KR101745930B1 - Method for preparing solid electrolyte material for all-solid-state lithium secondary battery using complex process and method for manufacturing all-solid-state lithium secondary battery comprising the same - Google Patents

Abstract

(A) preparing a solid electrolyte precursor by coprecipitation reaction of a metal nitrate including lanthanum nitrate and zirconium nitrate, a complexing agent, and a mixed aqueous solution containing a pH controlling agent; (b) washing and drying the solid electrolyte precursor; (c) mixing the dried solid electrolyte precursor, any one selected from tantalum (Ta) oxide and niobium (Nb) oxide, and a lithium source to prepare a mixture; And (d) calcining the mixture to prepare a Ta or Nb doped lithium lanthanum zirconium oxide (LLZO) solid electrolyte (Ta / Nb doped LLZO) doped with either tantalum or niobium A method for producing a solid electrolyte comprising the steps of: Thus, the ion conductivity can be improved by doping a different element such as niobium or tantalum, controlling the composition of the precursor and the lithium source to control the sintering property, and controlling the crystal structure. In addition, by using the above-described method for producing a solid electrolyte in a method for manufacturing a pre-solid lithium secondary battery, the efficiency of the battery can be improved.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a method for manufacturing a solid electrolyte for a full-solid lithium secondary battery by a composite process, and a method for manufacturing a pre- -SOLID-STATE LITHIUM SECONDARY BATTERY COMPRISING THE SAME}

The present invention relates to a process for preparing a solid electrolyte for a pre-solid lithium secondary battery by a combined process and a process for producing the pre-solid lithium rechargeable battery comprising the same, more particularly, to a process for preparing a pre- And controlling the crystal structure to control the ionic conductivity of the solid electrolyte.

Lithium secondary batteries have large electrochemical capacities, high operating potentials, and excellent charge / discharge cycle characteristics, so demand for portable information terminals, portable electronic devices, small household power storage devices, motorcycles, electric vehicles and hybrid electric vehicles . With the spread of such applications, improvement of safety and high performance of lithium secondary batteries are required.

Conventional lithium secondary batteries use a liquid electrolyte and are readily ignited when exposed to water in the air, thus posing a problem of stability. This stability problem is becoming more and more important as electric cars become more visible.

Recently, all solid-state secondary batteries using a solid electrolyte made of an inorganic material, which is a nonflammable material, have been actively studied for the purpose of improving safety. BACKGROUND ART Solid-state secondary batteries are attracting attention as a next-generation secondary battery in terms of safety, high energy density, high output, long life, simplification of manufacturing process, enlargement / compactification of batteries, and low cost.

The former solid secondary battery is composed of the anode / solid electrolyte layer / cathode. Of these, the solid electrolyte of the solid electrolyte layer is required to have high ion conductivity and low electron conductivity. Also, a solid electrolyte is included in the constituent elements of the anode and cathode layers, which are electrode layers. A mixed conductive material having both ionic conductivity and electron conductivity is advantageous for the solid electrolyte used in the electrode layer.

The solid electrolyte satisfying the requirements of the solid electrolyte layer of the all solid secondary battery includes a sulfide system, an oxide system, and the like. The sulfide-based solid electrolyte has a problem that a resistance component is generated by an interface reaction with a cathode active material or a negative electrode active material, a hygroscopic property is strong, and a hydrogen sulfide (H ₂ S) gas is generated.

Japanese Patent Publication No. 4,779,988 discloses a pre-solid lithium secondary battery having a laminate structure of a positive electrode / solid electrolyte layer / negative electrode and comprising a sulfide-based solid electrolyte layer.

And oxide-based solid electrolyte has _{LLTO (Li 3x La 2 / (} 3x) TiO 3) system, and so on _{LLZO (Li 7 La 3 Zr 2} O 12) system is well known, the grain boundary resistance is relatively compared with the system of which LLTO LLZO, which is known to have high but dislocation-free properties, is attracting attention as a promising material.

