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

Abstract

The present invention relates to a solid electrolyte for an all-solid-state battery and an all-solid-state battery comprising same. The solid electrolyte for an all-solid-state battery, according to one embodiment of the present invention, is composed of an oxide material containing Li, Mg, Zn, P, and Cl.

Description

Solid electrolyte for all-solid-state batteries and all-solid-state batteries containing the same

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

[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 prior art described above, 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, and an all-solid-state battery including the same.

[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, Mg, Zn, P, and Cl.

[0008] According to one embodiment of the present invention, LiCl may be included in an amount of 8 mol% or more.

[0009] According to one embodiment of the present invention, LiCl may be included in an amount of 14 mol% or less.

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

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

[0012] 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, MgO, ZnO, P2O5, and LiCl.

[0013] A solid electrolyte for an all-solid-state battery according to one embodiment of the present invention has an ionic conductivity of 5×10 -5 It can be more than S / cm.

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

[0015] 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.

[0016] According to one embodiment of the present invention, a solid electrolyte for an all-solid-state battery is an oxide-based solid electrolyte, and is formed of an oxide containing Li, Mg, Zn, P, and Cl, thereby enabling low-temperature sintering and having excellent ionic conductivity.

[0017] Figure 1 is a perspective view schematically showing an all-solid-state battery.

[0018] Figure 2 is a drawing showing an example of a cross-section of an all-solid-state battery.

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

[0020] FIG. 4 and FIG. 5 are graphs showing the results of XRD analysis after sintering of solid electrolytes according to examples and comparative examples of the present invention.

[0021] Figure 6 is a graph showing the results of FT-IR analysis before and after sintering of solid electrolytes according to examples and comparative examples of the present invention.

[0022] Figure 7 is an electron microscope image of a solid electrolyte according to an embodiment of the present invention.

[0023] Figure 8 is an electron microscope image of a powder before sintering of a solid electrolyte according to an embodiment of the present invention.

[0024] Figure 9 is an electron microscope image of a pellet obtained by hot-pressing a solid electrolyte powder according to an embodiment of the present invention.

[0025] Figure 10 is a graph showing the results of EIS analysis of pellets obtained by hot-pressing solid electrolyte powder according to an embodiment of the present invention.

[0026] [Explanation of symbols]

[0027] 10: All-solid-state batteries

[0028] 11: Bipolar layer

[0029] 12: Cathode layer

[0030] 13: Solid electrolyte layer

[0031] 14, 15: External electrode

[0032] 16: Case

[0033] 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.

[0034] 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.

[0035] 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.

[0036] Fig. 1 is a perspective view schematically illustrating an all-solid-state battery, and Fig. 2 is a drawing schematically illustrating a cross-section of the all-solid-state battery. The all-solid-state battery according to one embodiment of the present disclosure can be formed into a small chip shape as a so-called laminated ceramic battery and can be used in small electronic devices such as wearable electronic devices.

[0037] Referring to FIGS. 1 and 2, the all-solid-state battery (10) includes a positive electrode layer (11), a negative electrode layer (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).

[0038] In one embodiment, the positive electrode layer (11) may be formed by applying a positive electrode active material layer to at least one surface of the positive electrode collector, and the negative electrode layer (12) may be formed by applying a negative electrode active material layer to at least one surface of the negative electrode collector. For example, the electrode layer located at the uppermost layer based on the stacking direction may be formed by applying a positive electrode active material layer to one surface of the positive electrode collector, and the electrode layer located at the lowermost layer may be formed by applying a negative electrode active material layer to one surface of the negative electrode collector. In addition, the electrode layers located between the uppermost and lowermost layers may be formed by applying a positive electrode active material layer to both surfaces of the positive electrode collector, or by applying a negative electrode active material layer to both surfaces of the negative electrode collector.

[0039] The positive electrode active material layer may include a positive electrode active material and optionally a solid electrolyte. In addition, the positive electrode active material layer may optionally further include additives such as a binder or a conductive agent.

