A high-rate, high-capacity, long-cycle ternary lithium ion battery and a preparation method thereof

Abstract

The application discloses a ternary lithium ion battery with high rate, high capacity and long cycle and a preparation method thereof. The positive electrode of the battery adopts a ternary positive active material, and a composite conductive agent of single-walled carbon nanotubes and conductive carbon black; the negative electrode adopts a composite of a silicon-based material and a 4-6 C rate type graphite, and cooperates with a composite conductive agent with a specific proportion and a mixed binder containing sodium carboxymethyl cellulose, butyl rubber and polyacrylic acid. In the preparation, a dry process of dry powder mixing and blow molding is adopted to manufacture the pole piece, and a 10 C rate pulse charging pretreatment step is introduced after liquid injection and before formation. Through the above-mentioned synergistic scheme, the battery internal resistance is significantly reduced, the fast charging capacity and the cycle life are improved, the battery has excellent comprehensive performance of high rate, high capacity and long cycle, and is especially suitable for application scenes such as electric tools which need large current and long-lasting endurance.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery technology, and particularly relates to a high-rate, high-capacity, long-cycle ternary lithium-ion battery and its preparation method. Background Technology

[0002] Ternary lithium-ion batteries are considered the most competitive electrochemical energy storage technology due to their light weight, high specific energy / specific power, and long lifespan. Their applications are becoming increasingly widespread in low-altitude fields such as drones, power tools like robotic dogs, and 3C digital products. With advancements in battery management system technology, the challenges of large-scale integration have been overcome, gradually making them an ideal power source for new chemical energy storage technologies. Ternary lithium-ion batteries are categorized into three main types based on their operating conditions: high-power, high-capacity, and high (low) temperature batteries. In the high-power market, lithium iron phosphate (LFP) batteries, due to their nano-layered cathode materials, exhibit excellent rate performance, achieving ultra-high rate performance of 10C-15C discharge current and ultra-long cycle life, thus dominating the mainstream power battery market. However, LFP batteries suffer from low specific capacity and low processing compaction, resulting in low actual battery capacity and very short discharge time, which restricts their promotion in the power tool market. For example, power tool batteries are categorized into household, professional, and industrial grades based on their operating conditions, from low to high. While LFP batteries meet the requirements for low precision and short continuous operating time in these applications, they are insufficient for the longer continuous operating time demands of professional and industrial applications. Therefore, it is necessary to develop lithium-ion batteries with other material systems that offer higher capacity. Lithium-ion batteries using lithium nickel cobalt manganese oxide (NCM) cathode materials will achieve a capacity of 2.6 Ah (18650 type), approximately 60% larger than traditional LFP batteries, and their rate performance will reach the 10C discharge capability of LFP. Rate-capacity lithium-ion batteries using traditional graphite combined with NCM cathodes have a market capacity of around 2.0 Ah and a cycle life (30A discharge) of around 500 cycles. When the capacity is increased to 2.5Ah, or even 2.6Ah or 3.0Ah, silicon-based materials need to be used. However, the cycle life (20A discharge) of ternary cathode silicon-based anode lithium-ion batteries with traditional processes and formulations is within 200.1 to 350 cycles, especially after increasing the battery's fast charging performance, the cycle life will be even shorter. How to improve capacity and rate cycle performance, while catering to customers' super-fast charging technology, requires seeking special processes and materials. This invention patent combines multiple processes and new materials to provide a comprehensive solution with advantages in multiple parameters such as high current, super-fast charging, and long cycle life. It increases the cycle life to twice the market demand (300 cycles), while providing a 5-8 minute fast ion channel, allowing the charge to quickly increase from 0 to 80% during charging, while also taking into account higher capacity or energy density. Compared with the market-widely available 2.0Ah small-capacity products, the capacity will reach 2.5Ah, or even 2.6Ah or 3.0Ah.

[0003] The key to achieving high-rate discharge capability in lithium-ion batteries lies in reducing internal resistance. Taking the existing 18650 ternary lithium battery as an example, with an internal resistance of 20 milliohms, the discharge efficiency at 5C-8C is 85%. Reducing the internal resistance to 17 milliohms achieves 90% efficiency at 8C, and further reducing it to 15 milliohms achieves 85% efficiency at 10C. The rate discharge efficiency is limited by internal resistance, determined by Joule's law. To effectively improve the battery's chemical energy conversion efficiency, it's necessary to reduce internal resistance to decrease the conversion between chemical energy and heat, and to lower the casing temperature to reduce thermal energy conversion. Implementing tabless-free technology in small batteries is very difficult, resulting in low yields. Therefore, high-rate batteries, besides increasing the contact area between the current collector traction tabs (tabs) and the casing, also need to reduce the internal resistance of the films at both the positive and negative electrodes, shorten the ion transfer path, improve ion mobility, and provide a comfortable ion and electron transfer channel.

