JPWO2013132592A1 - Sulfide solid state battery system and control method for sulfide solid state battery - Google Patents

Abstract

The main object of the present invention is to provide a sulfide solid state battery system and a sulfide solid state battery control method capable of improving cycle characteristics. The present invention comprises a solid battery having a positive electrode layer, a negative electrode layer, and a solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer, and a control means capable of controlling the charge stop voltage of the solid battery, LiNixCoyMnzO2 (x + y + z = 1 and 0.32 <x, y, z <0.34) is used, and a sulfide solid electrolyte is used at least for the solid electrolyte layer, and graphite charges lithium ions when charging the solid battery. A sulfide solid state battery system in which the charge stop voltage of the solid battery is controlled by the control means so that the charge is stopped at 4.3 V or less with respect to the potential to be stored and released. A control method for a sulfide solid state battery in which the charge stop voltage of the solid state battery is controlled so that the charge is stopped at 4.3 V or less with reference to the potential for inserting and extracting lithium ions. .

Description

  The present invention relates to a sulfide solid state battery system and a method for controlling a sulfide solid state battery.

  Lithium ion secondary batteries have a higher energy density than conventional secondary batteries and can be operated at a high voltage. For this reason, it is used as a secondary battery that can be easily reduced in size and weight in information equipment such as a mobile phone, and in recent years, there is an increasing demand for large motive power such as for electric vehicles and hybrid vehicles.

  A lithium ion secondary battery has a positive electrode layer and a negative electrode layer, and an electrolyte layer disposed between them. Examples of the electrolyte used for the electrolyte layer include non-aqueous liquid and solid substances. Are known. When a liquid electrolyte (hereinafter referred to as “electrolytic solution”) is used, the electrolytic solution easily penetrates into the positive electrode layer and the negative electrode layer. Therefore, an interface between the active material contained in the positive electrode layer or the negative electrode layer and the electrolytic solution is easily formed, and the performance is easily improved. However, since the widely used electrolyte is flammable, it is necessary to mount a system for ensuring safety. On the other hand, when a solid electrolyte that is flame retardant (hereinafter referred to as “solid electrolyte”) is used, the above system can be simplified. Therefore, a lithium ion secondary battery (hereinafter referred to as a “solid battery”) having a layer containing a solid electrolyte (hereinafter referred to as “solid electrolyte layer”) is referred to as a stacked positive electrode layer, solid electrolyte. The three layers of the negative electrode layer and the negative electrode layer may be collectively referred to as an “electrode body”).

  As a technique related to such a lithium ion secondary battery, for example, Patent Document 1 discloses that one or more secondary batteries having a lithium ion conductive solid electrolyte and charging and / or discharging of the secondary battery are controlled. Control means, and the control means charges a secondary battery in which an abnormality is detected in the voltage and / or current during charging with a pulse wave and / or a low charging voltage. A discharge device is disclosed. Further, in Patent Document 1, a secondary battery is charged, an abnormality occurring in the secondary battery is detected, and a pulse and / or a pulse is applied to the secondary battery in which an abnormality in voltage and / or current is detected. Alternatively, a secondary battery charge / discharge control method in which charging is performed at a low voltage is also disclosed.

JP 2010-40198 A

  With the technique disclosed in Patent Document 1, the deterioration of the secondary battery cannot be determined until an abnormality is detected. Therefore, the charge / discharge cycle characteristics of the secondary battery (hereinafter referred to as “cycle characteristics”) may be deteriorated.

  Then, this invention makes it a subject to provide the control method of the sulfide solid battery system and sulfide solid battery which can improve cycling characteristics.

As a result of intensive studies, the present inventors used LiNi _x Co _y Mn _z O ₂ (x + y + z = 1 and 0.32 <x, y, z <0.34; the same applies hereinafter) as the positive electrode active material. The sulfide solid state battery was found to have different durability (cycle characteristics) depending on the operating voltage. Specifically, the charging upper limit voltage of the sulfide solid battery using LiNi _x Co _y Mn _z O ₂ as the positive electrode active material, 4.3 V or less based on the potential of graphite is absorbing and releasing lithium ions (charging upper limit In the following explanation regarding voltage, it is found that the expression of “based on the potential at which graphite absorbs and releases lithium ions may be omitted” can improve cycle characteristics. did. Further, the present inventors have conducted intensive result of examination, the discharge lower limit voltage of the sulfide solid battery using LiNi _x Co _y Mn _z O ₂ as the positive electrode active material, based on the potential of graphite is absorbing and releasing lithium ions The cycle characteristics are improved by setting the voltage to 3.4 V or higher (in the following description of the discharge lower limit voltage, the expression “graphite is based on the potential at which lithium ions are occluded and released” may be omitted). I found out that it would be possible. Further, the present inventors have conducted intensive result of examination, the discharge lower limit voltage of the sulfide solid battery using LiNi _x Co _y Mn _z O ₂ as the positive electrode active material, based on the potential of graphite is absorbing and releasing lithium ions Thus, it was found that by setting the charging upper limit voltage to 4.4 V or higher, the charging upper limit voltage is 4.4 V based on the potential at which graphite absorbs and releases lithium ions, and it is possible to obtain good cycle characteristics. The present invention has been completed based on these findings.

In order to solve the above problems, the present invention takes the following means. That is,
A first aspect of the present invention is a solid battery having a positive electrode layer and a negative electrode layer, and a solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer, and a control means capable of controlling the charge stop voltage of the solid battery. LiNi _x Co _y Mn _z O ₂ is used for the positive electrode layer, and a sulfide solid electrolyte is used for at least the solid electrolyte layer, and the potential at which the graphite occludes and releases lithium ions during charging of the solid battery is obtained. This is a sulfide solid state battery system in which the charge stop voltage of the solid state battery is controlled by the control means so that the charge is stopped at 4.3 V or less with reference.

