TWI606019B - Crystal particle production method - Google Patents

Description

Method for producing crystalline particles

The present invention relates to a method for producing LTP or LATP crystal particles which are resistant to the incorporation of impurities, have high crystallinity, and are excellent in dispersibility.

A lithium-based composite oxide crystal having a Na-superionic conductor (NASICON) type crystal structure is a solid electrolyte of a lithium ion battery because it is chemically stable and exhibits high lithium ion conductivity at room temperature. The material is expected. In the solid electrolyte material, in order to achieve high performance of the battery, reduction of impurities, high crystallization, and fine particles are desired.

Here, it has a NASICON type crystal structure, and is represented by the general formula (I) Li _1+x Al _x Ti _2-x (PO ₄ ) ₃ (0≦x≦1.0)---(I)

Crystals of the lithium-based composite oxide (hereinafter referred to as "LTP or LATP crystal"; in the above formula (I), LTP crystals when x = 0, and LATP crystals when 0 < x ≦ 1.0) It has chemical stability and high lithium ion conductivity which are obtained by a solid electrolyte material, and does not have a rare element, and is easy to manufacture. Therefore, LTP or LATP is crystallized in the lithium-based composite oxide crystal, and is also expected as the solid electrolyte material. Therefore, it is particularly strongly desired to crystallize impurities of LTP or LATP. Reduction, high crystallization and micronization.

At present, as a production method of LTP or LATP crystal, a solid phase method, a sol-gel method, or a vitrification method is generally used, but in any of the methods, pulverization is required to achieve microparticulation. When the pulverization is carried out, there is a problem that the impurity is mixed or the crystal structure is deformed, which causes a decrease in lithium ion conductivity. Further, in order to make the particle size distribution sharp and a high pulverization technique is required, a technique of realizing pulverization without pulverization is sought.

Therefore, it is proposed that a plurality of oxides which are raw materials for LTP or LATP crystals are melted together with Ca ₃ (PO ₄ ) ₂ to be vitrified, and the glass is subjected to heat treatment and acid treatment to thereby produce LTP or LATP crystals. Method of porous body (refer to Patent Document 1).

Prior art literature

Patent literature

Patent Document 1: Japanese Patent No. 2656415

However, in the porous body of LTP or LATP crystal produced by the production method described in Patent Document 1, a large amount of Ca is contained as an impurity, and crystallinity is low, and in order to obtain crystal particles excellent in dispersibility, it is necessary to carry out Smash.

In view of the above, the present invention provides a method for producing LTP or LATP crystal particles which are capable of reducing the incorporation of impurities, having high crystallinity, and excellent dispersibility.

The inventors of the present application have made an effort to study the above problems, and as a result, found that Li ₂ O:1+x, Al ₂ O ₃ :x, TiO ₂ :4-2x (0) are produced by molar ratio. ≦x≦1), P ₂ O ₅ :3+y, ZnO: glass larger than y and smaller than 3y (1≦y≦4), and secondly, the glass is heat-treated to be crystallized, and further treated by acid In addition, it is possible to selectively elute a substance other than LTP or LATP crystals, and it is possible to obtain LTP or LATP crystal particles which are excellent in crystallinity and excellent in dispersibility without pulverization, and have completed the invention of the present application.

That is, the means for solving the above problem is as follows.

A method for producing LTP or LATP crystal particles, comprising: producing a molar ratio of Li ₂ O: 1+x (0≦x≦1)

Al ₂ O ₃ :x

TiO ₂ : 4-2x

P ₂ O ₅ :3+y(1≦y≦4)

ZnO: Glass larger than y and smaller than 3 y. Next, the glass is heat-treated to be crystallized, and substances other than LTP or LATP crystals are selectively eluted by acid treatment.

2. The production method according to 1, wherein ZnO in the material of the glass is greater than y and 2 y or less in terms of a molar ratio.

According to the present invention, it is possible to reduce the incorporation of impurities, and to have high crystallinity. LTP or LATP crystal particles excellent in bulk.

