Electrode material, electrode, secondary battery, battery pack, and vehicle

Abstract

To provide an electrode material capable of realizing a secondary battery capable of exhibiting excellent rapid charge / discharge characteristics and cycle life characteristics.SOLUTION: An electrode material according to an embodiment includes an active material particle including a niobium-titanium composite oxide having an average composition in which the molar ratio of niobium to titanium (MNb / MTi) is greater than 2, and at least one element A selected from the group consisting of potassium, iron and phosphorus. The active material particles contain the element A at a concentration in the range of 100 ppm to 2000 ppm.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] FIELD Embodiments of the present invention relate to an electrode material, an electrode, a secondary battery, a battery pack, and a vehicle. [Background technology]

[0002] In recent years, research and development of high-energy-density secondary batteries, including nonaqueous electrolyte secondary batteries such as lithium-ion secondary batteries, has been actively pursued. Nonaqueous electrolyte secondary batteries are expected to be used as power sources for vehicles such as hybrid electric vehicles and electric vehicles, as well as for uninterruptible power supplies in mobile phone base stations. Furthermore, due to the rapidly increasing demand for power sources for mobile services such as autonomous industrial robots and drones, secondary batteries are required to have not only high energy density but also other excellent performance characteristics such as rapid charge / discharge capability and long-term reliability. For example, secondary batteries capable of rapid charge / discharge not only significantly shorten charging times but also enable efficient recovery of regenerative energy, thereby significantly extending the daily operating time of vehicles and devices.

[0003] To enable rapid charging and discharging, electrons and lithium ions must be able to move quickly between the positive and negative electrodes. However, repeated rapid charging and discharging of batteries using carbon-based negative electrodes can cause dendrite deposition of metallic lithium on the electrode, which can lead to internal short circuits and the risk of heat generation or fire.

[0004] Therefore, batteries using metal composite oxides instead of carbon-based active materials for the anode have been developed. Among these, batteries using titanium oxide for the anode are capable of stable rapid charging and discharging and have a longer lifespan than batteries using carbon-based anodes.

[0005] However, titanium oxide has a higher potential relative to metallic lithium than carbonaceous materials, i.e., it is more noble. Furthermore, titanium oxide has a low capacity per weight. Therefore, batteries using titanium oxide as the anode have the problem of low energy density.

[0006] For example, the electrode potential of titanium oxide is approximately 1.5 V (vs. Li / Li) + ), which is higher (more noble) than the potential of a carbon-based negative electrode. The potential of titanium oxide is 3+ and Ti 4+ It is electrochemically limited because it is caused by an oxidation-reduction reaction between 1.5V (vs. Li / Li + It is also true that rapid charging and discharging of lithium ions can be performed stably at high electrode potentials of around 1000 kJ / cm. Therefore, it has been difficult to lower the electrode potential in order to improve the energy density.

[0007] On the other hand, the theoretical capacity per unit weight of titanium dioxide (anatase structure) is about 165 mAh / g, and that of Li4Ti5O 12 The theoretical capacity of spinel-type lithium-titanium composite oxides such as the one shown in Fig. 1 is approximately 180 mAh / g. On the other hand, the theoretical capacity of typical graphite-based electrode materials is 385 mAh / g or more. Thus, the capacity density of titanium oxides is significantly lower than that of carbon-based negative electrodes. This is because the crystal structure of titanium oxides has few sites for absorbing lithium, and lithium is easily stabilized within the structure, resulting in a lower effective capacity.

[0008] In view of the above, new electrode materials containing Ti and Nb are being investigated. Such niobium titanium composite oxide materials are expected to have high charge / discharge capacities. In particular, the composite oxide represented by TiNb2O7 has a high theoretical capacity exceeding 380 mAh / g. Therefore, the niobium titanium composite oxide is Li4Ti5O 12 However, there is a problem that the lifespan characteristics are short because the crystal structure undergoes significant changes due to lithium ions being inserted and removed from the crystal structure during rapid charging and charge / discharge cycling. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-168352 [Patent Document 2] US Patent Application Publication No. 2012 / 0052401 [Non-patent literature]

[0010] [Non-Patent Document 1] M.Gasperin, Journal of Solid State Chemistry 53, pp144-147 (1984) Summary of the Invention [Problem to be solved by the invention]

[0011] The present invention aims to provide an electrode material capable of realizing a secondary battery that can exhibit excellent rapid charge / discharge characteristics and cycle life characteristics, an electrode containing this electrode material, a secondary battery equipped with this electrode, a battery pack equipped with this secondary battery, and a vehicle equipped with this battery pack. [Means for solving the problem]

[0012] According to an embodiment, an electrode material is provided. The electrode material has a molar ratio of niobium to titanium (M Nb / M Ti ) is greater than 2, and at least one element A selected from the group consisting of potassium, iron, and phosphorus. Consists of The active material particles are provided. Element A is dissolved in the active material particles at a concentration in the range of 100 ppm to 2000 ppm. The crystallite size of the niobium titanium composite oxide is in the range of 50 nm to 130 nm. Niobium titanium composite oxide has the general formula Nb 2 M2 z Ti 1-z O 7 , general formula Nb 10-x M1 x Ti 2-yM2 y O 29 , general formula Nb 14-x M1 x Ti 1-y M2 y O 37 , and the general formula Nb 24-x M1 x Ti 1-y M2 y O 62 M1 is at least one element selected from the group consisting of Ta, Ti, V, Mo, and W. M2 is at least one element selected from the group consisting of Nb, Ta, Zr, Hf, and Sn. x satisfies 0≦x≦5, y satisfies 0≦y<1.0, and z satisfies 0.01≦z<1. .

[0013] According to another embodiment, an electrode is provided that includes an electrode material according to an embodiment.

[0014] According to another embodiment, there is provided a secondary battery comprising a positive electrode, a negative electrode, and an electrolyte. The negative electrode is an electrode according to the embodiment.

[0015] According to another embodiment, a battery pack including a secondary battery according to the embodiment is provided.

[0016] According to another embodiment, a vehicle including a battery pack according to an embodiment is provided. [Brief explanation of the drawings]

[0017] [Figure 1] Schematic diagram showing the crystal structure of monoclinic Nb2TiO7. [Figure 2] Schematic diagram showing the crystal structure of Figure 1 as viewed from another direction. [Figure 3] 1 is a cross-sectional view schematically illustrating an example of a secondary battery according to an embodiment. [Figure 4] FIG. 4 is an enlarged cross-sectional view of part A of the secondary battery shown in FIG. [Figure 5] FIG. 10 is a partially cutaway perspective view schematically showing another example of a secondary battery according to an embodiment. [Figure 6]FIG. 6 is an enlarged cross-sectional view of part B of the secondary battery shown in FIG. 5. [Figure 7] FIG. 1 is a perspective view schematically illustrating an example of a battery pack according to an embodiment. [Figure 8] FIG. 1 is an exploded perspective view schematically showing an example of a battery pack according to an embodiment. [Figure 9] FIG. 9 is a block diagram showing an example of an electrical circuit of the battery pack shown in FIG. 8. [Figure 10] 1 is a cross-sectional view schematically illustrating an example of a vehicle according to an embodiment. [Figure 11] FIG. 10 is a diagram schematically illustrating another example of a vehicle according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0018] The following describes embodiments with reference to the drawings. Common components throughout the embodiments are designated by the same reference numerals, and redundant explanations will be omitted. Each figure is a schematic diagram for explaining and facilitating understanding of the embodiments. While the shapes, dimensions, and ratios may differ from those of actual devices, these may be appropriately modified in design, taking into consideration the following explanation and known techniques.

[0019] (First embodiment) According to a first embodiment, an electrode material is provided. The electrode material has a molar ratio of niobium to titanium (M Nb / M Ti The active material particles contain a niobium-titanium composite oxide having an average composition in which R 1 ) is greater than 2, and at least one element A selected from the group consisting of potassium, iron, and phosphorus. The active material particles contain the element A at a concentration in the range of 100 ppm to 2000 ppm.

[0020] The molar ratio of niobium to titanium (M Nb / M Ti As an example of a niobium titanium composite oxide having an average composition where Nb 10 Ti2O 29 Phase, Nb 14 TiO 37 phase and Nb 24 TiO 62In the present specification and claims, the term "M titanium composite oxide" is used. Nb " indicates the amount of niobium atoms (number of moles) contained in the niobium titanium composite oxide, and "M Ti " indicates the amount (molar number) of titanium atoms contained in the niobium titanium composite oxide. These crystal phases have, for example, a monoclinic crystal structure. Nb 10 Ti2O 29 The phase may also have an orthorhombic crystal structure.

[0021] Molar ratio (M Nb / M Ti Another example of the crystalline phase contained in the niobium titanium composite oxide having an average composition in which the molar ratio (M Nb / M Ti ) is greater than 2. Nb / M Ti In the Nb2TiO7 phase having a composition where the molar ratio (M) is greater than 2, part of the titanium in the Nb2TiO7 phase is substituted with niobium. Nb / M Ti The Nb2TiO7 phase having a composition in which the molar ratio of niobium to titanium (M) is greater than 2 has, for example, a monoclinic crystal structure. Nb / M Ti ) is sometimes referred to as the "Nb / Ti ratio."

[0022] The Nb2TiO7 phase refers to a crystalline phase that is attributed to the crystal structure of Nb2TiO7. 10 Ti2O 29 The phase is Nb 10 Ti2O 29 This refers to the crystalline phase that is attributed to the crystal structure of Nb 14 TiO 37 The phase is Nb 14 TiO 37 This refers to the crystalline phase that is attributed to the crystal structure of Nb 24 TiO 62 The phase is Nb 24 TiO 62 This refers to the crystalline phase attributed to the crystal structure of

[0023] The basic skeleton of the crystal of niobium titanium composite oxide having an average composition with a Nb / Ti ratio of more than 2 is the Nb2TiO7 phase, Nb 10 Ti2O 29 Phase, Nb 14 TiO 37 phase and Nb 24 TiO 62 In other words, the niobium titanium composite oxide having an average composition in which the Nb / Ti ratio is greater than 2 may be at least one selected from the group consisting of Nb2TiO7 phase, Nb 10 Ti2O 29 Phase, Nb 14 TiO 37 phase and Nb 24 TiO 62 The niobium titanium composite oxide having an average composition in which the Nb / Ti ratio is greater than 2 may be composed of two or more of these four crystalline phases. In other words, the niobium titanium composite oxide having an average composition in which the Nb / Ti ratio is greater than 2 may have a mixed phase containing two or more crystalline phases having a composition in which the Nb / Ti ratio is greater than 2.

[0024] The electrode material according to the embodiment has a niobium to titanium molar ratio (M Nb / M Ti ) may be 2.

[0025] Nb2TiO7 phase with a composition of Nb / Ti ratio greater than 2, Nb 10 Ti2O 29 Phase, Nb 14 TiO 37 phase and Nb 24 TiO 62 When these phases have a monoclinic crystal structure, they all have a structure similar to that of monoclinic Nb2TiO7.

[0026] 1 and 2 show the skeletal structure of monoclinic Nb2TiO7. FIG. 1 is a schematic diagram showing the crystal structure of monoclinic Nb2TiO7. FIG. 2 is a schematic diagram showing the crystal structure of FIG. 1 as observed from another direction. Monoclinic Nb2TiO7 is a crystal structure in which the molar ratio of niobium to titanium (M Nb / M Ti ) is a niobium titanium composite oxide in which the cation ratio is 2.

[0027] As shown in FIG. 1, the crystal structure of the monoclinic niobium titanium composite oxide Nb2TiO7 has a skeletal structure 103 composed of metal ions 101 and oxide ions 102. Nb ions and Ti ions are randomly arranged at the positions of the metal ions 101 in a ratio of Nb:Ti=2:1. These skeletal structure portions 103 are arranged alternately in a three-dimensional manner, resulting in the presence of void portions 104 between the skeletal structure portions 103. These void portions 104 act as hosts for lithium ions. As shown in FIG. 1, these void portions 104 can occupy a large portion of the entire crystal structure. In addition, these void portions 104 can maintain a stable structure even when lithium ions are inserted.

[0028] In Fig. 1, regions 105 and 106 are portions having two-dimensional channels in the

[0100] direction and the

[0010] direction. As shown in Fig. 2, the crystal structure of the monoclinic niobium titanium composite oxide has void portions 107 in the

[0001] direction. These void portions 107 have a tunnel structure that is advantageous for the conduction of lithium ions, and serve as conductive paths in the

[0001] direction connecting regions 105 and 106. The existence of these conductive paths allows lithium ions to travel between regions 105 and 106.

[0029] As described above, the crystal structure of the monoclinic niobium titanium composite oxide Nb2TiO7 has a large equivalent intercalation space for lithium ions and is structurally stable. Furthermore, it has regions with two-dimensional channels through which lithium ions diffuse rapidly, and conductive paths in the

[0001] direction connecting these regions. As a result, the crystal structure of the monoclinic niobium titanium composite oxide Nb2TiO7 improves the intercalation and deintercalation of lithium ions into the intercalation space, and effectively increases the intercalation and deintercalation space for lithium ions. This makes it possible to provide high capacity and high rate performance.

[0030] Furthermore, when lithium ions are inserted into the void spaces 104, the metal ions 101 constituting the framework 103 are reduced to trivalent cations, thereby maintaining the electrical neutrality of the crystal. In monoclinic niobium titanium composite oxide, not only are Ti ions reduced from tetravalent to trivalent, but Nb ions are also reduced from pentavalent to trivalent. In other words, the reduction valence per weight of active material is large. Therefore, even when many lithium ions are inserted, the electrical neutrality of the crystal can be maintained. For this reason, monoclinic niobium titanium composite oxide has a higher energy density than compounds such as titanium oxide that contain only tetravalent cations. Specifically, the theoretical capacity of monoclinic niobium titanium composite oxide is approximately 387 mAh / g, which is more than twice that of titanium oxide with a spinel structure.

