Secondary battery, method for manufacturing the same, battery pack, and vehicle

Abstract

To provide a method for manufacturing a secondary battery having high output performance and durability, a secondary battery and a battery pack having high output performance and durability, and a vehicle mounted with the battery pack.SOLUTION: A method for manufacturing a secondary battery is provided including the steps of: preparing a secondary precursor including a positive electrode, a negative electrode, and an electrolyte; obtaining a processing potential adjustment state by adjusting negative electrode potential of the negative electrode within a range of 0.6 V or more and less than 1.5 V with oxidation-reduction potential of lithium as a reference; and holding the processing potential adjustment state at temperature of more than 60°C and 82°C or less.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] An embodiment of the present invention relates to a method for manufacturing a secondary battery, a secondary battery, a battery pack, and a vehicle. [Background technology]

[0002] In recent years, research and development of secondary batteries such as non-aqueous electrolyte secondary batteries, such as lithium ion secondary batteries, as high energy density batteries, has been actively promoted. Secondary batteries such as non-aqueous electrolyte secondary batteries are expected to be used as power sources for vehicles such as hybrid electric vehicles and electric vehicles, and for uninterruptible power sources for mobile phone base stations. Therefore, in addition to high energy density, secondary batteries are also required to have excellent other performances such as rapid charge and discharge performance and long-term reliability. For example, secondary batteries capable of rapid charge and discharge not only significantly reduce charging time, but also improve the power performance of vehicles such as hybrid electric vehicles and efficiently recover regenerative energy from power.

[0003] In order to enable rapid charging and discharging, it is necessary that electrons and lithium ions can move quickly between the positive and negative electrodes. However, when a battery using a carbon-based negative electrode is repeatedly charged and discharged rapidly, dendrites of metallic lithium are precipitated on the electrode, which may cause heat generation or fire due to an internal short circuit.

[0004] Therefore, batteries using metal composite oxides instead of carbonaceous materials for the anode have been developed. Oxide anodes ensure extremely high safety by completely suppressing lithium deposition due to their high operating potential. Among them, batteries using titanium oxide for the anode are capable of stable rapid charging and discharging, and have a longer life than batteries using carbon-based anodes.

[0005] For example, Li4Ti5O 12 Spinel-type lithium titanium oxide (TLO) is known as a strain-free material that does not expand or contract in volume during lithium insertion and desorption reactions. However, the theoretical capacity of TLO is only about 180 mAh / g, and its energy density is low.

[0006] Niobium titanium oxides such as Nb2TiO7 (TNO) have higher charge / discharge capacity than TLO, and their input performance (charging performance) is also higher than TLO. However, TNO tends to have the same or slightly lower output performance than TLO. In addition, TNO exhibits volumetric changes accompanying the insertion and desorption of lithium during charging and discharging, so TLO has an advantage in terms of cycle life performance. In detail, the volumetric changes cause cracks in the active material particles containing TNO, which breaks the electron conduction path in the negative electrode and reduces the proportion of the part of the negative electrode that participates in charging and discharging. In addition, the cracks increase the active surface of the active material particles, promoting side reactions between the active material and the electrolyte. This accelerates the formation of a coating on the negative electrode that inhibits the movement of lithium ions due to the decomposition of the electrolyte, and increases the internal resistance. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2015-92478 A [Patent Document 2] Patent Publication No. 2022-169205 [Patent Document 3] JP 2022-169208 A Summary of the Invention [Problem to be solved by the invention]

[0008] The present invention aims to provide a method for manufacturing a secondary battery that can obtain a secondary battery with high output performance and durability, a secondary battery and battery pack with high output performance and durability, and a vehicle equipped with this battery pack. [Means for solving the problem]

[0009] According to an embodiment, there is provided a method for producing a secondary battery, the method including the steps of: preparing a secondary battery precursor including a positive electrode, a negative electrode, and an electrolyte; adjusting the negative electrode potential of the negative electrode to within a range of 0.6 V or more and less than 1.5 V based on the oxidation-reduction potential of lithium to obtain a treated potential-adjusted state; and maintaining the treated potential-adjusted state at a temperature within a range of more than 60° C. and not more than 82° C.

[0010] According to another embodiment, there is provided a secondary battery manufactured by the manufacturing method according to the above embodiment.

[0011] According to yet another embodiment, there is provided a battery pack including the secondary battery according to the above embodiment.

[0012] According to yet another embodiment, a vehicle including the battery pack according to the above embodiment is provided. [Brief description of the drawings]

[0013] [Figure 1] FIG. 2 is a cross-sectional view illustrating an example of a secondary battery precursor according to the embodiment. [Diagram 2] FIG. 2 is an enlarged cross-sectional view of a portion A of the secondary battery precursor shown in FIG. [Diagram 3] FIG. 4 is a partially cutaway perspective view illustrating a schematic diagram of another example of a secondary battery precursor according to the embodiment. [Figure 4] 4 is an enlarged cross-sectional view of part B of the secondary battery precursor shown in FIG. 3. [Diagram 5] FIG. 4 is a cross-sectional view illustrating a secondary battery precursor according to an embodiment of the present invention; [Figure 6] 6 is a schematic cross-sectional view taken along line VI-VI of the secondary battery precursor shown in FIG. 5. [Figure 7] FIG. 1 is a perspective view illustrating an example of a battery pack according to an embodiment. [Figure 8] FIG. 1 is an exploded perspective view illustrating an example of a battery pack according to an embodiment. [Figure 9] 9 is a block diagram showing an example of an electric circuit of the battery pack shown in FIG. 8. [Figure 10]FIG. 1 is a partially see-through view illustrating an example of a vehicle according to an embodiment. [Figure 11] 1 is a diagram illustrating an example of a control system for an electrical system in a vehicle according to an embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Hereinafter, the embodiments will be described with reference to the drawings as appropriate. Note that the same reference numerals are used to designate common components throughout the embodiments, and duplicated descriptions will be omitted. Also, each figure is a schematic diagram for explaining the embodiments and for facilitating understanding thereof, and the shapes, dimensions, ratios, etc. may differ from those of the actual device, but these can be appropriately modified in design by taking into consideration the following explanation and known techniques.

[0015] Carboxymethyl cellulose (CMC) and styrene butadiene rubber (SBR) are known as binders to be included in electrodes. CMC is also used as a thickener in the slurry used to manufacture electrodes. In addition to its role as a binder for electrode components and a slurry thickener, CMC has been reported to have functions such as conformity to electrode active materials and prevention of side reactions. By applying an aqueous slurry containing CMC and SBR as binders to a TNO negative electrode, the cycle performance of the resulting battery is dramatically improved. Specifically, CMC and SBR exhibit high stress, and are therefore able to respond to some extent when the TNO shrinks.

[0016] Thus, in order to suppress the relatively large volume change accompanying the charge and discharge of niobium titanium oxide, it is effective to use a binder that is soluble or dispersible in water, such as CMC or SBR. However, when an aqueous slurry is used, gas generation during storage of the battery becomes significant. As a result of extensive investigation and research conducted by the inventors with great effort, it was found that when an aqueous slurry is prepared using such an oxide negative electrode, water molecules are adsorbed to the surface defects of the electrode active material. Furthermore, when the active material particles are refined for the purpose of improving the performance of the negative electrode, it is difficult to completely remove the moisture by a prior drying process. For example, moisture bound to the TNO surface defects in the -OH state is non-volatile, and therefore cannot be dried at a temperature within the heat resistance range of the binder.

[0017] If moisture is present in a non-aqueous electrolyte secondary battery, gas may be generated due to the moisture during operation of the battery. Examples of gases derived from moisture include hydrogen and oxygen. If a large amount of gas is generated in the battery, the battery will swell. In addition, if gas is present on the surface of the electrode active material, that part will not come into contact with the non-aqueous electrolyte, and the electrode reaction field will decrease. As a result, the current load of the remaining electrode interface will increase, and the battery resistance will increase.

[0018] As a means of preventing gas generation due to residual moisture from occurring during battery use, charging / discharging and aging processes are performed in advance during battery manufacture to remove the gas generated during these processes. For example, a battery container is temporarily sealed, charged to a specified state of charge (SOC), and aging is performed by holding the battery in that charged state for a certain period of time under a specific temperature environment. After that, the temporary seal is released in a vacuum environment to release the gas generated during aging, and then full sealing is performed again.

[0019] (First embodiment) According to a first embodiment, a method for manufacturing a secondary battery is provided. The manufacturing method includes the steps of preparing a secondary battery precursor, obtaining a treated potential adjustment state, and maintaining the secondary battery precursor in the treated potential adjustment state at a temperature in the range of more than 60°C and less than 82°C. The secondary battery precursor includes a positive electrode, a negative electrode, and an electrolyte. The treated potential adjustment state is obtained by adjusting the negative electrode potential of the negative electrode to a range of 0.6 V or more and less than 1.5 V based on the redox potential of lithium.

[0020] In this manufacturing method, the treatment of maintaining the secondary battery precursor in a treatment potential adjustment state at the above temperature corresponds to so-called aging. By aging under the above conditions, gas generation originating from water can be eliminated in the form of electrolysis of water or reductive decomposition of water and an organic solvent. Gas is generated in advance by promoting water decomposition by setting the potential of the negative electrode to a certain level or lower, and gas generation during subsequent storage is reduced by degassing. A part of the water decomposition reaction when propylene carbonate (PC) is included as an organic solvent in the electrolyte is shown below.

[0021] [ka]

[0022] [ka]

[0023] Therefore, according to this manufacturing method, it is possible to manufacture a secondary battery that exhibits high output performance and is excellent in life performance.

[0024] The process of adjusting the positive electrode potential and the negative electrode potential to the above range to obtain the treated potential adjustment state and the process of maintaining the treated potential adjustment state at the above-mentioned holding temperature are sometimes referred to as the "pretreatment" of the secondary battery to be manufactured. This pretreatment causes gas generation in advance during the secondary battery manufacturing stage, thereby reducing the amount of gas that may be generated during battery use. The gas generated in advance by the pretreatment is removed before the secondary battery manufacturing is completed.

[0025] The secondary battery precursor adjusted to the treatment potential adjustment state is held at a holding temperature of more than 60°C and not more than 82°C. By holding the temperature at a temperature higher than 60°C, the reaction that generates gas in advance, as exemplified above, can be promoted. This allows the effect to be obtained within a practical aging time. By holding the temperature at 82°C or lower, the reaction that generates undesirable by-products such as hydrogen fluoride (HF) can be suppressed. HF is, for example, PF6 - It is not preferable because it is generated by a side reaction between the anion of an electrolyte salt containing fluorine such as fluorine and water under high temperature conditions, and attacks the positive electrode and deteriorates the battery performance. The holding temperature is more preferably 65°C or higher and 81°C or lower, and even more preferably 70°C or higher and 80°C or lower.

[0026] The operating potential is the redox potential of metallic lithium (0 V vs. L / Li + It is known that in carbon-based anodes close to the oxidation-reduction potential of lithium (vs. L / Li), a solid electrolyte interlayer (SEI) film is formed that acts to protect the anode. The main component of the SEI film formed on carbon-based anodes is an alkoxide-based decomposition product derived from the electrolyte, but this component is thermally decomposable and decomposes at temperatures above 60°C. Therefore, maintaining a treatment potential adjustment state at temperatures above 60°C is more desirable for batteries using oxide-based anodes than for batteries using carbon-based anodes. More specifically, the potential of the anode is determined by the ratio of the oxidation-reduction potential of lithium (vs. L / Li + It is desirable to use a compound that is electrochemically stable in the range of 0.6 V to less than 1.5 V as the negative electrode active material. Since the formation of a thermally decomposable film is small in the negative electrode in this potential range, performance is not impaired even if the temperature exceeds 60°C. The more preferable range of treatment potential adjustment is 0.8 V to 1.4 V (vs. L / Li + ), and more preferably 1 V or more and 1.3 V or less (vs. L / Li + ).

