KR101945942B1 - Method for manufacturing cathode material composite and all-solid-state lithium secondary battery including the same - Google Patents

Abstract

The present invention relates to a method of manufacturing an anodic composite coated with an ion conductive solid electrolyte based on a sol-gel method and a method of manufacturing an all-solid-state lithium secondary battery including the same. The method includes: a first step of manufacturing a first metal solution including at least two kinds of first metal precursors and P precursors; a second step of mixing a chelate agent with the first metal solution; a third step of adding a second metal solution including second metal precursors, which are different from the first metal precursors, to the mixture of the first metal solution and the chelate agent; a fourth step of adding an esterified reaction catalyst after the third step; a fifth step of adding an anodic active material to at least one of the first to fourth steps; a sixth step of stirring the solution of the fifth step until the solvent becomes evaporated; and a seventh step of manufacturing an anodic composite coated with an ion conductive solid electrolyte by drying, carbonizing, and calcining the anodic active material/metal composite precursors of which solvent has been evaporated during the sixth step.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a positive electrode composite and a method for manufacturing the same,

The present invention relates to a positive electrode composite coated with an ion conductive solid electrolyte using a sol-gel method and a method for manufacturing a full solid lithium secondary battery comprising the same.

With the development of the environment-friendly automobile and energy storage market in conjunction with the recent development of the electric, electronic, communication and computer industries, development of low-cost lithium secondary batteries with high safety has become very important. In recent years, development of electric vehicles (EV), hybrid electric vehicles (HEV), and plug-in hybrid electric vehicles (PHEVs) have been actively developed due to rising energy prices and demands for environmental protection It is further required to develop a lithium secondary battery having excellent lifetime and capacity characteristics and low cost so that it can be commercialized in automobiles. As the use of lithium rechargeable batteries is expanded in this way, lithium rechargeable batteries are being developed in pursuit of high capacity, low cost, high safety, and large size. Especially, improvement of safety and high performance of lithium rechargeable batteries are required.

However, existing lithium secondary batteries have a problem of leakage and ignition with high liquidity due to the use of a liquid electrolyte, and safety problems are recognized more and more as the capacity and size of batteries are increased. Therefore, recently, for the purpose of improving safety, all solid lithium secondary batteries using inorganic solid electrolyte, which is a nonflammable material, have been actively studied. Further, all solid lithium secondary batteries are attracting attention as next generation batteries such as safety, high energy density and long life.

The solid lithium secondary battery is the most advantageous because it uses the solid electrolyte in place of the liquid electrolyte material used in the conventional lithium secondary battery and ensures perfect safety. The solid electrolyte is a core material for overcoming limitations of use of existing liquid electrolytes due to high capacity and high voltage of lithium secondary battery electrodes and securing the safety of high performance lithium secondary batteries.

Specifically, the pre-solid lithium secondary battery is composed of a positive electrode / a solid electrolyte / a negative electrode, and a solid electrolyte particle containing no organic solvent is pressed or mixed with a flexible material (polymer). Such a pre-solid lithium secondary battery is required to be improved in physical contact with an electrode by applying a solid electrolyte rather than a liquid.

Therefore, a pre-solid lithium secondary battery is required to uniformly combine an active material with an ion conductor in order to impart an ion conductive path to an electrode. In addition, it is important to develop low-cost cathode and anode materials in order to lower the cost of pre-solid lithium rechargeable batteries. Especially, the ratio of anode material to total material cost is large, so technology for lowering the production cost of cathode material is developed It is important to do.

An object of the present invention is to provide a positive electrode composite in which a cathode active material is coated with an ion conductive solid electrolyte using a sol-gel method, and a method for manufacturing a pre-solid lithium secondary battery comprising the same.

