Solid electrolyte for all solid-state battery

Abstract

This invention relates to a solid electrolyte for all-solid-state batteries. According to one embodiment of the invention, the solid electrolyte for all-solid-state batteries is formed from an oxide comprising Li, Mo, B, and Cl.

Description

[Technical Field]

[0001] This invention relates to a solid electrolyte for all-solid-state batteries. [Previous Technology]

[0002] Renewable batteries are used in various fields, from IT devices such as mobile phones to electric vehicles and energy storage devices.

[0003] As a secondary battery, lithium-ion batteries using liquid electrolytes are the most widely used. However, when an external impact is applied to the battery, there is a risk of leakage of the liquid electrolyte, so additional parts and devices are needed to ensure safety.

[0004] In recent years, to improve the safety of lithium-ion batteries, there has been active development of all-solid-state lithium-ion batteries using solid electrolytes. Solid electrolytes for all-solid-state lithium-ion batteries include polymer electrolytes, oxide electrolytes, and sulfide electrolytes. Among them, sulfide solid electrolytes have high ionic conductivity and excellent electrochemical performance based on particle deformability, but they have the problem of reacting with moisture in the air to produce toxic hydrogen sulfide gas. Polymer electrolytes have the advantage of relatively simple manufacturing processes and the ability to use existing lithium-ion battery processes, but they have the disadvantage of significantly low ionic conductivity.

[0005] Although oxide-based electrolytes have lower ionic conductivity than sulfide-based electrolytes, they are relatively higher and offer excellent safety advantages. Currently, oxide-based solid electrolytes with high ionic conductivity (above 10⁻⁴ S / cm), such as LAGP and LLZO, are under development. However, the narrow electrochemical voltage range and high-temperature sintering processes (above 1000°C) limit improvements in electrochemical performance of these solid electrolytes, potentially leading to increased production costs and limited usability. [Summary of the Invention]

[0006] The present invention is intended to solve the problems of the prior art mentioned above, and its purpose is to provide an oxide-based solid electrolyte for all-solid-state batteries that can be sintered at low temperatures and has excellent ionic conductivity.

[0007] According to an embodiment of the present invention, the solid electrolyte for an all-solid-state battery is composed of oxides containing Li, Mo, B and Cl.

[0008] According to an embodiment of the present invention, the solid electrolyte for all-solid-state batteries can satisfy LiCl / (Li2O+MoO3+B2O3)≥0.03 based on the molar ratio.

[0009] According to an embodiment of the present invention, the solid electrolyte for all-solid-state batteries can satisfy LiCl / (Li2O+MoO3+B2O3)≥0.10 based on the molar ratio.

[0010] According to an embodiment of the present invention, the solid electrolyte for all-solid-state batteries can satisfy 0.10≤LiCl / (Li2O+MoO3+B2O3)≤0.20 based on the molar ratio.

[0011] According to one embodiment of the present invention, the composition ratio of Li2O, MoO3 and B2O3 can be 10:1:14.

[0012] According to an embodiment of the present invention, the solid electrolyte for an all-solid-state battery may include LCB (Li4B7O12Cl) crystals and LMO (Li2MoO4) crystals.

[0013] According to an embodiment of the present invention, the solid electrolyte for an all-solid-state battery can be manufactured from a precursor powder containing Li2CO3, MoO3, B2O3 and LiCl.

[0014] According to an embodiment of the present invention, the ionic conductivity of the solid electrolyte for an all-solid-state battery can be 3.83×10-5S / cm or higher.

[0015] Effects of the Invention

[0016] According to one embodiment of the present invention, the solid electrolyte for all-solid-state batteries is an oxide-based solid electrolyte, which is formed from oxides containing Li, Mo, B and Cl, thereby enabling low-temperature sintering and exhibiting excellent ionic conductivity.

Implementation Method

[0022] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings to a degree that can be easily implemented by those skilled in the art to which the present invention pertains.

[0023] To clearly illustrate the present invention, descriptions of parts unrelated to the present invention have been omitted, and the same reference numerals are used to denote the same constituent elements throughout the specification. It should be understood that the specific shapes, structures, and characteristics described in the specification can be implemented by changing one embodiment to other embodiments without departing from the spirit and scope of the present invention, and the position or arrangement of individual constituent elements can also be changed without departing from the spirit and scope of the present invention.

