NONAQUEOUS ELECTROLYTE SECONDARY CELL CATHODE MATERIAL AND NONAQUEOUS ELECTROLYTE SECONDARY CELL EMPLOYING THE CATHODE MATERIAL

Abstract: Carbon fiber having cross sectional shape which satisfies area replenishment rate of 0.8 or more is used as anode material for non-aqueous electrolyte secondary battery. Alternatively, since value of fractal dimension of cross section high order structure of the random radial type carbon fiber can be utilized as material parameter for evaluating the cross sectional structure, carbon fiber in which the value of the fractal dimension is caused to fall within the range from 1.1 to 1.8 and the crystallinity has been controlled such that it falls within reasonable range is used as anode material for non-aqueous electrolyte secondary battery. Further, carbon fiber having cross section high order structure such that the central portion is radial type structure and the surface layer portion is random radial type structure is used as anode material for non-aqueous electrolyte secondary battery. Furthermore, it is also effective to use carbon fiber having notch structure at the cross section. In addition, graphitized carbon fiber having cross sectional portions different in the crystal structure at predetermined periods in the fiber length direction is made up. By crushing the graphitized carbon fiber thus obtained, carbon fiber crushed powder having less unevenness and predetermined aspect ratio can be easily made up.

Description: Technical Field This invention relates to anode material for a non-aqueous electrolyte secondary battery, which consists of carbon material particularly carbon in fiber form, and further relates to a non-aqueous electrolyte secondary battery using such anode material. Background Art Recent electronic technologies have conspicuously progressed so that, e.g., miniaturization and/or light weight of electronic equipments can be realized in succession. Followed by this, also for batteries as portable power supply (supply) (source), there has been still more increased demand of miniaturization, light weight and high energy density. Hitherto, as the secondary battery of general use, aqueous solution system batteries such as lead battery, or nickel/cadmium battery, etc. are the main current. These batteries can be satisfied to some extent in the cycle characteristic, but it cannot be said that they have satisfactory characteristic in points of battery weight and the energy density. On the other hand, studies/developments of non-aqueous electrolyte secondary batteries using lithium or lithium alloy as anode have been extensively carried out in recent years. Such batteries have excellent characteristics of high energy density, small self-discharge and light weight, but have the drawback that lithium is crystal-grown in dendrite form at the time of charging followed by development (progress) of the charge/discharge cycle and reaches the cathode so that there results the internal short. This is great hindrance to realization of practical use. As a battery which solves such problem, non-aqueous electrolyte secondary batteries using carbon material as the anode, which are so called lithium ion secondary battery, have been proposed and remarked. The lithium ion secondary battery utilizes doping/undoping of lithium into portion between carbon layers as the anode reaction. Even if charge/discharge cycle is developed, precipitation of crystal in dendrite form cannot be observed at the time of charging. Thus, such batteries exhibit satisfactory charge/discharge cycle characteristic. In this case, there are several carbon materials as carbon material which can be used as the anode of the lithium ion secondary battery. Among them, material which has been first put into practical use is coke and glass-shaped carbon. These materials are material having low crystallinity obtained after undergone heat-treatment at relatively low temperature, and has been commercialized as practical battery by using electrolytic solution mainly consisting of propylene carbon (PC). Further, also in graphite or the like which could not be used as anode when PC is used as main solvent, electrolytic solution mainly consisting of ethylene carbon (EC) is used so that arrival to usable level has been realized. As the graphite or the like, graphite in a scale form can be relatively easily obtained. Hitherto, such graphite or the like has been widely used as conductive material for alkali battery. This graphite or the like advantageously high crystallinity and high true density as compared to non-easily graphitized carbon material. Accordingly, if the anode is constituted by the graphite or the like, high electrode filling (packing ability can be obtained and the energy density of the battery is caused to be high. From this fact, it can be said that the graphite or the like is greatly expected material as the anode material. Meanwhile, most of the carbon materials exhibit form such as block form. In the case where such carbon materials are actually used as the battery, they are crushed or pulverized and are used in powder form. For this reason, even if the structure of carbon material is controlled so that the carbon material takes macro form or micro form by, e.g., physical or chemical treatment (processing), there are actual circumstances where the structure is disturbed by crushing, so its effect cannot be sufficiently obtained. On the contrary, in the case of carbon in fiber form (carbon fiber) obtained by carbonizing organic material in fiber form, it is easy to relatively control the carbon structure and there is no necessity of crushing. For this reason, such carbon fiber is advantageous when application to the anode is assumed. The structure of the carbon fiber greatly reflects the structure of organic fiber which is precursor. As organic fiber, there are organic fibers in which polymer such as polyacrylonitrile, etc. is caused to be material, and organic fibers in which pitch or the like such as petroleum pitch, etc. and mesophase pitch caused to be oriented are caused to be material, etc. These organic fibers all take fiber shape after undergone fiber-forming. By carbonizing these organic fibers, carbon fibers can be obtained. However, since they are fused when heat-treated at the time of carbonization so that there results broken fiber structure, they are carbonized after infusible processing is ordinarily implemented to the fiber surface by oxidation, etc. The carbon fiber obtained in this way has cross sectional structure originating in the organic material fiber structure and exhibits high order structure of, such as, for example, the type oriented in concentrical form which is so called onion-skin type, the radially oriented radial type and isotropically random type, etc. Graphite fibers obtained by graphitizing these carbon fibers have high true density and also have high crystallinity. However, also in the above-described carbon fibers, it cannot be said that there is no problem. Since, e.g., most of carbon fibers have circular cross section nearly equal to complete round, in the case where they are filled (packed) into the electrode, the so-called dead space takes place. Under the circumstances where there is increased requirement of high energy density with development of electronic equipments, the above-mentioned dead space constitutes great problem. Moreover, in lithium ion secondary battery, since the intercalation reaction is the main anode reaction, it is known that according as crystallinity of anode carbon material becomes higher, the capacity becomes large. In the carbon fiber, with respect to the fiber cross sectional structure of the