JPH05299102A - High molecular solid electrolyte battery - Google Patents

Abstract

PURPOSE:To obtain a solid electrolyte battery capable of suppressing the generation of such dendrite as to cause a short-circuit between electrode plates by increasing the charge and discharge characteristics. CONSTITUTION:Auxiliary high molecular solid electrolyte layers 21, 22 are respectively arranged between a positive electrode active substance layer 3 and a negative electrode active substance layer 1. The auxiliary high molecular solid electrolyte layers 21, 22 are formed of a high molecular compound having smaller molecular weight than the high molecular compound which constitutes the high molecular solid electrolyte layer 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polymer solid electrolyte battery.

[0002]

2. Description of the Related Art A typical battery uses a liquid electrolyte (electrolyte) as an electrolyte. However, when an electrolytic solution is used as the electrolyte, there is a problem that the electrolyte decreases due to liquid leakage and depletion. Therefore, a battery (solid electrolyte battery) has been proposed in which a solid electrolyte having ion conductivity is used as an electrolyte to suppress the decrease of the electrolyte. A typical solid electrolyte battery is a polymer solid electrolyte battery in which a polymer compound containing a negative electrode active material is used as an electrolyte. In this type of battery, it is necessary to increase the mechanical strength of the polymer solid electrolyte layer in order for the electrolyte to function as a separator. Therefore, conventionally, a polymer compound having a relatively high molecular weight is used for the polymer solid electrolyte layer to maintain its strength high.

[0003]

However, since a polymer compound has a high viscosity when the molecular weight is high, it is difficult to sufficiently adhere the active material layer and the polymer solid electrolyte layer in the conventional polymer solid electrolyte battery. could not. Further, the higher the molecular weight of the polymer compound, the lower the ionic conductivity. Therefore, when the solid polymer electrolyte layer is formed of a high molecular weight polymer compound, the metal ions of the negative electrode active material cannot be sufficiently diffused into the positive electrode active material layer, resulting in a low charge / discharge capacity of the battery. It has the characteristic that In particular, at low temperatures, there is a problem that the ionic conductivity decreases and the charge / discharge capacity decreases significantly. Further, if the active material layer and the electrolyte cannot be sufficiently adhered to each other, high-rate charge / discharge cannot be performed, and the current density at the interface portion between the negative electrode active material layer and the electrolyte, which has a small contact area, is high during charging. Then, there is a problem that a dendrite that causes a short circuit between the electrode plates is easily generated and the life of the battery is shortened.

An object of the present invention is to provide a polymer solid electrolyte battery which has a higher charge / discharge capacity than the conventional one and can be charged / discharged at a high rate.

Another object of the present invention is to provide a polymer solid electrolyte battery capable of suppressing generation of dendrite which causes a short circuit between electrode plates in a negative electrode active material layer.

[0006]

According to a first aspect of the present invention, a positive electrode active material layer and a positive electrode active material layer are provided for a solid polymer electrolyte battery in which a positive electrode active material layer, a solid polymer electrolyte layer, and a negative electrode active material layer are laminated. Auxiliary polymer solid electrolyte layer formed of a polymer compound having a lower molecular weight than the polymer compound forming the polymer solid electrolyte layer between at least one active material layer of the negative electrode active material layer and the polymer solid electrolyte layer To place.

In the second aspect of the present invention, the auxiliary polymer solid electrolyte layer is arranged between the polymer solid electrolyte layer and the positive electrode active material layer and between the polymer solid electrolyte layer and the negative electrode active material layer.

In the third aspect of the invention, the auxiliary polymer solid electrolyte layer is arranged between the polymer solid electrolyte layer and the negative electrode active material layer.

