JP2013041749A - Battery system - Google Patents

Abstract

A battery system including an electrolyte battery and capable of starting even at a low temperature of −30 ° C. or lower is provided.
The solid electrolyte has the formula Li _x M _y P _z S ₄ [wherein M is from Ge, Sb, Si, C, Sn, B, Al, Ga, In, Ti, Zr, V and Nb. X, y, and z represent atomic ratios, and satisfy x + my + 5z = 8 (m is the valence of M). And a peak at 2θ = 29.58 ° ± 0.50 ° in the X-ray diffraction measurement using CuKα ray, and the peak at 2θ = 29.58 ° ± 0.50 ° diffraction intensity of the _{I a,} the diffraction intensity of the peak position of 2θ = 27.33 ° ± 0.50 ° when the _{I B,} sulfide value of I B / _{I a} is less than 0.50 A battery system that combines a solid battery including a solid electrolyte and an electrolyte battery including an electrolyte as an electrolyte.
[Selection figure] None

Description

  The present invention relates to a battery system, and more particularly to a battery system that can be started even at a low temperature at which an electrolyte battery is difficult to operate by combining an electrolyte battery and a solid battery containing a specific sulfide solid electrolyte.

In recent years, electrolyte batteries, such as electrolyte lithium batteries, have been used in many fields because of their high voltage and high energy density. For this reason, the further performance improvement of an electrolyte battery is calculated | required.
In relation to the performance of the electrolyte battery, the ionic conductivity of the electrolyte solution decreases due to an increase in the viscosity of the electrolyte solution at a low temperature. Therefore, conventionally, a mixed solvent is used for the electrolyte solution to maintain the characteristics. However, there is a limit to the maintenance of characteristics by a mixed solvent, and a technique capable of suppressing a decrease in ionic conductivity at low temperatures has been studied.
On the other hand, a solid battery that does not use an electrolytic solution has been proposed, and the performance of the solid electrolyte used in the solid battery needs to be improved, and various studies have been made.

For example, Non-Patent Document 1 describes a sulfide solid electrolyte that is a crystalline Li ion conductor having a composition of Li _(4-x) Ge _(1-x) P _x S ₄ . As a specific example, the above formula shows that the Li ion conductivity is highest when x = 0.75, and that the Li ion conductivity is 2.2 × 10 ⁻³ S / cm at 25 ° C. .

  Patent Document 1 describes a power supply device in which a solid battery functioning at a high temperature and an electrolyte battery functioning at a low temperature are connected in parallel. As a specific example, in a power supply device in which an electrolyte battery using an electrolyte solution in which a lithium salt is dissolved in propylene carbonate and a solid lithium battery using a polymer solid electrolyte in which a lithium salt is dissolved in polyethylene oxide are connected in parallel, In the power supply device in which two solid electrolytes are connected in parallel, the discharge capacity at a temperature lower than 0 ° C. is almost equal to that of the electrolyte battery compared with the case where the discharge capacity is greatly reduced at 0 ° C. Yes.

Further, Patent Document 2 discloses a non-aqueous solution including a positive electrode including a lithium composite oxide as an active material, a negative electrode including graphite as an active material, an electrolytic solution in which LiPF ₆ is dissolved in an organic solvent as an electrolyte, and a separator. In the electrolyte lithium secondary battery, the ratio (volume%) of ethylene carbonate (x%), dimethyl carbonate (y%), and ethyl methyl carbonate (z%) as an organic solvent is 0 ≦ x ≦ 35, 10 ≦ y. A method for improving low-temperature discharge characteristics of a non-aqueous electrolyte lithium secondary battery satisfying ≦ 85, 5 ≦ z ≦ 80 is described. As a specific example, the discharge capacity can be reduced to about 0 V even at 0 ° C. depending on the selection of the composition ratio of the electrolytic solution, and the discharge capacity is reduced by about 45% at −20 ° C. at the optimum composition ratio. It has been shown that a non-aqueous electrolyte lithium secondary battery that can operate in a temperature range of from 0C to 80C is obtained.