[0027] The time for maintaining the treatment potential adjustment state is preferably 3 hours or more. From a practical viewpoint, the time for maintaining may be, for example, 72 hours or less. The time for maintaining is more preferably 6 hours or more and 48 hours or less, and even more preferably 18 hours or more and 36 hours or less.

[0028] The secondary battery precursor includes a positive electrode, a negative electrode, and an electrolyte. The positive electrode, the negative electrode, and the electrolyte will be described in detail below. The secondary battery precursor may further include a separator disposed between the positive electrode and the negative electrode. The negative electrode, the positive electrode, and the separator may constitute an electrode group. The electrolyte may be held in the electrode group.

[0029] The secondary battery precursor may further include an exterior member that houses the electrode group and the electrolyte.

[0030] Furthermore, the secondary battery precursor may further include a negative electrode terminal electrically connected to the negative electrode and a positive electrode terminal electrically connected to the positive electrode.

[0031] The secondary battery precursor can be prepared, for example, by housing a positive electrode, a negative electrode, and an electrolyte in an exterior member. A method for producing a positive electrode, a method for producing a negative electrode, and a method for preparing an electrolyte will be described later. It is desirable to prepare the secondary battery precursor in an inert atmosphere. By adopting an inert atmosphere, oxygen and carbon dioxide, which may be gas sources, can be avoided. It is desirable to prepare the positive and negative electrodes and adjust the electrolyte in an inert atmosphere. An example of the inert atmosphere is an argon atmosphere.

[0032] The form of the electrode group is not particularly limited, but may have, for example, a wound structure or a laminated structure.

[0033] An electrode group having a wound structure can be produced, for example, as follows: A positive electrode and a negative electrode are stacked with a separator between them to obtain a laminate of the positive electrode, the negative electrode, and the separator. After this laminate is wound, the resulting wound body is further pressed to produce a flat wound electrode group.

[0034] The electrode group having a laminated structure can be produced, for example, by laminating a positive electrode, a negative electrode, and a separator such that the separator is interposed between the positive electrode and the negative electrode. Here, a plurality of separators may be disposed between the positive electrode and the negative electrode, respectively, or a single separator may be folded, for example, zigzag, and the positive electrodes and the negative electrodes may be disposed alternately in the spaces formed by folding the separator.

[0035] The electrode group and the electrolyte are placed in an exterior member and temporarily sealed to prepare a secondary battery precursor. As the exterior member, for example, a container made of a laminate film or a metal container can be used, as described in detail below. The exterior member will be described in detail below.

[0036] When an exterior member made of a laminate film is used, the opening can be closed by, for example, heat sealing to perform temporary sealing. During temporary sealing, for example, a position outside the position where the main sealing is performed in the secondary battery as a manufactured product (a position closer to the opening edge) is closed by heat sealing.

[0037] When a metal container is used as an exterior member, for example, a liquid inlet for introducing an electrolyte provided on the outside of the container can be blocked with a sealing plug to perform temporary sealing. The liquid inlet can be provided on a lid of the metal container, such as a sealing plate. For example, a liquid electrolyte is poured into the metal container through the liquid inlet, and then a rubber plug is attached to the liquid inlet to perform temporary sealing.

[0038] The mode of temporary sealing is not limited to the above example.

[0039] It is desirable to dry the electrode group before carrying out temporary sealing. As mentioned above, in order to suppress the volume change of niobium titanium oxide and the like during charging and discharging, it is preferable to use a binder that is soluble or dispersible in water, such as CMC or SBR, in the negative electrode, but in that case, the amount of residual water may be large. In addition, when water is adsorbed on an electrode using fine active material particles, drying is difficult and the amount of residual water may be large. Specifically, even if drying is performed, the water content according to Karl Fischer moisture measurement at 200°C may be 250 ppm or more. Even if there is a lot of residual water at this point, if the negative electrode potential (vs. Li / Li) is reduced to 0.6 V or more and less than 1.5 V, which is below the decomposition potential of water, in pretreatment, the amount of residual water may be reduced. + ) at a temperature exceeding 60°C, the moisture is gasified and then released to the outside from the exterior member. In other words, water can be removed by high-temperature aging, which can be easily performed with a high-potential negative electrode such as an oxide-based negative electrode, so a large amount of residual water before aging can be tolerated.

[0040] Karl Fischer moisture content measurement can be performed as follows. A moist electrode sample is first fed into a thermal vaporizer using a nitrogen gas flow. The thermal vaporizer is preheated to 200°C, and the nitrogen gas flow is introduced into the measurement chamber of the Karl Fischer moisture content measurement device. The measurement is continued until the amount of moisture detected is the background amount or for a maximum of 5 minutes.

[0041] The negative electrode potential can be adjusted to the treatment potential adjustment state, for example, by subjecting the secondary battery precursor subjected to temporary sealing to an initial charge and discharge. Charge and discharge are performed so that an appropriate charge state is obtained so that the potentials of the positive electrode and the negative electrode are in the potential range in the above-mentioned treatment potential adjustment state. The charge state can be adjusted, for example, based on the battery voltage. The initial charge and discharge are performed to an appropriate charge state according to the active materials used in the positive electrode and the negative electrode and the design of each electrode, and the battery structure is brought into the treatment potential adjustment state. The battery structure may be brought into the treatment potential adjustment state by the initial charge, or the secondary battery precursor may be brought into the treatment potential adjustment state by, for example, the initial charge to a fully charged state (SOC 100%) followed by the initial discharge.

[0042] Alternatively, before assembling the secondary battery precursor, the positive electrode and the negative electrode can be charged and discharged separately to obtain a treated potential adjustment state. For example, a battery (e.g., a half cell) can be assembled using a positive electrode and a counter electrode made of lithium metal, and the positive electrode potential can be adjusted. Similarly, a battery (e.g., a half cell) can be assembled using a negative electrode and a counter electrode made of lithium metal, and the negative electrode potential can be adjusted. A secondary battery precursor in a treated potential adjustment state can be obtained by producing a secondary battery precursor using a positive electrode and a negative electrode each with an adjusted potential. For example, a negative electrode using a titanium-containing oxide as the negative electrode active material can be charged and discharged at a ratio of 10 mAhg -1 By charging to the above capacity, the voltage is 0.6 V or more and less than 1.5 V (vs. Li / Li + ) the negative electrode potential can be adjusted to within the range.

[0043] In the treatment potential adjustment state, it is preferable that the positive electrode potential of the positive electrode is adjusted to a range exceeding 3.9 V based on the redox potential of lithium. + ) when aging is performed, it is possible to remove the lithium carbonate adsorbed on the positive electrode by electrolysis or thermal reaction.

[0044] The charge and discharge for obtaining the treatment potential adjustment state is carried out, for example, at room temperature (for example, about 25° C.).

[0045] The obtained treated potential adjusted state is maintained at a temperature of more than 60°C and not more than 82°C. For example, the secondary battery precursor in the treated potential adjusted state is placed in a thermostatic chamber set at a temperature of more than 60°C and not more than 82°C. A temperature sensor may be connected to the surface of the secondary battery precursor for the purpose of managing and controlling the maintained temperature. After a certain time has passed, the secondary battery precursor is removed from the thermostatic chamber and cooled to, for example, room temperature.

[0046] The temperature and time conditions for maintaining the treated potential adjustment state are preferably set to conditions in which the voltage difference before and after the maintaining step is 100 mV to 300 mV. This voltage difference may be, for example, a difference between the charged state of the positive electrode and the charged state of the negative electrode caused by a reaction on the negative electrode, which may be expressed as a drop in battery voltage of 100 mV to 300 mV. By allowing the difference in the charged state to be dominant in this way, it is possible to limit the use of the low charged state region of the positive electrode, which has poor cycle performance.

[0047] The temporary seal is opened to release the gas generated by the pretreatment. After degassing, the exterior member is permanently sealed to obtain a secondary battery. For example, the secondary battery precursor is taken out of the thermostatic chamber and cooled to room temperature, and then the secondary battery precursor is placed in an inert atmosphere and the temporary seal is opened. A secondary battery can be obtained by permanently sealing the exterior member in a reduced pressure environment. Alternatively, a secondary battery can be obtained by permanently sealing the exterior member after the temporary seal is opened in a reduced pressure environment. The reduced pressure environment here refers to a vacuum state of, for example, about -90 kPa.

[0048] When a laminate film exterior member is used, the exterior member can be opened, for example, by cutting the exterior member at the position where the temporary sealing was performed, or by cutting off the temporarily sealed portion of the exterior member. The laminate film exterior member can be fully sealed, for example, by closing the opening caused by the opening by heat sealing. It is desirable to fully seal the exterior member at a position inside the position where the temporary sealing was performed (a position farther away from the opening edge).

[0049] When a metal container is used as an exterior member, it can be opened, for example, by removing the sealing plug used for temporary sealing. The metal container can be permanently sealed by welding, for example, a sealing plug made of a material that can be welded to the container to the opening (for example, the electrolyte injection port) created by unscrewing the plug.

[0050] After the treatment of holding at the holding temperature, the secondary battery may be adjusted to a charge state for shipment by charging and discharging. Charging and discharging to the shipping state may be performed, for example, before opening the temporary sealing and degassing, or after the secondary battery is fully sealed. After the fully sealed state, the capacity of the secondary battery may be confirmed by charging and discharging to confirm the quality of the product, and the secondary battery may be pre-charged and discharged.

[0051] A specific example will be described below. Here, an example will be described in which a laminate pack is used as an exterior member made of a laminate film.

[0052] An electrode group is prepared using a positive electrode and a negative electrode, and the electrode group is housed in a laminate pack. An electrolyte is injected into the laminate pack under an argon atmosphere, and then a temporary seal is applied by heat fusion under reduced pressure. An initial charge and discharge is performed, and the battery voltage is set to a predetermined voltage to adjust the potential of the positive and negative electrodes. The secondary battery precursor with the electrode potential adjusted is placed in a thermostatic chamber at a predetermined temperature, and after a certain period of time, it is removed from the thermostatic chamber and placed again in an argon atmosphere. The top of the laminate pack is opened, and the laminate pack is heat fused again under reduced pressure at a portion closer to the inside to perform a permanent seal.

[0053] The positive electrode, the negative electrode, the electrolyte, the separator, the exterior member, the negative electrode terminal, and the positive electrode terminal will be described in detail below.

[0054] 1) Positive electrode The positive electrode may include a positive electrode current collector and a positive electrode active material-containing layer. The positive electrode active material-containing layer may be formed on one side or both sides of the positive electrode current collector. The positive electrode active material-containing layer may optionally include a conductive agent and a binder in addition to the positive electrode active material.

[0055] As the positive electrode active material, for example, an oxide or a sulfide can be used. The positive electrode may contain one type of compound alone as the positive electrode active material, or may contain two or more types of compounds in combination. Examples of oxides and sulfides include compounds that can insert and remove Li or Li ions.

