Electrode assembly and rechargeable lithium battery comprising the same

Abstract

An electrode assembly, a method for manufacturing the electrode assembly, and a rechargeable lithium battery including the electrode assembly are provided. The electrode assembly includes electrodes and a coating on the electrodes. The coating includes nanofibers, and the nanofibers include polymers and compounds, the polymers including polyamic acid, polyimide, or combinations thereof.

Description

Technical Field

[0001] This disclosure relates to an electrode assembly and a rechargeable lithium battery including the electrode assembly. Background Technology

[0002] With the increasing prevalence of battery-powered electronic devices (such as mobile phones, laptops, and electric vehicles), the demand for rechargeable batteries with high energy density and high capacity is growing. Therefore, improving the performance of rechargeable lithium batteries can be advantageous.

[0003] A rechargeable lithium battery includes a positive electrode and a negative electrode containing active materials capable of inserting and deintercalating lithium ions, as well as an electrolyte solution, and generates electrical energy through oxidation and reduction reactions when lithium ions are deintercalated from the positive electrode and inserted into the negative electrode, and deintercalated from the negative electrode and inserted into the positive electrode. Summary of the Invention

[0004] Some example embodiments include an electrode assembly having desired or improved electrospinning properties, a method of manufacturing the electrode assembly, and a rechargeable lithium battery including the electrode assembly, the rechargeable lithium battery having improved battery characteristics by controlling the dielectric constant and conductivity of the electrospinning solution.

[0005] An electrode assembly according to some example embodiments includes an electrode and a coating on the electrode. The coating includes nanofibers, and the nanofibers include a polymer and a compound represented by the following chemical formula 1, wherein the polymer includes polyamic acid, polyimide, or a combination thereof.

[0006] Chemical Formula 1: .

[0007] In Formula 1, R1 to R4 are each independently or include at least one of hydrogen, C1 to C20 alkyl groups and combinations thereof.

[0008] A rechargeable lithium battery according to some example embodiments includes an electrode assembly and an electrolyte.

[0009] Electrode assemblies according to some example embodiments can improve electrospinning properties by controlling the dielectric constant and conductivity of the electrospinning solution, and rechargeable lithium batteries including such electrode assemblies can have improved battery characteristics. Attached Figure Description

[0010] Figures 1 to 4 This is a schematic diagram illustrating a rechargeable lithium battery according to some example embodiments.

[0011] Figure 5 This is a graph showing the measured dielectric constants of electrospinning solutions "a" and "b".

[0012] Figure 6 This is a graph showing the conductivity of electrospinning solution "a" and electrospinning solution "b".

[0013] Figure 7 This is a graph showing the dielectric constants measured for the electrospinning solutions prepared in Example 1, Example 2, Comparative Example 1, and Comparative Example 4.

[0014] Figure 8 This is a graph showing the conductivity of the electrospinning solutions prepared in Example 1, Example 2, Comparative Example 1, and Comparative Example 4.

[0015] Figure 9 This is a graph showing the imidization index measured at the imidization temperature of the electrospinning solutions prepared according to Example 1 and Comparative Example 1.

[0016] Figure 10 This is a scanning electron microscope (SEM) image of the surface of the coating on the negative electrode fabricated in Example 1.

[0017] Figure 11 The image is a scanning electron microscope (SEM) image of the surface of the coating on the negative electrode manufactured in Comparative Example 1.

[0018] Figure 12 This is an image of a coating manufactured by electrospinning the electrospinning solution prepared in Comparative Example 1 onto a silver Al foil using a single nozzle.

[0019] Figure 13 This is an image of the coating produced by electrospinning the electrospinning solution prepared in Example 1 onto a silver Al foil using a single nozzle.

[0020] Figure 14 The image shows the coating produced by electrospinning the electrospinning solution prepared in Comparative Example 1 onto a black negative electrode plate using multiple nozzles.

[0021] Figure 15 The image shows a coating produced by electrospinning the electrospinning solution prepared in Example 1 onto a black negative electrode plate using multiple nozzles.

[0022] Figure 16 This is a flowchart illustrating a method for manufacturing an electrode assembly according to an example embodiment. Detailed Implementation

[0023] Example embodiments are described in detail below. However, these embodiments are presented by way of example, and this disclosure is not limited thereto, and is defined by the scope of the claims described below.

[0024] As used herein, unless otherwise specifically defined, it is understood that when an element such as a layer, film, region, or substrate is referred to as being “on” another element, the element may be directly on the other element or there may be an intervening element between them.

[0025] Unless otherwise stated in this specification, items expressed in the singular may also include the plural. Furthermore, unless otherwise stated, “A or B” may mean “including A, including B, or including both A and B”.

[0026] As used herein, “their combination” refers to mixtures, laminates, complexes, copolymers, alloys, blends, reaction products, etc. of the components.

[0027] As used herein, unless otherwise defined, particle size can be the average particle size. Furthermore, particle size can refer to the average particle size (D50), which represents the diameter of particles having a cumulative volume of 50% of the particle size distribution. The average particle size (D50) can be measured by methods known to those skilled in the art, for example, by a particle size analyzer, or by a transmission electron microscope image or a scanning electron microscope image. Optionally, data analysis is performed using a dynamic light scattering measurement device, and the number of particles in each particle size range is counted. Thus, the average particle size (D50) value can be readily obtained by calculation. Optionally, the average particle size (D50) value can be measured using laser diffraction. When measured by laser diffraction, for example, the particles to be measured are dispersed in a dispersion medium and then introduced into a commercially available laser diffraction particle size measuring device (e.g., Microtrac MT 3000), and irradiated with ultrasound at approximately 28 kHz with an output of 60 W, to calculate the average particle size (D50) based on 50% of the particle size distribution in the measuring device.

[0028] When the terms “about” or “substantially” are used in conjunction with numerical values ​​in this specification, it is intended that the relevant numerical value include a tolerance of ±10% around the stated value. When a range is specified, the range includes all values ​​within that range, such as increments of 0.1%.

[0029] Electrode assembly An electrode assembly according to some example embodiments includes an electrode and a coating on the electrode. The coating includes nanofibers, and the nanofibers include a polymer and a compound represented by the following chemical formula 1, said polymer including at least one of polyamic acid, polyimide, and combinations thereof.

[0030] Chemical Formula 1: .

[0031] In Formula 1, R1 to R4 are each independently or include at least one of hydrogen, C1 to C20 alkyl groups and combinations thereof.

[0032] For example, the electrode may include a current collector and an electrode active material layer on the current collector, wherein the coating may be disposed on the electrode active material layer and may be integrated with the electrode active material layer.

[0033] The coating can form a separator between the positive and negative electrodes to reduce or prevent short circuits; therefore, rechargeable lithium batteries according to some example embodiments may not require a separate separator. In this way, because the rechargeable lithium batteries according to some example embodiments do not require a separate separator, the separator can be omitted during manufacturing. Furthermore, because a lamination process to combine the separator and electrodes is not required, the battery can be manufactured economically, and energy density can be increased while reducing battery size.

[0034] In some example embodiments, the battery can be manufactured by the following steps: stacking electrodes and counter electrodes such that the active material layer of the counter electrode contacts the coating to manufacture an electrode assembly; inserting the electrode assembly into a battery housing; and then injecting an electrolyte solution.

