WO2014002532A1

WO2014002532A1 - Secondary cell

Info

Publication number: WO2014002532A1
Application number: PCT/JP2013/056853
Authority: WO
Inventors: 嘉夫田川
Original assignee: 三菱自動車工業株式会社
Priority date: 2012-06-26
Filing date: 2013-03-12
Publication date: 2014-01-03
Also published as: JP5994977B2; JP2014007107A; CN104412438A

Abstract

A secondary cell in which are stacked pluralities of: positive electrodes (10a, 10b) equipped with an electrolytic solution and an electrode member (2) immersed for use in the electrolytic solution, the electrode member (2) having positive electrode active material layers (12, 13) formed on the surface of a positive electrode current collector foil (11); negative electrodes (20) having negative electrode active material layers (22, 23) formed on the surface of a negative electrode current collector foil (21); and separators (30) disposed between the positive electrodes (10a, 10b) and the negative electrodes (20). Each of the positive electrode active material layers (12, 13) and the negative electrode active material layers (22, 23) that face each other across a separator (30) constitute an electrode pair (41, 42). The electrode pairs (41, 42) comprise first electrode pairs (41) made from a first active material layer provided with a first property, which is relatively high-output and low-capacity, and second electrode pairs (42) made from a second active material layer provided with a second property, which is relatively low-output and high-capacity.

Description

Secondary battery

The present invention relates to a secondary battery.

Conventionally, a secondary battery such as a lithium ion secondary battery has been used as a battery for driving a motor mounted on an electric vehicle such as an electric vehicle or a plug-in hybrid vehicle. The secondary battery mounted on the electric vehicle has excellent output characteristics that respond to the large current output to drive the vehicle uphill, accelerates and cools, and excellent input characteristics that responds to the large current input during rapid charging and regeneration. In addition, high energy capacity characteristics that can be driven for a long time are required.

In order to improve the input / output characteristics and energy capacity characteristics of such a secondary battery, the secondary battery in which the electrode material is adjusted so that the resistance ratio of the positive electrode plate and the negative electrode plate falls within a predetermined range, or spirally wound The secondary battery which adjusted the application quantity of electrode material based on the curvature of the made electrode is proposed (for example, refer to patent documents 1 and 2).

JP, 2011-187186, A JP-A-9-180704

However, since the input / output characteristics of the secondary battery and the energy capacity characteristics are in a contradictory relationship, even with the secondary battery as described above, an excellent input / output characteristic capable of instantaneously taking in and out a large current, or a long time There is a problem that it is not possible to realize a secondary battery simultaneously having high energy capacity characteristics that can be driven.

Then, in view of such a situation, an object of the present invention is to provide a secondary battery which simultaneously has excellent input / output characteristics and high energy capacity characteristics.

The aspect of the present invention for solving the above problems is a secondary battery comprising an electrolytic solution and an electrode member used by being immersed in the electrolytic solution, wherein the electrode member is formed on the surface of a positive electrode current collector foil The positive electrode having the positive electrode active material layer, the negative electrode having the negative electrode active material layer formed on the surface of the negative electrode current collector foil, and the separator disposed between the positive electrode and the negative electrode; An electrode pair is formed of the positive electrode active material layer and the negative electrode active material layer opposed to each other through a separator, and the electrode pair has a first characteristic of relatively high output and low capacity. A second electrode pair comprising: a first electrode pair comprising an active material layer; and a second electrode pair comprising a second active material layer having a relatively low output and high capacity second characteristic. It is in the next battery.

According to the present invention, the first electrode pair having the relatively high output and low capacity first characteristics and the relatively low power and high capacity second characteristics in one electrode member Since the second electrode pair is provided, by using this as an electrode, it is possible to realize a secondary battery that simultaneously has excellent input / output characteristics and high energy capacity characteristics as a whole.

Here, the first active material layer of the first electrode pair and the second active material layer of the second electrode pair have a layer thickness, a coating amount, and an activity of forming a layer. Preferably, the first property and the second property correspond to differences in at least one of the types of substances.