[0056] Examples of such compounds include, for example, manganese dioxide (MnO2), iron oxide, copper oxide, nickel oxide, lithium manganese composite oxide (for example, Li x represented by Mn2O4 or LixMnO2, where 0 < x ≦ 1), lithium nickel composite oxide (for example, Li x represented by NiO2, where 0 < x ≦ 1), lithium cobalt composite oxide (for example, Li x represented by CoO2, where 0 < x ≦ 1), lithium nickel cobalt composite oxide (for example, Li x Ni 1-y Co y represented by O2, where 0 < x ≦ 1 and 0 < y < 1), lithium manganese cobalt composite oxide (for example, Li x Mn y Co 1-y represented by O2, where 0 < x ≦ 1 and 0 < y < 1), lithium manganese nickel composite oxide having a spinel structure (for example, Li x Mn 2-y Ni y represented by O4, where 0 < x ≦ 1 and 0 < y < 2), lithium phosphate having an olivine structure (for example, Li x represented by FePO4, where 0 < x ≦ 1; Li x Fe 1-y Mn y represented by PO4, where 0 < x ≦ 1 and 0 < y ≦ 1; Li x represented by CoPO4, where 0 < x ≦ 1), iron sulfate (Fe2(SO4)3), and vanadium oxide (for example, V2O5) and lithium nickel cobalt manganese composite oxide (Li x Ni 1-y-z Co y Mn z O2; 0 < x ≦ 1, 0 < y < 1, 0 < z < 1, y + z < 1) are included.

[0057] Among the above, examples of more preferable compounds as the positive electrode active material include lithium manganese composite oxide having a spinel structure (for example, Li x Mn2O4; 0 < x ≦ 1), lithium nickel composite oxide (for example, Li xNiO2; 0 < x ≤ 1), lithium cobalt composite oxide (e.g., Li x CoO2; 0 < x ≤ 1), lithium nickel cobalt composite oxide (e.g., Li x Ni 1-y Co y O2; 0 < x ≤ 1, 0 < y < 1), lithium manganese nickel composite oxide having a spinel structure (e.g., Li x Mn 2-y Ni y O4; 0 < x ≤ 1, 0 < y < 2), lithium manganese cobalt composite oxide (e.g., Li x Mn y Co 1-y O2; 0 < x ≤ 1, 0 < y < 1), lithium iron phosphate (e.g., Li x FePO4; 0 < x ≤ 1), and lithium nickel cobalt manganese composite oxide (Li x Ni 1-y-z Co y Mn z O2; 0 < x ≤ 1, 0 < y < 1, 0 < z < 1, y + z < 1) are included. When these compounds are used as the positive electrode active material, the positive electrode potential can be increased.

[0058] When a room temperature molten salt is used 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 x VPO4F where 0 ≤ x ≤ 1, a lithium manganese composite oxide, a lithium nickel composite oxide, a lithium nickel cobalt composite oxide, or a mixture thereof. Since these compounds have low reactivity with the room temperature molten salt, the cycle life can be improved. Details of the room temperature molten salt will be described later.

[0059] The primary particle size of the positive electrode active material is preferably 100 nm or more and 1 μm or less. 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 10 μm or less can allow the solid-state diffusion of lithium ions to proceed smoothly.

[0060] The specific surface area of the positive electrode active material is 0.1 m 2 / g or more and 10 m 2 / g or less. 2 A positive electrode active material having a specific surface area of ​​10m / g or more can secure sufficient sites for absorbing and releasing Li ions. 2 A positive electrode active material having a specific surface area of ​​100 / g or less is easy to handle in industrial production and can ensure good charge-discharge cycle performance.

[0061] The binder is blended to fill the gaps between the dispersed positive electrode active material and to bind the positive electrode active material and the positive electrode current collector. Examples of the binder include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdFPVdF), fluorine-based rubber, polyacrylic acid compounds, imide compounds, carboxymethyl cellulose (CMC), and salts of CMC. One of these may be used as the binder, or two or more may be used in combination as the binder.

[0062] The conductive agent is blended to improve the current collecting performance of the positive electrode active material and to reduce the contact resistance between the positive electrode active material and the positive electrode current collector. Examples of the conductive agent include carbonaceous materials such as vapor grown carbon fiber (VGCF), carbon black such as acetylene black, graphite, carbon fiber, graphene, carbon nanotube, carbon nanofiber, and fullerene. One of these may be used as the conductive agent, or two or more may be combined and used as the conductive agent. The conductive agent may also be omitted.

[0063] In the positive electrode active material-containing layer, the positive electrode active material and the binder are preferably mixed in proportions of 80% by mass to 98% by mass and 2% by mass to 20% by mass, respectively.

[0064] By making the amount of binder 2% by mass or more, sufficient electrode strength can be obtained. In addition, the binder can function as an insulator. Therefore, by making the amount of binder 20% by mass or less, the amount of insulator contained in the electrode is reduced, and the internal resistance can be reduced.

[0065] When a conductive agent is added, the positive electrode active material, the binder, and the conductive agent are preferably mixed in proportions of 77% by mass or more and 95% by mass or less, 2% by mass or more and 20% by mass or less, and 3% by mass or more and 15% by mass or less, respectively.

[0066] By setting the amount of the conductive agent to 3% by mass or more, the above-mentioned effects can be achieved. Also, by setting the amount of the conductive agent to 15% by mass or less, the ratio of the conductive agent in contact with the electrolyte can be reduced. If this ratio is low, decomposition of the electrolyte during high-temperature storage can be reduced.

[0067] The positive electrode current collector is preferably an aluminum foil or an aluminum alloy foil containing one or more elements selected from Mg, Ti, Zn, Ni, Cr, Mn, Fe, Cu, and Si.

[0068] The thickness of the aluminum foil or aluminum alloy foil is preferably 5 μm or more and 20 μm or less, more preferably 15 μm or less. The purity of the aluminum foil is preferably 99 mass% or more. The content of transition metals such as iron, copper, nickel, and chromium contained in the aluminum foil or aluminum alloy foil is preferably 1 mass% or less.

[0069] The positive electrode current collector may also include a portion on the surface of which the positive electrode active material-containing layer is not formed, and this portion can function as a positive electrode current collecting tab.

[0070] The positive electrode can be produced, for example, by the following method. First, a positive electrode active material, a conductive agent, and a binder are suspended in a solvent to prepare a slurry. This slurry is applied to one or both sides of a positive electrode current collector. Next, the applied slurry is dried to obtain a laminate of a positive electrode active material-containing layer and a current collector. Then, the laminate is pressed. In this manner, a positive electrode is produced.

[0071] Alternatively, the positive electrode may be prepared by the following method: First, a positive electrode active material, a conductive agent, and a binder are mixed to obtain a mixture. Then, the mixture is formed into pellets. Then, the pellets are placed on a positive electrode current collector to obtain a positive electrode.

[0072] 2) Negative electrode The negative electrode may include a negative electrode current collector and a negative electrode active material-containing layer. The negative electrode active material-containing layer may be formed on one side or both sides of the negative electrode current collector. The negative electrode active material-containing layer may optionally include a conductive agent and a binder in addition to the negative electrode active material.

[0073] The negative electrode active material includes, for example, a metal oxide. Examples of metal oxides that can be used as the active material include lithium titanate having a ramsdellite structure (e.g., Li 2+y Ti3O7, 0≦y≦3), lithium titanates with spinel structure (e.g., Li 4+x Ti5O 12 , 0≦x≦3), titanium dioxide (TiO2), anatase type titanium dioxide, rutile type titanium dioxide, niobium pentoxide (Nb2O5), hollandite type titanium composite oxide, orthorhombic titanium composite oxide, monoclinic type niobium titanium oxide, and niobium composite oxide.

[0074] The negative electrode preferably contains a niobium-containing oxide as the negative electrode active material. The niobium-containing oxide includes niobium titanium oxide and niobium composite oxide. The crystal structure of the niobium titanium oxide may be, for example, monoclinic. When the negative electrode active material contains monoclinic niobium titanium oxide, it is possible to achieve high rate performance in addition to excellent energy density. The reason for this is explained using Nb2TiO7, a type of monoclinic niobium titanium oxide, as an example. The crystal structure of Nb2TiO7 has a large equivalent insertion space for lithium ions and is structurally stable, and further has a region having a two-dimensional channel through which lithium ions diffuse quickly and a conduction path in the

[0001] direction connecting them. As a result, in the crystal structure of the monoclinic niobium titanium oxide Nb2TiO7, the insertion and desorption property of lithium ions into the insertion space is improved, and the insertion and desorption space of lithium ions is effectively increased. This makes it possible to provide high capacity and high rate performance.

[0075] An example of monoclinic niobium titanium oxide is Li x Ti 1-y M1 y Nb 2-z M2 c O 7+δ Here, 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≦x≦5, 0≦y<1, 0≦z<2, and -0.3≦δ≦0.3. Specific examples of monoclinic niobium titanium oxide include Li x Examples include Nb2TiO7 (0≦x≦5).

[0076] Another example of monoclinic niobium titanium oxide is Li x Ti 1-y M3 y+z Nb 2-z O 7-δHere, M3 is at least one selected from the group consisting of Mg, Fe, Ni, Co, W, Ta, and Mo. The subscripts in the composition formula are 0≦x≦5, 0≦y<1, 0≦z<2, and -0.3≦δ≦0.3.

[0077] Specific examples of niobium titanium oxide include, for example, Nb2TiO7, Nb2Ti2O9, and Nb 10 Ti2O 29 , Nb 14 TiO 37 and Nb 24 TiO 62 The niobium titanium oxide may be a substituted niobium titanium oxide in which at least a part of Nb and / or Ti is substituted with a different element. Examples of the substituted element include Na, K, Ca, Co, Ni, Si, P, V, Cr, Mo, Ta, Zr, Mn, Fe, Mg, B, Pb, and Al. The substituted niobium titanium oxide may contain one type of substituted element, or may contain two or more types of substituted elements.

[0078] The niobium titanium oxide may include titanium niobium oxide having an orthorhombic crystal structure. An example of an orthorhombic titanium niobium oxide is Li 2+v Na 2-w M4 b Ti 6-c-d Nb c M5 d O 14+σ Examples of compounds represented by the general formula Li 2+v Na 2-w M4 b Ti 6-c-d Nb c M5 d O 14+σwhere the subscript v is in the range of 0 ≦ v ≦ 4, the subscript w is in the range of 0 < w < 2, the subscript b is in the range of 0 ≦ b < 2, the subscript c is in the range of 0 < c < 6, the subscript d is in the range of 0 ≦ d < 3, the sum of the subscript c and the subscript d is in the range of 0 < c + d < 6, and the subscript σ is in the range of -0.5 ≦ σ ≦ 0.5. The element M4 is at least one selected from the group consisting of Cs, K, Sr, Ba, and Ca. The element M5 is at least one selected from the group consisting of Zr, Sn, V, Ta, Mo, W, Fe, Mn, and Al.

[0079] The niobium titanate may have an element ratio of niobium to other elements deviated from the theoretical value with respect to the above composition formula or general formula.

[0080] The negative electrode active material may contain one of the above niobium-containing oxides alone, or may contain a combination of two or more of the above.

[0081] In addition to the niobium-containing oxide, the negative electrode active material can further contain other compounds. Here, for convenience, the niobium-containing oxide is referred to as the first negative electrode active material, and other compounds as the negative electrode active material are referred to as the second negative electrode active material, respectively. The negative electrode active material can contain one or more first negative electrode active materials and one second negative electrode active material together, or can contain one or more first negative electrode active materials and two or more second negative electrode active materials together. The negative electrode active material contains the first negative electrode active material (niobium-containing oxide) at a ratio of, for example, 70% by mass or more, preferably 90% by mass or more. The negative electrode active material may contain only the first negative electrode active material (niobium-containing oxide). Alternatively, the negative electrode active material may contain only the second negative electrode active material.

[0082] Examples of the second negative electrode active material include the metal oxides exemplified above other than the niobium-containing oxide. The metal oxides other than the niobium-containing oxide include orthorhombic titanium oxides other than the above-described orthorhombic titanium niobate oxide.

