Lithium secondary battery

Provided is a novel lithium secondary battery including a positive electrode including a compound capable of occluding and discharging lithium, a negative electrode composed mainly of a carbon material which includes a graphite as an only or as a principal component, a separator between the positive electrode and the negative electrode; and an electrolyte solution of an electrolyte solute dissolved in a solvent including at least one specific cyclic compound. The lithium secondary battery has a large capacity, small self-discharge rate and excellent cycle characteristics and high charge-discharge efficiency.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a lithium secondary battery, and more 
specifically to improvement of a carbon material for a negative electrode 
of a lithium secondary battery, or to improvement of both a negative 
electrode and an electrolyte solution of a lithium secondary battery. 
2. Description of the Prior Art 
In recent years, carbon materials have been studied, instead of 
conventional lithium alloys, for the use of negative electrode material 
for lithium secondary batteries because 1 they have high flexibility and 2 
they do not cause mossy-shaped lithium to precipitate by electrolysis. 
The carbon material that has principally been studied for this purpose is 
coke (see U.S. Pat. No. 4,725,422), and graphite has hardly been studied. 
For instance, U.S. Pat. No. 4,725,422 discloses a secondary battery 
comprising for the negative electrode a carbon material having the spacing 
of (002) planes, d.sub.002. of at least 3.37 .ANG. and the crystallite 
size in the direction of c axis, Lc of not more than 220 .ANG.. The above 
carbon material is a kind of coke. 
Coke, however, hardly provides large-capacity batteries, since the amount 
of lithium introduced with coke negative electrode is not sufficiently 
large. 
To the best of the knowledge of the present inventors, the literatures that 
propose a secondary battery having a negative electrode comprising 
graphite are only U.S. Pat. No. 4,423,125 and U.S. Pat. No. 5,130,211. 
The above U.S. Pat. No. 4,423,125 discloses a secondary battery comprising 
for the negative electrode a carbon material having occluded lithium as an 
active material and as an electrolyte solution a solution of an 
electrolyte solute of LiAsF.sub.6 dissolved in a solvent of 1,3-dioxolane. 
According to the USP, a secondary battery having excellent cycle 
characteristics can then be obtained. 
The above known secondary battery is, however, inferior in many features 
such as capacity per unit weight of graphite (mAh/g), initial charge and 
discharge efficiency (%), battery capacity (mAh), self-discharge rate 
(%/month) and charge and discharge efficiency (%), not to mention cycle 
characteristics (cycle life), as shown by the data for the "conventional 
battery" in the later-described Examples. The battery therefore is not 
sufficiently satisfactory for practical purposes. 
This is considered to be due to polymerization of 1,3-dioxolane in the 
negative electrode side (reduction side). 
The above U.S. Pat. No. 5,130,211 discloses a secondary battery comprising 
for the negative electrode a carbon material having a degree of 
graphitization greater than about 0.40 .ANG., i.e. the spacing of (002) 
planes, d.sub.002 smaller than about 3.412 .ANG.. The above known 
secondary battery, however, is not necessarily excellent in the features 
mentioned above. 
SUMMARY OF THE INVENTION 
Accordingly, an object of the invention is to provide a lithium secondary 
battery having a negative electrode comprising specified graphite, having 
a large capacity, small self-discharge rate and excellent cycle 
characteristics and still having high initial charge and discharge 
efficiency. 
The above object can be achieved by providing a lithium secondary battery 
comprising: 
a negative electrode composed mainly of a carbon material which comprises, 
as an only or as a principal component, a graphite having: 
(a) a d-value of the lattice plane (002) obtained by the X-ray diffraction 
method thereof of 3.354 to 3.370 and 
(b) a crystallite size in the c-axis direction obtained by the X-ray 
diffraction method thereof of at least 200 .ANG., 
a positive electrode composed mainly of a compound capable of occluding and 
discharging lithium and which is not the graphite used for the negative 
electrode; 
a separator between said positive electrode and said negative electrode; 
and 
an electrolyte solution of an electrolyte solute dissolved in a solvent.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Examples of the compound that constitutes the positive electrode material 
in the present invention and is capable of occluding and discharging 
lithium are, as inorganic compounds, oxides having what is known as 
tunnel-shaped pores, such as MnO.sub.2, TiO.sub.2 and V.sub.2 O.sub.5, and 
metal chalcogenides such as TiS.sub.2 and MoS.sub.2 having laminar 
structure, among which preferred are composite oxides represented by the 
formula Li.sub.x MO.sub.2, or Li .sub.y M.sub.2 O.sub.4, wherein M is a 
transition element and 0.ltoreq..times..ltoreq.1 and 0.ltoreq.y.ltoreq.2. 
Concrete examples of the composite oxides are LiCoO.sub.2, LiMnO.sub.2, 
LiNiO.sub.2, LiCrO.sub.2 and LiMn.sub.2 O.sub.4. 
The positive electrode material is kneaded with a conductor such as 
acetylene black or carbon black and a binder such as 
polytetrafluoroethylene (PTFE) or polyvinylidene fluoride (PVdF), and the 
obtained mixture is used as a material for preparing the positive 
electrode. 
At this time, among the above conductive polymers and dopant-containing 
conductive polymers, those having high conductivity may be kneaded only 
with a binder, without incorporation of any conductor. 
The graphite used as an only or a principal component of the carbon 
material of the negative electrode of the lithium secondary battery in the 
present invention has the following properties 1 and 2. 1 a d-value 
(d.sub.002) of the lattice plane (002) obtained by the X-ray diffraction 
method thereof of 3.354 to 3.370 (unit: .ANG.); and 2 a crystallite size 
(Lc) in the c-axis direction obtained by the X-ray diffraction method 
thereof of at least 200 .ANG.. 
The use of a graphite having the above properties 1 and 2 results in a 
lithium secondary battery having a large discharge capacity and high 
initial charge-discharge efficiency. If the graphite used as the principal 
component of the carbon material of the negative electrode of the lithium 
secondary battery of the present invention has a d-value and an Lc falling 
outside of the above range, the discharge capacity and initial 
charge-discharge efficiency will be significantly lower. 
When a graphite further having one of the following properties 3.about.5 in 
addition to the above properties 1 and 2 is used, better battery 
characteristics are obtained, as shown in the later-described Examples. 3 
an average particle diameter of 1 to 30 .mu.m; 4 a specific surface area 
of 0.5 to 50 m.sup.2 /g; and 5 a true density of 1.9 to 2.25 g/cm.sup.3. 
Further desirable properties of the graphite used in the present invention 
are as follows. The crystallite size in the a-axis direction obtained by 
the X-ray diffraction method thereof is at least 200 .ANG.; the atomic 
ratio of H/C is not more than 0.1 and the G-value (1360 cm .sup.-1 /1590 
cm.sup.-1) in Raman spectroscopic analysis is at least 0.05. 
Any kind of graphite can be suitably used in the present invention, whether 
it be natural graphite, artificial graphite or kish as long as it has the 
properties required of the graphite as explained above. Here, kish is a 
carbon material having higher crystallinity than natural graphite and 
formed, when in iron mills iron is melted in the blast furnace at a 
temperature of at least 2,000.degree. C., by sublimation and the 
succeeding deposition onto the furnace wall and recrystallization of the 
carbon contained in the iron. Further these graphites may as required be 
used in combination. The artificial graphite herein includes 
graphite-based substances formed by processing or modifying graphite, such 
as swollen graphite. 
Examples of natural graphite are Sri Lanka graphite, Madagascar graphite, 
Korea flake-graphite, Korea earth-graphite and China graphite, and an 
example of artificial graphite is coke-origin-graphite. 
Table 1 shows the d-values of the lattice plane (002) and Lc's obtained by 
the X-ray diffraction method of the above natural graphites and artificial 
coke-origin-graphite. 
TABLE 1 
______________________________________ 
Lattice constant 
Crystallite 
d(002) (.ANG.) 
size, Lc (.ANG.) 
______________________________________ 
Natural graphite 
Sri Lanka 3.358 &gt;1,000 
Madagascar 3.359 &gt;1,000 
Korea (flake) 3.360 &gt;1,000 
Korea (earth) 3.365 230 
China 3.354 &gt;1,000 
Artificial coke- 
3,364 350 
origin-graphite 
______________________________________ 
Examples of commercially available natural graphite used in the present 
invention are "NG-2", "NG-2L", "NG-4", "NG-4L", "NG-7", "NG-7L", "NG-10", 
"NG-10L", "NG-12", "NG-12L", "NG-14" and "NG-14L", which are high-purity 
graphite having a purity of at least 99% and made by The Kansai Coke and 
Chemicals Co., Ltd.; "CX-3000", "FBF", "BF", "CBR", "SSC-3000", "SSC-600", 
"SSC-3", "SSC", "CX-600", "CPF-8", "CPF-3", "CPB-6S", "CPB", "96E", "96L", 
"96L-3", "90L-", "CPC", "S-87" and "K-3", (the foregoing are 
flake-graphites) and "S-3" and "AP-6", (the foregoing are earth-graphites) 
which are made by Chuetsu Graphite Works Co., Ltd.; "CSSP", "CSPE", "CSP" 
and "Super-CP", (the foregoing are flake-graphites), and "ACP-1000", 
"ACP", "ACB-150", "SP-5", "SP-5L", "SP-10", "SP-10L", "SP-20", "SP-20L" 
and "HOP" (the foregoing are high-purity graphite having a purity of at 
least 97.5%) which are made by Nippon Kokuen L.T.D. 
