JP5577718B2 - Negative electrode active material, method for producing the same, and secondary battery - Google Patents

Description

  The present invention relates to a negative electrode active material, a method for producing the same, and a secondary battery. More specifically, the present invention relates to a negative electrode active material that can be a low-cost, excellent safety and large capacity secondary battery, a method for producing the same Next battery.

  Conventionally, a secondary battery having low cost, excellent safety, and large capacity has been demanded. And various things are proposed as an electrode, an active material, and a separator which implement | achieve such a secondary battery. And as such an electrode and an active material, patent documents 1-3 disclose an electrode using a clay mineral.

  Patent Document 1 proposes an electrode to which a layered clay compound is added. By applying this electrode, a secondary battery having excellent initial charge / discharge characteristics can be realized. Patent Document 2 proposes an electrode body containing a clay mineral. By applying this electrode body, a secondary battery with improved mechanical strength can be realized. Patent Document 3 proposes a negative electrode active material to which a layered clay mineral such as montmorillonite is applied as a negative electrode active material for realizing an inexpensive and safe lithium secondary battery.

JP-A-8-279354 JP 2008-71757 A JP 2004-296370 A JP 2008-66094 A

  However, the secondary battery using the electrode body using the clay mineral and the negative electrode active material disclosed in Patent Documents 1 to 3 has a problem that the discharge capacity is not sufficient. Moreover, as a negative electrode active material used for the secondary battery, a carbon material such as graphite is widely applied. However, since the carbon material is flammable, there is a problem that a preventive measure against combustion is required.

  The present invention has been made in view of the above problems, and realizes a secondary battery that can sufficiently increase the discharge capacity of the secondary battery and that is excellent in safety without taking measures against combustion. It is a main object to provide a negative electrode active material and a method for producing the same.

  In order to achieve the above object, in the present invention, the position of the highest peak is shifted to the lower angle side with respect to the position of the highest peak in the X-ray diffraction spectrum measured for the untreated layered silicate mineral. Disclosed is a negative electrode active material comprising a high-capacity layered silicate mineral whose X-ray diffraction spectrum is measured.

  According to the present invention, since the high-capacity layered silicate mineral is considered to have a wide layer spacing, insertion of ions contributing to charge / discharge of the secondary battery in the high-capacity layered silicate mineral. -It is considered that desorption can be performed easily and in large quantities. Therefore, when a negative electrode active material composed of a high-capacity layered silicate mineral is applied to a secondary battery, the discharge capacity can be increased.

  In general, the layered silicate mineral is nonflammable and easily available, so that it is possible to obtain a secondary battery with excellent safety and low cost.

  In the above invention, the untreated layered silicate mineral is preferably a mica group layered silicate mineral.

  In the said invention, it is preferable that the said mica group layered silicate mineral is muscovite.

  In the said invention, it is preferable to contain further the metal element from which the said high capacity layered silicate mineral becomes an ion. Furthermore, it is because it can be set as a high capacity | capacitance negative electrode active material.

  In the present invention, a negative electrode characterized by having a firing step of firing a raw material composition containing an untreated layered silicate mineral, and using the fired raw material composition as a negative electrode active material A method for producing an active material is provided.

  According to the present invention, the high-capacity layered silicate mineral constituting the negative-electrode active material produced by the method for producing a negative-electrode active material is considered to have an increased layer spacing, so that the high-capacity layered silicate mineral In salt minerals, it is estimated that ions that contribute to charge / discharge of the secondary battery can be easily inserted and removed in large quantities. As a result, when the negative electrode active material is applied to a secondary battery, the discharge capacity can be increased.

  In the said invention, it is preferable to further have the mixing process which mixes the salt of the metal element which becomes an ion with the said untreated lamellar silicate mineral before the said baking process, and makes it the said raw material composition. This is because the discharge capacity of the secondary battery can be further increased.

  In the said invention, it is preferable to apply the mica group layered silicate mineral as said untreated layered silicate mineral.

  In the said invention, it is preferable to apply muscovite as said mica group layered silicate mineral.

  The present invention also provides a secondary battery comprising a negative electrode layer containing the negative electrode active material, a positive electrode layer, and an electrolyte sandwiched between the negative electrode layer and the positive electrode layer. To do.

  According to the present invention, the layer capacity of the high-capacity layered silicate mineral constituting the negative electrode active material contained in the secondary battery is considered to be widened. It is presumed that the insertion / extraction of ions contributing to charging / discharging of the secondary battery can be performed easily and in large quantities. As a result, when a negative electrode active material composed of a high capacity layered silicate mineral is applied to a secondary battery, the discharge capacity can be increased.

  The present invention has an effect that the discharge capacity of the secondary battery can be sufficiently increased and a secondary battery excellent in safety can be realized without taking measures to prevent combustion.

