KR20190100612A - All solid lithium secondary battery having improved electric potential stability and method for manufacturing the same - Google Patents

Abstract

The present invention provides an all-solid-state lithium secondary battery, which comprises: a positive electrode comprising a positive electrode active material, a first lithium lanthanum zirconium oxide (LLZO), a first binder including a first polymer and a second polymer, and a conductive material; a negative electrode comprising lithium metal; and a composite solid electrolyte layer between the positive electrode and the negative electrode, comprising a second lithium lanthanum zirconium oxide (LLZO) and a second binder including a first polymer and a second polymer. In the all-solid-state lithium secondary battery of the present invention, a discharge capacity and cycle characteristics of the battery can be enhanced by using a binder including polyethylene oxide and polyvinylidene fluoride in the positive electrode and the composite solid electrolyte layer.

Description

All-solid-state lithium secondary battery with excellent potential stability and its manufacturing method {ALL SOLID LITHIUM SECONDARY BATTERY HAVING IMPROVED ELECTRIC POTENTIAL STABILITY AND METHOD FOR MANUFACTURING THE SAME}

The present invention relates to an all-solid-state lithium secondary battery and a method for manufacturing the same, an all-solid-state lithium secondary battery including a positive electrode and a composite solid electrolyte layer prepared using a binder containing polyethylene oxide and polyvinylidene fluoride It is about a method.

Lithium secondary batteries have high electrochemical capacity, high operating potential, and excellent charge / discharge cycle characteristics. Therefore, they are in demand for portable information terminals, portable electronic devices, small household power storage devices, motorcycles, electric vehicles, and hybrid electric vehicles. It is increasing. The proliferation of such applications is required to improve the safety and performance of lithium secondary batteries.

Conventional lithium secondary batteries ignite easily when exposed to water in the air due to the use of a liquid electrolyte has always raised safety issues. This safety issue is becoming more and more an issue as electric vehicles become visible.

Accordingly, recently, all-solid-state secondary batteries using solid electrolytes made of inorganic materials, which are non-combustible materials, have been actively researched for the purpose of improving safety. All-solid-state secondary batteries are attracting attention as next-generation secondary batteries in terms of safety, high energy density, high output, long life, simplification of manufacturing process, battery size / compact size and low cost.

The core technology of the all-solid-state secondary battery is to develop a solid electrolyte showing high ion conductivity. Solid electrolytes for all-solid-state secondary batteries known to date include sulfide solid electrolytes and oxide solid electrolytes.

Korean Unexamined Patent Publication No. 2012-0132533 discloses an all-solid lithium secondary battery having excellent output characteristics using a sulfide-based solid electrolyte as an electrolyte. However, sulfide solid electrolytes have a problem in that hydrogen sulfide (H ₂ S) gas, which is a toxic gas, is generated.

Oxide solid electrolytes show lower ionic conductivity than sulfide solid electrolytes, but have recently attracted attention due to their excellent stability. Oxide-based solid electrolytes are wet and dry depending on the manufacturing process, and the double wet method is considered to be excellent in terms of cost and battery performance, and when a cathode and a solid electrolyte layer are manufactured by the wet method, an oxide-based solid electrolyte material is used. By controlling the interface of the mechanical properties (binding) can be maintained. However, the internal resistance of the battery is increased by the deterioration of the electrochemical properties of the polymer material of the positive electrode and the solid electrolyte layer according to the conventional method, and there is a problem that the discharge capacity and the cycle characteristics of the cell may be reduced.

SUMMARY OF THE INVENTION An object of the present invention is to provide an all-solid lithium secondary battery having improved discharge capacity and cycle characteristics by using a binder containing polyethylene oxide and polyvinylidene fluoride in a positive electrode and a composite solid electrolyte layer. have.

In addition, the manufacturing cost is reduced by manufacturing an all-solid-state lithium secondary battery using a binder including polyethylene oxide and polyvinylidene fluoride in the positive electrode and the composite solid electrolyte layer, between active materials / active materials, between solid electrolyte particles, and electrolyte / It is to provide a method for manufacturing an all-solid-state lithium secondary battery that can further reduce the internal resistance of the battery by controlling the interfacial reaction between the electrodes.

According to an aspect of the present invention, a cathode including a cathode active material, a first lithium lanthanum zirconium oxide (LLZO), a first binder and a conductive material comprising a first polymer and a second polymer; A negative electrode comprising lithium metal; And a composite solid electrolyte layer comprising a second lithium lanthanum zirconium oxide (LLZO) and a second binder including a first polymer and a second polymer between the positive electrode and the negative electrode. .

The first polymer and the second polymer are each independently polyethylene oxide, polyethylene glycol, polyacrylonitrile, polyvinyl chloride, polymethylmethacrylate, polypropylene It may include one or more selected from oxide (polypropyleneoxide), polydimethylsiloxane (polydimethylsiloxane), polyvinylidene fluoride (polyvinylidenefluoride), polyvinylidenecarbonate (polyvinylidenecarbonate) and polyvinylpyrrolidinone (polyvinyl pyrrolidinone).

The first polymer may include polyethylene oxide, and the second polymer may include polyvinylidene fluoride.