[0009]

[Function] A polymer compound having a low molecular weight has a lower viscosity than a polymer compound having the same material and a high molecular weight. Therefore, the molecular weight is higher than that of the polymer compound which forms the solid polymer electrolyte layer between the active material layer of at least one of the positive electrode active material layer and the negative electrode active material layer and the solid polymer electrolyte layer as in the invention of claim 1. When an auxiliary polymer solid electrolyte layer formed of a polymer compound having a low level is placed, the auxiliary polymer solid electrolyte layer penetrates into the active material layer, and the contact area (reaction area) between the electrolyte layer and the active material layer is reduced. To increase. In the present invention, since the solid polymer electrolyte layer having a high molecular weight is provided as in the conventional case, the strength required for the electrolyte layer to function as a separator can be maintained. Therefore, according to the present invention, it is possible to obtain a battery having a high charge / discharge capacity and capable of high-rate charge / discharge without lowering the strength of the electrolyte layer. Further, in the polymer solid electrolyte battery, as shown in the model in which Li ⁺ is used as an ion shown in FIG. 5, the negative electrode active material material (lightly trapped in the side chain S branched from the main chain P of the polymer compound ( Li ⁺ )
Is moved to the adjacent side chain S by the movement of the side chain S, so that ion conduction is performed. The lower the molecular weight of a polymer compound, the higher the degree of freedom of the side chain and the easier it is for the side chain to move.Therefore, a polymer compound with a lower molecular weight will have more side chain motion than a polymer compound with the same high molecular weight. Easy to have high ionic conductivity. Therefore, according to the present invention, by disposing the auxiliary polymer solid electrolyte layer, the ionic conductivity in the solid electrolyte as a whole is increased. If the thickness of the high molecular weight solid polymer electrolyte layer is reduced by the amount of the auxiliary solid polymer electrolyte layer, there is an advantage that the ionic conductivity in the electrolyte can be increased. When an auxiliary polymer solid electrolyte layer is arranged between the polymer solid electrolyte layer and the positive electrode active material layer and between the polymer solid electrolyte layer and the negative electrode active material layer as in the invention of claim 2, the negative electrode is obtained. Diffusion of metal ions of the active material into the positive electrode active material layer becomes easy. When the auxiliary solid polymer electrolyte layer is disposed between the solid polymer electrolyte layer and the negative electrode active material layer as in the third aspect of the present invention, the contact area between the negative electrode active material layer and the electrolyte is increased, and thus the negative electrode active material is formed. The current density at the interface between the material layer and the electrolyte is reduced, and it is possible to suppress the generation of dendrite that causes a short circuit between the electrode plates.

[0010]

EXAMPLE An example in which the polymer solid electrolyte battery of the present invention is applied to a lithium polymer solid electrolyte battery will be described in detail below with reference to the drawings. FIG. 1 is a schematic sectional view of a lithium polymer solid electrolyte battery. In FIG. 1, 1 is a solid polymer electrolyte layer, 2 is an auxiliary solid polymer electrolyte layer, 3 is a positive electrode active material layer, 4 is a negative electrode active material layer, 5 is a positive electrode current collector, 6 is a negative electrode current collector, and 7 is hot melt. The polymer solid electrolyte layer 1 is composed of a polymer compound such as methoxyoligoethyleneoxypolyphosphazene (MEP7) having the following molecular formula and lithium perchlorate (LiClO ₄ ).
And the like, and is formed of a mixture with a negative electrode active material.

[0011]

[Chemical 1] In the above formula, the larger the value of n, the longer the main chain of the polymer compound and the larger the molecular weight of the polymer compound.

