Solid electrolyte for all solid-state lithium-ion battery and manufacturing method therefor

Abstract

The method for manufacturing a solid electrolyte using an LLZ material for a lithium-ion battery comprises the steps of: providing a starting material in which lanthanum nitrate [La(NO3)3.6H2O] and zirconium nitrate [ZrO(NO3)2.6H2O] are mixed at a mole ratio of 3:2; forming an aqueous solution by dissolving the starting material; forming a precipitate by putting ammonia, which is a complex agent, and sodium hydroxide, which adjusts the pH of a reactor, into the aqueous solution, mixing the same, and then co-precipitating the mixture; forming a primary precursor powder by cleaning, drying and pulverizing the precipitate; forming a secondary precursor powder by mixing lithium powder [LiOH.H2O] with the primary precursor powder and ball-milling the mixture so as to solidify the lithium; and forming a solid electrolyte powder by heat-treating the secondary precursor powder.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]The present application is a National Stage entry of International Patent Application No. PCT / KR2014 / 005739, entitled “Solid Electrolyte for All Solid-State Lithium-Ion Battery and Manufacturing Method Therefor, and filed 27 Jun. 2014, which is specifically incorporated by reference herein for all that it discloses or teaches. The present application further claims priority to Korean Patent Application No. 10-2013-0078499 filed 4 Jul. 2013, which is also specifically incorporated by reference herein for all that it discloses or teaches.TECHNICAL FIELD[0002]The present invention relates to an electrolyte for an all-solid-state battery, which is a solid electrolyte for a lithium-ion battery and a method of manufacturing the same capable of synthesizing an LLZ material that is a garnet-structure nano solid electrolyte having high ion conductivity and an excellent electrochemical potential window, and a method of manufacturing the same.BACKGR...

AI Technical Summary

Benefits of technology

This patent describes a method of making a garnet-structure oxide solid electrolyte using co-precipitation. The method allows for the creation of a particular crystal structure of the solid electrolyte material, which has a high degree of ion conductivity. By controlling the heat treatment conditions, the solid electrolyte can be made with either a cubic or tetragonal structure, and both have exceptional room temperature ion conductivity. This method also allows for the manufacturing of high-density solid electrolyte pellets and results in a solid electrolyte material with a remarkably high bulk ion conductivity.

Problems solved by technology

Accordingly, studies on secondary batteries are actively being conducted, while multiple technical problems happen.

However, a lithium-ion battery using a liquid electrolyte containing an organic solvent has difficulty in guaranteeing safety of the battery against overcharge and thermal properties.

In particular, to efficiently deal with an industrial demand for development of medium and large-sized lithium-ion batteries for electric cars and power storage, safety of a battery as well as high energy density is one of crucial issues.

However, since the conventional polymer solid electrolytes use lithium salt, which cannot be defined basically as complete solid electrolytes, there are fundamental limitations in resolving safety issues.

Meanwhile, inorganic solid electrolytes are slightly unfavorable for flexibility, unlike organic (polymer) solid electrolytes.

However, these materials have limitations despite electrochemical properties thereof.

Although a perovskite composition ((La, Li)TiO3) and an NASICON composition (LiTi2(PO4)3) exhibit a relatively high ion conductivity of about 10−3˜10−5 S / cm, these solid electrolytes have a potential window of about 1.5 to 5.0 V or 2.5 to 5.0 V, exhibiting very unsafe electrochemical properties in negative potential.

Thus, these electrolytes have limitations in realizing an all-solid-state lithium-ion battery for high voltage.

That is, perovskite and NASICON oxide solid electrolytes are relatively excellent in ion conductivity and yield, but exhibit limited potential window characteristics, having limitations in application to next-generation medium and large-size all-solid-state lithium-ion batteries required to employ a high-energy-density anode material and a low-potential high-capacity cathode material.

However, sulfide solid electrolytes show a basic property of strongly reacting with a high-voltage anode material of 4.0 V and a 0 V cathode material (lithium) and thus have a new problem in controlling an interfacial reaction between solid electrolytes and electrodes.

Although most studies are focused on this field, there is not yet any solution for practical use.

In particular, sulfide solid electrolytes are required to have high purity, can be treated only under particular conditions, for example, nitrogen or argon atmosphere, and cause environmental problems.

Thus, sulfide solid electrolytes are inappropriate as environment-friendly energy storage materials.

Thus, despite intensive studies and hard work, sulfide solid electrolytes exhibit electrochemical properties of electrodes and batteries, making it difficult to evolve into commercial materials.

To sum up, as described above, the foregoing polymer solid electrolytes is advantageous in flexibility and workability but have a limitation in improving ion conductivity at room temperature, half ion conductivity and half yield as compared with inorganic materials, and a limitation in application due to a reduced potential window range and use of lithium salt.

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