The first binder comprises 500 to 1,400 parts by weight of the polyethylene oxide, based on 100 parts by weight of the polyvinylidene fluoride, and the second binder is the polyvinylidene fluoride ) 100 parts by weight, the polyethylene oxide (Polyethylene oxide) may include 2,000 to 3,600 parts by weight.

The first and second lithium lanthanum zirconium oxides (LLZO) are each independently lithium or gallium doped lithium lanthanum zirconium oxide (LLZO),

The lithium lanthanum zirconium oxide (LLZO) doped with aluminum is represented by the following Chemical Formula 1,

The lithium lanthanum zirconium oxide (LLZO) doped with gallium may be represented by the following Chemical Formula 2.

[Formula 1]

Li _x La _y Zr _z Al _w O ₁₂ (5≤x≤9, 2≤y≤4, 1≤z≤3, 0 <w≤1)

[Formula 2]

Li _x La _y Zr _z Ga _m O ₁₂ (5≤x≤9, 2≤y≤4, 1≤z≤3, 0 <m≤4)

The lithium lanthanum zirconium oxide (LLZO) doped with aluminum or gallium may include at least one structure selected from a cubic structure and a tetragonal structure.

The lithium lanthanum zirconium oxide (LLZO) doped with aluminum or gallium may have a single phase cubic structure.

The positive electrode includes 1 to 30 parts by weight of the first lithium lanthanum zirconium oxide (LLZO), 10 to 90 parts by weight of the first binder, and 10 to 30 parts by weight of the conductive material, based on 100 parts by weight of the positive electrode active material, The composite solid electrolyte layer may include 10 to 90 parts by weight of the second binder based on 100 parts by weight of the second lithium lanthanum zirconium oxide (LLZO).

The cathode active material may be a three-component lithium metal oxide (NMC) of Ni-Co-Mn represented by Chemical Formula 3 below.

[Formula 3]

LiNi _p Co _q Mn _r O ₂ (0 <p <0.9, 0 <q <0.5, 0 <r <0.5, p + q + r = 1)

The conductive material may include at least one selected from carbon black, acetylene black, and ketjen black.

The negative electrode containing the lithium metal (a) a substrate containing lithium; And (b) an intaglio pattern including a plurality of holes formed in an intaglio on one surface of the substrate.

The intaglio pattern may include one or more of a circle, an oval, a polygon, a rhombus, and a line.

The intaglio pattern may have a depth of 50 to 500 μm.

The substrate may have a thickness of 20 to 1,000 μm.

The all-solid-state lithium secondary battery is a three-component lithium metal oxide (NMC) of Ni-Co-Mn, lithium lanthanum zirconium oxide (LLZO) doped with aluminum, polyethylene oxide and polyvinylidene fluoride (Polyvinylidene fluoride) A binder comprising a, and a positive electrode comprising carbon black; A negative electrode comprising lithium metal; And a composite solid electrolyte layer comprising a binder including lithium lanthanum zirconium oxide (LLZO) and polyethylene oxide and polyvinylidene fluoride doped with gallium between the anode and the cathode. can do.

According to another aspect of the 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 composite solid electrolyte layer comprising a second lithium lanthanum zirconium oxide (LLZO) and a second binder; (c) stacking the positive electrode and the composite solid electrolyte layer to manufacture a laminate; And (d) disposing a negative electrode including a lithium metal on the composite solid electrolyte layer of the laminate.

In the manufacturing method of the all-solid-state lithium secondary battery, step (c) laminates the positive electrode and the composite solid electrolyte layer, and pressurizes at a pressure of 0.1 to 1.0 MPa in the temperature range (T) of Equation 1 below to laminate the laminate. It may be a step of preparing.

[Equation 1]

Tm-35 ℃ ≤T≤ Tm + 55 ℃

In Formula 1, when T _m1 <T _m2 , Tm = T _m1 , T _m1 > T _m2 , Tm = T _m2 , and when T _m1 = T _m2 , Tm = T _m1 ,

Here, T _m1 is the melting temperature of the first polymer, T _m2 is the melting temperature of the second polymer.

The first binder comprises polyethylene oxide and polyvinylidene fluoride, the second binder comprises polyethylene oxide and polyvinylidene fluoride, Step (c) may be a step of stacking the positive electrode and the composite solid electrolyte layer and pressurizing at a temperature range of 30 ° C. to 120 ° C., preferably 40 ° C. to 60 ° C., to prepare a laminate.

The method of manufacturing the all-solid-state lithium secondary battery may further include pressing the resultant of step (d) in a temperature range T of Equation 1 below.

[Equation 1]

Tm-35 ℃ ≤T≤ T _m + 55 ℃

In Formula 1, when T _m1 <T _m2 , Tm = T _m1 , T _m1 > T _m2 , Tm = T _m2 , and T _m1 = T _m2 , Tm = T _m1 ,

Here, T _m1 is the melting temperature of the first polymer, T _m2 is the melting temperature of the second polymer.

Step (a) may be a step of casting a slurry in which a cathode active material, a first lithium lanthanum zirconium oxide (LLZO), a first binder, and a conductive material are mixed and then dried to manufacture a cathode.

