Separator for lithium batteries with improved high-temperature safety and lithium batteries containing the same

Abstract

A separator for a lithium battery with improved high-temperature safety and a lithium battery including the same are provided. The separator is a glass fiber-based separator and may be coated with a solid electrolyte. A lithium battery including the separator (e.g., a lithium metal primary battery) can have high stability at high temperatures, and accordingly, can be easily utilized in fields requiring high-temperature environments, such as oil drilling.

Description

Technology Field

[0001] The present application relates to a separator in which an ion-conductive material is formed as a coating layer on a separator material composed of glass fibers, and a battery including the same, thereby providing a lithium lithium battery with significantly improved high-temperature performance and lifespan characteristics. More specifically, according to an embodiment of the present application, a separator for a lithium metal primary battery capable of operating stably at high temperatures and a lithium metal primary battery including the same are provided, and a lithium metal primary battery including the separator according to an embodiment of the present application has high-temperature stability and can be utilized for oil drilling, etc. Background Technology

[0002] With the rapid development of the electronics, telecommunications, and computer industries, portable electronic communication devices such as camcorders, mobile phones, and laptop PCs are making remarkable progress. Consequently, the demand for lithium batteries as a power source to operate these devices is increasing day by day. In particular, recently, research and development is actively underway not only in Korea but also in Japan, Europe, and the United States, regarding applications such as electric vehicles, uninterruptible power supplies, power tools, and satellites, as well as as an eco-friendly power source for larger devices, in addition to being a power source for portable electronic devices.

[0003] Generally, the structure of a lithium-lithium battery consists of a positive electrode containing a lithium-transition metal composite oxide, a negative electrode capable of absorbing and extracting lithium ions, a separator interposed between the positive electrode and the negative electrode, and an electrolyte that facilitates the movement of lithium ions.

[0004] Generally, the role of a separator is to provide high ion permeability by retaining the electrolyte, in addition to isolating the anode and cathode. Furthermore, separators equipped with a shutdown function—where a portion of the separator melts to block pores—have recently been proposed to interrupt the current when a large amount of current flows due to causes such as a partial short circuit. Additionally, a technology has been proposed to prevent contact between the electrode plates by making the separator surface area larger than that of the anode and cathode plates; however, in this case, it must additionally possess the function of preventing the separator from shrinking due to the rise in internal battery temperature, thereby preventing internal short circuits where the two plates come into contact. In particular, lithium-ion batteries, which require larger sizes and higher energy densities in line with recent trends, maintain a continuous high-rate charge / discharge state, causing the internal temperature to rise; therefore, higher heat resistance and thermal safety are required than those demanded by conventional separators. The problem to be solved

[0005] The technical problem that the present application aims to solve is to provide a separator for a lithium battery with improved high-temperature safety and a lithium battery including the same.

[0006] The technical problems that the present invention aims to solve are not limited to those described above. means of solving the problem

[0007] To solve the above technical problem, a separator for a lithium battery with improved high-temperature safety is provided.

[0008] According to one embodiment, the separator for the lithium battery may comprise a base separator manufactured using glass fibers and a solid electrolyte provided on the surface of the base separator.

[0009] According to one embodiment, the glass fiber may include borosilicate.

[0010] According to one embodiment, the charge and discharge characteristics of the lithium battery may be controlled according to the amount of coating of the solid electrolyte provided on the surface of the base separator.

[0011] According to one embodiment, the glass fibers may randomly intertwine to form a network to form the base separator.

[0012] According to one embodiment, the insulation failure rate may be controlled according to the length of the glass fiber.

[0013] According to one embodiment, the solid electrolyte may include LATP.

[0014] According to one embodiment, each of the glass fibers included in the base separator may have a straight shape extending in one direction.

[0015] To solve the above technical problem, the present application provides a lithium battery.

[0016] According to one embodiment, the lithium battery may include a lithium battery separator according to the embodiments described above, a positive electrode having a positive active material comprising a lithium transition metal oxide, and a negative electrode having a carbon-based negative active material and spaced apart from the positive electrode with the lithium battery separator in between. Effects of the invention

[0017] A lithium battery separator according to an embodiment of the present application may include a base separator manufactured using glass fibers and a solid electrolyte provided on the surface of the base separator.

