Secondary battery

Abstract

Provided is a secondary battery with which excellent battery characteristics can be obtained. The secondary battery comprises a positive electrode, a negative electrode, and an electrolyte. The negative electrode includes a negative electrode active material layer and a negative electrode coating film provided on the surface of the negative electrode active material layer. The negative electrode coating film contains a fluorine compound having a carbon-fluorine bond. In the analysis of the negative electrode coating film using a fluorine-19 nuclear magnetic resonance spectroscopy, two or more peaks are detected within a range in which a chemical shift is -90 ppm to -70 ppm, inclusive, and the coupling constant of the two or more peaks is 50 Hz or less.

Description

secondary battery 【0001】 The present technology relates to 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, and an electrolyte solution, and various studies have been conducted on the configuration of these secondary batteries. 【0003】 Specifically, an electrode coating liquid used in electrochemical devices such as lithium ion secondary batteries contains a fluorine-containing compound, a fluorine-containing ether compound, and at least one compound selected from the group consisting of a metal compound, a boron compound, and a silicon compound (see, for example, Patent Document 1). 【0004】 International Publication No. 2022 / 215516 【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 secondary battery that can provide excellent battery characteristics. 【0007】 According to one embodiment of the present disclosure, there is provided a secondary battery including a positive electrode, a negative electrode, and an electrolyte. The negative electrode includes a negative electrode active material layer and a negative electrode coating provided on the surface of the negative electrode active material layer. The negative electrode coating includes a fluorine compound having a carbon-fluorine bond. Analysis of the negative electrode coating using fluorine-19 nuclear magnetic resonance spectroscopy detects two or more peaks within a chemical shift range of −90 ppm to −70 ppm, and the coupling constant for the two or more peaks is 50 Hz or less. 【0008】According to a secondary battery of one embodiment of the present technology, an anode coating is provided on a surface of an anode active material layer, and the anode coating contains a fluorine compound having a carbon-fluorine bond. In analysis of the anode coating using fluorine-19 nuclear magnetic resonance spectroscopy, two or more peaks are detected within a chemical shift range of −90 ppm or more and −70 ppm or less, and the coupling constant for the two or more peaks is 50 Hz or less, so that excellent battery characteristics can be obtained. 【0009】 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. 【0010】 FIG. 1 is a perspective view showing the configuration of a secondary battery according to an embodiment of the present technology. FIG. 2 is a cross-sectional view showing the configuration of the battery element shown in FIG. 1. FIG. 3 is a plan view showing the configuration of each of the positive electrode and negative electrode shown in FIG. 2. FIG. 4 is a diagram for explaining the analysis results of the negative electrode coating using fluorine-19 nuclear magnetic resonance spectroscopy. FIG. 5 is a block diagram showing the configuration of an application example of a secondary battery. FIG. 6 is a cross-sectional view showing the configuration of a test secondary battery. 【0011】 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. Secondary battery 1-1. Configuration 1-2. Physical properties 1-3. Operation 1-4. Manufacturing method 1-5. Actions and effects 2. Modifications 3. Uses of secondary battery 【0012】 1. Secondary Battery First, a secondary battery according to an embodiment of the present technology will be described. 【0013】 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. 【0014】 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. 【0015】 The type of electrode reactant is not particularly limited, but specifically includes light metals such as alkali metals and alkaline earth metals. 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, we will take the case where the electrode reactant is lithium as an example. A secondary battery that obtains battery capacity by utilizing the absorption and desorption of lithium is called a lithium secondary battery (or lithium ion secondary battery). In this secondary battery, lithium is absorbed and desorbed in the ionic state. 【0017】 <1-1. Configuration> Fig. 1 shows a perspective configuration of a secondary battery. Fig. 2 shows a cross-sectional configuration of a battery element 20 shown in Fig. 1. Fig. 3 shows the planar configurations of the positive electrode 21 and the negative electrode 22 shown in Fig. 2. 【0018】 1 shows a state in which the exterior film 10 and the battery element 20 are separated from each other, and a cross section of the battery element 20 taken along the XZ plane is shown by a broken line. Fig. 2 shows only a part of the battery element 20. Fig. 3 shows a state in which the positive electrode 21 and the negative electrode 22 are not wound. 【0019】 As shown in FIGS. 1 and 2, this secondary battery includes an exterior film 10, a battery element 20, a positive electrode lead 31, a negative electrode lead 32, and sealing films 41 and . 【0020】 The secondary battery described here uses an exterior film 10 as an exterior member for housing a battery element 20. Therefore, the secondary battery shown in Fig. 1 is a so-called laminate film type secondary battery. 【0021】 1, the exterior film 10 is a flexible or pliable exterior member, and has a sealed bag-like structure when the battery element 20 is housed therein. As a result, the exterior film 10 houses the positive electrode 21, the negative electrode 22, the separator 23, and an electrolyte solution (not shown), which will be described later. 【0022】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 for accommodating the battery element 20, and the recessed portion 10U is a so-called deep-drawn portion. 【0023】 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. 【0024】 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. 【0025】 [Battery Element] The battery element 20 is housed in an exterior film 10. This battery element 20 is a so-called power generation element, and as shown in Figures 1 and 2, includes a positive electrode 21, a negative electrode 22, a separator 23, and an electrolyte (not shown). 【0026】 Here, battery element 20 is a so-called wound electrode body, and therefore positive electrode 21 and negative electrode 22 are wound around winding axis P while facing each other with separator 23 interposed therebetween. This winding axis P is a virtual axis extending in the Y-axis direction, as shown in FIG. 【0027】 There are no particular limitations on the three-dimensional shape of battery element 20. Here, battery element 20 has a flat three-dimensional shape, and therefore the shape of a cross section (cross section along the XZ plane) of battery element 20 intersecting winding axis P is a flat shape defined by major axis J1 and minor axis J2. 【0028】The major axis J1 is an imaginary axis extending in the X-axis direction and has a length greater than that of the minor axis J2. The minor axis J2 is an imaginary axis extending in the Z-axis direction intersecting the X-axis direction and has a length less than that of the major axis J1. Here, the three-dimensional shape of the battery element 20 is a flattened cylinder, and therefore the cross-sectional shape of the battery element 20 is a flattened, approximately elliptical shape. 