Fig. 1 is a view showing an X-ray diffraction pattern of crystallized glass in the process of producing LATP crystal particles of Example 1.

2 is a view showing an X-ray diffraction pattern of crystallized glass in the process of producing LATP crystal particles of Example 2. FIG.

3 is a view showing an X-ray diffraction pattern of crystallized glass in the process of producing LATP crystal particles of Example 3. FIG.

4 is a view showing an X-ray diffraction pattern of crystallized glass in the process of producing LATP crystal particles of Comparative Example 1. FIG.

FIG. 5 is a view showing an X-ray diffraction pattern of the crystallized glass in the production process of the LATP crystal particles of Comparative Example 2. FIG.

6 is a view showing an X-ray diffraction pattern of crystallized glass in the process of producing LATP crystal particles of Comparative Example 3. FIG.

Fig. 7 is a view showing an X-ray diffraction pattern of LATP crystal particles of Example 1.

8 is a view showing an X-ray diffraction pattern of LATP crystal particles of Example 2. FIG.

Fig. 9 is a view showing an X-ray diffraction pattern of LATP crystal particles of Example 3.

10 is an X-ray diffraction pattern showing LATP crystal particles of Comparative Example 1. Figure.

FIG. 11 is a view showing an X-ray diffraction pattern of LATP crystal particles of Comparative Example 2. FIG.

FIG. 12 is a view showing an X-ray diffraction pattern of LATP crystal particles of Comparative Example 3. FIG.

Fig. 13 is a view showing a reflected electron image of the LATP crystal particles of Example 1.

Fig. 14 is a view showing a reflected electron image of the LATP crystal particles of Example 2.

Fig. 15 is a view showing a reflected electron image of the LATP crystal particles of Example 3.

FIG. 16 is a view showing a reflected electron image of the LATP crystal particles of Comparative Example 1. FIG.

17 is a view showing a reflected electron image of LATP crystal particles of Comparative Example 2.

FIG. 18 is a view showing a reflected electron image of the LATP crystal particles of Comparative Example 3. FIG.

19 is a view showing an energy dispersive spectrometer (EDS) spectrum of LATP crystal particles of Example 1. FIG.

20 is a view showing an EDS spectrum of LATP crystal particles of Example 2. FIG.

21 is a view showing an EDS spectrum of LATP crystal particles of Example 3. FIG.

22 is a view showing an EDS spectrum of LATP crystal particles of Comparative Example 1. FIG.

FIG. 23 is a view showing an EDS spectrum of LATP crystal particles of Comparative Example 2. FIG.

FIG. 24 is a view showing an EDS spectrum of LATP crystal particles of Comparative Example 3. FIG.

Hereinafter, a method for producing LTP or LATP crystal particles according to an embodiment of the present invention will be specifically described.

In the method for producing LTP or LATP crystal particles of the present embodiment, when vitrification is performed, raw materials corresponding to each of Li ₂ O, Al ₂ O ₃ , TiO ₂ , P ₂ O ₅ , and ZnO can be respectively used. Oxides, hydroxides, carbonates, nitrates, and phosphates are used as raw materials.

<Li ₂ O>

Li ₂ O is a component constituting LTP or LATP crystals, and the molar ratio at the time of vitrification is 1+x. The relationship between x and Al ₂ O ₃ and TiO _{2 to be} described later is 0 or more and 1 or less. When x is greater than 1, the crystalline structure of LATP may collapse. Further, x is more preferably 0.8 or less. Further, x is more preferably 0.6 or less. ₂ O as the starting material component Li, for example, using a phosphate LiPO _3, Li ₂ CO ₃ and the like carbonates.

<Al ₂ O ₃ >

Al ₂ O ₃ is a component constituting the LATP crystal, and the molar ratio at the time of vitrification is x. Al ₂ O ₃ as a raw material component, for example using Al (PO _{3) 3} and the like phosphate and Al (OH) ₃ hydroxide and the like.