It is a figure explaining the 1st embodiment of the manufacturing method of the negative electrode active material in this invention. It is a figure explaining the 2nd embodiment of the manufacturing method of the negative electrode active material in this invention. It is a schematic sectional drawing which shows an example of the secondary battery in this invention. It is a figure which shows the result of the X-ray-diffraction measurement about the muscovite of Example 1, and the muscovite of the comparative example 1. It is a figure which shows the result of the charging / discharging characteristic evaluation obtained about Example 1. FIG. It is a figure which shows the result of the charging / discharging characteristic evaluation obtained about Example 2. FIG.

  Hereinafter, the negative electrode active material, the manufacturing method thereof, and the secondary battery of the present invention will be described in detail.

A. Negative electrode active material First, the negative electrode active material of the present invention will be described. The negative electrode active material of the present invention is an X-ray diffraction spectrum in which the position of the highest peak is shifted to the lower angle side with respect to the position of the highest peak in the spectrum of X-ray diffraction measured for the untreated layered silicate mineral. It is composed of a high-capacity layered silicate mineral that is measured.

  Such a high-capacity layered silicate mineral is usually obtained by subjecting an untreated layered silicate mineral to a predetermined treatment or the like. The high-capacity layered silicate mineral and the untreated layered silicate mineral in the present invention are layered silicate minerals having the same crystal structure, but have a lattice constant corresponding to the shift amount of the highest peak position described above. It has a difference.

  When the negative electrode active material of the present invention is composed of the above high-capacity layered silicate mineral, the discharge capacity of the secondary battery is increased when the negative electrode active material of the present invention is applied to the negative electrode layer of the secondary battery. The secondary battery can be made safe and inexpensive.

  When the negative electrode active material of the present invention is applied to a secondary battery, it is presumed that the discharge capacity is increased for the following reason.

  That is, the difference in lattice constant between the high-capacity layered silicate mineral and the untreated layered silicate mineral is that the layer spacing of the high-capacity layered silicate mineral is wider than the layer spacing of the untreated layered silicate mineral. Indicates that In addition, since the layer spacing of the high-capacity layered silicate mineral is widened, in the high-capacity layered silicate mineral, the insertion / desorption of ions contributing to charging / discharging of the secondary battery is easily performed in large quantities. It becomes possible. As a result, when a negative electrode active material composed of a high capacity layered silicate mineral is applied to a secondary battery, the discharge capacity can be increased. Hereinafter, the high-capacity layered silicate mineral having such characteristics will be described in detail.

1. High-capacity layered silicate mineral The high-capacity layered silicate mineral used in the present invention has the highest peak in the X-ray diffraction spectrum of the untreated layered silicate mineral. The position is shifted to the low angle side from the position. The high-capacity layered silicate mineral is obtained by subjecting an untreated layered silicate mineral to a predetermined treatment or the like. Hereinafter, the untreated layered silicate mineral, the shift amount, the treatment method, and the like will be described.

(1) Untreated layered silicate mineral The high-capacity layered silicate mineral used in the present invention is obtained by subjecting an untreated layered silicate mineral to a predetermined treatment as described above. This untreated layered silicate mineral means a layered silicate mineral that has not been subjected to any treatment that affects the position of the highest peak of the X-ray diffraction spectrum after mining. It includes those subjected to general processing, that is, processing such as polishing, cutting and cleaning. Such an untreated layered silicate mineral is not particularly limited as long as a high-capacity layered silicate mineral can be obtained by performing a predetermined treatment or the like. For example, serpentine-kaolin Group, talc-pyrophyllite group, mica group, interlayer defect type mica, brittle mica group, chlorite group, mixed layer mineral and the like.

  Here, as the layered silicate mineral belonging to the serpentine-kaolin group in the present invention, for example, lizardite, amicite, nepoite, keriaite, fraponite, kaolinite, dickite, nacrite, halloysite (plate-like), audinite, etc. Is mentioned. Examples of the layered silicate mineral belonging to the talc-pyrophyllite group in the present invention include talc, willemsite, kerolite, pimelite, pyrophyllite and the like. Examples of the layered silicate mineral belonging to the mica group in the present invention include phlogopite, yeastite, sericite, polylithiolite, muscovite, abrasive mica, soda mica, and the like.

  Examples of the layered silicate mineral belonging to the above-described interlaminar defect type mica in the present invention include illite, sea chlorite, brammerlite, and wonnesite. Examples of the layered silicate mineral belonging to the brittle mica group in the present invention include clintonite, Kinoshita, bidet mica, pearl mica, and the like. Examples of the layered silicate mineral belonging to the chlorite group in the present invention include penantite, donbasite, kukuite and the like. Examples of the layered silicate mineral belonging to the mixed layer mineral in the present invention include crucareite, rectolite, tosudite, lnjanite, salioite and the like.

  As the layered silicate mineral in the present invention, among those mentioned above, the layered silicate mineral of mica group and interlayer defect type mica is preferable. As the layered silicate mineral belonging to the mica group, phlogopite, muscovite, and the like are preferable. In the present invention, muscovite is particularly preferable as the layered silicate mineral belonging to the mica group.

