WO2019059035A1

WO2019059035A1 - Carbon black and method for producing same

Info

Publication number: WO2019059035A1
Application number: PCT/JP2018/033564
Authority: WO
Inventors: 章史八尾; 啓之大森; 聖唯鈴木
Original assignee: セントラル硝子株式会社
Priority date: 2017-09-19
Filing date: 2018-09-11
Publication date: 2019-03-28
Also published as: JP2019053953A

Abstract

This carbon black is a surface-modified carbon black used as a conductive aid for an electrode of a non-aqueous electrolyte secondary battery, and is characterized in that the BET specific surface area is at least 35 m2/g and less than 100 m2/g, the ratio of fluorine atoms to carbon atoms, i.e., the F/C ratio, is at least 0.002 and less than 0.025, and the ratio of oxygen atoms to carbon atoms, i.e., the O/C ratio, is at least 0.01 and less than 0.1 as measured by XPS analysis. Since the element ratios of fluorine and oxygen on the surface of the carbon black are controlled within the appropriate ranges by a surface modification treatment, the cycle characteristics of a non-aqueous electrolyte secondary battery can be improved compared to the case in which an untreated carbon black is used.

Description

Carbon black and method for producing the same

The present invention relates to a carbon black used as a conductive aid in an electrode of a non-aqueous electrolyte secondary battery represented by a lithium ion secondary battery, a method for producing the same, an electrode for a non-aqueous electrolyte secondary battery containing the carbon black and a method for producing the same The present invention relates to a method, a non-aqueous electrolyte secondary battery including the electrode.

For the positive electrode and the negative electrode of non-aqueous electrolyte secondary batteries such as lithium ion secondary batteries, a composite oxide of metal is mainly used for the positive electrode as an active material, and a carbon-based material such as graphite is mainly used for the negative electrode. A paste-type electrode is used in which a paste containing carbon black or graphite fine powder as a conductive additive and a binder is applied to a metal foil as a current collector to form an electrode layer on the current collector. .

In recent years, the number of electric vehicles adopting a lithium ion secondary battery is increasing. The important characteristics of the non-aqueous electrolyte secondary battery for automobiles are the output characteristics showing the magnitude of the amount of current allowed to flow per unit time, and the cycle characteristics capable of maintaining the discharge capacity even when charging and discharging are repeated.

In order to improve the output characteristics of the non-aqueous electrolyte secondary battery, it is important to reduce the internal resistance of the battery as much as possible. Therefore, the conductive aid forming the conductive network in the electrode is uniform throughout the electrode material and There is a technique to reduce the electrode resistance by dispersing it in high concentration. Since carbon black has a structure in which primary particles called a structure are linked in a chain-like manner, it is necessary to use a dispersant in order to prevent aggregation and breakage of the structure and to appropriately disperse it in the electrode material. Patent Document 1 discloses a method of uniformly dispersing a positive electrode active material and a carbon material which is a conductive additive by using a nitrogen-based surfactant as a dispersant. Further, Patent Document 2 discloses a method of stably dispersing a positive electrode active material, a binder, and a carbon material which is a conductive support agent by using a triazine derivative or the like as a dispersant.

On the other hand, as a surface modification method of carbon black, Patent Document 3 discloses a method of improving affinity with a matrix by fluorinating carbon black added to oil, plastic, rubber and the like. In addition, Patent Document 4 is a method of improving the dispersibility of carbon black by oxidizing carbon black by causing carbon black to be added to a paint, ink, resin, etc. to coexist with fluorine and oxygen at a predetermined ratio. It is disclosed.

Further, in Patent Document 5, the above-mentioned fluororesin melts a mixture of a carbon-based conductive material such as carbon black or carbon fiber hydrophilically treated with fluorine gas preferably diluted with oxygen and an electrode active material in the presence of the fluororesin. Disclosed is a method for producing a lithium battery having a high output and high energy density by using an electrode material composited by firing at a temperature or more and a temperature not exceeding the temperature at which the electrode active material is thermally decomposed.

