KR20240025143A - Method of manufacturing solid electrolyte composite sheet with improved durability, and method of manufacturing all solid lithium secondary battery comprising same - Google Patents

Abstract

The present invention includes the steps of (a) pulverizing a lithium lanthanum zirconium oxide (LLZO) solid electrolyte to produce first LLZO solid electrolyte particles; (b) preparing a dispersion solution containing the first LLZO solid electrolyte particles and a solvent; and (c) sonicating the dispersion solution to produce second LLZO solid electrolyte particles. The method for producing a composite solid electrolyte sheet with improved durability according to the present invention includes: The manufacturing method of an all-solid lithium secondary battery including this applies pulverization and ultrasonic dispersion to control the particle size of the solid electrolyte powder to be small and disperse it effectively, thereby increasing the filling rate of solid electrolyte particles in the composite solid electrolyte sheet, thereby increasing the solid electrolyte powder despite the thin sheet thickness. It can effectively prevent Li dendrite, and ultimately improve the lifespan characteristics of the all-solid-state lithium secondary battery by increasing the Li ion transition constant.

Description

Method for manufacturing a composite solid electrolyte sheet with improved durability and a method for manufacturing an all-solid lithium secondary battery containing the same {METHOD OF MANUFACTURING SOLID ELECTROLYTE COMPOSITE SHEET WITH IMPROVED DURABILITY, AND METHOD OF MANUFACTURING ALL SOLID LITHIUM SECONDARY BATTERY COMPRISING SAME}

The present invention relates to a method for manufacturing a composite solid electrolyte sheet with improved durability and a method for manufacturing an all-solid lithium secondary battery containing the same, and more specifically, to a method using finely divided solid electrolyte particles manufactured by applying pulverization and ultrasonic dispersion. It relates to a method of manufacturing a composite solid electrolyte sheet with improved durability (life characteristics) and a method of manufacturing an all-solid lithium secondary battery including the same.

Lithium secondary batteries have large electrochemical capacity, high operating potential, and excellent charge/discharge cycle characteristics, so they are in demand for applications such as portable information terminals, portable electronic devices, small household power storage devices, motorcycles, electric vehicles, and hybrid electric vehicles. It is increasing. With the spread of such uses, there is a demand for improved safety and higher performance of lithium secondary batteries.

Conventional lithium secondary batteries still use a liquid electrolyte, and Ni-rich NCM high-capacity anode materials with low thermal stability are used to increase the driving range of electric vehicles. As high energy density battery packs are used, they easily ignite in the event of an accident. Safety issues are always being raised.

Therefore, various battery solutions are being developed to address concerns about safety, limitations in increasing energy density, and high cost burden, which were pointed out as limitations of existing lithium secondary batteries. Candidates for next-generation innovative secondary batteries that will replace the current lithium secondary batteries (LiB) include metal-air batteries (Li-Air), lithium-sulfur batteries (Li-S), all-solid-state lithium secondary batteries, and sodium ion batteries (SIB). It is mainly being developed, and among these, all-solid-state lithium secondary batteries have become the most realistic alternative due to the relatively fast pace of technological development over the past 10 years and the expectation that it can solve the safety problem, which is a chronic concern of lithium secondary batteries. In addition to safety, another advantage of all-solid-state lithium secondary batteries is that multiple single cells can be mounted in series in one case, simplifying the control system and creating a battery pack with high energy density.

An all-solid-state secondary battery consists of an anode/solid electrolyte layer/cathode, of which the solid electrolyte of the solid electrolyte layer requires high ionic conductivity and low electronic conductivity.

Solid electrolytes that satisfy the requirements for the solid electrolyte layer of an all-solid-state secondary battery include sulfide-based and oxide-based electrolytes. Among these, the sulfide-based solid electrolyte has problems in that a resistance component is generated by an interfacial reaction with the positive electrode active material or the negative electrode active material, it is highly hygroscopic, and hydrogen sulfide (H ₂ S) gas, a toxic gas, is generated.

Oxide-based solid electrolytes have better stability in the atmosphere than sulfide-based solid electrolytes, and are expected to be relatively more competitive in terms of ease of handling.

Looking at oxide crystal materials, garnet type Li ₇ La ₃ Zr ₂ O ₁₂ (LLZO), NASICON type Li _1.3 Al _0.3 Ti _1.7 (PO ₄ ) ₃ (LATP), ferroskite type La _0.51 Li _0.34 TiO _2.94 (LLTO), etc. It has an ionic conductivity of up to about 10 ^-3 S/cm.

