US20030160215A1

US20030160215A1 - Coated carbonaceous particles particularly useful as electrode materials in electrical storage cells, and methods of making the same

Info

Publication number: US20030160215A1
Application number: US10/066,080
Authority: US
Inventors: Zhenhua Mao; H. Romine; Mark Carel
Original assignee: ConocoPhillips Co
Current assignee: ConocoPhillips Co
Priority date: 2002-01-31
Filing date: 2002-01-31
Publication date: 2003-08-28
Also published as: EP1472327A1; US20050247914A1; JP4303126B2; JP2005515957A; WO2003064560A1; EP1472327A4; US20080090148A1; CN1625593A; KR100956251B1; CN1625593B; CA2471015C; MY139584A; CA2471015A1; KR20040086320A; US7323120B2; US9096473B2

Abstract

A process for the production of coated carbonaceous particles, and the coated carbonaceous particles produced thereby of which process comprises the steps of: providing particles of a carbonaceous material; providing particles of a carbonaceous material; providing a coating of a fusible, carbon residue forming material onto the surface of said particles; stabilizing the coated particles by subjecting said particles to an oxidation reaction using an oxidizing agent; subsequently carbonizing the coated particles; and, optionally thereafter graphitizing the coated particles. The coated carbonaceous particles find particular use in electrodes of electrical storage cells, especially rechargeable lithium ion storage cells.

Description

The present invention relates to graphitic materials which are useful as electrodes in batteries. More particularly the present invention relates to coated carbonaceous particles which find particular use as electrode materials, as well as methods for the manufacture of said coated carbonaceous particles.

Carbonaceous materials are widely used in electrical storage cells, also referred to as “batteries” due to their efficiency and reasonable cost. Various forms of carbonaceous materials are used. One such carbonaceous material is graphite, which is known to be useful in rechargeable storage cells, also referred to as “rechargeable batteries”. In a salient example, graphitic materials are known to be useful as anode materials in rechargeable lithium ion, “Li-ion” storage cells. Li-ion cells are mainly used as the power sources in portable electronic devices.

As opposed to other classes of rechargeable batteries, i.e., e.g., nickel-cadmium and nickel-metal hydride storage cells, Li-ion cells are increasingly popular due to their relatively higher storage capacity, and their easily rechargeable nature. Due to such higher storage capacity per unit mass or unit volume, Li-ion cells may be produced which meet specific storage and current delivery requirements as they are smaller than similarly rated, nickel-cadmium and nickel-metal hydride storage cells. Consequently, Li-ion cells are popularly used in a growing number of devices, i.e., digital cameras, digital video recorders, computers, etc., where small sized devices are particularly desirable from a utility or consumer standpoint. Nonetheless, rechargeable Li-ion storage cells are not without their shortcomings, certain of which are dependent upon their materials of construction.

Popular types of Li-ion storage cells include electrodes formed of mesophase carbon micro beads (MCMB) or micronized mesophase carbon fiber (MMCF). However, both MCMB and MMCF are relatively expensive due to relatively complex manufacturing processes required for these materials. Further types of Li-ion storage cells include electrodes formed of comminuted or milled graphitic materials which are derived from purified natural graphite or synthetic graphite. While these materials exhibit satisfactory storage capacity, they unfortunately exhibit a low initial charging efficiency on their first cycle. Typically, the charging efficiency of these materials ranges widely, usually from as little as about 40% to as high as about 90%. It is known that the efficiency of these comminuted or milled graphitic materials is strongly dependent upon the morphology of the comminuted or milled graphitic particles. Due to their irregular nature, these pulvurent comminuted or milled graphitic materials frequently suffer from a low packing density which also limits the density from any electrode formed therefrom, which also limits the operating characteristics of a rechargeable storage cell. Also, due to their irregular nature, processing these pulvurent comminuted or milled graphitic materials into electrodes is difficult. In such electrodes formed from pulvurent comminuted or milled graphitic materials, it has been suggested that poor operating characteristics is in part attributable to the formation of a passive film on the surfaces of these pulvurent materials. Such a film is frequently described in the art as being a solid electrolyte interface (“SEI”). The formation of this SEI irreversibly consumes a quantifiable amount, frequently a significant amount of lithium ions (typically 15 to 50%) present in the cathode upon cell assembly or use.

Accordingly there exists a real and continuing need in the art for improved materials useful in the manufacture of storage cells, particularly rechargeable storage cells which exhibit improved operating characteristics. There also exist needs in the art for improved methods for the manufacture of improved materials useful in the manufacture of such storage cells, as well as for improved storage cells containing said improved materials.

In one aspect the present invention provides graphitic materials which comprise coated carbonaceous particles, wherein the coating layer is formed of an oxidized, carbon residue forming material, which coating layer may be also graphitized. These coated carbonaceous particles are particularly useful in the manufacture of electrodes in electrical storage cells, particularly in rechargeable electrical storage cells.

A further aspect of the invention are free-flowing coated carbonaceous particles with substantially smooth coatings formed of an oxidized, carbon residue forming material, which coating layer may be also graphitized.

In further aspects of the invention there are provided methods for the manufacture of such coated carbonaceous particles.

A still further aspect of the invention relates to the use of said coated carbonaceous particles in electrical storage cells, particularly in rechargeable batteries.

In a yet further aspect of the invention there are provided methods for the manufacture of electrical storage cells, particularly rechargeable batteries which include said coated carbonaceous particles.

These and other aspects and features of the invention will become apparent from the following description of the invention and preferred embodiments thereof.

In one aspect the present invention provides processes for the manufacture of coated carbonaceous particles, which materials exhibit improved operating characteristics when used as electrodes in electrical storage cells, particularly in rechargeable electrical storage cells. Generally the process contemplates the steps of:

providing particles of a carbonaceous material;

providing a coating of a fusible, carbon residue forming material onto the surface of said particles;

stabilizing the coated particles by subjecting said particles to an oxidation reaction using an oxidizing agent;

subsequently carbonizing the coated particles; and,

thereafter optionally, but preferably graphitizing the coated particles.

Preferably the process provides particles having a substantially smooth coatings.

Particles of carbonaceous material are required for the practice of the invention. These may be obtained from a variety of sources, examples of which include pitches, petroleum and coal tar cokes, synthetic and natural graphites, soft carbons derived from organic and natural polymers as well as other sources of carbonaceous materials which are known in the manufacture of prior art electrodes although these sources are not elucidated here. Preferred sources of carbonaceous materials include calcined or uncalcined petroleum cokes, as well as natural and synthetic graphite. Particularly preferred sources of carbonaceous materials include calcined and un-calcined, highly crystalline “needle” cokes. Thus, preferred carbonaceous materials are either graphitic or form graphite on heating to graphitization temperatures of 2200° C. or higher. Fine particles of such materials are conveniently provided by milling, crushing, grinding or by any other means which can be used to provide a pulvurent carbonaceous material having particles of dimensions which are suitable for use in the formation of electrodes. Although the principles of the present invention are believed to be applicable to carbonaceous particles of varying sizes and particle size distributions, preferred carbonaceous particles having average particle sizes of up to about 150 mm, more preferably from about 5 mm to about 70 mm, and most preferably average particle sizes in the range of about 5 mm to about 45 mm are particularly preferred. Further, it is preferred that within these ranges, the particle size distribution is preferably such that not more than 10% of the particles are smaller than 5 μm, not more than 10% of the particles are larger than 60 μm; further it is still more preferred that in addition to such a particle size distribution that the mean particle size is 10 to 30 μm

According to a step of the inventive process, the carbonaceous particles are provided with a fusible, carbon residue forming material as a coating material. Preferred for use as the coating material are carbon residue forming materials which can be reacted with an oxidizing agent. Exemplary useful coating materials include heavy aromatic residues from petroleum, chemical process pitches; lignin from pulp industry; phenolic resins, and carbohydrate materials such as sugars and polyacrylonitriles. Especially preferred for use as coating materials are petroleum and coal tar pitches, and lignin which are readily available and have been observed to be effective as fusible, carbon residue forming materials.

It is to be understood that the carbon residue forming material may be any material which, when thermally decomposed in an inert atmosphere to a carbonization temperature of 850° C. or an even greater temperature, forms a residue which is “substantially carbon”. It is to be understood that “substantially carbon” indicates that the residue is at least 90% wt. carbon, preferably at least 95% wt. carbon. It is also preferred that the carbon residue forming material form at least 10% and preferably at least 40% and more preferably at least 60% carbon residue on carbonization, based on the original mass of the carbon residue forming material.

Any useful technique for coating the carbonaceous particles may be used. By way of non-limiting examples, useful techniques include the steps of: liquefying the carbon residue forming material by a means such as melting or forming a solution with a suitable solvent combined with a coating step such as spraying the liquefied carbon residue forming material onto the carbonaceous particles, or dipping the carbonaceous particles in the liquefied carbon residue forming material and subsequently drying out any solvent. Further useful techniques include selective precipitation of a carbon residue forming material on the carbonaceous particles which may be preferred in certain circumstances.

A further technique which may be used includes providing a dry coating of the carbon residue forming material onto the carbonaceous particles such as by mixing or tumbling these materials until a coating of the carbon residue material is provided on the surface of the carbonaceous particles, after which the dry coating is then fused to provide a coating upon the surface of the carbonaceous particles. While any of these coating techniques may be practiced, preferred methods include those which provide a relatively uniform coating thickness of the carbon residue forming material on the carbonaceous particles and which minimize clumping or agglomeration of the coated particles. The amount of the carbon residue forming material deposited on the carbonaceous particles may also vary widely, and it is understood that this amount depends in part on factors including the uniformity of the coating and the specific form and surfaces of the carbonaceous particles. Although the amount of coating may vary from as little as 1% wt. to as much as 50% wt., expressed as the percentage of the mass of the coating relative to the total mass of the coated particles as measured by weighing the dry particles before and after coating, preferably the amount of coating ranges from about 2.5% wt. to about 25% wt., more preferably ranges from about 5% wt. to about 20% wt.

