JP3526707B2 - Negative electrode active material for non-aqueous electrolyte secondary battery and non-aqueous electrolyte secondary battery - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a negative electrode active material for a non-aqueous electrolyte secondary battery and a non-aqueous electrolyte secondary battery.

[0002]

2. Description of the Related Art Today, a society for a secondary battery that is small, lightweight and has a long charging interval is used as a power source for portable devices such as mobile phones, portable terminals, video cameras and the like, which are rapidly becoming widespread, or as a power source for electric vehicles. Demands are becoming stronger.

Among rechargeable and reusable rechargeable batteries, secondary batteries such as lead acid batteries, nickel-cadmium batteries, and nickel-hydrogen batteries which use an aqueous electrolyte obtain a high battery voltage exceeding the decomposition voltage of water. It is not possible. However, the lead-acid battery has a higher battery voltage due to the overvoltage. On the other hand, the non-aqueous electrolyte secondary battery (also referred to as a non-aqueous secondary battery) uses a non-aqueous solvent for the electrolyte, and thus can obtain a higher battery voltage than the above-described secondary battery using an aqueous electrolyte. . For this reason, non-aqueous secondary batteries have high battery capacity and energy density, so they can be made smaller and lighter, and demand for them as power sources for portable devices is growing rapidly. In order to realize the above, further improvement in battery performance is required.

The non-aqueous secondary battery comprises a positive electrode composed of a positive electrode active material capable of absorbing and releasing lithium and a current collector, and a negative electrode active material capable of absorbing and releasing lithium and a current collector. It is composed of a negative electrode including a body, an electrolytic solution in which a lithium salt is dissolved in a non-aqueous solvent, a separator, a battery container, and the like. In such a secondary battery, lithium is released from the positive electrode active material during charging,
It is occluded in the negative electrode active material, and during discharge, lithium is conversely released from the negative electrode active material and occluded in the positive electrode active material.

As a negative electrode active material suitable for a non-aqueous secondary battery having a high energy density, it is preferable to use metallic lithium containing the largest amount of lithium per unit weight, focusing only on the battery capacity and the energy density. . However, when metallic lithium is used as the negative electrode active material, lithium does not deposit uniformly on the negative electrode surface during charging, but deposits in a dendritic form,
This penetrates the separator and short-circuits the negative electrode and the positive electrode, which may cause heat generation or ignition, which is very dangerous. Further, there is a problem that metal lithium deposited in a dendritic form falls off from the negative electrode and the charge / discharge cycle life is shortened. Due to these problems, metallic lithium has not been put to practical use as a negative electrode active material for a non-aqueous secondary battery, although it has the highest lithium capacity.

At present, a commercially available non-aqueous secondary battery negative electrode active material is referred to as a carbon material having a relatively high crystallinity (hereinafter also referred to as a graphite material) represented by graphite or a non-graphitizable carbon. Carbon material with relatively low crystallinity (hereinafter,
Non-graphitizable carbon material) and the like are used.

When a graphite material is used as the negative electrode active material of a non-aqueous secondary battery, the negative electrode potential stabilizes at a substantially constant value from the initial stage of discharge to the final stage. Therefore, it is necessary to secure a stable battery electrode thickness until the final stage of discharge. You can However, the theoretical charge / discharge capacity of the graphite material is 372 mAh / g at the maximum, and in reality, it is about 280 to 330 mAh / g. Therefore, in order to manufacture a non-aqueous secondary battery having a higher energy density, a negative electrode active material having a higher charge / discharge capacity is desired.

Further, in the case of a graphite material, lithium intercalated between layers of a graphite crystal having a layered structure has a strong interaction with graphite at the time of charging, so that once inserted, it is not easy to release lithium. Therefore, the current density during discharge cannot be increased. Further, it has been pointed out that when the charge and discharge are repeated, the crystallinity of graphite collapses and the volume of the negative electrode increases. Further, there is a problem that the non-aqueous electrolytic solution is easily decomposed as compared with other carbon materials such as non-graphitizable carbon material.

On the other hand, the non-graphitizable carbon material has a charge / discharge capacity of 400 to 700 mAh / g, which is superior to the graphite material in this respect. However, in the non-graphitizable carbon material, the negative electrode potential continues to rise from the beginning of discharge,
When used in a non-aqueous electrolyte secondary battery, the battery voltage continues to drop with discharge. Therefore, although the non-graphitizable carbon, which is the negative electrode active material, still has enough lithium that can be released due to discharge, further discharge occurs at a low voltage, so it is used as a power source. There is a problem that you cannot do it. As a result, the charge / discharge capacity that can be practically used as the battery capacity is 300 mAh / g, which is almost equal to that of the graphite material.
It may only be a degree. In addition, since the interaction between non-graphitizable carbon and lithium is excessively weak, there is a known problem that the holding power when occluding lithium is weak and self-discharge easily occurs.

Boron carbonitride, which has a layered structure similar to graphite and in which a part of carbon is replaced by boron and nitrogen, has been proposed as a negative electrode active material having a high charge / discharge capacity which replaces the carbon material. ing. When boron carbonitride is used as the negative electrode active material of a non-aqueous secondary battery, the stable negative electrode potential is maintained from the initial stage to the final stage of discharge, and boron carbonitride has a high charge / discharge capacity of 375 mAh / g. It is known (Japanese Patent Laid-Open Nos. 5-290843 and 5-314976).

However, such a boron carbonitride material is generally in the form of powder, and is used as a negative electrode active material so that the negative electrode active material does not fall off or peel from the current collector during charge / discharge. It has been practiced to add a binder such as polyvinylidene fluoride in an amount of 5 to 15% by weight to strengthen the bonding between powders. This binder does not participate in the charge / discharge reaction associated with the insertion and desorption of lithium, has a very low bulk density, and occupies a large volume when added to the negative electrode active material. There is a problem that the capacity is reduced.

For example, when the effect of the addition amount of the binder not contributing to the charge / discharge reaction on the charge / discharge capacity of the negative electrode having a constant volume is calculated, the capacity is at least about 5% by weight when the addition amount of the binder is 5% by weight. It can be estimated that the capacity decreases by 10% and the capacity decreases by at least about 25% when the added amount is 15% by weight.
Therefore, at the same time as using a material having a high charge / discharge capacity such as boron carbonitride as the negative electrode active material, the material falls off from the current collector.
Solving the problem of peeling has been a serious problem for producing a secondary battery with high battery capacity.

[0013]

Therefore, even if the amount of the binder added is reduced, a negative electrode active material for a non-aqueous secondary battery using boron carbonitride that does not easily fall off or peel off from the current collector. Development was strongly demanded.

[0014]

Therefore, the present inventor has conducted earnest research from various angles in order to solve the above problems. As a result, when boron carbonitride fibers in which the C plane of boron carbonitride is preferentially oriented in the direction parallel to the fiber axis are used for the negative electrode active material of a non-aqueous secondary battery, even if a small amount of a binder is added. It was found that the negative electrode active material was prevented from falling off and peeling from the current collector, and the present invention was completed here.

That is, the present invention has a structure in which a 6-membered ring formed by bonding carbon, boron and nitrogen is connected to each other in the plane direction of the 6-membered ring (C-face) and laminated. A boron carbonitride fiber comprising boron carbonitride having at least a part of the C plane oriented substantially parallel to the fiber axis of the boron carbonitride fiber, and the degree of orientation of the C plane. Is 0.70 or more, and is a negative electrode active material for a non-aqueous electrolyte secondary battery made of boron carbonitride fiber.

Another aspect of the present invention is to collect a negative electrode formed by joining the negative electrode active material for a non-aqueous electrolyte secondary battery to a current collector and a positive electrode active material made of a material capable of inserting and extracting lithium. A non-aqueous electrolyte secondary battery, wherein a positive electrode joined to an electric body is separated by a separator and is housed in a battery container together with the non-aqueous electrolyte.

The present invention will be described in detail below.

Boron carbonitride is a substance formed by chemically bonding boron of group III of the periodic table, carbon of group IV of the periodic table and nitrogen of group V of the periodic table, Present (1)
A structure formed by three-dimensionally combining carbon, boron and nitrogen, that is, boron carbonitride having the same structure as the diamond structure unless the kinds of elements occupying atomic positions are distinguished, and (2) carbon Boron carbonitride having a structure in which a plane (hereinafter also referred to as a C plane) formed by connecting a 6-membered ring formed by bonding boron and nitrogen to each other in the plane direction of the 6-membered ring is known is known. ing.

