JP2013077529A - Storage element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a storage element allowing a plurality of active materials to sufficiently exhibit their respective performances.SOLUTION: A storage element comprises a plurality of electrode groups 10A-10D electrically connected in parallel to each other. Each of the plurality of electrode groups 10A-10D comprises: a positive electrode having a positive electrode active material; a negative electrode having a negative electrode active material; and a separator disposed between the positive electrode and the negative electrode. In each of the plurality of electrode groups 10A-10D, the positive electrode active material and the negative electrode active material have a uniform structure. At least two electrode groups of the plurality of electrode groups 10A-10D differ from each other in at least one of the positive electrode active material and the negative electrode active material.

Description

  The present invention relates to a power storage device, and more specifically, an electrode group in which a positive electrode having a positive electrode active material, a negative electrode having a negative electrode active material, and a separator disposed between the positive electrode and the negative electrode are wound. The present invention relates to an electricity storage element including at least two.

  Storage elements are used as non-electrolyte secondary batteries such as lithium ion secondary batteries, capacitors such as lithium ion capacitors and ultracapacitors. Such power storage elements are disclosed in, for example, Japanese Patent Application Laid-Open No. 2006-278256 (Patent Document 1), Japanese Patent Application Laid-Open No. 8-315860 (Patent Document 2), Japanese Patent Application Laid-Open No. 2010-15852 (Patent Document 3), and Japanese Patent Application Laid-Open No. 2009. -227171 (Patent Document 4) and the like.

  Patent Document 1 discloses a nonaqueous electrolyte secondary battery including a positive electrode having a positive electrode active material in which olivine type lithium manganese phosphate and spinel type lithium manganate are mixed. Patent Document 2 discloses a nonaqueous electrolyte secondary battery including a positive electrode having a positive electrode active material made of a mixture of a lithium cobalt composite oxide and a lithium manganese composite oxide.

  Patent Document 3 discloses a lithium ion secondary battery including a negative electrode in which negative electrode active material layers containing different active materials are applied to a current collector foil in a stripe shape. Patent Document 4 discloses a lead-free battery including a negative electrode obtained by applying and baking to a separated region of a current collector foil without mixing zinc and carbon.

JP 2006-278256 A JP-A-8-315860 JP 2010-15852 A JP 2009-227171 A

  When active materials having different compositions are mixed as in Patent Documents 1 and 2, each active material is randomly present in the active material layer (mixture layer). It is hard to be demonstrated. Furthermore, depending on the mixing ratio of the active materials, the respective performances may be offset.

  In addition, as in Patent Documents 3 and 4, when each active material having a different composition is applied to each of the partitioned areas of a single current collector foil, manufacturing conditions such as drying, pressing, and coating weight are used. The degree of freedom is limited. For this reason, since it cannot manufacture on the conditions optimal for each active material, the performance of each active material cannot fully be exhibited.

  In view of the above problems, an object of the present invention is to provide a power storage element that can sufficiently exhibit the performances of a plurality of active materials.

  The electricity storage device of the present invention includes a plurality of electrode groups electrically connected in parallel, and each of the plurality of electrode groups includes a positive electrode having a positive electrode active material, a negative electrode having a negative electrode active material, and a positive electrode and a negative electrode. Each of the plurality of electrode groups has a single configuration of the positive electrode active material and the negative electrode active material, and in at least two electrode groups of the plurality of electrode groups, the positive electrode active material And at least one of the negative electrode active materials is different.

  According to the electricity storage device of the present invention, since each of the plurality of electrode groups has a single active material configuration, the manufacturing conditions for forming each electrode group are manufactured under conditions optimal for each active material. can do. In addition, since at least two of the plurality of electrode groups have different active material configurations, the power storage element has two or more active materials manufactured under optimum conditions. Therefore, it is possible to provide a power storage element that can sufficiently exhibit each of the performances of the plurality of active materials.

  In the electricity storage device of the present invention, at least one of the positive electrode active material and the negative electrode active material can be different in at least two of the plurality of electrode groups.

  Thereby, the electrical storage element which can fully exhibit each performance by the component of several active material can be obtained.

  In the electricity storage device of the present invention, three or more electrode groups are provided, and among the plurality of electrode groups, an electrode group disposed on the relatively outer side and an electrode group disposed on the relatively inner side The structure of at least one of the positive electrode active material and the negative electrode active material can be made different.

  In the electricity storage element, the inner side is hotter than the outer side, so that an electrode disposed on the inner side can be obtained by using an active material having higher heat resistance than the electrode group disposed on the outer side for the electrode group disposed on the inner side. The difference in deterioration between the group and the electrode group disposed on the outside can be reduced. For this reason, durability can be improved as the whole electrical storage element.

  In the electricity storage device of the present invention, the positive electrode includes a positive electrode base material, a positive electrode mixture layer formed on the positive electrode base material, and having a positive electrode active material, a conductive additive, and a positive electrode binder. A negative electrode base material; and a negative electrode mixture layer formed on the negative electrode base material and having a negative electrode active material and a negative electrode binder. In at least two electrode groups of the plurality of electrode groups, a separator, a positive electrode base material In addition, at least one of the conductive auxiliary agent, the positive electrode binder, the negative electrode base material, and the negative electrode binder may be different.

  Thereby, in the active material which has a different structure, the separator, base material, conductive support agent, and binder suitable for each active material can be selected. For this reason, since performance can be more fully exhibited in each electrode group, a power storage element with improved performance can be obtained.

  In the electricity storage device of the present invention, preferably, the negative electrode active material of at least one of the at least two electrode groups is crystalline carbon, and the negative electrode active material of at least one of the remaining electrode groups is Amorphous carbon.

  By having crystalline carbon, capacity and output performance can be increased. By having amorphous carbon, input performance can be improved. Therefore, when the negative electrode active material of at least one of the plurality of electrode groups is crystalline carbon and the negative electrode active material of the remaining at least one electrode group is amorphous carbon, each active material is good Therefore, a high-capacity and high-input / output storage element can be realized.

Preferably in the electric storage element, at least one electrode group of the at least two electrode groups, the positive electrode active _{material, LiFePO 4, Li a Ni x} Mn y Co (1-xy) O 2 (0 ≦ a ≦ 1 .1, 0 <x <1, 0 <y <1, x + y <1) and Li _a Ni _x Co _y Al _z M _b O ₂ (0.3 ≦ a ≦ 1.05, 0.7 ≦ x ≦ 0) .87, 0.1 ≦ y ≦ 0.27, 0.03 ≦ z ≦ 0.1, 0 ≦ b ≦ 0.1, M is at least one selected from metal elements other than Ni, Co and Al) Is at least one selected from the group consisting of

Thus, the safety by LiFePO ₄ performance, _{Li a Ni x Mn y Co (} 1-xy) O 2 and _{Li a Ni x Co y Al z} M b at least one of performance due to O ₂ of large performance An expressed power storage element can be realized.

Preferably, in the electric storage element of the present invention, the positive electrode active material of the at least one electrode group of the at least two electrode groups are _{Li a Ni x Mn y Co (} 1-xy) O 2 (0 ≦ a ≦ 1.1, 0 <x <1, 0 <y <1, x + y <1), and the positive electrode active material of at least one of the remaining electrode groups is LiMn ₂ O ₄ .

By having Li _a Ni _x Mn _y Co _(1-xy) O ₂ , the capacity can be increased. By having LiMn ₂ O ₄ , safety can be improved. Thus, the positive electrode active material of the at least one electrode group Li _a of the plurality of electrode groups Ni _x Mn in _{y Co (1-xy) O} 2, a positive electrode active material is LiMn ₂ O of at least one electrode group of the remainder _If it is ₄ , good performance of each active material can be exhibited, so that a high-capacity and high-safety energy storage device can be realized.

  As described above, according to the present invention, it is possible to provide a power storage element that can sufficiently exhibit each of the performances of a plurality of active materials.

It is a perspective view which shows roughly the electrical storage element in embodiment of this invention. It is a perspective view which shows roughly the inside of the container of the electrical storage element in embodiment of this invention. It is sectional drawing which shows schematically the inside of the container of the electrical storage element in embodiment of this invention, and is sectional drawing along line III-III in FIG. It is a schematic diagram which shows roughly the electrode group which comprises the electrical storage element in embodiment of this invention. It is an expansion schematic diagram which shows roughly the positive electrode or negative electrode which comprises the electrode group in embodiment of this invention. It is a schematic diagram which shows roughly the inside of the container of the electrical storage element in the modification of embodiment of this invention. 4 is a schematic diagram schematically showing the inside of a container of a lithium ion secondary battery such as Comparative Example 1. FIG. It is a schematic diagram which shows roughly the inside of the containers of lithium ion secondary batteries, such as this invention example 4. FIG.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following drawings, the same or corresponding parts are denoted by the same reference numerals, and description thereof will not be repeated.

  With reference to FIGS. 1-5, the nonaqueous electrolyte secondary battery which is an example of the electrical storage element which is one embodiment of this invention is demonstrated.

  As shown in FIGS. 1 to 3, the nonaqueous electrolyte secondary battery 1 of the present embodiment is attached to a container 2, a plurality of electrode groups 10 </ b> A to 10 </ b> D accommodated in the container 2, and the container 2. A positive terminal 21 and a negative terminal 22 are provided.

  As illustrated in FIG. 1, the container 2 includes a main body 3 that houses the plurality of electrode groups 10 </ b> A to 10 </ b> D and a lid 4 that covers the main body 3. The main body 3 and the lid 4 are made of, for example, a stainless steel plate and are welded to each other. An opening for exposing the positive electrode terminal 21 and the negative electrode terminal 22 to the outside of the container 2 is formed in the lid 4, and the positive electrode terminal 21 and the negative electrode terminal 22 are disposed in the opening. Further, the lid 4 is provided with an electrolytic solution injection part 5. The electrolyte solution injection unit 5 is for injecting an electrolyte solution therein and is sealed when the nonaqueous electrolyte secondary battery 1 is used.

  As shown in FIGS. 2 and 3, a plurality of electrode groups 10 </ b> A to 10 </ b> D are accommodated in the main body 3. The plurality of electrode groups 10A to 10D are electrically connected in parallel. In the present embodiment, four electrode groups 10A to 10D are juxtaposed in the container 2, the electrode groups 10A and 10D are disposed relatively outside in the container 2, and the electrode groups 10B and 10C are containers. 2 is relatively located on the inner side.

  As shown in FIG. 4, each of the plurality of electrode groups 10A to 10D includes positive electrodes 11A to 11D, separators 12A to 12D, and negative electrodes 13A to 13D. In each of the electrode groups 10A to 10D, the separators 12A to 12D are disposed on the negative electrodes 13A to 13D, the positive electrodes 11A to 11D are disposed on the separators 12A to 12D, and the separators 12A to 12D are disposed on the positive electrodes 11A to 11D. It is wound in an arranged state and formed into a cylindrical shape. That is, in each of the electrode groups 10A to 10D, separators 12A to 12D are formed on the outer peripheral side of the negative electrodes 13A to 13D, and the positive electrodes 11A to 11D are formed on the outer peripheral side of the separators 12A to 12D. Separator 12A-12D is formed in the outer peripheral side. In the present embodiment, in each of the plurality of electrode groups 10A to 10D, the insulating separators 12A to 12D are disposed between the positive electrodes 11A to 11D and the negative electrodes 13A to 13D. Therefore, the positive electrodes 11A to 11D and the negative electrode 13A ˜13D is not electrically connected.

  The positive electrodes 11A to 11D are electrically connected to the positive electrode terminal 21 (see FIG. 1), and the negative electrodes 13A to 13D are electrically connected to the negative electrode terminal 22 (see FIG. 1).

