Battery and battery pack

Abstract

According to an embodiment, a battery is provided. The battery includes a positive electrode, a negative electrode, and an electrolyte. The positive electrode includes a first oxide. A ratio B / A of an area B of a peak having a peak top in a range of 683 eV or more and 686 eV or less to an area A of a peak having a peak top in a range of 851 eV or more and 868 eV or less in a hard X-ray photoelectron spectroscopy on a surface of the positive electrode is 0.07 or more and 0.20 or less. The negative electrode includes a lithium-titanium-containing oxide. A ratio D / C of an area D of a peak having a peak top in a range of 685 eV or more and 687.5 eV or less to an area C of a peak having a peak top in a range of 455 eV or more and 469 eV or less in a hard X-ray photoelectron spectroscopy on a surface of the negative electrode is 0.75 or more and 1.8 or less. The electrolyte includes a carboxylic acid ester and a cyclic carbonate. A volume of the carboxylic acid ester is 2.3 times or more with respect to a volume of the cyclic carbonate.

Description

Technical Field

[0001] Embodiments of the present invention relate to batteries and battery packs. Background Technology

[0002] In recent years, non-aqueous electrolyte batteries have not only been expected to replace gasoline as a power source for electric vehicles (EVs) and hybrid electric vehicles (HEVs), but also to be used in large-scale systems such as electric aircraft and energy storage. Therefore, there is a demand for improved capacity characteristics, high-current output performance, and safety.

[0003] Lithium nickel manganese cobalt oxide is used as a positive electrode active material in non-aqueous electrolyte batteries. Increasing the nickel (Ni) content in lithium nickel manganese cobalt oxide can yield a high-capacity positive electrode active material.

[0004] As a method to improve the safety of non-aqueous electrolyte batteries, a method is proposed in which flame-retardant solvents such as fluorinated solvents or solvents with high flash points are used as the solvent for the electrolyte.

[0005] Existing technical documents Patent documents Patent Document 1: International Publication No. 2021 / 199485 Patent Document 2: Japanese Patent Application Publication No. 2016-38997 Summary of the Invention

[0006] The problem that the invention aims to solve The problem to be solved by this invention is to provide a battery with high safety and high input / output performance.

[0007] Methods for solving problems According to an embodiment, a battery is provided. The battery includes a positive electrode, a negative electrode, and an electrolyte. The positive electrode includes an oxide containing a transition metal. The transition metal includes nickel, cobalt, and manganese. The number A of nickel atoms in the oxide when the total number of atoms of the transition metals is set to 1 is... Ni The ratio of the area B of the peak with a peak apex in the range of 683 eV to 686 eV to the area A of the peak with a peak apex in the range of 851 eV to 868 eV is 0.07 or more and 0.20 or less. The anode contains a lithium-titanium oxide. In the hard X-ray photoelectron spectrum of the anode surface, the ratio of the area D of the peak with a peak apex in the range of 685 eV to 687.5 eV to the area C of the peak apex in the range of 455 eV to 469 eV is 0.75 or more and 1.8 or less. The electrolyte contains a carboxylic acid ester and a cyclic carbonate. The volume of the carboxylic acid ester is 2.3 times or more than the volume of the cyclic carbonate.

[0008] According to other embodiments, a battery pack is provided. The battery pack includes the battery involved in the embodiments. Attached Figure Description

[0009] Figure 1 This is a cross-sectional view obtained by cutting a battery along the thickness direction in one of the embodiments.

[0010] Figure 2 yes Figure 1 Enlarged cross-sectional view of part A.

[0011] Figure 3 This is a partial cutaway perspective view of a battery, representing another example of the implementation method.

[0012] Figure 4 This is a perspective view of another example of the electrode assembly included in a battery, representing another example of an embodiment.

[0013] Figure 5 This is an exploded perspective view of a battery pack, representing one example of an implementation method.

[0014] Figure 6 It means Figure 5 The diagram shows a block diagram of the electrical circuitry of the battery pack.

[0015] Figure 7 This is an example of the hard X-ray photoelectron spectrum of the positive electrode contained in the battery involved in the implementation.

[0016] Figure 8 This is another example of the hard X-ray photoelectron spectrum of the positive electrode contained in the battery involved in the implementation.

[0017] Figure 9 This is an example of the hard X-ray photoelectron spectrum of the negative electrode contained in the battery involved in the implementation.

[0018] Figure 10 This is another example of the hard X-ray photoelectron spectrum of the negative electrode contained in the battery involved in the implementation. Detailed Implementation

[0019] The embodiments will now be described with reference to the accompanying drawings. It should be noted that common components in the embodiments are labeled with the same symbols, and repeated descriptions are omitted. Furthermore, the drawings are schematic diagrams to aid in the explanation and understanding of the embodiments; their shapes, dimensions, proportions, etc., may differ from actual devices, and these can be appropriately modified with reference to the following description and well-known techniques.

[0020] (First Embodiment) According to a first embodiment, a battery is provided. The battery includes a positive electrode, a negative electrode, and an electrolyte. The positive electrode includes an oxide containing a transition metal. The transition metal includes nickel, cobalt, and manganese. The number A of nickel atoms in the oxide when the total number of atoms of the transition metals is set to 1 is... Ni The ratio of the area B of the peak with a peak apex in the range of 683 eV to 686 eV to the area A of the peak with a peak apex in the range of 851 eV to 868 eV is 0.07 or more and 0.20 or less. The anode contains a lithium-titanium oxide. In the hard X-ray photoelectron spectrum of the anode surface, the ratio of the area D of the peak with a peak apex in the range of 685 eV to 687.5 eV to the area C of the peak apex in the range of 455 eV to 469 eV is 0.75 or more and 1.8 or less. The electrolyte contains a carboxylic acid ester and a cyclic carbonate. The volume of the carboxylic acid ester is 2.3 times or more than the volume of the cyclic carbonate.

[0021] In this specification, "the number of nickel atoms A in an oxide containing nickel, cobalt, and manganese, wherein the total number of transition metal atoms in the oxide is set to 1" is sometimes used. Ni Oxides with a content of 0.7 or higher are recorded as the first oxide.

[0022] An oxide containing nickel, cobalt, and manganese, wherein the total number of nickel atoms in the oxide is set to 1. Ni Oxides with a content of 0.7 or higher (first oxide) have high capacity. However, while first oxide has high capacity, it also has low thermal stability. Therefore, cathodes containing first oxide tend to exotherm.

[0023] Previously, solvents composed of a mixture of linear and cyclic carbonates were used as electrolytes. While cyclic carbonates have a relatively high dielectric constant, promoting lithium-ion dissociation and facilitating lithium-ion conduction, they also have a low decomposition initiation temperature and are easily decomposed.

[0024] Therefore, when a positive electrode containing the first oxide is combined with a conventional electrolyte, electrolyte decomposition is readily achieved. In particular, cyclic carbonates are readily decomposed. This leads to the problem of gas generation. Furthermore, since heat is generated during the electrolyte decomposition reaction, this heat further facilitates the decomposition reaction. This problem is easily caused, for example, when the battery is overcharged. When the battery is overcharged, the energy of the positive electrode containing the first oxide may become excessively high. If such a positive electrode comes into contact with the electrolyte, the electrolyte decomposition reaction is particularly easy to occur.

[0025] In contrast, the electrolyte contained in the battery according to the embodiments comprises a carboxylic acid ester and a cyclic carbonate. The volume of the carboxylic acid ester is more than 2.3 times that of the cyclic carbonate.

[0026] Carboxylic esters have high dielectric constants and low viscosity. Therefore, even when the proportion of carboxylic esters in the electrolyte is increased, the ionic conductivity of the electrolyte can be maintained at a high level. Consequently, electrolytes containing carboxylic esters and cyclic carbonates can improve input / output performance due to their high ionic conductivity.

[0027] Furthermore, carboxylic acid esters have a higher decomposition initiation temperature compared to cyclic carbonates. In an electrolyte, the higher the content of carboxylic acid esters relative to cyclic carbonates, the greater the potential for improved electrolyte stability. In this embodiment, the volume of carboxylic acid esters in the electrolyte is at least 2.3 times that of the cyclic carbonates. Therefore, the stability of the electrolyte is improved, and even when combined with a cathode containing a first oxide, the generation of gas and heat is less likely. This improves safety. However, from the viewpoint of maintaining a high ionic conductivity of the electrolyte, it is necessary for the electrolyte to contain cyclic carbonates.

[0028] Carboxylic acid esters are prone to reduction and decomposition at the negative electrode due to their low stability at low potentials. The battery described in this embodiment contains a lithium-titanium oxide with a relatively high potential at the negative electrode, thus preventing the negative electrode potential from becoming too low. Therefore, the generation of gases caused by the reduction and decomposition of carboxylic acid esters at the negative electrode can be suppressed, thereby improving input / output performance.

[0029] The ratio B / A of the area of ​​peaks with apexes in the range of 683 eV to 686 eV in the Hard X-ray Photoelectron Spectroscopy (HAXPES) of the cathode surface to the area of ​​peaks with apexes in the range of 851 eV to 868 eV can be used as an indicator of the degree of exposure of the first oxide in the cathode surface.

[0030] For example, a low B / A ratio may mean that the first oxide occupies a large proportion of the surface of the cathode. That is, it may mean that the first oxide is exposed to a greater extent on the surface of the cathode.

[0031] Conversely, a high B / A ratio likely means that the first oxide occupies a small proportion on the surface of the positive electrode. For example, since a film is formed in at least a portion of the surface of the positive electrode, it means that the exposure of the first oxide is small. Therefore, it is possible to suppress the reaction between the carboxylic acid ester contained in the electrolyte and the first oxide. Therefore, the oxidative decomposition of the carboxylic acid ester can be suppressed. Therefore, the heat generated by the battery due to the decomposition of the electrolyte can be reduced, and gas generation can be suppressed. Therefore, for example, even under high-temperature environments, gas generation can be suppressed.

[0032] In the battery described in this embodiment, the B / A ratio is 0.07 or higher. Therefore, the exposure of the first oxide on the surface of the positive electrode is suppressed. Thus, the oxidative decomposition of carboxylic acid esters can be suppressed. Furthermore, since the heat dissipation of the battery can be reduced, safety can be improved. Moreover, since the B / A ratio is 0.20 or lower, the amount of film formed on the surface of the positive electrode is not excessive. Therefore, the movement of charge within the battery can be smoothly maintained, and thus the resistance can be kept low.

[0033] The ratio D / C of the area of ​​peaks with apexes in the hard X-ray photoelectron spectrum of the negative electrode surface in the range of 685 eV to 687.5 eV to the area of ​​peaks with apexes in the range of 455 eV to 469 eV can be used as an indicator of the degree of exposure of lithium titanium oxides in the surface of the negative electrode.