In order to accomplish the object of the present invention, the present invention provides a method for producing a positive electrode composite for an all-

(a) a first step of preparing a first metal solution comprising at least two first metal precursors and a P precursor;

(b) a second step of mixing the chelating agent with the first metal solution;

(c) adding a second metal precursor and a second metal precursor different from the first precursor precursor to the mixture of the first metal precursor and the chelating precursor;

(d) a fourth step of adding an esterification reaction promoter after the third step;

(e) adding a cathode active material to at least one of the first to fourth steps;

(f) stirring the solution until the solvent evaporates after the fifth step; And

and (g) drying, carbonizing and calcining the cathode active material / metal composite precursor in which the solvent has been evaporated in the sixth step, thereby preparing a cathode composite coated with an ion conductive solid electrolyte. And a manufacturing method thereof.

According to an embodiment of the present invention, the cathode active material is preferably added after the fourth step of adding an esterification reaction promoter.

In order to accomplish still another object of the present invention, the present invention provides a positive electrode composite comprising 50 to 90% by weight of a positive electrode composite prepared according to the present invention; 5 to 20% by weight of a conductive agent; And 5 to 30% by weight of an ion conductive polymer binder to prepare a slurry; And

And a step of preparing the slurry in the form of a sheet using a casting method. The present invention also provides a method for producing a pre-solid lithium secondary battery.

According to the method for producing a positive electrode composite according to an embodiment of the present invention, a positive electrode composite in which an ion conductive solid electrolyte is coated on a positive electrode active material can be manufactured. Therefore, ion conductivity can be increased at the positive electrode to improve battery characteristics such as charge / discharge and electrode cycle characteristics This excellent secondary battery can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a flow chart illustrating a method of manufacturing a positive electrode composite using a sol-gel method according to an embodiment of the present invention. FIG.
2 shows XRD analysis results of a pure LATP synthetic powder which is an ion conductive solid electrolyte.
FIG. 3 shows the results of Example 1 (1 wt% LATP-NCM), Example 2 (2.5 wt% LATP-NCM) and Example 3 (10 wt%, LTAP-NCM) , And Comparative Example 1 (NCM).
4 shows TEM analysis results of the positive electrode composite according to Example 2 and Example 3 of the present invention.
5 shows the results of charging / discharging performance evaluation of all solid lithium secondary batteries manufactured according to Examples 1 to 3 of the present invention.
6 shows the cycle characteristics of a full solid lithium secondary battery produced according to Example 2 of the present invention.

Hereinafter, the present invention will be described in more detail. However, this is for the purpose of helping understanding of the present invention, and thus does not limit the scope of the present invention.

A method for preparing a positive electrode composite for a full-solid-state battery according to an embodiment of the present invention includes: a first step of preparing a first metal solution including at least two first metal precursors and a P precursor; A second step of mixing a chelating agent with the first metal solution; A third step of adding a second metal solution containing a second metal precursor different from the first metal precursor to the mixture of the first metal solution and the chelating agent; A fourth step of adding an esterification reaction promoter and esterifying the esterification reaction accelerator after the third step; A fifth step of adding and stirring the cathode active material to at least one of the first to fourth steps; A sixth step of stirring the mixture of the fifth step until the solvent evaporates; And a seventh step of preparing a cathode composite coated with an ion conductive solid electrolyte by drying, carbonizing and calcining the cathode active material / metal composite precursor in which the solvent has evaporated in the sixth step.

Preferably, the method for preparing a positive electrode composite for a full-solid-state battery according to an embodiment of the present invention includes a first step of preparing a first metal solution containing at least two first metal precursors and a P precursor; A second step of mixing a chelating agent with the first metal solution; A third step of adding a second metal solution containing a second metal precursor different from the first metal precursor to the mixture of the first metal solution and the chelating agent; A fourth step of adding an esterification reaction promoter after the third step; A fifth step of adding the cathode active material after the fourth step; Stirring the mixture until the solvent evaporates after the fifth step; And a seventh step of preparing a cathode composite coated with an ion conductive solid electrolyte by drying, carbonizing and calcining the cathode active material / metal composite precursor in which the solvent has evaporated in the sixth step (see FIG. 1).

