Lithium ion battery with high-stability electrode

Abstract

The present invention provides a lithium ion battery comprising a positive electrode comprising one or more nickel-rich ternary positive electrode materials, more particularly, the material is LiNixMnyCozO2 or LiNixAlyCozO2, where the sum of x, y and z is 1 and x is at least 0.8. The battery further comprises a negative electrode made of silicon, silicon oxide, carbon nanotubes, metal lithium, graphene, graphite and other materials, a porous polymer diaphragm with the porosity of 30%-90%, and an electrolyte. More particularly, the nickel-rich positive electrode material also comprises a gel-free adhesive, the adhesive is modified polyvinylidene fluoride (PVDF) grafted with a monomer, the monomer contains at least one unsaturated carbon-carbon double bond and a functional group, and defluorination and crosslinking can be prevented when the polyvinylidene fluoride is in contact with the nickel-rich positive electrode material through modification.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. Patent Application 18 / 894,017, filed September 24, 2024, and the disclosure of which is incorporated herein by reference in its entirety. TECHNICAL FIELD

[0002] The present invention relates to lithium-based batteries. More specifically, the present invention relates to lithium-ion batteries with high-stability electrodes. BACKGROUND

[0003] In recent years, rechargeable lithium-ion batteries have dominated the energy market due to the rising environmental awareness and the goal of achieving carbon neutrality. From portable electronic devices to electric vehicles, lithium-ion batteries are used, and therefore, how to improve the energy density of lithium-ion batteries is quite important to solve the endurance problem of electric vehicles. Several common strategies currently under development include replacing graphite with metal lithium as the negative electrode, developing solid-state electrolytes, and using high-nickel content ternary systems as positive electrode materials.

[0004] Due to the limited specific capacity of current positive electrode materials, the high specific capacity (3860 milliampere hours per gram) of lithium metal negative electrodes has not yet been fully realized. Since the 1980s, LiCoO2 has been commonly used as a positive electrode material, but due to the high cost of cobalt and its relatively low capacity, its application is limited, and therefore, replacing cobalt in the layered structure with other transition metals can improve battery performance. For example, Li[Ni x Co y Mn z ]O2(x+y+z=1) (NCM) or Li[Ni x Co y Al z ]O2(x+y+z=1) (NCA) has the characteristics of high capacity and high voltage, and the specific capacity (milliampere hours per gram) of NCM increases with the increase of nickel content. Rich nickel NCM ternary positive electrode materials with high reversible capacity, such as NCM811 or NCA811, are considered an ideal choice to enhance the energy density of the next generation of lithium metal batteries.

[0005] Polyvinylidene fluoride (PVDF) is one of the most commonly used binders in positive electrodes because of its unique properties, such as high chemical resistance, good thermal stability, excellent processability, and excellent mechanical properties. However, when used as a binder for nickel-rich positive electrodes, there are still several problems to be solved.

[0006] Firstly, the rich nickel positive electrode slurry gels quickly. The common method of manufacturing NCM positive electrodes includes mixing active material (NCM powder), conductive carbon and polyvinylidene fluoride binder with a suitable solvent (usually N-methyl pyrrolidone) to form a uniform positive electrode slurry; then the slurry is coated onto an aluminum foil and dried thoroughly; the resulting electrode is then pressed or calendered to the desired porosity and punched into the desired shape. However, the high nickel content in the layered oxide causes LiNiO2 to become unstable, resulting in the formation of LiOH or Li2CO3, which is one of the main obstacles to the commercialization of rich nickel positive electrode materials. In the mass production process, these impurities will cause the pH value of the electrode slurry to rise, triggering the cross-linking of polyvinylidene fluoride (PVDF) and causing the slurry to gel, which will increase the difficulty of controlling the electrode preparation process on a large-scale production line, as the viscosity of the gel will change in an unpredictable manner. Figure 1

