JP2003303589A - Negative electrode for lithium secondary battery, lithium secondary battery using the same, and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the generation of a gap at an interface between a solid electrolyte and an electrode caused by the movement of ion at the inside of the electrolyte, and to cope with the mechanical deformation in a state of keeping the electric bonding of the electrolyte and the electrode. <P>SOLUTION: This invention is made to improve a negative electrode for a lithium secondary battery mounted in a state of being kept into contact with the lithium ion conductive solid electrolyte 13. The negative electrode is composed of a negative electrode collector 21, and a Cs-Rb alloy 26 including metallic lithium 16 and mounted at a solid electrolyte 13 side of the negative electrode collector 21, and a weight ratio of metallic lithium 16 included in the Cs-Rb alloy 26, to the Cs-Rb alloy 26 is Li:Cs-Rb=5:1 through 1:8. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a negative electrode for a lithium secondary battery formed in contact with a lithium ion conductive solid electrolyte, a lithium secondary battery using this negative electrode, and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, as an electrolyte of a lithium secondary battery, an electrolytic solution in which a lithium salt is dissolved in an organic solvent has been used. A battery using this electrolytic solution has characteristics of high ionic conductivity and large battery capacity because the electrolytic solution as a constituent material is composed of an organic electrolytic solution. However, since the organic electrolytic solution is flammable, ensuring safety is a major issue as the voltage becomes higher. With respect to these problems, a solid-state battery using a non-flammable solid electrolyte instead of a flammable organic electrolyte is attracting attention because it leads to the development of a highly reliable battery. As the solid electrolyte, one using an inorganic material or a polymer material has been developed, and is used in a crystalline or amorphous state in order to exert its characteristics. Thinning is possible by stacking solid electrolytes by methods such as coating, so thin and lightweight miniaturization of various electronic application devices such as video recording devices, notebook personal computers and portable information terminal devices such as mobile phones. Can meet the demands of

It is the principle of battery function that the redox reaction of ions and electrons conducting through the electrolyte at the interface between the electrode and the electrolyte continues stably, and the reaction involves mass transfer of ions. Then, as a result of the reaction, movement of the interface occurs. In a lithium secondary battery that used an electrolyte solution as the electrolyte, the change in the electrode volume could be compensated for by the flow of the electrolyte solution, so the electrolyte solution is always in contact with the electrode even if the interface between the electrode and the electrolyte moves. It was possible to
In a secondary battery using a solid electrolyte as an electrolyte, it is an important technical issue to keep the interface between the electrode and the electrolyte in contact with each other. If a gap is created at the interface between the electrode and the electrolyte, the electrochemical reaction will stop and the movement of ions will be hindered, so it will not be possible to maintain the prescribed performance, and it will not be possible to obtain the standard current amount during charging and discharging. This is a problem. In a conventional secondary battery using a solid electrolyte, the bonding interface keeps good electrochemical contact at the time of its manufacture, but the volume of the electrode is increased due to expansion / contraction caused by intercalation and deintercalation of ions. When the change occurs, there is a problem that strain is accumulated between the solid electrolyte and the electrode, which interrupts the ion transfer path and impairs the cycle charge / discharge characteristics.

In order to solve such a problem, peeling between the electrode and the solid electrolyte is suppressed, good adhesion at the interface is continuously maintained, and the oxidation-reduction reaction of conduction ions is stably continued. Methods are being researched and developed. A solid secondary battery has been disclosed in which blocking of an ion transfer path caused by a mismatch of strain due to expansion and contraction of a solid electrolyte and an active material is reduced as much as possible (Japanese Patent Laid-Open No. 2000-331684). In this publication, an active material made of a sintered body of an inorganic oxide having a volume change rate of 1.5% or less in a discharge terminated state with respect to a charge terminated state is used, and a bonding interface between the active material and the solid electrolyte is fired by hot pressing. The adhesiveness is increased and the blocking of the ion transfer path is reduced as much as possible. Also,
A solid electrolyte battery is disclosed in which a transition metal element contained in a positive electrode active material is diffused into a solid electrolyte on the positive electrode side, and a transition metal element contained in a negative electrode active material is diffused into a solid electrolyte on the negative electrode side (Japanese Patent Application Laid-Open No. 2000-242242). 2001-093535). In this technique, the transition metal element contained in the active material of the electrode is diffused into the solid electrolyte to strengthen the bond between the electrode and the solid electrolyte. Also disclosed is a method for producing an all-solid secondary battery in which a green formed body obtained by laminating a positive electrode material containing a binder, a solid electrolyte, and a negative electrode material is heated by microwaves and fired (JP-A-2001-210360). In this manufacturing method,
By irradiating microwaves for a short time to selectively dissolve the binder, a dense bonding interface with the particles can be formed.

