KR102327215B1 - Glass ceramics for low temperature co-sintering of electrode and electrolyte and solid state battery using the same - Google Patents

Abstract

The present invention proposes a glass electrolyte capable of simultaneous firing at a low temperature after integrally stacking an electrode and an electrolyte as an electrolyte for a lithium secondary all-solid-state battery. Specifically, Li _1.2+x Fe _0.2+x Ti _1.8-x (PO ₄ ) _3-y (BO ₃ ) _y or Li ₂ Sn _0.5 (BO ₃ ) _1-x (PO ₄ ) _x Fe instead of Ti intermediate oxide a, mesh oxide PO ₄ instead of replacing the BO ₃ or ionic conductor is _{Li 1.5-x M x a 0.5} (a = Sn, Ti) (PO 4) was added to the intermediate or modified oxide with a mesh size oxide _1..5 BO ₃ Then, by mixing sucrose with the composition and melting it in a reducing atmosphere, it is a glass electrolyte having high ionic conductivity of ^{10 -4} to 10 ^{-5 S/cm at a temperature 200 to 300°C lower than before, and has excellent lithium ion conductivity.} It provides a new glass electrolyte. A composite electrolyte and a composite electrode are manufactured by mixing this glass electrolyte with an electrolyte and an electrode in the range of 13 to 33 wt%, and a cell in which the composite electrolyte and composite electrode are laminated and integrated is simultaneously fired at a low temperature of 750 to 825° C. battery can be manufactured. According to the present invention, it is possible to laminate and integrate an all-solid-state battery at a low temperature without an interfacial reaction between the electrode and the electrolyte, and a new sintering aid and glass electrolyte can be manufactured simply and inexpensively, and the performance of the all-solid-state battery can be improved. .

Description

Glass electrolyte for low temperature co-sintering of electrode and electrolyte and solid state battery using the same

The present invention relates to an electrolyte for an all-solid-state battery, and in particular, a glass electrolyte capable of simultaneous firing at a low temperature after integrating and laminating an electrode and an electrolyte, and a composite electrolyte, a composite electrode, and a composite battery cell using the glass electrolyte.

Recently, lithium secondary batteries have various uses and demand is increasing. In particular, it is being applied to electric vehicle batteries such as HEVs, FHEVs, and EVs, as well as starting to be used as a power source for energy storage systems. Moreover, as it is applied to electric vehicles and high-capacity power sources, high-tech phones and higher performance are being pursued.

The liquid electrolyte used in the existing lithium secondary battery has a risk of ignition due to problems such as dendrite formation, flammability, and leakage. Research on conversion to non-flammable inorganic solid electrolytes is being focused. When such an inorganic solid electrolyte is used in an all-solid-state battery, there is no risk of fire and the manufacturing process can be simplified. There are oxide-based and sulfide-based solid electrolytes, and oxide-based electrolytes have great advantages in that they are stable in contact with lithium and in the atmosphere, but have problems such as lower ionic conductivity and high interfacial resistance than sulfide-based electrolytes. In the case of sulfide systems, ion conductivity is high, but resistance components are generated by interfacial reaction with positive electrode active material or negative electrode active material, and they are vulnerable to moisture, and there are problems that hydrogen sulfide gas, a toxic gas, is generated. .

Recently, it has been reported that sintering a perovskite-type or garnet-type oxide-based electrolyte at a high temperature can compensate for the disadvantages of sulfide- ^{based electrolytes due to their high ionic conductivity of 10 -3} to 10 ^{-4 S/cm.} have. _{Among these oxide-based electrolytes, Li 7} La ₂ Zr ₂ O ₁₃ (hereinafter, LLZO) is an electrolyte that can be synthesized in a large amount in an oxidizing (atmospheric) atmosphere. When LLZO solid electrolyte is synthesized at 900°C or higher for a long period of time, cubic LLZO is synthesized, but in order to be densified, it must be sintered at 1200 to 1250°C to have a stable cubic structure and high ionic conductivity. However, during high-temperature sintering, Li volatilization occurs, and the sintering range is narrow, making sintering difficult. On the other hand, materials mainly used as anodes in all-solid-state batteries include LiCoO _2, LiNiO ₂ , LiMn ₂ O ₄ , LiCoPO _{4 ,} Li[Ni _0.5~0.8 Co _0.25~0.1 Mn _0.25~0.1 ]O ₂ (hereinafter referred to as NCM), etc. This has been widely used recently. This cathode material is synthesized at 850~1000℃, and at a temperature higher than that, a second phase is generated and Li is volatilized.

In order to integrally laminate and sinter the LLZO and the positive electrode, the reaction between the electrolyte and the positive electrode must be sintered at 850° C. or lower, which is below the synthesis temperature of the positive electrode. In order to lower the sintering temperature of the electrolyte from 1200 to 1250°C to 850°C or less, a low-temperature sintering aid is required. remedies are needed

According to Patent Publication No. 10-2019-0078804, Li ₇ La ₃ Zr ₂ O ₁₂ (garnet type) solid electrolyte is _{mixed with Li 3} BO ₃ (hereinafter LBO)-based glass frit by 0.1 to 25% (weight), and after molding 900 Sintered at ~1200°C (preferably 1000-1150°C). When the added LBO content was 12 to 16% by weight, the ionic conductivity was 1.18 to 1.28×10 ^-4 S/cm, and when it was 4 to 8 percent, it was 1.12 to 1.54×10 ^-5 S/cm. At this time, the LBO powder is a chelating agent (citric acid C ₆ H ₈ O ₇ , synthesized at 90~250℃, aminocarboxylic acid, polyphosphoric acid, ethylenediamine C ₂ H ₄ (NH ₂ ) ₂ ), etc.) and solvent ethylene glycol, H After dissolving a lithium source and a boron source material in a mixture composed of _{2 O and dimethyl ether, an esterification reaction was performed.} This powder was calcined in an oxidizing atmosphere at 600-800° C. to prepare an LBO glass frit. In this technology, LBO is used as a sintering aid, but there is a problem that the sintering temperature is too high as 1000~1150℃.

In Patent Registration No. 10-0883044, a crystalline first material (primary phosphate compound) is included in the active material, and the solid electrolyte is a crystalline second material having lithium ion conductivity (diphosphoric acid compound: dibasic phosphate compound-Li _1+x M ^Ⅲ _x Ti ^Ⅳ _2-x (PO ₄ ) ₃ (M ^Ⅲ is Al, Y, Ga, In, La, 0 ≤ x ≤ 0.6) A laminate comprising an active material layer and a solid electrolyte layer was prepared. A laminate was prepared at 700-1000° C. or less by including 0.1 to 10% by weight of an amorphous oxide (one having a softening point of 700 to 950° C.) in either the active material layer or the solid electrolyte layer. _{In addition, Li 4} P ₂ O ₇ in any one of the positive electrode, negative electrode, and electrolyte was added and sintered under water vapor and atmospheric gas. The amorphous oxide used in this technology has the composition of 62~72wt.%SiO ₂ -1 _{~15wt.%Al 2} O ₃ -14~20Na ₂ O-0~3wt%MgO-0~10wt%CaO-0~15wt%BaO As the softening temperature is high, the sintering temperature is high as well as the ionic conductivity is low.

In Solid State Ionics 118(1999)853, _{15wt% of 0.44LiBO 2} -0.56LiF was added to the electrolyte and active material as a sintering aid when manufacturing an all-solid-state battery, and sintered at 750° C. In this case, due to insufficient sintering, the interfacial bonding between the electrolyte and the active material was insufficient. In Solid State Ionics 47 (1991), 257-264, when LiTi ₂ (PO ₄ ) ₃ with high ionic conductivity in NASICON structure is sintered at 1200℃ alone, sintering property is low, and the ionic conductivity is about 10 ^-6 S/cm. Therefore, as a sintering aid, Li ₃ PO ₄ I It was reported that the ionic conductivity could be improved by adding _{Li 3} BO _{3 and sintering LiTi 2} (PO ₄ ) _{3 at 800~900℃.} However, the ion conductivity of the sintering aid ^{is low as 10 -6} ~ 10 ^-7 S/cm, and the sintering temperature is also high.

