JP2004134295A - Nonaqueous electrolyte battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nonaqueous electrolyte battery in which charge and discharge capacity is large, and which is less liable to deterioration in cycles. <P>SOLUTION: This battery is provided with a negative electrode 1 composed of lithium metal or a material capable of storing and releasing lithium, an electrolyte containing lithium salt, and a positive electrode 3 composed of graphite intercalation compound. As the host material of the graphite intercalation compound used for the positive electrode 3, a material obtained by carrying out heat treatment of a carbon material containing boron or boron compound, and by intercalating an electron attracting substance is used. The electron attracting substance to intercalate with the graphite intercalation compound contains at least one kind selected from CoCl<SB>2</SB>, NiCl<SB>2</SB>, CuCl<SB>2</SB>, CrCl<SB>3</SB>, FeCl<SB>3</SB>, and MnCl<SB>2</SB>. <P>COPYRIGHT: (C)2004,JPO

Description

【００５６】
実施例１〜３０に挙げた中で、残存ホウ素量の範囲０．０５重量％〜１０．９８重量％では、１０サイクルまでではあるが、容量劣化は認められなかった。これらの実施例１〜３０に比べて、ホウ素を含まない黒鉛層間化合物を使用した比較例の場合は、顕著な容量劣化が認められた。また、残存ホウ素量が０．０５〜１１重量％の範囲の外、即ち、０．０５重量％未満あるいは１１重量％を超えている実施例では、若干ではあるが容量劣化が認められた。
【００５７】
【発明の効果】
以上の実施例にて詳細に説明したように、正極に用いる黒鉛層間化合物のホスト材料として、ホウ素またはホウ素化合物を含有する炭素材料を熱処理して電子吸引性物質をインターカレートして得られた物質を用いる本発明にあっては、黒鉛層間化合物を作成する際に結晶構造が破壊されたり配向性の劣化をもたらすことがなく、その黒鉛層間化合物を用いることにより充放電容量が大きくサイクル劣化しにくい非水電解質電池を構成することが出来る。
【図面の簡単な説明】
【図１】コイン型セルに作製した非水電解質電池を示す図である。
【図２】実施例１の放電曲線を示すグラフである。
【図３】実施例１のサイクル特性を示グラフである。
【符号の説明】
１　負極活物質
２　セパレータ
３　正極活物質
４　集電体[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a nonaqueous electrolyte battery including a negative electrode made of lithium metal or a material capable of inserting and extracting lithium, an electrolyte containing a lithium salt, and a positive electrode made of a graphite intercalation compound.
[0002]
[Prior art]
In a secondary battery, it is known that a positive electrode or a negative electrode is composed of a compound having a layered structure or a graphite interlayer compound.
For example, in Patent Document 1, FeCl 2 is used as a positive electrode active material.₂ ⁻Using graphite intercalation compound, lithium for negative electrode⁻A secondary battery using a graphite intercalation compound and using a solid electrolyte is described. During discharge, an initial open circuit voltage of 3.5 V, an average load current of 14 μA and an average open circuit voltage of 3.3 V are obtained with a load resistance of 100 kΩ.
[0003]
At this time, the guest species of the graphite intercalation compound used for the positive electrode is an electron-withdrawing substance that forms a charge transfer complex with π orbitals with graphite. The charge transfer complex can be represented by the general formula Cn (AXy), where A is a coordinating metal atom or a non-metal atom in a high valence state, and X is an electron-withdrawing non-metal atom. When used as a cathode, the discharge reaction is represented by the following equation (2).
xe⁻+ XM⁺+ (CnAXy) → (MxCnAXy) (Equation 2)
Examples of such an electron-withdrawing substance that forms a π-orbital charge transfer complex with graphite include AsF.₅, BCl₃, BF₃, Br₂, BrF₃, CdCl₂, Cl₂, CoCl₂, CrO₃, CrCl₃, CuCl₂, CuBr₂, FeCl₂, FeCl₃, FeBr₃, NiCl₂, IF₅, ICl₃, MoF₆, MoCl₅, PF₅, PtCl₄, ReCl₄, RhCl₃, RuCl₃, SbF₅, SbF₃Cl₂, SbCl₅, TiF₄, WF₆, WCl₆And many others. As a host material for intercalating such a guest species, a material having a developed graphite structure such as natural or artificial graphite or fiber is used.
