KR101753977B1 - Active material for battery, nonaqueous electrolyte battery, and battery pack - Google Patents

Abstract

An object of the present invention is to provide a battery active material capable of realizing a non-aqueous electrolyte cell excellent in input / output characteristics and cycle characteristics.
The battery active material 300 according to one embodiment includes particles including a core phase 301 and a shell phase 302. The shell phase 302 surrounds at least a portion of the core phase 301. The core phase 301 contains the first monoclinic niobium titanium composite oxide. The shell phase 302 contains a second single crystal niobium titanium composite oxide. The oxidation number of titanium contained in the core phase 301 is larger than the oxidation number of titanium included in the shell phase 302 or the oxidation number of niobium included in the shell phase 302 Is greater than the number.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a battery active material, a nonaqueous electrolyte battery,

An embodiment of the present invention relates to a battery active material, a nonaqueous electrolyte battery, and a battery pack.

Recently, non-aqueous electrolyte batteries such as lithium ion secondary batteries have been developed as high energy density batteries. The nonaqueous electrolyte battery is expected to be used as a power source for a vehicle such as a hybrid car or an electric car, or a power source for a large-sized shaft. Particularly for automotive applications, nonaqueous electrolyte batteries are also required to have other properties such as rapid charge-discharge performance and long-term reliability. The nonaqueous electrolyte battery capable of rapid charging and discharging has an advantage that the charging time is remarkably short, and also the power performance can be improved in the hybrid vehicle, and the regenerative energy of the power can be efficiently recovered.

Rapid charge / discharge is possible by electron and lithium ions moving rapidly between the positive electrode and the negative electrode. In the battery using the carbon-based negative electrode, dendrites of metallic lithium were deposited on the electrode by repeating rapid charging and discharging. The dendrite generates an internal short circuit, and as a result, there is a fear of generation of heat or ignition.

Therefore, a battery using a metal composite oxide as a negative electrode active material instead of a carbonaceous material has been developed. Particularly, a battery using titanium oxide as a negative electrode active material is capable of stable rapid charging and discharging and has a characteristic that its lifetime is longer than that of a carbon-based negative electrode.

Titanium oxide, however, has a higher potential for metal lithium than the carbonaceous, i.e., "noble ". In addition, titanium oxide has a low capacity per weight. For this reason, a battery using titanium oxide has a problem of low energy density.

For example, the electrode potential of titanium oxide is about 1.5 V on the basis of metal lithium, which is higher than the potential of the carbon-based anode, that is, the "ear ". The electric potential of the titanium oxide is electrostatically limited because it is caused by the oxidation-reduction reaction between Ti ^{3 +} and Ti ^{4 +} when the lithium is electrochemically intercalated and deintercalated. It is also true that rapid charging / discharging of lithium ions can be stably performed at a high electrode potential of about 1.5V. Therefore, it is practically difficult to lower the electrode potential in order to improve the energy density.

On the other hand, regarding the capacity per unit weight, the theoretical capacity of the lithium-titanium composite oxide such as Li ₄ Ti ₅ O ₁₂ is about 175 mAh / g. On the other hand, the theoretical capacity of a general graphite electrode material is 372 mAh / g. Thus, the capacitance density of titanium oxide is significantly lower than that of the carbon-based negative electrode. This is because a site in which lithium is occluded in the crystal structure of titanium oxide is small, but lithium is stabilized in the structure, so that the practical capacity is lowered.

In view of the above, a new electrode material containing Ti and Nb has been studied. Particularly, the composite oxide represented by TiNb ₂ O ₇ has a theoretical capacity of 387 mAh / g since Li is compensated for Ti from 4 to 3 and Nb from 5 to 3 during Li intercalation. As described above, the composite oxide represented by TiNb ₂ O ₇ has attracted attention because it can exhibit a high capacity.

However, the niobium titanium composite oxide TiNb ₂ O ₇ has a low electronic conductivity in a state in which Li is not occluded. For this reason, in the nonaqueous electrolyte battery including the niobium titanium composite oxide TiNb ₂ O ₇ , the overvoltage in the low SOC region becomes large, and as a result, there is a problem that the input / output characteristics of the battery are deteriorated.

Japanese Patent Application Laid-Open No. 2013-164934

An object of the present invention is to provide a battery active material capable of realizing a nonaqueous electrolyte battery excellent in input / output characteristics and cycle characteristics, a nonaqueous electrolyte battery including the battery active material, and a battery pack including the nonaqueous electrolyte battery.

According to the first embodiment, a battery active material is provided. This battery active material contains particles including a core phase and a shell phase. The shell phase surrounds at least a portion of the core. The core phase contains the first monoclinic niobium titanium composite oxide. The shell phase contains the second monoclinic niobium titanium composite oxide. The oxidation number of titanium contained on the core is larger than the oxidation number of titanium contained in the shell or the oxidation number of niobium contained on the core is larger than the oxidation number of niobium included in the shell.

According to the second embodiment, a nonaqueous electrolyte battery is provided. This nonaqueous electrolyte battery includes a negative electrode including a battery active material according to the first embodiment, a positive electrode, and a nonaqueous electrolyte.

According to the third embodiment, a battery pack is provided. This battery pack comprises the nonaqueous electrolyte battery according to the second embodiment.

According to the present invention, there is provided a battery active material capable of realizing a nonaqueous electrolyte battery having excellent input / output characteristics and cycle characteristics, a nonaqueous electrolyte battery including the battery active material, and a battery pack having the nonaqueous electrolyte battery.

1 is a schematic diagram showing the crystal structure of a niobium titanium composite oxide Nb ₂ TiO ₇ .
Fig. 2 is a schematic diagram showing the crystal structure of Fig. 1 in another direction. Fig.
3 is a schematic cross-sectional view of a battery active material of a first example according to the first embodiment.
4 is a schematic cross-sectional view of a battery active material of a second example according to the first embodiment.
5 is a schematic cross-sectional view of a battery active material of a third example according to the first embodiment.
6 is a part of an XPS chart relating to each of some examples of the battery active material according to the first embodiment and another battery active material.
Fig. 7 is another example of an XPS chart relating to each of the battery active materials of some examples and the other battery active materials according to the first embodiment. Fig.
8 is a SEM photograph of an example of a battery active material according to the first embodiment.
9 is an SEM photograph of another battery active material.
10 is a schematic sectional view of an example non-aqueous electrolyte cell according to the second embodiment.
11 is an enlarged cross-sectional view of part A of Fig.
12 is a schematic cross-sectional view of a non-aqueous electrolyte cell of another example according to the second embodiment.
13 is an enlarged cross-sectional view of a portion B in Fig.
14 is an exploded perspective view of an example battery pack according to the third embodiment.
Fig. 15 is a block diagram showing an electric circuit of the battery pack of Fig. 14; Fig.
16 is a view showing the relationship between the pressure applied to the active material and the conductivity of each of the active materials of Example 1, Example 2 and Comparative Example 1. Fig.
17 is a first charge-discharge curve for each of the active materials of Examples 1 to 6 and Comparative Example 1;
18 is a diagram showing the relationship between the pressure and the electric conductivity applied to the active material in each of the active materials of Example 1, Example 2, Examples 5 to 7, and Comparative Examples 1 and 2. Fig.
19 is a first charge / discharge curve for each of the active materials of Examples 1 and 7 and Comparative Example 2;
20 is a graph showing the cycle characteristics of the test cells of Examples 1 to 6 and Comparative Example 1. Fig.
21 is a graph showing the rate characteristics of the test cells of Examples 1 to 6 and Comparative Example 1. Fig.
22 is a graph showing rate retention capacity retention ratios of the test cells of Examples 1 to 6 and Comparative Example 1. Fig.
23 is a view showing the relationship between the pressure applied to the active material and the conductivity of each of the active materials of Example 7, Example 6, and Comparative Example 1. Fig.

Hereinafter, embodiments will be described with reference to the drawings. Throughout the embodiments, common components are denoted by the same reference numerals, and redundant description is omitted. In addition, each of the drawings is a schematic diagram for explaining the embodiments and facilitating the understanding thereof, and the shapes, dimensions, and ratios thereof are different from those of the actual apparatus, but they can be appropriately designed and modified by taking the following description and well- have.

(First Embodiment)

According to the first embodiment, a battery active material is provided. This battery active material contains particles including a core phase and a shell phase. The shell phase surrounds at least a portion of the core. The core phase contains the first monoclinic niobium titanium composite oxide. The shell phase contains the second monoclinic niobium titanium composite oxide. The oxidation number of titanium contained on the core is larger than the oxidation number of titanium contained in the shell or the oxidation number of niobium contained on the core is larger than the oxidation number of niobium included in the shell.

The monoclinic niobium titanium composite oxide can be provided with a battery capable of stable repetitive rapid charging / discharging without impairing the rate performance and energy density for the reasons described below.

First, an example of the crystal structure of the monoclinic niobium titanium composite oxide will be described with reference to Fig.

1 is a schematic diagram showing the crystal structure of a niobium titanium composite oxide Nb ₂ TiO ₇ , which is an example of a monoclinic niobium titanium composite oxide. Fig. 2 is a schematic diagram showing the crystal structure of Fig. 1 from another direction. Fig.

As shown in FIG. 1, the crystal structure of the monoclinic niobium titanium composite oxide Nb ₂ TiO ₇ is such that the metal ion 101 and the oxide ion 102 constitute the framework structure portion 103. Nb ions and Ti ions are randomly arranged in the metal ion 101 in a ratio of Nb: Ti = 2: 1. These skeletal structure portions 103 are three-dimensionally alternately arranged, so that void portions 104 are present between the skeletal structure portions 103. This void portion 104 becomes a host of lithium ions. The void portion 104 may occupy a large portion of the whole crystal structure as shown in Fig. In addition, the void portion 104 can stably maintain the structure even when lithium ions are inserted.

In FIG. 1, the region 105 and the region 106 are portions having a two-dimensional channel in the [100] direction and the [010] direction. As shown in Fig. 2, the void portion 107 exists in the [001] direction in the crystal structure of the monoclinic niobium titanium composite oxide. This void portion 107 has a tunnel structure favorable to the conduction of lithium ions and becomes a conductive path in the [001] direction connecting the region 105 and the region 106. [ The presence of this conductive path makes it possible for the lithium ion to pass between the region 105 and the region 106. [

As described above, the crystal structure of the monoclinic niobium titanium composite oxide Nb ₂ TiO _{7 has} a structure in which equivalent insertion spaces of lithium ions are large and structurally stable, and regions having two-dimensional channels with fast diffusion of lithium ions and regions A conductive path in the [001] direction exists. Thereby, in the crystal structure of the monoclinic niobium titanium composite oxide Nb ₂ TiO ₇ , the insertion desorption of lithium ions into the insertion space is improved, and the insertion desorption space of lithium ions is effectively increased. This makes it possible to provide high capacity and high rate performance.

