JP2013157090A - Lithium ion conductive solid electrolyte - Google Patents

Lithium ion conductive solid electrolyte Download PDF

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JP2013157090A
JP2013157090A JP2012014552A JP2012014552A JP2013157090A JP 2013157090 A JP2013157090 A JP 2013157090A JP 2012014552 A JP2012014552 A JP 2012014552A JP 2012014552 A JP2012014552 A JP 2012014552A JP 2013157090 A JP2013157090 A JP 2013157090A
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lithium ion
solid electrolyte
linbo
conductive solid
fluoride
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JP5910112B2 (en
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Hiroiku Tsunoda
宏郁 角田
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Tdk Corp
Tdk株式会社
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    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02EREDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00Enabling technologies or technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10Energy storage
    • Y02E60/12Battery technologies with an indirect contribution to GHG emissions mitigation
    • Y02E60/122Lithium-ion batteries
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02TCLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00Road transport of goods or passengers
    • Y02T10/60Other road transportation technologies with climate change mitigation effect
    • Y02T10/70Energy storage for electromobility
    • Y02T10/7005Batteries
    • Y02T10/7011Lithium ion battery

Abstract

A lithium ion conductive solid electrolyte material exhibiting high lithium ion conductivity is provided.
A fluoride is added to a lithium ion conductive solid electrolyte material mainly composed of LiNbO 3 . The fluoride is particularly preferably LiF. The fluoride content in the lithium ion conductive solid electrolyte material is preferably 15 wt% or more and 35 wt% or less. Accordingly, the lithium ion conductive solid electrolyte material exhibits high lithium ion conductivity.
[Selection figure] None

Description

  The present invention relates to a lithium ion conductive solid electrolyte.

  In recent years, with the rapid spread of information communication devices such as personal computers and mobile phones, the importance of batteries as power sources is rapidly increasing. Recently, hybrid vehicles and electric vehicles have been attracting attention from the viewpoint of environmental considerations and fuel efficiency, and batteries are mounted on these vehicles. Among various types of batteries, lithium ion batteries having a particularly high energy density are attracting attention.

  Currently, commercially available lithium ion batteries use flammable organic solvents as electrolyte solvents, and it is necessary to add a safety device to the batteries to ensure safety, which increases costs and reduces productivity. Has brought. Further, in order to ensure higher safety, further improvements in battery material and structure are required.

On the other hand, an all-solid battery using a solid as an electrolyte has been proposed. Since all solid-state batteries do not use combustible materials as constituent members, the safety device can be simplified, and manufacturing costs can be reduced and productivity can be improved. Lithium niobate (LiNbO 3 ) is known as a solid electrolyte layer used in such an all-solid battery. (Patent Documents 1 to 3)

Conventionally, LiNbO 3 solid electrolyte material has low lithium ion conductivity, and it has been considered that the required performance as the solid electrolyte layer of the all-solid battery described above cannot be satisfied. However, when used as an interface control material between the positive electrode material and the solid electrolyte instead of the solid electrolyte itself, an excellent effect is recognized. For example, in an all-solid battery composed of a sulfide-based solid electrolyte and a positive electrode active material LiCoO 2 , a reaction occurs at the solid electrolyte-positive electrode interface, so that a sufficient output density as a battery cannot be obtained. It has been reported that the power density can be improved by coating a LiNbO 3 layer of several nm (Non-patent Document 1).

In this case, since the film thickness of LiNbO 3 is as thin as several nm, the resistance of the LiNbO 3 layer does not increase even if the ionic conductivity is low, but the ionic conductivity is insufficient for use as the solid electrolyte itself. . Non-Patent Document 1 shows that a good interface can be formed with the positive electrode active material LiCoO 2 and the ionic conductor LiNbO 3, so if LiNbO 3 can be used for the solid electrolyte layer itself, it is unstable in the atmosphere. An all-solid battery can be realized with a stable oxide without using a sulfide-based solid electrolyte. For this purpose, the low lithium ion conductivity of LiNbO 3 described above is an important issue to be solved.

JP 59-71264 A JP 2009-218124 A JP 2010-251257 A

Electrochemistry Communications: Volume 9, Issue 7, Pages 1486-1490 (2007)

  The present invention has been made in view of the above, and an object thereof is to provide a lithium ion conductive solid electrolyte having high lithium ion conductivity.

