JP2008270201A - Positive electrode material for lithium ion battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a positive electrode material for a lithium ion battery having high capacity and suppressing deterioration in charge discharge at high potential, and to provide a lithium ion battery using the same. <P>SOLUTION: In the positive electrode material for the lithium ion battery represented by general formula: xLiMO<SB>2</SB>-(1-x)Li<SB>2</SB>NO<SB>3</SB>, oxidation treatment is performed. In the formula, 0<x<1; M is one or more transition metals having an average oxidation state of 3+; N is one or more transition metals having an average oxidation state of 4+. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a positive electrode material for a lithium ion battery, a method for producing the same, and a lithium ion battery using the positive electrode material for a lithium ion battery. The positive electrode material for a lithium ion battery and the lithium ion battery using the same of the present invention are used, for example, as a driving power source for motors of 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. In addition, for electric vehicles, it is necessary to bring the distance for one charge closer to a gasoline engine vehicle, and a battery with higher energy 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 has been studied as a positive electrode material that can 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 or Ni) is 200 mAh / g. Therefore, it is expected as a high-capacity positive electrode candidate material that can exhibit a large electric capacity exceeding (see, for example, Patent Document 1).
JP-A-9-55211

However, the solid solution positive electrode using Li ₂ MnO ₃ which is a high capacity positive electrode candidate material described in Patent Document 1 has a large discharge capacity, but if the charge / discharge potential is high, the cycle characteristics are poor. There was a problem that it deteriorated easily by repeated discharge. For this reason, even a lithium ion battery using such a solid solution positive electrode as a high-capacity positive electrode has a problem that the cycle durability under a high-capacity usage condition is poor, and it deteriorates immediately when charging / discharging at a high potential. It was.

  Therefore, an object of the present invention is to provide a positive electrode material for a lithium ion battery that has a high capacity and suppresses deterioration due to charging and discharging at a high potential, and a lithium ion battery using the same.

  As a result of intensive studies to solve the above problems, the present inventors have completed the present invention by obtaining the following knowledge. In other words, the high-capacity positive electrode candidate material is oxidized as the main active material of the positive electrode, and more specifically, the electrode is formed and charged and discharged within a potential range that does not exceed a predetermined potential, thereby enabling cycle durability under high-capacity use conditions It has been found that the present invention can be improved, and the present invention has been completed.

  That is, the present invention has the general formula

It can achieve by the positive electrode material for lithium ion batteries represented by these, The oxidation process is given, The positive electrode material for lithium ion batteries characterized by the above-mentioned. Here, x in the above general formula is a number satisfying 0 <x <1, M is one or more transition metals having an average oxidation state of 3+, and N is an average oxidation state of 4+. One or more transition metals.

In the positive electrode material for a lithium ion battery and the lithium ion battery using the same of the present invention, the Li ₂ MnO ₃ electrochemically inactive layered lithium composite oxide and the solid solution positive electrode with high capacity charge / discharge at high voltage Cycle characteristics are greatly improved. As a result, a high energy lithium ion battery with good cycle durability can be manufactured.

  The positive electrode material for the lithium ion battery of the present invention has a general formula

The positive electrode material for a lithium ion battery represented by the formula is characterized by being subjected to an oxidation treatment. Here, x in the above general formula is a number satisfying 0 <x <1, M is one or more transition metals having an average oxidation state of 3+, and N is an average oxidation state of 4+. One or more transition metals. The lithium ion battery of the present invention is characterized by using the positive electrode material for a lithium ion battery of the present invention as a main active material of the positive electrode.

A positive electrode material of the so-called solid solution system represented by such a general formula: xLiMO ₂ · (1-x) Li ₂ NO ₃ is expected as a high-capacity material, but has a high potential that expresses a high capacity. When the battery is charged up to 2 hours, there is a problem that deterioration due to charge / discharge is quick. On the other hand, the mechanism of the effect is not yet well understood, but the present inventors have found that the problem can be greatly improved by oxidation treatment. As a result, the solid solution positive electrode material of the present invention can provide a positive electrode material for a lithium ion battery having high capacity and good cycle durability. Furthermore, the lithium ion battery of the present invention is excellent in that a battery having high energy density and good cycle durability can be formed by using the solid solution positive electrode material of the present invention as a main active material of the positive electrode.

  That is, according to the present invention, the cycle durability at a high capacity of concern can be greatly improved. Although the cycle deterioration mechanism of the present invention cannot be determined yet, it is considered as follows. The portion of the plateau seen in the initial charge curve (see the example diagram below) is not yet clearly understood, but according to one theory, the dianion of oxygen in the solid solution cathode crystal It is considered a process in which lithium ions are released while being oxidized. When this reaction occurs, a significant change in the crystal structure occurs, and it is assumed that the subsequent charge / discharge cycle deterioration occurs as a result. The present invention does not cause a significant change in the crystal structure from the beginning, but is performed by oxidation treatment such as charging, charging / discharging, oxidation with an oxidizing agent corresponding to charging, oxidation using a redox mediator in a lower potential region. A gentle transition to a more stable arrangement and a stable structure of constituent elements proceeds. With this gentle transition, even if the voltage is increased further and charging is performed through the plateau region, the structure has already been stabilized, so charging / discharging including a high potential region capable of developing a high capacity is possible. I think I will be able to withstand the cycle. As another idea, a film corresponding to the surface protective film (SEI) of the negative electrode is formed on the surface of the positive electrode active material by performing an oxidation treatment (such as charging) at a predetermined potential or lower. By forming the coating, it is considered that the surface of the active material particle is stabilized by being protected or fixed by the stable coating even when the constituent elements in the plateau region of the initial charge curve are greatly moved. You can also. The present invention (of oxidation treatment) may be applied in the state of a positive electrode active material powder, applied even when an electrode is configured, or applied after a battery is assembled with a negative electrode. Application to the battery can be carried out by applying the application condition (oxidation process condition) of the present invention in consideration of the potential profile of the capacitance of the negative electrode to be combined.

  Hereinafter, embodiments of a positive electrode material for a lithium ion battery and a lithium ion battery using the same according to the present invention will be described with reference to the drawings. The technical scope of the present invention is based on the description of the claims. It should be defined 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 secondary battery according to the present invention can have a high capacity, it can be suitably used as a drive power source for a vehicle, and can be sufficiently applied to a lithium ion secondary battery for a portable device such as a mobile phone. Is possible.

  That is, the lithium ion secondary battery that is the subject of the present invention may be any one that uses the above-described positive electrode material for a lithium ion battery of the present invention as the main active material of the positive electrode. There is no particular limitation.

