Nonaqueous secondary battery

A nonaqueous secondary battery comprising a cathode, an anode and a nonaqueous electrolyte disposed and sealed between the cathode and the anode wherein the anode is made of a carbon material as its active material, in which the carbon material comprises a fine core particle of a metal or an alloy thereof, and a carbon layer which is arranged and stacked in an onion-like shell configuration centering on the fine core particle, at least part of the carbon layer having a crystal structure in which graphite-like layers are stacked and the fine core particle having an average diameter of about 10 to 150 nm.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to nonaqueous secondary batteries. More 
particularly it relates to a nonaqueous secondary battery using a carbon 
material as an anode. 
2. Description of the Related Art 
Along with the reduction in the size of electronic apparatus and 
conservation of electric power, a stronger demand is made on creating a 
secondary battery of an alkali metal type having a high energy density in 
which an alkali metal such as lithium or the like is used. However, when 
an alkali metal is used in an anode, batteries using a lithium metal, for 
example, there is a drawback in that a repetition of charging and 
discharging cycles produces a dendrite on the lithium metal thereby 
causing an internal short circuit in batteries. On the other hand, a 
lithium/aluminum alloy has been proposed as a substitute for the lithium 
metal. Use of the alloy suppresses the generation of a dendrite. However 
such batteries using the alloy as an anode have a short cycle life in the 
deep discharge depth. Thus no essential improvement is made. Consequently 
attention focussed on a carbon material excellent in cycle properties and 
safety, which material permits lithium to be intercalated and 
deintercalated in the form of an ion, in particular, a certain kind of 
carbon material in which lithium is intercalated to form an interlayer 
compound is accompanied by an electrochemical reaction such as 
intercalation and deintercalation of lithium ions in an organic 
electrolyte including a lithium salt thus enabling a reversible 
oxidation-reduction reaction. Carbon materials are quite promising for use 
as an anode of lithium secondary batteries. Thus intense study has been 
made of secondary batteries using carbon materials. 
Carbon has various forms because graphite-like planes are expanded in two 
dimensions and stacked in various ways. Thus it is possible to obtain 
various carbons depending on starting materials and production methods. 
Carbons can be classified into several groups from the viewpoint of 
orientation state or fine structure thereof. They include random 
orientation microtexture in which graphite-like layers are stacked at 
random, a planar orientation microtexture in which graphite-like layers 
are oriented along a reference plane, an axial orientation microtexture in 
which graphite-like layers are oriented along an axis (including coaxial 
cylindrical structures in which graphite-like layers are cylindrically 
oriented relative to a reference axis, and radial structure in which 
graphite-like layers are radially oriented relative to a reference axis), 
and a point orientation microtexture in which graphite-like layers are 
stacked around a reference point (including concentric structures in which 
graphite-like layers are spherically oriented relative to a reference 
point though not in a complete texture, a radial structure in which 
graphite-like layers are radially oriented relative to a reference point). 
It is known that carbon having the same interlayer spacing has a different 
function owing to differences in arrangement of graphite-like layers. 
When carbon is used as an anode active material, the quantity of lithium 
inserted between carbon layers is one lithium atom relative to six carbon 
atoms, namely C.sub.6 Li at most. Thus the theoretical capacity of carbon 
per unit weight is 372 mAh/g. 
Carbon materials conventionally used as an anode are disclosed in Japanese 
Laid-Open Patent No. SHO. 62-90863, Japanese Laid-Open Patent No. SHO. 
62-122066, Japanese Laid-Open Patent No. SHO 63-213267, Japanese Laid-Open 
Patent No. HEI. 1-204361, Japanese Laid-Open Patent No.HEI. 2-82466, 
Japanese Laid-Open Patent No. HEI. 3-252053, Japanese Laid-Open Patent No. 
HEI. 3-285273 and Japanese Laid-Open Patent No. HEI. 3-289068. The carbon 
material disclosed in these patent publications does not exhibit a 
sufficient capacity in the potential range in that can be used as an 
actual battery, because of a linear increase in potential during the 
deintercalation of lithium, even if the carbon material has a certain 
capacity as seen from cokes used as a electrode material. When an 
electrode is manufactured by using a carbon material, bulk density is an 
important factor although a real density is also required. Since the shape 
and size of carbon particles provide the bulk density, it is difficult to 
raise the capacity density per unit volume with a fibrous carbon as shown 
in the embodiment of Japanese Laid-Open Patent No. SHO. 62-90863, Japanese 
Laid-Open Patent No. HEI. 2-82466, Japanese Laid-Open Patent No. HEI. 
285273, and Japanese Laid-Open Patent No. HEI. 3-289068. On the other 
hand, a pyrolytic carbon prepared by the CVD technique as disclosed in 
Japanese Laid-Open Patent No. SHO. 63-24555 exhibits a high charge and 
discharge stability. It is, however, difficult to make a thick film 
electrode and to obtain a large capacity electrode with that method. Then 
as shown in Japanese Laid-Open Patent No. HEI. 4-296448, deposited carbon 
is stripped and ground into powders. Such powders are thought to provide a 
thick film in film forming processes. However, these powders are not 
suitable for use in such processes, because the carbon is flaky and 
stripping deposited carbon is troublesome in production. 
Furthermore, as seen in Japanese Laid-Open Patent No. 63-230512, a powdered 
graphite cannot provide sufficient capacity as an active material of 
batteries because no orientation graphite-like layer is observed. 