(2) Shift amount The high-capacity layered silicate mineral used in the present invention has the highest peak position in the X-ray diffraction spectrum of the untreated layered silicate mineral. It is shifted to the low angle side from the position. The high-capacity layered silicate mineral and the untreated layered silicate mineral have the same chemical composition and the same crystal structure, but have a difference in lattice constant corresponding to this shift amount. . Furthermore, the difference in lattice constant is due to the fact that the layer spacing of the high-capacity layered silicate mineral is such that untreated layered silicates can be easily and massively inserted and desorbed ions that contribute to charge / discharge of the secondary battery. It is presumed to indicate that it is wider than the mineral spacing.

  In the present invention, the above-described highest peak position (incidence angle (2θ) at the highest peak) is shifted as the amount of insertion / desorption of ions contributing to charge / discharge of the secondary battery is easy and large. As long as it is a shift amount corresponding to the increase in the layer spacing of the high-capacity layered silicate mineral as in the case of, it is not particularly limited, but within the range of 0.1 ° to 1.0 ° It is preferable that

  In particular, when the untreated layered silicate mineral used in the present invention is muscovite, it is preferably within a range of 0.1 ° to 0.6 °.

(3) Treatment method The high-capacity layered silicate mineral used in the present invention is obtained by subjecting the untreated layered silicate mineral to a predetermined treatment or the like. Such treatment is not particularly limited as long as the treatment can obtain the highest peak position relationship in the X-ray diffraction spectrum as described above for the untreated layered silicate mineral. There may be mentioned physical treatment such as mechanical treatment and thermal treatment, and chemical treatment such as treatment with chemicals such as acid and alkali. In the present invention, a baking treatment described in the method for producing a negative electrode active material described later can be cited as a preferred treatment method.

(4) Others The high-capacity layered silicate mineral used in the present invention may further contain a metal element that becomes an ion. Here, the metal element that becomes an ion is a metal element that becomes an ion that contributes to charge and discharge in a secondary battery in which the negative electrode active material composed of the high-capacity layered silicate mineral used in the present invention is applied to the negative electrode layer. Specifically, lithium (Li), sodium (Na), and the like can be given. In the present invention, lithium (Li) is particularly preferable. This is because the discharge capacity of the secondary battery can be increased.

  In the present invention, when the high-capacity layered silicate mineral further contains a metal element that becomes the ions, when the high-capacity layered silicate mineral is applied to a secondary battery, the secondary battery is charged and discharged. It is presumed that insertion / extraction of contributing ions is further facilitated, whereby the discharge capacity of the secondary battery can be further increased. Here, it is not clear why the high-capacity layered silicate mineral can further increase the discharge capacity of the secondary battery by further containing the metal element that becomes the ions, but it is estimated as follows.

  That is, when the high-capacity layered silicate mineral further contains a metal element that becomes the ion, in the secondary battery in which the negative electrode active material composed of the high-capacity layered silicate mineral is applied to the negative electrode layer, charge and discharge The metal element of an ion that contributes to charge / discharge is contained in the high-capacity layered silicate mineral in advance before the start of. Due to this, when charging / discharging is performed in this secondary battery, it is considered that insertion / desorption of ions contributing to charging / discharging of the secondary battery is further facilitated in the high-capacity layered silicate mineral. .

  And, the metal element that becomes such ions is not particularly limited as long as it is contained in the high-capacity layered silicate mineral, but preferably exists between the layers of the high-capacity layered silicate mineral. preferable.

  Whether or not the high-capacity layered silicate mineral contains a metal element that becomes such an ion can be confirmed by, for example, ICP emission analysis.

2. Negative electrode active material The negative electrode active material in this invention is comprised from the said high capacity | capacitance layered silicate mineral. For this reason, the discharge capacity of the secondary battery which applied the negative electrode active material in this invention to the negative electrode layer can be enlarged. Further, since the layered silicate mineral is easily available, it has an advantage that it is advantageous in terms of cost. Furthermore, it can be said that the layered silicate mineral is excellent in safety because it is not flammable as compared with the carbon-based material conventionally applied to the negative electrode active material.

  Such a negative electrode active material of the present invention is used for a negative electrode layer of a secondary battery, but the secondary battery to which the negative electrode active material of the present invention is applied is preferably an all-solid secondary battery. This is because the all-solid-state secondary battery can be simplified in safety device as compared with a secondary battery to which a liquid electrolyte is applied, and thus is excellent in manufacturing cost and productivity. The secondary battery to which the negative electrode active material of the present invention is applied is preferably a lithium secondary battery. This is because the lithium secondary battery has higher battery efficiency than the secondary battery to which ions other than lithium ions are applied.