In the boron carbonitride fiber of the present invention, the 6-membered ring formed by combining carbon, boron and nitrogen as described above is used.
It is made of boron carbonitride (hereinafter also referred to as boron carbonitride) having a structure in which the surfaces formed by connecting in the surface direction of the member rings are laminated.

The boron carbonitride according to the present invention has, for example, a structure in which C planes are laminated with regularity between the planes such as a structure of hexagonal boron nitride in boron nitride or a structure of graphite in carbon. Containing boron carbonitride and / or boron carbonitride having a laminated structure lacking regularity between C planes, for example, a turbostratic structure in boron nitride or carbon. You may have.

The laminated structure of the boron carbonitride can be confirmed from the diffraction peak from the C plane by X-ray diffraction. This diffraction peak is 2θ = 24 to 26 when the X-ray is CuKα ray.
The distance between the laminated C planes, which appears at the position of ° and is calculated from the position of the diffraction peak, is about 3 to 4 angstroms.

The boron carbonitride has a structure similar to that of boron carbonitride because it contains carbon-boron and carbon-nitrogen bonds in addition to carbon-carbon and boron-nitrogen bonds. It is distinguished from carbon having a graphite structure and the like, and boron nitride having a hexagonal structure and the like or a mixture thereof. The presence of carbon-boron and carbon-nitrogen bonds is represented by X
It can be confirmed by line photoelectron spectroscopy (also referred to as XPS) or Raman spectroscopy.

In the case of X-ray photoelectron spectroscopy, the XPS spectrum of carbon-bonded boron is X-ray of nitrogen-bonded boron.
It shifts to the lower energy side than the PS spectrum. On the other hand, the XPS spectrum of nitrogen bonded to carbon shifts to a higher energy side than the XPS spectrum of nitrogen bonded to boron. Therefore, the carbon-boron bond and the carbon-nitrogen bond in boron carbonitride can be confirmed by measuring the XPS spectra of boron and nitrogen in the boron carbonitride fiber by X-ray photoelectron spectroscopy.

Further, according to Raman spectroscopy, carbon - carbon bond composed only of graphite and boron - Raman spectra of hexagonal boron nitride comprising only nitrogen bond each 1570 cm ^-1, peak at 1370 cm ^-1 In contrast to boron carbonitride containing carbon-boron bond and carbon-nitrogen bond, about 1430 cm in between.
A spectrum having a peak at a position centered at ^-1 is obtained.

The composition of the boron carbonitride is not particularly limited, but preferably, in the boron-carbon-nitrogen ternary phase diagram, the boron composition is 1 atm% or more and 90 atm%.
98at in the following regions and carbon composition of 2atm% or more
A composition contained in a region corresponding to a product set of a region of m% or less and a region of nitrogen composition of 1 atm% or more and 60 atm% or less (hereinafter also referred to as region A), and more preferably boron. In a ternary phase diagram of carbon-nitrogen, a straight line connecting a point of 100 atm% of carbon and a point of 80 atm% of boron-20 atm% of nitrogen, and 100 atm% of carbon
And a region surrounded by a straight line connecting a point of 20 atm% of boron and a point of 80 atm% of nitrogen and a region corresponding to a product set of the region A, more preferably boron-carbon-nitrogen. In the ternary phase diagram of
A straight line connecting the point of m% and the point of 80 atm% boron-20 atm% of nitrogen, the point of 100 atm% carbon and the boron 40a.
A composition contained in a region corresponding to a product set of a region A and a region surrounded by a straight line connecting a point of tm% -60 atm% of nitrogen, most preferably boron-carbon-nitrogen ternary state In the figure, carbon 100 atm% point and boron 6
A straight line connecting a point of 0 atm% and 40 atm% of nitrogen, a point of 100 atm% of carbon and 40 atm% of boron and 60 a of nitrogen
It is the composition contained in the region corresponding to the intersection of the region A and the region surrounded by the straight line connecting the tm% points.

Boron carbonitride having a high carbon content can be produced by a method such as using a nitrile compound as a raw material or a material having a high carbon content contained in a primary amine hydrohalide. Further, boron carbonitride having a low carbon content can be produced by a method of heating boron carbonitride precursor fiber in ammonia. At this time, the carbon content can be controlled by the conditions such as the heating temperature of the heat treatment in ammonia.

The boron carbonitride fiber used in the present invention contains the above-mentioned boron carbonitride as a constituent component.

The orientation degree of the C plane (hereinafter, also referred to as orientation degree) is used as an index showing the orientation distribution of the C plane of boron carbonitride with respect to the fiber axis of the boron carbonitride fiber. The boron carbonitride fiber in the present invention is characterized by having an orientation degree of 0.70 or more. The tensile strength of the boron carbonitride fiber having an orientation degree of less than 0.7 does not substantially depend on the orientation degree,
Its value is also low. On the other hand, when the degree of orientation is 0.7 or more,
The tensile strength of boron carbonitride fiber shows a remarkable improvement in proportion to the degree of orientation. For example, when the typical value is shown, the degree of orientation is 0.55.
The tensile strengths of boron carbonitride fibers of 0.66 and 0.66 are 440 MPa and 900 MPa, respectively, whereas the tensile strength of boron carbonitride fibers of 0.82 degree of orientation is 1900M.
It was Pa.

As will be described later in the method for producing a non-aqueous secondary battery, when the negative electrode is composed of boron carbonitride fibers, the boron carbonitride fibers are kneaded together with a conductivity-imparting agent, a binder and a solvent. It At this time, when the orientation degree of the boron carbonitride fiber is less than 0.70, the boron carbonitride fiber is broken and crushed in the kneading process at the time of producing the negative electrode because the tensile strength is low, When the amount of the binder added is small, it may be easily detached and peeled from the current collector, which is not preferable. Therefore, the degree of orientation of boron carbonitride fiber is 0.70.
The above is preferable.

The above-mentioned degree of orientation can be determined by an X-ray diffraction method based on the X-ray intensity distribution on the Debye ring generated by the diffraction from the C plane of the boron carbonitride fiber. The method of measuring the degree of orientation by the X-ray diffraction method will be described below.

As X-rays used for diffraction, copper Kα rays monochromated by a nickel filter (hereinafter referred to as CuKα rays) are used, and the diffraction intensity is measured by a transmission method.

A sample to be subjected to X-ray diffraction in which a bundle of tens or hundreds of boron carbonitride fibers is made parallel to each other as much as possible and fixed with a small amount of collodion or the like. And Hereinafter, this is referred to as an X-ray diffraction test piece.

The diffraction intensity may be measured either by taking a photograph of a diffraction image or by using an X-ray diffractometer.

When the diffraction intensity is measured by taking a photograph of a diffraction image, the fiber axis of the boron carbonitride fiber of the X-ray diffraction specimen is in the plane perpendicular to the incident X-ray, The X-ray diffraction sample is fixed so that the incident X-rays irradiate the boron carbonitride fiber bundle of the X-ray diffraction sample. At this time, incident X
The direction of the fiber axis of the boron carbonitride fiber of the X-ray diffraction sample in the plane perpendicular to the line may be any direction as long as the relative direction to the diffraction image can be specified. However,
Here, for the sake of explanation, it is assumed that the fiber shaft is fixed vertically.

An X-ray photosensitive film for photographing a diffraction image is set on the side opposite to the direction of the incident X-ray with respect to the X-ray diffraction sample. The X-ray photosensitive film should be perpendicular to the direction of incident X-rays. The distance from the X-ray diffraction sample to the X-ray photosensitive film (hereinafter, also referred to as the camera length) depends on the diffraction from the C plane of the boron carbonitride fiber constituting the boron carbonitride fiber of the X-ray diffraction sample. The distance must be large enough to capture the entire Debye ring. The radius (D) of the Debye ring on the X-ray photosensitive film is calculated by the equation (1).

D = L × tan (2θ) (1) where L is the camera length, 2θ is the Bragg's angle with respect to the C plane of boron carbonitride constituting the boron carbonitride fiber of the sample for X-ray diffraction. It is a diffraction angle that satisfies the diffraction condition. In the case of boron carbonitride fiber, if the incident X-ray is CuKα ray, 2θ is 24 to 2
It is in the range of 6 °. Therefore, the camera length L may be set so that a circle having a radius D centered on the intersection of the direction of the incident X-ray and the X-ray photosensitive film is contained in the X-ray film.