Furthermore, metal particles in the center and carbon particles are large, 
although carbon deposits on the surface of metal at the center of 
on-ion-like structure in such a manner that carbon covers the surface of 
the metal. 
Thus it is not possible to obtain with carbon materials disclosed in the 
above patent publications carbon electrodes that can be practically used. 
Consequently it is difficult to obtain a satisfactory capacity with 
nonaqueous secondary batteries. 
Accordingly the present invention is intended to overcome the above 
described unfavorable conditions. 
SUMMARY OF THE INVENTION 
An object of the present invention is to provide a large capacity 
nonaqueous secondary battery by developing a carbon material having a 
large intercalation amount of lithium. 
Accordingly the present invention provides a nonaqueous secondary battery 
comprising a cathode, an anode and a nonaqueous electrolyte disposed and 
sealed between a cathode and an anode wherein the anode is made of a 
carbon material in which the carbon material comprises a fine core 
particle of a metal or an alloy thereof, and a carbon layer which is 
arranged and stacked in an onion-like shell texture centering on the fine 
core particle, at least part of the carbon layer having a crystal 
structure in which graphite-like layers are stacked and the fine core 
particle have an average diameter of about 10 to 150 nm.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
For the cathode of the nonaqueous battery of the present invention can be 
used such active materials as Li.sub.x M.sub.y N.sub.z O.sub.2 (wherein M 
is either of Fe, Co or Ni, N is a transition metal, 4B group or 5B group 
metal, and x, y, z represent either 0 or a positive number), LiMnO, 
MnO.sub.2, V.sub.2 O.sub.5, amorphous-V.sub.2 O.sub.5, TiS.sub.2, FeOCl, 
polyaniline, polypyrrol, polythiophene, polyacethylene, polyphenylene or 
the like. Part of these cathodes can be formed by admixing a conductive 
material and/or binder, or solid electrolyte in some cases. The mixing 
ratio can be defined as 100 wt.pts. of an active material as opposed to 5 
to 50 wt.pts. of conductive material, and 1 to 30 wt.pts. of binder. 
Examples of the conductive materials include carbons like carbon blacks 
(such as acetylene black, thermal black, channel black or the like), 
graphite powders and metal powders to which the conductive material is not 
restricted. Examples of the binders include without limitation fluorine 
polymers such as polytetrafluoroethylene, or polyvinyldene fluoride and 
polyolefins such as polyethylene or polypropylene. 
In the anode of the battery of the present invention, the carbon material 
is an active material which can intercalate and deintercalate Li.sup.+. 
In accordance with the present invention, carbon atoms are regularly 
arranged to form a carbon layer having graphite-like planes as shown in 
FIG. 5. These graphite-like planes are arranged and stacked in an 
onion-like shell microtexture around the fine core particles. The 
graphite-like layer in which graphite-like planes are arranged in an 
onion-like structure are arranged in a concentric manner relative to the 
fine core particles. 
A study on the fine structures of this onion-like carbon material shows 
that the following three factors are extremely important improving the 
discharge capacity of batteries. In other words, the carbon material with 
a favorable charge and discharge capacity has the following morphological 
characteristics. 
1. The carbon material contains particles having an approximately spherical 
in configuration and graphite-like layers arranged in a concentric 
spherical microtexture. Preferably particles have cores approximately at 
the center thereof. 
2. The carbon material, which is an accumulation of particles, has an 
average diameter of 40 to 200 nm or less. Particles may form an 
aggregation, i.e., an aggregation having a size preferably ranging between 
0.1 to 80 .mu.m. 
3. The crystal structure thereof is incomplete compared with graphite 
crystal structure. The mean of interlayer spacing of the (002) plane when 
the carbon material is measured with the X-ray wide angle method, the 
crystal size of the (002) plane and the (110) plane are large enough for a 
lithium ion to occupy a sufficient amount for intercalation and 
deintercalation. 
One particle of this onion-like microtexture constitutes a primary 
particle, which aggregates in plural numbers to form a secondary body. 
Preferably the primary particles of the carbon material have an average 
diameter of 40 to 200 nm. Furthermore when these particles form an 
aggregation, i.e., a secondary body, preferably the size may be about 0.1 
to 80 .mu.m. When the average diameter of the primary particles of the 
carbon material becomes larger than 200 nm, the efficient area of contact 
with the electrolyte in an electrode reaction becomes relatively small so 
that the charge and discharge power of batteries including such larger 
particles is small. In addition, when the average diameter of the primary 
particles of the carbon material become smaller than 40 nm, the lithium 
ion cannot occupy a sufficient place therein. Thus the battery cannot 
obtain a large capacity relative to the unit weight. 
The carbon material of the present invention can be used of a starting 
material of a gas-like or a dewdrop-like state on a sample base where a 
metal, its alloy or compound which has the catalytic action of the metal 
to be fine core particles, is present. Thus the carbon material forms an 
approximately spherical structure with the core placed approximately at 
the center. An observation of the carbon material with an electron 
microscope shows that layers of graphite-like layers are arranged in a 
concentric configuration to form a concentric spherical structure 
(onion-like structure). These structures form the primary particles. 
Otherwise they form an aggregation of the primary particles having a 
concentric spherical structure. Here the concentric spherical structure 
comprises a spherical shell-like arrangement of graphite-like layers of 
carbon centering on VIII element included in the center thereof (see FIG. 