<TiO ₂ >

TiO ₂ is a component constituting LTP or LATP crystals, and the molar ratio at the time of vitrification is 4-2x. TiO ₂ as a raw material component, for example, using a phosphate TiP ₂ O _7, TiO ₂ and other oxide.

<P ₂ O ₅ >

P ₂ O ₅ is a component constituting LTP or LATP crystals, and is a component of zinc pyrophosphate which is precipitated during heat treatment after vitrification, and has a molar ratio of 3+y at the time of vitrification. The relationship between y and Li ₂ O, Al ₂ O ₃ and TiO ₂ is 1 or more and 4 or less. When y is less than 1, it is difficult to vitrify. When y is more than 4, the glass becomes stable, and it is difficult to precipitate crystals by heat treatment after vitrification. Further, y is more preferably 1.5 or more and 3.5 or less. Further, y is more preferably 2 or more and 3 or less. As a raw material of the P ₂ O ₅ component, for example, an acid such as phosphate or H ₃ PO ₄ or an oxide such as P ₂ O ₅ can be used.

<ZnO>

ZnO is a component of zinc pyrophosphate precipitated during heat treatment after vitrification, and the molar ratio at the time of vitrification is larger than y and less than 3 y. When ZnO is y or less, in addition to LTP or LATP crystals, titanium pyrophosphate crystal which is not eluted by acid may precipitate during heat treatment after vitrification. In addition, when ZnO is 3 y or more, zinc phosphate crystals and zinc pyrophosphate crystals which may be eluted by acid are precipitated during heat treatment after vitrification, and some Zn may be contained in LTP or LATP crystals and may remain as impurities. Further, the molar ratio of ZnO is more preferably greater than y and not more than 2y. When the molar ratio of ZnO is 2 y or less, the sub crystalline phase other than the zinc pyrophosphate crystal can be reduced at the time of crystallizing the glass, and the possibility of remaining impurities of the LTP or LATP crystal particles is lowered. As a raw material of the ZnO component, for example, a phosphate such as Zn(PO ₃ ) ₂ or an oxide such as ZnO can be used.

<Production of glass>

As a glass raw material, an oxide, a hydroxide, a carbonate, a nitrate, a phosphate, or the like corresponding to each raw material of each component is weighed and mixed in a predetermined ratio. Then, the mixed raw material is put into a platinum crucible which is not reactive with a glass raw material or the like, and is heated to 1200 ° C to 1500 ° C in an electric furnace, and stirred while being melted, and then clarified and homogenized by an electric furnace. Then, the melt is poured into a water tank sufficiently filled with water to be quenched by water quenching, thereby producing glass.

<heat treatment>

Next, the obtained glass is heat-treated at two stages of from 10 ° to 30 hours at 400 ° C to 600 ° C and 700 ° C to 900 ° C. By this heat treatment, crystallized glass in which LTP or LATP crystal particles are precipitated and zinc pyrophosphate crystals are mainly precipitated as a eluted phase can be obtained, and LTP or LATP having a diameter of 0.1 μm to 10 μm can be obtained by acid treatment described later. Crystallized particles.

<acid treatment>

Further, the obtained crystallized glass is immersed in 1N to 5N nitric acid or 1N to 5N hydrochloric acid at 30 ° C to 90 ° C for 3 hours to 24 hours to carry out an acid treatment. In the case of immersion, stirring is preferably carried out by a stirrer or the like. By the acid treatment, the eluted phase mainly containing zinc pyrophosphate crystals other than the LTP or LATP crystals is eluted. After the acid treatment, LTP or LATP crystals are separated from the acid solution using a filter paper or the like, thereby obtaining LTP or LATP crystal particles having a diameter of 0.1 μm to 10 μm.

According to the method for producing LTP or LATP crystal particles of the present embodiment, which is configured as described above, in the case of vitrification, zinc pyrophosphate crystals are mainly precipitated as a eluted phase, so that the solubility of the eluted phase to the acid is higher than that of the conventional one. Higher, it can reduce the residual of the eluted components in the acid treatment. Therefore, the incorporation of impurities is reduced, whereby LTP or LATP crystal particles having high crystallinity and excellent dispersibility can be produced.

