JP2019160781A - Positive electrode and lithium ion secondary battery - Google Patents

Abstract

To provide a positive electrode and lithium ion secondary battery using the same, capable of improving charge rate characteristics and load discharge characteristics.SOLUTION: A positive electrode 20 includes a positive electrode active material layer 24 with positive electrode active material, conductive auxiliary agent and binding agent on a positive electrode collector 22. A reflection factor Rc of a wavelength 550 nm in the surface of the positive electrode active material layer 24 is 2.0≤Rc≤12.0%.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a positive electrode and a lithium ion secondary battery.

In recent years, non-aqueous electrolyte secondary batteries have been put into practical use as power sources for small electronic devices such as laptop computers, mobile phones, and video cameras as home appliances become increasingly portable and cordless. This non-aqueous electrolyte secondary battery is composed of a positive electrode, a negative electrode, a separator, and a non-aqueous electrolyte, and research and development relating to lithium cobaltate (LiCoO ₂ ) is actively promoted as a positive electrode active material used for the positive electrode. Many proposals have been made so far.

For example, in a lithium secondary battery including a positive electrode using a lithium-transition metal composite oxide as an active material, BeO, MgO, CaO, SrO, BaO, ZnO, Al ₂ O ₃ , CeO ₂ , As are formed on the surface of the positive electrode. There has been proposed a lithium secondary battery in which a film made of ₂ O ₃ or a mixture of two or more thereof is formed (see, for example, Patent Document 1).

  Further, in a battery that can be reversibly charged and discharged a plurality of times, comprising a negative electrode, a positive electrode, and a non-aqueous electrolyte containing a lithium salt, Ti, Al, Sn, Bi, Cu, Si, Ga, W, A positive electrode characterized by using a metal containing at least one selected from Zr, B, and Mo and / or an intermetallic compound obtained by combining a plurality of these, and / or an oxide coated thereon, and A used battery has been proposed (see, for example, Patent Document 2).

  On the other hand, the nonaqueous electrolyte secondary battery using lithium cobaltate as the positive electrode active material has a capacity limit (currently, 140 mAh / g or less is the use limit), and the constituent element cobalt is a rare metal. And because it is expensive, it has major problems in terms of stable supply and cost.

  As a positive electrode active material that replaces this, a nonaqueous electrolyte secondary battery using lithium nickelate in which cobalt of lithium cobaltate is replaced with nickel has attracted attention (see Patent Document 3). By using this lithium nickelate, it is possible to increase the capacity of about 190 mAh / g, and there is a great expectation for practical use because it is rich in nickel as a constituent element and economically excellent.

  With regard to the low thermal stability, which has been a problem in the past as a problem of lithium nickelate, the recent research and development has shown a dramatic improvement by adding trace elements such as aluminum (see Patent Document 4). ).

On the other hand, a lithium ion secondary battery using a phosphoric acid compound as a positive electrode active material having excellent thermal stability has attracted attention and has been reported to exhibit high battery characteristics. A typical example is lithium iron phosphate (LiFePO ₄ ), and lithium manganese phosphate (LiMnPO ₄ ) operating at a higher voltage has been actively developed. (For example, see Patent Documents 5 and 6)

JP-A-8-236114 Japanese Patent Laid-Open No. 11-16666 Japanese Patent Laid-Open No. 9-219199 JP-A-11-135123 Canadian Patent No. 2270771 Japanese translation of PCT publication No. 2004-509058

  However, the methods of the prior art still do not satisfy the characteristics required for the lithium ion secondary battery, and among them, further improvement in charge rate characteristics and load discharge characteristics is required.

  The present invention has been made in view of the above-described problems of the prior art, and an object thereof is to provide a positive electrode capable of improving charge rate characteristics and load discharge characteristics, and a lithium ion secondary battery using the positive electrode. To do.

As a result of intensive studies, the inventors of the present invention have developed a wavelength on the surface of the positive electrode active material layer in a positive electrode including a positive electrode active material layer having a positive electrode active material, a conductive additive, and a binder on the positive electrode current collector. It has been found that by setting the reflectance Rc of 550 nm within a predetermined range, high charge rate characteristics and load discharge characteristics can be obtained.
That is, in order to solve the above problems, the following means are provided.

  The positive electrode according to the first aspect includes a positive electrode active material layer having a positive electrode active material, a conductive additive, and a binder on a positive electrode current collector, and has a wavelength of 550 nm on the surface of the positive electrode active material layer. The reflectance Rc is 2.0 ≦ Rc ≦ 12.0%.

  By setting the reflectance Rc on the surface of the positive electrode active material layer within a predetermined range, the charge rate characteristic and the load discharge characteristic are improved. Although its effect is not clear, it is considered that the reflectance Rc of the surface of the positive electrode active material layer reflects the smoothness on the surface of the positive electrode active material layer and the surface compression state of the positive electrode active material on the surface of the positive electrode active material layer. It is done.

  That is, by controlling the smoothness on the surface of the positive electrode active material layer, it is estimated that a high charge rate characteristic can be obtained by increasing the reaction field with the electrolytic solution on the surface of the positive electrode active material layer.

  In addition to suppressing the impregnation of excessive electrolyte solution on the surface of the positive electrode active material by compressing the surface of the positive electrode active material layer on the surface of the positive electrode active material layer, it is high by achieving both high reactivity and suppression of side reactions. It is estimated that load discharge characteristics can be obtained.

  As a method for controlling the reflectance Rc at a wavelength of 550 nm on the surface of the positive electrode active material layer to a specific range, for example, it is possible to change depending on the rolling pressure at the time of electrode rolling, the number of times of rolling, the heating conditions at the time of rolling, and the like. .

  Furthermore, regardless of the surface compression state of the positive electrode active material layer, when the reflectance Rc on the surface of the positive electrode active material layer is controlled within a predetermined range, it is considered that the charge rate characteristics and load discharge characteristics are also improved.

  This is because the reflectivity Rc on the surface of the positive electrode active material layer suppresses the side reaction on the surface of the positive electrode active material layer, and the permeability of the electrolyte from the surface of the positive electrode active material layer to the inside of the positive electrode active material layer. It is estimated that charging rate characteristics and load discharge characteristics are improved by achieving both improvements.

  As a different method for controlling the reflectance Rc at a wavelength of 550 nm on the surface of the positive electrode active material layer to a specific range, for example, it is possible to control by polishing the surface of the electrode obtained after rolling or applying a top coat. Is possible.

The positive electrode according to the first aspect includes a compound represented by the following general formula (1) as a main component as a positive electrode active material, and a reflectance Rc1 at a wavelength of 550 nm on the surface of the positive electrode active material layer is 8. It may be 0 ≦ Rc1 ≦ 12.0%.
Li _x Ni _y M _1-y O _z (1)
(0 <x ≦ 1.1, 0 ≦ y <0.5, 1.9 ≦ z ≦ 2.1 is satisfied, and M has at least one selected from Co, Mn, Al, Fe, and Mg)

  By setting the reflectance Rc1 in the positive electrode containing the compound represented by the general formula (1) as a main component as the positive electrode active material in the above range, the charge rate characteristics can be further improved.

In the positive electrode according to the above aspect, the density dc1 of the positive electrode active material layer may be 3.1 ≦ dc1 ≦ 4.1 g / cm ³ .

In the positive electrode according to the above aspect, the supported amount Lc1 per unit area in the positive electrode active material layer may be 13.0 ≦ Lc1 ≦ 25.0 mg / cm ² .

The positive electrode according to the first aspect includes a compound represented by the following formula (2) as a main component as a positive electrode active material, and a reflectance Rc2 at a wavelength of 550 nm on the surface of the positive electrode active material layer is 3.5. <= Rc2 <= 7.8% may be sufficient.
Li _x Ni _y M _1-y O _z (2)
(0 <x ≦ 1.1, 0.5 ≦ y ≦ 1, 1.9 ≦ z ≦ 2.1, M has at least one selected from Co, Mn, Al, Fe, and Mg)

  By setting the reflectance Rc2 in the positive electrode containing the compound represented by the general formula (2) as a main component as the positive electrode active material in the above range, the load discharge characteristics can be further improved.

In the positive electrode according to the above aspect, the density dc2 of the positive electrode active material layer may be 3.0 ≦ dc2 ≦ 3.8 g / cm ³ .

In the positive electrode according to the above aspect, the supported amount Lc2 per unit area in the positive electrode active material layer may be 12.0 ≦ Lc2 ≦ 24.0 mg / cm ² .

The positive electrode according to the first aspect includes a compound represented by the following formula (3) as a main component as a positive electrode active material, and a reflectance Rc3 at a wavelength of 550 nm on the surface of the positive electrode active material layer is 2.0. <= Rc3 <= 5.8% may be sufficient.
_{Li x M y O z PO 4} ···· (3)
(0 <x ≦ 1.1, 0 <y ≦ 1.1, 0 ≦ z ≦ 1.0 is satisfied, and M is at least one selected from Ni, Co, Mn, Al, Fe, Mg, Ag, and V Have)

  By setting the reflectance Rc3 in the positive electrode containing the compound represented by the general formula (3) as a main component as the positive electrode active material in the above range, the charge rate characteristics can be further improved.

In the positive electrode according to the aspect described above, the density dc3 of the positive electrode active material layer may be 1.8 ≦ dc3 ≦ 2.5 g / cm ³ .

In the positive electrode according to the above aspect, the supported amount Lc3 per unit area in the positive electrode active material layer may be 8.0 ≦ Lc3 ≦ 15.0 mg / cm ² .

  A lithium ion secondary battery according to a second aspect includes any one of the positive electrodes according to the first aspect, a negative electrode including a negative electrode active material layer having a negative electrode active material on a negative electrode current collector, a separator, And a reflectance Ra at a wavelength of 550 nm on the surface of the negative electrode active material layer is 7.5 ≦ Ra ≦ 16.0%.

  By combining a negative electrode in which the reflectance Ra on the surface of the negative electrode active material layer is adjusted to a predetermined range, the charge rate characteristic and the load discharge characteristic are further improved.

  Similarly to the reflectance Rc on the surface of the positive electrode active material layer, the reflectance Ra on the surface of the negative electrode active material layer also reflects the smoothness on the surface of the negative electrode active material layer and the surface compression state of the negative electrode active material on the surface of the negative electrode active material layer. it seems to do.

  Therefore, by combining a negative electrode whose reflectance Ra on the surface of the negative electrode active material layer is in the range of 7.5 ≦ Ra ≦ 16.0%, the charge rate characteristics and load discharge of a lithium ion secondary battery using the negative electrode are combined. It is estimated that the characteristics will be improved.

  In the lithium ion secondary battery according to the second aspect, the ratio Rc1 / Ra of the reflectance Rc1 on the surface of the positive electrode active material layer and the reflectance Ra on the surface of the negative electrode active material layer is 1.00 <Rc1 / Ra. ≦ 1.53 may be sufficient.

  In the lithium ion secondary battery according to the second aspect, the ratio Rc2 / Ra of the reflectance Rc2 on the surface of the positive electrode active material layer and the reflectance Ra on the surface of the negative electrode active material layer is 0.29 ≦ Rc2 / Ra. <1.00 may be sufficient.

  In the lithium ion secondary battery according to the second aspect, the ratio Rc3 / Ra of the reflectance Rc3 on the surface of the positive electrode active material layer and the reflectance Ra on the surface of the negative electrode active material layer is 0.13 ≦ Rc3 / Ra. It may be ≦ 0.75.

  According to this configuration, the lithium ion secondary battery using the same has good charge rate characteristics. It is presumed that the lithium ion exchange is suitably performed in addition to the electrolyte solution impregnation on the positive electrode active material layer and negative electrode active material layer surfaces and the suppression of side reactions.

  In addition, it can be seen that the preferable range of the ratio of the reflectance Rc of the positive electrode active material layer and the reflectance Ra on the surface of the negative electrode active material layer differs depending on the reflectance on the surface of the positive electrode active material used and the surface of the positive electrode active material layer.

  This is presumed to be because, in addition to the reaction state with the electrolyte solution on the positive electrode surface using each positive electrode active material, the preferred state of the positive electrode surface with respect to the impregnation of the electrolyte solution inside the positive electrode is different. ing.

  In the lithium ion secondary battery according to the second aspect, the negative electrode active material may contain a carbon material having a graphite structure.

  When the negative electrode having the above reflectance contains a carbon material having a graphite structure as the negative electrode active material, it has particularly good charge rate characteristics.

  It is presumed that this is because both the impregnation of the electrolytic solution and the suppression of side reactions can be achieved without excessively reducing the lithium ion deinsertion sites of the carbon material having a graphite structure on the surface of the negative electrode active material layer.

In the lithium ion secondary battery according to the second aspect, the non-aqueous electrolyte includes a non-aqueous solvent and an electrolyte, the non-aqueous solvent contains ethylene carbonate, and the content of the ethylene carbonate is the non-aqueous solvent. 10 to 30 vol. %.

  According to this configuration, it has a good charge rate characteristic. It is presumed that this is because a part of the electrode surface is decomposed and an excellent film can be formed while suppressing excessive decomposition of ethylene carbonate as a film component.

  The present invention makes it possible to provide a positive electrode for a lithium ion secondary battery capable of improving the charge rate characteristics and load discharge characteristics, and a lithium ion secondary battery using the same.

It is a cross-sectional schematic diagram of the lithium ion secondary battery concerning this embodiment.

  Hereinafter, the present embodiment will be described in detail with appropriate reference to the drawings. In the drawings used in the following description, in order to make the characteristics of the present invention easier to understand, there are cases where the characteristic parts are enlarged for the sake of convenience, and the dimensional ratios of the respective components are different from actual ones. is there. The materials, dimensions, and the like exemplified in the following description are examples, and the present invention is not limited to them, and can be appropriately modified and implemented without departing from the scope of the invention.

(Lithium ion secondary battery)
FIG. 1 is a schematic cross-sectional view of a lithium ion secondary battery according to this embodiment. A lithium ion secondary battery 100 shown in FIG. 1 mainly includes a laminated body 40, a case 50 that accommodates the laminated body 40 in a sealed state, and a pair of leads 60 and 62 connected to the laminated body 40. Although not shown, the nonaqueous electrolyte is housed in the case 50 together with the laminate 40.

  The stacked body 40 is configured such that the positive electrode 20 and the negative electrode 30 are disposed to face each other with the separator 10 interposed therebetween. The positive electrode 20 is obtained by providing a positive electrode active material layer 24 on a plate-like (film-like) positive electrode current collector 22. The negative electrode 30 is obtained by providing a negative electrode active material layer 34 on a plate-like (film-like) negative electrode current collector 32.