In addition, when the lithium ion is inserted into the void portion 104, the crystal structure of the metal ion 101 constituting the skeleton structure portion 103 is reduced three times, whereby the electrical neutrality of the crystal is maintained. In the monoclinic niobium titanium composite oxide, Ti ions are reduced not only from four sides to three sides, but also Nb ions are reduced from five sides to three sides. For this reason, the reducing agent is large per weight of the active material. Therefore, even if a lot of lithium ions are inserted, it is possible to maintain the electrical neutrality of the crystal. For this reason, the monoclinic niobium titanium composite oxide has a higher energy density than a compound such as titanium oxide containing only tetravalent cations. Specifically, the theoretical capacity of the monoclinic niobium titanium composite oxide is about 387 mAh / g, which is twice or more the value of the titanium oxide having the spinel structure.

The niobium titanium composite oxide also has a lithium storage potential of about 1.5 V (vs. Li / Li ⁺ ). Therefore, by using an active material containing a monoclinic niobium titanium composite oxide, it is possible to provide a battery capable of stable repeated charging / discharging.

From the above, it is possible to realize a nonaqueous electrolyte battery capable of exhibiting excellent rapid charge / discharge performance and having a high energy density by using an active material containing a monoclinic niobium titanium composite oxide.

In the particles included in the battery active material according to the first embodiment, the core phase and the shell phase each include such a monoclinic niobium titanium composite oxide. However, the number of oxidized or niobium oxides of titanium contained in the core is greater than the number of oxidized or niobium oxidized titanium contained in the shell phase. This means that in the particle, the second monoclinic niobium titanium composite oxide contained in the shell has the same monoclinic crystal structure as the first monoclinic niobium titanium composite oxide but has a similar crystal structure to the first monoclinic niobium titanium composite oxide contained on the core . That is, the particles included in the battery active material according to the first embodiment include a monoclinic niobium titanium composite oxide, and at least a part of its surface is reduced.

Since the battery active material according to the first embodiment having such a structure contains particles having oxygen deficiency on its surface, it can have excellent electron conductivity as compared with an active material whose surface does not contain particles not oxygen-deficient. The reduced shell phase has a single crystal structure similar to that of the core phase. Therefore, the battery active material according to the first embodiment can maintain the initial efficiency and the initial capacity, and can exhibit the same excellent capacity and high rate characteristics as the active material including the unreduced monoclinic niobium titanium composite oxide. As a result, the battery active material according to the first embodiment can realize a nonaqueous electrolyte battery excellent in input / output characteristics and cycle characteristics.

When the battery active material according to the first embodiment is used in a non-aqueous electrolyte cell as a negative electrode active material, lithium is occluded in the first and second single-crystal-structured niobium-titanium composite oxides by charging. As described above, in the first and second single-crystal niobium titanium composite oxides, the valence of niobium and titanium is changed by intercalating lithium. Also, in the battery active material according to the first embodiment, lithium may remain in the first and second single-crystal-structured niobium-titanium composite oxides even when discharged to the discharge end voltage in the non-aqueous electrolyte cell. In this case, it is assumed that niobium and titanium are reduced by lithium occluded in the crystal structure, and the actually measured values are corrected. The values of niobium and titanium in the first and second monoclinic niobium titanium composite oxides Singer. A specific method will be described later.

In the battery active material according to the first embodiment, it is preferable that the first monoclinic niobium titanium composite oxide contained on the core is a niobium titanium composite oxide expressed by the composition formula Nb ₂ TiO ₇ . The battery active material comprising the niobium titanium composite oxide expressed by the composition formula Nb ₂ TiO ₇ can realize a nonaqueous electrolyte battery capable of exhibiting excellent rapid charge and discharge performance and having a high energy density as described above.

In the niobium titanium composite oxide represented by the composition formula Nb ₂ TiO ₇ , oxygen deficiency may occur in the raw material or the intermediate product during its preparation. Inevitable impurities contained in the raw materials and impurities incorporated in the preparation may be present in the prepared monoclinic oxide. Therefore, the first monoclinic niobium titanium oxide composite oxide sometimes contains an oxide having a composition excluded from the stoichiometric ratio represented by the composition formula Nb ₂ TiO ₇ due to the above-mentioned unavoidable factors. For example, a monoclinic oxide having a composition represented by the composition formula Nb ₂ TiO _{7 -δ} (0 <?? 0.3) may be prepared due to unavoidable oxygen defects occurring during the preparation of monoclinic oxide.

When the first monoclinic niobium titanium composite oxide is a niobium titanium composite oxide represented by the composition formula Nb ₂ TiO ₇ , the second monoclinic niobium titanium composite oxide included in the shell phase has an oxidation number of titanium of 4 or less, 5. Preferably, in the second monoclinic niobium titanium composite oxide contained in the shell phase, the oxidation number of niobium is 4 or more and less than 5. Also preferably, in the second monoclinic niobium titanium composite oxide contained in the shell phase, the number of titanium oxides is greater than 3 and less than or equal to 4.

The second single-crystal niobium titanium composite oxide preferably has the same crystal structure as the single-crystal niobium titanium composite oxide represented by the composition formula Nb ₂ TiO ₇ . The monoclinic niobium titanium composite oxide having the same crystal structure as that of the monoclinic niobium titanium composite oxide represented by the composition formula Nb ₂ TiO ₇ can exhibit excellent rapid charge / discharge performance due to the same principle as the above-described principle, It is possible to realize a non-aqueous electrolyte cell having density.

In the particles comprising the core phase containing the first monoclinic niobium titanium composite oxide and the shell phase comprising the second monoclinic niobium titanium composite oxide, the molar ratio of niobium to titanium is 0 < Nb / Ti & desirable. The battery active material according to the first embodiment containing particles having a molar ratio Nb / Ti of more than 0 and not more than 2 can contribute to the improvement of the electronic conductivity. The molar ratio of niobium to titanium is more preferably 0.02? Nb / Ti? 2.

The second single-crystal niobium titanium composite oxide has a composition formula Nb _{1 . 33} Ti _{0 . 67} O &lt; _{4 &} gt ;. The second single-crystal niobium titanium composite oxide has a composition represented by the composition formula Nb _{1 . 33} Ti _{0 . 67} O ₄ , by the above-described inevitable factors, the composition formula Nb _{1 . 33} Ti _{0 .} There is a case containing an oxide having a composition deviating from the stoichiometric ratio represented by the ₆₇ O _4.

The thinner the thickness on the shell, the better the rate characteristic of the nonaqueous electrolyte battery capable of realizing the battery active material according to the first embodiment. The shell phase preferably has a thickness of 50 nm or less. It is also preferable that the shell phase has a thickness of 1 nm or more. The shell phase preferably has a thickness corresponding to not less than 0.6% and not more than 30% of the particle diameter of the particles contained in the battery active material, more preferably not less than 1% and not more than 10%.

The battery active material according to the first embodiment may further include a carbon layer covering the particles. This carbon layer can further enhance the electronic conductivity between particles. This carbon layer may be in the state of, for example, amorphous carbon. Alternatively, the carbon layer may be in a form having crystallinity, for example, graphite. The battery active material according to the first embodiment may not contain a carbon layer.

The particles included in the battery active material according to the first embodiment may be primary particles or secondary particles formed by agglomeration of primary particles. The average primary particle diameter of the particles is preferably 3 탆 or less. The particles having an average primary particle diameter of 3 탆 or less can sufficiently promote the storage of Li and can sufficiently improve the electron conductivity. The average primary particle diameter of the particles is preferably 0.2 탆 or more. It is more preferable that the average primary particle diameter of the particles is in the range of 0.5 占 퐉 to 1.5 占 퐉. The average secondary particle diameter of the particles is preferably in the range of 5 占 퐉 to 12 占 퐉, and more preferably in the range of 5 占 퐉 to 10 占 퐉.

Next, the battery active material according to the first embodiment will be described in more detail with reference to the drawings.

3 is a schematic cross-sectional view of the battery active material of the first example according to the first embodiment. 4 is a schematic cross-sectional view of a battery active material of a second example according to the first embodiment. 5 is a schematic sectional view of a battery active material of a third example according to the first embodiment.

The battery active material 300 of the first example shown in Fig. 3 is primary particles. The battery active material 300 shown in FIG. 3 includes a core phase 301. The core phase 301 contains the first monoclinic niobium titanium composite oxide. The battery active material 300 shown in FIG. 3 further includes a shell 302. The shell phase 302 contains a second single crystal niobium titanium composite oxide. The shell phase 302 surrounds the core phase 301.

The battery active material 300 of the second example shown in Fig. 4 is secondary particles. The battery active material 300 shown in FIG. 4 includes a plurality of core phases 301. The plurality of core phases (301) coagulate with each other to form secondary particles. The battery active material 300 shown in Fig. 4 further includes a shell phase 302 surrounding secondary particles including a plurality of core phases 301.

The battery active material 300 of the third example shown in Fig. 5 is a secondary particle formed by aggregating the battery active material 300 of the first example shown in Fig.

3 to 5, there is a boundary between the core 301 and the shell 302 so that the core 301 and the shell 302 can be distinguished from each other. However, as described above, the first monoclinic niobium titanium composite oxide contained in the core phase 301 and the second monoclinic niobium titanium composite oxide included in the shell phase 302 have the same crystal structure. Therefore, there is no boundary between the core phase 301 and the shell phase 302 in practice.

(Manufacturing method)

The battery active material according to the first embodiment can be produced, for example, by the following method.

First, particles of a monoclinic niobium titanium composite oxide are prepared.

The particles of the monoclinic niobium titanium composite oxide can be produced, for example, by the following method.

A. Liquid Synthesis

The particles of the monoclinic niobium titanium composite oxide can be produced, for example, by a liquid phase synthesis method described below. In the liquid phase synthesis method, the reaction proceeds in a state where the Nb element and the Ti element are mixed at the atomic level.

First, an acidic solution (hereinafter referred to as an acidic solution A) in which a Ti compound is dissolved and an acidic solution (hereinafter referred to as an acidic solution B) in which an Nb compound is dissolved are mixed.

Each of the acid solutions (A) and (B) has a pH of 5 or less, more preferably 2 or less. By setting the pH of each of the acidic solutions (A) and (B) to 5 or less, the Ti compound or the Nb compound is stably maintained in a state dissolved in the solvent, and hydrolysis does not occur before mixing the alkali solution, It is possible to prevent the gelation of (A) and (B).