Examples of commercially available artificial graphites usable in the 
present invention are "RA-3000", "RA-15", "RA-44", "GX-600" and "G-6S" 
which are made by Chuetsu Graphite Works Co., Ltd.; "HAG-15", "PAG-15", 
"SGS-25", "SGS-15", "SGS-5", "SGS-1", "SGP-25", "SGP-15", "SGP-5", 
"SGP-1", "SGO-25", "SGO-15", "SGO-5", "SGO-1", "SGX-25", "SGX-15", "SGX-5" 
and "SGX-1" made by Nippon Kokuen L.T.D., as well as high-purity graphite 
having a purity of at least 99.9% from the same manufacturer, including 
"QP-2", "QP-5", "QP-10" and "QP-20". 
Examples of commercially available artificial graphites produced by further 
processing or modifying graphite are "APO-Pi5", "AOP-B5", "AOP-A5" and 
"AOP-T1" which are made by Nippon Kokuen L.T.D. and have increased 
dispersibility into resins by surface-treating natural graphite powder 
with pitch, an acrylic resin or a titanate. 
Kish as described before and available from The Kansai Coke and Chemicals 
Co., Ltd., which does not fall into the category of the above natural and 
artificial graphites, is also usable as the carbon material of the present 
invention. 
The carbon material used in the present invention may consist only of one 
of the above graphites or, may comprise it as a principal component while 
incorporating other carbon materials. 
The electrolyte solution used in the present invention utilizes a solvent 
comprising a specific organic compound, that is, at least one cyclic 
compound selected from the group consisting of ethylene carbonate (EC), 
ethylene thiocarbonate, .gamma.-thiobutyrolactone, .alpha.-pyrrolidone, 
.gamma.-butyrolactone (.gamma.-BL), propylene carbonate, 1,2-butylene 
carbonate, 2,3-butylene carbonate, .gamma.-valerolactone, 
.gamma.-ethyl-.gamma.-butyrolactone, .beta.-methyl-.gamma.-butyrolactone, 
thiolane, pyrazolidine, pyrrolidine, tetrahydrofuran, 
3-methyltetra-hydrofuran, sulfolane, 3-methylsulfolane, 2-methylsulfolane, 
3-ethylsulfolane and 2-ethylsulfolane. 
Preferred among the above cyclic compounds are those having no 
readily-decomposable groups, i.e. ethylene carbonate, ethylene 
thiocarbonate, .gamma.-thiobutyrolactone, .alpha.-pyrrolidone, 
.gamma.-butyrolactone, thiolane, pyrazolidine, pyrrolidine, 
tetrahydrofuran and sulfolane. These preferred cyclic compounds are stable 
and do not generate gases under the oxidation-reduction atmosphere during 
charge and discharge of the battery and in this point differ from other 
cyclic compounds having readily decomposable methyl groups or the like 
which are readily absorbed on active points of graphite, such as propylene 
carbonate, 1,2-butylene carbonate, 2,3-butylene carbonate, 
.gamma.-valerolactone, .gamma.-ethyl-.gamma.-butyrolactone and 
.beta.-methyl-.gamma.-butyrolactone. Thus, with the preferred cyclic 
compounds insertion of lithium into graphite is not hindered during charge 
and there does not occur polarization due to gas overpotential during 
charge or discharge. 
The electrolyte solution in the present invention may comprise only one of 
the above solvents or, as required, two or more. 
Examples of preferred solvents are, those consisting of single solvent, 
such as ethylene carbonate, .gamma.-butyrolactone and sulfolane, mixed 
solvents comprising ethylene carbonate and .gamma.-butyrolactone and mixed 
solvents comprising ethylene carbonate, .gamma.-butyrolactone and 
sulfolane, among which more preferred for the purpose of providing a large 
battery capacity and high initial charge-discharge efficiency are ethylene 
carbonate, .gamma.-butyrolactone and sulfolane. Particularly preferred is 
ethylene carbonate. 
Where a mixed solvent of ethylene carbonate with .gamma.-butyrolactone or 
sulfolane is used, the use of a mixed solvent containing 20% to 80% by 
volume of ethylene carbonate results in remarkably large battery capacity 
in high-rate discharge. 
Ethylene carbonate (m.p.: 39.degree. to 40.degree. C.) or sulfolane (m.p.: 
28.9.degree. C.), which is solid at room temperature, may be used after 
being dissolved in an ether-based low-boiling point solvent, such as 
1,2-dimethoxyethane (DME), 1,2-diethoxy-ethane (DEE) or 
ethoxymethoxyethane (EME) or an ester-based low-boiling point solvent such 
as dimethyl carbonate (DMC) or diethyl carbonate (DEC). Even 
.gamma.-butyrolactone, which is liquid at room temperature, is preferably 
used in the form of a mixed solvent comprising one of the above 
low-boiling point solvents, for the purpose of permitting the resulting 
battery to develop excellent low-temperature characteristics. 
Among the mixed solvents used in the present invention and comprising a 
cyclic compound and a low-boiling point solvent, those comprising a cyclic 
carbonate and dimethyl carbonate are excellent in, particularly, high-rate 
discharge characteristics thanks to high conductivity of dimethyl 
carbonate, while those comprising a cyclic carbonate and diethyl carbonate 
are particularly excellent in low-temperature discharge characteristic 
thanks to the low viscosity and high ion conductivity at low temperatures 
of diethyl carbonate. 
The term "low-boiling point solvents" herein means those having a boiling 
point of not more than 150.degree. C. 
Where mixed solvents comprising one of the above low-boiling point solvents 
and ethylene carbonate is used, the use of a mixed solvent containing 20% 
to 80% by volume of ethylene carbonate results in remarkably large battery 
capacity in high-rate discharge. When a mixed solvent containing at least 
20% by volume of ethylene carbonate is used as an electrolyte solvent, the 
lithium secondary battery of the present invention will have a remarkably 
large discharge capacity. 
The electrolyte solution in the present invention is prepared by 
dissolving, in the above-described solvent, an electrolyte solute such as 
LiPF.sub.6, LiBF.sub.4, LiClO.sub.4, LiCF.sub.3 SO.sub.3, LiC.sub.4 
F.sub.9 SO.sub.3, LiN(CF.sub.3 SO.sub.2).sub.2 or LiAsF.sub.6. 
These solutes are dissolved in the solvent to a concentration of preferably 
0.1 to 3 moles/liter, more preferably 0.5 to 1.5 moles/liter. 
FIG. 1 is a graph showing the charge-discharge cycle characteristics of the 
battery of the present invention comprising graphite (Lc: 2000 .ANG.; 
d.sub.002 : 3.354 .ANG.; Average Particle Diameter: 12 .mu.m; Specific 
Surface Area: 7.5 m.sup.2 /g; True Density: 2.25 g/cm.sup.3) as a negative 
electrode material and a comparison battery comprising coke (Lc: 45 .ANG.; 
d.sub.002 : 3.462 .ANG.; Average Particle Diameter: 14 .mu.m; Specific 
Surface Area: 4.2 m.sup.2 /g; True Density: 2.04 g/cm.sup.3) as a negative 
electrode. The ordinate of the graph represents the potential of the 
negative electrode against Li/Li.sup.+ single electrode potential, and 
the abscissa represents the capacity (mAh/g) per gram of the carbon 
material (graphite or coke). 
In the FIGURE, the solid line shows the charge-discharge cycle 
characteristics of the battery of the present invention and the broken 
line that of the comparison battery, while the arrow marks indicate the 
direction of the negative electrode potential increasing or decreasing, 
during discharge or charge. The charge-discharge characteristics of the 
FIGURE were obtained with the batteries both utilizing an electrolyte 
solvent of a 1/1 by volume mixed solvent of ethylene carbonate and 
dimethyl carbonate containing 1M (mole/liter) LiPF.sub.6. 
The charge-discharge characteristic of the comparison battery are first 
explained with reference to FIG. 1. The negative electrode potential, 
which is about 3 (V) before initial charge (point a), gets closer to the 
Li/Li+ single electrode potential (this is the base, i.e. 0 V, for the 
negative electrode potential values of the ordinate), as the initial 
charge proceeds and Li is occluded in coke, and finally reaches the point 
b (negative electrode potential: 0 V, capacity: about 300 mAh/g). The 
color of coke turns light brown or red at this point. The first discharge 
is then conducted. The negative electrode potential increases with the 
proceeding of the discharge and finally reaches the point c (capacity: 50 
to 100 mAh/g) that shows discharge termination potential (about 1 V). In 
the course of the first discharge the negative electrode potential does 
not retrace the route followed during the initial charge but reaches the 
point c, thus presenting hysteresis. This is due to the fact that an 
amount of Li corresponding to P in the FIGURE has been caught by the coke 
and that, in the electrode reaction during the succeeding charge-discharge 
cycles, only the remaining Li in an amount of Q can participate in the 
reaction. The negative electrode potential changes, when charge-discharge 
cycle is repeated thereafter, in cycles as c.fwdarw.b.fwdarw.c.fwdarw.b . 
. . . 
The charge-discharge cycle of the battery of the present invention is next 
explained. In the same manner as with the comparison battery, the negative 
electrode potential, which is about 3 (V) before initial charge (point a), 
gets closer to the Li/Li.sup.+ single electrode potential, as the initial 
charge proceeds and Li is occluded in graphite, and finally reaches the 
point d where the potential against the single electrode potential is 0 V 
(capacity: 375 mAh/g). The color of graphite turns gold at the point d, 
which, as well as X-ray diffraction, indicates that C.sub.6 Li has been 
formed. The first discharge is then conducted. The negative electrode 
potential increases with the proceeding of the discharge and finally 
reaches the point e (capacity: 25 mAh/g) that shows discharge termination 
potential (about 1 V). The negative electrode potential changes, when 
charge-discharge cycle is repeated thereafter, in cycles as 
e.fwdarw.d.fwdarw.e.fwdarw.d . . . . 
