Carbonaceous electrode and compatible electrolyte

The inventions provides a battery which comprises a first electrode, a counter electrode which forms an electrochemical couple with said first electrode, and an electrolyte. The first electrode comprises graphite particles having an interlayer distance spacing of 002 planes (d.sub.002) as determined by x-ray diffraction of 0.330 to 0.340 nanometers (nm), a crystallite size in the direction of c-axis (L.sub.c) being greater than about 90 nanometers (nm) and less than about 1000 nanometers, and at least 90 percent by weight of said graphite particles having a size less than about 24 microns (.mu.m). The electrolyte comprises a solvent mixture and a solute; the solvent mixture comprises (i) ethylene carbonate (EC), and (ii) a solvent selected from the group consisting of propylene carbonate (PC), butylene carbonate (BC), and mixtures thereof with the ethylene carbonate being present in an amount by weight which is at least as great as the amount of any other solvent. Optionally, the solvent mixture further comprises one or more other organic solvents selected from the group consisting of methyl ethyl carbonate (MEC), diethyl carbonate (DEC), dipropyl carbonate (DPC), dimethyl carbonate (DMC), and mixtures thereof.

FIELD OF THE INVENTION 
This invention relates to electrochemical cells and batteries, and more 
particularly, to improved electrodes for such batteries. 
BACKGROUND OF THE INVENTION 
Lithium batteries are prepared from one or more lithium electrochemical 
cells. Such cells typically include an anode (negative electrode) of 
metallic lithium, a cathode (positive electrode) typically a transition 
metal chalcogenide and an electrolyte interposed between electrically 
insulated, spaced apart positive and negative electrodes. The electrolyte 
typically comprises a salt of lithium dissolved in one or more solvents, 
typically nonaqueous (aprotic) organic solvents. By convention, during 
discharge of the cell, the negative electrode of the cell is defined as 
the anode. During use of the cell, lithium ions (Li+) are transferred to 
the negative electrode on charging. During discharge, lithium ions (Li+) 
are transferred from the negative electrode (anode) to the positive 
electrode (cathode). Upon subsequent charge and discharge, the lithium 
ions (Li+) are transported between the electrodes. Cells having metallic 
lithium anode and metal chalcogenide cathode are charged in an initial 
condition. During discharge, lithium ions from the metallic anode pass 
through the liquid electrolyte to the electrochemically active material of 
the cathode whereupon electrical energy is released. During charging, the 
flow of lithium ions is reversed and they are transferred from the 
positive electrode active material through the ion conducting electrolyte 
and then back to the lithium negative electrode. 
Lithium batteries, with metallic lithium electrodes, have a limited life 
cycle due to the degradation of the metallic lithium electrodes. Lithium 
is attacked and/or passivated by electrolytes. This results in formation 
of lithium powder with a very high surface area at the interface between 
the metallic lithium and the electrolyte. The formation of high surface 
area lithium powder is undesirable because it reacts violently with 
moisture and air. 
It has recently been suggested to replace the lithium metal anode with a 
carbon anode, that is, a carbonaceous material, such as non-graphitic 
amorphous coke, graphitic carbon, or graphites, which are intercalation 
compounds. This presents a relatively advantageous and safer approach to 
rechargeable lithium as it replaces lithium metal with a material capable 
of reversibly intercalating lithium ions, thereby providing the sole 
called "rocking chair" battery in which lithium ions "rock" between the 
intercalation electrodes during the charging/discharging/recharging 
cycles. Such lithium metal free cells may thus be viewed as comprising two 
lithium ion intercalating (absorbing) electrode "sponges" separated by a 
lithium ion conducting electrolyte usually comprising a lithium salt 
dissolved in nonaqueous solvent or a mixture of such solvents. Numerous 
such electrolytes, salts, and solvents are known in the art. Such carbon 
anodes may be prelithiated prior to assembly within the cell having the 
cathode intercalation material. However, such preintercalation may present 
problems as it is known that prelithiated carbon electrodes are highly 
reactive. Such carbon anodes are preferably lithiated in situ. In one 
embodiment, such prelithiation occurs against a metallic lithium electrode 
which is later replaced with the cathodic active material electrode of the 
final cell. In another embodiment, the carbon-based negative electrode is 
assembled with lithium-containing cathode and/or lithium-containing 
electrolyte which provides the necessary lithium to form an Li.sub.x C 
anode in situ. In such a case, in an initial condition, such cells are not 
charged. In order to be used to deliver electrochemical energy, such cells 
must be charged in order to transfer lithium to the carbon from the 
lithium-containing cathode and/or electrolyte. During discharge, the 
lithium is transferred from the anode back to the cathode as described 
above. 
One drawback of the carbon anode is that upon initial charging of the cell, 
when lithium is intercalated into the host carbon, some irreversibility 
occurs in which lithium and/or the cell electrolyte are consumed, 
resulting in an initial capacity loss for the cell and a reduction of the 
cell's overall performance. For example, when the anode material Li.sub.x 
C is prepared in situ in a cell in order to obtain a state of charge and 
render the anode to a reduced state, some of the lithium which is 
transferred to the anode upon initial charging, is irretrievably 
intercalated into the anode in an irreversible process. Some of the 
intercalated lithium is, therefore, not deintercalated from the anode 
during subsequent discharge resulting in the loss of capacity since 
lithium is not available for electrochemical interaction to produce 
electrical energy. The progressive loss of capacity during use is referred 
to as "capacity fade". 
Based upon the short comings of such carbon-based cells there remains a 
need for electrochemical cells that are capable of providing improved 
performance. Therefore, what is needed is an improved anode material which 
is an alternative to present metallic lithium anodes and a compatible 
electrolyte which simultaneously fulfills the requirement of high 
reactivity, good charge rate capabilities, acceptable life cycle, specific 
rate, stability, and low cost. There is also needed an improved 
electrochemical cell which does not suffer the initial loss of cycling 
capability and the further progressive loss known as capacity fade during 
use. 
SUMMARY OF THE INVENTION 
The present invention provides an electrochemical cell or battery which has 
a non-metal negative electrode (anode). The battery comprises a negative 
electrode having an active material consisting of graphite particles 
having an interlayer distance spacing of 002 planes (c/2, d.sub.002) as 
determined by x-ray diffraction of 0.330 to 0.340 nanometers (nm), 
preferably 0.3350 to 0.3360 nanometers, and most preferably 0.3355 
nanometers. The graphite particles have a crystallite size in the 
direction of the c-axis (L.sub.c) being greater than about 90 nanometers, 
up to about 1000 nanometers; preferably greater than 90 nanometers and 
less than 200 nanometers, and most desirably greater than 100 nanometers 
and less than 200 nanometers. The parameter L.sub.c is a well known 
parameter defining the size of crystalline domains to characterize at 
least partially graphitized (ordered) carbon, and in this case, graphite. 
Graphite is made up of carbon layers of approximate dimension L.sub.a in 
the a-b plane and L.sub.c in the c-axis direction as defined above which 
designate the regions which scatter coherently within themselves x-rays. 
As used herein, the designation L.sub.c refers to the direction in the 
c-axis of the size of a region which scatter x-rays coherently, similarly, 
L.sub.a refers to the a-b plane. Accordingly, each ordered, crystalline, 
carbon grain is made up of many small regions, each characterized by 
L.sub.a and L.sub.c, which scatter x-rays incoherently with respect to one 
another, that is, region to region. 
The graphite particles of the invention are further characterized by 90 
percent by weight of such particles having a size less than about 48 
microns, desirably less than about 24 microns, and preferably 90 percent 
by weight of the graphite particles have a size less than about 16 
microns. Most preferably, the graphite particles are characterized by a 
median size (d.sub.50) of at least about 3 microns and less than or equal 
to about 22 microns. 
Most preferably, the graphite particle size distribution is such that 
essentially all of the graphite particles have a size less than about 48 
microns, 94 percent of the particles are less than 16 microns, and the 
median size is about 8.1 microns. Such particles are designated as SFG-15 
further described below. Another type of suitable particles have particle 
size distribution where essentially all of the graphite particles are less 
than 32 microns, and more preferably at least 95 percent of the particles 
are less than 12 microns, and where the median size is 5.8 microns. Such 
particles are designated as SFG-10 and further described hereinbelow. 