Further, as a method of chemically assisting adhesion,
A battery in which a gel polymer solid electrolyte adhesive layer gelled with a monomer having a yield stress smaller than that of the solid electrolyte is interposed at the interface is disclosed (JP-A-200).
1-023695). In this battery, by interposing a gel-like polymer solid electrolyte adhesive layer having a yield stress smaller than that of the solid electrolyte at the interface, the volume change due to gelation of the gel-like solid electrolyte layer and the electrode during charge / discharge Since peeling between the electrode and the gelled polymer solid electrolyte layer due to the volume change of the battery is suppressed, the battery characteristics can be improved such that the discharge capacity can be increased. Furthermore, a gel electrolyte composition containing a specific cyclohexane derivative as a gelling agent on the surface of the electrolyte and a method of using the same have been disclosed (Japanese Patent Laid-Open No. 2000-030528). By stacking a layer of a gel electrolyte composition containing a specific cyclohexane derivative as a gelling agent on the surface of the solid electrolyte thin film, it can be brought into good contact with the electrode surface.

[0006]

However, since the solid electrolyte and the electrode material are designed so as to maximize the transport characteristics of ions and electrons, as in the techniques disclosed in the above-mentioned publications, When the composition near the interface is continuously changed by reaction or surface modification to improve the mechanical adhesion, it is inevitable that the composition near the interface will be different from the composition of the electrolyte or electrode material. The change in the composition near the interface has a problem of limiting the function of the entire battery. The object of the present invention is to prevent the occurrence of a gap at the interface between the solid electrolyte and the electrode due to the movement of ions inside the electrolyte, and to prevent mechanical deformation while maintaining electrical contact between the electrolyte and the electrode. An object of the present invention is to provide a corresponding negative electrode for a lithium secondary battery, a lithium secondary battery using the same, and a method for manufacturing the same.

[0007]

The invention according to claim 1 is
As shown in FIG. 1, a lithium ion conductive solid electrolyte 1
3 is an improvement of the negative electrode 27 for a lithium secondary battery provided in contact with No. 3. Its characteristic configuration is constituted by a negative electrode current collector 21 and a Cs-Rb alloy 26 containing metallic lithium 16 provided on the solid electrolyte 13 side of the negative electrode current collector 21, and C
Metallic lithium 16 and Cs- contained in the s-Rb alloy 26
The weight ratio with the Rb alloy 26 is Li: Cs-Rb = 5: 1 to
It is at 1: 8. In the invention according to claim 1,
A negative electrode current collector 21 and a Cs-Rb alloy 26 provided on the solid electrolyte 13 side of the negative electrode current collector 21 and containing metallic lithium 16.
And constitute the negative electrode 27. The Cs-Rb alloy 26 used for the negative electrode 27 is characterized in that it is liquid at room temperature, has electrical conductivity, has a redox potential higher than that of lithium, and does not form a solid solution with metallic lithium. A liquid negative electrode 27 composed of a Cs-Rb alloy 26 which is liquid at room temperature and which contains metallic lithium 16 so as to cope with mechanical deformation while maintaining electrical connection between the electrolyte and the electrode.
Therefore, it is possible to solve the problem that a gap is generated at the interface between the solid electrolyte and the electrode due to the movement of the working ions inside the electrolyte, resulting in separation. In addition, even if metallic lithium is deposited on the negative electrode side interface of the solid electrolyte in the form of dendrite,
Unlike the conventional negative electrode, this liquid negative electrode is fluidized and deformed, so that electrical contact is maintained.

