KR102397881B1 - Method of manufacturing all solid lithium secondary battery comprising high density solid electrolyte and method of manufacturing bipolar all solid lithium secondary battery comprising the same - Google Patents

Abstract

The present invention comprises the steps of: (a) manufacturing a positive electrode comprising a positive electrode active material, a first lithium lanthanum zirconium oxide (LLZO), a first binder, and a conductive material; (b) preparing a solid electrolyte sheet including a second lithium lanthanum zirconium oxide (LLZO) and a second binder; (c) preparing a solid electrolyte layer by roll-pressing the solid electrolyte sheet a plurality of times; (d) preparing a laminate by laminating the positive electrode and the solid electrolyte layer; and (e) disposing an anode including lithium metal on the solid electrolyte layer of the laminate; The method for manufacturing an all-solid-state lithium secondary battery of the present invention and the method for manufacturing a bipolar all-solid-state lithium secondary battery including the same have an effect of having a high energy density.

Description

A method for manufacturing an all-solid-state lithium secondary battery comprising a high-density solid electrolyte sheet and a method for manufacturing a bipolar all-solid-state lithium secondary battery comprising the same SECONDARY BATTERY COMPRISING THE SAME}

The present invention relates to a method for manufacturing an all-solid-state lithium secondary battery and a method for manufacturing a bipolar all-solid-state lithium secondary battery comprising the same, and more particularly, to a method for manufacturing an all-solid-state lithium secondary battery including a high-density solid electrolyte sheet and the method including the same It relates to a method for manufacturing a bipolar all-solid-state lithium secondary battery.

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

As a conventional lithium secondary battery uses a liquid electrolyte, it easily ignites when exposed to water in the air, so safety issues have always been raised. These safety issues are becoming more and more issues as electric vehicles become visible.

Accordingly, research on an All-Solid-State Secondary Battery using a solid electrolyte made of an inorganic material, which is a non-flammable material, has been actively conducted in recent years for the purpose of improving safety. All-solid-state secondary batteries are attracting attention as next-generation secondary batteries from the viewpoints of safety, high energy density, high output, long life, simplification of manufacturing processes, enlargement/compactness of batteries, and low cost.

All-solid-state lithium secondary batteries do not use flammable organic solvents and use non-flammable electrolyte materials, so there is no risk of fire or explosion, and high-voltage cathode materials and lithium metal can be applied because of their excellent potential safety. Accordingly, high energy density is possible. For this, the loading amount of the positive electrode material and the ratio of the active material must be increased, and the thickness of the solid electrolyte and lithium metal must be reduced. In addition, when cells are stacked in a bipolar structure, there is a problem in that the solid electrolyte is damaged and a short circuit occurs during the charging process, so a method is needed to reduce the thickness of the solid electrolyte and improve the mechanical properties.

It is an object of the present invention to solve the above problems, to increase the loading amount and the active material ratio of the positive electrode, to prevent the utilization rate of the active material from being lowered by rolling the positive electrode a plurality of times, to improve the high voltage stability, the positive electrode active material An object of the present invention is to provide a method for manufacturing an all-solid-state lithium secondary battery that can realize excellent discharge capacity even at high loading by controlling the interface of

In addition, by rolling the solid electrolyte a plurality of times, the density is increased and the thickness is decreased, so that it can be used as a single layer without stacking multiple layers, and a composite solid electrolyte layer with improved mechanical properties can be manufactured. is to provide

Another object of the present invention is to provide a method for manufacturing a bipolar all-solid-state lithium secondary battery having a high energy density by increasing the loading amount and the active material ratio of the positive electrode and reducing the thickness of the solid electrolyte layer.

According to one aspect of the present invention, (a) manufacturing a positive electrode comprising a positive electrode active material, a first lithium lanthanum zirconium oxide (LLZO), a first binder and a conductive material; (b) preparing a solid electrolyte sheet including a second lithium lanthanum zirconium oxide (LLZO) and a second binder; (c) preparing a solid electrolyte layer by roll-pressing the solid electrolyte sheet a plurality of times; (d) preparing a laminate by laminating the positive electrode and the solid electrolyte layer; and (e) disposing an anode including lithium metal on the solid electrolyte layer of the laminate;

Step (c) is (c-1) a first rolling step of roll-pressing the solid electrolyte sheet at a rolling ratio of 10 to 30%; and (c-2) a second rolling step of roll-pressing the solid electrolyte sheet on which the first rolling has been performed at a rolling ratio of 30 to 50%.

In step (c-1), the first rolling may be performed repeatedly 1 to 3 times, and in step (c-2), the second rolling may be performed repeatedly 1 to 10 times.

Step (c-1) may be performed at a pressure of 0.5 to 5 MPa, and step (c-2) may be performed at a pressure of 5 to 10 MPa.

The solid electrolyte layer may have a thickness of 40 to 60 μm.

After step (a), the positive electrode is roll-pressed a plurality of times to prepare a pressed positive electrode (a'); may further include.

Step (a') is (a'-1) a first rolling step of roll-pressing the positive electrode at a rolling ratio of 10 to 30%; and (a'-2) a second rolling step of roll-pressing the positive electrode on which the first rolling has been performed at a rolling ratio of 30 to 50%.

In step (a'-1), the first rolling may be performed repeatedly 1 to 3 times, and in step (a'-2), the second rolling may be performed by repeating 1 to 10 times.

Step (a'-1) may be performed at a pressure of 0.5 to 5 MPa, and step (a'-2) may be performed at a pressure of 5 to 10 MPa.

The loading amount of the positive electrode may be 13 to 14 mg/cm ² .

1 to 10 parts by weight of the first lithium lanthanum zirconium oxide (LLZO) based on 100 parts by weight of the positive electrode active material; 1 to 20 parts by weight of the first binder; and 1 to 10 parts by weight of the conductive material.