In the case of NASICON type LATP material, it is an oxide-based material and has very excellent moisture stability in the air and relatively excellent ionic conductivity, but has the narrowest potential window, which limits the selection of cathode materials.

Therefore, ionic conductivity and potential window are the key factors in designing an all-solid-state lithium secondary battery with high energy density, and garnet-type LLZO material is considered to be the best material that satisfies all of the above conditions.

The purpose of the present invention is to solve the above problems, a method for manufacturing a composite solid electrolyte sheet with improved durability (life characteristics) using finely divided solid electrolyte particles manufactured by applying pulverization and ultrasonic dispersion, and an all-solid lithium secondary battery containing the same. It is about manufacturing method.

In addition, by manufacturing a composite solid electrolyte sheet containing solid electrolyte particles, the filling rate of solid electrolyte particles in the sheet increases, enabling effective prevention of Li dendrite despite a thin sheet thickness, and ultimately resulting in an increase in Li ion transition constant. It relates to a method of manufacturing a composite solid electrolyte sheet that improves the cycle characteristics and lifespan characteristics of an all-solid lithium secondary battery and a method of manufacturing an all-solid lithium secondary battery including the same.

According to one aspect of the present invention, (a) pulverizing a lithium lanthanum zirconium oxide (LLZO) solid electrolyte to produce first LLZO solid electrolyte particles; (b) preparing a dispersion solution containing the first LLZO solid electrolyte particles and a solvent; and (c) sonicating the dispersion solution to produce second LLZO solid electrolyte particles.

In step (a), the grinding may be performed by one or more processes selected from the group consisting of an air jet mill, a planetary ball mill process, and a mortar and pestle grinding process.

In step (a), the average particle size (d ₅₀ ) of the first LLZO solid electrolyte particles may be 7 to 15 ㎛.

The solvent may include one or more selected from the group consisting of isopropyl alcohol (IPA), acetonitrile (ACN), and ethanol.

In step (c), the sonication may be performed for 30 minutes to 2 hours.

In step (c), the average particle size (d ₅₀ ) of the second LLZO solid electrolyte particles may be 1 to 15 ㎛.

In step (c), the average particle size (d ₅₀ ) of the second LLZO solid electrolyte particles may be 1.5 to 3.5 ㎛.

In step (c), the average particle size (d ₁₀ ) of the second LLZO solid electrolyte particles may be 0.05 to 0.5 ㎛.

In step (c), the average particle size (d ₁₀ ) of the second LLZO solid electrolyte particles may be 0.09 to 0.2 ㎛.

In step (c), the second LLZO solid electrolyte particles may have a bimodal size distribution including a first size distribution and a second size distribution.

The solid electrolyte particles having the first size distribution may have a size of 0.05 to 1 ㎛, and the solid electrolyte particles having the second size distribution may have a size of 0.09 to 200 ㎛.

The size of the solid electrolyte particles having the first size distribution may be 0.05 to 0.09 ㎛, and the size of the solid electrolyte particles having the second size distribution may be 0.09 to 150 ㎛, preferably greater than 0.09 to 150 ㎛. .

The LLZO solid electrolyte may be represented by the following formula (1).

[Formula 1]

_{Li _ _ _ _ _ _} )

The following LLZO solid electrolyte may be represented by Formula 1 above.

According to one aspect of the present invention, (a) pulverizing a lithium lanthanum zirconium oxide (LLZO) solid electrolyte to produce first LLZO solid electrolyte particles; (b) preparing a dispersion solution containing the first LLZO solid electrolyte particles and a solvent; (c) sonicating the dispersion solution to produce second LLZO solid electrolyte particles; and (e) manufacturing a composite solid electrolyte sheet including the second LLZO solid electrolyte particles and a second binder.

Here, the second binder is polyethylene oxide, nitrile butadiene rubber (NBR), polyethylene glycol, polyacrylonitrile, polyvinyl chloride, and polymethyl methacrylate. 1 selected from the group consisting of (polymethylmethacrylate), polypropyleneoxide, polydimethylsiloxane, polyvinylidenefluoride, polyvinylidenecarbonate, and polyvinyl pyrrolidinone It may include more than one species.

According to another aspect of the present invention, (A) manufacturing a positive electrode including a positive electrode active material, a first LLZO solid electrolyte, a first binder, and a conductive material; (B) manufacturing a solid electrolyte sheet including a second LLZO solid electrolyte and a second binder; (C) manufacturing a laminate by laminating the positive electrode and the solid electrolyte sheet; and (D) disposing a negative electrode containing lithium metal on the solid electrolyte sheet of the laminate.

