JP2001015162A - Solid electrolyte battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve ionic conductivity of electrodes, to prevent the deterioration of cycle characteristic caused by increase in the internal impedance, and to provide a battery with superior load characteristic by providing a negative electrode active material layer including a negative electrode active material, a positive electrode active material layer including a positive electrode active material, and a polymer electrolyte and by including inorganic solid electrolyte powder in the negative electrode active layer and the positive electrode active layer. SOLUTION: Preferably, this solid electrolyte battery is so formed that inorganic solid electrolyte powder is lithium ionic conductor with ionic conductivity at 25 deg.C 1.0×10-4 S/cm or more and the content of the inorganic solid electrolyte powders is within a range not less than 1 wt.% and not more than 50 wt.% relative to a negative electrode active material or a positive electrode active material. This battery is provided with a negative electrode 2, a positive electrode 3, and a polymer solid electrolyte 4 arranged therebetween, and is sealed by an external case 5 of an insulating material. A negative electrode terminal 6 and a positive electrode terminal are connected to the negative electrode 2 and the positive electrode 3 respectively, the negative electrode 2 comprises a negative electrode active material layer 2a and a negative electrode current collecting element 2b, and the positive electrode 3 comprises a positive electrode active material layer 3 and a positive electrode current collecting element 3b.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a solid electrolyte battery provided with a solid electrolyte.

[0002]

2. Description of the Related Art As electronic devices such as video tape recorders and other communication devices, such as communication devices, have become smaller and lighter, the batteries used as their power sources are lighter, smaller and thinner. Is required.

[0003] Accordingly, a solid polymer electrolyte battery using polyethylene oxide, polyphosphazene or the like as an electrolyte material has been actively studied. This polymer solid electrolyte battery has a solid electrolyte and does not have to worry about liquid leakage, so there is no need to use a metal battery can for the exterior material unlike an electrolyte battery, and it can be made relatively lightweight and heat resistant. It has advantages such as excellent performance and simplification of the battery configuration.

For example, when a polymer solid electrolyte, particularly a solid electrolyte containing no electrolyte solution in a polymer matrix, is used in a battery, the contact between the negative electrode and the positive electrode and the electrolyte is a solid-to-solid contact. Therefore, only the electrode and the solid polymer electrolyte are in contact with each other on their surfaces. On the other hand, in the electrolyte battery, since the electrolyte is a liquid, the electrolyte permeates into the inside of the electrode. For this reason, it is more difficult for the solid polymer electrolyte battery to ensure uniform and sufficient ionic conductivity to the inside of the electrode, and the internal impedance of the battery becomes higher than for the electrolyte-based battery in which the electrolyte is a liquid. It is difficult to obtain the rate and sufficient load characteristics.

[0005] Therefore, in a secondary battery using a solid electrolyte, a certain amount of a solid electrolyte to be used as an electrolyte is previously contained in both or either of the anode active material layer and the cathode active material layer. In this case, a polymer solid electrolyte is used for a polymer solid electrolyte battery, and an inorganic solid electrolyte is used for an inorganic solid electrolyte battery. The contact area with the ionic conductor is improved to ensure ionic conductivity.

[0006]

The ionic conductivity can be improved by including a solid electrolyte in the negative electrode active material layer or the positive electrode active material layer. However, on the other hand, when the content of the solid electrolyte in the electrode active material layer increases,
There is a problem that the active material density in the electrode is relatively low, and the actual battery capacity is low.

The present invention has been proposed in view of such a conventional situation, and has been proposed to improve the ionic conductivity of electrodes of a solid electrolyte battery and prevent deterioration of cycle characteristics and the like due to an increase in internal impedance. It is another object of the present invention to provide a solid electrolyte battery having excellent load characteristics.

[0008]

A solid electrolyte battery according to the present invention, which achieves the above objects, comprises a negative electrode active material layer containing a negative electrode active material, a positive electrode active material layer containing a positive electrode active material, and a polymer solid electrolyte. Wherein the negative electrode active material layer or the positive electrode active material layer contains an inorganic solid electrolyte powder.

The solid electrolyte battery according to the present invention having the above-described structure ensures sufficient ion conductivity without substantially lowering the battery capacity, and suppresses deterioration of cycle characteristics caused by an increase in internal impedance. Reduce and achieve excellent load characteristics.

