Active material, manufacturing method thereof, electrode, and secondary battery

Abstract

An active material according to the present invention contains, as constituent elements: lithium; silicon; oxygen; a first element including at least one of boron and phosphorus; a second element including at least one of an alkali metal element (excluding lithium), a transition element, and a typical element (excluding lithium, silicon, oxygen, boron, phosphorus, an alkali metal element, and an alkaline-earth metal element); and a third element including an alkaline-earth metal element. The content of silicon in all constituent elements excluding lithium, oxygen, and carbon is 60-98 atomic%. The content of the first element in all constituent elements is 1-15 atomic%. The content of the second element in all constituent elements is 1-34 atomic%. The content of the third element in all constituent elements is 0-6 atomic%. In an XPS spectrum (binding energy (eV) on the horizontal axis and spectral intensity on the vertical axis) of Si2p as measured by using X-ray photoelectron spectroscopy (XPS), a first peak having an apex in a binding energy range of 100-102 eV is detected. In a Raman spectrum (Raman shift (cm-1) on the horizontal axis and spectral intensity on the vertical axis) as measured by using Raman spectroscopy, a second peak having an apex in a Raman shift range of 600 cm-1 to 640 cm-1, inclusive, is detected.

Description

[Technical Field]

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

[0002] A wide variety of electronic devices, such as mobile phones, are becoming widespread. Therefore, secondary batteries are being developed as a power source that is compact, lightweight, and has a high energy density. These secondary batteries contain electrodes (positive and negative electrodes) and an electrolyte solution, and the electrodes contain active materials that participate in electrode reactions. Because the configuration of a secondary battery affects its characteristics, various studies have been conducted on the configuration of the secondary battery.

[0003] Specifically, silicon dioxide is heated to generate silicon oxide gas, and the silicon oxide gas is condensed to produce silicon oxide (SiO x ) powder has been obtained (see, for example, Patent Documents 1 and 2). In order to improve the cycle characteristics of secondary batteries using silicon oxide as the negative electrode active material, other elements have been 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, pyroxene silicate compounds have been used, and tin oxide (SnO x ) is used as a heat-reduced product (see, for example, Patent Documents 5 and 6). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 63-103815 [Patent Document 2] Japanese Patent Application Laid-Open No. 2007-290890 [Patent Document 3] Japanese Patent Application Laid-Open No. 2011-192453 [Patent Document 4] International Publication No. 2019 / 031518 Brochure [Patent Document 5] International Publication No. 2014 / 050086 Brochure [Patent Document 6] Japanese Patent Application Laid-Open No. 2014-232680 Summary of the Invention

[0005] Various studies have been conducted to improve the battery characteristics of secondary batteries, but the charge / discharge characteristics of the secondary batteries are still insufficient and there is room for improvement.

[0006] Therefore, there is a demand for an active material that can provide excellent charge / discharge characteristics, a method for producing the same, an electrode, and a secondary battery.

[0007] An active material according to one embodiment of the present technology comprises, as constituent elements, a first element including at least one of lithium, silicon, oxygen, boron, and phosphorus, a second element including at least one of an alkali metal element (excluding lithium), a transition element, and a typical element (excluding lithium, silicon, oxygen, boron, phosphorus, an alkali metal element, and an alkaline earth metal element), and a third element including an alkaline earth metal element. The silicon content of all constituent elements excluding lithium, oxygen, and carbon is 60 atomic % to 98 atomic %, the first element content of all constituent elements is 1 atomic % to 15 atomic %, the second element content of all constituent elements is 1 atomic % to 34 atomic %, and the third element content of all constituent elements is 0 atomic % to 6 atomic %. In the XPS spectrum of Si2p measured using X-ray photoelectron spectroscopy (XPS), the horizontal axis represents binding energy (eV) and the vertical axis represents spectral intensity. A first peak is detected within the binding energy range of 100 eV to 102 eV. In the Raman spectrum measured using Raman spectroscopy, the horizontal axis represents Raman shift (cm). -1 ) and the vertical axis is the spectral intensity), the Raman shift is 600 cm -1 More than 640cm -1 A second peak is detected that has an apex within a range that is:

[0008] A method for producing an active material according to one embodiment of the present technology includes preparing a silicate glass containing, as constituent elements, a first element including silicon, oxygen, boron, and / or phosphorus; a second element including at least one of an alkali metal element (excluding lithium), a transition element, and a typical element (excluding lithium, silicon, oxygen, boron, phosphorus, an alkali metal element, and an alkaline earth metal element); and a third element including an alkaline earth metal element; mixing the silicate glass with a carbon source to form a mixture of the silicate glass and the carbon source; heating the mixture to form an active material precursor containing silicon, oxygen, the first element, the second element, and the third element as constituent elements; and electrochemically, chemically, or thermally adding lithium to the active material precursor to produce an active material containing lithium, silicon, oxygen, the first element, the second element, and the third element as constituent elements. The silicon content in this active material (all constituent elements excluding lithium, oxygen, and carbon) is 60 atomic % or more and 98 atomic % or less, the first element content in this active material is 1 atomic % or more and 15 atomic % or less, the second element content in this active material is 1 atomic % or more and 34 atomic % or less, and the third element content in this active material is 0 atomic % or more and 6 atomic % or less.

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

[0011] According to an embodiment of the present technology, the active material, electrode, or secondary battery contains lithium, silicon, oxygen, a first element, a second element, and a third element as constituent elements, and the contents of each constituent element satisfy the above-mentioned conditions. Furthermore, in the active material, a first peak is detected in the XPS spectrum of Si2p measured using X-ray photoelectron spectroscopy, and a second peak is detected in the Raman spectrum measured using Raman spectroscopy. Therefore, excellent charge / discharge characteristics can be obtained.

[0012] According to the method for producing an active material of one embodiment of the present technology, silicate glass containing silicon, oxygen, a first element, a second element, and a third element as constituent elements is mixed with a carbon source, the mixture of the silicate glass and the carbon source is heated to form an active material precursor, and lithium is added to the active material precursor electrochemically, chemically, or thermally to produce an active material, and the contents of each constituent element in the active material satisfy the above-mentioned conditions. Therefore, an active material with excellent charge / discharge characteristics can be obtained.

[0013] Note that the effects of the present technology are not necessarily limited to the effects described here, but may be any of a series of effects related to the present technology described below. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a cross-sectional view illustrating a configuration of an active material according to an embodiment of the present technology. [Figure 2] 1 is an example of an analysis result (XPS spectrum of Si2p) of an active material using XPS. [Figure 3] 1 shows an example of an analysis result (Raman spectrum) of an active material using Raman spectroscopy. [Figure 4] 1 is a flowchart illustrating a method for producing an active material according to an embodiment of the present technology. [Figure 5] 1 is a perspective view illustrating a configuration of an electrode and a secondary battery (laminate film type) according to an embodiment of the present technology. [Figure 6]FIG. 6 is a cross-sectional view illustrating the configuration of the battery element shown in FIG. [Figure 7] 7A and 7B are plan views illustrating the configurations of the positive electrode and the negative electrode shown in FIG. 6. [Figure 8] FIG. 1 is a block diagram illustrating a configuration of an application example of a secondary battery. [Figure 9] FIG. 1 is a cross-sectional view showing the configuration of a test secondary battery (coin type). DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, an embodiment of the present technology will be described in detail with reference to the drawings. The description will be made in the following order. 1. Active material (method of manufacturing active material) 1-1.Configuration 1-2.Physical properties 1-3. Manufacturing method 1-4. Action and effects 2. Electrodes and secondary batteries 2-1.Configuration 2-2.Operation 2-3. Manufacturing method 2-4. Action and effects 3. Variations 4. Uses of secondary batteries

[0016] <1. Active material (method for manufacturing active material)> First, an active material according to an embodiment of the present technology will be described. Note that 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 also be described below.

[0017] This active material is a substance that participates in an electrode reaction. More specifically, the active material is a material that can occlude and release an electrode reactant, 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 reactant in an ionic state. 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, and specific examples include secondary batteries and capacitors.

[0019] The type of electrode reactant is not particularly limited, but specifically includes alkali metals, alkaline earth metals, and light metals such as aluminum. Alkali metals include lithium, sodium, and potassium, and alkaline earth metals include beryllium, magnesium, and calcium.

[0020] <1-1.Configuration> First, the structure of the active material will be described. Fig. 1 shows the cross-sectional structure of an active material 100, which is an example of the active material.

[0021] Here, the active material 100 includes a central portion 101 and a coating portion 102, as shown in Fig. 1. Note that, in Fig. 1, for the sake of simplicity, the three-dimensional shape of the central portion 101 is shown as a sphere, but the three-dimensional shape of the central portion 101 is not particularly limited.

[0022] [Center] The central portion 101 is the main portion of the active material 100 that absorbs and releases an electrode reactant, and contains one or more types of lithium-containing carbon-reduced silicate glass.

[0023] This lithium-containing carbon-reduced silicate glass differs from ordinary silicate glass in that it is a material obtained by carbon-reducing and lithium-doping silicate glass, as will be described later. More specifically, silicate glass, which is a raw material, is carbon-reduced using a carbon source as a reducing agent to form carbon-reduced silicate glass, and then the carbon-reduced silicate glass is doped with lithium to form the lithium-containing carbon-reduced silicate glass.