[0004]
[Patent Document 1]
JP-A-58-102464
[0005]
[Problems to be solved by the invention]
However, in this type of conventional battery, since a graphite intercalation compound is produced using a graphite material as a host material, a problem that the charge capacity is reduced by intercalating the guest species. was there. This is mainly due to destruction of the crystal structure of the positive electrode material and deterioration of the orientation. In other words, with the charge-discharge cycle, relatively large anions of molecular size are repeatedly absorbed and released into the graphite material, which causes the graphite crystals to collapse, resulting in cracks in the particles, and some of the particles cannot be charged or discharged. This is because it changes to a different form. That is, when a non-aqueous electrolyte battery is configured using a graphite intercalation compound that causes such crystal structure destruction and deterioration of orientation, not only does the charge / discharge capacity decrease, but also the cycle deterioration accelerates. Would.
[0006]
In the present specification, “graphitization” refers to a solid phase transition due to thermal energy from amorphous carbon to graphite, and specifically, a temperature of 2500 ° C. or higher regardless of the degree of crystallinity after graphitization. Means heat treatment. Further, the “carbon material” refers to a solid substance containing carbon atoms as a main component, and does not specify the regularity of the arrangement. Similarly, "graphite material" means a solid material having a crystal structure in which carbon atoms are contained as a main component and the carbon atoms are arranged with three-dimensional regularity, and the graphitized material is used. Is not relevant. The graphite material is included in a part of the carbon material.
[0007]
The present invention has been made to solve the above problems, and an object of the present invention is to provide a non-aqueous electrolyte battery having a large charge / discharge capacity and hardly causing cycle deterioration.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, the present invention uses a graphite material obtained by heat-treating a carbon material containing boron or a boron compound as a host material when producing a graphite intercalation compound.
[0009]
Graphite materials obtained by heat-treating carbon materials containing boron or boron compounds have a high degree of crystallinity, but are partially defect-inserted, making it difficult for guest species to intercalate. Therefore, destruction of the crystal structure and deterioration of the orientation can be suppressed.
[0010]
The magnitude of d (002) representing the crystallinity of the graphite material into which boron has been introduced is related to the charge / discharge capacity of the battery, and the peak intensity ratio of the Raman spectrum represents the amount of introduced defects. For batteries, it relates to cycle characteristics.
[0011]
That is, the nonaqueous electrolyte battery according to claim 1 of the present invention includes a negative electrode made of a material capable of inserting and extracting lithium metal or lithium, an electrolyte containing a lithium salt, and a positive electrode made of a graphite intercalation compound. In a non-aqueous electrolyte battery, as a host material of a graphite intercalation compound used for the positive electrode, a material obtained by heat-treating a carbon material containing boron or a boron compound and intercalating an electron-withdrawing material is used, It is characterized by the following.
[0012]
Ordinary synthetic graphite materials are prepared by subjecting organic materials such as petroleum pitch, coal tar pitch, condensed polycyclic hydrocarbon compounds and organic polymer compounds to an inert gas atmosphere such as nitrogen or argon gas or helium gas at 300 to 700 ° C. After carbonization, it is produced by heat treatment (graphitization) at 2500 ° C. or higher, preferably 3000 ° C. or higher. In addition, naturally occurring graphite materials often have a crystal structure that is comparable to or better than the synthetic graphite described above. Since the highly graphitized synthetic graphite material or natural graphite material as described above has a large crystallite size and a small lattice distortion between adjacent hexagonal mesh planes, the amount of lattice defects existing inside the crystallite is small. It is.