The starting materials for the respective acid solutions (A) and (B) are not particularly limited, but a hydroxide, a sulfide, an oxide, a salt, an alkoxide and an organic substance containing Ti or Nb may be added to a suitable solvent such as pure water, ethanol, Dissolved solution may be used.

There is no particular limitation for the starting material, but, for example, sulfuric acid Ti as a Ti compound titanyl (TiOSO _4), titanium oxide (TiO _2), oxalic acid titanium ammonium _{((NH 4) 2 TiO (} C 2 O 4) · H 2 O), metatitanic acid (TiO (OH) ₂ ), titanium isocyanate (C ₁₂ H ₂₈ O ₄ Ti), titanium chloride (TiCl ₄ ) and the like. Examples of the Nb compound include niobium chloride (NbCl ₅ ), niobium hydroxide (Nb (OH) ₅ ), niobium ammonium oxalate (C ₂ H ₈ N ₂ O ₄ .Nb), and niobium oxide (Nb ₂ O ₅ ) .

The aqueous solution and the stable solution can be mixed and used as they are. However, when a metal chloride, a metal alkoxide or the like is used, for example, hydrolysis proceeds and it may be difficult to obtain coprecipitate precipitates. Therefore, Needs to be. The temperature at the time of mixing is preferably room temperature, but it may be heated when starting materials which are difficult to dissolve are used.

The molar concentration of Ti in the acidic solution (A) is not particularly limited, but is preferably in the range of 0.01 to 10 mol / l, more preferably in the range of 0.1 to 5.0 mol / l.

The molar concentration of Nb in the acidic solution (B) is not particularly limited, but is preferably in the range of 0.01 to 10 mol / l, more preferably in the range of 0.1 to 5.0 mol / l.

When the molar concentration of Ti or Nb in each of the acidic solutions (A) and (B) is not lower than the lower limit value, the concentration of Ti or Nb is not too low, and as a result, the precipitation amount of coprecipitate precipitates becomes sufficient and productivity is improved. Further, when the molar concentration of Ti or Nb in each of the acidic solutions (A) and (B) is not more than the upper limit value, the concentration of Ti or Nb is not too high, and as a result, hydrolysis is difficult to occur, So that the quality of the battery active material is improved.

(A) and (B) are mixed so that the molar ratio (Nb / Ti) of Nb / Ti is in the range of 1 <Nb / Adjust. More preferably, 1.3 < Nb / Ti &lt; 2. Here, the molar ratio is a molar ratio at the time of charging, and may be different from the composition ratio of Nb and Ti in the active material after the production. The solvent thus obtained is a liquid having fluidity, and hydrolysis does not occur and gelation does not occur.

Further, in this embodiment, not only the acidic solutions (A) and (B) are separately prepared and then mixed, but also a solution (hereinafter referred to as a solution (C)) in which the Ti compound and the Nb compound are dissolved from the beginning . The pH of the solution (C) is preferably 5 or less, more preferably 2 or less. By setting the pH of the solution (C) to 5 or less, hydrolysis does not occur before mixing the alkali solution, and gelation of the solution (C) can be prevented.

When pH adjustment is required in the preparation of the acidic solutions (A), (B) and (C), pH adjustment may be performed using an inorganic acid such as sulfuric acid or hydrochloric acid or an organic acid such as acetic acid.

The Ti compound and the Nb compound contained in the solution (C) may be the same as the Ti compound and the Nb compound contained in the acidic solutions (A) and (B), respectively. A suitable solvent such as pure water, ethanol, or an acid may be used as the solvent. The molar ratio (Nb / Ti) of Nb / Ti contained in the solution (C) is preferably in the range of 1 <Nb / Ti? 2, more preferably 1.3 <Nb / Ti?

The molar concentration of Ti and Nb in the solution (C) is not particularly limited, but is preferably in the range of 0.01 to 10 mol / l, more preferably 0.1 to 5.0 mol / l in terms of Ti . The Nb content is preferably in the range of 0.01 to 10 mol / l, and more preferably in the range of 0.1 to 5.0 mol / l.

When the molar concentration of Ti and Nb in the solution (C) is not lower than the lower limit value, the concentration of Ti and Nb is not too low, and as a result, the deposition amount of the coprecipitate precipitates becomes sufficient and the productivity is improved. When the molar concentration of Ti and Nb in the solution (C) is not more than the upper limit value, the concentration of Ti and Nb is not too high, and as a result, hydrolysis does not easily occur and deposition of the coprecipitate precipitates stably, Is improved.

Next, the coprecipitate precipitates are precipitated by mixing the alkali solution as the pH adjuster into the mixed solution containing the Ti compound and the Nb compound prepared as described above. The pH adjuster is preferably an alkali solution, preferably pH 8 or higher, more preferably pH 12 or higher. it is preferable that the coprecipitate precipitate can be precipitated with a small liquid amount in the solution having a large pH. As the pH adjuster, for example, ammonia water having a concentration of 35 wt% is used. Other than ammonia water, sodium hydroxide, potassium hydroxide, lime water and the like can be used. The reaction temperature is preferably from 10 캜 to 80 캜, and is appropriately selected in consideration of the coagulation degree and particle shape of the coprecipitate obtained.

As a mixing method, a method of dropping a pH adjusting agent into a mixed solution containing a Ti compound and an Nb compound, or a method of dropping a mixed solution containing a Ti compound and an Nb compound in a pH adjusting agent. It is possible to control the degree of aggregation and the shape of the precipitate depending on the method of dropping the liquid, the speed and the timing. More preferably, it is preferable to gradually add the pH adjuster in small amounts in the mixed solution from the viewpoint of suppressing excessive aggregation. The pH of the mixed solution containing Ti and Nb is adjusted to the alkali side by adding a pH adjusting agent. The pH can be adjusted while monitoring the precipitation condition of the coprecipitate precipitate, but the pH is set in the range of 1 to 10, preferably in the range of 6 to 9 as a standard. Thus, coprecipitated precipitates containing Ti and Nb can be precipitated.

Next, the deposited coprecipitated precipitate is washed. As the solution for cleaning, for example, pure water is preferably used. As a criterion for washing, the pH of the waste solution after washing is in the range of 6 to 8, more preferably, until the pH becomes closer to neutrality. After sufficiently washing, filtration and drying are performed to obtain a precursor powder.

The thus obtained precursor is a complex coprecipitated precipitate in which Nb and Ti are mixed, more preferably a complex hydroxide of amorphous. As described above, the amorphous precursor powder in which Ti and Nb are homogeneously mixed can increase the reactivity at the time of calcination, so that the Nb-Ti composite oxide can be calcined at a lower temperature and in a shorter time than in the conventional solid phase reaction method and the like. The temperature and time in the process can be suppressed.

Precursor powder after filtration and drying may be aggregated. In addition, the particle size of the primary particles may be uneven depending on the kind of the raw material. In such a case, it is preferable to perform pulverization by a mechanical milling method such as a ball mill or a bead mill.

Next, the obtained precursor powder is calcined. The firing is carried out at a temperature in the range of 400 占 폚 to 1450 占 폚. The baking time is 1 to 12 hours. More preferably, the firing temperature is 950 to 1100 占 폚, and the firing time is 1 to 5 hours. By firing under these conditions, an image containing the niobium-titanium composite oxide can be formed.

When the firing temperature is 800 ° C or more, grain growth or intergranular bonding proceeds. Therefore, from the viewpoint of improving the crystallinity while suppressing grain growth and intergranular necking, an annealing process at a temperature within the range of 600 to 800 占 폚 for 1 to 24 hours can be added before and after the calcination.

The firing of the precursor may be performed preferably by rapid heating at a temperature elevation rate of 30 DEG C / min or more to a temperature of 1000 DEG C or higher and heat treatment. The production of TiNb ₂ O ₇ is produced at a temperature of 900 ° C or higher, whereas the production of anatase type titanium dioxide at 400 ° C and the formation of rutile titanium dioxide at 800 ° C are started. For this reason, if the heating rate is low, titanium dioxide is first produced, so that the rutile-type titanium dioxide oxide after firing may be separated and precipitated as TiNb ₂ O ₇ independently.

The firing atmosphere may be in an atmosphere of an inert gas such as nitrogen, argon, or helium, or in a vacuum atmosphere, but an oxidizing atmosphere is preferable for obtaining an oxide, and more specifically, an atmosphere is preferable. It may also be fired in an atmospheric environment in which the oxygen concentration is intentionally increased.

The powder after firing may have particles necked or excessively grown. Therefore, pulverization by a mechanical milling method such as a ball mill or a bead mill is preferable because fine particles can be formed. However, if the mechanical pulverization is performed, the crystallinity of the active material may be damaged. In this case, the annealing process is preferably performed again at a temperature in the range of 600 ° C to 800 ° C for 1 to 24 hours after the above-described process.

When the particle size after firing is 1 占 퐉 or less, it is preferable to assemble by a method such as spray drying because the liquid property is stabilized even when the dispersibility of the slurry in the electrode manufacturing step is improved.

B. Solid phase recipe

The solid phase method is a method of synthesizing a product by weighing and mixing the powder raw materials so as to have a predetermined composition and then performing heat treatment. An example of a method of producing active material particles containing niobium and titanium by a solid phase method will be described below.

First, the starting materials are mixed so that the Nb / Ti ratio becomes a predetermined molar ratio. The starting material is not particularly limited, and examples of the Ti-containing compound include titanium oxide and titanium oxyhydroxide. As the Nb-containing compound, niobium oxide and niobium hydroxide can be used. It is known that the niobium-titanium composite oxide has a plurality of phases such as TiNb ₂ O ₇ , Ti ₂ Nb ₁₀ O ₂₉ , and TiNb ₂₄ O ₆₂ . When the particle diameter of the starting material is large, uniform dispersion of the Nb element and the Ti element takes time when the Nb element and the Ti element are thermally diffused at the time of calcination. Therefore, TiNb ₂ O ₇ and Ti ₂ Nb ₁₀ O ₂₉ , TiNb ₂₄ O _62, and the like can be formed. Therefore, it is preferable that the particle size of the raw material is 5 占 퐉 or less, more preferably 1 占 퐉. These are mixed by a method such as a ball mill, a vibration mill, or a bead mill. However, this mixing is performed with a time limit so as not to impair the crystallinity of the raw material of the powder. The mixing method may be either wet or dry.