JP, 2011-14457, A JP, 2013-73724, A Japanese Patent Application Laid-Open No. 60-191011 JP-A-9-40881 JP 2015-228290 A JP, 2016-9564, A

It is known that carbon black used as a conductive additive has poor dispersibility in paste. Therefore, dispersants such as surfactants are used together with the paste. However, according to Patent Document 6, the surfactant described in Patent Document 1 has a problem that when it uses lithium cobaltate used as a general positive electrode active material, decomposition occurs at the time of battery reaction, and therefore the cycle characteristics are inferior. It is pointed out that there is. In addition, it is pointed out that the compound described in Patent Document 2 is insufficient in dispersibility and is not excellent in oxidation stability, so that problems remain in cycle characteristics. Also, the dispersant is an impurity for the battery.

Patent Documents 3 and 4 disclose that the dispersion state is improved by subjecting a carbon-based material to fluorine treatment, and Patent Document 5 discloses a carbon-based conductive material for obtaining a composited electrode material. Is described as being treated with fluorine gas diluted with oxygen to make it hydrophilic, but the evaluation in the case where surface-modified carbon black is used as a conductive aid for electrodes of lithium ion secondary batteries is particularly It was not mentioned.

Therefore, the present invention can improve the dispersibility in the paste by subjecting the carbon black to the surface modification treatment, and can improve the cycle characteristics of the non-aqueous electrolyte secondary battery as compared with the case of no treatment. Method of producing carbon black for conductive support agent of electrode of water electrolyte secondary battery, and carbon black obtained by the method

As a result of various studies made by the present inventors to achieve the above object, in order to obtain a carbon black suitable as a conductive aid for an electrode for a non-aqueous electrolyte secondary battery such as a lithium ion secondary battery, It has been found that it is necessary to control the elemental ratio of fluorine and oxygen on the surface of the modified carbon black in an appropriate range. The surface is modified with fluorine at a specific temperature (hereinafter referred to as "fluorination treatment") using a treatment gas with the concentration of fluorine gas set in a specific range and the remainder being an inert gas, and then contact with gaseous water It has been found that the element ratio can be controlled by performing post-treatment, and the internal resistance of the battery can be lowered and the cycle characteristics of the battery can be improved by using an electrode using carbon black treated with fluorine. The

That is, the present invention is a carbon black used as a conductive aid for a non-aqueous electrolyte secondary battery having a positive electrode, a negative electrode, and an electrolyte, and has a BET specific surface area of 20 m ² / g or more and less than 100 m ² / g. The ratio of fluorine atom to carbon atom, that is, the ratio of F / C is 0.002 or more and less than 0.025, and the ratio of oxygen atom to carbon atom, that is, O / The carbon black having a C ratio of 0.01 or more and less than 0.1 is provided.

Further, the present invention is that the 95 m ² / g or less of carbon black comprising a BET specific surface area set at 25m ² / g or more, at 50 ° C. from 10 ° C., fluorine treatment of contacting with the processing gas consisting of fluorine gas and inert gas Carbon black, comprising the steps of: a fluorine gas concentration in the processing gas is 0.01 to 5% by volume, and a carbon black after fluorine treatment is brought into contact with gaseous water; Also provided is a method of making the method.

According to the present invention, by performing surface modification treatment on carbon black, the cycle characteristic of the non-aqueous electrolyte secondary battery can be improved as compared with the case of no treatment, and the conductivity assistant of the electrode of the non-aqueous electrolyte secondary battery It becomes possible to provide a method for producing carbon black for use as an agent and carbon black obtained by the method. Further, according to the present invention, the dispersibility of carbon black in the electrode production paste can be improved.

Hereinafter, embodiments of the present invention will be described below. Note that the scope of the present invention is not limited to these descriptions, and can be appropriately changed and implemented without departing from the spirit of the present invention other than the following examples.

First, the carbon black of the present invention and the method for producing the same will be described. The carbon black of the present invention is a surface-modified carbon black, and is produced by performing a fluorine treatment step on the carbon black and further performing a post treatment step.

