JPWO2014136650A1 - Method for producing lithium ion conductive glass ceramics, lithium ion conductive glass ceramics and lithium ion secondary battery - Google Patents

Abstract

(A) The raw material mixture is in mol% unit converted to oxide, 25% or more and 50% or less of SiO ₂ , 10% or more and 45% or less of ZrO ₂ , more than 0% and 30% or less of P ₂ O ₅ , and Preparing a raw material mixture by preparing a raw material so as to contain 5% or more and 40% or less Na ₂ O, and obtaining an object to be processed made of glass ceramics in the process of melting, cooling and solidifying the raw material mixture; and b) a process for ion-exchange treatment of the object to be processed in a molten salt containing lithium ions.

Description

  The present invention relates to a method for producing a lithium ion conductive glass ceramic, a lithium ion conductive glass ceramic, and a lithium ion secondary battery.

  Lithium ion secondary batteries are used as small and high capacity drive power sources in various fields such as automobiles, personal computers, and mobile phones.

  Currently, organic solvent-based liquid electrolytes such as diethyl carbonate and ethyl methyl carbonate are used as electrolytes for lithium ion secondary batteries. However, an organic solvent-based liquid electrolyte may be decomposed or deteriorated when a high voltage is applied.

  Therefore, an inorganic solid electrolyte that is nonflammable and has high stability against voltage application is expected as an electrolyte for the next-generation lithium ion secondary battery. For example, inorganic solid electrolytes made of ceramics and inorganic solid electrolytes made of glass ceramics (glass containing crystals, also called crystallized glass) have been proposed.

As an inorganic solid electrolyte made of glass ceramics, for example, Li _{1 + x + y} (Al, Ga) _x (Ti, Ge) _2-x Si _y P _3-y O ₁₂ (where 0 ≦ a ≦ 1, 0 ≦ y ≦ 1 There is proposed a material composed of (A).

JP 2007-66703 A

  The inorganic solid electrolyte made of glass ceramics of Patent Document 1 has titanium and germanium. Titanium and germanium ions can have multiple valence states. Therefore, at the time of charge / discharge of the lithium ion secondary battery, the valence state of titanium ions and germanium ions may change, and battery characteristics such as cycle characteristics may become unstable. In particular, titanium and germanium are likely to change in valence state due to a reduction reaction when metallic lithium is used for the negative electrode, and the potential window becomes narrow and unstable.

  There is a problem as described above, and there is a demand for an inorganic solid electrolyte for a lithium ion secondary battery in which stability of battery characteristics such as cycle characteristics and ion conductivity are further improved.

  In view of the above-described problems, an object of the present invention is to provide a method for producing a lithium ion conductive glass ceramic that is relatively stable with respect to metallic lithium and has improved ion conductivity. Another object of the present invention is to provide a lithium ion secondary battery having a lithium ion conductive glass ceramic produced by such a method and a solid electrolyte containing the lithium ion conductive glass ceramic.

According to one embodiment, (a) the raw material mixture is 25% or more and 50% or less of SiO ₂ , 10% or more and 45% or less of ZrO ₂ , and more than 0% and 30% or less in terms of mol% converted to oxide. raw materials were blended to obtain a raw material mixture, the raw material mixture to be treated made of glass ceramics in the process of solidifying melted cooled to include a P _{2 O 5,} and 5% to 40% of Na 2 _O There is provided a method for producing a lithium ion conductive glass ceramic, comprising: a step of obtaining a body; and (b) a step of subjecting the object to be treated to an ion exchange treatment in a molten salt containing lithium ions.

  In the method for producing a lithium ion conductive glass ceramic, the object to be processed may have a NASICON type crystal structure.

  In the manufacturing method of the said lithium ion conductive glass ceramics, you may have the process of processing the thickness of the said processing body into 1 mm or less between the process of said (a) and said (b).

  In the method for producing a lithium ion conductive glass ceramic, the melting may be performed by heating the raw material mixture at a temperature of 1400 ° C. or higher and 1700 ° C. or lower.

  In the method for producing a lithium ion conductive glass ceramic, the cooling may be performed at a cooling rate of 0.2 ° C./min to 2 ° C./min.

  In the method for producing a lithium ion conductive glass ceramic, the ion exchange treatment is performed at a temperature of 200 ° C. or more and 500 ° C. or less, and the object to be processed is held in the molten salt containing lithium ions for 24 hours to 120 hours. May be implemented.

  Moreover, according to another form, the lithium ion conductive glass ceramics manufactured by the above methods are provided.