In Laid-Open Patent Publication No. 10-2017-0008539, 1 to 20 weight percent _{of an amorphous lithium ion conductor 50Li 2} O·35.7B ₂ O ₃ ·14.3SiO ₂ is added to an oxide of a garnet structure doped with tantalum (Ta). Therefore, when sintering at 700°C for 3 to 15 hours, the ionic conductivity was 10 ^-6 to 10 ^-8 S/cm, although there was a difference depending on the amount added. When sintering at 900°C, which is the temperature at which the electrode and the electrolyte react, when 5-20% of an ion conductor is added, the ionic conductivity of the electrolyte is 10 ^-5 to 10 ^-7 S/cm. When a small amount of 1 to 5% of an ion conductor was added to LLZO at 1050° C. and sintered, an electrolyte having an ionic conductivity of ^{10 -4} to 10 ^{-5 S/cm was obtained.} Here, the ion conductor is an oxide (Li ₂ O, B ₂ O ₃ , SiO ₂ , CaO, BaO, MgO, TiO ₂ , GeO ₂ , Sb ₂ O ₃ ) and a phosphate compound or a sulfide (Li ₂ S, Li ₂ SO _{4 ).} , Li ₃ PO ₄ , P ₂ O ₅ , P ₂ O _{3 ,} SiS _{2 ,} SnS, TaS ₂ , P ₂ S ₅ ), etc. in combination of 3 or more types 0.5 after heat treatment at 1000~1250℃ for 3~10 hours It is pulverized to a particle size of ~2 μm. This technology cannot achieve the desired performance in an all-solid-state battery unless sintering at a high temperature of 1050° C. or higher, and the ionic conductivity of the ion conductor is low, and the manufacturing method is complicated.

In Patent Publication No. 10-2017-0034581, Li _x La _y Zr _z O ₁₂ ( 6≤x≤9, 2≤y≤4, 1≤z≤3 ) and Li _{0 . 33} La _{0 . 55} TiO ₃ A solid electrolyte with high ionic conductivity of ^{2.2-3.3×10 -4} S/cm is prepared by adding and mixing 1-50 wt% of a sintering aid to phosphorus conductive solid oxide and then sintering at 250-750° C. for 1-4 hours. reported that it did. The sintering aids were lithium nitrate, lithium carbonate, lithium sulfate, and lithium acetate. It has not been confirmed whether the prepared electrolyte can be mixed with the positive electrode and simultaneously sintered at a low temperature. In Korean Patent Publication No. 10-2017-0133316, oxide crystals (perovskite type-La-Li-Ti-O or garnet type-Li-La-Zr-O) and glass-ceramics (phosphate compound LATP) as electrolytes , LAGP) of at least one lithium ion conductor and a sintering temperature of less than 600 ℃ species and ion conductivity of 5 × 10 ^-7 S / cm or more germanium (Ge), silicon (Si), boron (B), phosphorus (P), etc. It has been reported that a battery was manufactured by mixing one of the lithium ion conductors of a lithium ion conductor at a low temperature of 600° C. or less and laminating it with an electrode.

In J.Power Sources 196 (2011) 764-767, when LiCoO ₂ is deposited as a thin film on the surface of LLZO pellets and sintered at 937K to integrate the electrode and the electrolyte, between the electrode layer and the electrolyte layer during the heat treatment process As shown in Figure 1 in La ₂ CoO ₄ It was reported that there was a problem in the formation of an impurity phase. Also, in J. Power Source, 81-82 (1999) 853-858, LTP(LiTi ₂ (PO ₄ ) ₃ )/LiCoO ₂ was prepared by SPS (Spark-plasma-sintering) method. When sintering after lamination pelletization, the protons react during the sintering process to generate a second phase that does not contribute to the charge/discharge reaction, and the sintering interface is electrochemically inactivated. have. The generation of the second phase varies depending on the sintering temperature. In the case of sintering at 1000°C, as shown in FIG. 2, CoO, Co ₃ O ₄ phases, and when sintering at a temperature of 800° C. or higher, CoTiO ₃ , Co ₂ TiO ₄ , LiCoPO ₄ phases are generated. did.

Most of these prior arts refer to sintering only the electrolyte, and the material used as a sintering aid only lowers the sintering temperature, but has low ionic conductivity and a high manufacturing cost due to a complicated process. In addition, even if the electrolyte and the positive electrode are laminated and sintered at the same time, the sintering temperature is high as high as 850 ° C. And by allowing them to react with each other, a second different compound is generated at the interface of the electrolyte layer, causing a problem in that the resistance is increased.

The present invention has been devised under the technical background described above, and an object of the present invention is to provide a glass electrolyte having high ionic conductivity as well as a sintering aid capable of sintering at 850° C. or lower at the same time by integrating an electrolyte and a positive electrode composite.

Another object of the present invention is to provide a lithium secondary all-solid-state battery cell by simultaneous sintering at 850° C. or less through a composite of a glass electrolyte and a crystalline electrolyte and a composite of a glass electrolyte and a positive electrode.

In addition, other objects and technical features of the present invention will be presented in more detail in the following detailed description.

In order to achieve the above object, the present invention is _{Li 1 .5- x M x A 0} .5 (PO 4) 1. 5 BO 3, ( where, M is a metal element, A is Sn or Ti, 0 <x < _{1.5), Li 1 .2+ x Fe} 0 .2+ x Ti 1 .8-x (PO 4) 3- y (BO 3) y ( wherein, 0 <x <0.3, 0 <y <3), or _{Li 2 Sn 0 .5 (BO 3} ) 1- x (PO 4) x ( where, 0 <x <1) as a modifier oxide or an intermediate oxide as one of the glass-based oxide selected from SnO, TiO _2, Al ₂ O ₅ , Fe ₂ O ₃ , P ₂ O ₅ or B ₂ O ₃ All-solid-state battery, characterized in that the addition of a mesh oxide - provides a glass electrolyte for low-temperature co-sintering of the electrode.

The invention _{also, Li 1 .5- x M x A} 0 .5 (PO 4) 1. 5 BO 3, ( where, M is a metal element, A is Sn or Ti, 0 <x <1.5) , Li 1 _{.2+ x Fe 0 .2+ x Ti 1} .8-x (PO 4) 3- y (BO 3) y ( wherein, 0 <x <0.3, 0 <y <3), or Li ₂ Sn _{0. Prepare any one glass-based oxide raw material selected from 5} (BO ₃ ) _{1- x} (PO ₄ ) _x (here, 0 < x < 1), and 5 to 20 wt% of the total blending amount of the raw material All-solid comprising the step of mixing sucrose, adding Li raw material in excess of 5 to 10 wt% with respect to the amount of Li, melting the mixed raw materials in an atmospheric atmosphere in the range of 900 to 1350° C., and pulverizing the obtained melt Provided is a method for manufacturing a glass electrolyte for battery electrolyte-electrode low-temperature co-sintering.

The present invention is also prepared by mixing the above-mentioned glass electrolyte and crystalline electrolyte, and is composed of 17 to 33% of the glass electrolyte and 67 to 83% of the crystalline electrolyte by weight, and has an ionic conductivity of 10 ^-4 to 10 ^-5 It provides a composite electrolyte, characterized in that S / cm.

