Manufacturing method of secondary batteries and secondary batteries

Abstract

This invention provides a secondary battery that generates little gas during manufacturing and exhibits excellent lifespan performance at high temperatures, as well as a method for manufacturing the secondary battery. The method for manufacturing the secondary battery includes: a step of preparing a battery structure having a positive electrode, a negative electrode, and an electrolyte; a step of obtaining a processing potential adjustment state by adjusting the positive electrode potential of the positive electrode to a range of 4.3V to 4.8V based on the redox potential of lithium and adjusting the negative electrode potential of the negative electrode to a range of 0.5V to 1.1V based on the redox potential of lithium; and a step of maintaining the battery structure in the processing potential adjustment state. The positive electrode comprises Li... x M1O2 represents a nickel-containing oxide. M1 is a metallic element containing at least 50% Ni by elemental ratio, and 0

Description

Technical Field

[0001] The embodiments of the present invention relate to a method for manufacturing a secondary battery and a secondary battery. Background Technology

[0002] In recent years, research and development of secondary batteries, such as non-aqueous electrolyte secondary batteries (like lithium-ion batteries), has been actively pursued as high-energy-density batteries. These secondary batteries are expected to be used in hybrid electric vehicles, electric vehicles, and as uninterrupted power supplies for mobile phone base stations. Therefore, in addition to high energy density, secondary batteries are required to possess excellent performance characteristics such as rapid charge / discharge capabilities and long-term reliability.

[0003] Commercially available non-aqueous electrolyte secondary batteries include, for example, those that use lithium transition metal composite oxides containing Co, Mn, Ni, etc. as positive electrode active materials and carbonaceous materials or titanium oxides as negative electrode active materials.

[0004] It is known that with repeated use of secondary batteries, the active materials of the positive or negative electrode deteriorate, leading to a decrease in battery capacity and other degradation processes. One cause of this degradation is, for example, the reaction between the active materials and the electrolyte (liquid electrolyte). Methods to suppress this reaction include, for example, forming a film on the surface of the active materials to prevent electrolyte decomposition (side reactions) and thus suppress battery performance degradation. Previously, there was a strong demand for secondary batteries that could suppress performance degradation even in high-temperature environments.

[0005] To suppress side reactions between the electrolyte and electrodes in secondary batteries, a technique is known to form a protective coating on the electrode surface, such as on the surface of the electrode active material layer. By suppressing side reactions, battery life can be improved. Although the composition of the protective coating varies, insufficient thickness and uniformity of the protective coating can lead to electrolyte and electrolyte salt decomposition, resulting in gas generation and poor battery life performance. Furthermore, excessively thick protective coatings generally lead to increased resistance and deterioration of input / output characteristics, resulting in a tendency for capacity reduction. Summary of the Invention

[0006] The manufacturing method of the secondary battery according to the embodiment includes the following steps: a step of preparing a battery structure having a positive electrode, a negative electrode, and an electrolyte; a step of obtaining a processing potential adjustment state by adjusting the positive electrode potential of the positive electrode to a range of 4.3V to 4.8V based on the redox potential of lithium and adjusting the negative electrode potential of the negative electrode to a range of 0.5V to 1.1V based on the redox potential of lithium; and a step of maintaining the battery structure in the processing potential adjustment state. The positive electrode contains Li...x A nickel-containing oxide represented by M1O2. M1 is a metal element containing at least 50% or more of Ni in terms of elemental ratio, and 0 < x ≤ 1. The negative electrode contains a titanium-containing oxide. The electrolyte contains a sulfur-containing compound.

[0007] According to other embodiments, a secondary battery manufactured by the manufacturing method of the above embodiments can be provided.

[0008] Based on the above, a manufacturing method of a secondary battery that can provide a secondary battery with less gas generation during manufacturing and excellent life performance in a high-temperature environment, and a secondary battery with excellent life performance in a high-temperature environment can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 It is a cross-sectional view schematically showing an example of the battery structure of the embodiment.

[0010] Figure 2 It is Figure 1 A cross-sectional view of an enlarged portion A of the battery structure shown in

[0011] Figure 3 It is a partially cutaway perspective view schematically showing another example of the battery structure of the embodiment.

[0012] Figure 4 It is Figure 3 A cross-sectional view of an enlarged portion B of the battery structure shown in

[0013] Figure 5 It is a cross-sectional view schematically showing another example of the battery structure of the embodiment.

[0014] Figure 6 It is along Figure 5 A schematic cross-sectional view taken along line VI-VI of the battery structure shown in

[0015] SYMBOL DESCRIPTION

[0016] 1... electrode group, 2... outer packaging member, 3... negative electrode, 3a... negative electrode current collector, 3b... negative electrode active material-containing layer, 4... separator, 5... positive electrode, 5a... positive electrode current collector, 5b... positive electrode active material-containing layer, 6... negative terminal, 7... positive terminal, 8... negative electrode gasket, 9... positive electrode gasket, 10... sealing plate, 11... control valve, 16... negative electrode lead, 17... positive electrode lead, 18... liquid injection port, 19... sealing plug, 100... battery structure. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0017] Hereinafter, the embodiments will be described with appropriate reference to the drawings. It should be noted that the same reference numerals are assigned to the common components in the embodiments, and repeated descriptions are omitted. In addition, each figure is a schematic diagram for facilitating the description and understanding of the embodiments, and there are differences in its shape, size, ratio, etc. from the actual device, but they can be appropriately designed and changed in reference to the following description and well-known technologies.

[0018] [First Embodiment]

[0019] According to the first embodiment, a method for manufacturing a secondary battery is provided. The manufacturing method includes: a process of preparing a battery structure, a process of obtaining a processed potential adjustment state, and a process of maintaining the battery structure in the processed potential adjustment state. The battery structure includes a positive electrode, a negative electrode, and an electrolyte. The positive electrode includes a nickel-containing oxide. The nickel-containing oxide is represented by the general formula Li x M1O2. In the general formula of the nickel-containing oxide, M1 is a metal element containing at least 50% or more of Ni in terms of elemental ratio, and 0 < x ≤ 1. The negative electrode includes a titanium-containing oxide. The electrolyte contains a sulfur-containing compound. The processed potential adjustment state is obtained by adjusting the positive electrode potential of the positive electrode to be within the range of 4.3 V to 4.8 V (vs. Li / Li + ) based on the redox potential of lithium and adjusting the negative electrode potential of the negative electrode to be within the range of 0.5 V to 1.1 V (vs. Li / Li + ).

[0020] As an example of a method for forming a protective film on the surface of an electrode to stabilize the performance of a secondary battery such as a non-aqueous electrolyte battery, aging or a treatment for reacting an additive added to the electrolyte can be cited. If such a treatment is carried out at a high temperature and a high charge state (for example, a high State of Charge; high SOC), it is possible that electrolyte decomposition, gas generation, and potential shift are likely to occur simultaneously with the formation of the film. In order to avoid such a situation, if the treatment is carried out at a low temperature and a low SOC, although electrolyte decomposition can be suppressed, the formation of the film may become insufficient. In this case, the advantages of the film are not effectively utilized, and the battery performance may not be fully exhibited. For example, if the effect of suppressing electrolyte decomposition cannot be obtained through the film, the battery resistance may increase due to electrolyte decomposition every time charge and discharge are performed.

[0021] In the method for manufacturing a secondary battery according to the first embodiment, after preparing a battery structure equivalent to a precursor of the secondary battery, it includes maintaining the battery structure in a state where the positive electrode potential is adjusted to 4.3 V to 4.8 V (vs. Li / Li + ) and the negative electrode potential is adjusted to 0.5 V to 1.1 V (vs. Li / Li +The post-treatment, which adjusts the processing potential, enables the formation of a film to a degree that inhibits electrolyte decomposition and is effective. This post-treatment is equivalent to so-called aging.

[0022] The positive and negative electrode potentials under the processing potential adjustment state correspond to the potential ranges reached by the positive and negative electrodes respectively under a charging state that is higher than the charging and discharging operating range of a battery using nickel-containing oxides in the active material of the positive electrode and titanium-containing oxides in the active material of the negative electrode. In other words, the processing potential adjustment state is equivalent to a state of charging beyond the full charge state, i.e., an overcharge state.

[0023] The film formation using the above post-processing tends to occur primarily on the positive electrode surface. A small amount of film may also form on the negative electrode surface. The positive electrode surface referred to here may, for example, be the surface of the positive electrode active material containing the layer, as described later. Similarly, the negative electrode surface may, for example, be the surface of the negative electrode active material containing the layer, as described later.

[0024] The coating is thought to be formed by the reaction of metal ions present in the electrolyte with sulfur-containing compounds contained in the electrolyte on the surface of the electrode active material containing a layer. Examples of metal ions include nickel in the positive electrode, cobalt and manganese in the positive electrode, or niobium in the negative electrode. Niobium in the negative electrode can be an example of niobium contained in a titanium oxide, specifically a niobium-titanium composite oxide, which is included as the negative electrode active material. By covering at least a portion of the surface of the active material with a coating of this type, the surface of the active material can be modified, and the reaction between the active material and the electrolyte can be suppressed. As a result, gas generation can be suppressed, and excellent lifetime performance can be exhibited even in high-temperature environments. High-temperature environments are, for example, 45°C to 80°C.

[0025] The battery structure includes a positive electrode, a negative electrode, and an electrolyte. Details of each of the positive electrode, negative electrode, and electrolyte are described below. The battery structure may further include a separator disposed between the positive and negative electrodes. The negative electrode, positive electrode, and separator can constitute an electrode assembly. The electrolyte can be held within the electrode assembly.

[0026] In addition, the battery structure can be further equipped with an outer packaging component to accommodate the electrode assembly and electrolyte.

[0027] Furthermore, the battery structure can further include a negative terminal electrically connected to the negative electrode and a positive terminal electrically connected to the positive electrode.