Further, according to the method for producing LTP or LATP crystal particles of the present embodiment, when ZnO in the glass material is larger than y by mole ratio and 2 y or less, the possibility of residual impurities of LTP or LATP crystal particles is further reduced.

[Examples]

Hereinafter, the method for producing LTP or LATP crystal particles of the present invention will be specifically described by way of examples and comparative examples, but the present invention is not limited to the examples.

<Example 1>

Using LiPO ₃ , Al(PO ₃ ) ₃ , Zn(PO ₃ ) ₂ , TiO ₂ , and ZnO as raw materials, Li ₂ O: 1.2, Al ₂ O ₃ : 0.2, and TiO ₂ : 3.6 were prepared in terms of molar ratio. , P ₂ O ₅ : 6, ZnO: 6 glass. That is, a glass having a molar ratio of x = 0.2 and y = 3 and ZnO of 2 y in the above embodiment was produced. Next, the glass was heat-treated at two stages of 520 ° C for 20 hours and 850 ° C for 20 hours to obtain crystallized glass. The acid-treated glass was immersed in 5N nitric acid at 60 ° C for 12 hours to carry out an acid treatment, and then the particles were recovered by filtration to obtain LATP crystal particles of Example 1.

<Example 2>

LiPO ₃ , Al(PO ₃ ) ₃ , Zn(PO ₃ ) ₂ , TiO ₂ , and ZnO were used as raw materials to prepare Li ₂ O: 1.3, Al ₂ O ₃ : 0.3, and TiO ₂ : 3.4 in terms of molar ratio. , P ₂ O ₅ : 5, ZnO: 4 glass. That is, a glass having a molar ratio of x = 0.3 and y = 2 and ZnO of 2 y in the above embodiment was produced. Next, the glass was heat-treated at two times of 480 ° C for 20 hours and at 820 ° C for 20 hours to obtain crystallized glass. The acid-treated glass was immersed in 3N hydrochloric acid at 60 ° C for 12 hours to carry out an acid treatment, and then the particles were recovered by filtration to obtain LATP crystal particles of Example 2.

<Example 3>

LiPO ₃ , Al(PO ₃ ) ₃ , Zn(PO ₃ ) ₂ , TiO ₂ , and ZnO were used as raw materials to prepare Li ₂ O: 1.4, Al ₂ O ₃ : 0.4, and TiO ₂ : 3.2 in terms of molar ratio. , P ₂ O ₅ : 6, ZnO: 7 glass. That is, a glass having a molar ratio of x = 0.4 and y = 3 and ZnO of 2.3 y in the above embodiment was produced. Next, the glass was heat-treated at two times of 470 ° C for 20 hours and 790 ° C for 20 hours to obtain crystallized glass. The acid-treated glass was immersed in 3N hydrochloric acid at 60 ° C for 12 hours to carry out an acid treatment, and then the particles were recovered by filtration to obtain LATP crystal particles of Example 3.

<Comparative Example 1>

LiPO ₃ , Al(PO ₃ ) ₃ , Ca(PO ₃ ) ₂ , TiO ₂ , and CaCO _{3 were} used as raw materials to prepare Li ₂ O: 1.3, Al ₂ O ₃ : 0.3, and TiO ₂ in terms of molar ratio: 3.4, P ₂ O ₅ : 5.2, CaO: 6.6 glass. Next, the glass was heat-treated at two times of 580 ° C for 20 hours and at 700 ° C for 12 hours to obtain crystallized glass. The acidified glass was immersed in 5N nitric acid at 60 ° C for 12 hours to carry out an acid treatment, and then a porous body was obtained by filtration. The obtained porous body was pulverized by a ball mill for 12 hours to obtain LATP crystal particles of Comparative Example 1.