[0004] Therefore, miniaturized ternary lithium-ion batteries such as the 18650 have drawbacks such as short high-current cycle times, long charging times (over 1 hour), and short operating time, which severely restrict their application in special scenarios such as power tools. To effectively improve the overall battery performance and provide customers with a better quality experience, a multi-pronged approach is needed. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the deficiencies and defects mentioned in the background art above, and to provide a ternary silicon-based lithium-ion battery with strong high-current charging and discharging, ultra-long cycle life and operating time, and its preparation method.

[0006] To solve the above-mentioned technical problems, the technical solution proposed by this invention is as follows:

[0007] A high-rate, high-capacity, long-cycle ternary lithium-ion battery includes a positive electrode, a negative electrode, a separator, and an electrolyte. The positive electrode comprises a current collector, a positive electrode active material, a positive electrode conductive agent, and a positive electrode binder. The mass ratio of the positive electrode active material, the positive electrode conductive agent, and the positive electrode binder is 97.0–98.4:0.8–1.7:0.8–1.3. The positive electrode active material is a ternary lithium nickel cobalt manganese oxide or lithium nickel cobalt aluminum oxide. The positive electrode conductive agent is a composite conductive agent obtained by mixing single-walled carbon nanotubes and conductive carbon black in a mass ratio of 5–10:90–95. The positive electrode binder is polyvinylidene fluoride. The negative electrode sheet comprises a current collector, a negative electrode active material, a negative electrode conductive agent, and a negative electrode binder. The mass ratio of the negative electrode active material, the negative electrode conductive agent, and the negative electrode binder is 95.7–97.8:1.0–1.7:1.2–2.6. The negative electrode active material is a composite material obtained by mixing silicon-based materials and 4–6 C-type rate-multiplied graphite at a mass ratio of 5–9:91–95. The negative electrode conductive agent is a composite conductive agent obtained by mixing single-walled carbon nanotubes and conductive carbon black at a mass ratio of 8–15:85–92. The negative electrode binder is a mixed adhesive obtained by mixing sodium carboxymethyl cellulose, styrene-butadiene rubber, and polyacrylic acid at a mass ratio of 1.0–1.5:2.0–2.5:6.0–8.0.

[0008] In the aforementioned ternary lithium-ion battery, preferably, the current collector of the positive electrode and / or the negative electrode is a foamed metal, wherein the foamed metal is selected from at least one of foamed nickel, foamed copper and foamed aluminum.

[0009] Preferably, the positive electrode sheet is prepared by the following method: after mixing the dry powders of the positive electrode active material, the positive electrode conductive agent and the positive electrode binder, the mixture is blown onto a current collector with a thickness of 90 to 180 μm, then extruded and molded, then coated with adhesive, and dried and molded again to obtain the positive electrode sheet; The negative electrode sheet is prepared by the following method: the dry powders of the negative electrode active material, negative electrode conductive agent and negative electrode binder are mixed and blown onto a current collector with a thickness of 90 to 180 μm, then extruded and shaped, coated with adhesive, and dried and shaped again to obtain the negative electrode sheet.

[0010] Preferably, the N / P ratio of the negative electrode to the positive electrode is 1.01 to 1.10.

[0011] Preferably, the silicon-based material is a silicon-oxygen material, a silicon-oxygen material pre-treated with magnesium, a silicon-oxygen material pre-treated with lithium, or a silicon-carbon material after sand milling. The core of the silicon-based material is amorphous silicon or silicon grains with a grain size ≤2nm, and the core is surrounded by a carbon shell of 2-6 μm.

[0012] Preferably, the specific capacity of the negative electrode active material is 400–500 mAh / g, and the specific surface area of ​​the 4–6 C-type rate-adjustable graphite is 1.5–2.5 m². 2 / g.

[0013] Preferably, the separator has a thickness of 9–15 μm and includes a base film and a coating layer with a thickness of 0.1–3 μm; the base film is at least one of polypropylene, polyethylene, and polyethylene oxide; and the coating layer is at least one of aluminum oxide, aramid, and rare earth oxides.

