JP2024043464A - Active materials, electrodes, secondary batteries, battery packs, and vehicles - Google Patents

Abstract

[Problem] To provide an active material, an electrode, a secondary battery, a battery pack, and a vehicle that can realize a high-capacity secondary battery. [Solution] To provide an active material including a complex oxide including a structure including a plurality of rhenium oxide type blocks of different sizes, and the rhenium oxide type blocks are connected at least non-periodicly by octahedral edge sharing. The rhenium oxide type blocks include an octahedral structure composed of oxygen and a metal element, and are composed of corner sharing of the octahedral structure. The complex oxide is represented by a general formula LiaMbNbMocOd, where M is any one or more selected from the group consisting of Ti, V, Ta, Fe, Co, Mn, Ni, Bi, Sb, As, P, Cr, W, B, Na, K, Mg, Al, Ca, Y, and Si, and 0≦a≦b+2+3c, 0≦b≦1.5, 0≦c≦0.5, and 2.33≦d/(1+b+c)≦2.50. [Selected Figure] Figure 2

Description

Embodiments of the present invention relate to active materials, electrodes, secondary batteries, battery packs, and vehicles.

In recent years, research and development of secondary batteries such as lithium ion secondary batteries and non-aqueous electrolyte secondary batteries as high energy density batteries has been actively conducted. Secondary batteries are expected to be used as power sources for vehicles such as hybrid cars and electric cars, or as uninterruptible power sources for mobile phone base stations. Therefore, in addition to energy density, secondary batteries are required to have excellent other performances such as rapid charging and discharging performance and long-term reliability.

A typical negative electrode of a lithium-ion battery is a carbon-based negative electrode using a carbonaceous material such as graphite as an active material. When a battery using a carbon-based negative electrode is repeatedly charged and discharged rapidly, dendrites of metallic lithium are precipitated on the electrode, which may cause heat generation or fire due to an internal short circuit. Therefore, a battery with a high negative electrode operating potential has been developed by using a metal composite oxide instead of a carbonaceous material for the negative electrode. For example, a battery using a spinel-type lithium titanium composite oxide Li ₄ Ti ₅ O ₁₂ for the negative electrode has a high average operating potential of 1.55 V (vs. Li/Li ⁺ ), so that Li dendrite precipitation does not progress, allowing stable rapid charging and discharging, and also operates at a potential where the reduction side reaction of the electrolyte is unlikely to occur, so that the life is longer than that of a battery using a carbon-based negative electrode. However, in a battery using Li ₄ Ti ₅ O ₁₂ for the negative electrode, the theoretical capacity of the active material is low at 175 mAh/g, and there is a problem that the energy density is lower than that of a battery equipped with a carbon-based negative electrode.

Therefore, monoclinic niobium titanium oxide TiNb ₂ O ₇ is being considered. It is an active material that exhibits high capacity while having an operating potential near 1 V (vs. Li/Li ⁺ ) based on the oxidation-reduction potential of lithium. For this reason, it is expected that a volumetric energy density exceeding that of a carbon-based negative electrode can be obtained. However, in order to fully popularize electric vehicles, it is desired that the energy density of lithium-ion secondary batteries will further increase in the future from the perspective of improving cruising range, etc., and it is necessary to develop even higher capacity quick-charging batteries. It is hoped that

JP2012-99287A JP 2021-061223 Publication International Publication No. 2019/234248

Nature, 559, 556-563(2018) J. Mater. Chem. A, 2019, 7, 6522-6532 International Tables for Crystallography (2006). 1st online ed. Chester: International Union of Crystallography. “Powder X-ray Analysis in Practice” First Edition (2002) Edited by the Japanese Society of Analytical Chemistry X-ray Analysis Research Council Edited by Izumi Nakai and Fujio Izumi (Asakura Shoten)

The purpose of the embodiment is to provide active materials and electrodes that can realize a high-capacity secondary battery, a high-capacity secondary battery and battery pack, and a vehicle equipped with the battery pack.

According to the embodiment, the composite oxide includes a plurality of rhenium oxide blocks having different sizes, and the rhenium oxide blocks are connected without periodicity by sharing at least an octahedral edge. An active material is provided. The rhenium oxide type block includes an octahedral structure composed of oxygen and a metal element, and is configured by sharing the vertices of the octahedral structure. The composite oxide is represented by the general formula Li _a M _b NbMo _c O _d . Here, M is from the group consisting of Ti, V, Ta, Fe, Co, Mn, Ni, Bi, Sb, As, P, Cr, W, B, Na, K, Mg, Al, Ca, Y and Si. One or more of the selected ones, and 0≦a≦b+2+3c, 0≦b≦1.5, 0≦c≦0.5, and 2.33≦d/(1+b+c)≦2.50. .

According to another embodiment, an electrode is provided that includes the active material.

According to yet another embodiment, a secondary battery including a positive electrode, a negative electrode, and an electrolyte is provided. The positive electrode or negative electrode is the electrode described above.

According to a particularly other embodiment, a battery pack including the above-mentioned secondary battery is provided.

Further, according to the embodiment, a vehicle including the battery pack described above is provided.

FIG. 2 is a schematic diagram showing an example of a crystal structure that may be contained in a complex oxide contained in the active material according to the embodiment. FIG. 1 is a schematic diagram showing an example of a crystal structure included in a composite oxide included in an active material according to an embodiment. 1 is a cross-sectional view schematically showing an example of a secondary battery according to an embodiment. FIG. 4 is an enlarged cross-sectional view of section A of the secondary battery shown in FIG. 3. FIG. 3 is a partially cutaway perspective view schematically showing another example of the secondary battery according to the embodiment. FIG. 6 is an enlarged cross-sectional view of part B of the secondary battery shown in FIG. 5; FIG. 1 is a perspective view schematically showing an example of an assembled battery according to an embodiment. FIG. 1 is an exploded perspective view schematically showing an example of a battery pack according to an embodiment. 9 is a block diagram showing an example of an electric circuit of the battery pack shown in FIG. 8. FIG. 1 is a partially transparent view schematically showing an example of a vehicle according to an embodiment. 1 is a diagram schematically showing an example of a control system related to an electrical system in a vehicle according to an embodiment. 3 is a graph showing a spectrum obtained by wide-angle X-ray scattering measurement of the composite oxide of the active material in Example 1. 3 is a graph showing a spectrum obtained by wide-angle X-ray scattering measurement of the composite oxide of the active material in Example 2. 1 is a graph showing a spectrum obtained by wide-angle X-ray scattering measurement of the composite oxide of the active material in Example 3. 3 is a graph showing a spectrum obtained by wide-angle X-ray scattering measurement of the composite oxide of the active material in Comparative Example 1. 1 is a graph showing enlarged spectra obtained by wide-angle X-ray scattering measurement of the composite oxides of the active materials in Examples 1 to 3 and Comparative Example 1. Graph showing initial charge/discharge curves in Example 1-3 and Comparative Example 1.

In order to obtain a high-capacity material, it is desirable to select a material that provides a large amount of charge compensation upon insertion of carrier ions (for example, lithium ions). For this purpose, a composite oxide containing molybdenum (Mo), which is a hexavalent element, can be used as a compound with higher capacity, for example. However, as for molybdenum-niobium composite oxide materials, there have been no reports of battery materials with high molybdenum content ratios.

Hereinafter, embodiments will be described with reference to the drawings. In the following description, components that perform the same or similar functions are designated by the same reference numerals throughout all the drawings, and redundant description will be omitted. Each figure is a schematic diagram for explaining the embodiment and facilitating understanding thereof, and the shape, dimensions, ratio, etc. thereof may differ from the actual device, but these are based on the following explanation and known technology. The design can be changed as appropriate.

(First embodiment)
According to the first embodiment, an active material including a composite oxide including a structure including a plurality of rhenium oxide type blocks having different sizes is provided. The rhenium oxide type blocks are connected without periodicity by sharing at least the octahedral edges. The rhenium oxide type block contains an octahedral structure composed of oxygen and metal elements. Furthermore, the rhenium oxide type block has an octahedral structure with shared vertices. The above composite oxide is represented by the general formula Li _a M _b NbMo _c O _d . In the general formula, M is a group consisting of Ti, V, Ta, Fe, Co, Mn, Ni, Bi, Sb, As, P, Cr, W, B, Na, K, Mg, Al, Ca, Y and Si. At least one selected from Each subscript in the formula satisfies 0≦a≦b+2+3c, 0≦b≦1.5, 0≦c≦0.5, and 2.33≦d/(1+b+c)≦2.50, respectively.
Further, the subscript b may be within the range of 0≦b≦1.4.

Such an active material may be an active material for a battery. The active material may be, for example, an electrode active material used in an electrode of a secondary battery such as a lithium ion battery or a nonaqueous electrolyte battery. More specifically, the active material may be, for example, a negative electrode active material used for a negative electrode of a secondary battery.

A composite oxide represented by the above general formula Li _a M _b NbMo _c O _d (the element M and each subscript are as described above; hereinafter omitted) and having a structure including the above-mentioned rhenium oxide type block structure is used as an electrode active material. By using it as a secondary battery, a high-capacity secondary battery can be realized.

<Crystal structure>
The composite oxide contained in the active material according to the first embodiment corresponds to a part of the oxide material having a Wadsley-Roth phase structure, which is a crystalline phase in oxide materials containing niobium. It has been reported that the Wadsley-Roth phase has a crystalline structure in the range of 2.33≦ _AO /AM≦2.65, where AO is the number of oxygen atoms and _AM is the number of metal elements, respectively, with respect to the ratio of oxygen _O to metal element _M in the composition. For example, in the case _{of TiNb2O7} , the crystalline structure is on the reduction side, with _AO / _AM =2.33.

Here, reduction means that the proportion of oxygen in the structure is low. The Wadsley-Roth phase is an oxygen-metal octahedral apex-sharing structure that forms a rhenium oxide-type block structure. It has a crystal structure in which rhenium type blocks (ReO ₃ type blocks) are connected in two dimensions. The crystal structure on the reduction side has a rhenium oxide type block with a small size. Although the rhenium oxide type crystal structure has voids into which many Li can be inserted, due to its highly symmetrical crystal structure, the bond length between the metal element and the oxygen element is required to eliminate charge repulsion when Li is inserted. is difficult to change. Therefore, the rhenium oxide type crystal structure can be said to be a structure in which Li insertion is restricted due to charge repulsion when Li is inserted. Here, when the crystal structure is on the reduction side, A _O /A _M becomes smaller, so the number of oxygen in the structure decreases, and the size of the rhenium oxide type block becomes smaller. As a result, when Li is intercalated, a crystal structure can be obtained in which the volume can expand due to a change in the bond length between the metal element and the oxygen element. For this reason, although it has a wide void by including a rhenium oxide type crystal structure, there are no restrictions on structural change when Li is inserted, so a large amount of Li can be inserted.

The composite oxide included in the active material according to the first embodiment also has a reduced crystal structure like TiNb ₂ O ₇ , which makes it possible to insert more lithium (Li) into the crystal structure. , a crystal structure with a large reversible capacity has been obtained. In other words, the crystal structure of such a composite oxide is a reduction side crystal structure belonging to the Wadsley-Roth phase consisting of three elements including molybdenum and the metal element M in addition to niobium.

FIG. 1 shows a schematic diagram of an example of a crystal structure that may be included in a composite oxide represented by the general formula Li _a M _b Nb Mo _c O _d . This example has a crystal structure in which the ratio of the number of atoms A O of oxygen O to the number A _{M of} atoms of the metal element M included as a constituent element is A _O /A _M =2.50. FIG. 1 shows a unit cell in the [001] direction when the crystal structure is viewed along the c-axis direction. The space group notation of the crystal structure belongs to I ^- 4, and the space group number is assigned as 82. The space group referred to here refers to the International Tables for Crystallography (Non-Patent Document 3), specifically, Vol.A: Space-group symmetry (2nd online edition (2016); ISBN: 978-0- 470-97423-0, doi: 10.1107/97809553602060000114). However, the space groups are P4 (space group number 75), I4 (space group number 79), P ^- 4 (space group number 81), P4 ₂ /n (space group number 86), I4/m (space group number 87). ), P4nc (space group number 104), P ^- 42 ₁ c (space group number 114), P ^- 4n2 (space group number 118), which are similar to I ^- 4 (space group number 82) or fourfold symmetry axes. It is also possible to explain the assignment using a simple cubic lattice with a reversal axis, and changes can occur if the composition deviates from the stoichiometric ratio by adjusting the composition ratio, or if the structure is distorted due to the presence of a different phase. It is possible to do so. The crystal structure 10 includes an octahedron 10a and a tetrahedron 10b each composed of a metal element 18 and an oxygen element 19. The octahedrons 10a are connected to each other by sharing vertices to form a rhenium oxide type block (ReO ₃ type block). The size of the block is 3×3=9 octahedrons 10a. The nine blocks of rhenium oxide type form planes in the a-axis direction and the b-axis direction by sharing the edges of the octahedron 10a or the vertices of the tetrahedron 10b. A crystal structure is constructed by connecting a plurality of planes including these nine octahedrons 10a on the c-axis side by sharing octahedral edges or sharing tetrahedral vertices.

