Negative electrode for secondary battery, and secondary battery

Abstract

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

Description

Negative electrode for secondary battery and secondary battery

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

[0002] Due to the widespread use of various electronic devices such as mobile phones, secondary batteries have been developed as small, lightweight power sources that can provide high energy density. These secondary batteries contain a positive electrode, a negative electrode (secondary battery negative electrode), and an electrolyte solution, and various studies have been conducted on the configuration of these secondary batteries.

[0003] Specifically, the negative electrode active material layer contains ceramic nanoparticles (MgO) together with the negative electrode active material (carbon material) (see, for example, Patent Document 1). The anode active material contains (CH 2 OCO 2 Li) 2 (See, for example, Patent Document 2.) At least one of the positive electrode, the negative electrode, and the non-aqueous electrolyte contains a basic compound, and the basic compound converts the anion (NO - ) and cations (Mg 2+ ) (see, for example, Patent Document 3). The binder of the electrode contains a polymer compound, and the polymer compound has an anion (NO3 - or NO2 - ) and cations (Mg 2+ ) (see, for example, Patent Document 4).

[0004] Japanese Patent Application Laid-Open No. 2007-305545 Japanese Patent Application Laid-Open No. 2020-513138 Japanese Patent Application Laid-Open No. 2015-090860 Japanese Patent Application Laid-Open No. 2014-077134

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

[0006] There is a demand for a negative electrode for a secondary battery and a secondary battery that are capable of achieving excellent battery characteristics.

[0007] According to one embodiment of the present technology, there is provided a negative electrode for a secondary battery, the negative electrode active material layer including an alkali metal carbonate compound and a magnesium compound, the alkali metal carbonate compound having a carbonate bond (—OC(═O)O—) and including an alkali metal element as a constituent element, and the magnesium compound including magnesium as a constituent element.

[0008] A secondary battery according to an embodiment of the present technology includes a positive electrode, a negative electrode, and an electrolyte solution, and the negative electrode has a configuration similar to that of the negative electrode for a secondary battery according to the embodiment of the present technology described above.

[0009] According to the negative electrode for a secondary battery or the secondary battery of one embodiment of the present technology, the negative electrode for a secondary battery includes a negative electrode active material layer, and the negative electrode active material layer includes an alkali metal carbonate compound and a magnesium compound, so that excellent battery characteristics can be obtained.

[0010] Note that the effects of the present technology are not necessarily limited to the effects described here, but may be any of a series of effects related to the present technology described below.

[0011] Fig. 4 is a cross-sectional view showing a configuration of a negative electrode for a secondary battery according to an embodiment of the present technology; Fig. 5 is a perspective view showing a configuration of a secondary battery according to an embodiment of the present technology; Fig. 6 is a cross-sectional view showing a configuration of the battery element shown in Fig. 2; Fig. 7 is a plan view showing a configuration of a positive electrode shown in Fig. 3; Fig. 8 is a plan view showing a configuration of a negative electrode shown in Fig. 3; Fig. 9 is a perspective view for explaining a manufacturing method of a secondary battery; and Fig. 10 is a block diagram showing a configuration of an application example of a secondary battery.

[0012] Hereinafter, an embodiment of the present technology will be described in detail with reference to the drawings. The description will be made in the following order: 1. Negative electrode for secondary battery 1-1. Configuration 1-2. Operation 1-3. Manufacturing method 1-4. Action and effect 2. Secondary battery 2-1. Configuration 2-2. Operation 2-3. Manufacturing method 2-4. Action and effect 3. Modification 4. Use of secondary battery

[0013] 1. Negative electrode for secondary battery First, a negative electrode for secondary battery (hereinafter simply referred to as "negative electrode") according to one embodiment of the present technology will be described.

[0014] The negative electrode described here is used in a secondary battery, which is an electrochemical device. However, the negative electrode may also be used in electrochemical devices other than secondary batteries. Specific examples of other electrochemical devices include primary batteries and capacitors.

[0015] This negative electrode absorbs and releases an electrode reactant during the electrode reaction of the electrochemical device. The type of electrode reactant is not particularly limited, but specifically, it is a light metal such as an alkali metal or alkaline earth metal. Specific examples of alkali metals include lithium, sodium, and potassium, and specific examples of alkaline earth metals include beryllium, magnesium, and calcium.

[0016] In the following, an example will be given in which the electrode reactant is lithium. At the negative electrode, lithium is absorbed and released in an ionic state during the electrode reaction.

[0017] <1-1. Structure> Fig. 1 shows a cross-sectional structure of an anode 100, which is an example of an anode. As shown in Fig. 1, the anode 100 includes an anode active material layer 120. Here, the anode 100 further includes an anode current collector 110 that supports the anode active material layer 120.

[0018] [Negative Electrode Current Collector] The negative electrode current collector 110 is a conductive support that supports the negative electrode active material layer 120, and has a pair of surfaces on which the negative electrode active material layer 120 is provided. The negative electrode current collector 110 contains one or more types of conductive materials such as metal materials, and a specific example of the conductive material is copper.

[0019] The surface of the negative electrode current collector 110 is preferably roughened by electrolysis or the like, because the adhesion of the negative electrode active material layer 120 to the negative electrode current collector 110 is improved by utilizing the so-called anchor effect.

[0020] However, the negative electrode current collector 110 may be omitted. That is, the negative electrode 100 may include only the negative electrode active material layer 120 without including the negative electrode current collector 110.

[0021] [Negative Electrode Active Material Layer] The negative electrode active material layer 120 contains an alkali metal carbonate compound and a magnesium compound. Here, the negative electrode active material layer 120 further contains a negative electrode active material that absorbs and releases lithium. However, the negative electrode active material layer 120 may further contain one or more of other materials such as a negative electrode binder and a negative electrode conductive agent.

[0022] Here, the negative electrode active material layer 120 is provided on both sides of the negative electrode current collector 110. However, the negative electrode active material layer 120 may be provided on only one side of the negative electrode current collector 110. The method for forming the negative electrode active material layer 120 is not particularly limited, but specifically includes a coating method or the like.

[0023] (Negative electrode active material) The type of the negative electrode active material is not particularly limited, but specifically, it is any one or more of materials such as carbon materials and metal-based materials. That is, the negative electrode active material may be only a carbon material, only a metal-based material, or both a carbon material and a metal-based material. This is because a high energy density can be obtained. However, the type of the negative electrode active material may be a material other than each of the carbon material and the metal-based material.

[0024] Carbon material is a general term for materials containing carbon as a constituent element. The crystal structure of carbon material changes little during lithium absorption and desorption, so a high energy density can be stably obtained in the negative electrode active material layer 120. In addition, carbon material also functions as a negative electrode conductive agent, improving the conductivity of the negative electrode active material layer 120.

[0025] 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, but is specifically 0.37 nm or more. The interplanar spacing of the (002) plane of graphite is not particularly limited, but is specifically 0.34 nm or less.

[0026] Specific examples of carbon materials include pyrolytic carbons, cokes, glassy carbon fibers, organic polymer compound calcined bodies, activated carbon, and carbon blacks. Examples of cokes include pitch coke, needle coke, and petroleum coke. Organic polymer compound calcined bodies are calcined (carbonized) polymer compounds such as phenolic resins and furan resins at an appropriate temperature. Alternatively, the carbon material may be low-crystalline carbon heat-treated at a temperature of approximately 1000°C or less, or amorphous carbon. The shape of the carbon material is not particularly limited, but may be one or more of the following: fibrous, spherical, granular, and flaky.

[0027] The metal-based material is a general term for materials containing, as constituent elements, one or more of metal elements and semimetal elements that can form an alloy with lithium. Metal-based materials have a higher energy density, and therefore, a higher energy density can be obtained in the negative electrode active material layer 120.

[0028] This metallic material may be a simple substance, an alloy, a compound, a mixture of two or more of these, or a material containing one or more of these phases. The "simple substance" described here refers to a general simple substance, and therefore the simple substance may contain trace amounts of impurities. In other words, the purity of the simple substance is not necessarily limited to 100%.

[0029] However, 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 metalloid elements as constituent elements. Furthermore, an "alloy" may also contain one or more non-metallic elements as constituent elements. The structure of the metallic material is not particularly limited, but specifically may be one or more of the following: a solid solution, a eutectic (eutectic mixture), an intermetallic compound, or a mixture of two or more of these.

[0030] Specific examples of metal elements and metalloid elements include magnesium, boron, aluminum, gallium, indium, silicon, germanium, tin, lead, bismuth, cadmium, silver, zinc, hafnium, zirconium, yttrium, palladium, and platinum.

[0031] Among these, the metal-based material is preferably a silicon-containing material. Silicon-containing materials have excellent lithium absorption and desorption capabilities, and therefore, 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 may be silicon alone, a silicon alloy, a silicon compound, a mixture of two or more of these, or a material containing one or more of these phases.

[0032] Silicon alloys contain, as constituent elements other than silicon, any one or more of metal elements such as tin, nickel, copper, iron, cobalt, manganese, zinc, indium, silver, titanium, germanium, bismuth, antimony, and chromium. Silicon compounds contain, as constituent elements other than silicon, any one or more of non-metal elements such as carbon and oxygen. However, silicon compounds may also contain, as constituent elements other than silicon, any one or more of the metal elements described for silicon alloys.

