Power storage device, and method for producing layered material

Abstract

This power storage device 2a is provided with a first electrode 3a, a second electrode 3b, and an electrolyte solution 4. At least one selected from the group consisting of the first electrode 3a and the second electrode 3b is an electrode 1a containing a layered material 15. The electrolyte solution 4 contains a lithium salt. This lithium salt has at least one ion selected from the group consisting of: an anion in which four or more atoms of the same type are bonded to a central atom; and a bis(fluorosulfonyl)imide ion. A layer 15a includes a main body 15b and an end 15c. The main body 15b has a composition MmXn. M is at least one element selected from the group consisting of group 3 elements, group 4 elements, group 5 elements, group 6 elements and group 7 elements. X includes at least one atom selected from the group consisting of a carbon atom and a nitrogen atom. The molar ratio rLB of lithium 15l contained in the layered material 15 relative to the main body 15b is greater than 0 and not greater than 2.

Description

Energy storage device and method for manufacturing layered material

[0001] This disclosure relates to an energy storage device and a method for manufacturing a layered material.

[0002] In recent years, a material called MXene has attracted attention. MXene is a two-dimensional (2D) material, and as described below, it is a layered material having one or more layers. MXene generally exists in the form of particles of such layered materials, and these particles can be in the form of powder, flakes, or sheets.

[0003] Currently, research is being conducted on the application of MXene to electrochemical capacitors. For example, Non-Patent Literature 1 describes that when two-dimensional titanium carbide, a type of MXene, is produced by etching Al from Ti3AlC2, using a solution of lithium fluoride and hydrochloric acid increases the capacitance per unit volume.

[0004] Michael Ghidiu et al., “Conductive two-dimensional titanium carbide 'clay' with high volumetric capacitance”, Nature volume 516, pages78-81 (2014)

[0005] This disclosure provides an energy storage device that can exhibit high energy storage performance while having electrodes containing a predetermined layered material.

[0006] The energy storage device of this disclosure comprises a first electrode, a second electrode, and an electrolyte, wherein at least a portion of the first electrode and at least a portion of the second electrode are arranged apart from each other in the electrolyte, at least one selected from the group consisting of the first electrode and the second electrode is an electrode comprising a layered material, the electrolyte comprises a lithium salt having at least one selected from the group consisting of anions and bis(fluorosulfonyl)imide ions in which four or more atoms of the same type are bonded to a central atom, and the layered material is M m X nThe electrode comprises a body having the composition of and a layer including an end present on the surface of the body, and lithium, wherein in the body, M is at least one selected from the group consisting of Group 3, Group 4, Group 5, Group 6, and Group 7 elements, X includes at least one selected from the group consisting of carbon atoms and nitrogen atoms, n is 1 or more and 4 or less, m is greater than n and 5 or less, and the electrode satisfies at least one condition selected from the group consisting of (I) and (II) below: (I) The molar ratio of the lithium contained in the layered material to the body is greater than 0 and 2 or less. (II) The capacitance per unit volume of the electrode is Ag / Ag + 120 F / cm in the sweep range from -2.0 V to 0 V relative to the reference electrode. 3 That's all.

[0007] This disclosure provides a novel energy storage device capable of exhibiting high energy storage performance.

[0008] Figure 1 is a schematic diagram showing an example of an energy storage device. Figure 2 is a schematic diagram showing an example of a layered material. Figure 3 is a schematic diagram showing an example of an electrode. Figure 4 is a schematic diagram showing another example of an electrode. Figure 5 is a schematic diagram showing an example of an electrode material for an energy storage device. Figure 6 is a graph showing the results of X-ray diffraction (XRD) measurements of the layered materials and precursor Ti3AlC2 according to Example 1, Example 8, Comparative Example 5, Comparative Example 11, and Comparative Example 17. Figure 7 is a graph showing the results of X-ray diffraction measurements of the layered material and precursor Ti2AlC according to Example 10. Figure 8 is a graph showing the results of X-ray diffraction measurements of the layered material and precursor Mo2Ga2C according to Example 14.

[0009] (Knowledge forming the basis of this disclosure) As described in Non-Patent Literature 1, it is conceivable to use MXene in electrodes of energy storage devices such as electrochemical capacitors. Therefore, the inventors have diligently studied energy storage devices in which at least one electrode is an MXene-containing electrode. As a result, it has been newly discovered that in order to improve the energy storage performance of an energy storage device, not only the MXene-containing electrode but also the combination of the MXene-containing electrode and the electrolyte is important. The inventors have newly discovered that an energy storage device comprising an electrode containing a predetermined layered material and a predetermined electrolyte can exhibit high energy storage performance. Based on this new knowledge, the inventors have completed the energy storage device of this disclosure.

[0010] (Embodiments) Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. The present disclosure is not limited to the following embodiments.

[0011] Figure 1 is a schematic diagram showing an example of an energy storage device. As shown in Figure 1, the energy storage device 2a comprises a first electrode 3a, a second electrode 3b, and an electrolyte 4. At least a portion of the first electrode 3a and at least a portion of the second electrode 3b are arranged apart from each other in the electrolyte 4. At least a portion of the first electrode 3a and at least a portion of the second electrode 3b may be immersed in the electrolyte 4 or may be in contact with a separator 7 impregnated with the electrolyte 4. At least one selected from the group consisting of the first electrode 3a and the second electrode 3b is an electrode 1a containing a layered material 15. The electrolyte 4 contains a lithium salt. This lithium salt contains anions and bis(fluorosulfonyl)imide ions (FSI) in which four or more atoms of the same type are bonded to a central atom. - It has at least one selected from the group consisting of ).

[0012] Figure 2 is a schematic diagram showing an example of a layered material 15. As shown in Figure 2, the layered material 15 includes a layer 15a and lithium 15l. Layer 15a includes a main body 15b and an end 15c. The main body 15b is M m X nIt has the composition. The terminal 15c exists on the surface of the main body 15b. In the main body 15b, M is at least one selected from the group consisting of Group 3 elements, Group 4 elements, Group 5 elements, Group 6 elements, and Group 7 elements. X contains at least one selected from the group consisting of carbon atoms and nitrogen atoms. n is 1 or more and 4 or less. m is greater than n and 5 or less. The electrode 1a satisfies at least one condition selected from the group consisting of the following (I) and (II). (I) The molar ratio r LB of lithium 15l contained in the layered material 15 to the main body 15b is greater than 0 and 2 or less. (II) The capacitance per unit volume of the electrode 1a is within the sweep range of -2.0 V to 0 V with respect to the Ag / Ag + reference electrode, and is 120 F / cm 3 or more.

[0013] Since the electrolytic solution 4 contains the above lithium salt and the electrode 1a satisfies at least one condition selected from the group consisting of the above (I) and (II), the power storage device 2a is likely to exhibit high power storage performance. For example, compared with the case where the electrolytic solution does not contain the above lithium salt and contains an electrolyte other than this lithium salt, the power storage device 2a is likely to exhibit high power storage performance. The reason is not clear. It is considered that the lithium salt in the electrolytic solution 4 contains an anion having a high steric symmetry such as an anion in which four or more atoms of the same kind are bonded to the central atom, and / or an anion having a relatively small ionic radius, so that the lithium salt is likely to be inserted into the layered material 15. If the lithium salt is likely to be inserted into the layered material 15, the power storage device 2a is likely to exhibit high power storage performance.

[0014] The lithium salt contained in the electrolyte 4 is not limited to a specific lithium salt, as long as it contains at least one selected from the group consisting of anions and bis(fluorosulfonyl)imide ions in which four or more atoms of the same type are bonded to a central atom. The anion is, for example, a monovalent anion. Examples of this lithium salt are lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium sulfate (Li2SO4), and lithium bis(fluorosulfonyl)imide (LiFSI). Preferably, the lithium salt contains at least one selected from the group consisting of LiPF6, LiBF4, and LiFSI. In this case, the energy storage device 2a is more likely to exhibit high energy storage performance.

[0015] In the energy storage device 2a, the electrode 1a may satisfy only condition (I) above, or only condition (II). Preferably, the electrode 1a satisfies both conditions (I) and (II). In this case, the energy storage device 2a is more likely to exhibit high energy storage performance.

[0016] As described above, the layered material 15 contains lithium 15l. As a result, the energy storage device 2a tends to exhibit higher energy storage performance compared to, for example, an energy storage device equipped with electrodes containing MXene that do not contain lithium 15l. The reason for this is not clear. Lithium readily forms a solvation structure. This is thought to expand the interlayer distance d between layers 15a, making it easier for cations or anions contained in the electrolyte to be inserted into or detached from the layered material 15. For this reason, the energy storage device 2a tends to exhibit high energy storage performance. Note that the lithium 15l does not originate from the lithium contained in the electrolyte 4.

