Negative electrode for secondary battery, and secondary battery

Abstract

The secondary battery includes a positive electrode, a negative electrode including a negative electrode active material layer containing an alkali metal carbonate compound and a magnesium compound, and an electrolyte solution. The alkali metal carbonate compound has a carbonate bond (-OC (= O) O-) and contains an alkali metal element as a constituent element, and the magnesium compound contains magnesium as a constituent element.

Description

Technical Field

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

[0002] As various electronic devices such as mobile phones are becoming more popular, secondary batteries are being developed as small, lightweight power sources with high energy density. The secondary battery includes a positive electrode, a negative electrode (negative electrode for secondary batteries), and an electrolyte, and various studies have been conducted on the structure of the secondary battery.

[0003] Specifically, the negative electrode active material layer contains a negative electrode active material (carbon material) and ceramic nanoparticles (MgO) (for example, see Patent Document 1). The anode active material contains (CH2OCO2Li)2 as a lithium ion conductive additive (for example, see Patent Document 2). At least one of the positive electrode, the negative electrode, and the non-aqueous electrolyte contains an alkaline compound containing anions (NO2 - ) and cations (Mg 2+ ) (For example, refer to Patent Document 3.). The electrode binder contains a polymer compound, and the polymer compound contains anions (NO3 - or NO2 - ) and cations (Mg 2+ ) (For example, refer to Patent Document 4.).

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Publication No. 2007-305545

[0007] Patent Document 2: Japanese Patent Application No. 2020-513138

[0008] Patent Document 3: Japanese Patent Application Publication No. 2015-090860

[0009] Patent Document 4: Japanese Patent Application Publication No. 2014-077134 Summary of the invention

[0010] Although various studies have been conducted on the configuration of secondary batteries, the battery characteristics of the secondary batteries are still insufficient, and thus there is room for improvement.

[0011] A negative electrode for a secondary battery and a secondary battery that can provide excellent battery characteristics are desired.

[0012] A negative electrode for a secondary battery according to an embodiment of the present technology includes a negative electrode active material layer, the negative electrode active material layer including an alkali metal carbonate compound having a carbonate bond (-OC(=O)O-) and containing an alkali metal element as a constituent element, and a magnesium compound containing magnesium as a constituent element.

[0013] A secondary battery according to an embodiment of the present technology includes a positive electrode, a negative electrode, and an electrolyte solution. The negative electrode has the same configuration as that of the negative electrode for a secondary battery according to the embodiment of the present technology described above.

[0014] According to a secondary battery negative electrode or a secondary battery according to an embodiment of the present technology, the secondary battery negative electrode includes a negative electrode active material layer, and the negative electrode active material layer contains an alkali metal carbonate compound and a magnesium compound, so that excellent battery characteristics can be obtained.

[0015] It should be noted that the effects of the present technology are not necessarily limited to the effects described here, and may be any of a series of effects related to the present technology described later. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a cross-sectional view showing the structure of a negative electrode for a secondary battery in one embodiment of the present technology.

[0017] Figure 2 It is a perspective view showing the structure of a secondary battery in one embodiment of the present technology.

[0018] Figure 3 Yes means Figure 2 A cross-sectional view showing the structure of a battery element.

[0019] Figure 4 Yes means Figure 3 A top view of the structure of the positive electrode shown.

[0020] Figure 5 Yes means Figure 3 A top view of the structure of the negative electrode shown.

[0021] Figure 6 It is a perspective view for explaining a method for manufacturing a secondary battery.

[0022] Figure 7 It is a block diagram showing the configuration of an application example of a secondary battery. DETAILED DESCRIPTION

[0023] Hereinafter, one embodiment of the present technology will be described in detail with reference to the drawings. It should be noted that the order of the description is as follows.

[0024] 1. Negative electrode for secondary batteries

[0025] 1-1. Composition

[0026] 1-2. Action

[0027] 1-3. Manufacturing method

[0028] 1-4. Function and effect

[0029] 2. Secondary battery

[0030] 2-1. Composition

[0031] 2-2. Action

[0032] 2-3. Manufacturing method

[0033] 2-4. Actions and effects

[0034] 3. Modifications

[0035] 4. Uses of secondary batteries

[0036] <1. Negative electrode for secondary batteries>

[0037] First, a negative electrode for a secondary battery (hereinafter simply referred to as “negative electrode”) according to an embodiment of the present technology will be described.

[0038] The negative electrode described here is used for a secondary battery as an electrochemical device. In addition, the negative electrode can also be used for other electrochemical devices other than secondary batteries. Specific examples of other electrochemical devices are primary batteries and capacitors.

[0039] The negative electrode intercalates and deintercalates the electrode reaction substance during the electrode reaction of the electrochemical device. The type of the electrode reaction substance is not particularly limited, and specifically, it is a light metal such as an alkali metal and an alkaline earth metal. Specific examples of alkali metals are lithium, sodium, and potassium, and specific examples of alkaline earth metals are beryllium, magnesium, and calcium.

[0040] Hereinafter, the case where the electrode reaction substance is lithium is taken as an example. In the negative electrode, lithium is inserted and released in an ionic state during the electrode reaction.

[0041] <1-1. Structure>

[0042] Figure 1 FIG. 2 shows a cross-sectional structure of a negative electrode 100 as an example of a negative electrode. Figure 1 As shown, the negative electrode 100 includes a negative electrode active material layer 120 . Here, the negative electrode 100 further includes a negative electrode collector 110 that supports the negative electrode active material layer 120 .

[0043] [Negative electrode current collector]

[0044] The negative electrode current collector 110 is a conductive support for supporting the negative electrode active material layer 120, and has a pair of surfaces provided with the negative electrode active material layer 120. The negative electrode current collector 110 includes any one or two or more conductive materials such as metal materials, and a specific example of the conductive material is copper.

[0045] The surface of the negative electrode current collector 110 is preferably roughened by electrolysis or the like. This is because the adhesion of the negative electrode active material layer 120 to the negative electrode current collector 110 can be improved by utilizing a so-called anchor effect.

[0046] In addition, the negative electrode current collector 110 may be omitted. That is, the negative electrode 100 may not include the negative electrode current collector 110 but may include only the negative electrode active material layer 120 .

[0047] [Negative Electrode Active Material Layer]

[0048] The negative electrode active material layer 120 includes an alkali metal carbonate compound and a magnesium compound. Here, the negative electrode active material layer 120 further includes a negative electrode active material that inserts and extracts lithium. In addition, the negative electrode active material layer 120 may further include any one or more of other materials such as a negative electrode binder and a negative electrode conductive agent.

[0049] Here, the negative electrode active material layer 120 is provided on both surfaces of the negative electrode current collector 110. Alternatively, the negative electrode active material layer 120 may be provided only on one surface of the negative electrode current collector 110. The method for forming the negative electrode active material layer 120 is not particularly limited, and specifically, a coating method or the like is used.

[0050] (Negative electrode active material)

[0051] The type of negative electrode active material is not particularly limited, and specifically, it is any one or more of materials such as carbon materials and metal materials. That is, the negative electrode active material can be only carbon materials, only metal materials, or both carbon materials and metal materials. This is because high energy density can be obtained. In addition, the type of negative electrode active material can also be other materials other than carbon materials and metal materials.

[0052] Carbon material is a general term for materials containing carbon as a constituent element. Since the crystal structure of the carbon material hardly changes during the insertion and extraction of lithium, a high energy density can be stably obtained in the negative electrode active material layer 120. In addition, since the carbon material also functions as a negative electrode conductive agent, the conductivity in the negative electrode active material layer 120 is improved.

[0053] Specific examples of carbon materials include graphitizable carbon, non-graphitizable carbon, and graphite. The graphite may be natural graphite, artificial graphite, or both. The interplanar spacing of the (002) plane of non-graphitizable carbon is not particularly limited, and is specifically 0.37 nm or more. The interplanar spacing of the (002) plane of graphite is not particularly limited, and is specifically 0.34 nm or less.

[0054] In addition, specific examples of carbon materials are pyrolytic carbons, cokes, glassy carbon fibers, organic polymer compound sintered bodies, activated carbon, and carbon black. The cokes include pitch coke, needle coke, and petroleum coke. The organic polymer compound sintered body is a sintered product obtained by sintering (carbonizing) polymer compounds such as phenolic resin and furan resin at an appropriate temperature. In addition, the carbon material can be low-crystalline carbon obtained by heat treatment at a temperature below about 1000°C, or it can be amorphous carbon. The shape of the carbon material is not particularly limited, and specifically, it is any one or more of fibrous, spherical, granular, and flaky.

[0055] Metallic materials are a general term for materials containing any one or more of metal elements and semi-metal elements that can form an alloy with lithium as constituent elements. Since metallic materials have a higher energy density, a higher energy density can be obtained in the negative electrode active material layer 120 .

[0056] The metal-based material may be a monomer, an alloy, a compound, a mixture of two or more thereof, or a material containing one or more phases thereof. The "monomer" described herein refers only to a general monomer, so the monomer may also contain trace impurities. That is, the purity of the monomer is not necessarily limited to 100%.

[0057] In addition, the "alloy" described here includes not only materials containing two or more metal elements as constituent elements, but also materials containing one or more metal elements and one or more semi-metal elements as constituent elements. In addition, the "alloy" may also contain one or more non-metallic elements as constituent elements. The structure of the metal-based material is not particularly limited, and specifically, it is any one or more of a solid solution, a eutectic (eutectic mixture), an intermetallic compound, and two or more coexistences thereof.

[0058] Specific examples of the metal element and the semi-metal element are magnesium, boron, aluminum, gallium, indium, silicon, germanium, tin, lead, bismuth, cadmium, silver, zinc, hafnium, zirconium, yttrium, palladium, platinum and the like.

[0059] Among them, the metal-based material is preferably a silicon-containing material. The silicon-containing material has excellent ability to insert and remove lithium, so a significantly high energy density can be obtained in the negative electrode active material layer 120. The silicon-containing material is a general term for materials containing silicon as a constituent element. That is, the silicon-containing material can be a silicon monomer, a silicon alloy, a silicon compound, or a mixture of two or more thereof, or a material containing one or more phases thereof.