[0028] Battery structures can be prepared, for example, by housing a positive electrode, a negative electrode, and an electrolyte within an outer packaging component. The methods for manufacturing the positive electrode, the negative electrode, and the electrolyte are described below. The preparation of the battery structure is preferably carried out under an inert atmosphere. Furthermore, the preparation of the battery structure is preferably carried out in a dry environment. By using an inert atmosphere and a dry environment, it is possible to avoid the generation of gases such as oxygen, carbon dioxide, and hydrogen. The manufacturing of the positive and negative electrodes and the adjustment of the electrolyte are also preferably carried out under an inert atmosphere and a dry environment. For example, an argon atmosphere can be cited as an example of an inert atmosphere.

[0029] There are no particular limitations on the shape of the electrode assembly; for example, it can have a wound structure or a stacked structure.

[0030] A wound electrode assembly can be fabricated as follows: A positive electrode and a negative electrode are stacked with a separator sandwiched between them, resulting in a laminate of positive electrode, negative electrode, and separator. After winding this laminate, a flat wound electrode assembly can be fabricated by further pressing the resulting coil.

[0031] A stacked electrode assembly can be fabricated, for example, by stacking a positive electrode, a negative electrode, and a separator with the separator sandwiched between the positive and negative electrodes. Here, multiple separators can be disposed between the positive and negative electrodes respectively, or a single separator can be folded into a zigzag shape, and the positive and negative electrodes can be alternately disposed in the space created by folding the separator back.

[0032] When using outer packaging components made of laminated film, a temporary seal can be achieved, for example, by using heat-melt adhesive to close the opening. In a temporary seal, for example, a secondary battery, which is a finished product, is sealed at a location further outward (closer to the end of the opening) than where a formal seal would be performed, using heat-melt adhesive.

[0033] When using a metal container as the outer packaging component, a temporary seal can be achieved, for example, by plugging the electrolyte inlet located on the outside of the container with a sealing plug. The inlet can be, for example, located on the lid of the metal container such as a sealing plate. For instance, after liquid electrolyte is injected into the metal container through the inlet, a temporary seal is achieved by installing a rubber stopper in the inlet.

[0034] The forms of temporary sealing are not limited to the examples mentioned above.

[0035] The adjustment of the positive and negative electrode potentials towards the processing potential adjustment state can be achieved, for example, by subjecting the temporarily sealed battery structure to initial charge and discharge followed by recharging. Alternatively, the initial charge and discharge can be performed directly in a manner consistent with the processing potential adjustment state. Charging and discharging are performed to obtain a suitable State of Charge (SOC) by ensuring that the potentials of the positive and negative electrodes fall within the aforementioned processing potential adjustment state's potential range. The SOC can be adjusted, for example, based on the battery voltage. The battery structure is set to the processing potential adjustment state by performing an initial charge and discharge until a suitable SOC is reached, based on the active materials used in the positive and negative electrodes and the design of each electrode.

[0036] Alternatively, before assembling the battery structure, the positive and negative electrodes can be individually charged and discharged to achieve a processed potential adjustment state. For example, the positive electrode potential can be adjusted by assembling a battery (e.g., a half-cell) using a positive electrode and a counter electrode formed of lithium metal. Similarly, the negative electrode potential can be adjusted by assembling a battery (e.g., a half-cell) using a negative electrode and a counter electrode formed of lithium metal. By fabricating the battery structure using the positive and negative electrodes with adjusted potentials respectively, a battery structure in a processed potential adjustment state can be obtained.

[0037] A specific example of a method for adjusting a battery structure to a potential-adjusting state is illustrated. In this example, a structure is prepared that incorporates LiNi... 0.8 Co 0.1 Mn 0.1 The present invention describes a battery structure using lithium nickel cobalt manganese composite oxide (represented by O2) as the positive electrode active material and Nb2TiO7 as the negative electrode active material, and describes a method for adjusting the positive and negative electrode potentials to a processing potential adjustment state by charging and discharging the battery structure.

[0038] The aforementioned positive and negative electrodes, along with an electrolyte containing a sulfur compound, are housed in an outer packaging component, which is then temporarily sealed to prepare the battery structure. The battery structure is subjected to its first charge-discharge cycle under the following conditions: The battery structure is charged at 25°C with a constant current of 0.2C until the battery voltage reaches 3V, and then charged with a constant voltage of 3V. Constant voltage charging is performed until the total time for constant current charging and constant voltage charging reaches 10 hours. Through this initial charging in constant current constant voltage mode (CCCV mode), the positive electrode potential in this example battery structure can reach 4.2V (vs. Li / Li). + The negative electrode potential can be 1.2V (vs. Li / Li). +In this example, the SOC achieved through the aforementioned CCCV charging is set to 100%. After the initial charge, the battery structure is discharged at a constant current of 0.2C at 25°C until the battery voltage reaches 1.5V. In this example, the SOC achieved through the aforementioned constant current discharge is set to 0%. It should be noted that the current values ​​during constant current charging and discharging are expressed in units where 1C is defined as the current value at which the battery is discharged from 100% SOC to 0% SOC in one hour.

[0039] Next, the battery structure is charged at 25°C with a constant current of 0.2C until the battery voltage reaches, for example, 3.3V. Then, it is further charged at the constant voltage of 3.3V achieved through constant current charging until the current value is concentrated at 1 / 20C. By charging the battery structure with this constant current constant voltage (CCCV), the positive electrode potential in this example battery structure can become 4.4V (vs. Li / Li). + The negative electrode potential can be 1.1V (vs. Li / Li). + The SOC achieved under this condition becomes 120%. That is, an overcharge state, i.e., a processing potential adjustment state, can be obtained.

[0040] The process of maintaining the battery structure in a potential-adjusted state through post-processing is preferably performed at a temperature below 60°C. More preferably, the temperature at which the battery structure is maintained in the potential-adjusted state is below 45°C. By performing the treatment to maintain the battery structure in the potential-adjusted state at a relatively low temperature, electrolyte decomposition can be further suppressed. Considering the film formation reaction, the temperature at which the treatment is performed is preferably 25°C or higher.

[0041] The battery structure is preferably kept in the processing potential adjustment state for 72 hours or less. By keeping the upper limit of the holding time at 72 hours, excessive film formation and electrolyte decomposition can be avoided. The holding time is more preferably 24 hours or less. The holding time is preferably 3 hours or more, more preferably 6 hours or more, and even more preferably 12 hours or more. When the holding time is longer, there is a tendency to better utilize the film to suppress electrolyte decomposition, thereby improving the life performance of the secondary battery.

[0042] The holding temperature maintained in the processing potential adjustment state through post-processing can be controlled, for example, by placing the battery structure in the processing potential adjustment state into a thermostatic bath set to a predetermined temperature. Furthermore, when using a thermostatic bath to control the holding temperature, the moment the battery structure is placed in the thermostatic bath is set as the start time of the holding time, and the moment the battery structure is removed from the thermostatic bath is set as the end time of the holding time.

[0043] Open the temporary seal to release the gas generated by post-treatment. After exhausting the gas, perform a formal seal on the outer packaging member to obtain a secondary battery. For example, after cooling the battery structure taken out from the thermostat to room temperature, place the battery structure in an inert atmosphere and open the temporary seal. By performing the formal seal of the outer packaging member in a reduced-pressure environment, a secondary battery can be obtained. Alternatively, after opening the temporary seal in a reduced-pressure environment, a secondary battery can be obtained by performing the formal seal of the outer packaging member. The reduced-pressure environment mentioned here is, for example, a vacuum state of about -90 kPa.

[0044] In the case of using an outer packaging member made of a laminated film, for example, by cutting the outer packaging member at the position where the temporary seal is applied, or separating the portion of the outer packaging member where the temporary seal is applied, the opening can be made. The formal seal of the outer packaging member made of a laminated film can be performed, for example, by closing the opening made by opening through heat melting and bonding. The formal seal of the outer packaging member is preferably performed on a position closer to the inside (a position farther from the opening end) than the position where the temporary seal is performed.

[0045] In the case of using a metal container as the outer packaging member, for example, by removing the sealing plug used in the temporary seal, the opening can be made. By welding a sealing plug formed of a material that can be welded to the container, for example, at the opening (e.g., the electrolyte injection port) made by opening the plug, a formal seal can be performed on the metal container.

[0046] It is also possible to perform charge and discharge after the post-treatment to adjust the charging state for shipping the secondary battery. The charge and discharge to the shipping state can be performed, for example, before opening the temporary seal for exhausting the gas, or after performing the formal seal of the secondary battery. In addition, after the formal seal, it is also possible to perform capacity confirmation of the secondary battery using charge and discharge for quality confirmation of the product, activation charge and discharge of the secondary battery, etc.

[0047] Hereinafter, the positive electrode, negative electrode, electrolyte, separator, outer packaging member, negative electrode terminal, and positive electrode terminal will be described in detail.

[0048] (1) Positive electrode

[0049] The positive electrode contains a nickel-containing oxide represented by the general formula Li x M1O2 as a positive electrode active material. In the above general formula, M1 is a metal element containing at least 50% Ni in terms of elemental ratio. In addition, the subscript x in the general formula is within the range of 0 < x ≤ 1.

[0050] The positive electrode may include a positive electrode active material-containing layer containing a positive electrode active material. The positive electrode may further include a positive electrode current collector.

[0051] The positive electrode active material-containing layer can be formed on one side or both sides (front and back) of the positive electrode current collector. The positive electrode active material-containing layer may optionally contain a conductive agent and a binder in addition to the positive electrode active material.

[0052] Specific examples of the nickel-containing oxide described above include lithium nickel composite oxides (for example, compounds represented by Li x NiO2, where 0 < x ≤ 1), lithium nickel cobalt composite oxides (for example, compounds represented by Li x Ni 1-y Co y O2, where 0 < x ≤ 1 and 0 < y ≤ 0.5), and lithium nickel cobalt manganese composite oxides (for example, compounds represented by Li x Ni 1-z-w Co z Mn w O2, where 0 < x ≤ 1, 0 < z < 0.5, 0 < w < 0.5, and z + w ≤ 0.5).

[0053] The positive electrode active material may contain one of the above nickel-containing oxides alone, or may contain two or more of the above in combination.

