WO2022145645A1

WO2022145645A1 - Active material coated with solid electrolyte, electrode, and all-solid-state battery using same

Info

Publication number: WO2022145645A1
Application number: PCT/KR2021/013791
Authority: WO
Inventors: 박건호; 조우석; 김경수; 유지상
Original assignee: 한국전자기술연구원
Priority date: 2020-12-30
Filing date: 2021-10-07
Publication date: 2022-07-07
Also published as: KR20220097560A

Abstract

The present invention relates to an active material coated with a solid electrolyte, an electrode, and an all-solid-state battery using same, and the purpose of the present invention is to enhance the performance of the all-solid-state battery by enlarging the ion contact area between the active material and the solid electrolyte. The active material for an all-solid-state battery according to the present invention comprises a source active material and a coating layer formed by coating a chloride-based solid electrolyte on the surface of the source active material.

Description

An active material coated with a solid electrolyte, an electrode, and an all-solid-state battery using the same

The present invention relates to an all-solid-state battery, and more particularly, to an active material coated with a solid electrolyte that can improve the performance of an all-solid-state battery by expanding the ionic contact area between the active material and the solid electrolyte, an electrode, and an all-solid-state battery using the same it's about

As the demand for electric vehicles and large-capacity power storage devices increases, various batteries have been developed to satisfy them.

Lithium secondary batteries have been widely commercialized because of their excellent energy density and output characteristics among various secondary batteries. As a lithium secondary battery, a lithium secondary battery (hereinafter referred to as a 'liquid-type secondary battery') including a liquid-type electrolyte containing an organic solvent is mainly used.

However, in the liquid type secondary battery, the liquid electrolyte is decomposed by the electrode reaction, causing the battery to expand, and the risk of ignition due to leakage of the liquid electrolyte is pointed out. In order to solve the problems of the liquid-type secondary battery, a lithium secondary battery (hereinafter referred to as an 'all-solid-state battery') to which a solid electrolyte having excellent stability is applied is attracting attention.

Solid electrolytes can be divided into sulfide-based, oxide-based and chloride-based electrolytes. Since sulfide-based solid electrolytes have high lithium ion conductivity and are stable over a wide voltage range compared to oxide-based solid electrolytes, sulfide-based solid electrolytes are mainly used as solid electrolytes for all-solid-state batteries.

Sulfide-based solid electrolytes have a high ionic conductivity similar to that of conventional organic liquid electrolytes, and have excellent mechanical ductility, which is why they are attracting attention as solid electrolytes for bulk-type all-solid-state batteries.

However, since the sulfide-based solid electrolyte is very vulnerable to moisture in the air, there is a problem of easily generating toxic hydrogen sulfide (H ₂ S) gas when in contact with moisture. In addition, when the sulfide-based solid electrolyte is exposed to a high voltage environment, the sulfide ion (S ² - ) is easily oxidized and its chemical characteristics are changed.

On the other hand, there is a problem in that it is difficult to achieve large-area contact with the active material because the solid electrolyte is difficult to deform mechanically, compared to the liquid electrolyte that easily wets the active material in the battery, which acts as a factor impairing the performance of the all-solid-state battery are doing

[Prior art literature]

[Patent Literature]

Unexamined Patent Publication No. 2019-0079135 (2019.07.05.)

In order to construct an all-solid-state battery having such excellent performance, it is preferable to use an active material coated with a solid electrolyte uniformly. However, the sulfide-based solid electrolyte is easily oxidized on the surface of the active material, making it unsuitable for use as a coating layer.

Therefore, there is a need for a solid electrolyte coating technology capable of achieving sufficient ionic contact with a small amount while having excellent electrochemical and oxidation stability.

An object of the present invention is to provide an active material coated with a solid electrolyte, an electrode, and an all-solid-state battery using the same, which can improve the performance of an all-solid-state battery by increasing the ionic contact area between the active material and the solid electrolyte.

In order to achieve the above object, the present invention provides a raw material active material; and a coating layer formed by coating the surface of the raw material with a chloride-based solid electrolyte.

The chloride-based solid electrolyte is Li _2-2x M ² _1+x X ₄ (0≤x≤0.5, M ² is at least among Be, Mg, Ca, Sr, Ba, Mn, Fe, Co, Ni, Cu and Zn one, and X may be at least one of F, Cl, and Br).