[0033] Specific examples of silicon alloys include SiB 4 , SiB 6 , Mg 2 Si, Ni 2 Si, TiSi 2 , MoSi 2 , CoSi 2 , NiSi 2 , CaSi 2 , CrSi 2 , Cu 5 Si, FeSi 2 , MnSi 2 , NbSi 2 , TaSi 2 , VSi 2 , WSi 2 , ZnSi2 and SiC, etc. However, the composition of the silicon alloy (the mixture ratio of silicon and metal elements) can be changed as desired.

[0034] Specific examples of silicon compounds include Si 3 N 4 , Si 2 N 2 O, SiO x (0<x≦2) and LiSiO, etc. However, the range of x may be 0.2<x<1.4.

[0035] In particular, it is preferable that the negative electrode active material contains both a carbon material and a silicon-containing material, because this prevents damage to the negative electrode active material layer 120 while ensuring the battery capacity during the electrode reaction (charging and discharging) of a secondary battery using the negative electrode 100.

[0036] Specifically, silicon-containing materials, which are metal-based materials, have the advantage of having a high theoretical capacity, but are prone to severe expansion and contraction during charging and discharging. On the other hand, carbon materials have the disadvantage of having a low theoretical capacity, but are also prone to expansion and contraction during charging and discharging. Therefore, by using a carbon material and a silicon-containing material in combination, a high theoretical capacity can be obtained while suppressing the expansion and contraction of the anode active material layer 120 during charging and discharging. As a result, as described above, damage to the anode active material layer 120 is suppressed while ensuring the battery capacity. Specific examples of damage to the anode active material layer 120 include cracking of the anode active material layer 120 and detachment of the anode active material layer 120.

[0037] (Alkali Metal Carbonate Compound) As described above, the alkali metal carbonate compound is contained in the negative electrode active material layer 120. As a result, the alkali metal carbonate compound is dispersed in the negative electrode active material layer 120.

[0038] This 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 one or two or more. Specific examples of alkali metal elements are lithium, sodium, and potassium, as described above. The type of alkali metal carbonate compound may be one or two or more.

[0039] The reason why the anode active material layer 120 contains an alkali metal carbonate compound is that a good coating is formed on the surface of the anode active material during charge and discharge. This coating is derived from the alkali metal carbonate compound and has a high-density pore structure. Therefore, by covering the surface of the highly reactive anode active material, the coating protects the surface of the anode active material, thereby providing a barrier function that protects the surface of the anode active material from the electrolyte while ensuring the input and output of lithium to and from the anode active material. Furthermore, the coating follows the expansion and contraction of the anode active material during charge and discharge, thereby reinforcing the physical strength of the anode active material and thus providing a stress relaxation function that suppresses damage to the anode active material.

[0040] (Specific Configuration) The type of alkali metal carbonate compound is not particularly limited, but among them, the alkali metal carbonate compound is lithium carbonate (Li 2 CO 3 ), the first alkali metal carbonate compound and the second alkali metal carbonate compound, because a coating film derived from the alkali metal carbonate compound is more likely to be formed stably.

[0041] The first alkali metal carbonate compound is any one or more of the compounds represented by formula (1). As is clear from formula (1), this first alkali metal carbonate compound has one carbonate bond.

[0042] R1-OC(=O)O-M1 (1) (R1 is an alkyl group. M1 is an alkali metal element.)

[0043] The type of alkyl group is not particularly limited, but specific examples include methyl, ethyl, and propyl groups. However, the alkyl group may be linear or branched. Details regarding the alkali metal element are as described above.

[0044] A specific example of the first alkali metal carbonate compound is lithium methyl carbonate (H 3 C—OC(═O)O—Li), lithium ethyl carbonate (H 5 C 2 —OC(═O)O—Li), lithium propyl carbonate (H 7 C 3 —OC(═O)O—Li), sodium methyl carbonate (H 3 C—OC(═O)O—Na), sodium ethyl carbonate (H 5 C 2 —OC(═O)O—Na), sodium propyl carbonate (H 7 C 3 -OC(=O)O-Na), potassium methyl carbonate (H 3 C—OC(═O)O—K), potassium ethyl carbonate (H 5 C 2 —OC(═O)O—K) and potassium propyl carbonate (H 7 C 3 -OC(=O)O-K), etc.

[0045] The second alkali metal carbonate compound is any one or more of the compounds represented by formula (2). As is clear from formula (2), this second alkali metal carbonate compound has two carbonate bonds.

[0046] M2-OC(═O)O-R2-OC(═O)O-M3 (2) (R2 is an alkylene group. M2 and M3 are each an alkali metal element.)

[0047] The type of alkylene group is not particularly limited, but specific examples include methylene, ethylene, and propylene groups. However, the alkylene group may be linear or branched. Details regarding the alkali metal element are as described above.

[0048] A specific example of the second alkali metal carbonate compound is dilithium methylene dicarbonate (Li—OC(═O)O—CH 2 —OC(═O)O—Li), dilithium ethylene dicarbonate (Li—OC(═O)O—C 2 H 4 —OC(═O)O—Li), dilithium propylene dicarbonate (Li—OC(═O)O—C 3 H 6 —OC(═O)O—Li), disodium methylene dicarbonate (Na—OC(═O)O—CH 2 —OC(═O)O—Na), disodium ethylene dicarbonate (Na—OC(═O)O—C 2 H 4 —OC(═O)O—Na), disodium propylene dicarbonate (Na—OC(═O)O—C 3 H 6 —OC(═O)O—Na), dipotassium methylene dicarbonate (K—OC(═O)O—CH 2 —OC(═O)O—K), dipotassium ethylene dicarbonate (K—OC(═O)O—C 2 H 4 —OC(═O)O—K) and dipotassium propylene dicarbonate (K—OC(═O)O—C 3 H 6 -OC(=O)O-K), etc.

[0049] 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, because this makes it easier to form a stable coating derived from the alkali metal carbonate compound.

[0050] (Content) 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 % in particular, because this makes it easier to stably form a coating film derived from the alkali metal carbonate compound.

[0051] In addition, when the negative electrode active material layer 120 contains two or more types of alkali metal carbonate compounds, the "content of the alkali metal carbonate compounds in the negative electrode active material layer 120" described here is the sum of the contents of the respective alkali metal carbonate compounds.

[0052] (Confirmation Procedure and Calculation Procedure) The procedure for confirming whether or not an alkali metal carbonate compound is contained in the negative electrode active material layer 120 and the procedure for calculating the content of the alkali metal carbonate compound in the negative electrode active material layer 120 are as described below.

[0053] First, the negative electrode current collector 110 is peeled off from the negative electrode active material layer 120 of the negative electrode 100, thereby recovering 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 dismantling the secondary battery.

[0054] Next, the negative electrode active material layer 120 is washed with a washing solvent, and then the negative electrode active material layer 120 is dried. The type of washing solvent is not particularly limited, but specifically, it is an organic solvent such as acetone. The environmental conditions during drying are not particularly limited, but specifically, it may be an inert gas atmosphere using argon gas or the like, or a dry environment.

[0055] Subsequently, 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 extraction solution is not particularly limited, but specifically, lithium bis(trifluoromethanesulfonyl)imide (LiN(CF 3 SO 2 ) 2 ) dimethyl sulfoxide-d 6 Solution (LiTFSI DMSO-d 6 ) etc. This gives an extract.

[0056] Next, the extract is analyzed using nuclear magnetic resonance. Here, the nuclear magnetic resonance is performed using proton nuclear magnetic resonance ( 1 H NMR) and carbon-13 nuclear magnetic resonance ( 13If a peak attributed to the alkali metal carbonate compound is detected, it is confirmed that the alkali metal carbonate compound is contained in the negative electrode active material layer 120.

[0057] 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 proton nuclear magnetic resonance spectroscopy, and peaks are detected at 61.0 ppm, 65.8 ppm, and 156.9 ppm in carbon-13 nuclear magnetic resonance spectroscopy.

[0058] Furthermore, when the alkali metal carbonate compound is a second alkali metal carbonate compound (dilithium ethylene dicarbonate), a peak is detected at 3.63 ppm in proton nuclear magnetic resonance spectroscopy, and peaks are detected at 62.7 ppm and 166.2 ppm in carbon-13 nuclear magnetic resonance spectroscopy.

[0059] Next, when an alkali metal carbonate compound is contained in the negative electrode active material layer 120, the weight of the partial structure (alkali metal carbonate compound) in the extract is calculated by comparing the integral value of the signal corresponding to the partial structure of the organic coating component with the integral value of the signal of the internal standard substance. The type of internal standard substance is not particularly limited, but specifically, 3-(trimethylsilyl)propionic acid-d 4 Sodium, etc.

[0060] 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 following calculation formula is used: content of the alkali metal carbonate compound in the negative electrode active material layer 120 (wt %) = (weight of the alkali metal carbonate compound / weight of the negative electrode active material layer 120) × 100.

[0061] In addition, when checking whether or not an alkali metal carbonate compound is contained in the negative electrode active material layer 120, infrared spectroscopy may be used instead of nuclear magnetic resonance spectroscopy.

[0062] For example, when the alkali metal carbonate compound is a second alkali metal carbonate compound (dilithium ethylene dicarbonate), the reaction temperature is 1650 cm -1 , 1395 cm -1 , 1305 cm -1 , 1080cm -1 and 820 cm -1 A peak is detected in each of the

[0063] (Magnesium Compound) As described above, the magnesium compound is contained in the negative electrode active material layer 120. As a result, 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.

