阅读说明：本技术 蓄电装置用组合物以及使用该蓄电装置用组合物的蓄电装置用隔板和蓄电装置 (Composition for electricity storage device, and separator for electricity storage device and electricity storage device using same ) 是由 杉原良介 渡边桂一 爪田觉 石本修一 于 2018-04-27 设计创作，主要内容包括：需要与以往的锂化合物相比即使在还原气氛中使用时也能够抑制蓝变(还原)所引起的导电性的显现、而且能够抑制以往的蓄电装置中成为问题的使用时和经时变化中的二氧化碳、氢气、氟气等各种气体的产生的蓄电装置用组合物。本发明的蓄电装置用组合物的特征在于,以X射线衍射图谱中的2θ(衍射角)＝18.4±0.1°的峰强度(A)与2θ(衍射角)＝43.7±0.1°的峰强度(B)的强度比(A/B)为1.10以上的Li<Sub>2</Sub>TiO<Sub>3</Sub>作为主成分。(There is a need for an electricity storage device that can suppress the occurrence of conductivity due to blue discoloration (reduction) even when used in a reducing atmosphere as compared with conventional lithium compounds, and can suppress the generation of various gases such as carbon dioxide, hydrogen, fluorine, and the like during use and change with time, which have been problematic in conventional electricity storage devicesA composition is provided. The composition for an electric storage device is characterized in that the intensity ratio (A/B) of the intensity of a peak (A) with a 2 theta (diffraction angle) of 18.4 + -0.1 DEG to the intensity of a peak (B) with a 2 theta (diffraction angle) of 43.7 + -0.1 DEG in an X-ray diffraction pattern is 1.10 or more of Li 2 TiO 3 As the main component.)

1. A composition for an electric storage device, characterized in that the intensity ratio (A/B) of the intensity of a peak (A) with a 2 theta (diffraction angle) of 18.4 + -0.1 DEG to the intensity of a peak (B) with a 2 theta (diffraction angle) of 43.7 + -0.1 DEG in an X-ray diffraction pattern is 1.10 or more of Li₂TiO₃As the main component.

2. A separator for an electrical storage device, characterized by using the composition for an electrical storage device according to claim 1.

3. An electricity storage device, characterized in that the separator for an electricity storage device according to claim 2 is used.

Technical Field

The present invention relates to a composition used for an electric storage device such as a lithium ion battery or an electric double layer capacitor. More specifically, the present invention relates to a lithium titanate (Li) having a specific peak ratio₂TiO₃) A composition for an electricity storage device, which is capable of suppressing the appearance of conductivity due to blue discoloration (reduction) even when used in a reducing atmosphere as compared with conventional lithium compounds as a main component.

Further, it relates to a lithium titanate (Li) having a specific peak ratio₂TiO₃) A separator for an electric storage device and an electric storage device, wherein generation of various gases such as carbon dioxide, hydrogen, fluorine and the like during use and change over time, which have been problematic in conventional electric storage devices, can be suppressed as a main component without lowering the battery characteristics.

Background

In recent years, power storage devices such as lithium ion batteries and electric double layer capacitors have been rapidly put into practical use because they can be made compact despite their high capacity.

However, such a power storage device has the following problems: gases such as carbon dioxide, hydrogen, and fluorine gas are generated in the power storage device due to the mixing of impurities (for example, unreacted lithium carbonate remaining in the active material) and moisture present in the power storage device, or the oxidative decomposition of the electrolyte solution and the material constituting the electrode due to use. The gas causes a reduction in battery characteristics of the power storage device, and when the generation of the gas continues, the gas causes a serious phenomenon such as leakage from the power storage device, a shape change (expansion), and finally ignition and explosion.

Here, among such gases, there are gases (carbon dioxide) generated by the degradation (decomposition) of unreacted lithium carbonate with time or the oxidative decomposition of the electrolyte by repeating charge and discharge, and in addition to such gases, protons (H) which cause hydrogen gas or fluorine gas are generated⁺). Specifically, there are: protons (H) generated by electrolysis of water itself that has permeated into the power storage device⁺) (ii) a Lithium hexafluorophosphate (LiPF) is used in the electrolyte₆) Lithium tetrafluoroborate (LiBF)₄) When used as an electrolyte, the electrolyte may be decomposed into BF due to the decomposition of the electrolyte₄ ^-、PF₆ ^-The plasma anions react with moisture penetrating into the power storage device to form Hydrogen Fluoride (HF) and further dissociate to form protons (H)⁺) And the like. Then, the protons are bonded to each other to generate hydrogen gas, or fluorine ions dissociated from Hydrogen Fluoride (HF) are bonded to each other to generate fluorine gas.

