JP6676289B2 - Positive electrode for non-aqueous electrolyte secondary battery - Google Patents

Description

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

  At present, electric devices such as non-aqueous electrolyte secondary batteries such as lithium ion secondary batteries used for mobile devices such as mobile phones have been commercialized. In general, an electric device such as a non-aqueous electrolyte secondary battery includes a positive electrode in which a positive electrode active material or the like is applied to a current collector and a negative electrode in which a negative electrode active material or the like is applied to a current collector. It is configured to be connected via an electrolyte layer holding a liquid or a non-aqueous electrolyte gel. Then, ions such as lithium ions are occluded and released in the electrode active material, and a charge / discharge reaction of the battery occurs.

  By the way, in recent years, it has been required to reduce the amount of carbon dioxide to cope with global warming. Therefore, electric devices such as non-aqueous electrolyte secondary batteries having a low environmental load are used not only in portable devices and the like but also in power supply devices for electric vehicles such as hybrid vehicles (HEV), electric vehicles (EV), and fuel cell vehicles. It is being used.

Above all, non-aqueous electrolyte secondary batteries intended for application to electric vehicles are required to have high output and high capacity. As a positive electrode active material used for a positive electrode of a nonaqueous electrolyte secondary battery for an electric vehicle, for example, a lithium cobalt-based composite oxide such as LiCoO ₂ , which is a composite oxide having a layered crystal structure, obtains a high voltage of 4V class. And has a high energy density, so that it has already been widely put to practical use. However, the raw material, cobalt, is scarce in terms of resources and is expensive, so there is concern about the supply of raw materials in view of the possibility that demand will continue to expand significantly in the future. Also, the price of cobalt raw materials may rise. Therefore, a composite oxide having a low cobalt content is desired.

Spinel-based lithium manganese composite oxides (eg, LiMn ₂ O ₄ ) are inexpensive and highly safe, and function as a 4V-class positive electrode material between compositions with λ-MnO ₂ . Since the spinel-based lithium manganese composite oxide has a three-dimensional host structure different from the layered crystal structure such as that of LiCoO ₂ or the like, most of the theoretical capacity can be used, and it is expected that the capacity retention rate is excellent. ing.

  However, in practice, it has been confirmed that a lithium ion secondary battery using a spinel-based lithium manganese composite oxide as a positive electrode material is inevitably subject to capacity deterioration in which the capacity gradually decreases due to repeated charging and discharging. I have. As described above, the spinel-based lithium manganese composite oxide has a large problem in practical use due to its low capacity retention rate.

  Therefore, as a technique for solving such a problem of a low capacity retention rate of the spinel-based lithium manganese composite oxide, a technique using a spinel-based lithium manganese composite oxide having a smaller specific surface area as a positive electrode active material has been proposed.

For example, Patent Document 1 discloses that a spinel-based lithium manganese composite oxide containing an excessive amount of lithium, containing fluorine or sulfur, and having a specific surface area of 0.5 m ² / g or less is used as a positive electrode active material. ing. In addition, the spinel-based lithium-manganese composite oxide must have a stable crystal structure in which fluorine or sulfur is doped in oxygen vacancies occupying the crystal structure, and have a small crystal size caused by containing excessive lithium. , And that the secondary particles have a smooth surface. Furthermore, by using such a spinel-based lithium manganese composite oxide as a positive electrode active material of a lithium ion secondary battery, elution of manganese from the spinel-based lithium manganese composite oxide is suppressed, and charging of the lithium ion secondary battery is performed. It is disclosed that the discharge cycle life characteristics (capacity maintenance rate) are improved.

JP-A-2002-373655

  However, examinations by the present inventors have revealed that a nonaqueous electrolyte secondary battery using the technique described in Patent Document 1 has insufficient capacity characteristics. Therefore, to improve the capacity characteristics, we attempted to mix positive electrode active materials containing lithium nickel-based composite oxide and spinel-based lithium manganese composite oxide.As a result, sufficient performance was obtained for the capacity retention rate of several hundred cycles. I found a new issue that may not exist.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a positive electrode for a non-aqueous electrolyte secondary battery that can improve the capacity retention of the non-aqueous electrolyte secondary battery.

  The present inventors have intensively studied. As a result, the specific surface area of the spinel lithium manganese composite oxide contained in the positive electrode active material is less than a certain value, and the mass ratio and specific surface area of the lithium nickel composite oxide and the spinel lithium manganese composite oxide It has been found that the above problem can be solved by the ratio having a predetermined relationship, and the present invention has been completed.

That is, according to one aspect of the present invention,
A positive electrode current collector, and a positive electrode active material layer formed on the surface of the positive electrode current collector and including a positive electrode active material including a lithium nickel composite oxide and a spinel lithium manganese composite oxide,
The specific surface area of the spinel-based lithium manganese composite oxide is more than 0 and less than 0.75 m ² / g;
The mixing ratio represented by the ratio of the mass of the spinel lithium manganese composite oxide to the mass of the lithium nickel composite oxide (the mass of the spinel lithium manganese composite oxide / the mass of the lithium nickel composite oxide) is represented by A And
It is represented by the ratio of the specific surface area of the spinel lithium manganese composite oxide to the specific surface area of the lithium nickel composite oxide (specific surface area of spinel lithium manganese composite oxide / specific surface area of lithium nickel composite oxide). When the specific surface area ratio is B,
A is greater than 0 and less than 3.00,
A positive electrode for a non-aqueous electrolyte secondary battery is provided, wherein A / B, which is the ratio of A to B (mixing ratio A / specific surface area ratio B), is greater than 0.40.

  ADVANTAGE OF THE INVENTION According to this invention, the positive electrode for non-aqueous electrolyte secondary batteries which can improve the capacity maintenance rate of a non-aqueous electrolyte secondary battery can be provided.

Basics of a flat (laminated) non-aqueous non-aqueous non-aqueous electrolyte lithium ion secondary battery which is one embodiment of a non-aqueous electrolyte secondary battery including the positive electrode for a non-aqueous electrolyte secondary battery according to one embodiment of the present invention FIG. 2 is a schematic sectional view showing a configuration. 1 is a perspective view showing the appearance of a flat lithium ion secondary battery which is a typical embodiment of a nonaqueous electrolyte secondary battery including a positive electrode for a nonaqueous electrolyte secondary battery according to one embodiment of the present invention.

According to one embodiment of the present invention, a positive electrode current collector and a positive electrode active material formed on a surface of the positive electrode current collector and including a positive electrode active material including a lithium nickel-based composite oxide and a spinel-based lithium manganese composite oxide A specific surface area of the spinel-based lithium manganese composite oxide is more than 0 and less than 0.75 m ² / g, and the spinel-based lithium manganese composite oxide is based on the mass of the lithium nickel-based composite oxide. The mixing ratio represented by the mass ratio (mass of spinel-based lithium-manganese composite oxide / mass of lithium-nickel-based composite oxide) is A, and the spinel-based lithium is based on the specific surface area of the lithium-nickel-based composite oxide. Ratio of the specific surface area of the manganese composite oxide (specific surface area of spinel-based lithium manganese composite oxide / lithium nickel-based composite acid When the specific surface area ratio represented by the specific surface area (B) is B, the A is more than 0 and less than 3.00, and is the ratio of the A to the B (mixing ratio A / specific surface area ratio B). Provided is a positive electrode for a non-aqueous electrolyte secondary battery, wherein A / B is greater than 0.40.

  The present inventors speculate as follows regarding the mechanism by which the positive electrode for a nonaqueous electrolyte secondary battery according to one embodiment of the present invention improves the capacity retention of a nonaqueous electrolyte secondary battery including the same. .

  As a positive electrode active material for a non-aqueous electrolyte secondary battery, a spinel-based lithium manganese composite oxide having a specific surface area of less than a certain value is used in order to suppress the elution of manganese. Then, as the positive electrode active material for the non-aqueous electrolyte secondary battery, a lithium nickel composite oxide is further used together with the spinel lithium manganese composite oxide. At this time, by making the value of the mixing ratio A less than a certain value, the content of the spinel-based lithium manganese composite oxide in the positive electrode active material becomes relatively small, and the deterioration of the battery capacity due to the elution of manganese is reduced. I do.

  Furthermore, in a non-aqueous electrolyte secondary battery using a positive electrode active material containing such a lithium nickel-based composite oxide and a spinel-based lithium manganese composite oxide, by suppressing the deterioration of the positive electrode active material due to overdischarge, The capacity retention rate can be improved.

  Overdischarge occurs due to a difference in acceptability of lithium ions during discharge between the lithium nickel composite oxide and the spinel lithium manganese composite oxide. In general, lithium nickel-based composite oxides are easier to release lithium ions at the time of charging and less likely to accept lithium ions at the time of discharging than spinel-based lithium manganese composite oxides. As a result, the spinel-based lithium manganese composite oxide accepts the lithium ions emitted by the lithium nickel-based composite oxide in addition to the lithium ions emitted by the spinel-based composite oxide during charging. The spinel-based lithium manganese composite oxide undergoes an irreversible reaction with lithium ions that have been excessively received, thereby lowering the capacity retention.