The LLZO has a cubic and tetragonal structure, and has a higher ionic conductivity when it has a cubic structure than a tetragonal structure. In order to manufacture a cubic LLZO solid electrolyte having a high ionic conductivity, sintering must be performed at a high temperature of 1,200 ° C or more, so that it is difficult to manufacture a cubic structure having a high ionic conductivity. In addition, There was a problem that volatilization occurred.

Therefore, there is a difference in the ion conductivity depending on the crystal structure, so it is necessary to develop a technique for manufacturing a LLZO solid electrolyte having high ion conductivity by controlling the sintering property and the like.

An object of the present invention is to solve the above problems and to provide a niobium or tantalum niobium powder which is doped with a hetero element such as niobium or tantalum and controls a sintering property by controlling a composition of a precursor and a lithium source, And a method of manufacturing a LLZO solid electrolyte doped with tantalum.

Another object of the present invention is to improve the efficiency of a battery by using the above-described method for producing a solid electrolyte in a method for manufacturing a pre-solid lithium secondary battery.

According to one aspect of the present invention, there is provided a method for preparing a solid electrolyte precursor, comprising: (a) preparing a solid electrolyte precursor by coprecipitation reaction of a metal nitrate salt containing lanthanum nitrate and zirconium nitrate, a complexing agent and a pH- (b) washing and drying the solid electrolyte precursor; (c) mixing the dried solid electrolyte precursor, any one selected from tantalum (Ta) oxide and niobium (Nb) oxide, and a lithium source to prepare a mixture; And (d) calcining the mixture to prepare Ta or Nb doped lithium lanthanum zirconium oxide (LLZO) solid electrolyte (Ta / Nb doped LLZO) doped with any one of tantalum and niobium. ; Wherein the solid electrolyte is a solid electrolyte.

The lithium tantalum zirconium oxide (LLZO) solid electrolyte (Ta / Nb doped LLZO) doped with any one of tantalum and niobium may be represented by the following chemical formula 1.

[Chemical Formula 1]

_{Li x La y Zr z A a} O 12

Where A is Ta or Nb,

5? X? 9, 2? Y? 4, 1? Z? 3, 0 <a?

The step (a) may be a step of preparing a solid electrolyte precursor by coprecipitation reaction with a mixed aqueous solution in which a metal nitrate aqueous solution containing lanthanum nitrate and zirconium nitrate is mixed with an aqueous complexing agent solution and a pH adjusting agent aqueous solution.

In step (a), the coprecipitation reaction may be performed in the Taylor vortex state.

Step (a) can be carried out in a Quattro Taylor vortex reactor.

The Taylor vortex state Taylor number may be 550 to 1,500.

The Taylor number of the Taylor vortex state may be 630 to 800.

The complexing agent may be ammonia water or sodium hydroxide.

The lanthanum nitrate may be La (NO ₃ ) ₃ .6H ₂ O, and the zirconium nitrate may be ZrO (NO ₃ ) ₂ .2H ₂ O.

The molar ratio of La: Zr contained in the metal nitrate aqueous solution may be a: b, a may be 2 to 4, and b may be 1 to 3.

In step (b), the precursor may be dried and then pulverized by a ball-mill process to produce a precursor in powder form.

The lithium content of the lithium source of step (c) is 100 to 100 parts by weight of the lithium content of the solid electrolyte which is the product of step (d) To 115 parts by weight.

The mixing of step (c) may be performed by a ball-mill process so that mixing and grinding are performed together.

The molar ratio of La: Zr: (Ta or Nb) contained in the mixture may be a: b: c, a may be 2 to 4, b may be 1 to 3, and c may be 0.1 to 0.5.

The molar ratio of La: Zr: (Ta or Nb) contained in the mixture may be a: b: c, a may be 2 to 4, b may be 1 to 3, and c may be 0.20 to 0.35.