Each of the positive electrode and the solid electrolyte sheet further includes a composite lithium salt, and the composite lithium salt is lithium perchlorate (LiClO ₄ ), lithium hexafluorophosphate (LiPF ₆ ), lithium tetrafluoroborate (LiBF ₄ ), lithium Bisfluorosulfonylimide (Li(FSO ₂ ) ₂ N), LiFSI), lithium trifluoromethanesulfonylimide (LiN(CF ₃ SO ₂ ) ₂ , LiTFSI), lithium triflate (LiCF ₃ SO ₃ ) ), difluoro(bis(oxalato))lithium phosphate (LiPF ₂ (C ₂ O ₄ ) ₂ ), tetrafluoro(oxalato) lithium phosphate (LiPF ₄ (C ₂ O ₄ )), difluoro Rho (oxalato) lithium borate (LiBF ₂ (C ₂ O ₄ )) and bis (oxalato) lithium borate (LiB(C ₂ O ₄ ) ₂ ) may include two or more selected from the group consisting of .

The complex lithium salt may include lithium perchlorate (LiClO ₄ ) and lithium bisfluorosulfonylimide (Li(FSO ₂ ) ₂ N), LiFSI).

The positive active material may include a lithium-nickel-cobalt-manganese-based oxide (NCM) represented by Formula 1 .

[Formula 1]

Li _1+a Ni _x Co _y Mn _z O ₂ (0≤a≤0.2, 0<x<1, 0<y<1, 0<z<1, x+y+z=1)

The lithium-nickel-cobalt-manganese oxide (NCM) is LiNi _0.4 Co _0.2 Mn _0.4 O ₂ , LiNi _0.5 Co _0.2 Mn _0.3 O ₂ , LiNi _1/3 Co _1/3 Mn _1/3 O ₂ , LiNi _0.6 Co _0.2 Mn _0.2 O ₂ and LiNi _0.8 Co _0.1 Mn _0.1 O ₂ At least one selected from the group consisting of may be included.

The first and second lithium lanthanum zirconium oxide (LLZO) may be represented by Formula 2 below.

[Formula 2]

Li _x Al _p Ga _q La _y Zr _z O ₁₂ (5≤x≤9, 0≤p≤4, 0≤q≤4, 2≤y≤4, 1≤z≤3)

The first and second binders are polyethyleneoxide, polyethyleneglycol, polyacrylonitrile, polyvinylchloride, polymethylmethacrylate, polypropyleneoxide. , polydimethylsiloxane, polyvinylidenefluoride, polyvinylidenecarbonate, and polyvinyl pyrrolidinone may include at least one selected from the group consisting of.

The conductive material may include at least one selected from the group consisting of carbon black, acetylene black, Ketjen black, carbon fibers, carbon nanotubes, and graphene.

In another aspect of the present invention, (a) forming on one surface of the bipolar current collector, the positive electrode active material, the first lithium lanthanum zirconium oxide (LLZO), forming a positive electrode comprising a first binder and a conductive material; (b) forming a negative electrode formed on the other surface of the bipolar current collector and including lithium metal; (c) preparing a bipolar laminate structure of a solid electrolyte layer/anode/bipolar current collector/anode by locating a solid electrolyte layer on the anode of the laminate; (d) manufacturing a laminate by stacking a plurality of the bipolar laminate structures in series; and (e) bipolar by laminating a positive electrode/positive electrode current collector on the solid electrolyte layer positioned at the top of the laminate, and stacking a solid electrolyte layer/negative electrode/negative electrode current collector on the positive electrode positioned at the bottom of the laminate. It provides a method of manufacturing a bipolar all-solid-state lithium secondary battery comprising; manufacturing an all-solid-state lithium secondary battery.

The bipolar current collector may include at least one selected from the group consisting of aluminum/copper clad (Al/Cu clad), stainless metal (SUS), nickel, and a nickel alloy.

The negative electrode current collector includes at least one selected from the group consisting of copper, nickel, silver, aluminum/copper clad (Al/Cu clad) and stainless steel (SUS), and the positive electrode current collector includes aluminum, aluminum alloy, titanium , and may include at least one selected from the group consisting of aluminum/copper clad (Al/Cu clad) and stainless steel (SUS).

The method of manufacturing an all-solid-state lithium secondary battery of the present invention increases the loading amount and the active material ratio of the positive electrode, and by rolling the positive electrode a plurality of times, it is possible to prevent a decrease in the utilization rate of the active material and improve the high voltage stability. In addition, by controlling the interface of the positive electrode active material, excellent discharge capacity can be realized even at a high loading amount.

In addition, by rolling the solid electrolyte a plurality of times, the density is increased and the thickness is decreased, so that it can be used as a single layer without stacking multiple layers, and there is an effect that a solid electrolyte layer with improved mechanical properties can be manufactured.

In addition, the method of manufacturing a bipolar all-solid-state lithium secondary battery of the present invention has an effect of having a high energy density.

1 is a flowchart of a method for manufacturing an all-solid-state lithium secondary battery according to the present invention.
2 is a schematic view showing a rolling process step in the manufacturing method of the all-solid-state lithium secondary battery according to the present invention.
3 is a structural diagram of an all-solid-state lithium secondary battery unit cell (pouch type) according to the present invention.
4 is a structural diagram of a three-stage bipolar all-solid-state lithium secondary battery according to the present invention.
5 to 8 are graphs showing the charging and discharging characteristics of prototypes finally assembled with the bipolar all-solid-state lithium secondary batteries prepared according to Device Example 2 and Device Comparative Examples 5 to 8 as a pouch case.
9 and 10 are FIB cross-sectional SEM images of the bipolar stacked structures according to Device Example 1 and Device Comparative Example 1. FIG.

Since the present invention can apply various transformations and can have various embodiments, specific embodiments are illustrated and described in detail in the detailed description. However, this is not intended to limit the present invention to specific embodiments, and should be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the present invention. In describing the present invention, if it is determined that a detailed description of a related known technology may obscure the gist of the present invention, the detailed description thereof will be omitted.

In addition, terms including ordinal numbers such as first, second, etc. to be used below may be used to describe various elements, but the elements are not limited by the terms. The above terms are used only for the purpose of distinguishing one component from another. For example, it may be named first without departing from the scope of the present invention.

In addition, when it is said that a certain component is "formed" or "stacked" on another component, it may be formed or laminated by being directly attached to the front surface or one surface on the surface of the other component, but in the middle It should be understood that there may be other components in the .