[0014] Preferably, by mass percentage, the electrolyte comprises 81.6 wt%–88.3 wt% of carbonate-based solvent, 10.0 wt%–14.0 wt% of lithium hexafluorophosphate, 0.5 wt%–1.2 wt% of vinylene carbonate, 0.5 wt%–1.2 wt% of ethylene sulfate, 0.5 wt%–1.2 wt% of fluoroethylene carbonate, and 0.2 wt%–0.8 wt% of lithium difluorophosphate; the carbonate-based solvent is composed of ethylene carbonate and methyl ethyl carbonate in a mass ratio of 0.3–1.5:1.

[0015] Based on a general inventive concept, this invention also provides a method for preparing a high-rate, high-capacity, long-cycle ternary lithium-ion battery, comprising the following steps: (1) The positive electrode, separator, and negative electrode are made into a battery cell by winding or stacking. (2) The battery cell obtained in step (1) is installed into the housing and injected with the electrolyte; (3) After the battery is filled with electrolyte in step (2), it is placed at 40-50 °C for 4-8 h or at room temperature for 20-28 h, and then subjected to a 10C rate pulse charging pretreatment for 5 min; the pulse charging method is: charge at 10C rate for 1 s and then place for 20 s, and repeat the charging and placing steps. (4) The battery after step (3) is placed under formation treatment to obtain the ternary lithium-ion battery.

[0016] In the above preparation method, preferably, the electrolyte injection coefficient is 1.5 to 3.5 g / Ah.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention uses foamed metal as the current collector for the positive and / or negative electrodes, combined with a dry process in which dry powder containing active materials, conductive agents, and binders is directly blown into the pores of the foamed metal and then extruded. The three-dimensional network structure of the foamed metal significantly increases the contact area between the current collector and the electrode material. Simultaneously, the dry extrusion process creates a near-embedded, close contact between the electrode material and the current collector. Together, they construct a highly efficient three-dimensional electron transport network, significantly reducing the internal resistance of the electrode membrane. Furthermore, the use of a specific ratio of single-walled carbon nanotubes and conductive carbon black composite conductive agent further facilitates electron migration channels.

[0018] 2. By introducing specific silicon-based materials with high specific capacity (400-500 mAh / g) into the negative electrode and combining them with 4-6 C rate-type graphite, the overall specific capacity of the negative electrode is improved by utilizing the silicon-based materials, increasing the capacity of the 18650 battery from the traditional 2.0 Ah to 2.5 Ah or even 3.0 Ah. On the other hand, the excellent fast-charging acceptance of rate-type graphite and the improvement of lithium-ion diffusion dynamics by the specific structure of silicon-based materials (amorphous or nanocrystalline combined with carbon coating) endow the battery with excellent fast-charging performance. Combined with a specific 10C pulse charging pretreatment process during the first charge, the composition and structure of the solid electrolyte interface film are optimized during the formation stage, fully opening the fast ion transport channel of the negative electrode.

[0019] 3. This invention, through systematic design of the electrode formulation, separator, and electrolyte, comprehensively reduces the battery's internal resistance and improves ion mobility. The use of a thin or functionally coated separator with a thickness of 9–15 μm shortens the ion transport path. The electrolyte employs a solvent system of ethylene carbonate and ethyl methyl carbonate in a specific ratio, synergistically supplemented with lithium hexafluorophosphate and various functional additives (ethyleneene carbonate, ethylene sulfate, fluoroethylene carbonate, and lithium difluorophosphate). The resulting SEI film is dense, stable, and has high ionic conductivity, effectively suppressing side reactions caused by the volume expansion of the silicon-based anode during cycling. These measures work together to ensure that the internal ion transport system remains efficient and stable under continuous high-current charge and discharge conditions, fundamentally guaranteeing a long cycle life. Detailed Implementation

[0020] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below in conjunction with the specification and preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0021] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0022] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0023] The silicon-based material used in the following examples is KSC-1B silicon-oxygen material from Hunan Jinsi Technology Co., Ltd., which has a silicon grain size of ≤2 nm in the core and a carbon shell of 2 to 6 μm outside the core.

[0024] The 4-6 C rate-capacity graphite used in the following examples is BTR T-Max's 6C ultra-fast charging synthetic graphite, with a specific surface area of ​​1.5-2.5 m².2 / g. 4-6 C rate-type graphite refers to graphite materials that can maintain good charge and discharge performance at rates from 4C to 6C.

[0025] The ternary nickel-cobalt-manganese main material used in the following examples and comparative examples is composed of NCM523 and NCM811, wherein the mass fraction of NCM523 is 20%~50%.