  For example, when the lithium ion secondary battery is distinguished by form / structure, it can be applied to any conventionally known form / structure such as a stacked (flat) battery or a wound (cylindrical) battery. Is.

  In addition, when viewed in terms of electrical connection (electrode structure) in a lithium ion secondary battery, it can be applied to both the above-described (internal parallel connection type) battery and bipolar (internal serial connection type) battery. It is.

  When distinguished by the type of electrolyte layer in the lithium ion secondary battery, a solution electrolyte type battery using a solution electrolyte such as a nonaqueous electrolyte solution for the electrolyte layer, a polymer battery using a polymer electrolyte for the electrolyte layer, etc. It can be applied to any conventionally known 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.

  In addition, by adopting a laminated (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.

  Accordingly, in the following description, a lithium ion secondary battery (internal parallel connection type) and a bipolar (internal series connection type) lithium ion secondary battery using the positive electrode material of the present invention will be described with reference to the drawings. Explain, but should not be limited to these.

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

  As shown in FIG. 1, in the non-bipolar lithium ion secondary battery 10 of this embodiment, a laminate film composed of a polymer and a metal is used for the battery exterior material 22, and the entire periphery is heat-sealed. The power generation element (battery element) 17 is housed and sealed by joining together. 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, an electrolyte layer 13, and both surfaces of the negative electrode current collector 14 (the lowermost layer and the lowermost layer of the power generation element). The upper layer has a structure in which a negative electrode plate having a negative electrode (negative electrode active material layer) 15 formed on one side 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 only on one side of the outermost layer positive electrode current collector 11 a located in both outermost layers of the power generation element (battery element; laminate) 17. In addition, by changing the arrangement of the positive electrode plate and the negative electrode plate in FIG. 1, the outermost negative electrode current collector (not shown) is positioned in both outermost layers of the power generation element (battery element) 17, and the outermost layer negative electrode Also in the case of the current collector, 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 the lithium ion battery of the present invention, a bipolar flat type (stacked type) lithium ion secondary battery (hereinafter simply referred to as a bipolar lithium ion secondary battery, or bipolar). 1 is a schematic cross-sectional view schematically showing the entire structure of a secondary battery.

  As shown in FIG. 2, in the bipolar lithium ion secondary battery 30 of the present embodiment, a substantially rectangular power generation element (battery element) 37 in which a charge / discharge reaction actually proceeds is sealed inside the battery exterior material 42. Has a structured. As shown in FIG. 2, the power generation element 37 of the bipolar secondary battery 30 of the present embodiment has an electrolyte layer 35 sandwiched between one or more bipolar electrodes 34, and adjacent bipolar electrodes 34. The positive electrode (positive electrode active material layer) 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 (battery 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 (battery 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 side of the positive electrode side outermost layer current collector 31 a located in the outermost layer of the power generation element (battery element) 37. Similarly, a negative electrode (negative electrode active material layer) 33 may be formed only on one side of the outermost current collector 31b on the negative electrode side located in the outermost layer of the power generation element (battery 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.

  Also, in the bipolar lithium ion secondary battery 30, the power generation element (battery element; laminate) 37 portion is sealed in a battery exterior material (exterior package) 42, and the positive electrode tab 38 and the negative electrode tab 39 are connected to the battery exterior material 42. It is preferable to have a structure taken out to the outside. 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, the following description will be made with a focus on the respective constituent requirements of the above-described non-bipolar lithium ion secondary battery, but the same constituent requirements and manufacturing method are also applied to each constituent requirement and manufacturing method of the bipolar lithium ion secondary battery. Needless to say, it can be configured or manufactured as appropriate. Moreover, an assembled battery and a vehicle can also be comprised using the non-bipolar lithium ion secondary battery and / or bipolar lithium ion secondary battery of this invention.

First, in the present invention, as a characteristic configuration, the main active material of the positive electrode (positive electrode active material layer) is expressed by a general formula: xLiMO _2. (1-x) Li ₂ NO _3. A solid solution positive electrode material for a lithium ion battery is characterized by being subjected to an oxidation treatment.

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

Moreover, as the M of LiMO ₂ that is electrochemically active in the solid solution represented by the general formula: xLiMO ₂ · (1-x) Li ₂ NO ₃ , one or more whose average oxidation state is 3+ The transition metal is not particularly limited. 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 high capacity and good cycle durability can be produced.

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, one average oxidation state is 4+ Any transition metal may be used as long as it is not particularly limited. N in the above formula may be 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 high capacity and good cycle durability can be produced.

In the positive electrode material for a lithium ion battery of the present invention, the solid solution positive electrode material represented by the general formula: xLiMO ₂ · (1-x) Li ₂ NO ₃ is subjected to an oxidation treatment. Such oxidation treatment is not particularly limited. For example,
(1) Charging or charging / discharging in a predetermined potential range, specifically, a low potential that does not cause a significant change in the solid solution positive electrode crystal structure from the beginning as described in the cycle durability mechanism of the present invention described above. Charging or charging / discharging in the area;
(2) Oxidation with an oxidizing agent (for example, halogen such as bromine or chlorine) corresponding to charging;
(3) Oxidation using redox mediator;
And the like.

  Here, the oxidation treatment method (1) will be described in detail in the oxidation treatment method for a positive electrode material for a lithium ion battery according to the present invention, which will be described later.

  Further, the oxidizing agent used in the oxidation method (2) is not particularly limited, and for example, halogen such as bromine and chlorine can be used. These oxidizing agents may be used alone or in combination. Oxidation with an oxidizing agent can be gradually oxidized by dispersing solid solution fine particles in a solvent in which the solid solution does not dissolve, and blowing and dissolving the oxidizing agent into the dispersion.

  Further, as the redox mediator (electron transfer agent) used in the oxidation treatment method of (3) above, a compound having a suitable redox potential and electron mobility, forming a radical, or electrochemical accepting or donating electrons. Active compounds. As the redox mediator, for example, a series of derivatives in which the para-position of triphenylamine is blocked and stabilized can be used. Among them, those in which hydrogen at the para-position and / or meta-position is substituted with a halogen such as bromine can be preferably used. These can be preferably used because the oxidation-reduction potential can be finely controlled by the position, type and number of substituents. In addition, various transition metal complexes that are stable with an appropriate redox potential can also be preferably used. An example of this is a complex of 2,2'-bipyridine and its derivatives such as ruthenium and osmium. In addition, what can be used as a redox shuttle for preventing overcharge of a so-called lithium ion battery, and those having an appropriate oxidation-reduction potential can be suitably used. These redox mediators may be used alone or in combination. It may be used step by step from a low oxidation-reduction potential to a high stepwise one. Further, it is also effective to oxidize stepwise while using a high oxidation-reduction potential and controlling the reaction amount with certainty. It is also preferable to carry out reduction by using this in reverse and to put in a process corresponding to the discharge of the battery electrode or to repeat the process corresponding to charge (oxidation) and discharge (reduction). Oxidation using a redox mediator can be performed, for example, using a platinum net as a working electrode, a counter electrode separated by an ion conductive diaphragm, and a reference electrode as necessary, as follows. That is, a solid solution is dispersed in an electrolyte solution in which a redox mediator is dissolved, and the redox mediator is oxidized while the potential of the working electrode is controlled with respect to the reference electrode. Can be made.