JP 2003-282154 A JP 2004-342626 A

Journal of the Electrochemical Society, 148 (7) A742-A756 (2001)

However, according to these known techniques, it has been difficult to obtain a battery system that includes an electrolyte battery and can be started at a low temperature of 0 ° C. or lower.
Accordingly, an object of the present invention is to provide a battery system including an electrolyte battery and capable of starting even at a low temperature of 0 ° C. or lower.

As a result of intensive studies aimed at achieving the above object, the present inventors have been able to improve the low temperature characteristics to some extent by using a mixed solvent in the electrolytic solution. The present inventors have found that the essential solution of the decrease in conductivity has not been reached, and have further studied to complete the present invention.
Therefore, the present invention provides a solid electrolyte having the formula Li _x M _y P _z S _{4 wherein} M is Ge, Sb, Si, C, Sn, B, Al, Ga, In, Ti, Zr, V and It is an element selected from Nb, x, y, and z represent an atomic ratio, and satisfy x + my + 5z = 8 (m is the valence of M). And a peak at 2θ = 29.58 ° ± 0.50 ° in the X-ray diffraction measurement using CuKα ray, and the peak at 2θ = 29.58 ° ± 0.50 ° diffraction intensity of the _{I a,} the diffraction intensity of the peak position of 2θ = 27.33 ° ± 0.50 ° when the _{I B,} sulfide value of I B / _{I a} is less than 0.50 The present invention relates to a battery system in which a solid battery including a solid electrolyte and an electrolyte battery including an electrolyte as an electrolyte are combined.

  According to the present invention, it is possible to obtain a battery system including an electrolyte battery and capable of starting at a low temperature of 0 ° C. or lower, for example, −30 ° C. or lower.

FIG. 1 is a schematic diagram of a battery system according to an embodiment of the present invention. FIG. 2 is an X-ray diffraction spectrum showing characteristics of an example of a solid electrolyte that can be applied to the solid battery used in the battery system according to the embodiment of the present invention. FIG. 3 is an X-ray diffraction spectrum showing characteristics of a solid electrolyte that cannot be applied to the present invention. FIG. 4 is a graph showing the temperature dependence of the diffusion coefficient of the solid electrolyte in the embodiment of the present invention and the solid electrolyte that cannot be applied to the present invention. FIG. 5 is a graph showing a comparison of the temperature dependence of the Li ion conductivity of a solid electrolyte in an embodiment of the present invention and a solid electrolyte that cannot be applied to the present invention. FIG. 6 is a graph showing a colle-coll plot (25 ° C.) of the all-solid-state batteries obtained in the examples and comparative examples. FIG. 7 is a graph showing Arrhenius plots of all solid state batteries obtained in Examples and Comparative Examples.

In particular, in the present invention, the following embodiments can be mentioned.
1) The battery system in which the solid state battery and the electrolyte battery are connected in parallel.
2) The battery system, wherein the solid electrolyte has a Li ion conductivity of 5 × 10 ⁻⁴ S / cm or more at −30 ° C.
3) The solid electrolyte has the formula Li _(4-a) M _(1-a) P _a S ₄ [wherein M is an element selected from Ge, Si and C, and a is 0.4 ≦ a ≦ 0.8 is satisfied. ] The battery system having the composition
4) The battery system in which the solid state battery is connected to a heater for heating the electrolyte battery.

In the present invention, the solid electrolyte has the formula Li _x M _y P _z S ₄ [wherein M is Ge, Sb, Si, C, Sn, B, Al, Ga, In, Ti, Zr, V, and Nb. X, y, and z represent an atomic ratio, and satisfy x + my + 5z = 8 (m is the valence of M). And a peak at 2θ = 29.58 ° ± 0.50 ° in the X-ray diffraction measurement using CuKα ray, and the peak at 2θ = 29.58 ° ± 0.50 ° diffraction intensity of the _{I a,} the diffraction intensity of the peak position of 2θ = 27.33 ° ± 0.50 ° when the _{I B,} sulfide value of I B / _{I a} is less than 0.50 The battery system needs to be a combination of a solid battery containing a solid electrolyte and an electrolyte battery containing an electrolyte as an electrolyte, whereby the solid electrolyte is high at a low temperature of 0 ° C. or lower, for example, −30 ° C. or lower. By having Li ion conductivity, the combined battery as a whole can be started at a low temperature of 0 ° C. or lower, for example, −30 ° C. or lower.