In a sulfide solid state battery using LiNi _x Co _y Mn _z O ₂ as a positive electrode active material, it is possible to increase the capacity maintenance rate after repeated charge and discharge of 1000 cycles by setting the charge stop voltage to 4.3 V or less. become. Therefore, according to the first aspect of the present invention, a sulfide solid state battery system capable of improving the cycle characteristics can be provided.

According to a second aspect of the present invention, there is provided a solid battery having a positive electrode layer and a negative electrode layer, and a solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer, and control means capable of controlling a discharge stop voltage of the solid battery. LiNi _x Co _y Mn _z O ₂ is used for the positive electrode layer, and a sulfide solid electrolyte is used for at least the solid electrolyte layer, and the potential at which graphite absorbs and releases lithium ions during discharge of the solid battery is obtained. This is a sulfide solid state battery system in which the discharge stop voltage of the solid state battery is controlled by the control means so that the discharge is stopped at 3.4 V or more on the basis.

In sulfide solid battery using LiNi _x Co _y Mn _z O ₂ as the positive electrode active material, by a discharge stop voltage or 3.4 V, it is possible to increase the capacity retention after repeated charge-discharge 1000 cycles become. Therefore, according to the 2nd aspect of this invention, the sulfide solid state battery system which can improve cycling characteristics can be provided.

A third aspect of the present invention controls a solid state battery having a positive electrode layer and a negative electrode layer, and a solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer, and a charge stop voltage and a discharge stop voltage of the solid battery. Possible control means, LiNi _x Co _y Mn _z O ₂ is used for the positive electrode layer, and a sulfide solid electrolyte is used for at least the solid electrolyte layer, and graphite absorbs lithium ions during discharge of the solid battery. The discharge stop voltage of the solid battery is controlled by the control means so that the discharge is stopped at 3.4 V or higher with reference to the discharge potential, and the potential at which graphite absorbs and releases lithium ions when the solid battery is charged. This is a sulfide solid state battery system in which the charging stop voltage of the solid state battery is controlled by the control means so that the charging is stopped at 4.4 V or less with reference to the above.

In a sulfide solid state battery using LiNi _x Co _y Mn _z O ₂ as a positive electrode active material, by setting the discharge stop voltage to 3.4 V or more, good cycle characteristics can be obtained even when the charge upper limit voltage is 4.4 V. It becomes possible to obtain. Therefore, according to the 3rd aspect of this invention, the sulfide solid state battery system which can improve cycling characteristics can be provided.

A fourth aspect of the present invention is a method for controlling a solid state battery having a positive electrode layer and a negative electrode layer, and a solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer, wherein the positive electrode layer has a LiNi _x Co _y Mn _z O ₂ is used, and at least the solid electrolyte layer is a sulfide solid electrolyte. When the solid battery is charged, charging stops at 4.3 V or less with reference to the potential at which graphite absorbs and releases lithium ions. As described above, the control method of the sulfide solid state battery controls the charge stop voltage of the solid state battery.

In a sulfide solid state battery using LiNi _x Co _y Mn _z O ₂ as a positive electrode active material, it is possible to increase the capacity maintenance rate after repeated charge and discharge of 1000 cycles by setting the charge stop voltage to 4.3 V or less. become. Therefore, according to the 4th aspect of this invention, the control method of the sulfide solid state battery which can improve cycling characteristics can be provided.

A fifth aspect of the present invention, the positive electrode layer and negative electrode layer, and a method for controlling a solid state battery having a solid electrolyte layer disposed between the positive electrode layer and negative electrode layer, LiNi _x Co _y in the positive electrode layer Mn _z O ₂ is used, and at least the solid electrolyte layer is a sulfide solid electrolyte. When the solid battery is discharged, the discharge stops at 3.4 V or higher with respect to the potential at which graphite absorbs and releases lithium ions. As described above, this is a control method for a sulfide solid state battery in which the discharge stop voltage of the solid state battery is controlled.

In sulfide solid battery using LiNi _x Co _y Mn _z O ₂ as the positive electrode active material, by a discharge stop voltage or 3.4 V, it is possible to increase the capacity retention after repeated charge-discharge 1000 cycles become. Therefore, according to the fifth aspect of the present invention, it is possible to provide a control method for a sulfide solid state battery capable of improving cycle characteristics.

A sixth aspect of the present invention is a method for controlling a solid state battery having a positive electrode layer and a negative electrode layer, and a solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer, wherein the positive electrode layer has LiNi _x Co _y Mn _z O ₂ is used, and at least the solid electrolyte layer is a sulfide solid electrolyte. When the solid battery is discharged, the discharge stops at 3.4 V or higher with respect to the potential at which graphite absorbs and releases lithium ions. In order to control the discharge stop voltage of the solid battery and charge the solid battery so that the charge is stopped at 4.4 V or lower with reference to the potential at which graphite absorbs and releases lithium ions. It is a control method of a sulfide solid state battery which controls the charge stop voltage of the battery.

In a sulfide solid state battery using LiNi _x Co _y Mn _z O ₂ as a positive electrode active material, by setting the discharge stop voltage to 3.4 V or more, good cycle characteristics can be obtained even when the charge upper limit voltage is 4.4 V. It becomes possible to obtain. Therefore, according to the sixth aspect of the present invention, it is possible to provide a control method for a sulfide solid state battery capable of improving cycle characteristics.

In the present invention, the above-described LiNi _x Co _y Mn _z O ₂ includes those added with a trace amount of an element (for example, Al, Mg, W, Zr, etc.) different from the element of the positive electrode. When the positive electrode layer contains a positive electrode active material and a solid electrolyte, the “positive electrode element” includes an element constituting the positive electrode active material and an element constituting the solid electrolyte.

  ADVANTAGE OF THE INVENTION According to this invention, the control method of the sulfide solid state battery system and sulfide solid state battery which can improve cycling characteristics can be provided.