Calcination of step (d) may be carried out at a temperature of 650 to 950 占 폚.

After step (d), (e) preparing a solid electrolyte sintered body by sintering a LLZO solid electrolyte doped with any one selected from the group consisting of tantalum and niobium; . &Lt; / RTI &gt;

The sintering may be performed at a temperature of 1,000 to 1,300 ° C.

The solid electrolyte may be a single-phase cubic structure.

According to another aspect of the present invention, there is provided a method of manufacturing a pre-solid lithium secondary battery including the method of manufacturing the solid electrolyte.

The LLZO solid electrolyte of the present invention can improve the ion conductivity by doping a different element such as niobium or tantalum, controlling the composition of the precursor and the lithium source to control the sintering property, and controlling the crystal structure.

In addition, by using the above-described method for producing a solid electrolyte in a method for manufacturing a pre-solid lithium secondary battery, the efficiency of the battery can be improved.

1 is a flowchart sequentially showing a method for producing an LLZO solid electrolyte of the present invention.
Figure 2 is a schematic diagram of a Kuett Taylor vortex reactor.
3 shows an XRD analysis of the LLZO solid electrolytes prepared according to Examples 1 to 3. FIG.
4 shows the XRD analysis of the LLZO solid electrolytes prepared according to Comparative Examples 4 to 6. FIG.
5 shows the XRD analysis of the LLZO solid electrolytes prepared according to Examples 7 and 8. Fig.
6 shows an SEM image analysis of the LLZO solid electrolyte prepared according to Example 7, Example 8 and Comparative Example 1. Fig.
7 shows the impedance analysis of the LLZO solid electrolyte prepared according to Examples 7, 8 and Comparative Example 1. Fig.

The invention is capable of various modifications and may have various embodiments, and particular embodiments are exemplified and will be described in detail in the detailed description. It is to be understood, however, that the invention is not to be limited to the specific embodiments, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

Also, when an element is referred to as being "formed" or "laminated" on another element, it may be directly attached or laminated to the front surface or one surface of the other element, It will be appreciated that other components may be present in the &lt; / RTI &gt;

The singular expressions include plural expressions unless the context clearly dictates otherwise. In the present application, the terms "comprises" or "having" and the like are used to specify that there is a feature, a number, a step, an operation, an element, a component or a combination thereof described in the specification, But do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, or combinations thereof.

1 is a flowchart sequentially showing a method for producing a hetero-element-doped solid electrolyte of the present invention. Hereinafter, a method for manufacturing a hetero-element-doped solid electrolyte of the present invention will be described with reference to FIG.

First, a metal nitrate including lanthanum nitrate and zirconium nitrate, Complexing agent , a pH control agent mixed solution is subjected to a coprecipitation reaction Solid electrolyte  A precursor is prepared (step a).

The step (a) may be a step of preparing a solid electrolyte precursor by coprecipitation reaction with a mixed aqueous solution in which a metal nitrate aqueous solution containing lanthanum nitrate and zirconium nitrate is mixed with an aqueous complexing agent solution and a pH adjusting agent aqueous solution.

The complexing agent may be ammonia water, sodium hydroxide or the like, preferably ammonia water.

The pH adjusting agent may be sodium hydroxide, ammonia or the like, preferably sodium hydroxide.

The pH adjusting agent may adjust the pH of the mixed solution to 10 to 12, preferably 10.5 to 11.5, and more preferably 10.8 to 11.2.

The lanthanum nitrate may be La (NO ₃ ) ₃ .6H ₂ O, and the zirconium nitrate may be ZrO (NO ₃ ) ₂ .2H ₂ O.

The molar ratio of La: Zr contained in the metal nitrate solution may be a: b, a may be 2 to 4, and b may be 1 to 3.

The coprecipitation reaction may be performed in a Taylor vortex state, preferably in a Couette-Taylor vortices reaction vessel.

