JP2012089246A - Electrode plate for nonaqueous electrolyte secondary battery, nonaqueous electrolyte secondary battery, and battery pack - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrode plate for a nonaqueous electrolyte secondary battery having an excellent input characteristic, a nonaqueous electrolyte secondary battery including the electrode plate and having an excellent high input and output characteristic, and a battery pack.SOLUTION: An electrode plate for a nonaqueous electrolyte secondary battery 10 includes: a collector 1; and an electrode active material layer 2 formed on at least a part of the surface of the collector 1. The electrode active material layer 2 includes a first electrode active material and a second electrode active material, and the second electrode active material fastens the first electrode active materials together and fastens the first electrode active material and the collector 1. In addition, the second electrode active material includes a lithium composite oxide including a metal selected from the group excluding lithium and the lithium as a metal elements and having a spinel structure.

Description

  The present invention relates to a positive electrode plate for a non-aqueous electrolyte secondary battery, a non-aqueous electrolyte secondary battery, and a battery pack.

  A non-aqueous electrolyte secondary battery represented by a lithium ion secondary battery has a high energy density and a high voltage, and has a memory effect during charging / discharging (when the battery is charged before it is completely discharged, Since there is no phenomenon in which the capacity decreases, it is used in various fields such as portable devices and large devices.

In addition, efforts are being made to reduce CO ₂ emissions on a global scale, which is representative of plug-in hybrid vehicles and electric vehicles that contribute to CO ₂ reduction in terms of reducing dependence on oil and enabling driving with low environmental impact. The development and popularization of next-generation clean energy vehicles is urgently needed. Driving power that does not depend on gasoline is essential for the development and popularization of next-generation clean energy vehicles. As this driving force, a non-aqueous electrolyte secondary battery represented by a lithium ion secondary battery is expected.

  The non-aqueous electrolyte secondary battery is composed of a positive electrode plate, a negative electrode plate, a separator, and an organic electrolyte. And as said positive electrode plate and negative electrode plate, what equips the collector surface, such as metal foil, with the electrode active material layer formed by apply | coating an electrode active material layer forming liquid is generally used.

  The electrode active material layer forming liquid includes active material particles that can be charged / discharged by showing a lithium ion insertion / release reaction, a resin binder, and a conductive material (however, when the active material also exhibits a conductive effect, In some cases, the conductive material may be omitted), or, if necessary, other materials may be used and kneaded and / or dispersed in an organic solvent to prepare a slurry. Then, the electrode active material layer forming liquid is applied to the current collector surface, then dried to form a coating film on the current collector, and if necessary, an electrode plate having the electrode active material layer is manufactured by pressing. The method is general (for example, paragraphs [0019] to [0026] in Patent Document 1, paragraph 1 [Claim 1], paragraphs [0051] to [0055]).

  At this time, the active material particles contained in the electrode active material layer forming liquid are particles dispersed in the liquid, and are not easily fixed to the current collector surface only by being applied to the current collector surface. It is a material that easily peels from the body. Therefore, the electrode active material layer in the conventional electrode plate is generally formed by fixing the active material particles on the current collector via a resin binder. Therefore, it is essential that the conventional electrode active material layer contains a certain amount of resin binder.

JP 2006-310010 A JP 2006-107750 A

  Lithium ion secondary batteries are being developed for fields that require high input / output characteristics such as electric vehicles, hybrid vehicles, and power tools. In addition, secondary batteries used in relatively small devices such as mobile phones are also expected to improve high output / input characteristics because the devices tend to be multifunctional.

  In order to improve the input / output characteristics of the secondary battery, it is necessary to lower the impedance of the battery. For this purpose, it is effective to lower the impedance of an electrode plate such as a positive electrode plate or a negative electrode plate.

  As described above, a certain amount of resin binder is essential in the conventional electrode active material layer. Of course, when a large amount of resin binder is contained, there is an advantage that the state in which the electrode plate and the electrode active material layer are strongly bound is easily maintained. However, on the other hand, the presence of the resin binder between the active material particles makes it necessary for ions and electrons to move around the resin binder, resulting in a long ion and electron movement distance. As a result, it works negatively to reduce the impedance of the electrode plate, and it may take time to charge and discharge the non-aqueous electrolyte secondary battery. May interfere.

  The present invention provides a positive electrode plate for a non-aqueous electrolyte secondary battery excellent in output / input characteristics, a non-aqueous electrolyte secondary battery having such a positive electrode plate and excellent in high input / output characteristics, and a battery pack. The purpose is to enable provision.

That is, the present invention
(1) A positive electrode plate for a nonaqueous electrolyte secondary battery comprising a current collector and an electrode active material layer formed on at least a part of the surface of the current collector,
The electrode active material layer contains a first electrode active material and a second electrode active material,
The second electrode active material adheres the first electrode active materials to each other and the first electrode active material and the current collector,
The second electrode active material comprises a lithium composite oxide having a metal selected from the group of metals other than lithium and lithium as a metal element and having a spinel structure. Positive electrode plate for electrolyte secondary battery,
(2) The second electrode active material contains a lithium manganese composite oxide containing manganese and lithium as metal elements, and the positive electrode plate for a non-aqueous electrolyte secondary battery according to (1),
(3) The second electrode active material contains a LiMn ₂ O ₄ positive electrode plate for a non-aqueous electrolyte secondary battery according to (1),
(4) The second electrode active material comprises a material in which a part of manganese constituting LiMn ₂ O ₄ is substituted with a metal selected from the group of metals other than lithium and manganese. The positive electrode plate for a non-aqueous electrolyte secondary battery according to (1) above.
(5) The non-aqueous electrolyte secondary battery according to any one of (1) to (4), wherein the second electrode active material covers at least a part of the surface of the first electrode active material. Positive plate,
(6) The electrode active material layer according to any one of (1) to (5), including a portion where the crystal lattices are continuous in a part of the adjacent second electrode active materials. A non-aqueous electrolyte secondary battery positive electrode plate,
(7) A positive electrode plate for a non-aqueous electrolyte secondary battery comprising a current collector and an electrode active material layer formed on at least a part of the surface of the current collector,
The electrode active material layer has a plurality of nuclei made of a first electrode active material and dispersed in the electrode active material layer, and an enclosure made of a second electrode active material and surrounding the nuclei,
The enclosure has the nuclei fixed between the nuclei and the current collector,
There are a plurality of the enclosures, and among these plurality of enclosures, at least a part of adjacent enclosures are connected to each other, or the enclosures are continuous without distinction,
Of the enclosure, an enclosure in the vicinity of the current collector is connected to the surface of the current collector,
The second electrode active material comprises a lithium composite oxide having a metal selected from the group of metals other than lithium and lithium as a metal element and having a spinel structure. Positive electrode plate for electrolyte secondary battery,
(8) The second electrode active material contains a lithium manganese composite oxide containing manganese and lithium as metal elements, the positive electrode plate for a nonaqueous electrolyte secondary battery according to (7) above,
(9) The second electrode active material contains a LiMn ₂ O ₄ positive electrode plate for a non-aqueous electrolyte secondary battery according to (7),
(10) The second electrode active material comprises a material in which a part of manganese constituting LiMn ₂ O ₄ is replaced with a metal selected from the group of metals other than lithium and manganese. The positive electrode plate for a non-aqueous electrolyte secondary battery according to (7) above,
(11) The crystal lattice of the first electrode active material constituting the nucleus and the crystal of the second electrode active material constituting the envelope at the interface between the nucleus and the envelope surrounding the nucleus. The positive electrode plate for a nonaqueous electrolyte secondary battery according to any one of (7) to (10), wherein there is a region where the lattice is joined discontinuously,
(12) There are a plurality of the enclosures, and some of the adjacent enclosures are connected to each other,
In some of the enclosures that are connected to each other, the second electrode active material that constitutes one enclosure and the second electrode active material that constitutes the other enclosure are connected by making the crystal lattices continuous with each other. A positive electrode plate for a non-aqueous electrolyte secondary battery according to any one of (7) to (11),
(13) A nonaqueous electrolyte secondary battery comprising at least a positive electrode plate, a negative electrode plate, a separator provided between the positive electrode plate and the negative electrode plate, and an electrolyte solution containing a nonaqueous solvent,
The positive electrode plate is a positive electrode plate for a non-aqueous electrolyte secondary battery according to any one of (1) to (12) above, a non-aqueous electrolyte secondary battery,
(14) A storage case, a non-aqueous electrolyte secondary battery including a positive electrode terminal and a negative electrode terminal, and a protection circuit having an overcharge and over-discharge protection function are provided, and the non-aqueous electrolyte secondary battery is provided in the storage case. In the battery pack configured to house the battery and the protection circuit,
The non-aqueous electrolyte secondary battery includes at least a positive electrode plate, a negative electrode plate, a separator provided between the positive electrode plate and the negative electrode plate, and an electrolyte solution containing a non-aqueous solvent. A secondary battery,
The gist is a battery pack, wherein the positive electrode plate is the positive electrode plate for a non-aqueous electrolyte secondary battery according to any one of (1) to (12).

  According to the present invention, it is possible to obtain a positive electrode plate for a non-aqueous electrolyte secondary battery having excellent input / output characteristics. By providing such a positive electrode plate in a non-aqueous electrolyte secondary battery and a battery pack, high output can be achieved. Batteries and battery packs with excellent input characteristics can be easily provided.

  Further, according to the present invention, it is possible to obtain a positive electrode plate for a non-aqueous electrolyte secondary battery including an electrode active material layer that can realize high-speed charge / discharge of the non-aqueous electrolyte secondary battery. By providing a positive electrode plate in a non-aqueous electrolyte secondary battery and battery pack, a battery and battery pack that can be charged and discharged at high speed can be easily provided.

(1A) is a schematic view showing a cross section when the positive electrode plate of the present invention is cut substantially perpendicularly to the current collector surface. (1B) is a schematic diagram showing the surface of the electrode active material layer in the positive electrode plate of the present invention. (2A) to (2D) are schematic cross-sectional views showing examples of current collectors used in the present invention. It is a schematic sectional drawing in one form of a nonaqueous electrolyte secondary battery. It is a schematic exploded view in one embodiment of the battery pack of this invention. FIG. 3 is a diagram showing the results of an X-ray diffraction analysis test in Example 1. 6 is a scanning electron micrograph of the positive electrode plate of Example 8. FIG.

[Positive electrode plate for non-aqueous electrolyte secondary battery]
The positive electrode plate 10 for a non-aqueous electrolyte secondary battery of the present invention (hereinafter sometimes simply referred to as “positive electrode plate”) is formed on the current collector 1 and at least a part of the surface of the current collector 1. And an electrode active material layer 2 (FIG. 1A) (FIG. 1B).

(Current collector 1)
The current collector 1 is not particularly limited as long as it is generally used as the current collector 1 in the positive electrode plate 10 for a non-aqueous electrolyte secondary battery. As the current collector 1, for example, an aluminum foil, a nickel foil or the like formed from a single substance or an alloy is preferably used, but is not limited thereto. The current collector 1 may be subjected to a surface processing treatment on the surface on which the electrode active material layer 2 is to be formed, if necessary. Examples of the surface processing treatment include those in which surface treatment such as laminating processing of a conductive material on the surface of a current collecting base material constituting the current collector, chemical polishing treatment, corona treatment, oxygen plasma treatment is performed. It is done. Alternatively, the current collector may be physically provided with any unevenness on the surface.

  A more specific example of the current collector used in the present invention will be described using the examples of the positive electrode plates 20, 20 ′, 20 ″, 20 ′ ″ for the non-aqueous electrolyte secondary battery shown in FIGS. 2A to 2D. Explained.

  As the current collector 1, as shown in the positive electrode plate 20 for a non-aqueous electrolyte secondary battery in FIG. 2A, a current collector made of only a current collecting substrate 3 such as a metal foil having a current collecting function is used. be able to. Examples of the current collecting base 3 include the aluminum foil and nickel foil described above. In such a case, the electrode active material layer 2 is provided on at least a part of the surface 101 of the current collecting base material 3.

  As the current collector 1, as the current collector 1 ′ used in the positive electrode plate 20 ′ for the nonaqueous electrolyte secondary battery shown in FIG. 2B, the current collector 1 itself has a current collecting function on the upper surface of the current collecting substrate 3. A current collector 1 ′ provided with an arbitrary conductive layer 4 having conductivity can be used. The electroconductive layer 4 should just show electroconductivity of the grade which does not prevent the movement of the electron between the electrode active material layer 2 and the current collection base material 3. FIG. For example, the conductive layer 4 is provided with a laminated layer made of a predetermined metal or metal alloy, a layer in which arbitrary conductive fine particles are deposited by plating or sputtering, or one or more conductive thin films. It may be a layer or the like, and is not limited to these examples. In the current collector 1 ′, the surface of the conductive layer 4 becomes the surface 102 of the current collector 1 ′, and the electrode active material layer 2 is provided on at least a part of the surface 102. FIG. 2B shows a mode in which the current collector 1 ′ has a single conductive layer 4. However, the configuration of the current collector 1 ′ is not limited to this, and the conductive layer 4 may have a stacked configuration in which two or more arbitrary conductive layers are stacked.

  As the current collector 1, a current collecting base material 3 that itself has a current collecting function, like the current collector 1 ″ used in the positive electrode plate 20 ″ for a non-aqueous electrolyte secondary battery shown in FIG. 2C. A current collector 1 ″ having an intermittent layer 5 formed intermittently on the upper surface can be used. The intermittent layer 5 may be a conductive layer similar to the conductive layer 4 described above, or may be a layer that does not exhibit conductivity. In the positive electrode plate 20 ″ for the non-aqueous electrolyte secondary battery, the surface of the current collector 1 ″ is the surface 103 which is the surface of the intermittent layer 5 and the current collecting base material 3 where the intermittent layer 5 is not provided. It consists of a surface 103 ′ which is its own surface. At this time, the electrode active material layer 2 can be formed so as to be in contact with both the surface 103 and the surface 103 ′. In the positive electrode plate 20 ″ for a non-aqueous electrolyte secondary battery, the intermittent layer 5 may or may not have conductivity. Even if the intermittent layer 5 is a non-conductive layer, the electrode active material layer 2 is in direct contact with the current collector base 3 on the surface 103 ′ of the current collector 1 ″. And the current collector 1 ″ ensure the movement of electrons. However, from the viewpoint of reducing the electric resistance of the positive electrode plate 20 ″ for the nonaqueous electrolyte secondary battery itself, it is preferable that the intermittent layer 5 also exhibits conductivity.