1 is a diagram illustrating a sulfide solid state battery system 10. FIG. It is a figure explaining the sulfide solid battery system 20. FIG. It is a figure which shows the relationship between a charge upper limit voltage and a capacity | capacitance maintenance factor. It is a figure which shows the relationship between a charge upper limit voltage and an internal resistance increase rate. It is a figure which shows the relationship between a discharge minimum voltage and a capacity | capacitance maintenance factor. It is a figure which shows the relationship between a discharge minimum voltage and an internal resistance increase rate. It is a figure explaining the relationship between a charge upper limit voltage and a capacity | capacitance maintenance factor. It is a figure explaining the relationship between a charge upper limit voltage and an internal resistance increase rate.

  The present invention will be described below with reference to the drawings. In the drawings shown below, the description of the outer casing and the like of the solid battery is omitted. In addition, the form shown below is an illustration of this invention and this invention is not limited to the form shown below.

1. First Embodiment FIG. 1 is a diagram for explaining a control method for a sulfide solid state battery system 10 and a sulfide solid state battery 1 according to a first embodiment of the present invention. In FIG. 1, the sulfide solid state battery 1 and the control means 2 are shown in a simplified manner. A sulfide solid state battery system 10 shown in FIG. 1 includes a sulfide solid state battery 1 and a control unit 2 capable of controlling a charge stop voltage of the sulfide solid state battery 1. The sulfide solid battery 1 is connected to a positive electrode layer 1x and a negative electrode layer 1z, a solid electrolyte layer 1y disposed therebetween, a positive electrode current collector 1p connected to the positive electrode layer 1x, and a negative electrode layer 1z. Negative electrode current collector 1m. The positive electrode layer 1x includes at least a positive electrode active material and a solid electrolyte, LiNi _x Co _y Mn _z O ₂ is used as the positive electrode active material, and a sulfide solid electrolyte is used as the solid electrolyte. The solid electrolyte layer 1y includes a sulfide solid electrolyte. The negative electrode layer 1z includes a negative electrode active material and a solid electrolyte. Graphite is used as the negative electrode active material, and a sulfide solid electrolyte is used as the solid electrolyte. In the sulfide solid state battery system 10, the control means 2 incorporates a control program capable of controlling the charging of the sulfide solid state battery 1 so that the charge stop voltage of the sulfide solid state battery 1 is 4.3V or less. . In the sulfide solid battery system 10, for example, a signal is sent from the control means 2 to a charger (not shown) so as to stop charging when the voltage of the sulfide solid battery 1 reaches 4.3V, and the sulfide solid battery 1 is sulfided. The solid-state battery 1 is controlled so that the charge stop voltage is 4.3 V or less.

The sulfide solid state battery 1 using LiNi _x Co _y Mn _z O ₂ as the positive electrode active material improves the cycle characteristics by setting the upper limit voltage to 4.3 V or less (capacity maintenance ratio after repeated charge and discharge). And suppressing an increase in the rate of increase in internal resistance after repeated charging and discharging (the same applies hereinafter). Therefore, according to the sulfide solid battery system 10, cycle characteristics can be improved. In addition, a control method for a sulfide solid state battery capable of improving cycle characteristics by controlling the charge stop voltage of the sulfide solid state battery 1 so that the charge stop voltage is 4.3 V or less is provided. can do.

In the present invention, the shape of the positive electrode active material (LiNi _x Co _y Mn _z O ₂ ) included in the positive electrode layer 1x can be, for example, a particulate form. The average particle size (D50) of the positive electrode active material is, for example, preferably from 1 nm to 100 μm, and more preferably from 10 nm to 30 μm. Further, the content of the positive electrode active material in the positive electrode layer 1x is not particularly limited, but is preferably 40% or more and 99% or less in mass%, for example.

As the sulfide solid electrolyte which can be used for the positive electrode layer _{1x, Li 2 S-SiS 2} , LiI-Li 2 S-SiS 2, LiI-Li 2 S-P 2 S 5, LiI-Li 2 S _{-P 2 O 5, LiI-Li} 2 S-P 2 S 5 -LiO 2, LiI-Li 3 PO 4 -P 2 S 5, Li 2 S-P 2 S 5 or the like can be exemplified.

In the present invention, the positive electrode active material is ion-conductive from the viewpoint of making it easy to prevent an increase in battery resistance by making it difficult to form a high resistance layer at the interface between the positive electrode active material and the sulfide solid electrolyte. It is preferable to coat with a functional oxide. Examples of the lithium ion conductive oxide that coats the positive electrode active material include a general formula Li _x AO _y (A is B, C, Al, Si, P, S, Ti, Zr, Nb, Mo, Ta, or W). And x and y are positive numbers). Specifically, Li ₃ BO ₃ , LiBO ₂ , Li ₂ CO ₃ , LiAlO ₂ , Li ₄ SiO ₄ , Li ₂ SiO ₃ , Li ₃ PO ₄ , Li ₂ SO ₄ , Li ₂ TiO ₃ , Li ₄ Ti ₅ Examples include O ₁₂ , Li ₂ Ti ₂ O ₅ , Li ₂ ZrO ₃ , LiNbO ₃ , Li ₂ MoO ₄ , LiTaO ₃ , Li ₂ WO _{4 and the} like. The lithium ion conductive oxide may be a complex oxide. As the composite oxide covering the positive electrode active material, any combination of the above lithium ion conductive oxides can be employed. For example, Li ₄ SiO ₄ —Li ₃ BO ₃ , Li ₄ SiO ₄ —Li ₃ PO ₄ etc. can be mentioned. Further, when the surface of the positive electrode active material is coated with an ion conductive oxide, the ion conductive oxide only needs to cover at least a part of the positive electrode active material, and covers the entire surface of the positive electrode active material. Also good. In addition, the thickness of the ion conductive oxide covering the positive electrode active material is, for example, preferably from 0.1 nm to 100 nm, and more preferably from 1 nm to 20 nm. The thickness of the ion conductive oxide can be measured using, for example, a transmission electron microscope (TEM).

