KR20210148810A - Manufacturing method of complex electrolyte for solid-state lithium secondary cell - Google Patents

Abstract

The present invention relates to a method of producing a complex electrolyte for a solid-state lithium secondary cell, in which the complex electrolyte is produced by mixing an oxide electrolyte of Li_(7-3x)B_xLa_3Zr_2O_12 and a glass electrolyte of Li_1.5-Sn_0.4-Nb_0.1-(PO_4)_3-BO_3 or Li_(1.2+y)·EFe_(0.2+y)·Ti_(1.8-y)·(PO_4)_(3-z)·(BO_3)z, such that simultaneous firing with a positive electrode at a lower temperature of 850°C or lower is possible, ionic conductivity is high, and the cost is reduced due to simplified process steps.

Description

Manufacturing method of composite electrolyte for all-solid lithium secondary battery {MANUFACTURING METHOD OF COMPLEX ELECTROLYTE FOR SOLID-STATE LITHIUM SECONDARY CELL}

The present invention relates to a method for manufacturing a composite electrolyte for an all-solid lithium secondary battery, and specifically, by mixing an oxide-based crystalline and an amorphous oxide that can serve as a sintering aid to prepare a composite electrolyte, a positive electrode at a low temperature of 850 ° C. or less It relates to a method for manufacturing a composite electrolyte for an all-solid-state lithium secondary battery that can be simultaneously fired with, has high ionic conductivity, and has reduced cost by simplifying process steps.

Lithium secondary batteries used in next-generation electric vehicles or energy storage devices for power storage use liquid electrolytes, so ignition or explosion accidents occur frequently due to problems such as dendrite formation, flammability, and leakage. Since the energy density is less than 300 W·Eh/kg, it cannot travel long distances compared to the current gasoline car with a single charge. It is still high enough to be used as an energy storage device for electric vehicles or power storage.

Recently, in order to improve the stability, energy density, and price problems of lithium secondary batteries, research for manufacturing an all-solid-state lithium secondary battery by replacing the liquid electrolyte in a lithium secondary battery with a non-flammable inorganic solid electrolyte is attracting attention. If 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.

Solid electrolyte materials include inorganic sulfide-based, amorphous oxide-based, crystalline (garnet-based, perovskite, etc.), and NASICON & LISICON-based glass-ceramics electrolytes, and organic polymers. based (including hybrid) electrolytes.

Oxide-based materials 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 materials. In the case of sulfide type ^{, it has a high ionic conductivity of 1x10 -2} S/cm, but a resistance component is generated by an interface reaction with a narrow potential window, a positive electrode active material or a negative electrode active material, and it is vulnerable to moisture, and is a toxic gas, hydrogen sulfide (H ₂ S) gas. There are problems such as harm to human body due to occurrence. Polyelectrolytes have a low conductivity of Li ions at room temperature, so performance is realized only when the cell temperature is maintained at 60-80 ° C.

Recently, when a garnet (Li ₇ La ₂ Zr ₂ O ₁₃ or less LLZO)-type oxide electrolyte is synthesized at 900° C. for about 10 hours, cubic LLZO is synthesized, but at a level of ^{1x10 -3} -1x10 ^{-4 S/cm} In order to obtain the ionic conductivity of However, during high-temperature sintering, Li volatilization occurs, and the sintering range is narrow, making sintering difficult.

On the other hand, materials mainly used in the anode 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 and the like. , this cathode material is synthesized at 850-950 ° C. At a temperature higher than that, a second phase is generated and Li is volatilized.

In order to simultaneously sinter the aforementioned LLZO and anode by integrating and stacking, the sintering temperature of the anode and the electrolyte must be set to 850° C. or less to control the reaction between the electrolyte and the anode. In order to sinter the electrolyte by lowering the sintering temperature from 1200-1250 ℃ to 850 ℃ or less, a low-temperature sintering-type sintering aid is required. This sintering aid should not lower the ionic conductivity of the electrolyte.

