JP5970284B2 - All solid battery - Google Patents

Description

  The present invention relates to an all-solid battery.

  In recent years, demand for safe and high-performance secondary batteries has increased due to the development of wireless electronic device technologies such as portable devices, the development of natural energy storage technologies, and the spread of electric vehicles and the like. As an example of such a secondary battery, conventionally, in a lithium secondary battery, a configuration using an organic electrolyte layer in which a lithium salt is dissolved in a flammable organic solvent is known as an electrolyte layer. However, in a battery using a liquid organic electrolyte layer, there is a possibility that the organic electrolyte layer leaks or ignites, and further improvement in safety has been desired. Thus, in recent years, in order to ensure higher safety, all-solid-state batteries using solid electrolyte layers instead of liquid electrolyte layers have been developed. As solid electrolyte layers of all solid state batteries, oxide-based lithium ion conductive solid electrolytes, sulfide-based lithium ion conductive solid electrolytes, and the like have been proposed (see, for example, Patent Documents 1 to 3).

JP 2010-45019 A JP 2009-140910 A JP 2012-48890 A

  Among the solid electrolytes mentioned above, the sulfide-based lithium ion conductive solid electrolyte can generate hydrogen sulfide by reacting with moisture. Therefore, in order to improve safety, oxide-based lithium ion conductive It is desirable to use a solid electrolyte. On the other hand, when the solid electrolyte layer and the pair of electrodes contain an oxide-based lithium ion conductive solid electrolyte, although safety is improved, it is difficult to make good contact between the solid electrolyte layer and the electrode, Battery performance may be reduced. For example, if the electrical contact state is insufficient at the interface between the solid electrolyte layer and the electrode, the internal performance of the battery is increased, or the battery performance is deteriorated such that a sufficient capacity for functioning as a battery cannot be secured. There is a case. As a technique for improving the contact between the solid electrolyte layer and the electrode, a technique for sintering a laminate of the solid electrolyte layer and the electrode at a high temperature (for example, 600 ° C. to 1000 ° C.) is known. However, when the above laminate contains an oxide-based lithium ion conductive solid electrolyte, when the laminate is exposed to a high temperature environment, the constituent materials of the solid electrolyte layer and the electrode react to change the battery characteristics. Battery performance may be reduced. Therefore, an all-solid battery having higher battery performance while ensuring safety has been desired. In addition, in the conventional all-solid-state battery, it has been desired to simplify the manufacturing process, facilitate the manufacture, and improve safety not only when the battery is manufactured but also when the battery is used.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following aspects.

(1) According to the 1st form of this invention, an all-solid-state battery provided with the positive electrode layer, the negative electrode layer, and the electrolyte layer comprised by an oxide type lithium ion conductive solid electrolyte is provided. . In this all solid state battery, the positive electrode layer is formed by mixing sulfur (S), which is a positive electrode active material, a sulfide-based lithium ion conductive solid electrolyte, and conductive carbon. According to this form of the all-solid-state battery, since the positive electrode layer includes the sulfide-based lithium ion conductive solid electrolyte, the electrolyte layer constituted by the oxide-based lithium ion conductive solid electrolyte and the positive electrode active material sulfur The battery performance can be improved by combining.

(2) In the all-solid-state battery according to the first embodiment, the sulfide-based lithium ion conductive solid electrolyte is represented by the following formula (1): XLi ₂ S- (1-X) P ₂ S ₅ (1) (Wherein X is 0.65 ≦ X ≦ 0.80); and may be a solid electrolyte represented by: According to this form of the all-solid-state battery, it becomes easy to ensure good contact between the solid electrolyte layer and the electrode by setting the softness of the sulfide-based lithium ion conductive solid electrolyte to a desired state.

(3) In the all-solid-state battery according to the first aspect, the ratio of the weight of the sulfur to the total weight of the sulfur and the sulfide-based lithium ion conductive solid electrolyte in the positive electrode layer is A / 100. The value of A may be 30 ≦ A ≦ 70. According to the all solid state battery of this embodiment, the performance of the all solid state battery can be improved.

(4) In the all-solid-state battery of the first aspect, the ratio of the weight of the sulfur to the total weight of the sulfur and the sulfide-based lithium ion conductive solid electrolyte in the positive electrode layer is A / 100. The value of A is 30 ≦ A ≦ 55, and the ratio of the weight of the conductive carbon to the total weight of the sulfur and the sulfide-based lithium ion conductive solid electrolyte is B / 100. The value of B may be 3 ≦ B ≦ 100. According to the all solid state battery of this embodiment, the performance of the all solid state battery can be improved.

(5) In the all solid state battery of the first aspect, the ratio of the weight of the sulfur to the total weight of the sulfur and the sulfide-based lithium ion conductive solid electrolyte in the positive electrode layer is A / 100. The value of A is 55 <A ≦ 70, and the ratio of the weight of the conductive carbon to the total weight of the sulfur and the sulfide-based lithium ion conductive solid electrolyte is B / 100. The value of B may be 4 ≦ B ≦ 20. According to the all solid state battery of this embodiment, the performance of the all solid state battery can be improved.

(6) In the all solid state battery according to the first aspect, the conductive carbon may be ketjen black. According to the all solid state battery of this embodiment, the performance of the all solid state battery can be improved.

(7) According to the 2nd form of this invention, an all-solid-state battery provided with the positive electrode layer, the negative electrode layer, and the electrolyte layer comprised by an oxide type lithium ion conductive solid electrolyte is provided. . In this all solid state battery, the positive electrode layer is formed by mixing a metal sulfide, which is a positive electrode active material, and a sulfide-based lithium ion conductive solid electrolyte. According to this form of the all-solid-state battery, since the positive electrode layer includes the sulfide-based lithium ion conductive solid electrolyte, the electrolyte layer constituted by the oxide-based lithium ion conductive solid electrolyte and the metal that is the positive electrode active material The battery performance can be improved by combining the sulfide.

(8) In the all-solid-state battery according to the second aspect, the positive electrode active material may be selected from FeS ₂ and FeS. According to the all solid state battery of this embodiment, the performance of the all solid state battery can be improved.

(9) In the all-solid-state battery according to the second aspect, the sulfide-based lithium ion conductive solid electrolyte has the following formula (1): XLi ₂ S- (1-X) P ₂ S ₅ (1) (Wherein X is 0.65 ≦ X ≦ 0.80); and may be a solid electrolyte represented by: According to this form of the all-solid-state battery, it becomes easy to ensure good contact between the solid electrolyte layer and the electrode by setting the softness of the sulfide-based lithium ion conductive solid electrolyte to a desired state.

(10) In the all-solid-state battery according to the second aspect, the positive electrode active material is FeS ₂ ; in the positive electrode layer, the total weight of the positive electrode active material and the sulfide-based lithium ion conductive solid electrolyte When the ratio of the weight of the positive electrode active material to A / 100 is expressed as A / 100, the value of A may be 40 ≦ A ≦ 80. According to the all solid state battery of this embodiment, the performance of the all solid state battery can be improved.

(11) In the all-solid-state battery of the second aspect, the positive electrode layer is further mixed with conductive carbon; in the positive electrode layer, the positive electrode active material and the sulfide-based lithium ion conduction When the ratio of the weight of the conductive carbon to the total weight of the conductive solid electrolyte is expressed as B / 100, the value of B may be B ≦ 40. According to the all solid state battery of this embodiment, the performance of the all solid state battery can be improved.

(12) In the all-solid-state battery of the first embodiment, constant current charge / discharge was performed a plurality of times at 25 ° C. with a current density of 0.064 mA / cm ² , a discharge cut voltage of 1 V, and a charge cut voltage of 3 V. The discharge capacity at the second cycle may be 200 mA / g or more. According to this form of the all solid state battery, high battery performance can be ensured.

(13) In the all-solid-state battery according to the second embodiment, constant current charge / discharge is performed a plurality of times at 25 ° C. with a current density of 0.064 mA / cm ² , a discharge cut voltage of 0.3 V, and a charge cut voltage of 3 V. The discharge capacity at the second cycle when performed may be 200 mA / g or more. According to this form of the all solid state battery, high battery performance can be ensured.