  The positive electrode active material layer 24 and the negative electrode active material layer 34 are in contact with both sides of the separator 10. Leads 62 and 60 are connected to the ends of the positive electrode current collector 22 and the negative electrode current collector 32, respectively, and the ends of the leads 60 and 62 extend to the outside of the case 50. In FIG. 1, the case 50 has one laminated body 40 in the case 50, but a plurality of laminated bodies 40 may be laminated.

(Positive electrode)
The positive electrode 20 includes a positive electrode current collector 22 and a positive electrode active material layer 24 provided on the positive electrode current collector 22.

  The positive electrode according to the present embodiment includes a positive electrode active material layer having a positive electrode active material on a positive electrode current collector, and a reflectance Rc at a wavelength of 550 nm on the surface of the positive electrode active material layer is 2.0 ≦ Rc ≦ 12.0. %.

(First embodiment)
The positive electrode according to the first embodiment includes a positive electrode active material layer having a positive electrode active material on a positive electrode current collector, and contains a compound represented by the following general formula (1) as a main component as the positive electrode active material. The reflectance Rc1 at a wavelength of 550 nm on the surface of the positive electrode active material layer is 8.0 ≦ Rc1 ≦ 12.0%.
Li _x Ni _y M _1-y O _z (1)
(0 <x ≦ 1.1, 0 ≦ y <0.5, 1.9 ≦ z ≦ 2.1 is satisfied, and M has at least one selected from Co, Mn, Al, Fe, and Mg)

  In the positive electrode according to the first embodiment, the reflectance Rc1 at a wavelength of 550 nm on the surface of the positive electrode active material layer is particularly preferably 9.5 ≦ Rc1 ≦ 10.5%.

  By setting the reflectance Rc1 on the surface of the positive electrode active material layer within the above range, particularly good charge rate characteristics can be obtained.

  When the reflectance Rc1 is in the above range, it is presumed that the effect of suppressing the excessive impregnation of the electrolyte solution on the surface of the positive electrode active material layer and achieving both the high reactivity and the suppression of the side reaction is the highest. ing.

In the positive electrode according to the first embodiment, the density dc1 in the positive electrode active material layer is preferably 3.1 ≦ dc1 ≦ 4.1 g / cm ³ . The density dc1 in the positive electrode active material layer is more preferably 3.3 ≦ dc1 ≦ 3.9 g / cm ³ , and more preferably 3.5 ≦ dc1 ≦ 3.7 g / cm ³ .

In the positive electrode according to the first embodiment, the supported amount Lc1 per unit area in the positive electrode active material layer is preferably 13.0 ≦ Lc1 ≦ 25.0 mg / cm ² .

  In the positive electrode according to this embodiment, the porosity Pc1 in the positive electrode active material layer is preferably 21.0 ≦ Pc1 ≦ 25.0%, and more preferably 23.0 ≦ Pc1 ≦ 24.0%. .

  More preferably, the positive electrode according to the first embodiment simultaneously satisfies the density dc1 in the positive electrode active material layer and the value of the porosity Pc1 in the positive electrode active material layer.

  By simultaneously satisfying dc1, Pc and 1 in the positive electrode active material layer, not only suppressing excessive impregnation of the electrolytic solution and achieving both high reactivity and suppression of side reactions, but also the electrolytic solution inside the positive electrode active material layer It is presumed that a high charge rate characteristic can be obtained by increasing the diffusion effect.

(Positive electrode active material)
Examples of the positive electrode active material that is a compound represented by the general formula (1) include LiNi _1/3 Mn _1/3 Co _1/3 O ₂ and LiNi _0.2 Co _0.8 O _2. A material containing Ni, Mn, or Co as a main component or a lithium-containing transition metal oxide represented by LiCoO ₂ can be used.

Among these, it is preferable to use a lithium-containing transition metal oxide represented by LiCoO ₂ , LiNi _1/3 Mn _1/3 Co _1/3 O ₂ .

  These lithium-containing transition metal oxides are preferable because they have high structural stability, are easy to synthesize, and obtain sufficient charge rate characteristics.

  Note that the positive electrode active material represented by the general formula (1) does not need to have the stoichiometric amount of oxygen expressed by this composition formula, and includes a wide range of oxygen-deficient materials. In other words, those identified as the same composition system by X-ray diffraction or the like are targeted.

  Therefore, in addition to the positive electrode active material represented by the general formula (1), a part of Ni or M may be substituted with a different element, the concentration gradient of elements in the positive electrode active material, the surface of the positive electrode active material, At least a portion may be covered with an oxide, carbon, or the like.

  Moreover, the positive electrode active material layer concerning this embodiment may contain the positive electrode active material which has as a main component the positive electrode active material represented by the said General formula (1), and has a different composition.

Examples of positive electrode active materials having different compositions include lithium nickelate (LiNiO ₂ ), lithium manganate (LiMnO ₂ ), lithium manganese spinel (LiMn ₂ O ₄ ), and a general formula: LiNi _x Co _y M _z O ₂ (x + y + z = 1, 0.5 ≦ x <1, 0 ≦ y <1, 0 ≦ z <1, and M is one or more elements selected from Al, Mg, Nb, Ti, Cu, Zn, and Cr) Composite metal oxides, lithium vanadium compounds (LiVOPO ₄ , Li ₃ V ₂ (PO ₄ ) ₃ , LiV ₂ O ₅ , Li ₂ VP ₂ O ₇ ), olivine-type LiMPO ₄ (where M is Co, Ni, Mn, Fe, showing Mg, Nb, Ti, Al, Zr, at least one element selected from V), lithium titanate _{(Li 4} Ti _{5 O 12)} composite metal oxide such as, Po Acetylene, polyaniline, polypyrrole, polythiophene, polyacene, etc., and the existing positive electrode active material a lithium ion capable of occluding and releasing it.

  In the positive electrode active material according to the first embodiment, the content as a main component means that the content of the positive electrode active material that is the compound represented by the general formula (1) is 50% by mass with respect to the entire positive electrode active material. Indicates greater than.

  When the positive electrode active materials having different compositions are contained, the positive electrode active material represented by the general formula (1) with respect to the total of the positive electrode active materials represented by the general formula (1) and the positive electrode active materials having different compositions. The content of the substance is preferably 60% by mass or more, more preferably 80% by mass or more, and particularly preferably 95% by mass or more.

(Second embodiment)
The positive electrode according to the second embodiment includes a positive electrode active material layer having a positive electrode active material on a positive electrode current collector, and contains a compound represented by the following formula (2) as a main component as the positive electrode active material, The reflectance Rc2 at a wavelength of 550 nm on the surface of the positive electrode active material layer is 3.5 ≦ Rc2 ≦ 7.8%.
Li _x Ni _y M _1-y O _z (2)
(0 <x ≦ 1.1, 0.5 ≦ y ≦ 1, 1.9 ≦ z ≦ 2.1, M has at least one selected from Co, Mn, Al, Fe, and Mg)

  In the positive electrode according to the second embodiment, the reflectance Rc2 at a wavelength of 550 nm on the surface of the positive electrode active material layer is particularly preferably 4.3 ≦ Rc2 ≦ 6.3%.

  By setting the reflectance Rc2 on the surface of the positive electrode active material layer in the above range, particularly good load discharge characteristics can be obtained.

  When the reflectance Rc2 is in the above range, it is presumed that the effect of suppressing the excessive electrolyte solution impregnation on the surface of the positive electrode active material layer and achieving both the high reactivity and the suppression of the side reaction is the highest. ing.

The positive electrode according to the second embodiment is preferably density dc2 in the positive electrode active material layer is ^{3.0 ≦ dc2 ≦ 3.8g / cm 3} , is 3.2 ≦ dc2 ≦ 3.6g / cm ³ It is more preferable.

In the positive electrode according to the second embodiment, the supported amount Lc2 per unit area in the positive electrode active material layer is preferably 12.0 ≦ Lc2 ≦ 15.0 mg / cm ² .

  In the positive electrode according to the second embodiment, the porosity Pc2 in the positive electrode active material layer is preferably 21.0 ≦ Pc2 ≦ 25.0%, and preferably 23.0 ≦ Pc2 ≦ 24.5%. More preferred.

  The positive electrode according to the second embodiment more preferably satisfies the density dc2 in the positive electrode active material layer and the porosity Pc2 in the positive electrode active material layer at the same time.

  By simultaneously filling dc2 and Pc2 in the positive electrode active material layer, it is possible not only to suppress excessive impregnation of the electrolytic solution and to achieve both high reactivity and suppression of side reactions, but also to maintain the electrolyte solution inside the positive electrode active material layer. It is assumed that high load discharge characteristics can be obtained by increasing the diffusion effect.

(Positive electrode active material)
Examples of the positive electrode active material that is a compound represented by the general formula (2) include LiNi _0.8 Co _0.2 O ₂ and LiNi _0.85 Co _0.10 Al _0.05 O _2. Ni, Co containing as a main component, or Ni, Co, Mn represented by LiNi _0.8 Mn _0.1 Co _0.1 O ₂ , LiNi _0.6 Mn _0.2 Co _0.2 O ₂ A lithium-containing transition metal oxide containing as a main component can be used.

Among these, as represented by LiNi _0.85 Co _0.10 Al _0.05 O ₂ , a part of Ni or Co substituted with Al, or LiNi _0.8 Mn _0.1 Co _{0. A} lithium-containing transition metal oxide represented by ₁ O ₂ , LiNi _0.6 Mn _0.2 Co _0.2 O _{2 and} having a high Ni content is preferable because a high discharge capacity can be obtained.

  Note that the positive electrode active material represented by the general formula (2) does not need to have the stoichiometric amount of oxygen expressed by this composition formula, and widely includes oxygen-deficient materials. In other words, those identified as the same composition system by X-ray diffraction or the like are targeted.

  Therefore, in addition to the positive electrode active material represented by the general formula (2), a part of Ni or M may be substituted with a different element, the concentration gradient of elements in the positive electrode active material, the surface of the positive electrode active material, At least a portion may be covered with an oxide, carbon, or the like.

  Moreover, the positive electrode active material layer concerning 2nd embodiment may contain the positive electrode active material which has a positive electrode active material represented by the said General formula (2) as a main component, and has a different composition.

Examples of positive electrode active materials having different compositions include lithium cobaltate (LiCoO ₂ ), lithium manganate (LiMnO ₂ ), lithium manganese spinel (LiMn ₂ O ₄ ), and a general formula: LiNi _x Co _y M _z O ₂ (x + y + z = 1, 0 ≦ x <0.5, 0.5 ≦ y <1, 0 ≦ z <1, M is one or more elements selected from Al, Mg, Nb, Ti, Cu, Zn, and Cr) Composite metal oxides represented, lithium vanadium compounds (LiVOPO ₄ , Li ₃ V ₂ (PO ₄ ) ₃ , LiV ₂ O ₅ , Li ₂ VP ₂ O ₇ ), olivine type LiMPO ₄ (where M is Co, Ni, Mn, shown Fe, Mg, Nb, Ti, Al, Zr, at least one element selected from V), complex metal oxides such as lithium titanate _{(Li 4} Ti _{5 O 12)} Polyacetylene, polyaniline, polypyrrole, polythiophene, polyacene, etc., and the existing positive electrode active material a lithium ion capable of occluding and releasing it.

  In the positive electrode active material according to the second embodiment, the content as a main component means that the content of the positive electrode active material that is the compound represented by the general formula (2) is 50% by mass with respect to the entire positive electrode active material. Indicates greater than.

  When the positive electrode active materials having different compositions are contained, the positive electrode active materials represented by the general formula (2) with respect to the total of the positive electrode active materials represented by the general formula (2) and the positive electrode active materials having different compositions. The content of the substance is preferably 60.0% by mass or more, more preferably 80.0% by mass or more, and particularly preferably 95.0% by mass or more.

(Third embodiment)
The positive electrode according to the third embodiment includes a positive electrode active material layer having a positive electrode active material on a positive electrode current collector, and contains a compound represented by the following formula (3) as a main component as the positive electrode active material, The reflectance Rc3 at a wavelength of 550 nm on the surface of the positive electrode active material layer is 2.0 ≦ Rc3 ≦ 5.8%.
_{Li x M y O z PO 4} ···· (3)
(0 <x ≦ 1.1, 0 <y ≦ 1.1, 0 ≦ z ≦ 1.0 is satisfied, and M is at least one selected from Ni, Co, Mn, Al, Fe, Mg, Ag, and V Have)

  In the positive electrode according to the third embodiment, the reflectance Rc2 at a wavelength of 550 nm on the surface of the positive electrode active material layer is particularly preferably 3.2 ≦ Rc3 ≦ 4.9%.

  By setting the reflectance Rc3 on the surface of the positive electrode active material layer within the above range, particularly good load discharge characteristics can be obtained.

  When the reflectance Rc3 is in the above range, it is presumed that the effect of suppressing the excessive impregnation of the electrolyte solution on the surface of the positive electrode active material layer and achieving both the high reactivity and the suppression of the side reaction is the highest. ing.

In the positive electrode according to the third embodiment, the density dc3 in the positive electrode active material layer is preferably 1.8 ≦ dc3 ≦ 2.5 / cm ³ , and 1.9 ≦ dc3 ≦ 2.3 g / cm ³ . It is more preferable.

In the positive electrode according to the third embodiment, the supported amount Lc3 per unit area in the positive electrode active material layer is preferably 12.0 ≦ Lc3 ≦ 15.0 mg / cm ² .

  In the positive electrode according to the third embodiment, the porosity Pc3 in the positive electrode active material layer is preferably 21.0 ≦ Pc3 ≦ 25.0%, and preferably 23.0 ≦ Pc3 ≦ 24.5%. More preferred.

  More preferably, the positive electrode according to the third embodiment simultaneously satisfies the density dc3 in the positive electrode active material layer and the porosity Pc3 in the positive electrode active material layer.

  By simultaneously filling dc3 and Pc3 in the positive electrode active material layer, it is possible not only to suppress excessive impregnation of the electrolytic solution and to achieve both high reactivity and suppression of side reaction, but also to maintain the electrolyte solution inside the positive electrode active material layer. It is assumed that high load discharge characteristics can be obtained by increasing the diffusion effect.

(Positive electrode active material)
Examples of the positive electrode active material that is a compound represented by the general formula (3) include those having an olivine structure represented by LiFePO ₄ and LiMnPO ₄ , and LiFe _x Mn _1-x PO ₄ (0 <x < A solid solution represented by 1) or a phosphoric acid compound represented by LiVOPO ₄ can be used.