The Taylor number in the Taylor vortex state can be from 550 to 1,500, preferably from 630 to 800, more preferably from 630 to 700.

Figure 2 is a schematic diagram of a Taylor vortex reactor.

Referring to FIG. 2, a quattroiler vortex reactor capable of performing a quattroiler vortex reaction comprises an external stationary cylinder and an internal rotating cylinder rotating therein. The inner rotating cylinder has a rotating axis coinciding with the longitudinal axis of the outer fixed cylinder. The inner rotating cylinder and the outer fixed cylinder are spaced apart from each other at a predetermined interval, and a fluid passage through which reaction liquid flows is formed between the inner rotating cylinder and the outer fixed cylinder. When the inner rotating cylinder is rotated, the fluid located in the inner rotating cylinder side in the fluid passage tends to flow out in the direction of the external fixed cylinder due to the centrifugal force. As a result, the fluid becomes unstable and is regularly rotated along the rotating axis, A vortex of the pair arrangement is formed. This is vortexed by Taylor or Kuett Taylor. Quettaire vortices can produce precursors more advantageously than conventional coprecipitation reactors by promoting coprecipitation reactions.

At this time, the Kuet-Taylor reactor can use Taylor number (Ta), a dimensionless variable, to distinguish the characteristics of the fluid flow and to define the corresponding area for each characteristic. The Taylor number (Ta) is expressed as a function of the Reynolds number (Reynolds number, Re) and is expressed by Equation 1 as follows.

[Formula 1]

In Equation 1, w denotes the angular velocity of the inner cylinder, r _i denotes the radius of the inner cylinder, d denotes the parallel distance between the two cylinders, and v denotes the kinematic viscosity. In general, the value of Ta is adjusted using RPM (RPM) expressed in terms of the angular speed of the inner cylinder. Generally, when a fluid flows between two plates, shear stress causes a quet flow, and similarly, between two cylinders, a low RPM causes a quet flow. However, if the RPM of the inner cylinder exceeds a certain threshold value, the quet flow becomes a new steady state Kuet-Taylor flow and Taylor vortex that can not be seen in the quat flow. The Taylor vortex consists of a pair of vortexes and is positioned in the toroidal direction with the feature of line symmetry. Therefore, counterclockwise rotating vortices exist on both sides of the vortex rotating in the clockwise direction, and the vortices affect each other. Increasing the RPM of a certain size in the Kuett-Taylor stream will transform the Taylor vortex into a new flow due to the instability of the Taylor vortex, which will have an azimuthal wavenumber. This flow is called Wavy vortex flow, and the mixing effect at this time may be higher than the Kuett-Taylor flow.

Next, the solid electrolyte precursor is washed and dried (step b).

The solid electrolyte precursor may be dried and then pulverized by a ball-mill process to produce a precursor in powder form.

The powder-form precursor may be molded to produce a precursor in the form of a pellet.

Next, the dried Solid electrolyte  Precursor, Tantalum ( Ta ) Oxide and niobium (Nb) oxide, and a lithium source are mixed to prepare a mixture (step c).

The mixing is carried out with a ball-mill so that mixing and grinding can be carried out together.

The lithium content of the lithium source is 100 (parts by weight) based on 100 parts by weight of the lithium content of the solid electrolyte which is the product of step (d) To 115 parts by weight, preferably from 101 to 112 parts by weight, and more preferably from 103 to 111 parts by weight.

Wherein the molar ratio of La: Zr: (Ta or Nb) contained in the mixture is a: b: c, a is 2 to 4, b is 1 to 3, c is 0.1 to 0.5, 4, b may be 1 to 3, and c may be 0.20 to 0.35.

(Ta or Nb) means any one selected from Ta and Nb.

Finally, Calcination Tantalum  And niobium Doped ( Ta  or Nb  doped) lithium lanthanum zirconium oxide (&quot; LLZO ) The solid electrolyte (Ta / Nb doped LLZO)  (Step d).