[0007] Methods for improving the stability of the positive electrode slurry include, for example, US20210043938A1, by adding oxalic acid to the positive electrode slurry to reduce the pH value to improve stability, however, oxalic acid itself is an impurity that can have side effects on battery performance; US009257696B2 and US9343744B2 use tetrafluoroethylene (TFE) and / or hexafluoropropylene (HFP) as monomers to synthesize P(VDF-co-TFE-co-HFP) to try to replace some hydrogen atoms with fluorine atoms to increase its resistance to defluorination, thereby improving the stability of the slurry, however, these monomers are harmful substances in themselves and must be synthesized under high pressure, the preparation process is dangerous, in addition, the addition of tetrafluoroethylene and hexafluoropropylene can increase the viscosity of the slurry and reduce the adhesion of the binder.

[0008] Secondly, the polyvinylidene fluoride binder has insufficient bonding strength. During the charge and discharge cycle of the battery, the positive electrode material will undergo volume shrinkage and expansion, causing strain fatigue of the electrode, so the bonding strength between the active material and the current collector and the flexibility of the electrode must be high enough to prolong the life of the battery. Polyvinylidene fluoride is a semi-crystalline thermoplastic fluoropolymer with low polarity, so its adhesion is insufficient, especially when used to prepare a rich nickel positive electrode. US20190252685A1 and patent WO2008129041A1 attempt to incorporate a small amount of acrylic acid (AA) or methacrylic acid (MAA) into polyvinylidene fluoride, however, this synthesis process is also carried out under high pressure, and the content of acrylic acid or methacrylic acid is too low (<5%), and the final effect is not very ideal.

[0009] ​Third, transition metals are easily dissolved from nickel-rich NCM cathode materials during battery charge-discharge cycles. Since the dissolution of transition metal ions from the nickel-rich cathode into the electrolyte is unavoidable, the reduction in lithium-ion insertion sites in the main structure leads to a rapid decrease in capacity, and this process is accelerated under high temperature and high operating voltage conditions.

[0010] Therefore, although some, such as those containing Co 2+ Mn 2+ and Ni 2+ The binding energy of the carboxylic acid, sulfonic acid and amide functional groups of polyvinylidene fluoride is higher than that of polyvinylidene fluoride, but the art is still looking for new adhesive materials and formulations to provide better chemical stability to effectively overcome the above-mentioned technical obstacles, and the present invention meets this need. Summary of the Invention

[0011] This invention provides a lithium-ion battery with a highly stable electrode to solve the above-mentioned technical problems.

[0012] According to a first aspect of the present invention, a lithium-ion battery is provided. The lithium-ion battery comprises: The cathode includes one or more nickel-rich ternary cathode materials having the following chemical formula: LiNi x Mn y Co z O2 or LiNi x Al y Co z O2, wherein the sum of x, y and z is equal to 1, and x is greater than or equal to 0.8; the positive electrode also includes one or more conductive agents and a gel-free binder; The negative electrode includes one or more materials selected from silicon, silicon oxide, carbon nanotubes, lithium metal, graphene, or graphite. At least one porous polymer membrane having a porosity of about 30% to 90%; and Electrolytes.

[0013] According to one embodiment of the present invention, the gel-free adhesive is modified polyvinylidene fluoride grafted with one or more monomers, wherein the monomers include at least one unsaturated carbon-carbon double bond and one or more functional groups, so that when the modified polyvinylidene fluoride is in contact with nickel-rich cathode material, no defluorination and crosslinking reactions occur.

[0014] According to one embodiment of the present invention, the functional group is selected from acrylic acid group, methacrylic acid group, phosphate group, polyethylene glycol group, sulfonic acid group, sulfuric acid group, sulfite group or cyano group.

[0015] According to one embodiment of the present invention, the gel-free adhesive can promote the formation of an inorganic-rich positive electrode electrolyte interface on the positive electrode surface.