In addition, there is a possibility that BF is decomposed from an electrolyte₄ ^-、PF₆ ^-The plasma reacts with unreacted lithium carbonate to produce carbon dioxide.

Therefore, gas-absorbing materials containing various compounds (mainly lithium compounds) as the main component have been developed so far for absorbing the generated gas (patent documents 1 to 3). Specifically, patent document 1 describes: a lithium composite oxide is used as an absorbing material for carbon dioxide, and zeolite is used as an absorbing material for hydrogen (refer to claims 2, 3 and [0012] to [0014] of patent document 1). Patent document 2 describes: lithium hydroxide is used as an absorbing material for carbon dioxide, hydrogen gas, and the like (refer to claim 3 and [0009], [0010] of patent document 2). Patent document 3 describes: carbonates of alkaline earth metals are used as an absorbing material for fluorine gas (refer to claims 1, 3, 4 and [0014] of patent document 3).

Patent document 4 describes a carbon dioxide absorbing material obtained by mixing lithium carbonate powder, lithium oxide powder and titanium dioxide powder at a specific ratio (see claim 1 and [0028 ] of patent document 4)]) Non-patent document 1 discloses that a lithium composite oxide can be used as an absorbing material for carbon dioxide (refer to "novel CO" on page 12 of non-patent document 1)₂The characteristics of the absorbent material ").

Disclosure of Invention

Problems to be solved by the invention

However, these documents all aim at absorbing the generated gas, and do not aim at suppressing the generation of the gas itself, that is, capture of protons (H) that are a gas generation source⁺) The purpose itself (technical idea).

Therefore, the various absorbing materials described in these documents may prevent leakage, shape change (swelling), ignition, explosion, and the like, but do not change the point of gas generation (generation of an electrolyte, oxidative decomposition of a material constituting an electrode, and the like), and thus cannot prevent degradation of battery characteristics.

Further, since the lithium compound forms lithium ions in the electric storage device and migrates, when the lithium compound exists in the vicinity of the negative electrode or on the negative electrode side as described in patent documents 1 to 4, the lithium ion is reduced (blue change occurs), and thus conductivity is exhibited, and a short circuit (short) phenomenon occurs.

Therefore, when a lithium compound is conventionally used, it is generally used as a material for a positive electrode. In addition, when a lithium compound is used as a material of the separator, the lithium compound is used in a form of being disposed and applied to the positive electrode side (a form of not being exposed to the negative electrode side), but there is a problem that the manufacturing process becomes complicated in order to form such a form.

As a result of intensive studies made by the inventors of the present application, the following findings were obtained: by using lithium titanate having a specific peak ratio as a main component, it is possible to suppress the development of conductivity due to blue shift (reduction) even when used in a reducing atmosphere as compared with a conventional lithium compound. In particular, the following findings were obtained: when used as a material for a separator, it is not necessary to form a configuration in which the separator is disposed and applied to the positive electrode side (a configuration in which the separator is not exposed to the negative electrode side) as in the conventional case, and it is not necessary to adopt a complicated manufacturing process.

In addition, the following findings were obtained: the development of conductivity due to blue discoloration (reduction) can be suppressed, and the generation of various gases such as carbon dioxide, hydrogen, fluorine gas, etc., which have been problematic in conventional power storage devices during use and change over time, can be suppressed, and specifically, protons (H) which are a gas generation source can be captured⁺) Itself.

The present invention has been made in view of the above-described conventional problems, and an object thereof is to provide a composition for an electricity storage device, which can suppress the occurrence of conductivity due to blue discoloration (reduction). Further, it is an object of the present invention to provide a separator for an electric storage device and an electric storage device using the composition for an electric storage device.