According to this, it is possible to express the first characteristic and the second characteristic by the difference in thickness of the active material layer, the difference in coating amount, or the difference in kind of active material. Therefore, in one electrode member, the first electrode pair having the first characteristic of relatively high output and low capacity, and the second characteristic of relatively low output and high capacity are provided. Since two electrode pairs are provided, by using this as an electrode, it is possible to realize a secondary battery that simultaneously has excellent input / output characteristics and high energy capacity characteristics.

Here, the positive electrode and the negative electrode respectively have active material layers on both sides of the current collector foil, and at least one of the positive electrode and the negative electrode corresponds to the first characteristic on one side of the current collector foil. It is preferable to have the first active material layer and to have the second active material layer corresponding to the second characteristic on the other surface.

According to this, since active material layers having different input / output characteristics and capacitance characteristics are respectively formed on both surfaces of at least one of the current collector foils of the positive electrode and the negative electrode, the input / output characteristics and the capacitance characteristics are contained in one electrode member. A plurality of different active material layers are provided. Therefore, as a whole, it is possible to realize a secondary battery simultaneously having excellent input / output characteristics and high energy capacity characteristics.

Here, it is preferable that a plurality of holes be formed in the current collector foil of the positive electrode and the negative electrode.

According to this, by providing the holes in the current collector foil, when the potentials of the active material layer after charging and discharging are different, lithium ions may flow through the holes of the current collector foil even in the active material layer. Can facilitate the relaxation of the potential.

Further, it is preferable that a plurality of the first electrode pairs and the second electrode pairs are stacked or wound.

According to this, the surface area of each of the active material layers can be increased by stacking or winding a plurality of electrode pairs, so that the input / output characteristics and the energy capacity characteristics of the secondary battery can be further enhanced. it can.

According to the secondary battery of the present invention, it is possible to realize a secondary battery which simultaneously has excellent input / output characteristics and high energy capacity characteristics.

FIG. 1 is a perspective view of a secondary battery according to Embodiment 1. FIG. 2 is a schematic cross-sectional view of the secondary battery of FIG. 1 taken along line XX ′. FIG. 2 is a partially enlarged cross-sectional schematic view of a secondary battery electrode member according to a first embodiment. It is a related figure of the output time of each electrode pair and the current value which show the 1st characteristic of the rechargeable battery concerning Embodiment 1, and the 2nd characteristic. FIG. 2 is a view showing a charging state of the secondary battery according to Embodiment 1. 5 is a perspective view of a current collector foil according to Embodiment 2. FIG. FIG. 7 is a partially enlarged cross-sectional schematic view of a secondary battery electrode member according to a third embodiment.

Hereinafter, the present invention will be described in detail based on embodiments.

(Embodiment 1)
The secondary battery according to the present embodiment is a laminated lithium ion secondary battery, and is mounted, for example, on the bottom (below the floor) of an electric vehicle, which is an electric vehicle, and supplies power to a traveling motor of the electric vehicle. It is a thing.

A secondary battery according to Embodiment 1 of the present invention and an electrode member used therefor will be described with reference to FIGS. 1 to 3. FIG. FIG. 1 is a perspective view of a laminate type lithium ion secondary battery according to this embodiment, FIG. 2 is a schematic sectional view taken along line XX ′ of FIG. 1, and FIG. 3 is a secondary view shown in FIG. It is a partially expanded cross-section schematic diagram of the electrode member of a battery.

As shown in FIG. 1 and FIG. 2, the laminate type lithium ion secondary battery 1 has a rectangular flat laminate outer package 3 in which the electrode member 2 is housed, and short sides on both sides in the longitudinal direction of the laminate outer package 3. And a positive electrode terminal 4 and a negative electrode terminal 5 for extracting power from the electrode member 2. The electrode member 2 is a stack of a plurality of positive electrodes 10 and a plurality of negative electrodes 20 with a separator 30 interposed therebetween. The plurality of positive electrodes 10 are electrically connected to the positive electrode terminal 4, and the plurality of negative electrodes 20 are connected to the negative electrode terminal 5. Connected. In addition, the electrode member 2 is immersed in the electrolytic solution 6 in the laminate exterior body 3.