  Moreover, the positive electrode layer 1x can be produced using a known binder or thickener that can be contained in the positive electrode layer of the lithium ion secondary battery. Examples of such a binder include acrylonitrile butadiene rubber (ABR), butadiene rubber (BR), polyvinylidene fluoride (PVdF), styrene butadiene rubber (SBR), and the like, and carboxymethyl cellulose (CMC) as a thickener. ) And the like.

  Furthermore, the positive electrode layer 1x may contain a conductive material that improves conductivity. Examples of the conductive material that can be included in the positive electrode layer 1x include carbon materials such as vapor grown carbon fiber, acetylene black (AB), ketjen black (KB), carbon nanotube (CNT), and carbon nanofiber (CNF). In addition, a metal material that can withstand the environment when the sulfide solid state battery 1 is used can be exemplified.

  The positive electrode layer 1x can be produced by a known method. For example, when the positive electrode layer 1x is produced using a slurry-like positive electrode composition prepared by dispersing the positive electrode active material, solid electrolyte, and binder in a liquid, heptane or the like is exemplified as a usable liquid. A nonpolar solvent can be preferably used. Further, the thickness of the positive electrode layer 1x is, for example, preferably 0.1 μm or more and 1 mm or less, and more preferably 1 μm or more and 100 μm or less. Moreover, in order to make it easy to improve the performance of the sulfide solid state battery 1, the positive electrode layer 1x is preferably manufactured through a pressing process. In this invention, the pressure at the time of pressing the positive electrode layer 1x can be about 500 MPa.

  The solid electrolyte layer 1y can contain a known sulfide solid electrolyte. Examples of such a sulfide solid electrolyte include the sulfide solid electrolyte that can be contained in the positive electrode layer 1x. In addition, the solid electrolyte layer 1y may contain a binder that binds the solid electrolytes from the viewpoint of developing plasticity. As such a binder, the said binder etc. which can be contained in the positive electrode layer 1x can be illustrated. However, in order to facilitate high output, the solid electrolyte layer 1y having a sulfide solid electrolyte uniformly dispersed can be formed by preventing excessive aggregation of the sulfide solid electrolyte and the like. The binder contained in the electrolyte layer 1y is preferably 5% by mass or less.

  The solid electrolyte layer 1y can be produced by a known method. For example, when the solid electrolyte layer 1y is manufactured through a process in which a slurry-like solid electrolyte composition prepared by dispersing the sulfide solid electrolyte or the like in a liquid is applied to the positive electrode layer 1x, the negative electrode layer 1z, or the like, Examples of the liquid for dispersing the electrolyte and the like include heptane and the like, and a nonpolar solvent can be preferably used. The content of the solid electrolyte material in the solid electrolyte layer 1y is mass%, for example, preferably 60% or more, more preferably 70% or more, and particularly preferably 80% or more. The thickness of the solid electrolyte layer 1y varies greatly depending on the configuration of the battery. For example, the thickness is preferably 0.1 μm or more and 1 mm or less, and more preferably 1 μm or more and 100 μm or less.

Moreover, as a negative electrode active material contained in the negative electrode layer 1z, the well-known negative electrode active material which can occlude / release lithium ion can be used suitably. Examples of such a negative electrode active material include graphite such as highly oriented graphite (HOPG), and other carbon active materials, oxide active materials, metal active materials, and the like may be used together with graphite. . The other carbon active material is not particularly limited as long as it contains carbon, and examples thereof include mesocarbon microbeads (MCMB), hard carbon, and soft carbon. Examples of the oxide active material include Nb ₂ O ₅ , Li ₄ Ti ₅ O ₁₂ , and SiO. Examples of the metal active material include In, Al, Si, and Sn. Further, a lithium-containing metal active material may be used as the negative electrode active material. The lithium-containing metal active material is not particularly limited as long as it is an active material containing at least Li, and may be Li metal or Li alloy. Examples of the Li alloy include an alloy containing Li and at least one of In, Al, Si, and Sn. The shape of the negative electrode active material can be, for example, particulate or thin film. The average particle diameter (D50) of the negative electrode active material is, for example, preferably from 1 nm to 100 μm, and more preferably from 10 nm to 30 μm. Further, the content of the negative electrode active material in the negative electrode layer 1z is not particularly limited, but is preferably 40% or more and 99% or less in mass%, for example.

  Furthermore, the negative electrode layer 1z may contain a solid electrolyte, a binder that binds the negative electrode active material or the solid electrolyte, a conductive material that improves conductivity, and a thickener. As the solid electrolyte, binder, conductive material, and thickener that can be contained in the negative electrode layer 1z, the solid electrolyte, binder, conductive material, and thickener that can be contained in the positive electrode layer 1x. Etc. can be illustrated.

  The negative electrode layer 1z can be produced by a known method. For example, when the negative electrode layer 1z is prepared using a slurry-like negative electrode composition prepared by dispersing the negative electrode active material or the like in a liquid, heptane or the like may be exemplified as the liquid in which the negative electrode active material or the like is dispersed. A nonpolar solvent can be preferably used. Moreover, the thickness of the negative electrode layer 1z is, for example, preferably 0.1 μm or more and 1 mm or less, and more preferably 1 μm or more and 100 μm or less. Moreover, in order to make it easy to improve the performance of the sulfide solid state battery 1, the negative electrode layer 1z is preferably manufactured through a pressing process. In the present invention, the pressure when pressing the negative electrode layer 1z is preferably 400 MPa or more, more preferably about 600 MPa.