[0016] According to one embodiment of the present invention, the gel-free adhesive has a molecular weight of at least 1.1 x 10⁻⁶. 6 Dalton.

[0017] According to one embodiment of the present invention, the lithium fluoride / carbonyl group ratio and the lithium fluoride / lithium carbonate ratio at the inorganic-rich positive electrode electrolyte interface are greater than 1.0 and greater than 2.0.

[0018] According to an embodiment of the present invention, a method for preparing the modified polyvinylidene fluoride grafted with one or more monomers includes: Activate the polyvinylidene fluoride backbone to generate reaction sites thereon; and One or more monomers are grafted onto the reaction site.

[0019] According to one embodiment of the present invention, the polyvinylidene fluoride backbone is activated by ozone treatment, plasma treatment, ultraviolet treatment or gamma ray irradiation treatment.

[0020] According to one embodiment of the present invention, the grafting process is carried out in water or a water / alcohol solution.

[0021] According to one embodiment of the present invention, the grafting process is carried out in an inert gas, the reaction temperature ranges from 40°C to 80°C, and the reaction time is from 1 to 50 hours.

[0022] According to one embodiment of the present invention, the gel-free adhesive improves the thermal stability of the positive electrode to 120°C.

[0023] According to one embodiment of the present invention, the specific energy density of the battery is at least 300 Wh / kg. Attached Figure Description

[0024] Referring to the accompanying drawings, embodiments of the present invention will be described in more detail below, wherein:

[0025] Figure 1 The crosslinking mechanism of polyvinylidene fluoride under alkaline conditions was demonstrated, which leads to gelation of the positive electrode slurry.

[0026] Figure 2 The preparation process of modified polyvinylidene fluoride is shown;

[0027] Figure 3 Fourier transform infrared absorption spectra of commercially available lithium battery binder (HSV900) and modified polyvinylidene fluoride;

[0028] Figure 4The peel force test between the positive electrode active material and the aluminum current collector is shown, using commercially available lithium battery binder (HSV900) and modified polyvinylidene fluoride as binders respectively.

[0029] Figures 5A-5B The initial coulombic efficiencies of coin cells using commercially available lithium-ion battery binder (HSV900) and modified polyvinylidene fluoride as positive electrode binders are shown. Figure 5A ) and the first cycle charge-discharge curve ( Figure 5B );as well as

[0030] Figure 6 The discharge rate tests of button batteries using commercially available lithium battery binder (HSV900) and modified polyvinylidene fluoride as positive electrode binders are shown. Detailed Implementation

[0031] In the following description, lithium-ion batteries with highly stable electrodes are listed as preferred embodiments. It will be apparent to those skilled in the art that modifications, including additions and / or substitutions, can be made without departing from the scope and spirit of the invention. Specific details may be omitted below to avoid obscuring the invention; however, this document is prepared to enable those skilled in the art to practice the techniques disclosed herein without excessive experimentation.

[0032] In lithium-ion battery electrodes, the binder plays a specific structural role within the electrode. The following provides a detailed explanation of the structural relationships between the binder, the positive electrode, and the electrolyte.

[0033] The positive electrode consists of active material particles (such as nickel-rich ternary compounds like NCM or NCA), conductive additives (such as carbon black), and a binder (such as polyvinylidene fluoride). The active material is responsible for storing and releasing lithium ions during charge-discharge cycles; the conductive additives ensure good conductivity within the electrode; and the binder is a polymer that bonds the active material and conductive additives together, providing mechanical integrity and flexibility to the electrode. Therefore, the binder ensures a tight bond between the electrode particles and between them and the current collector (typically aluminum foil), thus maintaining the structural integrity of the electrode over multiple cycles.

[0034] During the initial charge-discharge cycle, the electrolyte on the positive electrode surface decomposes to form the positive electrode electrolyte interface, which is a passivation layer located on the surface of the positive electrode particles and composed of inorganic and organic compounds (such as lithium fluoride and lithium carbonate). This helps protect the positive electrode from further electrolyte decomposition and stabilizes the electrode / electrolyte interface.