[0034] For example, a low D / C ratio may mean that the proportion of lithium-containing titanium oxide on the surface of the negative electrode is large. That is, it may mean that the degree of exposure of lithium-containing titanium oxide on the surface of the negative electrode is large.

[0035] Conversely, a high D / C ratio likely means that the proportion of lithium-titanium oxide on the negative electrode surface is small. For example, since a film is formed in at least a portion of the negative electrode surface, it means that the degree of exposure of lithium-titanium oxide is small. Therefore, it is possible to suppress the reaction between the carboxylic acid ester contained in the electrolyte and the lithium-titanium oxide. Consequently, since the reductive decomposition of the carboxylic acid ester can be suppressed, gas generation can be suppressed.

[0036] In the battery according to the embodiment, the D / C ratio is 0.75 or higher. Therefore, the exposure of lithium-containing titanium oxides on the surface of the negative electrode is suppressed. Thus, the reductive decomposition of carboxylic acid esters can be suppressed. Furthermore, since the D / C ratio is 1.8 or lower, the amount of film formed on the surface of the negative electrode is not excessive. Therefore, charge movement within the battery can proceed smoothly, and thus the resistance can be maintained at a low level. Therefore, the battery according to the embodiment improves safety and input / output performance.

[0037] The battery involved in the implementation method will be further explained.

[0038] The battery involved in the embodiment can be, for example, a lithium battery or a lithium-ion battery with lithium ions as carriers. The battery involved in the embodiment can also be a secondary battery. The secondary battery can also be a non-aqueous electrolyte secondary battery with a non-aqueous electrolyte.

[0039] The first oxide is preferably an oxide represented by the general formula Li x Ni 1-y-z Co y Mn z O2, where x satisfies 0 < x ≤ 1, y satisfies 0 < y < 0.3, and z satisfies 0 < z < 0.3.

[0040] When the first oxide is an oxide represented by the general formula Li x Ni 1-y-z Co y Mn z O2, the transition metals contained in the first oxide are composed of nickel, cobalt, and manganese.

[0041] As described before, when the total atomic number of transition metals in the first oxide is set to 1, the atomic number A of nickel Ni is 0.7 or more. In the above general formula Li x Ni 1-y-z Co y Mn z O2, the sum of the subscripts of nickel, cobalt, and manganese as transition metals is 1. That is, when the first oxide is an oxide represented by the general formula Li x Ni 1-y-z Co y Mn z O2, when the total atomic number of transition metals is set to 1, the atomic number A of nickel Ni corresponds to 1 - y - z, the subscript of nickel in the general formula. In the general formula Li x Ni 1-y-z Co y Mn z O2, 1 - y - z is 0.7 or more.

[0042] The positive electrode involved in the embodiment may contain positive electrode active material particles containing a first oxide. In the particle size distribution pattern obtained by laser diffraction scattering of the positive electrode active material particles, the ratio of d90 to d10, d90 / d10, is preferably 4 or less. The particle size distribution is a cumulative frequency distribution based on volume, accumulated from the side with the smallest particle size. d10 is the particle size where the cumulative frequency from the smallest particle size side of the cumulative frequency distribution is 10%. d90 is the particle size where the cumulative frequency from the smallest particle size side of the cumulative frequency distribution is 90%. A small value for d90 / d10 indicates small particle size inhomogeneity. If the particle size inhomogeneity of the positive electrode active material particles is small, grain boundaries that could contribute to increased resistance are less likely to form. Therefore, the resistance of the positive electrode can be reduced.

[0043] Furthermore, when the first oxide contained in the positive electrode active material particles is a single crystal, the d90 / d10 of the positive electrode active material particles can be 4 or less.

[0044] Generally, if active material particles crack, it is due to an increase in the surface area of ​​the active material particles, and the performance of the battery containing these active material particles may change. For example, active material particles may crack due to expansion and contraction during charging and / or discharging. The more repeated the charge-discharge cycles, the more likely the particles are to crack.

[0045] If the first oxide contained in the positive electrode active material particles is a single crystal, cracking of the positive electrode active material particles is less likely to occur. As a result, the increase in the surface area occupied by the first oxide due to particle cracking can be suppressed, thus suppressing the contact between the first oxide and the electrolyte. Therefore, the decomposition of the electrolyte can be further suppressed.

[0046] When the first oxide contained in the positive electrode active material particles is a single crystal, the d90 / d10 ratio of the positive electrode active material particles can be 4 or less. Furthermore, the average particle size can be 2 μm or more and 8 μm or less. Additionally, the breaking strength can be 30 MPa or more and 300 MPa or less. In other words, when the d90 / d10 ratio, average particle size, and / or breaking strength of the positive electrode active material particles are within the above ranges, since the first oxide contained in the positive electrode active material particles can be a single crystal, the increase in the specific surface area of ​​the first oxide due to cracking of the positive electrode active material particles can be suppressed. Therefore, electrolyte decomposition can be suppressed. Consequently, the exothermic reaction and gas generation due to electrolyte decomposition can be suppressed. Therefore, battery safety and input / output performance can be improved.

[0047] When positive electrode active material particles are subjected to repeated charge-discharge cycles, particle cracking is likely to occur. Therefore, in the case of a secondary battery according to the embodiment, if the d90 / d10, average particle size, and / or destructive strength of the positive electrode active material particles are within the above-mentioned range, the decomposition of the electrolyte can be more effectively suppressed, and this is preferred.

[0048] The battery involved in the embodiments will be described in further detail below.

[0049] The carboxylic acid ester contained in the electrolyte is preferably free of fluorine atoms. Compared with carboxylic acid esters containing fluorine atoms, carboxylic acid esters free of fluorine atoms can reduce gas production and lower electrical resistance.

[0050] Examples of carboxylic acid esters that do not contain fluorine atoms include those represented by the characteristic formula R-COO-R', where R and R' are C6, C7, C8, C9 ... x H y The indicated hydrocarbon group is a carboxylic acid ester. The subscripts x and y preferably satisfy y = 2x + 1. That is, R and R' are each preferably saturated hydrocarbon groups. Since saturated hydrocarbon groups consist of only x carbon atoms and y hydrogen atoms, they do not contain fluorine atoms. Furthermore, saturated hydrocarbon groups are preferred because they are considered to have lower reactivity compared to unsaturated hydrocarbon groups containing unsaturated bonds such as double bonds.

[0051] Examples of carboxylic acid esters that do not contain fluorine atoms and are represented by the characteristic formula R-COO-R', where R and R' are saturated hydrocarbon groups, include propyl propionate, ethyl propionate, methyl propionate, ethyl acetate, methyl acetate, propyl butyrate, ethyl butyrate, and methyl butyrate.

[0052] The fewer carbon atoms contained in one molecule of a carboxylic acid ester, the higher the dielectric constant and the lower the viscosity tend to be. A higher dielectric constant or lower viscosity of a carboxylic acid ester tends to improve conductivity. Therefore, fewer carbon atoms per molecule of a carboxylic acid ester leads to better input / output performance. However, the number of carbon atoms in one molecule of a carboxylic acid ester is preferably 6 or more. Carboxylic acid esters with 6 or more carbon atoms per molecule have lower flammability compared to carboxylic acid esters with 5 or fewer carbon atoms. Therefore, in addition to ease of handling, battery safety is improved. The number of carbon atoms in one molecule of a carboxylic acid ester is preferably 6. Among carboxylic acid esters with 6 carbon atoms per molecule, propyl propionate is most preferred.

[0053] In hard X-ray photoelectron spectroscopy of the cathode surface, Ni2p atoms belonging to nickel atoms can be detected, for example, in the range of 851 eV above and 868 eV below. 3 / 2 Peaks. Ni2p peaks belonging to nickel atoms can be detected. 3 / 2The peak range can be above 851.0 eV and below 868.0 eV. Ni2p 3 / 2 The peak can have a apex in the range of 851 eV to 868 eV. A peak with a apex in the range of 683 eV to 686 eV can be, for example, the F1s peak belonging to lithium fluoride (LiF). The F1s peak belonging to lithium fluoride (LiF) can have a apex in the range of 683.0 eV to 686.0 eV.

[0054] That is, the ratio B / A of the area B of the peak with a apex in the range of 683 eV to 686 eV to the area A of the peak with a apex in the range of 851 eV to 868 eV can be used as an indicator of the degree of presence of lithium fluoride relative to nickel atoms on the surface of the cathode. In the surface of the cathode, nickel atoms may, for example, be contained in a first oxide. Lithium fluoride may, for example, be contained in a film.

[0055] A higher B / A ratio could mean a greater degree of lithium fluoride exposed on the cathode surface relative to the presence of nickel atoms. In other words, it could mean a larger amount of film formed on the cathode surface. More specifically, for example, a higher B / A ratio can occur when a large amount of lithium fluoride-containing film is formed, or when the proportion of lithium fluoride in the film is high. Alternatively, a higher B / A ratio can also occur by reducing the number of nickel atoms exposed on the cathode surface due to the formation of a film.

[0056] Conversely, a smaller B / A ratio means less film is formed on the surface of the positive electrode. In this case, resistance can be reduced, thus contributing to improved input / output performance.

[0057] In the hard X-ray photoelectron spectroscopy of the negative electrode surface, in the range of 455 eV above and 469 eV, for example, Ti2p atoms belonging to titanium atoms can be detected. 1 / 2 Peaks and Ti2p 3 / 2 Peak. Ti2p peaks belonging to titanium atoms can be detected. 1 / 2 Peaks and Ti2p 3 / 2 The peak range can be above 455.0 eV and below 469.0 eV. Ti2p 1 / 2 Peaks and Ti2p 3 / 2 The peak can have a apex in the range of 455 eV to 469 eV. A peak with a apex in the range of 685 eV to 687.5 eV can be, for example, the F1s peak belonging to lithium fluoride (LiF). The lower limit of the range in which the F1s peak belonging to lithium fluoride (LiF) has a apex can be 685.0 eV.

[0058] That is, the ratio D / C of the area D of the peak with a apex in the range of 685 eV to 687.5 eV to the area C of the peak with a apex in the range of 455 eV to 469 eV can be used as an indicator of the degree of presence of lithium fluoride relative to titanium atoms on the surface of the negative electrode. In the surface of the negative electrode, titanium atoms may, for example, be contained in a lithium-containing titanium oxide. Lithium fluoride may, for example, be contained in the coating.

[0059] A higher D / C ratio could mean a greater degree of lithium fluoride exposed on the negative electrode surface relative to the presence of titanium atoms. In other words, it could mean a larger amount of film formed on the negative electrode surface. More specifically, for example, a higher D / C ratio can occur when a large amount of lithium fluoride-containing film is formed, or when the proportion of lithium fluoride in the film is high. Alternatively, a higher D / C ratio can also occur by reducing the number of titanium atoms exposed on the negative electrode surface due to the formation of a film.

