Power storage device composition, power storage device separator using power storage device composition, and power storage device
11302993 · 2022-04-12
Assignee
Inventors
- Ryosuke Sugihara (Osaka, JP)
- Keiichi Watanabe (Osaka, JP)
- Satoru TSUMEDA (Tokyo, JP)
- Shuichi Ishimoto (Tokyo, JP)
Cpc classification
H01M4/485
ELECTRICITY
C01P2002/72
CHEMISTRY; METALLURGY
H01M10/0525
ELECTRICITY
C01P2002/74
CHEMISTRY; METALLURGY
H01G11/06
ELECTRICITY
International classification
H01M10/0525
ELECTRICITY
Abstract
There is demand for a power storage device composition that: compared to past lithium compounds, can suppress development of conductivity caused by blue discoloration (reduction), even when used in a reducing atmosphere; and can inhibit the generation of gases, such as carbon dioxide gas, hydrogen gas, and fluoride gas, that has been a problem in past power storage devices during use and with aging. This power storage device composition is characterized by including, as a principal component, Li.sub.2TiO.sub.3 that has an x-ray diffraction pattern for which the intensity ratio (A/B) of the peak intensity (A) at a diffraction angle of 2θ=18.4±0.1° and the peak intensity (B) at a diffraction angle of 2θ=43.7±0.1° is at least 1.10.
Claims
1. A power storage device composition comprising, as a principal component, Li.sub.2TiO.sub.3 that has an X-ray diffraction pattern for which an intensity ratio (A/B) of a peak intensity (A) at a diffraction angle of 2θ=18.4±0.1° to a peak intensity (B) at a diffraction angle of 2θ=43.7±0.1° is 1.10 to 1.50.
2. A power storage device separator comprising the power storage device composition according to claim 1.
3. A power storage device comprising the power storage device separator according to claim 2.
4. The power storage device composition according to claim 1, wherein the intensity ratio (A/B) is 1.10 to 1.33.
5. The power storage device separator comprising the power storage device composition according to claim 4, wherein the power storage device separator has a lightness of L value of 87 to 93.
6. The power storage device comprising the power storage device separator comprising the power storage device composition according to claim 4, wherein the power storage device has a leakage current of 0.12 to 0.43 mAh.
Description
BRIEF DESCRIPTION OF DRAWINGS
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DESCRIPTION OF EMBODIMENTS
Examples
(11) Next, power storage device compositions according to the present invention will be described in detail on the basis of Examples and Comparative Examples. It is to be understood that the present invention is not limited to Examples described below.
Example 1
(12) First, 300 g of anatase titanium oxide (AMT-100, manufactured by TAYCA Corporation) whose moisture content had been adjusted to 9% by weight and 266 g of lithium hydroxide were wet-mixed. A ratio Li/Ti (molar ratio) at this time was 1.98. Next, the resulting mixture was fired in air at 750° C. for two hours. Thus, a power storage device composition of Example 1, the composition including 213-type lithium titanate (Li.sub.2TiO.sub.3) as a principal component, was produced.
Example 2
(13) A power storage device composition of Example 2, the composition including 213-type lithium titanate (Li.sub.2TiO.sub.3) as a principal component, was produced as in Example 1 except that the firing temperature was 850° C.
Example 3
(14) A power storage device composition of Example 3, the composition including 213-type lithium titanate (Li.sub.2TiO.sub.3) as a principal component, was produced as in Example 1 except that the firing temperature was 650° C.
Comparative Example 1
(15) A power storage device composition of Comparative Example 1, the composition including 213-type lithium titanate (Li.sub.2TiO.sub.3) as a principal component, was produced as in Example 1 except that the firing temperature was 550° C.
Comparative Example 2
(16) A power storage device composition of Comparative Example 2, the composition including 213-type lithium titanate (Li.sub.2TiO.sub.3) as a principal component, was produced as in Example 1 except that the firing temperature was 450° C.
Comparative Example 3
(17) A power storage device composition of Comparative Example 3, the composition including 213-type lithium titanate (Li.sub.2TiO.sub.3) as a principal component, was produced as in Example 1 except that the ratio Li/Ti (molar ratio) was 1.84.