The diffracted X-ray intensity mainly varies depending on the amount of boron carbonitride fiber of the X-ray diffraction sample, the crystallite diameter of boron carbonitride constituting the boron carbonitride fiber, and the like. In order to obtain a diffraction image, it is necessary to adjust the X-ray exposure time. In order to confirm whether or not the exposure time is appropriate, it is sufficient to change the exposure time for the same X-ray diffraction sample and take a diffraction image to confirm that the obtained degree of orientation does not change. .

The intensity of the diffracted X-rays can be determined by developing the exposed X-ray photosensitive film and quantifying the degree of blackening with a microdensitometer. When the C plane of boron carbonitride is oriented parallel to the fiber axis direction of the boron carbonitride fiber, on the Debye ring photographed on the X-ray photosensitive film, the center of the Debye ring (incident X-ray and X
X-ray diffraction test piece for X-ray diffraction, and the degree of blackening of the film in the direction perpendicular to the fiber axis of the boron carbonitride fiber (hereinafter also referred to as the equatorial line direction) becomes maximum, and the Debye ring A diffraction intensity distribution is generated which passes through the center and is parallel to the fiber axis of boron carbonitride of the specimen for X-ray diffraction (hereinafter, also referred to as meridian direction) so that the degree of blackening of the film becomes minimum. The position of the diffraction intensity measurement point on the Debye ring is determined by the central angle φ from the reference point on the Debye ring, and the intensity of the diffracted X-ray on the Debye ring is obtained as a function thereof. At this time, the X-ray intensity on the Debye ring is the intensity obtained by adding the intensity of the diffracted X-ray from the C plane of the boron carbonitride fiber and the intensity of the background.
Therefore, in order to obtain the net intensity of the diffracted X-ray from the C plane, the change in the X-ray intensity in the radial direction of the Debye ring is obtained to obtain the background intensity in the Debye ring, which is the X-ray intensity in the Debye ring. Deduct from. When the intensity of the diffracted X-ray from the C plane is obtained as a function of the central angle φ, two peaks having a maximum at the position corresponding to the equatorial line direction are obtained. For each peak, the full width at half maximum is measured in units of degrees, and the average (H) is calculated. The degree of orientation (π) can be calculated by the equation (2) using the obtained H [Carbon Material Society of Japan, “Development and Evaluation Method of Carbon Fiber”]
118 (1989). ].

Π = (180−H) / 180 (2) An X-ray diffractometer can also be used to measure the diffraction intensity. A known diffractometer can be used,
Hereinafter, a diffractometer of a type in which the axis of the diffractometer is vertical and the scanning surface of the X-ray counter is horizontal will be described. When using an X-ray diffractometer, the X-ray diffraction sample can be fixed and
A fiber sample stage having a mechanism capable of rotating the X-ray diffraction sample in a plane perpendicular to the line by 360 degrees is used.

First, the diffraction angle of the C-plane of boron carbonitride constituting the boron carbonitride fiber of the X-ray diffraction sample satisfying the Bragg diffraction condition is determined by the transmission method. X on the fiber sample stand
The sample for line diffraction is fixed, and the fiber axis of the boron carbonitride fiber of the sample for X-ray diffraction is fixed vertically. In this state, X-rays are made incident, and 2θ of an X-ray counter, that is, a diffractometer is scanned to measure the diffraction angle by the C plane of boron carbonitride.

Next, the X-ray counter tube was fixed at the diffraction angle of the C-plane, the X-rays were made incident, and the X-ray diffraction specimen fixed on the fiber sample stage was set to 360 in a plane perpendicular to the incident X-rays. Rotate by degrees and measure the corresponding diffracted X-ray intensity. Now, the rotation angle of the X-ray diffraction test piece is α (however, the unit is degree), and α is 0 degree when the fiber axis of the boron carbonitride fiber of the X-ray diffraction test piece is vertical. When the C-plane of the boron carbonitride constituting the boron carbonitride fiber of the X-ray diffraction specimen is oriented in the fiber axis direction of the boron carbonitride fiber, α is diffracted at 0 degrees and 180 degrees. A peak having a maximum X-ray intensity appears. At this time, it is necessary to correct the intensity of the diffracted X-ray by subtracting the intensity of the background, as in the method of taking a photograph of the diffraction image described above.
For each peak, the full width at half maximum is measured in units of degrees, and the average (H) is used to calculate the degree of orientation (π) from equation (2).
Can be calculated.

The sectional shape of the boron carbonitride fiber is not particularly limited. The cross section of the fiber is usually circular, oval, although it varies depending on the manufacturing method and conditions of the boron carbonitride fiber,
Alternatively, it may be a polygon such as a triangle or a quadrangle. If the cross section is circular, the diameter corresponds to the minor axis, if the shape is elliptical, the average of the shorter diameter and the longer diameter corresponds to the minor diameter, and if the shape is polygonal, the shortest diagonal and the longest. The average of the diagonals corresponds to the minor axis. However, when the cross section is a triangle, the average of the shortest side and the longest side corresponds to the short diameter.

It is preferable that the shorter diameter of the boron carbonitride fiber is smaller because generally the tensile strength is higher and the flexibility is improved, but the boron carbonitride fiber having a too short diameter becomes difficult to handle. . The minor axis of the boron nitride fiber is 0.
It is preferably 5 to 100 μm, more preferably 1 to 60 μm, and further preferably 1 to 40 μm.

The method for producing the boron carbonitride fiber having a high degree of orientation of 0.70 or more in the present invention is not particularly limited.
Typically, it can be manufactured as follows.

(A) First, an adduct of a boron trihalide and a nitrile compound is reacted with an ammonium halide or a primary amine hydrohalide in the presence of boron trihalide to give boron carbonitride. Precursor (hereinafter,
(Also referred to as precursor).

Examples of the boron trihalide include boron trifluoride, boron trichloride, boron tribromide and boron triiodide, which can be used without particular limitation.

As the nitrile compound, a known compound having a nitrile group can be used without particular limitation. Specifically, acetonitrile, propionitrile, capronitrile, acrylonitrile, crotonnitrile,
Tolunitrile, benzonitrile, i-butyronitrile,
Examples thereof include n-butyronitrile, isovaleronitrile, malononitrile, succinonitrile, glutaronitrile, adiponitrile, pimelonitrile and suberonitrile. When the carbon number contained in the nitrile compound increases,
The carbon contained in the precursor is increased, and the carbon amount contained in the carbonitride-boronized fiber obtained by the heat treatment can be increased.

As the ammonium halide, ammonium fluoride, ammonium chloride, ammonium bromide,
Examples thereof include ammonium iodide. Ammonium chloride can be mentioned as a preferable example of ammonium halide.

As the primary amine hydrohalide,
Primary amine hydrofluoride, primary amine hydrochlorate,
Examples thereof include primary amine hydrobromide, primary amine hydroiodide and the like. As a preferred example of the primary amine hydrohalide, a primary amine hydrochlorate (hereinafter,
Primary amine hydrochloride).

The primary amine hydrochloride has the general formula: RNH ₂ ·
A compound represented by HCl, in which R is an alkyl group such as a methyl group, an ethyl group and a propyl group, and an aryl group such as a phenyl group, a tolyl group and a xylyl group is used without limitation.
When the carbon number of R is increased, the carbon contained in the boron nitride precursor is increased, and the carbon content contained in the boron carbonitride fiber obtained by the heat treatment can be increased.

To obtain the boron nitride fiber of the present invention,
First, a boron nitride precursor is synthesized by reacting an adduct of the boron trihalide and the nitrile compound with an ammonium halide or a primary amine hydrohalide.

The adduct of the boron trihalide with the nitrile compound is a product in which the boron halide is additionally bonded to the non-bonding electron pair of the nitrogen atom of the nitrile group, and It easily reacts with a nitrile compound to form an adduct. The method for producing the adduct is not particularly limited. For example, a method of dropping boron trihalide into a solution of a nitrile compound in an organic solvent at room temperature, a method of dissolving the nitrile compound in an organic solvent and then blowing a boron trihalide, or a method of trihalogenating the organic solvent. The adduct can be formed by, for example, a method of dissolving boron and then dropping a nitrile compound.
Since the boron trihalide and the nitrile compound easily react to form an adduct, they may be contacted with each other immediately before the reaction.