[0017] If electrode 1a satisfies condition (I), then the molar ratio r LB The molar ratio r is preferably 1.8 or less, more preferably 1.5 or less, even more preferably 1.2 or less, and particularly preferably 1.0 or less. LBIt is particularly desirable to be 0.8 or less, very desirable to be 0.5 or less, extremely desirable to be 0.40 or less, and most desirable to be 0.38 or less. For example, the molar ratio r LB If the molar ratio r is greater than 0.38, some of the lithium 15L may precipitate as a lithium compound. However, LB If the molar ratio r is 2 or less, even if lithium compound deposition occurs, the effect of the lithium compound deposition on the energy storage performance of the energy storage device 2a will be small, and the energy storage device 2a will be able to exhibit high energy storage performance. LB For example, r is 0.01 or higher, preferably 0.03 or higher, more preferably 0.05 or higher, even more preferably 0.060 or higher, and particularly preferably 0.063 or higher. LB Molar ratio r is preferably greater than 0 and 1.8 or less, more preferably greater than 0 and 1.5 or less, even more preferably greater than 0 and 1.2 or less, and particularly preferably greater than 0 and 1.0 or less. LB The molar ratio r is preferably greater than 0 and 0.8 or less, very preferably greater than 0 and 0.5 or less, extremely preferably greater than 0 and 0.40 or less, and most preferably greater than 0 and 0.38 or less. LB Preferably, it is 0.01 or more and 0.8 or less, more preferably 0.03 or more and 0.5 or less, even more preferably 0.05 or more and 0.40 or less, and particularly preferably 0.063 or more and 0.38 or less.

[0018] If electrode 1a satisfies condition (II), the capacitance per unit volume of electrode 1a is preferably 130 F / cm². 3 The above applies, and more preferably 140 F / cm 3 The above is preferable, and more preferably 150 F / cm 3 That concludes the explanation. The capacitance per unit volume of electrode 1a can be measured, for example, according to the method described in the examples.

[0019] If we represent the atoms or groups of atoms forming the terminal 15c as T, then layer 15a is M m X n T sIt has the following composition. s is any number.

[0020] In the main body 15b, the arrangement of M and X is not limited to a specific arrangement. For example, in the main body 15b, M is arranged at the vertices of octahedrons so as to form an octahedron array, which is an arrangement of multiple octahedrons sharing edges. In addition, X is arranged inside each octahedron.

[0021] Lithium 15L may also be in a cation state.

[0022] The arrangement of lithium 15l in the layered material 15 is not limited to a specific arrangement. For example, lithium 15l is arranged on the surface of layer 15a. Preferably, the layered material 15 comprises multiple layers 15a, and lithium 15l is arranged between the multiple layers 15a. This makes it easier for the energy storage device 2a to exhibit high energy storage performance.

[0023] In the main body 15b of the layered material 15, n and m are not limited to any specific values, as long as n is between 1 and 4 and m is greater than n and 5 or less. n may be, for example, 1, 2, 3, or 4, or it may be a value that satisfies the conditions 1 < n < 2, 2 < n < 3, or 3 < n < 4. For example, if defects such as vacancies exist in the crystals that make up the main body 15b, n may not be an integer. m may, for example, satisfy the condition m = n + 1.

[0024] In the main body 15b, preferably, n is 1 and m is 2, or n is 2 and m is 3. In this case, the energy storage device 2a is more likely to exhibit high energy storage performance.

[0025] In the main body 15b, M is not limited to a specific atom, as long as it is at least one selected from the group consisting of Group 3, Group 4, Group 5, Group 6, and Group 7 elements. Preferably, M includes at least one selected from the group consisting of Ti and Mo. In this case, the energy storage device 2a is more likely to exhibit high energy storage performance. M may include only at least one selected from the group consisting of Ti and Mo, or it may include elements other than Ti and Mo.

[0026] In the main body 15b, X may contain carbon atoms. In this case, the energy storage device 2a is more likely to exhibit high energy storage performance. X may contain only carbon atoms, only nitrogen atoms, or both carbon atoms and nitrogen atoms.

[0027] In the main body 15b, X may further contain oxygen atoms. The oxygen atom content in X may be 20% to 80% or 30% to 75% based on the number of atoms. Furthermore, even if it is not intended that X contain oxygen atoms, oxygen atoms may be included in X by substituting carbon atoms from the raw materials. The oxygen atom content in X may be less than 20%, 10% or less, 5% or less, 1% or less, or 0.1% or less based on the number of atoms. X may not contain oxygen atoms at all.

[0028] The terminator 15c is not limited to a specific atom or group of atoms, as long as it is an atom or group of atoms that can exist on the surface of the main body 15b. For example, the terminator 15c contains an atom having an electronegativity greater than the electronegativity of M contained in the main body 15b. In this case, the terminator 15c is more likely to exist on the surface of the main body 15b in the desired state, and the energy storage device 2a is more likely to exhibit high energy storage performance. Examples of atoms having an electronegativity greater than the electronegativity of M are hydrogen atoms, oxygen atoms, halogen atoms, chalcogen atoms, nitrogen atoms, phosphorus atoms, carbon atoms, and antimony atoms. Electronegativity is electronegativity based on Pauling's definition.

[0029] The terminator 15c may include, for example, at least one selected from the group consisting of a hydroxyl group, a hydrogen atom, a halogen atom, a chalcogen atom, an amino group, a phosphorus atom, and an antimony atom. In this case, the terminator 15c is more likely to exist on the surface of the main body 15b in a desired state.

[0030] The layered material 15 may have, for example, a multilayer structure in which multiple layers 15a are stacked apart from each other. In this case, two adjacent layers 15a do not have to be completely separated and may include contact areas. The layered material 15 may also have a single-layer structure composed of only one layer 15a. The aggregate of the single-layer or multilayer structure composed of the layered material 15 may be particles such as powder and flakes.

[0031] The thickness of layer 15a is not limited to a specific value. For example, the thickness of layer 15a may be between 0.5 nm and 5 nm, or between 0.5 nm and 3 nm. This thickness can vary depending on the number of atomic layers formed by M.

[0032] The maximum dimension of layer 15a in the in-plane direction perpendicular to the thickness direction of layer 15a is not limited to a specific value. For example, the maximum dimension may be 0.1 μm or more and 200 μm or less, or it may be 1 μm or more and 40 μm or less.

[0033] When the layered material 15 has a multilayer structure, the distance d between layers 15a in the multilayer structure is not limited to a specific value. The distance d may be, for example, 0.1 nm or more and 10 nm or less, or it may be 0.1 nm or more and 5 nm or less, or it may be about 1 nm.

[0034] When the layered material 15 has a multilayer structure, the maximum dimension of the layered material 15 in the in-plane direction perpendicular to the thickness direction of the layer 15a is not limited to a specific value. The maximum dimension may be, for example, 0.1 μm or more and 200 μm or less, or 1 μm or more and 40 μm or less.

[0035] When the layered material 15 has a multilayer structure, cations other than lithium may be present between adjacent layers 15a in the thickness direction of the layer 15a. An example of a cation is a proton (H + These include alkali metal ions, alkaline earth metal ions, quaternary ammonium ions, and quaternary phosphonium ions. Anions or solvents coordinated to cations present between layers 15a may be present. Examples of anions and solvents coordinated to cations include halide ions, H2O, and propylene carbonate.

[0036] If the layered material 15 has a multilayer structure, the number of layers 15a contained in the layered material 15 is two or more, and may be 20 to 100,000 or 1,000 to 20,000. The thickness of the layered material 15 in the thickness direction of the layers 15a is not limited to a specific value. Its thickness may be, for example, 0.1 μm to 200 μm, or 1 μm to 40 μm.

[0037] If the layered material 15 has a multilayer structure, the number of layers 15a included in the layered material 15 may be six or less. In this case, the layered material 15 is referred to as a low-layer structure.

[0038] In an aggregate of layered material 15, for example, the majority of the aggregate may consist of single-layer layered material 15 and / or low-layer structures. For example, 50 volume percent or more of the aggregate may consist of single-layer layered material 15 and / or low-layer structures.

[0039] The above dimensions and distances may be calculated by number averaging based on micrographs from, for example, scanning electron microscopes (SEM), transmission electron microscopes (TEM), atomic microscopes (AFM), etc. In this case, for example, the above dimensions and distances may be calculated by number averaging 40 or more data points. Alternatively, the above dimensions and distances may be calculated as distances in real space calculated based on the position of the (002) plane in reciprocal lattice space in X-ray diffraction (XRD) measurements.

[0040] Figure 3 is a schematic diagram showing an example of an electrode 1a. In electrode 1a, the layered material 15 is arranged in contact with, for example, a conductive substrate 12. Electrode 1a has, for example, an MXene-containing layer 11 containing the layered material 15, and the MXene-containing layer 11 has the surface shape of electrode 1a. The MXene-containing layer 11 is arranged on the conductive substrate 12. The MXene-containing layer 11 may be composed substantially only of the layered material 15. In the MXene-containing layer 11, a conductive additive may be present between the layered material 15s. The conductive additive includes, for example, at least one selected from the group consisting of carbon black, acetylene black, Ketjen black, and carbon nanotubes. A binder may be present between the layered material 15s. The binder includes, for example, a resin and includes at least one selected from the group consisting of polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), and styrene-butadiene rubber.

[0041] The conductive substrate 12 is not limited to a specific substrate as long as its surface is conductive. The conductive substrate 12 may also be a current collector, and examples of current collectors are aluminum foil or copper foil. The surface of the conductive substrate 12 may be smooth or may have irregularities.