The chloride-based solid electrolyte is Li _3-x M ³ _1-x M ⁴ _x X ₆ (0≤x<1, M ³ is one of Sc, Y, Er, Yb, Cr, Fe and Co, M ⁴ is One of Ti, Zr, and Hf, and X may be at least one of F, Cl, and Br).

The raw material active material is LiCoO ₂ , NCM-based (including at least one doping element other than Ni, Co and Mn), NCA-based (including at least one doping element other than Ni, Co and Al), LiM _x Mn _2-x O ₄ (including M=Al, Ni, Cr, high voltage spinel) and olivine-based (LiFePO ₄ , LiM _x Fe _1-x PO ₄ (M=Ni, Co, Si)) at least one anode selected from the group consisting of material may be included.

The coating layer may be formed by physically mixing the raw material active material and the chloride-based solid electrolyte.

The present invention also provides a raw material active material, an active material having a coating layer formed by coating the surface of the raw material active material with a chloride-based solid electrolyte; and a sulfide-based solid electrolyte; provides an electrode for an all-solid-state battery comprising.

And the present invention provides an all-solid-state battery including the electrode.

According to the present invention, a coating layer with a chloride-based solid electrolyte can be formed on the surface of the raw material active material by uniformly mixing the raw material active material and the chloride-based solid electrolyte in a mechanical (physical) mixer such as a revolving mixer.

By forming the coating layer with the chloride-based solid electrolyte on the surface of the raw material active material as described above, the ionic contact area between the raw material active material and the solid electrolyte can be enlarged, thereby improving the performance of the all-solid-state battery.

And, by using a chloride-based solid electrolyte as a material for the coating layer, an all-solid-state battery having an active material coated with a chloride-based solid electrolyte can provide improved atmospheric stability and high voltage stability.

1 is a view showing an electrode for an all-solid-state battery including an active material coated with a chloride-based solid electrolyte on the surface of a raw active material according to the present invention.

FIG. 2 is a view showing an electrode for an all-solid-state battery in which a raw material active material and a solid electrolyte are mixed according to Comparative Example 1. Referring to FIG.

3 is a graph showing the results of X-ray diffraction analysis of active materials according to Examples and Comparative Examples.

4 is a FESEM photograph of active materials according to Examples and Comparative Examples.

5 is a graph showing charge/discharge curves of all-solid-state batteries including active materials according to Examples and Comparative Examples.

It should be noted that, in the following description, only parts necessary for understanding the embodiments of the present invention will be described, and descriptions of other parts will be omitted without departing from the gist of the present invention.

The terms or words used in the present specification and claims described below should not be construed as being limited to their ordinary or dictionary meanings, and the inventors have appropriate concepts of terms to describe their invention in the best way. It should be interpreted as meaning and concept consistent with the technical idea of the present invention based on the principle that it can be defined in Accordingly, the embodiments described in this specification and the configurations shown in the drawings are only preferred embodiments of the present invention, and do not represent all of the technical spirit of the present invention, so various equivalents that can be substituted for them at the time of the present application It should be understood that there may be variations and variations.

Hereinafter, embodiments of the present invention will be described in more detail with reference to the accompanying drawings.

Referring to FIG. 1 , the electrode 100 for an all-solid-state battery according to the present invention includes an active material 40 . Here, the active material 40 includes a raw active material 10 and a coating layer 30 coated with a chloride-based solid electrolyte on the surface of the raw active material 10 . That is, the active material 40 according to the present invention has a structure in which the chloride-based solid electrolyte 30 is coated on the surface of the raw active material 10 .

As a method of forming the coating layer 30 on the raw material 10 , a mechanical (physical) coating method using a mechanical (physical) mixer such as a corotatory mixer may be used. The active material 40 on which the coating layer 30 is formed can be obtained by mixing the raw material 10 and the chloride-based solid electrolyte into a corotatory mixer.

The active material 40 for an all-solid-state battery according to the present invention will be described in detail as follows.

As the raw material active material 10, an oxide-based active material having excellent mechanical strength may be used. And the chloride-based solid electrolyte has excellent mechanical ductility.