[0064] This magnesium compound contains magnesium as a constituent element. The types of elements other than magnesium contained in the magnesium compound are not particularly limited and can be selected arbitrarily. The type of magnesium compound may be one type or two or more types.

[0065] The reason why the negative electrode active material layer 120 contains a magnesium compound together with an alkali metal carbonate compound is that the magnesium compound acts self-sacrificially during charge and discharge, and therefore reacts and decomposes preferentially over the alkali metal carbonate compound. This allows the magnesium compound to suppress the reaction and decomposition of the alkali metal carbonate compound. Therefore, even after repeated charge and discharge, a coating derived from the alkali metal carbonate compound is likely to be formed stably and continuously, and the functions of the coating (barrier function and stress relaxation function) are likely to be maintained.

[0066] (Specific Configuration) The type of magnesium compound is not particularly limited, but a specific example of the magnesium compound is magnesium fluoride (MgF 2 ), magnesium oxide (MgO), magnesium nitride (Mg 3 N 2 ) and magnesium carbonate (MgCO 3 ) etc. This is because the reaction and decomposition of the alkali metal carbonate compound can be sufficiently suppressed, and the function of the coating can be sufficiently maintained.

[0067] The magnesium compound may already be contained in the negative electrode active material layer 120 before the first charge / discharge of the secondary battery.

[0068] Alternatively, the magnesium compound may not be contained in the anode active material layer 120 before the first charge / discharge of the secondary battery, but may be contained in the anode active material layer 120 for the first time after the secondary battery is charged and discharged. That is, the magnesium compound may not be present in the anode active material layer 120 before the first charge / discharge, but may be formed inside the anode active material layer 120 by utilizing a charge / discharge reaction after the first charge / discharge, and may therefore be present in the anode active material layer 120.

[0069] The type of material that can form a magnesium compound using this charge-discharge reaction is not particularly limited, but specifically, magnesium nitrate (Mg(NO 3 ) 2 ) and magnesium carbonate (Mg(CO 3 ) 2 ) etc.

[0070] (Content) 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 % in particular, because the reaction and decomposition of the alkali metal carbonate compound are easily suppressed sufficiently, and the function of the coating film is easily maintained sufficiently.

[0071] In addition, when the negative electrode active material layer 120 contains two or more types of magnesium compounds, the "content of the magnesium compounds in the negative electrode active material layer 120" described here is the total content of each magnesium compound.

[0072] (Confirmation Procedure and Calculation Procedure) The procedure for confirming whether or not a magnesium compound is contained in the negative electrode active material layer 120 and the procedure for calculating the content of the magnesium compound in the negative electrode active material layer 120 are as described below.

[0073] First, the negative electrode current collector 110 is peeled off from the negative electrode active material layer 120 of the negative electrode 100, thereby recovering 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 dismantling the secondary battery.

[0074] Next, the negative electrode active material layer 120 is washed with a washing solvent, and then the negative electrode active material layer 120 is allowed to dry naturally. The type of washing solvent is not particularly limited, but specifically, it is an organic solvent such as dimethyl carbonate. The environmental conditions during drying are not particularly limited, but specifically, it is the inside of a glove box into which an inert gas such as argon gas has been introduced.

[0075] Next, a sample for analysis is prepared using conductive carbon double-sided tape (conductive carbon double-sided tape (8 mm x 20 m) model number 7311 manufactured by Nissin EM Co., Ltd.), and then the sample is moved from inside the glove box into the inside of an X-ray photoelectron spectroscopy (XPS) analyzer. In this case, the sample is introduced into the XPS analyzer while preventing the sample from being exposed to the atmosphere.

[0076] Next, the sample is analyzed using an XPS apparatus. If a peak derived from the magnesium compound is detected, it is confirmed that the negative electrode active material layer 120 contains the magnesium compound.

[0077] For example, when the magnesium compound is magnesium oxide, a peak is detected near a binding energy of about 50.4 eV, and when the magnesium compound is magnesium fluoride, a peak is detected near a binding energy of about 50.9 eV.

[0078] The XPS device that can be used is an X-ray photoelectron spectrometer such as PHI 5000 VersaProbe manufactured by ULVAC-PHI, Inc. The analysis conditions were as follows: X-ray source = monochromated Al-Kα ray (1486.6 eV), X-ray spot diameter = 100 μmφ, photoelectron escape angle = 45°, and charge neutralization = neither an electron gun (flood gun) nor an Ar ion gun was used.

[0079] Next, when a magnesium compound is contained in the negative electrode active material layer 120, the ratio between the area of ​​the peak derived from the magnesium compound normalized based on the relative sensitivity and the area of ​​the peak derived from each element contained in the negative electrode active material layer 120 is calculated, and the weight of the magnesium compound is calculated based on this ratio.

[0080] 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 using the following formula: content of the magnesium compound in the negative electrode active material layer 120 (wt %) = (weight of the magnesium compound / weight of the negative electrode active material layer 120) × 100.

[0081] (Negative Electrode Binder) The negative electrode binder contains one or more materials selected from synthetic rubbers and polymer compounds. Specific examples of synthetic rubbers include styrene-butadiene rubbers, fluorine-containing rubbers, and ethylene-propylene-diene. Specific examples of polymer compounds include polyvinylidene fluoride, polyimide, and carboxymethyl cellulose.

[0082] (Negative electrode conductive agent) The negative electrode conductive agent contains one or more conductive materials such as carbon materials, and specific examples of the conductive materials are graphite, carbon black, acetylene black, ketjen black, etc. However, the conductive material is not limited to carbon materials, and may be a metal material, a polymer compound, etc.

[0083] <1-2. Operation> In the negative electrode 100, the negative electrode active material in the negative electrode active material layer 120 absorbs lithium in an ionic state during the electrode reaction, and the negative electrode active material releases lithium in an ionic state.

[0084] <1-3. Manufacturing Method> When manufacturing the negative electrode 100, first, a negative electrode active material, an alkali metal carbonate compound, and a magnesium compound are mixed together to form a negative electrode mixture. In this case, the negative electrode mixture may contain a negative electrode binder, a negative electrode conductive agent, and the like, as necessary.

[0085] 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 may be an aqueous solvent or an organic solvent. In this case, the solvent containing the negative electrode mixture may be stirred using a stirring device such as a mixer.

[0086] Here, an anode mixture containing an anode active material, an alkali metal carbonate compound, and a magnesium compound is prepared, and then an anode mixture slurry is prepared using the anode mixture. However, it is also possible to prepare an anode mixture containing an anode active material, prepare an anode mixture slurry using the anode mixture, and then add the alkali metal carbonate compound and the magnesium compound to the anode mixture slurry.

[0087] Finally, the negative electrode mixture slurry is applied to both surfaces of the negative electrode current collector 110 to form the negative electrode active material layer 120. After this, 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.

[0088] As a result, the negative electrode active material layers 120 are formed on both sides of the negative electrode current collector 110, and the negative electrode 100 is completed.

[0089] <1-4. Functions and Effects> According to this negative electrode 100, the negative electrode active material layer 120 contains an alkali metal carbonate compound and a magnesium compound.

[0090] In this case, because the negative electrode active material layer 120 contains an alkali metal carbonate compound, as described above, a good coating derived from the alkali metal carbonate compound is formed on the surface of the negative electrode active material during charging and discharging of a secondary battery using the negative electrode 100. This utilizes the barrier function of the coating to suppress the decomposition reaction of the electrolyte on the surface of the negative electrode active material while ensuring the input and output of lithium. In addition, the stress relaxation function of the coating is utilized to suppress damage to the negative electrode active material due to expansion and contraction.

[0091] Furthermore, because the negative electrode active material layer 120 contains both an alkali metal carbonate compound and a magnesium compound, as described above, the magnesium compound reacts and decomposes preferentially over the alkali metal carbonate compound during charge and discharge, thereby suppressing the reaction and decomposition of the alkali metal carbonate compound. This facilitates stable and continuous formation of a coating derived from the alkali metal carbonate compound even after repeated charge and discharge, making it easier to maintain the functions of the coating (barrier function and stress relaxation function). This continuously suppresses the decomposition reaction of the electrolyte on the surface of the negative electrode active material, and continuously prevents damage to the negative electrode active material due to expansion and contraction.

[0092] For these reasons, the discharge capacity is less likely to decrease even when charging and discharging are repeated, and therefore, a secondary battery using the negative electrode 100 can have excellent battery characteristics.

[0093] In particular, if the alkali metal carbonate compound contains one or more of lithium carbonate, the first alkali metal carbonate compound, and the second alkali metal carbonate compound, a coating derived from the alkali metal carbonate compound is more likely to be formed stably, thereby achieving a greater effect.

[0094] In this case, if the alkali metal element (M1) in formula (1) relating to the first alkali metal carbonate compound is lithium, and the alkali metal elements (M2 and M3) in formula (2) relating to the second alkali metal carbonate compound are lithium, a coating derived from the alkali metal carbonate compound is more likely to be formed stably, thereby achieving a greater effect.

[0095] Furthermore, if the magnesium compound contains one or more of magnesium fluoride, magnesium oxide, magnesium nitride, and magnesium carbonate, the reaction and decomposition of the alkali metal carbonate compound is likely to be sufficiently suppressed, and the functionality of the coating film is likely to be sufficiently maintained, resulting in a greater effect.

[0096] Furthermore, if 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 derived from the alkali metal carbonate compound is more likely to be formed stably, and therefore a greater effect can be obtained.

[0097] Furthermore, if 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 are likely to be sufficiently suppressed, and the function of the coating film is likely to be sufficiently maintained, resulting in a greater effect.