In order to lower the sintering temperature to 850 °C or less, in Patent Document 1, 4-16 wt% of Li ₃ BO ₃ is mixed with Li ₇ La ₃ Zr ₂ O ₁₂ at 1000-1150 ° C. In Non-Patent Document 1, electrolyte and active material 15 wt% of 0.44LiBO ₂ -0.56LiF was added to 750 ° C. In Non-Patent Document 2, Li ₃ PO ₄ or Li ₃ BO _{3 was added to LiTi 2} (PO ₄ ) ₃ at 800-900 ° C., Patent Document 2 _{In 2, 5-20 wt% of 50Li 2} O·E35.7B ₂ O ₃ 3·E14.3SiO ₂ was added to a garnet-structured oxide doped with tantalum (Ta) and sintered at 700° C. for 3-15 hours. did In addition, in Patent Document 3, oxide crystals (perovskite type-La-Li-Ti-O or garnet type-Li-La-Zr-O) and glass-ceramics (phosphate compound LATP, LAGP) as electrolyte At least one lithium ion conductor was mixed and sintered at 600°C or lower. However, the sintering temperature of Patent Document 1 is too high, and the non-patent document 1 is not sintered sufficiently, so that the internal resistance is very large, and the charge/discharge current value is very small. In Patent Document 2, the ionic conductivity was 1x10 ^-5 -1x10 ^-8 S/cm, indicating a low ionic conductivity. Patent Document 3 has a disadvantage in that the ionic conductivity of the lithium ion conductor added as a sintering aid is low.

Patent literature and non-patent literature mention only sintering the electrolyte, but in the case of a sintering aid, it only lowers the sintering temperature, and the ionic conductivity is low and the manufacturing cost is high because the process is complicated.

On the other hand, in Non-Patent Document 3, when sintering at 850 ° C. or higher, there is a reaction between the electrolyte and the anode. In the _{case of integrating the electrode and the electrolyte by coating the LiCoO 2} as a thin film on the surface of the LLZO pellet, between the electrode layer and the electrolyte layer during the heat treatment process reported that there is a problem in that the _{La 2} CoO ₄ impurity phase is formed as shown in FIG. 1 . In addition, in Non-Patent Document 4, when LTP (LiTi ₂ (PO ₄ ) ₃ )/LiCoO ₂ is laminated and sintered by SPS (Spark-plasma-sintering) method, as in FIG. 2 , CoTiO ₃ , Co ₂ TiO ₄ , LiCoPO ₄ , CoO, Co ₃ O _4, etc., because the second phase is generated, the interface is electrochemically inactivated and there is a problem in that the structure collapses.

In a lithium secondary all-solid-state battery, when the electrolyte and the positive electrode are laminated and fired at the same time, the sintering must be carried out at a low temperature of 850 °C or less. To do this, a sintering aid is required because the sintering temperature of the electrolyte must be lowered from a high temperature of 1200-1250 °C to a low temperature of 850 °C or less.

Therefore, as mentioned above, in order to solve the problem of the sulfide-based or polymer-based electrolyte and the problem of the reaction with the electrode by sintering at a high temperature, the all-solid-state battery must be sintered at a low temperature of 850° C. or less.

Korean Patent Publication No. 10-2019-0078804 Republic of Korea Patent Publication No. 10-2017-0008539 Republic of Korea Patent Publication No. 10-2017-0133316

Solid State Ionics 118 (1999) 853 Solid State Ionics 47 (1991), 257-264 J. Power Sources 196 (2011) 764-767 J. Power Source, 81-82 (1999) 853-858

Accordingly, an object of the present invention is to design and mix an oxide-based crystalline and an amorphous oxide that can serve as a sintering aid as an electrolyte raw material. A composite electrolyte can be manufactured at a low price by simplifying the three-step process of mixing, melting, and pulverizing, and adding sucrose in an amount of 10 wt% relative to the total amount of amorphous oxide to give a reducing atmosphere at low temperature. To prepare a composite electrolyte with high ionic conductivity and capable of simultaneous firing with the anode at a temperature of 850 °C or less.