radial type, crystallinity is easy to be improved, whereas crack is easy to take place in parallel to fiber axis by expansion/contraction at the time of charge/discharge and the fiber structure is easy to be broken. Accordingly, in the carbon fiber of the radial type structure, large capacity can be obtained, but reversibility of the charge/discharge cycle is not sufficient. For this reason, as the anode carbon material, carbon fibers of the random radial type in which the radial structure and the random structure are mixed are the main current. However, since the fiber diameter is small and the cross section takes circular shape, rearrangement of the carbon layer surface is difficult to take place, thus making it possible to have high crystallinity, e.g., as in the case of graphite in the scale form. Further, in the case of the carbon fiber, since the orientation state of the cross section becomes uneven in the fiber length direction, there is also the inconvenience that crack is apt to take place in the fiber axis direction at the time of crushing and cutting. Since the carbon fiber is not in block form as in the case of the ordinary graphite material, crushing is not required under strong condition. However, it is necessary to finely crush and cut carbon fiber so that a fixed (predetermined) aspect ratio is provided. This crushing/cutting of carbon fiber involves various difficulties as compared to crushing of carbon material in block form. Thus, as previously described, not only crack is easy to take place, but also it is difficult to allow material parameter such as aspect ratio, etc. to be fixed. From these reason, there is nothing but to say that the battery made up by using conventional graphitized carbon fiber has insufficient capacity in the existing states and has low industrial reliability. In the post-published document JP-A-09293504 is described a non-aqueous electrolyte secondary battery provided with a negative electrode made of carbon material, a positive electrode which can be doped with and dedoped from lithium, and a non-aqueous electrolyte, which is formed by dissolving an electrolyte in a non-aqueous solvent. The negative electrode is made of a carbon fiber material. The carbon fibers have formed in their cross-section a notch. The notch is having a notch angle of 2° or more and 150° or less. Disclosure of the Invention An object of this invention is to provide more practical carbon in fiber form (carbon fiber) which is high in the electrode filling (packing) ability, is excellent in crystallinity, is easy to be cut, and has less variations (unevenness) of material parameter, and to thereby provide a non-aqueous electrolyte secondary battery of high energy density and high reliability. The inventors of this application have obtained various findings as the result of the fact that they have energetically and repeatedly studied. This invention has been completed on the basis of these findings, and contemplates to attain the above-described object by implementing various improvements to carbon fiber. According to the invention is provided an anode material for a non-aqueous electrolyte secondary battery, the anode material consisting of carbon fibers capable of carrying out doping/undoping of lithium, wherein in the cross section of the carbon fibers a portion of the carbon fiber is missing, so that a notch is formed and a notch structure is provided. In a preferred embodiment the notch is extending from the geometrical center of gravity of the cross section to the outer circumference of the cross section and a notch angle is formed between the sides of the notch. The cross section of the carbon fiber preferably has a circular shape and the notch is extending from the center of the cross section to the circumference of the cross section and a notch angle is formed at the center between the sides of the notch. The notch angle is caused to be 2° to 150°. Thus, even in the case where carbon fiber of the radial type structure is employed, carbon fiber having high capacity and strength tolerable to expansion/discharge can be realized. Further is provided a non-aqueous electrolyte secondary battery, comprising: an anode consisting of carbon material capable of carrying out doping/undoping of lithium, the carbon material including an anode material as described above; a cathode, and a non-aqueous electrolytic solution in which an electrolyte is dissolved in a non-aqueous solvent. Brief Description of the Drawings Fig. 1 is a view showing a cross sectional shape of a carbon fiber having a notch structure. FIG. 2 is a cross sectional view showing an example of shape of discharge hole for producing carbon fiber having notch structure. FIG. 3 is a view showing an example of cross sectional shape of graphitized carbon fiber. FIG. 4 is a cross sectional view showing an example of structure of non-aqueous electrolyte secondary battery. FIG. 5 is a view showing another example of cross sectional shape of the graphitized carbon fiber. FIG. 6 is a view showing a further example of cross sectional shape of the graphitized carbon fiber. FIG. 7 is a view showing a more further example of cross sectional shape of the graphitized carbon fiber. FIG. 8 is a view showing a still more further example of cross sectional shape of the graphitized carbon fiber. FIG. 9 is a view showing a further different example of cross sectional shape of the graphitized carbon fiber. FIG. 10 is a view showing a still further different example of cross sectional shape of graphitized carbon fiber. FIG. 11 is a characteristic view showing the relationship between area replenishment rate (degree) of fiber cross section and capacity. FIG. 12 is a characteristic view showing the relationship between circularity of fiber cross section and capacity maintenance ratio. FIG. 13 is a view showing an example of measurement of fractal dimension. FIG. 14 is a characteristic diagram showing the relationship between spacing of (002) plane of carbon fiber and capacity. FIG. 15 is a characteristic diagram showing the relationship between fractal dimension value and capacity maintenance ratio. FIG. 16 is a model view showing an example of discharge hole used for producing carbon fiber in which the central portion is of the radial type structure and the surface layer portion is of the random radial type structure. FIG. 17 is a characteristic diagram showing the relationship between ratio of the radial type structure and capacity. FIG. 18 is a characteristic diagram showing the relationship between ratio of the radial type structure and capacity maintenance ratio. FIG. 19 is a characteristic diagram showing the relationship between notch angle in carbon fiber having notch structure and capacity. FIG. 20 is a characteristic diagram showing the relationship between notch angle in carbon fiber having notch structure and capacity maintenance ratio. FIG. 21 is a schematic perspective view showing graphitized carbon fiber having cross sectional portions different in the crystal structure at predetermined period in the fiber length direction and carbon fiber crushed powder obtained by crushing the same. FIG. 22 is a characteristic diagram showing the relationship between aspect ratio of carbon fiber crushed powder and capacity maintenance ratio. Best Mode for Carrying Out the Invention The graphitized carbon fiber having notch structure will now be described. By allowing the high order structure of the carbon fiber cross section to be of notch structure, carbon fiber having high capacity and strength tolerable to expansion/contraction at the time of charge/discharge can be realized. Namely, in the cross sectional high