The battery characteristics of the battery of the present invention and 
that of comparison are compared based on the charge-discharge 
characteristics shown in FIG. 1. The battery of the present invention has 
a large initial charge capacity per gram of graphite of about 375 mAh/g 
(point d) at the initial charge, while the comparison battery has a small 
charge capacity per gram of coke of about 300 mAh/g (point b). 
Furthermore, with the battery of the present invention the capacity per 
gram of graphite up to the discharge termination potential, 1 V, is as 
large as about 350 mAh/g (d-e), while that per gram of coke with the 
comparison battery is as small as 200 to 250 mAh/g (b-c). 
This fact means that the battery of the present invention has higher 
charge-discharge efficiency than that of the comparison battery. 
It is also noted that: while the charge-discharge curve of the battery of 
the present invention is almost flat during discharge of from the point d 
to e and shows a rapid increase of negative electrode potential when the 
discharge process comes close to the point e, the charge-discharge curve 
of the comparison battery gradually increases when proceeding from the 
point b to c. 
This fact means that the battery of the present invention is superior to 
the comparison battery in the flatness of discharge voltage. 
That the battery of the present invention has higher charge-discharge 
efficiency and flatter discharge voltage than those of the comparison 
battery further means that the battery of the present invention has larger 
discharge capacity than the comparison battery. 
Other features of the invention will become apparent in the course of the 
following description of exemplary embodiments which are given for 
illustration of the invention and are not intended to be limiting thereof. 
EXAMPLES 
Example 1 (Example 1--1.about.1-3) 
(Preparation of Positive Electrode) 
Cobalt carbonate and lithium carbonate were mixed in a atom ratio of Co:Li 
of 1:1, and the mixture was heat treated at 900.degree. C. in the air for 
20 hours to give LiCoO.sub.2. 
The LiCoO.sub.2 thus obtained as a positive electrode material was mixed 
with a conductor of acetylene black and a binder of fluororesin dispersion 
0.1 g/cc of polytetrafloroethylene (PTFE) dispersed in water! in a ratio 
by weight of 90:6:4 to give a material for preparing a positive electrode. 
The material was rolled onto an aluminum foil (thickness: 20 .mu.m) that 
served as a current collector and heat treated under vacuum at a 
temperature of 250.degree. C. for 2 hours, to give a positive electrode. 
(Preparation of negative electrode) 
Materials for preparing a negative electrode were obtained by mixing each 
of China natural graphite (Lc&gt;1000 .ANG.; d.sub.002 =3.354 .ANG.; Average 
Particle Diameter: 12 .mu.m; Specific Surface Area: 7.5 m.sup.2 /g; True 
Density: 2.25 g/cm.sup.3), artificial graphite (Lc=350 .ANG.; d.sub.002 
=3.364 .ANG.; Average Particle Diameter: 10 .mu.m; Specific Surface Area: 
10 m.sup.2 /g; True Density: 2.25 g/cm.sup.3), and Lonza graphite (Lc=260 
.ANG.; d.sub.002 =3.363 .ANG.; Average Particle Diameter: 15 .mu.m; 
Specific Surface Area: 14.0 m.sup.2 /g; True Density: 2.25 g/cm.sup.3), 
all with a particle diameter of 2 .mu.m to 14 .mu.m (average particle 
diameter: 12 .mu.m), with a binder of fluororesin dispersion 0.1 g/cc of 
PTFE dispersed in water! in a ratio by weight of 95:5. These materials 
were each rolled on a current collector of an aluminum foil (thickness: 20 
.mu.m) and heat treated under vacuum at 250.degree. C. for 2 hours, to 
give negative electrodes each containing one of the above carbon 
materials. When a graphite having an average particle diameter of 1 to 30 
.mu.m is used for the negative electrode, the lithium secondary battery of 
the present invention will have a large discharge capacity and high 
initial charge-discharge efficiency. 
(Preparation of Electrolyte Solution) 
An electrolyte solution was prepared by dissolving LiPF6 in a 1/1 by volume 
mixed solvent of ethylene carbonate and dimethyl carbonate to a 
concentration of 1 mole/liter. The use of ethylene carbonate in an amount 
of 20% to 80% by volume based on the volume of the solvent results in 
remarkably large discharge capacity. 
(Preparation of batteries BA 1 through 3) 
Cylindrical nonaqueous electrolyte solution secondary batteries (battery 
size: 4.2 mm diameter, 50.0 mm height) were prepared from the above 
positive electrode, negative electrode and electrolyte. BA1, BA2 and BA3 
denote those utilizing, as a carbon material, natural graphite (Example 
1--1), artificial graphite (Example 1-2) and Lonza graphite (Example 1-3), 
respectively. An ion-permeable polypropylene sheet (CELGARD, made by 
Daicel Co.) was used as a separator. 
FIG. 2 is a sectional view of the thus prepared battery BA1 (or 2, or 3), 
which comprises a positive electrode 1, a negative electrode 2, a 
separator 3 interposed between and separating these two electrodes, a 
positive electrode lead 4, a negative electrode lead 5, a positive 
electrode external terminal 6, a negative electrode can 7 and other parts. 
The positive electrode 1 and the negative electrode 2 are housed in the 
negative electrode can 7, while being spirally wound up with the separator 
3 inter-posed between them, the separator containing an electrolyte 
solution injected thereinto. The positive electrode 1 is connected via the 
positive electrode lead 4 to the positive electrode external terminal 6 
and the negative electrode 2 is connected via the negative electrode lead 
5 to the negative electrode can 7. The battery is thus capable of 
permitting the chemical energy generated inside it to be taken out as 
electrical energy. 
Comparison Example 1 
Example 1-1 was repeated except for using coke (Lc=45 .ANG.; d.sub.002 
=3.462 .ANG.; Average Particle Diameter: 14 .mu.m; Specific Surface Area: 
4.2 m.sup.2 /g; True Density: 2.04 g/cm.sup.3) as a negative electrode 
material, to prepare a comparison battery BC1. 
Charge-Discharge Characteristics of the Batteries 
FIG. 3 is a graph showing the charge-discharge characteristics at 250 mA 
(constant-current discharge) from the second cycle on of the batteries BA1 
through BA3 of the present invention and the comparison battery BC1, where 
the ordinate represents the voltage (V) and the abscissa represents the 
time (h). FIGS. 4 and 5 each show the charge-discharge characteristics of 
the battery BA1 or BA2 as compared with that of the comparison battery 
BC1, where the ordinate represents the negative electrode potential (V) 
against Li/Li.sup.+ single electrode potential and the abscissa 
represents the charge-discharge capacity (mAh/g). It is understood from 
these FIGURES that the batteries BA1 through BA3 of the present invention 
are superior to the comparison battery BC1 in charge-discharge 
characteristics. FIG. 6 is a graph showing the cycle characteristics of 
the batteries BA1 and BA2 of the present invention and the comparison 
battery BC1, with the ordinate representing the discharge capacity (mAh/g) 
and the abscissa the cycle number. As seen from the FIGURE, the batteries 
BA1 and BA2 of the present invention develop better cycle characteristics 
than the comparison battery BC1. These batteries were also, after being 
charged, kept at a room temperature for 1 month and tested for storage 
capability. Then, the self-discharge rate was 2 to 5%/month for the 
batteries BA1 through BA3 of the present invention and 15%/month for the 
comparison battery BC1. 
Example 2 
Example 1--1 was repeated except for using, instead of the China natural 
graphite, a mixture of 100 parts by weight of the natural graphite and 5 
parts by weight of carbon black having an Lc of 8 .ANG., to obtain a 
battery, BA5, according to the present invention. 
FIG. 7 is a graph showing the cycle characteristics of the thus prepared 
battery BA5, where the ordinate represents the discharge capacity of the 
battery (mAh/g) and the abscissa the cycle number. FIG. 7 also shows for 
comparison purposes the cycle characteristics of the battery BA1 utilizing 
as a carbon material graphite only and the battery BC1 utilizing coke. 
As seen from the FIGURE, the battery BA5 develops, thanks to little 
dropping off of the carbon material from the electrode, better cycle 
characteristics than that utilizing graphite only, to say nothing of that 
utilizing coke. 
Example 3 
Example 1--1 was repeated except for using, instead of the 1/1 by volume 
mixed solvent of ethylene carbonate (EC) and dimethyl carbonate (DMC) as 
an electrolyte solvent, a 1/1 by volume mixed solvent of ethylene 
carbonate and diethyl carbonate (DEC), a 1/1 by volume mixed solvent of 
ethylene carbonate and dipropyl carbonate (DPC) and 1,3-dioxolane 
(1,3-DOL), respectively, to prepare a battery BA6 according to the present 
invention, a comparison battery BC2 and a conventional battery. 
FIG. 8 is a graph showing the charge-discharge characteristics of these 
batteries, with the ordinate representing the negative electrode potential 
(V) and the abscissa representing the charge-discharge capacity. 
As seen from the FIGURE, the battery BAS develops, like that of BA1, better 
charge-discharge characteristics than the comparison battery BC2 and the 
conventional battery. 
Example 4 
Negative electrodes were prepared from 13 types of carbon materials having 
different d-values (d.sub.002) of the lattice plane (002) obtained by the 
X-ray diffraction method thereof. The properties of the carbon materials 
are shown in Table 2. The X-ray diffraction method was conducted under the 
following measuring conditions (hereinafter the same will apply). 
Radiation source: CuK .alpha. 
Slit conditions: divergence slit 1.degree., scattering slit 1.degree. and 
receiving slit 0.3 mm. 
Gonioradius: 180 mm 
Graphite curved crystalline monochromator. 
Using the 13 negative electrodes thus prepared 13 batteries were obtained 
in the same manner as in Example 1. 