  Note that the positive electrode active material represented by the general formula (3) does not need to have the stoichiometric oxygen amount represented by this composition formula, and includes a wide range of oxygen-deficient materials. In other words, those identified as the same composition system by X-ray diffraction or the like are targeted.

  Therefore, in addition to the positive electrode active material represented by the general formula (3), a part of M or P may be substituted with a different element, and the concentration gradient of elements in the positive electrode active material or the surface of the positive electrode active material At least a portion may be covered with an oxide, carbon, or the like.

  Moreover, the positive electrode active material layer concerning 3rd embodiment may contain the positive electrode active material which has the positive electrode active material represented by the said General formula (3) as a main component, and has a different composition.

Examples of positive electrode active materials having different compositions include lithium cobaltate (LiCoO ₂ ), lithium manganate (LiMnO ₂ ), lithium manganese spinel (LiMn ₂ O ₄ ), and a general formula: LiNi _x Co _y M _z O ₂ (x + y + z = 1, 0 ≦ x ≦ 1.0, 0 ≦ y <1, 0 ≦ z <1, M is one or more elements selected from Al, Mg, Nb, Ti, Cu, Zn, and Cr) Composite metal oxide, lithium vanadium compound (LiV ₂ O ₅ , Li ₂ VP ₂ O ₇ ), NASICON type Li ₃ M ₂ (PO ₄ ) ₃ (where M is one or more selected from V, Fe, and Mo) A phosphoric acid compound represented by Li ₂ MP ₂ O ₇ (where M is one or more selected from Co, Ni, Mn, Fe, Mg, Nb, Ti, Al, Zr, and V) Elements Shown), complex metal oxides such as lithium titanate _{(Li 4 Ti 5 O 12)} , polyacetylene, polyaniline, polypyrrole, polythiophene, polyacene, etc., and the existing positive electrode active material a lithium ion capable of occluding and releasing it.

  In the positive electrode active material according to the third embodiment, the content as the main component means that the content of the positive electrode active material that is the compound represented by the general formula (3) is 50% by mass with respect to the entire positive electrode active material. Indicates greater than.

  When the positive electrode active materials having different compositions are contained, the positive electrode active material represented by the general formula (3) with respect to the total of the positive electrode active materials represented by the general formula (3) and the positive electrode active materials having different compositions. The content of the substance is preferably 60.0% by mass or more, more preferably 70.0% by mass or more, and particularly preferably 80.0% by mass or more.

  The content of each positive electrode active material in the positive electrode active material layer according to the present embodiment is calculated by determining the content of each element using elemental analysis after specifying the compound species to be contained by X-ray diffraction measurement. Can do.

  In addition to the positive electrode active material, the positive electrode active material layer according to the present embodiment may include members such as a conductive additive and a binder.

(Conductive aid)
Examples of the conductive aid include carbon powders such as carbon blacks, carbon nanotubes, carbon materials, metal fine powders such as copper, nickel, stainless steel and iron, a mixture of carbon materials and metal fine powders, and conductive oxides such as ITO. Can be mentioned.

(Binder)
The binder binds the active materials to each other and also binds the active materials to the current collector 22. The binder is not particularly limited as long as the above-described bonding is possible. For example, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoro Ethylene-perfluoroalkyl vinyl ether copolymer (PFA), ethylene-tetrafluoroethylene copolymer (ETFE), polychlorotrifluoroethylene (PCTFE), ethylene-chlorotrifluoroethylene copolymer (ECTFE), polyvinyl fluoride A fluororesin such as (PVF) is used.

  In addition to the above, as the binder, for example, vinylidene fluoride-hexafluoropropylene-based fluororubber (VDF-HFP-based fluororubber), vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene-based fluororubber (VDF-HFPPTFE-based) Fluororubber), vinylidene fluoride-pentafluoropropylene-based fluororubber (VDF-PFP-based fluororubber), vinylidene fluoride-pentafluoropropylene-tetrafluoroethylene-based fluororubber (VDF-PFP-TFE-based fluororubber), vinylidene fluoride Ride-perfluoromethyl vinyl ether-tetrafluoroethylene fluoro rubber (VDF-PFMVE-TFE fluoro rubber), vinylidene fluoride-chlorotrifluoroethylene fluoro rubber It may be used vinylidene fluoride-based fluorine rubbers such as rubber (VDF-CTFE-based fluorine rubber).

  Further, an electron conductive conductive polymer or an ion conductive conductive polymer may be used as the binder. Examples of the electron conductive conductive polymer include polyacetylene. In this case, since the binder also functions as a conductive material, it is not necessary to add a conductive material. Examples of the ion conductive conductive polymer include those obtained by combining a polymer compound such as polyethylene oxide and polypropylene oxide with a lithium salt or an alkali metal salt mainly composed of lithium.

  The contents of the positive electrode active material, the conductive material, and the binder in the positive electrode active material layer 24 are not particularly limited. The constituent ratio of the positive electrode active material in the positive electrode active material layer 24 is preferably 90.0% or more and 98.0% or less in terms of mass ratio. The constituent ratio of the conductive material in the positive electrode active material layer 24 is preferably 1.0% to 3.0% by mass ratio, and the constituent ratio of the binder in the positive electrode active material layer 24 is 2. It is preferably 0% or more and 5.0% or less.

  By making content of a positive electrode active material and a binder into the said range, it can prevent that the quantity of a binder is too small and it becomes impossible to form a strong positive electrode active material layer. In addition, the amount of the binder that does not contribute to the electric capacity increases, and the tendency that it is difficult to obtain a sufficient volume energy density can be suppressed.

  In addition, by setting the content of the positive electrode active material and the conductive material in the above range, sufficient electronic conductivity can be obtained in the positive electrode active material layer, and high volume energy density and output characteristics can be obtained.

(Positive electrode current collector)
The positive electrode current collector 22 may be a conductive plate material, and for example, a metal thin plate such as aluminum, copper, or nickel foil, or an alloy thin plate thereof may be used. Among these, it is preferable to use an aluminum metal thin plate having a light weight.

(Negative electrode)
The negative electrode 30 includes a negative electrode current collector 32 and a negative electrode active material layer 34 provided on the negative electrode current collector 32.

  In the negative electrode according to this embodiment, the reflectance Ra at a wavelength of 550 nm on the surface of the negative electrode active material layer is preferably in the range of 7.5 ≦ Ra ≦ 16.0%.

  By using the negative electrode according to the present embodiment, high charge rate characteristics can be obtained. It is considered to reflect the smoothness on the surface of the negative electrode active material layer and the surface compression state of the negative electrode active material on the surface of the negative electrode active material layer, and the reflectance Ra on the surface of the negative electrode active material layer is 7.5 ≦ Ra ≦ 16. It is estimated that the charge rate characteristics are improved by combining the negative electrode in the range of 0.0%.

(Negative electrode active material)
As the material for the negative electrode active material, various materials that are used as negative electrode active materials for known lithium secondary batteries can be used. Examples of the material of the negative electrode active material include, for example, carbon materials such as graphite, hard carbon, soft carbon, MCMB, silicon, silicon-containing compounds such as silicon oxide represented by SiO _x (0 <x <2), Examples include metal lithium, metal or metalloid that forms an alloy with lithium, alloys thereof, amorphous compounds mainly composed of oxides such as tin dioxide, and lithium titanate (Li ₄ Ti ₅ O ₁₂ ). . Examples of the metal that forms an alloy with metallic lithium include aluminum, silicon, tin, and germanium.

  As the negative electrode active material according to the present embodiment, it is preferable to use a carbon material having a graphite structure, and it is particularly preferable to use at least one of artificial graphite and natural graphite.

  Moreover, the negative electrode active material layer according to the present embodiment may contain negative electrode active materials having a carbon composition having a graphite structure as a main component and different compositions. Among them, a metal or a semimetal that forms an alloy with lithium typified by silicon and these alloys exhibit high charge / discharge capacity, and therefore, it is preferable to use a mixture of a carbon material having a graphite structure.

  When negative electrode active materials having different compositions are contained, the content of the carbon material having a graphite structure is 70.0% by mass or more with respect to the total of the carbon materials having a graphite structure and the negative electrode active materials having different compositions. Is more preferably 90.0% by mass or more, and particularly preferably 95.0% by mass or more.

  Moreover, the negative electrode active material layer according to the present embodiment may include members such as a conductive additive and a binder in addition to the negative electrode active material.

(Negative electrode conductive material)
Examples of the conductive material include carbon powder such as carbon black, carbon nanotube, carbon material, fine metal powder such as copper, nickel, stainless steel and iron, a mixture of carbon material and fine metal powder, and conductive oxide such as ITO. It is done. Among these, carbon powders such as acetylene black and ethylene black are particularly preferable. In the case where sufficient conductivity can be ensured with only the negative electrode active material, the lithium ion secondary battery 100 may not include a conductive additive.

(Binder)
As the binder, the same as the positive electrode can be used. In addition, for example, cellulose, styrene / butadiene rubber, ethylene / propylene rubber, polyimide resin, polyamideimide resin, acrylic resin, or the like may be used as the binder.

  The contents of the negative electrode active material, the conductive material, and the binder in the negative electrode active material layer 34 are not particularly limited. The constituent ratio of the negative electrode active material in the negative electrode active material layer 34 is preferably 90.0% or more and 98.0% or less in terms of mass ratio. The constituent ratio of the conductive material in the negative electrode active material layer 34 is preferably 0% or more and 3.0% or less in terms of mass ratio, and the constituent ratio of the binder in the negative electrode active material layer 34 is 2.0% by mass ratio. It is preferably 5.0% or less.

  By making content of a negative electrode active material and a binder into the said range, it can prevent that the quantity of a binder is too small and it becomes impossible to form a strong negative electrode active material layer. In addition, the amount of the binder that does not contribute to the electric capacity increases, and the tendency that it is difficult to obtain a sufficient volume energy density can be suppressed.

  Further, by setting the contents of the negative electrode active material and the conductive material in the above ranges, sufficient electronic conductivity can be obtained in the negative electrode active material layer, and high volume energy density and output characteristics can be obtained.

(Negative electrode current collector)
The negative electrode current collector 32 may be any conductive plate material, and for example, a metal thin plate such as aluminum, copper, or nickel foil, or an alloy thin plate thereof may be used. Among these, it is preferable to use a copper metal thin plate.

  Instead of providing the negative electrode active material layer 34, lithium ions may be deposited as metallic lithium on the surface of the negative electrode current collector 32 during charging, and the metallic lithium deposited during discharging may be dissolved as lithium ions. In this case, since the negative electrode active material layer 34 is not necessary, the volume energy density of the battery can be improved. In that case, a copper foil can be used as the negative electrode current collector 32.

  A high charge rate characteristic can be obtained by using the positive electrode 20 and the negative electrode 30 in the lithium ion secondary battery according to the present embodiment in the above-described manner.

  In particular, the ratio Rc1 / Ra of the reflectance Rc1 on the surface of the positive electrode active material layer and the reflectance Ra on the surface of the negative electrode active material layer is preferably 1.00 <Rc1 / Ra ≦ 1.53, and 1.22. It is more preferable that <Rc1 / Ra ≦ 1.38.

  The ratio Rc2 / Ra of the reflectance Rc2 on the surface of the positive electrode active material layer and the reflectance Ra on the surface of the negative electrode active material layer is preferably 0.29 ≦ Rc2 / Ra <1.00, and 0.44 It is more preferable that ≦ Rc2 / Ra ≦ 0.63.

  The ratio Rc3 / Ra of the reflectance Rc3 on the surface of the positive electrode active material layer and the reflectance Ra on the surface of the negative electrode active material layer is preferably 0.13 ≦ Rc3 / Ra ≦ 0.75, and 0.39 More preferably, Rc3 / Ra ≦ 0.60.

  It is presumed that the lithium ion exchange is suitably performed in addition to the electrolyte solution impregnation on the positive electrode active material layer and negative electrode active material layer surfaces and the suppression of side reactions.

(Separator)
The separator 18 only needs to be formed of an electrically insulating porous structure, for example, a single layer of a film made of polyethylene, polypropylene or polyolefin, a stretched film of a laminate or a mixture of the above resins, or cellulose, polyester and Examples thereof include a fiber nonwoven fabric made of at least one constituent material selected from the group consisting of polypropylene.

(Nonaqueous electrolyte solution)
In the non-aqueous electrolyte solution, an electrolyte is dissolved in a non-aqueous solvent, and a cyclic carbonate and a chain carbonate may be contained as a non-aqueous solvent.

  The cyclic carbonate is not particularly limited as long as it can solvate the electrolyte, and a known cyclic carbonate can be used. For example, ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), fluoroethylene carbonate (FEC), or the like can be used.

  The chain carbonate is not particularly limited as long as the viscosity of the cyclic carbonate can be reduced, and a known chain carbonate can be used. Examples thereof include diethyl carbonate (DEC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC). In addition, methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, γ-butyrolactone, 1,2-dimethoxyethane, 1,2-diethoxyethane, and the like may be mixed and used.

  The non-aqueous solvent according to this embodiment contains ethylene carbonate, and the content of the ethylene carbonate is 10 to 30 vol. % Is preferred.

  It is presumed that this is because a part of the electrode surface is decomposed and an excellent film can be formed while suppressing excessive decomposition of ethylene carbonate as a film component.

  Moreover, you may use the nonaqueous electrolyte concerning this embodiment in combination with a gel electrolyte or a solid electrolyte.

Examples of the electrolyte include LiPF ₆ , LiClO ₄ , LiBF ₄ , LiCF ₃ SO ₃ , LiCF ₃ , CF ₂ SO ₃ , LiC (CF ₃ SO ₂ ) ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiN (CF ₃ Lithium salts such as CF ₂ SO ₂ ) ₂ , LiN (CF ₃ SO ₂ ) (C ₄ F ₉ SO ₂ ), LiN (CF ₃ CF ₂ CO) ₂ , LiBOB can be used. In addition, these lithium salts may be used individually by 1 type, and may use 2 or more types together. In particular, LiPF ₆ is preferably included from the viewpoint of conductivity.

When LiPF ₆ is dissolved in a non-aqueous solvent, the concentration of the electrolyte in the non-aqueous electrolyte is preferably adjusted to 0.5 to 2.0 mol / L. When the concentration of the electrolyte is 0.5 mol / L or more, the conductivity of the nonaqueous electrolytic solution can be sufficiently secured, and a sufficient capacity can be easily obtained during charging and discharging. Moreover, by suppressing the electrolyte concentration to within 2.0 mol / L, it is possible to suppress an increase in the viscosity of the non-aqueous electrolyte, to sufficiently secure the mobility of lithium ions, and to obtain a sufficient capacity during charging and discharging. It becomes easy.