【0029】 (Positive Electrode) As shown in Fig. 2, the positive electrode 21 includes a positive electrode current collector 21A and a positive electrode active material layer 21B. However, the positive electrode current collector 21A may be omitted. 【0030】 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. 【0031】 The positive electrode active material layer 21B contains one or more types of positive electrode active materials that absorb and release lithium. However, the positive electrode active material layer 21B may further contain one or more types of other materials such as a positive electrode binder and a positive electrode conductive agent. The method for forming the positive electrode active material layer 21B is not particularly limited, but specifically includes a coating method. 【0032】 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. 【0033】 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. 【0034】 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. 【0035】 The positive electrode binder contains one or more of materials such as synthetic rubber and polymer compounds. Specific examples of synthetic rubber include styrene-butadiene rubber, fluorine-containing rubber, and ethylene-propylene-diene. Specific examples of polymer compounds include polyvinylidene fluoride, polyimide, and carboxymethyl cellulose. 【0036】 The positive electrode conductive agent contains one or more conductive materials such as a carbon material, a metal material, and a conductive polymer compound, and specific examples of the carbon material include graphite, carbon black, acetylene black, and ketjen black. 【0037】Here, as shown in Fig. 3, the positive electrode active material layer 21B is provided on a portion of the surface of the positive electrode current collector 21A. More specifically, the positive electrode active material layer 21B is not provided on either one end region or the other end region of the positive electrode current collector 21A in the longitudinal direction (the left-right direction in Fig. 3), but is provided only in a middle region of the positive electrode current collector 21A. In Fig. 3, the positive electrode active material layer 21B is shaded. 【0038】 2, the negative electrode 22 includes a negative electrode current collector 22A, a negative electrode active material layer 22B, and a negative electrode coating 22C. However, the negative electrode current collector 22A may be omitted. 【0039】 The negative electrode current collector 22A has a pair of surfaces on which the negative electrode active material layer 22B is provided. The negative electrode current collector 22A contains a conductive material such as a metal material, and a specific example of the conductive material is copper. 【0040】 The negative electrode active material layer 22B includes one or more types of negative electrode active materials that absorb and release lithium. However, the negative electrode active material layer 22B may further include one or more types of other materials, such as a negative electrode binder and a negative electrode conductive agent. The method for forming the negative electrode active material layer 22B is not particularly limited, and specifically includes one or more types of a coating method, a vapor phase method, a liquid phase method, a thermal spraying method, and a firing method (sintering method). 【0041】 Here, the anode active material layer 22B is provided on both sides of the anode current collector 22A. However, the anode active material layer 22B may be provided on only one side of the anode current collector 22A on the side where the anode 22 faces the cathode 21. 【0042】 The type of negative electrode active material is not particularly limited, but specific examples include carbon materials and metal-based materials, because high energy density can be obtained. 【0043】 Specific examples of carbon materials include graphitizable carbon, non-graphitizable carbon, and graphite, etc. The graphite may be natural graphite, artificial graphite, or both. 【0044】Metallic materials are a general term for materials containing one or more of metal elements and semi-metal elements that can form an alloy with lithium as constituent elements, and specific examples of the metal elements and semi-metal elements include silicon and tin. This metallic material may be a simple substance, an alloy, a compound, a mixture of two or more of these, or a material containing two or more of these phases. However, the simple substance may contain any amount of impurities. A specific example of a metallic material is TiSi 2　 and SiO x　 (0<x≦2 or 0.2<x<1.4), etc. 【0045】 The details regarding the negative electrode binder are the same as those regarding the positive electrode binder, and the details regarding the negative electrode conductive agent are the same as those regarding the positive electrode conductive agent. 【0046】 The surface of the metal-based material may be partially or entirely covered with a carbon material, the details of which are as described above. 【0047】 The details regarding the negative electrode binder are the same as those regarding the positive electrode binder, and the details regarding the negative electrode conductive agent are the same as those regarding the positive electrode conductive agent. 【0048】 The anode coating 22C is provided on the surface of the anode active material layer 22B, and therefore coats the surface of the anode active material layer 22B. 【0049】 Here, the anode coating 22C covers the entire surface of the anode active material layer 22B. However, the anode coating 22C may cover only a portion of the surface of the anode active material layer 22B. In this case, a plurality of anode coatings 22C spaced apart from one another may cover the surface of the anode active material layer 22B. 【0050】 Specifically, the anode coating 22C includes one or more fluorine compounds and has carbon-fluorine bonds, which are covalent bonds between carbon and fluorine, and the number of carbon-fluorine bonds is not particularly limited. 【0051】Predetermined physical property conditions are satisfied with respect to the physical properties of the anode 22, more specifically, the physical properties of the anode coating 22C present on the outermost surface of the anode 22. The physical properties of the anode coating 22C will be described in detail later. 【0052】 The composition of the fluorine compound is not particularly limited as long as it satisfies the predetermined physical property conditions for the anode coating 22C, as described above. The composition of the fluorine compound will also be described in detail later. 【0053】 3, the anode active material layer 22B is provided on the entire surface of the anode current collector 22A, more specifically, on the entire region of the anode current collector 22A in the longitudinal direction (the left-right direction in FIG. 3). As a result, the anode coating 22C is provided on the entire region of the anode active material layer 22B in the longitudinal direction, similar to the anode active material layer 22B. In FIG. 3, the anode coating 22C is shaded. 【0054】 The negative electrode 22 includes one facing portion R1 and two non-facing portions R2. The facing portion R1 is a portion that is substantially involved in charge-discharge reactions because the negative electrode active material layer 22B faces the positive electrode active material layer 21B. In contrast, the non-facing portion R2 is a portion that is not substantially involved in charge-discharge reactions because the negative electrode active material layer 22B does not face the positive electrode active material layer 21B. Here, the facing portion R1 is disposed between the two non-facing portions R2. 