Still another group of preferred graphite particles has a graphite size 
distribution wherein essentially all of the particles have particle size 
less than about 12 microns, at least about 96 percent of the particles 
have a size less than about 6 microns, and the median size of the graphite 
particles is about 3.2 microns. Such particles are designated as SFG-6 and 
further described hereinbelow. The specific surface area of the graphite 
particles, as determined by the Brunauer-Emmett-Teller (BET) method is 
preferably greater than about 4 square meters per gram and up to about 16 
square meters per gram, and preferably greater than about 6 and up to 
about 12 square meters per gram. 
The electrolyte usable with the specific carbons of the invention is a 
mixture of solvents. In one embodiment, the mixture of solvents comprises: 
(i) ethylene carbonate; and (ii) a solvent selected from the group 
consisting of propylene carbonate (PC), butylene carbonate (BC), and 
mixtures of PC and BC. It is preferred that the EC is present in an amount 
by weight which is at least as great as the amount of the selected 
solvent, namely, the PC, the BC, or the mixture of PC and BC. In another 
embodiment, the mixture of solvents comprises propylene carbonate and 
ethylene carbonate, with the ethylene carbonate being present in an amount 
by weight which is at least as great as the amount of the propylene 
carbonate. Desirably, the solvent mixture comprises EC and PC in a weight 
ratio of 50EC:50PC to 75EC:25PC. Alternatively, the mixture desirably 
comprises 50EC:50BC. If desired, one or more additional organic solvents 
may be included in the solvent mixture. Such other organic solvents are 
selected from the group consisting of methyl ethyl carbonate (MEC), 
diethyl carbonate (DEC), dipropyl carbonate (DPC), dimethyl carbonate 
(DMC), and mixtures thereof. A preferred solvent mixture includes EC, PC 
and DMC where the EC is present in an amount not less than the amount by 
weight of the DMC and as stated earlier the EC is present is an amount by 
weight not less than of the PC. Accordingly, such solvent mixture 
preferably comprises the weight ratio of 1/3EC:1/3PC:1/3DMC and up to 
50EC:25PC:25DMC. This corresponds to 1EC:1PC:1DMC to 2EC:1PC:1DMC. In 
still another desirable embodiment, the solvent mixture comprises 
1EC:1PC:1BC to 2EC:1PC:1BC. Regardless of the nature of the one or more 
additional organic solvents besides EC and PC, the one or more other 
organic solvents preferably have a boiling point less than the boiling 
point of EC due to its tendency to solidify at ambient temperatures. As 
can be seen, it is desirable that the amount by weight of EC be at least 
as great as any other single solvent component, as exemplified by 
1/3EC:1/3PC:1/3DMC and 50EC:25PC:25DMC. It is preferred that the EC be the 
largest single component of the solvent mixture, as exemplified by 
75EC:25PC and 50EC:25PC:25DMC. In other words, EC preferably constitutes a 
major portion of the solvent mixture by weight, or is at least as great as 
any other single component. 
In preparing a battery constituting the negative electrode described above 
and the electrolyte, essentially any counter electrode may be selected so 
long as it is capable of reacting electrochemically with the graphite 
negative electrode material. Preferred are lithium transition metal oxide 
compounds. The negative electrode and positive electrode are assembled in 
a battery with an electrolyte which provides ionic conductivity between 
the positive and negative electrode. Typically and preferably, the 
electrolyte is in the form of an electrolyte separator which further 
comprises a solid matrix forming a network with voids interpenetrated by 
the solvent mixture, and a solute. Essentially any type of electrolyte 
separator arrangement may be selected so long as the solvent consists of 
the preferred organic solvents mentioned above. In one embodiment, the 
electrolyte separator has a solid matrix which is a polymeric acrylate 
formed from acrylate precursors which are applied to a surface of the 
cathode or anode and then polymerized to form an electrolyte/electrode 
composite. In another embodiment the matrix is a porous polypropylene or 
polyethylene sheet or a sheet of fiber glass material placed between the 
anode and cathode. The nature of the electrolyte separator is not critical 
so long as it is used with the solvent mixture of the invention along with 
the stated graphite negative electrode defined by the invention. 
Objects, features, and advantages of the invention include an improved 
electrochemical cell or battery based on alkali metal, and preferably 
lithium, which has improved charging and discharging characteristics; a 
large discharge capacity; and which maintains its integrity over a 
prolonged life cycle as compared to presently used anodes. Another object 
is to provide an electrolyte mixture which is stable with respect to the 
graphite negative electrode, which demonstrates high performance, and 
which does not readily decompose or evaporate. Still another object is to 
provide an anode active material which is an alternative to metallic 
alkali anodes, lithium, sodium, potassium, and particularly lithium 
anodes. It is also an object of the present invention to provide cells 
which can be manufactured more economically and relatively more 
conveniently and safely than present carbon-based and lithium anodes. And 
to provide cells with carbon-based anodes that are compatible with 
electrolytes which avoid problems with undesired reactivity.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The present invention provides an electrochemical cell or battery, which 
has a non-metal negative electrode (anode). That is, no solid metal active 
material is used in the cell. Rather than the conventional solid lithium 
metal anode, the active material of the new anode comprises a specific 
type of carbon powder having unique operating advantages when used in 
combination with a specifically selected compatible electrolyte. 
Before describing the invention, it is useful to understand the problems 
associated with present carbon anode batteries which deter their use. 
Generally, the carbonaceous materials (carbons) known to be usable as 
intercalation carbon anode materials may, for discussion purposes, be 
classified in several distinct groups. One group contains highly 
structured, highly crystalline, highly graphitic, anisotropic graphites 
having a nearly perfect layered structure and preferably formed as 
synthetic graphites and heat treated up to about 3000.degree. C. Examples 
are the SFG series of synthetic graphites and the KS series of synthetic 
graphites as supplied by the manufacturer Lonza G. & T., Limited (Sins, 
Switzerland). A second distinct group contains graphitic carbons which 
have relatively very large crystal size (L.sub.c greater than 2000) and 
are fully graphitized, typically, graphitized cokes, such as, supplied 
under the name Super SG and BG by Superior Graphite Corporation (USA). A 
third class of carbons are non-graphitic carbons. These are considered 
amorphous, non-crystalline, disordered, and are generally petroleum cokes 
and carbon blacks, such as, supplied by Lonza under the designation FC-250 
and Conoco (USA) under the designation X-30. They have a turbostratic 
structure, show a steep voltage profile and intercalate only up to 0.5 Li 
per C.sub.6 (Li.sub.0.5 C.sub.6, LiC.sub.12). 
Lithiated petroleum coke (Li.sub.x C.sub.12) is usable in combination with 
a variety of electrolytes without excessive deterioration of the 
electrolyte solvent. However, the performance of such lithiated petroleum 
cokes is relatively poor due to sloping voltage profile and limited 
intercalation capacity. 
Graphite has a higher lithium intercalation/deintercalation capacity, 
theoretically about LiC.sub.6. It has double the intercalation capacity, 
and a flat voltage curve near zero volts relative to lithium. The 
theoretical capacity of a graphite anode is 372 mAh/g based upon a 
stoichiometry of LiC.sub.6. Despite these theoretical advantages, 
graphites have not found favor for use in lithium batteries. This is 
because the use of graphite as a negative electrode material presents a 
problem when graphite is used with a preferred propylene carbonate 
electrolyte solvent. Cells containing graphite and propylene carbonate and 
other similar electrolytes suffer from very poor reversible capability 
during delithiation (deintercalation). In addition, electrolyte 
decomposition occurs, and significant gas is released, posing a safety 
risk. The electrolyte decomposition is thought to be because graphite has 
many active sites in its structure as compared with graphitic carbon 
(having large crystallized size L.sub.c greater than 1,000 to 2,000), and 
as compared to cokes which are amorphous. 
It has been found that if a graphite negative electrode is used in an 
electrolyte containing propylene carbonate as the solvent, the solvent is 
apparently absorbed into the active sites of the graphite negative 
electrode and readily generates gas through decomposition. As a result, 
the decomposition of the solvent prevents lithium ion as an active 
material from intercalating into the graphite on charging the battery and 
causes an increase in polarization; consequently, the battery capacity is 
decreased. In other words, it is thought that the graphite is catalytic 
and causes breakdown of propylene carbonate. Such decomposition of the 
propylene carbonate results in the evolution of the gas, probably 
propylene. 