As shown in FIG. 5, the positive electrodes 11A to 11D constituting the electrode groups 10A to 10D include positive electrode current collector foils 11A1 to 11D1 and positive electrode material mixture layers 11A2 to 11D2 formed on the positive electrode current collector foils 11A1 to 11D1. Have. Negative electrodes 13A to 13D constituting electrode groups 10A to 10D have negative electrode current collector foils 13A1 to 13D1 and negative electrode mixture layers 13A2 to 13D2 formed on negative electrode current collector foils 13A1 to 13D1. In the present embodiment, the positive electrode mixture layers 11A2 to 11D2 and the negative electrode mixture layers 13A2 to 13D2 are formed on the front and back surfaces of the positive electrode current collector foils 11A1 to 11D1 and the negative electrode current collector foils 13A1 to 13D1, respectively. The present invention is not particularly limited to this structure. For example, the positive electrode mixture layers 11A2 to 11D2 and the negative electrode mixture layers 13A2 to 13D2 may be formed on the front or back surfaces of the positive electrode current collector foils 11A1 to 11D1 and the negative electrode current collector foils 13A1 to 13D1. However, the negative electrode mixture layers 13A2 to 13D2 face the positive electrode mixture layers 11A2 to 11D2.
In the present embodiment, the positive electrode and the negative electrode current collector foil are described as examples of the positive electrode and the negative electrode substrate, but the positive electrode and the negative electrode substrate are not limited to a foil shape.

  The positive electrode mixture layers 11A2 to 11D2 include a positive electrode active material, a conductive additive, and a binder. The negative electrode mixture layers 13A2 to 13D2 have a negative electrode active material and a binder. The negative electrode mixture layers 13A2 to 13D2 may further have a conductive additive.

  In each of the plurality of electrode groups 10A to 10D, the configuration of the positive electrode active material and the negative electrode active material is single. That is, the positive electrode active material and the negative electrode active material having different configurations are not included in each of the electrode groups 10A to 10D.

  In at least two electrode groups among the plurality of electrode groups 10A to 10D, the configuration of at least one of the positive electrode active material and the negative electrode active material is different. That is, the configurations of the positive electrode active material and / or negative electrode active material of at least two electrode groups of the plurality of electrode groups 10A to 10D and the positive electrode active material and / or negative electrode active material of the remaining electrode group are different. In the present embodiment, the configuration of at least one of the positive electrode active material and the negative electrode active material is different between the electrode groups 10A and 10D arranged on the outer side and the electrode groups 10B and 10C arranged on the inner side.

  Here, “configuration” refers to, for example, components, amounts, porosity, particle diameter, and the like. This point will be described below.

“Single component” means that when the coefficients (composition ratios) of the elements included in the composition formula of the active material are compared, the difference in the values is less than 5%, or the elements are different It means that the ratio of elements to be replaced is less than 5%, and “the components are different” means that the difference in coefficient of each element is 5% or more, or among the elements in the composition formula of the active material , It means that 5% or more of at least one of them is substituted with a different element. For example, in LiCoO ₂ and LiCo _(1-c) Me _c O ₂ (Me is an arbitrary metal element), when c is less than 0.05, the component is single, and when c is 0.05 or more Have different ingredients.

  “Quantity is single” means that the difference in mass or density is less than 3%, and “difference in quantity” means that the difference in mass or density is 3% or more. .

“Porosity is single” means that the difference in porosity calculated by the following formulas (1) and (2) is less than 2%, and “different porosity” means This means that the difference in porosity calculated by the formulas (1) and (2) is 2% or more.
Porosity (%) = 100 − {(coating density / true density) × 100} (1)
Coating density (g / cm ³ ) = application weight (g / cm ² ) / active material layer thickness (cm) Formula (2)

“Single particle size” means that the difference in average particle size D ₅₀ measured by a laser diffraction particle size distribution analyzer is less than 20%, and “different particle sizes” means laser diffraction type. It means that the difference of the average particle diameter D ₅₀ measured by the particle size distribution measuring device is 20% or more.

  In each of the plurality of electrode groups 10A to 10D, all of the configurations of the positive electrode active material and the negative electrode active material are single, and in at least two electrode groups of the plurality of electrode groups 10A to 10D, At least one of at least one of the material and the negative electrode active material is different.

In at least two electrode groups in which at least one of the positive electrode active material and the negative electrode active material is different, at least one of the separator, the positive electrode current collector foil, the conductive additive, the positive electrode binder, the negative electrode current collector foil, and the negative electrode binder is different. Is preferred. In the case of the present embodiment, since the electrode groups 10A and 10D and the electrode groups 10B and 10C have different configurations of at least one of the positive electrode active material and the negative electrode active material, at least one of the following a) to f): It is preferable that
a) The configuration of the separators 12A and 12D is different from the configuration of the separators 12B and 12C.
b) The configuration of the positive electrode current collector foils 11A1 and 11D1 is different from the configuration of the positive electrode current collector foils 11B1 and 11C1.
c) The configuration of the negative electrode current collector foils 13A1 and 13D1 is different from the configuration of the negative electrode current collector foils 13B1 and 13C1.
d) The configuration of the conductive additive of the positive electrode mixture layers 11A2 and 11D2 is different from the configuration of the conductive additive of the positive electrode mixture layers 11B2 and 11C2.
e) The configuration of the positive electrode binder of the positive electrode mixture layers 11A2 and 11D2 and the configuration of the positive electrode binder of the positive electrode mixture layers 11B2 and 11C2 are different.
f) The configuration of the negative electrode binder of the negative electrode mixture layers 13A2 and 13D2 is different from the configuration of the negative electrode binder layers of the negative electrode mixture layers 13B2 and 13C2.

  In addition, when three or more electrode groups are arranged and there are two or more electrode groups having the same configuration of the positive electrode active material and the negative electrode active material, the positive electrode active material and the negative electrode active material are In each of the same electrode group, the configurations of the separator, the positive electrode current collector foil, the conductive additive, the positive electrode binder, the negative electrode current collector foil, and the negative electrode binder may be the same or different.

Here, the “configuration” of the separator and the positive electrode (negative electrode) current collector foil is the component, amount, thickness, etc. of the separator and the positive electrode (negative electrode) current collector foil, and the “configuration” of the conductive assistant and the binder is: These are components, amounts, particle diameters, and the like of the conductive aid and the positive electrode (negative electrode) binder. “Different components” means that the composition formulas are not the same in organic compounds, and that in inorganic compounds, the difference in the proportion of elements contained in each component is 5% or more. “Different amounts” means that the difference in mass or density is 3% or more. “Different in thickness” means that the difference in thickness is 10% or more. “Different particle diameters” means that the difference in average particle diameter D ₅₀ measured by a laser diffraction particle size distribution analyzer is 20% or more.

  In each of the plurality of electrode groups 10A to 10D, the number of turns, the thickness, and the like may be different or may be single.

  Further, in the present embodiment, the nonaqueous electrolyte secondary battery 1 provided with four electrode groups 10A to 10D as a plurality of electrode groups has been described as an example. However, as shown in FIG. If it has at least 2 electrode group 10A, 10B, it will not specifically limit.

  In this embodiment, a nonaqueous electrolyte battery is described as an example of a power storage element. However, the present invention is not limited to a nonaqueous electrolyte battery, and can be applied to, for example, a capacitor. When the present invention is used as a nonaqueous electrolyte battery, a lithium ion secondary battery is preferably used. When the present invention is used as a capacitor, a lithium ion capacitor or an ultracapacitor is preferably used.

Next, the effect of the nonaqueous electrolyte secondary battery 1 in the present embodiment will be described.
In the non-aqueous electrolyte secondary battery 1 of the present embodiment, since each of the plurality of electrode groups 10A to 10D has a single configuration of the positive electrode active material and the negative electrode active material, the electrode groups 10A to 10D are formed. The production conditions can be the optimum conditions for each positive electrode active material and negative electrode active material. Moreover, since at least one of the positive electrode active material and the negative electrode active material is different in at least two of the plurality of electrode groups 10A to 10D, two or more types of positive electrode and negative electrode active materials manufactured under optimum conditions are used. At least one of the following. Therefore, each of the good performances of the plurality of active materials can be sufficiently exhibited.

  Thus, the nonaqueous electrolyte secondary battery 1 that sufficiently exhibits each of the good performances of the plurality of active materials can make use of the advantages of each active material and compensate for the disadvantages. Therefore, a non-aqueous electrolyte secondary battery having desired performance such as safety, high capacity, high output, durability, charge / discharge efficiency, state of charge (hereinafter referred to as SOC), detection, cryogenic performance, and productivity is realized. can do.

  Hereinafter, the effect of the nonaqueous electrolyte secondary battery 1 in the present embodiment will be described in more detail by taking a specific configuration as an example.

(First example)
An electrode group having a spinel manganese-based active material such as LiMn ₂ O ₄ as a positive electrode active material or an iron phosphate active material represented by the general formula LiFePO ₄ , and Li _a Ni _x Co _y Al _z M _b O as _a positive electrode active material ₂ (0.3 ≦ a ≦ 1.05, 0.7 ≦ x ≦ 0.87, 0.1 ≦ y ≦ 0.27, 0.03 ≦ z ≦ 0.1, 0 ≦ b ≦ 0.1, M is Ni, at least one nickel is represented by one) active material or Li _a selected from metal elements except Co and _{Al Ni x Mn y Co (1} -xy) O 2 (0 ≦ a ≦ 1.1 , 0 <x <1, 0 <y <1, x + y <1), and a nonaqueous electrolyte secondary battery provided with an electrode group having a ternary active material.

  A spinel manganese-based active material and an iron phosphate active material have high safety, but are greatly deteriorated in a high-temperature environment. Nickel-based active materials and ternary-based active materials have a large capacity, but are slightly less safe against external impacts. In the non-aqueous electrolyte secondary battery 1 shown in FIGS. 2 and 3, the positive electrode active materials of the electrode groups 10A and 10D arranged on the outside are spinel manganese-based active materials or iron phosphate active materials and arranged on the inner side. The positive electrode active materials of the electrode groups 10B and 10C are nickel-based active materials or ternary active materials. In the nonaqueous electrolyte secondary battery 1 shown in FIG. 6, the positive electrode active material of the electrode group 10 </ b> A at a position relatively close to the external side when the battery pack is mounted is a spinel manganese-based active material or an iron phosphate active material. The positive electrode active material of the electrode group 10B at a relatively far position is a nickel-based active material or a three-component active material. As a result, deterioration of the spinel manganese-based active material or iron phosphate active material due to heat storage in the center of the battery can be suppressed, and the safety performance of the spinel manganese-based active material or iron phosphate active material can be exhibited. In addition, the large capacity performance of the nickel-based active material and the ternary-based active material can be exhibited. For this reason, the non-aqueous electrolyte secondary battery 1 that achieves both high safety and high capacity can be realized.

  Furthermore, an electrode group using an iron phosphate active material having a flat charge / discharge curve as a positive electrode active material, and a nickel-based active material or a ternary active material having an inclined charge / discharge curve as a positive electrode active material Since the nonaqueous electrolyte secondary battery 1 includes the electrode group, the SOC can be detected. Thus, the performance of the nonaqueous electrolyte secondary battery 1 can be further improved by appropriately selecting the configuration of the active material.

In the ternary active material, | x−y | <0.05 is preferable from the viewpoint of further manifesting the above effects.
Further, in compounds such as LiMn ₂ O ₄ and LiFePO ₄ , Li, transition metal, P, and O may be substituted with different elements. Even in this case, the same effect as described above is obtained.

(Second example)
A nonaqueous electrolyte secondary battery including an electrode group having graphite as crystalline carbon as a negative electrode active material and an electrode group having amorphous carbon will be described. Graphite has high capacity and output performance, but input performance is not sufficient. Amorphous carbon has a lower discharge capacity than graphite, but has excellent input performance. Therefore, when the negative electrode active material of at least one of the plurality of electrode groups is graphite and the negative electrode active material of at least one of the remaining electrode groups is amorphous carbon, each active material is good. Therefore, the non-aqueous electrolyte secondary battery 1 with high capacity and high input / output can be realized.