According to a further step of the inventive process, the coating of the carbonaceous particles are rendered partly or completely infusible, preferably by oxidative stabilization. The coating of the carbonaceous particles are stabilized by subjecting said particles to an oxidation reaction using an oxidizing agent under appropriate reaction conditions. Generally, only mild to moderate reaction conditions are required. Typically the oxidation reaction is satisfactorily performed by contacting the coated carbonaceous particles with an oxidizing agent at elevated temperatures or by contacting the coated carbonaceous particles with an oxidizing agent at mild conditions and activating the oxidizing agent at elevated temperatures. Contact with the oxidizing agent can occur at ambient temperatures (approx. 20° C.) or at moderately elevated temperatures, (up to approx. 400° C.). Activation of the oxidizing agent would typically occur at moderately elevated temperatures up to 400° C. Preferably, the temperature of the oxidation reaction is maintained below the instantaneous melting point of the coating material, so to ensure that melting point of the coating material is not exceeded during the oxidation reaction.

The manner of practice of this step of the inventive process is understood to be dependent upon the form of the oxidizing agent utilized, which may be solid, liquid or gaseous under the reaction conditions. Likewise, various oxidation reaction processes and reaction conditions may be practiced and are considered to be within the scope of the present invention.

Wherein the oxidizing agent is a solid, it is required only that the solid oxidizing agent be placed in sufficiently intimate contact with the coated carbonaceous particles such that, under appropriate reaction conditions, a satisfactory degree of oxidation is obtained. This is most effectively accomplished by forming a liquid solution of the oxidizing agent, applying this solution to the coated particles and drying. When practical, it is preferred to apply the carbon residue forming material and oxidant coatings at the same time in a single step. Where necessary, the oxidizing agent can be brought to suitable reaction conditions in order to insure the initiation and success of an oxidation reaction. Such conditions may take place under ambient pressure and temperature conditions (approximately 20° C., 1 atm) however, depending upon the nature of the oxidizing agent, the nature of the coating material, as well as in part the nature and form of any reaction vessel which may be used for the oxidation reaction, it may be desirous to modify the temperature and/or pressure, or both from ambient. Typically, elevating the temperature up to 400° C. facilitates the initiation and the subsequent oxidation reaction, but in fact, any temperature up to the degradation temperature of the coating material can be successfully used. With regard to the nature of any reaction vessel, any conventionally used reaction vessel or device can be used. With regard to the identity of solid oxidizing agents, by way of non-limiting examples, these include: inorganic and organic oxidizers such as metal oxides and salts such as alkali nitrates and alkali sulfates such as are represented by MNO ₃and M₂SO₄, where M denotes an alkali metal, as well as M′O_xwhere M′ represents a transition metal. Exemplary solid oxidizing agents further include inorganic salts such as sodium nitrate (NaNO₃) and organic salts, as well as those described in the following examples.

Where the oxidizing agent is a liquid, it is required only that the oxidizing agent be provided in a liquid form which is compatible with the coated carbonaceous particles. It is clearly contemplated that the oxidizing agent itself need not constitute 100% of the liquid, but rather that the oxidizing agent be provided as a solution, suspension, or other fluid which comprises an oxidizing agent or agents therein. It is anticipated that when the oxidizing agent is supplied as a solution or suspension, it may be desirable to include a drying step so to dry the coated particles. It is contemplated that the oxidizing agent, when present in a liquid form, is also compatible with the coated carbonaceous particles namely, that any portion of the liquid does not act to undesirably degrade or solubilize the fusible, carbon residue forming material or for that matter, the carbonaceous particles themselves. By way of non-limiting example, exemplary oxidizing agents which are provided in a liquid form include various oxidizing acids such as nitric acid, perchlorate acid, phosphorous acid, sulfuric acid, as well as aqueous and non-aqueous solutions containing oxidizing salts such as peroxides and KMnO ₄Additional liquid oxidizing agents include peroxides and aryl quinones, as well as those described in one or more of the examples.

The nature of the condition of the oxidizing reaction is not critical to the practice of the invention particularly wherein the oxidizing agent is in a liquid form. Rather, it is only required that the reaction conditions be appropriate to insure the oxidation of at least a portion of the coating provided to the carbonaceous particles such that they form a stabilized coating thereupon. Any conventional reactor, and appropriate reaction conditions can be used. As described previously, with respect to solid oxidizing agents, the reaction conditions can take place at ambient temperature and pressure conditions, or may require different conditions depending upon the coating, the nature of the carbonaceous particles, the reaction vessel, and of course, the nature of the oxidizing agent utilized. With regard to reactor vessels, stirred reactor vessels which are optionally pressurized are conveniently used.

Where the oxidizing agent is gaseous, again it is required only that this gaseous oxidizing agent be brought into sufficient intimate contact with the coated carbonaceous particles under appropriate reaction condition in order to insure the oxidization reaction of the carbon residue forming material. According to this aspect of the invention, a gaseous oxidizing agent may be most convenient to use in many circumstances due to the fact that under appropriate reaction conditions, good mixing and contact with the coated carbonaceous particles is easily achievable. By way of non-limiting example, exemplary gaseous oxidizing agents include: oxygen, sulfur fumes, gaseous oxides and halogens. Preferred oxidizing agents include oxygen, nitrogen oxide gas, as well as, under certain conditions, air, which of course includes an appreciable proportion of oxygen gas.

With regard to the reaction conditions required, wherein the oxidizing agent is gaseous, again, it is required only that such reaction conditions be appropriate to insure the oxidization of the carbon residue forming material which is present on the carbonaceous particles. Under certain conditions, ambient pressure and temperature may be sufficient, but yet again as described with reference to the other forms of oxidizing agents described previously, it may be advantageous to insure that slightly elevated temperatures and/or pressures, e.g., temperatures in the range of between 30° C.-400° C. and/or slightly elevated pressures, e.g., 1-10 atm. be established to initiate or maintain the oxidation reaction. Again, it is understood that the appropriate reaction conditions are highly dependant upon the nature of the carbon residue forming material used to coat the carbonaceous particles, the specific gaseous oxidizing agent, as well as the reaction vessel itself. Useful reaction vessels are those which necessarily can contain, or bring into contact, the gaseous oxidizing agent with the coated carbonaceous particles and while many conventional vessels can be used, the use of the fluidized bed reactor is preferred. Utilization of a fluidized bed reactor wherein the gas flow stream comprises the gaseous oxidizing agent is preferred as effective intimate contact between the gaseous oxidizing agent and the coated carbonaceous particles are reliably assured.

According to a further step of the inventive process the reacted coated carbonaceous particles are subsequently carbonized and graphitized. The coated and stabilized carbonaceous particles are heated to a desired temperature in a suitable atmosphere so to be carbonized and graphitized. The temperature range for the carbonization is typically between 550° C. and 1500° C. but can extend up to 2200° C., and for graphitization is greater than 2200° C., preferably greater than 2800° C.

According to this further step, heating of the coated and stabilized carbonaceous particles takes place under appropriate reaction conditions in order to insure a high degree, or a complete carbonization thereof. With regard to the temperature required to insure carbonization, desirably this is achieved by raising the temperature in a controlled manner from a starting temperature, usually ambient temperature, to the final carbonization temperature which typically falls within the above-identified range of about 550° C.-1500° C.

With regard to the temperature rise, this can vary due to the nature of the reacted coated carbonaceous particles, as well as the reaction conditions and apparatus used. With regard to the apparatus, typically conventional ovens are quite satisfactorily used, although it is preferred that sealed ovens wherein a specific atmosphere can be maintained during the carbonization process are used. Sealed ovens wherein a reduced pressure may be maintained, especially vacuum ovens are particularly advantageous. With regard to the atmospheric conditions for the carbonization process, the atmosphere may be ambient air up to about 850° C. but an inert atmosphere is preferred at temperatures above about 400° C. Suitable inert atmospheres include nitrogen, argon, helium, etc. which are non-reactive with the heated coated carbonaceous particles.

With regard to the temperature conditions, these can vary widely but generally, the rate of temperature rise to which the reacted coated carbonaceous particles are subjected in order to achieve carbonization thereof is on the order of 0.5° C.-20° C./min. Such a controlled temperature rise insures that good carbonization results are achieved. Preferably however the coated carbonaceous particles are heated to a final carbonization temperature gradually, and with at least one intermediate heat treatment step where prior to the final carbonization temperature used in a process, the coated carbonaceous particles are heated to an intermediate temperature, and maintained at that intermediate temperature for an interval of time. The intermediate temperature or the period for which such intermediate temperature is maintained may vary, and will be understood to depend from process to process. It is to be understood that the inclusion of one or more such periods of time during which the particles are maintained at such intermediate temperatures is beneficial in facilitating the polymerization or other ordering of the coating present on the carbonaceous particles. Indeed, the practice of several such intermediate heat treatment steps is further preferred over the practice of a single heat treatment step in that the provision of more than one heat treatment steps in which the coated particles are maintained at a constant temperature is believed to impart improved characteristics to the coated carbonaceous particles over particles which have undergone but one or no such heat treatment step. It is further to be understood that during the heating of the coated carbonaceous particles particular attention must be paid to ensure that neither the temperatures attained during this heating process, nor the rate of the temperature rise during any part of the heating process be such that the instantaneous melting point of the coating upon the carbonaceous particles is exceeded. More simply stated, the thermal degradation of the coating is to be effected by a controlled temperature rise wherein the process temperature is maintained at or below the instantaneous melting point of the coating where said melting point is generally increasing with time during the process. In view of this requirement, preferred heating processes are those which exhibit slower rates of temperature rise. Particular preferred examples of such heat treatment steps are described with reference to one or more of the Examples.

Subsequent to the attainment of the maximum temperature use for the carbonization process, the carbonaceous particles having a carbonized coating may be cooled to ambient temperature, although this is not an essential requirement. Again, the cooling rate is desirably controlled, i.e., to be within about 3° C.-100° C./min. although, this cooling rate has been observed to be typically far less limiting than the rate of temperature rise during the carbonization process.