In view of the difficulties mentioned above, namely, that propylene 
carbonate is usable only with non-graphitic anodes and is not usable with 
crystalline, ordered planar structure graphitic anodes. It has recently 
been suggested to use dimethyl carbonate (DMC) in combination with 
ethylene carbonate (EC) for any type of carbonaceous anode. See for 
example U.S. Pat. Nos. 5,352,548 and 5,192,629, each of which is 
incorporated by reference in its entirety. Moreover, such electrolyte is 
undesirable since the DMC readily evaporates leaving behind the EC which 
quickly solidifies, rendering the cell useless. 
Except for the present invention, there is not known to be a successful use 
of a propylene carbonate based electrolyte solvent in combination with 
graphite anode active material. 
The invention provides, for the first time, a specific type of graphite 
negative electrode active material which is successfully used in 
combination with a solvent comprising propylene carbonate, which maintains 
a high reversible specific capacity, and demonstrates minimal first cycle 
capacity loss, heretofore unexpected and surprising in view of 
difficulties posed by graphite anodes operating in the presence of 
propylene carbonate. 
The present invention provides an electrochemical cell or battery which has 
a heretofore unexpected first cycle capacity loss of less than about 25 
percent of the first cycle charge capacity and which is characterized by a 
negative electrode having a reversible capacity of greater than about 330 
milliamp hours per gram (mAh/g). Advantageously, the cells of the 
invention having the specific graphite of the invention demonstrates 
reversible specific capacity of 339 to 351 milliamp hours per gram (mAh/g) 
and a first cycle capacity loss in a range of 18 to 22 percent. Specific 
graphites exhibiting this type of behavior are as exemplified by graphitic 
material sold under the designation SFG by Lonza G. & T., Limited (Sins, 
Switzerland). Specifically, the graphites are designated as SFG-6.TM., 
SFG-10.TM., and SFG-15.TM.. Each of these graphites has an ash content of 
0.15 percent by weight maximum, a moisture content of 0.5 percent by 
weight maximum, and an interlayer distance of 0.3354 to 0.3358. Each of 
these graphites is also characterized by a crystallite size L.sub.c of 
greater than 90 and less than 1000 nanometers. Each of these graphites is 
also characterized by a density determined by the Xylene method of 2.26 
grams per cubic centimeter and by the Scott method 0.07 to 0.09 grams per 
cubic centimeter. The features of the specific graphites are included in 
Table I along with comparative data for other graphites tested. Further 
characteristics for the three specific graphites of the invention will now 
be described, and are shown in Tables II and III. 
The preferred SFG-6 and 10 have many values the same as that for SFG-15 in 
Table II. The desirable SFG-6 and 10 have the same ash content, moisture 
content, interlayer distance, purity, and d.sub.002 as are shown in Table 
II for SFG-15. The SFG-6, 10, and 15 series differ in particle size, 
crystalline size (L.sub.c), BET area, and density according to the Scott 
method. The undesirable graphite SFG-44 has very different particle size, 
crystalline size (L.sub.c), BET area, and density according to the Scott 
method. 
SFG-6.TM. has a crystalline size L.sub.c greater than 100 nanometers, a BET 
surface area of 15.2 square meters per gram, and a particle size 
distribution wherein essentially 100 percent by weight of the particles 
have a size less than 12 microns, 97 percent by weight less than 8 
microns, 95.8 percent by weight less than 6 microns, and a median particle 
size of 3.2 microns. The density in Xylene is as per SFG-15, but density 
by the Scott method for SFG-6 is 0.07 grams per cubic centimeter. (Table 
III.) 
SFG-10.TM. has a crystalline size L.sub.c greater than 150 nanometers, a 
BET surface area of 11.1 square meters per gram, and a particle size 
distribution based on percent by weight as follows: essentially 100 
percent less than 32 microns, 94.9 percent less than 12 microns, 75 
percent less than 8 microns, and a median particle size of 5.8 microns. 
(Table III.) The density is the same as that stated for SFG-6, in Xylene 
and per Scott. 
SFG-15.TM. has a crystalline size L.sub.c greater than 120 nanometers, a 
BET surface area of about 8.8 square meters per gram, and a particle size 
distribution where essentially 100 percent of the particles have a size 
less than 48 microns, 99 percent of the particles have a size less than 24 
microns, 94 percent of the particles have a size less than 16 microns, and 
a median particle size of 8.1 microns. 
Each of the three graphites of the invention, SFG-6, 10, and 15 have an 
interlayer distance spacing of 002 planes of preferably 0.3355. This 
interlayer distance spacing is designated in the literature as c/2 or 
d.sub.002. Each of the above graphites is anisotropic, which means that 
one or more fundamental physical properties, for example, electronic 
resistivity, varies with direction. The specific graphites designated 
above as SFG-6, 10, and 15 have high anistropy. 
Physical features of the invention as defined above are obtained by 
measurements from x-ray wide angle diffraction. Analysis of x-ray 
diffraction by crystals is well known in the art. According to analysis by 
Bragg diffraction, any set of equally spaced planes in a crystal acts as a 
set of mirrors for x-rays; for constructive interference, the beam must be 
incident on a set of planes that such a glancing angle .theta. indicated 
by: 2d.theta.=m.lambda., where d is the distance between planes and m is 
an integer. Therefore, as is well known in the art, the lattice constance 
for carbon material is determinable from 002 lines. Crystallite size along 
the c-axis (L.sub.c) and the a-axis (L.sub.a) is determinable from half 
widths of 002 and 110 lines, respectively, by x-ray diffraction with an 
internal standard. A typical internal standard for carbon analysis is 
silicon used with CUK.alpha. radiation. A description of the x-ray wide 
angle diffraction analysis method is given in U.S. Pat. No. 4,945,014 
incorporated herein by reference in its entirety. The term "d.sub.002 " is 
used interchangeably with the term "C/2". From methods such as described 
in the '014 patent, one is able to obtain lattice constant, a, the average 
plane spacing, d.sub.002 (C/2), and the size of the crystallite domains, 
L.sub.a and L.sub.c, to character carbons. L.sub.a and L.sub.c are 
normally determined using the Scherrer equations as defined in the '014 
patent incorporated herein by reference. Using the widths of the 002 and 
110 peaks it is possible to obtain values for L.sub.a and L.sub.c as shown 
in Column 14 of U.S. Pat. No. 4,945,014 previously incorporated by 
reference in its entirety. Such analysis is based on the understanding 
that each carbon grain is made up of many small regions characterized by 
L.sub.a and L.sub.c, which scatter x-rays incoherently with respect to one 
another; the small regions which scatter coherently within themselves are 
defined by L.sub.a and L.sub.c. 
The electrolyte usable with the specific carbons of the invention is a 
mixture of solvents. In one embodiment, the mixture of solvents comprises: 
(i) ethylene carbonate; and (ii) a solvent selected from the group 
consisting of propylene carbonate (PC), butylene carbonate (BC), and 
mixtures of PC and BC. It is preferred that the EC is present in an amount 
by weight which is at least as great as the amount of the selected 
solvent, namely, the PC, the BC, or the mixture of PC and BC. In another 
embodiment, the mixture of solvents comprises propylene carbonate and 
ethylene carbonate, with the ethylene carbonate being present in an amount 
by weight which is at least as great as the amount of the propylene 
carbonate. Desirably, the solvent mixture comprises EC and PC in a weight 
ratio of 50EC:50PC to 75EC:25PC. Alternatively, the mixture desirably 
comprises 50EC:50BC. 
If desired, one or more additional organic solvents may be included in the 
solvent mixture. Such other organic solvents are selected from the group 
consisting of methyl ethyl carbonate (MEC), diethyl carbonate (DEC), 
dipropyl carbonate (DPC), dimethyl carbonate (DMC), and mixtures thereof. 