  Further, an electrode group using graphite having a flat charge / discharge curve as a negative electrode active material and an electrode group using amorphous carbon having a sloped charge / discharge curve as a negative electrode active material are nonaqueous electrolyte secondary batteries. By providing 1, SOC detection becomes possible. Thus, the performance of the nonaqueous electrolyte secondary battery 1 can be further improved by appropriately selecting the configuration of the active material.

(Third example)
The non-aqueous electrolyte secondary battery 1 having the same active material components but different active material amounts in at least two electrode groups will be described. When the application weight of the active material is increased, the amount of the active material can be increased, so that the capacity can be increased. However, since the electrode becomes thick, charging / discharging (input / output performance) at a large current is not sufficient. When the coating weight is reduced, the electrode is thinned, so that the input / output performance is improved. However, since the ratio of the current collecting foil in the electrode is increased, the energy density is decreased. Therefore, among the plurality of electrode groups, the weight of the positive electrode (negative electrode) active material of at least one electrode group is relatively large, and the weight of the positive electrode (negative electrode) active material of at least one of the remaining electrode groups is relatively large. If it is too small, good performance of each electrode can be exhibited, so that the non-aqueous electrolyte secondary battery 1 with high energy density and high input / output can be realized.

(Fourth example)
The non-aqueous electrolyte secondary battery 1 having the same active material components but different active material porosity in at least two electrode groups will be described. The porosity of the active material can be adjusted by the load applied after applying the active material. When the porosity is increased, the amount of the active material is reduced, so that the input / output performance can be increased, but the capacity is not sufficient. If the porosity is reduced, the energy density can be increased, but the output is not sufficient because the resistance is increased. Therefore, the porosity of the positive electrode (negative electrode) of at least one of the plurality of electrode groups is relatively large, and the porosity of the positive electrode (negative electrode) of at least one of the remaining electrode groups is relatively small. Since the good performance of each active material can be exhibited, the non-aqueous electrolyte secondary battery 1 having high input / output performance and high energy density can be realized.

Next, the effect of the preferable form of the nonaqueous electrolyte secondary battery 1 is demonstrated.
A preferred form of the non-aqueous electrolyte secondary battery 1 is a separator, a positive electrode (negative electrode) current collector foil, a conductive auxiliary agent and a positive electrode (negative electrode) in at least two electrode groups having different configurations of at least one of a positive electrode active material and a negative electrode active material. ) At least one configuration of the binder is different. Thereby, in the positive electrode (negative electrode) active materials having different configurations, it is possible to select a separator, a positive electrode (negative electrode) current collector foil, a conductive additive, and a positive electrode (negative electrode) binder suitable for each positive electrode (negative electrode) active material. it can. For this reason, since performance can be more fully exhibited in each electrode group, a power storage element with improved performance can be obtained.

  Hereinafter, the effect of the more preferable form of the nonaqueous electrolyte secondary battery 1 will be described in more detail by taking a specific configuration as an example.

(First example)
A cobalt-based active material such as LiCoO ₂ and a ternary active material used as a positive electrode active material have a high potential. It is preferable that the separator of the electrode group having an active material having a high potential includes an inorganic layer in order to suppress oxidation. An iron phosphate active material used as another positive electrode active material has a low potential. It is preferable that the separator of the electrode group having an active material having a low potential does not include an inorganic layer in order to reduce deterioration and increase energy density. Thus, in at least two electrode groups having different configurations of the positive electrode active material, the performance of the nonaqueous electrolyte secondary battery 1 is further improved by selecting the separator components so as to be suitable for each positive electrode active material. Can do.

(Second example)
As shown in FIG. 2 and FIG. 3, the nonaqueous electrolyte secondary battery 1 having three or more electrode groups, the electrode groups 10A and 10D arranged on the outer side, and the electrodes arranged on the inner side When at least one of the positive electrode active material and the negative electrode active material is different between the groups 10B and 10C, the separators 12A and 12D of the electrode groups 10A and 10D arranged on the outer side preferably include an inorganic layer. It is preferable that the separators 12B and 12C of the electrode groups 10B and 10C disposed on the substrate do not include an inorganic layer or have an inorganic layer and have good air permeability. The electrode groups 10A and 10D located on the outer side are more susceptible to external impact than the electrode groups 10B and 10C located on the inner side. However, since the separator including the inorganic layer is less susceptible to thermal shrinkage, the internal short circuit is caused by the external impact. Even if it generates heat, it can prevent the heat from running away. By using a separator that does not have an inorganic layer in the internal electrode groups 10B and 10C, or has an inorganic layer, but has good air permeability, clogging of the separator in a high temperature durability test can be suppressed. Degradation of the secondary battery 1 can be prevented. Therefore, the configuration of each active material is different between the internal electrode group and the external electrode group, and the separator of the component corresponding to the configuration of each active material is used, so that the safety of the nonaqueous electrolyte secondary battery 1 can be improved. The energy density can be improved while improving the properties.

  In this embodiment, each of the plurality of electrode groups has a single configuration of the positive electrode active material and the negative electrode active material, and at least two of the plurality of electrode groups have different negative electrode active material components. The effect of the device was investigated.

(Invention Example 1)
In Invention Example 1, a lithium ion secondary battery including the two electrode groups 10A and 10B shown in FIG. 6 was manufactured as follows.

First, the electrode group 10A will be described.
90% by weight of graphite as a negative electrode active material and 10% by weight of polyvinylidene fluoride (PVDF) as a binder were mixed, and N-methylpyrrolidone as a solvent was added to this mixture to form a negative electrode mixture paste. . A negative electrode mixture paste of 1.5 g / 100 cm ² was applied to both sides of a 10 μm-thick copper foil as a negative electrode current collector foil, dried, and then compressed by applying a load of 100 kgf / cm with a roll press. Molded. This produced the strip-shaped negative electrode. The size of the negative electrode was 220 cm in length, 13 cm in width, and the total thickness of the negative electrode current collector foil and the negative electrode mixture layers on both sides was 120 μm.

86% by weight of LiFePO ₄ as a positive electrode active material, 7% by weight of acetylene black as a conductive additive, and 7% by weight of PVDF are mixed, and N-methylpyrrolidone as a solvent is added to this mixture to form a positive electrode mixture paste. did. 3.2 g / 100 cm ² of positive electrode mixture paste was applied to both sides of a 20 μm thick aluminum foil as a positive electrode current collector foil, dried, and then compressed by applying a 500 kgf / cm load with a roll press. Molded. Thereby, a strip-like positive electrode was produced. The size of the positive electrode was 210 cm in length, 13 cm in width, and the total thickness of the positive electrode current collector foil and the positive electrode mixture layers on both sides was 190 μm.

A positive electrode tab and a negative electrode tab were attached to each of the positive electrode and the negative electrode.
Further, a microporous polyolefin membrane having a width of 12 cm and a thickness of 25 μm was prepared as a separator.

  Next, the positive electrode, the separator, the negative electrode, and the separator were laminated in this order and wound into a long cylindrical shape. This produced electrode group 10A.

The electrode group 10B was basically the same as the electrode group 10A, but differed in the negative electrode. Specifically, 90% by weight of hard carbon as a negative electrode active material and 10% by weight of PVDF as a binder were mixed, and a solvent was added to this mixture to form a negative electrode mixture paste. A negative electrode mixture paste of 1.0 g / 100 cm ² was applied to both sides of a negative electrode current collector foil of 10 μm thick copper foil as a negative electrode current collector foil, dried, and then subjected to a load of 400 kgf / cm by a roll press. Was applied for compression molding. The size of the strip-shaped negative electrode was 220 cm in length, 13 cm in width, and the total thickness of the negative electrode current collector foil and the negative electrode mixture layers on both sides was 120 μm.

  Next, the two electrode groups 10A and 10B are juxtaposed inside the main body 3 of the container 2, and the positive electrode tab and the negative electrode tab of each electrode group 10A and 10B are electrically connected in parallel. The lid 4 was attached to the main body 3 by welding to the terminal 21 and the negative electrode terminal 22, respectively.

1M LiPF ₆ (EC: DMC: DEC = 40: 40: 20) was injected as an electrolyte from the electrolyte injection part 5 of the lid 4. Thereafter, the electrolyte injection part 5 was sealed. The lithium ion secondary battery of Example 1 of the present invention was manufactured through the above steps.

(Comparative Example 1)
As shown in FIG. 7, the lithium ion secondary battery 100 of Comparative Example 1 is different from Example 1 of the present invention in that it includes one electrode group 100A having a negative electrode mixture layer containing a single negative electrode active material. It was.

  Specifically, for the formation of the negative electrode, similarly to the electrode group 10A of Example 1 of the present invention, a negative electrode mixture paste was formed, applied to both surfaces of the negative electrode current collector foil, dried, and then rolled. Then, compression molding was performed by applying a load of 100 kgf / cm. The negative electrode had a length of 430 cm, a width of 13 cm, and a total thickness of the negative electrode current collector foil and the negative electrode mixture layers on both sides of 120 μm.

For the formation of the positive electrode, as in Example 1 of the present invention, a positive electrode mixture paste was formed, applied to both surfaces of the positive electrode current collector foil, dried, and then applied with a load of 500 kgf / cm by a roll press. And compression molded. The positive electrode had a length of 420 cm, a width of 13 cm, and a total thickness of the positive electrode current collector foil and both positive electrode mixture layers of 190 μm.
Moreover, the same separator as Example 1 of this invention was prepared.

  Next, the positive electrode, the negative electrode, and the separator were wound in the same manner as in Invention Example 1 to produce an electrode group 100A. Next, similarly to Example 1 of the present invention, the electrode group 100A was accommodated in the container 2, and an electrolyte was injected to manufacture a lithium ion secondary battery of Comparative Example 1.

(Comparative Example 2)
The lithium ion secondary battery of Comparative Example 2 was basically the same as the lithium ion secondary battery of Comparative Example 1, except that the negative electrode active material was hard carbon instead of graphite.

(Comparative Example 3)
As shown in FIG. 7, the lithium ion secondary battery 100 of Comparative Example 3 is a first invention example in that it includes one electrode group 100A having a negative electrode mixture layer in which two types of negative electrode active materials are mixed. Was different.

Specifically, 45% by weight of graphite and 45% by weight of hard carbon as a negative electrode active material and 10% by weight of PVDF as a binder are mixed, and N-methylpyrrolidone as a solvent is added to this mixture to mix the negative electrode. An agent paste was formed. 1.3 g / 100 cm ² of the negative electrode mixture paste was applied on both sides of the same negative electrode current collector foil as in Example 1 of the present invention, dried, and then subjected to compression molding by applying a load of 300 kgf / cm with a roll press. did. The negative electrode had a length of 430 cm, a width of 13 cm, and a total thickness of the negative electrode current collector foil and the negative electrode mixture layers on both sides of 120 μm.

  The positive electrode was formed in the same manner as in Comparative Example 1. Moreover, the same separator as Example 1 of this invention was prepared.

  Next, the positive electrode, the negative electrode, and the separator were wound in the same manner as in Invention Example 1 to produce an electrode group 100A. Next, in the same manner as in Example 1 of the present invention, this electrode group 100A was accommodated in the container 2, and an electrolyte was injected to manufacture a lithium ion secondary battery of Comparative Example 3.

(Comparative Example 4)
As shown in FIG. 7, the lithium ion secondary battery 100 of Comparative Example 4 includes one electrode group 100 </ b> A having a negative electrode mixture layer formed in a region where each of the two types of negative electrode active materials is partitioned. This was different from Example 1 of the present invention.

Specifically, 90% by weight of graphite as a first negative electrode active material and 10% by weight of PVDF as a binder are mixed, and N-methylpyrrolidone as a solvent is added to this mixture to add a first negative electrode compound. An agent paste was formed. 90% by weight of hard carbon as a second negative electrode active material and 10% by weight of PVDF as a binder are mixed, and N-methylpyrrolidone as a solvent is added to this mixture to form a second negative electrode mixture paste. did. On each surface of the negative electrode current collector foil similar to Example 1, 1.5 g / 100 cm ² of the first negative electrode mixture paste was applied to the half area, and 1.0 g / 100 cm to the remaining half area. ^2nd 2nd negative mix paste was apply | coated. After drying this, it was compression molded by applying a load of 300 kgf / cm with a roll press. The negative electrode had a length of 430 cm, a width of 13 cm, and a total thickness of the negative electrode current collector foil and the negative electrode mixture layers on both sides of 120 μm.

