KR20240037724A - Lithium recharegable battery - Google Patents

Abstract

The present invention relates to a cathode substrate; A porous layer containing inorganic fine particles containing barium, barium organic acid or barium inorganic acid and a dispersant; and a positive electrode substrate. It relates to a lithium secondary battery comprising a.

Description

Lithium secondary battery {LITHIUM RECHAREGABLE BATTERY}

The present invention relates to a lithium secondary battery including a porous layer formed on a negative electrode substrate and having excellent long-term battery life.

Recently, as technology development and demand for mobile devices increase, the demand for secondary batteries capable of charging and discharging as an energy source is rapidly increasing, and accordingly, much research is being conducted on secondary batteries that can meet various needs. In addition, secondary batteries are proposed as a solution to air pollution from existing gasoline and diesel vehicles that use fossil fuels, such as electric vehicles (EV), hybrid electric vehicles (HEV), and plug-in hybrid electric vehicles. It is also attracting attention as a power source for (Plug-in HEV) etc.

When a short circuit occurs in a lithium secondary battery due to contact between the positive and negative electrodes, extreme heat generation occurs and explosion follows. Accordingly, a porous separator was used, but the porous separator of the secondary battery shows extreme heat shrinkage behavior at a temperature of about 100 ℃ or higher due to the material characteristics and characteristics of the manufacturing process, including stretching, which causes a short circuit between the anode and the cathode. there is.

Accordingly, there is a need for research on lithium secondary batteries that can achieve stability and long battery life characteristics at high temperatures and include a separator with excellent coating properties.

The present invention is to provide a lithium secondary battery with improved lifespan characteristics, charging capacity, and discharging capacity while having high high-temperature stability and robust structural stability.

The present invention relates to a cathode substrate; A porous layer formed on the cathode substrate and including a binder resin, a dispersant, and inorganic fine particles. A positive electrode substrate formed on the porous layer, wherein the inorganic fine particles are barium, barium organic acid, or barium. It provides a lithium secondary battery that includes an inorganic acid, and the porous layer includes 110 to 5000 parts by weight of the inorganic fine particles relative to 100 parts by weight of the binder resin.

Hereinafter, a lithium secondary battery according to an embodiment of the invention will be described in detail.

Terms or words used in this specification and claims should not be construed as limited to their usual or dictionary meanings, and the inventor may appropriately define the concept of terms in order to explain his or her invention in the best way. It must be interpreted with meaning and concept consistent with the technical idea of the invention based on the principle that it exists.

Unless otherwise defined in this specification, all technical and scientific terms have the same meaning as commonly understood by those skilled in the art to which the present invention pertains. The terminology used in the description herein is merely to effectively describe specific embodiments and is not intended to limit the invention.

As used herein, singular forms include plural forms unless phrases clearly indicate the contrary.

As used herein, the meaning of "comprising" is to specify a specific characteristic, area, integer, step, operation, element, and/or component, and to specify another specific property, area, integer, step, operation, element, component, and/or group. It does not exclude the existence or addition of .

Since the present invention can be subject to various changes and can take various forms, specific embodiments will be illustrated and described in detail below. However, this is not intended to limit the present invention to a specific disclosed form, and should be understood to include all changes, equivalents, and substitutes included in the spirit and technical scope above.

In this specification, for example, when the positional relationship between two parts is described as 'on top', 'on top', 'on the bottom', 'next to', etc., it is called 'immediately' or 'directly'. One or more other parts may be placed between the two parts unless an expression is used.

In this specification, for example, when a temporal relationship is described as 'after', 'successfully', 'next to', 'before', etc., the expressions 'immediately' or 'directly' are not used. Cases that are not consecutive may also be included.

In this specification, the term 'at least one' should be understood to include all possible combinations from one or more related items.

According to one embodiment of the invention, an anode substrate; A porous layer formed on the cathode substrate and including a binder resin, a dispersant, and inorganic fine particles. A positive electrode substrate formed on the porous layer, wherein the inorganic fine particles are barium, barium organic acid, or barium. A lithium secondary battery is provided, which includes an inorganic acid, and the porous layer includes 110 to 5000 parts by weight of the inorganic fine particles relative to 100 parts by weight of the binder resin.

The present inventors have developed a lithium secondary battery in which a porous layer containing the above-described binder particles, inorganic fine particles, and dispersant is positioned between the negative electrode substrate and the positive electrode substrate, and the porous layer containing the above-described binder particles, inorganic fine particles, and dispersant By including it, the lithium secondary battery can prevent structural stability or battery performance from being deteriorated even at high temperatures of 100 ℃ or higher. In addition, it has high high temperature stability and solid structural stability while improving life characteristics, charging capacity, and discharging capacity. The invention was completed after confirming through experiments that the porous layer has excellent coating properties and can create a uniform surface.

In particular, the porous layer included in the lithium secondary battery can replace the function of an existing polymer separator, and the barium, barium organic acid or barium inorganic acid and dispersant contained in the porous layer have low reactivity with the electrolyte solution, so the lithium secondary battery can replace the function of the existing polymer separator. Gas generation within the battery and battery swelling can be minimized, and the porous layer can be prevented from being deformed or having physical properties deteriorated due to heat shrinkage even at temperatures above about 100°C.

Specifically, the porous layer may include a binder resin, a dispersant, and inorganic fine particles.

The porous layer can form micro-unit pores by adjusting the type of inorganic fine particles, the size of the inorganic fine particles, the content of the inorganic fine particles, and the content of the binder resin, and can also control the pore size and porosity. That is, as the porous layer contains a binder resin and inorganic fine particles, the porosity of the porous layer satisfies 30% to 90%, and the pores of the porous layer may have a diameter of 0.01 ㎛ to 10 ㎛. there is.

The inorganic fine particles are the main component of forming the porous layer, and serve to form fine pores by leaving empty spaces between the inorganic fine particles, and also serve as a kind of spacer that can maintain the physical shape of the porous layer.

The inorganic fine particles must be electrochemically stable and do not undergo oxidation and/or reduction reactions in the operating voltage range of the applied battery. In particular, when inorganic fine particles with ion transport ability are used, performance can be improved by increasing the ion conductivity within the lithium secondary battery. In addition, when inorganic particles with a high dielectric constant are used as inorganic fine particles, the ionic conductivity of the electrolyte solution can be improved by contributing to an increase in the degree of dissociation of electrolyte salts, such as lithium salts, in the liquid electrolyte.

Specifically, the inorganic fine particles may include barium, barium organic acid, or barium inorganic acid. Barium, barium organic acid, or barium inorganic acid has low moisture content and low reactivity with lithium salt in the electrolyte solution, making it stable in the electrolyte solution. In addition, barium, barium organic acid, or barium inorganic acid may cause decomposition of water when water is combined on the surface, or, as it has a strong binding force with water, it suppresses side reactions that occur due to reaction with electrolyte and moisture, thereby preventing gas generation. Not only is it small, but it can also have the effect of increasing the long-term life characteristics of the battery. Accordingly, gas generation and battery swelling in the lithium secondary battery containing barium, barium organic acid, or barium inorganic acid are minimized, thereby realizing excellent battery life characteristics and realizing a stable effect in the battery.

More specifically, the inorganic fine particles may include at least one type of barium inorganic acid selected from the group consisting of barium titanate (BaTiO ₃ ) and barium sulfate (BaSO ₄ ).

As the inorganic fine particles include one or more barium inorganic acids selected from the group consisting of barium titanate (BaTiO ₃ ) and barium sulfate (BaSO ₄ ), the low water content and electrolyte of barium, barium organic acid or barium inorganic acid as described above. Due to the low reactivity with the lithium salt, the reactivity with the electrolyte is low, so gas generation and battery swelling due to side reactions of the electrolyte with barium, barium organic acid, or barium inorganic acid in the lithium secondary battery are minimized, and the lithium secondary battery of the above embodiment has excellent performance. Battery life characteristics can be realized.

As described above, in the lithium secondary battery of one embodiment, the porous layer may include a dispersant.

As the porous layer contains inorganic fine particles containing barium, barium organic acid or barium inorganic acid and a dispersant at the same time, the dispersibility of the inorganic fine particles contained in the porous layer is improved, thereby improving the coating properties of the finally manufactured porous layer. Excellent surface quality of the porous layer can be achieved.

In order to maximize the improvement of the dispersibility of inorganic fine particles, the dispersant may have an amine value of 1 mg KOH/g or more and 90 mg KOH/g or less.

