Solid electrolyte for all solid-state battery and solid-state battery comprising the same

Abstract

This invention relates to a solid electrolyte for an all-solid-state battery and an all-solid-state battery comprising the same. According to one embodiment of the invention, the solid electrolyte for an all-solid-state battery is formed from an oxide comprising Li, Mg, Zn, P, and Cl.

Description

[Technical Field]

[0001] This invention relates to a solid electrolyte for an all-solid-state battery and an all-solid-state battery comprising the same. [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 excellent electrochemical performance due to their high ionic conductivity and 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, their ionic conductivity is relatively high, offering the advantage of excellent safety. Currently, oxide-based solid electrolytes with high ionic conductivity (above 10⁻⁴ S / cm), such as LAGP and LLZO, are under development. However, these solid electrolytes face limitations in improving electrochemical performance due to their narrow electrochemical voltage range and high-temperature sintering processes (above 1000℃), leading to increased production costs and potentially limited availability. [Summary of the Invention]

[0006] The present invention is intended to solve the problems of the prior art described above, and its object 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, and an all-solid-state battery containing the same.

[0007] According to an embodiment of the present invention, the solid electrolyte for an all-solid-state battery is formed from an oxide comprising Li, Mg, Zn, P and Cl.

[0008] According to one embodiment of the present invention, it may contain more than 8 mol% LiCl.

[0009] According to one embodiment of the present invention, it may contain less than 14 mol% LiCl.

[0010] According to an embodiment of the present invention, the solid electrolyte for an all-solid-state battery may contain 28-33 mol% Li2O, 17-25 mol% MgO, 4-12 mol% ZnO and 28-33 mol% P2O5.

[0011] According to an embodiment of the present invention, the solid electrolyte for an all-solid-state battery may include lithium zinc phosphate (LiZnPO4) crystals and lithium magnesium zinc (Li2MgZn) crystals.

[0012] According to an embodiment of the present invention, the solid electrolyte for an all-solid-state battery can be manufactured from precursor powders containing Li2CO3, MgO, ZnO, P2O5 and LiCl.

[0013] The ionic conductivity of the solid electrolyte for an all-solid-state battery according to an embodiment of the present invention can be 5×10-5S / cm or higher.

[0014] An all-solid-state battery according to an embodiment of the present invention includes an anode layer, a cathode layer, and a solid electrolyte layer. Here, the solid electrolyte layer may be formed of an oxide comprising Li, Mg, Zn, P, and Cl.

[0015] Furthermore, the solid electrolyte for all-solid-state batteries according to the present invention may further include other additional components without impairing the technical concept of the present invention.

Implementation Method

[0025] 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.

[0026] 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.

[0027] Therefore, the detailed description that follows is not intended to be restrictive, but should be understood as including the scope of the invention as claimed in the claims and all equivalent scopes thereof.

[0028] Figure 1 is a schematic perspective view of the all-solid-state battery, and Figure 2 is a schematic cross-sectional view of the all-solid-state battery. The all-solid-state battery of one embodiment disclosed herein is a so-called multilayer ceramic battery, which can be formed in the form of a wafer and can be used in small electronic devices such as wearable electronic devices.

[0029] Referring to Figures 1 and 2, the all-solid-state 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 can be coated and formed on at least one side of each current collector and contact the solid electrolyte layer (13).

[0030] In one embodiment, the anode layer (11) can be formed by coating at least one side of the anode current collector with an anode active material layer, and the cathode layer (12) can be formed by coating at least one side of the cathode current collector with a cathode active material layer. For example, the electrode layer located at the uppermost segment based on the stacking direction can be formed by coating one side of the anode current collector with an anode active material layer, and the electrode layer located at the lowermost segment can be formed by coating one side of the cathode current collector with a cathode active material layer. Moreover, the electrode layer located between the uppermost and lowermost segments can be formed by coating both sides of the anode current collector with an anode active material layer, or by coating both sides of the cathode current collector with a cathode active material layer.

[0031] The anode active material layer may contain an anode active material and may optionally contain a solid electrolyte. Furthermore, the anode active material layer may optionally contain additives such as binders or conductive agents.

[0032] The anode active material is not particularly limited as long as it can ensure sufficient capacity of the all-solid-state battery (10). For example, the anode active material may include lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium iron phosphorus oxide, lithium manganese oxide, or a combination thereof.