  Next, the oxidation treatment method for the positive electrode material for a lithium ion battery of the present invention is not particularly limited, but preferably the oxidation treatment is charging or charging / discharging within a predetermined potential range. Is desirable. That is, as an effective oxidation treatment method for the solid solution system positive electrode material of the present invention, charging or charging / discharging is performed in a state where the battery is configured or an electrode or a configuration corresponding to the electrode so as not to exceed a predetermined maximum potential. It is effective to do. This is because a positive electrode for a lithium ion battery having a high capacity and good cycle durability and a battery having a high energy density can be produced.

  Preferably, charge / discharge is performed under the condition that the highest potential in the predetermined potential range is 3.9 V or more and less than 4.6 V, more preferably 4.4 V or more and less than 4.6 V with respect to the lithium metal counter electrode. It is desirable to carry out a cycle. That is, the upper limit potential of charging / discharging is 3.9 V or more and less than 4.6 V, more preferably 4.4 V or more and less than 4.6 V, in terms of lithium metal or a potential converted to lithium metal. The number of cycles required for charging / discharging can be effectively applied from 1 to 30 times. By performing oxidation treatment by charging / discharging within the above range, it is excellent in that a positive electrode for a lithium ion battery having a high capacity and good cycle durability and a battery having a high energy density can be produced. checking). In particular, as shown in the examples to be described later, when charging or charging / discharging with the maximum potential of about 4.8 V in order to obtain a high capacity after the oxidation treatment, particularly remarkable effects such as cycle durability are effective. It can be expressed in Furthermore, in this case, it is preferable to increase the upper limit potential gradually (stepwise) after the charge / discharge at the initial predetermined upper limit potential in order to improve durability.

  As described above, in the present invention, after the charge and discharge are performed for 1 to 30 cycles under the condition that the maximum potential in the predetermined potential range is 4.4 V or more and less than 4.6 V with respect to the lithium metal counter electrode, It is desirable to gradually increase the maximum potential in a predetermined potential range of charge / discharge. In particular, 4.7V, 4.8Vvs. When using up to the high potential capacity of Li (use of high capacity), the maximum potential of the charge / discharge potential in the oxidation treatment is increased stepwise as described above, so that the durability of the electrode can be maintained even in a short oxidation treatment. It is excellent in that the property can be improved (see Examples described later).

  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 oxidation process when increasing the maximum potential (upper limit potential) in a predetermined potential range of charge / discharge in stages (the number of cycles required for charge / discharge at each stage was added. The 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.

  It is effective that the final maximum potential (end maximum potential) when increasing the maximum potential (upper limit potential) in a predetermined potential range of charge / discharge stepwise is 4.6V to 4.9V. . However, the oxidation treatment is not limited to the above range, and the oxidation treatment may be performed up to a higher termination maximum potential as long as the above effects can be achieved.

  However, in the present invention, it is only necessary to perform charging in the predetermined potential range described above. The maximum potential in the predetermined potential range at this time is also charged under the condition of 3.9 V or more and less than 4.6 V, more preferably 4.4 V or more and less than 4.6 V with respect to the lithium metal counter electrode as described above. It is desirable to do.

  Note that the minimum potential in the predetermined potential range is not particularly limited, and charging / discharging is performed under conditions 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 counter electrode. It is desirable to perform 30 cycles. By performing the oxidation treatment by charging or charging / discharging within the above range, it is excellent in that a positive electrode for a lithium ion battery having a high capacity and good cycle durability and a battery having a high energy density can be produced (details will be described later). See Examples).

  The charge / discharge potential (V) refers to a potential per unit cell (unit cell).

  Moreover, in the oxidation treatment method of the positive electrode material for lithium ion batteries of the present invention, the temperature of the electrode material charged and discharged as the oxidation treatment is arbitrarily set as long as it does not impair the effects of the present invention. Can do. 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 viewpoint, it is desirable to carry out at room temperature that does not require special heating and cooling (see Examples 1 to 5 and the like described later).

  Moreover, it is desirable to perform at higher temperature than room temperature from the point which can express a bigger capacity | capacitance and can improve cycling durability by short-time charging / discharging process (Examples 6-8 mentioned later and Example 1). (See -5 for comparison). In this case, the temperature of the electrode material charged and discharged as the oxidation treatment may be 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.

  The step (time) for applying the oxidation treatment method for a positive electrode material for a lithium ion battery of the present invention is not particularly limited. For example, as described above, the oxidation treatment can be performed in a state where a battery is configured, or in a configuration corresponding to an electrode or an electrode. That is, any of the application in the state of the positive electrode active material powder, the application by constituting the electrode, and the application after assembling the battery together with the negative electrode may be used. Application to the battery can be carried out by applying the application condition (oxidation process condition) of the present invention in consideration of the potential profile of the capacitance of the negative electrode to be combined. Here, in the case where the battery is configured, it is superior in that the oxidation treatment of a large number of electrodes can be performed at a time, rather than the individual electrodes or the respective configurations corresponding to the electrodes. On the other hand, when it is performed for each individual electrode or each electrode-corresponding configuration, it is easier to control conditions such as the oxidation potential than the state in which the battery is configured, and variations in the degree of oxidation to individual electrodes occur. It is excellent in a difficult point.

In addition, the method for producing the solid solution represented by the general formula: xLiMO ₂ · (1-x) Li ₂ NO ₃ before the oxidation treatment is not particularly limited, and a conventionally known production method is appropriately used. Can be done. 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 was added thereto and mixed for a predetermined time (for example, 30 minutes) in an automatic mortar. 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 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 represented by the above general formula: xLiMO ₂ · (1-x) Li ₂ NO ₃ before the oxidation treatment is performed by X-ray diffraction (XRD), inductive coupling, as performed in Examples described later. It can be analyzed using plasma (ICP) elemental analysis.