[0040] The cathode active material is not particularly limited as long as it can secure sufficient capacity of the all-solid-state battery (10). For example, the cathode active material may include lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium iron phosphate, lithium manganese oxide, or a combination thereof.

[0041] The conductive agent of the positive electrode active material layer is not particularly limited as long as it is conductive and does not cause a chemical change in the all-solid-state battery (10). For example, conductive agents may include graphite such as natural graphite or artificial graphite, carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, and summer black, conductive fibers such as carbon fiber or metal fiber, metal powders such as fluorinated carbon, aluminum, and nickel powder, conductive whiskey such as zinc oxide or potassium titanate, conductive metal oxides such as titanium oxide, and conductive materials such as polyphenylene derivatives.

[0042] A binder may be used to improve the bonding strength between the active material and the conductive agent. Examples of binders include polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-dienhe polymer (EPDM), sulfonated EPDM, styrene butadiene rubber, fluoroelastomer, or various copolymers.

[0043] A porous body such as a mesh or mesh-shaped positive electrode collector can be used, and a porous metal plate such as stainless steel, nickel, or aluminum can be used. In addition, the positive electrode collector can be coated with an oxidation-resistant metal or alloy film to prevent oxidation.

[0044] The negative electrode active material layer may include a negative electrode active material and optionally a solid electrolyte. In addition, the negative electrode active material layer may optionally further include additives such as a binder or a conductive agent.

[0045] The negative active material may be a carbon-based material, silicon, silicon oxide, silicon-based alloy, silicon-carbon-based material composite, tin, tin-based alloy, tin-carbon composite, metal oxide, or a combination thereof, and may include lithium metal and / or a lithium metal alloy.

[0046] The negative active material layer may also optionally include a conductive agent and a binder, as described for the positive active material layer.

[0047] A porous body such as a mesh or mesh-shaped negative electrode collector can be used, and a porous metal plate such as stainless steel, nickel, or aluminum can be used. In addition, the negative electrode collector can be coated with an oxidation-resistant metal or alloy film to prevent oxidation.

[0048] In one embodiment, a margin insulating layer (not shown) may be additionally disposed along the edges of the positive electrode layer (11) and the negative electrode layer (12). The margin insulating layer is positioned on the solid electrolyte layer (13) and may be formed laterally adjacent to the edges of the positive electrode active material layer or the negative electrode active material layer. Accordingly, the margin insulating layer may be positioned in the same layer of the positive electrode layer (11) and the negative electrode layer (12), respectively.

[0049] The margin insulation layer may include an insulating material having 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.

[0050] Additionally, the margin insulating layer may include an oxide-based solid electrolyte used in the solid electrolyte layer (13). However, the material included in the margin insulating layer is not limited thereto and may include various materials.

[0051] The positive electrode layer (11) and the negative electrode layer (12) of the all-solid-state battery (10) can be connected to external electrodes (14, 15), respectively. The external electrodes (14, 15) can 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.

[0052] According to one embodiment of the present invention, the all-solid-state battery (10) is configured such that a cathode layer (11), a cathode layer (12), and a solid electrolyte layer (13) are each formed of multiple layers and alternately laminated to form a cell stack. In FIG. 2, the cathode layers (11) and the anode layers (12) are alternately arranged and the solid electrolyte layer (13) is arranged between them. However, the arrangement of the cathode layers (11), the cathode layers (12), and the solid electrolyte layer (13) is not limited to what is illustrated. In one embodiment, a protective layer (not shown) made of an insulating material may be formed on the top and bottom of the cell stack.

[0053] According to one embodiment of the present invention, an all-solid-state battery (10) may include a case (16) configured to surround a cell stack. External electrodes (14, 15) may be arranged at both ends of the case (16).

[0054] The external electrodes (14, 15) may include a conductive metal and glass. The conductive metal may be, for example, a conductive metal including copper (Cu), nickel (Ni), tin (Sn), palladium (Pd), platinum (Pt), gold (Au), silver (Ag), tungsten (W), titanium (Ti), lead (Pb), or an alloy thereof.