[0024] Therefore, the detailed description that follows is not intended to be restrictive, but should be understood as including the scope of the claims in the claims and all equivalent scopes thereof.

[0025] Figure 1 is a cross-sectional view of an all-solid-state battery.

[0026] Referring to Figure 1, the all-solid-state lithium-ion battery (10) includes an anode layer (11), a cathode layer (12), and a solid electrolyte layer (13). The solid electrolyte layer (13) is disposed between the anode layer (11) and the cathode layer (12) and can contact the anode layer (11) and the cathode layer (12) respectively. The anode layer (11) and the cathode layer (12) can each have a current collector and an active material layer. The active material layer of the electrode layer is coated and formed on at least a portion of each current collector and can contact the solid electrolyte layer (13).

[0027] The anode layer (11) and cathode layer (12) of the all-solid-state lithium-ion battery (10) can be connected to external electrodes (14, 15), respectively. The external electrodes (14, 15) can be connected to the exposed terminals of each current collector of the anode layer (11) and cathode layer (12), thereby serving as the anode and cathode, respectively. Furthermore, the all-solid-state lithium-ion battery (10) may further include a casing (not shown) to prevent the anode layer (11) and cathode layer (12) from being exposed to the outside.

[0028] According to an embodiment of the present invention, the all-solid-state lithium-ion battery (10) can be composed of a plurality of layers, each consisting of an anode layer (11), a cathode layer (12), and a solid electrolyte layer (13), and the layers are stacked alternately in a plurality of layers, which is a so-called multilayer ceramic battery (MLCB). FIG1 illustrates a configuration in which the anode layer (11) and the cathode layer (12) are arranged alternately and the solid electrolyte layer (13) is arranged in between there; however, the configuration of the anode layer (11), the cathode layer (12), and the solid electrolyte layer (13) is not limited to that shown in the figure.

[0029] According to an embodiment of the present invention, the all-solid-state lithium-ion battery (10) can be formed in the form of a small chip and can be used in small electronic devices such as wearable electronic devices.

[0030] According to one embodiment of the present invention, the anode layer (11), the cathode layer (12), and the solid electrolyte layer (13) can be integrally sintered. That is, they can be integrally sintered in the form of the stacked components of an all-solid-state lithium-ion battery (10). For this purpose, low-temperature sintering is required, and therefore the solid electrolyte is required to have excellent low-temperature characteristics.

[0031] According to an embodiment of the present invention, the solid electrolyte layer (13) contains an oxide-based solid electrolyte as a solid electrolyte.

[0032] As oxide-based solid electrolytes, there are known sodium superionic conductors (Nasicon type) such as LAGP and garnet type such as LLZO. It is known that through continuous research and development, the ionic conductivity of such oxide-based solid electrolytes has been improved to the level of 10-4 S / cm.

[0033] However, there are limitations to further improving the ionic conductivity using the aforementioned sodium superionic conductor type and garnet type oxide-based solid electrolytes. Furthermore, while sintering these oxide-based solid electrolytes at temperatures above 1000°C can achieve a certain degree of excellent ionic conductivity, as mentioned above, the increased manufacturing costs due to high-temperature sintering are unavoidable. In particular, when high-temperature sintering is performed, it is practically impossible to integrally sinter the solid electrolyte with the anode and cathode layers.

[0034] In one embodiment of the present invention, the sintering temperature is reduced and excellent ionic conductivity is ensured by using a new oxide-based solid electrolyte that overcomes the limitations of such conventional oxide-based solid electrolytes.

[0035] According to an embodiment of the present invention, the solid electrolyte for an all-solid-state battery can be formed from oxides containing Li, Mo, B and Cl. Specifically, according to an embodiment of the present invention, the solid electrolyte can contain Li2O, MoO3, B2O3 and LiCl.

[0036] In the composition of the solid electrolyte, Li2O can function as a network modifier, providing Li ions to improve ionic conductivity.