Hereinafter, embodiments of the present invention will be described in detail with reference to FIGS.
As shown in FIG. 1, a battery system 1 according to an embodiment of the present invention includes a solid battery 2 including a solid electrolyte according to the present invention and an electrolyte battery 3 including an electrolyte as an electrolyte connected in parallel. The temperature of the electrolyte battery detected by the temperature sensor 4 provided in the battery 3 is sent to the battery ECS 5, and the temperature of the electrolyte battery 3 is determined from the relationship between the electrolyte temperature input in advance and the ionic conductivity. When it is determined that it is necessary to raise the temperature, the solid battery 7 including the solid electrolyte is connected to the heater 8 in order to warm the electrolyte battery 3 by applying heat 6 based on an instruction from the battery ECS 5. .
In FIG. 1, the electrolyte battery and the solid battery are connected in parallel, but may be connected in series.

Although only one electrolyte battery is shown in FIG. 1, the number of electrolyte batteries can be any number, and a plurality of electrolyte batteries can be connected in parallel or in series. .
According to the battery system of the above embodiment, the Li ion conductivity of the solid electrolyte contained in the solid battery in the present invention is high even under a low temperature environment, for example, 0 ° C. or lower, for example −30 ° C. or lower. Thus, it is possible to discharge only with the solid battery until it is determined that the temperature of the electrolyte battery has risen to reach a temperature that can be started, and when the temperature of the electrolyte battery rises, the battery can be discharged with the electrolyte battery and the solid battery.
When the temperature of the electrolyte battery rises, warming of the electrolyte battery by the heater 7 connected to the solid battery 6 is stopped by an instruction from ECS.

The solid electrolyte used for the solid state battery in the battery system according to the embodiment of the present invention has the formula: Li _x M _y P _z S ₄ [wherein, M is Ge, Sb, Si, C, Sn, B, Al, Ga, It is an element selected from In, Ti, Zr, V and Nb, x, y and z represent atomic ratios, and satisfy x + my + 5z = 8 (m is the valence of M). And a peak at a position of 2θ = 29.58 ° ± 0.50 ° in the X-ray diffraction measurement using CuKα ray as shown in FIG. The value of I _B / I _A when the diffraction intensity of the peak at 58 ° ± 0.50 ° is I _A and the diffraction intensity of the peak at 2θ = 27.33 ° ± 0.50 ° is I _B. Is a sulfide solid electrolyte in which is less than 0.50.
The sulfide solid electrolyte may have a Li ion conductivity of preferably 10 ⁻³ S / cm or more at −30 ° C. and 10 ⁻⁴ S / cm or more at −70 ° C.
Therefore, the solid battery to which the solid electrolyte is applied can be used at −70 ° C. or higher.

On the other hand, even if the conventionally known sulfide solid electrolyte has the composition represented by the above formula, as shown in FIG. 3, 2θ = 29.58 in the X-ray diffraction measurement using CuKα ray. ° has a peak at the position of ± 0.50 °, the diffraction intensity of the peak of the 2θ = 29.58 ° ± 0.50 ° and _{I a,} the position of 2θ = 27.33 ° ± 0.50 ° the diffraction intensity of the peak when the _{I B,} the value of I B / _{I a} is a solid electrolyte is 0.50 or more.
The above conventional sulfide solid electrolyte, Li ion conductivity, but is 10 -3 ^{S / cm} or more at room temperature, but the value at -73 ° C. is not measured, 10 from the slope of the curve ^- It can be ⁷ S / cm or less.

The solid electrolyte in the present invention is preferably represented by the formula: Li _(4-a) M _(1-a) P _a S ₄ [wherein M is an element selected from Ge, Si and C, and x is 0.4 ≦ a ≦ 0.8 is satisfied. And has a peak at a position of 2θ = 29.58 ° ± 0.50 ° in X-ray diffraction measurement using CuKα ray, and the above 2θ = 29.58 ° ± 0.50 °. The value of I _B / I _A is less than 0.50 where the diffraction intensity of the peak at IA is I _A and the diffraction intensity of the peak at 2θ = 27.33 ° ± 0.50 ° is I _B. Examples thereof include sulfide solid electrolytes, preferably those satisfying 0.4 ≦ a in the above formula, particularly those satisfying 0.5 ≦ a, and those satisfying a ≦ 0.8 are preferable.