Step (b) may be a step of preparing a composite solid electrolyte layer by coating a slurry of a mixture of second lithium lanthanum zirconium oxide (LLZO) and a second binder on a substrate.

According to another aspect of the 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 composite solid electrolyte layer comprising a second lithium lanthanum zirconium oxide (LLZO) and a second binder; (c ′) preparing a laminate by disposing a composite solid electrolyte layer on the cathode, a composite solid electrolyte layer on the cathode, and a cathode including lithium metal on the composite solid electrolyte layer; And (d ') manufacturing the all-solid-state lithium secondary battery by pressing the laminate in a temperature range T of the following Equation 1. The method of manufacturing an all-solid-state lithium secondary battery is provided.

[Equation 1]

Tm-35 ℃ ≤T≤ T _m + 55 ℃

In Formula 1, when T _m1 <T _m2 , Tm = T _m1 , T _m1 > T _m2 , Tm = T _m2 , and T _m1 = T _m2 , Tm = T _m1 ,

Here, T _m1 is the melting temperature of the first polymer, T _m2 is the melting temperature of the second polymer.

In the all-solid-state lithium secondary battery of the present invention, the discharge capacity and the cycle characteristics of the battery may be improved by using a binder including polyethylene oxide and polyvinylidene fluoride in the positive electrode and the composite solid electrolyte layer, unlike the prior art.

In addition, the manufacturing method of the all-solid-state lithium secondary battery of the present invention by using a binder containing polyethylene oxide and polyvinylidene fluoride in the positive electrode and the composite solid electrolyte layer by the wet method to produce an all-solid lithium secondary battery by reducing the manufacturing cost In addition, there is an effect of reducing the internal resistance of the battery by controlling the interfacial reaction between the active material / active material, the solid electrolyte particles, the electrolyte / electrode.

1 is a schematic diagram of an all-solid-state lithium secondary battery of the present invention.
2 is an enlarged photograph of the surface of the anode including the patterned lithium metal 10 times and b 100 times.
3A is an enlarged photograph of the entire surface of the tool, and b is a part thereof.
4A is a graph showing charge and discharge characteristics of an all-solid-state lithium secondary battery manufactured according to Example 1 and Comparative Example 1 in one cycle and FIG. 4B.
5 is a graph showing the cycle characteristics of the all-solid-state lithium secondary battery prepared according to Example 1 and Comparative Example 1.

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

However, the following descriptions are not intended to limit the present invention to specific embodiments, and detailed descriptions of well-known techniques related to the present invention will be omitted when it is determined that the present invention may obscure the gist of the present invention. .

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this application, the terms "comprise" or "having" are intended to indicate that there is a feature, number, step, operation, component, or combination thereof described in the specification, and one or more other features or It should be understood that it 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 of an all-solid-state lithium secondary battery of the present invention. However, this is presented as an example, by which the present invention is not limited and the present invention is defined only by the scope of the claims to be described later.

Hereinafter, the all-solid-state lithium secondary battery of the present invention will be described in detail with reference to FIG. 1.

The all-solid-state lithium secondary battery of the present invention includes a cathode including a cathode active material, a first lithium lanthanum zirconium oxide (LLZO), a first binder including a first polymer and a second polymer, and a conductive material; A negative electrode comprising lithium metal; And a composite solid electrolyte layer including a second lithium lanthanum zirconium oxide (LLZO) and a second binder including a first polymer and a second polymer between the anode and the cathode.

The first polymer and the second polymer are each independently polyethylene oxide, polyethylene glycol, polyacrylonitrile, polyvinyl chloride, polymethylmethacrylate, polypropylene It may include one or more selected from oxide (polypropyleneoxide), polydimethylsiloxane (polydimethylsiloxane), polyvinylidene fluoride (polyvinylidenefluoride), polyvinylidenecarbonate (polyvinylidenecarbonate) and polyvinylpyrrolidinone (polyvinyl pyrrolidinone).

The first polymer may include polyethylene oxide, and the second polymer may include polyvinylidene fluoride.

The first binder comprises 500 to 1,400 parts by weight of the polyethylene oxide, based on 100 parts by weight of the polyvinylidene fluoride,

The second binder may include 2,000 to 3,600 parts by weight of the polyethylene oxide based on 100 parts by weight of the polyvinylidene fluoride.

By using a binder containing polyvinylidene fluoride (PVDF) in the positive electrode and the composite solid electrolyte layer, the interface between the active material / active material and the solid electrolyte particles can be controlled, and the electrochemically high voltage and excellent stability By including PVDF, the charging voltage can be increased. In addition, PVDF can increase the energy density of the cell / module by reducing the thickness of the film by improving the mechanical properties of the composite solid electrolyte layer while maintaining ion conductivity.

The first and second lithium lanthanum zirconium oxides (LLZO) are each independently aluminum or gallium-doped lithium lanthanum zirconium oxide (LLZO), and the lithium lanthanum zirconium oxide (LLZO) doped with aluminum is represented by Formula 1 below. The lithium lanthanum zirconium oxide (LLZO) doped with gallium may be represented by the following Chemical Formula 2.