  The positive electrode was formed in the same manner as in Comparative Example 1. Moreover, the same separator as Example 1 of this invention was prepared.

  Next, the positive electrode, the negative electrode, and the separator were wound in the same manner as in Invention Example 1 to produce an electrode group 100A. Next, in the same manner as in Example 1 of the present invention, this electrode group 100A was accommodated in the container 2, and an electrolyte was injected to manufacture a lithium ion secondary battery of Comparative Example 4.

(Evaluation method)
The lithium ion secondary batteries of Invention Example 1 and Comparative Examples 1 to 4 were evaluated for SOC detection, capacity, and durability.

  The SOC detection is evaluated by the gradient of the closed circuit voltage (hereinafter referred to as OCV) in the vicinity of SOC 50%. Specifically, the OCV measurement is performed in increments of 1% from SOC 49% to SOC 51%, and SOC 49% to SOC 50%. It was measured by averaging the amount of change in OCV during the period until and the amount of change in OCV between SOC 50% and SOC 51%.

The capacity was measured as follows. The battery was charged to a predetermined upper limit voltage at a constant current of 1 CA, and then charged to a predetermined lower limit voltage at a constant current of 1 CA. The discharge capacity at this time was defined as “capacity”.
In addition, 1CA is a current value when a battery charged to the upper limit voltage is discharged in 1 hour.
The combinations of the lower limit voltage and the upper limit voltage in each example were as follows. Example 1 (2.5V-3.6V), Examples 2-4, 6 (2.5V-4.2V), Example 5 (2.5V-4.0V).

  The durability is evaluated by a capacity retention rate. Specifically, after charging to a voltage corresponding to SOC 80% at a constant current of 2 CA in a constant temperature bath set to a predetermined temperature, SOC 20 at a constant current of 2 CA. It was measured by dividing the capacity after a predetermined number of cycles of a cycle test for discharging to a voltage corresponding to% by the capacity before the cycle.

(Evaluation results)
As for the OCV slope near SOC 50%, Example 1 of the present invention is 4 mV / SOC%, Comparative Example 1 is 0 mV / SOC%, Comparative Example 2 is 8 mV / SOC%, and Comparative Example 3 is 4 mV / SOC. % And Comparative Example 4 was 4 mV / SOC%. Although Example 1 of the present invention was smaller than Comparative Example 2 in which the ratio of hard carbon was large, SOC detection was better than Comparative Example 1 that did not contain hard carbon. From this, it was found that Example 1 of the present invention can exhibit the performance of hard carbon as a negative electrode active material.

  Regarding the capacity, Example 1 of the present invention was 85 (relative ratio), Comparative Example 1 was 100 (relative ratio), Comparative Example 2 was 70 (relative ratio), and Comparative Example 3 was 85 (relative ratio). Yes, Comparative Example 4 was 80 (relative ratio). Inventive Example 1 was smaller in capacity than Comparative Example 1 in which the ratio of graphite was large, but larger in capacity than Comparative Example 2 that did not contain graphite, and was further formed by dividing two active material regions. The capacity was larger than 4. From this, it was found that the lithium ion secondary battery of Inventive Example 1 can exhibit the performance of graphite as a negative electrode active material.

  Regarding the capacity retention after a cycle test at 25 ° C., Example 1 of the present invention is 85%, Comparative Example 1 is 80%, Comparative Example 2 is 90%, and Comparative Example 3 is 70%. Example 4 was 60%. Invention Example 1 was less durable than Comparative Example 2 where the ratio of hard carbon was large, but was higher than that of Comparative Example 1 containing no hard carbon. Furthermore, Invention Example 1 was able to improve the durability compared to Comparative Example 3 in which two types of active materials were mixed and Comparative Example 4 in which two regions of active materials were formed. From this, it was found that the lithium ion secondary battery of Inventive Example 1 can exhibit the performance of hard carbon as the negative electrode active material.

  As described above, according to the present example, each of the plurality of electrode groups has a single configuration of the positive electrode active material and the negative electrode active material, and in at least two electrode groups of the plurality of electrode groups, the negative electrode active material It was confirmed that each of the plurality of negative electrode active materials can sufficiently exhibit their respective performances by having different components.

  In the present embodiment, the structure of the positive electrode active material and the negative electrode active material is single in each of the plurality of electrode groups, and the weight of the negative electrode active material is different in at least two electrode groups of the plurality of electrode groups. The effect of was investigated.

(Invention Example 2)
In Invention Example 2, a lithium ion secondary battery including the two electrode groups 10A and 10B shown in FIG. 6 was produced as follows.

First, the electrode group 10A will be described.
92% by weight of graphite as a negative electrode active material and 8% by weight of PVDF as a binder were mixed, and N-methylpyrrolidone as a solvent was added to this mixture to form a negative electrode mixture paste. A negative electrode mixture paste of 2.0 g / 100 cm ² was applied to both sides of a 10 μm thick copper foil as a negative electrode current collector foil, dried, and then compressed by applying a 150 kgf / cm load with a roll press. Molded. This produced the strip-shaped negative electrode. The size of the negative electrode was 180 cm in length, 13 cm in width, and the total thickness of the negative electrode current collector foil and the negative electrode mixture layers on both sides was 150 μm.

90% by weight of LiMn ₂ O ₄ as a positive electrode active material, 3% by weight of acetylene black as a conductive additive, and 7% by weight of PVDF are mixed, and N-methylpyrrolidone as a solvent is added to this mixture to mix the positive electrode A paste was formed. 1.1 g / 100 cm ² of a positive electrode mixture paste was applied to both sides of a 20 μm-thick aluminum foil as a positive electrode current collector foil, dried, and then a load of 250 kgf / cm was applied by a roll press. Compression molded. Thereby, a strip-like positive electrode was produced. The size of the positive electrode was 170 cm in length, 13 cm in width, and the total thickness of the positive electrode current collector foil and the positive electrode mixture layers on both sides was 80 μm.

A positive electrode tab and a negative electrode tab were attached to each of the positive electrode and the negative electrode.
Moreover, the same separator as Example 1 of this invention was prepared.

  Next, the positive electrode, the separator, the negative electrode, and the separator were laminated in this order and wound into a long cylindrical shape. This produced electrode group 10A.

The electrode group 10B was basically the same as the electrode group 10A, but differed in the negative electrode. Specifically, a negative electrode paste similar to the electrode group 10A was applied to both sides of the negative electrode current collector foil at 0.5 g / 100 cm ² , dried, and then a 150 kgf / cm load was applied by a roll press. And compression molded. The size of the strip-shaped negative electrode was 320 cm in length, 13 cm in width, and the total thickness of the negative electrode current collector foil and the negative electrode mixture layers on both sides was 50 μm.

  Next, similarly to Example 1 of the present invention, two electrode groups 10A and 10B were accommodated in the container 2, and an electrolyte was injected to manufacture a lithium ion secondary battery of Example 2 of the present invention.

(Comparative Example 5)
As shown in FIG. 7, the lithium ion secondary battery 100 of Comparative Example 5 is different from Example 2 of the present invention in that it includes one electrode group 100A including a negative electrode mixture layer having one type of negative electrode active material. It was.

Specifically, a negative electrode mixture paste similar to that of Invention Example 2 was formed. A negative electrode mixture paste of 2.0 g / 100 cm ² was applied to both surfaces of a negative electrode current collector foil similar to Example 2 of the present invention, dried, and then subjected to compression molding by applying a load of 150 kgf / cm with a roll press. did. The negative electrode had a length of 350 cm and a width of 13 cm, and the total thickness of the negative electrode current collector foil and the negative electrode mixture layers on both sides was 150 μm.

  For the formation of the positive electrode, as in Example 2 of the present invention, a positive electrode mixture paste was formed, applied to both surfaces of the positive electrode current collector foil, dried, and then a load of 250 kgf / cm was applied with a roll press. And compression molded. The positive electrode had a length of 340 cm, a width of 13 cm, and a total thickness of the positive electrode current collector foil and the positive electrode mixture layers on both sides was 80 μm.

  Next, a separator similar to Example 2 of the present invention was prepared, and the positive electrode, the negative electrode, and the separator were wound in the same manner as Example 2 of the present invention to produce an electrode group 100A. Next, in the same manner as in Example 2 of the present invention, the electrode group 100A was accommodated in the container 2, and an electrolytic solution was injected to manufacture a lithium ion secondary battery of Comparative Example 5.

(Comparative Example 6)
The lithium ion secondary battery of Comparative Example 6 was basically the same as Comparative Example 5, except that the weight of the negative electrode mixture paste applied to the negative electrode current collector foil was 0.5 g / 100 cm ² . It was different.

(Comparative Example 7)
As shown in FIG. 7, the lithium ion secondary battery 100 of Comparative Example 7 includes one electrode group 100 </ b> A having a negative electrode mixture layer formed in regions in which two types of negative electrode active materials are partitioned. This was different from Example 2 of the present invention.

Specifically, a negative electrode mixture paste similar to that of Invention Example 2 was formed. On each surface of the same negative electrode current collector foil as that of Example 2 of the present invention, 2.0 g / 100 cm ² was applied to the half area, and 0.5 g / 100 cm ² of the negative electrode mixture paste was applied to the other half area. did. After drying this, it was compression molded by applying a load of 100 kgf / cm with a roll press. The negative electrode had a length of 350 cm and a width of 13 cm, and the total thickness of the negative electrode current collector foil and the negative electrode mixture layers on both sides was 150 μm.

  The positive electrode was formed in the same manner as in Comparative Example 5. Moreover, the same separator as Example 2 of this invention was prepared.

  Next, a positive electrode, a negative electrode, and a separator were wound in the same manner as in Invention Example 2 to produce an electrode group 100A. Next, in the same manner as in Example 2 of the present invention, the electrode group 100A was accommodated in the container 2, and an electrolyte was injected to manufacture a lithium ion secondary battery of Comparative Example 7.

(Evaluation method)
The lithium ion secondary batteries of Invention Example 2 and Comparative Examples 5 to 7 were evaluated for capacity and output.
The capacity was measured in the same manner as in Example 1. The combination of the lower limit voltage and the upper limit voltage was 2.5V-4.2V.
The output was measured as follows. Each battery was fully charged and then discharged for 10 seconds at each current value of 0.2, 1, 2, 4 CA. A VI plot was created from the current value and the voltage after discharge, linearly approximated by the least square method, and the current value when extrapolating to a point where the voltage was 2.0 V was calculated. The current value at this time was multiplied by a lower limit voltage (2.0 V here) to obtain an output.

(Evaluation results)
Regarding the capacity, Example 2 of the present invention was 90 (relative ratio), Comparative Example 5 was 100 (relative ratio), Comparative Example 6 was 80 (relative ratio), and Comparative Example 7 was 70 (relative ratio). there were. For this reason, it turned out that the lithium ion secondary battery of this invention example 2 can demonstrate the performance of a negative electrode with much quantity of an active material.

  Regarding output, Example 3 of the present invention is 80 (relative ratio), Comparative Example 5 is 30 (relative ratio), Comparative Example 6 is 100 (relative ratio), and Comparative Example 7 is 50 (relative ratio). there were. For this reason, it turned out that the lithium ion secondary battery of the example 2 of this invention can exhibit the performance of a negative electrode with relatively little quantity of an active material.

  As described above, according to the present example, each of the plurality of electrode groups has a single configuration of the positive electrode active material and the negative electrode active material, and in at least two electrode groups of the plurality of electrode groups, the negative electrode active material It was confirmed that the performance of each of the plurality of negative electrodes can be sufficiently exhibited by the difference in the amount of.

  In this example, the effect of different separator configurations was investigated in at least two electrode groups having different positive electrode active material configurations.