[0026] Example 1 A high-rate, high-capacity, long-cycle ternary lithium-ion battery of the present invention includes a positive electrode, a negative electrode, a separator, and an electrolyte, and is prepared by the following method: (1) Preparation of the positive electrode: According to the mass parts, take 1 part conductive carbon black (SP), 0.1 part single-walled carbon nanotubes (CNT), 1.0 part polyvinylidene fluoride (PVDF), and 97.9 parts ternary nickel-cobalt-manganese main material, mix them to form a dry powder, blow and press it onto a 180 μm thick foamed aluminum substrate, then extrude and mold it, coat it with a PVDF oil-based (NMP) adhesive solution with a solid content of 1%, and dry and mold it again to obtain a positive electrode with an areal density of 1.20 g / dm. 2 Electrode sheets with a width of 57 mm are cold-rolled to a density of 3.35 g / cm. 3 Compacted positive electrode sheet.

[0027] (2) Preparation of negative electrode sheet: According to the mass parts, take 1.0 part conductive carbon black (SP), 0.1 part single-walled carbon nanotubes (CNT), 0.2 part sodium carboxymethyl cellulose (CMC), 0.4 part styrene-butadiene rubber (SBR), 1.2 parts polyacrylic acid (PAA) adhesive, and 97.1 parts negative electrode active material (specific capacity of 400-460 mAh / g); the negative electrode active material is a composite of 7.1 parts silicon-based material and 90 parts 4-6 C type rate-type graphite, mixed to form a dry powder, blown onto a 160 μm thick foamed aluminum substrate, extruded and molded, coated with an aqueous adhesive of CMC / SBR / PAA with a solid content of 26.5%, and dried and molded again to obtain a negative electrode surface density of 0.53 g / dm. 2 Electrode sheets with a width of 59 mm are cold-rolled to a density of 1.58 g / cm³. 3 Compacted negative electrode sheet.

[0028] (3) Preparation of the isolation membrane: Take a 9 μm thick polypropylene (PP) base film and coat two 1 μm Al2O3 ceramic coating layers on both sides to obtain an 11 μm PP base film-Al2O3 ceramic coating layer isolation membrane.

[0029] (4) Preparation of electrolyte: Take 88 parts by mass of carbonate-based solvent, 10 parts of lithium hexafluorophosphate, 0.5 parts of vinylene carbonate, 0.5 parts of vinyl sulfate, 0.5 parts of fluoroethylene carbonate and 0.5 parts of lithium difluorophosphate; wherein the carbonate-based solvent is composed of vinyl carbonate and methyl ethyl carbonate in a mass ratio of 1:1.

[0030] (5) Assembly of ternary lithium-ion battery: The above positive and negative electrode sheets are de-powdered at the tab position and welded to the current collector. After welding and coating, they are aligned with the separator, wound, inserted into the shell, the tab is welded, and the roller groove is filled with the above electrolyte. The electrolyte injection coefficient is 2.0 g / Ah. After the electrolyte injection is sealed, it is left at room temperature for 24 h and then subjected to a 10 C rate pulse charging pretreatment for 5 min. The pulse charging method is as follows: charge at 10 C rate for 1 s and then leave for 20 s, then charge at 10 C rate for 1 s and leave for 20 s, and so on, repeating the charging and leaving steps until the total pulse charging pretreatment time is 5 min. Then it is converted to conventional formation to prepare a 18650 cylindrical lithium-ion battery with a capacity of ~2500 mAh, which is the ternary lithium-ion battery of the present invention.

[0031] Comparative Example 1 A lithium-ion battery is prepared by the following method: By weight, the positive electrode uses 1.7 parts SP, 97.0 parts ternary nickel-cobalt-manganese main material, and 1.3 parts PVDF binder; the negative electrode uses 1.0 part SP, 96 parts negative electrode graphite, and 1.5 parts CMC+SBR mixed adhesive. The positive and negative electrode slurries are coated on 13μm aluminum foil and 6μm copper foil respectively, dried and shaped, and their areal densities are adjusted. After cold rolling, slitting, positive and negative electrode sheeting, winding, casing, tab welding, roller grooving, liquid injection and sealing, and standing for formation and capacity testing, a ~2500 mAh 18650 cylindrical lithium-ion battery is prepared.

[0032] Performance testing: Two 18650 cylindrical lithium-ion batteries from Example 1 and Comparative Example 1 were taken as two replicates. They were charged at 25 °C with a constant current of 1 C or 4 A, then switched to constant voltage charging with a cutoff current of 0.02 C. After resting for 10 min, they were discharged at 20 A. After discharge, they were rested for 10 min. Cyclic tests were performed according to this resting and charge-discharge method, with a voltage range of 2.5 V to 4.2 V.