Before the carbon black performing fluorine process BET specific surface area (hereinafter, may be referred to as untreated carbon black) is preferably not more than 25 m ² / g or more ^{^{95m 2 / g, 30m 2 /}} g or more 75 m ² It is more preferable that it is / g or less. Examples of such carbon black include furnace black obtained by an oil furnace method in which oil is incompletely burned, and acetylene black obtained by an acetylene method in which acetylene gas is thermally decomposed. For example, carbon black commercially available from TIMCAL as Super PTM can be used. The BET specific surface area does not change significantly before and after the fluorine treatment, and usually changes within ± 10%. Therefore, the BET specific surface area of carbon black after the fluorine treatment and post treatment according to the method of the present invention (hereinafter sometimes referred to as treated carbon black or surface modified carbon black) is 20 m ² / g or more and 100 m ² / g less than, preferably not more than 25 or more 95 m ² / g, is 30 m ² / g or more 75 m ² / g or less. The BET specific surface area of carbon black is measured by the method according to ASTM D 3037.

First, in the present invention, it is preferable to remove the water adsorbed to the untreated carbon black by heating or vacuum degassing before performing the fluorine treatment. This is because if water remains, it reacts with fluorine to generate hydrogen fluoride, which may adversely affect the production apparatus and the like.

In the fluorination process of the present invention, carbon black is usually charged into a cylindrical container. Here, by flowing a processing gas adjusted to have a fluorine concentration in a predetermined range, fluorination, ie, a fluorine atom is chemically bonded to the surface of carbon black to form a C—F bond. The container material can be safely processed if it is a metal material, but from the viewpoint of corrosion resistance, a stainless steel material such as SUS304 or SUS316 or nickel is desirable from the viewpoint of corrosion resistance.

The processing gas in fluorine processing consists of fluorine gas and an inert gas. The concentration of fluorine gas in the processing gas is 0.01 to 5% by volume, preferably 0.05 to 4% by volume. When the fluorine gas concentration is in this range, it is possible to obtain a carbon black having a desired range of F / C ratio and O / C ratio after post-treatment, and good cycle characteristics without increasing the internal resistance value. A non-aqueous electrolyte secondary battery is obtained. It is preferable that neither fluorine nor a gas other than the inert gas, for example, oxygen, be mixed in the processing gas, and even if mixed, the concentration of the mixed gas is preferably 1% by volume or less. For example, when oxygen is mixed in the processing gas, it becomes difficult to control the O / C ratio after post-treatment to a desired O / C ratio, and the reaction with carbon black rapidly proceeds, and in some cases, There is a possibility of dust explosion.

If the treatment temperature is higher than 50 ° C, explosion may occur due to the progress of fluorination more than expected, or if the temperature is lower than 10 ° C, equipment and energy for cooling may be needed to create a cooling state. Since the cost is an issue, processing at around room temperature is desirable. However, when heat is generated when the carbon black contacts fluorine, the device may be cooled using cooling water or the like to control the reaction.

With regard to the treatment time, sufficient time is required for carbon black and fluorine to contact evenly, and it is desirable to secure 10 minutes or more, and more desirably 30 minutes or more. If it is too long, the performance as a conductive additive is not affected, but the production efficiency is lowered, so it is desirable to be within 2 hours. Further, after the fluorine treatment, in order to remove as much as possible of the fluorine physically adsorbed to the carbon black, that is, the fluorine which does not contribute to the surface modification, it is preferable to deaerate under vacuum.

The processing pressure is not particularly limited, but from the viewpoint of safety, it is preferably 700 Torr (93.3 kPa) or less, and more preferably 500 Torr (66.7 kPa) or less. Further, in order to obtain a sufficient reaction rate, the pressure is preferably 10 Torr (1.3 kPa) or more, and more preferably 50 Torr (6.7 kPa) or more. The preferable flow rate of the processing gas may vary depending on the size and the structure of the reaction apparatus, and may be appropriately adjusted.

After the fluorine treatment, the carbon black is subjected to a post-treatment step by exposing it to gaseous water, for example, the atmosphere containing a predetermined humidity or water vapor. Post-treatment steps can be carried out at 10-30 ° C., but can be treated at ambient or ambient temperature without heating. In addition, when exposed to the atmosphere of 30 to 80% in relative humidity, treatment may be performed for 2 to 48 hours, and in the case of exposure to water vapor of 100% relative humidity, 30 minutes to 2 hours or less. You can do the processing.

