JP5446195B2 - Lithium ion battery system and manufacturing method thereof - Google Patents

Description

  The present invention relates to a lithium ion battery system and a method of manufacturing the same. The lithium ion battery system of the present invention is used as a power source for driving motors of vehicles such as electric vehicles, fuel cell vehicles, and hybrid electric vehicles.

  In recent years, various electric vehicles are expected to be widely used for solving environmental and energy problems. Secondary batteries have been intensively developed as in-vehicle power supplies such as motor drive power supplies that hold the key to commercialization of these electric vehicles. However, in order to spread widely, it is necessary to make the battery high performance and cheaper. Further, for electric vehicles, it is necessary to bring the one-charge travel distance closer to a gasoline engine vehicle, and a battery with a higher energy density is desired.

In order to make the battery have a high energy density, it is necessary to increase the amount of electricity stored per unit mass of the positive electrode and the negative electrode. A so-called solid solution positive electrode material has been studied as a positive electrode material that may meet this demand. Among them, the solid solution of the electrochemically inactive layered Li ₂ MnO ₃ and the electrochemically active layered LiMO ₂ (where M is a transition metal such as Co, Ni, Mn, Fe) is It is expected as a high-capacity positive electrode candidate material capable of exhibiting a large electric capacity exceeding 200 mAh / g (see, for example, Patent Document 1).
JP-A-9-55211

  However, even a lithium ion battery using the solid solution positive electrode described in Patent Document 1 as a high-capacity positive electrode has poor cycle durability under high-capacity use conditions, and deteriorates as soon as charging and discharging are repeated at a high potential. There was a problem that.

  In response to such a problem, the present inventor has found that the cycle durability can be greatly improved by pretreating the positive electrode at a potential somewhat lower than the charge / discharge potential in the high capacity use condition in the initial stage.

  The present inventor has the following technical problems in order to perform the above-described pre-charge / discharge treatment after constituting a battery using this positive electrode so as to be suitable for mass production without being satisfied with the above solution. I found out. In other words, when a battery is configured using this positive electrode to further configure a power system for an electric vehicle (battery system in which a plurality of batteries are connected in series), a negative electrode (such as silicon) having a non-flat charge / discharge curve and the positive electrode In many cases, a battery is configured by combining the two. In such a battery, after the battery is configured, if the potential of the positive electrode is regulated and the above charge / discharge pretreatment is performed, the potential of the negative electrode changes with charging. It has been found that there is a technical problem that the above-described charge / discharge pretreatment cannot be performed properly.

  Therefore, an object of the present invention is to appropriately perform pre-charge / discharge pretreatment of a battery in which the positive electrode potential is regulated even in a lithium ion battery system in which a plurality of batteries using a solid solution positive electrode and a negative electrode having a non-flat charge / discharge curve are connected in series. It is to provide a battery system that can.

  The inventor incorporated a third electrode in addition to the positive electrode and the negative electrode into one or more batteries of the battery system, and detected the positive electrode potential of this battery relative to the potential of the third electrode by passing the same current through the entire battery system. It has been found that the above problem can be solved by pre-charging and discharging the entire battery system at once. Based on this knowledge, the present invention has been achieved.

  That is, an object of the present invention is to provide a battery system in which a plurality of batteries are connected in series so that the positive electrode of the battery including the third electrode insulated from the positive electrode and the negative electrode has a predetermined potential range with respect to the third electrode. This can be achieved by a battery system in which the same current is applied to the whole to perform pre-charge / discharge treatment.

The battery constituting the battery system is a lithium ion battery in which a main positive electrode active material is represented by a general formula: xLiMO ₂ · (1-x) Li ₂ NO ₃ . X in the above general formula is a number satisfying 0 <x <1, M is one or more transition metals whose average oxidation state is 3+, and N is one type whose average oxidation state is 4+ The above transition metals.

  In the present invention, even in a battery system in which a plurality of batteries using a solid solution positive electrode and a negative electrode having a non-flat charge / discharge curve are connected in series, the charge / discharge pretreatment of the battery in which the potential of the positive electrode is regulated can be appropriately performed, and the cycle characteristics are good. A high-capacity lithium-ion battery system can be constructed.

  The battery system of the present invention is a battery system in which a plurality of batteries are connected in series, and at least one battery includes a third electrode that is electronically insulated from the positive electrode and the negative electrode. It is characterized by being subjected to a pre-charge / discharge treatment for a battery that regulates the above.

Here, the battery constituting the battery system is a lithium ion battery in which a main positive electrode active material is represented by a general formula: xLiMO ₂ · (1-x) Li ₂ NO ₃ . In the lithium ion battery, a battery having a uniform surface density of the positive electrode and the negative electrode and uniform capacity is preferably used. In the above general formula, x is a number satisfying 0 <x <1, M is one or more transition metals having an average oxidation state of 3+, and N has an average oxidation state of 4+. One or more transition metals.

  In addition, the charge / discharge pretreatment of the battery in which the potential of the positive electrode is regulated refers to lithium ions connected in series so that the positive electrode of the battery including the third electrode is in a predetermined potential range with respect to the third electrode. It means that the same current is applied to the whole battery system to perform pre-charge / discharge treatment. With this configuration, it is possible to construct a lithium ion battery system with high capacity and good cycle durability.

That is, a positive electrode material of a so-called solid solution system represented by the general formula: xLiMO ₂ · (1-x) Li ₂ NO ₃ is expected as a high-capacity material, but is charged to a high potential to develop a high capacity. When used in such a manner, there is a problem that deterioration due to charge and discharge is rapid (see FIG. 7 ). Among the first, second, and fifth charge / discharge curves when charged to a high potential at this time, the first charge curve is simply referred to as “initial charge curve” or “initial charge curve”. Also called “charge curve”. In contrast, the mechanism of the effect is not yet fully understood, but the maximum potential is set to the initial region of the plateau part (flat part) of the first charging curve (potential width from the lower limit to the upper limit of the flat part). It was found that when the pre-charge / discharge pretreatment is performed at a potential corresponding to the range from the lower limit to the lower limit + 30%). Furthermore, when a battery system connected in series is configured using this battery, the same current always flows through any battery. Further, when configuring a battery system connected in series, it is usually configured so that the surface density of the positive electrode and the negative electrode is made uniform, the capacities are made uniform, and the battery capacity variation is reduced. Therefore, in such a normal series-connected battery system, if a reference electrode (third electrode) is attached to one battery, and the whole series-connected battery system is charged and discharged while detecting the potential change of the positive electrode of the battery with respect to it. The present inventors have found that all the batteries can be pre-charged / discharged at one time (see FIGS. 3, 4B, and 6). As a result, in the lithium ion battery system of the present invention, a battery system with high energy density and good cycle durability is constructed by using a positive electrode for a lithium ion battery whose main active material is the solid solution positive electrode material of the present invention. It is excellent in that it can be done.

  In other words, a so-called solid solution positive electrode material is easily deteriorated by repeated charge / discharge when it is used as a high-capacity positive electrode with a high charge / discharge potential. Cycle durability at high capacity can be greatly improved. Although the cycle durability improvement mechanism cannot be determined yet, it is considered as follows. The plateau part of the initial charge curve is not yet clearly understood, but according to one theory, the process in which the dianion of oxygen in the solid solution cathode crystal is oxidized and lithium ions are released. It is believed that. When this reaction occurs, a significant change in the crystal structure occurs, and it is assumed that subsequent charge / discharge cycle deterioration occurs as a result. Without causing a significant change in the crystal structure from the beginning, the constituent elements can be made more stable by performing (repeating) some charge / discharge cycles with the highest potential corresponding to the initial region of the plateau part of the first charge curve. A gentle transition to placement and stability is made. As a result, even if the voltage is further increased and charging is performed through the plateau region described above, the structure has already been stabilized, so a charge / discharge cycle including a high potential region capable of developing a high capacity is achieved. I think I will be able to withstand. The present invention forms a battery using this positive electrode active material, forms a battery system in which a plurality of the positive electrode active materials are connected in series and can be applied to an electric vehicle, and then performs charge / discharge pretreatment on the positive electrode in question. A manufacturing method and a battery system stabilized thereby are provided. According to the present invention, it is possible to provide a stabilized battery system having a high capacity and good cycle durability and a method for manufacturing the same.

  Hereinafter, an embodiment of a lithium ion battery constituting a lithium ion battery system (hereinafter also simply referred to as a battery system) of the present invention and a battery system formed by connecting a plurality of them in series will be described with reference to the drawings. However, the technical scope of the present invention should be determined based on the description of the scope of claims, and is not limited to the following forms. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted. In addition, the dimensional ratios in the drawings are exaggerated for convenience of explanation, and may be different from the actual ratios.

  First, since the lithium ion battery constituting the battery system of the present invention can have a high capacity, it can be suitably used as a battery system for a vehicle drive power source and the like, and a battery system for portable devices such as a portable personal computer and a cellular phone. It is also fully applicable to.

That is, the lithium ion battery used in the present invention uses a so-called solid solution positive electrode material in which the main positive electrode active material is represented by the general formula: xLiMO _2. (1-x) Li ₂ NO _3. The other configuration requirements are not particularly limited.

  For example, when the lithium ion battery is distinguished by its form / structure, it can be applied to any conventionally known form / structure, such as a stacked (flat) battery or a wound (cylindrical) battery. is there. By adopting a stacked (flat) battery structure, long-term reliability can be secured by a sealing technique such as simple thermocompression bonding, which is advantageous in terms of cost and workability.

  Moreover, when viewed in terms of electrical connection form (electrode structure) in a lithium ion battery, it can be applied to both non-bipolar (internal parallel connection type) batteries and bipolar (internal series connection type) batteries. is there.

  Conventionally known, such as a solution electrolyte type battery using a solution electrolyte such as a non-aqueous electrolyte for the electrolyte layer, a polymer battery using a polymer electrolyte for the electrolyte layer when distinguished by the type of electrolyte layer in the lithium ion battery It can be applied to any electrolyte layer type. The polymer battery is further divided into a gel electrolyte type battery using a polymer gel electrolyte (also simply referred to as a gel electrolyte) and a solid polymer (all solid) type battery using a polymer solid electrolyte (also simply referred to as a polymer electrolyte). It is done.

  Therefore, in the following description, the non-bipolar (internal parallel connection type) lithium ion secondary battery and the bipolar (internal series connection type) lithium ion secondary battery used in the battery system of the present invention are very simple with reference to the drawings. Explained. However, the technical scope of the lithium ion battery of the present invention should not be limited to these.

  FIG. 1 shows a typical embodiment of a lithium ion battery used in the present invention, a flat (stacked) lithium ion secondary battery (hereinafter simply referred to as a non-bipolar lithium ion secondary battery or non-bipolar). 1 is a schematic cross-sectional view schematically showing the overall structure of a secondary battery.