In order to achieve the above object, the lithium ion conductive solid electrolyte material of the present invention is characterized by containing a LiNbO 3 lithium ion conductor and a fluoride.

According to this configuration, LiNbO 3 and fluoride coexist so that the lithium ion conductive solid electrolyte material can obtain high lithium ion conductivity. The cause of this effect is not necessarily clear, but lithium ion vacancies are induced in LiNbO 3 in the vicinity of the LiNbO 3 and fluoride interface, and these vacancies form a lithium ion conduction path. This is thought to be more active.

Furthermore, the content of LiF in the lithium ion conductive solid electrolyte material of the present invention is preferably 15% by weight or more and 35% by weight or less. By setting it as the above range, it is possible to obtain a lithium ion conductive solid electrolyte material exhibiting a high ion conductivity of 1 × 10 −5 S / cm or more, which is considered as a standard of practicality in all solid lithium ion secondary batteries. it can.

When the content of fluoride is less than 15% by weight, the interface between LiNbO 3 and fluoride is not sufficiently formed, and thus the effect of the present invention tends to be insufficient. When the fluoride content exceeds 35% by weight, the absolute amount of LiNbO 3 to be a lithium ion conduction path is insufficient, and the effect of the present invention tends to be insufficient.

According to the present invention, it is possible to provide a lithium ion conductive solid electrolyte material having higher lithium ion conductivity than when only conventional LiNbO 3 is used as a solid electrolyte.

The lithium ion conductive solid electrolyte material of this embodiment is a solid electrolyte made of a mixture of LiNbO 3 and fluoride. By mixing LiNbO 3 and fluoride, the lithium ion conductivity of the lithium ion conductive solid electrolyte material is improved. Specifically, it is a lithium ion conductive solid electrolyte mainly composed of LiNbO 3 and further contains a fluoride. Here, “comprising LiNbO 3 as a main component” means that the LiNbO 3 content in the lithium ion conductive solid electrolyte is 50% by weight or more.

Lithium ions conduct ions in the compound through lithium ion vacancies, but the amount of lithium ion vacancies is not sufficient when only LiNbO 3 is used. By mixing the LiNbO 3 and fluoride, lithium ions LiNbO 3 is attracted toward the fluorine in the fluoride in the vicinity of the interface LiNbO 3. Thereby, it is considered that lithium ion vacancies are induced in LiNbO 3 and lithium ions are conducted through the vacancies. This is presumed to improve the lithium ion conductivity of the lithium ion conductive solid electrolyte material.

The fluoride contained in the lithium ion conductive solid electrolyte material of the present embodiment is lithium fluoride (LiF), sodium fluoride (NaF), calcium fluoride (CaF 2 ), strontium fluoride (SrF 2 ), barium fluoride. (BaF 2 ) or the like can be used as appropriate, but LiF is particularly preferable. Since Li in LiF is also a constituent element of LiNbO 3 , it is difficult to generate an impurity phase that hinders ion conduction at the interface between LiNbO 3 and fluoride, and the improvement in lithium ion conductivity is remarkable.

The content of fluoride contained in the lithium ion conductive solid electrolyte material of the embodiment is preferably 15% by weight or more and 35% by weight or less. It is assumed that the lithium ion conductivity is improved by the addition of the fluoride due to the effect of the interface between LiNbO 3 and the fluoride, for example, LiF, but when the addition amount is less than 15% by weight, the interface to be formed There is little increase in lithium ion conductivity. On the other hand, when the content of fluoride exceeds 35% by weight, the lithium ion conductivity tends to decrease, and excessive addition has an adverse effect. This is because the volume of LiNbO 3 responsible for lithium ion conduction decreases, and the lithium ion conduction path itself decreases.

The lithium ion conductive solid electrolyte material of the present embodiment can be manufactured by, for example, a solid phase reaction method using a compound made of a complex of LiNbO 3 and fluoride. Lithium carbonate, lithium hydroxide, lithium nitrate or the like can be used as the lithium source, and niobium oxide can be used as the niobium source. For example, when lithium carbonate and niobium oxide are used as raw materials, each raw material weighed in a predetermined amount is mixed in a ball mill, and the mixed powder is fired at 1100 ° C. to obtain a LiNbO 3 powder. Can do. A desired mixture can be obtained by sufficiently mixing the powder and any powder of a fluoride such as LiF, NaF, and CaF 2 in the above-described weight ratio, molding, and firing.

