Solid electrolyte for all-solid-state battery

Abstract

The present invention relates to a solid electrolyte for an all-solid-state battery. The solid electrolyte for an all-solid-state battery according to an embodiment of the present invention comprises Li2O, V2O5, P2O5, and LiCl.

Description

Solid electrolyte for all-solid-state batteries

[0001] The present invention relates to a solid electrolyte for an all-solid-state battery.

[0002] Recently, the use of secondary batteries has increased significantly in various fields, from IT devices such as mobile phones to electric vehicles and energy storage devices.

[0003] Among secondary batteries, lithium-ion batteries, which use liquid electrolytes, are the most widely used. However, liquid electrolytes pose a risk of leakage if the battery is subjected to external shocks, necessitating the use of additional components and devices to ensure safety.

[0004] Recently, active development of all-solid-state batteries using solid electrolytes has been underway to improve the safety of secondary batteries. Solid electrolytes for all-solid-state batteries include polymer electrolytes, oxide electrolytes, and sulfide electrolytes. Sulfide solid electrolytes have the highest ionic conductivity, but they have the problem of reacting with moisture to produce hydrogen sulfide gas. Polymer electrolytes offer the advantages of a relatively simple process and compatibility with existing lithium-ion battery processes, but their significantly low ionic conductivity is a drawback.

[0005] Oxide-based electrolytes offer superior safety compared to sulfide-based electrolytes, but their ionic conductivity is relatively low. Furthermore, oxide-based electrolytes typically require high sintering temperatures, typically exceeding 1,000°C, which can significantly increase manufacturing costs.

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

[0007] A solid electrolyte for an all-solid-state battery according to one embodiment of the present invention includes Li2O, V2O5, P2O5, and LiCl.

[0008] According to one embodiment of the present invention, the molar ratio of Li2O, V2O5 and P2O5 may be 1:2:1.

[0009] A solid electrolyte for an all-solid-state battery according to one embodiment of the present invention may contain 10 mol% of LiCl.

[0010] A solid electrolyte for an all-solid-state battery according to one embodiment of the present invention has an ionic conductivity of 2.40×10 -4 2.50×10 -4 It could be S / cm.

[0011] A solid electrolyte for an all-solid-state battery according to one embodiment of the present invention may have a transition temperature of 270°C to 290°C.

[0012] A solid electrolyte for an all-solid-state battery according to one embodiment of the present invention can be prepared from a composition comprising Li2CO3, V2O5, P2O5 precursor powder, and LiCl.

[0013] In addition, the solid electrolyte for an all-solid-state battery according to the present invention may further include other additional components within a range that does not impair the technical idea of ​​the present invention.

[0014] According to one embodiment of the present invention, a solid electrolyte for an all-solid-state battery includes Li2O, V2O5, P2O5, and LiCl, thereby enabling low-temperature sintering and having excellent ionic conductivity.

[0015] Figure 1 is a drawing schematically showing a cross-section of an all-solid-state battery.

[0016] Figure 2 is a graph showing the results of XRD measurements before sintering of a solid electrolyte according to one embodiment and a comparative example of the present invention.

[0017] Figure 3 is an electron microscope image of a solid electrolyte according to an embodiment of the present invention.

[0018] Hereinafter, with reference to the attached drawings, a preferred embodiment of the present invention will be described in detail to a degree that a person having ordinary skill in the art to which the present invention pertains can easily practice the present invention.

[0019] To clearly explain the present invention, descriptions of parts irrelevant to the present invention have been omitted, and the same reference numerals are assigned to the same components throughout the specification. It should be understood that specific shapes, structures, and characteristics described in the specification may be modified and implemented from one embodiment to another without departing from the spirit and scope of the present invention, and that the location or arrangement of individual components may also be changed without departing from the spirit and scope of the present invention.

[0020] Accordingly, the detailed description set forth below is not intended to be limiting, and the scope of the present invention should be accepted as encompassing the scope claimed in the claims and all scopes equivalent thereto.

[0021] Figure 1 is a drawing schematically showing a cross-section of an all-solid-state battery.

[0022] Referring to Fig. 1, the all-solid-state battery (10) includes a positive electrode (11), a negative electrode (12), and a solid electrolyte layer (13). The solid electrolyte layer (13) is disposed between the positive electrode (11) and the negative electrode (12), and can be in contact with the positive electrode (11) and the negative electrode (12), respectively. The positive electrode (11) and the negative electrode (12) can each have a positive electrode active material layer and a negative electrode active material layer, and the positive electrode active material layer and the negative electrode active material layer can each be in contact with the solid electrolyte layer (13).

[0023] The positive electrode (11) and the negative electrode (12) can each be joined to the solid electrolyte layer (13) by sintering. That is, the positive electrode (11), the negative electrode (12), and the solid electrolyte layer (13) can be sintered as one body.