Means for solving the problems

In order to achieve the above object, a composition for an electric storage device according to the present invention is characterized in that the composition is expressed in terms of 2 θ (diffraction angle) in an X-ray diffraction pattern of 18.4An intensity ratio (A/B) of the peak intensity (A) of + -0.1 DEG to the peak intensity (B) of 43.7 + -0.1 DEG in terms of 2 theta (diffraction angle) is 1.10 or more of Li₂TiO₃As the main component.

The separator for an electricity storage device of the present invention is characterized by using the composition for an electricity storage device of the present invention.

The power storage device of the present invention is characterized by using the separator for a power storage device of the present invention.

Effects of the invention

According to the composition for an electric storage device of the present invention, it is possible to obtain a composition for an electric storage device that can suppress the occurrence of electric conductivity due to blue discoloration (reduction) even when used in a reducing atmosphere, as compared with a conventional lithium compound.

Further, by using lithium titanate having a specific peak ratio as a main component, an electric storage device can be obtained which can suppress generation of various gases such as carbon dioxide, hydrogen, fluorine gas, and the like during use and with time, which have been problematic in conventional electric storage devices, without deteriorating the performance of the electric storage device (while reducing a leak current).

Specifically, as shown in the following reaction formula, the lithium ions in the composition for an electric storage device of the present invention are ion-exchanged with protons generated in the electric storage device, whereby protons (H) serving as a gas generation source can be captured⁺) Itself.

In addition, the gas composition for an electric storage device according to the present invention can capture carbon dioxide by an ion exchange reaction between titanate ions and carbonate ions.

Li₂TiO₃+2H⁺→H₂TiO₃+2Li⁺(proton Capture ═ ion exchange reaction)

Li₂TiO₃+CO₂→Li₂CO₃+TiO₂(CO₂Absorption)

In addition, when the composition for an electric storage device of the present invention is used for a separator of an electric storage device, even in a form in which the composition for an electric storage device of the present invention is slightly exposed to the negative electrode side of the separator (even if strict manufacturing management is not performed such that a lithium compound is not exposed to the negative electrode side as in the case of a conventional separator), an electric storage device in which generation of various gases can be suppressed without causing a decrease in battery characteristics can be obtained.

(basic structure)

The composition for an electric storage device of the present invention is 213 type lithium titanate (Li) among lithium titanates₂TiO₃) An intensity ratio (A/B) of a peak intensity (A) with a 2 theta (diffraction angle) of 18.4 + -0.1 DEG to a peak intensity (B) with a 2 theta (diffraction angle) of 43.7 + -0.1 DEG in an X-ray diffraction pattern, the intensity ratio (A/B) being 1.10 or more₂TiO₃As the main component. Thus, the composition for an electric storage device of the present invention contains Li having a specific peak ratio₂TiO₃As a result, the main component can suppress the development of conductivity due to blue discoloration (reduction) even when used in a reducing atmosphere as compared with conventional lithium compounds.

Here, since lithium titanate is generally produced (synthesized) by mixing and firing a Li source and a Ti source as raw materials, not only Li is synthesized₂TiO₃And also synthesize spinel type (Li)₄Ti₅O₁₂) Ramsdellite type (LiTi)₂O₄: type 124, Li₂Ti₃O₇Type 237), etc.

Therefore, the term "as a main component" in the present invention means that even when lithium titanate having various structures is contained as described above, Li is contained₂TiO₃The lithium titanate having the composition of (1) as a main component. In particular, with Li₂TiO₃The content of lithium titanate having the composition of (3) is 70% or more. More preferably 90% or more, and most preferably 95% or more.

(X-ray diffraction Pattern)

Further, the composition for an electric storage device of the present invention is obtained by mixing Li₂TiO₃In the crystal structure of (2), a represents a peak intensity at which the characteristic peak 2 θ (diffraction angle) of the 002 plane is 18.4 ± 0.1 °, and Li represents₂TiO₃The intensity ratio (a ÷ based on the characteristic peak intensity of the 113 plane 2 θ (diffraction angle) of the crystal structure (B) is defined as the peak intensity of 43.7 ± 0.1 ° in BB) Is 1.10 or more of Li₂TiO₃As the main component. That is, the composition for an electric storage device of the present invention has Li grown in the 002 plane direction₂TiO₃With such a feature, a composition can be obtained which can suppress the development of conductivity due to blue discoloration (reduction) even when used in a reducing atmosphere, as compared with conventional lithium compounds.