<Comparative Example 2>

LiPO ₃ , Al(PO ₃ ) ₃ , Zn(PO ₃ ) ₂ , TiO ₂ , and ZnO were used as raw materials to prepare Li ₂ O: 1.4, Al ₂ O ₃ : 0.4, and TiO ₂ : 3.2 in terms of molar ratio. , P ₂ O ₅ : 6, ZnO: 9 glass. That is, a glass having a molar ratio of x = 0.4 and y = 3 and ZnO of 3 y in the above embodiment was produced. Next, the glass was heat-treated at two times of 460 ° C for 20 hours and 810 ° C for 20 hours to obtain crystallized glass. The acid-treated glass was immersed in 5N nitric acid at 60 ° C for 12 hours to carry out an acid treatment, and then the particles were recovered by filtration to obtain LATP crystal particles of Comparative Example 2.

<Comparative Example 3>

Using LiPO ₃ , Al(PO ₃ ) ₃ , Zn(PO ₃ ) ₂ , TiP ₂ O ₇ , and TiO ₂ as raw materials, and preparing Li ₂ O: 1.4, Al ₂ O ₃ : 0.4, TiO by molar ratio ₂ : 3.2, P ₂ O ₅ : 6, ZnO: 3 glass. That is, a glass having a molar ratio of x = 0.4 and y = 3 and ZnO was set to y in the above embodiment was produced. Next, the glass was heat-treated at two times of 440 ° C for 20 hours and 790 ° C for 20 hours to obtain crystallized glass. The acid-treated glass was immersed in 5N nitric acid at 60 ° C for 12 hours to carry out an acid treatment, and then the particles were recovered by filtration to obtain LATP crystal particles of Comparative Example 3.

<Comparative Example 4>

Using LiPO ₃ , Al(PO ₃ ) ₃ , Zn(PO ₃ ) ₂ , TiO ₂ , and ZnO as raw materials, Li ₂ O: 1.2, Al ₂ O ₃ : 0.2, and TiO ₂ : 3.6 were prepared in terms of molar ratio. , P ₂ O ₅ : 8, ZnO: 12 glass. That is, a glass having a molar ratio of x = 0.2 and y = 5 and ZnO of 2.4 y in the above embodiment was produced. Even if the glass is heat-treated at a melting point or lower, no crystals are precipitated.

<Comparative Example 5>

Using LiPO ₃ , Al(PO ₃ ) ₃ , Zn(PO ₃ ) ₂ , TiP ₂ O ₇ , TiO ₂ as a raw material, and preparing Li ₂ O:1.1, Al ₂ O ₃ :0.1, TiO by molar ratio ₂ : 3.8, P ₂ O ₅ : 3.5, ZnO: 1 melt, the melt was not vitrified even after water quenching and quenching. That is, it is not possible to produce glass in the molar ratio of x=0.1, y=0.5 and ZnO of 2y in the above embodiment.

<X-ray diffraction spectrum of crystallized glass>

Crystallization during the production of LATP crystal particles of Examples 1 to 3 and Comparative Examples 1 to 3 was investigated by an X-ray diffraction apparatus Ultima IV (manufactured by Rigaku). X-ray diffraction spectrum of glass. The X-ray diffraction spectra of Examples 1 to 3 and Comparative Examples 1 to 3 are shown in FIGS. 1 to 3 and 4 to 6, respectively. As shown in FIG. 1 and FIG. 2, it was found that LATP crystals and zinc pyrophosphate crystals were precipitated in Examples 1 and 2. As shown in FIG. 3, it was found that in the third embodiment, LATP crystals and zinc pyrophosphate crystals and a part of the sub crystalline phase were precipitated. As shown in FIG. 4, it was found that the LATP crystal and the calcium pyrophosphate crystal and the sub crystalline phase were precipitated in Comparative Example 1. As shown in FIG. 5, it was found that in Comparative Example 2, LATP crystals, zinc phosphate crystals, and a sub crystalline phase were precipitated. As shown in Fig. 6, it was found that in Comparative Example 3, LATP crystals and titanium pyrophosphate crystals and a sub crystalline phase were precipitated.