  The above is the description regarding the characteristic structural requirements of the lithium ion battery of the present invention, and the other structural requirements are not particularly limited. Therefore, in the following, regarding the other constituent elements other than the characteristic constituent elements of the lithium ion battery of the present invention, the non-bipolar lithium ion secondary battery shown in FIG. 1 and FIG. A description will be given focusing on the secondary battery. However, the present invention is not limited to these.

[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.

  The material (material) of the positive electrode active material and the negative electrode active material is not particularly limited as long as it has the characteristic constituent requirements of the lithium ion battery of the present invention, and depends on the type of battery. What is necessary is just to select suitably.

Specifically, as the positive electrode active material, the positive electrode material for a lithium ion battery of the present invention represented by the above general formula; xLiMO ₂ · (1-x) Li ₂ NO ₃ is used as the main active material of the positive electrode. It is.

As the positive electrode active material, the positive electrode material for a lithium ion battery of the present invention represented by the above general formula; xLiMO ₂ · (1-x) Li ₂ NO ₃ may be used alone, and further as necessary. Other conventionally known positive electrode active materials may be used in combination.

As the negative electrode active material, any negative electrode active material usually used in a lithium ion secondary battery may be used. Specifically, carbon or a lithium-transition metal composite oxide can be suitably used. The carbon or lithium-transition metal composite oxide that is the negative electrode active material is not particularly limited, and natural graphite, artificial graphite, carbon black, acetylene black, activated carbon, carbon fiber, coke, soft carbon, hard Carbon such as carbon (non-graphitizable carbon material), carbon such as crystalline carbon material and non-crystalline carbon material; lithium-tin alloy, lithium-silicon alloy, and lithium alloy with other elements added thereto; lithium-titanium composite Examples thereof include lithium-transfer metal composite oxides such as oxides (lithium titanate: Li ₄ Ti ₅ O ₁₂ ), but are not limited thereto. These may be used alone or in combination of two or more.

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

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

  The thickness of 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, and is usually about 1 to 500 μm.

  The negative electrode (negative electrode active material layer) can be formed by any method of kneading, sputtering, vapor deposition, CVD, PVD, ion plating and thermal spraying in addition to a method of applying (coating) a normal slurry. . 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.

  Electrode (positive electrode and negative electrode) is a conductive material (hereinafter also referred to as a conductive additive), binder, electrolyte (polymer matrix, ion conductive polymer, electrolytic solution, etc.) for enhancing electronic conductivity, and ion conductivity. For example, an electrolyte supporting salt (lithium salt) may be included.

  Examples of the conductive material include acetylene black, carbon black, graphite, and carbon fiber. By including a conductive additive, the conductivity of electrons generated at 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 lithium salt used according to the kind of battery. The electrolyte supporting salt (lithium _{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 Organic acid anion salts such as ₃ SO ₂ ) ₂ N and Li (C ₂ F ₅ SO ₂ ) ₂ N, or a mixture thereof can be used. However, it is not necessarily limited to these.

  Active material, conductive material, binder, electrolyte (polymer matrix, ion-conducting polymer, electrolyte, etc.), the amount of electrode constituent materials such as electrolyte support salt (lithium salt), etc. It is preferable to determine in consideration of ionic conductivity.

[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 tangling.

  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, and among them, PEO, PPO and copolymers thereof, or PVdF-HFP is desirably used. Moreover, as a plasticizer, it is possible to use the electrolyte solution normally used for a lithium ion battery. And such electrolyte, which electrolyte salt dissolved in a solvent, as the _{electrolyte, LiPF 6, LiBF 4, LiClO} 4, LiAsF 6, LiTaF 6, LiAlCl 4, Li 2 B 10 Cl 10 inorganic acid anions such as As a solvent, at least one selected from organic acid anion salts such as ionic salt, LiCF ₃ SO ₃ , Li (CF ₃ SO ₂ ) ₂ N, Li (C ₂ F ₅ SO ₂ ) ₂ N, etc. Ethylene carbonate (EC), propylene carbonate (PC), γ-butyrolactone (GBL), dimethyl carbonate (DMC), diethyl carbonate (DEC) and mixtures thereof are preferred.

  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. Here, as the _{electrolyte, 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, Li (C ₂ F ₅ SO ₂ ) ₂ N, and the solvent is EC, PC, GBL, DMC, DEC and mixtures thereof Is 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.

[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 (battery 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. 3 is a perspective view showing an appearance of a stacked flat non-bipolar or bipolar lithium ion secondary battery which is a typical embodiment of the lithium ion battery according to the present invention.

  As shown in FIG. 3, the stacked 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 (battery 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 (battery element) 57 includes a positive electrode tab 58 and a negative electrode tab 59. It is sealed in a state where it is pulled out to the outside. Here, the power generation element (battery element) 57 corresponds to the power generation elements (battery elements) 17 and 37 of the non-bipolar or bipolar lithium ion secondary batteries 10 and 30 shown in FIG. 1 or FIG. To do. 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.

  The lithium ion battery of the present invention is not limited to the 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 removal of the tabs 58 and 59 shown in FIG. 3 is not particularly limited. For example, the positive electrode tab 58 and the negative electrode tab 59 may be drawn out from the same side, or 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. It is not limited to what is shown. 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 of the present invention is used as 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. It can be suitably used.

[Battery]
The assembled battery of the present invention is formed by connecting a plurality of lithium ion secondary batteries of the present invention. Specifically, at least two or more are used, and are configured by serialization, parallelization, or both. Capacitance and voltage can be freely adjusted by paralleling in series. In the assembled battery of the present invention, the non-bipolar lithium ion secondary battery and the bipolar lithium ion secondary battery of the present invention are used, and these are combined in series, in parallel, or in series and in parallel. Thus, an assembled battery can also be configured.

  4 is an external view of a typical embodiment of the assembled battery according to the present invention, FIG. 4A is a plan view of the assembled battery, FIG. 4B is a front view of the assembled battery, and FIG. It is a side view of an assembled battery.

  As shown in FIG. 4, an assembled battery 300 according to the present invention forms a small assembled battery 250 in which a plurality of lithium ion secondary batteries of the present invention are connected in series or in parallel to be detachable. It is also possible to form a plurality of possible small battery packs 250 connected in series or in parallel. As a result, it is possible to form the assembled battery 300 having a large capacity and a large output suitable for a vehicle driving power source and an auxiliary power source that require a high volume energy density and a high volume output density. 4A is a plan view of the assembled battery, FIG. 4A is a front view, and FIG. 4C is a side view. The small assembled battery 250 that can be attached / detached has an electrical connection means such as a bus bar. The assembled battery 250 is stacked in a plurality of stages using the connection jig 310. How many non-bipolar or bipolar lithium ion secondary batteries are connected to create the assembled battery 250 and how many assembled batteries 250 are stacked to produce the assembled battery 300 are mounted. What is necessary is just to determine according to the battery capacity and output of the vehicle (electric vehicle) to be.

