Solid electrolyte for all-solid-state battery

Abstract

The present invention relates to a solid electrolyte for an all-solid-state battery. A solid electrolyte for an all-solid-state battery according to an embodiment of the present invention is composed of an oxide containing Li, Mo, B, and Cl.

Description

Solid electrolyte for all-solid-state batteries

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

[0002] Secondary batteries are used in a variety of fields, from IT devices such as mobile phones to electric vehicles and energy storage devices.

[0003] Lithium-ion batteries, which use liquid electrolytes, are the most widely used secondary batteries. 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 lithium-ion batteries using solid electrolytes has been underway to improve the safety of lithium-ion batteries. Solid electrolytes for all-solid-state lithium-ion batteries include polymer electrolytes, oxide electrolytes, and sulfide electrolytes. Sulfide-based solid electrolytes exhibit excellent electrochemical performance due to their high ionic conductivity and particle deformation capabilities. However, they react with moisture in the air to generate toxic hydrogen sulfide gas. Polymer electrolytes have the advantage of a relatively simple process and the ability to utilize existing lithium-ion battery processes, but their significantly low ionic conductivity is a drawback.

[0005] Oxide electrolytes have lower ionic conductivity than sulfide electrolytes, but are relatively high, and have the advantage of excellent safety. Currently, there are 10 types of electrolytes, including LAGP and LLZO. -4 Oxide-based solid electrolytes with high ionic conductivities exceeding S / cm are being developed. However, these solid electrolytes have limitations in enhancing electrochemical performance due to their narrow electrochemical voltage range and high-temperature sintering process (over 1,000°C). This can increase production costs and limit their usability.

[0006] The present invention is intended to solve the problems of the above-described prior art, and its purpose is to provide an oxide-based 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 is composed of an oxide containing Li, Mo, B, and Cl.

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

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

[0010] According to one embodiment of the present invention, a solid electrolyte for an all-solid-state battery 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 may be 10:1:14.

[0012] A solid electrolyte for an all-solid-state battery according to one embodiment of the present invention is LCB (Li4B7O 12 Cl) crystals and LMO (Li2MoO4) crystals.

[0013] A solid electrolyte for an all-solid-state battery according to one embodiment of the present invention can be manufactured from a precursor powder including Li2CO3, MoO3B2O3, and LiCl.

[0014] A solid electrolyte for an all-solid-state battery according to one embodiment of the present invention has an ionic conductivity of 3.83×10 -5 It can be more than S / cm.

[0015] According to one embodiment of the present invention, a solid electrolyte for an all-solid-state battery is an oxide-based solid electrolyte, which is formed of an oxide containing Li, Mo, B, and Cl, thereby enabling low-temperature sintering and having excellent ionic conductivity.

[0016] Figure 1 is a drawing showing an example of a cross-section of an all-solid-state battery.

[0017] FIG. 2 is a graph showing the results of XRD analysis of pre-sintering powder of a solid electrolyte according to embodiments of the present invention.

[0018] Figure 3 is a graph showing the results of XRD analysis of powder before sintering of solid electrolyte according to comparative examples of the present invention.

[0019] Figure 4 is a graph showing the results of XRD analysis after sintering of a solid electrolyte according to embodiments of the present invention.

[0020] Figure 5 is a graph showing the results of XRD analysis after sintering of solid electrolytes according to comparative examples of the present invention.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] Figure 1 is a drawing showing an example of a cross-section of an all-solid-state battery.

[0025] Referring to FIG. 1, an all-solid-state lithium ion 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 layer (11) and the negative electrode layer (12), and can be in contact with the positive electrode layer (11) and the negative electrode layer (12), respectively. The positive electrode layer (11) and the negative electrode layer (12) can each have a current collector and an active material layer, and the active material layer of the electrode layer is formed by being applied to at least one surface of each current collector, and can be in contact with the solid electrolyte layer (13).

[0026] The positive electrode layer (11) and the negative electrode layer (12) of the all-solid-state lithium ion battery (10) may be connected to external electrodes (14, 15), respectively. The external electrodes (14, 15) may be connected to the exposed terminals of the current collectors of the positive electrode layer (11) and the negative electrode layer (12), thereby serving as positive and negative electrodes, respectively. In addition, the all-solid-state lithium ion battery (10) may further include a case (not shown) that prevents the positive electrode layer (11) and the negative electrode layer (12) from being exposed to the outside.