[0013]
Normally, when anions and molecules are electrochemically occluded in such a graphite material, the graphite crystals collapse, and the reversible storage / release capacity decreases as the charge / discharge cycle progresses. This is because the hexagonal mesh planes constituting the graphite crystal are stacked only by the weak van der Waals' force, so if anions with a molecular size larger than the distance between the hexagonal mesh planes intercalate, they are easily cleaved. It is because.
[0014]
On the other hand, although it is only the initial cycle, it is generally known that the capacity capable of storing and releasing anions is higher as the crystallinity is higher, and that the stability of the discharge curve is excellent.
[0015]
The present inventors, when the above intercalation reaction is repeatedly performed, by highly developing the degree of crystallinity of the graphite material, and by increasing the stability of the crystal structure by introducing a defect in a part thereof, It has been found that the cycle characteristics can be improved while maintaining the capacity. That is, a substance obtained by heat-treating boron or a carbon material containing a boron compound and intercalating an electron-withdrawing substance is used as a host material of the graphite intercalation compound used for the positive electrode.
[0016]
As a typical method for producing a graphite material containing a boron compound, a boron or boron compound powder is added and mixed to a graphitizable carbon material or its starting material, or a carbon precursor, and heat treatment (carbonization or graphitization) is performed. ).
[0017]
As a starting material of the graphitizable carbon material, various pitches such as coal tar pitch or petroleum pitch are representative. These pitches are obtained through a purification or reforming process such as distillation, extraction, thermal decomposition, dry distillation, etc. of a raw material such as coal tar or crude oil.
[0018]
Organic polymer compounds such as condensed polycyclic polynuclear aromatics (COPNA resin) and polyvinyl chloride resins using aromatic compounds such as naphthalene, phenanthrene, anthracene, pyrene, perylene and acenaphthylene as raw materials can also be used. Since these starting materials pass through a liquid phase state at about 350 ° C. during the heat treatment step, the production of polycondensed polycyclic hydrocarbon compounds and the three-dimensional lamination thereof easily progress, Regions are formed, producing a carbon precursor. The precursor is in a state where it can easily give a graphite material by a subsequent heat treatment. Using the above organic material as a starting material, carbonization is performed at 300 to 700 ° C. in an inert gas atmosphere such as nitrogen gas, argon gas or helium gas, and then calcined at a maximum temperature of about 900 to 1500 ° C. Generates graphitizable carbon.
[0019]
Examples of the obtained carbon material include easily graphitizable carbon materials such as mesophase pitch-based carbon fiber, vapor grown carbon fiber, pyrolytic carbon, mesocarbon microbeads, pitch coke or petroleum coke, and needle coke.
[0020]
There is no particular problem when boron or boron compound is added to the starting material or to the carbon precursor or the generated carbon material. In any case, in order to enhance the dispersibility at the time of mixing, it is desirable that the particles are previously ground to an average particle diameter of 200 μm or less, preferably about 50 μm or less. As an example of boron or a boron compound, any compound that contains a boron atom in addition to boron alone can be applied. For example, boride ceramics such as cobalt boride, hafnium boride, and zirconium boride;₄C, B₆Boron carbide such as C, B₂O₃, B₄O₅Such as boron oxide, orthoboric acid or metaboric acid, and salts thereof.
[0021]
By carbonizing or graphitizing the carbon material mixed with boron or boron compound obtained as described above at a heat treatment temperature of 1400 ° C. or more, preferably 2000 ° C. or more in the above-mentioned inert gas atmosphere, boron is obtained. Alternatively, a graphite material containing a boron compound is obtained.
[0022]
In addition to the above method, the above-mentioned boron or boron compound may be added to the graphite material, and then heat treatment may be performed in an inert gas atmosphere at a temperature of 2400 ° C. or higher, preferably about 3000 ° C. Examples of graphite materials include polycrystalline graphite materials such as mesophase pitch-based carbon fibers, vapor-grown carbon fibers, pyrolytic carbon, mesocarbon microbeads, pitch coke or petroleum coke graphitized at a heat treatment temperature of 2400 ° C. or more. And various synthetic graphite materials and various natural graphite materials.