[0098] Furthermore, if the negative electrode active material layer 120 contains a negative electrode active material, and the negative electrode active material contains a carbon material and a silicon-containing material, damage to the negative electrode active material layer 120 is suppressed while the battery capacity is guaranteed, and therefore, a higher effect can be obtained.

[0099] 2. Secondary Battery Next, a secondary battery according to an embodiment of the present technology to which the negative electrode 100 is applied will be described.

[0100] The secondary battery described here is a secondary battery that obtains battery capacity by utilizing the absorption and desorption of electrode reactants, and is equipped with a positive electrode, a negative electrode, and an electrolyte.

[0101] The charge capacity of the negative electrode is preferably larger than the discharge capacity of the positive electrode. That is, the electrochemical capacity per unit area of ​​the negative electrode is preferably larger than the electrochemical capacity per unit area of ​​the positive electrode. This is to prevent deposition of electrode reactants on the surface of the negative electrode during charging.

[0102] In the following, as described above, an example will be given in which the electrode reactant is lithium. A secondary battery that obtains battery capacity by utilizing the absorption and desorption of lithium is a so-called lithium ion secondary battery. In this lithium ion secondary battery, lithium is absorbed and desorbed in the ionic state.

[0103] <2-1. Configuration> Fig. 2 shows a perspective configuration of a secondary battery, and Fig. 3 shows a cross-sectional configuration of the battery element 20 shown in Fig. 2. Fig. 4 shows a planar configuration of the positive electrode 21 shown in Fig. 3, and Fig. 5 shows a planar configuration of the negative electrode 22 shown in Fig. 3. However, Fig. 2 shows a state in which the exterior film 10 and the battery element 20 are separated from each other.

[0104] As shown in Figures 2 and 3, this secondary battery includes an exterior 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 and 52.

[0105] The secondary battery described here is a so-called laminate film type secondary battery, since it uses the flexible or pliable exterior film 10 as an exterior member, as described above.

[0106] 2, the exterior film 10 is an exterior member that houses the battery element 20, and has a bag-like structure that is sealed when the battery element 20 is housed inside. As a result, the exterior film 10 houses an electrolyte solution together with a positive electrode 21 and a negative electrode 22, which will be described later.

[0107] Here, the exterior film 10 is a single film-like member that is folded in a folding direction F. The exterior film 10 is provided with a recessed portion 10U (a so-called deep drawn portion) for accommodating the battery element 20.

[0108] Specifically, the exterior film 10 is a three-layer laminate film in which a fusion layer, a metal layer, and a surface protection layer are laminated in this order from the inside out, and when the exterior film 10 is folded, the outer peripheral edges of the opposing fusion layers are fused to each other. The fusion layer contains a polymer compound such as polypropylene. The metal layer contains a metal material such as aluminum. The surface protection layer contains a polymer compound such as nylon.

[0109] However, the configuration (number of layers) of the exterior film 10 is not particularly limited, and may be one layer, two layers, or four or more layers.

[0110] [Battery Element] As shown in FIGS. 2 to 5 , the battery element 20 is a power generating element including a positive electrode 21, a negative electrode 22, a separator 23, and an electrolyte (not shown), and is housed inside the exterior film 10.

[0111] Here, the battery element 20 is a so-called laminated electrode body, and therefore the positive electrodes 21 and the negative electrodes 22 are alternately laminated with separators 23 interposed therebetween. The number of the positive electrodes 21, the negative electrodes 22, and the separators 23 is not particularly limited and can be set arbitrarily.

[0112] (Positive Electrode) As shown in Figures 3 and 4, the positive electrode 21 includes a positive electrode current collector 21A and a positive electrode active material layer 21B. In Figure 4, the positive electrode active material layer 21B is shaded.

[0113] The positive electrode current collector 21A has a pair of surfaces on which the positive electrode active material layer 21B is provided. The positive electrode current collector 21A contains a conductive material such as a metal material, and a specific example of the conductive material is aluminum.

[0114] The positive electrode active material layer 21B contains one or more types of positive electrode active materials that absorb and release lithium, but may also contain one or more types of other materials such as a positive electrode binder and a positive electrode conductive agent.

[0115] Here, the positive electrode active material layer 21B is provided on both sides of the positive electrode current collector 21A. However, the positive electrode active material layer 21B may be provided on only one side of the positive electrode current collector 21A, on the side where the positive electrode 21 faces the negative electrode 22. The method for forming the positive electrode active material layer 21B is not particularly limited, but specifically includes a coating method or the like.

[0116] The type of positive electrode active material is not particularly limited, but specifically includes a lithium-containing compound. This lithium-containing compound is a compound containing lithium and one or more transition metal elements as constituent elements, and may further include one or more other elements as constituent elements. The type of other element is not particularly limited as long as it is an element other than lithium and transition metal elements, but specifically includes elements belonging to Groups 2 to 15 of the long period periodic table. The type of lithium-containing compound is not particularly limited, but specifically includes oxides, phosphate compounds, silicate compounds, borate compounds, and the like.

[0117] A specific example of the oxide is LiNiO 2 , LiCoO 2 , LiCo 0.98 Al 0.01 Mg 0.01 O 2 , LiNi 0.5 Co 0.2 Mn 0.3 O 2 , LiNi 0.8 Co 0.15 Al 0.05 O 2 , LiNi 0.33 Co 0.33 Mn 0.33 O 2 , Li 1.2 Mn 0.52 Co 0.175 Ni 0.1 O 2 , Li 1.15 (Mn 0.65 Ni 0.22 Co 0.13 ) O 2 and LiMn 2 O 4 Specific examples of phosphate compounds include LiFePO 4 , LiMnPO 4 , LiFe 0.5 Mn 0.5 P.O. 4 and LiFe 0.3 Mn 0.7 P.O. 4 And so on.

[0118] The details regarding the positive electrode binder and the positive electrode conductive agent are the same as the details regarding the negative electrode binder and the negative electrode conductive agent described above.

[0119] 4, a portion of the positive electrode current collector 21A protrudes, and thus the positive electrode current collector 21A includes a portion that protrudes outward beyond the positive electrode active material layer 21B (hereinafter referred to as the "protruding portion of the positive electrode current collector 21A"). Since the positive electrode active material layer 21B is not provided on the protruding portion of the positive electrode current collector 21A, the protruding portion of the positive electrode current collector 21A functions as a positive electrode terminal 31. Details of the positive electrode terminal 31 will be described later.

[0120] On both surfaces of the positive electrode current collector 21A (excluding the positive electrode terminal 31), the positive electrode active material layer 21B is provided only on a part of the positive electrode current collector 21A. Therefore, the part of the positive electrode current collector 21A on which the positive electrode active material layer 21B is not provided is not covered with the positive electrode active material layer 21B and is exposed.

[0121] Specifically, as shown in Fig. 4, the positive electrode current collector 21A includes a covered portion 21AX and an uncovered portion 21AY. The covered portion 21AX is located in the center of the positive electrode current collector 21A and is the portion where the positive electrode active material layer 21B is formed. The uncovered portion 21AY is located around the covered portion 21AX and is a frame-shaped portion where the positive electrode active material layer 21B is not formed. As a result, the covered portion 21AX is covered with the positive electrode active material layer 21B, while the uncovered portion 21AY is exposed and not covered by the positive electrode active material layer 21B.

[0122] (Negative Electrode) The negative electrode 22 has a configuration similar to that of the negative electrode 100. Specifically, the negative electrode 22 includes a negative electrode current collector 22A and a negative electrode active material layer 22B, as shown in Figures 3 and 5. In Figure 5, the negative electrode active material layer 22B is shaded.

[0123] The configuration of the anode current collector 22A is similar to that of the anode current collector 110, and the configuration of the anode active material layer 22B is similar to that of the anode active material layer 120. That is, the anode active material layer 22B contains an alkali metal carbonate compound and a magnesium compound.

[0124] Here, as shown in FIG. 5 , a portion of the negative electrode current collector 22A protrudes, and therefore the negative electrode current collector 22A includes a portion that protrudes outward beyond the negative electrode active material layer 22B (hereinafter referred to as the "protruding portion of the negative electrode current collector 22A").

[0125] The protruding direction of the protruding portion of the negative electrode current collector 22A is the same as the protruding direction of the protruding portion of the positive electrode current collector 21 A. In addition, the position of the protruding portion of the negative electrode current collector 22A is such that it does not overlap with the protruding portion of the positive electrode current collector 21 A when the positive electrodes 21 and the negative electrodes 22 are alternately stacked with the separators 23 interposed therebetween.

[0126] 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 the negative electrode terminal 32. Details of the negative electrode terminal 32 will be described later.

[0127] On both surfaces of the negative electrode current collector 22A (excluding the negative electrode terminal 32), the negative electrode active material layer 22B is provided over the entire negative electrode current collector 22A. Therefore, the entire negative electrode current collector 22A is not exposed and is covered with the negative electrode active material layer 22B.

[0128] Specifically, as shown in FIG. 5 , the negative electrode active material layer 22B includes a facing portion 22BX and a non-facing portion 22BY. The facing portion 22BX is a portion facing the covered portion 21AX. That is, the facing portion 22BX is a portion involved in charge-discharge reactions because it faces the positive electrode active material layer 21B. The non-facing portion 22BY is a portion facing the non-covered portion 21AY. That is, the non-facing portion 22BY does not face the positive electrode active material layer 21B but faces the positive electrode current collector 21A, and therefore is not involved in charge-discharge reactions. In FIG. 5 , to make the formation range of the covered portion 21AX (positive electrode active material layer 21B) easier to understand, the formation range of the covered portion 21AX (the boundary between the facing portion 22BX and the non-facing portion 22BY) is indicated by a dashed line.