[0035] As another example, both the positive and negative electrodes can be manufactured by the following steps: forming a coating according to some example embodiments; stacking the positive and negative electrodes such that the respective coatings come into contact with each other to form an electrode assembly; inserting the stacked positive and negative electrodes into a housing; and then injecting an electrolyte solution to manufacture a battery.

[0036] As another example, all-solid-state rechargeable batteries can be fabricated by stacking (e.g., sequentially stacking) electrodes and counter electrodes on a coating.

[0037] Meanwhile, when using electrodes according to some example embodiments, a diaphragm can be inserted separately between the positive and negative electrodes, depending on the required specifications.

[0038] In various example embodiments, the coating can be integrated with the electrodes to achieve strong adhesion, while achieving desired or improved permeability and physical strength between the positive and negative electrodes. Even with a thin thickness, it can effectively isolate the two electrodes and improve the cycle life characteristics of the battery by reducing or preventing the growth of lithium dendrites formed during charge and discharge.

[0039] Furthermore, the fact that the coating and the electrode active material layer are integrated can refer to the state in which a portion of the coating component penetrates into the electrode active material layer by forming the coating directly on the electrode active material layer through electrospinning, and can also refer to the region where the electrode active material layer component and the coating component are mixed with each other at the interface between the electrode active material layer and the coating.

[0040] According to some example embodiments, compared to forming a coating on the electrode active material layer using general coating methods or fabricating a coating separately in film form and then stacking it on the electrode active material layer, the electrode can make the electrode active material layer and the coating bond more firmly and exhibit higher adhesion.

[0041] In this way, when the cross-section of the electrode assembly is photographed using a scanning electron microscope (SEM), the fact that the coating and the electrode active material layer are integrated can be clearly seen. Although the electrode active material layer and the coating are distinguishable, the interface (boundary portion) between the electrode active material layer and the coating can appear to be non-uniform (uneven), or a region where the components of the electrode active material layer and the coating are mixed can appear at the interface between the electrode active material layer and the coating with a given thickness.

[0042] Furthermore, because the electrode active material layer and the coating are integrated, they are in close contact with each other, allowing the interface between the electrode active material layer and the coating to be formed in a dense, pore-free form.

[0043] In this way, because the coating is integrated with the electrode active material layer, the coating can exist in a state of more robust bonding with the electrode active material layer. Therefore, since there are no issues of layer separation or slippage during the battery manufacturing process, the physical strength and durability of the battery are improved, and processability is also improved.

[0044] Typically, when the electrospinning solution (spinning dosing) has poor electrospinning properties, the electrospinning solution will not spin into fibers, causing the electrospinned film to become wet or the electrospinning solution to drip (and form droplets), which may lead to a reduction in the functionality of the coating formed by electrospinning.

[0045] Therefore, electrode assemblies according to some example embodiments may include a coating that has desired or improved properties, such as strength and adhesion, by controlling the properties of the electrospinning solution itself to significantly improve the electrospinning properties of the electrospinning solution.

[0046] According to some example embodiments, the coating includes nanofibers, wherein the nanofibers include polymers, and the polymers include at least one of polyamic acid, polyimide, and combinations thereof.

[0047] Polyamic acid can be or includes compounds having a carboxyl group (-COOH), in which case the carboxyl group of polyamic acid can react with imidazole compounds described below to improve the dielectric constant and conductivity of the electrospinning solution.

[0048] For example, based on a 100 wt% coating, the polymer content can be in the range of about 90 wt% to about 99.9 wt%, such as about 90 wt% to about 99 wt%, about 90 wt% to about 95 wt%, or about 95 wt% to about 99 wt%. When the above-mentioned polymer content range is met, the dielectric constant and conductivity of the electrospinning solution are improved, thereby enabling the formation of a coating with desired or improved electrospinning properties, as well as desired or improved mechanical strength and adhesion.

[0049] For example, based on 100 wt% of polymer, the polyimide content can be greater than or equal to about 70 wt%, for example, greater than or equal to about 80 wt%, greater than or equal to about 90 wt%, or greater than or equal to about 95 wt%. When the above-mentioned range of polyimide content is met, an electrode assembly comprising a coating having desired or improved mechanical strength and desired or improved adhesion due to the high imidization rate can be formed.

[0050] For example, the polymer may also include other polymers having a carboxyl group (-COOH), such as poly(methacrylic acid), poly(acrylic acid), poly(maleic acid), poly(butadiene acid), and combinations thereof.

[0051] The coating according to some example embodiments includes nanofibers, wherein the nanofibers comprise compounds represented by the following chemical formula 1.

[0052] Chemical Formula 1: .

[0053] In Formula 1, R1 to R4 are each independently or include at least one of hydrogen, C1 to C20 alkyl groups and combinations thereof.

[0054] The compound represented by Formula 1 may be or includes imidazole compounds. Imidazole compounds may be or include an alkaline catalyst added to the electrospinning solution and may be electrospinned together with the polymer to be included in a coating according to some example embodiments.

[0055] In imidazole compounds, nitrogen atoms with unshared electron pairs can react with and ionize the hydrogen atoms of the carboxyl group (-COOH) included in the aforementioned polymer, thereby forming imidazole salts. This reaction can improve the dielectric constant and conductivity of the electrospinning solution, and significantly enhance the electrospinning properties when the electrospinning solution is electrospinned.

[0056] For example, in Formula 1, R1 to R4 may each be or include at least one of hydrogen, C1 to C5 alkyl groups, and combinations thereof. As an example, R1 to R4 may each be or include at least one of hydrogen, C1 to C3 alkyl groups, and combinations thereof. As another example, all of R1 to R4 may be or include hydrogen. Compounds represented by Formula 1 may not have aromatic substituents.

[0057] For example, a compound represented by Formula 1 may include at least one of imidazole, 1-methylimidazolium, 1-ethylimidazolium, 2-methylimidazolium, 4-methylimidazolium, 1,2-dimethylimidazolium, 2-ethyl-4-methylimidazolium, and combinations thereof.

[0058] For example, compounds represented by Formula 1 can be or include monomeric compounds rather than polymers, and can have relatively small molecular weights or molecular sizes and high mobility compared to polymeric compounds. Therefore, compounds represented by Formula 1 can more readily react with and ionize the carboxyl groups included in the aforementioned polymers, thus better fulfilling their role as base catalysts.

[0059] For example, coatings can be formed by electrospinning. When a coating is formed in film form by simply spinning a spinning solution, a low dielectric constant of the spinning solution may be advantageous in order to reduce or prevent the generation of static electricity in the manufactured film. Coatings according to some example embodiments are formed by electrospinning an electrospinning solution having a high dielectric constant and conductivity, and therefore can have improved or superior mechanical strength and adhesion compared to coatings formed by simply spinning films.

[0060] For example, based on a 100 wt% coating, the content of the compound represented by Formula 1 can range from about 0.1 wt% to about 10 wt%, for example, from about 0.5 wt% to about 7.5 wt% or from about 1 wt% to about 5 wt%. When the amount of the compound is within the above range, the dielectric constant and conductivity of the electrospinning solution are improved, thereby enabling the formation of a coating with desired or improved electrospinning properties, as well as desired or improved mechanical strength and adhesion.