[0024] In Fig. 1, an all-solid-state battery (10) is illustrated as including one layer each of a positive electrode (11), a negative electrode (12), and a solid electrolyte layer (13), but the present invention is not limited thereto, and an all-solid-state battery may be configured in a form in which the positive electrode, the negative electrode, and the solid electrolyte layer are each composed of multiple layers. Alternatively, the all-solid-state battery may be configured in a form in which a positive electrode, a negative electrode, and a solid electrolyte layer are alternately laminated in multiple layers, a so-called laminated all-solid-state battery.

[0025] The solid electrolyte layer (13) according to one embodiment of the present invention includes an oxide-based electrolyte as a solid electrolyte.

[0026] As oxide-based solid electrolytes, Nasicon type such as LAGP and Garnet type such as LLZO are known, and through continuous research and development, the ionic conductivity of these oxide-based solid electrolytes has been increased to 10 -4 It is known to have improved to the S / cm level.

[0027] However, there are limitations to further improving ionic conductivity with the above-mentioned NASICON-type and garnet-type oxide-based solid electrolytes. Furthermore, these oxide-based solid electrolytes are sintered at high temperatures exceeding 1,000°C. Therefore, even if a certain degree of excellent ionic conductivity can be achieved, as described above, the increased manufacturing costs due to high-temperature sintering inevitably increase. Furthermore, the sintering process required for densification and reduction of interfacial resistance in all-solid-state batteries can lead to unintended thermal decomposition of surrounding materials, such as conductive additives and active materials.

[0028] In one embodiment of the present invention, a novel oxide-based solid electrolyte is used to overcome the limitations of conventional oxide-based solid electrolytes, thereby securing excellent ionic conductivity while lowering the sintering temperature.

[0029] A solid electrolyte for an all-solid-state battery according to one embodiment of the present invention may have an oxide crystal structure. In one embodiment, the solid electrolyte for an all-solid-state battery may include Li, V, P, and Cl. For example, the solid electrolyte for an all-solid-state battery may include Li2O, V2O5, P2O5, and LiCl.

[0030] According to one embodiment of the present disclosure, Li2O can function as a network modifier and plays a role in providing Li ions, thereby improving ionic conductivity.

[0031] According to one embodiment of the present disclosure, V2O5 can function as an auxiliary network former. The addition of V can also enhance ionic conductivity by increasing the incorporation of nonbridging oxygen (NBO) and creating additional pathways in the network structure.

[0032] According to one embodiment of the present disclosure, P2O5 can function as a primary network former. Additionally, P2O5 can play a role in lowering the sintering temperature.

[0033] According to one embodiment of the present disclosure, LiCl can serve to improve ionic conductivity by increasing the amount of Li ions in the solid electrolyte. Furthermore, the Cl ions of LiCl enter the network structure, forming a network structure in which two types of anions coexist, thereby expanding the volume of the network structure.

[0034] A solid electrolyte according to one embodiment of the present invention comprises the above-described Li2O, V2O5, P2O5, and LiCl, thereby providing Li ions and securing a flow path for Li ions while lowering the sintering temperature of the solid electrolyte, thereby obtaining excellent ionic conductivity.

[0035] A solid electrolyte according to one embodiment of the present invention can be prepared from a composition comprising Li2CO3, V2O5, P2O5 precursor powder, and LiCl. According to one embodiment of the present invention, the precursor powder and LiCl are mixed and ground, then melted, and the melt is then cooled and ground into fine particles.

[0036] The transition temperature of the solid electrolyte according to one embodiment of the present invention is about 270°C to about 290°C.

[0037] A solid electrolyte according to one embodiment of the present invention may include an oxide-based electrolyte having a NASICON crystal structure and a sintering agent. In one embodiment, the solid electrolyte may include 95 mass% or more of the oxide-based electrolyte and 5 mass% or less of the sintering agent.

[0038] According to one embodiment of the present invention, when the solid electrolyte is sintered at 600°C to 610°C, the ionic conductivity at room temperature is about 1.03×10 -4 About 2.50×10 -4 It represents S / cm.

[0039] Hereinafter, the present invention will be described in more detail with reference to specific embodiments and test examples of the present invention.

[0040]

[0041] Example

[0042] A precursor powder for the production of a solid electrolyte was prepared by mixing 25 mol% of Li2CO3, 550 mol% of V2O, and 525 mol% of P2O. 10 to 20 mol% of LiCl was added to the precursor powder, mixed, and then transferred to an Al crucible and melted at 900°C for 30 minutes. The homogenized melt was then poured onto a brass quenching roller, cooled to room temperature, crushed, and sieved to obtain a powder in the form of cullet. The cullet was then crushed in a mortar with a pistol and jet-milled to reduce the powder particle size to less than 200 μm.

