 N / cm and 0.35 N / cm, respectively. The coatings were prone to peeling off during cycling, and the capacity retention rate was significantly lower than that of Example 1. In Example 4, dynamic argon gas was used to make the plasma uniformly cover the current collector, and the surface etching was more thorough. The bonding strength and capacity retention rate were further improved compared with Example 1. This verifies that plasma treatment can enhance coating bonding and cycling stability by optimizing the surface state of the current collector.

[0074] In Comparative Example 5, direct drying was used, which easily resulted in the formation of a hard shell on the wet coating surface. When the internal solvent overflowed, it damaged the interface between the coating and the current collector, reducing the adhesion and making the coating prone to cracking during cycling. In Example 5, by slowly increasing the temperature and gradually removing the solvent, the interface was avoided and the adhesion was significantly increased. This demonstrates that multi-stage slow heating and drying can improve the density and adhesion of the coating and extend the cycle life.

[0075] In Comparative Example 4, manual lamination easily leads to misalignment of the electrode and separator, obstructing the lithium-ion migration path and significantly reducing the 1C rate performance ratio. In Comparative Example 6, the aluminum-plastic film, lacking a zirconium oxide coating, is prone to micro-cracks after long-term aging of the heat-sealing layer, resulting in a 2.35% mass loss rate in one year. Disassembly revealed obvious leakage. In Example 1, the zirconium oxide coating forms a dense protective barrier, blocking electrolyte penetration, with a mass loss rate of only 0.08% and no leakage. This demonstrates that the zirconium oxide coating can significantly improve sealing reliability and prevent performance degradation caused by electrolyte loss.

[0076] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention.

Claims

1. A method for preparing a lithium-ion battery, characterized in that, Includes the following steps: Prepare a mixture of lithium nickel cobalt manganese oxide, conductive carbon black, polyvinylidene fluoride and alumina nanoparticles, add N-methylpyrrolidone, and stir to make a positive electrode slurry for the battery. Then prepare a mixture of graphite, silica nanoparticles, graphene, carbon nanotubes, sodium carboxymethyl cellulose and styrene-butadiene rubber, add deionized water and stir. During the stirring process, add 0.1% polyethylene glycol dispersant to make a negative electrode slurry for the battery. The copper foil for the negative electrode and the aluminum foil for the positive electrode are placed in a plasma processor. Argon gas is introduced into the plasma processor to treat the copper foil and the aluminum foil. After treatment, the positive electrode slurry and the negative electrode slurry are injected into a slot coating machine. The slot coating machine coats the positive electrode slurry and the negative electrode slurry onto the surfaces of the copper foil and the aluminum foil respectively, forming a wet coating on the surfaces of the copper foil and the aluminum foil. The copper foil and aluminum foil coated with the wet coating are placed in a vacuum drying oven, which is then subjected to low vacuum pre-baking, high vacuum deep baking and high vacuum drying in sequence, so that the wet coating is dried into a dry coating, and a positive electrode sheet and a negative electrode sheet are obtained. The positive electrode and the negative electrode are cut into corresponding electrode sizes and rolled. After the rolling process is completed, positioning pins are set on the stacking table. The separator, the positive electrode, the separator and the negative electrode are sequentially placed on the positioning pins and aligned. After alignment, the positioning pins are removed and the cells are stacked. The cells are then formed by hot pressing. Prepare an aluminum-plastic film, spray zirconium oxide nano-ceramic particles onto the inner side of the heat-sealing layer of the aluminum-plastic film and dry it, put the battery cell into the treated aluminum-plastic film, and perform pre-sealing and main sealing, and then inspect it to obtain the battery body, inject electrolyte into the qualified battery body and seal it, and then obtain the lithium-ion battery through formation treatment, capacity testing and packaging.

2. The method for preparing a lithium-ion battery according to claim 1, characterized in that, The slot coating machine is equipped with an ultrasonic vibration mechanism. During coating, the ultrasonic vibration mechanism has a vibration frequency of 20-30kHz, a power of 50-100W, and a coating speed of 5-8m / min. The coating width of the positive electrode paste on the copper foil is 0.1-0.12mm, and the coating width of the negative electrode paste on the aluminum foil is 0.08-0.1mm.

3. The method for preparing a lithium-ion battery according to claim 1, characterized in that, The low vacuum pre-drying process involves a vacuum degree of -0.05 MPa, a temperature of 60°C, and is combined with infrared heating with a wavelength of 2-5 μm and a power of 100-150 W, with a drying time of 30 min. The vacuum degree of the high vacuum deep drying is raised to -0.09MPa and the temperature is raised to 80℃, while the power of the infrared heating is reduced to 80-100W and the drying time is 45min. The high-vacuum drying process maintains a vacuum level of -0.09 MPa, raises the temperature to 100°C, and takes 15 minutes.

4. The method for preparing a lithium-ion battery according to claim 1, characterized in that, The electrolyte is a mixed solution of lithium hexafluorophosphate with ethylene carbonate, diethyl carbonate and dimethyl carbonate, wherein the volume ratio of lithium hexafluorophosphate with ethylene carbonate, diethyl carbonate and dimethyl carbonate is 1:1:

1.

5. The method for preparing a lithium-ion battery according to claim 1, characterized in that, The formation process involves charging to 3.6V at 0.1C and letting it stand for 1 hour, then charging to 4.2V at 0.2C and letting it stand for 0.5 hours.

6. The method for preparing a lithium-ion battery according to claim 1, characterized in that, During plasma processing, the flow rate of argon gas is 10-15 sccm, the processing power of the plasma processor is 300-400W, the processing pressure is 0.1-0.2MPa, and the processing time is 30-60s.

7. The method for preparing a lithium-ion battery according to claim 1, characterized in that, The zirconium oxide nano-ceramic particles have a particle size of 30-50 nm, the coating thickness of the zirconium oxide nano-ceramic particles sprayed onto the surface of the aluminum-plastic film is 5-8 μm, the drying temperature of the aluminum-plastic film sprayed with the zirconium oxide nano-ceramic particles is 75-85℃, and the drying time is 25-35 min.

8. The method for preparing a lithium-ion battery according to claim 1, characterized in that, The pre-sealing temperature of the aluminum-plastic film is 120-130℃, the pre-sealing pressure is 0.2-0.4MPa, and the pre-sealing time is 8-12s. The main sealing temperature of the aluminum-plastic film is 180-190℃, the main sealing pressure is 0.7-0.9MPa, and the main sealing time is 18-22s. The battery body is inspected using a helium mass spectrometer leak detector.

9. A method for preparing a lithium-ion battery according to claim 1, characterized in that, The mass ratio of the lithium nickel cobalt manganese oxide, the conductive carbon black, the polyvinylidene fluoride and the alumina nanopowder is 96:2:1.5:0.5, and the mass ratio of the graphite, the silica nanoparticles, the graphene, the carbon nanotubes, the sodium carboxymethyl cellulose and the styrene-butadiene rubber is 95:2:1:1:2:

1.

10. A lithium-ion battery, characterized in that, The lithium-ion battery is prepared using the method for preparing a lithium-ion battery as described in any one of claims 1-9.

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