The method for producing the sulfide fixed electrolyte will be described for the case where M = Ge in the formula: Li _(4-a) M _(1-a) P _a S ₄ .
Li ₂ S, P ₂ S ₅ and GeS ₂ are mixed in an inert gas atmosphere, and the resulting mixture is subjected to a solid phase reaction under vacuum to obtain a crystalline material, and the obtained crystalline material is mixed in a mill After pulverization, it can be obtained by heating at a temperature of about 400 to 700 ° C.
In the formula Li _(4-a) Ge _(1-a) P _a S ₄ , the ratio (molar ratio) of the three kinds of compounds can be appropriately selected so that x is in the preferred range.

In the manufacturing method, by adding a step of heating again after pulverizing the crystalline material, it becomes possible to further increase the crystallinity of the crystalline material, and 2θ = in X-ray diffraction measurement using CuKα rays. It has a peak at the position of 29.58 ° ± 0.50 °, the diffraction intensity of the peak of the 2θ = 29.58 ° ± 0.50 ° and _{I a, 2θ = 27.33 ° ±} 0.50 ° _A sulfide solid electrolyte having a value of I _B / I _A of less than 0.50 can be obtained when the diffraction intensity of the peak at the position of I is I _B.

Applying the above production method, the sulfide-fixed electrolyte in the present invention is obtained in the same manner when M = Sb, Si, C, Sn, B, Al, Ga, In, Ti, Zr, V, or Nb. Can do. That is, considering the valence of each element, 0.4 ≦ a, particularly 0.5 ≦ a is satisfied in the formula Li _(4-a) M _(1-a) P _a S ₄ , and a ≦ 0 And a sulfide solid electrolyte containing these elements can be obtained from Li ₂ S, P ₂ S ₅ and sulfides of each element satisfying.

As shown in FIG. 4, the solid electrolyte in the present invention is compared with Li ₇ P ₃ S ₁₁ , αLi ₃ PS ₄ , βLi ₃ PS ₄ , and γLi ₃ PS ₄ which are conventionally known solid electrolytes at room temperature. It is understood that the diffusion coefficient is about 10 to 1000 times, and the low temperature characteristics are very good as compared with these materials at a low temperature of 0 ° C. or lower, for example, −30 ° C. or lower.
In addition, as shown in FIG. 5, a conventionally known solid electrolyte exhibits a relatively high Li ion conductivity at a temperature of room temperature or higher, but the Li ion conductivity decreases significantly as the temperature decreases, compared to this. It is understood that the solid electrolyte in the present invention maintains a relatively high Li ion conductivity even at a low temperature of 0 ° C. or lower, such as −30 ° C. or lower, particularly −73 ° C.

  Further, from FIG. 5, in an electrolytic solution containing a mixed solvent of ethylene carbonate and propylene carbonate, which is an example of a conventional electrolytic solution, Li ion conductivity from around −30 ° C. due to an increase in viscosity, freezing, etc. as the temperature decreases. It is understood that it falls extremely. In the case of the electrolytic solution, since the counter ion of Li ion also moves simultaneously, the actual amount of Li ion movement is half of the amount shown in FIG. Although one type of electrolytic solution is shown in FIG. 5, the same phenomenon can occur with other electrolytic solutions.

  On the other hand, the solid electrolyte in the present invention has high Li ion conductivity even when the temperature is lowered, and only Li ions can move, so the Li ion conductivity is the same as the electrolyte. However, the net charge transfer can be doubled.

The solid state battery in the battery system of the present invention includes a positive electrode as a main constituent material, and a solid electrolyte and a negative electrode in the present invention.
The positive electrode may have a positive electrode forming material layer including a positive electrode active material laminated on a positive electrode current collector.
The positive electrode current collector can be made of, for example, a metal material such as aluminum, nickel, or stainless steel.