Step (B) is (B-1) pulverizing the second LLZO solid electrolyte to produce first LLZO solid electrolyte particles; (B-2) preparing a dispersion solution containing the first LLZO solid electrolyte particles and a solvent; (B-3) preparing second LLZO solid electrolyte particles by sonicating the dispersion solution; and (B-4) manufacturing a solid electrolyte sheet including the second LLZO solid electrolyte particles and a second binder.

The second LLZO solid electrolyte may be represented by the following formula (1).

[Formula 1]

_{Li _ _ _ _ _ _} )

The positive electrode active material is lithium iron phosphate (LiFePO ₄ ), lithium nickel cobalt aluminum oxide (NCA), lithium cobalt oxide (LiCoO ₂ ), lithium nickel oxide (LiNiO ₂ ), and lithium manganese oxide. (LiMn ₂ O ₄ ) and lithium nickel cobalt manganese oxide (NCM).

The first LLZO solid electrolyte may be represented by the following formula (1).

[Formula 1]

_{Li _ _ _ _ _ _} )

The first and second binders are polyethylene oxide, nitrile butadiene rubber (NBR), polyethylene glycol, polyacrylonitrile, polyvinyl chloride, and polymethyl methane, respectively. From the group consisting of polymethylmethacrylate, polypropyleneoxide, polydimethylsiloxane, polyvinylidenefluoride, polyvinylidenecarbonate, and polyvinyl pyrrolidinone. It may include one or more selected types.

The method for manufacturing a composite solid electrolyte sheet with improved durability of the present invention and the manufacturing method for an all-solid lithium secondary battery including the same can control the particle size of the solid electrolyte powder to be small and effectively disperse it by applying pulverization and ultrasonic dispersion.

In addition, the present invention manufactures a composite solid electrolyte sheet containing solid electrolyte particles, thereby increasing the filling rate of solid electrolyte particles in the sheet, effectively preventing Li dendrite despite a thin sheet thickness, and increasing the Li ion transition constant. As a result, the cycle characteristics and lifespan characteristics of the all-solid-state lithium secondary battery can ultimately be improved.

1 is a schematic diagram showing a method for manufacturing solid electrolyte particles according to the present invention.
2A to 2D are SEM analysis images of solid electrolyte particles according to Comparative Example 1 and Examples 1 to 3.
3A to 3D are particle size distribution curves of solid electrolyte particles according to Comparative Example 1 and Examples 1 to 3.
Figure 4 is a graph showing repeated charging and discharging of a symmetrical cell containing the solid electrolyte sheet according to Example 4 and Comparative Example 3 according to current density.
Figure 5 is a graph of charge and discharge characteristics of an all-solid lithium secondary battery according to Device Example 1 and Device Comparative Example 1.
Figure 6 is a graph of cycle characteristics of an all-solid lithium secondary battery according to Device Example 1 and Device Comparative Example 1.
Figure 7 is a diagram showing the lithium ion transport path within the composite electrolyte sheet of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings so that those skilled in the art can easily implement the present invention.

However, the following description is not intended to limit the present invention to specific embodiments, and in describing the present invention, if it is determined that a detailed description of related known technology may obscure the gist of the present invention, the detailed description will be omitted. .

The terminology used herein is only used to describe specific embodiments and is not intended to limit the invention. Singular expressions include plural expressions unless the context clearly dictates otherwise. In this application, terms such as “comprise” or “have” are intended to designate the presence of features, numbers, steps, operations, components, or a combination thereof described in the specification, but are not intended to indicate the presence of one or more other features or It should be understood that this does not exclude in advance the possibility of the presence or addition of numbers, steps, operations, components, or combinations thereof.

1 is a schematic diagram showing a method for manufacturing solid electrolyte particles according to the present invention. Hereinafter, with reference to FIG. 1, the method for manufacturing solid electrolyte particles of the present invention and the method for manufacturing an all-solid lithium secondary battery including the same will be described in detail.

The present invention includes the steps of (a) pulverizing a lithium lanthanum zirconium oxide (LLZO) solid electrolyte to produce first LLZO solid electrolyte particles; (b) preparing a dispersion solution containing the first LLZO solid electrolyte particles and a solvent; and (c) sonicating the dispersion solution to produce second LLZO solid electrolyte particles.

In step (a), the grinding may be performed by one or more processes selected from the group consisting of an air jet mill, a planetary ball mill process, and a mortar grinding process, and is preferably performed by a planetary ball mill process. You can.