[0018] The glass fiber constituting the base separator above not only has high stability at high temperatures, but also can have high ionic conductivity due to the solid electrolyte provided on the surface of the glass fiber.

[0019] According to one embodiment, the separator can be used in a lithium metal primary battery and has high stability at high temperatures, so it can be used in equipment such as oil drilling. Brief explanation of the drawing

[0020] FIGS. 1 and FIGS. 2 are drawings for illustrating a separator coated with a solid electrolyte according to an embodiment of the present application. Figure 3 is an SEM image of a straight glass fiber (long fiber) having a diameter of 5.5 to 8 μm according to an experimental example of the present application. Figure 4 is an SEM image of a curved glass fiber (short fiber) having a diameter of 1 to 5 μm according to an experimental example of the present application. Figure 5 is an SEM image of a base separator prepared using a 6 mm long fiber as shown in Figure 3. Figure 6 is an SEM image of a base separator prepared by mixing short fibers of lengths 12 mm and 6 mm as shown in Figure 3. Figure 7 is an SEM image of a base separator manufactured using a 12 mm long fiber as shown in Figure 3. FIGS. 8 and 9 are graphs evaluating the charge and discharge characteristics of a lithium battery including a separator according to an embodiment of the present application. FIG. 10 is a graph evaluating the charge / discharge characteristics of a lithium battery according to temperature in an embodiment of the present application. Specific details for implementing the invention

[0021] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the attached drawings. However, the technical concept of the present invention is not limited to the embodiments described herein and may be embodied in other forms. Rather, the embodiments introduced herein are provided to ensure that the disclosed content is thorough and complete and to sufficiently convey the concept of the present invention to those skilled in the art.

[0022] Additionally, although terms such as first, second, third, etc., have been used to describe various components in the various embodiments of this specification, these components should not be limited by such terms. These terms are used merely to distinguish one component from another. Accordingly, what is referred to as the first component in one embodiment may be referred to as the second component in another embodiment. Each embodiment described and illustrated herein also includes its complementary embodiment. Furthermore, in this specification, "and / or" is used to mean including at least one of the components listed before and after it.

[0023] In the specification, singular expressions include plural expressions unless the context clearly indicates otherwise. Furthermore, terms such as "comprising" or "having" are intended to specify the existence of the features, numbers, steps, components, or combinations thereof described in the specification, and should not be understood as excluding the existence or addition of one or more other features, numbers, steps, components, or combinations thereof. Additionally, in the following description of the invention, if it is determined that a detailed description of related known functions or configurations could unnecessarily obscure the essence of the invention, such detailed description will be omitted.

[0025] According to an embodiment of the present application, a separator is provided in which an ion-conductive material is formed as a coating layer on a separator material composed of glass fibers, and a battery including the same is provided, and a lithium lithium battery with significantly improved high-temperature performance and lifespan characteristics is provided.

[0026] In order to improve the characteristics of lithium batteries in a conventional high-temperature environment, the binder for separator coating was controlled, a polymer coating layer or a ceramic coating layer (Al2O3, etc.) was introduced into a porous polyolefin (polymer), the composition was controlled through a combination of polyolefins (polymers), the composition of an organic solvent electrolyte was controlled, the electrolyte additive was controlled, the electrode additive was controlled, or the composition of the cathode active material was controlled.

[0027] In addition, conventional technology uses polymer-based membranes, and the maximum operating temperature is 60 degrees. At temperatures above 80 degrees, shrinkage of the polymer (polyolefin), etc. occurs, which increases the risk of rupture and ignition, making it difficult to use.

[0028] On the other hand, according to an embodiment of the present application, a separator can be manufactured using glass fibers coated with an oxide-based solid electrolyte composition such as LATP.

[0030] FIGS. 1 and FIGS. 2 are drawings for illustrating a separator coated with a solid electrolyte according to an embodiment of the present application.