A preferred solvent mixture includes EC, PC and DMC where the EC is 
present in an amount not less than the amount by weight of the DMC and as 
stated earlier the EC is present is an amount by weight not less than of 
the PC. Accordingly, such solvent mixture preferably comprises the weight 
ratio 1EC:1PC:1DMC, corresponding to 1/3EC:1/3PC:1/3DMC and up to 
50EC:25PC:25DMC. This corresponds to 1EC:1PC:1DMC to 2EC:1PC:1DMC. In 
still another desirable embodiment, the solvent mixture comprises 
1EC:1PC:1BC to 2EC:1PC:1BC. Regardless of the nature of the one or more 
additional organic solvents besides EC and PC, the one or more other 
organic solvents preferably have a boiling point less than the boiling 
point of EC due to its tendency to solidify at ambient temperatures. 
In preparing a battery constituting the negative electrode described above 
and the electrolyte, essentially any counter electrode may be selected so 
long as it is capable of reacting electrochemically with the graphite 
negative electrode material. Preferred are lithium transition metal oxide 
compounds. The negative electrode and positive electrode are assembled in 
a battery with an electrolyte which provides ionic conductivity between 
the positive and negative electrode. Typically and preferably, the 
electrolyte is in the form of an electrolyte separator which further 
comprises a solid matrix forming a network with voids interpenetrated by 
the solvent mixture in solute. Essentially any type of electrolyte 
separator arrangement may be selected so long as the solvent consists of 
the preferred organic solvents mentioned above. In one embodiment, the 
electrolyte separator has a solid matrix which is a polymeric acrylate 
formed from acrylate precursors which are applied to a surface of the 
cathode or anode and then polymerized to form an electrolyte/electrode 
composite. In another embodiment the matrix is a porous polypropylene or 
polyethylene sheet or a sheet of fiber glass material placed between the 
anode and cathode. The nature of the electrolyte separator is not critical 
so long as it is used with the solvent mixture of the invention along with 
the stated graphite negative electrode defined by the invention. 
The propylene carbonate has a boiling point of approximately 240.degree. C. 
and a melting temperature of approximately -49.degree. C. It is a ringed 
structure. Other characteristics are as shown in Table IV. The ethylene 
carbonate has a boiling point of 248.degree. C., a melting temperature of 
about 39.degree. C. to 40.degree. C., and is also a ringed structure. The 
optional third solvent mixture component is preferably dimethyl carbonate 
which contains a carbon situated between two single bond oxygens and 
carrying a double bond to a third oxygen. Each of the single bonded oxygen 
are bonded in turn to respective methanes. The DMC has a boiling 
temperature of 91.degree. C. and a melting temperature of 4.6.degree. C. 
As can be seen in Table IV, the boiling temperature of DMC is lower than 
the boiling temperature of the EC and lower than the boiling temperature 
of the PC which means the DMC is considerably more volatile. As can also 
be seen from Table IV, the melting temperature of DMC is lower than the 
melting temperature of EC. It is preferred that if one or more additional 
organic solvents are added to the basic EC/PC mixture of the invention, 
that such added organic solvent have a boiling temperature lower than that 
of the EC and preferably a melting temperature lower than the EC in order 
to help maintain the EC solvent in a liquid state. 
In one embodiment, the lithium battery of the invention does not contain 
any metallic lithium. Such battery or cell comprises the electrolyte, 
positive electrode having an intercalation active material, and a negative 
electrode comprising the specific graphite of the invention. The graphite 
of the invention is in an initial condition, before charge (precharge) 
state or fully discharged state. In a lithiated, partially or fully 
charged state, the graphite active material is rendered to a state of 
charge represented by Li.sub.x C.sub.6 where x is greater than 0 and less 
than or equal to 1. Since the negative electrode is graphite without any 
lithium in an initial before charge state it is necessary to provide 
lithium for cell operation preferably in situ from the metallic lithium 
counter electrode which is then removed and replaced by the desired 
cathode intercalation active material; or from another component of the 
cell such as from a lithium-containing insertion compound of the cathode 
or a lithium-containing electrolyte. 
In one embodiment, the lithium is provided in situ from the cathode 
(positive electrode) which is a lithium-containing compound. The positive 
electrode contains either a lithiated insertion compound or a lithium 
compound able to deintercalate lithium to provide lithium ions for 
transport to the negative electrode. During an initial charge of the cell, 
the positive electrode deintercalates lithium for intercalation into the 
negative electrode, and during discharge the positive electrode inserts 
lithium while lithium is extracted from the graphite negative electrode. 
The process is repeated during subsequent charge and discharge. Examples 
of such lithium-containing compounds are lithium transition metal 
chalcogenide compounds. 
The term chalcogenide is generally taken to indicate compounds of oxygen, 
sulfur, selenium, and tellurium, accordingly, lithium transition metal 
oxygen compounds are included. Representative examples are Li.sub.x 
Mn.sub.2 O.sub.4, LiCoO.sub.2, LiNiO.sub.2, LiNiVO.sub.4, LiCoVO.sub.4, 
mixtures such as LiCoNiO.sub.2 and LiTmO.sub.2 where Tm is a transition 
metal or combinations of transition metals, and mixtures thereof. In a 
desirable embodiment, the positive electrode is a lithium metal oxide such 
as lithium manganese oxide. The cathode preferably is Li.sub.x Mn.sub.2 
O.sub.4 with x equal to 1 in an as prepared, initial condition. The 
positive electrode active material (cathode) is characterized by its 
ability to deintercalate lithium ions during charge so that lithium ions 
may be intercalated into the graphite negative electrode. During charging 
of the battery, the quantity x in the positive electrode Li.sub.x Mn.sub.2 
O.sub.4 declines from about 1 down to about 0. In the ideal case, all of 
the lithium would be deintercalated from the positive electrode and the 
value of x would decline to 0. Since some of the lithium may not be 
deintercalated during cell operation, subsequent charge and discharge, the 
value of x generally varies, with x being greater than 0 and less than or 
equal to 1. 
In an alternative embodiment, the electrolyte comprises a lithium compound 
from which lithium ions may be released for intercalation, in situ, into 
the uncharged graphite negative electrode. A preferred lithium compound of 
the electrolyte is a lithium salt. Examples include LiPF.sub.6, 
LiAsF.sub.6, LIB.sub.4, LiClO.sub.4, and LiCF.sub.3 SO.sub.3. 
In still another embodiment, some portion of the lithium intercalated into 
the graphite negative electrode upon charge is supplied by the lithium 
compound contained in the electrolyte, and some portion of the lithium is 
supplied to the negative electrode during charge by deintercalation from 
the positive electrode active material. 
As can be seen from the embodiments described above, advantageously the 
cell may be prepared in a discharged condition. In another embodiment, the 
negative electrode graphite is prepared in a precharged condition either 
external of the cell, or internally in the cell against a metallic lithium 
counter electrode where such metallic electrode is then replaced with the 
cathode material described hereinabove. The desired electrochemical 
battery is prepared using this prelithiated graphitic anode in combination 
with the desired cathode containing the desired positive electrode active 
material, forming the battery (cell) of the invention. 
A description of the electrochemical cell or battery which uses the novel 
active material and electrolyte of the invention will now be described. By 
convention, an electrochemical cell comprises a first electrode, a counter 
electrode which reacts electrochemically with the first electrode, and an 
electrolyte which is capable of transferring ions between the electrodes. 
A battery refers to one or more electrochemical cells. Referring to FIG. 
1, an electrochemical cell or battery (10) has a negative electrode side 
(12), a positive electrode side 14, and an electrolyte/separator 16 
therebetween. The negative electrode is the anode during discharge, and 
the positive electrode is the cathode during discharge. The negative 
electrode side includes current collector 18, typically of nickel, iron, 
stainless steel, and copper foil, and negative electrode active material 
20. The positive electrode side includes current collector 22, typically 
of aluminum or stainless steel, and such foils having a protective 
conducting coating foil, and a positive electrode active material 24. The 
electrolyte/separator 16 is typically a solid electrolyte, or separator 
and liquid electrolyte. Solid electrolytes typically refer to polymeric 
matrixes which contain an ionic conductive medium. Liquid electrolytes 
typically comprise a solvent and an alkali metal salt which form an 
ionically conducting liquid. In this latter case, the separation between 
the anode and cathode is maintained, for example, by a relatively inert 
layer of material such as glass fiber. The electrolyte is not an essential 
feature of the invention. Essentially, any ionically conducting 
electrolyte may be used. Essentially any method may be used to maintain 
the positive and negative electrodes spaced apart and electrically 
insulated from one another in the cell. Accordingly, the essential 
features of the cell are the positive electrode, a negative electrode 
electrically insulated from the positive electrode, and an ionically 
conducting medium between the positive and negative electrodes. Examples 
of a suitable separator/electrolyte, solvents, and salts are described in 
U.S. Pat. No. 4,830,939 showing a solid matrix containing an ionically 
conducting liquid with an alkali metal salt where the liquid is an aprotic 
polar solvent; and U.S. Pat. Nos. 4,935,317; 4,990,413; 4,792,504; and 
5,037,712. Each of the above patents is incorporated herein by reference 
in its entirety. 