B. Next, the manufacturing method of the negative electrode active material in this invention is demonstrated. The manufacturing method of the negative electrode active material in this invention can be divided roughly into two embodiments. Hereinafter, the manufacturing method of the negative electrode active material in the present invention will be described separately for the first embodiment and the second embodiment.

1. First Embodiment First, a first embodiment of the method for producing a negative electrode active material of the present invention will be described. The method for producing a negative electrode active material according to the present embodiment includes a firing step of firing an untreated layered silicate mineral, and a material obtained by firing the raw material composition is used as a negative electrode active material. is there.

  According to this embodiment, the high-capacity layered silicate mineral constituting the negative electrode active material obtained by the method for producing a negative electrode active material is the highest in the X-ray diffraction spectrum measured for the untreated layered silicate mineral. An X-ray diffraction spectrum in which the highest peak position is shifted to the lower angle side with respect to the peak position is measured. Therefore, when a negative electrode active material composed of such a high-capacity layered silicate mineral is applied to a secondary battery, the discharge capacity can be increased for the reason described in the section “A. Negative electrode active material”. .

  FIG. 1 is a diagram for explaining a first embodiment of a method for producing a negative electrode active material in the present invention. In the manufacturing method shown in FIG. 1, first, an untreated layered silicate mineral is prepared as a starting material. Next, the untreated layered silicate mineral is fired (firing step). Next, an untreated layered silicate mineral is fired as a negative electrode active material. Hereinafter, the manufacturing method of the negative electrode active material of this embodiment is demonstrated in detail.

(1) Starting material In the manufacturing method of the negative electrode active material in this embodiment, an untreated layered silicate mineral is prepared as a starting material. This untreated layered silicate mineral is the same as that described in the section “A. Negative electrode active material 1. High capacity layered silicate mineral (1) Untreated layered silicate mineral”. Description is omitted.

(2) Firing step In the firing step in the present embodiment, the untreated layered silicate mineral is fired. Various firing conditions in this step will be described below.

  First, the firing temperature when firing an untreated layered silicate mineral will be described. This calcining temperature is obtained by calcining an untreated layered silicate mineral at this calcining temperature, and the position of the highest peak of the X-ray diffraction spectrum measured for it is measured for the high-capacity layered silicate mineral. Although it will not specifically limit if it shifts to the low angle side to the position of the highest peak of the spectrum of X-ray diffraction, it is preferable that it is 400 to 1100 degreeC. This is because the firing temperature increases as much as possible within the range in which the untreated layered silicate mineral is not decomposed, so that the amount of shift by which the position of the highest peak is shifted to the lower angle side becomes larger.

  In particular, the firing temperature when the untreated layered silicate mineral in this embodiment is muscovite is preferably 600 ° C to 1000 ° C.

  Next, the firing time for firing the untreated layered silicate mineral to obtain a high-capacity layered silicate mineral will be described. The firing time described here refers to a time for maintaining the above-described firing temperature when firing an untreated layered silicate mineral. This firing time is obtained by firing an untreated layered silicate mineral at this firing time, so that the position of the highest peak of the X-ray diffraction spectrum measured for it is measured for the high-capacity layered silicate mineral. If it shifts to the low angle side to the position of the highest peak of the spectrum of X-ray diffraction, it will not specifically limit. The firing time may be appropriately determined according to the kind of the untreated layered silicate mineral and the firing temperature described above, and specifically, is within a range of 0.1 hour to 20 hours. Is preferred. This is because if the firing time is made as long as possible within the range in which the untreated layered silicate mineral is not decomposed, the amount of shift by which the position of the highest peak is shifted to the lower angle side becomes larger.

  Next, an atmosphere in which an untreated layered silicate mineral is fired to obtain a high-capacity layered silicate mineral will be described. The firing in this step may be performed in air or in a non-oxidizing atmosphere as long as the above-described high-capacity layered silicate mineral can be obtained. Specific examples of the non-oxidizing atmosphere include an inert gas atmosphere and a reducing atmosphere. Examples of the method of firing in an inert gas atmosphere include a method of firing while circulating an inert gas such as Ar.

2. Second Embodiment Next, a second embodiment of the method for producing a negative electrode active material of the present invention will be described. The method for producing a negative electrode active material according to this embodiment includes a mixing step of mixing an untreated layered silicate mineral with a salt of a metal element that becomes an ion to form a raw material composition, and a baking step of baking the raw material composition. And having the raw material composition fired as a negative electrode active material.

  According to this embodiment, the high-capacity layered silicate mineral constituting the negative-electrode active material obtained by the method for producing a negative-electrode active material is ionized compared to the high-capacity layered silicate mineral in the first embodiment. The metal element to be further contained. The metal element that becomes an ion is a metal element of an ion that contributes to charge and discharge in a secondary battery in which a negative electrode active material composed of such a high-capacity layered silicate mineral is applied to the negative electrode layer. A. Negative electrode active material 1. High-capacity layered silicate mineral (4) Others The same as described above.