  According to another aspect, there is provided a lithium ion secondary battery having a positive electrode, a negative electrode, and a solid electrolyte disposed between the two electrodes, wherein the solid electrolyte is manufactured by the method as described above. Provided is a lithium ion secondary battery that is a solid electrolyte containing conductive glass ceramics.

  The present invention can provide a method for producing a lithium ion conductive glass ceramic that is relatively stable with respect to metallic lithium and has improved ion conductivity. Moreover, in this invention, the lithium ion secondary battery which has a solid electrolyte containing the lithium ion conductive glass ceramics manufactured by such a method and this lithium ion conductive glass ceramics can be provided.

It is the figure which showed typically the lithium ion secondary battery of this embodiment. 2 is an X-ray diffraction pattern of an evaluation sample of Example 1. FIG. 6 is a diagram showing an X-ray diffraction pattern of an evaluation sample of Example 2. FIG. 6 is a diagram showing an X-ray diffraction pattern of an evaluation sample of Example 3. FIG. 6 is a diagram showing an X-ray diffraction pattern of an evaluation sample of Example 4. FIG. 6 is a diagram showing an X-ray diffraction pattern of an evaluation sample of Example 5. FIG.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. However, the present invention is not limited to the following embodiments, and the following embodiments are not departed from the scope of the present invention. Various modifications and substitutions can be made.

  In the present specification, unless otherwise specified, the production method of lithium ion conductive glass ceramics and the content of each component in the lithium ion conductive glass ceramics obtained thereby are in mol% units converted to oxides. It expresses by. This is a unit when the content of each component converted to oxide is expressed as a percentage when the total content of each component converted to oxide is 100 mol%.

(Method for producing lithium ion conductive glass ceramics)
The method for producing the lithium ion conductive glass ceramic of the present embodiment is as follows:
(A) The raw material mixture is in mol% unit converted to oxide, 25% or more and 50% or less of SiO ₂ , 10% or more and 45% or less of ZrO ₂ , more than 0% and 30% or less of P ₂ O ₅ , and Preparing a raw material mixture by preparing a raw material so as to contain 5% or more and 40% or less Na ₂ O, and obtaining an object to be processed made of glass ceramics in the process of melting, cooling and solidifying the raw material mixture;
(B) performing an ion exchange process on the object to be processed in a molten salt containing lithium ions.

  The manufacturing method of this embodiment may have the process of processing the said to-be-processed object into 1 mm or less between a process (a) and a process (b).

  Moreover, the manufacturing method of this embodiment does not need to have the process to heat-process after a process (a) and before a process (b). That is, the glass ceramic obtained in the process of melting and cooling the raw material mixture in the step (a) is once cooled to a predetermined temperature (for example, room temperature), and then is not heat-treated in the step (b). Ion exchange treatment may be performed.

  In the present embodiment, the object to be processed made of glass ceramics preferably has a clear diffraction peak in an X-ray diffraction pattern by X-ray diffraction measurement using CuKα rays, and has a diffraction peak with a half-value width of 3 ° or less. More preferably.

  In the present embodiment, the object to be processed made of glass ceramics preferably has a NASICON type crystal structure.

  Here, the identification of the “crystal structure” is performed by performing X-ray diffraction measurement of an object, and collating the obtained X-ray diffraction pattern based on a JCPDS (Joint of Commitment on Powder Diffraction Standards) card, Can be easily identified.

  Hereinafter, each step will be described in detail.

(Process (a))
In the process of preparing the raw material mixture by preparing the raw material mixture so that the raw material mixture contains SiO ₂ , ZrO ₂ , P ₂ O ₅ , and Na ₂ O in the following ranges, and melting and cooling the raw material mixture to solidify An object to be processed made of glass ceramics is obtained.
SiO ₂ : 25% to 50%, preferably 30% to 45%, more preferably 32% to 43%.
ZrO ₂ : 10% to 45%, preferably 15% to 40%, more preferably 17% to 38%.
P ₂ O ₅ : more than 0% and 30% or less, preferably 2% or more and 25% or less, more preferably 5% or more and 20% or less.
Na ₂ O: 5% to 40%, preferably 10% to 35%, more preferably 15% to 30%.

SiO ₂ is an essential component for expanding the composition range (hereinafter also referred to as vitrification range) to become glass and obtaining glass ceramics having a NASICON type crystal structure. If the content of SiO ₂ is too small, it becomes difficult to obtain glass ceramics having a NASICON type crystal structure. Therefore, SiO ₂ is set to 25% or more. Further, since glass ceramics having a NASICON type crystal structure can be obtained more stably, SiO ₂ is preferably 30% or more, and more preferably 32% or more.