[0024] In the lithium-containing carbon-reduced silicate glass formed using this carbon reduction treatment and lithium doping treatment, the use of a carbon source as a reducing agent promotes the reduction reaction of the raw material silicate glass, and the silicate glass is reduced (activated) so that it can sufficiently absorb and release electrode reactants. That is, in a normal reduction treatment using a reducing gas as a reducing agent, the silicate glass is hardly reduced, whereas in a special reduction treatment (carbon reduction treatment) using a carbon source as a reducing agent, the silicate glass is sufficiently reduced. As a result, the lithium-containing carbon-reduced silicate glass formed using the carbon-reduced silicate glass has physical properties that are different from those of silicate glass. The physical properties of the lithium-containing carbon-reduced silicate glass will be described in detail below.

[0025] Specifically, the lithium-containing carbon-reduced silicate glass contains lithium, silicon, oxygen, a first element, a second element, and a third element as constituent elements.

[0026] In this lithium-containing carbon-reduced silicate glass, the content of each constituent element among all the constituent elements excluding lithium, oxygen, and carbon is set to be within a predetermined range. The content of each constituent element represents what percentage of atoms the content of each constituent element corresponds to when the content of all the constituent elements excluding lithium, oxygen, and carbon is taken as 100 atomic %. Note that the content (atomic %) of each constituent element is calculated based on the analysis results of the lithium-containing carbon-reduced silicate glass using scanning electron microscopy / energy dispersive X-ray spectrometry (SEM: Scanning Electron Microscope / EDX: Energy dispersive X-ray spectrometry).

[0027] (Lithium) Lithium is an auxiliary constituent element of the lithium-containing carbon-reduced silicate glass. As described above, in the manufacturing process of the active material 100, after the carbon-reduced silicate glass is formed using the carbon reduction treatment, the carbon-reduced silicate glass is doped with lithium, and thus lithium is contained as a constituent element in the lithium-containing carbon-reduced silicate glass. That is, the lithium-containing carbon-reduced silicate glass is a material in which lithium is doped into the carbon-reduced silicate glass.

[0028] The content of lithium in the lithium-containing carbon-reduced silicate glass is not particularly limited and can be arbitrarily set.

[0029] (Silicon) Silicon is a main constituent element of the lithium-containing carbon-reduced silicate glass. The content of silicon among all the constituent elements excluding lithium, oxygen, and carbon is 60 atomic % to 98 atomic %.

[0030] (Oxygen) Oxygen is another main constituent element of the lithium-containing carbon-reduced silicate glass and can form an oxide with silicon. Therefore, the lithium-containing carbon-reduced silicate glass contains SiO x (where x satisfies 0 < x ≤ 2) as the main component. This SiOx In this case, nano-silicon is thought to be dispersed in amorphous silicon dioxide (SiO2). x In this case, it is believed that silicon capable of absorbing and releasing electrode reactants is present in the glass component.

[0031] (1st element) The first element includes one or more of the network-forming elements, more specifically, one or both of boron and phosphorus. When silicate glass includes the first element as a constituent element together with silicon and oxygen, the silicate glass is easily reduced by a carbon-based reduction treatment. This makes it easier to form a carbon-based reduced silicate glass easily and stably using a carbon-based reduction treatment.

[0032] The network former is a general term for a series of elements that can form a network former (network-forming oxide). Therefore, the first element may include germanium in addition to the above-mentioned boron and phosphorus.

[0033] The content of the first element in all constituent elements excluding lithium, oxygen, and carbon is 1 atomic % to 15 atomic % because this allows the silicate glass to be sufficiently reduced in the carbon reduction treatment.

[0034] When the first element contains two or more elements, the content of the first element is the sum of the contents of each element. This also applies to the content of the second element and the content of the third element, which will be described later, when there are two or more types of elements and the content is the sum of the contents of each constituent element.

[0035] (second element) The second element includes one or more of alkali metal elements, transition elements, and typical elements. This is because, unlike the third element described below, the second element, even if contained as a constituent element in silicate glass, has almost no effect on the reducibility of the silicate glass in a carbon reduction treatment. Therefore, even if the silicate glass contains the second element as a constituent element, the silicate glass is sufficiently reduced in a carbon reduction treatment.

[0036] The term "alkali metal elements" refers to a group of elements in Group 1 of the long-form periodic table. However, lithium is excluded from the alkali metal elements described here. Therefore, specific examples of alkali metal elements include sodium and potassium.

[0037] The transition element is a general term for a series of elements belonging to Groups 3 to 11 of the long-form periodic table, and specifically includes scandium, titanium, iron, zirconium, cerium, etc. However, the type of transition element is not particularly limited as long as it is an element belonging to Groups 3 to 11 of the long-form periodic table, and 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.

[0038] The term "typical element" refers to a series of elements belonging to Groups 1, 2, and 12 to 18 of the long-form periodic table. However, lithium, silicon, oxygen, boron, phosphorus, alkali metal elements, and alkaline earth metal elements are excluded from the typical elements described here. Therefore, specific examples of typical elements described here include aluminum, sulfur, chlorine, zinc, and bismuth. However, the type of typical element is not particularly limited as long as it is an element belonging to Groups 1, 2, and 12 to 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.

[0039] The content of the second element in all constituent elements excluding lithium, oxygen, and carbon is 1 atomic % to 34 atomic %. This is because even if the silicate glass contains the second element as a constituent element, the silicate glass can be sufficiently reduced in the carbon reduction treatment.

[0040] (3rd element) The third element is any constituent element of the lithium-containing carbon-reduced silicate glass, and therefore the lithium-containing carbon-reduced silicate glass may or may not contain the third element as a constituent element.

[0041] The third element includes one or more of the alkaline earth metal elements, which is a general term for a series of elements belonging to Group 2 of the long-form periodic table, specifically magnesium, calcium, strontium, and barium.

[0042] However, the content of the third element in all constituent elements excluding lithium, oxygen, and carbon is 0 atomic % to 6 atomic %.

[0043] The lower limit of the content of the third element is 0 atomic % because, as described above, the third element is an optional constituent element of the lithium-containing carbon-reduced silicate glass, and therefore the lithium-containing carbon-reduced silicate glass does not have to contain the third element as a constituent element.

[0044] On the other hand, the upper limit of the content of the third element is 6 atomic % because, as mentioned above, the third element affects the reducibility of silicate glass in carbon reduction treatment, and therefore the content of the third element must be within a range that does not affect the reducibility of silicate glass in carbon reduction treatment.

[0045] Specifically, when the content of the third element is greater than 6 atomic %, the amount of the third element present in the silicate glass is too large, and the silicate glass is hardly reduced in the carbon reduction treatment, so that carbon-reduced silicate glass is not substantially formed. On the other hand, when the content of the third element is 6 atomic % or less, the amount of the third element present in the silicate glass is appropriately suppressed, and the silicate glass is easily reduced in the carbon reduction treatment, so that carbon-reduced silicate glass is substantially formed.

[0046] [Coating] The covering portion 102 covers a part or the whole of the surface of the central portion 101. However, when the covering portion 102 covers a part of the surface of the central portion 101, a plurality of covering portions 102 may cover the surface of the central portion 101 at a plurality of locations that are spaced apart from one another.

[0047] The coating portion 102 is electrically conductive because it contains carbon as a constituent element. The reason is that the surface of the central portion 101 is covered with the electrically conductive coating portion 102, thereby improving the electronic conductivity of the active material 100 compared to when the surface of the central portion 101 is not covered with the coating portion 102. The material for forming the coating portion 102 is not particularly limited as long as it contains carbon as a constituent element.

[0048] Specifically, as will be described later, coating portion 102 is a coating formed by utilizing the thermal decomposition of the carbon source when a mixture of silicate glass and a reducing agent (carbon source) is heated in the active material production process (carbon reduction treatment) to coat the surface of core portion 101. In this case, coating portion 102 may contain the carbon source as it is, or may contain a decomposition product of the carbon source (organic decomposition carbon), or may contain both.

[0049] The thickness of the covering portion 102 is not particularly limited. This is because even if only a small amount of the covering portion 102 is present on the surface of the central portion 101, the electronic conductivity of the active material 100 is improved compared to when no covering portion 102 is present on the surface of the central portion 101.

[0050] <1-2. Physical properties> Next, a description will be given of the physical properties of the active material 100. Below, two types of physical properties (first physical property and second physical property) defined based on the analysis results of the active material 100 using X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy will be described in order.

[0051] [First physical property] 2 shows an example of an 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 represents binding energy (eV) and the vertical axis represents spectral intensity. However, the analysis result described here is the analysis result after argon ion sputtering (sputtering time = 1000 seconds).

[0052] In Figure 2, the XPS spectrum of lithium-containing carbon-reduced silicate glass (solid line) is shown, along with the XPS spectrum of silicate glass (dashed line). That is, by subjecting silicate glass for which the XPS spectrum (dashed line) is detected to a carbon reduction treatment and lithium doping treatment, lithium-containing carbon-reduced silicate glass for which the XPS spectrum (solid line) is detected can be obtained. Note that in Figure 2, the range of binding energies from 100 eV to 102 eV is shaded.

[0053] As shown in FIG. 2, the lithium-containing carbon-reduced silicate glass has physical properties different from those of silicate glass in the analysis results using XPS (shape of the XPS spectrum).

[0054] Specifically, a peak XA (first peak) is detected in the XPS spectrum (solid line) of the lithium-containing carbon-reduced silicate glass, and this peak XA has an apex XAT within the binding energy range of 100 eV to 102 eV.

[0055] In contrast, a peak XB is detected in the XPS spectrum (dashed line) for silicate glass. This peak XB does not have a vertex XBT within the binding energy range of 100 eV to 102 eV, but has a vertex XBT outside that range.

