JP5354984B2 - Lithium secondary battery - Google Patents

Description

  The present invention relates to a lithium secondary battery, and in particular, a positive electrode plate in which a positive electrode mixture containing a lithium-containing complex oxide and a positive electrode conductive material is applied to a current collector, and a non-removable lithium ion that can be occluded and released by charging and discharging. The present invention relates to a lithium secondary battery having a negative electrode plate in which a negative electrode mixture containing a crystalline carbonaceous material and a negative electrode conductive material is applied to a current collector.

  Lithium secondary batteries are widely used as power sources for portable devices such as VTR cameras, notebook computers, and mobile phones, taking advantage of the high energy density. On the other hand, in the automobile industry, in order to cope with environmental problems, an electric vehicle (EV) using only a battery as a power source and a hybrid electric vehicle (HEV) using both an internal combustion engine and a battery as a power source are used. Development has been accelerated and some have been put to practical use. A battery serving as a power source for EVs and HEVs is required to have not only high energy density but also high output and high capacity performance, and lithium secondary batteries are attracting attention as batteries that meet these requirements.

  In order to increase the output of the lithium secondary battery, the electrode reaction area is increased by reducing the particle diameter of the material used for the positive and negative electrode plates or by reducing the thickness of the positive and negative electrode plates, It is necessary to improve the electron conductivity and lithium ion diffusibility in the material layer. In order to improve the electron conductivity, it is necessary to reduce the resistance such as adding a conductive material or increasing the positive / negative electrode mixture density to secure an electron conduction network. It is necessary to secure a space for the nonaqueous electrolyte to penetrate into the material layer. As a technique for increasing the output of a lithium secondary battery, for example, a technique for securing an electron conduction network by setting an average particle diameter of a positive electrode active material and a pore volume in a positive electrode mixture layer is disclosed ( Patent Document 1).

JP 2005-158623 A

  However, in order to use a lithium secondary battery as a power source for EVs and HEVs, not only high output and high capacity that affect acceleration performance, etc., but also a long battery life to cope with the long-term use period of electric vehicles. There is also a need to make it. The extension of the life here means that not only the battery capacity but also the decrease in output is suppressed and the electric energy supply capability necessary for running the electric vehicle is satisfied over a long period of time. With the technology of Patent Document 1, it is possible to achieve high output by securing an electron conduction network, but it is difficult to obtain sufficient performance from the viewpoint of extending the life. On the other hand, if the proportion of the conductive material is increased too much in order to improve the electronic conductivity of the positive electrode plate, the proportion of the positive electrode active material is decreased and the output is reduced. On the other hand, if the proportion of the conductive material is reduced too much, the electrical resistance at the positive electrode plate increases, causing a decrease in output.

  In view of the above-described case, an object of the present invention is to provide a lithium secondary battery that can achieve both high output and long life.

In order to solve the above-described problems, the present invention provides a positive electrode plate in which a positive electrode mixture containing a lithium-containing double oxide and a positive electrode conductive material is applied to a current collector, and a non-occlusion / release of lithium ions by charging and discharging. A negative electrode plate comprising a current collector and a negative electrode mixture comprising a crystalline carbonaceous material and a negative electrode conductive material, and the positive electrode conductive material and lithium are disposed on the surface of the lithium-containing complex oxide. The additive containing material is mechanochemically treated, and the mechanochemically treated lithium-containing double oxide has a specific surface area ratio with the positive electrode conductive material and additive of lithium-containing double oxide: (positive electrode conductive material + added) Material) = 50: 50 to 95: 5, and the positive electrode mixture is prepared by mixing the mechanochemically treated lithium-containing double oxide and the mechanochemically treated lithium-containing double oxide. Wherein the current collector and a binder for coated on is one that was mixed.

In the present invention, since the specific surface area ratio in the mechanochemically treated lithium-containing double oxide is lithium-containing double oxide: (positive electrode conductive material + additive) = 50: 50 to 95: 5, the lithium-containing double oxide By subjecting the surface of the positive electrode conductive material to mechanochemical treatment , the mechanochemical treatment can be performed without compounding the conductive material in addition to the mechanochemically treated lithium-containing double oxide and without increasing the thickness of the positive electrode mixture layer. The ratio of the lithium-containing double oxide in the positive electrode mixture in which the chemically-treated lithium-containing double oxide and the binder are mixed can be increased, so that the output can be increased. By adding mechanochemical treatment to the additive material containing, it is possible to extend the life.

In this case, the positive Gokushirube material may be amorphous carbon. At this time, the mechanochemically treated lithium-containing double oxide has a specific surface area ratio of the positive electrode conductive material and the additive to lithium-containing double oxide: (positive electrode conductive material + additive) = 60: 40 to 95: 5. It can be. Such a positive electrode conductive material can be carbon black. Further, the additive may be lithium carbonate.