In a method for manufacturing a composite electrolyte for an all-solid-state lithium ion secondary battery according to an embodiment of the present invention for solving the above problems, the raw materials are mixed and maintained at 900-1000° C. for 15-25 hours, so that Li _7-3x B _x La ₃ synthesizing an oxide electrolyte containing Zr ₂ O _{12 ;} The raw materials are mixed and dried to Li _1.5 -Sn _0.4 -Nb _0.1 -(PO ₄ ) ₃ -BO ₃ and Li _1.2+y EFe _{0.2+y ETi 1.8-y} E(PO ₄ ) _3-z E( BO ₃ ) preparing a glass electrolyte powder comprising at least one of z; and mixing the glass electrolyte powder with the oxide electrolyte heated to 1100-1500° C. and maintaining it for 10-40 minutes to obtain a composite electrolyte melt, wherein x is a rational number from 0 to 1, and y is from 0 to 0.3 is a free number, and z is an integer of 0 to 3, and 5-15 parts by weight of sucrose is added based on 100 parts by weight of the glass electrolyte raw material mixture in the glass electrolyte powder manufacturing step.

The composite electrolyte may be sintered at 850° C. or lower, and/or may have an ionic conductivity of ^{1×10 −6 S/cm or more.}

In Li _7-3x B _x La ₃ Zr ₂ O ₁₂ , x may be a rational number of 0.15-0.25.

The Li _7-3x B _x La ₃ Zr ₂ O ₁₂ is Li _6.4 Al _0.2 La ₃ Zr ₂ O ₁₂ , and/or the Li _1.2+y · EFe _0.2+y · _{ETi 1.8-y} · E(PO ₄ ) _3-z · E(BO ₃ )z may be Li _1.5 · EFe _0.5 · _{ETi 1.5} · E(BO ₃ ) ₃ .

The raw material of the oxide electrolyte _{includes at least one selected from the group consisting of LiOH·EH 2} O, La ₂ O ₃ , Al ₂ O ₃ and ZrO ₂ , and the raw material of the glass electrolyte is LiOH·EH ₂ O, SnO, Nb ₂ O ₅ , Fe ₂ O ₃ , TiO ₂ , H ₃ PO ₄ and H ₃ BO ₃ At least one selected from the group consisting of may be included.

When preparing the oxide electrolyte and/or the glass electrolyte, LiOH·EH ₂ O may be used in excess of 10% of the equivalent.

In addition, the composite electrolyte for an all-solid-state lithium ion secondary battery according to an embodiment of the present invention for solving the above other problems may be manufactured in the same manner as described above.

Details of other embodiments are included in the detailed description.

According to embodiments of the present invention, for a lithium secondary battery that can be used as a dendrite suppression layer because the electrolyte and the electrode can be laminated and integrated at a low-temperature sintering temperature of 850 ° C. or less and fired at the same time, and there is no reaction with lithium metal A composite electrolyte can be prepared.

In addition, the eutectic melting point is lowered by adding a sucrose reducing agent to the raw material of the glass electrolyte containing the metal oxide and melting in an atmospheric atmosphere, so that the composite electrolyte can be obtained at a temperature lower than 250 ° C. can be increased and the manufacturing cost can be lowered.

In addition, the existing complicated process up to five steps can be simplified to a three-step process as shown in FIG. 3 , thereby reducing the manufacturing cost.

Therefore, the composite electrolyte prepared according to the present invention can solve the current lithium secondary battery safety problem, and can achieve simplification and low cost of the process, so that it can be utilized in medium and large-sized storage devices.

1 is a cross-sectional projection electron micrograph and EDS analysis curve of the interface of a _{conventional material LiCoO 2} /LLZO (Li ₇ La ₃ Zr ₂ O _{12 ).}
FIG. 2 is a view showing that the second phase is generated at the interface between the electrolyte and the positive electrode when _{LTP/LiCoO 2 is laminated by the conventional SPS method and sintered at 800° C. or higher.}
3 is a flow chart comparing the conventional composite electrolyte manufacturing process with the composite electrolyte manufacturing process according to an embodiment of the present invention.
4 is an impedance curve of _{an oxide crystal Li 6.4} Al _0.2 La ₃ Zr ₂ O ₁₂ electrolyte derived according to an experimental example of the present invention.
5 is a graph showing a crystal phase of a composite electrolyte prepared by mixing a glass electrolyte and an oxide electrolyte according to an experimental example of the present invention.
6 is a graph showing the impedance (impedance) of a composite electrolyte prepared by mixing a glass electrolyte and an oxide electrolyte according to an experimental example of the present invention.