[0037] In the composition of the solid electrolyte, MoO3 and B2O3 can function as network forming agents and as low-temperature components to reduce the sintering temperature.

[0038] In the composition of the solid electrolyte, LiCl plays a role in improving ionic conductivity by increasing the amount of Li ions and Cl ions. At this time, the increased Cl ions are free ions, which can move into the network structure and increase the lattice constant of the oxide crystal structure. Therefore, in the crystal structure, a wider migration path for Li ions is ensured, thereby further improving the ionic conductivity.

[0039] According to one embodiment of the present invention, the composition ratio of Li2O, MoO3 and B2O3 can be 10:1:14.

[0040] In one embodiment, the solid electrolyte, based on mole ratio, can satisfy mathematical formula 1.

[0041] [Mathematical Formula 1] LiCl / (Li2O+MoO3+B2O3)≥0.03

[0042] In another embodiment, the solid electrolyte, based on mole ratio, can satisfy mathematical formula 2.

[0043] [Mathematical Formula 2] LiCl / (Li2O+MoO3+B2O3)≥0.10

[0044] In yet another embodiment, the solid electrolyte, based on mole ratio, can satisfy mathematical formula 3.

[0045] [Mathematical Formula 3] 0.10≤LiCl / (Li2O+MoO3+B2O3)≤0.20

[0046] According to an embodiment of the present invention, the solid electrolyte may include LCB (lithium chloroborate, Li4B7O12Cl) crystals and LMO (lithium molybdate, Li2MoO4) crystals.

[0047] Thus, according to an embodiment of the present invention, the solid electrolyte for an all-solid-state battery is formed from an oxide containing Li, Mo, B and O, thereby enabling sintering at a temperature of approximately 500°C and exhibiting excellent ionic conductivity. Furthermore, since low-temperature sintering is possible, the solid electrolyte layer and the electrode can be sintered simultaneously, thereby simplifying the manufacturing process and improving quality.

[0048] A solid electrolyte according to an embodiment of the present invention can be manufactured from precursor powders containing Li2CO3, MoO3, B2O3 and LiCl. Specifically, a solid electrolyte according to an embodiment of the present invention can be manufactured by the following process: (1) Preparing precursor powders containing Li2CO3, MoO3, B2O3 and LiCl. (2) Uniformly mixing the precursor powders by dry or wet mixing. (3) Melting the mixture of precursor powders at a temperature of 1,000°C to 1,200°C. (4) Rapidly cooling the melt to room temperature. (5) Crushing the cooled melt into microparticles. (6) Granulating the pulverized material and sintering it at a temperature of about 500°C.

[0049] The solid electrolyte obtained by the process described above exhibits an ionic conductivity of approximately 9.34 × 10⁻⁸ or higher at room temperature. More preferably, the solid electrolyte exhibits an ionic conductivity of 3.83 × 10⁻⁵ S / cm or higher.

[0050] On the other hand, the solid electrolyte according to one embodiment of the present invention has excellent ionic conductivity and is non-hygroscopic. Therefore, even if moisture flows into the all-solid-state battery, the battery performance will not decrease, and stable and excellent performance can be maintained.

[0051] Example

[0052] Precursor powders containing Li2CO3, MoO3, B2O3 and LiCl (batch size 100g) were prepared. At this time, the mixing ratio of Li2CO3, MoO3 and B2O3 was fixed, and the amount of LiCl added was varied to prepare a total of six precursor powders.

[0053] To ensure the homogeneity of the solid electrolytes, the precursor powders were thoroughly mixed by ball milling or mechanical mixing. Furthermore, the precursor powders were placed in a crucible and melted at approximately 1,000°C for about 30 minutes. The melt was then rapidly cooled on a quenching roller, pulverized, and sieved to obtain micron-sized fine powders. The powders were then granulated and sintered at approximately 500°C for about 3 hours to produce six types of solid electrolytes.

[0054] The composition of the solid electrolyte manufactured as described above is shown in Table 1. Regarding the composition ratio of the solid electrolyte, in order to compare with the comparative example described later, the calculation was based on the other components except LiCl, that is, based on the sum of the other components except LiCl being 100 mol%.