[0056] From these findings, the following trends can be derived from the analysis results (shape of the XPS spectrum) of the active material 100 using XPS. In the case of lithium-containing carbon-reduced silicate glass, the raw material silicate glass is sufficiently reduced using a carbon-reduction treatment, and the carbon-reduced carbon-reduced silicate glass is then doped with lithium, resulting in the detection of a peak XA having an apex XAT. In contrast, in the case of silicate glass, the raw material has not yet been subjected to a carbon-reduction treatment or a lithium-doping treatment, resulting in the detection of a peak XB having an apex XBT. Therefore, based on the results of the XPS analysis, it is possible to identify whether the object being analyzed is a lithium-containing carbon-reduced silicate glass or a silicate glass. Therefore, the lithium-containing carbon-reduced silicate glass formed using a carbon-reduction treatment and a lithium-doping treatment has physical properties different from those of silicate glass in that it has the first physical property related to XPS described above.

[0057] The procedure described here makes it possible to identify the material of center portion 101 of active material 100. That is, when center portion 101 is analyzed using XPS, if peak XA is detected, center portion 101 contains lithium-containing carbon-reduced silicate glass, whereas if peak XB is detected, center portion 101 contains silicate glass.

[0058] As described above, silicate glass is hardly reduced by a normal reduction treatment, and therefore, even if a normal reduction treatment is performed using silicate glass, the silicate glass is hardly reduced, and therefore peak XB should be obtained, but not peak XA.

[0059] [Second physical property] 3 shows an example of the analysis results (Raman spectrum) of the active material 100 using Raman spectroscopy to explain the second physical property. In this Raman spectrum, the horizontal axis is the Raman shift (cm -1 ) and the vertical axis represents the spectral intensity.

[0060] In Figure 3, the Raman spectrum (solid line) of lithium-containing carbon-reduced silicate glass is shown, along with the Raman spectrum (dashed line) of silicate glass. That is, by subjecting silicate glass from which the Raman spectrum (dashed line) is detected to carbon reduction treatment and lithium doping treatment, lithium-containing carbon-reduced silicate glass from which the Raman spectrum (solid line) is detected can be obtained. Note that in Figure 3, the Raman shift of the silicate glass from which the Raman spectrum (dashed line) is detected is 600 cm. -1 ~640cm -1 The range where

[0061] As shown in FIG. 3, the lithium-containing carbon-reduced silicate glass has physical properties different from those of silicate glass in the analysis results (shape of the Raman spectrum) using Raman spectroscopy.

[0062] Specifically, in the Raman spectrum (solid line) of the lithium-containing carbon-reduced silicate glass, a peak RA (second peak) is detected. This peak RA has a Raman shift of 600 cm -1 ~640cm -1 The vertex RAT is within the range.

[0063] In contrast, the Raman spectrum for silicate glass (dashed line) shows a peak RB, which occurs at a binding energy of 600 cm -1 ~640cm -1 For reference, the Raman spectrum of crystalline silicon has a bond energy of 510 cm -1 ~525cm -1 Peaks having an apex within the range

[0064] From these facts, the following tendency can be derived from the analysis results (shape of the Raman spectrum) of the active material 100 using Raman spectroscopy. In the lithium-containing carbon-reduced silicate glass, the raw material silicate glass is sufficiently reduced by carbon reduction treatment, and the carbon-reduced silicate glass is then doped with lithium. -1 ~640cm -1 A peak RA having an apex RAT within the range is detected. In contrast, in silicate glass, because the glass has not yet been subjected to carbon reduction treatment and lithium doping treatment, a peak RB having an apex RBT outside the above range is detected. Therefore, the lithium-containing carbon-reduced silicate glass formed using carbon reduction treatment and lithium doping treatment has physical properties different from those of silicate glass in that it has the second physical property related to Raman spectroscopy described above.

[0065] The procedure described here makes it possible to identify the material of center portion 101 of active material 100. That is, when center portion 101 is analyzed using Raman spectroscopy, if peak RA is detected, center portion 101 contains lithium-containing carbon-reduced silicate glass, whereas if peak RB is detected, center portion 101 contains silicate glass.

[0066] As described above, silicate glass is hardly reduced by a normal reduction treatment. Therefore, even if a normal reduction treatment is performed using silicate glass, the silicate glass is hardly reduced, and therefore, peak RA is not obtained, but peak RB is obtained.

[0067] [summary] For these reasons, in active material 100 in which central portion 101 contains lithium-containing carbon-reduced silicate glass, peak XA is detected in the XPS spectrum of Si2p measured using XPS (first physical property), and peak RA is detected in the Raman spectrum measured using Raman spectroscopy (second physical property). Therefore, when active material 100 (central portion 101) is analyzed using both XPS and Raman spectroscopy, if both of the above-mentioned peaks XA and RA are detected, active material 100 contains lithium-containing carbon-reduced silicate glass.

[0068] In contrast, if one or both of peaks XA and RA are not detected when active material 100 is analyzed using both XPS and Raman spectroscopy, then active material 100 does not contain lithium-containing carbon-reduced silicate glass.

[0069] The reason why active material 100 (central portion 101) containing lithium-containing carbon-reduced silicate glass has the first and second physical properties is as follows.

[0070] First, the reduction reaction proceeds more rapidly in lithium-containing carbon-reduced silicate glass than in silicate glass, so the above-mentioned SiO x As a result, the crystallinity of the glass material containing as a main component is optimized, which makes it easier for the active material 100 to occlude and release the electrode reactant sufficiently and stably, and also makes it easier for the active material 100 to continuously occlude and release the electrode reactant even when the electrode reaction is repeated.

[0071] Furthermore, since the lithium-containing carbon-reduced silicate glass contains lithium as a constituent element, i.e., the lithium-containing carbon-reduced silicate glass is doped with lithium in advance (so-called pre-doped), the irreversible capacity decreases during the first electrode reaction using lithium as the electrode reactant.

[0072] <1-3. Manufacturing method> Next, a description will be given of a method for manufacturing the active material 100. Fig. 4 shows a flow chart for explaining the method for manufacturing the active material 100. Note that the step numbers in parentheses described below correspond to the step numbers shown in Fig. 4.

[0073] When manufacturing the active material 100, first, powdered silicate glass, which is a raw material, is prepared (step S1). In this case, silicate glass that has already been synthesized may be obtained by purchasing or the like, or silicate glass may be synthesized by oneself.

[0074] This silicate glass has almost the same structure as the lithium-containing, carbon-reduced silicate glass, except that it does not have the first and second physical properties described above because it has not yet been subjected to carbon reduction treatment or lithium doping treatment. That is, the silicate glass contains silicon, oxygen, a first element, a second element, and a third element as constituent elements. Details of the first element, the second element, and the third element are as described above.

[0075] In addition, when synthesizing silicate glass, silicon dioxide (SiO2) is mixed with the respective sources of the first, second, and third elements, and then the mixture is heated. Conditions such as the heating temperature and heating time can be set as desired.

[0076] The supply sources are compounds containing each of the constituent elements. The type of compound is not particularly limited, but specific examples include oxides of each of the constituent elements. That is, the supply sources of the first element include boron trioxide (BO) and phosphorus pentoxide (PO). The supply sources of the second element include sodium oxide (NaO), potassium oxide (KO), scandium oxide (ScO), titanium oxide (TiO), zirconium oxide (ZrO), cerium oxide (CeO), hafnium oxide (HfO), tantalum oxide (TaO), tungsten oxide (WO), aluminum oxide (AlO), phosphorus pentasulfide (PS), lithium sulfide (LiS), magnesium sulfide (MgS), silicon tetrachloride (SiCl), zinc oxide (ZnO), bismuth oxide (BiO), and antimony oxide (SbO). Sources of the tertiary element include magnesium oxide (MgO), calcium oxide (CaO), strontium oxide (SrO) and barium oxide (BaO).

[0077] This causes silicon dioxide to form a solid solution with the respective supply sources of the first, second, and third elements, forming a glass body containing silicon, oxygen, the first, second, and third elements as constituent elements, thereby synthesizing silicate glass.

[0078] After preparing silicate glass, the silicate glass is mixed with a carbon source to obtain a mixture (step S2). The carbon source is a general term for materials that can serve as a carbon supply source, and specifically refers to one or both of a carbon material and a carbonizable organic substance. That is, the carbon source may be a carbon material alone, a carbonizable organic substance alone, or both.

[0079] Carbon materials include non-fibrous carbon and fibrous carbon. Non-fibrous carbon includes carbon black, and fibrous carbon includes carbon nanotubes and carbon nanofibers. Carbonizable organic materials include sugars and polymeric compounds. Sugars include sucrose, maltose, and cellulose. Polymeric compounds include polyimide, polyvinylidene fluoride, polymethyl methacrylate, polyvinylpyrrolidone, polyvinyl alcohol, and polyacrylic acid. This is because silicate glass is sufficiently reduced in the carbon reduction process. Also, as described below, a coating portion 102 with sufficient conductivity can be easily and stably formed using a carbon source.

[0080] In this case, the mixture may be stirred using a stirring device, and conditions such as the stirring speed and stirring time can be set arbitrarily.

[0081] 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 binder is not particularly limited, but specifically, it is one or more types of polymer compounds such as polyvinylidene fluoride, polyimide, and polymethyl methacrylate. The type of solvent is not particularly limited, but specifically, it is one or more types of organic solvents such as N-methyl-2-pyrrolidone. A binder solution in which the binder is dissolved in a solvent in advance may also be used.

[0082] Next, the mixture is heated (step S3). In this case, one or more types of heating equipment such as an oven are used. The heating temperature, heating time, and other conditions can be set arbitrarily. Specifically, the heating temperature is 700°C to 1400°C, and the heating time is 1 hour to 20 hours.

[0083] When a mixture containing a binder is used, the mixture may be heated in two stages. Specifically, the mixture is first preheated to dry it. The preheating conditions 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. Next, the dried mixture is pulverized. Finally, the pulverized mixture is subjected to main heating. The main heating conditions 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.