[0083] As an example of an orthorhombic titanium oxide other than the orthorhombic titanium niobium oxide, Li 2+a M I 2-b Ti 6-c M II d O 14+σ In this case, the compound represented by M I is at least one selected from the group consisting of Sr, Ba, Ca, Mg, Na, Cs, Rb and K. II is at least one selected from the group consisting of Zr, Sn, V, Ta, Mo, W, Y, Fe, Co, Cr, Mn, Ni, and Al. The subscripts in the composition formula are 0≦a≦6, 0≦b<2, 0≦c<6, 0≦d<6, and -0.5≦σ≦0.5. Specific examples of orthorhombic titanium oxide include Li 2+a Na2Ti6O 14 (0≦a≦6).

[0084] The negative electrode active material may be contained in the negative electrode active material-containing layer in the form of particles. The negative electrode active material particles may be in the form of primary particles or secondary particles formed by agglomeration of primary particles. The negative electrode active material particles may be a mixture of primary particles and secondary particles.

[0085] The conductive agent is blended to improve the current collecting performance and to suppress the contact resistance between the active material and the current collector. Examples of the conductive agent include carbonaceous materials such as vapor grown carbon fiber (VGCF), carbon black such as acetylene black, graphite, carbon nanotubes and carbon nanofibers. One of these may be used as the conductive agent, or two or more may be used in combination as the conductive agent. Alternatively, instead of using the conductive agent, a carbon coat or an electronically conductive inorganic material coat may be applied to the surface of the active material particles. In addition, the current collecting performance of the active material-containing layer can be improved by using the conductive agent and coating the active material surface with carbon or a conductive material.

[0086] The binder is blended to fill the gaps between the dispersed active materials and to bind the negative electrode active material and the negative electrode current collector. The negative electrode desirably contains a material that can be dissolved or dispersed in water as a binder. Examples of such binders include styrene butadiene rubber, carboxymethyl cellulose (CMC), salts of CMC, polyacrylic acid, polymers of polyacrylic acid, and acrylic rubber. One of these may be used as the binder, or two or more may be used in combination as the binder.

[0087] In the negative electrode active material-containing layer, the negative electrode active material, the conductive agent, and the binder are preferably contained in a ratio of 70% by mass or more and 96% by mass or less, 2% by mass or more and 28% by mass or less, and 2% by mass or more and 28% by mass or less, respectively. By making the amount of the conductive agent 2% by mass or more, the current collection performance of the negative electrode active material-containing layer can be improved. Also, by making the amount of the binder 2% by mass or more, the binding property between the negative electrode active material-containing layer and the current collector becomes sufficient, and excellent cycle performance can be expected. On the other hand, it is preferable to make the conductive agent and the binder 28% by mass or less, respectively, in order to increase the capacity.

[0088] The density of the negative electrode active material-containing layer (excluding the current collector) is 1.8 g / cm 3 More than 2.8g / cm 3 A negative electrode having a density of the negative electrode active material-containing layer within this range is excellent in energy density and electrolyte retention. The density of the negative electrode active material-containing layer is preferably 2.1 g / cm or less. 3 More than 2.6g / cm 3 It is more preferable that:

[0089] The negative electrode current collector is made of a material that is electrochemically stable at a potential at which lithium (Li) is inserted into and removed from the negative electrode active material. 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 or more and 20 μm or less. A negative electrode current collector having such a thickness can balance the strength and weight reduction of the negative electrode.

[0090] The negative electrode current collector may also include a portion on the surface of which the negative electrode active material-containing layer is not formed, and this portion can function as a current collecting tab.

[0091] The negative electrode can be produced, for example, by the following method. First, a negative electrode active material, a conductive agent, and a binder are suspended in a solvent to prepare a slurry. This slurry is applied to one or both sides of a negative electrode current collector. Next, the applied slurry is dried to obtain a laminate of a negative electrode active material-containing layer and a current collector. Then, this laminate is pressed. In this manner, a negative electrode is produced.

[0092] Alternatively, the negative electrode may be prepared by the following method: First, the negative electrode active material, the conductive agent, and the binder are mixed to obtain a mixture, and then the mixture is molded into pellets. The pellets are then placed on a negative electrode current collector to obtain a negative electrode.

[0093] 3) Electrolyte As the electrolyte, for example, a liquid nonaqueous electrolyte or a gel nonaqueous electrolyte can be used. The liquid nonaqueous electrolyte is prepared by dissolving an electrolyte salt as a solute in a liquid solvent such as an organic solvent. The concentration of the electrolyte salt is preferably 0.5 mol / L or more and 2.5 mol / L or less.

[0094] Examples of the electrolyte salt include lithium salts such as lithium perchlorate (LiClO4), lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium hexafluoroarsenate (LiAsF6), and lithium bistrifluoromethylsulfonylimide (LiN(CF3SO2)2), and mixtures thereof. The electrolyte salt is preferably one that is difficult to oxidize even at high potentials, and LiPF6 is most preferred.

[0095] 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). These organic solvents can be used alone or as a mixed solvent.

[0096] The electrolyte may contain further additives in addition to the electrolyte salt. For example, at least one selected from the group consisting of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI; LiN(SO2CF3)2), lithium bis(fluorosulfonyl)imide (LiFSI; LiN(SO2F)2), lithium difluorophosphate (LiDFP; LiPO2F2), lithium difluorooxalatoborate (LiDFOB; LiBF2(C2O4)), lithium bisoxalatoborate (LiBOB; LiB[(OCO)2]2), and lithium triflate (LiOtF; LiCF3SO3, also known as lithium trifluoromethanesulfonate) may be contained in the electrolyte. These additives have high temperature resistance and are not easily deteriorated even when held at high temperatures in the above-mentioned pretreatment. In addition, these additives can generate an effective coating by reacting with water or by electrochemical decomposition. Specifically, they can consume electric charge to form a SEI (Solid Electrolyte Interlayer) protective coating. Therefore, by adding the additive to the electrolyte, a protective film can be formed on the positive electrode and / or negative electrode during pretreatment. By covering at least a part of the active material surface of the electrode with such a protective film, the active material surface 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 life performance can be exhibited even in a high temperature environment.

[0097] The gelled non-aqueous electrolyte is prepared by combining a liquid non-aqueous electrolyte with a polymeric material, such as polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), polyethylene oxide (PEO), or a mixture thereof.

[0098] Alternatively, as the nonaqueous electrolyte, in addition to liquid nonaqueous electrolytes and gel nonaqueous electrolytes, room temperature molten salts containing lithium ions (ionic melts), polymer solid electrolytes, inorganic solid electrolytes, and the like may be used.

[0099] Room temperature molten salts (ionic melts) refer to organic salts consisting of a combination of organic cations and anions that can exist as a liquid at room temperature (15°C or higher and 25°C or lower). Room temperature molten salts include room temperature molten salts that exist as a liquid by themselves, room temperature molten salts that become liquid when mixed with an electrolyte salt, room temperature molten salts that become liquid when dissolved in an organic solvent, and mixtures of these. In general, the melting point of room temperature molten salts used in secondary batteries is 25°C or lower. In addition, organic cations generally have a quaternary ammonium skeleton.

[0100] The polymer solid electrolyte is prepared by dissolving an electrolyte salt in a polymer material and solidifying it.

[0101] The inorganic solid electrolyte is a solid substance that has Li-ion conductivity. Here, Li-ion conductivity is defined as a Li-ion conductivity of 1×10 -6 It means that the inorganic solid electrolyte has a lithium ion conductivity of 1.0 S / cm or more. Examples of the inorganic solid electrolyte include oxide-based solid electrolytes and sulfide-based solid electrolytes. Specific examples of the inorganic solid electrolyte are as follows.

[0102] The oxide-based solid electrolyte has a NASICON (Sodium (Na) Super Ionic Conductor) type structure and is represented by the general formula Li 1+x It is preferable to use a lithium phosphate solid electrolyte represented by Mα2(PO4)3. In the above general formula, Mα is, for example, one or more selected from the group consisting of titanium (Ti), germanium (Ge), strontium (Sr), zirconium (Zr), tin (Sn), aluminum (Al), and calcium (Ca). The subscript x is within the range of 0≦x≦2.

[0103] A specific example of a lithium phosphate solid electrolyte having a NASICON structure is Li 1+x Al x Ti 2-x LATP compound represented by (PO4)3, where 0.1≦x≦0.5; Li 1+x Al y Mβ 2-yA compound represented by (PO4)3, where Mβ is one or more selected from the group consisting of Ti, Ge, Sr, Zr, Sn, and Ca, 0 ≦ x ≦ 1, and 0 ≦ y ≦ 1; Li 1+x Al x Ge 2-x A compound represented by (PO4)3, where 0 ≦ x ≦ 2; and, Li 1+x Al x Zr 2-x A compound represented by (PO4)3, where 0 ≦ x ≦ 2; Li 1+x+y Al x Mγ 2-x Si y P 3-y O 12 A compound represented by, where Mγ is one or more selected from the group consisting of Ti and Ge, 0 < x ≦ 2, and 0 ≦ y < 3; Li 1+2x Zr 1-x Ca x Examples of the compound represented by (PO4)3, where 0 ≦ x < 1, can be given.

[0104] In addition, as the oxide-based solid electrolyte, in addition to the above lithium phosphate solid electrolyte, Li x PO y N z An amorphous LIPON compound represented by, where 2.6 ≦ x ≦ 3.5, 1.9 ≦ y ≦ 3.8, and 0.1 ≦ z ≦ 1.3 (for example, Li 2.9P O 3.3 N 0.46 ); A garnet-type structure La 5+x A x La 3-x Mδ2O 12 A compound represented by, where A is one or more selected from the group consisting of Ca, Sr, and Ba, Mδ is one or more selected from the group consisting of Nb and Ta, and 0 ≦ x ≦ 0.5; Li3Mδ 2-x L2O 12 A compound represented by, where Mδ is one or more selected from the group consisting of Nb and Ta, L may contain Zr, and 0 ≦ x ≦ 0.5; Li 7-3x Al x La3Zr3O 12 A compound represented by, where 0 ≦ x ≦ 0.5; Li 5+x La3Mδ 2-x Zr x O 12where Mδ is at least one selected from the group consisting of Nb and Ta, and 0≦x≦2. LLZ compounds (e.g., Li7La3Zr2O 12 ); and La 2 / 3-x Li x Examples of such compounds include those represented by TiO3, where x is 0.3≦x≦0.7.

[0105] One or more of the above compounds can be used as the solid electrolyte. Two or more of the above solid electrolytes can also be used.

[0106] 4) Separator The separator is formed, for example, from a porous film containing polyethylene (PE), polypropylene (PP), cellulose, or polyvinylidene fluoride (PVdF), or a synthetic resin nonwoven fabric. From the viewpoint of safety, it is preferable to use a porous film formed from polyethylene or polypropylene. This is because these porous films melt at a certain temperature and are capable of cutting off electric current.

[0107] 5) Exterior materials As the exterior member, for example, a container made of a laminate film or a metal container can be used.

[0108] The thickness of the laminate film is, for example, 0.5 mm or less, preferably 0.2 mm or less.

[0109] The laminate film is a multi-layer film including a plurality of resin layers and a metal layer interposed between the resin layers. The resin layers include polymeric materials such as polypropylene (PP), polyethylene (PE), nylon, and polyethylene terephthalate (PET). The metal layer is preferably made of aluminum foil or aluminum alloy foil for weight reduction. The laminate film can be molded into the shape of the exterior member by sealing it by heat fusion.

[0110] 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.