[0055] The glass component included in the external electrode (14, 15) may have a composition in which oxides are mixed. The glass component 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 at least one of zinc (Zn), titanium (Ti), copper (Cu), vanadium (V), manganese (Mn), iron (Fe), and nickel (Ni), the alkali metal may be selected from at least one of lithium (Li), sodium (Na), and potassium (K), and the alkaline earth metal may be selected from at least one of magnesium (Mg), calcium (Ca), strontium (Sr), and barium (Ba).

[0056] The method for forming the external electrodes (14, 15) is not particularly limited. For example, they may be formed by dipping the cell stack into a conductive paste containing a conductive metal and glass, or by printing the conductive paste on the surface of the cell stack using a screen printing method or a gravure printing method. In addition, various methods may be used, such as applying the conductive paste on the surface of the cell stack or transferring a dried film of the conductive paste to the cell stack to form the electrodes.

[0057] The case (16) can perform the function of protecting the cell stack including the anode layer (11), the cathode layer (12) and the solid electrolyte layer (13) from being exposed to the outside. The case (16) is required to have moisture permeability, heat resistance, insulation, etc. to protect the internal components from external moisture, heat, electricity, etc., and is also required to have high resistance to chemical corrosion along with long-term stability.

[0058] According to one embodiment of the present invention, an all-solid-state battery (10) can be manufactured by stacking a cathode layer (11), a cathode layer (12), a solid electrolyte layer (13), a case (16), etc. and then sintering them integrally. In order to prevent the characteristics of the electrode layer, etc. from deteriorating during this sintering process, each component including the solid electrolyte layer (13) must be sintered at a low temperature, for example, a temperature of 700°C or lower.

[0059] In this way, the solid electrolyte of the all-solid-state battery (10) according to one embodiment of the present invention is required to have excellent low-temperature characteristics.

[0060] The solid electrolyte layer (13) according to one embodiment of the present invention includes an oxide-based electrolyte as a solid electrolyte.

[0061] 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.

[0062] 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.

[0063] 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.

[0064] A solid electrolyte for an all-solid-state battery according to one embodiment of the present invention may be formed of an oxide containing Li, Mg, Zn, P, and Cl. Specifically, the solid electrolyte according to one embodiment of the present invention may contain Li2O, MgO, ZnO, P2O5, and LiCl.

[0065] In solid electrolytes, Li2O can function as a network modifier and improve ionic conductivity by providing Li ions.

[0066] In solid electrolytes, MgO can function as a network modifier and improve the coefficient of thermal expansion and adhesion.

[0067] In solid electrolytes, ZnO can function as an intermediate, i.e., ZnO can function as a network former or network modifier depending on its concentration in the composition.

[0068] In solid electrolytes, P2O5 can function as a network former and as a low-temperature component, it plays a role in lowering the sintering temperature.

[0069] In solid electrolytes, LiCl enhances ionic conductivity by increasing the concentration of Li and Cl ions. These 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.

[0070] In one embodiment, the solid electrolyte may comprise at least 8 mol% LiCl.

[0071] In one embodiment, the solid electrolyte may comprise up to 14 mol% LiCl.

[0072] A solid electrolyte according to one embodiment of the present invention may include 28 to 33 mol% of Li2O, 17 to 25 mol% of MgO, 4 to 12 mol% of ZnO, and 28 to 33 mol% of P2O5.

[0073] A solid electrolyte according to one embodiment of the present invention may include lithium zinc phosphate (LiZnPO4) crystals and lithium magnesium zinc (Li2MgZn) crystals.

[0074] In this way, the solid electrolyte for an all-solid-state battery according to one embodiment of the present invention is composed of oxides including Li, Mg, Zn, P, and Cl, and thus can be sintered at a temperature of about 700°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.