[0031] In addition, niobium titanium composite oxide has a lithium absorption potential of about 1.5 V (vs. Li / Li+). Therefore, by using an electrode material containing monoclinic niobium titanium composite oxide, it is possible to provide a battery that is capable of stable repeated rapid charging and discharging.

[0032] Furthermore, a niobium titanium composite oxide having an average composition with an Nb / Ti ratio of more than 2 can realize a secondary battery that can exhibit excellent rapid charge / discharge characteristics and cycle life characteristics for the reasons explained below.

[0033] Niobium titanium composite oxides having an average composition with an Nb / Ti ratio greater than 2 have a higher Nb content than Nb2TiO7 phases having an Nb / Ti ratio greater than 2. Therefore, crystal phases having an Nb / Ti ratio greater than 2 have more bonds (Nb-O) between Nb and oxygen that constitute the skeleton. The bond strength between Nb, a pentavalent cation, and oxygen (Nb-O) is stronger than the bond strength between Ti, a tetravalent cation, and oxygen (Ti-O). Therefore, crystal phases having an Nb / Ti ratio greater than 2 can maintain a more stable crystal skeleton structure even when lithium ions are inserted, compared to Nb2TiO7 having an Nb / Ti ratio greater than 2. That is, niobium titanium composite oxides having an average composition with an Nb / Ti ratio greater than 2 have excellent life performance during rapid charge / discharge and repeated charge / discharge cycles.

[0034] In addition, orthorhombic Nb 10 Ti2O 29 In the Nb2TiO7 phase and the Nb2TiO7 phase having a composition in which the Nb / Ti ratio is greater than 2 due to element substitution, the bonding strength between Nb—O is stronger than the bonding strength between Ti—O, and therefore the same effect can be obtained.

[0035] On the other hand, niobium-titanium composite oxides containing a crystalline phase with a composition having an Nb / Ti ratio greater than 2 tend to be difficult to pulverize due to particle sintering. This tendency is likely to occur during industrial synthesis. The difficulty in pulverization is thought to be due to the strong Nb-O bond, which tends to result in hard particles with high hardness. Furthermore, sintering also becomes more likely when niobium or titanium in the crystalline structure is replaced with a different element other than niobium, titanium, and tantalum. Here, the different elements do not include potassium, iron, or phosphorus. In other words, the different elements referred to here refer to elements other than niobium, titanium, tantalum, potassium, iron, and phosphorus. Because tantalum has properties very similar to those of niobium and titanium, it has been found that the properties of the crystalline structure are unlikely to change even when tantalum replaces niobium or titanium. Therefore, compared to the Nb2TiO7 phase with an Nb / Ti ratio of 2, a crystalline phase with an Nb / Ti ratio greater than 2 is more likely to produce coarse, hard particles.

[0036] To obtain active material particles with excellent rapid charge / discharge performance, high crystallinity and small particle size are necessary. Conventionally, when niobium-titanium composite oxides containing a crystalline phase with a composition having an Nb / Ti ratio of greater than 2 are crushed, a strong force must be applied during crushing for the reasons mentioned above, resulting in low crystallinity and poor rapid charge / discharge performance. Furthermore, fine powder of less than 0.2 μm produced by strong crushing does not contribute to charge / discharge and can contribute to reduced charge / discharge efficiency and life performance, resulting in a short charge / discharge cycle life.

[0037] In the electrode material according to the embodiment, active material particles containing a niobium titanium composite oxide having an average composition with an Nb / Ti ratio greater than 2 further contain at least one element A selected from the group consisting of potassium, iron, and phosphorus. The element A exists, for example, in a solid solution state in the niobium titanium composite oxide. Furthermore, since the concentration of element A is within the range of 100 ppm to 2000 ppm, a portion of the Nb-O bond is weakened. This is because at least one of an Nb-K-O bond, an Nb-Fe-O bond, and an Nb-P-O bond is formed in the crystal. The Nb-K-O bond, the Nb-Fe-O bond, and the Nb-P-O bond all have weaker bond strength than the Nb-O bond. Therefore, compared to a case where element A is not included, coarse particles can be reduced in size by performing less intense pulverization without reducing the crystallinity of the niobium titanium composite oxide, and the generation of fine powder less than 0.2 μm caused by pulverization can be suppressed.

[0038] Furthermore, by weakening some of the bonding strength between Nb-O within the crystal, it is expected that when lithium ions diffuse within the crystal, the structural change near element A, which has a weak bonding strength, will be alleviated without destroying the basic skeletal structure. As a result, the crystal structure can be maintained stably even during repeated charge and discharge, which is expected to extend the lifespan.

[0039] When element A is potassium, the crystals that make up the niobium titanium composite oxide contain Nb-K-O bonds within the crystals. In this case, potassium not only weakens the bonds between niobium and the oxide ions, but also fills defects in the lattice that tend to trap lithium ions, improving charge / discharge performance.

[0040] When element A is iron, the crystals constituting the niobium titanium composite oxide contain Nb-Fe-O bonds within the crystals. In this case, the electron orbitals of the iron ions are effective in weakening the bonds between the niobium and the oxide ions, and also have the effect of improving electronic conductivity and reducing electrode resistance.

[0041] When element A is phosphorus, the crystals constituting the niobium titanium composite oxide contain Nb-PO bonds in the crystals. In this case, the strong covalent bond between phosphorus and oxide ions effectively weakens the bond between niobium and oxide ions.

[0042] If the concentration of element A is less than 100 ppm, it is difficult to obtain the effect of weakening the bonding force between Nb—O. If the concentration of element A exceeds 2000 ppm, it is undesirable because it tends to cause only specific crystal axes to grow, resulting in the generation of coarse particles. The concentration of element A is preferably in the range of 200 ppm to 1500 ppm. The concentration of element A refers to the mass [mg / kg] of element A contained in the solid, for example, the mass of element A contained in the active material particles. The concentration of element A can be analyzed by inductively coupled plasma (ICP) emission spectroscopy, which will be described later.

[0043] Although element A may be distributed uniformly throughout the active material particles, it is preferable that the concentration of element A be highest at the particle interface. The high concentration of element A at the particle interface allows coarse particles to be reduced in size with a weaker crushing force after firing. As a result, a large crystallite size can be maintained.

[0044] As a result of the above, the electrode material according to the embodiment contains active material particles with high crystallinity and a stable basic skeleton, and has a low proportion of fine powder. Therefore, it can exhibit excellent rapid charge-discharge characteristics and cycle life characteristics. The electrode material according to the embodiment may consist only of active material particles.

[0045] Hereinafter, the electrode material according to the embodiment will be described in more detail.

[0046] The electrode material contains, as an active material, a niobium titanium composite oxide having an average composition with a Nb / Ti ratio greater than 2.

[0047] The composition of the Nb2TiO7 phase having a composition with a molar ratio of niobium to titanium (Nb / Ti) greater than 2 can be represented, for example, by the general formula Nb2M2 z Ti 1-z O7. Here, z satisfies 0 < z < 1. Also, when Li is inserted into the Nb2TiO7 phase having a composition with a Nb / Ti ratio greater than 2, the composition can be represented by Li d Nb2M2 z Ti 1-z O7 (0 ≦ d ≦ 5).

[0048] Nb 10 Ti2O 29 The phase composition can be represented, for example, by the general formula Nb 10-x M1 x Ti 2-y M2 y O 29 When lithium ions are inserted into the Nb 10 Ti2O 29 phase, the composition can be represented by Li a Nb 10-x M1 x Ti 2-y M2 y O 29 (0 ≦ a ≦ 22).

[0049] Nb 14 TiO 37 The phase composition can be represented, for example, by the general formula Nb 14-x M1 x Ti 1-y M2y O 37 It can be expressed as: 14 TiO 37 When lithium ions are inserted into the phase, the composition is Li b Nb 14-x M1 x Ti 1-y M2 y O 37 It can be expressed as (0≦b≦29).

[0050] Nb 24 TiO 62 The composition of the phase is, for example, the general formula Nb 24-x M1 x Ti 1-y M2 y O 62 It can be expressed as: 24 TiO 62 When lithium ions are inserted into the phase, the composition is Li c Nb 24-x M1 x Ti 1-y M2 y O 62 It can be expressed as (0≦c≦49).

[0051] In the above general formula, M1 is at least one additive element selected from the group consisting of Ta, Ti, V, Mo, and W, M2 is at least one additive element selected from the group consisting of Nb, Ta, Zr, Hf, and Sn, x satisfies 0≦x≦5, and y satisfies 0≦y<1.0. When the niobium titanium composite oxide contains Ta, the crystal constituting the niobium titanium composite oxide may contain Nb-Ta-O bonds within the crystal. In this case, when lithium is inserted into the crystal structure, niobium is preferentially oxidized and reduced, but tantalum maintains its bond with the oxide ion, thereby having the effect of stabilizing the crystal structure.

[0052] A composition with an Nb / Ti ratio of greater than 2 is preferable because it can increase electronic conductivity. If x is greater than 5, the amount of Nb reduced by Li insertion will be less than the number of Li host sites, which may result in a low electrode capacity. If y is greater than 1.0, the framework structure may become unstable, potentially reducing cycle life.

[0053] <Form> The form of the active material particles (active material) contained in the electrode material according to the embodiment is not particularly limited. The active material particles may be in the form of, for example, primary particles or secondary particles formed by aggregation of primary particles. The active material particles may also be a mixture of primary particles and secondary particles.

[0054] The active material particles may have a carbon-containing layer on their surfaces. However, element A is present inside the carbon-containing layer. The carbon-containing layer may be attached to the surface of the primary particles or the surface of the secondary particles. Alternatively, the active material particles may contain secondary particles formed by agglomeration of primary particles having a carbon-containing layer attached to their surfaces. Such secondary particles can exhibit excellent conductivity because carbon is present between the primary particles. An embodiment containing such secondary particles is preferable because the active material-containing layer can exhibit lower resistance.

[0055] <Particle size> The active material particles contained in the electrode material preferably have a volume frequency 10% (D10) in the range of 0.3 μm to 2.0 μm in a particle size distribution chart obtained by laser diffraction scattering. If D10 is smaller than 0.3 μm, side reactions with the electrolyte tend to increase, resulting in reduced charge / discharge efficiency and cycle life performance. If D10 is larger than 2.0 μm, rapid charge / discharge performance tends to decrease. D10 is more preferably in the range of 0.5 μm to 1.0 μm.

[0056] Furthermore, in a particle size distribution chart, the 90% volume frequency (D90) is preferably in the range of 5 μm to 30 μm. If D90 is smaller than 5 μm, the electrode tends to peel off from the current collector, resulting in a decrease in lifespan. If D90 is larger than 30 μm, rapid charge / discharge performance tends to decrease. It is more preferable that D90 be in the range of 6 μm to 10 μm.

[0057] A high D10 value means that there is little fine powder, and a low D90 value means that there are few coarse particles. In other words, this means that the particle size distribution tends to be sharp. Although a sharp particle size distribution is not necessarily desirable, it is possible to evaluate whether the particle size distribution is sharp or not based on the ratio of D10 to the volume frequency 50% (D50) and the ratio of D50 to D90.

[0058] It is preferable that the ratio D10 / D50 is within the range of 0.10 to 0.60 and the ratio D50 / D90 is within the range of 0.20 to 0.50. This allows active material particles with smaller particle diameters to be dispersed in the gaps between active material particles with larger particle diameters, thereby shortening the diffusion distance of lithium ions within the crystal. This allows for both improved rapid charge / discharge performance and excellent life performance. If the ratio D10 / D50 is less than 0.1 or the ratio D50 / D90 is less than 0.20, the particle size distribution is uneven, making it difficult to increase the electrode density. It is preferable that the ratio D10 / D50 is within the range of 0.15 to 0.30 and the ratio D50 / D90 is within the range of 0.20 to 0.40. If the ratio D10 / D50 is greater than 0.60 or the ratio D50 / D90 is greater than 0.50, the flexibility of the electrode is impaired, which may make it difficult to form the electrode into a wound body.

[0059] The D50 of the active material particles according to the embodiment is not particularly limited, but is within the range of 0.5 μm to 30 μm, for example.

[0060] The active material particles may be secondary particles formed from the primary particles, and in this case, the particle size of the secondary particles is not particularly limited.

[0061] <Crystalline> The crystallite size of the niobium titanium composite oxide having an average composition with an Nb / Ti ratio of more than 2 is, for example, in the range of 50 nm to 130 nm, and preferably in the range of 95 nm to 130 nm. In this case, the electrode material can achieve excellent rapid charge / discharge characteristics.

[0062] Furthermore, niobium titanium composite oxides containing the Nb2TiO7 phase with a composition in which the Nb / Ti ratio is greater than 2 show two peaks at 2θ = 44° ± 1.0° in the diffraction pattern obtained by powder X-ray diffraction using a Cu-Kα radiation source, and the intensity ratio of these two peaks (I H / I L ) is preferably less than 1. The peak intensity ratio relating to the Nb2TiO7 phase having a composition in which the Nb / Ti ratio is greater than 2 is also referred to as the first peak intensity ratio. When the first peak intensity ratio is less than 1, it can be determined that the niobium titanium composite oxide containing the Nb2TiO7 phase having a composition in which the Nb / Ti ratio is greater than 2 has high crystallinity.

[0063] Also, Nb 10 Ti2O 29 Phase, Nb 14 TiO 37 phase and Nb 24 TiO 62 Niobium titanium composite oxide containing at least one selected from the group consisting of the phases has two peaks at 2θ=44°±1.0° in the diffraction pattern obtained by powder X-ray diffraction using a Cu-Kα radiation source, and the intensity ratio of these two peaks (I H / I L ) is preferably less than 1.5. 10 Ti2O 29 Phase, Nb 14 TiO 37 phase and Nb 24 TiO 62 The peak intensity ratio for each phase is also referred to as the second peak intensity ratio. If the second peak intensity ratio is less than 1.5, the niobium titanium composite oxide can be determined to have high crystallinity.