[0060] Conversely, a smaller D / C ratio means less film is formed on the surface of the negative electrode. In this case, resistance can be reduced, thus contributing to improved input / output performance. An upper limit for the D / C ratio could be, for example, 1.80.

[0061] Next, the battery involved in the implementation method will be described in more detail with reference to the accompanying drawings.

[0062] Reference Figure 1 and Figure 2 An example of the battery will be described. Figure 1 The flat battery shown includes a flat electrode assembly 1, an outer packaging component 2, a positive terminal 7, a negative terminal 6, and an electrolyte (not shown). The outer packaging component 2 is a bag-shaped outer packaging component made of laminated film. The electrode assembly 1 is housed in the outer packaging component 2.

[0063] Figure 1 and Figure 2 The battery shown contains a wound electrode assembly 1. The wound electrode assembly is as follows: Figure 2 As shown, it comprises a positive electrode 3, a negative electrode 4, and a separator 5, and is formed by rolling the stacked material, consisting of the negative electrode 4, separator 5, positive electrode 3, and separator 5 sequentially from the outside into a vortex shape and then pressing it into shape. The electrolyte is held in the electrode assembly.

[0064] The positive electrode 3 includes a positive current collector 3a and a layer 3b containing a positive active material. The layer 3b contains the positive active material. The layer 3b containing the positive active material is formed on both sides of the positive current collector 3a. The negative electrode 4 includes a negative current collector 4a and a layer 4b containing a negative active material. The layer 4b contains the negative active material. In the outermost portion of the negative electrode 4, the layer 4b containing the negative active material is formed only on one side of the inner surface of the negative current collector 4a. In other portions of the negative electrode 4, the layer 4b containing the negative active material is formed on both sides of the negative current collector 4a.

[0065] like Figure 1 As shown, near the outer periphery of electrode assembly 1, the positive terminal 7 is electrically connected to the positive electrode 3. Furthermore, the negative terminal 6 is electrically connected to the outermost negative electrode 4. The positive terminal 7 and the negative terminal 6 extend to the outside through an opening in the outer packaging member 2. The battery is not limited to the above-described configuration. Figure 1 and Figure 2 The battery configuration shown can, for example, be configured as follows: Figure 3 The structure shown is as described.

[0066] exist Figure 3 In the square battery shown, the electrode assembly 10 is housed within a bottomed rectangular cylindrical metal container 12, which serves as the outer packaging component. A rectangular cover 13 is welded to the opening of the container 12. The flat electrode assembly 10 may, for example, have the same shape as the referenced... Figure 1 and Figure 2 The electrode assembly 1 described herein has the same configuration.

[0067] One end of the negative lead 14 is electrically connected to the negative current collector, and the other end is electrically connected to the negative terminal 15. The negative terminal 15 is fixed in the rectangular cover 13 by an airtight seal with glass material 16 inserted in it. One end of the positive lead 17 is electrically connected to the positive current collector, and the other end is electrically connected to the positive terminal 18 fixed on the rectangular cover 13.

[0068] The negative electrode lead 14 is made of materials such as aluminum or aluminum alloys containing elements such as Mg, Ti, Zn, Mn, Fe, Cu, and Si. In order to reduce the contact resistance with the negative electrode current collector, the negative electrode lead 14 is preferably made of the same material as the negative electrode current collector.

[0069] The positive electrode lead 17 is made of materials such as aluminum or aluminum alloys containing elements such as Mg, Ti, Zn, Mn, Fe, Cu, and Si. In order to reduce the contact resistance with the positive current collector, the positive electrode lead 17 is preferably made of the same material as the positive current collector.

[0070] It should be noted that, Figure 3The battery illustrated in the diagram uses a wound electrode assembly (wound electrode assembly) formed by winding the separator together with the positive and negative electrodes. However, instead of a wound electrode assembly, a stacked electrode assembly (stacked electrode assembly) can also be used as electrode assembly 10. An example of such a stacked electrode assembly is shown below. Figure 4 middle. Figure 4 The electrode assembly 11 shown is constructed by folding the diaphragm 5 in a zigzag manner, with positive electrodes 3 and negative electrodes 4 alternately arranged in the folded portions. Specifically, the positive electrodes 3, 4, 3, and 4 are arranged sequentially among the diaphragms 5 sandwiched within the zigzag folded diaphragm 5. Positive electrode collector tab 3c and negative electrode collector tab 4c protrude from one long side of the zigzag folded diaphragm 5. The positive electrode collector tab 3c and negative electrode collector tab 4c are arranged in a manner that does not overlap with each other.

[0071] It should be noted that the order of positive electrode 3 and negative electrode 4 is not limited to this. Figure 4 The order shown can also be configured as negative electrode 4, positive electrode 3, negative electrode 4, positive electrode 3.

[0072] In reference Figure 4 The stacked electrode assembly 11 described above serves as... Figure 3 When the electrode assembly 10 of the battery shown in the diagram is used, each of the multiple positive current collector tabs 3c can be electrically connected to the positive lead 17. Furthermore, each of the multiple negative current collector tabs 4c can be electrically connected to the negative lead 14.

[0073] (Manufacturing method) Examples of battery manufacturing methods according to the embodiments include: preparing a positive electrode and a negative electrode; housing the positive electrode and the negative electrode in an outer packaging component; injecting an electrolyte into the outer packaging component; sealing the outer packaging component to obtain a battery precursor; and aging the battery precursor to obtain a battery. It should be noted that the battery precursor may be initially charged before aging. After aging, the gas inside the battery may be removed.

[0074] The positive electrode can be manufactured, for example, by the following method. First, a slurry is prepared by suspending the positive electrode active material, conductive agent, and binder in a solvent. This slurry is then coated onto one or both sides of the positive electrode current collector. Next, the coated slurry is dried to obtain a laminate containing the positive electrode active material and the positive electrode current collector. This laminate is then pressed. The positive electrode is manufactured by operating in this manner.

[0075] Alternatively, the positive electrode can be manufactured using the following method. First, a mixture is prepared by mixing the positive electrode active material, a conductive agent, and a binder. Next, this mixture is shaped into granules. Then, by placing these granules onto the positive electrode current collector, the positive electrode can be obtained.

[0076] The negative electrode can be fabricated, for example, by the following method. First, a slurry is prepared by suspending the negative electrode active material, conductive agent, and binder in a solvent. This slurry is then coated onto one or both sides of the negative electrode current collector. Next, the coated slurry is dried to obtain a laminate containing the negative electrode active material and the negative electrode current collector. Finally, the laminate is pressed. This process is repeated to fabricate the negative electrode.

[0077] Alternatively, the negative electrode can be manufactured using the following method. First, a mixture is prepared by mixing the negative electrode active material, a conductive agent, and a binder. Next, this mixture is shaped into granules. Then, by placing these granules onto the negative electrode current collector, the negative electrode can be obtained.

[0078] By placing a diaphragm between the positive and negative electrodes as described above, an electrode assembly can be fabricated. In the electrode assembly, a positive terminal can be electrically connected to the positive electrode, and a negative terminal can be electrically connected to the negative electrode.

[0079] After housing the electrode assembly with positive and negative terminals inside a pouch-shaped outer packaging component made of laminated film, leaving an opening for electrolyte injection, the portion outside the opening is sealed by heat fusion (heat sealing). Next, electrolyte is injected into the pouch-shaped outer packaging component through the opening, and the opening is sealed by heat fusion. Heat fusion can also be performed under reduced pressure. This yields the battery precursor.

[0080] Next, the battery precursor is aged at temperatures above room temperature. Alternatively, an initial charge can be performed at room temperature (e.g., 25°C) before aging. Or, the battery can be discharged after the initial charge, followed by aging.

[0081] Through aging, the electrolyte decomposes, resulting in the formation of a coating on at least a portion of the surfaces of the positive and negative electrodes. Specifically, for example, by reacting the positive and / or negative electrodes with the electrolyte, the decomposition products of the electrolyte adhere to at least a portion of the surfaces of the positive and negative electrodes, forming a coating. Electrolyte decomposition and coating formation can also occur during the first charge.

[0082] Specifically, in the positive electrode, a film can be formed on at least a portion of the surface of the first oxide. As a result, the proportion of the first oxide on the positive electrode surface can be reduced. Therefore, the ratio B / A in the HAXPES of the positive electrode surface can be set to 0.07 or more and 0.20 or less. In the negative electrode, a film can be formed on at least a portion of the surface of the lithium titanium-containing oxide. As a result, the proportion of the lithium titanium-containing oxide on the negative electrode surface can be reduced. Therefore, the ratio D / C can be set to 0.75 or more and 1.8 or less.

[0083] The manufacturing conditions are explained in detail below.

[0084] Aging can be performed, for example, on the battery precursor in an environment with a temperature of 40°C or higher and 80°C or lower for a period of 12 hours or more and 100 hours or less. Before aging, it is preferable to set the battery voltage to a range of 2.05V or higher and 2.3V or lower through the first charge or the discharge after the first charge, and then perform aging.

[0085] The higher the aging temperature or the longer the aging time, the easier it is for the electrolyte to decompose. Furthermore, the higher the battery voltage supplied during aging, the easier it is for the electrolyte to decompose.

[0086] Although details are described below, electrolytes may contain substances containing lithium and fluorine atoms. Substances containing lithium and fluorine atoms readily form a lithium fluoride coating on the positive and / or negative electrodes by decomposing during aging.

[0087] The negative electrode, positive electrode, and electrolyte will be described below. In addition to these components, the separator, outer packaging components, positive terminal, and negative terminal that may also be included in the battery of the embodiment will also be described below.

[0088] (negative electrode) The negative electrode may comprise a negative current collector and a layer containing a negative active material. The layer containing the negative active material may be formed on one or both sides of the negative current collector. The layer containing the negative active material may comprise the negative active material and optionally a conductive agent and a binder. Lithium-titanium oxides, for example, may be included in the negative electrode as a negative active material.

[0089] The negative electrode of the battery described in this embodiment contains a lithium-titanium oxide, which increases the lithium intercalation potential. A higher lithium intercalation potential in the negative electrode makes it easier to suppress electrolyte decomposition, which is preferable. The negative electrode preferably exhibits a value of 1.5V (vs. Li / Li) relative to the redox potential of lithium. + The Li intercalation potential is above 1.

[0090] A coating may be formed in at least a portion of the surface of the negative electrode. The coating may, for example, contain fluorine atoms. The fluorine atoms may, for example, be lithium fluoride (LiF) contained in the coating. The coating may be present in at least a portion of the surface of a layer containing the negative electrode active material, or it may coat at least a portion of the surface of the negative electrode active material particles. The coating may be film-like or layered.