FIG. 2 shows a schematic diagram of another example of a crystal structure that may be included in the composite oxide represented by the general formula Li _a M _b Nb Mo _c O _d . Figure 2 shows the structure of _three ReO blocks viewed from the stacking direction. The _three ReO blocks (for example, block 15a) surrounded by thick lines and the _three ReO blocks (for example, block 15d) shown only by thin lines are different in the plane in which the metal element 18 is arranged. This example is characterized by having no periodicity of structure. Blocks of different sizes exist connected according to the Wadsley-Roth phase arrangement method. One side of a block is 2 blocks for a small block and 6 blocks for a large block. For example, the block 15a is made up of 3 x 3 octahedrons 11a, the block 15b is made up of 2 x 3 octahedrons 11a, the block 15c is made up of 2 x 4 octahedrons 11a, and the block 15d is made up of 2 x 4 octahedra 11a. The block 15e consists of 2 x 2 octahedrons 11a, the block 15e consists of 3 x 6 octahedrons 11a, the block 15f consists of 5 x 3 octahedrons 11a, and the block 15g consists of 4 x 4 octahedrons 11a. It consists of an octahedron 11a. These sizes can be freely adjusted depending on the metal/oxygen ratio depending on the mixed state of elements M, Nb, and Mo, and are not limited. Although the majority are connected by octahedral edge sharing 17, some may also include tetrahedral vertex sharing by the tetrahedron 11b. Compared to FIG. 1, there are fewer tetrahedra, and by replacing the vertex connections of the tetrahedron with the edge connections of the octahedron, the number of octahedral edge sharing increases, and thus the octahedral lattice distortion increases. The large lattice strain of the octahedron facilitates structural relaxation due to changes in bond length during Li insertion, making it possible to increase the amount of Li insertion. Furthermore, since the octahedral edge sharing is included without a periodic structure, the asymmetry of the skeleton is maintained even when the amount of Li inserted is increased. Therefore, in the crystal structure of FIG. 2, the reversible capacity is further improved than that of the crystal structure of FIG. Therefore, by including the crystal structure shown in FIG. 2 in the active material, it is possible to improve the capacity.

In the crystal structure shown in Figure 2, it is possible to adjust the metal/oxygen ratio, which changes with changes in the composition ratio, by changing the size of the ReO ₃ type block and the number of connections in octahedral edge sharing and tetrahedral vertex sharing. Therefore, the oxygen/metal ratio can be changed by changing the composition ratio, and can be freely adjusted within the composition range of the general formula Li _a M _b Nb Mo _c O _d .

Molybdenum element (Mo) can be incorporated into the crystal structure not only in a hexavalent state but also in a tetravalent or pentavalent state. The valence of Mo is determined by adjusting the charge balance depending on the amount of metal elements other than Mo in the crystal structure shown in FIG. 1 or 2 and the amount of oxygen. In the case of a hexavalent element, the charge compensation upon insertion of Li with an M element such as Ti is a three-electron reaction, so the theoretical capacity of Li that can be inserted can be increased. The element in the tetravalent or pentavalent state is arranged in the crystal structure in such a way that electrons are supplied to the d-band of the Mo element. Therefore, by including a tetravalent or pentavalent Mo element, the conductivity can be changed and battery performance can be improved. It is known that the Wadsley-Roth phase containing molybdenum has a high (noble) operating potential. When comparing oxides containing titanium and niobium, for example, the titanium-niobium-molybdenum composite oxide, which is one aspect of the first embodiment, has a crystal structure containing a high concentration of molybdenum element. This allows the operating potential to be higher than that of TiNb ₂ O ₇ . As a result, the operating potential is in a potential range where there are few reduction side reactions of the electrolytic solution, and high life performance can be exhibited.

The valence of Mo may be included in the crystal structure in a state higher than the valence estimated from the crystal structure of FIG. 1 or 2 and the balance between the amount of oxygen and the metal element. In this case, it is presumed that cation vacancies are formed and included in the crystal structure in order to adjust the charge balance. Including cationic vacancies within the structure can improve the electronic conductivity of the active material, thereby improving battery performance. On the other hand, since cationic vacancies have the effect of locally trapping Li within the structure, too many cationic vacancies are undesirable from the viewpoint of inhibiting Li movement within the solid.

Furthermore, in such an active material, it is also possible to form oxygen vacancies by setting the amount of Mo element to be smaller than the ideal composition. Formation of oxygen vacancies improves the electronic conductivity of the active material, thereby improving battery performance. On the other hand, too large an amount of oxygen vacancies causes charge repulsion of Li. Therefore, too large an amount of oxygen vacancies is not preferable because it inhibits the movement of Li.

In the general formula Li _a M _b NbMo _c O _d , the subscript d reflects the amount of cation vacancies and oxygen vacancies.

The structure shown in Figure 2 can be confirmed by observation using a high-angle annular dark-field method using a scanning transmission electron microscope, which will be described later. In addition, the composition state of the crystal structures shown in Figures 1 and 2 contained in the complex oxide can be estimated based on the diffraction diagram (diffraction spectrum) of powder X-ray diffraction using a Cu-Kα radiation source. In the diffraction spectrum of powder X-ray diffraction using a Cu-Kα radiation source, the intensity ratio between the peak intensity I1 of the most intense peak P1 appearing within the range of 2θ = 25.05 ± 0.25° and the peak intensity I2 of the most intense peak P2 appearing within the range of 2θ = 24.00 ± 0.2° indicates the degree of mixing of the crystal structure of Figure 1 and the crystal structure of Figure 2 in the complex oxide.

The position of peak P2 does not change significantly between the crystal structures in Figures 1 and 2, as there is no major difference in the length in the stacking axis direction, and since the peak positions overlap, it appears to exist as one peak. looks like. On the other hand, the main peak for the structure in Figure 1 appears at the position of 2θ = 25.4 ± 0.10 and is assigned to the (420) plane, but due to changes in the crystal structure, the main peak in the structure in Figure 2 appears along the plane direction of the ReO ₃ block. The main peak position due to the apparent average period changes in the lower angle direction. When I1/I2≦0.1, it means that the crystal structure of the composite oxide is mainly composed of the structure shown in FIG. When I1/I2>0.1, it means that at least a part of the crystal structure has changed to the crystal structure shown in FIG. Further, when I1/I2≧1, the structure shown in FIG. 2 may occupy most of the crystal structure of the composite oxide.

The composite oxide represented by the general formula Li _a M _b Nb Mo _c O _d can further contain an element M different from them in addition to Nb element and Mo element as metal elements. In the structure shown in FIG. 2, the structure can be maintained by changing the oxygen/metal composition ratio due to charge compensation, changing the size of the ReO ₃ type block, and changing the octahedral edge sharing and tetrahedral vertex sharing of the connection part. Mo element can be included in the structure by adjusting the valence in the structure from 4 to 6. Furthermore, as described above, oxygen vacancies and cation vacancies can be easily created in the structure of such active materials. Therefore, there is a high degree of freedom in adjusting the charge balance in the structure, and it is therefore possible to freely select the element M. M elements consist of Ti, V, Ta, Fe, Co, Mn, Ni, Bi, Sb, As, P, Cr, W, B, Na, K, Mg, Al, Ca, Y, Zr and Si. At least one can be selected from the group. In the above general formula, the subscript b may satisfy, for example, 0<b.

The above-mentioned M element can be included in the crystal structure, for example, as a metal element constituting the above-mentioned tetrahedron or octahedron. Furthermore, the M element may exist in the active material in a form that is not included in the crystal structure of the composite oxide.

For example, the elements vanadium (V) and phosphorus (P) can be included in the crystal structure as pentavalent elements. Titanium (Ti), zirconia (Zr), and silicon (Si) can be included in the structure as tetravalent elements. Iron (Fe), chromium (Cr), aluminum (Al), bismuth (Bi), antimony (Sb), boron (B), arsenic (As), cobalt (Co), manganese (Mn), nickel (Ni), and yttrium (Y) can be incorporated into the crystal structure as a trivalent element. Magnesium (Mg) and calcium (Ca) can be incorporated into the crystal structure as divalent elements. Potassium (K) and sodium (Na) can be incorporated into the crystal structure as monovalent elements. Among these elements, tetravalent elements have a higher charge than trivalent or lower valent elements, so they can be included in large amounts without reducing the oxygen/metal ratio in the structure, and the Mo ratio in the structure can be increased. This is preferable since it is possible to increase the temperature. In particular, the titanium (Ti) element is the element that can be included in the largest amount in the structure, and since its ionic radius is close to that of the pentavalent Nb element, it is easy to incorporate into the structure, and is therefore the most preferable among the M elements.

Tantalum (Ta) can replace the Nb element as a pentavalent element. Since Ta and Nb belong to the same group of elements on the periodic table, they have similar physical and chemical properties. Therefore, it is possible to obtain equivalent battery performance even if Nb is replaced with Ta.

Tungsten (W) can replace a part of the Mo element as a hexavalent element. Generally, it is known that the Wadsley-Roth phase containing W has high rate performance because the Li diffusion rate in the solid is fast. Therefore, inclusion of W makes it possible to further improve the rate performance of the active material.

<Active material particles>
The active material according to the first embodiment may take the form of particles, for example. That is, such an active material may be represented by the general formula Li _a M _{b NbMoc} O _d and may be composed of particles of a composite oxide containing the above-mentioned crystal structure. The active material may be a single primary particle, a secondary particle formed by agglomerating a plurality of primary particles, or a mixture thereof.

The average primary particle diameter of the active material is preferably 10 μm or less, more preferably 5 μm or less, and even more preferably 3 μm or less. When the average primary particle diameter of the active material is small, the diffusion distance of lithium ions within the primary particles is short, so lithium ion diffusivity tends to increase. Furthermore, when the average primary particle diameter of the active material is small, the reaction area increases, so the reactivity between the active material and lithium ions increases, and the lithium ion insertion/extraction reaction tends to improve.

The average secondary particle diameter of the active material is preferably 1 μm or more and 50 μm or less. By setting the average secondary particle diameter of the active material within this range, it is possible to improve productivity during electrode manufacturing and to obtain a battery with good performance. This average secondary particle diameter means a particle diameter at which the volume integrated value is 50% in the particle size distribution determined by a laser diffraction type particle size distribution measuring device.

The BET specific surface area of the active material is preferably 3.0 m ² /g or more and 120 m ² /g or less, more preferably 4.0 m ² /g or more and 110 m ² /g or less. Using an active material with a high specific surface area can improve the discharge rate performance of the battery. Furthermore, by using an active material with a low specific surface area, the life performance of the battery can be improved. can be made into something.

The BET specific surface area means the specific surface area determined by the nitrogen BET (Brunauer, Emmet and Teller) method. The method for determining the specific surface area based on the nitrogen BET method will be described in detail later.

<Manufacturing method>
The active material according to the first embodiment can be manufactured as follows.

(liquid phase synthesis)
Although there are no particular limitations on the production of the composite oxide, it can be synthesized, for example, by a solid phase reaction method, a sol-gel method, a hydrothermal synthesis method, or the like. As an example of this, a method for producing a titanium-niobium-molybdenum composite oxide (ie, element M=Ti) using a sol-gel method will be described.

As starting materials, titanium compounds, niobium compounds, and molybdenum compounds are used. Examples of the titanium compound include titanium tetraisopropoxide, titanyl sulfate, titanium chloride, titanium ammonium oxalate and its hydrate, titanium hydroxide, and titanium oxide. Examples of the niobium compound include niobium chloride, ammonium niobium oxalate and its hydrate, niobium hydroxide, and niobium oxide. Examples of molybdenum compounds include molybdenum chloride, ammonium molybdate and its hydrates, molybdenum hydroxide, and molybdenum oxide. When an element other than Ti is selected as the element M, or when another element is selected together with Ti, a compound containing the selected element M is appropriately substituted for the titanium compound or used in combination.

It is preferable to dissolve the starting materials in pure water or acid beforehand to prepare a solution. By dissolving them in solution, it is possible to obtain a dry gel in which each element is homogeneously mixed, thereby increasing reactivity. If the starting materials cannot be dissolved in pure water, they are dissolved using acid.

Examples of the acid used to dissolve the raw material include citric acid and oxalic acid, but it is preferable to use oxalic acid from the viewpoint of solubility. For example, when using oxalic acid, the concentration is preferably 0.5M or more and 1M or less. When dissolving, it is preferable to use a temperature of 70° C. or higher to shorten the reaction time.

If it is difficult to dissolve the raw materials, the reaction can also proceed as a dispersion. In this case, the average particle diameter of the raw material contained in the dispersion liquid is preferably 3 μm or less, more preferably 1 μm. After preparing a solution (or dispersion) of each compound in a predetermined composition ratio, the solution is neutralized with an ammonia aqueous solution while being heated and stirred to adjust the pH. A gel solution is obtained by adjusting the pH. By setting the pH to 5 or more and 8 or less, it is possible to form a gel containing each raw material homogeneously, and thereby a dry gel with good reactivity during firing can be obtained.

Subsequently, the gel solution is heated to near its boiling point to evaporate water and promote gelation. After gelation, water is further evaporated and dried to obtain a dry gel. During gelation and drying, for example, the entire solution can be evaporated and concentrated to obtain a dry gel. The dry gel produced by evaporating and concentrating the entire solution is preferably pulverized before firing to reduce the average particle size to 10 μm or less, more preferably 5 μm or less. This makes it possible to reduce the particle size after firing. The resulting dry gel is fired.

It is more preferable to use a spray dryer in the process of evaporating the solvent to gel and obtain a dried gel. By spraying, it is possible to form fine droplets of the sol solution. By drying in the form of fine droplets, it is possible to prevent particle aggregation that occurs during solvent drying, making it possible to reduce the particle size after drying and reduce the number of coarse particles. This increases the homogeneity of the reaction during the firing of the precursor and also makes it possible to suppress particle aggregation during firing. The drying temperature during spray drying is preferably 100°C or higher and 200°C or lower.

When firing the dry gel, pre-calcination is performed at 200°C or higher and 500°C or lower for a firing time of 1 hour or more and 10 hours or less. This makes it possible to burn off excess organic components, thereby increasing the reactivity during the main firing.