  As shown in FIG. 1, in the non-bipolar lithium ion secondary battery 10, a battery film 22 is made of a polymer-metal composite laminate film, and the entire periphery thereof is bonded by thermal fusion. Thus, the power generation element 17 is housed and sealed. That is, the substantially rectangular power generation element 17 in which the charge / discharge reaction actually proceeds has a structure sealed inside the laminate sheet that is the battery exterior material 22. In addition, the sealing part (refer code | symbol 23 of FIG. 3) is formed by joining all the peripheral parts of the battery exterior material 22 by heat sealing | fusion.

  Here, the power generation element 17 includes a positive electrode plate having a positive electrode (positive electrode active material layer) 12 formed on both surfaces of the positive electrode current collector 11 (one surface for the outermost layer of the power generation element), an electrolyte layer 13, and a negative electrode current collector 14. The negative electrode plate in which the negative electrode (negative electrode active material layer) 15 was formed on both surfaces is laminated. At this time, the positive electrode (positive electrode active material layer) 12 on one surface of one positive electrode plate and the negative electrode (negative electrode active material layer) 15 on one surface of one negative electrode plate adjacent to the one positive electrode plate face each other through the electrolyte layer 13. Thus, a plurality of layers of the positive electrode plate, the electrolyte layer 13, and the negative electrode plate are laminated in this order.

  As a result, the adjacent positive electrode (positive electrode active material layer) 12, electrolyte layer 13, and negative electrode (negative electrode active material layer) 15 constitute one unit cell layer 16. Therefore, it can be said that the lithium ion secondary battery 10 of the present embodiment has a configuration in which a plurality of single battery layers 16 are stacked and electrically connected in parallel. Note that the positive electrode (positive electrode active material layer) 12 is formed on only one side of the outermost positive electrode current collector 11 a located in both outermost layers of the power generation element 17. In addition, by changing the arrangement of the positive electrode plate and the negative electrode plate in FIG. 1, the outermost layer negative electrode current collector (not shown) is positioned in both outermost layers of the power generation element 17, and the outermost layer negative electrode current collector In some cases, the negative electrode (negative electrode active material layer) 15 may be formed only on one side.

  Further, the positive electrode tab 18 and the negative electrode tab 19 that are electrically connected to the respective electrode plates (positive electrode plate and negative electrode plate) are connected to the positive electrode current collector 11 and the negative electrode of each electrode plate via the positive electrode terminal lead 20 and the negative electrode terminal lead 21. It is attached to the current collector 14 by ultrasonic welding or resistance welding. Accordingly, the positive electrode tab 18 and the negative electrode tab 19 that are electrically connected to the positive electrode current collector 11 and the negative electrode current collector 14 are sandwiched between the heat fusion portions and exposed to the outside of the battery exterior material 22. It has a structure.

  FIG. 2 shows another typical embodiment of a lithium ion battery used in the present invention, a bipolar flat (stacked) lithium ion secondary battery (hereinafter simply referred to as a bipolar lithium ion secondary battery, FIG. 2 is a schematic cross-sectional view schematically showing the entire structure of a secondary type secondary battery).

  As shown in FIG. 2, the bipolar lithium ion secondary battery 30 has a structure in which a substantially rectangular power generation element 37 in which a charge / discharge reaction actually proceeds is sealed inside a battery exterior member 42. That is, the power generation element 37 is accommodated in the battery outer packaging material 42, and the entire peripheral portion of the battery outer packaging material 42 is joined by thermal fusion or the like, so that the sealing portion (see reference numeral 23 in FIG. 3) is formed. By forming, the inside of the battery exterior material 42 is sealed.

  The power generation element 37 of the bipolar secondary battery 30 according to the present embodiment has an electrolyte layer 35 sandwiched between one or two or more bipolar electrodes 34, and a positive electrode (positive electrode active material layer) of adjacent bipolar electrodes 34. ) 32 and the negative electrode (negative electrode active material layer) 33 are opposed to each other. Here, the bipolar electrode 34 has a structure in which a positive electrode (positive electrode active material layer) 32 is provided on one surface of the current collector 31 and a negative electrode (negative electrode active material layer) 33 is provided on the other surface. That is, in the bipolar secondary battery 30, a bipolar electrode having a positive electrode (positive electrode active material layer) 32 on one surface of the current collector 31 and a negative electrode (negative electrode active material layer) 33 on the other surface. A power generation element 37 having a structure in which a plurality of 34 are stacked via an electrolyte layer 35 is provided.

  The adjacent positive electrode (positive electrode active material layer) 32, electrolyte layer 35, and negative electrode (negative electrode active material layer) 33 constitute one single battery layer (= battery unit or single cell) 36. Therefore, it can be said that the bipolar secondary battery 30 has a configuration in which the single battery layers 36 are stacked. Further, a seal portion (insulating layer) 43 is disposed around the unit cell layer 36 in order to prevent liquid junction due to leakage of the electrolyte from the electrolyte layer 35. By providing the seal portion (insulating layer) 43, the adjacent current collectors 31 can be insulated and a short circuit due to contact between the adjacent electrodes (the positive electrode 32 and the negative electrode 33) can be prevented.

  In addition, the positive electrode side electrode 34a and the negative electrode side electrode 34b located in the outermost layer of the power generation element 37 may not have a bipolar electrode structure. For example, a structure in which the positive electrode (positive electrode active material layer) 32 or the negative electrode (negative electrode active material layer) 33 only on one side necessary for the current collectors 31a and 31b (or terminal plates) may be provided. A positive electrode (positive electrode active material layer) 32 may be formed on only one surface of the positive electrode-side outermost layer current collector 31 a located in the outermost layer of the power generation element 37. Similarly, a negative electrode (negative electrode active material layer) 33 may be formed on only one side of the outermost current collector 31b on the negative electrode side located in the outermost layer of the power generation element 37. In the bipolar lithium ion secondary battery 30, the positive electrode tab 38 and the negative electrode tab 39 are provided on the positive electrode side outermost layer current collector 31 a and the negative electrode side outermost layer current collector 31 b at both the upper and lower ends, respectively. 40 and the negative terminal lead 41 are joined. However, the positive electrode side outermost layer current collector 31 a may be extended to form a positive electrode tab 38, and may be derived from a laminate sheet that is the battery exterior material 42. Similarly, the negative electrode side outermost layer current collector 31b may be extended to form a negative electrode tab 39, which may be similarly derived from a laminate sheet that is the battery outer packaging material 42.

  Further, the bipolar lithium ion secondary battery 30 also has a structure in which the power generation element 37 portion is sealed in a battery exterior material (exterior package) 42 under reduced pressure, and the positive electrode tab 38 and the negative electrode tab 39 are taken out of the battery exterior material 42. It is good. This is because such a structure can prevent external impact and environmental degradation during use. The basic configuration of the bipolar lithium ion secondary battery 30 can be said to be a configuration in which a plurality of stacked single battery layers (single cells) 36 are connected in series.

  As described above, regarding each constituent requirement and manufacturing method of the non-bipolar lithium ion secondary battery and the bipolar lithium ion secondary battery, the electrical connection form (electrode structure) in the lithium ion secondary battery is different. Except for this, it is basically the same. Therefore, below, it demonstrates using the above non-bipolar type lithium ion secondary battery. However, the bipolar lithium ion secondary battery can be configured or manufactured by appropriately using the same configuration requirements and manufacturing method.

  First, in the battery system of the present invention, at least one battery includes a third electrode that is electronically insulated from the positive electrode and the negative electrode. FIG. 3 schematically shows how the third electrode of the non-bipolar lithium ion secondary battery including the third electrode electronically insulated from the positive electrode and the negative electrode is installed in the battery system of the present invention. It is a general | schematic fragmentary sectional view.

  The basic configuration of the non-bipolar lithium ion secondary battery 10a including the third electrode shown in FIG. 3 is the same as the configuration of the non-bipolar lithium ion secondary battery 10 shown in FIG. In the battery 10 a shown in FIG. 3, a third electrode 25 is provided between the electrolyte layer 13 that is electronically insulated from the positive electrode (positive electrode active material layer) 12 and the negative electrode (negative electrode active material layer) 15. The third electrode 25 is connected to a third electrode tab 27 via a third electrode terminal lead 26 as necessary. The third electrode tab 27 is led out to the outside through the sealing portion 23 of the battery exterior material 22 (see FIGS. 3 and 4B). However, the third electrode terminal lead 26 may be extended to form a third electrode tab 27 and may be derived from a laminate sheet that is the battery exterior material 22.

  Hereinafter, each component of the battery described above will be described.

[Current collector]
The current collector is not particularly limited with respect to any of the non-bipolar type and the bipolar type lithium ion secondary battery. Specifically, the current collector is at least one type of current selected from the group consisting of iron, chromium, nickel, manganese, titanium, molybdenum, vanadium, niobium, aluminum, copper, silver, gold, platinum, and carbon. A current collector made of a current material can be used. In the present invention, a clad material of nickel and aluminum, a clad material of copper and aluminum, or a plating material of a combination of these current collector materials can be preferably used. Further, a current collector in which the surface of a metal (excluding aluminum) as the current collector material is coated with aluminum as another current collector material may be used. Moreover, you may use the electrical power collector which bonded together the metal foil which is two or more said electrical power collector materials depending on the case. Although the thickness of a collector is not specifically limited, Usually, it is about 1-100 micrometers.

[Electrodes (positive electrode and negative electrode)]
The configurations of the positive electrode (positive electrode active material layer) and the negative electrode (negative electrode active material layer) are not particularly limited for both non-bipolar and bipolar lithium ion secondary batteries, and known positive electrodes and negative electrodes are applicable. . The electrode includes a positive electrode active material if the electrode is a positive electrode and a negative electrode active material if the electrode is a negative electrode.

(Positive electrode active material)
As a material (material) of the positive electrode active material, any material may be used as long as the positive electrode material represented by the above general formula; xLiMO ₂ · (1-x) Li ₂ NO ₃ is used as the main positive electrode active material.

  Here, x in the above general formula may be a number satisfying 0 <x <1.

In addition, the electrochemically active M of LiMO _{2 in} the solid solution positive electrode material represented by the general formula: xLiMO ₂ · (1-x) Li ₂ NO ₃ has an average oxidation state of 3+. There is no particular restriction as long as it is one or more transition metals. M in the above formula may be one or more elements selected from Mn, Ni, Co, Fe, V, and Cr, but preferably selected from Mn, Ni, Co, and Fe. One or more elements are desirable. This is because when these transition metals are used, a positive electrode for a lithium ion battery having a higher capacity and better cycle durability can be produced. In particular, a solid solution positive electrode using electrochemically active layered LiMO ₂ has a low meaning as an active material of a high-capacity positive electrode candidate material unless Ni is contained. Therefore, as M in the above formula, those containing Ni are particularly preferable.