Moreover, the manufacturing method of a lithium ion conductive solid electrolyte material is not limited to a solid-phase reaction method, You may use thin film preparation methods, such as sputtering method and a pulse laser deposition (PLD) method. For example, a target made of LiNbO 3 and LiF is prepared by the same method as the solid phase reaction method, and a lithium ion conductive solid electrolyte material made of a mixture of LiNbO 3 and LiF is formed by the above method. Can be produced. Alternatively, a target made of LiNbO 3, may be formed as a composite target of a combination of a target consisting of a LiF. Further, the fluoride film is not limited to LiF, and a film such as NaF or CaF 2 can be formed in the same manner.

The lithium ion conductive solid electrolyte material of the present embodiment can be used, for example, as a part of the solid electrolyte layer and the solid electrolyte layer of the all solid lithium ion secondary battery. In this case, members known in the field of lithium ion secondary batteries can be widely used as constituent members other than the solid electrolyte, for example, the positive electrode, the negative electrode, the terminal member, and the outer case. For example, by using LiCoO 2 as the positive electrode and metallic lithium as the negative electrode, and stacking in the order of positive electrode / lithium ion conductive solid electrolyte material / negative electrode of the present embodiment, an electrode body of an all-solid battery can be easily obtained. it can. The battery body may be accommodated in a laminate case or a metal can with a terminal member and may be a lithium ion secondary battery, or may be covered with a resin material such as polyimide to be a lithium ion secondary battery.

The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has any configuration that has substantially the same configuration as the technical idea described in the claims of the present invention and that exhibits the same effects. Are included in the technical scope. In addition, the mixing of fluoride with oxide lithium ion conductors other than LiNbO 3 may be expected to have the same effect as the present invention. For example, Li 14 ZnGe 4 O 16 , Li 1.3 Ti 1.7 Al 0.3 (PO 4 ) 4 , La 0.667-x Li 3x TiO 3 (0 <x <0.16), Li 3− x PO 4−x N x , (0 <x <1), Li 9 AlSiO 8 , Li 7 La 3 Zr 2 O 12, etc. can be expected to improve lithium ion conductivity by mixing with fluoride.

EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example and a comparative example, this invention is not limited to a following example.
Example 1

Each powder of Li 2 CO 3 and Nb 2 O 5 as raw materials was mixed with an ethanol solvent by a ball mill to obtain a slurry. The mixed powder obtained by drying the solvent from the slurry was fired at 1100 ° C. for 5 hours to obtain a LiNbO 3 compound. Such LiNbO 3 was coarsely pulverized with a mortar, and the powder was finely pulverized with an ethanol solvent by a ball mill.

The LiNbO 3 fine powder and LiF were weighed so that the amount of LiF mixed was 10% by weight with respect to the whole raw material powder, and again mixed well with an ethanol solvent in a ball mill. The mixed powder obtained by drying the solvent was molded using a die having a diameter of 12 mm, and then fired at 900 ° C. to obtain a lithium ion conductive solid electrolyte material of Example 1.
(Examples 2 to 7)

The lithium ions of Examples 2 to 7 were prepared in the same manner as in Example 1 except that the amount of LiF mixed was 15% by weight, 20% by weight, 25% by weight, 30% by weight, 35% by weight, and 40% by weight, respectively. A conductive solid electrolyte material was obtained.
(Examples 8 to 10)

Lithium ion conductive solid electrolyte materials of Examples 8 to 10 were obtained in the same manner as in Example 1 except that 20% by weight, 25% by weight, and 30% by weight of NaF were added in place of LiF.
(Examples 11 to 13)

Lithium ion conductive solid electrolyte materials of Examples 11 to 13 were obtained by the same production method as Example 1 except that CaF 2 was added in an amount of 20% by weight, 25% by weight, and 30% by weight in place of LiF.
(Comparative Example 1)

A lithium ion conductive solid electrolyte material of Comparative Example 1 was obtained by the same production method as in Example 1 except that no fluoride was mixed.
(Evaluation of Examples 1 to 13 and Comparative Example 1)

  After processing the lithium ion conductive solid electrolyte materials obtained in Examples 1 to 13 and Comparative Example 1 into pellets having a thickness of 1 mm, Au sputtering was performed on both sides of the pellets to obtain a sample on which gold electrodes were formed. It was. Lithium ion conductivity was calculated from the impedance measurement results of these samples. The results are shown in Table 1.