The singular expression includes the plural expression unless the context clearly dictates otherwise. In the present application, terms such as “comprise” or “have” are intended to designate that a feature, number, step, operation, component, part, or combination thereof described in the specification exists, but one or more other features It should be understood that this does not preclude the existence or addition of numbers, steps, operations, components, parts, or combinations thereof.

1 is a flowchart of a manufacturing method of an all-solid-state lithium secondary battery according to the present invention, and FIG. 2 is a schematic diagram showing a rolling process step in the manufacturing method of an all-solid-state lithium secondary battery according to the present invention.

Hereinafter, a method of manufacturing an all-solid-state lithium secondary battery will be described in detail with reference to FIGS. 1 and 2 . However, this is provided as an example, and the present invention is not limited thereto, and the present invention is only defined by the scope of the claims to be described later.

First, a positive electrode including a positive electrode active material, first lithium lanthanum zirconium oxide (LLZO), a first binder, and a conductive material is prepared (step a).

If step (a) is described in more detail, a positive electrode may be manufactured by casting a slurry in which a positive electrode active material, first lithium lanthanum zirconium oxide (LLZO), a first binder, and a conductive material are mixed and then dried.

After step (a), the positive electrode is roll-pressed a plurality of times to prepare a pressed positive electrode (a'); may further include.

Step (a') is (a'-1) a first rolling step of roll-pressing the positive electrode at a rolling ratio of 10 to 30%; and (a'-2) a second rolling step of roll-pressing the positive electrode on which the first rolling has been performed at a rolling ratio of 30 to 50%.

In step (a'-1), the first rolling may be repeated 1 to 3 times, and in step (a'-2), the second rolling may be performed 1 to 10 times.

If the first rolling is performed more than 3 times, the rolling effect is insignificant, which is not preferable, and if the second rolling is performed more than 10 times, the positive electrode may be damaged, which is not preferable.

Step (a'-1) may be performed at a pressure of 0.5 to 5 MPa, and step (a'-2) may be performed at a pressure of 5 to 10 MPa.

In order to obtain a positive electrode having a desired thickness, if the pressure is pressed at 5~8Mpa from the beginning without the first rolling process, the electrode or electrolyte may be torn or damaged, but after the first rolling process, a second rolling with high pressure is applied. When the process is performed, the active material or electrode has a shape and can be rolled to a desired thickness up to the target.

The loading amount of the positive electrode may be 13 to 14 mg/cm ² , and the positive loading amount per unit area means the weight of the positive electrode active material coated on the positive electrode current collector per unit area.

1 to 10 parts by weight of the first lithium lanthanum zirconium oxide (LLZO) based on 100 parts by weight of the positive electrode active material; 1 to 20 parts by weight of the first binder; and 1 to 10 parts by weight of the conductive material.

The positive electrode further includes a complex lithium salt, and the complex lithium salt is lithium perchlorate (LiClO ₄ ), lithium hexafluorophosphate (LiPF ₆ ), lithium tetrafluoroborate (LiBF ₄ ), lithium bisfluorosulfonyl imide (Li(FSO ₂ ) ₂ N), LiFSI), lithium trifluoromethanesulfonylimide (LiN(CF ₃ SO ₂ ) ₂ , LiTFSI), lithium triflate (LiCF ₃ SO ₃ ), difluoro (bis(oxalato))lithium phosphate (LiPF ₂ (C ₂ O ₄ ) ₂ ), tetrafluoro(oxalato)lithium phosphate (LiPF ₄ (C ₂ O ₄ )), difluoro(oxalato) ) lithium borate (LiBF ₂ (C ₂ O ₄ )) and bis(oxalato) lithium borate (LiB(C ₂ O ₄ ) ₂ ) containing two or more selected from the group consisting of, preferably lithium perchlorate ( LiClO ₄ ) and lithiumbisfluorosulfonylimide (Li(FSO ₂ ) ₂ N), LiFSI).

The positive active material may include a lithium-nickel-cobalt-manganese-based oxide (NCM) represented by Formula 1 .

[Formula 1]

Li _1+a Ni _x Co _y Mn _z O ₂ (0≤a≤0.2, 0<x<1, 0<y<1, 0<z<1, x+y+z=1)

The lithium-nickel-cobalt-manganese oxide (NCM) is LiNi _0.4 Co _0.2 Mn _0.4 O ₂ , LiNi _0.5 Co _0.2 Mn _0.3 O ₂ , LiNi _1/3 Co _1/3 Mn _1/3 O ₂ , LiNi _0.6 Co _0.2 Mn _0.2 O ₂ and LiNi _0.8 Co _0.1 Mn _0.1 O ₂ At least one selected from the group consisting of may be included.

The conductive material may include at least one selected from the group consisting of carbon black, acetylene black, Ketjen black, carbon fibers, carbon nanotubes, and graphene.

Next, a solid electrolyte sheet including a second lithium lanthanum zirconium oxide (LLZO) and a second binder is prepared (step b).

In more detail, the solid electrolyte sheet may be manufactured by coating the slurry in which the second lithium lanthanum zirconium oxide (LLZO) and the second binder are mixed by a doctor blade method.

The solid electrolyte sheet further includes a composite lithium salt, and the composite lithium salt is lithium perchlorate (LiClO ₄ ), lithium hexafluorophosphate (LiPF ₆ ), lithium tetrafluoroborate (LiBF ₄ ), lithium bisfluoro Sulfonylimide (Li(FSO ₂ ) ₂ N), LiFSI), lithium trifluoromethanesulfonylimide (LiN(CF ₃ SO ₂ ) ₂ , LiTFSI), lithium triflate (LiCF ₃ SO ₃ ), di Fluoro(bis(oxalato))lithium phosphate (LiPF ₂ (C ₂ O ₄ ) ₂ ), tetrafluoro(oxalato)lithium phosphate (LiPF ₄ (C ₂ O ₄ )), difluoro(oxide) Salato) lithium borate (LiBF ₂ (C ₂ O ₄ )) and bis(oxalato) lithium borate (LiB(C ₂ O ₄ ) ₂ ) may include two or more selected from the group consisting of, preferably may include lithium perchlorate (LiClO ₄ ) and lithium bisfluorosulfonylimide (Li(FSO ₂ ) ₂ N), LiFSI).