The general _{formula: xLiMO 2 · (1-x} ) Li 2 NO 3 in an electrochemically inert of solid solution represented as the N of _Li 2 NO _3, 1 kind average oxidation state is 4+ Any transition metal may be used as long as it is not particularly limited. N in the above formula is preferably one or more elements selected from Mn, Zr and Ti. This is because when these transition metals are used, a positive electrode for a lithium ion battery having a higher capacity and better cycle durability can be produced.

As the positive electrode active material, a positive electrode material represented by the above general formula; xLiMO ₂ · (1-x) Li ₂ NO ₃ may be used alone, or, if necessary, another positive electrode known in the art. An active material may be used in combination. Other positive electrode active materials include LiMn ₂ O ₄ , LiCoO ₂ , LiNiO ₂ , Li (Ni—Co—Mn) O _2, and lithium—such as those in which some of these transition metals are substituted with other elements A transition metal complex oxide is mentioned. In addition, for example, a lithium-transition metal phosphate compound, a lithium-transition metal sulfate compound, and the like can be given. In some cases, two or more other positive electrode active materials may be used in combination. Preferably, it is a lithium-transition metal composite oxide from the viewpoint of capacity and output characteristics, but it is needless to say that other positive electrode active materials may be used.

Here, in the positive electrode active material, the content of the main active material represented by the above general formula; xLiMO ₂ · (1-x) Li ₂ NO ₃ is 50% by mass or more, preferably 70% by mass or more. Preferably it is 85 mass% or more, More preferably, it is 95 mass% or more. Among them, it is particularly desirable to use a solid solution system material represented by the above general formula that can exhibit a large electric capacity exceeding 200 mAh / g in the total amount (100 mass%).

(Negative electrode active material)
The material (material) of the negative electrode active material is not particularly limited, and may be appropriately selected according to the type of battery.

As the negative electrode active material, any negative electrode active material usually used in a lithium ion secondary battery may be used. Specifically, carbon, a lithium alloy, or a lithium transition metal composite oxide can be suitably used. Examples of the carbon include crystalline carbon materials such as natural graphite, artificial graphite, carbon black, acetylene black, activated carbon, carbon fiber, coke, soft carbon, and hard carbon (non-graphitizable carbon material), and amorphous carbon materials. For example, carbon. Examples of the lithium alloy include a lithium-tin alloy, a lithium-silicon alloy, and a lithium alloy obtained by adding other elements thereto, and examples of the transition metal composite oxide include a lithium titanium composite oxide (lithium titanate: Li ₄ Ti ₅ O ₁₂ ) And the like. However, it is not limited to these. These may be used alone or in combination of two or more.

  In the present invention, as described above, even in a lithium ion battery system in which a plurality of batteries using a solid solution positive electrode and a negative electrode having a non-flat charge / discharge curve are connected in series, the charge / discharge pretreatment of the battery in which the potential of the positive electrode is regulated is performed. An object of the present invention is to provide a high capacity battery system with good cycle characteristics. From this point of view, as the negative electrode active material, a lithium-tin alloy, a lithium-silicon alloy, and a lithium alloy obtained by adding other elements to these can form a negative electrode having a high capacity and a non-flat charge / discharge curve. Can be suitably used.

  The average particle diameter of each active material contained in each positive electrode active material layer and negative electrode active material layer is not particularly limited, but is preferably 1 to 20 μm from the viewpoint of increasing the output. In the present specification, the “particle diameter” means the maximum distance L among the distances between any two points on the contour line of the active material. As the value of “average particle diameter”, the average particle diameter of particles observed in several to several tens of fields using an observation means such as a scanning electron microscope (SEM) or a transmission electron microscope (TEM). The calculated value shall be adopted. The particle diameters and average particle diameters of other components can be defined in the same manner.

  When the optimum particle size for expressing the unique effect of each active material is different, the optimum particle size for expressing each unique effect may be blended and used. It is not always necessary to make the particle size uniform.

  The thickness of the positive electrode (positive electrode active material layer: one side) and the negative electrode (negative electrode active material layer: one side) may be determined as appropriate in consideration of the intended use of the battery (emphasis on output, energy, etc.) and ion conductivity. Both are usually about 1 to 500 μm.

The positive electrode (positive electrode active material layer) and the negative electrode (negative electrode active material layer) can be applied by any of sputtering, vapor deposition, CVD, PVD, ion plating, and thermal spraying methods in addition to the usual method of applying (coating) slurry. It can also be formed. As the negative electrode active material suitable for such a forming method, carbon, lithium metal, lithium aluminum alloy, lithium tin alloy, lithium silicon alloy and the like can be suitably used in addition to lithium titanate. The positive electrode active material only needs to include a positive electrode material represented by the above general formula; xLiMO ₂ · (1-x) Li ₂ NO ₃ .

  The electrodes (positive electrode and negative electrode) are made of a conductive material (hereinafter also referred to as a conductive additive) for enhancing electronic conductivity, a binder, an electrolyte (a polymer matrix containing a lithium salt for imparting ion conductivity, high ion conductivity). Molecules, electrolytes, etc.).

  Examples of the conductive material (also referred to as a conductive additive) include acetylene black, carbon black, graphite, and carbon fiber. By including a conductive material, the conductivity of electrons generated in the electrode can be increased and the battery performance can be improved.

  Examples of the binder include polyvinylidene fluoride (PVdF), styrene butadiene rubber, and polyimide. However, it is not necessarily limited to these.

  The conductive binder having the functions of the conductive material and the binder may be used in place of the conductive material and the binder, or may be used in combination with one or both of the conductive material and the binder. Commercially available TAB-2 (manufactured by Hosen Co., Ltd.) or the like can be used as the conductive binder.

  Examples of the electrolyte include ion conductive polymers (solid polymer electrolytes) including lithium salts such as polyethylene oxide (PEO), polypropylene oxide (PPO), and copolymers thereof.

What is necessary is just to select the said lithium salt used according to the kind of battery. For example, inorganic acid anion salts such as LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , LiTaF ₆ , LiAlCl ₄ , Li ₂ B ₁₀ Cl ₁₀ ; LiCF ₃ SO ₃ , Li (CF ₃ SO ₂ ) ₂ N, Li Organic acid anion salts such as (C ₂ F ₅ SO ₂ ) ₂ N; mixtures thereof and the like can be used. However, it is not necessarily limited to these.

  The active material, conductive material, binder, electrolyte (polymer matrix, ion-conductive polymer, electrolyte, etc.), and the amount of electrode constituent materials such as lithium salt are determined for the intended use of the battery (emphasis on output, energy, etc.) It is preferable to determine in consideration of ionic conductivity. At this time, the capacity of the negative electrode is somewhat larger than the capacity of the positive electrode from the viewpoint of preventing lithium metal deposition on the negative electrode, or the area of the positive electrode active material layer is reduced from the viewpoint of preventing lithium deposition on the edge of the negative electrode active material layer. Needless to say, it is desirable to apply a well-known technique in the technical field of the present invention, such as making the area smaller than the area of the negative electrode active material layer.

[Electrolyte layer]
The electrolyte layer may be in a liquid, gel, or solid phase for any of the non-bipolar and bipolar lithium ion secondary batteries. In consideration of safety when the battery is damaged and prevention of liquid junction, the electrolyte layer is preferably a solid electrolyte such as a gel polymer electrolyte layer or an all-solid electrolyte layer. By using a solid electrolyte (which will be described later in detail, including a polymer gel electrolyte, a solid polymer electrolyte, and an inorganic solid electrolyte) as the electrolyte layer, it becomes possible to prevent liquid leakage. This is because it is possible to construct a lithium ion battery with high reliability that prevents entanglement.

  By using a gel polymer electrolyte layer (polymer gel electrolyte) as the electrolyte layer, the fluidity of the electrolyte is lost, the electrolyte is prevented from flowing out to the current collector, and the ionic conductivity between the layers can be blocked. . Examples of the gel electrolyte host polymer include PEO, PPO, PVdF, polyvinylidene fluoride-hexafluoropropylene copolymer (PVdF-HFP), PAN, PMA, and PMMA. Moreover, as a plasticizer, it is possible to use the electrolyte solution normally used for a lithium ion battery.

  The gel polymer electrolyte (polymer gel electrolyte) is produced by including an electrolyte solution usually used in a lithium ion battery in an all solid polymer electrolyte such as PEO or PPO. PVdF, PAN, PMMA, and the like, in which the electrolyte solution is held in a polymer skeleton having no lithium ion conductivity, also corresponds to the gel polymer electrolyte (polymer gel electrolyte). The ratio of the polymer constituting the gel polymer electrolyte (polymer gel electrolyte) and the electrolytic solution is not particularly limited. When 100% of the polymer is an all solid polymer electrolyte and 100% of the electrolytic solution is a liquid electrolyte, the intermediate is All are included in the concept of gel polymer electrolyte (polymer gel electrolyte). An inorganic solid electrolyte having ion conductivity such as an inorganic solid such as ceramic corresponds to the all solid electrolyte. Therefore, the polymer gel electrolyte, the solid polymer electrolyte, and the inorganic solid electrolyte are all included in the solid electrolyte.

  As the electrolyte layer, a conventionally known material can be used. Specifically, (a) polymer gel electrolyte (gel polymer electrolyte), (b) all solid polymer electrolyte (polymer solid electrolyte, inorganic solid electrolyte), (c) liquid electrolyte (electrolyte) or (d ) Separators (including non-woven fabric separators) impregnated with these electrolytes can be used.

(A) Gel polymer electrolyte (polymer gel electrolyte)
The gel polymer electrolyte (polymer gel electrolyte) refers to an electrolyte solution held in a polymer matrix. By using a gel polymer electrolyte as the electrolyte, the fluidity of the electrolyte is lost, and it is easy to cut off the ionic conductivity between each layer by suppressing the outflow of the electrolyte to the current collector layer such as a conductive polymer film. Is excellent.

Examples of the polymer matrix (polymer) or the gel electrolyte host polymer used as the polymer gel electrolyte include polymers having polyethylene oxide in the main chain or side chain (PEO), polymers having polypropylene oxide in the main chain or side chain ( PPO), polyethylene glycol (PEG), polyacrylonitrile (PAN), polymethacrylic acid ester, polyvinylidene fluoride (PVdF), a copolymer of polyvinylidene fluoride and hexafluoropropylene (PVdF-HFP), poly (methyl methacrylate) ( PMMA) and copolymers thereof are desirable. Among these, it is desirable to use PEO, PPO and their copolymers, or PVdF-HFP. Moreover, as a plasticizer, it is possible to use the electrolyte solution normally used for a lithium ion battery. Such an electrolytic solution is obtained by dissolving an electrolyte salt in a solvent. As the electrolyte _{(salt), LiPF 6, LiBF 4,} LiClO 4, LiAsF 6, LiTaF 6, LiAlCl 4, Li 2 B 10 Cl 10 inorganic acid anion salts such _{as, LiCF 3 SO 3, Li (} CF 3 SO 2 ) At least one selected from organic acid anion salts such as ₂ N and Li (C ₂ F ₅ SO ₂ ) ₂ N is desirable. As the solvent, ethylene carbonate (EC), propylene carbonate (PC), γ-butyrolactone (GBL), dimethyl carbonate (DMC), diethyl carbonate (DEC) and mixtures thereof are desirable.

