JPH1154118A - Electrode for secondary battery and secondary battery using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrode which can impart high battery capacity by using a carbon material obtained by heat-treating resin which has a structure containing a skeleton by connecting phenol or its derivative by a methylene group and on which absorbance in the vicinity of the specific wave number of an infrared absorption spectrum is not maximum. SOLUTION: A carbon material obtained by heat treating resin on which absorbance in the vicinity of 825 cm<-1> is not maximum in an infrared absorption spectrum of the resin having a structure containing a skeleton by connecting phenol or its derivative on which an electric potential change is basically small by a methylene group, is used as an electrode. Therefore, battery capacity can be increased while keeping a characteristic such as an electric potential change is small. This carbon material is amorphous, and is suitable since the battery capacity can be increased. To put it concretely, the resin to be used is desirable to be a phenol formaldehyde resin, and in its infrared absorption spectrum, absorbance in the vicinity of 760 and/or 880 cm<-1> is larger than absorbance in the vicinity of 825 cm<-1> .

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrode for a secondary battery and a secondary battery using the same, and more particularly to a secondary battery which generates an electromotive force by entering and exiting lithium ions and the like by absorbing and releasing ions such as lithium ions. The present invention relates to an electrode for use and a secondary battery using the same.

[0002]

2. Description of the Related Art In recent years, the use of chargeable / dischargeable so-called secondary batteries has been increasingly widespread, and accordingly, demands for higher capacity have been increasing. Such demands have been mainly addressed by means of improving the capacity of Ni-Cd (nickel-cadmium) secondary batteries. As a result, the capacity has been improved to about 175 mAh / g at present.

On the other hand, non-aqueous electrolyte batteries using an alkali metal such as lithium for the negative electrode are widely used as power sources for electronic devices and the like because of their high energy density. In particular, recently, research and development of secondary batteries have been promoted.

[0004] However, in the case of a secondary battery using lithium metal for the negative electrode, the metal may precipitate in a dendrite shape on the negative electrode during overcharge, and as a result, a regular voltage may not be generated.

Therefore, a non-aqueous electrolyte secondary battery has been proposed in which lithium metal is doped or alloyed in carbonaceous materials or compounds, instead of using lithium metal for the negative electrode.

[0006] In these secondary batteries, the possibility of dendrite generation is lower than when lithium metal is used as it is as a negative electrode.

For example, in a secondary battery using graphite as a carbonaceous material, the lithium-graphite intercalation compound specific to graphite takes the form of lithium, instead of being in a metallic state.
It is kept in graphite in an ionic state. For this reason, precipitation of dendrite which may occur when metallic lithium is used for the negative electrode does not occur. In addition, in terms of energy density, a capacity of 372 mAh / g is obtained in the first stage in which lithium ions are held between the layers of graphite. This is about 2700 higher capacity than the conventional Ni-Cd secondary battery, but is 3700 when metal lithium is used as the negative electrode.
The capacity is about 1/10 compared to mAh / g.

Further, recently, among carbon materials,
1500 ° C or lower, which is relatively lower than graphitizing organic substances,
In particular, attempts have been made to use amorphous carbon obtained by treating at a heat treatment temperature in the range of about 600 ° C. to 1300 ° C. for an electrode such as a negative electrode.

In this case, the capacity varies greatly depending on the organic material used as the starting material, and when the specific starting material is used, the capacity is higher than that when graphite is used, such as 400 mAh / g or more. Has been obtained.

As described above, the performance of a secondary battery can be improved by using graphite or an amorphous carbon material having a lower processing temperature for an electrode such as a negative electrode instead of metallic lithium. Is coming.

[0011]

However, it is considered that an amorphous carbon material other than graphite may be used in order to increase the capacity of the battery. When a chemical substance is used, the battery capacity can be increased, but the potential fluctuation is large, and when a battery is formed using this, the voltage of the battery decreases during use.

On the other hand, when a non-graphitizable substance is used as a starting material, the potential change is small, but the battery capacity tends to be small as compared with the case where a graphitizable substance is used.

The present invention provides a structure having a skeleton in which phenol or a derivative thereof is connected to a phenol or a derivative thereof by a methylene group. The present invention provides an electrode for a secondary battery that can exhibit a large battery capacity when applied to a secondary battery using a carbon material obtained by firing a resin having the electrode. The purpose is to realize a large battery capacity.