[0035] In summary, the binder is a crucial component of the positive electrode solid structure, maintaining the integrity and stability of the electrode, while the electrolyte facilitates ion transport. The positive electrode-electrolyte interface, formed between the positive electrode material and the electrolyte, also plays a vital role in the overall performance and lifespan of the battery.

[0036] According to a first aspect of the present invention, a lithium-ion battery is provided. This lithium-ion battery includes several specific components to enhance its performance and stability. A core component of the invention is a positive electrode, comprising one or more nickel-rich ternary positive electrode materials selected from those having LiNi... x Mn y Co z O2 or LiNi x Al y Co z The key feature of O2 chemical formula materials, particularly nickel-rich materials, is that they have higher energy density and better performance characteristics than traditional cathode materials. In these chemical formulas, the sum of x, y, and z is equal to 1, and x is greater than or equal to 0.8 to ensure a high nickel content, thereby improving the specific capacity of the cathode.

[0037] The positive electrode also contains one or more conductive agents to improve conductivity and employs a gel-free binder. As used herein, "gel" refers to a semi-solid material whose consistency ranges from soft and brittle to hard and robust. A gel is characterized by being primarily composed of a diluted cross-linked system and does not flow in a steady state, although its liquid components can still move through the network. While primarily composed of liquid, the gel exhibits solid-like characteristics due to the three-dimensional cross-linked network within the liquid. Cross-linking imparts structure and adhesive properties to the gel, making it a liquid molecule dispersed within a solid framework. Therefore, a "gel-free" binder indicates that it does not possess the aforementioned cross-linking properties, thus exhibiting predictable rheological properties and allowing for the production of positive electrodes via automated machine manufacturing techniques.

[0038] To produce a gel-free cathode, this invention employs modified polyvinylidene fluoride (PVDF) using a modified binder grafted with one or more monomers. This gel-free binder addresses common issues in battery manufacturing, such as slurry stability and electrode performance. The monomers grafted onto the PVDF include at least one unsaturated carbon-carbon double bond and various functional groups, thus preventing defluorination and crosslinking of the modified PVDF upon contact with nickel-rich cathode materials. These functional groups include acrylic acid, methacrylic acid, phosphoric acid, polyethylene glycol, sulfonates, sulfates, sulfites, and cyano groups, which enhance the binder's adhesion and chemical stability.

[0039] In some embodiments, the monomer includes, but is not limited to, acrylic acid, methacrylic acid, 2-acrylamido-2-methylpropanesulfonic acid, 2-hydroxyethyl methacrylate phosphate, acrylonitrile, 2-(trifluoromethyl)acrylic acid, potassium salt of 3-sulfopropyl methacrylate, and polyethylene glycol monomethyl ether methacrylate.

[0040] The negative electrode of this battery comprises one or more materials selected from silicon, silicon oxide, carbon nanotubes, lithium metal, graphene, or graphite. These materials possess high capacity and stability, effectively improving the overall performance of the battery. The battery also includes a porous polymer separator with a porosity of approximately 30-90% to physically separate the positive and negative electrodes while simultaneously allowing ion conduction, contributing to the battery's safety and efficiency.

[0041] In addition, this lithium-ion battery also includes an electrolyte, which is crucial for ion transport between the positive and negative electrodes. Besides providing mechanical support, the gel-free binder facilitates the formation of an inorganic-rich positive electrode electrolyte interface layer on the positive electrode surface, enhancing battery stability and performance. Specifically, this inorganic-rich positive electrode electrolyte interface layer has a lithium fluoride / carbonyl group ratio greater than 1.0 and a lithium fluoride / lithium carbonate ratio greater than 2.0.