The invention according to claim 2 is the invention according to claim 1, which is a negative electrode for a lithium secondary battery in which the Cs-Rb alloy 26 comprises 30 to 80% by weight of Cs and 70 to 20% by weight of Rb. The invention according to claim 3 is, as shown in FIG. 1, a lithium secondary battery 28 including a positive electrode 12, a negative electrode 27, and a lithium ion conductive solid electrolyte 13 provided between the positive electrode 12 and the negative electrode 27. Is an improvement. The characteristic configuration is that the negative electrode 27 has the negative electrode current collector 21 and the negative electrode current collector 2
1 and the Cs-Rb alloy 26 that is provided on the solid electrolyte 13 side and that contains the metallic lithium 16, and the metallic lithium 16 and the Cs-Rb alloy 2 that are included in the Cs-Rb alloy 26.
The weight ratio with 6 is Li: Cs-Rb = 5: 1 to 1: 8. In the invention according to claim 3, when the conventional secondary battery is charged and discharged, a gap is formed at the interface between the solid electrolyte and the electrode to cause a peeling state, or a dendrite-like precipitate is generated at the interface. However, in the secondary battery 28 of the present invention, the lithium ion conductive solid electrolyte 13 is used as the electrolyte so that the electrolyte can be mechanically deformed while maintaining electrical contact between the electrolyte and the electrode.
The negative electrode current collector 21 and the negative electrode current collector 2 are used for the negative electrode 27.
1 and a Cs-Rb alloy 26 which is provided on the side of the solid electrolyte 13 and which contains metallic lithium 16 and is liquid at room temperature.
The secondary battery having such a structure can solve the problem of peeling at the interface between the negative electrode and the solid electrolyte.

In the invention according to claim 4, as shown in FIG. 2, a sheet or foil-shaped positive electrode current collector 11, a sheet or foil-shaped positive electrode 12, and a sheet-shaped lithium ion conductive solid electrolyte 13 are provided. The steps of stacking in order to form the positive electrode sheet material 14, and Li in an inert gas atmosphere at a temperature of 0 ° C. or less.
The weight ratio of metal 16, Rb metal 17, and Cs metal 18 is 10
A sheet of negative electrode current collector 21 is provided with a metal layer 19 in a ratio of 1: 1 to 4: 1 to 4 on one side thereof.
2 and the positive electrode sheet material 14 and the negative electrode sheet material 22 in an inert gas atmosphere at a temperature of 0 ° C. or less so that the positive electrode current collector 11 and the negative electrode current collector 21 are on the outside. A step of forming the laminated body 23 by stacking the layers, and FIG.
As shown in FIG. 5, the laminate 23 is formed by aluminum vapor deposition films 24 and 24 so that the positive electrode sheet-like portion 14a and the negative electrode sheet-like portion 22a are exposed in an inert gas atmosphere at a temperature of 0 ° C. or less. The step of encapsulating and vacuum-sealing, and as shown in FIG. 4, by placing the vacuum-sealed laminate 23 in an atmosphere at room temperature and alloying the Rb metal 17 and the Cs metal 18, the liquid negative electrode 27, a step of applying a voltage to the exposed positive electrode sheet-like portion 14a and the exposed negative electrode sheet-like portion 22a to carry out initial charging, respectively, as shown in FIG. And a step of consuming electric power from the exposed portion 14a of the positive electrode sheet-shaped portion and the exposed portion of the negative electrode sheet-shaped material 22a to perform an initial discharge. The invention according to claim 5 is the invention according to claim 4, wherein as shown in FIG. 2, a foil-shaped Li metal 16, a foil-shaped Rb metal 17, and a foil-shaped Cs metal 18 are laminated. This is a method for manufacturing a lithium secondary battery in which the metal layer 19 is formed. The invention according to claim 6 is the invention according to claim 4, wherein granular Li metal, granular Rb metal and granular Cs metal are dispersed in an organic solvent, and the organic solvent is a sheet-shaped negative electrode current collector. Is a method for producing a lithium secondary battery, in which a metal layer is formed by applying the organic solvent to the coated layer and removing the organic solvent from the coated layer.