Advantages and features of the present invention, and methods for achieving them, will become apparent with reference to the embodiments described below in detail. However, the present invention is not limited to the embodiments disclosed below, but will be implemented in various different forms, and only the embodiments allow the disclosure of the present invention to be complete, and those of ordinary skill in the art to which the present invention pertains. It is provided to fully inform the person of the scope of the invention, and the present invention is only defined by the scope of the claims.

The terminology used herein is for the purpose of describing the embodiments and is not intended to limit the present invention. In this specification, 'and/or' includes each and every combination of one or more of the recited items. The singular also includes the plural, unless the phrase specifically states otherwise. As used herein, 'comprises' and/or 'comprising' does not exclude the presence or addition of one or more other elements in addition to the stated elements. Numerical ranges indicated using '-' or 'to' indicate a numerical range including the values listed before and after as the lower and upper limits, respectively, unless otherwise stated. 'About' or 'approximately' means a value or numerical range within 20% of the value or numerical range recited thereafter.

In addition, in describing the components of the embodiment of the present invention, terms such as first, second, A, B, (a), (b), etc. may be used. These terms are only for distinguishing the elements from other elements, and the essence, order, or order of the elements are not limited by the terms.

Unless otherwise defined, all terms (including technical and scientific terms) used herein may be used with the meaning commonly understood by those of ordinary skill in the art to which the present invention belongs. In addition, terms defined in a commonly used dictionary are not to be interpreted ideally or excessively unless clearly specifically defined.

In the description of the embodiment of the present invention, if it is determined that a detailed description of a related known configuration or function interferes with the understanding of the embodiment of the present invention, the detailed description thereof will be omitted.

The manufacturing method of the composite electrolyte for an all-solid-state lithium ion secondary battery according to an embodiment of the present invention includes (a) mixing the raw materials and maintaining the mixture at 900-1000° C. for 15-25 hours to Li _7-3x B _x La ₃ Zr ₂ synthesizing an oxide electrolyte containing O ₁₂ , (b) mixing and drying the raw materials to Li _1.5 -Sn _0.4 -Nb _0.1 -(PO ₄ ) ₃ -BO ₃ and Li _1.2+y EFe _{0.2+y ETi Preparing a glass electrolyte powder comprising at least one of 1.8-y} · E(PO ₄ ) _3-z · E(BO ₃ )z, and (c) the glass in the oxide electrolyte heated to 1100-1500 ° C. and mixing the electrolyte powder and maintaining the mixture for 10-40 minutes to obtain a composite electrolyte melt, and may further include (d) grinding the composite electrolyte melt.

In step (a) described above _{, one or more raw materials selected from the group consisting of LiOH·EH 2} O, La ₂ O ₃ , Al ₂ O ₃ and ZrO ₂ are weighed and mixed according to the equivalent weight, and then pulverized for 40-60 hours. After drying at 80-120° C., maintaining at 900-1000° C. for 15-25 hours _{to synthesize Li 7-3x} B _x La ₃ Zr ₂ O ₁₂ , which is a Garnet-type oxide electrolyte.

The x may be a rational number of 0 to 1, preferably, a rational number of 0.15-0.25. The oxide electrolyte may be Li _6.4 Al _0.2 La ₃ Zr ₂ O ₁₂ , but is not limited thereto.

In step (b) described above, one or more raw materials selected from the group consisting _{of LiOH·EH 2} O, SnO, Nb ₂ O ₅ , Fe ₂ O ₃ , TiO ₂ , H ₃ PO ₄ and H ₃ BO _{3 are added to an equivalent weight.} Weigh, mix for 4-8 hours, and dry at 80-120 ° C. for 20-28 hours. Li _1.5 -Sn _0.4 -Nb _0.1 -(PO ₄ ) ₃ -BO ₃ and/or Li _1.2+y EFe _{0.2+ y} · ETi _1.8-y · E(PO ₄ ) _3-z · E(BO ₃ )z This is a step of preparing a powder.