[0042] The gel-free adhesive has a molecular weight of at least 1.1 x 10⁻⁶. 6 The Dalton scale is used to ensure sufficient mechanical strength and flexibility. The process of grafting monomers onto polyvinylidene fluoride (PVDF) to prepare modified PVDF includes activating PVDF to generate active sites. Activation of PVDF can be achieved primarily through methods such as ozone treatment, plasma treatment, ultraviolet treatment, or gamma ray radiation treatment. Once activated, the monomers can be grafted onto the active sites in an inert gas environment in water or water / alcohol solution at a reaction temperature of 40-80°C for a reaction time of 1-50 hours.

[0043] like Figure 2 The process of grafting monomers onto the polyvinylidene fluoride (PVDF) backbone will be further explained below. This process comprises two steps: the first step involves activating PVDF through ozone treatment, plasma treatment, ultraviolet treatment, or gamma ray radiation, generating active sites (such as free radicals) on the PVDF backbone; the second step involves grafting the monomers onto the active sites of the activated PVDF as side chains via free radical polymerization. The monomers contain carbon-carbon double bonds in their chemical structure, which enable free radical polymerization with the active sites of the activated PVDF, as well as functional groups that contribute to the adhesive's performance.

[0044] In some embodiments, since the grafting process involves free radical polymerization, it is carried out in an inert gas (such as nitrogen or argon). Depending on the solubility of the monomer in water or a water / alcohol mixture, the process may be carried out in an aqueous or water / alcohol solution. The preferred concentration range of the monomer in the solution is 50-500 g / L, more preferably 100-300 g / L; the ideal reaction temperature range is 40-100°C, more preferably 40-80°C; the preferred reaction time is 1-50 hours, more preferably 4-24 hours. After the reaction is complete, unreacted monomers are removed by repeated washing with water or water / alcohol, and the mixture is dried at 60-100°C to obtain modified polyvinylidene fluoride.

[0045] Furthermore, the gel-free binder enhances the thermal stability of the positive electrode, enabling it to operate effectively at temperatures up to 120°C. This thermal stability is crucial for maintaining battery performance and safety under a variety of operating conditions. In addition, the described lithium-ion battery achieves a specific energy density of at least 300 Wh / kg, making it highly efficient in applications requiring high energy density, such as electric vehicles and portable electronic devices.

[0046] Overall, the detailed structure and composition of the lithium-ion battery provided by this invention represent a significant advancement in terms of energy density, thermal stability, and fabrication feasibility, overcoming many limitations in current battery technology.

[0047] Example

[0048] Example 1: Preparation of modified polyvinylidene fluoride

[0049] To prepare modified polyvinylidene fluoride (PVDF-25), 3 grams of HSV900 (a polyvinylidene fluoride with a molecular weight of approximately 900,000 Daltons) were weighed and treated with ozone at room temperature for 60 minutes, with an oxygen flow rate set at 5 liters / minute, resulting in an ozone concentration of approximately 60 g / m³. After ozone treatment, HSV900 was placed in a three-necked flask equipped with a thermocouple and a nitrogen inlet; subsequently, 10 grams of 2-(trifluoromethyl)acrylic acid and 80 grams of deionized water were added to the flask. The solution containing HSV900 was purged with nitrogen for 40 minutes to remove any residual oxygen or ozone, and then the temperature of the solution was raised to 80°C, and grafting was performed under nitrogen protection. After 6 hours, the solution was cooled to room temperature, and the modified polyvinylidene fluoride (PVDF-25) was recovered by filtration and washed at least three times with copious amounts of deionized water to remove unreacted monomers. Finally, PVDF-25 was dried at 80°C for 10 hours.

[0050] Fourier transform infrared spectroscopy tests were performed on HSV900 and PVDF-25. Figure 3The 1710 cm⁻¹ was not observed in the spectrum of the HSV900. -1 The absorption peak at 1710 cm⁻¹ is observed in the spectrum of PVDF-25; in contrast, the absorption peak at 1710 cm⁻¹ is observed in the spectrum of PVDF-25. -1 A small peak can be observed at this point. The appearance of this peak is due to the carbonyl group of 2-(trifluoromethyl)acrylic acid, which further confirms the successful grafting of 2-(trifluoromethyl)acrylic acid onto polyvinylidene fluoride.