[0111] The metal container is made of, for example, aluminum or an aluminum alloy. The aluminum alloy preferably contains elements such as magnesium, zinc, and silicon. When the aluminum alloy contains transition metals such as iron, copper, nickel, and chromium, the content of the transition metals is preferably 100 ppm by mass or less.

[0112] The shape of the exterior member is not particularly limited. The shape of the exterior member may be, for example, flat (thin), rectangular, cylindrical, coin-shaped, or button-shaped. The exterior member can be appropriately selected depending on the battery dimensions and the application of the battery.

[0113] 6) Negative terminal The negative electrode terminal can be made of a material that is electrochemically stable at the Li absorption / release potential of the negative electrode active material and has electrical conductivity. Specifically, the material of the negative electrode terminal can be copper, nickel, stainless steel, aluminum, or an aluminum alloy containing at least one element selected from the group consisting of Mg, Ti, Zn, Mn, Fe, Cu, and Si. The material of the negative electrode terminal is preferably aluminum or an aluminum alloy. The negative electrode terminal is preferably made of the same material as the negative electrode current collector in order to reduce the contact resistance with the negative electrode current collector.

[0114] 7) Positive terminal The positive electrode terminal has a potential range of 3V to 4.5V with respect to the redox potential of lithium (vs. Li / Li + ) and can be formed from a material that is electrically stable and conductive. Examples of the material for the positive electrode terminal include aluminum and an aluminum alloy containing at least one element selected from the group consisting of Mg, Ti, Zn, Mn, Fe, Cu, and Si. The positive electrode terminal is preferably formed from the same material as the positive electrode current collector in order to reduce the contact resistance with the positive electrode current collector.

[0115] <Powder X-ray diffraction> The crystal structure of the compound contained as the active material can be confirmed by powder X-ray diffraction (XRD: X-Ray diffraction). For example, a Rigaku SmartLab or an equivalent device is used as the powder X-ray diffraction measurement device. The measurement conditions are as follows: X-ray source: Cu target Output: 45kV 200mA Soller slit: 5° for both incidence and reception Step width (2θ): 0.02 deg Scan speed: 20deg / min Semiconductor detector: D / teX Ultra 250 Sample plate holder: Flat glass sample plate holder (thickness 0.5 mm) Measurement range: 5°≦2θ≦90°.

[0116] Next, the secondary battery precursor used in the method for producing a secondary battery according to the embodiment will be described more specifically with reference to the drawings.

[0117] Fig. 1 is a cross-sectional view showing an example of a secondary battery precursor in a simplified manner, and Fig. 2 is an enlarged cross-sectional view of part A of the secondary battery precursor shown in Fig. 1.

[0118] A secondary battery precursor 100 shown in Figures 1 and 2 includes a bag-shaped exterior member 2 shown in Figure 1, an electrode group 1 shown in Figures 1 and 2, and an electrolyte (not shown). The electrode group 1 and the electrolyte are stored in the bag-shaped exterior member 2. The electrolyte (not shown) is held in the electrode group 1.

[0119] The bag-shaped exterior member 2 is made of a laminate film including two resin layers and a metal layer interposed between them.

[0120] As shown in Fig. 1, the electrode group 1 is a flat wound-type electrode group. As shown in Fig. 2, the flat wound-type electrode group 1 includes a negative electrode 3, a separator 4, and a positive electrode 5. The separator 4 is interposed between the negative electrode 3 and the positive electrode 5.

[0121] The negative electrode 3 includes a negative electrode current collector 3a and a negative electrode active material-containing layer 3b. In the negative electrode 3, in a portion located at the outermost shell of the wound-type electrode group 1, the negative electrode active material-containing layer 3b is formed only on the inner surface side of the negative electrode current collector 3a as shown in Fig. 2. In the other portions 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.

[0122] The positive electrode 5 includes a positive electrode current collector 5a and a positive electrode active material-containing layer 5b formed on both sides of the positive electrode current collector 5a.

[0123] As shown in Fig. 1, the negative electrode terminal 6 and the positive electrode terminal 7 are located near the outer peripheral end of the wound electrode group 1. The negative electrode terminal 6 is connected to a portion located at the outermost shell of the negative electrode current collector 3a. The positive electrode terminal 7 is connected to a portion located at the outermost shell of the positive electrode current collector 5a. The negative electrode terminal 6 and the positive electrode terminal 7 extend to the outside from an opening of the bag-shaped exterior member 2.

[0124] A thermoplastic resin layer is provided on the inner surface of the bag-shaped exterior member 2, and the opening of the bag-shaped exterior member 2 is closed by heat sealing. In both the temporary sealing performed before the treatment for holding the secondary battery precursor 100 in a state in which the electrode potential has been adjusted and the main sealing performed after the treatment and degassing, the opening of the bag-shaped exterior member 2 is closed by, for example, heat sealing. The position at which heat sealing is performed during temporary sealing is, for example, closer to the opening end than the position at which heat sealing is performed in the main sealing.

[0125] The liquid electrolyte may be injected from the opening of the bag-shaped exterior member 2 before the temporary sealing is performed, for example. For example, the opening of the bag-shaped exterior member 2 is closed by heat sealing except for a part, and the liquid electrolyte is injected through the part that is not heat sealed. Then, the part into which the electrolyte has been injected is closed by heat sealing to perform the temporary sealing.

[0126] The secondary battery precursor according to the embodiment is not limited to the secondary battery precursor having the configuration shown in FIGS. 1 and 2, and may be, for example, the one having the configuration shown in FIGS.

[0127] Fig. 3 is a partially cutaway perspective view showing a schematic diagram of another example of a secondary battery precursor according to an embodiment of the present invention Fig. 4 is an enlarged cross-sectional view of part B of the secondary battery precursor shown in Fig. 3 .

[0128] A secondary battery precursor 100 shown in Figures 3 and 4 includes an electrode group 1 shown in Figures 3 and 4, an exterior member 2 shown in Figure 3, and an electrolyte (not shown). The electrode group 1 and the electrolyte are housed in the exterior member 2. The electrolyte is held in the electrode group 1.

[0129] The exterior member 2 is made of a laminate film including two resin layers and a metal layer interposed between them.

[0130] The electrode group 1 is a laminated type electrode group, as shown in Fig. 4. The laminated type electrode group 1 has a structure in which negative electrodes 3 and positive electrodes 5 are alternately laminated with separators 4 interposed therebetween.

[0131] The electrode group 1 includes a plurality of negative electrodes 3. Each of the plurality of negative electrodes 3 includes a negative electrode current collector 3a and a negative electrode active material-containing layer 3b supported on both sides of the negative electrode current collector 3a. The electrode group 1 also includes a plurality of positive electrodes 5. Each of the plurality of positive electrodes 5 includes a positive electrode current collector 5a and a positive electrode active material-containing layer 5b supported on both sides of the positive electrode current collector 5a.

[0132] The negative electrode current collector 3a of each negative electrode 3 includes a portion on one side where the negative electrode active material-containing layer 3b is not supported on any surface. This portion serves as a negative electrode current collector tab 3c. As shown in FIG. 4, the negative electrode current collector tab 3c does not overlap with the positive electrode 5. The negative electrode current collector tabs 3c are electrically connected to a belt-shaped negative electrode terminal 6. The tip of the belt-shaped negative electrode terminal 6 is pulled out to the outside of the exterior member 2.

[0133] Although not shown, the positive electrode current collector 5a of each positive electrode 5 includes a portion on one side where the positive electrode active material-containing layer 5b is not supported on any surface. This portion serves as a positive electrode current collector tab. The positive electrode current collector tab does not overlap with the negative electrode 3, similar to the negative electrode current collector tab 3c. The positive electrode current collector tab is located on the opposite side of the electrode group 1 to the negative electrode current collector tab 3c. The positive electrode current collector tab is electrically connected to a strip-shaped positive electrode terminal 7. The tip of the strip-shaped positive electrode terminal 7 is located on the opposite side of the negative electrode terminal 6 and is drawn out to the outside of the exterior member 2.

[0134] Still another example of the battery structure will be described with reference to Fig. 5 and Fig. 6. Fig. 5 is a cross-sectional view showing a schematic diagram of still another example of the secondary battery precursor according to the embodiment. Fig. 6 is a schematic cross-sectional view taken along line VI-VI of the battery structure shown in Fig. 5.

[0135] The electrode group 1 is housed in an exterior member 2 made of a rectangular cylindrical metal container. The electrode group 1 includes a negative electrode 3, a separator 4, and a positive electrode 5. The electrode group 1 has a structure in which the separator 4 is interposed between the positive electrode 5 and the negative electrode 3 and wound in a spiral shape to form a flat shape. An electrolyte (not shown) is held in the electrode group 1. As shown in FIG. 5, a strip-shaped negative electrode lead 16 is electrically connected to each of a plurality of points on the end of the negative electrode 3 located on the end face of the electrode group 1. In addition, a strip-shaped positive electrode lead 17 is electrically connected to each of a plurality of points on the end of the positive electrode 5 located on this end face. The plurality of negative electrode leads 16 are connected to the negative electrode terminal 6 in a bundled state as shown in FIG. 6. In addition, although not shown, the positive electrode lead 17 is also electrically connected to the positive electrode terminal 7 in a bundled state.

[0136] A metal sealing plate 10 is fixed to an opening of a metal exterior member 2 by welding or the like. The negative electrode terminal 6 and the positive electrode terminal 7 are each drawn out to the outside through an extraction hole provided in the sealing plate 10. A negative electrode gasket 8 and a positive electrode gasket 9 are disposed on the inner circumferential surface of each extraction hole of the sealing plate 10 to prevent a short circuit due to contact with the negative electrode terminal 6 and the positive electrode terminal 7, respectively. By disposing the negative electrode gasket 8 and the positive electrode gasket 9, the airtightness of the secondary battery can be maintained.

[0137] A control valve 11 (safety valve) is disposed on the sealing plate 10. When the internal pressure in the exterior member 2 increases due to gas generation, the generated gas can be released to the outside from the control valve 11. In FIG. 5, the control valve 11 is disposed in the center of the sealing plate 10, but the position of the control valve 11 may be an end portion of the sealing plate 10. The control valve 11 may be omitted.

[0138] The sealing plate 10 is also provided with a liquid inlet 18. The electrolyte can be injected through this liquid inlet 18. The liquid inlet 18 can be closed with a sealing plug 19 after the electrolyte is injected. The liquid inlet 18 and the sealing plug 19 may be omitted. In the case of temporary sealing performed before performing a treatment of holding the secondary battery precursor 100 at a holding temperature in a state where the electrode potential has been adjusted, for example, a rubber sealing plug 19 can be used. In the case of main sealing performed after the treatment and deaeration, 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 in a state where the liquid inlet 18 is closed.

[0139] The method for producing a secondary battery according to the first embodiment includes maintaining a secondary battery precursor having a positive electrode, a negative electrode, and an electrolyte in a treatment potential adjustment state in which the negative electrode potential is adjusted to within a range of 0.6 V or more and less than 1.5 V based on the oxidation-reduction potential of lithium. The secondary battery precursor is maintained at a temperature within a range of more than 60° C. and not more than 82° C. in the treatment potential adjustment state. With this production method, a secondary battery can be produced that exhibits high output performance and suffers little performance degradation and gas generation even when charge-discharge cycles are repeated.

[0140] Second embodiment According to a second embodiment, a secondary battery is provided, which is a secondary battery manufactured by the manufacturing method according to the first embodiment.

[0141] The secondary battery according to the second embodiment is a secondary battery obtained by carrying out the above-mentioned pretreatment on the secondary battery precursor in the manufacturing method according to the first embodiment. Therefore, the secondary battery may be, for example, a nonaqueous electrolyte secondary battery or a lithium ion nonaqueous electrolyte secondary battery.