[0060] The alloy of silicon contains any one or two or more of metal elements such as tin, nickel, copper, iron, cobalt, manganese, zinc, indium, silver, titanium, germanium, bismuth, antimony and chromium as constituent elements other than silicon. In addition, the compound of silicon contains any one or two or more of non-metallic elements such as carbon and oxygen as constituent elements other than silicon. In addition, the compound of silicon may contain any one or two or more of a series of metal elements described in relation to the alloy of silicon as constituent elements other than silicon.

[0061] Specific examples of silicon alloys include SiB4, SiB6, Mg2Si, Ni2Si, TiSi2, MoSi2, CoSi2, NiSi2, CaSi2, CrSi2, Cu5Si, FeSi2, MnSi2, NbSi2, TaSi2, VSi2, WSi2, ZnSi2, and SiC. In addition, the composition of the silicon alloy (mixing ratio of silicon and metal elements) can be arbitrarily changed.

[0062] Specific examples of silicon compounds are Si3N4, Si2N2O, SiO x (0<x≤2) and LiSiO, etc. In addition, the range of x may be 0.2<x<1.4.

[0063] In particular, the negative electrode active material preferably contains both a carbon material and a silicon-containing material. This is because during the electrode reaction (charge and discharge) of the secondary battery using the negative electrode 100, damage to the negative electrode active material layer 120 can be suppressed while maintaining the battery capacity.

[0064] In detail, silicon-containing materials, which are metal-based materials, have the advantage of high theoretical capacity, but have the risk of rapid expansion and contraction during charge and discharge. On the other hand, carbon materials have the risk of low theoretical capacity, but have the advantage of being difficult to expand and contract during charge and discharge. Therefore, by using carbon materials and silicon-containing materials in combination, it is possible to obtain a high theoretical capacity while suppressing the expansion and contraction of the negative electrode active material layer 120 during charge and discharge. Thus, as described above, it is possible to suppress the damage of the negative electrode active material layer 120 while ensuring the battery capacity. It should be noted that specific examples of damage to the negative electrode active material layer 120 are cracking of the negative electrode active material layer 120 and shedding of the negative electrode active material layer 120.

[0065] (Alkali Metal Carbonates)

[0066] As described above, the alkali metal carbonate compound is contained in the negative electrode active material layer 120 . Thus, the alkali metal carbonate compound is dispersed in the negative electrode active material layer 120 .

[0067] The alkali metal carbonate compound has a carbonate bond (-OC(=O)O-) and contains an alkali metal element as a constituent element. The number of carbonate bonds may be only one or more than two. As described above, specific examples of alkali metal elements are lithium, sodium, potassium, etc. It should be noted that the type of the alkali metal carbonate compound may be only one or more than two.

[0068] The negative electrode active material layer 120 includes an alkali metal carbonate compound because a good coating is formed on the surface of the negative electrode active material during charge and discharge. The coating is a coating derived from an alkali metal carbonate compound and has a high-density pore structure. Therefore, the coating covers the surface of the negative electrode active material with high reactivity, thereby protecting the surface of the negative electrode active material, so the coating has a function of protecting the surface of the negative electrode active material from the influence of the electrolyte while ensuring the input and output of lithium in the negative electrode active material (barrier function). In addition, since the coating follows the expansion and contraction of the negative electrode active material during charge and discharge, thereby enhancing the physical strength of the negative electrode active material, the coating has a function of suppressing the damage of the negative electrode active material (stress relaxation function).

[0069] (Specific composition)

[0070] The type of the alkali metal carbonate compound is not particularly limited, and the alkali metal carbonate compound preferably contains any one or two or more of lithium carbonate (Li2CO3), a first alkali metal carbonate compound, and a second alkali metal carbonate compound, because a film derived from the alkali metal carbonate compound can be easily and stably formed.

[0071] The first alkali metal carbonate compound is any one or two or more of the compounds represented by formula (1). As can be seen from formula (1), the first alkali metal carbonate compound has one carbonate bond.

[0072] R1-OC(=O)O-M1…(1)

[0073] (R1 is an alkyl group. M1 is an alkali metal element.)

[0074] The type of the alkyl group is not particularly limited, and specific examples thereof include methyl, ethyl, and propyl groups. In addition, the alkyl group may be linear or branched. The details of the alkali metal element are as described above.

[0075] Specific examples of the first alkali metal carbonate compound are methyl lithium carbonate (H3C-OC(=O)O-Li), ethyl lithium carbonate (H5C2-OC(=O)O-Li), propyl lithium carbonate (H7C3-OC(=O)O-Li), methyl sodium carbonate (H3C-OC(=O)O-Na), ethyl sodium carbonate (H5C2-OC(=O)O-Na), propyl sodium carbonate (H7C3-OC(=O)O-Na), methyl potassium carbonate (H3C-OC(=O)OK), ethyl potassium carbonate (H5C2-OC(=O)OK) and propyl potassium carbonate (H7C3-OC(=O)OK), etc.

[0076] The second alkali metal carbonate compound is any one or two or more of the compounds represented by formula (2). As can be seen from formula (2), the second alkali metal carbonate compound has two carbonate bonds.

[0077] M2-OC(=O)O-R2-OC(=O)O-M3…(2)

[0078] (R2 is an alkylene group. M2 and M3 are alkali metal elements.)

[0079] The type of the alkylene group is not particularly limited, and specific examples thereof include methylene, ethylene, and propylene. In addition, the alkylene group may be linear or branched. The details of the alkali metal element are as described above.

[0080] Specific examples of the second alkali metal carbonate compound are dilithium methylene dicarbonate (Li-OC(=O)O-CH2-OC(=O)O-Li), dilithium ethylene dicarbonate (Li-OC(=O)O-C2H4-OC(=O)O-Li), dilithium propylene dicarbonate (Li-OC(=O)O-C3H6-OC(=O)O-Li), disodium methylene dicarbonate (Na-OC(=O)O-CH2-OC(=O)O-Na ... ethylene dicarbonate (Na-OC(=O)O-CH2-OC(=O)O- Sodium salt (Na-OC(=O)O-C2H4-OC(=O)O-Na), disodium propylene dicarbonate (Na-OC(=O)O-C3H6-OC(=O)O-Na), dipotassium methylene dicarbonate (K-OC(=O)O-CH2-OC(=O)OK), dipotassium ethylene dicarbonate (K-OC(=O)O-C2H4-OC(=O)OK) and dipotassium propylene dicarbonate (K-OC(=O)O-C3H6-OC(=O)OK), etc.

[0081] In particular, in the first alkali metal carbonate compound represented by formula (1), the alkali metal element (M1) is preferably lithium, and in the second alkali metal carbonate compound represented by formula (2), the alkali metal elements (M2 and M3) are preferably lithium. This is because a film derived from the alkali metal carbonate compound can be easily and stably formed.

[0082] (content)

[0083] The content of the alkali metal carbonate compound in the negative electrode active material layer 120 is not particularly limited, but is preferably 0.2 wt % to 0.8 wt % because a coating film derived from the alkali metal carbonate compound can be easily and stably formed.

[0084] It should be noted that, when the negative electrode active material layer 120 contains two or more alkali metal carbonate compounds, the “content of the alkali metal carbonate compound in the negative electrode active material layer 120 ” described herein is the total content of each alkali metal carbonate compound.

[0085] (Confirmation steps and calculation steps)

[0086] The step of confirming whether the negative electrode active material layer 120 contains the alkali metal carbonate compound and the step of calculating the content of the alkali metal carbonate compound in the negative electrode active material layer 120 are as follows.

[0087] First, the negative electrode current collector 110 is separated from the negative electrode active material layer 120 in the negative electrode 100 to recover the negative electrode active material layer 120. When a secondary battery including the negative electrode 100 is used, the negative electrode 100 is recovered by disassembling the secondary battery.

[0088] Next, after the negative electrode active material layer 120 is cleaned with a cleaning solvent, the negative electrode active material layer 120 is dried. The type of the cleaning solvent is not particularly limited, and specifically, it is an organic solvent such as acetone. The environmental conditions during drying are not particularly limited, and specifically, it can be an inert gas atmosphere using argon gas or the like, or it can be a dry environment.

[0089] Next, the negative electrode active material layer 120 is placed in an extraction solution to perform an extraction process (extraction time = 15 minutes). The type of the extraction solution is not particularly limited, and specifically, it is a dimethyl sulfoxide-d6 solution (LiTFSI DMSO-d6) of lithium bis(trifluoromethanesulfonyl)imide (LiN(CF3SO2)2). Thus, an extraction solution can be obtained.

[0090] Next, the extract was analyzed using nuclear magnetic resonance. Here, as the nuclear magnetic resonance method, proton nuclear magnetic resonance ( 1 H NMR) and carbon-13 NMR ( 13C NMR). Thus, when a peak attributable to the alkali metal carbonate compound is detected, it can be confirmed that the negative electrode active material layer 120 contains the alkali metal carbonate compound.

[0091] For example, when the alkali metal carbonate compound is the first alkali metal carbonate compound (lithium ethylene carbonate), peaks are detected at 3.44 ppm and 3.72 ppm in the proton nuclear magnetic resonance method, and peaks are detected at 61.0 ppm, 65.8 ppm, and 156.9 ppm in the carbon 13 nuclear magnetic resonance method.

[0092] When the alkali metal carbonate compound was the second alkali metal carbonate compound (ethylene dicarbonate dilithium salt), a peak was detected at 3.63 ppm in the proton nuclear magnetic resonance method, and peaks were detected at 62.7 ppm and 166.2 ppm in the carbon 13 nuclear magnetic resonance method.

[0093] Next, when the negative electrode active material layer 120 contains an alkali metal carbonate compound, the weight of the partial structure (alkali metal carbonate compound) in the extract is calculated by comparing the integral value of the signal of the partial structure corresponding to the organic coating component with the integral value of the signal of the internal standard substance. The type of the internal standard substance is not particularly limited, and specifically, it is 3-(trimethylsilyl) propionic acid-d4 sodium or the like.

[0094] Finally, based on the weight of the negative electrode active material layer 120 and the weight of the alkali metal carbonate compound, the content of the alkali metal carbonate compound in the negative electrode active material layer 120 is calculated. In this case, the calculation formula of the content of the alkali metal carbonate compound in the negative electrode active material layer 120 (weight %) = (weight of the alkali metal carbonate compound / weight of the negative electrode active material layer 120) × 100 is used.