The first and second lithium lanthanum zirconium oxide (LLZO) may be represented by the following formula (2), preferably represented by the following formula (3).

[Formula 2]

Li _x Al _p Ga _q La _y Zr _z O ₁₂ (5≤x≤9, 0≤p≤4, 0≤q≤4, 2≤y≤4, 1≤z≤3)

[Formula 3]

Li _7-3w Al _w La ₃ Zr ₂ O ₁₂ (0.1≤w≤0.4)

The first and second lithium lanthanum zirconium oxide (LLZO) may include a single-phase cubic structure.

The first and second binders are polyethyleneoxide, polyethyleneglycol, polyacrylonitrile, polyvinylchloride, polymethylmethacrylate, polypropyleneoxide. , polydimethylsiloxane, polyvinylidenefluoride, polyvinylidenecarbonate, and polyvinyl pyrrolidinone may include at least one selected from the group consisting of, preferably may include polyethyleneoxide, and more preferably, the first binder may include polyethyleneoxide having an average molecular weight (Mv) of 400,000 to 1,000,000, and the second binder has an average molecular weight ( Mv) may include 100,000 to 400,000 polyethylene oxide (Polyethylene oxide).

The thickness of the solid electrolyte sheet may be 30 to 150 μm.

Next, the solid electrolyte sheet is roll-pressed a plurality of times to prepare a solid electrolyte layer (step c).

Step (c) is (c-1) a first rolling step of roll-pressing the solid electrolyte sheet at a rolling ratio of 10 to 30%; and (c-2) a second rolling step of roll-pressing the solid electrolyte sheet on which the first rolling has been performed at a rolling ratio of 30 to 50%.

In step (c-1), the first rolling may be repeatedly performed 1 to 3 times, and in step (c-2), the second rolling may be repeatedly performed 1 to 10 times or more.

If the first rolling is performed more than 3 times, the rolling effect is insignificant, which is not preferable, and if the second rolling is performed more than 10 times, the solid electrolyte sheet may be damaged, which is not preferable.

Step (c-1) may be performed at a pressure of 0.5 to 5 MPa, and step (c-2) may be performed at a pressure of 5 to 10 MPa.

In order to obtain a solid electrolyte having a desired thickness (about 50㎛), if the pressure is pressed at 5~8Mpa from the beginning without the first rolling process, the electrode or electrolyte may be torn or damaged, but after the first rolling process, high When the second rolling process of applying pressure is performed, the active material or electrode has a shape, so that it can be rolled to a thickness up to a desired target.

If rolling with a strong pressure from the beginning, the solid electrolyte sheet may be torn or the particles of LLZO may be damaged, so it is preferable to divide the rolling into steps (c-1) and (c-2), and by rolling at different pressures, high capacity It is possible to manufacture a solid electrolyte layer with high strength.

The solid electrolyte layer may have a thickness of 40 to 60 μm.

Next, the positive electrode and the solid electrolyte layer are laminated to prepare a laminate (step d).

In more detail, the positive electrode and the solid electrolyte layer may be laminated, and the laminate may be manufactured by pressing at a temperature of 30° C. to 90° C. with a pressure of 0.01 MPa to 1.0 MPa.

The pressurization may be performed for 0.1 minutes to 5 minutes, preferably for 0.1 minutes to 2 minutes.

Finally, an all-solid-state lithium secondary battery is prepared by disposing a negative electrode including lithium metal on the solid electrolyte layer of the laminate (step e).

More specifically, a negative electrode containing lithium metal is laminated on the solid electrolyte layer of the laminate and pressurized at a temperature of 30° C. to 90° C. at a pressure of 0.01 MPa to 1.0 MPa to form an all-solid-state lithium secondary battery. can be manufactured.

The pressurization may be performed for 0.1 minutes to 5 minutes, preferably for 0.1 minutes to 2 minutes.

3 is a structural diagram of an all-solid-state lithium secondary battery unit cell (pouch type) according to the present invention, and FIG. 4 is a structural diagram of a three-stage bipolar all-solid-state lithium secondary battery according to the present invention. Hereinafter, a method of manufacturing a bipolar all-solid-state lithium secondary battery will be described in detail with reference to FIGS. 3 and 4 .

A method of manufacturing a bipolar all-solid-state lithium secondary battery includes the steps of (a) forming a positive electrode formed on one surface of a bipolar current collector, and including a positive electrode active material, a first lithium lanthanum zirconium oxide (LLZO), a first binder, and a conductive material ; (b) forming a negative electrode formed on the other surface of the bipolar current collector and including lithium metal; (c) preparing a bipolar laminate structure of a solid electrolyte layer/anode/bipolar current collector/anode by locating a solid electrolyte layer on the anode of the laminate; (d) manufacturing a laminate by stacking a plurality of the bipolar laminate structures in series; and (e) bipolar by laminating a positive electrode/positive electrode current collector on the solid electrolyte layer positioned at the top of the laminate, and stacking a solid electrolyte layer/negative electrode/negative electrode current collector on the positive electrode positioned at the bottom of the laminate. It may include a method of manufacturing a bipolar all-solid-state lithium secondary battery comprising; manufacturing an all-solid-state lithium secondary battery.

The bipolar current collector may include at least one selected from the group consisting of aluminum/copper clad (Al/Cu clad), stainless metal (SUS), nickel, and a nickel alloy.

The negative electrode current collector includes at least one selected from the group consisting of copper, nickel, silver, aluminum/copper clad (Al/Cu clad) and stainless steel (SUS), and the positive electrode current collector includes aluminum, aluminum alloy, titanium , and may include at least one selected from the group consisting of aluminum/copper clad (Al/Cu clad) and stainless steel (SUS).

Bipolar all-solid-state lithium based on a unit cell in which a solid electrolyte layer is formed between the positive electrode and the negative electrode by stacking a bipolar laminate structure in which a solid electrolyte layer is combined with a positive electrode and a negative electrode respectively formed on one side and the other side of the bipolar current collector A secondary battery can be manufactured.