By the way, in this embodiment, the solid polymer electrolyte layer 1 is made of MEP7 having a molecular weight of about 1.2 million,
It has a thickness of 80 μm. The auxiliary solid polymer electrolyte layer 2 includes a first auxiliary solid polymer electrolyte layer 21 disposed between the positive electrode active material layer 3 and the solid polymer electrolyte layer 1, a negative electrode active material layer 4, and a solid polymer electrolyte. The second auxiliary polymer solid electrolyte layer 22 is disposed between the second auxiliary polymer solid electrolyte layer 22 and the layer 1. The first auxiliary polymer solid electrolyte layer 21 is formed in a state of being in close contact with the positive electrode active material layer 3 and the polymer solid electrolyte layer 1, and the second auxiliary polymer solid electrolyte layer 22 is the negative electrode active material layer 4. And the solid polymer electrolyte layer 1 are in close contact with each other. First and second auxiliary solid polymer electrolyte layers 21, 22
Like the solid polymer electrolyte layer 1, is also formed of a mixture of MEP7 and lithium perchlorate.
As the material, a material having a lower molecular weight than MEP7 forming the polymer solid electrolyte layer 1 is used. In this example, the first and second auxiliary polymer solid electrolyte layers 21 and 22 were formed using MEP7 having a molecular weight of about 100,000, and each layer had a thickness of 20 μm. The ratio of the thickness of the solid polymer electrolyte layer 1 to the auxiliary solid polymer electrolyte layer 2,
In addition, the molecular weight of each polymer compound forming each of the electrolyte layers 1 and 2 is within a range in which the electrolyte layer can maintain the strength as a separator and the capacity of the battery can be increased. The positive electrode active material layer 3 is formed of a vanadium pentoxide xerogel film (V ₂ O ₅ .nH ₂ O), and the positive electrode active material layer 3 is formed so that the outer peripheral end surface 5 b is left on the surface 5 a of the positive electrode current collector 5. Is formed in. The negative electrode active material layer 4 is composed of a metallic lithium foil, and is arranged so as to leave the outer peripheral end face 6b on the surface 6a of the negative electrode current collector 6. The positive electrode current collector 5 and the negative electrode current collector 6 are metal foils made of nickel or the like, and both the current collectors 5 and 6 have the same size. Each of the positive electrode current collector 5 and the negative electrode current collector 6 constitutes a part of the outer case of the battery and also functions as a terminal. The hot melt 7 is a frame member that melts from the surface side when heated and exhibits adhesiveness. The hot melt 7 is the outer peripheral end surface 5 of the current collectors 5 and 6.
The ring corresponding to b and 6b is a ring having a rectangular shape, and is specifically formed of a polyolefin resin. The outer peripheral end surfaces 5b and 6b of the current collectors 5 and 6 are connected to the hot melt 7 to assemble the battery.

Next, a method of manufacturing this lithium solid electrolyte battery will be described. First, an amorphous V ₂ O ₅ 2% by weight solution is applied to one surface 5a of the positive electrode current collector 5 made of nickel foil having a thickness of 20 μm by screen printing or the like, and then dried to dry the positive electrode current collector 5 A vanadium pentoxide xerogel film (V ₂ O) having a thickness of about 10 μm is formed on the surface 5a.
_A positive electrode active material layer 3 composed of ₅ · nH ₂ O) was prepared. Next, 10% by weight of MEP7 having a molecular weight of about 100,000, which is a kind of polyphosphazene derivative, was added, and 6% by weight of LiClO ₄ was dissolved in 1,2-dimethoxyethane (DME). A solution for a molecular solid electrolyte was prepared, and this solution was applied onto the positive electrode active material layer 3 so as to entirely cover the positive electrode active material layer 3. As the solution containing the negative electrode active material, other than LiClO ₄ , LiPF ₆ , Li
BF ₄ , LiSO ₃ CF ₃ or the like can be used. Then, this was dried to volatilize DME to form a first auxiliary polymer solid electrolyte layer 21 having a thickness of 20 μm. Next, it contains 10% by weight of MEP7 having a molecular weight of about 1.2 million.
A solution for a solid polymer electrolyte in which 6 wt% of LiClO ₄ with respect to EP7 was dissolved in DME was prepared, and this solution was applied onto the first auxiliary solid polymer electrolyte layer 21. Then, this was dried to prepare a polymer solid electrolyte layer 1. Next, similar to the method of forming the auxiliary polymer solid electrolyte layer 21, 10% by weight of MEP7 having a molecular weight of about 100,000 is added, and 6% by weight of LiClO ₄ is added to this MEP7.
-Preparation of a solution for a solid polymer electrolyte dissolved in dimethoxyethane (DME), and adding this solution to a 30 μm thick Li
It was applied to one surface of the negative electrode active material layer 4 made of foil. Then, this was dried to form a second auxiliary polymer solid electrolyte layer 22 having a thickness of 20 μm on the negative electrode active material layer 4. After that, the second auxiliary solid polymer electrolyte layer 22 is brought into close contact with the solid polymer electrolyte layer 1, and the negative electrode active material layer 4 provided with the second auxiliary solid polymer electrolyte layer 22 is attached to the solid polymer electrolyte layer. Placed on top of 1. Next, the outer peripheral end portion 5 of the positive electrode current collector 5
The hot melt 7 is placed on top of the negative electrode active material layer 4
The negative electrode current collector 6 is placed so as to cover the hot melt 7 and the hot melt 7, and the hot melt 7 is completely connected to the outer peripheral end portions 5b and 6b of the current collectors 5 and 6 by heating, so that the solid polymer electrolyte battery Was manufactured.