(14) In the all-solid-state battery according to the first or second embodiment, the oxide-based lithium ion conductive solid electrolyte may have the following formula (2): Li _{1 + Y} Al _Y M _2-Y (PO ₄ ) ₃ (2); (wherein M is at least one selected from the group consisting of germanium, titanium, hafnium, and zirconium, and Y is 0 <Y <1); It is good also as being. According to the all solid state battery of this embodiment, the performance of the all solid state battery can be improved.

(15) In the all-solid-state battery according to the first or second aspect, in the oxide-based lithium ion conductive solid electrolyte, M in the formula (2) may be germanium. According to the all solid state battery of this embodiment, the performance of the all solid state battery can be improved.

(16) In the all-solid-state battery according to the first or second aspect, the oxide-based lithium ion conductive solid electrolyte may have Y = 0.5 in the formula (2). According to the all solid state battery of this embodiment, the performance of the all solid state battery can be improved.

  The present invention can be implemented in various forms other than the above. For example, it can be realized in the form of a laminate of an electrolyte layer and an electrode, a manufacturing method of an all-solid battery, or an electronic device in which the all-solid battery is mounted as a power source.

It is sectional drawing showing schematic structure of an all-solid-state battery. It is sectional drawing showing schematic structure of an all-solid-state battery. It is a figure showing the result of having compared the composition and performance of each sample. It is a figure showing the result of having compared the composition and performance of each sample. It is explanatory drawing which shows the result of having performed charging / discharging measurement. It is explanatory drawing which shows the result of having performed charging / discharging measurement. It is explanatory drawing which shows the result of having performed charging / discharging measurement. It is explanatory drawing which shows the result of having performed charging / discharging measurement. It is explanatory drawing which put together the relationship between the addition amount of electroconductive carbon, and discharge capacity. It is explanatory drawing which put together the relationship between the mixing rate of iron sulfide and discharge capacity. It is explanatory drawing which put together the relationship between the addition amount of electroconductive carbon, and discharge capacity.

A. First embodiment:
A-1: Configuration of all solid state battery:
FIG. 1 is a cross-sectional view illustrating a schematic configuration of an all solid state battery 10 according to a first embodiment of the present invention. As shown in FIG. 1, the all solid state battery 10 includes a battery body 15 in which the layers 20, 30, and 40 are stacked, and a pair of current collectors 50 and 60 that sandwich the battery body 15 on both sides.

  The battery body 15 includes a solid electrolyte layer 40, a positive electrode layer 20 formed on one surface of the solid electrolyte layer 40, and a negative electrode layer 30 formed on the other surface of the solid electrolyte layer 40. Prepare. The current collectors 50 and 60 are plate members having conductivity. The current collectors 50 and 60 are formed of, for example, a conductive metal material selected from nickel (Ni), titanium (Ti), iron (Fe), copper (Cu), aluminum (Al), and alloys thereof. be able to. As a constituent material of the current collectors 50 and 60, stainless steel (SUS) is particularly preferable. Or you may form the electrical power collectors 50 and 60 with a carbon material. Below, each part which comprises the battery main body 15 of the all-solid-state battery 10 is demonstrated in detail.

A-2. Detailed configuration of the positive electrode layer:
The positive electrode layer 20 is formed by mixing sulfur (S), which is a positive electrode active material, a sulfide-based lithium ion conductive solid electrolyte, and conductive carbon.

Examples of the sulfide-based lithium ion conductive solid electrolyte include a Li ₂ S—P ₂ S ₅ system, a LiI—Li ₂ S—P ₂ S ₅ system, a LiI—Li ₂ S—B ₂ S ₃ system, and a LiI. A solid electrolyte selected from -Li ₂ S-SiS ₂ -based solid electrolyte, thiolysicon, Li ₁₀ GeP ₂ S _{12 and the} like can be used. Here, as the Li ₂ S—P ₂ S ₅ -based solid electrolyte, it is preferable to use a solid electrolyte represented by the following formula (1).
_{XLi 2 S- (1-X)} P 2 S 5 ... (1)
(In the formula, X is 0.65 ≦ X ≦ 0.80.)

The sulfide-based lithium ion conductive solid electrolyte preferably has higher ionic conductivity. Specifically, the ionic conductivity of the sulfide-based lithium ion conductive solid electrolyte is preferably 10 ⁻⁵ S / cm or more, and more preferably 10 ⁻⁴ S / cm or more. Further, it is desirable that the sulfide-based lithium ion conductive solid electrolyte is sufficiently soft, that is, a material having a smaller Young's modulus. Specifically, the Young's modulus of the sulfide-based lithium ion conductive solid electrolyte is preferably 0.08 to 30 GPa, and more preferably 0.08 to 20 GPa. In the sulfide-based lithium ion conductive solid electrolyte represented by the formula (1), by setting X in the formula to a range of 0.65 ≦ X ≦ 0.80, the ionic conductivity and Young's modulus can be easily obtained. The above-described preferable range can be obtained. However, in the sulfide-based lithium ion conductive solid electrolyte represented by the formula (1), X in the formula may be a value outside the above range.

The sulfide-based lithium ion conductive solid electrolyte can be produced, for example, by mixing raw material compounds by mechanical milling. For example, when producing a Li ₂ S—P ₂ S ₅ solid electrolyte, Li ₂ S and P ₂ S ₅ weighed so as to have a desired ratio are prepared and mechanical milling is performed. . Thereby, an amorphous (glassy) Li ₂ S—P ₂ S ₅ -based solid electrolyte is obtained.

  The sulfide-based lithium ion conductive solid electrolyte may be produced by a method other than the mechanical milling described above. Further, for example, when heat is applied to the sulfide-based lithium ion conductive solid electrolyte in the manufacturing process of the all-solid battery 10, at least a part of the sulfide-based lithium ion conductive solid electrolyte may be crystallized. As described above, the sulfide-based lithium ion conductive solid electrolyte may be entirely amorphous glass, or may be partially crystallized glass ceramics (a mixture of amorphous and crystalline). It may be a ceramic that is entirely crystallized.

  Examples of the conductive carbon include ketjen black, acetylene black (for example, Denka Black and Denka Black are registered trademarks), and furnace black (for example, Vulcan manufactured by Cabot Corporation). In order to sufficiently secure an electron conductive network in the positive electrode layer 20 and to sufficiently reduce the volume resistivity of the positive electrode layer 20, it is desirable that the conductive carbon has a smaller particle diameter. Therefore, it is desirable to use ketjen black or acetylene black as the conductive carbon.

In the positive electrode layer 20, when the ratio of the weight of sulfur to the total weight of sulfur as the positive electrode active material and the sulfide-based lithium ion conductive solid electrolyte is expressed as A / 100, the value of A is 30 ≦ A It is desirable that ≦ 70. By setting it as such a structure, the performance of the all-solid-state battery 10 can be improved easily. Specifically, for example, constant current charging / discharging of the all-solid-state battery 10 was performed a plurality of times under the conditions of 25 ° C. with a current density of 0.064 mA / cm ² , a discharge cut voltage of 1 V, and a charge cut voltage of 3 V. It is possible to easily increase the discharge capacity of the second cycle to 200 mA / g or more.

  At this time, when the ratio of the weight of the conductive carbon to the total weight of the sulfur and the sulfide-based lithium ion conductive solid electrolyte is expressed as B / 100, the value of B may be 2 or more, or 3 or more. Also good. The value of B may be 20 or less, or 15 or less. However, the value A can be less than 30 and can be more than 70. Further, the value of B can be set to a value less than 2, and can be set to a value exceeding 20.

Further, in the positive electrode layer 20, when the value A is 30 ≦ A ≦ 55, the value B is preferably 3 ≦ B ≦ 100, and more preferably 4 ≦ B ≦ 100. . Alternatively, in the positive electrode layer 20, when the value A is 55 <A ≦ 70, the value B is preferably 3 ≦ B ≦ 20, and more preferably 4 ≦ B ≦ 20. . By setting it as such a structure, the performance of the all-solid-state battery 10 can be improved easily. Specifically, for example, constant current charging / discharging of the all-solid-state battery 10 was performed a plurality of times under the conditions of 25 ° C. with a current density of 0.064 mA / cm ² , a discharge cut voltage of 1 V, and a charge cut voltage of 3 V. It is possible to easily increase the discharge capacity of the second cycle to 200 mA / g or more.