[vehicle]
The vehicle of the present invention is characterized in that the lithium ion battery of the present invention or an assembled battery formed by combining a plurality of these is mounted. When the high-capacity positive electrode of the present invention is used, a battery having a high energy density can be configured. Therefore, when such a battery is mounted, 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 lithium ion battery of the present invention or an assembled battery formed by combining a plurality of these can be used as a power source for driving a vehicle. This is because the use of the lithium ion battery of the present invention or a combination battery composed of a plurality of these in a 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. 5 is a conceptual diagram of a vehicle equipped with the assembled battery of the present invention.

  As shown in FIG. 5, in order to mount the assembled battery 300 on a vehicle such as the electric vehicle 400, the battery pack 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 assembled battery 300 is mounted is not limited to the position 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 assembled battery 300 as described above has high durability and can provide 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. A vehicle equipped with the assembled battery of the present invention can be widely applied to a hybrid vehicle, a fuel cell vehicle and the like in addition to an electric vehicle as shown in FIG.

[Method of manufacturing lithium ion battery]
Next, the method for producing the lithium ion battery of the present invention is not particularly limited, except that the method for oxidizing the positive electrode material of the present invention described above is performed in an appropriate step, and is conventionally known. This method can be applied.

  Therefore, below, it demonstrates about the manufacturing method of the lithium ion secondary battery of this invention other than the oxidation processing method of the positive electrode material of this invention demonstrated above. However, the production method of the present invention is not limited to these.

  For the production of a battery having an electrolyte as an electrolyte, the negative electrode was slightly enlarged from the positive electrode and the negative electrode prepared as described above, and each was dried for one day in a 90 ° C. vacuum dryer. Between the positive electrode and the negative electrode, the positive electrode and the negative electrode are alternately laminated through a 25 μm thick porous polypropylene film so that the outermost side becomes the negative electrode. This laminate is formed. In this laminate, positive and negative leads are taken out and placed in an aluminum laminate film back, and an electrolytic solution is injected with a liquid injector, and sealed under reduced pressure to obtain a battery.

  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 a criterion for determining whether or not the configuration requirement (technical scope) of the present invention is satisfied without depending on the manufacturing history (in other words, the method for detecting infringement of rights of the present invention).

  (1) The basic configuration of the present invention is the following two inventions (namely, the invention of the positive electrode material for lithium ion batteries (first invention) and the invention of the oxidation treatment method (production method) of the positive electrode material for lithium ion batteries) (Second invention)).

First invention: General _formula: XLiMO in _{2 · (1-x) Li} 2 NO 3, oxidizing treatment before use (hereinafter, also referred to as pre-oxidation treatment) cathode material for lithium ion batteries, characterized in that subjected to It is. Here, x in the formula is larger than 0 and smaller than 1, M is one or more transition metals having an average oxidation state of 3+, and N is one or more transition metals having an average oxidation state of 4+.

  Second invention: A method for oxidizing a positive electrode material for a lithium ion battery according to the first invention, wherein the oxidation treatment before use is charging or charging / discharging in a predetermined potential range. This is a method for oxidizing a positive electrode material for a battery.

(2) Judgment criteria (infringement detection method) as to whether or not the configuration requirement (technical scope) of the present invention is satisfied (see comparison of Example 9 and Comparative Example 6 described later)
(I) Prepare (obtain) a battery that is considered to satisfy the constituent requirements (technical scope) of the present invention (infringes the right), disassemble the battery in a discharged state, take out the positive electrode, Construct a battery as a counter electrode. In addition, the battery mounted on the device is configured as an initial charge / discharge several times at the single cell stage after the battery configuration, a module battery (small assembled battery 250 in FIG. 4), and an assembled battery, and further mounted on the device. After the initial charge / discharge inspection, it may be put on the market. Therefore, a battery 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. 13 (after 50 cycles) shows a comparison between the case where the oxidation pretreatment (= oxidation treatment before use) is performed and the case where it is not performed according to the present invention. In FIG. 13, a dQ / dE curve in which data is plotted when the charge / discharge pretreatment (= charge / discharge treatment before use), which is the oxidation pretreatment of the present invention, is plotted is “with pretreatment”. On the other hand, the dQ / dE curve obtained by plotting the data when the oxidation pretreatment of the present invention is not applied is “no pretreatment”.

  From the comparison of waveforms in the 3.0V to 3.3V region from FIG. 13, the positive electrode material subjected to the pre-oxidation treatment of the present invention shows a characteristic peak at 3.2V. On the other hand, those not subjected to the oxidation pretreatment of the present invention do not have this peak.

  The presence or absence of this peak makes it possible to determine whether or not the constituent requirements (technical scope) of the present invention are satisfied (in other words, an infringement of the rights of the present invention can be found). Also, even if the batteries are shipped in 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 a disassembly inspection is performed, it can be determined whether or not the constituent requirements (technical scope) of the present invention are satisfied with the same determination criteria (the presence or absence of a characteristic peak of 3.2 V) (in other words, the present invention Can find infringements).

(3) Physical meaning of the oxidation pretreatment of the present invention By the oxidation 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 remarkable. However, 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-oxidation treatment 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.

On the other hand, since the rearrangement of ions inside the crystal gradually proceeds by the oxidation pretreatment of the present invention, the cycle endurance is achieved to reach a stable layered structure without greatly disturbing the initial layered structure. It is thought that sex 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.

1. Synthesis of Solid Solution Cathode Material A sample 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.

2. Analysis of Synthetic Sample (1) XRD: XRD patterns of the obtained samples (5 types of solid solution cathode materials) are shown in FIG.

(2) Elemental analysis: Table 1 shows the results of elemental analysis of the obtained samples (5 types of solid solution positive electrode materials) by ICP. When the coefficient of the lower composition formula of each sample in Table 1 (the above general formula: xLiMO ₂ · (1-x) Li ₂ NO ₃ ) is multiplied by the conversion factor, the upper composition of each sample in Table 1 It becomes the expression notation. That is, the notation of the composition formula in the upper part of each 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 addition, in FIGS. 6-8, and also in the following description, the description of the composition formula of the upper stage of each sample of Table 1 may be used.