The calcination may be carried out at a temperature of 650 to 950 占 폚, preferably 700 to 950 占 폚, more preferably 700 to 900 占 폚.

The calcination can be carried out for 1 to 10 hours, preferably for 1 to 5 hours, more preferably for 1 to 3 hours. However, the calcination time is not necessarily limited to this, and may be varied depending on the calcination temperature.

The lithium tantalum zirconium oxide (LLZO) solid electrolyte (Ta / Nb doped LLZO) doped with any one of tantalum and niobium may be represented by the following chemical formula 1.

[Chemical Formula 1]

_{Li x La y Zr z A a} O 12

Where A is Ta or Nb,

5? X? 9, 2? Y? 4, 1? Z? 3, 0 <a?

After step (d), the following steps may be additionally performed.

remind Tantalum  And niobium, Doped LLZO Solid electrolyte  And sintered to prepare a solid electrolyte sintered body (step e).

The sintering may be carried out at a temperature of 1,000 to 1,300 ° C, preferably 1,050 to 1,250 ° C, more preferably 1,080 to 1,220 ° C.

The sintering may be performed for 3 to 20 hours, preferably for 2 to 15 hours, more preferably for 3 to 10 hours. However, the sintering time is not necessarily limited to this, and may vary depending on the sintering temperature.

The solid electrolyte may be a single-phase cubic structure.

The solid electrolyte has a cubic structure in terms of ion conductivity, and in the case of a tetragonal structure, ion conductivity can be lowered.

The present invention also provides a method for producing a pre-solid lithium secondary battery including the above-described method for producing a solid electrolyte.

[Example]

Hereinafter, preferred embodiments of the present invention will be described. However, this is for illustrative purposes only, and thus the scope of the present invention is not limited thereto.

Example  1: niobium Doped LLZO Solid electrolyte  Produce

Lanthanum nitrate (La (NO ₃ ) ₃ .6H ₂ O) and zirconium nitrate (ZrO (NO ₃ ) ₂ .2H ₂ O) were weighed so that the molar ratio of La: Zr was 3: 2 and then dissolved in distilled water A metal nitrate solution having a molar concentration of 1 mol was prepared.

Referring to Figure 2, a solid electrolyte was prepared using a Quattro Taylor vortex reactor. The Kuett Taylor vortex reactor includes a solution injecting section 1, a temperature adjusting solution discharging section 2, a temperature adjusting solution injecting section 3, a reaction solution drain section 4, a reactant (slurry type) A stirring rod 6, a solution reaction part 7, and a reaction solution temperature adjusting part 8. A proper amount of 0.6 mol of ammonia water and an aqueous solution of sodium hydroxide was added to the metal nitrate solution and complexing agent through the injection part 1 of the quattroiler vortex reactor to adjust the pH to 11, The time was 4 hr, and the stirring speed of the stirring rod was 1300 rpm, and the precursor in the form of a liquid slurry was discharged to the discharge portion 5. The Taylor number in the coprecipitation reaction of the Kuett Taylor vortex reactor was 640 or more.

The prepared precursor was washed with purified water, dried, and then pulverized with a ball-mill. Here, niobium oxide (Nb ₂ O ₅ ) and lithium hydroxide hydrate (LiOH · H ₂ O) were mixed in a ball-mill to prepare a mixture to prepare pellets. At this time, niobium oxide was weighed so that 0.25 mole of niobium (Nb) was added to 3 moles of lanthanum (La) of the precursor. In addition, the lithium hydroxide hydrate content of the mixture was such that the Li content in the lithium hydroxide hydrate was 110 wt% (10 wt% excess) relative to 100 wt% Li in the final solid electrolyte. The prepared pellets were calcined at a temperature of 900 DEG C for 2 hours and then pulverized to prepare a powdery niobium-doped LLZO solid electrolyte.

