JP2021026921A - Active material, electrode for lithium sulfur battery, and lithium sulfur battery - Google Patents

Abstract

To provide an active material which is suitable as a constituent of an electrode of an all-solid type lithium ion battery or lithium sulfur battery, and an electrode for a lithium sulfur battery and a lithium sulfur battery which include the active material.SOLUTION: An active material according to the present invention comprises a compound in which Li atoms in Li2S are partially substituted with a polyvalent atom originating from a Group II element, Group III element or Group XIII element of the periodic table, wherein the compound has a diffraction pattern of Li2S substantially according to X-ray diffraction.SELECTED DRAWING: Figure 1

Description

The present invention relates to an active material suitable as a constituent material such as a positive electrode constituting a lithium-sulfur battery, an electrode for a lithium-sulfur battery, and a lithium-sulfur battery.

Secondary batteries with high charge / discharge capacity are being actively developed for terminal devices such as mobile phones and electric vehicles. As a secondary battery capable of charging and discharging, a lithium ion battery has been put into practical use, and the charging / discharging capacity is about 170 mAh / g. Therefore, in recent years, a lithium-sulfur battery using a positive electrode active material containing sulfur having a theoretical capacity as high as about 1670 mAh / g has been attracting attention. In particular, an all-solid-state lithium-sulfur battery using a solid electrolyte as an electrolyte does not elute lithium polysulfide into an electrolyte solution, which is a problem in lithium-sulfur batteries using a liquid electrolyte, so that the charge / discharge capacity can be maintained and the service life can be extended. Suitable for conversion. In addition, since no flammable organic solvent is used, there is no risk of liquid leakage or ignition, and it is expected from the viewpoint of safety.
However, since sulfur has insulating properties, the electron conductivity and lithium ion conductivity of the positive electrode are very low, and the above theoretical capacity tends to be insufficiently exhibited. Therefore, other compounds are used together with sulfur as an active material. Attempts have been made. For example, Patent Document 1 discloses an electrode material containing sulfur and at least one of compounds containing a sulfur atom, a conductive substance, and a solid electrolyte containing a lithium atom, a phosphorus atom, and a sulfur atom. Lithium sulfide and lithium polysulfide (Li ₂ S ₂ , Li ₂ S ₄ , Li ₂ S ₈ ) are exemplified as the compound containing an atom, and it is described that this is used as an active material.

Further, as an active material for a lithium ion battery, for example, the techniques described in Patent Documents 2 to 3 are known. Patent Document 2 discloses a positive electrode active material for a lithium ion battery containing Li, Mo and S as constituent elements. Patent Document 3 describes lithium polysulfide and transition metal sulfides (titanium sulfide, molybdenum sulfide, vanadium sulfide, cobalt sulfide, nickel sulfide, iron sulfide, chromium sulfide, manganese sulfide, zinc sulfide). A method for producing a sulfide transition metal lithium-based positive electrode active material for a lithium ion battery is disclosed, which comprises a step (A) of obtaining a sulfide transition metal lithium-based positive electrode active material by mixing the product and the like.

International Publication No. 2013-76955 JP 2015-76180 JP-A-2017-142950

The charge / discharge capacity of the lithium-sulfur battery disclosed in Examples of Patent Documents 2 and 3 is only about 1/10 of the theoretical value, and a high charge capacity has not been obtained.
An object of the present invention is to provide an active material for providing a lithium-sulfur battery having a high charge capacity, an electrode for a lithium-sulfur battery, and a lithium-sulfur battery.

The present invention is shown below.
[1] A compound in which a part of the Li atoms are substituted with polyvalent atom derived from the second group elements of the periodic table, the group 3 element or Group 13 element in the Li 2 _S, the X-ray diffraction, active material, characterized in that substantially comprises a compound having the diffraction pattern of Li 2 _S.
[2] The active material according to the above [1] used in a lithium-sulfur battery.
[3] An electrode for a lithium-sulfur battery, which comprises the active material according to the above [1] or [2].
[4] A lithium-sulfur battery comprising the electrode for a lithium-sulfur battery according to the above [3].

The active material of the present invention is suitable for forming an electrode (preferably a positive electrode) that provides a lithium-sulfur battery having a high charge capacity. Further, it is possible to provide a solid-state battery having high electrical conductivity and exhibiting excellent battery performance.

5 is an X-ray diffraction image of the active materials A1 to A4 obtained in Experimental Examples 1-1 to 1-4. 5 is an X-ray diffraction image of the active materials A5 to A8 obtained in Experimental Examples 1-5 to 1-8. It is an X-ray diffraction image of the active material A9 obtained in Experimental Example 1-9. 6 is an X-ray diffraction image of the active materials A10 to A13 obtained in Experimental Examples 1-10 to 1-13. It is an X-ray diffraction image of the active material A14 obtained in Experimental Example 1-14. It is a graph which shows the charging characteristic of the lithium-sulfur battery obtained in Experimental Examples 2-1 to 2-4. It is a graph which shows the charging characteristic of the lithium-sulfur battery obtained in Experimental Example 2-5-2-8. It is a graph which shows the graph which shows the charging characteristic of the lithium-sulfur battery obtained in Experimental Example 2-9. It is a graph which shows the charging characteristic of the lithium-sulfur battery obtained in Experimental Example 2-10-2-13. It is a graph which shows the charging characteristic of the lithium-sulfur battery obtained in Experimental Example 2-14. It is the schematic sectional drawing which shows the measurement cell for charge test containing the all-solid-state lithium-sulfur battery produced in [Example].

