WO2013141241A1 - Solid-state electrolyte layer, and all-solid-state lithium secondary battery - Google Patents

Description

Solid electrolyte layer and all-solid lithium secondary battery

The present invention relates to a solid electrolyte layer and an all solid lithium secondary battery. More specifically, the present invention relates to a solid electrolyte layer capable of extending the cycle life of an all-solid lithium secondary battery, and an all-solid lithium secondary battery including the solid electrolyte layer.

Lithium secondary batteries have high voltage and high capacity, and are therefore widely used as power sources for mobile phones, digital cameras, video cameras, notebook computers, electric vehicles and the like. Generally, lithium secondary batteries in circulation use a liquid electrolyte in which an electrolytic salt is dissolved in a non-aqueous solvent as an electrolyte. Since non-aqueous solvents contain a lot of flammable solvents, it is desired to ensure safety.
In order to ensure safety, an all-solid lithium secondary battery using a so-called solid electrolyte material in which an electrolyte is formed from a solid material without using a non-aqueous solvent has been proposed (for example, Japanese Patent Laid-Open No. 2009-2009). No. 81140: Patent Document 1).
Patent Document 1 proposes an all-solid lithium secondary battery that uses lanthanum lithium titanate as a solid electrolyte layer and an active material selected from lithium titanate, iron sulfide, titanium sulfide, and tungsten oxide as a negative electrode. Yes.
In K. Iwamoto, N. Aotani, K. Takada, S. Kondo, Solid State Ionics, 70/71 (1994) 658 (Non-Patent Document 1), Li ₂ S—SiS ₂ —Li ₃ is used as the solid electrolyte layer. An all-solid lithium secondary battery using PO ₄ and using a Li metal layer as a negative electrode has been proposed.
Further, in Japanese Patent Application Laid-Open No. 2009-218124 (Patent Document 2), an all solid lithium secondary battery using Li ₂ SP—S ₂ S ₅ as a solid electrolyte layer and using a Li layer formed by vapor deposition as a negative electrode. Has been proposed.

K. Iwamoto, N. Aotani, K. Takada, S. Kondo, Solid State Ionics, 70/71 (1994) 658

JP 2009-81140 A JP 2009-218124 A

In the field of lithium ion secondary batteries using a liquid electrolyte layer, the Li metal layer has the maximum energy density as a negative electrode, and thus its practical use has been desired in the past. However, when a Li metal layer is used for the negative electrode, a problem that the cycle life is shortened due to a short circuit between the negative electrode and the positive electrode due to the generation of dendrites (dendritic crystals) has been reported and has not yet been put into practical use. .
On the other hand, in the field of all-solid lithium secondary batteries, it has been proposed in Non-Patent Document 1 to use a Li metal layer for the negative electrode, but dissolution of Li between the negative electrode and the solid electrolyte layer is proposed. In addition, no report examples of the results of examination on the behavior during precipitation were found to the extent that the inventors could know.
Further, in Patent Document 2, it is proposed to use a Li layer formed by vapor deposition for the negative electrode. However, in order to use the Li metal layer for the negative electrode, there is no consideration about improving the surface state of the solid electrolyte layer. It has not been.

The inventors of the present invention confirmed the above behavior. As a result, although there is no clear evidence of resin-like crystal precipitation that can short-circuit the negative electrode and the positive electrode in a lithium ion secondary battery, we confirmed a decrease in the resistance of the solid electrolyte layer that suspects that some short-circuiting phenomenon has occurred did. Therefore, the inventors have intensively studied to find out that the occurrence of a short-circuit phenomenon can be reduced by devising the configuration of the solid electrolyte layer, thereby providing an all-solid secondary battery having a long cycle life. Arrived.

Thus, according to the present invention, a solid electrolyte layer for an all-solid lithium secondary battery interposed between the negative electrode and the positive electrode,
The solid electrolyte layer is
(1) a content layer of a solid electrolyte material;
(2) A solid electrolyte layer for an all-solid lithium secondary battery, comprising a metal layer selected from a metal that can be alloyed with Li and Li, formed by a vapor phase method, at least on the negative electrode side of the containing layer Is provided.