Example 2: Preparation of niobium-doped LLZO solid electrolyte

Calcination LLZO solid electrolyte was prepared in the same manner as in Example 1, except that the reaction was carried out at a temperature of 800 ° C instead of 900 ° C.

Example 3: Manufacture of niobium-doped LLZO solid electrolyte

Calcination LLZO solid electrolyte was prepared in the same manner as in Example 1, except that the reaction was carried out at a temperature of 700 캜 instead of 900.

Example 4: Preparation of tantalum-doped LLZO solid electrolyte

Except that tantalum oxide (Ta ₂ O ₅ ) was used instead of niobium oxide (Nb ₂ O ₅ ), and tantalum was added in a ratio of 0.3 mol in place of 0.25 molar part of niobium, tantalum-doped LLZO A solid electrolyte was prepared.

Example 5: Preparation of tantalum-doped LLZO solid electrolyte

Tantalum oxide (Ta ₂ O ₅ ) was used instead of niobium oxide (Nb ₂ O ₅ ), and 0.3 mol of tantalum was added instead of 0.25 molar part of niobium. LLZO solid electrolyte was prepared in the same manner as in Example 1, except that the reaction was carried out at a temperature of 800 ° C instead of 900 ° C.

Example  6: Tantalum Doped LLZO Solid electrolyte  Produce

Except that tantalum oxide (Ta ₂ O ₅ ) was used in place of niobium oxide (Nb ₂ O ₅ ), 0.3 mol of tantalum was substituted for 0.25 molar part of niobium and calcination was carried out at 700 ° C. instead of 900 A LLZO solid electrolyte was prepared in the same manner as in Example 1.

Example  7: Tantalum Doped LLZO Solid electrolyte  Produce

The LLZO solid electrolyte prepared according to Example 4 was sintered at a temperature of 1,100 ° C to prepare a pellet-shaped LLZO solid electrolyte sintered body.

Example  8: Niobium Doped LLZO Solid electrolyte  Produce

The LLZO solid electrolyte prepared according to Example 1 was sintered at a temperature of 1,100 ° C to prepare a pellet-shaped LLZO solid electrolyte sintered body.

Comparative Example 1: Production of LLZO solid electrolyte without hetero-element doping

A powdered LLZO solid electrolyte was prepared in the same manner as in Example 1, except that niobium oxide was not used. Thereafter, the sintered body was sintered at a temperature of 1,100 DEG C to prepare a pellet-shaped LLZO solid electrolyte sintered body.

The production conditions of the solid electrolytes prepared according to Examples 1 to 8 and Comparative Example 1 are summarized in Table 1 below.

division Heterogeneous elemental oxide For lanthanum 3 molar fraction
Heterogeneous molar fraction Calcination temperature (캜) Sintering temperature (℃) Example 1 Niobium oxide 0.25 900 - Example 2 Niobium oxide 0.25 800 - Example 3 Niobium oxide 0.25 700 - Example 4 Tantalum oxide 0.3 900 - Example 5 Tantalum oxide 0.3 800 - Example 6 Tantalum oxide 0.3 700 - Example 7 Tantalum oxide 0.3 900 1,100 Example 8 Niobium oxide 0.25 900 1,100 Comparative Example 1 - - 900 1,100

[Test Example]

Test Example  One: calcination  Temperature dependence of niobium ( Nb ) or Tantalum ( Ta ) Doped LLZO Solid electrolyte  X-ray Diffraction (XRD) analysis

FIG. 3 shows XRD analysis results of the niobium-doped LLZO solid electrolytes prepared according to Examples 1 to 3. FIG. 4 shows XRD analysis results of the tantalum-doped LLZO solid electrolytes prepared according to Examples 4 to 6. FIG.