[0129] The negative electrode active material layer 22B is provided on the entire surface of both sides of the negative electrode current collector 22A, while the positive electrode active material layer 21B is provided on only a portion (coating portion 21AX) of both sides of the positive electrode current collector 21A in order to prevent lithium released from the positive electrode active material layer 21B during charging from being deposited on the surface of the negative electrode 22.

[0130] 3, the separator 23 is an insulating porous film interposed between the positive electrode 21 and the negative electrode 22, and allows lithium ions to pass through while preventing contact (short circuit) between the positive electrode 21 and the negative electrode 22. The separator 23 contains a polymer compound such as polyethylene.

[0131] (Electrolyte) The electrolyte is a liquid electrolyte that is impregnated into each of the positive electrode 21, the negative electrode 22, and the separator 23, and contains a solvent and an electrolyte salt.

[0132] Here, the solvent contains one or more types of non-aqueous solvents (organic solvents), and the electrolyte solution containing the non-aqueous solvent is a so-called non-aqueous electrolyte solution. This non-aqueous solvent contains esters and ethers, more specifically, carbonate ester compounds, carboxylic acid ester compounds, and lactone compounds. This is because the dissociation of the electrolyte salt is improved and the mobility of ions is also improved.

[0133] The carbonate ester compounds include cyclic carbonate esters and chain carbonate esters, etc. Specific examples of cyclic carbonate esters include ethylene carbonate and propylene carbonate, and specific examples of chain carbonate esters include dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate.

[0134] The carboxylic acid ester compound is a chain carboxylic acid ester, etc. Specific examples of the chain carboxylic acid ester include ethyl acetate, ethyl propionate, propyl propionate, and ethyl trimethylacetate.

[0135] The lactone compound is lactone, etc. Specific examples of lactone include γ-butyrolactone and γ-valerolactone.

[0136] The ethers may be 1,2-dimethoxyethane, tetrahydrofuran, 1,3-dioxolane, 1,4-dioxane, or the like.

[0137] The electrolyte salt contains one or more light metal salts such as lithium salts. Specific examples of lithium salts include lithium hexafluorophosphate (LiPF 6 ), lithium tetrafluoroborate (LiBF 4 ), lithium trifluoromethanesulfonate (LiCF 3 SO 3 ), lithium bis(fluorosulfonyl)imide (LiN(FSO 2 ) 2 ), lithium bis(trifluoromethanesulfonyl)imide (LiN(CF 3 SO 2 ) 2 ), lithium tris(trifluoromethanesulfonyl)methide (LiC(CF 3 SO 2 ) 3 ), lithium bis(oxalato)borate (LiB(C 2 O 4 ) 2 ), lithium monofluorophosphate (Li 2 PFO 3 ) and lithium difluorophosphate (LiPF 2 O 2 ) etc. This is because a high battery capacity can be obtained.

[0138] The content of the electrolyte salt is not particularly limited, but specifically, it is 0.3 mol / kg to 3.0 mol / kg relative to the solvent, because high ionic conductivity can be obtained.

[0139] The electrolytic solution may further contain one or more additives, including, but not limited to, unsaturated cyclic carbonates, fluorinated cyclic carbonates, sulfonates, phosphates, acid anhydrides, nitrile compounds, and isocyanate compounds.

[0140] Specific examples of unsaturated cyclic carbonates include vinylene carbonate, vinylethylene carbonate, and methyleneethylene carbonate. Specific examples of fluorinated cyclic carbonates include monofluoroethylene carbonate and difluoroethylene carbonate. Specific examples of sulfonic acid esters include propane sultone and propene sultone. Specific examples of phosphate esters include trimethyl phosphate and triethyl phosphate. Specific examples of acid anhydrides include succinic anhydride, 1,2-ethanedisulfonic anhydride, and 2-sulfobenzoic anhydride. Specific examples of nitrile compounds include succinonitrile. Specific examples of isocyanate compounds include hexamethylene diisocyanate.

[0141] 4, the positive electrode terminal 31 is electrically connected to the positive electrode 21, more specifically, to the positive electrode current collector 21A. As described above, in the battery element 20, the positive electrodes 21 and the negative electrodes 22 are alternately stacked with the separators 23 interposed therebetween, and therefore the battery element 20 includes a plurality of positive electrodes 21. As a result, the secondary battery includes a plurality of positive electrode terminals 31.

[0142] The positive electrode terminal 31 includes 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 includes the same material as the material forming the positive electrode current collector 21A.

[0143] As described above, the protruding portion of the positive electrode current collector 21A functions as the positive electrode terminal 31, and therefore the positive electrode terminal 31 is physically integrated with the positive electrode current collector 21A. This is because the connection resistance between the positive electrode current collector 21A and the positive electrode terminal 31 decreases, and the electrical resistance of the entire secondary battery decreases.

[0144] As will be described later, the positive electrode terminals 31 are joined to one another using a joining method such as welding, and thus form a single lead-shaped joint portion 31Z as shown in FIG.

[0145] 5 , the negative electrode terminal 32 is electrically connected to the negative electrode 22, more specifically, to the negative electrode current collector 22A. As described above, in the battery element 20, the positive electrodes 21 and the negative electrodes 22 are alternately stacked with the separators 23 interposed therebetween, and therefore the battery element 20 includes a plurality of negative electrodes 22. As a result, the secondary battery includes a plurality of negative electrode terminals 32.

[0146] The negative electrode terminal 32 includes 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 includes the same material as the material forming the negative electrode current collector 22A.

[0147] As described above, the protruding portion of the negative electrode current collector 22A functions as the negative electrode terminal 32, and therefore the negative electrode terminal 32 is physically integrated with the negative electrode current collector 22A. This is because the connection resistance between the negative electrode current collector 22A and the negative electrode terminal 32 decreases, and the electrical resistance of the entire secondary battery decreases.

[0148] As will be described later, the negative electrode terminals 32 are joined to one another using a joining method such as welding, and thus form a single lead-shaped joint portion 32Z as shown in FIG.

[0149] 2, the positive electrode lead 41 is connected to the joint 31Z and is led out of the exterior film 10. The positive electrode lead 41 contains a conductive material such as a metal material, and specifically contains the same material as the material forming the positive electrode current collector 21A. The shape of the positive electrode lead 41 is not particularly limited, but specifically may be either a thin plate shape, a mesh shape, or the like.

[0150] As shown in FIG. 2 , the negative electrode lead 42 is connected to the joint portion 32Z and is led out of the exterior film 10. The negative electrode lead 42 contains a conductive material such as a metal material, and specifically, contains the same material as the material forming the negative electrode current collector 22A. The lead-out direction of the negative electrode lead 42 is the same as the lead-out direction of the positive electrode lead 41. 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.

[0151] [Sealing Film] The sealing film 51 is inserted between the exterior film 10 and the positive electrode lead 41, and the sealing film 52 is inserted between the exterior film 10 and the negative electrode lead 42. However, one or both of the sealing films 51 and 52 may be omitted.

[0152] The sealing film 51 is a sealing member that prevents outside air and the like from entering the interior of the exterior film 10. The sealing film 51 contains a polymer compound such as polyolefin that has adhesiveness to the positive electrode lead 41, and a specific example of the polymer compound is polypropylene.

[0153] The configuration of the sealing film 52 is the same as the configuration of the sealing film 51, except that the sealing film 52 is a sealing member that has adhesiveness to the negative electrode lead 42. That is, the sealing film 52 contains a polymer compound such as polyolefin that has adhesiveness to the negative electrode lead 42.

[0154] <2-2. Operation> This secondary battery operates as described below.

[0155] During charging, lithium is released from the positive electrode 21 of the battery element 20 and is absorbed into the negative electrode 22 via the electrolyte. During discharging, lithium is released from the negative electrode 22 of the battery element 20 and is absorbed into the positive electrode 21 via the electrolyte. During charging and discharging, lithium is absorbed and released in an ionic state.

[0156] 6 shows a perspective view corresponding to FIG. 2 in order to explain a method for manufacturing a secondary battery. However, in FIG. 6, instead of the battery element 20, a laminate 20Z used to manufacture the battery element 20 is shown. Details of the laminate 20Z will be described later.

[0157] When manufacturing a secondary battery, the positive electrode 21 and the negative electrode 22 are fabricated and an electrolyte solution is prepared according to the procedure described below as an example, and then the positive electrode 21, the negative electrode 22, and the electrolyte solution are used to assemble a secondary battery, and a stabilization process for the secondary battery is performed. Below, reference is made to Figures 1 to 5, which have already been described, as needed.

[0158] [Fabrication of Positive Electrode] First, a paste-like positive electrode mixture slurry is prepared by adding a mixture (positive electrode mixture) of a positive electrode active material, a positive electrode binder, and a positive electrode conductive agent to a solvent. This solvent may be an aqueous solvent or an organic solvent. Next, the positive electrode mixture slurry is applied to both surfaces (excluding the positive electrode terminal 31) of the positive electrode current collector 21A to which the positive electrode terminal 31 is integrated, thereby forming the positive electrode active material layer 21B. Finally, the positive electrode active material layer 21B is compression-molded using a roll press or the like. In this case, the positive electrode active material layer 21B may be heated, or the compression molding may be repeated multiple times. As a result, the positive electrode active material layer 21B is formed on both surfaces of the positive electrode current collector 21A, thereby fabricating the positive electrode 21.