3). 
Preferably, as for the carbon in the carbon material, the mean of 
interlayer spacing of the (002) plane ranges about 0.336 to 0.360 nm, the 
crystallite size (Lc) in the from (002) direction ranges from about 5 to 
20 nm, and the crystallite size (La) in the (110) direction ranges from 
about 10 to 25 nm. In the carbon material thus containing fine core 
particles at the center thereof a catalytic action is observed in the 
pyrolysis of hydrocarbons thus providing the carbon material with a high 
crystallinity while maintaining the same spherical structure. Since the 
mean of interlayer spacing is narrow, a low charge-discharge potential can 
be maintained at the intercalation and deintercalation of lithium. 
Furthermore, it seems that since the crystallite size is considerably 
large, the site where lithium intercalates or deintercalates increases to 
give a large capacity. Still further, graphite-like layers are arranged in 
a concentric spherical configuration, the (002) plane produced by the 
intercalation and deintercalation of lithium has a favorable resistance 
against contraction and expansion. Thus the use of the carbon material of 
the present invention provides a secondary battery with a large capacity 
and excellent cycle properties. 
The method for preparing a carbon material containing the above fine 
particles at the center thereof is exemplified as follows. 
Hydrocarbons or the derivatives thereof that are used for preparing the 
carbon material may be any of aliphatic hydrocarbons, aromatic 
hydrocarbons or cycloaliphatic hydrocarbons. They include benzene, 
toluene, xylene, naphthalene, anthracene, pylene, pyridine, allylbenzene, 
hexamethylbenzene, aniline, phenol, 1,2-dibromoethylene, 2-butine, 
methane, ethane, propane, butane, pentane, hexane, cyclohexane, 
acethylene, ethylene, pentene, propene, biphenyl, diphenylacethylene, 
styrene, acrylonitrile, pyrrole or thiophene and derivatives thereof 
(substituted with a halogen atom, hydroxyl group, sulfonic acid group, 
nitro group, nitroso group, amino group, carboxyl group or the like); 
creosote oil, ethylene bottom oil, natural gas or heavy oil of coal or 
petroleum type. The carbon material can be prepared by converting the 
above material into a gas-like or dewdrop-like state, pyrolyzing the 
converted material under nonoxidation atmosphere and depositing the thus 
formed material on the periphery of fine core particles. 
The pyrolysis of the above hydrocarbon or derivative thereof is performed 
in the presence of fine core particles that engage in catalytic action in 
gas phase. The fine core particle suitably has a diameter of about 10 to 
150 nm. Preferably it comprises a metal selected from the group consisting 
of VIII group elements such as iron, nickel, cobalt, ruthenium, rhodium, 
palladium, osmium, iridium and platinum or an alloy or a compound thereof. 
More preferably the fine core particles are formed of either organic or 
inorganic compounds of nickel such as nickel sulfate, nickel carbonate, 
nickel chloride, nickel sulfate, nickel oxide, nickel nitrate, nickel 
oxalate, nickel acetate, nickel formate, nickel benzoate, nickel stearate, 
nickel phosphinate, nickel phosphate and nickel pyrophosphate. 
Compounds having a particle diameter of 100 meshes or less are used in the 
following embodiments. In actuality, the compounds are decomposed before 
carbon begins to deposit. The particle diameter of the starting compound 
does not exert a large influence. 
Such fine core particles form approximately at the center of the carbon 
material in the pyrolysis of hydrocarbons while depositing the pyrolyzed 
carbon on the periphery of the fine core particles. When a fine core 
particle is present that forms a catalyst in the above gas phase 
pyrolysis, the crystallinity of the carbon material can be made higher 
with the catalysis. In such case, preferably the content of core particles 
relative to the carbon is 0.005 to 10 atm %. When the content is 0.005 atm 
% or less, the effect of the catalyst is insufficient. When the content is 
10 atm % or more, the relative quantity of the carbon becomes smaller, 
which results in insufficient capacity of a battery. 
The conditions for the pyrolysis which can be expected to provide catalysis 
are as follows. The material in gaseous or dewdrop state is supplied to a 
reactor at a temperature lower than the temperature of starting pyrolysis 
at a flow rate of 0.5 to 50 cm/minutes and at a supply rate of about 0.05 
to 20 mol/cm. The pyrolysis can be conducted in two stage temperature 
regions. The first stage temperature region ranges between room 
temperature to 1000.degree. C., preferably from about 300.degree. to 
900.degree. C. The second stage temperature ranges from about 650.degree.0 
to 1300.degree. C., preferably from about 750.degree. to 1200.degree. C. 
The pyrolysis is performed while heating the two temperature regions at a 
rate of about 0.1 to 20.degree. C./minutes. The mode for raising the 
temperature need not be at an equal rate, but may be a zigzag multi-stage 
raising, slow-raising at the first stage followed by rapid-raising, 
rapid-raising at the first stage followed by slow-raising, maintaining a 
certain level midway followed by raising and once lowering in the midway 
followed by raising again. Furthermore the supply rate and the flow rate 
of the material in gaseous or dewdrop state need not be constant and can 
vary in the above mentioned ranges. The temperature can be elevated or 
lowered either step by step or in a continuous manner within the above 
ranges. Thus an infinite number of combinations can be present depending 
on the temperature raising mode, or the supply rate and the flow rate of 
the material in gaseous or dewdrop state. The appropriate combination can 
be appropriate selected depending on the kind of materials. 