[0042] Figure 4 is a schematic diagram showing another example of electrode 1a. As shown in Figure 4, electrode 1a is composed only of the MXene-containing layer 11. Thus, electrode 1a may have a single-layer structure containing the layered material 15.

[0043] The shape of electrode 1a is not limited to a specific shape. Electrode 1a may be plate-shaped, rod-shaped, or cylindrical.

[0044] The density of electrode 1a is not limited to a specific value. Its density is, for example, 1.5 g / cm³. 3 Above, 2.0g / cm 3 The above, or 2.5 g / cm³ 3 The above is the preferred value, preferably 3.0 g / cm³. 3 That is all. The density is more preferably 3.5 g / cm³. 3The above is preferable, and more preferably 4.0 g / cm³. 3 The above applies, with 4.5 g / cm³ being particularly preferable. 3 That's all. Its density is, for example, 10 g / cm³. 3 The following applies:

[0045] The thickness of the electrode 1a described above is not limited to a specific value. Its thickness may be, for example, 3 μm or more, or 5 μm or more. Its thickness may be, for example, 500 μm or less.

[0046] Electrode 1a can be fabricated, for example, using electrode material for energy storage devices. Figure 5 is a schematic diagram showing an example of electrode material for energy storage devices. As shown in Figure 5, electrode material 1k for energy storage devices is, for example, an aggregate of layered material 15. This aggregate is, for example, powder of layered material 15. Electrode material 1k for energy storage devices may also be a mixture containing layered material 15. This mixture, in addition to layered material 15, contains at least one selected from the group consisting of, for example, conductive additives and binders. The mixture may be a powder, a dispersion, or a slurry.

[0047] The method for manufacturing the layered material 15 is not limited to a specific method. For example, the method for manufacturing the layered material 15 is M m AX n The process involves mixing lithium hydroxide with a processed product from which at least some of the A atoms of a precursor having the composition of the above have been removed. In this case, for example, lithium 15l is more easily arranged in the layered material 15 in the desired state, and the energy storage device 2a is more likely to exhibit higher energy storage performance. The lithium hydroxide used in the production of the layered material 15 may be used in the form of an aqueous solution.

[0048] The layered material 15 can be made, for example, by reacting lithium hydroxide with layer 15a. Layer 15a is, for example, M m AX nIt can be synthesized by selectively etching A atoms from a precursor having the following composition. In the composition of the precursor, M collectively represents the metal atoms corresponding to M in the main body 15b of layer 15a, and m and n correspond to m and n in the main body 15b, respectively. A is an element of group 12, 13, 14, 15, or 16, and A may be at least one element selected from the group consisting of Al, Zn, Ga, In, Tl, Si, Ge, Sn, Pb, P, As, S, and Cd. Preferably, A is Al. This precursor is called MAX, and M m X n It has a crystal structure in which one layer composed of A atoms is placed between two layers represented by M. m X n In each layer, M is positioned at the vertices of the octahedrons, forming an octahedron array which is an arrangement of multiple octahedrons sharing edges. In addition, X is positioned inside each octahedron. In other words, M m X n Each layer has a crystal lattice in which M atoms are arranged to form an octahedron, and X atoms are arranged inside the octahedron. The structure of MAX is not limited to a specific structure, but for example, when m = n+1 is satisfied, it has a structure in which one layer of X atoms is arranged between (n+1) M atomic layers. In addition, it has repeating units in which an A atomic layer is arranged adjacent to the (n+1)th M atomic layer.

[0049] In MAX, the A atom layer is removed by selective etching of A atoms. This exposes M m X n The surface of the layer is modified by at least one selected from the group consisting of hydroxyl groups, hydrogen atoms, halogen atoms, chalcogen atoms, amino groups, phosphorus atoms, and antimony atoms, which are derived from an etching agent. In this way, the terminal 15c is formed.

[0050] An etching agent used for selective etching of A atoms is, for example, fluoride ions F -It contains. The etching agent preferably contains lithium fluoride and hydrochloric acid. This makes it easier for the terminal 15c to form in the desired state. The etching agent may also be hydrofluoric acid. Selective etching of A atoms may be performed using a molten salt of a Lewis acid such as CuCl2, or using HCl at high temperature and pressure. Selective etching of A atoms may be performed using halogen gases such as Br2 and I2, or using an organic solution in which halogens such as Br2 and I2 are dissolved.

[0051] The etched material may be washed with an acid, such as hydrochloric acid. In this case, any remaining etching agent can be removed. Also, cations, such as lithium, contained in the layered material 15 can be replaced with protons. For example, using an etching agent containing lithium fluoride and hydrochloric acid, M m AX n By removing at least some of the A atoms from a precursor having the above composition and washing the resulting product with acid, less lithium fluoride remains in the washed product. Therefore, when the product is subsequently mixed with lithium hydroxide, the lithium 15l is more easily arranged in the layered material 15 in the desired state.

[0052] The layered material 15 may be manufactured from a precursor other than MAX. For example, two M m X n The layered material 15 may be produced from a precursor in which two or more A atomic layers are arranged between the layers by selective etching of A atoms. In this case as well, the layered material 15 can be produced by mixing the treated product obtained by selective etching of A atoms from the precursor with lithium hydroxide.

[0053] After selectively etching A atoms from a precursor such as MAX, the material may be subjected to processes such as ultrasonic treatment, handshake, or shaking using an automatic shaker. These processes can promote the separation (delamination) of layers 15a in the layered material 15. This can result in a layered material 15 having, for example, a single-layer structure or a low-layer structure. For example, handshake or shaking using an automatic shaker can impart a desired shear stress between layers 15a from the viewpoint of separating the layers 15a. For example, consider the case where the layered material 15 has a single-layer structure or a low-layer structure. In this case, the ratio of the dimensions of the layered material 15 in the thickness direction of the layers 15a to the dimensions of the layered material 15a in the in-plane direction of the layers 15a is small. Even in such cases, handshake or shaking using an automatic shaker can impart a desired shear stress between layers 15a from the viewpoint of separating the layers 15a, making the layered material 15 less prone to breakage and easier to maintain in the desired size.

[0054] In the layered material 15, some A atoms derived from a precursor such as MAX may remain. The amount of A atoms remaining in the layered material 15 is, for example, 10% by mass or less of the A atom content in the precursor, preferably 8% by mass or less, and more preferably 6% by mass or less. Depending on the application of the layered material 15, the amount of A atoms remaining in the layered material 15 may be greater than 10% by mass of the A atom content in the precursor.

[0055] The layered material 15 may be produced by a method other than selectively etching A atoms from a precursor such as MAX. The layered material 15 may be produced by a method that includes heat treatment of metal M, graphite, and a halide of M inside a sealed tube. The sealed tube is, for example, a quartz tube. In this case, the layered material 15 can be produced by mixing the treated material obtained by the heat treatment with lithium hydroxide. The layered material 15 may also be produced by a method that includes chemical vapor deposition (CVD) using metal M, a halide of M, and CH4 or N2. In this case, the layered material 15 can be produced by mixing the treated material obtained by this CVD method with lithium hydroxide.

[0056] The electrode 1a can be manufactured, for example, by forming an electrode material 1k for energy storage devices into a predetermined shape such as a film or sheet. For example, a method including suction filtration can be applied to manufacture the electrode 1a. In addition, the electrode 1a may be manufactured using a coating method such as spray coating, bar coating, or dip coating.

[0057] The electrode 1a may be manufactured using a precursor of the layered material 15 or a modified version of the layered material 15. For example, coated particles are obtained by coating the surface of polymer particles such as polystyrene with the layered material 15 in a solvent. Next, the solvent is removed and the aggregate of coated particles is formed into a film. Then, hollow particles are formed in which the layered material 15 remains in a shell-like form while removing the polymer by high-temperature treatment or the like. The electrode 1a may be manufactured in this way. In this case, the performance of the energy storage device tends to be higher. For example, the Coulomb efficiency of the energy storage device tends to be higher.

[0058] The electrode 1a may be manufactured by forming a layer containing a layered material 15 on a conductive substrate 12 such as a current collector.

[0059] The energy storage device 2a is not limited to a specific device. The energy storage device 2a may be, for example, an electrochemical capacitor or a secondary battery. The energy density stored in an electrochemical capacitor is generally (1 / 2) × CV 2 This is calculated as follows: Here, C is the specific volume [F / cm²]. 3 The unit of energy density is F / g, where V is the operating potential range [V]. 2 / cm 3 or FV 2 It can be expressed as / g. On the other hand, the energy density stored in an electrochemical capacitor can generally be expressed in units of Wh / L or Wh / kg.

[0060] The specific capacitance C of an electrochemical capacitor is measured using a three-electrode method with a half-cell, on either the positive or negative electrode. 3p [F / cm] 3Or consider the case where F / g is known. In this case, the specific capacitance C of the full cell constructed using that electrode as both the positive and negative electrode. f [F / cm] 3 Or F / g] is (1 / 4)C 3p It can be estimated to be equal to .