On the surface of carbon black, C--F groups and the like are generated by fluorine treatment. In the post-treatment step, the C—F group on the surface of carbon black is converted to a C—OF group, a C—OH group, a COOH group or the like by the action of H ₂ O, and the surface is modified. The surface-modified carbon black is considered to improve the dispersibility in the paste for electrode production as compared to before the modification. It is estimated that this conversion is completed about one hour after the end of the post-treatment process. However, some of the C-F group in the carbon black, due to differences in binding conditions with other carbon atoms of the carbon atoms to which fluorine atoms are bonded, are firmly bonded to F is C, H ₂ O Remains without reacting.

The hydrogen fluoride generated in the post-treatment step can be removed by vacuum degassing thereafter.

At this time, the ratio of fluorine atoms to carbon atoms, that is, the F / C ratio is 0.002 or more and less than 0.025, which is measured by XPS (X-ray photoelectron spectroscopy) analysis of the surface of the post-treatment carbon black surface Yes, preferably 0.005 or more and 0.02 or less. Further, the ratio of oxygen atoms to carbon atoms, that is, the O / C ratio is preferably 0.01 or more and less than 0.1, and more preferably 0.02 or more and less than 0.08. If the F / C ratio and the O / C ratio are within the above ranges, the dispersibility in the paste for electrode preparation is improved while suppressing the increase in the resistance derived from fluorine and carbon, and the carbon black becomes a network It becomes easy to form.

If the F / C ratio and O / C ratio of carbon black after the post-treatment process are high and there are too many fluorine atoms or oxygen atoms on the surface of carbon black, the internal resistance of the battery will increase and the cycle characteristics of the battery Getting worse. Although the cause is not clear, the present inventors speculate as follows. For example, it is considered that the contact resistance between the carbon black and the carbon black becomes high in the network formed by the fluorine atom and the oxygen atom on the surface of the carbon black becoming an impurity and forming the carbon black. In addition, when there are too many fluorine atoms and oxygen atoms, excessive fluorination reaction destroys the condensed benzene ring of carbon black, and as a result, the movement of π electrons on carbon black is inhibited, and the conductivity of carbon black itself is It is thought that it gets worse.

Next, a non-aqueous electrolyte secondary battery using the carbon black of the present invention will be described. An electrolyte for a non-aqueous electrolyte secondary battery, an alkali metal ion including lithium ion and sodium ion, or an anode material capable of reversibly inserting and desorbing an alkaline earth metal ion; lithium ion and sodium ion An electrochemical device using a positive electrode material in which an alkali metal ion or an alkaline earth metal ion can be reversibly inserted and detached is referred to as a non-aqueous electrolyte secondary battery.

The non-aqueous electrolyte secondary battery of the present invention is characterized by using the carbon black after the treatment of the present invention, and the other components used in general non-aqueous electrolyte secondary batteries are used. That is, it comprises a positive electrode and a negative electrode capable of absorbing and releasing lithium, a current collector made of metal foil, a separator, a container, and the like.

The negative electrode is not particularly limited, but materials in which alkali metal ions such as lithium ion and sodium ion, or alkaline earth metal ions can be reversibly inserted and released are used, and the positive electrode is not particularly limited. However, materials in which alkali metal ions such as lithium ion and sodium ion, or alkaline earth metal ions can be reversibly inserted and released are used.

When the treated carbon black of the present invention is used as a conductive aid for the negative electrode, a negative electrode active material capable of inserting and extracting lithium ions and the like, a binder, a treated carbon black and a dispersion medium are mixed to make a slurry Then, it is applied to a metal foil which is a current collector, dried and pressurized to form a negative electrode layer. As various materials capable of absorbing and desorbing lithium ions and the like, for example, when the cation is lithium, lithium metal as an anode material, alloys and intermetallic compounds of lithium and other metals, artificial graphite and natural materials Graphite, carbon materials such as activated carbon, metal oxides, metal nitrides and the like are used.

