31, a value obtained by dividing the length measured along the surface of the positive electrode mixture layer 31 by a length of a straight line parallel to the surface of the positive electrode 11, and serves as an index indicating the degree of unevenness on the surface of the positive electrode mixture layer 31. A greater tortuosity factor signifies a greater surface unevenness. The surface tortuosity factor of the positive electrode mixture layer 31 is more preferably 1.25 or greater, and particularly preferably 1.30 or greater. The upper limit value of the tortuosity factor is more preferably 1.95, and particularly preferably 1.90.

For measuring the surface tortuosity factor of the positive electrode mixture layer 31, it is possible to use the electron micrograph of the cross-section of the positive electrode 11 used for measuring the average thickness. Specifically, in the 160-μm length range of the reference line Z, the length (L) along the surface of the positive electrode mixture layer 31 is measured, and the tortuosity factor is calculated by the formula L μm/160 μm.

The positive electrode mixture layer 31 has, for example, a layer thickness variation coefficient of 0.01 to 0.30 and a layer surface tortuosity factor of 1.2 to 2.0. When the layer thickness variation coefficient and the like of the positive electrode mixture layer 31 are within the above-noted ranges, it is considered that appropriate surface unevenness is formed on the positive electrode mixture layer 31 so that the reaction resistance becomes reduced, and the internal resistance can be reduced without affecting other battery performance features. In other words, the surface of the positive electrode mixture layer 31 has unevenness formed thereon that satisfies the above-described variation coefficient and tortuosity factor.

The positive electrode mixture layer 31 is formed by, for example, applying a positive electrode mixture slurry containing the positive electrode active material, the conductive agent, the binder, and the like to a surface of the positive electrode core 30, and then drying the applied film. Generally, the applied film of the positive electrode mixture layer 31 is compressed in order to increase the packing density of the positive electrode active material, but if the applied film is simply compressed, the surface of the mixture layer becomes flat, so that surface unevenness that satisfies the above-noted variation coefficient and tortuosity factor would not be formed. An example method of forming desired unevenness on the surface of the positive electrode mixture layer 31 is a method in which an applied film of the surface layer 32 is formed on the applied film of the positive electrode mixture layer 31, and subsequently the positive electrode mixture layer 31 and the surface layer 32 are compressed. Since the applied film of the positive electrode mixture layer 31 before compression has surface unevenness, by compressing the positive electrode mixture layer 31 together with the surface layer 32 instead of compressing the positive electrode mixture layer 31 alone, the unevenness of the applied film is allowed to remain on the surface of positive electrode mixture layer 31.

The positive electrode 11 may have the surface layer 32 provided on the surface of the positive electrode mixture layer 31. A preferred surface layer 32 is composed mainly of an inorganic compound, has lower conductivity than the positive electrode mixture layer 31, and is more preferably an insulation layer. The surface layer 32 may be removed after the compression step, but is preferably not removed and allowed to remain on the surface of the positive electrode mixture layer 31 in consideration of reduction of manufacturing costs, suppression of internal short circuits, suppression of heat generation upon occurrence of short circuits, and the like resulting from not performing the removal step.

The surface layer 32 covers the entire surface of the positive electrode mixture layer 31 and constitutes the outermost surface layer of the positive electrode 11. The surface layer 32 contains, for example, an inorganic compound and a binder, and its surface (i.e., the outermost surface S of the positive electrode 11) is substantially flat. Accordingly, the surface tortuosity factor of the surface layer 32 is small, and is, for example, less than 1.2. On the other hand, at the interface between the surface layer 32 and the positive electrode mixture layer 31, unevenness resulting from the unevenness on the surface of the positive electrode mixture layer 31 is formed.

The inorganic compound contained in the surface layer 32 is a compound in which Li insertion/extraction does not occur due to solid-phase redox reaction at a potential of 2.5 V or higher (with respect to Li/Li+), and which does not function as a positive electrode active material. The inorganic compound is, for example, at least one of an oxide, hydroxide, oxyhydroxide, borate, phosphate, and sulfate that contains at least one metal element selected from Al, Sn, W, Nb, Mo, Si, and Ba. The content of the inorganic compound in the surface layer 32 is preferably 80% by mass or higher, and more preferably 90 to 99% by mass, relative to the mass of the surface layer 32.