The present invention also provides a composite positive electrode using the above-described glass electrolyte, including a positive electrode active material, a crystalline electrolyte and a glass electrolyte, and a conductor, wherein the ratio of positive electrode active material: crystalline electrolyte: glass electrolyte: conductor is 50-52: 22.0- 35.5: 8-20: provides a composite anode, characterized in that 4.5-9. The crystal electrolyte compounded with the glass electrolyte may be, for example, Al doped LLZO, NCM611 or NCM811 as a cathode active material, and ITO, Ag, Cu, Pd, Ketjen Black, or C as a conductor.

The present invention also provides a composite electrolyte prepared by mixing the above-described glass electrolyte and a crystalline electrolyte, and a composite positive electrode including a positive electrode active material, a crystalline electrolyte and a glass electrolyte, and a conductor as a composite positive electrode using a glass electrolyte, in a pellet or sheet type. to provide an all-solid-state battery, characterized in that obtained by manufacturing an integrated battery cell, and sintering the battery cell at 750 to 825° C. for 2 to 48 hours in an atmospheric atmosphere.

According to the present invention, a glass electrolyte capable of being sintered at a low temperature while having high ionic conductivity is provided, and in a lithium secondary all-solid-state battery, the electrolyte and the electrode are laminated and integrated and can be fired at 850° C. or less at the same time.

In addition, since it is possible to use an electrode material having a high voltage and a high capacity, optimizing it can reduce the space compared to the LIB and provide a high energy density.

On the other hand, when a sucrose reducing agent is added to a raw material of a glass electrolyte containing a metal oxide and melted in an atmospheric atmosphere, the metal oxide component is transferred to the metal component and the eutectic point is lowered, so that the glass electrolyte can be obtained at a temperature 250 ° C or more lower than when melting in the air. In addition, it is possible to prevent crystal precipitation or devitrification in the melting process, thereby increasing the reliability of the material and lowering the manufacturing cost.

In addition, if the organic electrolyte is replaced with a solid electrolyte, safety problems such as explosion and ignition, which are issues of current lithium secondary batteries, can be solved, and additional secondary accidents can occur within extreme conditions such as high temperature, shock, and damage. can significantly reduce the risk of

In addition, process simplification and lamination can achieve low cost, high capacity, and high output, and thus can be applied to medium and large storage devices.

Since the solid electrolyte material proposed in the present invention does not react with lithium metal and has high lithium ion conductivity, it can be used as a protective lithium electrode or dendrite suppression layer of lithium metal.

1a and 1b are cross-sectional projection electron microscopy (TEM) images and EDS analysis curves _{of the LiCoO 2} /LLZO (Li ₇ La ₃ Zr ₂ O _{12 ) interface.
2a and 2b show the interface between the electrolyte and the anode when LTP/LiCoO 2} is laminated and sintered at 800° C. or higher by SPS (Spark-plasma-sintering) method _{, CoO,Co 3} O ₄ , CoTiO ₃ , Co ₂ TiO ₄ , LiCoPO ₄ Photo from which phase 2 was created
3 shows the thermal expansion curve of the crystal electrolyte and the electrode (LCZO linearly expands up to 1000 ° C or higher with the electrolyte currently used, but LCO expands at 820 ° C, NCM 870 ° C, and LTO rapidly decreases at 950 ° C or higher as an anode indicates that)
Figure 4 shows the particle size and distribution of the pulverized crystalline electrolyte (d) and the glass electrolyte (c) for use in the present invention (the average particle size of the glass electrolyte should be smaller than that of the crystalline)
5a and 5b are the softening curves observed with a high-temperature microscope of Samples 2-11.
Figure 6 is Li ₂ O—FeO (TiO ₂ )-B ₂ O ₃ (P ₂ O ₅ ) Impedance curve of the glass electrolyte
7 is a molten state appearance depending on whether sucrose is added (the case of adding sucrose is better vitrified than without addition)
Figure 8 is NASICON-type LiTi ₂ (PO ₄ ) ₃ and Li _{1 . 2 Fe 0 .2 ~ 0.5 Ti 0} .8 ~ 1.5 (PO 4) 3- y (BO 3) y system impedance curve of the glass electrolyte
9 is Li _{1 . 4} Al _{0 . 1 Sn 0 .5 (PO 4)} 1. hot micrograph of the electrolyte of the glass ₅ BO ₃ Composition
10 is an X-ray diffraction analysis pattern for confirming crystallinity after melting the glass electrolyte;
11A and 11B are X-ray diffraction patterns after melting glass electrolyte and sintering ((a) after melting at 1350°C, (b) after firing at 825°C)
12 is a microstructure after sintering the electrolyte at 825° C. for 2 hours.
13 shows the composite electrolyte and composite anode sheets manufactured using the tape forming method, before and after sintering at 800° C. for 24 hours after stacking and integrating -composite anode side, composite electrolyte side-battery cell shape (composite anode sheet 6 to 10 sheets, electrolyte 1~2 sheets stacking thickness of about 150~180㎛, electrolyte thickness of 10~20㎛)

The present invention proposes a glass electrolyte capable of sintering at a low temperature while having high ionic conductivity, and a low-temperature co-sintering all-solid-state battery using the same.

Oxide sealed case of the solid electrolyte and stable in contact with the atmosphere with lithium and having excellent advantages, but the ionic conductivity in 10 ^-4 S / cm, and a problem of high interface resistance, a glass oxide-based solid electrolyte has a conductivity of 10 ^-4 to Compared to 10 ^-5 S/cm, the thickness is 0.2~0.5mm, so the ohmic resistance is large, so the flat area is reduced during charging and discharging, and the electrode capacity is also reduced, resulting in very low energy density.

On the other hand, in order to apply an oxide-based solid electrolyte to an all-solid-state battery, it is impossible to apply it by cold pressing because of its inflexible and brittle characteristics. In particular, in order to control the thickness, a sintering process at a high temperature is essential. Commercially available acid-based electrolytes include perovskite-type Li _{0 . 33} La _{0 . 56} TiO _{3 ,} NASICON-type LiTi ₂ (PO ₄ ) ₃ and garnet-type Li ₇ La ₃ Zr ₂ O ₁₂ , and the sintering temperature to exhibit high ionic conductivity is 1200° C. or higher. However, during high-temperature sintering, side reactions such as formation of an impurity phase between the electrode and the electrolyte are likely to occur. In addition, most cathode materials are synthesized at 850 ~ 1000 °C, and at a temperature higher than that, a second phase is generated and Li is volatilized.

When the electrolyte and the positive electrode composite are laminated and sintered at the same time, when the sintering temperature is higher than 850°C, Li volatilization is severe, and in the sintering process of the composite, the electrode active material and the solid electrolyte react with oxygen in the atmosphere, or oxygen in the positive electrode is released As a result, the transition metal acts as a catalyst to react with each other, thereby generating a second other compound at the electrolyte layer interface, thereby increasing the resistance. Therefore, there is a need for a sintering aid capable of sintering by laminating an electrolyte and an electrode at 850° C. or less at the same time.

As a sintering aid, what has been proposed so far is Li ₃ BO _{3 ,} Li ₄ P ₂ O _{7 and} other di, triphosphate compounds, 0.44LiBO ₂ -0.56LiF, Li ₃ PO ₄ , 62~72wt%SiO ₂ -1~15wt %Al ₂ O ₃ -14~20wt%Na ₂ O-0~3wt%MgO-0~10wt%CaO-0~15wt%BaO, oxide (Li ₂ O, B ₂ O ₃ , SiO ₂ , CaO, BaO, MgO, TiO ₂ , GeO ₂ , Sb ₂ O ₃ ) and phosphate compounds or sulfides (Li ₂ S, Li ₂ SO ₄ , Li ₃ PO ₄ , P ₂ O ₅ , P ₂ O _{3 ,} SiS _{2 ,} SnS, TaS _{2 )} , P ₂ S ₅ ) in combination of three or more, lithium nitrate, lithium sulfate, lithium acetate, etc., lithium ion conductors such as germanium (Ge), silicon (Si), boron (B), phosphorus (P), etc. There is a mixture of one of them. Usually Li ₃ BO _{3 ,} Li ₄ P ₂ O ₇ and Li ₃ PO ₄ It has the disadvantage of low ionic conductivity.