In the method for producing a positive electrode composite for an all solid state battery according to an embodiment of the present invention, the at least two first metal precursors include Li or Al as a first metal, and the second metal precursor contains Ti as a second metal .

In addition, the first metal precursor of the present invention is preferably a nitrate, phosphorus, or sulfur oxide of the first metal. For example, as a precursor of _{Li LiNO 3, Li 2 CO 3} , Li 2 SO 4 And LiCl may be used. Al (NO ₃ ) ₃ .XH ₂ O (where X is an integer of 1 to 15), AlCl ₃ , Al ₂ (SO ₄ ) ₃ , Al [OCH (CH ₃ ] ₂ ] ₃ and Al (PO ₃ ) ₃ may be used.

In addition, as the first metal precursor, a precursor of the first metal selected from the group consisting of Al, Cr, Ga, Fe, Sc, In, Lu, Y and La may be used. As the second metal precursor, Ge and Zr may be used as the precursor of the second metal.

Preferably, the first metal precursor is at least one selected from LiNO ₃ , Li ₂ CO ₃ , Li ₂ SO ₄ , Al (NO ₃ ) ₃ .XH ₂ O (where X is an integer of 1 to 15) And the P precursor may be at least one selected from NH ₄ H ₂ PO ₄ and H ₃ PO ₄ .

According to another embodiment of the present invention, the second metal precursor is an esterified metal of the second metal. For example, as a precursor of _{Ti Ti (C 3 H 7 O} ) 4, Ti (OCH 2 CH 2 CH 2 CH 3) 4 , and _{Ti [OCH (CH 3) 2} ] at least one element selected from the group consisting of ₄ May be used, and preferably Ti (C ₃ H ₇ O) ₄ may be used.

In addition, according to the method of preparing the positive electrode composite according to one embodiment of the present invention, the chelating agent may be citric acid or acetic acid, preferably citric acid. It is preferable that the chelating agent is added in an amount corresponding to the molar amount of the first metal precursor, the second metal precursor and the P precursor.

As the solvent used for the first metal solution or the second metal solution, distilled water, ethylene glycol, ethanol, dimethyl ether, alcohol or the like may be used. Preferably, the solvent of the first metal solution is distilled water, As the solvent of the second metal solution, a lower alcohol having 1 to 10 carbon atoms may be used.

According to the method for preparing a positive electrode composite according to an embodiment of the present invention, the esterification reaction promoter may be ethylene glycol, glucose, or the like.

According to the method of preparing a positive electrode composite according to an embodiment of the present invention, the ion conductive solid electrolyte is preferably an ion conductive solid electrolyte LATP having the following general formula (1).

≪ Formula 1 >

Li _x Al _y Ti _z (PO ₄ ) ₃

(Where 1? X? 1.5, 0.1? Y? 0.5, and 1? Z?

According to the method of manufacturing a positive electrode composite according to an embodiment of the present invention, the positive electrode active material may include a nickel cobalt manganese (NCM) active material having the following formula (2).

(2)

LiNi _p Co _q Mn _r O ₂

(Where 0 <p <0.9, 0 <q <0.5, 0 <r <0.5 and p + q + r = 1)

The method of manufacturing a positive electrode composite according to an embodiment of the present invention may further include a step of maintaining the mixed solution of the third step at a temperature of 70 to 90 ° C at a rate of 100 to 300 rpm for 10 minutes to 2 hours . If the temperature is lower than 70 ° C, the solvent may be evaporated too slowly, which may take a long time, and residual impurities may not be sufficiently removed. If the temperature exceeds 90 ° C, There is a possibility that sufficient dispersion of the liver is difficult. The stirring time is not limited thereto and may be varied depending on the stirring temperature. Further, since the mixture is mixed by stirring, a gel-like gel-like composition can be produced.