Specific examples of the inorganic compound include: oxides such as titanium oxide (TiO₂), aluminum oxide (Al₂O₃), tin oxide (SnO₂), tungsten oxide (WO₃), niobium oxide (Nb₂O₅), molybdenum oxide (MoO₃), and silicon oxide (SiO₂); hydroxides such as magnesium hydroxide (Mg(OH)₂); oxyhydroxides such as boehmite (AlOOH); phosphates such as lithium phosphate (Li₃PO₄); and sulfates such as barium sulfate (BaSO₄). Among the foregoing, titanium oxide (TiO₂) and boehmite (AlOOH) are preferable. The volume-based D50 of the inorganic compound is preferably 0.05 μm to 1 μm, and more preferably 0.1 μm to 0.8 μm. With such values, the porosity and pore size of the surface layer 32 can be easily adjusted to within desired ranges.

As the binder contained in the surface layer 32, the same type of binder as the binder used for the positive electrode mixture layer 31 can be used, which may be a fluororesin such as PTFE or PVdF, PAN, polyimide, acrylic resin, polyolefin, or the like. The content of the binder is, for example, 0.5 to 3% by mass relative to the mass of the surface layer 32.

The average thickness of the surface layer 32 is preferably less than the average thickness of the positive electrode mixture layer 31. Specifically, the average thickness of the surface layer 32 on one side of the positive electrode core 30 is 0.1 μm to 10 μm, preferably 0.5 μm to 9 μm, and more preferably 1 μm to 8 μm. When the thickness of the surface layer 32 is too small, it becomes difficult to maintain the surface unevenness of the positive electrode mixture layer 31 in the positive electrode 11 compression step. Further, the thickness variation coefficient of the surface layer 32 (i.e., standard deviation of thickness/average thickness) is, for example, 0.3 or greater. The average thickness of the surface layer 32 is measured by a method similar to that used for the average thickness of the positive electrode mixture layer 31.

The surface layer 32 is a porous layer, and does not impede penetration of the electrolyte. The porosity of the surface layer 32 is, for example, 25 to 55%, and is preferably 30 to 45% in consideration of reducing the internal resistance, suppressing heat generation upon occurrence of internal short circuits, and the like. The porosity of the surface layer 32 is measured by the following method.

(1) Using a calibration curve derived from X-ray fluorescence intensities of surface layers having known weights per unit area (or coating weights), determine the weight per unit area of the inorganic compound particles contained in the surface layer 32 based on the X-ray fluorescence intensity.

(2) Calculate the true volume (Vt) of the inorganic compound particles based on the true density and weight per unit area of the inorganic compound particles.

(3) Calculate the apparent volume (Va) of the surface layer 32 based on the area and average thickness of the surface layer 32.

(4) Calculate the porosity (P) of the surface layer 32 by the following formula:

P=100−100Vt/Va

[Negative Electrode]

The negative electrode 12 comprises a negative electrode core and a negative electrode mixture layer provided on a surface of the negative electrode core. For the negative electrode core, it is possible to use: a foil of a metal that is stable in the potential range of the negative electrode 12, such as copper; a film having such a metal disposed on its surface layer; and the like. The thickness of the negative electrode core is, for example, 5 μm to 25 μm. The negative electrode mixture layer contains a negative electrode active material and a binder, and is preferably provided, for example, on both sides of the negative electrode core excluding the portion to which the negative electrode lead 21 is connected.

As the negative electrode active material, the negative electrode mixture layer contains, for example, a carbon-based active material that reversibly occludes and releases lithium ions. Preferred carbon-based active materials are graphite including natural graphite such as scaly graphite, massive graphite, and earthy graphite, and artificial graphite such as massive artificial graphite (MAG) and graphitized mesophase carbon microbeads (MCMB). Further, as the negative electrode active material, a Si-based active material composed of at least one of Si and a Si-containing compound may be used. A carbon-based active material and a Si-based active material may be used in combination.

