Negative electrode active material for secondary battery, negative electrode for secondary battery, and secondary battery

Abstract

This negative electrode active material for secondary batteries contains negative electrode active material particles containing: a first substance that contains silicon oxide; and a second substance that contains at least one of copper, a copper compound, tungsten, and molybdenum oxide and that is attached to the surface of the first substance. The maximum peak in a Raman spectrum of the negative electrode active material particles falls in the range of 470-490 cm-1.<sp / > In an XRD spectrum, a peak appears in each of the range of 37±1° and the range of 44±1°, a peak appears in the range of 40±1°, or a peak appears in in either one of the ranges of 23±1°, 25±1°, 37±1°, 41±1°, 54±1°, and 60±1°.

Description

[Technical Field]

[0001] The present technology relates to a negative electrode active material for a secondary battery, a negative electrode for a secondary battery, and a secondary battery. [Background technology]

[0002] Secondary batteries are widely used as power sources for various electronic devices such as mobile phones. Secondary batteries that are small, lightweight, and capable of providing high energy density are desirable. Secondary batteries include a positive electrode, a negative electrode, and an electrolyte. The negative electrode contains a negative electrode active material that participates in charge-discharge reactions.

[0003] Various studies have been conducted on negative electrode active materials. Specifically, for example, a negative electrode active material in which particles made of Si or SiO are coated with porous MoO2 has been proposed (e.g., For example, see Patent Documents 1 and 2. Furthermore, negative electrode active materials in which particles made of Si or SiO are coated with Cu (copper) have also been proposed (for example, see Patent Documents 3 to 5). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-152125 [Patent Document 2] Japanese Patent Application Laid-Open No. 2015-68864 [Patent Document 3] Japanese Patent Application Laid-Open No. 2013-191463 [Patent Document 4] Japanese Patent Application Laid-Open No. 2006-244813 [Patent Document 5] Japanese Patent Application Laid-Open No. 2004-146292 Summary of the Invention

[0005] Although various studies have been conducted on the battery characteristics of secondary batteries, there is still room for further improvement in the battery characteristics.

[0006] Therefore, there is a demand for a negative electrode active material for a secondary battery, a negative electrode for a secondary battery, and a secondary battery that can provide excellent battery performance.

[0007] The negative electrode active material for a secondary battery according to one embodiment of the present disclosure has negative electrode active material particles including a first substance containing silicon oxide and a second substance containing at least one of copper, a copper compound, tungsten, and molybdenum oxide and attached to the surface of the first substance. The Raman spectrum of the negative electrode active material particles detected by Raman spectroscopy shows a Raman spectrum of 470 cm -1 More than 490cm -1 The XRD spectrum of the negative electrode active material particles detected by X-ray diffraction (XRD) has peaks in the ranges of 37±1° and 44±1°, or in the range of 40±1°, or in the range of 23±1°, 25±1°, 37±1°, 41±1°, 54±1°, or 60±1°. At least one of the peak intensity in the range of 227 eV to 240 eV and the peak intensity in the range of 930 eV to 938 eV in the photoelectron spectrum of the negative electrode active material particles detected by X-ray photoelectron spectroscopy (XPS) is 25% or less of the peak intensity in the range of 98 eV to 104 eV in the photoelectron spectrum of only the first object detected by X-ray photoelectron spectroscopy.

[0008] The negative electrode for a secondary battery and the secondary battery according to one embodiment of the present disclosure have the above-described negative electrode active material for a secondary battery according to one embodiment of the present disclosure.

[0009] According to one embodiment of the present disclosure, a secondary battery anode active material, a secondary battery anode, or a secondary battery includes a first object containing silicon oxide and a second object containing at least one of copper, a copper compound, tungsten, and molybdenum oxide attached to the surface of the first object. The anode active material particles have a predetermined profile. This allows battery reactants to easily reach the first object, facilitating the occlusion and release of the battery reactants. This is suitable for achieving excellent battery performance.

[0010] Note that the effects of the present disclosure 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]

[0011] [Figure 1] FIG. 1 is a diagram schematically illustrating the configuration of a negative electrode active material for a secondary battery according to one embodiment of the present disclosure. [Figure 2] FIG. 2 is a perspective view illustrating a configuration of a secondary battery (including a negative electrode for a secondary battery) according to an embodiment of the present technology. [Figure 3] FIG. 3 is a cross-sectional view showing the configuration of the battery element shown in FIG. [Figure 4] FIG. 4 is a block diagram showing the configuration of an application example of a secondary battery. [Figure 5] FIG. 5 is a cross-sectional view showing the structure of a test secondary battery. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, an embodiment of the present disclosure will be described in detail with reference to the drawings. The description will be made in the following order. 1.Negative electrode active material for secondary batteries 1-1.Configuration 1-2. Manufacturing method 1-3. Action and effects 2. Secondary battery (negative electrode for secondary battery) 2-1.Configuration 2-2.Operation 2-3. Manufacturing method 2-4. Action and effects 3. Variations 4. Uses of secondary batteries

[0013] <1. Negative electrode active material for secondary batteries> First, a negative electrode active material for a secondary battery according to an embodiment of the present technology will be described.