  Moreover, the well-known electroconductive material which can be used as the collector of a solid battery can be used for the positive electrode collector 1p. Examples of such a conductive material include a conductive material containing one or more elements selected from the group consisting of Ni, Cr, Au, Pt, Al, Fe, Ti, Zn, and C (stainless steel ( SUS)).

  Moreover, the well-known electroconductive material which can be used as a collector of a solid battery can be used for the negative electrode collector 1m. As such a conductive material, a conductive material (including stainless steel (SUS) including one or more elements selected from the group consisting of Cu, Ni, Fe, Ti, Co, Zn, and C is included. ).

  The sulfide solid state battery 1 can be used in a state of being housed in a known exterior body. As the exterior body, a known laminate film that can be used in a solid battery can be used, and as such a laminate film, a resin laminate film, a film obtained by vapor-depositing a metal on a resin laminate film, or the like Can be illustrated.

  Moreover, the control means 2 can use suitably the well-known apparatus which can be used when controlling the charge stop voltage of a battery. In the sulfide solid state battery system 10, the configuration for controlling the charging of the sulfide solid state battery 1 so that the charge stop voltage of the sulfide solid state battery 1 is 4.3 V or less is a configuration unique to the present invention. Known devices can be used as appropriate as the devices themselves used when performing proper charge control.

2. Second Embodiment FIG. 2 is a diagram for explaining a control method for the sulfide solid state battery system 20 and the sulfide solid state battery 1 according to the second embodiment of the present invention. In FIG. 2, the sulfide solid state battery 1 and the control means 3 are shown in a simplified manner. In FIG. 2, the same reference numerals as those used in FIG. 1 are attached to the same configurations as those of the sulfide solid state battery system 10, and description thereof will be omitted as appropriate.

  A sulfide solid state battery system 20 shown in FIG. 2 includes a sulfide solid state battery 1 and control means 3 capable of controlling the charge stop voltage and the discharge stop voltage of the sulfide solid state battery 1. In the sulfide solid state battery system 20, the control means 3 can control the discharge of the sulfide solid state battery 1 so that the discharge stop voltage of the sulfide solid state battery 1 is 3.4 V or more, and the sulfide solid state battery A control program capable of controlling the charging of the sulfide solid state battery 1 is incorporated so that the charging stop voltage of the battery 1 is 4.4 V or less. In the sulfide solid battery system 20, for example, when the voltage of the sulfide solid battery 1 reaches 3.4 V, the sulfide solid battery 1 and a device (not shown) (electric power from the sulfide solid battery 1 are stopped) so that the discharge is stopped. Is disconnected according to an instruction from the control means 3, so that the discharge stop voltage of the sulfide solid state battery 1 is controlled to be 3.4 V or higher. Further, at the time of charging the sulfide solid state battery 1, a signal is sent from the control means 3 to a charger (not shown) so as to stop the charge when the voltage of the sulfide solid state battery 1 reaches 4.4V. The charging stop voltage of the solid battery 1 is controlled to be 4.4V or less.

Sulfide solid state battery 1 using LiNi _x Co _y Mn _z O ₂ as the positive electrode active material, it also charged to 4.4V obtain excellent cycle characteristics when the discharge stop voltage is above 3.4V It is possible to obtain a high capacity retention rate after repeated charge / discharge and to suppress an increase in the internal resistance increase rate after repeated charge / discharge. Therefore, according to the sulfide solid state battery system 20, cycle characteristics can be improved. Further, the discharge stop voltage of the sulfide solid state battery 1 is controlled so that the discharge stop voltage becomes 3.4 V or more, and the charge stop voltage of the sulfide solid state battery 1 so that the charge stop voltage becomes 4.4 V or less. By adopting a form in which the control is performed, it is possible to provide a method for controlling a sulfide solid state battery capable of improving the cycle characteristics.

  In the above description regarding the present invention, the sulfide solid state battery system 10 including the control means 2 capable of controlling the charging of the sulfide solid state battery 1 so that the charge stop voltage is 4.3 V or less, the control method thereof, and the discharge Sulfide solid state battery system 20 provided with control means 3 capable of controlling charging / discharging of sulfide solid state battery 1 so that the stop voltage becomes 3.4 V or more and the charge stop voltage becomes 4.4 V or less, and the control thereof. Although the method has been described, the present invention is not limited to these forms. The present invention provides a sulfide solid state battery system having a control means capable of controlling the discharge of the sulfide solid state battery 1 so that the discharge stop voltage becomes 3.4 V or higher, instead of the control means 2 and the control means 3. And it is also possible to set it as the control method of the sulfide solid state battery which controls discharge of the sulfide solid state battery 1 so that the discharge stop voltage becomes 3.4 V or more. Even in such a form, the cycle characteristics of the sulfide solid state battery 1 can be improved.

1. Preparation of sulfide solid state battery [Preparation of cathode active material coat-1]
LiNbO ₃ is coated on a positive electrode active material (LiNi _1/3 Co _1/3 Mn _1/3 O ₂ ) having an average particle size of 4 μm in an atmospheric environment by using a rolling fluid coating apparatus (manufactured by POWREC Co., Ltd.) By firing in an atmospheric environment, a positive electrode active material coated with an ion conductive oxide (hereinafter, this positive electrode active material may be referred to as a “first positive electrode active material”) was produced.

[Preparation of positive electrode active material coat-2]
A positive electrode active material coated with an ion-conducting oxide in the same manner as described above except that LiNbO ₃ was coated and baked in a dry environment having a dew point of −30 ° C. or less (hereinafter, this positive electrode active material) Is sometimes referred to as a “second positive electrode active material”.