[0095] It should be noted that, when confirming whether the negative electrode active material layer 120 contains the alkali metal carbonate compound, infrared spectroscopy may be used instead of nuclear magnetic resonance.

[0096] For example, when the alkali metal carbonate compound is the second alkali metal carbonate compound (ethylene dicarbonate dilithium salt), at 1650 cm -1 、1395cm -1 、1305cm -1 、1080cm -1 and 820cm -1 Peaks were detected at the

[0097] (Magnesium compounds)

[0098] As described above, the magnesium compound is contained in the negative electrode active material layer 120. Thus, the magnesium compound is dispersed in the negative electrode active material layer 120. Therefore, the alkali metal carbonate compound and the magnesium compound are dispersed in the negative electrode active material layer 120 while being mixed with each other.

[0099] The magnesium compound contains magnesium as a constituent element. The type of element other than magnesium contained in the magnesium compound is not particularly limited and can be selected arbitrarily. It should be noted that the type of the magnesium compound may be only one type or may be two or more types.

[0100] The negative electrode active material layer 120 includes an alkali metal carbonate compound and a magnesium compound because the magnesium compound acts self-sacrificially during charge and discharge, so the magnesium compound reacts and decomposes preferentially over the alkali metal carbonate compound. Thus, the reaction and decomposition of the alkali metal carbonate compound can be suppressed by the magnesium compound. Therefore, even if charge and discharge are repeated, it is easy to stably and continuously form a film derived from the alkali metal carbonate compound, so it is easy to maintain the function (barrier function and stress relaxation function) of the film.

[0101] (Specific composition)

[0102] The type of magnesium compound is not particularly limited, and specific examples of the magnesium compound include magnesium fluoride (MgF2), magnesium oxide (MgO), magnesium nitride (Mg3N2), and magnesium carbonate (MgCO3). This is because the reaction and decomposition of the alkali metal carbonate compound can be easily suppressed, so the function of the coating can be easily maintained.

[0103] It should be noted that the magnesium compound may be already contained in the negative electrode active material layer 120 before the first charge and discharge of the secondary battery.

[0104] Alternatively, the magnesium compound may not be included in the negative electrode active material layer 120 before the initial charge and discharge of the secondary battery, and may be included in the negative electrode active material layer 120 after the charge and discharge of the secondary battery. That is, the magnesium compound may not exist in the negative electrode active material layer 120 before the initial charge and discharge, but may be formed inside the negative electrode active material layer 120 by the charge and discharge reaction after the initial charge and discharge, and thus exist in the negative electrode active material layer 120.

[0105] The type of material that can form a magnesium compound by utilizing this charge-discharge reaction is not particularly limited, and specific examples include magnesium nitrate (Mg(NO 3 ) 2 ) and magnesium carbonate (Mg(CO 3 ) 2 ).

[0106] (content)

[0107] The content of the magnesium compound in the negative electrode active material layer 120 is not particularly limited, but is preferably 0.01 wt % to 5 wt % because the reaction and decomposition of the alkali metal carbonate compound are easily suppressed, and thus the function of the coating is easily maintained.

[0108] It should be noted that, when the negative electrode active material layer 120 contains two or more magnesium compounds, the “content of the magnesium compound in the negative electrode active material layer 120 ” described here is the total content of each magnesium compound.

[0109] (Confirmation steps and calculation steps)

[0110] The step of confirming whether the negative electrode active material layer 120 contains the magnesium compound and the step of calculating the content of the magnesium compound in the negative electrode active material layer 120 are as follows.

[0111] First, the negative electrode current collector 110 is peeled off from the negative electrode active material layer 120 in the negative electrode 100 to recover the negative electrode active material layer 120. When a secondary battery including the negative electrode 100 is used, the negative electrode 100 is recovered by disassembling the secondary battery.

[0112] Next, after the negative electrode active material layer 120 is cleaned with a cleaning solvent, the negative electrode active material layer 120 is naturally dried. The type of the cleaning solvent is not particularly limited, and specifically, it is an organic solvent such as dimethyl carbonate. The environmental conditions during drying are not particularly limited, and specifically, it is the inside of a glove box into which an inert gas such as argon is introduced.

[0113] Next, after preparing a sample for analysis using a conductive carbon double-sided tape (Conductive carbon double-sided tape (8 mm×20 m) Model 7311 manufactured by Nissin EM Co., Ltd.), the sample was moved from the inside of the glove box to the inside of an X-ray photoelectron spectroscopy (XPS) apparatus. In this case, the sample was introduced into the XPS apparatus while preventing the sample from being exposed to the atmosphere.

[0114] Next, the sample was analyzed using an XPS apparatus. When a peak derived from the magnesium compound was detected, it was confirmed that the negative electrode active material layer 120 contained the magnesium compound.

[0115] For example, when the magnesium compound is magnesium oxide, a peak is detected near a bond energy of about 50.4 eV, and when the magnesium compound is magnesium fluoride, a peak is detected near a bond energy of about 50.9 eV.

[0116] It should be noted that as an XPS apparatus, an X-ray photoelectron spectrometer PHI 5000 VersaProbe manufactured by ULVAC PHI Co., Ltd. can be used. The analysis conditions are: X-ray source = monochromatized Al-Kα ray (1486.6 eV), X-ray spot diameter = 100 μmφ, photoelectron escape angle = 45°, charge neutralization = electron gun (Flood Gun) and Ar ion gun are not used.

[0117] Next, when the magnesium compound is contained in the negative electrode active material layer 120 , the weight of the magnesium compound is calculated based on the ratio of the area of ​​the peak derived from the magnesium compound and the area of ​​the peak derived from each element contained in the negative electrode active material layer 120 standardized based on the relative sensitivity.

[0118] Finally, based on the weight of the negative electrode active material layer 120 and the weight of the magnesium compound, the content of the magnesium compound in the negative electrode active material layer 120 is calculated. In this case, the calculation formula: content of the magnesium compound in the negative electrode active material layer 120 (weight %) = (weight of the magnesium compound / weight of the negative electrode active material layer 120) × 100 is used.

[0119] (Negative electrode binder)

[0120] The negative electrode binder includes any one or more of materials such as synthetic rubber and polymer compounds. Specific examples of synthetic rubber are styrene-butadiene rubber, fluorine rubber, and EPDM rubber. Specific examples of polymer compounds are polyvinylidene fluoride, polyimide, and carboxymethyl cellulose.

[0121] (Negative electrode conductive agent)

[0122] The negative electrode conductive agent includes any one or more conductive materials such as carbon materials, and specific examples of the conductive materials are graphite, carbon black, acetylene black, and Ketjen black. In addition, the conductive material is not limited to carbon materials, and may also be a metal material and a polymer compound.

[0123] <1-2. Action>

[0124] In the negative electrode 100 , in the negative electrode active material layer 120 during electrode reaction, lithium is ionically inserted into and released from the negative electrode active material in the negative electrode active material state.

[0125] <1-3. Manufacturing method>

[0126] When manufacturing the negative electrode 100, first, the negative electrode active material, the alkali metal carbonate compound and the magnesium compound are mixed to form a negative electrode mixture. In this case, the negative electrode mixture may contain a negative electrode binder and a negative electrode conductive agent as needed.

[0127] Next, the negative electrode mixture is added to the solvent to prepare a paste-like negative electrode mixture slurry. The type of solvent is not particularly limited, and it can be an aqueous solvent or an organic solvent. In this case, a stirring device such as a stirrer can also be used to stir the solvent into which the negative electrode mixture is added.

[0128] Here, after preparing a negative electrode mixture containing a negative electrode active material, an alkali metal carbonate compound and a magnesium compound, a negative electrode mixture slurry is prepared using the negative electrode mixture. However, it is also possible to prepare a negative electrode mixture containing a negative electrode active material, prepare a negative electrode mixture slurry using the negative electrode mixture, and then add the alkali metal carbonate compound and the magnesium compound to the negative electrode mixture slurry.

[0129] Finally, the negative electrode active material layer 120 is formed by applying the negative electrode mixture slurry on both sides of the negative electrode current collector 110. Thereafter, the negative electrode active material layer 120 may be compression-molded using a roll press or the like. In this case, the negative electrode active material layer 120 may be heated, or the compression molding may be repeated multiple times.

[0130] Thus, the negative electrode active material layer 120 is formed on both surfaces of the negative electrode current collector 110 , and the negative electrode 100 is completed.

[0131] <1-4. Functions and effects>

[0132] According to the negative electrode 100 , the negative electrode active material layer 120 includes an alkali metal carbonate compound and a magnesium compound.

[0133] In this case, since the negative electrode active material layer 120 includes an alkali metal carbonate compound, as described above, when the secondary battery using the negative electrode 100 is charged and discharged, a good coating derived from the alkali metal carbonate compound is formed on the surface of the negative electrode active material. Thus, by utilizing the barrier function of the coating, the decomposition reaction of the electrolyte on the surface of the negative electrode active material can be suppressed while ensuring the input and output of lithium. In addition, by utilizing the stress relaxation function of the coating, the damage of the negative electrode active material caused by expansion and contraction can be suppressed.

[0134] Moreover, since the negative electrode active material layer 120 includes an alkali metal carbonate compound and a magnesium compound, as described above, during charge and discharge, the magnesium compound reacts and decomposes preferentially over the alkali metal carbonate compound, thereby suppressing the reaction and decomposition of the alkali metal carbonate compound. Thus, even if charge and discharge are repeated, it is easy to stably and continuously form a coating derived from the alkali metal carbonate compound, so it is easy to maintain the function (barrier function and stress relaxation function) of the coating. Therefore, the decomposition reaction of the electrolyte on the surface of the negative electrode active material can be continuously suppressed, and the damage of the negative electrode active material caused by expansion and contraction can be continuously suppressed.

[0135] As described above, even if charge and discharge are repeated, the discharge capacity is unlikely to decrease, and therefore, in a secondary battery using the negative electrode 100 , excellent battery characteristics can be obtained.