According to the present invention, since the specific surface area ratio in the mechanochemically treated lithium-containing double oxide is lithium-containing double oxide: (positive electrode conductive material + additive) = 50: 50 to 95: 5, Since the positive electrode conductive material is mechanochemically treated on the surface of the oxide, the conductive material is not blended in addition to the mechanochemically treated lithium-containing double oxide, and the thickness of the positive electrode mixture layer is not increased. The ratio of the lithium-containing double oxide in the positive electrode mixture in which the mechanochemically treated lithium-containing double oxide and the binder are mixed can be increased, and the output of the lithium-containing double oxide can be increased. In addition, it is possible to obtain an effect that the life can be extended by the mechanochemical treatment of the additive containing lithium.

  Embodiments of a cylindrical lithium ion secondary battery to which the present invention is applied will be described below with reference to the drawings.

(Constitution)
As shown in FIG. 1, the cylindrical lithium ion secondary battery 20 of this embodiment has a bottomed cylindrical battery container 7 made of steel plated with nickel. The battery container 7 accommodates an electrode group 6 in which a strip-like positive electrode plate W1 and a negative electrode plate W3 are wound in a spiral cross section through a separator W5 on a hollow cylindrical shaft core 1 made of polypropylene.

  A copper negative electrode current collecting ring 5 for collecting electric potential from the negative electrode plate is disposed below the electrode group 6. The outer peripheral surface of the lower end portion of the shaft core 1 is fixed to the inner peripheral surface of the negative electrode current collecting ring 5. The end of the negative electrode lead piece 3 led out from the negative electrode plate W3 is joined to the outer peripheral edge of the negative electrode current collecting ring 5 by welding. A copper negative electrode lead plate 8 for electrical conduction is welded to the lower part of the negative electrode current collecting ring 5, and the negative electrode lead plate 8 is joined to the inner bottom of the battery container 7 which also serves as a negative electrode external terminal by resistance welding. Yes.

  On the other hand, on the upper side of the electrode group 6, an aluminum positive electrode current collecting ring 4 for collecting the electric potential from the positive electrode plate W <b> 1 is disposed on an almost extension line of the shaft core 1. The positive electrode current collecting ring 4 is fixed to the upper end portion of the shaft core 1. The edge part of the positive electrode lead piece 2 led out from the positive electrode plate W1 is joined by welding to the periphery of the collar part integrally protruding from the periphery of the positive electrode current collecting ring 4. A battery lid that also serves as a positive electrode external terminal is disposed above the positive electrode current collecting ring 4. The battery lid is composed of a lid case 12, a lid cap 13, a valve retainer 14 that keeps airtightness, and a cleavage valve (internal gas discharge valve) 11 that is cleaved by an increase in internal pressure. It is assembled by caulking and fixing the periphery of 12. One side of two positive electrode lead plates 9 in which ribbon-shaped aluminum foils are laminated is joined to the upper surface of the positive electrode current collecting ring 4 by welding. Another side of the positive electrode lead plate 9 is joined to the lower surface of the lid case 12 constituting the battery lid. The other ends of the two positive electrode lead plates 9 are joined by welding.

The battery lid is caulked and fixed to the upper part of the battery container 7 via an insulating and heat resistant EPDM resin gasket 10. For this reason, the inside of the lithium ion secondary battery 20 is sealed. In addition, a nonaqueous electrolytic solution (not shown) that can infiltrate the entire electrode group 6 is injected into the battery container 7. The non-aqueous electrolyte is obtained by dissolving 1 mol / liter of lithium hexafluorophosphate (LiPF ₆ ) as a lithium salt in a mixed solvent of ethylene carbonate, dimethyl carbonate and diethyl carbonate in a volume ratio of 1: 1: 1. It is used.

  The electrode group 6 is formed so that the positive electrode plate W1 and the negative electrode plate W3 are not directly in contact with each other through, for example, a porous polyethylene separator W5 having a thickness of 40 μm and capable of passing lithium ions. It is wound around. The positive electrode lead piece 2 and the negative electrode lead piece 3 are arranged on both end surfaces of the electrode group 6 on the opposite sides. Insulation coating is applied to the entire circumference of the collar surface of the electrode group 6 and the positive electrode current collecting ring 4. For the insulation coating, an adhesive tape in which a hexamethacrylate adhesive material is applied to one side of a polyimide base material is used. The pressure-sensitive adhesive tape is wound one or more times from the peripheral surface of the collar portion to the outer peripheral surface of the electrode group 6.