Even when LiPF ₆ is mixed with another electrolyte, the lithium ion concentration in the non-aqueous electrolyte is preferably adjusted to 0.5 to 2.0 mol / L, and the lithium ion concentration from LiPF ₆ is 50 mol%. More preferably, it is contained.

(Measurement of reflectance)
The reflectances Rc and Ra according to the present embodiment can be measured using a commercially available spectrocolorimeter or the like.

  The reflectance Rc on the surface of the positive electrode active material layer and the reflectance Ra on the surface of the negative electrode active material layer according to the present embodiment are controlled by post-processing after molding the positive electrode active material layer and the negative electrode active material layer, and molding conditions. can do.

  As a method for controlling the reflectance, it is possible to change the rolling pressure according to the rolling pressure at the time of electrode rolling, the number of rolling, the heating condition at the time of rolling, and the like. It can also be controlled by the material and surface shape of the rolling plate and rolling roll used during rolling.

  Moreover, you may grind | polish the surface of the electrode obtained after rolling, or give a topcoat. In the case of applying a top coat, it is preferable to use a conductive top coat liquid in order to suppress deterioration of battery characteristics.

(Method for producing positive electrode 20 and negative electrode 30)
Next, a method for manufacturing the positive electrode 20 and the negative electrode 30 according to this embodiment will be described.

  A binder and a solvent are mixed with the positive electrode active material or the negative electrode active material. If necessary, a conductive additive may be further added. As the solvent, for example, water, N-methyl-2-pyrrolidone or the like can be used. The mixing method of the components constituting the paint is not particularly limited, and the mixing order is not particularly limited. The paint is applied to the current collectors 22 and 32. There is no restriction | limiting in particular as an application | coating method, The method employ | adopted when producing an electrode normally can be used, For example, the slit die-coating method and a doctor blade method are mentioned.

  Subsequently, the solvent in the paint applied on the current collectors 22 and 32 is removed. The removal method is not particularly limited, and the current collectors 22 and 32 to which the paint is applied may be dried, for example, in an atmosphere of 80 ° C. to 150 ° C.

  Then, the electrode on which the positive electrode active material layer 24 and the negative electrode active material layer 34 are formed in this way is subjected to a press treatment by a roll press device or the like as necessary. The reflectance on the surfaces of the positive electrode active material layer 24 and the negative electrode active material layer 34 can be controlled by adjusting the pressing pressure, the number of times of pressing, and the shape of the pressing material of the pressing device.

  Through the above steps, an electrode in which the electrode active material layers 24 and 34 are formed on the current collectors 22 and 32 is obtained.

(Method for producing lithium ion secondary battery)
Then, the manufacturing method of the lithium ion secondary battery which concerns on this embodiment is demonstrated. The method for manufacturing a lithium ion secondary battery according to the present embodiment includes a positive electrode 20 containing the active material, a negative electrode 30, a separator 10 interposed between the positive electrode and the negative electrode, and a nonaqueous electrolyte solution containing a lithium salt. And a step of enclosing the outer body 50 in the exterior body 50.

  For example, the positive electrode 20 including the active material described above, the negative electrode 30 and the separator 10 are stacked, and the positive electrode 20 and the negative electrode 30 are heated and pressed with a press tool from a direction perpendicular to the stacking direction. 20, the separator 10 and the negative electrode 30 are brought into close contact with each other. Then, for example, a lithium ion secondary battery can be manufactured by putting the laminate 40 into a bag-shaped outer package 50 prepared in advance and injecting a non-aqueous electrolyte solution containing the lithium salt. Instead of injecting the nonaqueous electrolyte solution containing the lithium salt into the outer package, the laminate 40 may be impregnated in advance with the nonaqueous electrolyte solution containing the lithium salt.

  The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has any configuration that has substantially the same configuration as the technical idea described in the claims of the present invention and exhibits the same function and effect. Are included in the technical scope.

  As mentioned above, although embodiment concerning this invention was described in detail, it is not limited to the said embodiment, A various deformation | transformation is possible. For example, in the above-described embodiment, the laminated film type lithium ion secondary battery has been described. However, the present invention can be similarly applied to a lithium ion secondary battery having a structure in which a positive electrode, a negative electrode, and a separator are wound or folded. it can. Furthermore, it can apply suitably also about lithium ion secondary batteries, such as a cylindrical shape, a square shape, and a coin type, as a battery shape.

  Hereinafter, based on the above-described embodiment, the present invention will be described in more detail using examples and comparative examples.

Example 1
(Preparation of positive electrode)
As a positive electrode active material, 97 parts by weight of LiCoO ₂ , 1.5 parts by weight of PVDF (HSV-800) as a binder, and 1.5 parts by weight of carbon black (Super-P) as a conductive assistant are weighed, and a solvent. Was dispersed in N-methyl-2-pyrrolidone (NMP) as a slurry. The obtained slurry was applied onto an aluminum foil having a thickness of 15 μm, and the solvent was removed by drying at a temperature of 120 ° C. for 30 minutes. Then, the press process was performed by linear pressure 2000kgf / cm using the roll press apparatus which heated the roll for rolling to 81 degreeC. After the press treatment, air-cooling was regarded as one cycle, and after three-cycle press treatment, a positive electrode was produced by punching into an electrode size of 18 mm × 22 mm using a mold.

  The reflectance Rc1 at a wavelength of 550 nm on the surface of the obtained positive electrode active material layer was measured using a spectrocolorimeter (manufactured by KONICA MINOLTA: SPECTRO PHOTOMETER CM-5). The average of three measurements was used, and Rc1 of the obtained positive electrode was 8.0%.

The obtained positive electrode was cut into a 10 cm ² square, and the density dc1 of the positive electrode active material layer, the supported amount Lc1 per unit area, and the porosity Pc1 were calculated. As a result, dc1 = 3.80 g / cm ³ and Lc1 = 14. The concentration was 1 mg / cm ² and Pc1 = 23.0%.

(Preparation of negative electrode)
A slurry was prepared by weighing 96 parts by mass of graphite powder as the negative electrode active material, 2.5 parts by weight of styrene / butadiene rubber as the binder, and 1.5 parts by weight of carboxymethylcellulose as the thickener and dispersing in water. The obtained slurry was applied on a copper foil having a thickness of 15 μm, and the solvent was removed by drying at a temperature of 120 ° C. for 30 minutes. Then, the press process was performed by the linear pressure of 500 kgf / cm using the roll press apparatus which heated the roll for rolling to 82 degreeC. After the press treatment, air cooling was defined as one cycle, and a three-cycle press treatment was performed.

  A negative electrode was produced by punching into a 19 mm × 23 mm electrode size using a mold.

  The reflectance Ra at a wavelength of 550 nm on the surface of the obtained negative electrode active material layer was measured using a spectrocolorimeter (manufactured by KONICA MINOLTA: SPECTRO PHOTOMETER CM-5). The average of three measurements was used, Ra of the obtained positive electrode and negative electrode was 7.8%, and the ratio of Rc1 to Ra was Rc1 / Ra1.03.

(Nonaqueous electrolyte solution)
LiPF ₆ as an electrolyte is dissolved to 1.3 mol / L in a non-aqueous solvent in which ethylene carbonate (EC), propylene carbonate (PC), and ethyl methyl carbonate (EMC) are mixed as a non-aqueous electrolyte solution. Used. The volume ratio of EC, PC, and EMC in the non-aqueous solvent was EC: PC: EMC = 10: 10: 80.

(Separator)
A polyethylene microporous membrane having a thickness of 20 μm (porosity: 40%, shutdown temperature: 134 ° C.) was prepared.

(Production of battery cells)
The positive electrode for a lithium ion secondary battery and the negative electrode for a lithium ion secondary battery were laminated via a polyethylene separator to produce an electrode laminate. This was used as one electrode body, and an electrode laminate composed of four layers was produced by the same production method. In addition, since the said positive electrode and negative electrode are equipped with each mixture layer on both surfaces, they are comprised by 3 negative electrodes, 2 positive electrodes, and 4 separators. Furthermore, in the negative electrode of the electrode laminate, a negative electrode lead made of nickel is attached to the protruding end of the copper foil not provided with the negative electrode mixture layer, while the positive electrode mixture layer is provided in the positive electrode of the electrode laminate. The positive electrode lead made of aluminum was attached to the protruding end portion of the aluminum foil that was not formed by an ultrasonic fusion machine. Then, this electrode laminate was fused to an aluminum laminate film for an exterior body, and the laminate film was folded to insert the electrode body into the exterior body. A closed portion was formed by heat-sealing except for one side around the exterior body, and a non-aqueous electrolyte was injected from this opening. And the opening part of the said exterior body was sealed by heat sealing, decompressing with a vacuum sealing machine, and the laminate type battery cell in Example 1 was produced. The battery cell was produced in a dry room.

(Example 2)
In the production of the positive electrode, the battery cell of Example 2 was produced in the same manner as in Example 1 except that the roll for rolling during the press treatment was heated to 88 ° C.

(Example 3)
In the production of the positive electrode, a battery cell of Example 3 was produced in the same manner as in Example 1 except that the roll for rolling during the press treatment was heated to 91 ° C.

Example 4
In the production of the positive electrode, a battery cell of Example 4 was produced in the same manner as in Example 1 except that the roll for rolling during the press treatment was heated to 97 ° C.

(Example 5)
In the production of the positive electrode, the battery cell of Example 5 was produced in the same manner as in Example 1 except that the roll for rolling during the press treatment was set to 105 ° C.

(Example 6)
In the production of the positive electrode, the battery cell of Example 6 was produced in the same manner as in Example 1 except that the roll for rolling during the press treatment was set to 70 ° C.

(Example 7)
In the production of the positive electrode, the battery cell of Example 7 was produced in the same manner as in Example 1 except that the roll for rolling during the press treatment was set to 54 ° C.

(Example 8)
In the production of the positive electrode, a battery cell of Example 8 was produced in the same manner as in Example 3 except that the linear pressure during the press treatment was 1050 kgf / cm.

Example 9
In the production of the positive electrode, a battery cell of Example 9 was produced in the same manner as in Example 3 except that the linear pressure during the press treatment was 1120 kgf / cm.

(Example 10)
In the production of the positive electrode, the battery cell of Example 10 was produced in the same manner as in Example 3 except that the linear pressure during the press treatment was 1500 kgf / cm.

(Example 11)
In the production of the positive electrode, the battery cell of Example 11 was produced in the same manner as in Example 3 except that the linear pressure during the press treatment was 1850 kgf / cm.

(Example 12)
In the production of the positive electrode, the battery cell of Example 12 was produced in the same manner as in Example 3 except that the linear pressure during the press treatment was 2600 kgf / cm.

(Example 13)
In the production of the positive electrode, the battery cell of Example 13 was produced in the same manner as in Example 3 except that the linear pressure during the press treatment was 3000 kgf / cm.

(Example 14)
In the production of the positive electrode, the battery cell of Example 14 was prepared in the same manner as in Example 3, except that the amount of slurry applied was adjusted so that the supported amount Lc1 per unit area was 12.0 mg / cm ^2. Produced. It was 12.1 mg / cm < ² > when the carrying amount Lc1 per unit area of the produced positive electrode was measured.

(Implementation 15)
In the production of the positive electrode, the battery cell of Example 15 was prepared in the same manner as in Example 3 except that the amount of slurry applied was adjusted so that the supported amount Lc1 per unit area was 13.0 mg / cm ^2. Produced. It was 12.8 mg / cm < ² > when the carrying amount Lc1 per unit area of the produced positive electrode was measured.

(Example 16)
In the production of the positive electrode, the battery cell of Example 16 was prepared in the same manner as in Example 3 except that the amount of slurry applied was adjusted so that the supported amount Lc1 per unit area was 15.5 mg / cm ^2. Produced. It was 15.4 mg / cm < ² > when the carrying amount Lc1 per unit area of the produced positive electrode was measured.

(Example 17)
In the production of the positive electrode, the battery cell of Example 17 was prepared in the same manner as in Example 3 except that the amount of slurry applied was adjusted so that the supported amount Lc1 per unit area was 16.0 mg / cm ^2. Produced. When the carrying amount Lc1 per unit area of the produced positive electrode was measured, it was 16.1 mg / cm ² .

(Example 18)
In the production of the positive electrode, the battery cell of Example 18 was prepared in the same manner as in Example 3 except that the amount of slurry applied was adjusted so that the supported amount Lc1 per unit area was 20.0 mg / cm ^2. Produced. When the carrying amount Lc1 per unit area of the produced positive electrode was measured, it was 20.1 mg / cm ² .

(Example 19)
In the production of the positive electrode, the battery cell of Example 19 was prepared in the same manner as in Example 3 except that the amount of slurry applied was adjusted so that the supported amount Lc1 per unit area was 25.0 mg / cm ^2. Produced. When the carrying amount Lc1 per unit area of the produced positive electrode was measured, it was 25.0 mg / cm ² .

(Example 20)
In the production of the positive electrode, the battery cell of Example 20 was prepared in the same manner as in Example 3, except that the amount of slurry applied was adjusted so that the supported amount Lc1 per unit area was 25.5 mg / cm ^2. Produced. When the carrying amount Lc1 per unit area of the produced positive electrode was measured, it was 25.5 mg / cm ² .

(Example 21)
In the production of the negative electrode, a battery cell of Example 21 was produced in the same manner as in Example 3 except that the roll for rolling during the press treatment was heated to 75 ° C.

(Example 22)
In the production of the negative electrode, a battery cell of Example 22 was produced in the same manner as in Example 3, except that the roll for rolling during the press treatment was heated to 79 ° C.

(Example 23)
In the production of the negative electrode, a battery cell of Example 23 was produced in the same manner as in Example 3 except that the roll for rolling during the press treatment was heated to 89 ° C.

(Example 24)
In the production of the negative electrode, a battery cell of Example 24 was produced in the same manner as in Example 3 except that the roll for rolling during the press treatment was heated to 96 ° C.

(Example 25)
In the production of the negative electrode, a battery cell of Example 25 was produced in the same manner as in Example 3 except that the roll for rolling during the press treatment was heated to 98 ° C.

(Example 26)
In the production of the negative electrode, a battery cell of Example 26 was produced in the same manner as in Example 3 except that the roll for rolling during the press treatment was heated to 108 ° C. and the number of presses was 5 cycles.