[0027] According to one embodiment of the present invention, the all-solid-state lithium ion battery (10) may be configured as a so-called multilayer ceramic battery (MLCB) in which a cathode layer (11), an anode layer (12), and a solid electrolyte layer (13) are each formed of multiple layers and alternately laminated. In Fig. 1, the cathode layer (11) and the anode layer (12) are alternately arranged and a solid electrolyte layer (13) is arranged between them. However, the arrangement of the cathode layer (11), the anode layer (12), and the solid electrolyte layer (13) is not limited to what is illustrated.

[0028] According to one embodiment of the present invention, an all-solid-state lithium ion battery (10) can be formed in a small chip shape and can be used in small electronic devices such as wearable electronic devices.

[0029] According to one embodiment of the present invention, the positive electrode layer (11), the negative electrode layer (12), and the solid electrolyte layer (13) can be integrally sintered. That is, each component of the all-solid-state lithium ion battery (10) can be integrally sintered in a laminated form. To achieve this, low-temperature sintering is required, and therefore, the solid electrolyte is required to have excellent low-temperature characteristics.

[0030] The solid electrolyte layer (13) according to one embodiment of the present invention includes an oxide-based electrolyte as a solid electrolyte.

[0031] 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.

[0032] However, there are limits 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. In particular, when high-temperature sintering is performed, it becomes practically impossible to sinter the solid electrolyte integrally with the positive and negative electrode layers.

[0033] In one embodiment of the present invention, a novel oxide-based solid electrolyte is used that overcomes the limitations of conventional oxide-based solid electrolytes, thereby securing excellent ionic conductivity while lowering the sintering temperature.

[0034] A solid electrolyte for an all-solid-state battery according to one embodiment of the present invention may be composed of an oxide containing Li, Mo, B, and Cl. Specifically, the solid electrolyte according to one embodiment of the present invention may contain Li2O, MoO3, B2O3, and LiCl.

[0035] In the composition of the solid electrolyte, Li2O can function as a network modifier and improve ionic conductivity by providing Li ions.

[0036] In the composition of the solid electrolyte, MoO3 and B2O3 can function as network formers and, as low-temperature components, play a role in lowering the sintering temperature.

[0037] In the composition of a solid electrolyte, LiCl enhances ionic conductivity by increasing the concentration of Li and Cl ions. The increased Cl ions can migrate as free ions within the network structure, increasing the lattice constant of the oxide crystal structure. This, in turn, widens the path for Li ions to migrate within the crystal structure, further enhancing ionic conductivity.

[0038] According to one embodiment of the present invention, the composition ratio of Li2O, MoO3 and B2O3 may be 10:1:14.

[0039] In one embodiment, the solid electrolyte may satisfy Equation 1 based on the molar ratio.

[0040] [Mathematical Formula 1]

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

[0042] In another embodiment, the solid electrolyte may satisfy Equation 2 based on the molar ratio.

[0043] [Equation 2]

[0044] LiCl / (Li2O + MoO3 + B2O3)≥ 0.10

[0045] In another embodiment, the solid electrolyte may satisfy Equation 3 based on the molar ratio.

[0046] [Equation 3]

[0047] 0.10 ≤ LiCl / (Li2O + MoO3+ B2O3) ≤ 0.20

[0048] A solid electrolyte according to one embodiment of the present invention is LCB (lithium chloroborosite, Li4B7O 12 Cl) crystals and LMO (lithium molybdate, Li2MoO4) crystals.

[0049] In this way, the solid electrolyte for an all-solid-state battery according to one embodiment of the present invention is composed of oxides containing Li, Mo, B, and Cl, and thus can be sintered at temperatures of around 500°C while exhibiting excellent ionic conductivity. Furthermore, since low-temperature sintering is possible, the solid electrolyte layer can be sintered simultaneously with the electrode, thereby simplifying the process and improving quality.

[0050] A solid electrolyte according to one embodiment of the present invention can be manufactured from a precursor powder including Li2CO3, MoO3, B2O3, and LiCl. Specifically, a solid electrolyte according to one embodiment of the present invention can be manufactured through the following process.