The y may be a rational number from 0 to 0.3, and z may be an integer from 0 to 3. The Li _1.2+y · EFe _{0.2 +y · ETi 1.8-y} · E(PO ₄ ) _3-z · E(BO ₃ )z may be Li _1.5 · EFe _0.5 · _{ETi 1.5} · E(BO ₃ ) ₃ , but is not limited thereto.

In one embodiment, 5-15 parts by weight of sucrose may be added and mixed together with respect to 100 parts by weight of the total amount of the glass electrolyte raw material mixed in the preparation of the glass electrolyte powder. Sucrose can be melted at a temperature 200-300 ℃ lower than the temperature of the existing atmospheric melting atmosphere by changing the melting atmosphere to a reducing atmosphere.

In the preparation of the oxide electrolyte and/or the glass electrolyte, LiOH·EH ₂ O may be used in an amount exceeding 10% of the equivalent, and thus loss due to Li volatilization may be offset.

Step (c) described above is a step to obtain a composite electrolyte melt by heating the prepared oxide electrolyte to 1100-1500 ° C, mixing the glass electrolyte powder, and maintaining it for 10-40 minutes. Preferably, the temperature may be 1300-1400 ° C. and the holding time can be 20-40 minutes.

Step (d) described above is a step for pulverizing the prepared composite electrolyte melt to a level of 1-10 μm for use in a lithium secondary battery.

The composite electrolyte prepared through this step can be sintered at 850 °C or lower. In addition, ^{it may have an ionic conductivity of 1x10 -6} S/cm or more, preferably, an ionic conductivity of 1x10 ^-5 S/cm or more.

Preparation Example 1: Oxide electrolyte LLZO (Li _6.4 Al _0.2 La ₃ Zr ₂ O ₁₂ ) synthesis

As a raw material for synthesizing the oxide electrolyte Li _6.4 Al _0.2 La ₃ Zr ₂ O _{12 , LiOH·EH 2 O is used as the Li source, and La 2} O ₃ , Al ₂ O ₃ is used as the La, Al and Zr source. and ZrO ₂ were used. Weigh the above raw materials, put them in a Nalgene bottle, put zirconia balls of Φ5 and 10 mm and anhydrous alcohol, and then grind and mix them in a ball mill and an attrition mill for 48 hours. did At this time, since Li is highly volatile at high temperature, the Li source material was added in excess of 10% of the equivalent. The mixture was dried at 100° C. until constant weight, and then placed in an alumina crucible. An oxide electrolyte was synthesized by placing an alumina crucible filled with the mixture in an electric furnace having a silicon carbide (SiC) heating element, and heating the temperature to 950 °C at a rate of 2 °C per minute, and then maintaining the temperature at 950 °C for 20 hours.

Preparation Example 2: Preparation of Glass Electrolyte Powder

As a raw material for manufacturing the glass electrolytes Li _1.5 -Sn _0.4 -Nb _0.1 -(PO ₄ ) _{3 -BO 3} and Li _1.5 · EFe _0.5 · _{ETi 1.5} · E(BO ₃ ) ₃ , LiOH·EH as a Li source _{2 O is used, SnO, Nb 2} O ₅ , Fe ₂ O ₃ and TiO ₂ are used as Sn, Nb, Fe and Ti sources, _{H 3} PO ₄ is used as P source, and B source is used. H ₃ BO ₃ was used. The above raw materials were measured and put into a Nalgen bottle, zirconia balls of Φ10 mm and anhydrous alcohol were added, and then mixed in a ball mill for 6 hours. After drying the mixture in a dryer at 100° C. for 24 hours, it was molded into pellets of Φ2 x h0.1 in to prepare a glass electrolyte powder. At this time, in order to melt at a temperature lower than the existing melting temperature, _{10% of sucrose (C 12} H ₂₂ O ₁₁ ) was added and mixed with respect to the total weight of the glass electrolyte mixture, because the addition of sucrose reduces the melting atmosphere. This is because melting is possible at a temperature 200-300 ℃ lower than the temperature of the existing atmospheric melting atmosphere by changing the atmosphere. In addition, since Li is highly volatile at high temperature, 10% more than the Li source was added. The chemical composition, melting temperature, ionic conductivity, etc. of the glass electrolyte are shown in Table 1 below.

