Producing coated graphitic anode powders by extracting pitch from high volatile matter coke and coating the same in-situ
View Patent ↗This invention relates to a process for making carbon coated graphitic anode powders for use in batteries including rechargeable lithium-ion batteries wherein the process includes a side product isotropic pitch for use as a precursor in other products and more preferably, as a coating material for other powder or particle products. The process includes the steps of solvent extraction of volatile materials from high volatile material green coke powder. When a desirable amount of the volatile materials have been extracted, the solvent strength is altered to cause some of the volatile materials to precipitate on the powder particles to coat the same. The coated and solvent-extracted particles are then separated from the solvent and oxidatively stabilized, then carbonized and preferably graphitized. The volatile materials remaining in the solvent are valuable and are recovered for use in other processes and other products.
1. A process for making carbon coated graphitic anode powder for use in batteries wherein the process comprises:
a) providing green coke having high volatile matter of at least about ten weight percent volatile matter;
b) mixing the high volatile matter green coke with a liquid solvent at a selected solvent to carbon ratio to form a solvent suspension and also to extract volatile matter from the green coke, wherein the solvent is selected from the group consisting of toluene, benzene, and xylene;
c) altering the solvent strength of the solvent suspension and cause volatile matter that has been extracted from the green coke to precipitate on the coke particles and form a coating thereon, wherein the altering the solvent strength comprises adding anti-solvent to the solvent suspension and the anti-solvent is selected from the group consisting of pentane, hexane, heptane, octane, and nonane;
d) separating the solvent with residual dissolved volatile material from the coated green coke particles;
e) stabilizing the coated green coke particles by oxidative stabilization while heating to a temperature of at least 200° C. in an oxygen containing environment;
f) carbonizing the stabilized coated green coke particles to a temperature of at least 600° C. in an inert environment; and
g) graphitizing the coated carbonized coke particles to a temperature of at least 2200° C.
2. The process for making carbon coated graphitic anode powder according to claim 1 , further including the step of recovering dissolved volatile matter from the separated solvent liquid from step d).
3. The process for making carbon coated graphitic anode powder according to claim 1 wherein the step of oxidative stabilization is performed such that the temperature is progressively raised so that the coating remains infusible during the stabilization process until a desired temperature is attained for a predetermined period of time.
4. The process for making carbon coated graphitic anode powder according to claim 1 wherein the graphitization temperature is between 2500° C. and 3200° C.
5. The process for making carbon coated graphitic anode powder according to claim 1 wherein the carbonization temperature is between 600° C. and 1600° C.