If the content of SiO ₂ is too large, it is difficult to melt the raw material mixture. Therefore, SiO ₂ is set to 50% or less. Further, since it becomes easy to lower the viscosity at the time of melting of the raw material mixture, and it becomes easy to precipitate crystals having a NASICON type crystal structure in the obtained glass ceramic, SiO ₂ is preferably 45% or less, and 43% or less. More preferably.

ZrO ₂ is an essential component for obtaining glass ceramics having a NASICON type crystal structure. If the content of ZrO ₂ is too small, it becomes difficult to obtain glass ceramics having a NASICON type crystal structure, so ZrO ₂ is made 10% or more. Further, it becomes easier to precipitate crystals having a crystal structure of the NASICON type, ZrO ₂ is preferably 15% or more, and more preferably 17% or more.

If the content of ZrO ₂ is too large, it is difficult to melt the raw material mixture, so ZrO ₂ is set to 45% or less. In addition, since the viscosity of the raw material mixture during melting is easily lowered, and crystals having a NASICON type crystal structure are easily precipitated in the obtained glass ceramic, ZrO ₂ is preferably set to 40% or less, and 38% or less. More preferably.

P ₂ O ₅ is an essential component for expanding the vitrification range and obtaining glass ceramics having a NASICON type crystal structure. If P ₂ O ₅ is not contained, glass ceramics having a NASICON type crystal structure cannot be obtained. Therefore, P ₂ O ₅ is set to exceed 0%. Further, since glass ceramics having a NASICON type crystal structure can be obtained more stably, P ₂ O ₅ is preferably 2% or more, and more preferably 5% or more.

If the content of P ₂ O ₅ is too large, it is difficult to obtain glass ceramics having a NASICON type crystal structure, and the hygroscopicity is likely to deteriorate, so P ₂ O ₅ is set to 30% or less. Further, it becomes easier to precipitate crystals only having a crystal structure of the NASICON type obtained glass ceramic, it is preferred that the P ₂ O ₅ is 25% or less, and more preferably 20% or less.

Na ₂ O is an essential component for obtaining glass ceramics having a NASICON type crystal structure. If the content of Na ₂ O is too small, the ion conductivity of the lithium ion conductive glass ceramic obtained later by ion exchange treatment will be low, so Na ₂ O is made 5% or more. Further, since glass ceramics having a NASICON type crystal structure can be obtained more stably, Na ₂ O is preferably 10% or more, and more preferably 15% or more.

Volatilization becomes violently Na 2 _O alkali component during the melting of the content is too large raw material mixture (Na), the glass ceramics becomes difficult to obtain with a crystal structure of the NASICON type of interest, Na 2 _O is 40% or less. In addition, Na ₂ O is preferably 35% or less, and more preferably 30% or less, because an objective glass ceramic having a NASICON crystal structure can be obtained more stably.

  By preparing the raw materials so as to include each component in the above range, crystals can be precipitated while preventing the compositional deviation due to the volatilization of the raw materials in the process of melting the raw material mixture and cooling to solidify. Moreover, it becomes easy to precipitate a crystal having a NASICON type crystal structure.

  In addition, as a component of the raw material mixture, lithium ion conductivity, which is relatively stable with respect to metallic lithium, is prevented by substantially not including an element whose valence state changes due to a reduction reaction, such as titanium or germanium. Glass ceramics can be obtained.

Specifically, the raw material mixture is SiO _{2 of} 25% to 50%, ZrO _{2 of} 10% to 45%, P ₂ O _{5 of} more than 0% to 30% and Na of 5% to 40%. It is preferable to prepare the raw material so as to contain ₂ O.

In addition, the raw material mixture contains 30% to 45% SiO ₂ , 15% to 40% ZrO ₂ , 2% to 25% P ₂ O ₅ , and 10% to 35% Na ₂ O. It is more preferable to prepare the raw materials so as to include them.

Further, the raw material mixture contains SiO _{2 of} 32% to 43%, ZrO _{2 of} 17% to 38%, P ₂ O _{5 of} 5% to 20%, and Na ₂ O of 15% to 30%. It is more preferable to prepare the raw materials so as to include them.