  In the secondary battery in which the negative electrode active material composed of the high capacity layered silicate mineral obtained by the present embodiment is applied to the negative electrode layer, “A. Negative electrode active material 1. High capacity layered silicate mineral (4) Others” As described in the item, the high-capacity layered silicate mineral contains in advance an ion metal element that contributes to charge / discharge before charge / discharge is started. And when charging / discharging is performed in this secondary battery, it is thought that insertion / extraction of the ion which contributes to charging / discharging of this secondary battery becomes still easier in the said high capacity | capacitance layered silicate mineral.

  Thereby, it is thought that the discharge capacity of the secondary battery which applied the negative electrode active material obtained by the manufacturing method of the negative electrode active material in this embodiment to a negative electrode layer can be enlarged more.

  FIG. 2 is a diagram for explaining a second embodiment of the method for producing a negative electrode active material in the present invention. In the manufacturing method shown in FIG. 2, first, an untreated layered silicate mineral and a salt of a metal element that becomes an ion are prepared as starting materials. Next, an untreated layered silicate mineral is mixed with a salt of a metal element that becomes an ion to obtain a raw material composition (mixing step). Next, the raw material composition is fired (firing step), and the fired raw material composition is used as a negative electrode active material. Hereinafter, the manufacturing method of the negative electrode active material of this embodiment is demonstrated in detail.

(1) Starting material In the manufacturing method of the negative electrode active material in this embodiment, the raw material layered silicate mineral and the salt of the metal element used as an ion are prepared as a starting material. This untreated layered silicate mineral is the same as that described in the section of “A. Negative electrode active material 1. High capacity layered silicate mineral (1) Untreated layered silicate mineral”. Omitted.

  As the salt of the metal element used as the ion used in this embodiment, the raw material composition obtained by mixing with an untreated layered silicate mineral in the firing step described later is fired to obtain the ion as described above. Although it will not specifically limit if the high capacity | capacitance layered silicate mineral containing a metal element is obtained, For example, lithium salt, sodium salt, etc. can be mentioned. Of these salts, lithium salts are preferred. This is because, in a secondary battery in which a negative electrode active material obtained using a lithium salt is applied to a negative electrode layer, ions that contribute to charging and discharging become lithium ions, so that the discharge capacity of the secondary battery can be increased.

Furthermore, the lithium salt used in this embodiment is not particularly limited, and may be an inorganic lithium salt or an organic lithium salt. Examples of the inorganic lithium salt include LiNO ₃ (lithium nitrate), Li ₂ CO ₃ (lithium carbonate), Li ₂ SO ₄ (lithium sulfate), LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , LiCl, LiF, and LiBr. , LiI, LiAlCl _{4 and the} like. Of these, LiNO ₃ (lithium nitrate) and the like are preferable. Examples of the organic lithium salt, for _example, a _{LiCF 3 SO 3, LiN (CF} 3 SO 2) 2, LiN (C 2 F 5 SO 2) 2, LiC (CF 3 SO 2) 3 and the like.

(2) Mixing step In the mixing step in this embodiment, the untreated layered silicate mineral and the salt of the metal element that becomes the ions are mixed to obtain a raw material composition.

  Moreover, in the mixing step in the present embodiment, the ratio of mixing the untreated layered silicate mineral and the salt of the metal element that becomes the ion is as described above by using the raw material composition obtained by mixing at that ratio. Although it will not specifically limit if the high capacity | capacitance layered silicate mineral containing the metal element used as an ion is obtained, By a molar ratio, untreated layered silicate mineral: The salt of the metal element used as an ion = It is preferably 1: 0.1 to 1:10, and particularly preferably 1: 0.3 to 1: 0.5.

  Among them, when the untreated layered silicate mineral is a salt of a metal element that becomes ionic with muscovite, the mixing ratio is not particularly limited, but in molar ratio, The muscovite: lithium salt is preferably 1: 0.1 to 1: 9, and more preferably 1: 0.3 to 1: 0.5.

(3) Firing step In the firing step in the present embodiment, the raw material composition obtained in the mixing step is fired. The various firing conditions in this step are the same as those described in “B. Method for producing negative electrode active material 1. First embodiment (2) Firing step”, and thus the description thereof is omitted here.

C. Secondary Battery Next, the secondary battery of the present invention will be described. A secondary battery of the present invention includes a negative electrode layer containing the negative electrode active material described above, a positive electrode layer, and an electrolyte layer sandwiched between the negative electrode layer and the positive electrode layer. is there.

  According to the present invention, it is considered that the layer spacing of the high-capacity layered silicate mineral constituting the negative electrode active material described above is widened. For this reason, insertion / extraction of ions to / from the negative electrode active material is facilitated. Therefore, the discharge capacity of the secondary battery in which the negative electrode active material described above is applied to the negative electrode layer can be increased.