[0061] For example, for coatings, the polymer and the compound represented by Formula 1 may be included in a weight ratio ranging from about 95:5 to about 99.9:0.1, for example, from about 99:1 to about 99.5:0.5 or from about 99.5:0.5 to about 99.9:0.1. When the above weight ratio range is met, the dielectric constant and conductivity of the electrospinning solution are improved, thereby enabling the formation of a coating with desired or improved electrospinning properties, mechanical strength, and adhesion.

[0062] For example, coatings formed by electrospinning include nanofibers, and the nanofibers can have a three-dimensional network structure, such as a woven or nonwoven structure. Therefore, when nanofibers have a three-dimensional network structure (e.g., a woven or nonwoven structure), they can have the advantage of minimizing the resistance to Li ion migration.

[0063] For example, the average diameter of the nanofibers can be in the range of about 50 nm to about 500 nm, such as about 50 nm to about 300 nm, about 50 nm to about 100 nm, or about 60 nm to about 100 nm. When the above numerical ranges are met, the coating can exhibit desired or improved air permeability, adhesion, and mechanical strength.

[0064] The diameter of a nanofiber can refer to the widest diameter among the fiber diameters measured based on the cross-section of each nanofiber, and can be measured in a direction perpendicular to the length direction of the nanofiber. The average diameter of the aforementioned nanofibers can be calculated by randomly measuring the cross-sectional diameters of approximately 20 fibers in a scanning electron microscope image of the coating surface and then calculating their arithmetic mean.

[0065] The presence of nanofibers in a three-dimensional network structure can refer to a porous structure containing multiple pores.

[0066] For example, the average diameter of the pores included in the nanofibers can be in the range of about 50 nm to about 500 nm, such as about 50 nm to about 300 nm, about 50 nm to about 100 nm, or about 60 nm to about 100 nm. When the above-mentioned average diameter range is met, the coating can exhibit desired or improved permeability, adhesion, and mechanical strength through pores of a substantially uniform and appropriately sized structure.

[0067] Pore ​​diameter refers to the diameter of a single pore included in a nanofiber with a three-dimensional network structure. It can be defined as the longest axis of the cross-section that runs through the pore. The average pore diameter can be represented by the arithmetic mean of the cross-sectional diameters of approximately 20 pores in an SEM image of the coating surface.

[0068] For example, the coating thickness can be in the range of about 1 μm to about 25 μm, for example, greater than or equal to about 5 μm, or greater than or equal to about 8 μm and less than or equal to about 20 μm, less than or equal to about 15 μm, or less than or equal to about 10 μm. When the coating thickness is within the above range, it can exhibit a reasonably high density, thus more effectively reducing or suppressing the formation of Li dendrites during charge and discharge.

[0069] Method for manufacturing electrode assemblies A method for manufacturing an electrode assembly according to some example embodiments includes: preparing an electrospinning solution comprising a prepolymer, a compound represented by chemical formula 1, and a solvent, the prepolymer comprising polyamic acid; electrospinning the electrospinning solution onto an electrode surface; and heat-treating the electrospinning solution to form a coating.

[0070] For example, an electrospinning solution can be prepared by first dissolving the prepolymer in a solvent, then adding the compound represented by Formula 1 and stirring. Stirring can be performed using commonly used methods, such as a coating mixer. In this case, high-viscosity solutions can be mixed rapidly, and mixing can be achieved efficiently by using vibration and rotation simultaneously or concurrently.

[0071] For example, the prepolymer can be an intermediate before the final polymerization into the aforementioned polymer, and can be transformed into a polymer through another polymerization or curing process.

[0072] The prepolymer may include polyamic acid having a carboxyl group (-COOH), in which case the carboxyl group of the polyamic acid may react with an imidazole compound described below to improve the dielectric constant and conductivity of the electrospinning solution.

[0073] In addition to polyamic acid, the prepolymer may also include other polymers having carboxyl groups (-COOH), and in this case, the carboxyl groups of the imidazole compound and other polymers can react to improve the dielectric constant and conductivity of the electrospinning solution. For example, other polymers may include at least one of poly(methacrylic acid), poly(acrylic acid), poly(maleic acid), poly(butadiene acid), and combinations thereof.

[0074] Based on a 100 wt% electrospinning solution, the prepolymer content can be in the range of about 5 wt% to about 20 wt%, for example, about 5 wt% to about 15 wt%, about 5 wt% to about 10 wt%, or about 10 wt% to about 15 wt%.

[0075] Based on a 100 wt% electrospinning solution, the content of the compound represented by Formula 1 can be in the range of about 0.1 wt% to about 5 wt%, for example, about 0.1 wt% to about 2.5 wt%, about 0.1 wt% to about 1 wt%, about 0.5 wt% to about 1 wt%, or about 0.1 wt% to about 0.5 wt%.

[0076] When the contents of the prepolymer and the compound represented by Formula 1 are within the above-mentioned numerical range, the dielectric constant and conductivity of the electrospinning solution are improved, thereby enabling the formation of coatings with desired or improved electrospinning properties, mechanical strength, and adhesion.

[0077] For example, the solvent included in the electrospinning solution may include at least one of dimethylacetamide, dimethyl acetate, dimethylformamide, dimethyl sulfoxide, acetone, and combinations thereof.

[0078] For example, the viscosity of the prepolymer can be in the range of about 8000 mPa·s to about 9900 mPa·s, for example, about 9000 mPa·s to about 9900 mPa·s or about 9000 mPa·s to about 9500 mPa·s. When the above viscosity range is met, a coating with desired or improved electrospinning properties and mechanical strength can be formed by using an electrospinning solution with a suitable range of dielectric constant and conductivity.

[0079] The viscosity of the prepolymer can be measured using an iQ Rheometer (HAAKE) at 25°C, where the zero-shear viscosity is measured at 0.1 s⁻¹. -1 up to 1000s -1 The shear rate was determined by a scan within the specified range.

[0080] For example, the dielectric constant of the electrospinning solution can be in the range of about 70 pF / m to about 100 pF / m, for example, about 70 pF / m to about 90 pF / m or about 75 pF / m to about 80 pF / m.

[0081] For example, the conductivity of the electrospinning solution can be in the range of about 2000 μS to about 8000 μS, such as about 2000 μS to about 5000 μS, about 2000 μS to about 4000 μS, or about 3000 μS to about 4000 μS.

[0082] The dielectric constant and conductivity of the electrospinning solution can be measured simultaneously at 25°C by applying an AC signal using a rheometer (MCR 703, Anton Paar), and the values ​​can be measured at 50 Hz among the frequencies of 50 Hz, 1 kHz, 20 kHz, 50 kHz and 100 kHz.

[0083] When the dielectric constant and conductivity of the electrospinning solution meet the above-mentioned numerical range, a coating with desired or improved electrospinning properties, as well as desired or improved mechanical strength and adhesion, can be formed.

[0084] In the examples, a method for manufacturing an electrode assembly according to some example embodiments includes electrospinning an electrospinning solution onto an electrode surface.

