RECYCLED GRAPHITE FOR LI-ION BATTERIES
A method of producing a purified graphite from a recycled battery stream for use in as anode material in Li-ion batteries is described. The method comprises a leaching step to obtain a precipitate comprising graphite by filtration, which is then iteratively roasted as a slurry with an aqueous solution of a hydroxide base and subsequently washed to form a purified graphite.
1 . A method of producing a purified graphite from a recycled battery stream comprising:
leaching a black mass of exhausted lithium-ion batteries to obtain a leach solution and a precipitate comprising graphite;
sintering the precipitate by
preparing a slurry of the precipitate with a first aqueous solution of a hydroxide base having a concentration of hydroxide of ≤40% by weight and
roasting the slurry of the precipitate at a temperature of <250° C. to form a sintered precipitate;
sintering the sintered precipitate by
preparing a slurry of the sintered precipitate with a second aqueous solution of a hydroxide base having a concentration of hydroxide of ≤40% by weight, and
roasting the slurry of the sintered precipitate at a temperature of <250° C. to form a sintered graphite; and
washing the sintered graphite to form a purified graphite.
2 . The method of claim 1 , wherein the slurry of the precipitate is prepared with a ratio of the precipitate to the first aqueous solution of about 1:1 to 1:4.
3 . The method of claim 1 , wherein the slurry of the sintered precipitate is prepared with a ratio of the sintered precipitate to the second aqueous solution of about 1:1 to 1:4.
4 . The method of claim 1 , wherein the concentration of the first aqueous solution and the concentration of the second aqueous solution are the same.
5 . The method of claim 1 , wherein the concentration of the first aqueous solution, the concentration of the second aqueous solution, or both is from 10% to 35% by weight.
6 . The method of claim 1 , wherein the concentration of the first aqueous solution, the concentration of the second aqueous solution, or both is from 20% to 30% by weight.
7 . The method of claim 1 , wherein the hydroxide base is NaOH or KOH.
8 . The method of claim 1 , wherein the slurry of the precipitate, the slurry of the sintered precipitate, or both is roasted at a temperature of from 100° C. to 225° C.
9 . The method of claim 1 , wherein the slurry of the precipitate, the slurry of the sintered precipitate, or both are roasted for a time of from 1 to 20 hours.
10 . The method of claim 9 , wherein the time is from 1 to 15 hours.
11 . The method of claim 1 , wherein the precipitate further comprises a ceramic impurity.
12 . The method of claim 11 , wherein the ceramic impurity is alumina.
13 . The method of claim 1 , wherein the sintered graphite is washed with an aqueous wash solution to a pH of from 6 to 10.
14 . The method of claim 13 , wherein the aqueous wash solution is water.
15 . The method of claim 13 , wherein the aqueous wash solution is an aqueous alkaline solution having a concentration of base that is ≤0.1M.
16 . The method of claim 13 , wherein, after washing the sintered graphite with the aqueous wash solution, further washing with an acidic wash solution followed by washing with water.
17 . The method of claim 16 , wherein the acidic wash solution comprises HCl or sulfuric acid.
18 . The method of claim 1 , wherein the precipitate comprises graphite having a purity of from 82% to 97%.
19 . The method of claim 1 , wherein the purified graphite has a purity of greater than 99.5%.
20 . A method of producing a purified graphite from a recycled battery stream comprising:
leaching a black mass of exhausted lithium-ion batteries to obtain a leach solution and a precipitate comprising graphite having a purity of from 82% to 97% and a ceramic impurity comprising alumina;
sintering the precipitate by:
preparing a slurry of the precipitate with an aqueous NaOH solution having a concentration of hydroxide of from 20% to 30% by weight and
roasting the slurry of the precipitate at a temperature of from 150° C. to 220° C. to form a sintered precipitate;
sintering the sintered precipitate by:
preparing a slurry of the sintered precipitate with the aqueous NaOH solution, and
roasting the slurry of the sintered precipitate at a temperature of from 150° C. to 220° C. to form a sintered graphite; and
washing the sintered graphite with an aqueous wash solution to form a purified graphite having a purity of greater than 99.5%.