[0014] The negative electrode active material for secondary batteries (hereinafter simply referred to as "negative electrode active material") described here is a material that absorbs and releases an electrode reactant, and is used in the negative electrode of a secondary battery to promote the electrode reaction.

[0015] The type of electrode reactant is not particularly limited, but specifically includes light metals such as alkali metals and alkaline earth metals. Alkali metals include lithium, sodium, and potassium, and alkaline earth metals include beryllium, magnesium, and calcium.

[0016] In the following, an example will be given in which the electrode reactant is lithium. That is, the negative electrode active material is a substance that absorbs and releases lithium as an electrode reactant, and the lithium is absorbed and released in the negative electrode active material in an ionic state.

[0017] <1-1.Configuration> The negative electrode active material for a secondary battery has, for example, a plurality of negative electrode active material particles 3. Each of the plurality of negative electrode active material particles 3 includes a first object 1 and a second object 2, as shown in Fig. 1, for example. Note that Fig. 1 is an explanatory diagram schematically illustrating one negative electrode active material particle 3.

[0018] The first object 1 is a particulate object containing silicon oxide such as SiO or SiO2 as a main component. The average particle size of the first object 1 is not particularly limited, but is, for example, from 1 μm to 10 μm, and preferably from 2 μm to 6 μm. It is desirable that the first object 1 have an amorphous structure.

[0019] In addition to silicon oxide, the first object 1 may further include one or more materials containing silicon as a constituent element as a negative electrode material capable of absorbing and releasing an electrode reactant. Hereinafter, materials containing silicon as a constituent element will be referred to as "silicon-based materials."

[0020] The type of silicon-based material is not particularly limited as long as it contains silicon as a constituent element. That is, the silicon-based material may be silicon alone, a silicon alloy, or a silicon compound. The silicon-based material may be two or more of silicon alone, a silicon alloy, and a silicon compound, or may be a material that contains at least one or more of these phases. However, the term "single element" refers only to a simple element in the general sense (which may contain trace amounts of impurities), and is not limited to a material with 100% purity.

[0021] The silicon alloy may contain silicon together with one or more metal elements as constituent elements, or may contain silicon together with one or more metal elements and one or more metalloid elements as constituent elements, or may contain any one or more non-metallic elements as constituent elements.

[0022] Specifically, the silicon alloy contains, for example, one or more of the following constituent elements other than silicon: boron, tin, nickel, copper, iron, cobalt, manganese, zinc, indium, gold, silver, titanium, germanium, bismuth, antimony, and chromium.

[0023] Specific examples of silicon alloys and silicon compounds include SiB4, SiB6, Mg2Si, Ni2Si, TiSi2, MoSi2, CoSi2, NiSi2, CaSi2, CrSi2, Cu5Si, FeSi2, MnSi2, NbSi2, TaSi2, VSi2, WSi2, ZnSi2, Si3N4, Si2N2O, and LiSiO.

[0024] The second object 2 contains at least one of copper, a copper compound, tungsten, and molybdenum oxide as its main component, and is attached to the surface of the first object 1. The second object 2 is attached in an island or patchy pattern so as to selectively cover the surface of the first object 1. A plurality of second objects 2 are scattered on the surface of the first object 1 so as to selectively cover the surface. The plurality of second objects 2 may be partially connected to each other. The sizes of the plurality of second objects 2 may differ from each other. FIG. 1 schematically illustrates the outer shape of the second object 2 as being part of an ellipsoid or part of a sphere. However, the shape of the second object in the present disclosure is not limited to this and may be other shapes, such as a shape including a partially uneven portion. In any case, the entire surface of the first object 1 is not covered by the second object 2, but rather a portion of the surface of the first object 1 is exposed.

[0025] The copper compound contained in the second object 2 is, for example, at least one of CuO, Cu2O, CuCO3, and Cu(OH)2. The molybdenum oxide contained in the second object 2 is, for example, at least one of MoO2 and MoO3. The second object 2 preferably has an amorphous structure. The second object 2 has a thickness of, but is not particularly limited to, for example, 1 nm or less.

[0026] The Raman spectrum of the negative electrode active material particles 3 detected by Raman spectroscopy is very similar to the Raman spectrum of only the first object 1 detected by Raman spectroscopy. -1 More than 490cm -1 The Raman spectrum has a maximum peak in the following range. This means that amorphous silicon is present in the surface layer of the negative electrode active material particles 3. In other words, this means that part of the surface of the first object 1 is not covered by the second object 2 but is exposed. Note that when detecting the above Raman spectrum, the excitation wavelength is set to, for example, 532 nm.

[0027] The XRD spectrum of the negative electrode active material particles 3 measured by X-ray diffraction (XRD) has peaks in the ranges of 37±1° and 44±1°, and in the range of 40±1°, or in any of the ranges of 23±1°, 25±1°, 37±1°, 41±1°, 54±1°, and 60±1°. Note that when measuring the XRD spectrum, for example, Cu Kα radiation of 0.154 nm is used and the measurement is performed at an acceleration voltage of 40 kV.