  In the positive electrode layer 20, sulfur as a positive electrode active material, sulfide-based lithium ion conductive solid electrolyte as an ion conduction aid, and conductive carbon as an electron conduction aid are dispersed sufficiently uniformly. It is desirable that Therefore, the particle size of sulfur in the positive electrode layer 20 is desirably 200 μm or less, and more desirably 75 μm or less. When the positive electrode layer 20 is produced, for example, mixing by mechanical milling is performed in order to sufficiently atomize and uniformly mix sulfur, sulfide-based lithium ion conductive solid electrolyte, and conductive carbon. Is desirable. The positive electrode layer 20 can be obtained by, for example, press molding the sufficiently mixed material powder of the positive electrode layer.

  For mechanical milling, various devices such as a planetary ball mill, a rotating ball mill, a vibrating ball mill, and a stirring ball mill can be used. Among them, the planetary ball mill in which the pot rotates and the base plate revolves can efficiently generate high impact energy. Therefore, it is particularly preferable to use a planetary ball mill in order to sufficiently atomize the material of the positive electrode layer and mix it uniformly.

  The constituent material of the positive electrode layer 20 is hardly lost due to volatilization / decomposition or the like in the manufacturing process of the all-solid battery 10 using the positive electrode layer 20 and the positive electrode layer 20. Therefore, the ratio of the sulfur, the sulfide-based lithium ion conductive solid electrolyte, and the conductive carbon constituting the positive electrode layer 20 of the all-solid battery 10 and the composition of the sulfide-based lithium ion conductive solid electrolyte are manufactured. It can be considered that it coincides with the preparation rate of time.

Further, when the all-solid battery 10 is charged, sulfur that is the positive electrode active material changes to lithium sulfide (Li ₂ S). Therefore, the component containing the sulfur atom in the positive electrode layer 20 can be in a state where the simple sulfur and Li ₂ S are mixed according to the charge / discharge history of the all-solid battery 10.

A-3. Detailed configuration of the negative electrode layer:
The negative electrode layer 30 includes a negative electrode active material. As the negative electrode active material, a material that can occlude and release lithium ions or both occlude and release can be used. Specifically, for example, lithium metal or lithium alloy can be used. Examples of lithium alloys include lithium-aluminum alloy (Li-Al), lithium-tin alloy (Li-Sn), lithium-silicon alloy (Li-Si), lithium-silver alloy (Li-Ag), and lithium- An indium alloy (Li-In) or the like can be used.

  The negative electrode layer 30 may be further mixed with a sulfide-based lithium ion conductive solid electrolyte in addition to the negative electrode active material. For example, when a metal material having a relatively high Young's modulus (relatively hard), such as a Li—Al alloy, a Li—Ag alloy, or a Li—Sn alloy, is used as the negative electrode active material, sulfide-based lithium ion conduction By mixing the conductive solid electrolyte with the negative electrode layer 30, the performance of the all-solid battery 10 can be improved. This is because the sulfide-based lithium ion conductive solid electrolyte functions as a binder for press-molding the negative electrode layer 30 or for press-bonding the negative electrode layer 30 and the solid electrolyte layer 40. In addition, when the sulfide-based lithium ion conductive solid electrolyte is mixed in the negative electrode layer 30, the performance of the all-solid battery 10 can be improved by functioning as an ion conduction aid.

  When the negative electrode layer 30 is produced, in the case of mixing the sulfide-based lithium ion conductive solid electrolyte in addition to the negative electrode active material, for example, a ball mill is used in order to sufficiently finely mix the two and uniformly mix them. It is desirable to perform mixing. The negative electrode layer 30 can be obtained by, for example, press molding the sufficiently mixed material powder of the negative electrode layer. Alternatively, in the case where the negative electrode layer 30 is composed only of lithium metal or lithium alloy, which is a negative electrode active material, the negative electrode layer 30 may be prepared in the form of a metal plate.

  In the positive electrode layer 20 and / or the negative electrode layer 30, a resin may be further mixed as a binder for binding the particles of the electrode active material and joining to the solid electrolyte layer 40. As such a binder, for example, a resin selected from polyvinylidene fluoride, polytetrafluoroethylene, polyvinyl acetate, polymethyl methacrylate, and polyethylene can be used.

A-4: Detailed configuration of the solid electrolyte layer:
The solid electrolyte layer 40 is a plate-like member made of an oxide-based lithium ion conductive solid electrolyte. Examples of the oxide-based lithium ion conductive solid electrolyte include, for example, a phosphoric acid compound having a NASICON structure represented by the following formula (2) or a substituted product obtained by substituting a part thereof with another element, Li ₇ La ₃ It has a perovskite structure or a perovskite-like structure, such as a lithium ion conductor having a garnet-type structure or a garnet-type-like structure such as a Zr ₂ O _12- type lithium ion conductor, or a Li-La-Ti—O-type lithium ion conductor. A lithium ion conductor or the like can be used.
Li _{1 + Y} Al _Y M _2-Y (PO ₄ ) ₃ (2)
(Wherein M is at least one selected from the group consisting of germanium, titanium, hafnium, and zirconium, and Y is 0 <Y <1)

Among the oxide-based lithium ion conductive solid electrolytes described above, the solid electrolyte in which M in the formula (2) is one selected from germanium and titanium is particularly excellent in lithium ion conductivity. In addition, among the oxide-based lithium ion conductive solid electrolytes described above, the solid electrolyte in which M in the formula (2) is one selected from germanium, hafnium and zirconium has a relatively low reducibility, and the electrode Reaction with the component which comprises a layer can be suppressed. Therefore, as the oxide-based lithium ion conductive solid electrolyte, it is preferable to use a solid electrolyte in which M in the formula (2) is germanium. Among solid electrolytes in which M in the formula (2) is germanium, a solid electrolyte in which Y = 0.5 in the formula (2), that is, Li _1.5 Al _0.5 Ge _1.5 (PO ₄ ) ₃ is particularly preferable.

  The solid electrolyte layer 40 is desirably dense. Specifically, the relative density with respect to the theoretical density of the solid electrolyte layer 40 is preferably 80% or more, and more preferably 90% or more. Here, the relative density can be obtained using the Archimedes method. By setting the relative density to 80% or more, the internal resistance of the all-solid battery 10 can be easily reduced. Moreover, the short circuit through the solid electrolyte layer 40 can be suppressed by setting the relative density to 80% or more, as will be described later.

  The solid electrolyte layer 40 is preferably a sintered body. Thereby, the density of the solid electrolyte layer 40 can be improved more easily, and the above-described relative density can be easily realized. In order to produce the solid electrolyte layer 40 that is a sintered body, for example, a solid phase reaction method may be used. The solid-phase reaction method is a well-known method in which powder raw materials such as oxides, carbonates, and nitrates are weighed and mixed so as to have a desired composition and then fired. However, if a sufficiently dense solid electrolyte layer 40 is obtained, the solid electrolyte layer 40 may be manufactured by a method that does not involve sintering.

Further, the solid electrolyte layer 40 preferably has an ionic conductivity of 10 ⁻⁵ S / cm or more, and more preferably 10 ⁻⁴ S / cm or more. By carrying out like this, the internal resistance of all the solid-state battery 10 can be reduced, and the fall of battery performance can be suppressed.

A-5. All-solid battery manufacturing method:
In order to manufacture the all solid state battery 10, the positive electrode layer 20, the solid electrolyte layer 40, and the negative electrode layer 30 described above are prepared, and these are laminated in this order to manufacture the battery body 15. When the battery body 15 is manufactured, the positive electrode layer 20 and the solid electrolyte layer 40 may be joined by applying pressure while suppressing heating, and may be applied by applying pressure without heating. preferable. The positive electrode layer 20 may not be exposed to a high temperature not lower than the melting point of sulfur throughout the manufacturing process. In the following description, pressurization without heating is also referred to as a cold press. In addition, at the time of pressurization for joining, heating at a temperature lower than the melting point of sulfur may be performed.