(Invention Example 3)
In Invention Example 3, a lithium ion secondary battery including the two electrode groups 10A and 10B shown in FIG. 6 was produced as follows.

First, the electrode group 10A will be described.
90% by weight of LiNi _0.8 Co _0.15 Al _0.05 O ₂ as a positive electrode active material, 4% by weight of acetylene black as a conductive additive, and 6% by weight of PVDF as a binder are mixed, and N as a solvent is added to this mixture. -Pyrrolidone was added to form a positive electrode mixture paste. A positive electrode mixture paste of 2.0 g / 100 cm ² was applied to both sides of a 20 μm thick aluminum foil as a positive electrode current collector foil, dried, and then a 200 kgf / cm load was applied by a roll press. Compression molded. Thereby, a strip-like positive electrode was produced. The size of the positive electrode was 210 cm in length, 10 cm in width, and the total thickness of the positive electrode current collector foil and the positive electrode mixture layers on both sides was 100 μm.

As a negative electrode active material, 90% by weight of graphite and 10% by weight of PVDF were mixed, and N-pyrrolidone as a solvent was added to this mixture to form a negative electrode mixture paste. A negative electrode mixture paste of 1.0 g / 100 cm ² was applied to both sides of a 10 μm-thick copper foil as a negative electrode current collector foil, dried, and then applied with a load of 100 kgf / cm by a roll press. Compression molded. This produced the strip-shaped negative electrode. The size of the negative electrode was 220 cm in length, 10 cm in width, and the total thickness of the negative electrode current collector foil and the negative electrode mixture layers on both sides was 100 μm.

A positive electrode tab and a negative electrode tab were attached to each of the positive electrode and the negative electrode.
Further, a microporous polyolefin membrane having a width of 9 cm and a thickness of 40 μm was prepared as a separator.

  Next, the positive electrode, the separator, the negative electrode, and the separator were laminated in this order and wound into a long cylindrical shape. This produced electrode group 10A.

The electrode group 10B was basically the same as the electrode group 10A, but differed in the positive electrode and the separator. Specifically, 90% by weight of LiMn ₂ O ₄ as a positive electrode active material, 3% by weight of acetylene black as a conductive auxiliary agent, and 7% by weight of PVDF as a binder are mixed, and the electrode group 10A is mixed with this mixture. The same solvent was added to form a positive electrode mixture paste. A positive electrode material mixture paste of 3.2 g / 100 cm ² was applied to both surfaces of the positive electrode current collector foil, dried, and then compression molded by applying a load of 250 kgf / cm with a roll press. The size of the belt-like positive electrode was 150 cm in length, 10 cm in width, and the total thickness of the positive electrode current collector foil and the positive electrode mixture layers on both sides was 140 μm.

A positive electrode tab and a negative electrode tab were attached to each of the positive electrode and the negative electrode.
Further, a polyolefin microporous film having a width of 9 cm and a thickness of 20 μm was prepared as a separator.

  Next, the positive electrode, the separator, the negative electrode, and the separator were laminated in this order and wound into a long cylindrical shape. This produced electrode group 10B.

  Next, similarly to Example 1 of the present invention, two electrode groups 10A and 10B were accommodated in the container 2, and an electrolyte was injected to manufacture a lithium ion secondary battery of Example 3 of the present invention.

(Comparative Example 8)
As shown in FIG. 7, the lithium ion secondary battery 100 of Comparative Example 8 is an invention example 3 in that it includes one electrode group 100 </ b> A having a positive electrode mixture layer in which two types of positive electrode active materials are mixed. Was different.

Specifically, 45% by weight of LiNi _0.8 Co _0.15 Al _0.05 O _{2 and} 45% by weight of LiMn ₂ O ₄ as a positive electrode active material, 4% by weight of acetylene black as a conductive additive, and 6% by weight of PVDF as a binder %, And N-methylpyrrolidone as a solvent was added to the mixture to form a positive electrode mixture paste. 2.6 g / 100 cm ² of the positive electrode mixture paste was applied to both surfaces of the same positive electrode current collector foil as in Example 3 of the present invention, dried, and then subjected to compression molding by applying a load of 250 kgf / cm with a roll press. did. The positive electrode had a length of 360 cm, a width of 10 cm, and a total thickness of the positive electrode current collector foil and both positive electrode mixture layers of 120 μm.

  Regarding the formation of the negative electrode, as in Example 3 of the present invention, a negative electrode mixture paste was formed, applied to both surfaces of the negative electrode current collector foil, dried, and then a load of 100 kgf / cm was applied with a roll press. And compression molded. The negative electrode had a length of 370 cm and a width of 10 cm, and the total thickness of the negative electrode current collector foil and the negative electrode mixture layers on both sides was 100 μm.

  Next, a positive electrode, a negative electrode, and a separator having a thickness of 40 μm were wound in the same manner as in Invention Example 3 to produce an electrode group 100A. Next, similarly to Example 3 of the present invention, the electrode group 100A was accommodated in the container 2, and an electrolyte was injected to manufacture a lithium ion secondary battery of Comparative Example 8.

(Comparative Example 9)
The lithium ion secondary battery of Comparative Example 9 was basically the same as Comparative Example 8, but differed in that the thickness of the separator was 20 μm.

(Evaluation method)
The capacity and safety of the lithium ion secondary batteries of Invention Example 3 and Comparative Examples 8 and 9 were evaluated.
The capacity was measured in the same manner as in Example 1. The combination of the lower limit voltage and the upper limit voltage was 2.5V-4.2V.
Safety was measured by investigating whether smoke or ignition would occur when an iron nail was passed through the center of a fully charged battery.

(Evaluation results)
Regarding the capacity, Example 3 of the present invention was 95 (relative ratio), Comparative Example 8 was 90 (relative ratio), and Comparative Example 9 was 100 (relative ratio). Therefore, the lithium ion secondary battery of the present invention Example 3, was found to be exhibited performance of LiNi _0.8 Co _0.15 Al _0.05 O ₂ of the positive electrode active material.

About safety | security, this invention example 3 and the comparative example 8 were favorable, and the comparative example 9 was not favorable at the point which smoked. Therefore, the lithium ion secondary battery of the present invention Example 3 was found to be perform as LiMn ₂ O ₄ positive electrode active material.

In addition, in Example 3 of the present invention, the thickness of the separator of the electrode group 10A including LiNi _0.8 Co _0.15 Al _0.05 O ₂ as the positive electrode active material is large, and the separator of the electrode group 10B including LiMn ₂ O ₄ as the positive electrode active material is used. Since the thickness was small, the performance of each positive electrode active material could be exhibited more.

  As described above, according to this example, it was confirmed that the performance of the positive electrode active material can be remarkably exhibited by the difference in the separator configuration in at least two electrode groups having different configurations of the positive electrode active material.

  In this example, the effect of different configurations of the positive electrode current collector foil was examined in at least two electrode groups having different configurations of the positive electrode active material.

(Invention Example 4)
In Invention Example 4, a lithium ion secondary battery including the three electrode groups 10A, 10B, and 10D shown in FIG. 8 was produced as follows.

First, the electrode groups 10A and 10D will be described.
90% by weight of LiNi _0.8 Co _0.15 Al _0.05 O ₂ as a positive electrode active material, 4% by weight of acetylene black as a conductive additive, and 6% by weight of PVDF as a binder are mixed, and N as a solvent is added to this mixture. -Methylpyrrolidone was added to form a positive electrode mixture paste. A positive electrode mixture paste of 1.6 g / 100 cm ² was applied to both surfaces of a 30 μm-thick aluminum foil as a positive electrode current collector foil, dried, and then a 200 kgf / cm load was applied by a roll press. Compression molded. Thereby, a strip-like positive electrode was produced. The size of the positive electrode was 290 cm in length, 13 cm in width, and the total thickness of the positive electrode current collector foil and the positive electrode mixture layers on both sides was 80 μm.

As a negative electrode active material, 90% by weight of hard carbon and 10% by weight of PVDF were mixed, and N-methylpyrrolidone as a solvent was added to this mixture to form a negative electrode mixture paste. A negative electrode mixture paste of 0.7 g / 100 cm ² was applied to both sides of a 10 μm thick copper foil as a negative electrode current collector foil, dried, and then a load of 400 kgf / cm was applied by a roll press. Compression molded. This produced the strip-shaped negative electrode. The size of the negative electrode was 300 cm in length, 13 cm in width, and the total thickness of the negative electrode current collector foil and the negative electrode mixture layers on both sides was 80 μm.

A positive electrode tab and a negative electrode tab were attached to each of the positive electrode and the negative electrode.
Moreover, the same separator as Example 1 of this invention was prepared.

  Next, the positive electrode, the separator, the negative electrode, and the separator were laminated in this order and wound into a long cylindrical shape. Thereby, electrode groups 10A and 10D were produced.

The electrode group 10B was basically the same as the electrode groups 10A and 10D, but differed in the positive electrode and the separator. Specifically, 90% by weight of LiMn ₂ O ₄ as a positive electrode active material, 4% by weight of acetylene black as a conductive auxiliary agent, and 6% by weight of PVDF as a binder are mixed, and a solvent is added to this mixture. Thus, a positive electrode mixture paste was formed. This positive electrode mixture paste was applied to both surfaces of a 20 μm thick aluminum foil as a positive electrode current collector foil, dried, and then compression molded by applying a load of 250 kgf / cm with a roll press. The size of the strip-like positive electrode was 220 cm in length, 13 cm in width, and the total thickness of the positive electrode current collector foil and the positive electrode mixture layers on both sides was 120 μm.

A positive electrode tab and a negative electrode tab were attached to each of the positive electrode and the negative electrode.
Moreover, the same separator as Example 1 of this invention was prepared.

  Next, the positive electrode, the separator, the negative electrode, and the separator were laminated in this order and wound into a long cylindrical shape. This produced electrode group 10B.

  Next, the electrode groups 10A and 10D are accommodated in the container 2 so that the electrode groups 10B are located on the outer side and the electrode groups 10B are located on the inner side. A lithium ion secondary battery of Invention Example 4 was produced.

(Comparative Example 10)
As shown in FIG. 7, the lithium ion secondary battery 100 of Comparative Example 10 is a fourth invention example in that it includes one electrode group 100 </ b> A having a positive electrode mixture layer in which two types of positive electrode active materials are mixed. Was different.

Specifically, 45% by weight of LiNi _0.8 Co _0.15 Al _0.05 O _{2 and} 45% by weight of LiMn ₂ O ₄ as a positive electrode active material, 4% by weight of acetylene black as a conductive additive, and 6% by weight of PVDF as a binder %, And N-methylpyrrolidone as a solvent was added to the mixture to form a positive electrode mixture paste. 2.1 g / 100 cm ² of positive electrode mixture paste was applied to both sides of an aluminum foil with a thickness of 30 μm as a positive electrode current collector foil, dried, and then compressed by applying a load of 250 kgf / cm with a roll press. Molded. The positive electrode had a length of 740 cm, a width of 13 cm, and a total thickness of the positive electrode current collector foil and the positive electrode mixture layers on both sides was 100 μm.

  As for the formation of the negative electrode, as in Example 4 of the present invention, a negative electrode mixture paste was formed, applied to both sides of the negative electrode current collector foil, dried, and then a load of 400 kgf / cm was applied with a roll press. And compression molded. The negative electrode had a length of 750 cm, a width of 13 cm, and a total thickness of the positive electrode current collector foil and the negative electrode mixture layers on both sides was 100 μm.

  Next, a separator similar to that of Inventive Example 4 was prepared, and the positive electrode, the negative electrode, and the separator were wound in the same manner as in Inventive Example 4 to produce an electrode group 100A. Next, in the same manner as Example 4 of the present invention, the electrode group 100A was accommodated in the container 2, and an electrolyte was injected to manufacture a lithium ion secondary battery of Comparative Example 10.

(Comparative Example 11)
The lithium ion secondary battery of Comparative Example 11 was basically the same as Comparative Example 10 except that the thickness of the positive electrode current collector foil was 20 μm.

