Active material, electrode, and secondary battery

Abstract

This active material includes as constituent elements a first element including at least one of silicon, oxygen, boron, and phosphorous, a second element including at least one of an alkali metal element, a transition element, and a typical element (excluding silicon, oxygen, boron, phosphorous, alkali metal elements, and alkaline earth metal elements), and a third element including an alkaline earth metal element. The silicon content in the total constituent elements excluding oxygen and carbon is 60-98 at% (inclusive), the first element content in the total constituent elements is 1-25 at% (inclusive), the second element content in the total constituent elements is 1-34 at% (inclusive), and the third element content in the total constituent elements is 0-6 at% (inclusive). In an XPS spectrum (where the horizontal axis is binding energy (eV) and the vertical axis is spectral intensity) of Si2p measured using X-ray photoelectron spectroscopy (XPS), a first peak is detected, the first peak having a top in a range in which the binding energy is 102-105 eV (inclusive), and a shoulder on a side of the top where the binding energy is lower. In a Raman spectrum (where the horizontal axis is the Raman shift (cm-1) and the vertical axis is spectral intensity) measured using Raman spectroscopy, two peaks having tops in a range in which the Raman shift is 435 cm-1 to 465 cm-1 (inclusive) are detected. The active material has a plurality of pores, and in the pore distribution (where the horizontal axis is the pore diameter (μm) of the pores and the vertical axis is the change rate of mercury penetration) measured using mercury porosimetry, a third peak is detected, the third peak having a top in a range in which the pore diameter is 0.01-10 μm (inclusive).

Description

Technical Field

[0001] The present technology relates to an active material, a method for manufacturing the same, an electrode, and a secondary battery.

Background Art

[0002] A variety of electronic devices such as mobile phones have become widespread. Therefore, development of secondary batteries is underway as a power source that is small and lightweight and can obtain a high energy density. This secondary battery includes an electrolytic solution together with electrodes (a positive electrode and a negative electrode), and the electrodes contain an active material involved in an electrode reaction. Since the configuration of the secondary battery affects battery characteristics, various studies have been made on the configuration of the secondary battery.

[0003] Specifically, by heating silicon dioxide to generate silicon oxide gas and condensing the silicon oxide gas, powder of silicon oxide (SiO x ) is obtained (see, for example, Patent Documents 1 and 2). In order to improve cycle characteristics and the like of a secondary battery using silicon oxide as a negative electrode active material, a different element is added to the silicon oxide (see, for example, Patent Documents 3 and 4). In order to obtain a negative electrode active material for high-capacity applications, a pyroxene silicate compound is used, and a heat-reduced product of tin oxide (SnO x ) using a reducing gas is used (see, for example, Patent Documents 5 and 6).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Patent Document 6

Summary of the Invention

[0005] Although various studies have been made to improve the battery characteristics of secondary batteries, the charge / discharge characteristics and swelling characteristics of the secondary batteries are still not sufficient, so there is room for improvement.

[0006] Therefore, an active material capable of obtaining excellent charge / discharge characteristics and excellent swelling characteristics, a method for producing the same, an electrode, and a secondary battery are desired.

[0007] The active material according to one embodiment of the present technology includes silicon, oxygen, a first element containing at least one of boron and phosphorus, a second element containing at least one of an alkali metal element, a transition element, and a typical element (excluding silicon, oxygen, boron, phosphorus, an alkali metal element, and an alkaline earth metal element), and a third element containing an alkaline earth metal element as constituent elements. The content of silicon in all constituent elements excluding oxygen and carbon is 60 atomic% or more and 98 atomic% or less, the content of the first element in all constituent elements is 1 atomic% or more and 25 atomic% or less, the content of the second element in all constituent elements is 1 atomic% or more and 34 atomic% or less, and the content of the third element in all constituent elements is 0 atomic% or more and 6 atomic% or less. In the XPS spectrum of Si2p measured using X-ray Photoelectron Spectroscopy (XPS) (the horizontal axis is binding energy (eV) and the vertical axis is spectrum intensity), a first peak having a vertex within a range where the binding energy is 102 eV or more and 105 eV or less and having a shoulder on the side where the binding energy is smaller than the vertex is detected. In the Raman spectrum measured using Raman spectroscopy (the horizontal axis is Raman shift (cm -1 ) and the vertical axis is spectrum intensity), the Raman shift is 435 cm -1 or more and 465 cm -1A second peak having vertices within the following range is detected. In a pore distribution having a plurality of pores and measured using the mercury intrusion method (the horizontal axis is the pore diameter (μm) of the pores and the vertical axis is the change rate of the mercury intrusion amount), a third peak having vertices within the range where the pore diameter is 0.01 μm or more and 10 μm or less is detected.

[0008] A method for manufacturing an active material according to an embodiment of the present technology includes silicon, oxygen, a first element containing at least one of boron and phosphorus, a second element containing at least one of an alkali metal element, a transition element, and a typical element (excluding silicon, oxygen, boron, phosphorus, alkali metal elements, and alkaline earth metal elements), and a third element containing an alkaline earth metal element as constituent elements, and prepares a silicate glass having a plurality of pores, mixes the silicate glass with a carbon source to form a mixture of the silicate glass and the carbon source, and heats the mixture to manufacture an active material containing silicon, oxygen, the first element, the second element, and the third element as constituent elements. The content of silicon in the active material (all constituent elements excluding oxygen and carbon) is 60 atomic% or more and 98 atomic% or less, the content of the first element in the active material is 1 atomic% or more and 25 atomic% or less, the content of the second element in the active material is 1 atomic% or more and 34 atomic% or less, and the content of the third element in the active material is 0 atomic% or more and 6 atomic% or less.

[0009] An electrode according to an embodiment of the present technology contains an active material, and the active material has a configuration similar to the configuration of the active material according to the embodiment of the present technology described above.

[0010] A secondary battery according to an embodiment of the present technology includes a positive electrode, a negative electrode containing an active material, and an electrolyte, and the active material has a configuration similar to the configuration of the active material according to the embodiment of the present technology described above.

[0011] According to the active material, electrode, or secondary battery of one embodiment of the present technology, the active material contains silicon, oxygen, a first element, a second element, and a third element as constituent elements and has a plurality of pores, and the content of each constituent element satisfies the above-described conditions. Further, in the active material, a first peak is detected in the XPS spectrum of Si2p measured using X-ray photoelectron spectroscopy, a second peak is detected in the Raman spectrum measured using Raman spectroscopy, and a third peak is detected in the pore distribution measured using mercury intrusion porosimetry. Therefore, excellent charge-discharge characteristics and excellent swelling characteristics can be obtained.

[0012] According to the manufacturing method of the active material of one embodiment of the present technology, a silicate glass containing silicon, oxygen, a first element, a second element, and a third element as constituent elements and having a plurality of pores is mixed with a carbon source, and then the mixture of the silicate glass and the carbon source is heated to manufacture the active material, and the content of each constituent element in the active material satisfies the above-described conditions. Therefore, an active material having excellent charge-discharge characteristics and excellent swelling characteristics can be obtained.

[0013] Note that the effects of the present technology are not necessarily limited to the effects described here, and may be any of a series of effects related to the present technology described later.

Brief Description of the Drawings

[0014]

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Mode for Carrying Out the Invention

[0015] Hereinafter, an embodiment of the present technology will be described in detail with reference to the drawings. The order of description is as follows. 1. Active material (method for manufacturing active material) 1-1. Configuration 1-2. Physical properties 1-3. Manufacturing method 1-4. Action and effect 2. Electrode and secondary battery 2-1. Configuration 2-2. Operation 2-3. Manufacturing method 2-4. Action and effect 3. Modification example 4. Applications of secondary batteries

[0016] <1. Active material (method for manufacturing active material)> First, the active material according to an embodiment of the present technology will be described. Since the method for manufacturing the active material according to an embodiment of the present technology is a method for manufacturing the active material described here, the method for manufacturing the active material will be described together below.

[0017] This active material is a substance involved in the electrode reaction. More specifically, the active material is a substance capable of occluding and releasing an electrode reaction substance, and is used as an electrode material in an electrochemical device that operates using an electrode reaction. In this case, the active material occludes and releases the electrode reaction substance in an ionic state. Note that the active material may be used as an electrode material for a positive electrode (positive electrode active material) or as an electrode material for a negative electrode (negative electrode active material).

[0018] The use of the active material is not particularly limited as long as it is an electrochemical device that operates using an electrode reaction, but specifically, it is a secondary battery, a capacitor, etc.

[0019] The type of the electrode reaction substance is not particularly limited, but specifically, it is a light metal such as an alkali metal, an alkaline earth metal, and aluminum. The alkali metals include lithium, sodium, potassium, etc., and the alkaline earth metals include beryllium, magnesium, calcium, etc.

[0020] <1-1. Configuration> First, the configuration of the active material will be described. Each of FIG. 1 and FIG. 2 shows a cross-sectional configuration of an active material 100 which is an example of the active material.

[0021] As shown in FIG. 1 and FIG. 2 respectively, this active material 100 has a plurality of pores 103. Here, as shown in FIG. 1, the active material 100 includes a central portion 101 and a coating portion 102, and the central portion 101 may have the plurality of pores 103 described above. Alternatively, as shown in FIG. 2, the active material 100 includes a central portion 101 and a coating portion 102, and each of the central portion 101 and the coating portion 102 may have the plurality of pores 103 described above. In each of FIG. 1 and FIG. 2, in order to simplify the illustration content, the case where the three-dimensional shape of the central portion 101 is spherical is shown, but the three-dimensional shape of the central portion 101 is not particularly limited.

[0022] [Central portion] The central part 101 is the main part of the active material 100 that occludes and releases electrode reactants. As described above, this central part 101 has a plurality of pores 103, and more specifically, it contains carbon-reduced silicate glass having a plurality of pores 103 (hereinafter referred to as "porous carbon-reduced silicate glass"). This porous carbon-reduced silicate glass is different from ordinary silicate glass (hereinafter simply referred to as "silicate glass"). As will be described later, it is a material obtained by carbon-reducing a silicate glass having a plurality of pores 103 (hereinafter referred to as "porous silicate glass") using a carbon source as a reducing agent. However, the type of the porous carbon-reduced silicate glass may be only one type or two or more types.

[0023] In the porous carbon-reduced silicate glass formed using this carbon reduction treatment, due to the use of the carbon source as a reducing agent, the reduction reaction of the porous silicate glass as the raw material is promoted, so that the porous silicate glass is reduced (activated) so as to be able to sufficiently occlude and release electrode reactants. That is, in the normal reduction treatment using a reducing gas as a reducing agent, the porous silicate glass is hardly reduced, whereas in the special reduction treatment (carbon reduction treatment) using a carbon source as a reducing agent, the porous silicate glass is sufficiently reduced. Thereby, the porous carbon-reduced silicate glass has physical properties different from those of the silicate glass. Details of the physical properties of the porous carbon-reduced silicate glass will be described later.

[0024] Specifically, the porous carbon-reduced silicate glass contains silicon, oxygen, a first element, a second element, and a third element as constituent elements.

[0025] In this porous carbon-reduced silicate glass, the content of each constituent element among all the constituent elements excluding oxygen and carbon is set to be within a predetermined range. The content of each constituent element represents the number of atomic percent corresponding to each constituent element when the content of all the constituent elements excluding oxygen and carbon is taken as 100 atomic percent. The content (atomic percent) of each constituent element is calculated based on the analysis results of the porous carbon-reduced silicate glass using a scanning electron microscope / energy dispersive X-ray spectrometry (SEM:Scanning Electron Microscope / EDX:Energy dispersive X-ray spectrometry).

[0026] (Silicon) Silicon is a major constituent element of the porous carbon-reduced silicate glass. The content of silicon among all the constituent elements excluding oxygen and carbon is 60 atomic percent to 98 atomic percent.

[0027] (Oxygen) Oxygen is another major constituent element of the porous carbon-reduced silicate glass and can form oxides with silicon. For this reason, the porous carbon-reduced silicate glass contains SiO x (where x satisfies 0 < x ≤ 2) as a main component. In this SiO x , it is considered that nanosilicon is dispersed in amorphous silicon dioxide (SiO2). Or, in SiO x , it is considered that silicon capable of sufficiently occluding and releasing electrode reactants exists in the glass component.