  When the negative electrode layer 30 is mixed with a sulfide-based lithium ion conductive solid electrolyte, the negative electrode layer 30 and the positive electrode layer 20 are simultaneously bonded to the solid electrolyte layer 40 by pressure while suppressing heating. be able to. Alternatively, even when the negative electrode layer 30 is formed of a member having a relatively small Young's modulus, specifically, a lithium metal plate member or a Li-In alloy plate member, Special heating can be dispensed with. Therefore, it becomes possible to simplify the manufacturing process by joining the negative electrode layer 30 to the solid electrolyte layer 40 simultaneously with the positive electrode layer 20. In particular, when lithium metal is used as the negative electrode active material, if there is a step of firing the negative electrode layer 30, the lithium metal reacts with the oxide-based lithium ion conductive solid electrolyte constituting the solid electrolyte layer 40, Battery performance decreases. Since the negative electrode layer 30 can be joined by pressurization while suppressing heating, the manufacturing process can be simplified while securing battery performance even when lithium metal is used as the negative electrode active material. Alternatively, the negative electrode layer 30 may be formed on the solid electrolyte layer 40 separately from the bonding of the positive electrode layer 20 by depositing and depositing a negative electrode active material on the solid electrolyte layer 40.

  After the battery body 15 is fabricated, the all-solid battery 10 can be completed by sandwiching and fixing the battery body 15 between the pair of current collectors 50 and 60.

  According to the all solid state battery 10 of the first embodiment configured as described above, since the solid electrolyte layer 40 is composed of an oxide-based lithium ion conductive solid electrolyte, the all solid state battery 10 reacts with moisture. This reduces the amount of sulfide-based lithium ion conductive solid electrolyte that can generate hydrogen sulfide. Therefore, the safety at the time of manufacture and use of the all solid state battery 10 can be enhanced. Furthermore, since the sulfide-based lithium ion conductive solid electrolyte having a smaller Young's modulus than the oxide-based lithium ion conductive solid electrolyte is mixed in the positive electrode layer 20, the positive electrode layer 20 is bonded to the positive electrode layer 20. Heating during pressing can be suppressed. That is, the sulfide-based lithium ion conductive solid electrolyte generally has a softer and easier-to-elongate property than the oxide-based lithium ion conductive solid electrolyte, so even if heating during pressurization is suppressed (for example, by performing a cold press) In addition, the contact between the positive electrode layer 20 and the solid electrolyte layer 40 can be ensured satisfactorily. Thereby, the internal resistance of the all-solid-state battery 10 can be reduced. Further, by suppressing the heating during pressurization as described above, a positive electrode layer containing sulfur having a relatively low melting point (orthogonal sulfur of 112.8 ° C.) as a positive electrode active material is bonded to the solid electrolyte layer. It becomes possible to obtain an all-solid-state battery. Sulfur exhibits a very large theoretical capacity density of 1675 mAh / g. Therefore, the performance of the all-solid-state battery can be improved by using sulfur having a large theoretical capacity density as the positive electrode active material and forming a good interface between the positive electrode layer 20 and the solid electrolyte layer 40. it can.

  Moreover, according to the all-solid-state battery 10 of 1st Embodiment, since the solid electrolyte layer 40 comprised by an oxide type lithium ion conductive solid electrolyte is formed densely, when using the all-solid-state battery 10, Even when the temperature of the all-solid battery 10 rises, a short circuit through the solid electrolyte layer 40 can be suppressed. That is, even when the temperature of the all-solid battery 10 is equal to or higher than the melting temperature of the positive electrode active material and the positive electrode active material is melted, the molten positive electrode active material passes through the solid electrolyte layer 40 toward the negative electrode layer 30 side. It is possible to suppress movement and suppress short circuit.

  Moreover, according to the all-solid-state battery 10 of 1st Embodiment, since the solid electrolyte layer 40 comprised by an oxide type lithium ion conductive solid electrolyte is formed densely, moisture is contained in the all-solid-state battery 10. Even if a situation occurs, the short circuit of the all-solid battery 10 can be suppressed. That is, the sulfide-based lithium ion conductive solid electrolyte has a property of dissolving when moisture is present. Therefore, when a situation where moisture exists in the all solid state battery 10, the sulfide-based lithium ion conductive solid electrolyte provided in the electrode layer may be dissolved. Even in such a case, since the solid electrolyte layer 40 is dense, the dissolved sulfide-based lithium ion conductive solid electrolyte does not move through the solid electrolyte layer 40, and the all-solid battery Short circuit inside 10 can be suppressed.

  Furthermore, according to the all-solid-state battery 10 of 1st Embodiment, since the positive electrode layer 20 is equipped with the sulfide type lithium ion conductive solid electrolyte which has a soft property, the positive electrode layer 20 and the solid electrolyte layer 40 of The strength of the interface can be maintained well. Therefore, even when the inside of the all-solid battery 10 expands or contracts due to charging / discharging of the all-solid battery 10, it is possible to reduce the possibility that a crack or the like is generated inside the battery.

B. Second embodiment:
FIG. 2 is a cross-sectional view illustrating a schematic configuration of the all solid state battery 100 of the second embodiment. The all solid state battery 100 of the second embodiment has the same configuration as the all solid state battery 10 of the first embodiment except that the positive electrode layer 120 is provided instead of the positive electrode layer 20. For this reason, the same reference numerals are assigned to portions common to the first embodiment, and detailed description thereof is omitted.

B-1. Detailed configuration of the positive electrode layer:
The positive electrode layer 120 is formed by mixing a metal sulfide that is a positive electrode active material and a sulfide-based lithium ion conductive solid electrolyte.

As the metal sulfide, for example, iron sulfide, lithium sulfide, copper sulfide, iron sulfide, titanium sulfide, nickel sulfide, or the like can be used. Examples of the iron sulfide include FeS ₂ (iron disulfide), FeS (iron (II) sulfide), and Fe ₂ S ₃ (iron (III) sulfide). In order to improve battery performance, it is particularly preferable to use FeS ₂ .

Examples of the sulfide-based lithium ion conductive solid electrolyte include a Li ₂ S—P ₂ S ₅ system, a LiI—Li ₂ S—P ₂ S ₅ system, a LiI—Li ₂ S—B ₂ S ₃ system, and a LiI. A —Li ₂ S—SiS ₂ -based solid electrolyte, thiolysicon, or the like can be used. Here, as the Li ₂ S—P ₂ S ₅ -based solid electrolyte, it is preferable to use a solid electrolyte represented by the following formula (1).
_{XLi 2 S- (1-X)} P 2 S 5 ... (1)
(In the formula, X is 0.65 ≦ X ≦ 0.80.)

The sulfide-based lithium ion conductive solid electrolyte preferably has higher ionic conductivity. Specifically, the ionic conductivity of the sulfide-based lithium ion conductive solid electrolyte is preferably 10 ⁻⁵ S / cm or more, and more preferably 10 ⁻⁴ S / cm or more. Further, it is desirable that the sulfide-based lithium ion conductive solid electrolyte is sufficiently soft, that is, a material having a smaller Young's modulus. Specifically, the Young's modulus of the sulfide-based lithium ion conductive solid electrolyte is preferably 0.08 to 30 GPa, and more preferably 0.08 to 20 GPa. In the sulfide-based lithium ion conductive solid electrolyte represented by the formula (1), by setting X in the formula to a range of 0.65 ≦ X ≦ 0.80, the ionic conductivity and Young's modulus can be easily obtained. The above-described preferable range can be obtained. However, in the sulfide-based lithium ion conductive solid electrolyte represented by the formula (1), X in the formula may be a value outside the above range.

The sulfide-based lithium ion conductive solid electrolyte can be produced, for example, by mixing raw material compounds by mechanical milling. For example, when producing a Li ₂ S—P ₂ S ₅ solid electrolyte, Li ₂ S and P ₂ S ₅ weighed so as to have a desired ratio are prepared and mechanical milling is performed. . Thereby, an amorphous (glassy) Li ₂ S—P ₂ S ₅ -based solid electrolyte is obtained.

  The sulfide-based lithium ion conductive solid electrolyte may be produced by a method other than the mechanical milling described above. Further, for example, when heat is applied to the sulfide-based lithium ion conductive solid electrolyte in the manufacturing process of the all-solid battery 10, at least a part of the sulfide-based lithium ion conductive solid electrolyte may be crystallized. As described above, the sulfide-based lithium ion conductive solid electrolyte may be entirely amorphous glass, or may be partially crystallized glass ceramics (a mixture of amorphous and crystalline). It may be a ceramic that is entirely crystallized.