[0054] In addition to the above nickel-containing oxides, the positive electrode active material may further contain other compounds. For the sake of convenience, the above nickel-containing oxides are respectively referred to as the first positive electrode active material, and other compounds as the positive electrode active material are referred to as the second positive electrode active material. The positive electrode active material may contain one or more of the first positive electrode active materials and one second positive electrode active material together, or may contain one or more of the first positive electrode active materials and two or more of the second positive electrode active materials together. The positive electrode active material contains the first positive electrode active material (the above nickel-containing oxide) in a proportion of 50% by mass or more, preferably 80% by mass or more. The positive electrode active material may also contain only the first positive electrode active material (the above nickel-containing oxide).

[0055] Examples of the second positive electrode active material include, for example, manganese dioxide (MnO2), iron oxide, copper oxide, nickel oxide, lithium manganese composite oxides (for example, compounds represented by Li x Mn2O4 or Li x MnO2, where 0 < x ≤ 1), lithium cobalt composite oxides (for example, compounds represented by Li x CoO2, where 0 < x ≤ 1), lithium manganese cobalt composite oxides (for example, compounds represented by Li x Mn v Co 1-v O2, where 0 < x ≤ 1 and 0 < v < 1), lithium manganese nickel composite oxides having a spinel structure (for example, compounds represented by Li x Mn2-s Ni s O4 represents a compound where 0 < x ≤ 1 and 0 < s < 2), lithium phosphorus oxides having an olivine structure (e.g., represented by Li x FePO4 represents a compound where 0 < x ≤ 1; represented by Li x Fe 1-t Mn t PO4 represents a compound where 0 < x ≤ 1 and 0 < t ≤ 1; represented by Li x CoPO4 represents a compound where 0 < x ≤ 1), iron sulfate (Fe2(SO4)3), vanadium oxides (e.g., V2O5) and represented by Li x Ni 1-j-k Co j Mn k O2 represents a compound where 0 < x ≤ 1, 0.5 < j < 1, 0.5 < k < 1 and 0.5 < j + k < 1 (lithium nickel cobalt manganese composite oxide containing less than 50% of Ni in metal elements by element ratio).

[0056] When using a room temperature molten salt as the electrolyte of the battery, it is preferable to use a positive electrode active material containing lithium iron phosphate, a compound represented by Li i VPO4F and 0 ≤ i ≤ 1, lithium manganese composite oxide, lithium nickel composite oxide, lithium nickel cobalt composite oxide, or a mixture thereof. These compounds have low reactivity with the room temperature molten salt, and thus can improve the cycle life. Details of the room temperature molten salt are described below.

[0057] The primary particle size of the positive electrode active material is preferably 100 nm to 1 μm. The positive electrode active material with a primary particle size of 100 nm or more is easy to handle in industrial production. The positive electrode active material with a primary particle size of 1 μm or less can enable the solid-state diffusion of lithium ions to proceed smoothly.

[0058] The specific surface area of the positive electrode active material is preferably 0.1 m 2 / g to 10 m 2 / g. The positive electrode active material with a specific surface area of 0.1 m 2 / g or more can sufficiently ensure the insertion / extraction sites of Li ions. The positive electrode active material with a specific surface area of 10 m 2 / g or less is easy to handle in industrial production and can ensure good charge-discharge cycle performance.

[0059] For the determination of specific surface area, a method is used where the surface of powder particles is subjected to adsorption of molecules with a known adsorption area at liquid nitrogen temperature, and the specific surface area of ​​the sample is calculated from the amount of adsorption. The most commonly used method is the BET method, which utilizes the low-temperature, low-humidity physical adsorption of inert gases. This BET method is based on the Langmuir theory, which extends monolayer adsorption theory to multilayer adsorption, and is the most famous theory for calculating specific surface area. The specific surface area calculated in this way is called the BET specific surface area.

[0060] Conductive agents are used to improve the current-collecting performance of the positive electrode active material and suppress contact resistance with the positive electrode current collector. Examples of conductive agents include acetylene black, carbon black, graphite, carbon fiber, graphene, carbon nanotubes, carbon nanofibers, and fullerenes. One of these can be used as a conductive agent, or two or more can be combined. Alternatively, the conductive agent can be omitted.

[0061] Binders are used to bond the positive electrode active material to the conductive agent. Examples of binders include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), fluororubber, polyacrylonitrile, and polyethylene oxide. One of them can be used as a binder, or two or more can be combined to form a binder.

[0062] The preferred proportions of the positive electrode active material, conductive agent, and binder contained in the positive electrode active material layer are 80%–95% by mass, 3%–18% by mass, and 2%–17% by mass, respectively. The conductive agent, when present in an amount of 3% by mass or more, achieves the aforementioned effects. When the conductive agent is present in an amount of 18% by mass or less, the decomposition of electrolytes on the surface of the conductive agent under high-temperature storage is reduced. When the binder is present in an amount of 2% by mass or more, sufficient positive electrode strength is obtained. When the binder is present in an amount of 17% by mass or less, the amount of insulating material (binder) in the positive electrode is reduced, thereby reducing internal resistance.

[0063] 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.

[0064] The thickness of the aluminum foil or aluminum alloy foil is preferably 5 μm to 20 μm, 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 in the aluminum foil or aluminum alloy foil is preferably 1% by mass or less.

[0065] Furthermore, the positive current collector can be contained in the portion of its surface where no positive active material layer is formed. This portion can function as a current collector tab.

[0066] 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 layer and the current collector. Afterward, the laminate is pressed. The positive electrode is manufactured by operating in this manner.

[0067] 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.

[0068] (2) Negative electrode

[0069] The negative electrode contains a titanium oxide as the negative electrode active material. Examples of titanium oxides include niobium-titanium composite oxide. The negative electrode may contain a negative electrode active material layer. The negative electrode may further contain a negative electrode current collector.

[0070] The negative electrode active material containing layer can be formed on one side or both sides of the negative electrode current collector. In addition to containing the negative electrode active material, the negative electrode active material containing layer can arbitrarily contain conductive agents and binders.

[0071] The crystal structure of niobium-titanium composite oxides can be, for example, monoclinic. If the negative electrode active material contains a monoclinic niobium-titanium composite oxide, high rate performance can be achieved in addition to excellent energy density. The reasoning is explained using Nb₂TiO₇, one type of monoclinic niobium-titanium composite oxide, as an example. The crystal structure of Nb₂TiO₇ has a large equivalent intercalation space for lithium ions and is structurally stable. Furthermore, it contains regions with two-dimensional channels for rapid lithium ion diffusion and conduction paths connecting them in the

[001] direction. Therefore, in the crystal structure of the monoclinic niobium-titanium composite oxide Nb₂TiO₇, the intercalation and deintercalation of lithium ions into the intercalation space is improved, and the intercalation and deintercalation space for lithium ions is effectively increased. Thus, high capacity and high rate performance can be provided.

[0072] As an example of monoclinic niobium-titanium composite oxides, Li can be cited. a Ti 1-b M1 b Nb 2-c M2 c O 7+δThe 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 formula are 0 ≤ a ≤ 5, 0 ≤ b < 1, 0 ≤ c < 2, and -0.3 ≤ δ ≤ 0.3. As a specific example of a monoclinic niobium-titanium composite oxide, Li can be cited. a Nb2TiO7 (0≤a≤5).

[0073] Other examples of monoclinic niobium-titanium composite oxides include Li a Ti 1-b M3 b+c Nb 2-c O 7-δ The compound represented is M3, which is selected from at least one of the following groups: Mg, Fe, Ni, Co, W, Ta, and Mo. The subscripts in the formula are 0 ≤ a ≤ 5, 0 ≤ b < 1, 0 ≤ c < 2, and -0.3 ≤ δ ≤ 0.3.

[0074] Specific examples of niobium-titanium composite oxides include Nb₂TiO₇, Nb₂Ti₂O₉, and Nb₂TiO₇. 10 Ti2O 29 、Nb 14 TiO 37 and Nb 24 TiO 62 Niobium-titanium composite oxides can also be substituted niobium-titanium composite oxides in which at least a portion of Nb and / or Ti is replaced by a different element. Examples of substituent elements include Na, K, Ca, Co, Ni, Si, P, V, Cr, Mo, Ta, Zr, Mn, Fe, Mg, B, Pb, and Al. Substituent niobium-titanium composite oxides may contain one or more substituent elements.

[0075] Niobium-titanium composite oxides can also be substances in which the elemental ratio of niobium to other elements deviates from the theoretical value relative to the general formula or composition described above. For example, it is preferable that the amount of niobium is greater than the theoretical value of niobium to other elements. In this way, when adjusting the negative electrode potential, niobium ions dissolve from the negative electrode into the electrolyte during the initial charging, which can promote the uniform formation of a sulfur-containing film on the negative electrode surface. Therefore, there is a tendency to obtain a negative electrode with excellent high-temperature resistance.

[0076] Other examples of titanium-containing oxides (besides niobium-titanium composite oxides) include lithium titanate (e.g., Li) with an orthorhombic manganese oxide structure. 2+d Ti3O7, 0≤d≤3), lithium titanate with spinel structure (e.g., Li), 4+ d Ti5O 12, (0 ≤ d ≤ 3), titanium dioxide (TiO2), anatase titanium dioxide, rutile titanium dioxide, niobium pentoxide (Nb2O5), manganobarium type titanium composite oxide, and orthorhombic titanium composite oxide.

[0077] As an example of the orthorhombic titanium composite oxide, Li 2+e M4 2-f Ti 6-g M5 h O 14+σ The compound represented by. Among them, M4 is at least one selected from the group consisting of Sr, Ba, Ca, Mg, Na, Cs, Rb, and K. M5 is at least one selected from the group consisting of Zr, Sn, V, Nb, Ta, Mo, W, Y, Fe, Co, Cr, Mn, Ni, and Al. Each subscript in the composition formula is 0 ≤ e ≤ 6, 0 ≤ f < 2, 0 ≤ g < 6, 0 ≤ h < 6, -0.5 ≤ σ ≤ 0.5. As a specific example of the orthorhombic titanium-containing composite oxide, Li 2+e Na2Ti6O 14 (0 ≤ e ≤ 6).