  The positive electrode plate W1 constituting the wound group 6 has an aluminum foil as a positive electrode current collector, and the negative electrode plate W3 has a rolled copper foil as a negative electrode current collector. In this example, the thicknesses of the aluminum foil and the rolled copper foil are set to 20 μm and 10 μm, respectively. Uncoated portions of the positive electrode mixture W2 and the negative electrode mixture W4 are formed on the side edges on one side in the longitudinal direction of the aluminum foil and the rolled copper foil, respectively. The uncoated part is cut out in a comb shape, and the positive electrode lead piece 2 and the negative electrode lead piece 3 are formed in the remaining part of the cutout.

  In the positive electrode plate W1, a positive electrode mixture containing a lithium-containing double oxide as a positive electrode active material is applied to both surfaces of an aluminum foil, and a positive electrode mixture layer W2 is formed. The surface of the lithium-containing composite oxide is mechanochemically treated with a conductive material and an additive containing lithium (hereinafter simply referred to as additive). In this example, lithium manganate (Mitsubishi Chemical Co., Ltd.) as the lithium-containing composite oxide, graphite-based carbon material (JSP, manufactured by Nippon Graphite Industries Co., Ltd.) as the conductive material, or carbon black of amorphous carbon material (Electrochemical Industry Co., Ltd., HS-100) and lithium carbonate (Honjo Chemical Co., Ltd.) are used as additives.

  Here, the mechanochemical treatment will be described. In the mechanochemical treatment, mechanical energy such as impact, shear, grinding, friction and compression is applied to the fine particles. A part of the added mechanical energy is accumulated in the fine particles, and the activity / reactivity of the fine particle surface is enhanced, whereby a reaction (mechanochemical reaction) with surrounding substances can be caused.

  Lithium manganate, the conductive material, and the additive are dry-mixed using a planetary mixer. At this time, the ratio of lithium manganate to the conductive material and the additive (lithium manganate: (conductive material + additive)) is set in the range of 50:50 to 95: 5 in terms of the specific surface area ratio. The obtained mixed powder is compressed and ground to form a powder (hereinafter referred to as mechanochemically treated powder) in which a conductive material and an additive are mechanochemically treated on the surface of lithium manganate.

  As a method of compressing and grinding the mixed powder, in this example, a compression and grinding type pulverizer (Miracle KCK-32, manufactured by Asada Tekko Co., Ltd.) is used. The compression mill type pulverizer includes a screw feeder that forms a constant internal space and continuously supplies a certain amount of lithium manganate, a conductive material and an additive at a rotational speed, and a fixed blade fixed to a fixed shaft of the screw feeder. And a rotating blade. The mechanochemical reaction is caused by adjusting the compressive shear stress according to the shape of the fixed blade and the rotating blade, the number of rotations, and the supply amount of each material. By this reaction, mechanochemically treated powder is formed.

  The positive electrode composite material contains a mechanochemically treated powder and a binder (binder) polyvinylidene fluoride (hereinafter abbreviated as PVDF) in a mass ratio of 95: 5 (mechanochemically treated powder: PVDF). Has been. When the positive electrode mixture is applied to the aluminum foil, N-methylpyrrolidone (hereinafter abbreviated as NMP) is used as a viscosity adjusting solvent, and a slurry-like solution is prepared by kneading substantially uniformly. The prepared solution is applied substantially uniformly and substantially uniformly on both surfaces of the aluminum foil and dried to form the positive electrode mixture layer W2. After drying, the positive electrode plate W1 is pressed and cut so as to have a positive electrode active material application portion thickness of 70 μm that does not include an aluminum foil.

  On the other hand, in the negative electrode plate W3, an amorphous carbon material (amorphous carbon material) is used as the negative electrode active material. In the negative electrode plate W3, the negative electrode mixture containing an amorphous carbon material is applied substantially uniformly and substantially uniformly on both surfaces of the rolled copper foil, and the negative electrode mixture layer W4 is formed. In the negative electrode mixture, an amorphous carbon material, a conductive material, and PVDF as a binder are blended in a mass ratio of 80:10:10. When the negative electrode mixture is applied to the rolled copper foil, the viscosity is adjusted with NMP as a viscosity adjusting solvent, and the negative electrode mixture layer W4 is formed in the same manner as the positive electrode plate W1. After drying, the negative electrode plate W3 is pressed and cut so as to have a negative electrode active material application portion thickness of 70 μm that does not include a rolled copper foil.

(Action etc.)
Next, the operation and the like of the lithium ion secondary battery 20 of the present embodiment will be described.

In this embodiment, mechanochemically processed powder is blended in the positive electrode mixture layer W2. In the mechanochemically treated powder, a carbon material as a conductive material and a lithium carbonate as an additive material are mechanochemically treated on the surface of lithium manganate (positive electrode active material). By this mechanochemical treatment powder is blended, it is possible to eliminate mechanochemical treatment powders other conductive material in the positive electrode. Thereby, since the ratio of the lithium manganate in the positive electrode mixture layer W2 increases, it is possible to increase the output and capacity of the obtained lithium ion secondary battery 20.