  FIG. 3 is a schematic cross-sectional view showing an example of the secondary battery in the present invention. The secondary battery 10 includes a negative electrode layer 1 containing a negative electrode active material, a positive electrode layer 2, and an electrolyte layer 3 sandwiched between the negative electrode layer 1 and the positive electrode layer 2. Hereinafter, the secondary battery of this invention is demonstrated for every structure.

1. Negative electrode layer First, the negative electrode layer in the present invention will be described. The negative electrode layer is a layer containing a negative electrode active material and a solid electrolyte.

  As the negative electrode active material in the present invention, the negative electrode active material described in “A. Negative electrode active material” is used. As explained in “A. Negative electrode active material”, the layer spacing of the high-capacity layered silicate mineral constituting the negative electrode active material is estimated to be wider than that of the untreated layered silicate mineral. For this reason, when this negative electrode active material is used for the negative electrode layer, when charging / discharging is performed in the secondary battery, insertion / extraction of ions contributing to charging / discharging of the secondary battery is facilitated in this negative electrode active material. It is considered to be. Therefore, the discharge capacity of a secondary battery in which this negative electrode active material is applied to the negative electrode layer can be increased.

In the present invention, in the case of an all-solid secondary battery, the negative electrode layer may contain a solid electrolyte layer. Such a solid electrolyte is not particularly limited as long as it has ion conductivity, and examples thereof include an oxide solid electrolyte and a sulfide solid electrolyte. In the present invention, the solid electrolyte is preferably a sulfide solid electrolyte. This is because the sulfide solid electrolyte has high ionic conductivity and can improve the ionic conductivity of the negative electrode layer. Examples of the sulfide solid electrolyte in the present invention include Li ₇ P ₃ S ₁₁ .

  The negative electrode layer may contain a conductive material. By adding a conductive material, the conductivity of the negative electrode layer can be improved. Examples of the conductive material used in the present invention include acetylene black, ketjen black, and carbon fiber.

  Furthermore, the negative electrode layer may contain a binder and a thickener. Examples of the type of binder used in the present invention include water-based binders such as carboxymethyl cellulose (CMC). And as a kind of thickener, rubber-type thickeners, such as a styrene butadiene rubber (SBR), etc. can be mentioned. Moreover, it is preferable that the thickness of a negative electrode layer exists in the range of 0.1 micrometer-1000 micrometers, for example.

2. Electrolyte Layer Next, the electrolyte layer in the present invention will be described. The electrolyte layer in the present invention is a layer formed between the positive electrode layer and the negative electrode layer. The electrolyte layer is not particularly limited as long as it is a layer capable of conducting ionic conduction, but is preferably a solid electrolyte layer. This is because an all-solid battery with high safety can be obtained. The thickness of the solid electrolyte layer is, for example, preferably in the range of 0.1 μm to 1000 μm, and more preferably in the range of 0.1 μm to 300 μm. Moreover, as a formation method of a solid electrolyte layer, the method of compression-molding a solid electrolyte material etc. can be mentioned, for example. As such a solid electrolyte used for the solid electrolyte layer, the same one as described in “C. Secondary battery 1. Negative electrode layer” can be used.

  Further, the electrolyte layer in the present invention may be a layer composed of an electrolytic solution. By using the electrolytic solution, a high output secondary battery can be obtained. Moreover, electrolyte solution contains a salt and an organic solvent (nonaqueous solvent) normally.

3. Next, the positive electrode layer in the present invention will be described. The positive electrode layer in the present invention is a layer containing at least a positive electrode active material, and may contain at least one of a solid electrolyte material, a conductive material and a binder as necessary.

Examples of the positive electrode active material include LiCoO ₂ , LiMnO ₂ , Li ₂ NiMn ₃ O ₈ , LiVO ₂ , LiCrO ₂ , LiFePO ₄ , LiCoPO ₄ , LiNiO ₂ , LiNi _1/3 Co _1/3 Mn _1/3 O _2. Etc.

  Examples of the conductive material include acetylene black, ketjen black, and carbon fiber. Examples of the type of the binder include a fluorine-containing binder. In addition, it is preferable that the thickness of a positive electrode layer exists in the range of 0.1 micrometer-1000 micrometers, for example.

4). Other Configurations The secondary battery of the present invention has at least the positive electrode layer, the electrolyte layer, and the negative electrode layer described above. Furthermore, it usually has a positive electrode current collector for collecting current of the positive electrode layer and a negative electrode current collector for collecting current of the negative electrode active material. Examples of the material for the positive electrode current collector include SUS, aluminum, nickel, iron, titanium, and carbon. Of these, aluminum is preferable. On the other hand, examples of the material for the negative electrode current collector include SUS, copper, nickel, and carbon. Of these, copper is preferable. In addition, the thickness and shape of the positive electrode current collector and the negative electrode current collector are preferably selected as appropriate according to the application of the secondary battery. Moreover, the battery case of a general secondary battery can be used for the battery case used for this invention. Examples of the battery case include a SUS battery case. When the secondary battery of the present invention is an all-solid battery, the power generation element may be formed inside the insulating ring.