The volume-based D50 of the negative electrode active material is, for example, 5 μm to 30 μm, and preferably 10 μm to 25 μm. The packing density of the negative electrode active material in the negative electrode mixture layer is preferably 1.2 g/cm³or higher. With such values, the energy density of the battery can be increased. Further, when unevenness is formed on the surface of the negative electrode mixture layer, a higher packing density of the negative electrode active material leads to a more notable effect of internal resistance reduction due to the surface unevenness of the negative electrode mixture layer. While the upper limit value of the packing density is not particularly defined, it is, for example, 2.0 g/cm³or 1.7 g/cm³.

As the binder contained in the negative electrode mixture layer, fluororesins, PAN, polyimides, acrylic resins, polyolefins and the like can be used as with the positive electrode 11, but styrene-butadiene rubber (SBR) is preferably used. Further, the negative electrode mixture layer preferably additionally contains CMC or a salt thereof, polyacrylic acid (PAA) or a salt thereof, polyvinyl alcohol (PVA), or the like. Among the foregoing, use of SBR in combination with CMC or a salt thereof or PAA or a salt thereof is preferred.

Similar to the positive electrode mixture layer 31, the negative electrode mixture layer may have appropriate unevenness on the surface, and may have a layer thickness variation coefficient (standard deviation of thickness/average thickness) of 0.01 to 0.30. The variation coefficient is more preferably 0.015 or greater, and particularly preferably 0.020 or greater. The upper limit value of the variation coefficient is more preferably 0.28, and particularly preferably 0.25. The average thickness of the negative electrode mixture layer on one side of the negative electrode core is, for example, 30 μm to 100 μm, preferably 40 μm to 90 μm, and more preferably 50 μm to 80 μm. The average thickness of the negative electrode mixture layer is measured by the same method as that used for the average thickness of the positive electrode mixture layer 31.

The negative electrode mixture layer may have a layer surface tortuosity factor of 1.2 to 2.0. The tortuosity factor is more preferably 1.25 or greater, and particularly preferably 1.30 or greater. The upper limit value of the tortuosity factor is more preferably 1.95, and particularly preferably 1.90. The negative electrode mixture layer has, for example, a layer thickness variation coefficient of 0.01 to 0.30 and a layer surface tortuosity factor of 1.2 to 2.0. In other words, the surface of the negative electrode mixture layer has unevenness formed thereon that satisfies the above-described variation coefficient and tortuosity factor. The tortuosity factor of the negative electrode mixture layer is measured by the same method as that used for the tortuosity factor of the positive electrode mixture layer 31.

The negative electrode 12 may have a surface layer provided on the surface of the negative electrode mixture layer. The surface layer of the negative electrode 12 is composed of a material similar to that of the surface layer 32 described above, and also has similar thickness and porosity. The surface layer may be removed after the unevenness is formed on the surface of the negative electrode mixture layer, but is preferably allowed to remain on the surface of the negative electrode mixture layer. The negative electrode 12 is manufactured by, for example, forming an applied film of the surface layer on an applied film of the negative electrode mixture layer, and subsequently compressing the negative electrode mixture layer together with the surface layer.

[Separator]

As the separator 13, a porous sheet having ion permeability and insulating property is used. Specific examples of the porous sheet include a microporous thin film, a woven fabric, and a non-woven fabric. As the material of the separator 13, olefin resins such as polyethylene and polypropylene, cellulose, and the like are preferred. The separator 13 may have either a single-layer structure or a laminated structure. A heat-resistant layer or the like may be formed on the surface of the separator 13.

EXAMPLES

While the present disclosure will now be described in more detail using Examples, the present disclosure is not limited to these Examples.