[0023]
Natural graphite is produced in China, Madagascar, Brazil, Sri Lanka, etc. In the state of the ore, impurities other than graphite are contained in a large amount. Therefore, even when mixed with boron or a boron compound and subjected to a heat treatment at 2400 ° C. or more, diffusion of boron into the graphite hardly proceeds, and the ore is homogeneous. It is difficult to obtain a graphite material containing boron. Therefore, it is necessary to remove these impurities in advance. For example, these impurities can be removed by dissolving these impurities in an acidic aqueous solution such as hydrogen fluoride, hydrogen chloride, sulfuric acid, and nitric acid or a mixed acid thereof, an alkaline aqueous solution such as caustic soda, or an organic solvent. Further, heat treatment at 500 ° C. or more in a flow of halogen gas such as fluorine or chlorine gas can also remove impurities and purify the graphite material.
[0024]
Here, as shown in the non-aqueous electrolyte battery according to claim 2, the electron-withdrawing substance intercalating into the graphite intercalation compound is CoCl 2.₂, NiCl₂, CuCl₂, CrCl₃, FeCl₃, MnCl₂And at least one type selected from the group consisting of:
[0025]
The non-aqueous electrolyte battery according to claim 3 is characterized in that the host material of the graphite intercalation compound satisfies both requirements (a) and (b) below.
(A) The carbon material having a graphite crystal structure has an average spacing d (002) of (002) planes of 3.365 Å or less.
(B) Raman spectrum analysis using an argon ion laser beam having a wavelength of 5145 Å^-1Near the peak P_A, 1360cm^-1Near the peak P_BAnd P_AThe peak intensity of I_A, P_BThe peak intensity of I_BIn this case, the R value defined by the following equation (1) is 0.35 or more.
R value = I_B/ I_A(Equation 1)
[0026]
In general, information obtained from a vibration spectrum of Raman scattering includes a molecular structure, an arrangement of atoms, and the like. For example, natural graphite, which is considered to be almost perfect single crystal, is 1580 cm.^-1One Raman band is shown in the vicinity, but 1580 cm for artificial graphite made of polycrystal, activated carbon made of unorganized carbon or glassy carbon^-1In addition to the one corresponding to the nearby band, 1360cm^-1One Raman band also appears in the vicinity. 1580cm^-11360cm for the intensity of the band generated near^-1The relative intensity ratio of the bands appearing in the vicinity generally increases with an increase in unwoven carbon in the sample, and decreases with an increase in graphite crystallites.
Therefore, the R value (the relative intensity ratio) defined in the invention of claim 3 of the present application is often used as a parameter indicating the degree of graphitization.
[0027]
For example, the R value has a close relationship with the crystallite size La in the a-axis direction obtained from X-ray diffraction, and 1 / La (the reciprocal of La) obtained from various carbon materials is used as the R value. When plotted on the other hand, a linear relationship was recognized (F. Tuinstra @ and @ JL Koenig, J. Chem. Phys.,53, 1126 (1970)), and there is a report that an empirical formula of La (Angstrom) ー ム 44 / R can be obtained recursively.
[0028]
On the other hand, the plane distance d (002) of the (002) plane of the carbon material described in the present application can be measured by a powder X-ray diffraction method (117th Committee of the Japan Society for the Promotion of Science, Carbon,25, 36 (1963)). The above-mentioned plane spacing d (002) generally decreases as the heat treatment temperature increases, and eventually approaches as close as 3.354 angstroms, which is the same plane spacing of the ideal graphite crystal, but does not fall below this value. . For example, graphite material has a crystal structure in which hexagonal mesh planes composed of carbon atoms are stacked with three-dimensional regularity, but ordered graphite-like stacked parts and disorderly stacked parts are mixed. It is also possible to think that it is in the state of having done. Assuming that the ratio of the disordered stacked portion to the whole is p, d (002) = 3.440−0.086 × (1−p²) Is reported (PE Franklin, Acta. Cryst., 4, 235 (1951)), and the interplanar spacing d (002) is often used as a parameter indicating the degree of graphitization. Was.