order structure in the carbon fiber, a structure such that a portion of carbon fiber shown in FIG. 1 is lacking or missing, i.e., notch structure is provided in advance. Thus, even if the carbon portion is high crystallinity, the structure distortion occurring by expansion/contraction taking place at the time of charge/discharge can be absorbed by its notch portion. As a result, reversibility of the charge/discharge cycle can be improved. In the above-mentioned notch structure, the cycle reversibility varies by difference of angle that the center and the fiber diameter outer circumference of the carbon fiber cross section shown in FIG. 1B form (hereinafter referred to as "notch angle"). Theoretically, it is known that the interlayer portion is swollen by about 10% by intercalation to the graphite structure. If the notch angle is small, the structure distortion taking place by expansion/contraction occurring at the time of charge/discharge fails to be absorbed. As a result, the structure breakage takes place. On the other hand, if the notch angle is large, the carbon structure portion is decreased so that the capacity is lowered. For this reason, while it is possible to suitably select the notch angle in dependency upon the purpose, it is preferable that its angle is 2° or more and is 150° or less. With respect to the cross sectional shape except for circular shape, definition is made such that the geometrical center of gravity is caused to be center and angle that its center and the fiber outer circumference form is caused to be notch angle. In measurement of the notch angle of the carbon fiber having notch structure at the cross section, the fiber cross section is observed by the electron microscope, thus making it possible to measure angle by picture image or photographic picture image. In the cross sectional high order structure in the carbon fiber, according as the ratio to take the radial type structure becomes high, higher capacity can be obtained. However, the above-mentioned structure distortion has a tendency to take place. For this reason, there may be suitably selected the cross sectional structure such as the random radial type, etc. in which, e.g., the random type structure except for the radial type structure is mixed in dependency upon the purpose. In this case, since the strength of the carbon fiber itself is increased, the notch structure is provided, thereby permitting reversibility of the charge/discharge cycle to be further satisfactory. The above-mentioned carbon fiber having the notch structure can be made up (prepared) by using discharge hole T having an outlet shape such that baffle plate is provided so that wedge is inserted in fiber-forming of organic fiber as shown in FIG. 2, for example. However, the outlet shape is not limited to such shape. In addition, if notch structure can be formed at the cross sectional structure of organic fiber which is the precursor, any other methods can be applied. On the other hand, although cathode material used in combination with such anode consisting of carbon fiber or graphitized carbon fiber is not particularly limited, it is preferable that the cathode material includes sufficient quantity of Li. For example, compound metal oxide consisting of lithium and transition metal, or interlayer compound including Li, etc. represented by the general expression LiMO 2 (M indicates at least one of Co, Ni, Mn, Fe, Al, V, Ti) is suitable. Particularly, since this invention aims at attaining high capacity, the cathode is required to include Li corresponding to charge/discharge capacity of 250 mAh or more per anode carbon material 1g in the steady state (after, e.g., five charge/discharge operations are repeated). It is more preferable to include Li corresponding to charge/discharge capacity of 300 mAh or more. It is to be noted that it is not necessarily required that Li ions are all delivered from the cathode material, but it is essentially required that there exists Li (ion) corresponding to charge/discharge capacity of 250 mAh or more per carbon material 1g within the battery. In addition, quantity of Li (ions) is assumed to be judged by measuring discharge capacity of the battery. The anode material is .used in the non-aqueous electrolyte secondary battery. In this non-aqueous electrolyte solution secondary battery, non-aqueous electrolytic solution in which electrolyte is dissolved in non-aqueous solvent is used as electrolytic solution. In this example, since graphite material is used as the anode in this invention, conventional propylene carbonate (PC) cannot be used as main solvent of non-aqueous solvent, and it is therefore the premise that solvents except for the above are used. As solvent suitable as the main solvent, ethylene carbonate (EC) is first mentioned, but there is also suitable compound of the structure in which hydrogen element of EC is replaced by halogen element. Moreover, although reactive with graphite material as in the case of PC, a portion of EC as main solvent or compound of the structure in which hydrogen atom of EC is replaced by halogen element is replaced by a very small quantity of second component solvent, whereby satisfactory characteristic can be obtained. As the second component solvent, there can be used PC, butylene carbonate, 1, 2-dimethoxyethane, 1, 2-diethoxymethane, γ-butyrolactone, valerolactone, tetrahydrofuran, 2-methyltetrahydrofuran, 1, 3-dioxolan, 4-methyl-1, 3-dioxolan, sulforan, methyl sulforan, etc. It is preferable that the second component solvent is less than 10 % by volume as its quantity of addition. Further, the third component solvent may be added with respect to main solvent, or with respect to mixed solvent of the main solvent and the second component solvent to realize improvement in conductivity, decomposition suppression of EC and improvement in low temperature characteristic, and to allow degree of reaction with lithium metal to be low, thus to improve safety. As the first mentioned solvent of the third component, chain carbonic ester such as DEC (diethyl carbonate) or DMC (dimethyl carbonate), etc. is suitable. Moreover, unsymmetrical (asymmetrical) chain carbonic ester such as MEC (methyl ethyl carbonate) or MPC (methyl propyl carbonate), etc. is suitable. The mixing ratio of chain carbonic ester which serves as the third component with respect to main solvent or mixed solvent of main solvent and the second component solvent (main solvent or mixed solvent of main solvent and second component solvent: third component solvent) is preferably caused to fall within the range from 10:90 to 60:40, and is more preferably caused to fall within the range from 15:85 to 40:60. As the solvent of the third component, mixed solvent of MEC and DMC may be employed. It is preferable that the MEC-DMC mixing ratio is caused to fall within the range indicated by 1/9≤d/m≤8/2 when MEC volume is designated at m and DMC volume is designated at d. Moreover, it is preferable that the mixing ratio between main solvent or mixed solvent of the main solvent and the second component solvent and MEC-DMC which serves as solvent of the third component is caused to fall within the range indicated by 3/10≤(m+d)/T≤7/10 when MEC volume is designated at m, DMC volume is designated at d and the entire volume of the solvent is designated at T. On the other hand, as electrolyte dissolved into the non-aqueous solvent, any one or more kinds of solvents which can be used in the battery of this kind may be used in the mixed state as occasion demands. For example, LiPF 6 is preferable. In addition to the above, however, LiClO 4 , LiAsF 6 , LiBF 4 , LiB(C 6 H 5 ) 4 , CH 3 SO 3 Li, CF 3 SO 3 