  When the intermittent layer 5 exhibits conductivity, as shown in FIG. 2D, an electrode active material layer 2 ′ is selectively provided only on the intermittent layer 5 on the surface of the current collector 1 ″. You may comprise positive electrode plate 20 '' 'for nonaqueous electrolyte secondary batteries. That is, the electrode active material layer 2 ′ may be selectively provided on at least a part of the surface 103 of the surface of the current collector 1 ″. Alternatively, although not shown, when the intermittent layer 5 does not exhibit conductivity, the electrode active material layer 2 ′ may be selectively provided on at least a part of the surface 103 ′ of the current collector 1 ″.

  The above description of the current collectors 1, 1 ′, 1 ″ is an example and does not limit the current collector used in the present invention. As illustrated above, the current collector used in the present invention may be only the current collecting base material 3 having a current collecting function. In such an embodiment, the current collector 1 provided with the electrode active material layer 2 is used. The surface refers to the surface of the current collecting base material 3. Alternatively, in the present invention, the current collector 1 may have a current collecting base material 3 having a current collecting function and an arbitrary laminated layer provided on the current collecting base material 3. In such an aspect, the surface of the current collector 1 on which the electrode active material layer 2 is provided is within a range in which the movement of electrons is ensured in at least one region between the current collector base material 3 and the electrode active material layer 2. The surface of the said laminated layer, the current collection base material 3 surface in which the laminated layer is not provided, or both the surface of the said laminated layer and the current collection base material 3 surface in which the laminated layer is not provided is pointed out.

  As the current collectors 1, 1 ′, 1 ″, those having a heat resistant temperature of 800 ° C. or lower, further 600 ° C. or lower, and particularly 400 ° C. or lower can be selected. The selection of the current collectors 1, 1 ′, 1 ″ is determined by the relationship with the temperature of the heating step in the manufacturing method of the present invention described later. In the present invention, for example, the electrode active material layer 2 can be formed directly on the current collector 1 at a heating temperature of 400 ° C. or lower. Therefore, the current collector 1, 1 ′, 1 ″ can be selected from those having a heat resistant temperature of 800 ° C. or lower, more preferably 600 ° C. or lower, particularly 400 ° C. or lower. The positive electrode plate of the present invention in which the electrode active material layer 2 is directly formed can be provided.

  The thickness of the current collectors 1, 1 ′, 1 ″ is not particularly limited as long as it is a thickness that can generally be used as a current collector for a positive electrode plate for a non-aqueous electrolyte secondary battery, but is 10 μm to 200 μm. Preferably, it is 15 micrometers-50 micrometers.

(Configuration of electrode active material layer 2)
The electrode active material layer 2 is configured to contain a first electrode active material and a second electrode active material. In the electrode active material layer 2, the second electrode active material fixes the first electrode active materials to each other, and the second electrode active material fixes the first electrode active material to the current collector. Yes. At this time, the second electrode active material is a material that exhibits a lithium ion insertion / release reaction and is also a binding material that binds the first electrode active material to the deposition target.

  According to the positive electrode plate of the present invention, it is possible to form a state in which the first electrode active material is directly fixed to the current collector by the second electrode active material. This indicates that the electrode active material layer 2 can be directly laminated on the current collector 1. Furthermore, when the electrode active material layer 2 is laminated directly on the current collector 1, the movement of electrons between the electrode active material layer 2 and the current collector 1 becomes very smooth. In addition, since the second electrode active material exhibits a lithium ion insertion / release reaction, the active material contained in the electrode active material layer 2 includes not only the first electrode active material but also the second electrode active material. It will be added. For this reason, when the second electrode active material is included in the electrode active material layer 2, it is possible to substantially contribute to an increase in the electrode capacity of the positive electrode plate 10.

  In the present invention, the fixation by the second electrode active material includes the following two modes. First, between the adherends (for example, between the first electrode active material, between the first electrode active material and the current collector surface, or when using a conductive material, the conductive material and the first In some cases, a second electrode active material serving as a binder is interposed between the electrode active materials 1 and between the conductive material particles to fix them together (hereinafter referred to as “fixing mode 1”). Secondly, when the objects to be adhered are in direct contact with each other, and the objects to be adhered are adhered by the presence of the second electrode active material that surrounds the contact portion and becomes a binding material (hereinafter referred to as “adhesion mode”). 2 ”). The fixing by the second electrode active material may be a fixing state specified in any of the fixing modes 1 and 2 described above. Therefore, only one of the fixing modes 1 and 2 may be formed in the electrode active material layer 2, or both of the fixing modes 1 and 2 may coexist. In particular, the fixing mode 2 tends to increase as the particle size of the first electrode active material contained in the electrode active material layer 2 decreases. Further, as the particle diameter of the conductive material particles that may be added as an additive in the electrode active material layer 2 becomes smaller, the fixing mode 2 tends to increase as in the case of the first electrode active material.

  In the case where the electrode active material layer 2 includes both the fixing modes 1 and 2, the present invention exhibits an excellent effect in terms of improving the conductivity. In order to understand the above effects, attention is particularly paid to the adhesion between the conductive material particles in the electrode active material layer 2 including the conductive material particles. When the conductive material particles are fixed by the fixing mode 1, the binding material is the second electrode active material, and therefore, compared with the conventional resin binder, the electrons between the conductive material particles It is difficult to become an obstacle to interaction. Furthermore, when the conductive material particles are fixed by the fixing mode 2, since the particles are in direct contact with each other, the flow of electrons is naturally smooth, and excellent conductivity is ensured. . The same effect can be said for the adhering of the conductive material particles and the first electrode active material. In addition, even at the boundary between the current collector 1 and the electrode active material layer 2, the second electrode active material in which the current collector 1 surface and the first electrode active material and conductive material particles become a binding material It is fixed by the presence of a binding substance around the contact portion because they are in direct contact with each other. Therefore, for the same reason as described above, the flow of electrons between the current collector 1 and the electrode active material layer 2 is smooth. That is, the positive electrode plate of the present invention is present in the electrode active material layer 2 so that the second electrode active material functions as a binder, and various constituent materials are fixed by the fixing modes 1 and 2. Therefore, it is possible to keep the electric resistance low.

  In addition to the first electrode active material and the second electrode active material, the electrode active material layer 2 contains any material such as a conductive material and a resin material as long as the effect of the present invention can be exhibited. It may be included.

(Structure of electrode active material layer 2)
Referring to the structure of the electrode active material layer 2, the electrode active material layer 2 includes a plurality of nuclei 6 dispersed in the electrode active material layer 2 and an enclosure surrounding the plurality of nuclei 6 as shown in FIG. 1A. And a body 7.

  In the electrode active material layer 2, the nucleus 6 is made of the first electrode active material, and the enclosure 7 is made of the second electrode active material. The nucleus 6 may be primary particles, secondary particles, or a mixture of these. The enclosure 7 is not limited to a structure composed only of the second electrode active material, and includes a component other than the second electrode active material as long as the second electrode active material is a main component. The body is also included. The fact that the second electrode active material is the main component means that the proportion (% by weight) of a substance other than the second electrode active material in one enclosure 7 does not exceed the weight% of the second electrode active material. It shall be shown.

  The enclosure 7 existing in the vicinity of the current collector 1 is connected to the surface of the current collector 1, thereby completing the positive electrode plate 10 of the present invention including the electrode active material layer 2 directly on the current collector 1. Is done. The electrode active material layer 2 has voids 8 everywhere. When a battery is constructed using the positive electrode plate 10, the non-aqueous electrolyte passes through the voids 8 and the electrode active material layer 2. It can penetrate inside.

  FIG. 1B is a schematic view showing the surface of the electrode active material layer 2. The surface of the electrode active material layer 2 is mainly covered with the enclosure 7, and the nucleus 6 may be exposed in some places. In addition, voids 8 are present everywhere on the surface of the electrode active material layer 3.

  There are a plurality of surrounding bodies 7 surrounding the core body 6, and one or a plurality of surrounding bodies 7 surrounds one core body 6. Among these plurality of enclosures 7, a part of adjacent enclosures 7 may be connected to each other. Alternatively, the surrounding body 7 surrounding the core body 6 may be continuously connected without being distinguished from each other. Alternatively, in the electrode active material layer 2 in the present invention, the plurality of enclosures 7 and the enclosures 7 that are continuous without distinction may be mixed. Since the electrode active material layer 2 is configured so that the core body 6 is surrounded by the envelope body 7, it is possible to obtain the positive electrode plate 10 having more excellent input / output characteristics.

  By the way, the 2nd electrode active material which comprises the enclosure 7 is crystalline. In the embodiment of the present invention in which a part of the adjacent envelopes 7 are connected to each other, the connection between the adjacent envelopes 7 includes a portion where the crystal lattice of the second electrode active material is continuous. Is desirable because the film adhesion of the electrode active material layer 2 is improved, thereby contributing to the improvement of the input / output characteristics. Whether or not the crystal lattice of the second electrode active material is continuous in at least a part of the enclosures 7 is determined by the crystal lattice of the first electrode active material and the crystal lattice of the second electrode active material described later being continuous. It is possible to confirm using transmission electron microscope observation similarly to the confirmation method of whether to do.

  The envelope 7 is not particularly limited with respect to the aspect of the envelope 7 itself, for example, the size, shape, and distribution. For example, the enclosure 7 may be in the form of fine particles. In that case, a large number of minute particulate enclosures 7 may surround one or all of the aggregates of two or more of the core bodies 6. At this time, part of the fine-particle nuclei 6 may be fixed to each other.

  The enclosure 7 may be non-particulate. At this time, the envelope body 7 may be a continuous body that fills the gaps of the core bodies 6 leaving the gaps. The above continuum surrounds a plurality of nuclei 6 leaving a gap. However, when the individual nuclei 6 are viewed, the entire surface of one nuclei 6 is surrounded by a wrapping 7 that is a continuum. It may be surrounded, or a surface that is not surrounded by the envelope 7 that is a continuous body may exist on the surface of one core body 6.

  The envelope 7 may constitute a continuous coating layer in the form of a film, a pleat, or a hump that surrounds two or more aggregates of the nuclei 6. The covering layer surrounds the plurality of nuclei 6 with leaving gaps, but when the individual nuclei 6 are viewed, the entire surface of one nuclei 6 forms an envelope 7 that forms the covering layer. It may be surrounded, or on the surface of one core body 6, there may be a surface that is not surrounded by the surrounding body 7 that is a covering layer.

  In addition, the surface of the enclosure 7 has a large number of projections densely observed regardless of whether it is observed on a smooth surface, a regular or irregular shape, when magnified with a scanning electron microscope at a magnification of 50,000 times. The surface state is not limited at all.

  The shape of the enclosure 7 and the manner in which the enclosure 7 surrounds the core 6 do not limit the present invention. That is, the envelope body 7 in the present invention surrounds at least a part of the core body 6 and the envelope bodies 7 are connected to each other or the envelope body 7 is a continuous body. Any material may be used as long as the envelope body 7 in the vicinity of the body 10 is connected to the surface of the current collector 1 to fix the core body 6 on the current collector 7 and constitute the electrode active material layer 2. One feature of the envelope 7 in the present invention is that at least a part of the envelopes 7 are joined and connected to each other regardless of whether the envelope 7 is particulate or non-particulate. Thus, it is possible to satisfactorily form a conductive path that can be an electron movement path when electrons move in the electrode active material layer 2. In this respect, it is distinguished from a structure that is a simple aggregate of particles and in which the particles are in contact with each other but does not have a portion that is substantially bonded to each other. The enclosure 7 in the present invention can be distinguished from the particle aggregate that is in the form of particles but does not have a portion that is substantially bonded to each other by observing a transmission electron micrograph. Note that the enclosures are connected and connected to each other in the target enclosure, in which the second lattice of the second electrode active material constituting one enclosure and the second continuous constituting the other enclosure. It shall indicate that there is a structure in which the crystal lattice of the active material is continuous.

(Dual structure of nucleus 6 and enclosure 7)
The structure of the electrode active material layer 2 can be constituted by a so-called double structure composed of a nucleus 6 and an enclosure 7. This dual structure can be visually understood from scanning electron micrographs. Further, the double structure can be understood from the viewpoint of a method for producing a positive electrode plate described later. That is, in the method for producing the positive electrode plate, the electrode active material layer forming liquid is applied onto the current collector 1 to form a coating film, and the second electrode active material is deposited in the coating film. At that time, on the current collector 1 on which the coating film is formed, the existing first electrode active material contained in the coating film constitutes the core body 6 and surrounds the core body 6 so as to surround it. Two electrode active materials are generated to form the enclosure 7. As a result, the double structure is completed.

  Regarding the above-mentioned double structure composed of the nucleus 6 and the enclosure 7, there is one feature particularly when focusing on the interface between the nucleus 6 and the enclosure 7. The first electrode active material constituting the core body 6 is a crystalline compound. The second electrode active material constituting the enclosure 7 also has crystallinity because it exhibits a lithium ion insertion / release reaction. Here, at the interface between the two formed at the time when the crystalline first electrode active material constituting the core body 6 is surrounded by the crystalline second electrode active material constituting the envelope body 7, It was found that there are regions where the crystal lattice is continuous and discontinuous regions. In particular, when the crystal lattice of the first electrode active material constituting the core body 6 and the crystal lattice of the second electrode active material constituting the enclosure 7 are different, the crystals of both are present in the entire interface between the two. The grid becomes discontinuous. The continuity of the crystal lattice can be confirmed by observing the crystal lattice with a transmission electron microscope.