As shown in FIG. 3, the positive electrode 10 of the electrode member 2 has a positive electrode active material layer formed on both sides of the positive electrode current collector foil 11, and the relatively thin first positive electrode active material layer 12 is on both sides. And a positive electrode 10b having a relatively thick second positive electrode active material layer 13 formed on both sides. On the other hand, in the negative electrode 20, the relatively thin first negative electrode active material layer 22 is formed on one surface of the negative electrode current collector foil 21, and the relatively thick second negative electrode active material layer 23 is formed on the other surface. It is The positive electrodes 10a and 10b and the negative electrode 20 are alternately stacked with the separator 30 interposed therebetween, and the first positive electrode active material layer 12 of the positive electrode 10a and the first negative electrode active material layer 22 of the negative electrode 20 The second positive electrode active material layer 13 of the positive electrode 10b and the second negative electrode active material layer 23 of the negative electrode 20 face each other with the separator 30 in between. Then, the portion where the first positive electrode active material layer 12 and the first negative electrode active material layer 22 face each other through the separator 30 becomes the first electrode pair 41, and the second positive electrode active material layer through the separator 30. A portion where the first electrode active material layer 13 and the second electrode active material layer 23 face each other is the second electrode pair 42. In the present embodiment, two first electrode pairs 41 and two second electrode pairs 42 alternate. It has a stacked structure.

Here, the first electrode pair 41 in which the first positive electrode active material layer 12 and the first negative electrode active material layer 22 face each other through the separator 30 has relatively high output and low capacity first characteristics. The second electrode pair 42 in which the second positive electrode active material layer 13 and the second negative electrode active material layer 23 face each other through the separator 30 has a relatively low output and a high capacity. It has the two characteristics.

In the present embodiment, active material layers having relatively different thicknesses, that is, a first electrode pair 41 composed of relatively thin first positive electrode active material layer 12 and first negative electrode active material layer 22; By forming the electrode member 2 including the second electrode pair 42 composed of the relatively thick second positive electrode active material layer 13 and the second negative electrode active material layer 23, two opposing battery characteristics are provided. And a secondary battery.

Here, the first characteristic of relatively high output and low capacity means, in this case, high input / output characteristics and low energy capacity characteristics as compared to the second characteristic, and is relatively low. The second characteristic of the output and high capacity means that the input / output characteristic is low and the energy capacity characteristic is high as compared with the first characteristic.

Such first and second characteristics will be described with reference to FIG. FIG. 4 shows the relationship between the output time of the secondary battery and the output current value.

As shown in FIG. 4, in the portion of the first electrode pair 41, since the first positive electrode active material layer 12 and the first negative electrode active material layer 22 are thin, the internal resistance of the active material layer is reduced. Although current input / output is possible, the total amount of active material is small, so the duration (capacity) is small. On the other hand, the portion of the second electrode pair 42 having the thick second positive electrode active material layer 13 and the second negative electrode active material layer 23 has an internal resistance compared with the first electrode pair 41 because the active material layer is thick. Although a large current can not flow as much as the first electrode pair 41, the thicker the active material layer, the higher the energy capacity, and therefore, a larger capacity can be obtained. In the present embodiment, the former is the first characteristic, and the latter is the second characteristic.

Here, the first electrode pair 41 including the relatively thin first positive electrode active material layer 12 and the relatively thin first negative electrode active material layer 22 will be further described. The charge and discharge of the lithium ion secondary battery proceed by migration (diffusion) of lithium ions between the positive electrode and the negative electrode, so the distance of lithium ion migration is short, ie, the thickness of the active material layer is small. Can lower the internal resistance and improve the input / output characteristics, while reducing the capacitance. That is, the first electrode pair 41 composed of the first positive electrode active material layer 12 and the first negative electrode active material layer 22 has an excellent response to a large current input / output and a rapid potential change. It has input / output characteristics but low capacity, and has high power and low capacity first characteristics.