[Preparation of positive electrode layer]
A heptane solution containing 5% by mass of a butadiene rubber-based binder solution, a positive electrode active material (first positive electrode active material or second positive electrode active material), a sulfide solid electrolyte (Li ₂ S containing LiI) having an average particle size of 2.5 μm -P ₂ S ₅ -based glass ceramic), and conductive auxiliary agent (vapor-grown carbon fiber), was placed in a polypropylene container. And after stirring this for 30 second with an ultrasonic dispersion device (the SMT Co., Ltd. make, UH-50. The following is the same.), A shaker (the Shibata Kagaku Co., Ltd., TTM-1) is the same in the following. )) For 3 minutes, and further stirred for 30 seconds with an ultrasonic dispersion device. Thus, the composition which performed stirring-shaking-stirring was used for the positive electrode collector (carbon coating Al foil (Showa Denko Co., Ltd. product, SDX. "SDX") by the blade method using an applicator. Is a registered trademark of Showa Denko Packaging Co., Ltd.))). Thereafter, the positive electrode current collector coated with the composition was dried on a hot plate at 100 ° C. for 30 minutes to prepare a positive electrode layer.

[Preparation of negative electrode layer]
A heptane solution containing 5% by mass of a butadiene rubber-based binder solution, a negative electrode active material (natural graphite carbon having an average particle size of 10 μm (manufactured by Mitsubishi Chemical Corporation)), and a sulfide solid electrolyte having an average particle size of 2.5 μm (Li ₂ S—P ₂ S ₅ glass ceramic containing LiI) was put in a polypropylene container. And after stirring this for 30 seconds with an ultrasonic dispersion device, it was made to shake for 30 minutes with a shaker. Thus, the composition which performed stirring and shaking was applied on the negative electrode electrical power collector (Cu foil) with the blade method using the applicator. Thereafter, the negative electrode current collector coated with the composition was dried on a hot plate at 100 ° C. for 30 minutes to prepare a negative electrode layer.

[Production of solid electrolyte layer]
A heptane solution containing 5% by weight of a butadiene rubber-based binder solution and a sulfide solid electrolyte (Li ₂ S—P ₂ S ₅ glass ceramic containing LiI) having an average particle diameter of 2.5 μm are placed in a polypropylene container. It was. And after stirring this for 30 seconds with an ultrasonic dispersion device, it was made to shake for 30 minutes with a shaker. Thus, the composition which performed stirring and shaking was applied on Al foil by the blade method using the applicator. Thereafter, the Al foil coated with the composition was dried on a hot plate at 100 ° C. for 30 minutes, and the dried coated product was peeled off from the Al foil to obtain a solid electrolyte layer.

[Production of sulfide solid state battery]
After pressing at 1TF / cm 2 to put the solid electrolyte layer produced by the above method to mold 1 cm ^{2 (≒} 98 MPa), on one side, the positive electrode layer or the second electrode active containing a first cathode active material The positive electrode layer formed on the surface of the positive electrode current collector was disposed so that the positive electrode layer containing the substance and the solid electrolyte layer were in contact with each other, and pressed at 1 tf / cm ² (≈98 MPa). Thereafter, the negative electrode layer formed on the surface of the negative electrode current collector is disposed on the opposite side (the side where the positive electrode layer is not disposed) so that the negative electrode layer and the solid electrolyte layer are in contact with each other, and 4 tf / cm ² ( A sulfide solid state battery was fabricated by pressing at ≈392 MPa.

2. Charge / Discharge Cycle Characteristic Test <Example 1>
A sulfide solid state battery produced using a positive electrode layer containing the first positive electrode active material was used. (1) After constant current charging to 4.1V at 0.5 hour rate (2C rate), (2) pause for 10 minutes, then (3) at 0.5 hour rate (2C rate) The process of (1) to (4) of (4) resting for 10 minutes after discharging at a constant current to 2.5 V was repeated over 1000 cycles in a 60 ° C. environment. In addition, the capacity | capacitance confirmation and resistance measurement which were mentioned later were implemented several times in the middle to 1000 cycles.
The sulfide solid state battery after 1000 cycles was charged at a constant current-constant voltage to 4.55 V at a 3 hour rate (1 / 3C rate) and then rested for 10 minutes. Then, the discharge capacity when performing constant current discharge to 3.0 V at a 3-hour rate (1 / 3C rate) was determined. Then, the ratio (= discharge capacity after 1000 cycles / discharge capacity after 1 cycle × 100), which was obtained in the same manner, was defined as the capacity retention rate [%].
The sulfide solid state battery after 1000 cycles was charged with a constant current-constant voltage up to 3.6 V corresponding to a final current of 1/100 C, and then suspended for 10 minutes. Thereafter, constant current discharge was carried out at a rate of 0.33 hours (3C rate) for 5 seconds, and the internal resistance (R = ΔV / ΔI) of the battery was determined from the voltage drop and current value at this time. Then, compared with the internal resistance of the battery after one cycle, obtained in the same manner, the ratio (= the internal resistance after 1000 cycles / the internal resistance after one cycle × 100) is expressed as an internal resistance increase rate [%]. did.
Table 1, FIG. 3, FIG. 4, FIG. 7, FIG. 7, and FIG. 8 show the conditions of the charge / discharge cycle, the results of the capacity retention rate, and the results of the internal resistance increase rate in Example 1. 3 and 7, the vertical axis represents the capacity maintenance rate [%], and the horizontal axis represents the charging upper limit voltage [V]. Moreover, the vertical axis | shaft of FIG.4 and FIG.8 is internal resistance increase rate [%], and a horizontal axis is charge upper limit voltage [V]. 3 and 7 show better performance on the upper side of the paper, and FIGS. 4 and 8 show better performance on the lower side of the paper.

<Example 2>
Charging / discharging was performed over 1000 cycles under the same conditions as in Example 1 except that a sulfide solid state battery prepared using a positive electrode layer containing the first positive electrode active material was used and the charge stop voltage was set to 4.3 V. Carried out. And the capacity | capacitance maintenance factor and the internal resistance increase rate were calculated | required on the same conditions as Example 1. FIG. Table 1, FIG. 3, FIG. 4, FIG. 7, FIG. 7, and FIG. 8 show the conditions of the charge / discharge cycle, the results of the capacity retention rate, and the results of the internal resistance increase rate in Example 2.