(Evaluation method)
The capacity and safety of the lithium ion secondary batteries of Invention Example 4 and Comparative Examples 10 and 11 were evaluated. The capacity was measured in the same manner as in Example 1. The combination of the lower limit voltage and the upper limit voltage was 2.5V-4.2V. Safety was measured in the same manner as in Example 3.

(Evaluation results)
Regarding the capacity, Example 4 of the present invention was 95 (relative ratio), Comparative Example 10 was 90 (relative ratio), and Comparative Example 11 was 100 (relative ratio). Therefore, the lithium ion secondary battery of the present invention Example 4 were found to be exhibited performance of LiNi _0.8 Co _0.15 Al _0.05 O ₂ of the positive electrode active material.

About safety | security, this invention example 4 and the comparative example 10 were favorable, and the comparative example 11 was not favorable at the point which smoked. Therefore, the lithium ion secondary battery of the present invention Example 4 was found to be perform as LiMn ₂ O ₄ positive electrode active material.

In addition, in Example 4 of the present invention, the thickness of the positive electrode current collector foil of the electrode groups 10A and 10D including LiNi _0.8 Co _0.15 Al _0.05 O ₂ as the positive electrode active material is large, and the electrode including LiMn ₂ O ₄ as the positive electrode active material Since the thickness of the positive electrode current collector foil of group 10B was small, the performance of each positive electrode active material could be exhibited more.

  From the above, according to this example, it was confirmed that the performance of the positive electrode active material can be remarkably exhibited by the difference in the configuration of the positive electrode current collector foil in at least two electrode groups having different configurations of the positive electrode active material. did.

  In this example, the effect of the arrangement of the electrode groups when three or more electrode groups were provided was examined.

(Invention Example 5)
In Invention Example 5, a lithium ion secondary battery including the three electrode groups 10A, 10B, and 10D shown in FIG. 8 was manufactured as follows.

First, the electrode groups 10A and 10D will be described.
86% by weight of LiFePO ₄ as a positive electrode active material, 7% by weight of acetylene black as a conductive auxiliary agent, and 7% by weight of PVDF as a binder are mixed, and N-methylpyrrolidone as a solvent is added to this mixture. A positive electrode mixture paste was formed. 3.2 g / 100 cm ² of positive electrode mixture paste was applied to both sides of an aluminum foil with a thickness of 20 μm as a positive electrode current collector foil, dried, and then applied with a load of 500 kgf / cm by a roll press. Compression molded. Thereby, a strip-like positive electrode was produced. The size of the positive electrode was 140 cm in length, 13 cm in width, and the total thickness of the positive electrode current collector foil and the positive electrode mixture layers on both sides was 190 μm.

As a negative electrode active material, 90% by weight of graphite and 10% by weight of PVDF were mixed, and N-methylpyrrolidone as a solvent was added to this mixture to form a negative electrode mixture paste. A negative electrode mixture paste of 1.5 g / 100 cm ² was applied to both sides of a 10 μm-thick copper foil as a negative electrode current collector foil, dried, and then applied with a load of 100 kgf / cm by a roll press. Compression molded. This produced the strip-shaped negative electrode. The size of the negative electrode was 150 cm in length, 13 cm in width, and the total thickness of the negative electrode current collector foil and the negative electrode mixture layers on both sides was 120 μm.

A positive electrode tab and a negative electrode tab were attached to each of the positive electrode and the negative electrode.
Moreover, the same separator as Example 1 of this invention was prepared.

  Next, the positive electrode, the separator, the negative electrode, and the separator were laminated in this order and wound into a long cylindrical shape. Thereby, electrode groups 10A and 10D were produced.

The electrode group 10B was basically the same as the electrode groups 10A and 10D, but differed in the positive electrode. Specifically, 86% by weight of LiNi _0.8 Co _0.15 Al _0.05 O ₂ as a positive electrode active material, 7% by weight of acetylene black as a conductive additive, and 7% by weight of PVDF as a binder are mixed, and this mixture A solvent was added to form a positive electrode mixture paste. This positive electrode mixture paste was applied to both surfaces of a 20 μm thick aluminum foil as a positive electrode current collector foil, dried, and then compression molded by applying a load of 200 kgf / cm with a roll press. The size of the strip-like positive electrode was 160 cm in length, 13 cm in width, and the total thickness of the positive electrode current collector foil and the positive electrode mixture layers on both sides was 160 μm.

A positive electrode tab and a negative electrode tab were attached to each of the positive electrode and the negative electrode.
Moreover, the same separator as Example 1 of this invention was prepared.

  Next, the positive electrode, the separator, the negative electrode, and the separator were laminated in this order and wound into a long cylindrical shape. This produced electrode group 10B.

  Next, the electrode groups 10A and 10D are accommodated in the container 2 so that the electrode groups 10B are located on the outer side and the electrode groups 10B are located on the inner side. A lithium ion secondary battery of Invention Example 5 was produced.

(Comparative Example 12)
As shown in FIG. 7, the lithium ion secondary battery 100 of Comparative Example 12 is a sixth invention example in that it includes one electrode group 100 </ b> A having a positive electrode mixture layer in which two types of positive electrode active materials are mixed. Was different.

Specifically, 43% by weight of LiFePO ₄ as a positive electrode active material and 43% by weight of LiNi _0.8 Co _0.15 Al _0.05 O _2, 7% by weight of acetylene black as a conductive additive, and 7% by weight of PVDF as a binder And N-methylpyrrolidone as a solvent was added to the mixture to form a positive electrode mixture paste. A positive electrode mixture paste of 3.0 g / 100 cm ² was applied to both sides of an aluminum foil having a thickness of 20 μm as a positive electrode current collector foil, dried, and then compressed by applying a load of 400 kgf / cm with a roll press. Molded. The positive electrode had a length of 450 cm and a width of 13 cm, and the total thickness of the positive electrode current collector foil and the positive electrode mixture layers on both sides was 180 μm.

  As for the formation of the negative electrode, as in Example 5 of the present invention, a negative electrode mixture paste was formed, applied to both surfaces of the negative electrode current collector foil, dried, and then a load of 100 kgf / cm was applied with a roll press. And compression molded. The negative electrode had a length of 460 cm, a width of 13 cm, and a total thickness of the negative electrode current collector foil and the negative electrode mixture layers on both sides of 110 μm.

  Next, a separator similar to Example 5 of the present invention was prepared, and the positive electrode, the negative electrode, and the separator were wound in the same manner as Example 5 of the present invention to produce an electrode group 100A. Next, in the same manner as Example 5 of the present invention, this electrode group 100A was accommodated in the container 2, and an electrolyte was injected to manufacture a lithium ion secondary battery of Comparative Example 12.

(Comparative Example 13)
As shown in FIG. 7, the lithium ion secondary battery 100 of Comparative Example 13 includes one electrode group 100 </ b> A having a positive electrode mixture layer formed in a region where each of two types of positive electrode active materials is partitioned. This was different from Example 5 of the present invention.

Specifically, 86% by weight of LiFePO ₄ as a first positive electrode active material, 7% by weight of acetylene black as a conductive auxiliary agent, and 7% by weight of PVDF as a binder are mixed, and this mixture is used as a solvent. N-methylpyrrolidone was added to form a first positive electrode mixture paste. 86% by weight of LiNi _0.8 Co _0.15 Al _0.05 O ₂ as a second positive electrode active material, 7% by weight of acetylene black as a conductive auxiliary agent, and 7% by weight of PVDF as a binder are mixed, and a solvent is added to this mixture. N-methylpyrrolidone was added to form a second positive electrode mixture paste. On each surface of the negative electrode current collector foil similar to Example 5 of the present invention, 3.2 g / 100 cm ² of the first positive electrode mixture paste was applied to the half area, and 2.7 g / 100 cm to the remaining half area. ^2nd 2nd positive mix paste was apply | coated. After drying this, it was compression molded by applying a load of 400 kgf / cm with a roll press. The negative electrode had a length of 420 cm and a width of 13 cm, and the total thickness of the positive electrode current collector foil and the positive electrode mixture layers on both sides was 190 μm.

  The negative electrode was formed in the same manner as in Comparative Example 12. Moreover, the same separator as Example 5 of this invention was prepared.

  Next, the positive electrode, the negative electrode, and the separator were wound in the same manner as in Invention Example 5 to produce an electrode group 100A. Next, similarly to Example 5 of the present invention, the electrode group 100A was accommodated in the container 2, and an electrolyte was injected to manufacture a lithium ion secondary battery of Comparative Example 13.

(Evaluation method)
The durability and safety of the lithium ion secondary batteries of Invention Example 5 and Comparative Examples 12 and 13 were evaluated. Durability was measured basically in the same manner as in Example 1, but differed in that the capacity retention after a 45 ° C. 500 cycle test was used. Safety was evaluated by investigating whether smoke or ignition would occur when the battery was fully charged and the vicinity of the center was crushed with a round bar jig.

(Evaluation results)
Regarding the capacity retention after the 45 ° C. 500 cycle test, Example 5 of the present invention was 80%, Comparative Example 12 was 70%, and Comparative Example 13 was 30%. Therefore, it was found that the lithium ion secondary battery of Inventive Example 5 can exhibit the performance of LiNi _0.8 Co _0.15 Al _0.05 O _{2 as} the positive electrode active material.

About safety | security, this invention example 5 and the comparative example 12 were favorable, and the comparative example 11 was not favorable. For this reason, it was found that the lithium ion secondary battery of Inventive Example 5 can exhibit the performance of the positive electrode active material LiFePO ₄ .

  As described above, in each of the plurality of electrode groups, the configuration of the positive electrode active material and the negative electrode active material is single, and the components of the positive electrode active material are different in at least two electrode groups of the plurality of electrode groups. It was confirmed that each of the performances of the plurality of positive electrode active materials can be sufficiently exhibited.

Furthermore, the present invention Example 5, LiFePO ₄ is has a low characteristic heat resistance, the electrode group 10A with LiFePO ₄ as an active material, since the placing 10D on the outer side, the heat storage to the battery It is possible to reduce the influence of. For this reason, it turned out that the durability of the lithium ion secondary battery of Invention Example 5 can be further improved.

  As described above, according to this example, when three or more electrode groups were provided, it was confirmed that durability could be improved by disposing an electrode group having an active material with low heat resistance on the outside side.

  In this example, the effect of the arrangement of the electrode groups when three or more electrode groups were provided was examined.

(Invention Example 6)
In Example 6 of the present invention, a lithium ion secondary battery including the three electrode groups 10A, 10B, and 10D shown in FIG. 8 was manufactured as follows.

First, the electrode groups 10A and 10D will be described.
90% by weight of LiMn ₂ O ₄ as a positive electrode active material, 4% by weight of acetylene black as a conductive auxiliary agent, and 6% by weight of PVDF as a binder are mixed, and N-methylpyrrolidone as a solvent is added to this mixture. In addition, a positive electrode mixture paste was formed. A positive electrode material mixture paste of 3.2 g / 100 cm ² was applied to both surfaces of a 20 μm-thick aluminum foil as a positive electrode current collector foil, dried, and then a load of 250 kgf / cm was applied by a roll press. Compression molded. Thereby, a strip-like positive electrode was produced. The size of the positive electrode was 110 cm in length and 10 cm in width, and the total thickness of the positive electrode current collector foil and the positive electrode mixture layers on both sides was 140 μm.

As a negative electrode active material, 92% by weight of graphite and 8% by weight of PVDF were mixed, and N-methylpyrrolidone as a solvent was added to this mixture to form a negative electrode mixture paste. A negative electrode mixture paste of 1.0 g / 100 cm ² was applied to both sides of a 10 μm-thick copper foil as a negative electrode current collector foil, dried, and then applied with a load of 100 kgf / cm by a roll press. Compression molded. This produced the strip-shaped negative electrode. The size of the negative electrode was 120 cm in length, 10 cm in width, and the total thickness of the negative electrode current collector foil and the negative electrode mixture layers on both sides was 100 μm.