[0136] In particular, when the alkali metal carbonate compound contains any one or two or more of lithium carbonate, the first alkali metal carbonate compound, and the second alkali metal carbonate compound, a film derived from the alkali metal carbonate compound is easily and stably formed, and thus a higher effect can be obtained.

[0137] In this case, if the alkali metal element (M1) in the formula (1) regarding the first alkali metal carbonate compound is lithium, and the alkali metal elements (M2 and M3) in the formula (2) regarding the second alkali metal carbonate compound are lithium, it is easy to stably form a film derived from the alkali metal carbonate compound, so that a higher effect can be obtained.

[0138] In addition, if the magnesium compound contains any one or more of magnesium fluoride, magnesium oxide, magnesium nitride and magnesium carbonate, the reaction and decomposition of the alkali metal carbonate compound can be easily suppressed, thereby making it easy to fully maintain the function of the coating, thereby achieving a higher effect.

[0139] In addition, when the content of the alkali metal carbonate compound in the negative electrode active material layer 120 is 0.2 wt % to 0.8 wt %, a coating film derived from the alkali metal carbonate compound can be easily and stably formed, so that a higher effect can be obtained.

[0140] In addition, when the content of the magnesium compound in the negative electrode active material layer 120 is 0.01 wt % to 5 wt %, the reaction and decomposition of the alkali metal carbonate compound can be sufficiently suppressed, thereby making it easy to fully maintain the function of the coating, thereby achieving a higher effect.

[0141] In addition, if the negative electrode active material layer 120 includes a negative electrode active material including a carbon material and a silicon-containing material, damage to the negative electrode active material layer 120 can be suppressed while ensuring the battery capacity, thereby achieving a higher effect.

[0142] <2. Secondary batteries>

[0143] Next, a secondary battery according to an embodiment of the present technology to which the negative electrode 100 is applied will be described.

[0144] The secondary battery described here is a secondary battery that can obtain battery capacity by inserting and extracting electrode reaction materials, and includes a positive electrode, a negative electrode, and an electrolyte.

[0145] The charge capacity of the negative electrode is preferably greater than the discharge capacity of the positive electrode. That is, the electrochemical capacity per unit area of ​​the negative electrode is preferably greater than the electrochemical capacity per unit area of ​​the positive electrode. This is to inhibit the electrode reaction material from precipitating on the surface of the negative electrode during the charging process.

[0146] As described above, the case where the electrode reaction material is lithium is taken as an example. A secondary battery that obtains battery capacity by inserting and extracting lithium is a so-called lithium ion secondary battery. In this lithium ion secondary battery, lithium is inserted and extracted in an ionic state.

[0147] <2-1. Structure>

[0148] Figure 2 The three-dimensional structure of the secondary battery is shown. Figure 3 Shows Figure 2 The cross-sectional structure of the battery element 20 is shown. Figure 4 Shows Figure 3 The planar structure of the positive electrode 21 shown, Figure 5 Shows Figure 3 The plane structure of the negative electrode 22 shown. Figure 2 A state in which the outer package film 10 and the battery element 20 are separated from each other is shown.

[0149] like Figure 2 as well as Figure 3 As shown, the secondary battery includes an outer film 10 , a battery element 20 , a plurality of positive electrode terminals 31 , a plurality of negative electrode terminals 32 , a positive electrode lead 41 , a negative electrode lead 42 , and sealing films 51 , 52 .

[0150] As described above, the secondary battery described here uses the outer film 10 having flexibility or elasticity as an outer casing member, and is therefore a so-called laminated film type secondary battery.

[0151] [Outer packaging film]

[0152] like Figure 2 As shown, the outer film 10 is an outer packaging member for housing the battery element 20, and has a bag-like structure that is sealed with the battery element 20 housed therein. Thus, the outer film 10 houses the positive electrode 21, the negative electrode 22, and the electrolyte solution described later.

[0153] Here, the outer film 10 is a single film-shaped member, and is folded in a folding direction F. The outer film 10 is provided with a recessed portion 10U (so-called deep-drawn portion) for accommodating the battery element 20 .

[0154] Specifically, the outer packaging film 10 is a three-layer laminated film in which a welding layer, a metal layer, and a surface protection layer are sequentially stacked from the inside. When the outer packaging film 10 is folded, the outer peripheral edges of the mutually opposed welding layers are welded to each other. The welding 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.

[0155] The structure (number of layers) of the outer film 10 is not particularly limited, and may be one layer, two layers, or four or more layers.

[0156] [Battery components]

[0157] like Figure 2~Figure 5 As shown, the battery element 20 is a power generation element including a positive electrode 21 , a negative electrode 22 , a separator 23 , and an electrolyte solution (not shown), and is housed inside an outer film 10 .

[0158] Here, since the battery element 20 is a so-called laminated electrode body, positive electrodes 21 and negative electrodes 22 are alternately laminated via separators 23. The number of each of the positive electrodes 21, negative electrodes 22 and separators 23 is not particularly limited and can be arbitrarily set.

[0159] (positive electrode)

[0160] like Figure 3 as well as Figure 4 As shown, the positive electrode 21 includes a positive electrode current collector 21A and a positive electrode active material layer 21B. Figure 4 In FIG. 1 , the positive electrode active material layer 21B is shaded.

[0161] The positive electrode current collector 21A has a pair of surfaces provided with a positive electrode active material layer 21B. The positive electrode current collector 21A is made of a conductive material such as a metal material, and a specific example of the conductive material is aluminum.

[0162] The positive electrode active material layer 21B contains any one or two or more of positive electrode active materials that occlude and deocclude lithium. In addition, the positive electrode active material layer 21B may further contain any one or two or more of other materials such as a positive electrode binder and a positive electrode conductive agent.

[0163] Here, the positive electrode active material layer 21B is provided on both surfaces of the positive electrode collector 21A. Alternatively, the positive electrode active material layer 21B may be provided only on one surface of the positive electrode collector 21A on the side where the positive electrode 21 faces the negative electrode 22. The method for forming the positive electrode active material layer 21B is not particularly limited, and specifically, a coating method or the like is used.

[0164] The type of positive electrode active material is not particularly limited, specifically, it is a lithium-containing compound, etc. The 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 types of other elements are not particularly limited as long as they are elements other than lithium and transition metal elements, specifically, they are elements belonging to Groups 2 to 15 in the long-period periodic table. The type of lithium-containing compound is not particularly limited, specifically, it is an oxide, a phosphate compound, a silicate compound, a boric acid compound, etc.

[0165] 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 are LiFePO4, LiMnPO4, LiFe 0.5 Mn 0.5 PO4 and LiFe 0.3 Mn 0.7 PO4, etc.

[0166] The details of each of the positive electrode binder and the positive electrode conductive agent are the same as the details of each of the negative electrode binder and the negative electrode conductive agent described above.

[0167] Here, if Figure 4 As shown, since a part of the positive electrode collector 21A protrudes, the positive electrode collector 21A includes a portion protruding outward from the positive electrode active material layer 21B (hereinafter referred to as "the protruding portion of the positive electrode collector 21A"). Since the positive electrode active material layer 21B is not provided on the protruding portion of the positive electrode collector 21A, the protruding portion of the positive electrode collector 21A functions as the positive electrode terminal 31. It should be noted that the details of the positive electrode terminal 31 will be described below.

[0168] The positive electrode active material layer 21B is provided on only a portion of the positive electrode collector 21A on both sides (except the positive electrode terminal 31). Therefore, the portion of the positive electrode collector 21A where the positive electrode active material layer 21B is not provided is not covered by the positive electrode active material layer 21B and is exposed.

[0169] Specifically, if Figure 4 As shown, the positive electrode current collector 21A includes a covering portion 21AX and a non-covering portion 21AY. The covering portion 21AX is located in the central portion of the positive electrode current collector 21A and is a portion where the positive electrode active material layer 21B is formed. The non-covering portion 21AY is located around the covering portion 21AX and is a frame-shaped portion where the positive electrode active material layer 21B is not formed. Thus, the covering portion 21AX is covered by the positive electrode active material layer 21B, and the non-covering portion 21AY is not covered by the positive electrode active material layer 21B and is exposed.

[0170] (negative electrode)

[0171] The negative electrode 22 has the same configuration as that of the negative electrode 100. Specifically, Figure 3 as well as Figure 5 As shown, the negative electrode 22 includes a negative electrode current collector 22A and a negative electrode active material layer 22B. Figure 5 In FIG. 1 , the negative electrode active material layer 22B is shaded.

[0172] The configuration of the negative electrode collector 22A is the same as that of the negative electrode collector 110, and the configuration of the negative electrode active material layer 22B is the same as that of the negative electrode active material layer 120. That is, the negative electrode active material layer 22B contains an alkali metal carbonate compound and a magnesium compound.

[0173] Here, if Figure 5 As shown, since a part of the negative electrode current collector 22A protrudes, the negative electrode current collector 22A includes a portion protruding outward from the negative electrode active material layer 22B (hereinafter referred to as “the protruding portion of the negative electrode current collector 22A”).

[0174] The protrusion of the negative electrode collector 22A protrudes in the same direction as the protrusion of the positive electrode collector 21A. The protrusion of the negative electrode collector 22A is located at a position that does not overlap with the protrusion of the positive electrode collector 21A when the positive electrodes 21 and the negative electrodes 22 are alternately stacked with the separator 23 interposed therebetween.

[0175] Since the negative electrode active material layer 22B is not provided on the protruding portion of the negative electrode current collector 22A, the protruding portion of the negative electrode current collector 22A functions as a negative electrode terminal 32. The negative electrode terminal 32 will be described in detail later.

[0176] The negative electrode active material layer 22B is provided on both surfaces of the negative electrode collector 22A (except the negative electrode terminal 32 ) on the entire negative electrode collector 22A. Therefore, the entire negative electrode collector 22A is not exposed but is covered with the negative electrode active material layer 22B.