[0031] Referring to FIGS. 1 and 2, a glass fiber may be provided, and a solid electrolyte may be coated on the surface of the glass fiber.

[0032] For example, the glass fiber may be a straight long glass fiber with a fiber diameter of 5.5 to 8 μm. Alternatively, the glass fiber may be a curved microglass fiber with a fiber diameter of 1 to 5 μm. That is, the glass fiber may be defined as a curved short fiber when the fiber diameter is relatively thin, and as a straight long fiber when the fiber diameter is relatively thick.

[0033] The surface of the glass fiber may be coated with an oxide-based solid electrolyte such as LATP (Lithium Aluminum Titanium Phosphate). For example, a slurry may be prepared by mixing a solid electrolyte powder, a binder, and a solvent, and the glass fiber may be coated with the solid electrolyte by providing the slurry on the surface of the glass fiber, thereby providing a separator according to an embodiment of the present application.

[0034] For example, the slurry can be coated onto the glass fiber by various methods such as spray coating, roll-to-roll coating, screen printing, or dip coating. Additionally, after coating, as shown in FIG. 2, the solid electrolyte may conformally cover the entire surface of the glass fiber. Alternatively, the solid electrolyte may not cover a portion of the glass fiber.

[0035] Or, as another example, the solid electrolyte is Li7La3Zr2O 12 , Li7La3ZrNb 0.5 Y 0.5 O 12 , LLZO-0.3B2O3, Li7La3Zr 1.7 Ge 0.3 O 12 , Li 6.65 Ga 0.15 La3Zr 1.90 Sc 0.10 O 12 , LiPON, Li 1.70 Al 0.61 Ge 1.35 P 3.04 O 12 (melt-quench), Li 1.5 Al 0.5 Ge 1.5 (PO4)3, Li 0.34 La 0.51 TiO 2.94 , Li 0.29 La 0.57 TiO3, Li 3 / 8 Sr 7 / 16 Ta 3 / 4 Zr 1 / 4It may include at least one of O3.

[0036] Alternatively, as another example, the solid electrolyte may be selected as one of the perovskite types, which have excellent capacity and output characteristics when ionic conductivity is high.

[0037] In addition, when the separator according to an embodiment of the present application is utilized in a lithium metal primary battery, the solid electrolyte is LLZO(Li7La3Zr2O 12 It may include ). Therefore, the solid electrolyte may have high chemical stability with lithium metal and may be doped with Al or Ga to improve electrochemical properties and thermal stability.

[0038] A separator can be manufactured using the glass fiber before the solid electrolyte is coated on the glass fiber. In other words, a membrane is manufactured using the glass fiber, and a slurry containing the solid electrolyte is provided on the membrane manufactured from the glass fiber, thereby manufacturing the separator.

[0041] Below, the results of the characteristic evaluation of other membranes in specific experimental examples of the present application are described.

[0042] Preparation of long fibers and short fibers according to experimental examples

[0043] FIG. 3 is an SEM image of a straight glass fiber (long fiber) having a diameter of 5.5 to 8 μm according to an experimental example of the present application, and FIG. 4 is an SEM image of a curved glass fiber (short fiber) having a diameter of 1 to 5 μm according to an experimental example of the present application.

[0044] As shown in FIGS. 3 and 4, long fibers and short fibers were prepared, and a membrane (base separator) was manufactured using a long fiber (glass fiber) with a diameter of approximately 8 μm as shown in FIG. 3. In FIGS. 3 and 4, the short fiber and the long fiber are borosilicate glass fibers.

[0046] Figure 5 is an SEM image of a base membrane manufactured using long fibers of length 6 mm as shown in Figure 3, Figure 6 is an SEM image of a base membrane manufactured by mixing short fibers of lengths 12 mm and 6 mm as shown in Figure 3, and Figure 7 is an SEM image of a base membrane manufactured using long fibers of length 12 mm as shown in Figure 3.