Moreover, according to the present invention, the solid electrolyte layer for an all solid lithium secondary battery interposed between the negative electrode and the positive electrode,
The solid electrolyte layer is
(1) Li ₂ S—M _x S _y (M is selected from P, Si, Ge, B, Al, Ga, and x and y are numbers giving a stoichiometric ratio depending on the type of M) A solid electrolyte material containing layer represented by:
(2) A solid electrolyte layer for an all-solid lithium secondary battery, comprising a metal layer selected from a metal that can be alloyed with Li and Li, formed by a vapor phase method, at least on the negative electrode side of the containing layer Is provided.
Furthermore, according to this invention, the all-solid-state lithium secondary battery provided with the positive electrode and the negative electrode, the positive electrode and the negative electrode, and the said solid electrolyte layer interposed between the positive electrode and the negative electrode is provided.

ADVANTAGE OF THE INVENTION According to this invention, the solid electrolyte layer which can extend the cycle life of an all-solid-state lithium secondary battery, and the all-solid-state lithium secondary battery provided with the solid electrolyte layer can be provided.
Further, when the metal layer is a Li layer, an In layer, or a Li—In alloy layer, a solid electrolyte layer that can further extend the cycle life can be provided.
Furthermore, when M _x S _y is P ₂ S ₅ , it is possible to provide a solid electrolyte layer capable of extending the cycle life.

Further, when Li ₂ S—M _x S _y contains Li ₂ S and M _x S _{y in a} ratio of 50:50 to 90:10 (molar ratio), a solid electrolyte capable of further extending the cycle life Can provide a layer.
Furthermore, when a negative electrode consists of a Li metal layer or a Li alloy layer, an all-solid lithium secondary battery having a high capacity and a long cycle life can be provided.

It is a graph which shows the relationship between the constant current application time of Li symmetrical cell of Example 1, and cell potential (vs. Li). It is a graph which shows the relationship between the constant current application time of Li symmetrical cell of the comparative example 1, and cell potential (vs. Li). 3 is a schematic cross-sectional view of an all solid lithium secondary battery of Example 2. FIG. 6 is a graph showing the relationship between the capacity of the all solid lithium secondary battery of Example 2 and the cell potential. 3 is a schematic cross-sectional view of an all-solid lithium secondary battery of Example 3. FIG. 10 is a graph showing the relationship between the capacity of the all solid lithium secondary battery of Example 3 and the cell potential.

It is a graph which shows the relationship between the capacity | capacitance of the all-solid-state lithium secondary battery of Example 3, and the number of charging / discharging cycles. It is a graph which shows the relationship between the capacity | capacitance and cell potential of the all-solid-state lithium secondary battery of Example 3 and Comparative Example 2. 10 is a graph showing the relationship between the capacity of the all solid lithium secondary battery of Comparative Example 3 and the cell potential. 4 is an electron micrograph of the surface of the In layer of the solid electrolyte layer in the all solid lithium secondary battery of Example 4 before charging and discharging. 4 is an electron micrograph after charging / discharging of the surface of the In layer of the solid electrolyte layer in the all-solid lithium secondary battery of Example 4. FIG.

The all solid lithium secondary battery of the present invention includes a negative electrode and a positive electrode, and a solid electrolyte layer interposed between the negative electrode and the positive electrode.
(Solid electrolyte layer)
The solid electrolyte layer is
(1) For example, Li ₂ S—M _x S _y (M is selected from P, Si, Ge, B, Al, Ga, and x and y are numbers giving a stoichiometric ratio depending on the type of M. A solid electrolyte material containing layer represented by
(2) A metal layer selected from metals that can be alloyed with Li and Li, formed by a vapor phase method, is provided on at least the negative electrode side of the containing layer.

(A) Solid electrolyte material Any solid electrolyte material can be used as long as it can be used for an all-solid lithium secondary battery. In addition to the above _{Li 2 S-M x S y} , for _{example, Li 3 PO 4, LiPO 4} -x N x (0 <x ≦ 1), Li x La y TiO 3 (0 <x <1,0 <y < 1) etc. are mentioned. The solid electrolyte material is preferably Li ₂ S—M _x S _y described below.
(I) M _x S _y
In M _x S _y that is a sulfide, M is selected from P, Si, Ge, B, Al, and Ga, and x and y are numbers that give a stoichiometric ratio depending on the type of M. The six elements that can be used as M can have various valences, and x and y can be set according to the valences. For example, P can be trivalent and pentavalent, Si can be tetravalent, Ge can be divalent and tetravalent, B can be trivalent, Al can be trivalent, and Ga can be trivalent. Specific examples of M _x S _y include P ₂ S ₅ , SiS ₂ , GeS ₂ , B ₂ S ₃ , Al ₂ S ₃ , Ga ₂ S _{3 and the} like. These specific M _x S _y may be used alone or in combination of two or more. Of these, P ₂ S ₅ is particularly preferred.