[0084] This allows the silicate glass to be subjected to carbon reduction treatment, so that the silicate glass is sufficiently reduced using a carbon source as a reducing agent. x Since the crystalline state of SiO x As a result, a carbon-reduced silicate glass containing the carbon-reduced silicate glass as a main component is synthesized. Thus, a central portion 101 containing the carbon-reduced silicate glass is obtained.

[0085] Moreover, as described above, in the carbon reduction process, carbon (organic matter decomposition carbon) is deposited on the surface of the core 101 by utilizing the thermal decomposition of the carbon source used as the reducing agent, and the coating portion 102 containing that carbon as a constituent element is formed so as to cover the surface of the core 101.

[0086] From these, an active material precursor including the core portion 101 and the covering portion 102 is produced (step S4).

[0087] Finally, lithium is electrochemically, chemically, or thermally added to the active material precursor (step S5) to bond lithium to oxygen, which is a trap site in the active material precursor.

[0088] When lithium is electrochemically added to the active material precursor, an electrochemical device is fabricated using an electrode containing the active material precursor according to the procedure described below, and then the electrochemical device is charged. Conditions such as charging conditions are not particularly limited and can be set arbitrarily.

[0089] When lithium is chemically added to the active material precursor, the active material precursor is immersed in an organic lithium solution. The type of organic lithium solution is not particularly limited, but specifically, it can be one or more types of lithium naphthalenide solution. The conditions such as the concentration of the organic lithium solution and the immersion time are not particularly limited and can be set as desired.

[0090] When lithium is thermally added to the active material precursor, the mixture of the active material precursor and lithium is heated. The conditions, such as the mixing ratio of the active material precursor to lithium and the heating conditions, are not particularly limited and can be set arbitrarily.

[0091] This process results in the active material precursor being doped with lithium, resulting in the introduction of lithium into the active material precursor. In other words, lithium is doped into the carbon-reduced silicate glass, resulting in the synthesis of lithium-containing carbon-reduced silicate glass containing lithium as a constituent element. Thus, core portion 101 containing lithium-containing carbon-reduced silicate glass is formed.

[0092] From these, an active material 100 including a core 101 and a coating 102 is produced (step S6). In the active material 100 (core 101) including the lithium-containing carbon-reduced silicate glass produced using the carbon reduction treatment and lithium doping treatment, the physical properties of the silicate glass change due to the carbon reduction treatment and lithium doping treatment. Therefore, the active material 100 has the above-mentioned two types of physical properties (first physical property and second physical property).

[0093] When manufacturing this active material 100, the composition of the silicate glass used as a raw material is adjusted so that the content of each constituent element among all constituent elements excluding lithium, oxygen, and carbon satisfies the above-mentioned conditions. Specifically, the content of silicon in the active material 100 is 60 atomic % to 98 atomic %, the content of the first element in the active material 100 is 1 atomic % to 15 atomic %, the content of the second element in the active material 100 is 1 atomic % to 34 atomic %, and the content of the third element in the active material 100 is 0 atomic % to 6 atomic %.

[0094] <1-4. Actions and Effects> According to the active material 100 and the manufacturing method thereof described above, the following actions and effects can be obtained.

[0095] [Actions and effects of active materials] The active material 100 includes a lithium-containing carbon-reduced silicate glass.

[0096] Specifically, the active material 100 contains lithium, silicon, oxygen, a first element, a second element, and a third element as constituent elements, and the content of each of the constituent elements among all constituent elements excluding lithium, oxygen, and carbon satisfies the above-mentioned conditions. Second, in the analysis result (XPS spectrum of Si2p) of the active material 100 measured using XPS, a peak XA having an apex XAT 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 an apex RAT is detected (second physical property).

[0097] As a result, unlike the case where the first and second physical properties are not obtained, as described above, the reduction reaction of the silicate glass proceeds sufficiently, and SiO x As a result, the crystallinity of the glass material containing as a main component is optimized, which makes it easier for the active material 100 to occlude and release the electrode reactant sufficiently and stably, and also makes it easier for the active material 100 to continuously occlude and release the electrode reactant even when the electrode reaction is repeated.

[0098] Moreover, because the active material 100 already contains lithium as a constituent element, the irreversible capacity decreases during the initial electrode reaction using lithium as an electrode reactant. Therefore, in a device using the active material 100, a high capacity can be obtained from the initial electrode reaction.

[0099] For these reasons, an electrochemical device using the active material 100 can achieve excellent charge / discharge characteristics.

[0100] In particular, when active material 100 includes core 101 and coating 102, the surface of core 101, which includes lithium-containing carbon-reduced silicate glass, is coated with conductive coating 102. This improves the electronic conductivity of active material 100, thereby achieving even greater effects.

[0101] [Actions and Effects of the Manufacturing Method of the Active Material] According to the method for producing active material 100, silicate glass containing silicon, oxygen, a first element, a second element, and a third element as constituent elements is mixed with a carbon source, the mixture of silicate glass and carbon source is heated to form an active material precursor (carbon-reduced silicate glass), and lithium is then added to the active material precursor to produce active material 100 (lithium-containing carbon-reduced silicate glass). This produces active material 100 containing a lithium-containing carbon-reduced silicate compound whose contents of each constituent element satisfy the above-mentioned conditions and which has two physical properties (first and second physical properties). This allows for the production of active material 100 with excellent charge-discharge characteristics.

[0102] Moreover, SiO x Since the active material 100 containing as a main component can be produced by simple and inexpensive processes such as mixing and heating, there is no need to use complicated and expensive processes such as co-evaporation of two types of evaporation sources (SiO2 and Si). Therefore, the active material 100 can be produced easily and stably at low cost.

[0103] In particular, if the carbon source contains a carbon material, the silicate glass is sufficiently reduced in the carbon reduction treatment, and the coating portion 102 having sufficient conductivity is easily and stably formed, thereby achieving a greater effect.

[0104] 2. Electrodes and secondary batteries 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. Note that, since the electrode according to the embodiment of the present technology is a part (one component) of the secondary battery, the electrode will also be described below.

[0105] In the following, the active material described above is used as a negative electrode active material, and therefore, a case where the active material is used in a negative electrode will be described.

[0106] The secondary battery described here is a secondary battery that obtains battery capacity by utilizing the absorption and desorption of electrode reactants, and is equipped with a positive electrode, a negative electrode, and an electrolyte.

[0107] In this secondary battery, the charge capacity of the negative electrode is larger than the discharge 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 deposition of electrode reactants on the surface of the negative electrode during charging.

[0108] In the following, an example will be given in which the electrode reactant is lithium. A secondary battery that utilizes the absorption and desorption of lithium, which is an electrode reactant, is a so-called lithium ion secondary battery.

[0109] <2-1.Configuration> Fig. 5 shows a perspective view of the secondary battery. Fig. 6 shows a cross-sectional view of the battery element 20 shown in Fig. 5. Fig. 7 shows the planar configurations of the positive electrode 21 and the negative electrode 22 shown in Fig. 6.

[0110] However, Fig. 5 shows a state in which the exterior film 10 and the battery element 20 are separated from each other, and a cross section of the battery element 20 taken along the XZ plane is shown by a broken line. Fig. 6 shows only a part of the battery element 20. Fig. 7 shows a state in which the positive electrode 21 and the negative electrode 22 are separated from each other.

[0111] 5 to 7, this secondary battery includes an exterior film 10, a battery element 20, a positive electrode lead 31, a negative electrode lead 32, and sealing films 41 and 42. The secondary battery described here is a laminate film type secondary battery that uses a flexible (or pliable) exterior film 10.

[0112] [Exterior film and sealing film] 5, the exterior film 10 is a flexible exterior member that houses the battery element 20, and has a sealed bag-like structure with the battery element 20 housed inside. Therefore, the exterior film 10 houses an electrolyte solution together with a positive electrode 21 and a negative electrode 22, which will be described later.

[0113] Here, the exterior film 10 is a single film-like member that is folded in a folding direction F. The exterior film 10 is provided with a recessed portion 10U (so-called deep drawn portion) for accommodating the battery element 20.

[0114] Specifically, the exterior film 10 is a three-layer laminate film in which a fusion layer, a metal layer, and a surface protection layer are laminated in this order from the inside out, and when the exterior film 10 is folded, the outer peripheral edges of the opposing fusion layers 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.

[0115] However, the configuration (number of layers) of the exterior film 10 is not particularly limited, and may be one layer, two layers, or four or more layers.

[0116] 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.

[0117] The sealing film 41 is a sealing member that prevents outside air and the like from entering the inside of the exterior film 10. The sealing film 41 also contains a polymer compound such as polyolefin that has adhesiveness to the positive electrode lead 31, and the polyolefin is polypropylene or the like.

[0118] The configuration of the sealing film 42 is the same as the configuration of the sealing film 41, except that the sealing film 42 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.

[0119] [Battery element] As shown in FIGS. 5 and 6, the battery element 20 is a power generating element including a positive electrode 21, a negative electrode 22, a separator 23, and an electrolyte (not shown), and is housed inside the exterior film 10.

[0120] 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 stacked on top of each other with a 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 an imaginary 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.

[0121] The three-dimensional shape of battery element 20 is not particularly limited. Here, battery element 20 has a flat shape, and therefore a cross section of battery element 20 intersecting winding axis P (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 an imaginary axis that extends in the X-axis direction and has a length greater than that of minor axis J2, and minor axis J2 is an imaginary axis that extends in the Z-axis direction intersecting with the X-axis direction and has a length smaller than that of major axis J1. Here, the three-dimensional shape of battery element 20 is a flat cylindrical shape, and therefore the cross section of battery element 20 has a flat, approximately elliptical shape.