Two types of batteries a and b were manufactured in order to investigate the characteristics of the polymer solid electrolyte battery of this example. The battery a is the battery of this embodiment, and the battery b is the conventional battery. The electrolyte layer of the battery b is a polymer solid electrolyte layer having a thickness of 120 μm formed by using only MEP7 having a molecular weight of about 1.2 million, and the structure other than the electrolyte of the battery b is the same as that of the battery a. These batteries a and b are stored at a temperature of 0 ° C for 25
Constant-current continuous discharge was performed at a current density of μA / cm ² until the voltage reached 2 V, and the discharge characteristics of the batteries a and b at low temperature were measured. FIG. 2 shows the measurement result. In the figure, the horizontal axis represents the change in the X value of the discharge product Li _x V ₂ O ₅ , and the vertical axis represents the battery voltage. From this figure, it can be seen that the battery a of the present invention has a higher discharge capacity at low temperatures than the conventional battery b.

Next, at a temperature of 25 ° C., both batteries a and b are set to 1
Constant-current continuous discharge was performed up to 2 V at current densities of 00 μA / cm ² and 500 μA / cm ² , and the high rate discharge characteristics of each battery were measured. FIG. 3 shows the measurement result. In the figure, the curves a1 and a2 are 100 μA / cm ² and 500, respectively.
3 is a characteristic curve of a battery of the present invention continuously discharged at a current density of μA / cm ² , where curves b1 and b2 are 100 μA / cm, respectively.
² is a characteristic curve of a conventional battery continuously discharged at current densities of ² and 500 μA / cm ² . From this figure, the battery a of the present invention is 1
It can be seen that the discharge capacity is higher than that of the conventional battery b at both 00 μA / cm ² and 500 μA / cm ² .

[0016] Then after discharging to 2V at a current density of 25 .mu.A / cm ² at a temperature of 25 ° C., by repeating charge and discharge for charging to 4.2V at a current density of 25 .mu.A / cm ² in cell a and b, The cycle life characteristics of the batteries a and b were examined.
FIG. 4 shows the measurement results. From this figure, battery a of the present invention
The discharge capacity of is about 8% of the discharge capacity of conventional battery b.
It can be seen that the battery a of the present invention has a longer battery life than the conventional battery b. In this figure, the reason why the battery reaches the end of its life is not that the positive electrode active material deteriorates but that dendrites are deposited on the negative electrode active material and a short circuit occurs inside the battery.