The invention according to claim 7 relates to claims 4 to 6.
The invention according to any one of the aspects, wherein the one or both of the Cs metal and the Rb metal is a metal recovered from fly ash containing the metal. The invention according to claim 8 is the invention according to claim 7, wherein the fly ash is cement kiln ash, industrial waste melting furnace ash, or general waste incinerator ash.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described with reference to the drawings. As shown in FIG. 1, the lithium secondary battery negative electrode 27 of the present invention is provided in contact with the lithium ion conductive solid electrolyte 13. The characteristic configuration is that the negative electrode current collector 21 and the Cs-Rb alloy 26 that is provided on the solid electrolyte 13 side of the negative electrode current collector 21 and contains the metallic lithium 16 are included in the Cs-Rb alloy 26. The weight ratio of lithium 16 and Cs-Rb alloy 26 is Li: C.
The negative electrode has s-Rb of 5: 1 to 1: 8. Cs-R
The alloy b is a liquid at room temperature, has electrical conductivity, has a redox potential of about 0.1 V more than lithium, and is characterized by not forming a solid solution with metallic lithium. Suitable as an electrode for secondary batteries.
At the time of forming the secondary battery, a small amount of metallic lithium 16 is suspended in the Cs-Rb alloy 26. Since the liquid negative electrode 27 is made of a Cs-Rb alloy that contains metallic lithium and is liquid at room temperature so as to cope with mechanical deformation while maintaining electrical connection between the solid electrolyte and the electrode, movement of working ions inside the electrolyte is achieved. As a result, it is possible to solve the problem that a gap is created at the interface between the solid electrolyte and the electrode, and peeling occurs. Further, even if metallic lithium is deposited on the negative electrode side interface of the solid electrolyte in the form of dendrite, unlike the conventional negative electrode, the liquid negative electrode is flow-deformed, so that electrical connection is maintained.

The weight ratio of the metallic lithium 16 contained in the Cs-Rb alloy 26 to the Cs-Rb alloy 26 is Li: Cs-.
Rb = 5: 1 to 1: 8. The preferred weight ratio is Li:
Cs-Rb = 5: 1 to 1: 5. Metallic lithium 16
If the weight ratio of Cs-Rb alloy 26 to Cs-Rb alloy is less than 5: 1, it is not effective in suppressing delamination due to dendrite growth.
When the weight ratio exceeds 1: 8, the concentration of metallic lithium suspended in the Cs-Rb alloy decreases, and there is a problem that the overvoltage when discharging the battery increases. Cs-Rb alloy is Cs
It is an alloy composed of 30 to 80% by weight and Rb of 70 to 20% by weight. Cs 45-60 wt% and Rb 55-40 wt%
Alloys consisting of are preferred. 8 even if Cs is less than 30% by weight
Even if it exceeds 0% by weight, the Cs-Rb alloy does not liquefy at the operating temperature of the secondary battery, and delamination cannot be prevented.

A method for manufacturing the lithium secondary battery of the present invention will be described with reference to the drawings. First, as shown in FIG.
A sheet-shaped positive electrode current collector 11, a sheet-shaped positive electrode 12, and a sheet-shaped lithium ion conductive solid electrolyte 13 are laminated in this order to form a positive-electrode sheet-shaped material 14. An Al metal plate is used for the sheet-shaped positive electrode current collector 11. Examples of the sheet-shaped positive electrode 12 include a lithium cobalt-based composite oxide typified by LiCoO ₂ , a lithium nickel-based composite oxide typified by LiNiO ₂ , and a lithium manganese-based composite oxide typified by LiMn ₂ 0 ₄ . A known positive electrode active material is mixed with a conductive additive (acetylene black) and a polymer to form a paste, which is used. As the lithium ion conductive solid electrolyte 13, a crystalline or amorphous ion conductive substance made of an inorganic substance or an organic substance is used,
As the crystalline solid electrolyte, LiPO ₄ , LiZr ₂ (P
O ₄ ) ₃ , LiSiO ₄ , Li _0.5 La _0.5 TiO ₃ , Li
₃ (Ge, V) O ₄ , LiN ₃ and LISION type, β-Fe ₂
Examples thereof include (SO ₄ ) type compounds. Examples of the amorphous inorganic _{material, LiI-Li 2 0-P} 2 0 5, Li 2 S-SiS 2,
LiCl-Li ₂ O, and the like. Since the liquid electrode is formed on the negative electrode side of the lithium ion conductive solid electrolyte 13, the solid electrolyte 13 has a shape including a rectangular bottom plate 13a and a peripheral wall 13b formed around the bottom plate 13a in advance. The above shape is formed by sintering and forming, or by machining.

