JP2011044369A - Nonaqueous electrolyte battery - Google Patents

Abstract

Disclosed is a nonaqueous electrolyte battery in which the discharge capacity is unlikely to decrease even after repeated charging and discharging.
A non-aqueous electrolyte battery 100 includes a positive electrode layer 1, a negative electrode layer 2, and a solid electrolyte layer 3 disposed between the electrode layers. The solid electrolyte layer 3 included in the battery 100 includes an outer peripheral region 3t including an outer peripheral portion thereof, and an inner region 3r surrounded by the outer peripheral region 3t, and the Li ion conductivity in the outer peripheral region 3t is determined by the inner region 3r. Lower than the Li ion conductivity. By setting it as such a structure, since it can suppress that Li ion concentrates on the outer periphery part of the negative electrode layer 2 at the time of charge of the battery 100, the deterioration of the said outer periphery part can be prevented. As a result, the battery 100 is less likely to have a reduced discharge capacity even during repeated charging and discharging.
[Selection] Figure 1

Description

  The present invention relates to a non-aqueous electrolyte battery including a positive electrode layer, a negative electrode layer, and a solid electrolyte layer disposed between these electrode layers. In particular, the present invention relates to a non-aqueous electrolyte battery in which the discharge capacity does not easily decrease even during repeated charge and discharge.

  A power source of a relatively small electric device such as a portable device is provided with a positive electrode layer having a positive electrode current collector and a positive electrode active material layer, a negative electrode layer having a negative electrode current collector and a negative electrode active material layer, and a gap between these electrode layers. A non-aqueous electrolyte battery having an electrolyte layer is used. Among nonaqueous electrolyte batteries, in particular, a Li ion battery that performs charge and discharge by movement of Li ions between the positive and negative electrode layers has a high discharge capacity while being small (see, for example, Patent Document 1).

JP-A-8-180904

  However, the battery of Patent Document 1 has a problem that the discharge capacity tends to decrease while charging and discharging are repeated, that is, the cycle characteristic is poor. This is presumably because Li ions tend to concentrate in the vicinity of the outer peripheral edge of the negative electrode layer when the battery is charged, and the negative electrode layer and the solid electrolyte layer deteriorate in the vicinity as charging and discharging are repeated. In particular, when the negative electrode layer is smaller than the solid electrolyte layer, most of the Li ions that move in a larger portion of the solid electrolyte layer than the negative electrode layer are concentrated on the outer peripheral edge of the negative electrode layer when the battery is charged. The deterioration of the negative electrode layer and the solid electrolyte layer is remarkable.

  The present invention has been made in view of the above circumstances, and one of its purposes is to provide a nonaqueous electrolyte battery in which the discharge capacity does not easily decrease even after repeated charge and discharge, that is, a nonaqueous electrolyte battery excellent in cycle characteristics. There is to do.

(1) The nonaqueous electrolyte battery of the present invention is a nonaqueous electrolyte battery including a positive electrode layer, a negative electrode layer, and a solid electrolyte layer disposed between these electrode layers. The solid electrolyte layer provided in the nonaqueous electrolyte battery of the present invention includes an outer peripheral region including an outer peripheral edge portion thereof, and an inner region surrounded by the outer peripheral region, and Li ion conductivity in the outer peripheral region is determined by the Li ion conductivity in the inner region. It is characterized by being lower than ionic conductivity.

  According to the configuration of the nonaqueous electrolyte battery of the present invention, the movement of Li ions is limited in the outer peripheral region than in the inner region. As a result, Li ions can be less likely to concentrate in the vicinity of the outer peripheral edge of the negative electrode layer during battery charging, and deterioration of the portion can be suppressed. That is, since it is possible to prevent the vicinity of the outer peripheral edge of the negative electrode layer from being deteriorated as the battery is charged and discharged, the battery has excellent cycle characteristics.

(2) As one form of the nonaqueous electrolyte battery of the present invention, the boundary line between the outer peripheral region and the inner region is inside the contour line formed at the outer peripheral edge of the negative electrode layer when the nonaqueous electrolyte battery is viewed in plan view. It is preferable to be located at.

  If it is the said structure, concentration of Li ion in the outer periphery part vicinity of a negative electrode layer can be suppressed more effectively. This is particularly effective when a negative electrode layer having a smaller area than the solid electrolyte layer is formed when the battery is viewed in plan.

(3) As one form of this invention nonaqueous electrolyte battery, an outer peripheral area | region can further be comprised from the several area | region from which Li ion conductivity differs in the thickness direction. Here, some of the plurality of regions formed in the outer peripheral region may have higher Li ion conductivity than the inner region, and when the Li ion conductivity is averaged over the entire outer peripheral region, the outer peripheral region is It is sufficient that the Li ion conductivity is lower than that of the inner region.