Specifically, the dispersant may have an amine value of 1 mg KOH/g or more, 10 mg KOH/g or more, 90 mg KOH/g or less, 80 mg KOH/g or less, 60 mg KOH/g or less, and 50 mg KOH/g or less. 1 mg KOH/g or more but 90 mg KOH/g or less, 1 mg KOH/g or more but 80 mg KOH/g or less, 1 mg KOH/g or more and 60 mg KOH/g or less, 1 mg KOH/g or more 50 mg KOH /g or less, 10 mg KOH/g or more 90 mg KOH/g or less, 10 mg KOH/g or more 80 mg KOH/g or less, 10 mg KOH/g or more 60 mg KOH/g or less, 10 mg KOH/g or less 50 It may be less than mg KOH/g.

As the amine value of the dispersant is 1 mg KOH/g or more and 90 mg KOH/g or less, the dispersant interacts with the surface of the inorganic particles through electrostatic attraction to suppress agglomeration between particles, containing barium, barium organic acid, or barium inorganic acid. By improving the dispersibility of inorganic fine particles, excellent surface quality of the porous layer can be realized.

If the amine value of the dispersant is less than 1 mg KOH/g, the interaction of the dispersant with the inorganic particles decreases, resulting in poor dispersibility of the inorganic fine particles, and if the amine value is more than 90 mg KOH/g, the content of functional groups included in the dispersant depends on As this increases, the performance of the final manufactured battery may deteriorate.

More specifically, the dispersant may include polyurethane having an amine titer of 1 mg KOH/g to 90 mg KOH/g.

That is, the dispersant may be 1 mg KOH/g or more, 10 mg KOH/g or more, 90 mg KOH/g or less, 80 mg KOH/g or less, 60 mg KOH/g or less, and 50 mg KOH/g or less, 1 mg KOH/g or more, 90 mg KOH/g or less, 1 mg KOH/g or more, 80 mg KOH/g or less, 1 mg KOH/g or more, 60 mg KOH/g or less, 1 mg KOH/g or more, 50 mg KOH/g or less, 10 mg KOH/g or more, 90 mg KOH/g or less, 10 mg KOH/g or more, 80 mg KOH/g or less, 10 mg KOH/g or more, 60 mg KOH/g or less, 10 mg KOH/g or more, 50 mg KOH It may include polyurethane having an amine number of /g or less.

The type of the dispersant is not greatly limited as long as it is a polyurethane that satisfies the above-mentioned amine value. For example, the dispersant is selected from the group consisting of BYK-163, BYK-9076, BYK-9077, BYK-2155, and BYK-2200. It may contain one or more dispersants. Preferably, the dispersant may include BYK-163 or BYK-9076.

The porous layer may include 110 to 5,000 parts by weight of the inorganic fine particles relative to 100 parts by weight of the binder resin. The weight portion of the binder resin and inorganic fine particles can be calculated based on the solid content weight.

Specifically, the porous layer may include 110 parts by weight or more, 150 parts by weight, 5000 parts by weight or less, 1000 parts by weight or less, 900 parts by weight or less of the inorganic fine particles relative to 100 parts by weight of the binder resin, and 110 parts by weight. Not less than 5000 parts by weight, not less than 110 parts by weight but not more than 1000 parts by weight, not less than 110 parts by weight but not more than 900 parts by weight, not less than 150 parts by weight but not more than 5000 parts by weight, not less than 150 parts by weight but not more than 1000 parts by weight, not less than 150 parts by weight but not more than 900 parts by weight It can be included below.

The porous layer can form micro-unit pores by controlling the type of inorganic fine particles, the size of the inorganic fine particles, the content of the inorganic fine particles, and the content of the binder resin, and can also control the pore diameter and porosity. That is, as the porous layer contains 110 to 5000 parts by weight of the inorganic fine particles relative to 100 parts by weight of the binder resin, the porosity of the porous layer may satisfy 30% or more and 90% or less, and the porous layer's The pores may have a diameter of 0.01 ㎛ or more and 10 ㎛ or less.

When the porous layer contains less than 110 parts by weight of the inorganic fine particles relative to 100 parts by weight of the binder resin, the content of the binder resin becomes too large, resulting in a decrease in the empty space formed between the inorganic fine particles, resulting in a decrease in pore diameter and Porosity may be reduced and final cell performance may deteriorate. In addition, when the porous layer contains more than 5000 parts by weight of the inorganic fine particles relative to 100 parts by weight of the binder resin, the content of the binder resin is excessively reduced and the peeling resistance is weakened due to weakened adhesion between the inorganic fine particles. The mechanical properties of the porous layer may decrease.

Meanwhile, the porous layer may include 3 to 50 parts by weight of the dispersant based on 100 parts by weight of the binder resin. The weight portion of the binder resin and dispersant may be calculated based on the solid weight.

Specifically, the porous layer may include 3 parts by weight or more, 5 parts by weight or more, 50 parts by weight or less, and 30 parts by weight or less of the dispersant relative to 100 parts by weight of the binder resin. It may contain 3 parts by weight or more and 30 parts by weight or less, 5 parts by weight or more and 50 parts by weight or less, and 5 parts by weight or more and 30 parts by weight or less.

The porous layer can form micro-unit pores by controlling the type of inorganic fine particles, the size of the inorganic fine particles, the content of the inorganic fine particles, and the content of the binder resin, and can also control the pore diameter and porosity. That is, as the porous layer contains 3 to 50 parts by weight of the dispersant relative to 100 parts by weight of the binder resin, the porosity of the porous layer may satisfy 30% or more and 90% or less, and the pores of the porous layer may be 0.01%. It may have a diameter of ㎛ or more and 10 ㎛ or less.

If the porous layer contains less than 3 parts by weight of the dispersant relative to 100 parts by weight of the binder resin, the dispersant is contained in an excessively small amount, resulting in poor coating properties of the porous layer and increased cohesion between particles, resulting in the composition for forming a porous layer This heterogeneity may cause poor battery performance due to a decrease in the coating quality of the porous layer and the occurrence of cracks or holes in the final manufactured porous layer.

Additionally, when the porous layer contains more than 50 parts by weight of the dispersant based on 100 parts by weight of the binder resin, the content of the functional group included in the dispersant increases, and the performance of the final manufactured battery may deteriorate.

Additionally, the porous layer may include 1 part by weight or more and 10 parts by weight or less of the dispersant based on 100 parts by weight of the inorganic fine particles. The inorganic fine particles and the weight portion of the inorganic fine particles can be calculated based on the solid weight.

Specifically, the porous layer may contain 1 part by weight or more, 2 parts by weight or more, 3 parts by weight or more, 10 parts by weight or less, 9 parts by weight or less, and 5 parts by weight or less of the dispersant relative to 100 parts by weight of the inorganic fine particles. Can be 1 part by weight or more and 10 parts by weight or less, 1 part by weight or more and 9 parts by weight or less, 1 part by weight or more and 5 parts by weight or less, 2 parts by weight or more and 10 parts by weight or less, 2 parts by weight or more and 9 parts by weight or less, 2 parts by weight. It may be included in an amount of not less than 5 parts by weight, not less than 3 parts by weight but not more than 10 parts by weight, not less than 3 parts by weight but not more than 9 parts by weight, and not less than 3 parts by weight and not more than 5 parts by weight.

The porous layer can form micro-unit pores by controlling the type of inorganic fine particles, the size of the inorganic fine particles, the content of the inorganic fine particles, and the content of the binder resin, and can also control the pore diameter and porosity. That is, as the porous layer contains 1 part by weight to 10 parts by weight of the dispersant relative to 100 parts by weight of the inorganic fine particles, the porosity of the porous layer may satisfy 30% to 90%, and the porous layer The pores may have a diameter of 0.01 ㎛ or more and 10 ㎛ or less.

When the porous layer contains less than 1 part by weight of the dispersant relative to 100 parts by weight of the inorganic fine particles, the dispersant is contained in an excessively small amount, resulting in poor coating properties of the porous layer, and the cohesion between particles increases, forming a porous layer. The composition may become heterogeneous, resulting in poor battery performance due to a decrease in coating quality of the porous layer and the occurrence of cracks or holes in the final manufactured porous layer.

In addition, when the porous layer contains more than 9.5 parts by weight of the dispersant relative to 100 parts by weight of the inorganic fine particles, the content of the functional group contained in the dispersant increases, which may deteriorate the performance of the finally manufactured battery.

In the lithium secondary battery of the above embodiment, the porous layer may have a porosity of 30% or more and 90% or less.