Li, LiN(CF 3 SO 2 ) 2 , LiC(CF 3 SO 2 ) 3 , LiCl, LiBr, etc. More practical embodiments to which this invention is applied will now be described in detail on the basis of the experimental results. Initially, studies have been made in connection with the area replenishment rate (degree) and circularity of carbon fiber used as anode material. Embodiment 1 (not part of the invention) (a) Manufacture of anode material Coal system pitch was held for five (5) hours at 425°C in the atmosphere of inactive gas to obtain coal system mesophase pitch of softening point of 220°C. At this time, the mesophase percentage content was 92 %. The coal system mesophase pitch thus obtained was caused to undergo discharging and fiber-forming at a predetermined extraction pressure at 300°C to obtain precursor fiber. Thereafter, this precursor fiber was caused to experience infusible processing at 260°C to calcine the precursor fiber thus processed at temperature of 1000°C in the atmosphere of inactive gas to obtain carbon fiber. Further, this carbon fiber is heat-treated at temperature of 3000°C in the atmosphere of inactive gas to allow it to undergo air (wind) crushing to obtain sample powder of graphitized carbon fiber. The cross sectional shape of the sample powder thus obtained was observed by the electron microscopic observation to determine shape and dimensions of the fiber. Moreover, the area replenishment rate (degree) and the circularity were calculated. In this example, in calculation, it was assumed that arbitrary twenty (20) sample particles are extracted to use its average value. The result is shown in Table 1. The bulk density was determined by the method described in JIS K-1469. Similarly, its result is shown in the Table 1. In addition, the cross sectional shape of the carbon fiber thus obtained is shown in FIG. 3. (b) Making up of cathode active material Lithium carbonate of 0.5 mol and cobalt carbonate of 1 mol were mixed to bake this mixture for five (5) hours at temperature of 900°C in air to thereby obtain LiCoO 2 . As the result of the fact that the X-ray diffraction measurement was conducted with respect to the material thus obtained, its peak was well in correspondence with peak of LiCoO 2 registered in JCPDS file. Then, the sample powder was used as anode material to actually make up non-aqueous electrolyte secondary battery of the cylindrical type. The configuration of the battery is shown in FIG. 4. (c) Making up of the anode 1 Graphitized carbon fiber powder 90 weight part and polyvinylidene fluoride (PVDF) 10 weight part as binding agent were mixed to prepared anode mix to disperse it into N-methyl pyrolidone serving as solvent to prepare anode mix slurry (in paste state). Belt-shaped copper foil of thickness of 10 µm was used as an anode collector 10 to coat the anode mix slurry on both surfaces of the collector to dry it thereafter to compression-mold it at predetermined pressure to make up belt-shaped anode 1. (d) Making up of cathode 2 The LiCoO 2 thus obtained was crushed so that LiCoO 2 powder such that accumulated 50 % particle diameter obtained by the laser diffraction method is 15 µm is provided. Then, this LiCoO 2 powder 95 weight part and lithium carbonate powder 5 weight part were mixed to mix 91 weight part of this mixture, graphite 6 weight part as conductive agent and polyvinyledene fluoride 3 weight part as binding agent to prepare cathode mix to disperse it into N-methyl pyrolidone to prepare cathode mix slurry (in paste state). Belt-shaped aluminum foil of thickness of 20 µm was used as a cathode collector 11 to uniformly coat the cathode mix slurry on both surfaces of this collector to dry it thereafter to compression-mold it, thus to make up belt-shaped cathode 2. (e) Assembling of the battery The belt-shaped anode 1 and the belt-shaped cathode 2 which have been made up in a manner as described above are stacked in order of the anode 1, separator 3, the cathode 2, separator 3 through separator consisting of micro porous polypropylene film having thickness of 25 µm thereafter to wound it large number of times, thus to make up spiral type electrode body having outside (outer) diameter of 18 mm. The spiral type electrode body thus made up is accommodated within a steel battery can 5 to which nickel plating has been implemented. Then, insulating plates 4 are disposed at upper and lower both surfaces of the spiral type electrode to draw a cathode lead 13 of aluminum from anode collector 11 so that it is caused to be conductive with a battery cover 7 to draw an anode lead 12 of nickel from an anode collector 10 to weld it at the battery can 5. Within this battery can 5, electrolytic solution in which LiPF 6 is dissolved at a ratio of 1 mol/1 is poured into equi-volmetric mixture solvent of EC and DMC. Then, the battery can 5 is caulked through a sealing gasket 6 of which surface is coated by asphalt to fix a safety valve unit 8 having current interrupting mechanism, a PTC element 9 and the battery cover 7 to keep air-tightness within the battery thus to make up cylindrical non-aqueous electrolyte secondary battery having diameter of 18 mm and height of 65 mm. Embodiment 2 (not part of the invention) Graphitized carbon fiber was manufactured similarly to the embodiment 1 except that there is used precursor fiber obtained by holding coal system pitch for two (2) hours at 425°C in the atmosphere of inactive gas to hold it for two (2) hours at 400°C under methane gas flow thereafter to further hold it for twenty four (24) hours at 350°C in the atmosphere of inactive gas to allow the heat-treated coal system mesophase pitch (mesophase percentage content is 95 %) to undergo discharge and fiber-forming, and to further make up non-aqueous electrolyte secondary battery. Also in this example, the fiber shape and the average dimension are determined in a manner similar to the embodiment 1 with respect to powder of the graphitized carbon fiber thus obtained to calculate the area replenishment rate (degree) and the circularity, and to measure bulk density. The result is shown in the Table 1. In addition, the fiber cross sectional shape is shown in FIG. 5. Embodiment 3 (not part of the invention) Graphitized carbon fiber was manufactured in a manner similar to the embodiment 1 except that there is used precursor fiber obtained by holding petroleum system pitch for three (3) hours at 430°C in the atmosphere of inactive gas to allow heat-treated petroleum system mesophase pitch having softening point of 210°C to undergo discharge and fiber-forming, and to make up non-aqueous electrolyte secondary battery. Also in this example, the fiber shape and the average dimension were determined in a manner similar to the embodiment 1 with respect to powder of the graphitized carbon fiber thus obtained to calculate the area replenishment rate (degree) and circularity, and to measure bulk density. The result is shown in the Table 1. In addition, the fiber cross sectional shape is shown in FIG. 6. Embodiment 4 (not part of the invention) Precursor fiber was made up in a manner similar to the embodiment 3 except that fiber-formabte discharge hole which is more flat than that of the embodiment 3 is used thereafter to manufacture graphitized carbon fiber in a manner similar to the embodiment 1, and to make up non-aqueous electrolyte secondary battery. Also in this example, the fiber shape and the average dimension were determined in a manner similar to the embodiment 1 with respect to powder of the graphitized carbon fiber thus obtained to calculate the area replenishment rate (degree) and circularity, and to measure bulk density. The result is shown in Table 1. In addition, the