  In addition, when the proportion of the conductive material is increased in order to improve the electron conductivity in the conventional positive electrode mixture layer, it is necessary to increase the amount of the positive electrode active material in order to ensure output. For this reason, the thickness of the positive electrode mixture layer is increased, and the volume energy density of the lithium ion secondary battery is reduced. In contrast, in this embodiment, the mechanical energy applied in the mechanochemical treatment increases the activity / reactivity of the surface of the lithium manganate, and the conductive material and the additive material are mechanochemically treated on the surface of the lithium manganate. Is done. For this reason, the conductive performance of the mechanochemically treated conductive material on the surface of lithium manganate is maximized, so that the electron conduction in the positive electrode mixture layer W2 can be achieved without adding a conductive material in addition to the mechanochemically treated powder. Can be improved. Thereby, by setting only the ratio of lithium manganate, it is possible to increase the output and capacity of the lithium ion secondary battery 20 without reducing the volume energy density. Further, since the mechanochemically treated powder is formed only by mechanical operation, the powder preparation work can be facilitated.

  Furthermore, in the present embodiment, since the additive material lithium carbonate is mechanochemically treated on the surface of the lithium manganate, it is possible to suppress a decrease in capacity due to repeated charge and discharge and to extend the life. Although this action has not been fully elucidated, it can be inferred as follows. That is, in lithium manganate, lithium ions are occluded and released with charge / discharge, but the occlusion / release property may be reduced by repeated charge / discharge. On the other hand, it is considered that the decrease in the occlusion / release property was suppressed by the mechanochemical treatment of the additive containing lithium such as lithium carbonate on the surface of the lithium manganate.

  Furthermore, in this embodiment, since the lithium manganate, the conductive material, and the additive are mechanochemically processed, the dispersion state of the lithium manganate, the conductive material, and the additive is equalized during the preparation of the positive electrode mixture. Can do. For this reason, since the lithium manganate, the conductive material, and the additive are not distributed unevenly in the positive electrode mixture layer 2, an electron conduction network can be secured and the electron conductivity can be improved.

  In the present embodiment, an example in which a compression grinder is used for the mechanochemical treatment is shown, but the present invention is not limited to this. Any method and apparatus may be used as long as sufficient mechanical energy can be applied to the mixed powder of lithium manganate, conductive material, and additive to cause a mechanochemical reaction. Examples of such an apparatus include a ball mill such as a planetary ball mill that uses a rotational force, a vibration force, or the like to pulverize powder with a large number of spheres.

  Further, in this embodiment, lithium manganate is exemplified as the positive electrode active material, but the present invention is not limited to this, and lithium ions can be occluded and released, and a sufficient amount of lithium is inserted in advance. That's fine. As the positive electrode active material, a lithium-containing double oxide such as a lithium transition metal double oxide may be used. Alternatively, a material obtained by replacing or doping a part of lithium or transition metal in the crystal with another element may be used. Further, the crystal structure is not particularly limited, and may be a spinel crystal structure or a layered crystal structure.

  Furthermore, in this embodiment, an example of a graphite-based or amorphous carbon material is shown as a conductive material to be mechanochemically treated on the surface of lithium manganate. However, the present invention is not limited to these, and the conductive material What is necessary is just to have sex. Examples of the carbon material include various graphite materials such as natural graphite and artificial graphite, and coke, and amorphous carbon materials such as carbon black. Also in the particle shape, scale-like, spherical, fibrous, massive, etc. There is no particular limitation. In consideration of further improving the output characteristics and life characteristics, it is preferable to use an amorphous carbon material rather than a graphite-based carbon material. When an amorphous carbon material is used for the conductive material, the ratio of lithium manganate to the conductive material and the additive (lithium manganate: (conductive material + additive)) is 60:40 in terms of the specific surface area. It is preferable to set in the range of ~ 95: 5. Moreover, although lithium carbonate was illustrated as an additive, this invention is not limited to this, For example, the compound containing lithium, such as lithium nitrate, can be used.

  Furthermore, in this embodiment, 1 mol / liter of lithium hexafluorophosphate is dissolved in a mixed solvent in which ethylene carbonate, dimethyl carbonate, and diethyl carbonate are mixed at a volume ratio of 1: 1: 1 in a non-aqueous electrolyte. However, the present invention is not limited to this. As the non-aqueous electrolyte, a non-aqueous electrolyte generally used for a lithium ion secondary battery can be used.