[0033] As shown in Table 1, the battery of Example 1 retains 84-86% of its capacity after 500 cycles, while the battery of Comparative Example 1 decays to approximately 80% after 200 cycles. This demonstrates that the technical solution of the present invention significantly improves the charging and discharging performance at higher rates. The results indicate that the ternary lithium-ion battery provided in this embodiment has the advantages of high rate capability, high capacity, and long cycle life, and exhibits significant advantages in high-current cycling.

[0034] Table 1. Comparison of room temperature capacity retention (1 C or 4 A charge 8 C discharge) of 18650 type 2.5 Ah ternary lithium-ion batteries

[0035] Example 2: A high-rate, high-capacity, long-cycle ternary lithium-ion battery of the present invention includes a positive electrode, a negative electrode, a separator, and an electrolyte, and is prepared by the following method: (1) Preparation of the positive electrode: According to the mass parts, take 1.2 parts of conductive carbon black (SP), 0.1 parts of single-walled carbon nanotubes (CNT), 1.2 parts of polyvinylidene fluoride (PVDF), and 97.9 parts of ternary nickel-cobalt-manganese main material, mix them to form a dry powder, blow and press it onto a 150 μm thick foamed aluminum substrate, then extrude and mold it, coat it with a PVDF oil-based (NMP) adhesive solution with a solid content of 1%, and dry and mold it again to obtain a positive electrode with an areal density of 1.22 g / dm. 2 Electrode sheets with a width of 57 mm are cold-rolled to a density of 3.40 g / cm³. 3 Compacted positive electrode sheet.

[0036] (2) Preparation of negative electrode sheet: According to the mass parts, take 1.3 parts conductive carbon black (SP), 0.1 parts single-walled carbon nanotubes (CNT), 0.2 parts sodium carboxymethyl cellulose (CMC), 0.4 parts styrene-butadiene rubber (SBR), 1.6 parts polyacrylic acid (PAA) adhesive, and 96.4 parts negative electrode active material (specific capacity of 400-460 mAh / g); the negative electrode active material is a composite of 8.5 parts silicon-based material and 87.9 parts 4-6 C-type rate-multiplier graphite, mixed to form a dry powder, blown onto a 160 μm thick foamed aluminum substrate, extruded and molded, coated with an aqueous adhesive of CMC / SBR / PAA with a solid content of 25.5%, and dried and molded again to obtain a negative electrode surface density of 0.55 g / dm. 2 Electrode sheets with a width of 59 mm are cold-rolled to a density of 1.56 g / cm³. 3 Compacted negative electrode sheet.

[0037] (3) Preparation of the isolation membrane: Take a 13 μm thick polypropylene (PP) base film and coat two 1 μm Al2O3 ceramic coating layers on both sides to obtain a 15 μm PP base film-Al2O3 ceramic coating layer isolation membrane.

[0038] (4) Preparation of electrolyte: Take 88 parts by mass of carbonate-based solvent, 10 parts of lithium hexafluorophosphate, 0.5 parts of vinylene carbonate, 0.5 parts of vinyl sulfate, 0.5 parts of fluoroethylene carbonate and 0.5 parts of lithium difluorophosphate; wherein the carbonate-based solvent is composed of vinyl carbonate and methyl ethyl carbonate in a mass ratio of 1:1.

[0039] (5) Assembly of ternary lithium-ion battery: The above positive and negative electrode sheets are de-powdered at the tab position and welded to the current collector. After welding and coating treatment, they are aligned with the separator, stacked (8 positive and 9 negative) and welded to the current collector. They are then put into the shell, sealed, and injected with the above electrolyte. The electrolyte injection coefficient is 3.5 g / Ah. After the electrolyte injection is sealed, the battery is left to stand at room temperature for 24 h. Then, a pulse charging pretreatment of 10 C rate is performed for 5 min. The pulse charging method is as follows: charge at 10 C rate for 1 s and then stand for 20 s, then charge at 10 C rate for 1 s and then stand for 20 s. Repeat the charging and standing steps until the total pulse charging pretreatment time is 5 min. Then, conventional formation is performed to prepare a 75120XX soft-pack lithium-ion battery with a capacity of ~2500 mAh, which is the ternary lithium-ion battery of the present invention.