[0028] (First element) The first element contains one or more of the network-forming elements, and more specifically, contains one or both of boron and phosphorus. When the porous silicate glass contains the first element as a constituent element together with silicon and oxygen, the porous silicate glass is likely to be sufficiently reduced in the carbon reduction treatment. As a result, the porous carbon-reduced silicate glass is likely to be easily and stably formed using the carbon reduction treatment.

[0029] The mesh-forming elements are a general term for a series of elements capable of forming a mesh-forming body (mesh-forming oxide). Therefore, the first element may include, in addition to the above-mentioned boron and phosphorus, germanium and the like.

[0030] The content of the first element among all the constituent elements excluding oxygen and carbon is 1 atomic % to 25 atomic %. This is because the porous silica glass is likely to be sufficiently reduced in the carbon reduction treatment.

[0031] When the first element contains two or more kinds of elements, the content of the first element is the sum of the contents of the respective elements. In the case where the number of element types is two or more, the fact that the content is the sum of the contents of the respective constituent elements is the same for the content of the second element and the content of the third element described later.

[0032] (The second element) The second element contains one or more of alkali metal elements, transition elements, and typical elements. This second element, unlike the third element described later, hardly affects the reducibility of the porous silica glass in the carbon reduction treatment even if it is contained as a constituent element in the porous silica glass. For this reason, even if the porous silica glass contains the second element as a constituent element, the porous silica glass is sufficiently reduced in the carbon reduction treatment.

[0033] The alkali metal elements are a general term for a series of elements belonging to Group 1 of the long-period type periodic table, and specifically include lithium, sodium, potassium, and the like.

[0034] The transition elements are a general term for a series of elements belonging to Groups 3 to 11 of the long-period type periodic table, and specifically include scandium, titanium, iron, zirconium, cerium, and the like. However, the types of transition elements are not particularly limited as long as they are elements belonging to Groups 3 to 11 of the long-period type periodic table. Therefore, in addition to the series of elements such as scandium described above, other elements such as lanthanum, hafnium, tantalum, and tungsten may also be used.

[0035] The typical elements are a general term for a series of elements belonging to Groups 1, 2, and 12 - 18 of the long - form periodic table. However, silicon, oxygen, boron, phosphorus, alkali metal elements, and alkaline earth metal elements are excluded from the typical elements described herein. Thus, the typical elements described herein are, specifically, aluminum, sulfur, chlorine, zinc, bismuth, etc. The types of typical elements are not particularly limited as long as they are elements belonging to Groups 1, 2, and 12 - 18 of the long - form periodic table. Therefore, in addition to the series of elements such as aluminum described above, other elements such as antimony may also be used.

[0036] The content of the second element among all the constituent elements excluding oxygen and carbon is 1 atomic % - 34 atomic %. This is because even if the porous silica glass contains the second element as a constituent element, the porous silica glass is likely to be sufficiently reduced in the carbon reduction treatment.

[0037] (The third element) The third element is any constituent element of the porous carbon - reduced silica glass. Therefore, the porous carbon - reduced silica glass may or may not contain the third element as a constituent element.

[0038] This third element contains any one or two or more of the alkaline earth metal elements. This alkaline earth metal element is a general term for a series of elements belonging to Group 2 of the long - form periodic table, and specifically includes magnesium, calcium, strontium, barium, etc.

[0039] However, the content of the third element among all the constituent elements excluding oxygen and carbon is 0 atomic % - 6 atomic %.

[0040] The lower limit value of the content of the third element being 0 atomic % is because, as described above, the third element is any constituent element of the porous carbon - reduced silica glass, so the porous carbon - reduced silica glass may not contain the third element as a constituent element.

[0041] On the other hand, the upper limit of the content of the third element is 6 atomic %, because, as described above, the third element affects the reducibility of the porous silicate glass in the carbon reduction treatment, and thus the content of the third element needs to be within a range that does not affect the reducibility of the porous silicate glass in the carbon reduction treatment.

[0042] Specifically, when the content of the third element is greater than 6 atomic %, due to the excessive amount of the third element present in the porous silicate glass, the porous silicate glass is hardly reduced in the carbon reduction treatment, so that the porous carbon-reduced silicate glass is not substantially formed. On the contrary, when the content of the third element is 6 atomic % or less, due to the appropriate suppression of the amount of the third element present in the porous silicate glass, the porous silicate glass is easily reduced in the carbon reduction treatment, so that the porous carbon-reduced silicate glass is substantially formed.

[0043] [Coated portion] The coated portion 102 covers a part or all of the surface of the central portion 101. However, when the coated portion 102 covers a part of the surface of the central portion 101, a plurality of coated portions 102 may cover the surface of the central portion 101 at a plurality of locations spaced apart from each other.

[0044] Since this coated portion 102 contains carbon as a constituent element, it has conductivity. The fact that the conductive coated portion 102 covers the surface of the central portion 101 improves the electron conductivity of the active material 100 as compared with the case where the coated portion 102 does not cover the surface of the central portion 101. The material for forming the coated portion 102 is not particularly limited as long as it contains carbon as a constituent element.

[0045] Specifically, as will be described later, the coating portion 102 is a film formed on the surface of the central portion 101 by utilizing the thermal decomposition of the carbon source when a mixture of porous silicate glass and a reducing agent (carbon source) is heated in the manufacturing process (carbon reduction treatment) of the active material. In this case, the coating portion 102 may contain the carbon source as it is, may contain the decomposition product (organic matter decomposed carbon) of the carbon source, or may contain both.

[0046] As described above, the coating portion 102 may or may not have a plurality of pores 103. That is, the pores 103 may be provided only in the central portion 101 and may not be provided in the coating portion 102, or may not be provided only in the central portion 101 but may also be provided in the coating portion 102. Whether the coating portion 102 has a plurality of pores 103 is determined according to the type of the carbon source described above. Details of the relationship between the type of the carbon source and the presence or absence of the plurality of pores 103 will be described later.

[0047] The average pore diameter of the plurality of pores 103 provided in the central portion 101 and the average pore diameter of the plurality of pores 103 provided in the coating portion 102 may be the same as each other or may be different from each other. When the presence or absence of the plurality of pores 103 in the coating portion 102 is determined according to the type of the carbon source, the average pore diameter of the plurality of pores 103 provided in the coating portion 102 tends to be smaller than the average pore diameter of the plurality of pores 103 provided in the central portion 101.

[0048] The thickness of the coating portion 102 is not particularly limited. As long as the coating portion 102 exists even slightly on the surface of the central portion 101, the electron conductivity of the active material 100 is improved as compared with the case where the coating portion 102 does not exist at all on the surface of the central portion 101.

[0049] <1-2. Physical properties> Next, the physical properties of the active material 100 will be described. Below, the three types of physical properties (the first physical property, the second physical property, and the third physical property) defined based on the analysis results of the active material 100 using X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and mercury intrusion porosimetry will be described in order.

[0050] [First Physical Property] Figure 3 shows an example of the analysis result (XPS spectrum of Si2p) of the active material 100 using XPS to explain the first physical property. In this XPS spectrum, the horizontal axis indicates the binding energy (eV), and the vertical axis indicates the spectrum intensity. However, the analysis result described here is the analysis result after argon ion sputtering (sputtering time = 1000 seconds).

[0051] Figure 3 also shows the XPS spectrum (solid line) for porous carbon-reduced silicate glass and the XPS spectrum (dashed line) for porous silicate glass. That is, by subjecting the porous silicate glass from which the XPS spectrum (dashed line) is detected to carbon reduction treatment, porous carbon-reduced silicate glass from which the XPS spectrum (solid line) is detected can be obtained. In addition, in Figure 3, the range where the binding energy is 102 eV to 105 eV is shaded.

[0052] As shown in Figure 3, the porous carbon-reduced silicate glass has physical properties different from those of the porous silicate glass in the analysis result (shape of the XPS spectrum) using XPS.

[0053] Specifically, in the XPS spectrum (solid line) for the porous carbon-reduced silicate glass, a peak XA (the first peak) is detected. This peak XA has a peak top XAT within the range where the binding energy is 102 eV to 105 eV, and has a shoulder XAS on the side where the binding energy is smaller than that of the peak top XAT (the right side in Figure 3). This shoulder XAS is a shoulder-shaped part where a part in the middle of the peak XA having the peak top XAT protrudes toward the low binding energy side, that is, a stepped part.

[0054] On the other hand, in the XPS spectrum (dashed line) for silicate glass, peak XB is detected. This peak XB has its apex XBT within the range where the binding energy is 102 eV to 105 eV, but does not have a shoulder (the stepped portion corresponding to shoulder XAS) on the side where the binding energy is lower than that of the apex XBT.

[0055] From these facts, regarding the analysis results (the shape of the XPS spectrum) of the active material 100 using XPS, the following tendencies can be derived. In the porous carbon-reduced silicate glass, since the raw material, porous silicate glass, has been sufficiently reduced using a carbon reduction treatment, peak XA having shoulder XAS together with apex XAT is detected. On the other hand, in the porous silicate glass, since the carbon reduction treatment has not been performed yet, only peak XB having apex XBT is detected. Therefore, based on the analysis results using XPS, it is possible to specify whether the object to be analyzed is porous carbon-reduced silicate glass or porous silicate glass. Thus, the porous carbon-reduced silicate glass formed using a carbon reduction treatment has physical properties different from those of the porous silicate glass in that it has the above-described first physical property regarding XPS.

[0056] By the procedure described here, the material of the central portion 101 of the active material 100 can be specified. That is, when analyzing the central portion 101 using XPS, if peak XA is detected, the central portion 101 contains porous carbon-reduced silicate glass, whereas if peak XB is detected, the central portion 101 contains porous silicate glass.

[0057] Note that, as described above, porous silicate glass is hardly reduced by a normal reduction treatment. Therefore, even if a normal reduction treatment is performed using porous silicate glass, since the porous silicate glass is hardly reduced, peak XB should be obtained without obtaining peak XA.

[0058] Here, as described above, peak XA for the porous carbon-reduced silicate glass has a shoulder XAS, whereas peak XB for the porous silicate glass does not have a shoulder. Therefore, even by the procedure described below, it is possible to identify whether the object to be analyzed is either the porous carbon-reduced silicate glass or the porous silicate glass.

[0059] First, the width in the middle of peak XA in the height direction is larger than the width in the middle of peak XB in the height direction. For this reason, the full width at half maximum (FWHM) of peak XA becomes larger than the FWHM of peak XB, and more specifically, it is 4.0 eV or more. Since the FWHM of peak XA becomes 4.0 eV or more while the FWHM of peak XB does not become 4.0 eV or more, by examining the FWHM instead of examining the presence or absence of the shoulder XAS, it is also possible to identify whether the object to be analyzed is either the porous carbon-reduced silicate glass or the porous silicate glass. That is, even when it is difficult to judge the presence or absence of the shoulder XAS because the shoulder XAS is small, the type of the object to be analyzed can be identified by examining the FWHM.

[0060] Second, the area in the middle of peak XA becomes larger than the area in the middle of peak XB. Along with this, when each of peaks XA and XB is decomposed into five Si-derived peaks (Si 0 peak, Si 1+ peak, Si 2+ peak, Si 3+ peak, and Si 4+ peak), the area ratio S2 / S1 of peak XA becomes larger than the area ratio S2 / S1 of peak XB, and more specifically, it is 0.85 or more.

[0061] Here, area S1 is the area of the Si 4+ peak, and area S2 is the sum of the area of the Si 0 peak, the area of the Si 1+ peak, the area of the Si 2+ peak, and the area of the Si 3+ peak. Each of areas S1 and S2 can be calculated using the analysis (calculation) function of the XPS apparatus.

[0062] The area ratio S2 / S1 of peak XA is 0.85 or more, while the area ratio S2 / S1 of peak XB is less than 0.85. Therefore, instead of examining the presence or absence of shoulder XAS, by examining the area ratio S2 / S1, it is also possible to identify whether the object to be analyzed is porous carbon-reduced silicate glass or porous silicate glass. That is, as described above, since shoulder XAS is small, even when it is difficult to determine the presence or absence of the shoulder XAS, the type of the object to be analyzed can be identified by examining the area ratio S2 / S1.

[0063] [Second Physical Property] FIG. 4 shows an example of the analysis result (Raman spectrum) of the active material 100 using Raman spectroscopy in order to explain the second physical property. In this Raman spectrum, the horizontal axis indicates the Raman shift (cm -1 ), and the vertical axis indicates the spectrum intensity.