[0061] The electrolyte 4 is, for example, a non-aqueous electrolyte containing the lithium salt described above. In this case, the operating potential range of the energy storage device 2a tends to be larger. A larger operating potential range is advantageous from the viewpoint of increasing the energy density that can be stored in the energy storage device 2a. Because the electrolyte 4 is a non-aqueous electrolyte, there are fewer constraints on the operating potential range and usable temperature range of the energy storage device compared to when the electrolyte 4 is an aqueous electrolyte.

[0062] As shown in Figure 1, in the energy storage device 2a, the electrolyte 4 is contained inside the cell 5, and the inside of the cell 5 is divided by a separator 7 into a space where the first electrode 3a is located and a space where the second electrode 3b is located. The first electrode 3a and the second electrode 3b are electrically connected to terminals 6a and 6b located outside the cell 5, respectively.

[0063] The separator 7 is not limited to any particular separator, as long as it does not hinder the movement of electrolyte ions contained in the electrolyte 4. The separator 7 is, for example, a dielectric film. Examples of dielectric films are porous films of polyolefins such as polypropylene and polytetrafluoroethylene. The separator 7 may also contain glass fibers.

[0064] The material of cell 5 is not limited to a specific material. The material of cell 5 may be a metal material such as stainless steel, a resin material such as polytetrafluoroethylene, or other materials. Cell 5 may be sealed or open. There may or may not be voids inside cell 5.

[0065] The first electrode 3a and the second electrode 3b may be arranged, for example, inside the cell 5, with a separator 7 placed between the first electrode 3a and the second electrode 3b, and a laminate including the first electrode 3a, the separator 7, and the second electrode 3b wound around it.

[0066] As described above, at least one electrode selected from the group consisting of the first electrode 3a and the second electrode 3b is electrode 1a. For example, the first electrode 3a may function as the positive electrode and the second electrode 3b may function as the negative electrode. At electrode 1a, for example, exchange of electrolyte ions contained in the electrolyte solution 4 with electrons takes place.

[0067] For example, only the first electrode 3a may be electrode 1a. In this case, the second electrode 3b may be made of carbon material such as activated carbon, carbon nanotubes, and graphene, or Li4Ti5O 12 These may include the following. Only the second electrode 3b may be electrode 1a. In this case, the first electrode 3a may include graphite, activated carbon, and carbon nanotubes as electrode material. When only the first electrode 3a or the second electrode 3b is electrode 1a, the electrodes that are not electrode 1a may be composed substantially only of electrode material, or they may be configured such that a binder exists between the electrode materials. The binder may include, for example, a resin. The binder may include, for example, at least one selected from the group consisting of polytetrafluoroethylene, polyvinylidene fluoride, and styrene-butadiene rubber. Both the first electrode 3a and the second electrode 3b may be electrode 1a.

[0068] Each of the first electrode 3a and the second electrode 3b may be configured as a freestanding film, or it may have a configuration in which a film and / or membrane containing electrode material is formed on a conductive substrate such as a current collector. The current collector is not limited to a specific current collector as long as it is conductive. The current collector may include, for example, stainless steel, aluminum, or an aluminum alloy.

[0069] The electrolyte 4 includes, for example, an electrolyte and a non-aqueous solvent. The electrolyte 4 may also include an ionic liquid. The electrolyte is dissolved in the non-aqueous solvent and exists as a cation or anion.

[0070] In addition to the lithium salts mentioned above, electrolyte 4 may also contain, for example, cations from the following cation group or anions from the following anion group as an electrolyte. <Cation group> Sodium ion (Na +), potassium ions (K + ), magnesium ions (Mg 2+ ), zinc ions (Zn 2+ ), 1-ethyl-3-methylimidazolium ion (EMIM + ), tributylmethylammonium ion (TrBMAm + ), tetrabutylammonium ion (TeBAm + ), tributylethylphosphonium ion (TrBEPh + ), tributylmethylphosphonium ion (TrBMPh + ), 1-butyl-1-methylpyrrolidinium ion (1B1MPy + ), 1-methyl-1-propylpyrrolidinium ion (1M1PPy + ), tetraethylammonium ion (Et4N + , TEA + ), and protons (H + ) <Anion group> Diethyl phosphate ion (DEPh - ), bis(trifluoromethanesulfonyl)imide ion (TFSI - ), Trifluoromethanesulfonate ion (Triflate - ), chloride ions (Cl - ), bromide ions (Br - ), and iodide ions (I - )

[0071] The non-aqueous solvent that may be included in the electrolyte 4 is not limited to a specific non-aqueous solvent. The electrolyte 4 may, for example, include at least one selected from the following group of solvents. The non-aqueous solvent may consist of only one type of solvent or a mixture of multiple types of solvents. <Solvent Group> Propylene carbonate (PC), gamma butyrolactone (gBL), ethylene carbonate (EC), ethyl methyl carbonate (EMC), dimethoxyethane (DME), dimethyl carbonate (DMC), diethyl carbonate (DEC), diglyme (G2), triglyme (G3), tetraglyme (G4), and acetonitrile (AN)

[0072] The non-aqueous solvent that may be included in the electrolyte 4 may preferably contain at least one selected from the group consisting of propylene carbonate, ethylene carbonate, dimethyl carbonate, and acetonitrile. In this case, the energy storage device 2a is more likely to exhibit high energy storage performance.

[0073] The electrolyte 4 may, if necessary, contain predetermined additives in addition to the solvent and electrolyte.

[0074] When terminals 6a and 6b of the energy storage device 2a are connected to a load, the energy storage device 2a discharges. Conversely, when terminals 6a and 6b of the energy storage device 2a are connected to a power source, the energy storage device 2a is charged.

[0075] Depending on the combination of electrode material and electrolyte 4, the energy storage device 2a may be configured as a pseudocapacitor or hybrid capacitor that includes a Faraday reaction.

[0076] (Note) Based on the above description, the following technology is disclosed. (Technology 1) A first electrode, a second electrode, and an electrolyte, wherein at least a portion of the first electrode and at least a portion of the second electrode are arranged apart from each other in the electrolyte, at least one selected from the group consisting of the first electrode and the second electrode is an electrode containing a layered material, the electrolyte contains a lithium salt having at least one selected from the group consisting of anions and bis(fluorosulfonyl)imide ions in which four or more atoms of the same type are bonded to a central atom, and the layered material is M m X nA power storage device comprising a body having the composition of and a layer including an end present on the surface of the body, and lithium, wherein in the body, M is at least one selected from the group consisting of Group 3, Group 4, Group 5, Group 6, and Group 7 elements, X includes at least one selected from the group consisting of carbon atoms and nitrogen atoms, n is 1 or more and 4 or less, m is greater than n and 5 or less, and the electrode satisfies at least one condition selected from the group consisting of (I) and (II) below. (I) The molar ratio of the lithium contained in the layered material to the body is greater than 0 and 2 or less. (II) The capacitance per unit volume of the electrode is Ag / Ag + 120 F / cm in the sweep range from -2.0 V to 0 V relative to the reference electrode. 3That is all. (Technology 2) The energy storage device according to Technology 1, wherein the lithium salt comprises at least one selected from the group consisting of LiPF6, LiBF4, and lithium bis(fluorosulfonyl)imide. (Technology 3) The energy storage device according to Technology 1 or 2, wherein the electrode satisfies both conditions (I) and (II). (Technology 4) The energy storage device according to any one of Technology 1 to 3, wherein the termination comprises an atom having an electronegativity greater than the electronegativity of M. (Technology 5) The energy storage device according to any one of Technology 1 to 4, wherein the termination comprises at least one selected from the group consisting of a hydroxyl group, a hydrogen atom, a halogen atom, a chalcogen atom, an amino group, a phosphorus atom, and an antimony atom. (Technology 6) The energy storage device according to any one of Technology 1 to 5, wherein n is 1 and m is 2, or n is 2 and m is 3. (Technical 7) The energy storage device according to any one of Technical 1 to 6, wherein M comprises at least one selected from the group consisting of Ti and Mo. (Technical 8) The energy storage device according to any one of Technical 1 to 7, wherein X comprises a carbon atom. (Technical 9) The energy storage device according to any one of Technical 1 to 8, wherein the layered material comprises a plurality of layers, and the lithium contained in the layered material is arranged between the plurality of layers. (Technical 10) The energy storage device according to any one of Technical 1 to 9, wherein the electrolyte further comprises at least one selected from the group consisting of propylene carbonate, ethylene carbonate, dimethyl carbonate, and acetonitrile. (Technical 11) The energy storage device according to any one of Technical 1 to 10, wherein the electrode is a negative electrode. (Technical 12) A method for manufacturing a layered material, comprising using an etching agent containing lithium fluoride and hydrochloric acid to etch M m AX n The process includes removing at least some A atoms from a precursor having the composition of to obtain a treated product, washing the treated product with acid, and mixing the treated product with lithium hydroxide, wherein the layered material is M m X nA method for producing a layered material comprising a body having the composition of and an end having a terminal on the surface of the body, wherein the precursor and the body are: M is at least one selected from the group consisting of Group 3, Group 4, Group 5, Group 6, and Group 7 elements; A is at least one selected from the group consisting of Group 12, Group 13, Group 14, Group 15, and Group 16 elements; X includes at least one selected from the group consisting of carbon atoms and nitrogen atoms; n is 1 or more and 4 or less; m is greater than n and 5 or less; and the molar ratio of the lithium in the layered material to the body is greater than 0 and 2 or less. (Technical 13) A method for producing a layered material according to Technical 12, wherein the end has an electronegativity greater than the electronegativity of M. (Technical 14) A method for producing a layered material according to Technical 12 or 13, wherein the terminator includes at least one selected from the group consisting of a hydroxyl group, a hydrogen atom, a halogen atom, a chalcogen atom, an amino group, a phosphorus atom, and an antimony atom. (Technical 15) A method for producing a layered material according to any one of Technical 12 to 14, wherein n is 1 and m is 2, or n is 2 and m is 3. (Technical 16) A method for producing a layered material according to any one of Technical 12 to 15, wherein M includes at least one selected from the group consisting of Ti and Mo. (Technical 17) A method for producing a layered material according to any one of Technical 12 to 16, wherein X includes a carbon atom. (Technical 18) A method for producing a layered material according to any one of Technical 12 to 17, wherein the layered material comprises a plurality of layers, and the lithium contained in the layered material is arranged between the plurality of layers. (Technical 19) A method for producing a layered material according to any one of Technical 12 to 18, wherein A contains Al.