The main firing is preferably carried out at a firing temperature of 600°C or higher and 800°C or lower, and for a firing time of 1 hour or more and 10 hours or less. By performing firing in such a temperature range, it is possible to obtain the desired phase while suppressing sublimation of molybdenum.

The powder after firing may have a high average particle size due to the formation of aggregates. In this case, it is preferable to adjust the predetermined average particle size by pulverization.

After mechanical pulverization, the powder may have an amorphous surface. In this case, when used as an active material for a battery, overvoltage is generated during Li insertion/desorption, which may increase side reactions. For this reason, it is preferable to perform the annealing treatment again. The annealing temperature is below the main firing temperature, and is preferably 500°C or more and 800°C or less.

<Various measurement methods>
The method for measuring the active material will be explained below. Specifically, confirmation of the composite oxide, measurement of the average particle diameter of active material particles, and measurement of the specific surface area of the active material will be explained.

When using an active material contained in a battery electrode as a sample, a measurement sample is prepared by performing pretreatment using the following method. First, the battery is completely discharged. The battery is then disassembled in a glove box under an argon atmosphere and the electrodes are removed. Next, the electrode taken out is washed using a solvent such as ethyl methyl carbonate. For each measurement to be performed, further processing is performed to prepare a sample with an appropriate morphology.

(Confirmation of complex oxide)
Confirmation that the active material has the above-mentioned crystal structure and contains a complex oxide represented by the general formula Li _a M _b NbMo _c O _d can be confirmed using wide-angle X-ray diffraction (XRD) method, high-angle annular dark field (High Angle Annular Dark Field) This can be carried out by combining annular dark-field (HAADF) method, inductively coupled plasma (ICP) emission spectrometry, and inert gas dissolution-infrared absorption spectroscopy. The crystal structure can be determined by wide-angle XRD method and HAADF method, and the elemental composition can be determined by ICP emission spectrometry and inert gas dissolution-infrared absorption spectroscopy. Moreover, in the spectrum obtained by XRD measurement, the intensity ratio (I1/I2) of the above-mentioned main peak can be determined. The valence of an element can be measured by, for example, photoelectron spectroscopy (XPS) using characteristic X-rays.

XRD measurement is performed as follows. First, active material particles are thoroughly ground to obtain a powdered sample. The average particle diameter of the powdered sample is preferably 20 μm or less. This average particle diameter can be determined using a laser diffraction particle size distribution analyzer.

Next, this powdered sample is filled into the holder portion of a glass sample plate, and the surface is flattened. For example, a glass sample plate with a holder portion having a depth of 0.2 mm can be used.

Next, this glass sample plate is placed in a powder X-ray diffractometer, and an XRD spectrum is measured using Cu-Kα rays. Specific measurement conditions are, for example, as follows:
X-ray diffraction device: SmartLab manufactured by Rigaku Co., Ltd.
X-ray source: CuKα rays Output: 40kV, 200mA
Package measurement name: General purpose measurement (concentrated method)
Incidence parallel slit opening angle: 5°
Incident longitudinal restriction slit length: 10mm
Light receiving PSA: None Light receiving parallel slit opening angle: 5°
Monochromatic method: Kβ filter method Measurement mode: Continuous Incidence slit width: 0.5°
Light receiving slit width: 20mm
Measurement range (2θ): 5~70°
Sampling width (2θ): 0.01°
Scan speed: 1° to 20°/min.

In this way, an XRD spectrum related to the active material is obtained. In this XRD spectrum, the horizontal axis shows the incident angle (2θ), and the vertical axis shows the diffraction intensity (cps). The scan speed can be adjusted within a range such that the main peak count of the XRD spectrum is 50,000 counts or more and 150,000 counts or less.

When the active material contained in a battery electrode is used as a sample, the electrode after cleaning obtained by carrying out the above-mentioned pretreatment is cut to an area approximately equal to the area of the glass sample plate holder to be used as the measurement sample.

Next, the obtained measurement sample is directly attached to a glass holder and subjected to XRD measurement.

The peak intensity in the XRD spectrum is derived by the following method. The ratio (S/N ratio) between the peak height (Signal=S) and noise (Noise=N) on the spectrum is made sufficiently large so as not to affect the calculation of the peak intensity. After the background is estimated and divided by an appropriate function, the peak corresponding to the Kα2 line is estimated and divided. The background can be estimated by methods such as the Sonneveld-Visser method, the spline function method, and the background function method. Kα2 radiation is removed by the Rachinger method and Ladell method. After identifying all peaks within the range of 2θ=20° to 30° for the processed spectrum, peak fitting is performed using the least squares method. For example, a pseudo-Voigt function is used as the peak function. When calculating peaks, if peaks originating from other mixed active materials, conductive agents, current collectors, and other battery components overlap, care should be taken to exclude the corresponding peaks. For example, materials other than the active material that may be included in the electrode, such as a current collector, a conductive agent, and a binder, are measured using XRD, and the XRD pattern derived from these materials is determined. Next, if there is a peak considered to be derived from the active material and a peak of another material that overlaps in the measurement sample, the peak of the material other than the active material is separated. In this way, an XRD spectrum is obtained in which the main peak related to the crystal structure contained in the active material is separated. Peaks P1 and P2 are determined based on the peak top position of the main peak, and their peak intensity ratio I1/I2 is determined.

In order to more precisely confirm whether the crystal structure contained in the measured sample belongs to the tetragonal crystal structure shown in FIG. 1 described above, the Rietveld method is used. This can be confirmed by using, for example, RIETAN-FP as an analysis program and confirming that the R _wp value, which is a reliability factor, is at least 20% or less, more preferably 15% or less. At this time, if a peak containing impurities is present and overlaps with the phase targeted for analysis, analysis accuracy may be deteriorated. In this case, it is preferable to perform analysis excluding portions that clearly overlap with peaks derived from impurities from the analysis range. However, if the sample contains materials other than the active material according to the first embodiment, if the orientation of the sample is extremely high, or if coarse particles are mixed, this will change the intensity ratio. Rather, the structure is confirmed by confirming that there are no contradictions in the positions and relative intensities of all peaks assigned to the crystal structure. In addition, when the intensity of the spectrum is low and the background intensity is low, the R _wp value may become small, and the reliability factor does not have any meaning in its absolute value, but rather it is based on the goodness of fitting under certain measurement conditions. It is meaningful to make a relative judgment.

Regarding the analysis method using RIETAN-FP, for example, see Non-Patent Document 4 ("Powder X-ray analysis in practice" first edition (2002), edited by the Japan Society for Analytical Chemistry, X-ray Analysis Research Council, edited by Izumi Nakai, Fujio Izumi (Asakura) It is explained in detail in Chapter 9 "Let's use RIETAN-FP" of the bookstore).

Note that RIETAN-FP is a Rietveld analysis program that is distributed free of charge (as of August 2022) on its developer's web page on the Internet (http://fujioizumi.verse.jp/).

The structure shown in FIG. 2 does not have periodicity, so it is difficult to analyze it by XRD measurement. In order to confirm the structure shown in FIG. 2, it is preferable to directly observe the fine structure. The observation can be carried out by observation using the High Angle Annular Dark-Field (HAADF) method using a Scanning Transmission Electron Microscope (STEM). From the viewpoint of improving measurement resolution, it is preferable to use spherical aberration correction. The structure can be confirmed by acquiring an atomic image (10 nm × 10 nm) from a direction perpendicular to the ReO ₃ block and confirming the positional relationship of the metal elements that make up the ReO ₃ block.

The content of each element in the active material particles contained in the sample can be confirmed by ICP atomic emission spectrometry for metal elements. The amount of O element can be quantified by inert gas dissolution-infrared absorption spectroscopy, but precise quantification is difficult.

After the above-mentioned pretreatment, the active material particles contained in the electrode are further subjected to the following treatment. From the cleaned electrode, a member containing active material (e.g., the active material-containing layer described in the second embodiment) is peeled off, for example, from the electrode's current collector. The part peeled off from the electrode is heated in air for a short period of time (about 1 hour at 500°C) to burn off unnecessary parts such as binder components and carbon. The content of each element can then be quantified by ICP emission analysis or the like.

The measurement of the valence of the metal element contained in the complex oxide by the XPS method can be carried out as follows. It is preferable to use hard X-rays for the X-rays used in the measurement, since they have a deep detection depth and can measure a state closer to the bulk. Spectroscopic techniques using hard X-rays are also called HAXPES. The valence can be determined by checking the position of the binding energy of the narrow spectrum of each element. For example, for the Ti element, a tetravalent peak derived from Ti2p3 _/2 is observed at 459.0±0.4 eV. For the Mo element, a hexavalent peak derived from Mo3d5 _/2 is observed at 232.2±0.4 eV. For the Nb element, a pentavalent peak derived from Nb3d5 _/2 is observed at 207.5±0.4 eV. When a low valence element is contained, it can be determined by detecting a peak at a lower energy position than the previous valence. In particular, the Mo element may contain a valence of 5 or less.

Sample measurements are performed non-destructively to avoid changes in element valency. Therefore, when measuring the complex oxide contained in the electrode, the electrode is used as a sample without material extraction. Perform measurements with care so that charge-up during sample measurement does not affect the peak position. In order to avoid peak shifts due to charge-up, it is preferable to measure the electrode in a fully discharged state. If the electrode contains a conductive agent, charge-up can be reduced. Be careful, as long-term X-ray irradiation can damage the sample and cause the element valence to change. Furthermore, when materials with different structures are mixed, the peak may shift due to a change in bonding state, so be careful not to confuse this with a change in valence. When elements of different valences coexist, that is, when a spectrum includes a plurality of peaks, the spectrum can be separated by least squares fitting, and the mixture ratio can be estimated from the area ratio of the separated peaks.

Note that the content ratio of Li, represented by the subscript a in the general formula Li _a M _b Nb Mo _c O _d , changes depending on the charging state of the electrode in which the composite oxide is used as the active material. For example, in the composite oxide contained in the negative electrode, as the battery is charged, Li is inserted and the subscript a increases, and as the battery is discharged, Li is desorbed and the subscript a decreases.

(Measurement of average particle size)
The average primary particle size of the active material can be determined by observation using a scanning electron microscope (SEM). Specifically, the average primary particle size determined by SEM observation can be calculated by the following method.

First, the length of the longest axis and the length of the shortest axis are measured for the primary particles in the SEM image obtained by SEM observation, and the arithmetic mean of these is taken as the primary particle diameter. This measurement of primary particle diameter is performed on 100 randomly selected particles, and the average of these is taken as the average primary particle diameter.

The average secondary particle diameter of the active material can be determined from the particle size distribution measured using a laser diffraction type particle size distribution measuring device. A dispersion liquid diluted with N-methyl-2-pyrrolidone so that the concentration of the active material is 0.1% by mass to 1% by mass is used as a sample for this particle size distribution measurement. The particle size at which the volume integrated value is 50% in the obtained particle size distribution is defined as the average secondary particle size.

(Measurement of BET specific surface area)
The BET specific surface area of active material particles can be determined by the following method.

First, 4 g of active material is collected as a sample. Next, the evaluation cell of the measuring device is dried under reduced pressure at a temperature of 100° C. or higher for 15 hours to perform a degassing treatment. As the evaluation cell, for example, a 1/2 inch cell can be used. Next, the sample is placed in the measuring device. As the measuring device, for example, TriStar II3020 manufactured by Shimadzu Corporation-Micromeritics may be used. Next, while gradually increasing the pressure P (mmHg) of nitrogen gas in nitrogen gas at 77 K (the boiling point of nitrogen), the amount of nitrogen gas adsorbed (mL/g) of the sample is measured at each pressure P. Next, the value obtained by dividing the pressure P (mmHg) by the saturated vapor pressure P ₀ (mmHg) of nitrogen gas is set as the relative pressure P/P ₀ , and the adsorption amount is determined by plotting the amount of nitrogen gas adsorbed for each relative pressure P/P ₀ . Obtain the isotherm. Next, a BET plot is calculated from this nitrogen adsorption isotherm and the BET equation, and the specific surface area is obtained using this BET plot. Note that the BET multi-point method is used to calculate the BET plot.

The active material according to the first embodiment includes a structure including a rhenium oxide type block formed by an octahedral structure composed of oxygen and a metal element with shared vertices, and has a general formula Li _a M _b NbMo _c O _d Contains a complex oxide represented by In the above structure, a plurality of rhenium oxide blocks having different sizes are connected without periodicity by sharing at least an octahedral edge. In the above general formula, M consists of Ti, V, Ta, Fe, Co, Mn, Ni, Bi, Sb, As, P, Cr, W, B, Na, K, Mg, Al, Ca, Y and Si. One or more selected from the group. Subscripts a, b, c, and d are numbers that satisfy 0≦a≦b+2+3c, 0≦b≦1.5, 0≦c≦0.5, and 2.33≦d/(1+b+c)≦2.50. be. An electrode using the above composite oxide as an electrode active material has a high capacity per volume. Further, secondary batteries and battery packs using the above composite oxide as an electrode active material have a high capacity per volume. That is, such an active material exhibits high capacity.

Second Embodiment
According to a second embodiment, an electrode is provided.

The electrode according to the second embodiment includes the active material according to the first embodiment. This electrode may be a battery electrode containing the active material according to the first embodiment as a battery active material. The electrode as a battery electrode may be, for example, a negative electrode containing the active material according to the first embodiment as a negative electrode active material. Alternatively, the electrode may be a positive electrode containing the active material according to the first embodiment as a positive electrode active material.

Such an electrode may include a current collector and an active material-containing layer. The active material-containing layer may be formed on one or both sides of the current collector. The active material-containing layer may include an active material and, optionally, a conductive agent and a binder.