  In this embodiment, the raw material mixture is prepared such that each component is included in the above range to obtain the raw material mixture, and the raw material mixture is melted, cooled and solidified to precipitate crystals in the amorphous state. Can be made. That is, an object to be processed made of glass ceramics can be obtained directly in the process of melting and cooling the raw material mixture and solidifying it.

  Specifically, it is preferable to obtain an object to be processed made of glass ceramics through the following procedure.

  In a general method, raw materials are mixed to obtain a raw material mixture, and the raw material mixture is melted to obtain a melt. Specifically, a raw material mixture prepared by mixing raw materials so as to include each component in the above range is heated and melted by a general method to obtain a melt.

  A raw material will not be specifically limited if it is a raw material used for manufacture of normal glass ceramics. For example, raw materials include silica sand, sodium carbonate, diphosphorus pentoxide, zirconium oxide, sodium silicate, trisodium phosphate, ammonium phosphate, sodium metasilicate, sodium disilicate / n hydrate, sodium diphosphate Hydrates, sodium metaphosphate, sodium hexametaphosphate, zirconium hydroxide, and the like can be used.

  The melting temperature is preferably 1400 ° C. or higher and 1700 ° C. or lower, and more preferably 1450 ° C. or higher and 1650 ° C. or lower.

  Next, an object to be processed made of glass ceramics is obtained in the process of cooling and solidifying the melt. The melt is preferably solidified by slow cooling.

  Specifically, first, the melt is poured out on a carbon plate. In order to remove the distortion in the glass ceramic, the melt poured out on the carbon plate is heated at a glass transition temperature + 20 ° C. (for example, 750 ° C.) for 1 hour and then cooled to room temperature. The cooling rate in cooling from the glass transition temperature + 20 ° C. to room temperature is preferably 2 ° C./min or less, and more preferably 1 ° C./min or less. It is preferable to make the cooling rate slower because crystals are easily precipitated. Moreover, this cooling rate can be 0.2 degree-C / min or more. By slowly cooling and solidifying the melt, it is possible to remove distortion of the glass ceramic that is the obtained solidified product. When the melt is cooled and solidified, a constant temperature may be maintained for a certain time during the cooling in order to remove the distortion of the glass ceramic.

  In the present embodiment, an object to be processed made of glass ceramics is directly obtained in the process of heating and melting the raw material mixture to obtain a melt, and cooling and solidifying the melt. Therefore, the reheating process in the normal method for producing glass ceramics can be omitted. That is, it is not necessary to have a step of further heat-treating (for example, 800 ° C. or higher) the solidified product (glass ceramic) that has been melted and then cooled to room temperature.

  The object to be processed may be in any form. The object to be processed may be, for example, a block shape, a plate shape, or a disk shape.

(Process (b))
The object to be treated obtained in the step (a) is subjected to ion exchange treatment in a molten salt containing lithium ions to obtain lithium ion conductive glass ceramics.

  Through the ion exchange treatment, part or all of the sodium ions in the object to be treated are replaced with lithium ions. The ion-exchanged lithium ions are considered to be introduced into the sites occupied by sodium ions. Lithium ions introduced to the site occupied by sodium ions are easy to move, and therefore the degree of freedom is increased. This is because lithium ions have a smaller ionic radius than sodium ions. That is, lithium ion conductive glass ceramics having a large ion conductivity can be formed by ion exchange treatment.

  In addition, by subjecting an object to be processed made of glass ceramics to ion exchange treatment, sodium ions in the amorphous substance are also replaced with lithium ions. Thereby, since the ionic conductivity in an amorphous substance also improves, it is thought that the lithium ion conductive glass ceramics with higher ionic conductivity can be obtained.

  Further, when the object to be processed has a NASICON type crystal structure, it is considered that lithium ion conductive glass ceramics having higher ion conductivity can be obtained. This is because the NASICON type crystal structure originally has a characteristic that the ionic conductivity of sodium ions is relatively high. Therefore, when an object to be processed having a NASICON type crystal structure is subjected to ion exchange treatment with lithium ions, two steps of ionic conductivity, ie, good ion conductivity derived from the crystal structure and improvement of ion conductivity by the ion exchange treatment. Improvement effect is obtained. For this reason, it becomes possible to provide lithium ion conductive glass-ceramics with improved ion conductivity compared to the prior art.

  The conditions for the ion exchange treatment are not particularly limited as long as lithium ions can be introduced into some or all of the sites occupied by sodium ions in the object to be treated. For example, the ion exchange treatment may be performed by immersing the object to be processed in a molten salt containing lithium ions for a predetermined time. As the molten salt containing lithium ions, for example, lithium nitrate, lithium nitrite, lithium sulfate, lithium chloride, lithium fluoride, and a mixed salt thereof may be used.