A positive electrode tab and a negative electrode tab were attached to each of the positive electrode and the negative electrode.
A polyolefin microporous membrane having a width of 9 cm and a thickness of 20 μm was prepared as a separator.

  Next, the positive electrode, the separator, the negative electrode, and the separator were laminated in this order and wound into a long cylindrical shape. Thereby, electrode groups 10A and 10D were produced.

The electrode group 10B was basically the same as the electrode groups 10A and 10D, but differed in the positive electrode and the separator. Specifically, 90% by weight of LiNi _0.8 Co _0.15 Al _0.05 O ₂ as a positive electrode active material, 4% by weight of acetylene black as a conductive auxiliary agent, and 6% by weight of PVDF as a binder are mixed, and this mixture A solvent was added to form a positive electrode mixture paste. This positive electrode mixture paste was applied as a positive electrode current collector foil to both sides of 20 μm thick N-methylpyrrolidone, dried, and then compression molded by applying a load of 200 kgf / cm with a roll press. The size of the strip-like positive electrode was 140 cm in length and 10 cm in width, and the total thickness of the positive electrode current collector foil and the positive electrode mixture layers on both sides was 100 μm.

  A polyolefin microporous membrane having a width of 9 cm and a thickness of 40 μm was prepared as a separator.

  Next, the positive electrode, the separator, the negative electrode, and the separator were laminated in this order and wound into a long cylindrical shape. This produced electrode group 10B.

  Next, the electrode groups 10A and 10D are accommodated in the container 2 so that the electrode groups 10B are located on the outer side and the electrode groups 10B are located on the inner side. A lithium ion secondary battery of Invention Example 6 was produced.

(Comparative Example 14)
As shown in FIG. 7, the lithium ion secondary battery 100 of Comparative Example 14 is a sixth invention example in that it includes one electrode group 100 </ b> A having a positive electrode mixture layer in which two types of positive electrode active materials are mixed. Was different.

Specifically, 45% by weight of LiMn ₂ O _{4 and} 45% by weight of LiNi _0.8 Co _0.15 Al _0.05 O ₂ as the positive electrode active material, 4% by weight of acetylene black as the conductive assistant, and 6% by weight of PVDF as the binder %, And N-methylpyrrolidone as a solvent was added to the mixture to form a positive electrode mixture paste. A 2.6 g / 100 cm ² positive electrode mixture paste was applied to both sides of an aluminum foil having a thickness of 20 μm as a positive electrode current collector foil, dried, and then compressed by applying a load of 250 kgh / cm with a roll press. Molded. The positive electrode had a length of 360 cm, a width of 10 cm, and a total thickness of the positive electrode current collector foil and both positive electrode mixture layers of 120 μm.

  As for the formation of the negative electrode, as in Example 6 of the present invention, a negative electrode mixture paste was formed, applied to both surfaces of the negative electrode current collector foil, dried, and then a load of 100 kgf / cm was applied with a roll press. And compression molded. The negative electrode had a length of 370 cm and a width of 10 cm, and the total thickness of the negative electrode current collector foil and the negative electrode mixture layers on both sides was 100 μm.

  A polyolefin microporous membrane having a width of 9 cm and a thickness of 40 μm was prepared as a separator.

  Next, the positive electrode, the negative electrode, and the separator were wound in the same manner as in Invention Example 6 to produce an electrode group 100A. Next, in the same manner as in Example 6 of the present invention, the electrode group 100A was accommodated in the container 2, and an electrolytic solution was injected to manufacture a lithium ion secondary battery of Comparative Example 14.

(Comparative Example 15)
As shown in FIG. 7, the lithium ion secondary battery 100 of Comparative Example 15 includes one electrode group 100 </ b> A having a positive electrode mixture layer formed in a region where each of two types of positive electrode active materials is partitioned. This was different from Example 6 of the present invention.

Specifically, 90% by weight of LiMn ₂ O ₄ as the first positive electrode active material, 4% by weight of acetylene black as the conductive auxiliary agent, and 6% by weight of PVDF as the binder were mixed, and this mixture was mixed. N-methylpyrrolidone as a solvent was added to form a first positive electrode mixture paste. 90% by weight of LiNi _0.8 Co _0.15 Al _0.05 O ₂ as a second positive electrode active material, 4% by weight of acetylene black as a conductive auxiliary agent, and 6% by weight of PVDF as a binder are mixed, and a solvent is added to this mixture. N-pyrrolidone was added to form a second positive electrode mixture paste. On each surface of the positive electrode current collector foil similar to Example 6 of the present invention, 3.2 g / 100 cm ² of the first positive electrode material mixture paste was applied to the half area, and 2.0 g / 100 cm to the remaining half area. ^2nd 2nd positive mix paste was apply | coated. After drying, this was compression molded by applying a load of 250 kgf / cm with a roll press. The negative electrode had a length of 330 cm and a width of 10 cm, and the total thickness of the positive electrode current collector foil and the positive electrode mixture layers on both sides was 140 μm.

  The negative electrode was formed in the same manner as in Comparative Example 14. A separator similar to that in Comparative Example 14 was prepared.

  Next, the positive electrode, the negative electrode, and the separator were wound in the same manner as in Invention Example 6 to produce an electrode group 100A. Next, similarly to Example 6 of the present invention, the electrode group 100A was accommodated in the container 2, and an electrolyte was injected to manufacture a lithium ion secondary battery of Comparative Example 15.

(Evaluation method)
The lithium ion secondary batteries of Invention Example 6 and Comparative Examples 14 and 15 were evaluated for durability and safety. Durability was basically the same as that of Example 1, but differed in that the capacity retention rate after a 60 ° C. 300 cycle test was used. Safety was measured in the same manner as in Example 5.

(Evaluation results)
Regarding the capacity retention after the 60 ° C. 300 cycle test, Example 6 of the present invention was 60%, Comparative Example 14 was 50%, and Comparative Example 15 was 30%. Therefore, it was found that the lithium ion secondary battery of Inventive Example 6 can exhibit the performance of the positive electrode active material LiNi _0.8 Co _0.15 Al _0.05 O ₂ .

About safety | security, this invention example 6 and the comparative example 14 were favorable, and the comparative example 15 was not favorable. Therefore, it was found that the lithium ion secondary battery of Inventive Example 6 can exhibit the performance of the positive electrode active material LiMn ₂ O ₄ .

Further, in Example 6 of the present invention, LiMn ₂ O ₄ has a performance with low heat resistance, but the electrode groups 10A and 10D having LiMn ₂ O ₄ as the active material are arranged on the outside side. It is possible to reduce the influence due to heat storage. For this reason, it was found that the lithium ion secondary battery of Example 6 of the present invention can further improve the durability.

  As described above, according to this example, when three or more electrode groups were provided, it was confirmed that the heat resistance can be further improved by disposing an electrode group having an active material with low heat resistance on the outside side. .

  In this example, the effect of different separator configurations was investigated in at least two electrode groups having different positive electrode active material configurations.

(Invention Example 7)
In Invention Example 7, a lithium ion secondary battery provided with the two electrode groups 10A and 10B shown in FIG. 6 was produced as follows.

First, the electrode group 10A will be described.
90% by weight of LiNi _1/3 Mn _1/3 Co _1/3 O ₂ as a positive electrode active material, 4% by weight of acetylene black as a conductive additive, and 6% by weight of PVDF as a binder were mixed. N-pyrrolidone as a solvent was added to the mixture to form a positive electrode mixture paste. A positive electrode mixture paste of 2.0 g / 100 cm ² was applied to both sides of a 20 μm thick aluminum foil as a positive electrode current collector foil, dried, and then a 200 kgf / cm load was applied by a roll press. Compression molded. Thereby, a strip-like positive electrode was produced. The size of the positive electrode was 210 cm in length, 10 cm in width, and the total thickness of the positive electrode current collector foil and the positive electrode mixture layers on both sides was 100 μm.

As a negative electrode active material, 90% by weight of graphite and 10% by weight of PVDF were mixed, and N-pyrrolidone as a solvent was added to this mixture to form a negative electrode mixture paste. A negative electrode mixture paste of 1.0 g / 100 cm ² was applied to both sides of a 10 μm-thick copper foil as a negative electrode current collector foil, dried, and then applied with a load of 100 kgf / cm by a roll press. Compression molded. This produced the strip-shaped negative electrode. The size of the negative electrode was 220 cm in length, 10 cm in width, and the total thickness of the negative electrode current collector foil and the negative electrode mixture layers on both sides was 100 μm.

A positive electrode tab and a negative electrode tab were attached to each of the positive electrode and the negative electrode.
Further, a microporous polyolefin membrane having a width of 9 cm and a thickness of 40 μm was prepared as a separator.

  Next, the positive electrode, the separator, the negative electrode, and the separator were laminated in this order and wound into a long cylindrical shape. This produced electrode group 10A.

The electrode group 10B was basically the same as the electrode group 10A, but differed in the positive electrode and the separator. Specifically, 90% by weight of LiMn ₂ O ₄ as a positive electrode active material, 3% by weight of acetylene black as a conductive auxiliary agent, and 7% by weight of PVDF as a binder are mixed, and the electrode group 10A is mixed with this mixture. The same solvent was added to form a positive electrode mixture paste. A positive electrode material mixture paste of 3.2 g / 100 cm ² was applied to both surfaces of the positive electrode current collector foil, dried, and then compression molded by applying a load of 250 kgf / cm with a roll press. The size of the belt-like positive electrode was 150 cm in length, 10 cm in width, and the total thickness of the positive electrode current collector foil and the positive electrode mixture layers on both sides was 140 μm.

A positive electrode tab and a negative electrode tab were attached to each of the positive electrode and the negative electrode.
Further, a polyolefin microporous film having a width of 9 cm and a thickness of 20 μm was prepared as a separator.

  Next, the positive electrode, the separator, the negative electrode, and the separator were laminated in this order and wound into a long cylindrical shape. This produced electrode group 10B.

  Next, similarly to Example 1 of the present invention, two electrode groups 10A and 10B were accommodated in the container 2, and an electrolyte was injected to manufacture a lithium ion secondary battery of Example 7 of the present invention.

(Comparative Example 16)
As shown in FIG. 7, the lithium ion secondary battery 100 of Comparative Example 16 includes a single electrode group 100 </ b> A having a positive electrode mixture layer in which two types of positive electrode active materials are mixed. Was different.

Specifically, 45% by weight of LiNi _1/3 Mn _1/3 Co _1/3 O _{2 and} 45% by weight of LiMn ₂ O ₄ as the positive electrode active material, 4% by weight of acetylene black as the conductive auxiliary agent, 6% by weight of PVDF as an adhesive was mixed, and N-methylpyrrolidone as a solvent was added to this mixture to form a positive electrode mixture paste. 2.6 g / 100 cm ² of the positive electrode mixture paste was applied to both surfaces of the same positive electrode current collector foil as in Example 3 of the present invention, dried, and then subjected to compression molding by applying a load of 250 kgf / cm with a roll press. did. The positive electrode had a length of 360 cm, a width of 10 cm, and a total thickness of the positive electrode current collector foil and both positive electrode mixture layers of 120 μm.

  Regarding the formation of the negative electrode, as in Example 7 of the present invention, a negative electrode mixture paste was formed, applied to both surfaces of the negative electrode current collector foil, dried, and then a load of 100 kgf / cm was applied with a roll press. And compression molded. The negative electrode had a length of 370 cm and a width of 10 cm, and the total thickness of the negative electrode current collector foil and the negative electrode mixture layers on both sides was 100 μm.

  Next, a positive electrode, a negative electrode, and a separator having a thickness of 40 μm were wound in the same manner as in Invention Example 7 to produce an electrode group 100A. Next, similarly to Example 7 of the present invention, this electrode group 100A was accommodated in the container 2, and an electrolyte was injected to manufacture a lithium ion secondary battery of Comparative Example 16.

(Comparative Example 17)
The lithium ion secondary battery of Comparative Example 17 was basically the same as Comparative Example 16, but differed in that the thickness of the separator was 20 μm.