[0091] The negative electrode included in the battery according to the embodiments can be a negative electrode modified from a freshly manufactured negative electrode. In other words, it can be a negative electrode modified from a negative electrode included in a battery precursor supplied for the initial charging and aging stages. This is because, for example, after the battery precursor is assembled as described above, the negative electrode can react with the electrolyte during the initial charging and / or aging process. In this reaction, a coating can be formed in at least a portion of the surface of the negative electrode.

[0092] The density of the layer containing the negative electrode active material (excluding the negative electrode current collector) is preferably 1.8 g / cm³. 3 Above and 2.8g / cm 3 The following applies: The density of the layer containing the negative electrode active material within this range exhibits excellent energy density and electrolyte retention of the negative electrode. A more preferred density of the layer containing the negative electrode active material is 2.1 g / cm³. 3 Above and 2.6g / cm 3 the following.

[0093] The negative electrode active material may consist solely of lithium-titanium oxide, or may further contain other active materials. From the viewpoint of preventing the negative electrode potential from becoming too low, the negative electrode active material preferably contains 70% by mass or more of lithium-titanium oxide, more preferably 80% by mass or more. The upper limit of the proportion of lithium-titanium oxide in the negative electrode active material can be set to 100% by mass.

[0094] Examples of lithium-containing titanium oxides include lithium titanate (e.g., Lithium titanate with an orthorhombic manganese oxide structure). 2+ y Ti3O7, 0≤y≤3), lithium titanate with spinel structure (e.g., Li) 4+x Ti5O 12 (0≤x≤3). The types of lithium-containing titanium oxides can be set to one or more.

[0095] Examples of active materials other than lithium-containing titanium oxides include titanium dioxide (TiO2), anatase titanium dioxide, rutile titanium dioxide, niobium pentoxide (Nb2O5), alkali manganese oxide titanium composite oxides, orthorhombic titanium composite oxides, and monoclinic niobium titanium oxides. The types of other active materials can be one or more.

[0096] As an example of the orthorhombic titanium-containing composite oxides mentioned above, Li can be cited. 2+a M I 2-b Ti 6-c M II d O 14+σ The compound represented. Wherein, MI It is selected from at least one of the groups consisting of Sr, Ba, Ca, Mg, Na, Cs, Rb, and K. M II The composition is selected from at least one element in the group consisting of Zr, Sn, V, Nb, Ta, Mo, W, Y, Fe, Co, Cr, Mn, Ni, and Al. The subscripts in the composition formula are 0 ≤ a ≤ 6, 0 ≤ b < 2, 0 ≤ c < 6, 0 ≤ d < 6, and -0.5 ≤ σ ≤ 0.5. As a specific example of an orthorhombic titanium-containing composite oxide, Li can be cited. 2+a Na2Ti6O 14 (0≤a≤6).

[0097] As examples of the aforementioned monoclinic niobium titanium oxides, Li can be cited. x Ti 1-y M1 y Nb 2-z M2 z O 7+δ The compounds referred to herein. M1 is at least one selected from the group consisting of Zr, Si, and Sn. M2 is at least one selected from the group consisting of V, Ta, and Bi. The subscripts in the composition formulas are 0 ≤ x ≤ 5, 0 ≤ y < 1, 0 ≤ z < 2, and -0.3 ≤ δ ≤ 0.3. As a specific example of monoclinic niobium titanium oxides, Li can be cited. x Nb2TiO7 (0≤x≤5).

[0098] Other examples of monoclinic niobium titanium oxides include Li x Ti 1-y M3 y+z Nb 2-z O 7-δ The compound represented is M3, which is selected from at least one of Mg, Fe, Ni, Co, W, Ta, and Mo. The subscripts in the constituent formulas are 0≤x≤5, 0≤y<1, 0≤z<2, and -0.3≤δ≤0.3.

[0099] Conductive agents are used to improve current collection performance and suppress contact resistance between the negative electrode active material and the negative electrode current collector. Examples of conductive agents include carbonaceous materials such as vapor-grown carbon fiber (VGCF), carbon black such as acetylene black, graphite, carbon nanotubes, and carbon nanofibers. One of these can be used as a conductive agent, or two or more can be combined. Alternatively, instead of using a conductive agent, carbon coating or electronically conductive inorganic material coating can be applied to the surface of the negative electrode active material particles.

[0100] The binder is used to fill the gaps between the dispersed negative electrode active material and to bond the negative electrode active material to the negative electrode current collector. Examples of binders include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), fluororubber, styrene-butadiene rubber, polyacrylic acid compounds, imide compounds, carboxymethyl cellulose (CMC), and salts of CMC. One of these can be used as a binder, or a combination of two or more can be used as a binder.

[0101] In the layer containing the negative electrode active material, the negative electrode active material, conductive agent, and binder are preferably formulated in proportions of 68% by mass or more and 96% by mass or less, 2% by mass or more and 30% by mass or less, and 2% by mass or more and 30% by mass or less, respectively. By setting the amount of conductive agent to 2% by mass or more, the current-collecting performance of the layer containing the negative electrode active material can be improved. Furthermore, by setting the amount of binder to 2% by mass or more, the adhesion between the layer containing the negative electrode active material and the negative electrode current collector becomes sufficient, and excellent cycle performance can be expected. On the other hand, setting the amount of conductive agent and binder to 30% by mass or less is preferred for achieving high capacity.

[0102] The negative electrode current collector uses an electrochemically stable material at the potential for lithium (Li) insertion and extraction in the negative electrode active material. For example, the negative electrode current collector is preferably made of copper, nickel, stainless steel, or aluminum, or an aluminum alloy containing one or more elements selected from Mg, Ti, Zn, Mn, Fe, Cu, and Si. The thickness of the negative electrode current collector is preferably 5 μm or more and 20 μm or less. A negative electrode current collector with such a thickness achieves a balance between the strength and lightweight of the negative electrode.

[0103] Furthermore, the negative current collector can be included in the portion of its surface where no layer containing the negative active material is formed. This portion can function as a negative current collector tab.

[0104] (positive electrode) The positive electrode may comprise a positive current collector and a layer containing a positive active material. The layer containing the positive active material may be formed on one or both sides of the positive current collector. The layer containing the positive active material may comprise the positive active material and optionally a conductive agent and a binder.

[0105] A coating may be formed in at least a portion of the surface of the positive electrode. The coating may, for example, contain fluorine atoms. The fluorine atoms may, for example, be lithium fluoride (LiF) contained in the coating. The coating may be present in at least a portion of the surface of a layer containing the positive electrode active material, or it may coat at least a portion of the surface of the positive electrode active material particles. The coating may be film-like or layered.

[0106] The positive electrode included in the battery according to the embodiment may be a positive electrode changed from the freshly fabricated positive electrode. In other words, it may be a positive electrode changed from the positive electrode included in the battery precursor at a stage before the first charging and aging. This is because, for example, as described above, after assembling the battery precursor, the positive electrode and the electrolyte can react during the first charging and / or aging. In this reaction, a film can be formed on at least a part of the surface of the positive electrode.

[0107] The positive electrode active material may contain only the first oxide described above, or may further contain other negative electrode active materials. From the viewpoint of improving the battery capacity, the positive electrode active material preferably contains 80% by mass or more of the first oxide, and more preferably 90% by mass or more. The upper limit of the proportion of the first oxide in the positive electrode active material can be set to 100% by mass.

[0108] As other positive electrode active materials other than the first oxide, for example, sulfides or oxides other than the first oxide can be used. Examples of these sulfides and oxides include compounds capable of inserting and extracting Li or Li ions.

[0109] As such compounds, for example, it includes manganese dioxide (MnO2), iron oxide, copper oxide, nickel oxide, lithium manganese composite oxide (e.g., Li x Mn2O4 or Li x MnO2; 0 < x ≤ 1), lithium nickel composite oxide (e.g., Li x NiO2; 0 < x ≤ 1), lithium cobalt composite oxide (e.g., Li x CoO2; 0 < x ≤ 1), lithium nickel cobalt composite oxide (e.g., Li x Ni 1-y Co y O2; 0 < x ≤ 1, 0 < y < 1), lithium manganese cobalt composite oxide (e.g., Li x Mn y Co 1-y O2; 0 < x ≤ 1, 0 < y < 1), lithium manganese nickel composite oxide having a spinel structure (e.g., Li x Mn 2-y Ni y O4; 0 < x ≤ 1, 0 < y < 2), lithium phosphorus oxide having an olivine structure (e.g., Li x FePO4; 0 < x ≤ 1, Li x Fe 1-y Mn y PO4; 0 < x ≤ 1, 0 < y ≤ 1, Li xCoPO4; (0 < x ≤ 1), iron sulfate (Fe2(SO4)3), vanadium oxide (e.g., V2O5), and A Ni Lithium nickel cobalt manganese composite oxide with a content lower than 0.7. As a more specific example, a lithium manganese composite oxide having a spinel structure (e.g., Li x Mn2O4; (0 < x ≤ 1), lithium nickel composite oxide (e.g., Li x NiO2; (0 < x ≤ 1), lithium cobalt composite oxide (e.g., Li x CoO2; (0 < x ≤ 1), lithium nickel cobalt composite oxide (e.g., Li x Ni 1-y Co y O2; (0 < x ≤ 1, 0 < y < 1), lithium manganese nickel composite oxide having a spinel structure (e.g., Li x Mn 2-y Ni y O4; (0 < x ≤ 1, 0 < y < 2), lithium manganese cobalt composite oxide (e.g., Li x Mn y Co 1-y O2; (0 < x ≤ 1, 0 < y < 1), lithium iron phosphate (e.g., Li x FePO4; (0 < x ≤ 1), and A Ni Lithium nickel cobalt manganese composite oxide with a content lower than 0.7 (Li x Ni 1-y-z Co y Mn z O2; (0 < x ≤ 1, 0 < y < 1, 0 < z < 1, 0.3 < y + z < 1).

[0110] The binder is added to fill the gaps between the dispersed positive electrode active materials and to bond the positive electrode active materials to the positive electrode current collector. Examples of the binder include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), fluorine-based rubber, polyacrylic acid compounds, imide compounds, carboxymethyl cellulose (CMC), and salts of CMC. One of them can be used as the binder, or two or more of them can be combined and used as the binder.

[0111] Conductive agents are used to improve current collection performance and suppress contact resistance between the positive electrode active material and the positive electrode current collector. Examples of conductive agents include vapor-grown carbon fiber (VGCF), carbon black such as acetylene black, and carbonaceous materials such as graphite. One of them can be used as a conductive agent, or two or more can be combined. Alternatively, the conductive agent can be omitted.

[0112] In the layer containing the positive electrode active material, the positive electrode active material and the binder are preferably mixed in proportions of 80% or more and 98% or less by mass and 2% or more and 20% or less by mass, respectively.