On the other hand, LiTi ₂ (PO ₄ ) _{3 having a NASICON structure} Is Although it has high ionic conductivity, it cannot be used as a sintering aid for sintering with a crystalline electrolyte because its sinterability is very low even at 1200°C. In addition, _{in order to prepare LiTi 2} (PO ₄ ) ₃ by a melting method, It must be melted by mixing a strong reducing compound or melted at a high temperature of 1350°C or higher in a neutral or reducing atmosphere, and there is a problem in the process of severely corroding crucibles (platinum, alumina, zirconia, etc.) or refractories during manufacturing.

The present inventors tried to develop a glass electrolyte with high ionic conductivity as a sintering aid so that the electrolyte and positive electrode composite can be integrated and laminated and sintered at 850° C. or lower at the same time. After lamination at ℃ or lower, simultaneous sintering was performed to complete an all-solid-state battery.

Since the sintering temperature needs to be lowered below the reaction temperature by determining at which temperature the electrolyte and the electrode react, thermal expansion was measured for the electrolyte and the electrode to confirm this reaction, and the results are shown in FIG. 3 . The electrolyte, LALZO, expands linearly even at 1000°C or higher without a softening point. LCO, which is a cathode material, is rapidly expanding with a difference in expansion from electrolyte around 820℃, so it seems that the decomposition of LCO begins, Li[Ni _0.8 Co _0.1 Mn _0.1 ]O ₂ (hereinafter referred to as NCM ₈₁₁ )NCM ₈₁₁ NCM ₆₂₂ is judged to be softened by seeing that the expansion rapidly decreases around 850°C.

Based on these results, considering the electrolyte and electrode, a glass electrolyte material that can act as an electrolyte by itself as a sintering aid and high ionic conductivity was developed so that simultaneous sintering at a low temperature without interfacial reaction at a temperature of 850 ° C or less can be achieved. developed.

Specifically, in the present invention, Li ₃ BO _{3 which is a commonly known sintering aid} etc Instead of crystalline oxide, as a free oxide-based ion conductor, _{0.1 to 0.6 moles of SnO, Al 2} O ₃ , TiO ₂ as modified or intermediate oxides instead of ₃ moles of Li 2 O, and 1.5 moles of P ₂ O ₅ as a mesh oxide, Li added _{1 .5- x M x A 0 .5} (PO 4) 1. 5 BO 3 (M is a metallic element, A=Sn, Ti) A glass electrolyte having a composition is provided.

In addition, crystal-based oxide Nasicon-type LiTi ₂ (PO ₄ ) ₃ , Perovskite Li-La-Ti-O In place and the like, Li _{1 .2+} a glass-based oxide _{x Fe 0 .2+ x Ti 1 .8} -x (PO 4) 3- y (BO 3) y , or _{Li 2 Sn 0 .5 (BO 3} ) _{1- x} (PO ₄ ) _x Substituting the TiO ₂ intermediate oxide with Fe ₂ O _{3 as a composition,} P ₂ O ₅ To provide a glass electrolyte in which mesh oxide _{is substituted with B 2} O _{3 .}

The starting materials used for the glass electrolyte are _{1-2 moles Li 2} O, 0.2-0.5 moles Fe ₂ O ₃ , 1.5-1.8 moles TiO ₂ 1-3 moles P ₂ O ₅ , 1-3 moles B ₂ O ₃ And, in consideration of the volatilization of Li when melting into a glass electrolyte, _{the amount of the Li 2} O source may include more than 5 to 10 wt%. In addition, 5 to 20 wt% of sucrose as a reducing agent may be added to the total amount of the glass electrolyte starting material to be melted together to improve the melting property of the glassy furnace.

The mixture mixed with the above composition may be melted at 1350° C. for 30 minutes in an atmospheric atmosphere to prepare a glass electrolyte. This glass electrolyte can be mixed with a crystalline electrolyte and used as a sintering aid and an electrolyte for an all-solid secondary battery that can be sintered below 825 ° C. 10 ^-4 ~ 10 ^-5 S/ It was confirmed to have an ionic conductivity of cm. In particular, it is possible to melt in the atmospheric atmosphere at a low temperature 200 to 300 ° C lower than before, thereby lowering the manufacturing cost, and by pulverizing the particle size of the glass electrolyte that can serve as a sintering aid than the crystal electrolyte, the wettability characteristics during sintering are improved. made to be excellent.

In the present invention, when manufacturing the glass electrolyte, it may include the steps of balancing, mixing, melting, and pulverizing the glass electrolyte raw material to a particle size smaller than that of the crystalline electrolyte. In addition, as a method of manufacturing an all-solid-state battery using a glass electrolyte, the steps of preparing a composite electrolyte by mixing a glass electrolyte and a crystalline electrolyte, preparing a composite anode by mixing the composite electrolyte and an electrode, a composite electrolyte and a composite anode It may include the step of stacking and integrating and co-sintering at a low temperature of 825° C. or less. The composite electrolyte, the composite anode, and the laminated integrated all-solid-state battery may be molded into various shapes, such as pellets or sheets.

Hereinafter, the technical features and effects of the present invention will be described in more detail through specific examples.

free electrolyte Manufacturing I ( manufacturing example One)

Sintering aid of a glass powder the chemical composition of Li _x M _x A _{1 .5- 0} for _.5 (PO _{4) 1.} to 1.5mole Li ₂ O with respect to the modified oxide _{5 BO 3 (M = Al,} A = Sn, Ti) 0.5 mole SnO or TiO ₂ intermediate oxide, 0.7 mole P ₂ O ₅ and 0.5 mole B ₂ O ₃ mesh oxide were used as the sample composition in Table 1 to prepare a glass electrolyte for a sintering aid.

As a raw material for preparing the same chemical composition as Samples 1-1 to 1-3, Li ₂ O is LiOH·H ₂ O, SnO is SnO, TiO ₂ is TiO ₂ , P ₂ O ₅ is H ₃ PO ₄ , B ₂ O ₃ H ₃ BO ₃ was used. The above raw materials were weighed and mixed, and the glass mixture was put in a Nalgene _. bottle with Φ5 and 10mm alumina balls and anhydrous alcohol, and mixed in a ball mill for 6 hours. _{At this time, 5wt% of sucrose (C 12} H ₂₂ O ₁₁ ) was added to samples 1-1 to 1-3 based on the total weight of the glass mixture and mixed. In addition, since Li ₂ O is highly volatile at a high temperature, _{5 wt% more than the Li 2} O composition source was additionally added.

The addition and mixing of sucrose to the glass mixture is for melting at a temperature lower than the existing melting temperature, and by adding sucrose, the melting atmosphere is changed to a reducing atmosphere. (eutectic temperature) is lowered, and melting is possible at a temperature 200~300℃ lower than atmospheric atmosphere. The addition of sucrose has the advantage of simplifying the manufacturing process because other equipment for controlling the atmosphere is not required.

Mixture samples 1-1 to 1-3 mixed with the chemical composition of the above glass electrolyte were placed in an alumina crucible and maintained at 900 to 1000° C. for 30 minutes in an electric furnace having a silicon carbide (SiC) heating element to prepare a glass melt.