[0064] In FIG. 4, a Raman spectrum (solid line) related to porous carbon-reduced silicate glass and a Raman spectrum (dashed line) related to porous silicate glass are also shown. That is, by subjecting the porous silicate glass in which the Raman spectrum (dashed line) is detected to carbon reduction treatment, porous carbon-reduced silicate glass in which the Raman spectrum (solid line) is detected can be obtained. In FIG. 4, hatching is applied in the range where the Raman shift is 435 cm -1 ~465 cm -1 .

[0065] As shown in FIG. 4, porous carbon-reduced silicate glass has physical properties different from those of porous silicate glass in the analysis result (shape of the Raman spectrum) using Raman spectroscopy.

[0066] Specifically, in the Raman spectrum (solid line) related to porous carbon-reduced silicate glass, peak RA (second peak) is detected. This peak RA has a Raman shift of 435 cm -1 ~465 cm -1It has vertex RAT within a certain range.

[0067] On the other hand, in the Raman spectrum (dashed line) of porous silica glass, peak RB is detected. This peak RB has no vertex RBT within the range of 435 cm -1 ~465 cm -1 but has vertex RBT outside that range. For reference, in the Raman spectrum of crystalline silicon, a peak with a vertex within the range of 510 cm -1 ~525 cm -1 is detected.

[0068] From these facts, the following tendency can be derived regarding the analysis result (the shape of the Raman spectrum) of the active material 100 using Raman spectroscopy. In porous carbon-reduced silica glass, since the raw material porous silica glass is sufficiently reduced using carbon reduction treatment, peak RA with vertex RAT is detected within the range of 435 cm -1 ~465 cm -1 On the other hand, in porous silica glass, since carbon reduction treatment has not been performed yet, peak RB with vertex RBT outside the above range is detected. Therefore, porous carbon-reduced silica glass formed using carbon reduction treatment has physical properties different from those of porous silica glass in that it has the second physical property regarding the above Raman spectroscopy.

[0069] By the procedure described here, the material of the central part 101 of the active material 100 can be specified. That is, when analyzing the central part 101 using Raman spectroscopy, if peak RA is detected, the central part 101 contains porous carbon-reduced silica glass, whereas if peak RB is detected, the central part 101 contains porous silica glass.

[0070] Note that, as described above, porous silicate glass is hardly reduced by normal reduction treatment. Therefore, even if normal reduction treatment is performed using porous silicate glass, since the porous silicate glass is hardly reduced, peak RB should be obtained without obtaining peak RA.

[0071] [Third Physical Property] FIG. 5 shows an example of the analysis result (pore distribution) of the active material 100 using the mercury intrusion method in order to explain the third physical property. In this pore distribution, the horizontal axis indicates the pore diameter (μm), and the vertical axis indicates the change rate of the mercury intrusion amount. However, the value of the change rate of the mercury intrusion amount is a value normalized with the maximum value of the change rate of the mercury intrusion amount when the central portion 101 contains porous carbon-reduced silicate glass as 1.

[0072] In FIG. 5, together with the pore distribution (solid line) regarding the active material 100 containing porous carbon-reduced silicate glass in which the central portion 101 has a plurality of pores 103, the pore distribution (broken line) regarding the active material 100 containing carbon-reduced silicate glass in which the central portion 101 does not have a plurality of pores 103 (hereinafter referred to as "non-porous carbon-reduced silicate glass") is also shown. This non-porous carbon-reduced silicate glass is a material obtained by carbon-reducing treatment of silicate glass having no plurality of pores 103 (hereinafter referred to as "non-porous silicate glass") using a carbon source as a reducing agent. In FIG. 5, the pore distributions (solid line and broken line) when the coating portion 102 does not have pores 103 are shown, and hatching is applied to the range where the pore diameter is 0.01 μm to 10 μm.

[0073] As shown in FIG. 5, the active material 100 in which the central portion 101 contains porous carbon-reduced silicate glass has physical properties different from those of the active material 100 in which the central portion 101 contains non-porous carbon-reduced silicate glass in the analysis result (pore distribution) by the mercury intrusion method.

[0074] Specifically, in the pore size distribution (solid line) of the active material 100 in which the central portion 101 contains porous carbon-reduced silicate glass, a peak MA (the third peak) is detected. This peak MA has a peak point MAT within the range where the pore diameter is 0.01 μm to 10 μm.

[0075] On the other hand, in the pore size distribution (dashed line) of the active material 100 in which the central portion 101 contains non-porous carbon-reduced silicate glass, no peak is detected. In FIG. 5, the case where the pore size distribution (dashed line) of the active material 100 containing non-porous carbon-reduced silicate glass is flat is shown, but the pore size distribution (dashed line) may also be broad (a gently upwardly convex curve). Even in this case, it is certain that no peak is detected.

[0076] From these facts, the following tendency can be derived regarding the analysis results (pore size distribution) of the active material 100 using the mercury intrusion method. Since the central portion 101 containing porous carbon-reduced silicate glass has a plurality of pores 103, the peak MA is detected. On the other hand, since the central portion 101 containing non-porous carbon-reduced silicate glass does not have a plurality of pores 103, no peak is detected. Therefore, the active material 100 in which the central portion 101 contains porous carbon-reduced silicate glass has physical properties different from those of the active material 100 in which the central portion 101 contains non-porous carbon-reduced silicate glass in that it has the third physical property regarding the above-described mercury intrusion method.

[0077] The tendency (difference in physical properties) regarding the pore size distribution described here is not limited to the case where only the central portion 101 has a plurality of pores 103, but is similarly obtained even when each of the central portion 101 and the coating portion 102 has a plurality of pores 103.

[0078] When examining the rate of change of the mercury intrusion amount, the distribution of the rate of change of the mercury intrusion amount (the horizontal axis is the pore diameter (μm) and the vertical axis is the rate of change of the mercury intrusion amount) is measured by analyzing the active material 100 using the mercury intrusion method. In this case, a mercury porosimeter is used as the measuring device. In the measurement using a mercury porosimeter, while increasing the pressure P step by step, the mercury intrusion amount V into a plurality of pores 103 is measured, so the rate of change of the mercury intrusion amount (ΔV / ΔP) is plotted against the pore diameter. However, the mercury intrusion amount is a value measured when the surface tension of mercury = 485 mN / m, the contact angle of mercury = 130°, and the relationship between the pore diameter of the pore 103 and the pressure is approximated as 180 / pressure = pore diameter. In order to specify the pore diameter of the apex MAT of the peak MA, after measuring the pore size distribution described above, the pore diameter corresponding to the apex MAT of the peak MA may be examined.

[0079] [Summary] From these facts, in the active material 100 in which the central portion 101 contains porous carbon-reduced silicate glass, the peak XA is detected in the XPS spectrum of Si2p measured using XPS (first physical property), and the peak RA is detected in the Raman spectrum measured using Raman spectroscopy (second physical property). Therefore, by analyzing the active material 100 (central portion 101) using both XPS and Raman spectroscopy, when both of the above-described peaks XA and RA are detected, the active material 100 contains porous carbon-reduced silicate glass.

[0080] On the other hand, when analyzing the active material 100 using both XPS and Raman spectroscopy, if one or both of the peaks XA and RA are not detected, the active material 100 does not contain porous carbon-reduced silicate glass.

[0081] The active material 100 (central part 101) containing porous carbon-reduced silicate glass has the first physical property and the second physical property because the reduction reaction proceeds more than that of the porous silicate glass, and the crystallinity of the glass material containing SiOx as the main component described above is optimized. As a result, the active material 100 can easily occlude and release the electrode reaction material sufficiently and stably, and the active material 100 can easily occlude and release the electrode reaction material continuously even when the electrode reaction is repeated.

[0082] Further, in the active material 100 in which the central part 101 contains porous carbon-reduced silicate glass, a peak MA is detected in the pore distribution measured by the mercury intrusion method (third physical property).

[0083] The active material 100 containing porous carbon-reduced silicate glass has the third physical property because when the central part 101 (porous carbon-reduced silicate glass) expands and contracts during the electrode reaction, the stress during expansion and contraction is relaxed by using a plurality of pores 103. As a result, the expansion and contraction of the central part 101 are suppressed, so that the increase and decrease in the volume of the entire active material 100 are suppressed. Therefore, since the state of the active material 100 is likely to be maintained even when the electrode reaction is repeated, the active material 100 can more stably occlude and release the electrode reaction material.

[0084] The advantage that the stress during expansion and contraction is relaxed by using a plurality of pores 103 as described above is not limited to the case where only the central part 101 has a plurality of pores 103, and the same can be obtained even when each of the central part 101 and the coating part 102 has a plurality of pores 103.

[0085] <1-3. Manufacturing method> Next, the manufacturing method of the active material 100 will be described. FIG. 6 shows a flow for explaining the manufacturing method of the active material 100. The step numbers in parentheses described below correspond to the step numbers shown in FIG. 6.

[0086] When manufacturing the active material 100, first, powdery porous silicate glass as a raw material is prepared (step S1). In this case, porous silicate glass that has already been synthesized may be obtained using a method such as purchasing, or porous silicate glass may be synthesized by oneself.

[0087] Since this porous silicate glass has not yet been subjected to carbon reduction treatment, it has substantially the same structure as that of porous carbon-reduced silicate glass, except that it does not have the above-described first physical property and second physical property. That is, the porous silicate glass contains silicon, oxygen, a first element, a second element, and a third element as constituent elements. Details regarding each of the first element, the second element, and the third element are as described above.

[0088] When synthesizing porous silicate glass, silicon dioxide (SiO2) is mixed with a supply source for each of the first element, the second element, and the third element, and then the mixture is heated. Conditions such as the heating temperature and heating time can be arbitrarily set.

[0089] This supply source is a compound containing each constituent element. The type of the compound is not particularly limited, but specifically, it is an oxide of each constituent element, etc. That is, the supply source of the first element is boron trioxide (B2O5), phosphorus pentoxide (P2O5), etc. The supply source of the second element is sodium oxide (Na2O), potassium oxide (K2O), scandium oxide (ScO), titanium oxide (TiO2), zirconium oxide (Zr2O), cerium oxide (CeO), hafnium oxide (HfO2), tantalum pentoxide (Ta2O5), tungsten oxide (WO3), aluminum oxide (Al2O3), phosphorus pentasulfide (P2S5), lithium sulfide (Li2S), magnesium sulfide (MgS), silicon tetrachloride (SiCl4), zinc peroxide (ZnO2), bismuth oxide (BiO), antimony oxide (Sb2O3), etc. The supply source of the third element is magnesium oxide (MgO), calcium oxide (CaO), strontium oxide (SrO), barium oxide (BaO), etc.

[0090] As a result, silicon dioxide and the respective sources of the first element, the second element, and the third element are mutually solid-soluble. Thus, a glass body containing silicon, oxygen, the first element, the second element, and the third element as constituent elements is formed, so that porous silica glass is synthesized.

[0091] After preparing the porous silica glass, a mixture is obtained by mixing the porous silica glass with a carbon source (step S2). This carbon source is a general term for materials that can serve as a source of carbon, and specifically, it is one or both of a carbon material and a carbonizable organic substance. That is, as the carbon source, only a carbon material may be used, only a carbonizable organic substance may be used, or both may be used.

[0092] The carbon material is non-fibrous carbon, fibrous carbon, etc. The non-fibrous carbon is carbon black, etc., and the fibrous carbon is carbon nanotubes, carbon nanofibers, etc. The carbonizable organic substances are saccharides, polymer compounds, etc. The saccharides are sucrose, maltose, cellulose, etc. The polymer compounds are polyimide, polyvinylidene fluoride, polymethyl methacrylate, polyvinylpyrrolidone, polyvinyl alcohol, polyacrylic acid, etc. This is because in the carbon reduction treatment, the porous silica glass is sufficiently reduced. Also, as will be described later, by using the carbon source, the coating portion 102 having sufficient conductivity can be easily and stably formed.

[0093] In this case, the mixture may be stirred using a stirring device. Conditions such as the stirring speed and stirring time can be arbitrarily set.