[0085] The electrospinning process can be carried out by the following steps: setting up a nozzle assembly and a collection roller consisting of nozzles having an orifice size of about 23G (gauge) to about 30G at predetermined intervals; adding an electrospinning solution to the nozzles; setting the target substrate on the contact rollers; and then applying a voltage in the range of about 35kV to about 100kV to the nozzles.

[0086] The number of the aforementioned nozzles can be appropriately adjusted according to the type and content of the polymer included in the electrospinning solution, and can be, for example, in the range of about 1 to about 1,000.

[0087] The predetermined distance between the nozzle assembly and the target substrate can be in the range of approximately 10 cm to approximately 20 cm.

[0088] This is suitable when the nozzle orifice size is in the range of about 25G to about 30G, because a coating of the desired shape can be formed.

[0089] According to the electrospinning process, the polymer solution is spun into a fiber shape and stretched, and then spun onto the target substrate in the form of nanofibers to form a coating.

[0090] To explain this in more detail, the electrospinning solution is suspended in droplets at the nozzle due to surface tension. When a voltage is applied, charges accumulate on the surface of the electrospinning solution droplets, and repulsive forces occur between the charges. Therefore, the repulsive force between the charges is opposite to the direction of the solution's surface tension. When the voltage reaches a threshold point, a Taylor cone is formed, and the polymer solution is ejected from the Taylor cone nozzle and subjected to multiaxial stretching in the agitation zone. The nanofibers are collected by a collecting roller into a nonwoven fabric, thus forming an organic coating.

[0091] At this point, the electrospinning process can be carried out under conditions of temperature ranging from about 20°C to about 30°C and relative humidity ranging from about 0% to about 60%. When the electrospinning process is carried out under the above-mentioned temperature and relative humidity conditions, it has the advantage of maintaining the fiber with a predetermined thickness during spinning.

[0092] Furthermore, the rolling speed of the collecting roller can be adjusted to ensure an appropriate coating thickness; for example, the rolling speed of the collecting roller can be in the range of about 0.1 m / min to about 3 m / min. Additionally, the electrospinning solution can be adjusted to be discharged from the nozzle at a flow rate in the range of about 1 mL / min to about 100 mL / min.

[0093] Furthermore, by properly controlling the nozzle air, interference between nozzles can be minimized, ensuring substantially uniform electrospinning. The nozzle air can be controlled by flowing compressed air at a pressure ranging from approximately 0.01 MPa to approximately 0.5 MPa.

[0094] For example, the electrospinning process can be performed approximately two or more times.

[0095] Since nanofibers are formed through electrospinning, the resulting nanofibers can possess a three-dimensional network structure. Because the coating is formed via an electrospinning process, the solvent can easily evaporate, which is advantageous as it better reduces or suppresses the rebound phenomenon that damages the electrode due to solvent damage.

[0096] Next, a method for manufacturing an electrode assembly according to some example embodiments includes heat-treating an electrospinning solution after electrospinning to form a coating.

[0097] Heat treatment can be a process in which a prepolymer undergoes a polymerization reaction or a curing reaction. As an example, it can be a process in which a prepolymer including polyamic acid undergoes thermal imidization to produce polyamic acid.

[0098] For example, the heat treatment temperature can be in the range of about 200°C to about 400°C, for example, about 200°C to about 350°C, about 200°C to about 300°C, or about 200°C to about 250°C.

[0099] For example, by including compounds represented by Formula 1, the electrospinning solution can constitute a low-temperature reaction promoter for reacting the prepolymer at low temperatures. For example, compounds represented by Formula 1 can lower the imidization temperature of polyamic acid, thus allowing thermal imidization to be carried out at a relatively low temperature in the range of about 200°C to about 400°C. When thermal imidization is performed at low temperatures, an electrode assembly is formed comprising a coating that has desired or improved mechanical strength and improved electrospinning properties while minimizing electrode deformation.

[0100] For example, the boiling point of the compound represented by Formula 1 can be greater than about 200°C and less than or equal to about 400°C, for example, in the range of about 250°C to about 400°C, about 250°C to about 350°C, about 250°C to about 300°C, or about 250°C to about 260°C. When the above boiling point temperature range is met, the compound represented by Formula 1 can continue to act as a low-temperature reaction promoter even during the heat treatment process, and can remain in the coating even after the heat treatment, making it detectable.

[0101] After the coating is formed, further rolling can be performed. The rolling process can be carried out at a temperature ranging from about 25°C to about 110°C. When the rolling process is further performed, the coating is pressed, which can have the advantage of shortening the Li ion migration path and improving the movement of lithium ions during charging and discharging. In addition, by performing an additional rolling process, the coating and the electrode active material layer can be more effectively integrated.

[0102] Rechargeable lithium batteries According to some example embodiments, a rechargeable lithium battery includes the aforementioned electrode assembly and electrolyte.

[0103] Electrode assemblies may include positive electrode assemblies, negative electrode assemblies, or combinations thereof.

[0104] The positive electrode assembly may include a positive electrode and a coating on the positive electrode, and the negative electrode assembly may include a negative electrode and a coating on the negative electrode.

[0105] As an example, a positive electrode assembly may include a positive electrode current collector, a positive electrode active material layer on the positive electrode current collector, and a coating disposed on and integrally formed with the positive electrode active material layer. As an example, a negative electrode assembly may include a negative electrode current collector, a negative electrode active material layer on the negative electrode current collector, and a coating disposed on and integrally formed with the negative electrode active material layer.

[0106] Rechargeable lithium batteries can be classified according to their shape, such as cylindrical, prismatic, pouch-shaped, and coin-shaped. Figures 1 to 4 This is a schematic diagram illustrating a rechargeable lithium battery according to some example embodiments, wherein, Figure 1 It is a cylindrical battery. Figure 2 It is a prismatic battery, and Figure 3 and Figure 4 It is a pouch-shaped battery. (See reference) Figures 1 to 4 The rechargeable lithium battery 100 includes an electrode assembly 40 and a housing 50. The electrode assembly 40 has a separator 30 disposed between a positive electrode 10 and a negative electrode 20. The electrode assembly 40 is housed within the housing 50. The positive electrode 10, the negative electrode 20, and the separator 30 may be impregnated with an electrolyte solution (not shown). Figure 1 As shown, the rechargeable lithium battery 100 may include a sealing member 60 of the sealed housing 50. Figure 2 In this context, the rechargeable lithium battery 100 may include a positive electrode lead connector 11, a positive electrode terminal 12 connected to the positive electrode lead connector 11, a negative electrode lead connector 21, and a negative electrode terminal 22 connected to the negative electrode lead connector 21. For example... Figure 3 and Figure 4 As shown, the rechargeable lithium battery 100 includes Figure 4 The electrode terminals 70 shown in the figure or Figure 3 The positive electrode terminal 71 and negative electrode terminal 72 shown in the figure form an electrical path for guiding the current formed in the electrode assembly 40 to the outside of the rechargeable lithium battery 100.

[0107] The rechargeable lithium batteries according to some example embodiments can be used in, for example, automobiles, mobile phones and / or various types of electrical devices, but this disclosure is not limited thereto.

[0108] The construction of rechargeable lithium batteries is described in detail below.

[0109] positive electrode The positive electrode for a rechargeable lithium battery may include a current collector and a layer of positive electrode active material formed on the current collector. The positive electrode active material layer includes positive electrode active material and may also include a binder and / or a conductive material.