Example 1

[Preparation of Positive Electrode]

As the positive electrode active material, a lithium-containing transition metal composite oxide represented by Ni_0.88Co_0.09Al_0.03O₂(volume-based D50: 10 μm) was used. A positive electrode mixture slurry was prepared by mixing 100 parts by mass of the positive electrode active material, 1 part by mass of acetylene black, and 1 part by mass of polyvinylidene fluoride, and by using N-methyl-2-pyrrolidone (NMP) as the dispersion medium. Next, the positive electrode mixture slurry was applied to both sides of a positive electrode core made of aluminum foil at an amount of 0.028 g/cm²per side, and the applied films were dried to form positive electrode mixture layers on both sides of the positive electrode core.

As the inorganic compound constituting the surface layer, titanium oxide (volume-based D50: 0.2 μm) was used. A slurry for forming the surface layer was prepared by mixing 100 parts by mass of titanium oxide and 3 parts by mass of polyvinylidene fluoride, and by using NMP as the dispersion medium. Next, the slurry was applied to the surfaces of the positive electrode mixture layers to form surface layers on the surfaces of the positive electrode mixture layers. Subsequently, the positive electrode mixture layers and the surface layers were compressed using a roll press. A positive electrode having a positive electrode mixture layer and a surface layer formed in that order on both sides of the positive electrode core was thereby obtained.

In the positive electrode mixture layer, the density was 3.2 g/cm³, the average thickness was 60 μm, and the thickness variation coefficient (standard deviation of thickness/average thickness) was 0.029. In the surface layer, the average thickness was 2.5 μm, and the thickness variation coefficient was 0.696. These measurement results are shown in Table 1 below, together with the inorganic compound constituting the surface layer and a result of evaluation of the battery internal resistance. The methods for measuring the average thickness and density of each layer are as described above.

[Preparation of Negative Electrode]

As the negative electrode active material, graphite powder was used. A negative electrode mixture slurry was prepared by mixing 98.7 parts by mass of the negative electrode active material, 0.7 parts by mass of carboxymethyl cellulose (CMC), and 0.6 parts by mass of styrene-butadiene rubber (SBR), and by using water as the dispersion medium. Next, the negative electrode mixture slurry was applied to both sides of a negative electrode core made of copper foil at an amount of 0.013 g/cm²per side. The applied films were dried and compressed, and the product was cut into a predetermined electrode size. A negative electrode having negative electrode mixture layers formed on both sides of the negative electrode core was thereby obtained.

[Preparation of Non-Aqueous Electrolyte Solution]

Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) were mixed in a volume ratio of 3:3:4. A non-aqueous electrolyte solution was prepared by dissolving LiPF₆into this mixed solvent so as to attain a concentration of 1.2 mol/L.

[Preparation of Secondary Battery]

An aluminum lead was attached to the above-noted positive electrode, and a nickel lead was attached to the above-noted negative electrode. The positive and negative electrodes were wound with a polyethylene separator having a thickness of 14 μm located between the electrodes, to thereby prepare a spiral-type electrode assembly. The electrode assembly was placed in a bottomed cylindrical outer can having an outer diameter of 18.2 mm and a height of 65 mm. The non-aqueous electrolyte solution was injected therein, and then the opening of the outer can was sealed with a gasket and a sealing assembly. A 18650-type cylindrical non-aqueous electrolyte secondary battery was thereby obtained.

Examples 2 to 7

A positive electrode and a non-aqueous electrolyte secondary battery were obtained in the same manner as in Example 1 except that, instead of titanium oxide, the compound shown in Table 1 was used as the inorganic compound constituting the surface layer.

Comparative Example 1

A positive electrode and a non-aqueous electrolyte secondary battery were obtained in the same manner as in Example 1 except that, in preparing the positive electrode, the positive electrode mixture layer was compressed, then the slurry for forming the surface layer was applied to the surface of the compressed positive electrode mixture layer, and subsequently the surface layer was compressed.

Comparative Example 2

A positive electrode and a non-aqueous electrolyte secondary battery were obtained in the same manner as in Example 1 except that, in preparing the positive electrode, the surface layer was not formed.