[0094] Alternatively, a paste-like mixture may be obtained by adding a binder and a solvent to the mixture. In this case, it is preferable to stir the mixture using the stirring device described above. The type of the binder is not particularly limited, but specifically, it is any one or two or more of polymer compounds such as polyvinylidene fluoride, polyimide, and polymethyl methacrylate. The type of the solvent is not particularly limited, but specifically, it is any one or two or more of organic solvents such as N-methyl-2-pyrrolidone. Note that a binder solution in which the binder is dissolved in a solvent in advance may be used.

[0095] Finally, the mixture is heated (step S3). In this case, any one or two or more of heating devices such as an oven are used. Conditions such as the heating temperature and the heating time can be arbitrarily set. Specifically, the heating temperature is 700°C to 1400°C and the heating time is 1 hour to 20 hours.

[0096] Note that when using a mixture containing a binder, the mixture may be heated in two steps. Specifically, first, the mixture is preheated to dry the mixture. The conditions for the preheating are not particularly limited, but specifically, the heating temperature is 40°C to 500°C and the heating time is 10 minutes to 3 hours. Subsequently, the dried mixture is pulverized. Finally, the pulverized mixture is main-heated. The conditions for the main heating are not particularly limited, but specifically, the heating temperature is 700°C to 1200°C and the heating time is 1 hour to 20 hours.

[0097] As a result, the porous silica glass is carbon-reduced, so that the porous silica glass is sufficiently reduced using the carbon source as a reducing agent. That is, the crystal state of SiO x is optimized, and thus porous carbon-reduced silica glass containing SiO x as a main component is synthesized. Therefore, a central portion 101 including the porous carbon-reduced silica glass and having a plurality of pores 103 is formed.

[0098] Moreover, in the carbon reduction treatment, as described above, carbon (organic matter decomposed carbon) adheres to the surface of the central portion 101 by utilizing the thermal decomposition of the carbon source used as the reducing agent. Therefore, the coating portion 102 containing the carbon as a constituent element is formed so as to cover the surface of the central portion 101.

[0099] Here, the presence or absence of the plurality of pores 103 in the coating portion 102 is determined according to the type of the carbon source as described above. Specifically, when a carbon material (such as non-fibrous carbon and fibrous carbon) is used as the carbon source, the coating portion 102 having no plurality of pores 103 is likely to be formed. Further, when a carbonizable organic substance (such as saccharides and polymer compounds) is used as the carbon source, the coating portion 102 having a plurality of pores 103 is likely to be formed. Therefore, the presence or absence of the plurality of pores 103 in the coating portion 102 can be controlled according to the type of the carbon source.

[0100] From these, the active material 100 including the central portion 101 and the coating portion 102 and having a plurality of pores 103 is manufactured (step S4). When manufacturing this active material 100, the composition of the porous silicate glass used as the raw material is adjusted so that the content of each constituent element in all the constituent elements excluding oxygen and carbon satisfies the above conditions. Specifically, as described above, the content of silicon in all the constituent elements excluding oxygen and carbon is 60 atomic% to 98 atomic%, the content of the first element in all the constituent elements is 1 atomic% to 25 atomic%, the content of the second element in all the constituent elements is 1 atomic% to 34 atomic%, and the content of the third element in all the constituent elements is 0 atomic% to 6 atomic%.

[0101] In the active material 100 (central portion 101) including the porous carbon-reduced silicate glass manufactured by using the carbon reduction treatment, since the physical properties of the porous silicate glass change due to the carbon reduction treatment, the above-described first physical property and second physical property are obtained.

[0102] In addition, in the active material 100 containing porous carbon-reduced silicate glass produced using porous silicate glass as a raw material, since the structure of the porous silicate glass (porous structure) is reflected in the structure of the porous carbon-reduced silicate glass (the structure of the central portion 101), the above-described third physical property is obtained.

[0103] <1-4. Action and Effect> According to the above-described active material 100 and its manufacturing method, the actions and effects described below can be obtained.

[0104] [Action and Effect Regarding Active Material] The active material 100 contains porous carbon-reduced silicate glass.

[0105] Specifically, first, the active material 100 contains silicon, oxygen, a first element, a second element, and a third element as constituent elements, and the content of each constituent element among all constituent elements excluding oxygen and carbon satisfies the above-described conditions. Second, in the analysis result (XPS spectrum of Si2p) of the active material 100 measured using XPS, a peak XA having a vertex XAT and a shoulder XAS is detected (first physical property). Third, in the analysis result (Raman spectrum) of the active material 100 measured using Raman spectroscopy, a peak RA having a vertex RAT is detected (second physical property). Fourth, in the analysis result (pore distribution) of the active material 100 measured using mercury intrusion porosimetry, a peak MA having a vertex MAT is detected (third physical property).

[0106] As a result, as described above, unlike the case where the first physical property and the second physical property are not obtained, since the reduction reaction of the porous silicate glass proceeds sufficiently, the crystallinity of the glass material mainly containing SiO x is optimized. Therefore, the active material 100 can easily occlude and release the electrode reactant sufficiently and stably, and the active material 100 can easily continue to occlude and release the electrode reactant even when the electrode reaction is repeated.

[0107] Moreover, as described above, unlike the case where the third physical property is not obtained, the expansion and contraction of the central portion 101 (porous carbon-reduced silicate glass) are suppressed by utilizing a plurality of pores 103 during the electrode reaction. Therefore, the increase and decrease in the volume of the entire active material 100 are suppressed. Thus, the state of the active material 100 is more likely to be maintained even when the electrode reaction is repeated, and the active material 100 can more stably occlude and release the electrode reaction material.

[0108] From these facts, in an electrochemical device using the active material 100, excellent charge and discharge characteristics and excellent swelling characteristics can be obtained.

[0109] In particular, if the full width at half maximum of peak XA is 4.0 eV or more, since the central portion 101 contains a carbon-reduced silicate compound having the first physical property and the second physical property, excellent charge and discharge characteristics and excellent swelling characteristics can be obtained as described above. When peak XA is decomposed into five Si-derived peaks (Si 0 peak, Si 1+ peak, Si 2+ peak, Si 3+ peak, and Si 4+ peak), even when the area ratio S2 / S1 is 0.85 or more, for the same reason, excellent charge and discharge characteristics and excellent swelling characteristics can be obtained.

[0110] Also, if the active material 100 includes the central portion 101 and the coating portion 102, the surface of the central portion 101 containing porous carbon-reduced silicate glass is coated with the conductive coating portion 102. Therefore, the electron conductivity of the active material 100 is improved, and a higher effect can be obtained.

[0111] In this case, if the central portion 101 has a plurality of pores 103, the increase and decrease in the volume of the entire active material 100 are sufficiently suppressed, so a higher effect can be obtained. Also, if each of the central portion 101 and the coating portion 102 has a plurality of pores 103, the increase and decrease in the volume of the entire active material 100 are more suppressed, so a remarkably high effect can be obtained.

[0112] [Actions and Effects Related to the Method for Producing an Active Material] According to the method for producing the active material 100, after mixing porous silicate glass containing silicon, oxygen, a first element, a second element, and a third element as constituent elements with a carbon source, the mixture of the porous silicate glass and the carbon source is heated. As a result, an active material 100 containing a porous carbon-reduced silicate compound having the content of each constituent element satisfying the above-described conditions and having three types of physical properties (first physical property, second physical property, and third physical property) is produced. Therefore, an active material 100 having excellent charge and discharge characteristics and excellent swelling characteristics can be obtained.

[0113] Moreover, SiO x In order to produce the active material 100 mainly containing as a main component, only simple and inexpensive treatments such as a mixing treatment and a heat treatment are used, so there is no need to use complicated and expensive treatments such as a treatment of co-evaporating two types of evaporation sources (SiO2 and Si). Therefore, the active material 100 can be easily and stably produced at low cost.

[0114] In particular, if the carbon source contains a carbon material or the like, the porous silicate glass is sufficiently reduced in the carbon reduction treatment, and a coating portion 102 having sufficient conductivity is easily and stably formed, so that a higher effect can be obtained.

[0115] <2. Electrode and Secondary Battery> Next, a secondary battery according to an embodiment of the present technology, which is an application example of the above-described active material, will be described. Since the electrode according to an embodiment of the present technology is a part (a constituent element) of the secondary battery, the electrode will be described together below.

[0116] Hereinafter, since the above-described active material is used as a negative electrode active material, the case where the active material is used for the negative electrode will be described.

[0117] The secondary battery described here is a secondary battery in which battery capacity is obtained by utilizing the occlusion and release of electrode reactants, and includes an electrolytic solution together with a positive electrode and a negative electrode.

[0118] In this secondary battery, the charging capacity of the negative electrode is larger than the discharging capacity of the positive electrode. That is, the electrochemical capacity per unit area of the negative electrode is set to be larger than the electrochemical capacity per unit area of the positive electrode. This is to prevent the deposition of electrode reaction substances on the surface of the negative electrode during charging.

[0119] Hereinafter, the case where the electrode reaction substance is lithium will be taken as an example. A secondary battery that utilizes the intercalation and deintercalation of lithium as the electrode reaction substance is a so-called lithium-ion secondary battery.

[0120] <2-1. Configuration> FIG. 7 shows a perspective configuration of the secondary battery. FIG. 8 shows a cross-sectional configuration of the battery element 20 shown in FIG. 7. FIG. 9 shows a planar configuration of each of the positive electrode 21 and the negative electrode 22 shown in FIG. 8.

[0121] However, in FIG. 7, a state where the exterior film 10 and the battery element 20 are separated from each other is shown, and a cross-section of the battery element 20 along the XZ plane is indicated by a dashed line. In FIG. 8, only a part of the battery element 20 is shown. In FIG. 9, a state where the positive electrode 21 and the negative electrode 22 are separated from each other is shown.

[0122] As shown in FIGS. 7 to 9, this secondary battery includes an exterior film 10, a battery element 20, a positive electrode lead 31 and a negative electrode lead 32, and sealing films 41 and 42. The secondary battery described here is a laminated film type secondary battery using a flexible (or pliable) exterior film 10.

[0123] [Exterior Film and Sealing Films] As shown in FIG. 7, the exterior film 10 is a flexible exterior member that houses the battery element 20, and has a bag-like structure that is sealed in a state where the battery element 20 is housed inside. Therefore, the exterior film 10 houses the electrolyte together with the positive electrode 21 and the negative electrode 22 described later.

[0124] Here, the exterior film 10 is a single film-like member and is folded in the folding direction F. The exterior film 10 is provided with a recessed portion 10U (so-called deep drawing portion) for accommodating the battery element 20.

[0125] Specifically, the exterior film 10 is a three-layer laminated film in which a fusion layer, a metal layer, and a surface protection layer are laminated in this order from the inside. In the state where the exterior film 10 is folded, the outer peripheral edge portions of the fusion layers facing each other are fused to each other. The fusion layer contains a polymer compound such as polypropylene. The metal layer contains a metal material such as aluminum. The surface protection layer contains a polymer compound such as nylon.

[0126] However, the configuration (number of layers) of the exterior film 10 is not particularly limited, so it may be one layer or two layers, or four layers or more.

[0127] The sealing film 41 is inserted between the exterior film 10 and the positive electrode lead 31, and the sealing film 42 is inserted between the exterior film 10 and the negative electrode lead 32. However, one or both of the sealing films 41 and 42 may be omitted.

[0128] This sealing film 41 is a sealing member that prevents outside air and the like from entering the interior of the exterior film 10. The sealing film 41 contains a polymer compound such as polyolefin that has adhesiveness to the positive electrode lead 31, and the polyolefin is polypropylene or the like.

[0129] The configuration of the sealing film 42 is the same as that of the sealing film 41 except that it is a sealing member that has adhesiveness to the negative electrode lead 32. That is, the sealing film 42 contains a polymer compound such as polyolefin that has adhesiveness to the negative electrode lead 32.

[0130] [Battery Element] As shown in FIGS. 7 and 8, the battery element 20 is a power generation element including a positive electrode 21, a negative electrode 22, a separator 23, and an electrolytic solution (not shown), and is housed inside the exterior film 10.

[0131] This battery element 20 is a so-called wound electrode body. That is, in the battery element 20, the positive electrode 21 and the negative electrode 22 are laminated on each other with the separator 23 interposed therebetween, and the positive electrode 21, the negative electrode 22, and the separator 23 are wound around a winding axis P which is a virtual axis extending in the Y-axis direction. As a result, the positive electrode 21 and the negative electrode 22 are wound while facing each other with the separator 23 interposed therebetween.