【0055】 2, the separator 23 is an insulating porous film interposed between the positive electrode 21 and the negative electrode 22, and allows lithium to pass through in an ionic state while preventing a short circuit caused by contact between the positive electrode 21 and the negative electrode 22. The separator 23 contains a polymer compound such as polyethylene. 【0056】 (Electrolyte) The electrolyte is a liquid electrolyte, and is impregnated into each of the positive electrode 21, the negative electrode 22, and the separator 23. The electrolyte contains a solvent and an electrolyte salt. 【0057】 The solvent contains one or more types of non-aqueous solvents (organic solvents), and the electrolyte containing the non-aqueous solvent is a so-called non-aqueous electrolyte. 【0058】 The non-aqueous solvent is an ester, an ether, or the like, more specifically, a carbonate ester compound, a carboxylic acid ester compound, a lactone compound, or the like, because it improves the dissociation of the electrolyte salt and the mobility of ions. 【0059】 The carbonate ester compounds include cyclic carbonate esters and chain carbonate esters. Specific examples of the cyclic carbonate esters include ethylene carbonate and propylene carbonate, and specific examples of the chain carbonate esters include dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate. 【0060】 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. 【0061】 The lactone compound is lactone, etc. Specific examples of lactone include γ-butyrolactone and γ-valerolactone. 【0062】 The ethers may be 1,2-dimethoxyethane, tetrahydrofuran, 1,3-dioxolane, 1,4-dioxane, or the like. 【0063】 The non-aqueous solvent is an unsaturated cyclic carbonate, a fluorinated cyclic carbonate, a sulfonate, a phosphate, an acid anhydride, an isocyanate compound, or the like, because the electrochemical stability of the electrolyte solution is improved. 【0064】 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 isocyanate compounds include hexamethylene diisocyanate. 【0065】 In particular, it is preferable that the non-aqueous solvent contains one or more of the nitrile compounds, because this suppresses the decomposition reaction of the electrolyte during charge and discharge. 【0066】 The nitrile compound is a general term for compounds containing one or more cyano groups (-CN). A specific example of a nitrile compound containing one cyano group is acetonitrile. Specific examples of nitrile compounds containing two cyano groups are succinonitrile, glutaronitrile, adiponitrile, 3,3'-(ethylenedioxy)dipropionitrile, 1,2,3-propanetricarbonitrile, 1,3,5-pentanetricarbonitrile, 1,3,4-hexanetricarbonitrile, 1,3,6-hexanetricarbonitrile, 1,3,5-cyclohexanetricarbonitrile, and 1,3,5-benzenetricarbonitrile. 【0067】 Among these, the nitrile compound is preferably a compound containing two cyano groups, because the decomposition reaction of the electrolyte solution during charging and discharging is more effectively suppressed. 【0068】 The electrolyte salt contains one or more types of light metal salts such as lithium salts. 【0069】 A specific example of the lithium salt is 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. 【0070】 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. 【0071】 1 and 2 , the positive electrode lead 31 is a positive electrode terminal connected to the positive electrode current collector 21A of the positive electrode 21, and is led out of the exterior film 10. The positive electrode lead 31 contains a conductive material such as a metal material, and a specific example of the conductive material is aluminum. The shape of the positive electrode lead 31 is not particularly limited, but is specifically either a thin plate shape or a mesh shape. 【0072】 1 and 2 , the negative electrode lead 32 is a negative electrode terminal connected to the negative electrode current collector 22A of the negative electrode 22, and is led out of the exterior film 10. This negative electrode lead 32 contains a conductive material such as a metal material, and a specific example of the conductive material is copper. Here, the details regarding the lead-out direction and shape of the negative electrode lead 32 are the same as the details regarding the lead-out direction and shape of the positive electrode lead 31. 【0073】 1 , the sealing film 41 is inserted between the exterior film 10 and the positive electrode lead 31, and the sealing film 42 is inserted between the exterior film 10 and the negative electrode lead 32. However, one or both of the sealing films 41 and 42 may be omitted. 【0074】 The sealing film 41 is a sealing member that prevents outside air and the like from entering the inside of the exterior film 10. This sealing film 41 contains a polymer compound such as polyolefin that has adhesiveness to the positive electrode lead 31, and a specific example of the polyolefin is polypropylene. 【0075】 The configuration of the sealing film 42 is the same as the configuration of the sealing film 41, except that the sealing film 42 is a sealing member that has adhesiveness to the negative electrode lead 32. That is, the sealing film 42 contains a polymer compound such as polyolefin that has adhesiveness to the negative electrode lead 32. 【0076】 <1-2. Physical Properties> Next, the physical properties of the negative electrode coating 22C will be described. 【0077】 FIG. 4 shows the fluorine-19 nuclear magnetic resonance spectroscopy ( 19 4 shows an example of the analysis results of the anode coating 22C using F NMR, in order to explain the analysis results of the anode coating 22C. In FIG. 4, the horizontal axis represents chemical shift (ppm) and the vertical axis represents peak intensity (arbitrary units). 【0078】 [Physical Property Conditions] As described above, the anode coating 22C contains a fluorine compound, so that the physical properties of the anode coating 22C satisfy predetermined physical property conditions. 【0079】 in particular, 19 The negative electrode 22 is analyzed using F NMR. In this case, the negative electrode coating 22C present on the outermost surface of the negative electrode 22 is analyzed, and therefore the analysis results shown in FIG. 4 are obtained. 【0080】 19 The analysis results of the negative electrode coating 22C using F NMR satisfy two types of physical property conditions described below. 【0081】 First, two or more peaks P are detected within the chemical shift range of −90 ppm to −70 ppm. Figure 4 shows a case where two peaks P are detected within the chemical shift range of −90 ppm to −70 ppm. 【0082】 The peaks P are detected due to fluorine contained as a constituent element in the fluorine compound, more specifically due to carbon-fluorine bonds. The number of peaks P varies depending on the structure of the fluorine compound. 【0083】 ​Second, the coupling constant for two or more peaks P is 50 Hz or less. This coupling constant is a so-called spin coupling constant (or J value) and is calculated based on the formula: Coupling constant (Hz) = Measurement frequency F (Hz) × Chemical shift difference Δδ (ppm). 【0084】 The chemical shift difference Δδ is a value obtained by subtracting the chemical shift δ2 (ppm) corresponding to one peak P from the chemical shift δ1 (ppm) corresponding to the other peak P, and is therefore calculated based on the formula: chemical shift difference Δδ=chemical shift δ1−chemical shift δ2. 【0085】 As shown in FIG. 4, when two peaks P are detected, the coupling constant is calculated based on the difference Δδ between the chemical shifts of the two peaks P. 