[0029]
As described above, both the R value and the interplanar spacing d (002) defining the host material of the graphite intercalation compound used in the present invention are parameters indicating the degree of graphitization. For example, a synthetic graphite material graphitized so that the interplanar spacing d (002) is 3.365 angstroms or less, or a natural graphite material with a highly developed crystal having d (002) of 3.365 angstroms or less. Has a large crystallite size and a small lattice distortion between adjacent hexagonal mesh planes, so that the amount of lattice defects existing inside the crystallite is small. Therefore, when the Raman band of the graphite material as described above is measured, the R value is usually 0.25 or less.
[0030]
On the other hand, the host material of the graphite intercalation compound defined by the invention of claim 3 of the present application has an interplanar spacing d (002) of 3.365 angstroms or less, an R value of 0.35 or more, and It is completely different from the properties of synthetic or natural graphite materials. This is because, as described above, the degree of crystallinity of the graphite material is highly developed, and a defect is introduced into a part thereof. The amount of the introduced defect can be grasped by the R value calculated from the Raman spectrum.
[0031]
1360cm observed in various carbon materials^-1Is closely related to imperfections in the crystal structure of graphite, that is, defects in the crystal lattice. This band is caused by a vibration mode which is not present in the graphite crystal having a hexagonal lattice, and is Raman activated by a structural defect existing in the crystal. This is because the symmetry of the hexagonal lattice is reduced or lost due to structural defects. Therefore, it can be said that the R value reflects the amount of defects contained in the carbon structure.
[0032]
Here, when the R value is less than 0.35, the amount of defects introduced into the graphite material is too small, so that repeated charging and discharging will deteriorate the discharge capacity as described above, which is not preferable. When d (002) is larger than 3.365 angstroms as described above, the charge / discharge capacity becomes small, which is not preferable.
[0033]
Therefore, according to the invention of claim 3 of the present application, among graphite materials obtained by heat-treating a carbon material containing boron or a boron compound, the plane spacing d (002) is not more than 3.365 angstroms. , A graphite material that simultaneously satisfies that the R value is 0.35 or more was specified, and a chargeable / dischargeable nonaqueous electrolyte battery in which the graphite material was used as a host material of a graphite intercalation compound of a positive electrode was obtained.
[0034]
It should be noted that a phenomenon that can be positively inferred that a defect has been introduced into graphite crystals by heat-treating a carbon material containing boron or a boron compound is specified in the invention according to claim 3 of the present application. In addition to the matters mentioned above, it is recognized.
[0035]
For example, block graphite obtained by heat-treating a carbon material containing boron or a boron compound so that the interplanar spacing d (002) is 3.365 Å or less is pulverized to an average particle size of 30 μm or less. Even in this case, the graphite crystal measured by the X-ray wide-angle diffraction method is often attributed only to the hexagonal crystal, and there is often no substantial diffraction line attributed to the rhombohedral crystal.
[0036]
The graphite block containing a boron compound is obtained by adding a binder pitch or the like to a graphitizable carbon material such as petroleum coke or pitch coke, and kneading and pulverizing the mixture in a temperature atmosphere of 100 to 300 ° C. The mixture is further kneaded, and the mixture is shaped into a block and heat-treated at 2300 ° C. or higher, preferably 3000 ° C. or higher in an inert gas atmosphere.
[0037]
The host material of the graphite intercalation compound obtained as described above can sufficiently obtain the effects of the present invention.