When the carbon black after treatment of the present invention is used as a conductive additive for the positive electrode, a positive electrode active material capable of inserting and extracting lithium ions and the like, a binder, a carbon black after treatment, and a dispersion medium are mixed to form a slurry. Then, it is applied to a metal foil which is a current collector, dried and pressurized to form a positive electrode. In addition, before the slurry formation, the positive electrode active material and the post-treatment carbon black, the conductive additive and the like may be dry-mixed in a ball mill or the like. In the case of a lithium battery and a lithium ion secondary battery, as an active material, for example, a lithium-containing transition metal composite oxide such as LiCoO ₂ , LiNiO ₂ , LiMnO ₂ , LiMn ₂ O ₄ or the like, lithium-containing transition metal composite oxide thereof Mixture of a plurality of transition metals such as Co, Mn, Ni, etc., part of the transition metals of the lithium-containing transition metal complex oxides are substituted with metals other than the other transition metals, LiFePO ₄ called olivine , LiCoPO _4, phosphoric acid compound of a transition metal such as LiMnPO _4, oxides such as _{_{_{TiO 2, V 2 O 5,}}} MoO 3, is used to TiS _2, sulfides such as FeS or the like. Alternatively, conductive polymers such as polyacetylene, polyparaphenylene, polyaniline and polypyrrole, activated carbon, polymers generating radicals, carbon materials and the like are used.

The amount of the conductive aid contained in the electrode layer of the positive electrode layer or the negative electrode layer, that is, the amount of the conductive aid in the solid component in the slurry is preferably 0.1 to 20% by mass, 0.5 It is more preferable to include ~ 10% by mass, and further preferable to include 1 to 8% by mass.

As a binder used for the positive electrode or the negative electrode material, polytetrafluoroethylene, polyvinylidene fluoride, SBR resin or the like is used. Further, as the solvent, an organic solvent such as N-methyl-2-pyrrolidone (hereinafter referred to as “NMP”), an aqueous solvent such as water, or the like is used.

Examples of the present invention will be given below together with comparative examples, but the present invention is not limited to the following examples.

Example 1
<Preparation of carbon black after fluorine treatment and post treatment (hereinafter referred to as “after treatment”)>
Using untreated carbon black with a BET specific surface area of 62 m ² / g (Super P Li (trademark), manufactured by TIMCAL), enclose it in a container made of SUS 304 with a volume of 5 L, evacuate the inside, and adsorb to carbon black Removed water. Here, 200 Torr (26.7 kPa) of fluorine diluted to 0.05% by volume with nitrogen was enclosed, and then flowed for 30 minutes at a total flow rate of 0.5 SLM. The above reaction was performed at room temperature (25 ° C.). After the end of circulation, the inside of the container was sufficiently replaced with nitrogen. Thereafter, the inside of the vessel was again depressurized to a vacuum state and degassed overnight to remove as much as possible of the fluorine adsorbed to the carbon black. Subsequently, the inside of the container was repressurized to the atmospheric pressure and exposed to the atmosphere (air temperature 25 ° C., relative humidity 45 to 50%) for 24 hours. The processed carbon black obtained by these operations is XPS ("PHI VersaProbe II", manufactured by ULVAC-PHI, X-ray source: Al, X-ray: AlKα ray (1486.6 eV), output: 23.8 W, beam The surface composition was measured at a diameter of 100 μm. Also, the BET specific surface area was measured by a method in accordance with ASTM D 3037.

<Fabrication of positive electrode>
As a positive electrode active material, LiNi _1/3 Co _1/3 Mn _1/3 O ₂ (NCM) powder and the treated carbon black produced in Example 1 are dry-mixed for 30 minutes using a ball mill, and a binder is used. A certain polyvinylidene fluoride (hereinafter referred to as "PVDF") was uniformly dispersed in NMP in which it was dissolved in advance, mixed, and NMP for viscosity adjustment was further added to prepare an NCM mixture paste. This paste was applied onto an aluminum foil (current collector), dried at 100 ° C. for 1 hour, pressed with a roller at 4 kN / m ² , and then a test NMC positive electrode processed into a predetermined size was obtained. . The solid content ratio in the positive electrode was NCM: post-treatment carbon black: PVDF = 85: 5: 10 (mass ratio).