[0177] Specifically, if Figure 5 As shown, the negative electrode active material layer 22B includes an opposing portion 22BX and a non-opposed portion 22BY. The opposing portion 22BX is a portion that is opposed to the covered portion 21AX. That is, since the opposing portion 22BX is opposed to the positive electrode active material layer 21B, it is a portion that participates in the charge and discharge reaction. The non-opposed portion 22BY is a portion that is opposed to the non-covered portion 21AY. That is, the non-opposed portion 22BY is not opposed to the positive electrode active material layer 21B, but is opposed to the positive electrode collector 21A, and is therefore a portion that does not participate in the charge and discharge reaction. Figure 5 In FIG. 1 , in order to facilitate understanding of the formation range of the covering portion 21AX (positive electrode active material layer 21B), the formation range of the covering portion 21AX (the boundary between the facing portion 22BX and the non-facing portion 22BY) is indicated by a dotted line.

[0178] The negative electrode active material layer 22B is arranged on the entire two surfaces of the negative electrode collector 22A. In contrast, the positive electrode active material layer 21B is only arranged on a part of the two surfaces of the positive electrode collector 21A (covering portion 21AX) to suppress the precipitation of lithium released from the positive electrode active material layer 21B on the surface of the negative electrode 22 during charging.

[0179] (Diaphragm)

[0180] like Figure 3 As shown, 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 therethrough while preventing contact (short circuit) between the positive electrode 21 and the negative electrode 22. The separator 23 is made of a polymer compound such as polyethylene.

[0181] (Electrolyte)

[0182] The electrolyte solution is a liquid electrolyte and is impregnated in each of the positive electrode 21 , the negative electrode 22 , and the separator 23 , and contains a solvent and an electrolyte salt.

[0183] Here, the solvent includes any one or more of non-aqueous solvents (organic solvents), and the electrolyte containing the non-aqueous solvent is a so-called non-aqueous electrolyte. The non-aqueous solvent includes esters and ethers, and more specifically, carbonate compounds, carboxylate compounds, and lactone compounds. This is because it can not only improve the dissociation of the electrolyte salt, but also improve the ion mobility.

[0184] The carbonate-based compound is a cyclic carbonate, a chain carbonate, etc. Specific examples of the cyclic carbonate are ethylene carbonate and propylene carbonate, etc., and specific examples of the chain carbonate are dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, etc.

[0185] The carboxylate ester compound is a chain carboxylate, etc. Specific examples of the chain carboxylate are ethyl acetate, ethyl propionate, propyl propionate, ethyl trimethylacetate, and the like.

[0186] The lactone compound is lactone, etc. Specific examples of lactone are γ-butyrolactone and γ-valerolactone.

[0187] It should be noted that the ether may also be 1,2-dimethoxyethane, tetrahydrofuran, 1,3-dioxolane, 1,4-dioxane, and the like.

[0188] The electrolyte salt includes any one or more of light metal salts such as lithium salts. Specific examples of lithium salts are lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium trifluoromethanesulfonate (LiCF3SO3), lithium bis(fluorosulfonyl)imide (LiN(FSO2)2), lithium bis(trifluoromethanesulfonyl)imide (LiN(CF3SO2)2), lithium tris(trifluoromethanesulfonyl)methylide (LiC(CF3SO2)3), lithium bis(oxalate)borate (LiB(C2O4)2), lithium monofluorophosphate (Li2PFO3) and lithium difluorophosphate (LiPF2O2). This is because a high battery capacity can be obtained.

[0189] The content of the electrolyte salt is not particularly limited, but is specifically 0.3 mol / kg to 3.0 mol / kg relative to the solvent, because high ion conductivity can be obtained.

[0190] It should be noted that the electrolyte may further contain any one or more of the additives. The type of additive is not particularly limited, and specifically, it is unsaturated cyclic carbonate, fluorinated cyclic carbonate, sulfonic acid ester, phosphate, acid anhydride, nitrile compound and isocyanate compound.

[0191] Specific examples of unsaturated cyclic carbonates are vinylene carbonate, vinylethylene carbonate, and methyleneethylene carbonate. Specific examples of fluorinated cyclic carbonates are monofluoroethylene carbonate and difluoroethylene carbonate. Specific examples of sulfonic acid esters are propane sultone and propene sultone. Specific examples of phosphates are trimethyl phosphate and triethyl phosphate. Specific examples of anhydrides are succinic anhydride, 1,2-ethanedisulfonic anhydride, and 2-sulfobenzoic anhydride. Specific examples of nitrile compounds are succinonitrile. Specific examples of isocyanate compounds are hexamethylene diisocyanate.

[0192] [Positive terminal and negative terminal]

[0193] like Figure 4 As shown, the positive electrode terminal 31 is electrically connected to the positive electrode 21, more specifically, to the positive electrode collector 21A. In the battery element 20, as described above, since the positive electrode 21 and the negative electrode 22 are alternately stacked with the separator 23 interposed therebetween, the battery element 20 includes a plurality of positive electrodes 21. Thus, the secondary battery includes a plurality of positive electrode terminals 31.

[0194] The positive electrode terminal 31 is made of a conductive material such as a metal material, and the type of the conductive material is not particularly limited. Specifically, the positive electrode terminal 31 is made of the same material as the material forming the positive electrode current collector 21A.

[0195] Here, as described above, the protruding portion of the positive electrode collector 21A functions as the positive electrode terminal 31, so the positive electrode terminal 31 is physically integrated with the positive electrode collector 21A. This is because the connection resistance between the positive electrode collector 21A and the positive electrode terminal 31 is reduced, thereby reducing the resistance of the entire secondary battery.

[0196] As described later, the plurality of positive electrode terminals 31 are joined to each other using a joining method such as welding. Figure 2 As shown, a lead-shaped bonding portion 31Z is formed.

[0197] like Figure 5 As shown, the negative electrode terminal 32 is electrically connected to the negative electrode 22, more specifically, to the negative electrode collector 22A. In the battery element 20, as described above, since the positive electrode 21 and the negative electrode 22 are alternately stacked with the separator 23 interposed therebetween, the battery element 20 includes a plurality of negative electrodes 22. Thus, the secondary battery includes a plurality of negative electrode terminals 32.

[0198] The negative electrode terminal 32 is made of a conductive material such as a metal material, and the type of the conductive material is not particularly limited. Specifically, the negative electrode terminal 32 is made of the same material as the material forming the negative electrode collector 22A.

[0199] Here, as described above, since the protruding portion of the negative electrode collector 22A functions as the negative electrode terminal 32, the negative electrode terminal 32 is physically integrated with the negative electrode collector 22A. This is because the connection resistance between the negative electrode collector 22A and the negative electrode terminal 32 is reduced, thereby reducing the resistance of the entire secondary battery.

[0200] As described later, the plurality of negative electrode terminals 32 are joined to each other using a joining method such as welding. Figure 2 As shown, a lead-shaped bonding portion 32Z is ​​formed.

[0201] [Positive lead and negative lead]

[0202] like Figure 2 As shown, the positive electrode lead 41 is connected to the joint portion 31Z and is led out to the outside of the outer film 10. The positive electrode lead 41 includes a conductive material such as a metal material, and specifically includes the same material as the material forming the positive electrode collector 21A. The shape of the positive electrode lead 41 is not particularly limited, and specifically, it can be any of a thin plate shape and a mesh shape.

[0203] like Figure 2 As shown, the negative electrode lead 42 is connected to the joint portion 32Z and is led out to the outside of the outer film 10. The negative electrode lead 42 includes a conductive material such as a metal material, and specifically, includes the same material as the material forming the negative electrode collector 22A. It should be noted that the lead-out direction of the negative electrode lead 42 is the same as the lead-out direction of the positive electrode lead 41. In addition, the details of the shape of the negative electrode lead 42 are the same as the details of the shape of the positive electrode lead 41.

[0204] [Sealing film]

[0205] The sealing film 51 is inserted between the outer film 10 and the positive electrode lead 41, and the sealing film 52 is inserted between the outer film 10 and the negative electrode lead 42. In addition, one or both of the sealing films 51 and 52 may be omitted.

[0206] The sealing film 51 is a sealing member that prevents outside air and the like from entering the interior of the outer film 10. The sealing film 51 includes a polymer compound such as polyolefin that has close adhesion to the positive electrode lead 41, and a specific example of the polymer compound is polypropylene and the like.

[0207] The sealing film 52 has the same structure as the sealing film 51 , except that the sealing film 52 is a sealing member having close contact with the negative electrode lead 42 . That is, the sealing film 52 includes a polymer compound such as polyolefin having close contact with the negative electrode lead 42 .

[0208] <2-2. Action>

[0209] This secondary battery operates as described below.

[0210] During charge, lithium is extracted from the positive electrode 21 in the battery element 20, and the lithium is inserted into the negative electrode 22 via the electrolyte. On the other hand, during discharge, lithium is extracted from the negative electrode 22 in the battery element 20, and the lithium is inserted into the positive electrode 21 via the electrolyte. During these charge and discharge, lithium is inserted and extracted in an ionic state.

[0211] <2-3. Manufacturing method>

[0212] To explain the method of manufacturing a secondary battery, Figure 6 Shown with Figure 2The corresponding three-dimensional structure. Figure 6 In FIG. 2 , a laminate 20Z for producing the battery element 20 is shown instead of the battery element 20. It should be noted that the details of the laminate 20Z will be described later.

[0213] When manufacturing a secondary battery, after the positive electrode 21 and the negative electrode 22 are respectively manufactured and the electrolyte is prepared by the steps of an example described below, the positive electrode 21, the negative electrode 22 and the electrolyte are used to assemble a secondary battery, and the secondary battery is stabilized. Figure 1~Figure 5 .

[0214] [Production of positive electrode]

[0215] First, a mixture (positive electrode mixture) in which a positive electrode active material, a positive electrode binder and a positive electrode conductive agent are mixed with each other is put into a solvent to prepare a paste-like positive electrode mixture slurry. The solvent can be an aqueous solvent or an organic solvent. Next, the positive electrode mixture slurry is applied on both sides (except the positive terminal 31) of the positive electrode collector 21A in which the positive terminal 31 is integrated, thereby forming a positive electrode active material layer 21B. Finally, the positive electrode active material layer 21B is compression molded using a roller press or the like. In this case, the positive electrode active material layer 21B can be heated, or compression molding can be repeated multiple times. Thus, the positive electrode active material layer 21B is formed on both sides of the positive electrode collector 21A, thereby making the positive electrode 21.