[0064] Here, I H is the high-angle peak P H is the peak intensity of I L is the low-angle peak P L The two peaks that appear at 2θ=44°±1.0° are the peaks P L is the peak of the (0 0 5) plane, and the peak P H It is thought that this is the peak of the (-10 0 3) plane. The first peak intensity ratio (I H / I L When the second peak intensity ratio (I H / I L ) is less than 1.5, a composite oxide having high lithium ion conductivity and high capacity can be obtained.

[0065] The peak intensity ratio (I H / I L ) can be used as a guideline for determining whether a more preferable crystal structure, i.e., whether high crystallinity is obtained, is obtained within the above-mentioned particle size range in the niobium titanium composite oxide of the present embodiment having an average composition in which the Nb / Ti ratio is greater than 2.

[0066] <Powder X-ray diffraction measurement of electrode materials> Powder X-ray diffraction measurement of the electrode material can be carried out, for example, as follows. First, crush the target sample to the particle size ranges mentioned above (D10, D50, and D90). The crushed sample is loaded into a 0.2 mm deep holder formed on a glass sample plate. At this time, care is taken to ensure that the sample is loaded sufficiently into the holder. Care is also taken to load just the right amount of sample to avoid cracks, voids, etc. Next, another glass plate is pressed against the holder from the outside to flatten the surface of the sample loaded into the holder. Care is taken to ensure that the loading amount does not become too much or too little and does not result in unevenness above the base surface of the holder.

[0067] Next, the glass plate filled with the sample is placed in a powder X-ray diffractometer, and a diffraction pattern (XRD pattern; X-ray diffraction pattern) is obtained using Cu-Kα radiation.

[0068] Note that particle orientation may be significant depending on the particle shape of the sample. When the sample has a high degree of orientation, the peak position may shift or the intensity ratio may change depending on how the sample is packed. Samples with such a high degree of orientation are measured using a glass capillary. Specifically, the sample is inserted into a capillary, and the capillary is placed on a rotating sample stage for measurement. This measurement method can alleviate the orientation. As the glass capillary, it is preferable to use a Lindemann glass capillary with a diameter of 1 mm to 6 mm.

[0069] Furthermore, due to the influence of lithium ions remaining in the electrode, impurity phases such as lithium carbonate and lithium fluoride may be present in the powder X-ray diffraction measurement results. This can be prevented, for example, by using an inert gas atmosphere for the measurement or by cleaning the electrode surface. Even if impurity phases are present, it is possible to ignore these phases and perform analysis.

[0070] The powder X-ray diffraction measurement device used is, for example, SmartLab manufactured by Rigaku Co., Ltd. The measurement conditions are as follows: X-ray source: Cu target Output: 45kV 200mA Soller slit: 5° for both incident and receiving light Step width (2θ): 0.02 deg Scan speed: 20deg / min Semiconductor detector: D / teX Ultra 250 Measurement range: 5°≦2θ≦90° Sample plate holder: Flat glass sample plate holder (0.5 mm thick).

[0071] When using other devices, perform measurements using a standard Si powder for powder X-ray diffraction so that measurement results equivalent to the above are obtained, and adjust the measurement conditions so that the peak intensity and peak top position match those of the above device.

[0072] In the obtained diffraction pattern, among the two peaks that appear within the range of 2θ of 44° ± 1.0°, the peak intensity I of the high-angle side peak H and the peak intensity I of the low-angle side peak L are determined. Then, the ratio of the peak intensity of the high-angle side peak to the peak intensity of the low-angle side peak, that is, the peak intensity ratio (I H / I L ) is calculated.

[0073] Also, by analyzing the obtained XRD diffraction pattern by the Rietveld method, the crystallite size can be determined. In the Rietveld method, a diffraction pattern is calculated from a previously estimated crystal structure model. By fitting all of this calculated value and the measured value, parameters related to the crystal structure (lattice constant, atomic coordinates, occupancy, etc.) can be precisely analyzed. Thereby, the characteristics of the crystal structure of the synthesized oxide can be examined.

[0074] Here, the crystallite size is calculated from the Scherrer's equation shown in the following formula (1).

[0075]

Equation

[0076] <BET specific surface area> The BET (Brunauer, Emmett, Teller) specific surface area of the active material according to the embodiment is not particularly limited. However, the BET specific surface area is preferably 5 m 2 / g or more and less than 200 m 2 / g.

[0077] Specific surface area is 5m 2 / g or more, the contact area with the electrolyte can be secured, favorable discharge rate characteristics can be easily obtained, and the charging time can be shortened. 2 If the solubility is less than 1 / g, the reactivity with the electrolyte is not too high, thereby improving the life characteristics. In addition, the coating properties of the slurry containing the active material used in the production of the electrode described later can be improved.

[0078] Here, specific surface area is measured by adsorbing molecules with known adsorption areas onto the powder particle surfaces at liquid nitrogen temperature, and then determining the specific surface area of ​​the sample from the amount of adsorption. The most commonly used method is the BET method, which uses low-temperature, low-humidity physical adsorption of an inert gas. This is the most well-known method for calculating specific surface area, and extends the Langmuir theory, which is a theory of monolayer adsorption, to multilayer adsorption. The specific surface area determined in this way is called the BET specific surface area.

[0079] <Method for confirming the composition of complex oxides> The average composition of the niobium titanium composite oxide and the concentration of element A can be analyzed using, for example, inductively coupled plasma (ICP) emission spectroscopy.

[0080] <Confirmation of the solid solution state of complex oxides> The state of element A in the niobium titanium composite oxide and the state of the solid solution of elements M1 and M2 can be confirmed by transmission electron microscope (TEM)-energy dispersive X-ray spectroscopy (EDX). In addition, the concentration of element A inside the niobium titanium composite oxide particles and at the particle interface can be confirmed by element mapping analysis of the electrode cross section using scanning electron microscope (SEM)-EDX (energy dispersive X-ray spectroscopy).

[0081] <Measurement of electrode materials contained in electrodes> When the electrode material (active material) contained in the electrode is subjected to the above-mentioned powder X-ray diffraction measurement, ICP measurement, TEM-EDX measurement, specific surface area measurement by the BET method, and particle size distribution measurement by the laser diffraction scattering method, the target sample can be prepared, for example, as follows.

[0082] First, in order to understand the crystalline state of the active material, the niobium titanium composite oxide is placed in a state in which lithium ions are completely released. For example, when the negative electrode active material is the object of measurement, the battery is placed in a fully discharged state. However, even in a fully discharged state, residual lithium ions may remain in the negative electrode active material.

[0083] The battery is then disassembled in an argon-filled glove box, and the electrodes are removed and washed with a suitable solvent, such as ethyl methyl carbonate.

[0084] For powder X-ray diffraction measurements, the electrode cleaned as described above can be cut into a sample with the same area as the holder of the powder X-ray diffractometer, and the sample is then attached directly to a glass holder for measurement.

[0085] At this time, the peaks corresponding to the metal of the metal foil contained in the electrode are measured in advance using XRD to determine the positions of the peaks originating from the electrode substrate. The peak positions of other components, such as conductive additives and binders, are also measured and determined in advance using a similar method. If the peaks of the substrate material and the active material overlap, it is desirable to peel the active material from the substrate and measure it. This is to separate the overlapping peaks when quantitatively measuring the peak intensity. Of course, if these are known in advance, this step can be omitted.

[0086] For the measurement, the electrode layer may be physically peeled off from the current collector. Applying ultrasonic waves in a solvent facilitates peeling of the electrode layer from the current collector. An electrode powder sample can be prepared from the peeled electrode layer in this manner, or the active material particles can be isolated and subjected to the various measurements described above.

[0087] <Electrode material manufacturing method> The electrode material according to the embodiment can be produced by the synthesis method described below.

[0088] (Synthesis method) A niobium-titanium composite oxide having an average composition in which the molar ratio of niobium to titanium (Nb / Ti) is greater than 2 can be synthesized as follows. First, the starting materials are mixed. As the starting material containing niobium and titanium, an oxide or salt containing Nb and Ti is prepared. As the starting material containing element M1, an oxide or salt containing at least one element selected from the group consisting of Ta, Ti, V, Mo, and W is prepared. As the starting material containing element M2, an oxide or salt containing at least one element selected from the group consisting of Nb, Ta, Zr, Hf, and Sn is prepared. The salts used as starting materials are preferably salts that decompose at a relatively low temperature to produce an oxide, such as carbonates and nitrates.

[0089] These starting materials are mixed in a molar ratio that will result in the target composition. The resulting mixture is then pulverized to obtain a mixture that is as uniform as possible. The resulting mixture is then pre-baked (first baking). The pre-baking (first baking) is carried out in two or more stages at a temperature range of 500 to 900°C for a total of 10 to 40 hours. This allows for the production of highly uniform precursor particles.

[0090] Next, an oxide or salt containing at least one element A selected from the group consisting of potassium, iron, and phosphorus is prepared as a supply source of element A. The oxide or salt containing element A is added to the previously obtained precursor particles so that the concentration is within the range of 100 ppm to 2000 ppm, and wet-mixed. In this case, it is preferable to wet-mix the supply source containing element A with a raw material soluble in a solvent such as water, since this allows the element A to be uniformly distributed on the surface of the precursor particles.

[0091] Next, the mixture of precursor particles and element A obtained by wet mixing is subjected to main calcination (second calcination). The main calcination is preferably carried out at a temperature of 800°C to 1450°C for 1 to 10 hours. The main calcination is more preferably carried out at a temperature of 1000°C to 1450°C for 2.5 to 3.5 hours. By calcining at such a high temperature for a short period of time, the concentration of element A can be increased on the particle surface. The powder thus obtained is then subjected to mild pulverization in as short a time as possible, without applying as strong a shear as possible. For example, a roller compactor, a bead mill, or a ball mill can be used for this pulverization.

[0092] The D10, D50, and D90 of the resulting electrode material can be controlled by changing the milling conditions. For example, increasing the milling time tends to reduce the D10, D50, and D90. Furthermore, using milling media with smaller diameters tends to reduce the D10, D50, and D90. Alternatively, centrifuging the powder can capture particles with a small D10 or particles with a large D90. For example, the D10, D50, and D90 can be controlled by mixing the collected particles with a separately synthesized electrode material.

[0093] After pulverization, an annealing treatment may be performed. The annealing temperature is preferably 350°C or higher and 800°C or lower. By performing annealing treatment within this temperature range, it is possible to alleviate strain within the crystals and stabilize the crystalline state after pulverization. In other words, the crystallite size can be increased by annealing treatment. By performing main sintering after adding element A and combining this with a synthesis scheme in which pulverization is performed in a short time, active material particles with a large crystallite size can be obtained more effectively than with conventional annealing treatment.

[0094] As described above, when producing a niobium titanium composite oxide having an average composition in which the Nb / Ti ratio is greater than 2, by carrying out main sintering after the addition of element A and then mild pulverization, an electrode material having high crystallinity and a small proportion of fine powder can be obtained. For example, in a diffraction pattern obtained by powder X-ray diffraction of the electrode material thus obtained, if the electrode material contains an Nb2TiO7 phase having a composition in which the Nb / Ti ratio is greater than 2, the above-mentioned first peak intensity ratio may be less than 1. Furthermore, if the electrode material contains Nb 10 Ti2O 29 Phase, Nb 14 TiO 37 phase and Nb 24 TiO 62 When at least one of the phases is contained, the second peak intensity ratio may be less than 1.5.

[0095] The niobium titanium composite oxide synthesized by the above method may have lithium ions inserted therein by charging the assembled battery, or may be synthesized as a lithium-containing composite oxide by using a lithium-containing compound such as lithium carbonate as a starting material.

[0096] According to a first embodiment, an electrode material is provided. The electrode material has a molar ratio of niobium to titanium (M Nb / M TiThe electrode material comprises active material particles containing a niobium-titanium composite oxide having an average composition where the ratio of 1 to 2 is greater than 2, and at least one element A selected from the group consisting of potassium, iron, and phosphorus. The active material particles contain element A at a concentration in the range of 100 ppm to 2000 ppm. This electrode material contains active material particles with high crystallinity and a stable basic skeleton, and has a low proportion of fine powder, so it can exhibit excellent rapid charge / discharge characteristics and cycle life characteristics.

[0097] (Second embodiment) According to a second embodiment, an electrode is provided.

[0098] The electrode according to the second embodiment includes the electrode material according to the first embodiment. The electrode according to the embodiment may be a negative electrode or a positive electrode. The electrode according to the embodiment is, for example, a battery electrode, a secondary battery electrode, or a lithium secondary battery electrode. The electrode may be a negative electrode that includes the electrode material according to the first embodiment as a negative electrode material.

[0099] The electrode according to the second embodiment can include a current collector and an active material-containing layer. The active material-containing layer can be formed on one or both sides of the current collector. The active material-containing layer can include an active material and, optionally, a conductive agent and a binder.

[0100] The active material-containing layer may contain a single electrode material according to the first embodiment, or may contain two or more types of electrode materials according to the first embodiment, or may contain a mixture of one or more types of electrode materials according to the first embodiment and one or more types of other active materials.

[0101] For example, in the case of a negative electrode containing the electrode material according to the first embodiment as a negative electrode material, this negative electrode can contain an active material other than the niobium titanium composite oxide having an average composition with an Nb / Ti ratio of more than 2.