<Fabrication of graphite negative electrode>
A graphite powder is uniformly dispersed in NMP in which PVDF as a binder is previously dissolved as a negative electrode active material, mixed at 2000 rpm for 20 minutes using a kneader, NMP for viscosity adjustment is added, and graphite is mixed. An agent paste was prepared. This paste is applied on a copper foil (current collector), dried at 50 ° C. for 1 hour, pressed with a roller at 4 kN / m ² , and then processed into a predetermined size, to obtain a graphite negative electrode for test. The The solid content ratio in the negative electrode was set to graphite powder: PVDF = 90: 10 (mass ratio).

<Fabrication of non-aqueous electrolyte secondary battery>
A non-aqueous solvent was impregnated into an aluminum laminate outer packaging cell (capacity: 30 mAh) including the test NCM positive electrode, the test graphite negative electrode, and the cellulose separator, to obtain a non-aqueous electrolyte secondary battery. The volume ratio of ethylene carbonate (hereinafter "EC"), propylene carbonate (hereinafter "PC"), dimethyl carbonate (hereinafter "DMC") and ethyl methyl carbonate (hereinafter "EMC") as non-aqueous solvents is 2: 1: 3. Lithium hexafluorophosphate (hereinafter referred to as “LiPF ₆ ”) was dissolved as a solute in the solvent at a concentration of 1.0 mol / L using a mixed solvent of 4: 4 to prepare an electrolytic solution. In addition, said preparation was performed, maintaining a liquid temperature at 25 degreeC.

<Battery evaluation>
The following evaluation was implemented about each of the nonaqueous electrolyte secondary battery which concerns on an Example and a comparative example.

<Evaluation 1: Measurement of internal resistance of battery>
First, conditioning was performed under the following conditions at an ambient temperature of 25 ° C. using the manufactured cell. That is, as the initial charge and discharge, constant current constant voltage charging is performed at a charge upper limit voltage 4.3 V, 0.1 C rate (3 mA), and discharge is performed at a 0.2 C rate (6 mA) constant current up to the discharge termination voltage 3.0 V Thereafter, charge / discharge cycle of charging at constant current / constant voltage with 0.2C rate (6mA) with charge upper limit voltage of 4.3V and discharging at constant current with 0.2C rate (6mA) to final discharge voltage of 3.0V three times I repeated it. The internal resistance of the battery was then measured. Table 1 describes the measurement results of the internal resistance in each of the examples and the comparative examples. In addition, the numerical value of the internal resistance described in Table 1 is a relative value when the internal resistance of Comparative Example 1 is 100, and the lower the better.

<Evaluation 2: Measurement of high temperature cycle characteristics>
After performing the above conditioning, charge at constant current constant voltage at 3C rate (90mA) with charge upper limit voltage 4.3V at environmental temperature of 55 ° C and then discharge at 3C rate (90mA) constant current to discharge final voltage 3.0V This charge and discharge was repeated 100 cycles. The ratio of the discharge capacity at the 100th cycle to the initial (first cycle) discharge capacity was taken as the cycle capacity retention rate to evaluate the high temperature cycle characteristics of the cell. The numerical values of the cycle characteristics after 100 cycles shown in Table 1 are relative values when the discharge capacity retention ratio after 100 cycles of Comparative Example 1 is 100, and the higher, the better.

Example 2
In the preparation of carbon black after treatment, the same test as in Example 1 was conducted, except that the concentration of diluted fluorine used was 2 vol% and the contact time with fluorine was 10 minutes.

[Example 3]
The same test as in Example 1 was conducted except that the concentration of diluted fluorine used was 0.5 vol% when producing carbon black after treatment.

Example 4
The same test as in Example 1 was conducted except that the concentration of diluted fluorine used was 2 vol% when producing carbon black after treatment.

[Example 5]
The same test as in Example 1 was conducted except that the concentration of diluted fluorine used was 4 vol% when producing carbon black after treatment.

[Example 6]
The same test as in Example 5 was conducted except that the pressure at the time of contact with diluted fluorine was 50 Torr (6.7 kPa) when producing a carbon black after treatment.

[Example 7]
The same test as in Example 4 was conducted except that the pressure at the time of contacting with diluted fluorine was set to 500 Torr (66.7 kPa) in the preparation of carbon black after treatment.