Hereinafter, preferred examples are presented to help the understanding of the present invention. However, the following examples are only provided for easier understanding of the present invention, and the content of the present invention is not limited by the examples.

[Example]

Preparation Example 1: Preparation of aluminum doped lithium lanthanum zirconium oxide (Al-LLZO)

Lanthanum nitrate (La(NO ₃ ) ₃ .6H ₂ O), zirconium nitrate (ZrO(NO ₃ ) ₂ .2H ₂ O) so that the molar ratio of the starting material La:Zr:Al in distilled water is 3:2:0.25 and aluminum nitrate (Al(NO ₃ ) ₃ ·9H ₂ O) to prepare a starting material solution having a 1 molar concentration of the starting material.

An appropriate amount of the starting material solution, 0.6 mol of ammonia water, and an aqueous sodium hydroxide solution were added through the injection part of the Quett Taylor vortex reactor to obtain a mixed solution whose pH was adjusted to 11, the reaction temperature was 25 ° C, the reaction time was 4 hr, The stirring speed of the stirring rod was set to 1,300 rpm, and the precursor slurry in the form of a liquid slurry was discharged to the discharge unit by co-precipitation. In the co-precipitation reaction of the Quett Taylor vortex reactor, the Taylor number was set to 640 or more.

The precursor slurry was washed with purified water and dried for 24 h. After the dried precursor was pulverized with a ball mill, excess LiOH·H ₂ O was added and mixed with a ball mill to prepare a mixture. The LiOH·H ₂ O content of the mixture was added in excess of 3 wt% so that the content of Li in LiOH·H ₂ O was 103 parts by weight based on 100 parts by weight of Li in the generated solid electrolyte. The mixture was calcined at 900° C. for 2 hours and then pulverized to prepare aluminum-doped lithium lanthanum zirconium oxide (Al-LLZO).

Example 1: Preparation of positive electrode

A mixture was prepared such that the weight ratio of the NCM811 positive electrode active material, the solid electrolyte, the binder, and the conductive material was 88:1.2:8:2.8 (based on pure solids). That is, 1.36 parts by weight of Al-LLZO prepared according to Preparation Example 1, 9.09 parts by weight of PEO binder (molecular weight 600,000), and 3.18 parts by weight of conductive material Super-P were mixed based on 100 parts by weight of the positive active material to prepare a mixture.

At this time, the PEO binder includes a lithium salt mixed with polyethylene oxide (PEO, molecular weight 600,000) and LiClO ₄ and LiFSi, and the molar ratio of PEO and the lithium salt is [EO ]: [LiClO ₄ ]: [LiFSi] 13: 0.8: 0.2.

Specifically, first, the positive electrode active material, Al-LLZO and Super-p prepared according to Preparation Example 1 were weighed in the above weight ratio, and then mixed using a mortar for 30 minutes to prepare a mixed powder. The mixed powder was transferred to a container dedicated to a Thinky mixer, mixed with a PEO binder in the above weight ratio, mounted on a mixer, and mixed three times for 5 minutes at 2,000 rpm once to prepare a mixture. Next, a slurry was prepared by mixing acetonitrile (ACN) with the mixture to adjust the appropriate viscosity, putting a zircon ball, and mixing at 2,000 rpm for 5 minutes. The slurry was set to a loading amount of about 13.1 mg/cm ² and cast on aluminum foil to a thickness of about 70 μm. After that, the rolling process was repeated 1 to 2 times at a pressure of 1 to 3 Mpa to have a rolling rate of 20% of the initial thickness using a roll press, and then 1 at a pressure of 5 to 8 Mpa to have a rolling rate of 40% of the initial thickness. The rolling process was repeated 5 times to prepare a positive electrode (thickness of 51 μm).

Example 2: Preparation of solid electrolyte layer

A mixture was prepared so that the weight ratio of LLZO and the binder was 70:30. That is, a mixture was prepared by mixing 42.9 parts by weight of a PEO binder based on 100 parts by weight of Al-LLZO prepared according to Preparation Example 1.

At this time, the PEO binder includes a lithium salt mixed with polyethylene oxide (PEO, molecular weight 200,000) and LiClO ₄ and LiFSi, and the molar ratio of PEO and the lithium salt is [EO ]: [LiClO ₄ ]: [LiFSi] = 13 : 0.8 : 0.2.

Specifically, first, Al-LLZO and PEO binder prepared according to Preparation Example 1 were weighed in the above weight ratio, and then stirred at 2,000 rpm for 5 minutes using a Thinky mixer to prepare a mixture.

Acetonitrile (acetonitrile, ACN) was mixed with the mixture, and stirred with a sinky mixer to adjust the appropriate viscosity. Next, a slurry was prepared by adding a 2mm zircon ball and stirring at 2,000 rpm for 5 minutes with a syncy mixer. The slurry is cast to 100 μm through a casting blade, silicone-coated PET (polyethylene terephthalate) is added to both sides of the cast slurry, and a roll press is used to have a rolling rate of 20% of the initial thickness. The rolling process was performed by repeating 1 to 2 times with pressure, and then the rolling process was repeated 1 to 5 times at a pressure of 5 to 8 Mpa to have a rolling rate of 40% of the initial thickness to prepare a solid electrolyte layer (thickness 54). μm).

Comparative Example 1: Preparation of a positive electrode

A mixture was prepared such that the weight ratio of the NCM811 positive electrode active material, the solid electrolyte, the binder, and the conductive material was 88:1.2:8:2.8 (based on pure solids). That is, 1.36 parts by weight of Al-LLZO prepared according to Preparation Example 1, 9.09 parts by weight of a PEO binder (molecular weight 600,000), and 3.18 parts by weight of a conductive material Super-P were mixed based on 100 parts by weight of the positive active material to prepare a mixture.

At this time, the PEO binder contains polyethylene oxide (PEO, molecular weight 600,000) and LiClO ₄ (lithium salt), and the molar ratio of the PEO and the lithium salt is [EO]: [ LiClO ₄ ] = 15 : 1.