However, it would be important to conduct gas pyrolysis utilizing the 
catalytic action of fine core particles in two-stage temperature regions 
and under the predetermined temperature raising mode. The reason for this 
is not necessarily clear but, it seems that the two processes, the process 
of segmenting fine metal core particles to form a fine core particle in 
approximately the center of carbon and the process of stacking carbon on 
the fine core particle in spherical particle configuration, are occurring 
simultaneously, or either intermittently or continuously. 
When iron, nickel or cobalt is supplied into the system in the form of its 
compound, a fine core particle with an appropriate size can be provided in 
the carbon material by appropriately selecting the decomposition 
temperature of the compound as well as the decomposition temperature of 
its gaseous or dewdrop state. Consequently, the process of segmenting the 
above fine core particles is necessarily not required, thereby making it 
possible to perform the pyrolysis in selected and definite temperature 
regions. Among the above fine core particles, nickel is the most 
preferable. In particular, supplying nickel that constitutes fine core 
particles in the form of compound is preferable because the carbon 
material produced in the above process has excellent performance and the 
yield. 
Thus an appropriate control of the temperature and the time thereof can 
provide the carbon material having the most preferable crystal surface 
spacing and .the size of crystals. 
The carbon materials thus prepared are used as the anode active material. 
At this time, these carbon materials can be used as they are or in 
admixture with a conductive material and/or binder. The admixture ratio in 
a cathode can be applied thereto. 
The electrolyte applied to the nonaqueous secondary battery of the present 
invention can be prepared by dissolving a lithium salt in an organic 
solvent either in the form of a solid or a liquid. For example, organic 
electrolytic solutions, polymer solid electrolytes, inorganic 
electrolytes, molten salt or the like can be used. Among them, the organic 
electrolytic solution is the most preferable. Example of solvents for 
organic electrolytic solution includes esters such as propylene carbonate, 
ethylene carbonate, butylene carbonate, diethyl carbonate, 
.tau.-butyrolactone or the like, ethers such as substituted 
tetrahydrofuran such as 2-methyltetrahydrofuran, dimethylsulfoxide, 
sulfolane, methylsulfolane, acetonitrile, methyl formate, methyl acetate 
and the like which may be used singly or in admixture of two or more 
kinds. Propylene carbonate and an admixture thereof are preferable. 
In addition, the electrolytes include lithium salts such as lithium 
perchlorate, lithium tetrafluoroborate, lithium hexafluoroarsenate, 
lithium trifluoromethanesulfonate, lithium halide or lithium 
chloroaluminate. An admixture of two or more kinds of the electrolytes may 
be used. 
The electrolyte thus prepared is dehydrated with active alumina or metallic 
lithium. The amount of water in the electrolyte is desirably 1000 ppm or 
less, or more preferably 500 ppm or less, or more preferably 100 ppm or 
less. 
In addition, in place of this dehydration process, dehydrated solute and 
solvent may be used, or a combination thereof may be further used. 
As shown in FIG. 2, to the cathode 12 and the anode 10 thus prepared is 
connected when required a collector 9, 13 such as a foil or net made of 
nickel, aluminum or copper to be further connected to an external 
electrode. Between the cathode and the anode, the electrolyte, optionally 
together with a separator 11 such as microporous polypropylene film or a 
nonwoven cloth made of polypropylene and polyethylene may be disposed. In 
addition packing or hermetic seal 14 made of polypropylene or polyethylene 
is provided. 
Preferably, the operation of preparing these batteries is conducted in an 
inert gas like argon gas or extremely dry air separated from the external 
atmosphere to prevent the infiltration of moisture. 
The present invention will be illustrated in conjunction with the following 
examples, but they are not intended for limiting the scope of the 
invention. 
EXAMPLES 
Example 1 
Nickel oxide powder (having a mesh of 100 or less) 1.8 g was placed on a 
sample base 6 in a carbon preparing device shown in FIG. 1. Argon gas and 
propane gas were supplied respectively through a carrier gas supply line 1 
and a material gas supply line 2. By manipulating needle valves 3 and 4, 
the speed of supplying propane gas as a material gas was set to 0.53 
mol/h, and the gas flow rate was kept at 25.5 cm/min. The propane gas used 
as a material was pyrolyzed by changing the temperature at a temperature 
rising speed of 120.degree. C./min from room temperature to 750.degree. C. 
and a temperature rising speed of 1.degree. C./min from 750.degree. C. to 
1000.degree. C. to give 39.6 g of carbon material powders. The observation 
of carbon material thus prepared with a transmitting electron microscope 
showed that the primary particles have an average diameter of 100 nm and 
these carbon materials enclose nickel particles having an average diameter 
of 20 to 56 nm at the center thereof, thus forming a concentric spherical 
structure centering on nickel (see FIG. 3). By the way the particle 
diameter of an aggregation measured with a laser diffraction particle size 
distribution meter was 8.0 .mu.m. The reference numerals 5 and 7 in FIG. 1 
are schematic representations of a tube and a furnace, respectively. 