When the peak intensity ratio (a/B) is 1.10 or more, the upper limit is not particularly limited, but the effect of suppressing blue discoloration (reduction) is limited even if it is excessively increased, and therefore, the upper limit of the peak intensity ratio (a/B) is preferably set to 1.50. In addition, the peak intensity ratio (A/B) is preferably set to 1.10 to 1.33.

(Li Source)

The Li source as a raw material of the composition for an electric storage device of the present invention is not particularly limited, and various Li sources such as lithium carbonate, lithium hydroxide, and lithium nitrate can be used. In particular, lithium hydroxide is preferably used from the viewpoint of ease of production of the composition for an electric storage device having a specific peak intensity of the present invention.

(Ti source)

The Ti source as a raw material of the composition for an electric storage device of the present invention is not particularly limited as well as the Li source, and various titanic acid compounds such as metatitanic acid, anatase-type or rutile-type titanium oxide, titanium chloride, titanium sulfate, titanyl sulfate, and the like can be used. In particular, anatase-type titanium oxide is preferably used from the viewpoint of ease of production of the composition for an electric storage device having a specific peak intensity of the present invention.

In addition, when titanium oxide is used as the Ti source, the water content in the crystal structure thereof is preferably less than 25% by weight, more preferably less than 15% by weight, and most preferably less than 10% by weight. On the other hand, when titanium oxide having a water content of 25 wt% or more in the crystal structure is used, it is difficult to prepare the composition for an electric storage device of the present invention having a specific peak strength, which is not preferable. Here, the water content in the crystal structure refers to a weight reduction rate in a temperature range of 100 ℃ to 400 ℃ in thermogravimetric analysis (TG).

(luminance (L value))

In addition, the composition for an electric storage device of the present invention can suppress the appearance of conductivity due to reduction by setting a specific peak ratio, and thus exhibits a characteristic hue.

Here, it is known that lithium titanate generally turns blue when reduced, and therefore the composition for an electric storage device of the present invention suppresses blue change even before and after charging, specifically, shows a luminance (L value) of 80 or more. In addition, the composition with brightness (L value) of 82 ~ 93 is especially preferred.

(production method)

As a method for producing the composition for an electric storage device of the present invention, a known method can be used, but lithium titanate (Li) having a specific peak ratio can be obtained at a high content₂TiO₃) From the viewpoint of (1), the material is preferably produced by primary firing at a temperature of 650 ℃ or higher for 2 hours in the air. In particular, the ceramic is more preferably produced by primary firing at a temperature of 750 to 850 ℃ for 2 hours in the air.

In addition, in order to have the above Li₂TiO₃The content of lithium titanate having the composition of (1) is 95% or more, and strict Li/Ti (molar ratio) control is essential, and it is preferable that the Li/Ti (molar ratio) is 1.85 to 2.10. More preferably 1.90 or more and 2.05 or less, and most preferably 1.95 or more and 2.00 or less.

(separator for electric storage device)

The composition for an electric storage device of the present invention can be used as a material for an electric storage device such as a lithium ion battery or an electric double layer capacitor, and specifically can be used as a material for a positive electrode or a separator. In particular, when used as a material for a separator, the following advantages are obtained: the configuration of disposing and applying the coating on the positive electrode side as in the conventional art is not required, and the complicated manufacturing process is not required.

Drawings

FIG. 1 is an X-ray diffraction chart of a composition for a power storage device according to example 1.

FIG. 2 is an X-ray diffraction chart of the composition for a power storage device of example 2.

FIG. 3 is an X-ray diffraction chart of a composition for a power storage device according to example 3.

FIG. 4 is an X-ray diffraction chart of the composition for a power storage device of comparative example 1.

FIG. 5 is an X-ray diffraction chart of the composition for a power storage device of comparative example 2.

FIG. 6 is an X-ray diffraction chart of the composition for a power storage device of comparative example 3.

FIG. 7 is an X-ray diffraction chart of the composition for a power storage device of comparative example 4.

FIG. 8 is an X-ray diffraction chart of the composition for a power storage device of comparative example 5.

FIG. 9 is an X-ray diffraction chart of the composition for a power storage device of comparative example 6.

Fig. 10 is a schematic diagram showing the structure of the fabricated power storage device.

Detailed Description