3 and 4, the niobium-doped LLZO solid electrolyte prepared according to Example 3 exhibited a peak of lithium not participating in a partial reaction, and the peak intensity was low, indicating that the phase did not reach a sufficient degree of crystallization do. On the other hand, the peak pattern of the niobium-doped LLZO solid electrolyte prepared according to Example 1 showed a high peak intensity and showed almost no impurities. As a result of the Rietveld analysis, it was confirmed that the degree of crystallization was 84%, the temperature was 99% at a temperature of 800 ° C, and the temperature was 100% at a temperature of 900 ° C when the calcination temperature was 700 ° C when doped with niobium there was.

In addition, the tantalum-doped LLZO solid electrolytes prepared according to Examples 4 to 6, regardless of the calcination temperature, had higher peak strengths and lower impurity contents than the niobium-doped LLZO solid electrolytes prepared according to Examples 1 to 3 Peak pattern of cubic structure appeared. The crystallinity of the tantalum-doped LLZO solid electrolyte according to Example 6 was about 89%, and the crystallinity of the tantalum-doped LLZO solid electrolyte prepared according to Examples 4 and 5 was about 100%.

Therefore, it is considered that the LLZO solid electrolyte doped with tantalum is superior to the niobium - doped LLZO solid electrolyte and has a high cubic structure.

Test Example  2: Doped  Depending on the type of Lee Jongwon LLZO Solid electrolyte  Sintered body of XRD  analysis

5 shows XRD analysis results of the tantalum-doped LLZO solid electrolyte sintered body produced according to Example 7 and the niobium-doped LLZO solid electrolyte sintered body prepared according to Example 8. Fig.

According to Fig. 5, it was confirmed that the sintered bodies of LLZO solid electrolytes prepared according to Example 7 and Example 8 were all single-phase cubic structures.

Test Example  3: Doped  Depending on the type of Lee Jongwon LLZO Solid electrolyte  Sintered body of SEM  Image analysis

6 is a SEM image of the LLZO solid electrolyte sintered body produced according to Example 7, Example 8, and Comparative Example 1. FIG.

6, it was confirmed that the cross-section of the LLZO solid electrolyte sintered body manufactured according to Comparative Example 1 was not sufficiently sintered between particles. On the other hand, the cross-sections of the LLZO solid electrolyte sintered bodies produced according to Examples 7 and 8 were confirmed to be relatively dense. In particular, it was confirmed that the sintered body of the LLZO solid electrolyte produced according to Example 7 had a high-density microstructure such that the interface of particles was not observed.

Therefore, it is considered that the sintering property of the niobium or tantalum-doped LLZO solid electrolyte sintered body of the present invention is relatively superior to that of the LLZO solid electrolyte sintered body not doped with the hetero atom.

Test Example  4: Doped  Depending on the type of Lee Jongwon LLZO Solid electrolyte  Sintered body Impedance and ionic conductivity analysis

FIG. 7 shows the impedance and ionic conductivity analysis results of the LLZO solid electrolyte sintered bodies prepared according to Examples 7 and 8 and Comparative Example 1. FIG. Specifically, in the Nyquist plot graph of FIG. 6, a semicircle in the high frequency region and a straight line in the low frequency region can be identified. The total resistance of the contact in contact with the x- The ionic conductivity was calculated.

division Total ion conductivity (S / cm) Comparative Example 1 1.8 x 10 ^-5 Example 7 1.4 x 10 ^-4 Example 8 4.6 x 10 ^-5

Of Figure 7 and according to Table 2, the comparative example is the LLZO impedance of the solid electrolyte sintered body prepared according to 1 11,000 Ω · cm ^2, Example 8 of LLZO solid electrolyte sintered body with an impedance of 5,000 Ω · cm ^2, in Example 7 LLZO It was confirmed that the impedance of the solid electrolyte was 1,650 Ω · cm ² . Therefore, it was confirmed that the resistance of the tantalum-doped LLZO solid electrolyte sintered body is the lowest and the ionic conductivity is the highest.

Therefore, it is considered that the crystallinity and sintering characteristics of the tantalum-doped LLZO solid electrolyte sintered body are superior to those of the niobium-doped LLZO solid electrolyte.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, It is possible.