[0102] Other examples of active materials include lithium titanates with a ramsdellite structure (e.g., Li 2+yTi3O7, 0≦y≦3), lithium titanates with spinel structure (e.g., Li 4+x Ti5O 12 , 0≦x≦3), monoclinic titanium dioxide (TiO2), anatase titanium dioxide, rutile titanium dioxide, hollandite titanium composite oxide, and orthorhombic titanium-containing composite oxide. Furthermore, the electrode material may contain, as another active material, a niobium titanium composite oxide having an Nb / Ti ratio of 2. The proportion of niobium titanium composite oxide having an average composition with an Nb / Ti ratio of more than 2 in the active material particles contained in the electrode material is, for example, 50 mass% or more.

[0103] As an example of orthorhombic titanium-containing composite oxide, Li 2+a M(I) 2-b Ti 6-c M(II) d O 14+σ Examples of compounds represented by the formula (I) include compounds represented by the formula (I) above. Here, M(I) 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 subscripts in the composition formula are 0≦a≦6, 0≦b<2, 0≦c<6, 0≦d<6, and -0.5≦σ≦0.5. Specific examples of orthorhombic titanium-containing composite oxides include Li 2+a Na2Ti6O 14 (0≦a≦6).

[0104] The conductive agent is blended to improve current collection performance and reduce 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, and carbonaceous materials such as graphite. One of these may be used as the conductive agent, or two or more may be used in combination. Alternatively, instead of using a conductive agent, the surfaces of the active material particles may be coated with carbon or an electronically conductive inorganic material.

[0105] 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-containing rubber, styrene-butadiene rubber, polyacrylic acid compounds, imide compounds, carboxymethyl cellulose (CMC), and CMC salts. One of these may be used as the binder, or two or more may be used in combination as the binder.

[0106] The blending ratios of the electrode material, conductive agent, and binder in the active material-containing layer can be appropriately changed depending on the application of the electrode. For example, when the electrode is used as a negative electrode of a secondary battery, the electrode material, conductive agent, and binder are preferably blended in proportions of 68% by mass or more and 96% by mass or less, 2% by mass or more and 30% by mass or less, and 2% by mass or more and 30% by mass or less, respectively. By setting the amount of 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 binder to 2% by mass or more, sufficient binding between the active material-containing layer and the current collector can be achieved, and excellent cycle performance can be expected. On the other hand, it is preferable to set the amount of conductive agent and binder to 30% by mass or less each in order to achieve high capacity.

[0107] The current collector is made of a material that is electrochemically stable at the potential at which lithium (Li) is inserted into and extracted from the active material. For example, when the electrode material is used as a negative electrode material, the current collector is preferably made of copper, nickel, stainless steel, aluminum, or an aluminum alloy containing one or more elements selected from Mg, Ti, Zn, Mn, Fe, Cu, and Si. The thickness of the current collector is preferably 5 μm or more and 20 μm or less. A current collector with such a thickness can balance the strength and weight of the electrode.

[0108] The current collector may also include a portion on the surface of which no active material-containing layer is formed, and this portion can function as a current collecting tab.

[0109] The electrode can be produced, for example, by the following method. First, the electrode material according to the embodiment, 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 a current collector. Next, the applied slurry is dried to obtain a laminate of an active material-containing layer and a current collector. After that, this laminate is pressed. In this manner, the electrode is produced.

[0110] Alternatively, the electrode may be fabricated by the following method: First, an electrode material, a conductive agent, and a binder are mixed to obtain a mixture, and then the mixture is formed into pellets. These pellets are then placed on a current collector to obtain an electrode.

[0111] The electrode according to the second embodiment includes the electrode material according to the first embodiment, and therefore this electrode can realize a secondary battery that can exhibit excellent rapid charge / discharge characteristics and cycle life characteristics.

[0112] (Third embodiment) According to a 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. That is, the secondary battery according to the third embodiment includes an electrode including the electrode material according to the first embodiment as the negative electrode.

[0113] The secondary battery according to the embodiment may further include a separator disposed between the positive electrode and the negative electrode. The negative electrode, the positive electrode, and the separator may constitute an electrode assembly. The electrolyte may be held in the electrode assembly.

[0114] The secondary battery may further include an exterior member that houses the electrode group and the electrolyte.

[0115] Furthermore, the 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.

[0116] The secondary battery may be, for example, a lithium ion secondary battery, or a non-aqueous electrolyte secondary battery containing a non-aqueous electrolyte.

[0117] The negative electrode, positive electrode, electrolyte, separator, exterior member, negative electrode terminal, and positive electrode terminal will be described in detail below.

[0118] (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 can be the current collector and the active material-containing layer, respectively, that can be included in the electrode according to the second embodiment. The negative electrode active material-containing layer contains the electrode material according to the first embodiment as a negative electrode active material.

[0119] Details of the negative electrode that overlap with those described in the second embodiment will be omitted.

[0120] The density of the negative electrode active material-containing layer (excluding the current collector), i.e., the electrode density, is 1.8 g / cm 3 More than 3.5g / cm 3 A negative electrode having a negative electrode active material-containing layer with a density within this range is excellent in energy density and electrolyte retention. The density of the negative electrode active material-containing layer is preferably 2.5 g / cm or less. 3 More than 2.9g / cm 3 More preferably, it is:

[0121] The negative electrode can be produced, for example, by the same method as that for the electrode according to the second embodiment.

[0122] (2) Positive electrode The positive electrode may 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 may include a positive electrode active material and, optionally, a conductive agent and a binder.

[0123] As the positive electrode active material, for example, an oxide or a sulfide can be used. The positive electrode may contain, as the positive electrode active material, one type of compound alone, or may contain a combination of two or more types of compounds. Examples of the oxide and the sulfide include compounds into which Li or Li ions can be inserted and removed.

[0124] Examples of such compounds include, for example, manganese dioxide (MnO2), iron oxide, copper oxide, nickel oxide, lithium manganese composite oxide (for example, Li x Mn2O4 or Li x MnO2; 0 < x ≦ 1), lithium nickel composite oxide (for example, Li x NiO2; 0 < x ≦ 1), lithium cobalt composite oxide (for example, Li x CoO2; 0 < x ≦ 1), lithium nickel cobalt composite oxide (for example, Li x Ni 1-y Co y O2; 0 < x ≦ 1, 0 < y < 1), lithium manganese cobalt composite oxide (for example, Li x Mn y Co 1-y O2; 0 < x ≦ 1, 0 < y < 1), lithium manganese nickel composite oxide having a spinel structure (for example, Li x Mn 2-y [[ID=X]] y Ni y O4; 0 < x ≦ 1, 0 < y < 2), lithium phosphate having an olivine structure (for example, Li x FePO4; 0 < x ≦ 1, Li x Fe 1-y Mn y PO4; 0 < x ≦ 1, 0 < y < 1, Li x CoPO4; 0 < x ≦ 1), iron sulfate (Fe2(SO4)3), vanadium oxide (for example, V2O5), and lithium nickel cobalt manganese composite oxide (Li x Ni 1-y-z Co y Mn z O2; 0 < x ≦ 1, 0 < y < ) are included. [[ID=X]]

[0125] [[ID=X]] It should be noted that there seems to be an error in the original text where the formula in line 48 has a missing value after the last comma. I translated it as it is but this might need to be corrected in the original source for a complete and accurate representation. Also, there are some repeated tags in the source which might be a formatting issue. I've left them as they are according to the translation rules.Among the above, examples of more preferable compounds as the positive electrode active material include lithium manganese composite oxides having a spinel structure (for example, Li x Mn2O4; 0 < x ≦ 1), lithium nickel composite oxides (for example, Li x NiO2; 0 < x ≦ 1), lithium cobalt composite oxides (for example, Li x CoO2; 0 < x ≦ 1), lithium nickel cobalt composite oxides (for example, Li x Ni 1-y Co y O2; 0 < x ≦ 1, 0 < y < 1), lithium manganese nickel composite oxides having a spinel structure (for example, Li x Mn 2-y Ni y O4; 0 < x ≦ 1, 0 < y < 2), lithium manganese cobalt composite oxides (for example, Li x Mn y Co 1-y O2; 0 < x ≦ 1, 0 < y < 1), lithium iron phosphate (for example, Li x FePO4; 0 < x ≦ 1), and lithium nickel cobalt manganese composite oxides (Li x Ni 1-y-z Co y Mn z O2; 0 < x ≦ 1, 0 < y < 1, 0 < z < 1, y + z < 1) are included. When these compounds are used as the positive electrode active material, the positive electrode potential can be increased.

[0126] When a room temperature molten salt is used as the electrolyte of the battery, it is preferable to use a positive electrode active material containing lithium iron phosphate, Li x VPO4F (0 ≦ x ≦ 1), a lithium manganese composite oxide, a lithium nickel composite oxide, a lithium nickel cobalt composite oxide, or a mixture thereof. Since these compounds have low reactivity with the room temperature molten salt, the cycle life can be improved. Details of the room temperature molten salt will be described later.

[0127] The primary particle diameter of the positive electrode active material is preferably 100 nm or more and 1 μm or less. A positive electrode active material with a primary particle diameter of 100 nm or more is easy to handle in industrial production. A positive electrode active material with a primary particle diameter of 1 μm or less allows smooth diffusion of lithium ions within the solid.

[0128] The specific surface area of ​​the positive electrode active material is 0.1 m 2 / g or more 10m 2 / g or less is preferable. 2 A positive electrode active material with a specific surface area of ​​10m / g or more can secure sufficient sites for absorbing and releasing Li ions. 2 A positive electrode active material having a specific surface area of ​​0.15g / g or less is easy to handle in industrial production and can ensure good charge-discharge cycle performance.

[0129] The binder is blended to fill gaps between the dispersed positive electrode active material and to bind the positive electrode active material and the positive electrode current collector. Examples of binders include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), fluorine-containing rubber, polyacrylic acid compounds, imide compounds, carboxymethyl cellulose (CMC), and CMC salts. One of these may be used as the binder, or two or more may be used in combination as the binder.

[0130] The conductive agent is blended to improve current collection performance and reduce 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 the conductive agent, or two or more may be used in combination as the conductive agent. The conductive agent may also be omitted.

[0131] In the positive electrode active material-containing layer, the positive electrode active material and the binder are preferably mixed in proportions of 80% by mass to 98% by mass and 2% by mass to 20% by mass, respectively.

[0132] By using a binder amount of 2% by mass or more, sufficient electrode strength can be obtained. Furthermore, the binder can function as an insulator. Therefore, by using a binder amount of 20% by mass or less, the amount of insulator contained in the electrode is reduced, thereby reducing internal resistance.

[0133] When a conductive agent is added, the positive electrode active material, binder, and conductive agent are preferably mixed in proportions 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, respectively.

[0134] By setting the amount of conductive agent to 3% by mass or more, the above-mentioned effects can be achieved. Furthermore, by setting the amount of conductive agent to 15% by mass or less, the proportion of conductive agent in contact with the electrolyte can be reduced. This low proportion can reduce decomposition of the electrolyte during high-temperature storage.

[0135] The positive electrode current collector is preferably an aluminum foil or an aluminum alloy foil containing one or more elements selected from Mg, Ti, Zn, Ni, Cr, Mn, Fe, Cu, and Si.

[0136] 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. The purity of the aluminum foil is preferably 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.

[0137] The positive electrode current collector may also include a portion on the surface of which the positive electrode active material-containing layer is not formed, and this portion can function as a positive electrode current collecting tab.

[0138] The positive electrode can be produced, for example, using a positive electrode active material by the same method as that for the electrode according to the second embodiment.

[0139] (3) Electrolyte The electrolyte may be, for example, a liquid nonaqueous electrolyte or a gel nonaqueous electrolyte. The liquid nonaqueous 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.

[0140] Examples of electrolyte salts include lithium salts such as lithium perchlorate (LiClO), lithium hexafluorophosphate (LiPF), lithium tetrafluoroborate (LiBF), lithium hexafluoride (LiAsF), lithium trifluoromethanesulfonate (LiCFSO), and lithium bistrifluoromethylsulfonylimide (LiN(CFSO)), and mixtures thereof. The electrolyte salt is preferably one that is difficult to oxidize even at high potentials, and LiPF is most preferred.

[0141] Examples of organic solvents include cyclic carbonates such as propylene carbonate (PC), ethylene carbonate (EC), and vinylene carbonate (VC); linear carbonates such as diethyl carbonate (DEC), dimethyl carbonate (DMC), and methyl ethyl carbonate (MEC); cyclic ethers such as tetrahydrofuran (THF), 2-methyl tetrahydrofuran (2MeTHF), and dioxolane (DOX); linear ethers such as dimethoxyethane (DME) and diethoxyethane (DEE); γ-butyrolactone (GBL), acetonitrile (AN), and sulfolane (SL). These organic solvents can be used alone or in combination.

[0142] The gel-like non-aqueous electrolyte is prepared by combining a liquid non-aqueous electrolyte with a polymeric material, such as polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), polyethylene oxide (PEO), or a mixture thereof.

[0143] Alternatively, in addition to liquid nonaqueous electrolytes and gel nonaqueous electrolytes, room temperature molten salts containing lithium ions (ionic melts), polymer solid electrolytes, inorganic solid electrolytes, and the like may be used as the nonaqueous electrolyte.

[0144] Room-temperature molten salts (ionic melts) refer to organic salts consisting of a combination of organic cations and anions that can exist as a liquid at room temperature (15°C or higher and 25°C or lower). Room-temperature molten salts include room-temperature molten salts that exist as a liquid on their own, 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. Generally, the melting point of room-temperature molten salts used in secondary batteries is 25°C or lower. Furthermore, organic cations generally have a quaternary ammonium skeleton.

[0145] The solid polymer electrolyte is prepared by dissolving an electrolyte salt in a polymer material and solidifying it.

[0146] The inorganic solid electrolyte is a solid material that has Li-ion conductivity.

[0147] The electrolyte may be an aqueous electrolyte containing water.