[0113] Sufficient electrode strength can be obtained by setting the amount of binder to 2% by mass or more. Furthermore, the binder functions as an insulator. Therefore, if the amount of binder is set to 20% by mass or less, the amount of insulator contained in the electrode is reduced, thereby reducing internal resistance.

[0114] When a conductive agent is added, the positive electrode active material, binder and conductive agent are preferably mixed in proportions of 77% or more and 95% or less by mass, 2% or more and 20% or less by mass, and 3% or more and 15% or less by mass, respectively.

[0115] The aforementioned effects can be achieved by setting the amount of the conductive agent to 3% by mass or more. Furthermore, by setting the amount of the conductive agent to 15% by mass or less, the proportion of the conductive agent in contact with the electrolyte can be reduced. At this low proportion, electrolyte decomposition can be reduced under high-temperature storage conditions.

[0116] The positive current collector is preferably aluminum foil or aluminum alloy foil containing one or more elements selected from Mg, Ti, Zn, Ni, Cr, Mn, Fe, Cu and Si.

[0117] The thickness of the aluminum foil or aluminum alloy foil is preferably 5 μm or more and 20 μm or less, more preferably 15 μm or less. The purity of the aluminum foil is preferably 99% by mass or more. The content of transition metals such as iron, copper, nickel, and chromium contained in the aluminum foil or aluminum alloy foil is preferably 1% by mass or less.

[0118] Furthermore, the positive current collector can be included in the portion of its surface where no layer containing the positive active material is formed. This portion can function as a positive current collector tab.

[0119] (electrolytes) As the electrolyte, a non-aqueous electrolyte can be used, for example. The composition of the electrolyte contained in the battery of the embodiment can be a change from the composition of the electrolyte immediately after preparation (initial composition). This is because, for example, after assembling the battery precursor using the electrolyte immediately after preparation, the substances contained in the electrolyte can decompose during aging or the like.

[0120] As a non-aqueous electrolyte, for example, a liquid non-aqueous electrolyte or a gel-like non-aqueous electrolyte can be used.

[0121] Liquid non-aqueous electrolytes are prepared by dissolving an electrolyte salt, which is used as a solute, in an organic solvent.

[0122] Carboxylic esters and cyclic carbonates can be contained in electrolytes as organic solvents. The organic solvents may further include solvents other than carboxylic esters and cyclic carbonates.

[0123] As a carboxylic acid ester, the types of carboxylic acid esters described above can be used. The types of carboxylic acid esters contained in the electrolyte can be set to one or more.

[0124] Examples of cyclic carbonates include ethylene carbonate (EC), propylene carbonate (PC), and vinylene carbonate (VC). The number of cyclic carbonates can be one or more.

[0125] Examples of electrolyte salts include lithium salts such as lithium perchlorate (LiClO4), lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium hexafluoroarsenate (LiAsF6), lithium trifluoromethanesulfonate (LiCF3SO3), and lithium bis(trifluoromethanesulfonyl)imide (LiN(CF3SO2)2), as well as mixtures thereof. The electrolyte salt is preferably a substance that is difficult to oxidize even at high potentials, and LiPF6 is most preferred.

[0126] The concentration of the electrolyte salt is preferably above 0.5 mol / L and below 2.5 mol / L.

[0127] Solvents other than carboxylic acid esters and cyclic carbonates include, for example, chain carbonates such as dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC); cyclic ethers such as tetrahydrofuran (THF) and 2-methyl tetrahydrofuran (2MeTHF); chain ethers such as dimethoxyethane (DME); cyclic esters such as γ-butyrolactone (BL); acetonitrile (AN); and sulfolane (SL). These non-aqueous solvents can be used alone or in mixtures of two or more.

[0128] The electrolyte preferably contains substances containing lithium and fluorine atoms. Substances containing lithium and fluorine atoms can function as electrolyte salts or organic solvents, or can function as both.

[0129] Substances containing lithium and fluorine atoms preferably do not function as electrolyte salts. That is, the electrolyte preferably contains a different substance containing lithium and fluorine atoms than an electrolyte salt. When the electrolyte contains such a substance, the decomposition of the electrolyte salt can be suppressed. As a result, the formation of excessive film on the positive and / or negative electrodes can be suppressed. Examples of lithium and fluorine atoms containing substances that do not function as electrolyte salts include lithium phosphate (DFP) and lithium difluorobisoxalato phosphate (LiDFBOP). The types of substances containing lithium and fluorine atoms can be one or more.

[0130] If the electrolyte contains a large amount of the aforementioned lithium and fluorine atoms, the amount of film formed on the positive and negative electrodes can be increased. From the viewpoint of setting the B / A ratio in the HAXPES of the positive electrode surface to 0.07 or more and 0.20 or less, and the D / C ratio in the HAXPES of the negative electrode surface to 0.75 or more and 1.8 or less, the electrolyte preferably contains 0.1% by mass or more and 5% by mass of DFP and 0.1% by mass or more and 5% by mass of LiDFBOP.

[0131] The more LiDFBOP the electrolyte contains, the greater the amount of film that tends to form on the negative electrode.

[0132] LiDFBOP can inhibit the decomposition of electrolyte salts, and a coating can be formed through the decomposition of LiDFBOP itself. Therefore, the more LiDFBOP the electrolyte contains, the greater the amount of coating formed on the negative electrode tends to be. Thus, when the electrolyte contains LiDFBOP, the amount of coating formed on the negative electrode can be easily controlled within a preferred range, which is preferable.

[0133] Gel-like nonaqueous electrolytes are prepared by combining liquid nonaqueous electrolytes with polymeric materials. Examples of polymeric materials include polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), polyethylene oxide (PEO), or mixtures thereof.

[0134] (Diaphragm) The diaphragm can be formed, for example, from a porous membrane containing polyethylene (PE), polypropylene (PP), cellulose, or polyvinylidene fluoride (PVdF), or a nonwoven fabric made of synthetic resin. From a safety point of view, porous membranes made of polyethylene or polypropylene are preferred because these porous membranes melt at a certain temperature and can interrupt the current.

[0135] (Outer packaging components) The outer packaging component can be formed from a laminated film or made from a metal container. When using a metal container, the lid can be integral with the container or made into a separate component. The wall thickness of the metal container is more preferably 0.5 mm or less, or 0.2 mm or less. Examples of shapes for the outer packaging component include flat, square, cylindrical, coin-shaped, button-shaped, sheet-shaped, and stacked types. The outer packaging component can be used not only for small batteries mounted in portable electronic devices, but also for large batteries mounted in two-wheeled or four-wheeled automobiles.

[0136] The wall thickness of the laminated film outer packaging component is preferably 0.2 mm or less. Examples of laminated films include multilayer films comprising a resin film and a metal layer disposed between the resin films. For weight reduction, the metal layer is preferably aluminum foil or aluminum alloy foil. The resin film can be, for example, a polymer material such as polypropylene (PP), polyethylene (PE), nylon, or polyethylene terephthalate (PET). The laminated film can be heat-sealed and shaped into the outer packaging component.

[0137] The metal container is made of aluminum or an aluminum alloy. As an aluminum alloy, an alloy containing elements such as magnesium, zinc, and silicon is preferred. In the aluminum or aluminum alloy, the content of transition metals such as iron, copper, nickel, and chromium is preferably set to below 100 ppm, which significantly improves long-term reliability and heat dissipation under high-temperature environments.

[0138] Metal containers made of aluminum or aluminum alloys preferably have an average crystal grain size of 50 μm or less, more preferably 30 μm or less, and even more preferably 5 μm or less. By setting the average crystal grain size to 50 μm or less, the strength of the metal containers made of aluminum or aluminum alloys can be significantly increased, and further thinning of the container walls becomes possible. As a result, lightweight batteries with high output and excellent long-term reliability suitable for automotive applications can be achieved.

[0139] (Negative and positive extremes) The negative terminal, through a portion electrically connected to a portion of the negative electrode, functions as a conductor for the movement of electrons between the negative electrode and an external terminal. The negative terminal can, for example, be connected to a negative current collector, particularly a negative electrode tab. Similarly, the positive terminal, through a portion electrically connected to a portion of the positive electrode, functions as a conductor for the movement of electrons between the positive electrode and an external circuit. The positive terminal can, for example, be connected to a positive current collector, particularly a positive electrode tab. Both the negative and positive terminals are preferably made of a highly conductive material. When connected to a current collector, to reduce contact resistance, these terminals are preferably made of the same material as the current collector.

[0140] (Determination Method) The following describes the methods for analyzing the composition of HAXPES on the electrode surface, electrolytes, active materials, average particle size and particle size distribution, and the destructive strength of active material particles.

[0141] First, before any analysis, the method for removing the electrodes from the battery of the test subject will be explained.

[0142] (Method for removing the electrodes) First, discharge the battery. For example, discharge until the battery voltage reaches 1.5V. Then, disassemble the battery in an argon (Ar) atmosphere and remove the electrode assembly. Cut out the electrode to be analyzed from the removed electrode assembly. For example, if analyzing the positive electrode, cut out the positive electrode; if analyzing the negative electrode, cut out the negative electrode. Wash the cut-out electrode with a suitable solvent. For example, ethyl methyl carbonate can be used as a solvent. After immersing the washed electrode in the solvent for 1 hour, dry it under reduced pressure of -90 kPa for 3 hours. This process yields the electrode to be used as the sample for analysis.

[0143] (Analysis of electrode surfaces using HAXPES) Hard X-ray photoelectron spectroscopy (HAXPES) can be used as a method for analyzing the surfaces of the positive and negative electrodes.

[0144] The surface of the electrode used as the sample was measured under vacuum using a beamline equipped with a hard X-ray photoelectron spectroscopy device. The measurement conditions were set as follows: excitation energy 6 keV, photoelectron detection angle approximately 88°, and energy step approximately 0.1 eV.

[0145] The analysis methods for the HAXPES energy spectrum obtained as described above are divided into analyses for the positive electrode and analyses for the negative electrode, which will be explained below.

[0146] (Analysis of HAXPES energy spectrum of the cathode) For the method of analyzing the HAXPES energy spectrum obtained from the surface of the positive electrode and determining the areas A and B, refer to... Figure 7 , Figure 8 The following is an explanation. Figure 7 and Figure 8 In the above example, as an example of the positive electrode included in the battery according to the embodiment, the HAXPES energy spectrum obtained for the positive electrode included in the battery of Example 2 described later is shown. Hereinafter, in the HAXPES energy spectrum, the bonding energy (eV) is shown on the horizontal axis, and the photoelectron intensity (cps; counts per second) is shown on the vertical axis.

[0147] First, refer to Figure 7 The method for calculating the area A of peaks with apexes in the range of 851 eV and below 868 eV is explained. Figure 7 In the diagram, a0 represents a portion of the HAXPES energy spectrum obtained for the positive electrode included in Example 2. ab represents the background of the energy spectrum a0.