[0033] As a conductive agent for the anode active material layer, it is not particularly restricted as long as it does not induce chemical changes in the all-solid-state battery (10) and has conductivity. For example, as a conductive agent, carbon-based materials such as natural graphite or artificial graphite, carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, and summer black, conductive fibers such as carbon fiber or metal fiber, fluorinated carbon, aluminum powder, nickel powder, conductive zinc oxide, potassium titanate, conductive metal oxides such as titanium oxide, and conductive materials such as polyphenylene derivatives can be used.

[0034] To improve the bonding strength between the active material and the conductive agent, an adhesive can be used. As an adhesive, polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene-butadiene rubber, fluororubber, or various copolymers can be used.

[0035] As the anode current collector, a porous body such as a mesh or a perforated mesh shape can be used, and porous metal plates such as stainless steel, nickel, and aluminum can be used. Furthermore, to prevent oxidation, the anode current collector can be coated with an oxidation-resistant metal or alloy film.

[0036] The cathode active material layer may contain cathode active material and may optionally contain solid electrolyte. Furthermore, the cathode active material layer may optionally contain additives such as binders or conductive agents.

[0037] The cathode active material may be carbon-based materials, silicon, silicon oxides, silicon alloys, silicon-carbon composites, tin, tin alloys, tin-carbon composites, metal oxides or combinations thereof, and may contain lithium metal and / or lithium metal alloys.

[0038] The cathode active material layer may also optionally include conductive agents and adhesives as described in the anode active material layer.

[0039] As the cathode current collector, a porous body such as a mesh or a perforated shape can be used, and porous metal plates such as stainless steel, nickel, and aluminum can be used. Furthermore, to prevent oxidation, the cathode current collector can be coated with an oxidation-resistant metal or alloy film.

[0040] In one embodiment, an edge insulating layer (not shown) may be further disposed along the edges of the anode layer (11) and the cathode layer (12). The edge insulating layer is located on the solid electrolyte layer (13) and may be formed by laterally adjaculating the edges of the anode active material layer or the cathode active material layer. Therefore, the edge insulating layer may be located in the same layer in the anode layer (11) and the cathode layer (12), respectively.

[0041] The edge insulation layer may contain an insulating material with low ionic conductivity. For example, the insulating material may be a polyolefin such as polyethylene or polypropylene, a polyester such as polyethylene terephthalate (PET), a polyurethane, or a polyimide.

[0042] Furthermore, the edge insulating layer may contain the oxide-based solid electrolyte used in the solid electrolyte layer (13). However, the material contained in the edge insulating layer is not limited to this and may contain various materials.

[0043] The anode layer (11) and cathode layer (12) of the all-solid-state battery (10) can be connected to external electrodes (14, 15). 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 becoming the anode and cathode respectively.

[0044] According to one embodiment of the present invention, the anode layer (11), cathode layer (12), and solid electrolyte layer (13) of the all-solid-state battery (10) are formed by each being formed in a plurality of layers and stacked alternately in a plurality of layers to form a battery stack. FIG2 shows a configuration in which the anode layer (11) and cathode layer (12) are arranged alternately and the solid electrolyte layer (13) is arranged therebetween, but the configuration of the anode layer (11), cathode layer (12), and solid electrolyte layer (13) is not limited to that shown in the figure. In one embodiment, a protective layer (not shown) may be formed from an insulating material in the upper and lower sections of the battery stack.

[0045] According to one embodiment of the present invention, the all-solid-state battery (10) may include a housing (16) configured to surround the battery stack. External electrodes (14, 15) may be disposed at both ends of the housing (16).

[0046] The external electrodes (14, 15) may comprise a conductive metal and glass. The conductive metal may be, for example, a conductive metal comprising copper (Cu), nickel (Ni), tin (Sn), palladium (Pd), platinum (Pt), gold (Au), silver (Ag), tungsten (W), titanium (Ti), lead (Pb), or an alloy thereof.

[0047] The glass composition contained in the external electrodes (14, 15) may be a mixture of oxides. The glass composition may include, for example, silicon oxide, boron oxide, aluminum oxide, transition metal oxide, alkali metal oxide, alkaline earth metal oxide, or a combination thereof. Here, the transition metal may be selected from one or more of zinc (Zn), titanium (Ti), copper (Cu), vanadium (V), manganese (Mn), iron (Fe), and nickel (Ni); the alkali metal may be selected from one or more of lithium (Li), sodium (Na), and potassium (K); and the alkaline earth metal may be selected from one or more of magnesium (Mg), calcium (Ca), strontium (Sr), and barium (Ba).