  Here, in the positive electrode for a non-aqueous electrolyte secondary battery according to one embodiment of the present invention, A / B, which is the ratio of the mixing ratio A to the specific surface area ratio B (mixing ratio A / specific surface area ratio B), is higher than a predetermined value. Is also big. Here, as the value of the mixing ratio A increases and / or the value of the specific surface area ratio B decreases, the value of A / B increases. Here, when the value of the mixing ratio A increases, the content of the spinel-based lithium manganese composite oxide relatively increases. Then, excessive lithium ions released from the positive electrode active material during charging are reduced, and the occurrence of overdischarge is suppressed. Further, when the value of the specific surface area ratio B becomes smaller, the specific surface area of the spinel-based lithium manganese composite oxide becomes relatively smaller. Then, the amount of lithium ions accepted by the spinel-based lithium manganese composite oxide decreases, and the occurrence of overdischarge is suppressed. Thus, by making A / B larger than a certain value, the relationship between the amount of lithium ions released during charging and the amount of lithium ions accepted by the spinel-based lithium manganese composite oxide during discharging becomes optimal. As a result, such a positive electrode active material can suppress occurrence of overdischarge and improve the capacity retention of the nonaqueous electrolyte secondary battery.

  The above mechanism is based on a guess, and its correctness does not affect the technical scope of the present embodiment.

  Hereinafter, as a preferred embodiment of a non-aqueous electrolyte secondary battery including a positive electrode for a non-aqueous electrolyte secondary battery according to one embodiment of the present invention, a non-aqueous electrolyte lithium ion secondary battery that is mainly a type of non-aqueous electrolyte secondary battery The battery will be described, but is not limited to only the following embodiment.

  In this specification, “X to Y” indicating a range means “X or more and Y or less”. In the description of the drawings, the same elements will be denoted by the same reference symbols, without redundant description. In addition, the dimensional ratios in the drawings are exaggerated for convenience of description, and may be different from the actual ratios.

  The configuration of the nonaqueous electrolyte secondary battery including the positive electrode for a nonaqueous electrolyte secondary battery according to one embodiment of the present invention includes, for example, a positive electrode including a positive electrode active material layer and a positive electrode current collector, a negative electrode active material layer, and a negative electrode. Examples include a negative electrode including a current collector and an electrolyte. Here, the electrolyte may be in a form included in the separator. However, the positive electrode for a nonaqueous electrolyte secondary battery according to one embodiment of the present invention is not limited to this configuration, and can be preferably applied to a nonaqueous electrolyte secondary battery having another known configuration.

  FIG. 1 is a schematic cross-sectional view schematically showing a basic configuration of a flat (laminated) non-aqueous electrolyte non-aqueous electrolyte lithium ion secondary battery (hereinafter, also simply referred to as a “laminated battery”). As shown in FIG. 1, the stacked battery 10 of the present embodiment has a structure in which a substantially rectangular power generation element 21 in which a charge / discharge reaction actually proceeds is sealed inside a battery exterior material 29 which is an exterior body. Have. Here, the power generation element 21 has a configuration in which a positive electrode, a separator 17, and a negative electrode are stacked. The separator 17 contains a non-aqueous electrolyte (for example, a liquid electrolyte). The positive electrode has a structure in which a positive electrode active material layer 15 is disposed on both surfaces of a positive electrode current collector 12. The negative electrode has a structure in which a negative electrode active material layer 13 is disposed on both surfaces of a negative electrode current collector 11. Specifically, the negative electrode, the electrolyte layer, and the positive electrode are stacked in this order such that one positive electrode active material layer 15 and the negative electrode active material layer 13 adjacent thereto are opposed via the separator 17. Thereby, the adjacent positive electrode, electrolyte layer, and negative electrode constitute one unit cell layer 19. Therefore, it can be said that the stacked battery 10 illustrated in FIG. 1 has a configuration in which a plurality of unit cell layers 19 are stacked to be electrically connected in parallel.

  In each of the outermost layer positive electrode current collectors located on both outermost layers of the power generation element 21, the negative electrode active material layer 13 is disposed only on one surface, but the active material layers may be provided on both surfaces. That is, a current collector having an active material layer on both surfaces may be used as it is as an outermost current collector, instead of a current collector dedicated to the outermost layer having an active material layer provided only on one surface. In addition, the arrangement of the positive electrode and the negative electrode is reversed from that in FIG. 1 so that the outermost layer positive electrode current collector is located on both outermost layers of the power generating element 21, and one or both surfaces of the outermost layer positive electrode current collector are provided. A positive electrode active material layer may be provided.

  The positive electrode current collector 12 and the negative electrode current collector 11 are respectively provided with a positive electrode current collector (tab) 27 and a negative electrode current collector (tab) 25 that are electrically connected to each electrode (positive electrode and negative electrode). And is led out of the battery exterior material 29 so as to be sandwiched between the ends of the battery. The positive electrode current collector 27 and the negative electrode current collector 25 are each ultrasonically welded to the positive electrode current collector 11 and the negative electrode current collector 12 of each electrode via a positive electrode lead and a negative electrode lead (not shown) as necessary. Or may be attached by resistance welding or the like.

  Note that FIG. 1 illustrates a stacked (stacked) battery that is not a bipolar battery, but includes a positive electrode active material layer electrically connected to one surface of a current collector and an opposite side of the current collector. And a negative electrode active material layer electrically coupled to the surface of the negative electrode. In this case, one current collector also serves as a positive electrode current collector and a negative electrode current collector.

  Hereinafter, each member will be described in more detail.

[Positive electrode for non-aqueous electrolyte secondary battery]
The positive electrode for a non-aqueous electrolyte secondary battery has a positive electrode current collector and a positive electrode active material layer formed on the surface of the positive electrode current collector.

(Positive electrode current collector)
The material constituting the positive electrode current collector is not particularly limited, but preferably a metal is used. Specifically, examples of the metal include aluminum, nickel, iron, stainless steel, titanium, copper, and other alloys. In addition, a clad material of nickel and aluminum, a clad material of copper and aluminum, or a plated material of a combination of these metals can be preferably used. Further, a foil having a metal surface coated with aluminum may be used. Among them, aluminum, stainless steel, and copper are preferable from the viewpoint of electron conductivity and battery operating potential.

  The size of the current collector is determined according to the intended use of the battery. For example, if it is used for a large battery requiring a high energy density, a current collector having a large area is used. There is no particular limitation on the thickness of the current collector. The thickness of the current collector is usually about 1 to 100 μm.

  Further, when a negative electrode current collector is used in a negative electrode described later, the same one as described above can be used.

(Positive electrode active material layer)
The positive electrode active material layer contains a positive electrode active material. In this embodiment, the positive electrode active material essentially includes a lithium nickel composite oxide and a spinel lithium manganese composite oxide.

  Here, the positive electrode active material is represented by a ratio of the mass of the spinel lithium manganese composite oxide to the mass of the lithium nickel composite oxide (the mass of the spinel lithium manganese composite oxide / the mass of the lithium nickel composite oxide). The mixing ratio A is more than 0 and less than 3.00.

  When the mixing ratio A is 0, the positive electrode active material consists only of a lithium nickel-based composite oxide. The non-aqueous electrolyte lithium ion secondary battery using such a positive electrode active material has a problem that output characteristics on a low SOC (State Of Charge) side are low. When the mixing ratio A is 3.00 or more, the positive electrode active material contains a relatively large amount of the spinel-based lithium manganese composite oxide. A non-aqueous electrolyte lithium ion secondary battery using such a positive electrode active material cannot obtain a sufficient capacity retention rate because the degree of deterioration of the positive electrode active material due to elution of manganese increases.

  Furthermore, when the mixture ratio A is less than 3.00, the value of the mixture ratio A is increased, so that the capacity retention ratio is further improved. When the value of the mixing ratio A increases, the content of the lithium-nickel-based composite oxide in the positive electrode active material, in which the amount of lithium ions released upon charging per unit mass is larger than that of the spinel-based lithium-manganese composite oxide, is relatively high. Decrease. From this, it is considered that the further improvement of the capacity retention ratio is caused by the fact that excessive lithium ions released from the positive electrode active material during charging are reduced, thereby further suppressing the occurrence of overdischarge. From the viewpoint of such a capacity retention ratio, the mixing ratio A is preferably 0.25 or more and less than 3.00.

  Therefore, another preferred embodiment of the present invention is a positive electrode for a nonaqueous electrolyte secondary battery, wherein the mixing ratio A is more than 0.25 and less than 3.00.

  From the same viewpoint, the mixing ratio A is more preferably 0.25 or more and 2.00 or less, and further preferably 0.25 or more and 1.50 or less.

  In the positive electrode active material, the ratio of the specific surface area of the spinel lithium manganese composite oxide to the specific surface area of the lithium nickel composite oxide (the specific surface area of the spinel lithium manganese composite oxide / the specific surface area of the lithium nickel composite oxide) ) Is the specific surface area ratio B.

  Here, in the positive electrode active material, A / B, which is the ratio of the mixing ratio A to the specific surface area ratio B (mixing ratio A / specific surface area ratio B), is more than 0.40.

  When A / B is 0.40 or less, the non-aqueous electrolyte lithium ion secondary battery cannot obtain a sufficient capacity retention rate. Here, the decrease in A / B is caused by a decrease in the value of the mixture ratio A, an increase in the value of the specific surface area ratio B, or both.

  Here, the decrease in the value of the mixing ratio A means that the mass of the spinel-based lithium manganese composite oxide contained in the positive electrode active material relatively decreases and the mass of the lithium nickel-based composite oxide relatively increases. To do so. In such a case, as described above, the lithium nickel-based composite oxide emits a larger amount of lithium ions per unit mass than the spinel-based lithium-manganese composite oxide at the time of charging. It is thought that the release amount of excess lithium ions increases from. Then, it is considered that due to an excessive increase in lithium ions, overdischarge during charging becomes remarkable, and a sufficient capacity retention rate cannot be obtained.