【0086】 Although not specifically shown here, when three or more peaks P are detected, the coupling constant is calculated based on the maximum value among the multiple chemical shift differences Δδ for the three or more peaks P. As an example, when three peaks P are detected, two chemical shift differences Δδ are obtained, and therefore the coupling constant is calculated based on the larger value of the two chemical shift differences Δδ. 【0087】 [Reason] The reason why the two types of physical property conditions are satisfied for the physical properties of the anode coating 22C is that the state of the anode coating 22C containing a fluorine compound is electrochemically optimized. 【0088】 As a result, the surface of the anode active material layer 22B containing the highly reactive anode active material is properly protected by the anode coating 22C, thereby suppressing the decomposition reaction of the electrolyte on the surface of the anode 22. Furthermore, decomposition products such as the solvent and electrolyte salt are less likely to accumulate on the surface of the anode 22 during charge and discharge, making it less likely that the electrical resistance of the anode 22 will increase. 【0089】 Therefore, during charging and discharging, an increase in the electrical resistance of the negative electrode 22 is suppressed, and the decomposition reaction of the electrolyte is also suppressed, so that the discharge capacity is less likely to decrease even with repeated charging and discharging. 【0090】[Analysis Procedure] 19 The procedure for analyzing the negative electrode coating 22C using F NMR is as follows. 【0091】 The analytical equipment used was a Bruker INSTRUM Advance NEO 500 nuclear magnetic resonance spectrometer. The analytical conditions were: probe head = 5mmφ iProbeTBO (PI HR-TBO500-S1-BBF / H / F / D-5.0-Z FP), temperature control device = SmartCooler BCU II, magnetic field strength = 11.74736 T, temperature = 25°C, observation nucleus: 19F, observation frequency = 470.5453180 MHz, observation pulse = 25.0 μs, acquisition time = 3.59424 s, pulse wait time = 20 s, and number of integrations = 256. The chemical shift value was set to -80 ppm using lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) as the reference material. 【0092】 When analyzing the anode coating 22C, first, the secondary battery is disassembled to recover the anode 22. Next, the anode 22 is washed with a cleaning solvent to wash away the electrolyte adhering to the anode 22. The type of cleaning solvent is not particularly limited, but specifically, it is one or more organic solvents such as dimethyl carbonate. Next, the washed anode 22 is dried, and then the SEI film is extracted using an extraction solvent. The type of extraction solvent is not particularly limited, but specifically, it is one or more heavy solvents such as heavy water, heavy acetone, and heavy DMSO. In this case, lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) is added to the extraction solvent to obtain the SEI film using a nuclear magnetic resonance (NMR) spectrometer. 19 F NMR) as a reference material for analysis. 19 The surface of the negative electrode 22 (negative electrode coating 22C) is analyzed using F NMR. 【0093】When analyzing the anode coating 22C, it is preferable to analyze the anode coating 22C in the non-facing portion R2 rather than the facing portion R1, as shown in Fig. 3. As described above, the non-facing portion R2 is a portion that is not substantially involved in the charge / discharge reaction, and therefore, in the non-facing portion R2, the physical properties of the anode coating 22C can be examined accurately and with good reproducibility, regardless of the charge / discharge history (presence or absence of charge / discharge and the number of times, etc.). 【0094】 [Configuration of Fluorine Compound] As described above, the configuration of the fluorine compound is not particularly limited as long as the two physical property conditions regarding the physical properties of the anode coating 22C are satisfied. 【0095】 Specifically, anode coating 22C preferably contains one or more of the fluorinated alkoxides represented by formula (1). This is because the two physical property conditions are more likely to be satisfied for the physical properties of anode coating 22C, and therefore an increase in the electrical resistance of anode 22 during charge and discharge and a decomposition reaction of the electrolyte are sufficiently suppressed. 【0096】 R1R2R3COLi (1) (R1, R2, and R3 each represent a hydrogen group, an alkyl group, or a fluorinated alkyl group, provided that at least one of R1, R2, and R3 is a fluorinated alkyl group.) 【0097】 As described above, each of R1 to R3 is not particularly limited as long as it is any one of a hydrogen group, an alkyl group, and a fluorinated alkyl group. The types of R1 to R3 may be the same or different from one another. Of course, any two types of R1 to R3 may be the same as one another. 【0098】 The alkyl group may be linear or branched having one or more side chains. The number of carbon atoms in the alkyl group is not particularly limited, but is preferably 1 to 4. This is because the solubility and compatibility of the fluorinated alkoxide are improved, and thus the anode coating 22C containing the fluorinated alkoxide is more easily formed on the surface of the anode active material layer 22B. 【0099】Specific examples of alkyl groups include methyl, ethyl, propyl, and butyl groups. However, as mentioned above, alkyl groups are not limited to linear groups and may be branched. Thus, for example, the propyl group may be an n-propyl group or an isopropyl group. As another example, the butyl group may be an n-butyl group, a sec-butyl group, or a tert-butyl group. 【0100】 A fluorinated alkyl group is an alkyl group in which one or more hydrogen groups have been substituted with fluorine groups. Details of the alkyl group (structure and number of carbon atoms) are as described above. 【0101】 Specific examples of the fluorinated alkyl group include a perfluoromethyl group, a perfluoroethyl group, a perfluoropropyl group, and a perfluorobutyl group, etc. However, specific examples of the fluorinated alkyl group are not limited to a perfluoro group, and may include a monofluoromethyl group, a monofluoroethyl group, a monofluoropropyl group, a monofluorobutyl group, a trifluoroethyl group, and a hexafluoroisopropyl group, etc. 【0102】 However, as described above, one or more of R1, R2, and R3 are fluorinated alkyl groups. This is because fluorinated alkoxides contain one or more fluorine atoms as constituent elements. Therefore, compounds in which each of R1, R2, and R3 is either a hydrogen group or an alkyl group are excluded from the fluorinated alkoxides described here. 【0103】 In particular, two of R1, R2, and R3 are preferably fluorinated alkyl groups, because this makes it easier for the two types of physical property conditions to be satisfied with respect to the physical properties of anode coating 22C, thereby further suppressing an increase in the electrical resistance of anode 22 during charge and discharge and further suppressing the decomposition reaction of the electrolyte. 【0104】The number of carbon atoms in the fluorinated alkoxide is not particularly limited, but is preferably 3 to 5. This is because the two types of physical property conditions regarding the physical properties of anode coating 22C are more likely to be satisfied, and therefore an increase in the electrical resistance of anode 22 during charge and discharge is more suppressed, and the decomposition reaction of the electrolyte solution is more suppressed. 【0105】 Specific examples of fluorinated alkoxides include (CF 3　 ) 2　 HCOLi, (CF 3　 ) 2　 FCOLi, (CF 3　 CH 2　 ) 2　 HCl and (CF 3　 CF 2　 ) 2　 HCOLi, etc. 