Specifically, first, the positive electrode active material, Al-LLZO and Super-p prepared according to Preparation Example 1 were weighed in the above weight ratio, and then mixed using a mortar for 30 minutes to prepare a mixed powder. The mixed powder was transferred to a container dedicated to a Thinky mixer, mixed with a PEO binder in the above weight ratio, mounted on a mixer, and mixed three times for 5 minutes at 2,000 rpm once to prepare a mixture. Next, a slurry was prepared by mixing acetonitrile (ACN) with the mixture to adjust the appropriate viscosity, putting a zircon ball, and mixing at 2,000 rpm for 5 minutes. The slurry was set to a loading amount of 8.8 mg/cm ² and cast on aluminum foil to a thickness of about 60 μm. Thereafter, the rolling process was repeated 1 to 2 times at a pressure of 1 to 3 Mpa to have a rolling rate of 20% of the initial thickness using a roll press to prepare a positive electrode (thickness 50 μm).

Comparative Example 2: Preparation of a positive electrode

In Comparative Example 1, a positive electrode was manufactured in the same manner as in Comparative Example 1, except that the loading amount was set to 10.2 mg/cm ² instead of setting the loading amount to 8.8 mg/cm ² .

Comparative Example 3: Preparation of a positive electrode

In Comparative Example 1, a positive electrode was manufactured in the same manner as in Comparative Example 1, except that the loading amount was set to 11.4 mg/cm ² instead of setting the loading amount to 8.8 mg/cm ² .

Comparative Example 4: Preparation of a positive electrode

In Comparative Example 1, a positive electrode was manufactured in the same manner as in Comparative Example 1, except that the loading amount was set to 12.2 mg/cm ² instead of setting the loading amount to 8.8 mg/cm ² .

Comparative Example 5: Preparation of solid electrolyte layer

A mixture was prepared so that the weight ratio of LLZO and the binder was 70:30. That is, a mixture was prepared by mixing 42.9 parts by weight of a PEO binder based on 100 parts by weight of Al-LLZO prepared according to Preparation Example 1.

At this time, the PEO binder contains polyethylene oxide (PEO, molecular weight 200,000) and LiClO ₄ (lithium salt), and the molar ratio of the PEO and the lithium salt is [EO]: [ LiClO ₄ ] = 15 : 1.

Specifically, first, Al-LLZO and PEO binder prepared according to Preparation Example 1 were weighed in the above weight ratio, and then stirred at 2,000 rpm for 5 minutes using a Thinky mixer to prepare a mixture.

Acetonitrile (acetonitrile, ACN) was mixed with the mixture, and stirred with a sinky mixer to adjust the appropriate viscosity. Next, a slurry was prepared by adding a 2mm zircon ball and stirring at 2,000 rpm for 5 minutes with a syncy mixer. The slurry was cast on a silicone-coated PET (polyethylene terephthalate) film to a thickness of about 12 μm, and laminated 5 layers using a lamination equipment (Bio330D DIC Corporation) at a temperature of 60° C. to a thickness of about 60 μm. An electrolyte layer was prepared.

Device Example 1: Preparation of a bipolar stacked structure

A positive electrode layer was prepared by positioning the positive electrode prepared according to Example 1 on one side of a bipolar current collector, and a negative electrode including lithium metal (0.02 t) was placed on the other side of the bipolar current collector to prepare a negative electrode layer .

Then, the solid electrolyte layer prepared according to Example 2 was adhered on the negative electrode of the negative electrode layer using lamination equipment (Bio330D DIC Corporation) at a temperature of 45° C., and the solid electrolyte layer / negative electrode / bipolar current collector / positive electrode was pressed. was prepared to prepare a bipolar laminated structure.

Device Example 2: Preparation of bipolar all-solid-state lithium secondary battery

A positive electrode/positive electrode current collector was prepared by placing the positive electrode prepared according to Example 1 on the positive electrode current collector. In addition, the negative electrode layer was prepared by placing a negative electrode containing lithium metal (0.02t) on the negative electrode current collector, and using lamination equipment (Bio330D DIC Corporation) at a temperature of 45 ° C. on the negative electrode of the negative electrode layer in Example 2 A solid electrolyte layer/negative electrode/negative electrode current collector was prepared by adhering the prepared solid electrolyte layer.

After laminating two bipolar laminated structures prepared according to Device Example 1 in series and pressing to prepare a laminate, the solid electrolyte layer located on the top of the laminate and the positive electrode of the positive electrode/positive electrode current collector are in contact A bipolar all-solid-state lithium secondary battery in which three unit cells were stacked was manufactured by stacking the positive electrode positioned at the bottom of the stack and the solid electrolyte layer of the solid electrolyte layer/negative electrode/negative electrode current collector in contact with each other and pressing. .

Device Comparative Example 1: Preparation of a bipolar stacked structure

The positive electrode prepared according to Comparative Example 1 was used instead of the positive electrode prepared according to Example 1, and the solid electrolyte layer prepared according to Example 5 was used instead of the solid electrolyte layer prepared according to Example 2 A bipolar stacked structure was prepared in the same manner as in Device Example 1 except that

Device Comparative Example 2: Preparation of a bipolar stacked structure

The positive electrode prepared according to Comparative Example 2 was used instead of the positive electrode prepared according to Example 1, and the solid electrolyte layer prepared according to Example 5 was used instead of the solid electrolyte layer prepared according to Example 2 A bipolar stacked structure was prepared in the same manner as in Device Example 1 except that

Device Comparative Example 3: Preparation of a bipolar stacked structure

The positive electrode prepared according to Comparative Example 3 was used instead of the positive electrode prepared according to Example 1, and the solid electrolyte layer prepared according to Example 5 was used instead of the solid electrolyte layer prepared according to Example 2 A bipolar stacked structure was prepared in the same manner as in Device Example 1 except that

Device Comparative Example 4: Preparation of a bipolar stacked structure

The positive electrode prepared according to Comparative Example 4 was used instead of the positive electrode prepared according to Example 1, and the solid electrolyte layer prepared according to Example 5 was used instead of the solid electrolyte layer prepared according to Example 2 was used. A bipolar stacked structure was prepared in the same manner as in Device Example 1 except that