[0148] The aqueous electrolyte includes an aqueous solvent and an electrolyte salt. The aqueous electrolyte is, for example, liquid. The liquid aqueous electrolyte is an aqueous solution prepared by dissolving an electrolyte salt as a solute in an aqueous solvent. The aqueous solvent is, for example, a solvent containing 50% or more by volume of water. The aqueous solvent may be pure water.

[0149] The aqueous electrolyte may be a gel-like aqueous electrolyte obtained by combining an aqueous electrolytic solution with a polymeric material, such as polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), or polyethylene oxide (PEO).

[0150] The aqueous electrolyte preferably contains 1 mol or more of aqueous solvent per 1 mol of solute salt, and more preferably 3.5 mol or more of aqueous solvent per 1 mol of solute salt.

[0151] The presence of water in aqueous electrolytes can be confirmed by GC-MS (Gas Chromatography-Mass Spectrometry). The salt concentration and water content in aqueous electrolytes can be calculated using, for example, ICP (Inductively Coupled Plasma) optical emission spectrometry. The molar concentration (mol / L) can be calculated by weighing a specified amount of aqueous electrolyte and calculating the salt concentration. Furthermore, the number of moles of solute and solvent can be calculated by measuring the specific gravity of the aqueous electrolyte.

[0152] The aqueous electrolyte is prepared, for example, by dissolving an electrolyte salt in an aqueous solvent at a concentration of 1 to 12 mol / L.

[0153] To suppress electrolysis of the aqueous electrolyte, LiOH or Li2SO4 can be added to adjust the pH, preferably 3-13, more preferably 4-12.

[0154] (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 formed from polyethylene or polypropylene, because these porous films melt at a certain temperature and can interrupt current.

[0155] A solid electrolyte layer containing solid electrolyte particles can also be used as the separator. The solid electrolyte layer may contain one type of solid electrolyte particles or multiple types of solid electrolyte particles. The solid electrolyte layer may be a solid electrolyte composite membrane containing solid electrolyte particles. The solid electrolyte composite membrane is, for example, a membrane formed by molding solid electrolyte particles using a polymer material. The solid electrolyte layer may contain at least one selected from the group consisting of a plasticizer and an electrolyte salt. When the solid electrolyte layer contains an electrolyte salt, for example, the alkali metal ion conductivity of the solid electrolyte layer can be further increased.

[0156] Examples of polymeric materials include polyethers, polyesters, polyamines, polyethylenes, silicones, and polysulfides.

[0157] As the solid electrolyte, an inorganic solid electrolyte is preferably used. Examples of inorganic solid electrolytes include oxide-based solid electrolytes and sulfide-based solid electrolytes. As the oxide-based solid electrolyte, a lithium phosphate solid electrolyte having a NASICON structure and represented by the general formula LiM2(PO4)3 is preferably used. In the general formula, M is preferably at least one element selected from the group consisting of titanium (Ti), germanium (Ge), strontium (Sr), zirconium (Zr), tin (Sn), and aluminum (Al). More preferably, the element M contains any one of Ge, Zr, and Ti, and Al.

[0158] A specific example of a lithium phosphate solid electrolyte with a NASICON structure is LATP (Li 1+x Al x Ti 2-x (PO4)3), Li 1+x Al x Ge 2-x (PO4)3, Li 1+x Al x Zr 2-x(PO4)3 can be cited. In the above formula, x is within the range of 0 < x ≦ 5, and preferably within the range of 0.1 ≦ x ≦ 0.5. As the solid electrolyte, it is preferable to use LATP. LATP has excellent water resistance and is less likely to cause hydrolysis in a secondary battery.

[0159] Also, as the oxide-based solid electrolyte, amorphous LIPON (Li 2.9 PO 3.3 N 0.46 ), or garnet-type LLZ (Li7La3Zr2O 12 ) may be used.

[0160] (5) Outer packaging member As the outer packaging member, for example, a container made of a laminate film or a metal container can be used.

[0161] The thickness of the laminate film is, for example, 0.5 mm or less, and preferably 0.2 mm or less.

[0162] 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 contains, for example, polymer materials such as polypropylene (PP), polyethylene (PE), nylon, and polyethylene terephthalate (PET). The metal layer is preferably made of aluminum foil or an aluminum alloy foil for weight reduction. The laminate film can be formed into the shape of the outer packaging member by sealing through heat fusion.

[0163] The thickness of the wall of the metal container is, for example, 1 mm or less, more preferably 0.5 mm or less, and even more preferably 0.2 mm or less.

[0164] The metal container is made of, for example, aluminum or an aluminum alloy. The aluminum alloy preferably contains elements such as magnesium, zinc, and silicon. If the aluminum alloy contains transition metals such as iron, copper, nickel, and chromium, the content of these metals is preferably 100 mass ppm or less.

[0165] The shape of the exterior member is not particularly limited. The shape of the exterior member may be, for example, flat (thin), rectangular, cylindrical, coin-shaped, or button-shaped. The exterior member can be appropriately selected depending on the battery dimensions and the intended use of the battery.

[0166] (6) Negative terminal The negative electrode terminal can be formed from a material that is electrochemically stable at the Li absorption / desorption potential of the above-mentioned negative electrode active material and has electrical conductivity. Specifically, the material for the negative electrode terminal can be copper, nickel, stainless steel, aluminum, or an aluminum alloy containing at least one element selected from the group consisting of Mg, Ti, Zn, Mn, Fe, Cu, and Si. Aluminum or an aluminum alloy is preferably used 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.

[0167] (7) Positive terminal The positive electrode terminal has a potential range of 3V to 5V relative to the redox potential of lithium (vs. Li / Li + ) and can be formed from a material that is electrically stable and conductive. Examples of materials for the positive electrode terminal include aluminum and aluminum alloys 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.

[0168] Next, the secondary battery according to the third embodiment will be described in more detail with reference to the drawings.

[0169] Fig. 3 is a cross-sectional view schematically showing an example of a secondary battery according to Embodiment 3. Fig. 4 is an enlarged cross-sectional view of part A of the secondary battery shown in Fig. 3.

[0170] 3 and 4 includes a bag-shaped exterior member 2 shown in Fig. 3 and 4, an electrode group 1 shown in Fig. 4, and an electrolyte (not shown). The electrode group 1 and the electrolyte are housed in the bag-shaped exterior member 2. The electrolyte (not shown) is held in the electrode group 1.

[0171] The bag-shaped exterior member 2 is made of a laminate film including two resin layers and a metal layer interposed between them.

[0172] As shown in Fig. 3, the electrode group 1 is a flat wound electrode group. As shown in Fig. 4, the flat wound electrode group 1 includes a negative electrode 3, a separator 4, and a positive electrode 5. The separator 4 is interposed between the negative electrode 3 and the positive electrode 5.

[0173] The negative electrode 3 includes a negative electrode current collector 3a and a negative electrode active material-containing layer 3b. In the portion of the negative electrode 3 located at the outermost shell of the wound-type electrode group 1, the 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. 4. In the other portions of the negative electrode 3, the negative electrode active material-containing layer 3b is formed on both sides of the negative electrode current collector 3a.

[0174] The positive electrode 5 includes a positive electrode current collector 5a and positive electrode active material-containing layers 5b formed on both sides of the positive electrode current collector 5a.

[0175] As shown in FIG. 3, the negative electrode terminal 6 and the positive electrode terminal 7 are located near the outer peripheral edge of the wound electrode group 1. The negative electrode terminal 6 is connected to a portion located at the outermost shell of the negative electrode current collector 3a. The positive electrode terminal 7 is connected to a portion located at the outermost shell of the positive electrode current collector 5a. The negative electrode terminal 6 and the positive electrode terminal 7 extend to the outside from an 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 the thermoplastic resin layer.

[0176] The secondary battery according to the third 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.

[0177] Fig. 5 is a partially cutaway perspective view schematically showing another example of the secondary battery according to Embodiment 3. Fig. 6 is an enlarged cross-sectional view of part B of the secondary battery shown in Fig. 5.

[0178] 5 and 6 includes an electrode group 1 shown in Fig. 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 in the exterior member 2. The electrolyte is held in the electrode group 1.

[0179] The exterior member 2 is made of a laminate film including two resin layers and a metal layer interposed between them.

[0180] The electrode group 1 is a laminated electrode group, as shown in Fig. 6. The laminated electrode group 1 has a structure in which negative electrodes 3 and positive electrodes 5 are alternately laminated with separators 4 interposed therebetween.

[0181] 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 sides of the negative electrode current collector 3a. The electrode group 1 also 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 sides of the positive electrode current collector 5a.

[0182] The negative electrode current collector 3a of each negative electrode 3 includes a portion 3c on one side where no negative electrode active material-containing layer 3b is supported on any surface. This portion 3c serves as a negative electrode current collector tab. As shown in FIG. 6, the portion 3c serving as the negative electrode current collector tab does not overlap with the positive electrode 5. The multiple negative electrode current collector tabs (portions 3c) are electrically connected to a strip-shaped negative electrode terminal 6. The tip of the strip-shaped negative electrode terminal 6 is pulled out to the outside of the exterior member 2.

[0183] Although not shown, the positive electrode current collector 5a of each positive electrode 5 includes a portion on one side where the positive electrode active material-containing layer 5b is not supported on any surface. This portion functions as a positive electrode current collector tab. Like the negative electrode current collector tab (portion 3c), the positive electrode current collector tab does not overlap with the negative electrode 3. The positive electrode current collector tab is located on the opposite side of the electrode group 1 from the negative electrode current collector tab (portion 3c). The positive electrode current collector tab is electrically connected to a strip-shaped positive electrode terminal 7. The tip of the strip-shaped positive electrode terminal 7 is located on the opposite side from the negative electrode terminal 6 and is drawn out to the outside of the exterior member 2.

[0184] The secondary battery according to the third embodiment contains the active material according to the first embodiment as the negative electrode active material, and therefore, this secondary battery can exhibit excellent rapid charge / discharge characteristics and cycle life characteristics.

[0185] (Fourth embodiment) According to a fourth embodiment, there is provided a battery pack. The battery pack according to the fourth embodiment includes a plurality of secondary batteries according to the third embodiment.

[0186] In the battery pack according to the fourth embodiment, the cells may be electrically connected in series or in parallel, or may be connected in a combination of series and parallel.

[0187] Next, an example of a battery pack according to a fourth embodiment will be described with reference to the drawings.

[0188] Fig. 7 is a perspective view schematically showing an example of a battery pack according to the fourth embodiment. The battery pack 200 shown in Fig. 7 includes five cells 100a to 100e, four bus bars 21, a positive electrode lead 22, and a negative electrode lead 23. Each of the five cells 100a to 100e is a secondary battery according to the third embodiment.

[0189] The bus bar 21 connects, for example, the negative electrode terminal 6 of one cell 100a to the positive electrode terminal 7 of the adjacent cell 100b. In this way, the five cells 100 are connected in series by four bus bars 21. That is, the battery pack 200 in FIG. 7 is a five-series battery pack. Although an example is not shown, in a battery pack including a plurality of cells electrically connected in parallel, the plurality of cells can be electrically connected by, for example, connecting the negative electrode terminals to each other by a bus bar and connecting the positive electrode terminals to each other by a bus bar.

[0190] The positive terminal 7 of at least one of the five cells 100a-100e is electrically connected to a positive electrode lead 22 for external connection. The negative terminal 6 of at least one of the five cells 100a-100e is electrically connected to a negative electrode lead 23 for external connection.

[0191] The battery pack according to the fourth embodiment includes the secondary battery according to the third embodiment, and therefore, this battery pack can exhibit excellent rapid charge / discharge characteristics and cycle life characteristics.

[0192] (Fifth embodiment) According to a fifth embodiment, there is provided a battery pack. This battery pack includes the battery assembly according to the fourth embodiment. This battery pack may include a single secondary battery according to the third embodiment instead of the battery assembly according to the fourth embodiment.

[0193] The battery pack according to the fifth embodiment may further include a protection circuit. The protection circuit has a function of controlling the 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, automobile, etc.) may be used as the protection circuit for the battery pack.

[0194] The battery pack according to the fifth embodiment may further include external terminals for current flow. The external terminals for current flow are 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 terminals for current flow. When charging the battery pack, charging current (including regenerative energy from the power of an automobile or the like) is supplied to the battery pack through the external terminals for current flow.

[0195] Next, an example of a battery pack according to a fifth embodiment will be described with reference to the drawings.

[0196] Fig. 8 is an exploded perspective view schematically showing an example of a battery pack according to Embodiment 5. Fig. 9 is a block diagram showing an example of an electric circuit of the battery pack shown in Fig. 8.

[0197] The battery pack 300 shown in FIGS. 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).

[0198] The storage container 31 shown in Fig. 8 is a bottomed, square container having a rectangular bottom. The storage container 31 is configured to be able to accommodate a protective sheet 33, a battery pack 200, a printed wiring board 34, and wiring 35. The lid 32 has a rectangular shape. The lid 32 covers the storage container 31 to accommodate the battery pack 200 and other components. Although not shown, the storage container 31 and the lid 32 are provided with openings or connection terminals for connection to external devices and the like.

[0199] The battery pack 200 includes a plurality of cells 100, a positive electrode lead 22, a negative electrode lead 23, and an adhesive tape 24.

[0200] At least one of the plurality of cells 100 is a secondary battery according to the third embodiment. The plurality of cells 100 are electrically connected in series as shown in FIG. 9. The plurality of cells 100 may be electrically connected in parallel, or may be connected in a combination of series and parallel connections. When the plurality of cells 100 are connected in parallel, the battery capacity increases compared to when they are connected in series.

[0201] The adhesive tape 24 fastens the plurality of cells 100 together. Heat-shrinkable tape may be used to secure the plurality of cells 100 together instead of the adhesive tape 24. In this case, protective sheets 33 are placed on both side surfaces of the battery pack 200, and the heat-shrinkable tape is wrapped around the cells 100, and the heat-shrinkable tape is then thermally shrunk to bind the plurality of cells 100 together.