[0078] Among the above orthorhombic titanium composite oxides, the compound in which M5 contains at least Nb conforms to an example of a niobium-titanium composite oxide. As a specific example of the titanium-niobium composite oxide having such an orthorhombic structure, Li 2+m Na 2- n M6 p Ti 6-q-r Nb q M7 r O 14+σ The compound represented by. In the general formula Li 2+m Na 2-n M6 p Ti 6-q-r Nb q M7 r O 14+σ , the subscript m is in the range of 0 ≤ m ≤ 4, the subscript n is in the range of 0 < n < 2, the subscript p is in the range of 0 ≤ p < 2, the subscript q is in the range of 0 < q < 6, the subscript r is in the range of 0 ≤ r < 3, the sum of the subscripts q and r is in the range of 0 < q + r < 6, and the subscript σ is in the range of -0.5 ≤ σ ≤ 0.5. The element M6 is at least one selected from the group consisting of Cs, K, Sr, Ba, and Ca. The element M7 is at least one selected from the group consisting of Zr, Sn, V, Ta, Mo, W, Fe, Mn, and Al.

[0079] The negative electrode active material may contain one of the above-mentioned titanium oxides alone, or it may contain two or more of the above-mentioned materials in combination.

[0080] The negative electrode active material preferably contains a niobium-titanium composite oxide. For example, the niobium-titanium composite oxide is designated as the first titanium oxide, and other titanium oxides used as the negative electrode active material are designated as the second titanium oxide. The negative electrode active material may contain one or more first titanium oxides and one second titanium oxide, or it may contain one or more first titanium oxides and two or more second titanium oxides. The negative electrode active material is more preferably composed of the first titanium oxide (niobium-titanium composite oxide) at a proportion of 70% by mass or more, and even more preferably at a proportion of 90% by mass or more. The negative electrode active material may also contain only one or more first titanium oxides (niobium-titanium composite oxide).

[0081] Alternatively, the negative electrode active material may contain only one or more second titanium-containing oxides (titanium-containing oxides other than niobium-titanium composite oxides). Among the second titanium-containing oxides, it is preferable that the negative electrode active material contains one having a spinel structure and containing Li… 4+ d Ti5O 12 This represents lithium titanate with 0 ≤ d ≤ 3.

[0082] In addition to titanium oxide, the negative electrode active material may further contain other materials. Examples of other materials for the negative electrode active material include oxides of metals other than titanium, such as Nb₂O₅, metal sulfides, and Li alloy materials. The negative electrode active material may contain titanium oxide (a first titanium oxide and / or a second titanium oxide) at a proportion of 70% by mass or more, preferably at a proportion of 90% by mass or more.

[0083] The negative electrode active material can be contained in the negative electrode active material containing layer in the form of particles. The negative electrode active material particles can take the form of primary particles or secondary particles formed by the aggregation of primary particles. The negative electrode active material particles can also be a mixture of primary and secondary particles.

[0084] The average particle size (D) of the negative electrode active material particles 50 For example, the average particle size is in the range of 0.1 μm to 50 μm. The average particle size can be varied depending on the desired battery performance. For example, to improve fast charge / discharge performance, it is preferable to set the average particle size to 1.0 μm or less. This improves fast charge / discharge performance by reducing the diffusion distance of lithium ions in the crystal. The average particle size can be determined, for example, by laser diffraction. The average particle size refers, for example, to the median particle size D determined by laser diffraction scattering. 50 .

[0085] Whether the negative electrode active material contains secondary or primary particles can be determined by observation using a scanning electron microscope (SEM). Furthermore, SEM observation can be used to determine the average primary and average secondary particle sizes of the active material particles.

[0086] There are no particular limitations on the BET (Brunauer, Emmett, Teller) specific surface area of ​​the negative electrode active material. However, a BET specific surface area of ​​1 m² is preferred. 2 / g~20m 2 / g, more preferably 2m 2 / g~10m 2 / g.

[0087] If the specific surface area is 1m² 2 A specific surface area of ​​20 m² or higher ensures adequate contact area with the electrolyte, facilitating good discharge rate performance and shortening charging time. Conversely, a specific surface area of ​​20 m²... 2 When the concentration is below a certain value (e.g.), the reactivity with the electrolyte will not become excessively high, thus improving lifespan performance. Furthermore, it improves the coatability of the slurry containing the negative electrode active material used in the manufacture of the electrode, as described later.

[0088] The average primary particle size of the negative electrode active material particles is not particularly limited, but is preferably 0.05 μm to 2 μm, and more preferably 0.2 μm to 1 μm. The average secondary particle size of the negative electrode active material particles is not particularly limited, but is preferably 1 μm to 20 μm, and more preferably 3 μm to 10 μm.

[0089] Conductive agents are used to improve current-collecting performance and suppress contact resistance between the active material and the 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 or more of these can be used as a conductive agent. Alternatively, instead of using a conductive agent, carbon coating or electronically conductive inorganic material coating can be applied to the surface of the active material particles. Furthermore, by simultaneously using a conductive agent and coating the surface of the active material with carbon or a conductive material, the current-collecting performance of the active material containing the layer can be improved.

[0090] Binders are used to fill the gaps between dispersed active materials 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 them can be used as a binder, or two or more can be combined as a binder.

[0091] In the negative electrode active material containing layer, the negative electrode active material, conductive agent, and binder are preferably contained in proportions of 70% to 96% by mass, 2% to 28% by mass, and 2% to 28% by mass, respectively. By setting the amount of conductive agent to 2% by mass or more, the current-collecting performance of the negative electrode active material containing layer can be improved, thereby improving the high-current performance of the secondary battery. Furthermore, by setting the amount of binder to 2% by mass or more, the adhesion between the negative electrode active material containing layer and the current collector can be improved, thereby improving cycle performance. On the other hand, setting the amount of conductive agent and binder to 28% by mass or less is preferred for achieving high capacity.

[0092] The density of the negative electrode active material containing the layer (excluding the current collector) is preferably 1.8 g / cm³. 3 ~3.0g / cm 3 Anodes with a negative electrode active material layer density within this range exhibit excellent energy density and electrolyte retention. A more preferred density for the negative electrode active material layer is 2.1 g / cm³. 3 ~2.8g / cm 3 .

[0093] For the negative electrode current collector, a material electrochemically stable at the potential for lithium (Li) insertion and extraction in the negative electrode active material is used. The negative electrode current collector is preferably made of, for example, 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 to 20 μm. A negative electrode current collector with such a thickness achieves a balance between the strength and lightweight of the negative electrode.

[0094] Furthermore, the negative current collector can be contained in the portion of its surface where no negative active material layer is formed. This portion can function as a current collector tab.

[0095] 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 layer and the current collector. Afterward, the laminate is pressed. The negative electrode is fabricated by operating in this manner.

[0096] 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.

[0097] (3) Electrolytes

[0098] As the electrolyte, for example, a liquid non-aqueous electrolyte or a gel-like non-aqueous electrolyte can be used. A liquid non-aqueous electrolyte is prepared by dissolving an electrolyte salt, which is the solute, in an organic solvent. The concentration of the electrolyte salt is preferably 0.5 mol / L to 2.5 mol / L.

[0099] Examples of electrolyte salts include lithium salts such as lithium perchlorate (LiClO4), lithium hexafluoride phosphate (LiPF6), lithium tetrafluoride borate (LiBF4), lithium hexafluoride arsenide (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 not easily oxidized even at high potentials, with LiPF6 being the most preferred.

[0100] Examples of organic solvents include cyclic carbonates such as propylene carbonate (PC), ethylene carbonate (EC), and vinylene carbonate (VC); chain carbonates such as diethyl carbonate (DEC), dimethyl carbonate (DMC), and methyl ethyl carbonate (MEC); cyclic ethers such as tetrahydrofuran (THF), 2-methyl tetrahydrofuran (2MeTHF), and dioxolane (DOX); chain ethers such as dimethoxyethane (DME) and diethoxyethane (DEE); γ-butyrolactone (GBL); acetonitrile (AN); and sulfolane (SL).

[0101] These organic solvents can be used alone or as mixed solvents.

[0102] The electrolyte contains a sulfur-containing compound. The electrolyte may or may not contain niobium ions. The electrolyte may, for example, contain one or more sulfur-containing compounds selected from sulfonyl lactone compounds and sulfur-containing imide compounds.

[0103] The concentration of sulfur-containing compounds in the electrolyte is preferably 0.1% to 3% by mass, more preferably 0.5% to 1.5% by mass, relative to the electrolyte. For a secondary battery manufactured in a form with a concentration within the preferred range, it is possible to suppress the increase in resistance of the negative electrode caused by the formation of further excess film, and at the same time, it can exhibit the effect of suppressing gas generation.

[0104] Sulfolactone compounds include one or more selected from the group consisting of 1,3-propanesulfonolactone, 1,3-propenylsulfonolactone, 1,4-butanesulfonolactone, and 2,4-butanesulfonolactone. Sulfur-containing imide compounds include, for example, one or more selected from the group consisting of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and lithium bis(fluorosulfonyl)imide (LiFSI). Sulfur-containing compounds may include one or more selected from the group consisting of these compounds.

[0105] When the sulfur-containing coating formed by the negative electrode active material contains sulfur (S) derived from an imide compound, there is a tendency for the coating to be thinner compared to when it contains S derived from a sulfonyl lactone compound. Therefore, forming a coating containing S derived from an imide compound further reduces the resistance value, which is preferable. Consequently, when the electrolyte contains an imide compound, a low-resistance secondary battery can be achieved compared to when the electrolyte contains a sulfonyl lactone compound.

[0106] The preferred niobium ion concentration in the electrolyte is 0.01 mg / L to 300 mg / L, more preferably 1 mg / L to 100 mg / L. The niobium ion concentration in the electrolyte can be confirmed by high-frequency inductively coupled plasma (ICP) analysis.