Device Comparative Example 5: Preparation of bipolar all-solid-state lithium secondary battery

A bipolar all-solid-state lithium secondary battery was manufactured in the same manner as in Device Example 1, except that the bipolar stacked structure prepared according to Device Comparative Example 1 was laminated instead of the bipolar stacked structure prepared according to Device Example 1 did

Device Comparative Example 6: Preparation of bipolar all-solid-state lithium secondary battery

A bipolar all-solid-state lithium secondary battery was manufactured in the same manner as in Device Example 1, except that the bipolar stacked structure prepared according to Device Comparative Example 2 was stacked instead of stacked with the bipolar stacked structure prepared according to Device Example 1 did

Device Comparative Example 7: Preparation of bipolar all-solid-state lithium secondary battery

A bipolar all-solid-state lithium secondary battery was manufactured in the same manner as in Device Example 1, except that the bipolar stacked structure prepared according to Device Comparative Example 3 was stacked instead of stacked with the bipolar stacked structure prepared according to Device Example 1 did

Device Comparative Example 8: Preparation of bipolar all-solid-state lithium secondary battery

A bipolar all-solid-state lithium secondary battery was prepared in the same manner as in Device Example 1, except that the bipolar stacked structure prepared according to Device Comparative Example 4 was stacked instead of the bipolar stacked structure prepared according to Example 1 was stacked. .

[Test Example]

Test Example 1: Charge/discharge characteristics of bipolar all-solid-state lithium secondary battery

5 to 8 are graphs showing the charging and discharging characteristics of prototypes finally assembled with the bipolar all-solid-state lithium secondary batteries prepared according to Device Example 2 and Device Comparative Examples 5 to 8 as a pouch case. In Device Example 2, charging and discharging experiments were performed in the range of 9.0 to 12.6V with a charge/discharge current of 0.05C at 70° C., and Comparative Examples 5 to 8 were charged in the range of 9.0 to 12.9V with a charge/discharge current of 0.05C at 70°C. Discharge experiments were performed.

5 to 8 , the size of the positive electrode is about 4.3 cm x 2.7 cm, the open-circuit voltage (OCV) after charging is about 12.6V, and the average discharge voltage is 11.3V (measured in the device) of unit cell 1 When applied to dogs, it could be confirmed that the discharge voltage was almost identical to the discharge voltage of about 3.7V. As a result of discharging the bipolar all-solid-state lithium secondary battery prepared according to Device Example 2 at 70° C. with a current density of 0.05 C, discharge capacities of about 194 mAh/g and 25.9 mAh were realized. By using the high-strength electrolyte that has undergone the rolling process, the charging and discharging process of the cell could proceed smoothly even at a high loading level, and the discharge capacity could also be properly implemented by increasing the utilization rate of the positive electrode. When the energy density is calculated through this, the total volume based on the reaction area of Device Example 2 becomes 0.0004807L, and 0.026Ah (capacity) X 11.29V (voltage) = 0.2924Wh, that is, 608.3 Wh/L was realized. Therefore, it was confirmed that a cell/stack having a bipolar structure having a high energy density can be manufactured according to the present invention.

In addition, looking at the charge-discharge curves of Comparative Examples 5 to 8 of the devices comprising a solid electrolyte layer in which 5 layers of a solid electrolyte sheet are laminated, the charging/discharging proceeds without any problem in the cells with a loading level of 9 mg/cm ² or less (Comparative Device Example 5). It could be confirmed that the volumetric energy density was 412Wh/L. However, in Comparative Examples 6 to 8 of the devices in which the loading level (10 mg/cm ² or more) was increased for high energy density, mechanical properties were lowered due to the thin electrolyte, and a short circuit occurred during the charging process, and the loading level Accordingly, the charging process did not proceed and a short circuit occurred quickly, and the discharge capacity was not implemented properly.

Test Example 2: Comparison of Solid Electrolyte Layers

9 is a bipolar stacked structure according to Device Example 1, and FIG. 10 is an FIB cross-sectional SEM image of a bipolar stacked structure according to Device Comparative Example 1.

9 and 10 , in the case of the bipolar laminate structure according to Device Comparative Example 1, pores or cracks were confirmed due to the use of the stacked solid electrolyte layer. However, in the case of the bipolar laminate structure according to Device Example 1, it was confirmed that all pores disappeared and the density was high by using one solid electrolyte layer prepared through the roll press rolling process. As a result, the mechanical properties were improved, and it was confirmed that the charging and discharging of the cell proceeded smoothly even at a high loading level (13 mg/cm ² or more).

As mentioned above, although preferred embodiments of the present invention have been described in detail, the present invention is not limited to the above embodiments, and various modifications may be made by those skilled in the art within the scope of the technical spirit of the present invention. It is possible.

Claims (20)