[0043]

[0044] Comparative example

[0045] A precursor powder similar to the example was prepared, but LiCl was added in an amount of 0 mol% to 5 mol% relative to the total and mixed. Thereafter, a powder in the form of a glassy substance was obtained through the same process as the example.

[0046] The composition ratio of the solid electrolyte according to each of the examples and comparative examples described above is as described in Table 1.

[0047] Precursor powder composition (mol%)LiCl addition amount (mol%)Melting temperature (℃)Li2OV2O5P2O5Example 125502520900Example 225502515900Example 325502510900Comparative example 12550255900Comparative example 22550253900Comparative example 3255025-900

[0048]

[0049] For the solid electrolytes according to each of the examples and comparative examples manufactured as described above, the characteristics were confirmed through X-ray diffraction (XRD), digital thermal analysis (DTA), and high-temperature microscopy (HTM) imaging. In addition, the solid electrolyte pellets were manufactured and sintered at 390°C for 3 hours, and the characteristics after sintering were confirmed through SEM and XRD. Fig. 2 is a graph showing the results of XRD measurements before sintering of the solid electrolytes according to one example and comparative example of the present invention.

[0050] Referring to FIG. 2, it can be confirmed that the solid electrolyte according to one embodiment of the present invention has an amorphous state rather than a glass-ceramic state. Accordingly, the solid electrolyte according to one embodiment of the present invention may have a beneficial effect on fluidity during sintering.

[0051] FIG. 3 is an electron microscope image of a solid electrolyte according to one embodiment of the present invention, each image showing the sintered density after sintering. Referring to FIG. 3, it can be confirmed that the density generally decreases as the amount of LiCl added to Li2O, V2O5, and P2O5 increases.

[0052] The transition temperature, crystallization temperature, and ionic conductivity of the solid electrolyte according to each example and comparative example are as described in Table 2.

[0053]

[0054] Transition temperature (℃)Crystallization temperature (℃)Ionic conductivity (S / cm)Example 12673951.70×10 -4 Example 22713861.03×10 -4 Example 32784062.48×10 -4 Comparative example 12753862.21×10 -6 Comparative example 22814325.99×10 -6 Comparative example 33064462.00×10 -5

[0055]

[0056] Referring to Table 2, it is confirmed that the solid electrolyte according to the example in which 10 mol% or more of LiCl is added has a transition temperature of 267 to 278°C and a crystallization temperature of 386 to 406°C. In contrast, the solid electrolyte according to the comparative example has a transition temperature of 275°C or higher and a crystallization temperature of 386 to 446°C, which are relatively higher temperatures than the example. Thus, it can be confirmed that the solid electrolyte according to the example of the present invention has low-temperature characteristics. According to the example of the present invention, the electrochemical stability of the all-solid-state battery can be improved due to the low-temperature characteristics, and the manufacturing cost of the solid electrolyte can be reduced. In addition, referring to Table 2, the solid electrolyte according to the example in which LiCl is added has excellent ionic conductivity compared to the comparative example. In particular, the solid electrolyte of Example 3 has an ionic conductivity of 2.48×10 -4It is confirmed to have an excellent ionic conductivity of S / cm. That is, it can be confirmed that the ionic conductivity of the solid electrolyte can be greatly improved when the solid electrolyte containing Li2O, V2O5, P2O5, and LiCl has a specific composition ratio.

[0057] In this way, according to one embodiment of the present invention, the solid electrolyte comprises Li2O, V2O5, P2O5, and LiCl, thereby enabling low-temperature sintering while improving ionic conductivity.

[0058] Although the present invention has been described above with specific details such as specific components and limited examples, the above examples are provided only to help a more general understanding of the present invention, and the present invention is not limited thereto, and those with ordinary knowledge in the technical field to which the present invention pertains can make various modifications and variations based on this description.

[0059] Therefore, the idea of ​​the present invention should not be limited to the embodiments described above, and all things that are modified equally or equivalently to the claims described below as well as the claims are considered to fall within the scope of the idea of ​​the present invention.

Claims

1. As a solid electrolyte for all-solid-state batteries, Containing Li2O, V2O5, P2O5, and LiCl Solid electrolyte for all-solid-state batteries.

2. In paragraph 1, The molar ratio of Li2O, V2O5 and P2O5 is 1:2:

1. Solid electrolyte for all-solid-state batteries.

3. In paragraph 1, Containing 10 mol% LiCl, Solid electrolyte for all-solid-state batteries.

4. In paragraph 1, Ionic conductivity is 2.40×10 -4 2.50×10 -4 S / cm, Solid electrolyte for all-solid-state batteries.

5. In paragraph 1, The transition temperature is 270℃ to 290℃, Solid electrolyte for all-solid-state batteries.

6. In paragraph 1, A composition prepared from a composition comprising Li2CO3, V2O5, P2O5 precursor powder and LiCl. Solid electrolyte for all-solid-state batteries.

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