[Formula 1]

Li _x La _y Zr _z Al _w O ₁₂ (5≤x≤9, 2≤y≤4, 1≤z≤3, 0 <w≤1)

[Formula 2]

Li _x La _y Zr _z Ga _m O ₁₂ (5≤x≤9, 2≤y≤4, 1≤z≤3, 0 <m≤4)

The lithium lanthanum zirconium oxide (LLZO) doped with aluminum or gallium may include at least one structure selected from a cubic structure and a tetragonal structure. Preferably, the lithium lanthanum zirconium oxide (LLZO) doped with aluminum or gallium may be a single-phase cubic structure, and the cubic structure has high ion conductivity and excellent potential safety.

The positive electrode includes 1 to 30 parts by weight of the first lithium lanthanum zirconium oxide (LLZO), 10 to 90 parts by weight of the first binder, and 10 to 30 parts by weight of the conductive material, based on 100 parts by weight of the positive electrode active material,

The composite solid electrolyte layer may include 10 to 90 parts by weight of the second binder based on 100 parts by weight of the second lithium lanthanum zirconium oxide (LLZO).

The cathode active material may be a layered compound such as lithium cobalt oxide (LiCoO ₂ ), lithium nickel oxide (LiNiO ₂ ), or a compound substituted with one or more transition metals; Lithium manganese oxides such as Li _{1 + x} Mn _2-x O ₄ (where x is 0 to 0.33), LiMnO ₃ , LiMn ₂ O ₃ , LiMnO _2, and the like; Lithium copper oxide (Li ₂ CuO ₂ ); Vanadium oxides such as LiV ₃ O ₈ , LiFe ₃ O ₄ , V ₂ O ₅ , Cu ₂ V ₂ O ₇ and the like; Ni-site-type lithium nickel oxide represented by the formula LiNi _{1 - x} M _x O ₂ , wherein M = Co, Mn, Al, Cu, Fe, Mg, B or Ga, and x = 0.01 to 0.3; Formula LiMn _{2 - x} M _x O ₂ (wherein M = Co, Ni, Fe, Cr, Zn or Ta and x = 0.01 to 0.1) or Li ₂ Mn ₃ MO ₈ (wherein M = Fe, Co, Lithium manganese composite oxide represented by Ni, Cu or Zn); LiMn ₂ O _{4 in} which a part of Li in the formula is substituted with alkaline earth metal ions; Disulfide compounds; Fe ₂ (MoO ₄ ) ₃ ; Li [Ni _x Co _1-2x Nn _x O] _2, a three-component lithium metal oxide (NMC) of Ni-Co-Mn Li [Ni _1/3 Co _1/3 Nn _1/3 O] ₂ and the like, which can be represented by (0 <x <0.5), may be mentioned, but are not limited thereto.

The cathode active material may be a three-component lithium metal oxide (NMC) of Ni-Co-Mn represented by Chemical Formula 3 below.

[Formula 3]

LiNi _p Co _q Mn _r O ₂ (0 <p <0.9, 0 <q <0.5, 0 <r <0.5, p + q + r = 1)

The conductive material may be carbon black, acetylene black, Ketjen black, or the like, and preferably carbon black.

The negative electrode containing the lithium metal (a) a substrate containing lithium; And (b) an intaglio pattern including a plurality of holes formed in an intaglio on one surface of the substrate.

The intaglio pattern may include one or more of a circle, an oval, a polygon, a rhombus, and a line.

The intaglio pattern may have a depth of 50 to 500 μm.

The substrate may have a thickness of 20 to 1,000 μm.

The all-solid-state lithium secondary battery is preferably a three-component lithium metal oxide (NMC) of Ni-Co-Mn, lithium lanthanum zirconium oxide (LLZO) doped with aluminum, polyethylene oxide and polyvinylidene fluoride ( A binder comprising Polyvinylidene fluoride) and a cathode comprising carbon black; A negative electrode comprising lithium metal; And a composite solid electrolyte layer comprising a binder including lithium lanthanum zirconium oxide (LLZO), polyethylene oxide, and polyvinylidene fluoride doped with gallium between the anode and the cathode. can do.

Hereinafter, the manufacturing method of the all-solid-state lithium secondary battery of the present invention will be described in detail.

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

In more detail, the cathode may be manufactured by casting a slurry in which the cathode active material, the first lithium lanthanum zirconium oxide (LLZO), the first binder, and the conductive material are mixed and then dried.

The positive electrode may be manufactured by a wet method to improve the potential stability of an all-solid-state lithium secondary battery.

Next, the second lithium lanthanum zirconium oxide ( LLZO And a second solid binder is prepared (step b).

In more detail, a composite solid electrolyte layer may be prepared by coating a slurry on which a second lithium lanthanum zirconium oxide (LLZO) and a second binder are mixed on a substrate.

The substrate may be polyethylene terephthalate (PET), polyethylenenaphthalate (PEN), polyethersulfone (PES), polycarbonate (PC), polypropylene (PP), or the like, and preferably PET.

The coating may be any coating method that does not damage the substrate.

Next, the anode and the Composite solid electrolyte layer Stacked Laminates  To manufacture (step c).

Preferably, the positive electrode and the composite solid electrolyte layer may be stacked, and the laminate may be manufactured by pressing at a pressure of 0.1 to 1.0 MPa in the temperature range T of Equation 1 below.