Polyolefine powder as a binder in a ratio of 5 wt.% was admixed to 20 mg of 
this carbon material. The mixture was charged in a formed nickel plate, 
which was pressed under 400 kg/m.sup.2 at 160.degree. C. followed by 
drying in vacuo for 10 hours to prepare a carbon electrode. Then to 
evaluate this electrode, the electrode was subjected to a charge and 
discharge test on which a three electrode method was used. That is, it 
used Li/Li.sup.+ as a reference electrode, and 1M LiClO dissolved in a 
propylene carbonate as an electrolyte. Charge and discharge was performed 
by setting the charge termination potential to 0 V and discharge 
termination potential to 2.5 V. The result is shown in Tables 1 and 2. 
TABLE 1-a 
______________________________________ 
primary secondary 
particle particle 
diameter diameter 
shape structure (nm) (nm) 
______________________________________ 
Exp. 1 
spherical 
multiple spherical 
96 12.3 
shell structure 
Exp. 2 
spherical 
multiple spherical 
156 6.5 
shell structure 
Exp. 3 
spherical 
multiple spherical 
68 10.5 
shell structure 
Exp. 4 
spherical 
multiple spherical 
151 30 
shell structure 
Exp. 5 
spherical 
multiple spherical 
72 14 
shell structure 
Exp. 6 
spherical 
multiple spherical 
132 12 
shell structure 
Exp. 7 
spherical 
multiple spherical 
84 15.7 
shell structure 
______________________________________ 
TABLE 1-b 
______________________________________ 
core 
particle 
discharge 
d (002) Lc La core diameter 
capacity 
(nm) (nm) (nm) particle 
(nm) (mAh/g) 
______________________________________ 
Exp. 1 
0.338 10.3 19.4 Ni 18-48 199 
Exp. 2 
0.338 24.5 23.2 Ni 65-145 180 
Exp. 3 
0.338 17.2 Fe 23-48 174 
Exp. 4 
0.34 8 16 Ni 56-83 182 
Exp. 5 
0.337 12.5 22.2 Ni 15-52 221 
Exp. 6 
0.339 8.5 14.2 Ni 31-74 172 
Exp. 7 
0.336 5.1 Co 20-55 171 
______________________________________ 
TABLE 1-c 
______________________________________ 
primary secondary 
particle particle 
diameter diameter 
shape structure (nm) (.mu.m) 
______________________________________ 
Com. spherical 
multiple spherical 
41 0.2 
Exp. 1 shell structure 
Com. spherical 
multiple spherical 
60 0.25 
Exp. 2 shell structure 
Com. indefinite 
ribbon-like 0.3 
Exp. 3 
Com. fibrous coaxial cylin- 0.2, 2.54 
Exp. 4 drical 
Com. spherical 
lamellar 400 6 
Exp. 5 structure 
Com. indefinite 
non-orientation 
700 
Exp. 6 
Com. spherical 
lamellar 400 6 
Exp. 7 structure 
Com. spherical 
non-orientation 
3000 
Exp. 8 
Com. fiber coaxial cylin- 
Exp. 9 drical 
Com. fiber radial 
Exp. 10 
Com. fiber non-orientation 
Exp. 11 
Com. indefinite 5000 41 
Exp. 12 
______________________________________ 
TABLE 1-d 
______________________________________ 
core 
particle 
discharge 
d (002) Lc La core diameter 
capacity 
(nm) (nm) (nm) particle 
(nm) (mAh/g) 
______________________________________ 
Com. 0.37 0.9 none 148 
Exp. 1 
Com. 0.358 2 19.4 none 156 
Exp. 2 
Com. 0.341 11 -- -- 108 
Exp. 3 
Com. 0.345 3.2 -- -- 124 
Exp. 4 
Com. 0.349 1.3 -- -- 117 
Exp. 5 
Com. 0.374 1.1 -- -- 76 
Exp. 6 
Com. 0.344 17.3 -- -- 113 
Exp. 7 
Com. 0.352 1.7 -- -- 75 
Exp. 8 
Com. 0.338 22 25.1 -- -- 150 
Exp. 9 
Com. 0.37 3.5 -- -- 100 
Exp. 10 
Com. 0.344 2.3 -- -- 70 
Exp. 11 
Com. 0.339 90 62 -- -- 60 
Exp. 12 
______________________________________ 
As the capacity, values at 0 to 0.5 V are given (values at 0 to 2.5 V are 
given in comparative examples 7 through 11. 
TABLE 2 
______________________________________ 
discharge capacity (mAh) 
average voltage 
10 cycles 
50 cycles (V) 
______________________________________ 
Example 8 8.8 8.7 3.71 
Example 9 9.4 9.2 3.69 
Example 10 9.2 8.8 3.73 
Example 11 9.0 8.9 3.75 
Example 12 9.5 9.2 2.98 
Example 13 8.9 8.7 2.92 
Comparative 6.0 5.7 3.57 
Example 13 
Comparative 7.2 6.9 3.56 
Example 14 
Comparative 2.9 1.5 3.35 
Example 15 
______________________________________ 
The primary particle diameter in the present invention means the diameter 
of minimum unit particles that can be observed with a transmitting type 
electron microscope, and is an average value obtained in the actual 
measurement of the particles at an accessible portion thereof. 
On the other hand, the secondary particle diameter means the diameter of a 
secondary body formed by the aggregation of the minimum unit of the 
primary particles, and is given as a value having a peak diameter in the 
particle size distribution obtained by a laser diffraction particle size 
analyzer (SHIMADZU CO. SALD-1100). 