The active material-containing layer may contain only the active material according to the first embodiment, or may contain two or more types of active materials according to the first embodiment. Furthermore, it may include a mixture of one or more active materials according to the first embodiment and one or more other active materials. It is desirable that the content ratio of the active material according to the first embodiment to the total mass of the active material according to the first embodiment and other active materials is 10% by mass or more and 100% by mass or less.

For example, when the active material according to the first embodiment is included as a negative electrode active material, examples of other active materials include lithium titanate having a ramsdellite structure (for example, Li _2+x Ti ₃ O ₇ , 0≦ x≦3), lithium titanate having a spinel structure (e.g. Li _4+x Ti ₅ O ₁₂ , 0≦x≦3), titanium dioxide (TiO ₂ ), anatase titanium dioxide, rutile titanium dioxide, pentoxide Niobium (Nb ₂ O ₅ ), hollandite titanium composite oxide, orthorhombic titanium composite oxide, monoclinic niobium titanium oxide, niobium oxide, niobium titanium oxide, niobium molybdenum composite oxide, niobium Examples include tungsten composite oxide.

Examples of the rectangular titanium-containing composite oxide include compounds represented by Li _2+e M ^I _2-f Ti _6-g M ^II _h O _14+σ . Here, ^MI is at least one selected from the group consisting of Sr, Ba, Ca, Mg, Na, Cs, Rb and K. M ^II is at least one selected from the group consisting of Zr, Sn, V, Nb, Ta, Mo, W, Y, Fe, Co, Cr, Mn, Ni, and Al. The respective subscripts in the composition formula are 0≦e≦6, 0≦f<2, 0≦g<6, 0≦h<6, and −0.5≦σ≦0.5. A specific example of the rectangular titanium-containing complex oxide includes Li _2+e Na ₂ Ti ₆ O ₁₄ (0≦e≦6).

An example of the monoclinic niobium titanium oxide is a compound represented by Li _x Ti _1-y M1 _y Nb _2-z M2 _z O _7+δ . Here, M1 is at least one selected from the group consisting of Zr, Si, and Sn. M2 is at least one selected from the group consisting of V, Ta, and Bi. The respective subscripts in the composition formula are 0≦x≦5, 0≦y<1, 0≦z<2, and −0.3≦δ≦0.3. A specific example of the monoclinic niobium titanium oxide is Li _x Nb ₂ TiO ₇ (0≦x≦5).

Another example of monoclinic niobium titanium oxide is a compound represented by Li _x Ti _1-y M3 _y+z Nb _2-z O _7-δ . Here, M3 is at least one selected from the group consisting of Mg, Fe, Ni, Co, W, Ta, and Mo. The respective subscripts in the composition formula are 0≦x≦5, 0≦y<1, 0≦z<2, and −0.3≦δ≦0.3.

The conductive agent is blended to improve current collection performance and suppress contact resistance between the active material and the current collector. Examples of conductive agents include vapor grown carbon fiber (VGCF), carbon black such as acetylene black, graphite, carbonaceous materials such as carbon nanotubes and carbon nanofibers. One of these may be used as a conductive agent, or a combination of two or more may be used as a conductive agent. Alternatively, instead of using a conductive agent, the surface of the active material particles may be coated with carbon or an electronically conductive inorganic material. Furthermore, by using a conductive agent and coating the surface of the active material with carbon or a conductive material, the current collecting performance of the active material-containing layer can be improved.

The binder is blended to fill gaps between the dispersed active materials and to bind the active materials and the current collector. Examples of binders include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), fluorine rubber, styrene butadiene rubber, polyacrylic acid compounds, imide compounds, carboxymethyl cellulose cellulose; CMC), and salts of CMC. One of these may be used as a binder, or a combination of two or more may be used as a binder.

The blending ratio of the active material, conductive agent, and binder in the active material-containing layer can be changed as appropriate depending on the use of the electrode. For example, when the electrode is used as a negative electrode of a secondary battery, the active material (negative electrode active material), the conductive agent, and the binder are 68% by mass or more and 96% by mass or less, 2% by mass or more and 30% by mass or less, and It is preferably blended in a proportion of 2% by mass or more and 30% by mass or less. By setting the amount of the conductive agent to 2% by mass or more, the current collection performance of the active material-containing layer can be improved. Furthermore, by setting the amount of the binder to 2% by mass or more, the binding property between the active material-containing layer and the current collector becomes sufficient, and excellent cycle performance can be expected. On the other hand, it is preferable that the amount of the conductive agent and the binder be 30% by mass or less, respectively, in order to increase the capacity.

When the surface of the active material is coated with carbon or a conductive material, the amount of the coating material can be considered to be included in the amount of the conductive agent. The amount of carbon or conductive material covered is preferably 0.5% by mass or more and 5% by mass or less. A coating amount within this range can improve current collection performance and electrode density.

For the current collector, a material is used that is electrochemically stable at a potential at which lithium (Li) is inserted into and removed from the active material. For example, when the active material is used as a negative electrode active material, the current collector is copper, nickel, stainless steel, or aluminum, or selected from the group consisting of Mg, Ti, Zn, Mn, Fe, Cu, and Si. Preferably, it is made from an aluminum alloy containing one or more elements. The thickness of the current collector is preferably 5 μm or more and 20 μm or less. A current collector having such a thickness can balance the strength and weight of the electrode.

The current collector may also include a portion on whose surface the active material-containing layer is not formed. This portion can function as a current collecting tab.

The electrode can be produced, for example, by the following method. First, an active material, a conductive agent, and a binder are suspended in a solvent to prepare a slurry. This slurry is applied to one or both sides of the current collector. Next, the applied slurry is dried to obtain a laminate of the active material-containing layer and the current collector. Thereafter, this laminate is pressed. In this way, the electrode is produced.

Alternatively, the electrode may be produced by the following method. First, an active material, a conductive agent, and a binder are mixed to obtain a mixture. This mixture is then formed into pellets. Next, an electrode can be obtained by placing these pellets on a current collector.

The electrode according to the second embodiment contains the active material according to the first embodiment. Therefore, the electrode according to the second embodiment can realize a secondary battery with high capacity per volume.

Third Embodiment
According to the third embodiment, a secondary battery including a negative electrode, a positive electrode, and an electrolyte is provided. This secondary battery includes the electrode according to the second embodiment as the negative electrode or the positive electrode. That is, the secondary battery according to the third embodiment includes an electrode including the active material according to the first embodiment as a battery active material as a battery electrode. A secondary battery according to a desirable aspect includes the electrode according to the second embodiment as a negative electrode. That is, a secondary battery according to a desirable aspect includes an electrode including the active material according to the first embodiment as a battery active material as a negative electrode. Desired aspects will be described below.

Such a secondary battery may further include a separator disposed between the positive electrode and the negative electrode. The negative electrode, the positive electrode, and the separator can constitute an electrode group. An electrolyte may be retained in the electrode group.

Moreover, such a secondary battery can further include an exterior member that houses the electrode group and the electrolyte.

Furthermore, such a secondary battery may further include a negative electrode terminal electrically connected to the negative electrode and a positive electrode terminal electrically connected to the positive electrode.

The secondary battery according to the third embodiment may be, for example, a lithium secondary battery. Further, the secondary battery includes a non-aqueous electrolyte secondary battery containing a non-aqueous electrolyte.

Hereinafter, the negative electrode, positive electrode, electrolyte, separator, exterior member, negative electrode terminal, and positive electrode terminal will be explained in detail.

1) Negative electrode The negative electrode can include a negative electrode current collector and a negative electrode active material-containing layer. The negative electrode current collector and the negative electrode active material-containing layer may be included in the electrode according to the second embodiment, respectively. The negative electrode active material-containing layer contains the active material according to the first embodiment as a negative electrode active material.

Among the details of the negative electrode, parts that overlap with the details described in the second embodiment will be omitted.

The density of the negative electrode active material-containing layer (excluding the current collector) is preferably 1.8 g/cm ³ or more and 2.8 g/cm ³ or less. A negative electrode having a density of the negative electrode active material-containing layer within this range has excellent energy density and electrolyte retention. The density of the negative electrode active material-containing layer is more preferably 2.1 g/cm ³ or more and 2.6 g/cm ³ or less.

The negative electrode can be produced, for example, by the same method as the electrode according to the second embodiment.

2) Positive electrode The positive electrode can include a positive electrode current collector and a positive electrode active material-containing layer. The positive electrode active material-containing layer may be formed on one or both sides of the positive electrode current collector. The positive electrode active material-containing layer can contain a positive electrode active material and optionally a conductive agent and a binder.

As the positive electrode active material, for example, oxides or sulfides can be used. The positive electrode may contain one type of compound alone as a positive electrode active material, or may contain a combination of two or more types of compounds. Examples of oxides and sulfides include compounds capable of intercalating and deintercalating Li or Li ions.

Examples of such compounds include manganese dioxide (MnO ₂ ), iron oxide, copper oxide, nickel oxide, and lithium manganese composite oxide (for example, Li _x Mn ₂ O ₄ or Li _x MnO ₂ ; 0<x≦1). , lithium nickel composite oxide (e.g. Li _x NiO ₂ ; 0<x≦1), lithium cobalt complex oxide (e.g. Li _x CoO ₂ ; 0<x≦1), lithium nickel cobalt complex oxide (e.g. Li _x Ni _1-y Co _y O ₂ ; 0<x≦1, 0<y<1), lithium manganese cobalt composite oxide (e.g. Li _{x Mny} Co _1-y O ₂ ; 0<x≦1, 0<y< 1), lithium manganese nickel composite oxide with spinel structure (e.g. Li _x Mn _2-y Ni _y O ₄ ; 0<x≦1, 0<y<2), lithium phosphorus oxide with olivine structure (e.g. _x FePO ₄ ; 0<x≦1, Li _x Fe _{1-y Mny} PO ₄ ; 0<x≦1, 0<y≦1, Li _x CoPO ₄ ; 0<x≦1), iron sulfate (Fe ₂ (SO ₄ ) ₃ ), vanadium oxide (e.g. V ₂ O ₅ ), and lithium nickel cobalt manganese composite oxide (Li _x Ni _1-yz Co _y Mn _z O ₂ ; 0<x≦1, 0<y <1, 0<z<1, y+z<1).

Among the above, examples of compounds more preferable as positive electrode active materials include lithium manganese composite oxides having a spinel structure (for example, Li _x Mn ₂ O ₄ ; 0<x≦1), lithium nickel composite oxides (for example, Li _x NiO ₂ ; 0<x≦1), lithium cobalt complex oxide (e.g. Li _x CoO ₂ ; 0<x≦1), lithium nickel cobalt complex oxide (e.g. Li _x Ni _1-y Co _y O ₂ ; 0< x≦1, 0<y<1), lithium manganese nickel composite oxide having a spinel structure (e.g. Li _x Mn _2-y Ni _y O ₄ ; 0<x≦1, 0<y<2), lithium manganese cobalt Composite oxide (for example, Li _{x Mny} Co _1-y O ₂ ; 0<x≦1, 0<y<1), lithium iron phosphate (for example, Li _x FePO ₄ ; 0<x≦1), and lithium Nickel cobalt manganese composite oxide (Li _x Ni _1-yz Co _y Mn _z O ₂ ; 0<x≦1, 0<y<1, 0<z<1, y+z<1) is included. When these compounds are used as positive electrode active materials, the positive electrode potential can be increased.

When using a room temperature molten salt as the electrolyte of the battery, it is preferable to use a positive electrode active material containing lithium iron phosphate, Li _x VPO ₄ F (0≦x≦1), lithium manganese composite oxide, lithium nickel composite oxide, lithium nickel cobalt composite oxide, or a mixture thereof. These compounds have low reactivity with room temperature molten salts, so that the cycle life can be improved. Details of room temperature molten salts will be described later.

The primary particle size of the positive electrode active material is preferably 100 nm or more and 1 μm or less. A positive electrode active material having a primary particle size of 100 nm or more is easy to handle in industrial production. A positive electrode active material having a primary particle size of 1 μm or less allows lithium ions to diffuse smoothly in the solid.

The specific surface area of the positive electrode active material is preferably 0.1 m ² /g or more and 10 m ² /g or less. A positive electrode active material having a specific surface area of 0.1 m ² /g or more can sufficiently secure insertion and desorption sites for Li ions. A positive electrode active material having a specific surface area of 10 m ² /g or less is easy to handle in industrial production and can ensure good charge-discharge cycle performance.

The binder is blended to fill the gaps between the dispersed positive electrode active material and to bind the positive electrode active material to the positive electrode current collector. Examples of binders include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), fluorine-based rubber, polyacrylic acid compounds, imide compounds, carboxymethyl cellulose (CMC), and salts of CMC. One of these may be used as the binder, or two or more may be used in combination as the binder.

The conductive agent is blended to improve current collection performance and suppress contact resistance between the positive electrode active material and the positive electrode current collector. Examples of conductive agents include vapor grown carbon fiber (VGCF), carbon black such as acetylene black, and carbonaceous materials such as graphite. One of these may be used as a conductive agent, or a combination of two or more may be used as a conductive agent. Further, the conductive agent can also be omitted.

In the positive electrode active material-containing layer, the positive electrode active material and the binder are preferably blended in a proportion of 80% by mass or more and 98% by mass or less, and 2% by mass or more and 20% by mass or less, respectively.

Sufficient electrode strength can be obtained by setting the amount of the binder to 2% by mass or more. The binder can also function as an insulator. Therefore, when the amount of the binder is 20% by mass or less, the amount of insulator included in the electrode is reduced, so that the internal resistance can be reduced.