As shown in FIG. 1, the height D of the peripheral wall 13a of the solid electrolyte 13 is set in consideration of the volume expansion of the Cs-Rb alloy formed by liquefaction of the Cs metal foil and the Rb metal foil which will be described later. Set the height to satisfy the following formula. D ≧
(Li foil thickness) + [(Rb foil thickness) + (Cs foil thickness)] ×
1.07 (1) The height D of the peripheral wall 13a is the above formula (1).
If the height is not satisfied, the liquid negative electrode that will be formed later will flow out, causing a problem such as a short circuit.

Returning to FIG. 2, the Li metal foil 16, the Rb metal foil 17, and the Cs metal foil 18 are in a weight ratio of 10: 1 to 1: 1 to 4: 1 to 4 in an inert gas atmosphere at a temperature of 0 ° C. or less. The metal layer 19 containing the above is provided on one surface of a sheet-shaped negative electrode current collector 21 to form a negative electrode sheet-shaped material 22. The metal layer 19 is formed by stacking a foil-shaped Li metal 16, a foil-shaped Rb metal 17, and a foil-shaped Cs metal 18. Cs has a melting point of 28.5 ° C. and Rb has a melting point of 39.0 ° C.
Cs-at about 9 ° C, which is a temperature lower than the melting point of each metal.
Since the Rb alloy is alloyed, the handling temperature is 0 ° C. or lower. It is preferably -15 to -5 ° C.

Next, the positive electrode sheet material 14 and the negative electrode sheet material 22 are stacked in an inert gas atmosphere at a temperature of 0 ° C. or less so that the positive electrode current collector 11 and the negative electrode current collector 21 are on the outside. Together, the laminated body 23 is formed. As shown in FIG. 3, the laminated body 23 is formed by the aluminum vapor deposition film 24 so that the positive electrode sheet-shaped portion 14a and the negative electrode sheet-shaped portion 22a are exposed in an inert gas atmosphere at a temperature of 0 ° C. or less.
Encapsulate with 24 and vacuum seal. 4 (a) and 4
As shown in (b), the vacuum-sealed laminated body 23 is placed in an atmosphere at room temperature, and the Rb metal foil 17 and the Cs metal foil 18 are alloyed to form a Cs-Rb alloy 26. In this step, the Li metal foil 16 remains unchanged without any change.

Initial charging is performed by applying a voltage to the exposed portion 14a of the positive electrode sheet and the portion 22a of the negative electrode sheet. When the initial charge is performed, lithium ions (Li ⁺ ) move from the positive electrode side toward the negative electrode 27 through the solid electrolyte 13 as shown in FIG. 4C. At the interface between the negative electrode 27 and the solid electrolyte 13, the liquid negative electrode 2 composed of lithium ions in the solid electrolyte and the Cs-Rb alloy 26
The reduction reaction proceeds with the electrons (e ⁻ ) transmitted through the metal 7, and metallic lithium 16 is deposited on the surface of the solid electrolyte 13. When the deposited metallic lithium 16 grows to a certain size, it peels off from the surface of the solid electrolyte 13, and the Cs-Rb alloy 2
It diffuses into the liquid negative electrode 27 composed of 6. Liquid negative electrode 2
The concentration gradient of metallic lithium in 7 serves as a driving force for diffusion.
When the initial charging is completed, the concentration of metallic lithium in the Cs-Rb alloy becomes higher than that in the initial state by an amount corresponding to the amount of electricity charged.

Next, electric power is consumed from the exposed positive electrode sheet-like portion 14a and negative electrode sheet-like portion 22a to perform the initial discharge. When the initial discharge is performed,
As shown in (d), the metallic lithium 16 near the interface of the solid electrolyte 13 is oxidized at the interface of the solid electrolyte to become lithium ions (Li ⁺ ) and moves in the solid electrolyte 13 toward the positive electrode side. Since a concentration gradient of metallic lithium occurs near the electrolyte in the Cs-Rb alloy, this serves as a driving force for supplying metallic lithium to the electrolyte interface. At this time, Cs-R
Since the redox potential of the alloy b is slightly less than that of metallic lithium, it can exist stably. Through the above steps, the lithium secondary battery 28 of the present invention
Is manufactured. Generally, in a lithium secondary battery using a conventional electrolytic solution, metallic lithium grows like a resin on the negative electrode when rapidly charged, so the electrolytic solution is pierced and short-circuited with the positive electrode, or between the electrolyte layer and the negative electrode layer. Although there is a problem that a gap is generated and the performance as a battery is impaired, such a problem can be solved at the same time by applying the liquid negative electrode containing Cs-Rb alloy containing metallic lithium of the present invention. it can.