The glass melt is first coarsely pulverized into large particles using a jaw crusher, then finely pulverized in a dry manner to a level of 3 μm in a jet mill, and then ultrafine pulverized in a nanojet mill to average as shown in FIG. The particle size (D ₅₀ ) was set to 0.245 μm or less. At this time, nanojet mill grinding was performed by adding anhydrous ethanol solvent and Φ0.5-0.8mm zirconia balls together and grinding at 600rpm for 10 hours to complete a glass electrolyte for sintering aid.

free electrolyte Manufacturing II ( manufacturing example 2)

A glass electrolyte chemical composition _{Li 1 .2+ x Fe 0 .2+ x} Ti 1 .8-x (PO 4) 3- y (BO 3) y , or _{Li 2 Sn 0 .5 (BO 3} ) 1- x ( For PO ₄ ) _x , the TiO ₂ intermediate oxide was substituted _{with Fe 2} O _{3 ,} P ₂ O ₅ Mesh oxide is B ₂ O ₃ By substitution, a glass electrolyte for a sintering aid was prepared as in the compositions of Samples 3 to 14 of Table 2. At this time, sucrose was added to each sample to melt at a low temperature, and the Li source was included in excess in consideration of the volatilization of Li. The amount of sucrose was 10% based on the total weight of the mixture of the glass electrolyte starting materials (in addition to 10% for Sample 11, 15% and 20%), and the amount of excess Li was further mixed by 10% by weight with respect to the Li raw material source.

_{LiOH·H 2} O, α-Fe ₂ O ₃ , SnO, TiO ₂ , H ₃ PO ₄ , and H ₃ BO ₃ were used as raw materials for glass electrolyte with the same chemical composition as in Samples 3 to 14. After weighing according to the chemical composition of Table 2, alumina balls and anhydrous alcohol were put in a Nalgen bottle and mixed in a ball mill for 6 hours.

The mixture of Samples 3 to 14 was placed in an alumina crucible and maintained at 1350° C. for 30 minutes in a SiC electric furnace for a maximum operating temperature of 1500° C., and then melted into a glass electrolyte melt. The melting method and the powdering method were the same as in Preparation Example 1.

Ionic conductivity evaluation

The composition of Table 1 is shown in Table 3 by evaluating the ionic conductivity of the glass sample for sintering aid melted as in Preparation Example 1 at 25° C. using an impedance device. As a result of the evaluation, 1.5 mole Li and And Sn _{0 .5} (PO _{4) 1.5} Ti _{0 .5} (PO _{4) 1.} Composition composed of ₅ 4.65×10 ^-6 S/cm and It showed an ionic conductivity of 1.70×10 ^{-5 S/cm.} On the other hand, 1.4 moles Li and Al _{0 . 1 Sn 0 .5 (PO 4)} 1. Composition composed of ₅ The ionic conductivity value was 3.82×10 ^{-6 S/cm.} The ionic conductivity of the glass electrolyte was measured with an impedance device and the total resistance (bulk and interfacial resistance) was measured by the equivalent circuit method under the conditions of 1 Hz to 4 MHz. Ionic conductivity is C=R ^{(1-n)/ n} Q ^{1 / n} Calculated.

Substitution of Li may be in the range of 0 to 1.5 moles, _{and as a material substitutable with Li 2} O, the intermediate oxide is, for example, Al ₂ O ₃ , the substitution amount is 0.1 mole, and the content of Sn and Ti as the modifying oxide elements is, for example, For example, 0.4 to 0.5 moles, the substitution of B, which is a network oxide, can be replaced by, for example, 1 mole.

high temperature microscope Observation and evaluation of ionic conductivity

The composition of Table 2 was observed with a high temperature microscope to confirm whether co-sintering at a low temperature of 825° C. or less for the sample prepared by the method of Preparation Example 2 was possible, and the results are shown in FIG. 5 . In addition, the ionic conductivity was evaluated using an impedance device at 25°C, and it is shown in Table 4.

As a result of the evaluation, the glass electrolyte in which the secondary softening occurred at 800°C was sample 11, and the samples 6 and 10 were samples that softened at 600°C and continued to soften as the temperature increased. In addition, the composition in which softening began to occur around 800° C. and continued to soften was sample 9.

Therefore, in this Example, _{samples 6, 10 and 11 were suitable to use Li 2} O-FeO(TiO ₂ )-B ₂ O ₃ (P ₂ O ₅ )-based glass electrolyte for co-sintering at around 800°C.

The ionic conductivity of the electrolyte glass having the above chemical composition, see Fig. 6 and Table 4, when _{Li 1 .2 · Fe 0.2 · Ti} 1.8 · (PO 4) with increasing the addition amount to ₃ BO ₃ to 1.5mole ionic conductivity is lowered jidaga PO _{When 4} was 1 mole and BO ₃ was added 2 moles, 10 ^-4 S/cm was obtained. However _{, when only BO 3 was added without PO 4} , the ionic conductivity increased again. On the other hand, Fe ₂ O ₃ When the amount was increased to 0.5 moles and PO ₄ and BO ₃ were added by substitution, the ionic conductivity did not change significantly, but _{when only BO 3 was} added, the ionic conductivity increased.

Chemical compositions with high ionic conductivity of 10 ^-4 S/cm were Li _1.2 Fe _0.2 Ti _1.8 (PO ₄ )(BO ₃ ) ₂ and Li _1.5 Fe _0.5 Ti _1.5 (BO ₃ ) ₃ . Ion conductivity was measured and calculated in the same manner as in Experimental Example 1.

_{Li 1 .2 + x · Fe 0} .2 + x · Ti 1 .8-x · (PO 4) 3-y · (BO 3) y range of Li in the composition is the amount of 1.0 ~ 1.5mole, Fe 0.2 ~ Preferably, 0.5 moles, Ti is 1.5 to 1.8 moles, P is 1 to 3 moles, and B is 1 to 3 moles.

Particle size analysis

After the samples of Preparation Examples 1 and 2 were melted at 1350° C. for 30 minutes, the melt was taken out of the electric furnace and poured into a cooling device for rolling while cooling water flows to prepare a thin cullet. This thin flaky cartridge is coarsely pulverized to about 1~2mm with a jaw crusher equipped with a tungsten ruler (W jar), and then the previously coarsely pulverized glass electrolyte is treated with an alumina (Al ₂ O ₃ ) ruler (Jar). ) was finely pulverized to a level of about 3 μm with a jet mill equipped with. The glass electrolyte finely pulverized to about 3 μm is ultra-finely pulverized so that the average particle size is about 0.245 μm using Φ0.5 ~ Φ0.8 mm alumina media in a nano jet mill and anhydrous ethanol as a solvent. did. The preferred average particle size is 0.1 to 0.5 μm, and the particle size distribution is in the range of 0.01 to 3 μm. The particle size and distribution of the ultra-fine pulverized particles were analyzed using a nanoparticle size meter.

of sucrose Melting results according to the addition

In order to check how the melting temperature and the melt change depending on whether or not sucrose is added to the mixture when melting to prepare the glass electrolyte, a sample in which sucrose is not added to the chemical composition of the glass electrolyte in Preparation Example 1 was used. At 1100°C, the mixture to which sucrose was added was melted at 900°C to compare the molten shape, and the results are shown in FIG. 7 . In this case, the raw materials used, mixing, and melting were performed in the same manner as in Preparation Example 1. When sucrose was added, the melting temperature was 200°C lower than that without the addition of sucrose, and the vitrification state of the melt was excellent.

of sucrose Ion conductivity according to the amount added

It was confirmed how the ionic conductivity of the melt changes depending on the amount of sucrose added to the mixture when the glass electrolyte mixture is melted. Li _1.5 Fe _0.5 Ti _1.5 (BO ₃ ) ₃ (Sample 11) was added with 10%, 15%, and 20% of sucrose by weight and melted at 1350° C. for comparison. The results are shown in Table 5. At this time, the raw materials used, mixing, and melting were performed in the same manner as in Preparation Example 1. When the addition amount of sucrose was increased from 10 and 15 percent to 20 percent by weight, the ionic conductivity ^{improved from 10 -5} S/cm to 10 ^-4 S/cm.