[0107] Regarding the form of niobium ions in electrolytes, for example, those containing Nb 5+ 、Nb 4+ and Nb 3+ The niobium ions in the electrolyte can be derived from salts such as NbCl5. That is, NbCl5 salts can be dissolved in the electrolyte. When the battery structure is kept in a controlled potential adjustment state, a moderately high concentration of niobium ions in the electrolyte can promote film formation. If the niobium ion concentration is kept below a certain level, charging and discharging will not be hindered by niobium ions, and a long battery life can be expected.

[0108] 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.

[0109] Alternatively, as a non-aqueous electrolyte, in addition to liquid non-aqueous electrolytes and gel non-aqueous electrolytes, room-temperature molten salts (ionic melts) containing lithium ions, polymeric solid electrolytes, and inorganic solid electrolytes can also be used.

[0110] Room-temperature molten salts (ionic melts) refer to compounds formed by the combination of organic cations and anions that exist as liquids at room temperature (15℃~25℃). Room-temperature molten salts include those existing as liquid monomers, those that become liquid by mixing with electrolyte salts, those that become liquid by dissolving in organic solvents, or mixtures thereof. Generally, the melting point of room-temperature molten salts used in secondary batteries is below 25℃. Furthermore, the organic cations typically possess a quaternary ammonium framework.

[0111] Polymer solid electrolytes are prepared by dissolving electrolyte salts in polymer materials and then solidifying them.

[0112] Inorganic solid electrolytes are solid substances that have Li ion conductivity.

[0113] (4) Diaphragm

[0114] The membrane can be formed, for example, from a porous membrane containing polyethylene (PE), polypropylene (PP), cellulose, or polyvinylidene fluoride (PVdF), or from a nonwoven fabric made of synthetic resin. From a safety point of view, porous membranes made of polyethylene or polypropylene are preferred. This is because these porous membranes can melt at a certain temperature and block electric current.

[0115] (5) Outer packaging components

[0116] As outer packaging components, containers made of laminated film or metal containers can be used, for example.

[0117] The thickness of the laminate is, for example, 0.5 mm or less, preferably 0.2 mm or less.

[0118] As a laminated film, a multilayer film comprising multiple resin layers and a metal layer sandwiched between these resin layers is used. The resin layers include, for example, polymeric materials such as polypropylene (PP), polyethylene (PE), nylon, and polyethylene terephthalate (PET). For weight reduction, the metal layer is preferably made of aluminum foil or aluminum alloy foil. The laminated film is sealed using hot-melt bonding and can be shaped into an outer packaging component.

[0119] The thickness of the wall of the metal container is, for example, 1 mm or less, more preferably 0.5 mm or less, and even more preferably 0.2 mm or less.

[0120] Metal containers are made of materials such as aluminum or aluminum alloys. The aluminum alloy preferably contains elements such as magnesium, zinc, and silicon. If the aluminum alloy contains transition metals such as iron, copper, nickel, and chromium, their content is preferably less than 100 ppm by mass.

[0121] There are no particular limitations on the shape of the outer packaging components. The outer packaging components can be, for example, flat (thin), square, cylindrical, coin-shaped, or button-shaped. The outer packaging components can be appropriately selected based on the battery size and intended use.

[0122] (6) Negative extreme

[0123] The negative terminal can be formed from a material that is electrochemically stable at the insertion / deintercalation potential of the Li containing titanium oxide in the negative electrode and is conductive. Specifically, examples of materials for the negative terminal include copper, nickel, stainless steel, or aluminum, or an aluminum alloy containing at least one element selected from the group consisting of Mg, Ti, Zn, Mn, Fe, Cu, and Si. Aluminum or an aluminum alloy is preferred as the material for the negative terminal. To reduce the contact resistance with the negative electrode current collector, the negative terminal is preferably made of the same material as the negative electrode current collector.

[0124] (7) Positive extreme

[0125] The positive terminal can be in the potential range of 3V to 4.5V relative to the redox potential of lithium (vs. Li / Li). + The positive terminal is formed of a material that is electrically stable and conductive. Examples of materials for the positive terminal include aluminum, or aluminum alloys containing at least one element selected from the group consisting of Mg, Ti, Zn, Mn, Fe, Cu, and Si. To reduce the contact resistance with the positive current collector, the positive terminal is preferably formed of the same material as the positive current collector.

[0126] Powder X-ray Diffraction

[0127] The crystal structure of compounds included as active materials can be confirmed by powder X-ray diffraction (XRD). For example, the crystal structure of titanium oxides and other compounds included in negative electrode active materials, and the crystal structure of nickel oxides and other compounds included in positive electrode active materials can be confirmed by powder X-ray diffraction. Apparatus for powder X-ray diffraction measurement can be, for example, the SmartLab manufactured by Rigaku Corporation, or an equivalent device. The measurement conditions are set as follows:

[0128] X-ray source: Cu target

[0129] Output power: 45kV 200mA

[0130] Slatter slit: both incident and received light angles are 5°.

[0131] Step size (2θ): 0.02 degrees

[0132] Scanning speed: 20 degrees / minute

[0133] Semiconductor detector: D / teX Ultra 250

[0134] Sample plate holder: Flat glass sample plate holder (0.5mm thick)

[0135] Measurement range: 5°≤2θ≤90°.

[0136] Next, the battery structure used in the manufacturing method of the secondary battery according to the embodiment will be described in more detail with reference to the accompanying drawings.

[0137] Figure 1 This is a cross-sectional view that schematically illustrates an example of a battery structure according to an embodiment. Figure 2 It is Figure 1 An enlarged cross-sectional view of part A of the battery structure shown.

[0138] Figure 1 and Figure 2 The battery structure 100 shown has Figure 1 The bag-shaped outer packaging component 2 shown in the figure. Figure 1 and Figure 2 The electrode assembly 1 and the electrolyte (not shown) are shown. The electrode assembly 1 and the electrolyte are housed within a bag-shaped outer packaging component 2. The electrolyte (not shown) is held within the electrode assembly 1.

[0139] The bag-shaped outer packaging component 2 is made of a laminated film containing two resin layers and a metal layer sandwiched between them.

[0140] like Figure 1 As shown, electrode assembly 1 is a flat, wound electrode assembly. Flat and wound electrode assembly 1 is as follows... Figure 2 As shown, it includes a negative electrode 3, a separator 4, and a positive electrode 5. The separator 4 is sandwiched between the negative electrode 3 and the positive electrode 5.

[0141] The negative electrode 3 includes a negative electrode current collector 3a and a negative electrode active material containing a layer 3b. The outermost portion of the negative electrode 3 located in the wound electrode assembly 1 is as follows: Figure 2 As shown, the negative electrode active material containing layer 3b is formed only on the inner surface side of the negative electrode current collector 3a. In other parts of the negative electrode 3, the negative electrode active material containing layer 3b is formed on both sides of the negative electrode current collector 3a.

[0142] The positive electrode 5 includes a positive current collector 5a and a positive active material containing layer 5b formed on both sides of it.

[0143] like Figure 1 As shown, the negative terminal 6 and the positive terminal 7 are located near the outer periphery of the wound electrode assembly 1. The negative terminal 6 is connected to the outermost portion of the negative current collector 3a. Furthermore, the positive terminal 7 is connected to the outermost portion of the positive current collector 5a. These negative terminals 6 and positive terminals 7 extend outward from the opening of the bag-shaped outer packaging member 2.

[0144] A thermoplastic resin layer is provided on the inner surface of the bag-shaped outer packaging member 2, and the opening of the bag-shaped outer packaging member 2 is sealed by thermal fusion bonding. Whether it is a temporary seal performed before processing the battery structure 100 in a state of electrode potential adjustment, or a formal seal performed after processing and degassing, the opening of the bag-shaped outer packaging member 2 is sealed by thermal fusion bonding. The location where thermal fusion bonding is performed during temporary sealing is, for example, closer to the end of the opening than the location where thermal fusion bonding is performed during formal sealing.

[0145] Liquid electrolyte can be injected from the opening of the bag-shaped outer packaging component 2 before temporary sealing. For example, a portion remains while the opening of the bag-shaped outer packaging component 2 is sealed by heat fusion bonding, and liquid electrolyte is injected through the portion that remains without heat fusion bonding. Then, the portion containing the injected electrolyte is sealed by heat fusion bonding to achieve a temporary seal.

[0146] The battery structure described in the embodiments is not limited to... Figure 1 and Figure 2 The battery structure shown can also be, for example, a... Figure 3 and Figure 4 The battery configuration shown is shown.

[0147] Figure 3 This is a partial cutaway perspective view schematically illustrating other examples of battery structures in various embodiments. Figure 4 It is Figure 3 An enlarged cross-sectional view of part B of the battery structure shown.

[0148] Figure 3 and Figure 4 The battery structure 100 shown has Figure 3 and Figure 4 Electrode group 1 shown Figure 3 The outer packaging component 2 and the electrolyte (not shown) are shown. The electrode assembly 1 and the electrolyte are housed within the outer packaging component 2. The electrolyte is held within the electrode assembly 1.

[0149] The outer packaging component 2 is made of a laminated film containing two resin layers and a metal layer sandwiched between them.

[0150] Electrode group 1 as follows Figure 4 The electrode assembly shown is a stacked type. The stacked type electrode assembly 1 has a structure in which the negative electrode 3 and the positive electrode 5 are alternately stacked while a separator 4 is sandwiched between them.

[0151] The electrode assembly 1 includes multiple negative electrodes 3. Each negative electrode 3 has a negative current collector 3a and a negative active material containing layer 3b supported on both sides of the negative current collector 3a. Furthermore, the electrode assembly 1 includes multiple positive electrodes 5. Each positive electrode 5 has a positive current collector 5a and a positive active material containing layer 5b supported on both sides of the positive current collector 5a.

[0152] Each negative electrode 3's negative current collector 3a includes a portion 3c on one side containing a layer 3b on either surface that does not support the negative electrode active material. This portion 3c functions as a negative current collector tab. Figure 4 As shown, the portion 3c that functions as the negative collector tab does not overlap with the positive electrode 5. Furthermore, multiple negative collector tabs (parts 3c) are electrically connected to the strip-shaped negative terminal 6. The front end of the strip-shaped negative terminal 6 is led out to the outside of the outer packaging member 2.