Next, the obtained powder is fired. This firing corresponds to the firing of the precursor described above. However, since the solid phase method is a synthesizing method of advancing the reaction by thermal diffusion of the particle interface of the raw material, it is preferable to carry out calcination at a high temperature, and therefore, the calcination temperature is preferably within a range of 1000 deg. C or higher and 1400 deg. The baking time is preferably 10 hours or longer.

It is also possible to produce crystals having higher crystallinity while being more fine particles by performing the step of re-pulverizing the obtained powder and performing the annealing treatment once or plural times. The pulverization is carried out by wet milling of the beads. The annealing process herein corresponds to the annealing process described above for improving the crystallinity. The annealing temperature is preferably 700 ° C. to 1100 ° C., and the annealing time is preferably 1 to 5 hours.

C. sol-gel method

The sol-gel method is a method of synthesizing a powder by gelation by hydrolysis and polycondensation of a sol containing an alkoxide or the like, drying it, and then heat-treating it at a high temperature. An example of a method of producing active material particles containing niobium and titanium by the sol-gel method will be described below.

First, the starting solution is mixed so that the Nb / Ti ratio becomes a predetermined molar ratio. As the starting solution, a solution containing hydroxides, sulfides, oxides, salts, alkoxides and organic compounds containing Ti or Nb is used. As the Ti source, such as and the like _{TiOSO 4, TiO 2, (NH} 4) 2 TiO (C 2 O 4) · H 2 O, TiO (OH) 2, C 12 H 28 O 4 Ti, TiCl 4 have. Examples of the Nb source include NbCl ₅ , Nb (OH) ₅ , C ₂ H ₈ N ₂ O ₄ .Nb, and Nb ₂ O ₅ .

After thoroughly mixing the starting solution in a solution state, the hydrolysis is proceeded by adjusting the water content and the pH appropriately to obtain a gel state.

The gel-like substance is dried and then calcined to obtain a desired powder. The firing here corresponds to the firing of the precursor described above. The firing is preferably performed at a temperature within the range of 700 ° C to 1400 ° C. The firing time at this time is preferably from 1 hour to 24 hours. It may also include a step of pulverizing the precursor by a method such as a ball mill, a vibration mill, or a bead mill before the firing step.

Next, for example, the particles of the monoclinic niobium titanium composite oxide prepared as described above are subjected to a heat treatment in a reducing atmosphere. When the particles are heat-treated in a reducing atmosphere, the Nb element and / or the Ti element contained in the surface layer of the particles can be reduced. Thereby, the battery active material according to the first embodiment can be produced.

The reducing atmosphere is preferably a mixed gas atmosphere of Ar, He, or nitrogen containing hydrogen gas of 20% or less. The heat treatment in the reducing atmosphere is preferably baking at a temperature of 400 占 폚 to 1450 占 폚. And more preferably 700 ° C to 1100 ° C. The firing time is preferably 1 hour or less. According to this condition, the conductivity of the active material can be sufficiently increased while maintaining the battery capacity or the Li diffusion property to the active material particles.

For example, the particles of the monoclinic niobium titanium composite oxide are provided to the heat treatment without aggregation, whereby the same active material as the battery active material 300 of the first example shown in Fig. 3 can be obtained. On the other hand, after the particles of the monoclinic niobium titanium composite oxide are agglomerated into secondary particles, these secondary particles are subjected to the heat treatment to form the same active material as the battery active material 300 of the second example shown in Fig. 4 Can be obtained. Aggregation of the active material similar to that of the second example of the battery active material 300 can be removed by any means so that an active material containing the core phase and particles including the shell phase 302 surrounding the core phase can be obtained. The battery active material 300 shown in Fig. 5 can be obtained, for example, by agglomerating the battery active material 300 shown in Fig.

Further, carbon can be further complexed to the particles after the heat treatment. The method of combining with carbon is not particularly limited. Examples of the carbon source include saccharides, polyolefins, nitriles, alcohols, and organic compounds including other benzene rings. It is also possible to carry carbon black, graphite or the like by a mechanical method such as a planetary ball mill. After mixing with the calcined powder and the carbon source, the mixture is calcined in a reducing atmosphere or an inert atmosphere. The firing temperature is preferably 900 DEG C or lower. If the firing temperature exceeds 900 ℃, the reduction reaction of the Nb element is further proceeding there is a fear that the precipitation of more than (異相), such as NbO _2. As the atmosphere, an atmosphere such as the gas stream containing nitrogen, carbon dioxide, argon, and a reducing gas is preferable.

When the particle size after firing is 1 占 퐉 or less, it is preferable to assemble by a method such as spray drying because the liquid property is stabilized even when the dispersibility of the slurry in the electrode manufacturing step is improved.

&Lt; Powder X-ray diffraction measurement >

The crystal structure of the compound contained in the battery active material can be confirmed by powder X-ray diffraction measurement of the active material.

Powder X-ray diffraction measurement of the active material is performed as follows.

First, the target sample is pulverized until the average particle diameter becomes about 5 탆. The average particle diameter can be determined by laser diffraction. The pulverized sample is charged into a holder portion having a depth of 0.2 mm formed on a glass sample plate. At this time, make sure that the sample is sufficiently filled in the holder portion. Also, be careful that there is no cracks or voids due to insufficient filling of sample. Subsequently, another glass plate is used from outside to sufficiently pressurize and smooth. At this time, care should be taken not to cause unevenness from the reference surface of the holder due to excess or deficiency of the charged amount. Subsequently, a glass plate filled with the sample is placed in a powder X-ray diffractometer, and a diffraction pattern is obtained using a Cu-K? Line.

When the orientation of the sample is high, there is a possibility that the position of the peak shifts or the peak intensity ratio changes depending on the method of filling the sample. A sample with such a high degree of orientation is measured using a capillary tube. Specifically, a sample is inserted into a capillary tube, and the capillary is placed on a rotating sample table to measure it. By this measurement method, the orientation can be relaxed.

The active material contained in the battery as the electrode material can be measured as follows.

First, lithium ions are completely removed from the active material. For example, when the active material is used in the negative electrode, the battery is completely discharged. Thus, the crystal state of the active material can be observed. However, there are cases where residual lithium ions are present even in a discharged state. Next, the battery is disassembled in a glove box filled with argon to take out the electrode. Subsequently, the taken out electrode is washed with an appropriate solvent. As the cleaning solvent, for example, ethyl methyl carbonate and the like can be used. Next, the cleaned electrode is cut into an area approximately equal to the area of the holder of the powder X-ray diffraction apparatus to obtain a measurement sample. The thus obtained sample is directly attached to a glass holder and measured. At this time, the position of a peak derived from an electrode substrate such as a metal foil is measured in advance. Peaks of other components such as a conductive agent and a binder are also measured in advance. When the peak of the substrate overlaps with the peak of the active material, it is preferable that the layer containing the active material (for example, the active material layer described later) is peeled from the substrate and provided for measurement. This is to separate the superimposed peaks when quantitatively measuring the peak intensity. For example, the active material layer can be peeled off by irradiating the electrode substrate with ultrasonic waves in a solvent.

Next, the active material layer is sealed in a capillary, and the resultant is placed on a rotating sample table. An XRD pattern of the active material can be obtained after the influence of the orientation is reduced by this method.

The XRD pattern thus obtained is analyzed by the Rietveld method. In the Rietveld method, a diffraction pattern is calculated from a previously estimated crystal structure model. By fitting both the calculated value and the measured value, the parameters (lattice constant, atomic coordinates, occupancy, etc.) concerning the crystal structure can be analyzed precisely. Thus, the crystal structure characteristics of the compound contained in the active material to be measured can be investigated.

<Method of confirming the composition of the active material>

The composition of the battery active material can be confirmed by, for example, inductively coupled plasma emission spectroscopy.

&Lt; Analysis method of oxidation number of elements contained in active material particles >

The number of oxidation states of the elements contained in the active material particles can be analyzed by X-ray photoelectron spectroscopy (XPS) on the active material particles.

According to the X-ray photoelectron spectroscopy, information on the element information of the surface from the binding energy value of the binding electrons in the substance and the information about the valence and binding state from the energy shift of each peak is obtained. It can also be quantified using the peak area ratio.

The X-ray photoelectron spectroscopy on the surface of the active material particles can be carried out as follows.

First, the negative electrode is recovered from a battery in a discharged state. The recovered electrode is processed in the same manner as the electrode for XRD analysis to obtain a measurement sample.

The obtained measurement sample is placed in an ultra-high vacuum. In this state, the surface of the sample is irradiated with soft X-rays, and the photoelectrons emitted from the surface are detected by the analyzer. Since the length (average free path) through which the photoelectrons can travel within the material is several nanometers, the detection depth in this analysis method is several nanometers.

The inside of the active material can be obtained by cutting out the cross section of the electrode by ion milling or the like and providing it to the XPS analysis.

6 and 7 show charts obtained by X-ray photoelectron spectroscopy on the surface of several battery active materials.

6 is a part of an XPS chart relating to each of the battery active materials of some examples and the other battery active materials according to the first embodiment. 7 is another part of the XPS chart relating to each of the battery active materials of some examples and the other battery active materials according to the first embodiment.

6 and 7 are XPS charts of the niobium-titanium composite oxide particles (Sample A) which were not subjected to heat treatment in a reducing atmosphere. 6 and 7, the curved line indicated by the broken line represents a sample B (a) obtained by providing the same niobium-titanium composite oxide particle as the sample A to a heat treatment at 900 ° C for 30 minutes in an atmosphere of Ar-H ₂ &Lt; / RTI &gt; 6 and 7, the curved line indicated by the dotted line represents a sample C obtained by providing the same niobium-titanium composite oxide particle as the sample A to a heat treatment at 900 ° C for 60 minutes in an atmosphere of Ar-H ₂ (3% &Lt; / RTI &gt; 6 and 7, a curved line indicated by a thin line indicates that the same niobium-titanium composite oxide particle as the sample A was subjected to a heat treatment at 900 ° C for 90 minutes in an atmosphere of Ar-H ₂ (3%), D is an XPS chart.

From Fig. 6, it can be seen that the sample provided with the heat treatment in the reducing atmosphere has a strength near 206 eV larger than that of the sample not provided with the heat treatment. It can also be seen that the strength of the sample provided to the heat treatment for a longer period of time is large near 206 eV. On the other hand, in FIG. 6, the peak intensity near 207.3 eV representing Nb ⁵⁺ was substantially the same as the peak intensity of the sample A which was not provided for the heat treatment and the sample whose heat treatment time was long. It can be seen that the intensity in the vicinity of 206 eV is the intensity due ^to Nb ^{2+ to 4+} . It can also be seen that the peak near 207.3 eV is due to Nb ⁵⁺ . That is, from the XPS chart of FIG. 6, it can be seen that the heat treatment in the reducing atmosphere results in the niobium valence less than +5 on the surface of the titanium-niobium composite oxide.