FIG. 9 is a graph showing the relationship between the d.sub.002 value of a 
carbon material and the discharge capacity of the battery utilizing it, 
with the ordinate representing the discharge capacity (mAh/g) of the 
battery and the abscissa the d.sub.002 value of the carbon material used. 
As seen from the FIGURE, batteries utilizing a graphite having a d.sub.002 
of 3.354 to 3.370 have large discharge capacities. 
TABLE 2 
__________________________________________________________________________ 
K1 K2 K3 K4 K5 K6 K7 K8 K9 K10 
K11 
K12 
K13 
__________________________________________________________________________ 
d.sub.002 (.ANG.) 
3.354 
3.368 
3.378 
3.385 
3.401 
3.440 
3.569 
3.495 
3.556 
3.630 
3.710 
3.742 
3.781 
Lc (.ANG.) 2000 
2000 
810 
620 
43 30 25 11 9 12 15 17 8 
True Density (g/cm.sup.3) 
2.25 
2.25 
2.13 
2.10 
1.98 
1.92 
1.86 
1.72 
1.61 
1.45 
1.31 
1.13 
1.02 
Specific Surface Area (m.sup.2 /g) 
7.5 
6.3 
6.9 
7.0 
6.9 
7.2 
8.9 
9.3 
7.1 
6.8 
7.5 
8.1 
6.9 
Average Particle Diameter (.mu.m) 
12 
14 
12 
12 
12 10 15 12 14 16 11 12 12 
__________________________________________________________________________ 
Example 5 
Negative electrodes were prepared from 12 types of carbon materials having 
different true densities. The properties af the carbon materials are shown 
in Table 3. Using the 12 negative electrodes thus prepared 12 batteries 
were obtained in the same manner as in Example 1. 
FIG. 10 is a graph showing the relationship between the true density of a 
carbon material and the discharge capacity of the battery utilizing it, 
with the ordinate representing the discharge capacity (mAh/g) of the 
battery and the abscissa the true density (g/cm.sup.3) of the carbon 
material used. 
As seen from the FIGURE, batteries utilizing a graphite having a true 
density of 1.9 to 2.25 g/cm.sup.3 have large discharge capacities. 
TABLE 3 
__________________________________________________________________________ 
M1 M2 M3 M4 M5 M6 M7 M8 M9 M10 
M11 
M12 
__________________________________________________________________________ 
d.sub.002 (.ANG.) 
3.354 
3.354 
3.354 
3.370 
3.363 
3.377 
3.359 
3.363 
3.398 
3.440 
3.490 
3.601 
Lc (.ANG.) 790 
440 
2000 
410 
220 
205 
190 
175 
8.5 
18 12 11 
True Density (g/cm.sup.3) 
2.30 
2.29 
2.25 
2.15 
2.00 
1.91 
1.87 
1.80 
1.68 
1.52 
1.30 
1.03 
Specific Surface Area (m.sup.2 /g) 
6.9 
7.2 
7.5 
7.0 
6.1 
7.1 
7.0 
6.0 
7.0 
7.8 
9.9 
12 
Average Particle Diameter (.mu.m) 
12 
12 
12 
12 
16 
12 
10 
16 
12 14 12 14 
__________________________________________________________________________ 
Example 6 
Negative electrodes were prepared from 9 types of carbon materials having 
different average particle diameter. The properties of the carbon 
materials are shown in Table 4. Using the 9 negative electrodes thus 
prepared 9 batteries were obtained in the same manner as in Example 1. 
FIG. 11 is a graph showing the relationship between the average particle 
diameter (wherein the cumulative volume is 50% in particle size 
distribution) of a carbon material and the discharge capacity of the 
battery utilizing it, with the ordinate representing the discharge 
capacity (mAh/g) of the battery and the abscissa the average particle 
diameter (.mu.m) of the carbon material used. 
As seen from the FIGURE, batteries utilizing a graphite having an average 
particle diameter of 1 to 30 .mu.m have large discharge capacities. 
TABLE 4 
__________________________________________________________________________ 
N1 N2 N3 N4 N5 N6 N7 N8 N9 
__________________________________________________________________________ 
d.sub.002 (.ANG.) 
3.354 
3.354 
3.354 
3.354 
3.354 
3.354 
3.354 
3.354 
3.354 
Lc (.ANG.) 2000 
2000 
2000 
2000 
2000 
2000 
2000 
2000 
2000 
True Density (g/cm.sup.3) 
2.23 
2.23 
2.23 
2.23 
2.23 
2.23 
2.23 
2.23 
2.23 
Specific Surface Area (m.sup.2 /g) 
75 
30 
18 
15 
8.5 
2.0 
1.0 
0.3 
0.2 
Average Particle Diameter (.mu.m) 
0.25 
0.5 
1 
3 
10 
20 
30 
40 
50 
__________________________________________________________________________ 
Example 7 
Negative electrodes were prepared from 13 types of carbon materials having 
different specific surface areas. The properties of the carbon materials 
are shown in Table 5. Using the 13 negative electrodes thus prepared 13 
batteries were obtained in the same manner as in Example 1. 
FIG. 12 is a graph showing the relationship between the specific surface 
area (obtained a BET method employing N2 gas) of a carbon material and the 
discharge capacity of the battery utilizing it, with the ordinate 
representing the discharge capacity (mAh/g) of the battery and the 
abscissa the specific surface area (m.sup.2 /g) of the carbon material 
used. 
As seen from the FIGURE, batteries utilizing a graphite having a specific 
surface area of 0.5 to 50 m.sup.2 /g have large discharge capacities. 
TABLE 5 
__________________________________________________________________________ 
P1 P2 P3 P4 P5 P6 P7 P8 P9 P10 
P11 
P12 
P13 
__________________________________________________________________________ 
d.sub.002 (.ANG.) 
3.354 
3.354 
3.354 
3.354 
3.354 
3.354 
3.354 
3.354 
3.354 
3.354 
3.354 
3.354 
3.354 
Lc (.ANG.) 2000 
2000 
2000 
2000 
2000 
2000 
2000 
2000 
2000 
2000 
2000 
2000 
2000 
True Density (g/cm.sup.3) 
2.23 
2.23 
2.23 
2.23 
2.23 
2.23 
2.23 
2.23 
2.23 
2.23 
2.23 
2.23 
2.23 
Specific Surface Area (m.sup.2 /g) 
0.1 
0.4 
0.6 
1.0 
2.0 
3.3 
6.2 
12 
20 
40 
60 
100 
1000 
Average Particle Diameter (.mu.m) 
80 
38 
35 
30 
20 
16 
14 
5 
0.6 
0.4 
0.3 
0.15 
0.05 
__________________________________________________________________________ 
Example 8 
Negative electrodes were prepared from 11 types of carbon materials having 
different Lc's. The properties of the carbon materials are shown in Table 
6. Using the 11 negative electrodes thus prepared 11 batteries were 
obtained in the same manner as in Example 1. 
FIG. 13 is a graph showing the relationship between the Lc of a carbon 
material and the discharge capacity of the battery utilizing it, with the 
ordinate representing the discharge capacity (mAh/g) of the battery and 
the abscissa the Lc (.ANG.) of the carbon material used. 
As seen from the FIGURE, batteries utilizing a graphite having an Lc of at 
least 200 .ANG. have large discharge capacities. 
TABLE 6 
__________________________________________________________________________ 
Q1 Q2 Q3 Q4 Q5 Q6 Q7 Q8 Q9 Q10 
Q11 
__________________________________________________________________________ 
d.sub.002 (.ANG.) 
3.49 
3.46 
3.47 
3.47 
3.48 
3.376 
3.377 
3.367 
3.359 
3.359 
3.354 
Lc (.ANG.) 10 30 70 100 
115 
120 
150 
210 
1000 
1500 
2000 
True Density (g/cm.sup.3) 
1.90 
1.89 
1.89 
1.97 
1.99 
1.70 
1.80 
2.03 
2.24 
2.25 
2.25 
Specific Surface Area (m.sup.2 /g) 
6.5 
7.2 
8.1 
6.3 
7.2 
6.9 
7.0 
6.3 
6.7 
7.0 
7.5 
Average Particle Diameter (.mu.m) 
16 14 18 11 
12 
12 
12 
14 
11 
9 
12 
__________________________________________________________________________ 
Example 9 
Example 1--1 was repeated except for using mole/liter electrolyte solutions 
of LiPF.sub.6 in solvents as shown in Table 7, to prepare 21 types of 
batteries according to the present invention. The batteries thus prepared 
were discharged at 100 mA and tested for their graphite characteristics 
capacity per unit weight (mAh/g) and initial charge-discharge efficiency 
(%)!, battery characteristics battery capacity (mAh), self-discharge rate 
(%/month), cycle life (times) and charge-discharge efficiency (%)!. The 
results are shown in Table 7. 
Comparative Example 2 
Example 1--1 was repeated except for using an electrolyte solution of a 1 
mole/liter LiPF.sub.6 solution in 1,3-dioxolane, to prepare a conventional 
battery. The battery thus prepared was discharged at 100 mA and then 
tested for the same items as those in Example 9. The results are also 
shown in Table 7. 