In one embodiment, the electrolyte/separator comprises a solid polymeric 
matrix formed by polymerizing an organic or inorganic monomer which when 
used in combination with the other components of the electrolyte, renders 
the electrolyte solid. Suitable solid polymeric matrices are known in the 
art and include solid matrices formed from inorganic polymers, organic 
polymers, or mixtures comprising same. Preferably, the solid polymeric 
matrix is an organic matrix derived from a solid matrix forming monomer 
and from partial polymers of a solid matrix forming monomer. See, for 
example, U.S. Pat. No. 4,925,751, which is incorporated herein by 
reference. 
A particularly preferred solid polymeric matrix electrolyte is prepared 
from 36.26 grams of propylene carbonate, 3.45 grams of trimethyl propyl 
triacrylate, 36.26 grams of ethylene carbonate, and 13.79 grams of 
urethane acrylate which are combined at room temperature until homogenous. 
Then, 1.47 grams of polyethylene oxide film forming agent having a number 
average molecular weight of about 600,000 (available as Polyox WSR-205 
from Union Carbide Chemicals and Plastics, Danbury, Conn.) is added to the 
solution and then dispersed while stirring. The solution is then heated 
until the film forming agent is dissolved. The solution is then cooled to 
a temperature less than 48.degree. C. and then 8.77 grams of LiPF.sub.6 
(metal salt) are added to the solution while thoroughly mixing. The 
solution is preferably then degassed to provide for an electrolyte 
solution wherein little, if any, of the LiPF.sub.6 salt decomposes. Next, 
the electrolyte mixture is coated by a slot die coater or other variety of 
coater to a thickness of about 25 to 50 microns onto the surface of a 
dried electrode slurry, and preferably applied to the dried cathode 
slurry. In such a case, the solid electrolyte cell is assembled by 
laminating the anode half cell component to the cathode half cell 
component so that the electrolyte is positioned between the anode and the 
cathode. 
In another embodiment, the electrolyte used to form the completed cell is a 
combination of EC/PC and optionally one or more other organic solvents 
having a boiling less than the boiling point of the EC. The positive and 
negative electrodes are maintained in a separated condition using a fiber 
glass layer or a layer of porous polypropylene or porous polyethylene, 
about 25 microns thick. An example of a separator is sold under the 
designation Celgard.TM.. Hoechst-Celanese Corp., Celgard 2400.TM., porous 
polypropylene, 25 microns thick. 
The electrolyte composition typically comprises from about 5 to about 25 
weight percent of the inorganic salt based on the total weight of the 
electrolyte; preferably, from about 10 to 20 weight percent; and even more 
preferably from about 10 to about 15 weight percent. The percentage of 
salt depends on the type of salt and electrolyte solvent employed. 
For liquid electrolytes, the electrolyte composition typically comprises 
from about 80 to about 99 weight percent and preferably from about 85 to 
about 95 weight percent electrolyte solvent based on the total weight of 
the electrolyte. For solid electrolytes, the electrolyte composition 
typically comprises from about 40 to about 80 weight percent electrolyte 
solvent based on the total weight of the electrolyte; preferably from 
about 60 to about 80 weight percent; and even more preferably about 72 
weight percent. For solid electrolytes, the electrolyte composition 
typically comprises from about 5 to about 30 weight percent of the solid 
polymeric matrix based on the total weight of the electrolyte and 
preferably comprises from about 10 to about 20 weight percent. 
In summary, the graphite negative electrode of the invention essentially 
consists of the specific graphite material as described herein and a 
binder. The positive electrode of the invention is made by mixing a 
binder, the active material, and carbon powder (particles of carbon) which 
enhance conductivity of the active material. The binder composition is 
desirably a binder/electrolyte such as polymeric acrylates (plastics) 
which are x-linked by radiation curing or may be based on conventional 
electrolyte/binder systems. The binder/electrolyte is preferably the 
polymeric acrylate (plastic) with ionic conduction capability. After 
mixing, the resulting paste, containing the binder, active material, and 
carbon (for cathode), is coated onto a current collector, and any polymer 
content is polymerized, and cross-linked by heat radiation or other curing 
means. 
TABLE I 
__________________________________________________________________________ 
Coherence Median 
Interlayer 
Carbon Surface Area 
Length L.sub.c 
Density 
Particle 
Size d.sub.50 
Distance 
Material 
(m.sup.2 /g) (BET) 
(nm) (g/cm.sup.3).sup.2 
Size.sup.1 
(.mu.m) 
c/2 (nm) 
__________________________________________________________________________ 
SFG-6 15.2 &gt;100 2.26 &lt;6 3.2 0.3355 
SFG-10 11.1 &gt;150 2.26 &lt;12 5.8 0.3355 
SFG-15 8.8 &gt;120 2.26 &lt;16 8.1 0.3355 
SFG-44 4.2 &lt;200 2.26 &lt;48 22 0.3355 
KS-10 16 80 2.255 
&lt;12 5.9 0.3357 
KS-15 14 90 2.255 
&lt;16 7.7 0.3356 
KS-25 13 90 2.255 
&lt;24 10.5 0.3356 
BG-35 7 &gt;1000 0.195 
&lt;36 17 N/A 
F-399 23 &gt;1000 2.20 &lt;35 16 N/A 
MCMB-25-28 
N/A &gt;1000 2.24 37 22.5 0.336 
__________________________________________________________________________ 
.sup.1 Maximum size for at least 90% by weight of graphite particles, 
interpolated for F399 based on 87% less than 31 microns (.mu.m) , and 96% 
less than 44 micron (.mu.m). 
.sup.2 In xylene. 
Note: 
SFG and KS series are synthetic, anisotropic graphite. BG series is a 
flake natural graphite. F series is natural graphite. MCMB series is meso 
phase micro beads. 
TABLE II 
______________________________________ 
Graphite SPG-15 Specifications 
______________________________________ 
Guaranteed Values 
Ash (%) max 0.15 
Moisture (%) max 0.5 
Crystallite Height 
(nm) min 100 
Interlayer Distance 
(nm) 0.3354-0.3358 
Particle Size &lt;16 
(%) min, Laser 90 
micron 
______________________________________ 
Typical Values 
Purity 
Ash (%) 0.1 
Al (ppm) 35 
As (ppm) &lt;1 
Ca (ppm) 170 
Co (ppm) &lt;1 
Cr (ppm) 4 
Cu (ppm) &lt;1 
Fe (ppm) 135 
Mo (ppm) &lt;1 
Ni (ppm) 3 
Pb (ppm) &lt;1 
Sb (ppm) &lt;2 
Si (ppm) 450 
Ti (ppm) 7 
V (ppm) 2 
S (ppm) 60 
______________________________________ 
Crystallinity 
LC (nm) &gt;120 
c/2 (d.sub.002) 
(nm) 0.3355 
______________________________________ 
Density 
Xylene (g/ccm) 2.26 
Scott (g/ccm) 0.09 
______________________________________ 
Specific Surface Area 
BET (sqm/g) 8.8 
______________________________________ 
Particle Size Distribution (Laser Diffraction) 
&lt;2 micron (%) 2 
&lt;4 micron (%) 13 
&lt;6 micron (%) 30 
&lt;8 micron (%) 49 
&lt;12 micron (%) 79 
&lt;16 micron (%) 94 
&lt;24 micron (%) 99 
&lt;48 micron (%) 100 
d.sub.50 (.mu.m) 8.1 
______________________________________ 
TABLE III 
______________________________________ 
Graphite SPG-6 
Particle Size Distribution (Laser Diffraction) 
&lt;1 micron (%) 2.8 
&lt;1.5 micron (%) 5.1 
&lt;2 micron (%) 16.9 
&lt;3 micron (%) 47.7 
&lt;4 micron (%) 68.8 
&lt;6 micron (%) 95.8 
&lt;8 micron (%) 97.3 
&lt;12 micron (%) 100 
d.sub.50 (.mu.m) 3.2 
______________________________________ 
Graphite SFG-10 
Particle Size Distribution (Laser Diffraction) 
&lt;1 micron (%) 0.4 
&lt;2 micron (%) 4.8 
&lt;4 micron (%) 29.5 
&lt;6 micron (%) 57.1 
&lt;8 micron (%) 75.3 
&lt;12 micron (%) 94.9 
&lt;16 micron (%) 98.5 
&lt;32 micron (%) 100 
d.sub.50 (.mu.m) 5.8 
______________________________________ 
TABLE IV 
__________________________________________________________________________ 
Characteristics of Organic Solvents 
PC EC DMC DEC BC MEC DPC 
__________________________________________________________________________ 
Boiling Temperature (C) 
240 248 91.0 126 230 &lt;126 167-168 
Melting Temperature (C) 
-49 39-40 4.6 -43 -- -55 -- 
Density (g/cm.sup.3) 
1.198 1.322 1.071 
0.98 1.139 
1.007 
0.944 
Solution Conductivity (S/cm) 
2.1 = 10.sup.-9 
&lt;10.sup.-7 
&lt;10.sup.-7 
&lt;10.sup.-7 
&lt;10.sup.-7 
6 .times. 10.sup.-9 
&lt;10.sup.-7 
Viscosity (cp) at 25.degree. C. 