On the other hand, the second electrode pair 42 formed of the relatively thick second positive electrode active material layer 13 and the second negative electrode active material layer 23 will be described. In order to improve the energy capacity of the lithium ion secondary battery, it is necessary to increase the energy density of the active material layer. For this purpose, for example, the thickness of the active material layer may be increased. On the other hand, the movement distance of lithium ions is increased, which is disadvantageous for input / output characteristics. Therefore, the second electrode pair 42 composed of the second positive electrode active material layer 13 and the second negative electrode active material layer 23 has high energy capacity characteristics that can be driven for a long time, but has low input / output characteristics, It has the second characteristic of low output and high capacity.

In order to obtain a secondary battery having both the first and second characteristics, for example, the first negative electrode active material layer 22 and the second negative electrode active material layer 23 having different thicknesses may be used. In the present embodiment, a relatively thin first negative electrode active material layer 22 and a relatively thick second negative electrode active material layer 23 are provided on both sides of the negative electrode current collector foil 21. , And both the first and second characteristics. In the present embodiment, when the thickness of the first negative electrode active material layer 22 is 1 to 10 μm, the thickness of the second negative electrode active material layer 23 is preferably 10 to 100 μm, and the thickness of the first negative electrode active material layer 22 is When the thickness is 10 to 50 μm, the thickness of the second negative electrode active material layer 23 is preferably 50 to 200 μm.

In addition, the relatively thin first negative electrode active material layer 22 and the relatively thick second negative electrode active material layer 23 require positive electrode active material layers having lithium transfer amounts respectively corresponding to them. The first positive electrode active material layer 12 and the second positive electrode active material layer 13 correspond to each other to constitute a first electrode pair 41 and a second electrode pair 42. That is, during charging, between the first positive electrode active material layer 12 and the first negative electrode active material layer 22 and between the second positive electrode active material layer 13 and the second negative electrode active material layer 23. Transfer of lithium ions from one active material layer to the other active material layer at the time of discharge is made equal, the potential change is stabilized, control of the secondary battery is facilitated, and the reliability of the secondary battery is enhanced.

In the present embodiment, as the positive electrode 10, the positive electrode 10a having the relatively thin first positive electrode active material layer 12 on both surfaces of the positive electrode current collector foil 11 and the relatively thick on both surfaces of the positive electrode current collector foil 11 By using the positive electrode 10 b having the positive electrode active material layer 13 of No. 2, the first negative electrode active material layer 22 and the second negative electrode active material layer 23 are made to correspond. In view of the fact that it is easier to form positive electrodes of the same thickness on the front and back, it is preferable to use two types of positive electrodes 10a and 10b of different thicknesses, as compared to forming positive electrodes of different thicknesses on the front and back. There is. Of course, it goes without saying that a positive electrode may be used in which a thin first positive electrode active material layer 12 is provided on one side of the positive electrode current collector foil 11 and a thick second positive electrode active material layer 13 is provided on the other side.

As described above, the electrode member 2 according to the present embodiment forms the active material layers of different thicknesses in one electrode member 2 to achieve the first characteristic of relatively high output and low capacity. A plurality of first electrode pairs 41 are provided, and a plurality of second electrode pairs 42 having relatively low power and high capacity second characteristics are formed. By using this as an electrode, it is possible to realize a secondary battery simultaneously having excellent input / output characteristics and high energy capacity characteristics as a whole.

Here, as a positive electrode active material for forming the first positive electrode active material layer 12 and the second positive electrode active material layer 13, for example, metal oxides of layered structure type, metal oxides and metal compounds of spinel type, phosphoric acid A salt type metal oxide etc. are mentioned. The layered structure type metal oxide may, for example, be a lithium nickel composite oxide, a lithium cobalt composite oxide, or a ternary composite oxide (LiCo _1/3 Ni _1/3 Mn _1/3 O ₂ ). Preferably, lithium nickel oxide (LiNiO ₂ ) is mentioned as the lithium nickel composite oxide. The lithium cobalt-based composite oxide preferably includes lithium cobaltate (LiCoO ₂ ). The spinel-type metal oxides, lithium-manganese-based composite oxide such as lithium manganate (LiMn 2 _O ₄₎ can be mentioned. Examples of phosphate type metal oxides include lithium iron phosphate (LiFePO ₄ ) and lithium manganese phosphate (LiMnPO ₄ ). In the present embodiment, LiCo _1/3 Ni _1/3 Mn _1/3 O ₂ is used as the active material of the positive electrode, but the positive electrode active material applicable to the present invention is not limited thereto, and the exemplified positive electrode The present invention is not limited to the active material, and any other material that can cause a battery reaction at the positive electrode can be used.