[0051] High-temperature gel permeation chromatography (GPC) of polyvinylidene fluoride (PVDF) was performed at 80 °C using an Agilent PL-GPC120 system. A gel permeation column (PLgel 10 μm MIXED-B 300 x 7.5 mm) was used, and PVDF was dissolved in dimethylformamide and passed through the column at a flow rate of 1 mL / min. Polystyrene was used as a calibration standard for GPC. HSV900 and PVDF-25 were tested using the above method. The results showed that the molecular weight of HSV900 ranged from 800,000 to 1,500,000 Daltons, while the molecular weight of PVDF-25 ranged from 1,100,000 to 1,650,000 Daltons, indicating that the molecular weight increased by approximately 8-50% after graft modification. The results are shown in Table 1.

[0052] Table 1. Weight-average molecular weight results of high-temperature gel permeation chromatography, and the molecular weight ratio of PVDF-25 to the original polyvinylidene fluoride HSV900.

[0053] Alternatively, another modified polyvinylidene fluoride (PVDF) grafted with different monomers is provided. In short, 3 grams of HSV900 with a molecular weight of approximately 900,000 Daltons were weighed and treated with oxygen plasma at room temperature for 9 minutes. The treated HSV900 was then placed in a three-necked flask equipped with a thermocouple and a nitrogen inlet, and 12 grams of potassium 3-sulfopropyl methacrylate and 80 grams of deionized water were added to the flask. Nitrogen gas was bubbled through the solution containing HSV900 for 40 minutes to remove residual oxygen; the solution temperature was then raised to 70°C, and grafting was performed under nitrogen protection. After 16 hours, the solution was cooled to room temperature, the treated PVDF was recovered by filtration, and washed at least three times with copious amounts of deionized water to remove any unreacted monomers. The treated PVDF was then soaked in copious amounts of 1M sulfuric acid for 24 hours to convert the potassium sulfonate into sulfonic acid. Afterwards, the polyvinylidene fluoride was washed with a large amount of deionized water at least three times and dried at 80°C for 16 hours. The final polyvinylidene fluoride obtained was the sample PVDF-29.

[0054] Similarly, Fourier transform infrared spectroscopy tests were performed on HSV900 and PVDF-29. Figure 3 In the spectrum of HSV900, it also does not have a 1710 cm⁻¹. -1 The peak at 1710 cm⁻¹ was observed in the spectrum of PVDF-29; however, a peak at 1710 cm⁻¹ appeared in the spectrum of PVDF-29. -1 The small peak indicates the presence of a carbonyl group with sulfonic acid, meaning that this method can successfully graft monomers onto polyvinylidene fluoride.

[0055] Example 2: Preparation of positive electrode slurry

[0056] A positive electrode slurry was prepared by mixing 0.6 g of HSV900 or PVDF-25, 0.5 g of Super P conductive material, 8.9 g of NCM811, and 13 g of N-methylpyrrolidone. To accelerate the gelation process, 500 ppm of water was added to the slurry. The slurry was then placed in a sealed container and left at room temperature. After ten days, gelation was observed in the slurry containing HSV900 binder, while the slurry using PVDF-25 as a binder maintained good flowability.

[0057] Additionally, a positive electrode slurry consisting of 0.6 g HSV900 or PVDF-25, 0.5 g Super P conductive material, 8.9 g NCM811, and 13 g N-methylpyrrolidone was coated onto an aluminum current collector, dried, and then calendered to prepare the positive electrode. Next, the peel force between the positive electrode material and the aluminum current collector was tested, and the results are as follows: Figure 4 As shown, the adhesion strength when using PVDF-25 as an adhesive is significantly higher than that of the HSV900 group.