Methods of measuring the size of crystals using the X-ray wide angle 
diffraction method include, known methods such as disclosed in Carbon 
Material Experiment Technique 1, pages 55 to 63 compiled by Carbon 
Material Society (Published by Science and Technology Publishing Company) 
and Japanese Laid-Open Patent No. SHO. 61-111907. In addition, the form 
factor used was 0.9. 
Example 2 
Carbon was prepared in the same manner as Example 1 except that nickel 
powder (250 mesh) 1.6 g was used in place of nickel oxide to give 21.6 g 
of carbon powder. The observation of carbon powder thus obtained with a 
transmitting type electron microscope showed that they had the same 
structure as Example 1. Primary particles having a diameter of 112 to 176 
nm were observed. The average diameter thereof was 156 nm. Nickel 
particles in the center had a diameter of 65 to 145 nm. The secondary 
particles had a diameter of 65 .mu.m as determined by the measurement 
using a laser diffraction type particle size distribution meter. This 
carbon powder was used to prepare and evaluate a carbon electrode in the 
same manner as Example 1. 
Example 3 
Carbon was prepared in the same manner as Example 1 except that iron 
oxalate (100 or less mesh) 3.8 g was used in place of nickel oxide to give 
18.1 g of carbon powder. The observation of carbon powder thus obtained 
with a transmitting type electron microscope showed that they had the same 
structure as Example 1. The primary particles having a diameter of 46 to 
72 nm were observed. The average diameter thereof was 68 nm and the iron 
particles in the center had a diameter of 23 to 48 nm. In addition, the 
secondary particles had a diameter of 10.5 .mu.m as determined by 
measurement using a laser diffraction particle size distribution meter. 
This carbon powder was used to prepare and evaluate a carbon electrode in 
the same manner as Example 1. 
Example 4 
Carbon was prepared in the same manner as Example 1 except that iron 
oxalate (100 or less mesh) 4.6 g was used in place of nickel oxide to give 
25.1 g of carbon powder. The observation of carbon powder thus obtained 
with a transmitting type electron microscope showed that it had the same 
structure as Example 1. Primary particles having a diameter of 100 to 170 
nm were observed. The average diameter thereof was 151 nm and the nickel 
particles in the center had a diameter of 52 to 83 nm. In addition, the 
secondary particles had a diameter of 30 .mu.m as determined by 
measurement using a laser diffraction particle size distribution meter. 
This carbon powder was used to prepare and evaluate a carbon electrode in 
the same manner as Example 1. 
Example 5 
A mixture of 3.1 g of nickel nitrate (100 mesh or less) in place of nickel 
and 1.3 g of and nickel oxide (100 mesh or less) was used to prepare 
carbon by subjecting to pyrolysis at the same gas flow rate equal to 
Example 1 for 3 hours at 850.degree. C., thereby providing 41.3 g of 
carbon powder. The observation of carbon thus given with a transmitting 
type electron microscope showed that the carbon had a structure similar to 
Example 1. In the observation, it was made clear that the primary particle 
had a diameter of 55 to 87 nm, or an average diameter of 72 nm and the 
nickel particle in the center had a diameter ranging from 15 to 52 nm. In 
addition, the second particle had a diameter of 14 .mu.m as determined by 
measurement using a laser diffraction type particle size distribution 
meter. This carbon powder was used to prepare and evaluate a carbon 
electrode in the same manner as Example 1. 
Example 6 
Nickel oxide powder (100 mesh or less) 1.8 g was placed on a sample base 6 
of a carbon preparing device shown in FIG. 2 and benzene was used as 
material gas to operate the device so as to provide 0.15 mol/hr of benzene 
and a gas flow rate of 25.3 cm/min. The temperature rising profile was set 
to 12.degree. C./min. from room temperature to 700.degree. C., and 
1.4.degree. C./min. from 700.degree. to 950.degree. C. The material 
benzene was pyrolyzed to prepare carbon to provide 32.7 g of carbon 
powder. The observation of carbon thus prepared with a transmitting type 
electron microscope showed that the carbon had the same structure as 
Example 1, the primary particle had a diameter ranging between 80 to 152 
nm, and an average diameter of 132 nm, and the nickel powder in the center 
had a diameter ranging between 31 to 74 nm. In addition, as determined by 
measurement using a laser diffraction particle size distribution meter, 
the second particle had a diameter of 12 .mu.m. This carbon powder was 
used to prepare and evaluate a carbon electrode in the same manner as 
Example 1. 
Example 7 
Carbon was prepared in the same manner as Example 1 except that cobalt 
oxalate powder (100 mesh or less) 4.6 g was used in place of nickel oxide 
powder to provide 18.1 g of carbon powder. The observation of carbon thus 
given with transmitting type electron microscope showed that the carbon 
had the same structure as Example 1. In the observation it was made clear 
that the particle had a diameter ranging from 52 to 113 nm, the particle 
had an average diameter of 84 nm, and the cobalt particle in the center 
had a diameter ranging from 20 to 55 nm. In the measurement using a laser 
diffraction type particle size distribution meter the secondary particle 
has a diameter 15.1 .mu.m. This carbon powder was used to prepare a carbon 
electrode in the same manner as Example 1. 