Comparative Example 4
(18) A power storage device composition of Comparative Example 4 was produced as in Example 1 except that the ratio Li/Ti (molar ratio) was 2.11.
Comparative Example 5
(19) A power storage device composition of Comparative Example 5 was produced as in Example 1 except that 396 g of anatase titanium oxide (manufactured by TAYCA Corporation n) whose moisture content had been adjusted to 31% by weight was used as the Ti source.
Comparative Example 6
(20) A power storage device composition of Comparative Example 6 was produced as in Comparative Example 3 except that the firing temperature was 550° C.
(21) Measurement of Peak Intensity Ratio A/B and Measurement of X-Ray Diffraction
(22) Next, regarding each of the power storage device compositions produced in Examples 1 to 3 and Comparative Examples 1 to 6, measurement with an X-ray diffractometer (X'Pert, manufactured by Malvern Panalytical Ltd.) was conducted.
(23) A peak intensity (A) at a diffraction angle of 2θ=18.4±0.1° and a peak intensity (B) at a diffraction angle of 2θ=43.7±0.1° were measured, and a peak intensity ratio A/B was calculated from the peak intensities (A) and (B). According to the results, as shown in Table 1, the peak intensity ratio A/B of the power storage device composition of Example 1 was 1.25, the peak intensity ratio A/B of the power storage device composition of Example 2 was 1.33, the peak intensity ratio A/B of the power storage device composition of Example 3 was 1.10, the peak intensity ratio A/B of the power storage device composition of Comparative Example 1 was 0.98, the peak intensity ratio A/B of the power storage device composition of Comparative Example 2 was 0.34, the peak intensity ratio A/B of the power storage device composition of Comparative Example 3 was 0.98, the peak intensity ratio A/B of the power storage device composition of Comparative Example 4 was 1.09, the peak intensity ratio A/B of the power storage device composition of Comparative Example 5 was 1.03, and the peak intensity ratio A/B of the power storage device composition of Comparative Example 6 was 0.72.
(24) Table 1 shows the ratio Li/Ti (molar ratio), the firing temperature (° C.), the moisture content (% by weight) of the Ti source, and the peak intensity ratio (A/B) of each of the power storage device compositions produced in Examples 1 to 3 and Comparative Examples 1 to 6.
(25) TABLE-US-00001 TABLE 1 Moisture Peak Li/Ti Firing content of Ti intensity (molar temperature source ratio ratio) (° C.) (% by weight) (A/B) Example 1 1.98 750 9 1.25 Example 2 1.98 850 9 1.33 Example 3 1.98 650 9 1.10 Comparative Example 1 1.98 550 9 0.98 Comparative Example 2 1.98 450 9 0.34 Comparative Example 3 1.84 750 9 0.98 Comparative Example 4 2.11 750 9 1.09 Comparative Example 5 1.98 750 31 1.03 Comparative Example 6 1.84 550 9 0.72
(26) Next, power storage device separators were produced by using the power storage device compositions produced above, and power storage devices using the separators were produced. Evaluations of the effect of suppressing blue discoloration (measurement of lightness (L value)), the effect of inhibiting the generation of gases, and a battery characteristic (leakage current) were conducted.
(27) Production of Power Storage Device Separator
(28) First, 8.6 g of each of the power storage device compositions of Examples 1 to 3 and Comparative Examples 1 to 6 and 4.5 g of polyvinylidene fluoride were kneaded, and the resulting mixture was then diluted with 16.9 g of N-methyl-2-pyrrolidone (manufactured by Kishida Chemical Co., Ltd.) to prepare a coating material for a separator.
(29) Next, the above-prepared coating material for a separator was applied to a separator (manufactured by Nippon Kodoshi Corporation) using a wire bar. Thus, each separator for a power storage device was produced. Regarding the separator for a power storage device after application, the coating material for a separator was slightly exposed to a surface to be located on the negative electrode side in the production of a power storage device described below. Separators having four types (levels) of amounts of coating, namely, 10 g/m.sup.2, 20 g/m.sup.2, 40 g/m.sup.2, and 70 g/m.sup.2 were produced.