It is essential that boron trihalide be present during the reaction of the adduct with ammonium halide or primary amine hydrohalide. When boron trihalide is not present during the reaction, the yield of the boron nitride precursor of the present invention tends to decrease. Further, in the spinning step described below, when the boron carbonitride precursor fiber is spun by solution spinning, a reaction by-product insoluble in N, N-dimethylformamide (hereinafter also referred to as DMF) which is a spinning solvent is produced. Come on.

The boron trihalide may be present at least during the reaction between the boron trihalide / addition product of the nitrile compound and the ammonium halide or the primary amine hydrohalide. For example, when an excess of boron trihalide is used when forming an adduct of a nitrile compound and boron trihalide, unreacted boron trihalide may be allowed to coexist in the adduct in advance. good. The amount of boron trihalide added to the nitrile compound is 1.05 in terms of molar ratio (boron trihalide / nitrile compound).
It can be arbitrarily selected from the range of 2.00. But,
When the amount of boron trihalide added is small, components insoluble in the spinning solvent such as DMF are produced, and when the amount of boron trihalide added is large, the amount of boron trihalide that does not contribute to the reaction increases. A more preferable molar ratio of boron trihalide added to the nitrile compound is 1.1 to 1.5. At this time, the boron trihalide and the nitrile compound are 1
The amount of boron trihalide present during the reaction is in the range of 0.1 to 0.5 in terms of molar ratio (boron trihalide / adduct) to the adduct because it produces an adduct of 1: 1. Becomes

The concentration of the nitrile compound in the reaction solvent is not particularly limited, but it is preferably in the range of 0.1 to 10 mol / l. If the concentration of the nitrile compound is less than 0.1 mol / l, the amount of the boron nitride precursor obtained is small and it is not efficient, which is not preferable.
Further, if the concentration of the nitrile compound exceeds 10 mol / l, the amount of the adduct formed as a solid with respect to the solvent becomes too large, and the formation of the adduct becomes non-uniform, which is not preferable.

The amount of the ammonium halide or the primary amine hydrohalide salt added is 0.67 to a molar ratio to the nitrile compound (ammonium halide or primary amine hydrohalide salt / nitrile compound).
It is preferable to select from the range of 1.5. If the amount of ammonium halide or primary amine hydrohalide is large, a component insoluble in DMF is formed, and if the amount of nitrile compound is large, the amount of unreacted adduct tends to increase. It may be selected from the range of 1.2.

The solvent used for synthesizing the precursor of the present invention is not particularly limited, but when the precursor which is the reaction product is separated, it is easy to dissolve and remove the borazine compound which is the reaction by-product. preferable. From such a viewpoint, an organic solvent such as benzene, toluene, xylene, chlorobenzene is preferably selected.

The heating temperature for reacting the adduct with the ammonium halide or the primary amine hydrohalide is generally low at low temperatures and D at high temperatures.
The components insoluble in MF increase and the reaction yield decreases. Therefore, the heating temperature may be selected from the range of 100 ° C to 160 ° C. The heating time may vary depending on the temperature, but may be selected from the range of 3 to 30 hours.

By performing the above heat treatment, a boron nitride precursor is formed as an orange or brown precipitate.

As a reaction device for obtaining the boron nitride precursor, a known device can be used without particular limitation. However, since the addition product of boron trihalide and a nitrile compound and the boron nitride precursor are both hydrolyzed, the inside of the reaction system should be sufficiently dried with nitrogen gas, etc. It is necessary to place a hygroscopic agent such as calcium chloride in the open part of the device so that moisture inside does not enter.

(B) The precursor produced in step (a) is spun to form boron carbonitride precursor fibers (hereinafter also referred to as precursor fibers).

As the spinning method of the precursor fiber, a known spinning method such as a solution spinning method or a melt spinning method can be applied. For example, when the precursor fiber is formed by the solution spinning method, first, the precursor is dissolved in a soluble solvent to prepare a precursor solution (hereinafter, also referred to as a spinning solution).

Examples of the precursor-soluble solvent include DMF,
ε-caprolactam, chloronitrile, malonitrile,
N-methyl-β-cyanoethylformamide, N, N
-Diethylformamide and the like can be mentioned. By dissolving the precursor in the soluble solvent, an orange or brown transparent spinning solution can be obtained.

In the spinning solution used in the present invention, an acrylonitrile polymer may be added to the spinning solution for the purpose of improving spinnability. The acrylonitrile polymer is
It can be used without particular limitation as long as it is dissolved in a soluble solvent constituting the spinning solution and does not cause phase separation with the precursor in the spinning solution. Preferably, it is a polymer of acrylonitrile, or a polymerizable monomer other than acrylonitrile having a vinyl group such as vinyl acetate, acrylamide, methacrylic acid, methacrylic acid ester, acrylic acid, acrylic acid ester (hereinafter simply referred to as vinyl monomer) and acrylonitrile. Copolymers with are used. When a copolymer of acrylonitrile and a vinyl monomer is used, when the amount of the vinyl monomer constituting the copolymer increases, phase separation with the precursor tends to occur in the spinning solution. It is preferable that the composition of acrylonitrile constituting the copolymer is 85 mol% or more based on the total polymerizable monomers.

The weight average molecular weight of the acrylonitrile polymer used in the present invention is not particularly limited, but it is 10,000 to 20.
It is preferably in the range of 0,000.

The amount of the acrylonitrile polymer added to the spinning solution is not particularly limited, but it is not intended to produce the above-mentioned boron carbonitride fiber having a high carbon content, but the spinnability of the spinning solution. For the purpose of improving the above, the amount may be 0.01 to 5 parts by weight with respect to 100 parts by weight of the precursor.

The precursor solution thus prepared is spun to form a precursor fiber.

The preferred concentration range of the spinning solution depends on the spinning method, but is 0.01 to 3.0 g / ml, and the viscosity at that time is 10 to 100,000 poises. As a method for spinning the precursor fiber from the obtained spinning solution, a widely known method can be used. For example, by rotating a container having a small hole containing the spinning solution, the spinning solution is discharged by using centrifugal force, the spinning solution is discharged by gas pressure through the small hole, and a gear pump is used through the small hole. The precursor fiber can be spun by using a method of discharging the spinning solution.

The spinning temperature may vary depending on the solvent used, but is, for example, -60 to 200 ° C, preferably -10 to 10.
180 ° C., more preferably 0 to 160 ° C.

One of the methods for obtaining boron carbonitride fibers having an orientation degree of 0.70 or more is a method of heating precursor fibers while applying stress.

(C) The precursor fiber obtained in step (b) was applied with tensile stress in an inert gas atmosphere while applying 16
The boron carbonitride fiber of the present invention is obtained by heating at 00 to 2300 ° C.

That is, for boron carbonitride fibers having an orientation degree of 0.70 or more, 1600 to 2300 ° C., preferably 1650 to 2250 ° C., while applying tensile stress to the precursor fibers in an inert gas atmosphere, More preferably 170
It can be obtained by heat treatment at 0 to 2200 ° C.

Nitrogen, argon, helium or the like can be used as the atmospheric gas in the heat treatment in the inert gas atmosphere.

The heating device for heat-treating the precursor fiber in an inert gas atmosphere may have any structure capable of controlling the atmosphere by a chamber, a furnace core tube, or the like. The heating device of 1 is used without particular limitation. As the heat treatment method, a batch-type heat treatment in which a fixed amount of precursor fibers are heat-treated at one time, and a continuous precursor fiber is sequentially fed to a heating device that has been heated to a heat treatment temperature to perform heat treatment, and heat treatment is performed. There is a continuous heat treatment for winding and collecting fibers, and any heat treatment method may be used in the present invention. When performing batch heat treatment under an inert gas atmosphere, the precursor fiber is introduced into the heat treatment apparatus which has been preheated to the heat treatment temperature to perform the heat treatment, or the precursor fiber is added to the heat treatment apparatus. After the arrangement, the temperature can be raised to reach the heat treatment temperature for heat treatment.