Example 8 
The carbon material 50 mg prepared in Example 1 was used to prepare a 
carbon electrode, which was used as an anode. This was followed by 
pressuring and molding 300 mg of an admixture of 80 parts by weight of 
LiCoO.sub.2, 10 parts by weight of acetylene black as a conductive 
material and 10 parts by weight of polytetrafluoroethylene powder as a 
binder to prepare a pellet having a diameter of 15 nm and drying such 
pellet in vacuo for 12 hours or more thereby providing a cathode. As an 
electrolyte was used an electrolyte solution consisting of 1M LiClO 
dissolved in a propylenecarbonate. Furthermore a polypropylene-made 
nonwoven cloth was used as a separator to prepare a coin type battery as 
shown in FIG. 2. Charge and discharge test was performed by setting a 
charge termination voltage to 4.1 V, a discharge termination voltage to 
2.7 V (3.3 V to 1.5 V in Examples 12 and 13) and a current value to 1 mA 
to determine an average voltage and discharge capacity from the 10th cycle 
of the discharge curve. Table 2 shows the result of the test. 
Example 9 
A coin type battery was prepared in the same manner as Example 8 except 
that Example 1 of carbon was used as a carbon material for an anode and as 
an electrolyte was used a solution in which LiPF.sub.6 was dissolved at a 
ratio of 1 mol dm.sup.-3 to a solvent propylenecarbonate and 
diethylcarbonate and methyltetrahydrofuran are mixed in a ratio of 5:5:1. 
Then a charge and discharge test was performed. The result of the test is 
shown in Table 2. 
Example 10 
A coin type battery was prepared in the same manner as Example 8 except 
that the carbon material of Example 1 was used as an anode material, a 
synthetic fluorine rubber was used as a binder of an anode, and as an 
electrolyte was used an electrolyte solution consisting of 1M LiClO 
dissolved in a 50/50 volume percent mixture of propylenecarbonate and 
diethylcarbonate. Then a charge and discharge cycle test was performed. 
Example 11 
A coin type battery was prepared in the same manner as Example 8 except 
that as a cathode LiNiO.sub.2 was used, as an anode the carbon obtained in 
Example 1 was used and as an electrolyte was used an electrolyte solution 
consisting of 1M LiClO dissolved in a 50/50 volume percent mixture of 
ethylenecarbonate and diethylcarbonate. Then a charge and discharge test 
was performed. 
Example 12 
A coin type battery was prepared in the same manner as Example 8 except 
that as a cathode was used V.sub.2 O.sub.5, as an anode was used the 
carbon obtained in Example 1 , and as an electrolyte solution consisting 
of 1M LiClO dissolved in a 50/50 volume percent mixture of 
propylenecarbonate and diethylcarbonate. Then a charge and discharge test 
was performed. 
Example 13 
A coin type battery was prepared in the same manner as Example 8 except 
that as a cathode was used MnO.sub.2, as an anode was used the carbon 
obtained in Example 1, and as an electrolyte was used an electrolyte 
solution consisting of 1M LiClO dissolved in a 50/50 volume percent 
mixture of ethylenecarbonate and diethylcarbonate. 
Example 14 
A coin type battery was prepared in the same manner as Example 8 except 
that as a cathode was used LiMnO.sub.2, as an anode was used carbon 
obtained in Example 3 and as an electrolyte was used an electrolyte 
solution consisting of 1M LiClO dissolved in a 50/50 volume percent 
mixture of propylenecarbonate and diethylcarbonate. Then a charge and 
discharge cycle test was performed. 
Comparative Example 1 
Soot generated by an incomplete combustion of propane gas at 1200.degree. 
C. was deposited on a quartz bar, which was collected to be used for the 
evaluation of the carbon material. The observation of the carbon with a 
transmitting type electron microscope showed that the carbon particles 
were spherical. Primary particles having a diameter of 21 to 65 nm were 
observed and the average particle diameter thereof was 41 nm. The 
secondary particles had a diameter of 0.2 .mu.m as determined by 
measurement using a laser diffraction type particle size distribution 
meter. This carbon powder was used to prepare and evaluate a carbon 
electrode in the same manner as Example 1. 
Comparative Example 2 
Ethylene bottom oil was incompletely combusted at 1800.degree. C. to 
prepare a carbon black, which was used as a carbon material for 
evaluation. The observation of this carbon with a transmitting type 
electron microscope showed that carbon particles were spherical. Primary 
particles having a diameter 43 to 106 nm were observed and the average 
diameter thereof was 60 nm. In addition, these spherical primary particles 
had incomplete concentric spherical structure as shown in FIG. 4. The 
secondary particles had a diameter of 0.025 .mu.m as determined 
measurement using a laser diffraction particle size distribution meter. 
This carbon material was used to prepare and evaluate a carbon material in 
the same manner as Example 1. 
Comparative Example 3 
Carbon black used in Example 2 was subjected to 12 hours heat treatment at 
2800.degree. C. to provide a carbon material to be used for evaluation. 
The observation of this carbon material with a transmitting type-electron 
microscope showed that no spherical particles were formed and the carbon 
material had a hollow distorted shape accompanied by an advanced 
crystallization. 