[0077] The present disclosure will be further described below with reference to examples. Note that the following examples are illustrative and the present disclosure is not limited to these examples.

[0078] (Example 1) TiC powder, Ti powder, and Al powder were mixed in a zirconia mortar to obtain the mixed powder according to Example 1. These powders were provided by High-Purity Chemical Research Institute Co., Ltd. The molar ratio of TiC:Ti:Al in the mixed powder according to Example 1 was 2:1:1. The mixed powder according to Example 1 was fired at 1400 °C for 3 hours in an argon gas atmosphere to obtain the fired body (block) according to Example 1. The fired body according to Example 1 was pulverized in a zirconia mortar. Subsequently, using a zirconia ball with a diameter of 5 mm and a zirconia pot, the fired body according to Example 1 was pulverized with a wet ball mill in H2O so that the maximum particle size became 20 μm or less. In this way, the powder of the precursor according to Example 1 having the composition of Ti3AlC2 was obtained.

[0079] 160 g of LiF was dissolved in 2000 mL of an HCl solution with a concentration of 9 mol / L to obtain a LiF solution. 100 g of the powder of the precursor according to Example 1 was added to this LiF solution, and the LiF solution was stirred at 40 °C for 24 hours. Next, centrifugal separation and washing with water were repeated multiple times until the pH became 5 or more. Subsequently, suction filtration was performed, and the obtained residue was vacuum dried at 80 °C. As a result, the MXene powder according to Example 1 having the composition of Ti3C2T s was obtained. T represents an atom or functional group forming the end of the layered material, and s is an arbitrary number.

[0080] 10 g of the MXene powder according to Example 1 was added to 300 mL of an HCl solution with a concentration of 1 mol / L, and the HCl solution was stirred at room temperature in the range of 15 °C to 28 °C for 1 hour. Next, suction filtration was performed, and the obtained residue was vacuum dried at 80 °C. 1 g of the dried powder thus obtained was added to 100 mL of an aqueous lithium hydroxide solution with a concentration of 1 mol / L, and the aqueous lithium hydroxide solution was stirred at room temperature in the range of 15 °C to 28 °C for 1 hour. Next, washing with water and suction filtration were repeated multiple times, and the obtained residue was vacuum dried at 80 °C. As a result, the powder of the layered material according to Example 1 containing lithium was obtained.

[0081] A slurry was obtained by adding ultrapure water to the powder of the layered material according to Example 1 and mixing. This slurry was applied to an aluminum foil having an etched surface as a current collector using an applicator, and the resulting coating was vacuum-dried at 80°C to obtain an MXene-containing film. The laminate of the aluminum foil and the MXene-containing film was cut into a circular shape with a diameter of 16 mm in a plan view, and vacuum-dried at 110°C to obtain the electrode according to Example 1.

[0082] Next, a three-electrode electrochemical capacitor, which served as a half-cell for evaluation, was assembled. This half-cell was configured so that all of the applied voltage was distributed across the electrodes according to Example 1. The electrochemical capacitor was assembled inside a glove box under an argon gas atmosphere to simulate actual manufacturing and usage conditions.

[0083] The electrode according to Example 1 was used as the working electrode of the three-electrode cell. A 26 mm diameter activated carbon electrode (AC) coated on aluminum foil was used as the counter electrode of the three-electrode cell. This activated carbon electrode had a capacitance approximately 10 times or more that of the electrode according to Example 1. An Ag / Ag electrode manufactured by EC Frontier was used as the reference electrode of the three-electrode cell. + A reference electrode was used. A PC mixed solution of 0.1 mol / L silver nitrate and 0.1 mol / L tetrabutylammonium perchlorate was used as the internal solution of the reference electrode. A commercially available 1 mol / L LiPF6 / EC-DMC electrolyte was used as the electrolyte for the three-electrode cell. In this electrolyte, the volume ratio of EC to DMC was 1:1.

[0084] EC Frontier's SB3A battery evaluation cell was used as the cell body for the three-electrode cell. An activated carbon electrode was placed on the lower body, which is equipped with a counter electrode terminal and an O-ring, with the activated carbon film facing upwards. Next, a Whatman glass fiber filter, cut to a diameter of 28 mm, was placed on top of the activated carbon electrode as a separator. Subsequently, an electrode guide was placed on top of the separator, and the electrode was placed in the circular hole in the center of the electrode guide, with the MXene-containing film of the electrode according to Example 1 facing downwards. Next, an electrode retainer and a spring were placed on top of the electrode according to Example 1, and approximately 1 mL of electrolyte was added to the space in the lower body. Subsequently, an upper body equipped with an operating terminal and an insulating spacer was placed. The lower body and upper body were fixed together using bolts, wing nuts, and insulating sleeves. A reference electrode was inserted and fixed into the reference electrode holder provided on the upper body. In this way, an electrochemical capacitor, which is an evaluation half-cell, was assembled as an electrode evaluation cell.

[0085] (Electrochemical Measurement) Electrochemical measurements were performed using the evaluation half-cell, which is an electrochemical capacitor assembled as described above. The working electrode, counter electrode, and reference electrode of this electrochemical capacitor were connected to an external electrode. Using the Bio-Logic VMP-300 electrochemical measurement device and EC-Lab software, the sweep speed was set to 1 mV / s, and the sweep range was set from -2V to 0V relative to the reference electrode. These measurement conditions are such that the working electrode operates as both the positive and negative electrode, as the open-circuit potential of the working electrode is approximately -0.7V. In this way, cyclic voltammetry (CV) measurements were performed. Using the volume of the MXene-containing film on the aluminum foil, the capacitance (specific capacitance) per unit volume of the MXene-containing film of the electrode according to Example 1 [F / cm²] was determined from the CV measurement results of the evaluation half-cell. 3 The result was calculated. The results are shown in Table 1.

[0086] (Elemental Quantitative Analysis) Elemental quantitative analysis of Ti and Li in a sample obtained from the layered material powder according to Example 1 was performed using an inductively coupled plasma atomic emission spectrometer (ICP-AES) with an iCAP7400 Duo inductively coupled plasma atomic emission spectrometer manufactured by Thermo Fisher Scientific. Approximately 10 mg of the layered material powder according to Example 1 was mixed with nitric acid and hydrofluoric acid, heated in a sealed state to induce thermal decomposition, and then allowed to cool. The resulting powder was diluted with pure water to obtain a sample. This sample was subjected to elemental quantitative analysis. The elemental quantitative analysis measured Ti3C2T s The molar ratio of lithium content to other content was 0.27. The results are shown in Table 1.

[0087] (Example 2) Except for the points described below, the preparation of the layered material powder, the preparation of electrodes, the preparation of an electrochemical capacitor, electrochemical measurement, and elemental quantitative analysis were carried out in the same manner as in Example 1. The sweep range for the electrochemical measurement was set from -2.8V to -0.8V relative to the reference electrode. The results are shown in Table 1.

[0088] (Example 3) Except for the points described below, the preparation of the layered material powder, the preparation of electrodes, the preparation of an electrochemical capacitor, electrochemical measurement, and elemental quantitative analysis were carried out in the same manner as in Example 1. A commercially available 1 mol / L LiPF6 / PC electrolyte was used as the electrolyte for the electrochemical capacitor. The results are shown in Table 1.

[0089] (Example 4) Except for the points below, the preparation of the layered material powder, the preparation of electrodes, the preparation of an electrochemical capacitor, electrochemical measurement, and elemental quantitative analysis were carried out in the same manner as in Example 1. A commercially available 1 mol / L LiPF6 / PC electrolyte was used as the electrolyte for the electrochemical capacitor. The sweep range for the electrochemical measurement was set from -2.8V to -0.7V relative to the reference electrode. The results are shown in Table 1.

[0090] (Example 5) Except for the points described below, the preparation of the layered material powder, the preparation of electrodes, the preparation of an electrochemical capacitor, electrochemical measurement, and elemental quantitative analysis were carried out in the same manner as in Example 1. A commercially available 1 mol / L LiPF6 / AN electrolyte was used as the electrolyte for the electrochemical capacitor. The results are shown in Table 1.