(Ii) Mixing ratio of Li ₂ S—M _x S _y The mixing ratio of the two components is not particularly limited as long as it can be used as a solid electrolyte material.
The ratio of Li ₂ S to M _x S _y is preferably a ratio of 50:50 to 90:10 (molar ratio). If the Li ₂ S ratio is less than 50 or greater than 90, the conductivity may be low. A preferred ratio is 60:40 to 80:20, and a more preferred ratio is 70:30 to 80:20.

(Iii) Other components The solid electrolyte material may contain other components used in the all-solid lithium secondary battery in addition to Li ₂ S and M _x S _y . For example, electrolytes such as LiI and Li ₃ PO ₄ , active materials such as LiCoO ₂ and LiMn ₂ O ₄ , oxides of Fe, Zn and Bi, polyvinylidene fluoride, polytetrafluoroethylene, polyvinyl acetate, polymethyl methacrylate, A binder such as polyethylene may be used.
The active material may be provided with a film of a metal sulfide selected from Ni, Mn, Fe, and Co on the surface. Examples of the method for forming a film on the active material include a method in which the active material is immersed in a film precursor solution and then heat-treated, a method in which the film precursor solution is sprayed on the active material, and then heat-treated. It is done.

Method for manufacturing method the solid electrolyte material of (b) a solid electrolyte material, if Li ₂ S and M _x S _y and mixing possible ways other components as necessary is not particularly limited. In particular, it is preferable to manufacture by mechanical milling from the viewpoint of mixing the components more uniformly.
The mechanical milling process is not particularly limited to a processing apparatus and processing conditions as long as each component can be mixed uniformly.
As a processing apparatus, a ball mill can be used normally. A ball mill is preferable because large mechanical energy can be obtained. Among the ball mills, the planetary ball mill is preferable because the pot rotates and the platform rotates in the direction opposite to the direction of rotation, so that high impact energy can be efficiently generated.

Processing conditions can be set as appropriate according to the processing apparatus to be used. For example, when using a ball mill, the higher the rotational speed and / or the longer the processing time, the more uniformly the raw material mixture can be mixed. Note that “and / or” means A, B, or A and B when expressed as A and / or B. Specifically, when a planetary ball mill is used, the conditions are 50 to 600 revolutions / minute, treatment time of 0.1 to 20 hours, 1 to 100 kWh / kg of raw material mixture. More preferable processing conditions include a rotational speed of 200 to 500 rotations / minute, a processing time of 1 to 10 hours, and 6 to 50 kWh / kg of a raw material mixture.

(C) Content Layer of Solid Electrolyte Material The content layer of the solid electrolyte material can be obtained, for example, by pressing the solid electrolyte material so as to have a predetermined thickness. The thickness of the containing layer can be set to, for example, 0.1 to 1 mm.

(D) Metal layer A metal layer consists of a metal layer selected from the metal which can be alloyed with Li and Li. Examples of metals that can be alloyed with Li include In, Al, Sn, and Si. The metal layer that can be alloyed with Li may be an alloy layer with Li (for example, a Li—In alloy layer).
The metal layer is formed on at least the negative electrode side of the containing layer. The metal layer may cover a part of the negative electrode, but it is preferable to cover the entire surface from the viewpoint of further extending the cycle life. The metal layer may be formed on the positive electrode side of the containing layer.