  The ratio of the electrolytic solution in the gel electrolyte in the present invention is not particularly limited, but is preferably about several mass% to 98 mass% from the viewpoint of ionic conductivity. The present invention is particularly effective for a gel electrolyte having a large amount of electrolytic solution in which the proportion of the electrolytic solution is 70% by mass or more.

(B) All solid electrolyte (all solid polymer electrolyte, polymer solid electrolyte, inorganic solid electrolyte)
The use of an all solid electrolyte as the electrolyte is superior in that the fluidity of the electrolyte is lost, the electrolyte does not flow out to the current collector layer, and the ion conductivity between the layers can be blocked.

Examples of the all solid polymer electrolyte include known solid polymer electrolytes such as PEO, PPO, and copolymers thereof, and inorganic solid electrolytes having ion conductivity such as ceramics. The solid polymer electrolyte contains a lithium salt in order to ensure ionic conductivity. As the lithium salt, LiBF ₄ , LiPF ₆ , LiN (SO ₂ CF ₃ ) ₂ , LiN (SO ₂ C ₂ F ₅ ) ₂ , or a mixture thereof can be used.

(C) Liquid electrolyte (electrolyte)
Examples of the electrolytic solution include those obtained by dissolving an electrolyte salt in a solvent. As the electrolyte _{(salt), LiPF 6, LiBF 4,} LiClO 4, LiAsF 6, LiTaF 6, LiAlCl 4, Li 2 B 10 Cl 10 inorganic acid anion salts such _{as, LiCF 3 SO 3, Li (} CF 3 SO 2 ) At least one selected from organic acid anion salts such as ₂ N and Li (C ₂ F ₅ SO ₂ ) ₂ N is desirable. As the solvent, EC, PC, GBL, DMC, DEC and a mixture thereof are desirable.

(D) Separator impregnated with the electrolyte (including non-woven separator)
As the electrolyte that can be impregnated in the separator, the same electrolytes as those already described (a) to (c) can be used.

  Examples of the separator include a porous sheet and a nonwoven fabric made of a polymer that absorbs and holds the electrolyte.

  As the porous sheet, for example, a microporous separator can be used. Examples of the polymer include polyolefins such as polyethylene (PE) and polypropylene (PP); laminates having a three-layer structure of PP / PE / PP, polyimide, and aramid. The thickness of the separator cannot be uniquely defined because it varies depending on the intended use. However, in applications such as a secondary battery for driving a motor such as an electric vehicle (EV), a hybrid electric vehicle (HEV), and a fuel cell vehicle (FCV), the thickness is preferably 4 to 60 μm in a single layer or multiple layers. The separator preferably has a fine pore size of 1 μm or less (usually a pore size of about several tens of nm) and a porosity of 20 to 80%.

  As the nonwoven fabric, cotton, rayon, acetate, nylon, polyester; polyolefins such as PP and PE; conventionally known materials such as polyimide and aramid are used alone or in combination. The bulk density of the nonwoven fabric is not particularly limited as long as sufficient battery characteristics can be obtained by the impregnated polymer gel electrolyte. The porosity of the nonwoven fabric separator is preferably 50 to 90%. Furthermore, the thickness of the nonwoven fabric separator may be the same as that of the electrolyte layer, preferably 5 to 200 μm, particularly preferably 10 to 100 μm. When the thickness is less than 5 μm, the electrolyte retention deteriorates, and when it exceeds 200 μm, the resistance increases.

[Seal (also called sealant or peripheral insulating layer)]
For the bipolar lithium ion secondary battery, the seal part is used to prevent adjacent collectors in the battery from contacting each other and short-circuiting due to slight unevenness of the end of the laminated electrode. It arrange | positions at the peripheral part of a battery layer. Bipolar lithium ion secondary batteries are effectively used to prevent liquid junction due to leakage of the electrolyte layer. As the seal portion, for example, polyolefin resin such as PE and PP, epoxy resin, rubber, polyimide and the like can be used, and polyolefin resin is preferable from the viewpoint of corrosion resistance, chemical resistance, film-forming property, economy and the like. . However, it is not limited to these.

[Positive electrode and negative electrode tab]
In the non-bipolar and bipolar lithium ion batteries of the present invention, a tab (positive electrode tab and negative electrode) that is electrically connected to each current collector or to the outermost layer current collector for the purpose of taking out current outside the battery. Tab) is taken out of the battery case. Specifically, as shown in FIG. 1, a laminate sheet in which a positive electrode tab electrically connected to each positive electrode current collector and a positive electrode tab electrically connected to each negative electrode current collector are battery exterior materials. It is taken out outside. Alternatively, as shown in FIG. 2, a laminate in which a positive electrode tab electrically connected to the positive electrode outermost layer current collector and a negative electrode tab electrically connected to the negative electrode outermost layer current collector are battery outer packaging materials. It is taken out of the sheet.

  The material which comprises a tab (a positive electrode tab and a negative electrode tab) in particular is not restrict | limited, The well-known highly electroconductive material conventionally used as a tab for lithium ion secondary batteries can be used. As a constituent material of the tab, for example, metal materials such as aluminum, copper, titanium, nickel, stainless steel (SUS), and alloys thereof are preferable, and aluminum, copper, and the like are more preferable from the viewpoint of light weight, corrosion resistance, and high conductivity. Is preferable, and aluminum is particularly preferable. Note that the same material may be used for the positive electrode tab and the negative electrode tab, or different materials may be used. Moreover, it is good also as a positive electrode and a negative electrode tab by extending each electrical power collector or outermost layer electrical power collector, and you may connect the positive electrode and negative electrode tab which were prepared separately to each electrical power collector or outermost layer electrical power collector. .

[Positive electrode and negative electrode lead]
The positive electrode and the negative electrode lead are also used as necessary. For example, when directly taking out the positive electrode tab and the negative electrode tab to be output electrode terminals from each current collector or the outermost current collector, the positive electrode and the negative electrode lead may not be used.

  As a material for the positive electrode and the negative electrode lead, a lead used in a known lithium ion battery can be used. In addition, the parts removed from the battery exterior material should be heat-insulating so that they do not affect products (for example, automobile parts, especially electronic devices) by touching peripheral devices or wiring and causing leakage. It is preferable to coat with a heat shrinkable tube or the like.

[Third electrode]
As the reference electrode (lithium metal reference electrode), the third electrode 25 is connected to the positive electrode 12 (or the negative electrode 15) so that the potential of the positive electrode 12 of the battery relative to the potential of the third electrode 25 can be detected. It is necessary that ion movement can be performed (ion conductivity is ensured). Therefore, as described above, the third electrode 25 is provided between the electrolyte layer 13 that is sandwiched between the positive electrode 12 and the negative electrode 15 and in which Li ions move during charging and discharging.

  As a material constituting the third electrode 25, for example, Li, Sn—Li alloy or the like can be used.

  The third electrode 25 may be formed by coating or pasting the material constituting the third electrode 25 on the tip portion of the third electrode terminal lead 26. This is also because the potential of the positive electrode with respect to the (lithium metal) reference electrode can be detected appropriately using the third electrode as a reference electrode. In the form in which the third electrode 25 (reference electrode) is coated, tin is plated on the end (tip portion) of the nickel fine wire (third electrode terminal lead 26), which is reduced in the lithium electrolyte, Although the form etc. which are used as 3 electrodes 25 (Li plating) can be illustrated, it is not restrict | limited to these.

  The third electrode 25 only needs to be large enough to measure the potential with high accuracy as a reference electrode, and it is desirable to place a small electrode between the positive electrode 12 and the negative electrode 15 so as not to affect the battery reaction. . This is because if it is not placed between the positive electrode 12 and the negative electrode 15, there is a possibility of showing an incorrect potential.

[Third electrode terminal lead]
The third electrode terminal lead 26 connects the third electrode 25 and the third electrode tab 27. Therefore, a part of the third electrode terminal lead 26 can also be installed inside the electrolyte layer 13 that is electronically insulated from the positive electrode 12 and the negative electrode 15 (see FIG. 3). Therefore, it is necessary to be electrically insulated from the positive electrode 12 and the negative electrode 15. The third electrode terminal lead 26 does not function as a reference electrode, but may function as a terminal lead that extracts the potential of the third electrode 25 of the reference electrode (lithium metal reference electrode).

  From the above, as a material constituting the third electrode terminal lead 26, for example, Ni, stainless steel, Fe, or the like can be used.

[Third electrode tab]
The third electrode tab 27 is preferably bonded between the laminate sheets of the battery exterior material 22 at the sealing portion 23 and taken out of the battery (see FIGS. 3 and 4B). This is because such a structure can prevent external impact and environmental degradation during use. In particular, when used in a battery system for an electric vehicle, it is desirable to have a certain thickness so that the portion of the third electrode tab 27 taken out of the battery by an external impact is not broken. As an example, the same material and thickness as the electrode tab may be cut into a predetermined width as necessary.

  Further, as shown in FIG. 4B, the third electrode tab 27 may be taken out from the side different from the electrode tab or from the same side as shown in FIG. 4B.

  From the above, as a material constituting the third electrode tab 27, for example, nickel foil, stainless steel foil or the like can be used.

[Battery exterior materials]
As a battery exterior material, a conventionally known metal can case can be used, and a bag-like case that can cover a power generation element using a laminate film containing aluminum can be used. For example, a laminate film having a three-layer structure in which PP, aluminum, and nylon are laminated in this order can be used as the laminate film, but the laminate film is not limited thereto.

[Appearance structure of lithium ion secondary battery]
FIG. 4A is a perspective view showing the appearance of a stacked flat non-bipolar or bipolar lithium ion secondary battery which is a typical embodiment used in the battery system of the present invention. FIG. 4B is a perspective view showing the appearance of a laminated flat non-bipolar or bipolar lithium ion secondary battery which is a representative embodiment including the third electrode used in the battery system of the present invention. It is.

  As shown in FIG. 4A, the laminated flat lithium ion secondary battery 50 has a rectangular flat shape, and a positive electrode tab 58 and a negative electrode tab 59 for taking out electric power from both sides thereof. Has been pulled out. The power generation element 57 is wrapped by the battery outer packaging material 52 of the lithium ion secondary battery 50 and the periphery thereof is heat-sealed. The power generation element 57 is sealed in a state where the positive electrode tab 58 and the negative electrode tab 59 are pulled out to the outside. Has been. Here, the power generation element 57 corresponds to the power generation elements 17 and 37 of the non-bipolar or bipolar lithium ion secondary batteries 10 and 30 shown in FIG. 1 or FIG. Specifically, a plurality of single battery layers (single cells) 16 and 36 composed of positive electrodes (positive electrode active material layers) 12 and 32, electrolyte layers 13 and 35, and negative electrodes (negative electrode active material layers) 15 and 33 are laminated. It is a thing.