[Equation 1]

Tm-35 ℃ ≤T≤ Tm + 55 ℃

In Formula 1, when T _m1 <T _m2 , Tm = T _m1 , T _m1 > T _m2 , Tm = T _m2 , and when T _m1 = T _m2 , Tm = T _m1 ,

Here, T _m1 is the melting temperature of the first polymer, T _m2 is the melting temperature of the second polymer.

The pressurization may be preferably performed at a pressure of 0.1 to 1.0 MPa, more preferably 0.1 to 0.8 MPa.

The pressurization may be performed for 1 minute to 5 minutes, preferably 1 minute to 2 minutes.

The first binder comprises polyethylene oxide and polyvinylidene fluoride, the second binder comprises polyethylene oxide and polyvinylidene fluoride, Step (c) may be a step of stacking the positive electrode and the composite solid electrolyte layer and pressurizing at a temperature range of 30 ° C. to 120 ° C., preferably 40 ° C. to 60 ° C., to prepare a laminate.

The laminate is pressurized at a melting temperature or higher of the first polymer and the second polymer, so that the first binder and the second binder included in the composite solid electrolyte layer are melted and then bonded to each other to bond the anode and the composite solid electrolyte. The interfacial properties between the layers are improved, thereby reducing the internal resistance of the battery.

Finally, the above Laminate Composite Solid Electrolyte Layer  A negative electrode containing a lithium metal is disposed thereon to prepare an all-solid lithium secondary battery (step d).

After step (d) may optionally further comprise the step of pressing the resultant of step (d) at a pressure of 0.1 to 1.0 MPa in the temperature range (T) of the formula (1).

By the pressurization, the first binder included in the positive electrode and the second binder included in the composite solid electrolyte layer may be melted and then bonded, and the effect thereof is as described above in step (c).

Another method of manufacturing an all-solid-state lithium secondary battery includes (a ') preparing a cathode including a cathode active material, a first lithium lanthanum zirconium oxide (LLZO), a first binder, and a conductive material; (b ') preparing a composite solid electrolyte layer comprising a second lithium lanthanum zirconium oxide (LLZO) and a second binder; (c ′) preparing a laminate by disposing a composite solid electrolyte layer on the cathode, a composite solid electrolyte layer on the cathode, and a cathode including lithium metal on the composite solid electrolyte layer; And (d ') manufacturing the all-solid-state lithium secondary battery by pressurizing the laminate in the following temperature range (T).

By the pressurization, the first binder included in the positive electrode and the second binder included in the composite solid electrolyte layer may be melted and then bonded, and the effect thereof is as described above in step (c).

 EXAMPLE

Hereinafter, a preferred embodiment of the present invention will be described. However, this is for illustrative purposes and the scope of the present invention is not limited thereby.

Production Example  1: aluminum Doped  Preparation of Lithium Lanthanum Zirconium Oxide (Al-LLZO)

Lanthanum nitrate (La (NO ₃ ) ₃ · 6H ₂ O) and zirconium nitrate (ZrO (NO ₃ ) ₂ · 2H ₂ O) so that the molar ratio of La: Zr: Al, the starting material, 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 starting material concentration of 1 mole.

The starting solution of the Kuet Taylor vortex reactor was added with an appropriate amount of the starting material solution, 0.6 mol of ammonia water, and an aqueous sodium hydroxide solution as a complexing agent to obtain a mixed solution having a pH of 11, and a reaction temperature of 25 ° C., a reaction time of 4 hr, The stirring speed of the stirring rod was coprecipitated at 1,300 rpm to discharge the precursor slurry in the form of a liquid slurry to the discharge part. In the coprecipitation reaction of the Kuet Taylor vortex reactor, the Taylor number was set to 640 or more.

The precursor slurry was washed with purified water and then dried overnight. The dried precursor was ground in a ball mill, then excess LiOH.H ₂ O was added and mixed in a ball mill to prepare a mixture. The LiOH.H ₂ O content of the mixture was added in an excessive amount of 3 wt% to 103 parts by weight based on 100 parts by weight of Li in the solid electrolyte in which the content of Li in LiOH.H ₂ O was produced. The mixture was calcined at 900 ° C. for 2 hours and then ground to produce lithium lanthanum zirconium oxide (Al-LLZO) doped with aluminum.

Production Example  2: gallium Doped  Lithium lanthanum zirconium oxide ( Galium  doped lithium lanthanum zirconium oxide, Ga-LLZO)

Starting materials lanthanum nitrate (La (NO ₃ ) ₃ · 6H ₂ O), zirconium nitrate (ZrO (NO ₃ ) ₂ · 2H ₂ O) and gallium nitrate (Ga (NO ₃ ) ₃ · 9H ₂ O) A starting material solution was prepared by dissolving in distilled water such that the molar ratio of the element La: Zr: Ga is 3: 2: 0.25.

The starting material solution, ammonia water 0.6 mol, and sodium hydroxide aqueous solution is added as an appropriate amount to the mixed solution adjusted to pH 11, the reaction temperature is 25 ℃, the reaction time is 24hr, co-precipitation while stirring to form a precursor in the form of a liquid slurry A slurry was obtained.