When adding a conductive agent, the positive electrode active material, the binder, and the conductive agent each have a content of 77% by mass or more and 95% by mass or less, 2% by mass or more and 20% by mass or less, and 3% by mass or more and 15% by mass or less. It is preferable to mix them in proportions.

By setting the amount of the conductive agent to 3% by mass or more, the above-mentioned effects can be exhibited. Furthermore, by controlling the amount of the conductive agent to 15% by mass or less, the proportion of the conductive agent that comes into contact with the electrolyte can be lowered. When this ratio is low, decomposition of the electrolyte can be reduced during high temperature storage.

The positive electrode current collector is preferably an aluminum foil or an aluminum alloy foil containing one or more elements selected from the group consisting of Mg, Ti, Zn, Ni, Cr, Mn, Fe, Cu, and Si.

The thickness of the aluminum foil or aluminum alloy foil is preferably 5 μm or more and 20 μm or less, more preferably 15 μm or less. It is preferable that the purity of the aluminum foil is 99% by mass or more. The content of transition metals such as iron, copper, nickel, and chromium contained in the aluminum foil or aluminum alloy foil is preferably 1% by mass or less.

Further, the positive electrode current collector can include a portion on the surface of which the positive electrode active material-containing layer is not formed. This part can act as a positive electrode current collection tab.

The positive electrode can be produced, for example, using a positive electrode active material by the same method as the electrode according to the second embodiment.

3) Electrolyte As the electrolyte, for example, a liquid nonaqueous electrolyte or a gel nonaqueous electrolyte can be used. A liquid non-aqueous electrolyte is prepared by dissolving an electrolyte salt as a solute in an organic solvent. The concentration of the electrolyte salt is preferably 0.5 mol/L or more and 2.5 mol/L or less.

Examples of electrolyte salts include lithium perchlorate (LiClO ₄ ), lithium hexafluorophosphate (LiPF ₆ ), lithium tetrafluoroborate (LiBF ₄ ), lithium arsenic hexafluoride (LiAsF ₆ ), and trifluoromethane. Lithium sulfonate (LiCF ₃ SO ₃ ), and lithium bistrifluoromethylsulfonylimide (LiN(CF ₃ SO ₂ ) ₂ ), lithium bis(fluorosulfonyl)imide (LiN(SO ₂ F) ₂ ; LiFSI) Includes salts and mixtures thereof. The electrolyte salt is preferably one that is difficult to oxidize even at high potentials, and LiPF ₆ is most preferred.

Examples of organic solvents include cyclic carbonates such as propylene carbonate (PC), ethylene carbonate (EC), vinylene carbonate (VC); diethyl carbonate (DEC), dimethyl carbonate. chain carbonates such as (dimethyl carbonate; DMC), methyl ethyl carbonate (MEC); tetrahydrofuran (THF), 2-methyl tetrahydrofuran (2MeTHF), dioxolane (DOX); cyclic ethers such as dimethoxy ethane (DME), diethoxy ethane (DEE); γ-butyrolactone (GBL), acetonitrile (AN), and sulfolane (sulfolane; SL) is included. These organic solvents can be used alone or as a mixed solvent.

A gel nonaqueous electrolyte is prepared by combining a liquid nonaqueous electrolyte and a polymer material. Examples of polymeric materials include polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), polyethylene oxide (PEO), or mixtures thereof.

Alternatively, as the nonaqueous electrolyte, in addition to liquid nonaqueous electrolyte and gel nonaqueous electrolyte, room temperature molten salt containing lithium ions (ionic melt), polymer solid electrolyte, inorganic solid electrolyte, etc. may be used. Good too.

A room temperature molten salt (ionic melt) refers to a compound that can exist as a liquid at room temperature (15°C or higher and 25°C or lower) among organic salts consisting of a combination of an organic cation and an anion. Room temperature molten salts include room temperature molten salts that exist as a liquid by themselves, room temperature molten salts that become liquid when mixed with an electrolyte salt, room temperature molten salts that become liquid when dissolved in an organic solvent, and mixtures of these. In general, the melting point of room temperature molten salts used in secondary batteries is 25°C or lower. In addition, organic cations generally have a quaternary ammonium skeleton.

Polymeric solid electrolytes are prepared by dissolving an electrolyte salt in a polymeric material and solidifying it.

The inorganic solid electrolyte is a solid material that has Li ion conductivity. Here, having Li ion conductivity refers to exhibiting lithium ion conductivity of 1×10 ⁻⁶ S/cm or more at 25° C. Examples of the inorganic solid electrolyte include oxide-based solid electrolytes and sulfide-based solid electrolytes. Specific examples of the inorganic solid electrolyte are as follows.

As the oxide-based solid electrolyte, it is preferable to use a lithium phosphate solid electrolyte having a NASICON (Sodium (Na) Super Ionic Conductor) type structure and expressed by the general formula Li1 _{+xMα2 ( PO4} ) ₃ . In the above general formula, Mα is, for example, one or more selected from the group consisting of titanium (Ti), germanium (Ge), strontium (Sr), zirconium (Zr), tin (Sn), aluminum (Al), and calcium (Ca). The subscript x is within the range of 0≦x≦2.

Specific examples of lithium phosphate solid electrolytes having a NASICON structure include LATP compounds represented by Li1 _{+ xAlxTi2 -x} ( _PO4 ) ₃ , where 0.1≦x≦0.5; compounds represented by Li1 _{+ xAlyMβ2 -y} ( _PO4 ) ₃ , where Mβ is one or more selected from the group consisting of Ti, Ge, Sr, Zr, Sn, and Ca, and where 0≦x≦1 and 0≦y≦1; compounds represented by Li1 _{+ xAlxGe2 -x} ( _PO4 ) ₃ , where 0≦x≦2; and compounds represented by Li1 _{+ xAlxZr2 -x} ( _PO4 ) ₃ , where 0≦x≦2; Li1 _{+x+ yAlxMγ2 -} xSiyP3 _{- yO 12} , in which Mγ is 1 or more selected from the group consisting of Ti and Ge, and 0<x≦2, 0≦y<3; and a compound represented by Li _1+2x Zr _1-x Ca _x (PO ₄ ) ₃ , in which 0≦x<1.

In addition to the above-mentioned lithium phosphate solid electrolyte, examples of the oxide solid electrolyte include Li _x PO _y N _z 2.6≦x≦3.5, 1.9≦y≦3.8, and an amorphous LIPON compound where 0.1≦z≦1.3 (for example, Li _2.9 PO _3.3 N _0.46 ); represented by La ₅₊ xA _x La _3-x Mδ ₂ O ₁₂ with a garnet-type structure, where A is A compound in which one or more is selected from the group consisting of Ca, Sr, and Ba, and Mδ is one or more selected from the group consisting of Nb and Ta, and 0≦x≦0.5; Li ₃ Mδ _2-x L ₂ O ₁₂ , Mδ is one or more selected from the group consisting of Nb and Ta, and L may contain Zr and satisfies 0≦x≦0.5; Li _7-3x Al _x La ₃ Zr ₃ O ₁₂ , and 0≦x≦0.5; Li _5+x La ₃ Mδ _2-x Zr _x O ₁₂ , where Mδ is 1 or more selected from the group consisting of Nb and Ta, and 0≦ LLZ compound (for example, Li ₇ La ₃ Zr ₂ O ₁₂ ) where x≦2; and a perovskite-type structure represented by La _2/3-x Li _x TiO ₃ and 0.3≦x≦0.7; One example is a compound.

One or more of the above compounds can be used as a solid electrolyte. Two or more of the above solid electrolytes may be used.

Alternatively, instead of a non-aqueous electrolyte, a liquid aqueous electrolyte or a gel aqueous electrolyte can be used as the electrolyte. The liquid aqueous electrolyte is prepared by dissolving, for example, the above-mentioned electrolyte salt as a solute in an aqueous solvent. The gel aqueous electrolyte is prepared by compounding the liquid aqueous electrolyte with the above-mentioned polymer material. As the aqueous solvent, a solution containing water can be used. The solution containing water may be pure water or a mixed solvent of water and an organic solvent.

4) Separator The separator is formed from, for example, a porous film containing polyethylene (PE), polypropylene (PP), cellulose, or polyvinylidene fluoride (PVdF), or a synthetic resin nonwoven fabric. From the viewpoint of safety, it is preferable to use a porous film made of polyethylene or polypropylene. This is because these porous films melt at a certain temperature and are capable of blocking current.

5) Exterior member As the exterior member, for example, a container made of a laminate film or a metal container can be used.

The thickness of the laminate film is, for example, 0.5 mm or less, and preferably 0.2 mm or less.

As the laminate film, a multilayer film including a plurality of resin layers and a metal layer interposed between these resin layers is used. The resin layer includes a polymer material such as polypropylene (PP), polyethylene (PE), nylon, and polyethylene terephthalate (PET). The metal layer is preferably made of aluminum foil or aluminum alloy foil for weight reduction. The laminate film can be formed into the shape of the exterior member by sealing it by heat fusion.

The thickness of the wall of the metal container is, for example, 1 mm or less, more preferably 0.5 mm or less, still more preferably 0.2 mm or less.

The metal container is made of, for example, aluminum or an aluminum alloy. Preferably, the aluminum alloy contains elements such as magnesium, zinc, and silicon. When the aluminum alloy contains transition metals such as iron, copper, nickel, and chromium, the content is preferably 1% by mass or less.

The shape of the exterior member is not particularly limited. The shape of the exterior member may be, for example, flat (thin), square, cylindrical, coin, button, or the like. The exterior member can be appropriately selected depending on the battery dimensions and the intended use of the battery.

6) Negative electrode terminal The negative electrode terminal can be formed from a material that is electrochemically stable at the Li insertion/desorption potential of the above-mentioned negative electrode active material and has electrical conductivity. Specifically, the material of the negative electrode terminal includes copper, nickel, stainless steel, or aluminum, or at least one element selected from the group consisting of Mg, Ti, Zn, Mn, Fe, Cu, and Si. Examples include aluminum alloys. It is preferable to use aluminum or an aluminum alloy as the material for the negative electrode terminal. The negative electrode terminal is preferably made of the same material as the negative electrode current collector in order to reduce contact resistance with the negative electrode current collector.

7) Positive electrode terminal The positive electrode terminal must be formed from a material that is electrically stable and conductive in a potential range of 3 V or more and 4.5 V or less (vs. Li/Li ⁺ ) with respect to the oxidation-reduction potential of lithium. Can be done. Examples of the material for the positive electrode terminal include aluminum or an aluminum alloy containing at least one element selected from the group consisting of Mg, Ti, Zn, Mn, Fe, Cu, and Si. The positive electrode terminal is preferably formed from the same material as the positive electrode current collector in order to reduce contact resistance with the positive electrode current collector.

Above, an embodiment including the electrode according to the second embodiment as the negative electrode has been described. Among the embodiments of the secondary battery according to the third embodiment, in an embodiment including the electrode according to the second embodiment as the positive electrode, the following counter electrodes can be used as the negative electrode, which is the counter electrode to the positive electrode. At least one electrode selected from lithium metal, lithium metal alloy, graphite, silicon, silicon oxide, tin oxide, silicon, tin, and other alloys can be used as the negative electrode. A material that does not contain Li in the active material can be used as the negative electrode by pre-doping with Li element.

In an embodiment including the electrode according to the second embodiment as a positive electrode, the details of the positive electrode are the same as those described in the second embodiment, and therefore will be omitted.

Next, a secondary battery according to a third embodiment will be described in more detail with reference to the drawings.

FIG. 3 is a cross-sectional view schematically showing an example of a secondary battery. FIG. 4 is an enlarged cross-sectional view of section A of the secondary battery shown in FIG. 3. FIG.

The secondary battery 100 shown in Figures 3 and 4 includes an electrode group 1 shown in Figure 3, a bag-shaped exterior member 2 shown in Figures 3 and 4, and an electrolyte (not shown). The electrode group 1 and the electrolyte are stored in the bag-shaped exterior member 2. The electrolyte (not shown) is held in the electrode group 1.

The bag-like exterior member 2 is made of a laminate film including two resin layers and a metal layer interposed between them.

As shown in FIG. 3, the electrode group 1 is a flat wound electrode group. The electrode group 1, which is flat and wound, includes a negative electrode 3, a separator 4, and a positive electrode 5, as shown in FIG. Separator 4 is interposed between negative electrode 3 and positive electrode 5.

The negative electrode 3 includes a negative electrode current collector 3a and a negative electrode active material-containing layer 3b. In the part of the negative electrode 3 located at the outermost shell of the wound electrode group 1, a negative electrode active material-containing layer 3b is formed only on the inner surface side of the negative electrode current collector 3a, as shown in FIG. In other parts of the negative electrode 3, negative electrode active material-containing layers 3b are formed on both sides of the negative electrode current collector 3a.

The positive electrode 5 includes a positive electrode current collector 5a and positive electrode active material-containing layers 5b formed on both surfaces of the positive electrode current collector 5a.

As shown in FIG. 3, the negative electrode terminal 6 and the positive electrode terminal 7 are located near the outer peripheral end of the wound electrode group 1. As shown in FIG. This negative electrode terminal 6 is connected to the outermost shell portion of the negative electrode current collector 3a. Further, the positive electrode terminal 7 is connected to the outermost shell portion of the positive electrode current collector 5a. These negative electrode terminal 6 and positive electrode terminal 7 extend outside from the opening of the bag-shaped exterior member 2. A thermoplastic resin layer is provided on the inner surface of the bag-shaped exterior member 2, and the opening is closed by heat-sealing this layer.

The secondary battery according to the embodiment is not limited to the secondary battery having the configuration shown in FIGS. 3 and 4, but may be a battery having the configuration shown in FIGS. 5 and 6, for example.