[0202] One end of the positive electrode lead 22 is connected to the battery pack 200. One end of the positive electrode lead 22 is electrically connected to the positive electrode of one or more cells 100. One end of the negative electrode lead 23 is connected to the battery pack 200. One end of the negative electrode lead 23 is electrically connected to the negative electrode of one or more cells 100.

[0203] The printed wiring board 34 is installed along one of the shorter sides of the inner surface of the container 31. The printed wiring board 34 includes a positive connector 342, a negative connector 343, a thermistor 345, a protection circuit 346, wires 342a and 343a, an external terminal 350 for supplying current, a positive wire (positive wire) 348a, and a negative wire (negative wire) 348b. One main surface of the printed wiring board 34 faces one side of the battery pack 200. An insulating plate (not shown) is interposed between the printed wiring board 34 and the battery pack 200.

[0204] 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.

[0205] The thermistor 345 is fixed to one main surface of the printed wiring board 34. The thermistor 345 detects the temperature of each of the cells 100 and transmits the detection signal to the protection circuit 346.

[0206] The external terminals 350 for applying current are fixed to the other main surface of the printed wiring board 34. The external terminals 350 for applying current are electrically connected to devices located outside the battery pack 300. The external terminals 350 for applying current include a positive terminal 352 and a negative terminal 353.

[0207] 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 a positive wiring 348a. The protection circuit 346 is connected to the negative terminal 353 via a negative wiring 348b. The protection circuit 346 is also electrically connected to the positive connector 342 via a wiring 342a. The protection circuit 346 is electrically connected to the negative connector 343 via a wiring 343a. The protection circuit 346 is also electrically connected to each of the plurality of single cells 100 via wiring 35.

[0208] The protective sheet 33 is disposed on both inner surfaces of the long sides of the container 31 and on the inner surface of the short side that faces the printed wiring board 34 across the battery pack 200. The protective sheet 33 is made of, for example, resin or rubber.

[0209] The protection circuit 346 controls charging and discharging of the plurality of cells 100. Furthermore, the protection circuit 346 cuts off the electrical connection between the protection circuit 346 and external terminals 350 (positive terminal 352, negative terminal 353) for supplying electricity to an external device, based on a detection signal transmitted from the thermistor 345 or a detection signal transmitted from each cell 100 or the battery pack 200.

[0210] An example of the detection signal transmitted from the thermistor 345 is a signal indicating that the temperature of the cell 100 is equal to or higher than a predetermined temperature. An example of the detection signal transmitted from each cell 100 or the battery pack 200 is a signal indicating that overcharge, overdischarge, or overcurrent of the cell 100 is detected. When detecting overcharge 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.

[0211] The protection circuit 346 may be a circuit included in a device (such as an electronic device or an automobile) that uses the battery pack 300 as a power source.

[0212] As described above, the battery pack 300 is also provided with the external terminals 350 for current application. Therefore, the battery pack 300 can output current from the battery assembly 200 to an external device and input current from the external device to the battery assembly 200 via the external terminals 350 for current application. In other words, when the battery pack 300 is used as a power source, the current from the battery assembly 200 is supplied to the external device via the external terminals 350 for current application. When the battery pack 300 is charged, a charging current from the external device is supplied to the battery pack 300 via the external terminals 350 for current application. When the battery pack 300 is used as an in-vehicle battery, regenerative energy from the vehicle's power can be used as the charging current from the external device.

[0213] 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 and negative terminals of the external terminals for supplying current, respectively.

[0214] Such a battery pack is used in applications requiring excellent cycle performance when drawing a large current, for example. Specifically, this battery pack is used, for example, as a power source for electronic devices, a stationary battery, or an on-board battery for various vehicles. Examples of electronic devices include digital cameras. This battery pack is particularly suitable for use as an on-board battery.

[0215] 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, and therefore exhibits excellent rapid charge / discharge characteristics and cycle life characteristics.

[0216] (Sixth embodiment) According to a sixth embodiment, a vehicle is provided, which is equipped with the battery pack according to the fifth embodiment.

[0217] In the vehicle according to the sixth embodiment, the battery pack recovers, for example, regenerative energy for powering the vehicle. The vehicle may include a mechanism for converting the kinetic energy of the vehicle into regenerative energy.

[0218] Examples of the vehicle according to the sixth embodiment include two-wheeled to four-wheeled hybrid electric vehicles, two-wheeled to four-wheeled electric vehicles, power-assisted bicycles, and railroad cars.

[0219] The mounting position of the battery pack in a vehicle is not particularly limited. For example, when the battery pack is mounted in an automobile, the battery pack can be mounted in the engine compartment, the rear of the vehicle body, or under the seat of the vehicle.

[0220] 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, in parallel, or a combination of series and parallel connections. For example, if each battery pack includes a battery pack, the battery packs may be electrically connected in series, in parallel, or a combination of series and parallel connections. Alternatively, if each battery pack includes a single battery, the batteries may be electrically connected in series, in parallel, or a combination of series and parallel connections.

[0221] Next, an example of a vehicle according to a sixth embodiment will be described with reference to the drawings.

[0222] FIG. 10 is a partial perspective view schematically illustrating an example of a vehicle according to the embodiment.

[0223] A vehicle 400 shown in Fig. 10 includes a vehicle body 40 and a battery pack 300 according to the embodiment. In the example shown in Fig. 10, the vehicle 400 is a four-wheeled automobile.

[0224] The vehicle 400 may be equipped with a plurality of battery packs 300. In this case, the batteries (for example, single cells or assembled batteries) included in the battery packs 300 may be connected in series, in parallel, or in a combination of series and parallel connections.

[0225] 10 illustrates an example in which the battery pack 300 is mounted in an engine compartment located in the front of the vehicle body 40. As described above, the battery pack 300 may be mounted, for example, at the rear of the vehicle body 40 or under a seat. This battery pack 300 can be used as a power source for the vehicle 400. In addition, this battery pack 300 can recover regenerative energy for powering the vehicle 400.

[0226] Next, with reference to FIG. 11, an embodiment of a vehicle according to a sixth embodiment will be described.

[0227] Fig. 11 is a diagram that schematically shows an example of a control system related to an electrical system in a vehicle according to Embodiment 6. A vehicle 400 shown in Fig. 11 is an electric vehicle.

[0228] The vehicle 400 shown in FIG. 11 comprises a vehicle body 40, a vehicle power supply 41, a vehicle ECU (ECU: Electric Control Unit) 42 which is a higher-level control device of the vehicle power supply 41, an external terminal (terminal for connecting to an external power supply) 43, an inverter 44, and a drive motor 45.

[0229] Vehicle 400 has vehicle power supply 41 mounted, for example, in the engine compartment, the rear of the vehicle body, or under the seat. Note that in vehicle 400 shown in Fig. 11, the mounting location of vehicle power supply 41 is shown schematically.

[0230] The vehicle power supply 41 includes a plurality of (for example, three) battery packs 300a, 300b, and 300c, a battery management unit (BMU) 411, and a communication bus 412.

[0231] The battery pack 300a includes an assembled battery 200a and an assembled battery monitoring device 301a (for example, a voltage temperature monitor (VTM)). 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. The battery packs 300a-300c are the same as the battery pack 300 described above, and the assembled batteries 200a-200c are the same as the assembled battery 200 described above. The assembled batteries 200a-200c are electrically connected in series. The battery packs 300a, 300b, and 300c can each be removed independently and replaced with another battery pack 300.

[0232] Each of the assembled batteries 200a-200c includes a plurality of unit cells connected in series. At least one of the unit cells is a secondary battery according to the second embodiment. Each of the assembled batteries 200a-200c is charged and discharged via a positive terminal 413 and a negative terminal 414.

[0233] The battery management device 411 communicates with the assembled battery monitoring devices 301a-301c and collects information on the voltage, temperature, etc. of each of the cells 100 included in the assembled batteries 200a-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.

[0234] The battery management unit 411 and the assembled battery monitoring units 301a-301c are connected via a communication bus 412. In the communication bus 412, one set of communication lines is shared by multiple nodes (the battery management unit 411 and one or more assembled battery monitoring units 301a-301c). The communication bus 412 is a communication bus configured based on, for example, the CAN (Control Area Network) standard.

[0235] The battery pack monitoring devices 301a-301c measure the voltage and temperature of each of the cells constituting the battery packs 200a-200c based on commands received through communication from the battery management device 411. However, the temperature can be measured at only a few locations per battery pack, and it is not necessary to measure the temperature of all the cells.

[0236] The vehicle power supply 41 may also have an electromagnetic contactor (e.g., a switch device 415 shown in FIG. 11 ) that switches between electrical connection and disconnection between the positive terminal 413 and the negative terminal 414. The switch device 415 includes a pre-charge switch (not shown) that is turned on when the assembled batteries 200a-200c are being charged, and a main switch (not shown) that is turned on when the output from the assembled batteries 200a-200c is being supplied to a load. The pre-charge switch and the main switch each include a relay circuit (not shown) that is switched on or off by a signal supplied to a coil disposed near the switch element. Electromagnetic contactors such as the switch device 415 are controlled based on a control signal from the battery management device 411 or the vehicle ECU 42 that controls the operation of the entire vehicle 400.

[0237] The inverter 44 converts the input DC voltage into a three-phase alternating current (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 control signals from the battery management unit 411 or the vehicle ECU 42, which controls the operation of the entire vehicle. By controlling the inverter 44, the output voltage from the inverter 44 is adjusted.

[0238] The drive motor 45 is rotated by the electric power supplied from the inverter 44. The drive force generated by the rotation of the drive motor 45 is transmitted to the axles and drive wheels W via, for example, a differential gear unit.

[0239] Although not shown, vehicle 400 also includes a regenerative braking mechanism (regenerator). When vehicle 400 is braked, regenerative braking mechanism rotates drive motor 45 and converts kinetic energy into regenerative energy as electrical energy. The regenerative energy recovered by the regenerative braking mechanism is input to inverter 44 and converted into direct current. The converted direct current is input to vehicle power supply 41.

[0240] One terminal of a 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 a 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.

[0241] One terminal of a connection line L2 is connected to the positive terminal 413 of the vehicle power supply 41. The other terminal of the connection line L2 is connected to a positive input terminal 418 of the inverter 44. A switch device 415 is provided on the connection line L2 between the positive terminal 413 and the positive input terminal 418.

[0242] 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.

[0243] In response to operational inputs from the driver or the like, the vehicle ECU 42 coordinates with other management devices and control devices including the battery management device 411 to control the vehicle power supply 41, the switch device 415, the inverter 44, etc. Through the coordinated control of the vehicle ECU 42, etc., the output of power from the vehicle power supply 41 and the charging of the vehicle power supply 41 are controlled, thereby managing the entire vehicle 400. Data relating to the maintenance of the vehicle power supply 41, such as the remaining capacity of the vehicle power supply 41, is transferred between the battery management device 411 and the vehicle ECU 42 via a communication line.

[0244] The vehicle according to the sixth embodiment is equipped with the battery pack according to the fifth embodiment. Therefore, according to this embodiment, it is possible to provide a vehicle equipped with a battery pack that can exhibit excellent rapid charge / discharge characteristics and cycle life characteristics.

[0245] [Example] Examples will be described below, but the embodiments are not limited to the examples described below.

[0246] Examples 1 to 6 The electrode material was synthesized by the solid phase synthesis method described below. First, Nb 10 Ti2O 29 To obtain the active material particles, Nb2O5 particles and TiO2 particles were mixed in a dry ball mill at a molar ratio of 5:2. The resulting powder was placed in an alumina crucible and heated at 800°C for 10 hours. The resulting powder was then ground and mixed, and then pre-fired (first firing) at 800°C for 10 hours to obtain precursor particles. In Example 1, potassium carbonate (K2CO3) was added to the precursor particles so that the element K was 100 ppm in the resulting active material particles, and wet mixing was performed using pure water to obtain a wet mixture. Similarly, potassium carbonate was added to Example 2 at 200 ppm, Example 3 at 500 ppm, Example 4 at 1000 ppm, Example 5 at 1500 ppm, and Example 6 at 2000 ppm.

[0247] Next, the wet mixture of the precursor particles and K2CO3 was fired for 3 hours in a main firing (second firing) at a temperature of 1150°C. The powder thus obtained was pulverized in an agate ball mill using a 10 mm diameter pulverization medium at 500 rpm for 30 minutes to obtain the electrode materials according to Examples 1 to 6.

[0248] Example 7 An electrode material was synthesized in the same manner as in Example 1, except that iron chloride (FeCl3) was added to the obtained active material particles so that the element Fe was 500 ppm.

[0249] Example 8 An electrode material was synthesized in the same manner as in Example 1, except that orthophosphoric acid (H3PO4) was added to the obtained active material particles so that the element P was 500 ppm.

[0250] Examples 9 to 12 In order to adjust the particle size distribution, the grinding conditions of the electrode material synthesized in the same manner as described in Example 3 were changed.

[0251] In Example 9, the grinding time using an agate ball mill was shortened to 15 minutes. In Example 10, grinding was performed for 60 minutes using an agate ball mill containing grinding media with a volume ratio of 10 mm and 5 mm. In Example 11, the powder obtained after the main firing was first coarsely ground in a mortar, and the coarsely ground sample was dispersed in water and allowed to settle and separate, thereby collecting particles with a large D90. The collected particles with a large D90 were mixed with the particles obtained in Example 3 to obtain an electrode material. In Example 12, the electrode material obtained according to Example 3 was first centrifuged to collect particles with a small D10. The collected particles with a small D10 were mixed with the particles obtained in Example 3 to obtain an electrode material.