[0051] (1) Prepare precursor powder containing Li2CO3, MoO3, B2O3, and LiCl.

[0052] (2) The precursor powder is mixed uniformly through dry or wet mixing.

[0053] (3) The mixture of precursor powders is melted at a temperature of 1,000°C to 1,200°C.

[0054] (4) Rapidly cool the melt to room temperature.

[0055] (5) The cooled melt is crushed into fine particles.

[0056] (6) The crushed material is pelletized and sintered at a temperature of approximately 500°C.

[0057] The solid electrolyte obtained through the above process has a molecular weight of about 9.34×10 at room temperature. -8 It exhibits an ionic conductivity of 3.83×10 -5 It exhibits an ionic conductivity of more than S / cm.

[0058] Meanwhile, the solid electrolyte according to one embodiment of the present invention possesses excellent ionic conductivity and non-hygroscopicity. Accordingly, even if moisture enters the all-solid-state battery, the battery's performance is not degraded and it maintains stable and excellent performance.

[0059]

[0060] Example

[0061] Precursor powders (batch size 100 g) containing Li2CO3, MoO3, B2O3, and LiCl 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 types of precursor powders.

[0062] To ensure homogeneity of the solid electrolyte, precursor powders were sufficiently mixed through ball milling or mechanical mixing. The precursor powders were then placed in a crucible and melted at approximately 1,000°C for approximately 30 minutes. The melt was rapidly cooled on a quenching roller, pulverized, and then sieved to obtain micro-sized fine powders. The powders were then pelletized and sintered at approximately 500°C for approximately 3 hours, producing six types of solid electrolytes.

[0063] The composition of the solid electrolyte manufactured as described above is as described in Table 1. The composition ratio of the solid electrolyte was calculated based on the remaining components excluding LiCl for comparison with the comparative example described below, that is, based on the sum of the remaining components excluding LiCl being 100 mol%.

[0064] Classification Solid electrolyte composition (mol%) Li2OMoO3B2O3LiCl Example 1 404563 Example 2 404565 Example 3 404567 Example 4 4045610 Example 5 4045615 Example 6 4045620

[0065] Comparative example

[0066] Precursor powders (batch size 100 g) containing Li2CO3, MoO3, and B2O3 were prepared. At this time, a total of five types of precursor powders were prepared by partially changing the mixing ratio of Li2CO3, MoO3, and B2O3.

[0067] Afterwards, a solid electrolyte was manufactured through the same process as in the example.

[0068] The composition of the solid electrolyte according to the comparative example manufactured as above is as described in Table 2.

[0069] Classification Solid electrolyte composition (mol%) Li2OMoO3B2O3Comparative example 140456Comparative example 245550Comparative example 350644Comparative example 435560Comparative example 555540

[0070] FIG. 2 is a graph showing the results of XRD analysis on pre-sintering powder of a solid electrolyte according to embodiments of the present invention, and FIG. 3 is a graph showing the results of XRD analysis on pre-sintering powder of a solid electrolyte according to comparative examples of the present invention.

[0071] Referring to FIGS. 2 and 3, the XRD graphs for the pre-sintered powder of the solid electrolyte according to the embodiments and comparative examples of the present invention do not show any crystalline peaks. This indicates that the pre-sintered powder is in an amorphous state, and in such an amorphous state, it is difficult to form a lithium ion path that enables ion diffusion.

[0072] FIG. 4 is a graph showing the results of XRD analysis after sintering of a solid electrolyte according to embodiments of the present invention, and FIG. 5 is a graph showing the results of XRD analysis after sintering of a solid electrolyte according to comparative examples of the present invention.

[0073] Referring to FIGS. 4 and 5, the XRD graph of the solid electrolyte after sintering shows multiple crystal peaks. Specifically, the solid electrolyte according to the embodiments of the present invention is LCB (lithium chloroborosite, Li4B7O 12 Cl), LMO (lithium molybdate, Li2MoO4), etc., and the solid electrolyte according to the comparative examples of the present invention has crystals of LMO (lithium molybdate, Li2MoO4), LBO (lithium metaborate, LiBO2), etc. In such a crystallization structure, ions flow smoothly, resulting in excellent ionic conductivity. On the other hand, in Comparative Examples 3 and 5, crystallization did not occur after sintering, so it was not indicated in the graph of Fig. 5, and ionic conductivity was not measured as described below.