[Example 8]
The same test as in Example 4 was conducted, except that the concentration of diluted fluorine used was 4% by volume and the pressure at the time of contact with diluted fluorine was 500 Torr (66.7 kPa) in the preparation of carbon black after treatment .

[Example 9]
The same test as in Example 1 was conducted except that carbon black having a BET specific surface area of 45 m ² / g (Super C 45 (trademark), manufactured by TIMCAL) was used as untreated carbon black when producing carbon black after treatment. .

[Example 10]
The same test as in Example 9 was conducted, except that the treatment time at the time of contacting with diluted fluorine was made 90 minutes when producing a carbon black after treatment.

[Example 11]
The same test as in Example 2 was conducted, except that the treatment temperature was 40 ° C., and the treatment time was 10 minutes, in the preparation of the carbon black after treatment.

[Example 12]
Post-treatment carbon black was prepared at a treatment temperature of 40 ° C. and a treatment time of 10 minutes, except that water vapor at normal temperature (nitrogen gas with a relative humidity of 100%) was supplied for 1 hour in the post-treatment step. The same tests as in Example 2 were conducted.

Comparative Example 1
The same test as in Example 1 was conducted except that a fluorine-free nitrogen gas was circulated instead of the fluorine treatment step.

Comparative Example 2
The same test as in Example 1 was conducted except that the concentration of diluted fluorine used was 0.005 vol% when producing carbon black after treatment.

Comparative Example 3
The same test as in Example 1 was conducted except that the concentration of diluted fluorine used was 7% by volume when producing carbon black after treatment.

Comparative Example 4
The same test as in Example 1 was conducted, except that the concentration of fluorine was 4 vol%, the concentration of oxygen was 10 vol%, and the gas diluted with nitrogen was made to flow in preparation of carbon black after treatment.

Comparative Example 5
The same test as in Example 1 was conducted, except that the treatment temperature at the time of contact with diluted fluorine was 80 ° C., in the preparation of carbon black after treatment.

Comparative Example 6
The same test as in Example 1 was conducted except that oxygen gas was supplied in the post-treatment step when producing post-treatment carbon black.

Comparative Example 7
The same test as in Example 1 was carried out except that nitrogen gas was supplied in the post-treatment step when producing a carbon black after treatment.

Comparative Example 8
The same test as in Example 1 was carried out except that the carbon black used in Example 9 was used as untreated carbon black in the preparation of post-treatment carbon black, and nitrogen gas containing no fluorine was circulated in the fluorine treatment step. went.

The results of Examples 1 to 12 and the results of Comparative Examples 1 to 8 are summarized in Table 1.

From the results of Examples 1 to 12 and the results of Comparative Examples 1 to 8, a post-treatment step of bringing a diluted fluorine gas in the range of 0.05 to 5 vol% of fluorine concentration into contact with carbon black and contacting with gaseous water The ratio of fluorine atoms to carbon atoms, that is, the F / C ratio is 0.001 or more and less than 0.025, and the ratio of oxygen atoms to carbon atoms, that is, O / C ratio, as determined by XPS analysis. It can be seen that a carbon black can be obtained after treatment characterized in that In addition, non-aqueous electrolyte secondary batteries produced using treated carbon black in these ranges have a fluorine concentration outside the above range or compared to carbon black treated with diluted fluorine containing oxygen gas. It can be seen that the internal resistance value is lowered, and a high discharge capacity maintenance rate is maintained. In addition, it was found by XPS analysis that at least one functional group of C—OF group, C—OH group, or COOH group was present on the surface of the carbon black after the treatment of Examples 1 to 12.

On the other hand, according to the result of Comparative Example 2, when the fluorine concentration is 0.005% by volume, the surface modification hardly progresses, the F / C ratio and the O / C value hardly change, and the internal resistance value There was also no change in the cycle characteristics. Moreover, although the F / C ratio and the O / C value were largely increased at a fluorine concentration of 7 vol%, the internal resistance value increased and the cycle characteristics deteriorated, according to the result of Comparative Example 3. It is considered that this is because the fluorine concentration is too high, the surface roughness of the carbon black is remarkable, and the charge transport is inhibited.