[0216] [Production of negative electrode]

[0217] The negative electrode 22 is formed by the same steps as the above-mentioned steps for making the negative electrode 100. Specifically, first, a mixture (negative electrode mixture) in which a negative electrode active material, an alkali metal carbonate compound, a magnesium compound, and a negative electrode binder are mixed with each other is put into a solvent, thereby preparing a paste-like negative electrode mixture slurry. Next, the negative electrode mixture slurry is applied on both sides (except the negative terminal 32) of the negative electrode collector 22A in which the negative terminal 32 is integrated, thereby forming a negative electrode active material layer 22B. Finally, the negative electrode active material layer 22B is compression molded. Thus, the negative electrode active material layer 22B is formed on both sides of the negative electrode collector 22A, thereby manufacturing the negative electrode 22.

[0218] [Preparation of electrolyte]

[0219] The electrolyte salt is added to the solvent so that the electrolyte salt is dispersed or dissolved in the solvent, thereby preparing an electrolytic solution.

[0220] [Assembly of secondary battery]

[0221] First, if Figure 6As shown, a stacked body 20Z is produced by alternately stacking positive electrodes 21 and negative electrodes 22 with separators 23 interposed therebetween. The stacked body 20Z has the same structure as the battery element 20, except that the positive electrodes 21, negative electrodes 22 and separators 23 are not impregnated with an electrolyte.

[0222] Next, the plurality of positive terminals 31 are joined to each other by a joining method such as welding to form a joint portion 31Z, and then the positive electrode lead 41 is connected to the joint portion 31Z by a joining method such as welding. In addition, the plurality of negative terminals 32 are joined to each other by a joining method such as welding to form a joint portion 32Z, and then the negative electrode lead 42 is connected to the joint portion 32Z by a joining method such as welding.

[0223] Next, after the stacked body 20Z is accommodated in the recessed portion 10U, the outer packaging film 10 (welding layer / metal layer / surface protection layer) is folded so that the outer packaging films 10 face each other. Next, the outer peripheral edge portions of the two sides of the mutually facing welding layers are bonded to each other using a bonding method such as a heat welding method, so that the stacked body 20Z is accommodated in the bag-shaped outer packaging film 10.

[0224] Finally, after the electrolyte is injected into the bag-shaped outer packaging film 10, the outer peripheral edge portions of the remaining one side of the mutually opposed welded layers are bonded to each other using a bonding method such as a heat welding method. In this case, the sealing film 51 is inserted between the outer packaging film 10 and the positive electrode lead 41, and the sealing film 52 is inserted between the outer packaging film 10 and the negative electrode lead 42.

[0225] Thus, the electrolyte solution is impregnated in the laminate 20Z, thereby producing the battery element 20 as a laminated electrode body. Thus, the battery element 20 is sealed inside the bag-like outer film 10, thereby assembling a secondary battery.

[0226] [Stabilization of secondary batteries]

[0227] The assembled secondary battery is charged and discharged. Various conditions such as the ambient temperature, the number of charge and discharge times (cycle number), and the charge and discharge conditions can be set arbitrarily. Thus, a coating is formed on the surface of each of the positive electrode 21 and the negative electrode 22, so that the state of the secondary battery is electrochemically stabilized. Thus, the secondary battery is completed.

[0228] <2-4. Functions and effects>

[0229] According to this secondary battery, since the negative electrode 22 has the same configuration as that of the negative electrode 100 , excellent battery characteristics can be obtained for the reasons described above.

[0230] In particular, if the secondary battery is a lithium ion secondary battery, a sufficient battery capacity can be stably obtained by inserting and extracting lithium, and thus a higher effect can be obtained.

[0231] Other actions and effects related to the secondary battery are the same as those related to the negative electrode 100 .

[0232] <3. Modifications>

[0233] As described below, the configurations of the negative electrode 100 and the secondary battery described above can be modified as appropriate. In addition, any two or more of the series of modifications described below can be combined with each other.

[0234] [Modification 1]

[0235] exist Figure 4 In the embodiment, since the protruding portion of the positive electrode collector 21A also serves as the positive electrode terminal 31, the positive electrode terminal 31 is physically integrated with the positive electrode collector 21A. However, the positive electrode terminal 31 may be physically separated from the positive electrode collector 21A and thus separated from the positive electrode collector 21A. In this case, the positive electrode terminal 31 may be connected to the positive electrode collector 21A using a joining method such as welding.

[0236] In this case, the same effect can be obtained because the positive electrode terminal 31 is electrically connected to the positive electrode 21. In order to reduce the resistance of the entire secondary battery as the connection resistance is reduced, the positive electrode terminal 31 is preferably physically integrated with the positive electrode collector 21A.

[0237] Similarly, in Figure 5 In the embodiment, since the protruding portion of the negative electrode collector 22A also serves as the negative electrode terminal 32, the negative electrode terminal 32 is physically integrated with the negative electrode collector 22A. However, the negative electrode terminal 32 may be physically separated from the negative electrode collector 22A and thus separated from the negative electrode collector 22A. In this case, the negative electrode terminal 32 may be connected to the negative electrode collector 22A using a joining method such as welding.

[0238] In this case, the same effect can be obtained because the negative electrode terminal 32 is electrically connected to the negative electrode 22. In order to reduce the resistance of the entire secondary battery as the connection resistance is reduced, the negative electrode terminal 32 is preferably physically integrated with the negative electrode collector 22A.

[0239] [Modification 2]

[0240] exist Figure 2In the figure, a battery element 20 as a stacked electrode body is used. However, although not specifically illustrated here, a battery element as a wound electrode body can also be used. In this case, the positive electrode 21 has a strip-shaped structure, and the positive terminal 31 is electrically connected to the positive electrode collector 21A, and the negative electrode 22 has a strip-shaped structure, and the negative terminal 32 is electrically connected to the negative electrode collector 22A. Thus, the positive electrode 21 and the negative electrode 22 are wound opposite to each other via the separator 23. It should be noted that the number of positive terminals 31 can be only one, or more than two. The number of negative terminals 32 can also be only one, or more than two.

[0241] In this case, since the secondary battery can be charged and discharged by the battery element 20 , the same effect can be obtained.

[0242] [Variation 3]

[0243] The separator 23 which is a porous film is used. However, although not specifically shown here, a laminated separator including a polymer compound layer may also be used.

[0244] Specifically, the laminated separator includes a porous film having a pair of faces and a polymer compound layer disposed on one or both sides of the porous film. This is because the adhesion of the separator to each of the positive electrode 21 and the negative electrode 22 is improved, so the positional deviation of the battery element 20 can be suppressed. Thus, even if side reactions such as decomposition reactions of the electrolyte occur, the expansion of the secondary battery can be suppressed. The polymer compound layer includes polymer compounds such as polyvinylidene fluoride. This is because excellent physical strength and excellent electrochemical stability can be obtained.

[0245] It should be noted that one or both of the porous film and the polymer compound layer may contain any one or more of a plurality of insulating particles. This is because a plurality of insulating particles promote heat dissipation when the secondary battery is heated, so the safety (heat resistance) of the secondary battery is improved. The insulating particles include any one or more of insulating materials such as inorganic materials and resin materials. Specific examples of inorganic materials are aluminum oxide, aluminum nitride, boehmite, silicon oxide, titanium oxide, magnesium oxide, and zirconium oxide. Specific examples of resin materials are acrylic resins and styrene resins.

[0246] 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 membrane. In this case, a plurality of insulating particles may be added to the precursor solution as required.

[0247] When the laminated separator is used, the same effect can be obtained because lithium ions can move between the positive electrode 21 and the negative electrode 22. In this case, in particular, as described above, the safety of the secondary battery is improved, so a higher effect can be obtained.

[0248] [Variation 4]

[0249] An electrolyte solution is used as a liquid electrolyte. However, although not specifically shown here, an electrolyte layer as a gel electrolyte may also be used.

[0250] In the battery element 20 using the electrolyte layer, positive electrodes 21 and negative electrodes 22 are alternately stacked via separators 23 and electrolyte layers. The electrolyte layer is interposed between the positive electrode 21 and the separator 23, and between the negative electrode 22 and the separator 23.

[0251] Specifically, the electrolyte layer includes an electrolyte and a polymer compound, and the electrolyte is maintained by the polymer compound. This is because leakage of the electrolyte can be prevented. The electrolyte is composed as described above. The polymer compound includes polyvinylidene fluoride, etc. In the case of forming the electrolyte layer, a precursor solution including an electrolyte, a polymer compound, and a solvent is prepared, and then the precursor solution is coated on one or both sides of each of the positive electrode 21 and the negative electrode 22.

[0252] When the electrolyte layer is used, lithium ions can also move between the positive electrode 21 and the negative electrode 22 via the electrolyte layer, so the same effect can be obtained. In this case, in particular, as described above, since leakage of the electrolyte can be prevented, a higher effect can be obtained.

[0253] <4. Applications of secondary batteries>

[0254] The purpose (application example) of the secondary battery is not particularly limited. In electronic devices and electric vehicles, the secondary battery used as a power source can be a main power source or an auxiliary power source. The main power source is the power source that is used preferentially, regardless of the presence or absence of other power sources. The auxiliary power source can be a power source that is used instead of the main power source, or a power source that is switched from the main power source.

[0255] Specific examples of the use of secondary batteries are as follows. Electronic devices such as video cameras, digital still cameras, mobile phones, laptop computers, stereo headphones, portable radios, and portable information terminals; storage devices such as backup power supplies and memory cards; power tools such as electric drills and electric saws; battery packs mounted on electronic devices, etc.; medical electronic devices such as pacemakers and hearing aids; electric vehicles such as electric vehicles (including hybrid vehicles); power storage systems such as household or industrial battery systems that store electricity in advance in case of emergencies. In these uses, one secondary battery or multiple secondary batteries can be used.

[0256] The battery pack may use a single cell or a battery pack. An electric vehicle is a vehicle that uses a secondary battery as a driving power source, or a hybrid vehicle that also has other driving sources besides the secondary battery. In a home power storage system, the power stored in the secondary battery as a power storage source can be used to use home electrical products, etc.

[0257] Here, an example of application of the secondary battery will be described in detail. The configuration of the application example described below is just an example and can be modified as appropriate.