Active material of the present invention, a Group 2 element of some Li atoms of the periodic table in the Li 2 _S, compounds substituted with a polyvalent atom derived from the third group element or a Group 13 element (hereinafter, "Compound (A) ") is included. The active material of the present invention is useful as a component constituting an element of a lithium-sulfur battery.

The atoms contained in the compound (A) are at least Li atoms, S atoms, and polyvalent atoms derived from Group 2 elements, Group 3 elements, or Group 13 elements in the periodic table.
The Group 2 elements are preferably Mg, Ca, Sr, Ba and the like, and particularly preferably Mg and Ca.
The Group 3 element is preferably Sc, Y, La or the like, and particularly preferably Y.
The Group 13 element is preferably B, Al, Ga, In or the like, and particularly preferably Al.

The compound (A) can be represented by the following general formula (1).
Li _2-at M _t S (1)
(In the formula, M is an atom derived from a Group 2 element, a Group 3 element or a Group 13 element in the periodic table, and a is a valence of the atom M, where 0 <t ≦ 0.200. .)

Among the compounds represented by the general formula (1), preferable compounds from which a lithium-sulfur battery having excellent conductivity and high charge capacity can be obtained are exemplified below.
(A) The atom M is Mg or Ca, preferably 1.60 ≦ (2-at) <2.00 and 0 <t ≦ 0.200, more preferably 1.70 ≦ (2-at) ≦ 1. .90 and 0.050 ≦ t ≦ 0.150 Compound (a) Atom M is Al, preferably 1.40 ≦ (2-at) <2.00 and 0 <t ≦ 0.200. Compounds preferably 1.50 ≦ (2-at) ≦ 1.90 and 0.033 ≦ t ≦ 0.167

The compound (A) can further contain other atoms. Examples of other atoms include halogen atoms, hydrogen atoms, oxygen atoms and the like, and halogen atoms such as chlorine atom, bromine atom and iodine atom are preferable.
When the compound (A) contains a halogen atom, it can be represented by the following general formula (2). This compound is a compound in which some S atoms are replaced with halogen atoms.
Li _{2-au Muu} S _{(1-au / 2)} X _au (2)
(In the formula, M is an atom derived from a Group 2 element, a Group 3 element or a Group 13 element in the periodic table, X is a halogen atom, a is the valence of the atom M, and 0 < u ≦ 0.200.)

Among the compounds represented by the general formula (2), preferable compounds from which a lithium-sulfur battery having excellent conductivity and high charge capacity can be obtained are exemplified below.
(A) The atom M is Mg or Ca, preferably 1.60 ≦ (2-au) <2.00 and 0 <u ≦ 0.200, more preferably 1.70 ≦ (2-au) ≦ 1. .90 and 0.050 ≦ u ≦ 0.150 Compound (a) Atom M is Y, preferably 1.40 ≦ (2-au) <2.00 and 0 <u ≦ 0.200. Compounds preferably 1.50 ≦ (2-au) ≦ 1.90 and 0.033 ≦ u ≦ 0.167

In the present invention, the compound (A) X-ray diffraction when subjected to (hereinafter also referred to as "XRD") measurements, having a diffraction pattern of the substantially Li 2 _S. That is, in the X-ray diffraction image obtained by XRD measurement using CuKα ray as the X-ray source, the diffraction angle 2θ = 26.99 ± 0.1 °, 31.27 ± 0.1 °, 44.81 ± 0. Diffraction peaks can be seen at 1 ° and 53.09 ± 0.1 °.

The conductivity (AC impedance method, 70 ° C.) of the compound (A) is preferably 1.0 × 10 ^-9 S / cm or more, more preferably 1.0 × 10 ^-8 S / cm or more. However, the upper limit is usually 1.0 × 10 ^-1 S / cm.

The compound (A) contained in the active material of the present invention may be only one kind or two or more kinds.

The compound (A), producing a Li 2 _S, Group 2 elements of the periodic table, by contacting reacting a sulfide or halide containing multivalent atoms derived from the third group element or a Group 13 element can do. If necessary, lithium halogenated LiX (lithium chloride, lithium bromide, lithium iodide, etc.) can be used.

From the viewpoint of these reactivity, the compound raw material is preferably finely granular. The upper limit of the maximum length of the particles is preferably 100 μm, more preferably 50 μm. However, the lower limit is usually 0.01 μm.

In the contact reaction for producing the compound (A), a ball mill (planetary ball mill or the like), a vibration mill, a turbo mill, a mechanofusion, a disc mill or the like can be used. The method of using the compound raw material is not particularly limited, and the contact reaction may be carried out using all the raw materials, or the contact reaction may be carried out while gradually changing the type or supply amount of the raw materials. ..
The atmosphere of the reaction system in the contact reaction is not particularly limited, and may consist of an inert gas such as nitrogen gas or argon gas, dry air, or the like.