Example 8

A positive electrode and a non-aqueous electrolyte secondary battery were obtained in the same manner as in Example 1 except that, in preparing the positive electrode, the applied amount of slurry and the pressure during compression of the applied films were changed, so that a positive electrode mixture layer density of 3.5 g/cm³and a surface layer thickness of 4 μm were attained. The measurement results such as the thickness of each layer are shown in Table 2 below, together with the inorganic compound constituting the surface layer and a result of evaluation of the battery internal resistance.

Examples 9 and 10

A positive electrode and a non-aqueous electrolyte secondary battery were obtained in the same manner as in Example 8 except that the thickness of the surface layer was set to the thickness value shown in Table 2.

Example 11

In preparing a positive electrode, a slurry for forming the surface layer was prepared by mixing 100 parts by mass of boehmite (AlOOH; average particle size: 0.5 μm) and 3 parts by mass of acrylic resin, and by using water as the dispersion medium. Next, the slurry was applied to the surfaces of the positive electrode mixture layers at an amount of 8 g/m², and the applied films were dried to form surface layers on the surfaces of the positive electrode mixture layers. After compressing the positive electrode mixture layers and the surface layers using a roll press, the surface layers were removed by immersing the electrode plate in water and performing ultrasonication. A positive electrode having only the positive electrode mixture layers formed on both sides of the positive electrode core was thereby obtained. Regarding points other than the above, a non-aqueous electrolyte secondary battery was obtained in the same manner as in Example 8.

Comparative Example 3

A positive electrode and a non-aqueous electrolyte secondary battery were obtained in the same manner as in Example 8 except that, in preparing the positive electrode, the surface layer was not formed.

Example 12

A positive electrode and a non-aqueous electrolyte secondary battery were obtained in the same manner as in Example 2 except that, in preparing the positive electrode, the applied amount of slurry and the pressure during compression of the applied films were changed, so that a positive electrode mixture layer density of 3.7 g/cm³was attained. The measurement results such as the thickness of each layer are shown in Table 3 below, together with the inorganic compound constituting the surface layer and a result of evaluation of the battery internal resistance.

Examples 13 and 14

A positive electrode and a non-aqueous electrolyte secondary battery were obtained in the same manner as in Example 12 except that, in preparing the positive electrode, the solid content of the slurry was adjusted.

Comparative Example 4

A positive electrode and a non-aqueous electrolyte secondary battery were obtained in the same manner as in Example 12 except that, in preparing the positive electrode, the surface layer was not formed.

Example 15

A non-aqueous electrolyte secondary battery was obtained in the same manner as in Example 1 except that the positive electrode and the negative electrode were prepared by the following methods.

[Preparation of Positive Electrode]

As the positive electrode active material, a lithium-containing transition metal composite oxide (volume-based D50: 10 μm) represented by Ni_0.88Co_0.09Al_0.03O₂was used. A positive electrode mixture slurry was prepared by mixing 100 parts by mass of the positive electrode active material, 1 part by mass of acetylene black, and 1 part by mass of polyvinylidene fluoride, and by using N-methyl-2-pyrrolidone (NMP) as the dispersion medium. Next, the positive electrode mixture slurry was applied to both sides of a positive electrode core made of aluminum foil at an amount of 0.028 g/cm²per side. The applied films were dried and compressed, and the product was cut into a predetermined electrode size. A positive electrode having positive electrode mixture layers formed on both sides of the positive electrode core was thereby obtained.

[Preparation of Negative Electrode]

As the negative electrode active material, graphite powder was used. A negative electrode mixture slurry was prepared by mixing 98.7 parts by mass of the negative electrode active material, 0.7 parts by mass of carboxymethyl cellulose (CMC), and 0.6 parts by mass of styrene-butadiene rubber (SBR), and by using water as the dispersion medium. Next, the negative electrode mixture slurry was applied to both sides of a negative electrode core made of copper foil at an amount of 0.013 g/cm²per side, and the applied films were dried to form negative electrode mixture layers on both sides of the negative electrode core.