3. Electrode Evaluation (1) Electrode Preparation and Charge / Discharge Evaluation Method An electrode is an active material (using the above sample): conductive binder (TAB-2) = 20: 12 (mass ratio), kneading method Was formed into a pellet having a diameter of 16 mm, pressure-bonded to a stainless mesh having the same diameter, and heated and dried at 20 ° C. for 4 hours under vacuum to obtain a sample electrode. Here, a cell is assembled by using lithium foil as a counter electrode and glass filter paper (electrolyte membrane), and adding 1M LiPF ₆ EC: DMC = 1: 2 (volume ratio) electrolytic solution as the electrolytic cell. The charge / discharge characteristics were evaluated as follows.

(2) Charging / discharging test of electrode Charging / discharging of the cell using the electrode which used each sample as the positive electrode active material was constant current charging using 20 mA / g (current density: 0.2 mA / cm ² ) as a current value. Discharge was performed.

  Among these, in Examples 1 to 5, as the charge / discharge conditions as the oxidation treatment, five charge / discharge cycles in which the charge / discharge potential range was 2 V to 4.5 V (= maximum potential) were repeated. Then, the process which raises end voltage (upper limit electric potential) in steps until it charges / discharges in the range of 2V to 4.8V was performed. Charge / discharge as the use of the battery after the above treatment (in this case, the high-capacity battery use condition which is the object of the present invention) is 5 when the charge / discharge range is changed from 2V to 4.8V. The discharge capacity after the fifth cycle (after 5 cycles) is summarized in Table 2 as the results of Examples 1-5. In addition, the oxidation process (charge / discharge) in Examples 1 to 5, the process of increasing the end voltage (upper limit potential) stepwise, and the charge / discharge as the battery use after these processes are performed at room temperature. went.

  Moreover, in Comparative Examples 1-5, without performing charging / discharging as oxidation treatment in the predetermined potential range, charging / discharging potential range from 2V to 4.8V as charging / discharging as battery use from the beginning. Went. The discharge capacity at the fifth time (after 5 cycles) at this time is summarized in Table 2 as the results of Comparative Examples 1 to 5. In addition, charging / discharging as the battery use from the beginning in Comparative Examples 1-5 was also performed under the same temperature conditions (under room temperature) as in Examples 1-5.

  Furthermore, in Reference Example 1, as the charge / discharge conditions as the oxidation treatment, five charge / discharge cycles in a charge / discharge potential range of 2 V to 3.8 V (= maximum potential) were repeated. Then, the process which raises end voltage (upper limit electric potential) in steps until it charges / discharges in the range of 2V to 4.8V was performed. Charge / discharge as the use of the battery after the above treatment (in this case, the high-capacity battery use condition which is the object of the present invention) is 5 when the charge / discharge range is changed from 2V to 4.8V. The discharge capacity after the fifth cycle (after 5 cycles) is summarized in Table 2 as the result of Reference Example 1. In addition, the oxidation treatment (charge / discharge) in Reference Example 1, the treatment for gradually increasing the end voltage (upper limit potential), and the charge / discharge as the use of the battery after these treatments were also carried out in Examples 1 to 5. Under the same temperature conditions (under room temperature).

  As can be seen from Table 2 above, by repeating charging / discharging (oxidation treatment) with the charging upper limit potential set to 4.5 V before the charging upper limit potential is set to 4.8 V, a high capacity is developed up to 4.8 V. It can be seen that the charge / discharge cycle characteristics are greatly improved. In addition, the first time (first cycle, denoted as 1st in the figure) and the second time (second cycle, denoted as 2nd in the figure) when charging / discharging was performed under the charge / discharge conditions of the electrode of Comparative Example 1 And each charge-discharge curve of the 5th time (5th cycle, it describes as 5th in the figure) is shown in FIG. When charging / discharging was performed under the charge / discharge conditions of the electrode of Example 1 (including the time of oxidation treatment), the first time under the initial oxidation treatment conditions and the fifth time under the high-capacity battery usage conditions after the oxidation treatment Each charge / discharge curve is shown in FIG. The first charge / discharge curves under the initial oxidation treatment conditions are referred to as 4.5V first charge and 4.5V first discharge in the figure. Similarly, the fifth charge / discharge curve under the conditions of use of the high-capacity battery after the oxidation treatment is referred to as 4.8V fifth charge and 4.8V fifth discharge in the figure.

Examples 6 to 8: Charge / discharge test examples of the electrode of (2) at 50 ° C. Discharge of one _{Li [Ni 0.17 Li 0.2 Co 0.07} Mn 0.56] cells using the _{O 2} was positive electrode active material electrode, at 50 ° C., 20 mA as a current value / Constant current charge / discharge using g (current density: 0.2 mA / cm ² ) was performed.

Example 6
In Example 6, as the charge / discharge conditions as the oxidation treatment, two charge / discharge cycles with a charge / discharge potential range of 2 V to 4.5 V (= maximum potential) were repeated. Thereafter, without performing a process of gradually increasing the end voltage, the charge / discharge range from 2V is used as the charge / discharge as the use of the battery after the oxidation treatment (high capacity battery use condition which is the object of the present invention). The voltage was changed to 4.6 V, and charging / discharging (45 charging / discharging cycles including the oxidation treatment) was performed. The oxidation treatment (charge / discharge) in Example 6 and charge / discharge as the use of the battery after the oxidation treatment were performed at 50 ° C.

FIG. 9 is a constant current charge / discharge curve of the electrode of Example 6 at 50 ° C., and after charge / discharge oxidation treatment at a maximum potential of 4.5V twice, a charge / discharge potential range of 2.0V to 4.6V (lithium). It is a charging / discharging curve at the time of charging / discharging with respect to a counter electrode. Specifically, when charging / discharging was performed under the above-described charging / discharging conditions of the electrode of Example 6 (including during oxidation treatment), the first time under oxidation treatment conditions and the first time under high-capacity battery usage conditions (during oxidation treatment) 3) and 18th (20th time including oxidation treatment) charge / discharge curves are shown. That is, each charge / discharge curve showing the relationship between the charge / discharge capacity (mAh / g) of the electrode of Example 6 and the potential (V vs. Li / Li ⁺ ) of the positive electrode is shown. FIG. 10 is a diagram showing charge / discharge cycle characteristics of the electrode of Example 6 at 50 ° C. FIG. Specifically, the charge capacity and discharge capacity for every two charge / discharge cycles when the charge / discharge is performed under the above-described charge / discharge conditions (including the oxidation treatment) of the electrode of Example 6 are plotted. That is, it represents the relationship between the number of charge / discharge cycles of the electrode of Example 6 and the capacity (mAh / g). In FIG. 10, (◯) indicates the charge capacity, and (■) indicates the discharge capacity.