[0075] A solid electrolyte according to one embodiment of the present invention can be manufactured from a precursor powder including Li2CO3, MgO, ZnO, P2O5, and LiCl. Specifically, a solid electrolyte according to one embodiment of the present invention can be manufactured through the following process.

[0076] (1) Prepare precursor powder containing Li2CO3, MgO, ZnO, P2O5, and LiCl.

[0077] (2) The precursor powder is mixed uniformly through dry or wet mixing.

[0078] (3) The mixture of precursor powders is melted in an aluminum crucible at a temperature of approximately 1,100°C for 30 minutes.

[0079] (4) Rapidly cool the melt to room temperature.

[0080] (5) The cooled melt is crushed into fine particles.

[0081] (6) The crushed material is pelletized and sintered at a temperature of approximately 700°C.

[0082] The solid electrolyte obtained through the above process has a molecular weight of about 5×10 at room temperature. -5 It exhibits an ionic conductivity of more than S / cm. Preferably, the solid electrolyte is 1.4×10 -4 It exhibits an ionic conductivity of more than S / cm.

[0083] 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.

[0084]

[0085] Experimental example

[0086] Precursor powders (batch size 200 g) containing Li2CO3, MgO, ZnO, P2O5, and LiCl were prepared. At this time, a total of six types of precursor powders were prepared by varying the addition amounts of Li2CO3, MgO, ZnO, P2O5, and LiCl.

[0087] To ensure the homogeneity of the solid electrolyte, the precursor powder was sufficiently mixed through ball milling or mechanical mixing. Then, the precursor powder was placed in an aluminum crucible and melted at a temperature of approximately 1,100°C for approximately 30 minutes. The melt was rapidly cooled on a quenching roller, and the resulting powder was pulverized using a planetary ball mill and then sieved to obtain a micro-sized fine powder.

[0088] The composition of the fine powder manufactured as above is as described in Table 1.

[0089]

[0090] Classification Solid electrolyte composition (mol%) Li2OMgOZnOP2O5LiClExample 132.017.510.532.08.0Example 231.022.64.431.011.0Example 328.723.45.228.714.0Comparative Example 123.543.532.9--Comparative Example 231.031.030.0-8.0Comparative Example 335.117.712.235.1-Comparative Example 435.225.24.435.2-Comparative Example 528.322.24.228.317.0Comparative Example 627.022.13.927.020.0

[0091]

[0092] For the solid electrolyte composition in Table 1, a moisture stability test was performed by immersing it in water for more than 120 hours, and XRD (X-Ray Diffraction), DTA (Differential Thermal Analysis), FT-IR (Fourier Transform Infrared spectroscopy), and HTM (High Temperature Microscope) analyses were also performed.

[0093] Fig. 3 is a graph showing the results of XRD analysis on pre-sintering powders of solid electrolytes according to examples and comparative examples of the present invention. Specifically, Fig. 3 shows the results of XRD analysis on pre-sintering powders of solid electrolytes according to examples 1 and 2 and comparative examples 3 and 4.

[0094] Referring to Fig. 3, the XRD graphs for the pre-sintered powders of the solid electrolytes according to the above-described examples and comparative examples do not show any crystalline peaks. This indicates that the pre-sintered powders are in an amorphous state, and in such an amorphous state, it is difficult to form lithium ion paths that enable ion diffusion. However, although not shown, the composition according to comparative example 6 was a glass-ceramic rather than an amorphous one.

[0095] The results of the moisture stability test and the temperature characteristics measured through DTA and HTM analyses are as shown in Table 2. Meanwhile, as shown in the table below, temperature characteristics and the sintering process described below were not performed for Comparative Examples 1, 2, and 5, which had poor moisture stability, and Comparative Example 6, which was not amorphous.