In any of the heat treatment methods, when the precursor fiber is rapidly heated, the thermal decomposition products are rapidly desorbed, resulting in defects such as voids and cracks in the obtained boron carbonitride fiber. The strength may be extremely reduced. Therefore, it is preferable to perform the heat treatment at a heating rate of 100 ° C./min or less until the precursor fiber reaches the heat treatment temperature. The holding time at the heat treatment temperature depends on the amount of precursor fibers and the heat treatment temperature, but can be arbitrarily selected from the range of 0 to 10 hours. The holding time of 0 hour means that the heat treatment is terminated immediately after the precursor fiber reaches the heat treatment temperature, by lowering the temperature of the heating device or taking out the precursor fiber from the heating device.

In the heat treatment atmosphere in the heat treatment under the inert gas atmosphere, in any of the temperature raising process until reaching the heat treatment temperature, the holding process at the heat treatment temperature, and the temperature lowering process until the end of the heat treatment. That is, while the precursor fiber is in the chamber of the heating device, the furnace core tube, or the like in the inert gas atmosphere, the inert gas atmosphere is preferable. In order to create an inert gas atmosphere, the chamber of the heating device, the furnace core tube, or the like, which has been replaced with the inert gas, may be closed, or the inert gas may be passed through the chamber of the heating device, the furnace tube, or the like.

The heat treatment temperature in the heat treatment is 1600.
It can be arbitrarily selected from the range of 2300C. When the heat treatment temperature is lower than 1600 ° C., crystal orientation does not proceed sufficiently even if tensile stress is applied, and the degree of orientation may not reach 0.7. Further, since the decomposition reaction of boron carbonitride starts at 2300 ° C or higher, it is not preferable to perform the heat treatment at 2300 ° C or higher.

In the heat treatment, the method of applying the tensile stress to the precursor fibers is not particularly limited, but for example, when the heat treatment is performed in a batch system, the precursor fibers are hung vertically and the lower end thereof is suspended. A tensile stress can be applied by adding a weight. Further, the precursor fiber is 1600 to 2 in an inert gas atmosphere in the state where no tensile stress is applied.
When heat-treated at 300 ° C., it shrinks in the fiber axis direction depending on the heat-treatment temperature. Therefore, the precursor fiber is provided with a mold made of a material such as boron carbonitride that does not react with the precursor fiber and the boron carbonitride fiber produced by the heat treatment, and the mixture is left in an inert gas atmosphere at 1600 to 1600. 2300
If the heat treatment is performed at a temperature of 0 ° C., the heat shrinkage of the precursor fiber due to the heat treatment is prevented by the mold, and as a result, the heat treatment can be performed while applying a tensile stress to the precursor fiber. Further, when the heat treatment is performed in a continuous manner, the heat in the heat treatment of the precursor fiber is controlled by controlling the supply rate of the precursor fiber to the heat treatment apparatus and the winding speed of the fiber which has finished the heat treatment. The shrinkage can be controlled, and as a result, the heat treatment can be performed while applying the tensile stress.

The tensile stress applied to the precursor fiber in the heat treatment varies depending on the heat treatment temperature and the heat treatment time of the heat treatment, but when stress is applied by suspending a weight, the range is 0.1 to 1000 MPa. You can select it arbitrarily. If the applied stress is less than 0.1 MPa, the crystal orientation may be insufficient and the degree of orientation may not reach 0.7.
Further, if the applied stress is larger than 1000 MPa, the unoriented fiber may be broken. On the other hand, when the tensile stress is applied to the precursor fiber by limiting the shrinkage of the precursor fiber due to the heat treatment, or the rate at which the precursor fiber is supplied to the heat treatment apparatus and the fiber after the heat treatment are continuously processed. When the tensile speed is controlled by controlling the winding speed and limiting the heat shrinkage due to the heat treatment and applying the tensile stress to the precursor fiber, the stretching ratio is 4
It may be selected from the range of up to 32%. However, draw ratio (E)
Is defined by equation (3).

E = 100 × (Ls−Lf) / Lf (3) Lf does not limit the thermal contraction of the unit length boron carbonitride fiber, that is, the tensile stress is applied to the boron carbonitride fiber. Without heat treatment at a heat treatment temperature (T ° C), Ls represents the length of the fiber sample, and Ls is a fiber obtained by heat treatment at a heat treatment temperature (T ° C) by limiting the heat shrinkage of the boron carbonitride fiber having a unit length. Indicates the sample length.

When the stretching ratio is less than 4%, the tensile stress applied to the precursor fiber is insufficient and the degree of crystal orientation is 0.
It may not reach 70. If the draw ratio is higher than 32%, the precursor fiber may be broken during the heat treatment.

The outline of the constitution and manufacturing method of the non-aqueous electrolyte secondary battery using the negative electrode active material made of the boron carbonitride fiber is as follows.

First, using a kneader or a mixer, boron carbonitride fibers are kneaded with a solvent such as N-methylpyrrolidone to produce a paste. At this time, a conductivity-imparting agent such as graphite or acetylene black, or a binder such as polytetrafluoroethylene or polyvinylidene fluoride may be added. However, if the amounts of the conductivity-imparting agent and the binder are too large, the proportion of substances that do not participate in the charge / discharge reaction increases, and the capacity of the negative electrode decreases. Therefore, it is preferable to minimize the amounts of these conductivity-imparting agents and binders added. In the negative electrode active material composed of the boron carbonitride fiber of the present invention, compared with the conventional negative electrode active material composed of boron carbonitride having no fiber shape, even if a small amount of the binder is used, Does not fall off or peel off from the electric body.
Specifically, even if the added amount of the binder is 5% by weight or less, the binder does not fall off or peel off from the current collector.

The order in which the solvent, the conductivity-imparting agent and the binder are kneaded with the boron carbonitride fiber is not particularly limited. The conductivity-imparting agent and the binder may be kneaded with the solvent first, and then the carbon carbonitride fibers may be kneaded, or the boron carbonitride fibers and the binder may be mixed and then kneaded with the solvent.

After the paste is manufactured, the current collector is coated with, filled with, or impregnated with the paste to be bonded, and after drying and removing the solvent, pressure and cutting are performed to obtain a desired shape to obtain a negative electrode. The negative electrode and a positive electrode produced in the same manner are stacked in a strip shape with a separator interposed therebetween, and are cylindrically wound in the case of a cylindrical non-aqueous electrolyte secondary battery, or folded in the case of a rectangular non-aqueous electrolyte secondary battery. Overlapping, the electrode part is manufactured. After that, this electrode portion is inserted into a desired battery container, a nonaqueous electrolytic solution is injected, and then a safety device or the like is inserted and sealed.

For the positive electrode, current collector, non-aqueous electrolyte solution, separator, etc., the materials used in conventional non-aqueous electrolyte secondary batteries can be used without any problems.

Examples of the positive electrode active material include TiS ₂ , MoS ₂ ,
Sulfides such as FeS ₂ , chalcogen compounds such as selenides such as NbSe ₃ , or Cr ₂ O ₅ , Cr ₃ O ₈ , V
Oxides of transition metals such as ₃ O ₈ , V ₂ O ₅ and V ₆ O ₁₃ , Li
Mn ₂ O ₄ , Li ₂ MnO ₄ , LiV ₃ O ₅ , LiNiO ₂ ,
Storage of lithium such as complex oxides of lithium and transition metals such as LiCoO ₂ or conjugated polymers such as polyaniline, polyacetylene, polyparaphenylene, polyphenylene vinylene, polypyrrole, polythiophene, and crosslinked polymers having disulfide bonds Materials that can be released can be used.

The collector is preferably a strip-shaped thin plate or mesh made of copper, aluminum or the like.

As the non-aqueous electrolyte, propylene carbonate, ethylene carbonate, 1,2-dimethoxyethane, 1,2-diethoxyethane, γ-butyrolactone,
Tetrahydrofuran, 1,3-dioxolane, 4-methyl-1,3-dioxolane, diethyl ether, sulfolane, methylsulfolane, acetonitrile, propionitrile, etc., alone or in a mixture of two or more kinds of non-aqueous solvents, LiClO ₄ , LiPF ₆ , LiAsF ₆ , LiB
F ₄ , LiB (C ₆ H ₅ ) 4, LiCl, LiBr, CH _{3
SO 3 Li, CF 3 SO 3} Li nonaqueous electrolyte lithium salt is dissolved, such as can be also be used in any combination. The water contained as an impurity in the non-aqueous electrolyte at this time causes a side reaction during the charge-discharge reaction and adversely affects the charge-discharge cycle characteristics, so it is preferable to reduce it as much as possible. Specifically, the amount of water in the non-aqueous electrolyte is 200 p
It is preferably pm or less, more preferably 100 ppm or less.