Specifically, in the lithium secondary battery of the above embodiment, the porous layer has a porosity of 30% or more, 40% or more, 90% or less, 80% or less, 70% or less, 60% or less, 55% or less, 30% or more and 90%. or less, 30% or more and 80% or less, 30% or more and 70% or less, 30% or more and 60% or less, 30% or more and 55% or less, 40% or more but 90% or less, 40% or more and 80% or less, 40% or more and 70% or less , it may be 40% or more and 60% or less, or 40% or more and 55% or less.

The porosity of the porous layer can be implemented depending on the composition of the porous layer. Specifically, the porosity of the porous layer can be realized by adjusting the type of inorganic fine particles, the size of the inorganic fine particles, the content of the inorganic fine particles, and the content of the binder resin. As the porosity of the porous layer is 30% to 90%, high ionic conductivity can be realized by securing a passage for lithium ions in the electrolyte to be filled in the pores and providing the lowest possible resistance.

If the porosity of the porous layer exceeds 90%, the ability to secure the physical and electrochemical insulation characteristics of the separator between the anode and the cathode may deteriorate, which may lead to internal short circuit and reduced safety of the battery. If the porosity of the porous layer is less than 30%, lithium The path for ion movement is reduced and the resulting increase in cell resistance may lead to a decrease in battery capacity during rapid charging and discharging.

The porosity can be measured using the thickness, weight, and density of the porous layer components using a thickness measuring device and scale under vacuum-dried conditions for an electrode base sample on which a porous layer of unit area is formed.

Specifically, the porosity is determined by the following equation 1 using the ratio of the density obtained by measuring the volume and mass of the porous layer for a sample coated with the composition on an electrode substrate of a certain area and the theoretical density of the solid content of the coating composition. It can be calculated.

[Equation 1]

Porosity (%)= {1 - (actual density)/(theoretical density)} x 100.

The porous layer may include pores with a diameter of 0.01 ㎛ or more and 10 ㎛ or less.

Specifically, the porous layer is 0.01 ㎛ or more, 0.1 ㎛ or more, 0.3 ㎛ or less, 10 ㎛ or less, 5 ㎛ or less, 1 ㎛ or less, 0.5 ㎛ or less, 0.01 ㎛ or more 10 ㎛ or less, 0.01 ㎛ or more 5 ㎛ or less, 0.01 ㎛ or more. ㎛ or more 1 ㎛ or less, 0.01 ㎛ or more 0.5 ㎛ or less, 0.1 ㎛ or more 10 ㎛ or less, 0.1 ㎛ or more 5 ㎛ or less, 0.1 ㎛ or more 1 ㎛ or less, 0.1 ㎛ or more 0.5 ㎛ or less, 0.3 ㎛ or more 10 ㎛ or less, 0 .3㎛ It may include pores having a diameter of 5 ㎛ or less, 0.3 ㎛ or more and 1 ㎛ or less, or 0.3 ㎛ or more and 0.5 ㎛ or less.

The diameter of the pores of the porous layer may mean the longest diameter of the pores confirmed through a scanning electron microscope image (SEM) or a transmission electron microscope image (TEM) taken of a cross section of the porous layer.

The diameter of the pores of the porous layer may be determined depending on the composition of the porous layer. Specifically, the pore diameter of the porous layer can be realized by adjusting the type of inorganic fine particles, the size of the inorganic fine particles, the content of the inorganic fine particles, and the content of the binder resin. As the porous layer includes pores with a diameter of 0.01 ㎛ or more and 10 ㎛ or less, a passage for lithium ions in the electrolyte to be filled in the pores is secured and resistance is as low as possible, thereby providing high ionic conductivity.

If the pore diameter of the porous layer is less than 0.01 ㎛, the path for lithium ion movement is reduced, which may cause a decrease in battery capacity during rapid charging and discharging due to an increase in cell resistance. If the pore diameter of the porous layer is more than 10 ㎛, the positive electrode The ability to secure the physical and electrochemical insulating properties of the separator between the anode and the cathode may deteriorate, which may result in a short circuit inside the battery and reduced safety.

The diameter of the pores can be measured using a BET device under an N ₂ gas atmosphere for a porous layer sample formed on an electrode substrate.

As described above, the porosity and pore diameter of the porous layer can be implemented by adjusting the type of inorganic fine particles, the size of the inorganic fine particles, the content of the inorganic fine particles, and the content of the binder resin.

Specifically, the inorganic fine particles may have a diameter of 1 nm to 500 nm. The diameter of the inorganic fine particles may refer to the longest diameter of the inorganic fine particles confirmed through a scanning electron microscope image (SEM) or a transmission electron microscope image (TEM) taken of the cross section of the porous layer.

Specifically, the inorganic fine particles have a diameter, that is, a primary particle (single particle) diameter of 1 nm or more, 10 nm or more, 20 nm or more, 30 nm or more, 40 nm or more, 500 nm or less, 400 nm or less, and 300 nm. It may be 200 nm or less, 150 nm or less, 100 nm or less, 1 nm or more and 500 nm or less, 1 nm or more and 400 nm or less, 1 nm or more and 300 nm or less, 1 nm or more and 200 nm or less, 1 nm or more and 150 nm or less. , 1 nm or more and 100 nm or less, 10 nm or more and 500 nm or less, 10 nm or more and 400 nm or less, 10 nm or more and 300 nm or less, 10 nm or more and 200 nm or less, 10 nm or more and 150 nm or less, 10 nm and more than 100 nm ㎚ or less, 20 ㎚ or more and 500 ㎚ or less, 20 ㎚ or more and 400 ㎚ or less, 20 ㎚ or more and 300 ㎚ or less, 20 ㎚ and more and 200 ㎚ or less, 20 ㎚ and more and 150 ㎚ or less, 20 ㎚ and more and 100 ㎚ or less, 30 ㎚ and more 500 ㎚ Below, 30 ㎚ or more and 400 ㎚ or less, 30 ㎚ or more and 300 ㎚ or less, 30 ㎚ or more and 200 ㎚ or less, 30 ㎚ or more and 150 ㎚ or less, 30 ㎚ and more and 100 ㎚ or less, 40 ㎚ and more and 500 ㎚ or less, 40 ㎚ and more and 400 ㎚ or less, 40 nm It may be more than 300 nm or less, 40 nm or more and 200 nm or less, 40 nm or more and 150 nm or less, and 40 nm or more and 100 nm or less.

If the diameter of the inorganic fine particles is less than 1 ㎚, the dispersibility is reduced, making it difficult to control the physical properties of the porous layer, and if it exceeds 500 ㎚, the thickness of the porous layer increases and the mechanical properties may deteriorate. Due to excessively large pore size, the probability of internal short circuit occurring during battery charging and discharging increases.

That is, the lithium secondary battery of the above embodiment may include a porous layer that simultaneously includes nano-sized inorganic fine particles having a diameter of 1 nm to 500 nm and a binder resin.

As the porous layer simultaneously contains nano-sized inorganic fine particles with a diameter of 1 nm to 500 nm and a binder resin, the adhesion between particles and the interfacial peel strength are improved, resulting in excellent mechanical properties (flexibility) and insulating properties of the coating layer. Can be implemented simultaneously.

In addition, when the inorganic nanoparticles are included as nano-sized inorganic fine particles with a diameter of 1 nm to 500 nm, the process yield can be increased compared to the case where the inorganic material is included in the form of fibers, and coating density and thickness can be controlled. As this is possible, excellent ionic conductivity due to uniform pore formation can be achieved.

Additionally, the inorganic fine particles may have a D50 of 1 nm to 500 nm. The D50 may mean the cumulative 50% particle size based on mass from the smallest particle size measured using a laser diffraction scattering type particle size distribution measuring device.

Specifically, the inorganic fine particles have a D50 of 1 nm or more, 10 nm or more, 20 nm or more, 30 nm or more, 40 nm or more, 500 nm or less, 400 nm or less, 300 nm or less, 200 nm or less, 150 nm or less, It may be 100 nm or less, 1 nm or more and 500 nm or less, 1 nm or more and 400 nm or less, 1 nm or more and 300 nm or less, 1 nm or more and 200 nm or less, 1 nm or more and 150 nm or less, 1 nm or more and 100 nm or less, 10 nm More than 500 nm or less, more than 10 nm but less than 400 nm, more than 10 nm but less than 300 nm, more than 10 nm but less than 200 nm, more than 10 nm but less than 150 nm, more than 10 nm but less than 100 nm, more than 20 nm but less than 500 nm, 20 ㎚ or more 400 nm or less, 20 nm or more but 300 nm or less, 20 nm or more but 200 nm or less, 20 nm or more 150 nm or less, 20 nm or more but 100 nm or less, 30 nm or more but 500 nm or less, 30 nm or more but 400 nm or less, 30 ㎚ more than 300 ㎚ or less, 30 ㎚ or more 200 ㎚ or less, 30 ㎚ or more 150 ㎚ or less, 30 ㎚ or more 100 ㎚ or less, 40 ㎚ or more 500 ㎚ or less, 40 ㎚ or more 400 ㎚ or less, 40 ㎚ or more 300 ㎚ or less, 40 ㎚ or more 2 00㎚ Hereinafter, it may be 40 nm or more and 150 nm or less, or 40 nm or more and 100 nm or less.