[0122] (positive electrode) As shown in FIGS. 6 and 7, the positive electrode 21 includes a positive electrode current collector 21A and a positive electrode active material layer 21B.

[0123] The positive electrode current collector 21A has a pair of surfaces on which the positive electrode active material layer 21B is provided. The positive electrode current collector 21A contains a conductive material such as a metal material, and the metal material is aluminum or the like.

[0124] Here, the positive electrode active material layer 21B is provided on both sides of the positive electrode current collector 21A and contains one or more types of positive electrode active materials capable of absorbing and releasing lithium. However, the positive electrode active material layer 21B may be provided on only one side of the positive electrode current collector 21A, on the side where the positive electrode 21 faces the negative electrode 22. The positive electrode active material layer 21B may further contain one or more types 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 may be one or more types of coating methods, etc.

[0125] The type of positive electrode active material is not particularly limited, but specifically includes a lithium-containing compound. This lithium-containing compound is a compound containing lithium and one or more transition metal elements as constituent elements, and may further contain one or more other elements as constituent elements. The type of other element is not particularly limited as long as it is an element other than lithium and transition metal elements, but specifically includes elements belonging to Groups 2 to 15 of the long period periodic table. The type of lithium-containing compound is not particularly limited, but specifically includes oxides, phosphate compounds, silicate compounds, borate compounds, etc.

[0126] Specific examples of oxides 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 )O2 and LiMn2O4. Specific examples of phosphate compounds include LiFePO4, LiMnPO4, LiFe 0.5 Mn 0.5 PO4 and LiFe 0.3 Mn 0.7 PO4, etc.

[0127] The positive electrode binder contains one or more of synthetic rubbers and polymeric compounds. Synthetic rubbers include styrene-butadiene rubber, fluorine-containing rubber, and ethylene-propylene-diene. Polymeric compounds include polyvinylidene fluoride, polyimide, and carboxymethyl cellulose.

[0128] The positive electrode conductive agent contains one or more conductive materials such as carbon materials, such as graphite, carbon black, acetylene black, and ketjen black, but the conductive material may also be a metal material or a polymer compound.

[0129] Here, on both sides of the positive electrode current collector 21 A, the positive electrode active material layer 21B is provided only on a part of the positive electrode current collector 21 A. Therefore, the part of the positive electrode current collector 21 A on which the positive electrode active material layer 21B is not provided is not covered with the positive electrode active material layer 21B and is exposed.

[0130] Specifically, as shown in FIG. 7, the positive electrode current collector 21A extends in the longitudinal direction (X-axis direction) and includes a covered portion 21AX and a pair of uncovered portions 21AY. The covered portion 21AX is located in the center of the positive electrode current collector 21A in the longitudinal direction and is a portion where the positive electrode active material layer 21B is formed. The pair of uncovered portions 21AY is located at both ends of the positive electrode current collector 21A in the longitudinal direction and is a portion where the positive electrode active material layer 21B is not formed. As a result, the covered portion 21AX is covered with the positive electrode active material layer 21B, whereas the pair of uncovered portions 21AY are exposed and not covered with the positive electrode active material layer 21B. Note that in FIG. 7, the positive electrode active material layer 21B is lightly shaded.

[0131] (Negative electrode) As shown in FIGS. 6 and 7, the negative electrode 22 includes a negative electrode current collector 22A and a negative electrode active material layer 22B.

[0132] 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 contains a conductive material such as a metal material, and the metal material is copper or the like.

[0133] Here, the anode active material layer 22B is provided on both sides of the anode current collector 22A and contains one or more types of anode active materials capable of absorbing and releasing lithium. The configuration of this anode active material is the same as the configuration of the active material described above. However, the anode active material layer 22B may be provided on only one side of the anode current collector 22A, on the side where the anode 22 faces the cathode 21. The anode active material layer 22B may further contain one or more types of other materials, such as a anode binder and anode conductor. The method for forming the anode active material layer 22B is not particularly limited, and specifically includes one or more types of a coating method, a vapor phase method, a liquid phase method, a thermal spraying method, and a firing method (sintering method).

[0134] However, the negative electrode active material layer 22B may further contain other negative electrode active materials. The type of other negative electrode active material is not particularly limited, but specifically includes one or both of a carbon material and a metal-based material. This is because a high energy density can be obtained. Carbon materials include graphitizable carbon, non-graphitizable carbon, and graphite (natural graphite and artificial graphite). The metal-based material is a material containing, as a constituent element, one or more of a metal element and a metalloid element that can form an alloy with lithium. Specific examples of the metal element and the metalloid element include one or both of silicon and tin. This metal-based material may be a simple substance, an alloy, a compound, a mixture of two or more of these, or a material containing two or more of these phases. Specific examples of the metal-based material are TiSi2 and SiO x (0 <x≦2、または0.2<x<1.4)などである。

[0135] The details regarding the negative electrode binder and the negative electrode conductive agent are the same as the details regarding the positive electrode binder and the positive electrode conductive agent, respectively.

[0136] Here, the anode active material layer 22B is provided on the entire anode current collector 22A on both sides of the anode current collector 22A. Therefore, the entire anode current collector 22A is not exposed but is covered with the anode active material layer 22B.

[0137] Specifically, as shown in FIG. 7, 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 unopposed portions 22BZ. The pair of unopposed portions 22BZ are portions facing the pair of uncovered portions 21AY. In other words, the pair of unopposed portions 22BZ are portions that do not face the positive electrode active material layer 21B and are therefore not involved in charge / discharge reactions. In FIG. 7, the negative electrode active material layer 22B is darkly shaded.

[0138] The negative electrode active material layer 22B is provided on the entire surface of both sides of the negative electrode current collector 22A, while the positive electrode active material layer 21B is provided only on a part (coating portion 21AX) of both sides of the positive electrode current collector 21A in order to prevent lithium released from the positive electrode active material layer 21B during charging from being deposited on the surface of the negative electrode 22.

[0139] When determining whether the two types of physical properties (first and second properties) have been obtained after the fact, i.e., after the secondary battery is completed, it is preferable to use the unopposed portion 22BZ as the anode active material layer 22B from which to recover the anode active material for analysis. This is because the unopposed portion 22BZ is hardly involved in the charge / discharge reaction, and therefore the state (composition, physical properties, etc.) of the anode active material (lithium-containing carbon-reduced silicate glass) is likely to be maintained as it was when the anode 22 was formed without being affected by the charge / discharge reaction. This makes it possible to stably and reproducibly determine whether the two types of physical properties have been obtained even after the secondary battery has been used.

[0140] (separator) 6, 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. The separator 23 contains a polymer compound such as polyethylene.

[0141] (electrolyte) The electrolyte solution contains a solvent and an electrolyte salt, and is impregnated into each of the positive electrode 21, the negative electrode 22, and the separator 23.

[0142] The solvent contains one or more non-aqueous solvents (organic solvents), and the electrolyte containing the non-aqueous solvent is a so-called non-aqueous electrolyte. The non-aqueous solvents include esters and ethers, and more specifically, carbonate ester compounds, carboxylic acid ester compounds, and lactone compounds.

[0143] Carbonate compounds include cyclic carbonates and chain carbonates. Cyclic carbonates include ethylene carbonate and propylene carbonate, while chain carbonates include dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate. Carboxylate compounds include ethyl acetate, ethyl propionate, and ethyl trimethylacetate. Lactone compounds include γ-butyrolactone and γ-valerolactone. Ethers include the above-mentioned lactone compounds as well as 1,2-dimethoxyethane, tetrahydrofuran, 1,3-dioxolane, and 1,4-dioxane.

[0144] The non-aqueous solvent may be an unsaturated cyclic carbonate, a halogenated carbonate, a sulfonate, a phosphate, an acid anhydride, a nitrile compound, an isocyanate compound, or the like, because the chemical stability of the electrolyte solution is improved.

[0145] Specifically, unsaturated cyclic carbonates include vinylene carbonate, vinylethylene carbonate, and methyleneethylene carbonate. Halogenated carbonates include fluoroethylene carbonate and difluoroethylene carbonate. Sulfonic acid esters include propane sultone and propene sultone. Phosphate esters include trimethyl phosphate. Acid anhydrides include cyclic carboxylic acid anhydrides, cyclic disulfonic acid anhydrides, and cyclic carboxylic acid sulfonic acid anhydrides. Cyclic carboxylic acid anhydrides include succinic anhydride, glutaric anhydride, and maleic anhydride. Cyclic disulfonic acid anhydrides include ethanedisulfonic acid anhydride and propanedisulfonic acid anhydride. Cyclic carboxylic acid sulfonic acid anhydrides include sulfobenzoic anhydride, sulfopropionic anhydride, and sulfobutyric acid anhydride. Nitrile compounds include acetonitrile and succinonitrile. Isocyanate compounds include hexamethylene diisocyanate.

[0146] The electrolyte salt contains one or more light metal salts such as lithium salts. Examples of the lithium salt include lithium hexafluorophosphate (LiPF), lithium tetrafluoroborate (LiBF), lithium trifluoromethanesulfonate (LiCFSO), lithium bis(fluorosulfonyl)imide (LiN(FSO)), lithium bis(trifluoromethanesulfonyl)imide (LiN(CFSO)), lithium tris(trifluoromethanesulfonyl)methide (LiC(CFSO)), and lithium bis(oxalato)borate (LiB(CO)). The content of the electrolyte salt is not particularly limited, but is generally 0.3 mol / kg to 3.0 mol / kg relative to the solvent. This is because high ionic conductivity can be achieved.