It can also be seen from Fig. 7 that the sample provided with the heat treatment in the reducing atmosphere has a higher intensity near 457.1 eV than that of the sample not provided with the heat treatment. It can also be seen that the strength of the sample provided to the heat treatment for a longer period of time is large in the vicinity of 457 eV. On the other hand, in FIG. 7, the peak intensity near 458.8 eV representing Ti ⁴⁺ was substantially the same as the peak intensity of the sample A which was not provided for the heat treatment and the sample whose heat treatment time was long. It can be seen that the intensity in the vicinity of 457.1 eV is the intensity due ^to Ti ^{2+ to 3+} . It is also seen that the peak near 458.8 eV is the intensity due to Ti ⁴⁺ . That is, from the XPS chart of FIG. 7, it can be seen that the heat treatment in the reducing atmosphere results in the titanium having a valence of less than +4 on the surface of the titanium-niobium composite oxide.

Further, samples B to D were etched in the depth direction to perform XPS measurement, and a chart similar to Sample A was obtained. From these points, Samples B to D contain the core phase and the shell phase surrounding the core phase, and the oxidation number of niobium contained on the core is larger than the oxidation number of niobium included in the shell, and the oxidation number of titanium Which is larger than the oxidation number of titanium contained in the shell phase. That is, Samples B to D are the battery active materials according to the first embodiment. In Sample D, Ti and Nb of about 1% of the surface were lower in cost than in the inside.

&Lt; Determination method of the boundary between the shell phase and the core phase >

The boundary between the shell phase and the core phase is determined according to the following procedure.

First, by the XPS analysis described above, the oxidation number of Nb and Ti on the surface of the active material particles for a battery is examined. Next, the surface of the active material particles for a battery is cut by the Ar milling in the depth direction, and the number of oxidation of Nb and Ti on the newly exposed surface is again investigated using XPS analysis. Excavation by Ar and XPS analysis are repeated. The depth at which the oxidation number of Nb on the surface exposed by the excavation becomes +4 to +5 on the surface or the oxidation number of Ti on the surface exposed by the excavation is +3 to +4 is referred to as the shell surface of the battery active material Thickness.

<Observation of shape of active material>

The battery active material according to the first embodiment can be observed with a scanning electron microscope (SEM), for example.

Observation with a scanning electron microscope can be performed by preparing a measurement sample by the same method as that for preparing a measurement sample for X-ray photoelectron spectroscopy and observing it with a scanning electron microscope.

Scanning electron micrographs of several battery active materials are shown in Figs. 8 and 9. Fig.

8 is an SEM photograph of an example of the battery active material according to the first embodiment. 9 is an SEM photograph of another active material for a battery.

Specifically, FIG. 9 is an SEM image of a niobium titanium composite oxide particle which is not subjected to a heat treatment in a reducing atmosphere. 8 is an SEM image of active material particles obtained by heat treatment at 1000 占 폚 for 60 minutes in an atmosphere of Ar-H ₂ (3%).

On the SEM of Fig. 8, a plurality of active material particles 300 including the shell phase 302 on its surface are shown. As shown in Figure 8, the shell 302 is a smooth surface. On the other hand, the niobium titanium composite oxide particle 301 is shown on the SEM in Fig. 9, but does not have a smooth surface.

The battery active material according to the first embodiment includes particles including a core phase and a shell phase. The shell phase surrounds at least a portion of the core. The core phase contains the first monoclinic niobium titanium composite oxide. The shell phase contains the second monoclinic niobium titanium composite oxide. The oxidation number of titanium contained on the core is larger than the oxidation number of titanium contained in the shell or the oxidation number of niobium contained on the core is larger than the oxidation number of niobium included in the shell. Thereby, the battery active material according to the first embodiment can realize a nonaqueous electrolyte battery excellent in input / output characteristics and cycle characteristics.

(Second Embodiment)

According to the second embodiment, there is provided a nonaqueous electrolyte battery comprising the battery active material according to the first embodiment. The nonaqueous electrolyte battery includes a negative electrode, a positive electrode, and a nonaqueous electrolyte. The battery active material according to the first embodiment can be used in the negative electrode or the positive electrode, or in both the negative electrode and the positive electrode.

The nonaqueous electrolyte battery according to the second embodiment may further include a separator disposed between the positive electrode and the negative electrode. The positive electrode, negative electrode and separator can constitute an electrode group. The nonaqueous electrolyte can be held in the electrode group.

The nonaqueous electrolyte battery according to the second embodiment may further include an electrode assembly and an external member for accommodating the nonaqueous electrolyte.

The nonaqueous electrolyte battery according to the second embodiment may further include a positive electrode terminal electrically connected to the positive electrode and a negative electrode terminal electrically connected to the negative electrode. At least a part of the positive electrode terminal and at least a part of the negative electrode terminal can extend outside the exterior member.

The negative electrode, the positive electrode, the nonaqueous electrolyte, the separator, the external member, the positive electrode terminal, and the negative electrode terminal, which can be included in the nonaqueous electrolyte battery using the battery active material according to the first embodiment as the negative electrode, will now be described in detail.

(1) negative polarity

The negative electrode has a negative electrode collector and a negative electrode layer (negative electrode active material-containing layer) supported on one or both surfaces of the negative electrode collector.

The negative electrode layer may include a negative electrode active material, a conductive agent, and a binder.

As the negative electrode active material, the battery active material according to the first embodiment is used. As the negative electrode active material, the battery active material according to the first embodiment may be used alone, or may be used as a mixture with other active materials. Examples of other negative electrode active materials include anatase type titanium dioxide TiO ₂ , monoclinic titanium dioxide TiO ₂ (B), lithium titanate Li ₂ Ti ₃ O ₇ having a rhamstellite structure, lithium titanate Li ₄ Ti ₅ having a spinel structure O ₁₂ , niobium oxide, and niobium-containing complex oxides. These oxides can be suitably used because they have a specific gravity similar to that of the compound contained in the active material according to the first embodiment and are easily mixed and dispersed.

The conductive agent is compounded in order to enhance the current collecting performance of the active material and to suppress the contact resistance between the active material and the current collector. Examples of the conductive agent include carbonaceous materials such as acetylene black, carbon black and graphite.

The binder is compounded in order to fill the gaps of the dispersed negative active material and bind the negative active material and the current collector. Examples of the binder include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), fluorocarbon rubber, and styrene butadiene rubber.

The active material, the conductive agent and the binder in the negative electrode layer are preferably mixed in a proportion of 68 mass% or more and 96 mass% or less, 2 mass% or more and 30 mass% or less and 2 mass% or more and 30 mass% or less, respectively. When the amount of the conductive agent is 2 mass% or more, the current collecting performance of the negative electrode layer can be improved. When the amount of the binder is 2% by mass or more, sufficient bondability between the negative electrode layer and the current collector can be obtained, and further excellent cycle characteristics can be expected. On the other hand, each of the conductive agent and the binder is preferably 28% by mass or less in order to achieve a higher capacity.

As the negative electrode current collector, a material that is electrochemically stable at the insertion and extraction potential of lithium in the negative electrode active material is used. The negative electrode current collector is preferably made of an aluminum alloy containing at least one element selected from copper, nickel, stainless steel or aluminum or Mg, Ti, Zn, Mn, Fe, Cu and Si. The thickness of the negative electrode current collector is preferably 5 to 20 mu m. The negative electrode current collector having such a thickness can balance the strength and weight of the negative electrode.

The negative electrode is produced by, for example, suspending a negative electrode active material, a binder and a conductive agent in a commonly used solvent to prepare a slurry, applying the slurry to a current collector, drying the negative electrode layer, .

The negative electrode can also be produced by forming the negative electrode active material, the binder and the conductive agent in a pellet form to form a negative electrode layer and placing it on the current collector.

(2) Positive

The positive electrode may have a positive electrode collector and a positive electrode layer (positive electrode active material-containing layer) supported on one or both surfaces of the positive electrode collector.

The positive electrode layer may include a positive electrode active material and a binder.

As the positive electrode active material, oxides, sulfides, polymers, and the like can be used. For example, the storing and the lithium manganese dioxide (MnO _2), iron oxide, copper oxide, nickel oxide, lithium-manganese composite oxide (e.g. LixMn ₂ O ₄ or LixMnO _2), lithium nickel composite oxide (e.g. Li _x NiO _2), lithium cobalt composite oxide (e.g. Li _x CoO _2), lithium nickel cobalt composite oxide (for example, LiNi _{1 - y} Co _y O _2), lithium manganese cobalt composite oxide (e.g. Li _x Mn _y Co _{1 -y} O _2), lithium manganese nickel complex oxide having a spinel structure _{(Li x Mn 2 - y Ni} y O 4), lithium phosphate having up an empty structure _{(Li x FePO 4, Li x} Fe 1 - y Mn _y PO ₄ and Li _x CoPO ₄ ), iron sulfate (Fe ₂ (SO ₄ ) ₃ ), vanadium oxide (for example, V ₂ O ₅ ) and lithium nickel cobalt manganese composite oxide. In the above formula, 0 < x < = 1 and 0 &lt; As the positive electrode active material, one of these compounds may be used alone, or a plurality of compounds may be used in combination.

As the polymer, for example, a conductive polymer material such as polyaniline or polypyrrole, or a disulfide-based polymer material can be used. Sulfur (S) and carbon fluoride can also be used as the active material.

Examples of the more preferable active material include a lithium manganese composite oxide having a high positive electrode voltage (for example, Li _x Mn ₂ O ₄ ), a lithium nickel composite oxide (for example, Li _x NiO ₂ ), a lithium cobalt composite oxide (for example, Li _x CoO _2), lithium nickel cobalt composite oxide (for example, _{LiNi 1 -y Co y O 2)} , lithium manganese nickel complex oxide having a spinel structure (for example, _{Li x Mn 2 - y Ni y} O 4), lithium manganese Cobalt composite oxide (for example, Li _x Mn _y Co _{1 - y} O ₂ ), lithium iron phosphate (for example, Li _x FePO ₄ ), and lithium nickel cobalt manganese composite oxide. In the above formula, 0 < x < = 1 and 0 &lt;

Among them, when a non-aqueous electrolyte containing a room temperature molten salt is used, it is selected from lithium iron phosphate Li _x VPO ₄ F (0 <x? 1), a lithium manganese composite oxide, a lithium nickel composite oxide and a lithium nickel cobalt composite oxide It is preferable from the viewpoint of the cycle life. This is because the reactivity between the positive electrode active material and the room temperature molten salt is reduced.