[0153] Furthermore, although not shown, each positive electrode 5's positive current collector 5a includes a portion on one side containing a layer 5b that does not support the positive active material on any surface. This portion functions as a positive current collector tab. The positive current collector tab, like the negative current collector tab (part 3c), does not overlap with the negative electrode 3. Moreover, the positive current collector tab is located on the opposite side of the electrode group 1 relative to the negative current collector tab (part 3c). The positive current collector tab is electrically connected to the strip-shaped positive terminal 7. The front end of the strip-shaped positive terminal 7 is located on the opposite side of the negative terminal 6 and is led out to the outside of the outer packaging member 2.

[0154] In reference Figure 5 and Figure 6 At the same time, another example of a battery structure will be explained. Figure 5 This is a cross-sectional view that schematically illustrates another example of a battery structure according to an embodiment. Figure 6 It is along Figure 5 A schematic cross-sectional view of the battery structure along line VI-VI shown.

[0155] Electrode assembly 1 is housed within an outer packaging component 2 made of a rectangular cylindrical metal container. Electrode assembly 1 includes a negative electrode 3, a diaphragm 4, and a positive electrode 5. Electrode assembly 1 has a structure in which the diaphragm 4 is sandwiched between the positive electrode 5 and the negative electrode 3 and is wound into a spiral shape in a flattened manner. Electrolyte (not shown) is held within electrode assembly 1. Figure 5As shown, strip-shaped negative electrode leads 16 are electrically connected to multiple locations at the end of the negative electrode 3 located on the end face of electrode assembly 1. Similarly, strip-shaped positive electrode leads 17 are electrically connected to multiple locations at the end of the positive electrode 5 located on the same end face. These multiple negative electrode leads 16 are as follows... Figure 6 As shown, the lead 17 is connected to the negative terminal 6 in a bundled state. Furthermore, although not shown, the positive terminal lead 17 is also electrically connected to the positive terminal 7 in a similar bundled state.

[0156] A metal sealing plate 10 is fixed to the opening of a metal outer packaging component 2 by welding or the like. The negative terminal 6 and the positive terminal 7 are led out through removal holes provided in the sealing plate 10. On the inner circumferential surface of each removal hole in the sealing plate 10, a negative electrode washer 8 and a positive electrode washer 9 are respectively provided to prevent short circuits caused by contact with the negative terminal 6 and the positive terminal 7. By providing the negative electrode washer 8 and the positive electrode washer 9, the airtightness of the secondary battery can be maintained.

[0157] A control valve 11 (safety valve) is provided in the sealing plate 10. In the event of an increase in internal pressure within the outer packaging component 2 due to gas generated within the secondary battery, the generated gas can be released to the outside through the control valve 11. Figure 5 In this configuration, the control valve 11 is positioned at the center of the sealing plate 10, but the control valve 11 can also be located at the end of the sealing plate 10. The control valve 11 can also be omitted.

[0158] Furthermore, an injection port 18 is provided in the sealing plate 10. Electrolyte can be injected through this injection port 18. After the electrolyte is injected, the injection port 18 can be blocked by the sealing plug 19. The injection port 18 and the sealing plug 19 can also be omitted. When performing a temporary seal before processing to maintain the battery structure 100 in a state of electrode potential adjustment, for example, a rubber sealing plug 19 can be used. When performing a formal seal after processing and degassing, for example, a sealing plug 19 made of the same material as the sealing plate 10 is used and welded to the sealing plate 10 with the injection port 18 blocked.

[0159] The manufacturing method of the secondary battery according to the first embodiment includes: maintaining a battery structure having a positive electrode, a negative electrode, and an electrolyte in a processing potential adjustment state in which the positive electrode potential is adjusted to a range of 4.3V to 4.8V based on the redox potential of lithium, and the negative electrode potential is adjusted to a range of 0.5V to 1.1V based on the redox potential of lithium. The positive electrode contains Li... xA nickel-containing oxide represented by M1O2. Here, M1 is a metal element containing at least 50% or more of Ni in terms of elemental ratio, and 0 < x ≤ 1. The negative electrode contains a titanium-containing oxide. The electrolyte contains a sulfur-containing compound. Regarding the manufacturing method, gas generation can be suppressed less, and a secondary battery with excellent life performance in a high-temperature environment can be manufactured by this manufacturing method.

[0160] [Second Embodiment]

[0161] According to the second embodiment, a secondary battery is provided. This secondary battery is a secondary battery manufactured by the manufacturing method of the first embodiment.

[0162] The secondary battery of the second embodiment is a secondary battery obtained by holding the battery structure in the first embodiment's manufacturing method in the state where the above electrode potential adjustment has been performed. Therefore, this secondary battery can be, for example, a non-aqueous electrolyte secondary battery or a lithium-ion non-aqueous electrolyte secondary battery.

[0163] If compared with the battery structure equivalent to the secondary battery precursor before the electrode potential adjustment described in the first embodiment, except for being in the state of a completed product after pretreatment and the accompanying degassing and formal sealing, the details of the secondary battery of the second embodiment are the same as those of the battery structure described in the first embodiment. That is, the secondary battery of the second embodiment includes the positive electrode, negative electrode, and electrolyte for the first embodiment described above. In addition, the secondary battery of the second embodiment may include the separator, outer packaging member, positive terminal, and negative terminal described for the first embodiment above. Since the details are repetitive, the description is omitted.

[0164] However, the battery structure before post-treatment does not have a film on the electrode surface, and the positive and negative electrodes of the secondary battery have a film on their surfaces. In addition, the battery structure before post-treatment may be in a temporarily sealed state, and as a result, it is in a state where formal sealing has been performed on the secondary battery.

[0165] The secondary battery of the second embodiment is manufactured by the manufacturing method of the secondary battery of the first embodiment. Therefore, the secondary battery can exhibit high output performance, and even with repeated charge-discharge cycles, gas generation is less.

[0166] The secondary battery of the second embodiment is manufactured by the manufacturing method of the secondary battery of the first embodiment. Therefore, the secondary battery has excellent life performance in a high-temperature environment.

[0167] [Examples]

[0168] Examples will be described below, but the embodiments are not limited to the examples described below.

[0169] (Example 1)

[0170] The secondary battery was manufactured through the following steps.

[0171] <The Making of the Positive Electrode>

[0172] LiNi composite oxide was prepared as the positive electrode active material. 0.8 Co 0.1 Mn 0.1 O2 powder was used. Acetylene black was prepared as a conductive agent. Polyvinylidene fluoride (PVdF) was prepared as a binder. Next, the positive electrode active material, conductive agent, and binder were added to N-methylpyrrolidone (NMP) in a ratio of 90 parts by mass: 10 parts by mass: 10 parts by mass and mixed to prepare a positive electrode slurry. This positive electrode slurry was coated on both sides of a current collector made of aluminum foil with a thickness of 15 μm. The coating was then dried in a constant temperature bath at 120°C and pressed to obtain the positive electrode.

[0173] <Making the Negative Electrode>

[0174] Niobium-titanium composite oxide (Nb₂TiO₇) powder was prepared as the negative electrode active material. The average secondary particle size of the niobium-titanium composite oxide was 7.5 μm. The specific surface area of ​​the niobium-titanium composite oxide was 4.0 m². 2 / g. In addition, acetylene black was prepared as a conductive agent, and PVdF was prepared as a binder. Next, the negative electrode active material, conductive agent, and binder were added to NMP in a ratio of 90 parts by mass: 10 parts by mass: 10 parts by mass and mixed to prepare a negative electrode slurry. This negative electrode slurry was coated on both sides of a current collector made of aluminum foil with a thickness of 15 μm. Then, the coating was dried in a constant temperature bath at 120°C and pressed to obtain the negative electrode.

[0175] <Electrode Assembly Fabrication>

[0176] Two sheets of nonwoven polyethylene with a thickness of 25 μm were prepared as the separator. Next, the positive electrode, separator, negative electrode, and separator were sequentially stacked to obtain a laminate. This laminate was then wound into a vortex shape. A flat electrode assembly was fabricated by heating and pressing it at 80°C.

[0177] <Electrode assembly storage>

[0178] Next, a container was prepared using a 0.1 mm thick laminated film with a three-layer structure consisting of a nylon layer, an aluminum layer, and a polyethylene layer. The electrode assembly, prepared as before, was placed inside this container. Then, with a portion of the container's perimeter open, the interior of the container was dried in a vacuum at 80°C for 16 hours.

[0179] <Preparation of Liquid Non-Aqueous Electrolytes>

[0180] LiPF6 was dissolved at a concentration of 1 mol / L as the electrolyte in a mixed solvent of propylene carbonate (PC) and diethyl carbonate (DEC) (volume ratio 1:2). Then, 1,3-propanesulfonyl lactone (PS), as a sulfur-containing compound, was dissolved at a concentration of 1% by mass, as in the non-aqueous electrolyte. This yielded a liquid non-aqueous electrolyte. The preparation of the non-aqueous electrolyte was carried out in an argon chamber.

[0181] <Factory Construction of Battery Structures>

[0182] A non-aqueous electrolyte is injected into a container housing the electrode assembly. Then, the open portion of the container's periphery is heat-sealed to close it. This yields a battery structure with external dimensions of 11cm × 8cm × 0.3cm (excluding the tabs) and internal dimensions (the dimensions of the sealed portion) of 9cm × 7cm × 0.25cm.

[0183] Initial Charge

[0184] The battery structure was initially charged at 25°C using the following steps. First, the battery was charged at a constant current (CC) of 0.2C until it reached a voltage of 3V. Next, the battery was charged at a constant voltage (CV) of 3V. The constant voltage charging ended when the combined time of the constant current charging and constant voltage charging reached 10 hours. Furthermore, during the constant voltage charging, the charging termination potential at the positive terminal during the initial charging was 4.2V (vs. Li / Li). + The charging termination potential of the negative electrode becomes 1.2V (vs. Li / Li). + Adjust the conditions in this way. Set the state to SOC 100%.

[0185] <Initial Discharge>

[0186] Next, the battery structure was discharged at a constant current (CC) of 0.2C at 25°C until the voltage reached 1.5V.