【0106】 <1-3. Operation> The secondary battery operates as described below. 【0107】 During charging, in the battery element 20, lithium is released in an ionic state from the positive electrode 21, and the lithium is absorbed in an ionic state into the negative electrode 22 via the electrolyte. On the other hand, during discharging, in the battery element 20, lithium is released in an ionic state from the negative electrode 22, and the lithium is absorbed in an ionic state into the positive electrode 21 via the electrolyte. 【0108】 <1-4. Manufacturing Method> When manufacturing a secondary battery, the positive electrode 21 and the negative electrode 22 are each produced using the procedure described below as an example, and an electrolytic solution is prepared. Thereafter, the positive electrode 21, the negative electrode 22, and the electrolytic solution are used to assemble a secondary battery, and a stabilization process is performed on the assembled secondary battery. 【0109】 [Preparation of Positive Electrode] First, a positive electrode active material, a positive electrode binder, and a positive electrode conductive agent are mixed together to obtain a positive electrode mixture. Then, the positive electrode mixture is poured into a solvent to prepare a paste-like positive electrode mixture slurry. This solvent may be an aqueous solvent or an organic solvent. 【0110】Next, the positive electrode mixture slurry is applied to both surfaces of the positive electrode current collector 21A to form the positive electrode active material layer 21B. Finally, the positive electrode active material layer 21B is compression-molded using a compression device such as a press. In this case, the positive electrode active material layer 21B may be heated, or the compression molding may be repeated multiple times. 【0111】 As a result, the positive electrode active material layers 21B are formed on both sides of the positive electrode current collector 21A, and thus the positive electrode 21 is produced. 【0112】 [Fabrication of Negative Electrode] First, a negative electrode active material, a negative electrode binder, and a negative electrode conductive agent are mixed together to obtain a negative electrode mixture. Next, the negative electrode mixture is poured into a solvent to prepare a paste-like negative electrode mixture slurry. Details regarding the solvent are the same as those described for fabricating the positive electrode 21. Next, the negative electrode mixture slurry is applied to both sides of the negative electrode current collector 22A to form a negative electrode active material layer 22B. 【0113】 Next, a coating solution is prepared by adding a fluorine compound to a solvent. This solvent may be an aqueous solvent or an organic solvent. This coating solution is a preparatory solution for forming the anode coating 22C and may contain other materials such as a binder, as necessary. The binder contains one or more polymer compounds such as polyvinylidene fluoride. 【0114】 Subsequently, a coating liquid is applied to the surface of the anode active material layer 22B to form the anode coating 22C. 【0115】 Finally, the anode active material layer 22B and the anode coating 22C are compression-molded using a compression device such as a press. In this case, the anode active material layer 22B and the anode coating 22C may be heated, or the compression molding may be repeated multiple times. 【0116】 As a result, the anode active material layer 22B and the anode coating 22C are formed on both sides of the anode current collector 22A, and thus the anode 22 is produced. 【0117】 [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. 【0118】 [Assembly of Secondary Battery] First, the positive electrode lead 31 is connected to the positive electrode current collector 21A of the positive electrode 21 using a joining method such as welding, and the negative electrode lead 32 is connected to the negative electrode current collector 22A of the negative electrode 22 using a joining method such as welding. 【0119】 Next, the positive electrode 21 and the negative electrode 22 are stacked one on top of the other with the separator 23 interposed therebetween, and then the positive electrode 21, the negative electrode 22, and the separator 23 are wound together to produce a wound body (not shown). This wound body has a configuration similar to that of the battery element 20, except that the positive electrode 21, the negative electrode 22, and the separator 23 are not impregnated with an electrolyte solution and that it is cylindrical. Next, the wound body is pressed using a compression device such as a press to form it into a flat shape. 【0120】 Next, after the roll is accommodated in the recess 10U, the exterior film 10 (adhesive layer / metal layer / surface protection layer) is folded to face each other. Next, the outer peripheral edges of two sides of the opposing adhesive layers are joined together using an adhesive method such as heat fusion, thereby accommodating the roll in the bag-shaped exterior film 10. 【0121】 Finally, after injecting the electrolyte solution into the bag-shaped exterior film 10, the outer peripheral edges of the remaining sides of the opposing fusion layers are joined together using an adhesive method such as heat fusion. In this case, a sealing film 41 is inserted between the exterior film 10 and the positive electrode lead 31, and a sealing film 42 is inserted between the exterior film 10 and the negative electrode lead 32. 【0122】 This allows the wound body to be impregnated with the electrolyte, thereby producing the wound electrode body, the battery element 20. The battery element 20 is then sealed in the bag-shaped exterior film 10, thereby assembling the secondary battery. 【0123】[Stabilization Treatment of Assembled 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 battery element 20. This completes the secondary battery. 【0124】 <1-5. Actions and Effects> According to this secondary battery, the anode coating 22C is provided on the surface of the anode active material layer 22B, the anode coating 22C contains a fluorine compound, and two types of physical conditions are satisfied regarding the physical properties of the anode coating 22C. 【0125】 in particular, 19 In an analysis of the negative electrode coating 22C using F NMR, two or more peaks P are detected within a chemical shift range of −90 ppm to −70 ppm, and the coupling constant for the two or more peaks P is 50 Hz or less. 【0126】 In this case, as described above, the state of the anode coating 22C containing the fluorine compound is electrochemically optimized. As a result, the anode active material layer 22B containing the highly reactive anode active material is properly protected by the anode coating 22C, thereby suppressing the decomposition reaction of the electrolyte on the surface of the anode 22. Furthermore, decomposition products such as the solvent and electrolyte salt are less likely to accumulate on the surface of the anode 22 during charge and discharge, making it less likely that the electrical resistance of the anode 22 will increase. 【0127】 For these reasons, an increase in the electrical resistance of the negative electrode 22 during charging and discharging is suppressed, and the decomposition reaction of the electrolyte is suppressed, so that the discharge capacity is less likely to decrease even with repeated charging and discharging, thereby achieving excellent battery characteristics. 【0128】 In particular, if the anode coating 22C contains the fluorinated alkoxide shown in formula (1), two physical property conditions are more likely to be satisfied for the physical properties of the anode coating 22C. Therefore, an increase in the electrical resistance of the anode 22 during charge and discharge is sufficiently suppressed, and the decomposition reaction of the electrolyte is also sufficiently suppressed, thereby achieving a greater effect. 