[0028] Furthermore, the intensity of at least one of the peaks in the range of 227 eV to 240 eV and the range of 930 eV to 938 eV in the photoelectron spectrum of the negative electrode active material particles 3 detected by X-ray photoelectron spectroscopy (XPS) is 25% or less of the intensity of the peak in the range of 98 eV to 104 eV in the photoelectron spectrum of the first object 1 alone detected by X-ray photoelectron spectroscopy. The peak observed in the range of 227 eV to 240 eV corresponds to molybdenum oxide. The peak observed in the range of 930 eV to 938 eV corresponds to copper and copper compounds. The photoelectron spectrum is measured using, for example, a 0.989 nm Mg Kα ray at an acceleration voltage of 10 kV. The photoelectron spectrum is also measured for negative electrode active material particles 3 whose surfaces have been etched to a depth of 200 nm at an etching rate of 3 nm / sec or less using Ar ions accelerated at an acceleration voltage of 1 kV.

[0029] The composition ratio of Cu (copper) to Si (silicon) in the negative electrode active material particles 3, as determined from the photoelectron spectrum of the negative electrode active material particles 3 detected by X-ray photoelectron spectroscopy, is 1% or more and 3% or less.

[0030] The coverage of the second object with respect to the first object in the negative electrode active material particles 3, as determined from the photoelectron spectrum of the negative electrode active material particles 3 detected by X-ray photoelectron spectroscopy, is 1% or more and 3% or less.

[0031] <1-2. Manufacturing method> The negative electrode active material particles 3 are formed using, for example, a barrel sputtering device. Specifically, first, a powdered first object 1 is placed inside a polygonal barrel placed inside a chamber. The interior of the polygonal barrel is set to a predetermined temperature (e.g., 30°C). A target consisting of the raw material for the second object 2 is placed inside the chamber. In this state, the chamber is evacuated using a pump, and a predetermined gas (e.g., Ar gas) is supplied while the polygonal barrel is rotated so as to rotate forward and backward repeatedly at a predetermined rotation speed (e.g., 100 rpm) within a predetermined rotation angle range (e.g., ±60°). During this process, the target is heated (e.g., to a temperature of 30°C or higher and 100°C or lower), thereby selectively attaching the second object 2 to the surface of the first object 1 inside the polygonal barrel. Thereafter, heat treatment is performed as necessary to obtain the negative electrode active material particles 3.

[0032] <1-3. Actions and Effects> The negative electrode active material for a secondary battery according to the present disclosure has negative electrode active material particles 3 including a first object 1 containing silicon oxide and a second object 2 containing at least one of copper, a copper compound, tungsten, and molybdenum oxide attached to the surface of the first object 1, and the negative electrode active material particles 3 have a predetermined profile. Therefore, when applied to a secondary battery, battery reactants can easily reach the first object 1, and the battery reactants can be smoothly absorbed and released. This makes the negative electrode active material suitable for obtaining excellent battery performance.

[0033] More specifically, the negative electrode active material for a secondary battery of the present disclosure can improve the initial charge / discharge capacity compared to a material in which the second object 2 is not attached to the first object 1, or a material in which the surface of the first object 1 is uniformly covered with the second object 2.

[0034] <2. Secondary battery (negative electrode for secondary battery)> Next, a secondary battery according to an embodiment of the present disclosure will be described. Note that the negative electrode for a secondary battery according to an embodiment of the present disclosure (hereinafter simply referred to as "negative electrode") constitutes a part (one component) of the secondary battery, and therefore will be described below together with the secondary battery.

[0035] The secondary battery described here is a secondary battery that obtains battery capacity by utilizing the absorption and desorption of electrode reactants, and includes a positive electrode, a negative electrode, and an electrolytic solution, which is a liquid electrolyte. In this secondary battery, the charge capacity of the negative electrode is larger than the discharge capacity of the positive electrode to prevent the electrode reactants from depositing on the surface of the negative electrode during charging. In other words, 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.

[0036] In the following, an example will be given in which the electrode reactant is lithium. A secondary battery that obtains battery capacity by utilizing the absorption and desorption of lithium is known as a lithium ion secondary battery.

[0037] <2-1.Configuration> Fig. 2 shows a perspective view of the secondary battery, and Fig. 3 shows a cross-sectional view of the battery element 20 shown in Fig. 2. However, Fig. 2 shows a state in which the exterior film 10 and the battery element 20 are separated from each other, and Fig. 3 shows only a portion of the battery element 20.

[0038] 2, the 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 as an exterior member for housing the battery element 20.

[0039] [Exterior film and sealing film] 1, 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.

[0040] The three-dimensional shape of the exterior film 10 is not particularly limited, but specifically corresponds to the three-dimensional shape of the battery element 20. Here, the three-dimensional shape of the exterior film 10 is a flat, approximately rectangular parallelepiped, in accordance with the three-dimensional shape of the flat battery element 20 described below.

[0041] The configuration of the exterior film 10 (such as the material and number of layers) is not particularly limited, and it may be a single-layer film or a multi-layer film. The exterior film 10 is a single film that can be folded in the direction of the arrow F (dash-dotted line). The exterior film 10 is provided with a recess 10U as a so-called deep-drawn portion for accommodating the battery element 20.