[0047] Referring to FIGS. 5 to 7, the porosity, tensile strength, thermal properties at 200 degrees or less, and insulation failure rate of the base separator shown in FIG. 5 (ex1 in Table 1), the base separator shown in FIG. 6 (ex2 in Table 1), and the base separator shown in FIG. 7 (ex3 in Table 1) were evaluated as shown in [Table 1] below.

[0048] division ex1 (length 6mm) ex2 (length 12+6mm) ex3 (length 12mm) Porosity (%) 93.7 90.3 90.6 Tensile force (kgf / mm2) 7.54 7.23 12.38 Thermal properties (DSC) 200℃ or less stability stability stability Insulation failure rate (500V) 0.53% 5% 12.8%

[0050] As can be seen in [Table 1], compared to the base separator using 12mm and 6mm long fibers, it can be confirmed that the base separator using 6mm long fibers has a significantly lower insulation failure rate. In other words, it can be confirmed that manufacturing the base separator using glass fibers (long fibers) with a diameter of 8um and a length of 6mm is an efficient method that can significantly reduce the insulation failure rate.

[0052] Lithium battery manufacturing according to experimental example

[0053] As shown in Fig. 3, a base membrane was prepared using glass fibers (long fibers) with a diameter of 8 μm and a length of 6 mm, and the surface of the base membrane was coated with an LATP solid electrolyte. Specifically, the amount of LATP supplied to the base membrane was 9 mg / cm² 2 , 11mg / cm 2 , 16mg / cm 2 A separation membrane was manufactured while controlling it.

[0054] In addition, as shown in Fig. 4, a base membrane was prepared using glass fibers (short fibers) with a diameter of 3 μm and a length of 6 mm, and the surface of the base membrane was coated with an LATP solid electrolyte. Specifically, the amount of LATP supplied to the base membrane was 9 mg / cm² 2 , 11mg / cm 2 , 16mg / cm 2 A separation membrane was manufactured while controlling it.

[0055] A lithium transition metal oxide of NCM 811 composition was prepared as the cathode active material, carbon black was prepared as the conductive material, PVDF was prepared as the binder, and a 15 µm thick aluminum foil was prepared as the current collector. The cathode active material, conductive material, and binder were mixed in a weight ratio of 94:3:3 and coated onto the aluminum foil to manufacture the cathode.

[0056] Natural graphite was prepared as the cathode, carbon black as the conductive material, SBR (Styrene-Butadiene Rubber) and CMC (Carboxymethyl Cellulose) as binders, and a 10 µm thick copper foil was prepared as the current collector. An anode was prepared by coating the copper foil with natural graphite, carbon black, and SBR / CMC in a weight ratio of 96:1:3.

[0057] EC (Ethylene Carbonate) and EMC (Ethyl Methyl Carbonate) were prepared as electrolytes and mixed in a volume ratio of 3:7, VC (Vinylene Carbonate) at 1.5 vol% and PS (Propane Sultone) at 0.5 vol% were mixed as additives, and 1M LiPF6 was mixed.

[0059] FIGS. 8 and 9 are graphs evaluating the charge and discharge characteristics of a lithium battery including a separator according to an embodiment of the present application.

[0060] Referring to Fig. 8, in the experimental example described above, the charge and discharge characteristics of a lithium battery using a base separator with a glass fiber (long fiber) having a diameter of 8 μm and a length of 6 mm as shown in Fig. 3 were evaluated according to the coating amount (loading amount) of the solid electrolyte under 80 degrees conditions, and the results were shown in [Table 2] below.

[0061] LATP coating amount Capacity (mAh / cm 2 ) No coating 1.444 9mg / cm 2 1.448 11mg / cm 2 1.535 16mg / cm 2 1.468

[0062] Referring to Fig. 9, in the experimental example described above, the charge and discharge characteristics of a lithium battery using a base separator with a glass fiber (short fiber) having a diameter of 3 µm and a length of 6 mm, as shown in Fig. 4, were evaluated according to the coating amount (loading amount) of the solid electrolyte under 80 degrees conditions, and the results were shown in [Table 3] below.