When the composite electrolyte mixture is melted, the ionic conductivity of the melt may vary depending on the amount of sucrose added to the mixture and the excess amount of Li. Therefore, it will be apparent to those skilled in the art that it can be modified or embodied, and the scope of the present invention is not limited to the above-described embodiments.

sample Glass electrolyte composition Melting temperature and time (℃-min) Ion Conductivity (S/cm)

softening temperature (

One Li _1.5 -Sn _0.4 -Nb _0.1 -(PO ₄ ) ₃ -BO ₃ 1100-30 2.83 x 10 ^-7 570 1100-10 3.88 x 10 ^-7 600 2 Li _1.5 Fe _0.5 Ti _1.5 (BO ₃ ) ₃ 1350-30 5.29 x 10 ^-4 -

Preparation Example 3-1: Preparation of composite electrolyte (1)

The oxidized electrolyte synthesized in Preparation Example 1 was maintained at 950° C. for 20 hours and then heated to 1200° C. and 1350° C. at 20° C. per minute, respectively, and then the glass electrolyte powder of Preparation Example 2 was put into an alumina crucible containing an oxidizing electrolyte. and melted while maintaining for 20 minutes and 30 minutes, respectively, to prepare composite electrolyte melts as shown in Tables 2 and 3 below, respectively.

The composite electrolyte melt prepared as above was coarsely pulverized to large particles using a jaw crusher, then finely pulverized in a dry manner to a level of 3 μm in a jet mill, and pulverized in a ball mill for 48 hours before use. For ball mill grinding, anhydrous ethanol solvent and Φ0.8 mm zirconia balls were put together and then grinded at 150 rpm.

Preparation Example 3-2: Preparation of composite electrolyte (2)

As an oxide electrolyte, a composite electrolyte having the composition shown in Table 4 was prepared by substituting B for a part _{of Li in Li 7} La ₃ Zr ₂ O _{12 .} At this time, sucrose was added to melt at a low temperature, and in consideration of the volatilization of Li, the Li source material was added in excess of the equivalent by 10%. Sucrose and excess Li were mixed by adding 10 wt% of the total oxide electrolyte mixture. Mixing was measured according to the chemical composition of Table 4, and then zirconia balls and anhydrous alcohol were put in a Nalgen bottle and mixed in a ball mill for 24 hours. The mixture was placed in an alumina crucible and maintained at 1500° C. for 10 minutes using a superkanthal electric furnace for a maximum operating temperature of 1700° C. to prepare a composite electrolyte melt. The melting method and the powdering method were the same as in Preparation Example 3-1.

Furtherance Ionic conductivity (x S/cm) Li ₇ La ₃ Zr ₂ O ₁₂ 5.44 ^-5 Li _6.55 B _0.15 La ₃ Zr ₂ O ₁₂ 1.38/1.77 ^-5 Li _6.4 B _0.2 La ₃ Zr ₂ O ₁₂ 1.049 ^-4 Li _6.25 B _0.25 La ₃ Zr ₂ O ₁₂ 4.41-0 ⁶ Li _7.04 B _0.2 La ₃ Zr ₂ O ₁₂ 9.82 ^-6

Experimental Example 1

For the oxide electrolyte sample synthesized in Preparation Example 1, ionic conductivity was evaluated at 25° C. using an impedance device. Ion conductivity was obtained by measuring the total resistance (bulk and interfacial resistance) using an equivalent circuit method under the condition of 1 Hz-4 MHz with an impedance device. The ionic conductivity was calculated as ^{C=R (1-n)/n} Q ^1/n.