[0159] [Fabrication of Negative Electrode] The negative electrode 22 is formed using a procedure similar to that for fabricating the negative electrode 100 described above. Specifically, first, a mixture (negative electrode mixture) of a negative electrode active material, an alkali metal carbonate compound, a magnesium compound, and a negative electrode binder is poured into a solvent to prepare a paste-like negative electrode mixture slurry. Next, the negative electrode mixture slurry is applied to both surfaces (excluding the negative electrode terminal 32) of the negative electrode current collector 22A to which the negative electrode terminal 32 is integrated, thereby forming the negative electrode active material layer 22B. Finally, the negative electrode active material layer 22B is compression-molded. As a result, the negative electrode active material layer 22B is formed on both surfaces of the negative electrode current collector 22A, thereby fabricating the negative electrode 22.

[0160] [Preparation of Electrolyte Solution] An electrolyte salt is added to a solvent, whereby the electrolyte salt is dispersed or dissolved in the solvent, thereby preparing an electrolyte solution.

[0161] 6, positive electrodes 21 and negative electrodes 22 are alternately stacked with separators 23 interposed therebetween to produce a laminate 20Z. This laminate 20Z has the same configuration as the battery element 20, except that the positive electrodes 21, negative electrodes 22, and separators 23 are not impregnated with an electrolyte solution.

[0162] Next, the plurality of positive electrode terminals 31 are joined to one another using a joining method such as welding to form joints 31Z, and then the positive electrode lead 41 is connected to the joints 31Z using a joining method such as welding. Also, the plurality of negative electrode terminals 32 are joined to one another using a joining method such as welding to form joints 32Z, and then the negative electrode lead 42 is connected to the joints 32Z using a joining method such as welding.

[0163] Next, after the laminate 20Z is accommodated inside the recess 10U, the exterior film 10 (adhesive layer / metal layer / surface protection layer) is folded to face each other the exterior films 10. Next, the outer peripheral edges of two sides of the opposing adhesive layers are bonded to each other using an adhesive method such as heat fusion, thereby accommodating the laminate 20Z inside the bag-shaped exterior film 10.

[0164] Finally, after injecting an electrolyte solution into the bag-shaped exterior film 10, the outer peripheral edges of the remaining sides of the opposing fusion layers are bonded to each other using an adhesive method such as heat fusion. In this case, a sealing film 51 is inserted between the exterior film 10 and the positive electrode lead 41, and a sealing film 52 is inserted between the exterior film 10 and the negative electrode lead 42.

[0165] As a result, the laminate 20Z is impregnated with the electrolyte, thereby producing the battery element 20, which is a laminated electrode body. The battery element 20 is then sealed inside the bag-shaped exterior film 10, thereby assembling a secondary battery.

[0166] [Stabilization of Secondary Battery] The assembled secondary battery is charged and discharged. Various conditions, such as the ambient temperature, the number of charge / discharge cycles (number of cycles), and the charge / discharge conditions, can be set as desired. This forms a coating on the surface of each of the positive electrode 21 and the negative electrode 22, electrochemically stabilizing the state of the secondary battery. This completes the secondary battery.

[0167] <2-4. Actions and Effects> According to this secondary battery, the negative electrode 22 has the same configuration as the negative electrode 100, and therefore, for the reasons described above, excellent battery characteristics can be obtained.

[0168] In particular, if the secondary battery is a lithium ion secondary battery, a sufficient battery capacity can be stably obtained by utilizing the absorption and release of lithium, and therefore a greater effect can be obtained.

[0169] Other functions and effects of the secondary battery are similar to those of the negative electrode 100 .

[0170] 3. Modifications The configurations of the negative electrode 100 and the secondary battery described above can be modified as appropriate, as described below. However, any two or more of the modifications described below may be combined with each other.

[0171] 4, the protruding portion of the positive electrode current collector 21A also serves as the positive electrode terminal 31, and therefore the positive electrode terminal 31 is physically integrated with the positive electrode current collector 21A. However, since the positive electrode terminal 31 is physically separated from the positive electrode current collector 21A, it may be separated from the positive electrode current collector 21A. In this case, the positive electrode terminal 31 may be connected to the positive electrode current collector 21A using a joining method such as welding.

[0172] In this case, the same effect can be obtained because the positive electrode terminal 31 is electrically connected to the positive electrode 21. However, in order to reduce the electrical resistance of the entire secondary battery in accordance with the reduction in connection resistance, it is preferable that the positive electrode terminal 31 be physically integrated with the positive electrode current collector 21A.

[0173] 5 , the protruding portion of the negative electrode current collector 22A also serves as the negative electrode terminal 32, and therefore the negative electrode terminal 32 is physically integrated with the negative electrode current collector 22A. However, since the negative electrode terminal 32 is physically separated from the negative electrode current collector 22A, it may be separated from the negative electrode current collector 22A. In this case, the negative electrode terminal 32 may be connected to the negative electrode current collector 22A using a joining method such as welding.

[0174] In this case, the same effect can be obtained because the negative electrode terminal 32 is electrically connected to the negative electrode 22. However, in order to reduce the electrical resistance of the entire secondary battery in accordance with the reduction in connection resistance, it is preferable that the negative electrode terminal 32 be physically integrated with the negative electrode current collector 22A.

[0175] [Variation 2] In FIG. 2 , a battery element 20 that is a laminated electrode body is used. However, although not specifically illustrated here, a battery element that is a wound electrode body may also be used. In this case, the positive electrode 21 has a strip-shaped structure, and a positive electrode terminal 31 is electrically connected to the positive electrode current collector 21A, and the negative electrode 22 has a strip-shaped structure, and a negative electrode terminal 32 is electrically connected to the negative electrode current collector 22A. As a result, the positive electrode 21 and the negative electrode 22 are wound while facing each other with the separator 23 interposed therebetween. The number of positive electrode terminals 31 may be one or two or more. Similarly, the number of negative electrode terminals 32 may be one or two or more.

[0176] In this case, the secondary battery can be charged and discharged using the battery element 20, and the same effect can be obtained.

[0177] [Modification 3] A porous film separator 23 is used. However, although not specifically shown here, a laminated separator including a polymer compound layer may also be used.

[0178] Specifically, the laminated separator includes a porous membrane having a pair of surfaces and a polymer compound layer provided on one or both surfaces of the porous membrane. This is because the separator improves adhesion to each of the positive electrode 21 and the negative electrode 22, thereby suppressing misalignment of the battery element 20. This prevents swelling of the secondary battery even if a side reaction, such as a decomposition reaction of the electrolyte, occurs. The polymer compound layer includes a polymer compound such as polyvinylidene fluoride. This is because excellent physical strength and excellent electrochemical stability can be obtained.

[0179] One or both of the porous film and the polymer compound layer may contain one or more types of insulating particles. This is because the insulating particles promote heat dissipation when the secondary battery generates heat, thereby improving the safety (heat resistance) of the secondary battery. The insulating particles contain one or more types of insulating materials, such as inorganic materials and resin materials. Specific examples of inorganic materials include aluminum oxide, aluminum nitride, boehmite, silicon oxide, titanium oxide, magnesium oxide, and zirconium oxide. Specific examples of resin materials include acrylic resin and styrene resin.

[0180] When a laminated separator is produced, a precursor solution containing a polymer compound and a solvent is prepared, and then the precursor solution is applied to one or both sides of a porous film. In this case, multiple insulating particles may be added to the precursor solution as needed.

[0181] Even when this laminated separator is used, the same effect can be obtained because lithium ions are able to move between the positive electrode 21 and the negative electrode 22. In this case, as described above, the safety of the secondary battery is particularly improved, and therefore, even greater effects can be obtained.

[0182] [Modification 4] An electrolytic solution that is a liquid electrolyte is used. However, although not specifically illustrated here, an electrolyte layer that is a gel electrolyte may also be used.

[0183] In the battery element 20 using the electrolyte layer, the positive electrode 21 and the negative electrode 22 are alternately stacked with the separator 23 and the electrolyte layer interposed therebetween. The electrolyte layer is interposed between the positive electrode 21 and the separator 23, and also between the negative electrode 22 and the separator 23.

[0184] Specifically, the electrolyte layer contains a polymer compound together with an electrolytic solution, and the electrolytic solution is held by the polymer compound. This is because leakage of the electrolytic solution is prevented. The composition of the electrolytic solution is as described above. The polymer compound contains polyvinylidene fluoride, etc. When forming the electrolyte layer, a precursor solution containing the electrolytic solution, the polymer compound, a solvent, etc. is prepared, and then the precursor solution is applied to one or both surfaces of each of the positive electrode 21 and the negative electrode 22.

[0185] Even when this electrolyte layer is used, the same effect can be obtained because lithium ions can move between the positive electrode 21 and the negative electrode 22 via the electrolyte layer. In this case, particularly, as described above, leakage of the electrolyte solution is prevented, so that a greater effect can be obtained.

[0186] 4. Uses of Secondary Batteries There are no particular limitations on the uses (application examples) of secondary batteries. Secondary batteries used as power sources may be the main power source or auxiliary power source in electronic devices, electric vehicles, and the like. The main power source is a power source that is used preferentially regardless of the presence or absence of other power sources. The auxiliary power source may be a power source used in place of the main power source or a power source that can be switched from the main power source.