[0142] Compared with the secondary battery precursor before the electrode potential adjustment described in the first embodiment, the details of the secondary battery according to the second embodiment are similar to those of the secondary battery precursor described in the first embodiment, except that the secondary battery according to the second embodiment is in a state of a completed product after pretreatment and the associated degassing and main sealing. That is, the secondary battery according to the second embodiment includes the positive electrode, negative electrode, and electrolyte described above in the first embodiment. In addition, the secondary battery according to the second embodiment can include the separator, exterior member, positive electrode terminal, and negative electrode terminal described above in the first embodiment. Since the details are repeated, the description will be omitted.

[0143] However, in the secondary battery according to the second embodiment, components that may contribute to gas generation, such as residual moisture, are in a reduced state compared to the secondary battery precursor before pretreatment. This is because at least a part of the residual moisture is gasified and released outside the exterior member during pretreatment. In addition, the secondary battery precursor before pretreatment does not have a protective coating on the electrode surface, but the positive and negative electrodes in the secondary battery may have a protective coating on their surfaces. In addition, the secondary battery precursor before pretreatment may be in a provisionally sealed state, whereas the secondary battery is in a state where full sealing has been applied.

[0144] The secondary battery according to the second embodiment is manufactured by the method for manufacturing the secondary battery according to the first embodiment. Therefore, the secondary battery can exhibit high output performance, and the deterioration of performance and the generation of gas are small even when the charge / discharge cycle is repeated.

[0145] (Third embodiment) According to a third embodiment, there is provided a battery pack including a plurality of secondary batteries according to the second embodiment.

[0146] In such a battery pack, the individual cells may be electrically connected in series or parallel, or may be arranged in a combination of series and parallel connections.

[0147] Next, an example of a battery pack according to an embodiment will be described with reference to the drawings.

[0148] Fig. 7 is a perspective view showing an example of a battery pack. The battery pack 200 shown in Fig. 7 includes five cells 100a to 100e, four bus bars 21, a positive electrode lead 22, and a negative electrode lead 23. Each of the five cells 100a to 100e is a secondary battery according to the third embodiment.

[0149] The bus bar 21 connects, for example, the negative electrode terminal 6 of one cell 100a and the positive electrode terminal 7 of the adjacent cell 100b. In this way, the five cells 100 are connected in series by the four bus bars 21. That is, the battery pack 200 in FIG. 7 is a five-series battery pack. Although no example is shown, in a battery pack including a plurality of cells electrically connected in parallel, for example, the plurality of negative electrode terminals are connected to each other by a bus bar and the plurality of positive electrode terminals are connected to each other by a bus bar, so that the plurality of cells are electrically connected to each other.

[0150] The positive electrode terminal 7 of at least one of the five cells 100a to 100e is electrically connected to a positive electrode lead 22 for external connection. Also, the negative electrode terminal 6 of at least one of the five cells 100a to 100e is electrically connected to a negative electrode lead 23 for external connection.

[0151] The battery pack according to the third embodiment includes the secondary battery according to the second embodiment, and therefore can exhibit high output performance, and is less susceptible to deterioration in performance and gas generation even after repeated charge / discharge cycles.

[0152] (Fourth embodiment) According to a fourth embodiment, there is provided a battery pack. The battery pack includes the battery assembly according to the third embodiment. The battery pack may include a single secondary battery according to the second embodiment, instead of the battery assembly according to the third embodiment.

[0153] Such a battery pack may further include a protection circuit. The protection circuit has a function of controlling charging and discharging of the secondary battery. Alternatively, a circuit included in a device (e.g., electronic device, automobile, etc.) that uses the battery pack as a power source may be used as the protection circuit for the battery pack.

[0154] The battery pack may further include an external terminal for current flow. The external terminal for current flow is for outputting current from the secondary battery to the outside and / or inputting current from the outside to the secondary battery. In other words, when the battery pack is used as a power source, current is supplied to the outside through the external terminal for current flow. When the battery pack is charged, a charging current (including regenerative energy from the power of an automobile or the like) is supplied to the battery pack through the external terminal for current flow.

[0155] Next, an example of a battery pack according to an embodiment will be described with reference to the drawings.

[0156] Fig. 8 is an exploded perspective view showing an example of a battery pack, and Fig. 9 is a block diagram showing an example of an electric circuit of the battery pack shown in Fig. 8.

[0157] The battery pack 300 shown in Figs. 8 and 9 includes a container 31, a lid 32, a protective sheet 33, a battery pack 200, a printed wiring board 34, wiring 35, and an insulating plate (not shown).

[0158] 8 is a bottomed, square container having a rectangular bottom. The container 31 is configured to be capable of housing a protective sheet 33, a battery pack 200, a printed wiring board 34, and wiring 35. The lid 32 has a rectangular shape. The lid 32 covers the container 31 to house the battery pack 200 and the like. Although not shown, the container 31 and the lid 32 are provided with openings or connection terminals for connection to an external device or the like.

[0159] The battery pack 200 includes a plurality of cells 100, a positive electrode lead 22, a negative electrode lead 23, and an adhesive tape 24.

[0160] At least one of the plurality of unit cells 100 is a secondary battery according to the third embodiment. Each of the plurality of unit cells 100 is electrically connected in series as shown in FIG. 9. The plurality of unit cells 100 may be electrically connected in parallel, or may be connected in a combination of series and parallel connections. When the plurality of unit cells 100 are connected in parallel, the battery capacity is increased compared to when they are connected in series.

[0161] The adhesive tape 24 fastens the plurality of unit cells 100. The plurality of unit cells 100 may be fixed using heat shrink tape instead of the adhesive tape 24. In this case, the protective sheets 33 are disposed on both side surfaces of the battery pack 200, the heat shrink tape is wrapped around the battery pack 200, and the heat shrink tape is then thermally shrunk to bind the plurality of unit cells 100 together.

[0162] One end of the positive electrode lead 22 is connected to the battery pack 200. One end of the positive electrode lead 22 is electrically connected to the positive electrode of one or more cells 100. One end of the negative electrode lead 23 is connected to the battery pack 200. One end of the negative electrode lead 23 is electrically connected to the negative electrode of one or more cells 100.

[0163] The printed wiring board 34 is disposed along one of the short side surfaces of the inner surface of the container 31. The printed wiring board 34 includes a positive connector 342, a negative connector 343, a thermistor 345, a protection circuit 346, wiring 342a and 343a, an external terminal 350 for supplying electricity, a positive wiring (positive wiring) 348a, and a negative wiring (negative wiring) 348b. One main surface of the printed wiring board 34 faces one side of the battery pack 200. An insulating plate (not shown) is interposed between the printed wiring board 34 and the battery pack 200.

[0164] The other end 22a of the positive electrode lead 22 is electrically connected to the positive electrode connector 342. The other end 23a of the negative electrode lead 23 is electrically connected to the negative electrode connector 343.

[0165] The thermistor 345 is fixed to one main surface of the printed wiring board 34. The thermistor 345 detects the temperature of each of the cells 100, and transmits a detection signal to the protection circuit 346.

[0166] The external terminal 350 for current supply is fixed to the other main surface of the printed wiring board 34. The external terminal 350 for current supply is electrically connected to a device present outside the battery pack 300. The external terminal 350 for current supply includes a positive terminal 352 and a negative terminal 353.

[0167] The protection circuit 346 is fixed to the other main surface of the printed wiring board 34. The protection circuit 346 is connected to the positive terminal 352 via a positive wiring 348a. The protection circuit 346 is connected to the negative terminal 353 via a negative wiring 348b. The protection circuit 346 is also electrically connected to the positive electrode connector 342 via a wiring 342a. The protection circuit 346 is electrically connected to the negative electrode connector 343 via a wiring 343a. Furthermore, the protection circuit 346 is electrically connected to each of the plurality of single cells 100 via the wiring 35.

[0168] The protective sheet 33 is disposed on both inner surfaces in the long side direction of the container 31 and on the inner surface in the short side direction that faces the printed wiring board 34 via the battery pack 200. The protective sheet 33 is made of, for example, resin or rubber.

[0169] The protection circuit 346 controls charging and discharging of the multiple cells 100. In addition, the protection circuit 346 cuts off electrical connection between the protection circuit 346 and external terminals 350 (positive terminal 352, negative terminal 353) for supplying electricity to an external device, based on a detection signal transmitted from the thermistor 345, or a detection signal transmitted from each of the cells 100 or the battery pack 200.

[0170] An example of the detection signal transmitted from the thermistor 345 is a signal that detects that the temperature of the cell 100 is equal to or higher than a predetermined temperature. An example of the detection signal transmitted from each cell 100 or the battery pack 200 is a signal that detects overcharging, overdischarging, and overcurrent of the cell 100. When detecting overcharging or the like for each cell 100, the battery voltage may be detected, or the positive electrode potential or the negative electrode potential may be detected. In the latter case, a lithium electrode used as a reference electrode is inserted into each cell 100.

[0171] The protection circuit 346 may be a circuit included in a device (such as an electronic device or an automobile) that uses the battery pack 300 as a power source.

[0172] As described above, the battery pack 300 includes the external terminal 350 for current supply. Therefore, the battery pack 300 can output a current from the assembled battery 200 to an external device and input a current from the external device to the assembled battery 200 via the external terminal 350 for current supply. In other words, when the battery pack 300 is used as a power source, the current from the assembled battery 200 is supplied to the external device through the external terminal 350 for current supply. When the battery pack 300 is charged, a charging current from the external device is supplied to the battery pack 300 through the external terminal 350 for current supply. When the battery pack 300 is used as an in-vehicle battery, regenerative energy of the vehicle's power can be used as the charging current from the external device.

[0173] The battery pack 300 may include a plurality of assembled batteries 200. In this case, the assembled batteries 200 may be connected in series, in parallel, or in a combination of series and parallel connections. The printed wiring board 34 and the wiring 35 may be omitted. In this case, the positive electrode lead 22 and the negative electrode lead 23 may be used as a positive terminal 352 and a negative terminal 353, respectively, of the external terminal 350 for current supply.

[0174] Such a battery pack is used in applications that require excellent cycle performance, for example, when a large current is drawn. Specifically, the battery pack is used, for example, as a power source for electronic devices, a stationary battery, or an on-board battery for various vehicles. An example of the electronic device is a digital camera. The battery pack is particularly suitable for use as an on-board battery.

[0175] The battery pack according to the fourth embodiment includes the secondary battery according to the second embodiment or the battery pack according to the third embodiment, and therefore exhibits high output performance, and is less susceptible to deterioration in performance and gas generation even after repeated charge / discharge cycles.

[0176] Fifth embodiment According to a fifth embodiment, a vehicle is provided. The vehicle is equipped with the battery pack according to the fourth embodiment.

[0177] In such a vehicle, the battery pack, for example, recovers regenerative energy of the vehicle's motive power. The vehicle may include a mechanism (regenerator) that converts the kinetic energy of the vehicle into regenerative energy.

[0178] Examples of vehicles include, for example, two to four wheel hybrid electric vehicles, two to four wheel electric vehicles, power assisted bicycles, and rail vehicles.

[0179] The mounting position of the battery pack in the vehicle is not particularly limited. For example, when the battery pack is mounted in an automobile, the battery pack can be mounted in the engine compartment, the rear of the vehicle body, or under the seat of the vehicle.

[0180] The vehicle may be equipped with a plurality of battery packs. In this case, the batteries included in each battery pack may be electrically connected in series, electrically connected in parallel, or electrically connected in a combination of series and parallel connections. For example, when each battery pack includes a battery pack, the battery packs may be electrically connected in series, electrically connected in parallel, or electrically connected in a combination of series and parallel connections. Alternatively, when each battery pack includes a single battery, the batteries may be electrically connected in series, electrically connected in parallel, or electrically connected in a combination of series and parallel connections.