  When the 20th discharge curve at 50 ° C. in FIG. 9 is compared with the 4.8V 5th discharge curve at room temperature in FIG. 8, the discharge capacity larger than room temperature is obtained by the charge / discharge treatment at 50 ° C. and the use at that temperature. It can be seen that cycle durability is improved by short-time charge / discharge treatment. (The battery of Example 6 (50 ° C.) and Example 1 (room temperature) is that the cycle durability is improved by the charge / discharge treatment at a temperature of 50 ° C. and the use at that temperature for a short time. (Refer to the comparison between the number of charge / discharge cycles required for the charge / discharge treatment until use and the discharge capacity after use of the batteries of FIGS. 8 and 9). Further, FIG. 10 shows that a discharge capacity close to 300 mAh / g can be expressed relatively stably.

Example 7
In Example 7, as the charge / discharge conditions as the oxidation treatment, first, a charge / discharge cycle in which the charge / discharge potential range is 2 V to 4.45 V (maximum potential) is performed, and then the maximum potential is increased to 4.5 V. Then, two charge / discharge cycles were performed at a charge / discharge potential range of 2 V to 4.5 V (maximum potential). As charging / discharging (use of high-capacity battery, which is the object of the present invention) as a battery use after oxidation treatment, the charge / discharge range is changed from 2V to 4.6V (charging / discharging including during oxidation treatment). Discharge cycle 25 times). The oxidation treatment (charge / discharge treatment) in Example 7 and charge / discharge as the use of the battery after the oxidation treatment were performed at 50 ° C.

  FIG. 11 is a diagram showing the charge / discharge cycle characteristics at 50 ° C. similar to FIG. In FIG. 11, the maximum potential of the oxidation treatment in the initial charge / discharge is first set to 4.45V, and then the charge / discharge is performed once, and then the maximum potential is set to 4.5V, followed by the charge / discharge treatment twice. The charging / discharging cycle characteristic when charging / discharging as battery use is performed with 2.0 to 4.6V. Specifically, Example 7 is formed by plotting the charge capacity and discharge capacity every two charge / discharge cycles when charge / discharge is performed under the above-described charge / discharge conditions (including during oxidation treatment) of the electrode of Example 7. This represents the relationship between the number of charge / discharge cycles of the electrode and the capacity (mAh / g). Also in FIG. 11, (◯) indicates the charge capacity, and (■) indicates the discharge capacity.

  As a result of the charge / discharge test of the electrode of Example 7, it can be seen that a discharge capacity close to 300 mAh / g can be expressed relatively stably as in Example 6 as shown in FIG.

Example 8
In Example 8, as the charge / discharge conditions as the oxidation treatment, first. Two charge / discharge cycles were performed at a charge / discharge potential range of 2 V to 4.45 V (maximum potential). Next, as an oxidation treatment for gradually increasing the end voltage (maximum potential), the charge / discharge potential range is 2V to 4.5V, and the charge / discharge potential range is 2V to 4.6V. The charge / discharge cycle was performed twice, and the charge / discharge cycle was performed twice at a charge / discharge potential range of 2V to 4.7V. As charging / discharging (use of high-capacity battery, which is the object of the present invention) as a battery use after the oxidation treatment, the charge / discharge range is changed from 2V to 4.8V (charging / discharging including the time of oxidation treatment). 20 discharge cycles). In Example 8, the oxidation treatment (charge / discharge treatment) and charge / discharge as the use of the battery after the oxidation treatment were performed at 50 ° C.

  12 is a graph showing the charge / discharge cycle characteristics at 50 ° C. similar to those of FIG. In FIG. 12, unlike FIG. 10, the pattern of oxidation treatment by the initial charge / discharge is changed, and the maximum potential in a predetermined potential range in which charge / discharge is repeated is made higher. That is, a mode is adopted in which the highest potential in a predetermined potential range in the oxidation treatment is sequentially increased. Specifically, the charge / discharge is performed twice with the maximum potential in the initial charge / discharge set to 4.45V, then the charge / discharge treatment is performed twice with the maximum potential set to 4.5V, and then the maximum potential set to 4.6V. Charge and discharge twice, and further charge and discharge twice with the maximum potential set to 4.7 V (increase the maximum potential stepwise). It shows the charge / discharge cycle characteristics when the battery is charged / discharged at 4.8 V (relative to the lithium counter electrode). Specifically, Example 8 is formed by plotting the charge capacity and discharge capacity every two charge / discharge cycles when charge / discharge is performed under the above-described charge / discharge conditions (including during oxidation treatment) of the electrode of Example 8. This represents the relationship between the number of charge / discharge cycles of the electrode and the capacity (mAh / g). Also in FIG. 12, (◯) indicates the charge capacity and (■) indicates the discharge capacity.

  As a result of the charge / discharge test of the electrode of Example 8, it can be seen that a discharge capacity exceeding 300 mAh / g can be expressed relatively stably.

Example 9 and Comparative Example 6
In both Example 9 and Comparative Example 6, the above sample No. An electrode using 1 Li [Ni _0.17 Li _0.2 Co _0.07 Mn _0.56 ] O ₂ as a positive electrode active material is used as a positive electrode, and a cell is formed using lithium metal as a negative electrode. A charge / discharge test was conducted. In addition, the oxidation pre-treatment (pre-charge / discharge pre-treatment) in Example 9, the treatment for gradually increasing the end voltage (upper limit voltage), and the charge / discharge as the use of the battery after these treatments were performed at room temperature. I went there. Also in Comparative Example 6, charging / discharging as a battery was performed at room temperature without performing oxidation pretreatment (pre-charge / discharge pretreatment) and subsequent treatment for gradually increasing the final voltage (upper limit voltage). The cell was manufactured as follows.

20 mg of the active material (sample No. 1 above) and 12 mg of TAB-2 as the conductive binder were used, and pellets were prepared, and then pressed onto a stainless mesh current collector to form a positive electrode. The electrochemical test used a 2032 type coin cell. At this time, the negative electrode was prepared using an organic solvent of EC / DMC (EC: DMC = 1: 2 (volume ratio)) containing lithium metal as the negative electrode and 1M LiPF ₆ as the electrolyte. The cell was produced in a glove box under an argon atmosphere.