【0129】In this case, if two of R1, R2, and R3 in formula (1) are fluorinated alkyl groups, the two physical property conditions regarding the physical properties of anode coating 22C are more likely to be satisfied, thereby achieving a greater effect. Also, if the fluorinated alkoxide has 3 to 5 carbon atoms, the two physical property conditions regarding the physical properties of anode coating 22C are more likely to be satisfied, thereby achieving a greater effect. 【0130】 Furthermore, if the electrolyte solution contains a nitrile compound, the decomposition reaction of the electrolyte solution during charging and discharging is suppressed, thereby achieving a higher effect. 【0131】 Furthermore, if the secondary battery is a lithium secondary battery, a sufficient battery capacity can be stably obtained by utilizing the absorption and desorption of lithium, and therefore a greater effect can be obtained. 【0132】 2. Modifications Next, modifications of the secondary battery will be described. 【0133】 The configuration of the secondary battery can be modified as appropriate, as described below, although the series of modifications described below may be combined with each other. 【0134】 [Modification 1] A porous film separator 23 is used. However, although not specifically shown here, a laminated separator may also be used. 【0135】 Specifically, the laminated separator includes a porous membrane and a polymer compound. The porous membrane has a pair of surfaces, and the polymer compound layer is provided on one or both surfaces of the porous membrane. This is because the adhesion of the separator to each of the positive electrode 21 and the negative electrode 22 is improved, thereby suppressing miswinding of the battery element 20. This suppresses swelling of the secondary battery even if a decomposition reaction of the electrolyte occurs. The polymer compound layer includes a polymer compound such as polyvinylidene fluoride. Polyvinylidene fluoride has excellent physical strength and is electrochemically stable. 【0136】One or both of the porous film and the polymer compound layer may contain a plurality of insulating particles. This is because the plurality of insulating particles promotes 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 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. 【0137】 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. 【0138】 Even when this laminated separator is used, the same effect can be obtained because lithium can move in an ionic state 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, a greater effect can be obtained. 【0139】 [Modification 2] An electrolytic solution that is a liquid electrolyte is used. However, although not specifically shown here, an electrolyte layer that is a gel electrolyte may also be used. 【0140】 In the battery element 20 using the electrolyte layer, the positive electrode 21 and the negative electrode 22 are stacked with the separator 23 and the electrolyte layer interposed therebetween, and the positive electrode 21, the negative electrode 22, the separator 23, and the electrolyte layer are wound together. The electrolyte layer is interposed between the positive electrode 21 and the separator 23, and also between the negative electrode 22 and the separator 23. 【0141】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, and a solvent 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. 【0142】 Even when this electrolyte layer is used, the same effect can be obtained because lithium can move in an ionic state through the electrolyte layer between the positive electrode 21 and the negative electrode 22. In this case, leakage of the electrolyte solution is particularly prevented as described above, and therefore a greater effect can be obtained. 【0143】 3. Uses of Secondary Batteries Finally, uses of secondary batteries will be described. 【0144】 The use (application) of the secondary battery is not particularly limited. The secondary battery used as a power source may be a main power source for electronic devices, electric vehicles, etc., or an auxiliary power source. 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. 【0145】 Specific examples of uses for secondary batteries are as follows: Electronic devices such as video cameras, digital still cameras, mobile phones, laptop computers, headphone stereos, portable radios, and portable information terminals. Storage devices such as backup power supplies and memory cards. Power tools such as power drills and power saws. Battery packs installed in electronic devices. Medical electronic devices such as pacemakers and hearing aids. Electric vehicles such as electric cars (including hybrid cars). Power storage systems such as home or industrial battery systems that store power in preparation for emergencies. In these uses, one secondary battery may be used, or multiple secondary batteries may be used. 【0146】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. The home power storage system can use the power stored in the secondary battery, which is a power storage source, to power home electrical appliances, etc. 【0147】 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. 【0148】 Fig. 5 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. 【0149】 5, the battery pack includes a power supply 51 and a circuit board 52. The circuit board 52 is connected to the power supply 51 and includes a positive terminal 53, a negative terminal 54, and a temperature detection terminal 55. 【0150】 The power source 51 includes one secondary battery. The positive electrode lead of this secondary battery is connected to a positive electrode terminal 53, and the negative electrode lead is connected to a negative electrode terminal 54. The power source 51 can be connected to the outside via the positive electrode terminal 53 and the negative electrode terminal 54, and is therefore capable of charging and discharging. The circuit board 52 includes a control unit 56, a switch 57, a PTC element 58, and a temperature detection unit 59. However, the PTC element 58 may be omitted. 【0151】 The control unit 56 includes a central processing unit (CPU) and memory, and controls the overall operation of the battery pack. The control unit 56 detects and controls the usage state of the power source 51 as necessary. 【0152】When the voltage of power supply 51 (secondary battery) reaches the overcharge detection voltage or the overdischarge detection voltage, control unit 56 turns off switch 57 to prevent charging current from flowing through the current path of power supply 51. The overcharge detection voltage is not particularly limited, but specifically, it is 4.20 V±0.05 V, and the overdischarge detection voltage is not particularly limited, but specifically, it is 2.40 V±0.1 V. 【0153】 Switch 57 includes a charge control switch, a discharge control switch, a charging diode, a discharging diode, etc., and switches between the connection and disconnection of power supply 51 and an external device in response to instructions from control unit 56. Switch 57 includes a metal oxide semiconductor field effect transistor (MOSFET), etc., and the charge current and the discharge current are detected based on the ON resistance of switch 57. 【0154】 Temperature detection unit 59 includes a temperature detection element such as a thermistor. Temperature detection unit 59 measures the temperature of power supply 51 using temperature detection terminal 55 and outputs the temperature measurement result to control unit 56. The temperature measurement result measured by temperature detection unit 59 is used when control unit 56 controls charging and discharging in the event of abnormal heat generation, and when control unit 56 performs correction processing when calculating the remaining capacity. 