In this embodiment, Li metal foil and Cs are used.
After laminating the metal foil and the Rb metal foil to form a metal layer, the metal negative electrode was alloyed at room temperature to form a liquid negative electrode composed of a Cs-Rb alloy, and granular Li metal, granular Rb metal and granular Cs were formed. A metal layer may be formed by dispersing a metal in an organic solvent, applying this dispersion liquid to one surface of a sheet-shaped negative electrode current collector, and removing the organic solvent from the coating layer. Examples of the organic solvent used include highly volatile ethyl alcohol, hexane, hexanol and the like. Further, a volatile dispersant may be added together with the organic solvent. Further, as one or both of the Cs metal and the Rb metal, a metal recovered from fly ash containing these metals may be used. The fly ash in this case is cement kiln ash, industrial waste melting furnace ash, or general waste incinerator ash.

[0020]

EXAMPLES Next, examples of the present invention will be described in detail together with comparative examples.
explain. <Example 1> First, an Al metal plate was used as a positive electrode current collector.
Sheet-like LiCo as a polar active material _0.3Ni_0.7O₂To
Pre-rectangular bottom as lithium ion conductive solid electrolyte
Such as having a plate and a peripheral wall formed around the bottom plate
Shaped and sintered Li₂S-SiS₂The negative electrode current collector
Cu metal plate as the negative electrode material, and Li metal foil and Rb as the negative electrode material
A metal foil and a Cs metal foil were prepared respectively. Then, FIG.
As shown in, the positive electrode current collector, the positive electrode active material, and the solid electrolyte
Were laminated in this order to form a positive electrode sheet. temperature
Rb metal foil and Cs metal in an inert gas atmosphere of 0 ° C or less
The weight ratio of the foil is 50% by weight: 50% by weight.
The weight ratio of the foil and the Cs-Rb alloy (Li: Cs-Rb) is
Li metal foil and Rb metal in a ratio of 1: 0.5
A metal layer formed by laminating a foil and a Cs metal foil is used as a negative electrode current collector.
The sheet was provided on one surface to form a sheet for negative electrode. Temperature 0 ° C or higher
Under the inert gas atmosphere below, the sheet for positive electrode and the sheet for negative electrode
The positive electrode current collector and the negative electrode current collector are placed outside
To form a laminated body. Temperature 0 ° C or higher
In the inert gas atmosphere below, part of the sheet material for the positive electrode and negative
The laminated body is made of aluminum so as to expose a part of the sheet for poles.
It was covered with a vapor deposition film and vacuum-sealed. This vacuum sealed
The laminated body is placed in an atmosphere of room temperature of 27 ° C. and Rb
Metal foil and Cs metal foil are alloyed to form a liquid negative electrode
It was Next, a part of the exposed positive electrode sheet-like material
And a part of the negative electrode sheet-like material for initial charging by applying voltage.
The exposed sheet of positive electrode material and negative
The initial discharge is performed by consuming electric power from a part of the electrode sheet.
I got a secondary battery. The discharge current density is 1020μ
A / cm²And the cutoff voltage is 4.1 to 2.3V.
did. Charge and discharge this secondary battery once, five times and ten times.
The discharge capacity at the time of returning and the average discharge potential were measured.

<Example 2> Li metal of the negative electrode and Cs-Rb
A secondary battery was produced in the same manner as in Example 1 except that the weight ratio with the alloy (Li: Cs-Rb) was set to 1: 1, and the discharge current density was set to 64 μA / cm ^2, and Example 1 was obtained. It measured similarly. <Example 3> Example 1 except that the weight ratio (Li: Cs-Rb) of Li metal and Cs-Rb alloy of the negative electrode was set to 1: 1.
A secondary battery was prepared in the same manner as in, and the discharge current density was 510
The measurement was performed in the same manner as in Example 1 except that the value was μA / cm ² . <Example 4> Example 1 except that the weight ratio (Li: Cs-Rb) of Li metal and Cs-Rb alloy of the negative electrode was set to 1: 1.
A secondary battery was produced in the same manner as in Example 1 and measured in the same manner as in Example 1. <Example 5> Example 1 except that the weight ratio (Li: Cs-Rb) of Li metal and Cs-Rb alloy of the negative electrode was 1: 5.
A secondary battery was produced in the same manner as in Example 1 and measured in the same manner as in Example 1.