[0055] Table 1 distinguish Solid electrolyte composition (mol%) Li2O MoO3 B2O3 LiCl Example 1 40 4 56 3 Example 2 40 4 56 5 Example 3 40 4 56 7 Example 4 40 4 56 10 Example 5 40 4 56 15 Example 6 40 4 56 20

[0056] Comparative Example

[0057] Precursor powders containing Li2CO3, MoO3 and B2O3 (batch size 100g) were prepared. At this time, while partially changing the mixing ratio of Li2CO3, MoO3 and B2O3, a total of five precursor powders were prepared.

[0058] Then, a solid electrolyte is produced by the same process as in the embodiment.

[0059] The composition of the solid electrolyte of the comparative example manufactured as described above is shown in Table 2.

[0060] Table 2 distinguish Solid electrolyte composition (mol%) Li2O MoO3 B2O3 Comparative Example 1 40 4 56 Comparative Example 2 45 5 50 Comparative Example 3 50 6 44 Comparative Example 4 35 5 60 Comparative Example 5 55 5 40

[0061] Figure 2 is a graph showing the XRD analysis results of the powder of the solid electrolyte before sintering according to the embodiment of the present invention, and Figure 3 is a graph showing the XRD analysis results of the powder of the solid electrolyte before sintering according to the comparative example of the present invention.

[0062] Referring to Figures 2 and 3, the XRD patterns of the solid electrolyte powder before sintering according to the embodiments and comparative examples of the present invention do not show crystallization peaks. This indicates that the powder before sintering is in an amorphous state, in which it is difficult to form lithium-ion pathways that enable ion diffusion.

[0063] Figure 4 is a graph showing the XRD analysis results of the solid electrolyte after sintering according to the embodiment of the present invention, and Figure 5 is a graph showing the XRD analysis results of the solid electrolyte after sintering according to the comparative example of the present invention.

[0064] Referring to Figures 4 and 5, the XRD patterns of the sintered solid electrolyte show various crystallization peaks. Specifically, the solid electrolyte according to the embodiments of the present invention has crystals such as LCB (lithium chloroborate, Li4B7O12Cl) and LMO (lithium molybdate, Li2MoO4), while the solid electrolyte according to the comparative examples of the present invention has crystals such as LMO (lithium molybdate, Li2MoO4) and LBO (lithium metaborate, LiBO2). In this crystalline structure, ion flow is smooth, resulting in excellent ionic conductivity. On the other hand, in Comparative Examples 3 and 5, since crystallization was not performed after sintering, they are not marked in the patterns of Figure 5, and as described later, the ionic conductivity was not measured.

[0065] Next, the lattice constants of the LMO crystals of the solid electrolytes according to each embodiment were confirmed, as shown in Table 3.

[0066] Table 3 distinguish LMO lattice constant (Å) Example 1 14.1221 Example 2 14.1192 Example 3 14.173 Example 4 14.3618 Example 5 14.3808 Example 6 14.358

[0067] Referring to Table 3, it can be confirmed that the lattice constant of LMO generally increases with the increase of LiCl addition. In particular, comparing Examples 1 to 3 with Examples 4 to 6, it can be confirmed that the lattice constant of LMO in Examples 4 to 6 is large. Thus, with the increase of lattice constant, the mobility of Li ions in the crystal structure can be improved, which will improve the ionic conductivity.

[0068] Next, the results of the transfer temperature, crystallization temperature and ionic conductivity measurements of the solid electrolytes according to the embodiments and comparative examples are shown in Table 4.

[0069] Table 4 distinguish Transfer temperature (Tg, ℃) Crystallization temperature (Tc, ℃) Ionic conductivity (S / cm) Example 1 416 501 4.46×10 -6 Example 2 411 499 3.53×10 -7 Example 3 406 481 9.34×10 -8 Example 4 380 471 5.75×10 -5 Example 5 380 457 3.83×10 -5 Example 6 372 461 7.62×10 -5 Comparative Example 1 424 502 5.30×10 -8 Comparative Example 2 383 446 1.69×10 -8 Comparative Example 3 342 417 - Comparative Example 4 458 542 1.23×10 -8 Comparative Example 5 306 362 -

[0070] Referring to Table 4, it can be confirmed that the examples show a transfer temperature of about 420°C or less and a crystallization temperature of about 500°C or less, which are generally lower than those of the comparative examples. In particular, the solid electrolytes of Examples 4 to 6 have transfer temperatures of about 380°C or less and crystallization temperatures of about 471°C or less, respectively, showing excellent low-temperature characteristics.