<Example 3>
The same conditions as in Example 1 were used except that a sulfide solid state battery produced using a positive electrode layer containing the second positive electrode active material was used, the charge stop voltage was set to 4.4 V, and the discharge stop voltage was set to 3.4 V. The charging / discharging was performed over 1000 cycles. And the capacity | capacitance maintenance factor and the internal resistance increase rate were calculated | required on the same conditions as Example 1. FIG. Table 1, FIG. 5, and FIG. 6 show the conditions of the charge / discharge cycle, the result of the capacity retention rate, and the result of the internal resistance increase rate in Example 3. The vertical axis in FIG. 5 is the capacity retention rate [%], and the horizontal axis is the discharge lower limit voltage [V]. Moreover, the vertical axis | shaft of FIG. 6 is internal resistance increase rate [%], and a horizontal axis is discharge minimum voltage [V]. FIG. 5 shows better performance on the upper side of the paper, and FIG. 6 shows better performance on the lower side of the paper.

<Example 4>
The same conditions as in Example 1 were used except that a sulfide solid state battery produced using a positive electrode layer containing the second positive electrode active material was used, the charge stop voltage was set to 4.4 V, and the discharge stop voltage was set to 3.5 V. The charging / discharging was performed over 1000 cycles. And the capacity | capacitance maintenance factor and the internal resistance increase rate were calculated | required on the same conditions as Example 1. FIG. Table 1, FIG. 5, and FIG. 6 show the charge / discharge cycle conditions, the capacity retention rate result, and the internal resistance increase rate result in Example 4.

<Example 5>
The same conditions as in Example 1 were used except that a sulfide solid state battery produced using a positive electrode layer containing the second positive electrode active material was used, the charge stop voltage was 4.4 V, and the discharge stop voltage was 3.6 V. The charging / discharging was performed over 1000 cycles. And the capacity | capacitance maintenance factor and the internal resistance increase rate were calculated | required on the same conditions as Example 1. FIG. Table 1, FIG. 5, and FIG. 6 show the charge / discharge cycle conditions, capacity retention rate results, and internal resistance increase rate results in Example 5.

<Example 6>
The same conditions as in Example 1 were used except that a sulfide solid state battery produced using a positive electrode layer containing the first positive electrode active material was used, the charge stop voltage was set to 4.4 V, and the discharge stop voltage was set to 3.4 V. The charging / discharging was performed over 1000 cycles. And the capacity | capacitance maintenance factor and the internal resistance increase rate were calculated | required on the same conditions as Example 1. FIG. Table 1, FIG. 7 and FIG. 8 show the conditions of the charge / discharge cycle, the result of the capacity retention rate, and the result of the internal resistance increase rate in Example 6.

<Comparative Example 1>
Charging / discharging was performed over 1000 cycles under the same conditions as in Example 1 except that a sulfide solid state battery prepared using a positive electrode layer containing the first positive electrode active material was used and the charge stop voltage was set to 4.4 V. Carried out. And the capacity | capacitance maintenance factor and the internal resistance increase rate were calculated | required on the same conditions as Example 1. FIG. Table 1, FIG. 3, FIG. 4, FIG. 7, FIG. 7 and FIG. 8 show the charge / discharge cycle conditions, capacity retention rate results, and internal resistance increase rate results in Comparative Example 1.

<Comparative Example 2>
Charging / discharging was performed over 1000 cycles under the same conditions as in Example 1 except that a sulfide solid state battery prepared using a positive electrode layer containing the first positive electrode active material was used and the charge stop voltage was 4.55 V. Carried out. And the capacity | capacitance maintenance factor and the internal resistance increase rate were calculated | required on the same conditions as Example 1. FIG. Table 1, FIG. 3, FIG. 4, FIG. 7, FIG. 7 and FIG. 8 show the charge / discharge cycle conditions, capacity retention rate results, and internal resistance increase rate results in Comparative Example 2.

<Comparative Example 3>
The same conditions as in Example 1 were used except that a sulfide solid state battery prepared using a positive electrode layer containing the second positive electrode active material was used, the charge stop voltage was set to 4.4 V, and the discharge stop voltage was set to 3.0 V. The charging / discharging was performed over 1000 cycles. And the capacity | capacitance maintenance factor and the internal resistance increase rate were calculated | required on the same conditions as Example 1. FIG. Table 1, FIG. 5, and FIG. 6 show the charge / discharge cycle conditions, the capacity retention rate result, and the internal resistance increase rate result in Comparative Example 3.

3. Results As shown in Table 1, FIG. 3, and FIG. 4, from the results of Example 1, Example 2, Comparative Example 1, and Comparative Example 2, the charging upper limit voltage of the sulfide solid state battery is 4.3V. By making it below, the capacity retention rate increased and the internal resistance increase rate decreased. That is, by setting the upper limit voltage of the sulfide solid state battery to 4.3 V or less, the performance maintenance ratio after the charge / discharge cycle could be increased. Under the conditions of Example 1 and Example 2, the amount of expansion / contraction change of the positive electrode active material was small, and it was easy to maintain the contact between the positive electrode active material and the sulfide solid electrolyte. Note that, unlike a battery (liquid battery) in which an electrolytic solution is used, in a solid battery, when the active material and the electrolyte are difficult to contact due to expansion and contraction, the battery performance deteriorates. In the liquid battery, since the electrolytic solution penetrates between the active materials, the performance degradation due to the expansion and contraction of the active material is smaller than that of the solid battery.