The positive electrode forming material used to form the positive electrode can be the same as that used for a positive electrode in a general solid battery, for example, at least a positive electrode active material, and usually a solid material. It can be set as the positive electrode mixture which has electrolyte, a Li ion conductivity improvement material, and a binder further as needed.
As the positive electrode active material is not particularly limited, for example _{LiCoO 2, LiMn 2 O 4,} Li 2 NiMn 3 O 8, LiVO 2, LiCrO 2, LiFePO 4, LiCoPO 4, LiNiO 2, LiNi 1/3 Co 1 / ₃ Mn _1/3 O _{2 and the} like can be mentioned, among which LiNi _1/3 Co _1/3 Mn _1/3 O ₂ and LiCoO ₂ are preferred.
Examples of the solid electrolyte include the solid electrolytes described above.

Examples of the Li ion conductivity improver include carbon materials such as carbon black, acetylene black or ketjen black, carbon nanotubes, carbon nanofibers, fullerenes, etc., alone or in combination.
Examples of the binder include polymer materials such as polyaniline, polythiophene styrene butadiene rubber (SBR), polyacrylate, and polyvinylidene fluoride (PVdF).

  The thickness of the solid electrolyte layer is not particularly limited as long as it can have a desired energy density without being short-circuited. For example, it is in the range of 0.1 μm to 100 μm, and in particular, 0.1 μm to 50 μm. It is preferable that it is a thin layer within the range. Examples of the method of forming the solid electrolyte layer include a method of uniaxial compression molding of a powdered solid electrolyte.

The negative electrode may be formed on a surface of a solid electrolyte layer where the positive electrode is not formed.
As a negative electrode forming material used for forming such a negative electrode, for example, it has at least a negative electrode active material, usually further contains a solid electrolyte, and further contains a binder, a conductive material, and Li ions as necessary. It can be set as the negative mix which has a conductivity improving material.

There is no restriction | limiting in particular as said negative electrode active material, For example, a metal type active material and a carbon type active material can be mentioned. Examples of the metal active material include In, Al, Si, and Sn. The metal active material may be an inorganic oxide active material such as Li ₄ Ti ₅ O ₁₂ . On the other hand, examples of the carbon-based active material include graphite, mesocarbon microbeads (MCMB), graphite such as highly oriented graphite (HOPG), hard carbon, and soft carbon. Of these, graphite particles are particularly preferred. Graphite particles (eg, graphite) are excellent in conductivity because they can suitably occlude lithium ions as charge carriers.

The binder may be the same as the binder used in the negative electrode of a general lithium ion secondary battery, and various polymer materials that can function as a binder in the positive electrode component are preferably exemplified. .
Examples of the conductive material include carbon materials, metals that are difficult to alloy with lithium, conductive polymer materials, and the like, and carbon materials are preferred. As the carbon material, graphite, carbon black, carbon nanotube, carbon nanofiber, fullerene and the like can be used alone or in combination of two or more.
Examples of the Li ion conductivity improving material include the same materials as those used for the positive electrode forming material described above.

The negative electrode is usually laminated with a negative electrode current collector.
Examples of the negative electrode current collector include copper or an alloy containing copper as a main component. The shape of the negative electrode current collector is not particularly limited because it can vary depending on the shape of the solid state battery, and may be various forms such as a rod shape, a plate shape, a sheet shape, a foil shape, and a mesh shape. A copper foil having a thickness of about 5 to 100 μm is suitably used as the negative electrode current collector of the solid battery used as a high output power source for mounting on vehicles.

  The solid battery according to the present invention has a power generation element in which a positive electrode, a solid electrolyte layer, and a negative electrode are laminated as main constituents. Usually, an exterior covering the periphery of a unit cell including the power generation element and a current collector. The body may have an extraction electrode.

The exterior body is not particularly limited as long as it can cover the periphery of the solid unit cell.
The material of the exterior body is not particularly limited as long as it has insulating properties, and examples thereof include epoxy resins, polybutadiene resins, and the like.
The take-out electrode may be any electrode that has conductivity, and may be the same as that generally used for all-solid-state batteries.
Specific examples of the material for such an extraction electrode include stainless steel (SUS).
Examples of the shape include a foil shape and a lead shape.