The most preferred aspects of the invention result in the provision of a smooth coating upon individual carbonaceous particles. Preferably the stabilization of the coating is followed by controlled heating of the coated stabilized particles so as to effect carbonization of the coated particles with little or no clumping or self-adhesion of the individual particles. The desired results are coated particles with little or no broken fracture surfaces of the type which are characteristically form when the separate particles fuse and must be crushed or broken apart in order to provide a free flowing powder. Such fracture surfaces are desirably minimized or avoided as they are believed to contribute to low electrochemical efficiency when the particles are used as an anode material in rechargeable electrical storage cells, particularly in rechargeable lithium ion batteries.

According to a particularly preferred embodiment of the inventive process taught herein, the carbon residue forming coating is provided in a fluid form. It has been observed by the inventors that when the carbon residue forming coating is precipitated from a liquid, a smooth coating forms at the interface of the individual carbonaceous particles and with the surrounding liquid, smooth coating is retained when subsequently carbonized.

Although less advantageous, when the carbon residue forming coating is supplied as a solid, it is desirably fused on the surface of the carbonaceous particles in order to form a smooth coating thereon.

The stabilization step of the current invention is carried out to render the surface of the coating infusible to the subsequent carbonization step. Oxidative stabilization allows the smooth surface produced in the coating process to be preserved in the final coated particles of the instant invention, as the oxidative stabilization renders the surface of the coating infusible to the subsequent carbonization step.

Heat treatment of the stabilized coated particles is desirably conducted in a controlled manner in order to minimize fusion of the particles. One skilled in the art will recognize that highly stabilized, completely infusible coated particles can be heated relatively aggressively and quickly during carbonization. In contrast, relatively mildly stabilized coated particles require slower heating in order to avoid excessive melting of the coating and fusion of the particles. Use of a fluidized bed during stabilization and heat treatment is especially beneficial in preventing clumping and fusion of the coated particles.

Especially Preferred embodiments of the present invention produce a free-flowing powder of coated particles after the carbonization and/or graphitization steps, which particles exhibit little or no fusion among the particles, but can generally be broken into a free-flowing powder by simple mechanical agitation, such as by use of a stirring rod, or by rubbing between the thumb and forefinger. Where some fusion may have occurred between particles, and mechanical agitation is used to separate these particles which may result in the formation of new fracture surfaces, in the preferred embodiments of the invention these fracture surfaces do not comprise more than 10%, preferably no more than 2% of the total surface area of the particles. Such are considered as being substantially smooth coatings.

While it is preferred that the carbonized coated carbonaceous particles be graphitized before use, graphitization is not essential as the carbonized coated carbonized particles by the inventive process may be used in various applications, including in the formation of electrodes, particularly anodes in batteries, especially in rechargeable batteries. Preferably however, the carbonized coated carbonaceous particles are also graphitized by heating them to a still higher elevated temperature which is in excess of the temperatures reached during the carbonization step. The advantage of graphitization is many-fold, and most significantly the graphitization process frequently allows for the generation of a more ordered crystal lattice in the carbonaceous particles. A certain improved crystal lattice provides more regular and uniform structure, and is also believed to improve the charge capacity of a battery containing the coated carbonaceous particles described herein. Graphitization also removes impurities. This purification step is especially important when impure carbons such as natural graphite are used as the source of the carbonaceous particles of this invention. With regard to appropriate graphitization conditions, again these are to be understood to vary according to the specific nature of the carbonized, coated carbonaceous particles, as well as the reaction conditions required to bring about the graphitization. Generally, the same apparatus used for the carbonization step may also be conveniently used, it only being required that such device be capable of further elevating the temperature to a temperature or range of temperature wherein the effects of graphitization is observed to occur. Typically, graphitization occurs in the temperature range of about 2200° C.-3200° C., although lower or higher temperatures might also be used in this step. It is required only that a satisfactory degree of graphitization be obtained during this step, such that an approved charging capacity is achieved. With regard to the process conditions it is desired that it is in an inert atmosphere such as described previously also be present. Graphitization can immediately follow carbonization in which case the carbonized coated carbonaceous particles are retained in a reaction apparatus, i.e., an oven, and the temperature is raised up to an appropriate graphitization temperature. With regard to the rate of this temperature rise, desirably this is maintained in the same rate as that used for the carbonization step although, greater or lesser rates of temperature rise can also be utilized depending upon the nature of the carbonized, coated carbonaceous particles.

A key feature of the present invention is in an oxidation reaction which is carried out on the coated particles prior to carbonization of the coating. The oxidation reaction is believed to provide certain technical benefits. First, it is believed that the reacted coated particles are relatively infusible following oxidation, which is particularly desirable in view of subsequent process steps, and subsequent handling of the particles. Second, it is believed that the reacted coated particles are endowed with a surface which yields high efficiency when used as an electrode, particularly when the reacted coated particles are used in an anode material in a rechargeable storage cell, particularly in a rechargeable Li-ion cell.

A further aspect of the invention contemplates the use of the carbonized, and graphitized coated carbonaceous particles in electrodes, particularly anodes, of electrical storage cells, particularly in rechargeable batteries. According to this aspect of the invention, there is contemplated a method for the manufacture of an electrical storage cell which comprises the step of: incorporating into an anode of the electrical storage cell coated carbonaceous particles comprising coated carbonaceous particles having a coating layer formed of an oxidized, carbon residue forming material.

According to this aspect of the invention, the coated carbonaceous particles produced from the processes described above are formed using the conventional techniques into electrodes, particularly anodes. While not described with particularity herein, it is contemplated that known-art manufacturing techniques for the assemblage of such electrodes, as well as known-art devices which facilitate in the formation of such electrodes can be used. A particular advantage which is obtained by the use of the coated carbonaceous particles taught herein lies in the fact that due to their coating, they rarely fuse together thus resulting in a flowable powder. Such flowable powder not only facilitates in the transport of the carbonized coated carbonaceous materials, but also aids in the ultimate electrode as such provides a good degree of packing and uniformity. Such a good degree of packing of course very favorably impacts on the volumetric capacity of any battery, particularly a rechargeable battery of which these electrodes form a part, as, an increased charge carrying capacity per unit volume of the electrode permits for the decrease in the overall size of a battery while maintaining good performance characteristics thereof.

Another aspect of the current invention is that the coated carbonaceous particles of this invention have a very high first cycle efficiency. This high efficiency is developed by the process of this invention. First cycle efficiency of the coated carbonaceous particles of this invention are typically >90%. By comparison, first cycle efficiency is as low as 50% in the carbonaceous particles before coating and is typically 90% or less in coated particles by other techniques.

Another aspect of the present invention is an increase in gravimetric or specific capacity as a result of practicing the coating process. Specific capacity is typically increased by 2 to 5% in the graphitized coated particles of this invention.

Aspects of the present invention, including certain preferred embodiments are described in the following Examples of the present invention.

EXAMPLES

Example 1

Production of Fine Carbonaceous Particles [0049]
A “green” granular needle coke was first milled with a hammer mill, and subsequently milled into a fine powder with a jet mill. Subsequently, the resultant milled carbonaceous particles were classified to remove particles smaller than 1 μm. The resultant carbonaceous powder had particles sized in the range of between 1 μm and about 50 μm, and an average particle size of about 20 μm. [0050]
Production of Coated Carbonaceous Powder Particles [0051]
To a laboratory beaker was provided 4 g of a low melting point isotropic petroleum pitch (210° C. Mettler softening point, 75% carbon residue, <100 ppm ash isotropic petroleum pitch.) in 4 g of tetralin (C[0052] ₁₀H₁₂) at 140° C. In a second laboratory beaker was combined 20 g of the carbonaceous powder produced as described previously with 700 ml of xylene (C₆H₄(CH₃)₂) at 120° C. To the contents of the second beaker was gradually added the contents of the first beaker, and following the addition the resultant mixture was heated and maintained at 128° C. for 15 minutes under continuous stirring. Subsequently the heat source was removed, and while the continuous stirring was maintained the mixture was allowed to cool to ambient temperature (approx. 20° C.). The resultant solids were removed from the cooled mixture by first filtering the mixture on a vacuum funnel, and thereafter drying under vacuum at 120° C. for at least 3 hours. Due to the differences in solubility of the pitch in tetralin as opposed to the solubility of pitch in xylene at different temperatures, selective precipitation of higher melting point pitch could precipitate and deposit upon the carbonaceous powder particles. The final weight of the dried coated carbonaceous powder particles was about 21.1 g.
The amount of precipitated pitch on the carbonaceous powder was determined from the following equation: [0053]
(Final weight−initial weight)/Final Weight=amount of precipitated pitch
Therefore, the amount of precipitated pitch on the carbonaceous powder was established to account for 5 wt %. of the total mass of the coated carbonaceous powder particles. [0054]
A separate experiment was performed to determine the melting point and carbon residue yield of the coating produced by this Example. An identical solution of isotropic pitch in tetralin was added to an identical amount of xylene except that there was no carbonaceous pitch dispersed in the xylene. The pitch precipitate that formed had a melting point of 310° C. and exhibited a carbon residue amount of 84%. [0055]
Subsequently the coated carbonaceous powder of Example 1 was oxidized by thoroughly mixing the powder with 9 g of 1.5 wt % aqueous solution of NaNO[0056] ₃(A.C.S. reagent, ex. J.T.Baker, Inc.) The mixture was subsequently dried under vacuum at 80° C. and thereafter the dried mixture was then transferred to 50 ml alumina crucibles and inserted into a vacuum furnace. The crucibles were then slowly heated under vacuum conditions from about ambient temperature to 325° C. at a rate of 1° C./minute, at which point the crucibles were maintained under vacuum at 325° C. for 2 hours. This slow heating step provided suitable oxidation reaction conditions whereby the deposited coating could be oxidized and stabilized prior to any further processing steps or handling, and permitted the pitch coating to form a better ordered molecular structure. Following this oxidation step, the stabilized coated carbonaceous powder particles could then be carbonized at still higher temperature(s) with little or no change in their morphology and with little or no likelihood of the melting of the coating layer.
Although the stabilized coated carbonaceous powder particles could be used without further processing, according to preferred embodiments of the invention further process steps were practiced in order to ultimately graphitize the particles. [0057]
Following the heat conditioning step at 325° C. for 2 hours, the crucibles containing the stabilized coated carbonaceous powder particles were further heated in argon gas at a rate of 1° C./minute to a temperature of 350° C. at which point the crucibles were maintained at 350° C. for 2 hours. Thereafter the crucibles containing the stabilized coated carbonaceous powder particles were further heated at a rate of 1° C./minute to a temperature of 410° C. at which point the crucibles were maintained at this higher temperature for 2 hours. Subsequently the crucibles containing the stabilized coated carbonaceous powder particles were further heated at a rate of 5° C./minute to a temperature of 850° C. at which point the crucibles were maintained at 850° C. for 2 hours, after which heating of the oven was discontinued, the contents of the oven were allowed to cool to ambient temperature (approx. 20° C.). Also, it is to be understood that stabilized coated carbonaceous powder particles could be used after one or more heat treatments steps and without further processing, but according to preferred embodiments of the invention the particles are ultimately graphitized. [0058]
After the coated carbonaceous powder particles were cooled, they were graphitized by transferring them to a graphite crucible and then introducing the crucible to an induction furnace having an argon atmosphere, and first heating the crucible at a rate of 13° C./minute to a temperature of 2800° C. and thereafter heating the crucibles at a rate of 5° C./minute to 3000° C. at which time the temperature of the induction furnace was maintained at 3000° C. for a period of 45 minutes, after which graphitization was believed to be essentially complete. Subsequently the graphitized coated carbonaceous powder particles were removed from the crucibles. [0059]
The resultant powder particles demonstrated good powder flowability, and it did not appear that fusion of particles had taken place. [0060]