[0187] Specific examples of uses for secondary batteries are as follows: Electronic devices such as video cameras, digital still cameras, mobile phones, laptop computers, headphone stereos, portable radios, and portable information terminals; Storage devices such as backup power supplies and memory cards; Power tools such as power drills and power saws; Battery packs installed in electronic devices; Medical electronic devices such as pacemakers and hearing aids; Electric vehicles such as electric cars (including hybrid cars); Power storage systems such as home or industrial battery systems that store power in preparation for emergencies, etc. In these uses, one secondary battery may be used, or multiple secondary batteries may be used.

[0188] The battery pack may use a single cell or a battery pack. The electric vehicle is a vehicle that runs on a secondary battery as a driving power source, and may be a hybrid vehicle that also has a driving source other than the secondary battery. In a home power storage system, power stored in a secondary battery, which is a power storage source, can be used to power home electrical appliances, etc.

[0189] Here, an example of an application of the secondary battery will be specifically described. The configuration of the application described below is merely an example and can be modified as appropriate.

[0190] 7 shows the block configuration of a battery pack. The battery pack described here is a battery pack (a so-called soft pack) that uses one secondary battery, and is installed in electronic devices such as smartphones.

[0191] 7, the battery pack includes a power supply 71 and a circuit board 72. The circuit board 72 is connected to the power supply 71 and includes a positive terminal 73, a negative terminal 74, and a temperature detection terminal 75.

[0192] The power source 71 includes one secondary battery. The positive electrode lead of this secondary battery is connected to a positive electrode terminal 73, and the negative electrode lead is connected to a negative electrode terminal 74. The power source 71 can be connected to the outside via the positive electrode terminal 73 and the negative electrode terminal 74, and is therefore capable of charging and discharging. The circuit board 72 includes a control unit 76, a switch 77, a thermosensitive resistor (PTC element) 78, and a temperature detection unit 79. However, the PTC element 78 may be omitted.

[0193] The control unit 76 includes a central processing unit (CPU) and memory, and controls the operation of the entire battery pack. The control unit 76 detects and controls the usage state of the power source 71 as necessary.

[0194] When the voltage of the power supply 71 (secondary battery) reaches the overcharge detection voltage or the overdischarge detection voltage, the control unit 76 turns off the switch 77 to prevent the charging current from flowing through the current path of the power supply 71. The overcharge detection voltage is not particularly limited, but specifically, it is 4.20 V±0.05 V, and the overdischarge detection voltage is not particularly limited, but specifically, it is 2.40 V±0.1 V.

[0195] Switch 77 includes a charge control switch, a discharge control switch, a charge diode, a discharge diode, etc., and switches between the connection and disconnection of power supply 71 and an external device in response to instructions from control unit 76. Switch 77 includes a metal oxide semiconductor field effect transistor (MOSFET), etc., and the charge / discharge current is detected based on the ON resistance of switch 77.

[0196] 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 when the control unit 76 controls charging and discharging in the event of abnormal heat generation, and when the control unit 76 performs correction processing when calculating the remaining capacity.

[0197] An embodiment of the present technology will be described.

[0198] Examples 1 to 17 and Comparative Examples 1 to 3 As will be described below, secondary batteries were manufactured, and then the battery characteristics of the secondary batteries were evaluated.

[0199] [Manufacturing of Secondary Battery] The secondary battery (laminate film type lithium ion secondary battery) shown in FIGS. 2 to 5 was manufactured by the following procedure.

[0200] (Preparation of Positive Electrode) First, a positive electrode active material (a lithium-containing compound (oxide) LiNi 0.8 Co 0.15 Al 0.05 O 2 A positive electrode mixture was prepared by mixing 94 parts by mass of ethylenediamine fluoride (Eu), 3 parts by mass of a positive electrode binder (polyvinylidene fluoride), and 3 parts by mass of a positive electrode conductive agent (Ketjen black, an amorphous carbon powder). Subsequently, the positive electrode mixture was added to a solvent (N-methyl-2-pyrrolidone, an organic solvent), and the organic solvent was stirred to prepare a paste-like positive electrode mixture slurry. Subsequently, using a coating device, the positive electrode mixture slurry was applied to both sides (excluding the positive electrode terminal 31) of a positive electrode current collector 21A (aluminum foil having a thickness of 20 μm) to which a positive electrode terminal 31 was integrated. The positive electrode mixture slurry was then dried to form a positive electrode active material layer 21B. Finally, the positive electrode active material layer 21B was compression-molded using a roll press. Thus, the positive electrode 21 was produced.

[0201] (Preparation of Negative Electrode) First, 60 parts by mass of a negative electrode active material (artificial graphite, which is a carbon material) and 60 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 together to prepare a negative electrode mixture. Next, the negative electrode mixture was added to a solvent (N-methyl-2-pyrrolidone, an organic solvent), and the organic solvent was stirred to prepare a paste-like negative electrode mixture slurry.

[0202] Subsequently, an alkali metal carbonate compound and a magnesium compound were added to the negative electrode mixture slurry, and the negative electrode mixture slurry was stirred.

[0203] The alkali metal carbonate compound includes lithium carbonate (Li2 CO 3 ), a first alkali metal carbonate compound, and a second alkali metal carbonate compound were used. The first alkali metal carbonate compounds were lithium methyl carbonate (LMC), lithium ethyl carbonate (LEC), and lithium propyl carbonate (LPC). The second alkali metal carbonate compounds were dilithium ethylene dicarbonate (LEDC) and dilithium propylene dicarbonate (LPDC).

[0204] The magnesium compound is magnesium fluoride (MgF 2 ), magnesium oxide (MgO), and magnesium nitride (Mg 3 N 2 ) and magnesium carbonate (MgCO 3 ) was used.

[0205] Here, as an example of a method for synthesizing a second alkali metal carbonate compound, a method for synthesizing dilithium ethylene dicarbonate will be specifically described. To synthesize dilithium ethylene dicarbonate, an organic solvent (ethylene carbonate) and a tetrahydrofuran solution of lithium naphthalenide were mixed together, and the mixture was then allowed to stand (standing time = 1 day). As a result, the ethylene carbonate and lithium naphthalenide reacted with each other, synthesizing dilithium ethylene dicarbonate.

[0206] Next, using a coating device, the negative electrode mixture slurry was applied to both surfaces (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, and the negative electrode mixture slurry was then dried to form the negative electrode active material layer 22B. Finally, the negative electrode active material layer 22B was compression-molded using a roll press. In this way, the negative electrode 22 was produced.

[0207] For comparison, a negative electrode 22 was fabricated using the same procedure except that neither the alkali metal carbonate compound nor the magnesium compound was used. Also, for comparison, a negative electrode 22 was fabricated using the same procedure except that only one of the alkali metal carbonate compound and the magnesium compound was used.

[0208] (Preparation of Electrolyte Solution) First, an electrolyte salt (LiPF 6 ) was added, and the solvent was then stirred. The solvent used was a mixture of cyclic carbonates (ethylene carbonate and propylene carbonate), chain carbonates (dimethyl carbonate and ethyl methyl carbonate), and fluorinated cyclic carbonate (monofluoroethylene carbonate). The solvent composition (mass ratio) 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 of the solvent.

[0209] (Assembly of Secondary Battery) First, the positive electrode 21 and the negative electrode 22 were stacked together with the separator 23 (a microporous polyethylene film having a thickness of 15 μm) interposed therebetween to prepare a laminate 20Z.

[0210] Next, the positive electrode terminals 31 were welded together to form joints 31Z, and then the positive electrode lead 41 (aluminum foil) was welded to the joints 31Z. The negative electrode terminals 32 were welded together to form joints 32Z, and then the negative electrode lead 42 (copper foil) was welded to the joints 32Z.

[0211] Next, the exterior film 10 (fusion layer / metal layer / surface protective layer) was folded so as to sandwich the laminate 20Z accommodated in the recess 10U, and then the outer peripheral edges of two sides of the fusion layer were heat-sealed to each other, thereby accommodating the laminate 20Z inside the bag-shaped exterior film 10. As the exterior film 10, an aluminum laminate film was used, in which a fusion layer (a polypropylene film having a thickness of 30 μm), a metal layer (aluminum foil having a thickness of 40 μm), and a surface protective layer (a nylon film having a thickness of 25 μm) were laminated in this order from the inside.

[0212] Finally, after pouring the electrolyte solution into the bag-shaped exterior film 10, the outer peripheral edges of the remaining side of the fusion layer were heat-sealed to each other in a reduced pressure environment. In this case, a sealing film 51 (a polypropylene film having a thickness of 5 μm) was inserted between the exterior film 10 and the positive electrode lead 41, and a sealing film 52 (a polypropylene film having a thickness of 5 μm) was inserted between the exterior film 10 and the negative electrode lead 42. As a result, the laminate 20Z was impregnated with the electrolyte solution, and the battery element 20, which is a laminated electrode body, was produced.

[0213] Thus, the battery element 20 was sealed inside the exterior film 10, and a secondary battery was assembled.

[0214] After the secondary battery was completed, the content (wt %) of the alkali metal carbonate compound in the negative electrode active material layer 120 and the content (wt %) of the magnesium compound in the negative electrode active material layer 120 were calculated, and the results are shown in Table 1. The details of the calculation procedure are as described above.