As shown in Table 1, the lithium ion conductive solid electrolyte material to which fluoride was added had improved lithium ion conductivity than the solid electrolyte material of LiNbO 3 alone. In particular, when the fluoride was LiF and the mixed amount of LiF was 15 wt% to 35 wt% of the entire solid electrolyte, a highly practical lithium ion conductivity of 1 × 10 −5 S / cm or more was obtained.

Since LiF has a strong bond between Li and F and Li cannot easily conduct in LiF, it is presumed that lithium ion conduction is improved in the vicinity of the interface between LiNbO 3 and LiF. When the amount of LiF is less than 15% by weight, the interface is not sufficiently generated, and lithium ion conduction cannot be sufficiently obtained. Also, is more than 35 wt%, the too low amount of LiNbO 3 carrying lithium ion conductivity, it is presumed that reduction in lithium ion conductivity is observed. As is clear from Table 1, when the LiF mixing amount is 15% by weight to 35% by weight, significant improvement in lithium ion conduction is observed.

  Since the lithium ion conductive solid electrolyte material of the present invention has high lithium ion conductivity, it has excellent charge / discharge characteristics. Therefore, it can be suitably used as an electrolyte layer of a highly safe lithium ion battery.

Claims (3)

  1. A lithium ion conductive solid electrolyte comprising lithium niobate (LiNbO 3 ) and a fluoride.
  2.   2. The lithium ion conductive solid electrolyte according to claim 1, wherein the fluoride is contained in an amount of 15 wt% to 35 wt% of the lithium ion conductive solid electrolyte.
  3.   The lithium ion conductive solid electrolyte according to claim 1, wherein the fluoride is lithium fluoride (LiF).
JP2012014552A 2012-01-26 2012-01-26 Lithium ion conductive solid electrolyte Active JP5910112B2 (en)

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Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5971264A (en) * 1982-10-15 1984-04-21 Sanyo Electric Co Ltd Solid electrolyte battery
JPS59189566A (en) * 1983-04-11 1984-10-27 Canon Inc Thin film solid electrolyte and its manufacture
JP2008243736A (en) * 2007-03-28 2008-10-09 Arisawa Mfg Co Ltd Lithium ion secondary battery and its manufacturing method
JP2009218124A (en) * 2008-03-11 2009-09-24 Sumitomo Electric Ind Ltd Li ion-conductive solid electrolyte
JP2010244847A (en) * 2009-04-06 2010-10-28 Toyota Motor Corp Solid electrolyte material
JP2011081934A (en) * 2009-10-05 2011-04-21 Konica Minolta Holdings Inc Solid electrolyte and secondary battery

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5971264A (en) * 1982-10-15 1984-04-21 Sanyo Electric Co Ltd Solid electrolyte battery
JPS59189566A (en) * 1983-04-11 1984-10-27 Canon Inc Thin film solid electrolyte and its manufacture
JP2008243736A (en) * 2007-03-28 2008-10-09 Arisawa Mfg Co Ltd Lithium ion secondary battery and its manufacturing method
JP2009218124A (en) * 2008-03-11 2009-09-24 Sumitomo Electric Ind Ltd Li ion-conductive solid electrolyte
JP2010244847A (en) * 2009-04-06 2010-10-28 Toyota Motor Corp Solid electrolyte material
JP2011081934A (en) * 2009-10-05 2011-04-21 Konica Minolta Holdings Inc Solid electrolyte and secondary battery

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
JPN6015023407; SUN H Y, TAKEDA Y, IMANISHI N , YAMAMOTO O: 'Ferroelectric Materials as a Ceramic Filler in Solid Composite Polyethylene Oxide-Based Electrolytes' J Electrochem Soc Vol.147/No.7, 200007, Page.2462-2467 *

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