[0091] (Example 6) Except for the points described below, the preparation of the layered material powder, the preparation of electrodes, the preparation of an electrochemical capacitor, electrochemical measurement, and elemental quantitative analysis were carried out in the same manner as in Example 1. A commercially available 1 mol / L LiPF6 / AN electrolyte was used as the electrolyte for the electrochemical capacitor. The sweep range for the electrochemical measurement was set from -2.8V to -0.7V relative to the reference electrode. The results are shown in Table 1.

[0092] (Example 7) Except for the points below, the same procedure as in Example 1 was followed for the preparation of layered material powder, electrode fabrication, electrochemical capacitor fabrication, electrochemical measurement, and elemental quantitative analysis. A commercially available 1 mol / L LiBF4 / EC-DMC electrolyte was used as the electrolyte for the electrochemical capacitor. The results are shown in Table 1. In this electrolyte, the volume of EC to the volume of DMC was 1:1.

[0093] (Example 8) Except for the points below, the preparation of the layered material powder, the preparation of electrodes, the preparation of an electrochemical capacitor, electrochemical measurement, and elemental quantitative analysis were carried out in the same manner as in Example 1. 0.5 g of the above dried powder was added to 50 mL of a 4 mmol / L lithium hydroxide aqueous solution, and the lithium hydroxide aqueous solution was stirred for 1 hour at room temperature in the range of 15°C to 28°C. In slurry preparation, PVDF and N-methyl-2-pyrrolidone were added instead of ultrapure water. A commercially available 1 mol / L LiPF6 / PC electrolyte was used as the electrolyte for the electrochemical capacitor. The elemental quantitative analysis measured Ti3C2T s The ratio of lithium content to total content was 0.063. The results are shown in Table 1.

[0094] (Example 9) Except for the points described below, the preparation of the layered material powder, the preparation of electrodes, the preparation of an electrochemical capacitor, electrochemical measurement, and elemental quantitative analysis were carried out in the same manner as in Example 8. The sweep range for the electrochemical measurement was set from -2.8V to -0.7V relative to the reference electrode. The results are shown in Table 1.

[0095] (Example 10) TiC powder, Ti powder, and Al powder were mixed in a zirconia mortar to obtain the mixed powder according to Example 10. These powders were provided by Kojun Chemical Laboratory Co., Ltd. The molar ratio TiC:Ti:Al in the mixed powder according to Example 10 was 1:1.2:1.2. The mixed powder according to Example 10 was calcined at 1400°C for 3 hours in an argon gas atmosphere to obtain a calcined body (block) according to Example 10. The calcined body according to Example 10 was pulverized in a zirconia mortar. Subsequently, using a zirconia ball with a diameter of 15 mm and a zirconia pot, the calcined body according to Example 10 was pulverized in a wet ball mill in H2O until the maximum particle size was 20 μm or less. Next, the calcined body according to Example 10 was added to a 10 mol / L HCl solution, and the HCl solution was stirred for 3 hours to dissolve and remove the by-product Ti-Al alloy. Next, the residue was subjected to multiple suction filtration and washing with water, and then vacuum-dried at 60°C. In this way, a precursor powder having the composition Ti2AlC according to Example 10 was obtained.

[0096] 20 g of the precursor powder according to Example 10 was added to a 10% by mass HF solution, and the HF solution was stirred for 5 hours at room temperature in the range of 15°C to 28°C. Next, centrifugation and washing with water were repeated several times until the pH was 5 or higher. Subsequently, suction filtration was performed, and the obtained residue was vacuum-dried at 80°C. This resulted in Ti2CT s A powder of MXene according to Example 10 having the following composition was obtained. T represents an atom or functional group forming the end of the layered material, and s is any number.

[0097] One g of MXene powder according to Example 10 was added to 500 mL of a 1 mol / L lithium hydroxide aqueous solution, and the lithium hydroxide aqueous solution was stirred for one hour at room temperature in the range of 15°C to 28°C. Next, washing with water and suction filtration were repeated several times, and the resulting residue was vacuum-dried at 80°C to obtain the dried powder according to Example 10. Subsequently, the obtained dried powder was subjected to a series of processes of stirring in a 1 mol / L lithium hydroxide aqueous solution, washing with water, suction filtration, and vacuum drying, repeated three times. This obtained a layered material powder according to Example 10 that contains lithium. Except for the following points, electrodes were prepared in the same manner as in Example 1, and a half-cell for evaluation was assembled, and electrochemical measurements were performed. The layered material powder according to Example 10 was used instead of the layered material powder according to Example 1. A commercially available 1 mol / L LiPF6 / PC electrolyte was used as the electrolyte. The sweep range for electrochemical measurement was set to -2.0 V to -0.7 V relative to the reference electrode. Elemental quantitative analysis was performed in the same manner as in Example 1, except that the MXene powder according to Example 10 was used instead of the MXene powder according to Example 1. The Ti2CT measured by elemental quantitative analysis was s The molar ratio of lithium to the content was 0.38. The results are shown in Table 1.

[0098] (Example 11) Except for the points described below, the preparation of the layered material powder, the preparation of electrodes, the preparation of an electrochemical capacitor, electrochemical measurement, and elemental quantitative analysis were carried out in the same manner as in Example 10. The sweep range for the electrochemical measurement was set from -2.8V to -1.0V relative to the reference electrode. The results are shown in Table 1.

[0099] (Example 12) Except for the points below, the preparation of the layered material powder, the preparation of electrodes, the preparation of an electrochemical capacitor, electrochemical measurement, and elemental quantitative analysis were carried out in the same manner as in Example 10. A commercially available 1 mol / L LiBF4 / EC-DMC electrolyte was used as the electrolyte for the electrochemical capacitor. In this electrolyte, the volume of EC:volume of DMC was 1:1. The sweep range for the electrochemical measurement was set from -2.0V to 0V relative to the reference electrode. The results are shown in Table 1.

[0100] (Example 13) Production of a powder of a layered material, production of an electrode, production of an electrochemical capacitor, electrochemical measurement, and elemental quantitative analysis were carried out in the same manner as in Example 10, except for the following points. As the electrolyte of the electrochemical capacitor, a commercially available 1 mol / L LiBF4 / EC-DMC electrolyte was used. In this electrolyte, the volume ratio of EC:DMC was 1:1. The sweep range of the electrochemical measurement was set from -2.8 V to -0.7 V with respect to the reference electrode. The results are shown in Table 1.

[0101] (Example 14) Mo2C powder and Ga powder were mixed in an agate mortar to obtain a mixed powder according to Example 14. These powders were provided by High-Purity Chemical Laboratory Co., Ltd. The molar ratio of Mo2C:Ga in the mixed powder according to Example 14 was 1:8. The mixed powder according to Example 14 was fired at 850 °C for 80 hours in an argon gas atmosphere to obtain a fired body (block) according to Example 14. The fired body according to Example 14 was added to a 9 mol / L HCl solution to dissolve the remaining Ga. Subsequently, washing with water and suction filtration were repeated a plurality of times, and the obtained residue was vacuum dried at 60 °C. Thus, a powder of a precursor according to Example 14 having a composition of Mo2Ga2C was obtained.

[0102] 90 mL of a 12 mol / L HCl solution and 2 g of the precursor powder according to Example 14 were placed in a 300 mL PTFE hydrothermal synthesis sample container, and the sample container was placed inside a SUS pressure-resistant container for hydrothermal synthesis. Next, the heat-resistant container was allowed to stand at 140 °C for 6 days. Subsequently, washing with water and suction filtration were repeated a plurality of times, and the obtained residue was vacuum dried at 60 °C. Thereby, s a powder of MXene according to Example 14 having a composition of Mo2CT was obtained. T represents an atom or a functional group forming the end of the layered material, and s is an arbitrary number.

[0103] 0.4 g of MXene powder according to Example 14 was added to 40 mL of a 1 mol / L lithium hydroxide aqueous solution, and the lithium hydroxide aqueous solution was stirred for 1 hour at room temperature in the range of 15°C to 28°C. Next, washing with water and suction filtration were repeated several times, and the obtained residue was vacuum dried at 80°C. This obtained a layered material powder according to Example 14 that contains lithium. Except for the following points, electrodes were prepared and evaluation half-cells were assembled in the same manner as in Example 1, and electrochemical measurements were performed. The layered material powder according to Example 14 was used instead of the layered material powder according to Example 1. PTFE was further added in slurry preparation. A commercially available 1 mol / L LiPF6 / PC electrolyte was used as the electrolyte. Elemental quantitative analysis was performed in the same manner as in Example 1, except that the MXene powder according to Example 14 was used instead of the MXene powder according to Example 1. Mo2CT was measured by elemental quantitative analysis. s The molar ratio of lithium content to other content was 0.25. The results are shown in Table 1.

[0104] (Example 15) Except for the points described below, the preparation of the layered material powder, the preparation of electrodes, the preparation of an electrochemical capacitor, electrochemical measurement, and elemental quantitative analysis were carried out in the same manner as in Example 14. The sweep range for the electrochemical measurement was set from -2.8V to -0.6V relative to the reference electrode. The results are shown in Table 1.