Due to the mechanical properties of the raw material active material 10 and the chloride-based solid electrolyte, the coating layer 30 may be formed by coating the surface of the raw material active material 10 with the chloride-based solid electrolyte. That is, since the chloride-based solid electrolyte has higher electrochemical and oxidation stability than the sulfide-based solid electrolyte, it is suitable as the coating layer 30 for expanding the ionic contact area. And since the chloride-based solid electrolyte has excellent mechanical ductility as described above compared to the oxide-based or sulfide-based solid electrolyte, it is easy to apply the coating layer 30 on the surface of the raw material 10 even with a simple mechanical coating process. can be formed

Here, the oxide-based active material includes LiCoO ₂ , NCM-based (including at least one doping element other than Ni, Co and Mn), NCA-based (including at least one doping element other than Ni, Co and Al), LiM _x Mn _{2- x} O ₄ (including M=Al, Ni, Cr, high voltage spinel) and olivine-based (LiFePO ₄ , LiM _x Fe _1-x PO ₄ (M=Ni, Co, Si)) at least one selected from the group consisting of) of anode material can be used. For example, as the oxide-based active material, an oxide-based active material represented by Li[Ni _x Mn _y Co _z ]O ₂ (x+y+z=1) may be used.

As a chloride-based solid electrolyte, Li _2-2x M ² _1+x X ₄ (0≤x≤0.5, M ² is at least among Be, Mg, Ca, Sr, Ba, Mn, Fe, Co, Ni, Cu and Zn) one, and X may be at least one of F, Cl, and Br).

Or as a chloride-based solid electrolyte, Li _3-x M ³ _1-x M ⁴ _x X ₆ (0≤x<1, M ³ is one of Sc, Y, Er, Yb, Cr, Fe and Co, M ⁴ is one of Ti, Zr, and Hf, and X is at least one of F, Cl, and Br) may be used.

In this way, the electrode 100 for an all-solid-state battery can be manufactured based on the active material 40 according to the present invention. An all-solid-state battery may be manufactured based on the manufactured electrode 100 .

Here, the electrode 100 may include the active material 40 according to the present invention and a sulfide-based solid electrolyte. As the sulfide-based solid electrolyte, Li ₁₀ GeP ₂ S ₁₂ , Li ₃ PS ₄ or Li ₆ PS ₅ Cl may be used, but is not limited thereto.

The electrode 100 may be manufactured so that the mass ratio of the raw material 10, the chloride-based solid electrolyte, and the sulfide-based solid electrolyte is 75: 3 to 20: 5 to 22.

The electrode 100 may further include a binder and a conductive material. Since the binder and the conductive material may be materials generally used for manufacturing the electrode 100 , a description thereof will be omitted.

As such, the active material according to the present invention forms a coating layer with a chloride-based solid electrolyte on the surface of the raw material active material, thereby increasing the ionic contact area between the raw material active material and the solid electrolyte, thereby improving the performance of the all-solid-state battery.

[Examples and Comparative Examples]

All steps of manufacturing the active material, electrode, and all-solid-state battery according to Examples and Comparative Examples are performed in a glove box or dry room or in an inert gas atmosphere so as not to be exposed to oxygen or moisture in the atmosphere.

In order to confirm the physical and electrochemical properties of the active material according to the present invention, active materials according to Examples and Comparative Examples were prepared.

Chloride-based solid electrolyte

Li ₃ YCl ₆ solid electrolyte to be used as a coating layer was synthesized as follows. First, lithium chloride (LiCl) and yttrium chloride (YCl ₃ ) were sealed with zirconia balls in a zirconia container in a molar ratio of 3 to 1, and then a ball milling process was performed at 500 rpm for 10 hours to form Li ₃ YCl ₆ solid electrolyte. synthesized.

The room temperature ionic conductivity of the Li ₃ YCl ₆ solid electrolyte synthesized through the AC-impedance method was confirmed to be 0.45 mS/cm.

Comparative Example 1

An electrode according to Comparative Example 1 was prepared by mixing a raw material active material not coated with a chloride-based solid electrolyte and a Li ₆ PS ₅ Cl solid electrolyte in a mass ratio of 75 to 25.

The electrode 200 according to Comparative Example 1 may be displayed as shown in FIG. 2 . 2 is a view showing an electrode 200 for an all-solid-state battery in which the raw material active material 10 and the solid electrolyte 20 according to Comparative Example 1 are mixed. That is, the electrode 200 according to Comparative Example 1 has a structure in which the solid electrolyte 20 particles are disposed between the raw material active material 10 particles.