[0014]

In order to solve the above-mentioned problems, the present invention relates to a resin having a structure containing a skeleton in which phenol or a derivative thereof is linked by a methylene group, and the infrared light absorption spectrum of the resin. A secondary battery electrode using a carbon material obtained by heat-treating a resin whose absorbance near 825 cm ^-1 is not the maximum, and a secondary battery using the same as an electrode.

[0015] With such a configuration, when applied to a secondary battery, it has a strong tendency to be a non-graphitizable material, and basically has a small potential fluctuation. To provide a secondary battery electrode that can exhibit a large battery capacity when applied to a secondary battery using a carbon material obtained by firing a resin having a structure,
Further, in a secondary battery using this electrode, a large battery capacity is actually realized.

[0016]

DETAILED DESCRIPTION OF THE INVENTION The present invention according to claim 1 is a resin having a structure containing a skeleton in which phenol or a derivative thereof is linked by a methylene group, and has an absorbance near 825 cm ^-1 in an infrared light absorption spectrum thereof. Is an electrode for a secondary battery using a carbon material obtained by heat-treating a non-maximum resin.

With such a configuration, the electrode for a secondary battery can realize a secondary battery having a large battery capacity while suppressing potential fluctuations.

That is, according to the present invention, the absorbance around 825 cm ^-1 in the infrared absorption spectrum of a resin having a structure containing a skeleton in which phenol or its derivative having a small fluctuation in potential is basically connected by a methylene group is not the maximum. This is based on a novel finding that when a carbon material obtained by heat-treating a resin is used for an electrode for a secondary battery, the battery capacity can be increased while maintaining the characteristic of small potential fluctuation.

The absorbance near 825 cm ^-1 in the infrared absorption spectrum is considered to correspond to the monosubstituted phenol in the resin. It is determined that the battery capacity could be increased.

Here, it is preferable that the carbon material obtained by the heat treatment is an amorphous carbon material in that the battery capacity can be increased as compared with the graphite material. It is.

[0021] In other words, as claimed in claim 3 wherein the resin is around 760 cm ^-1 in its infrared absorption spectrum, of the 825cm ^-1 and near 880 cm ^-1 vicinity of absorbance, 760 cm ^-1 and around / or 880cm absorbance around ^-1, an electrode for a secondary battery using a carbon material obtained by heat treatment of the larger resin than absorbance around 825cm ^-1.

Even in such a configuration, 825 cm ^-1
Since a resin whose absorbance in the vicinity is not maximum is used, the electrode for a secondary battery can realize a secondary battery having a large battery capacity while suppressing a potential fluctuation to be small.

The absorbance near 760 cm ^-1 in the infrared light absorption spectrum corresponds to the disubstituted phenol in the resin, and the absorbance near 880 cm ^-1 corresponds to the trisubstituted phenol in the resin. Therefore, it is determined that the battery capacity was able to be increased by keeping the content of the monosubstituted phenol relatively low.

Of course, as described in claim 4, the resin may have the maximum absorbance near 760 cm ^-1 in the infrared light absorption spectrum. 880 cm in light absorption spectrum
The absorbance near ^-1 may be maximum.

Further, as set forth in claim 6, it is preferable that the heating temperature for curing the resin is 250 ° C. or less in order to cure the resin or to form an amorphous structure thereafter.

Further, as described in claim 7, the specific resin is preferably a phenol formaldehyde resin.

[0027] According to an eighth aspect of the present invention, there is provided an electrode for a secondary battery capable of inserting and extracting an alkali metal ion, wherein the alkali metal is preferably lithium. .

According to a tenth aspect of the present invention, there is provided an electrode for a secondary battery according to any one of the first to ninth aspects, the other electrode, the one electrode and the other electrode. And a negative electrode which is an electrode for a secondary battery according to claim 9, and a positive electrode, and between the negative electrode and the positive electrode, as described in claim 11. And an electrolyte containing a lithium compound disposed in the secondary battery.

The secondary battery having such a configuration is a secondary battery having a large battery capacity while suppressing the potential fluctuation.

Next, each embodiment of the present invention will be described more specifically. (Embodiment 1) In this embodiment, first, 28.2 g of phenol and 17.1 g of paraformaldehyde were respectively put in water to prepare a reaction solution.

Next, the reaction solution was heated to 50 ° C.
The reaction solution was heated to 80 ° C. with stirring, continued stirring for 30 minutes, and further stirred at 90 ° C. for 1 hour.

Next, after cooling to room temperature, acetic acid was added until the pH reached 6. The reaction solution was poured into an equal volume of methanol and then filtered, and the solid content after the filtration was washed in hot methanol for 15 minutes to obtain a phenol formaldehyde resin.