Example 2

A further sample of coated carbonaceous powder particles was produced in accordance with the process steps described above with reference to Example 1. According to this example however, initially there was provided to the first laboratory beaker 8.5 g of the low melting point isotropic petroleum pitch described in Example 1, which was added to 8.5 g of tetralin (C[0061] ₁₀H₁₂) at 140° C. The contents of the second laboratory beaker remained the same as in Example 1, but the resultant dried coated carbonaceous powder particles recovered exhibited a final dried weight of about 22.3 grams. Based on this information, the coating on the coated carbonaceous powder particles was determined to be about 10% wt. based on the total mass of the coated carbonaceous powder particles. These dried particles were then subsequently thoroughly mixed with 9 g of 3.8 wt % aqueous solution of NaNO₃(A.C.S. reagent, ex. J. T. Baker, Inc.) The mixture was subsequently dried under vacuum at 80° C. The dried mixture was subsequently oxidized, and heat treated in accordance with the steps described in Example 1, until graphitized coated carbonaceous powder particles were obtained. The resultant powder particles demonstrated good powder flowability, and it did not appear that fusion of particles had taken place.

Example 3

A further sample of coated carbonaceous powder particles was produced in accordance with the process steps described above with reference to Example 1. According to this example however, there was provided 10 g of the low melting point isotropic petroleum pitch described in Example 1, which was added to 10 g of tetralin (C[0062] ₁₀H₁₂) at 140° C. in the first laboratory beaker. The contents of the second laboratory beaker remained the same as in Example 1, but the resultant dried coated carbonaceous powder particles recovered exhibited a final dried weight of about 22.7 grams. Based on this information, the coating on the coated carbonaceous powder particles was determined to be about 12% wt. based on the total mass of the coated carbonaceous powder particles. These dried particles were then subsequently thoroughly mixed with 9 g of 4.5 wt % aqueous solution of NaNO₃(A.C.S. reagent, ex. J.T.Baker, Inc.) The mixture was subsequently dried under vacuum at 80° C. The dried mixture was subsequently oxidized, and heat treated in accordance with the steps described in Example 1, until graphitized coated carbonaceous powder particles were obtained. The resultant powder particles demonstrated good powder flowability, and it did not appear that fusion of particles had taken place.

Example 4

A further sample of coated carbonaceous powder particles was produced in accordance with the process steps described above with reference to Example 1. According to this example however, to the first laboratory beaker was provided 15 g of the low melting point isotropic petroleum pitch of Example 1, and 15 g of tetralin (C[0063] ₁₀H₁₂) at 140° C. The contents of the second laboratory beaker remained the same as in Example 1, but the resultant dried coated carbonaceous powder particles recovered exhibited a final dried weight of about 24 grams. Based on this information, the coating on the coated carbonaceous powder particles was determined to be about 17% wt. based on the total mass of the coated carbonaceous powder particles. These dried particles were then subsequently thoroughly mixed with 10 g of 6.0 wt % aqueous solution of NaNO₃(A.C.S. reagent, ex. J.T.Baker, Inc.) The mixture was subsequently dried under vacuum at 80° C. The dried mixture was subsequently oxidized, and heat treated in accordance with the steps described in Example 1, until graphitized coated carbonaceous powder particles were obtained. The resultant powder particles demonstrated good powder flowability, and it did not appear that fusion of particles had taken place.

Example 5

A further sample of coated carbonaceous powder particles was produced in accordance with the process steps described above with reference to Example 1. According to this example however, to the first laboratory beaker was provided 20 g of the low melting point isotropic petroleum pitch of Example 1, and 20 g of tetralin (C[0064] ₁₀H₁₂) at 140° C. The contents of the second laboratory beaker remained the same as in Example 1, but the resultant dried coated carbonaceous powder particles recovered exhibited a final dried weight of about 25.3 grams. Based on this information, the coating on the coated carbonaceous powder particles was determined to be about 21% wt. based on the total mass of the coated carbonaceous powder particles. These dried particles were then subsequently thoroughly mixed with 10 g of 8 wt % aqueous solution of NaNO₃(A.C.S. reagent, ex. J.T.Baker, Inc.) The mixture was subsequently dried under vacuum at 80° C. The dried mixture was subsequently oxidized, and heat treated in accordance with the steps described in Example 1, until graphitized coated carbonaceous powder particles were obtained. The resultant powder particles demonstrated good powder flowability, and it did not appear that fusion of particles had taken place.

Comparative Example 1

As a comparative example, the same milled green needle coke carbonaceous powder of Example 1 was graphitized and tested as an anode carbon in a lithium ion battery. This comparative example demonstrated the use of an uncoated graphitized carbonaceous powder particles. [0065]
Graphitization of these uncoated carbonaceous powder particles was achieved by transferring them to a graphite crucible, inserting the crucible to an induction furnace having an argon atmosphere, and first heating the crucible at a rate of 13° C./minute to a temperature of 2800° C. and thereafter heating the crucible at a rate of 5° C./minute to 3000° C. at which time the temperature of the induction furnace was maintained at 3000° C. for a period of 45 minutes. Subsequent to these heating steps graphitization was believed to be essentially complete. The crucibles containing the uncoated carbonaceous powder particles was then allowed to cool to ambient temperature, after which the powder particles were removed from the crucibles. [0066]
The resultant uncoated powder particles demonstrated good powder flowability. [0067]

Comparative Example 2

As a further comparison example there were utilized 20 grams of “as-milled” uncoated “green” carbonaceous particles, which were mixed in a laboratory beaker with 9 g of a 1.5 wt % aqueous solution of NaNO[0068] ₃(A.C.S. reagent, ex. J.T.Baker, Inc.) The mixture was subsequently dried under vacuum at 80° C. and thereafter the dried mixture was then provided to alumina crucibles and inserted into a vacuum furnace. These samples were subsequently subjected to the same heat treatment steps as outlined in Example 1, namely, heated under vacuum conditions from about ambient temperature to 325° C. at a rate of 1° C./minute, and thereafter maintained under vacuum at 325° C. for 2 hours. Next, the particles were further heated under argon at a rate of 1° C./minute to 350° C., and thereafter maintained at 350° C. for 2 hours and subsequently heated at a rate of 1° C./minute to a temperature of 410° C. and thereafter maintained under vacuum for 2 hours. Subsequently the crucibles containing these uncoated carbonaceous powder were further heated under argon at a rate of 5° C./minute to a temperature of 850° C. and then maintained at 850° C. for 2 hours, after which heating was discontinued, the contents of the oven were allowed to cool to ambient temperature (approx. 20° C.).
Graphitization of these uncoated carbonaceous powder particles was achieved by the same process described above with reference to Comparative Ex. 1. Again, the resultant uncoated powder particles demonstrated good powder flowability. [0069]
Evaluation of Electrical Capacity [0070]
The electrical charge capacity, as well as the irreversible electrical charge capacity loss of the powder particles according to Examples 1-5, as well as Comparative Examples 1 and 2 were evaluated by the following techniques. [0071]
Samples of a powder particle (5 g) were first thoroughly mixed with 3.82 grams of a solution of 0.382 g of polyvinylidene fluoride (PVDF, ex. Aldrich Chemical Co., Inc.) and 3.44 g of 1-methyl-pyrrolidinone (NMP, ex. Aldrich Chemical Co., Inc.) to which was also added 0.082 g of acetylene black (having an effective surface area of 80 m 21 g, ex. Alfa Aesar) in order to form uniform slurry. This slurry was then manually cast utilizing a doctor blade to form a thin film having a loading of about 10 mg/cm[0072] ²onto the rough side of an electrodeposited copper foil (10 μm, ex. Fuduka Metal Foil & Powder Co., Ltd.) The cast film was then dried on a hot plate at approx. 100° C. and pressed to a desired density (approx. 1.4 g/cm²) with a roll press. After the cast film was allowed to cool, a disc having an area of 1.5 cm²was then punched out from the film and weighed to determine the amount of the graphite powder. Subsequently this disc was further dried under vacuum at a temperature of 80° C. for approximately 15 minutes, and then the disc was transferred into a sealed box without exposing the disc to ambient air. The sealed box was filled with ultra-pure argon gas having oxygen and moisture levels of less than 1 ppm.
Subsequently the disc was used as the anode in the manufacture of a standard coin cell (2025 size) which was used as the test cell. The other electrode of the test cell was a foil of pure lithium (100 μm, ex. Alfa Aesar). A two layer separator was used in the test cell, a glass mat (GF/B Glass Microfibre Filter, ex. Whatman International Ltd.) as the first layer on the carbon electrode side, and a porous polypropylene film (available as Celgard® 2300, ex. Celgard Inc.). as the second layer on the lithium foil. The electrolyte of the test cell was a 1 M LiPF[0073] ₆in ethylene carbonate (EC)/diethyl carbonate (DEC)/dimethyl carbonate (DMC) solvent mixture (40/30/30) (available as specified by EM Industrial.) Test cells were produced utilizing the component described above according to conventional techniques, although the samples of powder particles were varied to ensure that at least one sample coin cell was produced incorporating a powder particle sample according to either one of the demonstrative examples, or according to one of the comparative examples. These powders were tested as the anode material in a coin cell configuration of carbon/separator/lithium metal at room temperature (˜25° C.). Two or three cells were made for each sample, the reported charge capacity and charge efficiency were the average value of the cells.
The capacity and charging efficiency of a specific powder particle sample was determined according to the following protocol. Utilizing a standard electrochemical test station (Model BT-2043, Arbin Instrument Corp.) an assembled test cell was first discharged at 1 mA (approx. 67 mA/g) to 0 volts and held at 0 volts for 2 hours or till current dropped to less than 50 μA whichever occurred first. Thereafter the assembled test cell was charged at 1 mA to 2 volts during which time the charge passed during charging was used to calculate the specific capacity of the graphite powder, while the ratio of the total charge passed during charging to the total charge passed during discharging was used to determine the first cycle efficiency. [0074]
Table 1 reports the test results for the seven samples of powder particles according to each of Examples 1-5, and each of Comparative Examples 1-2. [0075]