[0010]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows a configuration example of a solid electrolyte battery to which the present invention is applied. A solid electrolyte battery 1 according to the present invention includes a negative electrode 2, a positive electrode 3 disposed opposite to the negative electrode 2, a polymer solid electrolyte 4 disposed between the negative electrode 2 and the positive electrode 3, and an insulating material. And is hermetically sealed. A negative electrode terminal 6 is connected to the negative electrode 2, and a positive electrode terminal 7 is connected to the positive electrode 3, respectively.
The outer case 5 is sandwiched between sealing portions, which are peripheral portions.

The negative electrode 2 is formed by forming a negative electrode active material layer 2a containing a negative electrode active material on a negative electrode current collector 2b. As the negative electrode current collector 2b, for example, a metal foil such as a copper foil is used. The negative electrode active material contained in the negative electrode active material layer 2a differs depending on the type of battery to be manufactured, and is not particularly limited. For example, when manufacturing a lithium battery or a lithium ion battery, as a negative electrode active material, lithium metal or an alloy containing lithium metal, a carbonaceous material capable of inserting and extracting lithium metal, and an insertion and extraction of lithium metal are possible. Inorganic materials are used.

Examples of the lithium alloy include a lithium-aluminum alloy, a lithium-zinc alloy, a lithium-tin alloy, a lithium-lead alloy, and a lithium-indium alloy.

Examples of the carbonaceous material capable of inserting and extracting an alkali metal such as lithium include conductive polymers such as polyacetylene and polypyrrole, pyrolytic carbons, cokes (pitch coke, needle coke, petroleum coke, etc.). ), Graphites, non-graphitizable carbons, glassy carbons, organic polymer compound fired bodies (500
Fired under vacuum or inert gas flow at an appropriate temperature of ℃ or more. ), Carbon fiber, activated carbon and the like. Inorganic materials capable of inserting and extracting lithium include oxides such as tin oxide, iron oxide, and titanium oxide, siliconaceous materials or compounds thereof, and tin compounds.

The positive electrode 3 has a structure in which a positive electrode active material layer 3a containing a positive electrode active material is formed on a positive electrode current collector 3b. As the positive electrode current collector 3b, for example, a metal foil such as an aluminum foil is used. The positive electrode active material depends on the type of battery to be manufactured, and is not particularly limited.

For example, the cathode active material is not particularly limited as long as it is a material capable of inserting and extracting lithium when a lithium battery or a lithium ion battery is manufactured.
For example, the positive electrode active material may be a lithium-free metal oxide or metal sulfide such as TiS ₂ , MoS ₂ , NbSe ₂ , V ₂ O ₅ , or a general formula LixMO ₂ ( Here, M represents a transition metal such as Co, Ni, and Mn, and 0.05 ≦ x ≦ 1.10.) Or LiNi _p M1 _q M2 _r O ₂ (where M1 and M2 are Al,
It may be at least one element selected from Mn, Fe, Co, Ni, Cr, Ti and Zn, or may be a nonmetallic element such as P or B. Also, p + q + r = 1. ) Is used. In particular, as the positive electrode active material, it is preferable to use lithium cobalt oxide or lithium nickel oxide from the viewpoint that a high voltage and a high energy density can be obtained and cycle characteristics are excellent.

The solid polymer electrolyte 4 is not particularly limited as long as it is a compound of a polymer and a lithium salt and exhibits ionic conductivity. However, the polymer solid electrolyte 4 is a polyether-based polymer represented by polyethylene oxide exhibiting high ionic conductivity. It is preferable to use a molecular solid electrolyte and a derivative thereof, or a copolymer of polyphosphazene, polysiloxane, and polyether.

The lithium salt is not particularly limited as long as the electrolyte salt itself dissolves in the polyether copolymer and exhibits ionic conductivity. For example, lithium hexafluorophosphate (LiPF ₆ ), lithium perchlorate (LiClO ₄ ), arsenic hexafluoride (LiAs)
F ₆ ), lithium tetrafluoroborate (LiBF ₄ ), lithium trifluoromethanesulfonate (LiCF ₃ SO ₃ ),
A conventionally known lithium salt such as lithium bistrifluoromethylsulfonylimide ([LiN (CF ₃ SO ₂ ) ₂ ]) can be used.