Examples of the shape of the solid battery include a coin type, a laminate type, a cylindrical type, and a square type.
Moreover, the manufacturing method of the solid battery of this invention can use the method similar to the manufacturing method of a general solid battery except using the solid electrolyte in this invention. For example, the solid battery in the present invention can be manufactured by sequentially pressing the material constituting the positive electrode layer, the material constituting the solid electrolyte layer, and the material constituting the negative electrode layer.

As an electrolyte battery containing an electrolyte as an electrolyte in the present invention, any electrolyte battery, for example, a known electrolyte battery can be used.
According to the present invention, a battery system comprising a solid battery containing the sulfide solid electrolyte as a solid electrolyte in the present invention and an electrolyte battery containing an electrolyte as an electrolyte includes an electrolyte battery at -30 ° C or lower. Can be started at low temperatures.

Examples of the present invention will be described below.
The following examples are for illustrative purposes only and are not intended to limit the invention.
In each of the following examples, the physical properties of the electrolyte were measured by the following methods. Note that the following measurement methods and measurement devices are examples, and measurement methods and measurement devices that are considered equivalent by those skilled in the art can be used as well.
1) X-ray diffraction measurement method The solid electrolyte arbitrarily selected was measured using CuKα rays using the following apparatus.
Line diffraction measurement device: Rigaku Corporation, MiniFlex II
2) Diffusion coefficient measurement method: ⁶ Li diffusion in a ⁷ Li sample can be measured by neutron radiography.

3) Measurement of Li ion conductivity:
In a glove box in an argon atmosphere, an appropriate amount of the sample was weighed, put into a polyethylene terephthalate tube (inner diameter: 10 mm, outer diameter: 30 mm, height: 20 mm), and sandwiched between carbon tool steel S45C anvil powder molding jigs from above and below. . Next, it pressed (110 Mpa) using the uniaxial press, and the pellet with a diameter of 10 mm was shape | molded. Subsequently, about 15 mg of gold powder was placed on both sides of the pellet, uniformly deposited on the surface of the pellet, pressed and molded by pressing (550 MPa), and the pellet was placed in a sealed electrochemical cell capable of maintaining an argon atmosphere.
Using the obtained pellet, as a frequency response analyzer FRA (Frequency Response Analyzer), using an impedance / gain phase analyzer (solartron 1260) manufactured by Solartron, AC voltage ~, frequency range, integration time 0.2 seconds, Temperature: Measurement was started from the high frequency region in the range of 100 to -73 ° C. The measurement was performed using Zplot as the measurement software and Zview as the analysis software.

Example 1
1) Synthesis of solid electrolyte Li ₂ S (Nippon Kagaku Kogyo Co., Ltd.), P ₂ S ₅ (Aldrich Co., Ltd.) and GeS ₂ (High Purity Chemical Research Laboratory) are used as starting materials, and the formula: Li _(4-x) M _{( 1-x)} Each component is weighed at a ratio of x = 2/3 in P _x S ₄ to obtain a crystalline material by a solid phase reaction under vacuum, and the obtained crystalline material is mixed and pulverized by a mill Then, a sulfide solid electrolyte (shape: powder) was obtained by heating at 550 ° C. for 8 hours.

X-ray diffraction measurement using CuKα rays was performed on the obtained solid electrolyte.
Assuming that the diffraction intensity of the peak at 2θ = 29.58 ° ± 0.50 ° is I _A and the diffraction intensity of the peak at the position of 2θ = 27.33 ° ± 0.50 ° is I _B , I _B / I _A = 0.
Moreover, Li ion conductivity at room temperature (25 ° C.) = 1.2 × 10 ⁻² S / cm.
Moreover, the temperature dependence of Li ion conductivity in 100-73 degreeC is shown in FIG.