[0105] (Example 16) Except for the points described below, the preparation of the layered material powder, the preparation of electrodes, the preparation of an electrochemical capacitor, electrochemical measurement, and elemental quantitative analysis were carried out in the same manner as in Example 1. A commercially available 0.9 mol / L LiFSI / PC-EMC-DME electrolyte was used as the electrolyte for the electrochemical capacitor. The results are shown in Table 1.

[0106] (Example 17) Except for the points below, the preparation of the layered material powder, the preparation of electrodes, the preparation of an electrochemical capacitor, electrochemical measurement, and elemental quantitative analysis were carried out in the same manner as in Example 1. A commercially available 0.9 mol / L LiFSI / PC-EMC-DME electrolyte was used as the electrolyte for the electrochemical capacitor. The sweep range for the electrochemical measurement was set from -2.7V to -0.8V relative to the reference electrode. The results are shown in Table 1.

[0107] (Comparative Example 1) A slurry was obtained by mixing commercially available activated carbon, acetylene black, sodium carboxymethylcellulose, PFFE, and ultrapure water. This slurry was applied to an aluminum foil having an etched surface as a current collector using an applicator, and the resulting coating was vacuum-dried at 80°C to obtain an activated carbon-containing film. The laminate of the aluminum foil and the activated carbon-containing film was cut into a circular shape with a diameter of 16 mm in a plan view, and vacuum-dried at 110°C to obtain the electrode according to Comparative Example 1.

[0108] Except for using the electrode according to Comparative Example 1 instead of the electrode according to Example 1, the electrochemical capacitor was fabricated and electrochemical measurements were performed in the same manner as in Example 1. The results are shown in Table 2.

[0109] (Comparative Example 2) Except for the points below, the electrode, electrochemical capacitor, and electrochemical measurements were carried out in the same manner as in Comparative Example 1. A commercially available 1 mol / L LiPF6 / PC electrolyte was used as the electrolyte for the electrochemical capacitor. The sweep range for the electrochemical measurement was set to -2.0V to +0.5V relative to the reference electrode. The results are shown in Table 2.

[0110] (Comparative Example 3) Except for the points described below, the electrodes were prepared, the electrochemical capacitor was prepared, and electrochemical measurements were performed in the same manner as in Comparative Example 1. A commercially available 1 mol / L tetraethylammonium tetrafluoroborate (TEABF4) / PC electrolyte was used as the electrolyte for the electrochemical capacitor. The results are shown in Table 2.

[0111] (Comparative Example 4) Except for the points described below, the electrodes were prepared, the electrochemical capacitor was prepared, and electrochemical measurements were performed in the same manner as in Comparative Example 1. A commercially available 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMIMTFSI) electrolyte was used as the electrolyte for the electrochemical capacitor. The results are shown in Table 2.

[0112] (Comparative Example 5) 10 g of MXene powder prepared in the same manner as in Example 1 was added to 300 mL of HCl solution with a concentration of 1 mol / L, and the HCl solution was stirred for 1 hour at room temperature in the range of 15°C to 28°C. Next, suction filtration was performed, and the obtained residue was vacuum-dried at 80°C. This obtained the layered material powder according to Comparative Example 5. Except for the points described above and below, electrode preparation, electrochemical capacitor preparation, electrochemical measurement, and elemental quantitative analysis were performed in the same manner as in Example 1. In slurry preparation, PVDF and N-methyl-2-pyrrolidone were added instead of ultrapure water. The lithium content measured by elemental quantitative analysis was below the detection limit. The results are shown in Table 2.

[0113] (Comparative Example 6) Except for the points described below, the preparation of the layered material powder, the preparation of electrodes, the preparation of the electrochemical capacitor, electrochemical measurements, and elemental quantitative analysis were carried out in the same manner as in Comparative Example 5. A commercially available 1 mol / L TEABF4 / PC electrolyte was used as the electrolyte for the electrochemical capacitor. The results are shown in Table 2.

[0114] (Comparative Example 7) Except for the points described below, the preparation of the layered material powder, the preparation of electrodes, the preparation of the electrochemical capacitor, electrochemical measurements, and elemental quantitative analysis were carried out in the same manner as in Comparative Example 5. A commercially available EMITFSI electrolyte was used as the electrolyte for the electrochemical capacitor. The results are shown in Table 2.

[0115] (Comparative Example 8) Except for the points described below, the preparation of the layered material powder, the preparation of electrodes, the preparation of an electrochemical capacitor, electrochemical measurement, and elemental quantitative analysis were carried out in the same manner as in Example 1. A commercially available 1 mol / L TEABF4 / PC electrolyte was used as the electrolyte for the electrochemical capacitor. The results are shown in Table 2.

[0116] (Comparative Example 9) Except for the points described below, the preparation of the layered material powder, the preparation of electrodes, the preparation of an electrochemical capacitor, electrochemical measurement, and elemental quantitative analysis were carried out in the same manner as in Example 1. A commercially available EMITFSI electrolyte was used as the electrolyte for the electrochemical capacitor. The results are shown in Table 2.

[0117] (Comparative Example 10) Except for the points below, the preparation of the layered material powder, the preparation of electrodes, the preparation of an electrochemical capacitor, electrochemical measurement, and elemental quantitative analysis were carried out in the same manner as in Example 1. A commercially available 1 mol / L bis(trifluoromethanesulfonyl)imide lithium (LiTFSI) / G4 electrolyte was used as the electrolyte for the electrochemical capacitor. The results are shown in Table 2.

[0118] (Comparative Example 11) MXene powder prepared in the same manner as in Example 1 was used as the powder for the layered material according to Comparative Example 11. Except for this point, electrode preparation, electrochemical capacitor preparation, electrochemical measurement, and elemental quantitative analysis were performed in the same manner as in Example 1. The elemental quantitative analysis measured Ti3C2T s The molar ratio of lithium content to other content was 3.0. The results are shown in Table 2.

[0119] (Comparative Example 12) Except for the points described below, the preparation of the layered material powder, the preparation of electrodes, the preparation of an electrochemical capacitor, electrochemical measurement, and elemental quantitative analysis were carried out in the same manner as in Comparative Example 11. A commercially available 1 mol / L TEABF4 / PC electrolyte was used as the electrolyte for the electrochemical capacitor. The results are shown in Table 2.

[0120] (Comparative Example 13) Except for the points described below, the preparation of the layered material powder, the preparation of electrodes, the preparation of an electrochemical capacitor, electrochemical measurement, and elemental quantitative analysis were carried out in the same manner as in Comparative Example 11. A commercially available 1 mol / L LiTFSI / G4 electrolyte was used as the electrolyte for the electrochemical capacitor. The results are shown in Table 2.

[0121] (Comparative Example 14) Except for the points described below, the preparation of the layered material powder, the preparation of electrodes, the preparation of an electrochemical capacitor, electrochemical measurement, and elemental quantitative analysis were carried out in the same manner as in Comparative Example 11. A commercially available 1 mol / L LiTFSI / G3 electrolyte was used as the electrolyte for the electrochemical capacitor. The results are shown in Table 2.

[0122] (Comparative Example 15) Except for the points described below, the preparation of the layered material powder, the preparation of electrodes, the preparation of an electrochemical capacitor, electrochemical measurement, and elemental quantitative analysis were carried out in the same manner as in Example 10. A commercially available 1 mol / L TEABF4 / PC electrolyte was used as the electrolyte for the electrochemical capacitor. The sweep range for the electrochemical measurement was set from -2.0V to 0V relative to the reference electrode. The results are shown in Table 2.

[0123] (Comparative Example 16) Except for the points described below, the preparation of the layered material powder, the preparation of electrodes, the preparation of an electrochemical capacitor, electrochemical measurement, and elemental quantitative analysis were carried out in the same manner as in Example 10. A commercially available 1 mol / L TEABF4 / PC electrolyte was used as the electrolyte for the electrochemical capacitor. The sweep range for the electrochemical measurement was set from -2.8V to -0.7V relative to the reference electrode. The results are shown in Table 2.

[0124] (Comparative Example 17) A layered material powder was prepared in the same manner as in Example 1, except for the following points. In preparing the layered material powder, 100 mL of a 1 mol / L lithium chloride aqueous solution was used instead of a lithium hydroxide aqueous solution.

[0125] (X-ray diffraction) X-ray diffraction (XRD) measurements were performed on the layered materials according to Example 1, Example 8, Example 10, Example 14, Comparative Example 5, Comparative Example 11, and Comparative Example 17 using a Rigaku MiniFlex X-ray diffractometer. In addition, XRD measurements were performed on the precursor according to Example 1 having a Ti3AlC2 composition, the precursor according to Example 10 having a Ti2AlC composition, and the precursor according to Example 14 having a Mo2Ga2C composition. Figure 6 is a graph showing the results of XRD measurements for the layered materials according to Example 1, Example 8, Comparative Example 5, Comparative Example 11, and Comparative Example 17, as well as the precursor Ti3AlC2. Figure 7 is a graph showing the results of X-ray diffraction measurements for the layered material according to Example 10, as well as the precursor Ti2AlC. Figure 8 is a graph showing the results of X-ray diffraction measurements for the layered material according to Example 14, as well as the precursor Mo2Ga2C. In Figures 6, 7, and 8, the vertical axis represents the X-ray diffraction intensity expressed in arbitrary units, and the horizontal axis represents the diffraction angle 2θ [degrees]. The diffraction intensity on the vertical axis shows the relative relationship of diffraction intensities from a single XRD measurement, and does not show the relative results of diffraction intensities from multiple XRD measurements.