  As shown in FIG. 4B, the laminated flat lithium ion secondary battery 50a also has a rectangular flat shape, and a positive electrode tab 58 and a negative electrode tab 59 for taking out electric power from both sides thereof. Has been pulled out. Further, in order to detect the potential with the positive electrode 12 of the battery 50a using the third electrode as a reference electrode, the third electrode tab 27 connected to the third electrode via the third electrode terminal lead is a positive electrode tab 58, a negative electrode tab. It is drawn from a side different from 59.

  In addition, the lithium ion battery used for this invention is not restrict | limited to the thing of a laminated | stacked flat shape as shown in FIGS. For example, the wound type lithium ion battery may have a cylindrical shape, or may have a shape that is a flattened rectangular shape by deforming such a cylindrical shape. There is no particular limitation. In the said cylindrical shape thing, a laminate film may be used for the exterior material, and the conventional cylindrical can (metal can) may be used, for example, It does not restrict | limit.

  Also, the tabs 58 and 59 shown in FIG. 4A and the third electrode tab 27 shown in FIG. 4B are not particularly limited. For example, the positive electrode tab 58, the negative electrode tab 59, and further the third electrode tab 27 may be pulled out from the same side. Further, the positive electrode tab 58 and the negative electrode tab 59 may be divided into a plurality of parts and taken out from each side, and the present invention is not limited to the one shown in FIG. 4A. That is, the positive electrode tab 58 and the negative electrode tab 59 may divide and use the extracted electric power. Further, in a wound type lithium ion battery, instead of a tab, for example, a terminal may be formed using a cylindrical can (metal can).

  The lithium ion battery system of the present invention is a power source for driving a vehicle or an auxiliary power source that requires a high volume energy density and a high volume output density as a large capacity power source for an electric vehicle, a hybrid electric vehicle, a fuel cell vehicle, a hybrid fuel cell vehicle, etc. Can be suitably used.

  The battery system of the present invention is characterized by using a lithium ion battery system configured by connecting a plurality of the above-described batteries in series, and performing a pre-charge / discharge pretreatment of the battery with the positive electrode potential regulated as described below. To do.

[Battery system after pre-charge / discharge treatment]
In the battery system of the present invention, the battery system after the charge / discharge pretreatment may be used as it is and used as a power source for an electric vehicle or the like. Moreover, you may construct | assemble power supplies, such as an electric vehicle, in series or in parallel, or both using the battery system after performing the said charging / discharging pre-processing. Thus, the capacity and voltage can be freely adjusted by serialization and parallelization. Furthermore, you may construct | assemble power supplies, such as an electric vehicle by the battery system reconfigure | reconstructed by serialization or parallelization, or both using the battery of the battery system after performing the said charge / discharge pre-processing. In the case where the battery after the charge / discharge pretreatment is used and reconfigured in series or parallel or both to be a power source for an electric vehicle or the like, the battery provided with the third electrode is not necessarily It may not be used.

  In the present invention, using the non-bipolar secondary battery and its battery system after the charge / discharge pretreatment and the bipolar secondary battery and its battery system, these are connected in series, in parallel, or in series. It is also possible to construct a power source for an electric vehicle or the like by combining a plurality of them in parallel.

  FIG. 5 is an external view of a representative embodiment of the battery system of the present invention, FIG. 5A is a plan view of the battery system, FIG. 5B is a front view of the battery system, and FIG. It is a side view.

  As shown in FIG. 5, the battery system 300 according to the present invention further includes a plurality of detachable small battery systems 250 in which a plurality of batteries after the charge / discharge pretreatment are connected in series (or in parallel), It is formed by connecting in series or in parallel. As a result, it is possible to form a battery system 300 having a large capacity and a large output suitable for a vehicle drive power supply and an auxiliary power supply that require a high volume energy density and a high volume output density. 5A is a plan view of the battery system, FIG. 5A is a front view, and FIG. 5C is a side view. The small battery system 250 that can be attached and detached has an electrical connection means such as a bus bar. The battery system 250 is stacked in a plurality of stages using a connection jig 310. How many non-bipolar or bipolar lithium ion secondary batteries are connected to create the battery system 250, and how many battery systems 250 are stacked to make the battery system 300 are mounted. What is necessary is just to determine according to the battery capacity and output of the vehicle (electric vehicle) to be.

[Configuration of battery system and manufacturing method thereof]
FIG. 6 is a schematic view schematically showing the internal configuration of a small battery system that constitutes the battery system shown in FIG.

  As shown in FIG. 6, the charge / discharge pretreatment of the battery in which the potential of the positive electrode is regulated is such that the positive electrode 12 of the battery 50 a provided with the third electrode (reference electrode) 25 does not exceed a predetermined potential. It refers to pre-charging / discharging pretreatment by flowing the same current through the battery system (250) connected in series. By adopting such a configuration, a battery system with high capacity and good cycle durability can be constructed.

  The battery 50a including the third electrode (reference electrode) 25 may be connected in series to any position (connection order) of the battery group in the battery system.

The potential of the positive electrode 12 of the battery 50a is within a predetermined potential range with respect to the third electrode (lithium metal reference electrode 25) (= the positive electrode 12 of the battery 50a does not exceed the predetermined potential). The maximum potential of the positive electrode 12 of the battery 50a is controlled with respect to the lithium metal reference electrode 25 so as to correspond to the initial region of the plateau portion of the initial charge curve as shown in FIG. That's fine. Preferably, in the case of a positive electrode using Li [Ni _0.17 Li _0.2 Co _0.07 Mn _0.56 ] O ₂ as the positive electrode active material, the highest potential of the positive electrode 12 of the battery 50a is a lithium metal reference electrode. 25, the potential of the positive electrode may be controlled so as to be 3.9 V to 4.6 V, particularly 4.4 V to 4.6 V. That is, FIG. 7 is a drawing showing a charge / discharge curve of a positive electrode using Li [Ni _0.17 Li _0.2 Co _0.07 Mn _0.56 ] O ₂ as a positive electrode active material with respect to a lithium metal counter electrode. However, the potential of the flat portion of the initial charging curve varies depending on the type of positive electrode active material used. Therefore, by acquiring a charge / discharge curve of the positive electrode 12 of the battery 50a in advance for each positive electrode active material that can actually be used with respect to the lithium metal counter electrode, it corresponds to the initial region of the plateau portion of the initial charge curve. Thus, the potential of the positive electrode can be easily controlled. Here, the charge / discharge conditions for obtaining the charge / discharge curve of the positive electrode 12 of the battery 50a in advance are the same as those obtained in the same manner as the charge / discharge conditions of the pre-charge / discharge treatment. That is, the same electrode configuration (both positive electrode and counter electrode (= reference electrode) have the same composition), and constant current charge / discharge using the same current value (for example, current rate of 0.5 C or less) under the same temperature environment. Use what you have found. In the present invention, the highest potential with respect to the lithium metal reference electrode is synonymous with the highest potential converted to the lithium metal reference electrode.

  Moreover, the same electric current is sent through the whole battery system connected in series, and the charge / discharge pretreatment is performed. The charge / discharge performance depends on the particle size of the active material and the structure of the electrode in addition to the basic characteristics of the active material. Although it takes time to charge and discharge slowly, it has been confirmed that there is no problem. On the other hand, if the charge / discharge rate is too high, the pre-charge / discharge pretreatment of the present invention may not be sufficiently performed to the inside of the crystal. From this point of view, in the charge / discharge pretreatment, the charge / discharge method for flowing current to the whole battery system connected in series may be a constant current method or a constant current-constant voltage method. It is better not to have a large current value. From this point of view, the current value in the pre-charging / discharging treatment may be performed within a range that does not impair the operational effects of the present invention, and need not be specifically defined, but if it is intentionally defined, it depends on the particle diameter of the active material. It can be said that it is desirable to carry out at a current rate of 0.5 C or less (use a current rate of 0.5 C or less). However, since the above-described charge / discharge performance varies depending on the active material particle size and the electrode structure in addition to the basic characteristics of the active material, the charge / discharge pretreatment of the present invention In the technical scope of the present invention. That is, it can be said that it is desirable to use a current rate of 0.5 C or less as a current value flowing through the whole battery system connected in series at the time of charging and discharging in the pre-charge / discharge pretreatment, but it is not necessarily limited to such a condition. is not.

  The above-described pre-charge / discharge treatment of the battery in which the potential of the positive electrode is regulated will be described in more detail from the viewpoint of the method for producing the battery system of the present invention.

In the manufacturing method of the battery system of the present invention, the charge / discharge pretreatment uses the third electrode 25 as a reference electrode, and the maximum potential with respect to the Li metal reference electrode is 3.9 V or more and 4.6 V or less . It is a charge / discharge pretreatment for a battery that is charged and discharged under conditions under 1 to 30 cycles.

That is, limit the potential of the charge and discharge, the lithium metal reference electrode, 3.9V or 4.6V or less, a preferably may be performed charging and discharging in less 4.6V or 4.4 V, the charge and discharge required The number of cycles can be effectively applied from 1 to 30 times. By performing the charge / discharge pretreatment within the above range, the battery system is excellent in that it can produce a large amount of battery systems with high capacity and good cycle durability. In the battery system manufacturing method of the present invention, after the above charge / discharge pretreatment, in order to use the battery system at a high capacity, particularly when the charge / discharge is repeated at a maximum potential of about 4.8V, the remarkable cycle durability is achieved. It is possible to effectively exhibit effects such as sex.

  In the present invention, it is desirable to perform pre-charge / discharge pretreatment for the battery that gradually increases (increases in stages) the highest charge / discharge potential after the pre-charge / discharge pre-treatment. By performing the pre-charging / discharging treatment in this manner, the cycle durability can be improved even when used at a higher potential. In particular, 4.7V, 4.8Vvs. In the case of using up to a high potential capacity of Li (Li metal reference electrode) (using a high capacity), the maximum potential of the charge / discharge potential in the charge / discharge pretreatment is gradually increased as described above. It is excellent in that the durability of the electrode can be improved even by pre-charge / discharge pretreatment.