If the D50 of the inorganic fine particles is less than 1 nm, the dispersibility is reduced and it is not easy to control the physical properties of the porous layer, and if it exceeds 500 nm, the thickness of the porous layer increases and the mechanical properties may deteriorate. Due to excessively large pore size, the probability of internal short circuit occurring during battery charging and discharging increases.

Meanwhile, the porous layer has a porosity of 40% to 50%, and the inorganic fine particles may have a primary particle size of 30 nm to 100 nm. The primary particle size may refer to the D50 described above.

As described above, the porosity and pore diameter of the porous layer can be implemented by adjusting the type of inorganic fine particles, the size of the inorganic fine particles, the content of the inorganic fine particles, and the content of the binder resin. Therefore, as the porous layer contains inorganic fine particles with a primary particle size of 30 nm to 100 nm, a porosity of 40% or more and 50% or less can be realized, thereby realizing high ionic conductivity and preventing short circuit inside the battery. safety can be ensured by lowering the temperature.

In one embodiment, the porous layer may include a binder resin. The binder resin functions to connect and fix the inorganic fine particles.

Specifically, the binder resin is polyvinylidene fluoride, polyvinylidene fluoride-hexafluoro propylene, polyvinylidene fluoride-tetrafluoroethylene, polyvinylidene fluoride-trichloroethylene, and polyvinylidene fluoride. -Chlorotrifluoroethylene, polymethyl methacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinyl acetate, ethylene vinyl acetate copolymer, polyethylene oxide, cellulose acetate, cellulose acetate butylate, cellulose acetate propionate. , cyanoethyl pullulan, cyanoethyl polyvinyl alcohol, cyanoethyl cellulose, cyanoethyl sucrose, pullulan, carboxyl methyl cellulose, acrylonitrile-styrene-butadiene copolymer, polyurethane, polyacrylic acid, polyimide. , it may include one or more binder resins selected from the group consisting of polyetherimide and styrene butadiene rubber.

In the above embodiment, the thickness of the porous layer is not particularly limited, and considering the shape and type of the lithium secondary battery, the porous layer may have a thickness of 0.1 ㎛ or more and 100 ㎛ or less.

Specifically, the thickness of the porous layer is 0.1 ㎛ or more, 1 ㎛ or more, 10 ㎛ or less, 100 ㎛ or less, 50 ㎛ or less, 30 ㎛ or less, 20 ㎛ or less, 0.1 ㎛ or more and 100 ㎛ or less, 0.1 ㎛ or more and 50 ㎛ or less, 0.1 ㎛ to 30 ㎛, 0.1 ㎛ to 20 ㎛, 1 ㎛ to 100 ㎛, 1 ㎛ to 50 ㎛, 1 ㎛ to 30 ㎛, 1 ㎛ to 20 ㎛, 10 ㎛ to 100 ㎛, 10 It may be ㎛ or more and 50 ㎛ or less, 10 ㎛ or more and 30 ㎛ or less, and 10 ㎛ or more and 20 ㎛ or less.

If the thickness of the porous layer is too thin, a short circuit inside the cell may occur due to a decrease in insulation properties between electrodes, and if the thickness of the porous layer is too thick, a decrease in cell characteristics may occur due to an increase in overall cell resistance.

Meanwhile, in the lithium secondary battery of the above embodiment, the porous layer may be combined with the negative electrode substrate and/or the positive electrode substrate through an adhesive layer or adhesive pattern formed on at least one surface.

The adhesive layer or adhesive pattern may include commonly known adhesive components without limitation. For example, polyvinylidene fluoride-hexafluoropropylene, polyvinylidene fluoride-trichloroethylene, polyvinylidene fluoride-tetrafluoroethylene, polyvinylidene fluoride-trifluoroethylene, polyacrylic acid. It may include one or more polymer resins selected from the group.

The thickness of the adhesive layer or adhesive pattern is not particularly limited and may be adjusted, for example, to 0.01 ㎛ to 100 ㎛ considering the performance of the battery.

If the thickness of the adhesive layer or adhesive pattern is less than 0.01 ㎛, not only the adhesion to the negative electrode substrate and/or the positive substrate may be reduced, but also internal short circuit of the cell may occur due to deterioration of the insulation properties between electrodes, and if it exceeds 100 ㎛, the overall As cell resistance increases, cell characteristics may deteriorate.

In addition, the adhesive pattern may have a cross-sectional area of 0.01 ㎛ ² to 100 ㎛ ² , two or more may be formed on one side of the porous layer, and the bonding force with the negative electrode substrate and/or the positive electrode substrate or the lithium secondary battery. Considering structural safety, it may be located at a predetermined location on one side of the porous layer.

Additionally, the lithium secondary battery of the embodiment may further include an electrolyte interposed between the positive electrode and the negative electrode.

Specifically, the lithium secondary battery of one embodiment may include an electrode assembly wound with a separator between the positive electrode and the negative electrode, and a case in which the electrode assembly is built. In addition, the anode, the cathode, and the separator may be impregnated with an electrolyte.

Meanwhile, the lithium secondary battery of the embodiment may have a peeling strength of 250 gf/20 mm or more when the negative electrode substrate is peeled off at 90 degrees with respect to the positive electrode substrate. The peel strength can be implemented depending on the composition of the porous layer.

Specifically, the lithium secondary battery of one embodiment has a peeling strength of 250 gf/20 mm or more, 290 gf/20 mm or more, 500 gf/20 mm or less, and 400 gf when the negative electrode substrate is peeled off at 90 degrees with respect to the positive electrode substrate. /20 mm or less, 350 gf/20 mm or less, 250 gf/20 mm or more 500 gf/20 mm or less, 250 gf/20 mm or more 400 gf/20 mm or less, 250 gf/20 mm or more 350 gf/20 mm or less , 290 gf/20 mm or more and 500 gf/20 mm or less, 290 gf/20 mm or more and 400 gf/20 mm or less, and 290 gf/20 mm or more and 350 gf/20 mm or less.

In the lithium secondary battery, when the negative electrode substrate is peeled off at 90 degrees with respect to the positive electrode substrate, the peeling strength is 250 gf/20 mm or more, thereby achieving excellent adhesion between the porous layer and the positive electrode substrate.

The peel strength can be measured according to the ASTM D6862 measurement method using a Texture Analyzer.

Meanwhile, the negative electrode substrate includes a negative electrode material including a negative electrode active material, a conductive material, and a binder; And it may include a current collector supporting the negative electrode material.

The negative electrode active material includes a material capable of reversibly intercalating and deintercalating lithium ions, lithium metal, an alloy of lithium metal, a material capable of doping and dedoping lithium, and a transition metal oxide. It can be included.

Examples of materials that can reversibly intercalate and deintercalate lithium ions include crystalline carbon, amorphous carbon, or mixtures thereof as carbonaceous materials. Specifically, the carbonaceous material includes natural graphite, artificial graphite, Kish graphite, pyrolytic carbon, mesophase pitches, mesophase pitch based carbon fiber, These may be meso-carbon microbeads, petroleum or coal tar pitch derived cokes, soft carbon, and hard carbon.

The alloy of the lithium metal is Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, Sn, Bi, Ga, and Cd. It may be an alloy of lithium and a metal containing one or more types selected from the group consisting of.

Materials capable of doping and dedoping lithium include Si, Si-C composite, SiOx (0<x<2), and Si-Q alloy (where Q is an alkali metal, an alkaline earth metal, a group 13 element, a group 14 element, and a group 15 It is an element containing one or more types selected from the group consisting of elements, group 16 elements, transition metals, rare earth elements, and combinations thereof; however, Si is excluded), Sn, SnO ₂ , Sn-R alloy (above R is an element containing one or more selected from the group consisting of alkali metals, alkaline earth metals, group 13 elements, group 14 elements, group 15 elements, group 16 elements, transition metals, rare earth elements, and combinations thereof; provided, Sn is excluded.), etc. And, as a material capable of doping and dedoping lithium, at least one of the above examples and SiO ₂ can be used in combination. Q and R are Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Tc, Re, Bh, Fe , Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Tl, Ge, P, As, Sb, Bi, S , Se, Te, Po, etc.