  Further, as shown in Table 1, FIG. 5, and FIG. 6, from the results of Example 3, Example 4, Example 5, and Comparative Example 3, the discharge lower limit voltage of the sulfide solid state battery is set to 3. By setting it to 4 V or more, the capacity retention rate increased and the internal resistance increase rate decreased. That is, by setting the lower limit discharge voltage of the sulfide solid state battery to 3.4 V or higher, the performance maintenance ratio after the charge / discharge cycle could be increased. When the discharge lower limit voltage is lower than 3.4 V, the amount of change in the expansion and contraction of the positive electrode active material becomes large, and it becomes difficult to maintain the contact between the positive electrode active material and the sulfide solid electrolyte. As a result, the performance maintenance ratio is low. It is thought that it became. In the sulfide solid state battery using the first positive electrode active material and the sulfide solid state battery using the second positive electrode active material, the former showed better properties.

  Further, as shown in Table 1, FIG. 7 and FIG. 8, in particular, Example 6 in which the charging upper limit voltage was 4.4V and the discharging lower limit voltage was 3.4V, and the charging upper limit voltage was 4.4V. From the result of Comparative Example 1 in which the discharge lower limit voltage was 2.5 V, the discharge lower limit voltage of the sulfide solid state battery was set to 3.4 V or higher, so that the performance after the charge / discharge cycle was charged even to 4.4 V. It was confirmed that the maintenance rate could be increased. When the discharge lower limit voltage of the sulfide solid state battery is set to 3.4 V or higher, the performance maintenance ratio after the charge / discharge cycle can be increased even when charged to 4.4 V. The discharge lower limit voltage is 3.4 V. This is considered to be because the amount of change in expansion / contraction of the positive electrode active material is reduced, and deterioration due to expansion / contraction during charging can be suppressed by the amount of change in the expansion / contraction change.

DESCRIPTION OF SYMBOLS 1 ... Sulfide solid battery 1m ... Negative electrode collector 1p ... Positive electrode collector 1x ... Positive electrode layer 1y ... Solid electrolyte layer 1z ... Negative electrode layer 2, 3 ... Control means 10, 20 ... Sulfide solid battery system

Claims (6)

A solid battery having a positive electrode layer and a negative electrode layer, and a solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer, and a control means capable of controlling a charge stop voltage of the solid battery,
LiNi _x Co _y Mn _z O ₂ (x + y + z = 1 and 0.32 <x, y, z <0.34) is used for the positive electrode layer, and a sulfide solid electrolyte is used for at least the solid electrolyte layer. ,
When the solid battery is charged, the charge stop voltage of the solid battery is controlled by the control means so that the charge is stopped at 4.3 V or less with reference to the potential at which graphite absorbs and releases lithium ions. Solid battery system. A solid battery having a positive electrode layer and a negative electrode layer, and a solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer, and a control means capable of controlling a discharge stop voltage of the solid battery;
LiNi _x Co _y Mn _z O ₂ (x + y + z = 1 and 0.32 <x, y, z <0.34) is used for the positive electrode layer, and a sulfide solid electrolyte is used for at least the solid electrolyte layer. ,
The discharge stop voltage of the solid battery is controlled by the control means so that the discharge is stopped at 3.4 V or higher with respect to the potential at which graphite absorbs and releases lithium ions during the discharge of the solid battery. Solid battery system. A solid battery having a positive electrode layer and a negative electrode layer, and a solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer, and a control means capable of controlling the charge stop voltage and the discharge stop voltage of the solid battery. ,
LiNi _x Co _y Mn _z O ₂ (x + y + z = 1 and 0.32 <x, y, z <0.34) is used for the positive electrode layer, and a sulfide solid electrolyte is used for at least the solid electrolyte layer. ,
The discharge voltage of the solid battery is controlled by the control means so that the discharge is stopped at 3.4 V or higher with respect to the potential at which graphite absorbs and releases lithium ions during the discharge of the solid battery, and
When the solid battery is charged, the charge stop voltage of the solid battery is controlled by the control means so that the charge is stopped at 4.4 V or less with reference to the potential at which graphite absorbs and releases lithium ions. Solid battery system. A method for controlling a solid state battery having a positive electrode layer and a negative electrode layer, and a solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer,
LiNi _x Co _y Mn _z O ₂ (x + y + z = 1 and 0.32 <x, y, z <0.34) is used for the positive electrode layer, and a sulfide solid electrolyte is used for at least the solid electrolyte layer. ,
Control of a sulfide solid state battery that controls a charge stop voltage of the solid state battery so that the charge is stopped at 4.3 V or less with respect to a potential at which graphite absorbs and releases lithium ions when the solid state battery is charged. Method. A method for controlling a solid state battery having a positive electrode layer and a negative electrode layer, and a solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer,
LiNi _x Co _y Mn _z O ₂ (x + y + z = 1 and 0.32 <x, y, z <0.34) is used for the positive electrode layer, and a sulfide solid electrolyte is used for at least the solid electrolyte layer. ,
Control of the sulfide solid state battery that controls the discharge stop voltage of the solid state battery so that the discharge is stopped at 3.4 V or higher with respect to the potential at which graphite absorbs and releases lithium ions during the discharge of the solid state battery. Method. A method for controlling a solid state battery having a positive electrode layer and a negative electrode layer, and a solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer,
LiNi _x Co _y Mn _z O ₂ (x + y + z = 1 and 0.32 <x, y, z <0.34) is used for the positive electrode layer, and a sulfide solid electrolyte is used for at least the solid electrolyte layer. ,
Controlling the discharge stop voltage of the solid battery so that the discharge is stopped at 3.4 V or higher with respect to the potential at which graphite absorbs and releases lithium ions during the discharge of the solid battery; and
Control of the sulfide solid state battery that controls the charge stop voltage of the solid state battery so that the charge is stopped at 4.4 V or less with respect to the potential at which graphite absorbs and releases lithium ions when the solid state battery is charged. Method.

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