The constant current charge / discharge test was performed at room temperature, a voltage range of 2.0 V to 4.8 V, and a current density of 0.2 mA / cm ² . In Example 9, as the charge / discharge pretreatment which is the oxidation pretreatment of the present invention, the upper limit voltage was increased from 4.5V by 0.1V every two cycles until the upper limit voltage was 4.8V. The current density at this time was 0.2 mA / cm ² . The charge / discharge test for 50 cycles of the treatment cell did not count the charge / discharge cycles of the treatment step (pre-charge / discharge treatment). From the obtained charge / discharge data, the potential differentiation of the capacity was calculated using personal computer software Origin 6.0 professional, and the data of the cell (Example 9) subjected to the charge / discharge pretreatment and the cell not subjected to the comparison (Comparative Example 6). The results are shown in FIG.

  From the dQ / dE curve after 50 cycles shown in FIG. 13, a peak of about 3.1 V appears clearly in the untreated electrode of Comparative Example 6 (no pretreatment), and the charge / discharge pretreatment of Example 9 was performed. The electrode (with pretreatment) showed a tendency for a peak of 3.2 V to appear strongly. This result suggests that the structural changes between the untreated and treated electrodes are different (see the section “About the physical meaning of oxidation pretreatment of the present invention” in the specification).

  Moreover, the following is understood through the results of Examples 1 to 8, Comparative Examples 1 to 6, and Reference Example 1.

  4.7V, 4.8Vvs. It has been found that when the maximum potential of Li is used (high capacity use), the durability of the electrode is improved even in a short time if the maximum potential of the charge / discharge potential is increased stepwise. That is, 1 to 30 cycles of charging / discharging were performed under the condition that the maximum potential in the predetermined potential range was 4.4 V or more and less than 4.6 V with respect to the Li metal counter electrode in the oxidation (charging / discharging) treatment of the present invention. Further, when the maximum potential in the predetermined potential range for charging / discharging is increased stepwise, the above effect can be exhibited.

  In addition, by raising the temperature of the electrode material to be charged / discharged from room temperature to 35 to 80 ° C. (50 ° C. in the examples), a larger discharge capacity can be achieved than charging and discharging at room temperature, and in a short time It was found that the cycle durability was improved by the charge / discharge treatment.

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. 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. 4A and 4B are external views schematically showing typical embodiments of the assembled battery according to the present invention, in which FIG. 4A is a plan view of the assembled battery, FIG. 4B is a front view of the assembled battery, and FIG. It is a side view of a battery. It is a conceptual diagram of the vehicle carrying the assembled battery of this invention. It is drawing which showed the XRD pattern of the obtained sample (5 types of solid solution positive electrode materials). It is drawing which showed each charging / discharging curve of the 1st time, the 2nd time, and the 5th time when charging / discharging was performed on the charging / discharging conditions of the electrode of the comparative example 1. FIG. When charging / discharging was performed under the charge / discharge conditions of the electrode of Example 1 (including the time of oxidation treatment), the first time under the initial oxidation treatment conditions and the fifth time under the high-capacity battery usage conditions after the oxidation treatment It is drawing which showed each charging / discharging curve. It is a constant current charging / discharging curve at 50 degreeC of the electrode of Example 6, and after carrying out charging / discharging oxidation treatment twice at the maximum potential 4.5V, charging / discharging potential range 2.0V-4.6V (with respect to a lithium counter electrode) It is drawing which showed the charging / discharging curve at the time of charging / discharging. It is drawing which showed the charging / discharging cycling characteristics in 50 degreeC of the electrode of Example 6. FIG. Specifically, the charge / discharge cycle characteristics plotting the charge capacity and discharge capacity every two charge / discharge cycles when the charge / discharge is performed under the above-mentioned charge / discharge conditions (including the oxidation treatment) of the electrode of Example 6 are shown. It is a drawing. It is drawing which showed the charging / discharging cycling characteristics at 50 degreeC similar to FIG. 10 by the electrode of Example 7. FIG. It is drawing which showed the charging / discharging cycling characteristics in 50 degreeC similar to FIG. 10 by the electrode of Example 8. FIG. In the constant current charge / discharge test (50 cycles) with the electrodes of Example 9 and Comparative Example 6, the potential differentiation of the capacity was calculated from the obtained charge / discharge data using personal computer software (Origin 6.0 professional). It is the figure which showed the dQ / dE curve which each represented the data of the cell which performed the pre-processing, and the result of the cell which is not implemented.

Explanation of symbols

10 Non-bipolar lithium ion secondary battery,
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 (battery element; laminate),
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),
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,
250 Small assembled battery (module battery),
300 battery packs,
310 connection jig,
400 Electric car.

Claims (10)

General formula
(Where x is a number that satisfies 0 <x <1, M is one or more transition metals with an average oxidation state of 3+, and N is one or more with an average oxidation state of 4+. A positive electrode material for a lithium ion battery, wherein the positive electrode material is subjected to an oxidation treatment.   The positive electrode material for a lithium ion battery according to claim 1, wherein the M is one or more elements selected from Mn, Ni, Co, and Fe.   The positive electrode material for a lithium ion battery according to claim 1 or 2, wherein the N is one or more elements selected from Mn, Zr and Ti.   A lithium ion battery comprising the positive electrode material for a lithium ion battery according to claim 1 as a main active material of the positive electrode.   A vehicle equipped with the lithium ion battery according to claim 4. A method for oxidizing a positive electrode material for a lithium ion battery according to any one of claims 1 to 3,
An oxidation treatment method for a positive electrode material for a lithium ion battery, wherein the oxidation treatment is charging or charging / discharging in a predetermined potential range.   7. The lithium ion according to claim 6, wherein charging and discharging are performed for 1 to 30 cycles under a condition that a maximum potential in a predetermined potential range is 3.9 V or more and less than 4.6 V with respect to a lithium metal counter electrode. A method for oxidizing a positive electrode material for a battery.   8. The lithium according to claim 7, wherein charging and discharging are performed for 1 to 30 cycles under a condition that a maximum potential in the predetermined potential range is 4.4 V or more and less than 4.6 V with respect to a lithium metal counter electrode. A method for oxidizing a positive electrode material for an ion battery.   The maximum potential in the predetermined potential range is charged to and discharged from 1 to 30 cycles under the condition of 4.4 V or more and less than 4.6 V with respect to the lithium metal counter electrode. 9. The method of oxidizing a positive electrode material for a lithium ion battery according to claim 8, wherein the highest potential is raised stepwise.   The temperature of the electrode material to charge / discharge is 35 degreeC or more and 80 degrees C or less, The oxidation processing method of the positive electrode material for lithium ion batteries of Claim 8 or 9 characterized by the above-mentioned.