And, the transition metal oxide may be vanadium oxide, lithium vanadium oxide, lithium titanium oxide, etc.

The negative electrode current collector can generally be made to have a thickness of 3 to 500 ㎛. This negative electrode current collector is not particularly limited as long as it is conductive without causing chemical changes in the battery, for example, copper, stainless steel, aluminum, nickel, titanium, fired carbon, the surface of copper or stainless steel. Surface treatment with carbon, nickel, titanium, silver, etc., aluminum-cadmium alloy, etc. can be used. In addition, like the positive electrode current collector, the bonding power of the negative electrode active material can be strengthened by forming fine irregularities on the surface, and can be used in various forms such as films, sheets, foils, nets, porous materials, foams, and non-woven materials.

The negative electrode substrate may include a negative electrode active material containing at least one selected from the group consisting of carbonaceous materials and silicon compounds.

Here, the carbonaceous material is, as previously exemplified, natural graphite, artificial graphite, Kish graphite, pyrolytic carbon, mesophase pitch, mesophase pitch-based carbon fiber, carbon microspheres, petroleum or coal-based coke, softened carbon, and hardened carbon. It is a substance containing one or more types selected from the group consisting of. And, the silicon compound is a compound containing Si as previously exemplified, that is, Si, Si-C composite, SiOx (0<x<2), the Si-Q alloy, a mixture thereof, or at least one of these and SiO It may be a mixture of ₂ .

Additionally, the anode substrate may include micro silicon. When the anode substrate contains micro silicon, superior capacity can be achieved compared to when a carbonaceous material is used as the anode active material. Specifically, when specific micro silicon is used in the silicon compound, more than 80% of the remaining capacity can be maintained even after charging and discharging more than 500 times, and significantly superior energy density can be achieved compared to conventional lithium secondary batteries. Additionally, when the cathode contains micro silicon, the charge/discharge life of a solid battery using a solid electrolyte can be greatly increased, and the charging speed at room temperature can also be greatly improved.

The size of the micro silicon is not greatly limited, but for example, the micro silicon may have a diameter of 100 ㎛ or less, or 1 to 100 ㎛, or 1 to 20 ㎛.

The negative electrode active material may be included in an amount of 85% by weight to 98% by weight based on the total weight of the negative electrode material.

Specifically, the content of the negative electrode active material is 85% by weight or more, or 87% by weight, or 90% by weight or more, based on the total weight of the negative electrode material; And, it may be 98% by weight or less, or 97% by weight or less, or 96% by weight or less.

The content of the negative electrode active material is 85% to 98% by weight, 87% to 98% by weight, 90% to 98% by weight, 85% to 97% by weight, and 87% to 97% by weight relative to the total weight of the negative electrode material. %, it may be 90% by weight to 97% by weight, 85% by weight to 96% by weight, 87% by weight to 96% by weight, and 90% by weight to 96% by weight.

The conductive material is used to provide conductivity to the electrode.

The conductive material may be used without particular limitation as long as it has electronic conductivity without causing chemical changes in the battery. As a non-limiting example, the conductive material may include carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, summer black, and carbon fiber; Graphites such as natural graphite and artificial graphite; Metal powders or metal fibers such as copper, nickel, aluminum, and silver; Conductive whiskeys such as zinc oxide and potassium titanate; Conductive metal oxides such as titanium oxide; Alternatively, it may be a conductive polymer such as a polyphenylene derivative. As the conductive material, one or a mixture of two or more of the examples described above may be used.

The content of the conductive material can be adjusted within a range that does not cause a decrease in battery capacity while maintaining an appropriate level of conductivity. Preferably, the content of the conductive material may be 0.5% by weight to 10% by weight, or 1% by weight to 10% by weight, or 1% by weight to 5% by weight, based on the total weight of the anode material.

The binder is used to properly attach the negative electrode material to the current collector.

As a non-limiting example, the binder may be polyvinylidene fluoride (PVdF), vinylidene fluoride-hexafluoropropylene copolymer (PVdF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethyl Cellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene-butadiene rubber. (SBR), fluorine rubber, etc. As the binder, one or a mixture of two or more of the examples described above may be used.

The content of the binder can be adjusted within a range that does not cause a decrease in battery capacity while maintaining an appropriate level of adhesiveness. Preferably, the content of the binder may be 0.5% by weight to 10% by weight, or 1% by weight to 10% by weight, or 1% by weight to 5% by weight, based on the total weight of the negative electrode material.

As described above, the porous layer included in the lithium secondary battery may replace the function of an existing polymer separator, and accordingly, the lithium secondary battery may not include a porous polymer separator.

Meanwhile, optionally, the lithium secondary battery may further include a porous polymer substrate along with the porous layer.

The type of the porous polymer substrate is not greatly limited, but for example, polyethylene, polypropylene, polyethyleneterephthalate, polybutyleneterephthalate, polyester, poly Acetal, polyamide, polycarbonate, polyimide, polyetheretherketone, polyaryletherketone, polyetherimide, polyamideimide ( polyamideimide, polybenzimidazole, polyethersulfone, polyphenyleneoxide, cyclic olefin copolymer, polyphenylenesulfide and polyethylenenaphthalene. A polymer substrate formed from one or more polymers selected from the group consisting of or a mixture of two or more of them, or a multilayer, woven fabric, or non-woven fabric thereof, may be used.

The porous polymer substrate can adjust the type and thickness of the substrate, the diameter and number of pores, and especially the thickness of microfibers in the case of non-woven fabrics, taking into account melting temperature, convenience of manufacturing, porosity, ion movement, insulation, etc.

The thickness of the porous polymer substrate is not particularly limited and may be adjusted to, for example, 0.01 to 100 μm considering the performance of the battery.

The positive electrode substrate may include a positive electrode active material, a binder, a conductive material, and a positive electrode additive.

The positive electrode additive has the property of irreversibly releasing lithium during charging and discharging of a lithium secondary battery. Therefore, the positive electrode additive can be included in a positive electrode for a lithium secondary battery and serve as sacrificial positive electrode materials for prelithiation.

Specifically, the positive electrode substrate can be manufactured by applying a positive electrode mixture on a positive electrode current collector and then drying it, and if necessary, a filler can be further added to the mixture.

The cathode substrate includes a cathode material including a cathode active material, a conductive material, the sacrificial cathode material, and a binder; And, it includes a current collector that supports the positive electrode material.

As batteries move to higher capacity, the ratio of negative electrode active material in the negative electrode must be increased to increase battery capacity, and the amount of lithium consumed in the SEI layer accordingly increases. Therefore, the design capacity of the battery can be determined by calculating the amount of lithium consumed in the SEI layer of the cathode and then recalculating the amount of sacrificial cathode material to be applied to the anode.

The sacrificial cathode material may be included in an amount of more than 0% by weight and up to 15% by weight based on the total weight of the cathode material.

The content of the sacrificial cathode material is preferably greater than 0% by weight based on the total weight of the cathode material.

However, if the sacrificial cathode material is included in excess, the content of the cathode active material, which exhibits reversible charge/discharge capacity, is reduced, thereby reducing the capacity of the battery, and the remaining lithium in the battery is plated on the cathode, causing a short circuit or safety hazard of the battery. may hinder. Therefore, it is preferable that the content of the sacrificial cathode material is 15% by weight or less based on the total weight of the cathode material.

Specifically, the content of the sacrificial cathode material is more than 0% by weight, or more than 0.5% by weight, or more than 1% by weight, or more than 2% by weight, or more than 3% by weight, based on the total weight of the cathode material; And, it may be 15% by weight or less, or 12% by weight or less, or 10% by weight or less. The content of the sacrificial cathode material is 0.5% to 15% by weight, or 1% to 15% by weight, or 1% to 12% by weight, or 2% to 12% by weight, or 2% by weight, relative to the total weight of the cathode material. % to 10% by weight, or 3% to 10% by weight.

Examples of the positive electrode active material are not greatly limited, but include, for example, NCM (Li[Ni,Co,Mn]O ₂ ), NCMA (Li[Ni,Co,Mn,Al]O ₂ ), LiCoO ₂ , LiNiO ₂ , LiMnO ₂ , LiMn ₂ O ₂ , LiNi _1-d Co _d O ₂ , LiCo _1-d Mn _d O ₂ , LiNi _1-d Mn _d O ₂ (0≤d<1), Li(Ni _a Co _b Mn _c )O ₄ (0<a<2, 0<b<2, 0<c<2, a+b+c=2), LiMn _2-e Ni _e O ₄ , LiMn _2-e Co _e O ₄ ( or more 0 < e < 2), LiCoPO ₄ , LiFePO ₄ or a mixture of two or more types thereof may be used.