In the method of manufacturing the positive electrode composite according to one embodiment of the present invention, the seventh step is a step of drying at 90 to 120 ° C. for 10 to 36 hours, carbonization at 350 to 450 ° C. for 2 to 8 hours, For 5 to 20 hours.

In the method of manufacturing a positive electrode composite according to an embodiment of the present invention, the ion conductive solid electrolyte may be coated with 1 to 10 wt%, more preferably 1 to 3 wt%, based on the total weight of the positive electrode active material More preferably 2.5% by weight.

When the ion conductive solid electrolyte is coated in an amount less than 1% by weight, the ion conductive solid electrolyte may not be coated. When the ion conductive solid electrolyte is coated in an amount exceeding 10% by weight, ion conduction may be interrupted by the coating film.

In the method of manufacturing a positive electrode composite according to an embodiment of the present invention, the positive electrode active material may be added to at least one of the first to fourth steps, and after the addition of the esterification accelerator, .

The method of manufacturing a positive electrode composite according to an embodiment of the present invention may further include, after the seventh step, pelletizing and sieving the positive electrode active material by ball milling or manually.

In order to accomplish still another object of the present invention, a method for manufacturing a pre-solid lithium rechargeable battery according to the present invention comprises the steps of: preparing 50 to 90% by weight of a cathode active material, 5 to 20% by weight of a conductive agent, To 30% by weight of the slurry to prepare a slurry; And producing the slurry in a sheet form by a casting method.

The conductive agent is preferably at least one selected from the group consisting of Super-P, carbon nanotube (CNT), graphite, carbon, acetylene black, Ketjen black (KB), carbon black and carbon fiber.

According to the method of manufacturing a pre-solid lithium rechargeable battery according to an embodiment of the present invention, the ion conductive polymer binder may be formed of at least one selected from the group consisting of polyethylene oxide (PEO), polypropylene oxide (PPO), polytetrafluoroethylene (PTFE) (PVA). &Lt; / RTI &gt;

The ion conductive polymer binder may be contained in an amount of 5 to 30% by weight, and preferably 10 to 30% by weight.

When the content of the ion conductive polymeric binder is less than 5% by weight, the binding force and the ion transport path are reduced. When the content of the ion conductive polymer binder is more than 30% by weight, the energy density of the active material may be decreased.

The embodiments of the present invention are described in order to more fully explain the present invention to those skilled in the art, and the following embodiments may be modified into various other forms, It is not limited to the embodiment. Rather, these embodiments are provided so that this disclosure will be more faithful and complete, and will fully convey the scope of the invention to those skilled in the art.

Example  1 to Example  3

In the present invention, FIG. 1 is a flowchart illustrating a method of manufacturing a positive electrode composite according to an embodiment of the present invention.

&Lt; Preparation of positive electrode composite &

LiNO ₃ , Al (NO ₃ ) ₃ .XH ₂ O as a first metal precursor and NH ₄ H ₂ PO ₄ as a P precursor were dissolved in distilled water at a molar ratio of 1.3: 0.3: 3.0 as a starting material to form a first metal solution .

Citric acid was added to the first metal solution. Wherein the citric acid is added in the same molar ratio as the molar ratio of the metal dissolved in the first metal solution.

Separately, a second metal solution was prepared by dissolving Ti (C ₃ H ₇ O) ₄ in isopropyl alcohol in a 1:50 molar ratio.

A second metal solution was added to a solution in which the first metal solution and the citric acid were mixed so that the molar ratio of the first metal dissolved in the first metal solution and the second metal dissolved in the second metal solution became 4.6: .

The mixed solution was stirred at a stirring speed of 200 rpm for about 30 minutes while maintaining the temperature at 80 ° C, and glucose was added at the same molar ratio as that of citric acid for promoting the esterification reaction.