2.5 1.86 (at 40.degree. C.) 
0.59 0.75 2.52 0.65 -- 
Dielectric Constant at 20.degree. C. 
64.4 89.6 (at 40.degree. C.) 
3.12 2.82 -- -- -- 
Molecular Weight 
102.0 88.1 90.08 
118.13 
116.12 
104.10 
146.19 
H.sub.2 O Content 
&lt;10 ppm 
&lt;10 ppm &lt;10 ppm 
&lt;10 ppm 
&lt;10 ppm 
&lt;10 ppm 
&lt;10 ppm 
Electrolytic Conductivity 
5.28 6.97 11.00 
5.00 &lt;3.7 -- -- 
(mS/cm) 20.degree. C. 1M LiAsF.sub.6 
(1.9 mol) 
(1.5 mol) 
__________________________________________________________________________ 
TABLE A 
__________________________________________________________________________ 
Constant Current Cycling of Li/Carbon 
Cells Using EC/PC 50:50 w/1M LiPF6 
Carbon Material Reversible Specific 
1st Cycle Capacity 
of Half Cell 
Supplier 
Active Mass/[mg] 
Capacity/[mAh/g] 
Loss [%] 
__________________________________________________________________________ 
SFG-6 Lonza 
24.5 339 22 
SFG-10 Lonza 
25.6 344 19 
SFG-15 Lonza 
12.0 351 18 
SFG-44 Lonza 
15.6 0 100 
KS-10 Lonza 
17.5 74 89 
KS-15 Lonza 
12.2 105 95 
KS-25 Lonza 
14.9 0 100 
BG-35 Superior 
11.5 0 100 
F-399 Alumina 
17.5 200 57 
Trading 
MCMB25-28 Alumina 
48.0 225 29 
Trading 
50:50 by weight 
Mixed 
18.5 308 56 
MCMB2528/SFG-15 
Anode 
__________________________________________________________________________ 
Note: 
SFG and KS series are synthetic, anisotropic graphite. BG series is a 
flake natural graphite. F series is natural graphite. MCMB series is meso 
phase micro beads. 
TABLE B 
__________________________________________________________________________ 
Constant Current Cycling of Li/Carbon 
Cells Using EC/PC 25:75 w/1M LiPF6 
Carbon Material Reversible Specific 
1st Cycle Capacity 
of Half Cell 
Supplier 
Active Mass/[mg] 
Capacity/[mAh/g] 
Loss [%] 
__________________________________________________________________________ 
SFG-15 Lonza 
18 0 100 
MCMB25-28 Alumina 
30 293 46 
Trading 
50:50 by weight 
Mixed 
19 0 100 
MCMB2528/SFG-15 
Anode 
__________________________________________________________________________ 
TABLE C 
__________________________________________________________________________ 
Constant Current Cycling of Li/Carbon 
Cells Using EC/PC 75:25 w/1M LiPF6 
Carbon Material Reversible Specific 
1st Cycle Capacity 
of Half Cell 
Supplier 
Active Mass/[mg] 
Capacity/[mAh/g] 
Loss [%] 
__________________________________________________________________________ 
SFG-15 Lonza 
18.6 355 18 
SFG-44 Lonza 
16.7 305 68 
KS-10 Lonza 
17.5 189 77 
MCMB25-28 Alumina 
32.0 288 16 
Trading 
50:50 by weight 
Mixed 
18.3 311 23 
MCMB2528/SFG-15 
Anode 
__________________________________________________________________________ 
TABLE D 
__________________________________________________________________________ 
Constant Current Cycling of Li/Carbon 
Cells Using EC/PC/DMC 1:1:1 w/1M LiPF6 
Carbon Material Reversible Specific 
1st Cycle Capacity 
of Half Cell 
Supplier 
Active Mass/[mg] 
Capacity/[mAh/g] 
Loss [%] 
__________________________________________________________________________ 
SFG-15 Lonza 
18.2 346 22 
MCMB2828 Alumina 
28.0 0 100 
Trading 
50:50 by weight 
Mixed 
18.1 293 40 
MCMB2528/SFG-15 
Anode 
__________________________________________________________________________ 
TABLE E 
__________________________________________________________________________ 
Constant Current Cycling of Li/Carbon 
Cells Using PC/DMC 50:50 w/1M LiPF6 
Carbon Material Reversible Specific 
1st Cycle Capacity 
of Half Cell 
Supplier 
Active Mass/[mg] 
Capacity/[mAh/g] 
Loss [%] 
__________________________________________________________________________ 
SFG-15 Lonza 
18.1 0 100 
__________________________________________________________________________ 
TABLE F 
______________________________________ 
Active Rev. Specific 
First Cycle 
Supplier Mass Capacity (mAh/g) 
Capacity Loss 
______________________________________ 
SFG-15 Lonza 18.5 307 38% 
SFG-15 Lonza 18.5 324 36% 
KS-15 Lonza 12.2 105 93% 
KS-15 Lonza 12.2 90 94% 
______________________________________ 
TABLE G 
______________________________________ 
Electrode Rev. Specific 
First Cycle 
Material 
Active Mass (mg) 
Capacity (mAh/g) 
Capacity Loss 
______________________________________ 
Li.sub.x Mn.sub.2 O.sub.4 
45.0 119 10% 
Li.sub.x Mn.sub.2 O.sub.4 
45.0 110 11% 
______________________________________ 
EXAMPLE 
Positive Electrode 
The positive electrode containing LiMn.sub.2 O.sub.4 was prepared by the 
following method. For the positive electrode, the content was as follows: 
50 to 90 percent by weight active material (LiMn.sub.2 O.sub.4); 5 to 30 
percent carbon black as the electric conductive diluent; and 3 to 20 
percent binder preferably chosen to enhance ionic conductivity. The stated 
ranges are not critical. The amount of active material may range from 25 
to 85 weight percent. The formation of each electrode will now be 
described. The positive electrode was prepared from mixtures of 
lithium-manganese oxide (active material) and EPDM (ethylene propylene 
diene monomer) as the binder, Shawinigan Black.RTM. was used as the carbon 
powder conductive diluent. The carbon powder conductive diluent is used to 
enhance electronic conductivity of the lithium-manganese oxide. Shawinigan 
Black.RTM., available from Chevron Chemical Company, San Ramone, Calif., 
has a BET average surface area of about 70 .+-.5 square meters per gram. 