[0048] The method for forming the external electrodes (14, 15) is not particularly limited. For example, they can be formed by impregnating the battery stack with a conductive paste containing a conductive metal and glass, or by printing the conductive paste onto the surface of the battery stack using screen printing or gravure printing. In addition, various methods can be used, such as coating the surface of the battery stack with a conductive paste or transferring a dried film formed by drying the conductive paste onto the battery stack.

[0049] The housing (16) can protect the battery stack containing the anode layer (11), cathode layer (12) and solid electrolyte layer (13) from being exposed to the outside. In order to protect the internal structure from external moisture, heat, electricity, etc., the housing (16) needs to have moisture permeability, heat resistance, insulation, etc., as well as long-term stability and high resistance to chemical corrosion.

[0050] According to one embodiment of the present invention, an all-solid-state battery (10) can be manufactured by laminating an anode layer (11), a cathode layer (12), a solid electrolyte layer (13), a casing (16), etc., and then sintering them into one piece. In order not to degrade the characteristics of the electrode layers, etc., each component including the solid electrolyte layer (13) needs to be sintered at a low temperature, for example, below 700°C.

[0051] Thus, the solid electrolyte of the all-solid-state battery (10) according to an embodiment of the present invention needs to have excellent low-temperature characteristics.

[0052] According to an embodiment of the present invention, the solid electrolyte layer (13) contains an oxide-based electrolyte as a solid electrolyte.

[0053] 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.

[0054] 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, under high-temperature sintering conditions, it is practically impossible to sinter the solid electrolyte, anode layer, and cathode layer together.

[0055] 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.

[0056] According to an embodiment of the present invention, the solid electrolyte for an all-solid-state battery can be formed from oxides containing Li, Mg, Zn, P and Cl. Specifically, according to an embodiment of the present invention, the solid electrolyte can contain Li2O, MgO, ZnO, P2O5 and LiCl.

[0057] In solid electrolytes, Li2O can function as a network modifier, providing Li ions to improve ionic conductivity.

[0058] In solid electrolytes, MgO can function as a network modifier, thereby increasing the coefficient of thermal expansion and adhesion.

[0059] In solid electrolytes, ZnO can function as an intermediate. That is, depending on the concentration of ZnO in the composition, it can function as a network forming agent or a network modifying agent.

[0060] In solid electrolytes, P2O5 can function as a network forming agent and as a low-temperature component to reduce sintering temperature.

[0061] In solid electrolytes, LiCl plays a role in improving ionic conductivity by increasing the number of Li and Cl ions. At this time, the increased Cl ions can move into the network structure as free ions, thereby increasing the lattice constant of the oxide crystal structure. Therefore, the movement path of Li ions in the crystal structure can be made wider, thereby further improving ionic conductivity.

[0062] In one embodiment, the solid electrolyte may contain more than 8 mol% LiCl.

[0063] In one embodiment, the solid electrolyte may contain less than 14 mol% LiCl.

[0064] According to an embodiment of the present invention, the solid electrolyte may contain 28-33 mol% Li2O, 17-25 mol% MgO, 4-12 mol% ZnO and 28-33 mol% P2O5.

[0065] According to an embodiment of the present invention, the solid electrolyte may include lithium zinc phosphate (LiZnPO4) crystals and lithium magnesium zinc (Li2MgZn) crystals.

[0066] 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, Mg, Zn, P and Cl, thereby enabling sintering at a temperature of approximately 700°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.

[0067] The solid electrolyte according to an embodiment of the present invention can be manufactured from precursor powders containing Li2CO3, MgO, ZnO, P2O5 and LiCl. Specifically, the solid electrolyte according to an embodiment of the present invention can be manufactured by the following process.

[0068] (1)Prepare precursor powder containing Li2CO3, MgO, ZnO, P2O5 and LiCl.

[0069] (2)The precursor powder is mixed uniformly by dry or wet mixing.

[0070] (3) Melt the mixture of precursor powders in an aluminum crucible at a temperature of about 1,100°C for 30 minutes.

[0071] (4)Cool the molten material down to room temperature quickly.

[0072] (5)Pulverize the cooled melt into microparticles.

[0073] (6) The pulverized material is granulated and sintered at a temperature of about 700°C.