fiber cross sectional shape is shown in FIG. 7. Comparative example 1 Precursor fiber was made up in a manner similar to the embodiment 1 except that there is used fiber-formable discharge hole so that the fiber cross section takes right triangle thereafter to manufacture graphitized carbon fiber in a manner similar to the embodiment 1, and to make up non-aqueous electrolyte secondary battery. Also in this example, the fiber shape and the average dimension were determined in a manner similar to the embodiment 1 with respect to powder of the graphitized carbon fiber thus obtained to calculate area replenishment rate (degree) and circularity, and to measure bulk density. The result is shown in the Table 1. In addition, the fiber cross sectional shape is shown in FIG. 8. Comparative example 2 Precursor fiber was made up in a manner similar to the embodiment except that there is used fiber-formable discharge hole so that the fiber cross section takes right triangle thereafter to manufacture graphitized carbon fiber in a manner similar to the embodiment 1, and to make up non-aqueous electrolyte secondary battery. Also in this example, the fiber shape and the average dimension were determined in a manner similar to the embodiment 1 with respect to powder of the graphitized carbon fiber thus obtained to calculate area replenishment rate (degree) and circularity, and to measure bulk density. , The result is shown in the Table 1. In addition, the fiber cross sectional shape is shown in FIG. 9. Comparative example 3 Precursor fiber was made up in a manner similar to the embodiment 1 except that there is used fiber-formable discharge hole so that the fiber cross section takes complete round shape thereafter to manufacture graphitized carbon fiber in a manner similar to the embodiment 1, and to make up non-aqueous electrolyte secondary battery. Also in this example, the fiber shape and the average dimension were determined in a manner similar to the embodiment 1 with respect to powder of the graphitized carbon fiber thus obtained to calculate area replenishment rate (degree) and circularity, and to measure bulk density. The result is shown in the Table 1. In addition, the fiber cross sectional shape is shown in FIG. 10. (Evaluation) With respect to the respective batteries of the embodiments and the comparative examples made up as described above, 2.5 hour constant current/constant voltage charge operation was first carried out under the condition of charge current of 1A and the maximum charge voltage of 4.2 V thereafter to carry out discharge operation under the condition of discharge current 700 mA until voltage falls down to 2.75 V to measure the battery initial capacity. Its result is shown in Table 2. In addition, the relationship between the area replenishment rate (degree) and the battery initial capacity is shown in FIG. 11. Then, the charge/discharge cycle was repeatedly carried out to determine ratio of capacity (capacity maintenance ratio) of the 100-th cycle with respect to capacity of the second cycle (capacity maintenance ratio). In the cycle test, charge operation was conducted for 2.5 hours under the condition of the maximum charge voltage of 4.2 V and the charge current of 1A, and discharge operation was conducted under the condition of constant current of 700 mA until voltage falls down to 2.75 V. The capacity maintenance ratio was shown together in the Table 2. In addition, the relationship between circularity and capacity maintenance ratio is shown in FIG. 12. BATTERY CAPACITY mAh CAPACITY MAINTENANCE RATIO % EMBODIMENT 1 1589 92 EMBODIMENT 2 1572 90 EMBODIMENT 3 1463 95 EMBODIMENT 4 1526 81 COMPARATIVE EXAMPLE 1 1392 72 COMPARATIVE EXAMPLE 2 1384 75 COMPARATIVE EXAMPLE 3 1415 89 As is clear from the Table 2 and FIG. 14, the carbon fibers of the embodiments 1 to 4 having the area replenishment rate (degree) which features this invention exhibited high electrode filling ability and high capacity. Moreover, as is clear from the Table 2 and FIG. 12, the carbon fiber having a predetermined circularity which is the preferred embodiment also exhibited high bulk density and high cycle capacity maintenance ratio. It has been found that the non-aqueous electrolyte secondary battery using carbon fiber having a predetermined area replenishment rate (degree) and circularity has the excellent practical characteristic that high energy density and long cycle life time are caused to be compatible. Studies were then conducted in connection with difference of the characteristic by fractal dimension value of the cross section. Embodiment 5 (not part of the invention) Anode material was produced in a manner as described below. Coal system pitch was held for five (5) hours at 425°C in the atmosphere of inactive gas to obtain coal system mesophase pitch having softening point of 220°C. At this time, mesophase percentage content was 90%. The coal system mesophase pitch thus obtained was extruded in a pulse form, while applying ultrasonic wave thereto, by using discharge hole having inside diameter of 20 µm at 305°C to allow it to undergo discharge and fiber-forming while changing pressure. Thus, precursor fiber was obtained. Thereafter, infusible processing was conducted at 260°C to calcine it at temperature of 1000°C in the atmosphere of inactive gas. Thus, carbon fiber was obtained. Further, the carbon fiber was heat-treated at temperature of 3000°C in the atmosphere of inactive gas to allow the carbon fiber thus processed to undergo air crushing/milling. Thus, sample powder of graphitized carbon fiber was obtained. As the result of the fact that (002) spacing d 002 and FD value of the sample powder thus obtained are determined, d 002 was equal to 0.3363 nm, and FD was equal to 1.1. The method of measuring the fractal dimension (FD) value will now be described. Initially, in order to obtain picture image of the carbon fiber cross sectional structure, the cross section was observed under the acceleration voltage condition of 2 kv by using the electric field radiation type scanning electron microscope to take this still picture into the computer to divide the picture image thus obtained (FIG. 13A) into different five portions including the fiber central portions of 4 µm x 4 µm (consisting of pixels of 512x512) as shown in FIG. 13B. In the case where luminance of picture image is not uniform, Fourie transform or filtering processing is implemented to carry out smoothing thereafter to binarize respective picture images. In the case where there is necessity to more clarify the curve shape of the carbon network plane, image processing is implemented so that the white portion of the binarized picture image can be recognized as thin line (FIG. 13C). Calculation was carried out by using the equation (5) with respect to the above-described five picture images to determine fractal dimension d. d = - Δlog N (l)/Δlog l where l is total number of squares when picture image is divided into squares of certain size, and N is the number of squares overlapping with curve of carbon net plane when picture image is divided into squares of certain size. Namely, picture image is divided into lattices consisting of squares to calculate the number of squares overlapping with the curve of the carbon net plane to similarly carry out calculation while changing the size of square to determine average value with respect to five picture images. Further, such measurement was carried out with respect to ten (10) fibers to determine average value to allow it to be FD value. The fractal dimension (FD) value can be measured also by the method described in, e.g., Carbon Material Society Bulletin "Carbon TANSO 1995, No. 