TABLE 7 
__________________________________________________________________________ 
Graphite characteristics 
Battery characteristics 
(+) LiCoO.sub.2 /(-) graphite 
Capacity per 
Initial charge- 
Self- Cycle 
Charge-discharge 
Single solvent shown below 
unit weight 
discharge efficiency 
Capacity 
discharge rate 
life efficiency 
__________________________________________________________________________ 
Ethylene carbonate 
350 95 600 5 &gt;1,000 
100 
Propylene carbonate 
230 60 420 25 &gt;500 97 
1,2-Butylene carbonate 
270 65 360 20 &gt;300 95 
2,3-Butylene carbonate 
200 60 400 25 &gt;300 95 
Ethylene thiocarbonate 
190 80 350 10 &gt;300 95 
.gamma.-Thiobutyrolactone 
200 85 400 10 &gt;300 95 
.alpha.-pyrrolidone 
180 75 380 10 &gt;300 95 
.gamma.-butyrolactone 
320 95 500 5 &gt;1,000 
100 
valerolactone 
230 90 360 10 &gt;500 97 
.gamma.-ethyl-.gamma.-butyrolactone 
190 85 380 10 &gt;500 97 
.beta.-methyl-.gamma.-butyrolactone 
170 80 380 10 &gt;300 95 
Thiolane 200 80 400 15 &gt;300 95 
Pyrazolidine 
190 80 380 15 &gt;500 97 
Pyrrolidine 180 85 380 10 &gt;300 95 
Tetrahydrofuran 
230 90 420 10 &gt;500 97 
3-Methyltetrahydrofuran 
220 80 420 15 &gt;300 95 
Sulfolane 300 95 480 5 &gt;1,000 
100 
3-Methylsulfolane 
280 85 450 10 &gt;500 97 
2-Methylsulfolane 
260 80 450 10 &gt;500 97 
3-Ethylsulfolane 
250 85 440 15 &gt;300 95 
2-Ethylsulfolane 
250 85 440 15 &gt;300 95 
1,3-dioxolane 
100 60 150 50 &lt;50 70 
__________________________________________________________________________ 
Example 10 
Example 1--1 was repeated except for using electrolyte solutions of a 1 
mole/liter LiPF.sub.6 solution in each of the mixed solvents as shown in 
Table 8, to prepare 21 types of batteries according to the present 
invention. The batteries thus prepared were discharged at 100 mA and then 
tested for the same items as those in Example 9. The results are also 
shown in Table 8. 
TABLE 8 
__________________________________________________________________________ 
(+) LiCoO.sub.2 /(-) graphite 
Graphite characteristics 
Battery characteristics 
Dimethyl carbonate:solvent 
Capacity per 
Initial charge- 
Self- Cycle 
Charge-discharge 
shown below = 1:1 
unit weight 
discharge efficiency 
Capacity 
discharge rate 
life efficiency 
__________________________________________________________________________ 
Ethylene carbonate 
355 95 610 5 &gt;1,000 
100 
Propylene carbonate 
235 60 425 25 &gt;500 97 
1,2-Butylene carbonate 
270 65 360 20 &gt;300 95 
2,3-Butylene carbonate 
200 60 400 25 &gt;300 95 
Ethylene thiocarbonate 
190 80 350 10 &gt;300 95 
.gamma.-Thiobutyrolactone 
200 85 400 10 &gt;300 95 
.alpha.-pyrrolidone 
185 75 385 10 &gt;300 95 
.gamma.-butyrolactone 
310 95 520 5 &gt;1,000 
100 
valerolactone 
235 90 370 10 &gt;500 97 
.gamma.-ethyl-.gamma.-butyrolactone 
195 85 385 10 &gt;300 97 
.beta.-methyl-.gamma.-butyrolactone 
175 80 385 10 &gt;300 95 
Thiolane 205 80 410 15 &gt;300 95 
Pyrazolidine 
195 80 380 15 &gt;500 97 
Pyrrolidine 185 85 380 10 &gt;300 95 
Tetrahydrofuran 
235 90 425 10 &gt;500 97 
3-Methyltetrahydrofuran 
230 80 420 15 &gt;300 95 
Sulfolane 305 95 485 5 &gt;1,000 
100 
3-Methylsulfolane 
285 85 460 10 &gt;500 97 
2-Methylsulfolane 
265 80 450 10 &gt;500 97 
3-Ethylsulfolane 
250 85 440 15 &gt;300 95 
2-Ethylsulfolane 
250 85 440 15 &gt;300 95 
__________________________________________________________________________ 
Example 11 
Example 1--1 was repeated except for using electrolyte solutions of a 1 
mole/liter LiPF.sub.6 solution in each of the mixed solvents as shown in 
Table 9, to prepare 21 types of batteries according to the present 
invention. The batteries thus prepared were discharged at 100 mA and then 
tested for the same items as those in Example 9. The results are also 
shown in Table 9. 
TABLE 9 
__________________________________________________________________________ 
(+) LiCoO.sub.2 /(-) graphite 
Graphite characteristics 
Battery characteristics 
Dimethyl carbonate:solvent 
Capacity per 
Initial charge- 
Self- Cycle 
Charge-discharge 
shown below = 1:1 
unit weight 
discharge efficiency 
Capacity 
discharge rate 
life efficiency 
__________________________________________________________________________ 
Ethylene carbonate 
350 95 600 5 &gt;1,000 
100 
Propylene carbonate 
230 60 420 25 &gt;500 97 
1,2-Butylene carbonate 
260 65 350 20 &gt;300 95 
2,3-Butylene carbonate 
200 60 400 25 &gt;300 95 
Ethylene thiocarbonate 
185 80 345 10 &gt;300 95 
.gamma.-Thiobutyrolactone 
195 85 395 10 &gt;300 95 
.alpha.-pyrrolidone 
180 75 380 10 &gt;300 95 
.gamma.-butyrolactone 
300 95 500 5 &gt;1,000 
100 
valerolactone 
230 90 360 10 &gt;500 97 
.gamma.-ethyl-.gamma.-butyrolactone 
190 85 380 10 &gt;500 97 
.beta.-methyl-.gamma.-butyrolactone 
170 80 370 10 &gt;300 95 
Thiolane 200 80 400 15 &gt;300 95 
Pyrazolidine 
190 80 380 15 &gt;500 97 
Pyrrolidine 180 85 380 10 &gt;300 95 
Tetrahydrofuran 
230 90 420 10 &gt;500 97 
3-Methyltetrahydrofuran 
225 80 420 15 &gt;300 95 
Sulfolane 300 95 475 5 &gt;1,000 
100 
3-Methylsulfolane 
280 85 455 10 &gt;500 97 
2-Methylsulfolane 
260 80 450 10 &gt;500 97 
3-Ethylsulfolane 
250 85 445 15 &gt;300 95 
2-Ethylsulfolane 
250 85 440 15 &gt;300 95 
__________________________________________________________________________ 
Example 12 
Example 1--1 was repeated except for using electrolyte solutions of a 1 
mole/liter LiPF.sub.6 solution in each of the mixed solvents as shown in 
Table 10, to prepare 21 types of batteries according to the present 
invention. The batteries thus prepared were discharged at 100 mA and then 
tested for the same items as those in Example 9. The results are also 
shown in Table 10. 
TABLE 10 
__________________________________________________________________________ 
(+) LiCoO.sub.2 /(-) graphite 
Graphite characteristics 
Battery characteristics 
1,2-Dimethoxyethane: 
Capacity per 
Initial charge- 
Self- Cycle 
Charge-discharge 
solvent shown below = 1:1 
unit weight 
discharge efficiency 
Capacity 
discharge rate 
life efficiency 
__________________________________________________________________________ 
Ethylene carbonate 
360 95 620 10 &gt;300 95 
Propylene carbonate 
240 60 440 50 &gt;50 70 
1,2-Butylene carbonate 
280 65 380 40 &gt;100 80 
2,3-Butylene carbonate 
210 60 420 50 &gt;50 70 
Ethylene thiocarbonate 
200 80 370 20 &gt;200 90 
.gamma.-Thiobutyrolactone 
210 85 420 20 &gt;200 90 
.alpha.-pyrrolidone 
190 75 400 20 &gt;200 90 
.gamma.-butyrolactone 
330 95 520 10 &gt;300 95 
.gamma.-valerolactone 
240 90 380 20 &gt;200 90 
.gamma.-ethyl-.gamma.-butyrolactone 
200 85 400 20 &gt;200 90 
.beta.-methyl-.gamma.-butyrolactone 
180 80 400 20 &gt;200 90 
Thiolane 210 80 420 30 &gt;150 85 
Pyrazolidine 
200 80 400 30 &gt;150 85 
Pyrrolidine 190 85 400 20 &gt;200 90 
Tetrahydrofuran 
240 90 440 20 &gt;200 90 
3-Methyltetrahydrofuran 
230 80 440 30 &gt;150 85 
Sulfolane 310 95 500 10 &gt;300 95 
3-Methylsulfolane 
290 85 470 20 &gt;200 90 
2-Methylsulfolane 
270 80 470 20 &gt;200 90 
3-Ethylsulfolane 
260 85 460 30 &gt;150 85 
2-Ethylsulfolane 
260 85 460 30 &gt;150 85 
__________________________________________________________________________ 
Example 13 
Example 9 was repeated except for using LiNiO.sub.2 instead of LiCoO.sub.2 
as a positive electrode material, to prepare 21 types of batteries 
according to the present invention. The batteries thus prepared were 
discharged at 100 mA and then tested for the same items as those in 
Example 9. The results are also shown in Table 11. 