  If a region having a high Li ion conductivity and a region having a low Li ion conductivity are mixed as in the above configuration, the Li ion conductivity in the outer peripheral region can be prevented from becoming too low.

(4) As one form of the nonaqueous electrolyte battery of the present invention, when the outer peripheral region is further composed of a plurality of regions, the Li ion conductivity of the region located closest to the positive electrode layer among these regions is the other region. It is preferable that it is lower than Li ion conductivity.

  When the movement of Li ions is suppressed by the region where the Li ion conductivity is low on the positive electrode layer side, the amount of Li ions in the region on the negative electrode layer side in the outer peripheral region can be reduced. As a result, it is possible to effectively suppress deterioration in the vicinity of the outer peripheral edge portion of the negative electrode layer.

(5) As one form of this invention nonaqueous electrolyte battery, it is preferable that an outer peripheral area | region contains an oxide as a Li ion conductive substance, and an inner area | region contains a sulfide as a Li ion conductive substance.

In general, examples of the solid electrolyte having Li ion conductivity include oxides such as LiPON (lithium phosphate oxynitride glass) and sulfides such as Li ₂ S—P ₂ S ₅ . When the Li ion conductivity of the oxide-based solid electrolyte and the sulfide-based solid electrolyte is compared, the sulfide-based solid electrolyte tends to have a higher Li ion conductivity. Therefore, a sulfide-based material is preferable as the inner region material, and an oxide-based material is preferable as the outer peripheral material.

(6) As one form of the nonaqueous electrolyte battery of the present invention, the oxide-based solid electrolyte is preferably LiPON, and the sulfide-based solid electrolyte is preferably Li ₂ S—P ₂ S _5. .

  When the combination of the sulfide-based and oxide-based solid electrolyte is selected as described above, the negative electrode layer can be effectively prevented from being deteriorated while maintaining a high discharge capacity.

(7) As one form of the nonaqueous electrolyte battery of the present invention, when a sulfide is used for the solid electrolyte, it is preferable to provide a buffer layer for buffering the deviation of Li ions between the solid electrolyte layer and the positive electrode layer.

  Although the sulfide-based solid electrolyte is excellent in Li ion conductivity, Li ions are likely to be biased in the vicinity of the contact interface with the positive electrode layer, and as a result, the discharge capacity of the battery may be reduced. The buffer layer can buffer the deviation of Li ions and suppress a decrease in the discharge capacity of the battery. The material of the buffer layer will be described in detail in the embodiment.

  In the non-aqueous electrolyte battery of the present invention, even when charging and discharging are repeated, the negative electrode layer hardly deteriorates and the discharge capacity does not easily decrease. Therefore, when the nonaqueous electrolyte battery of the present invention is used as a power source of a portable device such as a mobile phone or a mobile personal computer, the long-term use of the portable device without being connected to a commercial power source is guaranteed for a long time. be able to.

It is a schematic block diagram of the nonaqueous electrolyte battery as described in an Example, (A) is a longitudinal cross-sectional view, (B) is a top view. It is a schematic block diagram of the nonaqueous electrolyte battery as described in a comparative example, and is a longitudinal cross-sectional view.

  Hereinafter, an embodiment of the present invention will be described with reference to FIG. FIG. 1 to be referred to is a schematic configuration diagram of a nonaqueous electrolyte battery 100 of an embodiment described later, and is merely one form of the nonaqueous electrolyte battery of the present invention.

[overall structure]
As shown in FIG. 1, the nonaqueous electrolyte battery (Li ion battery) 100 of the present invention includes a positive electrode layer 1, a negative electrode layer 2, and a solid electrolyte layer 3 disposed between the electrode layers 1 and 2. . The battery 100 functions as a battery by exchanging Li ions between the positive electrode layer 1 and the negative electrode layer 2. The most characteristic feature of the battery 100 of the present invention is the configuration of the solid electrolyte layer 3. Hereinafter, each configuration provided in the battery 100 will be described.

<Positive electrode layer>
The positive electrode layer 1 includes a positive electrode current collector 11 having a current collecting function and a positive electrode active material layer 12 formed on one surface side thereof. As the positive electrode current collector 11, for example, a single metal such as Al, Cu, or Ni, or an alloy such as stainless steel can be used. As the positive electrode active material contained in the positive electrode active material layer 12, for example, LiCoO ₂ and _{LiNiO 2, LiMnO 2, LiCo 0.5} Fe 0.5 O 2 , etc. can be utilized.