169, P.207 to 214". The above-mentioned sample powder was used as the anode material to make up cylindrical non-aqueous electrolyte secondary battery. The method of making up (preparing) cathode active material, the method of making up (preparing) electrode and the method of assembling the battery are similar to those of the previously described embodiment 1. Embodiment 6 (not part of the invention) Cylindrical non-aqueous electrolyte secondary battery was made up in a manner similar to the embodiment 5 except that discharge/fiber-forming was carried out in a modified pulse condition to obtain precursor fiber. The (002) spacing d 002 of the sample powder thus obtained was 0.3365 nm, and FD value was 1.2. Embodiment 7 (not part of the invention) Cylindrical non-aqueous electrolyte secondary battery was made up in a manner similar to the embodiment 5 except that discharge/fiber-forming was carried out in a further modified pulse condition to obtain precursor fiber. The (002) spacing d 002 of the sample powder thus obtained was 0.3367 nm, and FD value was 1.3. Embodiment 8 (not part of the invention) Cylindrical non-aqueous electrolyte secondary battery was made up in a manner similar to the embodiment 5 except that discharge/fiber-forming was carried out in a still further modified pulse condition to obtain precursor fiber. The (002) spacing d 002 of the sample powder thus obtained was 0.3372 nm, and FD value was 1.5. Embodiment 9 (not part of the invention) Cylindrical non-aqueous electrolyte secondary battery was made up in a manner similar to the embodiment 5 except that discharge/fiber-forming was carried out in a still more further modified pulse condition to obtain precursor fiber. The (002) spacing d 002 of the sample powder thus obtained was 0.3363 nm, and FD value was 1.3. Comparative example 4 Cylindrical non-aqueous electrolyte secondary battery was made up in a manner similar to the embodiment 5 except that discharge/fiber-forming was carried out in the state where no ultrasonic wave is applied to the discharge hole to obtain precursor fiber. The (002) spacing d 002 of the sample powder thus obtained was 0.3410 nm, and FD value was 1.8. Comparative example 5 Cylindrical non-aqueous solution secondary battery was made up in a manner similar to the embodiment 5 except that discharge/fiber-forming was carried out in the state where no ultrasonic wave is applied to the discharge hole to obtain precursor fiber. The (002) spacing d 002 of the sample powder thus obtained was 0.3361 nm, and FD value was 1.0. The result in the case where charge/discharge ability was measured with respect to carbon fibers used in the respective embodiments and comparative examples is shown in Table 3. In addition, the relationship between the (002) spacing d 002 and capacity is shown in FIG. 14. The charge/discharge ability measurement method will now be described. Test cell described below was made up to carry out the measurement. In preparing the test cell, pre-heat processing was first implemented to the above-mentioned sample powder under the condition of temperature rising speed of about 30°C/min., arrival temperature of 600°C and arrival temperature holding time of one hour in the atmosphere of Ar. Thereafter, polyvinylidene fluoride corresponding to 10 % by weight was added as binder to mix dimethyl formamide as solvent to dry it to prepare sample mix. Then, 37mg of the sample mix was weighted to mold it along with Ni mesh serving as collector so that pellet having diameter of 15.5 mm is provided to make up working electrode. The configuration of the test cell is as follows. Cell shape: Coin type cell (diameter 20mm, thickness 2.5 mm) Opposite electrode: Li metal Separator; polypropylene porous film Electrolytic solution: Solution in which LiPF 6 is dissolved in mixed solvent (1:1 in terms of volumetric ratio) of EC and DEC at concentration of 1 mol/l. The test cell constituted as described above was used to measure capacity per 1g of carbon material. In this case, doping of lithium into the working electrode (charging: strictly speaking, in this test method, charging is not carried out, but discharging is carried out in the process where lithium is doped into carbon material. However, in correspondence with the actual circumstances at actual battery, for convenience, this doping process is called charging and undoping process is called discharging) was carried out under the condition of constant current of 1 mA and constant voltage of 0V (Li/Li+) per cell, and the discharging (undoping process) was carried out under the condition of constant current of 1 mA per cell until terminal voltage falls down to 1.5 V to calculate capacity at that time. Then, with respect to the tubular (cylindrical) battery made up in the respective embodiments and comparative examples, there was repeatedly carried out charge/discharge cycle in which 2.5 hour constant current and constant voltage charge operation is conducted under the condition of charge current 1A and the maximum charge voltage of 4.2 V, and discharge operation is then conducted under the condition of current 700 mA until voltage falls down to 2.75 V. Thus, ratio of capacity of the 100-th cycle with respect to the capacity of the second cycle (capacity maintenance ratio) was determined. The result is shown in the above-mentioned Table 3. In addition, the relationship between FD value and capacity maintenance ratio is shown in FIG. 15. From the above-described result, it has been found that the carbon fiber which has controlled the FD value serving as index of the cross sectional structure of this invention is anode material excellent in the cycle characteristic and the charging/discharging ability as compared to the comparative example. Difference of the characteristic resulting from difference of the high order structure of the cross section of the carbon fiber was then examined. Embodiment 10 (not part of the invention) In this example, anode material was made up in a manner as described below. Coal system pitch was held for five (5) hours at 425°C in the atmosphere of inactive gas to obtain coal system mesophase pitch having softening point of 220°C. At this time, the mesophase percentage content was 92 %. The coal system mesophase pitch thus obtained was caused to undergo fiber-forming by using a discharge tube 15 of the double structure composed of a discharge outer tube 15a and a discharge inner tube 15b as shown in FIG. 16 at 300°C, thus to obtain precursor fiber. In this example, the diameter A of the discharge outer tube 15a was set to 20 µm, and the diameter B of the discharge inner tube 15b was set to 10 µm (B/A=0.5). Thereafter, infusible treatment was conducted at 260°C to calcine the article at temperature 1000°C in the atmosphere of inactive gas to obtain carbon fiber. Further, heat treatment was conducted at temperature of 3000°C in the atmosphere of inactive gas to carry out air crushing/milling to obtain sample powder of graphitized carbon fiber. The sample powder thus obtained has cross sectional shape by the electron microscopic observation as shown in FIG. 1. The above-mentioned sample powder was used as anode material to make up cylindrical non-aqueous electrolyte secondary battery. The method of making up the cathode active material, the method of making up the electrode and the method of assembling the battery are similar to those of the previously described embodiment 1. Embodiment 11 (not part of the invention) Cylindrical non-aqueous electrolyte secondary battery was made up in a manner similar to the embodiment 10 except that the discharge hole of B/A=0.7 is used to obtain precursor fiber. Embodiment 