The contact reaction may be carried out in the presence of a solvent. Examples of the solvent include alcohols, carboxylic acids, carboxylic acid esters, ethers, aldehydes, ketones, carbonic acid esters, nitriles, amides, nitros, phosphoric acid esters, halogenated hydrocarbons and the like. Be done.
When the contact reaction is carried out in the presence of a solvent, a suspension containing the compound (A) is usually obtained. Therefore, by removing the solvent thereafter, a solid composition containing the compound (A) can be obtained. This solid composition can be used as it is as the active material of the present invention.

The active material of the present invention may consist only of compound (A). As described above, the active material of the present invention is useful as a constituent component of an electrode for a lithium-sulfur battery, and as long as the lithium-sulfur battery has the desired performance, the active material of the present invention is compound (A). And other compounds may be used. When other compounds are contained, the upper limit of the content ratio is usually 49 parts by mass when the compound (A) is 100 parts by mass.

Active material of the present invention is suitable as a constituent of the positive electrode, other compounds capable of constituting the positive electrode, Li _x P _y S _z type sulfides, complex oxide, a composite hydroxides Solid electrolytes are preferred.
When the active material of the present invention is composed of compound (A) and another compound, it may be in either a form of a mixture separable from each other or a form in which both are integrated (including a form in which one covers the other). Good.

The conductivity of the active material of the present invention (AC impedance method, 70 ° C.) is preferably 1.0 × 10 ^-9 S / cm or more, more preferably 1.0 × 10 ^-8 S / cm or more. However, the upper limit is usually 1.0 × 10 ^-1 S / cm.

The active material of the present invention is suitable as a constituent material for electrodes of lithium-sulfur batteries. A lithium-sulfur battery usually includes a positive electrode, a negative electrode, and an electrolyte layer arranged between the positive electrode and the negative electrode (not shown). Further, a positive current collector that collects electricity from the positive electrode and a negative current collector that collects electricity from the negative electrode can be provided. The active material of the present invention containing the compound (A) is particularly suitable as a constituent material for a positive electrode of a lithium-sulfur battery having such a configuration.

Among the electrodes for lithium-sulfur batteries of the present invention, the positive electrode may further contain a binder, a solid electrolyte, a conductive auxiliary agent, and the like in addition to the compound (A).

Examples of the binder include fluororesins such as polytetrafluoroethylene (PTFE), polyhexafluoropropylene (PHFP), polyvinylidene fluoride (PVdF), and vinylidene fluoride / hexafluoropropylene copolymer; polyolefins such as polypropylene and polyethylene. Based resins: ethylene / propylene / non-conjugated diene rubber (EPDM, etc.), sulfonated EPDM, natural butyl rubber (NBR), etc. may be mentioned.

The solid electrolyte is not particularly limited, but is preferably Li ₃ PS ₄ , Li ₇ P ₃ S ₁₁ , Li _7-z PS _6-z X _z (X: Cl, Br, I, 0 ≦ z ≦ 1. 5), Li ₇ P ₂ S ₈ X (X: Cl, Br, I) and other sulfide-based solid electrolytes.
As the conductive auxiliary agent, those made of a carbon material, a metal powder, a metal compound, or the like can be used, and among these, a carbon material is preferably used. As carbon materials, plate-like conductive substances such as graphene; linear conductive substances such as carbon nanofibers and carbon nanotubes; carbon such as Ketjen black, acetylene black, denca black (trade name), thermal black, and channel black. Examples thereof include granular conductive substances such as black and graphite.

The positive electrode preferably contains the compound (A), a solid electrolyte, and a conductive auxiliary agent. In this case, the content ratio of the solid electrolyte and the conductive auxiliary agent is preferably 20 to 100 parts by mass and 10 to 50 parts by mass, more preferably 20 to 60 parts by mass, respectively, assuming that the content of the compound (A) is 100 parts by mass. It is a mass part and 15 to 30 parts by mass.

The thickness of the positive electrode in the energizing direction is not particularly limited, but is usually 5 μm or more, preferably 20 μm to 0.5 mm.

Among the electrodes for lithium sulfur batteries of the present invention, the negative electrode contains a negative electrode active material, and the negative electrode active material includes a carbon material; a metal such as lithium, indium, aluminum, silicon, or an alloy containing these; Sn _x O. _y , MoO _x , WO _x , Li _x CoO _y (LiCoO ₂ etc.), Li _x Mn _y Ni _z Co _w O (LiNi _1/3 Co _1/3 Mn _1/3 O ₂ etc.), Li _x CuP _x O Examples thereof include oxide (composite oxide) -based materials such as _y (LiCuPO _{4, etc.).} The negative electrode may further contain a binder, a conductive auxiliary agent, a solid electrolyte, and the like.

The thickness of the negative electrode in the energizing direction is not particularly limited, but is usually 1 μm or more, preferably 10 μm to 0.5 mm.