When FeS ₂ is used as the positive electrode active material in the positive electrode layer 120, the ratio of the weight of FeS ₂ to the total weight of FeS ₂ and the sulfide-based lithium ion conductive solid electrolyte is expressed as A / 100. , A is preferably 40 ≦ A ≦ 80. The value of A is more preferably 50 ≦ A ≦ 80, and more preferably 50 ≦ A ≦ 70. By setting it as such a structure, the performance of the all-solid-state battery 100 can be improved easily. Specifically, for example, constant current charging / discharging of the all-solid-state battery 100 is performed a plurality of times under the conditions of 25 ° C. with a current density of 0.064 mA / cm ² , a discharge cut voltage of 0.3 V, and a charge cut voltage of 3 V. When performed, the discharge capacity in the second cycle can be easily increased to 200 mA / g or more. However, the value of A can be less than 40, and can be greater than 80.

At this time, the positive electrode layer 120 may be further mixed with conductive carbon. In order to further improve the discharge capacity of the all-solid battery by mixing the conductive carbon, in the positive electrode layer 120, the conductive carbon of the conductive carbon relative to the total weight of FeS ₂ and the sulfide-based lithium ion conductive solid electrolyte is used. When the weight ratio is expressed as B / 100, the value of B is preferably B ≦ 40. Further, the value of B is more preferably B ≦ 30.

In the positive electrode layer 120, conductive carbon may be further mixed when a metal sulfide other than FeS ₂ is used as the positive electrode active material. For example, when the conductivity of the metal sulfide is lower than that of the conductive carbon, the conductivity of the entire positive electrode layer 120 can be increased and the resistance of the positive electrode layer 120 can be reduced by mixing the conductive carbon. . Thus, by reducing the resistance of the positive electrode layer 120, it becomes possible to secure a sufficient amount of discharge from the all-solid-state battery 100 even during high loads.

  Examples of the conductive carbon include ketjen black, acetylene black (for example, Denka Black and Denka Black are registered trademarks), and furnace black (for example, Vulcan manufactured by Cabot Corporation). In order to sufficiently secure an electron conductive network in the positive electrode layer 120 and sufficiently reduce the volume resistivity of the positive electrode layer 120, the conductive carbon desirably has a smaller particle diameter. Therefore, it is desirable to use ketjen black or acetylene black as the conductive carbon.

  In the positive electrode layer 120, a metal sulfide that is a positive electrode active material, a sulfide-based lithium ion conductive solid electrolyte that is an ion conduction aid, and a conductive carbon that is an electron conduction aid if further included. However, it is desirable to disperse sufficiently uniformly. Therefore, the particle size of the metal sulfide in the positive electrode layer 120 is desirably 200 μm or less, and more desirably 75 μm or less. When producing the positive electrode layer 120, for example, mixing by mechanical milling is performed in order to sufficiently atomize and uniformly mix sulfur, sulfide-based lithium ion conductive solid electrolyte, and conductive carbon. Is desirable. The positive electrode layer 120 can be obtained by, for example, press molding the sufficiently mixed material powder of the positive electrode layer.

  Note that the constituent material of the positive electrode layer 120 is hardly lost due to volatilization / decomposition or the like in the manufacturing process of the all-solid-state battery 100 using the positive electrode layer 120 and the positive electrode layer 120. Therefore, the ratio of the metal sulfide constituting the positive electrode layer 120 of the all-solid-state battery 100, the sulfide-based lithium ion conductive solid electrolyte, and the conductive carbon if further included, and the sulfide-based lithium ion conduction It can be considered that the composition of the conductive solid electrolyte coincides with the charge ratio at the time of production.

According to the all solid state battery 100 of the second embodiment configured as described above, the solid electrolyte layer 40 is composed of an oxide-based lithium ion conductive solid electrolyte, and therefore reacts with moisture in the all solid state battery 100. This reduces the amount of sulfide-based lithium ion conductive solid electrolyte that can generate hydrogen sulfide. Therefore, the safety of all solid state battery 100 can be improved. Furthermore, since the sulfide-based lithium ion conductive solid electrolyte having a Young's modulus smaller than that of the oxide-based lithium ion conductive solid electrolyte is mixed in the positive electrode layer 120, the positive electrode layer 120 is joined. Heating during pressing can be suppressed. That is, the sulfide-based lithium ion conductive solid electrolyte generally has a softer and easier-to-elongate property than the oxide-based lithium ion conductive solid electrolyte, so even if heating during pressurization is suppressed (for example, by performing a cold press) Also, the contact between the positive electrode layer 120 and the solid electrolyte layer 40 can be ensured satisfactorily. Thereby, the internal resistance of the all-solid-state battery 100 can be reduced. Furthermore, by suppressing heating during pressurization as described above, it is possible to obtain an all-solid battery by joining a positive electrode layer containing a metal sulfide having a relatively low melting point as a positive electrode active material to the electrolyte layer. become. Metal sulfides generally exhibit a very large theoretical capacity density. For example, the theoretical capacity density of FeS ₂ is 893.6 mAh / g. Therefore, by using a metal sulfide having a large theoretical capacity density as a positive electrode active material in this way and forming a good interface between the positive electrode layer 120 and the solid electrolyte layer 40, the performance of the all-solid-state battery is improved. be able to.

  Moreover, according to the all-solid battery 100 of 2nd Embodiment, since the solid electrolyte layer 40 comprised by an oxide type lithium ion conductive solid electrolyte is formed densely, moisture is contained in the all-solid-state battery 10. Even if a situation occurs, the short circuit of the all-solid-state battery 100 can be suppressed. That is, the sulfide-based lithium ion conductive solid electrolyte has a property of dissolving when moisture is present. Therefore, when a situation where moisture exists in all solid state battery 100, the sulfide-based lithium ion conductive solid electrolyte included in the electrode layer may be dissolved. Even in such a case, since the solid electrolyte layer 40 is dense, the dissolved sulfide-based lithium ion conductive solid electrolyte does not move through the solid electrolyte layer 40, and the all-solid battery Short circuit inside 100 can be suppressed.

  Furthermore, according to the all-solid-state battery 100 of 2nd Embodiment, since the positive electrode layer 120 is equipped with the sulfide type lithium ion conductive solid electrolyte which has a soft property, between the positive electrode layer 120 and the solid electrolyte layer 40, The strength of the interface can be maintained well. Therefore, even when the inside of the all solid state battery 100 expands or contracts due to charging / discharging of the all solid state battery 100, the possibility that a crack or the like is generated inside the battery can be reduced.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to the description of these examples.

  3 and 4 show samples S01 to S08, S11 to S17, S21 to S25, S31, S41, S51 to 56, and S61 to 64 as all solid state batteries, and compare the compositions and performance of the samples. It is a figure showing the result of having performed. Each of these all-solid-state batteries has a different configuration of the positive electrode layer. Below, the detail of manufacture of each sample is shown.

[Preparation of oxide-based lithium ion conductive solid electrolyte]
In each sample which is an all solid state battery, the solid electrolyte layer was composed of Li _1.5 Al _0.5 Ge _1.5 (PO ₄ ) ₃ which is an oxide-based lithium ion conductive solid electrolyte. The oxide-based lithium ion conductive solid electrolyte constituting the solid electrolyte layer was prepared by the following procedure. First, the raw materials GeO ₂ (manufactured by Kanto Chemical), Li ₂ CO ₃ (manufactured by Wako Pure Chemical Industries), (NH ₃ ) ₂ HPO ₄ (manufactured by Kishida Chemical), and Al ₂ O ₃ (manufactured by High Purity Chemical) Weighed with stoichiometric composition. Thereafter, the weighed raw materials were put together with zirconia balls in an alumina pot, and pulverized and mixed in an ethanol solvent for 15 hours. Next, ethanol was vaporized and heat treatment (firing) was performed at 900 ° C. for 2 hours. A ceramic binder was added to the heat-treated sample, and the sample after addition was put into an alumina pot together with zirconia balls, and pulverized and mixed in an ethanol solvent for 15 hours. The sample after pulverization and mixing was dried to evaporate ethanol to obtain a pre-molding powder (also referred to as “LAPG powder”) of an oxide-based lithium ion conductive solid electrolyte. Next, using a cold isostatic press (hereinafter also referred to as “CIP press”), a hydrostatic pressure of 1.5 t / cm ² was applied to the powder before molding to obtain a compact. The obtained molded body was heat-treated (fired) at 850 ° C. for 12 hours to obtain a sintered body of oxide-based lithium ion conductive solid electrolyte (also referred to as “LAGP sintered body”).