  The present inventors have inferred that the existence of a region in which the above-described crystal lattice is discontinuous contributes to improvement of cycle characteristics. The non-aqueous electrolyte secondary battery has deteriorated cycle characteristics due to deterioration or further destruction of the crystal structure while alkali ions such as lithium ions are repeatedly inserted into and desorbed from the crystal structure of the first electrode active material. To do. It is considered that the above-described deterioration / destruction of the crystal structure occurs along a continuous crystal lattice of the crystal structure. In this respect, as described above, the positive electrode plate of the present invention has a region in which the crystal lattices of both are discontinuous at the interface of the double structure composed of the nucleus and the enclosure showing the lithium ion insertion / release reaction. . For this reason, it is considered that the deterioration of the crystal structure generated in each of the first electrode active material constituting the nucleus and the second electrode active material constituting the enclosure does not affect each other in the discontinuous region. It was. Therefore, it is presumed that the cycle characteristics are unlikely to deteriorate, in other words, the double structure contributes to the display of good cycle characteristics.

  Regarding the structure of the electrode active material layer 2, the enclosure 7 only needs to cover at least a part of the surface of the core body 6. This is because, when one particle of the first electrode active material included in the electrode active material layer 2 is focused, as one aspect of the present invention, the second electrode active material is the first electrode active material. It shows that it may be in a state of covering at least a part of the particle surface. At this time, the 2nd electrode active material may exist in the state which has the exposed surface which can contact a non-aqueous electrolyte. This is because, in the fixing mode 1 or 2, the second electrode active material, a part of which is exposed so as to be in contact with the non-aqueous electrolyte, and the other first electrode active material, conductive material, It includes a second electrode active material that is not in contact with an electric body or the like and covers only a part of the particle surface of one first electrode active material. When operating a battery using the positive electrode plate 10, the second electrode has an exposed surface that covers at least a part of the particle surface of the first electrode active material and can be brought into contact with the non-aqueous electrolyte. The active material may undergo a lithium insertion / release reaction prior to the first electrode active material particles or along with the first electrode active material particles.

The inventors of the present invention have described the second electrode so that the positive electrode plate 10 covers at least part of the particle surface of the first electrode active material, or further has an exposed surface that can come into contact with the non-aqueous electrolyte. When the electrode active material is configured, it is estimated that the second electrode active material may be able to efficiently compensate for lithium ions lost during charging. In order to confirm the lithium ion supplementing effect by the second electrode active material, the following test can be performed. For the positive electrode plate 10, the amount of active material obtained by combining the first electrode active material and the second electrode active material is calculated, and the amount of active material per volume in the electrode active material layer is derived as Xg / cm ³ . Assuming a conventional positive electrode plate in which the electrode active material layer is configured not to include the second electrode active material from the electrode active material layer 2 of the positive electrode plate 10, the conventional positive electrode plate is It is designed so that the amount of active material per volume is Xg / cm ³ . This is referred to as a positive electrode plate B. When the positive electrode plate 10 and the positive electrode plate B are compared, it is recognized that the positive electrode plate 10 of the present invention has higher initial charge / discharge efficiency. That is, the improvement of the initial charge / discharge efficiency is recognized due to the presence of the second electrode active material. Regarding a mechanism in which the effect of improving the initial charge / discharge efficiency is exhibited when the positive electrode plate 10 has a configuration in which the second electrode active material exists so as to cover the surface of the first electrode active material. The details are not clear. In this regard, the present inventors have found that the second electrode active material that covers the surface of the first electrode active material has a thin film shape and a portion that covers the first electrode active material. However, it is presumed that lithium ions can be made to enter and exit the contacting side of the first electrode active material very easily, and thus lost lithium ions can be easily compensated. The positive electrode plate of the present invention can improve the initial charge / discharge efficiency as compared with the conventional positive electrode plate using only the resin binder containing the same amount of the first electrode active material particles per unit area. Preferably, the subsequent discharge capacity can be 95% or more, more preferably 98% or more with respect to the initial charge capacity of 100%.

  The thickness of the electrode active material layer 2 can be appropriately designed in consideration of the electrode capacity and input / output characteristics required for the positive electrode plate 10. In general, the thickness of the electrode active material layer 2 is designed to be 200 μm or less, more generally 100 μm or more and 150 μm or less. However, in the present invention, the electrode active material layer 2 can be formed very thin. Therefore, although depending on the particle diameter of the first electrode active material, the electrode active material layer 2 having a thickness of 300 nm or more and 200 μm or less can be formed. From the viewpoint that the electrode capacity can be improved while improving the input / output characteristics, the thickness of the electrode active material layer 2 is particularly preferably 300 nm to 150 μm, and more preferably 500 nm to 100 μm. That is, when the thickness of the electrode active material layer 2 is thin as in the above range, the first electrode active material has a small particle diameter, and the particle diameter is at least equal to or smaller than the film thickness of the electrode active material layer 2. It means that. Further, when the thickness of the electrode active material layer 2 is as thin as the above range, the distance between the first electrode active material and the current collector 1 in the electrode active material layer 2 is shortened. The resistance of the plate 10 can be lowered. In the present invention, the lower limit of the film thickness of the electrode active material layer 2 mainly depends on the particle diameter of the first electrode active material used, and the film thickness can be further reduced as the particle diameter is reduced. Is possible.

(First electrode active material)
The first electrode active material can be appropriately used as long as it is an active material exhibiting a lithium ion insertion / release reaction, and a positive electrode active material is selected.

The positive electrode active material that can be used as the first electrode active material is not particularly limited as long as it is an active material that exhibits a lithium ion insertion / release reaction generally used in a positive electrode plate for a nonaqueous electrolyte secondary battery. Not. Specific examples of the positive electrode active material include a lithium composite compound which is a composite compound of lithium and a non-lithium metal. Specifically, LiCoO ₂ , LiMn ₂ O ₄ , LiNiO ₂ , LiFeO _{2 can be given.} , LiNi _1/3 Co _1/3 Mn _1/3 O ₂ , LiNi _0.80 Co _0.15 Al _0.05 O ₂ and other lithium composite oxides, LiFePO ₄ and other lithium composite phosphates, etc. Can do. The non-lithium metal refers to a metal selected from the group of metals other than lithium.

  In general, a particulate active material is selected for the first electrode active material.

  The particle diameter of the active material particles used for the first electrode active material is not particularly limited, and those having an arbitrary size can be appropriately selected and used. In particular, according to the present invention in which active material particles having a small particle diameter are used, the total amount of the surface area of the active material particles in the electrode active material layer can be increased, and lithium in one active material particle can be increased. Since the moving distance can be shortened, the input / output characteristics can be dramatically improved. Therefore, when a higher input / output characteristic is required, it is desirable to select one having a small particle size. Specifically, the particle diameter of the active material particles to be used is preferably less than 10 μm, more preferably 5 μm or less, and particularly preferably 1 μm or less. In a conventional slurry-like electrode active material layer forming liquid using a resin binder, when the active material particle diameter used is less than 10 μm, the coating suitability tends to be poor, and when it is 5 μm or less, the formation is performed. The fluidity of the liquid is remarkably deteriorated, making it difficult to apply to mass production equipment such as a printing press. Further, if it is 1 μm or less, it tends to be difficult to disperse the active material particles in the forming liquid. On the other hand, when manufacturing this invention, since the above problems are avoided, the particle diameter of an active material particle can be selected arbitrarily.

  In the present invention and the present specification, the particle diameter of the first electrode active material contained in the electrode active material layer is determined by identifying the measured electron microscope observation data using a particle recognition tool. A particle size distribution graph can be created based on the shape data acquired from the recognized particle image, and can be calculated from the particle size distribution graph. The particle size distribution graph can be created, for example, by using an image analysis type particle size distribution measurement software (manufactured by Mount Tech Co., Ltd., MAC VIEW) based on an electron microscope observation result.

(Second electrode active material)
The second electrode active material comprises a lithium composite oxide having a metal selected from the group of metals other than lithium and lithium as metal elements and having a spinel structure. When the second electrode active material contains such a lithium composite oxide, lithium can be effectively inserted and removed from the positive electrode plate 10 for a non-aqueous electrolyte secondary battery, and the battery can be charged and discharged at high speed. Can be realized.

  The lithium composite oxide constituting the second electrode active material is preferably a lithium manganese composite oxide containing manganese and lithium as metal elements. Among the electrodes using lithium composite oxide as an active material, an electrode using lithium manganese composite oxide as an active material has a relatively high discharge potential, and the lithium manganese composite oxide is used as the second electrode. When the positive electrode plate used for the active material is used for the positive electrode plate of the non-aqueous electrolyte secondary battery, it is preferable in that it is easy to obtain a battery capable of taking out a larger voltage.

Examples of the lithium manganese composite oxide include LiMn ₂ O ₄ and those represented by a composition formula of LiMn _x1 M _{2 -x1} O ₄ . However, in the composition formula LiMn _x1 M _2-x1 O ₄ , x1 is 1.5 ≦ x1 <2. When x1 is in this range, a compound having a spinel structure is more easily formed. M represents a metal selected from the group of metals other than lithium and manganese. M is preferably lithium, boron, phosphorus, nitrogen, magnesium, aluminum, calcium, vanadium, titanium, chromium, nickel, iron, cobalt, copper, zinc, strontium, zirconium, niobium, molybdenum, tin, or These are combinations. Incidentally, the lithium metal oxide represented by the composition formula _LiMn x1 _{M 2-x1 O 4} can be obtained by a partial substitution products by replacing a portion of the metal M of Mn atoms LiMn ₂ O _4.

  In the electrode active material layer 2, the first electrode active material is a second electrode active material having a spinel structure, and is fixed to the current collector 1 while being fixed to each other. Will be. For this reason, it is possible to increase the speed of charging and discharging of the battery incorporating the positive electrode plate 10.

  It is not necessary for all the second electrode active materials contained in the electrode active material layer 2 to contribute to the adhesion between the current collector 1 and the first electrode active material and the adhesion between the first electrode active materials. . For example, in the second electrode active material, the first electrode active material is fixed only to the first electrode active material, and the first electrode active material is not fixed to the current collector. There may be things that do not.

  In the case where the second electrode active material is formed in the form of particles, the particle diameter is not particularly limited, and an arbitrary size can be appropriately formed and used. The particle diameter may be larger or smaller than the particles of the first electrode active material. In addition, as described for the particle diameter of the first electrode active material, considering that it becomes easy to improve the I / O characteristics when the particle diameter is reduced, the particle diameter of the second electrode active material is It is preferable to be within the preferable range of the particle diameter of the first electrode active material described above. In addition, the particle diameter of the second electrode active material can be specified by a method using data of an electron microscope observation result, similarly to the particle diameter of the first electrode active material.

  About the 2nd electrode active material, the location connected by the crystal lattice continuing may be included in at least one part of 2nd adjacent electrode active materials. It is inferred that the adhesion of the electrode active material layer 2 to the current collector 1 is improved when crystal lattices are continuous with each other in at least a part of the adjacent second electrode active materials. This improvement in adhesion may contribute effectively to the improvement in the input / output characteristics of the positive electrode plate 10. From the viewpoint of improving the adhesion of the electrode active material layer 2, it is more desirable that the portion where the crystal lattices of the adjacent second electrode active materials are continuous exist significantly in the electrode active material layer 2. In the present invention, whether or not the crystal lattices of the adjacent second electrode active materials are continuous can be confirmed by observing the crystal lattice of the cross section of the adjacent binder material in the electrode active material layer with a transmission electron microscope.

  In order to configure the electrode active material layer 2 so as to include a portion where crystal lattices in adjacent second electrode active materials are continuous, a positive electrode plate is formed according to a method for manufacturing a positive electrode plate for a non-aqueous electrolyte secondary battery described later. It is desirable to manufacture. In the manufacturing method described later, an electrode active material layer forming liquid is applied onto the current collector 1 to form a coating film, and the coating film is formed into the electrode active material layer 2 by performing means such as heating. At that time, on the current collector 1, the metal element-containing compound present around the first electrode active material causes a reaction such as thermal decomposition or oxidation, and the second electrode active material is formed around the first electrode active material. A lithium transition metal composite oxide that is an electrode active material is generated. At this time, if a part of the adjacent second electrode active materials (or their precursors) are bonded to each other, the crystal growth of the two easily proceeds simultaneously at the bonded portion. As a result of the simultaneous progress of crystal growth in the joint portion, the electrode active material layer of the present invention is configured to include a portion where crystal lattices in adjacent second electrode active materials are continuous.

  Since the second electrode active material is a lithium composite oxide, the moving distance of electrons that move between the current collector 1 and the electrode active material layer 2 can be shortened. As a result, the impedance of the positive electrode plate can be reduced, and as a result, the input / output characteristics can be improved.

  Further, the second electrode active material is used in place of or in combination with the conventional resin binder to fix the first electrode active materials to each other or to fix the first electrode active material on the current collector. So as to be contained in the electrode active material layer 2. Furthermore, since the second electrode active material is an active material similar to the binder first electrode active material and can undergo lithium ion insertion / release reaction, the electrode active material layer 2 has a resin binder. As compared with the conventional positive electrode plate in which the first electrode active material is fixed on the current collector or the like with the agent, the abundance of the active material is relatively increased. For this reason, in this invention, the whole electrode capacity | capacitance can be increased by presence of a 2nd electrode active material.

(Confirmation of lithium insertion / extraction of the second electrode active material)
The presence or absence of the lithium ion insertion / release reaction of the second electrode active material in the electrode active material layer 2 can be confirmed in advance using an electrochemical measurement method such as a cyclic voltammetry (CV) test method. it can.