[0074] Next, the lattice constant of the LMO crystal of the solid electrolyte according to each example is as shown in Table 5.

[0075] Classification 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

[0076] Referring to Table 3, it can be confirmed that the lattice constant of LMO generally increases as the amount of LiCl added increases. In particular, when 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. As the lattice constant increases, the mobility of Li ions in the crystal structure can be improved, which can lead to improved ionic conductivity.

[0077] Next, the transition temperature and crystallization temperature measured through DTA analysis of the solid electrolyte according to each example and comparative example, and the results of ionic conductivity measurement are as shown in Table 4.

[0078] Transition temperature (Tg, ℃)Crystallization temperature (Tc, ℃)Ionic conductivity (S / cm)Example 14165014.46×10 -6 Example 24114993.53×10 -7 Example 34064819.34×10 -8 Example 43804715.75×10 -5 Example 53804573.83×10 -5 Example 63724617.62×10 -5 Comparative example 14245025.30×10 -8 Comparative example 23834461.69×10 -8 Comparative Example 3342417 - Comparative Example 44585421.23×10 -8 Comparative example 5306362-

[0079] Referring to Table 4, it can be seen that the examples have transition temperatures of about 420°C or lower and crystallization temperatures of about 500°C or lower, which are generally lower than those of the comparative examples. In particular, the solid electrolytes of Examples 4 to 6 exhibit excellent low-temperature characteristics, with transition temperatures and crystallization temperatures of about 380°C or lower and about 471°C or lower, respectively.

[0080] In this way, according to embodiments of the present invention, low-temperature sintering is possible through excellent low-temperature characteristics.

[0081] Referring to Table 4, it can be confirmed that the examples in which LiCl was added had higher ionic conductivity than the comparative examples. Specifically, in the comparative examples, the ionic conductivity was not measured (Comparative Examples 3 and 5) or was 1.2×310 -8 5.30×10 -8 While the ionic conductivity is low, at the order of S / cm, in the examples it is 9.34×10 -8 It shows an ionic conductivity of more than S / cm. In particular, the ionic conductivity in Examples 4 to 6 is 3.83×10 -5 7.62×10 -5 As S / cm, 10 -5It exhibits high ionic conductivity at the level of S / cm.

[0082] In this way, it can be confirmed that the ionic conductivity is improved as the solid electrolyte contains LiCl in addition to Li2O, MoO3, and B2O3. Furthermore, it can be confirmed that the ionic conductivity of the solid electrolyte is significantly improved when the ratio of LiCl to the sum of Li2O, MoO3, and B2O3 based on the molar ratio is 0.10 or more (Examples 4 to 6).

[0083] As described above, this is presumed to be a result of improved ion mobility as the lattice constant of the crystals included in the solid electrolyte increases with the addition of LiCl.

[0084] 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.

[0085] 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, Composed of oxides containing Li, Mo, B and Cl Solid electrolyte.

2. In paragraph 1, Based on the molar ratio, LiCl / (Li2O + MoO3+ B2O3)≥ 0.03, Solid electrolyte.

3. In paragraph 2, Based on the molar ratio, LiCl / (Li2O + MoO3+ B2O3)≥ 0.10, Solid electrolyte.

4. In paragraph 3, Based on the molar ratio, Satisfying 0.10 ≤ LiCl / (Li2O + MoO3+ B2O3) ≤ 0.20, Solid electrolyte.

5. In paragraph 2, The composition ratio of Li2O, MoO3 and B2O3 is 10:1:

14. Solid electrolyte.

6. In paragraph 1, LCB(Li4B7O 12 Cl) crystals and LMO (Li2MoO4) crystals, Solid electrolyte.

7. In paragraph 1, Prepared from precursor powders containing Li2CO3, MoO3B2O3 and LiCl, Solid electrolyte.

8. In paragraph 1, Ionic conductivity is 3.83×10 -5 S / cm or more, Solid electrolyte.

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