In Comparative Example 4, since carbon black was treated with a gas obtained by diluting fluorine and oxygen with nitrogen, the O / C value of carbon black after treatment became high, the internal resistance value increased, and the cycle characteristics deteriorated. This is considered to be an increase in internal resistance because the fluorine treatment with fluorine and oxygen changes the cross-linked structure of carbon black and inhibits the carbon-carbon conductive path.

In Comparative Example 5, since the treatment temperature was 80 ° C., the fluorine treatment strongly proceeded, and the F / C ratio of the carbon black after treatment greatly increased. During the fluorine treatment, it is considered that the surface of the carbon black was roughened, the internal resistance value increased, and the cycle characteristics deteriorated.

In Comparative Example 6, the oxygen gas was exposed in the post-treatment step after the fluorine treatment, but it has a high F / C ratio equal to that of Comparative Example 7, and the CF group is changed to a COF group etc. An increase in the O / C ratio was observed, which appeared to be oxidation of terminal substituents that were in stable bound state. In Comparative Example 6, the internal resistance value was high, and the cycle characteristics decreased.

In Comparative Example 7, since the carbon black was subjected to a post-treatment step with an inert gas after the fluorine treatment, a large amount of fluorine component remained on the carbon black after the treatment, and the O / C ratio compared to the pre-treatment carbon black It is thought that there was also no formation of COH group or COOH group, because the internal resistance value was high and the cycle characteristics were low.

Claims

A carbon black used as a conductive aid for an electrode of a non-aqueous electrolyte secondary battery,
The BET specific surface area is 20 m 2 / g or more and less than 100 m 2 / g,
The ratio of fluorine atom to carbon atom, F / C ratio, determined by XPS analysis is 0.002 or more and less than 0.025, and the ratio of oxygen atom to carbon atom is O / C ratio, Carbon black which is 0.01 or more and less than 0.1.
The carbon black according to claim 1, wherein at least one functional group selected from the group consisting of a C-OF group, a C-OH group, and a COOH group is present on the surface of the carbon black.
The carbon black according to claim 1 or 2, wherein the F / C ratio is 0.005 or more and less than 0.02, and the O / C ratio is 0.02 or more and less than 0.08.
A collector, which is a metal foil,
An electrode layer formed on the current collector and containing the carbon black according to any one of claims 1 to 3 and an electrode active material,
An electrode for a non-aqueous electrolyte secondary battery comprising:
A positive electrode, a negative electrode, and an electrolyte;
The nonaqueous electrolyte secondary battery which is an electrode for nonaqueous electrolyte secondary batteries of Claim 4 in which any one or both of the said positive electrode and the said negative electrode are.
Carbon black having a BET specific surface area of 95 m 2 / g or less be at at 25m 2 / g or more and at 50 ° C. from 10 ° C., and the fluorine treatment step of contacting a process gas consisting of fluorine gas and inert gas, wherein, The concentration of fluorine gas in the processing gas is 0.01 to 5% by volume,
A post-treatment step of contacting the fluorinated carbon black with gaseous water;
The method for producing carbon black according to claim 1 or 2, comprising
7. The method for producing carbon black according to claim 6, wherein the carbon black after fluorine treatment is exposed to the atmosphere of 30 to 80% in relative humidity for 2 hours or more and 48 hours or less in the post-treatment step.
The method for producing carbon black according to claim 6, wherein the carbon black after fluorine treatment is exposed to water vapor for 30 minutes or more and 2 hours or less in the post-treatment step.
The carbon black according to any one of claims 6 to 8, comprising a step of performing a degassing step by placing the carbon black under a reduced pressure environment after the fluorine treatment step and before the post treatment step. Production method.
The method for producing carbon black according to any one of claims 6 to 9, further comprising the step of performing the degassing step by placing the carbon black in a reduced pressure environment after the post-treatment step.
A process of dispersing the carbon black according to claim 1 or 2 and an electrode active material in a dispersion medium to form a paste;
Applying the paste to a current collector and drying it;
A method for producing an electrode for a non-aqueous electrolyte secondary battery, comprising:
The method for producing an electrode for a non-aqueous electrolyte secondary battery according to claim 11, further comprising a binder and a viscosity modifier in the paste.