One example of the CV test will be described. As an example, LiCoO ₂ is selected as the first electrode active material, and LiMn ₂ O ₄ is selected as the lithium composite oxide that forms the second electrode active material. A coating film that does not contain the first electrode active material and contains the second electrode active material is formed on an aluminum foil to prepare a sample piece, and this sample piece is used for the CV test. Regarding the conditions of the CV test, the electrode potential is swept linearly within an appropriate voltage range of the first electrode active material. Specifically, when LiCoO ₂ is assumed as the first electrode active material, 3.0V The operation of sweeping from 4.2 to 4.2V and returning 4.2V as the return voltage to 3.0V is defined as one cycle and repeated for about three cycles. At this time, the scanning speed is preferably 1 mV / sec from the viewpoint of more reliably observing the redox reaction of LiMn ₂ O ₄ as the second electrode active material. Then, a current corresponding to the voltage is measured in each cycle to obtain a cyclic voltammogram. When the second electrode active material is LiMn ₂ O ₄ , when a cyclic voltammogram is viewed, an oxidation peak corresponding to the Li elimination reaction of LiMn ₂ O ₄ appears in the vicinity of about 3.9 V, and about 4 A reduction peak corresponding to the Li insertion reaction may appear in the vicinity of .1V. At this time, it can be confirmed that this LiMn ₂ O ₄ has a lithium ion insertion / release reaction. Conversely, when such a peak does not appear when the cyclic voltammogram is viewed, it can be determined that there is no lithium ion insertion / release reaction.

  In the present invention, the fact that the metal oxide does not exhibit a lithium ion insertion / elimination reaction does not mean the electrical properties unique to the metal oxide, but a metal contained as a binder in the electrode active material layer. It means that the oxide does not exhibit lithium ion insertion / release reaction in a voltage range suitable for the electrode active material particles contained in the electrode active material. This is because it is important that the metal oxide substantially inserts and desorbs lithium ions in the positive electrode plate.

  Thus, the presence / absence of the lithium ion insertion / release reaction of the lithium composite oxide scheduled to be contained in the electrode active material layer 2 can be confirmed in advance. In designing the positive electrode plate 10, a lithium composite oxide that has been confirmed in advance to exhibit a lithium ion insertion / release reaction is determined as the second electrode active material in the electrode active material layer 2.

  In addition, whether or not the lithium active material layer 2 of the positive electrode plate 10 contains a lithium composite oxide showing a lithium ion insertion / release reaction as the second electrode active material is confirmed as follows, for example. Can do. It is possible to estimate what lithium composite oxide is contained in the sample by cutting the electrode active material layer to prepare a sample and performing composition analysis of the sample. By forming a coating film composed of the estimated lithium composite oxide on an aluminum foil and subjecting it to a cyclic voltammetry test, it is determined whether or not the lithium composite oxide exhibits a lithium ion insertion / release reaction. I can confirm. Further, when the electrode active material layer 2 in the already completed positive electrode plate is observed with a transmission electron microscope and the crystal lattice of the lithium composite oxide is similar to the crystal lattice of a compound known as a conventionally known active material, The lithium composite oxide is a metal oxide that exhibits a lithium ion insertion / elimination reaction, and can be determined to be suitable as the second electrode active material.

(Combination of first electrode active material and second electrode active material)
The electrode active material layer 2 is not limited to the combination of the first electrode active material and the second electrode active material, and may be a combination of the same compounds.

  That the 1st electrode active material and the 2nd electrode active material are the same compounds means that both are the compounds which show the substantially same composition. At this time, the compounds having substantially the same composition include not only those having the same composition ratio shown in the chemical composition of the first electrode active material and the second electrode active material, but also depart from the spirit of the present invention. What is different in the range not to be included. Moreover, both compounds are the same even when any element is substituted in either one or both of the first electrode active material and the second electrode active material to the extent that they do not depart from the spirit of the present invention. I can understand.

  In addition, as a method of determining that the first electrode active material and the second electrode active material are the same compound by another means other than the analysis of the chemical composition, the crystal structure of the compound may be confirmed. That is, when the first electrode active material and the second electrode active material are observed with a transmission electron microscope and the crystal structures of the two compounds are the same, the two can determine the same compound. . Here, the same crystal structure means that the crystal structure is included in the same crystal phase. In other words, when the active material particles and the metal oxide are not the same, the crystal structures of the two are located in different crystal phases, and the narrowly defined identity based on the difference in the contrast of the crystal lattices. Not intended.

  When the first electrode active material and the second electrode active material are the same compound, both the first electrode active material and the second electrode active material have the same potential for taking in and out lithium ions during charging and discharging. It is possible to participate at a level, and it is possible to substantially increase the electrode capacity.

(Compounding ratio of the first electrode active material and the second electrode active material)
In the present invention, the mixing ratio of the first electrode active material particles and the second electrode active material contained in the electrode active material layer 2 is not particularly limited, and the first electrode active material used is not limited. It can be determined appropriately in consideration of the type and size of the particles, the function required for the second electrode active material, and the like.

  In the electrode active material layer 2, when the content of the second electrode active material is too small, the fixing force between the first electrode active material, the current collector 1, and the first electrode active material is set to a desired level. There is a risk that it will not be possible to list up to. Moreover, there is a possibility that it may not be able to sufficiently contribute to the speeding up of charge / discharge. Therefore, considering this point, when the mass ratio of the first electrode active material is 100 parts by mass, the mass ratio of the second electrode active material is preferably 10 parts by mass or more and 100 parts by mass or less. .

  It is in the electrode active material layer 2 that the second electrode active material is contained to such an extent that the current collector, the first electrode active material particles, and the first electrode active material can be sufficiently fixed to each other. It is possible to increase the electric capacity of the electrode active material layer 2 without making it necessary to increase the amount of the first electrode active material particles.

(Other materials)
The electrode active material layer 2 is not limited to what is comprised only from the 1st electrode active material and the 2nd electrode active material. The electrode active material layer 2 may be formed by adding further additives without departing from the spirit of the present invention. For example, a conductive material exemplified by a conductive carbon material such as carbon black may be added to the electrode active material layer 2 as an additive depending on conditions such as when better conductivity is desired. .

  When the conductive material is contained in the electrode active material layer, the content is not particularly limited, but generally, with respect to 100 parts by weight of the total amount of the first electrode active material and the second electrode active material, It is desirable that the ratio of the conductive material be 5 parts by weight or more and 20 parts by weight or less.

  Further, the present invention can sufficiently fix the first electrode active material on the current collector even if the amount of the resin binder is suppressed as much as possible or without using the resin binder. However, this does not prohibit the resin component from being contained in the electrode active material layer. For example, when a battery is assembled using the positive electrode plate 10, the electrode active material layer contains about 1% to 10% of a resin component in order to improve the permeability of the non-aqueous electrolyte into the pores of the electrode. May be allowed Thus, if necessary, a resin material may be included in the electrode active material layer in the present invention. Furthermore, in order to fix the first electrode active material, the second electrode active material and a resin binder may be used in combination. In this case, it is easy to improve the film strength.

[Use of positive electrode plate 10]
The positive electrode plate of the present invention can be used as a positive electrode plate of a non-aqueous electrolyte secondary battery.

  The positive electrode plate of the present invention has high input / output performance and high speed when compared with a conventional positive electrode plate in which an electrode active material layer is formed using a resin binder without containing the second electrode active material. Charging / discharging is possible. These can be confirmed by measuring the charge / discharge rate characteristics of the electrode using the positive electrode plate. In the positive electrode plate of the present invention, since the binding material for fixing the first electrode active material is the second electrode active material, it is possible to substantially increase the ratio of the active material in the positive electrode plate, This is very excellent in that the discharge capacity of the positive electrode plate (in this specification, the discharge capacity of the positive electrode plate is also simply referred to as “electrode capacity”) can be increased.

(Method for evaluating charge / discharge rate characteristics of electrode)
The input / output characteristics of the positive electrode plate of the present invention can be evaluated by determining the discharge capacity retention rate (%). That is, the discharge capacity retention rate is an evaluation of discharge rate characteristics, and it is understood that a positive electrode plate with improved discharge rate characteristics generally has improved charge rate characteristics as well. Therefore, when a desirable discharge capacity maintenance rate is indicated, it is evaluated that the charge / discharge rate characteristics have been improved. More specifically, for example, the discharge rate 1C is set so that the theoretical value of the discharge capacity (mAh) of the first electrode active material is completed in 1 hour, and becomes a reference for the discharge rate of 1C. A reference discharge rate is set, and the discharge capacity (mAh) actually measured at the reference discharge rate is defined as a discharge capacity maintenance rate of 100%. Then, the discharge capacity (mAh) when the discharge rate is further increased is measured, and the discharge capacity retention ratio (%) can be obtained by the following equation (1).

  In addition, the said discharge capacity is calculated | required by measuring the discharge capacity of electrode itself with a tripolar coin cell.

[Method for producing positive electrode plate for non-aqueous electrolyte secondary battery]
Next, a method for producing a positive electrode plate for a non-aqueous electrolyte secondary battery of the present invention (hereinafter sometimes simply referred to as “the production method of the present invention”) will be described.

  In the production method of the present invention, first, a metal element-containing compound that is a precursor of the second electrode active material, active material particles that are the first electrode active material, or further an optional additive is contained in a solvent. An electrode active material layer forming liquid is prepared. And the manufacturing method of this invention is the 2nd from the application | coating process which apply | coats the said electrode active material layer formation liquid to the desired area | region of the collector surface, and forms a coating film, and the metallic element containing compound contained in the said coating film. And an electrode active material layer forming step of depositing the electrode active material. In the production method of the present invention, since the positive electrode active material layer is laminated on the current collector, the electrode active material layer forming liquid contains active material particles for the positive electrode and a metal element-containing compound suitable for this. Add.

  In the production method of the present invention, the electrode active material layer forming liquid in which the metal element-containing compound is dissolved is applied onto a current collector, and a metal oxide is generated from the metal element-containing compound contained in the coating film to collect current. It is deposited on the body. At this time, the metal oxide generated on the current collector forms the second electrode active material, and a coating film is formed on the current collector so as to embrace the active material particles contained in the electrode active material layer forming liquid. The active material particles can be fixed on the current collector. In the fixing of the active material particles and the conductive material particles contained in the electrode active material layer forming liquid, in addition to the fixing mode 1, as shown as the fixing mode 2, the direct contact between the particles was kept good. A mode of fixing in a state is included. As described above, the factors that enable the fixed state as shown in the fixing modes 1 and 2 are that the metal element-containing compound is dissolved in the solvent and the active material particles in the manufacturing method of the present invention. When the electrode active material layer forming liquid mixed with is applied onto the current collector to form the electrode active material layer, the generated metal oxide is in direct contact between the active material particles or between the active material particles. It is inferred that it is to be generated around the contact portion. As a result, the manufacturing method of the present invention can manufacture a positive electrode plate that has good conductivity and can keep electric resistance low.

Active material particles:
Since the active material particles contained in the electrode active material layer forming liquid are the same as the positive electrode active material particles forming the first electrode active material already described above, the description thereof is omitted here. The electrode active material layer forming liquid used in the present invention is a case where active material particles having a small average particle diameter are used as compared with an electrode active material layer forming liquid using a conventional resin binder. The viscosity can be easily adjusted. In particular, the electrode active material layer forming liquid used in the production method of the present invention has a viscosity that reduces applicability even when the active material particles have a particle size of 10 μm or less, and even 1 μm or less. It has a desirable feature that no increase in the level of Therefore, a desired size can be selected for the particle diameter of the active material particles used.

Metal element-containing compounds:
The metal element-containing compound dissolved in the electrode active material layer forming liquid is contained in the electrode active material layer, and the active material particles are fixed to each other as a binder, and the active material particles are placed on the current collector. It is a second electrode active material precursor that is fixed and exhibits a lithium ion insertion / release reaction. Therefore, the metal element-containing compound is applied on the current collector in a state of being dissolved in a solution, and the metal constituting the second electrode active material described above according to the content of the electrode active material layer forming step. What is necessary is just to be able to produce an oxide. Whether or not the metal oxide produced from the metal element-containing compound to be used exhibits a lithium ion insertion / release reaction and is suitable as the second electrode active material is determined according to the preliminary experiment. A metal oxide produced from a metal element-containing compound by applying a solution containing the containing compound on a substrate such as glass and applying a treatment corresponding to the treatment of the electrode active material layer forming step such as heat treatment. It can confirm by obtaining the laminated body which laminated | stacked the layer containing this on a board | substrate, and implementing the cyclic voltammetry method mentioned above using this laminated body as a positive electrode plate.

  For example, examples of the metal element-containing compound include a combination of a lithium element-containing compound and one or more metal element-containing compounds containing manganese as a metal element. At this time, the combination of the metal element-containing compounds may be selected so that two kinds of metal elements of lithium and manganese are included as the entire combination of the selected compounds. Further, the metal element-containing compound used in the present invention may be an inorganic metal element-containing compound that does not contain carbon in the compound, or an organic metal constituted by containing carbon in the compound. It may be an element-containing compound. In the present invention and the present specification, the inorganic metal element-containing compound and the organic metal-containing compound may be collectively referred to simply as a metal element-containing compound.

  As the metal element-containing compound, a chloride, nitrate, sulfate, perchlorate, acetate, phosphate, bromate, carbonate, or the like of a metal element such as lithium element or manganese may be appropriately selected. . In the present invention, chloride, nitrate, and acetate are preferably used because they are easily available as general-purpose products. In particular, acetate is preferably used because it has good film-forming properties for a wide range of current collectors.

  For example, as the metal element-containing compound for generating the second electrode active material that is a metal oxide, the following Li element-containing compound, Mn element-containing compound can be used in combination as the main raw material, Furthermore, other raw materials can be used in combination as required.

  Examples of the Li element-containing compound include lithium citrate tetrahydrate, lithium perchlorate trihydrate, lithium acetate dihydrate, lithium nitrate, lithium phosphate, and lithium carbonate.