<Negative electrode layer>
The negative electrode layer 2 in FIG. 1 is composed of a negative electrode active material layer that also serves as a current collector. Of course, the negative electrode layer 2 may include a negative electrode current collector separately. Examples of the negative electrode active material contained in the negative electrode layer 2 include metal Li.

  Further, the negative electrode layer 2 shown in FIG. 1 is formed to be slightly smaller than the positive electrode layer 1 and a solid electrolyte layer 3 described later when the battery 100 is viewed in plan. This is because the solid electrolyte layer 3 is not formed so that the negative electrode layer 2 is not in contact with the positive electrode layer 1 at the side portion of the battery 100 when the constituent elements of the battery 100 are sequentially laminated from the positive electrode layer 1 by the vapor phase method. This is because the outer peripheral edge of the mask may be masked. Of course, the negative electrode layer 2 can be formed in the same area as the solid electrolyte layer 3 by devising the arrangement of the mask.

<Solid electrolyte layer>
The solid electrolyte layer 3 can be divided into an outer peripheral region 3t including its outer peripheral edge and an inner region 3r surrounded by the outer peripheral region 3t. The difference between the outer region 3t and the inner region 3r is that the Li ion conductivity in each region is different, and the Li ion conductivity in the outer region 3t is lower than that in the inner region 3r. Specifically, the Li ion conductivity of the inner region 3r is 1.0 × 10 ⁻⁶ S / cm or more, and the Li ion conductivity of the outer region 3t is 1.0 × 10 ⁻⁸ S / cm or more. The difference in Li ion conductivity between the lateral region 3r and the outer peripheral region 3t is preferably at least twice.

  As described above, the Li ion conductivity in the outer peripheral region 3t of the solid electrolyte layer 3 is kept low, and the movement of Li ions from the positive electrode layer 1 toward the negative electrode layer 2 is limited during charging, whereby the negative electrode layer 2 is charged during charging of the battery 100. Concentration of Li ions in the vicinity of the outer peripheral edge of can be alleviated. In particular, as shown by a black arrow in FIG. 1A, when the negative electrode layer 2 is smaller than the positive electrode layer 1 and the solid electrolyte layer 3, the vicinity of the outer peripheral edge of the negative electrode layer 2 is from the vertically lower part of the portion. In addition to the Li ions, Li ions also move from the outside of the portion. However, according to the configuration of the present invention, since the Li ion conductivity in the outer peripheral region 3t is low, the absolute amount of Li ions moving to the part is small, and the concentration of Li ions in the part can be suppressed.

Although not illustrated in FIG. 1, the simplest configuration for setting the outer peripheral region 3t to a lower Li ion conductivity than the inner region 3r is to configure both regions with solid electrolytes having different compositions. For example, the solid electrolyte may include an oxide-based solid electrolyte such as LiPON, and a sulfide-based solid electrolyte such as Li ₂ S—P ₂ S ₅ . In general, since the sulfide-based solid electrolyte has higher Li ion conductivity than the oxide-based solid electrolyte, the inner region 3r contains a sulfide-based material and the outer peripheral region 3t contains an oxide-based material. It is good to make it.

  As described above, the inner region 3r and the outer peripheral region 3t may be made of a uniform material, but are partially different so that a plurality of regions having different Li ion conductivity are formed in the thickness direction. You may comprise with a material. In particular, in the outer peripheral region 3t, in order to prevent the Li ion conductivity from becoming too low, the outer peripheral region 3t is composed of a plurality of regions in the thickness direction as shown in FIG. It is preferable to use a Li ion conductive material. In this case, the Li ion conductivity of the region (the portion of reference numeral 31 described later in the figure) located closest to the positive electrode layer 1 among the regions constituting the outer peripheral region 3t is set to other regions (the outer peripheral region 3t in the drawing). It is preferable to make it lower than that of the part 32 described later. When the outer peripheral region 3t is further composed of a plurality of small regions, the value obtained by averaging the Li ion conductivity of each small region is defined as the Li ion conductivity of the outer peripheral region 3t (inner region 3r).

  On the other hand, there is a preferable position also at the position of the boundary line between the outer peripheral region 3t and the inner region 3r. Specifically, the boundary line is preferably located inside the boundary line formed at the outer peripheral edge of the negative electrode layer 2 when the battery 100 is viewed in plan. In that case, since the flow of Li ions from the portion wider than the negative electrode layer 2 to the negative electrode layer 2 in the solid electrolyte layer 3 can be suppressed, the concentration of Li ions in the vicinity of the outer peripheral edge of the negative electrode layer 2 can be suppressed. .