[0187] Post-processing

[0188] Next, the battery structure was charged at a constant current (CC) of 0.2C at 25°C until it reached a voltage of 3.3V. Then, the battery was charged at a constant voltage (CV) of 3.3V until the current reached 1 / 20C. That is, the battery was charged under constant current and constant voltage (CCCV) conditions. As a result, the state of charge (SOC) of the battery structure was 120%. The battery structure was then placed in a 45°C thermostat and maintained for 24 hours. Afterward, the battery was placed in an argon chamber, the gases were purged, and it was heat-sealed again.

[0189] This process produced the secondary battery of Example 1.

[0190] (Examples 2-5)

[0191] The secondary battery was manufactured using the same method as in Example 1, except that the battery voltage during post-processing was changed to the voltage shown in Table 1 below.

[0192] (Comparative Example 1)

[0193] Except for changing the battery voltage, temperature, and time during post-processing to the voltage, temperature, and time shown in Table 1 below, a secondary battery was manufactured using the same method as in Example 1. It should be noted that in Comparative Example 1, since the post-processing time was set to zero, post-processing is considered to have been omitted.

[0194] (Comparative Examples 2-4)

[0195] Except for changing the battery voltage and temperature during post-processing to the voltage and temperature shown in Table 1 below, a secondary battery was manufactured using the same method as in Example 1.

[0196] Table 1 summarizes the manufacturing conditions of Examples 1-5 and Comparative Examples 1-4. Specifically, as described below. The column for "Sulfur-containing compound additives" shows the types of sulfur-containing compounds added to the electrolyte. "PS" in this column refers to 1,3-propanesulfonyl lactone. The columns for "Battery Voltage," "Positive Electrode Potential," and "Negative Electrode Potential" show the battery voltage when adjusted to the treatment potential adjustment state through post-treatment, and the corresponding positive and negative electrode potentials. The columns for "Aging Temperature" and "Aging Time" show the temperature and holding time of the thermostat used to maintain the battery structure in the treatment potential adjustment state through post-treatment.

[0197]

[0198] (Examples 6-8)

[0199] In Examples 6-8, the negative electrode was thinned by reducing the amount of negative electrode paste applied to the current collector during negative electrode fabrication. Except for changing the negative electrode fabrication conditions as described above and changing the battery voltage during post-processing to the voltages shown in Table 2 below, a secondary battery was manufactured using the same method as in Example 1. By thinning the negative electrode and changing the design potential, the positive and negative electrode potentials during post-processing became the values ​​shown in Table 2.

[0200] Table 2 summarizes the manufacturing conditions in Examples 6-8. The contents of each item are the same as those in Table 1.

[0201]

[0202] (Examples 9-12)

[0203] Except for changing the battery voltage and temperature during post-processing to the voltage and temperature shown in Table 3 below, a secondary battery was manufactured using the same method as in Example 1.

[0204] Table 3 summarizes the manufacturing conditions in Examples 9 to 12. The contents of each item are the same as those in Table 1.

[0205]

[0206] (Examples 13-15)

[0207] The secondary battery was manufactured using the same method as in Example 1, except that the post-processing time was changed to the time shown in Table 4 below.

[0208] Table 4 summarizes the manufacturing conditions in Examples 13-15. The contents of each item are the same as those in Table 1.

[0209]

[0210] (Examples 16-19)

[0211] The secondary battery was fabricated using the same method as in Example 1, except that the sulfur-containing compound added to the electrolyte was changed to lithium bis(fluorosulfonyl)imide (LiFSI) and the battery voltage during post-treatment was changed to the voltages shown in Table 5 below.

[0212] (Comparative Example 5)

[0213] Except that the sulfur-containing compound added to the electrolyte was changed to lithium bis(fluorosulfonyl)imide (LiFSI) and the battery voltage, temperature, and time during post-treatment were changed to the voltage, temperature, and time shown in Table 5 below, a secondary battery was manufactured using the same method as in Example 1. It should be noted that in Comparative Example 5, since the post-treatment time was set to zero, it is considered that the post-treatment was omitted.

[0214] (Comparative Example 6)

[0215] The secondary battery was fabricated using the same method as in Example 1, except that the sulfur-containing compound added to the electrolyte was changed to lithium bis(fluorosulfonyl)imide (LiFSI) and the battery voltage during post-treatment was changed to the voltages shown in Table 5 below.

[0216] Table 5 summarizes the manufacturing conditions of Examples 16-19 and Comparative Examples 5-6. The contents of each item are the same as those in Table 1.

[0217]

[0218] (Examples 20-21)

[0219] The secondary battery was manufactured using the same method as in Example 1, except that the sulfur-containing compound added to the electrolyte was replaced with the additives shown in Table 6 below and the battery voltage during post-treatment was changed to the voltages shown in Table 6 below.

[0220] Table 6 summarizes the manufacturing conditions in Examples 20 and 21. The contents of each item are the same as those in Table 1.

[0221]

[0222] (evaluate)

[0223] <Gas generation during manufacturing>

[0224] The amount of gas generated during the manufacture of each secondary battery in each embodiment and comparative example was measured as follows.

[0225] During post-processing, the battery volume before and after venting was measured. Specifically, the volume before the container was opened for venting and the volume after resealing were measured separately. The difference between the latter volume [ml] and the former volume [ml] was set as the gas generation amount [ml] ("Gas generation amount during manufacturing" = [Volume after venting] - [Volume before venting]). The results are shown in Tables 7 to 9 below.

[0226] <Storage Test>

[0227] Storage tests were conducted on each of the secondary batteries manufactured as examples and comparative examples, as follows.

[0228] The battery was charged at a constant current (CC) of 0.2C until it reached a voltage of 3V. Then, the battery was charged at a constant voltage (CV) of 3V until the current value reached 1 / 20C. That is, the battery was charged under constant current and constant voltage (CCCV) with the SOC set to 100%. The battery in this charged state was placed in a 55°C thermostatic bath. Every 10 days, the battery was removed from the 55°C thermostatic bath, cooled to 25°C, and then charged again at 3V CCCV before being placed back into the 55°C thermostatic bath. This process was repeated. After 60 days of storage in the thermostatic bath, the battery was cooled to 25°C, and its volume was measured. The difference between the volume before and after the test was defined as the gas production [ml] ("Gas production after 60 days" = [Volume before storage test] - [Volume after 60 days storage test]). The results are shown in Tables 7 to 9 below.

[0229] DC Resistance Measurement

[0230] For each secondary battery manufactured as an example and comparative example, the DC (Direct Current) resistance was measured before and after the above-described storage test, as follows.

[0231] The battery was discharged at a constant current (CC) of 0.2C until the voltage reached 1.5V. Then, the battery was charged at a constant current (CC) of 0.2C until the voltage reached 2.25V. Next, the battery was charged at a constant voltage (CV) of 2.25V until the current value reached 1 / 20C, setting the battery's state of charge (SOC) to 50%. The battery at SOC 50% was discharged at constant currents (CC) of 1C and 10C for 200ms each, and the DC resistance [mΩ] was calculated from the difference between the voltage and current values ​​at these discharge times.

[0232] The rate of increase in resistance during the storage test [mΩ / mΩ] is calculated by dividing the DC resistance [mΩ] measured after the 60-day storage test by the DC resistance [mΩ] measured before the storage test (“DC resistance increase rate after 60 days” = [DC resistance after 60-day storage test] / [DC resistance before storage test]). The results are shown in Tables 7 to 9 below.

[0233] Table 7 below summarizes the evaluation results of each secondary battery manufactured in Examples 1-15 and Comparative Examples 1-4. Table 8 below summarizes the evaluation results for Examples 16-19 and Comparative Examples 5-6. Table 9 below summarizes the evaluation results for Examples 20-21. In Tables 7-9, the column for "Gas Generation During Manufacturing" shows the measurement results of the amount of gas generated during post-processing. The column for "Gas Generation After 60 Days" shows the amount of gas generated during the above-described storage test. The column for "DC Resistance Increase Rate After 60 Days" shows the rate of increase in DC resistance observed during the above-described storage test. The "Gas Generation After 60 Days" and "DC Resistance Increase Rate After 60 Days," representing the results of the above-described storage test, serve as indicators of lifespan performance in high-temperature environments.

[0234]

[0235]

[0236]

[0237] Table 7 shows the evaluation results of the batteries in Examples 1-15 and Comparative Examples 1-4 in which 1,3-propanesulfonyl lactone (PS) was added as a sulfur-containing compound to the electrolyte. As shown in Table 7, for Examples 1-15, the amount of gas generated was low at both the time of manufacture and the storage test, and the rate of increase in resistance during the storage test was suppressed.

[0238] In Comparative Example 1, the gas generation amount was large and the resistance increase rate was high during the storage test. In Comparative Example 1, the post-treatment of adjusting the potentials of the positive and negative electrodes to the treatment potential adjustment state and maintaining them was omitted.

[0239] In Comparative Example 2, the gas generation amount during manufacturing was large. In Comparative Example 3, the resistance increase rate during the storage test was high. In Comparative Example 4, the gas generation amount during manufacturing was large, and in addition, although not shown in Table 7, the initial battery capacity was low. In these Comparative Examples 2 to 4, although post-treatment was performed, at least one of the potentials of the positive and negative electrodes at this time deviated from the positive electrode potential range of 4.3 V to 4.8 V (vs. Li / Li + ) and the negative electrode potential range of 0.5 V to 1.1 V (vs. Li / Li + ).

[0240] If the results of Examples 1 to 15 are compared with the results of Comparative Examples 1 to 4, it is found that by subjecting a battery containing nickel oxide Li x M1O2 (M1 is a metal element containing at least 50% Ni in terms of elemental ratio; 0 < x ≤ 1) in the positive electrode, a titanium-containing oxide in the negative electrode, and a sulfur-containing compound added to the electrolyte to a treatment of maintaining the treatment potential adjustment state where the positive electrode potential is in the range of 4.3 V to 4.8 V (vs. Li / Li + ) and the negative electrode potential is in the range of 0.5 V to 1.1 V, the gas generation amount during manufacturing and during high-temperature storage can be reduced, and the increase in battery resistance during high-temperature storage can be suppressed.