[0096] Moisture stabilityTransition temperature (Tg, ℃)Crystallization temperature (Tc, ℃)Sintering temperature (T sint , ℃) softening point (T soft , ℃)Half Ball(T half-ball , ℃)Example 1Pass379452451773776Example 2Pass407479487787789Example 3Pass395463453777780Comparative Example 1Fail-----Comparative Example 2Fail-----Comparative Example 3Pass396471462768770Comparative Example 4Pass421493498783794Comparative Example 5Fail-----Comparative Example 6------

[0097]

[0098] Referring to Table 2, all of the examples and comparative examples for which analysis was performed exhibited a transition temperature of 379°C to 421°C and a crystallization temperature of 452°C to 492°C. Among them, the compositions of Examples 1 to 3 were measured to have low transition temperatures and crystallization temperatures of 379°C to 407°C and 452°C to 479°C, respectively.

[0099] In addition, all of the examples and comparative examples for which analysis was performed show a low sintering temperature of less than 500°C. This means that the solid electrolyte can be sintered at a significantly lower temperature compared to conventional oxide-based solid electrolytes that are sintered at high temperatures of 1,000°C or higher.

[0100] After pelletizing the powder of the composition in Table 1 above, a solid electrolyte was manufactured by sintering at about 600°C and about 700°C for approximately 3 hours.

[0101] Table 3 shows the results of measuring the crystallinity, ionic conductivity, and electrical conductivity of solid electrolytes according to examples and comparative examples of the present invention. Ionic conductivity indicates the ionic conductivity characteristics of the solid electrolyte itself, and electrical conductivity indicates the electrical conductivity characteristics of an all-solid-state battery to which the solid electrolyte is applied.

[0102] Classification 600℃ firing 700℃ firing Crystallinity (%) Ionic conductivity (S / cm) Electrical conductivity (S / cm) Crystallinity (%) Ionic conductivity (S / cm) Electrical conductivity (S / cm) Example 1621.08×10 -5 1.48×10 -8 642.50×10 -5 3.99×10 -7 Example 2631.27×10 -5 3.37×10 -8 655.55×10 -5 4.13×10 -7 Example 3602.41×10 -6 7.00×10 -9 691.48×10 -4 1.75×10 -7 Comparative example 3453.16×10 -9 6.54×10 -11 501.08×10 -8 3.66×10 -10 Comparative example 4604.86×10 -9 5.21×10 -11 613.32×10 -8 4.11×10 -10

[0103]

[0104] Referring to Table 3, the solid electrolytes according to Examples 1 to 3 exhibit significantly higher ionic conductivity compared to the comparative examples. This suggests that the addition of LiCl contributes to improving the ionic conductivity of the solid electrolyte.

[0105] Meanwhile, in the case of crystallinity, it can be confirmed that the sintering temperature is higher at 700℃ than at 600℃, and accordingly, the ionic conductivity and electrical conductivity are also improved.

[0106] Figures 4 and 5 are graphs showing the results of XRD analysis after sintering of solid electrolytes according to examples and comparative examples of the present invention. Specifically, Figures 4 and 5 show the results of XRD analysis after sintering the solid electrolytes of Examples 1 and 2 and Comparative Examples 3 and 4 at about 600°C and about 700°C, respectively.

[0107] 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 embodiments of the present invention comprises lithium zinc phosphate (LiZnPO4) crystals and lithium magnesium zinc (Li2MgZn) crystals as main crystals. In such a crystallization structure, ion flow is smooth, resulting in excellent ionic conductivity.

[0108] 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.

[0109] Referring to (a) of Fig. 6, in the case of the powder before sintering of the solid electrolyte according to the embodiment and comparative example of the present invention, symmetrical and asymmetrical stretching vibrations of POP, (PO4) 3- A peak is observed due to the symmetric stretching vibration of PO2. On the other hand, referring to Fig. 6 (b), in the case of the solid electrolyte after sintering according to the examples and comparative examples of the present invention, a peak is observed due to the symmetric stretching vibration of PO2, PO -Peaks due to the asymmetric stretching vibrations of 2 and PO3, and the symmetric and asymmetric stretching vibrations of POP are observed at 600 cm -1 Peaks due to cationic groups with wavenumbers below 10 are observed.