  Here, it is not preferable that the boundary line is too much inside the contour line of the negative electrode layer 2 because most of the solid electrolyte layer 3 has low Li ion conductivity. Therefore, the boundary line is provided within a range of 2 to 3 mm inside from the contour line. Alternatively, the boundary line is set so that the area of the inner region 3r occupies 40% or more of the area of the negative electrode layer 2 when the battery 100 is viewed in plan.

<Buffer layer>
The nonaqueous electrolyte battery 100 basically includes a positive electrode layer 1, a negative electrode layer 2, and a solid electrolyte layer 3, but a buffer layer 4 may be provided between the positive electrode layer 1 and the solid electrolyte layer 3. The buffer layer 4 is necessary when a sulfide is used for the solid electrolyte layer 3, and is for reducing the bias of Li ions in the vicinity of the interface between the positive electrode layer 1 and the solid electrolyte layer 3. When Li ions are biased at the interface, a depletion layer is formed due to the bias, and the discharge capacity of the battery 100 is reduced. Therefore, by providing the buffer layer 4 and relaxing the unevenness of Li ions at the interface by the buffer layer 4, it is possible to suppress a decrease in the discharge capacity of the battery 100 due to charge / discharge. For example, LiNbO ₃ or LiTaO ₃ can be used as the material of the buffer layer 4.

  The nonaqueous electrolyte battery 100 of the present invention shown in FIG. 1 was actually produced and its cycle characteristics were evaluated. Moreover, the nonaqueous electrolyte battery 200 shown in FIG. 2 was produced as a comparative example, and the cycle characteristics were similarly evaluated.

[Nonaqueous Electrolyte Battery of Example]
<Production procedure>
First, in manufacturing the battery 100, a SUS substrate having a diameter of 16 mm was prepared. This SUS substrate constitutes the positive electrode current collector 11 of the battery 100.

A positive electrode active material layer 12 made of LiCoO ₂ having an average thickness of 5 μm was formed on the prepared SUS substrate by using a PLD (Pulsed Laser Deposition) method. The average thickness is the average of three or more different measured values. This definition of the average thickness is the same in the following description.

A buffer layer 4 made of LiNbO _{3 having an} average thickness of 0.02 μm was formed on the positive electrode active material layer 12 by excimer laser ablation. As described above, the buffer layer 4 is for buffering the deviation of Li ions in the vicinity of the boundary between the positive electrode active material layer 12 and the sulfide-based solid electrolyte layer 3 (sulfide layer 32) described later. is there.

  Next, the solid electrolyte layer 3 was formed on the buffer layer 4. The solid electrolyte layer 3 includes a portion made of an oxide-based solid electrolyte (oxide layer 31) and a portion made of a sulfide-based solid electrolyte (sulfide layer 32). Such a solid electrolyte layer 3 was formed as follows.

First, a mask having a diameter of 8 mm is applied to the central portion of the buffer layer 4, and LiPON (Li ion conductivity: 1 × 10 ⁻⁶ S) having an average thickness of 1 μm is formed on the unmasked buffer layer 4 using a sputtering method. / Cm) of the oxide layer 31 was formed. The oxide layer 31 formed with the buffer layer 4 masked is formed in an annular shape having an inner diameter of 8 mm and an outer diameter of 16 mm.

Next, Li ₂ S—P ₂ S ₅ (Li ion conductivity) is formed on the oxide layer 31 and the buffer layer 4 exposed from the center of the ring of the electrolyte layer 31 by using the PLD method without masking. : 5 × 10 ⁻⁵ S / cm) was formed. The average thickness of the oxide layer 31 formed on the buffer layer 4 is 1 μm, the thickness of the sulfide layer 32 formed on the oxide layer 31 is 9 μm, and the oxide layer 31, the sulfide layer 32, The average thickness of the solid electrolyte layer 3 as a whole was 10 μm. Here, when the battery 100 is viewed in plan, the portion where the oxide layer 31 exists is the outer peripheral region 3t, and the other portion is the inner region 3r.

  When the formation of the solid electrolyte layer 3 is completed, the negative electrode layer 2 is then formed. First, a mask is applied on the solid electrolyte layer 3 so that the central portion of the solid electrolyte layer 3 is exposed with a diameter of 12 mm, and the exposed portion is made of metal Li having a thickness of 1 μm using a vacuum deposition method. A negative electrode layer 2 was formed. The negative electrode layer 2 also serves as a negative electrode current collector.