In order to confirm the characteristics of the electrode 200 according to Comparative Example 1, an all-solid-state battery was manufactured by sequentially stacking a positive electrode, a solid electrolyte layer, and a negative electrode.

As a result of a charge/discharge test of the all-solid-state battery including the electrode 200 according to Comparative Example 1, the discharge capacity was confirmed to be 152 mAh/g.

Example 1

An electrode was prepared by coating a chloride-based solid electrolyte and a raw active material in a mass ratio of 75 to 3.95, and mixing it with a Li ₆ PS ₅ Cl solid electrolyte of 21.05%.

In order to confirm the characteristics of the electrode according to Example 1, an all-solid-state battery was manufactured by sequentially stacking a positive electrode, a solid electrolyte layer, and a negative electrode.

As a result of the charge/discharge test of the all-solid-state battery including the electrode according to Example 1, the discharge capacity was confirmed to be 166 mAh/g.

Example 2

An electrode was prepared by coating a chloride-based solid electrolyte and a raw material active material in a mass ratio of 75 to 8.33, and mixing it with a 16.67% Li ₆ PS ₅ Cl solid electrolyte.

In order to confirm the characteristics of the electrode according to Example 2, an all-solid-state battery was manufactured by sequentially stacking a positive electrode, a solid electrolyte layer, and a negative electrode.

As a result of the charge/discharge test of the all-solid-state battery including the electrode according to Example 2, the discharge capacity was confirmed to be 173 mAh/g.

Example 3

After coating the chloride-based solid electrolyte and the raw material active material in a mass ratio of 75 to 13.24, the electrode was prepared by mixing with 11.76% Li ₆ PS ₅ Cl solid electrolyte.

In order to confirm the characteristics of the electrode according to Example 3, an all-solid-state battery was manufactured by sequentially stacking a positive electrode, a solid electrolyte layer, and a negative electrode.

As a result of the charge/discharge test of the all-solid-state battery including the electrode according to Example 3, the discharge capacity was confirmed to be 179 mAh/g.

Example 4

The chloride-based solid electrolyte and the raw material were coated in a mass ratio of 75 to 18.75, and then mixed with 6.25% Li ₆ PS ₅ Cl solid electrolyte to prepare an electrode. In order to confirm the characteristics of the electrode according to Example 4, an all-solid-state battery was manufactured by sequentially stacking a positive electrode, a solid electrolyte layer, and a negative electrode.

As a result of the charge/discharge test of the all-solid-state battery including the electrode according to Example 4, the discharge capacity was confirmed to be 175 mAh/g.

Table 1 summarizes the performance evaluation results of the all-solid-state batteries according to Comparative Example 1 and Examples 1-4.

It can be seen that the all-solid-state battery according to Examples 1 to 4 has an improved discharge capacity compared to the all-solid-state battery according to Comparative Example 1.

Comparing the all-solid-state batteries according to Examples 1 to 4, when the mass ratio of the chloride-based solid electrolyte based on the raw material active material increases to 13.24%, the discharge capacity becomes the maximum, and exceeds 13.24%, it becomes 18,85% It can be seen that the discharge capacity decreases when

Referring to FIG. 3, as can be seen from the results of similar X-ray diffraction analysis for both the active materials according to Examples and Comparative Examples, it can be confirmed that there is no structural change of the raw material active material during the mechanical coating process according to Examples 1 to 4 .

Referring to FIG. 4 , as can be seen in the active materials according to Examples 1 to 3, it can be confirmed that the chloride-based solid electrolyte is uniformly coated on the oxide-based raw material through the mechanical coating process.

5 is a graph showing charge/discharge curves of all-solid-state batteries including active materials according to Examples and Comparative Examples. 5 is a charge-discharge curve of the all-solid-state battery according to Comparative Examples 1 and 4.

Referring to FIG. 5 , when the active material according to Example 4 coated with a chloride-based solid electrolyte is used, side reactions of the solid electrolyte do not occur at the initial stage of charging, and the ionic contact area between the active material and the solid electrolyte is improved. Compared with the active material according to Example 1, it can be seen that the improved discharge capacity is exhibited.

On the other hand, the embodiments disclosed in the present specification and drawings are merely presented as specific examples to aid understanding, and are not intended to limit the scope of the present invention. It is apparent to those of ordinary skill in the art to which the present invention pertains that other modifications based on the technical spirit of the present invention can be implemented in addition to the embodiments disclosed herein.