Further, as a negative electrode active material for forming the first negative electrode active material layer 22 and the second negative electrode active material layer 23, an active material which is usually used, for example, an amorphous carbon material such as graphite, soft carbon or hard carbon is used. It can be mentioned. The graphite may be artificial graphite or natural graphite. Further, metal lithium, metal oxide, metal sulfide, metal nitride and the like can be mentioned. Examples of metal oxides include tin oxide and silicon oxide. In the present embodiment, although graphite is used as the active material of the negative electrode, the negative electrode active material applicable to the present invention is not limited to this, and is not limited to the exemplified negative electrode active material. Anything that produces a cell reaction can be used.

In addition, when forming a positive electrode active material layer and a negative electrode active material layer, a binder may each be further contained in the positive electrode active material or the negative electrode active material, for example, polyvinylidene fluoride can be used. The positive electrode or negative electrode active material layer may contain a conductivity improver such as acetylene black.

In addition, the electrolytic solution 6 may be a mixed solution of a commonly used solvent such as ethylene carbonate and propylene carbonate which are cyclic carbonates, and dimethyl carbonate and ethyl methyl carbonate and diethyl carbonate which are chain carbonates. the organic electrolytic solution obtained by dissolving 1 molar degree per liter of lithium phosphate (LiPF ₆₎ and the like.

Next, FIGS. 5 (a) to 5 (c) show diagrams showing the state of charge (hereinafter referred to as "SOC") of the secondary battery of the present embodiment. Note that A in FIG. 5 corresponds to the charged state of the first electrode pair 41 formed of a relatively thin active material layer, and B in FIG. 5 is formed of a relatively thick active material layer. It corresponds to the charge state of the second electrode pair 42.

FIG. 5A shows the voltage when charging is started. When charging is started, the voltage rises rapidly because the first electrode pair 41 (A) having the relatively thin first anode active material layer 22 has a smaller internal resistance. Accompanying, charging also progresses rapidly. On the other hand, since the second electrode pair 42 (B) having the relatively thick second negative electrode active material layer 23 has a larger internal resistance than the first electrode pair 41, charging proceeds gradually. Go. That is, charging proceeds by the lithium ions desorbed from the positive electrode active material layer passing through the electrolytic solution and moving to the negative electrode active material layer through the separator. For this reason, the moving distance of lithium ions is short, that is, the first electrode pair 41 having the first negative electrode active material layer 22 charges faster and has the second negative electrode active material layer 23. The second electrode pair 42 travels later.

In FIG. 5 (b), the first electrode pair 41 having the relatively thin first negative electrode active material layer 22 and the second negative electrode active material layer 23 relatively thick are used. It is a figure which shows the voltage when the electric potential state of 2 electrode pair 42 is relieve | moderated. When charging is completed, the SOC of the first electrode pair 41 (A) is high, and the SOC of the second electrode pair 42 (B) is low. This is because the relatively thin first anode active material layer 22 has a relatively low capacity, and the charge amount is maximally satisfied within the allowable range from the above difference in charge rate, and it is relatively In the thick second negative electrode active material layer 23, since the capacity is relatively large, the charge amount is less than the allowable range in the same time. In order to reduce the difference in charge amount (potential difference), lithium ions move from the relatively thin first negative electrode active material layer 22 to the relatively thick second negative electrode active material layer 23 through the electrolytic solution. , And move to the equilibrium state.

FIG. 5 (c) is a diagram showing the voltage when the relaxation is completed. When the relaxation is completed, the voltage of the first electrode pair 41 having the relatively thin first anode active material layer 22 and the voltage of the second electrode pair 42 having the relatively thick second anode active material layer 23 Are the same.