As a result of the evaluation, as shown in FIG. 4 , the _{ionic conductivity of the oxide electrolyte Li 6.4} Al _0.2 La ₃ Zr ₂ O ₁₂ of the present invention was 2.34 x 10 ^-4 , 6.89 x 10 ^-4 S/cm.

Experimental Example 2

The crystalline phase generated for the composite electrolyte sample prepared in Preparation Example was evaluated for ionic conductivity at 25° C. using an impedance device as shown in FIG. 5 , and the graph is shown in FIG. 6 . The crystallinity of the existing oxide electrolyte was reduced by the glass electrolyte, and after the glass electrolyte was melted, some precipitated as crystals in the cooling process, and the peak appeared together.

Therefore, in the present invention, Li _1.5 · EFe _0.5 · _{ETi 1.5} · E(BO ₃ ) ₃ was more suitable _{than Li 1.5} -Sn _0.4 -Nb _0.1 -(PO ₄ ) _{3 -BO 3 as the glass electrolyte.} In this invention, _{Li 1.5} Fe _0.5 Ti _1.5 (BO ₃ ) ₃ having a high ^{ionic conductivity of 1x10 -4} s/cm is Li _1.2+x EFe _{0.2+x ETi 1.8-x} E(PO ₄ ) _3-y E(BO ₃ ) Since _{it was invented in the y} composition, it is preferable that the amount of Li is 1.2-1.5 moles, Fe is 0.2-0.5 moles, Ti is 1.5-1.8 moles, P is 1-3 moles, and B is 1-3 moles. do.

Table 5 below relates to the ionic conductivity of _{Li 1.2+x} · EFe _{0.2 +x · ETi 1.8-x} · E(PO ₄ ) _3-y · E(BO ₃ ) _{y-based glass electrolyte.}

Example 1

The ratio of the glass electrolyte Li _1.5 -Sn _{0.4 -Nb 0.1} -(PO ₄ ) ₃ -BO ₃ of Preparation Example 2 to the oxide electrolyte Li _6.4 Al _0.2 La ₃ Zr ₂ O ₁₂ of Preparation Example 1 was 0.2:0.8 and 0.35. A composite electrolyte was prepared in the same manner as: 0.65, except that the melting temperature and time were melted at 1200° C. for 20 minutes in the manufacturing method of Preparation Example 3-1. During melt manufacturing, sucrose was added and Li was added in the same manner as in Preparation Example 2 above.

As such, _{the composite electrolyte prepared using the Li 1.5} -Sn _0.4 -Nb _0.1 -(PO ₄ ) ₃ -BO ₃ glass electrolyte has an ionic conductivity of 1x10 ^-7 S/cm, and thus _{Li 1.5 · EFe 0.5} · _{ETi 1.5} · E( BO ₃ ) ₃ It can be used as a sintering aid because it is lower than a composite electrolyte prepared using a glass electrolyte, but it is difficult to use alone.

Example 2

_{Li 1.5} · EFe _{0.5 · ETi 1.5} · E(BO ₃ ) ₃ glass electrolyte of Preparation Example 2, which is an ion conductor and a sintering aid, was selected and the ratio of the oxide electrolyte Li _6.4 Al _0.2 La ₃ Zr ₂ O _{12 was 0.2:0.8} A composite electrolyte was prepared by mixing it in a ratio of 0.5:0.5. Li _1.5 · EFe _{0.5 · ETi 1.5} · E(BO ₃ ) _{3 The} composite electrolyte using the glass electrolyte was prepared in the same manner as in Preparation Example 3 except that the melting temperature and time were maintained at 1350° C. for 30 minutes to melt. During melt manufacturing, sucrose was added and Li excess was added as in Preparation Example 2 above.

As a result of confirming the crystallinity, when the amount of free electrolyte was large, the overall crystallinity was lowered, but when the ratio of the amount of free electrolyte was 0.2, it was analyzed that the crystal strength was high.

If the crystallinity is high, it may not be able to function as a glass, so it can be said that one with low crystallinity is suitable as a sintering aid after melting if possible.