[0038]
Graphite has a form belonging to a rhombohedral system (ABCABC ... lamination period) in addition to a crystal belonging to a hexagonal system (ABAB ... lamination period). The stack of hexagonal graphite hexagonal mesh planes is such that the second layer moves parallel to the first layer by (2/3, 1/3), and the third layer just overlaps the first layer. That is, it has an ABAB · ‥ structure that repeats every two layers. On the other hand, in rhombohedral graphite, the second layer is shifted by (2/3, 1/3) with respect to the first layer, and the third layer is further shifted by (1/3, 2/3) with respect to the first layer. The layers overlap the first layer. That is, it has an ABCABC ‥ structure that is repeated every three layers (Introduction to Carbon Materials, edited by the Society of Carbon Materials).
[0039]
Rhombohedral graphite is a lattice strain in the plane direction (a-axis) and vertical stacking direction (c-axis) of crystallites, such as artificial graphite in which crystals are highly developed or natural graphite having a very high degree of graphitization. Is a form of crystals that are introduced into a part of a very small hexagonal graphite material by grinding the material.
[0040]
In the initial stage of pulverization, a shear deformation occurs along the layer surface, reflecting a very weak bond between the graphite layer surfaces, and a rhombohedral structure appears. The carbon-carbon bond in the layer plane is very strong, and instead of destroying many of these bonds and introducing a large amount of defects, as a part of storing mechanical energy given by grinding, a hexagonal network with high flatness A rhombohedral structure is introduced by a partial displacement of the plane.
[0041]
The existence ratio of such a rhombohedral structure and a hexagonal structure can be verified by examining the intensity ratio of diffraction peaks obtained by the X-ray wide-angle diffraction method. When measuring with a Geiger flex type powder X-ray diffractometer using copper for the bulb, the diffraction angle (2θ / θ) may be scanned around 40 to 50 ° (hereinafter simply referred to as the diffraction angle). In this case, it is assumed that the measurement is performed using a Geiger-flex type powder X-ray wide-angle diffractometer using copper as a tube).
[0042]
In the case of a sample obtained by pulverizing graphite having a high degree of crystallinity, usually four diffraction lines can be observed in this spectral band. Each diffraction line has a hexagonal (100) plane and a (101) plane around 42.3 ° and 44.4 °, and a rhombohedral (100) plane near 43.3 ° and 46.0 °. The (101) plane and the (012) plane appear. The surface index of the rhombohedral system is expressed by indexing when a unit cell similar to that of the hexagonal system is taken. When the crystallinity of the graphite block before pulverization is low, even if the degree of pulverization is increased, a peak belonging to the rhombohedral system cannot be confirmed. This is because the hexagonal mesh plane has many defects and its planarity is low because the laminated structure is not sufficiently developed. For this reason, even if the pulverizing energy is applied, the entire plane is hard to shift, and it is difficult to introduce rhombohedral crystals.
[0043]
A synthetic graphite material graphitized so that d (002) is 3.365 angstroms or less, or a natural graphite material in which highly crystallized such that d (002) is 3.365 angstroms or less, is an average particle. When crushed to a diameter of about 30 μm or less, a rhombohedral structure is usually introduced. When anions are electrochemically occluded in such a graphite material, the graphite crystals collapse as described above, and the reversible occluding / releasing capacity decreases as the charge / discharge cycle progresses.
[0044]
However, a graphite material obtained by heat-treating (carbonizing or graphitizing) a carbon material containing boron or a boron compound is in a state in which boron has been replaced by carbon atoms constituting graphite crystals, or between layers of graphite layers laminated. It remains in the graphitized carbon material in the state of infiltration into the graphite, and it becomes possible to introduce defects into the graphite crystals. Therefore, in the graphite material containing a boron compound, even if d (002) is equal to or less than 3.365 angstroms, the flatness of the hexagonal mesh plane constituting the graphite crystal is reduced due to this defect, and the pulverization energy is reduced. Even if given, no deviation of the plane occurs, and as a result, it is difficult to introduce a rhombohedral structure. When such a graphite material is used as the positive electrode, deterioration of the capacity is extremely small even when charge / discharge cycles are repeated.