[0074] The solid electrolyte obtained by the above process exhibits an ionic conductivity of approximately 5 × 10⁻⁵ S / cm or higher at room temperature. More preferably, the solid electrolyte exhibits an ionic conductivity of 1.4 × 10⁻⁴ S / cm or higher.

[0075] On the other hand, the solid electrolyte according to an embodiment of the present invention has excellent ionic conductivity and non-hygroscopicity. 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.

[0076] Experimental Example

[0077] Precursor powders containing Li2CO3, MgO, ZnO, P2O5 and LiCl (batch size 200g) were prepared. At this time, a total of six precursor powders were prepared by setting different amounts of Li2CO3, MgO, ZnO, P2O5 and LiCl.

[0078] To ensure the homogeneity of the solid electrolyte, the precursor powder was thoroughly mixed by ball milling or mechanical mixing. Furthermore, the precursor powder was placed in an aluminum crucible and melted at a temperature of approximately 1,100°C for about 30 minutes. The melt was then rapidly cooled on a quenching roller, pulverized using a planetary ball mill, and sieved to obtain micron-sized fine powder.

[0079] The composition of the fine powder manufactured as described above is shown in Table 1.

[0080] [Table 1] distinguish Composition of solid electrolytes (mol%) Li2O MgO ZnO P2O5 LiCl Example 1 32.0 17.5 10.5 32.0 8.0 Example 2 31.0 22.6 4.4 31.0 11.0 Example 3 28.7 23.4 5.2 28.7 14.0 Comparative Example 1 23.5 43.5 32.9 - - Comparative Example 2 31.0 31.0 30.0 - 8.0 Comparative Example 3 35.1 17.7 12.2 35.1 - Comparative Example 4 35.2 25.2 4.4 35.2 - Comparative Example 5 28.3 22.2 4.2 28.3 17.0 Comparative Example 6 27.0 22.1 3.9 27.0 20.0

[0081] For the composition of the solid electrolyte in Table 1, a water stability test was performed by immersing it in water for 120 hours. At the same time, X-ray diffraction (XRD), differential thermal analysis (DTA), Fourier transform infrared spectroscopy (FT-IR), and high temperature microscopy (HTM) analysis were performed.

[0082] Figure 3 is a graph showing the XRD analysis results of the solid electrolyte powders before sintering according to the embodiments and comparative examples of the present invention. Specifically, Figure 3 shows the XRD analysis results of the solid electrolyte powders before sintering according to Examples 1 and 2, and Comparative Examples 3 and 4.

[0083] Referring to Figure 3, the XRD pattern of the solid electrolyte powder before sintering according to the aforementioned embodiments and comparative examples does not show a crystallization peak. This indicates that the powder before sintering is in an amorphous state, in which it is difficult to form a lithium-ion pathway that enables ion diffusion. Although not shown, the composition of Comparative Example 6 is glass-ceramic, not amorphous.

[0084] The results of the moisture stability test and the temperature characteristics measured by DTA and HTM analysis are shown in Table 2. On the other hand, as shown in the table below, for Comparative Examples 1, 2 and 5 with insufficient moisture stability and Comparative Example 6 which is not amorphous, the temperature characteristics were not measured and the sintering process described later was not performed.

[0085] [Table 2] distinguish Moisture stability Transfer temperature (Tg, ℃) Crystallization temperature (Tc, ℃) Sintering temperature (T) sint (℃) softening point (T) soft (℃) Half Ball (T) half-ball (℃) Example 1 qualified 379 452 451 773 776 Example 2 qualified 407 479 487 787 789 Example 3 qualified 395 463 453 777 780 Comparative Example 1 Unqualified - - - - - Comparative Example 2 Unqualified - - - - - Comparative Example 3 qualified 396 471 462 768 770 Comparative Example 4 qualified 421 493 498 783 794 Comparative Example 5 Unqualified - - - - - Comparative Example 6 - - - - - -

[0086] Referring to Table 2, all the examples and comparative examples for which analysis was performed showed a transfer temperature of 379°C to 421°C and a crystallization temperature of 452°C to 492°C. Among them, the transfer temperature and crystallization temperature of the compositions of Examples 1 to 3 were measured to be relatively low, at 379°C to 407°C and 452°C to 479°C, respectively.

[0087] Furthermore, all the examples and comparative examples analyzed showed a low sintering temperature of less than 500°C. This indicates that sintering can be performed at a significantly lower temperature compared to conventional oxide-based solid electrolytes sintered at temperatures above 1,000°C.