The specific surface area of the positive electrode active material is preferably 0.1 m 2 / g or more and 10 m 2 / g or less. The positive electrode active material having a specific surface area of 0.1 m &lt; 2 &gt; / g or more can sufficiently insulate and release sites for lithium ions. The positive electrode active material having a specific surface area of 10 m &lt; 2 &gt; / g or less can be easily handled in industrial production, and a satisfactory charge-discharge cycle performance can be ensured.

The binder is compounded to bind the positive electrode active material and the current collector. Examples of the binder include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), and fluorine-based rubber.

A conductive agent may be added to the positive electrode layer as necessary in order to increase the current collection performance and to suppress the contact resistance with the current collector. Examples of the conductive agent include carbonaceous materials such as acetylene black, carbon black and graphite.

The mixing ratio of the positive electrode active material and the binder in the positive electrode layer is preferably in the range of 80 mass% or more and 98 mass% or less in the positive electrode active material and 2 mass% or more and 20 mass% or less in the binder. When the amount of the binder is 2 mass% or more, sufficient electrode strength can be obtained. Also, by setting the amount of the binder to 20 mass% or less, the amount of the insulator blended in the electrode can be reduced and the internal resistance can be reduced.

When the conductive agent is added, the positive electrode active material, the binder and the conductive agent are mixed in a proportion of 77 mass% or more and 95 mass% or less, 2 mass% or more and 20 mass% or less and 3 mass% or more and 15 mass% or less, respectively . By setting the amount of the conductive agent to 3% by mass or more, the above-mentioned effects can be sufficiently exhibited. By setting the conductive agent to 15 mass% or less, it is possible to reduce the decomposition of the nonaqueous electrolyte on the surface of the positive electrode conductive agent under high temperature preservation.

It is preferable that the positive electrode current collector is an aluminum alloy foil or an aluminum alloy foil containing at least one element selected from Mg, Ti, Zn, Ni, Cr, Mn, Fe, Cu and Si.

The thickness of the aluminum foil or the aluminum alloy foil is preferably 5 占 퐉 or more and 20 占 퐉 or less, more preferably 15 占 퐉 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 the aluminum alloy foil is preferably 1 mass% or less.

The positive electrode can be prepared by, for example, suspending a positive electrode active material, a binder, and a conductive agent, if necessary, in a suitable solvent to prepare a slurry, applying the slurry to the positive electrode current collector and drying the positive electrode layer, .

The positive electrode can also be produced by forming a positive electrode active material, a binder and a conductive agent to be mixed as required in a pellet form to form a positive electrode layer and placing it on the positive electrode current collector.

(3) Non-aqueous electrolyte

The nonaqueous electrolyte may be, for example, a liquid nonaqueous electrolyte prepared by dissolving an electrolyte in an organic solvent, or a gelated nonaqueous electrolyte obtained by complexing a liquid electrolyte and a polymer material.

The liquid nonaqueous electrolyte is preferably one in which the electrolyte is dissolved in an organic solvent at a concentration of 0.5 mol / L to 2.5 mol / L.

Examples of the electrolyte include lithium perchlorate (LiClO ₄ ), lithium hexafluorophosphate (LiPF ₆ ), lithium tetrafluoroborate (LiBF ₄ ), lithium arsenic fluoride (LiAsF ₆ ), lithium trifluoromethanesulfonate (LiCF ₃ SO ₃ ) , bis-trifluoromethyl sulfonyl imide lithium is included a lithium salt, and mixtures thereof such as _{(LiN (CF 3 SO 2)} 2). The electrolyte is preferable as long as it is difficult to oxidize even at a high temperature. LiPF ₆ is most preferred.

Examples of the organic solvent include cyclic carbonates such as propylene carbonate (PC), ethylene carbonate (EC) and vinylene carbonate, diethyl carbonate (DEC), dimethyl carbonate (DMC) Chain carbonates such as methyl ethyl carbonate (MEC), cyclic ethers such as tetrahydrofuran (THF), 2-methyltetrahydrofuran (2MeTHF) and dioxolane (DOX), dimethoxyethane (DME) and diethoxy (DEE),? -Butyrolactone (GBL), acetonitrile (AN), and sulfolane (SL). These organic solvents can be used singly or as a mixed solvent.

Examples of the polymer material include polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), and polyethylene oxide (PEO).

(Ionic flame) containing a lithium ion, a polymer solid electrolyte, an inorganic solid electrolyte, or the like may be used for the nonaqueous electrolyte.

A room temperature molten salt (ionic flame) refers to a compound that can exist as a liquid at room temperature (15 to 25 ° C) in an organic salt containing a combination of an organic cation and an anion. The room temperature molten salt includes a room temperature molten salt existing as a single liquid, a room temperature molten salt to be mixed with an electrolyte, and a room temperature molten salt to be dissolved in an organic solvent. Generally, the melting point of a room temperature molten salt used in a non-aqueous electrolyte cell is 25 占 폚 or less. Organic cations also generally have a quaternary ammonium skeleton.

The polymer solid electrolyte is prepared by dissolving the electrolyte in a polymer material and solidifying it.

The inorganic solid electrolyte is a solid material having lithium ion conductivity.

(4) Separator

The separator may be formed of, for example, a porous film containing polyethylene, polypropylene, cellulose, or polyvinylidene fluoride (PVdF), or a nonwoven fabric made of a synthetic resin. Among them, the porous film formed of polyethylene or polypropylene can be melted at a constant temperature to cut off current, so that safety can be improved.

(5)

As the exterior member, for example, a laminate film having a thickness of 0.5 mm or less or a metallic container having a thickness of 1 mm or less can be used. The thickness of the laminated film is more preferably 0.2 mm or less. More preferably, the metal container has a thickness of 0.5 mm or less, and more preferably 0.2 mm or less.

Examples of the shape of the exterior member include flat (thin), square, cylindrical, coin, button, and the like. The sheathing member may be an outer sheath member for a small-sized battery or an outer sheath member for a large-sized battery to be loaded on, for example, a two-wheeled or four-wheeled vehicle, depending on the battery dimension.

As the laminate film, a multilayer film in which a metal layer is interposed between resin layers can be used. The metal layer is preferably an aluminum foil or an aluminum alloy foil for light weight. As the resin layer, a polymer material such as polypropylene (PP), polyethylene (PE), nylon, polyethylene terephthalate (PET) or the like can be used. The laminated film can be formed into a shape of an exterior member by performing sealing by thermal fusion.

The metal container may be formed of, for example, aluminum or an aluminum alloy. As the aluminum alloy, alloys containing elements such as magnesium, zinc, and silicon are preferable. When the alloy contains a transition metal such as iron, copper, nickel or chromium, the content thereof is preferably 1% by mass or less. Thus, the long-term reliability and heat radiation under high temperature environment can be dramatically improved.

(6) Positive and negative terminals

The negative electrode terminal can be formed of a material that is electrochemically stable and has conductivity at the Li intercalation / deactivation potential of the above-described negative electrode active material. Specifically, copper, nickel, stainless steel or aluminum can be mentioned. In order to reduce the contact resistance, a material similar to that of the negative electrode collector is preferable.

The positive electrode terminal can be formed of a material having electric stability and conductivity in the range of 3V to 5V, preferably 3V to 4.25V, relative to the lithium ion metal. Specifically, examples include aluminum alloys containing elements such as Mg, Ti, Zn, Mn, Fe, Cu and Si, and aluminum. In order to reduce the contact resistance, a material similar to that of the positive electrode collector is preferable.

Next, an example of the nonaqueous electrolyte battery according to the second embodiment will be described more specifically with reference to Figs. 10 and 11. Fig.

10 is a schematic cross-sectional view of an example non-aqueous electrolyte cell according to the second embodiment. 11 is an enlarged view of part A in Fig.

The flat non-aqueous electrolyte battery 10 shown in Fig. 10 has a flat-shaped wound electrode group 1 and a bag-shaped sheath member 2 accommodating the same. The bag-shaped sheathing member 2 includes a laminated film in which a metal layer is interposed between two resin films.

The flat wound electrode group 1 is formed by spirally winding a laminate stacked in the order of the negative electrode 3, the separator 4, the positive electrode 5 and the separator 4 from the outside and press-molding them. The negative electrode 3 in the outermost layer has a structure in which the negative electrode layer 3b is formed on one surface on the inner surface side of the negative electrode collector 3a as shown in Fig. And the negative electrode layer 3b is formed on both sides of the whole body 3a. The positive electrode 5 is formed by forming a positive electrode layer 5b on both surfaces of a positive electrode current collector 5a.

The negative electrode terminal 6 is connected to the negative electrode collector 3a of the negative electrode 3 on the outermost layer and the positive electrode terminal 7 is connected to the positive electrode 5 on the inner side of the wound electrode group 1, And is connected to the positive electrode current collector 5a. The negative electrode terminal 6 and the positive electrode terminal 7 extend outward from the opening of the bag-shaped sheathing member 2. For example, the liquid non-aqueous electrolyte is injected from the opening of the bag-shaped sheathing member 2. [ The wound electrode assembly 1 and the liquid nonaqueous electrolyte are completely sealed by interposing the openings of the bag-shaped sheathing member 2 with the negative electrode terminal 6 and the positive electrode terminal 7 and sealing the heat.

The nonaqueous electrolyte battery according to the second embodiment is not limited to the configurations shown in Figs. 10 and 11 described above, and may have the configurations shown in Figs. 12 and 13, for example.

12 is a partially cutaway perspective view schematically showing a non-aqueous electrolyte battery according to another example of the second embodiment. 13 is an enlarged view of a portion B in Fig.

The flat non-aqueous electrolyte cell 10 shown in Figs. 12 and 13 includes a stacked electrode assembly 11 and an outer member 12 accommodating the same. The exterior member 12 includes a laminated film in which a metal layer is interposed between two resin films.