(30) (Production of Power Storage Device)
(31) First, 520 g of orthotitanic acid (manufactured by TAYCA Corporation) and 218 g of lithium hydroxide monohydrate (manufactured by FMC Corporation) were wet-mixed, and the resulting mixture was then fired in air at 750° C., 700° C., 650° C., or 550° C. for two hours. Thus, fine particles Li.sub.4Ti.sub.5O.sub.12 having a specific surface area of 20 m.sup.2/g, 50 m.sup.2/g, 70 m.sup.2/g, or 100 m.sup.2/g were obtained.
(32) Next, the above-produced separators for power storage devices, positive electrodes in which activated carbon (AP20-0001, manufactured by AT electrode Co., Ltd.) was used as a positive electrode active material, and four types (levels) of negative electrodes in which the Li.sub.4Ti.sub.5O.sub.12 having a specific surface area of 20 m.sup.2/g, 50 m.sup.2/g, 70 m.sup.2/g, or 100 m.sup.2/g was used as a negative electrode active material were prepared.
(33) Each separator for a power storage device and the negative electrode active material were combined as described in Table 2, arranged (stacked) as illustrated in
(34) In addition to the power storage devices of Comparative Examples 7 to 12, a power storage device of Comparative Example 13 was also produced as a comparative example in which only a separator manufactured by Nippon Kodoshi Corporation (separator for a power storage device, the separator not having the coating material for a separator) was used.
(35) (Measurement of Lightness (L Value))
(36) Each of the power storage devices produced in Examples 4 to 12 and Comparative Examples 7 to 13 was charged up to 2.9 V at 25° C. The power storage device after charging was disassembled, and the separator was removed. Subsequently, the lightness (L value) of the separator was measured by using a color-difference meter (ZE6000, manufactured by Nippon Denshoku Industries Co., Ltd.).
(37) (Measurement of Leakage Current)
(38) Each of the power storage devices produced in Examples 4 to 12 and Comparative Examples 7 to 13 was charged up to 2.9 V at 60° C., and a constant voltage of 2.9 V was then maintained. Subsequently, 30 minutes after maintaining the constant voltage, a current value was measured as a leakage current.
(39) (Measurement of Amount of Gas Generated)
(40) First, an initial volume of each of the power storage devices produced in Examples 4 to 12 and Comparative Examples 7 to 13 was measured on the basis of the Archimedes' principle. Specifically, the power storage device was submerged in a water tank filled with water at 25° C., and the initial volume of the power storage device was calculated from a change in weight at that time.
(41) Next, charging and discharging of the power storage device was performed three cycles at 60° C., in a voltage range of 1.5 to 2.9 V, and at a charge/discharge rate of 0.5 C. Subsequently, the volume of the power storage device after charging and discharging was calculated by the same method as the measuring method described above. A change in the volume of the power storage device before and after charging and discharging was determined by the difference from the initial volume to measure an amount of gases generated from the power storage device. A rate of change in volume of the power storage device was also determined from a calculation formula below.
Rate of change in volume (%)=change in volume (mL)/initial volume (mL)×100
(42) Table 2 shows the results. According to the results, regarding each of the power storage devices of Examples 4 to 12, since a lithium titanate (Li.sub.2TiO.sub.3) having a peak intensity ratio A/B of at least 1.10 was applied to a separator, the lightness (L value) of the separator was a high value in a range of from 82 to 93. Thus, blue discoloration (reduction) was suppressed even in the state where the lithium titanate (Li.sub.2TiO.sub.3) was slightly exposed to a surface located on the negative electrode side.
(43) In contrast, regarding each of the power storage devices of Comparative Examples 7 to 12, the results showed that since a lithium titanate (Li.sub.2TiO.sub.3) having a peak intensity ratio A/B of less than 1.10 was applied to a separator, the lightness (L value) of the separator was a low value in a range of from 18 to 35. Thus, the lithium titanate (Li.sub.2TiO.sub.3) was subjected to blue discoloration (reduction).
(44) Next, regarding the leakage current, since blue discoloration (reduction) was suppressed in each of the power storage devices of Examples 4 to 12, the current value was a low value of 0.12 to 0.43 mAh.
(45) In contrast, the results showed that, in each of the power storage devices of Comparative Examples 7 to 12, since the lithium titanate (Li.sub.2TiO.sub.3) was subjected to blue discoloration (reduction), the current value was a high value of 0.87 to 0.96 mAh, which was substantially equal to the current value (0.92 mAh) of the power storage device of Comparative Example 13 in which only the separator (separator for a power storage device, the separator not having the coating material for a separator) was used.