Any separator can be used without any limitation as long as it has a low resistance to the movement of ions and is excellent in solution retention. For example, a polymer pore filter made of polypropylene, polyethylene, polyester, polyflon, etc., a glass fiber filter, a non-woven fabric, or a non-woven fabric made of glass fiber and these polymers described above can be used. Further, it is preferable to use a material that melts and closes the pores when the temperature inside the battery becomes high to prevent short circuit between the positive electrode and the negative electrode.

[0091]

INDUSTRIAL APPLICABILITY The negative electrode active material composed of boron carbonitride fibers having an orientation degree of 0.70 or more according to the present invention does not fall off or peel off from the current collector even if the addition amount of the binder is small. Has the effect. Therefore, the filling rate of the negative electrode active material in the negative electrode is increased, and a non-aqueous electrolyte secondary battery having a high battery capacity can be manufactured.

In the conventional powdery boron carbonitride, unless a large amount of a binder is added to bond the powders to each other, the powdery boron carbonitride easily falls off and peels from the current collector. On the other hand, when the boron carbonitride fiber of the present invention is used as the negative electrode active material, the fibers form a structure in which the fibers are entangled with each other, so that the binder is removed from the current collector even if a small amount of the binder is added, and peeling It is considered difficult to cause

[0093]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

In the following Examples and Comparative Examples, the respective capacities as negative electrode active materials were measured as follows. In addition, the boron carbonitride fibers after firing are all 1 cm
It was cut to the length and used.

Polyvinylidene fluoride as a binder and acetylene black as a conductivity-imparting agent were mixed with the negative electrode active material, and 500 mg of this mixture was mixed with 1 ml of N-methylpyrrolidone as a solvent and kneaded to form a paste. . Polyvinylidene fluoride and acetylene black were made to be 3% by weight and 5% by weight, respectively. This paste was dried in a vacuum dryer at 100 ° C. for 24 hours. 6 mg of a kneaded material containing this negative electrode active material was applied to a nickel net to obtain a negative electrode. For the non-aqueous electrolyte, LiCl0
_A solution prepared by dissolving 4 in an equal volume mixed solvent of ethylene carbonate and diethyl carbonate so as to have a concentration of 1 mol / liter was used. Also, use a cylindrical glass container as the battery container, and place two positive electrodes (using lithium) on both sides of one negative electrode and one reference electrode (using lithium) near the negative electrode. A nickel wire with a clip (glass tube coating) was hung from the lid to form a simple battery cell.

Using the charging / discharging device (manufactured by Hokuto Denko), a charging / discharging cycle test of the above simple battery cell was conducted to measure the capacity of the negative electrode active material. 30m in charge / discharge cycle test
The current value (constant) corresponding to A / g was used. The capacity of the negative electrode active material was calculated from the capacity = 30 × t (unit: mAh / g) by measuring the discharge time t (unit: time). Charge / discharge is 0 to the reference electrode.
It was performed within the range of 1.99V. The capacities in Examples and Comparative Examples were compared with each other at the time of initial discharge.

Whether or not the negative electrode active material was detached or peeled from the current collector was confirmed by direct visual observation after 20 charge / discharge cycle tests.

Example 1 A stirrer was attached to the middle tube of a three-necked flask having a capacity of 1 liter, a Dewar type cold finger in which a cylinder containing boron trichloride was connected to one of the side tubes, and a ball containing cooling tube was attached to the remaining side tubes. I installed each. A Dewar cold finger was attached to the ball cooling tube, and a calcium chloride tube was attached to the outlet of the cold finger. Dry nitrogen was passed through this device at 200 ml / min for 4 hours to dry the inside of the device.
Chlorobenzene 30 dried overnight over anhydrous sodium sulfate
0 ml and 16.4 g of acetonitrile were added. Two cold fingers were filled with dry ice-acetone and stirred with a stirrer. 60 g of boron trichloride was obtained from the cold fingers directly attached to the three-necked flask.
Was condensed and added dropwise over 2 hours. This produced a white boron trichloride-acetonitrile adduct. After the addition of boron trichloride was completed, the cold finger directly attached to the three-necked flask was removed, and 21.5 g of ammonium chloride dried overnight at 110 ° C. was added. When this suspension was heated to 125 ° C. for 8 hours, hydrogen chloride was hardly generated and a brown precipitate was formed. The precipitate formed was filtered off, washed with 100 ml of chlorobenzene and dried under reduced pressure to obtain 24 g of a precursor (yield 83%).

After dissolving 10 g of this precursor in 200 ml of DMF, 100 ml of DMF was removed by evaporation to obtain a uniform viscous solution. This solution has a diameter of 60 at 25 ° C.
A back pressure of 15 kg / cm ² was applied from a spinning nozzle having pores of μm, the mixture was discharged into dry air, and wound up to spin a continuous precursor fiber having a diameter of about 20 μm.
At this time, the viscosity of the spinning solution was 2.9 × 10 ⁴ poise, and the spinning speed was 1.8 m / min.

The spun precursor fiber was wound into a loop with a circumference of 192 mm, and the circumference was maintained while maintaining the loop shape.
The sample was placed on a 5 mm boron nitride mold and heat-treated as it was in a nitrogen stream. In the heat treatment, the temperature is increased at a rate of 1 ° C / min up to 400 ° C, 2 ° C / min from 400 ° C to 1600 ° C, and 10 ° C / min from 1600 ° C to 1800 ° C. Hold at 1800 ° C for 30 minutes, cool to 500 ° C at a cooling rate of 5 ° C / min,
Then, it was allowed to cool to room temperature. After the treatment, the boron carbonitride fiber remained in the state of being wound around the mold without breaking or unraveling. The stretch ratio at this time was 6.3%.

From the powder X-ray diffraction and the XPS spectra of boron and nitrogen, the obtained boron carbonitride fiber had a structure in which the C planes were laminated, and the structure had boron-carbon bonds and nitrogen. -It was confirmed that carbon bonds were present.
As a result of elemental analysis of this boron carbonitride fiber,
The composition was 44 atm% boron, 16 atm% carbon, and 40 atm% nitrogen.

The degree of orientation of this boron carbonitride fiber is 0.7.
2. The tensile strength was 1400 MPa.

Using the boron carbonitride fiber, the above-mentioned simple battery cell was prepared and a charge / discharge cycle test was conducted. The discharge capacity was 354 mAh / g. Although the amount of the binder added was as small as 3% by weight, the boron carbonitride fibers did not fall off or come off from the current collector.

Example 2 A precursor fiber prepared in the same manner as in Example 1 was treated with a surrounding 19
Winding in a loop shape of 2 mm, keeping the loop shape,
The sample was placed on a boron nitride frame having a circumference of 139 mm, and heat-treated as it was in a nitrogen stream. The heat treatment is performed at a heating rate of 1 ° C / min up to 400 ° C, and a heating rate of 2 ° C / min from 400 ° C to 1600 ° C, from 1600 ° C to 2000 ° C.
The temperature was raised at a temperature rising rate of 10 ° C / min, held at 2000 ° C for 30 minutes, cooled to 500 ° C at a cooling rate of 5 ° C / min, and then allowed to cool to room temperature. After the treatment, the boron carbonitride fiber remained in the state of being wound around the mold without breaking or unraveling. The stretching ratio at this time was 13.0%.

From the powder X-ray diffraction and the XPS spectra of boron and nitrogen, the obtained boron carbonitride fiber had a structure in which the C planes were laminated, and the structure had a boron-carbon bond and nitrogen. -It was confirmed that carbon bonds were present.

The orientation degree of this boron carbonitride fiber is 0.8.
2. The tensile strength was 1900 MPa.

Using the boron carbonitride fiber, the above-mentioned simple battery cell was prepared and a charge / discharge cycle test was conducted. The discharge capacity was 376 mAh / g. Although the amount of the binder added was as small as 3% by weight, the boron carbonitride fibers did not fall off or come off from the current collector.