2) Production of all-solid-state battery Positive electrode mixture LiCoO ₂ (Toda Kogyo Co., Ltd.) coated with LiNbO ₃ and the above solid electrolyte were weighed in a mass ratio of 70:30, mixed by a test tube mixer, and the positive electrode mixture was mixed. Produced.
Negative electrode mixture Li ₄ Ti ₅ O ₁₂ , the above solid electrolyte, and acetylene black (Electrochemical Co., Ltd.) were weighed in a mass ratio of 27.3: 63.6: 9.1, mixed with agate, and the negative electrode mixture was mixed. Produced.
Battery 65 mg of the above solid electrolyte was taken and placed in a cylinder made by Macor, and both ends were pressed at 1 ton / cm ² to form an electrolyte layer. Next, 16 mg of the positive electrode mixture was taken, placed on the electrolyte layer, and pressed at 1 ton / cm ² . Next, 40 mg of the negative electrode mixture was taken, put on the opposite side of the electrolyte layer from the positive electrode, and pressed at 4 ton / cm ² to produce an all-solid battery.
Both ends of the battery were sandwiched with SUS pins to form a current collector.

Comparative Example 1
Li ₂ S (Nippon Kagaku Kogyo) and P ₂ S ₅ (Aldrich) were weighed in a molar ratio of 75:25 and mixed with agate, then 1 g was taken into a zirconia pot (45 mL), and ZrO ₂ balls (10 φ10 pieces) were taken. ) At 370 rpm for 40 hours using a planetary ball mill (Fritch P7) to obtain 75Li ₂ S-25P ₂ S ₅ glass as a solid electrolyte. The ionic conductivity of this electrolyte was ⁴ × 10 ⁻⁴ S / cm at room temperature.
An all-solid battery was produced in the same manner as in Example 1 except that the electrolyte was changed to 75Li ₂ S-25P ₂ S ₅ .

Measurement of AC impedance The all-solid-state battery produced in Example 1 and Comparative Example 1 was subjected to one cycle of low-current charge / discharge in the range of 2.6 to 1 V with a charge / discharge device (manufactured by Toyo Tekinica), and then charged with current. To 2.6V.
After adjusting the voltage to 2.6 V, the battery impedance was measured in the range of −30 ° C. to 60 ° C. by measuring the AC impedance of the battery. For measurement, an impedance gain phase analyzer (Solatron 1260) manufactured by Solartron was used.
At each measurement, low current charging was performed with galvanostatic (0.01 mA / cm ² ) to eliminate the voltage dependence of resistance.
A coll-coll plot was obtained by AC impedance measurement.
The obtained result is shown in FIG.
As the resistance value, the value of R1 in FIG. 6 was adopted.
The temperature dependence of the resistance value R1 is shown in FIG.
FIG. 7 shows that the resistance of the battery is smaller when a solid electrolyte having higher ion conductivity is used. Moreover, the resistance value is small even at low temperatures, and it has been found that when a solid electrolyte having a crystal structure suitable for ion conduction is used in an all-solid battery, the output at low temperatures can be improved.

It is known that the relationship represented by the following Nernst-Einstein equation is established between the self-diffusion coefficient D and the conductivity σ (Li ion conductivity).
σ = [(fn (Ze) ² ) / (k _B T)] D
[K _B : Boltzban constant, T: absolute temperature, f: relationship coefficient, n: carrier concentration, Z: valence, e: elementary electric charge, σ: conductivity, D: diffusion coefficient]
From the above equation, the simulation result using the molecular dynamics calculation method was consistent with the experiment.
From the above, the simulation result using the molecular dynamics calculation method was consistent with the experiment. Moreover, since the model which fixed the structure is used, it turns out that a structure is deeply involved in conductivity.

Comparative Examples 2-18
1) Measurement of physical properties of known sulfide solid electrolyte Li ₇ P ₃ S ₁₁ , αLi ₃ PS ₄ , βLi ₃ PS _4, and γLi ₃ PS ₄ , which are conventionally known solid electrolytes, were measured for diffusion coefficients. The results are summarized in FIG.
The Li ion conductivity at 25 ° C. is shown below.
Li ₇ P ₃ S ₁₁ : 3.2 × 10 ⁻³ S / cm
βLi ₃ PS ₄ : 5.0 × 10 ⁻⁴ S / cm
γLi ₃ PS ₄ : 3.0 × 10 ⁻⁷ S / cm
The diffusion coefficient measured at 1327 to −73 ° C. for the obtained solid electrolyte is shown in FIG. 4 together with other results.
2) Measurement of conductivity of known electrolyte and electrolyte The conductivity of a known electrolyte and electrolyte was measured. The results are summarized in FIG.