The metal layer is formed by a vapor phase method. By forming it by a vapor phase method, it can be densely formed on the surface of the solid electrolyte material containing layer with good adhesion. As a result, the generation of dendritic crystals caused by dissolution and precipitation of Li during charge / discharge can be suppressed, so that the cycle life can be extended. Moreover, it is preferable that the metal layer is formed so that the unevenness on the surface of the metal layer is smaller than the unevenness on the surface of the containing layer. By forming in this way, the adhesion between the solid electrolyte layer and the negative electrode can be improved, and as a result, an all-solid lithium secondary battery having a long cycle life can be provided.
Examples of the vapor phase method include a vapor deposition method, a CVD method, and a sputtering method. Among these, the vapor deposition method is simple.
The thickness of the metal layer is not particularly limited as long as the reversibility of Li dissolution and precipitation can be improved. For example, the thickness can be 0.1 to 100 μm. A more preferred thickness is 0.3 to 10 μm.

(All-solid lithium secondary battery)
The all solid lithium secondary battery includes a positive electrode and a negative electrode, and a solid electrolyte layer interposed between the positive electrode and the negative electrode. The solid electrolyte layer includes a solid electrolyte material-containing layer and a metal layer. The all-solid lithium secondary battery can be obtained, for example, by laminating a positive electrode, a solid electrolyte layer, and a negative electrode and pressing them.
(A) Negative electrode A negative electrode is not specifically limited, Any negative electrode normally used for an all-solid-state lithium secondary battery can be used. In particular, the negative electrode is preferably made of a Li metal layer or a Li alloy layer (for example, a Li—In alloy, a Li—Sn alloy, a Li—Si alloy, a Li—Al alloy, etc.) from the viewpoint of increasing the energy density. The Li metal layer or the Li alloy layer is preferably a foil-like layer from the viewpoint of ease of production.

Moreover, you may use the negative electrode obtained by pressing a granular negative electrode active material other than the said Li metal layer or Li alloy layer. The negative electrode obtained by this pressing may contain a binder, a conductive agent, an electrolyte, and the like as necessary.
Examples of the granular negative electrode active material include metals such as Li, In, and Sn, alloys thereof, various transition metal oxides such as graphite and SnO, and the like.
Examples of the binder include polyvinylidene fluoride, polytetrafluoroethylene, polyvinyl acetate, polymethyl methacrylate, and polyethylene.
Examples of the conductive agent include natural graphite, artificial graphite, acetylene black, and vapor grown carbon fiber (VGCF).
Examples of the electrolyte include the above solid electrolyte materials. By including the solid electrolyte material in the negative electrode, electrons and ions can be exchanged more smoothly between the negative electrode and the solid electrolyte layer.
The negative electrode may include a current collector such as SUS (stainless steel), aluminum, or copper.

(2) Positive electrode A positive electrode is not specifically limited, Any positive electrode normally used for an all-solid-state lithium secondary battery can be used. The positive electrode may be composed only of the positive electrode active material, and may be mixed with a binder, a conductive agent, an electrolyte, and the like.
As the positive electrode active material, Li ₄ Ti ₅ O ₁₂ , LiCoO ₂ , LiMnO ₂ , LiVO ₂ , LiCrO ₂ , LiNiO ₂ , Li ₂ NiMn ₃ O ₈ , LiNi _1/3 Co _1/3 Mn _1/3 O ₂ , S, Li ₂ S, and the like.
Examples of the binder include polyvinylidene fluoride, polytetrafluoroethylene, polyvinyl acetate, polymethyl methacrylate, and polyethylene.
Examples of the conductive agent include natural graphite, artificial graphite, acetylene black, and vapor grown carbon fiber (VGCF).
Examples of the electrolyte include the above solid electrolyte materials. By including the solid electrolyte material also in the positive electrode, electrons and ions can be exchanged more smoothly between the positive electrode and the solid electrolyte layer.

The positive electrode can be obtained as a pellet by, for example, mixing a positive electrode active material and optionally a binder, a conductive agent, an electrolyte, and the like, and pressing the obtained mixture. Moreover, when using the metal sheet (foil) which consists of a metal or its alloy as a positive electrode active material, it can be used as it is.
The positive electrode may be formed on a current collector such as SUS, aluminum, or copper.