[0132] The three-dimensional shape of the battery element 20 is not particularly limited. Here, since the battery element 20 is flat, the cross-section of the battery element 20 intersecting the winding axis P (the cross-section along the XZ plane) has a flat shape defined by a major axis J1 and a minor axis J2. This major axis J1 is a virtual axis extending in the X-axis direction and having a length larger than that of the minor axis J2, and the minor axis J2 is a virtual axis extending in the Z-axis direction intersecting the X-axis direction and having a length smaller than that of the major axis J1. Here, since the three-dimensional shape of the battery element 20 is a flat cylindrical shape, the shape of the cross-section of the battery element 20 is a substantially flat elliptical shape.

[0133] (Positive Electrode) As shown in FIGS. 8 and 9, the positive electrode 21 includes a positive electrode current collector 21A and a positive electrode active material layer 21B.

[0134] The positive electrode current collector 21A has a pair of surfaces on which the positive electrode active material layer 21B is provided. This positive electrode current collector 21A contains a conductive material such as a metal material, and the metal material is aluminum or the like.

[0135] Here, the positive electrode active material layer 21B is provided on both sides of the positive electrode current collector 21A and contains any one or two or more of positive electrode active materials capable of occluding and releasing lithium. However, the positive electrode active material layer 21B may be provided only on one side of the positive electrode current collector 21A on the side where the positive electrode 21 faces the negative electrode 22. Further, the positive electrode active material layer 21B may further contain any one or two or more of other materials such as a positive electrode binder and a positive electrode conductive agent. The method for forming the positive electrode active material layer 21B is not particularly limited, but specifically, it is any one or two or more of coating methods and the like.

[0136] The type of the positive electrode active material is not particularly limited, but specifically, it is a lithium-containing compound or the like. This lithium-containing compound is a compound containing one or two or more transition metal elements as constituent elements together with lithium, and may further contain one or two or more other elements as constituent elements. The type of the other element is not particularly limited as long as it is an element other than each of lithium and the transition metal element, but specifically, it is an element belonging to Groups 2 to 15 in the long-period type periodic table. The type of the lithium-containing compound is not particularly limited, but specifically, it is an oxide, a phosphate compound, a silicate compound, a borate compound, and the like.

[0137] Specific examples of the oxide are LiNiO2, LiCoO2, LiCo 0.98 Al 0.01 Mg 0.01 O2, LiNi 0.5 Co 0.2 Mn 0.3 O2, LiNi 0.8 Co 0.15 Al 0.05 O2, LiNi 0.33 Co 0.33 Mn 0.33 O2, Li 1.2 Mn 0.52 Co 0.175 Ni 0.1 O2, Li 1.15 (Mn 0.65 Ni 0.22 Co 0.13)Such as O2 and LiMn2O4. Specific examples of the phosphate compound are LiFePO4, LiMnPO4, LiFe 0.5 Mn 0.5 PO4 and LiFe 0.3 Mn 0.7 PO4 and the like.

[0138] The positive electrode binder contains any one or two or more of synthetic rubbers and polymer compounds. The synthetic rubber is styrene-butadiene rubber, fluorine rubber, ethylene propylene diene, etc. The polymer compound is polyvinylidene fluoride, polyimide, carboxymethyl cellulose, etc.

[0139] The positive electrode conductive agent contains any one or two or more of conductive materials such as carbon materials, and the carbon materials are graphite, carbon black, acetylene black, ketjen black, etc. However, the conductive material may also be a metal material, a polymer compound, etc.

[0140] Here, on both sides of the positive electrode current collector 21A, the positive electrode active material layer 21B is provided only on a part of the positive electrode current collector 21A. Therefore, the portion of the positive electrode current collector 21A where the positive electrode active material layer 21B is not provided is not covered by the positive electrode active material layer 21B and is exposed.

[0141] Specifically, as shown in FIG. 9, the positive electrode current collector 21A extends in the longitudinal direction (X-axis direction) and includes a coated portion 21AX and a pair of non-coated portions 21AY. The coated portion 21AX is located at the central portion of the positive electrode current collector 21A in the longitudinal direction and is the portion where the positive electrode active material layer 21B is formed. The pair of non-coated portions 21AY are located at both ends of the positive electrode current collector 21A in the longitudinal direction and are the portions where the positive electrode active material layer 21B is not formed. Thereby, the coated portion 21AX is covered by the positive electrode active material layer 21B, while the pair of non-coated portions 21AY are not covered by the positive electrode active material layer 21B and are exposed. In FIG. 9, a light hatching is applied to the positive electrode active material layer 21B.

[0142] Negative electrode As shown in FIGS. 8 and 9, the negative electrode 22 includes a negative electrode current collector 22A and a negative electrode active material layer 22B.

[0143] The negative electrode current collector 22A has a pair of surfaces on which the negative electrode active material layer 22B is provided. The negative electrode current collector 22A includes a conductive material such as a metal material, and the metal material is copper or the like.

[0144] Here, the negative electrode active material layer 22B is provided on both surfaces of the negative electrode current collector 22A, and contains any one or two or more of negative electrode active materials capable of occluding and releasing lithium. The configuration of this negative electrode active material is the same as the configuration of the above-described active material. However, the negative electrode active material layer 22B may be provided only on one side of the negative electrode current collector 22A on the side where the negative electrode 22 faces the positive electrode 21. Further, the negative electrode active material layer 22B may further contain any one or two or more of other materials such as a negative electrode binder and a negative electrode conductive agent. The method for forming the negative electrode active material layer 22B is not particularly limited, but specifically, it is any one or two or more of a coating method, a vapor phase method, a liquid phase method, a spraying method, and a firing method (sintering method).

[0145] However, the negative electrode active material layer 22B may further contain other negative electrode active materials. The type of other negative electrode active materials is not particularly limited, but specifically, it is one or both of a carbon material and a metal-based material, etc. This is because a high energy density can be obtained. The carbon material is graphitizable carbon, non-graphitizable carbon, and graphite (natural graphite and artificial graphite), etc. The metal-based material is a material containing any one or two or more of metal elements and metalloid elements capable of forming an alloy with lithium as constituent elements, and specific examples of the metal elements and metalloid elements are one or both of silicon and tin, etc. This metal-based material may be a single substance, an alloy, a compound, a mixture of two or more of them, or a material containing two or more phases of them. Specific examples of the metal-based material are TiSi2 and SiO x(0 < x ≤ 2, or 0.2 < x < 1.4), etc.

[0146] Details regarding each of the negative electrode binder and the negative electrode conductive agent are the same as those regarding each of the positive electrode binder and the positive electrode conductive agent.

[0147] Here, on both sides of the negative electrode current collector 22A, the negative electrode active material layer 22B is provided over the entire surface of the negative electrode current collector 22A. For this reason, the entire negative electrode current collector 22A is not exposed and is covered by the negative electrode active material layer 22B.

[0148] Specifically, as shown in FIG. 9, the negative electrode current collector 22A extends in the longitudinal direction (X-axis direction), and the negative electrode active material layer 22B includes a pair of non-facing portions 22BZ. The pair of non-facing portions 22BZ are portions that face the pair of non-covered portions 21AY. That is, since the pair of non-facing portions 22BZ are portions that do not face the positive electrode active material layer 21B, they are portions that do not participate in the charge-discharge reaction. In FIG. 9, the negative electrode active material layer 22B is shown with a thick shading.

[0149] The reason that the positive electrode active material layer 21B is provided only on a part (covered portion 21AX) of both sides of the positive electrode current collector 21A, while the negative electrode active material layer 22B is provided over the entire surface of both sides of the negative electrode current collector 22A, is to prevent lithium released from the positive electrode active material layer 21B during charging from depositing on the surface of the negative electrode 22.

[0150] In addition, when examining whether the above three types of physical properties (the first physical property, the second physical property, and the third physical property) are obtained, that is, after the completion of the secondary battery, it is preferable to use the non-facing portion 22BZ as the negative electrode active material layer 22B for recovering the negative electrode active material for analysis. Since the non-facing portion 22BZ hardly participates in the charge-discharge reaction, the state (composition, physical properties, etc.) of the negative electrode active material (porous carbon-reduced silicate glass) is likely to be maintained as it was during the formation of the negative electrode 22 without being affected by the charge-discharge reaction. Thereby, even when the secondary battery has been used, it is possible to stably and reproducibly examine whether the three types of physical properties are obtained.

[0151] (Separator) The separator 23 is an insulating porous film interposed between the positive electrode 21 and the negative electrode 22, and allows lithium ions to pass through while preventing contact (short circuit) between the positive electrode 21 and the negative electrode 22. This separator 23 contains a polymer compound such as polyethylene.

[0152] (Electrolyte solution) The electrolyte solution contains a solvent and an electrolyte salt, and is impregnated in each of the positive electrode 21, the negative electrode 22, and the separator 23.

[0153] The solvent contains any one or two or more of non-aqueous solvents (organic solvents), and the electrolyte solution containing the non-aqueous solvent is a so-called non-aqueous electrolyte solution. The non-aqueous solvents are esters and ethers, etc., and more specifically, carbonate-based compounds, carboxylic acid ester-based compounds, and lactone-based compounds, etc.

[0154] The carbonate-based compounds are cyclic carbonates and chain carbonates, etc. The cyclic carbonates are ethylene carbonate and propylene carbonate, etc., and the chain carbonates are dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate, etc. The carboxylic acid ester-based compounds are ethyl acetate, ethyl propionate, and ethyl trimethylacetate, etc. The lactone-based compounds are γ-butyrolactone and γ-valerolactone, etc. The ethers are, in addition to the above-mentioned lactone-based compounds, 1,2-dimethoxyethane, tetrahydrofuran, 1,3-dioxolane, and 1,4-dioxane, etc.

[0155] Also, the non-aqueous solvents are unsaturated cyclic carbonates, halogenated carbonates, sulfonic acid esters, phosphoric acid esters, acid anhydrides, nitrile compounds, and isocyanate compounds, etc. This is because the chemical stability of the electrolyte solution is improved.

[0156] Specifically, the unsaturated cyclic carbonates include vinylene carbonate, vinyl ethylene carbonate, methylene ethylene carbonate, etc. The halogenated carbonates include fluoroethylene carbonate, difluoroethylene carbonate, etc. The sulfonic acid esters include propane sultone, propene sultone, etc. The phosphate esters include trimethyl phosphate, etc. The acid anhydrides include cyclic carboxylic acid anhydrides, cyclic disulfonic acid anhydrides, cyclic carboxylic acid sulfonic acid anhydrides, etc. The cyclic carboxylic acid anhydrides include succinic anhydride, glutaric anhydride, maleic anhydride, etc. The cyclic disulfonic acid anhydrides include ethanedisulfonic anhydride, propanedisulfonic anhydride, etc. The cyclic carboxylic acid sulfonic acid anhydrides include sulfobenzoic anhydride, sulfopropionic anhydride, sulfobutyric anhydride, etc. The nitrile compounds include acetonitrile, succinonitrile, etc. The isocyanate compounds include hexamethylene diisocyanate, etc.

[0157] The electrolyte salt contains any one or two or more of light metal salts such as lithium salts. The lithium salts include lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium trifluoromethanesulfonate (LiCF3SO3), lithium bis(fluorosulfonyl)imide (LiN(FSO2)2), lithium bis(trifluoromethanesulfonyl)imide (LiN(CF3SO2)2), lithium tris(trifluoromethanesulfonyl)methide (LiC(CF3SO2)3), and lithium bis(oxalato)borate (LiB(C2O4)2), etc. The content of the electrolyte salt is not particularly limited, but is 0.3 mol / kg to 3.0 mol / kg with respect to the solvent. This is because high ionic conductivity can be obtained.

[0158] [Positive electrode lead and negative electrode lead] As shown in FIG. 7, the positive electrode lead 31 is a positive electrode terminal connected to the positive electrode 21, and more specifically, it is connected to the positive electrode current collector 21A. This positive electrode lead 31 is led out from the inside to the outside of the exterior film 10 and contains a conductive material such as aluminum. The shape of the positive electrode lead 31 is not particularly limited, but specifically, it is either a thin plate shape or a mesh shape or the like.