  The temperature condition of the ion exchange treatment varies depending on the molten salt to be used. Further, the treatment time of the ion exchange treatment varies depending on temperature conditions, but may be, for example, 24 hours or more and 120 hours or less, preferably 24 hours or more and 80 hours or less. By setting the above temperature and treatment time, lithium ion conductive glass ceramics in which 90% or more of sodium ions in the object to be treated are replaced with lithium ions can be obtained.

  The manufacturing method of this embodiment may have the process (c) which processes the thickness of a to-be-processed object thinly before the ion exchange process of a process (b).

(Process (c))
The object to be processed obtained in the step (a) is thinned. Polishing etc. are mentioned as a processing method which makes a to-be-processed object thin.

  The thickness of the workpiece is preferably 1 mm or less, more preferably 0.6 mm or less, and even more preferably 0.25 mm or less. The thickness of the object to be processed is preferably 0.1 mm or more. By setting the thickness of the object to be processed to 0.1 mm or more and 1.0 mm or less, sodium ions and lithium ions can be ion-exchanged more quickly and efficiently in the step (b). Accordingly, the ion exchange treatment time can be shortened and / or the treatment temperature can be suppressed. Moreover, the manufacturing method of this embodiment prepares the to-be-processed object which consists of glass ceramics at a process (a), Then, the process to thin the to-be-processed object of a process (c) is performed, and the to-be-processed object of a process (b) Can be performed in the order of ion exchange treatment. The thinned object is only loaded with a temperature of about 200 to 500 ° C. during the ion exchange process. Therefore, the manufacturing method of the present embodiment can prevent defects such as warpage that are likely to occur on a thin glass substrate or the like.

(Lithium ion conductive glass ceramics)
The lithium ion conductive glass ceramic produced according to the present embodiment includes 25% to 50% SiO ₂ , 10% to 45% ZrO ₂ , more than 0% to 30% P ₂ O ₅ , and 5%. It is preferable to contain Na ₂ O of 40% or less, 30% or more and 45% or less of SiO ₂ , 15% or more and 40% or less of ZrO ₂ , 2% or more and 25% or less of P ₂ O ₅ , and 10% or more. More preferably, it contains 35% or less Na ₂ O, 32% or more and 43% or less SiO ₂ , 17% or more and 38% or less ZrO ₂ , 5% or more and 20% or less P ₂ O ₅ , and 15% or more More preferably, it contains 30% or less of Na ₂ O.

  In the present embodiment, the lithium ion conductive glass ceramic preferably has a clear diffraction peak in an X-ray diffraction pattern by X-ray diffraction measurement using CuKα rays, and has a diffraction peak with a half-value width of 3 ° or less. It is more preferable. The lithium ion conductive glass ceramics preferably has a NASICON type crystal structure.

In this embodiment, the ion conductivity of the lithium ion conductive glass ceramic is preferably 1.0 × 10 ⁻⁷ (S / cm) or more. In this specification, the ionic conductivity means a value obtained by AC impedance measurement at room temperature (20 ° C. or more and 25 ° C. or less; the same applies hereinafter). The ionic conductivity is obtained by measurement by an alternating current impedance method using a sample having electrodes formed on both sides. The ionic conductivity of the lithium ion conductive glass ceramic in the present embodiment is calculated from the arc diameter of the colle-core plot obtained by AC impedance measurement under the measurement conditions of applied voltage 50 mV and measurement frequency range 1 Hz to 1 MHz.

  The lithium ion conductive glass ceramic produced according to this embodiment can be applied to an inorganic solid electrolyte for a lithium ion secondary battery. For example, the solid electrolyte according to the present embodiment can be applied to a solid electrolyte for a metal-air battery or an all-solid battery.

(Lithium ion secondary battery)
The lithium ion conductive glass ceramic produced by the production method of the present embodiment can be used, for example, as a solid electrolyte of a lithium ion secondary battery, a metal-air battery, or an all-solid battery. FIG. 1 schematically shows an example of the configuration of a lithium ion secondary battery.

  As shown in FIG. 1, the lithium ion secondary battery 100 includes a cathode electrode 110, an anode electrode 150, and an electrolyte 120 between the electrodes.

For the cathode electrode 110, for example, LiCoO ₂ , LiMn ₂ O ₄ , LiFePO ₄ or the like is used. For the anode electrode 150, for example, metallic lithium, graphite, Li ₄ Ti ₅ O ₁₂ or the like is used. However, this is merely an example, and it will be apparent to those skilled in the art that other electrode materials may be used for both electrodes.