[0058] In addition, the preparation of the positive electrode slurry for the PVDF-29 sample was also tested in the same way. A positive electrode slurry was prepared by mixing 0.6 g of PVDF-29, 0.5 g of Super P conductive material, 8.9 g of NCM811, and 13 g of N-methylpyrrolidone, and then coated onto an aluminum current collector. The slurry was dried and rolled into a positive electrode, and the peel force between the positive electrode material and the aluminum current collector was tested. The results are as follows: Figure 4 As shown, the adhesion strength when using PVDF-29 as an adhesive is significantly higher than that of HSV900.

[0059] In summary, using PVDF-25 and PVDF-29 as binders in the preparation of cathode slurries offers significant advantages. Unlike HSV900, PVDF-25 maintains good flowability of the cathode slurry, preventing gelation over time. Furthermore, both PVDF-25 and PVDF-29 provide stronger adhesion between the cathode material and the aluminum current collector, enhancing the mechanical stability of the electrode. Additionally, the modified polyvinylidene fluoride binder improves adhesion, contributing to enhanced electrode integrity and overall performance. These technical benefits make lithium-ion battery electrodes more reliable and efficient.

[0060] For example, X-ray photoelectron spectroscopy (XPS) was used to analyze the ratios of lithium fluoride / carbonyl groups and lithium fluoride / lithium carbonate. The composition of the cathode using binders PVDF-25-8 and HSV900 was analyzed at both the surface and 20 nm depth, and the results are shown in Table 2. The ratios of lithium fluoride (XPS peak 685 eV) to organic components (derived from the XPS carbon-oxygen peak 287.3 eV) and lithium fluoride to unstable lithium carbonate (derived from the XPS peak 532 eV) can be used to assess the stability of the cathode-electrolyte interface formed on the cathode surface. A lithium fluoride / carbonyl group ratio greater than 1.0 and a lithium fluoride / lithium carbonate ratio greater than 2.0 are preferred, indicating the formation of a stable cathode-electrolyte interface on the cathode surface.

[0061] Table 2. Peak ratios of lithium fluoride / carbonyl groups and lithium fluoride / lithium carbonate in cathodes with different binders, analyzed using XPS.

[0062] Example 3: Evaluation of the performance of batteries using HSV900, PVDF-25, or PVDF-29 as positive electrode binders.

[0063] The coulombic efficiency and charge-discharge curves of a coin cell fabricated using HSV900 and PVDF-25 as positive electrode binders and graphite as the negative electrode were measured during the first charge-discharge cycle. The results are as follows: Figures 5A-5B As shown, the battery using PVDF-25 as the positive electrode binder exhibits a higher coulombic efficiency compared to the battery using HSV900 as the positive electrode binder. Furthermore, in rate testing, the coin cell battery using PVDF-25 as the positive electrode binder shows better capacity retention at high rates (e.g., above 5C) compared to the battery using HSV900 as the binder. Figure 6 ).

[0064] Similarly, the coulombic efficiency and charge-discharge curves of the first charge-discharge cycle of a coin cell prepared with PVDF-29 as the positive electrode binder and graphite as the negative electrode were measured, and the results are as follows: Figures 5A-5BAs shown, compared to batteries using HSV900 as the positive electrode binder, batteries using PVDF-29 as the positive electrode binder exhibit higher coulombic efficiency. Furthermore, in rate testing, they also demonstrate better capacity retention at high rates (e.g., above 5C). Figure 6 ).

[0065] In summary, using PVDF-25 and PVDF-29 as cathode binders for lithium-ion batteries offers significant advantages in electrode fabrication. Compared to commercially available HSV900, both PVDF-25 and PVDF-29 significantly improve the coulombic efficiency of the battery. Furthermore, under high-rate conditions, the modified polyvinylidene fluoride binder of this invention also enhances capacity retention, indicating that PVDF-25 and PVDF-29 are suitable binder materials for improving the performance and efficiency of lithium-ion batteries.