The stacked electrode assembly 11 has a structure in which the positive electrode 13 and the negative electrode 14 are alternately stacked with a separator 15 interposed therebetween as shown in Fig. A plurality of positive electrodes 13 are present and each includes a current collector 13a and a positive electrode active material containing layer 13b supported on both surfaces of the current collector 13a. A plurality of negative electrodes 14 are present and each includes a current collector 14a and a negative electrode active material containing layer 14b supported on both surfaces of the current collector 14a. One side of the current collector 14a of each negative electrode 14 protrudes from the positive electrode 13. The protruding current collector 14a is electrically connected to the strip negative terminal 16. The tip end portion of the band-shaped negative electrode terminal 16 is drawn out from the exterior member 12 to the outside. Although not shown, the current collector 13a of the positive electrode 13 protrudes from the negative electrode 14 located on the side opposite to the protruding side of the current collector 14a. The current collector 13a protruded from the negative electrode 14 is electrically connected to the band-shaped positive electrode terminal 17. [ The tip end portion of the band-shaped positive electrode terminal 17 is located on the side opposite to the negative electrode terminal 16 and is drawn out from the side of the outer casing member 12 to the outside.

Since the nonaqueous electrolyte battery according to the second embodiment includes the battery active material according to the first embodiment, excellent input-output characteristics and excellent cycle characteristics can be exhibited.

(Third Embodiment)

According to the third embodiment, a battery pack is provided. This battery pack includes the nonaqueous electrolyte battery according to the second embodiment.

The battery pack according to the third embodiment may have a plurality of non-aqueous electrolyte batteries. The plurality of nonaqueous electrolyte batteries may be electrically connected in series or electrically connected in parallel. Or a plurality of non-aqueous electrolyte batteries may be connected in a serial and parallel combination.

Hereinafter, an example of the battery pack according to the third embodiment will be described with reference to Figs. 14 and 15. Fig.

14 is an exploded perspective view of an example battery pack according to the third embodiment. 15 is a block diagram showing an electric circuit of the battery pack of Fig.

The battery pack 20 shown in Figs. 14 and 15 includes a plurality of unit cells 21. As shown in Fig. The unit cell 21 is an example flattened non-aqueous electrolyte battery according to the second embodiment described with reference to Figs. 10 and 11. Fig.

The plurality of unit cells 21 are stacked so that the negative terminal 6 and the positive electrode terminal 7 extending outward are aligned in the same direction and are fastened with the adhesive tape 22 to constitute the battery module 23 . The unit cells 21 are electrically connected to each other in series as shown in Fig.

The printed wiring board 24 is arranged so as to face the side surface of the unit cell 21 where the negative electrode terminal 6 and the positive electrode terminal 7 extend. 15, a thermistor 25, a protection circuit 26, and an energizing terminal 27 to an external device are mounted on the printed wiring board 24. As shown in Fig. An insulating plate (not shown) is provided on the surface of the printed wiring board 24 facing the battery module 23 in order to avoid unnecessary connection with the wiring of the battery module 23.

The positive electrode lead 28 is connected to the positive electrode terminal 7 positioned at the lowermost layer of the assembled battery 23 and the leading end thereof is inserted into the positive electrode connector 29 of the printed wiring board 24 and electrically connected thereto have. The negative electrode side lead 30 is connected to the negative electrode terminal 6 located on the uppermost layer of the assembled battery 23 and its tip end portion is inserted and electrically connected to the negative electrode side connector 31 of the printed wiring board 24 have. These connectors 29 and 31 are connected to the protection circuit 26 through the wirings 32 and 33 formed on the printed wiring board 24.

The thermistor 25 detects the temperature of the unit cell 21, and the detection signal is transmitted to the protection circuit 26. The protection circuit 26 can cut off the positive side wiring 34a and the negative side wiring 34b between the protection circuit 26 and the transmission terminal 27 to the external device under a predetermined condition. An example of a predetermined condition is when, for example, the detection temperature of the thermistor 25 is equal to or higher than a predetermined temperature. Further, another example of a predetermined condition is when, for example, overcharge, overdischarge, overcurrent, or the like of the unit cell 21 is detected. Detection of the overcharging or the like is performed for the entire single cell 21 or the whole battery module 23. When detecting the individual unit cells 21, 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 to be used as a reference electrode is inserted in the individual unit cell 21. In the case of the battery pack 20 shown in Figs. 14 and 15, wirings 35 for voltage detection are connected to the unit cells 21, respectively. A detection signal is transmitted to the protection circuit 26 through these wirings 35. [

A protective sheet 36 made of rubber or resin is disposed on each of three side surfaces of the battery module 23 except the side where the positive electrode terminal 7 and the negative electrode terminal 6 protrude.

The battery pack 23 is accommodated in the storage container 37 together with the protective sheet 36 and the printed wiring board 24. That is, the protective sheet 36 is disposed on each of the inner side surfaces in both the long side direction and the short side direction of the storage container 37, and the printed wiring board 24 is provided on the inner side opposite to the short side direction . The assembled battery 23 is placed in a space surrounded by the protective sheet 36 and the printed wiring board 24. The lid 38 is provided on the upper surface of the storage container 37.

Further, a heat-shrinkable tape may be used in place of the adhesive tape 22 for fixing the battery module 23. In this case, a protective sheet is disposed on both sides of the assembled battery and the heat-shrinkable tube is circulated around the heat-shrinkable tube, and then the heat-shrinkable tube is heat shrunk to bind the assembled battery.

Although FIGS. 14 and 15 show the case where the unit cells 21 are connected in series, they may be connected in parallel to increase the battery capacity. The assembled battery packs may be connected in series and / or in parallel.

The shape of the battery pack according to the third embodiment may be appropriately changed according to the use. As the use of the battery pack according to the third embodiment, it is desirable that the cycle characteristics in the large current characteristics are desired. Specific examples of applications include power sources for digital cameras, vehicles mounted on two- or four-wheel hybrid electric vehicles, two- or four-wheel electric vehicles, and assisted bicycles. The battery pack according to the third embodiment is particularly suitable for mounting on a vehicle.

Since the battery pack according to the third embodiment includes the nonaqueous electrolyte battery according to the second embodiment, it can exhibit excellent input / output characteristics and excellent cycle characteristics.

[Example]

EXAMPLES Hereinafter, examples will be described, but the present invention is not limited to the examples described below unless it goes beyond the gist of the present invention.

(Example)

&Lt; Preparation of single crystal niobium titanium composite oxide &

In the examples, an active material was prepared according to the following procedure.

As a starting material, a titanyl sulfuric acid sulfuric acid solution of 1 mol / l and an ethanol solution of 2 mol / l of niobium chloride were used. Both were mixed to obtain a transparent mixed solution free from precipitation of foreign matters such as hydroxides.

Next, ammonia water was added dropwise to this mixed solution with stirring. Thus, a white precipitate was obtained. The obtained precipitate was washed with pure water, filtered, and then dried with a heater at 80 ° C. The material obtained after drying was ground with a mortar to release the aggregation. Thus, a precursor powder was obtained.

The precursor powder thus obtained was heated to 1100 占 폚 at a heating rate of 30 占 폚 / min and fired in air for 1 hour. Thereafter, it was ground again into a bowl. Thus, an active material powder was obtained.

The active material powder obtained was found to have a ratio of Nb / Ti of 2 by ICP analysis. As a result of XRD measurement of the obtained active material powder, a peak belonging to the monoclinic Nb ₂ TiO ₇ phase was detected.

(Comparative Example 1)

A part of the monoclinic niobium titanium composite oxide powder obtained as described above was used as the active material of Comparative Example 1. Acetylene black as a conductive auxiliary agent and polyvinylidene fluoride (PVdF) as a binder were added to N-methylpyrrolidone (NMP) to obtain an active material of Comparative Example 1, thereby obtaining a slurry. At this time, the mass ratio of the active material: acetylene black: PVdF of Comparative Example 1 was set to 100: 5: 5. It is possible to suppress the loss of the conductive path due to the volume change at the time of charging / discharging of the active material by further inserting at least 10 parts by weight of the conductive auxiliary agent and at least 10 parts by weight of the binder. In order to confirm the utility of the surface reducing layer, The amount of the binder was slightly decreased.

The thus obtained slurry was applied to one surface of a current collector made of aluminum foil having a thickness of 12 占 퐉 to dry the coated film, and then the coating was provided to a press. Thus, an electrode having a weight per electrode unit area of 25 g / m 2 was produced.

<Fabrication of Test Cell>

The thus fabricated electrode was used as a working electrode, and a Li-metal was used as a counter electrode and a reference electrode, and a triple-pole type beaker cell was fabricated under an argon atmosphere.

On the other hand, the non-aqueous electrolyte was prepared by dissolving 1 mol / L LiTFSI supported salt in a mixed solvent of ethylene carbonate (EC) and diethyl carbonate (DEC) in a volume ratio of 1: 2. This non-aqueous electrolyte was injected into the triple-pole beaker cell prepared earlier under an argon atmosphere to prepare a test cell of Comparative Example 1. [

(Examples 1 and 2)

In Examples 1 and 2, the active materials of Examples 1 and 2 were prepared according to the following procedure.

First, another part of the single-crystal shaped niobium-titanium composite oxide powder prepared earlier was again divided into two parts.

Each of the two powders was subjected to a heat treatment at 900 캜 under an atmosphere of Ar-H ₂ (3%) in an electric furnace to obtain the active materials of Examples 1 and 2, respectively. The active material of Example 1 was provided for 30 minutes of heat treatment. The active material of Example 2 was provided for 60 minutes of heat treatment.

Test cells of Examples 1 and 2 were prepared in the same manner as in Comparative Example 1, using a part of each of the active materials of Example 1 and Example 2. [

&Lt; Measurement of conductivity &

With respect to the active materials of Examples 1 and 2 and Comparative Example 1, the relationship between the pressure applied to the active material and the conductivity was examined. Specifically, the following procedure was performed. The obtained active material was weighed (here, 1.5 g) and introduced into a powder resistance measuring system. The powder layer was compressed, and in the case of low resistance, the resistivity at different pressures was measured by a constant current application method by the four probe method. In the case of high resistance, it was measured by a constant voltage application method by a double ring probe method. The results are shown in Fig.

From Fig. 16, it is found that the active materials of Examples 1 and 2 are much higher in conductivity than the active material of Comparative Example 1. [

<Charging and discharging test for the first time>

Using the test cells of Examples 1 and 2 and Comparative Example 1, the first charge-discharge test was carried out in the following procedure. First, the battery was charged to 1.0 V at a constant current of 0.2C. Thereafter, the battery was maintained at a low voltage of 1.0 V for 10 hours, and then discharged for 10 minutes. Thereafter, the battery was discharged to 3.0V at a rate of 0.2C. Under this charge-discharge condition, the test cells of Examples 1 and 2 and the test cell of Comparative Example 1 were charged and discharged for the first time.

The first charge / discharge curve of the test cell of Example 1, Example 2 and Comparative Example 1 is shown in Fig. As shown in Fig. 17, the test cells of Example 1, Example 2 and Comparative Example 1 showed the same first charge / discharge curve.