[0159] As shown in FIG. 7, the negative electrode lead 32 is a negative electrode terminal connected to the negative electrode 22, and more specifically, it is connected to the negative electrode current collector 22A. This negative electrode lead 32 is led out from the inside to the outside of the exterior film 10 and contains a conductive material such as copper. Here, the leading-out direction of the negative electrode lead 32 is the same as that of the positive electrode lead 31. Note that the details regarding the shape of the negative electrode lead 32 are the same as the details regarding the shape of the positive electrode lead 31.

[0160] <2-2. Operation> During charging of the secondary battery, in the battery element 20, lithium is released from the positive electrode 21 and the lithium is occluded in the negative electrode 22 through the electrolyte. On the other hand, during discharging of the secondary battery, in the battery element 20, lithium is released from the negative electrode 22 and the lithium is occluded in the positive electrode 21 through the electrolyte. During these charging and discharging processes, lithium is occluded and released in an ionic state.

[0161] <2-3. Manufacturing Method> When manufacturing the secondary battery, the positive electrode 21 and the negative electrode 22 are produced and the electrolyte is prepared according to the procedure described below, and then the secondary battery is produced using the positive electrode 21, the negative electrode 22, and the electrolyte.

[0162] [Production of Positive Electrode] First, a paste-like positive electrode mixture slurry is prepared by introducing a mixture (positive electrode mixture) in which a positive electrode active material, a positive electrode binder, a positive electrode conductive agent, etc. are mixed with each other into a solvent. This solvent may be an aqueous solvent or an organic solvent. Subsequently, the positive electrode mixture slurry is applied to both sides of the positive electrode current collector 21A to form the positive electrode active material layer 21B. After that, the positive electrode active material layer 21B may be compression-molded using a roll press or the like. In this case, the positive electrode active material layer 21B may be heated, or the compression molding may be repeated a plurality of times. Thereby, since the positive electrode active material layer 21B is formed on both sides of the positive electrode current collector 21A, the positive electrode 21 is produced.

[0163] [Fabrication of Negative Electrode] The negative electrode 22 is formed by the same procedure as the above-described procedure for fabricating the positive electrode 21. Specifically, first, a paste-like negative electrode mixture slurry is prepared by introducing a mixture (negative electrode mixture) in which a negative electrode active material, a negative electrode binder, a negative electrode conductive agent, etc. are mixed with each other into a solvent. Subsequently, the negative electrode mixture slurry is applied to both sides of the negative electrode current collector 22A to form the negative electrode active material layer 22B. After that, the negative electrode active material layer 22B may be compression-molded. Thereby, since the negative electrode active material layer 22B is formed on both sides of the negative electrode current collector 22A, the negative electrode 22 is produced.

[0164] [Fabrication of Electrolyte] An electrolyte salt is introduced into a solvent. This solvent may be an aqueous solvent or an organic solvent. Thereby, since the electrolyte salt is dispersed or dissolved in the solvent, the electrolyte is prepared.

[0165] [Assembly of Secondary Battery] First, the positive electrode lead 31 is connected to the positive electrode current collector 21A of the positive electrode 21 using a welding method or the like, and the negative electrode lead 32 is connected to the negative electrode current collector 22A of the negative electrode 22 using a welding method or the like.

[0166] Subsequently, after laminating the positive electrode 21 and the negative electrode 22 with each other via the separator 23, a wound body is produced by winding the positive electrode 21, the negative electrode 22, and the separator 23. This wound body has the same configuration as that of the battery element 20, except that the positive electrode 21, the negative electrode 22, and the separator 23 are not impregnated with the electrolytic solution. Subsequently, the wound body is pressed using a press or the like to mold the wound body into a flat shape.

[0167] Subsequently, after accommodating the wound body inside the recessed portion 10U, the outer packaging films 10 (fusion layer / metal layer / surface protection layer) are folded so that the outer packaging films 10 face each other. Subsequently, using a heat fusion method or the like, the outer peripheral edge portions of two sides of the facing outer packaging films 10 (fusion layer) are joined to each other to accommodate the wound body inside the bag-shaped outer packaging film 10.

[0168] Finally, after injecting the electrolytic solution inside the bag-shaped outer packaging film 10, the outer peripheral edge portions of the remaining one side of the outer packaging film 10 (fusion layer) are joined to each other using a heat fusion method or the like. In this case, a sealing film 41 is inserted between the outer packaging film 10 and the positive electrode lead 31, and a sealing film 42 is inserted between the outer packaging film 10 and the negative electrode lead 32. As a result, since the wound body is impregnated with the electrolytic solution, the battery element 20 is produced and the battery element 20 is sealed inside the bag-shaped outer packaging film 10, so that the secondary battery is assembled.

[0169] [Assembly of Secondary Battery] The assembled secondary battery is charged and discharged. Various conditions such as the environmental temperature, the number of charge and discharge cycles (cycle number), and the charge and discharge conditions can be arbitrarily set. As a result, a film is formed on the surfaces of the positive electrode 21 and the negative electrode 22, so that the state of the secondary battery is electrochemically stabilized. Thus, a laminated film type secondary battery using the outer packaging film 10 is completed.

[0170] [Operation and Effect of Secondary Battery]<2-4. Operation and Effect> According to this secondary battery, the negative electrode active material of the negative electrode 22 has the same configuration as the above-described configuration of the active material. In this case, for the same reasons as described for the active material, the negative electrode active material is likely to occlude and release lithium sufficiently and stably, and while the expansion and contraction are suppressed even when the charge and discharge reactions are repeated, the negative electrode active material is likely to continuously occlude and release lithium. Therefore, excellent charge and discharge characteristics and excellent swelling characteristics can be obtained.

[0171] In particular, if the secondary battery is a lithium-ion secondary battery, since a sufficient battery capacity can be stably obtained by utilizing the occlusion and release of lithium, a higher effect can be obtained.

[0172] Other operations and effects of this secondary battery are the same as those of the above-described other operations and effects of the active material.

[0173] <3. Modification Example> Next, modification examples of the above-described active material and secondary battery will be described. The configurations of the active material and the secondary battery can be appropriately changed as described below. However, any two or more of the series of modification examples described below may be combined with each other.

[0174] [Modification Example 1] In FIG. 1, the active material 100 includes a coating portion 102 together with the central portion 101. However, the active material 100 may include only the central portion 101 and not include the coating portion 102. In this case, after manufacturing the active material 100 including the central portion 101 and the coating portion 102, the coating portion 102 may be removed. Also in this case, since the electrode reactant can be occluded and released in the active material 100 (central portion 101), the same effects can be obtained.

[0175] However, as described above, in order to improve the electron conductivity of the active material 100, it is preferable that the active material 100 includes the coating portion 102 together with the central portion 101.

[0176] [Modification Example 2] The separator 23, which is a porous membrane, was used. However, although not specifically illustrated here, a laminated separator including a polymer compound layer may also be used.

[0177] Specifically, the laminated separator includes a porous membrane having a pair of surfaces and a polymer compound layer disposed on one or both surfaces of the porous membrane. This is because the adhesion of the separator to each of the positive electrode 21 and the negative electrode 22 is improved, suppressing the displacement (warping) of the battery element 20. As a result, even if a decomposition reaction of the electrolytic solution or the like occurs, swelling of the secondary battery is suppressed. The polymer compound layer contains a polymer compound such as polyvinylidene fluoride. This is because polyvinylidene fluoride and the like are excellent in physical strength and electrochemically stable.

[0178] Note that one or both of the porous membrane and the polymer compound layer may contain any one or two or more of a plurality of insulating particles. This is because when the secondary battery generates heat, the plurality of insulating particles dissipate heat, improving the safety (heat resistance) of the secondary battery. The insulating particles contain any one or two or more of insulating materials such as inorganic materials and resin materials. Specific examples of the inorganic material include aluminum oxide, aluminum nitride, boehmite, silicon oxide, titanium oxide, magnesium oxide, and zirconium oxide. Specific examples of the resin material include acrylic resin and styrene resin.

[0179] When producing the laminated separator, a precursor solution containing a polymer compound, a solvent, etc. is prepared, and then the precursor solution is applied to one or both surfaces of the porous membrane. In this case, if necessary, a plurality of insulating particles may be added to the precursor solution.

[0180] Even in this case, since lithium ions can move between the positive electrode 21 and the negative electrode 22, the same effect can be obtained. In this case, in particular, as described above, since the warping of the battery element 20 is suppressed, a higher effect can be obtained.

[0181] [Modification Example 3] An electrolytic solution that is a liquid electrolyte was used. However, although not specifically illustrated here, an electrolyte layer that is a gel electrolyte may be used.

[0182] In the battery element 20 using the electrolyte layer, the positive electrode 21 and the negative electrode 22 are laminated on each other via the separator 23 and the electrolyte layer, and the positive electrode 21, the negative electrode 22, the separator 23, and the electrolyte layer are wound. This electrolyte layer is interposed between the positive electrode 21 and the separator 23 and is also interposed between the negative electrode 22 and the separator 23.

[0183] Specifically, the electrolyte layer contains a polymer compound together with the electrolytic solution, and the electrolytic solution is held by the polymer compound. This is because leakage of the electrolytic solution is prevented. The configuration of the electrolytic solution is as described above. The polymer compound includes polyvinylidene fluoride and the like. When forming the electrolyte layer, a precursor solution containing the electrolytic solution, the polymer compound, a solvent, etc. is prepared, and then the precursor solution is applied to one or both sides of each of the positive electrode 21 and the negative electrode 22.

[0184] Also in this case, since lithium ions can move between the positive electrode 21 and the negative electrode 22 via the electrolyte layer, the same effect can be obtained. In this case, as described above, since leakage of the electrolytic solution is prevented, a higher effect can be obtained.

[0185] [Modification Example 4] In FIG. 7, the secondary battery includes one positive electrode lead 31. However, the secondary battery may include two or more positive electrode leads 31. Also in this case, since the secondary battery can be energized using the positive electrode lead 31, the same effect can be obtained. In particular, when the number of positive electrode leads 31 increases, the electrical resistance of the battery element 20 decreases, so a higher effect can be obtained.

[0186] What has been described regarding the number of the positive electrode leads 31 also applies to the number of the negative electrode leads 32. That is, in FIG. 7, the secondary battery has one negative electrode lead 32, but the secondary battery may have two or more negative electrode leads 32. Also in this case, since the secondary battery can be energized by using the negative electrode lead 32, the same effects can be obtained. In particular, when the number of the negative electrode leads 32 increases, the electrical resistance of the battery element 20 decreases, so that higher effects can be obtained.

[0187] <4. Applications of the Secondary Battery> Next, the applications (application examples) of the above-described secondary battery will be described.

[0188] The applications (application examples) of the secondary battery are not particularly limited. The secondary battery used as a power source may be a main power source such as an electronic device and an electric vehicle, or an auxiliary power source. The main power source is a power source that is preferentially used regardless of the presence or absence of other power sources. The auxiliary power source is a power source used in place of the main power source or a power source that can be switched from the main power source.

[0189] Specific examples of the applications of the secondary battery are as follows. Electronic devices such as video cameras, digital still cameras, mobile phones, notebook personal computers, headphone stereos, portable radios, and portable information terminals. Storage devices such as backup power sources and memory cards. Electric tools such as electric drills and electric saws. Battery packs mounted on electronic devices and the like. Medical electronic devices such as pacemakers and hearing aids. Electric vehicles such as electric cars (including hybrid cars). Power storage systems such as household or industrial battery systems that store power for emergencies and the like. In these applications, one secondary battery may be used, or a plurality of secondary batteries may be used.

[0190] The battery pack may use single cells or assembled batteries. An electric vehicle is a vehicle that operates (runs) using a secondary battery as a driving power source, and may also be a hybrid vehicle that is equipped with a driving source other than the secondary battery. In a household power storage system, household electrical appliances and the like can be used by utilizing the power stored in the secondary battery that is the power storage source.

[0191] Here, a specific example regarding an application example of the secondary battery will be described. The configuration of the application example described below is merely an example and can be changed as appropriate.

[0192] FIG. 10 shows the block configuration of the battery pack. The battery pack described here is a battery pack (so-called soft pack) using one secondary battery, and is mounted on an electronic device typified by a smartphone.

[0193] As shown in FIG. 10, this battery pack includes a power source 51 and a circuit board 52. This circuit board 52 is connected to the power source 51 and includes a positive terminal 53, a negative terminal 54, and a temperature detection terminal 55.