  Examples of the Mn element-containing compound include manganese acetate (III) dihydrate, manganese nitrate (II) hexahydrate, manganese sulfate (II) pentahydrate, manganese oxalate (II) dihydrate, And manganese (III) acetylacetonate, manganese carbonate and the like.

  The combination ratio of the Li element-containing compound and the Mn element-containing compound used as the main raw material is not particularly limited, but the element composition ratio in the range of all kinds of compounds included as the metal element compound in the electrode active material layer forming liquid, When Li: Mn = X: 1, 0.5 ≦ X <1 is preferable, and 0.5 ≦ X ≦ 0.6 is more preferable.

  In the electrode active material layer forming liquid described above, the ratio of the total amount of the one or more metal element-containing compounds added in the solvent is 0.01 mol / L to 5 mol / L, particularly 0. 1 mol / L to 2 mol / L is preferable. When the concentration is 0.01 mol / L or more, the current collector and the electrode active material layer generated on the surface of the current collector are in good contact, and the active material particles forming the first electrode active material Fixing is achieved. Further, when the concentration is 5 mol / L or less, the electrode active material layer forming liquid can maintain a good viscosity enough to be applied to the current collector surface, and a uniform coating film is formed. Is done.

(Other additives)
In addition to the active material particles and the metal element-containing compound described above, other additives may be added to the electrode active material layer forming liquid without departing from the spirit of the present invention. As the conductive material and other additives, the same materials as described in the description of the electrode active material layer of the present invention can be used.

  When the conductive material is added to the electrode active material layer forming liquid, the active material particles generated on the current collector surface, or the active material particles and the total amount of metal oxides scheduled to be formed are 100 parts by weight. In addition, the addition amount of the conductive material is desirably 5 to 20 parts by weight. In addition, the above is not the meaning which excludes adding a conductive material exceeding 20 weight.

(solvent)
The solvent used for preparing the electrode active material layer forming liquid is not particularly limited. For example, water or a lower alcohol having a total carbon number of 5 or less, such as methanol, ethanol, isopropyl alcohol, propanol, and butanol. And diketones such as acetylacetone, diacetyl and benzoylacetone, ketoesters such as ethyl acetoacetate, ethyl pyruvate, ethyl benzoylacetate and ethyl benzoylformate, toluene, and a mixed solvent thereof.

  In addition, the electrode active material layer forming liquid requires active material particles, metal oxides, or other additives such as a conductive material as required in the electrode active material layer to be formed on the current collector. These amounts are determined in consideration of being included in the amounts. At that time, the ratio of the solute added to the solvent (that is, the active material particles, the metal element-containing compound and the optional additive) is determined by the coating property on the current collector in the coating process and the removal of the solvent in the heating process. Consider and adjust accordingly. Generally, when the electrode active material layer forming liquid is 100% by weight, the total amount of solutes contained is adjusted to be 30% to 70% by weight.

  Next, the electrode active material layer forming liquid prepared as described above is applied onto a current collector to form a coating film. The current collector used in the production method of the present invention is the same as the current collector used for the positive electrode plate for a non-aqueous electrolyte secondary battery.

  In the coating step in the production method of the present invention, a known coating method can be appropriately selected and implemented as a solution coating method. For example, the electrode active material layer forming liquid can be applied to any region of the current collector surface to form a coating film by printing, spin coating, dip coating, bar coating, spray coating, or the like. In addition, when the current collector surface is porous, has a large number of irregularities, or has a three-dimensional structure, the coating method is other than the above method, for example, a manual coating method. Is also possible. Note that the current collector used in the present invention is preferable because corona treatment, oxygen plasma treatment, and the like can be performed in advance as necessary to further improve the film forming property of the electrode active material layer.

  The amount of the electrode active material layer forming liquid applied to the current collector can be arbitrarily determined according to the use of the positive electrode plate to be produced. Since the electrode active material layer in the present invention can be formed very thin as described above, when it is desired to reduce the thickness, the final electrode active material layer has a thickness of 300 nm to 150 μm, particularly 500 nm. You may apply | coat thinly so that it may be set to about ~ 100 micrometers. As described above, a coating film for forming an electrode active material layer containing a metal element-containing compound that is a precursor of a metal oxide that is a binding material is formed by applying an electrode layer forming liquid to a substrate. .

  A pressing step may be further performed between the coating step and the electrode active material layer forming step described later, or after the electrode active material layer forming step described later. The said press process can be implemented by drying the said coating film for electrode active material layer formation formed on the electrical power collector as needed, removing a solvent, and pressing it after that. The pressing method can be carried out in the same manner as the press performed by applying a slurry-like electrode active material layer forming liquid containing a conventional resin binder on the current collector and drying it. . Thus, the manufacturing method of this invention can adjust the porosity of the electrode active material layer in the positive electrode plate finally manufactured by implementing a press process, and can increase a volume energy density.

  Next, the electrode active material layer forming step for depositing the second electrode active material from the metal element-containing compound contained in the coating film formed in the coating step will be described.

  The electrode active material layer forming step can be appropriately selected as long as it is a step of performing a method for precipitating the second electrode active material from the metal element-containing compound. For example, a heating step, a reduced pressure drying step, a reduced pressure heating step, or Examples of these combinations are exemplified, but the present invention is not limited thereto, and a step of implementing a means capable of forming, as an electrode active material layer, a coating film formed from an electrode active material layer forming liquid applied on a current collector If it is. For example, the electrode active material layer forming step may include two or more means such as a means for removing the solvent contained in the coating film and then a means for reacting the metal element-containing compound. . In addition, the solvent in the coating film is not limited to the case where it is removed by a treatment such as heating in the electrode active material layer forming step, and any other step performed between the coating step and the electrode active material layer forming step. May be removed.

  As the electrode active material layer forming step, a heating step of heating the coating film is preferably selected. In the heating step, oxygen can be efficiently provided to the metal element-containing compound by heating the metal element-containing compound in the presence of air. For this reason, a heating process is easy to implement as a process for obtaining metal oxides, such as lithium complex oxide.

  The heating step heats and decomposes the metal element-containing compound at a temperature equal to or higher than the thermal decomposition start temperature, and oxidizes the metal element contained therein to produce a metal oxide exhibiting a lithium insertion / release reaction. is there. In the heating process, the metal element-containing compound present in the coating film is thermally decomposed and oxidized, and the solvent contained in the coating film is removed (however, a pressing process is performed before the heating process). In this case, the solvent is substantially removed by drying before pressing). The heating method is not particularly limited as long as it is a heating method or a heating apparatus capable of heating the coating film at a heating temperature described later, and can be appropriately selected and carried out. Specific examples include a method of using a hot plate, an oven, a heating furnace, an infrared heater, a halogen heater, a hot air blower, or the like, or a combination of two or more. When the current collector to be used is planar, it is preferable to use a hot plate or the like for the heating step. In addition, when heating using a hot plate, it is preferable to install and heat the coating film surface side in a direction not in contact with the hot plate surface. The heating temperature varies depending on the type of the metal element-containing compound used. However, the metal element-containing compound is favorably thermally decomposed by heating the coating film in a temperature range of 150 ° C. to 800 ° C. An oxide is produced. Since the produced metal oxide exhibits a lithium ion insertion / release reaction, it is understood to be a second electrode active material. In this production method, the crystalline metal oxide is often formed. In this case, the crystalline metal oxide includes a microcrystalline state. Thus, the crystalline metal oxide has a high discharge capacity, and therefore, a positive electrode plate having a high discharge capacity can be formed.

  Here, generally, when producing a metal oxide using heating, it is necessary to heat the coating film at a temperature of at least about 800 ° C. or higher. On the other hand, in the production method of the present invention, the second electrode active material is generated even at a low heating temperature of 700 ° C. or lower, further 600 ° C. or lower, particularly 400 ° C. or lower. This is one of the characteristic points of the manufacturing method. In addition, it is possible to produce a metal oxide having excellent crystallinity even at a heating temperature as low as 700 ° C. or less, further 600 ° C. or less, particularly 400 ° C. or less. This point is also a special feature of the production method of the present invention. It is an advantage to be done. The relationship between the heating temperature described above and the development of crystallinity of the metal oxide produced is estimated as follows. That is, since the active material particles are contained in the electrode active material layer forming liquid, the generated metal oxide follows the crystallinity of the active material particles, and is 700 ° C. or lower, further 600 ° C. In particular, it is presumed that lithium insertion / extraction reaction is possible even at a heating temperature of 400 ° C. or lower, and a highly crystalline metal oxide is obtained. In particular, when the chemical composition of the active material particles to be mixed with the generated metal oxide is the same, this follow-up action is assumed to be remarkable.

  The heating step is performed at a heating temperature of 400 ° C. or less, so that the selection range of the current collector is widened, and the electrode active material layer can be directly formed on various current collectors. Since various effects, such as the point that cost merit improves by having low temperature, are preferable.

  The heating temperature is a temperature at which the second electrode active material can be formed. By the way, preliminarily, a solution in which a metal element-containing compound to be used is dissolved is applied on a suitable substrate and heated, and a film laminated on the substrate is cut to obtain a sample, and a composition analysis is performed. Whether or not the second electrode active material is formed can be determined by measuring the content ratio of the metal element and oxygen. Therefore, when the second electrode active material is generated by heating at a predetermined temperature condition, the metal element-containing compound used is at a temperature equal to or higher than the thermal decomposition start temperature on the substrate. Confirmed to be heated. That is, in the present invention, the “thermal decomposition start temperature of a metal element-containing compound” can be understood as a temperature at which the metal element-containing compound is decomposed by heating and the formation of a metal oxide can be started.

  In the heating step, when determining the heating temperature, it is desirable to further consider the heat resistance of the current collector, active material particles, conductive material, and the like used. For example, since the heat resistance of an aluminum foil generally used as a current collector for a positive electrode plate is around 660 ° C., the current collector may be damaged if the heating temperature exceeds 660 ° C. Therefore, the current collector, active material particles, etc. to be used are determined first, taking into account their heat resistance, taking into account their heat resistant temperature and thermal decomposition starting temperature, and selecting a metal element-containing compound. Also good. In the production method of the present invention, “heating temperature” means the highest temperature in the heating step. The heating mode in the heating step may be arbitrarily determined, for example, by gradually increasing the temperature, heating at a constant temperature, or heating at a stepped temperature.

  The positive electrode plate of the present invention may further contain a resin component in the electrode active material layer produced as described above. The electrode active material layer may further contain a resin component by, for example, applying a resin mixed solution to the surface of the electrode active material layer, or immersing the positive electrode plate in a resin mixed solution tank, A method of removing the solvent of the resin mixed solution impregnated in the electrode active material layer by infiltrating the gaps in the electrode active material layer and then drying, and leaving only the resin component inside the electrode active material layer. Can be mentioned. Thus, if it is the positive electrode plate of this invention which contains a resin component in an electrode active material layer, the bending tolerance of a positive electrode plate will improve by the presence of a resin component, and it can improve a process characteristic. In particular, when the resin component is a conventionally used resin binder, the film adhesion of the electrode active material layer to the current collector can be further improved.

  As the resin material contained in the resin mixed solution, for example, a conventional resin binder such as PVDF, styrene butadiene rubber (SBR), carboxymethoxy cellulose (CMC), or those listed in the viscosity modifier are selected. However, the present invention is not limited to this. The resin material is appropriately selected to have a size that can penetrate into the voids in the electrode active material layer. Examples of the solvent for the resin mixture include lower alcohols having a total carbon number of 5 or less such as methanol, ethanol, isopropyl alcohol, propanol, and butanol, diketones such as acetylacetone, diacetyl, and benzoylacetone, ethyl acetoacetate, and pyrubin. Ketoesters such as ethyl acetate, ethyl benzoylacetate and ethyl benzoylformate, pyrrolidones such as N-methylpyrrolidone (NMP), toluene, a mixed solvent thereof, water, and the like can be used. Can be mixed to prepare a resin mixed solution.

  The amount of the resin component contained in the electrode active material layer is desirably adjusted to such an extent that the input / output performance of the positive electrode plate is not deteriorated. That is, the resin component may be included in the electrode active material layer without departing from the spirit of the present invention.

[Nonaqueous electrolyte secondary battery]
Non-aqueous electrolyte secondary batteries are generally configured with a positive electrode plate and a negative electrode plate, and a separator such as a porous film made of polyolefin such as polyethylene provided between them. And is sealed and manufactured in a state where the non-aqueous electrolyte is filled in the container.

(Positive electrode plate)
The non-aqueous electrolyte secondary battery of the present invention is characterized in that, in particular, the above-described positive electrode plate 10 for a non-aqueous electrolyte secondary battery of the present invention is used as a positive electrode plate of a pair of electrode plates. As the negative electrode plate as the other electrode plate, a conventionally known negative electrode plate used in a non-aqueous electrolyte secondary battery can be appropriately used.

  As the nonaqueous electrolyte secondary battery of the present invention, a battery configured as shown in FIG. 3 can be exemplified.

  The non-aqueous electrolyte secondary battery in FIG. 3 has a negative electrode plate 50 in which an electrode active material layer 54 is provided on one side of a current collector 55 and an electrode active on one side of the current collector 1 combined therewith. A positive electrode plate 10 provided with the material layer 2 and a separator 70 such as a polyethylene porous film are provided between them. These are housed in the outer casings 81 and 82 and sealed and manufactured in a state where the outer casings 81 and 82 are filled with the non-aqueous electrolyte 90, thereby forming the non-aqueous electrolyte secondary battery 100. The

  As a conventionally known negative electrode plate, a copper foil such as an electrolytic copper foil or a rolled copper foil having a thickness of about 5 μm to 50 μm is used as a current collector, and an electrode active material constituting the negative electrode plate is formed on at least a part of the current collector surface. The material layer-forming composition is applied to obtain a coating film, and the coating film is dried and, if necessary, formed by pressing. The electrode active material layer forming liquid in the negative electrode plate generally includes an active material made of a carbonaceous material such as natural graphite, artificial graphite, amorphous carbon, carbon black, or a material obtained by adding a different element to these components, Alternatively, active materials such as materials capable of occluding and releasing lithium ions, such as metallic lithium and its alloys, tin, silicon, and alloys thereof, and other additives such as binders and conductive materials as needed are dispersed and mixed. In general.