(46) Furthermore, regarding the effect of inhibiting the generation of gases, the results showed that the amount (absolute quantity) of gases generated from each of the power storage devices of Examples 4 to 12 was smaller than that of the power storage device of Comparative Example 13 in which only the separator (separator for a power storage device, the separator not having the coating material for a separator) was used, and that the rate of change in volume of each of the power storage devices of Examples 4 to 12 was also lower than that of the power storage device of Comparative Example 13 (more specifically, the rate of change in volume was 5% or less).
(47) TABLE-US-00002 TABLE 2 Amount of Specific surface Initial Change in Rate of change Peak coating of area of negative Lightness volume of volume of in volume of intensity lithium electrode active of Leakage power power storage power storage Presence or absence ratio titanate material separator current storage device device device of lithium titanate (A/B) (g/m.sup.2) (m.sup.2/g) (L value) (mAh) (mL) (mL) (%) Example 4 Li.sub.2TiO.sub.3 (Example 1) 1.25 20 70 87 0.35 2.32 0.05 2.2 Example 5 Li.sub.2TiO.sub.3 (Example 2) 1.33 20 70 93 0.12 2.33 0.10 4.3 Example 6 Li.sub.2TiO.sub.3 (Example 3) 1.10 20 70 82 0.36 2.32 0.02 0.9 Example 7 Li.sub.2TiO.sub.3 (Example 1) 1.25 10 70 90 0.43 2.19 0.10 4.6 Example 8 Li.sub.2TiO.sub.3 (Example 1) 1.25 40 70 90 0.35 2.63 0.01 0.4 Example 9 Li.sub.2TiO.sub.3 (Example 1) 1.25 70 70 90 0.26 3.04 0.10 3.3 Example 10 Li.sub.2TiO.sub.3 (Example 1) 1.25 20 20 87 0.35 2.32 0.01 0.4 Example 11 Li.sub.2TiO.sub.3 (Example 1) 1.25 20 50 87 0.35 2.35 0.01 0.4 Example 12 Li.sub.2TiO.sub.3 (Example 1) 1.25 20 100 87 0.35 2.35 0.08 3.4 Comparative Li.sub.2TiO.sub.3 (Comparative 0.98 20 70 27 0.90 2.33 0.05 2.1 Example 7 Example 1) Comparative Li.sub.2TiO.sub.3 (Comparative 0.34 20 70 20 0.89 2.32 0.05 2.2 Example 8 Example 2) Comparative Li.sub.2TiO.sub.3 (Comparative 0.98 20 70 23 0.91 2.32 0.05 2.2 Example 9 Example 3) Comparative Li.sub.2Ti18 (Comparative 1.09 20 70 35 0.87 2.31 0.05 2.2 Example 10 Example 4) Comparative Li.sub.2TiO.sub.3 (Comparative 1.03 20 70 20 0.90 2.33 0.07 3.0 Example 11 Example 5) Comparative Li.sub.2TiO.sub.3 (Comparative 0.72 20 70 18 0.96 2.32 0.10 4.3 Example 12 Example 6) Comparative Absent — — 70 — 0.92 2.07 0.31 15.0 Example 13
(48) The above results showed the following. Since the power storage device composition according to the present invention includes, as a principal component, a lithium titanate (Li.sub.2TiO.sub.3) having a specific peak ratio, compared to past lithium compounds, development of conductivity caused by blue discoloration (reduction) can be suppressed, even when used in a reducing atmosphere. In addition, a leakage current can be reduced while development of conductivity caused by blue discoloration (reduction) is suppressed. Furthermore, it is possible to inhibit the generation of gases, such as carbon dioxide gas, hydrogen gas, and fluoride gas, that has been a problem in past power storage devices during use and with aging.
(49) The power storage device composition of the present invention can be used for power storage devices such as lithium-ion batteries and electric double-layer capacitors.
REFERENCE SIGNS LIST
(50) 1 power storage device 2 positive electrode 3 separator (including power storage device composition) 4 negative electrode 5 tab lead 6 case