[Evaluation of oxide-based lithium ion conductive solid electrolyte]
A LAGP sintered body was prepared as described above, and a sintered body having a diameter of 10 mm and a thickness of 0.8 mm was prepared. When the bulk density of this LAGP sintered body was measured by the Archimedes method, the bulk density was 3.33 g / cm ³ . When the relative density was determined based on this bulk density, the relative density was 97.6%.

Further, the ionic conductivity of the LAGP sintered body was measured by an AC impedance measurement method. Specifically, the measurement was performed by an electrochemical measurement system in which a frequency response analyzer 1255B manufactured by Solartron and a potentio / galvanostat 1470E were combined. The lithium ion conductivity at 28 ° C. was 5.0 × 10 ⁻⁴ S / cm.

[Preparation of sulfide-based lithium ion conductive solid electrolyte]
The sulfide-based lithium ion conductive solid electrolyte to be mixed in the electrode layer of each sample was prepared by the following procedure. First, in an argon atmosphere glove box (Miwa Seisakusho), Li ₂ S (Furuuchi Chemical) ) And P ₂ S ₅ (manufactured by Aldrich) at a molar ratio of 80:20. Using a planetary ball mill (manufactured by Fritsch, type P-6), the weighed raw materials were put into a zirconia pot together with zirconia balls, and mechanical milling was performed in an argon atmosphere at a rotation speed of 540 rpm for 9 hours. The sample after mechanical milling is also called “sulfide glass”.

[Production of First Positive Electrode Pellets (S01 to S08, S11 to S17, S21 to S25, S31)]
The positive electrode layers of the all-solid-state batteries of samples S01 to S08, S11 to S17, S21 to S25, and S31 are made of a first positive electrode pellet containing sulfur that is a positive electrode active material, sulfide glass, and conductive carbon. Configured. The first positive electrode pellet was produced as follows. In order to produce the first positive electrode pellet, first, a positive electrode mixture using sulfur, sulfide glass, and conductive carbon as raw materials was produced. The positive electrode mixture was prepared by weighing the above-described raw materials at a predetermined weight ratio shown in FIG. 3 and mixing them by mechanical milling. Here, in samples other than sample S31, as a sulfur used for producing the positive electrode mixture, a high-purity chemical reagent was pulverized until the particle size became 200 μm or less. Moreover, in sample S31, the reagent of 75 micrometer mesh pass made from a high purity chemical was used as sulfur used in order to produce a positive electrode compound material. The particle size refers to the maximum particle size in the image when the sample is observed with a scanning electron microscope. Of the positive electrode mixture obtained by mechanical milling, the positive electrode mixture of sample S24 was observed with a scanning electron microscope, and the particle size of the contained sulfur was 150 μm or less. When the positive electrode mixture of sample S31 was observed with a scanning electron microscope, the particle size of the contained sulfur was 70 μm or less. Note that ketjen black (manufactured by Mitsubishi Chemical, EC600JD, also referred to as KB) was used as the conductive carbon.

  Specifically, the mixing ratio of the raw materials in each sample is as follows. As shown in FIG. 3, in samples S01 to S08, the ratio of the weight of sulfur to the sum of the weight of sulfur and the weight of sulfide glass was set to 33.3%. In samples S11 to S17 and S31, the ratio of the weight of sulfur to the sum of the weight of sulfur and the weight of sulfide glass was set to 50%. Moreover, in sample S21-S25, the ratio of the weight of sulfur with respect to the sum total of the weight of sulfur and the weight of sulfide glass was 66.7%. And the addition ratio of electroconductive carbon was varied between samples in which the ratio of the weight of sulfur to the sum of the weight of sulfur and the weight of sulfide glass was the same. The amount of conductive carbon added is expressed as a relative value of the weight of conductive carbon, where the total weight of sulfur and sulfide glass is 100.

  Similarly, in the other samples shown in FIGS. 3 and 4, the mixing amount of the positive electrode active material and the sulfide glass is the weight of the positive electrode active material or the sulfide glass with respect to the total weight of the positive electrode active material and the sulfide glass. It is expressed as a ratio (% by weight). The amount of conductive carbon added is expressed as a relative value of the weight of conductive carbon, where the total weight of the positive electrode active material and sulfide glass is 100. In the following description and FIGS. 3 and 4, the relative mixing ratio of the conductive carbon as described above is also referred to as wt% for convenience.

  The above-described sulfur pulverization and weighing of each raw material were carried out in a glove box (manufactured by Miwa Seisakusho) having an argon atmosphere and a dew point of −60 ° C. or less. Mechanical milling was performed for 1 hour at a rotational speed of 380 rpm in an argon atmosphere using a 45 cc zirconia pot and 200 Φ4 mm zirconia balls using a planetary ball mill (Fritsch type P-6). The first positive electrode pellet is produced by laminating a SUS base material used as a current collector and about 15 mg of a positive electrode mixture in this order in a circular mold having a diameter of 10 mm that can be pressure-molded, and press-molding at 360 MPa. did.

[Preparation of second positive electrode pellet (S51 to S56)]
The positive electrode layer of the all-solid-state batteries of Samples S51 to S56 was composed of a second positive electrode pellet containing iron sulfide as a positive electrode active material and sulfide glass. In order to produce the second positive electrode pellet, first, a positive electrode mixture using iron sulfide (manufactured by high purity chemical) and sulfide glass as raw materials was produced. The positive electrode composite was prepared by weighing the above-described raw materials at a predetermined weight ratio shown in FIG. 4 and mixing them by mechanical milling.

  Specifically, in samples S51 to S56, the ratio of the weight of iron sulfide to the sum of the weight of iron sulfide and the weight of sulfide glass was changed in the range of 20 to 90% (see FIG. 4). Samples S51 to S56 do not contain conductive carbon.

  Each raw material was weighed in a glove box (manufactured by Miwa Seisakusho) with an argon atmosphere and a dew point of −60 ° C. or less. The conditions for mechanical milling and the conditions for producing the second positive electrode pellet by press-molding the positive electrode mixture together with the current collector were the same as those for the first positive electrode pellet.

[Production of third positive electrode pellet (S61 to S64)]
The positive electrode layer of the all-solid-state batteries of Samples S61 to S64 was composed of a third positive electrode pellet containing iron sulfide as a positive electrode active material, sulfide glass, and ketjen black. In order to prepare the third positive electrode pellet, first, a positive electrode mixture using iron sulfide (manufactured by high purity chemical), sulfide glass, and ketjen black (manufactured by Mitsubishi Chemical, EC600JD) as a raw material was prepared. The positive electrode composite was prepared by weighing the above-described raw materials at a predetermined weight ratio shown in FIG. 4 and mixing them by mechanical milling.

  Specifically, in samples S61 to S64, the ratio of the weight of iron sulfide to the sum of the weight of iron sulfide and the weight of sulfide glass was fixed at 50% (see FIG. 4). And the addition amount of electroconductive carbon was varied in the range of 0 to 50 weight% between each sample.

  The conditions for weighing each raw material, the conditions for mechanical milling, and the conditions for producing the third positive electrode pellet by press-molding the positive electrode mixture together with the current collector were the same as those for the second positive electrode pellet.