(Non-aqueous electrolyte)
The non-aqueous electrolyte used in the present invention is not particularly limited as long as it is generally used as a non-aqueous electrolyte for a non-aqueous electrolyte secondary battery, but a lithium salt is dissolved in an organic solvent. A non-aqueous electrolyte is preferably used.

Examples of the lithium salt include inorganic lithium salts such as LiClO ₄ , LiBF ₄ , LiPF ₆ , LiAsF ₆ , LiCl, and LiBr; LiB (C ₆ H ₅ ) ₄ , LiN (SO ₂ CF ₃ ) ₂ , LiC ( Organic compounds such as SO ₂ CF ₃ ) ₃ , LiOSO ₂ CF ₃ , LiOSO ₂ C ₂ F ₅ , LiOSO ₂ C ₄ F ₉ , LiOSO ₂ C ₅ F ₁₁ , LiOSO ₂ C ₆ F ₁₃ , and LiOSO ₂ C ₇ F ₁₅ Typical examples include lithium salts.

  Examples of the organic solvent used for dissolving the lithium salt include cyclic esters such as propylene carbonate and butylene carbonate, chain esters such as dimethyl carbonate and diethyl carbonate, cyclic ethers such as tetrahydrofuran and alkyltetrahydrofuran, and 1,2- Examples include, but are not limited to, chain ethers such as dimethoxyethane and 1,2-diethoxyethane.

  As the structure of the battery manufactured using the positive electrode plate, the negative electrode plate, the separator, and the nonaqueous electrolytic solution, a conventionally known structure can be appropriately selected and employed. For example, the structure which winds a positive electrode plate and a negative electrode plate in the shape of a spiral via the separator like a polyethylene porous film, and accommodates in a battery container is mentioned. As another aspect, a structure may be employed in which a positive electrode plate and a negative electrode plate cut into a predetermined shape are stacked and fixed via a separator, and are accommodated in a battery container. In any structure, after the positive electrode plate and the negative electrode plate are stored in the battery container, the lead wire attached to the positive electrode plate is connected to the positive electrode terminal provided in the outer container, while the lead wire attached to the negative electrode plate Is connected to a negative electrode terminal provided in the outer container, and the battery container is further filled with a nonaqueous electrification solution and then sealed to produce a nonaqueous electrolyte secondary battery.

  The non-aqueous electrolyte secondary battery using the positive electrode plate of the present invention can be used as a so-called non-aqueous electrolyte secondary battery used for a battery pack. That is, the battery pack of the present invention uses the positive electrode plate of the present invention, and a non-aqueous electrolyte secondary battery including a positive electrode terminal and a negative electrode terminal and a protection circuit having an overdischarge protection function are stored in a storage case. Composed. The battery pack of the present invention is equipped with a protection function for protecting the battery from, for example, overcharge, overdischarge, overcurrent, a short circuit of the battery peripheral circuit, a short circuit between the positive and negative electrodes, etc., in the nonaqueous electrolyte secondary battery itself. In addition, it may be a battery pack in which a protection circuit for preventing overcharge and overdischarge is housed and integrated in a storage case together with the non-aqueous electrolyte secondary battery. The battery pack of the present invention can be suitably used as a battery power supply device for a device that consumes a large amount of power relative to the scale of the device, such as a portable device such as a notebook computer, a camera, or a mobile phone.

[Battery pack]
FIG. 4 shows a schematic exploded view of a battery pack 30 of the present invention using a lithium ion secondary battery 31 which is a non-aqueous electrolyte secondary battery configured using the positive electrode plate of the present invention. The battery pack 30 includes a lithium ion secondary battery 31 housed in a resin container 36a, a resin container 36b, and an end case 37. At this time, a protection circuit for preventing overcharge and overdischarge between one end face of the lithium ion secondary battery 31 and a face including the positive electrode terminal 32 and the negative electrode terminal 33 and the end case 37. A substrate 34 is provided. The protection circuit board 34 includes an external connection connector 35. The external connection connector 35 is inserted into an external connection window 38a provided in the resin container 36a and an external connection window 38b provided in the end case 37. Connected to an external terminal. The protection circuit board 34 includes a charge / discharge safety circuit (not shown) for controlling charge / discharge, a wiring circuit for connecting the external connection terminal and the lithium ion secondary battery 31, and the like. In addition, the battery pack 30 can employ | adopt the structure of a conventionally well-known battery pack suitably except using the lithium ion secondary battery 31 in which the positive electrode plate of this invention was used. Although not shown, the battery pack 30 includes a positive electrode lead plate connected to the positive electrode terminal 32, a negative electrode lead plate connected to the negative electrode terminal 33, an insulator, and the like between the lithium ion secondary battery 31 and the end case 37. , May be provided as appropriate.

  In addition, the non-aqueous electrolyte secondary battery of the present invention using the positive electrode plate of the present invention has functions such as overcurrent blocking and battery temperature monitoring in addition to the above-described protection circuit, in addition to the usage mode for battery packs. And the protection circuit may be used by being integrated with the secondary battery itself. In such an embodiment, the battery pack can be used as a secondary battery having a protection function and a protection circuit without constituting a battery pack, and is highly versatile. In addition, some aspects mentioned above are only illustrations, and do not limit use of the positive electrode plate of this invention, or the nonaqueous electrolyte secondary battery of this invention at all.

Example 1
<Preparation of positive electrode plate for non-aqueous electrolyte secondary battery>
Li (CH ₃ COO) · 2H ₂ O [molecular weight: 102.02]: 2 g and Mn (CH ₃ COO) ₂ · 4H ₂ O as a compound that is a precursor of the lithium composite oxide that forms the second electrode active material [Molecular weight: 245.09]: 4.9 g was prepared, and this was added to 7 g of methanol as a solvent and mixed to prepare a second electrode active material precursor compound-containing liquid. Second electrode active material precursor compound-containing liquid: 10 g, LiNi _1/3 Co _1/3 Mn _1/3 O ₂ as positive electrode active material particles having an average particle diameter of 5 μm serving as the first electrode active material: 10 g Acetylene black (Denka Black, manufactured by Denki Kagaku Kogyo Co., Ltd.) (average particle size 50 nm): 1.2 g and vapor grown carbon fiber (Vapor Carbon Carbon Fiber: VGCF (manufactured by Showa Denko KK)) 0.25 g (length 10 μm to 20 μm), 10 g of a viscosity adjusting solution prepared by dissolving 0.2 g of a resin material (hydroxyethylcellulose) as a viscosity adjusting agent in 9.8 g of pure water, and 2 g of methanol as a solvent are mixed. And kneading with an Excel Auto Homogenizer (manufactured by Nippon Seiki Seisakusho Co., Ltd.) at a rotation speed of 7000 rpm for 15 minutes. The material layer forming liquid was prepared.

An aluminum plate having a thickness of 15 μm was prepared as a current collector, and the electrode active material layer forming liquid prepared above was applied to one surface side of the current collector in an amount such that the coating amount after drying was 30 g / m ^2. The electrode active material layer forming liquid prepared above was applied with an applicator to form a coating film for forming an electrode active material layer, and a heating step was performed as an electrode active material layer forming step.

  In the heating step, the current collector on which the electrode active material layer forming coating film is formed is placed in an electric furnace (high-temperature atmosphere box furnace, manufactured by Koyo Thermo Systems Co., Ltd., KB8610N-VP) in an air atmosphere, and takes 1 hour. The temperature was raised while heating from room temperature (25 ° C.) to 450 ° C., and then the heating was continued for 10 minutes while maintaining the temperature at 450 ° C., and then left to reach room temperature (heating step). Thereby, the electrode active material layer-forming coating film on the current collector formed an electrode active material layer, and a positive electrode plate was formed. Furthermore, this positive electrode plate was cut into a predetermined size (a disk having a diameter of 15 mm), and this was used as the positive electrode plate of Example 1. This positive electrode plate can be used as a positive electrode plate for a lithium ion secondary battery.

  During the heating step, a metal oxide is precipitated from the precursor compound of the second electrode active material. In addition, this metal oxide realizes adhesion between the active material particles constituting the first electrode active material and adhesion between the first electrode active material and the current collector. This state is confirmed by observing the positive electrode plate of Example 1 with a scanning electron microscope (magnification 30,000 times). The metal oxide is a lithium composite oxide and has a spinel structure, and this forms a second electrode active material.

  The fact that the metal oxide deposited from the precursor compound of the second electrode active material is a lithium composite oxide and has a spinel structure has been confirmed based on the following X-ray diffraction analysis test. It was.

X-ray diffraction analysis test:
Reference layer in the same manner as the electrode active material layer forming liquid used in Example 1 except that particles of LiNi _1/3 Co _1/3 Mn _1/3 O ₂ as the first electrode active material are not used. Using the reference layer forming solution, the forming solution is prepared, and the reference layer forming solution is applied onto the glass substrate in the same manner as in Example 1 to form a coating film, and the coating film is formed on the glass substrate. Then, the same step as the electrode active material layer forming step was performed to prepare a laminate in which the reference layer formed from the reference layer forming liquid was laminated on the current collector. Then, when the reference specimen 1 was set in an X-ray diffractometer and the X-ray diffraction spectrum of the reference layer laminated on the reference specimen 1 was confirmed, the peak of the spectrum was LiMn having a spinel structure. It coincided with the diffraction peak of ₂ O ₄ and the presence of crystals having a spinel structure in the reference layer was confirmed (FIG. 5). As a result, it was confirmed that the compound having a spinel structure was generated from the precursor compound contained in the electrode active material layer forming liquid by the electrode active material layer forming step. As an X-ray diffractometer, Smart Lab manufactured by Rigaku Corporation was used. Furthermore, the X-ray diffraction spectrum of the reference layer was assigned to the composition formula LiMn ₂ O ₄ by the integrated powder X-ray analysis software PDXL (manufactured by Rigaku Corporation). It was confirmed that LiMn ₂ O ₄ was generated from the precursor compound contained in the electrode active material layer forming liquid by the electrode active material layer forming step.

Film formation evaluation:
In preparing Example 1, the positive electrode plate obtained above was processed into a disk shape of a desired size. In the processing operation, the electrode active material layer was peeled off from the current collector, etc. It was possible to process without any defects. From this, it was confirmed that the film forming property of the electrode active material layer was good.

  Also in the examples and comparative examples shown below, as described above, when the positive electrode plate can be drawn into a disk shape without any problems, it is evaluated that the film forming property of the electrode active material layer is good. . On the other hand, part of the electrode active material layer is peeled off in the above-mentioned punching process, or the active material particles fall from the current collector, etc., and the processing is poor, and it is used as a working electrode of a tripolar coin cell described later In the case where a disk that can withstand the above is not formed, it is evaluated that the film forming property of the electrode active material layer is poor.

Film adhesion test:
Using the positive electrode plate of Example 1, a film adhesion test was performed. The adhesion test was performed by measuring the tensile strength according to JIS K6854-1 using a tensile tester (Tensilon). That is, a positive electrode plate for measuring adhesiveness (width 15 mm, length 200 mm) was prepared from the positive electrode plate obtained above in preparing Example 1, and an adhesive tape (Nichiban, Nystack, NW-25, A positive electrode plate for measuring adhesiveness was attached to a width 25 mm) with the electrode active material layer side facing the adhesive surface of the adhesive tape, and this was used as a test piece for measuring adhesiveness. A test piece for adhesion measurement was set on a tensile tester (Tensilon), a 90-degree peel test was performed under the conditions of a distance between chucks of 150 mm and a test speed of 100 mm / min, and a tensile strength (N / m) was measured. The results are shown in Table 2.

  The fact that the metal oxide deposited from the precursor compound is suitable as the second electrode active material can be confirmed by examining whether or not this metal oxide exhibits a lithium ion insertion / release reaction. . The presence or absence of the lithium ion insertion / elimination reaction was confirmed by the following cyclic voltammetry test.

Cyclic voltammetry test (CV test):
In the same manner as in the X-ray diffraction analysis test, a reference layer forming solution was prepared, and using the reference layer forming solution, a coating film was formed in the same manner as in Example 1, and a reference layer was formed on the current collector. The liquid is applied to form a coating film, and the current collector formed with the coating film is subjected to the same process as the electrode active material layer forming process to collect the reference layer formed from the reference layer forming liquid. A laminated body laminated on the electric body was prepared, and this was used as a reference specimen 1. Using this, it cut | judged in the disk shape of diameter 15mm similarly to Example 1, and prepared the test piece 1. FIG. In the reference layer of the laminate constituting the test piece 1, the same metal oxide as the lithium transition metal composite oxide in the electrode active material layer of the positive electrode plate of Example 1 is present. And the CV test was done using this test piece 1. In the CV test, the electrode potential was swept from 3.0 V to 4.3 V and then returned to 3.0 V as one cycle, and was repeated three cycles. At this time, the scanning speed was 1 mV / sec. In the cyclic voltammogram showing the results of the second cycle, an oxidation peak corresponding to the Li elimination reaction of LiMn ₂ O ₄ was observed near 3.9 V, and a reduction peak corresponding to the Li insertion reaction was confirmed near 4.1 V. . This confirmed that the metal oxide contained in the reference layer of the laminate of the test piece 1 exhibited a lithium ion insertion / release reaction. By the way, the metal oxide contained in the reference layer of the test piece 1 corresponds to the metal oxide contained in the electrode active material layer of Example 1. Therefore, the metal oxide contained in the electrode active material layer of Example 1 also has a lithium ion insertion / release reaction, and it was confirmed that the metal oxide is suitable as the second electrode active material. It was. The CV test was performed using VMP3 manufactured by Bio Logic.