Next, in order to cure this phenol formaldehyde resin, 1 ° C./minute from room temperature to 200 ° C.
, And then kept at 200 ° C. for 10 hours, cooled to room temperature, and cured.

The cured phenol formaldehyde resin was pulverized with a ball mill until it passed through a sieve of 75 μm.

FIG. 1A shows the result of measuring the infrared absorption spectrum of the obtained cured phenol formaldehyde resin powder.

According to FIG. 1A, the infrared light absorption spectrum
760cm^-1A gentle peak near
Have, 825cm^-1No peak near and 880
cm ^-1It can be seen that there is a maximum sharp peak in the vicinity.

Next, the cured phenol formaldehyde resin powder was heated from room temperature to 1000 ° C. at a rate of 2 ° C. per minute in a tubular electric furnace under a nitrogen atmosphere, and then held at 1000 ° C. for 1 hour to obtain an amorphous carbon material. I got

Then, 10% by weight of polyvinylidene fluoride (PVDF) was added as a binder to the obtained carbon material.
The mixture was mixed and applied on a copper foil having a thickness of 20 μm to prepare a negative electrode.

On the other hand, 10 wt% of PVDF was mixed as a binder with LiCoO ₂ powder, and the mixture was applied on a copper foil having a thickness of 20 μm to prepare a positive electrode.

Further, ethylene carbonate and diethyl carbonate are mixed in a ratio of 1:
1 mol / mol of LiPF ₆ was added to the organic solvent mixed at a ratio of 1.
1 to prepare an electrolytic solution.

Then, between the positive electrode and the negative electrode prepared as described above, a porous polypropylene impregnated with an electrolytic solution was sandwiched to produce a total of 10 coin batteries.

The average capacity of the ten batteries thus obtained was measured, and the results are shown in the following (Table 1).

[0043]

[Table 1]

(Embodiment 2) In this embodiment, a coin battery was manufactured in the same manner except that the paraformaldehyde of Embodiment 1 was changed to 15.3 g.

FIG. 1 shows the infrared absorption spectrum of the cured phenol formaldehyde resin powder obtained at this time.
(B) shows the average capacity of the battery in the above (Table 1).

According to FIG. 1B, the infrared light absorption spectrum
760cm^-1A gentle peak near
Have, 825cm^-1No peak near and 880
cm ^-1Having the largest sharp peaks near
Same as Form 1, but 760 cm^-1Gentle near
The peak increases relatively to 880 cm^-1The largest pi
Talks have slowed, and their difference is relatively decreasing.

Although the average capacity of the battery is smaller than that of the first embodiment, it is 372 mAh, which is the theoretical value of graphite.
/ G is a sufficiently large value.

(Embodiment 3) In this embodiment, a coin battery was manufactured in the same manner except that the paraformaldehyde of Embodiment 1 was changed to 13.5 g.

The infrared absorption spectrum of the cured phenol formaldehyde resin powder obtained at this time is shown in FIG.
Table 1 shows the average capacity of the battery in (c).

According to FIG. 1C, the infrared light absorption spectrum
760cm^-1With a peak near 88
0cm^-1Having a peak in the vicinity is the same as in the first embodiment.
Similar, but compared to the second embodiment,
m^-1The nearby peaks are sharper and largest,
825cm^-1A peak begins to be seen in the vicinity, 880 cm ^-1
It can be seen that the peaks in the vicinity have slowed down.

Although the average capacity of the battery is smaller than that of the first and second embodiments, it is 372 m, which is the theoretical value of graphite.
The value is sufficiently larger than Ah / g.

(Embodiment 4) In this embodiment, a coin battery was manufactured in the same manner as in Embodiment 1 except that 10.8 g of paraformaldehyde was used.

FIG. 1 shows the infrared absorption spectrum of the cured phenol formaldehyde resin powder obtained at this time.
(D) shows the average capacity of the battery in the above (Table 1).

According to FIG. 1D, the infrared light absorption spectrum has a peak near 760 cm ⁻¹ , as in the first embodiment. no peak near ^-1 are those largest sharper, but in the vicinity 825Cm ^-1 have increased sharper peaks, less than peak around 760 cm ^-1, no longer noticeable peak around 880 cm ^-1 You can see that it is.

Although the average capacity of the battery is smaller than that of the first to third embodiments, it is 372 which is the theoretical value of graphite.
It is also a value larger than mAh / g.

In FIGS. 1A to 1D, the vertical axis is shifted at a predetermined interval for convenience of comparison.