Ion Conductivity Comparison I

_{Li 3} BO _{3 previously} known as a lithium ion conductor Li _{1 . 5 Ti 0 .5 (PO 4)} 1. We compared the ion conductive property for ₅ BO _3. Li ₃ BO ₃ and Li _{1 . 5 Ti 0 .5 (PO 4)} 1. 5 BO 3 The chemical composition was weighed, mixed, and melted in the same manner as in Preparation Example 1. As a result of comparison, as shown in Table 6, Li ₃ BO ₃ had an ionic conductivity It showed a relatively low value of 7.83×10 ^{-7 S/cm,} Li _{1 . 5 Ti 0 .5 (PO 4)} 1. 5 BO 3 are order than 2 exhibited a high 1.70 × 10 ^-5 S / cm value.

Ion Conductivity Comparison II

Composition of a crystalline electrolyte having a NASICON-type crystal structure LiTi ₂ (PO ₄ ) ₃ And the present invention Li _1.2 Fe _0.2 Ti _1.8 (PO ₄ )(BO ₃ ) ₂ And Li _{1 . 5} Fe _{0 . 5} Ti _{1 .5} (BO ₃₎ The ion conductivity compared to compare the ion conductivity of _3, mixed in the same manner as in Preparation Example 2, melted. As a result, as shown in Table 7, the comparative composition LiTi ₂ (PO ₄ ) ₃ On the other hand, the ionic conductivity of 7.81 × 10 ^-7 _{S/cm, Li 1 of the present invention. 2} Fe _{0 . 2 Ti 1 .8 (PO 4)} (BO 3) 2 and Li _{1. 5} Fe _{0 . 5} Ti _{1 . 5} (BO ₃ ) ₃ showed high ionic conductivity values of ^{2.35×10 −4} S/cm and 5.29×10 ⁻⁴ S/cm, respectively, as shown in FIG. 8 .

Since the ionic conductivity of the glass electrolyte of the present invention is high, it was determined that the glass electrolyte would exhibit excellent battery characteristics when applied to an all-solid-state battery.

free electrolyte Softening Point Analysis

_{Li 1.4} Al _0.1 Sn _0.5 (PO ₄ ) _1.5 BO ₃ as a glass composition that is an ion conductor and a sintering aid in the chemical composition in Preparation Example 1 was selected. Modified oxide of Li ₂ O was substituted instead of the Al ₂ O ₃ as a dopant (dopant) 0.1mole, wherein an Al ₂ O ₃ dopant amount of 0.05 to 0.3 mol (mole) of a preferred 0.1mole. As an intermediate oxide, Sn was added instead of Ti. Li ₂ O-SnO-B ₂ O ₃ (P ₂ O ₅ )-based glass exhibits lower crystallinity when _{SnO and P 2} O ₅ are added together than when SnO is added alone. If the crystallinity is high, it may not function as a glass, so it can be said that one with low crystallinity is suitable as a sintering aid after melting if possible.

The addition of sucrose during melting, excess addition of Li, and the preparation method were carried out as in Preparation Example 1. At this time, as raw materials, LiOH·H ₂ O, SnO ₂ , Al ₂ O ₃ , H ₃ PO ₄ and H ₃ BO ₃ were used.

FIG. 9 shows thermal shrinkage and hot-stage microscope images of the glass electrolyte of this example observed with a high-temperature microscope (temperature increased by 5° C./min). Although the ionic conductivity was low, it showed a very low softening point. The transition point is around 670°C, the start of crystallization is 710°C, and complete wetting is occurring at 780°C. Therefore, if this system is used as a sintering aid and lithium ion conductor, an all-solid-state battery cell in which the electrolyte and the electrode are simultaneously fired at 750 to 800° C. can be manufactured.

free electrolyte Crystallinity Analysis I

Replacing the intermediate TiO ₂ oxide glass in electrolyte chemical composition as _{Li 1 .2+ x Fe 0 .2+ x} Ti 1 .8-x (PO 4) 3- y (BO 3) y as Fe ₂ O _3, and P ₂ O ₅ Mesh oxide is B ₂ O ₃ By substitution, glass electrolytes were prepared as shown in Samples 3 to 7 of Table 2. For example, the composition of the glass electrolyte of sample 3 Li _{1 . 2} Fe _{0 . 2} Ti _{1 .8} (PO ₄₎ samples _7-3 the glass electrolyte composition Li _{1. 2} Fe _{0 . 2 Ti 1 .8 (BO 3)} (PO 4) of 3mole having the same structure (mesh size) to convert to replace the ₃ BO ₃ to 1mole ~ 3mole ₃ instead. Mixing, melting, and grinding methods were the same as in Preparation Example 2. When the intermediate oxide and mesh oxide were substituted, the glass and crystallinity changes were confirmed. The crystal phase is shown in FIG. 10, and the change in ionic conductivity due to impedance is shown in FIG. 8 and Table 4.

According to the crystal phase analysis, 0.2 moles of SnO, which is a modifier oxide and can be a mesh oxide or an intermediate oxide, is _{replaced with Fe 2} O _{3 as an intermediate oxide in the Li 2} O-SnO(TiO ₂ )-B ₂ O ₃ (P ₂ O _{5 )-based composition.} and B ₂ O _{3 instead of P 2} O ₅ , which is a mesh oxide In case of melting by substitution B ₂ O ₃ As the amount of substitution increased, the crystallinity decreased and TiO ₂ appeared as the main crystal. PO ₄ is liberated _{as BO 3} is replaced, but TiO ₂ A single crystal was also present. Li _{1 with} only P ₂ O _{5 added. 5} Fe _{0 . 5} Ti _{1 . In the case of 5} (PO ₄ ) ₃ , it appeared as an amorphous phase.

free electrolyte Crystallinity Analysis II

A glass electrolyte chemical composition _{Li 1 .2+ x Fe 0 .2+ x} Ti 1 .8-x (PO 4) 3- y (BO 3) 0.5mole replacing the intermediate oxide TiO ₂ for _y in Fe ₂ O ₃ did, P ₂ O ₅ The mesh oxide was _{substituted with B 2} O ₃ 1-3 moles to prepare a glass electrolyte for low-temperature sintering as shown in Samples 8-11 in Table 2.

In order to convert the composition of the free electrolyte of Sample 8 to that of Sample 11, the amount of Fe as an intermediate oxide was increased from 0.2 moles to 0.5 moles, and instead, the Li and Ti amounts were decreased and at the same time PO ₄ was substituted with BO ₃ , Fe was 0.5 In the case of mole, crystallinity was decreased compared to the case of 0.2 mole, but the ionic conductivity was 10 ^-4 to 10 ^-6 S/cm as shown in Table 4 and FIG. 6 . Crystallinity is affected by Fe, and ionic conductivity is judged to be affected by the amount of _{PO 4} or BO _{3 rather than the amount of Fe.} From these results, it is predicted that the glass electrolyte induces a lower temperature during sintering with crystalline material, so that the positive electrode can be sintered at a temperature that does not react with the electrolyte. If the crystallinity is high, it may not function as a glass electrolyte, so it can be said that a glass electrolyte with low crystallinity after melting is suitable as a glass electrolyte for co-sintering. Examining from X-ray diffraction analysis, samples 5, 6, 7, 8, 9, and 11 were glass electrolytes suitable for low-temperature sintering temperature. On the other hand, samples 6, 7, and 11 showed high ^{ionic conductivity of 10 -4} to 10 ^{-5 S/cm among the glass electrolyte samples.} The ionic conductivity was _{lowered until PO 4} and BO ₃ were 1.5 moles, but when the amount of _{BO 3 was 2 moles and PO 4} was 1 mole, the ionic conductivity was very high.

free electrolyte Low temperature sintering possibility

Whether the glass electrolyte can be sintered at a low temperature and whether the ionic conductivity is maintained during low-temperature sintering was examined for Sample 11. After sintering, the crystal phase change and ionic conductivity were confirmed. The sintering conditions were the same as those of the composite electrolyte, sintering at 825° C. for 2 hours. The results are shown in FIG. 11 . When the crystal phases before and after sintering were compared, the intensity of crystals was lowered after sintering than before sintering due to the generation of a glass phase, but the phases of crystals remained the same. Before and after sintering the ionic conductivity is ^{7.23 × 10 -5 ~ 3.63 × 10} - ⁵ exhibited. It can be seen that even after sintering with a glass electrolyte, the crystal phase decreased and the same ionic conductivity was exhibited.

pellet type composite electrolyte

In order to develop a battery that is sintered at low temperature and can serve as an electrolyte and secure safety, as shown in Table 8, a composite electrolyte was prepared by mixing an ultrafine powder of a glass electrolyte and a crystalline electrolyte at a constant mixing ratio.