  The crystallinity of the electrode active material layer was confirmed by observation with a transmission electron microscope (magnification 2 million times). It was confirmed that there was a difference between the crystallinity of the first electrode active material and the crystallinity of the second electrode active material. It can be seen that there are regions where the crystal lattices of both are continuous and discontinuous regions at the interface between the first electrode active material and the second electrode active material.

<Production of tripolar coin cell>
The non-aqueous electrolyte was prepared as follows. Lithium hexafluorophosphate (LiPF ₆ ) is added as a solute to a mixed solvent of ethylene carbonate (EC) / dimethyl carbonate (DMC) (volume ratio = 1: 1), and the concentration of LiPF _{6 as} the solute is 1 mol. The concentration was adjusted to / L to obtain a non-aqueous electrolyte.

  Using the positive electrode plate of Example 1 as a working electrode, a metal lithium plate (15 mm diameter disc) as a counter electrode plate, a metal lithium plate (3 mm square) as a reference electrode, and the non-aqueous electrolyte prepared above as an electrolyte solution A tripolar coin cell was assembled using a porous polyethylene sheet as a separator, and this was designated as Example Test Cell 1. The example test cell 1 was subjected to the following charge / discharge test.

(Charge / discharge test)
In the example test cell 1, in order to carry out the discharge test of the working electrode, the example test cell 1 was first fully charged according to the following charge tests (charge test and discharge test).

(Charge test)
The test cell 1 was charged at a constant current (66 μA) (discharge rate: 0.1 C) under a 25 ° C. environment until the voltage reached 4.2 V, and the voltage reached 4.2 V. After that, the current was reduced until the voltage became 5% or less so that the voltage did not exceed 4.2 V, the battery was charged at a constant voltage, fully charged, and then rested for 10 minutes. The “0.1 C” corresponding to the value of the constant current means a current value (current value reaching the discharge end voltage) at which the constant current discharge is performed using the tripolar coin cell and the discharge ends in 10 hours. ) Means.

(Discharge test)
Thereafter, the fully charged example test cell 1 was subjected to a constant current (66 μA) (discharge) in an environment of 25 ° C. until the voltage changed from 4.2 V (full charge voltage) to 3.0 V (discharge end voltage). A constant current discharge at a rate of 0.1 C), a cell voltage (V) on the vertical axis, a discharge time (h) on the horizontal axis, a discharge curve is created, and the discharge capacity (mAh at 0.1 C of the working electrode) ) This value is the discharge capacity after one cycle based on the result of the combination of the first charge test and discharge test, and is the initial discharge capacity (mAh). The results are shown in Table 2.

(Rate characteristics test)
The discharge rate characteristics of the working electrode were evaluated based on the discharge capacity retention rate (%) with 0.1 C as the reference discharge rate and the discharge capacity at 0.1 C as the reference. Specifically, in addition to 0.1C, a charge / discharge test was conducted for a discharge rate of 40C to determine a discharge capacity (mAh) at 40C.

(Calculation of discharge capacity maintenance rate (%) based on discharge capacity at 0.1 C)
The 0.1C reference discharge capacity retention ratio (%) as a ratio of the discharge capacity at 40C discharge with respect to the discharge capacity at 0.1C discharge was calculated by the equation shown in the following equation 2. The results are shown in Table 2.

  Example Test cell 1 was used to conduct initial charge / discharge efficiency and cycle characteristic tests.

Initial charge / discharge efficiency:
The initial charge / discharge efficiency of Example 1 was determined as follows. That is, in the charging test using the example test cell 1, the vertical axis represents the applied current (mA), the horizontal axis represents the charging time (h), a charging curve was prepared, and the area (current x time was calculated). The charge capacity (μAh) of the positive electrode plate is obtained from the obtained area), and the measured value of the discharge capacity (μAh) of the positive electrode plate is similarly obtained in the above discharge test, and (actual discharge capacity (μAh) of the positive electrode plate) / ( The initial charge / discharge efficiency (%) was calculated from the equation: Actual charge capacity (μAh) of positive electrode plate) × 100. The results are shown in Table 2.

Cycle characteristics test:
The cycle characteristic test was carried out by a charge / discharge test in the case where the discharge rate was 3C. The charge / discharge test was performed by repeating a combination of one charge test and discharge test as one cycle and repeating this for 500 cycles. The cycle characteristic evaluation was evaluated according to the following evaluation criteria based on the value of the 500 cycle capacity retention rate (%). The results are shown in Table 2 . The 500 cycle discharge capacity retention rate (%) is obtained by dividing the discharge capacity (mAh) based on the 500th charge / discharge test by the discharge capacity (mAh) based on the 1st charge / discharge test. It is a value calculated by multiplying 100 by 100.

(Evaluation criteria for cycle characteristics)
500 cycle capacity maintenance rate is 80% or more and 100% or less ... (very good)
500 cycle capacity maintenance rate is 50% or more and less than 80% ... (good)
500 cycle capacity maintenance rate is less than 50% ... x (defect)

(Example 2)
The electrode active material was the same as in Example 1 except that 10 g of the positive electrode active material LiNi _0.80 Co _0.15 Al _0.05 O ₂ : 10 g having an average particle diameter of 8 μm was used (Table 1). A layer forming solution was prepared. Further, a positive electrode plate was prepared in the same manner as in Example 1 except that the electrode active material layer forming liquid was applied to the current collector in such an amount that the coating amount after drying was 27 g / m ^2. 2 positive electrode plate. At this time, the film forming property of the electrode active material layer was good. Further, using the positive electrode plate of Example 2, a film adhesion test was conducted in the same manner as in Example 1, and the results are shown in Table 2. Furthermore, a tripolar coin cell was assembled using the positive electrode plate of Example 2, and this was designated as Example Test Cell 2. Example Test cell 2 is used to measure the initial discharge capacity (mAh) of the working electrode, rate characteristic test is performed, 0.1C reference discharge capacity maintenance rate (%) is calculated, and initial charge / discharge efficiency (%) is calculated. It was measured. The results are shown in Table 2.

(Example 3)
LiNO ₃ [molecular weight: 68.95]: 1.4 g and Mn (NO ₃ ) ₂ .6H ₂ O [molecular weight: 287.04]: 11.5 g as a compound serving as a precursor of the second electrode active material (Table 1), and the same as in Example 1 except that these were added to methanol: 10 g and mixed to prepare a second electrode active material precursor compound-containing liquid. An active material layer forming solution was prepared. Further, using this electrode active material layer forming liquid, a positive electrode plate was prepared in the same manner as in Example 1, and this was used as the positive electrode plate of Example 3. At this time, the film forming property of the electrode active material layer was good. Further, using the positive electrode plate of Example 3, a film adhesion test was performed in the same manner as in Example 1, and the results are shown in Table 2. Further, in the same manner as in Example 1, a three-pole coin cell was assembled using the positive electrode plate of Example 3, and this was designated as Example Test Cell 3, and further using Example Test Cell 3, the initial discharge capacity ( mAh) and rate characteristic test were performed to calculate a 0.1 C standard discharge capacity retention rate (%), and to measure initial charge / discharge efficiency (%). The results are shown in Table 2.

Example 4
A positive electrode plate for a non-aqueous electrolyte secondary battery was prepared in the same manner as in Example 1, and cut into a predetermined size (a disk having a diameter of 15 mm) to obtain a disk-shaped positive electrode plate. The positive electrode plate was made.

  Next, the positive electrode plate of Example 4 was immersed in a dipping tank filled with the resin mixture prepared as described below, and the resin mixture was sufficiently permeated into the voids of the electrode active material layer of the positive electrode plate of Example 4. I let you. That is, after leaving the positive electrode plate of Example 4 in the immersion tank for 10 minutes at 25 ° C., the positive electrode plate of Example 4 was taken out of the immersion layer and heated to 150 ° C. It was set in the inside and dried for 15 minutes to remove the solvent of the resin mixture. Thus, a positive electrode plate in which the resin binder remained in the electrode active material layer was prepared, and this was used as the resin-impregnated positive electrode plate of Example 4. The resin mixed solution uses PVDF resin (Kureha Corp., KF # 1100) as a resin binder as a resin material, and NMP (Solvent) as a solvent so that the concentration of PVDF becomes 0.1%. It was prepared by mixing with Mitsubishi Chemical Corporation.

  The appearance of the resin material in the voids in the electrode active material layer of the positive electrode plate is confirmed by observing the cross section of the electrode active material layer with a scanning electron microscope. In this positive electrode plate, at least a part of the voids in the electrode active material layer of the positive electrode plate is sufficiently impregnated with the resin mixed liquid so that the resin material is present in the voids. It is reinforced.

  A positive electrode plate (resin-impregnated positive electrode plate) sufficiently impregnated with a resin mixed solution in the voids in the electrode active material layer was subjected to a film strength test of the electrode active material layer, and evaluated based on the following evaluation of the film strength test It was done. The evaluation results were found to be very good.

Film strength test:
In the film strength test, using a shaft (diameter 20 mm) of a bending tester (manufactured by SEPRO), the resin-impregnated positive electrode plate is bent 180 degrees around the shaft, and cracks are observed in the electrode active material layer. This was carried out by visually observing this. Regarding the evaluation method of the film strength test based on the measurement results, if no cracks are observed in the electrode active material layer when the resin-impregnated positive electrode plate is bent, the strength of the electrode active material layer is evaluated as extremely good. When it is recognized that one or two pieces are contained, the strength of the electrode active material layer is evaluated as good. When it is recognized that three or more cracks are contained, the strength of the electrode active material layer is poor. It was evaluated.

  Using the resin-impregnated positive electrode plate, a film adhesion test was performed in the same manner as in Example 1, and the results are shown in Table 2. Further, in the same manner as in Example 1, a three-electrode coin cell was assembled using a resin-impregnated positive electrode plate, which was designated as Example Test Cell 4, and further the Example Test Cell 4 was used to obtain the initial discharge capacity (mAh) of the working electrode. And a rate characteristic test were performed to calculate a 0.1 C reference discharge capacity retention rate (%), and an initial charge / discharge efficiency (%) was measured. The results are shown in Table 2.

(Examples 5 and 6)
In Examples 5 and 6, positive electrode active material LiCoO ₂ : 10 g having an average particle diameter of 1 μm and positive electrode active material LiNiO ₂ : 10 g having an average particle diameter of 4 μm were used as the active material particles forming the first electrode active material ( Table 1) Except that, an electrode active material layer forming solution was prepared in the same manner as in Example 1. Furthermore, using the electrode active material layer forming liquid in the same manner as in Example 1 except that the electrode active material layer forming liquid was applied to the current collector in an amount such that the coating amount after drying was 25 g / m ^2. The positive plates of Examples 5 and 6 were prepared. At this time, the film forming property of the electrode active material layer was good. Further, using the positive electrode plates of Examples 5 and 6, a film adhesion test was performed in the same manner as in Example 1, and the results are shown in Table 2. Further, a tripolar coin cell was assembled using the positive electrode plates of Examples 5 and 6, and designated as Example Test Cells 5 and 6. Example Test cells 5 and 6 are used to measure the initial discharge capacity (mAh) of the working electrode and perform rate characteristic tests to calculate a 0.1 C reference discharge capacity retention rate (%). ) Was measured. The results are shown in Table 2.

(Example 7)
In Example 7, Li (CH ₃ COO) · 2H ₂ O [molecular weight: 102.02]: 2 g and Mn (CH ₂ ) as a precursor compound for producing a lithium composite oxide that forms the second electrode active material. ₃ COO) ₂ .4H ₂ O [molecular weight: 245.1]: 8.8 g and Co (CH ₃ COO) ₂ .4H ₂ O [molecular weight: 249.1]: 1 g were prepared (Table 1). A positive electrode plate of Example 7 was prepared in the same manner as in Example 1 except that this was added to 10 g of methanol as a solvent and mixed to prepare a second electrode active material precursor compound-containing liquid. At this time, the film forming property of the electrode active material layer was good. Further, using the positive electrode plate of Example 7, a film adhesion test was performed in the same manner as in Example 1, and the results are shown in Table 2. Furthermore, a tripolar coin cell was assembled using the positive electrode plate of Example 7, and this was designated as Example Test Cell 7. Example Test cell 7 is used to measure the initial discharge capacity (mAh) of the working electrode, rate characteristic test is performed, 0.1C standard discharge capacity maintenance rate (%) is calculated, and initial charge / discharge efficiency (%) is calculated. It was measured. The results are shown in Table 2.

Note that a metal oxide is formed and deposited on the current collector from the precursor compound of the second electrode active material. This metal oxide is a lithium composite oxide and has a crystal structure corresponding to the spinel structure. It was confirmed based on the spectrum obtained by using the X-ray diffraction analysis test as in Example 1. Further, the spectrum of the metal oxide was assigned to the composition formula LiCo _0.2 Mn _1.8 O ₂ by the integrated powder X-ray analysis software PDXL (manufactured by Rigaku Corporation). Further, it was confirmed that the metal oxide was suitable as the second electrode active material by performing a CV test in the same manner as in Example 1 and observing an oxidation peak and a reduction peak in the cyclic voltammogram. In addition, the metal formed from the precursor compound of the second electrode active material is bonded to the active material particles forming the first electrode active material, and is bonded to the first electrode active material and the current collector. To realize. This state is confirmed by observing the positive electrode plate of Example 7 with a scanning electron microscope (magnification of 30,000 times) in the same manner as in Example 1.

(Example 8)
In Example 8, Li (CH ₃ COO) .2H ₂ O [molecular weight: 102.02]: 2 g and Mn (CH _{3 COO) 2 · 4H 2 O} [ molecular weight: 245.1]: and _{9.3g, Al (NO 3) 3} · 9H 2 O [ molecular weight: 375.13]: prepare 0.8 g (Table 1), A positive electrode plate of Example 8 was prepared in the same manner as in Example 1 except that this was added to 10 g of methanol as a solvent and mixed to prepare a second electrode active material precursor compound-containing liquid. At this time, the film forming property of the electrode active material layer was good. Further, using the positive electrode plate of Example 8, a film adhesion test was conducted in the same manner as in Example 1. The results are shown in Table 2. Further, a tripolar coin cell was assembled using the positive electrode plate of Example 8, and this was designated as Example Test Cell 8. Example Measurement of discharge capacity (mAh) of working electrode and rate characteristic test using test cell 8 to calculate 0.1C standard discharge capacity maintenance rate (%), and measurement of initial charge / discharge efficiency (%) did. The results are shown in Table 2.