[0181] Next, an example of a vehicle according to an embodiment will be described with reference to the drawings.

[0182] FIG. 10 is a partially see-through view that diagrammatically illustrates an example of a vehicle.

[0183] A vehicle 400 shown in Fig. 10 includes a vehicle body 40 and a battery pack 300 according to the fourth embodiment. In the example shown in Fig. 10, the vehicle 400 is a four-wheeled automobile.

[0184] The vehicle 400 may be equipped with a plurality of battery packs 300. In this case, the batteries (e.g., single cells or assembled batteries) included in the battery pack 300 may be connected in series, in parallel, or in a combination of series and parallel connections.

[0185] 10 illustrates an example in which the battery pack 300 is mounted in an engine room located in the front of the vehicle body 40. As described above, the battery pack 300 may be mounted, for example, in the rear of the vehicle body 40 or under a seat. This battery pack 300 can be used as a power source for the vehicle 400. In addition, this battery pack 300 can recover regenerative energy for the motive power of the vehicle 400.

[0186] Next, an embodiment of a vehicle according to the present embodiment will be described with reference to FIG.

[0187] Fig. 11 is a diagram illustrating an example of a control system for an electrical system in a vehicle. The vehicle 400 illustrated in Fig. 11 is an electric vehicle.

[0188] The vehicle 400 shown in FIG. 11 comprises a vehicle body 40, a vehicle power supply 41, a vehicle ECU (ECU: Electric Control Unit) 42 which is a higher-level control device of the vehicle power supply 41, an external terminal (terminal for connecting to an external power supply) 43, an inverter 44, and a drive motor 45.

[0189] The vehicle 400 has a vehicle power supply 41 mounted, for example, in an engine compartment, the rear of the vehicle body, or under a seat. Note that, in the vehicle 400 shown in FIG. 11, the mounting location of the vehicle power supply 41 is shown diagrammatically.

[0190] The vehicle power supply 41 includes a plurality of (eg, three) battery packs 300a, 300b, and 300c, a battery management unit (BMU) 411, and a communication bus 412.

[0191] The battery pack 300a includes an assembled battery 200a and an assembled battery monitoring device 301a (for example, VTM: Voltage Temperature Monitoring). The battery pack 300b includes an assembled battery 200b and an assembled battery monitoring device 301b. The battery pack 300c includes an assembled battery 200c and an assembled battery monitoring device 301c. The battery packs 300a to 300c are battery packs similar to the above-mentioned battery pack 300, and the assembled batteries 200a to 200c are assembled batteries similar to the above-mentioned battery pack 200. The assembled batteries 200a to 200c are electrically connected in series. The battery packs 300a, 300b, and 300c can be removed independently and replaced with another battery pack 300.

[0192] Each of the assembled batteries 200a to 200c includes a plurality of unit cells connected in series. At least one of the plurality of unit cells is the secondary battery according to the second embodiment. Each of the assembled batteries 200a to 200c is charged and discharged via a positive terminal 413 and a negative terminal 414.

[0193] The battery management device 411 communicates with the assembled battery monitoring devices 301a to 301c, and collects information on the voltage, temperature, and the like of each of the cells 100 included in the assembled batteries 200a to 200c included in the vehicle power supply 41. In this way, the battery management device 411 collects information on the maintenance of the vehicle power supply 41.

[0194] The battery management unit 411 and the assembled battery monitoring units 301a to 301c are connected via a communication bus 412. In the communication bus 412, one set of communication lines is shared by a plurality of nodes (the battery management unit 411 and one or more assembled battery monitoring units 301a to 301c). The communication bus 412 is a communication bus configured based on, for example, the CAN (Control Area Network) standard.

[0195] The battery pack monitoring devices 301a to 301c measure the voltage and temperature of each of the cells constituting the battery packs 200a to 200c based on commands communicated from the battery management device 411. However, the temperature can be measured at only a few points per battery pack, and it is not necessary to measure the temperatures of all the cells.

[0196] The vehicle power supply 41 may also have an electromagnetic contactor (for example, a switch device 415 shown in FIG. 11) that switches between the presence and absence of an electrical connection between the positive terminal 413 and the negative terminal 414. The switch device 415 includes a pre-charge switch (not shown) that is turned on when the assembled batteries 200a to 200c are charged, and a main switch (not shown) that is turned on when the output from the assembled batteries 200a to 200c is supplied to a load. Each of the pre-charge switch and the main switch includes a relay circuit (not shown) that is switched on or off by a signal supplied to a coil disposed near the switch element. The electromagnetic contactor such as the switch device 415 is controlled based on a control signal from the battery management device 411 or the vehicle ECU 42 that controls the operation of the entire vehicle 400.

[0197] The inverter 44 converts the input DC voltage into a three-phase alternating current (AC) high voltage for driving the motor. The three-phase output terminals of the inverter 44 are connected to the three-phase input terminals of the drive motor 45. The inverter 44 is controlled based on a control signal from the battery management device 411 or the vehicle ECU 42 for controlling the operation of the entire vehicle. By controlling the inverter 44, the output voltage from the inverter 44 is adjusted.

[0198] The drive motor 45 rotates by electric power supplied from the inverter 44. A driving force generated by the rotation of the drive motor 45 is transmitted to the axles and drive wheels W via, for example, a differential gear unit.

[0199] Although not shown, the vehicle 400 is also equipped with a regenerative braking mechanism (regenerator). The regenerative braking mechanism rotates the drive motor 45 when the vehicle 400 is braked, and converts kinetic energy into regenerative energy as electrical energy. The regenerative energy recovered by the regenerative braking mechanism is input to the inverter 44 and converted into a direct current. The converted direct current is input to the vehicle power source 41.

[0200] One terminal of a connection line L1 is connected to the negative terminal 414 of the vehicle power supply 41. The other terminal of the connection line L1 is connected to a negative input terminal 417 of the inverter 44. A current detection unit (current detection circuit) 416 in the battery management device 411 is provided between the negative terminal 414 and the negative input terminal 417 on the connection line L1.

[0201] One terminal of a connection line L2 is connected to the positive electrode terminal 413 of the vehicle power supply 41. The other terminal of the connection line L2 is connected to a positive electrode input terminal 418 of the inverter 44. A switch device 415 is provided in the connection line L2 between the positive electrode terminal 413 and the positive electrode input terminal 418.

[0202] The external terminal 43 is connected to the battery management unit 411. The external terminal 43 can be connected to, for example, an external power source.

[0203] In response to operational inputs from the driver or the like, the vehicle ECU 42 coordinates with other management devices and control devices including the battery management device 411 to control the vehicle power supply 41, the switch device 415, the inverter 44, etc. Through the coordinated control of the vehicle ECU 42, etc., the output of power from the vehicle power supply 41 and the charging of the vehicle power supply 41 are controlled, and the entire vehicle 400 is managed. Data relating to the maintenance of the vehicle power supply 41, such as the remaining capacity of the vehicle power supply 41, is transferred between the battery management device 411 and the vehicle ECU 42 via a communication line.

[0204] The vehicle according to the fifth embodiment is equipped with the battery pack according to the fourth embodiment, and therefore is capable of exhibiting high performance and is highly reliable. EXAMPLES

[0205] Examples will be described below, but the embodiments are not limited to the examples described below.

[0206] Example 1 <Preparation of positive electrode> Lithium nickel cobalt manganese composite oxide (LiNi) as the positive electrode active material 0.8 Co 0.1 Mn 0.1 A slurry was prepared by adding 100 parts by mass of O2 (NCM811), 5 parts by mass of acetylene black as a conductive agent, and 5 parts by mass of polyvinylidene fluoride (PVdF) as a binder to N-methylpyrrolidone (NMP) and mixing them. This slurry was applied to both sides of a current collector made of aluminum foil with a thickness of 12 μm, then dried and pressed, resulting in an electrode density (excluding the current collector) of 3.2 g / cm. 3 A positive electrode was prepared.

[0207] <Preparation of negative electrode> A slurry was prepared by adding 100 parts by mass of monoclinic niobium titanium oxide Nb2TiO7 as the negative electrode active material, 5 parts by mass of acetylene black and 2.5 parts by mass of carbon nanofiber as the conductive agent, 2.5 parts by mass of sodium carboxymethylcellulose (NaCMC) and 2.5 parts by mass of styrene butadiene rubber (SBR) as the binder, to water and mixing them. This slurry was applied to both sides of a current collector made of aluminum foil with a thickness of 12 μm, dried, and pressed, resulting in an electrode density (excluding the current collector) of 2.6 g / cm. 3 A negative electrode having the above structure was fabricated.

[0208] <Preparation of electrode groups> The positive electrode prepared above, a separator made of cellulose having a thickness of 15 μm, the negative electrode prepared above, and the separator were laminated in this order, and then wound in a spiral shape so that the negative electrode was located at the outermost periphery to prepare an electrode group. This was hot-pressed at 90° C. to prepare a flat electrode group having a width of 58 mm and a thickness of 3.0 mm. The obtained electrode group was housed in an exterior member made of a 0.1 mm thick laminate film composed of an aluminum foil having a thickness of 40 μm and a polypropylene layer formed on both sides of the aluminum foil, and vacuum dried at 120° C. for 24 hours. The water content of the electrode group after drying was determined by the Karl Fischer measurement described above. The measurement result was 550 mass ppm.

[0209] <Preparation of non-aqueous electrolyte> Under an argon atmosphere, lithium hexafluorophosphate (LiPF6) was dissolved in propylene carbonate (PC) at a concentration of 1.0 mol / L to prepare a liquid nonaqueous electrolyte (electrolytic solution).

[0210] The electrolyte solution thus prepared was poured into the electrode group housed in the dried laminate film under an argon atmosphere, and then the upper part of the laminate film was sealed under reduced pressure to obtain a provisionally sealed secondary battery (battery precursor).

[0211] <Aging> The temporarily sealed secondary battery was charged at room temperature (25°C) up to a battery voltage of 3.2 V, and the positive electrode potential was increased to 4.2 V (vs. Li / Li + ) and the negative electrode potential was 1 V (vs. Li / Li + ) respectively. The provisionally sealed secondary battery in the treated potential adjusted state was heated in a thermostatic chamber at a temperature of 62°C (holding temperature, i.e., aging temperature) for 24 hours (holding time, i.e., aging time). After aging was performed in this manner, the battery voltage of the secondary battery was measured to determine the voltage difference before and after aging. The voltage dropped by 155 mV due to aging.

[0212] <Gas release> After heating, the upper part of the temporarily sealed laminate pack was opened under an argon atmosphere, and then the pressure was reduced to discharge the gas, and the laminate film was sealed (full sealing) to obtain a secondary battery.

[0213] Example 2 A secondary battery was produced in the same manner as in Example 1, except that LiFSI was added as an additional additive to the liquid nonaqueous electrolyte at a ratio of 3 mass % relative to the entire solution.

[0214] (Examples 3-15, Comparative Examples 1-8) As shown in Tables 1 and 2 below, except that the binder used in the negative electrode, the additive to the electrolyte, and the pretreatment conditions were changed, a secondary battery was manufactured in the same manner as in Example 1. The binder of the negative electrode is shown by abbreviation, NaCMC stands for sodium carboxymethyl cellulose, SBR stands for styrene butadiene rubber, and PVdF stands for polyvinylidene fluoride. Some of the additives added to the electrolyte are also shown by abbreviation, LiFSI stands for lithium bis(fluorosulfonyl)imide, LiDFP stands for lithium difluorophosphate, and LiDFOB stands for lithium difluorooxalate borate. As for the pretreatment conditions, the positive electrode potential and negative electrode potential adjusted to obtain the treatment potential adjustment state, as well as the aging temperature and time (holding temperature and holding time) were changed. Each table also shows the water content of the electrode group measured before aging and the voltage difference (drop amount) before and after aging.