In the solid electrolyte battery according to the present embodiment, the above-described negative electrode active material layer 2a or positive electrode active material layer 3a
, An inorganic solid electrolyte powder is kneaded. The inorganic solid electrolyte powder is a lithium ion conductor having lithium ion conductivity and an ion conductivity at 25 ° C. of 1.0 × 10 ⁻⁴ S / cm or more. If the ionic conductivity at 25 ° C. is less than 1.0 × 10 ⁻⁴ S / cm, it is difficult to secure ionic conductivity that can function as a battery, and sufficient load characteristics cannot be obtained as a battery.

The inorganic solid electrolyte powder can be used without any particular limitation as long as it meets the above conditions. For example, as the inorganic solid electrolyte powder, Li ₂ O—SiO ₂ ,
_{Li 2 O-Al 2 O 3} , Li 2 O-P 2 oxide glass ceramics which O ₅ or the like as main components, La _0.51 Li _0.34 TiO _2.94
Or perovskite-based ceramics which these were added to different element, sulfide glass mainly composed of _{Li 2 S-SiS 2, Li} 2 S-GeS 2 , and the like.

It is assumed that the content of the inorganic solid electrolyte powder is more than 1% by weight and 50% by weight or less based on the anode active material layer 2a or the cathode active material layer 3a. When the content of the inorganic solid electrolyte powder is 1% by weight or less, the proportion of the ionic conductor in the negative electrode and / or the positive electrode is too small, so that it is difficult to secure the ionic conductivity and obtain sufficient load characteristics. Can not. Conversely, when the content of the inorganic solid electrolyte powder exceeds 50% by weight, the ionic conductivity increases, but as the inorganic solid electrolyte powder increases, the density of the negative electrode active material contained in the negative electrode 2 and / or the positive electrode 3 increases. , The density of the positive electrode active material contained in the battery decreases, and the battery capacity decreases.

Further, the particle diameter of the inorganic solid electrolyte powder is smaller than the particle diameters of the negative electrode active material and the positive electrode active material.
The more uniformly the inorganic solid electrolyte powder is dispersed, the larger the contact area between the electrode active material and the ionic conductor, and the better the ionic conductivity can be secured. When the particle diameter of the inorganic solid electrolyte powder is smaller than the particle diameter of the electrode active material, the inorganic solid electrolyte powder enters gaps between the electrode active materials, and the ionic conductivity is improved.

The electrolyte is not limited to a solid electrolyte containing no swelling solvent, but may be a gel electrolyte requiring a swelling solvent. Further, the shape of the battery is not particularly limited, and can be used in various shapes such as a film type, a wound type, a laminated type, a cylindrical type, a square type, a coin type, a button type and the like. Further, the above-described solid electrolyte battery may be a primary battery or a secondary battery.

[0023]

EXAMPLES Examples of the present invention and comparative examples will be described in detail, but the present invention is not limited to these examples. A solid electrolyte battery was manufactured as follows.

Example 1 LiCoO ₂ powder, graphite powder, polyvinylidene fluoride (hereinafter referred to as PVdF), La _0.51 Li
The mixing amount with _0.34 TiO _2.94 powder is 80: 6:
The mixture was weighed so as to be 3:11, and these powders were kneaded to prepare a positive electrode mixture. This positive electrode mixture was mixed with N-methyl-2.
-Dispersed in pyrrolidone to form a slurry-like liquid. This slurry-like liquid was applied on an aluminum current collector, dried, and then pressed. The one obtained through the above steps was used as the positive electrode 3.

After this positive electrode 3 was cut into a rectangle of 2 cm × 4 cm, a polyethylene oxide copolymer having an oligoalkyl ether side chain (molecular weight: 8
After the application of an acetonitrile solution in which (0000,000) and the LiBF ₄ complex were dissolved, acetonitrile as a solvent was removed by drying to obtain a 50-μm-thick film-shaped polymer solid electrolyte 4. Next, a lithium metal having a thickness of 30 μm was provided on the solid polymer electrolyte 4 as the negative electrode 2. A negative electrode terminal was connected to the negative electrode 2, and a positive electrode terminal was connected to the positive electrode 3, to obtain an electrode laminate. Finally, store this electrode laminate in an outer case,
The outer case was sealed. At this time, a laminate material in which a polyolefin-based polymer was coated on both sides of an aluminum foil was used for the outer case. Further, a positive electrode terminal and a negative electrode terminal were sandwiched between the sealing portions of the outer case to obtain a thin solid electrolyte battery 1.

Example 2 LiCoO ₂ powder, graphite powder, PVdF
And a cathode 0.5 was prepared in the same manner as in Example 1, except that the mixing amount of La _0.51 Li _0.34 TiO _2.94 powder was 70: 6: 3: 21 by weight, and the solid electrolyte battery 1 was produced in the same manner. Was prepared.