A metal oxide is formed and deposited on the current collector from the precursor compound of the second electrode active material. This metal oxide is a lithium transition metal composite oxide and corresponds to a spinel structure. Having a crystal structure was confirmed based on a spectrum obtained using an X-ray diffraction analysis test, as in Example 1. Further, the spectrum of the metal oxide was assigned to the composition formula LiAl _0.1 Mn _1.9 O ₂ by integrated powder X-ray analysis software PDXL (manufactured by Rigaku Corporation). Further, it was confirmed that the metal oxide was suitable as the second electrode active material by performing a CV test in the same manner as in Example 1 and observing an oxidation peak and a reduction peak in the cyclic voltammogram. In addition, the metal formed from the precursor compound of the second electrode active material is bonded to the active material particles forming the first electrode active material, and is bonded to the first electrode active material and the current collector. To realize. This state is confirmed by observing the positive electrode plate of Example 8 with a scanning electron microscope (magnification of 30,000 times) as in Example 1 (FIG. 6).

(Comparative Example 1)
An electrode active material layer forming liquid for forming an electrode active material layer was prepared as follows. First, LiNi _1/3 Co _1/3 Mn _1/3 O ₂ powder with an average particle diameter of 5 μm as active material particles: 10 g, acetylene black (Denka Black, Denki Kagaku Kogyo Co., Ltd.) as a conductive material: 1.2 g, and Using 1.0 g of polyvinylidene fluoride (PVDF) (manufactured by Kureha Co., KF # 1100) as a resin binder, adding 10 g of N-methylpyrrolidone (NMP) (manufactured by Mitsubishi Chemical Corporation) as an organic solvent, Excel The slurry was stirred for 15 minutes at a rotational speed of 7000 rpm with an autohomogenizer (Nippon Seiki Seisakusho Co., Ltd.) to prepare a slurry-like electrode active material layer forming solution.

The prepared electrode active material layer forming liquid was applied onto an aluminum plate having a thickness of 15 μm as a current collector so that the applied amount of the electrode active material layer forming liquid after drying was 32 g / m ^2. Was dried at 120 ° C. in an air atmosphere for 20 minutes to form an electrode active material layer.

  The current collector on which the electrode active material layer is formed is pressed using a roll press machine under the conditions of applied pressure: 0.1 ton / cm, speed 10 mm / second, and a predetermined size (a disk having a diameter of 15 mm). And vacuum-dried at 140 ° C. for 12 hours to obtain a positive electrode plate of Comparative Example 1. This positive electrode plate can be used as a positive electrode plate for a lithium ion secondary battery. At this time, the film forming property of the electrode active material layer was good. Further, using the positive electrode plate of Comparative Example 1, a film adhesion test was performed in the same manner as in Example 1. The results are shown in Table 2.

  Using the positive electrode plate of Comparative Example 1, a tripolar coin cell was assembled in the same manner as in Example 1, and this was designated as Comparative Example Test Cell 1. The initial discharge capacity (mAh) of the working electrode was measured and the rate characteristic test was conducted in the same manner as in Example 1 except that the comparative example test cell 1 was used instead of the example test cell 1. (%) Was calculated, a 500 cycle characteristic test was performed, and initial charge / discharge efficiency (%) was measured. The results are shown in Table 2.

(Comparative Examples 2 and 3)
In Comparative Examples 2 and 3, as active material particles, positive electrode active material LiNi _0.80 Co _0.15 Al _0.05 O ₂ : 10 g having an average particle diameter of 1 μm and positive electrode active material LiCoO _{2 having} an average particle diameter of 1 μm: 10 g, respectively. An electrode active material layer forming solution was prepared in the same manner as in Comparative Example 1 except that (Table 1) was used. Further, the positive electrode plates of Comparative Examples 2 and 3 were prepared in the same manner as in Comparative Example 1 except that the electrode active material layer forming liquid was applied to the current collector in an amount such that the coating amount after drying was 27 g / m ^2. Prepared. At this time, the film forming property of the electrode active material layer was good. Further, using the positive electrode plates of Comparative Examples 2 and 3, a film adhesion test was performed in the same manner as in Example 1. The results are shown in Table 2.

  Further, in the same manner as in Comparative Example 1, a tripolar coin cell was assembled using the positive plates of Comparative Examples 2 and 3, and this was designated as Comparative Example Test Cells 2 and 3. Comparative Example Similar to Comparative Example 1, except that test cells 2 and 3 were used, the initial discharge capacity (mAh) of the working electrode was measured, the rate characteristic test was performed, and the 0.1 C reference discharge capacity retention rate (%) was calculated. The initial charge / discharge efficiency (%) was also measured. The results are shown in Table 2.

(Comparative Example 4)
A positive electrode plate was prepared in the same manner as in Example 1 except that the heating step was performed in a nitrogen gas atmosphere as an inert gas atmosphere. This was used as the positive electrode plate of Comparative Example 4. At this time, the film forming property of the electrode active material layer was good. Further, using the positive electrode plate of Comparative Example 4, a film adhesion test was performed in the same manner as in Example 1. The results are shown in Table 2. Furthermore, a tripolar coin cell was assembled using the positive electrode plate of Comparative Example 4, and this was designated as Comparative Example Test Cell 4. The measurement of the discharge capacity (mAh) of the working electrode and the rate characteristic test were performed in the same manner as in Example 1 except that the comparative example test cell 4 was used, and a 0.1 C reference discharge capacity retention rate (%) was calculated. Initial charge / discharge efficiency (%) was measured. The results are shown in Table 2.

A metal oxide is generated and deposited on the current collector from the precursor compound of the second electrode active material. This metal oxide is a lithium transition metal composite oxide, but does not have a crystal structure corresponding to a spinel structure. This is confirmed by obtaining a spectrum using an X-ray diffraction analysis test, as in Example 1. Further, the spectrum of the metal oxide was assigned to the composition formula LiMnO ₂ by the integrated powder X-ray analysis software PDXL (manufactured by Rigaku Corporation).

  As shown in the results of the rate characteristics in Table 2, it was confirmed that the example maintained the high discharge capacity retention rate even if the discharge rate was higher than the comparative example, and was excellent in the rate characteristics. According to the positive electrode plate, it was confirmed that a battery capable of high-speed charge / discharge can be provided.

  In each of Examples 1 to 8, the first electrode active material is surrounded by the second electrode active material to form a double structure. This is because the first electrode active material has no nucleus, the second electrode active material is made of a metal oxide and forms a continuous enclosure without distinction, and the nucleus is surrounded by the enclosure. It is also shown that a state in which a double structure is formed is formed. Further, the first electrode active material which is a nucleus is surrounded by a plurality of enclosures, and adjacent enclosures are joined and connected to each other, thereby forming a double structure. Specifically, the state of such a double structure is also apparent from the scanning electron micrograph (FIG. 6) of the electrode active material layer in Example 8.

  When lithium insertion / extraction from the active material of the positive electrode plate is repeatedly performed, the active material deteriorates. The ease of progress of this deterioration appears in the cycle characteristics. That is, when the insertion and release of lithium are repeated, the decay of the active material crystal proceeds. It is presumed that the collapse of the crystal proceeds by cracking the active material along the crystal structure, and the progress of the crack is suppressed and the collapse of the active material is stopped at a portion where the crystal lattice is not continuous. On the other hand, when the crystal lattice is continuous, it is assumed that the collapse of the active material cannot be stopped and the collapse of the active material proceeds. Therefore, if there is a portion where the crystal structure is not continuous, it is assumed that the deterioration of the active material is delayed and the cycle characteristics are improved. Here, looking at the results of the cycle characteristic test for Example 1 and Comparative Example 1, it was confirmed that the cycle characteristic of Example 1 was improved over that of Comparative Example 1. That is, in Example 1, it was confirmed that the progress of deterioration of the active material could be delayed as compared with Comparative Example 1. This is different from Comparative Example 1 in Example 1, in which the presence of the first electrode active material and the second electrode active material was recognized, and the first electrode active material crystal and the second electrode active material were observed. This is presumed to be due to the fact that there are regions where the crystal lattices of both materials are continuous and discontinuous at the crystal interface of the material.

DESCRIPTION OF SYMBOLS 1, 1 ', 1'', 55 Current collector 2, 54 Electrode active material layer 3 Current collection base material 4 Conductive layer 5 Intermittent layer 6 Core body 7 Enclosure 8 Void 10 Positive electrode for nonaqueous electrolyte secondary battery Plate 20, 20 ′, 20 ″ Non-aqueous electrolyte secondary battery positive electrode plate 30 Battery pack 31 Lithium ion secondary battery 32 Positive electrode terminal 33 Negative electrode terminal 34 Protective circuit board 35 External connector 36 a, 36 b Resin container 37 End Case 38a, 38b External connection window 50 Nonaqueous electrolyte secondary battery negative electrode plate 70 Separator 81, 82 Exterior 90 Nonaqueous electrolyte 100 Nonaqueous electrolyte secondary battery

Claims (14)

A positive electrode plate for a non-aqueous electrolyte secondary battery comprising a current collector and an electrode active material layer formed on at least a part of the surface of the current collector,
The electrode active material layer contains a first electrode active material and a second electrode active material,
The second electrode active material adheres the first electrode active materials to each other and the first electrode active material and the current collector,
The second electrode active material comprises a lithium composite oxide having a metal selected from the group of metals other than lithium and lithium as a metal element and having a spinel structure. Positive electrode plate for electrolyte secondary battery.   2. The positive electrode plate for a non-aqueous electrolyte secondary battery according to claim 1, wherein the second electrode active material contains a lithium manganese composite oxide containing manganese and lithium as metal elements. The positive electrode plate for a non-aqueous electrolyte secondary battery according to claim 1, wherein the second electrode active material contains LiMn ₂ O ₄ . The second electrode active material contains a material in which a part of manganese constituting LiMn ₂ O ₄ is replaced with a metal selected from the group of metals excluding lithium and manganese. Item 4. A positive electrode plate for a nonaqueous electrolyte secondary battery according to Item 1.   5. The positive electrode plate for a non-aqueous electrolyte secondary battery according to claim 1, wherein the second electrode active material covers at least a part of the surface of the first electrode active material.   6. The non-aqueous electrolyte solution according to claim 1, wherein the electrode active material layer includes a portion where the crystal lattices are connected to each other in a part of the adjacent second electrode active materials. Secondary battery positive electrode plate. A positive electrode plate for a non-aqueous electrolyte secondary battery comprising a current collector and an electrode active material layer formed on at least a part of the surface of the current collector,
The electrode active material layer has a plurality of nuclei made of a first electrode active material and dispersed in the electrode active material layer, and an enclosure made of a second electrode active material and surrounding the nuclei,
The enclosure has the nuclei fixed between the nuclei and the current collector,
There are a plurality of the enclosures, and among these plurality of enclosures, at least a part of adjacent enclosures are connected to each other, or the enclosures are continuous without distinction,
Of the enclosure, an enclosure in the vicinity of the current collector is connected to the surface of the current collector,
The second electrode active material comprises a lithium composite oxide having a metal selected from the group of metals other than lithium and lithium as a metal element and having a spinel structure. Positive electrode plate for electrolyte secondary battery.   The positive electrode plate for a non-aqueous electrolyte secondary battery according to claim 7, wherein the second electrode active material contains a lithium manganese composite oxide containing manganese and lithium as metal elements. The positive electrode plate for a non-aqueous electrolyte secondary battery according to claim 7, wherein the second electrode active material contains LiMn ₂ O ₄ . The second electrode active material contains a material in which a part of manganese constituting LiMn ₂ O ₄ is replaced with a metal selected from the group of metals excluding lithium and manganese. Item 8. A positive electrode plate for a non-aqueous electrolyte secondary battery according to Item 7.   A crystal lattice of the first electrode active material constituting the nucleus body and a crystal lattice of the second electrode active material constituting the enclosure body at an interface between the nucleus body and the envelope body surrounding the nucleus body The positive electrode plate for a non-aqueous electrolyte secondary battery according to claim 7, wherein there are discontinuously joined regions. There are a plurality of the enclosures, and some of the adjacent enclosures are connected to each other,
In some of the enclosures that are connected to each other, the second electrode active material that constitutes one enclosure and the second electrode active material that constitutes the other enclosure are connected by making the crystal lattices continuous with each other. The positive electrode plate for nonaqueous electrolyte secondary batteries according to any one of claims 7 to 11, wherein the positive electrode plate includes any portion. A non-aqueous electrolyte secondary battery comprising at least a positive electrode plate, a negative electrode plate, a separator provided between the positive electrode plate and the negative electrode plate, and an electrolyte containing a non-aqueous solvent,
The said positive electrode plate is a positive electrode plate for nonaqueous electrolyte secondary batteries in any one of Claims 1-12, The nonaqueous electrolyte secondary battery characterized by the above-mentioned. A storage case; a non-aqueous electrolyte secondary battery including a positive electrode terminal and a negative electrode terminal; and a protection circuit having an overcharge and over-discharge protection function, wherein the storage case includes the non-aqueous electrolyte secondary battery and the In a battery pack configured to contain a protection circuit,
The non-aqueous electrolyte secondary battery includes at least a positive electrode plate, a negative electrode plate, a separator provided between the positive electrode plate and the negative electrode plate, and an electrolyte solution containing a non-aqueous solvent. A secondary battery,
The said positive electrode plate is a positive electrode plate for nonaqueous electrolyte secondary batteries in any one of Claim 1 to 12, The battery pack characterized by the above-mentioned.