12 (not part of the invention) Cylindrical non-aqueous electrolyte secondary battery was made up in a manner similar to the embodiment 10 except that discharge hole of B/A=0.3 is used to obtain precursor fiber. Embodiment 13 (not part of the invention) Cylindrical non-aqueous electrolyte secondary battery was made up in a manner similar to the embodiment 10 except that discharge hole of B/A=0.1 is used to obtain precursor fiber. Comparative example 6 Cylindrical non-aqueous electrolyte secondary battery was made up in a manner similar to the embodiment 10 except that discharge hole of B/A=1 is used to obtain precursor fiber having cross section of random radial structure 100 %. Comparative example 7 Cylindrical non-aqueous electrolyte secondary battery was made up in a manner similar to the embodiment 10 except that mesophase pitch of mesophase percentage content 98 % is used and discharge hole of B/A=1 is used to obtain precursor fiber having cross section of random radial structure 100 %. Test cells similar to those in the case of the embodiments 5 to 9 were made up with respect to carbon fibers used in the respective embodiments and comparative examples to measure charge/discharge ability. The measurement results and the cross sectional shapes are shown in Table 4. The cross sectional shapes were observed by the electron microscope. Further, 2.5 hour constant current/constant voltage charge operation was carried out under the condition of charge current of 1A and the maximum charge voltage of 4.2 V with respect to tubular (cylindrical) batteries made up in the respective embodiments and comparative examples thereafter to carry out discharge operation under the condition of discharge current 700 mA until voltage falls down to 2.75 V to measure the battery initial capacity. Its result is shown in the Table 4 and FIG. 17. In addition, charge/discharge cycle is repeatedly carried out to determine ratio of capacity of the 200-th cycle with respect to capacity of the second cycle (capacity maintenance ratio). In the cycle test, charge operation was carried out for 2.5 hours under the condition of the maximum voltage 4.2 V and the charge current 1A, and discharge operation was carried out under the condition of discharge current of 300 mA until voltage falls down to 2.75 V. The capacity of the second cycle and the capacity maintenance ratio of the 200-th cycle with respect to the second cycle are shown in the above-mentioned table 4 and FIG. 18. From the above-described result, it has been found that the carbon fiber in which the central portion is of the radial type structure and the surface layer portion is of the random radial structure can provide battery having well-balanced relationship between the battery capacity and cycle characteristic, high energy density, excellent cycle characteristic, and high reliability as compared to the comparative example. The characteristic of the carbon fiber having notch structure was then examined. Embodiment 14 (according to the invention) Anode material was produced in a manner as described below. Coal system pitch was held for five (5) hours at 425°C in the atmosphere of inactive gas to obtain coal system mesophase pitch having softening point 220°C. At this time, the mesophase percentage content was 92 %. The coal system mesophase pitch thus obtained was caused to undergo fiber-forming by using discharge hole (angle that baffle plate J forms is 3°) having diameter of 20 µm, which has shape shown in FIG. 2, at 300°C to obtain precursor fiber. Thereafter, infusible processing was conducted at 260°C to calcine the article at temperature 1000°C in the atmosphere of inactive gas to obtain carbon fiber. Notch angle of the fiber measured by the electron microscopic picture image was 2°. Further, heat treatment was conducted at temperature of 3000°C in the atmosphere of inactive gas to carry out air crushing/milling. Thus, sample powder of graphitized carbon fiber was obtained. The above-mentioned sample powder was used as the anode material to make up cylindrical non-aqueous electrolyte secondary battery. The method of making up cathode material, the method of making up electrode and the method of assembling battery are similar to those of the previously described embodiment 1. Embodiment 15 (according to the invention) Cylindrical non-aqueous electrolyte secondary battery was made up in a manner similar to the embodiment 14 except that the discharge hole in which angle that baffle plate J forms is 10° is used to obtain precursor fiber (notch angle is 8°). Embodiment 16 (according to the invention) Cylindrical non-aqueous electrolyte secondary battery was made up in a manner similar to the embodiment 14 except that the discharge hole in which angle that baffle plate J forms is 30°C is used to obtain precursor fiber (notch angle is 28°). Embodiment 17 (according to the invention) Cylindrical non-aqueous electrolyte secondary battery was made up in a manner similar to the embodiment 14 except that the discharge hole in which angle that baffle plate J forms is 50° is used to obtain precursor fiber (notch angle is 47°). Embodiment 18 (according to the invention) Cylindrical non-aqueous electrolyte secondary battery was made up in a manner similar to the embodiment 14 except that the discharge hole in which angle that baffle plate J forms is 70° is used to obtain precursor fiber (notch angle is 72°). Embodiment 19 (according to the invention) Cylindrical non-aqueous electrolyte secondary battery was made up in a manner similar to the embodiment 14 except that the discharge hole in which angle that baffle plate J forms is 90° is used to obtain precursor fiber (notch angle is 88°). Embodiment 20 (according to the invention) Cylindrical non-aqueous electrolyte secondary battery was made up in a manner similar to the embodiment 14 except that the discharge hole in which angle that baffle plate J forms is 125° is used to obtain precursor fiber (notch angle is 120°). Comparative example 8 Cylindrical non-aqueous electrolyte secondary battery was made up in a manner similar to the embodiment 14 except that the discharge hole including no baffle plate J is used to obtain precursor fiber (no notch). Comparative example 9 Cylindrical non-aqueous electrolyte secondary battery was made up in a manner similar to the embodiment 14 except that pich in which the mesophase percentage ratio is 30 % is used and discharge hole including no baffle plate J is used to obtain precursor fiber (no notch). Comparative example 10 Cylindrical non-aqueous electrolyte secondary battery was made up in a manner similar to the embodiment 14 except that the discharge hole in which angle that baffle plate J forms is 145° is used to obtain precursor fiber (notch angle is 140°). Test cells similar to those in the cases of the embodiments 5 to 9 were made up with respect to the carbon fibers used in the respective embodiments and comparative examples to measure charge/discharge ability. Its measured result is shown in Table 5. In addition, the relationship between notch angle and capacity is shown in FIG. 19. Further, with respect to the tubular (cylindrical) batteries made up in the respective embodiments and comparative examples, there was repeatedly carried out charge/discharge cycle in which 2.5 hour constant current/constant voltage charge operation is then carried out under the conditions of the charge current of 1A and the maximum charge voltage of 4.2 V and discharge operation is carried out under the condition of discharge current 700 mA until voltage falls down to 2.75 V. Thus, ratio of capacity of the 100-th cycle with respect to capacity of the second cycle (capacity