TABLE 11 
__________________________________________________________________________ 
(+) LiNiO.sub.2 /(-) graphite 
Graphite characteristics 
Battery characteristics 
Single solvent shown below 
Capacity per 
Initial charge- 
Self- Cycle 
Charge-discharge 
shown below = 1:1 
unit weight 
discharge efficiency 
Capacity 
discharge rate 
life efficiency 
__________________________________________________________________________ 
Ethylene carbonate 
350 95 550 5 &gt;1,000 
100 
Propylene carbonate 
230 60 370 25 &gt;500 97 
1,2-Butylene carbonate 
270 65 310 20 &gt;300 95 
2,3-Butylene carbonate 
200 60 350 25 &gt;300 95 
Ethylene thiocarbonate 
190 80 300 10 &gt;300 95 
.gamma.-Thiobutyrolactone 
200 85 350 10 &gt;300 95 
.alpha.-pyrrolidone 
180 75 330 10 &gt;300 95 
.gamma.-butyrolactone 
320 95 450 5 &gt;1,000 
100 
valerolactone 
230 90 310 10 &gt;500 97 
.gamma.-ethyl-.gamma.-butyrolactone 
190 85 330 10 &gt;500 97 
.beta.-methyl-.gamma.-butyrolactone 
170 80 330 10 &gt;300 95 
Thiolane 200 80 350 15 &gt;300 95 
Pyrazolidine 
190 80 330 15 &gt;500 97 
Pyrrolidine 180 85 330 10 &gt;300 95 
Tetrahydrofuran 
230 90 370 10 &gt;500 97 
3-Methyltetrahydrofuran 
220 80 370 15 &gt;300 95 
Sulfolane 300 95 430 5 &gt;1,000 
100 
3-Methylsulfolane 
280 85 400 10 &gt;500 97 
2-Methylsulfolane 
260 80 400 10 &gt;500 97 
3-Ethylsulfolane 
250 85 390 15 &gt;300 95 
2-Ethylsulfolane 
250 85 390 15 &gt;300 95 
__________________________________________________________________________ 
Example 14 
Example 9 was repeated except for using LiMn.sub.2 O.sub.4 instead of 
LiCoO.sub.2 as a positive electrode material, to prepare 21 types of 
batteries according to the present invention. The batteries thus prepared 
were discharged at 100 mA and then tested for the same items as those in 
Example 9. The results are also shown in Table 12. 
TABLE 12 
__________________________________________________________________________ 
(+) LiMn.sub.2 O.sub.4 /(-) graphite 
Graphite characteristics 
Battery characteristics 
Single solvent shown below 
Capacity per 
Initial charge- 
Self- Cycle 
Charge-discharge 
shown below = 1:1 
unit weight 
discharge efficiency 
Capacity 
discharge rate 
life efficiency 
__________________________________________________________________________ 
Ethylene carbonate 
350 95 580 5 &gt;1,000 
100 
Propylene carbonate 
230 60 400 25 &gt;500 97 
1,2-Butylene carbonate 
270 65 340 20 &gt;300 95 
2,3-Butylene carbonate 
200 60 380 25 &gt;300 95 
Ethylene thiocarbonate 
190 80 330 10 &gt;300 95 
.gamma.-Thiobutyrolactone 
200 85 380 10 &gt;300 95 
.alpha.-pyrrolidone 
180 75 360 10 &gt;300 95 
.gamma.-butyrolactone 
320 95 480 5 &gt;1,000 
100 
valerolactone 
230 90 340 10 &gt;500 97 
.gamma.-ethyl-.gamma.-butyrolactone 
190 85 360 10 &gt;500 97 
.beta.-methyl-.gamma.-butyrolactone 
170 80 360 10 &gt;300 95 
Thiolane 200 80 380 15 &gt;300 95 
Pyrazolidine 
190 80 360 15 &gt;500 97 
Pyrrolidine 180 85 360 10 &gt;300 95 
Tetrahydrofuran 
230 90 400 10 &gt;500 97 
3-Methyltetrahydrofuran 
220 80 400 15 &gt;300 95 
Sulfolane 300 95 460 5 &gt;1,000 
100 
3-Methylsulfolane 
280 85 420 10 &gt;500 97 
2-Methylsulfolane 
260 80 430 10 &gt;500 97 
3-Ethylsulfolane 
250 85 425 15 &gt;300 95 
2-Ethylsulfolane 
250 85 425 15 &gt;300 95 
__________________________________________________________________________ 
Example 15 
Example 1--1 was repeated except for using electrolyte solutions of a 1 
mole/liter LiPF.sub.6 solution in each of mixed solvents as shown in Table 
13, to prepare 5 types of batteries according to the present invention. 
The batteries thus prepared were discharged at 1 A and then tested for the 
same items as those in Example 9. The results are also shown in Table 13. 
TABLE 13 
__________________________________________________________________________ 
(+) LiCoO.sub.2 /(-) graphite 
Graphite characteristics 
Battery characteristics 
Ethylene carbonate:solvent 
Capacity per 
Initial charge- 
Self- Cycle 
Charge-discharge 
shown below = 1:1 
unit weight 
discharge efficiency 
Capacity 
discharge rate 
life efficiency 
__________________________________________________________________________ 
Dimethyl carbonate 
330 95 550 5 &gt;1,000 
100 
Diethyl carbonate 
310 95 530 5 &gt;1,000 
100 
1,2-Dimethoxyethane 
330 95 550 10 &gt;300 95 
1,2-Diethoxyethane 
310 95 530 10 &gt;300 95 
Ethoxymethoxyethane 
310 95 530 10 &gt;300 95 
__________________________________________________________________________ 
Example 16 
Example 1--1 was repeated except for using electrolyte solutions of a 1 
mole/liter LiPF.sub.6 solution in each of the mixed solvents as shown in 
Table 14, to prepare 5 types of batteries according to the present 
invention. The batteries thus prepared were discharged at 1 A and then 
tested for the same items as those in Example 9. The results are also 
shown in Table 14. 
TABLE 14 
__________________________________________________________________________ 
(+) LiCoO.sub.2 /(-) graphite 
Graphite characteristics 
Battery characteristics 
Sulfonane:solvent 
Capacity per 
Initial charge- 
Self- Cycle 
Charge-discharge 
shown below = 1:1 
unit weight 
discharge efficiency 
Capacity 
discharge rate 
life efficiency 
__________________________________________________________________________ 
Dimethyl carbonate 
240 95 430 5 &gt;1,000 
100 
Diethyl carbonate 
200 95 400 5 &gt;1,000 
100 
1,2-Dimethoxyethane 
240 95 430 10 &gt;300 95 
1,2-Diethoxyethane 
200 95 400 10 &gt;300 95 
Ethoxymethoxyethane 
200 95 400 10 &gt;300 95 
__________________________________________________________________________ 
Example 17 
Example 1--1 was repeated except for using, instead of LiPF.sub.6, each of 
the electrolyte solutes as shown in Table 15, to prepare 6 types of 
batteries according to the present invention. The batteries thus prepared 
were discharged at 100 mA and then tested for the same items as those in 
Example 9. The results are also shown in Table 5. 
Tables 7 through 15 shows that the batteries of the present invention 
develop better battery characteristics over all the items tested than 
those of the conventional battery. 
TABLE 15 
__________________________________________________________________________ 
(+) LiCoO.sub.2 /(-) graphite 
Ethylene carbonate: 
Graphite characteristics 
Battery characteristics 
dimethyl carbonate = 1:1; 
Capacity per 
Initial charge- 
Self- Cycle 
Charge-discharge 
Solute: shown below 
unit weight 
discharge efficiency 
Capacity 
discharge rate 
life efficiency 
__________________________________________________________________________ 
LiPF.sub.6 350 95 600 5 &gt;1,000 
100 
LiBF.sub.4 350 95 600 5 &gt;1,000 
100 
LiClO.sub.4 350 95 600 5 &gt;1,000 
100 
LiCF.sub.3 SO.sub.3 
350 95 600 5 &gt;1,000 
100 
LiC.sub.4 F.sub.9 SO.sub.3 
350 95 600 5 &gt;1,000 
100 
LiN(CF.sub.3 SO.sub.2).sub.2 
350 95 600 5 &gt;1,000 
100 
LiAsF.sub.6 350 95 600 5 &gt;1,000 
100 
__________________________________________________________________________ 
Example 18 
Example 1--1 was repeated except for using 11 electrolyte solutions of 1 
mole/liter of LiPF.sub.6 in each of mixed solvents of ethylene carbonate 
and .gamma.-butyrolactone in mixing ratios by volume of 100:0, 90:10, 
80:20, 70:30, 60:40, 50:50, 40:60, 30:70, 20:80, 10:90 and 0:100, 
respectively, to prepare 11 batteries. The batteries thus prepared were 
discharged at 100 mA and then tested for the relationship between the 
battery capacity and the mixing ratio by volume. 
FIG. 14 is a graph with the coordinate representing the battery capacity 
(mAh) and the abscissa the mixing ratio by volume (% by volume). As is 
understood from the FIGURE, with discharge at 100 mA the use of a solvent 
containing at least 20% by volume of ethylene carbonate results in large 
battery capacity. 
Example 19 
Example 1--1 was repeated except for using 11 electrolyte solutions of 1 
mole/liter of LiPF.sub.6 in each of mixed solvents of ethylene carbonate, 
.gamma.-butyrolactone and sulfolane in various mixing ratios by volume (% 
by volume) with the latter two being always mixed in the same amounts, to 
prepare 11 batteries. The batteries thus prepared were discharged at 100 
mA and then tested for the relationship between the battery capacity and 
the mixing ratio by volume. 
FIG. 15 is a graph with the coordinate representing the battery capacity 
(mAh) and the abscissa the mixing ratio by volume (% by volume). The 
FIGURE shows that, with discharge at 100 mA, the use of a solvent 
containing at least 20% by volume of ethylene carbonate results in large 
battery capacity. 
Example 20 
Example 1--1 was repeated except for using mixed solvents of 
tetrahydrofuran and dimethyl carbonate in various mixing ratios by volume 
(% by volume) and using LiNiO.sub.2 instead of LiCoO.sub.2 for the 
positive electrode, to prepare 11 batteries. The batteries thus prepared 
were discharged at 1 A and then tested for the relationship between the 
battery capacity and the mixing ratio by volume. 