[0194] The power source 51 includes one secondary battery. In this secondary battery, the positive electrode lead is connected to the positive terminal 53, and the negative electrode lead is connected to the negative terminal 54. Since this power source 51 can be connected to the outside via the positive terminal 53 and the negative terminal 54, it can be charged and discharged. The circuit board 52 includes a control unit 56, a switch 57, a thermistor element (PTC element) 58, and a temperature detection unit 59. However, the PTC element 58 may be omitted.

[0195] The control unit 56 includes a central processing unit (CPU), a memory, and the like, and controls the operation of the entire battery pack. This control unit 56 detects and controls the usage state of the power source 51 as necessary.

[0196] Note that when the voltage of the power supply 51 (secondary battery) reaches the overcharge detection voltage or the overdischarge detection voltage, the control unit 56 cuts off the switch 57 so that no charging current flows through the current path of the power supply 51. The overcharge detection voltage is not particularly limited, but specifically, it is 4.2V ± 0.05V. The overdischarge detection voltage is not particularly limited, but specifically, it is 2.4V ± 0.1V.

[0197] The switch 57 includes a charge control switch, a discharge control switch, a charging diode, a discharging diode, etc., and switches the connection between the power supply 51 and the external device according to an instruction from the control unit 56. This switch 57 includes a metal-oxide-semiconductor field-effect transistor (MOSFET), etc., and the charge and discharge current is detected based on the ON resistance of the switch 57.

[0198] The temperature detection unit 59 includes a temperature detection element such as a thermistor, measures the temperature of the power supply 51 using the temperature detection terminal 55, and outputs the measurement result of the temperature to the control unit 56. The measurement result of the temperature measured by the temperature detection unit 59 is used when the control unit 56 performs charge and discharge control during abnormal heat generation and when the control unit 56 performs correction processing during the calculation of the remaining capacity.

Example

[0199] The embodiments of the present technology will be described.

[0200] <Examples 1 to 8 and Comparative Examples 1 to 8> FIG. 11 shows the cross-sectional configuration of a coin-type secondary battery for testing. Hereinafter, the negative electrode active material was manufactured, and a coin-type secondary battery was fabricated using the negative electrode active material, and then the battery characteristics of the secondary battery were evaluated.

[0201] In a coin-shaped secondary battery, as shown in FIG. 11, a test electrode 201 is accommodated inside an outer cup 204, and a counter electrode 203 is accommodated inside an outer can 202. The test electrode 201 and the counter electrode 203 are laminated on each other with a separator 205 interposed therebetween, and the outer can 202 and the outer cup 204 are clamped to each other with a gasket 206. The electrolytic solution is impregnated in each of the test electrode 201, the counter electrode 203, and the separator 205.

[0202] [Manufacture of negative electrode active material] First, porous silicate glass as a raw material was prepared. The types of constituent elements (excluding oxygen and carbon) and the content (atomic %) of each constituent element of the porous carbon-reduced silicate glass synthesized using this porous silicate glass are as shown in Tables 1 and 2.

[0203] Note that the content of each constituent element was calculated based on the analysis results of the porous carbon-reduced silicate glass using SEM-EDX as described above. In this analysis using SEM-EDX, since the detection sensitivity of lithium is extremely low, the content of lithium becomes so small that it hardly affects the content of the second element. For this reason, the notation of the lithium content is omitted in Tables 1 and 2.

[0204]

Table 1

[0205]

Table 2

[0206] Subsequently, a mixture was obtained by mixing the porous silicate glass with a carbon source. As this carbon source, carbon black which is a carbon material (Examples 1 to 6 and Comparative Examples 1 to 8), polyimide which is a carbonizable organic substance (Example 7), and sucrose (Example 8) were used. In this case, the mixing ratio (weight ratio) was set to porous silicate glass:carbon source = 5:1.

[0207] Next, a binder solution (polyimide N-methyl-2-pyrrolidone solution, solid content = 18.6%) was added to the mixture, and the mixture was stirred (rotation speed = 2000 rpm, stirring time = 3 minutes) using a stirring device (a rotation-revolution mixer, Thinky Corporation, Awatori Rentaro) to prepare a slurry. In this case, the amount of binder solution added to the mixture was 10 wt% (solid content ratio).

[0208] Next, the slurry was dried in an oven (temperature = 80°C) to obtain a dried product, which was then pulverized to obtain pulverized flakes.

[0209] Next, the crushed flakes were placed inside the alumina boat, and then heated in an argon atmosphere using a vacuum gas replacement furnace (heating temperature = 950 ° C, heating time = 10 hours). In this case, the porous silicate glass was reduced (carbon reduction treatment) in the presence of a carbon source, and porous carbon-reduced silicate glass was synthesized, so that a central part containing the porous carbon-reduced silicate glass was formed. In addition, the surface of the central part was covered with decomposition products of the carbon source (organic decomposition carbon), etc., so that a coating part was formed. Thus, a flake-shaped negative electrode active material containing a central part and a coating part was obtained.

[0210] Finally, the flake-like negative electrode active material was pulverized using a mortar to obtain a powdered negative electrode active material, and the powdered negative electrode active material was then sieved using a mesh (53 μm).

[0211] When the state of the negative electrode active material was observed using a scanning electron microscope (SEM), it was found that the negative electrode active material did not melt and remained in powder form, even though the grinding frame was heated to a temperature (=950°C) higher than the glass transition temperature of the porous silicate glass (=approximately 700°C) during the carbon reduction treatment. This is thought to be because the center part containing the porous carbon-reduced silicate glass is covered by the coating part.

[0212] When the negative electrode active material was analyzed using X-ray diffraction analysis (XRD), a broad halo pattern was detected in the range where 2θ was 20° to 25°, despite the carbon reduction treatment of the porous silicate glass. Therefore, it was confirmed that the negative electrode active material (porous carbon-reduced silicate glass) was not crystallized.

[0213] Also, when the negative electrode active material was analyzed using Raman spectroscopy, distinct G-band and D-band were detected in the Raman spectrum. Therefore, it was confirmed that the central part was coated by the coating part containing carbon as a constituent element.

[0214] The results of analyzing the negative electrode active material using XPS are as shown in Table 2. In this case, based on the analysis results of the negative electrode active material (XPS spectrum of Si2p shown in Fig. 3) by the above-described procedure, the position of the apex XAT (binding energy: eV), the presence or absence of the shoulder XAS, the full width at half maximum of the peak XA (eV), and the area ratio S2 / S1 were examined.

[0215] The results of analyzing the negative electrode active material using Raman spectroscopy are as shown in Table 2. In this case, based on the analysis results of the negative electrode active material (Raman spectrum shown in Fig. 4) by the above-described procedure, the position of the apex RAT (Raman shift: cm -1 ) was examined.

[0216] When the negative electrode active material was analyzed using mercury intrusion porosimetry, in the analysis results of the negative electrode active material (pore size distribution shown in Fig. 5), a peak MA having an apex MAT was detected in the range where the pore diameter was 0.01 μm to 10 μm.

[0217] [Fabrication of Secondary Battery] According to the procedure described below, the test electrode 201 was fabricated, and after preparing the electrolytic solution, a coin-type secondary battery was fabricated using the test electrode 201 and the electrolytic solution.

[0218] (Fabrication of Test Electrode) Here, the test electrode 201 was made into a negative electrode. First, the above-mentioned negative electrode active material, a negative electrode binder precursor (a polyamic acid solution (polyimide precursor) U-Varnish-A manufactured by Ube Industries, Ltd.), and two types of negative electrode conductive agents (carbon powder KS6 manufactured by TIMCAL and acetylene black Denka Black (registered trademark) manufactured by Denka Co., Ltd.) were mixed with each other to obtain a negative electrode mixture. In this case, the mixing ratio (mass ratio) was set as negative electrode active material:negative electrode binder precursor:two types of negative electrode conductive agents = 7:0.5:1:0.25. Subsequently, after the negative electrode mixture was put into a solvent (N-methyl-2-pyrrolidone, an organic solvent), the solvent was stirred to prepare a paste-like negative electrode mixture slurry.

[0219] Subsequently, using a coating device, the negative electrode mixture slurry was applied to one side of a negative electrode current collector (a copper foil with a thickness of 15 μm), and then the negative electrode mixture slurry was heated and dried (heating temperature = 425°C) in a vacuum firing furnace. As a result, a negative electrode binder (polyimide) was synthesized, and a negative electrode active material layer containing the negative electrode active material, the negative electrode binder, and the negative electrode conductive agent was formed. Finally, after the negative electrode current collector with the negative electrode active material layer formed thereon was punched into a disc shape (outer diameter = 15 mm), the negative electrode active material layer was compression-molded using a roll press machine. Thus, the test electrode 201, which is a negative electrode, was fabricated.

[0220] Note that for comparison, the test electrode 201 was fabricated by the same procedure except that another negative electrode active material (silicon monoxide (SiO)) was used instead of the above-mentioned negative electrode active material (Comparative Example 8).

[0221] (Preparation of the counter electrode) As the counter electrode 203, a lithium metal plate was used. In this case, a lithium metal foil was punched into a disc shape (outer diameter = 15 mm).

[0222] (Preparation of the electrolyte) After adding an electrolyte salt (lithium hexafluorophosphate) to a solvent (ethylene carbonate, fluoroethylene carbonate, and dimethyl carbonate), the solvent was stirred. In this case, the mixing ratio (mass ratio) of the solvents was ethylene carbonate:fluoroethylene carbonate:dimethyl carbonate = 40:10:50. The content of the electrolyte salt was 1 mol / kg with respect to the solvent.

[0223] (Assembly of the secondary battery) First, the test electrode 201 was accommodated inside the exterior cup 204, and the counter electrode 203 was accommodated inside the exterior can 202. Subsequently, the test electrode 201 accommodated inside the exterior cup 204 and the counter electrode 203 accommodated inside the exterior can 202 were laminated on each other via a separator 205 (a microporous polyethylene film with a thickness of 5 μm) impregnated with the electrolytic solution. As a result, a part of the electrolytic solution impregnated in the separator 205 was impregnated into each of the test electrode 201 and the counter electrode 203. Finally, in a state where the test electrode 201 and the counter electrode 203 were laminated on each other via the separator 205, the exterior can 202 and the exterior cup 204 were clamped to each other via a gasket 206. Thus, since the test electrode 201, the counter electrode 203, the separator 205, and the electrolytic solution were encapsulated by the exterior can 202 and the exterior cup 204, a coin-type secondary battery was assembled.

[0224] (Stabilization of the secondary battery) The secondary battery was charged and discharged for 1 cycle in a normal temperature environment (temperature = 23°C). During charging, it was first charged at a constant current with a current of 0.1C until the voltage reached 4.2V, and then charged at a constant voltage with a voltage of 4.2V until the current reached 0.05C. During discharging, it was discharged at a constant current with a current of 0.1C until the voltage reached 2.5V. 0.1C is the current value at which the battery capacity (theoretical capacity) can be completely discharged in 10 hours, and 0.05C is the current value at which the battery capacity can be completely discharged in 20 hours. Thus, the coin-type secondary battery was completed.

[0225] [Evaluation of battery characteristics] When evaluating the charge-discharge characteristics as the battery characteristics of the secondary battery, the results shown in Table 2 were obtained. Here, as the charge-discharge characteristics, the charge characteristics, discharge characteristics, and cycle characteristics were examined.

[0226] When examining the charge-discharge characteristics, first, the secondary battery was charged in a normal temperature environment (temperature = 23°C), and the charge capacity (mAh) of the first cycle was measured. Thereby, based on the weight (g) of the negative electrode active material, the charge capacity per unit weight (mAh / g), which is an index for evaluating the charge characteristics, was calculated.

[0227] Subsequently, the secondary battery in the charged state was discharged in the same environment, and the discharge capacity (mAh) of the first cycle was measured. Thereby, based on the weight (g) of the negative electrode active material, the discharge capacity per unit weight (mAh / g), which is an index for evaluating the discharge characteristics, was calculated.

[0228] Subsequently, the secondary battery was repeatedly charged and discharged in the same environment until the number of cycles reached 100 cycles, and the discharge capacity (mAh) of the 100th cycle was measured. Finally, based on the calculation formula of capacity retention rate (%) = (discharge capacity of the 100th cycle / discharge capacity of the first cycle) × 100, the capacity retention rate, which is an index for evaluating the cycle characteristics, was calculated. The charge-discharge conditions were the same as those at the time of stabilization of the secondary battery.