The electrolyte layer is not particularly limited as long as it contains a solid electrolyte, but it is preferably substantially made of a solid electrolyte. _{Examples of the} solid electrolyte include sulfides such _{as (MoS x} , CuS _x , TiS _x , WS _x ), Li _x S _y , Li _x P _y S _{z; MoO x} , WO _x , VO _x , Li _x CoO _y , Li. _x MnO _y , Li _x NiO _y , Li _x VO _y , Li _x Mn _y Ni _z Co _w O, Li _x FeP _x O _y , Li _x MnP _x O _y , Li _x NiP _x O _y , Li _x CuP _x O _{Oxides or composite oxides such as y} (LiCuPO _4, etc.); serene products and the like can be mentioned.

The thickness of the electrolyte layer in the energizing direction is not particularly limited, but is usually 1 μm or more, preferably 10 μm to 0.5 mm.

The positive electrode current collector or the negative electrode current collector can be made of, for example, stainless steel, gold, platinum, copper, zinc, nickel, tin, aluminum, or an alloy thereof, and is a plate-like body or a foil-like body. , A mesh-like body and the like can be provided.

The lithium-sulfur battery of the present invention includes the above-mentioned electrode for the lithium-sulfur battery of the present invention. From the viewpoint of charge capacity, a lithium-sulfur battery including a positive electrode containing the compound (A), a solid electrolyte, and a conductive auxiliary agent is particularly preferable.

1. 1. Raw materials for production The raw materials used for the production of active materials are as follows.
(1) Lithium sulfide (Li _{2 S) powder "Li 2} S" (trade name) manufactured by Mitsuwa Chemical Co., Ltd. was used. The purity is 99.9% and the particle size is about 50 μm.
(2) Magnesium sulfide (MgS) powder "MgS" (trade name) manufactured by High Purity Chemical Laboratory Co., Ltd. was used. The purity is 99.9% and the particle size is several tens of μm.
(3) Calcium chloride (CaCl ₂ ) powder "CaCl ₂ " (trade name) manufactured by Aldrich was used. The purity is 99.9% and the particle size is 10 mesh or less.
(4) Calcium sulfide (CaS) powder "CaS" (trade name) manufactured by High Purity Chemical Laboratory Co., Ltd. was used. The purity is 99.9% and the particle size is about 50 μm.
(5) Aluminum sulfide (Al ₂ S _{3 ) powder “Al 2} S ₃ ” (trade name) manufactured by High Purity Chemical Laboratory Co., Ltd. was used. The purity is 98% and the particle size is about 50 μm.
(6) Yttrium chloride (YCl _{3 ) powder “YCl 3} ” (trade name) manufactured by High Purity Chemical Laboratory Co., Ltd. was used. The purity is 99.9% and the particle size is several mm.

2. 2. Production and evaluation of active material An active material was produced using the above raw materials, and the conductivity was measured by the following method.
<Measurement method of conductivity>
The active material was made into a disk-shaped test piece (size: radius 5 mm x height 0.3 mm) using a uniaxial hydraulic press machine, and placed in a measurement unit (glass container) in an argon gas atmosphere. Wrap the ribbon heater and heat insulating material connected to the temperature controller around the measuring unit (glass container), and gradually heat from room temperature using SOLATRON IMPEDANCE ANALYZER "S1260" (model name) at 70 ° C. The conductivity was measured. The conductivity was measured after allowing the test piece to stand for 1 hour after starting to hold the test piece at 70 ° C.

Experimental Example 1-1 (Production of Active Material A1 Containing _{Li 2 S)}
Lithium sulfide _(Li 2 S) powder Frisch Co. planetary ball mill with zirconia balls having a diameter of 15 mm: put in (container zirconia), at a rotational speed 600 rpm, the mechanical milling for 10 hours, an active material A1 Obtained.
The conductivity of the obtained active material A1 was measured and found to be 2 × 10 ^-10 S / cm at 70 ° C. Since the conductivity is low at room temperature and stable measured values cannot be obtained, the measurement was performed at 70 ° C.

Experimental Example 1-2 (Production of active material A2 containing _{Li 1.9} Mg _{0.05 S)}
Li, the molar ratio of Mg and S 1.9: 0.05: to be 1, were weighed and (2 S _Li) powder lithium sulfide, and magnesium sulfide (MgS) powder were mixed together .. Next, the mixed powder was placed in a planetary ball mill manufactured by Frisch (container: manufactured by zirconia) together with zirconia balls having a diameter of 15 mm, and mechanical milling was performed for 10 hours under the condition of a rotation speed of 600 rpm to obtain an active material A2.
X-ray diffraction measurement of the obtained active material A2 was carried out, but shifted to a lower angle side, it was confirmed to contain a compound having a diffraction pattern of the substantially Li 2 _S (see FIG. 1). Also, peaks other than Li 2 _S in the X-ray diffraction pattern is not observed, the active material A2 was estimated to consist of solid solution does not reach the solubility limit.
Moreover, when the conductivity of this active material A2 was measured, it was 8.0 × 10 ^-9 S / cm at 70 ° C.

Experimental Example 1-3 (Production of active material A3 containing _{Li 1.8} Mg _{0.1 S)}
Li, the molar ratio of Mg and S 1.8: 0.1: to be 1, except for using a lithium _(Li 2 S) powder sulfide, magnesium sulfide (MgS) powder, Experiment The same operation as in 1-2 was performed to obtain the active material A3.
X-ray diffraction measurement of the obtained active material A3 was carried out, but shifted to a lower angle side, it was confirmed to contain a compound having a diffraction pattern of the substantially Li 2 _S (see FIG. 1). Also, peaks other than Li 2 _S in the X-ray diffraction pattern is not observed, the active material A3 was estimated to consist of solid solution does not reach the solubility limit.
Moreover, when the conductivity of this active material A3 was measured, it was 9.2 × ^10-8 S / cm at 70 ° C.