Considering the first to fourth embodiments,
As the amount of paraformaldehyde added to phenol was reduced, 760 c
In the vicinity of m ⁻¹ , the peak gradually becomes sharp, and eventually becomes the maximum peak. In the vicinity of 825 cm ⁻¹ , the peak which was not present gradually becomes sharp, but does not become the maximum peak, and is 880 cm ^−1. In the vicinity, it can be seen that the first sharp peak gradually becomes dull and becomes smaller, and the capacity value also decreases with that. However, the theoretical value of graphite is 372 mAh /
It can also be confirmed that a value larger than g is realized.

Comparative Example 1 In this comparative example, a coin battery was fabricated in the same manner as in Example 1, except that the paraformaldehyde was changed to 9.0 g.

The infrared absorption spectrum of the cured phenol formaldehyde resin powder obtained at this time is shown in FIG.
(A) shows the average capacity of the battery in the following (Table 2).

[0060]

[Table 2]

[0061] According to FIG. 2 (a), the has a peak in the vicinity 760 cm ^-1 vicinity and 880 cm ^-1 although there are differences in shape in the infrared absorption spectrum is similar to the first embodiment , In comparison with the fourth embodiment,
760 cm ^-1 vicinity, 825cm ^-1 near and 880 cm ^-1
Clear peaks can be seen in the vicinity, but 825
The peak around cm ^-1 is the largest.

Further, the average capacity of the battery can no longer be realized only a value smaller than the theoretical value of 372 mAh / g of graphite.

(Comparative Example 2) In this comparative example, the first embodiment
8.0 g of the same amount of phenol and paraformaldehyde
And water were added to water to prepare a reaction solution, and the reaction solution was heated to 80 ° C. with stirring, kept stirring for 30 minutes, and further stirred at 90 ° C. for 2 hours. 0 g was added, and the mixture was stirred for 3 hours.

Next, after cooling to room temperature, the reaction solution was poured into an equal volume of methanol, filtered, and the solid content was washed in hot methanol for 15 minutes to obtain a phenol formaldehyde resin.

Next, in order to cure the phenol formaldehyde resin, 3.0 g of hexamethylenetetramine was added, and the temperature was raised from room temperature to 200 ° C. at a rate of 1 ° C./minute, and then maintained at 200 ° C. for 3 hours. Cooled to room temperature.

Then, a coin battery was manufactured in the same manner as in Embodiment 1 except that the cured phenol formaldehyde resin thus obtained was used.

FIG. 2 shows the infrared absorption spectrum of the cured phenol formaldehyde resin powder obtained at this time.
(B) shows the average capacity of the battery in the above (Table 2).

[0068] According to FIG. 2 (b), the has a peak in the vicinity 760 cm ^-1 vicinity and 880 cm ^-1 although there are differences in shape in the infrared absorption spectrum is similar to the first embodiment , comparing both forms 3 and Comparative example 1. FIG, 760 cm around ^{-1, 825cm -1} near and 8
Although any visible distinct peak near 80 cm ^-1, the peak near 825cm ^-1 becomes more clearly as the maximum one.

Further, the average capacity of the battery can no longer be realized only a value smaller than the theoretical value of 372 mAh / g of graphite.

In FIGS. 2A and 2B, the vertical axis is shifted at a predetermined interval for convenience of comparison.

Comprehensively studying through Embodiments 1 to 4 and Comparative Examples 1 and 2, when the amount of paraformaldehyde added to phenol is reduced, the infrared light absorption spectrum shows that near 760 cm ^-1. , The peak gradually becomes sharper, and then decreases again after reaching the maximum peak. At around 825 cm ⁻¹ , the peak which was not present gradually becomes sharper, and eventually becomes the maximum peak, and at around 880 cm ^−1. It can be seen that the first sharp peak tends to gradually decrease, and the capacitance value decreases accordingly. However, under the condition that the peak near 825 cm ^-1 does not become the maximum peak, the theoretical value of 372 which is the theoretical value of graphite is 372 cm ^-1.
While it can be confirmed that a value larger than mAh / g is realized, once the peak near 825 cm ^-1 is the maximum peak, a value larger than 372 mAh / g, which is the theoretical value of graphite, is realized. It is also understood that it becomes impossible.

In view of the results of Comparative Example 2, it is considered that this tendency does not change regardless of whether the pH is adjusted.