[Fabrication of fourth positive electrode pellet (S41)]
The positive electrode layer of the all-solid-state battery of sample S41 was composed of a fourth positive electrode pellet containing Li ₄ Ti ₅ O _{12 as} a positive electrode active material, sulfide glass, and ketjen black. In order to produce the fourth positive electrode pellet, first, Li ₄ Ti ₅ O ₁₂ (manufactured by Ishihara Sangyo) which is a positive electrode active material, sulfide glass, and Ketjen Black (manufactured by Mitsubishi Chemical, EC600JD) are used as raw materials. A positive electrode composite was produced. The positive electrode mixture was prepared by weighing the above Li ₄ Ti ₅ O ₁₂ , sulfide glass, and ketjen black at a weight ratio of 70:30:10 and mixing by mechanical milling. Mechanical milling was performed for 1 hour at a rotation speed of 230 rpm in an argon atmosphere using a 45 cc zirconia pot and 200 Φ4 mm zirconia balls using a planetary ball mill (Fritsch, P-6 type). The fourth positive electrode pellet is produced by laminating a SUS base material used as a current collector and about 15 mg of a positive electrode mixture in this order in a circular mold having a diameter of 10 mm that can be pressure-molded, and press-molding at 180 Mpa. did.

[Preparation of negative electrode pellet (other than S41)]
The negative electrode pellet used for providing the negative electrode layer provided in the all-solid-state battery other than sample S41 was prepared as follows. In order to produce a negative electrode pellet, first, a negative electrode mixture was produced using LiAl (manufactured by Honjo Metal) as a negative electrode active material and sulfide glass as raw materials. The negative electrode composite material was prepared by weighing the above-described LiAl and sulfide glass in an argon atmosphere at a weight ratio of 50:50 and mixing them using a mortar. The negative electrode pellet constituting the negative electrode layer is formed by laminating a SUS base material used as a current collector and about 50 mg of a negative electrode mixture in this order in a circular mold having a diameter of 10 mm, which can be pressure-molded, and press-molded at 360 Mpa. It was prepared.

[Preparation of negative electrode pellet (S41)]
The negative electrode pellet used for providing the negative electrode layer included in the all solid battery of sample S41 was prepared using the same negative electrode mixture as the negative electrode pellet for all solid batteries other than sample S41. Different. That is, it was produced by laminating a SUS base material used as a current collector and about 15 mg of a negative electrode mixture in this order in a circular mold having a diameter of 10 mm that can be pressure-molded, and press-molding at 180 Mpa.

[Battery fabrication]
Each all-solid-state battery was produced as follows. First, as described above, a LAGP sintered body was prepared as a solid electrolyte layer, and a sintered body having a diameter of 10 mm and a thickness of 350 μm was prepared. Moreover, the positive electrode pellet and negative electrode pellet corresponding to each all-solid-state battery were produced. Then, each member of the positive electrode pellet, the LAGP sintered body, and the negative electrode pellet was laminated in this order so that the SUS current collector of each pellet faced the outside to obtain a laminate. Then, by sandwiching the laminated body with a pressure of about 50 MPa through the SUS current collector, each member was fixed to produce an all-solid battery.

[Charge / discharge measurement]
For each all solid state battery, charge / discharge measurement was performed. In the samples S01 to S08, S11 to S17, S21 to S25, and S31 using sulfur as a positive electrode active material, the constant current charge / discharge test as the charge / discharge measurement has a current density of 0.064 mA / cm ² and a discharge cut voltage of 1V. The charge cut voltage was 3 V, and the conditions were 25 ° C. Further, in samples S51 to S56 and S61 to S64 using iron sulfide as a positive electrode active material, a constant current charge / discharge test as charge / discharge measurement was performed at a current density of 0.064 mA / cm ² and a discharge cut voltage of 0.3V. The cut voltage was set to 3V and the conditions were 25 ° C. Further, in sample S41 using Li ₄ Ti ₅ O ₁₂ as the positive electrode active material, the constant current charge / discharge test as the charge / discharge measurement was performed at a current density of 0.064 mA / cm ² , a discharge cut voltage of 1 V, and a charge cut voltage of 1 .7V, and the conditions were 25 ° C. In either case, a charge / discharge test apparatus (BTS2004H) manufactured by Nagano Co., Ltd. was used for the constant current charge / discharge test. Moreover, discharge capacity was calculated | required about each all-solid-state battery based on the result of the said charging / discharging measurement. The charge / discharge measurement was repeated twice, and the discharge capacity at the second cycle at which the value was more stable was determined.

  5-8 is explanatory drawing which shows the result of having performed charging / discharging measurement about each of sample S03, S13, S31, S62, and S41 as an example of charging / discharging measurement. FIG. 3 and FIG. 4 show the discharge capacity of each all solid state battery determined based on the result of such charge / discharge measurement. The discharge capacity was calculated by converting per unit weight of the positive electrode active material.

  FIG. 9 is an explanatory diagram summarizing the relationship between the amount of conductive carbon added and the discharge capacity based on the results of obtaining the discharge capacity for each of samples S01 to S08, S11 to S17, and S21 to S25. As shown in FIG. 9, even when the ratio of sulfur to the sum of the weight of sulfur and the weight of sulfide glass is 33.3% by weight, 50% by weight, or 66.7% by weight, the conductive When the amount of conductive carbon added was up to about 8.33% by weight, the discharge capacity increased as the amount of conductive carbon added increased. And when the addition amount of the conductive carbon further increased, the discharge capacity gradually decreased as the addition amount of the conductive carbon increased.

Here, among the samples, samples S02 to S07 (A = 33.3, 4.17 ≦ B ≦ 100), S12 to S16 (A = 50, 4.17 ≦ B ≦ 100), S22 to S24 (A = 66.7, 4.17 ≦ B ≦ 16.7) is a value of 200 mAh / g or more which is larger than the discharge capacity of sample S41 using Li ₄ Ti ₅ O ₁₂ as the positive electrode active material as the discharge capacity value. showed that. In addition, said A is a value of A when the ratio of the weight of a positive electrode active material with respect to the total weight of a positive electrode active material and a sulfide type lithium ion conductive solid electrolyte is represented as A / 100. Further, B is a value of B when the ratio of the weight of the conductive carbon to the total weight of the positive electrode active material and the sulfide glass is represented as B / 100.

  In contrast, samples S01 (A = 33.3, B = 2.08), S08 (A = 33.3, B = 150), S11 (A = 50, B = 2.08), S17 (A = 50, B = 150), S21 (A = 66.7, B = 2.08), S25 (A = 66.7, B = 66.7), the discharge capacity value was less than 200 mAh / g. It was. Regarding Samples S01, S11, and S21, since the amount of conductive carbon mixed is small, it is considered that a sufficient electron conduction path was not formed in the positive electrode layer, and the discharge capacity was suppressed. In addition, in Samples S08, S17, and S25, the amount of conductive carbon mixed is excessive, and the mixing ratio of sulfide glass is relatively small, so that an ion conduction path is not sufficiently formed in the positive electrode layer. It is thought that the discharge capacity was suppressed.

  Moreover, when the mixing ratio of sulfur and sulfide glass and the mixing ratio of conductive carbon are the same (A = 50, B = 8.33), and samples S13 and S31 having different particle sizes of sulfur are compared, Sample S31 with a smaller particle size had a larger discharge capacity (see FIG. 3).

  FIG. 10 is an explanatory diagram summarizing the relationship between the mixing ratio of iron sulfide and the discharge capacity based on the result of obtaining the discharge capacity for each of samples S51 to S56. As shown in FIG. 10, when the ratio of iron sulfide to the total weight of iron sulfide and sulfide glass is about 50 to 70% by weight, the discharge capacity increases as the mixing ratio of iron sulfide increases. . And when the mixing ratio of iron sulfide further increased, the discharge capacity gradually decreased as the mixing ratio of iron sulfide increased.

Here, among the samples, samples S52 to S55 (30 ≦ A ≦ 80, B = 0) are obtained from the discharge capacity of sample S41 using Li ₄ Ti ₅ O ₁₂ as the positive electrode active material as the discharge capacity value. Also showed a high value of 200 mAh / g or more. The values A and B are as described above. On the other hand, in the samples S51 (A = 20, B = 0) and S56 (A = 90, B = 0), the discharge capacity value was less than 200 mAh / g. Regarding sample S51, since the amount of conductive carbon mixed is small, it is considered that a sufficient electron conduction path was not formed in the positive electrode layer, and the discharge capacity was suppressed. In addition, for sample S56, the amount of conductive carbon mixed is excessive, and the mixing ratio of sulfide glass is relatively small, so that the formation of an ion conduction path is insufficient in the positive electrode layer, and the discharge is performed. It is thought that the capacity was suppressed.