  Here, as the electrolyte 120, a solid electrolyte containing the lithium ion conductive glass ceramic in the present embodiment is used.

  When the lithium ion conductive glass ceramic in the present embodiment is used as the electrolyte 120, higher safety can be provided to the lithium ion secondary battery than when a conventional organic solvent-based liquid electrolyte is used. In addition, the lithium ion conductive glass ceramic in the present embodiment has higher stability against voltage application than a conventional organic solvent-based liquid electrolyte. For this reason, when a large voltage is applied to the lithium ion secondary battery, the conventional problem that the electrolyte is decomposed or deteriorated is reduced.

  Furthermore, the lithium ion conductive glass ceramic in this embodiment has high lithium ion conductivity. Therefore, the lithium ion secondary battery 100 having the electrolyte 120 made of the lithium ion conductive glass ceramic according to the present embodiment exhibits better characteristics than a conventional lithium ion secondary battery using a solid electrolyte. be able to.

  Examples of the present embodiment and comparative examples are shown below. Examples 1 to 4 are examples, and example 5 is a comparative example. Table 1 shows the composition (mol% unit) of the raw material mixture and the ionic conductivity of the sample for evaluation obtained after the ion exchange treatment.

(Example 1)
(Preparation of sample for evaluation)
The sample for evaluation was produced in the following procedures, and the characteristics were evaluated.

  The raw material powder is weighed and mixed so that the raw material mixture contains each component in the composition shown in the column of “raw material mixture composition” of Example 1 in Table 1 below (indicated as the raw material mixture composition (mol%) in Table 1). Thus, a raw material mixture was obtained. Next, the raw material mixture was put in a platinum crucible, heated at 1650 ° C. for 120 minutes, and melted to obtain a melt of the raw material mixture. Next, the molten material was poured onto a carbon plate. In order to remove the distortion in the sample, the sample was heated at 830 ° C. for 1 hour, and then cooled to room temperature (25 ° C.) at a cooling rate of 1 ° C./min, that is, 13 hours and 25 minutes, to produce a block-like sample. Hereinafter, in this example, a sample obtained by heating and melting the raw material mixture to obtain a melt, and cooling and solidifying the melt is referred to as a sample before ion exchange treatment.

イオン交換処理前サンプルを粉砕し、ＣｕＫα線を用いたＸ線回折測定を行った。得られたＸ線回折パターンに明瞭な回折ピークが認められたことから、イオン交換処理前サンプルがガラスセラミックスであることが確認された。また、Ｘ線回折パターンのピーク解析の結果、イオン交換処理前サンプルは、ＮＡＳＩＣＯＮ型の結晶構造を有することが確認された。

The sample before the ion exchange treatment was pulverized, and X-ray diffraction measurement using CuKα rays was performed. Since a clear diffraction peak was observed in the obtained X-ray diffraction pattern, it was confirmed that the sample before the ion exchange treatment was glass ceramics. As a result of peak analysis of the X-ray diffraction pattern, it was confirmed that the sample before the ion exchange treatment had a NASICON type crystal structure.

  Next, the sample before the ion exchange treatment was polished until the thickness became 0.25 mm.

  Next, ion exchange treatment was performed using the sample before ion exchange treatment after polishing. The ion exchange treatment was performed by immersing the sample before the ion exchange treatment in a 400 ° C. lithium nitrate molten salt. The processing time was 72 hours. Thereby, the sample for evaluation was obtained.

  The sample for evaluation was subjected to X-ray diffraction measurement using CuKα rays. FIG. 2 shows an X-ray diffraction pattern of the evaluation sample. Before and after the ion exchange treatment, that is, the X-ray diffraction patterns of the sample before the ion exchange treatment and the sample for evaluation were hardly changed. From this result, it was confirmed that the sample for evaluation of Example 1 was the same glass ceramics as before the ion exchange treatment. Moreover, it was confirmed that the sample for evaluation of Example 1 has the same crystal structure as that before the ion exchange treatment, that is, the NASICON type crystal structure.

The composition of the sample for evaluation was measured by ICP analysis. As a result, SiO ₂ was 30%, ZrO ₂ was 35%, P ₂ O ₅ was 15%, Li ₂ O was 20%, and Na ₂ O was the detection limit. It was the following. It was confirmed that the sample for evaluation in which most of the sodium ions in the sample before the ion exchange treatment were replaced with lithium ions was obtained by the ion exchange treatment.