Experimental Example 1-4 (Production of active material A4 containing _{Li 1.7} Mg _{0.15 S)}
Li, the molar ratio of Mg and S 1.7: 0.15: to be 1, except for using a lithium _(Li 2 S) powder sulfide, magnesium sulfide (MgS) powder, Experiment The same operation as in 1-2 was performed to obtain the active material A4.
It was subjected to X-ray diffraction measurement of the obtained active material A4, slightly observed diffraction pattern of MgS, Although shifted to a lower angle side, a compound having a diffraction pattern of the substantially Li 2 _S Was confirmed to include (see FIG. 1). Further, the peak intensity ratio of the Li 2 _S and MgS in the X-ray diffraction pattern, the active material A4 was estimated to consist of solid solution has reached the solubility limit.
The conductivity of the active material A4 was measured and found to be 5.1 × ^10-8 S / cm at 70 ° C.

Experimental Example 1-5 (Production of active material A5 containing _{Li 1.9} Ca _0.05 S _0.95 Cl _0.1)
Li, Ca, the molar ratio of the S and Cl 1.9: 0.05: 0.95: so that 0.1, and lithium sulfide _(Li 2 S) powder, calcium chloride (CaCl ₂₎ powder And were weighed and these were mixed. Next, the mixed powder was placed in a planetary ball mill manufactured by Frisch (container: manufactured by zirconia) together with zirconia balls having a diameter of 15 mm, and mechanical milling was performed for 10 hours under the condition of a rotation speed of 600 rpm to obtain an active material A5.
X-ray diffraction measurement of the obtained active material A5 was carried out, but is shifted to a high angle side, it was confirmed to contain a compound having a diffraction pattern of the substantially Li 2 _S (see FIG. 2). The peaks marked with x in FIG. 2 are derived from Si mixed for verification of the peak position. Therefore, peaks other than Li 2 _S in the X-ray diffraction pattern is not observed, the active material A5 was estimated to consist of solid solution does not reach the solubility limit.
Moreover, when the conductivity of this active material A5 was measured, it was 2.4 × 10 ^-6 S / cm at 70 ° C.

Experimental Example 1-6 (Production of active material A6 containing _{Li 1.8} Ca _0.1 S _0.9 Cl _0.2)
Li, Ca, the molar ratio of the S and Cl 1.8: 0.1: 0.9: so that 0.2, and lithium sulfide _(Li 2 S) powder, calcium chloride (CaCl ₂₎ powder The same operation as in Experimental Example 1-5 was performed except that the active material A6 was obtained.
X-ray diffraction measurement of the obtained active material A6 was subjected to, but shifted to the high angle side, it was confirmed to contain a compound having a diffraction pattern of the substantially Li 2 _S (see FIG. 2). The peaks marked with x in FIG. 2 are derived from Si mixed for verification of the peak position. Therefore, peaks other than Li 2 _S in the X-ray diffraction pattern is not observed, the active material A6 was estimated to consist of solid solution does not reach the solubility limit.
Moreover, when the conductivity of this active material A6 was measured, it was 1.0 × ^10-5 S / cm at 70 ° C.

Experimental Example 1-7 (Production of active material A7 containing _{Li 1.7} Ca _0.15 S _0.85 Cl _{0.3)
Lithium sulfide (Li 2} S) powder and calcium chloride (CaCl ₂ ) powder so that the molar ratio of Li, Ca, S and Cl is 1.7: 0.15: 0.85: 0.3. The same operation as in Experimental Example 1-5 was performed except that the active material A7 was obtained.
X-ray diffraction measurement of the obtained active material A7 was subjected to, but shifted to the high angle side, it was confirmed to contain a compound having a diffraction pattern of the substantially Li 2 _S (see FIG. 2). The peaks marked with x in FIG. 2 are derived from Si mixed for verification of the peak position. Therefore, peaks other than Li 2 _S in the X-ray diffraction pattern is not observed, the active material A7 was estimated to consist of solid solution does not reach the solubility limit.
Moreover, when the conductivity of this active material A7 was measured, it was 5.2 × ^10-5 S / cm at 70 ° C.

Experimental Example 1-8 (Production of active material A8 containing _{Li 1.6} Ca _0.2 S _0.8 Cl _0.4)
Li, Ca, the molar ratio of the S and Cl 1.6: 0.2: 0.8: to 0.4, and lithium sulfide _(Li 2 S) powder, calcium chloride (CaCl ₂₎ powder The same operation as in Experimental Example 1-5 was carried out except that the active material A8 was obtained.
Was subjected to X-ray diffraction measurement of the obtained active material A8, slightly observed diffraction pattern of LiCl, also although shifted to a higher angle side, a compound having a diffraction pattern of the substantially Li 2 _S Was confirmed to include (see FIG. 2). Further, the peak intensity ratio of the Li 2 _S and LiCl in X-ray diffraction pattern, the active material A8 was estimated to consist of solid solution has reached the solubility limit.