[0110] Fig. 7 is an electron microscope image of a solid electrolyte according to an embodiment of the present invention, and specifically, is an SEM (scanning electron microscope) image of an unpolished cross-section of a solid electrolyte according to Example 3 of the present invention. Fig. 7 (a) is a 500x magnification image, and Fig. 7 (b) is a 5,000x magnification image.

[0111] Referring to FIG. 7, it can be confirmed that the solid electrolyte according to Example 3 of the present invention has uniformly distributed crystals with minimal porosity and clear grain boundaries after sintering. As such, the solid electrolyte according to one embodiment of the present invention exhibits excellent crystal growth and high densification, and the optimized microstructure of this solid electrolyte ensures strong grain boundary connectivity and excellent ionic conductivity.

[0112] Meanwhile, hot pressing was performed on the pre-sintering powder of the solid electrolyte according to Example 3 of the present invention to produce pellets, and their characteristics were additionally analyzed. Specifically, the pre-sintering powder of the solid electrolyte according to Example 3 was pressed at a pressure of about 40 MPa and a temperature of about 560°C for approximately 3 hours to form pellets.

[0113] FIG. 8 is an electron microscope image of a powder before sintering of a solid electrolyte according to an embodiment of the present invention, and FIG. 9 is an electron microscope image of a pellet obtained by hot-pressing the solid electrolyte powder according to an embodiment of the present invention. Each drawing includes images at 500x (a), 1,000x (b), 2,000x (c), and 5,000x (d) magnifications.

[0114] 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 / cm. 3 The density of the pellets manufactured after hot pressing is 2.149 g / cm 3 was measured as

[0115] Fig. 10 is a graph showing the results of EIS analysis of pellets obtained by hot-pressing solid electrolyte powder according to an embodiment of the present invention, and specifically, it is a graph showing the results of EIS analysis performed on pellets manufactured by hot-pressing the pre-sintering powder of the solid electrolyte according to Example 3. As shown, 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 about 2,600 ohms. In addition, the ionic conductivity and electrical conductivity of the solid electrolyte according to the present embodiment are 4.77×10, respectively. -5 S / cm and 5.42×10 -7 It was measured in S / cm.

[0116] In this way, when the solid electrolyte powder according to Example 3 of the present invention is pelletized through hot pressing, it is possible to achieve good ionic conductivity characteristics while increasing the density.

[0117] As can be confirmed through the experimental examples above, the ionic conductivity improves as the solid electrolyte contains LiCl in addition to Li2O, MgO, ZnO, and P2O5. In particular, it can be confirmed that the ionic conductivity improves significantly when the total composition contains LiCl at 8 mol% or more. However, it can be confirmed that when the LiCl content exceeds 17 mol%, it is not suitable as a solid electrolyte due to deterioration in moisture stability, etc.

[0118] 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.

[0119] 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, Mg, Zn, P and Cl. Solid electrolyte.

2. In paragraph 1, A solid electrolyte containing LiCl in an amount of 8 mol% or more.

3. In paragraph 1, A solid electrolyte containing LiCl in an amount of 14 mol% or less.

4. In paragraph 1, A solid electrolyte comprising 28-33 mol% Li2O, 17-25 mol% MgO, 4-12 mol% ZnO, 28-33 mol% P2O5, and 8-14 mol% LiCl.

5. In paragraph 1, Containing lithium zinc phosphate (LiZnPO4) crystals and lithium magnesium zinc (Li2MgZn) crystals, Solid electrolyte.

6. In paragraph 1, Manufactured from precursor powders containing Li2CO3, MgO, ZnO, P2O5 and LiCl, Solid electrolyte.

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

8. Bipolar layer, Cathode layer and Contains a solid electrolyte layer, The above solid electrolyte layer is made of an oxide containing Li, Mg, Zn, P and Cl. All-solid-state battery.

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