  Here, an increase in the value of the specific surface area ratio B means that the specific surface area of the spinel-based lithium manganese composite oxide contained in the positive electrode active material is relatively increased, and the specific surface area of the lithium nickel-based composite oxide is relatively large. It means that it decreases. Here, as described above, the lithium nickel-based composite oxide is less likely to accept lithium ions during discharge than the spinel-based lithium manganese composite oxide. Accordingly, in such a case, it is considered that the amount of lithium ions accepted by the spinel-based lithium manganese composite oxide during discharge increases. Then, it is considered that when the amount of lithium ions accepted by the spinel-based lithium manganese composite oxide becomes excessive, occurrence of overdischarge becomes remarkable, and a sufficient capacity retention rate cannot be obtained.

  Therefore, from the balance between the amount of lithium ions released from the positive electrode active material during charging and the amount of lithium ions accepted by the spinel-based lithium manganese composite oxide during discharging, if A / B is 0.4 or less, the non-aqueous electrolyte It is considered that the lithium ion secondary battery cannot achieve a sufficient capacity retention rate.

  From the same viewpoint, A / B is more preferably more than 0.40 and not more than 6.00, and more preferably more than 0.40 and not more than 2.50.

  Here, in the positive electrode active material, the ratio of the specific surface area of the spinel lithium manganese composite oxide to the specific surface area of the lithium nickel composite oxide (the specific surface area of the spinel lithium manganese composite oxide / the ratio of the lithium nickel composite oxide) The specific surface area ratio B represented by (surface area) is preferably 0.33 or more and 1.50 or less.

  When the specific surface area ratio B is 0.33 or more, the specific surface area of the spinel-based lithium manganese composite oxide contained in the positive electrode active material relatively increases, and the specific surface area of the lithium nickel-based composite oxide relatively increases. Decrease. As a result, the amount of excessive lithium ions released from the positive electrode active material during charging is reduced, so that the lithium nickel composite oxide sufficiently secures the acceptability of lithium, thereby further improving the capacity retention rate. .

  When the specific surface area ratio B is 1.50 or less, the specific surface area of the spinel-based lithium manganese composite oxide contained in the positive electrode active material is relatively reduced, and the specific surface area of the lithium nickel-based composite oxide is relatively small. Increase. As a result, the contribution of the spinel-based lithium manganese composite oxide to the battery capacity is reduced, and the decrease in the capacity retention rate due to elution is reduced.

  From the same viewpoint, it is more preferably 0.33 or more and 1.00 or less, and further preferably 0.60 or more and 1.00 or less.

  The ratio of the total amount of the lithium nickel composite oxide and the spinel lithium manganese composite oxide to 100% by mass of the total amount of the cathode active material contained in the cathode active material layer is preferably 50% by mass or more. It is preferably at least 70% by mass, more preferably at least 85% by mass, even more preferably at least 90% by mass, particularly preferably at least 95% by mass, most preferably at least 100% by mass.

  The thickness of the positive electrode active material layer is not particularly limited, and conventionally known knowledge about the battery can be appropriately referred to. For example, the thickness of each active material layer (the thickness of the active material layer on one side of the current collector) is about 2 to 100 μm, and preferably 5 to 100 μm.

-Lithium nickel composite oxide The composition of the lithium nickel composite oxide is not specifically limited as long as it is a composite oxide containing lithium and nickel. A typical example of a composite oxide containing lithium and nickel is a lithium nickel composite oxide (LiNiO ₂ ). However, a composite oxide in which some of the nickel atoms of the lithium-nickel composite oxide are substituted with other metal atoms is more preferable, and a preferable example is a lithium transition metal composite oxide having a layered crystal structure containing nickel, manganese, and cobalt. (Hereinafter, also simply referred to as “NMC composite oxide”) has a layered crystal structure in which lithium atomic layers and transition metal (Mn, Ni and Co are arranged in order) atomic layers are alternately stacked via oxygen atomic layers. And one Li atom is contained per one atom of the transition metal M, and the amount of Li that can be taken out is twice that of the spinel-based lithium manganese composite oxide, that is, the supply capacity is doubled, so that a high capacity can be obtained. it can. In addition, since it has higher thermal stability than LiNiO ₂ , it is particularly advantageous among nickel-based composite oxides used as a positive electrode active material.

  In this specification, the NMC composite oxide also includes a composite oxide in which part of a transition metal element is replaced by another element. In this case, other elements are not particularly limited, but Ti, Zr, Nb, W, P, Al, Mg, V, Ca, Sr, Cr, Fe, B, Ga, In, Si, Mo, Y, Examples include Sn, V, Cu, Ag, and Zn.

NMC composite oxide, since the theoretical discharge capacity is high, preferably the general formula _{(1): Li a Ni b} Mn c Co d M x O 2 ( In the formula, a, b, c, d, x Satisfies 0.9 ≦ a ≦ 1.2, 0 <b <1, 0 <c ≦ 0.5, 0 <d ≦ 0.5, 0 ≦ x ≦ 0.3, and b + c + d = 1. At least one element selected from Ti, Zr, Nb, W, P, Al, Mg, V, Ca, Sr, Cr and Fe). Here, a represents the atomic ratio of Li, b represents the atomic ratio of Ni, c represents the atomic ratio of Mn, d represents the atomic ratio of Co, and x represents the atomic ratio of M. Represents Here, in the general formula (1), it is more preferable that 0.3 ≦ b ≦ 0.9. When b is 0.3 or more, the capacity can be further increased. It is presumed that such an increase in capacity is caused by an increase in the number of lithium contributing to the reaction per unit mass. Further, when b is 0.9 or less, the safety can be further improved, and the effect of further improving the capacity retention rate can be obtained. It is presumed that such an improvement in the capacity retention ratio is caused by a decrease in the number of lithium per unit mass, which results in a decrease in the number of lithium entering and exiting the positive electrode active material layer.

Than this, a preferred form of the present invention, a lithium nickel-based composite oxide represented by the general formula _{(1): Li a Ni b} Mn c Co d M x O 2 ( In the formula, a, b, c, d , X are 0.9 ≦ a ≦ 1.2, 0.3 ≦ b ≦ 0.9, 0 <c ≦ 0.5, 0 <d ≦ 0.5, 0 ≦ x ≦ 0.3, b + c + d = And M is a non-aqueous composition having a composition represented by the following formula: M is at least one element selected from Ti, Zr, Nb, W, P, Al, Mg, V, Ca, Sr, Cr, and Fe. It is a positive electrode for an electrolyte secondary battery.

  In addition, from the above viewpoint, 0.3 ≦ b ≦ 0.8 or less is more preferable, and 0.4 ≦ b ≦ 0.6 is more preferable.

  Here, in the above formula (1), it is preferable that 0 <d ≦ 0.2.

  The composition of each element can be measured by, for example, inductively coupled plasma (ICP) emission spectrometry.

  Generally, it is known that nickel (Ni), cobalt (Co) and manganese (Mn) contribute to capacity and output characteristics from the viewpoint of improving the purity of a material and improving electronic conductivity. Ti, which is another element of the NMC composite oxide (M element in the general formula (1)), partially replaces the transition metal in the crystal lattice. From the viewpoint of cycle characteristics, a part of the transition element may be replaced by another element, and it is more preferable that 0 ≦ x ≦ 0.2 in the general formula (1). Since at least one selected from the group consisting of Ti, Zr, Nb, W, P, Al, Mg, V, Ca, Sr, Cr and Fe forms a solid solution, the crystal structure is stabilized. It is considered that the capacity of the battery can be prevented from lowering even when charge and discharge are repeated, and an excellent capacity retention ratio can be realized. The other element is at least one element selected from Al, Cr and Fe.

The NMC composite oxide is not particularly limited, but for example, LiNi _0.30 Mn _0.35 Co _0.35 O ₂ , LiNi _1/3 Mn _1/3 Co _1/3 O ₂ , LiNi _0.50 Mn _{0 .30 Co 0.20 O 2, LiNi 0.6} Mn 0.2 Co 0.2 O 2, LiNi 0.8 Mn 0.1 Co 0.1 O 2, LiNi 0.90 Mn 0.05 Co 0. ₀₅ O _{2 and the} like.

  The lithium nickel-based composite oxide also has a configuration of secondary particles formed by aggregating primary particles. And the average particle diameter (average primary particle diameter) of the primary particles is preferably 0.9 μm or less, more preferably 0.2 to 0.6 μm, and still more preferably 0.25 to 0.5 μm. . The average particle size of the secondary particles (average secondary particle size) is preferably 2 to 20 μm, more preferably 5 to 20 μm, and further preferably 5 to 15 μm. Further, the value of these ratios (average secondary particle diameter / average primary particle diameter) is preferably larger than 11, more preferably 15 to 50, and even more preferably 25 to 40. The primary particles constituting the lithium nickel-based composite oxide usually have a hexagonal crystal structure having a layered structure, and the size of the crystallite has a correlation with the size of the average primary particle size. Have. Here, the “crystallite” means the largest collection that can be regarded as a single crystal, and can be measured by a method of refining the crystal structure parameters from the diffraction intensity obtained by powder X-ray diffraction measurement or the like. The specific value of the crystallite diameter is not particularly limited, but is preferably 1 μm or less, more preferably 0.55 μm or less, and further preferably 0.4 μm or less. With such a configuration, it is possible to further reduce the amount of displacement during expansion and contraction of the active material, to suppress the occurrence of finer (cracked) secondary particles due to repeated charge and discharge, and to reduce the cycle. It can contribute to further improvement of characteristics. The lower limit of the crystallite diameter is not particularly limited, but is usually 0.02 μm or more. Here, in the present specification, the value of the crystallite diameter in the positive electrode active material particles is measured by the Rietveld method in which the crystallite diameter is calculated from the diffraction peak intensity obtained by powder X-ray diffraction measurement.