[0252] (Examples 13 to 18) An electrode material was synthesized in the same manner as in Example 1, except that NbO particles and TiO particles were mixed at an adjusted molar ratio to obtain a niobium titanium composite oxide with the composition shown in the "Composite oxide composition" column in Table 1 below, and at least one element selected from the group consisting of potassium carbonate (KCO), iron chloride (FeCl), and orthophosphoric acid (HPO) was added so that the concentration of element A would be the concentration shown in the "Element A / concentration" column in Table 1.

[0253] (Examples 19 to 32) An electrode material was synthesized in the same manner as in Example 1, except that NbO particles, TiO particles, and TaO particles were mixed at an adjusted molar ratio to obtain a niobium titanium composite oxide with the composition shown in the "Composite oxide composition" column in Tables 1 and 3 below, and at least one element selected from the group consisting of potassium carbonate (KCO), iron chloride (FeCl), and orthophosphoric acid (HPO) was added so that the concentration of element A would be the concentration shown in the "Element A / concentration" column in Table 1.

[0254] Example 33 Niobium titanium composite oxide, Nb2Sn 0.5 Ti 0.5An electrode material was synthesized in the same manner as in Example 1, except that the molar ratio of NbO particles, TiO particles, and SnO particles was adjusted and mixed so as to obtain O7, and potassium carbonate (KCO) and orthophosphoric acid (HPO) were added so that the concentration of element A became the concentration shown in the "Element A / Concentration" column in Table 1.

[0255] Example 34 Niobium titanium composite oxide, Nb 9.5 V 0.5 ZrTiO 29 An electrode material was synthesized in the same manner as in Example 1, except that the molar ratio of NbO particles, TiO particles, VO particles, and ZrO particles was adjusted and mixed so as to obtain a composition of 100% NbO, 100% TiO, 100% VO, and 100% ZrO, and potassium carbonate (KCO) and orthophosphoric acid (HPO) were added so that the concentration of element A became the concentration shown in the "Element A / Concentration" column in Table 1.

[0256] Example 35 Niobium titanium composite oxide, Nb 12.9 TaW 0.1 Ti 0.9 Hf 0.1 O 37 An electrode material was synthesized in the same manner as in Example 1, except that NbO particles, TiO particles, TaO particles, WO particles, and HfO particles were mixed at an adjusted molar ratio so as to obtain a composition of 1000 ppm or 1000 ppm, and potassium carbonate (KCO) and orthophosphoric acid (HPO) were added so that the concentration of element A would be the concentration shown in the "Element A / Concentration" column in Table 1.

[0257] Example 36 Niobium titanium composite oxide, Nb 11.5 Ta 2.5 Ti 0.6 Zr 0.4 O 37An electrode material was synthesized in the same manner as in Example 1, except that the molar ratio of NbO particles, TiO particles, TaO particles, and ZrO particles was adjusted and mixed so as to obtain the above, and potassium carbonate (KCO) and orthophosphoric acid (HPO) were added so that the concentration of element A became the concentration shown in the column "Element A / concentration" in Table 1.

[0258] Example 37 Niobium titanium composite oxide, Nb 19 Ta 4.9 Mo 0.1 Ti 0.7 Sn 0.3 O 62 An electrode material was synthesized in the same manner as in Example 1, except that NbO particles, TiO particles, TaO particles, MoO particles, and SnO particles were mixed at an adjusted molar ratio so as to obtain a composition of 1000 ppm or 1000 ppm, and potassium carbonate (KCO) and orthophosphoric acid (HPO) were added so that the concentration of element A would be the concentration shown in the "Element A / Concentration" column in Table 1.

[0259] (Comparative Examples 1 to 4) Nb 10 Ti2O 29 To obtain the above, Nb2O5 particles and TiO2 particles were mixed in a dry ball mill at a molar ratio of 5:2. The obtained powder was placed in an alumina crucible and heated at 800°C for 10 hours, after which it was pulverized and mixed, and then pre-fired (first firing) at 800°C for 10 hours. In Comparative Example 1, the obtained precursor particles were subjected to main firing at 1150°C for 3 hours without adding a source of element A (nothing was added).

[0260] In Comparative Example 2, potassium carbonate was added to the precursor particles obtained after the calcination so that the concentration of element K was 50 ppm, and the mixture was wet-mixed with pure water to obtain a wet mixture, which was then subjected to main calcination at a temperature of 1150°C for 3 hours.

[0261] Similarly, in Comparative Example 3, potassium carbonate was added to the precursor particles obtained after the preliminary calcination so that the concentration of element Na was 2200 ppm, and the mixture was wet-mixed and then subjected to the main calcination. In Comparative Example 4, sodium carbonate (Na2CO3) was added to the precursor particles obtained after the preliminary calcination so that the concentration of element Na was 500 ppm, and the mixture was wet-mixed and then subjected to the main calcination.

[0262] In each of Comparative Examples 1 to 4, the powder obtained after the main firing was pulverized using a 10 mmφ agate ball mill at 500 rpm for 30 minutes to obtain electrode materials according to Comparative Examples 1 to 4.

[0263] (Comparative Examples 5 to 7) The molar ratio of Nb2O5 particles and TiO2 particles was adjusted and mixed to obtain the niobium titanium composite oxide composition shown in the "Composite oxide composition" column of Table 1, and the mixture was then pulverized and mixed using a dry ball mill. The obtained powder was placed in an alumina crucible and fired at 1150°C for 12 hours to obtain a niobium titanium composite oxide powder. This niobium titanium composite oxide powder was then pulverized in an agate ball mill using 10 mm diameter pulverization media to a D50 of approximately 3 μm, and electrode materials according to Comparative Examples 5 to 7 were obtained.

[0264] (Comparative Example 8) Niobium titanium composite oxide, Nb 2.01 Ta 0.001 Ti 0.989 An electrode material was synthesized in the same manner as in Comparative Example 5, except that the molar ratio of Nb2O5 particles, TiO2 particles, and Ta2O5 particles was adjusted and mixed so as to obtain O7.

[0265] Comparative Example 9 Niobium titanium composite oxide, Nb 11.5 Ta 2.5 Ti 0.6 Zr 0.4 O 37 An electrode material was synthesized in the same manner as in Comparative Example 5, except that the molar ratio of Nb2O5 particles, TiO2 particles, Ta2O5 particles, and ZrO2 particles was adjusted and mixed so as to obtain the above.

[0266] (Comparative Example 10) Nb2O5 particles and TiO2 particles were used in a molar ratio of 1:1 so that Nb2TiO7 with an Nb / Ti ratio of 2 could be obtained, and they were mixed by a dry ball mill. The obtained powder was put into an alumina crucible, heated at a temperature of 800 °C for 10 hours, then pulverized and mixed, and calcined (first firing) again at a temperature of 800 °C for 10 hours. Potassium carbonate (K2CO3) was added to the obtained precursor particles so that the element K would be 500 ppm with respect to the obtained active material particles, and wet mixing was performed using pure water to obtain a wet mixture. Next, the wet mixture of the precursor particles and K2CO3 was fired at a temperature of 1150 °C for 3 hours in the main firing (second firing). The powder thus obtained was pulverized using an agate ball mill using pulverizing media with a diameter of 10 mm until the D50 became about 3 μm, whereby an electrode material according to Comparative Example 10 was obtained.

[0267] <ICP analysis> ICP analysis was performed on the electrode materials obtained in each example and each comparative example to confirm the average composition of the niobium-titanium composite oxide, the type and concentration of element A. These results are shown in Tables 1 and 3 below.

[0268] <Powder X-ray diffraction measurement and calculation of peak intensity ratio I H / I L calculation> Powder X-ray diffraction measurement described in the first embodiment was performed on the electrode materials obtained in each example and each comparative example under the conditions of a sampling interval of 0.01° and a scan rate of 2° / min. In the obtained diffraction pattern, in the phase attributed to monoclinic Nb2TiO7, within the range of 2θ = 44° ± 1.0°, two peaks, P H appearing on the high-angle side and P L appearing on the low-angle side appeared. The peak intensity ratio (I H / I L ) was calculated. Also, for the monoclinic Nb 10 Ti2O 29 phase, the monoclinic Nb 14 TiO 37 phase and the monoclinic Nb24 TiO 62 Similarly, the peak intensity ratio (I H / I L ) was calculated. Furthermore, the diffraction pattern was analyzed by the Rietveld method to examine the crystallite size. These results are shown in Tables 1 and 3.

[0269] <SEM-EDX observation of electrode materials> The electrode materials obtained in each Example and Comparative Example were embedded in resin, and the inside of the specimen was removed by ion milling. The inside of the specimen was then observed, and the concentration of element A present at the particle interface of the active material particles in each Example was confirmed. As a result, in Examples 1 to 37 and Comparative Examples 2 to 4, the concentration of element A present at the particle interface was highest.

[0270] <Laser diffraction scattering method> The particle size distribution of the electrode materials obtained in each Example and Comparative Example was measured by laser diffraction scattering to determine D10, D50, and D90. The ratios (D10 / D50) and (D50 / D90) were calculated from these values. The results are shown in Tables 2 and 4.

[0271] <Electrochemical measurements> Using the electrode materials obtained in each of the Examples and Comparative Examples, electrochemical measurement cells according to each Example were fabricated.

[0272] 100% by mass of the electrode material powder obtained in each example, 10% by mass of acetylene black as a conductive agent, 5% by mass of carbon nanofiber, and 10% by mass of polyvinylidene fluoride (PVdF) as a binder were added to N-methylpyrrolidone (NMP) and mixed to obtain a slurry. This slurry was applied to one side of a current collector made of aluminum foil with a thickness of 12 μm, dried, and pressed to obtain an electrode with a density of 2.4 g / cm. 3 The electrodes were fabricated.

[0273] On the other hand, an electrolyte solution was prepared by dissolving LiPF6 supporting salt at a concentration of 1 mol / L in a mixed solvent of ethylene carbonate (EC) and diethyl carbonate (DEC) in a volume ratio of 1:2.

[0274] A three-electrode beaker cell was fabricated using the obtained electrode as a working electrode, Li metal as a counter electrode and a reference electrode, and an electrolyte, and the electrochemical properties were evaluated as described below.

[0275] In this example, the three-electrode beaker cell used for this measurement uses lithium metal as the counter electrode, and therefore the electrode potentials of the examples and comparative examples are more noble than the counter electrode, and therefore operate as positive electrodes. Therefore, the definitions of charge and discharge are reversed when the electrodes of the examples and comparative examples are used as negative electrodes. To avoid confusion, in this example, the direction in which lithium ions are inserted into the electrode is referred to as "charge," and the direction in which they are desorbed is referred to as "discharge." The active material of this embodiment can be used as a negative electrode when combined with a known positive electrode material.

[0276] The fabricated electrochemical measurement cell was charged and discharged in a potential range of 1.0 V to 3.0 V relative to the metallic lithium electrode. The charge / discharge current was set to 0.2 C (time-discharge rate), and the 0.2 C discharge capacity was measured at room temperature. The 0.2 C discharge capacity serves as an index of energy density. To investigate rapid discharge characteristics, after measuring the 0.2 C discharge capacity, the cell was again charged at a 0.2 C charge current, and the 5 C rapid discharge capacity was measured at room temperature. The 5 C discharge capacity was then divided by the 0.2 C discharge capacity to determine the discharge capacity ratio (5 C / 0.2 C). The discharge capacity ratio (5 C / 0.2 C) serves as an index for evaluating rapid charge / discharge characteristics.

[0277] Next, in order to confirm that the electrode material (negative electrode material) according to the embodiment can be stably charged and discharged, a life test of repeating 0.2C charge and discharge in the potential range of 1.0V to 3.0V based on a metallic lithium electrode was performed on the cells of the embodiment and the comparative example under an environment of 45°C. 100 cycles of charge and discharge were performed under this condition (one cycle consists of charge and discharge), and the discharge capacity retention rate after 100 cycles was examined. In order to confirm the discharge capacity retention rate after 100 cycles, charge and discharge were performed again at 0.2C (hourly discharge rate), and the cycle capacity retention rate (%) when the initial discharge capacity was set to 100% was calculated by dividing the discharge capacity after 100 cycles by the initial discharge capacity and multiplying by 100. The discharge capacity retention rate after 100 cycles is an index for evaluating the cycle life characteristics. The above results are summarized in Tables 2 and 4.

[0278]

Table 1

[0279]

Table 2

[0280]

Table 3

[0281]

Table 4

[0282] An explanation will be given regarding the columns of "amounts of x, y, and z in the general formula" described in Tables 1 and 3. When the crystal phase constituting the niobium titanium composite oxide according to the corresponding example is "monoclinic Nb2TiO7", the z amount in the general formula Nb2M2 z Ti 1-z O7 shown. Here, M2 is at least one additive element selected from the group consisting of Nb, Ta, Zr, Hf, and Sn, and z satisfies 0 < z < 1.

[0283] In addition, the crystalline phase constituting the niobium titanium composite oxide according to the example is "monoclinic Nb 10 Ti2O 29 In the case of ", the general formula Nb 10-x M1 x Ti 2-y M2 y O 29 The amounts of x and y in the niobium titanium composite oxide of the corresponding example are shown. 14 TiO 37 In the case of ", the general formula Nb 14-x M1 x Ti 1-y M2 y O 37 The amounts of x and y in the niobium titanium composite oxide of the corresponding example are shown. 24 TiO 62 In the case of ", the general formula Nb 24-x M1 x Ti 1-y M2 y O 62 In the above general formula, M1 is at least one additional element selected from the group consisting of Ta, Ti, V, Mo, and W, M2 is at least one additional element selected from the group consisting of Nb, Ta, Zr, Hf, and Sn, x satisfies 0≦x≦5, and y satisfies 0≦y<1.0.