Example 3

In the same manner as in Preparation Example 3-2, a composite electrolyte was melted and prepared by substituting B for _{Li 7-3x} B _x La ₃ Zr ₂ O _{12 oxide electrolyte.} During melt manufacturing, sucrose was added and Li was added in the same manner as in Preparation Example 2 above.

As a result of the composite electrolyte preparation, as B was added instead of Li, the ionic conductivity increased up to 0.2 mole of B substitution, but gradually decreased when the substitution amount was 0.2 mole or more. When the amount of B substitution was 0.2 mole, the ionic conductivity was 1.04x10 ^-4 S/cm. If this composite electrolyte alone or a sintering aid is added, it will be possible to use it as a composite electrolyte at 850 °C.

In the above, the embodiment of the present invention has been mainly described, but this is only an example and does not limit the present invention. It will be appreciated that various modifications and applications not exemplified above are possible. For example, each component specifically shown in the embodiment of the present invention may be implemented by modification. And differences related to such modifications and applications should be construed as being included in the scope of the present invention defined in the appended claims.

Claims (7)

synthesizing an oxide electrolyte containing _{Li 7-3x} B _x La ₃ Zr ₂ O ₁₂ by mixing the raw materials and maintaining at 900-1000° C. for 15-25 hours;
The raw materials are mixed and dried to Li _1.5 -Sn _0.4 -Nb _0.1 -(PO ₄ ) ₃ -BO ₃ and Li _1.2+y EFe _{0.2+y ETi 1.8-y} E(PO ₄ ) _3-z E( BO ₃ ) preparing a glass electrolyte powder comprising at least one of z; and
Mixing the glass electrolyte powder with the oxide electrolyte heated to 1100-1500 ° C and maintaining it for 10-40 minutes to obtain a composite electrolyte melt,
wherein x is a rational number from 0 to 1, y is a rational number from 0 to 0.3, and z is an integer from 0 to 3,
In the glass electrolyte powder manufacturing step, 5-15 parts by weight of sucrose is added based on 100 parts by weight of the glass electrolyte raw material mixture.
A method for manufacturing a composite electrolyte for an all-solid lithium ion secondary battery. According to claim 1,
The composite electrolyte is
capable of sintering below 850 °C, and/or
1x10 ^-6 S/cm or higher ionic conductivity
A method for manufacturing a composite electrolyte for an all-solid lithium ion secondary battery. According to claim 1,
In Li _7-3x B _x La ₃ Zr ₂ O ₁₂ , x is a rational number of 0.15-0.25.
A method for manufacturing a composite electrolyte for an all-solid lithium ion secondary battery. 4. The method of claim 3,
The Li _7-3x B _x La ₃ Zr ₂ O ₁₂ is Li _6.4 Al _0.2 La ₃ Zr ₂ O ₁₂ , and/or
The Li _1.2+y · EFe _{0.2 +y · ETi 1.8-y} · E(PO ₄ ) _3-z · E(BO ₃ )z is Li _1.5 · EFe _0.5 · _{ETi 1.5} · E(BO ₃ ) ₃
A method for manufacturing a composite electrolyte for an all-solid lithium ion secondary battery. According to claim 1,
The raw material of the oxide electrolyte includes at least one selected from the group consisting _{of LiOH·EH 2} O, La ₂ O ₃ , Al ₂ O ₃ and ZrO _{2 ,}
The raw material of the glass electrolyte includes at least one selected from the group consisting _{of LiOH·EH 2} O, SnO, Nb ₂ O ₅ , Fe ₂ O ₃ , TiO ₂ , H ₃ PO ₄ and H ₃ BO _{3 .}
A method for manufacturing a composite electrolyte for an all-solid lithium ion secondary battery. 6. The method of claim 5,
When preparing the oxide electrolyte and/or the glass electrolyte, LiOH·EH ₂ O is used in excess of 10% of the equivalent
A method for manufacturing a composite electrolyte for an all-solid lithium ion secondary battery. The method of any one of claims 1 to 6 prepared by
Composite electrolyte for all-solid-state lithium-ion secondary batteries.

Images