[0215] (Stabilization of Secondary Battery) The secondary battery was subjected to one cycle of charge and discharge in a room temperature environment (temperature = 25°C). During charging, the battery was charged at a constant current of 0.1 C until the voltage reached 4.2 V, and then charged at a constant voltage of 4.2 V until the current reached 0.05 C. During discharging, the battery was discharged at a constant current of 0.1 C until the voltage reached 2.5 V. 0.1 C is the current value at which the battery capacity (theoretical capacity) is fully discharged in 10 hours, and 0.05 C is the current value at which the battery capacity is fully discharged in 20 hours.

[0216] As a result, a coating was formed on the surface of each of the positive electrode 21 and the negative electrode 22, which electrochemically stabilized the state of the secondary battery, thereby completing a laminate film type secondary battery.

[0217] [Evaluation of Battery Characteristics] When the cycle characteristics were evaluated as the battery characteristics, the results shown in Table 1 were obtained.

[0218] When evaluating the cycle characteristics, the secondary battery was first left in a low-temperature environment (temperature = 5°C) (leaving time = 3 hours), and then the secondary battery was charged and discharged in the same environment to measure the discharge capacity (discharge capacity at the first cycle).

[0219] Subsequently, the secondary battery was repeatedly charged and discharged in the same environment until the total number of cycles reached 300, and the discharge capacity (discharge capacity at the 300th cycle) was measured.

[0220] Finally, the capacity retention rate, which is an index for evaluating cycle characteristics, was calculated based on the formula: capacity retention rate (%)=(discharge capacity at 300th cycle / discharge capacity at 1st cycle)×100.

[0221] When charging, 3mA / cm 2 The battery was charged at a constant current density of 0.7 mA / cm until the voltage reached 4.2 V. 2 The battery was charged at a constant voltage until it reached 3 mA / cm. 2 The battery was discharged at a constant current density of 1000 kJ / s until the voltage reached 3.0 V.

[0222]

[0223] [Discussion] As shown in Table 1, the capacity retention rate varied greatly depending on the configuration of the negative electrode 22 .

[0224] In the following, the capacity retention rate when 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 comparison standard.

[0225] Specifically, when the anode active material layer 22B contained only an alkali metal carbonate compound (Comparative Example 2), the capacity retention rate increased slightly. Similarly, when the anode active material layer 22B contained only a magnesium compound (Comparative Example 3), the capacity retention rate increased slightly. Therefore, it is expected that the capacity retention rate will increase only slightly even if the anode active material layer 22B contains both an alkali metal carbonate compound and a magnesium compound.

[0226] However, when the anode active material layer 22B contained both an alkali metal carbonate compound and a magnesium compound (Examples 1 to 17), results contrary to the above-mentioned expectations were obtained: when the anode active material layer 22B contained both an alkali metal carbonate compound and a magnesium compound, the capacity retention rate increased significantly.

[0227] Here, the above-mentioned unexpected results will be explained in detail.

[0228] First, when the anode active material layer 22B contained only an alkali metal carbonate compound (Comparative Example 2), the increase in capacity retention was approximately 31.6%. Furthermore, when the anode active material layer 22B contained only a magnesium compound (Comparative Example 3), the increase in capacity retention was approximately 94.7%. Therefore, when the anode active material layer 22B contained both an alkali metal carbonate compound and a magnesium compound, the increase in capacity retention was expected to be approximately 126.3% (= 31.6% + 94.7%). This increase (approximately 126.3%) is a value exceeding 100%, and therefore appears to be sufficient at first glance. However, considering the need to improve cycle characteristics as much as possible, it is still insufficient.

[0229] In contrast, actual testing revealed that when the negative electrode active material layer 22B contained both an alkali metal carbonate compound and a magnesium compound (Example 7), the increase in capacity retention was approximately 326.3%. This increase (approximately 326.3%) is approximately 2.5 times the predicted increase (approximately 126.3%), and is significantly higher than expected. Therefore, it is a sufficient value when considering improving cycle characteristics as much as possible.

[0230] In particular, when the negative electrode active material layer 22B contains both an alkali metal carbonate compound and a magnesium compound, the advantageous tendency that the capacity retention rate becomes significantly higher is a special tendency that cannot be easily derived without actual verification.

[0231] In the cases where the anode active material layer 22B contained both an alkali metal carbonate compound and a magnesium compound (Examples 1 to 17), the following trends were particularly observed. First, a high capacity retention rate was obtained even when the type of alkali metal carbonate compound (lithium carbonate, the first alkali metal carbonate compound, and the second alkali metal carbonate compound) was changed. Second, a high capacity retention rate was obtained even when the type of magnesium compound was changed. Third, a high capacity retention rate was obtained when the content of the alkali metal carbonate compound in the anode active material layer 22B was 0.2 wt % to 0.8 wt %. Fourth, a high capacity retention rate was obtained when the content of the magnesium compound in the anode active material layer 22B was 0.01 wt % to 5 wt %.

[0232] [Summary] From the results shown in Table 1, a high capacity retention rate was obtained when the negative electrode active material layer 22B of the negative electrode 22 contained an alkali metal carbonate compound and a magnesium compound. Therefore, the cycle characteristics were improved, and excellent battery characteristics were obtained in the secondary battery.

[0233] The present technology has been described above with reference to an embodiment and examples. However, the configuration of the present technology is not limited to the configuration described in the embodiment and examples, and can be modified in various ways.

[0234] Specifically, the secondary battery has been described as having a laminate film structure, but the structure of the secondary battery is not particularly limited, and other battery structures such as a cylindrical type, a prismatic type, a coin type, and a button type may also be used.

[0235] The battery element has been described with respect to a stacked type and a wound type. However, the battery element structure is not particularly limited, and other structures, such as a zigzag type, may be used. In this zigzag type, the positive electrode and the negative electrode are folded in a zigzag pattern while facing each other with a separator interposed therebetween.

[0236] Furthermore, although the electrode reactant is lithium in the above description, the electrode reactant is not particularly limited. Specifically, as described above, the electrode reactant may be other alkali metals such as sodium and potassium, or alkaline earth metals such as beryllium, magnesium, and calcium. In addition, the electrode reactant may be other light metals such as aluminum.

[0237] The effects described in this specification are merely examples, and the effects of the present technology are not limited to the effects described in this specification. Therefore, other effects may be obtained with respect to the present technology.

[0238] The present technology can also be configured as follows. <1> A secondary battery comprising: a positive electrode; a negative electrode including a negative electrode active material layer; and an electrolyte; wherein the negative electrode active material layer includes an alkali metal carbonate compound and a magnesium compound; the alkali metal carbonate compound has a carbonate bond (—OC(═O)O—) and includes an alkali metal element as a constituent element; and the magnesium compound includes magnesium as a constituent element. <2> The alkali metal carbonate compound is lithium carbonate (Li 2 CO 3 ), a compound represented by formula (1), and a compound represented by formula (2). R1-OC(=O)O-M1 ... (1) (R1 is an alkyl group. M1 is an alkali metal element.) M2-OC(=O)O-R2-OC(=O)O-M3 ... (2) (R2 is an alkylene group. Each of M2 and M3 is an alkali metal element.) <3> The secondary battery according to <2>, in which in formula (1), the alkali metal element is lithium, and in formula (2), the alkali metal element is lithium. <4> The secondary battery according to any one of <1> to <3>, in which 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 <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 <1> to <5>, wherein the 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 <1> to <6>, wherein the negative electrode active material layer contains a negative electrode active material, the negative electrode active material containing a carbon material and a silicon-containing material. <8> The secondary battery according to any one of <1> to <7>, wherein the secondary battery is a lithium ion secondary battery. <9> A negative electrode for a secondary battery, comprising a negative electrode active material layer, the negative electrode active material layer containing an alkali metal carbonate compound and a magnesium compound, the alkali metal carbonate compound having a carbonate bond (—OC(═O)O—) and containing an alkali metal element as a constituent element, and the magnesium compound containing magnesium as a constituent element.

Claims

1. A positive electrode and a negative electrode including a negative electrode active material layer; Electrolyte and Equipped with the negative electrode active material layer contains an alkali metal carbonate compound and a magnesium compound, The alkali metal carbonate compound has a carbonate bond (—OC(═O)O—) and contains an alkali metal element as a constituent element, The magnesium compound contains magnesium as a constituent element. Secondary battery.

2. The alkali metal carbonate compound is lithium carbonate (Li 2 CO 3 ), which contains at least one of a compound represented by formula (1) and a compound represented by formula (2); The secondary battery according to claim 1 . R1-OC(=O)O-M1...(1) (R1 is an alkyl group. M1 is an alkali metal element.) M2-OC(=O)O-R2-OC(=O)O-M3...(2) (R2 is an alkylene group. Each of M2 and M3 is an alkali metal element.)

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

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

5. The content of the alkali metal carbonate compound in the negative electrode active material layer is 0.2% by weight or more and 0.8% by weight or less. The secondary battery according to claim 1 .

6. The content of the magnesium compound in the negative electrode active material layer is 0.01% by weight or more and 5% by weight or less. The secondary battery according to claim 1 .

7. 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. The secondary battery according to claim 1 .

8. It is a lithium-ion secondary battery. The secondary battery according to claim 1 .

9. A negative electrode active material layer is provided, the negative electrode active material layer contains an alkali metal carbonate compound and a magnesium compound, The alkali metal carbonate compound has a carbonate bond (—OC(═O)O—) and contains an alkali metal element as a constituent element, The magnesium compound contains magnesium as a constituent element. Negative electrode for secondary batteries.