FIG. 5 is a partially cutaway perspective view schematically showing another example of a secondary battery. FIG. 6 is an enlarged cross-sectional view of section B of the secondary battery shown in FIG.

The secondary battery 100 shown in FIGS. 5 and 6 includes an electrode group 1 shown in FIGS. 5 and 6, an exterior member 2 shown in FIG. 5, and an electrolyte not shown. The electrode group 1 and the electrolyte are housed within the exterior member 2. The electrolyte is held in the electrode group 1.

The exterior member 2 is made of a laminate film including two resin layers and a metal layer interposed between them.

As shown in FIG. 6, the electrode group 1 is a laminated electrode group. The laminated electrode group 1 has a structure in which negative electrodes 3 and positive electrodes 5 are alternately laminated with a separator 4 interposed therebetween.

The electrode group 1 includes a plurality of negative electrodes 3. Each of the plurality of negative electrodes 3 includes a negative electrode current collector 3a and a negative electrode active material-containing layer 3b supported on both surfaces of the negative electrode current collector 3a. Further, the electrode group 1 includes a plurality of positive electrodes 5. Each of the plurality of positive electrodes 5 includes a positive electrode current collector 5a and a positive electrode active material-containing layer 5b supported on both surfaces of the positive electrode current collector 5a.

The negative electrode current collector 3a of each negative electrode 3 includes a portion on one side on which the negative electrode active material-containing layer 3b is not supported. This portion functions as the negative electrode current collecting tab 3c. As shown in FIG. 6, the negative electrode current collector tab 3c does not overlap the positive electrode 5. Further, the plurality of negative electrode current collecting tabs 3c are electrically connected to the strip-shaped negative electrode terminal 6. The tip of the strip-shaped negative electrode terminal 6 is drawn out to the outside of the exterior member 2.

Further, although not shown, the positive electrode current collector 5a of each positive electrode 5 includes a portion on one side on which the positive electrode active material-containing layer 5b is not supported. This part acts as a positive electrode current collection tab. The positive electrode current collector tab does not overlap the negative electrode 3, similarly to the negative electrode current collector tab 3c. Further, the positive electrode current collecting tab is located on the opposite side of the electrode group 1 to the negative electrode current collecting tab 3c. The positive electrode current collector tab is electrically connected to the strip-shaped positive electrode terminal 7. The tip of the strip-shaped positive electrode terminal 7 is located on the opposite side to the negative electrode terminal 6 and is drawn out to the outside of the exterior member 2 .

The secondary battery according to the third embodiment includes the electrode according to the second embodiment. That is, the secondary battery according to the third embodiment includes an electrode containing the active material according to the first embodiment. Therefore, the secondary battery according to the third embodiment has a high capacity per volume.

(Fourth embodiment)
According to the fourth embodiment, an assembled battery is provided. The assembled battery includes a plurality of secondary batteries according to the third embodiment.

In such an assembled battery, each unit cell may be arranged electrically connected in series or in parallel, or may be arranged in a combination of series connection and parallel connection.

Next, an example of the assembled battery according to the fourth embodiment will be described with reference to the drawings.

FIG. 7 is a perspective view schematically showing an example of an assembled battery. The assembled battery 200 shown in FIG. 7 includes five single cells 100a to 100e, four bus bars 21, a positive lead 22, and a negative lead 23. Each of the five single cells 100a to 100e is a secondary battery according to the third embodiment.

The bus bar 21 connects, for example, the negative terminal 6 of one cell 100a and the positive terminal 7 of the adjacent cell 100b. In this way, the five single cells 100 are connected in series by the four bus bars 21. That is, the assembled battery 200 in FIG. 7 is a five-series assembled battery. Although an example is not shown, in an assembled battery including a plurality of cells electrically connected in parallel, for example, a plurality of negative terminals are connected to each other by a bus bar, and a plurality of positive terminals are connected to each other by a bus bar. This allows a plurality of single cells to be electrically connected.

The positive terminal 7 of at least one of the five single cells 100a to 100e is electrically connected to a positive lead 22 for external connection. Furthermore, the negative terminal 6 of at least one of the five single cells 100a to 100e is electrically connected to a negative lead 23 for external connection.

The assembled battery according to the fourth embodiment includes the secondary battery according to the third embodiment. Therefore, the capacity per volume of such an assembled battery is high.

(Fifth embodiment)
According to a fifth embodiment, a battery pack is provided. This battery pack includes the assembled battery according to the fourth embodiment. This battery pack may include a single secondary battery according to the third embodiment instead of the assembled battery according to the fourth embodiment.

Such a battery pack may further include a protection circuit. The protection circuit has a function of controlling charging and discharging of the secondary battery. Alternatively, a circuit included in a device that uses the battery pack as a power source (e.g., electronic equipment, automobiles, etc.) may be used as the protection circuit for the battery pack.

Further, such a battery pack may further include an external terminal for power supply. The external terminal for energization is for outputting current from the secondary battery to the outside and/or inputting current from the outside to the secondary battery. In other words, when the battery pack is used as a power source, current is supplied to the outside through the external terminal for energization. Furthermore, when charging the battery pack, charging current (including regenerated energy from the motive power of an automobile, etc.) is supplied to the battery pack through an external terminal for energization.

Next, an example of a battery pack according to an embodiment will be described with reference to the drawings.

FIG. 8 is an exploded perspective view schematically showing an example of a battery pack. FIG. 9 is a block diagram showing an example of the electric circuit of the battery pack shown in FIG. 8.

The battery pack 300 shown in Figures 8 and 9 includes a container 31, a lid 32, a protective sheet 33, a battery pack 200, a printed wiring board 34, wiring 35, and an insulating plate (not shown).

The storage container 31 shown in FIG. 8 is a bottomed square container having a rectangular bottom surface. The storage container 31 is configured to be able to accommodate the protective sheet 33, the assembled battery 200, the printed wiring board 34, and the wiring 35. The lid 32 has a rectangular shape. The lid 32 accommodates the assembled battery 200 and the like by covering the accommodation container 31. Although not shown, the container 31 and the lid 32 are provided with an opening or a connection terminal for connection to an external device or the like.

The assembled battery 200 includes a plurality of single cells 100, a positive lead 22, a negative lead 23, and an adhesive tape 24.

At least one of the multiple cells 100 is a secondary battery according to the third embodiment. Each of the multiple cells 100 is electrically connected in series as shown in FIG. 9. The multiple cells 100 may be electrically connected in parallel, or may be connected in a combination of series and parallel connections. When the multiple cells 100 are connected in parallel, the battery capacity is increased compared to when they are connected in series.

The adhesive tape 24 fastens the plurality of unit cells 100 together. Instead of the adhesive tape 24, a heat shrink tape may be used to fix the plurality of cells 100. In this case, the protective sheets 33 are arranged on both sides of the assembled battery 200, and after a heat-shrinkable tape is made to go around, the heat-shrinkable tape is heat-shrinked to bundle the plurality of unit cells 100.

One end of the positive electrode side lead 22 is connected to the assembled battery 200. One end of the positive electrode side lead 22 is electrically connected to the positive electrode of one or more unit cells 100. One end of the negative electrode side lead 23 is connected to the assembled battery 200. One end of the negative electrode side lead 23 is electrically connected to the negative electrode of one or more unit cells 100.

The printed wiring board 34 is installed along one of the inner surfaces of the container 31 in the short side direction. The printed wiring board 34 includes a positive connector 342, a negative connector 343, a thermistor 345, a protection circuit 346, wiring 342a and 343a, an external terminal 350 for energization, and a positive wiring (positive wiring) 348a. and a negative side wiring (negative side wiring) 348b. One main surface of the printed wiring board 34 faces one side of the assembled battery 200. An insulating plate (not shown) is interposed between the printed wiring board 34 and the assembled battery 200.

The other end 22a of the positive electrode lead 22 is electrically connected to the positive electrode connector 342. The other end 23a of the negative electrode lead 23 is electrically connected to the negative electrode connector 343.

Thermistor 345 is fixed to one main surface of printed wiring board 34. Thermistor 345 detects the temperature of each cell 100 and transmits the detection signal to protection circuit 346.

External terminal 350 for power supply is fixed to the other main surface of printed wiring board 34 . The external terminal 350 for energization is electrically connected to a device existing outside the battery pack 300. External terminal 350 for energization includes a positive terminal 352 and a negative terminal 353.

The protection circuit 346 is fixed to the other main surface of the printed wiring board 34. The protection circuit 346 is connected to the positive terminal 352 via the positive wiring 348a. The protection circuit 346 is connected to the negative terminal 353 via the negative wiring 348b. Furthermore, the protection circuit 346 is electrically connected to the positive connector 342 via a wiring 342a. The protection circuit 346 is electrically connected to the negative electrode side connector 343 via wiring 343a. Further, the protection circuit 346 is electrically connected to each of the plurality of unit cells 100 via the wiring 35.

The protective sheet 33 is disposed on both inner surfaces of the container 31 in the long side direction and on the inner surface of the container 31 in the short side direction facing the printed wiring board 34 with the assembled battery 200 interposed therebetween. The protective sheet 33 is made of resin or rubber, for example.

The protection circuit 346 controls charging and discharging of the plurality of unit cells 100. Furthermore, the protection circuit 346 connects the protection circuit 346 to an external terminal for energizing the external device based on the detection signal transmitted from the thermistor 345 or the detection signal transmitted from the individual cells 100 or the assembled batteries 200. 350 (positive side terminal 352, negative side terminal 353).

Examples of the detection signal transmitted from the thermistor 345 include a signal that detects that the temperature of the unit cell 100 is higher than a predetermined temperature. Examples of the detection signal transmitted from each single cell 100 or assembled battery 200 include signals that detect overcharging, overdischarging, and overcurrent of the single cell 100. When detecting overcharging or the like for each cell 100, the battery voltage may be detected, or the positive electrode potential or the negative electrode potential may be detected. In the latter case, a lithium electrode used as a reference electrode is inserted into each cell 100.

Note that as the protection circuit 346, a circuit included in a device (eg, an electronic device, an automobile, etc.) that uses the battery pack 300 as a power source may be used.

Moreover, this battery pack 300 is provided with the external terminal 350 for power supply, as described above. Therefore, this battery pack 300 can output current from the assembled battery 200 to an external device and input current from the external device to the assembled battery 200 via the external terminal 350 for energization. In other words, when the battery pack 300 is used as a power source, the current from the assembled battery 200 is supplied to the external device through the external terminal 350 for energization. Further, when charging the battery pack 300, a charging current from an external device is supplied to the battery pack 300 through the external terminal 350 for energization. When this battery pack 300 is used as an on-vehicle battery, regenerated energy from the motive power of the vehicle can be used as the charging current from an external device.

The battery pack 300 may include a plurality of assembled batteries 200. In this case, the assembled batteries 200 may be connected in series, in parallel, or in a combination of series and parallel connections. The printed wiring board 34 and the wiring 35 may be omitted. In this case, the positive electrode lead 22 and the negative electrode lead 23 may be used as the positive terminal 352 and the negative terminal 353, respectively, of the external terminal 350 for current supply.

Such a battery pack is used, for example, in applications that require excellent cycle performance when drawing a large current. Specifically, this battery pack is used, for example, as a power source for electronic equipment, a stationary battery, and an in-vehicle battery for various vehicles. An example of the electronic device is a digital camera. This battery pack is particularly suitable for use as a vehicle battery.

The battery pack according to the fifth embodiment includes the secondary battery according to the third embodiment or the battery pack according to the fourth embodiment. Therefore, the capacity per volume of the battery pack is high.

(Sixth embodiment)
According to a sixth embodiment, a vehicle is provided. This vehicle is equipped with the battery pack according to the fifth embodiment.

In such a vehicle, the battery pack, for example, recovers regenerative energy from the vehicle's motive power. The vehicle may also include a mechanism (regenerator) that converts the kinetic energy of the vehicle into regenerative energy.

Examples of vehicles include two-wheel to four-wheel hybrid electric vehicles, two-wheel to four-wheel electric vehicles, assisted bicycles, and railway vehicles.

The mounting position of the battery pack in the vehicle is not particularly limited. For example, when a battery pack is installed in a car, the battery pack can be installed in the engine compartment of the vehicle, at the rear of the vehicle body, or under the seat.

A vehicle may be equipped with multiple battery packs. In this case, the batteries included in each battery pack may be electrically connected in series, electrically in parallel, or electrically connected by a combination of series and parallel connections. Good too. For example, when each battery pack includes assembled batteries, the assembled batteries may be electrically connected in series or electrically connected in parallel, or a combination of series and parallel connections may be used to electrically connect the assembled batteries. may be connected to. Alternatively, if each battery pack includes a single battery, each battery may be electrically connected in series, electrically in parallel, or a combination of series and parallel connections. may be electrically connected.

Next, an example of a vehicle according to an embodiment will be described with reference to the drawings.

Figure 10 is a partially transparent view that shows a schematic diagram of an example vehicle.

A vehicle 400 shown in FIG. 10 includes a vehicle main body 40 and a battery pack 300 according to the fifth embodiment. In the example shown in FIG. 10, vehicle 400 is a four-wheeled automobile.

The vehicle 400 may be equipped with multiple battery packs 300. In this case, the batteries (e.g., cells or battery packs) included in the battery packs 300 may be connected in series, in parallel, or in a combination of series and parallel connections.

FIG. 10 illustrates an example in which the battery pack 300 is mounted in an engine room located in the front of the vehicle body 40. As described above, the battery pack 300 may be mounted at the rear of the vehicle body 40 or under the seat, for example. This battery pack 300 can be used as a power source for the vehicle 400. Furthermore, this battery pack 300 can recover regenerated energy from the motive power of the vehicle 400.