Example 3 LiCoO ₂ powder, graphite powder, PVdF
And a cathode 0.5 was prepared in the same manner as in Example 1 except that the mixing amount of La _0.51 Li _0.34 TiO _2.94 powder was 41: 6: 3: 50 by weight, and the solid electrolyte battery 1 was manufactured in the same manner. Was prepared.

[0028]Example 4 La_0.51Li_0.34TiO_2.94Li instead of powder_TwoO-
Al_TwoO_Three-TiO_Two−P _TwoO_FiveUsing powder, LiCoO_Two
Powder, graphite powder, PVdF, and Li_TwoO-
Al_TwoO_Three-TiO_Two−P_TwoO_FiveMix the amount of powder and
Except that the ratio is 90: 6: 3: 1.
A pole 3 is prepared, and a solid electrolyte battery 1 is prepared in the same manner.
did.

EXAMPLE 5 Instead of La _0.51 Li _0.34 TiO _2.94 powder, Li ₂ O—
With _{Al 2 O 3 -TiO 2 -P 2} O 5 powder, LiCoO ₂
Powder, graphite powder, PVdF, and Li ₂ O—
A positive electrode 3 was prepared in the same manner as in Example 1, except that the mixing amount with the Al ₂ O ₃ —TiO ₂ —P ₂ O ₅ powder was 80: 6: 3: 11 by weight, and the same method was used. A solid electrolyte battery 1 was produced.

EXAMPLE 6 Instead of La _0.51 Li _0.34 TiO _2.94 powder, Li ₂ O—
With _{Al 2 O 3 -TiO 2 -P 2} O 5 powder, LiCoO ₂
Powder, graphite powder, PVdF, and Li ₂ O—
A positive electrode 3 was prepared in the same manner as in Example 1, except that the mixing amount with the Al ₂ O ₃ —TiO ₂ —P ₂ O ₅ powder was 70: 6: 3: 21 by weight ratio, and the same method was used. Thus, a solid electrolyte battery 1 was produced.

EXAMPLE 7 Instead of La _0.51 Li _0.34 TiO _2.94 powder, Li ₂ O—
With _{Al 2 O 3 -TiO 2 -P 2} O 5 powder, LiCoO ₂
Powder, graphite powder, PVdF, and Li ₂ O—
The procedure was the same as in Example 1 except that the mixing ratio with the Al ₂ O ₃ —TiO ₂ —P ₂ O ₅ powder was 41: 6: 3: 50 by weight.

Example 8 Instead of La _0.51 Li _0.34 TiO _2.94 powder, Li ₂ O—
With _{Al 2 O 3 -TiO 2 -P 2} O 5 powder, LiCoO ₂
Powder, graphite powder, PVdF, and Li ₂ O—
A positive electrode 3 was prepared in the same manner as in Example 1, except that the mixing amount with the Al ₂ O ₃ —TiO ₂ —P ₂ O ₅ powder was 40: 6: 3: 51 by weight ratio, and the same method was used. Thus, a solid electrolyte battery 1 was produced.

Comparative Example In a positive electrode mixture, La _0.51 Li _0.34 TiO _2.94 powder, Li
Without containing an inorganic solid electrolyte powder such as ₂ O-Al ₂ O ₃ -TiO ₂ -P ₂ O ₅ powder, the mixing amount of the LiCoO ₂ powder, the graphite powder and the PVdF powder was 91:
A positive electrode 3 was prepared in the same manner as in Example 1 except that the ratio was 6: 3.
The solid electrolyte battery 1 was produced in the same manner.

The solid electrolyte battery 1 manufactured as described above was subjected to a discharge test. As a discharge test,
First, each solid electrolyte battery is placed in air at 50 ° C.
The battery was charged at a constant current of 0.1 mA, and after the battery voltage reached 4.2 V, the battery was charged at a constant voltage of 4.2 V. When the current value reached 10 μA, the battery was fully charged. After that, it is 0.1 to 3.0V
Constant current discharge was performed at mA. The rated capacity is defined as the discharge capacity when the constant current discharge at 0.1 mA is performed until the current voltage reaches 3.0 V.

In addition, 0.3 mA, 0.75 mA, 1.5
Similarly, constant current discharge was performed at mA, and the ratio (%) of the discharge capacity to the rated capacity at that time was determined.