Claims (20)

(a) preparing a solid electrolyte precursor by coprecipitation reaction of a mixed aqueous solution containing a metal nitrate including lanthanum nitrate and zirconium nitrate, a complexing agent, and a pH controlling agent in a Taylor vortex state;
(b) washing and drying the solid electrolyte precursor;
(c) mixing the dried solid electrolyte precursor, any one selected from tantalum (Ta) oxide and niobium (Nb) oxide, and a lithium source to prepare a mixture; And
(d) calcining the mixture to prepare Ta or Nb doped lithium lanthanum zirconium oxide (LLZO) solid electrolyte (Ta / Nb doped LLZO) doped with either tantalum or niobium step; To
Including,
Wherein the molar ratio of La: Zr: (Ta or Nb) contained in the mixture is a: b: c, a is 2 to 4, b is 1 to 3, c is 0.1 to 0.5,
Wherein the lithium-lanthanum zirconium oxide (LLZO) solid electrolyte (Ta / Nb doped LLZO) doped with any one selected from the group consisting of tantalum and niobium is represented by the following general formula (1).
[Chemical Formula 1]
_{Li x La y Zr z A a} O 12
Where A is Ta or Nb,
5? X? 9, 2? Y? 4, 1? Z? 3, 0 <a? delete The method according to claim 1,
Wherein step (a) is a step of preparing a solid electrolyte precursor by coprecipitation reaction of a mixed aqueous solution in which a metal nitrate aqueous solution containing lanthanum nitrate and zirconium nitrate is mixed with an aqueous complexing agent solution and a pH adjusting agent aqueous solution Gt; delete The method according to claim 1,
Wherein step (a) is carried out in a Quattro Taylor vortex reactor. 6. The method of claim 5,
Wherein the Taylor vortex state Taylor number is 550 to 1,500. The method according to claim 6,
Wherein the Taylor vortex state has a Taylor number of 630 to 800. &lt; RTI ID = 0.0 &gt; 11. &lt; / RTI &gt; The method according to claim 1,
Wherein the complexing agent is ammonia water or sodium hydroxide. The method according to claim 1,
Wherein the lanthanum nitrate is La (NO ₃ ) ₃ .6H ₂ O, and the zirconium nitrate is ZrO (NO ₃ ) ₂ .2H ₂ O. The method according to claim 1,
Wherein a molar ratio of La: Zr contained in said metal nitrate aqueous solution is a: b, a is 2 to 4, and b is 1 to 3. 6. The solid electrolytic solution according to claim 1, The method according to claim 1,
Wherein the step (b) further comprises a step of drying the precursor and then pulverizing the precursor by a ball-mill process to produce a powder-form precursor. The method according to claim 1,
The lithium content of the lithium source of step (c) is 100 to 100 parts by weight of the lithium content of the solid electrolyte which is the product of step (d) To 115 parts by weight of the solid electrolyte. The method according to claim 1,
Wherein the mixing of step (c) is performed by a ball-mill process so that mixing and grinding are performed together. delete The method according to claim 1,
Wherein the molar ratio of La: Zr: (Ta or Nb) contained in the mixture is a: b: c, a is 2 to 4, b is 1 to 3, and c is 0.20 to 0.35. Gt; The method according to claim 1,
Wherein the calcination of step (d) is carried out at a temperature of 650 to 950 占 폚. The method according to claim 1,
After step (d)
(e) sintering the LLZO solid electrolyte doped with any one selected from the group consisting of tantalum and niobium to prepare a solid electrolyte sintered body; &Lt; / RTI &gt; further comprising the steps of: 18. The method of claim 17,
Wherein the sintering is performed at a temperature of 1,000 to 1,300 ° C. The method according to claim 1,
Wherein the solid electrolyte is a single-phase cubic structure. A method for manufacturing a pre-solid lithium secondary battery comprising the manufacturing method of claim 1.

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