Experimental Example 1-9 (Production of active material A9 containing _{Li 1.9} Ca _{0.05 S)}
Li, the molar ratio of Ca and S of 1.9: 0.05: to be 1, were weighed and (2 S _Li) powder lithium sulfide, and calcium sulfide (CaS) powder were mixed together .. Next, the mixed powder was placed in a planetary ball mill manufactured by Frisch (container: manufactured by zirconia) together with zirconia balls having a diameter of 15 mm, and mechanical milling was performed for 10 hours under the condition of a rotation speed of 600 rpm to obtain an active material A9.
It was subjected to X-ray diffraction measurement of the obtained active material A9, slightly observed diffraction pattern of the CaS, Although shifted to a lower angle side, a compound having a diffraction pattern of the substantially Li 2 _S Was confirmed to include (see FIG. 3). Further, the peak intensity ratio of the Li 2 _S and CaS in X-ray diffraction pattern, the active material A9 was estimated to consist of solid solution has reached the solubility limit.
Moreover, when the conductivity of this active material A9 was measured, the value was not stable at 70 ° C. ^{and was 10-8} to ^10-9 S / cm.

Experimental Example 1-10 (Production of active material A10 containing _{Li 1.9} Al _{0.033 S)
Lithium sulfide (Li 2} S) powder and aluminum sulfide (Al ₂ S ₃ ) powder were weighed so that the molar ratio of Li, Al and S was 1.9: 0.033: 1. Was mixed. Next, the mixed powder was placed in a planetary ball mill manufactured by Frisch (container: manufactured by zirconia) together with zirconia balls having a diameter of 15 mm, and mechanical milling was performed for 10 hours under the condition of a rotation speed of 600 rpm to obtain an active material A10.
X-ray diffraction measurement of the obtained active material A10 was subjected to, but shifted to a lower angle side, it was confirmed to contain a compound having a diffraction pattern of the substantially Li 2 _S (see FIG. 4). Also, peaks other than Li 2 _S in the X-ray diffraction pattern is not observed, the active material A10 was estimated to consist of solid solution does not reach the solubility limit.
Moreover, when the conductivity of this active material A10 was measured, it was 3.0 × 10 ^-6 S / cm at 70 ° C.

Experimental Example 1-11 (Production of active material A11 containing _{Li 1.8} Al _{0.067 S)
Except for the use of lithium sulfide (Li 2} S) powder and aluminum sulfide (Al ₂ S ₃ ) powder so that the molar ratio of Li, Al and S is 1.8: 0.067: 1. , The same operation as in Experimental Example 1-10 was carried out to obtain active material A11.
X-ray diffraction measurement of the obtained active material A11 was subjected to, but shifted to a lower angle side, it was confirmed to contain a compound having a diffraction pattern of the substantially Li 2 _S (see FIG. 4). Also, peaks other than Li 2 _S in the X-ray diffraction pattern is not observed, the active material A11 was estimated to consist of solid solution does not reach the solubility limit.
Moreover, when the conductivity of this active material A11 was measured, it was 1.4 × ^10-5 S / cm at 70 ° C.

Experimental Example 1-12 (Production of active material A12 containing _{Li 1.7} Al _{0.1 S)}
Except for the use of _{lithium sulfide (Li 2} S) powder and aluminum sulfide (Al ₂ S ₃ ) powder so that the molar ratio of Li, Al and S is 1.7: 0.1: 1. , The same operation as in Experimental Example 1-10 was carried out to obtain active material A12.
X-ray diffraction measurement of the obtained active material A12 was subjected to, but shifted to a lower angle side, it was confirmed to contain a compound having a diffraction pattern of the substantially Li 2 _S (see FIG. 4). Also, peaks other than Li 2 _S in the X-ray diffraction pattern is not observed, the active material A12 was estimated to consist of solid solution does not reach the solubility limit.
Moreover, when the conductivity of this active material A12 was measured, it was 7.9 × 10 ^-6 S / cm at 70 ° C.

Experimental Example 1-13 (Production of active material A13 containing _{Li 1.5} Al _{0.167 S)}
Except for the use of _{lithium sulfide (Li 2} S) powder and aluminum sulfide (Al ₂ S ₃ ) powder so that the molar ratio of Li, Al and S is 1.5: 0.167: 1. , The same operation as in Experimental Example 1-10 was carried out to obtain active material A13.
X-ray diffraction measurement of the obtained active material A13 was subjected to, but shifted to a lower angle side, it was confirmed to contain a compound having a diffraction pattern of the substantially Li 2 _S (see FIG. 4). Also, peaks other than Li 2 _S in the X-ray diffraction pattern is not observed, the active material A13 was estimated to consist of solid solution does not reach the solubility limit.
Moreover, when the conductivity of this active material A13 was measured, it was 4.9 × 10 ^-5 S / cm at 70 ° C.