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples.
Example 1
Li ₂ S (purity 99.9%, manufactured by Idemitsu Kosan Co., Ltd.) and P ₂ S ₅ (purity 99%, manufactured by Aldrich) were charged into a planetary ball mill at a molar ratio of 80:20. After the addition, a solid electrolyte material (80Li ₂ S · 20P ₂ S ₅ ) having a particle size of 5 μm was obtained by mechanical milling. As the planetary ball mill, Pulverisette P-7 manufactured by Fritsch was used, and the pot and balls were made of zirconium oxide, and a mill containing 500 balls of 4 mm in diameter in a 45 ml pot was used. The mechanical milling process was performed for 20 hours in a dry nitrogen glove box at a rotation speed of 510 rpm, room temperature. This synthesis method is described in Akitoshi Hayashi et al. , Electrochemistry Communications 5 (2003) 111-114.

Next, the solid electrolyte material weighed 100 mg was pressed at a pressure of 370 MPa using a pellet molding machine having a molding part having an area of 0.785 cm ² , thereby containing a pellet-shaped solid electrolyte material containing layer (thickness of about 1 mm). )
Li layers (thickness: about 1 μm) were formed on the upper and lower surfaces of the containing layer using a vacuum deposition apparatus (VPC-060 manufactured by ULVAC) in which the obtained containing layer was placed in a glove box in an argon atmosphere. The formation conditions were such that a Li foil was put in a boat made of tungsten and the current was 50 mA and the deposition time was 60 seconds under a reduced pressure of 4 × 10 ⁻² Pa.
Through the above steps, a solid electrolyte layer having a structure of Li layer / containing layer / Li layer was obtained.

The Li solid cell was obtained by sandwiching the obtained solid electrolyte layer with Li foil, and this cell was subjected to galvanostatic measurement at a constant current of 0.05 mA. In order to confirm the behavior of the solid electrolyte layer due to repeated charge and discharge, the direction of the current applied to the cell was reversed every 10600 seconds. The measurement results are shown in FIG. FIG. 1 shows the relationship between the constant current application time and the cell potential (vs. Li).

Comparative Example 1
A Li symmetric cell was obtained in the same manner as in Example 1 except that the Li layer was not provided. The obtained cell was subjected to galvanostatic measurement in the same manner as in Example 1. The measurement results are shown in FIG.
1 and 2, the potential of the solid electrolyte layer of Comparative Example 1 that does not include the Li layer is 0 V with only one reversal of the current direction. In contrast, it can be seen that the solid electrolyte layer of Example 1 can maintain a constant potential even after several reversals of the current direction. These results mean that the solid electrolyte layer which can endure repeated charging / discharging is obtained by providing Li layer.

Example 2
A solid electrolyte layer was obtained by forming a Li layer on one side of the solid electrolyte material containing layer obtained in the same manner as in Example 1 in the same manner as in Example 1.
Raw materials comprising sulfur, acetylene black and the same solid electrolyte material as in Example 1 were weighed so as to have a weight ratio of 1: 1: 2, and charged into a planetary ball mill. As the planetary ball mill, Pulverisete P-7 manufactured by Fritsch was used, and the pot and balls were made of zirconium oxide, and a mill containing 160 balls having a diameter of 5 mm in a 45 ml pot was used. The sulfur used was Aldrich's sulfur (99.998%), having an average particle size of 50 μm, and the acetylene black used was Denka Black, manufactured by Denki Kagaku Kogyo, having an average particle size of 35 nm. Was.
The raw material mixture was mechanically milled by a planetary ball mill to obtain a composite. The processing conditions were 370 revolutions / minute, 5 hours, and about 50 kWh / raw material mixture 1 kg.

The composite powder 10 mg after treatment and 80 mg of the solid electrolyte powder were stacked and pressed (pressure 370 MPa) to obtain a two-layer pellet (positive electrode / solid electrolyte containing layer) having a diameter of 10 mm and a thickness of about 0.7 mm. A Li layer was formed in the same manner as in Example 1 on the surface on the solid electrolyte-containing layer side.
As the negative electrode, a 0.25 mm thick Li foil was used.
The positive electrode / solid electrolyte-containing layer and the negative electrode are laminated so that the Li layer is on the negative electrode side, the laminate is sandwiched between SUS plates, and pressed (pressure 120 MPa) to provide an all-solid lithium secondary battery (cell). Got. A schematic cross-sectional view of the obtained secondary battery is shown in FIG. In FIG. 3, 1 is a SUS plate (current collector), 2 is a Li foil (negative electrode), 3 is a Li layer (deposition layer), 4 is a solid electrolyte layer, 5 is a positive electrode, 6 is a solid electrolyte material, and 7 is a positive electrode. Means active material.