The planetary ball mill process includes grinding balls, and the grinding balls may include one or more selected from the group consisting of zirconia balls, alumina balls, ceramic balls, and agate balls.

In step (a), the grinding may be performed using a planetary ball mill mixer.

In step (a), the grinding may be performed for 30 to 150 minutes, preferably 50 to 120 minutes, more preferably 40 to 100 minutes.

In step (a), the average particle size (d ₅₀ ) of the first LLZO solid electrolyte particles may be 7 to 15 ㎛.

The solvent may include one or more selected from the group consisting of isopropyl alcohol (IPA), acetonitrile (ACN), ethanol, etc.

In step (c), the sonication may be performed for 30 minutes to 2 hours.

In step (c), the average particle size (d ₅₀ ) of the second LLZO solid electrolyte particles may be 1 to 15 ㎛, preferably 1.5 to 3.5 ㎛.

In step (c), the average particle size (d ₁₀ ) of the second LLZO solid electrolyte particles may be 0.05 to 0.5 ㎛, preferably 0.09 to 0.2 ㎛.

In step (c), the second LLZO solid electrolyte particles may have a bimodal size distribution including a first size distribution and a second size distribution.

The size of the solid electrolyte particles having the first size distribution may be 0.05 to 1 ㎛, and the size of the solid electrolyte particles having the second size distribution may be 0.09 to 200 ㎛, preferably having the first size distribution. The size of the solid electrolyte particles may be 0.05 to 0.09 ㎛, and the size of the solid electrolyte particles having the second size distribution may be 0.09 to 150 ㎛, preferably greater than 0.09 to 150 ㎛.

The lithium lanthanum zirconium oxide (LLZO) solid electrolyte may be represented by the following formula (1).

[Formula 1]

_{Li _ _ _ _ _ _} )

Here, r may preferably be 0<r≤1.

After step (c), (d) filtering and drying the second LLZO solid electrolyte particles may be further included.

In step (d), the drying may be performed at a temperature of room temperature to 150°C, preferably 50 to 130°C, more preferably 50 to 100°C.

According to one aspect of the present invention, (a) pulverizing a lithium lanthanum zirconium oxide (LLZO) solid electrolyte to produce first LLZO solid electrolyte particles; (b) preparing a dispersion solution containing the first LLZO solid electrolyte particles and a solvent; (c) sonicating the dispersion solution to produce second LLZO solid electrolyte particles; and (e) manufacturing a composite solid electrolyte sheet including the second LLZO solid electrolyte particles and a second binder.

Here, the second binder is polyethylene oxide, nitrile butadiene rubber (NBR), polyethylene glycol, polyacrylonitrile, polyvinyl chloride, and polymethyl methacrylate. 1 selected from the group consisting of (polymethylmethacrylate), polypropyleneoxide, polydimethylsiloxane, polyvinylidenefluoride, polyvinylidenecarbonate, and polyvinyl pyrrolidinone It may include more than one species.

In addition, the present invention includes the steps of (A) manufacturing a positive electrode including a positive electrode active material, a first LLZO solid electrolyte, a first binder, and a conductive material; (B) manufacturing a solid electrolyte sheet including a second LLZO solid electrolyte and a second binder; (C) manufacturing a laminate by laminating the positive electrode and the solid electrolyte sheet; and (D) disposing a negative electrode containing lithium metal on the solid electrolyte sheet of the laminate.

Step (B) includes (B-1) pulverizing the second LLZO solid electrolyte to produce first LLZO solid electrolyte particles; (B-2) preparing a dispersion solution containing the first LLZO solid electrolyte particles and a solvent; (B-3) sonicating the dispersion solution to produce second LLZO solid electrolyte particles; and (B-4) manufacturing a solid electrolyte sheet including the second LLZO solid electrolyte particles and a second binder.

The second LLZO solid electrolyte may be represented by the following formula (1).

[Formula 1]

_{Li _ _ _ _ _ _} )

Here, r may preferably be 0<r≤1.

The positive electrode active material is lithium iron phosphate (LiFePO ₄ ), lithium nickel cobalt aluminum oxide (NCA), lithium cobalt oxide (LiCoO ₂ ), lithium nickel oxide (LiNiO ₂ ), and lithium manganese oxide. (LiMn ₂ O ₄ ) and lithium nickel cobalt manganese oxide (NCM).

The first LLZO solid electrolyte may be represented by the following formula (1).

[Formula 1]

_{Li _ _ _ _ _ _} )

Here, r may preferably be 0<r≤1.

