MULTI-STAGE LITHIATION FOR CATHODE MATERIAL
A Li-ion cathode material is prepared by a multi-stage lithiation process that separates a total amount of lithium called for by the recycled battery to be used in a series of sintering stages. A leaching, ratio adjustment and coprecipitation sequence forms a cathode precursor having a predetermined ratio of metallic elements from a comingled recycling stream of Li-ion batteries. The precursor is sintered with a lithium salt in a sequence of stages, each having a portion of the total lithium quantity, for a predetermined duration and temperature. The initial sintering stage tends to define the crystallinity of the resulting active cathode material and has a particle size determined at least in part by the portion of lithium at each stage.
1 . A method of producing a cathode material from a recycled lithium-ion battery stream, comprising
sintering a combination of a lithium salt and a cathode material precursor comprising metallic elements selected from the group consisting of nickel, cobalt, and manganese in a Li: total metallic elements ratio of 1 to 1.1 by:
combining the cathode material precursor and a first portion of the lithium salt to form a first mixture having a Li: total metallic elements ratio that is less than or equal to 1,
heating the first mixture at a first sintering temperature of from 900-1200° C. for a first sintering time of from 2-10 hours to form a lithium-deficient sintered material,
combining the lithium-deficient sintered material and a remaining portion of the lithium salt to form a second mixture, and
heating the second mixture at a second sintering temperature of from 800-1000° C. for a second sintering time of from 5-15 hours to form the cathode material,
wherein the first sintering temperature is greater than the second sintering temperature and the first sintering time is less than the second sintering time.
2 . The method of claim 1 , wherein the cathode material precursor is prepared by:
leaching a black mass from the recycled lithium-ion battery stream to obtain an acidic aqueous leach solution of metal salts comprising a nickel salt, a cobalt salt, and a manganese salt in a molar ratio of metallic elements;
adjusting the molar ratio of the metallic elements in the leach solution to a selected molar ratio with additional metal salts; and
co-precipitating the metallic elements and the additional metal salts from the leach solution to form a cathode material precursor having the selected ratio.
3 . The method of claim 2 , wherein the black mass is leached with an aqueous acid.
4 . The method of claim 3 , wherein the aqueous acid comprises sulfuric acid.
5 . The method of claim 4 , wherein the aqueous acid further comprises hydrogen peroxide.
6 . The method of claim 5 , wherein the metallic elements are nickel, manganese, and cobalt.
7 . The method of claim 1 , wherein the lithium salt is lithium carbonate or lithium hydroxide.
8 . The method of claim 2 , wherein the selected molar ratio includes less than or equal to 50 mole % nickel and the lithium salt is lithium carbonate.
9 . The method of claim 2 , wherein the selected molar ratio includes greater than 60 mole % nickel and the lithium salt is lithium hydroxide.
10 . The method of claim 1 , wherein the first mixture and the second mixture are heated in a furnace having an oxygen-containing atmosphere flow.
11 . The method of claim 10 , wherein the oxygen-containing atmosphere is air.
12 . The method of claim 10 , wherein the flow is from 0.2 to 16 SCFM.
13 . The method of claim 1 , wherein the cathode material has a crystal structure determined by the Li: total metallic elements ratio of the first mixture, the first sintering temperature, and the first sintering time.
14 . The method of claim 13 , wherein the cathode material has a single crystal structure.
15 . The method of claim 13 , wherein the cathode material has a crystal structure determined by the crystal structure of the lithium-deficient sintered material.
16 . The method of claim 13 , wherein the lithium-deficient sintered material has a single crystal structure.
17 . The method of claim 1 , wherein the lithium-deficient sintered material has a particle size determined by the Li: total metallic elements ratio of the first mixture, the first sintering temperature, and the first sintering time.
18 . The method of claim 17 , wherein the particle size of the lithium-deficient cathode material is from 10 to 50 microns.
19 . The method of claim 1 , further comprising jet-milling the lithium-deficient cathode material prior to forming the second mixture.
20 . The method of claim 1 , further comprising jet-milling the cathode material.