FIG. 16 is a graph with the coordinate representing the battery capacity 
(mAh) and the abscissa the mixing ratio by volume (% by volume). The 
FIGURE shows that, with discharge at 1 A, the use of a mixed solvent 
containing 20 to 80% by volume of tetrahydrofuran results in remarkably 
large discharge capacity. 
Example 21 
Example 1--1 was repeated except for using mixed solvents of sulfolane and 
diethyl carbonate in various mixing ratios (% by volume) and using 
LiMn.sub.2 O.sub.4 instead of LiCoO.sub.2 for the positive electrode, to 
prepare 11 batteries. The batteries thus prepared were discharged at 1 A 
and then tested for the relationship between the battery capacity and the 
mixing ratio by volume. 
FIG. 17 is a graph with the coordinate representing the battery capacity 
(mAh) and the abscissa the mixing ratio by volume (% by volume). The 
FIGURE shows that, with discharge at 1 A, the use of a mixed solvent 
containing 20% to 80% by volume of sulfolane based on the volume of the 
solvent results in remarkably large discharge capacity. 
Example 22 
Example 1--1 was repeated except for using mixed solvents of ethylene 
carbonate, .gamma.-butyrolactone and dimethyl carbonate in various mixing 
ratios by volume (% by volume) with the former two always being mixed in 
the same amounts, to prepare 11 batteries. The batteries thus prepared 
were discharged at 100 mA and then tested for the relationship between the 
battery capacity and the mixing ratio by volume. 
FIG. 18 is a graph with the coordinate representing the battery capacity 
(mAh) and the abscissa the mixing ratio by volume (% by volume). The 
FIGURE shows that, with discharge at 100 mA, the use of a solvent 
containing ethylene carbonate results in large battery capacity. 
Example 23 
Example 1--1 was repeated except for using mixed solvents of ethylene 
carbonate, .gamma.-butyrolactone and diethyl carbonate in various mixing 
ratios by volume (% by volume based on the volume of the solvent) with the 
former two always being mixed in the same amounts, to prepare 11 
batteries. The batteries thus prepared were discharged at 100 mA and then 
tested for the relationship between the battery capacity and the mixing 
ratio by volume. 
FIG. 19 is a graph with the coordinate representing the battery capacity 
(mAh) and the abscissa the mixing ratio by volume (% by volume). The 
FIGURE shows that, with discharge at 100 mA, the use of a solvent 
containing ethylene carbonate results in large battery capacity. 
Example 24 
Example 1--1 was repeated except for using mixed solvents of ethylene 
carbonate and dimethyl carbonate in various mixing ratios by volume (% by 
volume) and using LiNiO.sub.2 instead of LiCoO.sub.2 for the positive 
electrode, to prepare 11 batteries. The batteries thus prepared were 
discharged at 1 A and then tested for the relationship between the battery 
capacity and the mixing ratio by volume. 
FIG. 20 is a graph with the coordinate representing the battery capacity 
(mAh) and the abscissa the mixing ratio by volume (% by volume). The 
FIGURE shows that, with discharge at 1 A, the use of a solvent containing 
20 to 80% by volume of ethylene carbonate results in remarkably large 
battery capacity. 
Example 25 
Example 1--1 was repeated except for changing the mixing ratio by volume (% 
by volume) of ethylene carbonate and diethyl carbonate, to prepare 11 
batteries. The batteries thus prepared were discharged at 1 A and then 
tested for the relationship between the battery capacity and the mixing 
ratio by volume. 
FIG. 21 is a graph with the coordinate representing the battery capacity 
(mAh) and the abscissa the mixing ratio by volume (% by volume). The 
FIGURE shows that, with discharge at 1 A, the use of a solvent containing 
20 to 80% by volume of ethylene carbonate results in remarkably large 
battery capacity. 
Example 26 
Example 1--1 was repeated except for using mixed solvents of ethylene 
carbonate, dimethyl carbonate and diethyl carbonate in various mixing 
ratios (% by volume) with the latter two always being mixed in the same 
amounts and using LiMn.sub.2 O.sub.4 instead of LiCoO.sub.2 for the 
positive electrode, to prepare 11 batteries. The batteries thus prepared 
were discharged at 1 A and then tested for the relationship between the 
battery capacity and the mixing ratio by volume. 
FIG. 22 is a graph with the coordinate representing the battery capacity 
(mAh) and the abscissa the mixing ratio by volume (% by volume). The 
FIGURE shows that, with discharge at 1 A, the use of a solvent containing 
20 to 80% by volume of ethylene carbonate results in remarkably large 
battery capacity. 
Additional Example 1 
In this Example, various graphite samples to be used as a negative 
electrode and having d-values very close to each other were used, and the 
relationship between the Lc and the discharge capacity per unit weight. 
(mAh/g) or the initial charge-discharge efficiency (%) of graphites was 
studied. A lithium metal plate was used as a positive electrode and a 
electrolyte solution of 1 mole/liter LiPF .sub.6 in a mixed solvent by the 
volume mixing ratio of 4:6 of ethylene carbonate and dimethyl carbonate 
was used as an electrolyte solution. The initial charge-discharge 
efficiency herein was calculated by a calculation formula: (discharge 
capacity at the first cycle)/(charge capacity at the first 
cycle)!.times.100. The results are shown in FIGS. 23 through 31, which 
used graphites having the following properties in Tables 16 through 24. 
TABLE 16 
______________________________________ 
A1 A2 A3 A4 A5 A6 A7 A8 
______________________________________ 
d.sub.002 (.ANG.) 
3.354 3.354 3.354 
3.354 
3.354 
3.354 
3.354 
3.354 
Lc (.ANG.) 
6.7 127 185 200 230 500 1000 2000 
True Density 
1.42 1.62 1.80 2.20 2.22 2.23 2.25 2.25 
(g/cm.sup.3) 
Average 10 12 12 12 12 12 12 12 
Particle 
Diameter (.mu.m) 
Specific 7.2 6.9 7.0 7.2 7.1 7.7 7.3 7.5 
Surface Area 
(m.sup.2 /g) 
______________________________________ 
TABLE 17 
__________________________________________________________________________ 
B1 B2 B3 B4 B5 B6 B7 B8 
__________________________________________________________________________ 
d.sub.002 (.ANG.) 
3.359 
3.359 
3.359 
3.359 
3.359 
3.359 
3.359 
3.359 
Lc (.ANG.) 
7.3 110 190 210 250 1000 1500 2000 
True Density 
1.59 
1.73 
1.87 
1.95 
2.20 
2.24 2.25 2.23 
(g/cm.sup.3) 
Average Particle 
10 10 10 10 10 11 9 10 
Diameter (.mu.m) 
Specific Surface 
6.8 7.2 7.0 7.1 6.9 6.7 7.0 7.2 
Area (m.sup.2 /g) 
__________________________________________________________________________ 
TABLE 18 
______________________________________ 
C1 C2 C3 C4 C5 C6 C7 
______________________________________ 
d.sub.002 (.ANG.) 
3.362 3.362 3.363 
3.363 
3.362 
3.363 3.361 
Lc (.ANG.) 
5.0 145 175 220 980 1750 1800 
True Density 
1.50 1.64 1.80 2.0 2.19 2.20 2.22 
(g/cm.sup.3) 
Average Particle 
16 16 16 16 16 16 17 
Diameter (.mu.m) 
Specific Surface 
5.0 5.9 6.0 6.1 5.8 5.7 5.5 
Area (m.sup.2 /g) 
______________________________________ 
TABLE 19 
__________________________________________________________________________ 
D1 D2 D3 D4 D5 D6 D7 D8 
__________________________________________________________________________ 
d.sub.002 (.ANG.) 
3.366 
3.367 
3.366 
3.367 
3.367 
3.367 
3.366 
3.368 
Lc (.ANG.) 
8.0 35 116 188 
210 
750 
1000 
2000 
True Density 
1.43 
1.79 
1.81 
1.89 
2.03 
2.19 
2.20 
2.25 
(g/cm.sup.3) 
Average Particle 
14 14 14 15 14 13 14 14 
Diameter (.mu.m) 
Specific Surface 
6.2 6.0 
5.9 6.5 
6.3 
6.2 
6.4 6.3 
Area (m.sup.2 /g) 
__________________________________________________________________________ 
TABLE 20 
__________________________________________________________________________ 
E1 E2 E3 E4 E5 E6 E7 E8 
__________________________________________________________________________ 
d.sub.002 (.ANG.) 
3.370 
3.370 
3.370 
3.370 
3.370 
3.370 
3.370 
3.370 
Lc (.ANG.) 
9.5 50 130 192 
215 
410 
790 1000 
True Density 
1.66 
1.165 
1.70 
1.81 
1.93 
2.15 
2.20 
2.23 
(g/cm.sup.3) 
Average Particle 
12 12 12 12 12 12 12 12 
Diameter (.mu.m) 
Specific Surface 
6.8 6.9 
7.0 6.9 
7.1 
7.0 
7.2 7.0 
Area (m.sup.2 /g) 
__________________________________________________________________________ 
TABLE 21 
______________________________________ 
F1 F2 F3 F4 F5 F6 F7 F8 
______________________________________ 
d.sub.002 (.ANG.) 
3.382 3.383 3.382 
3.382 
3.383 
3.382 
3.381 
3.381 
Lc (.ANG.) 
6.0 18 75 154 181 210 320 720 
True Density 
1.39 1.48 1.65 1.88 1.95 1.97 2.00 2.02 
(g/cm.sup.3) 
Average 12 12 14 12 12 14 14 12 
Particle 
Diameter (.mu.m) 
Specific 6.9 6.8 7.0 7.1 7.2 7.0 6.9 7.0 
Surface 
Area (m.sup.2 /g) 
______________________________________ 
TABLE 22 
______________________________________ 
G1 G2 G3 G4 G5 G6 G7 G8 
______________________________________ 
d.sub.002 (.ANG.) 