The first and second binders are polyethylene oxide, nitrile butadiene rubber (NBR), polyethylene glycol, polyacrylonitrile, polyvinyl chloride, and polymethyl methane, respectively. From the group consisting of polymethylmethacrylate, polypropyleneoxide, polydimethylsiloxane, polyvinylidenefluoride, polyvinylidenecarbonate, and polyvinyl pyrrolidinone. It may include one or more selected types.

The conductive material may include one or more selected from the group consisting of carbon black, acetylene black, Ketjen black, carbon fiber, carbon nanotube, and graphene.

The positive electrode and the solid electrolyte sheet further include a lithium salt, and the lithium salt is lithium trifluoromethanesulfonylimide (LiN(CF ₃ SO ₂ ) ₂ , LiTFSi), lithium perchlorate (LiClO ₄ ), and lithium hexamethylene. Fluorophosphate (LiPF ₆ ) and lithium tetrafluoroborate (LiBF ₄ ), lithium bisfluorosulfonylimide (Li(FSO ₂ ) ₂ N), LiFSI), lithium triflate (LiCF ₃ SO ₃ ), di Lithium fluoro(bis(oxalato))phosphate (LiPF ₂ (C ₂ O ₄ ) ₂ ), lithium tetrafluoro(oxalato)phosphate (LiPF ₄ (C ₂ O ₄ )), difluoro(oxalato) It may include at least one selected from lithium salato)borate (LiBF ₂ (C ₂ O ₄ )) and lithium bis(oxalato)borate (LiB(C ₂ O ₄ ) ₂ ).

[Example]

Hereinafter, the present invention will be described with reference to preferred embodiments. However, this is for illustrative purposes only and does not limit the scope of the present invention.

[Manufacture of solid electrolyte particles]

Example 1: LLZO-Ta-IPA

5 g of commercial LLZO-Ta solid electrolyte powder (TOSHIMA, 3N), which is Ta-doped LLZO, was placed in a planetary ball mill and ground at 400 rpm for 80 minutes to prepare pulverized LLZO-Ta solid electrolyte. Next, the pulverized LLZO-Ta solid electrolyte was added to a beaker containing the solvent isopropyl alcohol (IPA) to prepare a dispersion solution, and the dispersion solution was sonicated for 2 hours to mix the pulverized LLZO-Ta in the solvent. The LLZO-Ta solid electrolyte was evenly dispersed. Afterwards, it was filtered and dried at 110°C to prepare LLZO-Ta solid electrolyte particles. The ionic conductivity of the commercial Ta doped LLZO material purchased from Toshima was 8.7 x 10 ^-4 S/cm at room temperature.

Example 2: LLZO-Ta-ACN

LLZO-Ta solid electrolyte microparticles were prepared in the same manner as in Example 1, except that acetonitrile (ACN) was used instead of isopropyl alcohol (IPA).

Example 3: LLZO-Ta-Ethanol

LLZO-Ta solid electrolyte particles were prepared in the same manner as in Example 1, except that ethanol was used instead of isopropyl alcohol (IPA).

[Manufacture of composite solid electrolyte sheet]

Example 4

A mixture was prepared so that the weight ratio of the LLZO-Ta solid electrolyte particles prepared according to Example 2 and the PEO binder was 70:30. That is, a mixture was prepared by mixing 42.86 parts by weight of polyethylene oxide (PEO) binder based on 100 parts by weight of the LLZO-Ta solid electrolyte particles prepared according to Example 2. At this time, the PEO binder contained PEO (molecular weight 200,000) and LiTFSi (lithium salt), and the molar ratio of the PEO and the lithium salt was [EO]: [LiTFSi] 20:1.

Specifically, first, the LLZO-Ta solid electrolyte particles and PEO binder prepared according to Example 2 were weighed at the above weight ratio, and then the process of mixing at 1,800 rpm for 5 minutes using a Thinky mixer was repeated three times. A slurry was prepared. The slurry was cast to a thickness of 50 μm on a PET (polyethylene terephthalate) film coated on one side with silica (SiO ₂ ), and rolled at a pressure of 1 to 2 MPa using a roll press to have a rolling rate of 20% of the initial thickness. The rolling process was repeated twice to produce a solid electrolyte sheet with a thickness of 50 μm.