As the inorganic compound constituting the surface layer, titanium oxide (volume-based D50: 0.5 μm) was used. A slurry for forming the surface layer was prepared by mixing 100 parts by mass of titanium oxide and 3 parts by mass of acrylic resin, and by using water as the dispersion medium. Next, the slurry was applied to the surfaces of the negative electrode mixture layers at an amount of 8 g/m², and the applied films were dried to form surface layers on the surfaces of the negative electrode mixture layers. Subsequently, the negative electrode mixture layers and the surface layers were compressed using a roll press. A negative electrode having a negative electrode mixture layer and a surface layer formed in that order on both sides of the negative electrode core was thereby obtained.

In the negative electrode mixture layer, the density was 1.2 g/cm³, the average thickness was 66 μm, and the thickness variation coefficient was 0.029. In the surface layer, the average thickness was 2.5 μm, and the thickness variation coefficient was 0.766. These measurement results are shown in Table 4 below, together with the inorganic compound constituting the surface layer and a result of evaluation of the battery internal resistance.

Examples 16 to 21

A negative electrode and a non-aqueous electrolyte secondary battery were obtained in the same manner as in Example 15 except that, instead of titanium oxide, the compound shown in Table 4 was used as the inorganic compound constituting the surface layer.

Comparative Example 5

A negative electrode and a non-aqueous electrolyte secondary battery were obtained in the same manner as in Example 15 except that, in preparing the negative electrode, the negative electrode mixture layer was compressed, then the slurry for forming the surface layer was applied to the surface of the compressed negative electrode mixture layer, and subsequently the surface layer was compressed.

Comparative Example 6

A negative electrode and a non-aqueous electrolyte secondary battery were obtained in the same manner as in Example 15 except that, in preparing the negative electrode, the surface layer was not formed.

Example 22

A negative electrode and a non-aqueous electrolyte secondary battery were obtained in the same manner as in Example 16 except that, in preparing the negative electrode, the applied amount of slurry and the pressure during compression of the applied films were changed, so that a negative electrode mixture layer density of 1.5 g/cm³was attained. The measurement results such as the thickness of each layer are shown in Table 5 below, together with the inorganic compound constituting the surface layer and a result of evaluation of the battery internal resistance.

Examples 23 and 24

A negative electrode and a non-aqueous electrolyte secondary battery were obtained in the same manner as in Example 22 except that, in preparing the negative electrode, the solid content of the slurry was adjusted.

Comparative Example 7

A negative electrode and a non-aqueous electrolyte secondary battery were obtained in the same manner as in Example 22 except that, in preparing the negative electrode, the surface layer was not formed.

Example 25

A negative electrode and a non-aqueous electrolyte secondary battery were obtained in the same manner as in Example 15 except that, in preparing the negative electrode, the applied amount of slurry and the pressure during compression of the applied films were changed, so that a negative electrode mixture layer density of 1.7 g/cm³and a surface layer thickness of 4.2 μm were attained. The measurement results such as the thickness of each layer are shown in Table 6 below, together with the inorganic compound constituting the surface layer and a result of evaluation of the battery internal resistance.

Examples 26 and 27

A negative electrode and a non-aqueous electrolyte secondary battery were obtained in the same manner as in Example 25 except that the thickness of the surface layer was set to the thickness value shown in Table 2.

Example 28

In preparing a negative electrode, a slurry for forming the surface layer was prepared by mixing 100 parts by mass of boehmite (AlOOH; volume-based D50: 0.5 μm) and 3 parts by mass of acrylic resin, and by using water as the dispersion medium. Next, the slurry was applied to the surfaces of the negative electrode mixture layers at an amount of 8 g/m², and the applied films were dried to form surface layers on the surfaces of the negative electrode mixture layers. After compressing the negative electrode mixture layers and the surface layers using a roll press, the surface layers were removed by immersing the electrode plate in water and performing ultrasonication. A negative electrode having only the negative electrode mixture layers formed on both sides of the negative electrode core was thereby obtained. Regarding points other than the above, a non-aqueous electrolyte secondary battery was obtained in the same manner as in Example 25.