[0126] Figures 6, 7, and 8 suggest that the layered materials in Examples 1, 8, 10, 14, Comparative Example 5, 11, and 17 do not contain a precursor, and that the layered material MXene is generated from the precursor MAX.

[0127] According to Figure 6, the diffraction peaks corresponding to the (002) plane of the layered materials in Example 1, Example 8, and Comparative Example 11 are shifted to a lower angle than the diffraction peaks corresponding to the (002) plane of the layered materials in Comparative Examples 5 and 17. This suggests that the lattice constant of the c axis of the layered materials in Example 1, Example 8, and Comparative Example 11 is greater than the lattice constant of the c axis of the layered materials in Comparative Examples 5 and 17. Therefore, it is considered that lithium was inserted between the layers of the layered materials in Example 1, Example 8, and Comparative Example 11, increasing the interlayer distance and thus increasing the lattice constant of the c axis of these layered materials. According to Figure 6, c E1 ≒c CE11 > c E8 > c CE5 ≒cCE17 It is thought that they have the following relationship. E1 c is the lattice constant of the c axis of the layered material according to Example 1. CE11 This is the lattice constant of the c-axis of the layered material according to Comparative Example 11. E8 c is the lattice constant of the c axis of the layered material according to Example 8. CE5 This is the lattice constant of the c-axis of the layered material according to Comparative Example 5. CE17 This is the lattice constant of the c-axis of the layered material according to Comparative Example 17. This relationship is thought to correspond to the amount of lithium inserted between layers. Ti3C2T of the layered material according to Comparative Example 11 s The molar ratio of lithium content to the content of Ti3C2T in the layered material according to Example 1 is s The molar ratio of lithium content to the total content is greater than that of other elements. However, the c-axis lattice constant of the layered material in Example 1 and the c-axis lattice constant of the layered material in Comparative Example 11 are almost the same. For this reason, it is considered that the layered material in Comparative Example 11 contains lithium that is not inserted between layers. As described above, the lithium content measured by the elemental quantitative analysis of the layered material in Comparative Example 5 is below the detection limit, and it is considered that the layered material in Comparative Example 5 does not contain lithium. According to Figure 6, c CE5 ≒c CE17 Since this relationship is confirmed, it is considered that the layered material relating to Comparative Example 17 also does not contain lithium.

[0128] A comparison of the examples and comparative examples shows that when the molar ratio of lithium to the main body of the layered material is greater than 0 and 2 or less, and the electrolyte contains LiPF6, LiBF4, or LiFSI, the capacitance per unit volume of the electrode tends to be high. For example, the capacitance per unit volume of the electrode according to the example is 150 F / cm². 3The above is the result. When the molar ratio of lithium to the main body of the layered material is greater than 0 and less than or equal to 2, a predetermined amount of electrolyte is more easily inserted between the layers of the layered material, and it is thought that the energy storage performance of the energy storage device tends to be higher. When the molar ratio of lithium to the main body of the layered material is greater than 2, the amount of lithium that is not inserted between the layers of the layered material increases, and it is thought that this lowers the specific capacity of the electrode. Comparing the example and the comparative example, when the electrolyte of the electrolyte solution in the energy storage device contains lithium ions, lithium ions originating from the electrolyte solution are more easily inserted between the layers of the layered material according to the example. For this reason, the energy storage performance of the energy storage device tends to be higher. This is thought to be related to the fact that the interlayer ion species (atoms) of the layered material and the ion species of the electrolyte are the same. - BF4 - , or FSI - When anions such as are present, the specific capacity of the energy storage device tends to increase. This is because, in the electrolyte, the lithium between the layers of the layered material is affected by the PF6 of the electrolyte. - BF4 - , or FSI - It is thought that the coordination bonding between the layers expands the interlayer distance of the layered material, leading to a change in the electronic state. PF6 - BF4 - , and FSI - This is the bistrifluoromethylsulfonylamide ion (TFSI - Because its ionic radius is smaller compared to others, it is thought to be more likely to coordinate to lithium in the interlayers of layered materials. For this reason, if the electrolyte of the electrolyte solution contains at least one selected from the group consisting of anions in which four or more atoms of the same type are bonded to the central atom and bis(fluorosulfonyl)imide ions, it is thought that these anions are more likely to coordinate to lithium in the interlayers of layered materials.

[0129]

[0130]

[0131] The energy storage device described herein can be used in equipment and systems in various fields.

Claims

1. The device comprises a first electrode, a second electrode, and an electrolyte, wherein at least a portion of the first electrode and at least a portion of the second electrode are arranged apart from each other in the electrolyte, at least one selected from the group consisting of the first electrode and the second electrode is an electrode containing a layered material, the electrolyte contains a lithium salt having at least one selected from the group consisting of anions and bis(fluorosulfonyl)imide ions in which four or more atoms of the same type are bonded to a central atom, and the layered material is M m X n A power storage device comprising a body having the composition of and a layer including an end present on the surface of the body, and lithium, wherein in the body, M is at least one selected from the group consisting of Group 3, Group 4, Group 5, Group 6, and Group 7 elements, X includes at least one selected from the group consisting of carbon atoms and nitrogen atoms, n is 1 or more and 4 or less, m is greater than n and 5 or less, and the electrode satisfies at least one condition selected from the group consisting of (I) and (II) below. (I) The molar ratio of the lithium contained in the layered material to the body is greater than 0 and 2 or less. (II) The capacitance per unit volume of the electrode is Ag / Ag + 120 F / cm in the sweep range from -2.0 V to 0 V relative to the reference electrode. 3 That's all.

2. The energy storage device according to claim 1, wherein the lithium salt comprises at least one selected from the group consisting of LiPF6, LiBF4, and lithium bis(fluorosulfonyl)imide.

3. The energy storage device according to claim 1, wherein the electrode satisfies both conditions (I) and (II).

4. The energy storage device according to claim 1, wherein the termination includes an atom having an electronegativity greater than the electronegativity of M.

5. The energy storage device according to claim 1, wherein the terminal comprises at least one selected from the group consisting of a hydroxyl group, a hydrogen atom, a halogen atom, a chalcogen atom, an amino group, a phosphorus atom, and an antimony atom.

6. The energy storage device according to claim 1, wherein n is 1 and m is 2, or n is 2 and m is 3.

7. The energy storage device according to claim 1, wherein M includes at least one selected from the group consisting of Ti and Mo.

8. The energy storage device according to claim 1, wherein X comprises a carbon atom.

9. The energy storage device according to claim 1, wherein the layered material comprises a plurality of layers, and the lithium contained in the layered material is arranged between the plurality of layers.

10. The energy storage device according to claim 1, wherein the electrolyte further comprises at least one selected from the group consisting of propylene carbonate, ethylene carbonate, dimethyl carbonate, and acetonitrile.

11. The energy storage device according to claim 1, wherein the electrode is a negative electrode.

12. A method for producing a layered material, wherein an etching agent containing lithium fluoride and hydrochloric acid is used. m AX n The process includes removing at least some A atoms from a precursor having the composition of to obtain a treated product, washing the treated product with acid, and mixing the treated product with lithium hydroxide, wherein the layered material is M m X n A manufacturing method comprising a layer including a body having the composition of and an end present on the surface of the body, and lithium, wherein in the precursor and the body, M is at least one selected from the group consisting of Group 3, Group 4, Group 5, Group 6, and Group 7 elements, A is at least one selected from the group consisting of Group 12, Group 13, Group 14, Group 15, and Group 16 elements, X includes at least one selected from the group consisting of carbon atoms and nitrogen atoms, n is 1 or more and 4 or less, m is greater than n and 5 or less, and the molar ratio of the lithium in the layered material to the body is greater than 0 and 2 or less.

13. The method for producing a layered material according to claim 12, wherein the termination atom contains an atom having an electronegativity greater than the electronegativity of M.

14. The method for producing a layered material according to claim 12, wherein the terminus comprises at least one selected from the group consisting of a hydroxyl group, a hydrogen atom, a halogen atom, a chalcogen atom, an amino group, a phosphorus atom, and an antimony atom.

15. The method for manufacturing a layered material according to claim 12, wherein n is 1 and m is 2, or n is 2 and m is 3.

16. The method for producing a layered material according to claim 12, wherein M comprises at least one selected from the group consisting of Ti and Mo.

17. The method for producing a layered material according to claim 12, wherein X contains carbon atoms.

18. The method for manufacturing a layered material according to claim 12, wherein the layered material comprises a plurality of layers, and the lithium contained in the layered material is arranged between the plurality of layers.

19. The method for producing a layered material according to claim 12, wherein A comprises Al.

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