[0284] The following points can be read from Tables 1 to 4. In Examples 1 to 6, the tendency for pulverization to become easier as the concentration of element A (here, K) increases. For example, D10, D50, and D90 tended to decrease as the concentration of element A increased. Furthermore, the D10 values ​​in Examples 1 to 6 show that the inclusion of fine powder of 0.2 μm or less was suppressed.

[0285] In Examples 7 and 8, it was shown that when element A contained Fe or P, the same effect as when element A contained K was obtained.

[0286] In Example 9, D10 is greater than 2.0 μm, and therefore rapid discharge performance is inferior to that of the other Examples. On the other hand, in Example 10, D10 is smaller than 0.3 μm, and therefore rapid discharge performance is excellent, but cycle life performance is inferior to that of the other Examples.

[0287] Similarly, it can be seen that Example 11 had a D90 greater than 30 μm, and therefore had poorer rapid discharge performance than the other Examples, while Example 12 had a D90 smaller than 5 μm, and therefore tended to have poorer cycle life performance than the other Examples.

[0288] In Examples 13 to 18, even in the case of electrode materials containing niobium titanium composite oxides in which the Nb / Ti ratio is greater than 2 but other than 5, it can be seen that excellent rapid charge / discharge characteristics and cycle life characteristics were exhibited by containing element A at a concentration of 100 ppm to 2000 ppm.

[0289] In Examples 19 to 32, it was shown that by further inserting Ta into the crystals of the niobium titanium composite oxide, there was a tendency for the charge / discharge capacity to become larger while maintaining excellent rapid charge / discharge characteristics and cycle life characteristics.

[0290] It can be seen that in Examples 33 to 37, the rapid charge / discharge characteristics tended to improve when the niobium titanium composite oxide contained a different element other than Nb, Ti, and Ta.

[0291] The electrode materials according to Comparative Examples 1 and 5 to 9 contained niobium titanium composite oxides having an average composition with an Nb / Ti ratio of more than 2, but did not contain element A. As a result, the crystallite size was smaller than those of the Examples, and the D10 was also smaller, resulting in a large amount of fine powder being generated during pulverization. Therefore, the discharge capacity, rapid charge / discharge characteristics, and cycle life characteristics were all lower than those of the Examples.

[0292] As shown in Comparative Examples 2 and 3, electrode materials that did not contain element A at a concentration of 100 ppm to 2000 ppm did not have excellent battery characteristics. For example, in Comparative Example 3, the K concentration was excessively high, so only specific crystal axes grew and many coarse particles were included. As a result, not only the rapid charge / discharge characteristics and cycle life characteristics but also the discharge capacity were low.

[0293] As shown in Comparative Example 4, even when the electrode material contained Na at a concentration of 500 ppm, the rapid charge / discharge characteristics and cycle life characteristics were not improved.

[0294] As shown in Comparative Example 10, when the Nb / Ti ratio was 2, no improvement in rapid charge / discharge characteristics and cycle life characteristics was observed even when K was contained at a concentration of 500 ppm as element A. This is thought to be because, in a composition with an Nb / Ti ratio of 2, agglomerated particles are not easily generated by particle growth, and as a result, fine powder is not easily generated during pulverization, making it difficult to see the effect of adding K.

[0295] According to at least one embodiment and example described above, an electrode material is provided. The electrode material has a molar ratio of niobium to titanium (M Nb / M Ti The electrode material comprises active material particles containing a niobium-titanium composite oxide having an average composition where the ratio of 1 to 2 is greater than 2, and at least one element A selected from the group consisting of potassium, iron, and phosphorus. The active material particles contain element A at a concentration in the range of 100 ppm to 2000 ppm. This electrode material contains active material particles with high crystallinity and a stable basic skeleton, and has a low proportion of fine powder, so it can exhibit excellent rapid charge / discharge characteristics and cycle life characteristics.

[0296] 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 embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are intended to be included within the scope and spirit of the invention, as well as within the scope of the inventions described in the claims and their equivalents. The inventions described in the claims of the original application are as follows: [1] The molar ratio of niobium to titanium (M Nb / M Ti ) is greater than 2, and a niobium titanium composite oxide having an average composition At least one element A selected from the group consisting of potassium, iron, and phosphorus; The active material particles include The active material particles are an electrode material containing the element A at a concentration in the range of 100 ppm to 2000 ppm. [2] The niobium titanium composite oxide has a molar ratio of niobium to titanium (M Nb / M Ti ) is greater than 2, Nb2TiO7 phase, Nb 10 Ti2O 29 Phase, Nb 14 TiO 37 phase and Nb 24 TiO 62 The electrode material according to [1], which comprises at least one crystalline phase selected from the group consisting of: [3] The niobium titanium composite oxide has a molar ratio of niobium to titanium (M Nb / M Ti ) contains a Nb2TiO7 phase having a composition greater than 2, The diffraction pattern obtained by powder X-ray diffraction using a Cu-Kα radiation source for the niobium titanium composite oxide has a high-angle peak P within the range of 2θ=44°±1.0°. H and the low-angle peak P L and The low-angle peak P L Peak intensity I LThe high-angle peak P H Peak intensity I H The ratio (I H / I L ) is less than 1. [4] The niobium titanium composite oxide is Nb 10 Ti2O 29 Phase, Nb 14 TiO 37 phase and Nb 24 TiO 62 phases, The diffraction pattern obtained by powder X-ray diffraction using a Cu-Kα radiation source for the niobium titanium composite oxide has a high-angle peak P within the range of 2θ=44°±1.0°. H and the low-angle peak P L and The low-angle peak P L Peak intensity I L The high-angle peak P H Peak intensity I H The ratio (I H / I L ) is less than 1.5. [5] The electrode material according to any one of [1] to [4], wherein the crystallite diameter of the niobium titanium composite oxide is within a range of 95 nm to 130 nm. [6] The electrode material according to any one of [1] to [5], wherein the active material particles have a D10 in the range of 0.3 μm to 2.0 μm in a particle size distribution chart obtained by a laser diffraction scattering method. [7] The electrode material according to any one of [1] to [6], wherein the active material particles have a D90 in the range of 5 μm to 30 μm in a particle size distribution chart obtained by a laser diffraction scattering method. [8] The electrode material according to any one of [1] to [7], wherein, in a particle size distribution chart obtained by a laser diffraction scattering method, the ratio of D10 to D50 (D10 / D50) of the active material particles is within a range of 0.10 to 0.60, and the ratio of D50 to D90 (D50 / D90) is within a range of 0.20 to 0.50. [9] The niobium titanium composite oxide has a general formula Nb2M2 z Ti 1-z O7, a general formula Nb 10-x M1 x Ti 2-y M2 y O 29 ., a general formula Nb 14-x M1 x Ti[[ID=1 / 19]] 1-y M2 y O 37 , and a general formula Nb 24-x M1 x Ti 1-y M2 y O< / 62 and contains at least one compound selected from the group consisting of wherein M1 is at least one element selected from the group consisting of Ta, Ti, V, Mo and W, M2 is at least one element selected from the group consisting of Nb, Ta, Zr, Hf and Sn, x satisfies 0 ≦ x ≦ 5, y satisfies 0 ≦ y < 1.0, and z satisfies 0 < z < 1. The electrode material according to any one of [1] to [8].

[10] An electrode comprising the electrode material according to any one of [1] to [9].

[11] The electrode according to

[10] , wherein the electrode includes an active material-containing layer containing the electrode material.

[12] A secondary battery comprising a positive electrode, a negative electrode, and an electrolyte, wherein the negative electrode is the electrode according to

[10] or

[11] .

[13] A battery pack comprising the secondary battery according to

[12] .

[14] The battery pack according to

[13] , further comprising an external terminal for energization and a protection circuit.

[15] A battery pack comprising a plurality of the secondary batteries, wherein the secondary batteries are electrically connected in series, in parallel, or in a combination of series and parallel.

[16] A vehicle equipped with the battery pack according to any one of

[13] to

[15] .

[17] The vehicle according to

[16] , further comprising a mechanism for converting the kinetic energy of the vehicle into regenerative energy. [Explanation of symbols]

[0297] DESCRIPTION OF SYMBOLS 1...electrode group, 2...exterior member, 3...electrode (negative electrode), 3a...current collector (negative electrode current collector), 3b...negative electrode active material-containing layer, 3c...negative electrode current collecting tab, 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, 21...bus bar, 22...positive electrode side lead, 22a...other end, 23...negative electrode side lead, 23a...other end, 24...adhesive tape, 31...container, 32...lid , 33...protective sheet, 34...printed wiring board, 35...wiring, 40...vehicle body, 41...vehicle power supply, 42...electrical control device, 43...external terminal, 44...inverter, 45...drive motor, 100...secondary battery, 101...metal ion, 102...oxide ion, 103...skeletal structure portion, 104...void portion, 105 and 106...portion having two-dimensional channel, 107...void portion, 200...assembly Battery, 200a... battery pack, 200b... battery pack, 200c... battery pack, 300... battery pack, 300a... battery pack, 300b... battery pack, 300c... battery pack, 301a... battery pack monitoring device, 301b... battery pack monitoring device, 301c... battery pack monitoring device, 342... positive electrode connector, 343... negative electrode connector, 345... thermistor, 346... protection circuit, 342a... wiring, 343a... wiring Wire, 350...external terminal for current application, 352...positive terminal, 353...negative terminal, 348a...positive wiring, 348b...negative wiring, 400...vehicle, 411...battery management device, 412...communication bus, 413...positive terminal, 414...negative terminal, 415...switch device, 416...current detection unit, 417...negative input terminal, 418...positive input terminal, L1...connection line, L2...connection line, W...drive wheel.

Claims

1. The molar ratio of niobium to titanium (M Nb / M Ti Niobium having an average composition where a titanium composite oxide; and at least one element A selected from the group consisting of potassium, iron, and phosphorus, the element A is dissolved in the active material particles at a concentration in the range of 100 ppm to 2000 ppm; The crystallite size of the niobium titanium composite oxide is within a range of 50 nm to 130 nm, The niobium titanium composite oxide may be a compound represented by the general formula Nb 2 M2 z Ti 1-z O 7 or a compound represented by the general formula Nb 10-x M1 x Ti 2-y M2 y O 29 , general formula Nb 14-x M1 x Ti 1-y M2 y O 37 , and general formula Nb 24-x M1 x Ti 1-y M 2 y O 62 , An electrode material in which M1 is at least one element selected from the group consisting of Ta, Ti, V, Mo, and W, M2 is at least one element selected from the group consisting of Nb, Ta, Zr, Hf, and Sn, x satisfies 0≦x≦5, y satisfies 0≦y<1.0, and z satisfies 0.01≦z<1.

2. The niobium titanium composite oxide is 2. The electrode material according to claim 1, which satisfies at least one of the following: a crystal containing potassium as the element A and including an Nb—K—O bond; a crystal containing iron as the element A and including an Nb—Fe—O bond; and a crystal containing phosphorus as the element A and including an Nb—P—O bond.

3. The niobium titanium composite oxide has a molar ratio of niobium to titanium (M Nb / M Ti ) is 2 Nb having a composition larger than 2 TiO 7 Phase, Nb 10 Ti 2 O 29 Phase, Nb 14 TiO 37 phase and Nb 2 4 TiO 62 3. The method according to claim 1, wherein the crystalline phase is at least one selected from the group consisting of: The electrode material according to claim 1.

4. The niobium titanium composite oxide has a molar ratio of niobium to titanium (M Nb / M Ti ) is 2 Nb having a composition larger than 2 TiO 7 phase, The diffraction pattern obtained by powder X-ray diffraction using a Cu-Kα radiation source for the niobium titanium composite oxide has a high-angle peak P within the range of 2θ=44°±1.0°. H and low-angle peak P L and The low-angle peak P L Peak intensity I L The high-angle peak P H Peak intensity I H The ratio (I H / I L 3. The electrode material according to claim 1, wherein ) is less than 1.

5. The niobium titanium composite oxide contains Nb 10 Ti 2 O 29 Phase, Nb 14 TiO 37 phase and Nb 24 T iO 62 phases, The diffraction pattern obtained by powder X-ray diffraction using a Cu-Kα radiation source for the niobium titanium composite oxide has a high-angle peak P within the range of 2θ=44°±1.0°. H and low-angle peak P L and The low-angle peak P L Peak intensity I L The high-angle peak P H Peak intensity I H The ratio (I H / I L 3. The electrode material according to claim 1, wherein the σ is less than 1.

5.

6. 6. The electrode material according to claim 1, wherein the crystallite diameter of the niobium titanium composite oxide is in the range of 95 nm to 130 nm.

7. 7. The electrode material according to claim 1, wherein the active material particles have a particle size distribution chart obtained by a laser diffraction scattering method, in which D10 is in the range of 0.3 μm to 2.0 μm.

8. 8. The electrode material according to claim 1, wherein the active material particles have a particle size distribution chart obtained by a laser diffraction scattering method, and D90 is in the range of 5 μm to 30 μm.

9. 9. The electrode material according to claim 1, wherein, in a particle size distribution chart obtained by a laser diffraction scattering method, the ratio of D10 to D50 (D10 / D50) of the active material particles is in the range of 0.10 to 0.60, and the ratio of D50 to D90 (D50 / D90) is in the range of 0.20 to 0.

50.

10. An electrode comprising the electrode material according to any one of claims 1 to 9.

11. The electrode according to claim 10 , wherein the electrode comprises an active material-containing layer containing the electrode material.

12. A positive electrode and a negative electrode; and an electrolyte, The secondary battery, wherein the negative electrode is the electrode according to claim 10 or 11.

13. A battery pack comprising the secondary battery according to claim 12.

14. An external terminal for applying current; The battery pack of claim 13 further comprising a protection circuit.

15. 15. The battery pack according to claim 13, comprising a plurality of the secondary batteries, the secondary batteries being electrically connected in series, in parallel, or in a combination of series and parallel.

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