Experimental Example 1-14 (Production of active material A14 containing _{Li 1.5} Y _0.167 S _0.75 Cl _0.5)
Li, Y, the molar ratio of the S and Cl 1.5: 0.167: 0.75: so that 0.5, (2 S _Li) and a powder of lithium sulfide, yttrium chloride (YCl ₃₎ powder And were weighed and these were mixed. Next, the mixed powder was placed in a planetary ball mill manufactured by Frisch (container: manufactured by zirconia) together with zirconia balls having a diameter of 15 mm, and mechanical milling was performed for 10 hours under the condition of a rotation speed of 600 rpm to obtain an active material A14.
Was subjected to X-ray diffraction measurement of the obtained active material A14, was slightly observed diffraction pattern of LiYS _2, Although shifted to a lower angle side, it has a diffraction pattern substantially Li 2 _S It was confirmed that it contained a compound (see FIG. 5). Further, the peak intensity ratio of the Li ₂ S and LiYS ₂ in X-ray diffraction pattern, the active material A14 was estimated to consist of solid solution has reached the solubility limit.
Moreover, when the conductivity of this active material A14 was measured, it was 2.0 × ^10-5 S / cm at 70 ° C.

3. 3. Manufacture and Evaluation of Positive Electrode and Lithium-Sulfur Battery A positive electrode composite containing the active material of the above experimental example was prepared, and then a lithium-sulfur battery equipped with a positive electrode was prepared using this positive electrode composite.
Next, the measurement cell of FIG. 11 containing the obtained lithium-sulfur battery was prepared and a charging test was performed.

Experimental Example 2-1
In the following way, _Li 1.9 _{Mg 0.05} S-containing active material A2 of Example 1-2, a solid electrolyte _Li 7 _P 2 _S 8 I, and the mass of the carbon nanofibers is an electron conductive aid A positive electrode composite having a ratio of 50:40:10 was obtained.
_{First , lithium sulfide (Li 2} S) powder and magnesium sulfide (Mg S) powder, which are weighed so as to be Li _1.9 Mg _0.05 S-containing active material A2, and Li 1. formed by these. _{Li 7} P ₂ S ₈ I and carbon nanofibers (diameter: 0.1 μm, length: 20 μm) in which the ratio of the amount used to the active material A2 containing ₉ Mg _{0.05 S was 80% and 20%, respectively.} Was mixed. Then, the mixed powder was placed in a planetary ball mill manufactured by Frisch (container: manufactured by zirconia) together with zirconia balls having a diameter of 4 mm, and mechanical milling was performed for 10 hours under the condition of a rotation speed of 510 rpm to obtain a composite for a positive electrode.
_{Next, the Li 7} P ₂ S ₈ I powder, which is a solid electrolyte, was pressure-molded using a uniaxial hydraulic press to obtain a disk-shaped preformed body (radius: 5 mm, thickness: 0.5 mm). .. Then, in a state where the preformed body for the electrolyte layer is housed inside a tubular body made of polyetheretherketone (PEEK), the entire surface side of one of them is covered with the positive electrode composite obtained above. It was filled with 5 mg and pressure-molded using a uniaxial hydraulic press. Further, a Li-In alloy foil (thickness 0.1 mm, diameter 5 mm) is attached to the other surface of the preformed body for the electrolyte layer, and a positive electrode 21 (thickness about 30 μm) made of a positive electrode composite and Li an electrolyte layer 25 composed of ₇ P ₂ S ₈ I, to give a lithium-sulfur battery 20 of the all-solid-state form and a negative electrode 23 consisting of Li-an in alloy.
Then, stainless-nickel conductive portions were inserted from both sides of the tubular body containing the lithium-sulfur battery 20, and fixed with a jig to obtain a measurement cell 10 shown in FIG. Then, the measurement cell 10 was sealed in a glass container (not shown), the gas in the glass container was replaced with argon gas, and a charging test was performed. In the charging test, a glass container containing the measurement cell 10 was placed in an electric furnace set at 60 ° C., and a charging / discharging device “BTS-2004H” (model name) manufactured by NAGANO was used to perform 0.1-3.0 V vs Li. -In, C rate: 0.1 C. The result is shown in FIG.

Experimental Examples 2-2-2-4
In the same manner as in Experimental Example 2-1 of Li ₂ S-containing active material A1 of _{Experimental Example 1-1, Li 1.8} Mg _0.1 S-containing active material A3 of Experimental Example 1-3, or Experimental Example 1-4. The mass ratio of the active material A4 containing Li _1.7 Mg _0.15 S, the solid electrolyte Li ₇ P ₂ S ₈ I, and the carbon nanofibers as the electron conductive auxiliary agent is 50:40:10. The positive electrode composite of Experimental Example 2-2-2-4 was obtained.
Then, using these positive electrode composites, a lithium-sulfur battery 20 including a positive electrode electrode 21 was obtained in the same manner as in Experimental Example 2-1. Then, a charging test was conducted in the same manner as in Experimental Example 2-1. The result is shown in FIG.

6 that the use of electrodes in which a part of the Li atoms contains Li 2 _S-based compounds substituted with Mg atoms, it can be seen that the lithium-sulfur battery charge capacity is improved was obtained.