[0110] For example, the positive electrode may also include additives that can form a sacrificial positive electrode.

[0111] The positive electrode active material can be or includes compounds capable of intercalating and deintercalating lithium (lithiation intercalation compounds). For example, a composite oxide of lithium with at least one metal (such as or including at least one of cobalt, manganese, nickel, and combinations thereof) can be used.

[0112] The composite oxide can be or includes lithium transition metal composite oxides, and examples include at least one of lithium nickel oxides, lithium cobalt oxides, lithium manganese oxides, lithium iron phosphate compounds, cobalt-free lithium nickel manganese oxides, and combinations thereof.

[0113] As an example, a compound represented by any of the following chemical formulas can be used. Li a A 1-b X b O 2-c D c (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05); Li a Mn 2-b X b O 4-c D c (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05); Li a Ni 1-b-c Co b X c O 2-α D α (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.5, 0<α<2); Li a Ni 1-b- c Mn b X c O 2-α D α(0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.5, 0<α<2); Li a Ni b Co c L 1 d G e O2 (0.90≤a≤1.8, 0≤b≤0.9, 0≤c≤0.5, 0≤d≤0.5, 0≤e≤0.1); Li a NiG b O2 (0.90≤a≤1.8, 0.001≤b≤0.1); Li a CoG b O2 (0.90≤a≤1.8, 0.001≤b≤0.1); Li a Mn 1-b G b O2 (0.90≤a≤1.8, 0.001≤b≤0.1); Li a Mn2G b O4 (0.90≤a≤1.8, 0.001≤b≤0.1); Li a Mn 1-g G g PO4 (0.90≤a≤1.8, 0≤g≤0.5); Li (3-f) Fe2(PO4)3 (0≤f≤2); Li a FePO4 (0.90≤a≤1.8).

[0114] In the chemical formula, A is or includes at least one of Ni, Co, Mn, and combinations thereof; X is or includes at least one of Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, rare earth elements, and combinations thereof; D is or includes at least one of O, F, S, P, and combinations thereof; G is or includes at least one of Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, and combinations thereof; and L 1 It is or includes at least one of Mn, Al and combinations thereof.

[0115] For example, the positive electrode active material can be or includes a high-nickel positive electrode active material, based on 100 mol% of metals other than lithium in a lithium transition metal complex oxide, wherein the nickel content in the high-nickel positive electrode active material is greater than or equal to about 80 mol%, greater than or equal to about 85 mol%, greater than or equal to about 90 mol%, greater than or equal to about 91 mol%, or greater than or equal to about 94 mol% and less than or equal to about 99 mol%. High-nickel positive electrode active materials can achieve high capacity and can be applied to high-capacity, high-density rechargeable lithium batteries.

[0116] Based on a 100wt% positive electrode active material layer, the amount of positive electrode active material can be in the range of about 90wt% to about 99.5wt%, and based on a 100wt% positive electrode active material layer, the amounts of binder and conductive material can be in the range of about 0.5wt% to about 5wt%, respectively.

[0117] The binder improves the adhesion properties between the positive electrode active materials and between the positive electrode active materials and the current collector. Examples of binders may include at least one of the following, but are not limited to: polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, epoxy resin, (meth)acrylate resin, polyester resin, nylon, etc.

[0118] Conductive materials can impart conductivity to electrodes, and any material that does not cause adverse chemical changes and conducts electrons can be used in a battery. Examples of conductive materials may include: carbon-based materials, such as at least one of natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fibers, carbon nanofibers, and carbon nanotubes; metallic materials, including at least one of copper, nickel, aluminum, silver, etc., in the form of metal powder or metal fibers; conductive polymers, such as polyphenylene derivatives; or mixtures thereof.

[0119] The positive electrode current collector may include, but is not limited to, Al.

[0120] negative electrode The negative electrode for a rechargeable lithium battery includes a current collector and a layer of negative electrode active material on the current collector. The negative electrode active material layer includes negative electrode active material and may also include a binder and / or a conductive material.

[0121] For example, the negative electrode active material may include at least one of the following: materials capable of reversibly inserting / deintercalating lithium ions, lithium metal, lithium metal alloys, materials capable of doping / dedoping lithium, and transition metal oxides.

[0122] Materials capable of reversibly inserting / deintercalating lithium ions can include carbon-based negative electrode active materials, such as crystalline carbon, amorphous carbon, or combinations thereof. Crystalline carbon can be graphite, such as natural or artificial graphite in a shapeless, flake-like, spherical, or fibrous form. Amorphous carbon can be or includes at least one of soft carbon, hard carbon, mesophase pitch carbonization products, calcined coke, etc.

[0123] The lithium metal alloy includes an alloy of lithium and a metal such as or including at least one of Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, and Sn.

[0124] The material capable of doping / dedoping lithium can be or include a Si-based negative electrode active material or a Sn-based negative electrode active material. The Si-based negative electrode active material can include silicon, a silicon-carbon composite, SiO x (0 < x ≤ 2), a Si-Q alloy (where Q is or includes at least one of an alkali metal, an alkaline earth metal, a Group 13 element, a Group 14 element (excluding Si), a Group 15 element, a Group 16 element, a transition metal, a rare earth element, and a combination thereof), and at least one of their combinations. The Sn-based negative electrode active material can include at least one of Sn, SnO2, a Sn-based alloy, and their combinations.

[0125] The silicon-carbon composite can be or include a composite of silicon and amorphous carbon. According to some exemplary embodiments, the silicon-carbon composite can be in the form of silicon particles and amorphous carbon coated on the surface of the silicon particles. For example, the silicon-carbon composite can include secondary particles (cores) in which silicon primary particles are assembled and an amorphous carbon coating (shell) on the surface of the secondary particles. Amorphous carbon can also be present between the silicon primary particles. For example, the silicon primary particles can be coated with amorphous carbon. The secondary particles can be dispersed in an amorphous carbon matrix.

[0126] The silicon-carbon composite can also include crystalline carbon. For example, the silicon-carbon composite can include a core containing crystalline carbon and silicon particles and an amorphous carbon coating on the surface of the core.

[0127] The Si-based negative electrode active material or the Sn-based negative electrode active material can be mixed with a carbon-based negative electrode active material.

[0128] For example, the negative electrode active material layer can include about 90 wt% to about 99 wt% of the negative electrode active material, about 0.5 wt% to about 5 wt% of the binder, and about 0 wt% to about 5 wt% of the conductive material.

[0129] The binder can attach the negative electrode active material particles to each other and can also attach the negative electrode active material to the current collector. The binder can be or include a non-aqueous binder, an aqueous binder, a dry binder, or a combination thereof.

[0130] The non-aqueous binder can include at least one of polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene-propylene copolymer, polystyrene, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamideimide, polyimide, and their combinations.

[0131] The waterborne adhesive may be or include at least one of the following: styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, (meth)acrylonitrile-butadiene rubber, (meth)acrylic rubber, butyl rubber, fluororubber, polyethylene oxide, polyvinylpyrrolidone, polyepoxychlorohydrin, polyphosphazene, poly(meth)acrylonitrile, ethylene propylene diene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, (meth)acrylic resin, phenolic resin, epoxy resin, polyvinyl alcohol, and combinations thereof.