3.385 3.385 3.386 
3.385 
3.386 
3.387 
3.385 
3.385 
Lc (.ANG.) 
8.5 25 83 145 190 220 300 620 
True Density 
1.41 1.55 1.72 1.95 2.00 2.01 2.08 2.10 
(g/cm.sup.3) 
Average 12 12 12 12 12 12 12 12 
Particle 
Diameter (.mu.m) 
Specific 6.8 6.9 6.8 7.3 7.2 6.9 7.0 7.2 
Surface 
Area (m.sup.2 /g) 
______________________________________ 
TABLE 23 
______________________________________ 
H1 H2 H3 H4 H5 H6 H7 H8 
______________________________________ 
d.sub.002 (.ANG.) 
3.392 3.392 3.393 
3.392 
3.393 
3.392 
3.392 
3.393 
Lc (.ANG.) 
15 45 73 100 170 230 290 450 
True Density 
1.65 1.72 1.83 1.85 1.90 1.95 2.01 2.05 
(g/cm.sup.3) 
Average 12 12 12 12 12 12 12 12 
Particle 
Diameter (.mu.m) 
Specific 6.6 6.9 6.8 6.7 6.9 7.0 7.1 6.9 
Surface 
Area (m.sup.2 /g) 
______________________________________ 
TABLE 24 
______________________________________ 
I1 I2 I3 I4 I5 I6 I7 I8 
______________________________________ 
d.sub.002 (.ANG.) 
3.398 3.397 3.398 
3.397 
3.397 
3.398 
3.399 
3.398 
Lc (.ANG.) 
8.5 32 50 110 160 210 250 310 
True Density 
1.68 1.75 1.79 1.83 1.89 1.91 1.92 1.99 
(g/cm.sup.3) 
Average 12 12 12 12 12 12 12 12 
Particle 
Diameter (.mu.m) 
Specific 7.0 6.8 6.7 6.8 6.9 6.5 7.1 6.9 
Surface 
Area (m.sup.2 /g) 
______________________________________ 
As shown in FIGS. 23 through 27, where the graphites having a d-value of 
not more than 3.370 were used as negative electrodes, the discharge 
capacity and initial charge-discharge efficiency critically changed to a 
large extent starting at an Lc of 200 .ANG.. Accordingly, in the present 
invention, the critical d-value of the graphite to be used for the 
negative electrode has been found to be not more than 3.370 by conducting 
these experiments. 
The above-described critically changing phenomena were not observed with 
graphites having a d-value exceeding 3.370 (see FIGS. 28 through 31). 
That is, as seen from FIGS. 23 through 27, it can be understood that the 
graphites having a d-value of 3.354 to 3.370 and an Lc of at least 200 
.ANG. have a remarkably large discharge capacity and high initial 
charge-discharge efficiency. 
Additional Example 2 
In this Example, various graphite samples to be used as a negative 
electrode and having an Lc of at least 200 .ANG. (according to the present 
invention) and those having an Lc of less than 200 .ANG. (comparison 
samples) were used, and the relationship between the d-value and the 
discharge capacity per unit weight (mAh/g) or the initial charge-discharge 
efficiency (%) of graphites was studied. The experiment conditions 
employed here were the same as in Additional Example 1. The results are 
shown in FIGS. 32 through 35. 
The abscissa in the graphs of these FIGURES represent the d-value and, the 
ordinate represent the discharge capacity in FIGS. 32 and 34 and the 
initial charge-discharge efficiency in FIGS. 33 and 35. 
It can be understood from FIGS. 32 and 33 that, where the graphites having 
an Lc of at least 200 .ANG. were used as a negative electrode, those 
graphites that have a d-value of less than 3,370 sufficiently maintain at 
high levels the discharge capacity (see FIG. 32) and the initial 
charge-discharge efficiency (see FIG. 33). 
The above-described critical phenomena, i.e. marked dependency on a d-value 
of the discharge capacity and initial charge-discharge efficiency, were 
not observed with the graphites having an Lc of less than 200 .ANG. (see 
FIGS. 34 and 35). 
Thus, it can be understood from FIGS. 32 through 35 that the graphites 
having an Lc of at least 200 .ANG. and a d-value of not more than 3,370 
have a significantly large discharge capacity and remarkably high initial 
charge-discharge efficiency. 
Additional Example 3 
In this Example, various graphite samples to be used as a negative 
electrode and having the same d-value (3.354) and Lc (2000 .ANG.) were 
used, and the relationship between the specific surface area and the 
discharge capacity per unit weight (mAh/g) or the initial charge-discharge 
efficiency (%) of the graphites was studied. The experiment conditions 
employed here were the same as in Additional Example 1. The specific 
surface area herein was measured by the BET method and expressed in 
m.sup.2 /g. The results are shown in FIG. 36, which used graphites having 
the following properties in Table 25. 
TABLE 25 
__________________________________________________________________________ 
J1 J2 J3 J4 J5 J6 J7 J8 J9 J10 
__________________________________________________________________________ 
Average Particle 
80 50 40 38 35 30 20 16 14 10 
Diameter (.mu.m) 
Specific Surface 
0.1 
0.2 0.3 
0.4 
0.6 1.0 
2.0 
3.3 
6.2 8.5 
Area (m.sup.2 /g) 
__________________________________________________________________________ 
J11 
J12 
J13 
J14 
J15 
J16 
J17 
J18 
J19 
J20 
A8 
__________________________________________________________________________ 
Average Particle 
5 3 1 0.6 
0.5 
0.4 
0.3 
0.25 
0.15 
0.05 
12 
Diameter (.mu.m) 
Specific Surface 
12 15 18 20 30 40 60 75 100 
1000 
7.5 
Area (m.sup.2 /g) 
__________________________________________________________________________ 
It can be observed from FIG. 36, that with negative electrodes using a 
graphite having a specific surface area of 0.5 to 50 m.sup.2 /g the 
discharge capacity and the initial charge-discharge efficiency of the 
graphite critically change and are maintained at high levels. 
It can be also understood that with negative electrodes using a graphite 
having a specific surface area of, in particular, 1.0 to 18 m.sup.2 /g, 
still higher levels among the above excellent characteristics are stably 
maintained. 
Here, it has been found that graphites having a specific surface area of 
less than 0.5 m.sup.2 /g tend to be inferior, particularly, in the initial 
charge-discharge efficiency and those having a specific surface area 
exceeding, particularly, 50 m.sup.2 /g tend to show low discharge 
capacity. 
Thus, it can be understood that, in the present invention, among graphites 
having a d-value of 3.354 to 3.370 and an Lc of at least 200 .ANG., 
selection of those having a specific surface area in a range of 0.5 to 50 
m.sup.2 /g realizes excellent batteries that maintain the discharge 
capacity and initial charge-discharge efficiency at high levels. 
Additional Example 4 
In this Example, various graphite samples to be used as a negative 
electrode and having the same d-value (3.354 ) and Lc (2000 .ANG.) were 
used, and the relationship between the average particle diameter and the 
discharge capacity per unit weight (mAh/g) or the initial charge-discharge 
efficiency (%) of graphites was studied. The experiment conditions 
employed here were the same as in Additional Example 1. The average 
particle diameter herein is expressed in .mu.m. The results are shown in 
FIG. 37, which used graphites having the following properties in Table 26. 
TABLE 26 
__________________________________________________________________________ 
J1 J2 J3 J4 J5 J6 J7 J8 J9 J10 
__________________________________________________________________________ 
Average Particle 
80 50 40 38 35 30 20 16 14 10 
Diameter (.mu.m) 
Specific Surface 
0.1 
0.2 0.3 
0.4 
0.6 1.0 
2.0 
3.3 
6.2 8.5 
Area (m.sup.2 /g) 
__________________________________________________________________________ 
J11 
J12 
J13 
J14 
J15 
J16 
J17 
J18 
J19 
J20 
A8 
__________________________________________________________________________ 
Average Particle 
5 3 1 0.6 
0.5 
0.4 
0.3 
0.25 
0.15 
0.05 
12 
Diameter (.mu.m) 
Specific Surface 
12 15 18 20 30 40 60 75 100 
1000 
7.5 
Area (m.sup.2 /g) 
__________________________________________________________________________ 
It can be observed from FIG. 37, that with negative electrodes using a 
graphite having an average particle diameter of 1.0 to 30 .mu.m the 
discharge capacity and the initial charge-discharge efficiency of the 
graphite critically markedly change and are maintained at high levels. 
Here, it has been found that graphites having an average particle diameter 
of less than 1.0 .mu.m tend to be inferior, particularly, in the discharge 
capacity and those having an average particle diameter exceeding, 
particularly, 30 .mu.m tend to be poor both in the discharge capacity and 
the initial charge-discharge capacity. 
Thus, it can be understood that, in the present invention, among graphites 
having a d-value of 3,354 to 3,370 and an Lc of at least 200 .ANG., 
selection of those having an average particle diameter in a range of 1 to 
30 .mu.m realizes excellent batteries that maintain the discharge capacity 
and initial charge-discharge efficiency at high levels. 
In the above Examples, the present invention has been described when it is 
applied to cylindrical batteries. However, the present invention can be 
applied to batteries of any shape, such as square, flat or the like, and 
there are no restrictions with respect to the shape of the batteries of 
the present invention. 
Obviously, numerous modifications and variations of the present invention 
are possible in light of the above teachings. It is therefore to be 
understood that within the scope of the appended claims, the invention may 
be practiced otherwise than as specifically described herein.