[0040] Comparative Example 2 A lithium-ion battery is prepared by the following method: By weight, the positive electrode uses 1.7 parts SP, 97.0 parts ternary nickel-cobalt-manganese main material, and 1.3 parts PVDF binder; the negative electrode uses 1.0 part SP, 96 parts negative electrode graphite, and 1.5 parts CMC+SBR mixed adhesive. The positive and negative electrode slurries are coated on 13μm aluminum foil and 6μm copper foil respectively, dried and shaped, and their areal densities are adjusted. After cold rolling, cutting, die cutting of positive and negative electrodes, stacking, tab welding and adhesive application, casing, side sealing, liquid injection and sealing, and standing for formation and capacity testing, a 75120XX soft-pack lithium-ion battery with a capacity of ~2500mAh is prepared.

[0041] Performance testing: Two 75120XX soft-pack lithium-ion batteries obtained in Example 2 and Comparative Example 2 were taken as two replicate groups. They were charged at 25 °C with a constant current of 1 C or 4 A and then switched to constant voltage charging. The cutoff current was 0.02 C. After resting for 10 min, they were discharged at 20 A. After the discharge was completed, they were rested for 10 min. Cyclic tests were carried out according to this resting and charge-discharge method. The voltage range was 2.5 V to 4.2 V.

[0042] As shown in Table 2, the battery of Example 2 retains approximately 85% of its capacity after 700 cycles, while the battery of Comparative Example 2 decays to approximately 80% after 400 cycles. This demonstrates that the technical solution of the present invention significantly improves the rate-controlled charging and discharging performance. The results indicate that the ternary lithium-ion battery provided in this embodiment has the advantages of high rate capability, high capacity, and long cycle life, and exhibits significant advantages in high-current cycling.

[0043] Table 2. Comparison of Capacity Retention Rate of 2.5 Ah Ternary Lithium-ion Batteries of Model 75120XX at Room Temperature (1 C Charge, 8 C Discharge)

[0044] Example 3 A high-rate, high-capacity, long-cycle ternary lithium-ion battery of the present invention includes a positive electrode, a negative electrode, a separator, and an electrolyte, and is prepared by the following method: (1) Preparation of the positive electrode: According to the mass parts, take 1.5 parts of conductive carbon black (SP), 0.15 parts of single-walled carbon nanotubes (CNT), 1.2 parts of polyvinylidene fluoride (PVDF), and 97.15 parts of ternary nickel-cobalt-manganese main material, mix them to form a dry powder, blow and press it onto a 160 μm thick foamed aluminum substrate, then extrude and mold it, coat it with a PVDF oil-based (NMP) adhesive solution with a solid content of 1%, and dry and mold it again to obtain a positive electrode with an areal density of 1.21 g / dm. 2 Electrode sheets with a width of 57 mm are cold-rolled to a density of 3.35 g / cm. 3 Compacted positive electrode sheet.

[0045] (2) Preparation of negative electrode sheet: According to the mass parts, take 1.5 parts conductive carbon black (SP), 0.15 parts single-walled carbon nanotubes (CNT), 0.2 parts sodium carboxymethyl cellulose (CMC), 0.4 parts styrene-butadiene rubber (SBR), 1.8 parts polyacrylic acid (PAA) adhesive, and 95.95 parts negative electrode active material (specific capacity of 400-460 mAh / g); the negative electrode active material is a composite of 9.5 parts silicon-based material and 86.45 parts 4-6 C type rate-type graphite, mixed to form a dry powder, blown onto a 160 μm thick foamed aluminum substrate, extruded and molded, coated with an aqueous adhesive of CMC / SBR / PAA with a solid content of 25.2%, and dried and molded again to obtain a negative electrode with an areal density of 0.55 g / dm. 2 Electrode sheets with a width of 59 mm are cold-rolled to a density of 1.52 g / cm³. 3 Compacted negative electrode sheet.

[0046] (3) Preparation of the isolation membrane: Take a 13 μm thick polypropylene (PP) base film and coat two 1 μm Al2O3 ceramic coating layers on both sides to obtain a 15 μm PP base film-Al2O3 ceramic coating layer isolation membrane.

[0047] (4) Preparation of electrolyte: Take 88 parts by mass of carbonate-based solvent, 10 parts of lithium hexafluorophosphate, 0.5 parts of vinylene carbonate, 0.5 parts of vinyl sulfate, 0.5 parts of fluoroethylene carbonate and 0.5 parts of lithium difluorophosphate; wherein the carbonate-based solvent is composed of vinyl carbonate and methyl ethyl carbonate in a mass ratio of 1:1.