(Example 27)
In the production of the negative electrode, a battery cell of Example 27 was produced in the same manner as in Example 3 except that the roll for rolling during the press treatment was heated to 115 ° C. and the number of presses was 5 cycles.

(Example 28)
In the production of the negative electrode, a battery cell of Example 28 was produced in the same manner as in Example 1 except that the roll for rolling during the press treatment was heated to 89 ° C.

(Example 29)
A battery cell of Example 29 was made in the same manner as Example 1 except that LiNi _1/3 Mn _1/3 Co _1/3 O ₂ was used as the positive electrode active material.

(Example 30)
A battery cell of Example 30 was made in the same manner as Example 2 except that LiNi _1/3 Mn _1/3 Co _1/3 O ₂ was used as the positive electrode active material.

(Example 31)
A battery cell of Example 31 was made in the same manner as Example 3 except that LiNi _1/3 Mn _1/3 Co _1/3 O ₂ was used as the positive electrode active material.

(Example 32)
A battery cell of Example 32 was made in the same manner as Example 4 except that LiNi _1/3 Mn _1/3 Co _1/3 O ₂ was used as the positive electrode active material.

(Example 33)
A battery cell of Example 33 was made in the same manner as Example 5 except that LiNi _1/3 Mn _1/3 Co _1/3 O ₂ was used as the positive electrode active material.

(Example 34)
A battery cell of Example 34 was made in the same manner as Example 3 except that silicon oxide was used as the negative electrode active material.

(Example 35)
A battery cell of Example 35 was made in the same manner as Example 3 except that lithium titanate (Li ₄ Ti ₅ O ₁₂ ) was used as the negative electrode active material.

(Example 36)
A battery cell of Example 36 was made in the same manner as Example 3 except that a mixture of 48 parts by mass of graphite powder and 48 parts by mass of silicon oxide was used as the negative electrode active material.

(Example 37)
As in Example 3, except that the volume ratio of EC, PC, and EMC was set to EC: PC: EMC = 20: 10: 70 as the nonaqueous solvent of the nonaqueous electrolyte solution. The battery cell of Example 37 was produced.

(Example 38)
As in Example 3, except that the volume ratio of EC, PC, and EMC was EC: PC: EMC = 30: 10: 60 was used as the nonaqueous solvent for the nonaqueous electrolyte solution. The battery cell of Example 38 was produced.

(Example 39)
As in Example 3, except that the volume ratio of EC, PC, and EMC was EC: PC: EMC = 20: 20: 60 as the nonaqueous solvent for the nonaqueous electrolyte solution. The battery cell of Example 39 was produced.

(Example 40)
The battery cell of Example 40 was obtained in the same manner as in Example 3 except that the volume ratio of EC to EMC was set to EC: EMC = 30: 70 as the nonaqueous solvent for the nonaqueous electrolyte solution. Produced.

(Example 41)
The battery cell of Example 41 was obtained in the same manner as in Example 3 except that the volume ratio of EC and EMC was set to EC: EMC = 20: 80 as the nonaqueous solvent for the nonaqueous electrolyte solution. Produced.

(Example 42)
The battery cell of Example 42 was obtained in the same manner as in Example 3 except that the volume ratio of EC to EMC was set to EC: EMC = 10: 90 as the nonaqueous solvent for the nonaqueous electrolyte solution. Produced.

(Example 43)
As in Example 3, except that the volume ratio of EC, PC, and EMC was EC: PC: EMC = 40: 10: 50 as the nonaqueous solvent for the nonaqueous electrolyte solution. The battery cell of Example 43 was produced.

(Example 44)
As in Example 3, except that the volume ratio of FEC, PC, and EMC was set to FEC: PC: EMC = 10: 10: 80 as the nonaqueous solvent of the nonaqueous electrolyte solution. The battery cell of Example 44 was produced.

(Comparative Example 1)
In the production of the positive electrode, a battery cell of Comparative Example 1 was produced in the same manner as in Example 1 except that the roll for rolling during the press treatment was heated to 43 ° C.

(Comparative Example 2)
In the production of the positive electrode, a battery cell of Comparative Example 2 was produced in the same manner as in Example 1 except that the roll for rolling during the press treatment was heated to 110 ° C. and the number of presses was 3 cycles.

(Comparative Example 3)
A battery cell of Comparative Example 3 was produced in the same manner as Comparative Example 1, except that LiNi _1/3 Mn _1/3 Co _1/3 O ₂ was used as the positive electrode active material.

A battery cell of Comparative Example 4 was produced in the same manner as Comparative Example 2 except that LiNi _1/3 Mn _1/3 Co _1/3 O ₂ was used as the positive electrode active material.

  Regarding the positive electrode and the negative electrode used in Examples 2-36 and Comparative Examples 1-4, the reflectance Rc1 at a wavelength of 550 nm on the surface of the positive electrode active material layer and the reflection at a wavelength of 550 nm on the surface of the negative electrode active material layer are the same as in Example 1. The rate Ra was measured, and the ratio Rc1 / Ra was calculated. Further, the density dc1, the supported amount Lc1 per unit area, and the porosity Pc1 of the positive electrode active material layer were also measured in the same manner as in Example 1. The results are shown in Table 1 together with the results in Example 1.

(Example 45)
(Preparation of positive electrode)
95 parts by weight of LiNi _0.85 Co _0.10 Al _0.05 O ₂ as a positive electrode active material, 3.0 parts by weight of PVDF (HSV-800) as a binder, and carbon black (Super- 2.0 parts by weight of P) was weighed and dispersed in N-methyl-2-pyrrolidone (NMP) as a solvent to prepare a slurry. The obtained slurry was applied onto an aluminum foil having a thickness of 15 μm, and the solvent was removed by drying at a temperature of 120 ° C. for 30 minutes. Then, the press process was performed with the linear pressure of 1500 kgf / cm using the roll press apparatus which heated the roll for rolling to 81 degreeC. After the press treatment, air-cooling was regarded as one cycle, and after three-cycle press treatment, a positive electrode was produced by punching into an electrode size of 18 mm × 22 mm using a mold.

  The reflectance Rc2 at a wavelength of 550 nm on the surface of the obtained positive electrode active material layer was measured using a spectrocolorimeter (manufactured by KONICA MINOLTA: SPECTRO PHOTOMETER CM-5). The average of three measurements was used, and Rc2 of the obtained positive electrode was 3.5%.

The obtained positive electrode was cut into a 10 cm ² square, and the positive electrode active material layer density dc2, the supported amount Lc2 per unit area, and the porosity Pc2 were calculated. As a result, dc2 = 3.30 g / cm ³ , Lc2 = 13. It was 0 mg / cm ² and Pc2 = 23.0%.

  A battery cell of Example 45 was made in the same manner as Example 1 except that the above positive electrode was used. The ratio of the reflectances Ra and Rc2 at a wavelength of 550 nm on the surface of the negative electrode active material layer was Rc2 / Ra0.44.

(Example 46)
In the production of the positive electrode, a battery cell of Example 46 was produced in the same manner as in Example 45 except that the roll for rolling during the press treatment was heated to 88 ° C.

(Example 47)
In the production of the positive electrode, a battery cell of Example 47 was produced in the same manner as in Example 45 except that the roll for rolling during the press treatment was heated to 91 ° C.

(Example 48)
In the production of the positive electrode, a battery cell of Example 48 was produced in the same manner as in Example 45 except that the roll for rolling during the press treatment was heated to 97 ° C.

(Example 49)
In the production of the positive electrode, a battery cell of Example 49 was produced in the same manner as in Example 45, except that the roll for rolling during the press treatment was set to 105 ° C.

(Example 50)
In the production of the positive electrode, a battery cell of Example 50 was produced in the same manner as in Example 45 except that the roll for rolling during the press treatment was 105 ° C. and the number of presses was 3 cycles.

(Example 51)
In the production of the positive electrode, a battery cell of Example 51 was produced in the same manner as in Example 45, except that the roll for rolling during the press treatment was set to 72 ° C.

(Example 52)
In the production of the positive electrode, a battery cell of Example 52 was produced in the same manner as in Example 45 except that the roll for rolling during the press treatment was 118 ° C. and the number of presses was 5 cycles.

(Example 53)
In the production of the positive electrode, a battery cell of Example 53 was produced in the same manner as in Example 47, except that the linear pressure during the press treatment was 1000 kgf / cm.

(Example 54)
In the production of the positive electrode, a battery cell of Example 54 was produced in the same manner as in Example 47, except that the linear pressure during the press treatment was 1200 kgf / cm.

(Example 55)
In the production of the positive electrode, a battery cell of Example 55 was produced in the same manner as in Example 47, except that the linear pressure during the press treatment was 1400 kgf / cm.

(Example 56)
In the production of the positive electrode, a battery cell of Example 56 was produced in the same manner as in Example 47, except that the linear pressure during the press treatment was 1800 kgf / cm.

(Example 57)
In the production of the positive electrode, a battery cell of Example 57 was produced in the same manner as in Example 47 except that the linear pressure during the press treatment was 2000 kgf / cm.

(Example 58)
In the production of the positive electrode, a battery cell of Example 58 was produced in the same manner as in Example 47, except that the linear pressure during the press treatment was 2500 kgf / cm.

(Example 59)
In the production of the positive electrode, the battery cell of Example 59 was prepared in the same manner as in Example 47, except that the amount of slurry applied was adjusted so that the supported amount Lc2 per unit area was 11.0 mg / cm ^2. Produced. When the carrying amount Lc2 per unit area of the produced positive electrode was measured, it was 11.0 mg / cm ² .

(Example 60)
In the production of the positive electrode, the battery cell of Example 60 was prepared in the same manner as in Example 47 except that the amount of slurry applied was adjusted so that the supported amount Lc2 per unit area was 12.0 mg / cm ^2. Produced. It was 12.2 mg / cm < ² > when the load Lc2 per unit area of the produced positive electrode was measured.

(Example 61)
In the production of the positive electrode, the battery cell of Example 61 was prepared in the same manner as in Example 47, except that the amount of slurry applied was adjusted so that the supported amount Lc2 per unit area was 15.0 mg / cm ^2. Produced. It was 14.9 mg / cm < ² > when the carrying amount Lc2 per unit area of the produced positive electrode was measured.

(Example 62)
In the production of the positive electrode, the battery cell of Example 62 was prepared in the same manner as in Example 47 except that the amount of slurry applied was adjusted so that the supported amount Lc2 per unit area was 16.0 mg / cm ^2. Produced. It was 16.0 mg / cm < ² > when the carrying amount Lc2 per unit area of the produced positive electrode was measured.

(Example 63)
In the production of the positive electrode, the battery cell of Example 63 was made in the same manner as in Example 47 except that the amount of slurry applied was adjusted so that the supported amount Lc2 per unit area was 20.0 mg / cm ^2. Produced. It was 19.8 mg / cm < ² > when the carrying amount Lc2 per unit area of the produced positive electrode was measured.

(Example 64)
The battery cell of Example 64 was prepared in the same manner as in Example 47 except that the amount of slurry applied was adjusted so that the supported amount Lc2 per unit area was 24.0 mg / cm ² in the production of the positive electrode. Produced. It was 24.0 mg / cm < ² > when the carrying amount Lc2 per unit area of the produced positive electrode was measured.

(Example 65)
In the production of the positive electrode, the battery cell of Example 65 was prepared in the same manner as in Example 47 except that the amount of slurry applied was adjusted so that the supported amount Lc2 per unit area was 24.5 mg / cm ^2. Produced. It was 24.4 mg / cm < ² > when the carrying amount Lc2 per unit area of the produced positive electrode was measured.

Example 66
A battery cell of Example 66 was produced in the same manner as in Example 47 except that the negative electrode produced in Example 21 was used.

(Example 67)
A battery cell of Example 67 was made in the same manner as Example 47, except that the negative electrode produced in Example 22 was used.

(Example 68)
A battery cell of Example 68 was made in the same manner as Example 47, except that the negative electrode produced in Example 23 was used.

(Example 69)
A battery cell of Example 62 was made in the same manner as Example 47 except that the negative electrode produced in Example 24 was used.

(Example 70)
A battery cell of Example 70 was produced in the same manner as in Example 47 except that the negative electrode produced in Example 25 was used.

(Example 71)
A battery cell of Example 71 was made in the same manner as Example 47, except that the negative electrode produced in Example 26 was used.

(Example 72)
A battery cell of Example 72 was made in the same manner as Example 47, except that the negative electrode produced in Example 27 was used.

(Example 73)
A battery cell of Example 73 was made in the same manner as Example 45, except that the negative electrode produced in Example 28 was used.

(Example 74)
A battery cell of Example 74 was made in the same manner as Example 45, except that LiNi _0.6 Mn _0.2 Co _0.2 O ₂ was used as the positive electrode active material.

(Example 75)
A battery cell of Example 75 was made in the same manner as Example 46, except that LiNi _0.6 Mn _0.2 Co _0.2 O ₂ was used as the positive electrode active material.

(Example 76)
A battery cell of Example 76 was made in the same manner as Example 47, except that LiNi _0.6 Mn _0.2 Co _0.2 O ₂ was used as the positive electrode active material.

(Example 77)
A battery cell of Example 77 was made in the same manner as Example 48, except that LiNi _0.6 Mn _0.2 Co _0.2 O ₂ was used as the positive electrode active material.

(Example 78)
A battery cell of Example 78 was made in the same manner as Example 49 except that LiNi _0.6 Mn _0.2 Co _0.2 O ₂ was used as the positive electrode active material.

(Example 79)
A battery cell of Example 79 was made in the same manner as Example 45 except that LiNi _0.8 Mn _0.1 Co _0.1 O ₂ was used as the positive electrode active material.

(Example 80)
A battery cell of Example 80 was made in the same manner as Example 46, except that LiNi _0.8 Mn _0.1 Co _0.1 O ₂ was used as the positive electrode active material.

(Example 81)
A battery cell of Example 81 was made in the same manner as Example 47, except that LiNi _0.8 Mn _0.1 Co _0.1 O ₂ was used as the positive electrode active material.

(Example 82)
A battery cell of Example 82 was made in the same manner as Example 48, except that LiNi _0.8 Mn _0.1 Co _0.1 O ₂ was used as the positive electrode active material.

(Example 83)
A battery cell of Example 83 was made in the same manner as Example 49, except that LiNi _0.8 Mn _0.1 Co _0.1 O ₂ was used as the positive electrode active material.

(Example 84)
A battery cell of Example 84 was made in the same manner as Example 47, except that silicon oxide was used as the negative electrode active material.