As described above, the first electrode pair 41 having the relatively thin first negative electrode active material layer 22 is excellent in input characteristics because the response to a large current input such as charging, particularly rapid charging, is fast. Since the thickness is thin, the charge amount is immediately filled, and the energy capacity characteristic is lowered. On the other hand, in the second electrode pair 42 having the relatively thick second negative electrode active material layer 23, although the response to charging is slow, a high energy capacity can be secured because the thick portion. In FIG. 5, input characteristics and energy capacity characteristics for charging of the first electrode pair 41 formed of a relatively thin active material layer and the second electrode pair 42 formed of a relatively thick active material layer. It is needless to say that the same output characteristic and energy capacity characteristic are also applied to the discharge.

Therefore, by providing the first electrode pair 41 and the second electrode pair 42 made of active material layers of different thicknesses in one electrode member 2, a portion with excellent input / output characteristics and high energy capacity characteristics can be obtained. The part which it has will coexist. By using this as an electrode, it is possible to realize a secondary battery simultaneously having excellent input / output characteristics and high energy capacity characteristics as a whole.

In the embodiment described above, the active material layer is provided on both sides of the current collector foil to form the positive electrode or the negative electrode, but the electrode described above using the positive electrode and the negative electrode provided with the active material layer on only one side of the current collector foil The members can also be configured.

Second Embodiment
The present embodiment is a modification of the electrode member of the first embodiment, and as shown in FIG. 6, it is carried out using the positive electrode current collector foil 11A and the negative electrode current collector foil 21A provided with a plurality of through holes 50 on the entire surface. Except for the positive electrode and the negative electrode provided with the same active material layer as that of the first embodiment, the second embodiment is the same as the first embodiment.

The reason for using such a positive electrode current collector foil 11A and the negative electrode current collector foil 21A is to promote relaxation of the potential state of FIG. 5 (b) described above. That is, during relaxation of the potential state, for example, lithium ions also move from the relatively thin first negative electrode active material layer 22 to the relatively thick second negative electrode active material layer 23 via the through holes 50. And the transition to equilibrium is promoted.

In addition, the formation position of the through hole 50 is not limited to the illustrated one. For example, the formation density of the through hole 50 may be changed depending on the place, for example, the central part in the short direction of each current collector foil is short. It may be denser than the end of the direction. Further, the shape of the through hole 50 is not limited to a circular shape, and may be, for example, a substantially rectangular shape.

(Embodiment 3)
Embodiment 3 of the present invention will be described with reference to FIG. The third embodiment is a modified example of the configuration of the electrode member, and the same members as the first embodiment are denoted by the same reference numerals, and overlapping descriptions will be omitted.

In the first embodiment, in order to provide the first electrode pair 41 having the first characteristic and the second electrode pair 42 having the second characteristic, the relatively thin first positive electrode active material layer 12 and the first Although the negative electrode active material layer 22 of No. 1 and the relatively thick second positive electrode active material layer 13 and the second negative electrode active material layer 23 were formed, in the present embodiment, the positive electrode active material forming the active material layer The first characteristic and the second characteristic that are relatively different are provided by making the type of.

FIG. 7 is a partially enlarged cross-sectional schematic view of the electrode member according to the present embodiment. As shown in the figure, the electrode member 2A is provided with a positive electrode 10A having the first positive electrode active material layer 12A formed on one surface of the positive electrode current collector foil 11 and the second positive electrode active material layer 13A on the other surface. Do. Here, although the first positive electrode active material layer 12A and the second positive electrode active material layer 13A will be described later in detail, they are formed using different active materials and have different characteristics.

Specifically, the first positive electrode active material layer 12A is made of a kind of active material having the first characteristic of relatively high output and low capacity, and the second positive electrode active material layer 13A is relatively And a type of active material having the second characteristic of low power and high capacity. Therefore, although the thicknesses of the first positive electrode active material layer 12A and the second positive electrode active material layer 13A are substantially the same, they have different characteristics. Of course, the thickness may be changed simultaneously with the type of active material to make the first positive electrode active material layer 12A thinner and the second positive electrode active material layer 13A thicker.