TABLE 1

Irreversible

Coated Capacity capacity loss Efficiency

pitch (%) (mAh/g) (mAh/g) (%)

Comp. 1 0 314 301 51

Comp. 2 0 304 249 55

Ex. 1 5 322 166 66

Ex. 2 10 337 14 96

Ex. 3 12 330 14 96

Ex. 4 17 322 13 96

Ex. 5 21 318 13 96
It can been seen that the first cycle efficiency is greatly improved from 50% to 96% when the amount of coated pitch was increased to 10 wt %. The table also shows that the efficiency does not increase further when it reaches about 96%. In addition, the materials treated according to this invention yield a higher capacity than those that were not treated. [0076]

Example 6

A further sample of coated carbonaceous powder particles according to the invention was produced utilizing a commercially available milled synthetic graphite powder having particles sized less than 44 μm. (available as KS-44, ex. Lonza). To a first laboratory beaker was provided 8.5 g of athe low melting point isotropic petroleum pitch of Example 1 in 10 g of tetralin (C[0077] ₁₀H₁₂) at 140° C. A sample of 20 grams of the milled natural graphite powder particles were provided to a second laboratory beaker which contained 700 ml of xylene (C₆H₄(CH₃)₂) at 120° C. To the contents of the second beaker was gradually added the contents of the first beaker, and following the addition the resultant mixture was heated and maintained at 128° C. for 15 minutes under continuous stirring. Thereafter the heat source was removed, and while the continuous stirring was maintained the mixture was allowed to cool to ambient temperature (approx. 20° C.). The resultant solids were removed from the cooled mixture by first filtering the mixture on a vacuum funnel, and thereafter drying under vacuum at 120° C. for at least 3 hours. As discussed in Example 1, due to the differences in solubility of the pitch in tetralin as opposed to the solubility of pitch in xylene at different temperatures, selective precipitation of higher melting point pitch could precipitate and deposit upon the carbonaceous powder particles. The final weight of the dried coated carbonaceous powder particles was determined to be about 22.3 g, while the amount of precipitated pitch on the carbonaceous powder was determined to be 10% wt. of the total mass of the coated carbonaceous powder particles.
Subsequently the dried coated carbonaceous powder particles were thoroughly mixed with 9 g of 3.8 wt % aqueous solution of NaNO[0078] ₃(A.C.S. reagent, ex. J.T.Baker, Inc.) The mixture was subsequently dried under vacuum at 80° C. The dried mixture was subsequently subjected to the same heat treatment steps as outlined in Example 1, namely, heated under vacuum conditions from about ambient temperature to 325° C. at a rate of 1° C./minute, and thereafter maintained under vacuum at 325° C. for 2 hours. Next, the particles were further heated under argon at a rate of 1° C./minute to 350° C., and thereafter maintained at 350° C. for 2 hours and subsequently heated at a rate of 1° C./minute to a temperature of 410° C. and thereafter maintained for 2 hours. Subsequently the crucibles containing the coated carbonaceous powder was were further heated at a rate of 5° C./minute to a temperature of 850° C. and then maintained at 850° C. for 2 hours, after which heating was discontinued, and the contents of the oven were allowed to cool to ambient temperature (approx. 20° C.).
Graphitization of these coated carbonaceous powder particles was achieved by transferring them to a graphite crucible, inserting the crucible into an induction furnace having an argon atmosphere, and first heating the crucible at a rate of 13° C./minute to a temperature of 2800° C. and thereafter heating the crucible at a rate of 5° C./minute to 3000° C. at which time the temperature of the induction furnace was maintained at 3000° C. for a period of 45 minutes. Subsequent to these heating steps graphitization was believed to be essentially complete. The crucibles containing the coated carbonaceous powder particles was then allowed to cool to ambient temperature, after which the powder particles were removed from the crucibles. The resultant powder particles exhibited good flowability. [0079]
A sample of the coated carbonaceous powder particles produced according to this example was evaluated for their electrical performance characteristics utilizing the procedure described above under the heading “Evaluation of electrical capacity”. The results of the electrical performance evaluation are described on Table 2, following. [0080]

Example 7

A further sample of coated carbonaceous powder particles according to the invention was produced utilizing particles derived from a calcined petroleum needle coke (calcining temperature 1100° C.) having particles sized in the range of between 1 μm and about 50 μm, and an average particle size of about 20 μm. Similarly to the process described in Example 6, to a first laboratory beaker was provided 8.5 g of the low melting point isotropic petroleum pitch of Example 1 in 8.5 g of tetralin (C[0081] ₁₀H₁₂) at 140° C. A sample of 20 grams of the milled calcined petroleum coke powder particles were provided to a second laboratory beaker which contained 700 ml of xylene (C₆H₄(C₂H₃)₂) at 120° C. To the contents of the second beaker was gradually added the contents of the first beaker, and following the addition the resultant mixture was heated and maintained at 128° C. for 15 minutes under continuous stirring. Thereafter the heat source was removed, and while the continuous stirring was maintained the mixture was allowed to cool to ambient temperature (approx. 20° C.). The resultant solids were removed from the cooled mixture by first filtering the mixture on a vacuum funnel, and thereafter drying under vacuum at 120° C. for at least 3 hours. As discussed in Example 1, due to the differences in solubility of the pitch in tetralin as opposed to the solubility of pitch in xylene at different temperatures, selective precipitation of higher melting point pitch could precipitate and deposit upon the carbonaceous powder particles. The final weight of the dried coated carbonaceous powder particles was determined to be about 22.3 g, while the amount of precipitated pitch on the carbonaceous powder was determined to be 10% wt. of the total mass of the coated carbonaceous powder particles.
Subsequently the dried coated carbonaceous powder particles were thoroughly mixed with 9 g of 3.8 wt % aqueous solution of NaNO[0082] ₃(A.C.S. reagent, ex. J.T.Baker, Inc.) The mixture was subsequently dried under vacuum at 80° C. The dried mixture was subsequently subjected to the same heat treatment steps as outlined in Example 6, including the final graphitization process. The resultant powder particles exhibited good flowability.
A sample of the coated carbonaceous powder particles produced according to this example was evaluated for their electrical performance characteristics utilizing the procedure described above under the heading “Evaluation of electrical capacity”. The results of the electrical performance evaluation are described on Table 2, following. [0083]

Example 8

A still further sample of coated carbonaceous powder particles according to the invention was produced utilizing a different milled “green” petroleum needle coke having particles sized in the range of between 1 μm and about 50 μm, and an average particle size of about 20 μm. Similarly to the process described in Example 6, to a first laboratory beaker was provided 10 g of the low melting point isotropic petroleum pitch of Example 1 in 10 g of tetralin (C[0084] ₁₀H₁₂) at 140° C. A sample of 20 grams of the milled natural graphite powder particles were provided to a second laboratory beaker which contained 700 ml of xylene (C₆H₄(C₂H₃)₂) at 120° C. To the contents of the second beaker was gradually added the contents of the first beaker, and following the addition the resultant mixture was heated and maintained at 128° C. for 15 minutes under continuous stirring. Thereafter the heat source was removed, and while the continuous stirring was maintained the mixture was allowed to cool to ambient temperature (approx. 20° C.). The resultant solids were removed from the cooled mixture by first filtering the mixture on a vacuum funnel, and thereafter drying under vacuum at 120° C. for at least 3 hours. As discussed in Example 1, due to the differences in solubility of the pitch in tetralin as opposed to the solubility of pitch in xylene at different temperatures, selective precipitation of higher melting point pitch could precipitate and deposit upon the carbonaceous powder particles. The final weight of the dried coated carbonaceous powder particles was determined to be about 23 g, while the amount of precipitated pitch on the carbonaceous powder was determined to be 13% wt. of the total mass of the coated carbonaceous powder particles.
Subsequently the dried coated carbonaceous powder particles were thoroughly mixed with 9 g of 4.5 wt % aqueous solution of NaNO[0085] ₃(A.C.S. reagent, ex. J.T.Baker, Inc.) The mixture was subsequently dried under vacuum at 80° C. The dried mixture was subsequently subjected to the same heat treatment steps as outlined in Example 6, including the final graphitization process. The resultant powder particles exhibited good flowability.
A sample of the coated carbonaceous powder particles produced according to this example was evaluated for its electrical performance characteristics utilizing the procedure described above under the heading “Evaluation of electrical capacity”. The results of the electrical performance evaluation are described on Table 2, following. [0086]