The positive electrode active material may be included in an amount of 80% to 98% by weight based on the total weight of the positive electrode material. Specifically, the content of the positive electrode active material is 80% by weight or more, or 85% by weight, or 90% by weight, or 95% by weight or more, relative to the total weight of the positive electrode material; And, it may be 98% by weight or less.

The content of the positive electrode active material may be 80% by weight or more and 98% by weight or less, or 85% by weight or more and 98% by weight or less, or 90% by weight or more and 98% by weight or less, based on the total weight of the positive electrode material.

The positive electrode substrate may be formed by laminating a positive electrode material including the positive electrode active material, the conductive material, the sacrificial positive electrode material, and a binder on the current collector.

The filler is selectively used as a component to suppress expansion of the positive electrode, and is not particularly limited as long as it is a fibrous material that does not cause chemical changes in the battery. For example, olipine polymers such as polyethylene and polypropylene; Fibrous materials such as glass fiber and carbon fiber are used.

The conductive material, the binder, and the current collector included in the cathode material include all of the above-described information.

Meanwhile, the electrolyte may be used without particular limitation as long as it is known to be applicable to lithium secondary batteries in the technical field to which the present invention pertains. For example, the electrolyte may be an organic liquid electrolyte, an inorganic liquid electrolyte, a solid polymer electrolyte, a gel-type polymer electrolyte, a solid inorganic electrolyte, a molten inorganic electrolyte, an aqueous electrolyte, etc.

The aqueous electrolyte is a salt dissolved in an aqueous solvent such as water or alcohol. In the case of a lithium secondary battery using such an aqueous electrolyte, it is advantageous in terms of high ionic conductivity and safety of the aqueous electrolyte, and the process and manufacturing costs are also low. . In addition, batteries using an aqueous electrolyte solution have an environmental advantage over non-aqueous organic electrolytes.

Specifically, the electrolyte may include an aqueous solvent and a lithium salt.

The aqueous solvent is a solvent containing water, and is not particularly limited, but may contain 1% by weight or more of water based on the total weight of the aqueous solvent forming the electrolyte. Water may be used alone as the aqueous solvent, but a solvent miscible with water may also be used in combination.

The water-miscible solvent may be a polar solvent, and may include, for example, at least one selected from the group consisting of C1 to C5 alcohols and C1 to C10 glycol ethers.

For example, the C1 to C5 alcohols include methanol, ethanol, n-propanol, isopropanol, ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, It may be one or more selected from the group consisting of 1,4-butanediol, glycerol, and 1,2,4-butanetriol, but is not limited thereto.

In addition, the glycol ethers of C1 to C10 include ethylene glycol monomethyl ether (MG), diethylene glycol monomethyl ether (MDG), triethylene glycol monomethyl ether (MTG), polyethylene glycol monomethyl ether (MPG), and ethylene glycol monomethyl ether. Ethyl ether (EG), Diethylene glycol monoethyl ether (EDG), Ethylene glycol monobutyl ether (BG), Diethylene glycol monobutyl ether (BDG), Triethylene glycol monobutyl ether (BTG), Propylene glycol monomethyl ether It may be one or more selected from the group consisting of (MFG) and dipropylene glycol monomethyl ether (MFDG), but is not limited thereto.

The lithium salt contained in the electrolyte is dissolved in the aqueous solvent and acts as a source of lithium ions in the battery, enabling the operation of a basic lithium secondary battery and promoting the movement of lithium ions between the positive and negative electrodes. do.

Specifically, the lithium salt is LiPF ₆ , LiClO ₄ , LiAsF ₆ , LiBF ₄ , LiSbF ₆ , LiAl0 4 , LiAlCl ₄ , LiCF ₃ SO ₃ , LiC ₄ F ₉ SO ₃ , LiN( _{C 2 F 5} SO ₃ ) ₂ , LiN(C ₂ F ₅ SO ₂ ) ₂ , LiN(CF ₃ SO ₂ ) ₂ , LiN(SO ₂ F) ₂ (LiFSI, lithium bis(fluorosulfonyl)imide), LiCl, LiI, and LiB(C ₂ O4) It could be _2nd place. Preferably, the lithium salt may be LiPF ₆ , LiFSI, and mixtures thereof.

The lithium salt may be included in the electrolyte at a concentration of 0.1 M to 2.0 M. The lithium salt contained in the above concentration range enables excellent electrolyte performance by providing appropriate conductivity and viscosity to the electrolyte.

Alternatively, the electrolyte may include a non-aqueous organic solvent and a lithium salt.

The non-aqueous organic solvent may be used without particular limitation as long as it can serve as a medium through which ions involved in the electrochemical reaction of the battery can move.

Specifically, the non-aqueous organic solvent includes ester solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; ether-based solvents such as dibutyl ether and tetrahydrofuran; Ketone-based solvents such as cyclohexanone; Aromatic hydrocarbon solvents such as benzene and fluorobenzene; Dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (MEC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), and carbonate-based solvents such as propylene carbonate (PC); alcohol-based solvents such as ethyl alcohol and isopropyl alcohol; nitriles such as R-CN (R is a C2 to C20 straight-chain, branched or ring-structured hydrocarbon group, and may include a double bond aromatic ring or ether bond); Amides such as dimethylformamide; Dioxolanes such as 1,3-dioxolane; and sulfolane.

Among the above examples, a carbonate-based solvent may be preferably used as the non-aqueous organic solvent.

In particular, considering the charge/discharge performance of the battery and compatibility with the sacrificial cathode material, the non-aqueous organic solvent may be a cyclic carbonate (e.g., ethylene carbonate, propylene carbonate) with high ionic conductivity and high dielectric constant and a low viscosity. Mixtures of linear carbonates (e.g., ethyl methyl carbonate, dimethyl carbonate, diethyl carbonate) may be preferably used. In this case, it may be advantageous to achieve the above-mentioned performance by mixing the cyclic carbonate and the linear carbonate at a volume ratio of 1:1 to 1:9.

In addition, the non-aqueous organic solvent includes ethylene carbonate (EC) and ethyl methyl carbonate (EMC) mixed at a volume ratio of 1:2 to 1:10; Alternatively, a mixture of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) in a volume ratio of 1 to 3:1 to 9:1 may be preferably used.

The lithium salt contained in the electrolyte is dissolved in the non-aqueous organic solvent and acts as a source of lithium ions in the battery, enabling the operation of a basic lithium secondary battery and promoting the movement of lithium ions between the positive electrode and the negative electrode. It plays a role.

The lithium salt is LiPF ₆ , LiClO ₄ , LiAsF ₆ , LiBF ₄ , LiSbF ₆ , LiAl0 ₄ , LiAlCl ₄ , LiCF ₃ SO ₃ , LiC ₄ F ₉ SO ₃ , LiN(C ₂ F ₅ SO ₃ ) ₂ , LiN( C ₂ F ₅ SO ₂ ) ₂ , LiN(CF ₃ SO ₂ ) ₂ , LiN(SO ₂ F) ₂ (LiFSI, lithium bis(fluorosulfonyl)imide), LiCl, LiI, and LiB(C ₂ O4) _2, etc. there is. Specifically, the lithium salt may be LiPF ₆ , LiFSI, and mixtures thereof.

The lithium salt may be included in the electrolyte at a concentration of 0.1 M to 2.0 M. The lithium salt contained in the above concentration range enables excellent electrolyte performance by providing appropriate conductivity and viscosity to the electrolyte.

Optionally, the electrolyte may contain additives for the purpose of improving battery life characteristics, suppressing battery capacity reduction, and improving battery discharge capacity.

For example, the additives include haloalkylene carbonate compounds such as difluoroethylene carbonate, pyridine, triethyl phosphite, triethanolamine, cyclic ether, ethylene diamine, n-glyme, and tria hexaphosphate. It may be mead, nitrobenzene derivative, sulfur, quinone imine dye, N-substituted oxazolidinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxy ethanol, aluminum trichloride, etc. . The additive may be included in an amount of 0.1% to 5% by weight based on the total weight of the electrolyte.

The lithium secondary battery of the embodiment may be a lithium ion battery, a lithium ion polymer battery, or a lithium polymer battery, depending on the type of electrolyte and/or the type of separator.

The liquid electrolyte may be a lithium salt-containing non-aqueous electrolyte. The lithium salt-containing non-aqueous electrolyte is composed of a non-aqueous electrolyte and lithium, and non-aqueous electrolytes include, but are not limited to, non-aqueous organic solvents, organic solid electrolytes, and inorganic solid electrolytes.