[Explanation of code]

10: raw material active material

20: solid electrolyte

30: coating layer

40: active material

100, 200: electrode

Claims

raw material active material; and

a coating layer formed by coating the surface of the raw material with a chloride-based solid electrolyte;

An active material for an all-solid-state battery comprising a.
According to claim 1,

The chloride-based solid electrolyte is Li 2-2x M 2 1+x X 4 (0≤x≤0.5, M 2 is at least among Be, Mg, Ca, Sr, Ba, Mn, Fe, Co, Ni, Cu and Zn one, and X is at least one of F, Cl, and Br).
According to claim 1,

The chloride-based solid electrolyte is Li 3-x M 3 1-x M 4 x X 6 (0≤x<1, M 3 is one of Sc, Y, Er, Yb, Cr, Fe and Co, M 4 is One of Ti, Zr, and Hf, and X is at least one of F, Cl, and Br).
According to claim 1,

The raw material active material is LiCoO 2 , NCM-based (including at least one doping element other than Ni, Co and Mn), NCA-based (including at least one doping element other than Ni, Co and Al), LiM x Mn 2-x O 4 (including M=Al, Ni, Cr, high voltage spinel) and olivine-based (LiFePO 4 , LiM x Fe 1-x PO 4 (M=Ni, Co, Si)) at least one anode selected from the group consisting of An active material for an all-solid-state battery, comprising a material.
According to claim 1,

The coating layer is an active material for an all-solid-state battery, characterized in that it is formed by physically mixing the raw material active material and the chloride-based solid electrolyte.
an active material comprising a raw material active material, and a coating layer formed by coating the surface of the raw material active material with a chloride-based solid electrolyte; and

sulfide-based solid electrolyte;

An electrode for an all-solid-state battery comprising a.
7. The method of claim 6,

The chloride-based solid electrolyte is Li 2-2x M 2 1+x X 4 (0≤x≤0.5, M 2 is at least among Be, Mg, Ca, Sr, Ba, Mn, Fe, Co, Ni, Cu and Zn and X is at least one of F, Cl, and Br).
7. The method of claim 6,

The chloride-based solid electrolyte is Li 3-x M 3 1-x M 4 x X 6 (0≤x<1, M 3 is one of Sc, Y, Er, Yb, Cr, Fe and Co, M 4 is One of Ti, Zr, and Hf, and X is at least one of F, Cl, and Br).
7. The method of claim 6,

The raw material active material is LiCoO 2 , NCM-based (including at least one doping element other than Ni, Co and Mn), NCA-based (including at least one doping element other than Ni, Co and Al), LiM x Mn 2-x O 4 (including M=Al, Ni, Cr, high voltage spinel) and olivine-based (LiFePO 4 , LiM x Fe 1-x PO 4 (M=Ni, Co, Si)) at least one anode selected from the group consisting of An electrode for an all-solid-state battery comprising a material.
An all-solid-state battery comprising an electrode, comprising:

The electrode is

an active material comprising a raw material active material, and a coating layer formed by coating the surface of the raw material active material with a chloride-based solid electrolyte; and

sulfide-based solid electrolyte;

An all-solid-state battery comprising a.
11. The method of claim 10,

The chloride-based solid electrolyte is Li 2-2x M 2 1+x X 4 (0≤x≤0.5, M 2 is at least among Be, Mg, Ca, Sr, Ba, Mn, Fe, Co, Ni, Cu and Zn and X is at least one of F, Cl, and Br).
11. The method of claim 10,

The chloride-based solid electrolyte is Li 3-x M 3 1-x M 4 x X 6 (0≤x<1, M 3 is one of Sc, Y, Er, Yb, Cr, Fe and Co, M 4 is One of Ti, Zr and Hf, and X is at least one of F, Cl, and Br).
11. The method of claim 10,

The raw material active material is LiCoO 2 , NCM-based (including at least one doping element other than Ni, Co and Mn), NCA-based (including at least one doping element other than Ni, Co and Al), LiM x Mn 2-x O 4 (including M=Al, Ni, Cr, high voltage spinel) and olivine-based (LiFePO 4 , LiM x Fe 1-x PO 4 (M=Ni, Co, Si)) at least one anode selected from the group consisting of An all-solid-state battery comprising a material.