[0229] [Discussion] As is clear from Table 1 and Table 2, the charge-discharge characteristics (charge characteristics, discharge characteristics, and cycle characteristics) varied significantly depending on the composition and physical properties of the negative electrode active material.

[0230] Specifically, when the following conditions are satisfied regarding the composition of the negative electrode active material and the analysis results of the negative electrode active material (Si2p XPS spectrum and Raman spectrum) using XPS and Raman spectroscopy respectively (Examples 1 to 8), high charge capacity, high discharge capacity, and high capacity retention rate were obtained regardless of the type of carbon source, as compared with the cases where those conditions were not satisfied (Comparative Examples 1 to 7).

[0231] Conditions regarding the composition of the negative electrode active material: The negative electrode active material contains silicon, oxygen, a first element, a second element, and a third element as constituent elements. The content of silicon in all constituent elements (excluding oxygen and carbon) is 60 atomic % to 98 atomic %, the content of the first element in all constituent elements is 1 atomic % to 25 atomic %, the content of the second element in all constituent elements is 1 atomic % to 34 atomic %, and the content of the third element in all constituent elements is 0 atomic % to 6 atomic %.

[0232] Conditions regarding the analysis results of the negative electrode active material: In the XPS spectrum (Si2p) measured using XPS, a peak XA having a vertex XAT and a shoulder XAS shown in FIG. 3 (the position of the vertex XAT is within the range where the binding energy is 102 eV to 105 eV) is detected (First Physical Property). Also, in the Raman spectrum measured using Raman spectroscopy, a peak RA having a vertex RAT shown in FIG. 4 (the position of the vertex RAT is within the range where the Raman shift is 435 cm -1 ~465 cm -1 ) is detected (Second Physical Property).

[0233] In particular, when the above-described conditions regarding the composition of the negative electrode active material are satisfied and the above-described conditions regarding the analysis results of the negative electrode active material are satisfied, when the full width at half maximum is 4.0 eV or more, or the area ratio S2 / S1 is 0.85 or more, sufficient charge capacity and sufficient discharge capacity are obtained, and a high capacity retention rate is obtained.

[0234] In addition, when the above-described conditions regarding the composition of the negative electrode active material are satisfied and the above-described conditions regarding the analysis results of the negative electrode active material are satisfied, substantially equivalent performance was obtained as compared with the case where an existing other negative electrode active material (SiO) was used (Comparative Example 8).

[0235] Specifically, when a negative electrode active material satisfying the above-described conditions regarding the composition and analysis results was used, the charge capacity and the discharge capacity each decreased as compared with the case where other negative electrode active materials were used. However, each of the charge capacity and the discharge capacity became sufficiently high within an acceptable range.

[0236] Moreover, when a negative electrode active material satisfying the above-described conditions regarding the composition and analysis results was used, the capacity retention rate increased significantly as compared with the case where other negative electrode active materials were used.

[0237] Therefore, when a negative electrode active material satisfying the above-described conditions regarding the composition and analysis results was used, the capacity retention rate was remarkably improved while ensuring the charge capacity and the discharge capacity each as compared with the case where other negative electrode active materials were used.

[0238] <Examples 9 and 10 and Comparative Examples 9 and 10> As shown in Table 3, except that two types of diatomaceous earths (diatomaceous earth 1 and 2) which are porous silicate glasses satisfying the above-described conditions regarding the composition and analysis results were used as raw materials to synthesize porous carbon-reduced silicate glass, a secondary battery was fabricated in the same procedure, and then the battery characteristics of the secondary battery were evaluated. In this case, polyimide was used as the carbon source.

[0239] Diatomaceous earth 1 has a plurality of pores, and the composition (weight %) of the main components of the diatomaceous earth 1 is SiO2 = 91.1 wt%, Al2O3 = 4.0 wt%, CaO = 0.5 wt%, Fe2O3 = 1.3 wt%, Na2O + K2O = 1.1 wt%, and others = 1.0 wt% or less.

[0240] The diatomaceous earth 2 has a plurality of pores, and the composition (by weight %) of the main components of the diatomaceous earth 2 is SiO2 = 89.5% by weight, Al2O3 = 4.0% by weight, CaO = 0.5% by weight, Fe2O3 = 1.3% by weight, Na2O + K2O = 3.3% by weight, and the others = 1.0% by weight or less.

[0241] Based on the analysis results (pore distribution shown in Fig. 5) of the negative electrode active material containing the porous carbon-reduced silicate glass formed using the porous silicate glass, the position MAT of the peak MA (pore diameter (μm)) is as shown in Table 3.

[0242] For comparison, a secondary battery was fabricated by the same procedure except that two types of silicate glasses (silicate glass 1, 2), which are non-porous silicate glasses satisfying the above-described composition and analysis result conditions, were used as raw materials to form non-porous carbon-reduced silicate glass, and then the battery characteristics of the secondary battery were evaluated.

[0243] The composition of the silicate glass 1 is the same as that of the diatomaceous earth 1 except that it does not have a plurality of pores.

[0244] The silicate glass 2 does not have a plurality of pores, and the composition (by weight %) of the main components of the silicate glass 2 is SiO2 = 90.0% by weight, Al2O3 = 4.0% by weight, BaO = 2.0% by weight, Fe2O3 = 3.0% by weight, and the others = 1.0% by weight or less.

[0245] The analysis results (pore distribution shown in Fig. 5) of the negative electrode active material containing the non-porous carbon-reduced silicate glass formed using the non-porous silicate glass are as shown in Table 3.

[0246] Here, as the battery characteristics, the swelling characteristics (swelling characteristics of the test electrode 201) were also evaluated together with the above-described charging characteristics (charging capacity (mAh / g)).

[0247] When examining the swelling characteristics, first, after fabricating the test electrode 201, the thickness of the negative electrode active material layer (thickness before charging) was measured using a laser thickness gauge. In this case, after measuring the thickness of the test electrode 201, the thickness of the negative electrode active material layer was obtained by subtracting the thickness of the negative electrode current collector from the thickness of the test electrode 201. Also, the thickness of the negative electrode active material layer was determined three times at three arbitrarily different locations, and the average value of the three measured values was calculated.

[0248] Subsequently, following the above-described procedure, after fabricating a secondary battery using the test electrode 201, the secondary battery was charged. In this case, the secondary battery was charged at a current of 0.2C until it reached a fully charged state. 0.2C is the current value at which the battery capacity can be completely discharged in 5 hours.

[0249] Subsequently, the test electrode 201 was recovered by disassembling the charged secondary battery. Subsequently, the test electrode 201 was washed using a solvent (dimethyl carbonate, an organic solvent) to remove the electrolyte solution and the like adhering to the surface of the test electrode 201, and then the test electrode 201 was dried (drying temperature = 50°C and drying time = 15 minutes). Subsequently, following the above-described procedure, the thickness of the negative electrode active material layer (thickness after charging) was measured again.

[0250] Finally, based on the formula for the expansion rate (%) = [(thickness after charging - thickness before charging) / thickness before charging] × 100, the expansion rate, which is an index for evaluating the swelling characteristics, was calculated.

[0251]

Table 3

[0252] As shown in Table 3, when non-porous carbon-reduced silicate glass was used (Comparative Examples 9 and 10), a high charge capacity was obtained, but the expansion rate increased significantly.

[0253] On the other hand, when using porous carbon-reduced silicate glass (Examples 9 and 10), a charge capacity almost equivalent to that obtained when using non-porous carbon-reduced silicate glass (Comparative Examples 9 and 10) was obtained, while the expansion rate decreased significantly. More specifically, when using porous carbon-reduced silicate glass, a high charge capacity exceeding 900 mAh / g was obtained, and the expansion rate was almost halved.

[0254] [Summary] From the results shown in Tables 1 to 3, when the above-described conditions regarding the composition of the negative electrode active material are satisfied and the above-described conditions (the first physical property, the second physical property, and the third physical property) regarding the analysis results of the negative electrode active material are satisfied, the charge and discharge characteristics (charge characteristics, discharge characteristics, and cycle characteristics) are improved while the swelling characteristics are ensured. Therefore, excellent charge and discharge characteristics and excellent swelling characteristics were obtained in the secondary battery.

[0255] As described above, the present technology has been described with one embodiment and examples, but the configuration of the present technology is not limited to the configuration described in one embodiment and examples, and thus can be variously modified.

[0256] Although the battery structure of the secondary battery has been described in the case of being a laminate film type and a coin type, the type of the battery structure is not particularly limited. Specifically, the battery structure may be a cylindrical type, a square type, a button type, or the like.

[0257] Also, although the element structure of the battery element has been described in the case of being a wound type, the type of the element structure is not particularly limited. Specifically, the element structure may be a stacked type in which electrodes (a positive electrode and a negative electrode) are stacked, a ninety-nine-fold type in which the electrodes are folded in a zigzag manner, or others.

[0258] Furthermore, although the electrode reactant has been described in the case where it is lithium, the type of the electrode reactant is not particularly limited. Specifically, as described above, the electrode reactant may be another alkali metal such as sodium and potassium, or an alkaline earth metal such as beryllium, magnesium, and calcium. In addition, the electrode reactant may be another light metal such as aluminum.

[0259] The effects described in this specification are merely illustrative, and thus the effects of the present technology are not limited to the effects described in this specification. Therefore, other effects may be obtained with respect to the present technology.

Claims

1. Silicon, oxygen, a first element containing at least one of boron and phosphorus, a second element containing at least one of an alkali metal element, a transition element, and a representative element (excluding the silicon, oxygen, boron, phosphorus, alkali metal element, and alkaline earth metal element), a third element containing the alkaline earth metal element, and containing as constituent elements, the content of the silicon in all constituent elements excluding the oxygen and carbon is 60 atomic % or more and 98 atomic % or less, the content of the first element in all constituent elements is 1 atomic % or more and 25 atomic % or less, the content of the second element in all constituent elements is 1 atomic % or more and 34 atomic % or less, the content of the third element in all constituent elements is 0 atomic % or more and 6 atomic % or less, In the XPS spectrum of Si2p measured using X-ray photoelectron spectroscopy (XPS: X-ray Photoelectron Spectroscopy) (the horizontal axis is the binding energy (eV) and the vertical axis is the spectrum intensity), a first peak having a vertex within the range where the binding energy is 102 eV or more and 105 eV or less and having a shoulder on the side where the binding energy is smaller than the vertex is detected, In the Raman spectrum measured using Raman spectroscopy (the horizontal axis is the Raman shift (cm-1) and the vertical axis is the spectrum intensity), a second peak having a vertex within the range where the Raman shift is 435 cm-1 or more and 465 cm-1 or less is detected, having a plurality of pores, and in the pore size distribution measured using mercury intrusion porosimetry (the horizontal axis is the pore diameter (μm) of the pores and the vertical axis is the change rate of the mercury intrusion amount), a third peak having a vertex within the range where the pore diameter is 0.01 μm or more and 10 μm or less is detected, an active material.

2. The full width at half maximum of the first peak is 4.0 eV or more. The active material according to claim 1.

3. When the first peak is decomposed into a Si0 peak, a Si1+ peak, a Si2+ peak, a Si3+ peak, and a Si4+ peak, the ratio S2 / S1 of the sum S2 of the areas of the Si0 peak, the Si1+ peak, the Si2+ peak, and the Si3+ peak to the area S1 of the Si4+ peak is 0.85 or more. The active material according to claim 1 or claim 2.

4. A central part that includes the silicon, the oxygen, the first element, the second element, and the third element as constituent elements, and in which the first peak is detected in the XPS spectrum and the second peak is detected in the Raman spectrum, A coating part that covers at least a part of the surface of the central part and includes carbon as a constituent element, and the central part has the plurality of pores. The active material according to any one of claims 1 to 3.

5. Each of the central part and the coating part has the plurality of pores. The active material according to claim 4.

6. An electrode including the active material according to any one of claims 1 to 5.

7. A positive electrode, A negative electrode including the active material according to any one of claims 1 to 5, an electrolytic solution, and

8. A secondary battery that is a lithium ion secondary battery, The secondary battery according to claim 7.

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