The resulting secondary battery, performed under 25 ° C., subjected to 1-2 charge and discharge at a current density of 0.013mA / cm ^2, then 3-20 times of charge and discharge at a current density of 0.064mA / cm ² FIG. 4 shows the relationship between the capacitance and the cell potential in the case of the above.
FIG. 4 shows that the obtained secondary battery has a capacity of about 1000 mAhg ⁻¹ even after 20 charge / discharge cycles, and is a secondary battery with a long cycle life.

Example 3
Using the solid electrolyte material obtained in the same manner as in Example 1, a solid electrolyte layer and a positive electrode were produced as follows.
The solid electrolyte layer was obtained as follows.
The solid electrolyte material weighed 100 mg was pressed at a pressure of 370 MPa using a pellet molding machine having a molded part having an area of 0.785 cm ² to obtain a pellet-shaped solid electrolyte material containing layer (thickness of about 1 mm). It was.
A solid electrolyte was formed by forming an In layer (thickness: about 500 nm) on one side of the containing layer using a vacuum deposition apparatus (VPC-060 manufactured by ULVAC) in which the obtained containing layer was placed in a glove box in an argon atmosphere. A layer was obtained. The formation conditions were such that an In foil was put in a boat made of tungsten, the current was 50 mA, and the deposition time was 60 seconds under a reduced pressure of 4 × 10 ⁻² Pa.

The positive electrode was obtained as follows.
Li ₄ Ti ₅ O ₁₂ , acetylene black, and raw materials made of the same solid electrolyte material as in Example 1 were weighed to a weight ratio of 40:10:60 and mixed in a mortar. The Li ₄ Ti ₅ O ₁₂ used was obtained by crushing particles having an average particle size of about 5 μm manufactured by Titanium Industry Co., Ltd. using a planetary ball mill. As the planetary ball mill, Pulverisete P-7 manufactured by Fritsch is used, and the pot and balls are made of zirconium oxide. 50 balls of 4 mm in diameter are placed in a 45 ml pot and pulverized for 2 hours at a rotation speed of 200 rpm. went. The acetylene black used is the same as in Example 1.
10 mg of the composite after the treatment and 80 mg of the solid electrolyte powder were stacked and pressed (pressure 370 MPa) to obtain a two-layer pellet (positive electrode / solid electrolyte containing layer) having a diameter of 10 mm and a thickness of about 0.7 mm.

An all-solid lithium secondary battery (cell) was obtained in the same manner as in Example 1 except that the solid electrolyte layer and the positive electrode were used. A schematic cross-sectional view of the obtained secondary battery is shown in FIG. In FIG. 5, 1, 2, 4, 5, 6 and 7 are the same as those in FIG. 3, and 3a represents an In layer (deposition layer).
The obtained secondary battery was charged and discharged 1 to 5 times at a current of 0.05 mA at 25 ° C., charged and discharged 6 to 40 times at a current of 0.1 mA, and 41 to 4 at a current of 0.2 mA. FIG. 6 shows the relationship between the capacity and the cell potential when charging and discharging are performed 60 times.
FIG. 6 shows that the obtained secondary battery has a capacity of about 50 mAhg ⁻¹ even at 0.2 mA, and is a secondary battery with a long cycle life.

When the obtained secondary battery was charged and discharged 20 times each at a current of 0.05 mA, 0.1 mA, 0.2 mA, 0.3 mA, 0.4 mA, and 0.5 mA at 25 ° C. FIG. 7 shows the relationship between the capacity and the number of charge / discharge cycles. 0.05 mA corresponds to 0.13 mA / cm ² in terms of current density.
From FIG. 7, the obtained secondary battery can be charged and discharged 120 times, and a capacity of about 20 mAhg ⁻¹ or more was obtained even under a high current density of 0.5 mA (1.3 mA / cm ² ). It can be seen that this battery is relatively excellent in rate characteristics.