  Here, the number of cycles required for charging / discharging at each stage when the maximum potential (upper limit potential) in a predetermined potential range of charging / discharging is increased in stages is effectively in the range of 1 to 10 times. It is. However, the number of cycles may be larger as long as the above effect can be achieved without being limited to the above range. In addition, the number of charge / discharge cycles through the charge / discharge pretreatment process when increasing the maximum potential (upper limit potential) in a predetermined charge / discharge potential range in stages (add the number of cycles required for charge / discharge at each stage. The combined number of times is effectively in the range of 4 to 20 times. However, the number of cycles is not limited to the above range, and may be a larger number of cycles or a smaller number of cycles as long as the above effect can be achieved.

  In addition, 0.05 V to 0.1 V is effective as the potential increase (increase) for each time when the maximum potential (upper limit potential) in a predetermined charge / discharge potential range is increased stepwise. However, the present invention is not limited to the above range, and may be performed with a larger potential increase width (raising allowance) or with a smaller potential increase width (raising allowance) as long as the above effect can be achieved. You may go.

  The final maximum potential (end maximum potential) when raising the maximum potential (upper limit potential) in a predetermined potential range of charging / discharging stepwise may be 4.5 V or more and 5.0 V or less. If it is too high, side reactions will occur, and if it is too low, there will be no effect. Preferably, the voltage is 4.6V or more and 4.9V or less. However, the present invention is not limited to the above range, and the charge / discharge pretreatment may be performed up to a higher end maximum potential as long as the above effects can be achieved.

  In the pre-charging / discharging pretreatment of the present invention, it is preferable to finish charging when a predetermined maximum potential is reached during charging. This is because if charging is continued beyond a predetermined maximum potential, a so-called overcharge state may occur. From this point of view, it can be said that the upper limit value of the predetermined maximum potential is preferably about 5.0 V, and it is desirable not to perform further charging beyond this potential.

  In the charge / discharge pretreatment, the lowest potential (discharge end potential) with respect to the lithium metal reference electrode is not particularly limited by using the third electrode as a reference electrode. Specifically, it is desirable to perform charge and discharge for 1 to 30 cycles under the condition of 2 V or more and less than 3.5 V, more preferably 2 V or more and less than 3 V with respect to the lithium metal reference electrode. By performing the charge / discharge pretreatment within the above range, the battery system is excellent in that it has a high capacity, good cycle durability, and a high energy density battery system.

  Moreover, the temperature at the time of performing the pre-charging / discharging treatment of the present invention can be arbitrarily set as long as it is within a range that does not impair the effects of the present invention. Specifically, it may be performed at room temperature, may be performed at a temperature higher than room temperature, or may be performed at a temperature lower than room temperature. From the economical point of view, it is desirable to carry out at room temperature that does not require special heating and cooling.

  Moreover, it is desirable to carry out at a temperature higher than room temperature from the viewpoint that a larger capacity can be expressed and the cycle durability can be improved by a short charge / discharge pretreatment. The temperature at the time of performing the charge / discharge pretreatment at this time may be a temperature higher than room temperature, but is preferably 35 ° C. or higher and 80 ° C. or lower, and more preferably in the range of 40 to 60 ° C. The room temperature here means a temperature in a state where no special heating / cooling is performed, and it is in a range that can be said to be approximately 15 ° C. or more and less than 35 ° C. However, even if the temperature is out of the above range, it can be said that the temperature is at room temperature as long as the temperature is not in the state of special heating and cooling.

  As described above, the step (time) for performing the pre-charge / discharge treatment of the present invention is the state after the battery is constructed, specifically, the state of the battery system in which a plurality of batteries are connected in series as shown in FIG. Configuration). Thereby, the same electric current can be sent through the whole battery system, and the whole battery system can be pre-charged / discharged at a time, which can be said to be a manufacturing method suitable for mass production. It is preferable that all the batteries and all the single batteries used in this battery system have the same surface density of the positive electrode and the negative electrode and have the same capacity. This is because when the surface area of the positive and negative electrodes is made uniform and the areas of the opposing positive and negative electrodes are made constant, the positive electrode potential is regulated based on the reference electrode of the battery equipped with the reference electrode, The same current flows in all other connected batteries. Therefore, the positive electrodes of all the batteries can be processed simultaneously at the same time, and if the surface density is uniform and the electrode area is uniform, this process can be accurately performed for other batteries connected in series. This is because it is excellent in terms.

In addition, a method for producing a solid solution positive electrode material (main positive electrode active material) represented by the above general formula: xLiMO ₂ · (1-x) Li ₂ NO ₃ before charge / discharge pretreatment is particularly limited. Instead, a conventionally known production method can be used as appropriate. For example, as shown in the Examples, the composite carbonate method can be used as follows. That is, a predetermined amount of, for example, nickel sulfate, cobalt sulfate, and manganese sulfate, such as metal sulfate salts and metal nitrate salts of metal elements corresponding to M and N in the above formula, is prepared to prepare a mixed solution thereof. Ammonia water was added dropwise to this until pH 7 was reached, and a Na ₂ CO ₃ solution was further added dropwise to form a composite carbonate of Ni—Co—Mn (however, the M—N by the combination of M and N in the above formula). Different types of metal complex carbonates). Then, after suction filtration, it is washed with water and dried at a predetermined temperature and time (for example, at 120 ° C. for 5 hours). This is calcined at a predetermined temperature and time (for example, at 500 ° C. for 5 hours). A small excess of LiOH.H ₂ O is added thereto and mixed in an automatic mortar for a predetermined time (for example, 30 minutes). Thereafter, the main calcination is performed at a predetermined temperature and time (for example, at 900 ° C. for 12 hours), followed by rapid cooling using liquid nitrogen, whereby the above-described general formula: xLiMO ₂ (1 -X) A solid solution positive electrode material represented by Li ₂ NO ₃ can be produced. The last rapid cooling using liquid nitrogen is not particularly necessary, but can be said to be a useful processing operation in that a solid solution can be produced with a very beautiful state by performing such processing. .

In addition, the identification of the solid solution positive electrode material (main positive electrode active material) represented by the above general formula: xLiMO ₂ · (1-x) Li ₂ NO ₃ before the charge / discharge pretreatment was performed in Examples described later. X-ray diffraction (XRD), inductively coupled plasma (ICP) elemental analysis can be used.

The above is the description of the battery system of the present invention and the manufacturing method thereof [Vehicle]
The vehicle of the present invention is equipped with the battery system of the present invention. By mounting a battery system in which a plurality of high energy density batteries using the high-capacity positive electrode of the present invention are connected, a plug-in hybrid electric vehicle having a long EV travel distance or an electric vehicle having a long charge travel distance can be configured. In other words, the battery system of the present invention can be used as a power source for driving an electric vehicle. This is because the use of the battery system of the present invention for an electric vehicle results in a long-life and highly reliable automobile. Examples of such vehicles include hybrid vehicles, fuel cell vehicles, and electric vehicles (including automobiles such as passenger cars, trucks, and buses, four-wheeled vehicles such as light vehicles, and motorcycles and three-wheeled vehicles). Etc. However, the application is not limited to automobiles. For example, it can be applied to various power sources for moving vehicles such as other vehicles, for example, trains, and power sources for mounting such as uninterruptible power supplies. It is also possible to use as.

  FIG. 8 is a conceptual diagram of a vehicle equipped with the battery system of the present invention.

  As shown in FIG. 8, in order to mount the battery system 300 on a vehicle such as the electric vehicle 400, the battery system 300 is mounted under the seat at the center of the vehicle body of the electric vehicle 400. This is because if it is installed under the seat, the interior space and the trunk room can be widened. The place where the battery system 300 is mounted is not limited to under the seat, but may be a lower part of the rear trunk room or an engine room in front of the vehicle. The electric vehicle 400 using the battery system 300 as described above has high durability and can provide a sufficient output even when used for a long period of time. Furthermore, it is possible to provide electric vehicles and hybrid vehicles that are excellent in fuel efficiency and running performance. The vehicle equipped with the battery system of the present invention can be widely applied to a hybrid vehicle, a fuel cell vehicle and the like in addition to the electric vehicle as shown in FIG.

[Battery manufacturing method]
Next, the method for producing a battery that can be used in the battery system of the present invention is not particularly limited except that the above-described solid solution positive electrode material is used, and a conventionally known method is applied. Can be produced.

  Therefore, a battery manufacturing method that can be used in the battery system of the present invention to which a conventionally known method is applied will be briefly described below. However, the battery manufacturing method is not limited to these.

  The production of a battery in which the electrolyte is an electrolyte is made by cutting out a slightly larger negative electrode from a positive electrode and a negative electrode prepared by slurrying the forming materials of the positive electrode and the negative electrode, and vacuum-drying each of them at a predetermined temperature (eg, 90 ° C.). And dried for 1 day. The positive electrode and the negative electrode are alternately laminated between the positive electrode and the negative electrode with a separator having a predetermined thickness (for example, a 25 μm-thick polypropylene porous film) so that the outermost side becomes the negative electrode. And a negative electrode are bundled and a lead is welded to form a power generation element. A structure in which positive and negative leads are taken out from the power generation element is housed in an aluminum laminate film back, and an electrolytic solution is injected by a liquid injector, and sealed under reduced pressure to obtain a battery. In the battery including the third electrode, a separator 2 having a predetermined thickness is interposed between the positive electrode and the negative electrode used for any one (or more) of the plurality of unit cells (unit cells) constituting the battery. A sheet (for example, a 12.5 μm thick polypropylene porous film) is used. A third electrode terminal lead to which the third electrode is connected is sandwiched between the two separators. Thereafter, in the same manner as described above, the positive electrode and the negative electrode are alternately laminated so that the outermost side becomes a negative electrode via a serator. Each positive electrode and negative electrode are bundled and a lead is welded, and a third electrode tab is welded to the other end of the third electrode terminal lead to which the third electrode is not connected to form a power generation element. The power generation element has a structure in which positive and negative leads and a third electrode tab are taken out, placed in an aluminum laminate film back, injected with an electrolytic solution by a liquid injector, sealed under reduced pressure, and a third electrode. A battery equipped with

  When injecting the above electrolyte, seal a part of the sealing part with a suitable clip, etc. without heat sealing (bonding), and remove the gas generated in the pre-charge / discharge treatment. After degassing from the unsealed portion, the unsealed portion may be heat-sealed (joined) under reduced pressure.

  In addition to electrolyte batteries, electrolyte batteries, gel batteries, all-solid polymer batteries, and bipolar batteries using the electrolytes listed here can be produced by our well-known technology, so they are omitted here. To do.

  Next, a description will be given of criteria for determining whether or not the constituent requirements (technical scope) of the present invention are satisfied regardless of the manufacturing history.

  (1) The configuration of the present invention is the following two inventions (that is, the invention of the lithium ion battery system (first invention) and the invention of the method of manufacturing this lithium ion battery system (second invention)). .

  1st invention: In a battery system in which a plurality of batteries are connected in series, at least one battery includes a third electrode that is electronically insulated from the positive electrode and the negative electrode, and the potential of the positive electrode is regulated by using the third electrode as a reference electrode. The battery is subjected to pre-charging / discharging pretreatment.