The tap density of the lithium-nickel-based composite oxide is preferably 2.3 g / cm ^3, more preferably 2.4~2.9g / cm ^3. With such a configuration, high density of the primary particles constituting the secondary particles of the positive electrode active material is sufficiently ensured, and the effect of improving the cycle characteristics can be maintained.

Further, the specific surface area (BET specific surface area) of the lithium nickel-based composite oxide is preferably more than 0 and 1.00 m ² / g or less, more preferably 0.10 or more and 1.00 m ² / g or less. preferably not more than 0.30 or more 1.00 m ² / g, particularly preferably not more than 0.30 or more 0.90 m ² / g. When the specific surface area is in such a range, a reaction area is secured and the internal resistance of the battery is reduced, so that the occurrence of polarization during electrode reaction can be minimized.

  The BET specific surface area can be measured by a BET specific surface area measuring device (model: SA-9601) manufactured by Horiba, Ltd. (BET one-point method).

  Although the specific surface area of the lithium nickel composite oxide is not particularly limited, it can be controlled, for example, by adjusting the particle diameter of primary particles and / or secondary particles. Specifically, as a method of increasing the specific surface area, a method of reducing the particle diameter may be mentioned. In addition, as a method of reducing the specific surface area, a method of increasing the particle diameter can be mentioned. In addition, as a method for controlling the specific surface area, known means can be used, and the specific surface area can be controlled by a raw material, a composition, firing conditions, crushing conditions, sieving conditions, and the like.

Further, for the lithium nickel-based composite oxide, the diffraction peak of the (104) plane and the diffraction peak of the (003) plane obtained by powder X-ray diffraction measurement are defined as a diffraction peak intensity ratio ((003) / (104)). It is preferably 1.28 or more, more preferably 1.35 to 2.1. Further, the diffraction peak integrated intensity ratio ((003) / (104)) is preferably 1.08 or more, and more preferably 1.10 to 1.45. These rules are preferred for the following reasons. That is, the lithium nickel-based composite oxide has a layered rock salt structure in which a Li ⁺ layer and a Ni ³⁺ layer exist between oxygen layers. However, ^{Ni 3+} is easily reduced to ^{Ni 2+,} and because substantially equal to the ^{Ni 2+} ion radius (0.83Å) is Li ⁺ ion radius (0.90 Å), Ni to Li ⁺ defect occurring during active material synthesized ²⁺ is easily mixed. When Ni ²⁺ is mixed into the Li ⁺ site, a locally electrochemically inactive structure is formed, and diffusion of Li ⁺ is prevented. Therefore, when an active material having low crystallinity is used, there is a possibility that the charge / discharge capacity of the battery is reduced and the durability is reduced. The above definition is used as an index of the degree of crystallinity. Here, as a method of quantifying the crystallinity, as described above, the ratio of the intensity of the diffraction peak of the (003) plane to the intensity of the diffraction peak of the (104) plane and the ratio of the integrated intensity of the diffraction peak by the crystal structure analysis using X-ray diffraction are described above. Was used. When these parameters satisfy the above rules, the number of defects in the crystal is reduced, and a decrease in battery charge / discharge capacity and a decrease in durability can be suppressed. Note that such a crystallinity parameter can be controlled by a raw material, a composition, a firing condition, and the like.

  A lithium nickel-based composite oxide such as an NMC composite oxide can be prepared by selecting various known methods such as a coprecipitation method and a spray drying method. It is preferable to use the coprecipitation method because the preparation of the composite oxide according to this embodiment is easy. Specifically, as a method for synthesizing an NMC composite oxide, for example, a nickel-cobalt-manganese composite oxide is produced by a coprecipitation method as in the method described in JP-A-2011-105588. -It can be obtained by mixing and sintering a manganese composite oxide and a lithium compound. Hereinafter, a specific description will be given.

  Raw compounds of the composite oxide, for example, a Ni compound, a Mn compound, and a Co compound are dissolved in a suitable solvent such as water so as to have a desired composition of the active material. Examples of the Ni compound, Mn compound and Co compound include sulfates, nitrates, carbonates, acetates, oxalates, oxides, hydroxides, and halides of the metal element. Specific examples of the Ni compound, Mn compound, and Co compound include, but are not limited to, nickel sulfate, cobalt sulfate, manganese sulfate, nickel acetate, cobalt acetate, and manganese acetate. In this process, if necessary, a compound containing a metal element that replaces a part of the layered lithium metal composite oxide constituting the active material may be further mixed so that the composition of the active material is further increased. Good. For example, a compound containing at least one metal element such as Ti, Zr, Nb, W, P, Al, Mg, V, Ca, Sr, Cr, and Fe may be further mixed.

  A coprecipitation reaction can be performed by neutralization and precipitation using the above-mentioned raw material compound and an alkali solution. Thereby, a metal composite hydroxide and a metal composite carbonate containing the metal contained in the raw material compound are obtained. As the alkaline solution, for example, an aqueous solution of sodium hydroxide, potassium hydroxide, sodium carbonate, ammonia or the like can be used, but it is preferable to use sodium hydroxide, sodium carbonate or a mixed solution thereof for the neutralization reaction. . In addition, it is preferable to use an aqueous ammonia solution or an ammonium salt for the complex reaction.

  The addition amount of the alkali solution used for the neutralization reaction may be an equivalent ratio of 1.0 to the neutralized portion of all the metal salts contained therein, but it is preferable to add the alkali excess portion for pH adjustment.

  The amount of the aqueous ammonia solution or ammonium salt used for the complex reaction is preferably added so that the ammonia concentration in the reaction solution is in the range of 0.01 to 2.00 mol / L. It is preferable to control the pH of the reaction solution in the range of 10.0 to 13.0. The reaction temperature is preferably 30 ° C. or higher, more preferably 30 to 60 ° C.

  After that, the composite hydroxide obtained by the coprecipitation reaction is preferably subjected to suction filtration, washed with water, and dried. Next, the NMC composite oxide can be obtained by mixing the nickel-cobalt-manganese composite hydroxide with a lithium compound and firing the mixture. Examples of the Li compound include lithium hydroxide or a hydrate thereof, lithium peroxide, lithium nitrate, and lithium carbonate.

  The firing treatment may be performed in one stage, but is preferably performed in two stages (temporary firing and main firing). By the two-stage firing, the composite oxide can be obtained efficiently. The calcination conditions are not particularly limited and vary depending on the lithium raw material, so that it is difficult to uniquely define them. In addition, it is preferable that the heating rate is 1 to 20 ° C./min from room temperature. The atmosphere is preferably in the air or under an oxygen atmosphere. Here, in the case of synthesizing the NMC composite oxide using lithium carbonate as the Li raw material, the calcination temperature is preferably 500 to 900 ° C, more preferably 600 to 800 ° C, and further preferably 650. ７750 ° C. Furthermore, the calcination time is preferably 0.5 to 10 hours, more preferably 4 to 6 hours. On the other hand, the conditions for the main firing are not particularly limited, but the rate of temperature rise is preferably from room temperature to 1 to 20 ° C./min. The atmosphere is preferably in the air or under an oxygen atmosphere. In the case of synthesizing an NMC composite oxide using lithium carbonate as the Li raw material, the firing temperature is preferably 800 to 1200 ° C, more preferably 850 to 1100 ° C, and further preferably 900 to 1050 ° C. ° C. Further, the calcination time is preferably 1 to 20 hours, more preferably 8 to 12 hours.

  If necessary, when adding a trace amount of a metal element that replaces a part of the layered lithium metal composite oxide constituting the active material, as the method, nickel, cobalt, a method of previously mixing with manganate, Any method such as a method of adding simultaneously with nickel, cobalt, and manganate, a method of adding to the reaction solution during the reaction, and a method of adding to the nickel-cobalt-manganese composite oxide together with the Li compound may be used.

  The lithium nickel-based composite oxide can be produced by appropriately adjusting the reaction conditions such as the pH of the reaction solution, the reaction temperature, the reaction concentration, the addition speed, and the stirring time.

Spinel-based lithium-manganese composite oxide The spinel-based lithium-manganese composite oxide is typically a composite oxide having a composition of LiMn ₂ O ₄ and having a spinel structure and essentially containing lithium and manganese, For the specific configuration and manufacturing method, conventionally known knowledge such as JP-A-2000-77071 can be appropriately referred to.

  Further, the spinel-based lithium manganese composite oxide also includes a composite oxide in which a part of manganese is replaced by another metal element. Other elements in this case include, for example, Li, Mg, Al, Ti, V, Cr, and Fe.

  The spinel-based lithium manganese composite oxide also has a configuration of secondary particles formed by aggregating primary particles. And the average particle diameter of secondary particles (average secondary particle diameter) is preferably 2 to 50 μm, more preferably 5 to 50 μm, and still more preferably 7 to 20 μm.

Further, the specific surface area (BET specific surface area) of the spinel-based lithium manganese composite oxide is more than 0 and less than 0.75 m ² / g. If the specific surface area is 0.75 m ² / g or more, the degree of deterioration of the positive electrode active material due to elution of manganese increases, and a sufficient capacity retention rate cannot be obtained. From the same viewpoint and from the viewpoint of suppressing an increase in reaction resistance of the active material, the specific surface area of the spinel-based lithium manganese composite oxide is preferably 0.10 or more and less than 0.75 m ² / g, More preferably, it is 0.10 or more and 0.70 m ² / g or less, and still more preferably 0.30 or more and 0.60 m ² / g or less.

  The BET specific surface area can be measured by a BET specific surface area measuring device (model: SA-9601) manufactured by Horiba, Ltd. (BET one-point method).