[Manufacture of anode]

Example 5

A mixture was prepared so that the weight ratio of LiFePO ₄ (LFP) positive electrode active material, commercial LLZO-Ta solid electrolyte powder (TOSHIMA, 3N), conductive material, and binder was 70:5:5:20. That is, based on 100 parts by weight of LiFePO ₄ positive electrode active material, 7.14 parts by weight of commercial LLZO-Ta solid electrolyte powder (TOSHIMA, 3N) according to Preparation Example 1, 7.14 parts by weight of conductive material Super-P, and 28.57 parts by weight of PEO binder were mixed to form a mixture. was manufactured. At this time, the PEO binder included PEO (molecular weight 200,000) and LiClO ₄ (lithium salt), and the molar ratio of the PEO and the lithium salt was [EO]: [LiClO ₄ ] = 20:1.

Specifically, first, LiFePO ₄ cathode active material, commercial LLZO-Ta solid electrolyte powder (TOSHIMA, 3N), and Super-p were weighed in the above weight ratio and mixed for 30 minutes using a mortar to prepare a mixed powder. The mixed powder was transferred to a dedicated Thinky mixer container, mixed with PEO binder at the above weight ratio, placed in the mixer, and mixed at 1,800 rpm for 5 minutes, repeating the process three times to prepare a slurry. ACN was mixed in the middle of the mixing to adjust the viscosity to an appropriate level. The slurry was cast on aluminum foil and dried in an oven at 110°C for 24 hours to prepare a positive electrode with a loading amount of about 5 mg/cm ² .

[Manufacture of solid electrolyte particles]

Comparative Example 1: LLZO-Ta-80min (grinding)

5 g of commercial LLZO-Ta solid electrolyte powder (TOSIMA) was placed in a planetary ball mill and ground at 400 rpm for 80 minutes to prepare LLZO-Ta solid electrolyte particles. At this time, the average particle size (d ₅₀ ) of commercial LLZO-Ta solid electrolyte powder (TOSIMA) is ~10㎛, and has an ionic conductivity characteristic of 8.7 x 10 ^-4 S/cm at room temperature.

[Manufacture of composite solid electrolyte sheet]

Comparative Example 2

In Example 4, the solid electrolyte particles were prepared in the same manner as in Example 4, except that instead of using the LLZO-Ta solid electrolyte particles prepared according to Example 2, the LLZO-Ta solid electrolyte particles prepared according to Comparative Example 1 were used. An electrolyte sheet was prepared.

[Manufacture of all-solid-state lithium secondary battery]

Device Example 1

The positive electrode manufactured according to Example 5 and the solid electrolyte sheet manufactured according to Example 4 were punched into sizes of 14 and 16, respectively, and then laminated. Next, a laminate was manufactured by heating to about 60°C and pressing at 0.3 MPa for 0.5 minutes. A negative electrode containing 0.2 tons of lithium metal was placed on the solid electrolyte sheet of the laminate, heated to about 60°C and pressurized at 0.3 MPa for 0.5 minutes to manufacture an all-solid-state lithium secondary battery using a 2032 standard coin cell.

Device comparison example 1

In Device Example 1, all-solid lithium was manufactured in the same manner as Device Example 1, except that instead of using the solid electrolyte sheet prepared according to Example 4, the composite solid electrolyte sheet prepared according to Comparative Example 2 was used. A rechargeable battery was manufactured.

[Test example]

Test Example 1: SEM analysis

FIGS. 2A to 2D are SEM analysis images of the solid electrolyte particles according to Comparative Example 1 and Examples 1 to 3, and FIGS. 3A to 3D are particle size distribution curves of the solid electrolyte particles according to Comparative Example 1 and Examples 1 to 3.

According to FIGS. 2A to 2D, SEM images of solid electrolyte particles for Comparative Example 1 and Examples 1 to 3 can be seen. In Comparative Example 1, a separate dispersion process was not performed after the ball mill process, so the particles were aggregated in morphology. You can see that it has . However, when an ultrasonic dispersion process is performed using solvents of IPA, ACN, and ethanol as in Examples 1 to 3, relatively better dispersed particles can be observed than in Comparative Example 1. In particular, when ultrasonic dispersion is performed using the ACN solvent in Example 2, the state of the most well-dispersed particles can be observed, which confirms the results of the best dispersibility as shown in the particle size analysis results.

In addition, according to FIGS. 3A to 3D, Comparative Example 1 in which only the ball mill process was performed had an average particle size (d ₅₀ ) of 9.9627㎛, and Example 1 in which the ball mill process and ultrasonic dispersion were performed had an average particle size (d ₅₀ ) of 10.51630. ㎛, it was confirmed that the IPA solvent had almost no dispersion effect, as the particles were larger than those of Comparative Example 1. Example 2 showed an average particle size (d ₅₀ ) of 2.4261㎛, and Example 3 showed an average particle size (d ₅₀ ) of 7.3386㎛, showing that when ultrasonic dispersion was performed in acetonitrile (ACN), the solid electrolyte particles were evenly distributed. It was confirmed that it was dispersing.