  Furthermore, in the present embodiment, the cylindrical lithium ion secondary battery 20 is illustrated, but the present invention is not limited to the shape of the battery, and can be applied to, for example, a rectangular battery or other polygonal batteries. It is. Further, the battery structure to which the present invention can be applied may be other than a battery having a structure in which the upper lid is caulked and sealed to the battery can described above. As an example of such a structure, a battery in which the positive and negative external terminals penetrate through the battery lid and the positive and negative external terminals are pressed together through the shaft core in the battery container can be mentioned. Furthermore, it can be applied to a laminated battery instead of a wound battery in which positive and negative plates are wound. Moreover, in this embodiment, although the comparatively large sized lithium ion secondary battery used for the electric vehicle power supply was illustrated, of course, this invention is not restrict | limited to battery capacity, size, etc.

Next, examples of the lithium ion secondary battery 20 manufactured according to the present embodiment will be described. In addition, Example 7, Example 14, Example 18, and Example 22 are shown for reference. In addition, a comparative example produced for comparison is also shown.

Example 1
As shown in Table 1 below, in Example 1, the mass ratio of graphite-based carbon material (hereinafter referred to as B) as a conductive material and lithium carbonate (hereinafter referred to as C) as an additive is B. : C = 80: 20. The specific surface area ratio of lithium manganate (hereinafter referred to as “A”) and the combined powder of B and C (hereinafter referred to as “D”) is set to A: D = 95: 5. A mechanochemically treated powder was prepared. In the mechanochemical treatment, the load current of the compression grinder was set to 18 A, the cooling water temperature was set to 20 ° C., and the spindle rotation speed was set to 70 rpm. Using the obtained mechanochemically treated powder, a positive electrode mixture layer W2 was formed on an aluminum foil, and a lithium ion secondary battery 20 of Example 1 was produced.

(Example 2 to Example 7)
As shown in Table 1, in Examples 2 to 7, lithium ion secondary batteries 20 were produced in the same manner as in Example 1 except that the specific surface area ratio A: D between A and D was changed. Specific surface area ratio A: D is 90:10 in Example 2, 80:20 in Example 3, 70:30 in Example 4, 60:40 in Example 5, 50:50 in Example 6, and Example 7 was set to 40:60.

(Comparative Example 1)
As shown in Table 1, in Comparative Example 1, a lithium ion secondary battery was produced in the same manner as in Example 1 except that A and D were simply mixed and used without mechanochemical treatment. That is, in Comparative Example 1, the specific surface area ratio A: D is 95: 5.

(Comparative Example 2 to Comparative Example 7)
As shown in Table 1, Comparative Example 2 to Comparative Example 7 were the same as Comparative Example 1 except that the specific surface area ratio A: D between A and D was changed. Specific surface area ratio A: D is 90:10 in Comparative Example 2, 80:20 in Comparative Example 3, 70:30 in Comparative Example 4, 60:40 in Comparative Example 5, 50:50 in Comparative Example 6, and Comparative Example 7 was set to 40:60. That is, in Comparative Examples 2 to 7, the specific surface area ratio A: D is set to be the same as those in Examples 2 to 7, respectively.

(Example 8)
As shown in Table 2 below, in Example 8, a lithium ion secondary battery 20 was produced in the same manner as in Example 1 except that the mass ratio B: C of B and C was set to 95: 5. did. That is, in Example 8, mechanochemically treated powder having a specific surface area ratio A: D of 95: 5 is used.

(Examples 9 to 14)
As shown in Table 2, in Examples 9 to 14, lithium ion secondary batteries 20 were produced in the same manner as in Example 8 except that the specific surface area ratio A: D between A and D was changed. Specific surface area ratios A: D were 90:10 in Example 9, 80:20 in Example 10, 70:30 in Example 11, 60:40 in Example 12, 50:50 in Example 13, and Example 14 was set to 40:60.

(Comparative Example 8)
As shown in Table 2, in Comparative Example 8, a lithium ion secondary battery was produced in the same manner as in Example 8 except that A and D were simply mixed and used without mechanochemical treatment. That is, in Comparative Example 8, the specific surface area ratio A: D is 95: 5.

(Comparative Example 9 to Comparative Example 14)
As shown in Table 2, Comparative Examples 9 to 14 were the same as Comparative Example 8 except that the specific surface area ratio A: D between A and D was changed. Specific surface area ratio A: D is 90:10 in Comparative Example 9, 80:20 in Comparative Example 10, 70:30 in Comparative Example 11, 60:40 in Comparative Example 12, 50:50 in Comparative Example 13, and Comparative Example 14 was set to 40:60. That is, in Comparative Example 9 to Comparative Example 14, the specific surface area ratio A: D is set to be the same as that of Example 9 to Example 14, respectively.