The precursor slurry was washed with purified water and then dried for 24 hours. The dried precursor was ground in a ball mill, where the LiOH.H ₂ O content of the mixture was 110 parts by weight (10 wt% excess) based on 100 parts by weight of Li in the solid electrolyte in which the content of Li in LiOH.H ₂ O was produced. ). The mixture was calcined at 900 ° C. for 2 hours and then milled to produce gallium doped lithium lanthanum zirconium oxide (Ga-LLZO).

Preparation Example 3 Preparation of Positive Electrode

100 parts by weight of the positive electrode active material NMC (lithium nickel cobalt manganese oxide), 9.1 parts by weight of lithium lanthanum zirconium oxide (Al-LLZO) doped with aluminum prepared according to Preparation Example 1, 18.2 parts by weight of a conductive material Super-P, and 54.5 parts by weight of 1 binder (PEO + PVDF) were mixed to prepare a mixture of NMC (lithium nickel cobalt manganese oxide), aluminum-doped lithium lanthanum zirconium oxide (Al-LLZO), Super-P, and binder (PEO + PVDF). .

In this case, the binder (PEO + PVDF) is 900 parts by weight of polyethylene oxide (PEO), 100 parts by weight of polyvinylidene fluoride (PVDF), 145 parts by weight of lithium perchlorate (LiClO ₄ ), and acrylonitrile. (acetonitrile, ACN) 7,955 parts by weight to prepare a binder solution.

Specifically, first, based on 100 parts by weight of NMC (lithium nickel cobalt manganese oxide), 18 parts by weight of Super-p and 9 parts by weight of lithium-lanthanum zirconium oxide (Al-LLZO) doped with aluminum prepared according to Preparation Example 1 and a binder ( PEO + PVDF) was mixed at 54.5 parts by weight, and stirred at 2,000 rpm for about 5 minutes in a Thinky mixer to prepare a slurry. Next, the slurry was cast on aluminum foil and dried in vacuo to prepare a positive electrode. At this time, the loading amount of the electrode was prepared to about 4 mg / cm ² .

Preparation Example 4 Preparation of Positive Electrode

A positive electrode was manufactured in the same manner as in Preparation Example 3, except that the binder (PEO) was used instead of the binder (PEO + PVDF) in Preparation Example 3.

Preparation Example 5 Preparation of Composite Solid Electrolyte Layer

Gallium-doped lithium lanthanum prepared according to Preparation Example 2 by mixing 42.9 parts by weight of a binder (PEO + PVDF) with respect to 100 parts by weight of gallium-doped lithium lanthanum zirconium oxide (Ga-LLZO) prepared according to Preparation Example 2. A mixture of zirconium oxide (Ga-LLZO) and binder (PEO + PVDF) was prepared and stirred at 2,000 rpm for 5 minutes using a Thinky mixer.

In this case, the binder (PEO + PVDF) is 2,800 parts by weight of polyethylene oxide (PEO), 451 parts by weight of lithium perchlorate (LiClO ₄ ), and acrylonitrile, based on 100 parts by weight of polyvinylidene fluoride (PVDF). (acetonitrile, ACN) 11,200 parts by weight to prepare a binder solution.

ACN was mixed into the mixture and stirred with a syncy mixer to adjust to an appropriate viscosity. Next, 2 mm zircon balls were added and stirred for 5 minutes at 2,000 rpm with a syncy mixer to prepare a slurry. The slurry was cast on a polyethylene terephthalate (PET) film, dried at room temperature, and adjusted to have a thickness of 85 μm to prepare a composite solid electrolyte layer.

Preparation Example 6 Preparation of Composite Solid Electrolyte Layer

Instead of using gallium-doped lithium lanthanum zirconium oxide (Ga-LLZO) prepared in Preparation Example 5 in Preparation Example 5, aluminum-doped lithium lanthanum zirconium oxide (Al-LLZO) prepared in Preparation Example 1 was used. Composite, using a binder (PEO) instead of using a binder (PEO + PVDF), and to a thickness of 150 ㎛ instead of using a thickness of 85 ㎛ A solid electrolyte layer was prepared.

Preparation Example 7 Preparation of Patterned Lithium Metal Layer Cathode

2 is an enlarged photograph of the surface of a negative electrode including a patterned lithium metal 10 times, b is 100 times, a is an enlarged image of the entire surface of the tool, b is a portion enlarged.

Referring to FIGS. 2 and 3, a tool having a pattern spacing of about 400 μm and a pattern depth of about 200 μm was produced. The tool was fabricated by using SUS304 material, inputting a pattern into the program, performing primary processing by electric discharge processing, and applying heat treatment at 280 ° C. after Teflon coating on the metal surface to facilitate pattern forming of lithium metal.

A negative electrode including a lithium metal having a plurality of patterns formed on a surface of a lithium metal sheet having a thickness of 0.2 t (200 μm) was manufactured by applying a pressure of 0.3 MPa at room temperature using the tool. At this time, the depth of the pattern prepared by the above method is used to form a groove depth of about 50 ~ 100 ㎛ at a constant pressure on the upper 0.2t lithium metal using a tool of about 200㎛.