  The method for controlling the specific surface area of the spinel-based lithium manganese composite oxide is not particularly limited, but can be controlled, for example, by adjusting the particle diameter of primary particles and / or secondary particles. Specifically, as a method of increasing the specific surface area, a method of reducing the particle diameter may be mentioned. In addition, as a method of reducing the specific surface area, a method of increasing the particle diameter can be mentioned. In addition, as a method for controlling the specific surface area, known means can be used, and the specific surface area can be controlled by a raw material, a composition, firing conditions, crushing conditions, sieving conditions, and the like.

-Other components In addition to the above-described positive electrode active material, the positive electrode active material layer, if necessary, a positive electrode active material other than the above, a conductive auxiliary agent, a binder, an electrolyte (a polymer matrix, an ion conductive polymer, an electrolytic solution, etc.), Other additives such as a lithium salt for enhancing ionic conductivity may be further included.

  The conductive assistant refers to an additive compounded to improve the conductivity of the positive electrode active material layer. Examples of the conductive assistant include carbon materials such as carbon black such as Ketjen black and acetylene black, and carbon fibers. When the active material layer contains a conductive additive, an electron network inside the active material layer is effectively formed, which can contribute to improvement in output characteristics of the battery.

Examples of the electrolyte salt (lithium salt) include Li (C ₂ F ₅ SO ₂ ) ₂ N, LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , and LiCF ₃ SO ₃ .

  Examples of the ion conductive polymer include polyethylene oxide (PEO) -based and polypropylene oxide (PPO) -based polymers.

  The content of the material that can function as an active material in the positive electrode active material layer is not particularly limited, and can be adjusted by appropriately referring to known knowledge about a lithium ion secondary battery, and is from 85 to 99.5 mass. %.

  The binder used for the positive electrode active material layer is not particularly limited, and examples thereof include the following materials. Polyethylene, polypropylene, polyethylene terephthalate (PET), polyether nitrile, polyacrylonitrile, polyimide, polyamide, cellulose, carboxymethyl cellulose (CMC) and its salts, ethylene-vinyl acetate copolymer, polyvinyl chloride, styrene-butadiene rubber (SBR) ), Isoprene rubber, butadiene rubber, ethylene / propylene rubber, ethylene / propylene / diene copolymer, styrene / butadiene / styrene block copolymer and its hydrogenated product, styrene / isoprene / styrene block copolymer and its hydrogenated Polymer, polyvinylidene fluoride (PVdF), polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (F P), tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (PFA), ethylene / tetrafluoroethylene copolymer (ETFE), polychlorotrifluoroethylene (PCTFE), ethylene / chlorotrifluoroethylene copolymer (ECTFE) ), Fluororesins such as polyvinyl fluoride (PVF), vinylidene fluoride-hexafluoropropylene fluororubber (VDF-HFP fluororubber), vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene fluororubber (VDF-HFP) -TFE fluororubber), vinylidene fluoride-pentafluoropropylene fluororubber (VDF-PFP fluororubber), vinylidene fluoride-pentafluoropropylene-tetrafluoroethylene Fluorine rubber (VDF-PFP-TFE fluorine rubber), vinylidene fluoride-perfluoromethylvinyl ether-tetrafluoroethylene fluorine rubber (VDF-PFMVE-TFE fluorine rubber), vinylidene fluoride-chlorotrifluoroethylene fluorine Vinylidene fluoride fluororubbers such as rubber (VDF-CTFE fluororubber), epoxy resins, and the like. These binders may be used alone or in combination of two or more.

  The positive electrode for a nonaqueous electrolyte secondary battery can be manufactured by forming a positive electrode active material layer on a positive electrode current collector. The method for forming the positive electrode active material layer is not particularly limited. For example, a positive electrode active material slurry containing at least a positive electrode active material and a slurry viscosity adjusting solvent is applied on a positive electrode current collector, dried, and then compressed by a roll press or the like. Molding method is mentioned. The slurry viscosity adjusting solvent is not particularly limited, but for example, N-methyl-2-pyrrolidone (NMP) or the like can be used.

[Negative electrode active material layer]
The negative electrode active material layer contains an active material, and if necessary, a conductive additive, a binder, an electrolyte (a polymer matrix, an ion conductive polymer, an electrolytic solution, etc.), and other additions such as a lithium salt for enhancing ion conductivity. And an agent.

  The thickness of the negative electrode active material layer is not particularly limited, and conventionally known knowledge about the battery can be appropriately referred to. To give an example, the thickness of each active material layer (the thickness of the active material layer on one side of the current collector) is about 2 to 100 μm.

  The content of the material that can function as an active material in the negative electrode active material layer is the same as the content of the material that can function as an active material in the positive electrode active material.

  Other additives such as a conductive auxiliary agent, a binder, an electrolyte (a polymer matrix, an ion-conductive polymer, an electrolytic solution, etc.) and a lithium salt for enhancing ion conductivity are described in the above-mentioned column of the positive electrode active material layer. The same as

Examples of the negative electrode active material include carbon materials such as graphite (graphite), soft carbon, and hard carbon; lithium-transition metal composite oxides (eg, Li ₄ Ti ₅ O ₁₂ ); metal materials; and lithium alloy-based negative electrode materials. Is mentioned. In some cases, two or more negative electrode active materials may be used in combination. Preferably, from the viewpoint of capacity and output characteristics, a carbon material or a lithium-transition metal composite oxide is used as the negative electrode active material. In addition, it goes without saying that a negative electrode active material other than the above may be used.

  The average particle diameter (D50) of the negative electrode active material is measured by a laser diffraction type particle size distribution meter, and is preferably from 10 to 30 μm from the viewpoint of improving (handling) the initial charge capacity. When the value is equal to or more than the lower limit, the risk of a decrease in coatability due to a decrease in bulk density and the risk of deterioration in charge / discharge characteristics due to an increase in the specific surface area are further reduced. On the other hand, if the value is equal to or less than the upper limit value, the risk of poor appearance of the electrode due to deterioration of coating property due to clogging or streaking of the coater head is further reduced. From the same viewpoint, the thickness is more preferably 15 to 25 μm.

  The negative electrode active material layer preferably contains at least an aqueous binder. The aqueous binder has a high binding force. In addition to the fact that water as a raw material is easy to procure, water vapor is generated during drying, which significantly reduces capital investment in production lines and reduces environmental impact. There is.

  The aqueous binder refers to a binder using water as a solvent or a dispersion medium, and specifically includes a thermoplastic resin, a polymer having rubber elasticity, a water-soluble polymer, or a mixture thereof. Here, the binder containing water as a dispersion medium includes all expressed as a latex or an emulsion, and refers to a polymer that is emulsified with water or suspended in water, for example, a polymer latex that is emulsion-polymerized in a self-emulsifying system. And the like.

  Specific examples of the aqueous binder include styrene-based polymers (styrene-butadiene rubber (SBR), styrene-vinyl acetate copolymer, styrene-acrylic copolymer, etc.), acrylonitrile-butadiene rubber, methyl methacrylate-butadiene rubber , (Meth) acrylic polymers (polyethyl acrylate, polyethyl methacrylate, polypropyl acrylate, polymethyl methacrylate (methyl methacrylate rubber), polypropyl methacrylate, polyisopropyl acrylate, polyisopropyl methacrylate, polybutyl acrylate, polybutyl methacrylate, Polyhexyl acrylate, polyhexyl methacrylate, polyethylhexyl acrylate, polyethylhexyl methacrylate, polylauryl acrylate, polylau Ryl methacrylate, etc.), polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene copolymer, polybutadiene, butyl rubber, fluorine rubber, polyethylene oxide, polyepichlorohydrin, polyphosphazene, polyacrylonitrile, polystyrene, ethylene-propylene-diene copolymer Coalescing, polyvinylpyridine, chlorosulfonated polyethylene, polyester resin, phenolic resin, epoxy resin; polyvinyl alcohol (average degree of polymerization is preferably 200 to 4000, more preferably 1000 to 3000, saponification degree is preferably 80 mol% or more, more preferably 90 mol% or more) and a modified product thereof (ethylene / vinyl acetate = 1/80 mol% of vinyl acetate units in a copolymer having a molar ratio of 2/98 to 30/70) Product, 1-50 mol% partially acetalized product of polyvinyl alcohol, etc.), starch and its modified products (oxidized starch, phosphated starch, cationized starch, etc.), cellulose derivatives (carboxymethylcellulose (CMC), methylcellulose, hydroxypropyl) Cellulose, hydroxyethylcellulose, and salts thereof), polyvinylpyrrolidone, polyacrylic acid (salt), polyethylene glycol, a copolymer of (meth) acrylamide and / or (meth) acrylate [(meth) acrylamide polymer, (Meth) acrylamide- (meth) acrylate copolymer, alkyl (meth) acrylate (C 1-4) ester- (meth) acrylate copolymer, etc.), styrene-maleate copolymer , Polyacrylamide Modified Mannich, formalin condensation type resin (urea-formalin resin, melamine-formalin resin, etc.), polyamide polyamine or dialkylamine-epichlorohydrin copolymer, polyethyleneimine, casein, soybean protein, synthetic protein, mannangalactan derivative, etc. And water-soluble polymers. These aqueous binders may be used alone or in combination of two or more.

  From the viewpoint of binding properties, the aqueous binder may include at least one rubber-based binder selected from the group consisting of styrene-butadiene rubber, acrylonitrile-butadiene rubber, methyl methacrylate-butadiene rubber, and methyl methacrylate rubber. preferable. Further, the water-based binder preferably contains a styrene-butadiene rubber because of good binding properties.