On the other hand, as a negative electrode corresponding to the positive electrode 10A, a negative electrode in which a relatively thin first negative electrode active material layer 22 is formed on both surfaces of the negative electrode current collector foil 21 at a position facing the first positive electrode active material layer 12A. 20a is provided, and a negative electrode 20b having a relatively thick second negative electrode active material layer 23 formed on both surfaces of the negative electrode current collector foil 21 is provided at a position facing the second positive electrode active material layer 13A. . The first positive electrode active material layer 12A and the first negative electrode active material layer 22 constitute a first electrode pair 41A having a first characteristic, and the second positive electrode active material layer 13A and the second negative electrode The active material layer 23 constitutes a second electrode pair 42A having the second characteristic.

As in the first embodiment, the first characteristic means relatively high output and low capacity, and the second characteristic means relatively low output and high capacity.

As described above, in the first embodiment, the difference in characteristics between the first electrode pair 41 having the first characteristic and the second electrode pair 42 having the second characteristic constitutes each electrode pair. Although provided by making the thickness of the active material layer different, in the present embodiment, not the thickness of the active material layer but the type of the positive electrode active material is different, and the negative electrode active material layer is opposed to the positive electrode active material layer. By making the thickness of the material layer correspond to the characteristics of the positive electrode active material, the difference between the first and second characteristics is provided.

For example, an active material having high electron conductivity is applied to the first electrode pair 41A having the first characteristic of high output and low capacity. That is, in order to improve the input / output characteristics of the lithium ion secondary battery, for example, the internal resistance of the active material layer may be lowered, but if the electron conductivity is high, the surface of the active material during charging and discharging and The conduction of electrons between the active materials can be rapidly progressed to reduce the internal resistance of the active material layer. And, such an active layer can maintain high input / output characteristics.

On the other hand, an active material having a high energy capacity is applied to the second electrode pair 42A having the second characteristic of low output and high capacity. This is because in order to improve the energy capacity of the lithium ion secondary battery, it is necessary to increase the energy density (capacity) of the active material itself.

Here, a positive electrode active material having a first characteristic of high output and low capacity, and a positive electrode active material having a second characteristic of low output and high capacity will be described.

Whether or not it has high output characteristics can be determined based on the types of various active materials and their particle sizes and the amount of conductive aid added.

On the other hand, whether or not it has high capacity characteristics can be determined based on, for example, the theoretical capacity of the active material. The theoretical capacity of LiCoO ₂ is 274 mAh / g, the theoretical capacity of LiNiO ₂ is 274 mAh / g, the theoretical capacity of LiMn ₂ O ₄ is 148 mAh / g, and the theoretical capacity of LiFePO ₄ is 170 mAh / g. Thus, where LiCoO ₂ and LiNiO ₂ is, it can be determined to have the characteristics of relatively high capacity compared to LiMn ₂ O ₄ and LiFePO _4, LiFePO ₄ is relative compared to LiMn ₂ O ₄ Can be judged to have high capacity characteristics.

Thus, the first characteristic of high output and low capacity by relatively comparing the kind of active material and the particle diameter thereof, the amount of the conductive additive to be added, and the theoretical capacity, preferably the value of the actual capacity. The combination of the active material having the first property and the active material having the second characteristic of low output and high capacity can be selected. In the present embodiment, as the positive electrode active material forming the first positive electrode active material layer 12A, As a positive electrode active material for forming the second positive electrode active material layer 13A, a relatively high-output low-capacity LiMn ₂ O ₄ is used, and a relatively low-output high-capacity LiFePO ₄ is used.

Of course, the values of input / output characteristics and actual capacity of the active material layer fluctuate by changing the particle size of the active material, adding a conductive material, performing surface treatment, or performing crystal structure or bulk modification. The input / output characteristics and capacitance characteristics of the first positive electrode active material layer 12A and the second positive electrode active material layer 13A may be changed by simultaneously changing these values.

In addition, due to such modification of the active material, it has an active material having extremely excellent high-output and low-capacity first characteristics, and a low-power and extremely excellent high-capacity second characteristics contrary thereto. It is possible to form an active material, and by using an electrode member combining these, it is possible to realize a secondary battery simultaneously having further excellent input / output characteristics and high energy capacity characteristics.