[0042] Specifically, the exterior film 10 is a three-layered film, i.e., a laminate film, in which a fusion layer, a metal layer, and a surface protection layer are laminated in this order from the inside. When the exterior film 10 is folded, the outer peripheral edges of the opposing fusion layers are joined 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.

[0043] 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.

[0044] 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. A specific example of the polyolefin is polypropylene.

[0045] 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.

[0046] [Battery element] As shown in FIGS. 1 and 2, the battery element 20 is housed inside the exterior film 10, and includes a positive electrode 21, a negative electrode 22, a separator 23, and an electrolyte solution.

[0047] Battery element 20 is a so-called wound electrode body. That is, in battery element 20, positive electrode 21 and negative electrode 22 are stacked on top of each other with separator 23 interposed therebetween, and positive electrode 21, negative electrode 22, and separator 23 are wound around winding axis P, which is an imaginary axis extending in the Y-axis direction. Positive electrode 21 and negative electrode 22 are wound while facing each other with separator 23 interposed therebetween.

[0048] The three-dimensional shape of battery element 20 is a flat, approximately cylindrical body. That is, the shape of a cross section (cross section along the XZ plane) of battery element 20 intersecting winding axis P is a flat shape defined by major axis J1 and minor axis J2, more specifically, a flat, approximately elliptical shape. Major axis J1 is an imaginary axis that extends in the X-axis direction and has a relatively long length, and minor axis J2 is an imaginary axis that extends in the Z-axis direction that intersects with the X-axis direction and has a relatively short length.

[0049] (positive electrode) As shown in FIG. 3, the positive electrode 21 includes a positive electrode current collector 21A and a positive electrode active material layer 21B.

[0050] 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.

[0051] 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 that absorb and release 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 a positive electrode binder, a positive electrode conductive agent, and the like. The method for forming the positive electrode active material layer 21B is not particularly limited, but specifically includes a coating method, etc.

[0052] The positive electrode active material contains a lithium compound. This lithium compound is a compound containing lithium as a constituent element, more specifically, a compound containing lithium and one or more transition metal elements as constituent elements. This is because a high energy density can be obtained. However, the lithium compound may further contain one or more other elements (elements other than lithium and transition metal elements). The type of lithium compound is not particularly limited, but specific examples include oxides, phosphate compounds, silicate compounds, and borate compounds. Specific examples of oxides include LiNiO2, LiCoO2, and LiMn2O4, and specific examples of phosphate compounds include LiFePO4 and LiMnPO4.

[0053] The positive electrode binder contains one or more of synthetic rubber and polymer compounds. The synthetic rubber is styrene-butadiene rubber, and the polymer compound is polyvinylidene fluoride. The positive electrode conductor contains one or more of conductive materials such as carbon materials, and the carbon materials include graphite, carbon black, acetylene black, and ketjen black. However, the conductive material may also be a metal material or a polymer compound.

[0054] (Negative electrode) As shown in FIG. 3, the negative electrode 22 includes a negative electrode current collector 22A and a negative electrode active material layer 22B.

[0055] The negative electrode current collector 22A has a pair of surfaces on which the negative electrode active material layer 22B is provided. This negative electrode current collector 22A contains a conductive material such as a metal material, and the metal material is copper or the like.

[0056] Here, the negative electrode active material layer 22B is provided on both surfaces of the negative electrode current collector 22A and contains the above-described negative electrode active material. However, the negative electrode active material layer 22B may be provided only on one side of the negative electrode current collector 22A on the side where the negative electrode 22 faces the positive electrode 21. Further, the negative electrode active material layer 22B may further contain a negative electrode binder, a negative electrode conductive agent, and the like. The method for forming the negative electrode active material layer 22B is not particularly limited, but specifically, it is any one or two or more of coating methods, vapor phase methods, liquid phase methods, spraying methods, and firing methods (sintering methods).

[0057] Details regarding each of the negative electrode binder and the negative electrode conductive agent are the same as the details regarding each of the positive electrode binder and the positive electrode conductive agent.

[0058] In addition, the negative electrode active material layer 22B may further contain any one or two or more of other negative electrode active materials that occlude and release lithium. The other negative electrode active materials are one or both of carbon materials and metal-based materials, etc. This is because a high energy density can be obtained.

[0059] The carbon materials are graphitizable carbon, non-graphitizable carbon, and graphite (natural graphite and artificial graphite), etc. The metal-based material is a material containing any one or two or more of metal elements and semi-metal elements that can form an alloy with lithium as constituent elements, and the metal elements and semi-metal elements are one or both of silicon and tin, etc. Note that the metal-based material may be a single substance, an alloy, a compound, a mixture of two or more of them, or a material containing two or more of their phases. Specific examples of the metal-based material are TiSi2 and SiOx (0 < x < 1.5), etc. However, the above-described negative electrode active material (see FIG. 1) is excluded from the metal-based materials described here.

[0060] (separator) 3, 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.

[0061] (electrolyte) The electrolyte solution is impregnated into each of the positive electrode 21, the negative electrode 22, and the separator 23, and contains a solvent and an electrolyte salt.