Here, the battery constituting the battery system is a lithium ion battery in which a main positive electrode active material is represented by a general formula: xLiMO ₂ · (1-x) Li ₂ NO ₃ . X in the above general formula is a number satisfying 0 <x <1, M is one or more transition metals whose average oxidation state is 3+, and N is one type whose average oxidation state is 4+ The above transition metals.

  In addition, the pre-charging / discharging pretreatment of the battery in which the positive electrode potential is regulated is the same as the entire lithium ion battery system connected in series so that the positive electrode of the battery including the third electrode does not exceed a predetermined potential. This refers to pre-charging / discharging pretreatment by flowing current.

  2nd invention: The manufacturing method of the lithium ion battery system of 1st invention.

Here, the charge / discharge pretreatment of the first invention uses the third electrode as a reference electrode, and is charged under the condition that the maximum potential with respect to the lithium metal reference electrode is 3.9 V or more and 4.6 V or less. It is a pre-charge / discharge treatment for a battery that discharges for 1 to 30 cycles.

(2) Criteria for determining whether or not the constituent requirements (technical scope) of the present invention are satisfied (see comparison between Example 2 and Comparative Example 2 described later)
(I) A battery system that is considered to satisfy the configuration requirements (technical scope) of the present invention is prepared (obtained), the battery system is disassembled in a discharged state, the battery inside the battery system is further disassembled, and the positive electrode is taken out A battery using lithium metal as a counter electrode is constructed. In addition, after the battery is configured, the battery mounted on the device is initially charged and discharged several times at the single cell stage, and after being configured into the small battery system 250 (module battery) and battery system 300 (assembled battery) in FIG. In addition, there is a case where it is put on the market after the initial charge / discharge inspection after being mounted on the device. Therefore, the battery of the battery system that can be prepared (obtained) is considered to have undergone a charge / discharge test about 5 to 50 times after the battery configuration.

    (Ii) Therefore, a battery constituted by using the positive electrode taken out from the disassembled battery is subjected to a constant current charge / discharge test at room temperature in a voltage range of 2.0 V to 4.8 V.

    (Iii) A potential differentiation (dQ / dE) of the electric quantity (Q) is calculated from the obtained data and plotted against the potential (E).

  FIG. 9 (after 50 cycles) shows a comparison between the case where the pre-charge / discharge treatment is performed according to the present invention and the case where it is not performed. In FIG. 9, a dQ / dE curve obtained by plotting data when the charge / discharge pretreatment of the present invention is performed is indicated as “with pretreatment”. On the other hand, the dQ / dE curve obtained by plotting the data when the charge / discharge pretreatment of the present invention is not applied is “no pretreatment”.

  From comparison of waveforms in the region of 3.0V to 3.3V as shown in FIG. 9, the positive electrode material subjected to the charge / discharge pretreatment of the present invention shows a characteristic peak at 3.2V. On the other hand, those not subjected to the charge / discharge pretreatment of the present invention do not have this peak.

  It can be determined whether or not the constituent requirements (technical scope) of the present invention are satisfied by the presence or absence of this peak. Also, even if the battery system is shipped with a charge / discharge cycle that does not reach 50 cycles, several batteries are taken out and charged / discharged for 10 cycles, 20 cycles, 30 cycles, and 40 cycles, respectively. If the battery disassembly inspection is performed, it can be determined whether or not the configuration requirement (technical scope) of the present invention is satisfied based on the same determination criterion (the presence or absence of a characteristic peak of 3.2 V).

  As shown in FIG. 6, if the battery including the third electrode is used as it is in the battery system, it can be said that the probability of satisfying the configuration requirement (technical scope) of the present invention is extremely high. As described above, the determination criterion is effective when the battery system is constructed by intentionally removing the battery including the third electrode after the pre-charge / discharge treatment.

(3) About the physical meaning of the oxidation pretreatment of the present invention By the charge / discharge pretreatment of the present invention, the charge / discharge cycle characteristics in the high potential region of the positive electrode material (xLiMO ₂ · (1-x) Li ₂ NO ₃ ) are improved. Although it is remarkably improved, this mechanism is considered as follows. This material has a layered structure such as LiCoO ₂ , but the transition metal layer also contains Li ⁺ . When charged to the high potential region for expressing a high capacity, Li ⁺ not a layer of Li ⁺ only of the transition metal layer Li ⁺ and oxygen in the crystalline framework is released, the movement of large ions inside the crystal (rearrangements) are It is thought to happen. If the pre-charge / discharge pretreatment of the present invention is not performed, it is considered that the deterioration proceeds during the rapid rearrangement of ions. The deterioration mechanism is considered to be deteriorated by changing from a layered structure to a spinel structure by charge / discharge in a small region in the crystal, as was the case with conventional layered LiMnO ₂ .

Li ⁺ ion exchange with H ⁺ , which can occur by oxidative decomposition of the solvent at high potential, is more likely to occur due to the crystal surface opening or defects during this rapid ion rearrangement. This can accelerate the degradation.

In contrast to this, the charge / discharge pretreatment of the present invention gradually advances the rearrangement of ions inside the crystal, so that a cycle can be achieved to reach a stable layered structure without greatly disturbing the initial layered structure. It is thought that durability is improved. Candidates for a stable layered structure include a crystal structure with relatively fewer defects, a very small amount of Ni ²⁺ entering the lithium layer in the crystal as a pillar, and a very small number of nanocrystals. The thing which has the role of can be considered.

  Hereinafter, the present invention will be described in detail using examples.

Example 1 and Comparative Example 1
1. Synthesis of solid solution based positive electrode material (= positive electrode active material) The sample (solid solution based positive electrode material) was synthesized as follows using a composite carbonate method. Nickel sulfate, cobalt sulfate, and manganese sulfate are weighed in predetermined amounts to prepare a mixed solution thereof. Ammonia water is added dropwise until pH 7 is reached, and a Na ₂ CO ₃ solution is further added dropwise to add Ni—Co—. A complex carbonate of Mn was precipitated. While the Na ₂ CO ₃ solution was dropped, pH 7 was maintained with aqueous ammonia. Then, it filtered by suction, washed with water, and dried at 120 degreeC for 5 hours. This was calcined at 500 ° C. for 5 hours. A small excess of LiOH.H ₂ O was added thereto and mixed for 30 minutes in an automatic mortar. Thereafter, the main calcination was performed at 900 ° C. for 12 hours, followed by rapid cooling using liquid nitrogen.

The sample synthesized as described above (Li [Ni _0.17 Li _0.2 Co _0.07 Mn _0.56 ] O ₂ ) was identified by XRD and ICP. It was identified not only by XRD results but also by elemental analysis by ICP. The synthesized sample is a space group

A diffraction line showing a superlattice structure appeared at 20 to 23 °. The composition was as shown in Table 1. When the coefficient of the lower composition formula of the sample in Table 1 (the above general formula: xLiMO ₂ · (1-x) Li ₂ NO ₃ notation) is multiplied by the conversion factor, the upper composition formula of Table 1 is represented. Become. That is, the notation of the composition formula in the upper part of the sample in Table 1 is a notation when all are regarded as layered LiMO ₂ (M: one or more transition metals having an average oxidation state of 3+). In the following description, the notation of the sample may use the notation of the composition formula in the upper part of the sample in Table 1.

2. Production of Electrode and Battery Hard carbon having an average particle diameter of 21 μm was used as the negative electrode active material. The charge / discharge curve of hard carbon has a capacity of about 200 mAh / g near the lithium potential, and has a capacity of about 200 mAh / g with a gradient from that to around 1 V (see FIG. 10). There is an irreversible capacity of 100 mAh / g during charging and discharging. For this reason, if the battery is assembled and then charged, the potential of the negative electrode changes as the battery is charged, and the charge / discharge pretreatment by regulating the potential cannot be performed by a normal method. PVdF was used for the binder, and acetylene black was used as the conductive additive. An aluminum foil with a thickness of 20 μm was used for the positive electrode current collector, and a copper foil with a thickness of 15 μm was used for the negative electrode current collector. As the electrolytic solution, 1M LiPF ₆ EC: DEC (3: 7 vol%) (where EC is ethylene carbonate and DEC is diethyl carbonate) was used.

  In the production of the hard carbon negative electrode, the mass ratio of the active material and PVdF was 91: 9. An active material, PVdF, and an appropriate amount of NMP were added to a homogenizer container and well stirred and mixed to prepare a slurry. This slurry was applied onto a copper foil (negative electrode current collector) using a die coater and dried. Similarly to the positive electrode shown below, a negative electrode active material layer is formed on both sides of a copper foil (negative electrode current collector) and pressed to make the negative electrode active material layer portion 55 mm × 105 mm, and the negative electrode active material It was cut out leaving the lead part without the layer. The thickness of the negative electrode active material layer (one side) was 80 μm at the time of completion.

  Preparation of the positive electrode was carried out so that the electrode composition ratio (mass ratio) was active material (using the solid solution positive electrode material of the above sample): acetylene black: PVdF = 86: 7: 7, and an appropriate amount of NMP (N-methyl-2-pyrrolidone) was added and well stirred and mixed with a homogenizer. Thereafter, a certain amount of this slurry was applied to an aluminum foil (positive electrode current collector) using a die coater and dried. In this way, a positive electrode active material layer is formed on both surfaces of an aluminum foil (positive electrode current collector), and pressed by a roll press so that the positive electrode active material layer portion becomes 50 mm × 100 mm, and the positive electrode active material layer The lead portion without the material layer was left and cut out. The amount of active material per unit area was adjusted by repeating coating so that the reversible capacity was 0.9 with respect to the active material surface density of the hard carbon negative electrode. By such adjustment, an electrode having a small capacity variation (uniform electrode) was obtained for each of the positive electrode and the negative electrode, and the variation in the surface density of the electrodes was within 5%. Here, how to determine the surface density of the electrode: The mass of the electrode layer per unit area is obtained, and is multiplied by the mass ratio of the hard carbon (negative electrode active material) or the positive electrode active material in the electrode composition. Measured to obtain. The thickness of the positive electrode active material layer (one side) was 72 μm at the time of completion.

  Each of the positive electrode and negative electrode cut out above was dried for 1 day in a vacuum dryer at 90 ° C. and used. Between the positive electrode and the negative electrode, five positive electrodes are alternately laminated with six negative electrodes so that the outermost side is a negative electrode through two porous films made of polypropylene having a thickness of 25 μm, An aluminum laminate with a structure in which a positive electrode tab and a nickel negative electrode tab connected to each other through a positive electrode and a negative electrode lead are taken out from this power generation element (laminate) by bundling the negative electrode and welding a lead. The battery was placed in a film bag, and an electrolyte solution was injected with a liquid injector and sealed under reduced pressure to obtain a battery. In addition, the seal | sticker at this time was a temporary seal | sticker, and it was set as the structure which can be opened and sealed again after charging / discharging.