maintenance ratio) was determined. The result of the capacity maintenance ratio of the 100-th cycle with respect to the second cycle is shown in the above-mentioned table 5. In addition, the relationship between notch angle and capacity maintenance ratio is shown in FIG. 20. From the above-described result, it has been found that notch is provided at carbon fiber so that anode material excellent in the cycle characteristic is provided. The performance as the anode material of the carbon material formed by crushing carbon fiber having cross sectional portions in which crystal structures are different periodically in the fiber length direction. Embodiment 21 (not part of the invention) Anode material was produced in a manner as described below. Petroleum system pitch was held for five (5) hours at 425°C in the atmosphere of inactive gas to obtain petroleum system mesophase pitch having softening point 230°C. At this time, the mesophase percentage ratio was 91 %. The petroleum system mesophase pitch thus obtained was caused to undergo discharge and fiber-forming at a predetermined extraction pressure at 300°C while applying magnetic field in a pulse form every predetermined time interval by using discharge hole having inner diameter of 20 µm within which small probe for application of magnetic field is included. Thus, organic fiber was obtained. Thereafter, this organic fiber was caused to experience infusible processing at 260°C to calcine it at temperature of 1000°C in the atmosphere of inactive gas to obtain carbon fiber. Further, the carbon fiber thus obtained is heat-processed at temperature 3000°C in the atmosphere of inactive gas to allow it to be precursor graphitized fiber as shown in FIG. 21a to further air-crush the precursor graphitized fiber to allow it to be sample powder as shown in FIG. 21b. The aspect ratio of the sample powder thus obtained was expressed as A=1.3 and the specific surface area was 0.9 mm 2 /g. The above-mentioned sample powder was used as anode material to make up tubular (cylindrical) non-aqueous electrolyte secondary battery. The method of making up the cathode active material, the method of making up electrode and the method of assembling battery are similar to those of the previously described embodiment 1. Embodiment 22 (not part of the invention) Cylindrical non-aqueous electrolyte secondary battery was made up in a manner similar to the embodiment 21 except that discharge/fiber-forming is carried out in the modified application pulse condition of magnetic field to obtain organic fiber. The aspect ratio of the sample powder thus obtained was expressed as A=3.3 and the specific surface area thereof was 0.8 m 2 /g. Embodiment 23 (not part of the invention) Cylindrical non-aqueous electrolyte secondary battery was made up in a manner similar to the embodiment 21 except that discharge/fiber-forming is carried out in the further modified application pulse condition of magnetic field to obtain organic fiber. The aspect ratio of the sample powder thus obtained was expressed as A = 7.0 and the specific surface area thereof was 1.2 m 2 /g. Embodiment 24 (not part of the invention) Cylindrical non-aqueous electrolyte secondary battery was made up in a manner similar to the embodiment 21 except that ultrasonic wave is applied to the discharge hole front end in a pulse form in place of magnetic field to carry out discharge/fiber-forming to obtain organic fiber. The aspect ratio of the sample powder thus obtained was expressed as A = 9.3 and the specific surface area was 1.3 m 2 /g. Embodiment 25 (not part of the invention) Cylindrical non-aqueous electrolyte secondary battery was made up in a manner similar to the embodiment 21 except that discharge hole having fine holes therewithin is used in place of magnetic field to carry out discharge/fiber-forming while ejecting air in a pulse form from the fine holes to obtain organic fiber. The aspect ratio of the sample powder thus obtained was expressed as A = 41. 0 and the specific surface area thereof was 1.5 m 2 /g. Comparative example 11 Cylindrical non-aqueous electrolyte secondary battery was made up in a manner similar to the embodiment 21 except that no magnetic field is applied to the discharge hole. The aspect ratio of the sample powder thus obtained was expressed as A = 64 and the specific surface area was 2.0 m 2 /g. Test cells similar to the cases of the embodiments 5 to 9 were made up with respect to carbon fibers used in the respective embodiments and the comparative examples to measure charge/discharge ability (capacity). In addition, in the test cell, value obtained by subtracting discharge capacity from charge capacity was calculated as capacity loss. The measured result is shown in Table 6. Further, with respect to cylindrical batteries made up in the respective embodiments and the comparative examples, there was repeatedly carried out charge/discharge cycle in which 2.5 hour constant current/constant voltage charge operation is conducted under the condition of charge current of 1A and the maximum charge voltage of 4.2 V, and discharge operation is then conducted under the condition of discharge current 700 mA until voltage falls down to 2.75 V to determine ratio of capacity of the 100-th cycle with respect to capacity of the second cycle (capacity maintenance ratio). The result of the capacity maintenance ratio of the 200-th cycle with respect to the second cycle is shown in the above-mentioned Table 6. In addition, the relationship between the aspect ratio A and the capacity maintenance ratio is shown in FIG. 22. From the above-described result, it has been found that carbon fiber having cross sectional portions different in the crystal structure periodically in the fiber length direction is crushed, thereby making it possible to easily realize low aspect ratio, and that in the case where such crushed powder is used as anode material, non-aqueous electrolyte secondary battery excellent in the cycle characteristic can be obtained.

Claims: An anode material for a non-aqueous electrolyte secondary battery, the anode material consisting of carbon fibers capable of carrying out doping/undoping of lithium, wherein in the cross section of the carbon fibers a portion of the carbon fiber is missing, so that a notch is formed and a notch structure is provided. An anode material according to claim 1, wherein the notch is extending from the geometrical center of gravity of the cross section to the outer circumference of the cross section and a notch angle is formed between the sides of the notch. An anode material according to claim 1, wherein the cross section of the carbon fiber has a circular shape and the notch is extending from the center of the cross section to the circumference of the cross section and a notch angle is formed at the center between the sides of the notch. An anode material according to one of claims 2 or 3, wherein the notch angle is 2° or more and is 150° or less. A non-aqueous electrolyte secondary battery, comprising: an anode consisting of carbon material capable of carrying out doping/undoping of lithium, the carbon material including an anode material according to one of claims 1 to 3; a cathode, and a non-aqueous electrolytic solution in which an electrolyte is dissolved in a non-aqueous solvent.

Inventors: NAGAMINE MASAYUKI, NAKAJIMA NAOYUKI, OMARU ATSUO, NAGAMINE, MASAYUKI, NAKAJIMA, NAOYUKI, OMARU, ATSUO, NAGAMINE, MASAYUKI, SONY ENERGYTEC INC., NAKAJIMA, Naoyuki, Sony Energytec Inc., OMARU, ATSUO, SONY ENERGYTEC INC.
Applicants: SONY CORP, SONY CORPORATION
Application year: 1997
Main classification: H01M4
IPC codes: D01F9, H01M4, D01F11, H01M10, H01M6