Next, an embodiment of the vehicle according to the embodiment will be described with reference to FIG. 11.

FIG. 11 is a diagram schematically showing an example of a control system related to an electrical system in a vehicle. Vehicle 400 shown in FIG. 11 is an electric vehicle.

A vehicle 400 shown in FIG. 11 includes a vehicle main body 40, a vehicle power source 41, a vehicle ECU (Electric Control Unit) 42 which is a higher control device of the vehicle power source 41, and an external terminal (external terminal). It includes a terminal (for connection to a power source) 43, an inverter 44, and a drive motor 45.

The vehicle 400 has a vehicle power source 41 mounted, for example, in the engine room, at the rear of the car body, or under the seat. In addition, in the vehicle 400 shown in FIG. 11, the mounting location of the vehicle power source 41 is schematically shown.

The vehicle power supply 41 includes multiple (e.g., three) battery packs 300a, 300b, and 300c, a battery management unit (BMU) 411, and a communication bus 412.

The battery pack 300a includes an assembled battery 200a and an assembled battery monitoring device 301a (for example, VTM: Voltage Temperature Monitoring). The battery pack 300b includes an assembled battery 200b and an assembled battery monitoring device 301b. The battery pack 300c includes an assembled battery 200c and an assembled battery monitoring device 301c. Battery packs 300a to 300c are battery packs similar to battery pack 300 described above, and battery packs 200a to 200c are battery packs similar to battery pack 200 described above. The battery packs 200a to 200c are electrically connected in series. Battery packs 300a, 300b, and 300c can each be independently removed and replaced with another battery pack 300.

Each of the battery packs 200a to 200c includes a plurality of cells connected in series. At least one of the plurality of single cells is a secondary battery according to the third embodiment. The assembled batteries 200a to 200c are charged and discharged through a positive terminal 413 and a negative terminal 414, respectively.

The battery management device 411 communicates with the battery pack monitoring devices 301a to 301c and collects information on the voltage, temperature, and the like for each of the cells 100 included in the battery packs 200a to 200c included in the vehicle power supply 41. In this way, the battery management device 411 collects information on the maintenance of the vehicle power supply 41.

The battery management unit 411 and the assembled battery monitoring units 301a to 301c are connected via a communication bus 412. In the communication bus 412, a set of communication lines is shared by multiple nodes (the battery management unit 411 and one or more assembled battery monitoring units 301a to 301c). The communication bus 412 is a communication bus configured based on, for example, the CAN (Control Area Network) standard.

The assembled battery monitoring devices 301a to 301c measure the voltages and temperatures of individual cells forming the assembled batteries 200a to 200c based on commands communicated from the battery management device 411. However, the temperature can be measured at only a few locations per one assembled battery, and it is not necessary to measure the temperature of all single cells.

The vehicle power source 41 can also include an electromagnetic contactor (for example, a switch device 415 shown in FIG. 11) that switches the presence or absence of electrical connection between the positive terminal 413 and the negative terminal 414. The switch device 415 includes a precharge switch (not shown) that is turned on when the assembled batteries 200a to 200c are charged, and a precharge switch (not shown) that is turned on when the output from the assembled batteries 200a to 200c is supplied to the load. It includes a main switch (not shown). Each of the precharge switch and the main switch includes a relay circuit (not shown) that is turned on or off by a signal supplied to a coil located near the switch element. The electromagnetic contactors such as the switch device 415 are controlled based on control signals from the battery management device 411 or the vehicle ECU 42 that controls the operation of the vehicle 400 as a whole.

The inverter 44 converts the input DC voltage into a three-phase AC high voltage for driving the motor. The three-phase output terminals of the inverter 44 are connected to the three-phase input terminals of the drive motor 45. The inverter 44 is controlled based on a control signal from the battery management device 411 or the vehicle ECU 42 for controlling the operation of the entire vehicle. By controlling the inverter 44, the output voltage from the inverter 44 is adjusted.

The drive motor 45 is rotated by electric power supplied from the inverter 44 . The driving force generated by the rotation of the drive motor 45 is transmitted to the axle and the drive wheels W via, for example, a differential gear unit.

Although not shown, the vehicle 400 includes a regenerative brake mechanism (regenerator). The regenerative brake mechanism rotates the drive motor 45 when the vehicle 400 is braked, and converts kinetic energy into regenerative energy as electrical energy. The regenerative energy recovered by the regenerative brake mechanism is input to the inverter 44 and converted into direct current. The converted DC current is input to the vehicle power source 41.

One terminal of the connection line L1 is connected to the negative terminal 414 of the vehicle power supply 41. The other terminal of the connection line L1 is connected to the negative input terminal 417 of the inverter 44. A current detection unit (current detection circuit) 416 in the battery management device 411 is provided on the connection line L1 between the negative terminal 414 and the negative input terminal 417.

One terminal of the connection line L2 is connected to the positive terminal 413 of the vehicle power source 41. The other terminal of the connection line L2 is connected to the positive input terminal 418 of the inverter 44. A switch device 415 is provided between the positive terminal 413 and the positive input terminal 418 on the connection line L2.

The external terminal 43 is connected to the battery management device 411. The external terminal 43 can be connected to, for example, an external power source.

The vehicle ECU 42 coordinately controls the vehicle power source 41, the switch device 415, the inverter 44, etc. together with other management devices and control devices including the battery management device 411 in response to operation inputs from the driver or the like. Through cooperative control of the vehicle ECU 42 and the like, output of electric power from the vehicle power source 41, charging of the vehicle power source 41, etc. are controlled, and the entire vehicle 400 is managed. Data regarding maintenance of the vehicle power source 41, such as remaining capacity of the vehicle power source 41, is transferred between the battery management device 411 and the vehicle ECU 42 via a communication line.

A vehicle according to the sixth embodiment is equipped with the battery pack according to the fifth embodiment. Since the battery pack has a high capacity per volume, there is a high degree of freedom in vehicle design. Therefore, it is possible to provide a variety of vehicles without impairing vehicle performance.

Hereinafter, the above embodiment will be described in further detail based on examples. However, the present invention is not limited to the examples listed below.

<Synthesis>
(Example 1)
A titanium-niobium-molybdenum composite oxide was synthesized as follows.

As raw materials, ammonium niobium oxalate, ammonium molybdate, and titanium tetraisopropoxide were prepared. These raw materials were weighed according to a predetermined composition ratio. Ammonium niobium oxalate and ammonium molybdate were dissolved in pure water to prepare solution A. Next, titanium tetraisopropoxide was added to an aqueous oxalic acid solution with a concentration of 1M, and dissolved by heating and stirring to prepare solution B. After mixing solutions A and B, ammonia solution was added while heating and stirring to adjust the pH to 7, thereby obtaining a sol. The sol solution was spray-dried at a drying temperature of 180°C to evaporate the solvent, and a white precursor powder was obtained. The precursor powder was placed in an alumina crucible and fired in the air at 600°C for 4 hours. The fired product was then dry-pulverized, and the pulverized product was classified to adjust the particle size. In the manner described above, an active material powder was obtained.

(Example 2)
A composite oxide was synthesized in the same manner as in Example 1, except that the temperature at which the precursor was fired was changed to 700° C., and active material powder was obtained.

(Example 3)
A composite oxide was synthesized in the same manner as in Example 1, except that the temperature at which the precursor was fired was changed to 800° C., and an active material powder was obtained.

(Example 4-7)
A composite oxide was synthesized in the same manner as in Example 1, except that the weighing ratio of the raw materials was adjusted, and an active material powder was obtained.

(Comparative Example 1)
A composite oxide was synthesized and an active material powder was obtained in the same manner as in Example 1, except that the temperature for firing the precursor powder was changed to 900°C.

<Measurement>
The powders obtained in the above Examples and Comparative Examples were observed using a scanning transmission electron microscope. Specifically, as described above in detail, the microstructure was observed using a 10 nm x 10 nm image using a STEM-HAADF image with a spherical aberration correction function. In addition, wide-angle X-ray scattering measurements were performed. The measurements were performed according to the details described above. The obtained spectra were subjected to crystal structure analysis using the Rietveld method. In addition, ICP emission spectrometry and HAXPES measurements were performed.

Part of the obtained XRD spectra are shown in Figures 12 to 16. Figure 12 shows the spectrum for the complex oxide obtained in Example 1. Figure 13 shows the spectrum for the complex oxide obtained in Example 2. Figure 14 shows the spectrum for the complex oxide obtained in Example 3. Figure 15 shows the spectrum for the complex oxide obtained in Comparative Example 1. Figure 16 shows an enlarged spectrum of the range including peaks P1 and P2 of the crystal structure.

In the XRD spectrum of the composite oxide according to Example 1, two main peaks, peaks P1 and P2, were observed at the positions of 2θ=25.30° and 2θ=23.88°, respectively. On the other hand, in the XRD spectrum of the composite oxide according to Comparative Example 1, the main peak seen together with peak P2 is located at 2θ = 25.40°, which is not peak P1 but originates from the crystal structure in Figure 1 ( It was determined that the peak _P420 originates from the 420) plane. Regarding Example 2 and Example 3, the crystal structures of each of FIGS. 1 and 2 were mixed, but the peaks P ₄₂₀ and P1 derived from each overlapped, and peak P1 was seen as a shoulder on the low angle side. A broad composite peak was confirmed. Therefore, for Examples 2 and 3, simple fitting using a pseudo Voigt function was further performed to separate overlapping peaks (not shown).

Regarding the composite oxide obtained in Example 1, as a result of observing the fine structure using STEM-HAADF images, the size of the ReO ₃ blocks within the field of view was different, and the octahedral edge was shared without periodicity. The connected crystal structures were confirmed. From this, it was identified as the crystal structure shown in FIG. In different fields of view, connected parts that included shared tetrahedral vertices were also confirmed.

The metal ratio of the composite oxide obtained in Example 1 was calculated by ICP analysis, and it was calculated to be Ti:Nb:Mo=0.23:1.00:0.23. The valence was evaluated by HAXPES measurement. The Ti element was identified as tetravalent because a peak top of a single peak derived from Ti2p _3/2 was observed within the range of 459±0.4 eV. The Nb element was identified as pentavalent because a peak top of a single peak derived from Nb5d _3/2 was observed within the range of 207.5±eV. The Mo element was identified as having a mixture of a pentavalent peak and a hexavalent peak because a peak of Mo3d _5/2 derived from a hexavalent peak was observed at 232.2±0.3 eV and a different peak was confirmed to be mixed at a value 1 eV smaller than that peak. It was identified that the pentavalent peak and the hexavalent peak exist in a mixed state. It was estimated that the pentavalent and hexavalent elements were mixed at a 1:1 ratio based on the peak mixing ratio, and the average valence was assumed to be 5.5. The composition calculated based on this assumption is _{Ti0.23NbMo0.23O3.59 ,} so b = _0.23 , c = 0.23, and d = 3.59.

Regarding the composite oxide obtained in Example 2, it was confirmed that the crystal structures shown in FIGS. 1 and 2 were mixed together.

The metal ratio of the composite oxide obtained in Example 2 was calculated by ICP analysis, and was calculated to be Ti:Nb:Mo = 0.23:1.00:0.18. The valence was evaluated by HAXPES measurement in the same manner as in Example 1, and Ti was identified as 4, Nb as 5, and Mo as _5.3 . The composition formula calculated from the valence was _{Ti0.23NbMo0.18O3.47} . Therefore, b = _0.23 , c = 0.18, and d = 3.47.

It was confirmed that the composite oxide obtained in Example 3 contained a mixture of the crystal structures shown in Figures 1 and 2.

When the metal ratio of the composite oxide obtained in Example 3 was calculated by ICP analysis, it was calculated as Ti:Nb:Mo=0.23:1.00:0.18. When the valence was evaluated by HAXPES measurement in the same manner as in Example 1, Ti was found to be 4 valent, Nb was 5 valent, and Mo valence was 5.6. The compositional formula calculated from the valence was Ti _0.23 NbMo _0.18 O _3.49 . Therefore, b=0.23, c=0.18, and d=3.49.

Regarding the composite oxide obtained in Comparative Example 1, the crystal structure shown in FIG. 1 was confirmed. Furthermore, the results of structural analysis by XRD also agreed with the crystal structure shown in FIG. Specifically, it is a crystal structure assigned with space group notation I ^- 4 (space group number: 82), and has 3 × 3 = 9 rhenium oxide type block structures including a tetrahedral vertex sharing structure. The estimated model was a crystal structure in which the ratio of the number of oxygens to the number of metal elements in the unit cell was A _O /A _M =2.50. When such a crystal structure is used as an estimation model, fitting is performed to obtain a Rietveld method reliability factor R _wp value of 9.11% for all peaks excluding the out-of-phase that appears between 5° and 70°. Since it was confirmed that there were no contradictions in peak positions and relative intensities, it was identified as the above crystal structure. The lattice constants were calculated as a = b = 15.703 Å, c = 3.803 Å, 937.77 Å ³ .

Note that the main peak in the XRD spectrum of the composite oxide according to Comparative Example 1 shown in FIGS. 15 and 16 is the peak P ₄₂₀ derived from the (420) plane derived from the crystal structure of FIG. 1 as described above. It is judged that. As described above, Comparative Example 1 has been identified as the crystal structure shown in FIG. 1, and in this structure, the (420) plane appears largely from the atomic position, and the peak P1 does not appear with a distinguishable intensity. Furthermore, since the lattice constant containing many tetrahedra becomes large, the peak P1 does not appear in the range of 2θ=25.05±0.25°.