5. Secondary battery The secondary battery of the present invention is useful as, for example, a vehicle-mounted battery. Examples of the shape of the secondary battery of the present invention include a coin type, a laminate type, a cylindrical type, and a square type.

  Moreover, the manufacturing method of the secondary battery of this invention will not be specifically limited if it is a method which can obtain the secondary battery mentioned above, The method similar to the manufacturing method of a general secondary battery is used. be able to. For example, when the secondary battery of the present invention is an all-solid battery, as an example of the manufacturing method thereof, a material constituting the positive electrode layer, a material constituting the solid electrolyte layer, and a material constituting the negative electrode layer are sequentially pressed. Thus, a method of producing a power generation element, housing the power generation element in the battery case, and caulking the battery case can be exemplified.

  Hereinafter, the present invention will be described in more detail with reference to examples. First, Example 1 and Comparative Example 1 will be described.

[Example 1]
(Raw material pretreatment)
The muscovite was ground in a mortar for 20 minutes.

(Baking process)
The muscovite was fired at 900 ° for 2 hours. A firing furnace was used for firing.

(Electrode production)
First, baked muscovite, conductive material, carboxymethylcellulose (CMC), and styrene butadiene rubber (SBR) were mixed in a weight ratio of 88: 10: 1: 1 in N-methylpyrrolidone. Next, the composition was applied onto a Cu foil (thickness 10 μm, manufactured by Nihon Foil Co., Ltd.) which is a negative electrode current collector. Next, it pressed so that an electrode density might be set to 1.2 g / cm < ³ >, Next, it punched in the circle of (phi) 16mm, and obtained the negative electrode.

(Battery production)
First, the produced negative electrode and Li metal were applied as a negative electrode and a positive electrode, respectively, to produce a 2032 type coin cell. At this time, a separator made of PE is used as a separator, and LiPF is used as a solvent in which EC (ethylene carbonate), DMC (dimethyl carbonate) and EMC (ethyl methyl carbonate) are mixed at a volume ratio of 3: 4: 3 as an electrolytic solution. ₆ was dissolved at a concentration of 1M.

[Comparative Example 1]
A negative electrode and a battery were produced in the same manner as in Example 1 except that the muscovite was not fired.

[Evaluation 1]
(X-ray diffraction measurement)
X-ray diffraction measurement was performed on the muscovite baked at 900 ° C. used in Example 1 and the unfired muscovite used in Comparative Example 1. The results of X-ray diffraction measurements for the muscovite of Example 1 and the muscovite of Comparative Example 1 are shown in FIG.

(Electrochemical property evaluation)
The electrochemical characteristics of the batteries obtained in Example 1 and Comparative Example 1 were evaluated. The electrochemical characteristics are 0.1C (where 1C is the amount of electricity that can be fully charged in 1 hour), Li is inserted up to 0.01V, and then Li is desorbed up to 3V. Characteristics were evaluated. The results of the charge / discharge characteristics evaluation obtained for Example 1 are shown in FIG. Table 1 shows the results of the discharge capacities obtained in Example 1 and Comparative Example 1. Table 1 also shows the incident angle (2θ) at the highest peak of the X-ray diffraction spectrum obtained in the X-ray diffraction measurement described above.

  As described above, from the result of the evaluation 1, the incident angle (2θ) of the highest X-ray diffraction peak of the muscovite fired at 900 ° C. used in Example 1 is the same as that of the unfired used in Comparative Example 1. It was confirmed that the muscovite was shifted to the lower angle side with respect to the incident angle (2θ) of the highest X-ray diffraction peak of muscovite. That is, it was confirmed that the muscovite constituting the negative electrode produced in Example 1 had a wider layer spacing than the muscovite constituting the negative electrode produced in the comparative example. In addition, it was confirmed that the discharge capacity of the battery manufactured in Example 1 was larger than the discharge capacity of both of the batteries manufactured in Comparative Example 1.

  Therefore, in the battery manufactured in Example 1, the layer spacing of the muscovite constituting the negative electrode widens, so that ions can be easily inserted and removed from the negative electrode, and the discharge capacity is increased. it is conceivable that.

[Example 2]
(Raw material pretreatment)
The muscovite was ground in a mortar for 20 minutes.

(Preparation of raw material composition)
The muscovite and lithium nitrate (LiNO ₃ ) were mixed at a molar ratio of 1: 0.4 to obtain a raw material composition.

(Baking process)
The obtained raw material composition was fired at 900 ° for 2 hours. A firing furnace was used for firing.

(Electrode production)
First, the raw material composition after firing, the conductive material, carboxymethylcellulose (CMC), and styrene butadiene rubber (SBR) were mixed in N-methylpyrrolidone at a weight ratio of 88: 10: 1: 1. Next, the composition was applied onto a Cu foil (thickness 10 μm, manufactured by Nihon Foil Co., Ltd.) which is a negative electrode current collector. Next, it pressed so that an electrode density might be set to 1.2 g / cm < ³ >, Next, it punched in the circle of (phi) 16mm, and obtained the negative electrode.