【0155】 An embodiment of the present technology will be described. 【0156】 Examples 1 and 2 and Comparative Examples 1 and 2 As will be described below, secondary batteries were fabricated, and then the battery characteristics of the secondary batteries were evaluated. 【0157】 [Fabrication of Secondary Battery] Here, a test secondary battery was fabricated to simply evaluate the battery characteristics. Fig. 6 shows the cross-sectional structure of the test secondary battery, which is a so-called coin-type secondary battery. 【0158】 In the following, the configuration of the test secondary battery will be described, followed by a description of the test fabrication procedure. In this case, for the sake of simplicity, the test secondary battery will be referred to simply as a "secondary battery." 【0159】As shown in FIG. 6, this secondary battery includes a test electrode 61, a counter electrode 62, a separator 63, an exterior cup 64, an exterior can 65, a gasket 66, and an electrolyte (not shown). 【0160】 The test electrode 61 is housed in an exterior cup 64, and the counter electrode 62 is housed in an exterior can 65. The test electrode 61 and the counter electrode 62 are stacked together with a separator 63 interposed therebetween, and the test electrode 61, the counter electrode 62, and the separator 63 are each impregnated with an electrolyte. The exterior cup 64 and the exterior can 65 are crimped together with a gasket 66, so that the test electrode 61, the counter electrode 62, and the separator 63 are sealed inside the exterior cup 64 and the exterior can 65. 【0161】 (Preparation of Test Electrode) First, 94 parts by mass of a negative electrode active material (4 parts by mass of silicon oxide, which is a metallic material, and 90 parts by mass of artificial graphite, which is a carbon material), 1.5 parts by mass of a negative electrode binder (polyvinylidene fluoride), 2.5 parts by mass of a negative electrode conductive agent (2 parts by mass of carbon nanotubes and 0.5 parts by mass of graphite), and 2 parts by mass of a thickener (carboxymethyl cellulose) were mixed together to prepare a negative electrode mixture. 【0162】 Next, the negative electrode mixture was poured into a solvent (pure water as an aqueous solvent), and the solvent was stirred to prepare a paste-like negative electrode mixture slurry. 【0163】 Next, the negative electrode mixture slurry was applied to one surface of a negative electrode current collector (copper foil having a thickness of 8 μm) using a coating device, and then the negative electrode mixture slurry was dried to form a negative electrode active material layer. 【0164】 Next, a fluorine compound was added to a solvent (dimethyl carbonate) and the solvent was stirred to prepare a coating solution. The fluorine compound was hexafluoroisopropoxide (CF 3　 ) 2　 HClLi(LiHFIP)) was used. 【0165】 Subsequently, a coating solution was applied to the surface of the negative electrode active material layer using a coating device, and the coating solution was then dried to form a negative electrode coating containing a fluorine compound. 【0166】 Finally, the negative electrode active material layer and the negative electrode coating were compression-molded using a roll press, and the negative electrode current collector on which the negative electrode active material layer and the negative electrode coating were formed was cut into a disk shape, thereby producing a test electrode 61 (Examples 1 and 2). 【0167】 For comparison, a test electrode 61 was prepared in the same manner except that no negative electrode coating was formed (Comparative Example 1). 【0168】 (Preparation of Counter Electrode) First, a positive electrode active material (a lithium-containing compound (oxide) LiNi 0.80 Co 0.15 Al 0.05 O 2　 A positive electrode mixture was prepared by mixing 91 parts by mass of a positive electrode binder (polyvinylidene fluoride), 3 parts by mass of a positive electrode conductive agent (Ketjen black, an amorphous carbon powder), and 6 parts by mass of a positive electrode mixture. The positive electrode mixture was then added to a solvent (N-methyl-2-pyrrolidone, an organic solvent), and the solvent was stirred to prepare a paste-like positive electrode mixture slurry. 【0169】 Next, the positive electrode mixture slurry was applied to one surface of a positive electrode current collector (aluminum foil having a thickness of 10 μm) using a coating device, and then the positive electrode mixture slurry was dried to form a positive electrode active material layer. 【0170】 Finally, the positive electrode active material layer was compression-molded using a roll press, and then the positive electrode current collector on which the positive electrode active material layer was formed was cut into a disk shape, thereby producing a counter electrode 62. 【0171】 (Preparation of Electrolyte Solution) First, a solvent was prepared. As the solvent, a mixture of ethylene carbonate, which is a cyclic carbonate ester, and dimethyl carbonate, which is a chain carbonate ester, was used. In this case, the mixing ratio (weight ratio) of the solvents was cyclic carbonate ester:chain carbonate ester = 30:70. 【0172】 Next, an electrolyte salt (lithium hexafluorophosphate, which is a lithium salt) was added to the solvent, and the solvent was stirred. In this case, the content of the electrolyte salt was 1 mol / kg relative to the solvent. 【0173】 Finally, if necessary, a nitrile compound (succinonitrile (SN)) was added to the solvent, and the solvent was then stirred. In this case, the content of the nitrile compound in the electrolytic solution was 1 wt %. In this way, the electrolytic solution was prepared. 【0174】 For comparison, an electrolyte solution was prepared using the same procedure except that alcohol (isopropanol (IPA)) was added to the electrolyte solution instead of forming a negative electrode coating (Comparative Example 2). In this case, a test electrode 61 not including a negative electrode coating was produced. 【0175】 (Assembly of Secondary Battery) First, the test electrode 61 was housed in an exterior cup 64, and the counter electrode 62 was housed in an exterior can 65. Next, the test electrode 61 housed in the exterior cup 64 and the counter electrode 62 housed in the exterior can 65 were stacked together with a separator 63 (a microporous polyethylene film with a thickness of 20 μm) impregnated with an electrolytic solution interposed therebetween. In this case, the positive electrode active material layer and the negative electrode active material layer faced each other with the separator 63 interposed therebetween. 【0176】 Finally, in a state in which the test electrode 61 and the counter electrode 62 were stacked together with the separator 63 interposed therebetween, the exterior cup 64 and the exterior can 65 were crimped together via the gasket 66. As a result, the test electrode 61 and the counter electrode 62 were sealed inside the exterior cup 64 and the exterior can 65, and a secondary battery was assembled. 【0177】 (Stabilization Treatment of Assembled Secondary Battery) The secondary battery was subjected to one cycle of charge and discharge in a room temperature environment (temperature = 23°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 0.025 C at the same voltage of 4.2 V. 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 0.025 C is the current value at which the battery capacity is fully discharged in 40 hours. 