[0071] Thus, according to the embodiments of the present invention, low-temperature sintering can be performed by means of the excellent low-temperature characteristics.

[0072] Referring to Table 4, it can be confirmed that the ionic conductivity is higher in the examples with added LiCl compared to the comparative examples. Specifically, in the comparative examples, the ionic conductivity was not measured (Comparative Examples 3 and 5), or showed a low ionic conductivity of about 1.2 × 3 × 10⁻⁸ to 5.30 × 10⁻⁸ S / cm, while the examples showed an ionic conductivity of 9.34 × 10⁻⁸ S / cm or higher. In particular, the ionic conductivity in Examples 4 to 6 was 3.83 × 10⁻⁵ to 7.62 × 10⁻⁵ S / cm, showing a high ionic conductivity at the 10⁻⁵ S / cm level.

[0073] Thus, it can be confirmed that as the solid electrolyte contains LiCl in addition to Li2O, MoO3, and B2O3, the ionic conductivity increases. Furthermore, it can be confirmed that when the ratio of LiCl to the total of Li2O, MoO3, and B2O3, based on the molar ratio, is 0.10 or more (Examples 4 to 6), the ionic conductivity of the solid electrolyte is significantly improved.

[0074] It is speculated that this is because, as mentioned above, with the addition of LiCl, the lattice constant of the crystals contained in the solid electrolyte increases, thereby improving the ion mobility.

[0075] The present invention has been described above using specific constituent elements and limited embodiments. However, the foregoing embodiments are only provided to help to understand the present invention more fully. The present invention is not limited thereto. Anyone skilled in the art to which the present invention pertains can make various modifications and variations from such description.

[0076] Therefore, the concept of the present invention should not be limited to the previously described embodiments, and is not limited to the scope of the patent application described below. All owners of works that are equivalent to or have equivalent variations of the scope of the patent application are within the scope of the present invention. [Simplified Explanation of the Diagram]

[0017] Figure 1 is an example of a cross-sectional view of an all-solid-state battery.

[0018] Figure 2 is a graph showing the XRD analysis results of the powder of the solid electrolyte according to an embodiment of the present invention before sintering.

[0019] Figure 3 is a graph showing the XRD analysis results of the solid electrolyte powder before sintering according to the comparative example of the present invention.

[0020] Figure 4 is a graph showing the XRD analysis results of the solid electrolyte after sintering according to an embodiment of the present invention.

[0021] Figure 5 is a graph showing the XRD analysis results of the solid electrolyte of the comparative example according to the present invention after sintering.

Claims

1. A solid electrolyte, which is a solid electrolyte for all-solid-state batteries, wherein the solid electrolyte is formed from oxides containing Li, Mo, B and Cl, and contains LCB (Li4B7O12Cl) crystals and LMO (Li2MoO4) crystals.

2. The solid electrolyte as described in claim 1, which satisfies, based on molar ratio, that LiCl / (Li2O+MoO3+B2O3)≥0.

03.

3. The solid electrolyte as described in claim 2, which satisfies, based on molar ratio, LiCl / (Li2O+MoO3+B2O3)≥0.

10.

4. The solid electrolyte as described in claim 3, which satisfies 0.10≤LiCl / (Li2O+MoO3+B2O3)≤0.20 based on molar ratio.

5. The solid electrolyte as described in claim 2, wherein, The composition ratio of Li2O, MoO3 and B2O3 is 10:1:

14.

6. The solid electrolyte as claimed in claim 1, which is made from precursor powders comprising Li2CO3, MoO3, B2O3 and LiCl.

7. The solid electrolyte as described in claim 1 has an ionic conductivity of 3.83 × 10⁻⁵ S / cm or higher.

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