Example 3 A precursor fiber prepared in the same manner as in Example 1 was used in the surrounding 19
Winding in a loop shape of 2 mm, keeping the loop shape,
The sample was placed on a boron nitride frame having a circumference of 143 mm, and heat-treated as it was in a nitrogen stream. The heat treatment is performed at a heating rate of 1 ° C / min up to 400 ° C, and a heating rate of 2 ° C / min from 400 ° C to 1600 ° C, from 1600 ° C to 2000 ° C.
The temperature was raised at a temperature rising rate of 10 ° C / min, held at 2000 ° C for 30 minutes, cooled to 500 ° C at a cooling rate of 5 ° C / min, and then allowed to cool to room temperature. After the treatment, the boron carbonitride fiber remained in the state of being wound around the mold without breaking or unraveling. The stretch ratio at this time was 16.3%.

From the powder X-ray diffraction and the XPS spectra of boron and nitrogen, the obtained boron carbonitride fiber had a structure in which the C planes were laminated, and the structure had a boron-carbon bond and nitrogen. -It was confirmed that carbon bonds were present.

The orientation degree of this boron carbonitride fiber is 0.8.
5, the tensile strength was 2200 MPa.

Using the boron carbonitride fiber, the above-mentioned simple battery cell was prepared and a charge / discharge cycle test was conducted. The discharge capacity was 378 mAh / g. Although the amount of the binder added was as small as 3% by weight, the boron carbonitride fibers did not fall off or come off from the current collector.

Comparative Example 1 The precursor fiber produced in the same manner as in Example 1 was heat-treated in a nitrogen stream without applying tensile stress to the fiber. Heat treatment is performed at a heating rate of 1 ° C / mi up to 400 ° C
n, temperature rising rate of 2 ° C / mi from 400 ° C to 1600 ° C
n, temperature rising rate from 1600 ° C to 1800 ° C is 10 ° C /
The temperature was raised at min, held at 1800 ° C. for 30 minutes, cooled to 500 ° C. at a cooling rate of 5 ° C./min, and then allowed to cool to room temperature.

From the powder X-ray diffraction and the XPS spectra of boron and nitrogen, the obtained boron carbonitride fiber had a structure in which the C planes were laminated, and the structure had boron-carbon bonds and nitrogen. -It was confirmed that carbon bonds were present.

The orientation degree of this boron carbonitride fiber is 0.5.
5. The tensile strength was 800 MPa.

Using the boron carbonitride fiber, the above-mentioned simple battery cell was prepared and a charge / discharge cycle test was conducted. The discharge capacity was 351 mAh / g. However, after the charge-discharge cycle test, the boron carbonitride fibers were observed to fall off and peel off, and it was found that the boron carbonitride fiber could not withstand many charge-discharge cycles.

Comparative Example 2 Boron carbonitride fibers produced in the same manner as in Example 2 were pulverized into a powder having a particle size of 10 μm or less using an agate mortar.

Using the boron carbonitride powder, the above-mentioned simplified battery cell was prepared and a charge / discharge cycle test was conducted. The discharge capacity was 355 mAh / g. However, after the charge-discharge cycle test, the boron carbonitride fibers were observed to fall off and peel off, and it was found that the boron carbonitride fiber could not withstand many charge-discharge cycles.

Example 4 A stirrer was placed in the middle tube of a three-necked flask having a capacity of 1 liter, and a dropping funnel containing 128 g of boron tribromide in one of the side tubes.
A ball containing cooling tube was attached to the remaining side tube. A calcium chloride tube was attached to the outlet of the ball containing cooling tube. Dry nitrogen was passed through this device at 200 ml / min for 4 hours to dry the inside of the device, and then 300 ml of chlorobenzene and 16.4 g of acetonitrile dried overnight with anhydrous sodium sulfate were added. While stirring with a stirrer, boron tribromide was added dropwise from the dropping funnel over 2 hours. This produced a white boron tribromide-acetonitrile adduct. After the addition of boron tribromide was completed, the dropping funnel attached to the three-necked flask was removed, and 21.5 g of ammonium chloride dried at 110 ° C. overnight was added. The suspension was heated to 125 ° C. for 8 hours, filtered, washed with 100 ml of chlorobenzene and dried under reduced pressure to give a brown precipitate (48 g, yield 80%).
Got

After dissolving 15 g of this precursor in 200 ml of DMF, 100 ml of DMF was removed by evaporation to obtain a uniform viscous solution. This solution has a diameter of 60 at 25 ° C.
A back pressure of 15 kg / cm ² was applied from a spinning nozzle having pores of μm, and the mixture was discharged into dry air and wound up to spin a continuous precursor fiber having a diameter of about 20 μm.
At this time, the viscosity of the spinning solution was 2.9 × 10 ⁴ poise and the spinning speed was 1.9 m / min.

The spun precursor fiber was heat-treated in the same manner as in Example 2. The stretching ratio at this time was 12.8%.

From the powder X-ray diffraction and the XPS spectra of boron and nitrogen, the obtained boron carbonitride fiber had a structure in which the C planes were laminated, and the structure had boron-carbon bonds and nitrogen. -It was confirmed that carbon bonds were present.

The orientation degree of this boron carbonitride fiber was 0.8.
3. The tensile strength was 2000 MPa.

Using the boron carbonitride fiber, the above-mentioned simple battery cell was prepared and a charge / discharge cycle test was conducted. The discharge capacity was 369 mAh / g. Although the amount of the binder added was as small as 3% by weight, the boron carbonitride fibers did not fall off or come off from the current collector.

Example 5 A stirrer was attached to the middle tube of a three-necked flask having a capacity of 1 liter, a dropping funnel containing 16.4 g of acetonitrile was placed in one of the side tubes, and a ball-filled cooling tube was attached to the remaining side tubes. A calcium chloride tube was attached to the outlet of the ball containing cooling tube. Dry nitrogen was passed through this device at 200 ml / min for 4 hours to dry the inside of the device, and then 300 ml of chlorobenzene and 200 g of boron triiodide dried overnight with anhydrous sodium sulfate were added.
While stirring with a stirrer, acetonitrile was added dropwise from the dropping funnel over 2 hours. This produced a white boron triiodide-acetonitrile adduct. After the addition of boron triiodide was completed, the cold finger directly attached to the three-necked flask was removed, and 21.5 g of ammonium chloride dried at 110 ° C. overnight was added. The suspension was heated to 125 ° C. for 8 hours, filtered, washed with 100 ml of chlorobenzene and dried under reduced pressure to obtain 65 g of brown precipitate (yield 79%).

After dissolving 20 g of this precursor in 200 ml of DMF, 100 ml of DMF was removed by evaporation to obtain a uniform viscous solution. This solution has a diameter of 60 at 25 ° C.
A continuous pressure of 15 kg / cm @ 2 was applied from a spinning nozzle having pores of .mu.m, the mixture was discharged into dry air, and wound up to spin a continuous precursor fiber having a diameter of about 20 .mu.m.
At this time, the viscosity of the spinning solution was 2.8 × 10 4 poise and the spinning speed was 1.9 m / min.

The spun precursor fiber was heat-treated in the same manner as in Example 2. The stretching ratio at this time was 13.1%.

From powder X-ray diffraction and the XPS spectra of boron and nitrogen, the obtained boron carbonitride fiber had a structure in which the C planes were laminated, and the structure had boron-carbon bonds and nitrogen. -It was confirmed that carbon bonds were present.

The degree of orientation of this boron carbonitride fiber was 0.8.
0, the tensile strength was 1900 MPa.

Using the boron carbonitride fiber, the above-mentioned simple battery cell was prepared and a charge / discharge cycle test was conducted. The discharge capacity was 375 mAh / g. Although the amount of the binder added was as small as 3% by weight, the boron carbonitride fibers did not fall off or come off from the current collector.

Example 6 A stirrer was installed in the middle tube of a three-necked flask having a capacity of 1 liter, a Dewar cold finger in which a cylinder containing boron trichloride was attached to one of the side tubes, and a ball containing cooling tube was attached to the remaining side tubes. I installed each. A Dewar cold finger was attached to the ball cooling tube, and a calcium chloride tube was attached to the outlet of the cold finger. Dry nitrogen was passed through this device at 200 ml / min for 4 hours to dry the inside of the device, and then 300 ml of chlorobenzene and 16.4 g of acetonitrile dried overnight with anhydrous sodium sulfate were added. Two
Fill one cold finger with dry ice-acetone and stir with a stirrer. Boron trichloride 60 from a cold finger directly attached to a three-necked flask.
g was condensed and added dropwise over 2 hours. This produced a white boron trichloride-acetonitrile adduct. After the addition of boron trichloride was completed, the cold finger directly attached to the three-necked flask was removed, and 27.2 g of monomethylamine hydrochloride dried overnight at 110 ° C. was added. When this suspension was heated to 125 ° C. for 8 hours, hydrogen chloride was hardly generated and a brown precipitate was formed. The formed precipitate was separated by filtration, washed with 100 ml of chlorobenzene, and then dried under reduced pressure to obtain 25 g of a precursor (yield 80%).