[0132] When an aqueous binder is used as the negative electrode binder, it may also include a cellulose compound capable of imparting viscosity. The cellulose compound may include at least one of carboxymethyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose, and their alkali metal salts. The alkali metal may include at least one of Na, K, and Li.

[0133] The dry adhesive may be or include a fibrous polymer material, and may be or include at least one of, for example, polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, and combinations thereof.

[0134] Conductive materials are included to provide electrode conductivity, and any electrically conductive material can be used as a conductive material in the battery unless it causes an adverse chemical change. Examples of conductive materials include: carbon-based materials, such as at least one of natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, carbon nanofiber, carbon nanotube, etc.; metallic materials, including at least one of metal powder or metal fiber of copper, nickel, aluminum, silver, etc.; conductive polymers, such as polyphenylene derivatives; or mixtures thereof.

[0135] The negative electrode current collector may include at least one of copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal, and combinations thereof.

[0136] Electrolytes can include electrolyte solutions, solid electrolytes, or combinations thereof.

[0137] Electrolyte solutions used in rechargeable lithium batteries may include non-aqueous organic solvents and lithium salts.

[0138] Non-aqueous organic solvents constitute the medium for transporting ions that participate in the electrochemical reactions of the battery.

[0139] Non-aqueous organic solvents may be or include at least one of carbonate solvents, ester solvents, ether solvents, ketone solvents, alcohol solvents, aprotic solvents, and combinations thereof.

[0140] Carbonate solvents may include at least one of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), methyl ethyl carbonate (MEC), ethylene carbonate (EC), propylene carbonate (PC), and butyl carbonate (BC). Ester solvents may include at least one of methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, ethyl propionate, decanolactone, mevalonolactone, valproic acid lactone, caprolactone, etc. Ether solvents may include at least one of dibutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, dimethoxyethane, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, tetrahydrofuran, etc. Furthermore, ketone solvents may include cyclohexanone, etc. Alcohol solvents may include ethanol, isopropanol, etc. Aprotic solvents may include at least one of the following: nitriles, such as R-CN (wherein R is a C2 to C20 straight-chain, branched or cyclic hydrocarbon group, and may include double bonds, aromatic rings or ether bonds, etc.); amides, such as dimethylformamide; dioxolane, such as 1,3-dioxolane, 1,4-dioxolane, etc.; sulfolane, etc.

[0141] Non-aqueous organic solvents can be used alone or in mixtures of two or more types of solvents.

[0142] Furthermore, when using carbonate solvents, cyclic carbonates and chain carbonates can be mixed, and the cyclic carbonates and chain carbonates can be mixed in a volume ratio ranging from about 1:1 to about 1:9.

[0143] Lithium salts dissolved in organic solvents supply lithium ions in batteries, enabling rechargeable lithium batteries to operate and improving lithium ion transport between the positive and negative electrodes. Examples of lithium salts include LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiAlO2, LiAlCl4, LiPO2F2, LiCl, LiI, LiN(SO3C2F5)2, Li(FSO2)2N (lithium bis(fluorosulfonyl)imide; LiFSI), LiC4F9SO3, and LiN(C x F 2x+1 SO2)(C y F 2y+1 At least one of the following: (SO2) (x and y are integers in the range of 1 to 20), lithium trifluoromethane sulfonate, lithium tetrafluoroethane sulfonate, lithium difluoro(oxalate)borate (LiDFOB), lithium difluorobis(oxalate)phosphate (LiDFBOP), and lithium bis(oxalate)borate (LiBOB).

[0144] diaphragm Depending on the type of rechargeable lithium battery, a separator may be present between the positive and negative electrodes. The separator may include at least one of polyethylene, polypropylene, polyvinylidene fluoride, and multilayer films with two or more layers thereof, such as a mixed multilayer film of at least one of polyethylene / polypropylene bilayer separators, polyethylene / polypropylene / polyethylene trilayer separators, polypropylene / polypropylene / polypropylene trilayer separators, etc.

[0145] The diaphragm may include a porous substrate and a coating on one or both surfaces of the porous substrate, the coating comprising an organic material, an inorganic material, or a combination thereof.

[0146] The porous substrate may be or include a polymer membrane formed or comprising any one or more copolymers or mixtures of two or more of the following: polyolefins (such as polyethylene and polypropylene), polyesters (such as polyethylene terephthalate and polybutylene terephthalate), polyacetal, polyamide, polyimide, polycarbonate, polyetherketone, polyaryletherketone, polyetherimide, polyamideimide, polybenzimidazole, polyethersulfone, polyphenylene ether, cyclic olefin copolymers, polyphenylene sulfide, polyethylene naphthalate, glass fiber, and polytetrafluoroethylene (e.g., Teflon).

[0147] Organic materials may include polyvinylidene fluoride polymers or (meth)acrylic acid polymers.

[0148] Inorganic materials may include inorganic particles, such as or including at least one of Al2O3, SiO2, TiO2, SnO2, CeO2, MgO, NiO, CaO, GaO, ZnO, ZrO2, Y2O3, SrTiO3, BaTiO3, Mg(OH)2, boehmite and combinations thereof, but are not limited thereto.

[0149] Organic and inorganic materials can be mixed in a coating, or coatings containing organic materials and coatings containing inorganic materials can be stacked together.

[0150] Figure 16 This is a flowchart illustrating a method for manufacturing an electrode assembly according to an example embodiment. Figure 16In method 1600, operation 1610 is initiated by operation 1610, which includes preparing an electrospinning solution comprising a prepolymer, a compound represented by chemical formula 1, and a solvent, wherein the prepolymer comprises polyamic acid. For example, based on 100 wt% of the electrospinning solution, the content of the prepolymer is in the range of about 5 wt% to about 20 wt%. In another example, the viscosity of the prepolymer is in the range of about 9000 mPa·s to about 9900 mPa·s. In yet another example, the dielectric constant of the electrospinning solution is in the range of about 70 pF / m to about 100 pF / m. In yet another example, the conductivity of the electrospinning solution is in the range of about 2000 μS to about 8000 μS. Operation 1620 includes electrospinning the electrospinning solution onto an electrode surface. Operation 1630 includes heat-treating the above-described electrospinning solution to form a coating. For example, the heat treatment is performed at a temperature in the range of about 200°C to about 400°C.

[0151] Chemical Formula 1: ; In Formula 1, R1 to R4 each independently comprises at least one of hydrogen, C1 to C20 alkyl groups, and combinations thereof. In the example, based on a 100 wt% electrospinning solution, the content of the compound represented by Formula 1 ranges from about 0.1 wt% to about 5 wt%. In another example, the boiling point of the compound represented by Formula 1 is greater than about 200 °C and less than or equal to about 400 °C.

[0152] Examples and comparative examples of this disclosure are described below. However, the following examples are merely examples of this disclosure, and this disclosure is not limited to these examples.

[0153] Example: Example 1 First, 97.5 wt% artificial graphite, 1.0 wt% carboxymethyl cellulose, and 1.5 wt% styrene-butadiene rubber (SBR) were mixed in an aqueous solvent to prepare a negative electrode active material slurry. The negative electrode active material slurry was coated onto a copper current collector, dried, and rolled to form a negative electrode active material layer.