[0148] The background is set as the straight lines at the right and left ends of the area of ​​the object being subtracted from the background in the energy spectrum (the subtraction range). For example, when calculating area A, the right end of the subtraction range is set to 851 eV and the left end to 868 eV. The photoelectron intensities at the right and left ends are set as the average values ​​of the ranges ±0.5 eV at the right and left ends, respectively.

[0149] Subtracting the background ab from the energy spectrum a0 yields curve a1. By setting the range above 851 eV and below 868 eV as the integration range and integrating the intensity of curve a1, the area A of the peak with a apex in the range above 851 eV and below 868 eV can be calculated.

[0150] Next, refer to Figure 8 The method for calculating area B is explained. When calculating area B, the subtraction operation range is set to be above 681 eV and below 694 eV. Figure 8 In the figure, the curve obtained by setting the subtraction operation range to above 681eV and below 694eV and subtracting the background is shown as b1.

[0151] The curve b1 is separated by each peak. Specifically, assuming that curve b1 contains a first peak with a Gaussian function shape and a second peak with a pseudo-Voigt function shape that has a maximum value (peak) in the range above 683 eV and below 686 eV, a fitting is performed. Through fitting, curve b1 is separated into curve b2 containing the first peak and curve b3 containing the second peak. This operation yields curve b2, which contains the first peak with a maximum value (peak) in the range above 683 eV and below 686 eV.

[0152] By setting the range of 680 eV to 694 eV as the integration range and integrating the intensity of curve b2, the area B of the peak with a apex in the range of 683 eV to 686 eV can be calculated.

[0153] By dividing the area B obtained through the operation described above by the area A, the ratio B / A can be obtained. Figure 7 , Figure 8 In the positive electrode included in Example 2, the area A is 1,193,741, the area B is 158,801, and the ratio B / A is 0.13.

[0154] (Analysis of HAXPES energy spectrum of negative electrode) For the method of analyzing the HAXPES energy spectrum obtained from the surface of the negative electrode and determining the area C and area D, refer to Figure 9 , Figure 10 As explained below. Figure 9 and Figure 10 In this example, as an example of the negative electrode included in the battery according to the embodiment, the HAXPES energy spectrum obtained for the negative electrode included in the battery of Example 2 described later is shown.

[0155] First, refer to Figure 9 The method for calculating the area C of peaks with apexes in the range of 455 eV and below 469 eV is explained. Figure 9 In this diagram, c0 represents a portion of the HAXPES energy spectrum obtained for the negative electrode included in Example 2. cb represents the background of energy spectrum c0. The background range of 455 eV and below 469 eV is set as the subtraction range. Subtracting the background cb from the energy spectrum c0 yields graph c1. By setting the range of 455 eV and below 469 eV as the integration range and integrating the intensity of graph c1, the area C of the peak with a apex in the range of 455 eV and below 469 eV can be calculated.

[0156] Next, refer to Figure 10 The method for calculating the area D is explained. When calculating the area D, the subtraction operation range is set to be above 681 eV and below 694 eV. Figure 10 In the figure, the curve obtained by setting the subtraction operation range to above 681eV and below 694eV and subtracting the background is shown as d1.

[0157] The curve d1 is separated according to each peak. Specifically, assuming that curve d1 contains a first peak with a Gaussian function shape and a second peak with a pseudo-Voigt function shape that has a maximum value (peak) in the range of 685 eV to 687.5 eV, a fitting is performed. Through fitting, curve d1 is separated into curve d2 containing the first peak and curve d3 containing the second peak. This operation yields curve d2, which contains the first peak with a maximum value (peak) in the range of 685 eV to 687.5 eV.

[0158] By setting the range above 680 eV and below 694 eV as the integration range and integrating the intensity of curve d2, the area D of the peak with a apex in the range above 685 eV and below 687.5 eV can be calculated.

[0159] By dividing the area D obtained through the operation described above by the area C, the ratio D / C can be obtained. Figure 9 , Figure 10 In the negative electrode of Example 2 illustrated herein, the area C is 758510.8, the area D is 908960.0, and the ratio D / C is 1.2.

[0160] (Compositional analysis of electrolytes) The composition of the electrolyte can be determined by gas chromatography-mass spectrometry (GC-MS). GC-MS can, for example, determine the volume of carboxylic esters and cyclic carbonates contained in the electrolyte.

[0161] First, the battery under test is disassembled, and the electrolyte is extracted. The extracted electrolyte is analyzed by gas chromatography-mass spectrometry and ion chromatography. This analysis allows for the identification of the various components (solvent and solute) contained in the non-aqueous electrolyte. Furthermore, the components can be quantified using the peak areas of the curves obtained from this analysis. The ratios of each component are then calculated from the quantitative values.

[0162] (Compositional analysis of active substances) The composition of the active material contained in the electrode can be determined by powder X-ray diffraction (XRD) as described below. That is, it can be determined that the positive electrode contains a first oxide and the negative electrode contains a lithium-titanium oxide.

[0163] A powdered sample is obtained by peeling off the layer containing the active substance from the electrode used as the sample, for example, using a scraper.

[0164] The crystal structure of an active substance is identified by powder X-ray diffraction (XRD) of a powdered sample. The measurement is performed using CuKα rays as the source, within a measurement range of 2θ greater than 10° and less than 90°. This measurement yields the X-ray diffraction pattern of the compound contained in the selected particles.

[0165] As the apparatus for powder X-ray diffraction measurement, for example, the SmartLab manufactured by Rigaku Corporation is used. The measurement conditions are set as follows: X-ray source: Cu target Output power: 45kV, 200mA Sola Slit: Both incident and received light angles are 5° Step size: 0.02 deg Scanning speed: 20 deg / minute Semiconductor detector: D / teX Ultra 250 Sample plate holder: Flat glass sample plate holder (thickness 0.5mm) Measurement range: 10°≤2θ≤90°.

[0166] When using other apparatus, measurements were performed using standard Si powder for powder X-ray diffraction, in a manner that yielded the same measurement results as described above, with the peak intensity and peak position adjusted to be consistent with the apparatus described above.

[0167] (Determination of average particle size and particle size distribution) The average particle size and particle size distribution of the active material contained in the electrode can be determined by the laser diffraction / scattering method described below.

[0168] By separating the layer containing the active material from the current collector using an electrode such as a scraper, a powdered sample containing active material particles is obtained. Next, the powdered sample is placed into a measuring cell filled with N-methylpyrrolidone (NMP) until a measurable concentration is achieved. It should be noted that the capacity of the measuring cell and the measurable concentration vary depending on the particle size distribution measuring device. For the measuring cell containing NMP and the sample dissolved therein, ultrasound is applied for 5 minutes. The output power of the ultrasound is set, for example, in the range of 35W to 45W. For example, when using approximately 50 ml of NMP as a solvent, the solvent containing the sample is irradiated with ultrasound at an output power of approximately 40W for 300 seconds. Using such ultrasound irradiation can break up the agglomeration of conductive agent particles and active material particles. The measuring cell is then inserted into a particle size distribution measuring device using laser diffraction / scattering to determine the particle size distribution. Examples of particle size distribution measuring devices include the Microtrac 3100 and Microtrac 3000II (both manufactured by Microtrac BEL Co., Ltd.), or devices with equivalent functions. This allows the particle size distribution of the electrodes to be obtained.

[0169] The particle size distribution obtained by the above method is a cumulative frequency distribution based on volume, accumulated sequentially from the side with the smallest particle size. In the particle size distribution, the particle size d10, which has a cumulative frequency of 10% based on volume from the side with the smallest particle size, the particle size d50, which has a cumulative frequency of 50% based on volume from the side with the smallest particle size, and the particle size d90, which has a cumulative frequency of 90% based on volume from the side with the smallest particle size, are determined.

[0170] The obtained d50 is used as the average particle size. In addition, the ratio d90 / d10 is calculated from the obtained d10 and d90.

[0171] (Determination of the destructive strength of active substance particles) The positive electrode was extracted from the battery being tested using the method described above, and used as the test sample. The layer containing the positive electrode active material was peeled off from the current collector by immersing and stirring the positive electrode in an N-methyl-2-pyrrolidone solution. Particles with a diameter of 2 μm or more and 6 μm or less were selected from the peeled layer containing the positive electrode active material. These particles, having such a diameter, can be considered as positive electrode active material particles. The selected particles were used as test particles for the destructive strength test.

[0172] As the testing equipment, the Shimadzu MCT-510 micro compression tester can be used. Only a very small amount of test particles are dispersed onto the pressure plates of the testing equipment, and each particle is compressed. The breaking strength is calculated using the following formula.

[0173] Cs=2.8P / πd 2 Where Cs represents the breaking strength (numerical unit: N / mm) 2 P represents the test force (in N), and d represents the particle size (in mm). It should be noted that whether the test particles contain the first oxide can be confirmed by elemental analysis, such as ICP-based spectroscopy.

[0174] According to the first embodiment described above, a battery is provided. The battery includes a positive electrode, a negative electrode, and an electrolyte. The positive electrode includes an oxide containing a transition metal. The transition metal includes nickel, cobalt, and manganese. The number A of nickel atoms in the oxide when the total number of atoms of the transition metals is set to 1 is... Ni The ratio of the area B of the peak with a peak apex in the range of 683 eV to 686 eV to the area A of the peak with a peak apex in the range of 851 eV to 868 eV is 0.07 or higher and 0.20 or lower. The negative electrode contains a lithium-titanium oxide. In the hard X-ray photoelectron spectrum of the negative electrode surface, the ratio of the area D of the peak with a peak apex in the range of 685 eV to 687.5 eV to the area C of the peak apex in the range of 455 eV to 469 eV is 0.75 or higher and 1.8 or lower. The electrolyte contains a carboxylic acid ester and a cyclic carbonate. The volume of the carboxylic acid ester is more than 2.3 times that of the cyclic carbonate. Therefore, a battery with high safety and high input / output performance can be provided.

[0175] (Second Implementation) According to a second embodiment, a battery pack is provided. This battery pack includes the battery described in the first embodiment.

[0176] The battery pack according to the second embodiment may include one or more batteries (single cells) according to the first embodiment described above. The multiple batteries included in the battery pack may also be electrically connected in series or parallel to form a battery group. The battery pack may also include multiple battery groups.

[0177] Next, an example of a battery pack according to the second embodiment will be described with reference to the accompanying drawings.

[0178] Figure 5 This is an exploded perspective view of a battery pack, representing one example of an implementation method. Figure 6 It means Figure 5 A block diagram of the electrical circuit of the battery pack.

[0179] Figure 5 and Figure 6The battery pack 20 shown includes multiple individual cells 21. Each individual cell 21 can be used as a reference. Figure 1 The embodiment described herein involves a flat battery as an example.