[0258] Figure 7 The module structure of the battery pack is shown. The battery pack described here is a battery pack using one secondary battery (so-called soft pack), and is installed in electronic devices such as smartphones.

[0259] like Figure 7 As shown in FIG. 1 , the battery pack includes a power source 71 and a circuit board 72 . The circuit board 72 is connected to the power source 71 and includes a positive electrode terminal 73 , a negative electrode terminal 74 , and a temperature detection terminal 75 .

[0260] The power source 71 includes a secondary battery. In the secondary battery, a positive lead is connected to a positive terminal 73, and a negative lead is connected to a negative terminal 74. The power source 71 can be connected to the outside via the positive terminal 73 and the negative terminal 74, so that charging and discharging can be performed. The circuit substrate 72 includes a control unit 76, a switch 77, a thermistor element (PTC element) 78, and a temperature detection unit 79. In addition, the PTC element 78 can also be omitted.

[0261] The control unit 76 includes a central processing unit (CPU) and a memory, etc., and controls the operation of the entire battery pack. The control unit 76 detects and controls the use state of the power source 71 as needed.

[0262] It should be noted that when the voltage of the power source 71 (secondary battery) reaches the overcharge detection voltage or the overdischarge detection voltage, the control unit 76 cuts off the switch 77 so that the charging current does not flow through the current path of the power source 71. The overcharge detection voltage is not particularly limited, but is specifically 4.20V±0.05V, and the overdischarge detection voltage is not particularly limited, but is specifically 2.40V±0.1V.

[0263] The switch 77 includes a charge control switch, a discharge control switch, a charge diode, a discharge diode, etc., and switches the connection between the power supply 71 and the external device according to the instruction of the control unit 76. The switch 77 includes a field effect transistor (MOSFET) using a metal oxide semiconductor, etc., and the charge and discharge current is detected based on the on-resistance of the switch 77.

[0264] The temperature detection unit 79 includes a temperature detection element such as a thermistor. The temperature detection unit 79 measures the temperature of the power supply 71 using the temperature detection terminal 75, and outputs the temperature measurement result to the control unit 76. The temperature measurement result measured by the temperature detection unit 79 is used for the control unit 76 to perform charge and discharge control when abnormal heating occurs and to perform correction processing when the control unit 76 calculates the remaining capacity.

[0265] Example

[0266] Embodiments of the present technology will be described.

[0267] <Examples 1 to 17 and Comparative Examples 1 to 3>

[0268] As described below, after the secondary battery was manufactured, the battery characteristics of the secondary battery were evaluated.

[0269] [Manufacturing of Secondary Batteries]

[0270] The following steps were used to produce Figure 2~Figure 5 The secondary battery shown (laminated film type lithium ion secondary battery).

[0271] (Production of positive electrode)

[0272] First, 94 parts by mass of a positive electrode active material (LiNi as a lithium-containing compound (oxide)) was prepared. 0.8 Co 0.15 Al 0.05O2), 3 parts by mass of a positive electrode binder (polyvinylidene fluoride) and 3 parts by mass of a positive electrode conductor (ketjen black as amorphous carbon powder) are mixed with each other to form a positive electrode mixture. Next, the positive electrode mixture is put into a solvent (N-methyl-2-pyrrolidone as an organic solvent), and then the organic solvent is stirred to prepare a paste-like positive electrode mixture slurry. Next, a coating device is used to apply the positive electrode mixture slurry on both sides (except the positive terminal 31) of the positive electrode collector 21A (aluminum foil with a thickness of 20μm) integrated with the positive terminal 31, and then the positive electrode mixture slurry is dried to form a positive electrode active material layer 21B. Finally, the positive electrode active material layer 21B is compression-molded using a roller press. Thus, the positive electrode 21 is produced.

[0273] (Production of negative electrode)

[0274] First, 60 parts by mass of a negative electrode active material (artificial graphite as a carbon material) and 30 parts by mass of a negative electrode active material (silicon oxide (SiO x )) and 10 parts by mass of a negative electrode binder (styrene-butadiene rubber) were mixed with each other to prepare a negative electrode mixture. Next, the negative electrode mixture was put into a solvent (N-methyl-2-pyrrolidone as an organic solvent), and then the organic solvent was stirred to prepare a paste-like negative electrode mixture slurry.

[0275] Next, the alkali metal carbonate compound and the magnesium compound were added to the negative electrode mixture slurry, and the negative electrode mixture slurry was stirred.

[0276] As the alkali metal carbonate compound, lithium carbonate (Li2CO3), a first alkali metal carbonate compound, and a second alkali metal carbonate compound were used. As the first alkali metal carbonate compound, methyl lithium carbonate (LMC), ethyl lithium carbonate (LEC), and propyl lithium carbonate (LPC) were used. As the second alkali metal carbonate compound, ethylene dicarbonate dilithium salt (LEDC) and propylene dicarbonate dilithium salt (LPDC) were used.

[0277] As the magnesium compound, magnesium fluoride (MgF2), magnesium oxide (MgO), magnesium nitride (Mg3N2) and magnesium carbonate (MgCO3) are used.

[0278] Here, as an example of a method for synthesizing the second alkali metal carbonate compound, a method for synthesizing ethylene dicarbonate dilithium salt is specifically described. In the case of synthesizing ethylene dicarbonate dilithium salt, an organic solvent (ethylene carbonate) and a tetrahydrofuran solution of lithium naphthalene dicarboxylate are mixed with each other, and then the mixture is left standing (standing time = 1 day). Thus, ethylene carbonate and lithium naphthalene dicarboxylate react with each other, thereby synthesizing ethylene dicarbonate dilithium salt.

[0279] Next, the negative electrode mixture slurry was applied to both sides (excluding the negative electrode terminal 32) of the negative electrode current collector 22A (copper foil with a thickness of 15 μm) integrated with the negative electrode terminal 32 using a coating device, and then the negative electrode mixture slurry was dried to form the negative electrode active material layer 22B. Finally, the negative electrode active material layer 22B was compression-molded using a roller press. Thus, the negative electrode 22 was manufactured.

[0280] Note that, for comparison, the negative electrode 22 was produced by the same procedure except that both the alkali carbonate and the magnesium compound were not used. Also, for comparison, the negative electrode 22 was produced by the same procedure except that only one of the alkali carbonate and the magnesium compound was used.

[0281] (Preparation of electrolyte)

[0282] First, the electrolyte salt (LiPF6) was put into the solvent, and then the solvent was stirred. As the solvent, a mixture of ethylene carbonate and propylene carbonate as cyclic carbonates, dimethyl carbonate and ethyl methyl carbonate as chain carbonates, and monofluoroethylene carbonate as fluorinated cyclic carbonate was used. The composition (mass ratio) of the solvent was ethylene carbonate: propylene carbonate: dimethyl carbonate: ethyl methyl carbonate: monofluoroethylene carbonate = 27.5: 5: 60: 5: 2.5. The content of the electrolyte salt was 1.5 mol / kg relative to the solvent.

[0283] (Assembly of secondary batteries)

[0284] First, the positive electrode 21 and the negative electrode 22 were stacked on each other with the separator 23 (microporous polyethylene film with a thickness of 15 μm) interposed therebetween, thereby producing a stacked body 20Z.

[0285] Next, the plurality of positive terminals 31 are welded to each other to form a joint 31Z, and then the positive electrode lead 41 (aluminum foil) is welded to the joint 31Z. Also, the plurality of negative terminals 32 are welded to each other to form a joint 32Z, and then the negative electrode lead 42 (copper foil) is welded to the joint 32Z.

[0286] Next, the outer packaging film 10 (welding layer / metal layer / surface protection layer) is folded so as to sandwich the laminated body 20Z accommodated in the recessed portion 10U, and then the outer peripheral edge portions of the two sides of the welding layer are heat-fused to each other, thereby accommodating the laminated body 20Z in the bag-shaped outer packaging film 10. As the outer packaging film 10, an aluminum laminated film in which a welding layer (polypropylene film with a thickness of 30 μm), a metal layer (aluminum foil with a thickness of 40 μm), and a surface protection layer (nylon film with a thickness of 25 μm) are laminated in this order from the inside is used.

[0287] Finally, after the electrolyte is injected into the bag-shaped outer film 10, the outer peripheral edge portions of the remaining one side of the weld layer are heat-welded to each other in a reduced pressure environment. In this case, the sealing film 51 (polypropylene film with a thickness of 5 μm) is inserted between the outer film 10 and the positive electrode lead 41, and the sealing film 52 (polypropylene film with a thickness of 5 μm) is inserted between the outer film 10 and the negative electrode lead 42. Thus, the electrolyte is impregnated in the stacked body 20Z, and the battery element 20 as a stacked electrode body is manufactured.

[0288] Thus, the battery element 20 is sealed inside the outer film 10 , thereby assembling a secondary battery.

[0289] After the secondary battery was completed, the content (weight %) of the alkali carbonate compound in the negative electrode active material layer 120 and the content (weight %) of the magnesium compound in the negative electrode active material layer 120 were calculated, and the results are shown in Table 1. It should be noted that the details of the calculation steps are as described above.

[0290] (Stabilization of secondary batteries)

[0291] The secondary battery was charged and discharged for one cycle at room temperature (temperature = 25°C). During charging, constant current charging was performed at a current of 0.1C until the voltage reached 4.2V, and then constant voltage charging was performed at the voltage of 4.2V until the current reached 0.05C. During discharge, constant current discharge was performed at a current of 0.1C until the voltage reached 2.5V. 0.1C refers to the current value that completely discharges the battery capacity (theoretical capacity) within 10 hours, and 0.05C refers to the current value that completely discharges the battery capacity within 20 hours.

[0292] Thus, since a coating film is formed on the surface of each of the positive electrode 21 and the negative electrode 22, the state of the secondary battery is electrochemically stabilized. Thus, a laminated film type secondary battery is completed.

[0293] [Evaluation of battery characteristics]

[0294] As battery characteristics, cycle characteristics were evaluated, and the results shown in Table 1 were obtained.

[0295] When evaluating the cycle characteristics, the secondary battery was first left in a low temperature environment (temperature = 5° C.) (standing time = 3 hours). Next, the secondary battery was charged and discharged in the same environment to measure the discharge capacity (discharge capacity of the first cycle).