  FIG. 11 is an explanatory diagram summarizing the relationship between the amount of conductive carbon added and the discharge capacity based on the results of obtaining the discharge capacity for each of samples S53 and S61 to S64. As shown in FIG. 11, the discharge capacity increased as the amount of conductive carbon increased until the amount of conductive carbon added increased to about 5 to 10% by weight. And when the addition amount of the conductive carbon further increased, the discharge capacity gradually decreased as the addition amount of the conductive carbon increased. In addition, as shown in FIG. 11, the discharge capacity was improved in the sample in which the amount of conductive carbon added was 30% by weight or less than in the sample (S53) to which no conductive carbon was added. On the other hand, in the sample (S54) in which the amount of conductive carbon added was 50% by weight, the discharge capacity was lower than in the sample to which no conductive carbon was added. This is presumably because the influence of the relative decrease in the ion conduction path due to the addition of the conductive carbon is larger than the influence due to the increase in the electron conduction path due to the addition of the conductive carbon. However, in any sample, the value of the discharge capacity was 200 mAh / g or more.

[Measurement of initial resistance]
For each all solid state battery, the internal resistance (initial resistance) was measured. The initial resistance was measured by the AC impedance method. Specifically, the measurement was performed by an electrochemical measurement system in which a frequency response analyzer 1255B manufactured by Solartron and a potentio / galvanostat 1470E were combined. The value of the initial resistance of each sample at 28 ° C. is shown in FIGS.

  As shown in FIG. 3, among the samples using sulfur as the positive electrode active material (S01 to S08, S11 to S17, S21 to S25, S31), the sample in which the amount of conductive carbon added is 2.08% by weight. The initial resistance of S01, S11, and S21 exceeded 500Ω, but the initial resistance of the other samples was 500Ω or less. In addition, when samples S13 and S31 having different particle sizes of sulfur, which are positive electrode active materials, were compared, sample S3 having a smaller particle size of sulfur had a smaller initial resistance (S13: 200Ω, S31: 130Ω).

  Further, as shown in FIG. 4, when iron sulfide having higher conductivity than sulfur is used as the positive electrode active material (S51 to S56, S61 to 64), the mixing ratio of iron sulfide is 30% by weight or less. Samples other than the samples (S51, S52) to which no conductive carbon was added had an initial resistance of 1000Ω or less. In particular, when samples S53 and S61 to S64 were compared, it was confirmed that the initial resistance was reduced by adding conductive carbon (S53: 750Ω, S61 to S64: 400Ω or less).

  The present invention is not limited to the above-described embodiments, examples, and modifications, and can be realized with various configurations without departing from the spirit thereof. For example, the technical features in the embodiments, examples, and modifications corresponding to the technical features in each embodiment described in the summary section of the invention are to solve some or all of the above-described problems, or In order to achieve part or all of the above effects, replacement or combination can be performed as appropriate. Further, if the technical feature is not described as essential in the present specification, it can be deleted as appropriate.

DESCRIPTION OF SYMBOLS 10,100 ... All-solid-state battery 15 ... Battery main body 20,120 ... Positive electrode layer 30 ... Negative electrode layer 40 ... Solid electrolyte layer 50, 60 ... Current collector

Claims (14)

In an all-solid-state battery comprising a positive electrode layer, a negative electrode layer, and an electrolyte layer composed of an oxide-based lithium ion conductive solid electrolyte,
The positive electrode layer is formed by mixing sulfur (S) as a positive electrode active material, a sulfide-based lithium ion conductive solid electrolyte, and conductive carbon ,
In the positive electrode layer, when the ratio of the weight of sulfur to the total weight of the sulfur and the sulfide-based lithium ion conductive solid electrolyte is expressed as A / 100, the value of A is 30 ≦ A ≦ An all-solid-state battery, which is 70 . The all-solid-state battery according to claim 1 ,
In the positive electrode layer,
When the ratio of the weight of sulfur to the total weight of the sulfur and the sulfide-based lithium ion conductive solid electrolyte is expressed as A / 100, the value of A is 30 ≦ A ≦ 55,
When the ratio of the weight of the conductive carbon to the total weight of the sulfur and the sulfide-based lithium ion conductive solid electrolyte is expressed as B / 100, the value of B is 3 ≦ B ≦ 100. All-solid battery characterized by The all-solid-state battery according to claim 1 ,
In the positive electrode layer,
When the ratio of the weight of the sulfur to the total weight of the sulfur and the sulfide-based lithium ion conductive solid electrolyte is expressed as A / 100, the value of A is 55 <A ≦ 70,
When the ratio of the weight of the conductive carbon to the total weight of the sulfur and the sulfide-based lithium ion conductive solid electrolyte is expressed as B / 100, the value of B is 4 ≦ B ≦ 20. All-solid battery characterized by The all-solid-state battery according to any one of claims 1 to 3 ,
The all-solid-state battery, wherein the conductive carbon is ketjen black.   The all-solid-state battery according to any one of claims 1 to 4,
  The sulfide-based lithium ion conductive solid electrolyte has the following formula (1):
  XLi ₂ S- (1-X) P ₂ S ₅         ... (1)
(In the formula, X is 0.65 ≦ X ≦ 0.80)
  An all-solid battery characterized by being a solid electrolyte represented by In an all-solid-state battery comprising a positive electrode layer, a negative electrode layer, and an electrolyte layer composed of an oxide-based lithium ion conductive solid electrolyte,
The positive electrode layer is formed by mixing a metal sulfide that is a positive electrode active material and a sulfide-based lithium ion conductive solid electrolyte ,
The positive electrode active material is FeS ₂ ;
In the positive electrode layer, when the ratio of the weight of the positive electrode active material to the total weight of the positive electrode active material and the sulfide-based lithium ion conductive solid electrolyte is expressed as A / 100, the value of A is 40 <= A <= 80, The all-solid-state battery characterized by the above-mentioned. The all-solid-state battery according to claim 6 ,
The positive electrode layer is further mixed with conductive carbon,
In the positive electrode layer, when the ratio of the weight of the conductive carbon to the total weight of the positive electrode active material and the sulfide-based lithium ion conductive solid electrolyte is expressed as B / 100, the value of B is An all-solid battery, wherein B ≦ 40. The all-solid-state battery according to any one of claims 1 to 5 ,
With a current density of 0.064 mA / cm ² , a discharge cut voltage of 1 V, and a charge cut voltage of 3 V, the discharge capacity in the second cycle when performing constant current charge / discharge multiple times at 25 ° C. is 200 mA / g or more. An all-solid-state battery characterized by being. The all-solid-state battery according to claim 6 or 7 ,
When the current density is 0.064 mA / cm ² , the discharge cut voltage is 0.3 V, the charge cut voltage is 3 V, and the constant current charge / discharge is performed several times at 25 ° C., the discharge capacity at the second cycle is 200 mA / g. An all-solid battery characterized by the above.   The all-solid-state battery according to any one of claims 6 to 9,
  The positive electrode active material is FeS. ₂ And an all solid state battery selected from FeS.   It is an all-solid-state battery of any one of Claims 6-10,
  The sulfide-based lithium ion conductive solid electrolyte has the following formula (1):
  XLi ₂ S- (1-X) P ₂ S ₅         ... (1)
(In the formula, X is 0.65 ≦ X ≦ 0.80)
  An all-solid battery characterized by being a solid electrolyte represented by The all-solid-state battery according to any one of claims 1 to 11 ,
The oxide-based lithium ion conductive solid electrolyte has the following formula (2):
Li _{1 + Y} Al _Y M _2-Y (PO ₄ ) ₃ (2)
(Wherein M is at least one selected from the group consisting of germanium, titanium, hafnium, and zirconium, and Y is 0 <Y <1)
An all-solid battery characterized by being a solid electrolyte represented by The all-solid-state battery according to claim 12 ,
The oxide-based lithium ion conductive solid electrolyte is an all solid state battery in which M in the formula (2) is germanium. An all-solid-state battery according to claim 13 ,
The oxide-based lithium ion conductive solid electrolyte is Y = 0.5 in the formula (2), and is an all solid state battery.

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