[0215] [Table 1]

[0216] [Table 2]

[0217] (evaluation) <Resistance evaluation> The alternating current resistance (AC resistance) of each battery after aging treatment was measured. After adjusting the battery to a SOC (State of Charge) of 50%, the battery resistance was measured when a 1 kHz AC current was applied in a 25°C environment.

[0218] <Storage performance evaluation> After the aging treatment, each battery was adjusted to 100% SOC and then placed in a thermostatic chamber at 55°C. After one month of storage, the capacity retention rate, AC resistance increase rate, and gas generation rate were measured. The details of each measurement are described below.

[0219] <Cycle performance evaluation> A cycle test was performed on each battery after the aging treatment as follows. 1000 charge / discharge cycles were performed in a 70°C environment at a charge / discharge rate of 1C / 1C in the range of SOC 0% to 90%. After 1000 charge / discharge cycles, the capacity retention rate, AC resistance increase rate, and gas generation rate were measured. Each measurement was performed as follows.

[0220] The capacity retention rate was calculated as follows. Before and after the 55°C storage test and before and after the 70°C cycle test, the battery was charged and discharged in a 25°C environment at a charge / discharge rate of 1C / 1C in the range of SOC 0% to 100%. The discharge capacity was measured during discharge. The capacity retention rate was calculated by dividing the discharge capacity after the test by the discharge capacity before the test: capacity retention rate [%] = (capacity retention rate after test / capacity retention rate before test) x 100%.

[0221] The AC resistance increase rate was calculated as follows. Before and after each test, AC measurements were performed as described above. The increase in AC resistance after the test relative to the AC resistance before the test was divided by the AC resistance before the test to calculate the AC resistance increase rate: AC resistance increase rate [%] = [(AC resistance after test - AC resistance before test) / AC resistance before test] x 100%.

[0222] The amount of gas generated was calculated as follows. The battery volume before and after the test was measured by the Archimedes method, and the difference between them was taken as the amount of gas generated. The amount of gas generated was also normalized by the 0.2C capacity of the battery (unit: ccAh -1 ).

[0223] The evaluation results of each battery are shown in the following Tables 3 and 4. Specifically, the AC resistance after aging, and the capacity retention rate, AC resistance increase rate, and gas generation amount in each of the 55°C storage test and 70°C cycle test are summarized in the tables.

[0224] [Table 3]

[0225] [Table 4]

[0226] In the batteries produced in Examples 1-15, the AC resistance was low, and the capacity loss, resistance increase, and gas generation during storage at high temperatures and charge / discharge cycles were suppressed. In contrast, the battery produced in Comparative Example 1-8 showed a larger resistance increase in both high temperature tests and a larger capacity loss during storage. The gas generation amount of the battery in Comparative Example 1-5 was larger than that of Example 1-15 during either the storage test or the cycle test.

[0227] As shown by the evaluation results of the secondary batteries produced in each Example as described above, the production method described in the first embodiment makes it possible to produce secondary batteries having high output performance and suppressing performance degradation during repeated charge / discharge cycles.

[0228] According to at least one or more of the above-described embodiments and examples, a method for manufacturing a secondary battery is provided. The method includes a step of preparing a secondary battery precursor having a positive electrode, a negative electrode, and an electrolyte, a step of obtaining a treatment potential adjustment state by adjusting the negative electrode potential, and a step of holding the secondary battery precursor in the treatment potential adjustment state at a temperature in the range of more than 60° C. and not more than 82° C. In the step of obtaining the treatment potential adjustment state, the negative electrode is maintained at a temperature of 0.6 V (vs. Li / Li + ) or more than 1.5 V (vs. Li / Li + According to the above configuration, it is possible to provide a method for producing a highly durable secondary battery that exhibits high output performance and is less susceptible to performance degradation even after repeated charge / discharge cycles, and the secondary battery.

[0229] Although some embodiments of the present invention have been described, 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 forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and spirit of the invention, and are included in the scope of the invention and its equivalents described in the claims.

[0230] Several embodiments according to the present invention will be described below. [1] preparing a secondary battery precursor including a positive electrode, a negative electrode, and an electrolyte; a step of adjusting a negative electrode potential of the negative electrode to within a range of 0.6 V or more and less than 1.5 V based on the redox potential of lithium to obtain a treatment potential adjustment state; maintaining the treatment potential adjusted state at a temperature in the range of more than 60° C. and not more than 82° C.; A method for manufacturing a secondary battery comprising the steps of: [2] The method for producing a secondary battery according to [1], wherein the step of maintaining the treated potential adjusted state is carried out for 3 hours or more. [3] The method for producing a secondary battery according to any one of [1] to [3], wherein the negative electrode contains, as a binder, one or more selected from the group consisting of styrene-butadiene rubber, carboxymethyl cellulose, a salt of carboxymethyl cellulose, polyacrylic acid, a polymer of polyacrylic acid, and acrylic rubber. [4] The method for producing a secondary battery according to any one of [1] to [4], wherein the negative electrode contains, as a negative electrode active material, one or more niobium-containing oxides selected from the group consisting of monoclinic niobium titanium oxide, orthorhombic titanium niobium oxide, and niobium composite oxide. [5] The method for producing a secondary battery according to any one of [1] to [4], wherein in the treatment potential adjustment state, a positive electrode potential of the positive electrode is adjusted to a range exceeding 3.9 V based on a redox potential of lithium. [6] The method for producing a secondary battery according to [5], wherein the positive electrode contains, as a positive electrode active material, one or more selected from the group consisting of lithium manganese composite oxides having a spinel structure, lithium nickel composite oxides, lithium cobalt composite oxides, lithium nickel cobalt composite oxides, lithium manganese nickel composite oxides having a spinel structure, lithium manganese cobalt composite oxides, lithium iron phosphate, and lithium nickel cobalt manganese composite oxides. [7] The method for producing a secondary battery according to any one of [1] to [6], wherein a voltage difference before and after the step of maintaining the treatment potential adjustment state is 100 mV or more and 300 mV or less. [8] The method for producing a secondary battery according to any one of [1] to [7], wherein the electrolyte further contains one or more selected from the group consisting of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium difluorophosphate, lithium difluorooxalatoborate, lithium bis(oxalatoborate), and lithium triflate. [9] A secondary battery manufactured by the manufacturing method described in any one of [1] to [8].

[10] A battery pack comprising the secondary battery described in [9].

[11] An external terminal for supplying current; Protection circuit and The battery pack according to

[10] , further comprising:

[12] A battery comprising a plurality of the secondary batteries, The battery pack according to

[10] or

[11] , wherein the secondary batteries are electrically connected in series, in parallel, or in a combination of series and parallel.

[13] A vehicle equipped with a battery pack described in any one of

[10] to

[12] .

[0231]

[14] A vehicle as described in

[13] , including a mechanism for converting kinetic energy of the vehicle into regenerative energy. [Explanation of symbols]

[0232] Reference Signs List 1...electrode group, 2...exterior member, 3...negative electrode, 3a...negative electrode current collector, 3b...negative electrode active material-containing layer, 3c...negative electrode current collector tab, 4...separator, 5...positive electrode, 5a...positive electrode current collector, 5b...positive electrode active material-containing layer, 6...negative electrode terminal, 7...positive electrode terminal, 8...negative electrode gasket, 9...positive electrode gasket, 10...sealing plate, 11...control valve, 16...negative electrode lead, 17...positive electrode lead, 18...filling port, 19...sealing plug, 21 ...bus bar, 22...positive electrode lead, 22a...other end, 23...negative electrode lead, 23a...other end, 24...adhesive tape, 31...container, 32...lid, 33...protective sheet, 34...printed wiring board, 35...wiring, 40...vehicle body, 41...vehicle power source, 42...electrical control device, 43...external terminal, 44...inverter, 45...driving motor, 100...secondary battery precursor, 200...battery pack, 200a ... battery pack, 200b... battery pack, 200c... battery pack, 300... battery pack, 300a... battery pack, 300b... battery pack, 300c... battery pack, 301a... battery pack monitoring device, 301b... battery pack monitoring device, 301c... battery pack monitoring device, 342... positive connector, 343... negative connector, 345... thermistor, 346... protection circuit, 342a... wiring, 343a... wiring, 35 0...external terminal for current supply, 352...positive terminal, 353...negative terminal, 348a...positive wiring, 348b...negative wiring, 400...vehicle, 411...battery management device, 412...communication bus, 413...positive terminal, 414...negative terminal, 415...switch device, 416...current detection unit, 417...negative input terminal, 418...positive input terminal, L1...connection line, L2...connection line, W...drive wheel.

Claims

1. preparing a secondary battery precursor including a positive electrode, a negative electrode, and an electrolyte; a step of adjusting a negative electrode potential of the negative electrode to within a range of 0.6 V or more and less than 1.5 V based on the redox potential of lithium to obtain a treatment potential adjustment state; maintaining the treatment potential adjusted state at a temperature in the range of more than 60° C. and not more than 82° C.; A method for manufacturing a secondary battery comprising the steps of:

2. The method for producing a secondary battery according to claim 1 , wherein the step of maintaining the treated potential adjusted state is performed for 3 hours or more.

3. 3. The method for producing a secondary battery according to claim 1, wherein the negative electrode contains, as a binder, one or more selected from the group consisting of styrene-butadiene rubber, carboxymethyl cellulose, a salt of carboxymethyl cellulose, polyacrylic acid, a polymer of polyacrylic acid, and an acrylic rubber.

4. 3. The method for producing a secondary battery according to claim 1, wherein the negative electrode contains one or more niobium-containing oxides selected from the group consisting of monoclinic niobium titanium oxide, orthorhombic titanium niobium oxide, and niobium composite oxide as a negative electrode active material.

5. 3 . The method for producing a secondary battery according to claim 1 , wherein in the treatment potential adjustment state, the positive electrode potential of the positive electrode is adjusted to a range exceeding 3.9 V based on the oxidation-reduction potential of lithium.

6. 6. The method for producing a secondary battery according to claim 5, wherein the positive electrode contains, as a positive electrode active material, one or more selected from the group consisting of a lithium manganese composite oxide having a spinel structure, a lithium nickel composite oxide, a lithium cobalt composite oxide, a lithium nickel cobalt composite oxide, a lithium manganese nickel composite oxide having a spinel structure, a lithium manganese cobalt composite oxide, lithium iron phosphate, and a lithium nickel cobalt manganese composite oxide.

7. 3. The method for producing a secondary battery according to claim 1, wherein a voltage difference before and after the step of maintaining the treated potential adjusted state is 100 mV or more and 300 mV or less.

8. 3. The method for producing a secondary battery according to claim 1, wherein the electrolyte further comprises one or more selected from the group consisting of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium difluorophosphate, lithium difluorooxalatoborate, lithium bis(oxalatoborate), and lithium triflate.

9. A secondary battery produced by the method according to claim 1 or 2.

10. A battery pack comprising the secondary battery according to claim 9.

11. An external terminal for supplying electricity; Protection circuit and The battery pack of claim 10 further comprising:

12. A battery comprising a plurality of the secondary batteries, The battery pack according to claim 10 , wherein the secondary batteries are electrically connected in series, in parallel, or in a combination of series and parallel.

13. A vehicle equipped with the battery pack according to claim 10.

14. 14. The vehicle of claim 13, further comprising a mechanism for converting kinetic energy of the vehicle into regenerative energy.

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