Test Example 2: Charging and discharging characteristics of symmetrical cell

Figure 4 is a graph showing repeated charging and discharging of a symmetrical cell containing the solid electrolyte sheet according to Example 4 and Comparative Example 2 manufactured using Example 2, which has the best dispersion effect, according to current density. The charge/discharge characteristics of the symmetric cell were measured by manufacturing a lithium symmetric cell composed of Li/solid electrolyte sheet (thickness 50㎛) according to Example 4 or Comparative Example 2/Li at a current density of 0.1, 0.2, and 0.3 mA/cm ² at 70°C. Each was evaluated by repeating charging and discharging.

According to Figure 4, Example 4 showed lower overvoltage and more stable characteristics than Comparative Example 3 in terms of voltage change due to electrodeposition and desorption of lithium ions. This is expected to have an impact on improving lifespan characteristics.

Test Example 3: Battery charge/discharge characteristics and cycle characteristics

Figure 5 is a graph (0.1C) of charge and discharge characteristics of the all-solid-state lithium secondary battery according to Device Example 1 and Device Comparative Example 1, and Figure 6 is a graph of the all-solid-state lithium secondary battery according to Device Example 1 and Device Comparative Example 1. This is a cycle characteristics graph (0.1C (2cycle) -> 0.33C). At this time, L/W was ~5mg/cm ² and the operating temperature was 70℃.

According to Figure 5, when comparing the case of ultrasonic dispersion in ACN solvent after the ball mill process and the case without ultrasonic dispersion, the initial capacity of the battery after the ultrasonic dispersion process appears to be about 10 mAh/g smaller than the comparative example, but the charge/discharge curve Looking at , it was seen that there was no difference in cell resistance due to increase in resistance.

Also, referring to FIG. 6, although the initial capacity appears to be somewhat small in FIG. 5, the comparative example shows a rapid decline in life characteristics when charging and discharging is performed for more than 200 cycles. However, in the case of a battery using ultrasonically dispersed fine particles in an ACN solvent, the composite solid As the filling rate of solid electrolyte particles within the electrolyte sheet increases, Li dendrite can be effectively prevented despite the thin sheet thickness of 50μm, and the lifespan characteristics of the all-solid-state lithium secondary battery are ultimately improved due to the relatively increased diffusion coefficient of Li ions. And it was found

Test Example 4: Schematic diagram of the effect of grinding and ultrasonic dispersion process

Referring to FIG. 6, it can be seen that when the particles are controlled to be small by effectively dispersing the solid electrolyte by pulverizing it, a large amount of lithium ions are transferred through the interface and PEO-Li salt. The reason is that when small solid electrolyte particles are used, they have a high specific surface area, which increases the area in contact between PEO and Li salt.

The scope of the present invention is indicated by the claims described below rather than the detailed description above, and all changes or modified forms derived from the meaning and scope of the claims and their equivalent concepts should be construed as being included in the scope of the present invention. do.

Claims (20)