[0088] After granulating the powder with the composition of Table 1 above, it is sintered at about 600°C and about 700°C for about 3 hours to produce a solid electrolyte.

[0089] Table 3 shows the measurement results of crystallinity, ionic conductivity, and conductivity of the solid electrolytes according to the embodiments and comparative examples of the present invention. Ionic conductivity represents the ionic conductivity characteristics of the solid electrolyte itself, and conductivity represents the conductivity characteristics in an all-solid-state battery using the solid electrolyte.

[0090] [Table 3] distinguish Sintering at 600℃ Sintering at 700℃ Crystallinity (%) Ionic conductivity (S / cm) conductivity (S / cm) Crystallinity (%) Ionic conductivity (S / cm) conductivity (S / cm) Example 1 62 1.08×10 -5 1.48×10 -8 64 2.50×10 -5 3.99×10 -7 Example 2 63 1.27×10 -5 3.37×10 -8 65 5.55×10 -5 4.13×10 -7 Example 3 60 2.41×10 -6 7.00×10 -9 69 1.48×10 -4 1.75×10 -7 Comparative Example 3 45 3.16×10 -9 6.54×10 -11 50 1.08×10 -8 3.66×10 -10 Comparative Example 4 60 4.86×10 -9 5.21×10 -11 61 3.32×10 -8 4.11×10 -10

[0091] Referring to Table 3, the solid electrolytes of Examples 1 to 3 exhibited significantly higher ionic conductivity than the comparative examples. Therefore, it can be inferred that the addition of LiCl contributes to improving the ionic conductivity of the solid electrolyte.

[0092] On the other hand, it can be confirmed that, in terms of crystallinity, a higher degree of crystallinity is observed at a sintering temperature of 700°C compared to the case where the sintering temperature is 600°C, and consequently, the ionic conductivity and electrical conductivity are also improved.

[0093] Figures 4 and 5 are graphs showing the XRD analysis results of the solid electrolytes of the embodiments and comparative examples according to the present invention after sintering. Specifically, Figures 4 and 5 show the XRD analysis results of the solid electrolytes of Examples 1 and 2 and Comparative Examples 3 and 4 after sintering at about 600°C and about 700°C, respectively.

[0094] Referring to Figures 4 and 5, the XRD patterns of the sintered solid electrolyte show multiple crystallization peaks. Specifically, the solid electrolyte according to the embodiments of the present invention has lithium zinc phosphate (LiZnPO4) crystals and lithium magnesium zinc (Li2MgZn) crystals as the main crystals. In this crystalline structure, ion flow is smooth, thereby exhibiting excellent ionic conductivity.

[0095] Figure 6 is a graph showing the surface analysis results of Example 2 and Comparative Example 3 using Fourier transform infrared spectroscopy (FT-IR) equipment.

[0096] Referring to FIG6(a), in the case of the solid electrolyte powder before sintering according to the embodiments and comparative examples of the present invention, peaks caused by the symmetric and asymmetric stretching vibrations of POP and the symmetric stretching vibration of (PO4)3- were observed. Conversely, referring to FIG6(b), in the case of the solid electrolyte after sintering according to the embodiments and comparative examples of the present invention, peaks caused by the symmetric stretching vibrations of PO2, the asymmetric stretching vibrations of PO-2 and PO3, and the symmetric and asymmetric stretching vibrations of POP were observed, and peaks caused by cation groups having wavenumbers less than 600 cm-1 were also observed.

[0097] Figure 7 is an electron microscope image of a solid electrolyte according to an embodiment of the present invention. Specifically, it is a scanning electron microscope (SEM) image of an unpolished cross section of the solid electrolyte according to Embodiment 3 of the present invention. Figure 7(a) is a 500x image, and Figure 7(b) is a 5,000x image.

[0098] Referring to FIG7, it can be confirmed that the solid electrolyte according to Embodiment 3 of the present invention has minimal porosity and uniformly distributed crystals with clear grain boundaries after sintering. Thus, the solid electrolyte according to an embodiment of the present invention exhibits excellent crystal growth and high densification. The optimized microstructure of this solid electrolyte ensures strong grain boundary connectivity and excellent ionic conductivity.

[0099] On the other hand, the solid electrolyte powder before sintering according to Example 3 of the present invention was hot-pressed to produce granules, and its characteristics were further analyzed. Specifically, the solid electrolyte powder before sintering according to Example 3 was granulated by compressing it at a pressure of about 40 MPa and a temperature of about 560°C for approximately 3 hours.