Comparative Example 3

For comparative purposes a sample of the commercially available milled synthetic graphite powder as described in Example 6 was also evaluated for its electrical performance characteristics utilizing the procedure described above under the heading “Evaluation of electrical capacity”. The sample of the available milled synthetic graphite powder was used as obtained, and was not treated according to the present inventive process. The results of the electrical performance evaluation are described on Table 2, following. [0087]

Comparative Example 4

For comparative purposes a sample of milled calcined petroleum needle coke as described in Example 7 was also evaluated for its electrical performance characteristics utilizing the procedure described above under the heading “Evaluation of electrical capacity”. The sample of the available milled calcined coke was heat-treated in the same way as the coated carbonaceous particles of Example 7. The results of the electrical performance evaluation on the resultant graphite powder are described on Table 2, following. [0088]

Comparative Example 5

For comparative purposes a sample of milled “green” needle coke as described in Example 8 was also evaluated for its electrical performance characteristics utilizing the procedure described above under the heading “Evaluation of electrical capacity”. The sample of the available milled “green” coke was used as obtained, and was not treated according to the coating steps of the present inventive process. The uncoated coke powder was heated to form a graphite powder in the same way as in Example 8. The results of the electrical performance evaluation are described on Table 2, following. [0089]

TABLE 2

Irreversible

Capacity capacity loss Efficiency Coated pitch

(mAh/g) (mAh/g) (%) (%)

Ex. 6 344 22 94 10

Ex. 7 333 14 96 10

Ex. 8 341 14 96 13

Comp. Ex. 3 353 48 88 0

Comp. Ex. 4 304 386 44 0

Comp. Ex. 5 304 403 43 0
As is readily seen from the results reported in Table 2, the compositions according to the invention (Examples 6, 7 and 8) exhibited a high efficiency (>94%). The comparison examples and their untreated materials suffered from a much lower efficiency than the materials treated according to this invention, as well as suffering from a higher irreversible capacity loss. [0090]

Example 9

A further sample of coated carbonaceous powder particles according to the invention was produced according to an alternate technique for providing the coating to the particles. [0091]
In a laboratory beaker was provided 20 g of the low melting point isotropic petroleum pitch of Example 1 to 80 grams of 1-methyl-pyrrolidinone (NMP, ex. Aldrich Chemical Co., Inc.) to form a 20% wt. solution of the petroleum pitch. The solution was heated to approx. 60° C. under stirring, at which time 20 g of the milled “green” needle coke particles of Example 8 were introduced, and the contents of the beakers were stirred for a further 15 minutes to ensure homogeneity. Subsequently, resultant solids were removed from the mixture by first filtering the mixture utilizing a vacuum funnel, and thereafter drying under vacuum at 100° C. for at least 5 hours. The final weight of the dried coated carbonaceous powder particles was determined to be about 23.5 g, while the amount of precipitated pitch on the carbonaceous powder was determined to be 15% wt. of the total mass of the coated carbonaceous powder particles. [0092]
The dried coated carbonaceous powder particles were next thoroughly mixed with 12 g of 3 wt % aqueous solution of NaNO[0093] ₃(A.C.S. reagent, ex. J.T.Baker, Inc.) The mixture was subsequently dried under vacuum at 80° C. and thereafter the dried mixture was then provided to 50 cc alumina crucibles and inserted into a vacuum furnace. Thereafter the coated carbonaceous powder particles were subjected to the same heat treatment steps as described in Example 1, and ultimately graphitized coated carbonaceous powder particles were produced.
The electrical charge capacity, as well as the irreversible electrical charge capacity loss of the powder particles were evaluated utilizing the procedure described above under the heading “Evaluation of electrical capacity”. The results of the electrical performance evaluation are described on Table 3, following. [0094]

TABLE 3

Irreversible

Capacity capacity loss Efficiency

(mAh/g) (mAh/g) (%)

Ex. 9 339 29 92

Example 10

A further sample of coated carbonaceous powder particles according to the invention was produced according to an alternate technique for providing the coating to the particles. [0095]
In a laboratory beaker was provided 20 g of the low melting point isotropic petroleum pitch of Example 1 to 80 g of 1-methyl-pyrrolidinone (NMP, ex. Aldrich Chemical Co., Inc.) to form a 20% wt. solution of the petroleum pitch. The solution was heated to approx. 60° C. under stirring, at which time 20 g of the particulate calcined petroleum coke of Example 7 were introduced, and the contents of the beaker was stirred for a further 15 minutes to ensure homogeneity. Subsequently, resultant solids were removed from the mixture by first filtering the mixture utilizing a vacuum funnel, and thereafter drying under vacuum at 100° C. for at least 5 hours. The final weight of the dried coated carbonaceous powder particles was determined to be about 21 g, while the amount of precipitated pitch on the carbonaceous powder was determined to be 5% wt. of the total mass of the coated carbonaceous powder particles. [0096]
The dried coated carbonaceous powder particles were next thoroughly mixed with 11 g of 3 wt % aqueous solution of NaNO[0097] ₃(A.C.S. reagent, ex. J.T.Baker, Inc.). The mixture was subsequently dried under vacuum at 80° C. and thereafter the dried mixture was then provided to alumina crucibles and inserted into a vacuum furnace. Thereafter the coated carbonaceous powder particles were subjected to the same heat treatment steps as described in Example 1, and ultimately graphitized coated carbonaceous powder particles were produced.
The electrical charge capacity, as well as the irreversible electrical charge capacity loss of the powder particles were evaluated utilizing the procedure described above under the heading “Evaluation of electrical capacity”. The results of the electrical performance evaluation are described on Table 4, following. [0098]

TABLE 4

Irreversible

Coated pitch Capacity capacity loss Efficiency

(%) (mAh/g) (mAh/g) (%)

Ex. 10 5 343 22 94
As this example illustrated, a pitch coating level as little as 5 wt % on coke powder or coated carbon residue as little as 4 wt % still significantly suppresses the irreversible capacity loss according to this invention. [0099]

Example 11

A sample of coated carbonaceous powder particles according to the invention was produced demonstrating the use of lignin as the fusible, carbon residue forming material coating for carbonaceous powder particles. Additionally this example demonstrates a one-step coating and oxidation process. [0100]
In a laboratory beaker 2.0 g of lignin (Alkali Kraft, ex Aldrich Chemicals Co. Inc.) and 0.3 g of NaNO[0101] ₃were mixed in 9 g of 1 M KOH aqueous solution. This lignin has a carbon residue of about 47% and melting point of 300° C. Subsequently to the laboratory beaker was provided 20 g of the comminuted “green” granular coke particles as prepared used in Example 1, and the contents of the laboratory beaker were thoroughly mixed in a laboratory blender (Waring Commercial blender, Model 51BL31). Thereafter the mixture was removed from the laboratory blender, dried at 80° C. under vacuum for 12 hours. The final weight of the dried coated carbonaceous powder particles was determined to be about 22.4 g, while the amount of precipitated lignin on the carbonaceous powder was determined to be 10 wt % of the total mass of the coated carbonaceous powder particles.
Subsequently the dried coated carbonaceous powder particles were subjected to the same heat treatment steps as described in Example 1, and ultimately graphitized coated carbonaceous powder particles were produced. [0102]
The electrical charge capacity, as well as the irreversible electrical charge capacity loss of the powder particles were evaluated utilizing the procedure described above under the heading “Evaluation of electrical capacity”. The results of the electrical performance evaluation are described on Table 5, following. [0103]

TABLE 5

Irreversible

Coated Capacity capacity loss Efficiency

lignin (%) (mAh/g) (mAh/g) (%)

Ex. 11 10 330 21 94
The efficiency of the composition according to Example 11 demonstrate a significant and surprising improvement over the results reported for Comparative Example 5 on Table 2, demonstrating the surprising improvements achieved by the practice of the present invention. [0104]

Example 12

A sample of coated carbonaceous powder particles according to the invention was produced demonstrating the use of table sugar as the fusible, carbon residue forming material coating for carbonaceous powder particles. This sugar has a carbon residue of about 25%. [0105]
In a laboratory beaker 3 grams of table white sugar (House Recipe®, distributed by Sysco Corporation) and 0.3 grams of NaNO[0106] ₃were dissolved in 9 grams of de-ionized water. Subsequently to the laboratory beaker was provided 20 g of the comminuted “green” granular coke particles as prepared used in Example 1, and the contents of the laboratory beaker were thoroughly mixed in a laboratory blender (Waring Commercial blender, Model 51BL31). Thereafter mixture was removed from the laboratory beaker, dried under vacuum at 80° C. for 3 hours. The amount of coated sugar on the coke particles was determined to be about 13 wt %.
Subsequently the dried coated carbonaceous powder particles were subjected to the same heat treatment steps as described in Example 1, and ultimately graphitized coated carbonaceous powder particles were produced. [0107]
The electrical charge capacity, as well as the irreversible electrical charge capacity loss of the powder particles were evaluated utilizing the procedure described above under the heading “Evaluation of electrical capacity”. The results of the electrical performance evaluation are described on Table 6, following. [0108]

TABLE 6

Irreversible

Coated sugar Capacity capacity loss Efficiency

(%) (mAh/g) (mAh/g) (%)