(Example 85)
A battery cell of Example 85 was made in the same manner as Example 47, except that lithium titanate (Li ₄ Ti ₅ O ₁₂ ) was used as the negative electrode active material.

(Example 86)
A battery cell of Example 86 was made in the same manner as Example 47, except that a mixture of 48 parts by mass of graphite powder and 48 parts by mass of silicon oxide was used as the negative electrode active material.

(Example 87)
As Example 47, except that the volume ratio of EC, PC, and EMC was EC: PC: EMC = 20: 10: 70 was used as the nonaqueous solvent for the nonaqueous electrolyte solution. The battery cell of Example 87 was produced.

(Example 88)
As Example 47, except that the volume ratio of EC: PC: EMC was set to EC: PC: EMC = 30: 10: 60 as the nonaqueous solvent for the nonaqueous electrolyte solution. The battery cell of Example 88 was produced.

Example 89
As Example 47, except that the volume ratio of EC, PC, and EMC was EC: PC: EMC = 20: 20: 60 was used as the nonaqueous solvent for the nonaqueous electrolyte solution. The battery cell of Example 89 was produced.

(Example 90)
The battery cell of Example 90 was obtained in the same manner as in Example 47 except that the volume ratio of EC to EMC was set to EC: EMC = 30: 70 as the nonaqueous solvent for the nonaqueous electrolyte solution. Produced.

(Example 91)
The battery cell of Example 91 was obtained in the same manner as in Example 47 except that the volume ratio of EC to EMC was set to EC: EMC = 20: 80 as the nonaqueous solvent for the nonaqueous electrolyte solution. Produced.

(Example 92)
The battery cell of Example 92 was obtained in the same manner as in Example 47 except that the volume ratio of EC and EMC was set to EC: EMC = 10: 90 as the nonaqueous solvent for the nonaqueous electrolyte solution. Produced.

(Example 93)
As in Example 47, except that the volume ratio of EC, PC, and EMC was EC: PC: EMC = 40: 10: 50 was used as the nonaqueous solvent for the nonaqueous electrolyte solution. The battery cell of Example 93 was produced.

(Example 94)
As Example 47, except that the volume ratio of FEC, PC, and EMC was set to FEC: PC: EMC = 10: 10: 80 as the nonaqueous solvent for the nonaqueous electrolyte solution. The battery cell of Example 94 was produced.

(Comparative Example 5)
In the production of the positive electrode, a battery cell of Comparative Example 5 was produced in the same manner as in Example 41 except that the roll for rolling during the press treatment was heated to 45 ° C.

(Comparative Example 6)
In the production of the positive electrode, a battery cell of Comparative Example 6 was produced in the same manner as in Example 41 except that the roll for rolling during the press treatment was heated to 110 ° C. and the number of presses was 5 cycles.

(Comparative Example 7)
A battery cell of Comparative Example 7 was produced in the same manner as Comparative Example 5 except that LiNi _0.6 Mn _0.2 Co _0.2 O ₂ was used as the positive electrode active material.

(Comparative Example 8)
A battery cell of Comparative Example 8 was produced in the same manner as Comparative Example 6 except that LiNi _0.6 Mn _0.2 Co _0.2 O ₂ was used as the positive electrode active material.

(Comparative Example 9)
A battery cell of Comparative Example 9 was produced in the same manner as Comparative Example 5 except that LiNi _0.8 Mn _0.1 Co _0.1 O ₂ was used as the positive electrode active material.

(Comparative Example 10)
A battery cell of Comparative Example 10 was produced in the same manner as Comparative Example 6, except that LiNi _0.8 Mn _0.1 Co _0.1 O ₂ was used as the positive electrode active material.

  Regarding the positive electrode and the negative electrode used in Examples 46 to 86 and Comparative Examples 5 to 10, similarly to Example 44, the reflectance Rc2 at a wavelength of 550 nm on the surface of the positive electrode active material layer and the reflection at a wavelength of 550 nm on the surface of the negative electrode active material layer The rate Ra was measured, and the ratio Rc2 / Ra was calculated. Further, the density dc2, the supported amount Lc2 per unit area, and the porosity Pc2 of the positive electrode active material layer were also measured in the same manner as in Example 45. The results are shown in Table 2 together with the results in Example 45.

(Example 95)
(Preparation of positive electrode)
Weighing 88 parts by weight of LiFePO ₄ as a positive electrode active material, 6.0 parts by weight of PVDF (HSV-800) as a binder, and 6.0 parts by weight of carbon black (Super-P) as a conductive assistant, and solvent Was dispersed in N-methyl-2-pyrrolidone (NMP) as a slurry. The obtained slurry was applied onto an aluminum foil having a thickness of 15 μm, and the solvent was removed by drying at a temperature of 120 ° C. for 30 minutes. Then, the press process was performed by the linear pressure of 1200 kgf / cm using the roll press apparatus which heated the roll for rolling to 71 degreeC. After the press treatment, air-cooling was regarded as one cycle, and after three-cycle press treatment, a positive electrode was produced by punching into an electrode size of 18 mm × 22 mm using a mold.

  The reflectance Rc3 at a wavelength of 550 nm on the surface of the obtained positive electrode active material layer was measured using a spectrocolorimeter (manufactured by KONICA MINOLTA: SPECTRO PHOTOMETER CM-5). The average of three measurements was used, and Rc3 of the obtained positive electrode was 2.0%.

The obtained positive electrode was cut into a 10 cm ² square, and the positive electrode active material layer density dc3, the supported amount Lc3 per unit area, and the porosity Pc3 were calculated. As a result, dc3 = 2.00 g / cm ³ , Lc3 = 9. It was 8 mg / cm ² and Pc3 = 23.0%.

  A battery cell of Example 95 was made in the same manner as Example 1 except that the above positive electrode was used. The ratio of the reflectance Ra to Rc3 at a wavelength of 550 nm on the surface of the negative electrode active material layer was Rc3 / Ra0.25.

(Example 96)
In the production of the positive electrode, a battery cell of Example 96 was produced in the same manner as in Example 95, except that the roll for rolling during the press treatment was heated to 78 ° C.

(Example 97)
In the production of the positive electrode, a battery cell of Example 97 was produced in the same manner as in Example 95, except that the roll for rolling during the press treatment was heated to 81 ° C.

(Example 98)
In the production of the positive electrode, a battery cell of Example 98 was produced in the same manner as in Example 95, except that the roll for rolling during the press treatment was heated to 87 ° C.

Example 99
In the production of the positive electrode, a battery cell of Example 99 was produced in the same manner as in Example 95, except that the roll for rolling during the press treatment was set to 95 ° C.

(Example 100)
In the production of the positive electrode, a battery cell of Example 100 was produced in the same manner as in Example 95 except that the roll for rolling during the press treatment was 95 ° C. and the number of presses was 5 cycles.

(Example 101)
In the production of the positive electrode, a battery cell of Example 101 was produced in the same manner as in Example 95, except that the roll for rolling during the press treatment was set at 108 ° C. and the number of presses was 5 cycles.

(Example 102)
In the production of the positive electrode, a battery cell of Example 102 was produced in the same manner as in Example 97, except that the linear pressure during the press treatment was set to 900 kgf / cm.

(Example 103)
In the production of the positive electrode, a battery cell of Example 103 was produced in the same manner as in Example 97, except that the linear pressure during the press treatment was 1000 kgf / cm.

(Example 104)
In the production of the positive electrode, a battery cell of Example 104 was produced in the same manner as in Example 97, except that the linear pressure during the press treatment was 1500 kgf / cm.

(Example 105)
In the production of the positive electrode, a battery cell of Example 105 was produced in the same manner as in Example 97, except that the linear pressure during the press treatment was 1800 kgf / cm.

(Example 106)
In the production of the positive electrode, the battery cell of Example 106 was prepared in the same manner as in Example 97 except that the amount of slurry applied was adjusted so that the supported amount Lc3 per unit area was 7.7 mg / cm ^2. Produced. It was 7.8 mg / cm < ² > when the carrying amount Lc3 per unit area of the produced positive electrode was measured.

(Example 107)
In the production of the positive electrode, the battery cell of Example 107 was prepared in the same manner as in Example 97, except that the amount of slurry applied was adjusted so that the supported amount Lc3 per unit area was 8.0 mg / cm ^2. Produced. The amount Lc3 supported per unit area of the produced positive electrode was measured and found to be 8.0 mg / cm ² .

(Example 108)
In the production of the positive electrode, the battery cell of Example 108 was prepared in the same manner as in Example 97 except that the amount of slurry applied was adjusted so that the supported amount Lc3 per unit area was 12.0 mg / cm ^2. Produced. It was 12.1 mg / cm < ² > when the load Lc3 per unit area of the produced positive electrode was measured.

(Example 109)
In the production of the positive electrode, the battery cell of Example 109 was prepared in the same manner as in Example 97 except that the amount of slurry applied was adjusted so that the supported amount Lc3 per unit area was 14.8 mg / cm ^2. Produced. It was 15.0 mg / cm < ² > when the load Lc3 per unit area of the produced positive electrode was measured.

(Example 110)
In the production of the positive electrode, the battery cell of Example 110 was prepared in the same manner as in Example 97 except that the amount of slurry applied was adjusted so that the supported amount Lc3 per unit area was 15.5 mg / cm ^2. Produced. It was 15.3 mg / cm < ² > when the loading amount Lc3 per unit area of the produced positive electrode was measured.

(Example 111)
A battery cell of Example 111 was produced in the same manner as in Example 97 except that the negative electrode produced in Example 21 was used.

(Example 112)
A battery cell of Example 112 was produced in the same manner as in Example 97, except that the negative electrode produced in Example 22 was used.

(Example 113)
A battery cell of Example 113 was made in the same manner as Example 97 except that the negative electrode produced in Example 23 was used.

(Example 114)
A battery cell of Example 114 was made in the same manner as Example 97, except that the negative electrode produced in Example 24 was used.

(Example 115)
A battery cell of Example 115 was made in the same manner as Example 97, except that the negative electrode produced in Example 25 was used.

(Example 116)
A battery cell of Example 116 was made in the same manner as Example 97, except that the negative electrode produced in Example 26 was used.

(Example 117)
A battery cell of Example 117 was produced in the same manner as in Example 97 except that the negative electrode produced in Example 27 was used.

(Example 118)
A battery cell of Example 118 was made in the same manner as Example 95, except that the negative electrode produced in Example 28 was used.

(Example 119)
A battery cell of Example 119 was made in the same manner as Example 95, except that LiFe _0.4 Mn _0.6 PO ₄ was used as the positive electrode active material.

(Example 120)
A battery cell of Example 120 was made in the same manner as Example 96, except that LiFe _0.4 Mn _0.6 PO ₄ was used as the positive electrode active material.

(Example 121)
A battery cell of Example 121 was made in the same manner as Example 97, except that LiFe _0.4 Mn _0.6 PO ₄ was used as the positive electrode active material.

(Example 122)
A battery cell of Example 122 was made in the same manner as Example 98, except that LiFe _0.4 Mn _0.6 PO ₄ was used as the positive electrode active material.

(Example 123)
A battery cell of Example 123 was made in the same manner as Example 99, except that LiFe _0.4 Mn _0.6 PO ₄ was used as the positive electrode active material.

(Example 124)
A battery cell of Example 124 was made in the same manner as Example 95 except that LiVOPO ₄ was used as the positive electrode active material.

(Example 125)
A battery cell of Example 125 was made in the same manner as Example 96 except that LiVOPO ₄ was used as the positive electrode active material.

(Example 126)
A battery cell of Example 126 was made in the same manner as Example 97 except that LiVOPO ₄ was used as the positive electrode active material.

(Example 127)
A battery cell of Example 127 was made in the same manner as Example 98 except that LiVOPO ₄ was used as the positive electrode active material.

(Example 128)
A battery cell of Example 128 was made in the same manner as Example 99 except that LiVOPO ₄ was used as the positive electrode active material.

(Example 129)
A battery cell of Example 129 was made in the same manner as Example 97, except that silicon oxide was used as the negative electrode active material.

(Example 130)
A battery cell of Example 130 was made in the same manner as Example 97, except that lithium titanate (Li ₄ Ti ₅ O ₁₂ ) was used as the negative electrode active material.

(Example 131)
A battery cell of Example 131 was made in the same manner as Example 97, except that a mixture of 48 parts by mass of graphite powder and 48 parts by mass of silicon oxide was used as the negative electrode active material.

(Example 132)
As Example 97, except that the volume ratio of EC, PC, and EMC was EC: PC: EMC = 20: 10: 70 was used as the nonaqueous solvent for the nonaqueous electrolyte solution. The battery cell of Example 132 was produced.

(Example 133)
As Example 97, except that the volume ratio of EC: PC: EMC was set to EC: PC: EMC = 30: 10: 60 as the nonaqueous solvent for the nonaqueous electrolyte solution. The battery cell of Example 133 was produced.

(Example 134)
As Example 97, except that the volume ratio of EC, PC, and EMC was EC: PC: EMC = 20: 20: 60 was used as the nonaqueous solvent for the nonaqueous electrolyte solution. The battery cell of Example 134 was produced.

(Example 135)
The battery cell of Example 135 was obtained in the same manner as in Example 97 except that the volume ratio of EC to EMC was set to EC: EMC = 30: 70 as the nonaqueous solvent for the nonaqueous electrolyte solution. Produced.

(Example 136)
The battery cell of Example 136 was obtained in the same manner as in Example 97 except that the volume ratio of EC to EMC was set to EC: EMC = 20: 80 as the nonaqueous solvent for the nonaqueous electrolyte solution. Produced.

(Example 137)
The battery cell of Example 137 was obtained in the same manner as in Example 97 except that the volume ratio of EC to EMC was set to EC: EMC = 10: 90 as the nonaqueous solvent for the nonaqueous electrolyte solution. Produced.

(Example 138)
As Example 97, except that the volume ratio of EC, PC, and EMC was EC: PC: EMC = 40: 10: 50 was used as the nonaqueous solvent for the nonaqueous electrolyte solution. The battery cell of Example 138 was produced.

(Example 139)
As Example 97, except that the volume ratio of FEC, PC, and EMC was set to FEC: PC: EMC = 10: 10: 80 as the nonaqueous solvent for the nonaqueous electrolyte solution. The battery cell of Example 139 was produced.

(Comparative Example 11)
In production of the positive electrode, a battery cell of Comparative Example 11 was produced in the same manner as in Example 95, except that the roll for rolling during the press treatment was heated to 35 ° C.