(Evaluation method)
The capacity and safety of the lithium ion secondary batteries of Invention Example 7 and Comparative Examples 16 and 17 were evaluated.
The capacity was measured in the same manner as in Example 1. The combination of the lower limit voltage and the upper limit voltage was 2.5V-4.2V.
Safety was measured in the same manner as in Example 3.

(Evaluation results)
Regarding the capacity, Example 7 of the present invention was 95 (relative ratio), Comparative Example 16 was 90 (relative ratio), and Comparative Example 17 was 100 (relative ratio). For this reason, it was found that the lithium ion secondary battery of Example 7 of the present invention can exhibit the performance of the positive electrode active material LiNi _1/3 Mn _1/3 Co _1/3 O ₂ .

About safety | security, this invention example 7 and the comparative example 16 were favorable, and the comparative example 17 was not favorable at the point which smoked. Therefore, the lithium ion secondary battery of the present invention Example 7 was found to be perform as LiMn ₂ O ₄ positive electrode active material.

In addition, in Example 7 of the present invention, the thickness of the separator of the electrode group 10A including LiNi _1/3 Mn _1/3 Co _1/3 O ₂ as the positive electrode active material was large, and LiMn ₂ O ₄ was provided as the positive electrode active material. Since the thickness of the separator of electrode group 10B was small, the performance of each positive electrode active material was able to be exhibited more.

  As described above, according to this example, it was confirmed that the performance of the positive electrode active material can be remarkably exhibited by the difference in the separator configuration in at least two electrode groups having different configurations of the positive electrode active material.

  In this example, the effect of different configurations of the positive electrode current collector foil was examined in at least two electrode groups having different configurations of the positive electrode active material.

(Invention Example 8)
In Example 8 of the present invention, a lithium ion secondary battery including the three electrode groups 10A, 10B, and 10D shown in FIG. 8 was manufactured as follows.

First, the electrode groups 10A and 10D will be described.
90% by weight of LiNi _1/3 Mn _1/3 Co _1/3 O ₂ as a positive electrode active material, 4% by weight of acetylene black as a conductive additive, and 6% by weight of PVDF as a binder were mixed. N-methylpyrrolidone as a solvent was added to the mixture to form a positive electrode mixture paste. A positive electrode mixture paste of 1.6 g / 100 cm ² was applied to both surfaces of a 30 μm-thick aluminum foil as a positive electrode current collector foil, dried, and then a 200 kgf / cm load was applied by a roll press. Compression molded. Thereby, a strip-like positive electrode was produced. The size of the positive electrode was 290 cm in length, 13 cm in width, and the total thickness of the positive electrode current collector foil and the positive electrode mixture layers on both sides was 80 μm.

As a negative electrode active material, 90% by weight of hard carbon and 10% by weight of PVDF were mixed, and N-methylpyrrolidone as a solvent was added to this mixture to form a negative electrode mixture paste. A negative electrode mixture paste of 0.7 g / 100 cm ² was applied to both sides of a 10 μm thick copper foil as a negative electrode current collector foil, dried, and then a load of 400 kgf / cm was applied by a roll press. Compression molded. This produced the strip-shaped negative electrode. The size of the negative electrode was 300 cm in length, 13 cm in width, and the total thickness of the negative electrode current collector foil and the negative electrode mixture layers on both sides was 80 μm.

A positive electrode tab and a negative electrode tab were attached to each of the positive electrode and the negative electrode.
Moreover, the same separator as Example 1 of this invention was prepared.

  Next, the positive electrode, the separator, the negative electrode, and the separator were laminated in this order and wound into a long cylindrical shape. Thereby, electrode groups 10A and 10D were produced.

The electrode group 10B was basically the same as the electrode groups 10A and 10D, but differed in the positive electrode and the separator. Specifically, 90% by weight of LiMn ₂ O ₄ as a positive electrode active material, 4% by weight of acetylene black as a conductive auxiliary agent, and 6% by weight of PVDF as a binder are mixed, and a solvent is added to this mixture. Thus, a positive electrode mixture paste was formed. This positive electrode mixture paste was applied to both surfaces of a 20 μm thick aluminum foil as a positive electrode current collector foil, dried, and then compression molded by applying a load of 250 kgf / cm with a roll press. The size of the strip-like positive electrode was 220 cm in length, 13 cm in width, and the total thickness of the positive electrode current collector foil and the positive electrode mixture layers on both sides was 120 μm.

A positive electrode tab and a negative electrode tab were attached to each of the positive electrode and the negative electrode.
Moreover, the same separator as Example 1 of this invention was prepared.

  Next, the positive electrode, the separator, the negative electrode, and the separator were laminated in this order and wound into a long cylindrical shape. This produced electrode group 10B.

  Next, the electrode groups 10A and 10D are accommodated in the container 2 so that the electrode groups 10B are located on the outer side and the electrode groups 10B are located on the inner side. A lithium ion secondary battery of Invention Example 8 was produced.

(Comparative Example 18)
As shown in FIG. 7, the lithium ion secondary battery 100 of Comparative Example 18 includes a single electrode group 100 </ b> A having a positive electrode mixture layer in which two types of positive electrode active materials are mixed. Was different.

Specifically, 45% by weight of LiNi _1/3 Mn _1/3 Co _1/3 O _{2 and} 45% by weight of LiMn ₂ O ₄ as the positive electrode active material, 4% by weight of acetylene black as the conductive auxiliary agent, 6% by weight of PVDF as an adhesive was mixed, and N-methylpyrrolidone as a solvent was added to this mixture to form a positive electrode mixture paste. 2.1 g / 100 cm ² of positive electrode mixture paste was applied to both sides of an aluminum foil with a thickness of 30 μm as a positive electrode current collector foil, dried, and then compressed by applying a load of 250 kgf / cm with a roll press. Molded. The positive electrode had a length of 740 cm, a width of 13 cm, and a total thickness of the positive electrode current collector foil and the positive electrode mixture layers on both sides was 100 μm.

  Regarding the formation of the negative electrode, as in Example 8 of the present invention, a negative electrode mixture paste was formed, applied to both surfaces of the negative electrode current collector foil, dried, and then a load of 400 kgf / cm was applied by a roll press. And compression molded. The negative electrode had a length of 750 cm, a width of 13 cm, and a total thickness of the positive electrode current collector foil and the negative electrode mixture layers on both sides was 100 μm.

  Next, a separator similar to Example 8 of the present invention was prepared, and the positive electrode, the negative electrode, and the separator were wound in the same manner as Example 8 of the present invention to produce an electrode group 100A. Next, in the same manner as in Example 8 of the present invention, the electrode group 100A was accommodated in the container 2, and an electrolytic solution was injected to manufacture a lithium ion secondary battery of Comparative Example 18.

(Comparative Example 19)
The lithium ion secondary battery of Comparative Example 19 was basically the same as Comparative Example 18, except that the thickness of the positive electrode current collector foil was 20 μm.

(Evaluation method)
The lithium ion secondary batteries of Example 8 and Comparative Examples 18 and 19 were evaluated for capacity and safety. The capacity was measured in the same manner as in Example 1. The combination of the lower limit voltage and the upper limit voltage was 2.5V-4.2V. Safety was measured in the same manner as in Example 3.

(Evaluation results)
Regarding the capacity, Example 8 of the present invention was 95 (relative ratio), Comparative Example 18 was 90 (relative ratio), and Comparative Example 19 was 100 (relative ratio). Therefore, it was found that the lithium ion secondary battery of Inventive Example 8 can exhibit the performance of LiNi _1/3 Mn _1/3 Co _1/3 O _{2 as} the positive electrode active material.

About safety | security, this invention example 8 and the comparative example 18 were favorable, and the comparative example 19 was not favorable at the point which smoked. Therefore, the lithium ion secondary battery of the present invention Example 8 was found to be perform as LiMn ₂ O ₄ positive electrode active material.

In addition, in Example 8 of the present invention, the thickness of the positive electrode current collector foil of the electrode groups 10A and 10D including LiNi _1/3 Mn _1/3 Co _1/3 O ₂ as the positive electrode active material is large, and LiMn ₂ as the positive electrode active material. Since the thickness of the positive electrode current collector foil of the electrode group 10B provided with O ₄ was small, the performance of each positive electrode active material could be exhibited more.

  From the above, according to this example, it was confirmed that the performance of the positive electrode active material can be remarkably exhibited by the difference in the configuration of the positive electrode current collector foil in at least two electrode groups having different configurations of the positive electrode active material. did.

  As described above, the embodiments and examples of the present invention have been described, but it is also planned from the beginning to appropriately combine the features of the embodiments and examples. The embodiments and examples disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the embodiments and examples described above but by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims.

  DESCRIPTION OF SYMBOLS 1 Nonaqueous electrolyte secondary battery, 2 container, 3 main-body part, 4 lid | cover, 5 electrolyte injection part, 10A, 10B, 10C, 10D Electrode group, 11A, 11B, 11C, 11D Positive electrode, 11A1, 11B1, 11C1, 11D1 Positive electrode collector foil, 11A2, 11B2, 11C2, 11D2 Positive electrode mixture layer, 12A, 12B, 12C, 12D Separator, 13A, 13B, 13C, 13D Negative electrode, 13A1, 13B1, 13C1, 13D1 Negative electrode collector foil, 13A2, 13B2 , 13C2, 13D2 negative electrode mixture layer, 21 positive electrode terminal, 22 negative electrode terminal.

Claims (7)

A plurality of electrode groups electrically connected in parallel;
Each of the plurality of electrode groups includes a positive electrode having a positive electrode active material, a negative electrode having a negative electrode active material, and a separator disposed between the positive electrode and the negative electrode,
In each of the plurality of electrode groups, the configuration of the positive electrode active material and the negative electrode active material is single,
An electricity storage element in which at least one of the plurality of electrode groups is different in at least one of the positive electrode active material and the negative electrode active material.   The storage element according to claim 1, wherein at least one component of the positive electrode active material and the negative electrode active material is different in the at least two electrode groups. Comprising three or more electrode groups,
Of the plurality of electrode groups, at least one of the positive electrode active material and the negative electrode active material in the electrode group relatively disposed on the outer side and the electrode group relatively disposed on the inner side The electrical storage element of Claim 1 or 2 from which these differ. The positive electrode includes a positive electrode base material, a positive electrode mixture layer formed on the positive electrode base material and having the positive electrode active material, a conductive additive, and a positive electrode binder,
The negative electrode includes a negative electrode substrate, a negative electrode mixture layer formed on the negative electrode substrate, and having the negative electrode active material and a negative electrode binder,
The said at least 2 electrode group WHEREIN: At least 1 structure of the said separator, the said positive electrode base material, the said conductive support agent, the said positive electrode binder, the said negative electrode base material, and the said negative electrode binder differs. The electricity storage device according to item.   The negative electrode active material of at least one of the at least two electrode groups is crystalline carbon, and the negative electrode active material of at least one of the remaining electrode groups is amorphous carbon. The electrical storage element of any one of Claims 1-4. In at least one electrode group of the at least two electrode groups, the positive electrode active _{material, LiFePO 4, Li a Ni x} Mn y Co (1-xy) O 2 (0 ≦ a ≦ 1.1,0 < x <1, 0 <y <1, x + y <1) and Li _a Ni _x Co _y Al _z M _b O ₂ (0.3 ≦ a ≦ 1.05, 0.7 ≦ x ≦ 0.87, 0. 1 ≦ y ≦ 0.27, 0.03 ≦ z ≦ 0.1, 0 ≦ b ≦ 0.1, M is selected from the group consisting of at least one selected from metal elements other than Ni, Co and Al) The electric storage element according to claim 5, wherein the electric storage element is at least one kind. Wherein the positive electrode active material of the at least one electrode group of the at least two electrode groups are _{Li a Ni x Mn y Co (} 1-xy) O 2 (0 ≦ a ≦ 1.1,0 <x <1,0 <Y <1, x + y <1), and the positive electrode active material of at least one of the remaining electrode groups is LiMn ₂ O _4. 6. Power storage element.

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