[0062] The solvent contains one or more of non-aqueous solvents (organic solvents) such as carbonate ester compounds, carboxylic acid ester compounds, and lactone compounds, and the electrolyte solution containing the non-aqueous solvent is a so-called non-aqueous electrolyte solution. The electrolyte salt contains one or more of light metal salts such as lithium salts.

[0063] [Positive and negative leads] As shown in Fig. 2, the positive electrode lead 31 is a positive electrode terminal connected to the battery element 20 (positive electrode 21), and more specifically, connected to the positive electrode current collector 21A. The positive electrode lead 31 is led out 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.

[0064] As shown in FIG. 2 , the negative electrode lead 32 is a negative electrode terminal connected to the battery element 20 (negative electrode 22), and more specifically, is connected to the negative electrode current collector 22A. This negative electrode lead 32 is led out 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. 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.

[0065] <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 charge and discharge cycles, lithium is absorbed and released in an ionic state.

[0066] <2-3. Manufacturing method> According to the procedure described below, the positive electrode 21 and the negative electrode 22 are fabricated and an electrolyte solution is prepared, and then the positive electrode 21, the negative electrode 22, and the electrolyte solution are used to fabricate a secondary battery.

[0067] [Preparation of positive electrode] First, a positive electrode active material, a positive electrode binder, and a positive electrode conductive agent are mixed together to form a positive electrode mixture. Subsequently, the positive electrode mixture is introduced into a solvent to prepare a paste-like positive electrode mixture slurry. The type of solvent is not particularly limited, but specifically, it may be an aqueous solvent or a non-aqueous solvent (organic solvent). This aqueous solvent is, for example, pure water, and the details regarding the types of aqueous solvents described here also apply hereinafter. Finally, the positive electrode mixture slurry is applied to both sides of the positive electrode current collector 21A to form the positive electrode active material layer 21B. The positive electrode active material layer 21B may then be compression-molded using a roll press or the like. In this case, the positive electrode active material layer 21B may be heated, or the compression molding may be repeated multiple times. This produces the positive electrode 21.

[0068] [Preparation of negative electrode] Using the above-described negative electrode active material, negative electrode active material layers 22B are formed on both sides of the negative electrode current collector 22A using a procedure similar to that for producing the positive electrode 21. Specifically, the negative electrode active material, negative electrode binder, and negative electrode conductor are mixed together to form a negative electrode mixture, and the negative electrode mixture is then introduced into a solvent (aqueous solvent) to prepare a paste-like negative electrode mixture slurry. Subsequently, the negative electrode mixture slurry is applied to both sides of the negative electrode current collector 22A to form the negative electrode active material layers 22B. The negative electrode active material layers 22B may then be compression-molded. In this manner, the negative electrode 22 is produced.

[0069] [Preparation of electrolyte] An electrolyte salt is added to a solvent, whereby the electrolyte salt is dispersed or dissolved in the solvent, thereby preparing an electrolytic solution.

[0070] [Secondary battery assembly] First, the positive electrode lead 31 is connected to the positive electrode 21 (positive electrode current collector 21A) and the negative electrode lead 32 is connected to the negative electrode 22 (negative electrode current collector 22A) using welding or the like.

[0071] 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 (not shown). This wound body has a configuration similar to that of 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.

[0072] 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.

[0073] Finally, after injecting an 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, which is a wound electrode body, is produced, and the battery element 20 is sealed inside the bag-shaped exterior film 10, and a secondary battery is assembled.

[0074] [Secondary battery stabilization] 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 the negative electrode 22, etc., which electrochemically stabilizes the state of the secondary battery. This completes the laminate film type secondary battery.

[0075] <2-4. Actions and Effects> In the secondary battery of the present disclosure, the negative electrode 22 contains the above-described negative electrode active material for a secondary battery. Therefore, during charging and discharging, lithium, which is a battery reactant, easily reaches the first body 1, and lithium is smoothly absorbed and released. As a result, excellent battery performance can be obtained.

[0076] <3. Modifications> The configuration of the secondary battery can be modified as appropriate, as described below, although any two or more of the series of modifications described below may be combined with each other.

[0077] [Variation 1] 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.

[0078] 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 has improved adhesion to each of the positive electrode 21 and the negative electrode 22, making it less likely for the battery element 20 to shift position (winding misalignment). This makes it less likely for the secondary battery to swell 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.

[0079] 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 include inorganic particles and resin particles. Specific examples of inorganic particles include particles of aluminum oxide, aluminum nitride, boehmite, silicon oxide, titanium oxide, magnesium oxide, and zirconium oxide. Specific examples of resin particles include particles of acrylic resin and styrene resin.

[0080] When producing a laminated separator, a precursor solution containing a polymer compound and an organic 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.

[0081] Even when this laminated separator is used, lithium ions can move between the positive electrode 21 and the negative electrode 22, and the same effect can be obtained.

[0082] [Variation 2] An electrolyte 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 electrolyte solution.

[0083] 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.

[0084] 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 an electrolytic solution, a polymer compound, an organic 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.

[0085] Even when this electrolyte layer is used, lithium ions can move between the positive electrode 21 and the negative electrode 22 via the electrolyte layer, so the same effect can be obtained.