[0045]
The nonaqueous electrolyte battery according to claim 4 is characterized in that the ratio of boron present in the host material of the graphite intercalation compound is 0.05 to 11% by weight.
[0046]
The host material of the graphite intercalation compound specified in the invention of claims 1 to 3 of the present application is characterized in that boron or a carbon material containing a boron compound is obtained by heat treatment. In the host material of the graphite intercalation compound thus obtained, boron or the boron compound remains inside the crystal structure. The invention of claim 4 further clarifies the host material of the graphite intercalation compound expressed in the present invention by specifically defining the remaining amount of boron or boron compound as boron.
[0047]
The amount of boron or boron compound added to the carbon material or the graphite material is adjusted so that the boron content remaining in the graphite material after the heat treatment is in the range of 0.05 to 11% by weight as boron. The amount of boron or boron compound to be added must be appropriately set according to the starting material, carbon precursor, each stage before carbonization or graphitization, or the type (characteristics) of the carbon material or graphite material. If the residual amount after the heat treatment is less than 0.05% by weight, the amount of defects introduced by boron is too small, and the capacity is reduced in each cycle when charge and discharge are repeated, so that the effect of the present invention is sufficiently obtained. Not preferred. If it exceeds 11% by weight, a large amount of boron carbide (B) is contained in the graphite material.₄C) is produced and mixed, and these are not preferred because they do not participate in the charge / discharge reaction.
Therefore, in the present invention, the residual amount of boron is preferably 0.05% by weight to 11% by weight.
[0048]
BEST MODE FOR CARRYING OUT THE INVENTION
<1> Preparation of graphite material (host material of graphite intercalation compound)
Isobiolanthrone and 9,10-dihydroanthracene are mixed at a molar ratio of 1: 1 and paratoluenesulfonic acid is added to the mixture at a weight ratio of 15: 1 to give a sufficient amount. Was stirred. Thereafter, the mixture was heated to 150 ° C. while continuing stirring, and after maintaining this state for 5 hours, the mixture was neutralized by adding an ammonium hydrogen carbonate solution, and allowed to cool.
[0049]
The condensable polycyclic polynuclear aromatic thus obtained was charged into a graphite crucible and set in an electric furnace. In a nitrogen atmosphere, the temperature was raised to 350 ° C. at a rate of 70 ° C./hour and maintained for 15 hours, and then increased to 700 ° C. at a rate of 70 ° C./hour, and maintained for 1 hour to reduce the nitrogen flow. While maintaining the temperature, the solution was allowed to cool to room temperature.
[0050]
The obtained carbon precursor was once roughly pulverized by a stamp mill, then finely pulverized by a vibration type disk mill, and a powder passed through a # 391 mesh (mesh size: 38 μm) sieve was collected. This powder and a boron carbide powder (B) passed through a # 330 mesh (45 μm mesh) sieve₄C) were each mixed so as to be 0 to 27% by weight in terms of a boron conversion amount, and charged into a graphite crucible.
[0051]
The crucible was placed in an electric furnace, heated in a nitrogen atmosphere at a rate of 10 ° C./min, heat-treated at a maximum temperature of 2900 ° C. for 1 hour, and graphitized. The graphite material obtained as described above was analyzed using an X-ray diffractometer or the like, and the d (002) spacing, the peak intensity ratio of the Raman spectrum, and the residual boron concentration were measured. The results are shown in Table 1 below together with the results of the cycle characteristic test.
[0052]
<2> Preparation of graphite intercalation compound
For each of the graphite materials produced as in the above 1, a graphite intercalation compound was prepared by the following method.
Graphite material and NiCl₂Were mixed at a ratio of 1: 1 and dehydrated by maintaining at 300 ° C. under vacuum for 10 hours. This was placed in a glass tube and evacuated, and then chlorine gas was introduced at 1.5 atm and sealed. The glass tube was heated to 700 ° C. and held for 3 days. The resulting product is washed with acetonitrile to remove excess NiCl₂And dried with NiCl₂Was used as a guest species to obtain a graphite intercalation compound.