[0180] Multiple individual cells 21 are stacked in such a way that the negative terminal 51 and the positive terminal 61 extending to the outside are aligned in the same direction, and then bound together with adhesive tape 22 to form a battery pack 23. These individual cells 21 are as follows: Figure 6 They are electrically connected in series as shown in the diagram.

[0181] The printed circuit board 24 is arranged opposite to the sides extending from the negative terminal 51 and the positive terminal 61 of the single cell 21. On the printed circuit board 24, as... Figure 6 As shown, it is equipped with a thermistor 25, a protection circuit 26, and a terminal 27 for powering external devices. It should be noted that an insulating plate (not shown) is installed on the printed circuit board 24 on the side opposite to the battery pack 23 to avoid unnecessary connections with the wiring of the battery pack 23.

[0182] The positive terminal lead 28 is connected to the bottom positive terminal 61 of the battery pack 23, and its front end is electrically connected by inserting into the positive terminal connector 29 of the printed circuit board 24. The negative terminal lead 30 is connected to the top negative terminal 51 of the battery pack 23, and its front end is electrically connected by inserting into the negative terminal connector 31 of the printed circuit board 24. These connectors 29 and 31 are connected to the protection circuit 26 via wirings 32 and 33 formed in the printed circuit board 24.

[0183] Thermistor 25 detects the temperature of the individual cell 21, and its detection signal is sent to protection circuit 26. Protection circuit 26 can, under specified conditions, disconnect the positive-side wiring 34a and negative-side wiring 34b between protection circuit 26 and terminal 27 used for powering external devices. An example of the specified conditions is when the detection temperature of thermistor 25 reaches or exceeds a specified temperature. Other examples of the specified conditions include detecting overcharge, over-discharge, or overcurrent in the individual cell 21. This overcharge detection is performed on each individual cell 21 or the battery pack 23 as a whole. When detecting each individual cell 21, the battery voltage, positive electrode potential, or negative electrode potential can be detected. In the latter case, a lithium electrode used as a reference electrode is inserted into each individual cell 21. Figure 5 and Figure 6 In the case of battery pack 20, each individual battery 21 is connected to a wiring 35 for voltage detection. The detection signal is sent to the protection circuit 26 via these wiring 35.

[0184] Protective sheets 36 made of rubber or resin are respectively provided on the three sides of the battery pack 23, excluding the protruding sides of the positive terminal 61 and the negative terminal 51.

[0185] The battery pack 23, along with the protective sheets 36 and the printed circuit board 24, is housed within the storage container 37. Specifically, the protective sheets 36 are disposed on the two inner sides along the long side and the inner side along the short side of the storage container 37, and the printed circuit board 24 is disposed on the inner side opposite to the short side. The battery pack 23 is located within the space enclosed by the protective sheets 36 and the printed circuit board 24. A cover 38 is attached to the upper surface of the storage container 37.

[0186] It should be noted that heat-shrinkable tape can also be used to secure the battery pack 23 instead of adhesive tape 22. In this case, protective sheets are placed on both sides of the battery pack, and the heat-shrinkable tape is wrapped around it to shrink and bind the battery pack.

[0187] Figure 5 and Figure 6 The diagram shows a configuration where individual cells 21 are connected in series, but they can also be connected in parallel to increase battery capacity. Furthermore, the assembled battery packs can also be connected in series and / or parallel.

[0188] Furthermore, the design of the battery pack can be modified appropriately depending on the application. Preferably, the battery pack is used in applications where good cycle performance is desired when drawing large currents. Specific applications include powering digital cameras, two- to four-wheeled hybrid electric vehicles, two- to four-wheeled electric vehicles, and electric bicycles. The battery pack is particularly suitable for use in vehicles.

[0189] The battery pack according to the second embodiment includes the battery according to the first embodiment. Therefore, a battery pack with high safety and high input / output performance can be provided.

[0190] Example The following examples illustrate the invention in more detail, but the invention is not limited to the embodiments described below without departing from its spirit.

[0191] (Example 1) <The Making of the Positive Electrode> Prepare LiNi as positive electrode active material respectively 0.8 Co 0.1 Mn 0.1 O2 represents lithium-containing nickel-cobalt-manganese oxide (NCM811), acetylene black (AB) as a conductive agent, and polyvinylidene fluoride (PVdF) as a binder.

[0192] The prepared positive electrode active material was single-crystal NCM811 particles. The d90 / d10 ratio of these NCM811 particles was measured to be 3, the average particle size was 4 μm, and the breaking strength was 174 MPa. These measurements were performed using the methods described previously.

[0193] A positive electrode slurry was prepared by dispersing the positive electrode active material, conductive agent, and binder in N-methyl-2-pyrrolidone (NMP) as the dispersion medium at a mass ratio of 90:5:5. The positive electrode slurry was then coated onto a positive electrode current collector made of 15 μm aluminum foil and allowed to dry. This process yielded a single-sided unit area weight of 80 g / m². 2 The positive pole.

[0194] <Making the Negative Electrode> Li4Ti5O was prepared as the negative electrode active material. 12 The composition includes lithium titanium oxide (TLO), acetylene black (AB) as a conductive agent, and polyvinylidene fluoride (PVdF) as a binder. A negative electrode slurry is prepared by dispersing the negative electrode active material, conductive agent, and binder in an N-methyl-2-pyrrolidone (NMP) dispersion medium at a mass ratio of 90:5:5. The negative electrode slurry is then coated onto a negative electrode current collector made of 15 μm aluminum foil and dried. This process yields a single-sided unit area weight of 80 g / m². 2 The negative electrode.

[0195] <Preparation of Electrolytes> As solvent 1, propylene carbonate (PC) is prepared as a cyclic carbonate, and as solvent 2, propyl propionate (PP) is prepared as a carboxylic acid ester. The solvents are mixed in a ratio of 30% by volume to 70% by volume. LiPF6, as an electrolyte salt, is dissolved in the mixture at a concentration of 1 mol / L. Furthermore, lithium difluorophosphate (DFP) and lithium difluorodioxalate phosphate (LiDFBOP) are dissolved at concentrations of 0.5% by mass and 1.0% by mass, respectively.

[0196] <Battery Assembly> A resin membrane with a thickness of 15 μm is prepared as the separator. Within the space defined by the folded separator, the positive and negative electrodes are arranged such that a layer containing the positive active material and a layer containing the negative active material are positioned opposite each other through the separator. This process is used to fabricate the electrode assembly.

[0197] The fabricated electrode assembly was clamped in a laminated film and sealed on three sides by heat sealing, thus housing the electrode assembly in a pouch-like outer packaging component made of laminated film. At this point, one side of the laminated film was not heat-sealed, remaining an open opening. It was then placed in a dryer and vacuum-dried at 95°C for 12 hours. After vacuum drying, electrolyte was injected into the outer packaging component in a glove box with the dew point controlled below -50°C. After injection, the open side of the laminated film was heat-sealed under a reduced pressure of -90 kPa. This was then used as a battery precursor.

[0198] For the battery precursor, it was initially charged to 2.2V at 1C (the current value at which the battery is discharged from 100% State of Charge to 0% SOC in 1 hour), and then aged in a constant temperature bath at 60°C for 48 hours. After aging, one side of the outer packaging component was opened to vent the gas. After venting, the opened side was resealed under a reduced pressure of -90kPa. This process was used to produce the battery of Example 1.

[0199] (Examples 2-4) Except that the proportions of solvent 1 and solvent 2 are set to the values ​​recorded in Table 1, the battery is manufactured in the same manner as in Example 1.

[0200] (Comparative Example 1) Solvent 2 was changed to diethyl carbonate (DEC) as a chain carbonate, and the proportions of solvent 1 and solvent 2 were set to the values ​​recorded in Table 1. Otherwise, the battery was manufactured in the same manner as in Example 1.

[0201] (Compare Examples 2 and 3) The battery was manufactured in the same manner as in Example 1, except that the proportions of solvent 1 and solvent 2 were set to the values ​​recorded in Table 1. In Comparative Example 3, solvent 1 was not mixed, and the proportion of propyl propionate (PP) as solvent 2 was 100% by volume.

[0202] (Compare Examples 4 and 7) The battery was manufactured in the same manner as in Example 1, except that the proportions of solvent 1 and solvent 2 and the aging time were set to the values ​​recorded in Table 1.

[0203] (Comparative Example 5) The proportions of solvent 1, solvent 2, DFP concentration, and LiDFBOP concentration were set to the values ​​recorded in Table 1. Except as described above, the battery was fabricated in the same manner as in Example 1.

[0204] (Comparative Example 6) The negative electrode active material was changed to graphite. Furthermore, the proportions of solvent 1 and solvent 2 were set to the values ​​recorded in Table 1. Except for the above, the battery was manufactured in the same manner as in Example 1.

[0205] (Comparative Example 8) The battery was manufactured in the same manner as in Example 1, except that the addition of LiDFBOP was omitted.

[0206] (Performance Evaluation) For the batteries of the embodiments and comparative examples, the initial DC resistance and heat dissipation were tested as follows.

[0207] (DC resistance evaluation) The battery under test was charged at 25°C using a constant current, constant voltage (CCCV) method until it reached 2.75V. CCCV charging ended when the charge rate converged to 0.02C. Next, it was discharged to 50% of its 0.2C capacity. Then, while recording the voltage, it was discharged at a 10C current for 10 seconds. The voltage difference before and after the 10C discharge was divided by the current value to obtain the DC resistance (mΩ).

[0208] (Differential Scanning Calorimeter (DSC) Evaluation) A glass battery was assembled using a positive electrode taken from the battery of the test subject and a lithium metal electrode as the counter electrode. The glass battery was charged by CCCV at a charging rate of 0.1C until 4.2V. The glass battery was then disassembled, and the positive electrode was removed. The positive electrode removed from the glass battery was washed with ethyl methyl carbonate and then immersed in ethyl methyl carbonate for 1 hour. It was then dried under reduced pressure of -90 kPa for 3 hours. A powdered sample was obtained by separating the active material layer from the current collector of the dried positive electrode. 5 μg of the sample was measured and sealed in a flat-bottomed dish along with 60 μL of electrolyte. An electrolyte with the same composition as that used in the battery of the test subject was used. The heat release (mJ / mg) was recorded until 300°C was reached, starting at a temperature of 30°C and increasing at a rate of 5°C / min, to obtain the positive electrode DSC heat release.

[0209] The manufacturing conditions and performance evaluation results of the batteries of the above examples and comparative examples are shown in Tables 1 and 2. For Comparative Example 1, where DEC was used instead of carboxylic acid ester as solvent 2 in the manufacturing conditions, the "volume ratio of carboxylic acid ester to cyclic carbonate" was recorded as 0.00. In Comparative Example 3, since solvent 1 was omitted, the "solvent 1" column and the "volume ratio of carboxylic acid ester to cyclic carbonate" column are indicated by "-". In Comparative Example 6, since the D / C ratio could not be measured, the D / C column is indicated by "-".