Other suitable carbon blacks are sold under the designation Super P.TM. 
and Super S.TM. available from MMM, a subsidiary of Sedema, which carbons 
have BET surface areas of about 65 .+-.5 square meters per gram. (MMM 
Sedema, S.A., has its headquarters in Brussels, Belgium.) Examples of 
suitable polymeric binders include EPDM (ethylene propylene diene 
termonomers), PVDF (polyvinylidene difluoride), ethylene acrylic acid 
copolymer, EVA (ethylene vinyl acetate copolymer), copolymer mixtures, and 
the like. It is desirable to use either PVDF available from Polysciences 
Corporation with a molecular weight of 120,000 or EPDM available from 
Exxon Corporation and sold under the designation EPDM 2504.TM.. EPDM is 
also available from The Aldrich Chemical Company. The description of 
carbon powders and binders constitute representative examples and the 
invention is not limited thereby. For example, other carbon powders are 
available from Exxon Chemicals, Inc., Chicago, Ill. under the trade name 
Ketjen Black EC 600 JD.RTM. and polyacrylic acid of average molecular 
weight 240,000 is commercially available from BF Goodrich, Cleveland, Ohio 
under the name Good-Rite K702.TM.. The positive electrodes of the 
invention comprised mixtures of the active material LiMn.sub.2 O.sub.4, 
the binder (EPDM), and the carbon particles (Shawinigan Black.RTM.). These 
were mixed and blended together with a solvent. Xylene is a suitable 
solvent. The mixture was then coated onto an aluminum foil current 
collector to achieve a desired thickness for the final electrode. 
The Li.sub.x Mn.sub.2 O.sub.4 powders which form the basis of the active 
material for the cathode, can be prepared by a method as described by 
Barboux, Tarascon et al in U.S. Pat. No. 5,135,732, issued Aug. 4, 1992 
and incorporated by reference in its entirety. This reference is 
illustrative of a suitable method and is not limiting. This method 
produced active material which is used as the cathode (positive electrode) 
active material. Such methods are used to produce positive electrodes for 
use with negative electrodes of metallic lithium. There is also described 
a 3 volt lithium-manganese oxide cathode material for use with metallic 
anodes in an article entitled "A 3 Volt Lithium-Manganese Oxide Cathode 
for Rechargeable Lithium Batteries" by Haitao Huang and Peter Bruce as 
published in J. Electrochem. Soc., Volume 141, No. 7, July 1994. The 
manganese oxide cathode of the nominal general formula LiMn.sub.2 O.sub.4 
is prepared with a specific composition LiMn.sub.2 O.sub.4.1. These are 
considered to be essentially a defect lithium-manganese oxide spinel 
LiMn.sub.2 O.sub.4.1 prepared by a solution route. Accordingly, the term 
"nominal general formula Li.sub.1 Mn.sub.2 O.sub.4 " represents a family 
of suitable LiMn.sub.2 O.sub.4 type compositions including those with the 
defect spinel with a higher average oxidation state than the typical 
stoichiometric LiMn.sub.2 O.sub.4. Other spinel type materials are 
suitable, such as, Li.sub.2 Mn.sub.4 O.sub.9 and Li.sub.4 Mn.sub.5 
O.sub.12 as well as chemical manganese dioxide, a mixture 
.gamma./.beta.Mno.sub.2, and lithiated spinels. In the Huang et al 
process, a minor amount of carbon is added to the solution in order to 
achieve the defective spinel. However, such carbon is less than that 
typically included in a cathode formulation and additional carbon is 
typically added as described more fully below. 
Negative Electrode 
The negative electrode of the invention preferably comprises about 80 to 
about 95 percent by weight of the specific graphite particles, and more 
preferably about 90 percent by weight with the balance constituted by the 
binder. Preferably, the anode is prepared from a graphite slurry as 
follows. A polyvinylidene difluoride (PVDF) solution was prepared by 
mixing 300 grams of 120,000 MW PVDF (PolyScience) in 300 ml of dimethyl 
formamide. The mixture was stirred for 2 to 3 hours with a magnetic 
stirrer to dissolve all of the PVDF. The PVDF functions as a binder for 
the graphite in the anode. Next, a PVDF/graphite slurry was prepared by 
first adding 36 grams of graphite (SFG-15) into about 38.5 grams of the 
PVDF solution. The mixture was homogenized with a commercial homogenizer 
or blender. (For example, Tissue Homogenizer System from Cole-Parmer 
Instrument Co., Niles, Ill.). The viscosity of the slurry was adjusted to 
about 200 cp with additional PVDF solution. The slurry was coated onto a 
bare copper foil by standard solvent casting techniques, such as by a 
doctor blade type coating. (Alternatively, the slurry can be coated onto a 
copper foil having a polymeric adhesion promoter layer, described above.) 
In preparing the slurry, it is not necessary to grind or dry the graphite, 
nor is it necessary to add conductive carbon black to the graphite anode 
formulation. Finally, the electrodes are dried at approximately 
150.degree. C. for 10 hours to remove residual water prior to making the 
electrochemical cells. 
Electrolyte 
The electrolyte used to form the completed cell as tested in FIGS. 2 and 3 
comprised ethylene carbonate and propylene carbonate in a ratio of 1:1 by 
weight (1EC:1PC, by weight). The positive and negative electrodes were 
maintained in a separated condition using a fiber glass layer. The 
electrolyte salt was a concentration of 1M LiPF.sub.6 providing a liquid 
electrolyte which interpenetrated the void spaces of the fiber glass 
layer. 
Various methods for fabricating electrochemical cells and for forming 
electrode components are described herein. The invention is not, however, 
limited by any particular fabrication method as the novelty lies in the 
unique negative electrode material itself and combination of positive and 
negative electrode materials. Accordingly, additional methods for 
preparing electrochemical cells and batteries may be selected and are 
described in the art, for example, in U.S. Pat. No. 5,435,054 (Tonder & 
Shackle); U.S. Pat. No. 5,300,373 (Shackle); U.S. Pat. No. 5,262,253 
(Golovin); U.S. Pat. No. 4,668,595; and U.S. Pat. No. 4,830,939 (Lee & 
Shackle). Each of the above patents is incorporated herein by reference in 
its entirety. 
FIG. 2 shows a voltage profile of a rocking chair battery, based on 
LiMn.sub.2 O.sub.4 positive electrode and the graphite negative electrode 
of the invention, using the SFG-15 graphite. This was obtained in a 
three-electrode cell where the additional reference electrode (Li) is used 
in order to discriminate individual responses from the positive and 
negative electrodes. FIG. 2 is based on 29 mAh reversible capacity, 2.4 
milliamp hours per square centimeter, 12 square centimeter electrodes, a 
graphite active material loading of about 6.5 milligrams per square 
centimeter, and a LiMn.sub.2 O.sub.4 loading of about 18.4 milligrams per 
square centimeter. The electrochemical properties of the electrodes was 
determined using a 2-electrode cell whereby electrochemical and kinetic 
data are recorded using Electrochemical Voltage Spectroscopy (EVS) 
technique. Electrochemical and kinetic data were recorded using the 
Electrochemical Voltage Spectroscopy (EVS) technique. Such technique is 
known in the art as described by J. Barker in Synth, Met 28, D217 (1989); 
Synth. Met. 32, 43 (1989); J. Power Sources, 52, 185 (1994); and 
Electrochemica Acta, Vol. 40, No. 11, at 1603 (1995). The EVS 
voltage/capacity profile as shown in FIG. 2 is for the cell 
SFG-15/LiMn.sub.2 O.sub.4, with the EC/PC electrolyte in a weight ratio of 
50:50 EC/PC and including the LiPF.sub.6 salt. FIG. 2 clearly shows and 
highlights the very high and heretofore unexpected degree of reversibility 
of lithium ion reactions of the graphitic electrode of the invention. The 
negative electrode showed a performance of 374 milliamp hours per gram and 
the positive electrode showed a performance of 132 milliamp hours per gram 
on the first discharge. In FIG. 2 the capacity in is essentially 34.8 
milliamp hours and the capacity out is essentially 29.2 milliamp hours 
resulting in a capacity loss of approximately 5.6 milliamp hours 
corresponding to a remarkably low 16.1 percent loss. Accordingly, the 
electrochemical cell of the invention has a first cycle capacity loss of 
less than 20 percent and on the order of 10 to 20 percent where the first 
cycle capacity loss in percent is calculated according to Equation I. 