(a) preparing a positive electrode including a positive electrode active material, a first lithium lanthanum zirconium oxide (LLZO), a first binder, and a conductive material;
(a') roll-pressing the positive electrode a plurality of times to prepare a pressed positive electrode;
(b) preparing a solid electrolyte sheet including a second lithium lanthanum zirconium oxide (LLZO) and a second binder;
(c-1) a first rolling step of roll-pressing the solid electrolyte sheet at a rolling ratio of 10 to 30%;
(c-2) performing a second rolling of roll-pressing the solid electrolyte sheet on which the first rolling has been performed at a rolling ratio of 30 to 50% to prepare a solid electrolyte layer;
(d) laminating the pressed positive electrode and the solid electrolyte layer to prepare a laminate; and
(e) disposing a negative electrode including lithium metal on the solid electrolyte layer of the laminate;
In step (c-1), the first rolling is performed repeatedly 1 to 3 times,
In step (c-2), the second rolling is performed repeatedly 1 to 10 times,
step (c-1) is carried out at a pressure of 0.5 to 5 MPa,
Step (c-2) is carried out at a pressure of 5 to 10 MPa,
The thickness of the solid electrolyte layer is 40 to 60 μm,
The loading amount of the pressed positive electrode is 13 to 14 mg/cm ² The manufacturing method of the all-solid-state lithium secondary battery. delete delete delete delete According to claim 1,
Step (a') is
(a'-1) a first rolling step of roll-pressing the positive electrode at a rolling ratio of 10 to 30%; and
(a'-2) a second rolling step of roll-pressing the positive electrode, on which the first rolling has been performed, at a rolling ratio of 30 to 50%; 7. The method of claim 6,
In step (a'-1), the first rolling is performed repeatedly 1 to 3 times,
The method of manufacturing an all-solid-state lithium secondary battery, characterized in that the second rolling in step (a'-2) is repeated 1 to 10 times. 7. The method of claim 6,
step (a'-1) is carried out at a pressure of 0.5 to 5 MPa,
Step (a'-2) is a method of manufacturing an all-solid-state lithium secondary battery, characterized in that it is carried out at a pressure of 5 to 10 MPa. delete The method of claim 1,
The positive electrode is based on 100 parts by weight of the positive electrode active material,
1 to 10 parts by weight of the first lithium lanthanum zirconium oxide (LLZO);
1 to 20 parts by weight of the first binder; and
1 to 10 parts by weight of the conductive material; all-solid-state lithium secondary battery manufacturing method comprising a. According to claim 1,
Each of the positive electrode and the solid electrolyte sheet further comprises a composite lithium salt,
The complex lithium salt is lithium perchlorate (LiClO ₄ ), lithium hexafluorophosphate (LiPF ₆ ), lithium tetrafluoroborate (LiBF ₄ ), lithium bisfluorosulfonylimide (Li(FSO ₂ ) ₂ N), LiFSI), lithium trifluoromethanesulfonylimide (LiN(CF ₃ SO ₂ ) ₂ , LiTFSI), lithium triflate (LiCF ₃ SO ₃ ), difluoro(bis(oxalato))lithium phosphate (LiPF) ₂ (C ₂ O ₄ ) ₂ ), tetrafluoro (oxalato) lithium phosphate (LiPF ₄ (C ₂ O ₄ )), difluoro (oxalato) lithium borate (LiBF ₂ (C ₂ O ₄ ) ) and bis (oxalato) lithium borate (LiB(C ₂ O ₄ ) ₂ ) A method of manufacturing an all-solid-state lithium secondary battery comprising at least two selected from the group consisting of. 12. The method of claim 11,
The method for manufacturing an all-solid-state lithium secondary battery, wherein the composite lithium salt comprises lithium perchlorate (LiClO ₄ ) and lithium bisfluorosulfonylimide (Li(FSO ₂ ) ₂ N), LiFSI). According to claim 1,
The method for manufacturing an all-solid-state lithium secondary battery, wherein the positive active material comprises a lithium-nickel-cobalt-manganese oxide (NCM) represented by Formula 1.
[Formula 1]
Li _1+a Ni _x Co _y Mn _z O ₂ (0≤a≤0.2, 0<x<1, 0<y<1, 0<z<1, x+y+z=1) 14. The method of claim 13,
The lithium-nickel-cobalt-manganese oxide (NCM) is LiNi _0.4 Co _0.2 Mn _0.4 O ₂ , LiNi _0.5 Co _0.2 Mn _0.3 O ₂ , LiNi _1/3 Co _1/3 Mn _1/3 O ₂ , LiNi _0.6 Co _0.2 Mn _0.2 O ₂ and LiNi _0.8 Co _0.1 Mn _0.1 O ₂ A method of manufacturing an all-solid-state lithium secondary battery comprising at least one selected from the group consisting of. According to claim 1,
The method of manufacturing an all-solid-state lithium secondary battery, characterized in that the first and second lithium lanthanum zirconium oxide (LLZO) is represented by the following formula (2).
[Formula 2]
Li _x Al _p Ga _q La _y Zr _z O ₁₂ (5≤x≤9, 0≤p≤4, 0≤q≤4, 2≤y≤4, 1≤z≤3) According to claim 1,
The first and second binders are polyethyleneoxide, polyethyleneglycol, polyacrylonitrile, polyvinylchloride, polymethylmethacrylate, polypropyleneoxide. , polydimethylsiloxane (polydimethylsiloxane), polyvinylidene fluoride (polyvinylidenefluoride), polyvinylidene carbonate (polyvinylidenecarbonate) and polyvinyl pyrrolidinone (polyvinyl pyrrolidinone), characterized in that it contains at least one A method for manufacturing a solid lithium secondary battery. According to claim 1,
The method for manufacturing an all-solid-state lithium secondary battery, wherein the conductive material comprises at least one selected from the group consisting of carbon black, acetylene black, Ketjen black, carbon fibers, carbon nanotubes, and graphene. (a) forming a positive electrode formed on one surface of the bipolar current collector, the positive electrode including a positive electrode active material, first lithium lanthanum zirconium oxide (LLZO), a first binder, and a conductive material;
(b) forming a negative electrode formed on the other surface of the bipolar current collector and including lithium metal;
(c) preparing a bipolar laminate structure of a solid electrolyte layer/anode/bipolar current collector/anode by locating a solid electrolyte layer on the anode;
(d) manufacturing a laminate by stacking a plurality of the bipolar laminate structures in series;
(e) stacking a positive electrode / positive electrode current collector on the solid electrolyte layer located at the top of the laminate, and stacking a solid electrolyte layer / negative electrode / negative electrode current collector on the positive electrode located at the bottom of the laminate to obtain bipolar Preparing a solid lithium secondary battery;
A method of manufacturing a bipolar all-solid-state lithium secondary battery comprising a. 19. The method of claim 18,
Method of manufacturing a bipolar all-solid-state lithium secondary battery, wherein the bipolar current collector comprises at least one selected from the group consisting of aluminum/copper clad (Al/Cu clad), stainless metal (SUS), nickel, and a nickel alloy . 19. The method of claim 18,
The negative electrode current collector includes at least one selected from the group consisting of copper, nickel, silver, aluminum/copper clad (Al/Cu clad) and stainless steel (SUS),
The positive electrode current collector of a bipolar all-solid-state lithium secondary battery, characterized in that it comprises at least one selected from the group consisting of aluminum, aluminum alloy, titanium, aluminum / copper clad (Al / Cu clad) and stainless steel (SUS) manufacturing method.

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