Ex. 12 13 303 23 93

Example 13

A sample of coated carbonaceous powder particles according to the invention was produced demonstrating the use of ambient air as the oxidizing agent for the fusible, carbon residue forming material coating of carbonaceous powder particles. [0109]
To a laboratory beaker was provided 8.5 g of the low melting point isotropic petroleum pitch of Example 1 in 8.5 g of tetralin (C[0110] ₁₀H₁₂) at 140° C. In a second laboratory beaker was combined 20 g of the carbonaceous powder produced and as described with reference to Example 1 with 700 ml of xylene (C₆H₄(C₂H₃)₂) at 120° C. To the contents of the second beaker was gradually added the contents of the first beaker, and following the addition the resultant mixture was heated and maintained at about 128° C. for 15 minutes under continuous stirring. Subsequently the heat source was removed, and while the continuous stirring was maintained the mixture was allowed to cool to ambient temperature (approx. 20° C.). The resultant solids were removed from the cooled mixture by first filtering the mixture on a vacuum funnel, and thereafter drying under vacuum at 120° C. for at least 3 hours.
The dried powder weighed 22.3 g. The amount of precipitated pitch on the carbonaceous powder was determined to account for 10% wt. of the total mass of the coated carbonaceous powder particles. [0111]
Thereafter the coated carbonaceous powder particles were placed in a laboratory scale fluidized bed reactor and heated from ambient temperature at a heating rate of 10° C./minute to 275° C. and held for 30 minutes at 275° C. while the coated carbonaceous powder particles were fluidized using air as the fluidizing gas. Subsequently the reacted powder particles were transferred into a tube furnace (Linberg/Blue M) and carbonized in pure argon gas by heating from ambient temperature at a heating rate of 5° C./minute to 850° C., and once this temperature was reached, the coated carbonaceous powder particles were maintained at this temperature for 2 hours. The coated carbonaceous powder particles were subsequently withdrawn and allowed to cool. [0112]
Graphitization of the coated carbonaceous powder particles was achieved by next transferring them to a graphite crucible, inserting the crucible into an induction furnace having an argon atmosphere, and first heating the crucible at a rate of 13° C./minute to a temperature of 2800° C. and thereafter heating the crucible at a rate of 5° C./minute to 3000° C. at which time the temperature of the induction furnace was maintained at 3000° C. for a period of 45 minutes. Subsequent to these heating steps graphitization was believed to be essentially complete. The crucibles containing the coated carbonaceous powder particles were then allowed to cool to ambient temperature, after which the powder particles were removed from the crucibles. The resultant powder particles demonstrated good powder flowability, and it did not appear that fusion of particles had taken place. [0113]
The electrical charge capacity, as well as the irreversible electrical charge capacity loss of the powder particles were evaluated utilizing the procedure described above under the heading “Evaluation of electrical capacity”. The results of the electrical performance evaluation are described on Table 7, following. [0114]

TABLE 7

Irreversible

Coated pitch Capacity capacity loss Efficiency

(%) (mAh/g) (mAh/g) (%)

Ex. 13 10 330 14 96

Example 14

A further sample of coated carbonaceous powder particles according to the invention was produced demonstrating the use of ambient air as the oxidizing agent for the fusible, carbon residue forming material coating of carbonaceous powder particles. [0115]
In a laboratory beaker was provided 20 g of the low melting point isotropic petroleum pitch of Example 1 to 80 g of 1-methyl-pyrrolidinone (NMP, ex. Aldrich Chemical Co., Inc.) to form a 20% wt. solution of the petroleum pitch. The solution was heated to approx. 60° C. under stirring, at which time 20 g of the particlate calcined petroleum coke described in Example 7 was introduced, and the contents of the beaker was stirred for a further 15 minutes to ensure homogeneity. Subsequently, resultant solids were removed from the mixture by first filtering the mixture utilizing a vacuum funnel, and thereafter drying under vacuum at 100° C. for at least 5 hours. The final weight of the dried coated carbonaceous powder particles was determined to be about 21.5 g, while the amount of precipitated pitch on the carbonaceous powder was determined to be 7 wt % of the total mass of the coated carbonaceous powder particles. [0116]
Thereafter the coated carbonaceous powder particles were placed in a fluidized bed reactor as described in Example 13 and heated from ambient temperature at a heating rate of 10° C./minute to 275° C. and held for 30 minutes at 275° C. while the coated carbonaceous powder particles were fluidized using air as the fluidizing gas. Subsequently the reacted powder particles were transferred into a tube furnace as described in Example 13 and carbonized in pure argon gas by heating from ambient temperature at a heating rate of 5° C./minute to 850° C., and once this temperature was reached, the coated carbonaceous powder particles were maintained at this temperature for 2 hours. The coated carbonaceous powder particles were subsequently withdrawn and allowed to cool. [0117]
Graphitization of these coated carbonaceous powder particles was achieved by next transferring them to a graphite crucible, inserting the crucible to an induction furnace having an argon atmosphere, and first heating the crucible at a rate of 13° C./minute to a temperature of 2800° C. and thereafter heating the crucible at a rate of 5° C./minute to 3000° C. at which time the temperature of the induction furnace was maintained at 3000° C. for a period of 45 minutes. Subsequent to these heating steps graphitization was believed to be essentially complete. The crucibles containing the uncoated carbonaceous powder particles were then allowed to cool to ambient temperature, after which the powder particles were removed from the crucibles. [0118]
The electrical charge capacity, as well as the irreversible electrical charge capacity loss of the powder particles were evaluated utilizing the procedure described above under the heading “Evaluation of electrical capacity”. The results of the electrical performance evaluation are described on Table 8, following. [0119]

TABLE 8

Irreversible

Coated pitch Capacity capacity loss Efficiency

(%) (mAh/g) (mAh/g) (%)

Ex. 14 7 334 29 92

Comparative Example 6

For comparative purposes samples of coated carbonaceous powder particles which were not subjected to an oxidation reaction step were prepared by the following protocol. [0120]
To a laboratory beaker was provided 8.5 g of the low melting point isotropic petroleum pitch as described in Example 1 into 8.5 g of tetralin (C[0121] ₁₀H₁₂) at 140° C. In a second laboratory beaker was combined 20 g of the carbonaceous powder produced and as described with reference to Example 1 with 700 ml of xylene (C₆H₄(CH₃)₂) at 120° C. To the contents of the second beaker was gradually added the contents of the first beaker, and following the addition the resultant mixture was heated and maintained at about 128° C. for 15 minutes under continuous stirring. Subsequently the heat source was removed, and while the continuous stirring was maintained the mixture was allowed to cool to ambient temperature (approx. 20° C.). The resultant solids were removed from the cooled mixture by first filtering the mixture on a vacuum funnel, and thereafter drying under vacuum at 120° C. for at least 3 hours.
The amount of precipitated pitch on the carbonaceous powder was determined to account for 10% wt. of the total mass of the coated carbonaceous powder particles. [0122]
Thereafter the coated carbonaceous powder particles were placed in an alumina crucible, and the crucible was inserted into a tubular furnace (Linberg/Blue M), and therein heated from ambient temperature according to the following protocol: a first heating rate of 5° C./minute to 200° C. and held at that temperature for 30 minutes, followed by a second heating rate of 2° C./minute to 350° C. and held at that temperature for 2 hours, next heated at a third heating rate of 5° C./minute to 850° C. and held at that temperature for 2 hours and finally, cooling the coated carbonaceous powder particles at a rate of 5° C./minute to ambient temperature (approx. 20° C.). The recovered carbonaceous powder particles were observed to have conglomerated into a single cake, which was withdrawn from the crucible and first crushed into smaller pieces and then ball milled into a powder form. [0123]
Graphitization of these coated carbonaceous powder particles was achieved by next transferring them to a graphite crucible, inserting the crucible into an induction furnace having an argon atmosphere, and first heating the crucible at a rate of 13° C./minute to a temperature of 2800° C. and thereafter heating the crucible at a rate of 5° C./minute to 3000° C. at which time the temperature of the induction furnace was maintained at 3000° C. for a period of 45 minutes. Subsequent to these heating steps graphitization was believed to be essentially complete. The crucibles containing the carbonaceous powder particles was then allowed to cool to ambient temperature (approx. 20° C.), after which the powder particles were removed from the crucibles. [0124]
The electrical charge capacity, as well as the irreversible electrical charge capacity loss of the powder particles were evaluated utilizing the procedure described above under the heading “Evaluation of electrical capacity”. The results of the electrical performance evaluation are described on Table 9, following. [0125]

TABLE 9

Irreversible

Coated pitch Capacity capacity loss Efficiency

(%) (mAh/g) (mAh/g) (%)

Comp. Ex. 6 10 300 352 46
As can be understood from these results, particularly in comparison with the results of Ex. 2, as well as the results reported on Tables 7 and 8 where the pitch coated carbonaceous powder particles which had not been oxidized, but were simply carbonized in an inert atmosphere resulted in poor electrical charge capacity and poor charge efficiency. [0126]

Comparative Example 7

For further comparison, samples of coated carbonaceous powder particles not subjected to an oxidation reaction step were prepared by the heating protocol used to produce the compositions of Comparative Example 6. The comparison samples according to the instant Comparative Example differed in that the coated carbonaceous powder particles were prepared in the same manner as illustrated in Example 10. After carbonization, it was observed that the carbonaceous powder particles had conglomerated into a single cake. The carbon powder clump then was withdrawn from the crucible and first crushed into smaller pieces and then ball milled into a powder form before graphitization. [0127]
As in the prior Comparative Example's evaluation, the electrical charge capacity, as well as the irreversible electrical charge capacity loss of the powder particles according to the present Comparative Example were evaluated utilizing the procedure described above under the heading “Evaluation of electrical capacity”. The results of the electrical performance evaluation are described on Table 9, following. [0128]

TABLE 10

Irreversible

Coated pitch Capacity capacity loss Efficiency

(%) (mAh/g) (mAh/g) (%)

Comp. Ex. 7 5 317 106 75
As can be understood from these results, particularly in comparison with the results of Ex. 10 and the results reported on Tables 7 and 8, as well as the perfomance of the pitch coated carbonaceous powder particles which had not been oxidized, but were simply carbonized in an inert atmosphere resulted in improved, but still poor electrical charge capacity as compared to the sample according to Comparative Example 6. [0129]