Experimental Examples 2-5 to 2-8
In the same manner as in Experimental Example 2-1: Li _1.9 Ca _0.05 S _0.95 Cl _0.1- containing active material A5 of Experimental Example 1-5, Li _1.8 Ca _{0. of Experimental Example 1-6. 1} S _0.9 Cl _0.2- containing active material A6, Li of Experimental Example 1-7 _1.7 Ca _0.15 S _0.85 Cl _0.3- containing active material A7 or Li of Experimental Example 1-8 _{1. 6} Ca _0.2 S _0.8 Cl _{0.4- containing active material A8, Li 5.5} PS _4.5 Cl _1.5 , which is a solid electrolyte, and carbon nanofibers, which is an electron-conducting aid. The positive electrode composite of Experimental Example 2-5 to 2-8 was obtained at 50:40:10.
Then, using these positive electrode composites, a lithium-sulfur battery 20 including a positive electrode electrode 21 was obtained in the same manner as in Experimental Example 2-1. Then, a charging test (provided that the test temperature was 30 ° C.) was carried out in the same manner as in Experimental Example 2-1. The result is shown in FIG.

7 that when using the electrode containing Li 2 _S-based compounds partially substituted by Ca atoms of Li atoms, it can be seen that the lithium-sulfur battery charge capacity is improved was obtained.

Experimental Example 2-9
In the same manner as in Experimental Example 2-1 the Li _1.9 Ca _0.05 S-containing active material A9 of _{Experimental Example 1-9, the solid electrolyte Li 7} P ₂ S ₈ I, and the electron conductive auxiliary agent. A positive electrode composite having a mass ratio of 50:40:10 with carbon nanofibers was obtained.
Then, using this positive electrode composite, a lithium-sulfur battery 20 including a positive electrode electrode 21 was obtained in the same manner as in Experimental Example 2-1. Then, a charging test (provided that the test temperature: 60 ° C.) was performed in the same manner as in Experimental Example 2-1. The result is shown in FIG.

From FIG. 8, using an electrode containing Li 2 _S-based compounds partially substituted by Ca atoms of Li atoms, it can be seen that the lithium-sulfur battery charge capacity is improved was obtained.

Experimental Examples 2-10-2-13
In the same manner as in Experimental Example 2-1: Li _1.9 Al _0.033 S-containing active material A10 in Experimental Example _{1-10, Li 1.8} Al _0.067 S-containing active material A11 in Experimental Example 1-11, _{Li 1.7} Al _0.1 S-containing active material A12 of Experimental Example 1-12 _{or Li 1.5} Al _0.167 S-containing active material A13 of _{Experimental Example 1-13 and Li 5.5} PS which is a solid electrolyte. A positive electrode composite of Experimental Example 2-10 to 2-13 having a mass ratio of _4.5 Cl _{1.5 to carbon nanofibers as an electron conductive additive was obtained at 50:40:10.}
Then, using these positive electrode composites, a lithium-sulfur battery 20 including a positive electrode electrode 21 was obtained in the same manner as in Experimental Example 2-1. Then, a charging test (provided that the test temperature: 60 ° C.) was performed in the same manner as in Experimental Example 2-1. The result is shown in FIG.

From 9, using an electrode containing Li 2 _S-based compounds partially substituted by Al atoms Li atoms, it can be seen that the lithium-sulfur battery charge capacity is improved was obtained.

Experimental Example 2-14
In the same manner as in Experimental Example 2-1: Li _1.5 Y _0.167 S _0.75 Cl _{0.5- containing active material A14 of Experimental Example 1-14 and Li 5.5} PS _4.5 which is a solid electrolyte. A _{composite for a positive electrode having a mass ratio of Cl 1.5} and carbon nanofibers as an electron conductive auxiliary agent of 50:40:10 was obtained.
Then, using this positive electrode composite, a lithium-sulfur battery 20 including a positive electrode electrode 21 was obtained in the same manner as in Experimental Example 2-1. Then, a charging test (provided that the test temperature was 30 ° C.) was carried out in the same manner as in Experimental Example 2-1. The result is shown in FIG.

Than 10, the use of electrodes that includes a portion that Li 2 _S-based compounds substituted with Y atoms Li atoms, it can be seen that the lithium-sulfur battery charge capacity is improved was obtained.

The solid electrolyte of the present invention can be used as a power source for home appliances such as personal computers and cameras, portable electronic devices or communication devices such as power storage devices and mobile phones, electric tools such as power tools, and electric vehicles (EVs). , Is suitable as a constituent material of a lithium sulfur battery constituting a large battery mounted on a hybrid electric vehicle (HEV) or the like, that is, as a constituent material of an electrode for a lithium sulfur battery or an electrolyte layer.

10: Measurement cell for charge test 20: Lithium-sulfur battery 21: Positive electrode 23: Negative electrode 25: Electrolyte layer 27: PEEK tubular body 31: Press plate 33: Press pin 35: Tightening screw 37: Kapton (registered trademark) tape

Claims (4)

A compound in which a part of the Li atoms are substituted with polyvalent atom derived from the second group elements of the periodic table, the group 3 element or Group 13 element in the Li 2 _S, the X-ray diffraction, essentially active material which comprises a compound having the diffraction pattern of li 2 _S. The active material according to claim 1, which is used in a lithium-sulfur battery. An electrode for a lithium-sulfur battery, which comprises the active material according to claim 1 or 2. A lithium-sulfur battery including the electrode for a lithium-sulfur battery according to claim 3.

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