[0147] [Positive and negative leads] As shown in Fig. 5, the positive electrode lead 31 is a positive electrode terminal connected to the positive electrode 21, and more specifically, is connected to the positive electrode current collector 21A. The positive electrode lead 31 extends 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 may be either a thin plate shape or a mesh shape.

[0148] As shown in FIG. 5 , the negative electrode lead 32 is a negative electrode terminal connected to the negative electrode 22, and more specifically, is connected to the negative electrode current collector 22A. The 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 lead-out direction of the negative electrode lead 32 is the same as the lead-out direction 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.

[0149] <2-2. Operation> When the secondary battery is charged, lithium is released from the positive electrode 21 in the battery element 20 and is absorbed into the negative electrode 22 via the electrolyte. On the other hand, when the secondary battery is discharged, lithium is released from the negative electrode 22 in the battery element 20 and is absorbed into the positive electrode 21 via the electrolyte. During these charging and discharging times, lithium is absorbed and released in an ionic state.

[0150] <2-3. Manufacturing method> When manufacturing a secondary battery, the positive electrode 21 and the negative electrode 22 are fabricated and an electrolyte solution is prepared according to the procedure described below, and then the positive electrode 21, the negative electrode 22, and the electrolyte solution are used to fabricate a secondary battery.

[0151] [Preparation of positive electrode] First, a paste-like cathode mixture slurry is prepared by adding a mixture (cathode mixture) of a cathode active material, a cathode binder, a cathode conductor, and the like to a solvent. This solvent may be an aqueous solvent or an organic solvent. Next, the cathode mixture slurry is applied to both sides of the cathode current collector 21A to form the cathode active material layer 21B. After this, the cathode active material layer 21B may be compression-molded using a roll press or the like. In this case, the cathode active material layer 21B may be heated, or the compression molding may be repeated multiple times. As a result, the cathode active material layer 21B is formed on both sides of the cathode current collector 21A, thereby producing the cathode 21.

[0152] [Preparation of negative electrode] The negative electrode 22 is formed by a procedure similar to that for producing the positive electrode 21 described above. Specifically, first, a mixture (negative electrode mixture) of a negative electrode active material, a negative electrode binder, a negative electrode conductor, and the like is poured into a solvent to prepare a paste-like negative electrode mixture slurry. Next, the negative electrode mixture slurry is applied to both surfaces of the negative electrode current collector 22A to form the negative electrode active material layer 22B. Thereafter, the negative electrode active material layer 22B may be compression-molded. As a result, the negative electrode active material layer 22B is formed on both surfaces of the negative electrode current collector 22A, and the negative electrode 22 is produced.

[0153] [Preparation of electrolyte] An electrolyte salt is added to a solvent, which may be an aqueous solvent or an organic solvent, and the electrolyte salt is dispersed or dissolved in the solvent to prepare an electrolytic solution.

[0154] [Secondary battery assembly] First, the positive electrode lead 31 is connected to the positive electrode current collector 21A of the positive electrode 21 by welding or the like, and the negative electrode lead 32 is connected to the negative electrode current collector 22A of the negative electrode 22 by welding or the like.

[0155] Next, the positive electrode 21 and the negative electrode 22 are stacked together with the separator 23 interposed therebetween, and then the positive electrode 21, the negative electrode 22, and the separator 23 are wound together to produce a wound body. This wound body has the same configuration as the battery element 20, except that the positive electrode 21, the negative electrode 22, and the separator 23 are not impregnated with an electrolyte solution. Next, the wound body is pressed using a press or the like to form the wound body into a flat shape.

[0156] Next, after the roll is housed inside the recess 10U, the exterior films 10 (adhesive layer / metal layer / surface protection layer) are folded to face each other. Next, the outer peripheral edges of two sides of the facing exterior films 10 (adhesive layers) are joined together using a heat fusion method or the like, thereby housing the roll inside the bag-shaped exterior film 10.

[0157] Finally, after injecting the electrolyte solution into the bag-shaped exterior film 10, the outer peripheral edges of the remaining side of the exterior film 10 (bonding layer) are joined together using a heat fusion method or the like. In this case, a sealing film 41 is inserted between the exterior film 10 and the positive electrode lead 31, and a sealing film 42 is inserted between the exterior film 10 and the negative electrode lead 32. As a result, the wound body is impregnated with the electrolyte solution, and the battery element 20 is produced, and the battery element 20 is sealed inside the bag-shaped exterior film 10, and a secondary battery is assembled.

[0158] [Secondary battery assembly] The assembled secondary battery is charged and discharged. Various conditions, such as the ambient temperature, the number of charge / discharge cycles (number of cycles), and the charge / discharge conditions, can be set as desired. This forms a coating on the surface of each of the positive electrode 21 and the negative electrode 22, electrochemically stabilizing the state of the secondary battery. This completes a laminate film-type secondary battery using the exterior film 10.

[0159] <2-4. Actions and Effects> In this secondary battery, the negative electrode active material of the negative electrode 22 has the same configuration as the active material described above. In this case, for the same reasons as those described for the active material, the negative electrode active material is more likely to absorb and release lithium sufficiently and stably, so that the negative electrode active material is more likely to continuously absorb and release lithium even when charge and discharge reactions are repeated. In addition, the irreversible capacity during the initial charge and discharge is reduced, so that a high capacity can be obtained from the initial charge and discharge. Therefore, excellent charge and discharge characteristics can be obtained.

[0160] In particular, if the secondary battery is a lithium ion secondary battery, a sufficient battery capacity can be stably obtained by utilizing the absorption and release of lithium, and therefore a greater effect can be obtained.

[0161] Other functions and effects of this secondary battery are similar to those of the active material described above.

[0162] <3. Modifications> Next, modifications of the active material and secondary battery described above will be described. The configurations of the active material and secondary battery can be modified as appropriate, as described below. However, any two or more of the modifications described below may be combined with each other.

[0163] [Variation 1] In FIG. 1, the active material 100 includes a central portion 101 and a coating portion 102. However, the active material 100 may include only the central portion 101, without including the coating portion 102. In this case, the active material 100 including the central portion 101 and the coating portion 102 may be produced, and then the coating portion 102 may be removed. Even in this case, the active material 100 (central portion 101) can occlude and release an electrode reactant, and therefore the same effect can be obtained.

[0164] However, as described above, in order to improve the electronic conductivity of the active material 100, the active material 100 preferably includes the core portion 101 and the coating portion .

[0165] [Variation 2] A porous film separator 23 was used. However, although not specifically shown here, a laminated separator including a polymer compound layer may be used instead of the porous film separator 23.

[0166] 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 separator improves adhesion to each of the positive electrode 21 and the negative electrode 22, thereby suppressing misalignment (winding misalignment) of the battery element 20. This suppresses swelling of the secondary battery even if a decomposition reaction of the electrolyte solution occurs. The polymer compound layer includes a polymer compound such as polyvinylidene fluoride. This is because polyvinylidene fluoride and the like have excellent physical strength and are electrochemically stable.

[0167] One or both of the porous film and the polymer compound layer may contain one or more types of insulating particles. This is because the insulating particles dissipate heat when the secondary battery generates heat, improving the safety (heat resistance) of the secondary battery. The insulating particles contain one or more types of insulating materials such as inorganic materials and resin materials. Specific examples of inorganic materials include aluminum oxide, aluminum nitride, boehmite, silicon oxide, titanium oxide, magnesium oxide, and zirconium oxide. Specific examples of resin materials include acrylic resin and styrene resin.

[0168] When a laminated separator is produced, a precursor solution containing a polymer compound and a solvent is prepared, and then the precursor solution is applied to one or both sides of a porous film. In this case, multiple insulating particles may be added to the precursor solution as needed.

[0169] In this case, the same effect can be obtained because lithium ions are able to move between the positive electrode 21 and the negative electrode 22. In this case, particularly, as described above, the winding misalignment of the battery element 20 is suppressed, so that a greater effect can be obtained.

[0170] [Variation 3] An electrolytic solution, which is a liquid electrolyte, was used. However, although not specifically shown here, an electrolyte layer, which is a gel electrolyte, may be used instead of the electrolytic solution.

[0171] In the battery element 20 using the electrolyte layer, the positive electrode 21 and the negative electrode 22 are stacked with the separator 23 and the electrolyte layer interposed therebetween, and the positive electrode 21, the negative electrode 22, the separator 23, and the electrolyte layer are wound together. The electrolyte layer is interposed between the positive electrode 21 and the separator 23, and also between the negative electrode 22 and the separator 23.

[0172] Specifically, the electrolyte layer contains a polymer compound together with an electrolytic solution, and the electrolytic solution is held by the polymer compound. This is because leakage of the electrolytic solution is prevented. The composition of the electrolytic solution is as described above. The polymer compound contains polyvinylidene fluoride, etc. 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 surfaces of each of the positive electrode 21 and the negative electrode 22.

[0173] In this case, the same effect can be obtained because lithium ions can move between the positive electrode 21 and the negative electrode 22 via the electrolyte layer. In this case, as described above, leakage of the electrolyte solution is prevented, and therefore a greater effect can be obtained.

[0174] [Variation 4] In FIG. 5, the secondary battery has one positive electrode lead 31. However, the secondary battery may have two or more positive electrode leads 31. In this case, the secondary battery can be energized using the positive electrode leads 31, and the same effect can be obtained. In particular, as the number of positive electrode leads 31 increases, the electrical resistance of the battery element 20 decreases, and therefore a greater effect can be obtained.