  When styrene-butadiene rubber is used as the aqueous binder, it is preferable to use the above water-soluble polymer in combination from the viewpoint of improving coatability. Water-soluble polymers suitable for use in combination with styrene-butadiene rubber include polyvinyl alcohol and modified products thereof, starch and modified products thereof, cellulose derivatives (carboxymethylcellulose, methylcellulose, hydroxyethylcellulose, and salts thereof), polyvinyl alcohol and the like. Examples include pyrrolidone, polyacrylic acid (salt), or polyethylene glycol. Especially, it is preferable to combine styrene-butadiene rubber and carboxymethylcellulose (salt) as a binder. The content mass ratio of the styrene-butadiene rubber to the water-soluble polymer is not particularly limited, but is preferably styrene-butadiene rubber: water-soluble polymer = 1: 0.1 to 10, preferably 1: 1. : More preferably 0.5 to 2.

  Among the binders used for the negative electrode active material layer, the content of the aqueous binder is preferably 80 to 100% by mass, more preferably 90 to 100% by mass, and preferably 100% by mass.

The BET specific surface area of the negative electrode active material is not particularly limited, but is preferably from 0.5 to 10 m ² / g. When the specific surface area of the negative electrode active material is equal to or more than the lower limit, the possibility that the low-temperature characteristics deteriorate due to an increase in the internal resistance is further reduced. On the other hand, when the value is equal to or less than the upper limit, it is possible to more effectively prevent the side reaction from proceeding with an increase in the contact area with the electrolytic solution. In particular, if the specific surface area is too large, an overcurrent flows locally in the electrode surface due to the gas generated at the time of initial charging (the film is not fixed by the electrolyte additive), and the film is formed in the electrode surface. In some cases, non-uniformity may occur, and the life characteristics may deteriorate. However, if the value is equal to or less than the above upper limit, the risk can be further reduced. From the same viewpoint, more preferably 1.0~6.0m ² / g, more preferably from 1.5~4.2m ² / g.

  The negative electrode can be manufactured by forming a negative electrode active material layer on a negative electrode current collector. The method for forming the negative electrode active material layer is not particularly limited. For example, a negative electrode active material slurry containing at least a negative electrode active material and a slurry viscosity adjusting solvent is applied on a negative electrode current collector, dried, and then compressed by a roll press or the like. Molding method is mentioned. The slurry viscosity adjusting solvent is not particularly limited, but for example, N-methyl-2-pyrrolidone (NMP), ion-exchanged water and the like can be used.

[Separator (electrolyte layer)]
The separator has a function of retaining electrolyte and ensuring lithium ion conductivity between the positive electrode and the negative electrode, and a function as a partition between the positive electrode and the negative electrode.

  Examples of the form of the separator include a porous sheet separator and a nonwoven fabric separator made of a polymer or a fiber that absorbs and retains the electrolyte.

  As the separator of the porous sheet made of polymer or fiber, for example, a microporous (microporous membrane) can be used. Specific examples of the porous sheet made of the polymer or the fiber include polyolefins such as polyethylene (PE) and polypropylene (PP); and a laminate obtained by laminating a plurality of these (for example, three layers of PP / PE / PP). And a microporous (microporous membrane) separator made of polyimide, aramid, a hydrocarbon resin such as polyvinylidene fluoride-hexafluoropropylene (PVdF-HFP), glass fiber, or the like.

  The thickness of the microporous (microporous membrane) separator cannot be uniquely defined because it varies depending on the intended use. For example, in an application such as a secondary battery for driving a motor such as an electric vehicle (EV), a hybrid electric vehicle (HEV), and a fuel cell vehicle (FCV), the thickness may be 4 to 60 μm in a single layer or a multilayer. desirable. It is desirable that the micropore diameter of the microporous (microporous membrane) separator is 1 μm or less at maximum (usually, the pore diameter is about several tens nm).

  As the nonwoven fabric separator, conventionally known materials such as cotton, rayon, acetate, nylon, polyester; polyolefins such as PP and PE; polyimides and aramids are used alone or in combination. The bulk density of the nonwoven fabric is not particularly limited as long as sufficient battery characteristics can be obtained by the impregnated polymer gel electrolyte. Further, the thickness of the nonwoven fabric separator may be the same as that of the electrolyte layer, preferably 5 to 200 μm, and particularly preferably 10 to 100 μm.

  Further, as described above, the separator includes an electrolyte. The electrolyte is not particularly limited as long as it can exert such a function, and a liquid electrolyte or a gel polymer electrolyte is used. By using the gel polymer electrolyte, the distance between the electrodes is stabilized, the occurrence of polarization is suppressed, and the durability (cycle characteristics) is improved.

The liquid electrolyte has a function as a carrier for lithium ions. The liquid electrolyte has a form in which a lithium salt as a supporting salt is dissolved in an organic solvent as a plasticizer. Examples of the organic solvent used include carbonates such as ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), diethyl carbonate (DEC), and ethyl methyl carbonate (EMC). As the lithium _{salt, Li (CF 3 SO 2)} 2 N, Li (C 2 F 5 SO 2) 2 N, LiPF 6, LiBF 4, LiClO 4, LiAsF 6, LiTaF such 6, LiCF ₃ SO ₃ Compounds that can be added to the active material layer of the electrode can be employed as well. The concentration of the lithium salt is not particularly limited, but is preferably 0.8 to 1.2 M, more preferably 0.9 to 1.1 M, from the viewpoint of high ionic conductivity.

  The liquid electrolyte may further include additives other than the above-described components. Specific examples of such compounds include, for example, vinylene carbonate, methyl vinylene carbonate, dimethyl vinylene carbonate, phenyl vinylene carbonate, diphenyl vinylene carbonate, ethyl vinylene carbonate, diethyl vinylene carbonate, vinyl ethylene carbonate, and 1,2-divinyl ethylene carbonate. , 1-methyl-1-vinylethylene carbonate, 1-methyl-2-vinylethylene carbonate, 1-ethyl-1-vinylethylene carbonate, 1-ethyl-2-vinylethylene carbonate, vinylvinylene carbonate, allylethylene carbonate, vinyl Oxymethylethylene carbonate, allyloxymethylethylene carbonate, acryloxymethylethylene carbonate, Oxy methylethylene carbonate, ethynyl ethylene carbonate, propargyl carbonate, ethynyloxy methylethylene carbonate, propargyloxy ethylene carbonate, methylene carbonate, etc. 1,1-dimethyl-2-methylene-ethylene carbonate. Among them, vinylene carbonate, methyl vinylene carbonate and vinyl ethylene carbonate are preferred, and vinylene carbonate and vinyl ethylene carbonate are more preferred. One of these additives may be used alone, or two or more thereof may be used in combination. The concentration of such an additive in the electrolyte is not particularly limited, but is preferably 0.5 to 2.0% by mass.

  The gel polymer electrolyte has a configuration in which the above liquid electrolyte is injected into a matrix polymer (host polymer) made of an ion conductive polymer. The use of a gel polymer electrolyte as the electrolyte is excellent in that the fluidity of the electrolyte is lost and the ionic conductivity between the layers is cut off to facilitate the flow. Examples of the ion conductive polymer used as the matrix polymer (host polymer) include, for example, polyethylene oxide (PEO), polypropylene oxide (PPO), polyethylene glycol (PEG), polyacrylonitrile (PAN), polyvinylidene fluoride-hexafluoropropylene ( PVdF-HEP), poly (methyl methacrylate (PMMA), and copolymers thereof.

  The matrix polymer of the gel electrolyte can exhibit excellent mechanical strength by forming a crosslinked structure. In order to form a crosslinked structure, a suitable polymerization initiator is used to polymerize a polymerizable polymer for forming a polymer electrolyte (eg, PEO or PPO) by heat polymerization, ultraviolet polymerization, radiation polymerization, electron beam polymerization, or the like. A polymerization treatment may be performed.

  The separator is preferably a separator in which a heat-resistant insulating layer is laminated on a porous substrate (a separator with a heat-resistant insulating layer). The heat-resistant insulating layer is a ceramic layer containing inorganic particles and a binder. As the separator with a heat-resistant insulating layer, a high heat-resistant separator having a melting point or a thermal softening point of 150 ° C. or higher, preferably 200 ° C. or higher is used. By having the heat-resistant insulating layer, the internal stress of the separator, which increases when the temperature rises, is reduced, so that the effect of suppressing heat shrinkage can be obtained. As a result, induction of a short circuit between the electrodes of the battery can be prevented, so that a battery configuration in which performance degradation due to a rise in temperature hardly occurs is obtained. In addition, by having the heat-resistant insulating layer, the mechanical strength of the separator with the heat-resistant insulating layer is improved, and the separator is hardly broken. Further, the separator is unlikely to curl in the battery manufacturing process due to the effect of suppressing heat shrinkage and the high mechanical strength.

The inorganic particles in the heat-resistant insulating layer contribute to the mechanical strength of the heat-resistant insulating layer and the effect of suppressing heat shrinkage. The material used as the inorganic particles is not particularly limited. Examples include oxides of silicon, aluminum, zirconium, and titanium (SiO ₂ , Al ₂ O ₃ , ZrO ₂ , TiO ₂ ), hydroxides, and nitrides, and composites thereof. These inorganic particles may be derived from mineral resources such as boehmite, zeolite, apatite, kaolin, mullite, spinel, olivine and mica, or may be artificially produced. In addition, one kind of these inorganic particles may be used alone, or two or more kinds may be used in combination. Among these, from the viewpoint of cost, it is preferable to use silica (SiO ₂ ) or alumina (Al ₂ O ₃ ), and it is more preferable to use alumina (Al ₂ O ₃ ).

  The secondary average particle diameter of the heat-resistant fine particles is preferably from 100 nm to 4 μm, more preferably from 300 nm to 3 μm, and still more preferably from 500 nm to 3 μm from the viewpoint of dispersibility.