[0086] <4. Uses of secondary batteries> 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.

[0087] Specific examples of uses for secondary batteries are as follows: Electronic devices (including portable electronic devices) such as video cameras, digital still cameras, mobile phones, notebook 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, etc. In these uses, one or more secondary batteries may be used.

[0088] 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 as mentioned above, may be a hybrid vehicle that also has a driving source other than a secondary battery. In a home power storage system, it is possible to use home electrical appliances and the like by using the power stored in the secondary battery, which is a power storage source.

[0089] 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.

[0090] Figure 4 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.

[0091] 4, 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.

[0092] 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.

[0093] 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.

[0094] When the voltage of power supply 51 (secondary battery) reaches the overcharge detection voltage or 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. The overdischarge detection voltage is not particularly limited, but specifically, it is 2.4V±0.1V.

[0095] 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.

[0096] 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]

[0097] An embodiment of the present technology will be described.

[0098] <Example 1 and Comparative Example 1> The cross-sectional structure of a test secondary battery (coin type) is shown in Figure 5. 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 the battery characteristics of the secondary battery were evaluated.

[0099] 5, a test electrode 61 is housed inside an exterior cup 64, and a counter electrode 63 is housed inside an exterior can 62. The test electrode 61 and the counter electrode 63 are stacked together with a separator 65 interposed therebetween, and the exterior can 62 and the exterior cup 64 are crimped together with a gasket 66. The test electrode 61, the counter electrode 63, and the separator 65 are each impregnated with an electrolyte.

[0100] [Production of negative electrode active material] A negative electrode active material was produced according to the procedure described below.

[0101] (Production of negative electrode active material of Example 1) First, SiO powder was prepared as the first object 1 and placed in a polygonal barrel installed inside the chamber of a barrel sputtering apparatus. The SiO powder used had an average particle size of 4 μm. Next, a Cu target, the raw material for the second object 2, was prepared and placed inside the chamber of the barrel sputtering apparatus. The chamber was then evacuated using a pump and Ar gas was introduced. The target was then heated to a temperature of 30°C to 100°C using a heater, while the polygonal barrel was rotated forward and backward within a rotation angle range of ±60°, selectively attaching the second object 2 to the surface of the first object 1 inside the polygonal barrel. This resulted in a negative electrode active material composed of multiple negative electrode active material particles 3. The resulting negative electrode active material of Example 1 was subjected to Raman spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy to obtain a Raman spectrum, XRD spectrum, and photoelectron spectrum, respectively. As a result, a peak at 470 cm was detected in the Raman spectrum. -1More than 490cm -1 It was confirmed that the maximum peak was in the following range. This confirmed that amorphous silicon constituting the first object 1 was present in the surface layer of the negative electrode active material particle 3, that is, that a portion of the surface of the first object 1 was exposed. Furthermore, it was confirmed that the XRD spectrum had peaks in the range of 37±1° and 44±1°. This confirmed that Cu2O and Cu were present on the surface of the negative electrode active material particle 3.

[0102] (Negative electrode active material of Comparative Example 1) SiO powder with an average particle size of 4 μm was used as is. The photoelectron spectrum of the negative electrode active material of Comparative Example 1 was also detected by X-ray photoelectron spectroscopy. As a result, it was confirmed that the peak intensity in the range of 930 eV to 938 eV in the photoelectron spectrum of the negative electrode active material of Example 1 was 25% or less of the peak intensity in the range of 98 eV to 104 eV in the photoelectron spectrum of the negative electrode active material of Comparative Example 1.

[0103] [Fabrication of Secondary Batteries in Example 1 and Comparative Example 1] Using each of the above negative electrode active materials, a coin-type lithium ion secondary battery shown in FIG. 5 was fabricated according to the procedure described below.

[0104] (Preparation of test electrodes) First, 80 parts by mass of the negative electrode active material, 5 parts by mass of a negative electrode binder (styrene butadiene rubber), 10 parts by mass of a negative electrode conductive agent (carbon black), and 5 parts by mass of a thickener (carboxymethyl cellulose) were mixed together to prepare a negative electrode mixture. Next, the negative electrode mixture was added to a solvent (pure water, an aqueous solvent), and then kneaded using a planetary mixer to prepare a paste-like negative electrode mixture slurry. Next, the negative electrode mixture slurry was applied to one side of a negative electrode current collector (copper foil with a thickness of 12 μm) using a coating device, and the negative electrode mixture slurry was then heated and dried (heating temperature = 120 °C) and subsequently vacuum-dried to form a negative electrode active material layer. Finally, the negative electrode active material layer was compression-molded using a roll press. This produced a test electrode 61.

[0105] (Preparing for the opposite) Here, a lithium metal plate was used as the counter electrode 63 to fabricate a test secondary battery.

[0106] (Preparation of Electrolyte) After adding the electrolyte salt (lithium hexafluorophosphate) to the solvent (ethylene carbonate and ethyl methyl carbonate), the solvent was stirred. In this case, the mixing ratio (mass ratio) of the solvents was ethylene carbonate:ethyl methyl carbonate = 50:50, and the content of the electrolyte salt relative to the solvent was 1 mol / L (= 1 mol / dm 3 ) Thus, the electrolyte solution was prepared.