[0210] Examples 1-4 all feature low DC resistance and low heat generation. Therefore, high safety and high input / output performance become clear.

[0211] Comparative Example 1, which uses a chain carbonate instead of a carboxylic acid ester as solvent 2, has a smaller D / C value compared to Examples 1-4. This is believed to be because the chain carbonate is less prone to decomposition during aging than the carboxylic acid ester, and therefore less likely to form electrolyte decomposition products in Comparative Example 1. Suppressing the formation of electrolyte decomposition products results in a smaller amount of film adhering to the surface of the negative electrode. Therefore, it is believed that in the negative electrode included in Comparative Example 1, since the titanium atoms exposed on the negative electrode surface are less likely to be covered by a film, C is relatively larger than D, and the D / C value is smaller. Furthermore, Comparative Example 1 has higher DC resistance and higher positive electrode DSC heat release compared to Examples 1-4. This is believed to be because the chain carbonate included in Comparative Example 1 has lower ionic conductivity and lower resistance compared to the carboxylic acid ester.

[0212] Comparative Example 2, where the volume ratio of solvent 2 to solvent 1, i.e., the volume ratio of carboxylic acid ester to cyclic carbonate, is as low as 1.00, exhibits higher positive electrode DSC exothermic heat compared to Examples 1-4. This is believed to be because: compared to carboxylic acid ester, cyclic carbonate, which has a lower decomposition start temperature, has a larger volume, resulting in lower electrolyte stability, thus facilitating the exothermic process associated with gas generation.

[0213] Comparative Example 3, which does not contain cyclic carbonates, has a higher DC resistance compared to Examples 1-4. This is believed to be due to the fact that the electrolyte does not contain cyclic carbonates, resulting in a lower ionic conductivity.

[0214] Comparative Example 4, which had an extended aging time of 120 hours, and Comparative Example 5, which contained up to 6% by mass of LiDFBOP in the electrolyte, had a B / A value greater than 0.20 and a D / C value greater than 1.8. Compared to Examples 1-4, Comparative Examples 4 and 5 exhibited higher DC resistance.

[0215] In Comparative Example 4, it was believed that due to the excessively prolonged aging time, the electrolyte decomposition proceeded excessively, resulting in the excessive formation of a lithium fluoride-containing film on the surfaces of both the positive and negative electrodes. Furthermore, it was believed that Comparative Example 4, lacking LiPO2F2, did not inhibit the decomposition of the electrolyte salt. Therefore, it was also believed that an excessive lithium fluoride-containing film was formed.

[0216] In Comparative Example 5, it was believed that due to the large amount of LiDFBOP, an excessive film containing lithium fluoride was formed on the surfaces of both the positive and negative electrodes. It was assumed that this excessive film resulted in increased resistance.

[0217] In Comparative Example 6, where carbon material was used instead of lithium-titanium oxide as the negative electrode active material, the D / C ratio could not be measured. This is believed to be because the negative electrode does not contain titanium atoms, and therefore no peak was detected in the range of 455 eV to 469 eV. Furthermore, Comparative Example 6 had a higher DC resistance compared to Examples 1-4. This is believed to be because, since carbon material was used instead of lithium-titanium oxide as the negative electrode active material, the negative electrode potential became too low, resulting in easy reduction and decomposition of the carboxylic ester. This is believed to be due to the formation of an excessive film during this decomposition reaction.

[0218] Comparative Examples 7 and 8, which did not contain LiDFBOP, had a B / A value of less than 0.07 and a D / C value of less than 0.75. Furthermore, for Comparative Example 7, where the aging time was shortened to 10 hours, the B / A and D / C values ​​were even smaller. This is believed to be because the content of substances containing lithium and fluorine atoms in the electrolyte is lower, and because the aging time is shorter, the amount of lithium fluoride-containing film formed on the surfaces of the positive and negative electrodes is less. Comparative Examples 7 and 8, compared to Examples 1-4, have higher positive electrode DSC heat release.

[0219] According to at least one embodiment or example described above, a battery is provided. The battery includes a positive electrode, a negative electrode, and an electrolyte. The positive electrode includes an oxide containing a transition metal. The transition metal includes nickel, cobalt, and manganese. The number A of nickel atoms in the oxide when the total number of atoms of the transition metals is set to 1 is... NiThe ratio of the area B of the peak with a peak apex in the range of 683 eV to 686 eV to the area A of the peak with a peak apex in the range of 851 eV to 868 eV is 0.07 or higher and 0.20 or lower. The negative electrode contains a lithium-titanium oxide. In the hard X-ray photoelectron spectrum of the negative electrode surface, the ratio of the area D of the peak with a peak apex in the range of 685 eV to 687.5 eV to the area C of the peak apex in the range of 455 eV to 469 eV is 0.75 or higher and 1.8 or lower. The electrolyte contains a carboxylic acid ester and a cyclic carbonate. The volume of the carboxylic acid ester is more than 2.3 times that of the cyclic carbonate. Therefore, a battery with high safety and high input / output performance can be provided.

[0220] The inventions involved in the embodiments are described below.

[0221] [1] A battery comprising a positive electrode, a negative electrode, and an electrolyte. The aforementioned positive electrode contains an oxide containing a transition metal. The aforementioned transition metals include nickel, cobalt, and manganese. The number of nickel atoms A in the oxide when the total number of atoms of the transition metals is set to 1. Ni It is above 0.7. In the hard X-ray photoelectron spectrum of the aforementioned positive electrode surface, The ratio B / A of the area B of a peak with a apex in the range of 683 eV to 686 eV to the area A of a peak with a apex in the range of 851 eV to 868 eV is 0.07 or more and 0.20 or less. The aforementioned negative electrode contains lithium-titanium oxide. In the hard X-ray photoelectron spectrum of the aforementioned negative electrode surface, The ratio D / C of the area of ​​a peak with a apex in the range of 685 eV to 687.5 eV to the area of ​​a peak with a apex in the range of 455 eV to 469 eV is 0.75 or higher and 1.8 or lower. The electrolytes mentioned above include carboxylic esters and cyclic carbonates. The volume of the aforementioned carboxylic ester is more than 2.3 times that of the aforementioned cyclic carbonate.

[0222] [2] According to the battery described in [1], wherein the transition metal in the oxide comprises the nickel, cobalt, and manganese. The above oxides are in the general formula Li x Ni 1-y-z Co yMn z O2 indicates that for the above x, 0 < x ≤ 1, for the above y, 0 < y < 0.3, and for the above z, 0 < z < 0.3. In the above general formula, the value corresponding to the above A Ni i.e., 1 - y - z, is 0.7 or more.

[0223] [3] The battery according to [1] or [2], wherein the positive electrode contains positive electrode active material particles containing the above oxide. In the particle size distribution diagram obtained by laser diffraction scattering method for the above positive electrode active material particles, the ratio d90 / d10 of d90 to d10 is 4 or less.

[0224] [4] The battery according to any one of [1] to [3], wherein the positive electrode contains positive electrode active material particles containing the above oxide. The average particle size of the above positive electrode active material particles is 2 μm or more and 8 μm or less.

[0225] [5] The battery according to any one of [1] to [4], wherein the positive electrode contains positive electrode active material particles containing the above oxide. The breaking strength of the above positive electrode active material particles is 30 MPa or more and 300 MPa or less.

[0226] [6] A battery pack, which includes the battery according to any one of [1] to [5].

[0227] Several embodiments of the present invention have been described, but these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other ways, and various omissions, substitutions, and changes can be made without departing from the gist of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and similarly included in the scope of the invention described in the claims and its equivalents.

[0228] Explanation of symbols 1…Electrode assembly, 2…Outer packaging component, 3…Positive electrode, 3a…Positive current collector, 3b…Layer containing positive active material, 3c…Positive current collector tab, 4…Negative electrode, 4a…Negative current collector, 4b…Layer containing negative active material, 5…Separator, 6…Negative terminal, 7…Positive terminal, 11…Wound electrode assembly, 12…Container, 13…Lid, 14…Negative lead, 15…Negative terminal, 16…Glass material, 17…Positive lead, 18…Positive terminal, 20…Battery pack, 21…Single… 22… Battery, 23… Adhesive tape, 24… Battery pack, 25… Printed circuit board, 26… Thermistor, 27… Protection circuit, 28… Terminal for power supply, 29… Positive side lead, 30… Negative side lead, 31… Negative side connector, 32… Wiring, 33… Wiring, 34a… Positive side wiring, 34b… Negative side wiring, 35… Wiring, 36… Protective sheet, 37… Storage container, 38… Lid, 51… Negative terminal, 61… Positive terminal.

Claims

1. A battery comprising a positive electrode, a negative electrode, and an electrolyte. The positive electrode contains an oxide containing a transition metal. The transition metals include nickel, cobalt, and manganese. The number of nickel atoms A in the oxide when the total number of atoms of the transition metal is set to 1. Ni It is above 0.

7. In the hard X-ray photoelectron spectrum of the surface of the positive electrode, The ratio B / A of the area B of a peak with a apex in the range of 683 eV to 686 eV to the area A of a peak with a apex in the range of 851 eV to 868 eV is 0.07 or more and 0.20 or less. The negative electrode contains a lithium-titanium oxide. In the hard X-ray photoelectron spectrum of the surface of the negative electrode, The ratio D / C of the area of ​​a peak with a apex in the range of 685 eV to 687.5 eV to the area of ​​a peak with a apex in the range of 455 eV to 469 eV is 0.75 or higher and 1.8 or lower. The electrolyte comprises carboxylic esters and cyclic carbonates. The volume of the carboxylic ester is more than 2.3 times that of the cyclic carbonate.

2. The battery according to claim 1, wherein, In the oxide, the transition metal includes the nickel, the cobalt, and the manganese. The oxide is represented by the general formula Li x Ni 1-y-z Co y Mn z O2, where x satisfies 0 < x ≤ 1, y satisfies 0 < y < 0.3, and z satisfies 0 < z < 0.

3. In the general formula, with A Ni The corresponding value is 1-yz, which is 0.7 or higher.

3. The battery according to claim 1, wherein, The positive electrode contains positive electrode active material particles containing the oxide. In the particle size distribution diagram obtained by laser diffraction scattering of the positive electrode active material particles, the ratio of d90 to d10, d90 / d10, is less than 4.

4. The battery according to claim 1, wherein, The positive electrode contains positive electrode active material particles containing the oxide. The average particle size of the positive electrode active material particles is greater than 2 μm and less than 8 μm.

5. The battery according to claim 1, wherein, The positive electrode contains positive electrode active material particles containing the oxide. The destructive strength of the positive electrode active material particles is above 30 MPa and below 300 MPa.

6. A battery pack comprising the battery according to any one of claims 1 to 5.

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