The basis weight of the heat-resistant particles is not particularly limited, but from the viewpoint that more favorable ion conductivity can be obtained and the effect of maintaining the heat-resistant strength can be further enhanced, is 5 to 20 g / m2. ² , preferably 9 to 13 g / m2.

  The binder in the heat-resistant insulating layer has a role of bonding the inorganic particles or the inorganic particles and the resin porous substrate layer. With the binder, the heat-resistant insulating layer is formed stably, and peeling between the porous substrate layer and the heat-resistant insulating layer is prevented.

  The binder used for the heat-resistant insulating layer is not particularly limited. For example, carboxymethylcellulose (CMC), polyacrylonitrile, cellulose, ethylene-vinyl acetate copolymer, polyvinyl chloride, styrene-butadiene rubber (SBR), isoprene rubber Compounds such as butadiene rubber, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyvinyl fluoride (PVF), and methyl acrylate can be used as the binder. Among them, carboxymethyl cellulose (CMC), methyl acrylate, or polyvinylidene fluoride (PVDF) is preferably used. One of these compounds may be used alone, or two or more of them may be used in combination.

  The content of the binder in the heat-resistant insulating layer is preferably 2 to 20% by mass based on 100% by mass of the heat-resistant insulating layer. When the content of the binder is 2% by mass or more, the peel strength between the heat-resistant insulating layer and the porous base layer can be increased, and the vibration resistance of the separator can be improved. On the other hand, when the content of the binder is 20% by mass or less, the gap between the inorganic particles is appropriately maintained, so that sufficient lithium ion conductivity can be secured.

The heat shrinkage of the separator with a heat-resistant insulating layer is preferably 10% or less for both MD and TD after holding for 1 hour at 150 ° C. and ² gf / cm ² . By using such a material having high heat resistance, the heat generation of the positive electrode increases, and even if the internal temperature of the battery reaches 150 ° C., the contraction of the separator can be effectively prevented. As a result, induction of a short circuit between the electrodes of the battery can be prevented, so that a battery configuration in which performance degradation due to a rise in temperature hardly occurs is obtained.

[Positive current collector and negative current collector]
The material constituting the current collectors (25, 27) is not particularly limited, and a known highly conductive material conventionally used as a current collector for a lithium ion secondary battery can be used. As a constituent material of the current collector, for example, a metal material such as aluminum, copper, titanium, nickel, stainless steel (SUS), or an alloy thereof is preferable. From the viewpoint of light weight, corrosion resistance, and high conductivity, aluminum and copper are more preferable, and aluminum is particularly preferable. In addition, the same material may be used for the positive electrode current collector 27 and the negative electrode current collector 25, or different materials may be used.

[Positive electrode lead and negative electrode lead]
Although not shown, the current collector 11 and the current collector (25, 27) may be electrically connected via a positive electrode lead or a negative electrode lead. As the constituent materials of the positive electrode and the negative electrode lead, materials used in known lithium ion secondary batteries can be similarly employed. In addition, the parts removed from the exterior may be in contact with peripheral equipment or wiring, etc., causing a short circuit, which will not affect products (for example, automobile parts, especially electronic equipment, etc.). It is preferable to coat with a tube or the like.

[Battery exterior]
The non-aqueous electrolyte secondary battery including the positive electrode for a non-aqueous electrolyte secondary battery according to one embodiment of the present invention can include a battery casing. As the battery outer casing 29, a known metal can case can be used, and a bag-shaped case that can cover the power generating element and that uses a laminated film containing aluminum can be used. As the laminate film, for example, a laminate film having a three-layer structure in which PP, aluminum, and nylon are laminated in this order can be used, but the present invention is not limited thereto. Laminated films are desirable from the viewpoint that they are excellent in high output and cooling performance and can be suitably used for batteries for large-sized devices for EV and HEV. In addition, since the group pressure applied to the power generation element from the outside can be easily adjusted and the thickness of the electrolyte layer can be easily adjusted to a desired thickness, the outer body is more preferably a laminated film containing aluminum. The thickness of the laminate film is not particularly limited, but is preferably from 70 to 180 μm.

[Cell size]
FIG. 2 is a perspective view showing the appearance of a flat lithium ion secondary battery which is a typical embodiment of the secondary battery.

  As shown in FIG. 2, the flat lithium ion secondary battery 50 has a rectangular flat shape, and a positive electrode tab 58 and a negative electrode tab 59 for extracting electric power are drawn out from both sides thereof. I have. The power generating element 57 is wrapped by the battery outer material 52 of the lithium ion secondary battery 50 and the periphery thereof is heat-sealed, and the power generating element 57 is hermetically sealed with the positive electrode tab 58 and the negative electrode tab 59 drawn out. Have been. Here, the power generation element 57 corresponds to the power generation element 21 of the lithium ion secondary battery 10 shown in FIG. 1 described above. The power generating element 57 includes a plurality of unit cell layers (single cells) 19 each including a positive electrode (positive electrode active material layer) 15 for a nonaqueous electrolyte secondary battery, an electrolyte layer 17, and a negative electrode (negative electrode active material layer) 13. Things.

  Note that the lithium ion secondary battery is not limited to a stacked flat battery. The wound lithium ion secondary battery may have a cylindrical shape, or may have such a cylindrical shape deformed into a rectangular flat shape. It is not particularly limited. In the case of the cylindrical shape, there is no particular limitation, for example, a laminate film may be used for the exterior material, or a conventional cylindrical can (metal can) may be used. Preferably, the power generating element is clad with an aluminum laminated film. With this configuration, weight reduction can be achieved.

  The removal of the tabs 58 and 59 shown in FIG. 2 is not particularly limited. As shown in FIG. 2, the positive electrode tab 58 and the negative electrode tab 59 may be pulled out from the same side, or the positive electrode tab 58 and the negative electrode tab 59 may be divided into a plurality of parts and taken out from each side. It is not limited to. In a wound lithium ion battery, terminals may be formed using, for example, a cylindrical can (metal can) instead of a tab.

  In a general electric vehicle, the battery storage space is about 170L. Since cells and auxiliary equipment such as charge / discharge control devices are stored in this space, the storage space efficiency of the normal cells is about 50%. The cell loading efficiency in this space is a factor that governs the cruising distance of the electric vehicle. If the size of the single cell is reduced, the above-mentioned loading efficiency is impaired, and the cruising distance cannot be secured.

  Therefore, in the present invention, it is preferable that the battery structure in which the power generation element is covered with the outer package is large. Specifically, the length of the short side of the laminated cell battery is preferably 100 mm or more. Such a large battery can be used for vehicle use. Here, the length of the short side of the laminate cell battery refers to the shortest side. The upper limit of the length of the short side is not particularly limited, but is usually 400 mm or less.

[Volume energy density and rated discharge capacity]
In a general electric vehicle, the driving distance (cruising distance) per charge is required to be 100 km in the market. In consideration of such a cruising distance, the battery preferably has a volume energy density of 157 Wh / L or more, and a rated capacity of 20 Wh or more.

  Furthermore, the aspect ratio of the rectangular electrode is preferably 1 to 3, and more preferably 1 to 2. Note that the aspect ratio of the electrode is defined as the aspect ratio of the rectangular positive electrode active material layer. By setting the aspect ratio in such a range, there is an advantage that both the required performance of the vehicle and the mounting space can be achieved.

[Battery pack]
The nonaqueous electrolyte secondary battery including the positive electrode for a nonaqueous electrolyte secondary battery according to one embodiment of the present invention can be used as an assembled battery. An assembled battery is formed by connecting a plurality of batteries. More specifically, at least two or more are used for serialization and / or parallelization. It is possible to freely adjust the capacity and the voltage by making them serial and parallel.

  A plurality of batteries may be connected in series or in parallel to form a detachable small assembled battery. Then, a plurality of the small battery packs which can be attached and detached are further connected in series or in parallel, and a large capacity and a large capacity suitable for a vehicle drive power supply and an auxiliary power supply requiring a high volume energy density and a high volume output density are required. A battery pack having an output can also be formed. How many batteries are connected to create a battery pack, and how many small battery packs are stacked to produce a large capacity battery pack, depends on the battery capacity of the vehicle (electric vehicle) to be mounted. It may be determined according to the output.

[vehicle]
The nonaqueous electrolyte lithium ion secondary battery including the positive electrode for a nonaqueous electrolyte secondary battery according to one embodiment of the present invention maintains a discharge capacity even after long-term use, and has a good capacity retention rate. Further, the volume energy density is high. Vehicle applications such as electric vehicles, hybrid electric vehicles, fuel cell vehicles, and hybrid fuel cell vehicles require higher capacity and larger size and longer life than electric and portable electronic device applications. . Therefore, the nonaqueous electrolyte lithium ion secondary battery can be suitably used as a vehicle power supply, for example, a vehicle drive power supply or an auxiliary power supply.

  Specifically, a battery or an assembled battery obtained by combining a plurality of these batteries can be mounted on a vehicle. In this embodiment, since a long-life battery having excellent long-term reliability and output characteristics can be formed, when such a battery is mounted, a plug-in hybrid electric vehicle having a long EV mileage or an electric vehicle having a long charge mileage can be formed. . For example, a hybrid vehicle, a fuel cell vehicle, an electric vehicle (all four-wheel vehicles (commercial vehicles such as passenger cars, trucks, buses, light vehicles, etc.) This is because the use in a motorcycle (including a motorcycle) and a three-wheeled vehicle) results in a vehicle having a long life and high reliability. However, the application is not limited to automobiles. For example, other vehicles, for example, various power supplies for moving objects such as trains can be applied, and a mounting power supply such as an uninterruptible power supply. It is also possible to use as.