[0241] Table 8 shows the evaluation results of the batteries in Examples 16 to 19 and Comparative Examples 5 to 6 in which lithium bis(fluorosulfonyl)imide (LiFSI) is added as a sulfur-containing compound to the electrolyte. If the results of Examples 16 to 19 shown in Table 8 are compared with Comparative Examples 5 to 6, it is found that even when the sulfur-containing compound is changed from PS to LiFSI, by performing the treatment under the above conditions, the gas generation amount during manufacturing and during high-temperature storage can be reduced, and the increase in battery resistance during high-temperature storage can be suppressed.

[0242] Table 9 shows the evaluation results of the batteries in Examples 20 and 21 in which 1,3-propane sultone and 1,4-butane sultone are added as sulfur-containing compounds to the electrolyte respectively. From the results shown in Table 9, it is found that even when the sulfur-containing compound is changed, the gas generation amount during manufacturing and during high-temperature storage can be reduced, and the increase in battery resistance during high-temperature storage can be suppressed.

[0243] Regarding using lithium titanate Li4Ti5O with a spinel structure as the negative electrode active material 12A secondary battery manufactured by replacing the niobium-titanium composite oxide Nb2TiO7 can also reduce the amount of gas generated during manufacturing and high-temperature storage, and can suppress an increase in battery resistance during high-temperature storage.

[0244] According to at least one of the above-described embodiments and examples, a method for manufacturing a secondary battery is provided. The manufacturing method includes: a step of preparing a battery structure including a positive electrode, a negative electrode, and an electrolyte; a step of obtaining a processed potential adjustment state by adjusting the positive electrode potential to be within a range of 4.3 V to 4.8 V (vs. Li / Li + ) based on the redox potential of lithium and adjusting the negative electrode potential to be within a range of 0.5 V to 1.1 V (vs. Li / Li + ) based on the redox potential of lithium; and a step of maintaining the battery structure in the processed potential adjustment state. The positive electrode includes a nickel-containing oxide represented by the general formula Li x M1O2, in which M1 is a metal element containing at least 50% Ni in terms of elemental ratio, and 0 < x ≤ 1. The negative electrode includes a titanium-containing oxide. The electrolyte contains a sulfur-containing compound. With the above configuration, a method for manufacturing a secondary battery that can produce less gas during manufacturing and has excellent life performance in a high-temperature environment, and a secondary battery manufactured by the manufacturing method can be provided.

[0245] 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 at the same time are included in the scope of the invention described in the claims and equivalents thereof.

[0246] It should be noted that the above embodiments can be summarized into the following technical solutions.

[0247] (Technical Solution 1)

[0248] A method for manufacturing a secondary battery, comprising: a step of preparing a battery structure including a positive electrode, a negative electrode, and an electrolyte, wherein the positive electrode includes a compound represented by the general formula Li xNickel-containing oxide represented by M1O2, where M1 is a metal element containing at least 50% or more of Ni in terms of elemental ratio, and 0 < x ≤ 1, the negative electrode contains titanium-containing oxide, and the electrolyte contains a sulfur-containing compound; a step of obtaining a treatment potential adjustment state by adjusting the positive electrode potential of the above positive electrode to be within the range of 4.3V to 4.8V based on the redox potential of lithium and adjusting the negative electrode potential of the above negative electrode to be within the range of 0.5V to 1.1V based on the redox potential of lithium; and a step of maintaining the above battery structure in the above treatment potential adjustment state.

[0249] (Technical solution 2)

[0250] According to the above technical solution 1, wherein the step of maintaining the above battery structure in the above treatment potential adjustment state is carried out for 3 hours to 72 hours.

[0251] (Technical solution 3)

[0252] According to the above technical solution 1 or 2, wherein the step of maintaining the above battery structure in the above treatment potential adjustment state is carried out at a temperature of 60°C or lower.

[0253] (Technical solution 4)

[0254] According to any one of the above technical solutions 1 to 3, wherein the step of obtaining the above treatment potential adjustment state includes a step of charging the above battery structure at a constant current of 0.2C at 25°C.

[0255] (Technical solution 5)

[0256] According to the above technical solution 4, wherein the step of obtaining the above treatment potential adjustment state further includes, before the above 0.2C constant current charging: a step of charging the above battery structure at a constant current of 0.2C at 25°C to a battery voltage of 3V and then charging at a constant voltage of 3V; and a step of then discharging the above battery structure at a constant current of 0.2C at 25°C until the battery voltage reaches 1.5V.

[0257] (Technical solution 6)

[0258] According to any one of the above technical solutions 1 to 5, wherein the above sulfur-containing compound includes one or more selected from the group consisting of sultone compounds and imide compounds containing a sulfur atom.

[0259] (Technical solution 7)

[0260] According to the above-mentioned technical solution 6, the sulfur-containing compound includes at least the above-mentioned sulfonyl lactone compound, and the above-mentioned sulfonyl lactone compound includes one or more selected from the group consisting of 1,3-propanesulfonyl lactone, 1,3-propenesulfonyl lactone, 1,4-butanesulfonyl lactone and 2,4-butanesulfonyl lactone.

[0261] (Technical Solution 8)

[0262] According to the above technical solution 6 or 7, the sulfur-containing compound contains at least the above imide compound, and the imide compound contains one or more selected from the group consisting of lithium bis(trifluoromethanesulfonyl)imide and lithium bis(fluorosulfonyl)imide.

[0263] (Technical Solution 9)

[0264] According to any one of the above technical solutions 1 to 8, the concentration of the sulfur-containing compound in the electrolyte is 0.1% to 3% by mass relative to the electrolyte.

[0265] (Technical Solution 10)

[0266] According to any one of the above technical solutions 1 to 9, wherein the titanium-containing oxide contains a component selected from Li a Ti 1- b M1 b Nb 2-c M2 c O 7+δ The following are compounds: M1 is selected from at least one of the groups consisting of Zr, Si, and Sn; M2 is selected from at least one of the groups consisting of V, Ta, and Bi; 0 ≤ a ≤ 5; 0 ≤ b < 1; 0 ≤ c < 2; and -0.3 ≤ δ ≤ 0.3; and compounds with Li a Ti 1- b M3 b+c Nb 2-c O 7-δ M3 indicates that M3 is one or more monoclinic niobium-titanium composite oxides selected from the group consisting of at least one compound of Mg, Fe, Ni, Co, W, Ta, and Mo, 0≤a≤5, 0≤b<1, 0≤c<2, and -0.3≤δ≤0.3.

[0267] (Technical Solution 11)

[0268] A secondary battery is manufactured by any one of the manufacturing methods described in technical solutions 1 to 10 above.

Claims

1. A method for manufacturing a secondary battery, comprising: The process of preparing a battery structure having a positive electrode, a negative electrode, and an electrolyte, wherein the positive electrode comprises an electrolyte of the general formula Li x M1O2 represents a nickel-containing oxide, in which, M1 is a metal element containing at least 50% Ni in terms of elemental ratio, and 0 < x ≤ 1. The negative electrode contains a titanium-containing oxide, and the electrolyte contains a sulfur-containing compound; A step of obtaining a treatment potential adjustment state by adjusting the positive electrode potential of the positive electrode to be within the range of 4.3 V to 4.8 V based on the redox potential of lithium and adjusting the negative electrode potential of the negative electrode to be within the range of 0.5 V to 1.1 V based on the redox potential of lithium; and A step of maintaining the battery structure in the treatment potential adjustment state, The step of obtaining the treatment potential adjustment state includes: a step of charging the battery structure at a constant current of 0.2 C to a battery voltage of 3 V at 25°C and then charging at a constant voltage of 3 V; a step of discharging the battery structure at a constant current of 0.2 C to a battery voltage of 1.5 V at 25°C; and a step of further charging the battery structure at a constant current of 0.2 C at 25°C.

2. The method for manufacturing a secondary battery according to claim 1, wherein, The step of maintaining the battery structure in the treatment potential adjustment state is carried out for 3 hours to 72 hours.

3. The method for manufacturing a secondary battery according to claim 1 or 2, wherein, The step of maintaining the battery structure in the treatment potential adjustment state is carried out at a temperature of 60°C or lower.

4. The method for manufacturing a secondary battery according to claim 1 or 2, wherein, The sulfur-containing compound includes one or more selected from the group consisting of sultone compounds and imide compounds containing a sulfur atom.

5. The method for manufacturing a secondary battery according to claim 4, wherein, The sulfur-containing compound at least contains the sultone compound, and the sultone compound includes one or more selected from the group consisting of 1,3-propane sultone, 1,3-propene sultone, 1,4-butane sultone, and 2,4-butane sultone.

6. The method for manufacturing a secondary battery according to claim 4, wherein, The sulfur-containing compound at least contains the imide compound, and the imide compound includes one or more selected from the group consisting of lithium bis(trifluoromethanesulfonyl)imide and lithium bis(fluorosulfonyl)imide.

7. The method for manufacturing a secondary battery according to claim 1 or 2, wherein, The concentration of the sulfur-containing compound in the electrolyte is 0.1 mass% to 3 mass% relative to the electrolyte.

8. The method for manufacturing a secondary battery according to claim 1 or 2, wherein, The titanium-containing oxide contains a component selected from Li a Ti 1-b M1 b Nb 2-c M2 c O 7+δ The following compounds are defined as follows: M1 is selected from at least one of the groups consisting of Zr, Si, and Sn; M2 is selected from at least one of the groups consisting of V, Ta, and Bi; 0 ≤ a ≤ 5; 0 ≤ b < 1; 0 ≤ c < 2; and -0.3 ≤ δ ≤ 0.

3. a Ti 1-b M3 b+c Nb 2-c O 7-δ M3 indicates that M3 is one or more monoclinic niobium-titanium composite oxides selected from the group consisting of at least one compound of Mg, Fe, Ni, Co, W, Ta and Mo, 0≤a≤5, 0≤b<1, 0≤c<2, and -0.3≤δ≤0.

3.

9. A secondary battery manufactured by the manufacturing method according to any one of claims 1 to 8.

Images