Further, after stirring for about 30 minutes at a temperature of 80 캜, a cathode active material NCM was additionally added so that the coating amount of the final LATP was 1 wt% (Example 1), 2.5 wt% (Example 2 ) And 10% by weight (Example 3).

< All solids  Preparation of lithium secondary battery &gt;

The composite thus prepared, Super-P as a conductive agent, and ion conductive binder (PEO) were mixed at a weight ratio of 70:10:20 to prepare a slurry, and a positive electrode composite was prepared by a casting method at a loading amount of 10 mg / cm ² .

As the electrolyte, an Al-doped LLZO solid electrolyte based on a patent (KR 10-2015-0132466) based on the invention was prepared. The negative electrode was made of 2032 coin cells by applying Li metal and subjected to a charge- Respectively.

Comparative Example  One

As a comparative example, an XRD characteristic (see FIG. 3) was analyzed for a pure NCM cathode active material not coated with an ion conductive solid electrolyte and compared with the composite of Example (1-3). .

Test Example  One: Of LATP XRD  analysis

FIG. 2 shows the XRD analysis results of the LATP produced by the sol-gel synthesis process according to the method for producing the positive electrode composite according to one embodiment of the present invention.

2, XRD analysis of a pure LATP sol-gel synthesis powder not containing an NCM active material shows that a typical nacicon structure LATP material is formed, and it can be confirmed that a small amount of LATP material is formed on the NCM surface due to sol- LATP material information is available.

Test Example  2: Anodic composite XRD  analysis

Fig. 3 shows XRD analysis results of the anode composite coated with the ion conductor prepared according to Examples 1 to 3 and Comparative Example 1. Fig.

Referring to FIG. 3, XRD analysis of the positive electrode composite (LATP-NCM) coated with the NCM active material with different LATP contents showed no difference in peak according to the content of LATP in Examples 1 and 2, , It can be seen that NCM peaks mainly appear.

However, it can be seen that the peak intensity of the positive electrode composite (LATP-NCM) of Example 3 in which 10 wt% of LATP is coated appears to have a somewhat lower intensity, thus affecting the thickness of the surface coating.

Test Example  3: Anodic composite TEM  analysis

FIG. 4 is a TEM analysis result of the positive electrode composite coated with the ion conductive solid electrolyte prepared according to Example 2 and Example 3. FIG.

Referring to FIG. 4, in the case of Example 2 in which LATP is coated at 2.5 wt%, the crystal lines of the two materials intersect with each other, resulting in different directions.

However, in the case of Example 3 in which LATP is coated at 10 wt%, the LATP coating layer is distinct and shows a different crystal line from the NCM material.

Therefore, it can be seen that the content of the LATP ion conductor affects the surface characteristics of the positive electrode composite.

Test Example  4: Charging and discharging  Performance evaluation

Fig. 5 shows the charge / discharge performance evaluation results of all the solid lithium secondary batteries produced according to Examples 1 to 3. Fig.

Referring to FIG. 5, Example 1 and Example 2 show charge / discharge characteristics of about 38 mAh / g and 110 mAh / g, respectively, and Example 3 shows charge / discharge characteristics of about 75 mAh / g.

In the case of Example 2 in which 2.5 wt% of LATP is coated, it shows about 110 mAh / g, which is the best charge / discharge characteristic. Therefore, it can be seen that the LATP content should be appropriately maintained in the electrode active material.

Test Example  5: Cycle  Character rating

Fig. 6 shows the results of evaluation of cycle characteristics of the all-solid lithium secondary battery produced according to Example 2. Fig.

Referring to FIG. 6, the anode composite coated with 2.5 wt% of LATP exhibits excellent electrode cycling characteristics.