Similarly, the guest species is changed to CoCl.₂, CuCl₂, CrCl₃, FeCl₃, MnCl₂Was also prepared.
[0053]
<3> Battery fabrication and charge / discharge test
The graphite intercalation compound obtained as in the above 2 and PTFE were mixed at a ratio of 98: 2 and molded to prepare a positive electrode pellet. Lithium metal for the negative electrode and 1M LiClO for the electrolyte₄The coin-type cell shown in FIG. 1 was produced using / PC. In the figure, 1 is a negative electrode active material, 2 is a separator, 3 is a positive electrode active material, and 4 is a current collector. 0.1 mA / cm²A charge / discharge cycle was performed.
[0054]
<4> Examination of results
Table 1 summarizes the results of Examples 1 to 30 and Comparative Examples 1 to 6. FIG. 2 shows a discharge curve of Example 2, and FIG. 3 shows cycle characteristics.
[0055]
[Table 1]

[0056]
In Examples 1 to 30, in the range of the residual boron amount of 0.05% by weight to 10.98% by weight, capacity deterioration was not recognized although it was up to 10 cycles. Compared to Examples 1 to 30, in the case of the comparative example using the graphite intercalation compound containing no boron, remarkable capacity deterioration was observed. Further, in the examples in which the amount of residual boron is out of the range of 0.05 to 11% by weight, that is, less than 0.05% by weight or more than 11% by weight, although the capacity is slightly reduced, it is recognized.
[0057]
【The invention's effect】
As described in detail in the above examples, as a host material of a graphite intercalation compound used for a positive electrode, a carbon material containing boron or a boron compound was heat-treated, and was obtained by intercalating an electron-withdrawing substance. In the present invention using a substance, when the graphite intercalation compound is produced, the crystal structure is not destroyed or the orientation is not deteriorated. A difficult nonaqueous electrolyte battery can be configured.
[Brief description of the drawings]
FIG. 1 is a diagram showing a non-aqueous electrolyte battery manufactured in a coin cell.
FIG. 2 is a graph showing a discharge curve of Example 1.
FIG. 3 is a graph showing cycle characteristics of Example 1.
[Explanation of symbols]
1 negative electrode active material
2 separator
3 positive electrode active material
4 Current collector

Claims (4)

In a non-aqueous electrolyte battery including a negative electrode made of a material capable of inserting and extracting lithium metal or lithium, an electrolyte containing a lithium salt, and a positive electrode made of a graphite intercalation compound,
As a host material of the graphite intercalation compound used for the positive electrode, a substance obtained by heat-treating a carbon material containing boron or a boron compound and intercalating an electron-withdrawing substance is used,
Non-aqueous electrolyte battery characterized by the above-mentioned. The electron-withdrawing substance intercalating with the graphite intercalation compound includes at least one selected from the group consisting of CoCl ₂ , NiCl ₂ , CuCl ₂ , CrCl ₃ , FeCl ₃ , and MnCl _2. Non-aqueous electrolyte battery. The host material of the graphite intercalation compound satisfies both the following requirements (a) and (b):
The non-aqueous electrolyte battery according to claim 1, wherein:
(A) The average spacing d (002) of the (002) plane of the carbon material having a graphite crystal structure is 3.365 angstroms or less.
(B) in the Raman spectrum analysis using an argon ion laser beam having a wavelength of 5145 Å, has a peak _{P B} in the vicinity of the peak _P A, 1360 cm ^-1 in the vicinity of 1580 cm ^-1, the peak intensity of _{P A I A} , when the peak intensity of _{P B} was _{I B,} R value defined by the following equation (1) is 0.35 or more.
R value _{= I} B / I _A (Formula 1) A ratio of boron present in the host material of the graphite intercalation compound is 0.05 to 11% by weight;
The non-aqueous electrolyte battery according to claim 1, wherein:

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