As described above, the infrared light absorption spectrum of 760
around cm ^-1, when compared respectively absorbance around 825cm ^-1 and near 880 cm ^-1, using a carbon material as the absorbance is the largest is produced by heat-treating the resin is not a signal around 825cm ^-1 Thus, it can be understood that the battery capacity increases.

In each of the above embodiments, the temperature for obtaining an amorphous carbon material is 1000 ° C.
Needless to say, it is sufficient that an amorphous carbon material is obtained even if the temperature is not at this temperature. In this case, the rate of temperature rise and the holding time can be appropriately set.

The temperature for curing the resin is 200 ° C.
However, in consideration of the preconditions for obtaining the amorphous carbon material on curing of the resin and thereafter, 25
It is considered that the temperature should be 0 ° C. or less.

Although the description has been given of the case where the present invention is applied to a coin battery, the shape of the battery is not limited, and it is needless to say that the present invention can be applied to various shapes such as a cylindrical shape and a square shape.

Of course, the alkali metal ions to be inserted / extracted can be used without being limited to lithium ions as long as they can be inserted / extracted.

When lithium ions were used as the alkali metal ions as the battery electrolyte, LiPF was used.
₆ is dissolved in a mixed solvent of ethylene carbonate and diethyl carbonate, but another lithium salt such as one in which a lithium salt such as LiBF ₄ or LiAsF ₆ is dissolved in a mixed solvent of propyl carbonate and diethyl carbonate is shown. A solution dissolved in a solvent is also applicable. In the case of another alkali metal ion, a compound solution capable of providing this ion can be used as appropriate.

Although the case where a Co compound is used as the positive electrode has been described, a Ni compound, a Mn compound, an Fe compound or the like can be applied, and another electrode can be used.

Further, the carbon material described in each embodiment is:
Not only can it be used for the negative electrode, but if there is no functional problem such as occlusion and release of ions, it can be used for the positive electrode. It is.

[0081]

As is apparent from the above description, according to the present invention, a resin which is a raw material of a carbon material, which does not have the largest absorbance near 825 cm ^{-1 in the} infrared light absorption spectrum. By using, it is possible to obtain a secondary battery electrode capable of realizing a high-capacity secondary battery while maintaining high potential stability, and when this electrode is actually used for a secondary battery, Thus, a secondary battery having high potential stability and high battery capacity can be obtained.

[Brief description of the drawings]

FIG. 1 is a diagram showing an infrared absorption spectrum in each embodiment of the present invention.

FIG. 2 is a diagram showing an infrared absorption spectrum in each comparative example.

Continuation of the front page (72) Inventor Souji Tsuchiya Inside Matsushita Giken Co., Ltd. 3-1-1 Higashi-Mita, Tama-ku, Kawasaki

Claims (11)

[Claims] 1. A resin having a structure containing a skeleton in which phenol or a derivative thereof is linked by a methylene group, which is obtained by heat-treating a resin having an absorbance near 825 cm ⁻¹ in an infrared absorption spectrum that is not maximum. An electrode for a secondary battery using a carbon material. 2. The electrode for a secondary battery according to claim 1, wherein the carbon material obtained by the heat treatment is an amorphous carbon material. 3. The resin has an infrared absorption spectrum in the vicinity of 760 cm ⁻¹ , 825 cm ⁻¹ , and 880 c ^−1.
Of absorbance around m ^-1, 760 cm ^-1 and around / or 880cm absorbance around ^-1, rechargeable battery electrode larger claim 1 or 2, wherein than absorbance around 825cm ^-1. 4. The secondary battery electrode according to claim 3, wherein the resin has a maximum absorbance near 760 cm ⁻¹ in an infrared light absorption spectrum. 5. The electrode for a secondary battery according to claim 3, wherein the resin has a maximum absorbance near 880 cm ⁻¹ in an infrared light absorption spectrum. 6. The electrode for a secondary battery according to claim 1, wherein a curing heating temperature of the resin is 250 ° C. or less. 7. The electrode for a secondary battery according to claim 1, wherein the resin is a phenol formaldehyde resin. 8. The electrode for a secondary battery according to claim 1, which can occlude and release alkali metal ions. 9. The method according to claim 8, wherein the alkali metal is lithium.
The electrode for a secondary battery as described in the above. 10. The secondary battery electrode according to claim 1, wherein the one electrode, the other electrode, and an electrolyte disposed between the one electrode and the other electrode are provided. Having a secondary battery. 11. A secondary battery comprising the negative electrode as the electrode for a secondary battery according to claim 9, a positive electrode, and an electrolyte containing a lithium compound disposed between the negative electrode and the positive electrode.