[0048] (5) Assembly of ternary lithium-ion battery: The above positive and negative electrode sheets are de-powdered at the tab position and welded to the current collector. After welding and encapsulation, they are aligned with the separator, wound, inserted into the shell, the tab is welded, and the roller groove is filled with the above electrolyte. The electrolyte injection coefficient is 2.0 g / Ah. After the electrolyte injection is sealed, the battery is left to stand at room temperature for 24 h, and then subjected to a 10C rate pulse charging pretreatment for 5 min. The pulse charging method is as follows: charge at 10C rate for 1 s and then stand for 20 s, then charge at 10C rate for 1 s and then stand for 20 s, and so on, repeating the charging and standing steps until the total pulse charging pretreatment time is 5 min. Then, it is converted to conventional formation to prepare a 18650 cylindrical lithium-ion battery with a capacity of ~2500 mAh, thus obtaining the ternary lithium-ion battery of the present invention. Comparative Example 3 A lithium-ion battery is prepared by the following method: By weight, the positive electrode uses 1.7 parts SP, 97.0 parts ternary main material, and 1.3 parts PVDF binder; the negative electrode uses 1.0 part SP, 96 parts negative electrode graphite, and 1.5 parts CMC+SBR mixed adhesive. The positive and negative electrode slurries are coated on 13μm aluminum foil and 6μm copper foil respectively, dried and shaped, and their areal densities are adjusted. After cold rolling, slitting, positive and negative electrode sheeting, winding, casing, tab welding, roller grooving, liquid injection and sealing, and standing for formation and capacity testing, a ~2500mAh 18650 cylindrical lithium-ion battery is prepared.

[0049] Performance testing: Two 18650 cylindrical lithium-ion batteries from Example 3 and Comparative Example 3 were taken as two replicate groups. They were charged at 4 C constant current at 25 °C and then switched to constant voltage charging with a cutoff current of 0.02 C. After resting for 10 min, they were discharged at 1 C constant current. After the discharge was completed, they were rested for 10 min. Cyclic tests were performed according to this resting and charge-discharge method, with a voltage range of 2.5 V to 4.2 V.

[0050] As shown in Table 3, the battery in Example 3 retains approximately 90% of its capacity after 1000 cycles, while the battery in Comparative Example 3 decays to approximately 80% after 800 cycles, demonstrating a significant improvement in rate charging performance. These results indicate that the ternary lithium-ion battery provided in this embodiment possesses advantages such as high rate capability, high capacity, and long cycle life, exhibiting a clear advantage in high-current cycling.

[0051] Table 3. Comparison of Capacity Retention Rate of 18650 Type 2.5 Ah Ternary Lithium-ion Batteries at Room Temperature During Fast Charging (4 C Charge, 1 C Discharge)

[0052] In summary, the ternary silicon-based lithium-ion battery process formulation and preparation method provided by this invention, as well as the lithium-ion battery using this integrated system, have the following outstanding advantages: Compared with traditional graphite anodes, the capacity of the silicon-based anode provided by this invention is increased from ~350 mAh / g to 400-500 mAh / g, and the capacity of the 18650 ternary lithium-ion battery is increased from 2.0 Ah to 2.5 Ah and 3.0 Ah, respectively, with service life increased by 25% and 50%. Compared with the gradually commercialized silicon-based anode materials, this invention elevates the use of silicon-based materials to a new level. The cycle performance can completely replace traditional graphite, and the high-current cycle capability of the battery is comparable to that using pure graphite anodes. The cycle period is twice that of similar products, greatly extending the battery replacement frequency and application areas. For power tool batteries, the key parameter is high-current discharge capability. The fast ion electron channel provided by this integrated system greatly shortens the charging time from several hours to a few minutes, innovatively solving the charging capability problem of rate-capable batteries. It has strong high-current charging capability and achieves high power in both directions. Furthermore, the process integration provided by this invention is simple and economical, requiring no additional equipment and exhibiting strong production adaptability. It can be widely used in electric shavers, drones, VR devices, etc., and has great promotional value.

Claims

1. A high-rate, high-capacity, long-cycle ternary lithium-ion battery, comprising a positive electrode, a negative electrode, a separator, and an electrolyte, characterized in that, The positive electrode sheet comprises a current collector, a positive electrode active material, a positive electrode conductive agent, and a positive electrode binder, wherein the mass ratio of the positive electrode active material, the positive electrode conductive agent, and the positive electrode binder is 97.0–98.4:0.8–1.7:0.8–1.3; the positive electrode active material is ternary lithium nickel cobalt manganese oxide or lithium nickel cobalt aluminum oxide; the positive electrode conductive agent is a composite conductive agent obtained by mixing single-walled carbon nanotubes and conductive carbon black in a mass ratio of 5–10:90–95; and the positive electrode binder is polyvinylidene fluoride. The negative electrode sheet comprises a current collector, a negative electrode active material, a negative electrode conductive agent, and a negative electrode binder. The mass ratio of the negative electrode active material, the negative electrode conductive agent, and the negative electrode binder is 95.7–97.8:1.0–1.7:1.2–2.