(Cycle life characteristics)
Regarding the produced lithium ion secondary batteries of Examples 1 to 14 and Comparative Examples 1 to 14, the cycle life characteristics were evaluated as follows. That is, each lithium ion secondary battery was charged and then discharged, and the initial discharge capacity was measured in an atmosphere having an environmental temperature of 23 to 27 ° C. The charging conditions were a 4.2 V constant voltage, a limiting current of 5 A, and a charging time of 2.5 hours. The discharge conditions were a 5 A constant current and a final voltage of 2.7 V. In addition, after charging under the above-described charging conditions, charging / discharging under the same charging / discharging conditions was repeated 300 times in an atmosphere having an environmental temperature of 48 to 52 ° C. Thereafter, the discharge capacity at the 300th cycle was measured in the same manner as the measurement of the initial discharge capacity in an atmosphere at an ambient temperature of 23 to 27 ° C. As the capacity retention rate, the ratio of the discharge capacity at the 300th cycle to the initial discharge capacity was obtained as a percentage, and the cycle life characteristics were evaluated. The evaluation results (life results) of the life characteristics are shown in Table 3 below for Examples 1 to 7 and Comparative Examples 1 to 7, and are shown in Tables below for Examples 8 to 14 and Comparative Examples 8 to 14. 4 respectively.

  As shown in Tables 3 and 4, Examples 1 to 14 using mechanochemically treated powders obtained by mechanochemically treating the conductive material (B) and additive (C) on the surface of lithium manganate (A). In each of the lithium ion secondary batteries 20 of Comparative Examples 1 to 14, the specific surface area ratios A: D were set to be the same and the materials were mixed and used without mechanochemical treatment. Improved lifetime results were observed compared to the battery. Among them, in the lithium ion secondary batteries 20 of Examples 1 to 4 and Examples 8 to 11 in which the specific surface area ratio A: D is set to 70:30 to 95: 5, the capacity is maintained at 83% or more. The rate was shown, and it turned out that the lifetime reduction can be suppressed small.

(Output characteristics)
Further, the output characteristics of the manufactured lithium ion secondary batteries of Examples 1 to 14 and Comparative Examples 1 to 14 were evaluated as follows. That is, after measuring the initial discharge capacity, the battery was charged under the above-described charging conditions, subjected to 25 A constant current discharge, and further charged under the above-described charging conditions to discharge 50 A constant current. The output was calculated from each 10-second voltage. In Examples 1 to 7 (B: C = 80: 20), the output of each lithium ion secondary battery 20 was set to the same specific surface area ratio A: D. It calculated | required as a percentage with respect to the output of an ion secondary battery. For example, in the lithium ion secondary battery 20 of Example 1, the percentage with respect to the output of the lithium ion secondary battery of Comparative Example 1 was obtained. In Examples 8 to 14 (B: C = 95: 5), the output of each lithium ion secondary battery 20 was set to the same specific surface area ratio A: D. Comparative Examples 8 to 14 As a percentage of the output of the lithium ion secondary battery. The output evaluation results are shown in Table 5 for Examples 1 to 7 and in Table 6 for Examples 8 to 14, respectively.

  As shown in Tables 5 and 6, in each of the lithium ion secondary batteries 20 of Examples 1 to 14 using mechanochemically treated powder, the specific surface area ratio A: D was set to be the same, and each material Compared with the lithium ion secondary batteries of Comparative Examples 1 to 14, which were used simply by mixing, the output density showed a value exceeding 100%. Among them, in the lithium ion secondary batteries 20 of Examples 2 to 6 and Examples 9 to 13 in which the specific surface area ratio A: D was set to 50:50 to 90:10, an excellent value of 105% or more was excellent. The output improvement effect was able to be acquired.

  From the evaluation results of Examples 1 to 14 and Comparative Examples 1 to 14, the mechanochemically treated powders obtained by mechanochemically treating the conductive material and the additive on the surface of lithium manganate were used, and each was simply mixed. It was found that the lithium ion secondary battery 20 having a high output and a long life can be obtained as compared with the case where it is used. At this time, it became clear that the effect of improving the output or life was recognized by setting the specific surface area ratio of lithium manganate: (conductive material + additive) to 95: 5 to 50:50. Further, if the specific surface area ratio is 95: 5 to 70:30, the life can be further improved, and if the specific surface area ratio is 90:10 to 50:50, the high output can be further improved. I found that I can do it.

  Next, a comparison of lithium ion secondary batteries using an amorphous carbon material and a graphite-based carbon material as the carbon material of the conductive material to be mechanochemically treated with lithium manganate will be described. That is, in Examples 15 to 22, an amorphous carbon material is used as the conductive material. Further, although the carbon material is not limited to the amorphous carbon material, Comparative Examples 15 to 22 are obtained by using a graphite-based carbon material as the conductive material in order to simplify the explanation.