[Manufacture of All-Solid Lithium Secondary Battery]

Example 1 Fabrication of All Solid Lithium Secondary Battery

The positive electrode prepared according to Preparation Example 3 and the composite solid electrolyte layer prepared according to Preparation Example 5 were each punched to Ø16 size and then laminated. Next, it pressed by heating at about 40-60 degreeC, and manufactured the laminated body.

The patterned lithium metal layer was placed on the laminate to manufacture an all-solid lithium secondary battery using a coin cell of a 2032 standard.

Comparative Example 1: Fabrication of All-Solid Lithium Secondary Battery

Instead of using the positive electrode prepared according to Preparation Example 3 and the composite solid electrolyte layer prepared according to Preparation Example 5, except that the positive electrode prepared according to Preparation Example 4 and the composite solid electrolyte layer prepared according to Preparation Example 6 were used. Then, an all-solid lithium secondary battery was manufactured in the same manner as in Example 1.

[Test Example]

Test Example 1: Charging and Discharging Characteristics of an All-Solid Lithium Secondary Battery

4A is a graph showing charge and discharge characteristics of an all-solid-state lithium secondary battery manufactured according to Example 1 and Comparative Example 1 in one cycle and FIG. 4B. It was carried out in the 3.0 ~ 4.2V section with 0.1C charge-discharge current.

4A and 4B, it can be seen that the initial capacity when charging at 1 and 6 cycles up to 4.2V is about 130 mAh / g, showing almost similar characteristics.

Test Example 2: Cycle Characteristics of Conductor Lithium Secondary Battery

5 is a graph showing the cycle characteristics of the all-solid-state lithium secondary battery prepared according to Example 1 and Comparative Example 1. It was carried out in the 3.0 ~ 4.2V section with 0.1C charge-discharge current.

Referring to Figure 5, the discharge capacity retention rate according to the charge and discharge cycle (about 70 times) of the all-solid lithium secondary battery prepared according to Example 1 and the all-solid lithium secondary battery prepared according to Comparative Example 1 were 74%, As much as 54%, about 20% difference occurs.

In addition, polyethylene oxide (PEO) is generally excellent in ion conductivity, but when used as a binder of a solid electrolyte layer due to its weak mechanical properties (Comparative Example 1) At least 150 ㎛ thickness was required, but a small amount of polyvinylidene fluoride ( PVDF) application (Example 1) made it possible to reduce the thickness by about 50%.

Therefore, the all-solid-state lithium secondary battery prepared according to Example 1, in which PVDF was properly blended with PEO and applied as a binder, showed an initial discharge capacity similar to that of the all-solid-state lithium secondary battery prepared according to Comparative Example 1, but the cycle It was found that the reduction in capacity was small, resulting in excellent discharge capacity and cycle characteristics.

The scope of the present invention is shown by the following claims rather than the above description, and all changes or modifications derived from the meaning and scope of the claims and their equivalents should be construed as being included in the scope of the present invention. do.

Claims (20)