(Characteristic evaluation)
Ionic conductivity was measured by the following method using the sample for evaluation. First, gold films (thickness: about 200 nm) were formed on both surfaces of the evaluation sample by vapor deposition. Using the gold film as an electrode, a measurement voltage of 50 mV was applied between both electrodes, and impedance measurement was performed by an AC impedance method. For the measurement, Solartron 1260 (manufactured by Solartron) equipped with FRA (frequency response analyzer) was used, and the measurement frequency was 10 ⁷ Hz to 10 Hz. The ionic conductivity of the sample for evaluation of Example 1 was calculated from the arc diameter obtained from the Cole-Cole plot.

As a result of the measurement, the ionic conductivity was 5.5 × 10 ⁻⁵ S / cm.

(Example 2)
In Example 2, the raw material powder was weighed and mixed so that the raw material mixture contained each component with the composition shown in the column of “Raw material mixture composition” in Example 2 in Table 1 above to obtain a raw material mixture. In Example 2, the sample before the ion exchange treatment was polished until the thickness became 0.6 mm. The other production conditions were the same as in Example 1.

  The sample before ion exchange treatment and the sample for evaluation were subjected to X-ray diffraction measurement using CuKα rays. In FIG. 3, the X-ray-diffraction result of the sample for evaluation is shown.

  Before and after the ion exchange treatment, that is, the X-ray diffraction patterns of the sample before the ion exchange treatment and the sample for evaluation were hardly changed. Since the clear diffraction peak was recognized in the X-ray diffraction pattern, the sample before the ion exchange treatment and the evaluation sample were confirmed to be glass ceramics. Further, as a result of peak analysis of the X-ray diffraction pattern, it was confirmed that it had a NASICON type crystal structure.

As a result of measuring the composition of the sample for evaluation by ICP analysis, SiO ₂ was 42.5%, ZrO ₂ was 22.5%, P ₂ O ₅ was 15%, Li ₂ O was 20%, Na ₂ O was below the detection limit. It was confirmed that the sample for evaluation in which most of the sodium ions in the sample before the ion exchange treatment were replaced with lithium ions was obtained by the ion exchange treatment.

Using the evaluation sample, the ionic conductivity was measured by the method described above. As a result of the measurement, the ion conductivity of the sample for evaluation was 1.6 × 10 ⁻⁵ S / cm.

(Example 3)
In Example 3, the raw material powder was weighed and mixed so as to include each component in the composition shown in the column of “Raw material mixture composition” in Example 3 in Table 1 above to obtain a raw material mixture. Other manufacturing conditions were the same as in Example 2.

  The sample before ion exchange treatment and the sample for evaluation were subjected to X-ray diffraction measurement using CuKα rays. In FIG. 4, the X-ray-diffraction result of the sample for evaluation is shown.

  Before and after the ion exchange treatment, that is, the X-ray diffraction patterns of the sample before the ion exchange treatment and the sample for evaluation were hardly changed. Since the clear diffraction peak was recognized in the X-ray diffraction pattern, the sample before the ion exchange treatment and the evaluation sample were confirmed to be glass ceramics. Further, as a result of peak analysis of the X-ray diffraction pattern, it was confirmed that it had a NASICON type crystal structure.

The composition of the sample for evaluation was measured by ICP analysis. As a result, SiO ₂ was 40%, ZrO ₂ was 20%, P ₂ O ₅ was 10%, Li ₂ O was 30%, and Na ₂ O was the detection limit. It was the following. It was confirmed that the sample for evaluation in which most of the sodium ions in the sample before the ion exchange treatment were replaced with lithium ions was obtained by the ion exchange treatment.

Using the evaluation sample, the ionic conductivity was measured by the method described above. As a result of the measurement, the ion conductivity of the sample for evaluation was 4.1 × 10 ⁻⁶ S / cm.

(Example 4)
In Example 4, the raw material powder was weighed and mixed so that the raw material mixture contained each component with the composition shown in the column of “Raw material mixture composition” in Example 4 in Table 1 above to obtain a raw material mixture. Other manufacturing conditions were the same as in Example 2.

  The sample before ion exchange treatment and the sample for evaluation were subjected to X-ray diffraction measurement using CuKα rays. In FIG. 5, the X-ray-diffraction result of the sample for evaluation is shown.