[0154] Subsequently, an electrospinning solution was prepared by dissolving polyamic acid (viscosity: 9300 mPa·s, boiling point: 256 °C) in dimethyl acetate solvent and then adding imidazole. Here, a 100 wt% electrospinning solution comprises 10 wt% polyamic acid and 0.5 wt% imidazole.

[0155] Subsequently, the electrospinning solution was electrospinned into nanofibers on the surface of the negative electrode active material layer. Electrospinning was performed under the following conditions.

[0156] After positioning a nozzle assembly consisting of 52 nozzles with an orifice size of 25G at 15cm intervals and a collection roller, an electrospinning solution is added to the nozzles, and electrospinning is then performed at 26°C and 50% relative humidity by applying a voltage of 40kV to 50kV. Here, the speed of the collection roller is set in the range of 1m / min to 3m / min, and the electrospinning solution is set to be discharged from the nozzles at a solid content of 150μL / min. Furthermore, electrospinning is performed by flowing compressed air at a pressure of 0.1MPa.

[0157] Subsequently, thermal imidization is performed at 200°C to fabricate a negative electrode including a coating (thickness: 8 μm), the coating comprising a polymer containing polyamic acid and polyimide as well as imidazole, and formed on the surface of the negative electrode active material layer.

[0158] The coating prepared based on 100 wt% comprises 95 wt% polymer (polyamic acid: polyimide = 10:90 by weight) and 5 wt% imidazole.

[0159] Furthermore, SEM image analysis of the coating surface revealed that the nanofibers formed in the coating possess a three-dimensional network structure comprising multiple pores, with an average pore diameter of 80 nm.

[0160] Example 2 The negative electrode, including the coating (thickness: 8 μm), was manufactured in the same manner as in Example 1, except that the electrospinning solution was prepared by including polyamic acid with a viscosity of 8000 mPa·s.

[0161] Comparison Example 1 The copper current collector and the negative electrode active material layer formed on the copper current collector were prepared in the same manner as in Example 1.

[0162] Subsequently, polyamic acid (viscosity: 9300 mPa·s, boiling point: 256 °C) was dissolved in dimethyl acetate solvent to prepare an electrospinning solution. Here, a 100 wt% electrospinning solution includes 10 wt% polyamic acid.

[0163] Under the same conditions as in Example 1, the electrospinning solution was electrospinned in the form of nanofibers onto the surface of the negative electrode active material layer.

[0164] Subsequently, thermal imidization was performed at 200°C to fabricate a negative electrode comprising a coating (thickness: 8 μm) on the surface of the negative electrode active material layer.

[0165] Comparison Example 2 The copper current collector and the negative electrode active material layer formed on the copper current collector were prepared in the same manner as in Example 1.

[0166] Subsequently, polyacrylonitrile (PAN) and polyvinylidene fluoride (PVDF) were dissolved in dimethyl acetate solvent to prepare an electrospinning solution. Here, based on a 100 wt% electrospinning solution, the total amount of polyacrylonitrile and polyvinylidene fluoride was 15.8 wt%.

[0167] Under the same conditions as in Example 1, the electrospinning solution was electrospinned in the form of nanofibers onto the surface of the negative electrode active material layer.

[0168] Subsequently, thermal imidization was performed at 200°C to fabricate a negative electrode comprising a coating (thickness: 8 μm) on the surface of the negative electrode active material layer.

[0169] Comparison Example 3 The copper current collector and the negative electrode active material layer formed on the copper current collector were prepared in the same manner as in Example 1.

[0170] Subsequently, polyimide was dissolved in dimethyl acetate solvent to prepare an electrospinning solution. Here, based on a 100 wt% electrospinning solution, 25 wt% polyimide was included.

[0171] Under the same conditions as in Example 1, the electrospinning solution was electrospinned in the form of nanofibers onto the surface of the negative electrode active material layer to fabricate a negative electrode comprising a coating (thickness: 8 μm) on the surface of the negative electrode active material layer.

[0172] Compare Example 4 A negative electrode including a coating (thickness: 8 μm) was manufactured in the same manner as in Comparative Example 1, except that an electrospinning solution was prepared by including polyamic acid with a viscosity of 10000 mPa·s.

[0173] Evaluation example: Evaluation Example 1: Measurement of dielectric constant and conductivity based on the amount of imidazole Electrospinning solution "a" was prepared by dissolving polyamic acid (viscosity: 9300 mPa·s, boiling point: 256 °C) in dimethyl acetate solvent. Electrospinning solution "b" was prepared by dissolving polyacrylonitrile (PAN) and polyvinylidene fluoride (PVDF) in dimethyl acetate solvent.

[0174] While adding 0 wt% to 5 wt% imidazole to electrospinning solution "a" and electrospinning solution "b", the dielectric constant and conductivity of each electrospinning solution were measured, and the results are shown in... Figure 5 and Figure 6 middle.

[0175] Reference Figure 5 and Figure 6 The electrospinning solution “a” includes polyamic acid with carboxyl groups, wherein, with the addition of more imidazole, the polyamic acid reacts more with the imidazole and is ionized more, resulting in improved dielectric constant and conductivity of the electrospinning solution.

[0176] Conversely, since polyacrylonitrile (PAN) and polyvinylidene fluoride (PVDF), which are polymers included in the electrospinning solution "b", do not have carboxyl groups, the dielectric constant and conductivity of the electrospinning solution do not change even if imidazole is added to them.

[0177] Evaluation Example 2: Evaluation of the correlation between the properties of electrospinning solutions and the properties of electrospinning. The dielectric constant and conductivity of the electrospinning solutions of Examples 1 to 2, and Comparative Examples 1 and 4 were evaluated respectively, and the results are shown in... Figure 7 and Figure 8 middle.

[0178] For dielectric constant, the higher the surface charge density, the better the electrospinning properties, and for conductivity, electrospinning properties are particularly desirable or improved in the range of 2000 μS to 8000 μS.

[0179] Reference Figure 7 It was confirmed that the electrospinning solution of Comparative Example 1 had a dielectric constant of less than 70 pF / m, which was lower than that of Example 1, thus confirming the inadequacy of the electrospinning properties.

[0180] Reference Figure 8 Compared with the electrospinning solution of Example 1, it was confirmed that the electrospinning solution of Comparative Example 1 has a low conductivity of less than 2000 μS, which confirms the inadequacy of the electrospinning properties.

[0181] Furthermore, Comparative Example 4 exhibits a higher polyamic acid viscosity than Comparative Example 1, and refers to Figure 7 and Figure 8 Comparative Example 4 has a conductivity that does not meet the optimal range and exhibits a lower dielectric constant than Comparative Example 1, which confirms the deterioration of electrospinning properties.

[0182] Furthermore, Example 2 exhibits a lower polyamic acid viscosity than Example 1, wherein Example 2 has a higher dielectric constant than Example 1, but no conductivity within the optimal range, which confirms that the electrospinning properties are at an average level.

[0183] Evaluation Example 3: Evaluation of imidization rate (imidization index) The imidization rate of the electrospinning solutions of Example 1 and Comparative Example 1 was evaluated by measuring the imidization index based on the imidization temperature.