The negative electrode active material for forming the first and second negative electrode active material layers 22 and 23 may be appropriately selected from the active materials exemplified in Embodiment 1, and the thickness may be changed. As in the case of the positive electrode active material described above, the characteristics of the active material may be examined to make the negative electrode active material corresponding to the first characteristic different from the negative electrode active material corresponding to the second characteristic. The thickness may be changed simultaneously with the type.

As described above, as in the first embodiment, the electrode member 2A according to the present embodiment is also relatively low with the first electrode pair 41A having the first characteristic of relatively high output and low capacity. Since the second electrode pair 42A having the second characteristic of output and high capacity is provided, by using it as an electrode, a secondary battery simultaneously having excellent overall input / output characteristics and high energy capacity characteristics. Can be realized.

(Other embodiments)
In the embodiment described above, the laminated electrode in which the positive electrode and the negative electrode are stacked in the thickness direction is exemplified. However, a wound positive electrode in which a long positive electrode and a negative electrode are wound may be used. For example, in the example of the first embodiment, a wound-type electrode member is obtained by winding a total of seven layers including three layers constituting the positive electrode and four layers constituting the negative electrode as shown in FIG. be able to.

Moreover, although the electrode member for lithium ion secondary batteries was illustrated in embodiment mentioned above, it is not limited to this in particular, For example, applying to the lithium polymer secondary battery which utilized the gel-like polymer for electrolyte is possible it can. The present invention can also be applied to alkaline secondary batteries such as nickel cadmium batteries and nickel hydrogen batteries which are mounted on small portable electronic devices such as mobile phones and notebook computers.

Moreover, the container of the secondary battery which concerns on this embodiment, and a shape are a laminate type or a can type, However, It is not limited to this. For example, a coin type, a cylinder type, a button type, a sheet type, a square type, etc. may be sufficient. In addition, these secondary batteries may be connected in series or in parallel.

DESCRIPTION OF SYMBOLS 1 laminated type lithium ion secondary battery 2 electrode member 3 laminate exterior body 4 positive electrode terminal 5 negative electrode terminal 6 electrolyte solution 10 positive electrode 11 positive electrode current collector foil 12 1st positive electrode active material layer 13 2nd positive electrode active material layer 20 negative electrode 21 Negative electrode current collector foil 22 first negative electrode active material layer 23 second negative electrode active material layer 30 separator 41 first electrode pair 42 second electrode pair 50 through hole

Claims

A secondary battery comprising an electrolytic solution and an electrode member used by being immersed in the electrolytic solution,
The electrode member includes a positive electrode having a positive electrode active material layer formed on the surface of a positive electrode current collector foil, a negative electrode having a negative electrode active material layer formed on the surface of the negative electrode current collector foil, and the positive electrode and the negative electrode Forming a pair of electrodes by stacking the positive electrode active material layer and the negative electrode active material layer opposed to each other with the separator interposed therebetween;
The electrode pair comprises a first electrode pair comprising a first active material layer having a first characteristic of relatively high power and low capacity, and a second characteristic of relatively low power and high capacity. What is claimed is: 1. A secondary battery comprising: a second electrode pair comprising a second active material layer.
The first active material layer of the first electrode pair and the second active material layer of the second electrode pair have a layer thickness, a coating amount, and a type of active material forming the layer. The secondary battery according to claim 1, wherein at least one of the first and second characteristics corresponds to at least one of the first and second characteristics.
The positive electrode and the negative electrode each have an active material layer on both sides of the current collector foil, and at least one of the positive electrode and the negative electrode corresponds to the first characteristic on one side of the current collector foil. The secondary battery according to claim 1 or 2, further comprising the second active material layer corresponding to the second characteristic on the other surface thereof.
The secondary battery according to claim 3, wherein a plurality of holes are formed in the current collector foil of the positive electrode and the negative electrode.
5. The secondary battery according to claim 1, wherein a plurality of the first electrode pairs and the second electrode pairs are stacked or wound.