Comparative Example 4 
Vapor growth carbon fiber subjected to heat treatment at 1000.degree. C. 
was fragmented into small pieces to provide a carbon material. The 
observation of this carbon with a transmitting type electron microscope 
showed that the carbon had a fibrous configuration with an average 
thickness of 180 nm. Fine metal particles were observed on portions which 
can be regarded as a tip of fiber at the time of the growth thereof. Fine 
particles at the tip can be regarded as iron or a carbonated iron as seen 
from the fact that in the measurement using a laser diffraction particle 
size distribution meter the average particle diameter has two peaks of 
0.20 and 2.54 .mu.m. This carbon powder was used to prepare and evaluate a 
carbon electrode in the same manner as Example 1. 
Comparative Example 5 
Mesocarbon microbeads (products carbonated at 1000.degree. C.) were used as 
a carbon material for evaluation. The observation of this carbon material 
with a transmitting type electron microscope showed that the primary 
particle of the carbon had an average diameter of 400 nm. In the 
measurement using a laser diffraction particle size distribution meter the 
second particle diameter had a diameter of 6 .mu.m. This carbon powder was 
used to prepare and evaluate a carbon electrode in the same manner as 
Example 1. 
Comparative Example 6 
Activated carbon was fractured with a ball mill to be used as an active 
material. The observation of the activated carbon with a laser diffraction 
particle size distribution meter showed that the average diameter was 3.7 
.mu.m. This carbon was used in the same manner as Example 1 to prepare and 
evaluate a carbon electrode. 
Comparative Example 7 
Mesocarbon microbeads used in Comparative Example 5 were subjected to 12 
hours heat treatment at 2000.degree. C. to provide a carbon material for 
evaluation. The observation of these microbeads with a transmitting type 
electron microscope showed that the primary particle of carbon had an 
average particle diameter of 400 nm. This carbon powder was used to 
prepare and evaluate a carbon electrode in the same manner as Example 1. 
Comparative Example 8 
A spherical glassy carbon was used as a carbon material for evaluation. 
Measurement of these carbon materials with a laser diffraction type 
particle size distribution meter showed that the carbon had an average 
diameter of 13 .mu.m. The carbon material was used to prepare and evaluate 
a carbon electrode in the same manner as Example 1. 
Comparative Example 9 
A pitch base carbon fiber (subjected to 2600.degree. C. heat treatment) 
having an axial orientation (coaxial cylindrical structure) was used as a 
carbon material for evaluation. This carbon fiber 20 mg was bunched with a 
Ni line and dried in vacuo for 10 hours at 120.degree. C. to prepare and 
evaluate a carbon electrode in the same manner as Example 1. 
Comparative Example 10 
A pitch based carbon fiber (subjected to 2600.degree. C. heat treatment) 
having an axial orientation (radial orientation structure) was used as a 
carbon material for evaluation. This carbon fiber (20 mg) was bunched with 
a Ni line and dried in vacuo for 10 hours at 120.degree. C. to prepare and 
evaluate a carbon electrode in the same manner as Example 1. 
Comparative Example 11 
An active carbon fiber (heat treated at 2000.degree. C.) was used as a 
carbon material for evaluation. This carbon fiber was used to prepare and 
evaluate a carbon electrode in the same manner as Comparative Example 5. 
Comparative Example 12 
A device similar to the one used in Example 1 was used to deposit carbon on 
nickel powders (having an average diameter 3 .mu.m). As a material 
proprane gas was used while as a carrier argon gas was used. At a supply 
rate of 0.38 mol/hr and at a gas flow rate of 25.5 cm/hr, carbon was 
deposited for 40 minutes at a deposition temperature of 950.degree. C. to 
produce 1 g of nickel powders and 1.35 g of carbon powders. Microscopic 
observation of a carbon material thus obtained with a transmitting type 
electronic microscope showed that 1 to 3 .mu.m nickel powder was present. 
Carbon was deposited in such a manner that it covers the nickel powder, 
but no particular orientation was observed. The size of the secondary 
particle measured with a laser diffraction particle size distribution 
meter was 41 .mu.m. Carbon material powder thus obtained was used to 
prepare and evaluate a carbon electrode in the same manner as Example 1. 
Comparative Examples 13 through 15 
A coin type battery was prepared in the same manner as Example 8 except 
that carbon in Comparative Examples 3, 5, and 8 was used as a carbon 
material for anodes respectively in Comparative Examples 13, 14 and 15, 
followed by performing a charge and discharge test. 
Thus as described above, the effective area of contact with an electrolyte 
in an electrolyte reaction can be enlarged by using an approximately 
spherical carbon particle having a diameter of 5 .mu.m or less centering 
on the fine core particle. This facilitates intercalation and 
deintercalation between carbon layers on which the graphite-like layer is 
stacked. Owing to an increased ratio of carbon thus used, the capacity can 
be enlarged. 
Furthermore, with respect to the carbon material having a concentric 
spherical structure (onion-like structure) whose fine construction is not 
complete, the graphite-like layer of carbon arranged in a concentric 
configuration centering on the fine core particle thereof has a small 
width of the mean of interlayer spacing of (002) plane. This facilitates 
the intercalation and deintercalation of lithium between layers and 
further facilitates the diffusion of lithium into the graphite-like layer. 
Still further, the fine core particle having a catalyst action in the 
pyrolysis of carbon materials is added to increase the reaction rate and 
the crystallinity of carbon materials. Consequently, the crystal structure 
of graphite-like layer approximates a graphite structure so that the 
quantity of intercalation and deintercalation between lithium layers 
increases and the durability thereof can be improved owing to the stable 
structure.