<Comparative Example 1> Li metal of the negative electrode and Cs-Rb
A secondary battery was produced in the same manner as in Example 1 except that the weight ratio with the alloy (Li: Cs-Rb) was 1: 0.1, and the measurement was performed in the same manner as in Example 1. <Comparative Example 2> A secondary battery was prepared in the same manner as in Example 1 except that the weight ratio (Li: Cs-Rb) of the Li metal and the Cs-Rb alloy of the negative electrode was set to 1:10. It measured similarly to. Comparative Example 3 The same materials as in Example 1 were used except that Li _4.4 Si was used as the negative electrode material, and a positive electrode current collector, a positive electrode active material, a sheet-like lithium ion conductive solid electrolyte, a negative electrode current collector, and Negative electrode materials are laminated in this order, and the laminate is covered with an aluminum vapor deposition film so as to expose a part of the positive electrode sheet material and a part of the negative electrode sheet material, and vacuum-sealed to form a secondary battery. It was made. Example 1 was repeated except that the secondary battery thus obtained had a discharge current density of 64 μA / cm ^2.
It measured similarly to. <Comparative Example 4> Except that the discharge current density was set to 510μA / cm ² A secondary battery was prepared in the same manner as in Comparative Example 3, the discharge current density except that the 510μA / cm ² and in the same manner as in Example 1 It was measured.

<Comparative Test and Evaluation> Table 1 shows the discharge capacities and average discharge potentials obtained in Examples 1 to 5 and Comparative Examples 1 to 4, respectively.

[0024]

[Table 1]

As is clear from Table 1, Comparative Examples 1 and 2
In, the discharge capacity drastically decreases as the number of charge and discharge increases. In Comparative Example 3 in which the discharge current density is as small as 64 μA / cm ² , the discharge capacity and the average discharge potential are stable and do not decrease even if the number of charge / discharge cycles is advanced, but the discharge current density is 510
In Comparative Example 4 in which μA / cm ² was set, the discharge capacity drastically decreased as the number of charge / discharge cycles increased, and when the charge / discharge was performed 10 times, the discharge capacity could not be obtained. On the other hand, in Examples 1 to 5, it can be seen that the discharge capacity and the average discharge potential do not decrease and are stable even if the number of times of charging and discharging progresses.

[0026]

As described above, the present invention is an improvement of a negative electrode for a lithium secondary battery, which is provided in contact with a lithium ion conductive solid electrolyte. Its characteristic constitution is a negative electrode current collector and a negative electrode current collector. Cs-Rb alloy provided on the solid electrolyte side of the electric body and containing metallic lithium.
The weight ratio of the metallic lithium contained in the b alloy to the Cs-Rb alloy is Li: Cs-Rb = 5: 1 to 1: 8. Since it was a liquid negative electrode composed of a Cs-Rb alloy that was liquid at room temperature and contained metallic lithium so as to be able to cope with mechanical deformation while maintaining electrical connection between the electrolyte and the electrode, movement of working ions inside the electrolyte resulted in It is possible to solve the problem that a gap is generated at the interface between the solid electrolyte and the electrode, and peeling occurs.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a lithium secondary battery in the present embodiment.

FIG. 2 is a diagram showing a manufacturing process in a lithium secondary battery.

FIG. 3 is a cross-sectional view of a laminated body that has undergone vacuum deposition.

FIG. 4 is a partial configuration cross-sectional view in the manufacturing process of the present invention.

FIG. 5 is a partial configuration cross-sectional view in the manufacturing process of the present invention.