[0175] The explanation regarding the number of positive electrode leads 31 here also applies to the number of negative electrode leads 32. That is, although the secondary battery in FIG. 5 has one negative electrode lead 32, the secondary battery may have two or more negative electrode leads 32. In this case, the negative electrode leads 32 can be used to conduct electricity to the secondary battery, and the same effect can be obtained. In particular, when the number of negative electrode leads 32 increases, the electrical resistance of the battery element 20 decreases, and therefore a greater effect can be obtained.

[0176] <4. Uses of secondary batteries> Next, uses (application examples) of the above-mentioned secondary battery will be described.

[0177] The uses (application examples) of secondary batteries are not particularly limited. Secondary batteries used as power sources may be the main power source for electronic devices, electric vehicles, etc., or may be auxiliary power sources. A main power source is a power source that is used preferentially regardless of the presence or absence of other power sources. An auxiliary power source is a power source that is used in place of the main power source, or a power source that can be switched from the main power source.

[0178] Specific examples of uses for secondary batteries are as follows: Electronic devices such as video cameras, digital still cameras, mobile phones, laptop computers, headphone stereos, portable radios, and portable information terminals. Storage devices such as backup power supplies and memory cards. Power tools such as power drills and power saws. Battery packs installed in electronic devices. Medical electronic devices such as pacemakers and hearing aids. Electric vehicles such as electric cars (including hybrid cars). Power storage systems such as home or industrial battery systems that store power in preparation for emergencies. In these uses, one secondary battery may be used, or multiple secondary batteries may be used.

[0179] The battery pack may use a single cell or a battery pack. The electric vehicle is a vehicle that operates (travels) using a secondary battery as a driving power source, and may be a hybrid vehicle that also has a driving source other than the secondary battery. In a home power storage system, the power stored in the secondary battery, which is a power storage source, can be used to power home electrical appliances, etc.

[0180] Here, an example of an application of the secondary battery will be specifically described. The configuration of the application described below is merely an example and can be modified as appropriate.

[0181] Figure 8 shows the block diagram of a battery pack. The battery pack described here is a battery pack (a so-called soft pack) that uses one secondary battery, and is installed in electronic devices such as smartphones.

[0182] 8, the battery pack includes a power supply 51 and a circuit board 52. The circuit board 52 is connected to the power supply 51 and includes a positive terminal 53, a negative terminal 54, and a temperature detection terminal 55.

[0183] The power source 51 includes one secondary battery. In this secondary battery, the positive electrode lead is connected to a positive electrode terminal 53, and the negative electrode lead is connected to a negative electrode terminal 54. The power source 51 can be connected to the outside via the positive electrode terminal 53 and the negative electrode terminal 54, and is therefore capable of charging and discharging. The circuit board 52 includes a control unit 56, a switch 57, a thermosensitive resistor (PTC element) 58, and a temperature detection unit 59. However, the PTC element 58 may be omitted.

[0184] The control unit 56 includes a central processing unit (CPU) and memory, and controls the operation of the entire battery pack. The control unit 56 detects and controls the usage state of the power source 51 as necessary.

[0185] When the voltage of power supply 51 (secondary battery) reaches the overcharge detection voltage or the overdischarge detection voltage, control unit 56 turns off switch 57 to prevent charging current from flowing through the current path of power supply 51. The overcharge detection voltage is not particularly limited, but specifically, it is 4.2V±0.05V, and the overdischarge detection voltage is not particularly limited, but specifically, it is 2.4V±0.1V.

[0186] Switch 57 includes a charge control switch, a discharge control switch, a charge diode, a discharge diode, etc., and switches between the presence and absence of a connection between power supply 51 and an external device in response to an instruction from control unit 56. Switch 57 includes a field effect transistor (MOSFET) using a metal oxide semiconductor, etc., and the charge / discharge current is detected based on the ON resistance of switch 57.

[0187] Temperature detection unit 59 includes a temperature detection element such as a thermistor, measures the temperature of power supply 51 using temperature detection terminal 55, and outputs the temperature measurement result to control unit 56. The temperature measurement result measured by temperature detection unit 59 is used when control unit 56 controls charging and discharging in the event of abnormal heat generation, and when control unit 56 performs correction processing when calculating the remaining capacity. [Example]

[0188] An embodiment of the present technology will be described.

[0189] <Examples 1 to 4 and Comparative Examples 1 to 4> The cross-sectional structure of a test secondary battery (coin type) is shown in Figure 9. In the following, a negative electrode active material was produced, 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.

[0190] 9, in a coin-type secondary battery, a test electrode 201 is housed inside an exterior cup 204, and a counter electrode 203 is housed inside an exterior can 202. The test electrode 201 and the counter electrode 203 are stacked together with a separator 205 interposed therebetween, and the exterior can 202 and the exterior cup 204 are crimped together with a gasket 206. The test electrode 201, the counter electrode 203, and the separator 205 are each impregnated with an electrolyte.

[0191] [Production of negative electrode active material] First, silicate glass was prepared as a raw material. The contents (atomic %) of the constituent elements (silicon, first element, second element, and third element) of the lithium-containing carbon-reduced silicate glass synthesized using this silicate glass are shown in Table 1.

[0192] Subsequently, the silicate glass was mixed with a carbon source (carbon black, a carbon material) to obtain a mixture, in which the mixing ratio (weight ratio) of silicate glass to carbon source was 5:1.

[0193] Next, a binder solution (a solution of polyimide in N-methyl-2-pyrrolidone, 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, Awatori Rentaro, manufactured by Thinky Corporation) to prepare a slurry. In this case, the amount of binder solution added to the mixture was 10 wt% (solid content ratio).

[0194] Subsequently, the slurry was dried in an oven (temperature = 80°C) to obtain a dried product, which was then pulverized to obtain pulverized flakes.

[0195] Next, the pulverized flakes were placed inside an alumina boat and heated in an argon atmosphere using a vacuum gas exchange furnace (heating temperature = 950 °C, heating time = 10 hours). In this case, the silicate glass was reduced in the presence of a carbon source (carbon reduction treatment), synthesizing carbon-reduced silicate glass, and a core containing the carbon-reduced silicate glass was formed. In addition, decomposition products of the carbon source (organic decomposition carbon) and the like were deposited on the surface of the core, forming a coating. This resulted in an active material precursor comprising a core containing carbon-reduced silicate glass and a coating.

[0196] Next, in a glove box purged with argon gas, 50 cm of solvent (organic solvent N-butyl methyl ether) was added. 3 1.6 g of an organic compound (naphthalene) was added to the solution, and the solvent was stirred. As a result, the organic compound dissolved in the solvent, and a colorless, transparent solution was prepared. Next, 0.1 g of lithium foil (thickness = 0.8 mm), which is the lithium source, was added to the solvent, and the solution was stirred using a stirrer (stirring time = 5 hours). As a result, the lithium foil dissolved in the solution and reacted with the organic compound, and an organic lithium solution (lithium naphthalenide solution) was prepared.

[0197] Next, to chemically add lithium to the active material precursor, the active material precursor was introduced into an organic lithium solution in the glove box described above, and the active material precursor was reacted with the organic lithium solution (reaction time = 24 hours). The reactant was then removed from the organic lithium solution and filtered in a dry room. The reactant was then washed with a solvent (organic solvent, dimethyl carbonate), and then vacuum-dried (drying temperature = 80°C). This resulted in lithium being doped into the active material precursor (lithium doping treatment), synthesizing lithium-containing carbon-reduced silicate glass. Thus, a flake-shaped negative electrode active material was obtained, comprising a core containing lithium-containing carbon-reduced silicate glass and a coating portion.

[0198] 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).

[0199] For comparison, a negative electrode active material was produced in the same manner as above, except that the lithium doping treatment was not performed. This negative electrode active material had a core containing carbon-reduced silicate glass and a coating.

[0200] 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 a powder state, even though the grinding frame was heated to a temperature (950°C) higher than the glass transition temperature of silicate glass (approximately 700°C) during the carbon reduction treatment. This is thought to be because the core containing the lithium-containing carbon-reduced silicate glass was covered by the coating.

[0201] When the negative electrode active material was analyzed using X-ray diffraction (XRD), a broad halo pattern was detected within the 2θ range of 20° to 25°, even though the silicate glass had been subjected to carbon reduction treatment. This confirmed that the negative electrode active material (lithium-containing carbon-reduced silicate glass) was not crystallized.

[0202] Furthermore, when the negative electrode active material was analyzed using Raman spectroscopy, clear G and D bands were detected in the Raman spectrum, confirming that the core was covered with a coating containing carbon as a constituent element.

[0203] The results of analyzing the negative electrode active material using XPS are shown in Table 1. In this case, the position of the vertex XAT (binding energy: eV) was examined based on the analysis results of the negative electrode active material (XPS spectrum of Si2p shown in FIG. 2) using the procedure described above.

[0204] The results of analyzing the negative electrode active material using Raman spectroscopy are shown in Table 1. In this case, the position of the apex RAT (Raman shift: cm) was determined based on the analysis results of the negative electrode active material (Raman spectrum shown in FIG. 3) by the above-described procedure. -1 ) was investigated.

[0205] [Secondary battery production] According to the procedure described below, a test electrode 201 was fabricated and an electrolyte solution was prepared, and then a coin-type secondary battery was fabricated using the test electrode 201 and the electrolyte solution.

[0206] (Preparation of test electrodes) Here, a negative electrode was fabricated as test electrode 201. First, the above-described 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 together to prepare a negative electrode mixture. In this case, the mixing ratio (mass ratio) was set to negative electrode active material: negative electrode binder precursor: two types of negative electrode conductive agents = 7:0.5:1:0.25. Next, the negative electrode mixture was introduced into a solvent (N-methyl-2-pyrrolidone, an organic solvent), and the solvent was stirred to prepare a paste-like negative electrode mixture slurry.