_{Li 1} , which is the glass electrolyte sample 11, as a compounding condition that can be integrated by sintering at 825° C. or less _{. 5} Fe _{0 . 5 Ti 1 .5 (BO 3)} 3 crystals with an electrolyte of _{Li 7 La 3 Zr 2 O 12} (LLZO, two thousand ceramic raendeusa) 17-33% of the powder in a weight ratio: the composite electrolyte were mixed in a 67-83% blending ratio prepared. As the glass electrolyte, melted and pulverized as described above was used.

The combined composite electrolyte is placed in a jenbyeong _(Nalgene. Bottle) day with a zirconia ball with absolute ethanol and mixed with 48 hours in a ball mill (ball mill). Put the mixed composite electrolyte into a Φ15mm mold _{to form pellets with a pressure of 200kg f} / m ² so that the thickness becomes 0.2 ~ 0.3mm, and then press the molded pellets with cold hydrostatic pressure ( CIP) treatment to form a uniform molded body. The molded composite electrolyte pellets were sintered at 750 to 825° C. for 2 to 36 hours, and in this example, the physical properties were reviewed by sintering at 825° C. for 2 hours.

Table 8 shows the properties of pellets after sintering at 825° C. for 2 hours by using a glass electrolyte alone and a composite electrolyte in which the amount of glass electrolyte and the amount of crystal electrolyte are adjusted. As the amount of the glass electrolyte increased, the shrinkage increased. When the mixing ratio of the glass electrolyte and the crystalline electrolyte was 33:67 by weight, the shrinkage ratio was 24%, and sintering was completed. The glass electrolyte alone (GE) exhibited a shrinkage of 21%. On the other hand, the ionic conductivity did not show a significant difference between the glass electrolyte alone and the mixing ratio of the glass electrolyte and the crystalline electrolyte of ^{more than 1.62-2.59×10 -5 S/cm when the mixing ratio was 17:83-33:67.} At this time, the ionic conductivity of the sintered composite electrolyte was measured with an impedance device and the total resistance (bulk and interfacial resistance) was measured by the equivalent circuit method under the conditions of 1 Hz to 4 MHz. Ionic conductivity is C=R ^{(1-n)/ n} Q ^{1 / n} Calculated.

On the other hand, the microstructure was observed to determine the sintered state of a part of the composite electrolyte and is shown in FIG. 12 . In the case of sample CG-3, in which a glass electrolyte was mixed with a crystal electrolyte, it was observed that growth into grains was performed well.

From these results, it can be seen that the mixing ratio of the crystal electrolyte and the glass electrolyte of the composite electrolyte capable of being sintered at a low temperature of 825° C. or less is preferably 67 to 83 percent by weight of the crystal electrolyte and 17 to 33 percent by weight of the glass electrolyte.

pellet type Composite Anode Manufacturing

A lithium secondary all-solid-state battery consists of a positive electrode / a solid electrolyte / a negative electrode, and the solid electrolyte requires high ionic conductivity and low electronic conductivity, and the solid electrolyte included in the positive electrode and negative electrode must also have high ionic and electronic conductivity, and the positive electrode is also an electrolyte Simultaneous sintering, ion movement from the positive electrode to the electrolyte, and the electron movement of the insulated positive electrode by the addition of electrolyte require the addition of an ion conductor and an electrical conductor in addition to the positive electrode to make it complex.

As a composite anode of a stacked integrated all-solid-state battery, in this embodiment, LiNi _0.8 Co _0.1 Mn _0.1 anode (Icheon Ceramic Land Co.), Al doped LLZO crystalline solid electrolyte (ion conductivity 10 ^{-4 to 5} S/cm, Icheon Ceramic Land Co.), _{Li 1.5 Fe 0.5 Ti 1.5 (BO} 3) 3 into a glass electrolyte (ion conductivity of ^{10 -4 ~ 5 S / cm)} , Ketjen black (ketjenblack) me the electron conductor to the compounding ratio as shown in Table 8 jenbyeong _(Nalgene. bottle) mixed did. The combined composite anode was mixed with zirconia balls and absolute ethanol in a ball mill and mixed for 48 hours. A method of manufacturing a molded body using the mixed composite anode is the same as in Example 6. The molded composite anode pellets could be sintered by heat treatment at a temperature of 750 to 825° C. for 2 to 36 hours, and in this example, physical properties were shown in Table 9 by sintering at 825° C. for 2 hours. As the amount of glass electrolyte increased, the shrinkage and density increased, so that when sample CA-4 with an amount of free electrolyte of 20%, sintering was completed with a shrinkage of 23.1%. In addition, a certain degree of sintering density was achieved when the content of the free electrolyte was 20%.

sheet type composite electrolyte

In a sintered all-solid-state battery, when the electrolyte and electrodes are stacked, if the electrolyte layer is thick, it is difficult for Li ions to move through the electrolyte. In the current non-sintered all-solid-state battery, the thickness of the electrolyte layer is 50 μm or more, so there is a disadvantage in that Li ions cannot sufficiently move. On the other hand, in the present invention, in order to provide an all-solid-state battery in a sintered type, the thickness of the electrolyte is made as thin and thick as possible. In this embodiment, by making a thin electrolyte in a sheet type and stacking it on the electrode, it was attempted to solve the problem that Li ions are difficult to move through the electrolyte.

To fabricate the sheet, first, Li _{1 , which is the glass electrolyte sample 11 . 5} Fe _{0 . 5 Ti 1 .5 (BO 3)} 3 crystals with an electrolyte of Li ₇ La ₃ Zr ₂ O ₁₂ (hereinafter LLZO, Icheon Ceramic Land) powder was mixed in a weight ratio of 17 to 33 percent: 67 to 83 percent to prepare a composite electrolyte.

The compounded composite electrolyte was mixed at the ratio of Table 10 (weight ratio relative to powder 1) and slurried so as to have a viscosity of 400 to 1000 cps, and then a sheet was prepared by a tape casting method. . At this time were primarily pulverizing and dispersing the powder and half of the solvent 1, 2, a dispersing agent, and Φ0.5mm zirconia put the ball on day jenbyeong _(Nalgene. Bottle) 48 hour composite electrolyte powder by a ball mill at 120rpm. Second, in the first process, half of solvents 1 and 2, binder, plasticizer, and antifoaming agent were added to the well-dispersed composite electrolyte and mixed to prepare a slurry. As the tape forming conditions, a gap of 45 to 150 μm and a width of 15 cm were formed so that the actual sheet thickness was 15 to 30 μm. At this time, the molding speed was performed at 1 m/min. During molding, drying was performed at 20-30-35-40-50-55-60°C for each section.

sheet type composite anode

When stacking an electrolyte and an electrode in a sintered all-solid-state battery, the positive electrode is usually used as a support layer for the electrolyte. In addition, the positive electrode layer should be made of a sheet so that the capacity of the battery can be sufficiently produced. However, as described above, if an electrolyte is added for sufficient ion movement in the anode, the anode is insulated and electrons cannot move smoothly in the anode.