[0184] Specifically, referring to samples heat-treated at 350°C for 1 hour, Fourier transform infrared (FT-IR) spectra were performed on samples heat-treated at each imidization temperature (25°C, 140°C, 200°C) to calculate the intensity ratio of a specific peak as the imidization index, which is shown in... Figure 9 middle.

[0185] The imidization index is defined according to Equation 1 below.

[0186] Equation 1: Imidization index = .

[0187] Here, D 1500cm-1 It corresponds to the intensity of the peak of the benzene vibration, and D 1380cm-1 It is the intensity of the peak corresponding to the CNC stretching vibration of the imide group.

[0188] Reference Figure 9 As a result of measuring the imidization index at a low temperature of 200°C, it was confirmed that the imidization rate of Example 1, which included imidazole in the electrospinning solution, was increased compared with Comparative Example 1.

[0189] In addition, refer to Figure 9 The imidization temperature of Example 1 was lower than that of Comparative Example 1, which confirms that imidazole acts as a low-temperature imidization promoter.

[0190] Evaluation Example 4: Electrospinning Property Test Scanning electron microscope (SEM) images of the coating surfaces on the negative electrodes of Example 1 and Comparative Example 1 were taken, respectively, and are shown in... Figure 10 and Figure 11 middle.

[0191] Reference Figure 10 In the coating of Example 1, the polyimide nanofibers are formed and distributed substantially uniformly, which confirms the desired or improved electrospinning properties.

[0192] Reference Figure 11 In the coating of Comparative Example 1, polyimide nanofibers did not form properly, and the solvent in the electrospinning solution did not evaporate properly, which confirms that the electrospinning properties were greatly degraded.

[0193] Furthermore, the electrospinning solutions of Comparative Example 1 and Example 1 were electrospinned onto silver Al foil using a single nozzle to form coatings, and their images are shown below. Figure 12 and Figure 13 middle.

[0194] Furthermore, the electrospinning solutions of Comparative Example 1 and Example 1 were electrospinned onto a black negative electrode plate using multiple nozzles to form coatings, and their images are shown below. Figure 14 and Figure 15 middle.

[0195] Reference Figure 12 (Compare Example 1) and Figure 13 (Example 1) The electrospinning solution of Example 1 has such desirable or improved electrospinning properties that the nanofibers are coated substantially uniformly on the Al foil, making the Al foil appear white. In contrast, the electrospinning solution of Comparative Example 1 has such degraded electrospinning properties that the nanofibers cannot be properly coated, and it appears silver, i.e., the color of the Al foil itself.

[0196] Reference Figure 14 (Compare Example 1) and Figure 15 (Example 1) The electrospinning solution of Example 1 has such desirable or improved electrospinning properties that the nanofibers are coated substantially uniformly on the negative electrode plate, making the negative electrode plate appear white. In contrast, the electrospinning solution of Comparative Example 1 exhibits such degraded electrospinning properties that the nanofibers cannot be properly coated on the negative electrode plate, making the negative electrode plate appear black, i.e., the color of the negative electrode plate itself.

[0197] While this disclosure has been described in conjunction with exemplary embodiments now considered to be practical, it will be understood that the disclosure is not limited to the disclosed exemplary embodiments. Rather, the disclosure is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

[0198] Symbol explanation: 100: Rechargeable lithium battery; 10: Positive electrode 11: Positive electrode lead connector; 12: Positive electrode terminal 20: Negative electrode; 21: Negative electrode lead connector 22: Negative electrode terminal; 30: Diaphragm 40: Electrode assembly; 50: Housing 60: Sealing component; 70: Electrode terminal piece 71: Positive electrode connector; 72: Negative electrode connector.

Claims

1. An electrode assembly, the electrode assembly comprising: electrode; as well as A coating is applied to the electrode. The coating includes nanofibers. The nanofibers comprise a polymer and a compound represented by Formula 1, wherein the polymer comprises at least one of polyamic acid, polyimide, and combinations thereof: Chemical Formula 1: ； In Formula 1, R1 to R4 each independently include at least one of hydrogen, C1 to C20 alkyl groups, and combinations thereof.

2. The electrode assembly according to claim 1, wherein: The electrode includes a current collector and an electrode active material layer on the current collector, and The coating is disposed on the electrode active material layer and is integrated with the electrode active material layer.

3. The electrode assembly according to claim 1, wherein, Based on 100 wt% of the coating, the polymer content is in the range of 90 wt% to 99.9 wt%.

4. The electrode assembly according to claim 1, wherein, Based on 100 wt% of the polymer, the content of the polyimide is greater than or equal to 70 wt%.

5. The electrode assembly according to claim 1, wherein, The compound represented by Formula 1 includes at least one of imidazole, 1-methylimidazolium, 1-ethylimidazolium, 2-methylimidazolium, 4-methylimidazolium, 1,2-dimethylimidazolium, 2-ethyl-4-methylimidazolium, and combinations thereof.

6. The electrode assembly according to claim 1, wherein, Based on 100 wt% of the coating, the content of the compound represented by chemical formula 1 is in the range of 0.1 wt% to 10 wt%.

7. The electrode assembly according to claim 1, wherein, The polymer and the compound represented by Formula 1 are included in a weight ratio ranging from 95:5 to 99.9:0.

1.

8. The electrode assembly according to claim 1, wherein, The average diameter of the nanofibers is in the range of 50 nm to 500 nm.

9. The electrode assembly according to claim 1, wherein: The nanofibers include multiple pores; and The average diameter of the pore is in the range of 50 nm to 500 nm.

10. The electrode assembly according to claim 1, wherein, The thickness of the coating is in the range of 1 μm to 25 μm.

11. A method for manufacturing an electrode assembly, the method comprising the following steps: An electrospinning solution comprising a prepolymer, a compound represented by chemical formula 1, and a solvent is prepared, wherein the prepolymer comprises polyamic acid; The electrospinning solution is electrospinned onto the electrode surface; as well as The electrospinning solution is heat-treated to form a coating; Chemical Formula 1: ； In Formula 1, R1 to R4 each independently include at least one of hydrogen, C1 to C20 alkyl groups, and combinations thereof.

12. The method according to claim 11, wherein, Based on 100 wt% of the electrospinning solution, the content of the prepolymer is in the range of 5 wt% to 20 wt%.

13. The method according to claim 11, wherein, Based on 100 wt% of the electrospinning solution, the content of the compound represented by chemical formula 1 is in the range of 0.1 wt% to 5 wt%.

14. The method according to claim 11, wherein, The viscosity of the prepolymer is in the range of 9000 mPa·s to 9900 mPa·s.

15. The method according to claim 11, wherein, The dielectric constant of the electrospinning solution is in the range of 70 pF / m to 100 pF / m.

16. The method according to claim 11, wherein, The conductivity of the electrospinning solution is in the range of 2000 μS to 8000 μS.

17. The method according to claim 11, wherein, The heat treatment is carried out at a temperature in the range of 200°C to 400°C.

18. The method according to claim 11, wherein, The compound represented by chemical formula 1 has a boiling point greater than 200°C and less than or equal to 400°C.

19. A rechargeable lithium battery, said rechargeable lithium battery comprising: The electrode assembly according to any one of claims 1 to 10; as well as Electrolytes.

Images