[0107] (Secondary battery assembly) First, the test electrode 61 was placed inside the exterior cup 64, and the counter electrode 63 was placed inside the exterior can 62. Next, the test electrode 61 placed inside the exterior cup 64 and the counter electrode 63 placed inside the exterior can 62 were stacked together with a separator 65 (a microporous polyethylene film with a thickness of 25 μm) impregnated with an electrolyte interposed therebetween. In this case, a gasket 66 (a fluororesin film with a thickness of 1.1 mm) was interposed between the exterior cup 64 and the exterior can 62. Finally, the exterior cup 64 and the exterior can 62 were crimped together with the gasket 66 interposed therebetween.

[0108] As a result, the test electrode 61, the counter electrode 63, and the separator 65 were sealed inside the exterior cup 64 and the exterior can 62, and a coin-type secondary battery was assembled.

[0109] (Stabilization of secondary batteries) The secondary battery was charged and discharged for one cycle in a room temperature environment (temperature = 23°C). During charging, it was charged at a constant current of 0.2 C until the voltage reached 0.05 V, and then it was charged at a constant voltage of 0.05 V until the current reached 0.025 C. During discharging, it was discharged at a constant current of 0.2 C until the voltage reached 1.5 V. 0.2 C is the current value that fully discharges the battery capacity (theoretical capacity) in 5 hours, and 0.025 C is the current value that fully discharges the battery capacity in 40 hours.

[0110] This completed the coin-type secondary battery.

[0111] [Evaluation of battery characteristics] The initial charge / discharge capacity was evaluated as a battery characteristic of the secondary batteries, and the results shown in Table 1 were obtained. Here, each secondary battery was first charged in an environment of 23°C, and the charge capacity at that time was measured. Then, the battery was subsequently discharged and the discharge capacity was measured. Note that "charging" here refers to an operation in the direction in which lithium ions, which are the battery reactant, are absorbed into the negative electrode.

[0112] [Table 1]

[0113] In Table 1, the characteristic values ​​of Example 1 are shown as numerical values ​​normalized by setting the initial charge capacity, initial discharge capacity, and initial coulombic efficiency of Comparative Example 1 to 1. The coulombic efficiency is a value expressed as a percentage of the ratio of the discharge capacity during discharge to the charge capacity during charge, i.e., discharge capacity / charge capacity.

[0114] [Consideration] As shown in Table 1, it was confirmed that the Coulombic efficiency was improved in Example 1 compared to Comparative Example 1. Therefore, according to the secondary battery of the present disclosure, since the second object 2 is attached to the surface of the first object 1 in a scattered manner, lithium, which is a battery reactant, can easily reach the first object 1 during charging and discharging, and it was confirmed that lithium is smoothly absorbed and released.

[0115] The present disclosure has been described above with reference to an embodiment and examples, but the configuration of the present disclosure is not limited to the configuration described in the embodiment and examples, and various modifications are possible.

[0116] Although the secondary battery has been described as having a laminate film structure, the battery structure is not particularly limited. Specifically, the battery structure may be cylindrical, prismatic, coin-shaped, button-shaped, or the like.

[0117] Although the battery element has been described as having a wound structure, the structure of the battery element is not particularly limited. Specifically, the structure may be a stacked structure in which the electrodes (positive and negative electrodes) are stacked, or a zigzag-folded structure in which the electrodes are folded.

[0118] Furthermore, although the electrode reactant is lithium in the above description, 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.

[0119] The applications of the negative electrode active material for a secondary battery and the negative electrode for a secondary battery are not limited to secondary batteries, and they may be applied to other electrochemical devices such as capacitors.

[0120] 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. a first object containing an oxide of silicon; a second object containing at least one of copper, a copper compound, tungsten, and molybdenum oxide and attached to the surface of the first object; a negative electrode active material particle containing The Raman spectrum of the negative electrode active material particles detected by Raman spectroscopy was measured at 470 cm -1 490cm or more -1 It has a maximum peak in the following range: an XRD spectrum of the negative electrode active material particles detected by X-ray diffraction (XRD) has peaks in the range of 37±1° and the range of 44±1°, respectively, a peak in the range of 40±1°, or a peak in any of the ranges of 23±1°, 25±1°, 37±1°, 41±1°, 54±1°, or 60±1°; the intensity of at least one of the peaks in the range of 227 eV or more and 240 eV or less and the range of 930 eV or more and 938 eV or less in the photoelectron spectrum of the negative electrode active material particles detected by X-ray photoelectron spectroscopy (XPS) is 25% or less of the intensity of the peak in the range of 98 eV or more and 104 eV or less in the photoelectron spectrum of only the first object detected by X-ray photoelectron spectroscopy; a composition ratio of Cu (copper) to Si (silicon) in the negative electrode active material particles, determined from a photoelectron spectrum of the negative electrode active material particles detected by X-ray photoelectron spectroscopy, is 1% or more and 3% or less; The copper compound is CuO, Cu 2 O, CuCO 3 and Cu(OH) 2 and at least one of The molybdenum oxide is MoO 2 and MoO 3 At least one of the following is true: Negative electrode active material for secondary batteries.