Comparative Example 2
An all-solid lithium secondary battery was obtained in the same manner as in Example 3 except that the In layer was formed on the Li foil and the In layer was not formed on the solid electrolyte material-containing layer. The In layer was formed under the following conditions.
A negative electrode was obtained by forming an In layer (thickness: about 500 nm) on one side of a Li foil using a vacuum deposition apparatus (VPC-060 manufactured by ULVAC) in which a Li foil was placed in a glove box in an argon atmosphere. The formation conditions were such that an In foil was put in a boat made of tungsten, the current was 50 mA, and the deposition time was 60 seconds under a reduced pressure of 4 × 10 ⁻² Pa.
An all-solid lithium secondary battery (cell) was obtained in the same manner as in Example 1 except that the solid electrolyte layer and the positive electrode were used.

The obtained secondary battery was charged and discharged 10 times at 25 mA at a current of 0.05 mA. FIG. 8 shows the relationship between the capacity and the cell potential in the 10th charge / discharge. FIG. 8 also shows the relationship between the capacity and the cell potential in the 10th charge / discharge of the all-solid lithium secondary battery of Example 3.
From FIG. 8, the secondary battery having the solid electrolyte layer having the In layer on the containing layer of the solid electrolyte material has a larger capacity than the secondary battery having the negative electrode having the In layer on the Li foil. You can see that This result is considered to indicate that the amount of Li contributing to the charge / discharge reaction can be increased by providing the In layer on the solid electrolyte side by increasing the adhesion between the Li foil and the solid electrolyte layer.

Comparative Example 3
FIG. 9 shows the relationship between the capacity and the cell potential in the first charge / discharge of the all-solid lithium secondary battery obtained in the same manner as in Example 3 except that the In layer is not provided. In FIG. 9, it can be seen that a potential disturbance considered to be a short-circuit phenomenon occurs in the region A. On the other hand, in Example 3 and Comparative Example 2 in FIG. 8, such a disturbance is not seen even after 10 times of charge and discharge, so that the short-circuit phenomenon can be remarkably suppressed by providing the In layer. It is thought that there is.

Example 4
10 and 11 show electron micrographs before and after charging and discharging on the surface of the In layer of the solid electrolyte layer in Example 3. FIG. The photo after charging / discharging is after 120 times charging / discharging.
From these figures, it can be seen that a concavo-convex structure is not newly formed or a crack is not formed on the surface shape before and after charging and discharging. This result means that the ability of the solid electrolyte layer provided with the In layer to prevent a short circuit phenomenon is high.

1: SUS plate, 2: Li foil, 3: Li layer, 3a: In layer, 4: solid electrolyte layer, 5: positive electrode, 6: solid electrolyte material, 7: positive electrode active material

Claims (7)

A solid electrolyte layer for an all-solid lithium secondary battery interposed between the negative electrode and the positive electrode,
The solid electrolyte layer is
(1) a content layer of a solid electrolyte material;
(2) A solid electrolyte layer for an all-solid lithium secondary battery, comprising a metal layer selected from a metal that can be alloyed with Li and Li, formed by a vapor phase method, at least on the negative electrode side of the containing layer . A solid electrolyte layer for an all-solid lithium secondary battery interposed between the negative electrode and the positive electrode,
The solid electrolyte layer is
(1) Li ₂ S—M _x S _y (M is selected from P, Si, Ge, B, Al, Ga, and x and y are numbers giving a stoichiometric ratio depending on the type of M) A solid electrolyte material containing layer represented by:
(2) The all-solid lithium secondary according to claim 1, further comprising a metal layer selected from a metal that can be alloyed with Li and Li formed by a vapor phase method on at least the negative electrode side of the containing layer. Solid electrolyte layer for batteries. The solid electrolyte layer for an all-solid lithium secondary battery according to claim 1, wherein the metal layer is a Li layer, an In layer, or a Li-In alloy layer. The solid electrolyte layer for an all-solid lithium secondary battery according to claim ₂ , wherein the M _x S _y is P ₂ S ₅ . The all-solid-state lithium secondary battery according to claim 2, wherein the Li ₂ S-M _x S _y contains Li ₂ S and M _x S _{y in a} ratio of 50:50 to 90:10 (molar ratio). Solid electrolyte layer. An all-solid lithium secondary battery comprising: a positive electrode and a negative electrode; and the solid electrolyte layer according to claim 1 interposed between the positive electrode and the negative electrode. The all-solid-state lithium secondary battery according to claim 6, wherein the negative electrode is made of a Li metal layer or a Li alloy layer.

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