[0066] As used herein, the terms “approximately,” “substantially,” “essentially,” and “about” are used to describe and explain a small variation. When used in conjunction with an event or situation, the term can refer to the exact occurrence of the event or situation, or approximately the occurrence of the event or situation. The term “about,” as used herein, regarding a given value or range, typically refers to a range of ±10%, ±5%, ±1%, or ±0.5% of the given value or interval, which can be understood herein as ranging from one endpoint to another or between two endpoints. Unless otherwise stated, all ranges disclosed in this disclosure include endpoints. Furthermore, unless explicitly stated otherwise, the term “a” as used herein should be understood to include one or more; additionally, terms such as “first,” “second,” and “third” are used only as illustrative purposes and are not intended to give numerical meaning or to order them according to their importance.

[0067] The above description is provided for the purpose of illustrating and describing the invention, and is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Many modifications and variations will be apparent to those skilled in the art.

[0068] The above embodiments were chosen and described in order to best explain the principles of the invention and its practical application, thereby enabling other skilled in the art to understand the various embodiments of the invention and the various modifications suitable for the intended particular use.

Claims

1. A lithium-ion battery, characterized in that, include: A cathode comprising one or more nickel-rich ternary cathode materials, said material having the following chemical formula: LiNi x Mn y Co z O2 or LiNi x Al y Co z O2, wherein the sum of x, y and z is equal to 1, and x is greater than or equal to 0.8; the positive electrode also includes one or more conductive agents and a gel-free binder; A negative electrode comprising one or more materials, wherein the materials are selected from silicon, silicon oxide, carbon nanotubes, lithium metal, graphene, or graphite; Porous polymer membranes with a porosity of at least 30-90%; and Electrolytes; The gel-free adhesive is modified polyvinylidene fluoride grafted with one or more monomers, wherein the monomers include at least one unsaturated carbon-carbon double bond and one or more functional groups. When the modified polyvinylidene fluoride is in contact with the nickel-rich ternary cathode material, no defluorination or crosslinking reaction occurs. The functional group is selected from acrylic acid group, methacrylic acid group, phosphate group, polyethylene glycol group, sulfonic acid group, sulfuric acid group, sulfite group or cyano group.

2. The lithium-ion battery of claim 1, wherein the gel-free binder promotes the formation of an inorganic-rich positive electrode electrolyte interface on the surface of the positive electrode.

3. The lithium-ion battery of claim 1, wherein the gel-free binder has a molecular weight of at least 1.1 x 10⁻⁶. 6 Dalton.

4. The lithium-ion battery of claim 2, wherein the lithium fluoride / carbon oxide ratio at the inorganic-rich positive electrode electrolyte interface is greater than 1.0 and the lithium fluoride / lithium carbonate ratio is greater than 2.

0.

5. The lithium-ion battery as described in claim 1, wherein, The method for preparing the modified polyvinylidene fluoride grafted with one or more monomers includes: Activate the polyvinylidene fluoride backbone to generate reaction sites thereon; and One or more monomers are grafted onto the reaction site.

6. The lithium-ion battery as described in claim 5, wherein, The polyvinylidene fluoride backbone is activated by ozone treatment, plasma treatment, ultraviolet treatment, or gamma ray irradiation.

7. The lithium-ion battery of claim 5, wherein the grafting is performed in water or an water / alcohol solution.

8. The lithium-ion battery of claim 7, wherein the grafting is carried out in an inert gas, the reaction temperature ranges from 40°C to 80°C, and the reaction time is from 1 to 50 hours.

9. The lithium-ion battery of claim 1, wherein the gel-free binder improves the thermal stability of the positive electrode to 120°C.

10. The lithium-ion battery of claim 1, wherein the specific energy density of the battery is at least 300 Wh / kg.

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