[Explanation of symbols]

11 Positive electrode current collector 12 Positive electrode 13 Solid electrolyte 14 Sheet-like material for positive electrode 14a Part of sheet material for positive electrode 16 Li metal 17 Rb metal 18 Cs metal 19 Metal layer 21 Negative electrode current collector 22 Sheet-like material for negative electrode 22a Part of sheet material for negative electrode 23 Stack 24 Aluminum vapor deposition film 26 Cs-Rb alloy 27 Liquid negative electrode 28 Lithium secondary battery

Continued front page    F term (reference) 5H029 AJ11 AK03 AL11 AL12 AM12                       AM16 BJ04 CJ12 CJ16 CJ22                       CJ24 CJ28 HJ01 HJ12 HJ14                 5H050 AA14 BA17 CA08 CA09 CB11                       CB12 GA12 GA17 GA18 GA22                       GA24 GA27 HA01 HA12

Claims (8)

[Claims] 1. A negative electrode for a lithium secondary battery provided in contact with a lithium ion conductive solid electrolyte (13), comprising: a negative electrode current collector (21); and the solid electrolyte (13) of the negative electrode current collector (21). ) Side and contains Cs-Rb containing metallic lithium (16)
Alloy (26), wherein the weight ratio of the lithium metal (16) contained in the Cs-Rb alloy (26) to the Cs-Rb alloy (26) is Li: Cs-Rb.
= 5: 1 to 1: 8, the negative electrode for a lithium secondary battery. 2. The negative electrode for a lithium secondary battery according to claim 1, wherein the Cs-Rb alloy (26) comprises 30 to 80% by weight of Cs and 70 to 20% by weight of Rb. 3. A positive electrode (12), a negative electrode (27), and the positive electrode (12)
In a lithium secondary battery comprising a lithium ion conductive solid electrolyte (13) provided between the negative electrode (27) and the negative electrode (27), the negative electrode (27) is a negative electrode current collector (21), the negative electrode current collector (twenty one)
And a Cs-Rb alloy (26) containing metallic lithium (16) provided on the solid electrolyte (13) side of the metallic lithium (16) and the Cs-Rb alloy (26). The weight ratio with the Rb alloy (26) is Li: Cs-Rb.
= 5: 1 to 1: 8, a lithium secondary battery. 4. A positive electrode sheet obtained by laminating a sheet or foil-shaped positive electrode current collector (11), a sheet or foil-shaped positive electrode (12) and a sheet-shaped lithium ion conductive solid electrolyte (13) in this order. Forming the particulate matter (14) and Li metal (16) and Rb in an inert gas atmosphere at a temperature of 0 ° C or less.
The metal (17) and the Cs metal (18) are in a weight ratio of 10: 1 to 1: 4:
A sheet-like negative electrode current collector containing a metal layer (19) containing 1 to 4
A step of forming the negative electrode sheet-like material (22) on one surface of (21), and the positive electrode sheet-like material (14) and the negative electrode sheet-like material (22) in an inert gas atmosphere at a temperature of 0 ° C. or less. ) And the positive electrode current collector (11)
And a step of forming a laminated body (23) by stacking the negative electrode current collectors (21) so that they are on the outside, and a part (14a) of the positive electrode sheet-like material in an inert gas atmosphere at a temperature of 0 ° C. or less. ) And a part of the negative electrode sheet-like material (22a) is exposed so that the laminate (23) is covered with an aluminum vapor-deposited film and vacuum-sealed, and the vacuum-sealed laminate (23) ) In a room temperature atmosphere to form a liquid negative electrode (27) by alloying the Rb metal (17) with the Cs metal (18), and the exposed sheet material for positive electrode, respectively. A step of applying a voltage to a part (14a) and a part (22a) of the negative electrode sheet material to perform initial charging, and a part (14a) and the negative electrode sheet shape of the exposed positive electrode sheet material, respectively. And a step of consuming electric power from a part (22a) of the article to perform an initial discharge. 5. A foil-shaped Li metal (16) and a foil-shaped Rb metal (1
7) and foil-shaped Cs metal (18) are laminated to form a metal layer
The method for producing a lithium secondary battery according to claim 4, wherein (19) is formed. 6. A granular Li metal, a granular Rb metal and a granular Cs metal are dispersed in an organic solvent, the organic solvent is applied to one surface of a negative electrode current collector in sheet form, and the organic solvent is applied from the coating layer. The method for producing a lithium secondary battery according to claim 4, wherein the metal layer is formed by desorbing. 7. The method according to claim 4, wherein one or both of the Cs metal and the Rb metal is a metal recovered from fly ash containing the metal. 8. The method according to claim 7, wherein the fly ash is cement kiln ash, industrial waste melting furnace ash, or general waste incinerator ash.