(Comparative Example 12)
In the production of the positive electrode, a battery cell of Comparative Example 12 was produced in the same manner as in Example 95, except that the roll for rolling during the press treatment was heated to 100 ° C. and the number of presses was 5 cycles.

(Comparative Example 13)
A battery cell of Comparative Example 13 was produced in the same manner as Comparative Example 11 except that LiFe _0.4 Mn _0.6 PO ₄ was used as the positive electrode active material.

(Comparative Example 14)
A battery cell of Comparative Example 14 was produced in the same manner as Comparative Example 12 except that LiFe _0.4 Mn _0.6 PO ₄ was used as the positive electrode active material.

(Comparative Example 15)
A battery cell of Comparative Example 15 was produced in the same manner as Comparative Example 11 except that LiVOPO ₄ was used as the positive electrode active material.

(Comparative Example 16)
A battery cell of Comparative Example 16 was produced in the same manner as Comparative Example 12 except that LiVOPO ₄ was used as the positive electrode active material.

  Regarding the positive electrode and the negative electrode used in Examples 96 to 131 and Comparative Examples 11 to 16, similarly to Example 95, the reflectance Rc3 at a wavelength of 550 nm on the surface of the positive electrode active material layer and the reflection at a wavelength of 550 nm on the surface of the negative electrode active material layer The rate Ra was measured, and the ratio Rc3 / Ra was calculated. Further, the density dc3, the supported amount Lc3 per unit area, and the porosity Pc3 of the positive electrode active material layer were also measured in the same manner as in Example 95. The results are shown in Table 3 together with the results in Example 95.

(Measurement of charge rate characteristics)
Using the fabricated battery cells of Examples 1 to 131 and Comparative Examples 1 to 16, the charge rate characteristics were measured under the following conditions.

First, constant current charging is performed until the voltage reaches 4.3 V (vs. Li ^/ Li ⁺ ) at a current density of 0.1 C, and further 4.3 V (vs. Li) until the current density decreases to 0.05 C. / Li ⁺ ) was subjected to constant voltage charging.

After the end of the constant voltage charge, after a 5 minute rest period, constant current discharge was performed until the voltage became 2.5 V (vs. Li ^/ Li ⁺ ) at a current density of 0.1 C, and the initial charge and discharge were performed. It was.

After the first charge / discharge, constant current charging is performed until the voltage reaches 4.3 V (vs. Li ^/ Li ⁺ ) at a current density of 0.2 C, and then 4.3 V (until the current density decreases to 0.05 C ( vs. Li ^/ Li ⁺ ) was subjected to constant voltage charging, and the charge capacity at 0.2 C was measured.

After measuring the charge capacity at 0.2 C, after a 5-minute pause, constant current discharge was performed at a current density of 0.1 C until the voltage reached 2.5 V (vs. Li ^/ Li ⁺ ), and the battery cell was discharged. It was.

The discharged battery cell is charged at a constant current density of 2.0 C until the voltage reaches 4.3 V (vs. Li ^/ Li ⁺ ), and further 4.3 V until the current density decreases to 0.05 C. (Vs. Li ^/ Li ⁺ ) was subjected to constant voltage charging, and the charge capacity at 2.0 C was measured.

The ratio of the charge capacity at 2.0 C to the charge capacity at 0.2 C was calculated as an equation (Expression 1) as the charge rate characteristic, and the charge rate characteristic was evaluated.
(Equation 1)
Charging rate characteristic (%) = (charging capacity at 2.0 C / charging capacity at 0.2 C) * 100 (1)

(Measurement of load discharge characteristics)
Using the produced battery cells of Examples 1 to 131 and Comparative Examples 1 to 16, load discharge characteristics were measured under the following conditions.

First, constant current charging is performed until the voltage reaches 4.3 V (vs. Li ^/ Li ⁺ ) at a current density of 0.1 C, and further 4.3 V (vs. Li) until the current density decreases to 0.05 C. / Li ⁺ ) was subjected to constant voltage charging.

After the end of the constant voltage charge, after a 5 minute rest period, constant current discharge was performed until the voltage became 2.5 V (vs. Li ^/ Li ⁺ ) at a current density of 0.1 C, and the initial charge and discharge were performed. It was.

After the first charge / discharge, constant current charging is performed until the voltage reaches 4.3 V (vs. Li ^/ Li ⁺ ) at a current density of 0.2 C, and then 4.3 V (until the current density decreases to 0.05 C ( vs. Li ^/ Li ⁺ ) was performed at a constant voltage.

After charging, after resting for 5 minutes, constant current discharge was performed at a current density of 0.2 C until the voltage reached 2.5 V (vs. Li ^/ Li ⁺ ), and the discharge capacity at 0.2 C was measured.

After measuring the discharge capacity, after resting for 5 minutes, the discharged battery cells were charged at a current density of 2.0 C until the voltage reached 4.3 V (vs. Li ^/ Li ⁺ ), and the current was further increased. Constant voltage charging was performed at 4.3 V (vs. Li ^/ Li ⁺ ) until the density dropped to 0.05C.

After charging, after a pause of minutes, constant current discharge was performed at a current density of 2.0 C until the voltage reached 2.5 V (vs. Li ^/ Li ⁺ ), and the discharge capacity at 2.0 C was measured.

The ratio of the discharge capacity at 2.0 C to the discharge capacity at 0.2 C was calculated as an expression expressed by (Equation 2) as load discharge characteristics, and the load discharge characteristics were evaluated.
(Equation 2)
Load discharge characteristics (%) = (discharge capacity at 2.0 C / discharge capacity at 0.2 C) * 100 (2)

  The charge rate characteristics and load discharge characteristics of the battery cells of Examples 1-36 and Comparative Examples 1-4 are shown in Table 1, and the charge rate characteristics and load discharge of the battery cells of Examples 45-86 and Comparative Examples 5-10 are shown in Table 1. The results of the characteristics are shown in Table 2, and the results of the charge rate characteristics and load discharge characteristics of the battery cells of Examples 95 to 131 and Comparative Examples 11 to 16 are shown in Table 3, respectively.

  In Table 1, as shown from the results of Examples 1 to 7 and Comparative Examples 1 and 2, the positive electrode having a reflectance Rc1 at a wavelength of 550 nm on the surface of the positive electrode active material layer is 2.0 ≦ Rc1 ≦ 12.0% It was confirmed that the charge rate characteristics and the load discharge characteristics are greatly improved by using.

  In particular, as shown from the results of Examples 1 to 5, the compound represented by the general formula (1) is used as the positive electrode active material, and the reflectance Rc1 at a wavelength of 550 nm on the surface of the positive electrode active material layer is 8.0 ≦ It was confirmed that a particularly high charge rate characteristic was exhibited by setting Rc1 ≦ 12.0%. Further, as shown from the results of Examples 29 to 33 and Comparative Examples 3 and 4, it was confirmed that similar results were obtained even when different compounds represented by the general formula (1) were used as the positive electrode active material. did.

  The results of Examples 8 to 20 indicate that the density dc1 of the positive electrode active material layer, the loading amount Lc1 of the positive electrode active material layer, and the porosity Pc1 of the positive electrode active material layer each contribute to the charge rate characteristics. It can be seen that the charge rate characteristics are particularly improved in each specific range.

  Furthermore, from the results of Examples 21 to 28, Rc / Ra, which is the ratio of the reflectance Ra at a wavelength of 550 nm on the surface of the negative electrode active material layer and the reflectance Rc on the surface of the positive electrode active material layer, is controlled within a specific range. It turns out that the lithium ion secondary battery which shows a high charge rate characteristic by this can be obtained. Moreover, it turns out that a high charge rate characteristic is shown from the result of Examples 34-36 by using a carbon material as a negative electrode active material.

  Moreover, about the battery cell of Examples 1-36 and Comparative Examples 1-4 which evaluated the charge rate characteristic and the load discharge characteristic, the battery cell after evaluation was disassembled in the glove box in argon atmosphere, respectively. The positive electrode and the negative electrode were taken out, washed with dimethyl carbonate and dried. After drying, the reflectance Rc1 at a wavelength of 550 nm on the surface of the positive electrode active material layer and the reflectance Ra at a wavelength of 550 nm on the surface of the negative electrode active material layer were measured, and it was confirmed that there was no change before and after the evaluation.

  In Table 2, as shown from the results of Examples 45 to 52 and Comparative Examples 5 and 6, the positive electrode whose reflectance Rc2 at the wavelength of 550 nm on the surface of the positive electrode active material layer is 2.0 ≦ Rc2 ≦ 12.0% It was confirmed that the charge rate characteristics and the load discharge characteristics are greatly improved by using.

  In particular, as shown in the results of Examples 45 to 50, the compound represented by the general formula (2) was used as the positive electrode active material, and the reflectance Rc2 at a wavelength of 550 nm on the surface of the positive electrode active material layer was 3.5 ≦ It was confirmed that a particularly high load discharge characteristic was exhibited by setting Rc2 ≦ 7.8%. Moreover, as shown from the results of Examples 74 to 83 and Comparative Examples 7 to 10, it was confirmed that similar results were obtained even when different compounds represented by the general formula (2) were used as the positive electrode active material. did.

  From the results of Examples 53 to 65, it is shown that the density dc2 of the positive electrode active material layer, the loading amount Lc2 of the positive electrode active material layer, and the porosity Pc2 of the positive electrode active material layer each contribute to the load discharge characteristics. It can be seen that the load discharge characteristics are improved particularly in a specific range.

  Further, from the results of Examples 66 to 73, the ratio Rc / Ra, which is the ratio between the reflectance Ra at a wavelength of 550 nm on the surface of the negative electrode active material layer and the reflectance Rc on the surface of the positive electrode active material layer, is controlled within a specific range. It can be seen that a lithium ion secondary battery exhibiting high load discharge characteristics can be obtained. Moreover, it turns out that a high load discharge characteristic is shown from the result of Examples 84-86 by using a carbon material as a negative electrode active material.

  Moreover, about the battery cell of Example 45-86 and Comparative Examples 5-10 which evaluated the charge rate characteristic and the load discharge characteristic, the battery cell after evaluation was disassembled in the glove box in argon atmosphere, respectively. The positive electrode and the negative electrode were taken out, washed with dimethyl carbonate and dried. After drying, the reflectance Rc2 at a wavelength of 550 nm on the surface of the positive electrode active material layer and the reflectance Ra at a wavelength of 550 nm on the surface of the negative electrode active material layer were measured, and it was confirmed that there was no change before and after the evaluation.

  In Table 3, as shown from the results of Examples 95 to 101 and Comparative Examples 11 and 12, the positive electrode whose reflectance Rc3 at a wavelength of 550 nm on the surface of the positive electrode active material layer is 2.0 ≦ Rc3 ≦ 12.0% It was confirmed that the charge rate characteristics and the load discharge characteristics are greatly improved by using.

  In particular, as shown from the results of Examples 95 to 98, the compound represented by the general formula (3) was used as the positive electrode active material, and the reflectance Rc at a wavelength of 550 nm on the surface of the positive electrode active material layer was 2.0 ≦ It was confirmed that particularly high load discharge characteristics were exhibited by setting Rc3 ≦ 5.8%. Moreover, as shown from the results of Examples 119 to 128 and Comparative Examples 13 to 16, it was confirmed that similar results were obtained even when different compounds represented by the general formula (3) were used as the positive electrode active material. did.

  From the results of Examples 102 to 110, it is shown that the density dc3 of the positive electrode active material layer, the loading amount Lc3 of the positive electrode active material layer, and the porosity Pc3 of the positive electrode active material layer each contribute to the load discharge characteristics. It can be seen that the load discharge characteristics are improved particularly in a specific range.

  Furthermore, from the results of Examples 111 to 118, the ratio Rc3 / Ra, which is the ratio of the reflectance Ra at a wavelength of 550 nm on the surface of the negative electrode active material layer and the reflectance Rc3 on the surface of the positive electrode active material layer, is controlled within a specific range. It can be seen that a lithium ion secondary battery exhibiting high load discharge characteristics can be obtained. Moreover, it can be seen from the results of Examples 129 to 131 that high load discharge characteristics are exhibited by using a carbon material as the negative electrode active material.

  Moreover, about the battery cell of Examples 95-131 and Comparative Examples 11-16 which evaluated the charge rate characteristic and the load discharge characteristic, the battery cell after evaluation was disassembled in the glove box in argon atmosphere, respectively. The positive electrode and the negative electrode were taken out, washed with dimethyl carbonate and dried. After drying, the reflectance Rc3 at a wavelength of 550 nm on the surface of the positive electrode active material layer and the reflectance Ra at a wavelength of 550 nm on the surface of the negative electrode active material layer were measured, and it was confirmed that there was no change before and after the evaluation.

In Table 4, ethylene carbonate (EC) is contained as a non-aqueous solvent, and the content thereof is 10 to 30 vol. As a volume ratio in the non-aqueous solvent. It was confirmed that the charging rate characteristics and the load discharge characteristics are improved by the inclusion of%. In Examples 38 to 45 using LiCoO ₂ which is the compound of the general formula (1), the charge rate characteristics are particularly improved, and LiNi _0.85 Co _0.10 Al ₀ which is the compound of the general formula (2). It was found that load discharge characteristics were particularly improved in Examples 87 to 94 and Examples 132 to 139 using _.05 O ₂ or LiFePO ₄ which is a compound of the general formula (3).

(Example 140)
The battery of Example 140 is the same as Example 7 except that 80% by mass of LiCoO ₂ is used as the positive electrode active material 1 and 20% by mass of LiFePO ₄ is used as the positive electrode active material 2 as the positive electrode active material. A cell was made.

(Example 141)
The battery of Example 141 is the same as Example 6 except that 80% by mass of LiCoO ₂ is used as the positive electrode active material 1 and 20% by mass of LiFePO ₄ is used as the positive electrode active material 2 as the positive electrode active material. A cell was made.

(Example 142)
The battery of Example 142 is the same as Example 1 except that 80% by mass of LiCoO ₂ is used as the positive electrode active material 1 and 20% by mass of LiFePO ₄ is used as the positive electrode active material 2 as the positive electrode active material. A cell was made.

(Example 143)
The battery of Example 143 is the same as Example 2 except that 80% by mass of LiCoO ₂ is used as the positive electrode active material 1 and 20% by mass of LiFePO ₄ is mixed as the positive electrode active material 2 as the positive electrode active material. A cell was made.

(Example 144)
The battery of Example 144 was the same as Example 3 except that 80% by mass of LiCoO ₂ was used as the positive electrode active material 1 and 20% by mass of LiFePO ₄ was used as the positive electrode active material 2 as the positive electrode active material. A cell was made.