[0207] Next, the negative electrode mixture slurry was applied to one side of a negative electrode current collector (copper foil with a thickness of 15 μm) using a coating device, and then the negative electrode mixture slurry was heated and dried in a vacuum baking furnace (heating temperature = 425 °C). As a result, a negative electrode binder (polyimide) was synthesized, and a negative electrode active material layer containing a negative electrode active material, a negative electrode binder, and a negative electrode conductive agent was formed. Finally, the negative electrode current collector on which the negative electrode active material layer was formed was punched into a disk shape (outer diameter = 15 mm), and then the negative electrode active material layer was compression-molded using a roll press. This produced a test electrode 201, which was a negative electrode.

[0208] (Preparing for the opposite) A lithium metal plate was used as the counter electrode 203. In this case, a lithium metal foil was punched into a disk shape (outer diameter = 15 mm).

[0209] (Preparation of Electrolyte) An electrolyte salt (lithium hexafluorophosphate) was added to a solvent (ethylene carbonate, fluoroethylene carbonate, and dimethyl carbonate), and the solvent was then 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 relative to the solvent.

[0210] (Secondary battery assembly) First, the test electrode 201 was placed inside the exterior cup 204, and the counter electrode 203 was placed inside the exterior can 202. Next, the test electrode 201 placed inside the exterior cup 204 and the counter electrode 203 placed inside the exterior can 202 were stacked together with a separator 205 (a microporous polyethylene film with a thickness of 5 μm) impregnated with an electrolyte interposed therebetween. This allowed a portion of the electrolyte impregnated in the separator 205 to impregnate the test electrode 201 and the counter electrode 203, respectively. Finally, with the test electrode 201 and the counter electrode 203 stacked together with the separator 205 interposed therebetween, the exterior can 202 and the exterior cup 204 were crimped together with a gasket 206. Thus, the test electrode 201, the counter electrode 203, the separator 205, and the electrolyte were sealed between the exterior can 202 and the exterior cup 204, and a coin-type secondary battery was assembled.

[0211] (Stabilization of secondary batteries) The secondary battery was subjected to one cycle of charge and discharge in a room temperature environment (temperature = 23°C). During charging, it was charged at a constant current of 0.1C until the voltage reached 4.2V, and then charged at a constant voltage of 0.05C at that voltage of 4.2V. During discharging, it was discharged at a constant current of 0.1C until the voltage reached 2.5V. 0.1C is the current value that fully discharges the battery capacity (theoretical capacity) in 10 hours, and 0.05C is the current value that fully discharges the battery capacity in 20 hours. This completed the coin-type secondary battery.

[0212] [Evaluation of battery characteristics] The charge / discharge characteristics of the secondary battery were evaluated, and the results shown in Table 1 were obtained. Here, the charge / discharge characteristics examined were the charge characteristics, discharge characteristics, initial charge / discharge characteristics, and irreversible capacity characteristics.

[0213] When examining the charge-discharge characteristics, first, the charge capacity (mAh) at the first cycle was measured by charging the secondary battery in a room temperature environment (temperature = 23°C). From this, the charge capacity per unit weight (mAh / g), which is an index for evaluating the charge characteristics, was calculated based on the weight (g) of the negative electrode active material.

[0214] Next, the charged secondary battery was discharged in the same environment to measure the discharge capacity (mAh) at the first cycle, and the discharge capacity per unit weight (mAh / g), which is an index for evaluating the discharge characteristics, was calculated based on the weight (g) of the negative electrode active material.

[0215] Finally, the initial efficiency, an index for evaluating the initial charge-discharge characteristics, was calculated based on the formula: initial efficiency (%) = (discharge capacity at first cycle / charge capacity at first cycle) × 100. The irreversible capacity, another index for evaluating the irreversible capacity characteristics, was calculated based on the formula: irreversible capacity (mAh / g) = charge capacity per unit weight - discharge capacity per unit weight. The charge-discharge conditions were the same as those used during stabilization of the secondary battery.

[0216] [Table 1]

[0217] [Consideration] As is clear from Table 1, the charge / discharge characteristics (charge characteristics, discharge characteristics, initial charge / discharge characteristics, and irreversible capacity characteristics) varied significantly depending on the composition and physical properties of the negative electrode active material.

[0218] Specifically, when the following conditions were satisfied with respect to the composition of the negative electrode active material, and the following conditions were satisfied with respect to the analysis results of the negative electrode active material using XPS and Raman spectroscopy (XPS spectrum and Raman spectrum of Si2p), respectively, and the negative electrode active material was doped with lithium in advance (Examples 1 to 4), the discharge capacity was sufficiently increased relative to the charge capacity compared to when these conditions were not satisfied (Comparative Examples 1 to 4), and therefore high initial efficiency was obtained in accordance with the decrease in irreversible capacity.

[0219] Conditions for 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, in which the silicon content of all constituent elements (excluding lithium, oxygen, and carbon) is 60 atomic % to 98 atomic %, the first element content of all constituent elements is 1 atomic % to 15 atomic %, the second element content of all constituent elements is 1 atomic % to 34 atomic %, and the third element content of all constituent elements is 0 atomic % to 6 atomic %.

[0220] Conditions for the analysis results of negative electrode active material: In the XPS spectrum (Si2p) measured using XPS, a peak XA having a peak XAT shown in FIG. 2 (the position of the peak XAT is in the range of binding energy 100 eV to 102 eV) is detected (first physical property). In addition, in the Raman spectrum measured using Raman spectroscopy, a peak RA having a peak RAT shown in FIG. 3 (the position of the peak RAT is in the range of Raman shift 600 cm -1 ~640cm -1 (within a range of 1 / 2 s) is detected (second physical property).

[0221] [summary] From the results shown in Table 1, when the above-mentioned conditions regarding the composition of the negative electrode active material were satisfied and the above-mentioned conditions regarding the analysis results of the negative electrode active material (the first and second physical properties) were satisfied, the charge-discharge characteristics were improved, and therefore, excellent charge-discharge characteristics were obtained in the secondary battery.

[0222] The present technology has been described above with reference to an embodiment and examples. However, the configuration of the present technology is not limited to the configuration described in the embodiment and examples, and can be modified in various ways.

[0223] Although the secondary battery has been described as having a laminate film type and a coin type battery structure, the type of battery structure is not particularly limited. Specifically, the battery structure may be a cylindrical type, a square type, a button type, or the like.

[0224] Although the battery element has been described as having a wound structure, the type of element structure is not particularly limited. Specifically, the element structure may be a stacked structure in which electrodes (positive and negative electrodes) are stacked, a zigzag-folded structure in which the electrodes are folded, or other structures.

[0225] Furthermore, although the electrode reactant is lithium in the above description, the type of the electrode reactant is not particularly limited. Specifically, as described above, the electrode reactant may be other alkali metals such as sodium and potassium, or alkaline earth metals such as beryllium, magnesium, and calcium. In addition, the electrode reactant may be other light metals such as aluminum.

[0226] The effects described in this specification are merely examples, and 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. Lithium and Silicon and Oxygen and a first element including at least one of boron and phosphorus; a second element including at least one of sodium, potassium, scandium, titanium, iron, zirconium, cerium, lanthanum, hafnium, tantalum, tungsten, aluminum, sulfur, chlorine, zinc, bismuth, and antimony; a third element including at least one of magnesium, calcium, strontium, and barium; as a constituent element, the content of the silicon in all constituent elements excluding the lithium, the oxygen, and the carbon is 60 atomic % or more and 98 atomic % or less, the content of the first element in all the constituent elements is 1 atomic % or more and 15 atomic % or less, the content of the second element in all the constituent elements is 1 atomic % or more and 34 atomic % or less, the content of the third element in all the constituent elements is 0 atomic % or more and 6 atomic % or less, In an XPS spectrum of Si2p measured using X-ray photoelectron spectroscopy (XPS), where the horizontal axis represents binding energy (eV) and the vertical axis represents spectral intensity, a first peak is detected having an apex within a binding energy range of 100 eV or more and 102 eV or less; Raman spectra measured using Raman spectroscopy (horizontal axis is Raman shift (cm -1 ) and the vertical axis is the spectral intensity), the Raman shift is 600 cm -1 More than 640cm -1 A second peak is detected having an apex within a range that is: active material.

2. a central portion containing the lithium, 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 portion that coats at least a portion of the surface of the core portion and contains carbon as a constituent element; The active material of claim 1 , comprising:

3. preparing a silicate glass containing, as constituent elements, a first element including silicon, oxygen, and at least one of boron and phosphorus; a second element including at least one of sodium, potassium, scandium, titanium, iron, zirconium, cerium, lanthanum, hafnium, tantalum, tungsten, aluminum, sulfur, chlorine, zinc, bismuth, and antimony; and a third element including at least one of magnesium, calcium, strontium, and barium; mixing the silicate glass with a carbon source to form a mixture of the silicate glass and the carbon source; heating the mixture to form an active material precursor containing the silicon, the oxygen, the first element, the second element, and the third element as constituent elements; adding the lithium to the active material precursor electrochemically, chemically, or thermally to produce an active material containing the lithium, 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 the lithium, 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 15 atomic % or less, the content of the second element in the active material is 1 atomic % or more and 34 atomic % or less, The content of the third element in the active material is 0 atomic % or more and 6 atomic % or less. A method for producing an active material.

4. The carbon source includes at least one of a carbon material and a carbonizable organic substance. The method for producing the active material according to claim 3.

5. An electrode comprising the active material according to claim 1 or 2.

6. A positive electrode and A negative electrode containing the active material according to claim 1 or 2; Electrolyte and A secondary battery comprising:

7. It is a lithium-ion secondary battery. The secondary battery according to claim 6.

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