Organic solid electrolytes include, for example, polyethylene derivatives, polyethylene oxide derivatives, polypropylene oxide derivatives, phosphoric acid ester polymers, poly agitation lysine, polyester sulfide, polyvinyl alcohol, poly vinylidene fluoride, ionic A polymerization agent containing a dissociative group may be used.

Inorganic solid electrolytes include, for example, Li ₃ N, LiI, Li ₅ NI ₂ , Li ₃ N-LiI-LiOH, LiSiO ₄ , LiSiO ₄ -LiI-LiOH, Li ₂ SiS ₃ , Li ₄ SiO ₄ , Li Nitride, halide, sulfate, etc. of Li such as ₄ SiO ₄ -LiI-LiOH, Li ₃ PO ₄ -Li ₂ S-SiS ₂ may be used.

In addition, the lithium salt-containing non-aqueous electrolyte includes, for example, pyridine, triethyl phosphite, triethanolamine, cyclic ether, ethylene diamine, n-glyme, and hexamethylamine for the purpose of improving charge/discharge characteristics, flame retardancy, etc. Triamide phosphoric acid, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxyethanol, aluminum trichloride, etc. This may be added. In some cases, halogen-containing solvents such as carbon tetrachloride and ethylene trifluoride may be further included to provide incombustibility, and carbon dioxide gas may be further included to improve high-temperature preservation characteristics, and FEC (Fluoro-Ethylene Carbonate), PRS (Propene sultone), etc. can be further included.

In one specific example, lithium salts such as LiPF ₆ , LiClO ₄ , LiBF ₄ , LiN(SO ₂ CF ₃ ) ₂ , and the like are mixed with cyclic carbonate of EC or PC as a high dielectric solvent and DEC, DMC or EMC as a low viscosity solvent. A non-aqueous electrolyte containing lithium salt can be prepared by adding it to a mixed solvent of linear carbonate.

The lithium secondary battery is used in the field of portable electronic devices such as mobile phones, laptop computers, tablet computers, mobile batteries, and digital cameras; And it can be used as an energy source with improved performance and safety in the field of transportation such as electric vehicles, electric motorcycles, and personal mobility devices.

The lithium secondary battery may have various shapes, such as prismatic, cylindrical, or pouch-shaped.

The lithium secondary battery of another embodiment described above may be implemented as a battery module including the unit cell, a battery pack including the battery module, and a device including the battery pack as a power source.

At this time, specific examples of the device may be an electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, or a power storage system, but are not limited thereto.

The manufacturing method of the lithium secondary battery is not greatly limited, but for example, a porous layer forming composition containing a binder resin, a dispersant, and inorganic fine particles is applied to the negative electrode substrate and dried to form a porous layer on at least one side of the negative electrode substrate. forming a; It can be manufactured by a method for manufacturing a lithium secondary battery comprising.

The contents of the anode substrate, binder resin, inorganic fine particles, and porous layer include all of the contents described above.

forming a porous layer on at least one side of the anode substrate by applying a composition for forming a porous layer including a binder resin, a dispersant, and inorganic fine particles on the anode substrate and drying it; Thereafter, the step of assembling the anode substrate and the anode substrate on which the porous layer is formed through a process such as winding or stacking and then injecting an electrolyte solution may be further included.

In the step of forming a porous layer on at least one side of the anode substrate by applying and drying a porous layer forming composition containing a binder resin, a dispersant, and inorganic fine particles on the anode substrate, the porous layer forming composition is applied to the anode substrate. Apply to at least one side. Next, the anode substrate coated with the composition for forming a porous layer is dried to remove the solvent contained in the composition for forming a porous layer.

Forming a porous layer on at least one side of the anode substrate by applying a composition for forming a porous layer containing a binder resin, a dispersant, and inorganic fine particles on the anode substrate and drying it, using a conventional coating method known in the art. It can be used, for example, spin coating, dip coating, die coating, roll coating, comma coating, gravure coating, bar coating, curtain coating, extrusion, casting, screen printing, A variety of methods can be used, including inkjet printing, doctor blade, or a combination of these.

In addition, in the manufacturing method of the lithium secondary battery, the drying method is not particularly limited and known methods can be used, for example, drying with warm air, hot air, low humidity air, vacuum drying, and drying method by irradiation with infrared rays or electron beams. I can hear it.

The solvent used in the composition for forming the porous layer preferably has a solubility index similar to that of the binder resin to be used and has a low boiling point for uniform mixing and ease of subsequent solvent removal. The solvent is not particularly limited, but for example, acetone, tetrahydrofuran, methylene chloride, chloroform, dimethylformamide, N-methyl-2-pyrroli It may be one type or a mixture of two or more types selected from the group consisting of N-methyl-2-pyrrolidone (NMP) and cyclohexane.

According to the present invention, a lithium secondary battery can be provided that has improved lifespan characteristics, charging capacity, and discharging capacity while having high high temperature stability and robust structural stability.

Hereinafter, the operation and effects of the invention will be described in more detail through specific examples of the invention. However, this is presented as an example of the invention, and the scope of the invention is not limited by this in any way.

Example 1

(One) cathode manufacturing

Carbon-based and silicon-based powders were used as negative electrode active materials, carbon black was used as a conductive material, and styrene-butadiene rubber (SBR) and carboxymethyl cellulose (CMC) were used as binders at 95.5% by weight and 1%, respectively. A negative electrode slurry was prepared by adding it to N-methyl-2 pyrrolidone (NMP) as a solvent in weight%, 2.5% by weight, and 1% by weight. The negative electrode slurry was applied and dried on a copper (Cu) thin film, which is a negative electrode current collector, with a thickness of 10 ㎛, and roll pressed to prepare a negative electrode substrate.

(2) Anode manufacturing

97.5% by weight of lithium nickel cobalt manganese aluminum compound as a positive electrode active material, 1% by weight of carbon black as a conductive material, and 1.5% by weight of PVDF as a binder are added to N-methyl-2 pyrrolidone (NMP) as a solvent. A positive electrode slurry was prepared. The positive electrode slurry was applied and dried on an aluminum (Al) thin film, which is a positive electrode current collector, with a thickness of 10 μm, and then a positive electrode was manufactured by performing a roll press.

(3) Preparation of composition for forming porous layer

A binder polymer solution was prepared by adding 30 g of polyvinylidene fluoride-hexafluoropropylene copolymer (PVdF-HFP) to 170 g of NMP and dissolving at 80°C for about 6 hours or more. 7 g of barium titanate (BaTiO ₃ , diameter of primary particle (single particle): about 100 nm) and 0.21 g of BYK-163 (amine value: 10 mgKOH/g) were added to 20 g of the prepared polymer solution, and additional NMP was added. A composition for forming a porous layer was prepared by adjusting the solid content ratio of the composition to 30%.

(4) Battery manufacturing

The composition for forming a porous layer was coated on the prepared cathode using a bar coating method under 30% humidity and dried at 100° C. to form a porous layer with a thickness of 15 μm (porosity: 45%).

The cathode with the porous layer formed and the anode were assembled using a stacking method, and the assembled battery was filled with an electrolyte (ethylene carbonate (EC)/ethylmethyl carbonate (EMC) = 3/7 (volume ratio), lithium hexafluorocarbons. A lithium secondary battery was manufactured by injecting 1 mole of phosphate (LiPF ₆ ).

Example 2

When preparing the composition for forming a porous layer, 27 g of barium sulfate (BaSO ₄ , diameter of primary particle (single particle): approximately 70 nm) was added instead of barium titanate, and 0.81 g of BYK-163 (amine value: 10 mgKOH/g) was added. A lithium secondary battery was manufactured in the same manner as Example 1, except for the addition.

Example 3

A lithium secondary battery was prepared in the same manner as in Example 1, except that 5 g of barium titanate particles were added when preparing the composition for forming a porous layer, and 0.15 g of BYK-163 (amine value: 10 mgKOH/g) was added. .

Example 4

A lithium secondary battery was prepared in the same manner as in Example 1, except that 10 g of barium titanate particles were added when preparing the composition for forming a porous layer, and 0.3 g of BYK-163 (amine value: 10 mgKOH/g) was added. .

Comparative Example 1

A lithium secondary battery was manufactured in the same manner as in Example 1, except that 7 g of alumina particles (diameter of primary particles (single particles): about 350 nm) were added instead of barium titanate when preparing the composition for forming a porous layer. .

Comparative Example 2

When preparing the composition for forming a porous layer, the composition was the same as Example 1, except that 7 g of boehmite (Disperal 60, D50: 35㎛, manufactured by Sasol, D50: 35㎛, crystallite size (120 plane): about 60 nm) was added instead of barium titanate. A lithium secondary battery was manufactured using this method.