Example 15

A further sample of coated carbonaceous powder particles according to the invention was produced demonstrating the use of a liquid oxidizing agent for the fusible, carbon residue forming material coating of carbonaceous powder particles. [0130]
To a laboratory beaker was provided 8.5 g of the low melting point isotropic petroleum pitch described in Example 1in 8.5 g of tetralin (C[0131] ₁₀H₁₂) at 140° C. In a second laboratory beaker was combined 20 g of the carbonaceous powder produced and as described with reference to Example 1 with 700 ml of xylene (C₆H₄(CH₃)₂) at 120° C. To the contents of the second beaker was gradually added the contents of the first beaker, and following the addition the resultant mixture was heated and maintained at about 128° C. for 15 minutes under continuous stirring. Subsequently the heat source was removed, and while the continuous stirring was maintained the mixture was allowed to cool to ambient temperature (approx. 20° C.). The resultant solids were removed from the cooled mixture by first filtering the mixture on a vacuum funnel, and thereafter drying under vacuum at 120° C. for at least 3 hours. The resultant dried coated carbonaceous powder particles recovered exhibited a final dried weight of about 22.3 grams. The amount of precipitated pitch on the carbonaceous powder was determined to account for 10% wt. of the total mass of the coated carbonaceous powder particles.
Next the dried pitch-coated powder was poured into a third beaker containing a 35% wt. aqueous solution of nitric acid (HNO[0132] ₃) at 60° C., and oxidizing agent, and the resulting mixture was maintained at this temperature while stirring. Thereafter the solids were recovered by first filtering the mixture on a vacuum funnel, thoroughly washing the filtered solids with deionized water and thereafter drying under vacuum at 80° C. for at least 5 hours.
Subsequently the recovered coated carbonaceous powder particles were introduced into an alumina crucible and heated in an argon atmosphere from ambient temperature at a rate of 5° C./minute to a temperature of 850° C. at which point the crucibles were maintained at that temperature for 2 hours, after which the crucibles were allowed to cool at the rate of 5° C./minute to ambient temperature, i.e., 20° C. at which point the coated carbonaceous powder particles were removed from the crucibles. The resultant powder particles demonstrated good powder flowability, and it did not appear that fusion of particles had taken place. [0133]
Thereafter the coated carbonaceous powder particles were graphitized by providing them to a graphite crucible, inserting the crucible to an induction furnace having an argon atmosphere, and first heating the crucible at a rate of 13° C./minute to a temperature of 2800° C. and thereafter heating the crucible at a rate of 5° C./minute to 3000° C. at which time the temperature of the induction furnace was maintained at 3000° C. for a period of 45 minutes. Subsequent to these heating steps graphitization was believed to be essentially complete. The crucibles containing the coated carbonaceous powder particles were then allowed to cool to ambient temperature, after which the powder particles were removed from the crucibles. The resultant powder particles demonstrated good powder flowability, and it did not appear that fusion of particles had taken place. [0134]
The electrical charge capacity, as well as the irreversible electrical charge capacity loss of the powder particles were evaluated utilizing the procedure described above under the heading “Evaluation of electrical capacity”. The results of the electrical performance evaluation are described on Table 11, following. [0135]

TABLE 11

Irreversible

Coated pitch Capacity capacity loss Efficiency

(%) (mAh/g) (mAh/g) (%)

Ex. 15 10 330 14 96

Example 16

Further samples of coated carbonaceous powder particles according to the invention were produced which also utilized a liquid oxidizing agent as was used in Example 15. The compositions were prepared by the same protocol used to produce the compositions of Example 14. Namely, the dried pitch-coated powder prepared as shown in Example 14 was oxidized in a nitric acid solution as illustrated in Example 15 before carbonization and graphitization. [0136]
As in the prior Example's evaluation, the electrical charge capacity, as well as the irreversible electrical charge capacity loss of the powder particles according to the present Example were evaluated utilizing the procedure described above under the heading “Evaluation of electrical capacity”. The results of the electrical performance evaluation are described on Table 12, following. [0137]

TABLE 12

Irreversible

Coated pitch Capacity capacity loss Efficiency

(%) (mAh/g) (mAh/g) (%)

Comp. Ex. 16 7 338 26 93
The coated carbonaceous powder particles produced according to Examples 15 and 16, and their resultant excellent electrical properties demonstrate the utility of liquid oxidizing agents. [0138]
As is evident from the foregoing, the compositions provided by the invention provide high capacity and high efficiency carbon material which can be derived from a wide variety of sources. Additionally the compositions provided by the invention also feature good powder flowability, which is particularly beneficial during any handling or manufacturing steps necessary to form these materials into useful electrodes or into other articles not specifically described herein. [0139]
While described in terms of the presently preferred embodiments, it is to be understood that the present disclosure is to be interpreted as by way of illustration, and not by way of limitation, and that various modifications and alterations apparent to one skilled in the art may be made without departing from the scope and spirit of the present invention. [0140]

Claims

1. A process for the production of coated carbonaceous particles of which process comprises the steps of:

providing particles of a carbonaceous material;

subsequently carbonizing the coated particles; and,

optionally thereafter graphitizing the coated particles.

2. The process according to claim 1 wherein the carbonaceous particles are a pulvurent carbonaceous material selected from the group consisting of: pitches, calcined petroleum cokes, uncalcined petroleum cokes, highly crystalline cokes, coal tar cokes, synthetic graphites, natural graphites, soft carbons derived from organic polymers, and soft carbons derived from natural polymers.

3. The process according to claim 2 wherein the carbonaceous particles are a pulvurent carbonaceous material selected from the group consisting of: calcined petroleum cokes, uncalcined petroleum cokes, highly crystalline cokes, synthetic graphites, and natural graphites.

4. The process according to claim 1 wherein the carbonaceous particles have an average particle size of up to about 150 μm.

5. The process according to claim 4 wherein the carbonaceous particles have average particles sizes between about 5 μm and about 70 μm.

6. The process according to claim 5 wherein the carbonaceous particles have average particle sizes between about 5 μm and about 45 μm.

7. The process according to claim 1 wherein the carbon residue forming material is coated onto the surface of the carbonaceous particles by liquefying the carbon residue forming material, and contacting the liquefied carbon residue forming material with the fine particles of the carbonaceous material.

8. The process according to claim 1 wherein the carbon residue forming material is coated onto the surface of the carbonaceous particles by selectively precipitating a carbon residue forming material onto the carbonaceous particles.

9. The process according to claim wherein the carbon residue forming material is coated onto the surface of the carbonaceous particles in amounts of between 1% wt. and 50% wt.

10. The process according to claim 1 wherein the carbon residue forming material is coated onto the surface of the carbonaceous particles in amounts of between 2.5% wt. and 25% wt.

11. The process according to claim 1 wherein the oxidizing agent and the carbon residue forming material is applied to the fine particles of the carbonaceous material in a single step.

12. The process according to claim 1 wherein the oxidizing agent is a solid oxidizing agent selected from the group consisting of: inorganic and organic oxidizing agents.

13. The process according to claim 12 wherein the oxidizing agent is selected from the group consisting of: alkali nitrates and alkali sulfates such as are represented by MNO₃and M₂SO₄, where M denotes alkali metal; M′O_xwhere M′ represents a transition metal, inorganic salts, and organic salts.

14. The process according to claim 1 wherein the oxidizing agent is a liquid oxidizing agent.

15. The process according to claim 14 wherein the oxidizing agent is selected from the group consisting of: oxidizing acids, aqueous solutions containing oxidizing salts, non-aqueous solutions containing oxidizing salts, peroxides and aryl quinones.

16. The process according to claim 1 wherein the oxidizing agent is a gaseous oxidizing agent.

17. The process according to claim 16 wherein the oxidizing agent is a gaseous oxidizing agent selected from the group consisting of: oxygen, sulfur fumes, gaseous oxides, nitrogen oxide gas, ambient air and halogens.

18. Coated carbonaceous particles having a coating layer formed of an oxidized fusible carbon residue forming material.

19. Coated carbonaceous particles according to claim 18 having a coating layer formed of a graphitized, fusible oxidized carbon residue forming material.

20. Coated carbonaceous particles according to claim 18 having a substantially smooth coating.

21. The coated carbonaceous particles according to claim 18 wherein the carbonaceous particles are a pulvurent carbonaceous material selected from the group consisting of: petroleum pitches, calcined petroleum cokes, uncalcined petroleum cokes, highly crystalline cokes, coal tar cokes, synthetic graphites, natural graphites, soft carbons derived from organic polymers, and soft carbons derived from natural polymers.

22. The coated carbonaceous particles according to claim 18 wherein the fine carbonaceous particles are a pulvurent carbonaceous material selected from the group consisting of: calcined petroleum cokes, uncalcined petroleum cokes, highly crystalline cokes, synthetic graphites, and natural graphites.

23. Coated carbonaceous particles comprising coated fine carbonaceous particles having a coating layer formed of an oxidized, fusible carbon residue forming material according to claim 18.

24. An electrical storage cell comprising coated carbonaceous particles according to claim 18.

25. An electrical storage cell according to claim 24, wherein the electrical storage cell is a rechargeable electrical storage cell.

26. A method for the manufacture of an electrical storage cell which comprises the step of:

incorporating into an anode of the electrical storage cell the coated carbonaceous particles according to claim 18.

27. A process for the production of coated carbonaceous particles having substantially smooth coatings formed of an oxidized, carbon residue forming material which process comprises the steps of:

providing particles of a carbonaceous material;

providing a coating of a fusible, carbon residue forming material onto the surface of said particles by contacting the particles of the carbonaceous material with a liquid carbon residue forming material;

subsequently carbonizing the coated particles; and,

optionally thereafter graphitizing the coated particles.

28. Coated carbonaceous particles having substantially smooth coatings formed of an oxidized, carbon residue forming material produced by the process of claim 27.

29. Coated carbonaceous particles having substantially smooth coatings formed of an oxidized, carbon residue forming material.