(Battery production)
First, the produced negative electrode and Li metal were applied as a negative electrode and a positive electrode, respectively, to produce a 2032 type coin cell. At this time, a separator made of PE is applied as a separator, and a solution obtained by dissolving LiPF ₆ at a concentration of 1M in a solvent in which EC (ethylene carbonate) and DEC (diethyl carbonate) are mixed at a volume ratio of 3: 7 is applied as an electrolytic solution. did.

[Evaluation 2]
(X-ray diffraction measurement)
The raw material composition after firing in Example 2 was subjected to X-ray diffraction measurement.

(Electrochemical property evaluation)
The electrochemical characteristics of the battery obtained in Example 2 were evaluated. The electrochemical characteristics are 0.1C (where 1C is the amount of electricity that can be fully charged in 1 hour), Li is inserted up to 0.01V, and then Li is desorbed up to 3V. Characteristics were evaluated. The results of the charge / discharge characteristic evaluation obtained for Example 2 are shown in FIG. The results of the discharge capacity obtained in Example 2 are shown in Table 2 together with the results of the discharge capacity obtained in Example 1. Table 2 also shows the incident angle (2θ) at the highest peak of the X-ray diffraction spectrum obtained in the X-ray diffraction measurement described above.

  As described above, from the result of Evaluation 2, it was confirmed that the discharge capacity of the battery produced in Example 2 was larger than the discharge capacity of the battery produced in Example 1. The reason why the discharge capacity of the battery produced in Example 2 is larger than the discharge capacity of the battery produced in Example 1 is estimated as follows.

In the raw material composition after firing in Example 2 and the muscovite after firing in Example 1, the incident angle (2θ) at the highest peak of the X-ray diffraction spectrum is the same value. That is, in the battery produced in Example 2 and the battery produced in Example 1, it is considered that the layer spacing of muscovite constituting the negative electrode does not change. On the other hand, in Example 2, a raw material composition obtained by mixing muscovite and lithium nitrate (LiNO ₃ ) at a molar ratio of 1: 0.4 is applied, whereas in Example 1, baiyun is white. Applying mother. For this reason, in the battery produced in Example 2, unlike the battery produced in Example 1, the metal element (lithium) in which the muscovite constituting the negative electrode becomes lithium ions before the start of charging / discharging. Contains. Therefore, in the battery produced in Example 2, charging and discharging are performed because the muscovite constituting the negative electrode contains a metal element (lithium) that becomes lithium ions before starting charging and discharging. It is considered that the insertion / extraction of contributing lithium ions is further facilitated at the negative electrode. As a result, the discharge capacity of the battery produced in Example 2 is considered to be larger than that of the battery produced in Example 1.

DESCRIPTION OF SYMBOLS 1 ... Negative electrode layer 2 ... Positive electrode layer 3 ... Electrolyte layer 10 ... Secondary battery

Claims (8)

The spectrum of the X-ray diffraction in which the position of the highest peak is shifted to the lower angle side is measured with respect to the position of the highest peak in the spectrum of the X-ray diffraction measured for the untreated layered silicate mineral. It consists of a high-capacity layered silicate mineral with a larger discharge capacity than the layered silicate mineral,
A negative electrode active material for a secondary battery, which is a layered silicate mineral of a mica group. The negative electrode active material for a secondary battery according to claim 1, wherein the mica group layered silicate mineral is muscovite. The negative electrode active material for a secondary battery according to claim 1, wherein the high-capacity layered silicate mineral further contains a metal element that becomes an ion. A firing step of firing a raw material composition containing an untreated layered silicate mineral and shifting the position of the highest peak in the X-ray diffraction spectrum measured for the untreated layered silicate mineral to a lower angle side Have
A material obtained by firing the raw material composition as a negative electrode active material for a secondary battery ,
The method for producing a negative electrode active material for a secondary battery, wherein the untreated layered silicate mineral is a mica group layered silicate mineral. 5. The secondary battery according to claim 4, further comprising a mixing step of mixing the untreated layered silicate mineral with a salt of a metal element that becomes an ion to form the raw material composition before the firing step. For producing a negative electrode active material. The method for producing a negative electrode active material for a secondary battery according to claim 4 or 5, wherein a firing temperature in the firing step is in a range of 400 ° C to 1100 ° C. The method for producing a negative electrode active material for a secondary battery according to any one of claims 4 to 6, wherein the mica group layered silicate mineral is muscovite. It has the negative electrode layer containing the negative electrode active material for secondary batteries of any one of Claims 1-3, a positive electrode layer, and the electrolyte pinched | interposed between the said negative electrode layer and the said positive electrode layer. A secondary battery characterized by.

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