  Finally, the laminate after the formation of the negative electrode layer 2 was sealed in an aluminum laminate pack, and tab leads were drawn from the positive electrode current collector 11 and the negative electrode layer 2 (also serving as a current collector) to complete the battery 100.

<Charge / discharge test and results>
The battery completed as described above was charged up to 4.2 V at a constant current of 0.05 mA and charged and discharged with one cycle of the operation of discharging to 3 V for 100 cycles, and the discharge capacity at the 100th cycle was measured. . Then, the measured discharge capacity at the 100th cycle was divided by the discharge capacity at the 1st cycle and multiplied by 100 to obtain the capacity retention rate (%). It can be said that the higher the capacity retention rate is, the non-aqueous electrolyte battery that can maintain the initial discharge capacity at which charging / discharging starts, that is, the battery with excellent cycle characteristics.

  As a result of conducting the charge / discharge test under the above conditions on 10 samples having the configuration of the example, the average capacity retention rate of these samples was 91%.

[Nonaqueous electrolyte battery of comparative example]
<Production procedure>
Next, a non-aqueous electrolyte battery 200 having a configuration as shown in FIG. 2 was produced as a comparative battery. This battery 200 is different from the battery of the embodiment (battery 100 of FIG. 1) in the following points.

  First, as in the example, when the buffer layer 4 is formed on the positive electrode layer 1 and the solid electrolyte layer 3 is formed on the buffer layer 4, the average thickness is not applied to the buffer layer 4 without applying a mask. A solid electrolyte layer 3 made of sulfide having a thickness of 10 μm was formed. That is, the solid electrolyte layer 3 in the battery 200 of the comparative example has a configuration having uniform Li ion conductivity. Thereafter, the negative electrode layer 2 was formed and packaged in the same manner as in Example, and the battery 200 was completed.

<Charge / discharge test and results>
As a result of conducting the same charge / discharge test as that of the ten samples having the configuration of the comparative example described above, the average capacity retention rate of these samples was 48%.

[Summary]
As described above, it has been clarified that the nonaqueous electrolyte battery 100 of the example is superior in capacity retention rate than the nonaqueous electrolyte battery 200 of the comparative example.

  Note that the embodiment of the present invention is not limited to the above-described embodiment, and can be appropriately modified and implemented without departing from the gist of the present invention. For example, in the nonaqueous electrolyte battery 100 of FIG. 1, the boundary line between the outer peripheral region 3t and the inner region 3r may coincide with the contour line of the outer peripheral edge when the negative electrode layer 2 is viewed in plan view. It may overlap with a part of the contour line. In addition, the inner region 3r may be divided into a plurality of regions in the thickness direction.

  Since the nonaqueous electrolyte battery of the present invention is excellent in cycle characteristics, it can be suitably used as a power source for portable devices such as mobile phones and mobile personal computers.

DESCRIPTION OF SYMBOLS 100,200 Nonaqueous electrolyte battery 1 Positive electrode layer 11 Positive electrode collector 12 Positive electrode active material layer 2 Negative electrode layer 3 Solid electrolyte layer 3t Outer peripheral region 3r Inner region 31 Oxide layer 32 Sulfide layer 4 Buffer layer

Claims (7)

A non-aqueous electrolyte battery comprising a positive electrode layer, a negative electrode layer, and a solid electrolyte layer disposed between these electrode layers,
The solid electrolyte layer is
An outer peripheral region including the outer peripheral edge, and an inner region surrounded by the outer peripheral region,
The non-aqueous electrolyte battery characterized in that the Li ion conductivity in the outer peripheral region is lower than the Li ion conductivity in the inner region.   The boundary line between the outer peripheral region and the inner region is located inside a contour line formed at the outer peripheral edge portion of the negative electrode layer when the nonaqueous electrolyte battery is viewed in plan. Non-aqueous electrolyte battery.   The non-aqueous electrolyte battery according to claim 1, wherein the outer peripheral region further includes a plurality of regions having different Li ion conductivity in the thickness direction.   4. The nonaqueous electrolyte according to claim 3, wherein a Li ion conductivity of a region located closest to the positive electrode layer among regions constituting the outer peripheral region is lower than a Li ion conductivity of another region. 5. battery. The outer peripheral region contains an oxide as a Li ion conductive material,
The non-aqueous electrolyte battery according to claim 1, wherein the inner region contains a sulfide as a Li ion conductive material. The oxide is LiPON;
The non-aqueous electrolyte battery according to claim 5, wherein the sulfide is Li ₂ S—P ₂ S ₅ .   The nonaqueous electrolyte battery according to claim 5, further comprising a buffer layer that buffers a deviation of Li ions between the solid electrolyte layer and the positive electrode layer.

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