When the metal ratio of the composite oxide obtained in Comparative Example 1 was calculated by ICP analysis, it was calculated as Ti:Nb:Mo=0.23:1.00:0.15. The composition formula calculated from the number of elements and crystal structure was Ti _0.23 NbMo _0.15 O _3.45 . When the valence was evaluated by HAXPES measurement, the Ti valence was 4 valences, the Nb valence was 5 valences, and the Mo valence was 6 valences. The compositional formula calculated from the valence was Ti _0.23 NbMo _0.15 O _3.41 . Therefore, b=0.23, c=0.15, and d=3.41.

Table 1 below summarizes the results of structural analysis of the composite oxides synthesized in each Example and Comparative Example. Specifically, the composition formula derived by adding HAXPES measurement to ICP analysis and the peak intensity ratio I1/I2 of peak P1 and peak P2 in the XRD spectrum are shown.

As shown in Table 1, both Examples 1-7 and Comparative Example 1 had a composition represented by the above-mentioned general formula Li _a M _b NbMo _c O _d , and had a rhenium oxide type block composed of an octahedral structure. We were able to synthesize a complex oxide containing the structure. Further, regarding Examples 1-7, it was confirmed by STEM-HAADF observation that at least a part of the crystal structure contained the structure shown in FIG. 2. In particular, in Examples 1 and 4-6, since the peak intensity ratio I1/I2 in the XRD spectrum was 1 or more, it can be determined that the crystal structure shown in FIG. 2 was included as the main structure. On the other hand, as described above, both the STEM-HAADF image and the XRD spectrum of Comparative Example 1 matched the crystal structure shown in FIG. 1. Note that, as described above, the main peak in the spectrum of Comparative Example 1 belongs to the (420) plane, and the peak P1 does not appear in the spectrum. Therefore, in Comparative Example 1, the peak intensity I1 was set to zero, and thereby the peak intensity ratio I1/I2 was set to zero.

<Evaluation of battery performance>
Electrodes were produced as follows using the active material powders obtained in the above Examples and Comparative Examples.

First, 100 parts by mass of an active material, 6 parts by mass of a conductive agent, and 4 parts by mass of a binder were dispersed in a solvent to prepare a slurry. Composite material powder obtained by the method described above was used as the active material. As the conductive agent, a mixture of acetylene black, carbon nanotubes, and graphite was used. As the binder, a mixture of carboxymethyl cellulose (CMC) and styrene butadiene rubber (SBR) was used. Pure water was used as the solvent.

Next, the obtained slurry was applied to one side of the current collector, and the coating film was dried to form an active material-containing layer. As the current collector, an aluminum foil with a thickness of 12 μm was used. Next, the current collector and the active material-containing layer were pressed to obtain an electrode. The basis weight of the electrode was 60 g/m ² .

A non-aqueous electrolyte was prepared as follows. The electrolyte salt was dissolved in an organic solvent to obtain a liquid non-aqueous electrolyte. LiPF ₆ was used as the electrolyte salt. The molar concentration of LiPF ₆ in the non-aqueous electrolyte was 1 mol/L. As the organic solvent, a mixed solvent of ethylene carbonate (EC) and diethyl carbonate (DEC) was used. The volume ratio of EC and DEC was 1:2.

A three-electrode beaker cell was prepared using the electrode obtained by the above method as a working electrode, metal lithium foil as a counter electrode and reference electrode, and the nonaqueous electrolyte prepared by the above method.

The initial charge/discharge performance of each of the produced cells was evaluated. Specifically, first, the cell was charged at a temperature of 25° C. with a charging current of 0.2 C until the battery voltage reached 0.7 V, and then constant voltage charging was performed until the charging time reached 10 hours. Thereafter, the battery was discharged at a discharge current of 0.2C until the battery voltage reached 3.0V. The charge/discharge capacity at this time was measured, and the capacitance value per volume of the electrode active material-containing layer (excluding the current collector) was calculated for each of charging and discharging. In addition, the charge/discharge efficiency in the above-mentioned initial charge/discharge was calculated (initial charge/discharge efficiency=[(initial discharge capacity/initial charge capacity)×100%]).

FIG. 17 shows a graph showing initial charge/discharge curves of some beaker cells. The charging curve is shown as a curve extending from the top left to the bottom right of the graph. The discharge curve is shown as a curve extending from the lower left to the upper right of the graph.

Table 2 below summarizes the performance of the composite oxides synthesized in each example and comparative example as an active material for batteries. Specifically, the charging capacity and discharging capacity per volume, as well as the initial charging and discharging efficiency are shown.

The composite oxide contained in the active material obtained in Example 1-7 was expressed by the above-mentioned general formula Li _a M _b NbMo _c O _d and contained at least a portion of the crystal structure shown in FIG. On the other hand, although the composite oxide obtained in Comparative Example 1 satisfied the above general formula, its main crystal structure was the structure shown in FIG. As shown in Table 2, the active materials of Examples 1-7 exhibited higher charging and discharging capacities than the composite oxide of Comparative Example 1. Further, the initial charge/discharge efficiency obtained using the active materials of Examples 1-7 was comparable to that when Comparative Example 1 was used.

Therefore, a composite oxide having a crystal structure including the rhenium oxide type block structure described above, represented by the general formula Li _a M _b NbMo _c O _d , and having the crystal structure shown in FIG. It can be seen that it shows good initial charge/discharge efficiency as an electrode active material and has a high charge/discharge capacity per volume.

According to one or more embodiments and examples described above, an active material containing a composite oxide is provided. The composite oxide includes a rhenium oxide block composed of an octahedral structure composed of oxygen and a metal element with shared vertices, and a plurality of rhenium oxide blocks of different sizes are periodic and share at least the octahedral edges. It is represented by the general formula Li _a M _b NbMo _c O _d . Here, M in the formula is Ti, V, Ta, Fe, Co, Mn, Ni, Bi, Sb, As, P, Cr, W, B, Na, K, Mg, Al, Ca, Y and Si Any one selected from the group consisting of. Each subscript in the formula satisfies the relationships 0≦a≦b+2+3c, 0≦b≦1.5, 0≦c≦0.5, and 2.33≦d/(1+b+c)≦2.50, respectively. Such active materials can provide electrodes that can realize high-capacity secondary batteries, high-capacity secondary batteries and battery packs, and vehicles equipped with the battery packs.

Some embodiments according to the present invention will be described below.

[1] A structure including an octahedral structure composed of oxygen and a metal element, the octahedral structure including rhenium oxide type blocks formed by corner sharing, the rhenium oxide type blocks including a plurality of rhenium oxide type blocks having different sizes, and the rhenium oxide type blocks including a structure in which the rhenium oxide type blocks are connected at least by octahedral corner sharing without periodicity,
An active material comprising a composite oxide represented by the general formula Li _a M _b NbMo _c O _d , where M is one or more selected from the group consisting of Ti, V, Ta, Fe, Co, Mn, Ni, Bi, Sb, As, P, Cr, W, B, Na, K, Mg, Al, Ca, Y and Si, and 0≦a≦b+2+3c, 0≦b≦1.4, 0≦c≦0.5, and 2.33≦d/(1+b+c)≦2.50.
[2] A structure including an octahedral structure composed of oxygen and a metal element, the octahedral structure including rhenium oxide type blocks formed by corner sharing, the rhenium oxide type blocks including a plurality of rhenium oxide type blocks having different sizes, and the rhenium oxide type blocks including a structure in which the rhenium oxide type blocks are connected at least by octahedral corner sharing without periodicity,
An active material comprising a composite oxide represented by the general formula Li _a M _b NbMo _c O _d , where M is one or more selected from the group consisting of Ti, V, Ta, Fe, Co, Mn, Ni, Bi, Sb, As, P, Cr, W, B, Na, K, Mg, Al, Ca, Y and Si, and 0≦a≦b+2+3c, 0≦b≦1.5, 0≦c≦0.5, and 2.33≦d/(1+b+c)≦2.50.

[3] In the diffraction spectrum of the composite oxide obtained by powder X-ray diffraction using a Cu-Kα ray source, the peak intensity I1 of peak P1 appearing within the range of 2θ = 25.05 ± 0.25° and 2θ = 24.00 ± 0.20° The active material according to [1] or [2], wherein the peak intensity I2 of the peak P2 appearing within the range satisfies the relationship I1/I2>0.1.

[4] An electrode comprising the active material according to any one of [1] to [3].

[5] The electrode according to [4], including an active material-containing layer containing the active material.

[6] A positive electrode,
a negative electrode;
A secondary battery comprising an electrolyte,
A secondary battery, wherein the positive electrode or the negative electrode is the electrode according to [4] or [5].

[7] A battery pack comprising the secondary battery according to [6].

[8] An external terminal for supplying electricity;
The battery pack according to [7], further comprising a protection circuit.

[9] Equipped with a plurality of the secondary batteries,
The battery pack according to [7] or [8], wherein the secondary batteries are electrically connected in series, in parallel, or in a combination of series and parallel.

[10] A vehicle comprising the battery pack according to any one of [7] to [9].

[11] The vehicle according to [10], including a mechanism that converts kinetic energy of the vehicle into regenerative energy.

Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the gist of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are included in the scope of the invention and its equivalents described in the claims.

DESCRIPTION OF SYMBOLS 1... Electrode group, 2... Exterior member, 3... Negative electrode, 3a... Negative electrode current collector, 3b... Negative electrode active material containing layer, 4... Separator, 5... Positive electrode, 5a... Positive electrode current collector, 5b... Positive electrode active material containing Layer, 6... Negative electrode terminal, 7... Positive electrode terminal, 10... Crystal structure, 10a... Octahedron, 10b... Tetrahedron, 11... Crystal structure, 11a... Octahedron, 11b... Tetrahedron, 18... Metal element, 19... Oxygen Element, 21... Bus bar, 22... Positive electrode side lead, 23... Negative electrode side lead, 24... Adhesive tape, 31... Container, 32... Lid, 33... Protective sheet, 34... Printed wiring board, 35... Wiring, 40... Vehicle Main body, 41... Vehicle power source, 42... Electric control device, 43... External terminal, 44... Inverter, 45... Drive motor, 100... Secondary battery, 200... Assembled battery, 200a... Assembled battery, 200b... Assembled battery, 200c ... assembled battery, 300... battery pack, 300a... battery pack, 300b... battery pack, 300c... battery pack, 301a... assembled battery monitoring device, 301b... assembled battery monitoring device, 301c... assembled battery monitoring device, 342... positive electrode side connector , 343... Negative side connector, 345... Thermistor, 346... Protection circuit, 342a... Wiring, 343a... Wiring, 350... External terminal for energization, 352... Positive side terminal, 353... Negative side terminal, 348a... Positive side wiring, 348b... Negative side wiring, 400... Vehicle, 411... Battery management device, 412... Communication bus, 413... Positive electrode terminal, 414... Negative electrode terminal, 415... Switch device, 416... Current detection section, 417... Negative electrode input terminal, 418... Positive input terminal, L1...connection line, L2...connection line, W...drive wheel.

Claims (11)

The octahedral structure includes an octahedral structure composed of oxygen and a metal element, the octahedral structure includes rhenium oxide type blocks configured by corner sharing, the octahedral structure includes a plurality of rhenium oxide type blocks having different sizes, and the rhenium oxide type blocks include a structure in which the rhenium oxide type blocks are connected at least by octahedral edge sharing without periodicity,
An active material comprising a composite oxide represented by the general formula Li _a M _b NbMo _c O _d , where M is one or more selected from the group consisting of Ti, V, Ta, Fe, Co, Mn, Ni, Bi, Sb, As, P, Cr, W, B, Na, K, Mg, Al, Ca, Y and Si, and 0≦a≦b+2+3c, 0≦b≦1.4, 0≦c≦0.5, and 2.33≦d/(1+b+c)≦2.50. The octahedral structure includes an octahedral structure composed of oxygen and a metal element, the octahedral structure includes rhenium oxide type blocks configured by corner sharing, the octahedral structure includes a plurality of rhenium oxide type blocks having different sizes, and the rhenium oxide type blocks include a structure in which the rhenium oxide type blocks are connected at least by octahedral edge sharing without periodicity,
An active material comprising a composite oxide represented by the general formula Li _a M _b NbMo _c O _d , where M is one or more selected from the group consisting of Ti, V, Ta, Fe, Co, Mn, Ni, Bi, Sb, As, P, Cr, W, B, Na, K, Mg, Al, Ca, Y and Si, and 0≦a≦b+2+3c, 0≦b≦1.5, 0≦c≦0.5, and 2.33≦d/(1+b+c)≦2.50. In the diffraction spectrum of the composite oxide obtained by powder X-ray diffraction using a Cu-Kα ray source, the peak intensity I1 of peak P1 appearing within the range of 2θ = 25.05 ± 0.25° and the peak intensity I1 within the range of 2θ = 24.00 ± 0.20° 3. The active material according to claim 2, wherein the peak intensity I2 of the peak P2 that appears in satisfies the relationship I1/I2>0.1. An electrode comprising the active material according to claim 2 or 3. The electrode according to claim 4, comprising an active material-containing layer that contains the active material. a positive electrode;
a negative electrode;
A secondary battery comprising an electrolyte,
A secondary battery, wherein the positive electrode or the negative electrode is the electrode according to claim 4. A battery pack comprising the secondary battery according to claim 6. An external terminal for supplying electricity;
8. The battery pack of claim 7, further comprising a protection circuit. comprising a plurality of the secondary batteries,
The battery pack according to claim 7, wherein the secondary batteries are electrically connected in series, in parallel, or in a combination of series and parallel. A vehicle comprising the battery pack according to claim 7. The vehicle according to claim 10, including a mechanism that converts kinetic energy of the vehicle into regenerative energy.