[0100] Figure 8 is an electron microscope image of the solid electrolyte powder before sintering according to an embodiment of the present invention, and Figure 9 is an electron microscope image of particles obtained by hot pressing the solid electrolyte powder according to an embodiment of the present invention. Each figure includes images at 500x (a), 1,000x (b), 2,000x (c), and 5,000x (d).

[0101] Referring to Figures 8 and 9, it can be confirmed that the density of the solid electrolyte increases after hot pressing. Specifically, the density of the powder before sintering is 0.886 g / cm3, and the density of the particles manufactured after hot pressing is measured to be 2.149 g / cm3.

[0102] Figure 10 is a graph showing the EIS analysis results of particles obtained by hot pressing the solid electrolyte powder according to the embodiments of the present invention. Specifically, it shows the results of EIS analysis performed on particles manufactured by hot pressing the solid electrolyte powder according to Example 3 before sintering. As shown in the figure, after hot pressing the solid electrolyte powder according to Example 3 of the present invention, it meets the real impedance axis (x-axis) at an impedance of approximately 2,600 ohms. Furthermore, the ionic conductivity and conductivity of the solid electrolyte according to this embodiment were measured to be 4.77 × 10⁻⁵ S / cm and 5.42 × 10⁻⁷ S / cm, respectively.

[0103] Thus, by hot pressing, the solid electrolyte powder of Example 3 of the present invention is granulated, the density is increased, and good ionic conductivity characteristics can be achieved.

[0104] The above experimental examples confirm that the ionic conductivity increases when the solid electrolyte contains LiCl in addition to Li₂O, MgO, ZnO, and P₂O₅. In particular, when the overall composition contains 8 mol% or more of LiCl, the ionic conductivity is significantly improved. However, when the LiCl content is 17 mol% or more, it is confirmed that it is unsuitable as a solid electrolyte due to the decrease in water stability, etc.

[0105] 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 with ordinary knowledge in the art to which the present invention pertains can make various modifications and variations from such description.

[0106] 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]

[0016] Figure 1 is a schematic perspective view of an all-solid-state battery.

[0017] Figure 2 is a cross-sectional view of an all-solid-state battery.

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

[0019] Figures 4 and 5 are graphs showing the XRD analysis results of the solid electrolytes after sintering according to the embodiments and comparative examples of the present invention.

[0020] Figure 6 is a graph showing the FT-IR analysis results of the solid electrolytes of the embodiments and comparative examples according to the present invention before and after sintering.

[0021] Figure 7 is an electron microscope image of a solid electrolyte according to an embodiment of the present invention.

[0022] Figure 8 is an electron microscope image of the powder of the solid electrolyte before sintering according to an embodiment of the present invention.

[0023] Figure 9 is an electron microscope image of particles obtained by hot pressing the solid electrolyte powder according to the embodiment of the present invention.

[0024] Figure 10 is a graph showing the EIS analysis results of particles obtained by hot pressing the solid electrolyte powder according to the embodiment of the present invention.

Claims

1. A solid electrolyte for all-solid-state batteries, characterized in that it is formed from oxides containing Li, Mg, Zn, P and Cl, comprising 28-33 mol% Li₂O, 17-25 mol% MgO, 4-12 mol% ZnO, 28-33 mol% P₂O₅ and 8-14 mol% LiCl.

2. The solid electrolyte for all-solid-state batteries as described in claim 1, comprising lithium zinc phosphate (LiZnPO4) crystals and lithium magnesium zinc (Li2MgZn) crystals.

3. The solid electrolyte for all-solid-state batteries as described in claim 1, which is manufactured from precursor powders comprising Li2CO3, MgO, ZnO, P2O5 and LiCl.

4. The solid electrolyte for all-solid-state batteries as described in claim 1, having an ionic conductivity of 5 × 10⁻⁵ S / cm or higher.

5. An all-solid-state battery, characterized in that it comprises: an anode layer; a cathode layer; and a solid electrolyte layer, wherein the aforementioned solid electrolyte layer is formed of oxides comprising Li, Mg, Zn, P and Cl, comprising 28-33 mol% Li₂O, 17-25 mol% MgO, 4-12 mol% ZnO, 28-33 mol% P₂O₅ and 8-14 mol% LiCl.

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