A cathode including a cathode active material, a first lithium lanthanum zirconium oxide (LLZO), a first binder including a first polymer and a second polymer, and a conductive material;
A negative electrode comprising lithium metal; And
A composite solid electrolyte layer comprising a second lithium lanthanum zirconium oxide (LLZO) and a second binder including a first polymer and a second polymer between the anode and the cathode;
All-solid lithium secondary battery containing. The method of claim 1,
The first polymer and the second polymer are each independently polyethylene oxide, polyethylene glycol, polyacrylonitrile, polyvinyl chloride, polymethylmethacrylate, polypropylene At least one selected from oxide (polypropyleneoxide), polydimethylsiloxane (polydimethylsiloxane), polyvinylidene fluoride (polyvinylidene fluoride), polyvinylidene carbonate (polyvinylidene carbonate) and polyvinyl pyrrolidinone All-solid-state lithium secondary battery. The method of claim 2,
The first polymer comprises a polyethylene oxide (Polyethylene oxide), the second polymer comprises a polyvinylidene fluoride (Polyvinylidene fluoride), all-solid lithium secondary battery. The method of claim 3,
The first binder comprises 500 to 1,400 parts by weight of the polyethylene oxide, based on 100 parts by weight of the polyvinylidene fluoride,
The second binder is based on 100 parts by weight of the polyvinylidene fluoride (Polyvinylidene fluoride), the solid-state lithium secondary battery, characterized in that containing 2,000 to 3,600 parts by weight of polyethylene oxide. The method of claim 1,
The first and second lithium lanthanum zirconium oxides (LLZO) are each independently lithium or gallium doped lithium lanthanum zirconium oxide (LLZO),
The lithium lanthanum zirconium oxide (LLZO) doped with aluminum is represented by the following Chemical Formula 1,
The gallium doped lithium lanthanum zirconium oxide (LLZO) is an all-solid lithium secondary battery, characterized in that represented by the formula (2).
[Formula 1]
Li _x La _y Zr _z Al _w O ₁₂ (5≤x≤9, 2≤y≤4, 1≤z≤3, 0 <w≤1)
[Formula 2]
Li _x La _y Zr _z Ga _m O ₁₂ (5≤x≤9, 2≤y≤4, 1≤z≤3, 0 <m≤4) The method of claim 5,
The aluminum or gallium-doped lithium lanthanum zirconium oxide (LLZO) is an all-solid lithium secondary battery, characterized in that it comprises at least one structure selected from cubic (cubic) structure and tetragonal (tetragonal) structure. The method of claim 6,
The lithium lanthanum zirconium oxide (LLZO) doped with aluminum or gallium has a single-phase cubic structure. The method of claim 1,
The positive electrode includes 1 to 30 parts by weight of the first lithium lanthanum zirconium oxide (LLZO), 10 to 90 parts by weight of the first binder, and 10 to 30 parts by weight of the conductive material, based on 100 parts by weight of the positive electrode active material,
The composite solid electrolyte layer comprises 10 to 90 parts by weight of the second binder relative to 100 parts by weight of the second lithium lanthanum zirconium oxide (LLZO). The method of claim 1,
The cathode active material is an all-solid lithium secondary battery, characterized in that the three-component lithium metal oxide (NMC) of Ni-Co-Mn represented by the formula (3).
[Formula 3]
LiNi _p Co _q Mn _r O ₂ (0 <p <0.9, 0 <q <0.5, 0 <r <0.5, p + q + r = 1) The method of claim 1,
And the conductive material comprises at least one selected from carbon black, acetylene black, and ketjen black. The method of claim 1, wherein the negative electrode comprising a lithium metal
(a) a substrate comprising lithium; And
(B) an intaglio pattern comprising a plurality of holes formed intaglio on one surface of the substrate; all-solid-state lithium secondary battery comprising a. The method of claim 11,
The shape of the intaglio pattern is an all-solid lithium secondary battery, characterized in that it comprises one or more of the circle, oval, polygon, rhombus and linear. The method of claim 11,
All-in-one lithium secondary battery, characterized in that the depth of the intaglio pattern is 50 to 500 ㎛. The method of claim 11,
All-in-one lithium secondary battery, characterized in that the interval between the intaglio pattern and the other intaglio pattern is 200 to 600 ㎛. The method of claim 11,
An all-solid lithium secondary battery, characterized in that the thickness of the substrate is 20 to 1,000㎛. The method of claim 1,
The all-solid-state lithium secondary battery
Ni-Co-Mn-based lithium metal oxide (NMC), aluminum doped lithium lanthanum zirconium oxide (LLZO), polyethylene oxide (Polyethylene oxide) and polyvinylidene fluoride (Polyvinylidene fluoride) and carbon black Anode comprising a;
A negative electrode comprising lithium metal; And
A composite solid electrolyte layer comprising a binder including lithium lanthanum zirconium oxide (LLZO), polyethylene oxide, and polyvinylidene fluoride doped with gallium between the anode and the cathode;
All-solid-state lithium secondary battery comprising a. (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;
(b) preparing a composite solid electrolyte layer comprising a second lithium lanthanum zirconium oxide (LLZO) and a second binder;
(c) stacking the positive electrode and the composite solid electrolyte layer to manufacture a laminate; And
(d) disposing a negative electrode including lithium metal on the composite solid electrolyte layer of the laminate;
Method for producing an all-solid lithium secondary battery comprising. 18. The method of claim 17, wherein the manufacturing method of the all-solid lithium secondary battery
Step (c) is a step of stacking the positive electrode and the composite solid electrolyte layer, and in the temperature range (T) of the following formula 1, the step of producing a laminate by pressing at a pressure of 0.1 to 1.0 MPa Method of manufacturing a lithium secondary battery.
[Equation 1]
Tm-35 ℃ ≤T≤ Tm + 55 ℃
In Formula 1, when T _m1 <T _m2 , Tm = T _m1 , T _m1 > T _m2 , Tm = T _m2 , and when T _m1 = T _m2 , Tm = T _m1 ,
Here, T _m1 is the melting temperature of the first polymer, T _m2 is the melting temperature of the second polymer. The method of claim 17,
The first binder comprises polyethylene oxide and polyvinylidene fluoride,
The second binder comprises polyethylene oxide and polyvinylidene fluoride,
Step (c) is a step of stacking the positive electrode and the composite solid electrolyte layer and pressurized at a temperature of 30 ℃ to 120 ℃ to produce a laminate, characterized in that the manufacturing method of the all-solid lithium secondary battery. (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;
(b ') preparing a composite solid electrolyte layer comprising a second lithium lanthanum zirconium oxide (LLZO) and a second binder;
(c ′) preparing a laminate by disposing a composite solid electrolyte layer on the cathode, a composite solid electrolyte layer on the cathode, and a cathode including lithium metal on the composite solid electrolyte layer; And
(d ') manufacturing the all-solid-state lithium secondary battery by pressing the laminate in a temperature range T of the following Equation 1;
Method for producing an all-solid lithium secondary battery comprising.
[Equation 1]
Tm-35 ℃ ≤T≤ T _m + 55 ℃
In Formula 1, when T _m1 <T _m2 , Tm = T _m1 , T _m1 > T _m2 , Tm = T _m2 , and T _m1 = T _m2 , Tm = T _m1 ,
Here, T _m1 is the melting temperature of the first polymer, T _m2 is the melting temperature of the second polymer.

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