Composite anode composition: LiNi _0.8 Co _0.1 Mn _0.1 anode (manufactured by Icheon Ceramic Land), Al doped LLZO crystalline solid electrolyte (ionic conductivity 10 ^{-4 to 5} s/cm, Icheon Ceramic _{Land Co., Ltd.), Li 1.5} Fe _0.5 Ti _1.5 (BO ₃ ) ₃ Glass electrolyte (ion conductivity 10 ^{-4 to 5} S/cm) and electron conductor ITO (indium tin oxide) in a weight ratio of 52:23.5:20:4.5 in a Nalgene _. bottle was added and mixed. In order to produce a sheet of mixed composite anode, first, for the compounded composite anode 1 (in weight ratio with respect to composite powder 1), mix in the ratio of Table 10 and slurry so that the viscosity becomes 400~1000cps, and then, by the tape forming method. A sheet was prepared. At this time, the slurry preparation, tape forming method and conditions are the same as in Example 8.

Different types of conductors are used in oxidizing (air) atmosphere, neutral atmosphere sintering, or reduction sintering. Although 4.5% of Ithio is used as the electrical conductor in this embodiment, other conductors and content may be used depending on the sintering atmosphere.

For example, as a conductor, ITO, Ag, and Pd may be used in an oxidizing (atmospheric) atmosphere, Ag, Cu, and Pd in a neutral atmosphere, and Cu, C, or ketjenblack in a reducing atmosphere. At this time, it may be different depending on the amount of electrolyte or the type of conductor included in the positive electrode, but it is 3 to 15% by weight. The oxidizing atmosphere is ITO, and the content is preferably 4.5 to 9 percent.

pellet type battery cell

Using the composite anode as a support layer, an electrolyte was laminated thereon to prepare pellets.

The compounding ratio of the composite electrolyte was fixed at 75:25 by weight of the crystalline electrolyte and the glass electrolyte, and the mixing ratio of the composite anode was changed as shown in Table 11 by changing the amount of the glass electrolyte or the conductor. The mixing method, molding, sintering, etc. are the same as in Examples 6 and 7.

As a result of lamination with a composite electrolyte and a composite anode and sintering, the laminated pellets were judged to be sufficiently sintered under these conditions. When the amount of glass electrolyte was changed, the sintering shrinkage did not change significantly. This indicates that adding 15% or more as a sintering aid can play a sufficient role. At this time, the sintering density also showed a high value except for the reducing atmosphere sintering, so it was judged that the dense sintering was made.

From these results, when manufacturing a battery cell by stacking a composite electrolyte and a composite electrode, the mixing ratio of the crystalline electrolyte and the glass electrolyte is 75:25 by weight, and the mixing ratio of the positive electrode: the crystalline electrolyte: the glass electrolyte: the conductor in the composite anode is 50 to 52 It can be seen that :22~28.5:15~20:4.5~9 is preferable.

sheet type battery cell

Using the composite electrolyte and composite electrode sheet prepared in Examples 8 and 9, using the composite electrode as a support layer, the composite electrolyte was laminated and integrated thereon, and then simultaneously sintered to prepare a battery cell. In this case, the composition or manufacturing method of one sheet is the same as in Examples 8 and 9. The prepared composite anode sheets 6 to 10 sheets and composite electrolyte sheets 1 to 2 sheets were laminated on the composite anode in order of the composite electrolyte, and then laminated by pressing using a press at 5 MPa pressure at 65° C. for 1 minute. After lamination, using a hydrostatic molding machine (WIP), the thickness was about 150-250 μm in the green state, and the laminate was integrated and manufactured. In this case, the WIP condition was performed by preheating at 65° C. for 5 minutes and then maintained at a pressure of 23 Mpa for 30 minutes to fabricate a stacked and integrated cell as shown in FIG. 13 .

Low temperature simultaneous firing

This is an embodiment of sintering the stacked integrated cell at 810 ~ 850 °C for 24 hours in an atmospheric atmosphere (oxidizing atmosphere). As a result of sintering, when sintering at 810° C. or higher for 24 hours, it was judged that sintering was completed in view of the shrinkage rate. The shrinkage rate at a temperature of 810°C or higher was 20.4 to 20.8%, and there was no significant difference.

Although the present invention has been exemplarily described through preferred embodiments above, the present invention is not limited to such specific embodiments, and various forms within the scope of the technical spirit presented in the present invention, specifically, the claims may be modified, changed, or improved.

Claims (5)

_{Li 1 .5- x M x A 0} .5 (PO 4) 1. 5 BO 3, ( where, M is a metal element, A is Sn or Ti, 0 <x <1.5) ,
_{Li 1 .2+ x Fe 0 .2+ x} Ti 1 .8-x (PO 4) 3- y (BO 3) y ( wherein, 0 <x <0.3, 0 <y <3), or
_{Li 2 Sn 0 .5 (BO 3} ) 1- x (PO 4) x ( where, 0 <x <1) as a modifier oxide or an intermediate oxide as one of the glass-based oxide selected from SnO, TiO _2, Al ₂ O ₅ , Fe ₂ O ₃ , characterized in that _{P 2} O ₅ or B ₂ O ₃ Substituted with a mesh oxide
Electrolyte for all-solid-state batteries - Glass electrolyte for low-temperature co-sintering of electrodes.
_{Li 1 .5- x M x A 0} .5 (PO 4) 1. 5 BO 3, ( where, M is a metal element, A is Sn or Ti, 0 <x <1.5) ,
_{Li 1 .2+ x Fe 0 .2+ x} Ti 1 .8-x (PO 4) 3- y (BO 3) y ( wherein, 0 <x <0.3, 0 <y <3), or
_{Li 2 Sn 0 .5 (BO 3} ) preparing any one of the glass-containing oxide starting material is selected from _{1- x} (PO _{4) x} (where, 0 <x <1), and
Mixing sucrose in the range of 5-20 wt% of the total blending amount of the raw material,
Li raw material is added in an amount exceeding 5 to 10 wt% based on the amount of Li,
The mixed raw materials are melted in the atmospheric atmosphere in the range of 900 ~ 1350 ℃,
pulverizing the obtained melt;
A method for manufacturing a glass electrolyte for low-temperature co-sintering of electrolyte-electrode for all-solid-state batteries.
It is prepared by mixing the glass electrolyte prepared according to claim 2 and the crystal electrolyte,
It is composed of 17 to 33% of a glass electrolyte and 67 to 83% of a crystalline electrolyte by weight, and has an ionic conductivity of 10 ^-4 to 10 ^-5 S/cm.
complex electrolyte.
As a composite anode using the glass electrolyte prepared according to claim 2,
A composite comprising a cathode active material, a crystalline electrolyte, a glass electrolyte, and a conductor, wherein the ratio by weight of the cathode active material: crystalline electrolyte: glass electrolyte: conductor is 50 to 52: 22.0 to 35.5: 8 to 20: 4.5 to 9 anode.
A composite electrolyte prepared by mixing the glass electrolyte prepared according to claim 2 and a crystalline electrolyte;
As a composite positive electrode using the glass electrolyte prepared according to claim 2, a composite positive electrode including a positive electrode active material, a crystalline electrolyte, a glass electrolyte, and a conductor is laminated in a pellet or sheet type to prepare a battery cell,
Characterized in that obtained by sintering the battery cells at 750 ~ 825 ℃ 2 ~ 48 hours in an atmospheric atmosphere
all-solid-state battery

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