  In addition, a battery having a third electrode in addition to the positive electrode and the negative electrode was produced as follows. A schematic diagram of this battery is shown in FIG. 4B, and the insertion structure of the third electrode is shown in FIG. A nickel wire (third electrode terminal lead 26) with a diameter of 20 μm is attached by welding to a negative electrode nickel tab (third electrode tab 27), and a very small amount of lithium (third electrode 25) is attached to the tip. The nickel tab (third electrode tab 27) is inserted into the electrode tab (positive electrode and negative electrode tabs 58, 59) so that the portion is between the positive electrode 12 and the negative electrode 13, and between the two separators 13. Similarly, heat sealing was performed using a seal film. This seal film is wound around a tab, and is sandwiched between laminate films 22 (52) and heat-sealed for sealing.

3. Production of Lithium Ion Battery System Lithium ion in which a battery not including the third electrode is connected in series, and one battery including the third electrode is added in series connection, so that a total of 24 batteries are connected in series. A battery system was produced and used as the lithium ion battery system of Example 1 (see FIG. 6). For comparison, a lithium ion battery system in which a total of 24 batteries were connected in series using only a battery not including the third electrode was produced, and the lithium ion battery system of Comparative Example 1 was obtained.

  The charge / discharge pretreatment of the positive electrode of the lithium ion battery system of Example 1 was performed as follows. The battery system is connected to a charging / discharging device so that the potential of the positive electrode with respect to the third electrode of the battery having the third electrode can be measured, and at a current value of 0.1 A until the potential difference becomes 4.5V. After constant current charging, constant current discharge was performed until this potential difference became 2 V, and this was repeated 5 times. Further, the potential difference was changed from 4.5 V to 4.6 V, 4.7 V, and 4.8 V, and charging / discharging was performed twice each time (for each potential difference). Each battery was opened in a dry room in a discharged state, and sealed again under reduced pressure for degassing to obtain a lithium ion battery system.

  On the other hand, for the lithium ion battery system of Comparative Example 1, after repeating charging and discharging twice at a current of 0.1 A between 1.5 V and 4.8 V, each battery was opened and the reduced pressure seal was similarly applied. Thus, a lithium ion battery system was obtained. In Comparative Example 1, when charging and discharging twice, the first one of the 24 batteries connected in series is charged until the maximum voltage is 4.8 V, and the first of the 24 batteries connected in series is charged. One battery was discharged until the minimum voltage was 1.5 V (the following evaluation of the lithium ion battery system was performed in the same manner). Moreover, since the comparative example 1 is the voltage of the battery of a hard carbon counter electrode, it charged / discharged between 1.5V-4.8V so that the capacity | capacitance as a battery could fully be utilized.

4). Lithium-ion battery system evaluation Lithium-ion battery system evaluation is performed so that the voltage of each battery can be detected and charged until the maximum voltage of the series-connected battery reaches 4.7 V. Was charged and discharged 30 times at a constant current of 0.2 A. The discharge capacity of each lithium ion battery system after 30 times is shown as “Capacity (Ah) at 30th cycle” in Table 1. In the charge / discharge pretreatment, the constant current is set to 0.1A, and in the evaluation of the battery system, the constant current is set to 0.2A and the current value. More stable arrangement of the constituent elements, gentle transition to a stable structure) is carried out at a small current rate so that it is milder and more reliable.

  As can be seen from Table 1, according to the present invention, the lithium ion battery system using the series-connected solid solution system positive electrode as the active material is combined with the battery including the third electrode, so that The charge / discharge pretreatment necessary for durability can be simultaneously applied to all the batteries of the battery system. Therefore, it has been confirmed that it is possible to efficiently supply a large amount of a lithium ion battery system having a high capacity and excellent cycle durability.

Example 2 and Comparative Example 2
Both Example 2 and Comparative Example 2 were carried out in the same manner up to “3. Production of Lithium Ion Battery System” in Example 1 and Comparative Example 1, and in “4. Evaluation of Lithium Ion Battery System” above, In such a manner that the voltage can be detected, the battery is charged until the maximum voltage of the series-connected batteries is 4.8V, and is discharged until the minimum voltage of the series-connected batteries is 2.0V. The battery was charged and discharged 50 times.

  From the obtained charge / discharge data, the potential differentiation of the capacity was calculated using PC software: Origin 6.0 professional, and the data of the battery (Example 2) subjected to the charge / discharge pretreatment and the battery not subjected to the comparison (Comparative Example) The results of 2) are shown together in FIG.

  From the dQ / dE curve after 50 cycles shown in FIG. 9, a peak of about 3.1 V appears clearly in the battery not subjected to the pre-charge / discharge treatment of Comparative Example 2 (no treatment), and the charge / discharge of Example 2 The battery that had been pretreated (with pretreatment) showed a tendency for a peak of 3.2 V to appear strongly. This result suggests that the structural change between the battery which has not been subjected to the charge / discharge pretreatment and the battery which has been subjected to the charge / discharge pretreatment is different (in the specification, “the charge / discharge pretreatment of the present invention”). See the section on physical meaning).

1 is a schematic cross-sectional view schematically showing an outline of a laminated flat non-bipolar lithium ion secondary battery which is a typical embodiment of a lithium ion battery of the present invention. It is the cross-sectional schematic which represented typically the outline | summary of the laminated flat bipolar lithium ion secondary battery which is another typical embodiment of the lithium ion battery of this invention. FIG. 6 is a schematic partial cross-sectional view schematically showing a state of installing a third electrode of a non-bipolar lithium ion secondary battery including a third electrode that is electronically insulated from a positive electrode and a negative electrode. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view schematically showing an appearance of a stacked flat lithium ion secondary battery that is a typical embodiment of a lithium ion battery according to the present invention. A laminated flat non-bipolar or bipolar lithium ion secondary battery, which is a representative embodiment provided with a third electrode electronically insulated from a positive electrode and a negative electrode, used in the battery system of the present invention It is a perspective view showing the external appearance. 5A and 5B are external views schematically showing typical embodiments of the battery system of the present invention, in which FIG. 5A is a plan view of the battery system, FIG. 5B is a front view of the battery system, and FIG. 5C is a battery system. FIG. FIG. 6 is a schematic view schematically showing the internal configuration of a small battery system constituting the battery system shown in FIG. 5. A diagram showing charge-discharge curves of _{Li [Ni 0.17 Li 0.2 Co 0.07} Mn 0.56] O 2, the first time (1st), second round (2nd) and the fifth ( It is drawing which showed each charging / discharging curve of 5th). It is a conceptual diagram of the vehicle carrying the battery system of this invention. In the constant current charge / discharge test using the electrodes of Example 2 and Comparative Example 2, the potential differentiation of the capacity was calculated using the PC software from the obtained charge / discharge data, and the data of the cell subjected to the charge / discharge pretreatment were performed. It is the figure which showed the dQ / dE curve which each represented the result of the cell which is not. It is drawing which shows the charge curve of hard carbon.

Explanation of symbols

10 Non-bipolar lithium ion secondary battery,
10a Non-bipolar lithium ion secondary battery provided with a third electrode,
11 positive electrode current collector,
11a Outermost layer positive electrode current collector,
12, 32 positive electrode (positive electrode active material layer),
13, 35 electrolyte layer,
14 negative electrode current collector,
15, 33 negative electrode (negative electrode active material layer),
16, 36 single battery layer (= battery unit or single cell),
17, 37, 57 Power generation element,
18, 38, 58 positive electrode tab,
19, 39, 59 negative electrode tab,
20, 40 Positive terminal lead,
21, 41 Negative terminal lead,
22, 42, 52 Battery exterior material (for example, laminate film),
23 A sealing part in which a laminate sheet is heat-sealed,
25 third electrode,
26 Third electrode terminal lead,
27 Third electrode tab,
30 Bipolar lithium ion secondary battery,
31 current collector,
31a The outermost layer current collector on the positive electrode side,
31b The outermost layer current collector on the negative electrode side,
34 Bipolar electrode,
34a, 34b The electrode located in the outermost layer,
43 Sealing part (insulating layer),
50 lithium ion secondary battery,
50a lithium ion secondary battery provided with a third electrode;
250 Small assembled battery (module battery),
300 battery packs,
310 connection jig,
400 Electric car.

Claims (8)

The main cathode active material is a general formula
(Where x is a number satisfying 0 <x <1, M is one or more transition metals whose average oxidation state is 3+, and N is one or more types whose average oxidation state is 4+ In a lithium ion battery system in which a plurality of lithium ion batteries represented by
At least one battery includes a third electrode that is electronically insulated from the positive electrode and the negative electrode, and the potential of the positive electrode of the battery including the third electrode is defined with respect to the third electrode. ,
When the maximum potential is defined as 100% of the potential range from the lower limit to the upper limit of the plateau portion of the first charging curve, the potential range is 30% higher from the lower limit to the lower limit.
A lithium ion battery system, wherein the same current is supplied to the entire lithium ion battery system connected in series to perform pre-charging and discharging processes.   2. The lithium ion battery system according to claim 1, wherein the M is one or more elements selected from Mn, Ni, Co, and Fe.   3. The lithium ion battery system according to claim 1, wherein the N is one or more elements selected from Mn, Zr, and Ti. 4. The main positive electrode active material is Li [Ni _0.17 Li _0.2 Co _0.07 Mn _0.56 ] O ₂ If
The charge / discharge pretreatment is performed under a condition that a maximum potential with respect to a lithium metal reference electrode is 3.9 V or more and 4.6 V or less using the third electrode as a reference electrode. Item 4. The lithium ion battery system according to any one of Items 1 to 3. Vehicle equipped with a lithium ion battery system according to any one of claims 1-4. It is a manufacturing method of the lithium ion battery system in any one of Claims 1-3,
In the pre-charging / discharging pretreatment, the maximum potential with respect to the lithium metal reference electrode using the third electrode as a reference electrode is 100% of the potential range from the lower limit to the upper limit of the plateau portion of the first charging curve. A method for producing a lithium ion battery system, characterized in that it is a pre-charge / discharge pretreatment for a battery that is charged and discharged for 1 to 30 cycles in a potential range 30% higher from the lower limit to the lower limit . The method of manufacturing a lithium ion battery system according to claim 6 , wherein after the pre-charge / discharge treatment, a pre-charge / discharge pretreatment for gradually increasing the maximum potential of charge / discharge is performed. The main positive electrode active material is Li [Ni _0.17 Li _0.2 Co _0.07 Mn _0.56 ] O ₂ If
The charge / discharge pretreatment is performed under a condition that a maximum potential with respect to a lithium metal reference electrode is 3.9 V or more and 4.6 V or less using the third electrode as a reference electrode. Item 8. A method for producing a lithium ion battery system according to Item 6 or 7.