(Example 15)
As shown in Table 7 below, in Example 15, the mass ratio of carbon black of an amorphous carbon material (hereinafter referred to as E) as a conductive material and lithium carbonate (C) as an additive is E: C. = 80: 20. The mechanochemically treated powder was set so that the specific surface area ratio of the lithium manganate (A) and the powder combining E and C (hereinafter referred to as F) was A: F = 95: 5. Prepared. In the mechanochemical treatment, the load current of the compression grinder was set to 18 A, the cooling water temperature was set to 20 ° C., and the spindle rotation speed was set to 70 rpm. Using the obtained mechanochemically treated powder, a positive electrode mixture layer W2 was formed on an aluminum foil, and a lithium ion secondary battery 20 of Example 15 was produced.

(Example 16 to Example 18)
As shown in Table 7, in Examples 16 to 18, lithium ion secondary batteries 20 were produced in the same manner as in Example 15 except that the specific surface area ratio A: F between A and F was changed. The specific surface area ratio A: F was set to 80:20 in Example 16, 60:40 in Example 17, and 40:60 in Example 18, respectively.

(Comparative Example 15)
As shown in Table 7, in Comparative Example 15, the mass ratio of graphite-based carbon material (hereinafter referred to as G) as the conductive material and lithium carbonate (C) as the additive is G: C = 80: 20. Was set to be. Mechanochemically treated powder prepared and prepared such that the specific surface area ratio of lithium manganate (A) and powder combining G and C (hereinafter referred to as H) is A: H = 95: 5 A lithium ion secondary battery was fabricated in the same manner as in Example 15 except that the above was used.

(Comparative Example 16 to Comparative Example 18)
As shown in Table 7, Comparative Examples 16 to 18 were the same as Comparative Example 15 except that the specific surface area ratio A: H of A and H was changed. The specific surface area ratio A: H was set to 80:20 in Comparative Example 16, 60:40 in Comparative Example 17, and 40:60 in Comparative Example 18, respectively. That is, in Comparative Example 16 to Comparative Example 18, the specific surface area ratio A: H is set to be the same as the specific surface area ratio A: F of Examples 16 to 18, respectively.

(Example 19)
As shown in Table 8 below, in Example 19, a lithium ion secondary battery 20 was produced in the same manner as in Example 15 except that the mass ratio E: C of E and C was set to 95: 5. did. That is, in Example 19, mechanochemically treated powder having a conductive surface area of carbon black of an amorphous carbon material and a specific surface area ratio A: F of 95: 5 is used.

(Example 20 to Example 22)
As shown in Table 8, in Examples 20 to 22, lithium ion secondary batteries 20 were produced in the same manner as in Example 19 except that the specific surface area ratio A: F of A and F was changed. The specific surface area ratio A: F was set to 80:20 in Example 20, 60:40 in Example 21, and 40:60 in Example 22, respectively.

(Comparative Example 19)
As shown in Table 8, in Comparative Example 19, a lithium ion secondary battery was fabricated in the same manner as Comparative Example 15 except that the mass ratio G: C of G and C was set to 95: 5. That is, in Comparative Example 19, the conductive material is a graphite-based carbon material, and the specific surface area ratio A: H is 95: 5, which is the same as the specific surface area ratio A: F of Example 19.

(Comparative Example 20 to Comparative Example 22)
As shown in Table 8, Comparative Example 20 to Comparative Example 22 were the same as Comparative Example 19 except that the specific surface area ratio A: H of A and H was changed. The specific surface area ratio A: H was set to 80:20 in Comparative Example 20, 60:40 in Comparative Example 21, and 40:60 in Comparative Example 22, respectively. That is, in Comparative Examples 20 to 22, the specific surface area ratio A: H is set to be the same as the specific surface area ratio A: F of Examples 20 to 22, respectively.

(Output characteristics)
Regarding the produced lithium ion secondary batteries of Examples 15 to 22 and Comparative Examples 15 to 22, the output characteristics were evaluated in the same manner as the output characteristics evaluation of Examples 1 to 14 described above. In Examples 15 to 18 (E: C = 80: 20), the specific surface area ratio A: H is set so that the output of each lithium ion secondary battery 20 is the same as the specific surface area ratio A: F. It calculated | required as a percentage with respect to the output of the lithium ion secondary battery of the comparative examples 15-18. For example, in the lithium ion secondary battery 20 of Example 15, the percentage with respect to the output of the lithium ion secondary battery of Comparative Example 15 was obtained. In Examples 19 to 22 (E: C = 95: 5), the specific surface area ratio A: H so that the output of each lithium ion secondary battery 20 is the same as the specific surface area ratio A: F. Was determined as a percentage of the output of the lithium ion secondary batteries of Comparative Examples 19 to 22. The output evaluation results are shown in Table 9 for Examples 15 to 18 and in Table 10 for Examples 19 to 22, respectively.