(a) pulverizing the lithium lanthanum zirconium oxide (LLZO) solid electrolyte to produce first LLZO solid electrolyte particles;
(b) preparing a dispersion solution containing the first LLZO solid electrolyte particles and a solvent; and
(c) sonicating the dispersion solution to produce second LLZO solid electrolyte particles;
Method for producing solid electrolyte particles comprising: According to paragraph 1,
In step (a),
A method for producing solid electrolyte particles, characterized in that the grinding is performed by one or more processes selected from the group consisting of an air jet mill, a planetary ball mill process, and a mortar grinding process. According to paragraph 1,
In step (a),
A method for producing solid electrolyte particles, characterized in that the average particle size (d ₅₀ ) of the first LLZO solid electrolyte particles is 7 to 15㎛. According to paragraph 3,
A method for producing solid electrolyte particles, characterized in that the first LLZO solid electrolyte particles have a unimodal size distribution. According to paragraph 1,
A method for producing solid electrolyte particles, wherein the solvent includes at least one selected from the group consisting of isopropyl alcohol (IPA), acetonitrile (ACN), and ethanol. According to paragraph 1,
In step (c),
A method for producing solid electrolyte particles, characterized in that the ultrasonic treatment is performed for 30 minutes to 2 hours. According to paragraph 1,
In step (c),
A method for producing solid electrolyte particles, characterized in that the average particle size (d ₅₀ ) of the second LLZO solid electrolyte particles is 1 to 15㎛. In clause 7,
A method for producing solid electrolyte particles, characterized in that the average particle size (d ₅₀ ) of the second LLZO solid electrolyte particles is 1.5 to 3.5 ㎛. According to paragraph 1,
In step (c),
A method for producing solid electrolyte particles, characterized in that the average particle size (d ₁₀ ) of the second LLZO solid electrolyte particles is 0.05 to 0.5 ㎛. According to clause 9,
In step (c),
A method for producing solid electrolyte particles, characterized in that the average particle size (d ₁₀ ) of the second LLZO solid electrolyte particles is 0.09 to 0.2 ㎛. According to paragraph 1,
In step (c),
A method for producing solid electrolyte microparticles, characterized in that the second LLZO solid electrolyte microparticles have a bimodal size distribution including a first size distribution and a second size distribution. According to clause 11,
The solid electrolyte particles having the first size distribution have a size of 0.05 to 1 ㎛,
A method for producing solid electrolyte particles, characterized in that the size of the solid electrolyte particles having the second size distribution is 0.09 to 200 ㎛. According to clause 12,
The size of the solid electrolyte particles having the first size distribution is 0.05 to 0.09 ㎛,
A method for producing solid electrolyte particles, characterized in that the size of the solid electrolyte particles having the second size distribution is 0.09 to 150 ㎛. According to paragraph 1,
A method for producing solid electrolyte particles, characterized in that the lithium lanthanum zirconium oxide (LLZO) solid electrolyte is represented by the following formula (1).
[Formula 1]
_{Li _ _ _ _ _ _} ) (a) pulverizing the lithium lanthanum zirconium oxide (LLZO) solid electrolyte to produce first LLZO solid electrolyte particles;
(b) preparing a dispersion solution containing the first LLZO solid electrolyte particles and a solvent;
(c) sonicating the dispersion solution to produce second LLZO solid electrolyte particles; and
(e) manufacturing a composite solid electrolyte sheet containing the second LLZO solid electrolyte particles and a second binder;
Method for manufacturing a composite solid electrolyte sheet comprising: According to clause 15,
The second binder is polyethylene oxide, nitrile butadiene rubber (NBR), polyethylene glycol, polyacrylonitrile, polyvinyl chloride, and polymethylmethacrylate. ), polypropyleneoxide, polydimethylsiloxane, polyvinylidenefluoride, polyvinylidenecarbonate, and polyvinyl pyrrolidinone. A method for manufacturing a composite solid electrolyte sheet comprising: (A) manufacturing a positive electrode including a positive electrode active material, a first lithium lanthanum zirconium oxide (LLZO) solid electrolyte, a first binder, and a conductive material;
(B) manufacturing a solid electrolyte sheet including a second lithium lanthanum zirconium oxide (LLZO) solid electrolyte and a second binder;
(C) manufacturing a laminate by laminating the positive electrode and the solid electrolyte sheet; and
(D) disposing a negative electrode containing lithium metal on the solid electrolyte sheet of the laminate;
Manufacturing method of an all-solid lithium secondary battery comprising: According to clause 17,
Step (B)
(B-1) pulverizing the second lithium lanthanum zirconium oxide (LLZO) solid electrolyte to produce first LLZO solid electrolyte particles;
(B-2) preparing a dispersion solution containing the first LLZO solid electrolyte particles and a solvent;
(B-3) sonicating the dispersion solution to produce second LLZO solid electrolyte particles; and
(B-4) manufacturing a solid electrolyte sheet containing the second LLZO solid electrolyte particles and a second binder. A method for manufacturing an all-solid lithium secondary battery, comprising: According to clause 17,
A method of manufacturing an all-solid lithium secondary battery, characterized in that the second lithium lanthanum zirconium oxide (LLZO) solid electrolyte is represented by the following formula (1).
[Formula 1]
_{Li _ _ _ _ _ _} ) According to clause 17,
The positive electrode active material is lithium iron phosphate (LiFePO ₄ ), lithium nickel cobalt aluminum oxide (NCA), lithium cobalt oxide (LiCoO ₂ ), lithium nickel oxide (LiNiO ₂ ), and lithium manganese oxide. (LiMn ₂ O ₄ ) and lithium nickel cobalt manganese oxide (NCM). A method for manufacturing an all-solid-state lithium secondary battery, characterized in that it includes at least one selected from the group consisting of.