In the battery of this example, an auxiliary polymer solid electrolyte layer was arranged between the polymer solid electrolyte layer and the positive electrode active material layer, and between the polymer solid electrolyte layer and the negative electrode active material layer. However, the auxiliary polymer solid electrolyte layer may be disposed between the polymer solid electrolyte layer and either one of the positive electrode active material layer and the negative electrode active material layer. In particular, if an auxiliary polymer solid electrolyte layer is placed between the polymer solid electrolyte layer and the negative electrode active material layer, the current density at the interface between the negative electrode active material layer and the electrolyte becomes low, causing a short circuit between the electrode plates. The generation of such dendrites can be suppressed.

[0018]

According to the invention of claim 1, the polymer formed by the polymer solid electrolyte layer is provided between the polymer solid electrolyte layer and at least one of the positive electrode active material layer and the negative electrode active material layer. Since the auxiliary polymer solid electrolyte layer formed of a polymer compound having a lower molecular weight than the compound is arranged, a battery having a high charge / discharge capacity and capable of high-rate charge / discharge can be obtained. According to the invention of claim 2, since the auxiliary solid polymer electrolyte layer is arranged between the solid polymer electrolyte layer and the positive electrode active material layer and between the solid polymer electrolyte layer and the negative electrode active material layer, respectively, Diffusion of metal ions of the negative electrode active material into the positive electrode active material layer is facilitated, and the charge / discharge capacity of the battery is increased. According to the invention of claim 3, since the auxiliary polymer solid electrolyte layer is disposed between the polymer solid electrolyte layer and the negative electrode active material layer, generation of dendrites can be suppressed, and a long-life battery can be obtained. it can.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of a polymer solid electrolyte battery of an example of the present invention.

FIG. 2 is a diagram showing discharge characteristics at low temperature of a battery used for a test.

FIG. 3 is a diagram showing a high rate discharge characteristic of a battery used in a test.

FIG. 4 is a diagram showing cycle life characteristics of a battery used in a test.

FIG. 5 is a diagram showing how metal ions of a negative electrode active material are conducted in a polymer solid electrolyte.

[Explanation of symbols]

1 ... Polymer solid electrolyte layer, 2 ... Auxiliary polymer solid electrolyte layer, 3 ... Positive electrode active material layer, 4 ... Negative electrode active material layer.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Kensuke Hironaka, Kensuke Hironaka, 2-1-1, Nishishinjuku, Shinjuku-ku, Tokyo Within Shinjin Todenki Co., Ltd. (72) Inventor, Hayakawa, etc. 2-1-1 Shinshin-Toden Electric Co., Ltd. (72) Inventor Akio Komaki 2-1-1-1 Nishishinjuku, Shinjuku-ku, Tokyo Shinjin-Toden Electric Co., Ltd. (72) Inventor, Weibun Tokushima Prefecture 463 Kagasuno, Kawauchi-cho, Tokushima City Otsuka Chemical Co., Ltd. Tokushima Laboratory (72) Inventor Masatoshi Taniguchi 3-27 Otedori, Chuo-ku, Osaka City, Osaka Otsuka Chemical Co., Ltd.

Claims (3)

[Claims] 1. A polymer solid electrolyte battery in which a positive electrode active material layer, a polymer solid electrolyte layer, and a negative electrode active material layer are laminated, wherein at least one of the positive electrode active material layer and the negative electrode active material layer is an active material. Between the layer and the polymer solid electrolyte layer, an auxiliary polymer solid electrolyte layer formed of a polymer compound having a lower molecular weight than the polymer compound forming the polymer solid electrolyte layer is arranged. A characteristic polymer solid electrolyte battery. 2. The auxiliary polymer solid electrolyte layer is disposed between the polymer solid electrolyte layer and the positive electrode active material layer and between the polymer solid electrolyte layer and the negative electrode active material layer, respectively. The polymer solid electrolyte battery according to claim 1, wherein 3. The solid polymer electrolyte according to claim 1, wherein the auxiliary solid polymer electrolyte layer is disposed between the solid polymer electrolyte layer and the negative electrode active material layer. battery.