Lithium-rich nickel manganese oxide battery cathode materials and methods

1 . A method of forming an active material for a positive electrode of a lithium-ion battery, the method comprising:

quenching a powder of the active material in water,

wherein the water is at room temperature prior to the quenching, and

the powder of the active material is quenched at a rate of at least 1750° C./second, and

wherein the active material comprises a layered lithium-rich nickel manganese oxide, and

wherein after the step of quenching but before the active material is charged for a first charge, the layered lithium-rich nickel manganese oxide comprises a first crystal phase and a second crystal phase different than the first crystal phase, wherein the first crystal phase is a monoclinic crystal phase.

2 . The method of claim 1 , further comprising firing the active material powder prior to the quenching step.

3 . The method of claim 2 , wherein the active material is fired at a temperature of at least 800° C.

4 . The method of claim 2 , further comprising, after the quenching, mixing the active material with a binder without performing an additional firing step.

5 . The method of claim 1 , wherein excess Li, Ni and Mn atoms in the layered lithium-rich nickel manganese oxide are homogeneously and uniformly distributed throughout transition metal crystal lattice sites, such that there are no crystalline volumes greater than 3×3×3 nm in the material in which there is a greater than 3% difference between ratios of Ni, Mn and Li atoms compared to average ratios of the Ni, Mn and Li atoms of a bulk material.

6 . The method of claim 1 , wherein particles of the powder of the active material are in a shape of agglomerates which have an average size ranging from about 0.1 μm to about 20 μm, and the agglomerates of the powder of the active material are composed of crystallites having an average size ranging from about 25 nm to about 500 nm.

7 . The method of claim 6 , wherein:

the active material is substantially free of cobalt; and the active material is represented by a formula:

Li[M x Li (1/3-2x/3) Mn (2/3-x/3) ]O 2 where 0.19<x<0.26, and where M comprises Ni and at least one of Ti, Fe, Al or Cr.

8 . The method of claim 1 , wherein the powder of the active material is a combination of LiMO 2 R-3m and Li 2 MnO 3 C2/m phases, where M is at least one of Ni or Mn.

9 . The method of claim 1 , wherein the powder of the active material comprises a crystal structure, a majority of which possesses a C2/m symmetry.

10 . The method of claim 1 , wherein the powder of the active material comprises a crystal structure, a majority of which possesses a R-3m symmetry.

11 . The method of claim 1 , wherein the active material is represented by a formula:

Li[Ni x Li (1/3-2x/3) Mn (2/3-x/3) ]O 2 where 0<x<0.5.

12 . The method of claim 11 , wherein:

the active material is substantially free of cobalt; and the active material is represented by the formula:

Li[Ni x Li (1/3-2x/3) Mn (2/3-x/3) ]O 2 where 0.19<x<0.26.

13 . The method of claim 1 , wherein the water comprises an additive solvated therein.

14 . The method of claim 13 , wherein the water comprises from 0.01 moles per liter to 1.0 moles per liter of the additive.

15 . The method of claim 13 , wherein the additive comprises an acid.

16 . The method of claim 15 , wherein the acid is selected from sulfuric acid, citric acid, acetic acid, phosphoric acid, hydrochloric acid, ammonium phosphate, or combinations thereof.

17 . The method of claim 16 , wherein the acid comprises citric acid.

18 . The method of claim 13 , wherein the additive comprises a carbohydrate.

19 . The method of claim 18 , wherein the carbohydrate is selected from fructose, galactose glucose, lactose, maltose, sucrose, or a combination thereof.

20 . The method of claim 1 , further comprising placing the active material into the positive electrode of a lithium-ion battery cell which further comprises a negative electrode and an electrolyte, wherein:

the active material comprises rhombohedral and monoclinic phases prior to electrochemical cycling of the battery; and

the active material powder does not comprise the monoclinic phase after electrochemical cycling.

21 . The method of claim 20 , wherein:

a specific discharge capacity of the battery cell increases by at least 10% over 50 electrochemical cycles at charge rate of C/20 and discharge rate of C/2 in a voltage range of 2V to 4.8V at room temperature; and

the battery cell has a specific capacity of at least 230 mAh/g after the 50 electrochemical cycles at the discharge rate of C/2.

22 . The method of claim 1 , wherein the second crystal phase is a rhombohedral crystal phase.

23 . The method of claim 1 , wherein the active material is represented by the formula:

Li z (Mn y Ni 1-y ) 2-z O 2 , where z=1.16, and y=0.7.

24 . The method of claim 1 , wherein the active material is substantially free of cobalt.

25 . The method of claim 1 , wherein the active material is free of cobalt.