##EQU1## 
where FC stands for first cycle. FIG. 3 is an EVS of the differential 
capacity plot based on FIG. 2 for SFG-15/LiMn.sub.2 O.sub.4 with 1EC:1PC 
by weight, with LiPF.sub.6 salt. As can be seen from FIG. 3, the 
symmetrical nature of peaks indicates good electrochemical reversibility, 
with small peak separations on charge (above the axis) and discharge 
(below the axis). This corresponds to low overvoltage. There are no peaks 
that can be related to irreversible reactions. All peaks above the axis 
have corresponding peaks below. If electrolyte (i.e., PC) breakdown on 
graphite was present, there would have been an irreversible charge 
consumption around 3.2 volts of cell voltage on charge. Absence of such 
irreversible charge consumption is further evidence of the unique and 
unexpected advantage of the present invention. 
FIG. 4 is a two part graph with FIG. 4A showing the excellent 
rechargability of the LiMn.sub.2 O.sub.4 /graphite cell. FIG. 4B shows the 
excellent cycling and capacity of the cell. The capacity was determined at 
constant current cycling, plus or minus 1 milliamp per centimeter squared, 
for cycles 1 to 47; with a voltage range of 2.5 to 4.3 volts. As in the 
case for FIGS. 2 and 3, the cell electrolyte consists of 1EC:1PC by 
weight, with 1 molar LiPF.sub.6 ; and the separator is a glass fiber. As 
in the case of FIGS. 2 and 3 the LiMn.sub.2 O.sub.4 is estimated at 132 
milliamp hours per gram and the graphite anode of the invention is 
estimated at 374 milliamp hours per gram. 
It should be noted that FIGS. 4A (recharge ratio) and 4B (discharge 
capacity) show the performance of four LiMn.sub.2 O.sub.4 /graphite cells 
prepared in the same manner according to the invention. As shown in FIG. 
4A the recharge ratio is very high, at least 0.0986 after 47 cycles. As 
shown in FIG. 4B after up to 47 cycles, the capacity remains high at 
between about 0.017 and 0.02 amp hours or 17 to 20 milliamp hours. This 
performance is far in excess of the performance expected by a cell which 
contains a graphite negative electrode and a propylene carbonate solvent 
mixture. This result is truly advantageous and amazing, especially given 
that capacities are maintained over a large number of cycles. 
The remarkable performance of the specific graphites of the invention were 
further investigated to verify these heretofore unexpected results by 
comparison to other carbons (carbonaceous material) attempted to be used 
as electrode material. Such tests were conducted at constant current 
cycling. The carbon materials were cycled against metallic lithium anode 
using different electrolytes. In Table A the electrolyte was EC/PC in a 
50:50 weight percent with 1 molar LiPF.sub.6. In Table B the electrolyte 
was 25EC:75PC by weight with 1 molar LiPF.sub.6. In Table C the cell 
electrolyte was 75EC:25 PC with 1 molar LiPF.sub.6. In Table D the 
electrolyte was ethylene carbonate, propylene carbonate, and dimethyl 
carbonate in a ratio by weight of 1:1:1, also with 1 molar LiPF.sub.6 as 
the salt. The electrolyte of Table E consisted of propylene carbonate and 
dimethyl carbonate in a ratio of 50:50 with 1 molar LiPF.sub.6. Table F 
contains results for 50:50 by weight EC:BC (ethylene carbonate/butylene 
carbonate) with 1 molar LiPF.sub.6, at .+-.0.2 mA/cm.sup.2, 2.0-0.01 volts 
for SFG-15 and KS-15. Table G contains results of testing the same 
electrolyte as per Table F against the Li.sub.x Mn.sub.2 O.sub.4 active 
material, at 3.0-4.3 volts. In all cases, the test electrode and the 
lithium metal counter electrode were separated by a glass fiber which was 
interpenetrated by the electrolyte solvent comprising the organic solvents 
named above with 1 molar LiPF.sub.6 salt dissolved therein. More 
specifically, data as shown in Tables A through E was obtained using 
lithium metal/carbon half cells to compare the inventive graphite 
compositions to other carbon materials. Each half cell includes a lithium 
metal anode with an active material size of approximately 2.4 cm.sup.2 
area of the disk-shaped electrode. The cathode comprises the carbon 
material as shown in Tables A through E, with 10 percent by weight binder. 
The glass fiber separator is about 10 microns thick. The liquid 
electrolyte comprises a salt as stated for each of the respective cells 
identified in Tables A through E. The specific capacity of the anode 
material is at constant current cycling at about .+-.0.2 milliamps per 
square centimeter, and the first cycle capacity loss was measured for each 
half cell and calculated in accordance with Equation I stated earlier. The 
voltage limits were 2.0 and 0.01 volts. Results shown in Tables A through 
E will now be described. 
As can be seen in Results Table A, several types of carbons were tested to 
determine suitability in combination with EC/PC 50:50 by weight and 1M 
LiPF.sub.6. In Results Table A, only the graphite types SFG-6, 10, and 15 
showed reversible anode capacity in of over 300 milliamp hours per gram in 
combination with capacity loss less than 25 percent. This result is quite 
remarkable since synthetic graphites of similar particle size, KS-10 and 
15 demonstrated extremely poor results, namely, reversible capacity as low 
as 0 and first cycle capacity loss as high as 100 percent. The KS series 
of similar particle size has a very low L.sub.c compared to SFG. The 
BG-35, F-399, and MCMB 25-28 characterized by very high L.sub.c compared 
to SFG, showed consistently poor performance. 
Results Table B contains data showing performance where the electrolyte 
solvent contains a high concentration of PC with respect to EC, namely, 
25EC:75PC, by weight, with 1M LiPF.sub.6. In all cases, the reversible 
capacity is very poor and the first cycle capacity loss is on the order of 
45 to 100 percent. This shows the striking and heretofore unexpected 
sensitivity of the electrolyte solvent composition with respect to the 
carbon. 
Results Table C shows the combination of 75EC:25PC, by weight with 1M 
LiPF.sub.6. One of the graphites of the invention (SFG-15) is the only 
carbonaceous material showing a reversible specific capacity greater than 
300 milliamp hours per gram with a first cycle loss of less than 20 
percent. Only in the case where the undesirable MCMB 25-28 is mixed with 
SFG-15 (50:50 by weight) is there a capacity greater than 300 milliamp 
hours per gram. However, the loss is over 20 percent. 
Results Table D shows the constant current cycling of lithium/carbon cells 
using a ratio of ethylene carbonate (EC)/propylene carbonate (PC)/dimethyl 
carbonate (DMC) of 1:1:1 on a weight percent basis and includes 1 molar 
LiPF.sub.6 as the salt. As can be seen from Results Table D, the only cell 
showing reversible specific capacity greater than 300 milliamp hours per 
gram is with the SFG-15 graphite which shows a first cycle capacity loss 
of less than 25 percent. The performance of the other comparative cells 
demonstrates reversible specific capacity less than 300 milliamp hours per 
gram and a first cycle capacity loss of 40 to 100 percent. 
Results Table E shows the constant current cycling of an Li/graphite cell 
using propylene carbonate and dimethyl carbonate in a ration of 1:1 by 
weight with 1 molar LiPF.sub.6 salt dissolved therein. The SFG-15 graphite 
anode of the invention did not perform in this cell as the first cycle 
capacity loss was 100 percent. Results Tables B and E when examined 
carefully together demonstrate the extreme sensitivity of the type of 
carbon material, and of the composition, and concentration of components 
of the electrolyte. An electrolyte containing too great an amount of PC 
with respect to the EC does not perform; and an electrolyte containing 
only PC and DMC does not perform. 
The results in Table F show that a combination of EC/BC is workable with 
reasonably high reversible specific capacity 307 to 325 mAh/g with SFG-15, 
and first cycle irreversible capacity loss less than 40 percent. The KS-15 
has very poor performance in EC/BC. The remarkable stability of the 
electrolyte of the invention is shown in Table G, where EC/BC is tested 
against the Li.sub.x Mn.sub.2 O.sub.4 active material. The electrolyte 
comprising EC/PC is likewise stable when used with Li.sub.x Mn.sub.2 
O.sub.4. 
While this invention has been described in terms of certain embodiments 
thereof, it is not intended that it be limited to the above description, 
but rather only to the extent set forth in the following claims. 
The embodiments of the invention in which an exclusive property or 
privilege is claimed are defined in the following claims.