With respect to the solid electrolyte batteries of Examples 1 to 8 and Comparative Example, the rated capacity and the ratio of the discharge capacity to the rated capacity at the time of discharging at each current, together with the amount of the inorganic solid electrolyte powder, were added. It is shown in Table 1.

[0037]

[Table 1]

According to Table 1, the discharge capacity of the solid electrolyte battery 1 decreases as the discharge current increases, as compared with the reference rated capacity. Further, the solid electrolyte battery 1 of Comparative Example 1 has a lower rated capacity than the solid electrolyte batteries 1 of Examples 1 to 8 containing the inorganic solid electrolyte powder. In the solid electrolyte battery 1 of Comparative Example 1, which does not contain any inorganic solid electrolyte powder, when the discharge current value is large, the discharge capacity is extremely reduced, and is reduced to a value that cannot be measured.

On the other hand, in the solid electrolyte battery 1 in which the positive electrode 3 contains the inorganic solid electrolyte powder, the larger the content of the inorganic solid electrolyte powder, the larger the discharge capacity at the time of constant current discharge. However, when the content of the inorganic solid electrolyte powder exceeds 50% by weight as in Example 8, the value of the discharge capacity is significantly reduced. Also, when the content of the inorganic solid electrolyte powder is less than 1% by weight as in Example 4, the value of the discharge capacity is extremely reduced. Example 2 in which the content of the inorganic solid electrolyte powder is a value near the middle between 1 wt% and 50 wt%
And Example 5 shows the best load characteristics.

From the above, it can be seen that good load characteristics can be obtained when the content of the inorganic solid electrolyte powder is more than 1% by weight and 50% by weight or less.

In the embodiment of the present invention, an example is shown in which the positive electrode contains the inorganic solid electrolyte powder, but it may be contained in the negative electrode. Further, both the negative electrode and the positive electrode may contain an inorganic solid electrolyte powder.

The inorganic solid electrolyte powder that can be used in the present invention must be electrochemically stable in consideration of the reactivity with the positive electrode active material and the negative electrode active material, oxidation resistance, and the like. may be a satisfying substance such as the high ionic conductivity, La _0.51 Li _0.34 TiO _2.94 powder and _{Li 2 O-Al 2 O 3} -TiO 2 -P 2 O in no way limited to ₅ powder.

[0043]

As described above in detail, according to the solid electrolyte battery of the present invention, the ion conductivity of the electrodes of the solid electrolyte battery is improved, and the deterioration of the cycle characteristics caused by the increase of the internal impedance is reduced. And excellent load characteristics can be realized.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of a main part showing one configuration example of a solid electrolyte battery to which the present invention is applied.

[Explanation of symbols]

1 solid electrolyte battery, 2 negative electrode, 2a negative electrode active material layer,
2b negative electrode current collector, 3 positive electrode, 3a positive electrode active material, 3b
Cathode current collector, 4 solid polymer electrolyte, 5 outer case

Continued on the front page (72) Inventor Takeshi Horie 6-35, Kita-Shinagawa, Shinagawa-ku, Tokyo Sony Corporation F-term (reference) 5H029 AJ02 AJ05 AJ06 AK02 AK03 AK05 AL02 AL06 AL07 AL08 AL11 AL12 AL16 AM07 AM12 AM16 BJ04 CJ08 DJ09 DJ16 EJ05 EJ07 HJ01 HJ05 HJ14 HJ20

Claims (4)

[Claims] 1. A solid electrolyte battery comprising a negative electrode active material layer containing a negative electrode active material, a positive electrode active material layer containing a positive electrode active material, and a polymer solid electrolyte, wherein the negative electrode active material layer or the positive electrode active material layer is provided. A solid electrolyte battery characterized by containing an inorganic solid electrolyte powder therein. 2. The solid electrolyte battery according to claim 1, wherein the inorganic solid electrolyte powder is a lithium ion conductor having an ion conductivity of 1.0 × 10 ⁻⁴ S / cm or more at 25 ° C. . 3. The method according to claim 1, wherein the content of the inorganic solid electrolyte powder is in the range of more than 1% by weight and 50% by weight or less based on the negative electrode active material or the positive electrode active material. Solid electrolyte battery. 4. The solid electrolyte battery according to claim 1, wherein the particle diameter of the inorganic solid electrolyte powder is smaller than the particle diameters of the negative electrode active material and the positive electrode active material.