<X-ray diffraction spectrum of LATP crystal particles>

The X-ray diffraction spectrum of the LATP crystal particles of Examples 1 to 3 and Comparative Examples 1 to 3 was investigated by an X-ray diffraction apparatus Ultima IV (manufactured by Science). The X-ray diffraction spectra of Examples 1 to 3 and Comparative Examples 1 to 3 are shown in FIGS. 7 to 9 and 10 to 12, respectively. As shown in FIGS. 7 to 9, it is understood that the LATP crystal particles in Examples 1 to 3 are single phases of LATP crystals. As shown in FIG. 10 and FIG. 11, it can be seen that the peak of the sub crystalline phase can be seen in the LATP crystal particles in Comparative Example 1 and Comparative Example 2, and is not a single LATP crystal. phase. As shown in FIG. 12, it can be seen that the peak of the titanium pyrophosphate and the sub crystalline phase can be seen in the LATP crystal particles in Comparative Example 3, and is not a single phase of the LATP crystal.

<Reflected electron image of LATP crystal particles>

The reflected electron images of the LATP crystal particles of Examples 1 to 3 and Comparative Examples 1 to 3 were investigated by a scanning electron microscope S-3400N (manufactured by Hitachi, Ltd.). The reflected electron images of Examples 1 to 3 and Comparative Examples 1 to 3 are shown in Figs. 13 to 15 and Figs. 16 to 18, respectively. As shown in FIGS. 13 to 15, the LATP crystal particles in Examples 1 to 3 had a shape having high crystallinity similar to that of a quadrangular prism, and no aggregation was observed. As shown in FIG. 16, the LATP crystal particles in Comparative Example 1 had a shape in which the crystallinity of the angle was not remarkable, and a part of aggregation was observed. As shown in FIG. 17, in the LATP crystal particles of Comparative Example 2, a shape having a low crystallinity with a remarkable angle was observed. As shown in FIG. 18, in the LATP crystal particles of Comparative Example 3, a shape having high crystallinity was observed in some cases, but a shape having a low crystallinity with a remarkable angle was observed as a whole.

<EDS spectrum of LATP crystal particles>

The EDS spectra of the LATP crystal particles of Examples 1 to 3 and Comparative Examples 1 to 3 were investigated by an energy dispersive X-ray analyzer by INCA Energy (manufactured by Oxford Instruments). The EDS spectra of Examples 1 to 3 and Comparative Examples 1 to 3 are shown in FIGS. 19 to 21 and 22 to 24, respectively. As shown in FIG. 19 to FIG. 21, elements other than the elements constituting the LATP crystal were not detected in the LATP crystal particles of Examples 1 to 3. As shown in FIG. 22, in the LATP crystal particles of Comparative Example 1, except for the constitution In addition to the elements of LATP crystallization, Ca was also detected. As shown in FIG. 23 and FIG. 24, in the LATP crystal particles of Comparative Example 2 and Comparative Example 3, Zn was detected in addition to the elements constituting the LATP crystal.

The present invention has been described with reference to the drawings or embodiments, but it should be noted that various modifications and changes can be made in accordance with the present disclosure as long as they are employed by those skilled in the art. Therefore, it should be noted that such variations or modifications are encompassed within the scope of the invention.

Claims (2)

A method for producing a crystal particle, wherein the crystal particle is an LTP or LATP crystal particle, comprising: a molar ratio of Li ₂ O:1+x(0≦x≦1)Al ₂ O ₃ :x TiO ₂ : 4 - ₂ x P ₂ O ₅ : 3 + y (1 ≦ y ≦ 4) ZnO: glass larger than y and less than 3 y, and secondly, the glass is heat-treated to be crystallized by acid treatment. Substances other than LTP or LATP crystals are selectively eluted. The method for producing a crystal particle according to claim 1, wherein the ZnO in the glass material is greater than y in terms of a molar ratio and is 2 y or less.