【0178】 As a result, the state of the battery element 20 was electrochemically stabilized, and the secondary battery was completed. 【0179】 [Evaluation of Battery Characteristics] 19 The surface (negative electrode coating) of the test electrode 61 was analyzed using F NMR, and the results are shown in Table 1. 【0180】 The " 19 The "F NMR analysis results" column shows the items explained below. The "Peak P" column shows whether or not peak P was detected within the chemical shift range of -90 ppm to -70 ppm. The "Number" column shows the number of peaks P. The "Coupling constant (Hz)" column shows the coupling constant (Hz). 【0181】 Here, the cycle characteristics were evaluated as the battery characteristics using the procedure described below, and the results shown in Table 1 were obtained. 【0182】 When evaluating the cycle characteristics, first, the secondary battery was charged and discharged in a room temperature environment to measure the discharge capacity (discharge capacity at the first cycle). 【0183】 Subsequently, the secondary battery was repeatedly charged and discharged in the same environment until the total number of cycles reached 150, and the discharge capacity (discharge capacity at the 150th cycle) was measured. 【0184】 The charge / discharge conditions in the 1st to 150th cycles were the same as those in the stabilization treatment of the secondary battery after assembly described above. 【0185】 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 150th cycle / discharge capacity at 1st cycle)×100. 【0186】 【0187】 [Discussion] As shown in Table 1, the capacity retention rate varied greatly depending on the physical properties of the negative electrode coating. 【0188】 Specifically, when the negative electrode coating containing a fluorine compound is not provided on the surface of the negative electrode active material layer (Comparative Example 1), 19Since peak P was not detected in the analysis of the negative electrode coating using F NMR, two physical property conditions were not satisfied for the negative electrode coating, resulting in a decrease in the capacity retention rate. 【0189】 Similarly, in the case where the negative electrode coating containing a fluorine compound was not provided on the surface of the negative electrode active material layer, but the electrolyte contained alcohol (Comparative Example 2), the two physical property conditions regarding the physical properties of the negative electrode coating were not satisfied, resulting in a decrease in the capacity retention rate. 【0190】 In contrast, when a negative electrode coating containing a fluorine compound is provided on the surface of the negative electrode active material layer (Example 1), 19 Since peak P was detected in the analysis of the negative electrode coating using F NMR, two physical property conditions were satisfied for the negative electrode coating. Specifically, two peaks P were detected and the coupling constant was 50 Hz or less. This resulted in an increase in the capacity retention rate. 【0191】 In this case, the capacity retention rate was further increased, particularly when the electrolyte solution contained a nitrile compound (Example 2). 【0192】 [Summary] From the results shown in Table 1, when a negative electrode coating containing a fluorine compound was provided on the surface of the negative electrode active material layer and two types of physical property conditions were satisfied regarding the physical properties of the negative electrode coating, the cycle characteristics were improved, and therefore excellent battery characteristics were obtained. 【0193】 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. 【0194】 Specifically, the battery structure of the secondary battery has been described in relation to a laminate film type and a coin type, but the battery structure of the secondary battery of the present technology is not particularly limited. Specifically, the battery structure of the secondary battery may be a cylindrical type, a prismatic type, or the like. 【0195】The battery element has been described as having a wound structure. However, the structure of the battery element is not particularly limited, and may be a stacked structure or a zigzag structure. In the stacked structure, positive and negative electrodes are alternately stacked with a separator interposed therebetween, while in the zigzag structure, the positive and negative electrodes are folded in a zigzag pattern while facing each other with the separator interposed therebetween. 【0196】 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. 【0197】 The present technology can also be configured as follows. <1> A secondary battery including an electrolyte solution along with a positive electrode and a negative electrode, wherein the negative electrode includes: a negative electrode active material layer; and a negative electrode coating provided on a surface of the negative electrode active material layer, wherein the negative electrode coating includes a fluorine compound having a carbon-fluorine bond, wherein analysis of the negative electrode coating using fluorine-19 nuclear magnetic resonance spectroscopy detects two or more peaks within a chemical shift range of -90 ppm to -70 ppm, and wherein a coupling constant for the two or more peaks is 50 Hz or less. <2> The secondary battery according to <1>, wherein the negative electrode coating includes a fluorinated alkoxide represented by formula (1). R1R2R3COLi ... (1) (R1, R2, and R3 each represent a hydrogen group, an alkyl group, or a fluorinated alkyl group, provided that at least one of R1, R2, and R3 is a fluorinated alkyl group.) <3> The secondary battery according to <2>, wherein two of R1, R2, and R3 are fluorinated alkyl groups. <4> The secondary battery according to <2> or <3>, wherein the fluorinated alkoxide has a carbon number of 3 or more and 5 or less. <5> The secondary battery according to any one of <1> to <4>, wherein the electrolyte solution contains a nitrile compound. <6> The secondary battery according to any one of <1> to <5>, wherein the secondary battery is a lithium secondary battery. 【0198】 21...Positive electrode, 22...Negative electrode, 22B...Negative electrode active material layer, 22C...Negative electrode coating, P...Peak

Claims

[Claim 1] The system includes an electrolyte along with a positive electrode and a negative electrode. The aforementioned negative electrode is The negative electrode active material layer, A negative electrode coating provided on the surface of the negative electrode active material layer and Includes, The negative electrode coating contains a fluorine compound having a carbon-fluorine bond, In the analysis of the negative electrode coating using fluorine-19 nuclear magnetic resonance spectroscopy, two or more peaks were detected within the range of chemical shifts between -90 ppm and -70 ppm. The coupling constant for the two or more peaks is 50 Hz or less. Secondary battery. [Claim 2] The negative electrode coating contains a fluorinated alkoxide represented by formula (1), The secondary battery according to claim 1. R1R2R3COLi...(1) (Each of R1, R2, and R3 is a hydrogen group, an alkyl group, or a fluorinated alkyl group. However, at least one of R1, R2, and R3 is a fluorinated alkyl group.) [Claim 3] Two of R1, R2, and R3 are fluorinated alkyl groups. The secondary battery according to claim 2. [Claim 4] The number of carbon atoms in the fluorinated alkoxide is 3 or more and 5 or less. The secondary battery according to claim 2 or 3. [Claim 5] The electrolyte contains a nitrile compound. A secondary battery according to any one of claims 1 to 3. [Claim 6] Lithium-ion secondary batteries, A secondary battery according to any one of claims 1 to 3.