  Before and after the ion exchange treatment, that is, the X-ray diffraction patterns of the sample before the ion exchange treatment and the sample for evaluation were hardly changed. Since the clear diffraction peak was recognized in the X-ray diffraction pattern, the sample before the ion exchange treatment and the evaluation sample were confirmed to be glass ceramics. Further, as a result of peak analysis of the X-ray diffraction pattern, it was confirmed that it had a NASICON type crystal structure.

The composition of the sample for evaluation was measured by ICP analysis. As a result, SiO ₂ was 32.5%, ZrO ₂ was 22.5%, P ₂ O ₅ was 15%, Li ₂ O was 30%, Na ₂ O was below the detection limit. It was confirmed that the sample for evaluation in which most of the sodium ions in the sample before the ion exchange treatment were replaced with lithium ions was obtained by the ion exchange treatment.

Using the evaluation sample, the ionic conductivity was measured by the method described above. As a result of the measurement, the ion conductivity of the evaluation sample was 3.4 × 10 ⁻⁷ S / cm.

(Example 5)
In Example 5, the raw material powder was weighed and mixed so as to include each component in the composition shown in the column of “Raw material mixture composition” in Example 5 in Table 1 to obtain a raw material mixture. Other manufacturing conditions were the same as in Example 2.

  The sample before ion exchange treatment and the sample for evaluation were subjected to X-ray diffraction measurement using CuKα rays. In FIG. 6, the X-ray-diffraction result of the sample for evaluation is shown.

Before and after the ion exchange treatment, that is, the X-ray diffraction patterns of the sample before the ion exchange treatment and the sample for evaluation were hardly changed. As a result of peak analysis of the X-ray diffraction pattern, the sample before ion exchange treatment and the sample for evaluation are ZrSiO ₄ (h mark), Li ₃ PO ₄ (i mark), SiO ₂ (j mark), and ZrO ₂ (k mark). ). Further, it did not contain a NASICON type crystal structure. ZrO (m mark) is an internal standard substance put in the case of X-ray diffraction measurement.

Using the evaluation sample, the ionic conductivity was measured by the method described above. As a result of the measurement, the ionic conductivity of the sample for evaluation was as low as 2.9 × 10 ⁻⁸ S / cm.

  The preferred embodiments and examples of the present invention have been described in detail above. However, the present invention is not limited to the specific embodiments and examples described above, and is based on the gist of the present invention described in the claims. Various modifications and changes can be made within the range.

  This international application claims priority based on Japanese Patent Application No. 2013-042736 filed on March 5, 2013, the entire contents of which are incorporated herein by reference.

Claims (8)

(A) The raw material mixture is in mol% unit converted to oxide, 25% or more and 50% or less of SiO ₂ , 10% or more and 45% or less of ZrO ₂ , more than 0% and 30% or less of P ₂ O ₅ , and Preparing a raw material mixture by preparing a raw material so as to contain 5% or more and 40% or less Na ₂ O, and obtaining an object to be processed made of glass ceramics in the process of melting, cooling and solidifying the raw material mixture;
(B) a step of subjecting the workpiece to an ion exchange treatment in a molten salt containing lithium ions;
A method for producing a lithium ion conductive glass ceramic, comprising:   The method for producing a lithium ion conductive glass ceramic according to claim 1, wherein the object to be processed has a NASICON type crystal structure. Between the steps (a) and (b),
(C) The manufacturing method of the lithium ion conductive glass ceramics of Claim 1 or 2 which has the process of processing the thickness of the said to-be-processed object into 1 mm or less.   The said melting is a manufacturing method of the lithium ion conductive glass ceramics as described in any one of Claim 1 to 3 implemented by heating the said raw material mixture at the temperature of 1400 degreeC or more and 1700 degrees C or less.   The said cooling is a manufacturing method of the lithium ion conductive glass ceramics as described in any one of Claim 1 to 4 implemented by the cooling rate of 0.2 degree-C / min or more and 2 degrees-C / min or less.   The ion exchange treatment is performed by holding the object to be treated in a molten salt containing the lithium ions for 24 hours to 120 hours at a temperature of 200 ° C or higher and 500 ° C or lower. A method for producing a lithium ion conductive glass ceramic according to claim 1.   A lithium ion conductive glass ceramic produced by the method according to any one of claims 1 to 6. A lithium ion secondary battery having a positive electrode, a negative electrode, and a solid electrolyte disposed between the two electrodes,
The said solid electrolyte is a lithium ion secondary battery which is a solid electrolyte containing the lithium ion conductive glass ceramic manufactured by the method as described in any one of Claim 1 to 6.

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