2. a coverage of the second object with respect to the first object in the negative electrode active material particles, determined from a photoelectron spectrum of the negative electrode active material particles detected by X-ray photoelectron spectroscopy, of 1% or more and 3% or less; The negative electrode active material according to claim 1 .

3. The second object is attached in patches so as to selectively cover the surface of the first object. The negative electrode active material according to claim 1 or 2.

4. The second object is scattered in plurality so as to selectively cover the surface of the first object. The negative electrode active material according to claim 1 .

5. a negative electrode active material, The negative electrode active material is a first object containing an oxide of silicon; a second object containing at least one of copper, a copper compound, tungsten, and molybdenum oxide and attached to the surface of the first object; a negative electrode active material particle containing The Raman spectrum of the negative electrode active material particles detected by Raman spectroscopy was measured at 470 cm -1 490cm or more -1 It has a maximum peak in the following range: an XRD spectrum of the negative electrode active material particles detected by X-ray diffraction (XRD) has peaks in the range of 37±1° and the range of 44±1°, respectively, a peak in the range of 40±1°, or a peak in any of the ranges of 23±1°, 25±1°, 37±1°, 41±1°, 54±1°, or 60±1°; the intensity of at least one of the peaks in the range of 227 eV or more and 240 eV or less and the range of 930 eV or more and 938 eV or less in the photoelectron spectrum of the negative electrode active material particles detected by X-ray photoelectron spectroscopy (XPS) is 25% or less of the intensity of the peak in the range of 98 eV or more and 104 eV or less in the photoelectron spectrum of only the first object detected by X-ray photoelectron spectroscopy; a composition ratio of Cu (copper) to Si (silicon) in the negative electrode active material particles, determined from a photoelectron spectrum of the negative electrode active material particles detected by X-ray photoelectron spectroscopy, is 1% or more and 3% or less; The copper compound is CuO, Cu 2 O, CuCO 3 and Cu(OH) 2 and at least one of The molybdenum oxide is MoO 2 and MoO 3 At least one of the following is true: Negative electrode for secondary batteries.

6. a positive electrode, a negative electrode containing a negative electrode active material, and an electrolyte; The negative electrode active material is a first object containing an oxide of silicon; a second object containing at least one of copper, a copper compound, tungsten, and molybdenum oxide and attached to the surface of the first object; a negative electrode active material particle containing The Raman spectrum of the negative electrode active material particles detected by Raman spectroscopy was measured at 470 cm -1 490cm or more -1 It has a maximum peak in the following range: an XRD spectrum of the negative electrode active material particles detected by X-ray diffraction (XRD) has peaks in the range of 37±1° and the range of 44±1°, respectively, a peak in the range of 40±1°, or a peak in any of the ranges of 23±1°, 25±1°, 37±1°, 41±1°, 54±1°, or 60±1°; the intensity of at least one of the peaks in the range of 227 eV or more and 240 eV or less and the range of 930 eV or more and 938 eV or less in the photoelectron spectrum of the negative electrode active material particles detected by X-ray photoelectron spectroscopy (XPS) is 25% or less of the intensity of the peak in the range of 98 eV or more and 104 eV or less in the photoelectron spectrum of only the first object detected by X-ray photoelectron spectroscopy; a composition ratio of Cu (copper) to Si (silicon) in the negative electrode active material particles, determined from a photoelectron spectrum of the negative electrode active material particles detected by X-ray photoelectron spectroscopy, is 1% or more and 3% or less; The copper compound is CuO, Cu 2 O, CuCO 3 and Cu(OH) 2 and at least one of The molybdenum oxide is MoO 2 and MoO 3 At least one of the following is true: Secondary battery.

7. A first object containing a silicon oxide; a second object containing at least one of copper, a copper compound, tungsten, and molybdenum oxide and attached to the surface of the first object; a negative electrode active material particle containing the Raman spectrum of the negative electrode active material particles detected by Raman spectroscopy has a maximum peak in the range of 470 cm −1 or more and 490 cm −1 or less; an XRD spectrum of the negative electrode active material particles detected by X-ray diffraction (XRD) has peaks in the range of 37±1° and the range of 44±1°, respectively, a peak in the range of 40±1°, or a peak in any of the ranges of 23±1°, 25±1°, 37±1°, 41±1°, 54±1°, or 60±1°; the intensity of at least one of the peaks in the range of 227 eV or more and 240 eV or less and the range of 930 eV or more and 938 eV or less in the photoelectron spectrum of the negative electrode active material particles detected by X-ray photoelectron spectroscopy (XPS) is 25% or less of the intensity of the peak in the range of 98 eV or more and 104 eV or less in the photoelectron spectrum of only the first object detected by X-ray photoelectron spectroscopy; a coverage of the second object with respect to the first object in the negative electrode active material particles, determined from a photoelectron spectrum of the negative electrode active material particles detected by X-ray photoelectron spectroscopy, being 1% or more and 3% or less; the copper compound is at least one of CuO, Cu2O, CuCO3, and Cu(OH)2; The molybdenum oxide is at least one of MoO 2 and MoO 3 . Negative electrode active material for secondary batteries.

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