  In the above embodiment, a non-aqueous electrolyte lithium-ion secondary battery, which is a type of non-aqueous electrolyte secondary battery, has been exemplified.However, the present invention is not limited to this, and other types of non-aqueous electrolyte secondary batteries may be used. Can also be applied.

  Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to only the following Examples.

(Example 1)
1. Preparation of Electrolytic Solution A mixed solvent of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) (30:30:40 (volume ratio)) was used as a solvent. In addition, 1.0 M LiPF ₆ was used as a lithium salt. Further, 2% by mass of vinylene carbonate was added to 100% by mass of the total of the solvent and the lithium salt to prepare an electrolytic solution. Note that “1.0 M LiPF ₆ ” means that the concentration of the lithium salt (LiPF ₆ ) in the mixture of the mixed solvent and the lithium salt is 1.0 M.

2. Preparation of Positive Electrode for Nonaqueous Electrolyte Secondary Battery As positive electrode active materials, LiMC _0.50 Mn _0.30 Co _0.20 O ₂ having a specific surface area of 0.67 m ² / g, which is an NMC composite oxide, and spinel lithium manganese were prepared LiMnO ₂ of a composite oxide specific surface area 0.42 m ² / g. Next, when the whole positive electrode active material was set to 100% by mass, the NMC composite oxide and the spinel-based lithium manganese composite oxide were mixed so as to be 70% by mass and 30% by mass, respectively. The solid content of the positive electrode active material is 90% by mass, acetylene black is 5% by mass as a conductive additive, and polyvinylidene fluoride (PVdF) is 5% by mass as a binder. A mixture was prepared. To this solid content, an appropriate amount of N-methyl-2-pyrrolidone (NMP) as a slurry viscosity adjusting solvent was added to prepare a positive electrode slurry. Next, the positive electrode slurry was applied to both sides of an aluminum foil (20 μm) as a current collector, dried and pressed, and the coating amount of the positive electrode active material layer on one side was 19.7 mg / cm ² , and the thickness of both sides was 146 μm (including foil). 2) A positive electrode for a non-aqueous electrolyte secondary battery was prepared.

3. Preparation of negative electrode Coated natural graphite (average particle diameter (D50): 20.0 μm, BET specific surface area: 2.0 m ² / g) 95% by mass, acetylene black as a conductive additive 2% by mass, styrene-butadiene rubber as a binder A solid content comprising (SBR) 2% by mass and carboxymethyl cellulose (CMC) 1% by mass was prepared. To this solid content, an appropriate amount of ion exchange water as a slurry viscosity adjusting solvent was added to prepare a negative electrode slurry. Next, the negative electrode slurry was applied to both sides of a copper foil (15 μm) as a current collector, dried and pressed to produce a negative electrode having a coating amount of 9.1 mg / cm ^{2 on} one side and a thickness of 136 μm (including foil) on both sides. did.

4. Step of Completing Unit Cell The positive electrode for a non-aqueous electrolyte secondary battery prepared above was cut into a rectangular shape of 210 × 184 mm, and the negative electrode was cut into a rectangular shape of 215 × 188 mm (15 positive electrodes and 16 negative electrodes). The positive electrode and the negative electrode for the non-aqueous electrolyte secondary battery were alternately laminated via a 230 × 210 mm separator with a heat-resistant insulating layer. At this time, the heat-resistant insulating layer was laminated so as to be adjacent to the negative electrode active material layer. The separator with a heat-resistant insulating layer was produced as follows. 95% by mass of alumina particles as inorganic particles (BET specific surface area: 5 m ² / g, secondary average particle size: 2 μm) and 5 parts by weight of carboxymethyl cellulose as binder (water content per weight of binder: 9.12% by mass) Was uniformly dispersed in water to prepare an aqueous solution. The aqueous solution was applied to both surfaces of a microporous polyethylene (PE) film (film thickness: 20 μm, porosity: 55%) using a gravure coater. Next, the film was dried at 60 ° C. to remove water, and a separator with a heat-resistant insulating layer, which was a multilayer porous film having a total film thickness of 25 μm, in which a 3.5-μm heat-resistant insulating layer was formed on one surface of the porous film, was produced. At this time, the basis weight of the heat-resistant insulating layer is 15 g / m ² .

  A tab was welded to each of the positive electrode and the negative electrode for the nonaqueous electrolyte secondary battery, and sealed together with an electrolytic solution in an outer package made of an aluminum laminated film to complete a lithium ion secondary battery.

(Examples 2 to 9, Comparative Examples 1 and 2)
A lithium ion secondary battery was produced in the same manner as in Example 1 except that the specific surface area and the mixing ratio of the positive electrode active material in Example 1 were mixed as shown in Table 1 below.

  In Table 1 below, the NMC composite oxide is represented as NMC, and the spinel lithium manganese composite oxide is represented as LMO.

  Here, the MMC composite oxide and the spinel-based lithium manganese composite oxide having each specific surface area used in each Example and Comparative Example were prepared according to the particle diameter. The specific surface area (BET specific surface area) of each of the MMC composite oxide and the spinel-based lithium manganese composite oxide was measured with a BET specific surface area measuring device (model: SA-9601) manufactured by Horiba, Ltd. (BET one-point method). ).

  Then, for the obtained battery, a capacity retention ratio was determined by the following method. The results are shown in Table 1 below.

[Capacity maintenance rate]
The capacity maintenance ratio was measured with the charge / discharge voltage range of the battery being 2.5 V to 4.15 V. Specifically, after the battery temperature was set to 25 ° C. in a thermostat kept at 25 ° C., charging was performed at a constant current rate (CC) of 4.15 V at a current rate of 1 C, and then at a constant voltage (CV). The battery was charged for a total of 2.5 hours. Thereafter, after a pause time of 10 minutes was provided, the battery was discharged to 2.5 V at a current rate of 1 C, followed by a pause time of 10 minutes. A charge / discharge test was performed using these as one cycle. The rate of discharge after 300 cycles with respect to the initial discharge capacity was defined as the capacity retention rate. Table 1 shows the measurement results.

[Initial capacity]
After the initial charge and discharge, the battery was charged at 0.2C at 4.15 V CCCV for 6.5 hours, and then discharged at 2.5 V to measure the initial capacity.

[Capacity maintenance rate]
The capacity after 300 cycles was measured by the same measurement method as the initial capacity, and the capacity retention rate was calculated by (capacity after 300 cycles / initial capacity × 100).

  From the results shown in Table 1, from the comparison of Examples 1 to 9 and Comparative Examples 1 and 2, the use of the non-aqueous electrolyte secondary battery for the configuration of the present invention allows the lithium ion secondary battery to have a high capacity retention rate. It was confirmed to have.

10, 50 lithium ion secondary battery,
11 negative electrode current collector,
12 positive electrode current collector,
13 negative electrode active material layer,
15 positive electrode active material layer,
17 separator,
19 cell layers,
21, 57 power generation elements,
25 negative electrode current collector,
27 positive electrode current collector,
29, 52 Battery exterior material,
58 positive electrode tab,
59 Negative electrode tab.

Claims (8)

A positive electrode current collector, and a positive electrode active material layer formed on the surface of the positive electrode current collector and including a positive electrode active material including a lithium nickel composite oxide and a spinel lithium manganese composite oxide,
The spinel-based lithium manganese composite oxide has a specific surface area of 0.30 m ² / g or more and less than 0.75 m ² / g;
A is a mixing ratio represented by a ratio of the mass of the spinel-based lithium manganese composite oxide to the mass of the lithium nickel-based composite oxide, and
When the specific surface area ratio represented by the ratio of the specific surface area of the spinel lithium manganese composite oxide to the specific surface area of the lithium nickel composite oxide is B,
A is greater than 0 and less than 3.00,
B is 0.60 or more and 1.00 or less,
A / B is the ratio of the A to the B is Ri 0.40 exceeded der,
The lithium-nickel-based complex oxide, LiNiO 2, or nickel, manganese, lithium-transition metal composite oxide der layered crystal structure containing cobalt Ru, non-aqueous electrolyte secondary battery positive _electrode. The lithium specific surface area of the nickel-based composite oxide is less than 0.30 m ² / g or more 0.90 m ² / g, the non-aqueous electrolyte secondary battery positive electrode according to claim 1. The positive electrode for a nonaqueous electrolyte secondary battery according to claim 1, wherein the specific surface area of the spinel-based lithium manganese composite oxide is 0.30 m ² / g or more and 0.60 m ² / g or less. The positive electrode for a non-aqueous electrolyte secondary battery according to claim 1, wherein a specific surface area of the spinel-based lithium manganese composite oxide is 0.42 m ² / g or more and less than 0.75 m ² / g.   The positive electrode for a non-aqueous electrolyte secondary battery according to any one of claims 1 to 4, wherein the A / B is more than 0.40 and not more than 2.50.   The positive electrode for a non-aqueous electrolyte secondary battery according to any one of claims 1 to 5, wherein the mixing ratio A is 0.25 or more and less than 3.00. The lithium-nickel-based composite oxide is represented by the general formula _{(1): Li a Ni b} Mn c Co d M x O 2 ( In the formula, a, b, c, d, x is, 0.9 ≦ a ≦ 1.2, 0.3 ≦ b ≦ 0.9, 0 <c ≦ 0.5, 0 <d ≦ 0.5, 0 ≦ x ≦ 0.3, and b + c + d = 1, where M is Ti, Zr, Nb, W, P, Al, Mg, V, Ca, Sr, Cr, and at least one element selected from the group consisting of Fe). Positive electrode for non-aqueous electrolyte secondary batteries.   A non-aqueous electrolyte secondary battery comprising the positive electrode for a non-aqueous electrolyte secondary battery according to claim 1.