  4 and 5, the solid electrolyte in the present invention can have high Li ion conductivity at room temperature to −73 ° C., particularly 0 to −73 ° C., particularly −30 to −73 ° C. The solid battery used can operate at a temperature of 0 ° C. or lower, for example −30 ° C. or lower, preferably −73 ° C. or higher, and the electrolyte battery and an all solid battery including this solid electrolyte are connected in parallel. It is understood that the battery system can start even at a low temperature where the electrolyte battery is difficult to operate.

  According to the present invention, it is possible to obtain a battery system that can be started even at a low temperature at which an electrolyte battery is difficult to operate by combining an electrolyte battery and a solid battery containing a specific sulfide solid electrolyte.

DESCRIPTION OF SYMBOLS 1 Battery system of embodiment of this invention 2 Solid battery containing solid electrolyte in this invention 3 Electrolyte battery containing electrolyte as electrolyte 4 Temperature sensor 5 Battery ECS
6 Heat 7 Solid Battery Containing Solid Electrolyte in Present Invention 8 Heater Curve 1: Li ₁₀ GeP ₂ S ₁₂ Solid Electrolyte Curve 2: Glass-Ceramic Electrolyte Li7P3S11
Curve 3: Organic electrolyte 1M LiPF ₆ / EC-PC (50:50 vol.%)
Curve 4: glass electrolyte _{Li 2 S-SiS 2 -Li 3} PO 4
Curve 5: Ionic liquid electrolyte 1M LiP ₃ F ₄ / EMIBF ₄
Curve 6: doped Li ₃ N
Curve 7: Li _3.25 Ge _0.25 P _0.75 S ₄
Curve 8: Gel electrolyte 1M LiPF ₆ + PVDF-HFP (10 wt%)
Curve 9: LiSiCON: Li ₁₄ Zn (GeO ₄ ) ₄
Curve 10: Li ₃ N
Curve 11: La _0.5 Li _0.5 TiO ₃
Curve 12: LiPON
Curve 13: Li-βAlumina
Curve 14: Li _3.6 Si _0.6 P _0.4 O ₄
Curve 15: glass electrolyte _Li 2 _S-P 2 _{S 5}
Curve 16: Molecular electrolyte PEO-LiClO ₄ (10 wt.% TiO ₂ )
Curve 17: polymer electrolyte LiN (CF ₃ SO ₂ ) ₂ / (CH ₂ CH ₂ O) _n (n = 8)

Claims (5)

The solid electrolyte has the formula: Li _x M _y P _z S ₄ [wherein M is an element selected from Ge, Sb, Si, C, Sn, B, Al, Ga, In, Ti, Zr, V and Nb. X, y, and z represent atomic ratios, and satisfy x + my + 5z = 8 (m is the valence of M). )] And has a peak at a position of 2θ = 29.58 ° ± 0.50 ° in X-ray diffraction measurement using CuKα ray, and the above 2θ = 29.58 ° ± 0.50 °. Sulfide having a value of I _B / I _A of less than 0.50, where the diffraction intensity of the peak is I _A and the diffraction intensity of the peak at the position of 2θ = 27.33 ° ± 0.50 ° is I _B A battery system in which a solid battery including a solid electrolyte and an electrolyte battery including an electrolyte as an electrolyte are combined.   The battery system according to claim 1, wherein the solid battery and the electrolyte battery are connected in parallel. The battery system according to claim 1, wherein the solid electrolyte has a Li ion conductivity of 5 × 10 ⁻⁴ S / cm or more at −30 ° C. The solid electrolyte has the formula: Li _(4-a) M _(1-a) P _a S ₄ [wherein M is an element selected from Ge, Si and C, and a is 0.4 ≦ a ≦ 0. .8 is satisfied. The battery system according to any one of claims 1 to 3, which has a composition of   The battery system according to claim 1, wherein the solid state battery is connected to a heater for heating the electrolyte battery.

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