(Examples 3 to 6)

In Examples 3 to 6, the active materials of Examples 3 to 6 were prepared according to the following procedure.

First, another part of the monoclinic niobium titanium composite oxide powder prepared earlier was divided into four parts again.

Powder divided into four pieces was subjected to heat treatment in the same manner as in Examples 1 and 2 except that the temperature and time were changed. In Example 3, heat treatment was performed at 950 占 폚 for 30 minutes. In Example 4, heat treatment was performed at 950 占 폚 for 60 minutes. In Example 5, heat treatment was performed at 1000 占 폚 for 30 minutes. In Example 6, heat treatment was performed at 1000 占 폚 for 60 minutes. Thus, the active materials of Examples 3 to 6 were obtained, respectively.

Test cells of Examples 3 to 6 were prepared in the same manner as in Comparative Example 1, using a part of each of the active materials of Examples 3 to 6.

With respect to the active materials of Examples 3 to 6, the relationship between the pressure applied to the active material and the conductivity was examined in the same procedure as in Examples 1 and 2. [ As a result, the active materials of Examples 3 to 6 exhibited a conductivity superior to that of Comparative Example 1, as well as the active materials of Examples 1 and 2. The results of Examples 5 and 6 are shown in Fig. 18 together with the results of Example 1, Example 2 and Comparative Example 1.

<Charging and discharging test for the first time>

Charging and discharging tests were carried out for the first time using the test cells of Examples 3 to 6. Charging and discharging tests were carried out under the same conditions as in Example 1.

The first charge and discharge curves of the test cells of Examples 3 to 6 are shown in Fig. 17 together with the first charge and discharge curves of the test cells of Examples 1 and 2. As shown in Fig. 17, the test cells of Examples 1 to 6 showed similar first charge-discharge curves.

(Example 7)

In Example 7, the active material of Example 7 was prepared in accordance with the following procedure.

First, another part of the monoclinic niobium titanium composite oxide powder prepared in advance was mixed with a 5 wt% aqueous solution of sucrose and heated to about 70 캜 until water disappears. The thus obtained powder was heat-treated for 30 minutes in an atmosphere of Ar-H ₂ (3%) at 900 ° C to prepare a composite.

The obtained composite was subjected to heat treatment in the same manner as in Example 1 to obtain an active material of Example 7. [

Using a part of the active material of Example 7, a test cell of Example 7 was fabricated in the same procedure as in Comparative Example 1. [

(Comparative Example 2)

In Comparative Example 2, the active material of Comparative Example 2 was prepared in the same procedure as in Example 1 except that the heat treatment was performed for 24 hours.

Using a part of the active material of Comparative Example 2, the test cell of Comparative Example 2 was fabricated in the same procedure as in Comparative Example 1. [

With respect to the active material of Example 7, the relationship between the density and the electric conductivity was examined in the same manner as in Examples 1 and 2. As a result, the active material of Example 7 exhibited a conductivity superior to that of Comparative Example 1, in the same manner as the active materials of Examples 1 and 2.

Similarly, for the active material of Comparative Example 2, the relationship between the density and the conductivity was examined in the same manner as in Examples 1 and 2. As a result, the active material of Comparative Example 2 had a conductivity higher than that of Comparative Example 1 by six digits. The results of Comparative Example 2 are shown in Fig.

<Charging and discharging test for the first time>

Discharge tests were carried out for the first time using the test cells of Example 7 and Comparative Example 2. [ Charging and discharging tests were carried out under the same conditions as in Example 1.

The first charge / discharge curve of the test cell of Example 7 and Comparative Example 2 is shown in FIG. 19 together with the first charge / discharge curve of the test cell of Example 1.

As shown in Fig. 19, the test cell of Example 7 showed the same first charge-discharge curve as that of the test cell of Example 1. Fig.

On the other hand, as shown in Fig. 19, the test cell of Comparative Example 2 exhibited a significantly lower capacity than the cells of the first test cell of Example 1 and Example 7, respectively.

[Results of the first charge / discharge test]

The results of the first charge-discharge test on the evaluation cells of Examples 1 to 7 and Comparative Examples 1 and 2 are shown again in Table 1 below.

As can be seen from the above description and Table 1, the active materials of Examples 1 to 7 had superior conductivity as compared with the active material of Comparative Example 1, and the same capacity as that of Comparative Example 1 could be realized. On the other hand, in Comparative Example 2, evaluation cells exhibiting significantly lower capacities than Examples 1 to 7 and Comparative Example 1 were realized. This is presumably because the heat treatment in the reducing atmosphere was performed for a long time in Comparative Example 2, whereby the monoclinic niobium titanium composite oxide was completely reduced.

<Cycle Test>

Cycle tests were conducted on the test cells of Examples 1 to 6 and the test cell of Comparative Example 1. The results are shown in Fig. The cycle test was repeated after charging / discharging at 1C rate in a 45 ° C environment after the first charge / discharge and rate test at 25 ° C.

As can be seen from the results shown in Fig. 20, the test cells of Examples 1 to 6 were superior to the test cells of Comparative Example 1 in cycle characteristics. The reason why the cycle characteristics shown in Fig. 20 are low as a whole is that the amounts of the conductive material and the binder were small.

<Rate Test>

The rate test was carried out on the test cells of Examples 1 to 6 and the test cell of Comparative Example 1.

In the rate test, each test cell was discharged at an initial potential of 1.0 V (vs. Li / Li ⁺ ) to an end potential of 3.0 V (vs. Li / Li ⁺ ). The temperature environment was set at 25 캜. The discharges in the rate test were changed seven times for each test cell by changing the rates in the order of 0.2C, 1C, 2C, 5C, 10C, 20C and 0.2C.

Fig. 21 shows discharge capacities per weight of each active material obtained in each rate test. 22 shows the rate discharge capacity retention rate for each test cell. In Fig. 22, the discharge capacity at 0.2C for the first time for each test cell is set at 100, and the discharge capacities at 1C, 2C, 5C, 10C, and 20C and the second 0.2C are set as rate discharge capacity retention ratios , And a relative value.

As can be seen from Figs. 21 and 22, each of the test cells of Examples 1 to 6 exhibited a rate characteristic superior to that of Comparative Example 1. In addition, as shown in Fig. 22, in each of the test cells of Examples 1 to 6, the discharging capacity to the second 0.2C was 80% or more of the first discharging capacity. On the other hand, in the evaluation cell of Comparative Example 1, the discharging capacity at 0.2 C for the second time was less than 80% of the discharging capacity at 0.2 C for the first time. From these results, it can be seen that in the evaluation cells of Examples 1 to 6, deterioration due to discharge to a large current could be suppressed as compared with the evaluation cell of Comparative Example 1. [

<Conductivity Comparison of Active Materials of Examples 6 and 7 and Comparative Example 1>

With respect to the active material of Example 7 described above, the powder resistance was measured to confirm the conductivity. The results are shown in Fig.

23, the conductivity of the active material of Example 7 was higher than that of Example 6, and was higher than that of Comparative Example 1.

<Rate characteristics of evaluation cell of Example 7>

A rate test similar to that conducted for the evaluation cells of Examples 1 to 6 and Comparative Example 1 was conducted on the evaluation cell of Example 7. As a result, it was found that the same results as in Examples 1 to 6 were also obtained in the evaluation cell of Example 7. [

The battery active material according to at least one of the embodiments and examples described above includes particles including a core phase and a shell phase. The shell phase surrounds at least a portion of the core. The core phase contains the first monoclinic niobium titanium composite oxide. The shell phase contains the second monoclinic niobium titanium composite oxide. The oxidation number of titanium contained on the core is larger than the oxidation number of titanium contained in the shell or the oxidation number of niobium contained on the core is larger than the oxidation number of niobium included in the shell. This battery active material can realize a non-aqueous electrolyte cell excellent in input / output characteristics and cycle characteristics.

While several embodiments of the present invention have been described, these embodiments are provided by way of example and are not intended to limit the scope of the invention. These new embodiments can be implemented in various other forms, and various omissions, substitutions, and alterations can be made without departing from the gist of the invention. These embodiments and their modifications fall within the scope and spirit of the invention, and are included in the scope of the invention as defined in the claims and their equivalents.

1, 11: electrode group
2, 12: exterior member
3, 14: negative polarity
4, 15: Separator
5, 13: Positive
6, 16: negative terminal
7, 17: Positive electrode terminal
10: Non-aqueous electrolyte cell
20: Battery pack
21: Single cell
22: Adhesive tape
23:
24: printed wiring board
25: Thermistor
26: Protection circuit
37: storage container
101: metal ion
102: oxide ion
103: skeletal structure part
104: void portion
105 and 106: a portion having a two-dimensional channel
107: void portion
300: Battery active material
301: Core phase
302: Shell phase

Claims (11)

A core phase containing a first monoclinic niobium titanium composite oxide,
A second single-crystal niobium titanium composite oxide and a shell phase surrounding at least a part of the core
, &Lt; / RTI &gt;
Wherein the oxidation number of titanium contained in the core is larger than the oxidation number of titanium contained in the shell or the oxidation number of niobium contained in the core is larger than the oxidation number of niobium included in the shell. The method according to claim 1,
Wherein the first single crystal niobium titanium composite oxide is a niobium titanium composite oxide represented by a composition formula Nb ₂ TiO ₇ . 3. The method of claim 2,
Wherein the number of oxidation of titanium contained in the shell is less than 4, or the number of oxidation of niobium contained in the shell is less than 5. The method according to claim 1,
The second single crystal niobium titanium composite oxide has the same crystal structure as the single crystal niobium titanium composite oxide represented by the composition formula Nb ₂ TiO ₇ . The method according to claim 1,
Wherein the particles have a molar composition ratio of niobium to titanium of 0 < Nb / Ti &amp;le; 2. The method according to claim 1,
The second single crystal niobium titanium composite oxide has a composition formula Nb _{1 . 33} Ti _{0 . 67} O ₄ . The method according to claim 1,
And a carbon layer covering the particles. As a non-aqueous electrolyte cell,
A negative electrode comprising the battery active material according to any one of claims 1 to 7,
The positive electrode,
Non-aqueous electrolyte
And a nonaqueous electrolyte battery. As a battery pack,
A battery pack comprising the nonaqueous electrolyte battery according to claim 8. 10. The method of claim 9,
A plurality of said non-aqueous electrolyte cells,
Wherein the plurality of nonaqueous electrolyte batteries are electrically connected in series or parallel to each other, or connected in series and in parallel. As an automobile,
An automobile equipped with the battery pack according to claim 9.

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