[0296] Next, the secondary battery was repeatedly charged and discharged in the same environment until the total number of cycles reached 300 cycles, and the discharge capacity (discharge capacity at the 300th cycle) was measured.

[0297] Finally, based on the calculation formula: capacity retention rate (%)=(discharge capacity at the 300th cycle / discharge capacity at the 1st cycle)×100, the capacity retention rate, which is an index for evaluating the cycle characteristics, was calculated.

[0298] When charging, at 3mA / cm 2 The battery was charged at a constant current density of 4.2 V until the voltage reached 4.2 V, and then charged at a constant voltage of 4.2 V until the current density reached 0.7 mA / cm 2 When discharging, at 3mA / cm 2 The battery was discharged at a constant current density until the voltage reached 3.0 V.

[0299] [Table 1]

[0300] [Investigation]

[0301] As shown in Table 1, the capacity retention rate varies greatly depending on the configuration of the negative electrode 22 .

[0302] Hereinafter, the capacity retention rate in the case where the negative electrode active material layer 22B does not contain both the alkali metal carbonate compound and the magnesium compound (Comparative Example 1) is used as a comparative reference.

[0303] Specifically, when the negative electrode active material layer 22B contains only an alkali metal carbonate compound (Comparative Example 2), the capacity retention rate increases slightly. In addition, when the negative electrode active material layer 22B contains only a magnesium compound (Comparative Example 3), the capacity retention rate also increases slightly. Therefore, it can be expected that even if the negative electrode active material layer 22B contains both an alkali metal carbonate compound and a magnesium compound, the capacity retention rate increases only slightly.

[0304] However, when the negative electrode active material layer 22B contains both an alkali metal carbonate compound and a magnesium compound (Examples 1 to 17), results contrary to the above expectation are obtained. That is, when the negative electrode active material layer 22B contains both an alkali metal carbonate compound and a magnesium compound, the capacity retention rate is significantly increased.

[0305] Here, the results contrary to the above-mentioned expectations are described in detail.

[0306] First, when the negative electrode active material layer 22B contains only an alkali metal carbonate compound (Comparative Example 2), the increase rate of the capacity maintenance rate is about 31.6%. In addition, when the negative electrode active material layer 22B contains only a magnesium compound (Comparative Example 3), the increase rate of the capacity maintenance rate is about 94.7%. Therefore, when the negative electrode active material layer 22B contains both an alkali metal carbonate compound and a magnesium compound, the increase rate of the capacity maintenance rate is expected to be about 126.3% (=31.6%+94.7%). This increase rate (=about 126.3%) is a value exceeding 100%, so it is considered to be a sufficient value at first glance, but considering the improvement of the cycle characteristics as much as possible, it is still an insufficient value.

[0307] In contrast, actual verification found that when the negative electrode active material layer 22B contains both an alkali metal carbonate compound and a magnesium compound (Example 7), the increase rate of the capacity retention rate is about 326.3%. This increase rate (= about 326.3%) is about 2.5 times the expected increase rate (= about 126.3%), which is a significantly high value contrary to the expectation, so when considering improving the cycle characteristics as much as possible, this increase rate is a sufficient value.

[0308] In particular, the favorable tendency that the capacity retention rate significantly increases when the negative electrode active material layer 22B contains both the alkali metal carbonate compound and the magnesium compound is a special tendency that cannot be simply derived without actual verification.

[0309] In the case where the negative electrode active material layer 22B contains both an alkali metal carbonate compound and a magnesium compound (Examples 1 to 17), in particular, the following tendencies are obtained. First, even if the type of alkali metal carbonate compound is changed (lithium carbonate, a first alkali metal carbonate compound, and a second alkali metal carbonate compound), a high capacity maintenance rate can be obtained. Second, even if the type of magnesium compound is changed, a high capacity maintenance rate can be obtained. Third, when the content of the alkali metal carbonate compound in the negative electrode active material layer 22B is 0.2 wt% to 0.8 wt%, a high capacity maintenance rate is obtained. Fourth, when the content of the magnesium compound in the negative electrode active material layer 22B is 0.01 wt% to 5 wt%, a high capacity maintenance rate is obtained.

[0310] [Summarize]

[0311] According to the results shown in Table 1, when the negative electrode active material layer 22B of the negative electrode 22 contains the alkali metal carbonate compound and the magnesium compound, a high capacity retention rate is obtained. Therefore, since the cycle characteristics are improved, excellent battery characteristics can be obtained in the secondary battery.

[0312] As mentioned above, although the present technology has been described by taking one embodiment and an example, the configuration of the present technology is not limited to the configuration described in one embodiment and an example, and various modifications are possible.

[0313] Specifically, the case where the battery structure of the secondary battery is a laminated film type is described, but since the battery structure of the secondary battery is not particularly limited, other battery structures such as a cylindrical type, a square type, a coin type, and a button type may be used.

[0314] In addition, the case where the element structure of the battery element is a stacked type and a wound type is described. However, the element structure of the battery element is not particularly limited, and therefore other element structures such as a repeatedly folded type may also be used. In the repeatedly folded type, the positive electrode and the negative electrode are folded into a Z shape so as to face each other through a separator.

[0315] In addition, although the case where the electrode reaction material is lithium is described, the electrode reaction material is not particularly limited. Specifically, as described above, the electrode reaction material can be other alkali metals such as sodium and potassium, or alkaline earth metals such as beryllium, magnesium and calcium. In addition, the electrode reaction material can also be other light metals such as aluminum.

[0316] The effects described in this specification are merely examples, and therefore the effects of the present technology are not limited to the effects described in this specification. Therefore, other effects can also be obtained with respect to the present technology.

[0317] It should be noted that the present technology can also adopt the following configurations.

[0318] <1> A secondary battery comprising:

[0319] positive electrode;

[0320] a negative electrode, including a negative electrode active material layer; and

[0321] Electrolyte,

[0322] The negative electrode active material layer comprises an alkali metal carbonate compound and a magnesium compound.

[0323] The alkali metal carbonate compound has a carbonate bond (-OC(=O)O-) and contains an alkali metal element as a constituent element.

[0324] The magnesium compound contains magnesium as a constituent element.

[0325] <2> The secondary battery according to <1>,

[0326] The alkali metal carbonate compound includes at least one of lithium carbonate (Li 2 CO 3 ), a compound represented by formula (1), and a compound represented by formula (2).

[0327] R1-OC(=O)O-M1…(1)

[0328] (R1 is an alkyl group. M1 is an alkali metal element.)

[0329] M2-OC(=O)O-R2-OC(=O)O-M3…(2)

[0330] (R2 is an alkylene group. M2 and M3 are alkali metal elements.)

[0331] <3> The secondary battery according to <2>,

[0332] In the formula (1), the alkali metal element is lithium,

[0333] In the formula (2), the alkali metal element is lithium.

[0334] <4> The secondary battery according to any one of (1) to (3),

[0335] The magnesium compound includes at least one of magnesium fluoride, magnesium oxide, magnesium nitride and magnesium carbonate.

[0336] <5> The secondary battery according to any one of (1) to (4),

[0337] The content of the alkali metal carbonate compound in the negative electrode active material layer is 0.2 wt % or more and 0.8 wt % or less.

[0338] <6> The secondary battery according to any one of <1> to <5>,

[0339] A content of the magnesium compound in the negative electrode active material layer is 0.01 wt % or more and 5 wt % or less.

[0340] <7> The secondary battery according to any one of <1> to <6>,

[0341] The negative electrode active material layer contains a negative electrode active material.

[0342] The negative electrode active material includes a carbon material and a silicon-containing material.

[0343] <8> The secondary battery according to any one of <1> to <7>,

[0344] The secondary battery is a lithium ion secondary battery.

[0345] <9> A negative electrode for a secondary battery,

[0346] having a negative electrode active material layer,

[0347] The negative electrode active material layer comprises an alkali metal carbonate compound and a magnesium compound.

[0348] The alkali metal carbonate compound has a carbonate bond (-OC(=O)O-) and contains an alkali metal element as a constituent element.

[0349] The magnesium compound contains magnesium as a constituent element.

Claims

1. A secondary battery comprising: positive electrode; a negative electrode, comprising a negative electrode active material layer; and Electrolyte, The negative electrode active material layer comprises an alkali metal carbonate compound and a magnesium compound. The alkali metal carbonate compound has a carbonate bond, i.e., -OC(=O)O-, and contains an alkali metal element as a constituent element. The magnesium compound contains magnesium as a constituent element.

2. The secondary battery according to claim 1, wherein The alkali metal carbonate compound comprises at least one of lithium carbonate Li2CO3, a compound represented by formula (1) and a compound represented by formula (2), R1-OC(=O)O-M1…(1) In the formula, R1 is an alkyl group, M1 is an alkali metal element, M2-OC(=O)O-R2-OC(=O)O-M3…(2) In the formula, R2 is an alkylene group, and M2 and M3 are alkali metal elements.

3. The secondary battery according to claim 2, wherein: In the formula (1), the alkali metal element is lithium, In the formula (2), the alkali metal element is lithium.

4. The secondary battery according to any one of claims 1 to 3, wherein The magnesium compound includes at least one of magnesium fluoride, magnesium oxide, magnesium nitride and magnesium carbonate.

5. The secondary battery according to any one of claims 1 to 4, wherein The content of the alkali metal carbonate compound in the negative electrode active material layer is 0.2 wt % or more and 0.8 wt % or less.

6. The secondary battery according to any one of claims 1 to 5, wherein A content of the magnesium compound in the negative electrode active material layer is 0.01 wt % or more and 5 wt % or less.

7. The secondary battery according to any one of claims 1 to 6, wherein The negative electrode active material layer contains a negative electrode active material. The negative electrode active material includes a carbon material and a silicon-containing material.

8. The secondary battery according to any one of claims 1 to 7, The secondary battery is a lithium ion secondary battery.

9. A negative electrode for a secondary battery, having a negative electrode active material layer, The negative electrode active material layer comprises an alkali metal carbonate compound and a magnesium compound. The alkali metal carbonate compound has a carbonate bond, i.e., -OC(=O)O-, and contains an alkali metal element as a constituent element. The magnesium compound contains magnesium as a constituent element.

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