6. The negative electrode active material is a composite material obtained by mixing silicon-based materials and 4–6 C-type rate-multiplied graphite at a mass ratio of 5–9:91–95. The negative electrode conductive agent is a composite conductive agent obtained by mixing single-walled carbon nanotubes and conductive carbon black at a mass ratio of 8–15:85–92. The negative electrode binder is a mixed adhesive obtained by mixing sodium carboxymethyl cellulose, styrene-butadiene rubber, and polyacrylic acid at a mass ratio of 1.0–1.5:2.0–2.5:6.0–8.

0.

2. The ternary lithium-ion battery according to claim 1, characterized in that, The current collector of the positive electrode and / or the negative electrode is a foamed metal, which is selected from at least one of foamed nickel, foamed copper and foamed aluminum.

3. The ternary lithium-ion battery according to claim 1, characterized in that, The positive electrode sheet is prepared by the following method: the dry powders of the positive electrode active material, positive electrode conductive agent and positive electrode binder are mixed and blown onto a current collector with a thickness of 90 to 180 μm, then extruded and shaped, coated with adhesive, and dried and shaped again to obtain the positive electrode sheet. The negative electrode sheet is prepared by the following method: the dry powders of the negative electrode active material, negative electrode conductive agent and negative electrode binder are mixed and blown onto a current collector with a thickness of 90 to 180 μm, then extruded and shaped, coated with adhesive, and dried and shaped again to obtain the negative electrode sheet.

4. The ternary lithium-ion battery according to claim 3, characterized in that, The N / P ratio of the negative electrode to the positive electrode is 1.01 to 1.

10.

5. The ternary lithium-ion battery according to claim 1, characterized in that, The silicon-based material is a silicon-oxygen material, a silicon-oxygen material pre-treated with magnesium, a silicon-oxygen material pre-treated with lithium, or a silicon-carbon material after sand milling. The core of the silicon-based material is amorphous silicon or silicon grains with a grain size ≤2 nm, and the core is surrounded by a carbon shell of 2 to 6 μm.

6. The ternary lithium-ion battery according to claim 1, characterized in that, The specific capacity of the negative electrode active material is 400–500 mAh / g, and the specific surface area of ​​the 4–6 C type rate-adjustable graphite is 1.5–2.5 m². 2 / g.

7. The ternary lithium-ion battery according to claim 1, characterized in that, The separator has a thickness of 9–15 μm and includes a base film and a coating layer with a thickness of 0.1–3 μm; the base film is at least one of polypropylene, polyethylene, and polyethylene oxide; the coating layer is made of at least one of aluminum oxide, aramid, and rare earth oxides.

8. The ternary lithium-ion battery according to claim 1, characterized in that, The electrolyte comprises, by mass percentage, 81.6 wt%–88.3 wt% of carbonate-based solvent, 10.0 wt%–14.0 wt% of lithium hexafluorophosphate, 0.5 wt%–1.2 wt% of vinylene carbonate, 0.5 wt%–1.2 wt% of vinyl sulfate, 0.5 wt%–1.2 wt% of fluoroethylene carbonate, and 0.2 wt%–0.8 wt% of lithium difluorophosphate; the carbonate-based solvent is composed of vinyl carbonate and methyl ethyl carbonate in a mass ratio of 0.3–1.5:

1.

9. A method for preparing a high-rate, high-capacity, long-cycle ternary lithium-ion battery, characterized in that, Includes the following steps: (1) The positive electrode sheet, separator, and negative electrode sheet as described in any one of claims 1-8 are used to form a battery cell by winding or stacking. (2) The battery cell obtained in step (1) is installed into the housing and injected with the electrolyte as described in any one of claims 1-8; (3) After the battery is filled with electrolyte in step (2), it is placed at 40-50 °C for 4-8 h or at room temperature for 20-28 h, and then subjected to a 10C rate pulse charging pretreatment for 5 min; the pulse charging method is: charge at 10C rate for 1 s and then place for 20 s, and repeat the charging and placing steps. (4) The battery after step (3) is placed under formation treatment to obtain the ternary lithium-ion battery.

10. The preparation method according to claim 9, characterized in that, The electrolyte injection coefficient is 1.5 to 3.5 g / Ah.

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