After dissolving 10 g of this precursor in 200 ml of DMF, 100 ml of DMF was removed by evaporation to obtain a uniform viscous solution. This solution has a diameter of 60 at 25 ° C.
A back pressure of 15 kg / cm ² was applied from a spinning nozzle having pores of μm, and the mixture was discharged into dry air and wound up to spin a continuous precursor fiber having a diameter of about 20 μm.
At this time, the viscosity of the spinning solution was 3.0 × 10 ⁴ poise, and the spinning speed was 1.8 m / min.

The spun precursor fiber was heat-treated in the same manner as in Example 2. The stretch ratio at this time was 13.2%.

From the powder X-ray diffraction and the XPS spectra of boron and nitrogen, the obtained boron carbonitride fiber had a structure in which the C planes were laminated, and the structure had boron-carbon bonds and nitrogen. -It was confirmed that carbon bonds were present.

The orientation degree of this boron carbonitride fiber was 0.8.
0, the tensile strength was 1800 MPa.

Using the boron carbonitride fiber, the above-mentioned simplified battery cell was prepared and a charge / discharge cycle test was conducted. The discharge capacity was 373 mAh / g. Although the amount of the binder added was as small as 3% by weight, the boron carbonitride fibers did not fall off or come off from the current collector.

Example 7 A stirrer was attached to the middle tube of a three-necked flask having a capacity of 1 liter, a Dewar cold finger having a cylinder containing boron trichloride was attached to one of the side tubes, and a ball-filled cooling tube was attached to the remaining side tubes. I installed each. A Dewar cold finger was attached to the ball cooling tube, and a calcium chloride tube was attached to the outlet of the cold finger. After passing dry nitrogen at 200 ml / min for 4 hours to the device to dry the inside of the device, 300 ml of chlorobenzene and 41.2 g of benzonitrile dried overnight with anhydrous sodium sulfate were added. Two
Fill one cold finger with dry ice-acetone and stir with a stirrer. Boron trichloride 60 from a cold finger directly attached to a three-necked flask.
g was condensed and added dropwise over 2 hours. This produced a white boron trichloride-benzonitrile adduct. After the addition of boron trichloride was completed, the cold finger directly attached to the three-necked flask was removed, and 21.5 g of ammonium chloride dried overnight at 110 ° C. was added. When this suspension was heated to 125 ° C. for 8 hours, hydrogen chloride was hardly generated and a brown precipitate was formed. The formed precipitate was separated by filtration, washed with 100 ml of chlorobenzene and then dried under reduced pressure to obtain 27 g of a precursor (yield 79%).

After dissolving 10 g of this precursor in 200 ml of DMF, 100 ml of DMF was removed by evaporation to obtain a uniform viscous solution. This solution has a diameter of 60 at 25 ° C.
A back pressure of 15 kg / cm ² was applied from a spinning nozzle having pores of μm, and the mixture was discharged into dry air and wound up to spin a continuous precursor fiber having a diameter of about 20 μm.
At this time, the viscosity of the spinning solution was 2.9 × 10 ⁴ poise, and the spinning speed was 1.8 m / min.

The spun precursor fiber was heat-treated in the same manner as in Example 2. The stretch ratio at this time was 13.2%.

From the powder X-ray diffraction and the XPS spectra of boron and nitrogen, the obtained boron carbonitride fiber had a structure in which the C planes were laminated, and the structure had boron-carbon bonds and nitrogen. -It was confirmed that carbon bonds were present.

The orientation degree of this boron carbonitride fiber was 0.8.
2. The tensile strength was 1900 MPa.

Using the boron carbonitride fiber, the above-mentioned simple battery cell was prepared and a charge / discharge cycle test was conducted. The discharge capacity was 368 mAh / g. Although the amount of the binder added was as small as 3% by weight, the boron carbonitride fibers did not fall off or come off from the current collector.

Example 8 A stirrer was attached to the middle tube of a three-necked flask having a capacity of 1 liter, a Dewar type cold finger with a cylinder containing boron trichloride was attached to one of the side tubes, and a ball containing cooling tube was attached to the remaining side tubes. I installed each. A Dewar cold finger was attached to the ball cooling tube, and a calcium chloride tube was attached to the outlet of the cold finger. After passing dry nitrogen at 200 ml / min for 4 hours to the device to dry the inside of the device, 300 ml of chlorobenzene and 41.2 g of acrylonitrile dried overnight with anhydrous sodium sulfate were added.
Fill two cold fingers with dry ice-acetone and stir with a stirrer. Boron trichloride 6 from a cold finger directly attached to the three-necked flask.
0 g was condensed and added dropwise over 2 hours. This produced a white boron trichloride-acrylonitrile adduct.
After the addition of boron trichloride was completed, the cold finger directly attached to the three-necked flask was removed, and 21.5 g of ammonium chloride dried overnight at 110 ° C. was added. When this suspension was heated to 125 ° C. for 8 hours, hydrogen chloride was hardly generated and a brown precipitate was formed. The formed precipitate was separated by filtration, washed with 100 ml of chlorobenzene, and then dried under reduced pressure to obtain 24 g of a precursor (yield 77%).

After dissolving 10 g of this precursor in 200 ml of DMF, 100 ml of DMF was removed by evaporation to obtain a uniform viscous solution. This solution has a diameter of 60 at 25 ° C.
A back pressure of 15 kg / cm ² was applied from a spinning nozzle having pores of μm, and the mixture was discharged into dry air and wound up to spin a continuous precursor fiber having a diameter of about 20 μm.
At this time, the viscosity of the spinning solution was 2.9 × 10 ⁴ poise and the spinning speed was 1.9 m / min.

The spun precursor fiber was heat-treated in the same manner as in Example 2. The stretching ratio at this time was 13.1%.

From the powder X-ray diffraction and the XPS spectra of boron and nitrogen, the obtained boron carbonitride fiber had a structure in which the C planes were laminated, and the structure had a boron-carbon bond and nitrogen. -It was confirmed that carbon bonds were present.

The degree of orientation of this boron carbonitride fiber was 0.8.
1. The tensile strength was 1800 MPa.

Using the boron carbonitride fiber, the above-mentioned simplified battery cell was prepared and a charge / discharge cycle test was conducted. The discharge capacity was 369 mAh / g. Although the amount of the binder added was as small as 3% by weight, the boron carbonitride fibers did not fall off or come off from the current collector.

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Claims (3)

(57) [Claims] 1. A surface (C) formed by connecting a 6-membered ring formed by bonding carbon, boron and nitrogen in the plane direction of the 6-membered ring.
Plane) is a boron carbonitride fiber made of boron carbonitride having a laminated structure, wherein at least a part of the C plane is oriented substantially parallel to the fiber axis of the boron carbonitride fiber. A negative electrode active material for a non-aqueous electrolyte secondary battery, which comprises boron carbonitride fibers having a degree of orientation of the C plane of 0.70 or more. 2. A boron carbonitride fiber comprising: (a) an adduct of a boron trihalide and a nitrile compound and an ammonium halide or a primary amine hydrohalide in the presence of boron trihalide. Reacting to produce a boron carbonitride precursor, (b) spinning the boron carbonitride precursor to form a boron carbonitride precursor fiber, and (c) the boron carbonitride precursor fiber. The negative electrode active material for a non-aqueous electrolyte secondary battery according to claim 1, which is a boron carbonitride fiber obtained by heating at 1600 to 2300 ° C while applying tensile stress in an inert gas atmosphere. 3. A negative electrode formed by bonding the negative electrode active material for a non-aqueous electrolyte secondary battery according to claim 1 or 2 to a current collector, and a positive electrode active material made of a material capable of inserting and extracting lithium. A non-aqueous electrolyte secondary battery, wherein a positive electrode formed by bonding a substance to a current collector is separated by a separator and housed in a battery container together with the non-aqueous electrolyte.