(Example 145)
The battery of Example 145 is the same as Example 4 except that 80% by mass of LiCoO ₂ is used as the positive electrode active material 1 and 20% by mass of LiFePO ₄ is used as the positive electrode active material 2 as the positive electrode active material. A cell was made.

(Example 146)
The battery of Example 146 was the same as Example 5 except that 80% by mass of LiCoO ₂ was used as the positive electrode active material 1 and 20% by mass of LiFePO ₄ was used as the positive electrode active material 2 as the positive electrode active material. A cell was made.

(Example 147)
Except that a mixture of 80% by mass of LiNi _0.8 Mn _0.1 Co _0.1 O ₂ as the positive electrode active material 1 and 20% by mass of LiCoO ₂ as the positive electrode active material 2 was used as the positive electrode active material, A battery cell of Example 147 was made in the same manner as Example 51.

(Example 148)
Except that a mixture of 80% by mass of LiNi _0.8 Mn _0.1 Co _0.1 O ₂ as the positive electrode active material 1 and 20% by mass of LiCoO ₂ as the positive electrode active material 2 was used as the positive electrode active material, A battery cell of Example 148 was produced in the same manner as Example 45.

(Example 149)
Except that a mixture of 80% by mass of LiNi _0.8 Mn _0.1 Co _0.1 O ₂ as the positive electrode active material 1 and 20% by mass of LiCoO ₂ as the positive electrode active material 2 was used as the positive electrode active material, A battery cell of Example 149 was made in the same manner as Example 49.

(Example 150)
Except that a mixture of 80% by mass of LiNi _0.8 Mn _0.1 Co _0.1 O ₂ as the positive electrode active material 1 and 20% by mass of LiCoO ₂ as the positive electrode active material 2 was used as the positive electrode active material, A battery cell of Example 150 was made in the same manner as Example 50.

(Example 151)
In the production of the positive electrode, a battery cell of Example 151 was produced in the same manner as in Example 150 except that the roll for rolling during the press treatment was 109 ° C. and the number of presses was 3 cycles.

(Example 152)
In the production of the positive electrode, a battery cell of Example 152 was produced in the same manner as in Example 150 except that the roll for rolling during the press treatment was 113 ° C. and the number of presses was 5 cycles.

(Example 153)
Except that a mixture of 80% by mass of LiNi _0.8 Mn _0.1 Co _0.1 O ₂ as the positive electrode active material 1 and 20% by mass of LiCoO ₂ as the positive electrode active material 2 was used as the positive electrode active material, A battery cell of Example 153 was made in the same manner as Example 52.

(Example 154)
The battery of Example 154 was obtained in the same manner as Example 95 except that 80% by mass of LiFePO ₄ was used as the positive electrode active material 1 and 20% by mass of LiCoO ₂ was mixed as the positive electrode active material 2 as the positive electrode active material. A cell was made.

(Example 155)
The battery of Example 155 is the same as Example 97 except that 80% by mass of LiFePO ₄ is used as the positive electrode active material 1 and 20% by mass of LiCoO ₂ is mixed as the positive electrode active material 2 as the positive electrode active material. A cell was made.

(Example 156)
The battery of Example 156 is the same as Example 98 except that 80% by mass of LiFePO ₄ is used as the positive electrode active material 1 and 20% by mass of LiCoO ₂ is mixed as the positive electrode active material 2 as the positive electrode active material. A cell was made.

(Example 157)
The battery of Example 157 was the same as Example 99 except that 80% by mass of LiFePO ₄ was used as the positive electrode active material 1 and 20% by mass of LiCoO ₂ was used as the positive electrode active material 2 as the positive electrode active material. A cell was made.

(Example 158)
The battery of Example 158 was the same as Example 100 except that 80% by mass of LiFePO ₄ was used as the positive electrode active material 1 and 20% by mass of LiCoO ₂ was mixed as the positive electrode active material 2 as the positive electrode active material. A cell was produced.

(Example 159)
In the production of the positive electrode, a battery cell of Example 159 was produced in the same manner as in Example 154 except that the roll for rolling during the press treatment was 100 ° C. and the number of presses was 3 cycles.

(Example 160)
The battery of Example 160 is the same as Example 101 except that 80% by mass of LiFePO ₄ is used as the positive electrode active material 1 and 20% by mass of LiCoO ₂ is used as the positive electrode active material 2 as the positive electrode active material. A cell was made.

(Comparative Example 17)
The battery of Comparative Example 17 was the same as Comparative Example 1 except that 80% by mass of LiCoO ₂ was used as the positive electrode active material 1 and 20% by mass of LiFePO ₄ was mixed as the positive electrode active material 2 as the positive electrode active material. A cell was made.

(Comparative Example 18)
The battery of Comparative Example 18 is the same as Comparative Example 2 except that 80% by mass of LiCoO ₂ is used as the positive electrode active material 1 and 20% by mass of LiFePO ₄ is mixed as the positive electrode active material 2 as the positive electrode active material. A cell was made.

(Comparative Example 19)
Except that a mixture of 80% by mass of LiNi _0.8 Mn _0.1 Co _0.1 O ₂ as the positive electrode active material 1 and 20% by mass of LiCoO ₂ as the positive electrode active material 2 was used as the positive electrode active material, A battery cell of Comparative Example 19 was produced in the same manner as Comparative Example 9.

(Comparative Example 20)
Except that a mixture of 80% by mass of LiNi _0.8 Mn _0.1 Co _0.1 O ₂ as the positive electrode active material 1 and 20% by mass of LiCoO ₂ as the positive electrode active material 2 was used as the positive electrode active material, A battery cell of Comparative Example 20 was produced in the same manner as Comparative Example 10.

(Comparative Example 21)
The battery of Comparative Example 21 is the same as Comparative Example 11 except that 80% by mass of LiFePO ₄ is used as the positive electrode active material 1 and 20% by mass of LiCoO ₂ is mixed as the positive electrode active material 2 as the positive electrode active material. A cell was produced.

(Comparative Example 22)
The battery of Comparative Example 22 was the same as Comparative Example 12 except that 80% by mass of LiFePO ₄ was used as the positive electrode active material 1 and 20% by mass of LiCoO ₂ was mixed as the positive electrode active material 2 as the positive electrode active material. A cell was produced.

  Regarding the positive electrode and the negative electrode used in Examples 140 to 160 and Comparative Examples 17 to 22, the reflectance Rc at a wavelength of 550 nm on the surface of the positive electrode active material layer and the reflection at a wavelength of 550 nm on the surface of the negative electrode active material layer are the same as in Example 1. The rate Ra was measured, and the ratio Rc / Ra was calculated. Further, the density dc, the supported amount Lc per unit area, and the porosity Pc of the positive electrode active material layer were also measured in the same manner as in Example 1. The results are shown in Table 5 together with the results in Example 95.

  Examples 140 to 146 and Comparative Example 17 are shown in Table 5 for the reflectance Rc at a wavelength of 550 nm on the surface of the positive electrode active material layer, the density dc of the positive electrode active material layer, the loading Lc per unit area, and the porosity Pc. , 18 are Rc1, dc1, Lc1, and Pc1, respectively, because the main component is the compound represented by the general formula (1). In addition, Examples 147 to 153 and Comparative Examples 19 and 20 are Rc2, dc2, Lc2, and Pc2, respectively, since the compound represented by the general formula (2) is a main component. Examples 154 to 160 and Comparative Example 21 , And 22 represent Rc3, dc3, Lc3, and Pc3, respectively, since the compound represented by the general formula (3) is a main component.

  In Table 5, from the results of Examples 140 to 160 and Comparative Examples 17 to 22, the charge rate was within the range of 2.0 ≦ Rc ≦ 12.0% even when the compounds represented by different general formulas were mixed. It was confirmed that the characteristics and load discharge characteristics were excellent. Further, from the results of Examples 140 to 147, when the positive electrode containing the compound represented by the general formula (1) as a main component was used, 8.0 ≦ Rc1 ≦ 12.0% as in the results of Table 1. In some cases, it has been confirmed that high charge rate characteristics are exhibited. Similarly, when a positive electrode containing a compound represented by the general formula (2) as a component is used, high load discharge characteristics are obtained when 3.5 ≦ Rc2 ≦ 7.8%, as in the results of Table 2. When a positive electrode containing a compound represented by the general formula (3) as a component is used, high load discharge characteristics are exhibited when 2.0 ≦ Rc3 ≦ 5.8%, as in the results of Table 3. It was confirmed.

  Further, when Examples 140 to 146 and Examples 154 to 160 were compared, it was confirmed that either the charge rate characteristic or the load discharge characteristic was excellent depending on the compound contained as the main component as the positive electrode active material. From this result, it can be seen that the reflectance at a wavelength of 550 nm on the surface of the positive electrode active material layer and the compound species as the main component in the positive electrode are related to the obtained characteristics.

  According to the present invention, it is possible to provide a positive electrode capable of improving charge rate characteristics and load discharge characteristics and a lithium ion secondary battery using the positive electrode. These are suitably used as a power source for portable electronic devices, and are also used as electric vehicles and household and industrial storage batteries.

DESCRIPTION OF SYMBOLS 10 Separator 20 Positive electrode 22 Positive electrode collector 24 Positive electrode active material layer 30 Negative electrode 32 Negative electrode collector 34 Negative electrode active material layer 40 Laminate 50 Case 52 Metal foil 54 Polymer film 60, 62 Lead 100 Lithium ion secondary battery

Claims (19)

A positive electrode active material layer having a positive electrode active material, a conductive additive, and a binder on a positive electrode current collector,
The positive electrode whose reflectance Rc of wavelength 550nm is 2.0 <= Rc <= 12.0% in the surface of the said positive electrode active material layer. Containing as a main component a compound represented by the following formula (1) as the positive electrode active material;
The positive electrode according to claim 1, wherein a reflectance Rc1 at a wavelength of 550 nm on the surface of the positive electrode active material layer is 8.0 ≦ Rc1 ≦ 12.0%.
Li _x Ni _y M _1-y O _z (1)
(0 <x ≦ 1.1, 0 ≦ y <0.5, 1.9 ≦ z ≦ 2.1 is satisfied, and M has at least one selected from Co, Mn, Al, Fe, and Mg) The positive electrode according to claim 2, wherein a density dc1 of the positive electrode active material layer is 3.1 ≦ dc1 ≦ 4.1 g / cm ³ . The positive electrode according to claim ² , wherein a supported amount Lc1 per unit area in the positive electrode active material layer is 13.0 ≦ Lc1 ≦ 25.0 mg / cm ² . The positive electrode active material contains a compound represented by the following formula (2) as a main component,
The positive electrode according to claim 1, wherein a reflectance Rc2 at a wavelength of 550 nm on the surface of the positive electrode active material layer is 3.5 ≦ Rc2 ≦ 7.8%.
Li _x Ni _y M _1-y O _z (2)
(0 <x ≦ 1.1, 0.5 ≦ y ≦ 1, 1.9 ≦ z ≦ 2.1, M has at least one selected from Co, Mn, Al, Fe, and Mg) The positive electrode according to claim 5, wherein a density dc2 in the positive electrode active material layer is 3.0 ≦ dc2 ≦ 3.8 g / cm ³ . The positive electrode according to claim 5, wherein a supported amount Lc2 per unit area in the positive electrode active material layer is 12.0 ≦ Lc2 ≦ 24.0 mg / cm ² . Containing as a main component a compound represented by the following formula (3) as the positive electrode active material;
The positive electrode according to claim 1, wherein a reflectance Rc3 at a wavelength of 550 nm on the surface of the positive electrode active material layer is 2.0 ≦ Rc3 ≦ 5.8%.
_{Li x M y O z PO 4} ···· (3)
(0 <x ≦ 1.1, 0 <y ≦ 1.1, 0 ≦ z ≦ 1.0 is satisfied, and M is at least one selected from Ni, Co, Mn, Al, Fe, Mg, Ag, and V Have) The positive electrode according to claim 8, wherein a density dc3 in the positive electrode active material layer is 1.8 ≦ dc3 ≦ 2.5 g / cm ³ . The positive electrode according to claim 8, wherein a supported amount Lc3 per unit area in the positive electrode active material layer is 8.0 ≦ Lc3 ≦ 15.0 mg / cm ² . A positive electrode according to claim 1;
A negative electrode including a negative electrode active material layer having a negative electrode active material on a negative electrode current collector, a separator, and a non-aqueous electrolyte;
The lithium ion secondary battery whose reflectance Ra of wavelength 550nm in the surface of the said negative electrode active material layer is 7.5 <= Ra <= 16.0%. A positive electrode according to any one of claims 2 to 4, a negative electrode comprising a negative electrode active material layer having a negative electrode active material on a negative electrode current collector, a separator, and a non-aqueous electrolyte,
The lithium ion secondary battery whose reflectance Ra of wavelength 550nm in the surface of the said negative electrode active material layer is 7.5 <= Ra <= 16.0%.   The lithium ion secondary battery according to claim 12, wherein a ratio Rc1 / Ra of the reflectance Rc1 and the reflectance Ra is 1.00 <Rc1 / Ra ≦ 1.53. A positive electrode according to any one of claims 5 to 7, a negative electrode comprising a negative electrode active material layer having a negative electrode active material on a negative electrode current collector, a separator, and a non-aqueous electrolyte,
The lithium ion secondary battery whose reflectance Ra of wavelength 550nm in the surface of the said negative electrode active material layer is 7.5 <= Ra <= 16.0%.   The lithium ion secondary battery according to claim 14, wherein a ratio Rc2 / Ra of the reflectance Rc2 and the reflectance Ra is 0.29 ≦ Rc2 / Ra <1.00. A positive electrode according to any one of claims 8 to 10, a negative electrode comprising a negative electrode active material layer having a negative electrode active material on a negative electrode current collector, a separator, and a non-aqueous electrolyte,
The lithium ion secondary battery whose reflectance Ra of wavelength 550nm in the surface of the said negative electrode active material layer is 7.5 <= Ra <= 16.0%.   The lithium ion secondary battery according to claim 16, wherein a ratio Rc3 / Ra of the reflectance Rc3 and the reflectance Ra is 0.13 ≦ Rc3 / Ra ≦ 0.75.   The lithium ion secondary battery according to any one of claims 11 to 17, wherein the negative electrode active material contains a carbon material having a graphite structure.   The non-aqueous electrolyte includes a non-aqueous solvent and an electrolyte, and the non-aqueous solvent contains ethylene carbonate, and the content of the ethylene carbonate is 10 to 30 vol. The lithium ion secondary battery according to any one of claims 11 to 18, which is%.

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