Comparative Example 3

A lithium secondary battery was manufactured in the same manner as in Example 1, except that 7 g of magnesium hydroxide (diameter of primary particle (single particle): about 200 nm) was added instead of barium titanate when preparing the composition for forming a porous layer. .

Comparative Example 4

7 g of barium titanate (BaTiO ₃ , primary particle (single particle) diameter: approximately 100 nm) was sprayed on the cathode prepared in Example 1.

The barium titanate-sprayed cathode, the polyolefin separator, and the anode prepared in Example 1 were assembled using a stacking method, and the assembled battery was filled with an electrolyte (ethylene carbonate (EC)/ethylmethyl carbonate (EMC) = A lithium secondary battery was manufactured by injecting 3/7 (volume ratio), 1 mole of lithium hexafluorophosphate (LiPF ₆ ).

The manufactured lithium secondary battery was charged and discharged for one cycle to form a coating layer containing barium titanate on the surface of the negative electrode.

It was confirmed that detachment of the negative electrode active material occurred in the manufactured lithium secondary battery.

Comparative Example 5

The cathode prepared in Example 1 was immersed in an aqueous barium sulfate solution (concentration: 60%) to form a coating layer (15 ㎛ thick) containing barium sulfate on the cathode.

The negative electrode with the coating layer, the polyolefin separator, and the positive electrode prepared in Example 1 were assembled using a stacking method, and the assembled battery was filled with an electrolyte (ethylene carbonate (EC)/ethylmethyl carbonate (EMC) = 3/ A lithium secondary battery was manufactured by injecting 7 (volume ratio) and 1 mole of lithium hexafluorophosphate (LiPF6).

In the manufactured lithium secondary battery, it was confirmed that detachment of the negative electrode active material occurred upon contact between the negative electrode and the barium sulfate aqueous solution.

Experimental Example 1: Porous layer analysis

The thickness, porosity, and pore diameter of the porous layer of the lithium secondary batteries manufactured in each of the examples and comparative examples were analyzed and are shown in Table 1 below.

The porosity of each porous layer was calculated as follows. Measure the thickness of the porous layer to calculate the volume of the porous layer or coating layer for a certain area. Calculate the weight of the porous layer only, excluding the weight of the electrode base material and current collector, among the sample weight, and divide the volume from the weight to obtain the actual density of the porous layer. Calculated. The theoretical density when the solid composition of the porous layer was 100% concentrated was calculated, and the porosity was calculated using Equation 1 below.

[Equation 1]

Porosity (%)= {1 - (actual density)/(theoretical density)} x 100.

The pore diameter was measured using a BET instrument under N ₂ gas atmosphere for the sample coated on the electrode substrate.

Experimental Example 2: Peel Strength

The lithium secondary batteries manufactured in the above examples and comparative examples were fixed to a glass plate using double-sided tape with a width of 20 mm on the upper part of the negative electrode, and the peel strength of the first porous layer was measured by pulling 50 mm at 180 degrees. The strength was measured as the peeling strength of the porous layer using UTM (LLOYD INSTRUMENT LS 1) and is shown in Table 1 below.

Experimental Example 3: Long-term life characteristics

The lithium secondary batteries of Examples, Comparative Examples, and Reference Examples were cycled at 2.5 to 4.2 V at room temperature and 0.1 C-rate. Additionally, the charge capacity, discharge capacity, and discharge capacity maintenance rate during repeated cycles were measured through the material's capacity retention rate over 50 cycles, and are shown in Table 1 below.

porous layer peel strength
(gf/20mm) 1st cycle 50th cycle 50cycle retention thickness
(㎛) porosity
(%) Pore diameter
(㎛) discharge capacity
(mAh/g) charging capacity
(mAh/g) discharge capacity
(mAh/g) charging capacity
(mAh/g) Discharge capacity maintenance rate
(%) Example 1 15 45 0.4 324 151 168 148 165 98 Example 2 15 41 0.5 318 152 169 148 164 97 Example 3 15 44 0.4 330 148 164 143 159 97 Example 4 15 48 0.3 296 147 163 141 156 96 Comparative Example 1 15 59 0.6 311 150 167 134 149 89 Comparative example 2 15 39 0.3 325 151 168 139 155 92 Comparative example 3 15 52 0.5 309 149 166 134 149 90

As shown in Table 1, the porous layer formed in the lithium secondary battery of the example had a thickness of 15 ㎛, a porosity of 41% to 48%, and a pore diameter of 0.3 ㎛ to 0.5 ㎛.

In addition, the lithium secondary battery of the example was confirmed to have excellent electrode adhesion as the peeling strength of the porous layer from the positive electrode was 296 gf/20mm to 330 gf/20mm under electrolyte impregnation conditions.

In addition, the lithium secondary battery of the example has a discharge capacity of 141 mAh/g or more and 148 mAh/g or less after 50 cycles, a charge capacity of 156 mAh/g or more and 165 mAh/g or less, and a discharge capacity retention rate of 96% or more. It was confirmed that it had excellent battery characteristics and long-term lifespan characteristics as well, as it was found to be less than 98%.

On the other hand, the lithium secondary batteries of Comparative Examples 1 to 3 had a discharge capacity of only 139 mAh/g or less after 50 cycles, a charge capacity of only 155 mAh/g or less, and a discharge capacity maintenance rate of only 92% or less. was able to confirm.

Claims (15)

cathode substrate;
A porous layer formed on the anode substrate and containing a binder resin, a dispersant, and inorganic fine particles,
It includes a positive electrode substrate formed on the porous layer,
The inorganic fine particles include barium, barium organic acid or barium inorganic acid,
The porous layer is a lithium secondary battery comprising 110 to 5000 parts by weight of the inorganic fine particles relative to 100 parts by weight of the binder resin.
According to paragraph 1,
A lithium secondary battery wherein the dispersant has an amine value of 1 mg KOH/g or more and 90 mg KOH/g or less.
According to paragraph 1,
The dispersant is a lithium secondary battery comprising polyurethane having an amine value of 1 mg KOH/g to 90 mg KOH/g.
According to paragraph 1,
The porous layer is a lithium secondary battery comprising 3 to 50 parts by weight of the dispersant relative to 100 parts by weight of the binder resin.
According to paragraph 1,
The porous layer is a lithium secondary battery comprising 1 part by weight or more and 10 parts by weight or less of the dispersant relative to 100 parts by weight of the inorganic fine particles.
According to paragraph 1,
A lithium secondary battery in which the porous layer has a porosity of 30% or more and 90% or less.
According to paragraph 1,
The porous layer includes pores with a diameter of 0.01 ㎛ or more and 10 ㎛ or less.
According to paragraph 1,
A lithium secondary battery wherein the porous layer has a thickness of 0.1 ㎛ or more and 100 ㎛ or less.
According to paragraph 1,
A lithium secondary battery, wherein the inorganic fine particles have a diameter of 1 nm to 500 nm.
According to paragraph 1,
The porous layer has a porosity of 30% or more and 60% or less,
A lithium secondary battery wherein the inorganic fine particles have a primary particle size of 30 nm to 100 nm.
According to paragraph 1,
The inorganic fine particles are a lithium secondary battery comprising at least one type of barium inorganic acid selected from the group consisting of barium titanate (BaTiO ₃ ) and barium sulfate (BaSO ₄ ).
According to paragraph 1,
The binder resin is polyvinylidene fluoride, polyvinylidene fluoride-hexafluoro propylene, polyvinylidene fluoride-tetrafluoroethylene, polyvinylidene fluoride-trichloroethylene, polyvinylidene fluoride-chlorotri Fluoroethylene, polymethyl methacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinyl acetate, ethylene vinyl acetate copolymer, polyethylene oxide, cellulose acetate, cellulose acetate butylate, cellulose acetate propionate, cyanotype. Ethyl pullulan, cyanoethyl polyvinyl alcohol, cyanoethyl cellulose, cyanoethyl sucrose, pullulan, carboxyl methyl cellulose, acrylonitrile-styrene-butadiene copolymer, polyurethane, polyacrylic acid, polyimide, polyether A lithium secondary battery comprising at least one selected from the group consisting of mead and styrene butadiene rubber.
According to paragraph 1,
A lithium secondary battery, wherein the porous layer is coupled to the negative electrode substrate and/or the positive electrode substrate through an adhesive layer or adhesive pattern formed on at least one side.
According to paragraph 1,
A lithium secondary battery further comprising an electrolyte interposed between the positive electrode and the negative electrode.
According to paragraph 1,
The lithium secondary battery does not include a porous polymer separator.