[0063] LTPA coating amount Capacity (mAh / cm 2 ) No coating 0.418 9mg / cm 2 0.413 11mg / cm 2 0.412 16mg / cm 2 0.416

[0064] As can be seen in Figures 8 and 9, and [Table 2] and [Table 3], when a membrane is manufactured using long fibers compared to when a membrane is manufactured using short fibers, it can be confirmed that the membrane has a performance that is up to 3.7 times higher.

[0065] Furthermore, regarding the coating amount of LATP solid electrolyte, it can be confirmed that charge / discharge characteristics are improved when the base separator is coated compared to the uncoated case. In addition, the LATP coating amount is 9 mg / cm² 2 Exceeding 16 mg / cm² 2 When controlled to less than 6%, it can be confirmed that charge / discharge characteristics are improved by more than 6%. In other words, it can be confirmed that charge / discharge characteristics can be improved by more than 6% through a simple method of controlling the amount of LATP solid electrolyte coating on the surface of a base separator made of long fibers.

[0067] FIG. 10 is a graph evaluating the charge / discharge characteristics of a lithium battery according to temperature in an embodiment of the present application.

[0068] Referring to Fig. 10, in the experimental example described above, the charge and discharge characteristics of a lithium battery using a base separator with a glass fiber (long fiber) having a diameter of 8 μm and a length of 6 mm, as shown in Fig. 3, were evaluated at room temperature, 60°C, 80°C, 100°C, and 125°C, and are shown as in [Table 4] below.

[0069] temperature Capacity (mAh / cm 2 ) room temperature 1.379 60 degrees 1.468 80 degrees 1.535 100 degrees 0.965 125 degrees 0.356

[0070] As can be seen in Figure 10 and [Table 4], it can be confirmed that the capacity is maintained without degradation of charge / discharge characteristics from room temperature up to 80 degrees, and that the charge / discharge characteristics actually improve up to 80 degrees. In other words, it can be confirmed that it has high stability even at high temperatures. However, when the temperature exceeds 100 degrees, it can be confirmed that the charge / discharge characteristics deteriorate due to the excessive temperature rise.

[0072] Although the present invention has been described in detail using preferred embodiments, the scope of the invention is not limited to specific embodiments and should be interpreted by the appended claims. Furthermore, those skilled in the art will understand that many modifications and variations are possible without departing from the scope of the invention. Explanation of the symbols delete

Claims

Claim 1 A separator for a lithium battery comprising: a base separator manufactured using glass fibers; and a solid electrolyte coated on at least a portion of the surface of each of a plurality of glass fibers of the base separator, wherein the base separator comprises a plurality of glass fibers having a straight shape extending in one direction that are randomly entangled with each other to form a network, the glass fibers comprising borosilicate, and the solid electrolyte comprising LATP. Claim 2 A lithium battery separator according to claim 1, wherein the charge / discharge characteristics of the lithium battery including the lithium battery separator are controlled according to the coating amount of the solid electrolyte. Claim 3 In claim 2, the coating amount of the solid electrolyte is 9 mg / cm² 2 Exceeding 16 mg / cm² 2 A separator for a lithium battery comprising being controlled to less than, thereby improving the charge / discharge characteristics of the lithium battery. Claim 4 A separator for a lithium battery according to claim 1, wherein the insulation failure rate is controlled according to the length of the glass fiber. Claim 5 A separator for a lithium battery according to claim 4, wherein the glass fiber length is controlled to 6 mm, thereby reducing the insulation failure rate. Claim 6 A separator for a lithium battery according to claim 5, wherein the diameter of the glass fiber is 5.5 μm or more and 8 μm or less. Claim 7 A lithium battery comprising: a separator for a lithium battery according to claim 1; a positive electrode having a positive active material comprising a lithium transition metal oxide; and a negative electrode having a carbon-based negative active material, spaced apart from the positive electrode with the separator for the lithium battery in between. Claim 8 A lithium battery according to claim 7, wherein the charge / discharge characteristics of the lithium battery are improved at a temperature greater than 60 degrees and less than 100 degrees.

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