  As shown in Tables 9 and 10, Examples 15 to 15 using powders obtained by mechanochemical treatment of lithium manganate (A) with an amorphous carbon material (E) as a conductive material and lithium carbonate (C) as an additive. In the lithium ion secondary battery 20 of Example 22, the specific surface area ratio A: H was set to be the same as the specific surface area ratio A: F, respectively, and the graphite-based carbon material ( Compared to the lithium ion secondary batteries of Comparative Examples 15 to 22 using powders obtained by mechanochemical treatment of G) and lithium carbonate (C), the output density showed a value exceeding 100%. That is, it has been found that the power density can be improved by using an amorphous carbon material as the conductive material as compared with the graphite-based carbon material. Among them, in the lithium ion secondary batteries 20 of Examples 16 to 17 and Examples 20 to 21 in which the specific surface area ratio A: F was set to 60:40 to 80:20, an excellent value of 105% or more was excellent. The output improvement effect was able to be acquired.

(Cycle life characteristics)
Further, for the lithium ion secondary batteries of Examples 15 to 22 and Comparative Examples 15 to 22, the cycle life characteristics were evaluated in the same manner as the cycle life characteristics evaluation of Examples 1 to 14 described above. did. The evaluation results (life results) of the life characteristics are shown in Table 11 below for Examples 15 to 18 and Comparative Examples 15 to 18, and the tables below for Examples 19 to 22 and Comparative Examples 19 to 22 12 respectively.

  As shown in Tables 11 and 12, Examples 15 to 22 using powders obtained by mechanochemical treatment of lithium manganate (A) with carbon black (E) and lithium carbonate (C) as amorphous carbon materials. In the lithium ion secondary battery 20, the specific surface area ratio A: H is set to be the same as the specific surface area ratio A: F, and the graphite-based carbon material (G) and lithium manganate (A) are set. The improvement of the lifetime result was recognized compared with the lithium ion secondary battery of the comparative examples 15-22 using the powder which mechanochemically processed lithium carbonate (C). That is, it has been found that the lifetime result can be improved by using an amorphous carbon material as the conductive material as compared with the graphite-based carbon material. Among them, in the lithium ion secondary batteries 20 of Examples 15 to 17 and Examples 19 to 21 in which the specific surface area ratio A: F is set to 60:40 to 95: 5, the capacity is maintained at 84% or more. The rate was shown, and it turned out that the lifetime reduction can be suppressed small.

  From the evaluation results of Example 15 to Example 22 and Comparative Example 15 to Comparative Example 22, when mechanochemically treated powder obtained by mechanochemically treating the conductive material and additive on the surface of lithium manganate is used, the graphite material is used as the conductive material. It has been found that by using an amorphous carbon material, the lithium ion secondary battery 20 in which both output characteristics and cycle life characteristics are further improved can be obtained by using an amorphous carbon material as compared with the case where a carbon material is used. At this time, it became clear that the effect of improving the output or the life was recognized by setting the specific surface area ratio of lithium manganate: (conductive material + additive) to 95: 5 to 60:40. It was also found that high output can be further improved if the specific surface area ratio is 80:20 to 60:40.

  Since the present invention contributes to the manufacture and sale of lithium secondary batteries in order to provide a lithium secondary battery that can achieve both high output and long life, it has industrial applicability.

It is sectional drawing which shows the cylindrical lithium ion secondary battery of embodiment to which this invention is applied.

Explanation of symbols

6 Electrode group 20 Cylindrical lithium ion secondary battery (lithium secondary battery)
W1 Positive electrode plate W2 Positive electrode mixture layer W3 Negative electrode plate W4 Negative electrode mixture layer

Claims (5)

A positive electrode plate in which a positive electrode mixture including a lithium-containing complex oxide and a positive electrode conductive material is applied to a current collector, and an negative electrode composite including an amorphous carbon material capable of inserting and extracting lithium ions by charge and discharge and a negative electrode conductive material In a lithium secondary battery having a negative electrode plate coated with a material on a current collector, the positive electrode conductive material and an additive containing lithium are mechanochemically treated on the surface of the lithium-containing complex oxide , In the mechanochemically treated lithium-containing double oxide, the specific surface area ratio with the positive electrode conductive material and additive is lithium-containing double oxide: (positive electrode conductive material + additive) = 50: 50 to 95: 5. The mesochemically treated lithium-containing double oxide and a binder for applying the mechanochemically treated lithium-containing double oxide to the current collector Lithium secondary battery is characterized in that which has been engaged.   The lithium secondary battery according to claim 1, wherein the positive electrode conductive material is amorphous carbon. The mechanochemically treated lithium-containing double oxide has a specific surface area ratio with the positive electrode conductive material and additive of lithium-containing double oxide: (positive electrode conductive material + additive) = 60: 40 to 95: 5. The lithium secondary battery according to claim 2 , wherein the lithium secondary battery is provided. The positive Gokushirube material is a lithium secondary battery according to claim 2 or claim 3, wherein the carbon black. The lithium secondary battery according to any one of claims 1 to 4 , wherein the additive is lithium carbonate.

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