Comparative Example 8

A negative electrode and a non-aqueous electrolyte secondary battery were obtained in the same manner as in Example 25 except that, in preparing the negative electrode, the surface layer was not formed.

Each of the batteries of the Examples and the Comparative Examples was charged with a constant current of 1000 mA to a final charge voltage of 4.2 V, and then charged with a constant voltage of 4.2 V for 60 minutes. Next, the resistance between the terminals of the battery was measured using a low-resistance meter (by the AC 4-terminal method in which the measurement frequency was set to 1 kHz). The internal resistance value of each Example is a relative value obtained by assuming that the value measured for the battery of a corresponding Comparative Example is 100.

TABLE 1

Surface Layer
Positive Electrode Mixture Layer

Inorganic
Average
Variation
Density
Average
Variation
Tortuosity
Internal

Compound
Thickness μm
Coefficient
g/cm³
Thickness μm
Coefficient
Ratio
Resistance %

Example 1
TiO₂
2.5
0.696
3.2
60
0.029
1.47
97.0

Example 2
AlOOH
2.5
0.683
3.2
61
0.028
1.42
97.2

Example 3
SnO₂
2.5
0.732
3.2
61
0.030
1.52
99.5

Example 4
WO₃
2.5
0.661
3.2
59
0.028
1.42
99.0

Example 5
Nb₂O₅
2.5
0.744
3.2
60
0.031
1.57
99.6

Example 6
MoO₃
2.5
0.792
3.2
60
0.033
1.67
99.1

Example 7
SiO₂
2.5
0.708
3.2
61
0.029
1.47
99.3

Comparative
TiO₂
2.5
0.120
3.2
60
0.005
1.10
100.5

Example 1

Comparative
—
—
—
3.2
60
0.003
1.10
100

Example 2

TABLE 2

Surface Layer
Positive Electrode Mixture Layer

Inorganic
Average
Variation
Density
Average
Variation
Tortuosity
Internal

Compound
Thickness μm
Coefficient
g/cm³
Thickness μm
Coefficient
Ratio
Resistance %

Example 8
TiO₂
4.0
0.510
3.5
60
0.034
1.75
96.9

Example 9
TiO₂
2.5
0.708
3.5
61
0.029
1.49
96.0

Example 10
TiO₂
1.5
0.840
3.5
60
0.021
1.08
96.0

Example 11
Surface Layer Removed
3.5
60
0.029
1.49
95.5

Comparative
—
—
—
3.5
60
0.003
1.09
100

Example 3

TABLE 3

Surface Layer
Positive Electrode Mixture Layer

Inorganic
Average
Variation
Density
Average
Variation
Tortuosity
Internal

Compound
Thickness μm
Coefficient
g/cm³
Thickness μm
Coefficient
Ratio
Resistance %

Example 12
AlOOH
2.5
0.672
3.7
60
0.028
0.028
96.8

Example 13
AlOOH
7.5
0.768
3.7
60
0.032
0.032
96.1

Example 14
AlOOH
2.5
0.944
3.7
59
0.040
0.04
93.5

Comparative
—
—
—
3.7
60
0.003
0.003
100

Example 4

TABLE 4

Surface Layer
Negative Electrode Mixture Layer

Inorganic
Average
Variation
Density
Average
Variation
Tortuosity
Internal

Compound
Thickness μm
Coefficient
g/cm³
Thickness μm
Coefficient
Ratio
Resistance %

Example 15
TiO₂
2.5
0.766
1.2
66
0.029
1.47
97.3

Example 16
AlOOH
2.5
0.780
1.2
65
0.030
1.52
97.8

Example 17
SnO₂
2.5
0.660
1.2
66
0.025
1.27
99.3

Example 18
WO₃
2.5
0.806
1.2
65
0.031
1.57
99.1

Example 19
Nb₂O₅
2.5
0.754
1.2
65
0.029
1.47
99.5

Example 20
MoO₃
2.5
0.643
1.2
67
0.024
1.22
99.3