Claims (19)

A method of manufacturing a positive electrode composite for a solid-state battery,
(a) a first step of preparing a first metal solution comprising at least two first metal precursors and a P precursor;
(b) a second step of mixing the chelating agent with the first metal solution;
(c) adding a second metal precursor and a second metal precursor different from the first precursor precursor to the mixture of the first metal precursor and the chelating precursor;
(d) a fourth step of adding an esterification reaction promoter after the third step;
(e) adding a cathode active material to at least one of the first to fourth steps;
(f) stirring the solution of the fifth step until the solvent evaporates; And
(g) drying, carbonizing and calcining the cathode active material / metal composite precursor in which the solvent of the sixth step has been evaporated, thereby preparing a cathode composite coated with an ion conductive solid electrolyte; Lt; / RTI &gt;
Wherein the second metal precursor is an esterified product of Ti. The method according to claim 1,
Wherein the positive electrode active material is added after the fourth step. The method according to claim 1,
Wherein the first metal is Li or Al. &Lt; RTI ID = 0.0 &gt; 11. &lt; / RTI &gt; The method according to claim 1,
Wherein the first metal precursor is a nitrate, phosphorus, or sulfur oxide of the first metal. The method according to claim 1,
Wherein the chelating agent is citric acid. &Lt; RTI ID = 0.0 &gt; 11. &lt; / RTI &gt; The method according to claim 1,
Wherein the esterification reaction promoter is glucose. &Lt; RTI ID = 0.0 &gt; 11. &lt; / RTI &gt; The method according to claim 1,
And maintaining the mixed solution of the third step at a temperature of 70 to 90 DEG C at a rate of 100 to 300 rpm for 10 minutes to 2 hours. The method according to claim 1,
Wherein the seventh step is carried out at 90 to 120 ° C for 10 to 36 hours, then at 350 to 450 ° C for 2 to 8 hours, and then at 700 to 1000 ° C for 5 to 20 hours. A method for producing a positive electrode composite for a solid battery. The method according to claim 1,
Wherein the ion conductive solid electrolyte is coated in an amount of 1 to 10 wt% based on the total weight of the positive electrode composite. The method according to claim 1,
The first metal precursor, _{LiNO 3, Li 2 CO 3,} Li 2 SO 4, Al (NO 3) 3 · XH 2 O and at least one member selected from (wherein, X is an integer of 1 to 15)
Wherein the P precursor is at least one selected from NH ₄ H ₂ PO ₄ and H ₃ PO ₄ . The method according to claim 1,
Wherein the second metal precursor is Ti (C ₃ H ₇ O) ₄ . The method according to claim 1,
[7] The method of claim 1, further comprising, after the seventh step, grinding and sieving the positive electrode composite by a ball mill or manually. The method according to claim 1,
Wherein the ion conductive solid electrolyte is an ion conductive solid electrolyte LATP having the following general formula (1).
&Lt; Formula 1 >
Li _x Al _y Ti _z (PO ₄ ) ₃
(Where 1? X? 1.5, 0.1? Y? 0.5, and 1? Z? The method according to claim 1,
Wherein the cathode active material is a nickel cobalt manganese (NCM) active material represented by the following general formula (2).
(2)
LiNi _p Co _q Mn _r O ₂
(Where 0 <p <0.9, 0 <q <0.5, 0 <r <0.5 and p + q + r = 1) The method according to claim 1,
Wherein the solvent of the first metal solution is distilled water. The method according to claim 1,
Wherein the solvent of the second metal solution is a lower alcohol having 1 to 10 carbon atoms. 50 to 90% by weight of a positive electrode composite prepared according to any one of claims 1 to 16; 5 to 20% by weight of a conductive agent; And 5 to 30% by weight of an ion conductive polymer binder to prepare a slurry; And
And forming the slurry into a sheet form by a casting method. 18. The method of claim 17,
Wherein the ion conductive polymer binder is at least one selected from the group consisting of polyethylene oxide (PEO), polypropylene oxide (PPO), polytetrafluoroethylene (PTFE), and polyvinyl alcohol (PVA) Way. delete

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